ML103370169

Attachment 2, Vol. 2, to SBK-L-10185, Seabrook Station Response to Request for Additional Information NextEra Energy Seabrook License Renewal Environmental Report, References Requested for Docketing at the Seabrook Station Environmental Sit

ML103370169
Person / Time
Site:	Seabrook
Issue date:	11/23/2010
From:	NextEra Energy Seabrook
To:	Office of Nuclear Reactor Regulation
References
SBK-L-10185
Download: ML103370169 (898)

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{{#Wiki_filter:NEXTeraB E NER(-Y:7A.4 SBK-L-10185 Q tahmn AttachVment2, Vol. 2 SEABROOK ENVIRONMENTAL STUDIES, 1987.A CHARACTERIZATION OF BASELINE CONDITIONS IN THE HAMPTON-SEABROOK AREA, 1975-1987. A PREOPERATIONAL STUDY FOR SEABROOK STATION TECHNICAL REPORT XIX-II Prepared for NEW HAMPSHIRE YANKEE DIVISION PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE P.O. Box 700 Seabrook Station Seabrook, New Hampshire Prepared byýNORMANDEAU ASSOCIATES INC.25 Nashua Road Bedford, New Hampshire 03102 R-313 November 1988 TABLE OF CONTENTS PAGE 1.0 EXECUTIVE

SUMMARY

. .I........................

1.1 INTRODUCTION

........... ............ ......... 1 1.2 INTAKE MONITORING ....... ... ........... .**. 2 1.3 DISCHARGE MONITORING.................. ......... .4 1.3.1 Discharge Plume Monitoring4............4

1.3.2 Benthic

Monitoring ............. .5 1.3.3 Estuarine Monitoring ..... ........... .... 6 2.0 DISCUSSION .. .. .......... ..... ..... ........... ...... 9

2.1 INTRODUCTION

............ ........ 9 2.1.1 General Perspective.. ................ 9 2.1.2 Sources of Baseline Variability .............. 9 2.2 INTAKE AREA MONITORING. ... ... ........15 2.2.1 Plankton ........... 15 2.2.1*. Community Structure .... ....... 15 2.2.1.2 Selected Species. ....20 2.2.1.3 Spatial Variability ............. .. .25 2.2.2 Pelagic Fish ................ ............ ... 25 2.2.2.1 Temporal. ........... .... 25'2.2.2.2 Spatial ........... ...... 30 2.3 DISCHARGE AREA MONITORING .......................... 33 2.3.1 Plume Studies. ..... ...... .................. 33 2.3.1.1 Discharge Plume Zone. ............ ... 33'2.3.1.2 Intertidal/Shallow Subtidal Zone. 40 2.3.1.3 Estuarine Zone. ................ 47 2.3.2 Benthic Monitoring .... ....................... 56 2.3.2.1 Macroalgae and Macrofauna ..... ......56 2.3.2.2 Demersal Fish ................ .. 61 2.3,2.3 Epibenthic Crustacea. ...66 iii PAGE 3.0 RESULTS .......3.1 iPLANKTON AND WATER 3.1.1 Water Quali.., ..*. * ......QUALITY PARAMETERS ty Parameters-Seaso

3.1.2 Bivalve

Veliger Larvae.3.1.2.1 Community ... .3.1.2.2 Selected Species*. ..3.1.3 Macrozooplankton ...3.1.3.1 Community Structure 3.1.3.2 Selected Species. ..3.2 FINFISH .. ..... ............ ..3.2.1 Ichthyoplankton.......... ..3.2.1.1 Total Community ...3.2.1.2 Selected Species.3.2.2 Adult Finfish. ....3.2.2.1 Total Community .3.2.2.2 Selected Species. ..3.2.3 Finfish Appendix Tables. .3.3 BENTHOS ..... ............ .. .3.3.1 Estuarine Benthos ........... 3.3.1.1. Physical Environment. 3.3.1.2 Macrofauna........

3.3.2 Marine

Macroalgae.. ........3.3.2,. Macroalgal Community. 3..3.2.2 Selected Species.nal Cycles and 69 80 80 86 88 88 98 107 107 107 128 143 143 161 178 185 185 185 193 205 205 223 69 69 PAGE 3.3.3 Marine Macrofauna ...... ............. ...229 3.3.3.1 Algae Covered Ledge Community ........ ...229 3.3.3.2 Intertidal Bare Rock, FucoidLedge, and Chondrus Communities .............. 240 3.3.3.3 Subtidal Fouling Community. ...244 3.3.3.4 Modiolus modiolus Community ....246 3.3.4 Surface Fouling Panels ...... .......248 3.3.4.1 Seasonal Settlement Patterns. .......248 3.3.4.2 Patterns of Community Development ..255 3.3.5 Selected Benthic Species .................... 261 3.3.5.1 Mytilidae .......................... 261 3.3.5.2 Nucella lapillus. .... ...... ...267 3.3.5.3 Asteriidae ......................... 267 3.3.5.4 Pontogeneia inermis ..... ... ...269 3.3.5.5 Jassa falcatae ... ............ .270 3.3.5.6 Ampithoe rubricata. ............. ... 271 3.3.5.7 Strongylocentrotus droebachiensis ..272 3.3.6 Epibenthic Crustacea .... ..... ..... ...274 3.3.6.1 American Lobsters (ifomarus americanus). 274 3.3.6.2 Rock Crab (Cancer irroratus) and Jonah Crab (Cancer borealis). ........ 286 3.3.7 Mya arenaria (Soft-shell Clam) ........... .. 292 3.3.7.1 Larvae. ............... ........... 292 3.3.7.2 Reproductive.Patterns .... ....... 294 3.3.7.3 Hampton Harbor and Regional Popula-tion Studies. ............. ....294 3.3.8 Benthos Appendix Tables.. .................... 317 4.0 METHODS .......... .................... ............ ..347 4.1 GENERAL...... .. ... ......... .... ..347 4.2' COMMUNITY STRUCTURE ........... ............... ..356 4.3 SELECTED SPECIES/PARAMETERS ........... ..... 361 5.0 LITERATURE CITED .... ...... ...... 369-V LIST OF FIGURES PAGE 2.1-1. Schematic of sources and levels ofvariability in Seabrook Environmental Studies.... .......... .....2.2-1. Historical dates of occurrence and mean abundance'(excluding rare taxa) for seasonal groups formed by 3 numerical classification of microzooplan ton (No./m., 1978-1984), macrozoopiankton (No./1000 m , 1978-1984)., fish eggs ( o./1000 m ,.1976-1984), and fish larvae (No./1000 m-, 1976-1984) collections.... .........' 16 2.2-2. Percent composition, seasonal vs. annual variability (standard deviation) of log (x+l).abundance, and months of peak abundance for selected species of phytoplankton (thousands of cells/liter) and micro-zooplankton (No./m ), 1978-1987. .. ................. 21.2.2-3. Percent composition, seasonal vs. annual variability (standard deviation) of log (x+l) abundance, and 2 months of peak abundance for lobster larvae (No.41000 m ) and selected species of bivilve larvae (No./m ) and macro-zooplankton (No./1000 m ) ...... ............. ....... .22 2.2-4. Percent composition, seasonal vs. annual variability (standard diviation) of log (x+l) abundance (No./1000 m ), and months of peak abundance for selected species of fish larvae, i975-1987 ..23 2.2-5. Seasonal and annual changes>in composition and abundance of the pelagic fish community, based on catch per unit effort at gill net stations G., G2, and G3 combined, 1976-1987 .................. ....27 2.2-6. Percent composition, seasonal vs. annual variability (standard deviation) of log (x+l) abundance (catch per unit effort), and months of.peak abundance for selected species of fish, 1976-1987...... ......29 2.3-1. Seasonal vs. annual variability (standard deviation) and months of peak values for temperature (CC), salinity (ppt), dissolved oxygen (mg/l), and nutrients (pg/1) ........ ........ .34 2.3-2. Monthly mean surface and bottom temperature'(0 0), surface salinity (ppt), and surfaceý dissolved oxygen (mg/l) at station P2 for each year and over all years (1978-1986, except temperature, 1978-1984 and August 1986-December 1987) .................. ....35*Vi PAGE 2.3-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19. ... 39 2.3-4. Depth and abundance characterizations of species assem-blages identified by--isc 5iminant analysis of August collections of algae (g/T of dominant taxa) and marine benthos (thousands per m of dominant taxa) during 1978-D987. ............ ......................... .. 41 2.3-5. Percent composition (based on biomass) by depth strata for dominant macroalgae species at marine benthic stations in August, 1978-1987. ............. ...*. 42 2.3-6. Percent composition and nearfield (Sta. IMLW & 17)vs. farfield (Sta. 5MLW & 35) annual variability (standard deviation) of log (x+l) abundance for selected intertidal and shallow subtidal species of algae and benthos ...... ................. 46 2.3-7. Mean monthly seawater surface temperature and salinity with 95% confidence limits.taken at low tide in Brown's River (Sta. 3) in 1987 and over the entire study period (May 1979 -December 1987) ..... ....... 48 2.3-8. Annual geometric mean density (No./m2) and mean number of taxa per station of estuarine benthos, and annual mean salinity, at Brown's River and Hampton Harbor .50 2.3-9. Seasonal and annual changes in composition and abundance of the estuarine fish.community, based on catch per unit effort at beach seine Stations S1, S2 and S3 combined, 1976-1984 and 1987 ......... ....51 2.3-10. Percent composition by station for abundant species of fish collected in beach seines, all years combined, 1976-1987....... .... .............. 53 2.3-11. Annual Teans and 95% confidence limits of densities (No.'/ft ) of Mya arenaria young-of-the-year and spat in Hampton-Seabrook on Flat 1. ......... .......... 55 2.3-12. 'Number of adult clam licenses issued and the adult clam standing crop (bushels), Hampton-Seabrook Harbor, 1971-1987 ............ .......... ........ ...... 57 2.3-13 Percent composition and nearfield (Sta. 19) vs.farfield (Sta. 31) annual variability (standard deviation) of log (x+l) abundance for selected mid-depth benthic species, 1978-1987 ....60 vii PAGE 2.3-14. Seasonal andannual changes in composition and abundance of the demersal fish community, based on catch per unit effort at otter trawl stations Tl, T2 and T3 combined, 1976-1987.

• . .... ......62 2.3-15. Percent composition by station for abundant species of fish collected.

in otter trawls, all years combined, 1976-1987 .......................... .. .. .....64 2.3-16. Seasonal vs. annual variability (standard deviation) and months of peak abundance (catch per 15-trap effort) for adult lobsters and crabs ......... .....67 2.3-17. Size-class distribution (carapace length) of Ilomarus americanus at the discharge site, 1975-1987 ...... .. 68 3.1.1-1. Monthly mean temperature at Station P2, all years'mean and 95% confidence interval for 1978-1987 and monthly mean for 1987 for surface and bottom ... ..... 70 3.1.1-2. Differences between surface and bottom temperatures taken semi-monthly at Station P2, 1978-1987 ...... .. 71 3.1.1-3. Surface salinity and bottom salinity at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1987, and monthly means for 1987 ...... ...... .. ...... .73 3.1.1-4. Dissolved oxygen at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1987, and monthly means for 1987 for surface and bottom.. ................... ... ....74 3.1.1-5. Orthophosphate and total phosphorus at nearfield Station P2, monthly means and 95% confidence inter-vals over all years from 1978-1984 and 1986-1987, and monthly means for 1987 ... ............... ....75 3.1.1-6. Nitrite-nitrogen and nitrate-hitrogen concentrations at nearfield Station P2, monthly means and 95% con-fidence intervals over all years from 1978-1984 and, 1986-1987, and monthly means for 1987. ............. 76 3.1.1-7.ý Ammonia concentrations at nearfield Station P2, monthly means and 95% confidence intervals over all years from 1978-1984 and 1986-1987, and monthly means for 1987 .. ............ ..77 viii PAGE 3.1.2-1. Number of years present and number of years in high abundance ( 50% of seasonal peak abundance) of bivalve veliger larvae by week at Station P2, 1978-1987. Years enumerated.:'

a. 1976-1987;

b. 1978-1984, 1986-1987;

c. 1979-1984, 1986-1987

.82 3.1.2"-2. Weekly mean abundance and 95% confidence intervals. for Mytilus edulis larvae at nearfield Station P2 over all years, 1978-1987.. 87..... ....... 87 3.1.3-1. Log (x+i) abundance per 1000 cubic meters 'for Calanus finmarchicus copepodites and adults; monthly mean and 95% confidence interval over all years 1978-1984, 1986-1987 and monthly means for 1987 .......... 100 3.1.3-2. Log (x+l) abundance per 1000 cubic meters for Carcinus.maenas larvae and Crangon septemspinosa zoeae and post-larvae; monthly mean and 95% confidence interval' over all years 1978-1984, 1986-1987 and monthly means for 1987 ................. .......... ....... 103 3.1.3-3. Log (x+l) abundance per 1000 cubic meters for Neomysis americana; monthly mean and 95% confidence interval over all years 1978-1984, 1986-1987 and monthly means for 1987 and mean percent composition of Neomysis.americana lifestages over all years 1978-1984, 1986-1987 at nearfield Station P2. ........... 105 3.2.1-1. Mean and 95% confidence limits over all years and 1987 values, by month. for log (x+l) transformed abundance (No./1000 m ) for American sand lance and winter flounder larvae at Stations P2 and P3, July 1975 through December 1987 ..................... .... 132 3.2.1-2. Mean and 95% confidence limits over all years and 1987 values, by month, 3 for log (x+l) transformed abundances (No./1000 m ) for yellowtail flounder and Atlantic cod larvae Stations P2 and P3, July 1975 through December 1987 .... ...... .... .. ... ... 136 3.2.1-3. Mean and 95% confidence limits-over all years and 1987 values, by month, 3 for log (X+1) transformed abundances (No./1000 m ) for Atlantic mackerel and cunner larvae at Stations P2 and P3, July 1975 through December 1987 .......... ................... 138 ix PAGE 3.2.1-4. Mean and 95% confidence limits over all years and 1987 values, by month, for log (x+l) transformed '3 abundances (No./1000 m ) for hake6,and Atlantic, herring larvae at Stations P2 and P3, July 1975 through.December 1987. ...... ....... .... .........140 3.2.1-5. Mean and 95% confidence limits over all years and 1987 values, by month*3 for log (x+l) transformed abundances (No./1000 m ) for pollock larvae at Stations P2 and P3, July 1975 through De'cember 1987. 142 3.2.2-1. Catch per unit effort (mean number per 10 minute tow) of all species collected in otter trawls by year, station and all stations combined, 1976-198.7 144 3.2.2-2. Catch per unit effort (number per 24-hour set of one net., surface or bottom) of all species combined in gill nets by year, station and all stations combined, 1976-1987 ....... ...... .. 150 3.2.2-3. Catch per unit effort (mean number per seine haul)of all species collected in beach seines by year, -station and all stations combined, 1976-1984 and 1987 ..... ".. ..... ...*.*. ... .... ...... ..... ..... 157 3.2.2-4. Mean and 95% confidence limits over all years and 1987 values, by month, for log (x+l) transformed catch per unit effort (one 24-hr. set) for Atlantic herring and pollock at combined gill net stations G1, G2 and G3 from 1976-1987 ... ........ .......... .. 163 3.2.2-5. Mean and 95% confidence limits over all years, and 1987 values, by month, for. log (x+l) transformed catch per unit effort (one 24-hr. set for gill nets, one 10-min. tow for otter trawl) for Atlantic mackerel at combined gill net.Stations Gl, G2 and G3 and Atlantic cod at otter trawl Station T2, 1976-1987 ."........... ...... ..... ........... ".167 3.2.2-6. Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x+l) transformed catch per unit effort (one 10-mmn. tow) for hakes and yellowtail flounder at otter trawl Station T2, 1976-1987.... .... ...... ................... 169 x PAGE 3.2.2-7. Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x+l) transformed catch per unit effort (one 10-min. tow for otter trawls and one haul for beach seines) for winter flounder at otter trawl Station T2 1976-1987 and combined beach seine Stations S1, S2 and S3 1976-1984 and 1987 .......... ....... .......... .. .. 172 3.2.2-8. Mean and 95% confidence limits over all years and: 1987 values, by month, for log (x+l) transfored catch per 'unit effort (one 10-min. tow for otter trawl and one haul for beach seines) for rainbow smelt at otter trawl Station T2 1976-1987 and combined beach seine Stations S1, S2, and S3 from 1976-1984 and 1987....... ...... .......... ..175 3.2.2-9. Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x+l) transformed catch per unit effort (one haul for beach seines)for Atlantic silverside at combined beach seine Stations S13 S2 and ,S3 1976-1984 and 1987.. .......177 3.3.1-1. Mean monthly seawater surface temperature and salinity with 95% confidence limits taken at low tide in Brown's River over the entire study period (May 1979 -December 1987) and in 1987 ......................... 186 3.3.1-2. Mean annual salinity at low tide in Brown's River and in Hampton Harbor, and total annual precipita-tion from 1980 through 1987 .................. .... 190 3.3.1-3. Monthly outfall from the Seabrook Settling Basin from 1978-1987.in millions of gallons per day (GPD). 191 3.3.1-4. Yearly mean and 95% confidence limits for the log (x+l)density of macrofauna and number of taxa collected at subtidal estuarine stations sampled three times per year from 1978 through 1987 (excluding 1985). 196 3.3.1-5. Yearly mean and 95% confidence limits for the log (x+l)density of macrofauna and number of taxa collected at intertidal estuarine stations sampled three times per year from 1978 through 1987 (excluding 1985) ...197 3.3.1-6'. Yearly mean and 95% confidence limits for the log (x+l)density of Nereis diversicolor and Mya arenaria collected at subtidal estuarine stations three times per year from 1978 through 1987 (excluding 1985) ...200'xi PAGE 3.3.1-7. Yearly.mean and 95% confidence limits for the log (x+l)density of Nereis diversicolor and Mya arenaria.collected at intertidal.stations three times per year from 1978 through 1987 (excluding'1985) .......... 202 3.3.2-1. Number of macroalgae species in general collections at each marine benthic station for 1978-1984 (median, and range) and 1985-1987 (number collected each year) .............................. 206 3.3.2-2. A. Number of taxa and B. mean biomass at intertidal and subtidal benthic stations in August. .....208 3.3.2-3. Mean biomass (g/m 2) and 95% confidence limits for macroalgae collected in August at selected hear-field benthic stations ..... ................ .. 209 3.3.2-4. Relative abundance (% biomass) of dominant macroalgae at marine benthic stations (by station-depth group) in August 1978-1987 ... ............. .. ........ .... .. 211 3.3.2-5. Occurrence and peak biomass of the common and abundant macroalgae species over the range of benthic stations sampled in August 1978-1984 ..... .. 215 3.3.2-6. A. Mean and 95% confidence interval of log No./100 m 2 of kelps (1978-1987; Station 35: 1982-1987) and B. Percent frequencies and 95% confidence interval of dominant understory algae (1981-1987; Station 35: 1982-1987) in the shallow aind mid-depth subtidal zone. 219 3.3.2-7. Mean percent frequency and standard deviation of fucoid algae at two fixed transect sites in: the mean sea level zone (1983-19.87) ..... ...... .. 222 3.3.2-8. Mean biomass (g/m 2) and 95% confidence limits of Chondrus crispus at selected stations in May, August and November, Stations 17, 35: 1978-1987, Stations 35 and IMLW: 1982-1987) ........ ..... ......... .... 227 3.3.3-1. Number of taxa and overall abundance (No./square meter)over all years (1978-1987, Stations IMLW, 17, 19, 31;1982-1987, 5MLW, 35; 1979-1984, 1986-1987, 34;1978-1984, 1986-1987, 13, 4, 16) at intertidal and subtidal benthic stations ................ ............ 23Q 3.3.3-2. Annual mean abundance (No./square meter) and 95%confidence limits for macrofauna collected in August for nearfield Stations 1MLW (intertidal) and 17 (shallow subtidal) ....... .."....... ........ 232 xii PAGE 3.3.3-3. Annual number of taxa collected in August at intertidal Stations lMLW and 5MLW and shallow subtidal Stations 17 and 35... ......... ........ ...... ...... 233 3.3.3-4. Annual number of taxa 'ollected in August at Stations 16, 19, and 31 (mid-depth); and Stations 4, 13, and 34 (deep) ................ .................... ....... .234 3.3.3-5. Annual mean abundance (No./square meter) and 95%confidence limits for macrofauna collected in August for nearfield Stations 19 and 16 (mid-depth) and 4 (deep).. ........ ........... .... ...... .235 3.3.4-1. Faunal richness (number of different taxa over two replicates) in 1987 compared to mean species richness and +/-1 95 confidence limits from 1978-1987 on short term panels ............ ................. ...249 3.3.4-2. Species abundance (log x+l) in 1987 compared to mean species abundance (log x+l; +/-95% confidence limits)from 1978-1987 for non-colonial fauna on short-term. panels ........... ............. ... ........ 251 3.3.4-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19 ......256 2 3.3.6-1. Weekly mean log (x+l) abundance (No./1000 m ) of lobster larvae at Station P2, 1978-1987, all year's mean and 95% confidence

• intervalrand 1987. (No data collected January 1985-June 1986).) ...................

276*3.3.6-2. Comparisons of legal and sub-legal sized catch of ifomarus americanus at the discharge site, 1975-1987. 284 3.3.6-3. Size-class distribution (carapace length) of Homarus americanus at the discharge site, 1975-1987. ......285 3.3.6-4. Summary of female lobster catch data at the discharge site, 1974-1987 ............................... .... 287 3 3.3.6-5. Monthly mean log (x+l) abundance (No./1000 m.) of Cancer spp. larvae at Station P2, 1978-1987. .(No data collected January 1985-June 1986). ........... 288 3.3.7-1. Weekly log (x+l) abundance per cubic meter of lya arenaria larvae at Station P2, 1978-1987, all years'mean and 95% confidence interval and weekly mean for 1987 .... ............ ......... ....... ..293 xiii PAGE 3.3.7-2. Log (x+l) abundance per cubic.meter of Mya arenaria veligers at nearfield Station P2, farfield Station P7 and Hampton Harbor Station P1, 1982-1987 ........ 295.2 3.3.7-3. Abundance (No./ft ) of 1-mm size-classes of Mya arenaria in Hampton-Seabrook Harbor during early fall, 1974-1987.. ... ....... .... ...... ...... ..298 3.3.7-4. Annual mean density (number per square foot) and 95%confidence limits of young-of-the-year Mya arenaria (1-5 mm) at Hampton-Seabrook:Harbor, 1974-1987 ....300 3.3.7-5. Mean and 95% confidence limits of Mya arenaria spat (shell length !12 mm) densities (No.'/ft 2) at two northern New England estuaries, 1976 through 1984 and 1986 through,1987.. ....... ... .............. 301 3.3.7-6. Means and 95% confidence limits of spat, juvenile and adult log (x+l) densities at Flat 1, Hampton-Seabrook Harbor, 1974 through 1987. ........... ......... 303 3.3.7-7. Means and 95% confidence limits of spat, juvenile and adult log (x+l) densities at Flat 2, Hampton-Seabrook Harbor, 1974 through 1987.. ........... ...304 3.3.7-8. Means and 95% confidence limits of spat, juvenile and adult log (x+l) densities at Flat 4, Hampton-Seabrook Harbor, 1974 through 1987 ..... ....... ...... ... 305 3.3.7-9. Fall mean catch per unit effort for green crabs.(Carcinus maenas) in Hampton-Seabrook Harbor and its relationship to minimum winter temperature, 1978-1987. 308 3.3.7-10. Number of adult clam licenses issued and the adult clam standing crop (bushels), Hampton-Seabrook Harbor, 1971-1987. ...... ...... ........... ....... .. 312 4.1-1. Plankton sampling stations ...... ....... .. .348 4.1-2. Finfish sampling stations ..... ........ ....... ... .. 349 4.1-3. Benthic marine algae and macrofauna sampling stations. 351 4.1-4. Hampton-Seabrook, Estuary temperature/salinity, soft-shell clam (Mya arenaria), benthic transects and green crab (Carcinus maenas) sampling stations .... .......352 x4v PAGE 4.1-5. Locations of lobster and rock crab trapping areas. .354 4.1-6. Samplifig sites for May arenaria spat ... ......... ... 355-0 x.v LIST OF TABLES PAGE 2.1-1. Summary of Biological Communities and Species Monitored for each Potential Impact.Type ...13 2.2-1. Comparison of Densities of Top-Ranked Fish Egg, Fish Larvae, and Bivalve Larvae Taxa Collected Offshore at Station P2 and in Entrainment Samples at Seabrook Station from July 1986through June 1987 ....... ................................. 19 2.2-2. Summary of Nearfield/Farfield (P2 vs. P7) Spatial Differences in Plankton Communities and Selected Species ...... ......................... ... ...... 26 2.2-3. Catch Per Unit Effort by Depth for the Dominant Gill Net Species Over All Stations and Dates When Surface, Mid-Depth and Bottom Nets Were Sampled, 1980 Through 1987 ........... ............... ....... 32 2.3-1. Selected Benthic Species and Rationale for Selection ..43 2.3-2. Summary of Similarities in Abundance, Biomass, Frequency, or Length Among Years and Between Stations for Selected Macrofaunal and Macroalgal Species at Intertidal and Shallow Subtidal Depths .............. 45 2.3-3. Summary of Similarities in Abundance or Length Among Years and Between Stations for Selected Species in the Mid-Depth Zone .... .................. 59'3.1.1-1. Annual Means and Coefficients of Variation of Water Quality Parameters Measured During Plankton Cruises at nearfield Station P2, 1978-1984 and 1986-1987 ....... 79.3.1.2-1. Overall Percent Composition of Bivalvia Veliger Larvae in 76-pm Net Tows at Stations P1, P2 and P7 from Mid-April Through October, 1982-1987 ......... ..... .81 3.1.2-2. Densities of Dominant Bivalve Veliger Larvae in 76-ým Mesh Net Collections on or Near the Same Date at Near-field Station, P2, and Entrainment Station, El, April Through June 1987 ......... .. .... .... .. 85 3.1.3-1. Seasonal Groups Formed by Normal Classification of Macrozooplankton Collections From Nearfield Station P2, 1978-1984, and by Discriminant Analysis of Collections From July 1986-December 1987 ....I.... 90 xvi PAGE 3.1.3-2. Mean Abundance and Percent Frequency of Occurrence ,of Dominant Taxa Occurring in Seasonal Groups Formed by Normal Classification of Macrozooplankton Collections at Nearfield Station P2, 1978-1984, in Comparison to 1986 (July-December) and 1987 (January-December) as Classified by Discriminant Analysis ................ 91 3.1.3-3. Comparison of Percent Composition (and.Percent Frequency of Occurrence): of Species in Macrozooplankton Collections Among Stations P2, P5 and P7, January-December 1987 ........................ ....95 3.1.3-4. Summary' of 1987 Biweekly Abundance Comparisons Between Stations Made Using Wilcoxon's Two Sample Test ....96 3.1.3-5. Comparison of Rank (and Percent Frequency of Occurrence) of Dominant Species. in Macrozooplankton Collections Among Stations P2, P5 and P7 January-December 1987 97 3 3.1.3-6. Annual Geometric Mean Abundance (No./1000m3) and Upper and Lower 95% Confidence Limits of Selected Species of Macrozooplanktonjat Seabrook Nearfield Station (P2), 1978-1984 and 1987 .... .. ......... .* .99 3.1.3-7. Results of One-Way Analysis of Variance Among Years for Selected Species of Macrozooplankton at Nearfield Station P2, 1978-1984 and 1987 .i...... ............. 101 3.2.1-1. Distribution Among Weeks and Among Seasonal Assemblages of Samples of Fish Eggs Collected at Nearfield Stations P2 During January 1976 Through December 1987. ... ....... ........ .......... 108 3.2.1-2. Distribution Among Weeks and Among Seasonal Assemblages of Samples of Fish Larvae Collected at Nearfield Stations P2 During January 1976 Through December 1987 .... ..................... ....... .... 115 3.2.1-3. Comparison of Percent Abundance and Percent Frequency of Fish Egg Collections at Nearfield (P2), Farfield (P7), and Discharge (P5) Stations During 1987 ................................ 12.1 3.2.1-4. Comparison of Percent Abundance and Percent Frequency of Larval Fish Species at Nearfield (P2), Farfield (P7)and Discharge (P5) Stations During 1987 .......... ... 122*xvii PAGE 3.2.1-5. Summary of Monthly Flow (Millions of Gallons per day) through the Seabrook Circulating Water System, January-June 1987 ..... ............... 123 3.2.1-6. Ichthyoplankton Sampling Dates at Entrainment (El)and Nearfield (P2) Sampling Stations, January-June 1987.. ...... ... ................................... 125 3 3.2.1-7. Mean Abundance (No./1000m3) of Fish Eggs per Month at Stations El and P2, July 1986-June 1987. *.......... 126 3 3.2.1-8. Mean Abundance (No./1000m of Fish Larvae per Month at Stations. El and P2.. ... ... .. ...... .... .129 F 3.2.1-9. Geometric Mean of Seasons of Peak Abundance (Number per'1000 m ) by Year of Selected Fish Species Larvae-at Station P2 July 1975 through December 1987 ....... ...133 3.2.1-10. Results of One-Way Analysis of Variance amon§ years of log (x+l) Transformed Abundances (No./1000 m ) of Selected. Species During Selected Months, July 1985 Through December 1987 ................................ 134 3.2.2-1. Total Percent Composition by Year and All Years Combined for the Twelve Most Abundant Species in Otter Trawls During 1976 through 1987 at Stations Tl, T2 and T3 Combined ..................................... ...... 145 3.2.2-2. Total Percent Composition by Station of Abundant Species Collected in Otter Trawls, All Years Combined (1976-1987). ...... ................... 148 3.2.2-3. Total Percent Composition by'Year and All Years Combined for the Ten Most Abundant Species in Gill Net Samples During 1976 through 1987 at Stations GI, G2 and G3 Combined .................... 151 3.2.2-4. Total.Percent Composition by Station of Abundant Species Collected in Gill Nets, All Years and Depths Combined (1976-1987),. ..153 3.2.2-5. Total Percent Composition of Dominant Gill Net Species According to Depth (Surface and Off-bottom), All Years Combined (1976-1987).. ............ ... .... ... .* .154 3.2.2-6. Catch Per Unit Effort by Depth for the Dominant Gill Net Species over All Stations and Dates When Surface, Mid-Depth and Bottom Nets were:Sampled, 1980 through 1987 ..................... ... ....... .... .... 156 xviii PAGE 3.2.2-7. Total Percent Composition by Year for the Ten Most Abundant Species Collected in Beach Seines During 1976 through 1987 (excluding 1985 and 1986) at Stations SI, S2 and S3 Combined ..... .... ........... 3.2.2-8. Total Percent. Composition by Station of Abundant Species Collected in Beach-Seines, All Years Combined, April throughNovember (1976-1984., 1987) .' .158 160 3.2.2-9.3.2.2-10.3.2.2-11.3.2.2-12.Annual Geometric Mean CPUE for Selected Finfish Species.Results of One-Way Analysis of Variance Among Years of Log (x+l) Transformed Catch per Unit Effort for Selected Finfish Species for all Gill Net Stations Combined During 1976-1987 ....... .. .............. Results of One-Way Analysis of Variance Among Years of Log (x+i) Transformed Catch-per Unit Effort for Selected Finfish Species at Otter Trawl Station T1, During 1976-1987 .......... ............... ............Results of One-Way Analysis of Variance Among Years of Log (x+l) Transformed Catch per. Unit Effort for Selected Finfish Species for all Beach Seine Stations Combined During 1976-1984 and 1987............ ......... ....3.3.1-1 Annual Mean Temperature (0 C) and Salinity (ppt) at Both High and Low Slack Tide from Brown's River and Hampton Harbor from 1980-1987 .......... .................... 3.3.1-2 Total Precipitation (Water Equivalent in Inches) by Month and Year Taken At Logan International Airport, Boston, MA from January 1978 -December-1987 ......164 165.170 174 187 188 194 198 212 3.3.1-3 Mean Number of Taxa and the Geometric Mean Density (No./m 2) for Each Year and Overall Years With 95%Confidence Limits for Estuarine Stations at Brown's River (3) and Mill Creek (9) Sampled From 1978 Through 1987 (excluding 1985)... .................. ...... .. .3.3.1-4 Results of a paired t-test for Selected Biological Variablaes from. Paired Subtidal (Sta. 3-Sta. 9) and Intertidal (Sta. 3MLW-Sta. 9MWL) Stations Sampled Three Times per Year During 1978-1987 (excluding 1985) ....3.3.2-1 Relative Abundance of Dominant Macroalgae at Marine Benthic Stations in August of the Three Most Recent*Years (1985, 1986 and 1987).. ....... .. ... ....xix PAGE 3.3.2-2 Summary of Spatial Associations Identified From -Numerical Classification (1978-1984) and Verified with Discriminate Analysis (1978-1987) of Benthic Macroalgae Samples Collected in August. ....... ........... 213 3.3.2-3 Probability of 1978-1987 Macroalgae Sample Membership in Each Station Group Identified From Numerical Classi-fication (cluster analysis) of 1978-1987 August Benthic Data ...................... 217 3.3.2-4 Season and Yearly Mean Abundance and Percent Cover of Laminaria Saccharina From Transect Studies in The Shallow Subtidal Zone ......... ............. ............ 224 3.3.2-5 Results of Significance Tests on Macroalgae Selected Species, Chondrus crispus and Laminaria saccharina .. 225 3.3.2-6 Mean Biomass (g/m') and Standard Deviation (SD) of Chondrus crispus at Benthic Stations 17, 35, 1MLW, and 5MLW in August from 1978"to 1987 228 3.3.3-1 Station Groups Defined by Discriminant Analysis of Non-colonial Macrofauna Collected at Intertidal and Subtidal Benthic Stations, August 1978-1987 ....... .... 237 3.3.3-2 Median and Range of Percent Frequencies of the Dominant Fauna at Bare Rock, Fucoid Ledge and Chondrus zone Intertidal Sites at Stations 1 (Outer Sunk Rocks) and 5 (Rye Ledge) Monitored Nondestructively ......... 241 3.3.3-3 Estimated Density (per 1/4 M 2) of Selected Sessile Taxa on Triannual (4 Months' Exposure) Hard-Substrate Bottom Panels. ... ............. 245 3.3.3-4 Annual Mean Density (Per 1/4 M 2) and Standard Deviation of Modiolus modiolus observed at Subtidal Transect Stations, 1980-1987......... ..... ...... ..247 3.3.4-1 Dry Weight (g/Panel) Biomass on Short-Term Surface Fouling Panels by Year, Station and-Month. 252 3.3.4-2 Differences Observed on 1987 Nearfield Short-Term Panels Compared-to Baseline Period (1978-1986), and to Far-field Stations ..... ....... ..... ....... .... 253 3.3.4-3 Dry Weight (g/Panel).Biomass on-Monthly Sequential Surface Fouling Panels by Year, .Station and Month. ...257 3.3.4-4 Laminaria sp. Counts on Monthly Sequential Surface Fouling Panels by Area,. Station, Year and Month.... ... 260 xx PAGE 3.3.5-1 Annual Geometric Mean of the Abundance (No./m 2)of Selected Benthic Species Sampled Triannually in May, August, and November from 1978.through 1987 ............. 262 3.3.5-2 Results of One-Way Analysis of.Variance Among Years for the Log (x+l) Transformed Density (No./m 2) of Selected Benthic Species Sampled from 1978 through 19.87 ......263 3.3.5-3 Annual Mean Length (mm) and the 95% Confidence Interval (CI) for Selected Benthic Species Sampled Triannually in May August, and November at SelectedBenthic Stations from 1982 through 1987; ...* ............. 266 3.3..6-1 Percent Composition of Lobster Larvae Stages at Stations P2,.P5 and P7, 1978-1987.. ...... ......... 275 3-.3.6-2 Summary of Total LobsterCatch Per-Trip Effort, by Month and Year, at the Discharge Site (4) from 1974 through 1987 ............................ .... ...... ..279 3.3.6-3 Results of One-way ANOVA at the Discharge Site for Lobster (ff. americanus), Jonah Crab (C. borealis) and Rock Crab (C. irroratus) ......... ................. ...281 3.3.6-4 Paired t-test Comparisons of the Discharge Site (LI)and the Fairfield Station (L7) for Lobster (ff.americanus), Jonah Crab (C. borealis) and Rock Crab (C. irroratus) ........ ......................... 282 3.3.6-5 Comparisonof Crab Catch Statistics of Jonah Crab (Cancer borealis) and Rock Crab (Cancer irroratus) at the Discharge Site and Rye. Ledge, 1982-1987 ........ 290 3.3.7-1 Average.Catch per Unit Effort, Percent Female, and Percent Gravid Females for Carcinus maenas.Collected at Estuarine Stations from 1977-198-7. ................... 307 3.3.7-2 Estimated Distribution (Percent of Total) of Clam Diggers by Flat at Hampton Harbor, Spring 1980 through Fall 1987......... ........ ... ......... .... 311 3.3.7-3 Summary of Standing Crop Estimates of Adult Mya arenaria in Hampton Harbor, 1967 through 1987...... .314 xxi PAGE 3.3.7-4 Distribution (Percent of.Total Standing Crop) of Harvestable Clams by Flat at Hampton Harbor, 1979.through 1987 .................. ...316 4.1-1 Benthic Station Locations and Descriptions ... ..... .350 4.2-1 Summary of Community Analyses. 357 4.3-1, Analysis of Temporal and Spatial Patterns in Selected Taxa and Parameters-Methods and Data Calculations. ..362 F xxii LIST OF APPENDIX TABLES PAGE 3.2.1-1 Finfish Species Composition by Life Stage and Gear, July 1975-December 1987 ...... ........... ... ..... 179 3.3.1-1 Monthly Seawater Surface Temperature (0 C) and Salinity (ppt) Taken in Brown's River and Hampton Harbor, May 1979 -December 1987 ......... ........ 318 3.3.2-1 Macroalgae Species Recorded in General Collections From Benthic Stations Sampled From 1978 to 1987.(a,be). 319 3.3.2-2 Sparsely Occurring (< 5% frequency of occurrence) Macroalgae Taxa in August Benthic Destructive Samples, 1978-1987 ........ ........... .... ........... 323 3.3.2-3 A. Percent Frequency of Perennial and Annual Macroalgae Species and B. Percent Cover of perennial macroalgae! species per 0.25 m 2 at Fixed Intertidal Non-Destructive Sites.. ..... ....... ...... ......... .... .... .324 3.3.3-1 Species Used in Discriminant Analysis of Benthic Macrofauna .. ...... ........ ............ 329 3.3.4-1 Number (mean per two replicates) of Selected Non-Colonial Species Occurring on Short-term Fouling Panels by Month, Station, and Year .......... ........... ............. 330 3.3.4-2 Percent Frequency Occurrence (mean per two replicates) of Selected Colonial Species Occurring on Short-term Fouling Panels by Month, Station and Year ..... ........ 340 3.3.6-1. Summary of Legal Lobster Catch at the Discharge Site from 1974 through 1987 .. ................ 343 3.3.7-1 Summary of Mya arenaria Population Densities from Annual Fall Surveys in Hampton-Seabrook Harbor, 1971 through 1987 .... .................. 344 xxiii

SUMMARY

1.1 .INTRODUCTION Seabrook Environmental Studies began in 1969 to monitor the balanced indigenous marine communities in preparation for assessing the effects of Seabrook Station operation. As plant operation has not yet begun,.the study is inthe.preoperational or baseline monitoring phase.The purpose of the 1987 Seabrook Baseline Report is. to define the sources and magnitudes of naturally-occurring variability in the physical and biological environment around Seabrook Station.. A previous report (The 1986 Seabrook Baseline Report) summarized information collected through 1986.This report updates those results with one additional year of data.The optimal design of an impact assessment study ensures that a potential impact'is delineated from naturally-occurring variability. The Seabrook Monitoring-Program accomplishes this by (1) collectingdata before.and during operation to provide a '"'temporal control", and by (2) monitoring areas of potential impact as well as areas outside the inf.luence of the thermal plume to provide a !'spatial control". In each biological community, the experimental design of the program focuses on the.most variable aspect.For example, the species distributions of plankton and pelagic .fish change radically from season to season, but are similar throughout the coastal area.The sampling program collected data at least twice monthly to monitor-sea-sonal trends in abundance at a nearfield and farfield area. For benthic macrofauna and macroalgae, seasonality is less of an issue .in comparison to the marked changes in species composition with depth and substrate. "Benthic collections were made in the predominant substrate type, horizontal hard.bottom ledge, along nearfield and farfield transects at regular-depth inter-vals.' The'American lobster, soft-shell clam, and certain fish are of partic-ular concern because of their commercial or recreational importance. Data on all life stages of these species were collected.' The discussion of vari-ability focuses on the source of potential'impact (intake, discharge) and the biological community or physical parameter most likely to be affected.1 I.1.2 INTAKE MONITORING The goal of intake monitoring is to provide information on the number and type of organisms entrained or impinged by the Seabrook Station cooling water system. Zooplankton, ichthyoplankton, and pelagic fish are. the organisms which have the greatest potential for exposure to intake effects.During the study, both thenumber and type of entrainable organisms varied dramatically among seasons. The microzooplankton community shifted from a community predominated by copepods in spring, to one where bivalve larvae were most abundant in summer, to a low-density tintinnid community in fall and winter. Each year was slightly different from the previous depending on the natural thermal regime. Macrozooplankton assemblages were highly predictable from year to year, reflecting the population dynamics of the dominant copepods and the spring and summer reproductive activities of benthic fauna. Seasonal patterns of the bivalve larvae (including mussel and -soft shell clam larvae) and the fish egg and larvae species assemblages were the result of spawning activities of the adults. Species composition reflected the predominance of one or two species which were present during a discrete time period. Fish eggs were most abundant in spring and summer, bivalve larvae in summer and fall, and fish larvae in late winter and summer.Most of the species .that were represented in the zooplankton of the study area'are widely distributed throughout the Gulf of Maine; thus entrainment losses can be replenished by the nearshore populations. Two species with local adult populations contributing to the larval pool, cunner and soft-shell clam, have widespread nearshore larval populations, which lessens the potential for-entrainment impact.Beginning in June 1986,.Seabrook Station operated its cooling water system, although no power or.heated.discharge were produced. As expected, entrainment samples collected in the last half of 1986 and the first half of 1987 had species compositions of fish eggs, fish larvae, and bivalve larvae that were similar to samples collected offshore. Density levels for most of the entrained fish eggs and larvae were lower because the plant intake is not at the depth where ichthyoplankton are most concentrated. Species diversity 2 of ichthyoplankton entrainment samples was lower because of the less sive sampling effort. Density levels of bivalve larvae were similar to those offshore except during peak abundance periods, when entrained densities were lower.Potential intake effects on the pelagic fish community may be apparent from studying'the seasonal and annual movements of the six most abundant.species, which together constitute over 90% of the population. Of these, Atlantic herring is the most important; from September to April, it.makes up from 60-90% of the total gill net catch. The variability in overall catches was directly related to year-to-year variations in Atlantic herring catches. Another important consideration in intake effects is the depth distribution of the pelagic fish. Atlantic menhaden and occasionally Atlantic mackerel were more abundant in the mid-depth area, where intake structures are located, than they were at the surface or at the bottom.These species may potentially be'more susceptible than other pelagic fish to intake effects.* Benthic oriented (demersel) fish also may be affected by the'intakes if (1) they make excursions off the bottom in search of food and/or (2) they perceive the intake structures as protective or food-bearing. habitat. The characteristics of the demersal fish communities in the study.area are discussed below.To evaluate the impact of operation of the Circulating Water System on adult and juvenile pelagic and demersal fish species, impingement samples were obtained and evaluated by Seabrook Station personnel. Monitoring to date has identified that approximately 0.02 fish per million gallons of cooling water flow (1 fish/50 million gallons) will be impinged at Seabrook Station. These studies strongly suggest that the design and operation of the intake structures will protect the balanced indigenous fish population by minimizing the number of individuals entrained within the system and subse-quently impinged upon the travelling screens.3

1.3 DISCHARGE

MONITORING

1.3.1 Discharge

Plume Monitoring As the discharge plume will be concentrated in surface and near-surface waters, impact assessment will focus on parameters and organisms which are located primarily in this zone. Surface water quality, phyto-plankton, and lobster larvae have been monitored primarily for determining potential discharge plume effects. -Water quality parameters have histor-ically shown distinct seasonal patterns that were important in driving biological cycles. Surface and bottom temperatures reached their lowest points from January through March, then steadily.increased from August to October before beginning their fall decline. Dissolved oxygen had a seasonal pattern that was inversely related to temperature, with peak values in late winter and lowest values in fall. Year-to-year differences Were low.Salinity values were fairly stable, but highest in winter and lowest in spring, a result of high runoff. Nutrients had somewhat erratic seasonal cycles, but were generally lowest in summer and highest in fall and-winter. In general, the predictability of seasonal patterns and low year-to-year variability of most of the water quality parameters enhances their suit-ability for impact assessment. The phytoplankton community has shown the most seasonal and annual variability of any of the species assemblages monitored. Species composition. during peak periods varied from year to year. However, total phytoplankton abundanceand chlorophyll a were relatively similar among years and showed a, predictable seasonal cycle. Increases inirradiance typically initiated the spring bloom; densities usually decreased upon the decline in nitrogen-nutrients, coincident with thermocline.development. Densities usually. showed another increase in late-summer or fall. The phytoplankter-Gonyaulax sp.produces paralytic shellfish poisoning, or red tide in this and other coastal areas. This organism usually reached toxic levels (as measured in. Mytilus edul.is meat) in May or June in Hampton Harbor, closing flats to bivalve shellfish fishing for a period of one to seven weeks each year.4 Lobster larvae (Stages I-IV) have a strictly surface orientation. In coastal New Hampshire, successful recruitment of larvae is the single biggest factor in determining the level of adult catches. All stages were rare in the study area, generally occurring from June to October, with highest densities from late June through late August. Evidence suggests that waters off Hampton-Seabrook may be too cold for local production of lobster larvae, and those collected off Hampton-Seabrook actually originate from elsewhere in the Gulf of Maine and from Georges-Bank. Subsurface fouling panels, located three meters below the surface,.placed in the discharge plume area show timing, type, and abundances of settling benthic organisms. Benthic recruitment and community development have shown a seasonal pattern that was highly consistent from year to year.Recruitment and settling activity was low in winter and spring but intensi-fied from summer through fall.The intertidal andj shallow subtidal area near Sunk Rocks is outside the immediate plume area but might be exposed to slight elevations in tem-perature. Species composition of benthic macroalgae and macrofaunal com-munities in the intertidal and shallow subtidal areas changed with depth and substrate, but was highly similar among years. Individual species showed significant variations in recruitment levels from year. to year and among stations. Macrofauna length measurements, however, were a more stable parameter.

1.3.2 Benthic

Monitoring The mid-depth and deep subtidal areas are monitored to determine if, during operation, any discharge-impacts result from increased detritus levels. Year-to-year differences in the macroalgae and macrofaunal immun-ities have been small in comparison to variations with depth and substrate. The species composition was highly predictable and distinct for each depth-zone. Although individual macrofauna species appeared highly variable in 5 their annual abundance levels, these differences were usually not signifi-cant. Length measurements were not as variable as abundances and showed no differences among years.Demersal fish which inhabit or feed in the discharge area-are important because of their predominance in'the food chain as.well as for their commercial value. Six taxa constituted over 80% of-the total otter trawl catch. Long term trends in total catch were evident, as catches in 1980 and 1981 were almost.twice catches during the lowest years, 1977 and 1985. The demersal fish species composition basically changed twice per year, from a winter assemblage, when rainbow smelt were abundant, to an extended summer assemblage (April-November), when hakes and longhorn sculpin were abundant. Other dominants such as yellowtail and winter flounder were present year-round. Most of the fish captured, with the exception of hakes and winter flounder, were juveniles. !Because of its commercial importance, the American lobster was monitored in the discharge area. Seasonal patterns in catches were similar from year to year, and were affected by bottom temperatures, which influenced molting and activity levels. Catches usually increased to a peak in August or September, then declined. Decreases in catches in 1984 and 1985 of legal sized lobsters,. a primary concern to lobstermen, were a result of natural variation in combination with the effects of the change in the legal size limit instituted in 1984 by the State of New Hampshire. Lobsters which would have been of legal size under the old law were protected from harvest until their next molt. The catches of lobster in 1987 were the lowest of any year -during the 1975-1987 study period, showing a low total catch and low propor-.tion Of. the catch that was of legal size.1.3.3 Estuarine Monitoring Although the likelihood of a cooling water system operational impact on the Hampton-Seabrook estuary is low, temperature, salinity, benthos, fish, and the soft-shell clam were all monitored in this area.6 Temperature and salinity both showed~regular seasonal cycles.Maximum temperatures usually occurred in August with minima in January or February. Salinity levels had a less distinct pattern, but were usually lowest in spring, a result of increased runoff, and highest in summer.'Salinity levels in Brown's River were high from 1980-1982, coincident with low precipitation levels and highest discharge volumes of tunnel dewatering. through the Seabrook settling basin. By.1986, salinity levels had returned to pre-1980 levels. The estuarine benthic community-was highly'variable in species composition and abundance, but predominantly composed of surface and subsurface deposit-feeding polychaetes. The number of species, total abundance, and abundance of some of the dominant species increased during the period when salinity levels were higher than average, but have returned to the levels observed prior to the tunnel dewatering discharge. Estuarine fish included anadromous species as well as residents. Alewives and blueback herring pass into the estuary in spring, travelling upriver to spawn. Catch levels were affected by year class strength as well as water temperature and water level, which were influenced by rainfall and resulting runoff. Young-of-the-year and yearling rainbow smelt were occasionally and erratically caught in the estuary, but never constituted a substantial portion of the total catch. The predominant resident species was Atlantic silverside, which made up over two-thirds of the total catch and over 90% during their most abundant period, August through November. Varia-tions in abundance of this species was the single most important factor in year-to-year changes in total catch.The species of greatest concern in the Hampton-Seabrook estuary is the soft-shell clam. Density levels of spat, juveniles, and adults have been monitored in the estuary for 17 years. Densities of harvestable clams depend on a set of complex, interacting conditions. A successful'set of spat is crucial, but this factor alone does not ensurehigh densities of harvestable clams. Once settled, survival of young-of-the-year clams depends on protec-tion from its two main predators, green crabs and humans, as well as from 7 disease. In 1976, a large spatfall throughout the estuary resulted in high densities of harvestable clams in 1980-1982. Increased levels of predation prevented recruitment of the highly successful spatfalls in 1980 and 1981.Light spatfalls from 1982-1986 in combination with an increase in predation accounted for a precipitous decline in standing stock since 1983 and ensure that densities of harvestable clams will remain low for several more years.In addition, neoplasia, a cell growth disease fatal to clams, has been detected from clams in Hampton estuary. This may also be contributing to the decline of harvestable clams.8

2.1 INTRODUCTION

2.1.1 General

Perspective Environmental studies for Seabrook Station began in 1969 and focused on plant design and siting questions.. Once these questions were resolved, a monitoring program was designed which has examined the structure of all the major biological communities as.well as the distribution, abundance, and size of selected species within each community. The goal has-been to assess the temporal (seasonal and yearly) and spatial (nearfield and farfield) variability which has occurred during the baseline period. This report focuses on data collected since 1976 for fisheries studies and since 1978 for plankton and benthos studies as these years have maintained a con-sistent sampling design. -The purpose of this report is twofold: (1) to update results of the preoperational baseline monitoring program, summarized in NAI (1987b)with one additional year of data, and (2) provide a perspective on the sources and magnitude of naturally-occurring variability against which, impact assessment will be made. Variability is important because it is the issue on which sampling design is-focused and can be a major impediment to meaningful impact assessment. Therefore it is discussed first.2.1.2 Sources of Baseline Variability The optimal design of an impact study has four prerequisites that ensure that a potential impact is delineated from any naturally-occurring variability (Green 1979): (1) knowledge of the type, time and place of potential impact; (2) measurement of relevant environmental and biological variables; (3) monitoring before the potential impact occurs to provide a temporal control; (4) monitoring in an area unaffected by impact to serve *as 9 a spatial control. The experimental design of the Seabrook Environmental Program was structured to meet these prerequisites. A basic assumption was that there are two majorsources of-naturally-occurring variability: (1) that which occurs among different areas or stations, i.e., spatial, and (2) that which varies in time, from daily to weekly, monthly or annually. In the experimental design and analysis, we focused on the major source of variability in each community type and then determined the magnitude of variability in each community (Figure 2.1-1). In certain communities, particularly planktonic, where circulation patterns provide a similar habitat throughout the area, spatial variability was low, in comparison to seasonal. The study design therefore focuses on frequent sampling to monitor seasonal trends at only one nearfield and one farfield station. In other communities, particularly benthic, spatial variability has been higher than seasonal variability. Benthic sampling design has focused on the dominant substrate type in the discharge area, horizontal hard-bottom ledge, with paired nearfield and farfield stations representing the major depth zones. Finfish catches have shown both seasonal and spatial dif-ferences. Therefore, these studies make frequent(at least monthly) collec-tions in the area of the discharge as well as farfield areas to the north and south. Because the estuary is an aquatic nursery area and recreationally-important clam flat, baseline collections monitoring seasonal and annual patterns were also made there for operational phase comparison. Biological variability can be measured on two levels: species and community. A speqcis',,abundance, recruitment, size and/or growth are important for understanding operational impact, if any. For this reason, these parameters were monitored for selected species from each community type.. Species were chosen for more intensive study based on their commercial or numerical importance, sensitivity to temperature, potential as a nuisance organism, and habitat preference. Overall community structure, e.g., the number and type of species, total abundance and/or the dominance structure, may also be affected by plant operation in a way not detectable by monitoring .1.Q SOURCES OF VARIABILITY TEMPORAL-,<F.Cr z LU PREOPERATIONAL OPERATIONAL j LEVELS OF VARIABILITY SPECIES ASSEMBLAGE MULTIVARIATE ANALYSIS UNIVARIATE NUMERICAL CLASSIFICATION DISCRIMINANT FUNCTION ANALYSIS TIME SERIES ANOVA.I ANALYSIS Figure 2.1-1. Schematic of sources and levels of variability in Seabrook Environmental Studies.Seabrook Baseline Report, 1987. single species; therefore, the natural variation in-community structure was monitored at regular time intervals, determined by early studiesto be sufficient for this purpose.Appropriate statistical methods must'be used in conjunction with a well-planned experimental design in order to determine the sources and magnitude of variability. Annual and spatial variability in species-abundance and size were tested by using analysis of variance-or nonparametric analysis which will provide a means of evaluating the statistical signifi-cance of changes in the operational period. Spatial, seasonal, and annual variations in communitystructure were assessed first with numerical classi-*fication and then with discriminant analysis. Discriminant analysis provides a set of'criteria using the baseline collections against which operational phase collections may be compared.Identification of the sources and levels of variability utilizing the methods discussed above has its ultimate focus on the sources of poten-tial influence from plant operation, and the sensitivity of a community or parameter to that influence (Table 2.1-1). Naturally, a community or species might be affected by more than one aspect of the cooling water system;however, the focus here is on the aspect of'main concern. In general, intake (pumped) entrainment and impingement would potentially affect mainly plankton communities, including fish eggs and larvae, and pelagic fish. If they occur, thermal effects from the discharge (e.g. plume entrainment) would most likely affect nearshore surface water quality, phytoplankton, and intertidal and shallow subtidal benthos. Although no effects are anticipated in the estuary from the offshore discharge, fish and soft-shell clam populations have been monitored in that area to provide a baseline for operational phase comparisons. Bottom-dwelling organisms, including macrofauna, macroalgae, epibenthic crustaceans, and demersal fish, may be influenced by detritus potentially arising from moribund entrained plankton which is discharged with the cooling water. A previous impact assessment (NAI 1977e) has shown that the balanced indigenous community in the Seabrook study area should not be adversely influenced ,by the above factors. Results from the biological 12 TABLE 2.1-1.

SUMMARY

OF BIOLOGICAL COMMUNITIES AND SPECIES MONITORED FOR EACH POTENTIAL IMPACT TYPE. SEABROOK BASELINE REPORT, 1987.ILEVEL MONITORED SELECTED MONITORING SPECIES/AREA IMPACT TYPE SAMPLE TYPE- COMMUNITY PARAMETERS Intake Entrainment Impingement Thermal Plume Discharge Microzooplankton Macrozooplankton. Fish eggs Fish larvae Soft-shell clam larvae Cancer crab larvae Pelagic fish*Nearshore water quality Phytoplankton Lobster larvae Intertidal/shallow subtidal macroalgae and macrofauna Subsurface fouling community Mid-depth/deep macrofauna and macroalgae Bottom fouling community Demersal fish Lobster adults Cancer crab adults Estuarine temperature Soft-shell clam spat and adults.Estuarine fish x x x x x x x x x x x x x x x x x x x Plume Discharge x x x x x x x x x x Estuary Cumulative Sources x 13 communities, species and environmental parameters sampled will be discussed in light of the feature of the cooling water system which would have the greatest potential for affecting them.14

2.2 INTAKE

AREA MONITORING

2.2.1 Plankton

2.2..1.1 Community Structure An estimation of the number and type of plankton species affected by plant operation will depend on (1) the time of year, and (2) the degree of yearly variability. Results from the community analysis give an indication of the number and type of species present (and thus entrainable) at any particular time of year. These provide a multivariate "template" against which seasonal assemblages during plant operation may be compared. The selected species analysis enables a more precise estimate of the entrainable density for key species by examining their annual and seasonal variability. Knowledge of the within-year and among-year variability, allows for more reliable estimates of impact to.be made than if entrainment samples were taken in a single season and year.All of the planktonic communities had species assemblages that changed with season during the baseline period (Figure 2.2-1). These groups were differentiated primarily on the distribution and abundance of dominant species; however, the relative abundance or even absence of other species was also a factor. The type of species entrained will depend on the seasonal assemblage present at the time. Macrozooplankton assemblages have been distinct and consistent; showing high predictability from year-to-year. Macrozooplankton assemblages reflected mainly the population dynamics of the dominant copepods with reproductive activities of benthic organisms affecting spring and summer species composition. In 1987, each macrozooplankton sample exhibited the same species assemblage that had -been present at that time of year' during the collections in previous years. There .were'some shifts in species composition within those assemblages compared.to the earlier years.Centropages typicus in winter and spring and Calanus finsarchicus in summer both showed reduced importance in the macrozooplankton communities sampled in 1987.15 MICROZOOPLANKTON (No./m 3)MACROZOOPLANKTON (NoJ1000m 3)J F MO FISH EGGS (NoJI 000m 3)S I I I '1 I I I I I I KEY MEAN SEASONAL GROUP)ABUNDANCE-I 0 0 0 0 10-100 101-1,000 I 1,001-10,000 10,001-100,000 I 3 JI F I M I A I M 3 I J I A , 1, S 1 0 1 N 1 0 0 p>FISH LARVAE (NoJ1000m 3.)I t I I t "I I I " I " I> 100,000 4 DATES OF.OCCURRENCE

J F M A ? ' I" I J -I J I I 0 I I -Figure 2.2-1. Historical dates of occurrence and mean abundance (excluding raze taxa)for seasonal groups formed by numerical classification of microzooplankton (No./m , 1978-1984), macrozoopolmkton (No./1000 m , 1978-1 4), fish eggs (No./1000 m , 1976-1984), and fish larvae (No./1000 m ,1976-1984) collections.

Seabrook Baseline Report; 1987..1-6. lMicrozooplankton and planktonic'fish eggs had several overlapping groups in spring and summer, indicative of both'some year-to-year changes in community structure as well as a variable "transition period" in the late summer assemblage (Figure 2.2-1). The microzooplankton community typically shifted from one characterized rotifers in the spring, bivalve larvae in the summer, copepods in the fall, and tintinnids in the winter (NAI 1987b). Fish egg collections in 1987 were generally similar to previous years in their species composition and density. Exceptions in 1987 to the previously observed pattern were (1) absence of the previously important summer cunner-yellowtail flioinder-hake assemblage,'and (2) increased importance of two previously minor assemblages of late summer and fall species. The former was due to reduced abundances of two subdominant species in 1987, Atlantic mackerel and Atlantic whiting. The latter exception may have been influenced by the change in classification method from cluster analysis to discriminant analysis. Although species composition and abundances did not appear to differ substantially from past years, discriminant analysis placed greater emphasis on subdominant species in making group assignments, whereas cluster analysis emphasized the most abundant species.Seasonal assemblages of fish larvae could be divided into four major types based on their dominant taxa: fall-winter (predominated by Atlantic herring), winter-spring (American sand lance), spring (winter flounder, snailfishes, and radiated shanny) and summer-fall (cunner). Varia-tions in density of the major taxa, especially during transition periods, caused small changes in species composition leading to the formation of overlapping "subgroups". Seasonal patterns observed in 1987 were similar to previous years (Figure 2.2-1). There was increased importance in 1987 of a spring sand lance assemblage and a summer cunner assemblage, both charac-terized by low densities. The effects of plant operation will also depend on seasonal vaxia-tions in density. In most months, macrozo~plankton densities have histori-3 cally been over 100,000/1000 m (Figure 2.2-1). The level of entrainment will be fairly consistent, although different species will be involved in each season. Microzooplankton (through 1984) and pianktonic fish egg assem-17 blages (through 1987), on the other hand, had their greatest concentration in the spring and summer, when bivalve larvae and copepod nauplii (microzoo-plankton), and cunner eggs (fish eggs), were dominant, and group densities, were three orders of magnitude higher than in winter (Figure 2'2-'). Simi-larly, fish larvae were most abundant in late winter, when sand lance pre-dominated, and summer, when cunner predominated. The level of entrainment for these assemblages will vary more dramatically between seasons in compari-son to the ma'crozooplankton communities. -All of the dominant taxa typifying ,these planktonic assemblages in the vicinity of the Seabrook Station are widely distributed in the Gulf of Maine in either nearshore regions or open water. Two groups, bivalve larvae and cunner larvae, have local adult populations contributing to the larval' production; however, these species also have widespread nearshore populations which contribute to the total larval pool along this portion of the western Gulf of Maine.Beginning in June 1986, Seabrook Station operated its circulating water cooling system; no power or heated discharge were produced. Initial sampling of entrained fish egg, larvae, and bivalve larvae communities revealed them to be similar to those collected offshore, although the smaller sample volumes and less-frequent sample collection in the plant produced some expected differences. The top-ranked entrained fish egg and larvae species were similar to those from offshore collections (Table 2.2-1); however, the total number of taxa was lower, due to the less-intensive sampling effort.Abundances of most of the dominant species were lower in entrainment samples than in offshore samples, in some cases substantially so. This pattern is.probably a result of the different depths represented by the two types of samples. Seabrook Station's cooling water entrains organisms at a point five meters above the bottom where the total water depth is 17 m, whereas the oblique offshore tows sample the entire water column. The depth distribution of ichthyoplankton is typically uneven,,particularly for'eggs of some".species, which are heavily concentrated near the surface. Entrained bivalve larvae species were similar to those collected offshore; and, unlike the ichthyoplankton, densities were very similar. to those in offshore samples.When samples from the same day were compared, no significant differences in bivalve larvae densities were detected.18 TABLE 2.2-1.COMPARISON OF DENSITIES OF TOP-RANKED FISH EGG, FISH LARVAE, AND BIVALVE LARVAE TAXA COLLECTED OFFSHORE AT STATION P2 AND IN ENTRAINMENT SAMPLES AT SEABROOK STATION FROM JULY 1986 THROUGH JUNE 1987.SEABROOK BASELINE REPORT, 1987.DENSITYc DOMINANT SPECIES ENTRAINED (El) OFFSHORE (P2)a Fish eggs Cunner/yellowtail flounder Atlantic mackerel Rockling/hake Atlantic cod/haddock/witch flounder American plaice Windowpane Hake Pollock Fourbeard rockling 169 107 88.73 55 43 15 12 9 3390 1790 142 102 14 232 539.4 228 Fish larvaea Atlantic herring Seasnail American sand lance Grubby Rock gunnel Winter flounder American plaice b Bivalve larvae Modiolus modiolus Heteranomia squamula Mytilus edulis Mya arenaria 127 23 17 5 5 5 4 110 33 56 2 2 20 5 3480 2520 523 44 3910 2930 646 65 3..N% ./1900 m SNo. /m Average of monthly averages computed to compensate for unequal numbers of samples 19 2.2.1.2 Selected Species Nine species with various lifestages from the pelagic zooplank-ton communities were designated as selected species. The existence of seven to nine years of preoperational data allows an estimation of sea-sonal and annual variability. These species exhibited different degrees of numerical importance; their relative contributions to their respec-tive communities are shown in Figures 2.2-2 and 2.2-3.The zooplankton selected species (including various life-stages) historically have constituted less than 40% of the overall abundances (Figures 2.2-2. and 2.2-3). In both the microzooplankton-and macrozooplankton assemblages, other copepods typically have made a large contribution to overall abundances. In the microzooplankton, unidentified copepod nauplii and copepodites have been extremely abundant. In the macrozooplankton, copepods other than 'the selected species have historically been dominant over the year; however, the noncopepod selected species have been dominants in. certain seasons. All of the zooplankton selected species reached' peak:,abundance in spring and summer, with the exception of Neomysis americana, which has been most abundant in winter/spring. Selected species of fish larvae predominated in every season, constituting 79% of the total abundance overall (Figure 2.2-4). Generally, each of the species was present only for a brief time period that was fairly consistent from year to year. Timing of peaks in abundance in 1987 was consistent with previous years, with only minor variations. Sand lance abundance peaked a month earlier than usual. Atlantic cod, unique among these fish larvae in having two peaks per year rather than one, reached its highest abundance during the winter peak, which is usually secondary to the ,spring-summer peak 20 PEAK SEASON SPEAK MONTHS z 0 2E TEMPORAL VARIABILITY -4 3 "I peak month only ILl U z 4 z C, 0-j*AMONG MONTHS (n=12)o, AMONG YEARS (n.7 or 8)2 f"tt I 0 z 0 0 0 C.)40 30 20 10 0 IMPORTANCE

• MICROZOOR.ANKTON 2 PHYTOPRAUNK'CN E & C 0 0a U 0-~ca 00 C E& EC Uj a C 6 6 U* =66 6 U 0 6 U 0.4i CL &~ '( .C 66 0 6 0C 00.*0 2 0~ 00- 0 CO CL- CL Figure 2.2-2.Percent composition, seasonal vs. annual variability (standard deviation) of log (x+l) abundance, and months of peak abundance for selected species of phytoplankt0o (thousands of cells/liter) and microzooplankton (No./m ), 1978-1987.

Seabrook Baseline Report, 1987.21 0 12 10 8 6 4 2 0 PEAK SEASON.. .. I 1 'U PEAK MONTHS I TEMPORAL VARIABILITY LU 0-j 5-4-3 -{JL{I 0.A AMONG MONTHS (n -12)AMONG YEARS (n = 8 or 10)AMONG WEEKS (n = 26)AMONG WEEKS (n = 18)0 60-2: 0 F-0.0 C.ORQ IMPORTANCE

• MACROZOOPLAI'KTON
• BIVALVE LARVAE 40-20-0--cc 0..2 *..ccU* c~Figure.2.2-3.

Percent composition,, seasonal vs. annual variability (standard deviation) of log (x+l) abundance, and months of peak abundance for lobster larvae (No.ýl000 m ) and selected species of bivilve larvae (No./m ) and macro-zooplankton (No./1000 m ). Seabrook Baseline Report, 1987.22 PEAK SEASON H PEAK MONTHS I-z 0 2-12 10 8 6'4'2 0 TEMPORAL VARIABILITY 3* AMONG MONTHS (n=12)o AMONG YEARS (n=12 or 13)uJ 0 z z 0-j 2~1 T 1 I 0 30 I z 0 0 0~00 U 20 10 IMPORTANCE C-m U a <E , 0-Z C 0 ZC C C S al C-m AU" 0L Figure 2.2-4.Percent composition, seasonal vs. annual variability (standard d~viation) of log (x + 1) abundance (No./1000 m ), and months of peak abundance for selected species of fish larvae, 1975-1987. Seabrook Baseline Report, 1987.23 The plankton selected species showed varying degrees of year-to-year differences in abundance. For the phytoplankton and microzooplankton, among-year and within-year (seasonal) variations were about the same (Figure 2'.2-2). Macrozooplankton, bivalve larvae, and lobster larvae (Figure 2.2-3)and fish larvae (Figure 2.2-4) usually showed higher seasonal variability than among-year variability. Cancer sp. larvae were an exception, with very high variation among *as well as within years. Only. three of the nine selected fish larvae species showed significant differences among years.These analyses indicate the species composition of entrained organisms may be.fairly consistent over the years, although the actual number of organisms entrained could vary widely, particularly among seasons.Bivalve larvae studies were carried out in the intake area to address questions related to the potential reduction in abundances of.Iya arenaria larvae because of entrainment. Local current regimes and length of time spent in the plankton imply that nearshore Mya larvae populations origi-nate from spawning adult populations in local and more southern estuaries, e.g., Hampton-Seabrook, Merrimack River and Essex, Massachusetts (NAI 1982b).Spawning adults have been observed in Hampton Harbor and Plum Island Sound (a farfield site) typically from June through September, but as early as April and as late as the end of October in some years. Although larvae were observed throughout the spawning period, peak densities usually-did not occur until August or September (Figure 2.2-3); secondary peaks also occurred in May, or June in some years. Therefore, the magnitude of entrainment will depend on the time of year as well as the overall annual abundance in that particular year. Initial entrainment samples collected during the period of peak Mya larvae densities were similar in magnitude to those collected Off-shore (Table 2.2-1),. However, because larval densities in the nearshore area have shown no correlation with spat settlement densities (Section 2.3.1.3), entrainment estimates cannot be.used to determine the impact of plant opera-tion on the Hampton Harbor adult clam population. 24 2.2.1.3 Spatial Variability An optimal impact assessment design (Green 1979) has been used for.intake monitoring where comparisons of nearfield and farfield samples in both the preoperational and operational periods will be made. A determination of the similarity of nearfield and farfield plankton communities must be made in order to ascertain the suitability of the farfield station as a "control" area. Previous analyses of the microzooplankton, macrozooplankton, and fish egg and larval communities showed that differences among seasons and even dates within season were greater 'than those between nearfield and farfield stations (Table 2.2-2). Examination of data collected in 1987 supported these results. The communities in all cases were highly similar among stations. At the species level, some spatial differences were detected. In the macrozooplankton, two taxa, Pontogeneia inermis, and Diastylis sp., were more-abundant at the nearfield intake station.. This pattern may be due to a more complex substrate, cobble and sands, at the nearfield station in com-parison to the more uniform sandy bottom at the farfield station. Both taxa are tychoplanktonic and are thus closely associated with the substrate. Spatial differences were also observed between intake (P2) and discharge (P5)stations for those two taxa. No station differences occurred among fish eggs or larvae. Thus, with the exception of two macrozooplankton taxa, the farfield plankton station will provide an effective spatial control when examining post-operational plankton communities for possible impacts of Seabrook Station.2.2.2., Pelagic Fish 2.2.2.1 Temporal By studying the six dominant-species collected in gill nets, which together make up 90% of the population (Figure 2.2-5), any significant effects of plant operations on pelagic fish populations in the study area 25 TABLE 2.2-2.

SUMMARY

OF-NEARFIELD/FARFIELD (P2 VS. P7) SPATIAL DIFFERENCES IN PLANKTON COMMUNITIES AND SELECTED SPECIES. SEABROOK BASELINE REPORT, 1987.COMMUNITY DIFFERENCE BETWEEN P2 AND P7 Microzooplankton Community Selected species Bivalve Larvae Community Selected species None None None None Macrozooplankton Community Selected species Ichthyoplankton Egg Community Selected species Ichthyoplankton Larvae Community Selected species None Tychoplankters (Pontogeneia inermis, Diastylis sp.) P2>P7 None None None None 26 SEASONAL VARIATION M 30-20-10-0 1 1 I 1 I "I I I I I J JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DC-O 0 U)0 0-C.).I-.-z LU ILl" ,CL'100 60-.40 20-0-SAtlantic menhaden O pollock 0 Atlantic mackerel blueback herring Atlantic whiting* Atlantic herring, JAN FE MAR APR MAY JUN JUL AUG SEP COT NOV DEC ANNUAL VARIATION Uj w.30 2o-10-0 I I I I I I I I I I I I 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 z 0 0 0 I--z W C-)LU 100 60-40-20 OL YEAR I] Atlantic menhaden O3 pollock[ Atlantic mackerel* blueback herring A tlantic whiting Atlantic herring I I I7 I I I I I.98 I I I I 1 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 2.2-5. Seasonal and annual changes in composition and abundance of the pelagic fish community, based on catch per unit effort at gill net-stations Gi, G2, and G3 combined, 1976-1987. Seabrook Baseline Report, 1987.27 should be visible. The distribution of pelagic fish varied seasonally; two main seasonal groups of species, summer and winter, were identified from numerical classification results (NAI 1982c). From September to April, Atlantic herring constituted from 64% to 93% of gill net catches, while in summer months (May-August), other migratory species such as Atlantic whitiing (formerly known as silver hake) and Atlantic mackerel predominated (Figure 2.2-5). Pollock (predominantly age-two fish (NAI 1985b)) is a local resident which also made up a greater proportion of the pelagic nearshore community-during summer.In every year, Atlantic herring was the overall dominant pelagic fish in the area; however, it exhibited large annual abundance differences that were reflected in the annual percent composition .(Figure 2.2-5). When catch per unit effort (CPUE).peaked in the study area in 1980, Atlantic herring composed 82% of the total catch. From 1984 through 1987, when total catches were at their:lowest levels since the inception of the study, Atlantic herring constituted only 26-52% of the total catch (Figure 2.2-5).Atlantic herring are known to show high variability in catches spatially as well as seasonally and annually (Bigelow and Schroeder 1953). Most of the fish collected off Hampton-Seabrook were yearlings, particularly in the spring (NAI 1985b). Little is known about the habits of yearling herring, except that they seek out the warm waters of embayments in spring (Bigelow and Schroeder 1953).Inconsistency in seasonal patterns adds to the overall variability in pelagic fish distribution. Each of the selected species had its peak abundance during a short but distinct period of time (Figures.2.2-5 and 2.2-6). However, these seasonal fluctuations were variable among years, compounding the high annual variability, as evidenced by high coefficients of variation (approximately 150-250% for the three.selected species). This was particularly important for Atlantic herring,iwhose abundance was the single biggest determinant of overall catch levels (Figure 2.2-5). The number of individuals that will be impinged by the plant intake would therefore be expected to vary substantially among seasons and, to a lesser extent, among 28 PEAK SEASON S PEAK MONT.H.S'z I-0 2E TEMPORAL VARIABILITY " 3 0 AMONG MONTHS (n = 12, except n = 8for Atlantic silerside) o AMONG YEARS (n = 12, except n = 10 for Atlantic silverside) z z M 0-1 2 1 p 0 z 0 0 0.0 C., 80-60-40-20-0-IMPORTANCE 0 U U DEMERSAL SPECIES (TRAWLS)ESTUARINE SPECIES (SEINES)PELAGIC SPECIES (GILL NETS)H C-.4 E*m--- r--- r -iI 0z-0 3US.C, a a. 0 a 0.C6 0~~~1~~E U 3 0.0 C 0 Figure 2.2-6.Percent composition, seasonal vs. annual variability (standard deviation) of log (x+l) abundance (catch per unit effort), and months of peak abundance for selected species of fish, 1976-1987. Seabrook Baseline'Report, 1987.29 years. Because of this high variability of pelagic fish abundances, predict-ing abundances with high statistical precision would be difficult. Since the Circulating Water System began operation in' 1981, fish entrained within the system and subsequently impinged upon the travelling screens have been collected by Seabrook Station personnel to determine operational impact. During a five-month period in 1985, 970 individuals, representing 32 species, were collected from the Circulating Water System.These were dominated by grubby (Myoxocephalus aenaeus, 21%), snailfishes (Liparis sp., '21%), and longhorn sculpin (Myoxocephalus octodecemspinsus,' 11%). During a seven-month period of Station operation in 1986, 1212 individ-uals representing 35 species were collected. These were dominated by grubby (21%), windowpane (Scophthalmus aquosus, 12%), and longhorn sculpin (9%).Intermittent operation of the Circulating Water System during 19.87 resulted in a total of 502 individuals representing 21 species becoming impinged upon the travelling screens'. Of these, longhorn sculpin, winter flounder.(Pseudopleuronectes americanus), and windowpane made up 22%, 14%, and 13%, respectively, of those impinged. Operation of the Circulating Water System, in terms of both the number of pumps and whether the system operated at all, varied throughout the three-year period. Data obiained during full system operation will be reviewed along with these data to determine operational impacts on demersal and pelagic fish species.2.2.2.2 Spatial Areal differences will be less important than temporal differences in evaluating potential plant effects on pelagic fishes. Because'of their high degree of mobility, pelagic fish were not observed to be associated with any one habitat. As expected, relative abundances of the five most abundant taxa were very similar among stations, although catches were approximately 25% lower at the southern station GI (NAI 1987b). Differences in the verti-cal distribution of these species may be important, however, because the intake structures are located at mid-depth, 5 m above bottom in 17 m of 30 water. Only one of the eight most abundant species, Atlantic menhaden, was, more abundant at the intake (mid-water.) depth during the months sampled than at surface or bottom (Table 2.2-3).. However, this species was only slightly more abundant at mid-depth, and it only accounted for 2% of the pelagic fish in the study area. Two taxa, Atlantic whiting and pollock, were most abundant near the bottom, while Atlantic herring, mackerel and blueback herring were most abundant on the-surface (Table 2.2-3). These species may be less vulnerable to intake effects. In 1986, for the first time since 1980, Atlantic mackerel had highest catches in mid-depth nets (NAi 1987b), suggesting that they could occasionally be more prone to intake effects.These results indicated that *the most abundant and frequently-occurring pelagic species did not show a preference for mid-depth distribution, verifying earlier results and the rationale for mid-water placement of the intakes (NAI 1975a).31 f, TABLE 2.2-3. CATCH PER UNIT EFFORT a BY DEPTH FOR THE DOMINANT GILL NET SPECIES OVER ALL STATIONS AND DATES WHEN SURFACE, MID-DEPTH AND BOTTOM NETS WERE SAMPLED, 1980 THROUGH 1987. SEABROOK BASELINE REPORT, 1987,.CATCH PER UNIT EFFORT SPECIES SURFACE MID-DEPTH BOTTOM Atlantic herring. 6.3 3.5 2.3 Atlantic whiting 0.2 0.6 0.8 Atlantic mackerel 0.9. 0.4 0.4 Pollock 0.2 0.1 1.1 Alewife <0.1 <0.1 <0.1 Blueback herring 1.1 0.4 0.3 Atlantic menhaden 0.6 0.7 0.2 Rainbow smelt <0.1 <0.1 0.1 anUmberPer one 24-hour set of one net (surface, mid-depth or bottom)32

2.3 DISCHARGE

AREA MONITORING

2.3.1 Plume

Studies 2.3.1.1 Discharge Plume Zone Because the discharge plume's largest exposure will be to surface and near-surface waters, the primary focus in this section willbe on param-eters or organisms in this part of the water column, namely phytoplankton, lobster larvae, and nearfield water quality parameters. Other organisms, such as pelagic fish and ichthyoplankton will, of course, have some exposure to the discharge plume, but it is assumed that entrainment and/or impingement are the more important issues for these organisms. The water quality parameters measured showed distinct seasonal patterns that were important in driving biological cycles. Surface and bottom temperatures reached their lowest points from January through March, then steadily increased from April to August; temperatures were generally highest from August to October before beginning their fall decline (Figures 2.3-1 and 2.3-2). Surface temperatures had a more exaggerated seasonal cycle in comparison to bottom temperatures, with higher spring and summer tempera-tures. Temperatures in 1987 were average at the surface and below average at the bottom. Surface temperatures peaked in July in 1987; historically they have typically peaked in August (Figure 2.3-2).Surface dissolved oxygen had a seasonal pattern inversely related to temperature, with peak values in late winter and lowest values in fall (Figures 2.3-1 and 2.3-2). In 1987, seasonal patterns were similar to previous years, though November values were somewhat higher than the average.Surface salinity values were highest in winter and lowest in spring, a result of increased runoff. In 1987, salinities were generally lower than the average, particularly in April (Figure 2.3-2) as a result of high precipita-tion during, that month (see Section 3.3.1).33 .PEAK SEASON E PEAK MONTHS I-z.0 2-CD TEMPORAL VARIABILITY ,LU ,-I 20-i5 5-I 4 m AMONG MONTHS (n = 12)o AMONGYEARS(n=7to10) in 1 I 1i sO so H- ý j.ý0.5 a*0'a U a 0 U U a-a 0.0.C;E-o 0.CL A0 t0 0 E.gE X.0.0 0..0=6.0 X 0.CL0.0-+/-a ca or-U c.Figure.2.3-1. Seasonal vs. annual variability (standard deviation) and months of peak values for temperature (*C), salinity (ppt), dissolved oxygen (mg/l), and nutrients (gg/l).Seabrook Baseline Report, 1987. (For salinity, total phosphorus, nitrate, and ammonia values, multiply by 10.)34 Surface Temperature w w 20.-15-10-5-I-15-10-5-Bottom Temperature -- OVERALL MEAN....... 1987-OVERALL MEAN....... 1987 0-I I II I .........I 0 I 1 I I I I N I I *-E JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV CM MONTH I a I I .I .I I IA I a l JAN FEB MAR APR MAY JJUN JUL AUG SEP OCT NOV DEI MONTH Surface Dissolved Oxygen 34 -Surface Salinity 0 z',-0'I-CL a--U-I--r4 a-32 30 28 26 cc UJ F--Lu M (M-J-I 12-11 10-9--ALL YEARS MEAN-- -- 1987-ALL YEARS' MEAN......* 1987 24 8 I I I I I I I I I I I I ~JAN FEB MAR APR MAY JUN JUL AUG SEP OC NOV CM MONTH 0 ý 1 9 # I I I 1 9 9 1 .I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV CEM MONTH Figure 2.3-2. Monthly mean surface and bottom temperature (9C), surface salinity (ppt), and surface dissolved oxygen (mg/i) at station P2 for each year and over all years.(1978-1987, except temperature, 1978-1984 and August 1986-December 1987).Seabrook Baseline Report, 1987. Nitrogen and phosphorus nutrients had more erratic cycles than temperature, salinity, and dissolved oxygen, but generally had lowest levels in summer and highest in fall and winter (Figure 2.3-1).* Values in 1987 followed thepatterns observed 'in previous years except'for unusually high orthophosphate levels in June' and July, high levels of total phosphorus in September and October, and low levels (below detection limit) of'nitrite in March through June.The predictability of seasonal patterns 'and low year-to-year-variability of most of the water quality parameters (Figure 2.3-1) enhanced their suitability for impact assessment. Furthermore, they will provide information which can assist 'in separating natural biological variability from impact.The phytoplankton community has shown the most seasonal and annual variability of any species assemblage. Seasonal assemblages have changed rapidly and frequently, diminishing.the suitability of the community for short-term impact assessment (NAI 1985b). Some elements' of the phytoplankton community were relatively stable and predictable. For example, total phyto-plankton abundance was generally similar among years, with a predictable seasonal cycle that was closely tracked by biomass (chlorophyll a). Increases in irradiance typically initiated the spring bloom, and although the species composition varied 'from year-to-year, centric diatoms typically were among the first to appear. Densities usually diminished when nitrogen-nutrients declined and the thermocline developed. Thermal stratification prevents the replenishment of nutrients from deeper waters thereby limiting growth of spring dominants.* 1986 was unusual in that there was an uncharacteristic July peak caused by bluegreens and Leptocylindricus. Phytoplankton assem-blages from 1978 to 1980 were similar, based on the predominance of Skeletonema costatum, Rhizosolenia delicatula, and Phaeocystis pouchetti, while from 1981 through 1984, only Skeletonema costatum and .Chaetoceros spp.were consistent dominants. In the latter half of 1986, Skeletonerma continued to predominate,'along with the above-mentioned bluegreens. No phytoplankton collections were made in 1987; detailed results from previous studies are presented in NAI 1985b and 1987b.36 No spatial differences were observed in the.phytoplankton community either between intake (P2),and farfield (P7) areas or between intake (P2) and discharge,(P5) areas (NAI 1985b, 1987b)'.Skeletonema costatum was chosen as the selected phytoplankton species because. of its consistent predominance. Generally, there was a major peak in late summer or fall (Figure 2.2-2) and in some years there was aisq.Q.a smaller peak in the spring (NAI 1981f, 1982a) or winter (NAI 1980c, 1983a).Despite highly-variable peak abundances, no significant differences were detected among years (NAI 1987b). Furthermore, intake and dischargoY densities were statistically similar (NAI 1987b). Simultaneous nearfield/farfield comparisons of total phytoplankton abundances and Skeletonema costatum may be the most consistent parameters for monitoring primary..producers in the discharge plume area.Paralytic shellfish poisoning (PSP) levels in Mytilus edulis, as measured by the State of New Hampshire and Massachusetts Department of Public Health, has exceeded maximum levels allowable for human consumption every year from 1972 through 1986, usually for a period of 1-7 weeks (NAI 1987b).In 1987, however, PSP toxicity levels in Hampton Harbor mussels were below the detection limit throughout the April-December monitoring season (NAI 1988). In 1972, toxic levels were present in Hampton Harborfor a period of 16 weeks. Although Hampton Harbor flats have been closed each summer since 1976 to soft-shell clam diggers for conservation reasons, high PSP levels caused the closure of the harbor to all bivalve shellfish digging for several weeks each summer as well. Peak values in most years occurred in May or June, coinciding in Hampton Harbor and .the farfield area, Essex, MA. The maximum value recorded since 1972 was 8398 pg PSP per 100 g meat.Of the shellfish in the area with planktonic lifestages (Cancer crabs, lobster, and soft-shell clam larvae), only lobster larvae Stages I-IV have strictly a surface orientation, typically found in the top few centi-meters of water. The seasonality and variability of Cancer sp. larvae and Mya arenaria larvae were discussed in the intake area monitoring section.Successful recruitment of lobster larvae is the biggestfactor in the deter-37 .mining the level of adult lobster catches *(Harding et al. 1983). Lobster, larvae collected off Hampton-Seabrook'actually originate from warm waters in the Gulf of Maine and Georges Bank (Harding et al. 1983) and are driven into the area by a combination of winds and nontidal currents (Grabe et al.1983). Temperatures in the study area are not warm enough to allow plank-tonic development (Harding et al. 1983), reinforcing the fact that this area is probably not important in the production of lobster larvae. Lobster.larvae, which were rare throughout the study area, have typically been recorded from the first week in June to the second week in October (Figure 2.2-3).- In 1987, lobster larvae first appeared in early June, somewhat earlier than previous years. Maximum densities have. occurred overan eight-week period between late June and late August, during the period of maximum surface temperatures. Densities of all life stages were very low, averaging<2 per 1000 square meters (Figure 2.2-3). In. 1987 densities were somewhat 10w in comparison to previous years. Stage I and IV larvae have predom-inated, and stage II and IIl were extremely rare. Densities at the farfield station (P7) were consistently higher than at the nearfield station from 1982-1987. Discharge area (P5) densities in the last half of 1986 were intermediate between the nearfield and farfield areas.(NAI 1987b).Subsurface (-3 m) "fouling" panels placed in the projected inner and outer discharge plume area and at farfield areas, show the types, timing and abundances of shallow subtidal organisms which can settle on bare sub-strates. Short-term panels, exposed for one month, estimate recruitment levelswhile monthly sequential panels, exposed for 1-12 months (Figure 2.3-3), show the development of the fouling community. Biomass, density, and number of species showed patterns that were highly consistent from'year-to-year and between nearfield and farfield areas, reflecting the increase in settling activity in summer and fall. The individual macroinvertebrate taxa also had a predictable seasonal pattern. Only a few showed heavy recruitment before June (Balanus sp. in April and Hiatella sp. in early summer). In 1987, the overall patterns were similar to previous years, although-biomass on September short-term panels was much higher than in most past years.Surface panels should prove to be an effective monitoring tool for benthic settlement activity, particularly when compared to farfield stations.38 STATION 4 J F M A M J J A S 0 N D STATION 19 ,J F N A M J J A S 0 N D Mlytilidae 1982 .. -..1983 ...... .1984 .198 ....1986 a 1987 Hiatella sp. 1982 -. ............... 1983 ..... ............

• S 1984 .- ............." e.....1987 -*... .........-...

Jassa falcata 1982 J........1983 .-- .- ..----1984 a 1986-1987 Hudibranchia 1982 ............... 1983 ...................... 1986 ........1987 Tubularia sp. 1982 1983 ......1984 .......1986 a ..,....1987 Obelia sp. 1982 1983 -J... .........1984 ..... ...1 9 8 6 a ............ 1987 .." ..Balanus sp. 1982 ... ......... ...1983 ..1984 ....... .......1 9 86a ................ 1987 "" ,17 ...... M EII1 Nereis sp. 1982 ... ....1983 .................. 1984 .1986a 1987 ...... ;............... Polynoidae 1982 al ....1983 1984 1986 ................ 1987 Mytilidae 1982 ...... ......m 1983 ...... ..1983 1984 -...________1986 a 1987'n ......L Hiatella sp. 1982 1983 1984 1987 Jassa falcata 1982 1983 1984 1987................... ............ .......... M .-M, S ... ............ .. .............. .......m ( Nudiibrancr Tubularia Obltla sp Balanus s Hereis sp PolynoJda hia ...... U ...1...1983 ..........-..... 1984 ... -.... ....1987a s. 19872........ .e p. 1982 1983 .......1984 ...... .1987a .........1982 ......1983 N..- ...F 1983 ...... .........1984 --......... ....1986a a-- ..-.1987 --Km- --"'.11 ......p. 19.82........ .. ...1983...... 1984 .........1986a ... li ............ 1987 am ...... I M mi Mrrill 19i 2 ............... '1982 1986a .......... .1987 ................... e 1982 ...... ............... 1983 ......1984 ................ 1................ 1987 I present ... 1-25Z freqiency jJW 26-75 3 76-100 aNo fouling panelsplaced or collected from January 1985 through June 1986.Figure 2.3-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19. Seabrook Baseline Report, 1987.39 2.3.1.2 Intertidal/Shallow Subtidal Zone An area outside of the immediate surface plume area'that is being monitored for potential plume effects is Sunk Rocks.. Intertidal (MSL and MLW) and shallow subtidal (74.6 m) stations which are representative Of the.area were monitored on Outer Sunk Rocks (nearfield) and at Rye Ledge (farfield). Benthic algae and macroinvertebrate collections taken annually (August) at Stations 1MLW and 5MLW (intertidal) and Stations 17 and 35 (shallow siubtidal) exhibited species assemblages that were consistent and highly similar from year to year at each station (Figure 2.3-4). Each annual collection at a station was grouped (by discriminant analysis) with the majority of those collected in other years at-the same station (Sections 3.3.2 and 3.3.3)-. In 1987, macrofaunal and macroalgal collections were similar to those in previous years (the same species assemblages that were present at each station in previous years were found in 1987). The assemblages identified by this analysis were strongly related to the depths of the stations, particularly: for the algae, which exhibited a noticeable difference among depths in which species dominated the algal community (Figure 2.3-5).Colonial macrofaunal assemblages were somewhat less predictable from year-to-year (NAT 1985b). Intertidal colonial assemblages were distinct in their species composition, but those from shallow subtidal areas in most years were similar to those from mid-depth areas. In several years, assem-blages of colonial macrofaunal species were unique and unrelated to any other assemblages. Fourteen benthic species were selected for more intensive moni-toring becLuse of theirtrophic position, abundance and commercial or recreational value (Table 2.3-1). Parameters monitored included abund-ance (all taxa), size (fauna only), and reproduction (epibenthic crusta-ceans). All life stages of the commercially-important species were'studied. Some of these taxa were monitored in-the Sunk Rocks area while others wer examined as part of the discharge or estuarine studies.40 (n LU-j LL~0 LUI Z 25 20 15 10 5 0 DEPTH OCCURANCE O INTERTIDAL (STA. 1MLW, 5MLW)E SHALLOW (STA. 17,35)* MID-DEPTH (STA. 16, 19,31)* DEEP (STA. 13,4,34)5 4 3 ALGAE SPECIES ASSEMBLAGE 2 I At 0 LU-J 0.U.0 LU z 1400-1200-1000-800-600-400-200-0-ABUNDANCE 2 1 5 4 3.ALGAE SPECIES ASSEMBLAGE 25 20 15 10 5 0 DEPTH OCCURANCE 13 0 El U]U INTERTIDAL (SI". 1MLW, 5MLW)SHALLOW (STA. 17,35)MID-DEPTH (STA. 16, 19, 31)DEEP (STA. 13,4.34)I 5 3 1 2 BENTHIC SPECIES ASSEMBLAGE .'4 1000 100 ABUNDANCE>-Z LU 0 10 II I 6 Figure 2.13-4.5 3 1 -2 BENTHIC SPECIES ASSEMBLAGE. Depth and abundance characterizations of species assemblages identified by discriminant analysis of August collections of algae (g/m 2 of dominant taxa)-and marine benthos (thousands per m 2 of dominant taxa) during 1978-1987. Seabrook Baseline Report, 1987.41 100 -Li--'I.'I---, i--i~di -J~,i --~80-60 z 0 0.0 z w w IL..% %,I---I-I I / s I-,s---I--I--, ---% * , ,---I------I i-I,'-ss 1 II% .%* 'o Other Taxa E' Ptilota serrata E3 Phyllophora spp.[ Corallina officinalis Phycodrys rubens* Chondrus crispus* Mastocarpus stellatus 40 -4 20 MLW 4.6 9.6 11.6 18.3 19.7 MEAN DEPTH (m)Figure 2.3-5.Percent composition (based on biomass) by depth strata for dominant macroalgae species at marine benthic'stations in August, 1978-1987. Seabrook Baseline Report, 1987.42 TABLE 2.3-1. SELECTED BENTHIC SPECIES AND RATIONALE FOR SELECTION. SEABROOK BASELINE REPORT, 1987.SPECIES (COMMON'NAME) LIFESTAGEa RATIONALE Macroalgae Laminaria saccharina (kelp)Chondrus crispus (Irish moss)Benthic Invertebrates Ampithoe rubricata (amphipod) -Jassa falcata (amphipod) Pontogeneia inermis (amphipod) Nucella lapillus.(dog welk)Asteriidae (starfish) Strongylocentrotus droebrachiensis (green sea urchin)Dominant Bivalves Mytilus edulis (blue 'mussel)Mya arenaria (soft-shell clam)Epibenthic Crustaceans Carcinus maenas (green crab)Cancer borealis (Jonah crab)Cancer irroratus (rock crab)ifomarus americanus (American lobster)A A J,A J,A J,A J,A J J, A L,S,A L,S,A L, A L,J,A L,J,A L,J,A Habitat (canopy)-forming primary producer Habitat (understory)-forming primary producer; sporelings may be heat sensitive Intertidal/shallow subtidal community dominant Intertidal/shallow subtidal community dominant Subtidal, ubiquitous community dominant A major intertidal-predator of Mytilus edulis Predator, community dominant Potentially destructive herbivore Habitat former; spat may be heat*sensitive Recreational estuarine species;larvae entrainable A major predator of soft-shell clam spat Important predator and prey Important predator and prey Commercial species; larvae plume.entrainable aA = adult; J = Juvenile; L = Larvae; S =-Spat*43 Algal selected species had highly consistent biomass or abundance levels among years, with differences between nearfield and farfield stations observed in the shallow subtidal but not the intertidal. The algal dominant Chondrus crispus had low annual variability, with no significant differences in biomass among years from 1982-1987 in the intertidal zone and 1978-1987 in the shallow subtidal zone (Table 2.3-2). Intertidal biomass values of Chondrus were significantly'different between nearfield and farfield areas in both the intertidal zone and the shallow subtidal zone (Figure 2.3-6, Table 2.3-2). Densities of the dominant kelp, Laminaria saccharina showed no differences among years or between nearfield/farfield stations in the shallow subtidal (Figure 2.3-6, Table 2.3-2).Spatial heterogeneity and variations in recruitment success caused a high degree of variability in abundance of macrofaunal taxa (Figure 2.3-6).Significant differences in annual abundance were found among years for most of the taxa, and nearfield and farfield stations were almost always signifi-cantly different (Table 2.3-2). For these species, impact assessment will be most effective when the preoperational period is compared to the operational period within a given station. Few differences in the historically-observed trends were noted in 1987. The amphipod Ampithoe rubricata, once one of the intertidal dominants, continued its steady decline in abundance first noticed in 1982; in 1987, no A. rubricata were collected at either intertidal station (lMLW or 5MLW). Abundances of other taxa were within the range of previous years.Length measurements of macroinvertebrates were a more stable and'predictable parameter. In most cases, annual mean lengths were statistically similar among years and between stations. Specimens of the. gastropod Nucella lapillus were unusually large compared to previous years at the nearfield station (lMLW), but they were smaller than usual at the farfield'station (5MLW). Sea stars (Asteriidae) were smaller in 1987 than in any of-the previous five years when measurements were recorded, indicating successful recruitment of young-of-the-year. 44 TABLE 2.3-2.

SUMMARY

OF SIMILARITIESa IN ABUNDANCE, BIOMASS, FREQUENCY, OR LENGTH AMONG YEARS AND BETWEEN STATIONS, FOR SELECTED MACROFAUNAL.AND MACROALGAL SPECIES AT INTERTIDAL AND SHALLOW SUBTIDAL DEPTHS. SEABROOK BASELINE REPORT, 1987.AMONG YEARS NEARFIELD VS.FARFIELD SIMILAR DISSIMILAR Similar Nucella lapillus (L) Ampithoe rubricata(L) Jassa falcata (shallow Mytilidae (shallow sub-subtidal, panels) (L) tidal panels) (A)Mytilidae (MLW, shallow Mytilidae (panels)(L) tidal)(L)Laminaria saccharina (A) -Jassa falcata (panels) (A)Dissimilar Asteriidae (L) Jassa falcata (shallow subtidal) (A)Chondrus crispus (B) Ampithoe rubricata (A), (MLW, shallow subtidal)Nucella lapillus (A)Asteriidae (A)Mytilidae (MLW) (A)aResults from ANOVAs, paired t-tests, or Wilcoxon's summed ranks tests.(A) = abundance (L) = length (B) = biomass 45 TEMPORAL AND SPATIAL VARIABILITY m AMONG YEARS, NEARFIELD (n = 10 except n = 9 for Laminaria, and n = 7 for Asterifidae) 6 5 4 o AMONG YEARS, FARFIELD (n = 6)U.0 z z 0 0-.1 31j J1 0 1ý1. 'F 2 1 0 z.0 0 I-i 0 80-60 20-Shallow subtidal Intertidal IMPORTANCE N/A N/A N/A 0"1 1 1 a a- a.u a..... ---- .!Z *: a~-- -o.o~ ~= .~~. -o o o .~ --~a' a~o 0 Ea.3-J U-a.0 ~~* a-a-U 0.- -ma .0-*0 U--a U-S z -*n.2 a*0 a C U* -.~. *.~ a a a ~a--0 o :2 ~.2 U a a.Figure-2.3-6. Percent composition and nearfield (Sta. lMLW & 17) vs.farfield (Sta. 5MLW& 35) annual variability (standard deviation) of log-(x+l) abundance for selected intertidal and shallow subtidal species of algae and benthos.Seabrook Baseline Report, 1987. Abundance is No./m 2 except for Chondrus, which is g/m 2.46 2.3.1.3 Estuarine Zone Environmental studies in Hampton Harbor estuary include monitoring physical parameters (temperature and. salinity), fish populations, benthic macrofauna, and juvenile and adult soft-shell clams (Mya arenaria). One of.the main environmental issues in the Hampton-Seabrook estuary related to plant operation is whether the offshore intake and discharge will impact the adult clam population in HamptoniHarbor. The probability of impact from the most-likely source, entrainment of Mya larvae, is small (NAI 1977e); this is discussed in Section 2.2.2. Natural variability of juvenile and adult Mya arenaria will be discussed in this section.Temperature and salinity, monitored in Hampton Harbor and Brown's River since 1978, provide valuable information for interpreting biological phenomena. Maximum temperatures usually occurred in August, with minima in January or February (Figure 2.3-7); 1987 was-no exception to this pattern.Salinity levels had a less distinct seasonal cycle than temperatures, but were usually lowest in spring, coincident with increased runoff.. This was particularly true in April of 1987, when heavy rainfall, in addition to melting snow, caused severe flooding in New Hampshire .and Maine. In Brown's River, average annual salinity values remained high for a three-year period from 1980-1982, coinciding with low precipitation and highest discharge Volumes from the settling basin. This was the period when the maximum dewatering of the cooling tunnels took place, and the salinity of the settling pond's discharge water was relatively high. Salinity levels dropped, with fewer fluctuations, from 1983-1987, when discharge volumes decreased and precipitation returned to pre-1980 levels. Hampton Harbor salinities, which were not as susceptible to these influences because of the influx of a large volume of offshore waters, showed higher salinity and lower year-to-year variability than Brown's River.The benthic macrofaunal community in Mill Creek (Station 9) and Brown's River (Station 3) was typical of New England estuaries. The species composition was also consistent with that from other estuaries on the East Coast (McCall 1977; Watling 1975; Santos and Simon 1980; Whitlatch 1977).47 LU IL 25 20 15 10 5 0 1~Temperature MONTH a-I.-.z-J 25-20-15-10-Salinity-OVERALL MEAN 1987 5 0 I I I 1 I JAN FEB MAR APR MAY I I I .I I I i JUN JUL AUG SEP OCT NOV DM MONTH Figure 2.3-7.Mean monthly seawater surface temperature and salinity with 95% confidence limits taken at 1 ow tide in Brown's River (Sta. 3) in 1987 and over the entire study period (May 1979 -December 1987). Seabrook Baseline Report, 1987.48 Surface and subsurface deposit feeders predominated, including opportunistic polychaetes such as Streblosplo benedicti and Capitella capitata, with suspension feeders and omnivores forming an important component (NAI 1985b)..The most numerous species inhabiting estuaries are those which are resistant and resilient to the natural changes in the physical environment, such as fluctuating temperature, salinity, dissolved oxygen, and sediment grain size.In Mill*Creek.and Brown's River, the biological parameters measured were highly variable seasonally and annually which is typical of this physically heterogeneous'habitat; total density, numbers of taxa, and all of the dominant species tested showed significant differences among years and between stations. Some of this variability was related to changes in salin-ity. The combination of lower precipitation and higher levels of discharge from the settling basin from 1980 to 1982 apparently caused'higher and less-variable salinities in Brown's River. At the same time, total abundance and number of taxa increased (Figure 2.3-8), along with densities of Streblospio benedicti and Capitella capitata at that site. Higher salinity levels probably enhanced the habitat for more stenohaline species, and at the same time, opportunistic polychaetes invaded the changing habitat. Following an increase in precipitation and decrease in discharge volumes, these param-eters dropped to their lowest point in 1984; however, they had returned to pre-1980 levels by-1987.Important estuarine fish include both diadromous species as well as residents. Three anadromous fish pass into the estuary: rainbow smelt in winter and alewives and blueback herring ("river herring") in spring, travelling to upper reaches of local rivers to spawn. Rainbow smelt were caught at the entrance to. the estuary (Station T2) from December through March or April (see adult fish section 3.2.2). Abundances were significantly different among years, causing moderate baseline variability, making the detection of minor population changes unlikely. In spring and summer, sparse and erratic numbers of young-of-the-year and yearling smelt have been caught in beach seines (Figure 2.3-9), but no one age group (based on length-frequency) has been consistently dominant (NAI 1985b). Rainbow smelt have 49 ESTUARINE BENTHOS 10000-8000-6000-4000--50-40-30 I-z ra 0 x I-J, M z-20-10 2000-0--DB'JNfY NUMBER OFTAXA 0 1978 1979 1980 1981 1982 1983 I a .a 1984 1986, 1987 YEAR SALINITY 32-30-I-" 0., 0.28-26-no data 44 a a I I I 1978 1979 1980 I I I I 1981 1982 1983 1984 1986 1987 YEAR Figure 2.3-8. Annual geometric mean density (No./m 2 ) and mean number of taxa per station of estuarine benthos, and annual mean salinity, at Browns River and Hampton Harbor. Seabrook Baseline Report, 1987. No data were collected in 1985.50 400 -200 CL 0~SEASONAL VARIATION 0........ 0 ..APR M ' J A I APR MAY UUN JUL AUJG SEP OCT i NOV Z 0 U)0 0C 0 C.)z LU IL a-100-80-60-40"-20 1 M 03 U3 winter flounder Atlantic herring rainbow smeft pollock Fundulus sp.Atlantic silverside APR MAY JUN JUL AUG SEP OCT NOVi UJ 0.0 400-200-ANNUAL VARIATION n.1 z 0 C,)0 0 I-z.U C.Lu 100.80'60'40'20-0-j I I I a 1 1976 1977 1978 1979 1980 1981 YEAR I 1 1982 1983 1 I 1984 1987 0 in winter flounder Atlantic herring rainbow smelt pollock Fundulus sp.Atlantic silverside I .I ..I ..I I I .o 1976 1977 1978 1979 1980 1981 1982 1983 1984 1987 YEAR Figure 2.3-9.Seasonal and annual changes in composition and abundance of the estuarine fish community, based on catch per unit effort at beach seine stations SI, S2 and S3 combined 1976-1984 and 1987. Seabrook Baseline Report, 1987.51 never comprised a substantial portion of annual seine catches, and over all years (1976-1984 and 1987) averaged only 3% of the total catch. Data were not collected in 1985 and part of 1986. Catches in 1987 (April through November) were lower than average.River herring, which includes alewife and blueback herring, were monitored both in the Taylor River and in Hampton Harbor from 1980 to 1984.The size and length of the river herring "run" was shown to be variable, with the number of days that fish were observed. passing the Taylor River ladder ranging from 31 (1982) to 47 (1981)(NAI 1985b). New Hampshire Fish and Game has estimated run totals to range from 94,000 (1981) to 205,000 (1980) during the 1978-84 period (NAI 1985b). Their staff removed fish from the ladder during peak periods to stock'other water bodies. Changes in the run size were affected by year class strength. Periodicity of the run was, affected by water temperature and level which were in turn influenced by rainfall and the resulting runoff. Alewives and bluebacks were the third most abundant species caught in beach seines in the Browns River (S2) and Hampton River (SI),, respectively (Figure 2.3-10); however, this was caused by large but infrequent catches at these stations. In the estuary as a whole, these species constituted only about 6% of the total catch (1978-1987). Another species which uses the estuary is winter flounder. This species undergoes onshore/offshore migration, depending on the time of year (Bigelow and Schroeder 1953). Juveniles (age one and two, based on length-frequency analysis) were the main constituent in the estuary, primarily collected during the spring and summer (NAI 1985b). 'Recruitment was evident by the occurrence of young-of-the-year size classes. Total catches were somewhat variable, and Catches in 1987 were much lower than average in a;ll months but June and August (see Section 3.2.2).The dominant resident species in the estuary was Atlantic. silver-side, which typically comprised 67% of seine catches during the baseline period (1976-1987) and 90% within their abundant'period, August to November (Figure 2.3-9). The population was composed primarily of yearling fish but the occurrence of young-of-the-year size classes in spring indicated recruit-52 100-% % %% % %80-o others EO blueback herring[ rainbow smelt E2 Atlantic herring O American sand lance[ alewife 0 0 C.0 z LU LU M.60-40.-* pollock* mummichog 0 Atlantic silverside 20-0 'L S1 S2$3 STATION Figure 2.3-10. Percent composition by station for abundant species of fish collected in beach seines, all years combined, 1976-1984 and 1987. Seabrook Baseline Report, 1987.53 ment (NAI 1985b). Variability in total seine catch has been the result of high variability in catches of Atlantic silverside; catches were high from 1976-1981 (200-360 fish/haul) andmuch lower from.1982 -19871(60-100 fish/.haul) (Figure 2.3-9).Since the Hampton-Seabrook estuary contains the majority of New Hampshire's stock of the recreationally-important species, Mya arenaria, an:extensive sampling program (over 13 years) was undertaken in order to characterize the natural variability in densities of all lifestages. Of the potential impact types, larval stages will be most susceptible to intake effects and therefore are discussed in that section[(Section 2.2.1). Spat settlement densities appear to bear no relationship to the abundance or periodicity of Mya larvae in the nearshore waters (NAi 1982c). It would.appear that Mya veliger behavior (i.e. their "readiness" or competency to settle) combined with the timing of favorable:currents may be more important to settlement success than sheer numbers of larvae in the water column. Such conditions apparently existed in 1976, 1977, 1980, 1981 and 1984 when young-of-the-year spat densities were highest at flat 1 (Figure 2.3-11) and other flats. The 1976 year class in particular provided an important and rejuvenating recruitment.to the local population as shown by the high den-sities of 13-25 mm clams in 1977 and 1978 (Figure 2.3-11). Continued low densities of spat from 1983 through 1987 at flat 1 (Figure 2.3-11) and other flats suggest that the standing crop of adults will remain low for at least another three to four years.Once settled, survival of young-of-the year Mya depends on both the level of predation from its two main predators, the green crab and human clam diggers, and the absence of diseases such as neoplasia., Despite relatively heavy densities of young-of-the year in 1980, 1981, and 1984 on Flat 1, recruitment to yearling clams was minimal (Figure 2.3-11). This pattern was replicated throughout the estuary. Predation by green crabs, whose densities began to increase in 1980 and from 1983-1987 remained much higher than previous years, may have virtually eliminated the first and second year-class. Human predation is also an-important factor in the level of harves-54 ZO0 U1 x a.0wL_j CL 3.0-2.5-2.0-1.5-1.0-0.5-OLAT 1 YOUNG- OF-YEAR (1 -5 mm)II*J I.I I I I I I U.V I I l J I l I I 1. I I l I 74 75 76 77 78 79 80 81 82 83 84 85 86 87 YEAR SPAT (13 -25 mm)2.0-zO0 CIt (0 L ow 0 1.5-1.0o I I 0.5 -I T T T .1.0.0.1 -I -T t Y Y I I I £ I I I 1974 1975 1976 I a I I 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 2.3-11.Annual means and 95% confidence limits of densities (No./ft 2) of Mya arenaria young-of-the-year and spat in Hampton-Seabrook on Flat 1.. Seabrook Baseline Report, 1987.55 table clams, causing mortality to adults as well as spat and juveniles by disturbance. Digging activity has declined sharply from 1982 to 1985 with a small increase in 1986 as clam diggers switched to other.flats in an effort to harvest clams. Digging activity resumed its decline in 1987 (Figure 2.3-12). The standing stock has declined precipitously since 1983, lagging trends in digging activity by one year (Figure 2.3-12). Finally, the pres-ence of disease may add to the effects of predation. Neoplasia, a cell growth disease fatal to Mya, has been detected in 3-27% of-the Mya from Hampton Harbor flats 1 and 2; no incidence of this disease was found at flat 4 (Hillman 1986,. 1987).I...The ability to. assess impact in adult clams in Hampton estuary will depend on close monitoring of all of the factors important to recruitment and predation. Clam seeding by the State of New Hampshire during 1987 in tidal creeks running into Hampton Harbor may enhance spat densities, but the ultimate effect on harvestable clams depends on predation levels and disease.2.3.2 Benthic Monitoring 2.3..2.1 Macroalgae and Macrofauna Monitoring of the benthic organisms (macroinvertebrates, algae, demersal fish, and epibenthic crustaceans) was established to determine the extent of change (if any) to the. community structure in this zone as a result of plant operation. Changes could be manifested by (1) the enhancement of detritivores and suspension feeders, (2) the increased attraction of benthic feeders caused by locally-increased food supply, and/or (3) impact on organisms sensitive to the increased detritus resulting from moribund entrained organisms. Mid-depth and deep (10-20 m) benthic communities, int-luding macro-algae, macrofauna, and bottom panels, were sampled to monitor the preopera-tional benthic community. Year-to-year variations in community structure 56 -BUSHELS L--. C5EJSES 15000 -z Ca)CI)10000-5000-0 1 1 7 1 1 1 1 1 1 1979 I I 1 1971 1972 1973 1974 1975 1976 1977 .1978 1979 1980 1981 1982 1983 1984 1985 1986 1987-YEAR Figure 2.3-12. Number of adult clam licenses issued and the adult clam standing crop (bushels),,Hi{mpton-Seabrook Harbor, 1971-1987. Seabrook Baseline Report, 1987.57 were small in comparison to variations related to depth and substrate. The macroalgae community was highly similar among years, although less so than in.the intertidal .and shallow subtidal areas. Species composition of sample..collections in the mid-depth and deep subtidal areas during 1987 were similar to those taken at the same.station in previous years (Figure 2.3-4 and Section 3.3.2). The same was true for macrofauna, where all collections at the six mld-depth and deep stations had species assemblages which resembled those in previous years (Figure 2.3-4 and Section 3.3.3). Colonial macro-faunal assemblages in the mid-depth and deep areas differed from year-to-year, and did not show a distinct association with depth (NAI 1985b).Patterns in abundance and size distribution in selected benthic species were only slightly less predictable than species assemblage charac-teristics. The green sea urchin and the amphipod Pontogeneia inermis did not vary significantly in abundance among years, but mussels (Mytilidae) did (Table 2.3-3). There was relatively low variance in abundance among'years for most of the species (Figure 2.3-13), compared to, some of the more vari-able communities such as zooplankton and ichthyoplankton. Length measure-ments were a stable parameter; no differences among years were detected (Table 2.3-3).Few nearfield/farfield differences were noted in the mid-depth/deep region. In the macrofaunal and macroalgae community, all farfield stations were more similar to their nearfield counterparts than any other areas, indicating their suitability as "control" areas (NAi 1987b). Collections made in 1987 in all cases were most similar to the majority of collections from previous years at the same depth stratum (Figure 2.3-4). Most nearfield annual abundances and all nearfield lengths were statistically similar to those from the farfield area (Table 2.3-3). The only irregularity in spatial.distributions was in the macroalgae and macrofaunal community structure at mid-depth Station 16, which was more similar to ghýllow subtidal stations than those in its own depth zone. The predominance, of algae-covered-ledge-at this station caused increased amounts of algae and correspondingly higher abundances of herbivores. 58 TABLE 2.3-3.

SUMMARY

OF SIMILARITIESa IN ABUNDANCE OR LENGTH AMONG YEARS AND BETWEEN STATIONS FOR SELECTED SPECIES IN THE MID-DEPTH ZONE. SEABROOK BASELINE REPORT, 1987.AMONG YEARS NEARFIELD VS.FARFIELD SIMILAR DISSIMILAR Similar S. droebachiensis (A, L) Jonah crab Pontogeneia inermis (L) Modiolus modiolus Mytilidae (L)Dissimilar Pontogeneia inermis (A) Rock crab Lobster Winter flounder Hakes Yellowtail flounder Rainbow smelt Atlantic cod Mytilidae (A)aResults of ANOVAs, paired t-tests, or Wilcoxon's summed ranks tests.Abundance or catch unless otherwise noted.(L) = length (A) = abundance 59 TEMPORAL AND SPATIAL VARIABILITY 5-1.w z 0 z 0_j 4-3-2-* AMONG YEARS, NEARFIELD (n -10 except n = 8 for Modiolus)o AMONG YEARS, FARFIELD (n = 10 except n =8 for Modiolus)"°h 0*E.0r*'E E.0 0:a 0 z 00 C 0 00 a<'0w* a-.;C C Os o .C 00-s~. .0~ 0 U2 E 0 C z i!t IMPORTANCE 60-z 0 z LU 0 Ul I.=E Oj U CL 40-20-I N/A 0-I a sE=a-z V*0 E 0*0 a-0 6 I.=z UE .0.!S i 0 Z CL 2 C.Co 0 *-I Figure 2.3-13. Percent composition and nearfield (Sta. 19) vs. farfield (Sta. 31) annual variability (standard deviation) of log (x+l) abundance for selected mid-depth benthic species, 1978-1987. Seabrook Baseline Report, 1987.60 Because of apparent year-to-year stability in the annual community structure demonstrated above, the once-per-year August sampling provides a good baseline for monitoring potential changes in total numbers of taxa or individuals., Community structure analysis provides a simultaneous view of species numbers, abundance, diversity and dominance, and if changes occur at a particular place or time. Results also indicate that certain species in the study area, because their abundance or size patterns, are predictable and changes, if they occur, could be evaluated with these taxa.2.3.2.2 Demersal Fish Demersal fish which inhabit or feed in the discharge area are important not only because of their predominance in'the food chain but also because of their commercial value.' Six taxa comprised close to 80% of total otter trawl catches both across months and years (Figure 2.3-14). Effects, or lack thereof, should be evident from following the distribution of these six taxa, although the total number of taxa as well as rare and infrequently-occurring species have also *been monitored. Numerical classification of 1978-1982 data identified two basic seasonal groups: "winter" (December-March) and an extended "summer" period (April-November) (NAI 1983b). These two periods were evident from monthly relative abundances' (Figure 2.3-14)which show rainbow smelt were prominent mainly in winter, and hakes (red, white and spotted) and longhorn sculpin composed a greater proportion of the demersal population in summer. The overall community dominants, yellowtail and winter flounder, provided some temporal stability to this demersal community (Figure 2.3-14). Long-term trends were also evident; total catches were highest in 1980 and 1981 when catch per unit effort was almost twice as high as the CPUE in 1977 and 1985 (Figure 2.3-14), the two lowest years.Total catches steadily declined from 1981 through 1985, then increased slightly in 1986 and 1987. Variations in catch from year to year are lower than seasonal variations (Figure 2.2-6), even for winter flounder, which usually doesn't show a strong seasonal peak. Longhorn sculpin once accounted for an much as 27% of the total catch in 1984, but in 1986 and 1987 accounted for less than 10% (Figure 2.3-14).61 100-SEASONAL VARIATION w 0.C.50-0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC z 0 0..0 z C-, 0.100-80-60-40-0.0 0M 10 0" zlyv.ai rairbow smeft o3 Atlantic cod 0 winter flounder* longhorn sculpin* haked* yellowtail flounder JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N01V DEC 100 -ANNUAL VARIATION uJ 50-0-I I i I I I I I I I

• I I 76 77 78 79 80 81 82 83 84 85 86 87 1001 z 0 U)0 0.03 C.)I--z.U.0 0.80-60-40-20-13 rainbow smelt[3 Atlantic cod E3 winter flounder* longhorn sculpin hakes* yellowtail flounder I., 0-76 77 78 79 80 81 82 83 84 85 86 87.YEAR 1.Figure 2.3-14. Seasonal and annual changes in composition and abundance of the demersal fish community, based on catch per unit effort at otter trawl stations Ti, T2 and T3 combined, 1976-1987.

Seabrook BaselineReport, 1987.62 The age structure of the fish populations is also a factor con-tributing to abundance variability. Based on 1983 and 1984 length-frequency data and age-size information from the literature, the dominant age group collected at the nearfield trawl station (T2) was as follows: RECRUITMENT SPECIES DOMINANT AGE GROUP EVIDENT?a Atlantic cod Age one and two yes Hakes Several yes Yellowtail flounder Young-of-the-year yes Winter flounder Several .yes Rainbow smelt Young-of-the-year yes aFrom presence of young-of-the-year or yearlings during certain seasons (NAI 1985b)As with most of the fish sampled in this study, the majority of fish col-lected with otter trawls were juveniles. Only hakes and winter flounder had no one age class dominant, although presence of young-of-the-year for these as well as the other taxa indicated the timing of recruitment. Spatial differences are another important consideration with demersal fish. Farfield stations Tl and T3 were similar in overall catch per unit effort and relatively similar in species percent composition, although the relative contribution of sculpins and yellowtail flounder was reversed at the two stations (Figure 2.3-15). The nearfield station was most-unique, with total CPUE (averaged over all years) being 40% lower than at farfield sta-tions. This station also had a noticeable number of dates on which samples could not be collected due to the presence of commercial lobster traps.While CPUE calculations take this into account, the unavailability of data during certain fall months has likely affected catch statistics. Winter flounder and rainbow smelt (together) comprised 43% of the overall catch at T2, compared with 8-11% at the farfield stations. Most of the differences in total catch and species composition can be attributable to local habitat differences. T1 has a sandy bottom, T3 has sand mixed with cobble and shell 63 f 100 % %' ~, , , #J.60 -z 0 I,-0.0 Uj I--U U CL[o others o pollock[ skates* Atlantic cod[J rainbow smelt 0 winter flounder* longhorn sculpin* hakes* yellowtail flounder 40-20 -1~0 , T1 T2 T3 Figure 2.3-15.STATION Percent composition by station for abundant species of fish collected in otter trawls, all years combined, 1976-1987. Seabrook Baseline Report, 1987. -64 debris, and T2, although mainly sand, has high currents, often resulting in a great deal of drift algae. The nearfield station is also located off the mouth-of Hampton inlet and is influenced by tidal flow from the estuary.Thus, operational comparisons will have to focus on relative changes at a given station in species composition and the absolute abundance of selected species.All of the selected demersal fish monitored have shown signifi-cantly different abundances (CPUE) among stations, and three of the five species have also differed significantly among years (Table 2.3-3), implying that determination of* "control" conditions is difficult. For almost all of these taxa, precision in impact assessment is only moderate because of among-year variability. Knowledge of the age-structure of the population and use of age and growth parameters (NAI 1985b) can improve the ability to detect impacts.Age and growth parameters for two species, cunner '(1983-1984) and winter flounder (1982-1984), abundant in the nearfield discharge area were measured to provide additional precision to the catch estimates and a view of potential sublethal effects. Results for the first three years of life, when impact effects would be.most pronounced, can be summarized as follows: SPECIES GROWTH CUNNER WINTER FLOUNDER Sexes different? yes no Year classes different? yes yes. (age 1 & 2 only)Percent change detectable 2-5% 3.-,4%Thus, depending on the species, sex and year class differences will have to be considered if measuring age and growth during impact assessment. However, variability of age and growth statistics was low, giving better precision than abundance estimates. 65 2'3.2.3 Epibenthic Crustacea Becaus~e of its commercial importance, the American lobster has been studied in all of its life stages for 10-14 years. Average annual catches of all'lobsters was fairly stable, varying less than the average monthly catch (Figure 2.3-16). Catches did not differ significantly among years (Table 2.3-3). Variations in catches of legal-sized lobsters, a primary concern to lobstermen, were a result of natural variation combined with the-effects of the change in the legal size limit. Catches ranged from 7 to 10 per 15-trap effort during 1975-1986, then dropped to three/15 traps. in 1987. Although the variability was lower than that for total catches (Figure 2.3-16), this repre-sented a substantial difference to commercial lobstermen. Catches in the 67-79 mm size class (2-5/8 to 3-1/8 inches carapace length), lobsters which are approximately two years old, have been steadily increasing through 1985 despite decreased catches in the smaller size classes (one-year old lobsters)(Figure 2.3-17). In 1984, the legal size limit was increased by the State of New Hampshire from 3-1/8" (79.4 mm) to 3-3/16" (81.0 mm), and catches of legal-sized lobsters decreased to their lowest point in 1984 and 1985. A number of adults which would have been of legal size under the old law were not harvested, causing increased catches through 1985 in the 79-92 mm size class (3-5/8 to 4-1/8 inches), which now contained both legal and sublegal sizes. A decrease in catches in. 1986 in the 79-92 mm size class may have been linked to lower catches in the 54-67 mm size class in 1985.Lobsters have shown consistent seasonal patterns, with catches highest from August through October. Catches to the north (L7) have been*consistently (and significantly) higher than at the.discharge (LI).Annual catches of other epibenthic cr~ustaceans, Jonah crab and rock crab, were more variable (Figure 2.3-16).- Both species had increasing.. catches from 1982 through 1985, then slight decreases in 1986 and in 1987'.(nearfield station only). Catches of Jonah crab were generally highest in August (Figure 2.3-16), with no differences detected between nearfield and farfield stations. Rock crab catches, much lower than those. of .its sibling species, usually peaked in July or August, and were significantly greater at the nearfield station than at the farfield station. I 66 PEAK SEASON 12 10 z 0 8 6 4 2 0 0 PEAK MONTHS.0 At U a a22 C CM 0.0 .E w 0.z z 20-15-10-5-TEMPORAL VARIABILITY

• AMONG MONTHS (n = 6 Jun -Nov)o AMONG YEARS (n = 13 for lobsters, n = 6 for crabs)I I U. ..I., 1 0 E o..0 0 0-aJ U a,, S h..0 a ad 0 a-U,~0 a-S 0.a U r.0 o"0.0 aI U*o Figure 2.3-16.Seasonal vs. annual variability (standard deviation) and months of peak abundance (catch per 15-trap effort) for adult lobsters and crabs. Seabrook Baseline Report, 1987. (For CPUE of total lobsters, multiply by 10.)67 100 MD > 105 mm o 92 -105 mm 779-92mm* 67- 79 mm S54 -67 mm M <54mm C.I-c.I-IO.U C.I--C.60-40 co 20 0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 2.3-17.Size-class distribution (carapace length) of Homarus americanus at the discharge site, 1975-1987.

Seabrook Baseline Report, 1987.

3.0 RESULTS

3.1 PLANKTON AND WATER QUALITY PARAMETERS Plankton and water quality programs of the Seabrook baseline period have included water quality sampling, phytoplankton, microzooplankton, and macrozooplankton. During 1987 there was no additional sampling for phyto-plankton or microzooplankton. Results of those two programs were updated and presented in detail in last year's baseline report (NAI 1987b) and are not repeated here. The plankton and water quality programs presented in this 1987 baseline report are those for which sampling was conducted during 1987: water quality (Section 3.1.1), bivalve larvae (3.1.2), and macrozooplankton (3.1.3). The cummulative results for all plankton programs, including phyto-plankton and microzooplankton, are discussed in Section 2.0.3.1.1 Water Quality Parameters-Seasonal Cycles and Trends Three physical (temperature, salinity and dissolved oxygen) and five chemical_(orthophosphate, total phosphorus, nitrite, nitrate and ammonia) parameters were examined over a 10-year period to assess their temporal variability. Generally, parameters exhibited annual cycles with one or two peaks; ammonia showed no distinct pattern (Figures 3.1.1-1 through 3.1.1-7).Water temperature was monitored in the nearfield both continuously (Station ID, 1978-1986, NAI 1987B) and periodically during the semimonthly plankton cruises (Station P2, 1978-1987). Monthly mean values derived from both sampling methods were similar (NAI 1980c, 1980d, 1981f, 1982a, 1984a, 1985a). Continuous temperature data were not available for January 1985 through July 1986. Irradiance values, collected 1979-i984, and surface temperatures followed the same general annual cycle, with temperatlure peaks lagging irradiance peaks by one month (NAI 1985b). Bottom temperatures (depth 16 meters at MLW) showed truncated peaks which lagged one to three 69 Surface Lii 20-15 5-OVERALL MEAN 1987 0 I JA I iF iM I I JUN I I A J A N F E M A R A P R M A Y J U N J U L A U G 8 6 ' O CT N O V D B MONTH 15-1 Bottom 0 w CL 4 10-I .OVERALL MEAN 1987 0 JAN I .I I Ik .' r I I I I I'MAR APR MAY JUN JUL AUG -' IOCT NOV Dm MONTH Figure 3.1.1-1. Monthly mean temperature at station P2, all years' mean and 95% confidence interval for 1978-1987 and monthly mean for 1987 for surface and bottom. Seabrook Baseline Report, 1987.70 aU 0 I-4U 0 8-6-2-0-1978~M M- -1 2 1 2 '1 g 2 I I

• _I 2 1 2 1 2 I 2 1 2 1 2 1 2 1 2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1979 6-4-2-0-+ .£ a " ." I 2 1 2 1 2 2 1 2 1 2 1 2 1 2 1 2 1 2 .1 2 1 2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 0 C-.0 I--J 8 1980 6 4-2 0-2 121 2 122 1 2 1212 1 2 1 2 1 2 1 2 1 2 1 2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 8-1981 6-4-2-0-9KM 121212121212 JA E MA APR MAY JUN 121212121212 JUL AUG SEP OCT .NOV DEC a 0 I.-.I--JJ 68 6"4 2-1982 m liIlimi U 0 M--U-. ---2 ..I 1 1-11.-T.1 2 1 2 1 2 1 2 1 2 1212 1 2.1 2 1 2 1, 2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC B Figure 3.1.1-2. Differences between surface and bottom temperatures taken semi-monthly at station P2, 1978-1987.

Seabrook Baseline Report, 1987.71 0 0 I---J 0 I-0 nnl I---J I-J 4 I.--J nn 03 0 LI-w3 1983 6-4-2-2: 2 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 JAN FEB MAR APR MAY JUN JUL AUG- SEP OCT NOV DEC 10" 8 1984 6-4 2 0-2 1 2 1.2 1 2' 1 2 ¶ 2 1 2 1 2 I 2 1 2 1 2 1 2 1 2 6 JAN FEB. MAR APR MAY JUN JUL AU( SEP OCT NOV DEC 5 1985 4ý3 2-0-1 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 .1 2 1 2 1 2 1 2 8 JAN FEB MAR ARP MAY JUN JUL AUG SEP OCT NOV DEC 61986 6-4-2-2-4.* l l i I I I l I I I a I I , I I , i I , ".1 2.1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2'121 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 10 1i 10 8-6-I*-I 2-0-1 2 1 2 I 2 1 2 1 2 ¶ 2 1 2 1 2 1 2 1 2 ' 2 1 2 JAN FEB MAR APR ,MAY JUN JUL AUG SEP OCT NOV DEC Figure 3,1.1-2. (Continued) 72 a.z 4 U, 0"r" I--LU U)I--I'L 34-32-30-28-26-Surface Salinity-ALL YEARS! MEAN---.--. 1987 24 34-I I I I I I JAN FEB MAR APR MAY JUN JUL AUG MONTH .I I I L SEP OCT NOVEE Bottom Salinity 0 z 0 I..-LUl 0.I-4, 33-32-31 30--ALL YEARS MEAN....... 1987 29£ I I I I I I I I I I I 6 1 A I I a I a I a .I I JAN FEB MAR APR. MAY JUN JUL AUG SEP OCT NOV DEC MONTH Surface salinity and bottom salinity at nearfield station P2, monthly means and 95% confidence intervals over all years, 1978-1987, and monthly means for 1987.Seabrook Baseline Report, 1987.Figure 3.1.1-3.73 Surface Dissolved Oxygen 12-w cc, CL-o CC ALL YEARS! MEAN 1987 11-10-9-8 I I I i I I 1 I I l -J I JAN FEB MAR APR MAY JUN JUL AUG. SEP. OCT NOV DEC MONTH Bottom Dissolved Oxygen I 12 w I-C.33 ppt, though in 1987 peak salinities occurred in March at the bottom (32.4 ppt; Figure 3.1.1-3).. Salinities remained fairly uniform throughout the year, dropping only in spring between March and June, depending on the amount of spring runoff and rain. Significant rainfall in April of 1987 resulted in the lowest observed surface salinity for a single date (21.2 ppt).' Spring salinity concentra-tions typically reached lows of 28-3lppt. Bottom salinity exhibited the same seasonal pattern as the surface, but showed less variation within and among years (Figure 3.1.1-3). Annual mean salinities in 1987 for both surface and bottom were the lowest recorded. in this study, reflecting below average salinities throughout the year, especially in April, June (bottom only), November and December (Table 3.1.1-1, Figure 3.1.1-3). Dissolved oxygen peaks occurred February through April in both surface and bottom waters. Dissolved oxygen nadirs varied from August to November near the surface and the bottom (Figure 3.1.1-4). Surface and bottom dissolved oxygen values in 1987 were similar to previous years (Table 3.1.1-1) though November values were somewhat elevated (Figure 3l.i-4). Maximum orthophosphate and nitrate concentrations occurred in winter (Figures 3;1.1-5 and 3.1.1-6);nitrate was consistently lowest in midsummer. Total phosphorous and nitrite showed fall, winter and occasional spring peaks (Figures 3.1.1-5 and 78 TABLE 3.1.1-1. ANNUAL MEANS AND COEFFICIENTS OF VARIATION OF WATER QUALITY PARAMETERS MEASURED DURING PLANKTON CRUISES AT NEARFIELD STATION PZ, 1978-1984 AND 1986-1987. SEABROOK BASELINE REPORT, 1987.ANNUAL MEAN (AND COEFFICIENT OF VARIATION) PARAMETER 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 Temperature 0 C)surface 8.37 8.76 8.76 8".72 8.88 9.58 8.94 9.73 9.31 9.12 (66.93) (57.85) (57.86) (63.34) (53.02) (53.74) (55.72) (54.55) (49.57) (57.80)bottom 6.61 6.36 7.05 7.37. 7.36 7.32 6.93 8.03 7.58 6.39 (55.62) (47.96) (5Z.76) (59.11) (46.03) (44.43) (45.04) (47.81) (40.42) (45.95)Salinity (ppt)surface 31.68 31.82 32.17 31.89 31.84 31.04 30.68 32.15 31.68 30.65 (3.33) (3.84) (2.64) (2.16) (3.47) (4.39) (4.93) (2.26) IZ.44) (6.76)bottom 32.Z4 32.47 32.42 32.32 32.41 31.92 31.77 32.50 ý2.z0 31.48 (1.65) (2.77) (1.521) (1.41) (2.01) (2.12) (1.83) (1.54) (1.77) (2.66)Dissolved Oxygen (mg/l)surface 10.28 10.02 10.27 9.90 9.60 9.48 10.01. 9.67 9.88 9.89 (10.80) (13.39) (11.17) (12.70) (11.15) (7.73) (12.06) (10.42) (11.03) (9.92)bottom tO.O7 9.69 9.85 9.43 9.25 8.98 9.32 9.17 8.96. 9.73 p8.86) (14.67) (14.28) (17.90) (16.17) (11.99) (13.56) (15.36) (13.52) (11.64)Orthophosphated 19.58 9.75 i0.12 11.82 17.02 19.23 14.29 __b __c 18.08 (Pg/1i) (9.99) (52.59) (76.10) (30.83) (55.54) (44.47) (56.06) (45.25)Total phosphorusd "32.50 15.12 31.96 22.S0 Z4.61 25.83 24.17 __ _c 33.36 (Pg/1) (40.09) (63.09) (77.68) (33;93) (28.66) (35.05) (40.43). -- (40.30)d-b c Nitrited 2.12 1.71 3.17 2.92 2.30 2.05 1.02 -- -- 1.48 (Pg/1) (46.11) (66.58) (59.59) (53.13) (68.34) (54.34) (98.08) -- (98.00)Nitrated 52.08 38.33 48.33 45.42 37.17 51.83 36.75 --c 44.42 (Pg/1) (116.61) (101.24) (111.88) (94.41) (137.89) (106.62)' (117.47) (132.17)Ammoniad 51.46 47.42 104.17 36.25 <30.00a 27.32 16.57 b 53.33 (g/1l) (120.96) (42.93) (48.73) (64.73) (115.96) (70.82) (61.54)a Below detection limits (30 pg/1) of methods used in 1982.b Not measured in 1985.c-Measured July through December 1986 only.d Collected one meter below surface. 3.1.1-6). Ammonia maxima usually occurred in fall or spring. In 1980, when ammonia'concentrations were exceptionally high throughout the year, the peak occurred in July (Figure 3.1.1-7).Orthophosphate and total phosphorus concentrations in 1987 varied somewhat from baseline conditions. Orthophosphate concentrations in 1987 were bimodal with higher than normal values in February, June and July (Figure 3.1.1-5). Total phosphorus concentrations in 1987 were highly variable with higher than normal concentration in February, May, September; October and December. Nitrite concentrations in 1987 were well below normal March through June when no nitrite was detectable (<1.0 Vg/l at Station P2;November nitrite levels were above normal (Figure 3.1.1-6). Nitrate levels were typical of past years with somewhat higher than normal concentrations in February (Figure 3.1.1-6). Ammonia concentrations in 1987 were consistent with previous years, with slightly elevated levels in August and October through-December (Figure 3.1.1-7).3.1.2 Bivalvia Veliger Larvae 3.1.2.1 Community Bivalve veliger larvae were identified and enumerated from oblique tows of 76-jm mesh nets from April through October 1976-1987 at one or more of the Stations Pl, P2, .and P7 (see Section 3.3.7.1 for Mya arenarla results and Figure 4.1-1 for station locations). Mytilus edulis was clearly the dominant species, while ffeteranomia squamula, fifatella sp., Solenidae and IModiolus modiolus were secondary dominants (Table 3.1.2-1).Hiatella sp. was present April through October, with highest abundances usually occurring in June (Figure 3.1.2-1). Mytilus edulls, Solerkidae and Mya truncata were usually present by mid- to late May. Mytilus edulis and Mya truncata peaked primarily in June or July. Solenidae peaks were noted in June, late August, September, and October, possibly due to 80 0 0 TABLE 3.1.2-1.OVERALL PERCENT COMPOSITION OF BIVALVE VELIGER LARVAE IN 76-pm NET TOWS AT STATIONS a OCTOBER, 1982-1987 D1 Do AxrI D7 vIDnM -MTT'I-A'DDTT "TTDM'T'IrU.L SEABROOK BASELINE REPORT, 1987.1982 1983 1984 1986 1987 SPECIES P2 P7 P2 P7 P2 P7 P2 P7 Pi P2 P7 Mytilus edulis 44 54 59 47 77 83 61 54 74 62 56 ffeteranomia squamulab 21 14 4 17 4 3 12 15 8 8 25 ifiatella sp. 9 8 17 13 8 6 10 9 10 13 8 Modiolus modiolus 9 3 14 18 7 3 13 18 2 3 5 Spisula solidissima 6 8 1 1 1 <1 <1 1 <1 1 1 Solenidae 3 4 3 2 2 2 1 2 -4 10 3 Mya arenaria 4 5 1 <1 <1 <1 <1 <1 <1 <1 <1 Other Bivalvia 2 2 1 1 1 1 1 2 2 4 2 llya truncata 1 1 <1 <1 <1 <1 <1 <1 <1 <1 <1 Mfacoma balthica <1 <1 <1 <1 <1 <1 0 0 0 0 0 Placopecten magellanicus <1 <1 <1 <1 <1 1 <1 <1 <1 <1 <1 Teredo navalis 0 0 0 0 0 <1 <1 <1 <1 <1 <1 Only Mytilus edulis and Mfya arenaria were enumerated in 1985.bFormerly referred to as Anomia sp.

• YEARS PRESENT*YEARS HIGH ABUNDANCE I LU LU 10-8 6-4" 2 12-10-'8-'6-'4 12-10-.8-.6-4: 20 3 41 23411 213 411 2 3 4 1 2 123"4 1 2 3 4 APR MAY 1 JUN JUL AUG SEP OCT 1 Mytilus edulis (a)YEARS PRESENT YEARS HIGH ABUNDANCE A OC 41 AP AY JUN I"JL I AG I SEP "OCT L Modiolus modlolus (b)YEARS PRESENT YEARS HIGHABUNDANCE 34 APR 4r T -112 3 2j 23 4 1 123 41' 2 3 4 23 j JUN .JUL I AUG 1 SEP 1 OCT ,<, 4.12 -Heteranomia squamula (b)NYERPEST 10 0 YASH3 BNAC 8-6-4 2 0 311 3 41 2 3 41, 2j 3 4, 1 2 3. 41 23 IJ 2 ', APRI MAY I JUN JI U SEP I OCT U)LU 12-10-8-6-4-2-0-Solenidae (b)* YEARS PRESENT* YEARS HIGHABUNDANCE 3 411 2 4 112 4112 ' 112 3 4-11 2 3 4ýJ 2 3 4 APRI MAY I JUN I JUL -AUG 1 SEP I OCt Figure 3.1.2-1.Number of years present and number of years in high abundance (2 50% of seasonal peak abundance) of bivalve veliger larvae by week at station P2, 1978-1987.

Years enumerated:, a. 1976-1987;

b. 1978-1984, 1986-1987;

c. 1979-1984, 1986-1987.

Seabrook Baseline Report, 1987.82 a, w1 cc wU 10o Mya truncata (b) * .AP YERSPESN 8 -YEARS HI G ABUNDANCE 6.4- a 2]JPAUN JL AG SEP OCT 10- Placopecten magellanic~us (b)8-* YEARS HIGH ABUNDANCE 6 4 w 2-0 -3 4 APR 41.123 4 1123 41123 411 23 41 23 4 I JUN I JUL 1 AUG I SEP l OCT 1 u)ul I0 -Spisula solidissima (c)8 6 -N YEARS PRESENT , .in[ YEARS HIGH ABUNDANCE 4 2-0 3' 4 1 '32 3 .4 1 223 41 23 4 2 3 4 1 23 4 AP RI MAY JUN JUL AUG SEP OCT 8-Macoma balthica (c)a, wT 6-j 41 2 0 U]U]34 1 234123 411 2 3 4 1 3 4 2 3 4 1' 3 4 APR I IMAY JUN JUL AUG SEP ' OCT Figure 3.1.2-1. (Continued) 83 differential spawning of the three component species (Ensis directus, Siliqua costata, Siliqua squama). ffeteranomia squamula was usually present by early June, with highest abundances July through September. Modiolus modiolus was usually present by mid-June and has been highly variable in terms of peak abundance, with peaks in early'June (1978) and in early October (1986).Spisula solidissima and Macoma balthica usually were not observed until July and August, respectively; these taxa peaked in late summer or fall.Placopecten magellanicus-was present sporadically throughout the sampling'period, with no clear seasonal peak. In general, larval peak abundances and periods of occurrence in 1987 were comparable to previous years with some exceptions. In 1987, Spisula solidissima peaked in early June, slightly earlier than usual and, as in 1986, Macoma balthica larvae were not observed (NAI 1987b).Station P1 (Hampton Harbor), added to the sampling program in 1986, and offshore Stations P2 (nearfield, intake) and P7 (farfield) all displayed similar patterns of species composition and abundance. Entrainment samples were collected within Seabrook Station (El) July through December 1986 and April through June 1987. In both years, comparison with intake Station P2 demonstrated similar species composition at Station El but substantially lower larval densities. In 1987, Station El densities for ifiatella sp., Solenidae and Mya arenaria were substantially lower than densities observed at Station P2 (Table 3.1.2-2).Differences between Stations El and P2 may be attributed to dif- K ferences in sampling. Station El sampled water from the cooling water intake, at a depth of about ten meters, while Station P2 was sampled via oblique net tows which integrated the entire water column. In general, bivalve larvae are found in near-surface waters for the majority of their planktonic existence, thus fewer larvae would be expected at a depth of ten meters, and consequently lower abundances would be expected at Station El.Additional variation between stations may have been introduced by sampling at different times or different days, allowing small and large scale patchiness to affect the larval densities. 84 TABLE 3.1.2-2.DENSITIES OF DOMINANT BIVALVE VELIGER LARVAE IN 76-pm MESH NET COLLECTIONS ON OR NEAR THE SAME DATE AT NEARFIELD STATION, P2, AND ENTRAINMENT STATION, El, APRIL THROUGH JUNE 1987. SEABROOK BASELINE REPORT, 1987.APR APR APR MAY MAY JUN JUN JUN 21 22 30 07 26 01 03 08 ALL Mytilus edulls P2 <1 -0 0 0 4 -79 14 El -<1 0 0 0 ,- 2 61 11 Hiatella Sp. P2 23 -1084 1699 866 6433 -7320 2904 El -4 <1 363 256 -856 1237 453 Solenidae P2 <1 0 1 33 328 0 26403 4461 El -0 0 0 21 0 32 725 130 Mya arenaria P2 0 -0 0 0 0 -82 14 El -0 0 0 0 -0 6 <1-Sample not collected 85 3.1.2.2 Selected Species M* a arenaria This species is discussed in Section 3.3.7.Mytilus edulis Umboned veligers of Mytilus edulis were usually present by mid- to late May (Figure 3.1.2-1). Once present, they occurred consistently through-out the sampling program. The protracted presence of larvae was due to recruitment patterns and duration of larval lifestages. 'Major spawning events in Gulf of Maine mussel populations may be limited to-temperatures above 10-12 0 C (Podniesinski and McAlice 1986). Spawning of M. edulis in Long Island Sound was found to be asynchronous both.within and among local popula-tions and to occur over a two to three month period (Fell and Balsamo 1985).Spawning of some Long Island Sound mussel populations was also restricted by limited food availability for most of the year, resulting in sporadic spawning events (Newell et al. 1982). Therefore it is probable, based on the reproductive behavior of M. edulis, that recruitment of larvae to the plank-ton of New Hampshire coastal waters occurred throughout much of the sampling program. Recruitment from non-local sources was probable, as water masses may move large distances over the three to five weeks required for larval development at ambient temperatures (Bayne 1976). Delay of metamorphosis until suitable settlement conditions are encountered can prolong planktonic existence for up to 40 days, depending on temperature (Bayne 1976). These factors suggest that planktonic recruitment to the study area was intermit-tent and prolonged, and that duration of planktonic life varied over the sampling program as temperature conditions changed.Highest abundances of Mytilus edulis larvae usually occurred between early June and early July (Figure 3.1.2-2), although in 1980-1982 abundances in late August, September or October were as high as in early 3 *3 5 3 summer. Peak abundances ranged from 6 x 10 /m in 1982 to 3.3 x 10 /m in 1979 (NAI 1987b). The difficulty in assessing the variability in this 86 LU I-w D cc 0 w a-w 00 z 0_j 6 5 4 3-ALL YEARS WEEKLY MEAN------- 1987 WEEKLY MEAN\T".2 1 0 Apr-2 Apr-3 Apr-4May-l May-2May-3 May-4 Jun-I Jun-g Jun-3 Jun-4 Jul-I Jul-2 Jul-3 Jul-4 Aug-I Aug-2Aug-3Aug-4 Sep-I Sep-2 Sep-3 Sep-4 Oct-I Oct-2 Oct-3 Oct-4 Nbv-I MONTH AND WEEK Figure 3.1.2-2.Weekly mean abundance and 95% confidence intervals for Mytilus edulis larvae at nearfield station P2.over all years 1978-1987. Seabrook Baseline Report, 1987. population is probably compounded by patchiness caused by discontinuous recruitment both spatially and temporally (Bayne 197.6;.Podniesinski 1986).Collections taken within several days of one another, even during peak months, varied by zero to three orders of magnitude (NAI 1981c, 1984a).In 1986 and 1987, bivalve larvae were collected within Seabrook Station in order to estimate larval entrainment. In 1987, offshore and entrained M. edulis densities over all dates were similar (Table 3.1.2-2).However, in 198., some weekly densities differed substantially between the.two stations, probably a result of small-scale spatial and temporal varia-tions.Although variability was high among years, overall spatial vari-ability was low. Historically (i982-1984), no significant differences had been found between Stations P2 and P7 when weekly abundances were ranked (NAI 1985b).3.1.3 Macrozooplankton 3.1.3.1 Community Structure Temporal Patterns Historical analysis (1978-1984) of the macrozooplankton assemblage at the nearfield Station P2 showed seasonal changes that were heavily influ-enced by the population dynamics of dominant copepods Centropages typicus and Calanus finozarchicus, with other taxa, particularly meroplankton, exerting short-term influences, especially during the spring and summer (NAI 1985b).Historical seasonal assemblages (1978-1984) established by numerical classi-fication on the basis of similarities in species composition were verified by discriminant analysis, and in turn used to evaluate 1986 and 1987 collections. In all cases, new collections were placed in, the group with the majority of historical collections from the same time period. This is an indication of the similarity of 19.86 and 1987 assemblages with previous years.88 Winter abundances have been typically low, with the population composed mainly of copepods Centropages typicus (groups 1 and 2) and Metridia sp. (group 2 only)(Tables 3.1.3-1, 2). Winter abundances of C. typicus in 1987 were an order of magnitude lower than previous years, and 1986 and 1987 winter abundances of copepods Tortanus discaudatus and Temora.longicornis were higher than previous years (Table 3.1.3-2).The months of March and April were characterized by the beginning of the spring warming trend and initiation of thermocline formation (Section 3.1, Figure 3.1.1-2). Reproductive activities of barnacles at th'is time result in a tremendous influx of Cirripedia nauplii and cyprids, which distinguish this assemblage (group 3). Copepods Centropages typicus and Calanus finmarchicus are also dominant components of this assemblage (Tables 3.1.3-1,2). The late winter-early spring assemblage in 1987 was similar to previous years with the exception of C. typicus abundance levels, which were two orders of magnitude lower than the 1978-84 average (Table 3.1.3-2).Heavy rainfall in April, 1987 caused salinity to drop to the lowest value observed since the study began in 1978 (21.2 ppt at P2, NAI 1988). This may have affected C. typicus densities, as its reported salinity preference is above 30 ppt (Gosner 1971).In most years, spring collections were marked by a transitional assemblage (group 4), composed mainly of Calanus finmarchicus along with other microcrustaceans (C. typicus, Metridia sp., Evadne sp. and Temora longicornis), the holoplanktonic mollusc Limacina retroversa, and larvacean Oikopleura sp. (Table 3.1.3-2). The transitional period in 1987 consisted only of early May collections, coinciding with continued low surface salinity (Figure 3.1.1-3). Mean group densities of dominant taxa in 1987 were all an order of magnitude lower than those historically (1978-1984)(Table 3.3.1-2).Late spring-early summer (late May-July) conditions showed rapidly increasing surface temperatures along with stabilization of the thermocline (Figures 3.1.1-1, 3.1.1-2). Calanus finmarchicus was typically the dominant organism during this time period, which along with the larval decapods, 89 0 TABLE 3.1.3-1.SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS FROM NEARFIELD STATION P2, 1978-1984 AND BY DISCRIMINANT ANALYSIS OF COLLECTIONS FROM JULY 1986-DECEMBER 1987. SEABROOK BASELINE REPORT 1987.SAMPLING PERIOD a GROUP J F M A M J J A S 0 N. D 1 2-34 12 34 .2 34 12 34 12 34 12 34 12 34 12 34 12 34 12 34- 12 34 12 34 I Winter 1978-79, B9 8 3 2 B 9 8 8 B 4 3 2 3 8 82-83,83-84,85-86,86-87 3 9 4 B 3 3 A A 2 Late Fall 1987 4 "B 4 B'2 Winter 1980-1982 0 0 0 1 0 1 0 0 9 1 1 0.2 Z 3 Late Winter-Early Spring 2 4 1 9 3 9 8 9 8 4 8.4 B2.0 030 3 31 1 .2 2 2 4 4 4 B B B 4 Spring 1 9 0 9 9 0 3 101 2 4 B 5 LateSpring-Early Summer 2 8 8 0 8 0 2 9 4 9 3 91 93 40 B B 1244 A l 23B B3 4 B 6 Summer 8 9 8 0 8 8 0 8 9 9 1 4 3 A 01 3191 0 1 23 AB 23 424 2 234 A A A 3 4 'A B B A B B 7 Fall 8 0 9 2 8 0 9 9 8 1 4 9 03 12 1 0 1 1 IB 3 43 4 2 4 A B.4 A:, ~B" a year (1978-1984) represented by last digit; 1986=A; 1987=B. TABLE 3.1.3-2.MEAN ABUNDANCE AND PERCENT FREQUENCY OF OCCURRENCE OF DOMINANT TAXA OCCURRING IN SEASONAL GROUPS FORMED BY NORMAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS AT NEARFIELD STATION P2, 1978-1984, IN COMPARISON TO 1986 (JULY-DECEMBER) AND 1987 (JANUARY-DECEMBER) AS CLASSIFIED BY DISCRIMINANT ANALYSIS. SEABROOK BASELINE REPORT 1987.1978-1984 1986 1987 GROUP SPECIES MEAN % MEAN 3 %#/1000m FREQ. #/1000m FREQ. #/1000m FREQ.1 Winter 1978-1979, 1983, 1984,1986, 1987 Late Fall 1982,1983,1987

2. Winter F

• 1980-1982 3 Late, Winter-Early Spring Centropages typicus Cirripedia larva Pseudocalanus sp.Sagitta elegans Neomysis americana Tortanus discaudatus Temora longicornis Metridia sp.Centropages typicus Limacina retroversa Pseudocalanus sp.Centropages sp. copepodite Temora longicornis Calanus finmarchicus Neomysis americana Sagitta:elegans Tortanus, discaudatus Olikopleura sp.Cirripedia larva Centropages typicus Calanus finmarchicus Oikopleura sp.Pseudocalanus sp.20800 3700 2400 2200 1900 1200 320 35700 18900 13600 7900 4100 3200 3100 2400 2300 2100 2100 292000 72200 54100 21100 9900.212000 36500 29700 95 33 100 i00 100 95 90 100 100 93 93 93 86 100 100 100.100 100 100 93 100 93 100 100 92 100 10900 0 700 1700 37000 10900 3960 100 0 100 100 100 100 100 1700 80 3400 1400 1300 5060 6780 100 33 100 100 100 100 100 325000 900 124000 11500 1100 42000 500 800 100 100 1.00 100 100 100 100 100 4 Spring Calanus finmarchicus Limacina retroversa Oikopleura sp.(continued) r'3 TABLE 3.1.3-2. (Continued) 1978-1984 1986 1987 GROUP SPECIES MEAN % MEAN 3 MEAN %#/1000m FREQ. #/lO00m FREQ. #/1000m FREQ.4 Spring (cant)Centropages typicus 23800 92 600 i00 Metridia sp. 21500 83 0 0 Evadne sp. 19700 100 4100 100 Temora longicornis 15000. 83 2000 100 5 Late Spring- Calanus finmarchicus 101000 100 586000 100 86000 100 Early Summer Eualus pusiolus 37000 96 189000 100 12000 100 Metridia~sp..

30900 96 0 0 300 60 Meganyctiphanes norvegica 29000 88 60200 .100 1700 100 Cancer sp. zoea & megalopa 26600 100 66000 100 24000 100 Tortanus discaudatus 15300 96 0 0 2500 100 Centropages typicus 14000 80 43300 100 85000 100 Oikopleura sp. 13700 72 0 0 2700 100 Sagitta elegans 9700 96 800 100 1300 80 6 Summer Centropages typicus 263000 100 68000 100 386000 100 Calanus finmarchicus 206000 100 102000 100 45000 100 Cancer sp. z6ea &megalopa 78700 100 88000 100 66000 100 Podon sp. 54900 97 100 43 34000 60 Centropages sp. copepodite 17200 85 5300 86 16000 80 Eualus pusiolus 13000 100 17000 100 15000 100 Carcinus maenas zoea & megalopa 11800 100 36000 100 15000 100 Crangon septemspinosa 9900 100 27000 100 2400' 100 Centropages hamatus 2800 62 2600 86 11400 40 7 Fall Centropages typicus 145000 100 247000 100 38000 100 Podon sp. 13500 100 .700 100 1800 100.Centropages hamatus 5600 79 2900 100 18800 99 euphausiids and small copepods formed the basis of group 5 (Table 3.1.3-2).1987 collections in this group extended into.August, without a definite transition into the summer assemblage. Average group abundances of several species (Metridia sp., Meganyctiphanes norvegica, Tortanus discaudatus, and Oikopleura sp.) were an order of magnitude lower than 1978-1984 densities, coinciding with higher-than-average surface temperatures and continued lower-than-average salinity (Figures 3.1.1-1,3). The summer assemblage (mid-July -mid-October, group 6) occurred during the period of peak temperatures and maximum thermocline (Figures 3.1.1-1, 3.1.1-2; Table 3.1.3-1). Historically, populations of Calanus.finmarchicus and Centropages typicus reached peak or near-peak abundances. at this time, while abundance levels of other copepods .decreased. Meroplank-tonic larval stages of decapods Cancer sp., Carcinus maenas and Crangon septemspinosa, and cladoceran Podon-sp. all reached peak abundance during this period. The summer assemblage in 1987 was similar to previous years, with two exceptions. Calanus finmarchicus, an oceanic species (Gosner 1971), mean densities in group 6 were much lower than those observed historically (1978-1984). Estuarine species Centropages hamatus, which has a salinity preference of 1-31 ppt (Gosner 1971), had abundance levels that were an order of magnitude higher than historical average (Table 3.1.3-2). Low salinity levels, beginning in spring and continuing throughout the year, may have affected 1987 abundance levels of these two species.The fall macrozooplankton assemblage (group 7) coincided with declining temperatures and degradation of the thermocline, characterized by fewer species and lower abundance levels than previous assemblages. Histor-ically, copepod Centropages typicus has been the only taxon which occurred abundantly, with Podon sp. a secondary dominant in the group. 1987 collec-tions in group 7 had a similar species composition, with mean group abundance levels of these two species an order of magnitude lower than those observed historically (Table 3.1.3-2). The estuarine copepod Centropages hamatus, historically not an important component of this group, had fall densities in 1987 that were an order of magnitude higher than those observed historically (Table 3.1.3-2).93 F Spatial Patterns The spatial distribution of most holo- and meroplanktonic species in the study area are governed primarily by local currents. Hydrographic. studies on temperature and salinity have shown that nearfield Station P2, and farfield Station P7 are exposed to the same water mass '(NAI 1985a). Further-more, bivalve larvae studies suggest that areas at similar depths and dis-tances from shore (such as P2 and P5) have similar species composition (NAI.1977a). Thus no spatial differences in the mero- or holo-planktonic macro-zooplankton abundances, percent composition, or rank would be expected among Stations P2, P5 or P7. This has been confirmed in examinations of.the annual percent composition, percent frequency and rank dominance scores (RDS) of dominant species followed by nonparametric testing of apparent differences (NAI 1985b, 1987b).Species composition among holoplankton was similar among the three stations in 1987 as well.. Percent composition gives an idea of how total annual abundance compares among the three stations. ýCopepod Centropages typicus had highest percent composition at P2 and P7, and Cirripedia had second-highest percentages. At Station P5, Cirrlpedia were highest in percent composition, followed by C. typicus (Table 3.1.3-3). The only other difference noted among stations was a higher percent composition-of Temora longicornis at P7 in comparison to P2 and PS. These species did not show significant differences among, stations in semi-monthly abundances (Table 3.1.3-4). Rank dominance and percent frequency of occurrence give an indica-tion of how frequently a taxon has been a dominant. C. typicus and Calanus finmarchicus were the top two species in ranks at all three. stations (Table 3.1.3-5). Stations were similar in species ranks except for Pseudocalanus sp., which had a higher rank at Station P5 (3) than at P2 and P7 (6 and 5, respectively)(Table 3.1.3-5). In addition, Tortanus discsudatus had a higher rank (7) at P7 in comparison to P2 (11) and P5 (14)(Table 3.1.3-5). These species did not show significant differences in abundances (Table 3.1.3-4).94 TABLE 3.1.3-3. COMPARISON OF PERCENT COMPOSITION (AND PERCENT FREQUENCY OF OCCURRENCE) OF SPECIES IN MACROZOOPLANKTON COLLECTIONS AMONG STATIONS P2, P5 AND P7, JANUARY-DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.P2 P5 P7 Centropages typicus 33.0 (100) 22.5 (100) 24.3 (100)Cirripedia 19.6 (42) 34.6 (42) 10.8 (42)Calanus finmarchicus 16.1 (100) 17.1 (96) 14.3 (100)Temora longicornis 5.8 (96) 4.5 (96) 16.8 (96)Cancer sp. 5.7 (62) 4.2 (67) 6.5, (62)Podon sp. 2.7 (58) 1.2 (67) 1.4 (67)Pseudocalanus sp. 2.2 (92) 1.5 (100) 3.1 (96), Centropages hamatus 1.9 (75) 1.3 (50) 1.4 (71)Eualus pusiolus 1.7 (100) 2.6 (100) 3.9 (100)Carcinus maenas 1.5 (54) 1.2 (58) 1.9 (54)Centropages sp. 1.5 (79) 1.5 (83) 1.8 (88)Tortanus discaudatus 1.i (83) 0.5 (75) 1.0 (83)Oikopleura sp. 1.0 (92) 1.4 (83) 1.0 (88)Evadne sp. 1.0 (58) 1.3 (67) 0.8 (71)Limacina retroversa 0.3 (67) 0.1 (75) 2.9 (83)Sagitta elegans 0.6 (96) 0.2 (88) 2.2 (92)Obelia sp. 0.5 (42) 0.5 (62) 1.9 (58)mysis mixta 0.1 (29) <0.1 (29) 0.4 (25)Diastylis sp. <0.1 (92) <0.1 (79) <0.1 (62)95 TABLE 3.1.3-4.

SUMMARY

OF 1987 BIWEEKLY ABUNDANCE COMPARISONS BETWEEN STATIONS MADE USING WILCOXON'S TWO SAMPLE TEST. SEABROOK BASELINE REPORT, 1987.TEST PARAMETER TESTED P2 v. P5 P2 v. P7 P5 v. P7 Holoplankters Calanus finmarchicus NS NS NS Temora longicornis NS NS NS Centropages typicus.. NS NS NS Limacina retroversa NS NS NS Tortanus discaudatus NS NS NS Sagitta elegans NS NS NS Meroplankters Crangon septemspinosa NS NS NS.Carcinus maenas NS NS NS Cirripedia NS NS NS Tychoplankters Neomysis americana NS NS NS Pontogenela inermis P2>P5* P2>P7** NS Oedicerotidae NS NS NS Diastylis sp.- P2>P5** P2>P7*** P5>P7*Other Total Abundance NS NS NS*significant at .01<p<.05**highly significant at .O01<p<0.Ol

• • • very highly significant at p<.001.The probability of a type I error (falsely accepting a difference as significant) is 5% for any single test, but the probability of at least one type I error in this whole table '(which contains 52 pairwise comparisons) is much greater than 5%. Therefore, only results that are very highly. significant should be viewed as true differences.

F 96 TABLE 3.1.3-5.COMPARISON OF RANK a (AND PERCENT-FREQUENCY OF OCCURRENCE) OF DOMINANT SPECIES IN MACROZOOPLANKTON COLLECTIONS AMONG STATIONS P2, P5 AND P7, JANUARY-DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.P2 P5 P7 Centropages typicus 1/2 (100) 1 (96) 1 (100)Calanus finmarchicus 1/2 (100) 2 (96) 2 (100)Temora longicornis. 3 (96) 4 (96) 3 (96)Eualus pusiolus 4 (100) 5 (100) 4 (100)Crangon septemspinosa 5 (100) 6 *(96) 6 I(96) sp. 6 (92) 3' (100) 5 (96)Neomysis americana 7 (100) 11 (92) 11 (92)Oikopleura sp. 8 (92) 7 (83) 10 (83)Pontogeneia inermis 9 (100) 12 (96) 19 (79)Sagitta elegans 10 (96) 10 (88) 9 (92)Tortanus discaudatus 11 (83) 14 (75) 7 (88)Centropages sp. 13 (79) 8 (83) 8 (88)Oedicerotidae 14 (92) 9 (96) 13 (88)abased on Rank Dominance Score.97 Tycho- and hypoplanktonic species, on the other hand, are often strongly associated with particular substrate types. Substrate type and complexity, along with proximity to Hampton-Seabrook estuary, may account for some of the differences observed among tychoplankters. Historically, Neo-mysis americana, Pontogeneia inermis, and Diastylis sp. had higher abundances at P2 where substrate is sand and cobble than at P7, the station farthest to the north where the substrate is mainly sand (NAI 1985b). -A similar trend was confirmed -n 1987, although differences were very highly significant only for Diastylis sp. (the number of tests performed necessitates a more stringent significance.level to avoida type ITerror) (Table 3.3.1-4). At Station P5, where substrate is largely ledge outcrop and cobble, 1987 den-sities of P. inermis and Diastylis sp,. were lower than at P2-but did not meet significance level criteria. Amphipods in the family Oedicerotidae showed no significant difference.) in 1987 abundances among the three stations.3.1.3.2 Selected Species-Calanus finmarchicus Over the length of this study (1978-1984, 1987) Calanus, finmarchicus has been a dominant species in the macrozooplankton assemblage (Table 3.1.3-2). Historically, copepodites exhibited greater abundances than adults, a trend which continued in 1987 (Table 3.1.3-6). The major peak in copepodite and adult abundance usually occurred April through September. Low abundances, especially of copepodites, occurred during winter (Figure 3.1.3-1). In 1987 adults were not observed in May and November, though copepodites were still abundant. In general, temporal abundance patterns in 1987 were typical of previous years (Table 3.1.3-7). A more detailed description of the life history of Calanus finmarchicus and other selected species is available in the 19.84 baseline report (NAI 1984).98 TABLE 3.1.3-6.ANNUAL GEOMETRIC MEAN ABUNDANCE (No./1000 m 3). AND UPPER AND LOWER 95%CONFIDENCE LIMITS OF SELECTED SPECIES OF MACROZOOPLANKTON-AT SEABROOK NEARFIELD STATION P2, 1978-1984 AND 1987.SEABROOK BASELINE REPORT, 1987.SPECIES/LIFESTAGES 1978 1979 1980 1981. 1982 1983 1984 1987 Calanus finmarchicus MEAN 8,999 6,614 19,753 13,159 4,756 12,634 8,819 8,555 copepodites UCL 51,614 29,219 90,884 53,896 33,342 51,566 59,076 44,336 LCL. 1,568 1,496 4,293 3,212 668 3,095 .1,316 1,650 Calanus finmarchicus MEAN 767 129 .338 116 186 555 518 160 adults UCL 4,644 722 898 834 1,366 2,668 1,840 1,370 LCL 126 22 127 15 25 115 145 18 Carcinus maenas MEAN 41 22 42 40 40 93 64 62 larvae UCL 406 276 573. 592 512 1,394 722 904 LCL 3 1 2 2 2 5 5 3 Crangon septemspinosa MEAN 404 342 152 157 425 547 319 360 Zoeae and postlarvae UCL 3,002 2,573 1,222 1,464 2,538 2,760 1,595 1,771 LCL 54 45 18 16 71 108 63 72 Neomysis americana MEAN 154 40 252 400 651 494 758 258 all lifestages UCL 521 195 1,288 2i404 2,052 1,688 2,047 783 LCL 45 8 49 75 206 144 280 84 kO CALANUS FINMARCHICUS 6-COPEPODITES Zj~.i-5-4-:2'f-u-ALL YEARS-MEAN 1987 MEAN I 6 5 4 3 2 I i I I I I I * *UI AUG *PI I I JAN FEB MAR APR MAY JUN JUL Pd S EP .OCT t'2I V C;I'Oo)LUn.5,.U, 0,0 I I 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV D-n Figure 3.1.3-1.Log (x + 1) abundance per 1,000 cubic meters for Calanus finmarchicus copepodites and adults;.monthly mean and 95% confidence interval over all 1978-1984, 1986-1987 and monthly means for 1987.Seabrook Baseline Report, 1987.100 I 0 TABLE 3.1.3-7.RESULTS OF ONE-WAY ANALYSIS OF VARIANCE a AMONG YEARS FOR SELECTED SPECIES OF MACROZOOPLANKTON AT NEARFIELD STATION P2, 1978-1984 AND 1987. SEABROOK BASELINE REPORT, CD SOURCE OF SPECIES VARIATION df SS F MULTIPLE COMPARISONS Calanus finmarchicus YEARS 7 7.78 0.75NS copepodites ERROR 178 262.68 TOTAL 185 270.45 Calanus finmarchicus YEARS 7 21.47 1.65NS.adults ERROR 178 330.96 TOTAL 185 352.42 Carcinus maenas YEARS 7 4.06 0.21NS larvae ERROR 178 498.27 TOTAL 185 502.33 Crangon septemspinosa YEARS 7 7.08 0.63NS Zoeae and postlarvae ERROR 178 285.58 TOTAL 185 292.66 Neomysis americana YEARS 7 27.70 3.57 7 84 82 83 81 87 80 78 79 All lifestages. ERROR 178 197.36 TOTAL ;185 225.06 aBased on semi-monthly sampling periods NS = Not significant (p > 0.05)* = Significant (Q.05 2 p > 0.01)** = Highly signifIcant (0.01 p 2 0.001)* = Very highly significant (p 0.001)

3.2 FINFISH

3.2.1 Ichthyoplankton

3.2.1.1 Total Community Nearfield (P2) ichthyoplankton data collected from 1976 through 1987 were examined for temporal (seasonal and year-to-year) patterns in.species assemblages by discriminant analysis. Species composition and frequency of occurrence at the farfield station (P7) and at the discharge station (P5) were compared to data from P2 to detect any differences in ichthyoplankton communities among the sampling areas.Common names recognized by the American Fisheries Socigty (Robins et al. 1980) are used for fish species in the text. The common and scien-tific names for every species collected from 1975 to 1987 in the Seabrook ichthyoplankton and adult finfish programs are listed with their relative abundances by gear type in Appendix Table 3.2.1-1. No newly-recorded species were encountered during the 1987 surveys, although fourspot flounder, which previously were only captured as adults, occurred in ichthyoplankton samples for the first time in 1987.Temporal Patterns of Nearfield Fish Egg Assemblages Numerical classification of 1976-1984 data had shown that the species composition of fish eggs was highly seasonal in nature, with dif-.ferent species occurring at different times of the year and generally the same seasonal succession repeating each year (NAT 1985b). The basic pattern over the 1976-1984 baseline period wasýsummarized by nine groups of samples, each characterized by a particular assemblage of species occurring at a particular time of year (Table 3.2.1-1).107 a b TABLE 3.2.1-1. DISTRIBUTION. AMONG W4EEKS AND AMONG SEASONAL ASSEMBLAGES O= SAMPLES OF FISH EGGS COLLECTED AT HEARFIEEW STATION P2 DURING JANUARY 1976 THROUGH DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.C DISTRIBUTION OF SAMPLES GEOMETRIC e JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN DENSITY d 3 ASSEMBLAGE 1234 1234 1234 1234. 1234 1234 1234 1234 1234 1234 1234 DO!INANT-FISH EGGSd (NO.11000 a 1. FALL-HINTER Cod-pollock

2. WINTER-SPRING Plaice-cod 7917 24Z4 4A4A BBAB B BA 6 96 1z 7069 8797 8390 1033 1412 3144 3 33 4ZAA 4 44 A4BB B BA BACC B CB C C Atlantic cod Pollock 65 14 O 0 03 0 6819.1.3 2342 BB3 C4 B 7168 8283 3394 4AOA ABIC BCZ C 3 *4 B C 741 3 9AZ*04 1 2 4 A 0 American plaice Atlantic cod/haddock 56 43 3. SPRING Plaice-cunner/yellowtail 3868 B399 B03 34 AA BB 78 00 14 l 2C 3 4 American plaice Cunner/yellowtail flounder Atlantic cod/haddock 627 160 113 C A B C continued E TABLE 3.2.1-1. (Continued) 0 c DISTRIBUTION OF SAMPLES GEOMETRIC JAN FEB MAR APR MAY JUN JUL AUG. SEP OCT NOV DEC MEAN DENSITYe ASSEMBLAGE 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 1234 DOMINANT FISH EGGS (HO./1000 m 4. SPRING Cunner/yellowtail-mackerel 967 81C A98. IC BID 2 24 4 3A A 3, B 4C C A B C Cunner/yellowtail flounder Atlantic mackerel 2690 1210 I-.',0 5. SUMMER Cunner/yellowtail-hake 9680 7868 7160 7 4 3793 3971 9 71 034 4093 0 9 24B A104 4 3A B33 4B '44 Cunner/yellowtail flounder Hake 8910 2830 A B AB B 6. SUMER Hake-cunner/

yellowtail A ZC2B 3882 832 C C AC AZ33 2A A B34A A C 4A AB BC C Hake Cunner/yellowtail flounder Windowpane 3390 737 218 continued 0 TABLE 3.2.1-1. (Continued) 0-F-J 0: C DISTRIBUTION OF SAMPLES-GEOMETRIC e JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN DENSITY d 3 ASSEMBLAGE 1234 1234 1234 1234 1234 1Z34 1234 1Z34 1234 1234 1234 1234 DOMINANT FISH EGGS (NO./1000 m 7. SUMMER-FALL C 0996 843 Hake "210'Hake- 3130 9CC Fourbeard rockling 25 rockling-4BAI 1 Atlantic whiting 22 whiting B B3 3 C4 4 AC B B. SUMMER-FALL C 4 C4 C AO Hake/fourbeard rockling 84 Hake/ B C B Windowpane 18 rockling-windowpane

• .FALL A A A 7343 AAC Atlantic cod 20 Cod- BA4 CM Atlantic whiting 6 whiting- BA C Hake 5 hake B Fourbeard rockling 2 C a Within eAch month, Week I = dates 1-8, Week 2 dates 9-15, Week 3 = dates 16-23, and Week 4 dates 24-3i.b Assignment of samples from 1976 through 1984 to assemblages was based on numerical classification.

Samples from 1985 through 1987 were classified into the 1976-1984 azsamblages by discriminant functions. c Each symbol represents a single sampling dates symbol = last digit of collection year for samples from 1976-1984, A=1985, B=1986, C=1987. For example, samples collected the first week of January (dates 1-8) were classified as containing the Fall-Winter-Cod-Pollock egg assemblage in the years 1977, 1982, 1984, and 1986- and containing the Winter-Spring-Plaice-Cod egg dassemblage in the years 1990 and 1981.*dTaxa whose geometric mean densities were at least 5Z of the total of all taxa analyzed.e Based on 1976-1984 samples. Two of the groups (8 and 9) had lower within-group similarity values (NAI 1985b) and lower numbrs of samples than the other seven groups. They were..characterized by relatively low abundances of a few species that occurred during the fall (NAI 1987b)..Discriminant analysis agreed fairly well with numerical classifica-tion analysis in the recognition of the nine seasonal assemblages of eggs.Discriminant analysis assigned 196 of the 219 samples (89.5%) to the same group as that assigned by. the cluster analysis. The seasonal groupings of samples recognized by discriminent analysis included late fall-early winter (Group 1), winter-early spring (Group 2), spring (Groups 3-and 4), summer (Groups 5 and 6), late summer-early fall (Groups 7 and 8), and fall (Group 9). Table 3.2.1-1 shows which samples were classified into each group, and what the dominant species and their densities were within each group.The late fall-early winter cod-pollock assemblage (Group 1)appeared in 1987 from late November through the end of December. The Group 1 assemblage is characterized by moderate numbers of Atlantic cod and pollock 3 eggs (65 and 14 per 1000 m , respectively), with very low abundances of other species (5 0.3 per 1000 m3). In previous years most January samples were also classified into Group 1 by both cluster analysis and discriminant analysis. The January samples from 1987 had a species composition similar to that of previous years but these samples were.excluded from the analysis because of low densities. The second seasonal group, a winter-early spring plaice and cod/haddock assemblage, occurred in February and March in 1987, which was typical of the baseline years' pattern. Pollock eggs were replaced by American plaice eggs as a dominant species during this seasonal period.The spring plaice-cunner/yellowtail assemblage (Group 3) was present in April and May during 1987, similar to previous years. This group was characterized by an increase in the number of abundant species. In 1987, 3 fourbeard rockling was the most abundant species (295 per. 1000 m ), followed by American plaice and cunner/yellowtail flounder, with relatively few ill 3 Atlantic cod/haddock eggs (7 per 1000 m.) compared to 1976-1984 (NAI 1988).Most of the cunner/yellowtail flounder eggs at this time of year, while not.identified to species, are assumed to be yellowtail flounder since this species begins spawning in March, while cunner do not typically. begin spawning until June (Bigelow and Schroeder 1953).The spring cunner/yellowtail flounder-mackerel assemblage (Group 4), was present the last two weeks of May and the first three weeks of June in 1987, which was similar to the previous baseline summary-peri6d (1976 through 1984). It exhibited high abundances of cunner/yellowtail flounder and mackerel eggs. Fourbeard rockling and windowpane eggs were also abundant.A very abundant summer cunner-hake assemblage comprised the fifth group of the 1976-1984 baseline period. Generally, the Group 5 assemblage occurred from early June to late August or occasionally into September. Cunner/yellowtail flounder and hake eggs dominated egg collections during this period. Most of the eggs identified as cunner/yellowtail in these summer samples were probably cunner because yellowtail flounders spawn primarily in the spring whereas icunners spawn during the summer (NAI 1983b).Windowpane, Atlantic mackerel, fourbeard rockling, and Atlantic whiting eggs were-also abundant in this seasonal group. None of the sample collections in 1987 were classified into this group.A second summer group (Group 6) was a hake-cunner/yellowtail flounder assemblage. During the 1976-1984 summary baseline period, this assemblage occurred from early July to mid-September. Only four years were-represented (1978, 1982, 1983.and 1984), with the majority of-samples coming from the latter three years. During 1987, this assemblage first appeared in late June and was present through the end of August. This assemblage, which temporally overlapped the fifth group, usually had lower abundances of cunner/yellowtail eggs and higher-.abundances of hake eggs compared with Group 5. This assemblage was further characterized by moderate numbers of window-pane eggs. Other species also exhibited a decline from early summer 112 abundances. In 1987, cunner/yellowtail flounder eggs were very abundant during the late June through late August period, while hake eggs were moder-ately abundant (NAI 1988). The discriminant function analysis classified these samples with Group 6 rather than Group 5 mainly because of the absence of Atlantic mackerel and Atlantic whiting eggs during this period. These two species are often fairly abundant in July and'early August, and are charac-teristic of the Group 5 assemblage. In 1987, however, mackerel eggs last occurred during the third week of June, and whiting eggs did not appear until the last week in August.The seventh seasonal group, a late summer-early fall hake-rockling-whiting assemblage, was composed of samples collected from September to mid-October during the 1976-1984 baseline summary.period. The only years not represented in this assemblage were 1977 and 1982. During 1987, this assem-blage occurred during late August through the third week of October. Hake, although diminished in abundance in comparison, to its density in Group 6 samples, still dominated egg collections. During 1987, as in the past, other species continued their gradual seasonal decline (NAI 1988).A small summer-fall group (8), represented by only three samples during the 1976-1984 baseline period, temporally overlapped Groups 6 and 7.This egg assemblage contained most of the taxa occurring in Groups 6 and 7, but densities were generally lower. Four sampling dates in 1987 were classi-fied with this group.A small group of fall samples comprised Group 9. This assemblage was characterized by low to moderate densities of Atlantic cod eggs, along with modest numbers of eggs. ofspecies that are primarily late summer spawners: hake, Atlantic whiting, and fourbeard rockling. The samples from late October through the third week in November in 1987 were classified with this group.Overall, the classification of the 1987 samples of fish eggs by discriminant analysis followed a similar seasonal pattern compared with both numerical and discriminant classifications of samples from previous years, 113 with the exception of increasingly more importance being assigned to two minor groups (8 and 9) consisting of late summer and fall samples, and also the absence in 1987 of the major summer assemblage represented in previous years by Group 5.Atlantic herring, American sand lance, and winter flounder, which are important components of the larval assemblages discussed below, do not appear in the baseline analysis of fish eggs because these species have demersal rather than buoyant eggs. These eggs are rarely, if ever, collected in oblique tows through the water column.Temporal Patterns of Nearfield Larval Fish Assemblages Numerical'classification analysis of fish larva abundances at the nearfield station (P2) during the period 1976-1984 revealed the same high degree of seasonality as was observed among eggs (NAI 1985b). The seasonal succession of larval assemblages can be summarized by four major groups, fall-winter, winter-spring, spring, and summer, each containing from one to three subgroups (NAI 1985b). Discriminant analysis placed each of the 1985-1987 samples into-one of nine seasonal assemblages (Table 3.2.1-2).The first major group, fall-winter, consisted of two larval assemblages (Groups 1 and 2). Atlantic herring larvae were the dominant species in Group 1, which occurred from early October to mid-November in the 1976-1984 baseline period, (Table 3.2.1-2). Only a few other species were present during this period, all in very low abundances (NAI 1985b, 1986, 1987). During 1987 the Group 1 assemblage extended into the third week of January. Group 2 (late fall-early winter) was dominated by pollock and Atlantic herring, with the latter displaying decreased abundance from the collections earlier in the fall.114 a b TABLE 3.2.1-2 DISTRIBUTION AMONG WEEKS AND AMONG SEASONAL ASSEMBLAGES OF SAMPLES OF FISH LARVAE COLLECTED AT NEARFIELD STATION P2 DURING JANUARY 1976 THROUGH DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.C DISTRIBUTION OF SAMPLES GEOMETRIC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN DENSITYe d 3 ASSEMBLAGE 1234 1234 1234 1234 1234 1234 1234 124 1234 1234 1234. 1234 DC1MIHANT FISH LARVAE, (NO./1000 m 1. FALL Herring C 4496 BAO2 B13 24 4A BB ICC i'm 724A B B 13AB C 34BC 4C A C 069 8797 A90 3032 812 41A3 C 3 4' AA B C Atlantic herring Pollock Atlantic herring Atlantic cod 192 2. FALL-WINTER Pollock-herring 7AA 4A A B 19 12 3 3. WINTER Sand lance 997 300 C 4 A B C 68 14 2 A B B 4B 2 1208 American sand lance 199 4. WINTER-SPRING Sand lance -cod 2 3 CBC 7 C C C4 A C American sand lance Atlantic cod Snailfishes (Liparis spp.)10 1 1 continued TABLE 3.2.1-2. fContinued) c DISTRIBUTION OF SAMPLES GEOMETRIC" e JAN FEB MAR APR HAY JUN JUL AUG SEP OCT NOV DEC MEAN DENSITY ASSEMBLAGE 1234 1234 1234 1234 1234 1234 1234 1Z34 1234 1Z34 1234 1234 DOMINANT FISH LARVAEd (NO./1000 m3 S. WINTER-SPRING Sand lance-rock gunnel 2 C016 8168 7898 4 349 3293 930B BAO 4304 OB1 Z AAlA 1 2 3 BBZB 2 3 4 CC3C 3 4 A 4 4 B A B B C C American sand lance Rock gunnel Snailfishes (Liparis spp.)425 47 25 I-.6. SPRING Winter flounder-snailfish 69 7867 8684 29.3 0998 979A 84 A 3010 04B B3Z4 21A 43A 32B A3B 43 B4C A4 CA BA B CB C C Winter flounder Snailfishes (Lipari s spp.)Radiated shanny American plaice'Cunner-Fourbeard rockling Atlantic whiting 55 45 41 33 7. SUMMER Cunner-rockling 30 7868 7860 79C1 C3 3071 9373 33 4193 049c 4A A304 3 3 CC A2C 4 4 B3 C C4 414 77 29 continued TABLE 3.(.1-2. (Continued) c DISTRIBUTION OF SAMPLES GEOMETRIC JAN FEB. MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN DEHSITY d3 ASSEMBLAGE 1234 1234 1234 1234 123 1234 1234 1234 1234 1234 1234 1234 DOMINANT FISH LARVAE .(HO./1000 Mn 8. SUMMER CAB Ali8 8 40 Cunner 32 Cunner B BZAA A C AC.C 9. SUMMER-FALL C A B 2 0 96 83A Fourbeard rockling 22 Rockling 4 2 23 IC Windowpane 4 34 3 Witch flounder 3 AA C Hake 2 C Cunner .2 a Within each month, Week 1 = dates 1-8, Week 2 dates 9-15, Week 3 dates 16-23, and Week 4 dates 24-31., b Assignment of samples from 1976 through 1984 to assemblages was based on numerical classification. Samples from 1985 through 1987 were classified into the 1976-1984 assemblages by. discriminant functions. C Each symbol represents a single sampling date: symbol = last digit of collection year for samples from 1976-1984, A=1985, B=1986, C=1987. For example, samples collected in the first week of January (dates 1-8) were classified as containing the Fall-Winter-Pollock-Herring larval assemblage in the years 1977, 1981, 1985, and 1986, and containing the Winter-Sand Lance larval assemblage in the years 1982 and 1987.d.Taxa whose geometric mean densities were at least 57 of the total of all taxa analyzed.e Based onh 1976-1ý&4 samples. American sand lance larvae dominated the second major seasonal period, winter-spring, consisting of Groups 3, 4, and 5 (Table 3.2.1-2).Group 3 samples Were characterized by moderate abundances of American sand lance (199. per 1000 m 3) and relatively low numbers of a number'of other 3 winter species (5 6 per 1000 m ). This assemblage usually occurred from some time in December to about mid-February. Two samples from 1987 were classi-fied with this.group. The Group 4 assemblage consisted of four samples in winter and spring of 1976-1984 that had lower densities of larvae and fewer numbers of species than in Group 3, with sand lance still being the dominant species. An unusually large number of samples (six) from 1987 were classi-fied into this group, an indication that densities on those dates in 1987 were lower than typical for most years. Group 5 consisted of a large number of late winter and early spring samples characterized by high densities of 3 American sand lance (425 per.1000 m )and moderate densities of rock gunnel (47 per 1000m 3) and snailfishes (25 per 1000 m , primarily Liparis coheni).This larval assemblage usually was present approximately from mid-February to late April. Six dates from early February to early April in 1987 were classified with Group 5.A spring larval assemblage was usually present during May and June in 1976-1984. These samples comprised the third major seasonal group, Group 6., The spring as~in previous years, was characterized in 1987 by moderate numbers of winter flounder, snailfishes (primarily Liparis atlanticus), radiated shanny, and American plaice larvae. This assemblage was present from mid-May to mid-June in 1987.The fourth major seasonal group, summer-early fall, consisting of Groups 7, 8 and 9, typically lasted from early July to early October. Group 7, the largest of the three groups, was mainly characterized by high densi-ties of cunner larvae and moderate densities of fourbeard rockling and Atlantic whiting. Witch flounder, Atlantic mackerel, windowpane, and hake larvae were also important in these samples, which were primarily from July, August, and early September. Group 8 is distinguished from Group 7 by lower densities and fewer species, with cunner being the only important species..118 Group 9 consists of late summer and early fall samples characterized by a fourbeard rockling larval assemblage. Besides modest numbers of rockling, a few other species were occasionally important in these samples.(windowpane, witch flounder, hake, cunner), although both densities of larvae and numbers of species were characteristically low. This was also a relatively small group in 1976-1984 (n=14) that received several additions in 1985-1987 ,(n=10).In general, the results of the 1987 discriminant analysis for' fish larvae agreed with previous seasonal and species groupings determined by numerical classification (NAI 1985b): 94% of the 1976-1984 samples were classified by the discriminant functions into the same groups as by the cluster analysis, and the classification of 1985-1987 samples followed a similar seasonal pattern to those from the earlier years. In most cases where the two methods differed, the samples in question had relatively low numbers of larvae. For example, Group 8 was originally a small'group (only seven samples in the nine-year period 1976-1984), but in the last three years an additional 13 samples have been classified here by the discriminant function analysis, including four from 1987. This tendency of discriminant functions to assign greater importance to minor groups compared to the original numerical classification was also noted in the analysis of egg data.The two methods use different procedures to evaluate the similarity of individual samples with each other. Discriminant functions sometimes place greater emphasis on subdominant species in differentiating among groups, whereas the Bray-Curtis similarity index used in the cluster analys.isof the 1976-1984 data is strongly influenced by abundance, and thus places greater emphasis on the dominant species.Spatial Patterns-of Fish Eggs and Larvae Spatial comparison of abundance and species composition from the nearfield and farfield stations was previously done using numerical classi-fication for both fish eggs and larvae. Spatial (station) differences were 119 found to be less important than short-term temporal differences (NAI 1983b, 1984b). Samples collected on the same date at different stations (nearfield or farfield) more likely resembled each other than if collected one to two weeks apart at the same station. This similarity in species composition and abundance between nearfield and farfield sites was consistent with the known extent of water mass movements in the study area. During 1987, the relative abundance and frequency of occurrence of all taxa in ichthyoplankton samples were very similar among the three areas sampled for both eggs and larvae'(Tables 3.2.1-3 and 3.2.1-4).Tidal currents and longshore (northward and southward) currents in.the study area are typically in the range of 0.2 to 0.6 knots about 75% of the time (NAI 1980d). Currents of this magnitude would transport.a water mass about two nautical miles during a single tidal excursion, or about 5-15 miles in 24 hours during periods dominated by longshore flow. The distance from Nearfield Station P2 to P5 (1-1/2 miles) or to P7 (3-1/2 miles) is relatively short. Considering that, for example, a water mass sampled at Station P2 could very possibly have been located at Station P7 a few hours before sampling, rigorous treatment of these locations as distinct from each other in terms of plankton is not justified. Since previous baseline reports have confirmed statistically that ichthyoplankton densities and species composition do not differ among stations, and data from 1987 are very similar among stations (Tables .3.2.1-3 and 3.2.1-4) no further analysis was con-ducted.Entrainment Species Assemblages Although Seabrook Station was not generating-power or discharging heat in 1987., the circulating water system was operatedfor the entire yearý, however, pumps were&only operating consistently enough to run the entrainment sampling apparatus from January through June. The flow rates for the sam-pling dates for the first six months are found on Table 3.2.1-5. Flow rates-per month averaged between 240 and 480 million gallons per day- As a pre-liminary evaluation of entrainment effects, ichthyoplankton samples were 120 TABLE 3.2.1-3.COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF FISH EGG COLLECTIONS AT NEARFIELD-(P2), FARFIELD (P7) AND DISCHARGE (P5) STATIONS DURING 1987. SEABROOK BASELINE REPORT, 1987.NEARFIELD FARFIELD DISCHARGE PERCENT PERCENT PERCENT PERCENT PERCENT PERCENT ABUN- FRE- ABUN- FRE- ABUN- FRE-DANCE QUENCY DANCE QUENCY DANCE QUENCY Brevoortia tyrannus 0.00 0.00 <0.01 2.17 <0.01 2.17 Enchelyopus cimbrius 2.34 60.87 3.03 56.52 3.40 52.17 Enchelyopus/Urophycis 2.26 32.61 7.75 30.43 3.93 34.78 Gadidae/Glyptocephalus 0.29 36.96 0.55 39.13 0.37 36.96 Gadus morhua 0.26 56.52 0.55 58.70 0.32 58.70 Gadus/Melanogrammus 0.05 17.39 0.11 17.39 0.05 15.22 Glyptocephalus cynoglossus 0.15 '28-.26 0.43 36.96 0.31 32.61 Hippoglossoides platessoides 0.16 30.43 0.37 34.78 0.29 39.13 Labridae/Limanda 65.36 50.00 52.84 54.35 55.34 52.17 Limanda ferruginea <0.01 2.17 0.06 4.35 <0.01 2.17 Melanogrammus aeglefinus <0.01 4.35 <0.01 2.17 <0.01 2.17 Merluccius bilinearis 0.34 23.91 1.31 26.09 0.60 28.26 Osteichthyes 0.00 0.00 0.02 2.17 0.00 0.00 Pollachius virens 0.02 19.57 0.04 21.74 0.05 23.91 Scomber scombrus 19.18 13.04 19.57 19.57 26.17 13.04 Scophthalmus aquosus 3.19 43.48 2.82 43.48 2.78 47.83 Tautoga onitis 0.07 8.70 0.10 6.52 0.02 4.35 Tautogolabrus adspersus 3.96 32.61 7.26 28.26 3.16 '34.78 Urophycis sp. 2.35 45.65 3.20 43.48 3.21 47.83 121 TABLE 3.2.1-4.COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF LARVAL FISH SPECIES AT NEARFIELD (P2), FARFIELD (P7)AND DISCHARGE (P5) STATIONS DURING 1987. ONLY COMMON SPECIES ARE LISTED (PERCENT FREQUENCY AT LEAST 10% AT ONE OR MORE STATIONS). SEABROOK BASELINE REPORT, 1987.NEARFIELD FARFIELD.. DISCHARGE PERCENT PERCENT PERCENT PERCENT PERCENT PERCENT ABUN- FRE- ABUN- FRE- ABUN- FRE-DANCE QUENCY DANCE QUENCY DANCE. QUENCY Ammodytes. mericanus 7.70 45.65 5.10 43.48 4._82 45.65 Anguilla rostrata 0.02 13.04 0.02. 13.04 <0.01 2.17 Brevoortia tyrannus 1.50 8.70 1.05 10.87 2.23 13.04 Clupea harengus 3.70 54.35 7.17 50.00 4.25 52.17 Enchelyopus cimbrius 5.12 52.17 5.71 41.30 9.18 56.52 Gadus morhua 0.14 39.13 0.06 36.96 0.14 45.65 Glyptocephalus cynoglossus 0.99 26.09 1.58 36.96 1.68 36.96 Jippoglossoides platessoldes 0.49 23.91 0.15 23.91 0.19 21.74 Limanda ferruginea 0.29 17.39 1.78 36.96 1.18 28.26 Liparis atlanticus 2.99 21.74 0.53 17.39 0.94 21.74 Liparis coheni 0.39 28.26 0.24 30.43 0.38 36.96 Merluccius bilinearis 2.10 21.74 1.44 19.57 3.62 21.74 Myoxocephalus aenaeus 0.33 23.91 0.44 26.09 0.18 21.74 Myoxocephalus octodecemspinosus 0.18 19.57 0.25 17.39 0.21 26.09 Myoxocephalus scorpius 0.03 6.52 0.06 10.87 0.01 6.52 Pholis gunnellus 2.14 28.26 1.68 28.26 2.0.7 23.91 Pollachius virens 0.09 19.57 0.12 21.74 0.10 21.74 Pseudopleuronectes americanus 1.89 23.91 1.65 17.39 1.31 23.91 Scomber scombrus 40.82 13.04 48.79 15.22 53.72 15.22 Scophthalmus aquosus 0.24 30.43 0.27 26.09 0.38 '36.96 Sebastes sp. 0.20 13.04 0.12 13.04 0.16 15.22 Tautoga onitis 0.40 21.74 0.09 10.87 0.03 13.04 Tautogolabrus adspersus 25.04 36.96 20.22 36.96 10.61 41.30 Ulvaria subbifurcata 2.38 41.30 0.98, 43.48 1.96 41.30 Urophycis sp. 0.48 21.74 0.35 21.74. 0.33 28.26 I I.122 TABLE 3.2.1-5.MEAN MONTHLY FLOW (MILLIONS OF GALLONS PER DAY)THROUGH THE SEABROOK CIRCULATING WATER SYSTEM JANUARY -J-UNE 1987. SEABROOK BASELINE REPORT, 1987.MEAN FLOW NUMBER OF DAYS (millions of MONTH OPERATING gallons/day) JAN FEB MARCH APRIL MAY JUNE 31 28 31 30 31 30 367 480 432 411 240 266 123 .collected periodically in the intake pumphouse (Station El) from January 6 through June 10, 1987. Generally, entrainment samples were collected within hours of the offshore nearfield collections (Station P2), but not necessarily on the same day (Table 3.2.1-6). These two stations were chosen for compara-tive analysis because P2 is the closest offshore station to the intake structure (Figure 4.1-1). More samples were collected at the nearfield station (18 dates vs. 11), contributing to some differences discussed below.Since there were no samples collected at El for the month of March, data from, Station P2 for March were not used in any comparisons between stations.Entrainment pump sample volumes averaged 100 m3 (as designed) as compared to approximately 489 m3 for offshore towed net samples for the same time period (NAI 1987).Fish egg.taxa in entrainment samples had similar species composi-tion to thosein offshore nearfield collections (Table 3.2.1-7)... Atlantic mackerel, American plaice, cod/witch flounder, fourbeard rockling/hake, cunner/ yellowtail flounder, and windowpane were the six .most abundant taxa-in the in-plant samples. In general, mean abundances and the total number of taxa at Station P2 exceeded those observed in entrainment samples. -Species such as Atlantic mackerel, windowpane, and fourbeard rockling, which have large oil globules, exhibit characteristics similar to other buoyant species in the middle Atlantic bight (Kendall and Naplin 1981) in that they tend to be found more often at surface depths. Because of this tendency to concen-trate near the surface, eggs of these species were less abundant in the entrainment samples than in the oblique offshore. tows, because the plant intake draws water from well below the surface. Cunner/yellowtail flounder eggs were two orders of magnitude higher in abundance at Station P2 than at Station'El. Although this species lacks an oil globule, previous studies (NAI 1980, 1981) have shown that this species is present in much greater abundances in middle and surface depths. Species such as American plaice and Atlantic cod/witch flounder, which lack oil, may be less buoyant and there-fore more abundant in the bottom portions of the water column, thus'account-ing for the larger abundances observed in in-plant samples compared with 124 TABLE 3.2.1-6. ICHTHYOPLANKTON SAMPLING DATES AT ENTRAINMENT (El)AND NEARFIELD (P2) SAMPLING STATIONS, JANUARY " JUNE 1987. SEABROOK BASELINE REPORT, 1987.SAMPLING DATES MONTH WEEK El P2 January 1 6 5 2 -- 12 3 -- 21 4 -- 28 February 1 3 3 2 -- 12 3 17 18 4 -- 25 March, I -- 5 2 -- 12 3 -- 19 4 -- 25 April 1 2 8 2 16 --3 22 21 4 30 --May 1 7 7 2 -- 14 3 ....19 4 26 27 June 1 3 3 2 10 9 3 -- 18 4 29-- = Not sampled 125 3 TABLE 3.2.1-7. MEAN ABUNDANCE (HO./1000 m ) OF FISH EGGS PER MONTH SEABROOK BASELINE REPORT, 1987.AT STATIONS El AND P2 FROM JULY 1986 -JUNE 1987.1986 JUL AUG SEP OCT NOV DEC JUL-DEC MEAN SPECIES El Pz El P2 El PZ El PZ El P2 El P2 El P2 Cunner/Yellowtail flounder 1552 7611 8 862 0 96 260 14Z8 Rockling/Hake 466 530 58 776 7 400 0 10 88 206 Windowpane 155 177 20 232 26 7Z 0 2 33 81 Hake 34 4003 70 1415 56 504 5 11 0 <1 28 989 Pollock 0 1 5 1s 119 21 21 6 Cunner. 121 161 0 133 20 49 Atlantic cod 2 9 37 537 62 205 17 1z5 Fourbeard rockling 0 52 2 54 43 263 4 18 0 .< 8 65 Atlantic mackerel 17 0 3 0 Cod/Witch flounder 2 2 0 3 2 88 <1 16 Witch flounder 2 4 <1 <1 Atlantic whiting 0 3 2 30 0 6 0 <1 <1 7 Tautog 0 29 0 5 Unidentified species 0 1 0 3 0 ý<1 0 <1 Yellowtall flounder 0 1 0 <1 Cusk 0 <1 0 Number of Taxa 6 6 7 11 5 9 4 9 2 6 z 2 continued j7 TABLE 3.2.1-7. (Continued.) 1987* a JANUARY FEBRUARY APRIL MAY JUNE JAN-JUN MEAN SPECIES El P2 El P2 El P2 El P2 El PZ El PZ Atlantic mackerel 46 102 1,114 19,585 232 3937 American plaice 0 <1 2 3 166 *26 185 79 Z54 39 121 30 Cod/witch flounder 0 <1 223 48 396 178 124 45 Rockling/hake 226 6 219 322 89 66 Cunner/yellowtail flounder 15 .1 72 533 206 Z8,201 59 5747 Windowpane 12 147 256 1016 54 413 Fourbeard rockling 55 118 0 747 0 1248 11 4Z3 Cod/haddock 0 7 22 0 4 1 Atlantic cod 27 4 8 2 0 <1 15 40 10 9 Pollock 7 6 1 1 Lumpfish 1 0 <1 0 NUMBER OF TAXA 2 3 2 3 5 4 6 8 7 8 I-.N)-4 a March excluded because no entrainment samples were taken that month. offshore samples. Larger sample volumes and greater frequency~of collection contributed to the higher number of taxa found in the offshore samples compared to entrainment samples.Entrained fish larvae also followed trends in species composition similar to those observed in the offshore nearfield station collections (Table 3.2.1-8). Abundance of larvae at both stations was virtually identi-cal for all species, except American sand lance, which was four times higher at the offshore nearfield station thafi at the entrainment station. American sand lance larvae have been shown to prefer surface depths (Dalley and Winters 1987), which might explain the larger abundances for the offshore oblique tows at Station P2 (the cooling water intake is 5 m above the bottom in 17 m of water). As was the case for fish eggs, offshore collections, which had larger sample volumes and greater sampling frequency, exhibited a higher number of taxa than found at the nearfield station.3.2.1.2 Selected Species Larvae of nine fish species were selected for a detailed analysis of their within-year and among-year patterns of abundance because of their numerical dominance or importance as a recreational or commercial species.Analyses were based on a series of monthly means for Nearfield Station P2 samples collected from July 1975 through December 1987. These monthly means were averages of two to four tows on one to four dates within each month.Each of the nine species displayed distinct seasonal patterns of abundance. While fish larvae were present in every month, the larvae of each species exhibited a sharply defined period of only a few months' duration in which their peak abundance occurred. Values in other months were typically*much lower and were often zero. These seasonal fluctuations were the primary reason for the high within-year variances calculated for each species (NAI 1983b)..To reduce overall variability and improve statistical power, or ability to detect significant year-to-year differences in abundance, seasonal 128 TABLE 3.2.1-8. MEAN ABUNDANCE (NO./1000 m 3 OF FISH LARVAE MONTH AT STATIONS El AND P2. SEABROK BASELINE REPORT, 1987.1986 JUL AUG SEP OCT NOV DEC JUL-DEC MEAN SPECIES El P2 El P2 El P2 El P2 El P2 El P2 El P2 Atlantic herring 0 <1 1039 429 243 695 84 53 228 196 Pollock 7 17 9 3 3 3 Cunner 0 16 4 18 <1 2 <1 6 Fourbeard rockling 0 9 3 2 <1. C1 0 12 0 <1 <1 4 Radiated shanny 0 11 2 4 2 2 <1 3 Northern pipefish 0 2 0 <1 <1 <1 I I <1 <1 American sand lance 3 <1 <1 Unidentified species 0 <1 1 1 0 <1 <1 <1 Gadidae 0 <1 2 0 <1 <1 Goosefish 2 <l <1 <1 Seasnail 1 0 <l 0 Atlantic mackerel 0 13 .0 2 Witch flounder 0 2 0 8 0 2 Windowpane 0 5 a 1 0 <l 0 1 Atlantic cod 0 <1 0 3 0 <1 0 <1 Atlantic whiting 0 <1 .0 2 0 <1 0 <1 Arctic shanny 0 2 0 <1 Hake 0 <1 0 2 0 <1 Yellowtail flounder 0 <1 0 <1 NUMBER OF TAXA 0 7 4.49a4 3 , 4 6 3 5 (continued) TABLE 3.2.1-8. (Continued) 1987 JANUARY' FEBRUARY El P2 El P2 APRIL MAY El P2 El P2 JUNE El P2 a JAN-JUN MEAN El P2 SPECIES Seasnail American sand lance Grubby Rock gunnel Winter flounder American plaice Atlantic herring Atlantic cod Gulf snailfish Moustache sculpin 36 22 10 400 140 153 29, 42 0 <1 3 <1 54 20 0 1 151 20 37 2 0 <1 1 4 23 24 5 6 1 4 0 <l 0 2 1 <1 7 10 4 14 2 11 5 0 2 0 55 326 0 16 2 6 0 <l 5 141 O 13 0 2 0 <1 0 3 156, 14 49 0 6 36 12 10 44 75 10 38 42 8 6 15 3 3 3 1<1 72 123 5 5 43 12 7 1 8 0 0 CD Sculpin NUMBER OF TAXA 3 6 7 6 a 9 3 9 4 5 a March excluded because no entrainment samples were taken that month. mean abundances (and upper and lower confidence limits) were calculated using data only from sampling periods which encompassed the seasonal peak in larval abundance. These select periods included the season of maximum yearly abundance and approximately 90% of total yearly catch for each species.Abundances from this subset were used to test for significant differences among years with a one-way analysis of variance and when differences were found to be significant they were subjected to a Waller-Duncan K-ratio t-test for multiple comparisons. Because 1975 data only include July-December samples, that year was only included in the analysis of variance for those taxa whose peak season does not include months prior to July: hake, Atlantic herring, and pollock.The analysis of pollock data excludes 1987 because each year's peak season for pollock includes January and February of the following year, and 1988 data are not included in this baseline report.American Sand Lance American sand lance larvae continued to exhibit a December through July presence with peak abundance occurring from January through April (Figure 3.2.1-1). In 1987, abundances dropped off in April but continued through June, then dropped to zero in July. This broad peak was due pri-marily to two factors: an extended hatching period and a long planktonic stage for larvae (Bigelow and Schroeder 1953). Sand lance, the most abundant species over all years, has been highly variable (Table 3.2.1-9). Starting in 1976, with 353 larvae per 1000 cubic meters, abundances decreased in 1977 to 35 larvae per,1000 cubic meters, the lowest value for any year of the study. In 1978, the abundances of sand lance increased to 384 larvae per 1000 cubic meters, then in subsequent years alternately decreased then increased. The highest abundance for sand lance larvae was recorded in 1982 3 3 (44,8 larvae/1000 m3). Abundance for 1987 (87.9 larvae/1000 m3) was the third lowest abundance during the thirteen years of the study. Using the peak season data, a one-way analysis of variance showed no significant difference among years for log (x + 1) transformed abundances (Table 3.2.1-10).. 131 American sand lance 4 W~LU zc.OD 3 2-OVERALL MEAN 1987 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH winter flounder 3 LU M cn.1-M 2-OVERALL MEAN,........ 1987 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.1-1.Mean and 95% confidence limits over all years and 1987 values, by ýonth, for log (x+l) transformed abundance, (No./1O00 m ) for American sand lance and winter flounder larvae at stations P2 and P3, July 1975 through December 1987. Seabrook Baseline Report, 1987.132 3 TABLE 3.2.1-9. GEOMETRIC MEAN OF SEASON OF PEAK ABUNDANCE (NUMBER PER 1000 M3) BY YEAR OF SELECTED FISH SPECIES LARVAE AT STATION P2 JULY 1975 THROUGH DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.LO SPECIES (and months included)American sand lance (Jan-Apr)Winter flounder (Apr-Jul)Yellowtail flounder (Hay-Aug)Atlantic cod (Apr-Jul)Atlantic mackerel (May-Aug)Cunner (June-Sep) Hake (Jul-Sep )Atlantic herring (Oct-Dec)Pollock (Nov-Feb)1975 1976 a-352.9 12.5 3.7 4.7 2.6 21.1 6.5 0.5 197.0 144.7 12.2 27.7 1977 35.0 10.4 20.2 9.4 5.4 224.5 4.2 16.1 5.1 1978 384.0 17.6 4.1 16.1 2.3 30.3 2.7 2.1 1.9 1979 203.2 7.9 12.4 1.2 8.0 46.2 8.2 7.4 49.2 1980 219.7 9.S 6.5 3.4 24. Z 97.7 5.4 34.0 7.3 YEAR 1981 213.7 2.9 1.3 9.9 12.4 29.1 5.9 50.0 4.0 1982 447.7 12.4 0.3 2.8 4.3 22.6 2.4 62.7 2.1 1983 95.0 14.4 4.3 1.8 12.0 97.9 10.4 9.3 3.4 1984 73.8 19.7 2.8 2.1 8.4 22.7 7.8 40.3 22.8 1985 71.S Z2.4 2.2 1.3 11.7 40.7 10.0 21.5 13.8 1986 314.8 19.1 5.3 1.6 12.4 12.4 0.1 126.7 1.2 1987 87.9 15.4 1.7 0.6 8.5 255.2 3.2 28.8 b CONFIDENCE OVER-ALL LIMIT MEAN LOWER UPPER 147.0 99.9 216.0 13.8 9.2 20.7 3.6 2.4 5.2 2.5 1.7 3.6 9.0 5.3 14.7 48.4 29.7 78.6.4.4 2.6 7.0 30.9 19.8 47.7 7.0 4.6 10.3 a Sampling at P2 began in July Yearly mean not computed for 1975, excluding part of annual peak.pollock in 1987 because January and February 1988 data were not available. TABLE 3.Z.1-10. RESULTS OF ONE-HAY ANALYSIS OF VARIANCE AMONG YEARS OF LOG (x + 1) TRANSFORMED ABUNDANCES (NO. /1000 m3 ) OF SELECTED SPECIES DURING SELECTED MONTHS, JULY 1975 THROUGH DECEMBER, 1987. SEABROOK BASELINE REPORT, 1987.SPECIES (AND SOURCE OF MONTHS INCLUDED) VARIATION df SS F MULTIPLE COMPARISONS American sand lance (Jan-Apr)Hinter flounder (Apr-Jul)Yellowtail flounder (May-Augi) Atlantic cod (Apr-Jul)Atlantic mackerel (May-Aug)Years Error Total Years Error-Total Years Error Total Years Error Total Years Error Total Years Error Total Years Error Total Years Error Total Years Error Total 11 120 131 10.02 66.63 76.65 11 10.43 118 47.49 129 57.92 11 11.43 107 87.55 118 98.99 il 4.81 118 112.26 129 117.07 11 120 131 5.79 168.13 173.92 1.27S 0.45 HS 1.74 S 2.35 0.3 8 N5 1.46HS 1.95"78 81 77 76 80 82 84 83 86 85 79 87 Cunner (Jun-Sep)Hake (Jul-Sep)11 21.79 117 159.30 128 181.10 Atlantic herring (Oct-Dec)12 87 99 12 82 94 11 101 112 10.63 63.81 74.44 17.07 69.86 76.93 19.76 54.21 73.97 75 76 86 82 81 84 80 87 85 77 83 79 78 79 76 84 85 75 80 77 .81 83 82 78 86 Pollock (Nov- Feb)MS =not significant (p > 0.05)= significant (0.05 2p >'0.01)=highly significant (0.01 2: p > 0.001)=very highly 'sigrnificant (p :5 0.001.) Winter Flounder Winter flounder larvae; the fourth most abundant over all years of the nine selected species, are usually present from March through September, with the highest concentrations occurring in April through July (Figure 3.2.1-1). Very few specimens were encountered in March, August and September. In 1987, abundances followed the same general pattern as in previous years. Winter flounder larvae, highly variable in earlier years, 3 decreased to an all time low in 1981 (2.9 larvae/l000 m3) then increased 3 during the next four years to the highest abundance (22.4 larvae/1000 m3)recorded during the study. Since that time, the abundance has decreased in both 1986 and 1987 (Table 3.2.1-9). A one-way analysis of variance of the peak month data showed no significant difference among years (Table 3.2.1-10). Yellowtail Flounder Yellowtail flounder larvae normally occur from May through November, with peak abundances occurring from May through-August. In recent years there have been an increasing number of larvae present in April, with 1987 recording the highest abundance for that month (Figure 3.2.1-2). In 1987, abundances dropped to zero in May but then increased to normal values in June and followed the general pattern of abundance through November.Yellowtail flounder, like most of the selected species, has been highly variable from year to year (Table 3.2.1-9). Starting with the highest value in 1977 (20.2 larvae/l000 m 3) abundances generally decreased to the lowest value in 1982 (0.3 larvae/1000 m 3) and then varied from year to year through 1987. Abundance in 1987 (1.7 larvae/1000 m 3) was the third lowest abundance observed and was half the overall yearly geometric mean of 3.6 larvae per 1000 cubic meters. The one-way analysis of variance to test overall yearly differences in log-transformed means was not significant. 135 yellowtail flounder 2.0 Cn UjI.Z+co°Oo I n" ccJM'x t 00 1000 1.5-OVERALL MEAN 1987 0.5 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV CEC MONTH Atlantic cod 2.0 1.5 1.0 0.5 0.0-OVERALL MEAN 1987 I-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DC MONTH Figure 3.2.1-2.Mean and 95% confidence limits over all years and 1987 values, by for log (x+l) transformed abundances (No./l000 m ) for yellowtail flounder and Atlantic cod larvae stations P2 and P3, July 1975 through December 1987. Seabrook Baseline Report, 1987.136 Atlantic Cod Atlantic cod larvae occurred sporadically from 1976 through 1987 exhibitinga bimodal distribution with one peak lasting from November through January (late fall-winter) and the other (usually stronger) peak in April through July (spring-early summer, Figure 3.2.1-2). Cod larvae also exhibited a bimodal distribution in 1987, however the April through July peak was not as strong-as usual. In addition, this peak extended through August instead of decreasing as in previous years. Seasonal geometric meanabund-ance for Atlantic cod was only computed for the spring-early summer peak, due.to the usually higher abundances and the longer period of occurrence in comparison to the late fall-winter peak. In 1987, spring Atlantic cod larvae attained their lowest abundance (0.6 larvae/1000 m ) in the twelve years of the study, thus continuing to exhibit below-average abundance levels and a general declining trend which began in 1982 (Table 3.2.1-9). A one-way analysis of variance among years found the differences to be significant (Table 3.2.1-10). The Duncan-Waller multiple comparison test shows that 1978 abundances were significantly higher than in 1979 and 1983 through 1987, and 1977 and 1981 abundances were significantly higher than those in 1987.Atlantic Mackerel Atlantic mackerel larvae exhibited a May through August pattern of occurrence for all years combined, with peak abundances occurring in July and no larvae found in October through April (Figure 3.2.1-3). In 1987, mackerel larvae were only found in-June and July, with June having a much larger value than the overall mean. Seasonal mean abundances for mackerel larvae were variable throughout the study period but have generally been increasing since 3 1978 (2.3 larvae/1000 m ). The highest value occurred in 1980 (24.2 larvae/3 1000 m ) with the average over all years being 9.0 larvae per 1000 cubic meters. In 1987, the abundance was slightly lower than the overall mean (Table 3.2.1-9). A one-way analysis of variance found no significant dif-ference among log-transformed yearly means.137 Atlantic mackerel 4 cc zo PM.+OD-I'-3 2 2-OVERALL MEAN....... 1987 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV CEC MONTH I cunner 4 w.n-LU WLU zo 0_.1T-3 2-OVERALL MEAN....... 1987 I 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT -NOV DEC MONTH Figure 3.2.1-3.Mean and 95% confidence limits over all years and 1987 values, by Tonth, for log (x+l) transformed abundances (No./1000 m ) for Atlantic mackerel and cunner larvae at stations P2 and P3, July 1975 through December. 1987.Seabrook Baseline Report, 1987.138 Cunner Cunner larvae were present throughout June through September, following a pattern of occurrence similar to mackerel larvae. Cunner larvae peaked historically during July and August and usually disappeared by October (Figure 3.2.1-3). In 1987, values for June through October were all greater than the overall means for those months. Seasonal mean abundances for cunner larvae have been highly variable throughout the past twelve years (Table.3.3.2.1-9), with 1987 exhibiting the highest abundance (255.2 larvae/1000 m3)during this period. Cunner larvae were also the most abundant of the nine selected species in 1987. The one-way analysis of variance testing difference between the log-transformed yearly means showed no significant difference among the years.Hakes Hake larvae, like mackerel and cunner, are confined to a relatively short period of occurrence. Historically, they have increased through June and July peaking in August and September, decreasing in October, and almost disappearing in November (Figure 3.2.1-4).- In 1987, larvae were not caught until August, with the peak abundance not coming until September, and with values for October and November higher than the overall means for those months. Seasonal mean abundance was highly variable among years, with the general trend suggesting relatively high abundances followed by two or three years of relatively low abundances (Table 3.2.3-9). The abundance in 1986 (0.1 larvae/1000 m 3) was the lowest value in the past twelve years. The 1987 3 abundance was higher (3.2 larvae/1000 m ), but was still below the overall mean of 4.4 larvae per 1000 cubic meters. A one way analysis of variance showed no significant difference among yearly means.139 hake 2.0 LU 2 0 08..1,-*1.5 1.0 0.5 i*-- OVERALL MEAN... .... 1987 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Atlantic herring 3 LU 00 OoW.2-- OVERALL MEAN 1987 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP QCT NOV CEC MONTH Figure 3.2.1-4.Mean and 95% confidence limits over all years and 1987 values, by 9 onth, for log-(x+l) transformed abundances (No./1000 m ) for hake and Atlantic herring larvae at stations P2 and P3, July 1975 through December 1987.Seabrook Baseline Report, 1987.140 Atlantic Herring Atlantic herring larvae typically occurred throughout most of the year, except during June through September when abundances were either-at or near zero (Figure 3.2.1-4)' January through May saw medium to low abundances, and October through.December exhibited the peak values. In 1987, herring followed a pattern similar to that in previous years except that January through May and November abundances were higher and October was lower than their overall monthly means. As is the case with most of the other selected species, herring larvae have a highly variable seasonal mean abundance (Table 3.2.1-9). The highest abundances occurred in 1975 and 1976 3 (197 and 145 larvae/1000 m respectively),'the lowest in 1978 (2.1 larvae/1000 m 3),"averaging 30.9 larvae per 1000 cubic meters over all years..3 The 1987 abundances (28.8 larvae/1000 m ) were only slightly below the overall mean. A one-way analysis of variance testing the differences among years found them to be significant (Table 3.2.1-10). The Waller-Duncan multiple comparison test showed' three large overlapping groups of 'years, with 1978 'abundances being significantly lower-than those in 1975, 1976, and 1986, and 1979 abundances being significantly lower than those in 1975,.Pollock Pollock larvae exhibited an abundance pattern similar to that of herring larvae, with large abundances in November through February and decreasing abundances from March through June (Figure 3.2.1-5). During July through October few if any larvae were present.. The abundance of pollock larvae in 1987 was very low during most months, with only November and May slightly above their overall means. Seasonal peak abundances for pollock were highly variable from year to year (Table 3.2.1-9), with increasing abundances followed by two or three years of. decreasing abundances. In 1987, the seasonal mean was not computed for pollock because its period of peak abundance which began in November would continue into 1988. However,' the 1986 data which were not included in last year's baseline report were the 141 pollock 2.0 LU o-n zc.CaY 1.5 1.0 0.5-OVERALL MEAN 1987 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP. OCT NOV DEC MONTH Figure 3.2.1-5.Mean and 95% confidence limits over all years and 1987 values, by Tonth, for log (x+l) transformed abundances (No./1000 m ) for pollock larvae at stations P2 and P3,.July 1975 through December 1987. Seabrook Baseline Report, 1987.142 lowest encountered during the 1975 through 1986 baseline period (1.2 larvae/3 1000 m ). This severe drop in abundance follows the relatively high abundance in 1984 of 22.8 larvae per 1000 cubic meters. The one-way analysis of variance among yearly log-transformed means showed the differences to be very highly significant (Table 3.2.1-10). The Waller-Duncan-multiple com-parison test of the yearly means showed three overlapping groups of years.*Abundances in 1976, 1979, and 1984 were significantly higher than in 1978,.1982, and 1986; and abundances in 1979 were also significantly higher than in 1977, 1981, and 1983.3.2.2 Adult Finfish 3.2.2.1 Total Community Temporal*Patterns in the Demersal Fish Community Otter trawl catch per unit of effort (CPUE) for all stations and species combined during the 1976 through 1987 period rose from 50 fish/ten-minute tow (fish/tow) in 1977 to a peak of 95 fish/tow in 1980 and 1981 (Figure 3.2.2-1). CPUE subsequently declined through 1985 when an average of'43 fish/tow were collected. The CPUE increased to 52 fish/tow in 1987, possibly indicating an increase in the 10w abundances recorded since 1981.Changes in the annual composition of the demersal fish community were compared using percent composition of the dominant trawl species. Six taxa accounted for nearly 80.percent of the trawl catch abundance for all years combined (Table 3.2.2-1). Yellowtail flounder comprised the largest percentage of the annual catch (20-36%) in all years except 1983 and 1984, when it ranked second below longhorn sculpin. Beginning in 1980, the per-centage of yellowtail flounder in trawl collections consistently declined.until 1984 when that species represented only 18 percent of the total annual catch' Percent contribution of yellowtail flounder increased to 27 percent in 1985 ending a five-year decline; but dropped again in 1986 (20%) and 1987 (19%) to a level approaching the 1984 low. Hake species (red, white and 143 0 120-100-STATION TI..... -STATION T2....... STATION T3 ALL STATIONS COMBINED I-0 I.IJ l-U IL 3 I-z I--0 80 60-:1 ..% *%.1 ..-'* 9.* * .9.I '9.* I **

• 9.9 I 9.I I I I .9.I 9.* I 9.I .9.I I I'.1 I 40-9.9.9.* 9. -9. ~ .99. *1 I 9. I 9. .I 9..-9.9. 1 9. *-..9..-0-zu I I I I I I 76 77 78 79 80 81 I I I I I 81 82 83 84 85 86 87 YEAR Figure 3.2.2-1. Catch per unit effort (mean number per 10 minute tow) of all species collected in otter trawls by year) station, and all stations combined, 1976-1987.

Seabrook Baseline Report, 1987. 0 TABLE 3.2.2-1. TOTAL PERCENT COMPOSITION BY YEAR AND ALL YEARS COMBINED FOR THE TWELVE MOST ABUNDANT SPECIES IN OTTER TRAWLS DURING 1976 THROUGH 1987 AT STATIONS T1, TZ AND T3 COMBINED. SEABROOK BASELINE REPORT. 1987.Lfn PERCENT COMPOSITION ALL YEARS 1976 1977 1978 1979. 1980 1981 1982 1983 1984 198S 1986 1987 COMBINED Yellowtail flounder 36 Z9 Z3 , 34 33 28 22 19 18 27 20 19 27 Hake speciesa 18 30 19 9 8 14 19 10 13 15 14 10 15 Longhorn sculpin 5 8 ,9 13 is 17 16 24 27 22 9 9 14 Winter flounder 5 8 9 7 iz 15 -9 8 7 9 10 11 9 Atlantic cod 4 3 14 14 9 6 7 8 5 3 3 6 7 Rainbow smelt 13 3 .10 7 4 6 5 9 .7 1 3 15 7 Skate species b 3 5 2 2 2 2 3 7 8 11 14 11 5 Atlantic whiting 6 3 4 3 1 3. 4 1 <1 <I 8 1 3 Ocean pout 2 4 3 2 1 2 2 3 5 3 3 3 3 Pollock <1. <1 <1 4 7 2 1 2 <l <1 2 <1 2 Windowpane 2 2 1 <1 3 z 2 5 7 5 7 8 3 Haddock 3 2 <1 3 4 <1 2 1, <1 <1 <1 <1 2 Other species 3 3 5 2 1 3 8 3 2 3 7 5 3 Number of other species (25) (22) (26) (25) (Z2) (27) (28) (26) (26) (20) (21) (25) (43)a.bancludes red, white, and spotted hakes includes big, little, and thorny skates spotted hake) were the second-ranked taxon in trawl collections and comprised 15% of the catch for all years combined. The percent composition of hake species was variable over the years (8-30%) and showed no consistent long-term trends. Longhorn sculpin comprised 14% of the catch for all years.combined, and accounted for an increasingly larger percent of the catch from 1976 (5%) through 1984 (27%). In 1986 and 1987, their percent contribution to the total catch fell back to pre-1979 levels (<l0%). Winter flounder ranked fourth in percent abundance over all years (9%) and ranged from 5 to 15% of the total annual catch. *The percentage of winter, flounder in otter trawl collections gradually increased from 7% in 1984 to 11% in 1987.Atlantic cod ranked fifth over all years, and accounted for an. average of seven percent of the total.catch. Cod percent contribution was highest in 1978 and 1979 (14% each year), and lowest in 1977, 1985 and 1986 (3% each year). The percent contribution increased to 6% in 1987, but was still below the 12-year average (7%). Rainbow smelt, the sixth ranked taxon, fluctuated between 15% (1987) and 1% (1985) of the total annual catch, averaging 6% over all years. Percent composition in 1987 was the highest during the study period, with 1976 (13%) ranking second.The number of fish species (species richness) collected annually in otter trawls ranged from 32 to 40 and totaled 55 for all years combined (Table 3.2.2-1). .Seasonal changes in the demersal community were examined in past years by numerical classification of the trawl catches (NAI 1982c). Samples were'classified into two major groups, reflecting a "winter community" (December through March) and a "summer community" (April through November). Rainbow smelt was the only species that was consistently more abundant in the winter throughout the study area. Catches of hakes and longhorn sculpins were substantially greater in the summer.146 Spatial Patterns in the Demersal Fish Community Mean annual catch per unit of effort was similar at the offshore stations (Ti and T3), while CPUE at the shallower nearshore station (T2) was much lower (Figure 3.2.2-1). Despite the differences, mean annual CPUE for the three stations followed the same long-term abundance pattern from 1976 through 1987. As discussed previously, CPUE for all stations was low in 1977. peaked in 1980 and 1981, declined to lowest levels in 1985, and began to gradually increase in 1986 and 1987.Otter trawl catches at the offshore stations (TI and T3) were dominated by yellowtail flounder, hakes, and longhorn sculpin. (Table 3.2.2-2). Collectively, these species comprised over 60% of the catch for all years combined at Stations T1 and T3. Of lesser importance at these stations were Atlantic cod, Atlantic whiting and skates. The most notable difference in percent composition between Stations Ti and T3 was that yellow-J tail flounder predominated at Station TI while longhorn sculpin was more abundant at Station T3. In addition, cod, skates, and ocean pout comprised a larger percentage of the total catch at Station T3. This and other smaller differences in species composition between Stations TI and T3 may be attribu-table to different. bottom substrates. Station T1 has a sandy bottom, while the. bottom substrate at Station T3 is sand, littered with small cobble and shell debris (NAI 1988). Yellowtail flounder prefer any sandy bottom (Bigelow and Schroeder 1953). Otter trawl catches at the nearshore station (T2) were dominated by winter flounder, yellowtail flounder, rainbow smelt, and pollock, comprising 67% of the catch for all years combined. Hake and sculpin comprised a much smaller percentage at Station T2 than at Stations T1 and T3 while the opposite was true of winter flounder, rainbow smelt and pollock.Temporal Patterns in the Pelagic Fish Community Catch per unit of effort for gill nets (one 24-hour set) combined for all species showed a pattern somewhat similar to otter trawl catches 147 TABLE 3.2.2-2.TOTAL PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN OTTER TRAWLS, ALL YEARS COMBINED (1976-1987). SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION SPECIES T1 T2 T3 Yellowtail flounder 39 14 21 Hake speciesa 16 10 16 Longhorn sculpin 12 5 22 Atlantic cod 5 5 10 Rainbow smelt 5 17 3 Winter flounder 6 26 5 Atlantic whiting 4 1 3 Windowpane 4' 4 2 Skate species 3 2 8 Pollock 2 7 1 Ocean pout I' 3 4 Haddock 1 <1 3 Other species 2 5 2 Number of other species (42) (33) (38)a inlds includes red, white, and spotted hakes bincludes big, little, and thorny skates 148 (Figure 3.2.2-2). CPUE rose to a peak in 1980 of 29 fish/net and subse-quently declined to lowest levels in 1985 of 3 fish/net. In 1987 CPUE remained low and was virtually identical to levels encountered in 1984.Sampling frequency for gill nets has been less in recent years, and this change may have impacted the catch statistics. The pattern was not as.distinctive as with trawls, in that annual CPUE only ranged from 3 to 16 .with the exception of the 1980 peak. In addition, the gill net, peak catch occurred onlyduring 1980, while the trawl peak spanned both 1980 and 1981.The high 1980 CPUE for gill nets wa s due to unusually high catches of Atlantic herring and pollock (NAI 1981e).Atlantic herring ranked first in gill net collections during every year sampled, comprising from 25 to 82 percent of the total annual catch and averaging 63 percent for all years combined (Table 3.2.2-3). The percent'contribution of Atlantic herring to the annual gill net catch was highest in 1978, 1979 and 1980 (74, 80, and 82%, respectively) and lowest in 1984, 1985, and 1986 (26, 25 and 33%, respectively).- During all other years, Atlantic herring ranged from 44 to 63% of the total annual catch. In 1987 the percent of total annual catch for Atlantic herring (52%) was below the 12-year average. Atlantic whiting, blueback herring, pollock, and Atlantic mackerel collectively comprised 27% of the gill net catch for all years combined.These taxa were fairly consistently ranked among the top five dominant taxa during the 12-year period. Blueback herring, which ranked second in percent composition for 1987, was 16% of the total annual catch, the highest level during the 12-year period. Lower ranked taxa (e.g., alewife, Atlantic menhaden, hakes, rainbow smelt and Atlantic cod) comprised a more important portion of the total annual catch during 1984,' 1985 and 1986 when catch abundances were below normal and Atlantic herring accounted for a smaller percentage-of the total annual catch. In 1987 none of these species comprised more than 3% of the total annual catch. Species richness ranged from 19 to 31 species annually and totaled 47 for all years combined, with 1987 exhibiting the lowest value (19) in the past 11 years (1976-1986). No long-term trend of increasing or decreasing species richness was evident.149 50 40 I-0 U-LL w I-z w U-,3:_.)30 20 Ln 0 10 0 76 -77 78 79 80 81 82 83 84 85 86 87 YEAR Figure 3.2-2.2.Catch per unit effort (number per 24 hour set of one net, surface or bottom)of all species combined in gill nets by year, station, and all stations combined 1976-1987. Seabrook Baseline Report, 1987. 0 TABLE 3.2.2-3. TOTAL PERCENT COMPOSTION BY YEAR AND ALL YEARS COMBINED FOR THE TEN MOST ABUNDANT SPECIES IN GILL NET SAMPLES DURING 1976 THROUGH 1987 AT STATIONS G,. GZ AND G3 COHINED. SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION ALL YEARS 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 CO3MINED Atlantic herring 53 48 74 80 82 45 63 44 26 25 33 5z 63 Atlantic whiting 17 21 2 4 6 S 7 1 5 2 1 5 8 Blueback herring 5 11 14 2 2 2 10 12 9 9 15 16 8 Pollock 6 4 1 2 5 18 4 12 10 22 18 6 6 Atlantic mackerel 12 7 2 2 2 14 5 5 6 10 5 7 5 Alewife 2 2 <1, .<I 2 2 4 5 6 3 .2 2 Atlantic menhaden C1 3 <1 2 <1 <1 1 11 5 6 5 2 2 Hake speciesa 2 2 <1 1 <1 4 1 1 7 2 2 <1 Rainbow smelt I 1 <1 1 <1 <1 <1 1 6 2 4 3 1 Atlantic cod 1 <1 <1 <1 <1 <1 2 3 <1 2 2 1 Other species 2 <1 3 5 1 8 5 7 18 16 12 4 3-Number of other species (10) (16) (14) (13) (13) (19) (21) (18) (20) (14) (14) (9) (37)a includes red, white and spotted hake tn Seasonality of pelagic species was analyzed in previous reports (NAI 1982c;1983b). Two distinct sample groups were observed based on abundances of the dominant species: "summer"! (June-August) and."winter" (September-May). Atlantic mackerel and Atlantic whiting were more abundant in summer samples, while Atlantic herring were more numerous in winter catches. In 1987 the two summer dominants were more abundant in September and October, usually characterized as '-winter" months. Blueback herring and pollock showed inconsistent seasonal differences in abundance from 1976 through 1987.Spatial Patterns in the Pelagic Fish Community Mean annual catch per unit of effort at the three gill net Stations Gl, G2 and G3 showed similar fluctuations across years. (Figure 3.2.2-2).Mean annual CPUE peaked in 1980' at all stations. This peak was more evident at Stations G2 and G3 than at Station G1. Percent composition 'for the dominant species in gill net collections was similar among stations (Table 3.2.2-4). Atlantic herring was the dominant species at each gill net, sta-tion, accounting for 58 to 69 percent of the total catch for all years combined.. Blueback herring comprised a-larger percent of the total catch at G3 (10%) than at G1 or G2 (6% at each station). Also numerically important at each station were Atlantic whiting, Atlantic mackerel and pollock; each comprising, from 4 to 9 percent of the catch at the three stations for all years combined.Depth differences in species composition were analyzed by comparing percent composition in surface nets to that in off-bottom nets (3 m above the bottom) for all years combined (Table13.2.2-5). Atlantic herring was the dominant species in collections at both depths, with a slightly higher percent contribution in surface nets compared to off-bottom nets. The proportions of blueback herring and Atlantic mackerel were also higher in surface nets. Atlantic whiting, pollock, and hakes comprised a larger percent of the catch in the off-bottom nets. Atlantic menhaden and alewives 152 TABLE 3.2.2-4.TOTAL PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN GILL NETS, ALL YEARS AND DEPTHS COMBINED (1976-1987). SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION SPECIES Gi G2 G3 Atlantic herring 62 69 58 Atlantic whiting 8 6 .9 Blueback herring 6 6 10 Atlantic mackerel 5 4 5 Pollock 6 5 6 Hake speciesa 2 1 Atlantic menhaden 2. 1 2 Alewife 2 2 2 Rainbow smelt 1 1 1 Longhorn sculpin 1 1 <1 Atlantic cod 1 1 1 Bluefish 1 1 <1 All other species 3 2 3 Number of other species (25) (28) (25)1.aincludes red, white and spotted hakes 153 TABLE 3.2.2-5.TOTAL PERCENT COMPOSITION OF DOMINANT GILL NET SPECIES ACCORDING TO DEPTH (SURFACE AND OFF-BOTTOM), ALL YEARS COMBINED (1976-1987). SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION SPECIES SURFACE OFF-BOTTOM Atlantic herring 69 56 Blueback herring 10 5 Atlantic mackerel 7 3 Atlantic whiting 5 11 Atlantic menhaden 2 1 Alewife 2 1 Pollock 1 12 Rainbow smelt 1 1 Hake speciesa- <1 3 Other species 2 7 aincludes red, white, and spotted hakes 154 accounted for a similar percentage in both surface and off-bottom nets.'Trends in 1987 were similar to those encountered during the'past eleven years. Since 1980, mid-water nets have been set in addition to the surface and off-bottom nets during February, June and October. Comparison of CPUE among surface, mid-water and off-bottom nets on dates when all three nets were fished revealed that Atlantic menhaden was the only speciesthat was slightly more abundant in mid-water catches than in surface or off-bottom catches (Table 3.2.2-6). As was observed with the regular surface and off.-bottom gill net collections, Atlantic herring and Atlantic mackerel were most abundant in surface nets and least abundant in off-bottom nets. Blue-'back herring were also most abundant in surface nets but were least-abundant in off-bottom nets, and intermediate in abundance in mid-water nets.'Atlantic whiting, pollock, and rainbow smelt were most abundant in bottom nets. The alewife showed no depth preference, with low CPUE values (<l/net)at each depth. In 1987, Atlantic herring was most abundant in the off-bottom nets, intermediate in abundance in the mid-water nets and least abundant in surface nets, for those dates when all three nets were fished. Since all three nets were fished only three times during the year and since surface" nets showed a higher abundance than off-bottom nets throughout the rest of the year, the higher bottom-net abundance is probably due to chance variation. Temporal Patterns in the Estuarine Community Catch per unit of effort for seine stations combined for all species ranged from 60 to 362 fish/haul (Figure 3.2.2-3). Seine CPUE values were lower during the period 1982 through 1986 (60 to 114 fish/haul) than during the period 1976 through 1981 (200 to 362 fish/haul). Annual varia-.tions in beach seine CPUE were influenced primarily by annual catches of the Atlantic silverside,. which was the -most abundant species in seine collections each year (Table 3.2.2-7). The percent contribution of silversidesto the.total annual seine catch ranged from 47 to 88.percent annually. Atlantic silverside contributed 56% of the total annual catch in 1987, somewhat lower 155 TABLE 3.2.2-6.CATCH PER UNIT EFFORT a BY DEPTH FOR THE DOMINANT GILL NET SPECIES OVER ALL STATIONS AND DATES WHEN SURFACE, MID-DEPTH AND BOTTOM NETS WERE SAMPLED, 1980 THROUGH 1987. SEABROOK BASELINE REPORT, 1987.CATCH PER UNIT EFFORT SPECIES SURFACE MID-DEPTH BOTTOM Atlantic herring 6.3 3.5 2.3 Atlantic whiting 0.2 0.6 0.8 Atlantic mackerel 0.9 0.4 0.4 Pollock 0.2 0.1 1.1 Alewife <0.1 <0.1 <0.1 Blueback herring 1.1 0.4 0.3 Atlantic menhaden 0.6 0.7 0.2 Rainbow smelt <0.1 <0.1 0.1 1.a number per one 24-hour set of one net (surface, mid-depth or bottom),1 156 .1 700-600.-500-STATION Si STATIONS2 I.-0 LL LL LU, I-X Qc 400-....STATION $3-ALL STATIONS COMBINED* ",. .* * * ** S 300 -200 -100-0 I I I I I I I a 75 76 77 78 79 80 81 82 83 8 8 84 87 YEAR Figure 3.2.2-3.Catch per unit effort (mean number per seine haul) of alispecies collected in beach seines by year, station and all stations combined 1976-1984 and 1987.Seabrook Baseline Report, 1987. TABLE 3.2.2-7. TOTAL PERCENT COMPOSITION BY YEAR FOR THE TEN MOST ABUNDANT SPECIES COLLECTED IN BEACH SEINES DURING 1976 THROUGH 1987 (EXCLUDING 1985 AND 1986) AT STATIONS S1, S2 AND S3 COMBINED. SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION ALL YEARS 1976 19.77 1978 1979 1980 1981 1982 1983 1984 1987 COMBINED Atlantic silverside 74 55 75 60 68 88 57 47 48 56 67 Fundulus-speciesa 2s 23 5 3 4 2 10 8 7 3 8 Pollock. <1 <1 1 8 21 <1 7 5 1 2 5 Alewife <1 I <1 18 <1 <1 I <1 <1 <1 4 Rainbow'smelt 4 5 <1 5 <1 2 5 4 9 8 3 American: sand lance 2 9 8 <1 <1 <1 8 2 <1 0 3 Atlantic herring <1 <1 5 <1 4 f4 <1 7 8 2 3 Ninespia stickleback 1 4 1 <1 <1 <1 2 7 16 22 3 Hinter flounder <1 2 2 2 3 1 6 3 3 2 2 Blueback herring <1 Cl ,l I <1 <1 <1 14 <1 0 2 Other species 3 <1 .2 <2 2' 4 3 7. 4 <1 Number of other species (11) ( (17) (14) (12) (9) (12) (12) (13) (14) (12) (34)aincludes'mummichogs and striped killifish 00 than the average for all years combined (67%). Also important numerically were Fundulus species (primarily mummichog),. which consistently accounted for more than one percent of the catch (1-23% annually) and ranked among the top five dominant taxa in all years. All other species collected in seines fluctuated from year to year in their ranking and often comprised less than 1% of the total annual catch.. The total number of species collected per year ranged from 19 in 1980 to 27 in 1977. Data for the estuarine fish community for the years of 1985 and 1986 were not included in this year's report.Beach seines were not collected in 1985 and sampling effort was reduced in 1986 (no sampling in April, May and June).Seasonality of the estuarine fish community was analyzed previously using numerical classification (NAI 1983b, 1984b). The estuarine community was highly seasonal in all years, and all three seine stations exhibited similar seasonal changes in their fish assemblages. Catches in the spring were usually characterized by low abundance, and-species composition in early summer was highly variable among years. The most distinct group was the late summer-fall assemblage, which occurred yearly from August-November, and in which Atlantic silverside was the overwhelming dominant (NAI 1984b).Spatial Patterns in the Estuarine Fish Community Mean annual catch per unit of effort during the period 1976 through 1983 was usually highest at Station S3 and lowest at Station S1 (Figure 3.2.2-3). During 1984 and 1986, when catches were small relative to earlier years, mean annual CPUE was similar among the three stations, with Atlantic silverside. the dominant species at each station (Table 3.2.2-8). Stations S1 and S2 were comparable in their overall species composition, with silversides comprising 55 and 66% of the total catch (respectively) for all years com-bined and Fundulus sp. comprising 13% and 15% respectively. These stations were distinguished from each other and from Station S3 by a relatively/high proportion of blueback herring at Station Sl (6%) and American sand lance at Station S2 (4%). Atlantic silverside comprised a larger percentage of the 159 TABLE 3.2.2-8. TOTAL PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN BEACH SEINES,-ALL YEARS COMBINED, APRIL THROUGH NOVEMBER (1976-1984, 1987)., SEABROOK BASELINE REPORT, 1987.PERCENT COMPOSITION SPECIES s1 S2 S3 Atlantic silverside 66 55 77 Fundulus speciesa 13 15 <1 American sand lance 4 3 2 Blueback herring 6 <1 1 Ninespine stickleback 3 1 3 Atlantic herring 2 5 1 Winter flounder 2 1 3 Pollock 1 6 5 Gasterosteus speciesb 1 1 1 Alewife 1 10 <1 Rainbow smelt 1 1 6 Smooth flounder <1 <1 <1 All other species <1 <1 <1 Number of other species (22) (19) (25)bincludes mummichog and striped killifish includes threespine and blackspotted sticklebacks 160 catch at Station S3 (77%) than at Stations S1 and S2, and mummichogs accounted for a much smaller percentage (<1%). Because, of its proximity to.the harbor mouth, salinity, readings were higher at Station S3 than at Sl and S2 (NAI 1981). Fundulus species prefer a more brackish environment, explaining the larger numbers caught at S1 and S2 than at S3. Rainbow smelt, a species which prefers a more saline environment, accounted .for a larger percentage of the catch at Station S3 (6%) than at either Station Sl or S2 (1% for each station). Station S3 was also distinguished by a higher species richness (37) than at S2 (31) and Si (34). Trends in 1987 were similar to those encountered in previous years (NAI 1988).3.2.2.2 Selected Species General Species selections for examination of seasonal, annual, and spatial variations in abundance were determined by the following two criteria: high abundance in at least one life stage and gear type, and importance in local commercial or sport fisheries. The nine species selected and their primary collection methods were: Species Gear Type Atlantic herring, Atlantic mackerel Pollock.Atlantic cod Hakes (red, white and spotted)Yellowtailflounder Winter flounder Rainbow smelt Atlantic silverside gill nets gill nets gill nets otter trawl otter trawl otter trawl otter trawl and beach seine otter trawl and beach seine beach seine trends in of effort Comparison of yearly mean catches per unit of effort revealed population size, while comparison of monthly mean catches per unit provided additional information on seasonal cycles. Seasonal and 161 annual variability were then used to examine spatial and temporal differ-ences. Size-structure of fish populations also yields important information on age classes that use the area and supplies information on recruitment patterns. This information was examined thoroughly in the 1984 Baseline Report (NAI 1985b).Pelagic Species Atlantic Herring Atlantic herring were typically collected in high numbers during the spring and fall (Figure 3.2.2-4), with gill net CPUE values greatest March through May and October through December. The 1987 data generally followed-the overall mean with one exception, CPUE for January 1987 was higher than the overall mean. -Annual geometric mean CPUE of Atlantic herring rose from 1976 (3.4 fish/net) through 1978 (4.9 fish/net), leveled off through 1980 (4.2/net), and then declined steadily through 1985 (0.6/net), the lowest levels observed during the program (Table 3.2.2-9). Annual mean CPUE increased slightly in 1986 and 1987 (0.8 and 1.2 respectively)-but were still below the average mean for all years. A one-way analysis of variance showed significant differences in the yearly log transformed mean CPUE (Table 3.2.2-10). The Waller-Duncan K-ratio t-test for multiple comparison showed that 1978 and"1980, the years with the largest CPUE, were significantly different from 1984-1986, and that 1977 CPUE was significantly higher than that in 1985.Pollock Pollock gill. net catches were highest during spring and late fall,, and lowest during winter (Figure 3.2.2-4). The high catches in the springýand late fall reflected the inshore-offshore movement pollock undergo each.year.. CPUE for April, May and August in 1987 were lower than the overall mean CPUE. The low values might have been due to the fact that the gill nets 162 ATLANTIC HERRING Lu w 0.z 0 U-U, z I-n--OVERALL MEAN.. .,. 1987 1.0 0.5 JAN OCT NOV DEC MONTH POLLOCK w 0.C.)z.4 0-j 0.5 0.4 0.3 0.2 0.1 0.0-I OVERALL MEAN....... 1987 MEAN JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-4.Mean and 95% confidence limits over all years and 1987.values, by month, for log (x + 1) transformed catch per unit effort (one 24-hr. set) for Atlantic herring and Pollock at combined gill net stations Gl, G2 and G3 from 1976-1987. Seabrook Baseline Report, 1987.163 TABLE 3.2.2-9. ANNUAL GEOMETRIC MEANa CPUE FOR SEABROOK BASELINE REPORT, 1987.SELECTED FINFISH SPECIES.CONFIDENCE YEAR MEANb OVER INTERVAL, SPECIES STATION 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 ALL YEARS LONER UPPER Winter TI 1.27 3.11 2.82 2.53. 5.32 6.43 4.39 3.39 Z.71 3.24 4.60 4.99 3.53 3.12 3.98 flounder. TZ 3.79 4.87 7.18 8.90 17.49 17.10 9.55 7.72 5.50 5.65 3.71 4.32 7.16 6.04 8.45 T3 1.32 1.72. 3.Z0 Z.08 5.13 4.11 2.75 2.52 2.-26 1.08 2.56 4.47 2.58 2.22 2.99 T1-T3 Z.55 3.52, 4.91 4.81 10.33 10.Z6 6.41 4.85 3.73 3.58 4.04 4.87 4.95 4.39 5.56 S1-S3 1.87 3.60 3.06 4.98 5ý68 2.96 Z.94 1.90 2.88 Sc ID 1.00 2.87 2.38 3.43 Yellowtail Ti 33.50 26.34 18.88 33.54 44.88 40.47 ZZ.13 18.03 15.73 14.82 14.51 13.36 22.74 Z0.30 25.45 flounder T2 4.21 Z.58 1.78 4.73 7.05 4.67 5.Z8 2.62 1.03 2.91 1.83 2.62 3.17 Z.56 3.89 T3 20.57 12.50 13.12 21.82 27.68 17.98 10.31 8.Z7 7.66 8.40 4.83 7.53 11.92 10.59 13.41 TI-T3 20.50 14.19 11.76 21.50 28.39 23.01 14.68 11.31 8.66 9.87 8.01 8.93 13.90 12.62 15.30 Hake species Ti 6.77 7.57 6.63 3.82 .4.49 7.27 6.43 3.48 3.61 3.20 4.19 3.22 4.84 3.67 6.30 TZ 1.91 3.08 3.17 1.07 2.11 3.68 2.3Z 1.39 Z.40 1.01 2.36 1.38 2.07 1.58 2.65 T3 4.32 6.48 5.50 3.49 3.81 8.85 5.93 3.41 3.57 3.43 3.24 3.69 4.44 3.36 5.79 TI-T3 4.63 6.31 5.73 3.12 3.97 7.94 5.32 3.37 3.87 2.98 4.00 3.26 4.37 3.40 5.57 Atlantic cod Ti 1.83 .1.26 3.77 4.04 4.4Z 4.30 3.96 3.98 2.11 0.94 1.03 2.16 2.56 2.11 3.08 T2 0.33 0.30 1.30 2.00 1.47 1.50 1.75 0.81 0.60 0.14 0.55 0.71 0.88 0.ý6 1.13 T3 3.07 1.47 9.74 6.29 8.63 5.98 4.67 6.29 3.33 0.90 1.55 3.59 3.94 3.20 4.81 T1-T3 1.96 i.i1 5.40 5.21 5.72 4.51 3.90 4.14 2.19 0.81 1.16 2.50 Z.84 2.36 3.37 Rainbow smelt Ti 1.88 0.71 1.67 1.23 1.00. 1.10 0.92 1.41 0.89 0.30 0.63. 2.30 1.10 0.74 1.54 T2 2.26 0.94 4.63 1.73 1.60 2.48 1.21 2.89 1.69 0.64 1.34 3.28 1.89 1.33 Z.58 T3 1.59 0.74 1.15 1.07 0.80 0.44 0.72 0.37 0.48 0.37 0.38 1.03 0.73 0.48 1.01 T1-T3 Z.1z 0.85 2.92 1.58 1.33 1.75 1.06 1.56 1.11 0.54 0.86 Z.47 1.42 1.01 1.9z S1-S3 1.93 1.74 0.11 3.29 0.06 1.35 1.45 1.47 Z.20 HS ID 0.61 1.22 0.67 1.95 Atlantic G1-G3 3.43 3.62 4.89 2.84 4.Z3 1.75 1.71 1.75 0.65 0.58 0.84 1.Z5 2.00 1.50 2.59 herring Atlantic G1-63 0.60 0.49 0.21 0.13 0.36 0.52 0.25 0.33 0.19 0.27 0.15 0.24 0.30 '0.2z 0.40 mackerel Pollock- GI-G3 0.35 .0.37 0.15 0.19 0.99 0.87 0.20 0.68 0.38 0.47 0.74 0.23 0.44 0.34 0.56 Atlantic S1-S3 31.08 18.07 29.54 26.70 18.03 24.77 7.33 12.94 9.40 MS ID .9.92 .16.89 9.54 29.36 isilverside A) OTTER TRAWL (T) imean catch per tow per month at each station and mean of all stations.GILL NET (G) mean catch per 24 hour set of either level (surface orbottom) per month, a mean for all stations.SEINES (S) mean catch per haul per month, a mean for all stations.b) Otter Trawl (T) mean of 138 months; Gill Net (G) mean of 143 months; Seines (S) mean of 80 months.c) MS = not sampled.d ID = Insufficienti data for comparison with previous years (April -June not sampled) e TABLE 3.2.2-10.RESULTS OF ONE-NAY ANALYSIS OF VARIANCE AMONG YEARS OF LOG (x+l) TRANSFORMED CATCH PER UNIT EFFORT FOR SELECTED FINFISH SPECIES FOR ALL GILL NET STATIONS COIMBINED DURING ý1976-1987. SEABROOK BASELINE REPORT, 1987.SOURCE OF SPECIES VARIATION df SS F MULTIPLE COMPARISONS Atlantic herring Years 11 5.16 2.24'* 78 80 77 76 79 81 83 82 87 86 84 85 Error 131 Z7.38 Total 142 32.54 Atlantic mackerel Years 11 0.32 0.8 6 NS Error 131 4.43 Total 14Z 4.75 Pollock Years 11 0.87 Z.ZZ 80 81 86 83 85 84 77 76 87 82 79 78ýError 131 4.66 Total 142 5.53 , .U, NS = not significant (p > 0.05)= significant (0.05 2 p > 0.01)** highly significant (0.01 p > 0.001)= very highly significant (p : 0.001) were only set once a month for two days, thus decreasing the chances of the fish being encountered. Annual mean CPUE (all stations combined) for pollock varied from 0.2 to 1.0 fish/net and averaged 0.4 fish/net over all years (Table 3.2.2-9). The 1987 mean CPUE of 0.2 fish/net was one of the lowest encountered during the study period. A one-way analysis of variance showed a significant difference in the log-transformed CPUE among years (Table 3.2.2-10). Waller-Duncan's multiple comparison revealed that 1982, 1979, and 1978, the years with the lowest CPUE, were'significantly different from 1980 and 1981, and that the 1987 CPUE was significantly lower than that in 1980 (the highest year).Atlantic Mackerel Atlantic mackerel were present in gill net collections primarily from May to November with low CPUE January through April (Figure 3.2.2-5).Following a gradual increase in abundance May through July, monthly mean CPUE leveled off and remained at similar levels through November. In July and.August of 1987, no Atlantic mackerel were caught, which may have been due to the infrequency of the gill net collections. Catches in September and October were greater than their overall means. Catches for mackerel were variable over the years, with mean CPUE ranging from 0.1 to 0.6 fish/net, and averaging 0.3 fish/net (Table 3.2.2-9). The one-way analysis of variance showed no significant differences among yearly means of log-transformed data (Table 3.2.2-10). Demersal Species Atlantic Cod Atlantic cod were usually present in otter trawl catches throughout the year, with the highest catch per unit of effort (CPUE) in April, May and October through December (Figure 3.2.2-5). The 1987 monthly CPUE at T2 166 ATLANTIC MACKEREL z 0.z 0 U.(I)z 0-j 0.5 0.4 0.3 0.2 0.1 0.0 1.2-1.0-0.8-0.6-0.4-0.2-0.0*OVERALL MEAN------ 1987 JAN MAR APR MAY JUN JUL AUG SEP OCT MONTH ATLANTIC COD-- OVERALL MEAN 1987 (no Oc Data)JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-5.Mean and 95% confidence limits over.all years, and 1987 values, by month,'for log (x + 1) transformed catch per unit effort (one 24-hr. set for gill nets, one 10-mmn.tow for otter trawl) for Atlantic mackerel at combined gill net stations G1, G2 and G3 and Atlantic cod at otter trawl station T2, 1976-1987. Seabrook"Baseline Report, 1987.167 followed this trend, with peaks in May and December and low periods of abundance in February and March and June through August. No October data were collectedin 1987 at T2. because lobster pots in that area prevented trawling. In addition, no cod were collected in November, generally a peak period for this species. Length-frequency data analyzed in past years showed that the spring peak was primarily comprised of immature (age one and two)cod, while the fall peak consisted of young-of-the-year (age 0) to age five (NAI 1985). The annual mean CPUE (geometric mean averaged over the three stations) for cod rose from 1.1 fish/tow in 1977 to greater than 5.2 fish/tow from 1978 through 1980 (Table 3.2.2-9). Mean CPUE gradually declined from 1981 through 1985, the lowest level recorded during the study (0.8 fish/tow). However, mean CPUE increased in 1986 and 1987 (1.2 and 2.5 fish/tow, respec-tively.), indicating a possible reversal in the low abundances. A one-way analysis of variance revealed very highly significant differences among years at Station T1 (Table 3.2.2-11). The Waller-Duncan multiple comparison test showed that 1978 through 1983, the years of high abundance were significantly different from 1977, 1985 and 1986, the years of low abundance. Hakes Hake species (red, white and spotted) were present in high numbers at Station T2 from March through November, and in low numbers from December through February (Figure 3.2.2-6). Hake CPUE increased slowly in March through May, reaching a peak in June through October and then decreased in November. In 1987, mean CPUE followed this general trend. Although catches in May. and June were lower than usual, CPUE from July through September were greater than the mean CPUE for all years. Annual mean CPUE. (all three stations combined) ranged from 7.9 fish/tow in 1981 to 3.0 fish/tow in 1985, averaging 4.4 fish/tow overall (Table 3.2.2-9). In 1987, mean CPUE (3.3 fish/tow) was lower than the 12-year mean. The results of a one-way analysis of variance showed no significant differences in catch among years (Table 3.2.2-11).. 168 FHAKES CL 0~C.)z LU+0 cU 0 U-in-I.cc C, 0'-J CL Q 0..z LU 0 LL C,)z c-0.J 1.2 1.0 0.8 0.6 0.4 0.2 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH YELLOWTAIL FLOUNDER OVERALL MEAN 1987 (no Oct data)1.0 0.8 0.6 0.4 0.2 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV. DEC MONTH Figure 3.2.2-6.Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x + 1) transformed catch per unit effort (one 10-min. tow) for hakes and yellowtail flounder at otter trawl station T2, 1976-1987. Seabrook Baseline Report, 1987.169 TABLE 3.2.2-11. RESULTS OF ONE-NAY ANALYSIS OF- VARIANCE AMONG YEARS OF LOG (x+l) TRANSFORMED CATCH PER UNIT EFFORT FOR SELECTED FINFISH SPECIES AT OTTER TRAWL STATION Ti DURING 1976-1987. SEABROOK BASELINE REPORT, 1987.SOURCE OF'SPECIES VARIATION df SS F MULTIPLE COMPARISONS Winter flounder Years 11 2.56 4.86* 81 80 87 86 82 83 85 77 78 84 79 76'Error 132 6.31 Total 143 8.87 Yellowtail flounder Years 11 4.18 6.71 80 81 79 76 77 82 78 83 84 85 86 87 Error 132 7.48 Total 143 11.66 Hakes Years 11 1.98 0.5NS Error 132 47.72 Total 143 49.70 Atlantic cod Years* 11 3.94 3.32 80 81 79 83 82 .78 87 64 76 77 86 85 Error 13Z 14.23 Total 143 18.17 l Rainbow smelt Years 11 1.69 0.61HS Error 13Z 33.17 Total 143 34.86 NS = not significant (p > 0.05)= significant (0.05 : p > 0.01)*- = highly significant (0.01 k p > 0.001)= very highly significant (Op : 0.001)-.C Yellowtail Flounder Yellowtail flounder were collected year round in otter trawls at Station T2 (Figure 3.2.2-6) with monthly CPUE lower in June through September than in October through May. During June, August, and September of 1987, yellowtail CPUE was zero, well below the mean CPUE for these months over all years. No October data were collected in 1987 due to lobster pots in the trawling area. No distinct seasonal differences were noted for Stations TI and T3 (NAI 1986). Analysis of length-frequency data in previous years revealed the majority of individuals collected at Station T2 were young-of-the-year fish (< 18 cm) and were most abundant during November through March (NAI 1984). The low summer CPUE at T2 probably reflects the movement of these young-of-the-year fish to other areas. Annual mean CPUE (all three stations combined) ranged from 28.4 fish/tow in 1980 to 8.0 fish/tow in 1986.In 1987 CPUE increased slightly (8.9 fish/tow) but was still below the over-all year mean of 13.9 fish/tow (Table 3.2.2-9). Mean CPUE was greatest J at Station TI (22.7 fish/tow), intermediate at Station T3 (11.9 fish/tow) and lowest at Station T2 (3.2 fish/tow). The one-way analysis of variance among years was very highly significant, and Waller-Duncan's multiple comparison of yearly means showed six overlapping groups with 1987 CPUE significantly lower than in six of the 11 previous years (Table 3.2.2-10). Demersal and Estuarine Species Winter Flounder Winter flounder were present in otter trawl collections year-rqund, though not always at all three stations (NAI 1986). No distinct seasonal trend was apparent at Station T2, except mean CPUE was lowest in December and January (Figure 3.2.2-7). In 1987, CPUE for November, December and February were all below the overall mean. No October data were collected in-1987 due to lobster pots in the trawling area. Annual mean CPUE (all three stations combined) increased from a low of 2.6 fish/tow in 1976 to 10.3 fish/tow in -174 WINTER FLOUNDER (TRAWLS)z x a 0 LL (1)z F-0 0-j 1;4 -1.2-1.0-0.8-0.6-0.4-0.2-0.0*'~'~~".s I-OVERALL MEAN 1987 (no Oct data)I I I I , I I I .I JAN FEB MAR APR MAY JUN JUL AUG I I I SEP OCT NOV C MONTH WINTER FLOUNDER (SEINES)I 0.LU z 0U 0 U-1.0-0.8-0.6-0.4-0.2-0.0-'1.. 0 IA i I- i J A I O APR MAY JUN JUL AUG SEP OCT NOV MONTH Figure 3.2.2-7. Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x +.1) transformed catch per unit effort (one 10-min. tow for otter trawls andone haul for beach seines) for winter flounder at otter trawl station T2 1976-1987 and combined beach seine stations Sl, S2 and S3 1976-1984 and 1987. Seabrook Baseline Report, 1987.172 1980 and 1981, averaging 4.9 fish/tow over the 12-year period (Table 3.2.2-9). Annual mean CPUE declined from 1982 through 1985 but increased in 1986 and 1987 to present levels of 4.9 fish/tow. Mean CPUE values were highest at T2 (7.2 fish/tow) followed by Station Tl (3.5 fish/tow) and Station T3 (2.6 fish/tow). Results of the one-way analysis of variance among years was very highly significant (Table 3.2.2-11). The multiple comparisons of yearly catches.showed 1976 was significantly lower than all other years.Winter flounder were' also present. in beach seine collections from the Hampton-Seabrook estuary throughout the April through November sampling period (Figure 3.2.2-7). In 1987, monthly mean CPUE was much lower than.average for all months except June and August. Annual mean CPUE (all three stations combined) ranged from 1.0 fish/tow in 1987 to 5.7 fish/tow in 1980, with an average of 2.9 fish/tow (Table 3.2.2-9).. A one-way analysis of variance among years was highly significant, and the multiple comparisons of yearly catches showed 1980 and 1979 to be significantly higher than 1976, 1983, and 1987, and 1987 CPUE to be significantly lower than that in all years except 1976 and 1983 (Table 3.2.2-12). Beach seines were not collected in 1985 and insufficient data were collected in 1986 to use in this comparison. Rainbow Smelt Rainbow smelt were collected in otter trawls primarily during December through March (Figure 3.2.2-8). In 1987, monthly mean CPUE followed this same pattern except catches in November and December were higher than normal. Annual mean CPUE (all three stations combined) ranged from 2.9 fish/tow in 1978 to 0.5 fish/tow in 1985, averaging.1.4 fish/tow overall (Table 3.2.2-9). In 1987, mean CPUE (2.5 fish/tow) increased over 1986 values (0.9 fish/tow) indicating-a possible reversal in the low abundances experienced in 1985. Mean CPUE was greatest at Station T2 (1.9 fish/tow). followed by Station T1 (1.1 fish/tow).and Station T3 (0.7 fish/tow). Results of a one-way analysis of variance showed no significant differences in catch among years (Table 3.2.2-11). 173 TABLE-3.2.2-12. RESULTS OF'OHNE-WAY. ANALYSIS OF VARIANCE AMONG YEARS OF LOG (xt1) TRANSFORMED CATCH PER UNIT EFFORT FOR .SELECTED FINFISH SPECIES FOR ALL BEACH SEINE STATIONS COMBINED DURING 1976-1984 AND 1987.SEABROOK BASELINE REPORT, 1987.SOURCE OF SPECIES VARIATION df SS F MULTIPLE COMPARISONS Winter flounder Years 9 1.71 3.44 80 79 77 78 81 82 84 83 76 87 Error 70 3.86 Total 79 5.56 Rainbow smelt Years 9 2.79 1.02S Error 70 21.32 Total 79 24.11 NS Atlantic silversides Years 9 3.23 0.31 Error 70 80.98 Total 79 84.21 NS = not significant (p > 0.05)= significant (0.05 2 p > 0.01)= highly significant (0.01 p > 0.001)= .very highly significant (p : 0.001)p. RAINBOW SMELT (TRAWLS)LU 0.0 D z UJ 1-a W 0 IL z-j 2.2 2.0 1.8 1.6 1.4-OVERALL MEAN 1987 (no Oc data)0.A JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH RAINBOW SMELT (SEINES)LU n 9-0 z LU LU 0 I.(n z I-C, L 0: O1 1.8 1.6 1.4-OVERALL MEAN....... 1987 1.0 0.8 0.6 0.4 0.2 0.0 APR MAY JUN JUL AUG SEP OCT NOV MONTH *Figure 3.2.2-8.Mean and 95% confidence limits over all years and 1987 values, by month, for log (x + 1) transfored catch per unit effort (one 10-min. tow for otter trawl and one haul for beach seines) for rainbow smelt at otter trawl station T2 1976-1987 and combined beach seine stations Sl, S2, S3 from 1976-1984 and 1987. Seabrook Baseline Report, 1987.175 Rainbow smelt were also prevalent in beach seine collections in the Hampton-Seabrook estuary. Monthly CPUE was variable with large catches possible any month during the sampling period (Figure 3.2.2-8). In 1987 no fish were caught from .June through November. Annual mean CPUE (all three stations combined) ranged from 0.1 fish/seine in 1980 to 3.3 fish/seine in 1979, averaging 1.,2 fish/seine (Table 3.2.2-9). In 1987 mean CPUE decreased from 1984 values to the third lowest value during the past 12 years (0.6 fish/seine),. Station differences were evident, with mean CPUE much higher at Station S3 (1.7 fish/tow) than at either Station S2 (0.2 fish/tow) or Station Sl (0.1 fish/tow). A one-way analysis of variance on:the yearly log-transformed CPUE showed no significant difference among years (Table 3.2.2-12). Estuarine Species Atlantic Silverside Atlantic silverside were present in the Hampton-Seabrook estuary beach seine collections throughout the April through November sampling season in most years, with the largest CPUE values occurring from August through November (Figure 3.2.2-9). The CPUE for 1987 followed this' pattern, except September was much lower than the overall mean. The catches were highly variable throughout the years with annual mean CPUE ranging from 7.3 to 31.1 fish/haul and averaging 16.9 fish/haul overall (Table 3.2.2-9). The high variability might be due to the high mobility and schooling characteristics of this species.' The one-way analysis of variance showed no significant difference among years for log-transformed CPUE (Table 3.2.2-12). 176 ATLANTIC SILVERSIDE U.Vn z 0 I-2.8 2.4 2.0 1.6 1.2 0.8 OVERALL MEAN 1987 0.4 0.0 APR MAY JUN JUL AUG SEP OCT NOV MONTH Figure 3.2.2-9. Mean and 95% confidence limits over all years, and 1987 values, by month, for log (x + 1) transformed catch per unit effort-(one haul for beach seines) for Atlantic silverside at combined beach seine stations S1, S2 and S3 1976-1984 and 1987. Seabrook Baseline Report, 1987.177 I3 3.2.3 Finfish Appendix Tables* I 178 APPENDIX TABLE 3.2.1-1. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND GEAR, JULY 1975-DECEMBER 1987. SEABROOK BASELINE REPORT, 1987.ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAMEa COMMON NAMEa EGGS LARVAE TRAWLS NETS SEINES Acipenser oxyrhynchus Alosa aestivalis Alosa mediocris Al'sa pseudoharengus Alosa sapidissima Ammodytes americanus Anarhichas lupus Anchoa hepsetus Anguilla rostrata Apeltes quadracus Archosargus probatocephalus Aspidophoroides monopterygius Brevoortia tyrannus Brosme brosme Caranx hippos Centropristis striata Conger oceanicus Clupea harengus harengus Cryptacanthodes maculatus Cyclopterus lumpus Enchelyopus cimbrius Fundulus sp.c Gadus morhua Atlantic sturgeon blueback herring hickory shad alewife American shad American sand lance Atlantic wolffish striped anchovy American eel fourspine stickleback Rb R C R 0 0 R 0 0 R R A C 0 0 0 R R sheepshead C C 0 0 R R 0 alligatorfish Atlantic menhaden cusk crevalle jack black-sea bass conger eel Atlantic herring wrymouth lumpfish fourbeard rockling.mummichogc Atlantic cod.0 0 0 R R R ..R-R C 0 C C C C 0 A 0 R 0 R R C R C 0 (continued) 179 APPENDIX TABLE,3.2.1-1. (Continued).ICHTHYO-ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAMEa COMMON NAMEa EGGS LARVAE TRAWLS NETS SEINES Gadus/Melanogrammus Gasterosteus sp.d Glyptocephalus cynoglossus ffemitripterus americanus Ilippoglossoides platessoides fflippoglossus hippoglossus Labridae/Limanda Limanda ferruginea Liopsetta putnami Liparis atlanticus Liparis coheni f Liparis sp.Lophius americanus Lumpenus g lampretaeformis Lumpenus. maculatus Macrozoarces americanus Melanograxmus aeglefinus Menidia .menidia Menticirrhus saxatilis Merlucclus bilinearis Atlantic cod/haddock sticklebackd witch flounder sea raven American plaice Atlantic halibut cunner/yellowtail flounder e yellowtail flounder smooth flounder seasnail gulf snailfish snailfishf goosefish C R 0 C C C C 0 C C C 0 R 0 R A-C R C C C A R 0 0 R f 0 C 1, R snakeblenny daubed shanny 0 R 0.0 R R C R ocean pout haddock Atlantic silverside northern kingfish Atlantic whitingh C 0 R R A R R C C C C (continued) 180 APPENDIX TABLE. 3.2.1-1. (Continued) ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAME' COMMON NAMEa EGGS LARVAE TRAWLS NETS SEINES Microgadus tomcod Morone americana Morone saxatilis Mustelus canis Myoxocephalus aenaeus Myoxocephalus octodecemspinosus Myoxocephalus scorpius Odontaspis taurus Oncorhynchus kisutch Osmerus mordax Paralichthys dentatus Paralichthys oblongus Peprilus triacanthus Petromyzon marinus Pholis gunnellus Pollachius virens Pomatomus saltatrix Prionotus carolinus Prionotus evolans Prionotus sp.Pseudopleuronectes americanus Pungitius pungitius i Raja sp.Salmo. gairdneri Atlantic tomcod white perch striped bass smooth dogfish grubby longhorn sculpin shorthorn sculpin sand tiger coho salmon rainbow smelt summer flounder fourspot flounder butterfish sea lamprey rock gunnel pollock bluefish northern searobin striped searobin searobin winter flounder ninespine stickleback skate 'rainbow trout R R R 0 R C 0 R R 0 R R R C C 0 C 0 0 0 C C C 0 R R.R 0 0 R R C.0 R R R 0 R 0 R C C 0 C R C C R (continued) 181 APPENDIX TABLE 3.2.1-1. (Continued) ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL aa SCIENTIFIC NAME COMMON NAMEa EGGS LARVAE TRAWLS NETS: SEINES Salmotrutta brown trout 0 Salvelinus fontinalis brook trout R Scomber japonicus chub mackerel R Scomber scombrus Atlantic mackerel A A R C R Scophthalmus aquosus windowpane C C C -R 0 Sebastes sp.j redfish 0 Sphoeroides maculatus northern puffer R R Squalus acanthias spiny dogfish R R Stenotomus chrysops scup R 0 R Stichaeus punctatus Arctic shanny 0 Syngnathus fuscus northern pipefish C 0 R 0 Tautoga onitis tautog 0 R Tautogolabrus adspersus cunner A 0 0 R Torpedo nobiliana Atlantic torpedo R Triglops murrayi moustache sculpin 0 R Ulvaria subbifurcata radiated shanny C 0..C Urophycis 5 p.k hakek .A. C A 0 C 1 Footnotes: See next page.182 APPENDIX TABLE 3.2.1-1. (Continued) Footnotes: a Names are according to Robins et al. (1980) unless otherwise noted. Taxa usually identified to a different level are not included in this list to avoid duplication (e.g., Gadidae, Enchelyopus/Ulrophycis, Myoxocephalus sp.,- Urophycis chuss, etc.)Occurrence of each species is indicated by its relative abundance or frequency of occurrence for each lifestage or gear type: A " abundant (2 10% of total catch over all.years) C = common (occurring in 10% of-samples but < 10% of total catch)O occasional (occurring in < 10 and ? 1% of samples)R = rare (occurring in < 1% of samples)-= not usually identified to this taxonomic level at this lifestage cPredominantly Fundulus heteroclitis, mummichog, but may include a small number of Fundulus majalis, striped killifish. dTwo species of Gasterosteus have been identified from seine samples: G. aculeatus, threespine stickleback; and G. wheatlandi, blackspotted stickleback (both occurring commonly). eMay also include a small number of tautog.fThree species of Liparis have been identified from trawl samples: L. atlanticus, L. coheni, and L. inquilinus (inquiline snailfish). gspelling after Faber (1976).hPreviously called silver hake (NAI 1982a); Atlantic whiting was recommended by Kendall and Naplin (1981:707). iFour species of Raja have been identified from trawl samples: R. radiata, thorny skate (common); R. erinacea, little skate (common); R. binoculata, big skate (occasional); and R. eglanteria, clearnose skate (rare).3Previously called S .narinus. Recently S. mentella and S. fasciatus have also been reported to occur in the northwest Atlantic (Ni 1981a; 1981b)'. Sebastes in coastal New Hampshire waters are probably S. fasciatus (Dr. Bruce B. Collette, U.S.-National.Museum, pers. comm. April 1982), but larval descriptions are insufficient to allow distinction among the three species.*kThree species of Urophycis have been identified from trawl samples: U. chuss, red hake (common); U. tenuis, white hake'(common); and U. regia, spotted hake (rare).183 r 3.3 BENTHOS 3.3.1 Estuarine Benthos 3.3.1.1 Physical Environment Salinity and Temperature Weekly measurements of salinity and temperature at high and low slack tides in Brown's River and'Hampton Harbor were taken to investigate annual and monthly patterns. The Brown's River salinity station is just downstream from the.benthic transect, and about 0.5 km downstream from the settling basin outfall; the Hampton Harbor station is a control station away from the influence of the outfall (,Figure 4.1-4). Low tide collections in Brown's River represent the more extreme environmental conditions in compari-son to Hampton Harbor. The water is not as tempered by tidal influx of sea water, as is the Hampton Harbor station.Mean monthly salinity at low tide in Brown's River ranged from 17.5 +/- 4.6 ppt in April to 25.3 +/- 1.6 ppt in August during the nine-year. study period from May 1979 through December 1987 (Appendix Table 3.3.1-1, Figure 3.3.1-1, Table 3.3.1-1). In 1987, monthly salinities were within the 95% confidence limits of the nine-year averages except for April, May, and September, which had below-average salinities (Figure 3.3.1-1). Rainfall during April 1987 totaled 9.5 inches (Table 3.3.1-2), and nearly half of that.occurred on April 5 and 6 (National Climatic Data Center 1987), which-caused flood waters to reach a 10-year high in many New Hampshire areas. Rainfall in-late April was also well above average, which caused the mean salinity in May 1987 to be well below the nine-year average, despite a total rainfall of only 1.75 inches. .Again in September, the total rainfall was very high, and salinities were correspondingly low. In spite of having salinities which fell below the lower 95% confidence limit of the nine-year average during three months of 1987; the annual mean salinity was 20.1 ppt,* only very slightly below the average for the-study period (Table 3.3.1-1). Likewise, the annual precipitation was 45.5 inches, slightly above the average for the study period (42.18 inches).185 Salinity a-a-I-C,.30-25-20-15 -101-5-OVERALL MEAN---1987, ".."-" 0 I .I .a. I .I. I .I .I*JAN FEB MAR APR MAY JUN JUL AUG I I NOV I CEC MONTH Temperature Cr.0 a.25 20 15 10 5 0 JAN. FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.3.1-1.Mean monthly seawater surface temperature and salinity with 95% confidence limits taken at low tide in Brown's River over the entire study period (May 1979 -December 1987) and in 1987. Seabrook Baseline Report, 1987..186 TABLE 3.3.1-1.ANNUAL MEANa TEMPERATURE (°C) AND SALINITY (PPT) TAKEN AT BOTH HIGH AND LOW SLACK TIDE FROM BROWN'S RIVER AND HAMPTON HARBOR FROM 1980-1987. SEABROOK BASELINE REPORT, 1987.BROWN'S RIVER HAMPTON HARBOR LOW TIDE HIGH TIDE LOW TIDE HIGH TIDE TEMP SALINITY TEMP SALINITY TEMP SALINITY TEMP SALINITY.(ppt) (0 C) (ppt) (°C) (ppt)* (0 C) (ppt)1980 10.9 Z5.1 9.6 31.0 9.6 29.9 9.1 32.1 1981 10.6, 25.5 10.3 30.0 9.3 28.9 9.3 31.5 1982 10.7 22.8 9.9 30.0 10.2 27.3 9.2 31.2 1983 11.9 1.9.4 11.0 28.0 10.4 25.5 9.9 30.1 1984 11.9 18.1 10.6 28.4 10.4 25.8 9.4 30.2 1985 11.3 Z1.7 10.1 30.6 10.6 29.1 10.1 32.2 1986 10.3 ZO.4 9.6 30.2 10.0 Z7.7 9.4 31.5 b c b c 1987 -ZO.1 -28.7 10.0 27.5 8.9 30.7 OVERALL 11.1 21.6 10.2 29.6 10.1 27.7 9.4 31.2-j a Annual mean=Zmonthly mean temperature 12 months b No data were taken in 3anuary or February, thereforeno annual mean was computed.c No data were taken in February, therefore n =11 months. TABLE 3.3.1-2. TOTAL PRECIPITATION (WATER EQUIVALENT IN INCHES) BY MONTH AND YEAR TAKEk AT LOGAN INTERNATIONAL AIRPORT, BOSTON, HA FROM JANUARY 1978 -DECEMBER 1987.* SEA1ROOK BASELINE REPORT, 1987.MONTHLY TOTALS MONTH 1978 1979 1980 1981 198z 1983 1984 1985 1986 1987 JAN 8.12 10.55 0.74 0.95 4.69 5.03 2.31 1.12 3.42 7.28 FEB Z.87 3.46 0.88 6.65 2.66 5.00 7.81 1.83 Z.83 0.7Z MAR 2.46 3.03 5.37 0.62 2.17 9.72 6.82 2.29 3.42 4.27 APR 1.79 3.19 4.36 3.14 3.42 6.86 4.43 1.62 1.59 9.46 MAY 4.50 4.24 2.30 1.17 2.58 2.94 8.77 3.36 1.31 1.75 JUN 1.53 0.86 3.05 1.65 13.20 1.07 3.06 3.94 7.74 Z.62 JUL 1.48 2.36 2.2 0 3.47 4.22 1.07 4.43 3.51 3.96 0.8Z AUG 4.62 5.02 1.55 1.04 2.22 3.28 1.60 6.67 3.32 2.93 SEP 1.30 3.61 0.82 2.54 1.57 1.06 1.22 3.00 1.08 7.29 OCT 3.13 '3.14 4.14 3.43 3.19 3.74 5.18 1.65 3.27 2.73 NOV 2.21 3.29 3.01 4.78 3.42 8.89 1.68 6.39 6.01 3.49 DEC 3.63 1.42 0.97 6.27 1.27. 4.94 2.93 1.21 6.38 2.12 ANNUAL 37.64 .44.17 29.39 35.71 44.61 53.60 50.24 36.59 44.33 45.48 00 0O*Sourcet National Climatic Data Center. 1987.Federal Bldg., Ashville, NC.Local Climatological Data, Monthly Summary January-December. The mean monthly salinity at high tide in Brown's River ranged from 26.4 +/- 3.2 ppt in April to 31.5 +/- 1.1 ppt in January during the nine-year study period (Appendix Table 3.3.1-1, Figure 3.3.1-1). High tide salinity was always higher than low tide salinity due to the influx of more saline water from Hampton Harbor into Brown's River. The influx tempered.the extremeswhich.occurred at low tide due to environmental conditions; At the control station in Hampton Harbor, the mean monthly low tide salinity during the nine-year study period ranged from 24.1 +/- 3.8 ppt in April to 29.9 +/- 0.7 ppt in September (Appendix Table 3.3.1-1). The salinity in Hampton Harbor was always higher than in Brown's River (Appendix Table 3.3.1-1), due to its proximity to the inlet;Annual precipitation was inversely related to average yearly salinity during every year of the 1980-1987 study period in Hampton Harbor;when rainfall increased, salinity decreased (Figure 3.3.1-2). Brown's River generally-followed the same inverse relationship with rainfall except for 1981 and 1984." In 1981, average yearly low tide salinity decreased by 1.00 ppt in Hampton Harbor, but increased by 0.4 ppt in Brown's River (Table 3.3.1-1). In 1984, when average yearly low tide salinity in HamptonHarbor went up 0.3 ppt, it went down by 1.3 ppt in Brown's River. The Seabrook Station settling pond out fall usually contained fresh water from the sta-tion's sewage treatmentiplant and runoff from rainfall. During the years of highest discharge from November 1979 through November 1983 (Figure 3.3.1-3), the outfall became saline, containing mostly offshore sea water from tunnel dewatering, with salinities of approximately 31 ppt. In 1981, when the amount of discharge peaked, there was a slight (+0.4 ppt) increase in average yearly salinity in Brown's River when, the control station showed a decrease (-l.0.ppt) (Table 3.3.1-1). In 1984, when dewatering of the tunnels was terminated and saline discharges ended, the salinity in Brown's River dropped 1.3 ppt from the previous year, while salinity in Hampton Harbor rose 0.3 ppt. Since the salinity changes were small (+0.4 and -1.3 ppt), it is difficult to determine.whether they are due to natural variation, or marked the beginning and end of tunnel dewatering. 189 Station 3 6-SALINITY.. ... PRECIPITATION 0n-LU 24- .50 .22 .."40 2 I-I l 20 30 .9L 18 -* , ., ., .20 1980 .1981 1982 1983 1984 1985 1686 1987 YEAR Station 9 30 -- SALINITY 60....... PRECIPITATION LU 29- */ ,50 29 " "...........

• So°z S *** 40 30 2 -*~-3 FL* °26 .LU IL 25 ---- T.= .20 1980 1981 1982 1983 1984. 1985 1986 1987 YEAR Figure 3.3.1-2. Mean annual salinity at low tide in Brown's River (3) and in Hampton Harbor (9), and total annual precipitation from 1980 through 1987. Seabrook Baseline Report, 1987.190 5-4-01 Cn z 0 3-2-J4-cutfail with Increased salinity 0.J. **1 I I A 46.A f I5I I I I I I6 I i I I 5 I I I I j 5 I 5.I ~ I 5I I I I 5I I 5I I I I 5A I6I I5I I1I I1I I£0ON 0J MA MJ JA S 0N D JF MA MJ JAS 0N DJ F MAM J JASO6N DJ F MAM J J A SO0N 1978 1979 1980, i 981 1982 0 C9 LL 0 0 5 4 3 2 0 J F M A M.J J. A S 0 N D J F M A M J J A S 0 N 0 J F M A M.J J A B 0 N 0D1 F MA M J J A S ON 0 J F M A M J J A S 0 N D 1983 1984 1985 ' 1986 1987 Figure 3.3.1-3.Monthly outfall from the Seabrook Settling Basin from 1978-1987 in millions of gallons per day (GPD).Seabrook Baseline Report, 1987.191 Mean monthly temperature at low tide in Brown's River ranged from 0.9 +/- 0.8 0 C in January to 21.4 +/- i. 0C in July during the nine-year study ,period (Appendix Table 3.3.1-1, Figure 3.3.1-1).

In 1987, average monthly temperatures were within the 95% confidence limits of the nine-year monthly averages except for May which was slightly cooler in 1987 (Figure 3.3.1-1)and August, which was warmer. The mean average yearly temperature was not computed for Brown's River in 1987 because no data were collected in January or February, traditionally the coldest months of the year.In Hampton Harbor, average monthly temperatures at low tide ranged from 1.0 +/- 0.7 0 C in January to 18.6 +/- 1.0 0 C in August during the nine-year study period (Appendix Table 3.3.1-1). Hampton Harbor water at low tide was slightly warmer than Brown's River in November, December, January and colder during the rest of the year. The annual mean low tide temperature in Hampton Harbor in 1987 was 1O.0°C, very close to the nine-year average of 10.1 0 C (Table 3.3.1-1). In both Brown's River and Hampton Harbor, the 1987 monthly temperatures were close to the nine-year average (Figure 3.3.1-1).Sediment Yearly and seasonal differences in sediment collected in 1978-1984 indicated estuarine sediments were very patchy with spatial variability often exceeding annual variability (NAI 1985b). Yearly averages at subtidal stations (3 & 9) showed grain size was fine sand, which was usually poorly sorted with organic carbon ranging from 0.97 to 2.08% (NAI 1985b). The yearly averages for intertidal stations (3MLW and 9MLW) showed the grain size varied from fine sand to silt, which was often very poorly sorted. The percentage of organic carbon was higher than at subtidal stations and ranged from 1.56 to 5.86% (NAI 1985b). Although differences in low tide salinity in Brown's River appeared from 1980-1982, sediment parameters during that period were apparently within the range of natural variation. 192 3.3.1.2 Macrofauna The estuarine benthic communities in Brown's River (Station 3) and Mill Creek (Station 9) were usual for quiet, tidal creeks with fine-grained sediments, where average monthly salinity ranged from 18 ppt to 25 ppt (Appendix Table 3.3.1-1). Spatial distribution of organisms was very patchy, and large population fluctuations occurred seasonally, as is typical in estuarine habitats. Deposit and surface-deposit feeders predominated,, usually composing over 70% of the fauna at Stations 3, 9 and 9MLW (NAI 1985b). Three taxa cbmprised the majority of individuals: Streblosplo benedicti, Oligochaeta, and Capitella capitata. The clam worm, Nereis diversicolor, was very abundant intertidally in Brown s River (3MLW). The soft-shelled clam, Mya arenaria, was also present in substantial numbers at all sampling locations (Table 3.3.1-3).Total abundance of organisms (number/m 2) showed year-to-year variations that appear to be related to area-wide environmental trends. The years of highest overall abundance were 1980-1982, when the geometric mean annual abundance reached a 10-year high of 8424/mr 2 in 1981 (Table 3.3.1-3).The period of 1980-1982 was the period of lowest precipitation, highest salinity and highest discharge flow from the settling basin into Brown's River. The years 1983 and 1984 were the years of lowest salinities, highest precipitation, and highest temperatures for the study period (Tables 3.3.1-1.and 3.3.1-2). By 1984, total abundance at all four stations had declined greatly. In 1986, the total abundance (2980/mr 2) recovered and was close to'the abundance in the pre-outfall period, 1978 and 1979 (3514/M 2 and 4099/M 2 , respectively; Table 3.3.1-3). In 1987, total abundance reached all time lows at three of the four stations (Figures 3.3.1-4, 5). Extremely low salinities in April, May and September, 1987 (Figure 3.3.1-i) may have affected recruit-ment rate. When total abundances between corresponding subtidal and inter-tidal station pairs in Brown's.River and Mill Creek were tested with a paired t-test, no significant differences were found (Table 3.3.1-4).193 TABLE 3.3.1-3. MEAN NUMBER OF TAXA. AND THE GEOMETRIC MEAN DENSITY (No. /m 2) FOR EACH YEAR AND OVERALL YEARS WITH 95.CONFIDENCE LIMITS FROM ESTUARINE STATIONS AT BROWN'S RIVER (.3) AND MILL CREEK (9) SAMPLED FROM 1978 THROUGH 1987 (EXCLUDING 1985). SEABROOK BASELINE REPORT, 1987.1978 1979 1980 1981 1982 1983 1984 1986. 1987 ALL YEARS STATION MEAN LOWER UPPER No. of Taxa Total Abundance I.F-3 9 3MLH 9MLW MEAN 3 9 31LW 9MLW MEAN 3 9 3MLW 9MLW MEAN 3 9 3MLN 9MLW MEAN 35 26 28 28 29 41 34 37 35 37 38 47r 31 35 38 42 44 38 41 41 47 34 35 36 38 32 27 38 33 37 36 21 36 21 33 28 18 32 23 30 33 21 36 16 31 32 22 35 23 -Streblospio benedicti 34 20 27 27 3170 4616 4978 3619 2209 14,767 4260 6136 5695 3120 4512 6947 3514 4099 7344 367 123 193 106 26, 2396 439 505 1010 566 434 466 314 163 684 242 270 204 16 100 2910 87 186 318 574 810 1067 119 253 671 5360 11,277 6833 12,189 8424 525 525 928 2700 912 9331 2635 1244 1182 1198 2950 4335 4533 620 2819 726 3180 8022 2723 21ý7 5632 .1727 4271 11,383 11,151 5141 4302 653 5049 7796 4364 .1715 2980 995 3771 1064 552 .239 99 6 66 253 81 538 16 161 49 140 3584 525 535 1421 316 769 2354 3215 1560 1299 11 723 925 842 242 415. 58 375 Z189 556 Z25 95 133 315 1058 1603 162 528 131 356 350 29"2 382 968 215 288 565 2877 572 742 161 713 823 931 298 437 157 389 889 216 66 73 57 110'291 376 .28 808 113 223 540 208 124 l 197 26 -102 276 800 303 234 19 175 443 341 91 2Z8 42 145 40 37 33 35 2091 4162 1973 5126 3203 5694 3228 7898 3109 4575 153 417 57 343 482 1228 330 1587 263 534 189 525 170 743 176 469 410 1239 293 517 Oligochaeta 651 969 320 861 646 473, 277 244 320 318 Capitella capitata 3 9 31LW 9MLW MEAN 11 238 17 279 60 63 123 29 2453 29 138 45 125 40 269 55 118 57 102 107 218 422 182 302 195 (continued) TABLE 3.3.1-3. (Continued) 1978 1979 1980 1981 1982 1983 1984 1986 1987 ALL YEARS STATION MEAN LOWER UPPER Nereis diversicolor 3 9 9MLK MEAN Caulleriella Sp. B, 3 9 3MLW 9tILW MEAN Ln Mya arenaria 3 9 31LK 9MLW MEAN 83 172 158 21 29 41 800 1343 1169 170 164 101 125 183 167 330 221 10 40 106 174 8 298 42 147 69 158 265 427 106 224" 100 328 118 265 835 46 607 48 183 92 299 26 62 82 352 205 1613 241 410 1 292 3 43 17 181 246 179 400 237 452 45 50 52 43 107 41 7 7 43 2 22 975 220 296 987 150 645 135 57 513 184 6 114 223 45 89 143 18 116 2 3 1z 9 1 18 136 35 7 10 3 27 23 52 44 255 87 72 1634 278 325. 307 1 90 64 37 34 53 5 42 13Z 75 31 z2 30 69 148 168 157 34 53 157 117 103 22 13 27 61 141 70 86 13 73 96 134 98 55 19 42 89 70 163 12 4Z 381 1089 62 208 82 164 ,6 11 34 30 27 44 99 35 57 70 52 65 152 261 68 108 251 106 162 114 Yearly mean. Iseasonal means 3 seasons Seasonal mean= Etotal number per replicate 3 replicates Overall years' mean =,Eyeariy means 9 years -J I-U, z LU 0-J.5-4-6-5 4 3 2 1 Subtidal Station '3 H<C'C I--U.0 LU z 80 60 50 40 30 20 Subtidal Station 3 I I I.10 i I I I I Ii I 1 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR Subtidal Station 9 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR I Subtidal Station 9 I k x I-LL 0 cc z 80-70-60-50-40-30-20-10-0 I f I I I I I a a a a 1 a a a a a I ~ i *978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR.. I I I I i I I 1 1 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR Figure 3.3.1-4. Yearly mean and 95% confidence limits for the log (x+l)density of macrofauna and number of t axa collected at subtidal estuarine stations sampled three times per year from 1978 through 1987 (excluding 1985). Seabrook Baseline Report, 1987.196 -LI z LU 0-.4 5-4-3-2 Intertidal Station 3MLW TTTI _L 70 Intertidal Station 3MLW 60-x 50 u. 40 0" 30 LU IJJ 20 z 1 0" I a i a U I U I U *V 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR I I I I I I I I I 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR Intertidal I Station 9MLW Intertidal Station 9MLW 5-4-3-2-1-V U.0 z 70 -7o"-6o-50-40.30 10 0!I I I a I -a I 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR-I i I I I II i I I 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR Figure 3.3.1-5.Yearly mean and 95% confidence limits for the log (x+!)density of macrofauna and number of taxa collected at intertidal estuarine stations sampled three times year from 1978 through 1987 (excluding 1985). Baseline Report, 1987.197 TABLE 3.3.1-4.RESULTS OF A PAIRED t-TEST FOR SELECTED BIOLOGICAL VARIABLES FROM PAIRED SUBTIDAL (STA.3-STA.9) AND INTERTIDAL (STA.3MLW-STA.9MLW) STATIONS SAMPLED THREE TIMES PER YEAR DURING 1978-1987 (EXCLUDING 1985). SEABROOK BASELINE REPORT, 1987.STATION DEGREES OF VARIABLE PAIR FREEDOM t-VALUE* PR>ItI Number of Taxa Subtidal 26 2.12* 0.0441 Intertidal 26 -0.96 0.3450 Total Abundance Subtidal 26 -0.41 0.6816 Intertidal 26 -0.77 0.4491 Streblospio benedicti Subtidal 26 1.31 0.2010 Intertidal 26 0.15 0.8837 Capitella capitata Subtidal 26 -1.76 0.0906 Intertidal 26 -1.60 0.1215 Neris diversicolor Subtidal 26 .5.59*** 0.0001 Intertidal 26 5.59*** 0.0001 Caulleriella sp. B Subtidal 26 -0.51 0.6129 Intertidal 26 -0.37 0.7169 Mya arenaria Subtidal 26 -3.52** 0.0016 Intertidal 26 -2.12* 0.0442 Oligochaeta Subtidal 26 0.33 0.7406 Intertidal 26 -2.62* 0.0144*The t-value was computed for the difference between the log (X+/-l) of the abundance (No./m 2) taken seasonally (May, August, November) for nine years for a station pair for the important species and the total abundance of all non-colonial macroinvertebrates in a sample. Number of taxa is the mean for a season, and was not transformed. Negative t-values indicate that the station near the settling basin discharge, (3 or 3MLW) had a lower-mean value than the control station (Sta. 9 or 9MLW).* = significant differences at alpha =,0.05**= highly significant differences at alpha-= 0.01= very highly significant differences at alpha = 0.001 198 The seasonal cycle of total abundance showed density was usually highest in May or August at both intertidal and subtidal stations (NAI 1987b: Figure 3.3.1-4). The usual increase in abundance in spring or summer was probably due to the recruitment of one or more dominant taxa (NAT 1985b).The 1984 densities had no major seasonal peak at any of the four stations.It was also the second consecutive year of very high~precipitation (Table 3.3.1-2) and very low salinities (Figure 3.3.1-2). The low densities observed in Brown's River and Mill Creek in 1984 may have been related to spawning and recruitment failures in 1983 and 1984, caused by more extreme natural conditions. Similarly, rainfall in April, 1987 was at a 10-year high, and was also very high in September, and total abundance was at or near an all time low for-each of the four stations (Table 3.3.1-3).The mean number of taxa collected annually at all stations combined ranged from 22 taxa in 1984 to 41 in 1981 (Table 3.3.1-3), and significant differences were found among both years and stations (NAI 1987b: Table 3.3.1-4). The years 1980 through 1982 had the highest number of taxa collected, while 1984 and 1987 had the lowest number of taxa (Table 3.3.1-3, Figures 3.3.1-4, 5). The seasonal cycle at each of the four stations showed that the highest number of taxa usually occurred in August or May, and the lowest number occurred in November (NAI 1987b: Figure 3.3.1-5). The two subtidal stations had a higher number of taxa averaged over all years than the two intertidal stations. When a paired t-test was done between subtidal stations in Brown's River and Mill Creek, Brown's River was found to have a significantly higher number of taxa than Mill Creek. However, the intertidal stations were not significantly different (Table 3.3.1-4).The annual trend in the number of taxa seems to show a relationship with the mean annual salinity. When annual salinity dipped below 20 ppt, the number of taxa declined. Previous years (1983, 1984) showed decreases in numbers of taxa at most stations coincident with high spring rainfall and low salinity (NAi 1987b; Tables. 3.3.1-1, 2),, and a similar pattern was noted in 1987.199

1 SUBTIDAL STATION 3 Nereis 4 ]Mya w 0-j 3-2-1--d I-z Lu 0 0 ,.J 4-3-2-1-J>1 0 I I I I I I I 1 1 1978 1979 1980 1981 1982 1993-1984 1986 1987 YEAR 0 I i i 1978 1979 1980 i i I 1 1981 1982 1983 1984 YEAR 1986 1987 SUBTIDAL STATION 9 Nereis 4 3 2 Mya 5-z LU 0-j'.>C,).z wu a C 0-J 47 37 2-/1 VT 0 0 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR I I I I I I I I'1978 .1979 1980 1981 1982 1983 1984 1986 1987 YEAR Figure 3.3.1-6.Yearly mean and 95% confidence limits for the log. (x+l)density of Nereis diversicolor and Mya arenaria collected at subtidal estuaiine stations three times per year from 1978 through 1987 (excluding 1985).Seabrook Baseline Report, 1987.200 Streblospio benedicti is an opportunistic polychaete (Grassle and Grassle 1974), and one of the first to colonize after a perturbation of the environment (Rhoads et al. 1978). It is the most abundant species in the estuary, exhibiting-significant differences in abundance among both years and stations when tested with a two-way ANOVA (NAI 1987b: Table 3.3.1-4).All-time high geometric mean densities were reached in 1981 and 1982, during the period of'high salinity and settling pond discharge (Table 3.3.1-3).

In 1987 the population decreased dramatically to an overall density of only 58/M 2.When stations were compared, the two intertidal stations.had the highest densities, and the two subtidal stations had the lowest densities. No significant differences were found between station pairs in Brown's River or Mill Creek (Table 3.3.1-4). The seasonal cycle of S. benedicti indicated that extremely high densities occurred during any season at both intertidal and subtidal stations. Such high densities were rarely sustained into the next sampling period, causing tremendous population fluctuations (NAI 1987b: Figures 3.3.1-6,7). The class Oligochaeta was very abundant in the estuary. Compari-sons among years showedthe years of highest abundance were 1980-1983 when geometric mean population densities ranged from 646/mr 2 in 1981 to 931/m 2 in 1983 (Table 3.3.1-3). The years of lowest abundance included 1978 and 1987 when density (averaged over stations).was 119/M 2 and 157/mr 2 , respectively. Thus, the years before and after the period of highest salinity and discharge had similarly low densities. Interstation comparisons showed the stations with the highest. overall abundance were Station 9MLW and 9 and stations with the lowest abundance were Stations 3 and 3MLW (Table 3.3.1-3), but thes-e differences are too slight to be significant with a paired t-test (Table 3.3.1-4). The seasonal cycle of oligochaetes indicated that peak densities occurred during any season (NAI 1987b: Figures 3.3.1-6,7), but were not sustained. The opportunistic polychaete Capitella capitata was abundant in the estuary at both intertidal and subtidal stations, but had lower population densities than S. benedict! and Oligochaeta. The highest population den-sities averaged for all stations occurred from 1980-1983,.when overall 201 INTERTIDAL STATION 3MLW Nereis Mya z 0-j 5-4-3-2 1 7 z LU 0-j 4-3.2-1-0 I I I .I I I 1978 1979 1980 1981 1982 1983 YEAR I I I 1984 19861987 0.1 t! i j i i i ,i A 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR/INTERTIDAL STATION 9MLW Nereis Mya 0-J 4-3-2-1-L/z LU 0-j 4 3 2 1 0 0 I I -I 1978 1979 1980 1981 I-1982'EAR I r I .5 1983 1984 1986 1987 1978 1979 1980 1981 1982 1983 1984 1986 1987 YEAR Figure 3.3.1-7. Yearly mean and 95% confidence limits for the log (x+l)density of Nereis diversicolor. and Mya arenaria collected at intertidal stations three times per year from 1978 through 1987 (excluding 1985). Seabrook Baseline Report, 1987.202 geometric mean densities were between 269-443/m 2 (Table 3.3.1-3).. The years of lowest abundance were 1978, 1979, 1984, and 1987 when abundance was less than 100/mr 2 (Table 3.3.1-3). No significant differences were found between station pairs in Brown's River or Mill Creek using a paired t-test (Table 3.3.1-4), but densities were usually higher in Mill Creek (Table 3.3.1-3).Caulleriella sp. B is a polychete that was occasionally abundant in the estuary. Its annual geometric mean density at all stations ranged from 5/M 2 in 1987 to 183/M 2 in 1980 (Table 3.3.1-3). It rarely sustained densi-ties of over 100 for more than three consecutive years, and in 1987 it had annual densities of less than 10 at three of the four estuarine stationis (Table 3.3.1-3). No significant differences were found between Brown's River and Mill.Creek (Table 3.3.1-4).The clam worm, Nereis diversicolor, is a highly euryhaline species which can easily adapt to salinities ranging from 1-25 ppt. It is common where there is a mixture of fresh and salt water, and can penetrate up the estuary further than most "marine" worms (Pettibone 1963). It builds a fairly permanent U-shaped burrow, and unlike many nereids, fertilization and development occur in the burrow without a planktonic larval stage. It lives for about 18 months, and has one breeding season. Spawning occurs in late winter or early spring with a marked temperature change, and afterwards the females die. By the end of the first summer, juveniles are 10-20 mm in length.. Adults may reach up to 200 mm in length (Pettibone 1963). The geometric mean population densities at each of the four stations were usually highest from 1981-1982, and reached an all time low in 1987 (Table .3.3.1-3, Figures 3.3.1-6, 7). Both intertidal and subtidal stations at Brown's River had significantly higher densities than stations of comparable depth at Mill Creek (Table 3.3.1-4). Intertidal stations had higher densities than sub-tidal stations (Table 3.3.1-2), as expected, since the species is primarily intertidal (Pettibone 1963).203 Mya arenaria, the soft-shelled clam, is a euryhaline species that tolerates rapidly changing salinities, and can survive in sustained salini-ties as low as 4 ppt (Green 1969). In Hampton Harbor, the green crab,.Carcinus maenas is an important predator of Mya, and its abundance may affect the success of recently-sett'led young (Section 3.3.7). Recently-settled Mia were present at all estuarine stations, and overall densities were highest in 1979 and 1981 (265/m 2 and 237/M 2 , respectively), and lowest in 1986 and 1987 (19/M 2 and 42/m 2 , respectively) (Table 3.3.1-3). Significant differences were found among years and stations (NAI 1987b: Table 3.3.1-4) with the earlier years generally having higher densities, and Mill Creek having higher densities .than Brown's River. Likewise when intertidal and subtidal station pairs in Brown's River and Mill Creek were tested with a paired t-test, densities in Mill Creek were found to be significantly' higher (Table 3.3.1-4). Population densities in 1986 reached an all-time low at all four stations (Figure 3.3.1-6 and 7) and green crab densities in Hampton Harbor were very high (Figure 3.3.7-9). However, in 1984, when green-crab densities reached a 10-year high, clam densities were about average.In summary, changes throughout the estuary occurred in total abundance, number of taxa, and abundance of the most dominant species. As these changes were not site-specific, and occurred at Brown's River and Mill Creek at the same time (except in 1983), they were probably related to area-wide environmental variables such as precipitation and corresponding salinity changes, temperature, and abundance of predators and competitors. The period of high salinity and high settling pond discharge (1980-1983) showed population increases for most of the estuarine worms, total abundance, and number of taxa. Increases in the settling basin discharge volume probably acted in conjunctionwith low precipitation to increase salinity in Brown's River slightly. By 1986, physical and biological parameters had returned to the pre-1980 conditions, but in 1987 abundances for five of the six dominant taxa were at or near all-time lows in both Brown's River and Mill Creek. At the same time salinities reached a 10-year low during three months in 1987, due to heavy rainfall.. 204

3.3.2 Marine

Macroalgae 3.3.2.1 Macroalgal Community Species Collections From 1978 to 1987, 123 species of macroalgae were recorded from general species collections at 12 benthic stations (Appendix Table 3.3.2-1).As is typical of this region, 52% of these taxa were red algae (Rhodophyta), 25% were brown algae, and 23% were green algae (Mathieson et al. 1981a,b).Four of these species were collected only in 1985 and 1986: Devaleraea ramentaceum and Phyllophora traillii, which are red algae; and Petalonia zosterifolia and Soraplon kjellmanil, both brown algae. .D. ramentaceum and S. kjellmanii were collected only from tide pools. All four species have been previously collected from the nearshore open coast between Portsmouth and Seabrook, New Hampshire by Mathieson and Hehre (1986). Only one new species, Polysiphonia denudata, was recorded in 1987. This species, which was found only once (Station 5MLW), is an estuarine species and was likely a drift specimen from Hampton Harbor. Spatially, the highest number of taxa.collected throughout the historical period were in the mean low water (MLW)zone (a median of 57 at Station 5MLW); numbers decreased with increasing depth, with the fewest species collected at the deepest stations (Figure 3.3.2-1). Number of species collected also decreased with increasing eleva-tion from MLW (e.g., at the MSL stations). For the most part, the numbers of taxa collected at nearfield and farfield stations from 1978 to 1987 were similar. Exceptions were the MLW zone where more taxa were recorded at Rye Ledge (5MLW) than at the Outer Sunk Rocks (IMLW) and the mid-depth zone where fewer taxa were recorded at the station near the intake (Station 16) than at the farfield station (Station 31). Numbers of taxa collected in 1987 were within the range collected over the prior baseline period (1978-1985), with few exceptions. Two additional taxa were recorded at Stations 17 and 31 in 1987; however, these were not species new or unusual in the study area as a whole.205 62 ý-60-58 $4 52-50 ,48-46-44 42 40-38-36-34-32-30 28 26-24-22-20 18-16 14 12 10,-8 6 4 2 0-a MEDIAN RANGE b NUMBER OF SPECIES 0-1985 o -1987 0-1986 c NF = NEARFIELD FF = FARFIELD d SEE APPENDIX TABLE 3.3.2-1 FOR PERIODS OF COLLECTION AT EACH STATION b MLW MS L 0 MLW 0 f Um 0 MSL I 1 5 17 35 16 19 31 13 A 34 NFr FF NF FP "NF NF FF NF .NF PF INTERTIDAL SHALLOW MID-DEPTH DEEP.Figure 3.3.2-1.Number of macroalgae species in general collections at each marine benthic stationdfor 1978-1984 (median and range) and 1985-1987 (number collected each year).Seabrook Baseline Report, 1987.206 In several cases the number of taxa in 1987 general collections represented the highest (Stations 17,16,31,4) or near-highest (Stations 35 and 19) number collected during the baselineperiod. However, not all stations were sampled for the entire 1978-1987 period (See Appendix Table 3.3.2-1). Only at Station lMLW were numbers of taxa collected low in 1987, in fact they were the lowest on record.' Low., numbers of taxa and abundances were observed at several stations in 1987 for macrofauna in the benthic destructive collections. (Section 3.3.3).Annual Biomass Collections The effect of depth on light quality and quantity is reflected in the biomass of macroalgae and the number of taxa collected at the hard substrate (algal-covered rock and ledge) stations sampled from 1978 through 1987 (Figure 3.3.2-2). The numbers of taxa recorded were greatest at the intertidal (MLW) sites, declined to 20-25 taxa as depth increased to about 9.5 m, then declined to approximately 15 as depth increased to 20 m. Biomass values were similar at the intertidal and shallow subtidal stations, then declined until depth reached 18-20 m. Numbers of taxa and biomass values were generally similar between nearfield and farfield stations. However, mean biomass at Farfield Station 31 (Rye Ledge) was 46% greater than the Nearfield Station 19 (Discharge) and 42% less than Nearfield Station 16 (Intake). More taxa were recorded in the biomass samples from the farfield intertidal site (5MLW) than from the nearfield station (lMLW).A temporal presentation of annual August biomass levels (Figure 3.3.2-3) at the nearfield stations indicated no consistency among year.trends. At the intertidal Sunk Rocks site (lMLW), m6an biomass was lower during the 1978-1981 period than during the 1982-1986 period; the 1987 mean was more similar to the earlier period. At the shallow subtidal (17), mid-depth (19) and deep (4) stations there was some variability among years but it was relatively minor and there were no among year trends evident.207 60 50 g LMW LMW I-LL 0 Lu z 40-30-20 10-Depth (m) below MLW Q1m 13.7 m 16 31 18.3 m 19.7 m 19.7 m[I 0 -1MLW 5MLW 17 35 19 13 4 34 STATION.F 1500 °E 0 1000-500-0-I 1MLW 5MLW 17 35 16 31 19 13 4 34 STATION Figure 3.3.2-2.A. Number of taxa and B. mean biomass at and subtidal benthic stations in August.Table 3.3.2-1 for years each station was Seabrook Baseline Report, 1987.intertidal (See Appendix sampled)208 '5I STATION 1 MLW 2500 -STATION 17 C,, 0 1500-2100 50I0 2000-V)1500~~1000~0.500 -I I I *l I I I I.*'~*0 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR 1978 1979 1980 1981 1982 1983 1984 1985 1986-1987 YEAR STATION 19 1000-STATION 4 NS = NOT SAMPLED 750 -300 U)0 200 100 0-0 ,-4 Im .... I 0 I I I I I I I I I I I I I A I 1978 1979 1980 1981 1982 1963 1984 1985 1986 1987 YEAR '1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 3.3.2-3.Mean biomass (gMs/m 2) and 95A confidence limits for macroalgae collected in August at selected nearfield benthic stations (note differences in scale). Seabrook Baseline Report, 1987.209 The number of taxa collected at each station'in 1987 (NAI 1988) did not exceed the number collected during the baseline period (NAI 1987b) with.one exception. One more species was collected at Station 19 inbiomass samples than had previously been collected at that station; however, there were no taxa new to the study area.The depth differences among benthic stations were also reflected in the relative abundance (biomass) of the six taxa that were dominant during the baseline period (Figure 3.3.2-4). Ptilota serrata. was dominant at the deepest stations, Phyllophora spp. (P. truncata and P. pseudoceranoides) were most abundant atmid-depth stations, and Chondrus crispus was dominant in the shallow subtidal and intertidal. Relative abundances for .1987 showed this same pattern (Table 3.3.2-1). However, C. crispus made up a higher than average percentage of biomass in 1987 at Stations 1MLW, 35 and .16 with concomitantly lower percentages of Mastocarpus stellatus (Station IMLW only), Phyllophora spp. and Phycodrys rubens (Stations 35 and 16 only), respec-tively. 'The three other taxa listed in Table 3.3.2-1 were frequent sub-dominants. These six dominants combined typically represented more than 90%of the biomass at each station. The greatest exception to this occurred in 1987, when "other" taxa comprised between 10 and 25% of the biomass at seven of the 10 stations sampled. This was primarily due to the abundance of red algal epiphytes which were higher in 1987 (NAI i988a).Community Analysis Station differences in the macroalgae community were caused by the depth-related differences in species' relative abundance. Historically, six depth-related station groups had been identified from cluster analysis of August (1978-1984).samples (NAI 1985b; Table 3.3.2-2). Although several taxa had been found across all depths, each species had a depth zone within which it reached peak biomass (Figure 3.3.2-5); it. was the unique association of species' biomasses that resulted in a different community structure in each depth zone. Within each depth zone, the paired nearfield and farfield stations were most similar to each other (Table 3.3.2-2) .210 z cc 80-60-40 20 0 Plilota serrata O Phyllophora sop.o Corallina officinalis 0 Phycodrys rubens Chondrus crispus Mastocarpus stellatus* Other Taxa MLW 4.6 9.6 11.6 18.3 19.7 MEAN DEPTH (m)Figure 3.3.2-4.Relative abundance'(% biomass) of dominant macroalgae at marine benthic'stations (by station-depth group)in August, 1978-1987. Seabrook Baseline Report, 1987.211 TABLE 3.3.2-1. RELATIVE ABUNDANCE OF DOMINANT HACROALGAE AT MARINE BENTHIC STATIONS IN AUGUST OF THE THREE MOST RECENT YEARS (1985, 1986 AND 1987).SEABROOK BASELINE REPORT, 1987.RELATIVE ABUNDANCE (PERCENT)INTERTIDAL DEEP STATIONS STATIONS a a a a SPECIES YEAR 4 34 13 19 31 16 17 35 1MLH M1LH Chondrus crispus 1985 .. .. .. 0 43.6 -- 89.3 45.6 84.6 53.0 1986 0.1 0 0 0.4 38.6 3.7 89.8 52.6 62.8 83.5 1987 <0.1 0 0 0.3 22.9 18.1 81.6 71.8 97.5 73.0 Corallina officinalis 1s985 .. .. -- 9.6 15.3 -- 5.6 2.2 0.3 -17.9 1986 16.7 0 <0.1 2.8 20.0. 0.1 1.9 5.6 2.3 Z.6 1987 10.4 0 0 0.8 12.8 <0.1 2.7 8.3 0.1 1.4 Mastocarpus stellatus 1985 .. .. ... 0 0 -- 0 0 14.9 28.7 1986 0 0 0 0 0 0 0 0 34.8 13.7 1987 0 0 0 0 0 0 0 0 *2.0 25.1 Phycodrys rubens 1985 -- -- -- 17.7 5.0 -- 0.5 1.2 <0.1 <0.1 1986 0.8 0.3 3.4 22.5 Z.5 30.3 0.3 Z.0 <0.1 <0.1 1987 1.4 O.Z 15.2 12.5 5.7. 12.3 0.3 0.2 <0.1 <0.1 Phyllophora spp. 1985 .. .. .. 59.4 32.9 -2.1 26.8 <0.1 <0.1 1986 31.7 36.0 88.3 62.0. 35.2 59.6 2.2 29.4 <0.1 <0.1 1987 30.5 13.6 58.3 73.3 49.7 44.2 3.1 4.4 0 <0.1 Ptilota serrata 1985 --- -- -- 7.2 0.5 -- <0.1 <0.1 0 <0.1 1986 47.6 59.1 6.4 *3.4 0.8 .1.0 <0.1 <0.1 0 <0.1 1987 40.4 63.4 11.3 1.3 1.1 0.6 <0.1 <0.1 <0.1 0 All others 1985 -- -- -- 6.2 2.7 -- 2.4 24.3 0.2 0.4 1986 3.1 4.6 1.9 8.9 2.9 5.5 5.8 10.4 0.1 0.2 1987 17.3 22.8 15.2 11.8 7.8 24.8 12.3 15.3 0.4 0.5 a Not sampled in 1985. TABLE 3.3.2-2.

SUMMARY

OF SPATIAL ASSOCIATIONS IDENTIFIED FROM NUMERICAL CLASSIFICATION (1978-1984) AND VERIFIED WITH DISCRIMINATE ANALYSIS (1978-1987) OF BENTHIC MACROALGAE SAMPLES COLLECTED IN AUGUST. SEABROOK BASELINE REPORT, 1987.SAMPLE SIMILARITY-MEANb MEAN BETWEEN BIOMASS GROUP STA- DEPTH WITHIN STA- b GROUP NO. TIONS (m) STATION TIONS DOMINANT TAXAb (g/mi 2)13 18.3 4 19.7 34 19 11.6 31 16 (1984)16 9.4.68.84.71.78.80.87.- Phyllophora spp.Ptilota serrate Phycodrys rubens Polysiphona urceolata Scagelie corallina.70 Ptilota serrate Phyllophora spp.Corallina officenalls Scagelia corallina Phycodrys rubens.70 Phyllophora spp.Corallina officinalis Chondus crispus Phycodrys rubens Callophyllis cristata Ptilota serrate Phyllophora spp.Phycodrys rubens Cystoclonium purpureum Chondrus crispus Ceramium rubrum Callophyllis cristata 63.19 12.09 5.50 3.50 3.32 65.09 8.96 7.75 1.15 1.04 196.50 56.53 53.45 40.45 12.86 12.61 428.07 217.92 60.17 53*26 36.99.34.74 continued 213 A discriminant analysis was used as a comparative method to confirm results of the cluster analysis and to allow a comparison of 1985, 1986 and.1987 results with the previous baseline period;- Replicates were averaged in this analysis to av6id the influence of small-scale spatial variability and to be consistent with cluster analysis methods (NAI 1985b) and the macrofauna analysis (Section 3.3.3)., Species assemblages identified by discriminant analysis were, identical to those identified for the baseline period by cluster analysis.Samples collected from'1985-1987 were placed in the same group as the majority of samples from previous years, verifying the similarity in species composition (Table 3.3.2-3). Therefore, although there may be differences in the biomass of a species from sample to sample or year to year within a station group, the relationship among species biomass has been very consis-tent. The degree of differences at the species level is examined for two dominant macroalgae species in the "selected species"-section which follows.In order to monitor the algal community for new or infrequently occurring species which might bloom to "nuisance" levels, the rarer species occurrences were also examined. Twenty taxa occurred sparsely (less than 5%of the biomass collections) from 1978 to 1987 (Appendix Table 3.3.2-2). The only unusual occurrence reported to date was Bonnemalsonia hamifera which was.new to biomass collections in 1986 (Stations 5MLW, 31 and 35), and occurred in greater than 5% of the samples. This warmer water species has been recorded in Great Bay (Mathieson and Hehre 1986), but not at *offshore sites in this study prior to 1986. The recent occurrence may have been related to the increased water temperatures in the nearshore area in 1985 and 1986 (see Section3.1.1). More of the "sparsely occurring" taxa have also been recorded in recent years (NAi 1985b) and may be related to the same cause.Water temperatures in 1987 were lower than 1985 and 1986; in fact, the bottom temperatures (at the Intakes) averaged the second lowest over the 1978-1987 period. B. hamifera was not recorded at any stations in 1987 (NAI 1988a).216 TABLE 3.3.2-3.PROBABILITY OF 1978-1987 MACROALGAE SAMPLE MEMBERSHIP IN EACH STATION GROUP IDENTIFIED FROM NUMERICAL CLASSIFICATION (cluster analysis) OF 1978-1987 AUGUST BENTHIC DATA. SEABROOK BASELINE REPORT, 1987.DISCRIMINANT FUNCTION GROUP CLUSTER ANALYSIS GROUPa 2 3 4 5 6 10b 1 1 0 0 b 0 0 0 0 0 (9)2 0 100 0 0 0 0 (17)3 0 0 100 0 0 0 (21)4 0 0 0 100 0 0 (6)5 0 0 0 0 100 0 (16)6 0 0 0 0 0 100 (16)aSee Table 3.3.2-2 100 = sample percent probability of group membership (9) = number of samples per group 217 Kelp Transect Survey Spatial differences in kelp species abundance appear primarily attributable to depth differences. Laminaria saccharina has historically been most abundant at the shallower stations (Figure 3.3.2-6). LamInaria digitata has been shown to reach maximum abundance in the study area at Station 31 (9.4 m below MLW), whereas Agarum cribrosum's greatest abundance was at Station 19 (13.7 m below MLW)(NAI 1985b). Significant spatial dif-ferences between nearfield and farfield mid-depthstations (Stations 19 and 31), were found for some species, where L. digitata and Alaria esculenta were more abundant at Farfield Station 31 (NAI 1985b) Abundances recorded in 1987 followed similar spatial patterns to 1978-1984 occurrences (NAI 1988), but densities of L. saccharina were higher than past years in the shallow subtidal (17, 35) while densities of L. digitata were higher at the mid-depth stations (19 and 31). .J No consistent seasonal variation in abundance was observed for any species of kelp, probably because "juvenile" (<15 cm) plants were not'.enumerated; these plants are difficult to accurately count in situ because of their small size and high density (NAI 1984a, 1985b). Seasonal'variation in biomass was reflected in growth studies conducted prior to 1985; growth closely followed the solar irradiance and nutrient cycles (NAI 1985b). Stand density, which is controlled by substrate availability, recruitment and environmental conditions (e.g. storm disruption), showed some variability among years. Kelps, particularly Laminaria species, are quick-growing, opportunistic plants. Consequently, they are among the "pioneer" species that colonize freshly exposed substrate, adding to the year-to-year vari-ability in distribution. Measurements of percent frequency of occurrence of the three understory algae that were dominant at transect sites (Figure 3.3.2-6), showed differences among depths that were similar to those observed-from biomass collections (Figure 3.3.2-3). Chondrus crispus occurred more, frequently in the shallow subtidal zone whereas Phyllophora sp. and 218 A. Kelps Shallow Mid-depth 3-cn 3 W I-I.-*Li cc 2 z a.Z.* nea'field (17)3 fatileld (35)LU o-i I.-2-2 0 U, I--z 03.0-"r-BE B. -Understory algae 6~. c 66 c ~-a 66-I.4-u 2_j0 C 66 Shallow Mid-depth L.Z LL LL 1.-80-60-40-20-T in nearfield (17)[o far Meld (35)50 40 0 z 30 U.,20 U-T I 6 6 -.0 A--0 C.)0 0 .m m -0..-a..0.6 0 7 0 0.Figure 3.3.2-6.A. Mean and 95% confidence interval of log number/100 of kelps (1978-1987; station 35: 1982-1987) and B.Percent frequencies and 95% confidence interval of dominant understory algae (1981-1987; station 35: 1982-1987) in the shallow and mid-depth subtidal zone.Seabrook-Baseline Report, 1987..m2)219 Ptilota serrata were encountered more frequently in the mid-depth zone.Ptilota serrata occurred as frequently as Phyllophora sp. at Station 19 even though it was not at its peak biomass (Figure 3.3.2-5). Ptilota serrata was significantly lower and Chondrus crispus significantly higher at Station 31 (which is 9.5.m deep) than at Station 19, which is 13.7 m deep (NAI 1985b)..Patterns shown by the 1987 frequencies of occurrence were within the range observed historically, with one exception:' Ptilota serrata showed fewer occurrences at Station 19 than in past years (NAI 1988). Also, the frequency of this species equalled the lowest recorded value (in 1986) at the counter-part farfield station (31) (NAI 1988).Intertidal Fixed Quadrat and Transect Surveys In situ counts' of macroalgae in fixed quadrats at the intertidal stations (Stations 1 and 5) were conducted at mean low water (Site "D") and at mean sea level on bare ledge (Site "C") and fucoid-covered ledge (Site"B") habitats. These quadrats were set up in order to monitor the same exact habitat thus eliminating small-scale spatial variability and focusing on temporal variation. Appendix Table 3.3.2-3 shows the occurrence of those species recorded more than once in a.quadrat; other less common taxa (i.e., recorded only once in the study to date), were not included. Since the'quadrats (sites) have unique characteristics, each will be described in turn.The Bare Ledge Site (C), at the upper edge of the MSL (mean sea level) zone, was characteristic of "bare" ledge in the area, that is,' ledge not continuously covered by macroalgae. Although'highly seasonably variable, barnacles have been common in this quadrat (see Section 3.3.3 for faunal coverage). During the spring the annual greens, Urospora pencilliformis and Ulothrix flacca (at both stations), and the red algae, Bangia fuscopurpurea (Station 5MSL), have been abundant. Small, immature perennial Fucus sp..plants have also been found in this quadrat; although they occurred'fre-quently, their percent cover was usually less than 10%. Temporal variations in these fucoids have been observed over one to two year periods (Appendix. 220 Table 3.3.2-2). These variations are apparently not related to any seasonal or yearly trend but likely to plant loss and slow regrowth. Algae settlement and growth are controlled by balancing the opportunity for settling on available space versus the effects of Spatially, the bare rock quadrats have been generally similar, although temporal variations in Fucus sp. appeared spatially independent. The more persistent red, Porphyra sp.was unique to IMSL, while B. fuscopurpurea was unique to 5MSL (in these fixed quadrats).. The Fucoid Ledge Site (B), in the mid-MSL zone, is situated in the area of maximum fucoid algae cover. The perennial, Fucus vesiculosus, has been the major species within the quadrats, although some F. disticus-v. edentatus and Ascophylum nodusum (Station 5MSL) have been recorded-(Appendix Table 3.3.2-3). These fucoids were quite persistent and frequently occurring, although relatively 10w (<40%) coverages have been recorded at times, e.g., December 1982 (both stations) and winter/spring of 1984-1985 (at IMSL). The perennial red algae, Chondrus crispus and Mastocarpus stellatus occurred as understory algae at both stations, but in relatively low amounts (usually <10% frequency); the latter species was more persistent. Few other algae were common in these quadrats, except Porphyra sp. and Spongomorpha sp.both (both at Station IMSL only).Fixed line transects have also been surveyed in the MSL zone from 1983 to 1987 to quantify the areal coverage of the fucoid algae. In the fixed areas studied,-the percent frequency of occurrence of Ascopyllum nodosom was similar at both stations (Figure 3.3.2-7) while Fucus vesiculosus was almost twice as frequent at the nearfield station (lMLW). Some F. distichus var. edentatus was also recorded at IMLW, but none at the farfield site (5MLW). The degree of among year variability was low (21-33%CV) for the two dominant fucoids (Figure 3.3.2-7).The quadrat at Site D, in the MLW (mean low water) zone, is situ-ated in the area of maximum red algae cover.- Chondrus crispus and Mastocarpus stellatus dominated this zone; together they typically cover 80 to 1.00% of the substrate. Spatially, the frequency of occurrences at the two 221 I.100-80-100-100 Ascophyllum nodosum Fucus vesiculosis Fucus distichus var. edentatus 80-60-80 T LU LL.e 60 60-I Tr 40-2O-T 40 20 0 0-i--0 -L 1 MSL 5MSL 1 MSL 5MSL 1 MSL 5MSL STATION I .Figure 3.3.2-7. Mean percent frequency and standard deviation of fucoid algae at two fixed transect. sites in the mean sea level zone (1983-1987). Seabrook Baseline Report, 1987.222 stations' quadrats were generally similar for these two dominants although there has tended to be a greater frequency of C. crispus at 5MLW. Spatial differences included the occurrence of Fucus sp. which was persistent only at IMSL as overstory, and Corallina officianalis which was persistent at 5MSL as an understory species; small scale vertical differences between stations likely contributed to these species occurrence differences. 3.3.2.2 Selected Species Laminaria saccharina Laminaria saccharina has been one of two dominant canopy-forming kelps in the shallow subtidal zone (1 to 9 m deep) surrounding the Inner and Outer Sunk Rocks. Average seasonal densities (1979-1987) of adult planlt ranged from 1 to 11 plants/m 2 at the nearfield station (17), while average percent cover ranged from 3% to 43% (Table 3.3.2-4). Density varied greatly due to variability in the amount of substrate available for settlement combined with the contagious (clumped) distribution of these plants. At Station 17, annual mean densities were greatest in 1979 (981 plants/100 m 2), decreased to 285 plants/100 m 2 in 1982, and remained at that approximate level through 1987. The most precipitous change in density occurred between, April and July 1982 with an 85% drop in density. There had been a very large and dense stand of kelps in the western portion of this station which has since diminished since 1979; this has contributed to changes-observed in 1982. It can be hypothesized that due to scouring from the storm of 1978 larger amounts of substrate became available for Laminaria settlement, which resulted in higher densities in 1979; over timethese stands may have diminished to a more "typical" level (as in 1982) as substrate became recovered with understory algae. Over the last six years (1982-1987) when both nearfield and farfield stations were monitored, however, AnnuaI differences were not significant (Table 3.3.2-5). Average numbers of plants per quadrat were similar between the nearfield (17) and farfield (35)223 pl TABLE 3.3.2-4. SEASONAL.AND YEARLY MEAN ABUNDANCEa AND PERCENT COVER OF LAMINARIA SACCHARINA FROM TRANSECT STUDIES IN THE SHALLOW SUBTIDAL ZONE. SEABROOK BASELINE REPORT, 1987.2 2 NO./100 m % COVER NO./100 m % COVER 17 35 17 35 17 35 17 35 1979 Apr 1052 35 1984 Apr 311 209 9 9 Jul 888 43 Jul 252 209 13 18 Nov 1004 34 Oct 555 152 20 8 Mean 981 37 Mean 373 190 .14 12 1980 Apr 724 18 1985 Apr 340 159 i6 5* Jul 678 32 Jul 212 264 16 19 Nov 754 37 Oct 286 302 19 6 Mean 719 29 Mean 279 242 17 i0 1981 Apr 719 21 1986 Apr 278 757 17 21.Jul. 519 24 Jul 167 188 8 16 Nov 500 20 Oct 169 245 7 20 Mean 579 22 Mean 205 397 11 19 1982 Apr 588 25 .1987 Apr 71 195 5 13 Jul 88 669 .6 36 Jul 433 550 22 21 Oct 179 409 14 14 Oct 367 743 12 17 Mean 285 539 15 25 Mean 290 496 13 17 1983 Apr 83 104 3 5 Jul 217 376 13 18 Oct 693 207 13 11 Mean 331 229 10 11 a Only plants measuring _ 15 cm long were counted.bStation 17 = nearfield; Station 35 = farfield.1.S..224 TABLE 3.3.2-5. RESULTS OF SIGNIFICANCE TESTS ON MACROALGAE SELECTED SPECIES, CIJONDRUS CRISPUS AND LAMINARIA SACCIJARINA. SEABROOK BASELINE REPORT, 1987.A. CIIONDRUS CRISPUS BIOMASS (g/mr 2)Temporal (Year) Comparisons (1978-1987): one-way ANOVA of'Log (x+l) means STATION df SS F VALUE SIGNIFICANCEa lMLW 9 0.495 1.62 N.S.17 9 0.325 0.67 N.S.Spatial (Station) Comparisons (1982-1987): Paired t test of sample means STATIONS t SIGNIFICANCE COMPARISON 1MLW VS. 5 MLW 2.59

• Nearfield greater 17 VS. 35 2.92 ** Nearfield greater B. LAMINARIA SACCJARINA DENSITIES (NO./m 2)Temporal (Year) Comparisons (1982-1987):

Wilcoxon's Ranks Test STATIONS VARIABLE SIGNIFICANCE 17 and 35 years N.S.combined (1982-1987) Spatial (Station) Comparisons (1982-1987): Wilcoxon's Ranks.Test STATIONS VARIABLE SIGNIFICANCE 17 vs. 35 stations N.S.aN.S. Not significant Significant at p < .05 Significant at p < .01 225 stations over the entire 1982-1987 period (Table 3.3.2-5), but the kelp beds were more evenly distributed at Station 17 than at Station 35 (NAI 1985b), evidently because of differences in available substrate. Chondrus crispus Chondrus crispus (Irish moss) was the dominant understorylalgal species in the lower intertidal and shallow subtidal-zones near the Sunk Rocks (see Community Analysis section). Destructive samples were collected in May, August, and November from 1978 to 1987 (1982 to 1987 for Stations 35 and 5MLW); maximum biomass typically occurred in August at all stations, except 5MLW (Figure 3.3.2-8). Minimum values generally 6ccurred in May at subtidal stations; at 1MLW the lowest Values were generally found in the fall. However, confidence limits (calculated for 1978-87) implied a significant difference between minimum and maximum seasonal biomass only at Stations 17 and 35. Biomass values from 1987 generally differed very little from the historical data (NAI 1988). At intertidal Station 5MLW, biomass in 1987 was noticeably (about 50%) lower in May collections than in previous years (NAI 1988). These data continued to add to the natural variability of the baseline data at this station.August biomass values at Station 17 ranged from 574.9 g/m 2 in 1980 to 1272.7 g/m 2 in 1985 (Table 3.3.2-6). Overall biomass at Station 17 was significantly higher than that at Station 35 (Table 3.3.2-6). Peak biomass, at Station 1MLW was recorded in 1982 (1622.9 g/m 2), its minimum in 1978 (459.7 g/m 2); biomass at 1MLW was statistically different (at p <.05) from the farfield station.226 w w w U)U)0 z LU 1400 1 200o 1000-800 -T]MAY* AUGUST o3 NOVEMBER T 600 -400-200 10-B17 B35 B11 B51 STATION Figure 3.3.2-8 Mean biomass (gm/m2 ) and 95% confidence limits of Chondrus crispus at selected stations in May, August and November, Stations 17, 35: 1978-1987, Stations 35 and IMLW: 1982-1987) Seabrook Baseline Report, 1987. 2 TABLE 3.3.2-6.. MEAN BIOMASS (g/m ) AND STANDARD DEVIATION (SD)OF CHONDRUS CRISPUS AT BENTHIC STATIONS 17, 35, 1MLW, AND 5MLW IN AUGUST FROM 1978 TO 1987.SEABROOK BASELINE REPORT, 1987.SHALLOW SUBTIDAL, INTERTIDAL STATION 17 STATION 35 STATION 1MLW STATION 5MLW YEAR (NEARFIELD) (FARFIELD) (NEARFIELD) (FARFIELD) MEAN S.D. MEAN S.D. MEAN S.D. MEAN S .D.1978 860.3 535.7 NSa 459.7 532.9 NS 1979 7i3.8 301.8 NS 638.6 138.1 NS 1980 574.9 282.4 NS 797.8 262.1 NS 1981 1113.8 384.2 NS 917.3 558.1 NS 1982 593.6 194.5 491.9' 234.9 1622.9 345;3 1147.4 174.4 1983 853.8 243.5 .663.4 388.9 1539.6 129.1 994.3 461.8 1984 782.1 251.5 484.7 344.2 1612.4 263.8 457.3 321.7 1985 1272.7 366.2 544.3 428.4 1203.5 179.9 530.9 479.7 1986 1193.3 329.7 523.7 343.2 1154.4 723.1 857.7 258.0 1987 943.5 288.1 673.1 414.2 951.9 263.8, 628.6 312.7 ALL YEARS MEAN 890.2 563.5 1089.81 769.4 L.ii.a = Not sampled.228

3.3.3 Marine

Macrofauna 3.3.3.1 Algae Covered Ledge Community General Studies of the macrofaunal invertebrates off Hampton Beach, NiH*since 1978 have focused on the horizontal algae-covered ledge habitat in four depth zones: intertidal (MLW and MSL),'shallow subtidal (5 m), mid-depth (9-12 m) and deep (18-21 m)(Table 4.1-1). Nearfield stations near the intake and-discharge areas have paired farfield counterparts near Rye Ledge in the same depth zone (Figure 4.1-3) for an optimal impact assessment design (Green 1979). Macrofaunal studies include a community analysis of intertidal and subtidal habitats, a detailed examination of key species (see Section 3.3.5 also) and an investigation of the near-surface and bottom fouling community (see Section 3.3.4 also).Numbers of Taxa and Total Abundance Numbers of taxa and total abundance have been used to'monitor spatial and temporal trends in the macrofaunal community. These parameters have shown broadscale changes in relation to depth. The number of taxa generally increased with increasing depth, and nearfield stations had higher numbers of taxa in comparison to farfield stations (Figure .3.3.3-1). Total abundance showed a general decrease with increasing depth (Figure 3.3.3-1), mainly due to decreased numbers of mytilids (see Section 3.3.5).The intertidal area had highest abundance of all of the benthic stations, and nearfield and farfield stations had lower numbers of taxa than subtidal counterparts (Figure 3.3.3-1). Nearfield Station 1MLW had higher numbers of taxa and total abundance than its farfield counterpart, Station 5MLW (Figure 3.3.3-1). The presence of boulders at the farfield site may decrease available habitat space, in turn decreasing the total abundance and 229 Ca 0 z 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0"J U-..1MLW 5MLW 17 35 16 31 19 13 4 34 STATION 200000 180000 160000 140000 Ul 120000 100000 0 80000 C')60000 Z40000 2 0000 1MLW 5MLW 17 35 16 31 19 13 4 34 STATION Figure 3.3.3-1. Number of taxa and overall abundance (No./square meter)over all years (1978-1987, stations IMLW,. 17, 19, 31;1982-1987, 5MLW, 35; 1979-1984, 1986-1987, 34; 1978-84, 86-87, 13, 4, 16) at intertidal and subtidal benthic stations. Seabrook Baseline Report, 1987..17 I.230 number of taxa. The 1987 abundance levels at lMLW dropped from the extremely high levels recorded in 1986 to levels similar to previous years (Figure 3.3.3-2), in part due to decreases in mytilid abundances from their peak 1986 levels (see Section 3.3.5). The number of taxa in 1987 was the lowest ever recorded at intertidal stations: 60 at Station 1MLW and 64 at Station 5MLW (Figure 3.3.3-3). This could be a result of the prolonged period of low salinity in April and May (see Section 3.1.1). Bottom salinities were below 31.5 ppt for two to three months at Station P2. In addition, 1987 bottom temperatures at this station were approximately 3 0 C below average in August and September (Figure 3.1.1-1).The shallow subtidal stations (5Sm), Stations 17 and 35, had higher numbers of taxa than their intertidal counterparts but. lower numbers than mid-depth and deep areas (Figure 3.3.3-1). The nearfield station had a higher number taxa (227) in comparison to the farfield area (195) but slightly lower overall abundance (Figure 3.3.3-1). Number of taxa decreased at both stations in 1987, although the decrease was slight at Station 17, remaining within the range of previous years. Total abundance in 1987 decreased at Station 17 following peak levels in 1986 (Figure 3.3.3-2), due to decreases in Mytilidae and Lacuna vincta, which were exceptionally high in 1986 (NAI 1987b, 1988)..Mid-depth (9-12 m) stations, Stations 16, 31, and 19, continued the trend of increasing numbers of taxa and decreasing abundance with increasing depth. Numbers of taxa were consistently higher at Stations 19 and .16, where algae-covered ledge predominates and mussel beds comprise 25-40% of the habitat (Figure 3.3.3-1). In comparison, Station 31 was predominantly com-posed of mussel beds (60%) with cobble and algae-covered rocks also present (Table 4.1-1). Numbers of taxa in 1987 were the lowest encountered since.sampling began (Figure 3.3.3-4). Abundance levels at Station 16 were higher than at Station 31 which in turn were higher than at Station 19, because of the varying numbers of mytilids (Figure 3.3.3-1). Abundance levels in 1987 at Station 19 decreased from peak levels in 1986, (Figure 3.3.3-5), dimin-ished by lower mytilid densities (see Section 3.3.5). At Station 16, total abundance was the lowest recorded since sampling began in 1980 (Figure 3.3.3-5).231 I-Uj Uj 0 z 1000000 900000 800000 700000 600000 -500000 400000 300000 200000 -100000 0 INTERTIDAL (1MLW)T I 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 i YEAR 100000 SHALLOW SUBTIDAL (17)wr I-W cc 90000 80000 70000 60000 50000 40000 30000 20000 10000 1978 1979 19.80 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 3.3.3-2.Annual mean abundance (No./square meter) and 95%confidence limits for macrofauna collected in August for nearfield stations lMLW (intertidal) and 17 (shallow subtidal). Seabrook Baseline Report, 1987.232 I 120 -100-INTERTIDAL I.LU M wZ zE 80 60.40-20-1 MLW (nearfield) ....... 5MLW (farfleld) 0 1978 1979 I I I -I'1980 1981 1982 1983 I I I i 1984 1985 1986" 1987 YEAR LL 0 z 140" 120 100 60-40 -SHALLOW SUBTIDAL B17 (nearfield) ... 5 35 (farfield) 20-0 I I I I I 1978 1979 1980 1981 1 1 1982 1983 I I I 198 1984 1985 1986 1987 YEAR Figure 3.3.3-3.Annual number of taxa collected in August at intertidal stations IMLW and 5MLW and shallow subtidal stations 17 and 35. Seabrook Baseline Report, 1987.233 d AA I-LL.0 z 14U.-130-120 -110-100 90 80 1.MID-DEPTH-19 (nearfield) ..31 (farfield) 70 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR X U.0 zL z 150-140-130-120.110-100 90-80-DEEP-.4-4 (nearfield) ....... 34 (farlield) 70 a I I I I I I I I 1978 .1979 1980 1981 1982 1983 1.984 1985 1986 1987 YEAR.[4 x l-IL 0 U'z,&170-160-150-140-130-120-110-100-90 80-70 MID-DEPTH TO DEEP*13 (nearfield) ...... 16 (farfield) I I I I I I I I 1 .I 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 3.3.3-4.Annual number of taxa collected in August at stations 16, 19, and 31 (mid-depth); and stations 4, 13, and 34 (deep). Seabrook Baseline Report, 1987.234 N E z 80000 60000 40000 20000 MID-DEPTH (19)0 140000 120000 1978 1979 1980 1981 1982 1983 YEAR 1984 1985 1986 1 MID-DEPTH (16)E z E 6 100000 80000 60000 40000 20000 01 12000 10000-8000 -6000 -4000-2000 -0" 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR DEEP (4)V-i I ; !I I £ I *1978 1979 1980 1981 1982 1983 YEAR I

• I I I 1984 1985 1986 1987 Figure 3.3.3-5.Annual mean abundance (No./square meter) and 95%confidence limits for macrofauna collected in August for nearfield stations 19 and 16 (mid-depth) and 4 (deep). Seabrook Baseline Report, 1987.235 The deepest stations (18-21 m), Stations 4, 34 and 13, had the highest number of taxa and the lowest number of individuals in comparison to shallow and mid-depth areas (Figure 3.3.3-1).

The overall number of taxa has consistently been lowest at Station 13, which has a mixture of algae-covered ledge, mussel beds, and cobble, and highest at Station 4, where mussel beds predominate, with some algae-covered-ledge present. Station 34, slightly deeper at 21 m, has been intermediate in its number of taxa, and is pre-dominantly mussel bed (Figure 3.3.3-1, Table 4.1-1). Numbers of taxa in 1987 fell within the range of previous years at all.three stations (Figure 3.3.3-4). Density levels were highest at Station 13 and similar at Stations 4 and 34 (Figure 3.3.3-1). The abundance levels in 1987, while within the range of previous years, were slightly lower than average at Stations 4 (Figure 3.3.3-5) and 34 (NAI 1987b, 1988).Elevated abundances at Station 13 in 1986 were due mainly to high numbers of Balanus crenatus (10,323/M 2) and Lacuna vincta (4000/m 2)(NAI 1987a). In 1987, total abundances were similar to those observed in 1986, but instead were a result of high densities of Mytilidae, Balanus crenatus,*and fliatella sp. all averaging.from 4000-5000/mr 2 (NAI 1988).Community Structure The noncolonial, macrofaunal, hard-bottom community structure has historically shown changes related to depth (NAI 1987b). Intertidal, shallow subtidal, mid-depth, and deep areas were distinct in both species distri-butions and abundances. The 1987 collections showed highly similar species composition to collections from previous years (Table 3.3.3-1). In all cases, based on the similarity in species composition, the 1987 collections were placed in the group with the majority of historical collections from the same station (Table 3.3.3-1). The addition of 1987 data caused only a few changes in the within-group abundance of dominant taxa, underscoring the similarity of 1987 to previous years.236 TABLE 3.3.3-1. STATION GROUPS DEFINED BY DISCRIMINANT ANALYSIS OF NON-COLONIAL MACROFAUNA COLLECTrED AT SUBTIDAL BENTHIC STATIONS, AUGUST 1978-1987. SEABROOK BASELINE REPORT, 1987.INTERTIDAL AND STATION STATIONS SAMPLES/GROUP (YEARS)a GROUP DEPTH/SITE DOMINANT TAXA NO. /M 2 1 19(1978)31( 1978)4(1978)34(1980)4 Mid-depth -deep/discharge and control 2 3 13(1978,1981-84, 86,87)34(1983-84,86) --19(1979-87) 31(1979-87) 13(1979-80) 16(1984)4(1979-84,86,87) 34(1979,1981-8Z,1987) ZI Deep/discharge and control Hid-depth/discharge, ,intake, control deep/discharge Deep/discharge and control Pontogeneia inermis Mytilidae Hiatella sp.Asteriidae Caprella septentrionalis Anomia sp.Balanus crenatus Mytilidae Hiatella sp.Anomia sp..Balanus sp.Lacuna vincta Pontogeneia inermis Asteriidae Mytilidae Pontogeneia inermis Hiatella sp.Anomia sp.Caprella septentrionalis Balanus crenatus Molgula sp.Lacuna vincta Pontogeneia inermis Asteriidae Caprella sp.Caprella'septentrionalis Anomia sp.Balanus crenatus Musculus niger Mytilidae Lacuna vincta.Pontogeneia inermis Caprella septentrionalis Idotea phosphorea Jassa falcata Mytilidae Jaera marina Turtonia minuta Hiatella sp.Lacuna vincta Gammarellus angulosus Oliogochaeta Nucella lapillus 1550 621 322* 244*242 234 3427 17Z5 944 887 671 467 343 312 17797 1385 1Z62 1058 1004 699 535 493 519 334 487?_56 250 247 237 8723 4971 4043 20?_5 1944 1907 101630 7334 6483 5798 4895 4088 3908 3031 4 13 5 6 17(1978-87) 35(1982-87) 16(,1980-83,86,87) 1MLN(1978-87) 1MLN(1982-87) 22 16.Shallow -mid-depth/ discharge, intake Intertidal/Outer Sunk Rocks, Rye Ledge aNo samples collected at Station 34 in 1979 or 1985; Stations 5MLW and 35 in 1978-81; or Stations 16 and 13 in 1985. Differences in community structure among stations were indicated by differences in densities of dominant taxa as well as the species which are restricted to a certaindepth zone. The discriminant analysis relied on only 32 of the original 89 species used in the cluster analysis to form the station groups (Appendix Table 3.3.3-1)-. The most abundant species (i.e., Mytilidae spat, Pontogeneia inermis, Lacuna vincta, Caprella septentrionalis) were ubiquitous, and contributed little to the discrimination among stations.Less-abundant species, such as Nucella lapillus, Calliopius laeviusculus, Jassa falcata, Nereis pelagica, Jaera marina, and Musculus niger, accounted for the majority of the among-station variability. The intertidal habitat (Group 6) was the most distinct of all areas because'of the overwhelming predominance of Mytilidae spat (101,630/m

2) and the presence of species such as Nucellalapillus, Fabricia sabella, Hyale nilssoni, and Jaera marina, which were restricted to that area. Other dominants included the molluscs Turtonia minuta, Hiatella sp., and Lacuna vincta, and the amphipod Gammarellus angulosus.*

Intertidal collections made in 1987 were placed in this group based on similar species composition. However, a few of the individual species showed decreases in densities from peak levels noted in 1986, decreasing the overall group density from the 1978-1986 value (NAI 1987b). These included Mytilidae at Station IMLW only, and Iliatella sp. and Jaera marina at both IMLW and 5MLW (NAI 1987b, 1988).Mytilids at Station 5MLW reached their highest density since sampling began in 1982 (see Section 3.3.5).The shallow subtidal station group,(5) has included Station 17 and 35 in all years and Station 16 in 1980-1983 and 1986-1987 (Table 3.3.3-1).Mytilidae was still the predominant taxon, although less abundant than in the intertidal area. Aside from gastropod Lacuna vincta, dominants were peracarid crustaceans'such as Pontogeneia inermis, Caprella septentrionalis, Idotea phosphorea, and Jassa falcata (Table 3.3.3-1). Relatively high densities of the latter two species, along with Calliopius laeviusculus distinguished this area from other areas.. The addition of 1987 collections did not change the order of the dominant species, nor drastically alter the 238 within-group abundance. However, average group abundance levels of all taxa were lower than 1978-1986 levels due to decreases from the 1986 density levels (NAI 1987b, 1988). Species composition at Station 16, with depth of 10.7 m, was usually more similar to the shallower Stations 17 and 35 because of the predominance of uniform algae-covered ledge, causing increased biomass of algae (see Section 3.3.2). This, in turn, increased numbers of sub-dominant herbivorous species such as Lacuna vincta and Idotea phosphorea, which increased the similarity of this station's species composition.with that of shallow subtidal stations. Furthermore, flat ledge at Station 16 (with fewer mussel beds and boulders) prevented the accumulation of sediment and detritus, making it less suitable.than other mid-depth stations for species which need soft substrate such as Nichomache sp., Cistenides granulata and Cerastoderma pinnulatum. Mid-depth areas (Group 3),were characterized by a predominance of Mytilidae spat, with other molluscs (e.g., 3fiatella sp. and Anomia sp.) and amphipods (e.g.,.Pontogenela inermis and Capre1la septentrionalis) occurring in high numbers (Table 3.3.3-1). Stations 19 and 31 in most years were characterized by this assemblage, as were deep Station 13 and mid-depth Station 16 in one or two years. The 1987-collections at Stations 19 and 31 were similar to previous years, and thus placed in the same group. Densities of dominant molluscs Mytilidae and Hiatella sp. in 1987 decreased from the extremely high values recorded in 1985 and 1986 (see Section 3.3.5 and NAI 1987b, 1988).Stations with depths greater than 15 m formed several loosely-.associated deep station groups. All differed from shallower stations in the decreasing influence of molluscs, particularly the overwhelming predominance of Mytilidae spat, and the increased importance of crustaceans and other taxa. The majority of collections at deep stations (4, 34, 13) were placed in two groups. In some years, at Stations 4 and 34, peracarids (Pontogenela inermis, Caprella spp.) Asteriidae., and.molluscs (Anomia sp., Musculus niger)were the dominant taxa, forming Group 4 (Table 3.3.3-1). The 1987 collec-tions at Stations 4 and 34 were placed in Group 4 based on the similarity of 239 their species composition. In other. years, at Stations 13 and 34, Balanus spp., along with molluscs (Mytilidae, Anomia sp.,;Lacuna vincta and Iliatella sp.) were the most abundant taxa, causing these stations to be.distinct from other collections, forming Group 2. Collections made at Station 13 in 1987 were placed in this group, in part due to high densities of Balanus spp.(4698/M 2) (NAI 1988). The high within-group abundance of Balanus crenatus is deceptive, however, asit is heavily influenced by Station 34 in 1984, where Balanus crenatus averaged 12,233/M 2 (NAI 1985a), and 19.86 at Station 13, where this species averaged 10,323/mr 2 (NAI 1987a). A third group of four station collections, including mid-depth 19 and 31 and deep 4 and 34, was formed because they were unlike the other assemblages in having moderate-numbers of Mytilidae sp. and Iliatella sp. but low, numbers of Balanus spp. No collections from 1987 showed a similar species composition to this gfoup.-3.3.3.2 Intertidal Bare Rock, Fucoid Ledge, and Chondrus Communities Important species on fucoid-covered and bare rock ledge habitats at mean sea level (MSL) and Chondrus zone habitat at mean low water (MLW) were enumerated triannually at fixed stations on Outer Sunk Rocks (Station 1) and Rye Ledge (Station 5). The bare rock areas supported low percentages of algae such as Porphyra spp. at Station 1 and Fucus spp. mainly at Station 5 (Section 3.3.2). The predominant macrofaunal resident was Balanus spp., which had slightly higher frequencies in April following the spring recruit-ment period, than in July and December (Table 3.3.3-2). Gastropods Littorina littorea (at Station 5) and Littorina saxatilis (at both stations), chief consumers of Fucus sp., were also important constituents of the bari rock community, showing lower frequencies inApril than in July or December.Mytilidae spat occurred in low frequencies in July and December. Patterns of faunal distribution in 1987 were Similar to those observed in previous years with one exception. Nucella lapillus, normally not encountered in the bare rock zone, occurred in all three months in 1987 at Station 5 (NAI 1988).240 TABLE 3.3.3-2. MEDIAN AND, RANGE OF PERCENT FREQUENCIES' OF THE DOMINANT FAUNA AT BARE ROCK, FUCOID LEDGE, AND.CHONDRUS ZONE INTERTIDAL SITES AT STATIONS I (OUTER SUNK ROCKS) AND 5 (RYE LEDGE) MONITORED NONDESTRUCTIVELY. SEABROOK BASELINE REPORT, 1987.FUCOID LEDGEb BARE ROCKb CHONDRUS ZONEc APR JUL DEC APR JUL DEC APR JUL DEC Acmaea testudinalis 1 median 0 3. 10 0 0 0 13 13. 13 (range) (0-6) (0-19) (6-19) (0) (0) (0) (6-38) (6-25) (6-25)5 median 3 6 13 0 0 0 0 0 0 (range) (0-19) (0-38) (0-38) (0) (0) (0) (0) (0-13) (0-25)Balanus spp. 1 median 17 2 1 71 63, Z1 0 0 0 (range) (4-100) (1-38) (0-63i (19-100) (9-88) (1-88) (0-.47) (0-4) (0)5 median 35 23 4 93 78 64 0 0 0 (range) (15-100) (12-100) (1-88) (58-100) (24-100) (5-100) (0) (0) (0-3)Littorina littorea I median 0 0 0 0 .0 0 0 0 0 (range) (0) (0) (0-6) (0) (0-13) (0) (0) (0)S median 19 60 13 0 i3 .91 81 100 81 (range) (0-38). (44-75) (6-31) (0-6) (0-56) (50-100) (75-100) (100) (44-94)Littorina obtusata I median 0 6 6 0 0. 0 .0 0 0 (range) (0-6) (0-13) (6-19) (0) (0-19) (0) (0-6) (0-19) (0).5 median 7 10 7 0 3 0 0 0 0 (range) (0-25) (0-44) (0-44) (0-6) (0-19) (0-13) (0-13) (0) (0)Littorina saxatilis I median 0 0 0 7- 72 Z2 0 0 0* (range) (0) (0) *(0-6) (0-44) (0-88) (6-88) (0) (0) (0)5 median 0 0 0 28 .66 75 0 0 0 (range) (0-6)(0) (0-6) (0-81) (38-94) (6-100) (0)(0) (01)(continued) TABLE 3.3.3-2. (Continued) FUCOM LEDGEb BARE ROCKb CHONDRUS ZONEc APR JUL DEC APR JUL DEC APR JUL DEC Mytilidae 1 median 82 93 83 0 16 12 94, 93 68 (range) (21-100) (35-100) (43-100) (0-20) (0-40) (0-75) (54-95) (71-95) (15-85)5 median 6 1 3 0 6 15 41 27 3 (range) (2-100) (0-100) (0-100) (0-5) (0-38) (1-75) (10-72) (23-80) (0-48)Nucella lapillus 1 median 10 78 35 0 0 0 75 100 56 (range) (0-25) (25-100) (13-50) (0) (0) (0) (50-75) (100) (50-69).5 median 0 47 0 0 0 0 94 31 69 (range) (0) (13-81) (0-6) (0-94) (0-44) (0-56) ý(75-100) (13-44) (56-81)a Method of computing percent frequency varies among species (point-contact method for Mytilidae and Balanus since July 1983, bperceht frequency of occurrence for all other instances). 1982-1987, mean sea level.1985-1987, mean low water.N, N, Fucoid-covered ledge areas at mean sea level were characterized by a heavy cover (over 80%) of the perennial algae Fucus spp. (mainly F. vesiculosus), with an understory of perennial red algae (Mastocarpus stellata and Chondrus crispus). Highly-seasonal annual algae occurred in spring or spring and summer, particularly at Station 1 (Section 3.3.2).Mytilidae spat was the most common taxon at Station 1, with high percentages during all three sample periods (Table 3.3.3-2). Mytilidae usually did not show high frequencies at Station 5. Balanus spp. was also an important member of the fucoid ledge community and was more frequently encountered at Station 5. As on bare rock, frequencies were highest in April following spring recruitment and lowest in December. Balanus frequencies were exceptionally low in 1987'at Station 1 (NAi 1988). Nucella lapillus occurred mainly on the fucoid-covered ledge, most commonly encountered in July. Other important gastropods were Acmaea testudinalis and Littorina obtusata (most frequent in July and December) and Littorina littorea (almost exclusively occurring at Station 5).The intertidal community in the mean low water zone, the "Chondrus zone" was characterized by rock ledge with a thick cover of red algae, mainly Chondrus crispus and Mastocarpus stellata. Fucus spp. were also fre-quently encountered at Station 1 only (Section 3.3.2). Of the macrofaunal species that were monitored, Nucella lapillus and Mytilidae spat were the most frequently encountered. At Station 1, Nucella were more abundant in July than in April or December (Table 3.3.3-2). This-is consistent with other studies which show adult Nucella to be active from May through October, while juveniles tend to be active throughout the year (Menge 1978). On Rye Ledge (Station 5), Nucella was less-frequently encountered in July, a sea-sonal pattern that was-reversed from its nearfield counterpart. Seasonal movements of Nucella appeared unrelated to those of its main prey, Mytilidae. Mytilidae had medium-to-high frequencies in April and July at Station 1, with generally lower percentages in December. Mytilidae, historically not common at Station 5, settled in large numbers between December 1986 and April 1987, only to decrease by August (NAI 1987a, 1988). No relationship with abundance levels of either species at mean low water or with the fucoid community at 243 mean sea level were noted (NAI 1987a, 1988). Another important species in this community was the gastropod Littorina littorea, which occurred at Station 5 only throughout the year. Acmaea testudinalls was enumerated in.low-to-moderate frequencies at.Station 1 in all years and Station 5 in 1985 only (Table 3.3.3-2). Seasonal distributional patterns observed in 1987 were similar to previousyears. 3.3.3.3 Subtidal Fouling Community Data collected from subtidal bottom panels gives information on recruitment of benthic macrofaunal species. Balanus spp. (mainly Balanus crenatus, with some Balanus balanus) typically settled by April. Recruitment continued in some years after the April sampling-period so that densities were higher in the August samples, while in other years April sampling occurred near the settlement peak, so that densities were lower in August (Table 3.3.3-3). Densities in December were consistently low, as Balanus populations disappeared as a result of mortality or disturbance. The 1987 panels showed this .same pattern. Balanus spp. densities were higher at Station 31 in all years except 1984.Anomia sp. had a pattern of late-summer-fall recruitment. Although low densities of Anomia sometimes occurred on panels by August, numbers were typically highest by December's collections (Table 3.3.3-3).. Similar den-sities in August and December collections in 1984 suggested an earlier set than other years. In 1987, December densities were"lower than average at Station 31, suggesting recruitment was late or unsuccessful. Nearfield and farfield stations showed similar levels of Anomia.Hiatella sp., another sessile mollusc, showed highest densities by August collections, with most disappearing from panels by December. Den-sities in 1987 showed a similar seasonal pattern (Table 3.3.3-3). Numbers were generally higher at Station 31 than at Station 19 (1987 was an excep-'tion), a pattern not borne out in the natural environment. Especially high 244 TABLE 3.3.3-3. ESTIMATED DENSITY (PER 1/4 Mi 2) OF SELECTED PANELS. SEABROOK BASELINE REPORT, 1987.SESSILE TAXA ON TRIANNUAL (FOUR EXPOSURE) HARD-SUBSTRATE BOTTOM Un 1981 1982 1983 1984 1986a 1987 TAXA APR AUG DEC APR AUG DEC APR AUG DEC APR AUG DEC DEC APR AUG DEC Balanus spp. Sta. 19 7600 7950 1 1600 9250 0 2630 1409 0 25060 12,360 25 9 20683 750 z Sta. 31 MS MS MS 82803' 13023 26 35100 4304 0 19768 9Z90 46 9 48100 117. 0 Anomia sp. Sta.. 19 0 0 278 0 0 997 1 27 0 0 184 195 1017 2 4 .1669 Sta. 31 MS MS HS 0 0 1387 0 58 340 0 104 166 450 0 7 61 Hiatella sp. Sta. 19 " S HS MS HS HS MS 0 160

• 2 0 4345 20 4 1 3868 .5 Sta. 31 MS HS MS. MS MS MS 0 1369 2 1 19226 18 25 0 1235 53 Mytilidae Sta. 19 MS MS MS HS MS HS 0 19 19. 1 709 80 161 7 391 11 Sta. 31 MS MS MS MS MS MS 0 300 5 21 23018 80 77 17 572 39 MEAN AND STANDARD DEVIATION (SD) FOR ALL. YEARS (1981-1984, 1986 b,.1987)APR AUG DEC MtEAN SO MEAN SD MEAN SD Balanus spp. Sta. 19 11515 10725 6344 5071 6 10$ta. 31 46443 26864 6684 5650 16 20 Anomia sp. Sta.. 19 1 1 43 80 693 .640 Sta. 31 0 0 42 49 481 5Z9 Hiatella sp. Sta. 19 <i 1 2791 ZZ91 8 8 Sta. 31 <1 1 7277 10349 24 21 Hytilidae Sta.' 19 3 4 373 345 68 69 Sta. 31 13 11 7963 13038 50 35 MS = Not sampled.a bOnly December collections were made in 1986.Only December computations,include 1986.

densities on bottom panels in 1984 were reflected in higher densities in the natural environment in 1984 (NAI 1985a).Mytilidae spat generally had settled on bottom panels by August, with numbers diminishing by December (Table 3.3.3-3). In the natural environment, small mytilids appeared from August through October, but information from surface fouling panels suggests that settlement can take place throughout the 'year. Few, of these newly-settled mytilids survived through the winter in the natural habitat or on artificial substrate (NAI 1985b). Densities on bottom panels at Station 31 were usually much higher than at Station 19, a pattern which also occurred in the natural habitat (Section 3.3.5). However, in 1987, densities on bottom panels were similar between the two stations, unlike dens'Ities from the natural habitat.3.3.3.4 Modiolus modiolus Community As part of the subtidal nondestructive program, Modiolus modiolus populations were enumerated by divers along randomly pre-selected, radiating-transects at selected stations. Previous reports have demonstrated that there has been little seasonal variability in density levels (NAI 1985b).Over the eight-year period 1980-1987, no significant difference was detected between nearfield and farfield stations by a Wilcoxon's signed rank test (Table 3.3.3-4). Significant differences were detected among years using a Kruskal-Wallis test (p < 0.001, DF = 7). Densities were highest in 1982 and 1983, averaging over 110/M 2 (Table 3.3.3-4). In subsequent years, annual mean density was less than 100/mi 2 at both stations. The 1987 densities were lower than the 1980-1987 average at both stations (Table 3.3.3-4). Despite year-to-year fluctuations inllodiolus density, the community as a whole can be relatively persistent and is an important refuge from large predators for macroinvertebrates. At the 8 m depth off Portsmouth, N.H., Mlodiolus beds persisted for over five years. However, survival depended on the ability of Modiolus to avoid predation by Asterias vulgarls or dislodgement by attached kelps,which in turn are regulated.by grazing sea urchins (Witman 1985).246 TABLE 3.3.3-4. ANNUAL MEAN DENSITY (PER 1/4 m2i) AND STANDARD DEVIATION OF MODIOLUS MODIOLUS OBSERVED AT SUBTIDAL TRANSECT STATIONS, 1980-1987. SEABROOK BASELINE REPORT, 1987.ALL STATION 1980 1981 1982 1983 1984 1985 1986 1987 YEARS Nearfield MEAN 98 108 132 112 97 77, 90 97 101 (19) S 48 45 60 66 55 46 39 50 54 Farfield MEAN 119 93 121 116 88 93 62 67 95 (31) SD 44 54 64 50 38 44 42 44 52 Station 19 = Station 31 (p 0.08)",,

3.3.4 Surface

Fouling Panels The fouling panels program was designed to study both settlement patterns and community development. The short-term (ST) panels provided-information on the temporal sequence of settlement activity, while monthly sequential (MS) panels.provided information on growth and successional patterns of community structure. Surface fouling panels have been collected at nearfield (19, 4) and farfield (31, 34) stations since 1978 (except 34;since 1982). Panels were not collected, however, for the period January 1985 through June 1986. Panel collection:resumed in July 1986 and continued through December 1987.3.3.4.1 Seasonal Settlement Patterns Historically, species richness (number of taxa) on Seabrook short-term surface panels has incr'eased steadily throughout the summer and early fall and decreased in late fall (NAI 1987b). In 1987, faunal.richness increased rapidly to a peak in July (except Farfield Station 34, which peaked in June and. September), then declined steeply throughout late fall. In 1987, the mean number of taxa reached the lowest point since sampling began in 1978, with only one taxon reported from Station 31 (farfield) in February (Figure 3.3.4-1). The mean number of taxa was the highest ever reported (.19)in July at Station,19 (nearfield). For all baseline years combined, the mean number of taxa ranged between two (Station 4 in March) and 16 (Station 19 in July and Station 34 in September). Fauna appearing on the panels included bivalves, amphipods, polychaetes and colonials; all groups that have occurred previously on panels. Overall, in 1987 species richness in the offshore nearfield (Station 4) was.slightly higher than at the farfield station (34).However, faunal richnes's at nearfield Station 19 (near the discharge) was lower than farfield station 31.Over the baseline period, the greatest mean species abundance occurred in the summer and declined through the fall at all stations (NAI 1987b). Stations 4 (nearfield) and 34 (farfield) have followed-similar 248 @7 Nearfield (0 LL 0.IM ,U-0 20-18-16-14-12-10-8-6-4-2-0 Station 4 U-0.M)U-z 20-18-16-14-12-8-6-4-2-.0 Station 19-- OVERALL MEAN....... 1987-OVERALL MEAN....... 1987 A , i ........ ...*1 I I I lI I I I I I I JAN FEB MAR APR MAY JUN JUL AWG SEP OCT NOV D MONTH I I I I I , I I I I .I I It JAN FEB. MAR APR MAY JUN JUL AJUG SEP OCT NOV EEG MONTH Farfield r'.1 P4 1.0 U)U'U.0 U'W In 22 20 18 16 14 12 10 8 6 4 2 0 Station 34.U.0 U'W 20-*18-16-14-12-10-8-6-4-.2-0 Station 31 A I I I I I I I JAN FEB MAR APR MAYJUN JUL AUG SEP OCT NOV DOC MONTH I I I l I "I I I I I I. I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DE[C MONTH Figure.3.3.4-1. Faunal richness (number Of different taxa over two replicates) in 1987 compared to mean species richness and +/-95% confidence limits from 1978-1987 on short term panels. Seabrook Baseline Report, 1987.. temporal patterns; however, abundances at Station 34 were generally higher that atStation 4, especially in October and November. Species abundance patterns at Station 19 (nearfield) and Station 31 (farfield) have remained quite similar. The species abundance values for 1987 were comparable to past years, with a few notable exceptions (Figure 3.3.4-2). In July 1987, abundance values at all stations were higher than the mean of all .years combined, as. were abundance values in February (except Station 34). Compared to other years, mean species abundances were also higher in the~winter and early spring at Station 19 and during the late summer and early fall at Station 34. These deviations from the historical mean are specifically a reflection of differences in Mytilidae, Iliatella sp., Balanus sp. and Jassa falcata abundances (NAI 1988, 1986, 1987a, 1985a, 1984a, 1983a).The dry-weight biomass (g/panel) for short-.term panels followed the pattern observed for the seasonal distribution of density and species rich-ness. Historically, biomass values have been normally highest during August and September (1987b). Seasonal trends in 1987 were similar to baseline years, but in.1987 weights at all stations were exceptionally high in September in comparison to previous years (except for 1981)(Table 3'.3.4-1). Stations 4 (nearfield) and 34 (farfield) also exhibited substantial biomass increases in August, unlike past years. Total biomass at Station 31 peaked in October, a value which represents a notable increase over the baseline period at this station. High biomass values in 1987 at these three. stations were due to dense Tubularia sp. coverage and several large Mytilus edulis individuals (NAI 1988 and photographs in project file). Biomass values at Station 19 were similar to past years.Several dominant taxa on panels were monitored to determine their long-term'.recruitment patterns at nearfield (19, 4) and farfield (31, 34)stations. A summary of notable differences for each species on the 1987 short-term panels compared to the baseline period is shown in Table 3.3.4-2.250 7.IWear~ileld Station 4 Station 19 4 4-0-j w C.)z 3 2 0 w C-)z 4 in z 2-2-1 OVERALL MEAN....... 1987 0 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NCV [EC MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT Nov DEC MONTH Farfield r'.k-n 4 -1 Station 34+_x a, 0 LU z z D I4 3 2 1 0 x a, 0 z 4.3-2-1-Station 31 OVERALL MEAN.1987 0.8 I I I I I JAN FEB MAR APR MAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH I I 11 I I I I JUN JUL AUG SEP OCT NOV CEM MONTH species abundance non-colonial 1987.Figure 3.3.4-2.Species abundance (log x + 1) in 1987 compared to mean (log x + 1; +/-95% confidence limits) from 1978-1987 for fauna on short-term panels. Seabrook Baseline Report, U, t-n N)TABLE 3.3.4-1. DRY HEIGHT (g/PANEL) BIOMASS ON SHORT-TERM1 SURFACE FOULING PANELS BY YEAR, STATION AND MONTH.SEABROOK BASELINE REPORTS, 1987.YEAR STATION 3 F H A H 3 3 A S 0 N D 1980 19 .4 <.1 <.1 .5 .4 .5 .8 .5 .9 .9 .5 .8 31 .4 <.1 <.1 .7 .4 .4 .6 2.2 .6 .6 .6 .5 4 .4 <.1 <.1 .6 .4. .6 .8 .7 1.1 .4 1.2 .4 b.1981 19 .1 .2 .2 .2 m2 .4 3.2 9.0- .3 .2 .2 31 .1 .2 .2 .2 .1 .6 10.9 5.0 .8 .3 .2 4 .1 .1 .z .2 .2 .4 .7 9.5 .6 .3 .5 a 1982 19 <.1 .1 <.I .2 .4 .1 1.8 1.9 1.9 2.1 .1 .1 31 .1 .1 .1 .3 .1 .3 2.6 2.7 2.0 1.9 <.1 .1 4 .1 .1 .1 .3 .1 .1 1.5 2.0 2.3 2.0 .1 .1 34 -.1 .2 .1 .2- .2 .Z 1.7 1.6 1.9 2.3 .1 .1 1983 19 .1 .1 .1 .2 .2. .3 .3 .3 2.4 6.8 .1 .1 31 .1 .1 .1 .1 .2 .1 .1 .1. .9 <.I <.1 .1 4 .1 .1 <.1 .1 <.1 .3 <.1 2.0 1.1 1.1 .3' .1 34 .1 .1 .1 .1 .1 .3 .3 .4 2.8 6.3 .5 .3 1984 19 <.1 <.1 <.1 .1 .2 .1 <.1 .3 1.7 4.3 .8 .1 31 .1 .1 <.1 <.1 .5 .1 .8 .1 1.4 .5 .8 .1 4 <.1< <.1 <.1 .3 .3 .1 .5 2 .2 1.1 .1 34 <.I ...1 <.<.I. .5 .3 1.Z <.]b'1986 19 .5 .7 1.5 .2 .7 1.1 31 .Z 1.7 .8 .7 .2 .1 4 ..1 .3 1.0 .8 .2 .1 34 .1 .9 1.1- 1.7 4.9 <.1 1987 19 <.1 .1 <.1 <.1 .2 <.1 .2 .1 3.3 .6 .1 .1 31 <.j <.1< 1,1 .3 .<.1ý .5 .1 Z.1 4*.2 .2 <.I 4 <.1 .1 <.1 <.1 .1 .1 ,9 3.3 6.8 .5 .1 <.1 34 <.1 .! <,1 <.1 .1 .5 .5 5.4 9.1 2.2 .3 .3 a Station 34 was-first sampled in 1982.b f No fouling panels placed or collected in. January 1981, or from January 1985 through June 1986. TABLE 3.3.4-2. DIFFERENCES OBSERVED ON 1987-NEARFIELD SHORT-TERM PANELS COMPARED TO BASELINE PERIOD (1978-1986 ) AND TO FARFIELD STATIONS. SEABROOK BASELINE REPORT, 1987.SPATIAL TEMPORAL (NEARFIELD VS. FARFIELD (NEARFIELD 19 VS. 31 SPECIES 4,19) 4 VS. 34)Anomia sp.Station 19 September abundance higher com--.pared to baseline.Station 19 abundance higher in September vs.. Station 31 Station 34 higher in, September and October.vs. Station 4 Asteridae Balanus sp.No Differences Observed Abundances at 4 and 19 higher in April, May.and June (except in April 1980).Station 4 higher abun-dance during June and July (except in 1981).fliatella sp.Jassa falcata Station 4 abundance higher in July and and lower in August and September vs.Station 34 July through November abundance substantially higher at 31 vs. 19 July, September and October abundance higher at 34 vs. 4 Station 19 lower than 31 Station 19 abundance sub-stantially lower than 31 July through December.(continued) Lacuna vincta Mytilidae No differences observed Station 19 higher abun-dance in February and March; lower in June and August Station 4 higher in January, February, July and November;lower in December 253 TABLE 3.3.4-2.(Continued) SPATIAL TEMPORAL (NEARFIELD VS. FARFIELD (NEARFIELD 19 VS. 31 SPECIES 4,19) 4 VS. 34)Nudibranchia Abundance at-31 higher in July than at 19 Pontogeneia inermis Density extremely low Strongylocentrotus drobachiensis Density extremely low Diatoms No differences observed Obelia spp. No differences July percent frequency observed higher at 31 vs. 19 and at 34 vs. 4 Tubularia sp. Station 19 percent fre- High percent frequency quency higher in extends into November November at Station 4 vs. 34 Station 4 higher in July, and at Station 19 vs.October and November 31 a except at Station 34 which was 1982-1986 and from January 1985 through July 1986, when no panels were placed or collected. 1.254 1 Monthly mean abundances for these short-term panels species are shown for all years sampled in Appendix Tables 3.3.4-1 and 3.3.4-2. The panels' selected.species, Mytilidae, and Jasse falcata are discussed in Section 3.3-5.3.3.4.2 Patterns of Community Development Monthly sequential panels measure growth and successional patterns of community development. Historically, settlement activity has been most intense in the summer months and has continued into fall (NAI 1987b). In i987, the pattern of community development on monthly sequential panels was similar to that of previous years. A comparison of the settlement sequence and survival of species on nearfield.,(Stations 4 and 19) monthly panels is shown in Figure 3.3.4-3. Similar to previous years, settlement density in 1987 was high in summer months, especially for Mytilidae, Obelia spp'. and Balanus sp., and persisted throughout the fall. Densities and settlement patterns of Jasse falcata and Hiatella in 1987 reflect closely recent years in which panels were exposed for up to a full year (1982-1984). The hydroid Tubularia sp. settled earlier and more densely at Station 4 in 1987 than compared to previous years; similarly, settlement at.Station 19 was slightly more dense. Balanus sp. was a regular colonizer April through December in 1987 and exhibited higher frequencies at both Stations 4 and 19 in comparison to previous years. Nudibranchia were present earlier at Station 4 in 1987 than in the past, but summer and fall patterns of settlement and density-were similar to previous years, as were those of Polynoidae and Nereis sp.The patterns of community growth and-development are generally reflected

• in the biomass data from the monthly sequential panels (Table 3.3.4-3).

Over the baseline period, a pattern of increased biomass dry-weights has normally occurred from summer into the fall months (NAI 1987b).However, a sharp decline in biomass dry-weights in 1987 occurred at Station 19 (nearfield) and Station 31 (farfield) in September followed by increases in subsequent months. Stations 4 (nearfield) and 31 (farfield) also showed decreases in December. Consequently, overall biomass weights in 255 S TA TIO N 4 STITOA4STATIO0 19 J F H A N J JA 'S 0 N Hit i IMap .1982 ...... ......i~i 1983 ....1984 1986 a 1987 _ __ ......Hiatela sp. 1982 ....................... 1983 ........ .. ...1987 h~Jabr ancata 1982 ....-fl ......lhi 1987 ............... NuJhrsa nfalha 1982 .. .....1983 .....MM -1 1984 1986 TNuhlaria ep. 1982 ." M ..'" .1983 ........ ......1984 .... .-. -" 1986 ..... ...1987 ........~......oblia sp. 1982 IU'"IiIiI'" 1983. ....g.......1984 -.. .....196 -- 1987 -i1~Balanus sp. 1982 199 ...... ......1983 .... ...19864 1987 ............ Nerei. s sp. 1982 ............... 1983 .. .... ......1984 ..1986a -..... .......1987 C .. ..Polynnidae 1982 1983 .1984 ......-.1987 0. ............. a 1986 .....7.....1987 f.I.-present ... 1-25Z frequency 26-75 N 76-100 a fnulino nanels olaced or collected from January 1985 through June 1986.Figure 3.3.4-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19. Seabrook Baseline Report, 1987.-256 TABLE 3.3.4-3.DRY WEIGHT (g/panel) BIOMASS ON MONTHLY SEQUENTIAL SURFACE FOULING PANELS BY YEAR, STATION AND MONTH.SEABROOK BASELINE REPORT, 1987.YEAR STATION i F m A M 3 3 A S 0 ND a 1978 b 1979 1980 LJ1 c 1981 d 1982 1 e 1983 19 31 4 19 31 4 19 31 4 19 31 4 19 31 4 34 19 31, 4 34<. 1.1.2.1.7.8.7.1.2.4.6.4.5.6 1.2 2.0 7.0 52.4 1.5 8.8 46.4 2.2 14.5 34.0.7 1.8 19.1 130.0 1.9 2.6 6.5 19.5.8 1.3 4.2 86.1 758.8 735.7 804.8 257.2 47.6 266.0 184.5 55.4 151.7 221.5 514.9 173.3 77.5 82.5 92.0 205.9 70.1 310.5 94.2 974.9 689.7 105.9 414.1 213.9.1.1.2.1.4.8.2.1<.1.1.2.1.2 2.6 1.9 1.6 1.1..6.6.5.3.4.4 9.5 2.6 1.8 2.0.5.7.6 1.1 .6 2.i 3.8 2.7 3.0 17.8 24.1 32.3 32.1 20.4 32.3 36.7 113.3 13.7 5.2 5.8 56.2 129.9 589.1 392.3 155.5 382. 2 52.2 38.0 28.6 40.1 141.6 274.6 73.7 61.3'454.2 160.4 9.6 213.3 443.1 226.4 241.9 347.9 115.5 33.7 207.8 70.6 133.3 349.6 108.6 115.1 714.9 397.6 665.7 1.8 2.9 5.8.9 3.5 7.1 9.1 6.6 9.8 20.3 8.5 13.4 20.8 33.8 40.5 31.2 44.4 52.0 27.6 93.4 431.3 51.5 39.4 87.2 131.6 34.7 90.1 193..0 86.1 75.9 327.1 221.-0 28.0<.1.1<.1.7 18.7 40.5 2.0 11.0 17.8 1.1 6.9 7.7.1 .7 .8 .8 5.7 10.9 34.5 141.4 106.9 513.8 821.5 TABLE 3.3.4-3. (Continued) YEAR STATION 3 F M A M 3 3 A S 0 H D e".1984 19 <.1 .1 .5 .6 3.1 8.6 17.9 53.0 213.6 666.9 774.9 1117.6 31 .1 .2 1.2 1.9 Z.2 20.3 56.6 116.4 199.6 364.0 929.6 773.6 4 <.1 .1 .7 1.Z 1.4 2.7 4.8 52.5 23Z.4 363.6 583.4 1035.5 34 <.1 .2 .8 1.2 1.1 9.7 15.4 57.5 262.0 349.0 706.2 iz66.1 1986c'e 19 33.3 164.3 42Z.9 931.1 494.7 698.1 31 Z2.1 179.3 449.3 .857.7 716.8 883.3 4 20.8 157.1 357.0 899.0 481.3 1071.3 34 29.7 123.9 502.3 873.Z 576.9 952.6 e 1987 19 <.1 .7 1.8 .4 1.8 28.4 131.6 220.0 54.1 90.7 129.7 170.8 31 .1 .2 1.1 1.3 3.3 17.6 88.8 100.1 40.3 73.1 165.3 93.1 4 <.1 1.5 Z.1 1.5 1.7 21.9 6Z.9 49.3 60.3 75.5 114.0 85.2 34 <.1 .6 1.5 *1.5 Z.1 13.8 62.8. 95.Z 129.5 172.9 170.1. 167.5 a In 1978, biomass measured only from December monthly sequential panels.b Data not available for January 1979.Panels were not sampled in January 1981; or from January 1985 through June 1986.d Station 34 was first sampled in 1982.weights in 1983 through 1987 represent means calculated from two repolicate panels (10 x 10 cm).Ln S00 1987 were substantially lower than recent baseline years (1983-1986). Temporal patterns at paired stations, (19 vs. 31 and 4 vs. 34) were similar in 1987, but over all biomass values were depressed September through December, in comparison to 1983-1986 (NAI 1988 and photographs in project file).Laminaria spp. sporelings (mostly L. saccharina, but occasionally L. digitata) settlement on MS panels has been highly variable from year to year, but generally, more Laminaria spp. fronds have been present in July, August and September than later in the'year (NAI 1987b). Settlement was dense in 1987, especially at Station 19 and Stations 31 and 34 (Table 3.3.4-4). Settlement at Station 4 was slightly higher compared to recent years. The highest mean density comparedto past years occurred at Station 19 in 1987; a value similar to that of Station 31 at which-densities have historically far exceeded any 6ther station. Station 34 exhibited notably higher abundances throughout 1987 than those recorded at Station 4.259 0 a TABLE 3.3.4-4. LAMINARIA SP. COUNTS ON MONTHLY SEQUENTIAL SURFACE FOULING PANELS BY AREA, STATION, YEAR AND MONTH.SEABROOK BASELINE REPORT, 1987.b c AREA STATION YEAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN S.D.NEARFIELD 19 1980 0 0 10 19 10 18 14 23 31 13.9 10.22 1981 4 13 0 2 0 0 0 00 -Z.1 4.31 1982 53 54. 3Z 116 67 64 48 65 51 61.1 23.21 1983 0 10 8 3 34 25 38 21 16 17.2 13.35 1984 9 1 34 10 22 6 4 1 6 10.3 10.90 1986 8 3 1 3 4 0 3.2 2.79*i987 0 .22 69 102 27 176 85 63 97 71.2 52.80 dýFARFIELD 31 1980 0 0 -- 22 39 12 79 75 39 33.3 30.92 1981 4 0 6 19 0 1 0 5 5 -4.4 5.98 1982 108 98 7Z -92 104 95 122 103 64 95.3 17.85 1983 .0 97 126 i43 136 175 113 126 78 110.4 49.75 1984 2 16 23 22 49 19 26 21 13 21.2 12.59 1986 16 2 9 3 4 11 7.5 5.47 1987 0 31 73 125 161 41 154 109 48 82.4 57..28 NEARFIELD 4 1980 0 0 18 15s 4 4 5 18 29 10.3 -10.06 1981 3 1 0 0 0 0 0 0. 0 .4 1.01 1982 48 128 112 76 125 97 69 83 92 92.2 26.48 1983 0 0. 0 11 1 1 2 l0 0 1.7 3'.57 1984 z 1 2 .0 0 0 0 0 0 .6 .88 1986 7 0 1 0 0 0 1.3.. 2.80 1987 0 2 6 0 24 1 2 6 1 4.7 7.60 FARFIELD 34 198Z 27 51 46 69 65 50 53 47 65 52.6 12.83 1983 0 8 11 27 11 1 0 6 0 7.1. 8.78 1984 3 3 0 5 2 4 0 0 0 1.9 1.96 1986 1 5 0 0 0 1 1.2 1.94 1987 0 9 13 15 54 35 31 Z3. 43 24.6 17.66 a Fronds counted were L. saccharina and occasionallyL. digitata.b _ from Juy 8t g ue 6 No panels collected from January 1985 through June 1986.C No Laminaria sp. >3 cm(minijnum length for counting) present before April.d Data missing for Station 31 June 1980.

3.3.5 Selected

Benthic Species Seven macrofaunal taxa from the area of the discharge (nearfield) and from a control area off Rye Ledge (farfield) (Figure 4.1-3) were selected for intensive monitoring., Three nearfield/farfield stations pairs were.sampled: intertidal Stations 1MLW and 5MLW, 5-m Stations 17 and 35, and 9 to 12-m Stations 19 and 31. Selection of taxa was based on abundance, and/or trophic level (Table 2.3-1).3.3.5.1 Mytilidae Mytilidae, composed primarily of juvenile Myttilus edulis, was-the most abundant taxon at all three nearfield/farfield station pairs. Mytilus edulis reaches 100 mm in length (Gosner 1978), and is an important prey species for fish, sea stars, lobster, and gastropods. It clings to hard substrate with strong byssal threads, and is an important fouling organism.The geometric mean density for the entire 1978-1987 study period was highest intertidally, and generally decreased with increasing depth (Table 3.3.5-1), a trend also reported in NAI (1985b). The'highest density (geometric mean over all years) was 112,927/M 2 at intertidal Station 1MLW and the lowest was 1,553/M 2 at Station 19, which has a depth of about 12 m.Each station in the three nearfield/farfield station pairs was tested separately for annual differences. Significant differences in annual abundance occurred among years for five of the six stations when tested with a one-way ANOVA (Table 3.3.5-2). The year 1985. had the highest abundance at both 9 to 12-m stations (Stations 19 and 31), but 1985 had nearly the lowest.abundance at the 5-m stations (Stations 17 and 35) and for intertidal station 1MLW using the Waller-Duncan comparison test (Table 3.3.5-2). At the 5-m subtidal stations the -abundance was at the all time high in 1979 at Station 17, and was also very high in 1984 and 1987 at both 5-m stations. At inter-tidal Station 1 MLW, the highest abundance occurred in 1982.261 TABLE 3.3.5-1. ANNUAL-GEOMETRIC MEANa OF THE ABUNDANCE (No.//m') OF SELECTED BENTHIC SPECIES SAMPLED TRIANNUALLY IN MAY, AUGUST, AND NOVEMBER FROM 1978 THROUGH 1987. SEABROOK BASELINE REPORT, 1987.OVERALL YEARS TAXA STA 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 MEAN UPPER LOWER Ampithoe rubricata Asteriidae Jassa falcata.r'o Mytilidae ON Nucella lapillus Pontogeneia inermis Stronqylocentrotus droebachiensis 1MLW 5 1 8 b 5MLW 17-35 .-17 1007 35.1MLW 161,759 5MLW-17 1875 35-19 85 31 1437 1MLW 1355 5MLW -19 902 31 196 19 20 31 28 545 448 343 133 23 S -:88 15 1738 669 208-630 39 884 679 3389 3198 398-. -5307 4980 116,973 70,760 130,890 253,375 60,978"- 42,213 60,552 8789. 1269 2257 3490 963-1566 7328 307 905 2069 1776 ..1247 3338 13,422 13,650 1688 1095 2987 3973 1981 944 1586---649 783 538 599 584 762 562 400 390 650 554 470 70 152 281 80 15 60 73 142 72 55 9<1 392 167 660 2031 ,78,849 73.895 7980 13,416 6493 17,842 5176 909 386 512 29 33 3 <1 0 38 71 0 0 0 3 6 592 373 448 514 651.198 79 245 158 244 1622 2166 .1513 1248 1699 1465 1387 809 2110 3310 63,307 196.498 126,996 112,927 139,905 57,505 120.455 127,304 74.176 96,240 566 4744 5171 2658 3860 1055 5294 7981 4359 6764 6651 4943 3521 1553 2371 81,457- 3,995. 8000 6135 8815 3250 2559 1037 2152 2610 1378 .691 1326 914 .1188 604 908 308 585 745 280 773 105 379 505 188 135 99 75 117 35 23 17 45 62 20*405 103 917.1345 91,151.'57,170* 1830 2809.1018 4270 1775 703 460 284 48 32 a n =9 (3 replicates taken 3 times per year)b..-=not sampled a TABLE 3.3.5-2. RESULTS OF ONE-WAY ANALYSIS OF VARIANCE AMONG YEARS FOR THE LOG (x+1) TRANSFORMED DENSITY (No./m 2) OF SELECTED BENTHIC SPECIES SAMPLED FROM 1978 THROUGH 1987. SEABROOK BASELINE REPORT, 1987.STA- SOURCE OF SPECIES TION VARIATION df SS F MULTIPLE COMPARISONSb Ampithoe rubricata Nucella lapillus Jassa falcata IMLW Years Error Total 5MLW Years Error Total IMLW Years Error Total 5MLW Years Error Total 17 Years Error Total 35 Years Error Total 17 Years Error Total 35 Years Error Total 19 Year Error Total 31 Year Error Total 9 80 89 5 48 53 9 80 97.85 47.39 145.23 31.25 19.30 50.56 5.05 9.17 18. 35~15.54 4.90 79 78 80 81 82 83 84 82 83 84 85 86 87 84 `80 85 79 86 81 83 78 87 82 89 14.23*1 5 48 53 9 80 89 5 48 53 6 56 62 Asteriidae 0.89 8.30 9.19 7.69 28.69 36.38 4.78 22.41 27.19 4.37 5.94 10.31 7.72 16.93 24.65 6.78 36.03 42.82.5.48 26.06 31.54*2.38 8s 86 87 81 82 86 8s 87 78 79 80 84 83 2.05 NS 6.8739 1.03 NS 81 82 85 87 84 86 83 5 4h8 53 82 87 85 84 86 83 Pontogeneia inermis 9 80 89 9 80 89 1.67 NS 1.87 NS (continued] Ili as TABLE 3.3.5-2. (Continued) STA- SOURCE OF SPECIES .TION VARIATION df SS F MULTIPLE COMPARISONS Strongylocentrotus 19 Year 9 14.92 1.97 NS droebachiensis Error 80 67.26 Total 89 82.18 31 Year 9 6.04 1.51 HS Error 80 35.54 Total 89 41.58**Mytilidae IMLW Year 9 3.71 Z.38 82 86 78 81 87 79 84 80 85 83 Error 80 13.85 Total. 89 17.56 5LW Year 5 1.61 2.07 HS Error 48 7.49 Total, 53 9.10 17 Year 9 12.91 2.8.5 79 84, 87 86 82 81 78 80 83 85 Error 80 40.31 Total 89 53.21 35 Year 5 8.48 4.67 84 87 83 86 82 85 Error 48 17.4Z Total 53 25.90 19 Year 9 27.62 3.36 85 84 87 81 82 83 86 80 79 78 Error 80 72.67 Total: 89 100.29 31 Year 9 Z7.91 11.10 85 84 81 80 87 86 79 82 78 83 Error 80 22.34 ,._Total 89 50.25 bFor each year n=9 (3 sampling periods X 3 replicates) cHaller-Duncan multiple comparison test (S = not significant (p > 0.05)= significant (0.05 > p > 0.01)= highly significant (0.01 2 p > 0.001)= very highly significant (p-5 0.001) The Mytilidae collected usually ranged from less than I mm to 30 mm in length, and many of the smallest mytilids had settled on macroalgae rather than on the bottom or hard substrate, a pattern also observed by other investigators (Bayne 1965; Suchanek 1978). Information from surface fouling panels suggests that primary or secondary settlement takes place throughout the year, but is heaviest from June through October (NAI 1985b). The overall mean length of intertidal mytilids (3.2 mm) was slightly larger than subtidal mytilids, *(2.4 mm) (Table .3.3.5-3), even though intertidal population den-sities were much higher than subtidal densities. Mytilid lengths showed no significant differences between nearfield and farfield station pairs when tested with a two-way ANOVA (NAI 1987b: Table 3.3.5-4). Yearly differences in mean length for each of the nearfield/farfield station pairs were not significant (NAI 1987b: Table 3.3.5-4). In 1987, the lengths at the inter-tidal station pair were about average even though the density had increased; at subtidal station pairs the mean-lengths in 1987 were below average, and densities decreased at three of the four stations (Tables 3.3.5-1, 3), indicating below average growth and recruitment. The level of mytilid recruitment is indicated by the abundance on short term fouling panels set 3 m below the. surface at Stations 19 and 31 and exposed for one month intervals from 1978 through 1987. Recruitment was the highest ever at Station 31 in 1979, with a yearly average of 4687 spat per panel, and again in 1981 with 4082 spat per panel (Appendix Table 3.3.4-1).During the next two years, 1982 and 1983, recruitment was the lowest with just under 60 individuals per panel. Abundance in 1987 was below average at Station 19, but at Station 31, the 1987 abundance was the highest in six years, with 1187 spat per panel. Over 90% of the mytilids collected from panels at Stations 19 and 31 in 1987 were 3 mm or less in length (NAI 1988: Appendix Table 9-8)- Mytilid lengths at Stations 19 and 31 ranged from <1 mm to 20 mm in 1987 (NAI 1988: Appendix Table 9-7), about the same as previous years.265 TABLE 3.3.5-3.ANNUAL MEAN LENGTH omm) AND THE 9.5 CONFIDENCE INTERVAL (CI) FOR SELECTED BENTHIC SPECIES SAMPLED TRIANNUALLY IN NAY, AUGUST, AND NOVEMBER AT SELECTED STATIONS FROM 1982 THROUGH 1987. SEABROOK BASELINE REPO rT, 1987.OVERALL. 1982 1983 1984 1985 1986 1987 a TAXA STATION MEAN CI MEAN CI MEAN CI MEAN CI MEAN CI MEAN CI MEAN CI Ampithoe 1MLW 7.0 0.3 6.7 0.3 7.7 0.6 6.9 1.5 10.9 4.1 _- _rubricata 5MLW 7.8 0.4 7.6 0.5 8.5 0.8 8.9 ---Asteriidae .17 5.5 0.2 4.0 0.3 5.4 0.7 7.8 0.8 7.5 0.4 7.3 0.6 3.1 0.3 35 6.5 0.4 5.3 0.5 11.4 3.4 5.7 0.9 10.1 1.0 13.1 2.6 4.6 0.6 Jassa falcata 17 4.1 0.1 3.3 0.2 4.3 0.Z 4.4 0.2 4.5 O.Z 4.4 0.2 3.8 0.2 35 3.8 0.1 3.5 0.2 3.7 0.2 3.7 0,.1 4.5 0.2 4.1 0.2 3.5 0.1 Mytilidae IMLW 3.1 0.1 2.7 0.1 ý4.5 0.2 2.7 0.1 2.6 O.Z 2.8 0.1 3.1 0.2 5MLw 3,2 0.1 2.8 0.1 .3.2 0.2 2.9 0.1 3.0 0.1 4.o O.z 3.1 0.1 Mytilidae 17 2.3 0.0 1.9 0.1 2.1 0.1 2.8 0.1 2.4 O.Z 2.5 0.1 1.9 0.i 35 2.4 0.1 1.8 0.1 Z.1 0.1 3.1 0.2 2.4 0.1 *2.7 0.2 2.3 0.1 Mytilidae 19 2.1 0.0 2.0 0.1 2.3 0.1 2.1 0.1 Z.4 O.Z Z.3 0.1 1.8 0.1 31 2.7 0.1 2.2 0.2 1.9 0.i Z.1 0.1 3.5 0.1 4.1 0.3 2.0 0.1 Nucella 1NLH 6.1 0.2 8.0 0.3 3.3 O.Z 4.0 0.2 5.0 0.3 7.7 0.5 11.9 0.6 lapillus 51LN 5.9 0.2 5.7 0.5 6.2 0.6 6.9 0.6 6.3 0.5 6.2 0.5 4.3 0.4 Pontogeneia 19 4.9 0.1 4.4 0.3 5.2 0.3 4.9. O.Z 5.3 0.3 4.7 0.3 4.7 0.3 inermis 31 5.1 0.1 4.6 0.2 5.Z 0.3 4.6 0.2 5.8 0.3 5.z '0.Z 5.6 0.4 Strongrylocen-19 1.9 0.1 .1.8 0.3 1.8 0.5 1.7 0.3 2.7 0.4 1.5 0.3 1.7 0.2 trotus :31 1.9 0.1 1.7 0.2 2.3 0.3 1.7 0.2 2.5 0.6 1.5 0.2 1.7 0.3 droebachiensis ra ON sum of the lengths MEAN=total n b of all individuals measured in May, Auqust, and November umber of individuals measured in that year-= none collected 3.3.5.2 Nucella lapillus Nucella lapillus reaches 51 mm in length (Abbott 1974)., and is an abundant intertidal gastropod and an important predator, particularly on mytilid spat. Significant differences in abundance between stations were found between intertidal Stations IMLW and 5MLW from 1982 through 1986 (NAI.1987b: Table 3.3.5-2). The overall abundance at Station lMLW was more than double the overall abundance at Station 5MLW (Table 3.3.5-1)., Very highly significant differences among the years. 1978 through 1987 w'ere found for Station 1MLW with 1984 having the highest abundance and 1987 and. 1982 having the lowest abundances (Table 3.3.5-2). Farfield Station 5MLW was sampled from 1982-1987, and no significant .differences were found.among years (Table 3.3.5-2).Large .numbers of small Nucella* occurred in August or September, indicating recruitment occurred at that time (NAI 1985b). Larger individuals (10-25 mm) were collected in most months, but disappeared from November.1983 through June 1984. Previous studies have shown adult snails to be active only from May through October, retreating into crevices in the winter; while juveniles (2-5 mm) are more evenly dispersed throughout, the year (Menge 1978). The overall mean length for the 1982 through 1987 study period was 6.1 mm + 0.2 at Station 1MLW, and 5.9 mm + 0.2 at the farfield control (Table 3.3.5-3). The average yearly length ranged from 3.3 mm'at Station IMLW in 1983 to an unusually large 11.9 mm at Station 1MLW in 1987. No significant differences in the yearly mean length were found between stations or among years (NAi 1987b: Table 3.3.5-4).3.3.5.3 Asteriidae The Asteriidae collected are juveniles, too young to be assigned to genera. Two species of both Asterias and Leptasterfas can occur within the study area (Gosner 1978). Asteriidae are important predators on bivalves, particularly on the recently-settled stages, as well as other molluscs and barnacles (Gosner 1978).267 Significant differences in annual abundances-were found among years and between stations at subtidal Stations 17 and 35, sampled from 1982 through 1986 (NAI 1987b: Table 3.3.5-2). Station 17 had higher geometric mean densities during all years and the overall average density was over-three times higher than-at Station 35 (Table 3.3.5-1). Highly significant differences were found among years at both Station 17 and 35 when tested with one-way ANOVA (Table 3.3.5-2). The yearly trend was very similar at both stations: highest abundances occurred in 1982, 1985 and 1987 and lowest abundances occurred in 1983, 1984 and 1986 at both stations (Tables 3.3.5-1 and 2).A successful set of juvenile Asteriidae occurred in August of 1982 (NAI 1983a), and very little recruitment occurred in 1983 or 1984. In 1985 and 1987 annual densities were relatively high, indicating successful recruit-ment. Spatial and temporal changes in abundance and length seem to be related to the recruitment success of each year's cohort (NAI 1985b). The overall average length at Station 17 was 5.5 mm +/- 0.2, and at Station 35 it was 6.5 mm +/- 0.4 (Table 3.3.5-3). Yearly mean length of sea stars collected at Station 35 was usually greater than Station 17, and the two stations were significantly different according to the results of a two-way ANOVA (NAI 1987b: Table 3.3.5-4). Likewise, the mean seasonal length from 1982 through 1987 as compared with a paired t test, showed interstation differences were highly significant (N = 18 pairs, t = -4.08, probability of a greater t =0.008), with larger sea stars occurring at Station 35. The average yearly length ranged from 3.1 mm in 1987 to 7.8 mm in 1984 at Station 17, and from 4.6 mm in 1987 to 13.1 mm in 1986 at Station 35 (Table 3.3.5-3).A few recently-settled Asteriidae. were collected on.short term surface fouling panels from 1978 through 1987, and only occurred from July through September. All years except 1980 and 1981 had very low densities averaging less than one per panel per year (Appendix Table:3.3.4-1). 268 3.3.5.4 Pontogeneia inermis Pontogeneia inermis (maximum length, 11 mm) is a pelagic, cold water amphipod (Bousfield 1973), and a dominant species in benthic and macrozooplankton collections (NAI 1985b). It clings to submerged plants and algae from the lower intertidal to depths greater than 10 m (Bousfield 1973).Population densities

• were remarkably consistent from 1978-1986, and no significant differences were found among years with two-way ANOVAs (NAI 1987b: Table 3.3.5-2).

Likewise, when a one-way ANOVA was used to test, for differences among years, including 1987 data, no significant difference was found for either station (Table 3.3.5-2). However, interstation differences were significant, and the overall geometric mean abundance from 1978-1987 was 1.5 times higher at Station 19 than at Station 31 (Table 3.3.5-1).Ovigerous and brooding females were collected in low numbers from January through September (NAI 1985b). Recruitment, as indicated by a sharp increase in density and increased numbers in the 1 to 3-mm size class, took place between May and July. In fall and winter, abundance decreased, but average size increased as the population grew (NAI 1985b). The overallmean length for the 1982-1987 study period was 4.9 mm (95% confidence interval+ 0.1) at Station 19 and 5.1 mm +/- 0.1 at Station 31 (Table 3.3.5-3). No significant difference in mean lengths was found'between stations (NAI 1987b: Table 3.3.5-4). The average yearly length ranged from 4.4 mm at Station 19 in 1982 to 5.8 mm at Station 31 in 1985, with no significant difference among years (NAI 1987b: Tables 3.3.5-3 and 4). The 1987 data did not change the range of the annual mean lengths (Table' 3.3.5-3).Pontogeneia inermis was common on short term fouling panels, at Stations 19 and 31 from 1979 through 1983, but numbers-decreased sharply in 1984, 1986 and 1987 (no samples in 1985). Peak abundance usually occurred from Aprilthrough June, and annual mean abundances were highest in 1981 (Appendix Table 3.3.4-1).. By 1987 the average yearly abundance had declined to zero..269 (..3.3.5.5 Jassa falcata Jassa falcata (maximum length 9 mm) is a tube-building.amphipod, and a dominant fouling organism on hard substrates in areas with strong tidal and wave currents (Bousfield 1973). It is a suspension feeder and also preys on small crustaceans. Very highly significant differences in yearly abund--ance (1978-1987) were found for subtidal Station 17, but not for Station 35.At Station 17 yearly abundance was low from 1978-1980, peaked in 1981 and 1982, and declined to all time lows in 1983 and 1984. From 1985-1987 popu-lations were rebuilding, and yearly abundance was above average. Station 35 had a higher population density of Jesse than Station 17 during all years except 1985-1987. The mean geometric density at Station 35 for the 1982 through 1986 study period was 2110/M 2 and fluctuated between 809/mi 2 in 1987 and 5307/mi 2 in 1982 (Table 3.3.5-1).Most lifestages of Jassa were collected at Station 17 and 35,.ranging from gravid females to newly-hatched young (NAI 1985b). Gravid females were most abundant from April to November, and newly-recruited juveniles measuring 1-2 mm were most abundant in July, and were collected during the remainder of the year (NAI.1985b). The overall average length for the 1982-1987 study period was 4.1 mm at Station.17 and 3.8 mm at Station 35;interstation differences were not significant (NAI 1987b: Tables 3.3.5-3,4. Average yearly lengths ranged from 3.3 mm in 1982 at Station 17 to 4.5 mm in 1985 at Stations 17 and 35 (Table 3.3.5-3). .Densities on short term fouling panels, exposed for one-month intervals, from 1978 through 1987 give an indication of recruitment or settlement activity. From 1978-1987, substantial numbers, of young began appearing in July and continued to settle through October (NAI 1985b).Record high monthly densities occurred at Station 31 in 1987 from July through October, peaking in September with 541 individuals per panel., (Appendix Table 3.3.4-1). Mytilid spat densities were also high on'short term panels at Station 31 in 1987 (Appendix Table 3.3.4-1).270 3.3.5.6 Ampithoe rubricata Ampithoe rubricata (maximum length,. 14-20 mm) is an amphi-Atlantic boreal amphipod which constructs a nest among macroalgae (fucoids) and in mussel beds (Bousfield 1973). Average yearly densities have dropped steadily and significantly during the study period (NAI 1987b: Tables 3.3.5-1, 2), and populations at both Stations lMLW and 5MLW had virtually disappeared by 1986.Significant differences were found between stations, with Station iMLW having much higher densities than the farfield Station 5MLW (NAI 1987b: Table 3.3.5-2). During the extended study period between 1978 and 1987, the geometric mean yearly density declined significantly, ranging from 545/mr 2 in 1978 to o/m 2 in 1987 (Table 3.3.5-1). Ampithoe rubricata is a boreal species near its southern-zoogeographic limit, Long Island Sound (Bousfield 1973), and it may have been affected by increasing annual temperatures from 1980 through 1986 (Table 3.1.1-1).Ovigerous and brooding females were rare, but were occasionally collected from April through September (NAI 1985b). The-largest numbers of small (1-3 mm) individuals were collected from April through September, suggesting recruitment occurred during this time period. In 1983 and 1984, recruitment appeared depressed, accounting for both lower overall densities and larger mean size (NAI 1985b), and the trend continued through 1987. The overall mean length for the 1982 through 1987 study period was 7.0 mm at Station 1MLW, and 7.8 mm at Station 5MLW (Table 3.3.5-3), and no significant difference in the average yearly length was found between stations (NAI 1987b: Table 3.3.5-4). The average yearly length ranged from 6.7 mm at Station TILW in 1982, when young were present, to 10.9 mm at Stat-ion 1MLW in 1986, when only a few large specimens were collected (Table 3.3.5-3). When mean seasonal lengths were compared with a paired t test, interstation differences were not significant (n=6 pairs, t=0.21, probability of a greater t=0.843).271 3.3.5.7 Strongylocentrotus droebachiensis Strongylocentrotus droebachiensis, the green sea urchin, reaches 75 mm in diameter, and is an important prey species for lobster, cod and other fish, and sea stars (Gosner 1978). It is an omnivore, but prefers Laminaria saccharina over other common algal species (Larson.et al. 1980;Mannet al.-1984). When the macroalgal supply is depleted, it will prey on MytilUsledulis (Briscoe and Sebens 1988). It is subject to population explosions which can denude large areas of macroalgae, leaving barren rock (Breen and Mann 1976). No significantdifferences were found between.Stations 19 and 31 (NAI 1987b: Table 3.3.5-2) for the 1978-1987 study period.No significant differences were found among years at either station, when tested with a one-way ANOVA (Table 3.3.5-2). 'The geometric mean yearly population density over all years at nearfield Station 19 was 75/mi, and at farfield Station 31, it was.45/M 2.Yearly geometric mean density ranged from 15/m 2 in 1983 at 281/m 2 in 1981 at Station 19 (Table 3.3.5-1).W Most of the individuals collected subtidally were juvenile, mea-suring less than 3 mm in diameter, and recruitment of newly-settled young usually occurred in August and September (NAI 1985b). The average length for the 1982 through. 1987 study period was 1.9 mm at both stations (Table 3.3.5-3). Neither yearly nor interstation differences in average length were significant (NAI 1987b: Table 3.3.5-4). The average yearly length ranged from 1.5 mm at both Stations in .1986 to 2.7 mm at Station 19 in 1985.In order to account for adult individuals which were too large to be collected in the destructive program, urchins were enumerated in the subtidal transect program done by SCUBA divers. No more than 13 large (> 10 mm) sea urchins per year were counted inthree years of sampling (NAI 1986a, 1987a, 1988).Recently-settled sea urchins occurred occasionally in monthly samples from short term fouling panels set at Stations 19 and 31 during the 10 year study period (Appendix Table 3.3.4-1). Most were collected at 272 Station 19 from June through September 1981, when the yearly density averaged 1 per panel. The yearly density for all other years was less than one specimen per panel per year. The geometric mean yearly density from bottom samples reached an all-time high in 1981, at Station 19 (Table 3.3.5-1), and is a reflection of successful recruitment of young-of-the-year. 273 3.3.6 Epibenthic. Crustacea 3.3.6.1 American Lobsters (ifomarus americanus) Lobster Larvae Lobster larvae have been relatively rare during the ten-year, study period at Station P2. Mean-density of lobster larvae at the intake site was highest in 1978 (1.45/1000 M 2) and lowest in 1980 (0.46/1000 M 2) (Table 3.3.6-1). The mean number of lobster larvae caught in 1987 at Station P2 was slightly below the average of the other years sampled but similar to 1986.The maximum abundance of lobster larvae usually occurred in July-September (Figure 3.3.6-1). During 1987 lobster larvae first appeared in early-June at Station P2 which was earlier than most other sampling years and peaked in mid-July.The farfield sampling site, Station P7, was sampled beginning in 1982. The density of lobster larvae collected-at this station fell from 1.32/1000 mi 2 in 1982 to the lowest level in 1984 and increased again in 1985 and 1986 to the highest levels recorded in this study (Table.3.3.6-1). Abundances in 1987 were was similar to the 1986 levels. Abundances were always higher at Station P7 than P2; this difference was most pronounced in 1985 and 1986, when abundances at Station P7 were more than twice those at*Station P2. Larvae first appeared at Station P7 in late June during 1987.In 1986, a third station, P5, was added to the sampling regime, located in the vicinity of the intake structure. This station was sampled only from July 1 through October 14, 1986. Larval abundances were inter-mediate between abundances at Station P2 and P7 (Table 3.3.6-1). Larvae were observed from early July through mid-September matching the pattern at the other two stations in 1986,(NAI 1987).274 TABLE 3.3.6-1.PERCENT COMPOSITION OF LOBSTER LARVAE STAGES AT STATIONS P2, P5 AND P7, 1978-1987. SEABROOK BASELINE REPORT, i987.TOTAL % NO. OF MEANb PERCENT PER STAGE OF LARVAE, NO. OF STA- STAGES COL- LARVAE, YEAR TIONa I II III IV I AND IV LECTED COLLECTED 1978 P2 10.1 0.0 0.6 89.3 99.4 169 1.45 P7 ....... --- NS NS 1979 P2 7.0.8 2.5 1.7 25.0 95.8 120 1;18 P7 .. .......... NS NS 1980 P2 86.5 0.0 0.0 13.5 100.0 57 0.46 P7 ........... NS NS 1981 P2 31.8 1.9 6.5 59.8 91.6 107 0.86 P7 ........ ..... NS NS 1982 P2 3.2 0.0 0.0. 96.8 100.0 161 1.17 P7 3.8 0.0 0.5 95.6 99.4 185 1.32 1983 P2 41.4 0.8 4.9 52.9 94.3 115 0.79 P7 47.5 0.6 3.5 48.4. 95.9 162 1.10 1984 P2 14.6 11.5 21.8 52.1 66.7 79 0.57 P7 37.2 1.0 2.8 59.0 96.2 101 0.73 1985 P2 1.5 2.9 2.9 92.6 94.1 68 0.85 P7 7.0 2.1 2.1 88.8 95.0 143 1.91 1986 P2 .. .. 1.4 98.6 98.6 69 0.84 P5 3.5 .. ... 96.5 100.0 102 1.79 P7 21.6- .... 78.4 100.0 156 2.01 1987 P2 13.0 -- 1.4 85.5 98.5 69 0.92 P7 7.5 -- 92.5 100.0 146 1.94 a= Station P5 sampled from July 1 through October 14, 1986 only.b =X110i0 m 2 NS = Not sampled 275 1.2 1.0 0.8 MMEAN...... o.. 1987 z D C3'-1 0 0.2 0.0 2 3 4,1 2 3 4 1 2 3 MAY JUN JUL 411 2 3 .41 23 411 2 3 AUG SEP OCT 4 Figure 3.3.6-1.2 Weekly-mean log (x + 1) abundance (No./1000 m ) of lobster larvae 1978-1987, all year's mean and 95% confidence interval and 1987.January 1985-June1986). Seabrook Baseline Report, 1987.at Station P2 (No data collected Historically, StageI and IV larvae have dominated the collections at-both Stations P2 and P7, with few Stage II' or III larvae collected (Table 3.3.6-1). Stage I. larvae dominated the collections in 1979 and 1980, while Stage IV larvae dominated the collections in all other years. Stage II and III larvae collectively constituted 7% or less of the larvae collected except in 1984, when they made up 33% of the total abundance at Station P2. In 1983 and 1985,. the majority of lobster larvae were Stages I and IV at Stations P2 and P7 (Table 3.3.6-1). .During 1986, the pattern at Stations P5 and P7 was.-similar to.previous years. At Station P2, only Stages III and IV were collected-and the overwhelming majority of larvae were Stage IV. In 1987, Stage IV larvae dominated the collection at both stations with few Stage I larvae also at each station; a few Stage III larvae were collected only at Station'P2. No Stage II larvae were collected in 1987.Stage I larvae usually appeared at Station P2 during July with large peaks also occurring in June in 1980 and 1983. Peakabundance of Stage IV larvae varied in occurrence between July and August (NAI 1985b). Stage I larvae first appeared in 1985 in late May. at Station P7 (NAI 1986). Stage IV larvae were observed in late July at Stations P2 and P7. Stage IV larvae appeared at all stations and dominated the collections in 1986. Stage I larvae were observed at Station P2 in early June and early July at P5;however, collections did not begin until July at Station P5. At all three stations, Stage IV larvae were first observed in mid-July. During 1987, Stage I larvae appeared in early June and late June at Stations P2 (Figure 3.3.6-1) and P7 respectively. Stage IV larvae occurred in early July at both stations while Stage III larvae were collected in' early July at Station P2 only (NAI 1988).Trends in the occurrence of lobster larvae in this study have generally agreed with other lobster larvae studies in New England (Sherman and Lewis 1967; Lund and'Stewart .1970). An extensive review of New England lobster larvae studies (Fogarty and Lawton 1983) indicated that the period of peak abundance in the region coincided with that observed off New Hampshire. 277 waters, as described by this'study. -Also, the' high predominance of Stage I'and Stage IV larvae among years in this study has been shown to vary from year to'year in-other New England studies (Fogarty and Lawton 1983)..Abundances and occurence of lobster larvae in inshore areas have been associated with wind direction. Grabe et al. (1983) reported that 67%of Stage IV larvae were collected off the New Hampshire coast when winds were on- or along-i shore. Thermal differences between air and land masses, com-bined with predominantly light westerly summer winds, produced onshore winds during the day and offshore winds at night. In addition, hydrographic' studies in the Hampton/Seabrook area indicated a net drift northward or southward along the New Hampshire coastline. 'Combined,.these two actions suggested that lobster larvae were moved by nontidal water mass movements into New'Hampshire waters, and were then transported onshore by winds.A synthesis of lobster larvae distribution studies by Harding et J al. (1983) supports this hypothesis. They noted that lobster landings for all regions neighboring on the Gulf of Maine have been very similar since the mid-1940s. They interpret this to indicate a single lobster-stock with common recruitment. They further concluded that warm southwestern waters of the Gulf of Maine .and Georges Bank supply the Maine coast and adjoining areas with advanced larval stages, evidenced by a preponderance of Stage IV larvae in the cooler surface waters from southwestern Nova Scotia to Hampton, New Hampshire.( This may explain the abundance of'Stage IV lobster larvae in the present study. A recent examination of hydrographic drift studies (Harding and Trites 1988) also supports the theory of lobster larvae dispersion into the region through current transport. 'Adults Adult lobsters (legal and sublegal sizes combined) have been collected in the Vicinity of the discharge site (Ll) from 1974 to 1987 (Table 3.,3.6-2). During that period, the-highest monthly catch usually occurred 278 TABLE 3.3.6-2.-

SUMMARY

OF TOTAL LOBSTER CATCH PER TRIP EFFORT a, BY MONTH AND YEAR, AT THE DISCHARGE SITE (4) FROM 1974 THROUGH 1987. SEABROOK BASELINE REPORT, 1987.MONTH YEARLY YEAR JUN JUL AUG SEP OCT NOV AVERAGE 1974 41.7 51.2 73.6 103.0 78.6 59.7 68.0 1975 41.1 42.5 73.9 74.0 71.6 55.2 59.7 1976 35.0 40.7 68.6 69.1 63.7 48.0 54.2 1977 45.8 32.3 63.5 67.3 .54.5 61.1 53.7 1978 49..7 34.8 63.4 86.4 79.1 65.5 63.2 1979 54.1 57.6 61.5 62.8 69.9 58.8 61.4 1980 32.2 30.2 70.3 59.7 41.3 43.4 46.2 1981 38.1 42.5 80.2 94.3 65.6 59.3 63.3 1982 35.7 *52.3 *83.9 71.7 88.8 79.1 68..6 1983 49.2 39.9 89.3' 128.2 96.3 29.6 72.1 1984 49.9 28.2 72.1 .117.9 146.6 140.5 92.5 1985 25.'3 45.2 81.3 121.3 131.2 130.4 89.1 1986 32.4 37.5 75.0 86.9 80.5 99.7 68.7 1987 39.5 26.3 33.3 57.2 83.2 48.2 46.0 MONTHLY AVERAGE 40.7 40.1 70.7 85.7 82.2 69.9 aCatch per trip effort = total catch from 15 traps per trip.279 from August through October. Monthly catch was highest in September during 1987. However, in 1980 the greatest catch was in August; in 1979, 1982, 1984, and 1985, in October; and 'in 1986, November. June or July have had the, lowest monthly catches (Table 3.3.6-3). Data from 1945 to 1973 reported by the New England Fishery Management Council (1983) for the Maine lObstf fishery also indicate August, September and October as peak months in lobster abundance. Average yearly catches per fifteen-trap trips at the discharge station ranged from 46.2 in 1980 to 92.5 'in 1984 (Table 3.3.6-2). Lobster catch abundance was also high in 1985 (89.1), but dropped to average levels in 1986 (68.7). The average yearly catch for 1987 was 48.0 per fifteen-trap trip, the lowest average *since 1980..Results of one-way ANOVAs of lobster catch for years (1982-1987) and months at the discharge site indicated significant differences among months but not for years (Table 3.3.6-3). Multiple comparisons'among months also indicated August, September, October and November differed from catch during June and July. Among stations, lobster catch wassignificantly greater at the farfield station (L7). than at the discharge site (L1) (Table 3.3.6-4). The pattern of peak monthly abundances and the'greater abundance. of lobster catch at the farfield station is consistent throughout the study since sampling at the that station was begun in 1982.Adult lobster abundances have been related to seawater temperature. McLeese and Wilder (1958), Dow (1969) and Flowers and Saila (1972) have examined this relationship. In the Hampton/Seabrook study'area, continuous bottom temperature monitoring (1978-1984) at Station. ID, near the discharge area, was compared to monthly mean lobster catch. A relationship between bottom water temperature and lobster catch-was established at the discharge station (NAI 1985b). During June, catch declined as bottom water temperature increased; however, was probably caused by the onset of molting which would reduce the catchability of lobsters. Peak catch of adult lobsters usually occurred after bottom water temperatures reached approximately 10 0 C and lobsters had molted to legal lsize (NAI 1985b). As bottom temperatures cooled, catch declined in November, perhaps reflecting seasonal inshore movement patterns (Ennis 1984) or decreased activity level. Lobsters 280 TABLE 3.3.6-3. RESULTS OF ONE-WAY ANOVA AT THE DISCHARGE SITE FOR LOBSTER (H..AIIERICANUS), JONAH CRAB (C,. BOREALIS) AND ROCK CRAB C. IRRORATUS). SEABROOK BASELINE REPORT, 1987.SOURCE OF MULTIPLE SPECIES VARIATION df: ss. F-VALUE COMPARISONS Lobster Year 12 14011.66 1.62NS Error 65 46975.38 Total 77 60987.04, Month 5 26287.64 10.91*** 9 10 11 8 6 7 Error 72 .34699.40 Total 77 60987.04 Jonah Crab Year 5 405.95 1.70 Error 30 1428.89, Total 35 1834.84 Month -5 892.45 5.68*** 8 9 7 11 10 6 Error 30 942.38 Total 35 1834.83 Rock Crab Year 5 60.99 6.67*** 85 86 84 87 83 82 Error 30 54.89 Total 35 115.88 Month 5 28.60 1.97NS Error 30 87.29 Total 35 115.89 NS= Not Significant (p>0.05)*= significant (0.05>_p>0.01)

• • = highly significant (0.Ol>p>0.001)

= very highly significant (p<0.O01)281 TABLE 3.3.6-4. PAIRED t-TEST COMPARISONS OF THE DISCHARGE SITE (Li) AND THE FARFIELD STATION (L7) FOR LOBSTER (ff. AMERICANUS), JONAH CRAB (C. BOREALIS) AND ROCK CRAB (C. IRRORATUS). SEABROOK BASELINE REPORT, 1987.CATCH/15 TRAPS MEAN, SIGNIFICANT SPECIES Li .L7 DIFFERENCE n t. DIFFERENCES Lobster 46.0 '70.1 18.59 36 4.43*** L7 > LI Rock Crab 10.7. 10.4. 0.85 36 3.76*** Li > L7 Jonah Crab 11.2 11.5 0.18 36 0.24NS NS = Not Significant;

• p 0.001 typically show a seasonal migration pattern which is thought to maintain the population at the highest local water temperature (Campbell 1986). It is uncertain whether New Hampshire lobsters undergo seasonal migrations (NHFG 1974).Although the relationship between lobster catch and bottom water temperature has been shown to be significant for some months, the combined effects of molting and other factors such as food availability probably interact, affecting lobster catchability and its relationship to bottom temperature (NAI 1975b). Further, the New Hampshire Fish and Game Department conducted similar studies off the New Hampshire coast from 1971 through 1974 and concluded that bottom water temperature-did affect lobster catch, but was influenced by other factors as well (NHFG 1974).Low catches of lobsters in 1987 may be'temperature related. Bottom water temperatures at Station P2 were 1 to 3 0 C lower from July through October than the overall mean temperature (See Figure 3.1.1-1).

Also, benthic invertebrate abundances and numbers of taxa at Stations 17 and 19 in ,/the vicinity of the.discharge site were lower than previous years (See Figure 3.3..3-2) perhaps further indicating the effect of cooler bottom water temperatures. 282 Catch per effort of legal-sized lobsters at the discharge station averaged from 7 to 10 individuals per fifteen-trap trip from 1975 through 1986 (Appendix Table 3.3.6-1).. However, in 1987, this declined to three individuals per fifteen-trap trip. The catch of legal-sized lobsters consti-tuted *approximately 12% of the 'total catch during 1975-1981, but decreased slightly to approximately.10-11% of the total catch during 1982 and 1983. In 1984 despite having the highest yearly mean catches, the legal-sized lobster catch at the discharge, declined to approximately 7% of the total catch (Appendix Table 3.3.6-1; Figure 3.3.6-2). Legal-sized lobster catch increased slightly to 7.2 (10%) in 1986. In 1987, 6.7% of the lobster catch was of legal size, comparable to 1984 and 1985 catches. However, the total catch of lobsters in 1987 was the lowest yearly average since 1980 (Table 3.3.6-2). In 1984, an increase in the legal size limit for lobsters from 3-1/8" (79.2 mm) to 373/16" (80.9 mm) was enacted. Because of the change in the law, a number of adults which would have been legal-sized under the old size limit, were retained in the sublegal size class during 1984 and 1985, adding to those lobsters molting to legal-sized lobsters in 1986.Annual size-class distributions (Figure 3.3.6-3) indicate that the abundances of lobsters in the 42-54 and 54-67 mm size classes have steadily declined since 1975, while, catches in size class. 67-79 mm (2-5/8" to 3-1/8")have increased through 1985. Size classes above 79 mm have had low catch abundances, indicating that commercial fishing in the study area quickly removed the majority of lobsters as they attained minimum legal size.The increase in catch abundance within size class 88.9 mm since 1984 may be attributed to the increase, in the legal-size limit implemented by the State of New Hampshire. Lobsters in this size class, measuring 3'1/8" to 3-3/16" which had been available for harvest through 1983 were now protected until their next molt. New Hampshire inshore lobster landings reported for 1984, the first year the change was enacted, had decreased by nearly twenty-four percent based on information obtained from state-required annual reports. However, adjusting catch for a generally poor catch in the southern Gulf of Maine in 1984, the actual reduction that was due to the change in 283 0 0 100 80 a-W-a.60 40o 00 OOI 20 0 75 76 .77 78 79 80 81 82 83 84 85 8'6 87 YEAR Figure 3.3.6-2.Comparisons of legal and sub-legal sizdd catch of Ilomarus americanus at the Discharge Site, 1975-1987. Seabrook Baseline Report, 1987. Mi] >105 mm[o 92-105mm MJ 79- 92 mm 100-80-cc LO I-cn LU 0.I--C, 60-40 20 0-1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR Figure 3.3.6-3.Size-class distribution (carapace length) of ifomarus awericanus at the discharge site, 1975-1987. Seabrook Baseline Report, 1987. size limit was approximately 13% (Edward Spurr, NHFG, pers. comm.). This resulted in an estimated 28% loss in total catch weight in 1984 (Perry 1985).Preliminary data reported to the state in. 1986 -indicated that the catch weight had recovered (Edward Spurr, NHFG, pers. comm.). Data for 1987 were not available in time to be considered in this report. This agreed with results from this study, which showed an increase in legal-sized lobster catches in 1986 to 1983 levels (Appendix Table 3.3.6-1).Female lobsters have represented nearly 60% of the total catch for all years at the discharge (NAT 1984b) although percentages. have been lower (54-56%) in recent years. Egg-bearing female lobsters comprised 1.1% of the catch in 1987 slightly greater than in 1985 and 1986 but still consistent with previous years' data (Figure 3.3.6-4).3.3.6.2 Rock Crab (Cancer irroratus) and Jonah Crab (Cancer borealis)Larvae Cancer spp. (Cancer borealis and Cancer irroratus) larvae generally exhibited a pattern for all sampling years of very low or near-zero density from January through April with rapidly increasing numbers in May,'reaching peak abundance in August and declining density from October through December. At plankton Station P2, Cancer spp. larvae were usually most abundant during August,.except in 1981, 1983, and 1987 when density was greatest in July. (Figure 3.3.6-5). In 1987,'from July through December, the observed pattern was very similar to previous years.Adults Adult rock crab (C. irroratus) and-Jonah crab (C. borealis) catches have been monitored since 1975 at the discharge site (NAI 1985b). Since.1982, these populations have been monitored at two stations, the discharge site (LI),and at Rye Ledge (L7). Historically, catches of Jonah crabs have.286 64-62-.% FEMALES IN CATCH.......... % EGG BEARING FEMALES-1.6 I z Co w-.60 58-56-r3O-1* J:1-1.4 (I.w-1.2 4 w u,.-1.0 w 0-o.-0.8 co w-0.6 0.4 54-52ýI I I I I I i I I I I I 11 74 75 76 77 78 79 80 81 82 83 84 85 86 87 YEAR Figure 3.3.6-4. Summary of female lobster catch data at the Discharge Site, 1974-1987. Seabrook Baseline Report, 1987. 6 5 LU z z C, 0-1 4 3 Ili 00 Go 2-ALL YEARS' MEAN 1....... 1987 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV ME3 MONTH Monthly mean log (x + 1) abundance (No./1000 m ) of Canc'er spp. larvae at Station P2, 1978-1987. Seabrook Baseline Report, 1987. (No data collected January 1985-June 1986).Figure 3.3.6-5. been significantly greatest in August, although catches were occasionally higher in September at both stations (Table 3.3.6-5). Average monthly catches per fifteen-trap trip have ranged from 0.6 to 26.7 at the discharge station and from 3.0 to 31.5 at Rye Ledge from 1982 through. 1987 (Table 3.3.675). The total annual catch of Jonah crabs increased from 1982 through 1985, when catches were significantly higher than other years, and declined in -1986 at both stations (Table 3.3.6-5). In 1987, the decline continued at the discharge station but catch increased at Rye Ledge.Catches of Jonah crab at the discharge site from 1982 through 1987 were not significantly different from year to year. However, monthly catch data during August and September was significantly different than other months (Table 3.3.6-3). A paired t-test comparison of the discharge site and the farfield station, Rye Ledge, did not indicate a significant difference between the two sites (Table 3.3.6-4) for Jonah crab, however.Catch of rock crabs has ranged from 0.0 to 6.7 per fifteen-trap trip at the discharge station and from 0.0 to 2.9 at Rye ledge from 1982 through 1987. The catch of rock crabs has also been generally increasing from 1982 through 1985, when catches were higher than all other years;catches then.decreased in 1986 at both stations (Table 3.3.6-3). Rock crab catches have generally been greatest in July or August, and since 1984 have been greatest at the discharge station.Rock crab catches at the discharge site from 1982 through 1987 were significantly different from year to year (Table 3.3.6-3). Monthly catch data, however, was not significantly different. Comparison of station differences between the discharge site and the farfield station, Rye Ledge, indicated that the discharge site had significantly greater catch than at Rye Ledge (Table 3.3.6-4).Total catch of rock crabs has been low at both stations relative to the catch of Jonah crabs; this may be due to intra-specific competition between the two species of crabs (Richards et al. 1983). Also, rock crabs 289 1N,3 0 TABLE 3.3.6-5. COMPARISON. OF CRAB CATCH STATISTICS OF JONAH CRAB (CANCER BOREALIS) AND ROCK CRAB (CANCER IRRORATUS) AT THE DISCHARGE SITE AND RYE LEDGE, 1982-1987. SEABROOK BASELINE REPORT, 1987.CATCH PER PERCENT EGG UNIT EFFORT* PERCENT FEMALES BEARING FEMIALES A. DISCHARGE STATION 1982 1983 1984 1985 1986 1987 1982 1983 1984 1985 1986 1987 198Z 1983 1984 1985 1986 1987 JONAH CRAB JUN 2.7 2.8 3.6 9.3 7.5 0.6 57.1 61.3 53.1 64.7 63.9 28.6 3.8 0.0 6.3 2.0 1.2 0.0 JUL 3.9 6.9 4.5 14.2 9.6 9.2 51.9 70.8 57.1 59.6 71.7 63.3 0.0 2.3 4.1 0.0 3.8 5.0 AUG 4.9 1Z.1 11.5 26.7 26.6 .25.5 86.7 74.5 72.0 81.6 89.6 78.0 1.4 1.4 1.9 0.0 0.0 4.5 SEP 8.4 8.4 9.3 11.4 18.5 26.2 84.0 92.9 83.3 87.7 95.6 87.3 0.0 0.0 2.0 0.0 0.0 0.9 OCT 2.7 4.3 7.2 9.7 5.6 Z.5 80.0 88.2 81.6 85.6 88.7 84.0 0.0 0.0 0.0 0.0 0.0 0.0 NOV 3.0 1.8 8.9 11.7 6.2 1.4 74.0 81.3 69.7 72.6 81.1 91.4 0.0 0.0 0.0 0.0 0.0 0.0 YEARLY AVERAGE 4.3 6.1 7.5 14.0 13.3 11.3 72.3 78.2 69.5 75.5 85.8 78.5 0.9 0.6 Z.4 0.2 0.6 3.1 ROCK CRAB JUN 0.0 0.2 0.7 2.7 2.3 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 JUL 0.7 0.9 Z.0 5.3 3.7 4.2 21.7 9.1 6.9 1.6 0.0 18.8 0.0 0.0 0.0 0.0 0.0 0.0 AUG 0.0 1.0 3.4 6.7 3.2 2.5 0.0 0.0 8.3 00 2.4 39.4 0.0 0.0 0.0 0.0 0.0 0.0 SEP 0.0 0.2 1.5 0.6 1.2 1.2 0.0 0.0 12.5 0.0 7.7 27.3 0.0 0.0 0.0 0.0 0.0 0.0 OCT 0.1 0.0 0.2 3.3 1.7 0.1 0.0 0.0 50.0 57.6 36.8 0.0 0.0 0.0, 0.0 0.0 0.0 0.0 NOV 0.2 0.1 0.2 5.7 Z2. 0.0 0.0 0.0 50.0 45.6 46.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 YEARLY AVERAGE 0.2 0.4 1.3 4.1 Z.4 1.6 3.6 1.5 21.3 17.4 9.8 25.5 0.0 0.0 0.0 0.0 0.0 0.0 B. RYE LEDGE 1982 1983 1984 1985 1986 1987 1982 1983 1984 1985 1986 1987 1982 1983 1984 1985 1986 1987 JONAH CRAB JUN 3.6 4.4 5.9 7.7 5.9 1.3 37.4 50.0 41.5 36.5 50.8 14.3 7.4 2.1 1.9 0.2 3.1 0o0 JUL 3.2 12.6 6.4 16.0 8.6 7.7 50.2 56.7 .50.0 50.0 66.3 69.0 4.6 1.3 0.0 5.9 1.1 2.0 AUG 4.0 13.6 19.3 31.5 7.5 27.4 89.3 77.9 62.9 84.4 83.7 73.3 0.0 1.2 1.6 1.0 0.0 3.7 SEP 5.6' 9.8 11.4 9.8 11.4 20.1 91.8 82.7 86.4 92.9 88.8 77.0 0.0 0.0 2 .4 1.2 0.0 .1.2 OCT 3.4 4.6 8.3 7.7 7.4 1.6 70.9 86.5 78.0 84.4 95.1 81.3 0.0 0.0 2.0 0.0 0.0 0.0 NOV 3.5 3.0 8.5 13.1 7.3 1.3 75.1 70.0 80.0 70.2 79.5 61.9 0.0 '0.0 0.0 0.0 0.0 0.0 YEARLY AVERAGE 3.9 8.0 10.0 14.5 8.1 10.3 69.1 70.6 66.5 71.8 78.9 72.3 Z.0 0.8 1.3 1.2 0.6 2.6 ROCK CRAB JUN 0.2 0.4 O.Z 1.5 0.5 0.1 0.0 0.0 0.0 94.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 JUL 1.5 0.9 1.7 1.2 2.0 0.8 29.9 0.0 10.5 100.0 0.0 36.4 0.0 0.0 0.0 0.0 0.0 0.0 AUG 0.1 1.3 1.5 2.9 0.2 2.3 100.0 6.3 5.0 96.9 33.3 43.3 0.0 0.0 .0.0 0.0 0.0 0.0 SEP 0.1 0.2 1.6 0.8 0.2 1.4 0.0 0.0 16.7 100.0 0.0 9.1 0.0 0.0 0.0 0.0 0.0 0.0 OCT 0.0 0.0 0.6 1.6 0.5 0.1 0.0 0.0 0.0 37.5 83.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 NOV 10.1. 0.2 0.2 1.9 0.0 0.0 0.0 0.0 50.0 57.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 YEARLY AVERAGE 0.3 0.5 1.0 1.7 0.6 0.8 21.7 1.1 13.7 81.3 15.8 33.3 0.0 0.0 0.0 0.0. 0.0 0.',*Catch per unit effort = total catch from 15 traps per trip prefer sandy habitat which is available near the discharge site compared to rocky habitat preferred by Jonah crabs (Jefferies 1966; Bigford 1979).The percent of female crabs in the catch has been monitored-since 1982 (Table 3.3.6-5). The highest proportion of females at the discharge station occurred during September in most years, ranging from 83.3% to 95.6%.In 1987 the highest percentage of females was in November (91.4%). At Rye Ledge, they reached their greatest proportion in September or October (81.3 to 95.1%). Female catch of Jonah crabs generally increased from 1982 through 1987, particularly at the discharge, due to larger catches and higher pro-portions'of females. Trends of female rock crab occurrence were less defined than Jonah crabs due to the.low overall catch of rock crabs. In 1984-1986, catches of female rock crabs were generally greatest in the fall, but some earlier months had greater percentages in some years due to a lw catch comprised of only female crabs (Table 3.3.6-5). Percentages of females in 1987were higher'than mostof the previous years! catch figures. Egg-bearing Jonah crabs were most abundant in .1987 at both stations (about 3% of the total catch), occurring mainly in June or July, compared to generally less than 1% of the total catch at both stations from 1982 to 1986. No ovigerous rock crabs were collected in 1987 at either site, similar to findings from 1982 to 1986 (Table 3.3.6-5). This is as expected, considering the low catches of rock crabs and the low proportion of the population that would be ovigerous females.Width frequency distributions taken in 1985 and 1986 indicated that male Jonah crabs were slightly larger than females, although ovigerous females were.slightly larger than males in 1986 (NAI 1986,. 1987a). This trend generally continued in 1987; however, both females and ovigerous females were slightly larger than males. at the discharge site but at-Rye Ledge, males were slightly larger than females (NAI 1988). Due to low overall catch, trends in the size class distribution of rock crabs were less apparent. Male rock crabs were generally larger than females (NAI 1988).Gear selectivity had an influence on size distributions reported, since catches from lobster traps do not include the smaller size classes in the crab populations. 291 3.3.7 Mva arenaria (Soft-shell Clam)3.3.7.1 Larvae Mya arenaria larvae occurred in plankton samples May through October from 1978 to 1987 (Figure 3.3.7-1). Each year, maximum abundances were recorded in late summer or early fall, while in many years a secondary 3 peak also occurred in early summer. Peak densities observed in 1985 (63/mi)were the lowest encountered from 1978-1987. Theý late-summer peak (99/m3 ) in 1987 was higher than 1985, but much lower than the remaining years, 1978-1986. A late-summer peak in 1987 occurred from mid to late August, similar to 1981-1983. Factors influencing the timing and magnitude of the observed pattern of larval abundance are not fully understood. M. arenaria is known to spawn in the spring at temperatures greater than 4-6 0 C with summer spawning at 15-180C (Brosseau 1978). Maximum larval abundances in August and September coincided with water temperatures in Hampton Harbor that regularly exceeded 15-18 0 C. However, these temperatures also occurred frequently in June and July, which were characterized by much lower larval abundances, suggesting that temperature is a minimum requirement for spawning. In addition, recruitment of larvae of non-local origin is likely due to currents in the Gulf of Maine, which may move water masses and their entrained larvae significant distances before larval settlement. The late-summer peaks have been observed to be coincident with northward-flowing currents. This implies that these offshore larval peaks may in parthave a more southern estuarine component. Overall, factors controlling the occur-rence of M. arenaria larvae off Hampton Harbor Beach are complex, the result of environmental and biological factors including: adult condition at the time of spawning, temperature at spawning sites, location of spawning sites relative to prevailing coastal currents, water column stratification and .larval behavior.292 3.0-2.5-2.0-OVERALL MEAN------- .1987 W C.)z z W mW-0-C.0 W ow I 1.0-0.5-0.0-i I i I I 3 I I I I I 3 I I I I I I I 3 I I 2 I 4 i 3 4.1 2 34 1 2. 3"41 23 4 1 2 3 41 2-3 4 1. 2-3 4 JAN FEB MAR APR MAY JUN JUL Figure 3.3.7-1. Weekly log (x+l) abundance per cubic meter of Mya arenaria larvae at station P2, 1978-1987, all years' mean and 95% confidence interval and weekly mean for 1987.Seabrook Baseline Report, 1987. A comparison of larval densities at nearfield (P2) and farfield (P7) stations indicated similar patterns at the two stations, .1982-1984 and.1986-1987 (Figure 3.3.7-2). Only Station P2 was examined in 1985. In 1986 and 1987, Hampton Harbor Station P1 added in July 1986, was also similar to patterns at P2 and P7 (Figure 3.3.7-2).* 3.3.7.2 Reproductive Patterns Developing stages in the Mya reproductive cycle in the Hampton estuary appeared in March or early April during most years. Ripe individuals were observed between the second week in April and the third week in June.In most years, ripe individuals occurred at similar times at both Hampton Harborand Plum Island Sound, with the exception being 1984 (NAI 1985b).The onset of spawning in Hampton Harbor and Plum Island Sound, as indicated by the reproductive studies, usually occurred following the appear-ance of larvae in offshore tows. Only in 1980 and 1981 was spawning detected before larval occurrence. The peak larval abundance always occurred well after spawning had commenced, indicating both Hampton Harbor and Plum Island Sound clams may contribute to the large nearshore larval densities of late summer (NAI 1985b).3.3.7.3 Hampton Harbor and Regional Population Studies Hampton Harbor Spatfall 'The soft-shell clam population has been studied through intensive surveys of.spat and adults in Hampton Harbor (Appendix Table 3.3.7-1). These surveys have been supplemented by quantitative studies of regional spatfall , in nearby estuaries, where settlement is known to occur. Over a 14-year period,' the Hampton Harbor population has gone through substantial changes in abundance. The Mya population structure during the 1984-1987 period 294 Lu C.)z zw OEOw C.=.4.0-3.5-3.0-2.5-2.0-1.5-1.0-0.5-0.0-1982 STATION P2 STATION P7 I S S S S I I I APR-3 API- MAY-1 MAY-2 MAY-3 MAY-4 JUJN-1 ,3 JU-4 J *J1L-1 JUL-. JU31-3 _J.-4 AUGAI AUG- " SAUG-4 EP-1 SEP-2 SEP-3 SEP-4 0C-I OCT-3 OCT.4 MONTH 1983 W 0 z<C zuJ rn1J--'0 z ZW 0ZLU-C.)liWOw 0 W ,_j I 3.0-2.5-2.0-1.5-1.0-0.5-0.0--STATION P2.... ---STATION P7 I I I I I I I I I I I I I I i I I I I I I I I I 1 AP94 APR-4 MAY-I MAY-2 MAY-3 JAd-I JWN-2 4;U-3 41UN4 .1J1.-I JIL-S A 4L-114.-4 AUG- AUG-S AUGL AUG-.L -SEP-S SEP-S SEP-4 OCT-I OCT-2 OCT-S OCT4 MONTH 1984 3.0-2.5-2.0-1.5-1.0-0.5-0.0--STATION P2--------. STATION P7 I S I S I I S S

• a a a a a a a a i i a. I I I I a APR-3 APR-4 MAY-1 MAY-2 MAY-S MAY4 04-1 JANRl J4 J4-S J4-A 1 JUL- ,L- L-3 JUL-4 ALUG-1 AUG-2 AUG-3 AUG-4 SEP-I SEP-2 SEP-3 SEP-4A0CT-I OCT-, OCT4 MONTH Figure 3.3.7-2.Log (x+l) abundance per cubic meter of lya arenaria veligers at nearfield station P2, farfield station P7 and Hampton Harbor station PI, 1 9 8 2-1 9 8 7.aa, Seabrook Baseline Report, 1987.a. Only station P2 was examined for fya veligers in 1985.295 z L 0 U ow (1986 3.0-2.5-2.0-1.5-1.0-0.5-0.0--- STATION P2 STATION P7' STATION P1 AP4i2 APR4 MAY-I KAY-2 MAY-3 UAY-4 .A Lt4I.IM2 .lN A- i A;- j2 4.4A;L3J4 AUG-i AUG-2 ALG- AL44 SEP-I SEP- SEP-- OCT-I OCr.2 OCT-3 OCT-4 MONTH*1.1987 W C. l 4. 1_.j I 3.0-2.5-2.0-1.5-1.0-0.5-0.0--. STATION P2 STATION P7 STATION P1 U U £ U £ I I U I I U I U I I U U U I I I I I I U.1 AP.L APL- AY-1 MAY-2 MY-3 MY-, Md-I JLH2 JJN-3 A;.- A.Li JL-2 Jjt-3 A.I-4 ALG.I NUG-2 ALJG-3 AUG-4 SEP-I SEP-2 SEP-3 SEP-4 OCT-I OCT-2 OCT-3 OCT-MONTH Figure 3.3.7-2. (Continued)

.b. Station P1 was added in June 1986.iI 296 resembled that observed in 1974-1975, suggesting long-term trends based on the interaction of spatfall, and disturbance possibly due to natural and human.predation (Figure 3.3..7-3). The continuing decline in juvenile and adult (>25 mm) clam densities is partially the result of light spatfalls (1982-1987). The size distribution in 1974-1975 also indicated a-decreasing juvenile and adult (>25 mm) population with an absence of any clams between 5-25 mm in 1974 and 1975 except for the young-of-the-year settlement (1-5 mm). In 1976, a large settlement occurred at all flats (Figure 3.3.7-4)which initiated changes in the population during the 1976-1982 period. The current state of low juvenile and adult densities is not likely to be reversed without a significant spatfall.The 1976 spat settlement was the largest observed in the study;however, other important settlements occurred in 1977, 1980, 1981 and in 1984 (Figure 3.3.7-4). The 1976 recruitment was successful on all flats, while the spatfall in 1980 and 1981 was most successful on Flat 2 and in 1984 on Flat 4. In Hampton Harbor, the least-successful recruitment years occurred in 1974, 1982, and 1985-1987. Regional Spatfall The regional spatfall study verified that the large 1976 recruit-ment occurred throughout the region (Figure 3.3.7-5). Generally, spat recruitment was similar between estuaries, though variation between flats'within estuaries was often considerable. Overall, .1987 had the lowest abundance of spat observed in the regional study. In 1987, Flat 4 and Plum Island Sound spatfalls were the lowest observed during the 1976-1987 period while Flat 2 spatfall was higher than 1982 but lower than all other years.Yearling and Adult Clams Yearling clams (10-12 mm) became numerous in 19.77 following the 1976 spatfall and began showing a decline in 1981 at Flat 1 and 1982 at Flat'297 i IG77 1.10 I r L I .L " lL m ..L Ii ..... .. ................ .... °.; lr~ r .1:u ......... t. u .r.................... 21r...L I 0$O0 10!-I.1 lele /11 1878 *101979 1970.. ............. ..... --;. ........1. .. ... ......, , , + + ., + ... ....1617517 11.1 101.0 1980.I ... ..e...in ...... [~IIfliiiiiriii.ii....... II '~~ 20 20 30 s71 10 1 0 5 30 % ,1* S1 5 031:I........................ I. lIIuiill [! lh!IInuulrm ir L .............. 1974 I..1[1[...................... !JIII I ! lI[l!1 1 1.l., 1 1 1 1 ... ........... 1 ............Figure 3.3.7-3.. Abundance (No./ft 2) of 1-mm size classes of iy2a arenaria in Hampton-Seabrook Harbor during early fall, 1974-1987 (Note differences in abundance scale).Seabrook Baseline Report, 1987.298 1983 I ,1984................................. ............ IIIfhlIli 1982 -1985 UJ~ I~ i, ,2 .......... ......0. 198 I .... I tt I nn... .. ...... .....:. f17000 -I)!!!!. I fI .II ! I. ........... I..1287 Figure 3.3.7-3. (continued) 299 FLAT 1 3.0-2.5-2.0- I I_ 1.02 2.0 r-.0.00 1.5 I I I I I 74 75 76 -77 78 79 80 81 82 83f 84 85- 86 87 YEAR FLAT.2 3.0-... 2.5-IffI 2.0 z .0. .5-w *0.0 -,.74 75 76 77 78 79 80 81 82 83 84 85 86 87 YEAR FLAT 4 3.0-2.5-2.02.0-.0.0 I I I I I I I I 74 75 76 77 78 79 80 81 82 83 84 85 86 87 YEAR Figure 3.3.7-4. Annual mean density (number per square foot) and 95%.* confidence limits of young-of-the-year Mya arenaria (1-5 mm) .at Hampton-Seabrook Harbor, 1974-1987. Seabrook Baseline Report, 1987.300 x 0 U)z w, a 4 3 2 I I HAMPTON HARBOR FLAT 4 1 0 4 1976 1977 1978 1979 1980 1981 1982 1983 YEAR 1984 1985 1986 1987 HAMPTON HARBOR FLAT 2 x 0 z 0 3-I T I 2 1 I II I 1 0 3-1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR PLUM ISLAND SOUND (IPSWICH) MA.I x 0-J z wU a 2-1-I I.I I I I I I I 0 I I I I I I 1976 1977 1978 1979 1980 1981 1982 1983 1984 YEAR I 1 1985 1986 1987 Figure 3.3.7-5.Mean and 95% confidence limits of Mya arenaria spat (shell length 12 mm) densities (No./ft 2) at two.northern New England estuaries, 1976 through 1984 and 1986 through 1987. Seabrook Baseline Report, 1987.301 2 and Flat 4 (NAI 1982b, NAI 1983a). Juveniles (26-50 mm) age two to four years old, were relatively scarce from 1976 to 1978, but became abundant from 1979 to 1981 at all three flats. This pattern reflects the growth of the large sets of 1976 and 1977. The large spat sets of 1980 and 1981 did not result in increased densities of juveniles. High adult densities (>50 mm)were recorded in 1980 and have declined from 1983 through 1987 (Figures 3.3.7-6, 3.3.7-7 and 3,.3.7-.8). The 1980-1982 adult densities reflected the success of the 1976 and 1977 year classes; Subsequent decline resulted from the harvesting of these clams (see below) and the failure to recruit the spatfalls of 1980, 1981 and 1984 into the juvenile and adult size clams.The New Hampshire Fish and Game Department seeded Flat 5 with 45,000 juvenile clams in late June of 1987, but during a qualitative survey of Flat 5 in October, no clams from the seeding experiment were found.In order to better understand the patterns of population structure, growth and survivorship of the.one-year and older clams, the size-class density distributions were separated into year classes utilizing NORMSEP (Hasselblad 1966). This method attempts to fit normal distribution curves to complex frequency distributions so that the mean and standard deviation of each cohort can be estimated. A chi square test was also performed to test the difference between actual and predicted distributions. The resulting mean sizes and density for each year class for each year (1976-1984) were utilized to provide estimates of survivorship (density remaining) and growth.The relative paucity of juvenile and adult clams, 1985 through 1987, did not warrant a NORMSEP analysis for those years.The 1976 year class (Figure 3.3.7-3) was most easily traceable as few juvenile and adult clams existed when it entered the population. By November 1976, the clams reached a mean size of 2.5-mm. It took four years until these clams began appearing as harvestable adults.in 1980, with a mean size of 48 mm. Subsequent year classes experienced similar growth patterns, but older years were more-difficult to separate successfully. An examination of survivorship from the NORMSEP analysis of size density data, indicated that the 1980 to 1982 year lasses experienced far 302 2-Vi--= O-CI 3o x o 0 Lu-== C=13-25 mm SPAT I I 1-I.I I T T 0.1 7 -a a I I I I I I I 5 I I 1974 1975 1976 1977 1978 1979 1980 1981 YEAR 1982 1983 1984 1985 1986 1987 2 50 mm JUVENILE>J .1,-I-WIU~xc OLU-Jo.I I 1-I I I I I i T T " t K 0 1974 1975 1976 1977 1978l- I 1979 1980 198'1 YEAR i I I I I i 1982 1983 1984 1985 1986 1987 I-I-Z O xO COU 0OLu... 0.75 -0.50-0.25-0.00> 50 mm ADULT II I I I I I I I I I i T t~~I ~ I I I I i I I 1974 1975 1976 1977 1978 1979 1980 1981 YEAR,.1 I I I 1 1982 1983 1984 1985 1986 1987 Figure 3.3.7-6.Means and 95% confidence limits of spat, juvenile and adult log (x+l) densities at F.l.at 1i Hampton-Seabrook Harbor, 1974 through 1987. Seabrook Baseline Report, 1987.303 zo WLLjL xc U)i 0ow 1.5-1.0-0.5-13 -25 mm SPAT[I T T!0.0 I -97 I I I 1974 1975 1976 1977 1978 i I 1979 1980 1981 YEAR i I I I 1- 1-1982 1983 1984 1985. .1986 1987 LUJ 0Ow_J IL 0.6-0.5-0.4-0.3-0.2-0.1,-26 -50 mm JUVENILE.I I It I I T T T 0.0 I I I I I 1974 1975 1976 1977 1978 I -I 1979 1980 1981 YEAR.I I I I I I 1982 1983 1984 1985 1986 1987 V5 -ZO0-cc C4o 0oc 0 Jo 0.7-0.6-0.5-0.4-0.3-0.2-0.1 -0.0> 50 mm ADULT I II T I I I I I rTI If I I 1974 1975 1976 1977. 1978 1979 1980 1981 YEAR 1982 1983 1984 1985 1986 1987 Figure 3.3.7-7.Means and 95% confidence limits of spat, juvenile and adult log (x+l) densities at Flat 2, Hampton-Seabrook Harbor, 1974 through 1987. Seabrook Baseline Report, 1987.304 2.01 13 -25 mm SPAT V5 -zo0 xc 0ow_J 0.1.5 1.0-0.5-0.0 I I I I T T' T I-I -I 1974 1975 1976 1977 I I I iI 1 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 YEAR>2.01 26 -50 mm JUVENILE Z 0-zO ow xcc 0Ow_J 0.1.5-*1.0-0.5-I I I I I I I T T T 0.0;I IV I I I I i .i i I I i 1974 1975 1976 1977 1978 1979 1980 1981 1982 YEAR 1983 1984 1985 1986 1987 WI 1 xc-Ci 0Ow_J IL 0.6-0.4-0.2-> 50 mm ADULT III I I Ii~I I (I ' ---Lj ii *i I I T , i 1974 1975 1976 1977 1978 1979 1980' 1981 1982 1983 1984 1985 1986 1987'YEAR Figure 3.3.7-8. Means and 95% confidence limits of spat, juvenile and adult log (4+l) densities at Flat 4, Hampton-Seabrook Harbor, 1974 through 1987. Seabrook Baseline Report, 1987. -305 greater mortality during the first two years than was observed for the 1976 year class. The higher mortality for year classes 1980 through 1986 (Figure 3.3.7-3) corresponded to an increase in density of its main predator, the.green crab, during this period. Each year class during 1982-1986 appears to have been virtually eliminated by its second year.Predation and Harvestable Clam Resources Clams in Hampton Harbor are subject to predation pressure from two major sources: green crab consumption of spat (1-25 mm) and juvenile (26-50 mm) Mya, and humans who dig adult Mya (>50 mm) but also cause mortality to smaller clams by disturbing the flat. Sea gulls may also be major predators, as they are commonly observed picking-over clamdigger excavations for edible invertebrates, including spat and juvenile clams. The green crab (Carcinus maenas) is a major predator of Mya, with clams being a major source of food particularly in the fall months (Ropes 1969). Green crab, catches in Hampton*Harbor have shown a substantial increase in abundance since 1980 (Table 3.3.7-1). Maximum abundances usually occurred in the fall, with the highest number recorded in 1984. Green crab numbers, from 1983 to 1987 appear to have stabilized somewhat at higher densities, with fall abundances fluctu-atingbetween 69.3 (1985) and 123.9 (1984) CPUE (catch per unit effort).Green crabs generally feed more actively at temperatures above 9 0 C, and females are more active predators on Mya than males (Ropes 1969).'The presence of more females in the catch in Hampton Harbor from July through September (1981-1987) indicated greater predation pressure for the newly-, settled spat in the estuary. 'Continued high catches of males and females occurred until late November or December when temperatures declined below 7 0 C and activity decreased. Welch (1969) and Dow (1972) have shown that green crab abundances increased markedly when winter temperatures were warmer., Green crab CPUE by season 1978-19.87, showed an increase from fall of 1980 through 1984 and again in 1.986.. The increase in green crab abundance corresponded to elevated winterminimum temperatures observed from 1981-1984 (Figure 3.3.7-9); a 306 TABLE 3.3.7-1. AVERAGE CATCH PER UNIT EFFORT a, PERCENT FEMALE, AND PERCENT GRAVID FEMALES FOR CARCINUS MAENAS COLLECTED AT ESTUARINE STATIONS FROM 1977-1987, SEABROOK BASELINE REPORT, 1987.AVERAGE FECUNDITY SAMPLE CATCH PER PERCENT (% GRAVID YEAR PERIOD UNIT EFFORT FEMALE FEMALES)1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 Oct-Dec Apr-Jun Jul-Sep Oct7Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep.Oct-Dec Apr-Jun.Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec Apr-Jun Jul-Sep Oct-Dec 17.5 7.5 8.6 7.2 6.4 6.0 22.1 6.7 15.8 53.1 39.5 34.0 39.4 37.4.44.6 56.1 47.5 61.8 117.4 84.7 80.6 123.9 58 .3 54.8 ,69.3 52.6 53.5 113.5 62.0 76.0 70.8 47.4 76.7 56.5 56.5 50.0 60.0 60.0 52.4 50.0 66.7 60.0 67.7 54.5 61.5 80.0 66.7 61.5 66.7 61.5 54.5 73.0 58.3 56.5 68.8 58.3 71.4 73.7 56.5 68.2 73.9 66.4 0.3 7.0.3.2 0.5 6.0 0.6 0.0 8.4 2.3 0.0 4.6 1.6 0.0 4.1 0.8 0.0 3.7 1.0<0.1 2.4 1.2 0.0 3.9 1.0 0.0 6.6 0.7<0. 1 6.5 1.1 0.0 aNumber of C. maenas 24 hours, twice per per trap per day, month.eight "box" trapsfishing for 39._7 I LU IL C., 0 Ll.LL Lu I-IL 140 120 100 80 60-40 20-0--2.0 z 0 I-0 r., LU I-!..I.I 1978 1979 1980 1981 1982 1983 1984. 1985 1986 1987 YEAR Figure 3.3.7-9.Fall mean catch per unit effort for green crabs-(Carcinus maenas) in Hampton-Seabrook Harbor and its relationship to minimum winter temperature, 1978-1987. Seabrook Baseline Report, 1987.308 significant correlation (a = 0.05) was obtained between fall abundances (time of peak activity), 1980-1987, and the previous winter minimum temperature. Close examination of the yearly data indicated the type of response proposed by Welch (1969). Following the winter of 19,79-1980 when the temperature. minimum was high, the fall crab population showed a marked increase (Figure 3.3.7-9). A much lower minimum temperature in winter 1980-1981, and a somewhat-higher one in*1981-1982, resulted in a noticeable decrease in crab, density in the fall of 1981 followed,by a moderate increase in fall 1982.Higher minimum winter temperatures in 1983, 1984 and 1986 were associated with a marked rise in fall green crab catches. In. 1987 green crab CPUE decreased following a decrease in minimum winter temperature, the lowest since winter of 1981.The increase in green crab CPUE, and associated predation. in the years 1980-1987 can be observed in examination of the 1981-1987 Mya year classes, as estimated by densities of young-of-the-year clams (Figure 3.3.7-4). The 1981 year class, which was relatively large, showed decreased survivorship and substantially-reduced first and second year clams (Figure 3.3.7-3). In 1982, settlement was the poorest since. 1974 (Figure 3.3.7-4)and the subsequent mortality,' probably related to green crab predation, has virtually eliminated this year class (Figure 3.3.7-3).. Recruitment into Hampton Harbor clam populations, 1983-1987, has been very low, corresponding to high green crab abundances and low spat recruitment. Welch and Churchill (1983) reported the increase in near-surface temperature' at Boothbay Harbor, Maine, in the early 1970s along with an increase in green crab abundance. Although no green crab or temperature data are available for Hampton Harbor for this time period, catches 'from Kittery, Maine, showed a maximum crab occurrence (1973- 1975) corresponding to the reduction in younger year classes observed in Hampton Harbor prior to the 1976 settlement. Subsequent reductions in the reported sea surface tempera-'ture and related decreases in green crab abundance and predation along the southern Maine coast (Welch and Churchill 1983) may have also occurred in Hampton Harbor, which may have contributed to the survivorship of the strong 1976.and 1977 year classes.309 Recreational clam digging on 'the Hampton Harbor flats is the' most significant source of mortality for clams of >45. mm, but also is a source of mortality to spat and juvenile clams due to disturbance. Census figures indicate digging activity tripled from 1980. to 1981 (Table 3.3.7-2). This level of effort was maintained through 1982 before undergoing successive reductions 1983-1985. Digging activity increased slightly in 1986 over 1985 levels, but remained lower than in previous years, 1982-1984. Digging activity in 1987 was the lowest observed in the study 1980-1987. The changing-pattern of clam abundance on the Hampton Harbor flats is reflectedin the number of licenses issued by the State of New Hampshire (Figure 3.3.7-10). Changes in the number of licenses lag the changes in., standing.crop one to two years illustrating a typical predator-prey cycle.Diggers shifted some of their activity in late 1983 and 1984 from Flat 4 to Flat 2 (Table 3.3.7-2), probably in response to declining resources overall, and particularly at the most accessible area, Flat 4. As clam densities continued to sharply decline in 1985 and 1986 digger activity again shifted, from Flat 2.and Flat 4 to Flat 1, possibly due to slightly greater densities at Flat 1. In 1987, nearly 90% of digging activity was confined to Flat 1 and Flat 4 which had the highest remaining standing crop. Flat 2, Flat 3 and Flat 5 accounted for the remaining digging activity.Mortality to younger clams (<50 mm) from digging is dependent on the depth of burial, the size of the clams,. and the time of the year (Glude 1954). The highest survival is inversely proportional to-the depth of burial; the deepest burial tested (13 cm) resulted in the lowest survival.Clams 9-20 mm suffered the greatest mortality (51%) with 36-50 mm clams having only 31.5% mortality. No data has been collected on the amount of disturbance caused.by digging on the Hampton Harbor flats; however, Flat I and Flat 4, with the highest usage by clammers, would likely have suffered substantial mortality to young clams due to digging.Sarcomatous neoplasia, a lethal'form of cancer in Mya arenaria, has been observed in Hampton Harbor Mya populations (Hillman 1986, 1987). A 310 TABLE 3.z3.7-2.ESTIMATED DISTRIBUTION (PERCENT OFTOTAL) OF CLAM DIGGERS BY FLAT AT HAMPTON HARBOR, SPRING 1980 THROUGH FALL 1987.SEABROOK BASELINE REPORT, 1987.ESTIMATED a ESTIMATEDb TOTAL NUMBER OF DIGGER BUSHELS SEASON FLATS TRIPS HARVESTED 1 2 3 4 5 Springc 1980 12.5 17.9 1.7 52.5. 15.4 3,860 1,200 Falld 1980 11.3 18.4 3.3 55.1 11.8 2 , 7 0 0 e 840 Spring 1981 9.7 15.6 0.8 65.9 7.9 12,500 3,900 Fall 1981 13.9 12.9 0.2 63.8 9.1 7,060 2,200 Spring 1982 12.6 13.0 0.8 67.1 6.4 10,800 3,400 Fall 1982 26.6 8.5 0.7 60.7 3.5 9,300 2,900 Spring 1983 30.7 7.1 1.3 58.6 2.2 7,700 2,400 Fall 1983 29.4 14.7 0.5 54.7 0.? 6,690 2;,100 Spring 1984 22.1 26.4 0.6 49.9 1.0 6,200 1,950 Fall 1984 26.9 28.9 0.3 43.2 0.8 5,850 1,830 Spring 1985 51.6 11.3 0.4 36.1 0.8 6,940 2,169 Fall 1985 63.1 5.0 0.4 31.5 0.0 2,873. 898 Spring. 1986 59.3 6.4 0.3 33.4 0.6 6,210 1,941 Fall 1986 58.1 6.4 0.4 34.7 0.4 4,713 1,473 Spring 1987 39.4 8.1 1.5 49.0 2.0 1,763 551 Fall 1987 38.8 6.9 0.8 49.8 3.8 1,541 482 aBased primarily Saturday counts on Friday head counts at time of low slack water; most are assumed from observed Fri:Sat ratio (n=14 pairs) of b2.24 +/- .96; seasonal totals have approximate error of +/- 18%Assumes each clammer takes 10 quarts per trip; 1 bushel 32 quarts or 3.2 clammer..trips Includes the period 1 January through weekend before Memorial Day dIncludes the weekend after Labor Day through 31 December eBased on average Spring:Fall ratio forf1981 and 1982 (0.68 +/- .02)311

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LIENSES 15000-U)z w 10000-5000-I-.0 U I I I I I I- I 9 1 1973 i i 1 9 19 1.971 1972 1973 1974 11975 1976 1977 1978 1979 I 1 1 I I I 18 I 1980 1981 1982 : 1983 1984 ' 1985 1986 .1987 YEAR Figure 3.3.7-10.Number of adult clam licenses issued and the adult clam standing crop (bushels), Hampton-Seabrook Harbor, 1971-1987.

Seabrook Baseline Report, 1987. virus, similar to the B-type retroviruses, is known to initiate the disease in Mya (Oprandy et al. 1981). Although the infection has been observed in regions of relatively-pristine waters, the rate of infection may also.be enhanced by pollution-mediated deterioration of the environment (Reinisch et al. 1984). The infection'rate in some Mya populations may reach 100 percent with 100 percent mortality of infected clams (Farley et al. 1986). The incidence of sarcomatous neoplasms in Hampton Harbor Mya populations was observed in October 1986 and February 1987 (Hillman 1986, 1987). Neoplastic' infections were more prevalant in February, reaching 6% at Flat 1 ancL27% at Flat 2. Infections were absent from Flat 4. Assuming 100 percent mortality.of infected clams (Farley et al. 1986), Flats 1 and 2 may suffer significant disease-related reductions in clam production. However, since no historical data is available on the incidence of neoplasms in Hampton Harbor clam population, it is not known if current infection rates are typical or indictative of an increasing trend. .In 1987 clam flat surveys did indicate, however, that juvenile and adult densities fell by over 50% at Flat 1 and Flat 2 while Flat 4 remained unchanged. Harvestable Clams The patterns discussed above have resulted in substantial changes in the number of harvestable clams on the Hampton flats (Table 3.3.7-3). The greatest-adult standing stock in Hampton Harbor was reported by Ayer (1968)for 1967. Subsequent'years .indicated a gradual.decline in available adult clams to a low of six bushels/acre in 1977 and 1978. In 1976, the State of New Hampshire applied more stringent clamming regulations, closing the flats for the summer (Memorial Day to Labor Day) and eliminating digging on Sundays and holidays. Survival of the 1976 year class made a substantial increase in the standing. crop in 1980, four years after settlement. The number of harvestable clams continued to-increase in 1981 as more of the 1976 and part of the 1977 year class became harvestable. 313 TABLE 3.3.7-3.

SUMMARY

OF STANDING CROP ESTIMATES OF ADULTa MYA ARENARIA IN HAMPTON HARBOR, 1967 THROUGH 1987.SEABROOK BASELINE REPORT, 1987.ESTIMATED-NUMBER TOTAL ESTIMATED OF BUSHELS NUMBER OF DATE PER ACRE OF BUSHELS November 1967 July 1969 November 1971 November 1972 November 1973 November 1974 November 1975 November 1976 November 1977 November 1978.November 1979 October 1980 October 1981 October 1982 October 1983 October 1984 November 1985 October 1986 October 1987 152 b 103 94 58 41 56 29 11 6.6 9 54 75 55 78 54 39 23 8 23,400b 15,840 13,020 8,920 6,310 8,690 4,945 1,350 1,060 940 1,400 8,890 12,400 9,200 13,020 8,821 4,615 2,793 976 I i aShell length >50 mm bFrom Ayer (1968)1.314 Through 1984, the number of harvestable bushels had not decreased substantially. However, in 1985 through 1987, the harvestable standing crop dropped precipitously.(Table 3.3.7-3), reflecting poor recruitment observed in 1980-i984, increased predation by green crabs,; and continued human dis-turbance. Since recruitment has remained low through 1987, the trend of decreasing adult standing crop will likely continue for at least another three to four years, assuming a successful spatfall in 1988.The distribution of clams by flat has changed since 1980 when the'1976 year class became harvestable (Tables 3.3.7-2, 3.3.7-4). Flat 1 showed*a continuous increase in its percentage of adult clams through 1984, while Flat 4 showed a steady decrease. In 1985 the percentage of harvestable clams decreased on Flat 1 and increased on Flat 4, followed by increases on Flats 1 and 2 and a decrease on Flat 4 during 1986 (Table 3.3.7-2). In 1987, the percentage of harvestable clams increased at Flat 4, while decreasing at Flat 1 and Flat 2, reflecting the stabilization of clam populations at Flat 4 at low levels, while populations on Flat 1 and Flat 2 continued to decline.315 TABLE 3.3.7-4. DISTRIBUTION (PERCENT OF TOTAL STANDING CROP) OF HARVESTABLE CLAMS BY FLAT AT HAMPTON HARBOR, 1979 THROUGH .1987. SEABROOK BASELINE REPORT, 1987.YEAR FLATS 1 2 3 4 5 1979 33.3 6.2 2.2 55.7 2.5 1980 45.1 10.5 1.0 39.5 3.9 1981 53.0 7.3 1.5 34.4 3.7 1982 52.2 7.0 1.0 38.4 1.3.1983 62.9 25.6 0.5 10.5 0.5 1984 72.0 13.6 1.9 11.5 0.9 1985 60.2 14.6 NS 25.1- NS 1986 63.0 21.9 NS 15.1 NS.1987 40.0 15.9 NS 44.2 NS i 316 -3.3.8 Benthos Appendix Tables 317 APPENDIX TABLE 3.3.1-1, MEAN MONTHLY SEAWATER SURFACE TEMPERATURE (<C) AND SALINITY (ppt) TAKEN IN BROWN'S RIVER AND HAMPTON HARBOR, MAY 1979- DECEMBER 1987.SEABROOK BASELINE REPORT, 1987.* BROWN'S RIVER i HAMPTON HARBOR.1 ----- ----------- +------------

---------------------

HIGH-TIDE 1 LOW-TIDE 1 HIGH-TIDE

• 1 LOW-TIDE 1------ ---------------

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+----------- TEMPERATURE MEAN I CI I MEAN I CI I MEAN I CI I MEAN I CI JAN 1 FEB MAR APR MAY JUN JUL AUG 1 SEP 1 OCT 1 NOV I DEC-.....- + -...... + -...... +...... -+ .....-.+ .....-.+.....-- .+....-..I.1.01 1.261 1.21 0.861 3.71 0.88: 7.1: 0.771 13.21 1.811 15.81 0.971 18.01 0.991 18.81 1.051 16.01 0.891 12.21 1.011 8.21 0.871 4.81 1.231 0.91 1.91 4.71 9.81 14.71 19.21 21.41 20.81 18.01 12.31 7.31 2.91 0.801 1.161 0.521 0.771 0.711 1.141 0.951 1.421 1.11i 1.171 1.581 0.611 2.51 2.31 3.71 6.31 10.11~13.41 15.81 16.81 14.6: 12.31 9.11 5.51 0.911 0.891 0.611 0.871 0.581 0.741 0.841 0.851 0.971 0.711 0.761 0.781 1.01 1.71 4.11 8.11 12.81 16.41 18.41 18.61 16.21 12.21 8.3,1 3.81 0.691 0.681 0.771 0.681 0.611 0.821 0.841 0.971 0.911 0.801 1.181 0.821 BROWN'S RIVER I HAMPTON HARBOR II ............................------------------- +---------------------------------I I HIGH-TIDE 1 LOW-TIDE I HIGH-TIDE 1 LOW-TIDE I ------ +----------------.----------------.------------ !SALINITY I MEAN I CI I MEAN I CI I MEAN I CI I MEAN I CI i ------ ---+...... -+ -......+-.....--+-.....--+-.....--+-....-.--- ......1 JAN 1 FEB IMAR ,APR 1 MAY IJUN[JUL 1AUG 1 SEP 1 OCT INOV 1 DEC 31.51 29.41 28.71 26.41 29.01 28.81 30.31 30.51 30.71 30.41 30.11 30.31 1.091 2.701 2.021 3.241 1.681 1.861 1.031 0.431 1.021 0.871 1.611 2.061 24.01 19.51 17.51 17.51 20.61 21.21 24.11 25.31 24.81 23.61 21.11 20.11.2.761 4.111 3.861 4.561 3.051 3.361 1.911 1.581 2.561 1.481 3.291 3.961 32.11 31.61 31.11 30.01 30.01 30.31 31.01 31.31 31.51 31.61 31.91 31.71 0.671 0.761 0.981 1.841 1.071 1.061 0.561 0.431 0.311 0.311 0.401 0.711 28.41 27.51 24.91 24.11 26.81 27.41 28.9: 29.81 29.91 29.31 28.31 27.51 2;021 2.931 2.411 3.821 1.89!2.391 0.811 0.621 0.721 0,751 1.511 2.441 318 APPENDIX TABLE 3.3.2-1. MACROALGAE SPECIES RECORDED IN GENERAL COLLECTIONS FROM BENTHIC STATIONS SAMPLED FROM 1978 TO 1987 (a,b,e). SEABROOK BASELINE REPORT, 1987.SPECIES INTERTIDAL SUBTIDAL 1 5 MSL MLW MSL MLW 17 35 16 19 31 13 4 34 Chlorophyta Acrochaete viridis Blidingia minima Bryopsis plumosa Chaetomorpha sp.Chaetomorpha aerea Chaetomorpha brachygona Chaetomorpha linum Chaetomorpha melagonium Chaetomorpha picquotiana Cladophora sericea Codiolum petrocelidis Enteromorpha sp.Enteromorpha intestinalls Enteromorpha linza Enteromorpha prolifera Monostroma grevillei Monostroma pulchrum Pseudendoclonium submarinum Rhizoclonium tortuosum Spongomorpha sp.Spongomorpha arcta Spongomorpha 'spinescens Ulothrix flacca Ulva lactuca Ulvaria obscuraf Ulvaria oxysperma Urospora penicilliformis Urospora wormskjoldii Xc X X X X X X X X dX X X X X X X X Xd X X X X X X X X X X X X X X X Xd X X X X X. X ,X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Xxd X X X XX X X X X X XC X X Xc x X X X X X, X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X x X Phaeophyta Agarum cribrosum Alaria esculenta Ascophyllum nodosum Chordaria flagelliformis Desmarestla aculeata Desmarestia viridis X X X X X X X Xd X X X X X dX X X X X X X X X X X X X X X X X x X X X k (continued) 319 APPENDIX TABLE 3.3.2-1. -(Continued) SPECIES INTERTIDAL SUBTIDAL 1 5 MSL MLW MSL MLW 17 35 16 19 31 13 4 34.Phaeophyta (cont)Ectocarpus fasciculatus Ectocarpus siliculosus-Elachista fucicola Fucus sp.Fucus distichus Fucus distichus ssp.distichus Fucus distichus ssp.edentatus Fucus distichus ssp.evanescens Fucus vesiculosus Fucus vesiculosus v.spiralis Giffordia granulosa Laminaria sp.Laminaria. digitata Laminaria saccharina Leathesia difformis Petalonia fascia Petalonia zosterifolia Petroderma maculiforme Pilayella littoralis Ralfsia verrucosa Saccorhiza dermatodea Scytosiphon lomentaria Sorapion kjellmanii Sphacelaria cirrosa Sphacelaria plumosa Sphacelaria radicans Spongonema tomentosum X X X X X X X X X X X Xd X X Xd Xd X X X X X X X X X X X X X X X X X X X X X Xd X X X X X X Xd X X d X X X X X X X X X Xd X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Rhodophyta Ahnfeltia plicata Antithamnionella floccosa Audouinella sp.Audouinella purpurea Bangia atropurpurea Bonnemaisonia. hamifera X X X X X X X X X X X X X X X X X X X X X X X X X X XC X X X X (continued) 320 APPENDIX.TABLE 3.3.2-1. (Continued) SPECIES INTERTIDAL SUBTIDAL 1 5 MSL MLW MSL MLW 17 35 16 19 31 13 4 34 Rhodophyta (cont)Callithamnion tetragonum Callophyllis cristata Ceramium deslongchampii

v. hooperi'Ceramium rubrum Ceratocolax hartzii Chondrus crispus Choreocolax polysiphoniae Clathromorphum circumscriptum Clathromorphum compactum Colaconema secundata Corallina officinalis Cystoclonium purpureum v. cirrhosum Dermatolithon pustulatum Devaleraea ramentacea Dumontia contorta Erythrotrichia carnea Gloiosphonia capillarqs Mastocarpus stellatus-Gymnogongrus crenulatus Halosaccion ramentaceum liildenbrandia rubra Leptophytum foecundum Leptophytum laeve Lithophyllum corallinae Lithothamnion glaciale Melobesia lejolisii Membranoptera alata Palmaria palmata Petrocelis cruenta Petroderma maculiforme Peyssonnelia rosenvingii Phycodrys rubens Phyllophora sp..Phyllophora pseudocera-noides Phyllophora traillii Phyllophora truncata Phymatolithon sp.Xd X X dX X xd x x X X x x x X X X X X X X X X -X X X X X .X X X x xd x x X X X X X X X x x X *X X x X .X X X x x x x x x x x X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X.X X X X X X X Xd d d X X Xd X X X X X Xd X Xd X X d Xd x X X X X X X XX X X' X X X X X X X X X X XX X X X -X X X X X X X X X X X x X X x Xd X X X* X**X d X X X X x X X X .X X.X X X X X X X X X X X X X X X x X X x X X X X'X X X X X X x x X X X X X X X X'X.X xx X X X X X X X X X X X XX X X X X X -X X x x (continued)

X X x 321 APPENDIX TABLE 3.3.2-1. (Continued) SPECIES INTERTIDAL SUBTIDAL 1 5 MSL MLW MSL MLW 17 35 16 19 31 13 4 34 Rhodophyta (cont)Phymatolithon laevegatium X X X X X X X X Phymatolithon lenormandii X X X X X X X X X Phymatolithon rugulosum X, X X X Plumaria elegans X X X X X*Polyides rotundus X X X X X X X Polysiphonia denudata d X Polysiphonia flexicaulis X X X X X X X Polysiphonia harveyi X. Xc X X X X Polysiphonia lanosa X X X X X X X X X Polysiphonia nigra X X X X Polysiphonia nigrescens X d X X X X X X Polysiphonia urceolata X X X X X X X X X X X X Porphyra leucosticta X X X X X X Porphyra miniata X X X X X Porphyra umbilicalis X X X X X X Pseudolithoderma extensum X Ptilota serrata X X X X X X X X X X Rhododermis-elegans d X Rhodomela confervoides X X X X X X X X Rhodophyllis dichotoma X X X X X X X X Rhodophysema elegans X X X X X X Scagelia.corallina X X X X X X X X X X Turnerella pennyi X X aCollections from May, Aug, Nov except in 1982-84 when: STA 4, 13, 16, 34 collected Aug. only bSTA 1MLW, 5MLW, 17, 19, 31, 35 collected all months, STA 1, 4, 13, 17, 19, 31 -1978-1987; STA 4, 13 not sampled in 1985 STA 34 -1979-1987, except 1985 STA 16 -.1980-1987, except.1985 STA-5MLW, 35 -1982-1987 dNot collected in 1978-82 period, but recorded in earlier collections eCollected in tide pools only.eG. Robin South, 1986 and William Randolph Taylor, 1962 were used for ftaxonomic nomenclature and identification. " Species name changes: IMastocarpus stellatus was Gigartina stellata.Ulvaria obscura was Monostroma fuscum var. blytii_Ulvaria oxysperma was Monostroma oxyspermum _322 APPENDIX TABLE 3.3.2-2. SPARSELY OCCURRING (< 5% frequency of occurrence) MACROALGAE TAXA IN AUGUST BENTHIC DESTRUCTIVE SAMPLES, 1978-1987T SEABROOK BASELINE REPORT, 1987.Monostroma oxyspermum Enteromorpha sp.Enteromorpha intestinalis Enteromorpha linza Enteromorpha prolifera Ectocarpus siliculosus Giffordia granulosa Sphacelaria cirrosa Desmarestia viridis Petalonia fascia Scytosiphon lomentaria Dumontia contorta Ceramium deslongchampii Plumaria elegans Polysiphonia sp.Polysiphonia denudata Polysiphonia harveyi Gigartinales Entocladia viridis Spongonema tomentosuln 323 APPENDIX TABLE 3.3.2-3.A. PERCENT FREQUENCY OF PERENNIAL AND ACROALGAE SPECIES AND B. PERCENT COVER OF PERENNIAL MACROALGAE SPECIES PER 0.25 m AT FIXED INTERTIDAL NON-DESTRUCTIVE SITES.SEABROOK BASELINE REPORT, 1987.A. PERCENT FREQUENCY QUADRAT B (ISL) QUADRAT C J(SL) QUADRAT D (MLN)d FUCOID LEDGE BARE LEDGE L CHONDRUS ZONE YEAR APR JUL DEC APR JUL DEC APR JUL DEC PERENNIAL ALGAE Station 1 Species a Fucuslspp.a 1982 100 100 88 31 31 44 1983 100 100 94 6 44 56 1984 100 88 69 81 88 94 1985 75 81 87 63 94 6 10 2 16 1986 94 100 94 6 6 0 25 75 60 1987 75 81 75 0 0 0 44 13 0 Chondrus crispus 1982c 0b 0 0 0 0 0 1983 p 0 z 0 0 0 1984 2 0 7 0 0 0 1985 0 8 ý1 0 0 0 21 27 47 1986 8 z 1 0 0 0 45 20 36 1987 0 0 3 0 0 0 20 37 53 Mastocarpus, stellatus 1982 0 0 "0 0 0 1983 p 6 9 0 0. 0 1984 7 2 5 0 0 0 1985 3 8 21 0 0 0 21 65 47 1986 12 19 9 0 0 0 47 65 .48 1987. 9 0 17 0 0 0 47 71 3Z No Station.5 Species I Ascophyllum nodosuma 1982 1983 1984 1985 1986 1987 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0 0 0 0.0 0 0 0 6 (continued) N, Ul APPENDIX TABLE 3.3.2-3. (Continued) A. PERCENT FREQUENCY QUADRAT B (MSL) QUADRAT C (MSL) QUADRAT D (MLWId FUCOID LEDGE BARE LEDGE CHONDRUS ZONE YEAR APR JUL DEC APR JUL DEC APR JUL DEC PERENNIAL ALGAE Station 5 Species a 1Fucus spp. 1982 62 69 31 12 12 6 1983 .81 100 100 0 13 0 1984 100 100 94 0 13 *63 1985 94 88 94 69 94 100 0 0 0 1986 94 94 94 .94 100 100 0 0 0 1987 88 81 88 100 100 100 0 0 0 Chondrus crispus 1982c 0 0 0 .0 0 0 1983 1 2 0 0 0 0 1984 1 0 0 0 0 0 1985 0 8 1 0 0 0 0 45 39 1986 3 3 1 0 0 0 30 54 48 1987 .0 0 0 0 0 0 54 48 41 Mastocarpus stellatus 1982c 0 0 0 0 0 0 1983 5 2 4 .0 0 0 1984 5 5 7 0 0 0 1985 8 4 8 0 0 0 0 51 43 1986 4 2 11 0 0 0 49 41 44 1987 15 13 19 0 0 0 53 56 56 Corallina officinalis 1982 0 0 0 0 0 0 1983 0 0 0 0 0 0 1984 0 0 0

• 0 0 0 1985 0 0 0 0 '0 0 15 33 31 1986 0 0 0 0 0 0 21 37 65 1987 0 0 0 l0 0 0 30 52 45.(continued]

APPENDIX TABLE 3.3.2-3. (Continued) A. PERCENT FREQUENCY QUADRAT B (MSL) QUADRAT C (NSL) QUADRAT D (MLN)d FUCOID LEDGE BARE LEDGE CHONDRUS ZONE YEAR APR JUL DEC APR JUL DEC APR. JUL DEC ANNUAL ALGAE Station 1 Species Porphyra sp. 1982 0 0 0 0 0 1983 p 0 0 15 78 21 1984 3 9 1 8 43 1 1985 9 17 0 2 0 0 0 0 0 1986 0 8 3 0 3 1 0 0 0 1987 2 0.6 0 0.6 9 0 9 0 Spongomorpha sp. 1982 0 0 0 0 0 0 1983 0 0 0 0 0 0 1984 1 1 0 0 0 0 1985 5 0 0 0 0 0 27 0 0 1986 z1 0 0 0 0 0 0 0 0 1987 1 0 0 0 0 0 2 0 0 Urospora 1982 0 0 0 0 0 0 pencilliformis/ 1983 p 0 0 85 0 0 Ulothrix flacca 1984 0 0 0 99 0 0 1985 0 0 0 2 0 0 0 0 0 1986 0 0 0 57 0 0 0 0 0 1987 0 0 0 80 0 0 0 0 0 Station 5 Species La ON Bangia fuscopurpurea .1982 1983 1984 1985 1986 1987 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 100 25 74 24 75 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (continued) APPENDIX TABLE 3.3.Z-3. (Continued) A. PERCENT FREQUENCY QUADRAT B (MSL) QUADRAT C (MSL) QUADRAT D (MLW)d FUCOID LEDGE BARE LEDGE CHONDRUS ZONE YEAR APR JUL DEC APR JUL DEC APR ,JUL DEC Station 5 Species'Urospora 1982 0 0 0 100 0 0 pencilliformis/ 1983 0. 0 0 75 0 0 Ulothrix flacca 1984 0 0 0 100 0 0 1985 0 0 0 91 0 0 0 0 0 1986 5 0 0 71 0 0 0 0 0 1987 0 0 0" 33 0 0 0 0 0 Rhizoclonium sp. 1982 0 0 0 0 0 0 1983 0 0 0 0 0 0.1984 0 0 0 0 0 0 1985 0 0 0 O 0 0 0 0 0 1986 0 0 0 0 0 0 0 14 0 1987- 0 0 0 0 0 0 2 2 1 (continued) r'3 00 APPENDIX TABLE 3.3.2-3. (Continued) B. PERCENT COVER QUADRAT B (HSL) QUADRAT C (MSL) QUADRAT D (MLW)d FUCOID LEDGE BARE LEDGE CHONDRUS ZONE YEAR APR JUL DEC APR JUL DEC APR JUL DEC Station I Species Fucus spp.e 1982 92 99 25 5 5 1 1983 95 8S 75 2 1 5 1984 75 95 36 4 4 40 1985 25 60 70. 8 10 <1 38 13 13 1986 85 100 85 <1 <1 0 13 69 38 1987 98 90 95 0 .0 0 30 15 18 Station 5 Species Ascophyllum nodosum e 1982 20 1s 5 0 0 0 1983 0 3 5 0 0 0 1984 3 0 0 0 0 0.1985 0 10 0 0 0 0 0 0 0 1986 0 0 0 0 0 0 0 0 0 1987 0 0 0 0 0 0 0 0 0 e Fucus spp. i982 60 75 2 0 1 <1 1983 95 97 90 0 <1 .0 1984 92 97 80 0 <1 Cl 1985 95 89 94 <1. <1 15 0 0 0 1986 60 65 95 15 20 40 0 0 0 1987 75 100 .95 12 2O 30 0 0 0 a Percent frequency of fucoid algae is.based on presence of holdfasts only bPresent; Z frequency not recorded*Z frequency not recorded with similar method in 1982 dMLW quadrat initiated in 1985 Percent cover of fucoid algae is based on whole plant. APPENDIX TABLE 3.3.3-1. SPECIES USED IN DISCRIMINANT ANALYSIS OF BENTHIC MACROFAUNA. Ampithoe rubricata Balanus crenatus Calliopius laeyiusculus Caprella sp.Cancer sp.Caulleriella sp.Cerastoderma pinnulatum Cingula aculeus.Dendrodoa sp.Dodecaceria sp.Eulalia viridis Fabricia sabella Gammarus oceanicus Gammarellus angulosus Golfingia sp.Harmothoe imbricata Hiatella sp.Idotea phosphorea Jaera marina Jassa falcata Lacuna vincta Littorina littorea Musculus niger Nereis pelagica Nucella lapillus Ophiura robusta Ophiura sp.Sabellidae Thelepus cincinnatus Terebellidae Tonicella marmorea Velutina velutina 329 APPENDIX TABLE 3.3.4-I. NUMBER (MEAN PER TWO REPLICATES) OF SELECTED NON-COLONIAL SPECIES OCCURRING ON SHORT-TERM FOULING PANELS BY MONTH, STATION, AND YEAR. SEABROOK BASELINE REPORT, 1987.SPECIES=ANOMIA SP.......................................................................................................... .JAN : FEB 1 MAR 1 APR 1 MAY 1 JUN 1 JUL I AUG 1 SEP 1 OCT 1 NOV 1 DEC ; ALL 1 ISTA 1978 O 0: oi i O 01i 0" :O 1: O! 0! 01, 1! 0!!19 1979 o, 0: 0 OI O0 01 11; 31 -1 11 O 01 1l: 1980 O O0 OI 01 O 01 11 111 61 201 01 01 31 1981 i i 01 11 01 O" 01 31 O 241' O0 21 11 31 1982 01 01 01 .0: 1I I: 1: 0: 121 41 11 11 2: 1983 ,1 1 01 01 O0 11 1: 11 1i 2: 01 11 0 11 1984 " 01 O0 1! 01 01 01 11 51 .1I 1I 1I O 1I 1986 1 i i i i 31 01 221 21 71 01 61 1987 ! 0! O0 Ii 01 O0 '0 41 01 491 41 21 11 51 1STA 1978 1 O0 i O0 O0 0! 11 01 01 11 O0 01. 0 01 131 1979 1 01 O0 01 01 01 01 61 261 1! 21 01 01 31 i 1980 1 O0 01 01 O0 0: 01 31 1! 91 101. 21 O0 21 1981 1 1 01 11 oi. 11 li 31 481 31 Oi 11 11 51 1982 l 01 01 01 01 O0 .1! O0 21 31 31 1I 01 11 1983 1 O0 11 O0 01 01' O0 O0 11 -11 11 171 01 21 1984 1. 01 01 01 O0 O0 01 1O 51 01 01. 11 O0 01 1986 1 i i i i i 1 61 01 431 71 1I O0 91 1987 1 01 O0 11 01 01 01 21 01 231 71 11 OI 31 ISTA 19781 01 01 01 O 01. O 01 01 01 01 01 01 01 104 1979 1 O0 01 O0 01 01 0! 01 211 O0 1! 01 01 21 1980 01 .01 01 01 01 01, 11 51 171 21 11 11 21 i 1981 1 i O 01 O .0! O 01 41 61 21 01 O0 I1 1982 1 01 O0 01 O0 O0 O0 11 41 91 51 01 O0 21 1983 1 O0 0; 01 01 O0 01. 01 01 o0 O0 21. 01 0!1984 1 01 .0 O0 0: O1 11. 01 O0 O0 01 O0 01 01 1986 1 1 i i I i 11 11 81 101 11 01 31 1987 1 21 01 01 O0 0i 01 61 31 571 11 21 O0 61 1STA 1982 1 O0 I I U O1 01 01 01 1I 41 21 .11 01 1I 134. 1983 1 O 01 0!1 I O 0! 01 31 11 1I 71 O0 11 i 1984 O0 11 11 I 1 01 OI O0 11 21 O0 21 O0. O0 i 19861 1 1 1.1.1 31 11 91 331 101 O0 91 i 1987 1 01 O0 01 01 O0 I 1I 11, 1151 141 01 01 11i 330 APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=ASTERIDAE JAN I FEB 1 MAR I APR 1 MAY 1 JUN'I JUL..1 AUG 1 SEP OCI NOV DEC ALL 1 STA 19781 01 O 0! 01 01 0! 0: 0! 0i 0! 0: 0i:19 1979 0: Oi O! 0: 0: 0: Ii 1: 0; 0: 0i Oi " .0 1980 01 01 01 0! 01 01 21 1: Oi 1 1i! 0! 01 1981 0! 01: 01 0i 0: 1! 0: 33: 0i 0! *0 .31 1982 01 O0 O Oi .Or Oi 1i Oi Or Oi Oi 01 0i 19831 0i 01 01 01 01 0; 01 Oi Or Oi Oi or o!" 19841 0i 01 01 O 01 01 .0 O 01 .010 O O 0 0i 1986 1 1 i 1 1! O l* 01 01O O 0;1987 1 01 O 01i 0 01 01 11 01 01 01 Ol 01 0: 1STA 1978 1 O 1 Oi 0i 0i 0i 0i 01 oi. OO 0 0 01 131 1979 l1. 01 0! O O 0; 01 41 51 O O 01 O 1: 1980

• 01 01 01 01 0! 01 61 O 01 01 01 01 11 1981 i 0i 0i 0! 01 0: ii 0i 71 01 01 01 1I.19821 O 0i O 0; 0i .0 O 01 01 0i O 10 01 19831 0; 0i 0i 01 0i 01 O' 0i O0 Oi O: Oi O0 19841 01 0i 0i 01 0! 01 1; O 0 01 01 01 01 1986 1 .1 i 1 i. 0i 01 0i 01 0! 01 0!1987 1 0i 0! 0i O 0: 0! 1I 01 0! 01 .0 0! 01 STA .1978 0i 0! 0! 01 Oi 01 O Oi O! Or O: 0 O!104 .19791 Oi 01 01 01 O 0! Ii 0 1i 01 0i 0! 01 1980 1 01 01 O Oi 0i 01 11 1: 0! 11 01 0! 0!1981 1 i O 01 0i 0; 01 41 31 21 01 01 01 1i.19821 01 01 0i 01 O 01 01 0 O 0; 01 01 01 19831 01 01 0! O 01 0! 0! 01 01 010 1 01 01 1984 1 01 0 01 0; 01 0 0! 0! 0 11 11 01 0!19861 i1 i i i
• I I 01 O 01 1l 0i O 0: 19871 01 01 01 01 O 0i 1I 0i 01 01 11 O0 01 STA 19821 01 010 O 0 O 01 O 0i 0 01 01. ! O 01 134 19831 01 01 O O 01 0! 1I 01 01 010 O 0; 0i 1984 1 01 01 01 01 01 O 0! 01 11 01 .0.1 0! 0i 1. 1986 1 i O 0i 01 01 01 .01 v 0 19871 0i 0! 01 0! 0i 0i 11 i 0 Oi I1!01' , O 01 331 AFFENDIX TABLE 3.3.4-1. (Continued)

SPECIES=BALANUS SP..i I I JAN 1 FEB 1 MAR 1 APR IMAY 1 JUN 1 JUL 1 AUGI SEP 1 OCT 1 NOV I DEC I ALL I -------------------------------------------------------------

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++ --+------ +---- ------------ I 1STA 1978 119 1979.1980 1981 1982 1 1983 1 1984 1986 1 1987 1STA 1978 131 1979 1980 1 1981. 1 1982 19831 1984 1986 1987 1 1STA 1978 104 1979 1 1980 1 1981 1 1982 1 1983 1984 1 1986 1 1987 1 1STA 1982 1 134 1983 1 1984 1 1986 1 1987 1 0o 01 01 01 oI 01 0 1 01 0I 01 01 01 01 01 01 01 0I 01 01 11 01 01.01 01 01 I OI 0 01.0 01 01 01 01 0 1 0I 01 0 1 0 1 0 1 0 1 0 1 OI 01 01 01 11 01 01 0 1 0 1 0 1 0 1 0 1 0 1 II 0O1 I O1 41 01 121 51 01 5321 11 0. 01 01 01 11 11 0; 21 1I1 01 21 .41 I I I 01 351 341 01 O1 71 01 .41 101 31 1821 01 0: 0! 11 0! 11 61 01 01 51 01 31 111 I I I 21 211 501 O 01 11 01 01 21 01 1281 O0 0! 01 0 0 11 51 o0 .o1 10i 01 01 21 I I .I O 31- 211 11 O Ii 01. 11 31 01 11 41 i I I I I 01 101 71.11 Oi 0:1 41 01.01 10: 01 32l 1O 321 01 21 71 61 0!I I 21 01 11 41 11 61 21 11 11 11 0: 31 61 01 21 2 1 I1 21 11 0 1 OI 31 121 01 11 31 11 131 01 Oi 0 1 31 11 01 O0 O0 0I O0 O0 01 01 01 51.0!11 01 II 0!31 Oi 01 01 Oi Oli 0i 1!1i 1!1i 01 11i O0 Of 0O 01 01 0O 0!11 01 01 01 01 31 01 01 O I I oi I I 01 451 0 1 011 01 21 01 11 0iI OI 01 01 01 91 0 1 11 01 11 01 161 01 11 01 11 01 11 0; 21 0 1 .01 01 81 01 .01 01 01 01 111 01 01 01 11 0 1 1 11 0 1 01i 0 1 0 1 01 21 0 1 0 1 0 1 0 1 0 1 11 0 1 0 1 0 1 21 K I 332 APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=HIATELLA SP..JAN 1 FEB 1 MAR 1 APR 1 MAY 1 JUN 1 JUL AUG : SEP I OT 1 NOV 1 DEC ALL:--+....-..-+...-- ---+-......-+-......-+-......-+-......-+-......-+..-....+....-+..-.-+-.-..+ -.+.---ISTA 1978 119 1979 1980 1981 1 1982 1983 1984 1 1986 1 1987 1 ISTA. 1978 131 1979 1 19801 1981 1982 19831 1984 1 1986 1987 1 ISTA 1978 104 1979 19801 1981 1982 1 S.1983 1 1984 1 1986 1 1987 1 ISTA 1982 1 134 1983 1 1984 1 1986 1 1 1987, 1 01 11 01 I 11 01 01 01 01 01 01 011 01 31 0 1 0 1 0 1 01 01 011 11 1 01 0 1 11 01 31 0 1 0 1 0 1 0 1 I1 01 11 01 I I I1 01 01 01 0 1 0 1 0 1 11 0 1 0 1 0 1 0 1 0 1 11-01 11 O I " I 01 01 0 1 0 1 0 1 0 1 0 1 11 0 1 0 1 0 1 0 1 0 1 0 1 01 01 I I 0 1 0 1 0 1 11 0 1 0 1 1 1 0 1 0 I 0 1 0O1 31 281 31 2701 1I 01 111 1931 91 01 01 5041 611 621 .261 21 2741. 2471 61 2861 4: 1221 101 51 61 11 311 381 9i 21.11 681 601 51 I1 1 1 1301 11 71 01 281 31: 1 131 31 541 31 51 21 21 801 831 14441 21 01 9311 2491 721 221 311 3321 .911 2381 681 01 461 41 41 21 01 161 361 -221 31 81 441 1401 71 11 1 411 21, 91 01 621 491 21 1I 01 101 61 321 2i 01 621 471 271 41 01 671 481 .501 141 71 3771 3021 51 561 21 241 121 291 141 11 361 121 241 Ii 21 301 391 61 31 I 1 551 31 31 01 731 2271 221 541 71 651 61 341 161 01 151 231 341 01 31 261 561 31 11 I I 92i 51 51 01 721 1631 531 741 1 : 71 51.21 41 21 31 21 11 21 1 31 61'II.11 01 41 21 21 II 21 41 21 21 1 51 41 11 241 41 1 .01 01 01 01 o1 01 41 01 11 11 31 01 01 01 51 11 01 11 II 21 11 01 11 21 11 21 21 21 21 91.01 01 291 21. 201 11 551 11 7At 41 131.oi 71 11 111 11 241 01 61 11 61 01 1341 11 1071 01 701 11 51 11 71 11 171 11 91 01 101 01 51 01 131 01 151 01 681 01 71 01 61 11 71 41 111 01 321 01 121 41 71 01 81 21 231 01 311 333 I..APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=JASSA FALCATA.1 JAN 1 FEB 1 MAR 1 APR 1 MAY 1 JUN 1 JUL.1 AUG 1'SEP 1 OCT .NOV 1 DEC 1 ALL 1 I----------------------------------------------------------- --- --+ ----+-- -+- _-+ -.---+ ---1STA 1978 119 1979'1980<1981 1982 1983* 1984 1986.1987 1STA 1978 1 131 1979 1980 1981 1982 1 1983 1984 1986 1987 1 1STA 1978:04 1979 19801 i -1981 !i 1982 i 1983: i 1984 i 1986 1987 1 1STA 1982. 1 134 1983 1984 1 1986 1 1987 1 0: 2: i 61 0!11 0!0;Oi 01 O1 11 Oi 11 01 2 0:.11 116 116 11 01 14: 01 2: 01 0 0 : 01 0: 01 0: 0*1 0O 1: 0:i I 1: 0 1: Oi oi 2: 0:i O:.0: 0: 0: O: 1: 01 1: I.0: O0 41 OI Ili 0: 1: 0! 11 01 i: OI II 0 3: O 31 1: 61 11 6: Oi Oi 21 171 I I 01 4: 0: 41 01 11 0: 0: Oi I Oi 0: 0: 0oi 31 01 0: 1I Oi 11' 01 01 Oi 13: 51 1241 13: 101 1I 2: 461 9! O0 21 0!21 10 181 381 251: 51 31 5: 8: 2311 1451 91 51 121 71 761 .341 121 01 31 591 191 40: 51 71 251 351 111 401 91 i 41 51 361 .31 31 31 461 231 101 441 131 291 71 791 71 41 11 341 3241 981 Ii 41 21 91 561 281 101 161 21 01 01 281 951 81 51 221 171 501 1131 121 141 O0 51 81 211 131 11 121 131 91 211 341 801 i 91 351 371 51 71 31 3311 1311 5411 3191 181 1I 31 91 151 21 1i 31 31 131 11 41 31 11 361 01 231 401 71 01 01 111 .51 791 741 11 Ii 51 451 381 251 21 21 ' 221 81 161 331 71 121 221 501 521 351.0: 21 1I 41 .11 11 141 181 81 221 321 11 1: 11 121 131 281 01 81 6: 121 191 41 21 21 .21 31 191 -211 i Ol 41 41 21 81 11 621 01 101 461 411 0O 201 81 141 41 171:41 11 9l 81 21 IlI 81 111 01 21 01 I;661 11l 381 41 5i 31 21 ,31 O1 I: 141 161 71 91.381 131 121 Ili 81 121 121 391 111 131 221 51 15!161 1121 31 21 9: 211 161 101 151 21 81 61 41 41 31.334 APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=LACUNA VINCTA----------.

---

..............

1 1 JAN 1 FEB 1 MAR 1 APR 1 MAY 1 JUN JUL 1 AUG 1 SEP 1 OCT 1 NOV 1 DEC 1 ALL 1 S. ..+ ...+. .....+. ..----+- -.....-+ -... .+ -... .+ -... .+ -... .+-" .. +- --1 ---------------------------------------------------------------------------------------------------- 7--j 1STA 1978 1 O O I 1 0 0! 0i O: 11 0 0i O O 0!119 1979 1 01 01 0i 01 0i 11 0: .0! O 0; 0i 41 01 1980 1 1 01 01 41 O 0: 1 0: 131 21 1:1I 21 1981 1 1 0: 0! 0. Oi :I: O 0: 401 O0 21 11 41 1982 11 01 01 01 11 01 01 01 11 11 11 01 01.1983 01: .-0 01 O 0: 1 O 01 141 171 31 31 31 1984 1 01 01 01 01! O O 11 0 0! 0: 21 01 O I 1986 1 1 1 1 1 1 1 11 1! 41 51 31 O1 21 1 1987 1 01 01 01 01 O1 01 01 11 71 21 01 O Ii ISTA 1978 1 O 1 01 01 01 1I 01 11 01 101 41 01 1I 131 1979 1 0 01 11 01 01 61 71 111 11 31 11 01 21 1980 1 Oi O .0 11 01 01 11 01 161 31 51 11 21 1981 1 1 01 01 11 01 61 01 311 211 71 1: 41 61 1982 1 01 0i 01 O 01 11 01 01 11 01 01 11 0!1983 1 0: O 01 Oi 01 O OL 01 71 31 11 .' I 19841 11 01 01 O O1I 11 01.11.01 01 121 01 11 19861 1 1 1 1. 1 1 21 31 31 31 01 O 21'1987 01 01 01 O 01 O 11 21 131 51 01 O 21 ISTA 1978 1 0: O 01 O O1 O O 01 01 01 1i 11 O0 104 1979. 1 01 O 01 01 01 01 21 21 11 01 21 11 11 1980 11 11 0! 01 01 O 0 i 01 01 11I 01 01 01 11 1981 1 1 01 O 0! 0! 0; 21 01 101 61 11 51 21 1982 .11 O1 01 0; 0! ii O Ii 81 21 01 01 1i 1983 1 01 01 01 O 0! 111 .01 21 1I 21 21 Ii 1984 1 O 01 0! 01 01 01 0i 1I 01 0: 11 O O 1986- ! 1* I I I I 0: 0i 11 21 31 1: 1i 1987 1 O O 01 01 O 0i I! 11 21 11 01 01 01:STA 1982 1 01 oi0 0i 01 01 0! 01 01 11 1! 1! 0: 0: 134 1983 1 11 01 01 01 01 0i 01 01 11 51 31 11 11" 1984 1 01 01 O O! 11 01 01 01 01 01 41 0: 0O 1 1986 1 1 .1 1 1 1 1 O 1 2 : 2 i I I 9 6I *I I I I I 01. 01 21 41 21 11 11 1 1987 1 01 01 01 01 O O 01 O1 1 21 01 O 01 335 APPENDIX TABLE 3.3.4-1.' (Continued) SPECIES=MYTILIDAE 1 JAN 1 FEB 1 MAR 1 APR MAY 1 JUN 1 JUL .AUG 1 SEP I OCT 1 NOV. 1 DEC 1 ALL 1 1STA 1978 1 11 19 1979 21 1980 1 111 1981 .i 1982 201 19831 21 1984 1 61 1986 1 1987 1 201 1STA 1978. 21 131 1979 1 41 1980 i 191 1981 i 1982 1 341 1983 1 1I 1984 1 4511 1986 1 1 1987 1 81 1STA 1978 21 104 1979 1 1I 1980 i 41 1981 ; i 1982

• 101 1983 1i 1984 1 111 1986 1 i* 1987 1 451:STA 1982 1 61 134 1983 1 21 i 1984 1 561 i 1986 1 , 1987 1 181 11 21 51 21.61 0o 19!i 241ý41 11i 41 01i 21 141 41 1I 241 21 31 21 71 741 11 2li 211 101 91 I 11 161 341 1821 41551 101 30: 0! 11 4221 21 11 11 5901 7765.1 3561 251 741 801 "1091 8171 11 521 41 70: 46721 24921 34851 3891 501 651 9411 11 21 21 .5761 9051 6091 403631 3701 341 931 39051 1i 31 16; 801 106: 871 4361 811 141. 41 731 21 1: 11 561 3601 1101 1691 12831 531 181 1711 II 01 31 41 19481 2021 2131 1321 861 81 2181 1 1 9201 601 871 1741 2561 291 2541 131 01 Ii 11 27341 591 1511 911 901 ". 31 2651 0i 31 161 1201 2531 2951 261 601 71 11 741 01 121 21 21521 282301 256101 371 241 1481 221 46871 21 161 31 1741 142071 61441 10001 3351 1331 741 18421 41 Il 21 9821 14931 32631 382291 4811 471 3961 40821 7: 61 21 961 1361 851 225: 371 111 381 571 01 1! 01 761 1711 1481 731 621 951 411 551 21 1: 61 20: 37621 3551 981 231 7471 61 4561 1 1 1 8111 831 1981 8381 541 201 3341 1i 11 61 41 126651 2721 2161 7881 2701 61 11871 01 01 11 321 701 361 41 121 31 51 151 1: 11 01 5751 16371 6691 431 521 40: 201 2531 21 81 141 141 38531 10731 7681 1101 301 211 4931 0! 01 01 2771 4811 681 180411 3831 81 1471 17641 01 101 5: 281 1181 631 3251 381 61 31 521 0: Ii 11 1611 541 5991 361 231 291 331 781 2i 01 18: 121 9561 1591 681 51 161. 51 1051 i i i 1 3051 541 29.1 371 381 231 811 0: 01 01 1: 66001 5151 2161 291 891 21. 6311 51 41 01 331 511 181 951 171 91 51 211 1 Ii 01 341 1001 1611 421 2501 831 501 601 21 Ii Ii 71 11531 911 261 141 881- 21 1211 i I .' 3681 841 371 8381 2661 341 2711 0i 51 01 21 55941 10711 3071 1711. 231 141 6011 336 APPENDIX TABLE 3.3.4-1. (Continued)

SPECIES=NUDIBRANCHIA i 1 JAN 1 FEB I MAR I APR'IMAY 1 JUN I JUL 1 AUG 1 SEP 1 OCT I NOV I DEC !.ALL I ISTA 1978 01 0 i 0: 0! 0: 0! 0i 11 01 41 1 0i 119 19791 0: 1 OI 0! 0: 0! 01 21 16: 0; 0: 81 0i 21 1980 01 0i Oi 01 O 0: 151 41 161 261 11 01. 51" .1981 1 01 0i 0: 01 01 301 11 491 61 .51 Oi 81 1982 1 01 01 0i 0i 0! 0! 31 21 711 11 " 1I 01 71 1983 1 0! 01 0i 01 1 Ii 31 51 741 1: 01 11 71 1984 Oi .0i 01 01 0: 1 01 11. 171 981 01 01 101 , 19861 i 1 1 1 i 21 O0 51 21 0i Oi 1I 19871 01 01 : 1 0 0i 11 31 1I 11 0: 21 0: 1: 1STA 19781 Oi I 0i 0i O 01 01 01 01 21 Oi 01 0i 131 1979 1, 11 0i 0i 01 01 I 0! 0: 21 21 21 1I 1I 1980 0i 0i 0i 0i 0i 01 Ii 1i 51 71 Ii 1I 21 1981 11 01 01 O 0 01 01 131 11 471 01 Ii. 01 61 19821 01 01 0i 01 0; 21 1! 31 201 01 Ii 01 21 1983 1 01 01 01 01 0i 01 81 41 41 11 01 0i I1 1984 1 0i 0; O 01 1: 0: 31 31 81 21 81 01 21 1986 1 i I I 1 l 11 O I0 01 0i 01 19871 O O 0i 01 O; 21 221 31 11 0 1 01 01 21 1STA 1978 1 01 01 01 01 01 01 01 31 11 01 0! 11 01:04 1979 1 01 01 O 01 01 01 O 11 0: 21 11 5! 11 19801 01 01 01 01 ! 01O 391 01 201 21 01 .0 51 1981 i 01 01 01 01 01 1: 261 81 431 01 0i 71 19821 01 01 0i 0i O 01 231 51 2671 71 11 01 261 1983 Oi 01 O 1 0 O 51 11 41 01 .21 Ii 11 I 1984 1 01 01 O 01 01 0i 11. 11 21 01 1: 11 01 1986 1 i i 1 .1 41 11 31 1! 11 01 1!1987 1 01 01 0! 01 21 01 .11 11 01 01 O 0i 01 ISTA 1982 1 01 01 01 01 O 01 1: 11 281 11 11 01 31.134. 1983 1 01 O 01 .01 11 71 11 41 21 01 01 1: 11 i 1984 1 0: 01 01 01 11 Ii 21 11 41 01 21 11 11 1 1986 1 1 i i I I 1i 0i 61 41 01. 01 21 i 1987 1 01 0; 01 O -0i 11 31 01 01 01 O 01 0!337 APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=PONTOGENEIA INERMIS 1 JAN 1 FEB 1 MAR 1 APR. 1 MAY 1 JUN 1 JUL- 1 AUG 1 SEP 1 OCT 1 NOV 1 DEC 1 ALL !I ISTA 1978 0: .01 i O O! O 01 01 01 O11 0! O 01*119 1979 i 01- O 01 O 11 O 01. 11 O 11 11 O 01 1980 1 O 0 1! 01 01 I 01 1: 21 21 31 0: 0: 1!1981 i 41 01 O 61 11: 01 01 31 0! 1! '0 21 19821 0; 01 0 O 0: 7: 1i 01 0: 01 0: Oi 11 1983 01 0i 1I Oi 0! 61 1! 1I 01 1: 01 11 1!19841 O1" .01 01 01 1i 1i 01 1I 01 O .1: 01 01 19861 i i i i 1 11 O 11 11 01 O 01 19871 01 0! 0: 0: O 01 0; 0! 01 0! 0 01 O STA 1978 O i 0i 01 01 01 01 01 01 01 O 01 01 131 1979 0 11 0i 01 161 11 O O 0i 21 1i 11 21 1980. 1 01 11 21 1I 31 31 21 0: 01 11 .01 01 11 i 1981 1 1 O 0 01 331 171 5: 01 01 Oi 1! 0! 5!1982 1 01 01 O 1I 11 61 O O1 I1 O 01 Oi I.1983 0i O 11, 131 O 9i i" 3i O O 0i O 21 1984 1 01 01 01 O 81 1 11 .21 O 11 11. O0 1I 1986 i 1 1 1 1 .11 11 0; 01 11 1O O0 1987 -O 0 Oi Oi Oi l ii O! Oi 0: 0; 0: Oi Oi 0: 1 STA .19781 01. Oi 01 O O 01 O 01 01 O 01 0! 01 104 .1979.1 01 O 01 01 01 01 01 01 O1 O 01 01 01 1980 1 O O 01 O I 11 1! 01 1I 31 01 01 O1 01 19811 i O O 01 O O 01 O O O0 O1 01 Oi 1982 1 01 Ol 01 .01 lI 01 01 31 01 1I O 01 1983. 0: 01 01' O O 81 21 01 O O' 01. O I 1984 1 01 01 O; O I1 11 O 0! 21 1! O 0; O i 1986 1 i i i I: ii I: 1 : 0: O 0O Oi 1987 1 O 01 0. O, 0 01. 01 O 01 O O O I! 01 1STA 1982 1 01 O. Oi 0! O 21 0! 0i 1I 01 0! 11 O1 134. 1983 1 01 0! O 0! 01 21 0! .01 0i O 01 0! 01 i 1984 O .01 01 O O 01 O O O 1I O 01 O 1 1986., I I i 0O O1 O 11 01 O 0!19871 O O 01 01 01 01 01 01 0 .1 01. 01 W01 W-------------------------------------------------------------------------------338 APPENDIX TABLE 3.3.4-1. (Continued) SPECIES=STRONGYLOCENTROTUS DROEBACHIENSIS JAN 1 FEB 1 MAR 1 APR I MAY JUN 1 JUL I AUG ['SEP 1 OCT I NOV 1 DEC 1 ALL : 1STA. 1978 119 1979 19801 1981 1982 1983 1984 1986 1987 STA 1978 131 1979 1980 1981 1982 1983 1984 1986 1987 ISTA 1978 104 1979 1980-1981 1982 1 1983 1984 1986 1987 STA 1982 134 1983 1984 1986 1987 01 01 0i i 01 0: 0I i 0o 01 01 O: 01i 01 o: 01 01i'I 01 11 O: 0 i.01 0i.0 01-Oi 0 1i 01 O: O: 0i 0 a:0 0 :1 01i 0[ ol 0:i 0 i I I 0 i 01 0 01 01 01Q 0 o 0i 01 0 I Oi 0l O i O! ýOI I J .01 11 01 0i 01 Oi 11 01i 01 01 I .i I. !01 .01 21 01 21 11 01 01 1 0: 0Oi 41 1I 0i 31 01 01 21. I 0I 0Oi Ii. 0:.01 01 01 31 1i 01 Oi II O 0 01 01 01 41 O 01 01 11 01 1: 11 01 001 21 0o 01 01 01 11 01 Oi 041 01 01 11 I 0I 0 21 21 0i.4! 01 01 11 11 i 01 21 01i I IOi Oi Oi 11. 01 01 31 O 11 11 01 01 11 01 01 01 01 0i 0i 01i 0i 01 0!01i_Oli-0-01i 01i 01i 01i 01i 01i 01i 01i.01 01i 01i 01i 01i 01i 01i 0l 01 0i 0i 01 01 01. 01 01 01i 01 '11 01 01 01 01 01 01.0 1 01 01 01 0: 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 .0i 01 01 01. 01 01 0i 01i 01 01 01 01 01!0 1 01 01 01 01 01 01i 01i 339 APPENDIX TABLE 3.3.4-2. PERCENT FREQUENCY OCCURRENCE (MEAN PER TWO REPLICATES) OF SELECTED COLONIAL SPECIES OCCURRING ON SHORT-TERM FOULING PANELS BY MONTH, STATION, AND YEAR.SEABROOK BASELINE REPORT, 1987.SPECIES=DIATOMSa ./.1 1 JAN 1 FEB .1 MAR 1 APR 1 MAY I JUN JUL I AUG ý SEP 1 OCT I NOV I DEC !ALL-------------------------------------------- +/--+- ----- ---------

---

ISTA 1978 1 , ..119 1979 1 1 1 1 1 1 1 1 1 1.1 -980 1 1 1 1 I l. I 1 1981 1 281 531 991 1001 991 .100: 1001 31 1001 851 131 711 1982 1 391 461 661 941 I0oo 100: 621 99: 981 52: 29: 851 741 1983 921 931 93: 1001 1001 1001 991 1001 1001 1001 1001 971 98: 1984 1 851 841 1001 1001 1001 100! 100: 1001 1001 1001 1001 98: 971 1986 1 1 1 I Vi 1 951 941 1001 991 1OO0 1001 98: 1987 131 801 691 100: 1001 1001 851 841 1001 0: 01 841 681 ISTA 1978 1 .1 1 1 1 1:31 1979 .4 1 " 1 1 " 1 .1 1 1 1 1980 1 1 11 1 1 1 I 1981 1 1 911 481 971 991 1001 751 1001 91 971 961 101 751"I 1982. 1 10: 1001 100 100 lOO 971 100: 921 100: 38: 6: 61 471 691 I 1983 631 501 831 971 1001- 991 1001 711 991 1001 1001 84: 871 1 1984 1 1001 951 981 981 1001 1001 1001 981 1001 1001 1001 611 961 1 1986 1 i 1.01 961 1001 1001 961 1001 821 .I 1987 "181 901 731 951 1001 1001 941 871 1001 94. 891 731 84: ISTA 1978 1 1 I 1 1 1 1 1 104 19791 1 1 1

• 1 1 1 19801 1 1 1 1 1 1 1 I I I I ,.1981 1 1 971 681 901 1001 98: 01 1001 -921 951 851 111 761 1982 1 411 771 801 981 961 991. 871 921 1001 1001 1001 981 911 1983 1 621 961 991 891 1001 1001 791 921 1001 991 991 921 921 1984 1 94 1001 961 941' 1001 1001 791 981 971 1001 1001 971 961"1986 1 1 1 1 1 511 1001 1001 951 821 981 881 1987 921 481 901 1001 1001 1001 791 991 951 751 851 821 871 STA 1982 1 101 721 981 1001- 961 1001 541 481 721 921 771 821 781 134 1983 1 941 941 971 961 991 981 1001 961 1001 1001. 991 971 971.I 1984 1 1001 921 961 1001 1001 1001 1001 611 991 1001- 1001 701 .931 1 1986 1 1 1 1 1 1 1 971 1001 1001 1001 1001 1001 1001 1 1987 1 781 921 841 981 1001 1001 931 981 981 1001 931 *681 921 aDiatoms were not evaluated for % frequency occurrence in 1978-1980 at Stations 19, 31 and 4.340 APPENDIX TABLE 3.3.4-2. (Continued)

SPECIES=OBELIA SPP.I JAN I FEBE MAR 1 APR 1 MAY 1 JUN 1 JUL : AUG 1 SEP G OCT I NOV I DEC ALL 1----- --+--------

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--- +- ......-+-- ......-- --...- -- .-+ -..+ -..+-. .+-.+.- .------+1STA 1978k 119 1979.i .1980* '1981 1982 1983 1984 1986 1987 1 1STA 1978 1:31 1979 19801 1981 1982 19831 1984 1986 1987 ISTA 1978 1:04 1979 1980 1981 1982 1 1983 1 1984 1 1986 1 1987 1 1STA 1982 1 134 1983 1 1984 1 1 1986 1 I 1987 1 0 01i 01i 01i 01i 01i 01 01 01 01i 01i 0: 0i OI 01 01 i 0o 01i 01i O0 0I 0I 01 O0 0i O0 0O: Oi 0Oi oi 0i 0i 01 01 01i 01i 01i 01t 01 01 01i.0!01i 0i 0!01: 01i 01 01 01i O0 Oi 01i O0 0!01 O0 01

• 01! 01 11i 11 6 61 0i 0: 33: 01 01 O1 0 41 11 1 01 61 OI I 01 I OI 01 .11 131 o0 .0: Oi I 01: 10: 01 01 171 0: 301 0 O O3 01: 0i 01 Oi 01 01 521 01 01 01 0 I 1 151 0i 01 681 01 01: 01 01
• 01i 01 1I 41 11 0 : -01 01 I I 01 3L 191.01
• 1 310 01 0! 01 i I 0O I 6I 30O 0l 61 301 01 01 .01 1I 01 21 01 181 0: 01 01 01 O! Oi Of Oi 01 81 .I0 O0.01 01 01 01 01 01 i I0i O0 2] Oi 0 Oi 01 O! 0 01 01
• 01
• 01 110 0~ 21 0 1i 0 01i 01: 01; 01 01i 01i 01
• 01 01i 01 O0 f 01 01 11 01 11 01 21 01 01 01 0: .01i 01 01i 31 31.. I i i1 231 01 21 201 01 01 01 01 61 1001 161 01 01 .0 1 01 71:01 0i 21 0i 01 .0 * .0 01 O Oi 0: 01 151 01: 01i 01 01i 01 01i 01 0 O0 21 31 01 1i 01.01 01 Oi O1 0: 11 11 0i 01 0: 41 11 51 61 O0 111 Oi I i Oi 21.Oi 01 11 01 31 341 APPENDIX TABLE 3.3.4-2. (Continued)

SPECIES=TUBULARIA SR.JAN 1 FEB 1 MAR 1 APR 1 MAY. 1 JUN 1 JUL 1 AUG 1 SEP 1 OCT 1NOV .DEC 1 ALL 1 1 +--------

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+- -------------- -+-+_ -_ -- --------.------+-------+--+-+-. 1STA 1978 1.119 1979 1 19801 1981 1 ,. 1982 1 i 1983 i 1984 19861 1987 1STA 1978 131 1979 i 1980 1 i 1981 1 i 1982 1 i 19831 1 -1984 1 i 1986 1-1987 1 ISTA 1978 1 104 1979. 1 1980 1 1981 1 1982 1 1983 1 1984 1 1986 1 1987 1 STA 1982 1 134 1983 1 1984 1 1 1986 1 1987 1 0o 0 i 01i 01i 0 01i 0 i 01i 01i o 01i 01i 01i 01i 01i 0 : 01i i 0o 0o*01 01 0o 01i 01i I 01 01 01 01 01 01i 01i 01i 01i 01 01 01i 01i 01i 01: 01i 01i 01: 01ý01i 01i 01: 01i 0 i 01i 01i I.01 01 01 01 01 01 01 01 01!0 i 01i 01i 01i 01i 01 01 01i 01i 01i 01i 01 01 01i i 01 01 01 01 01 O.0i 0 1 01 581 301 131 .01 0 21 21 0 01 01 01 01 301 391 41 71 01 1001 1001 1001 331 31 01 16: 201 491 01 01 0i 31 131 1001 1001 61 01 11 441 971 961 121 i 01 11 .281 581 .531 01 81 631 1001 1001 591 01 11 991 831 121 101 01 781 01 Ol 01 01 0i 01 381 31 41 11 O 0: 1001 1001 711 421 0! O 101 11 01 0: 0i 21 01 21 31 01 0! 01 11. 501 91 951 I 01 0l 201 01 01 01 211 121 1001 901 151 01 11 01 01 I I!0: .211 401 21 31 I1 0 01 1 I 71 11 11 01 O 11l 100L 91 01 01 01 31 321 71 .11I 01 71 1001 861 501 61 01 01 61 01 01 361 S 01i 01 01 81 391 01 1001 1001 1001 751 671 01 01 01. 01 01. 111 01 41 841 1001 1001 341 01 01 01 161 91 901 i 01 31 141 951 1001 01 981 .1001 1001 1001 21 01 91.01 01 01 71 01 311 01 71 181 201 11 211 01 231 01 271 01 191 11 71 O 41 61 291 01 11 11 11 11 131 01 31 01 201 Oi 61 0! 11i O: Ili 01 111 31 51 11 211 01 31 11 81 01 371 31 i1 141 281 O 101 01 351 01 331 I.342 APPENDIX TABLE 3.3.6-1.

SUMMARY

OF LEGAL LOBSTER CATCH AT THE DISCHARGE SITE FROM 1974 THROUGH 1987.SEABROOK BASELINE REPORT, 1987.MONTH YEARLY YEAR JUN JUL AUS SEP OCT NOV AVERAGE.1987 2.0 1.7 4.8 3.3 3.6 3.2 3.1 1986 3.6 6.8 7.1 6.7 8.9 12.3 7.2 1985 1.4 8.6 5.9 7.7 7.8 7.6 6.5 1984 2.3 1.8 11.0 4.3 10.7 9.0 6.9 1983 2.5 4.6 11.0 7.0 13..8 4.2 7.2 1982 2.1 9.6 9.7 7.6 10.0 8.5 7.9 1981 4.7 9.2 11.2 12.1 10.0 10.9 9.7 1980 2.9 4.5 12.5 12.2 6.2 7.7 7.7 1979 6.1 8.8 8.8 8.8 12.4 11.2- 9.4 1978 7.1 4.0 12.8 14.6 11.4 9.8 10.0 1977 5.9 4.2 13.9 9.9 7.3 9.4 8.4 1976 3.3 8.8 12.4 7.5 9.2 10.1 8.6 1975 2.7 5.7 9.5 8.0 10.0 10.1 7.7 1974 ND 6.7 9.8 11.2 9.0 12.2 9.8 MONTHLY AVERAGE 3.6. 6. 1 10.0 8.6 9.3 9.0 ND -No Data aCatch per trip effort = legal catch from 15 traps per trip.343 APPENDIX TABLE 3.3.7-1.

SUMMARY

OF MYA ARENARIA POPULATION DENSITIES FROM ANNUAL FALL SURVEYS IN HAMPTON-SEABROOK HARBOR, 1971 THROUGH 1987. SEABROOK BASELINE REPORT, 1987.NUMBER OF SAMPLES MEAN DENSITY (No./tO)COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (i to 25 mm) (26 to 50 mm) (>50 mm)Flat 1 1971 18 18 48 6.8 2.1 1972 18 18 110 8.1 3.3 1973 36 18 44 2.5 .3 1974 64 18 2 3.7 2.1 1975 57 18 31 0.8 1.1 1976 49 18 580 >0.1 0.3 1977 60 14 437 >0.1 0.2 1978 63 14 209 1.4 >0.1 1979 62 20 40 30.4 0.1 1980 30 20 90 72.0 1.7 1981 25 25 45 44.7 3.7 1982 25 25 6 13.1 2.8 1983 40 40 21ý 21.1 4.2.1984 40 45 57 6.2 3.4 1985 106 71 5 .1.4 1.6 1986 75 .70 9 0.2. 0.7 1987 70 55 7 0.1 0.2/I Flat 2 1971 1972 1973 1974 1975 1976 1977.1978 1979.1980 1981 1982 1983 1984 1985 1986 1987 9 9 18 25 25 19 33 29 32 40 25 15 40 40 51 53 55 9 9 9 9 9 9 7 7 9 25 25 25 25 25 25.20 20 91 i52 136 0 5 198 49 8 31 253 519 7 19 25 21 9 13*4.8 2.2 3.8 1.3 0.0>0. 1 0.0 3.9 3.5.3.9 1.0 0.2 4.4 0.9>0.1>0.1>0. 1 3.8 1.4 1.1 1.3 0.5 0.1>0.1 0.2 0.2 2.2 0.9 0.9 5.4 1.7 0.5 0.3 0.1 (continued) 344 APPENDIX TABLE 3.3.7-1. (Continued) NUMBER OF SAMPLES MEAN DENSITY (No./ft 2)COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (1 to 25 mm) (26 to 50 mm) (>50 mm)Flat 3 1971 6 6 74 *4.7 4.6 1972 6 6 39 1.6 0.4 1973 12 6 8 3.6 2.2 1974 16 6 1 0.7 .1.5 1975 17 6 1 0.0 0.5 1976 24 5 321 >0. 1 0.3.1977 20 6 43 >0.1 >0.1 1978 23 6 71 2.1 0oI 1979 12 4 6 1.0 0.0 1980 40' 25 56 0.5 0.4 1981 25 25 .51 0.1 0.4 1982 15 25 4 0.2 0.3 1983 40 25 12 0.1 0.2 1984 40j* 30 32 0.1 0.4 1985 .NS 25 12 NS NS 1986 NS 24 8 NS NS 1987 NS 25 9 NS NS Flat 4.1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986)1987 12 12 24 39 38 68 42.51 66 25 25 25 25.25 36 38 40 12 12 12 12 12 18 11 11 18 25 25 25 25 25 25 30 20.106 138 18 3 39 475 245 172 97 96.236 24 45 82 16 12.12 17.6 10.6 3.8 2.8 0.3>0. 1>0. 1 16.8 36.3 47.2 49.4 12.3 2.8 1.0 0.3 0.2 0.3 2.8 2.3 0.6 1.7 0.4>0.1>0.1>0.i1 0.6 3.2 2.3 2.2 1.0 0.9 0.6 0.2 0.2 (continued). 345 i APPENDIX TABLE 3.3.7-1. -(Continued) NUMBER OF SAMPLES MEAN DENSITY (No./ft 2), COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (1'to 25 mm) (26 to 50,mm) (>5Q.min)Flat 5 1971 9 9 176 1.3 1.6 1972 9 9 196 3.8 2.3 1973 21 11 23 1.0 0.4 1974 33 12 2 >0.1 0.1.1975 20 8 5 0.0 >0.1 1.976 14 12 309 0.0 >0.1 1977 38 9 64 >0.1 >0.1 1978 38 7 32 4.8 >0.i 1979. 28 8 8 2.0 >0.1 1980 40 20 65 2.2 0.8 1981 25 25 409 0.3 0.7 1982 15 25 43 >0.1 0.2 1983 40 25 25 0.0 0.1 1984 40 25 16 >0.1 0.1 1985 NS 33 15 NS NS 1986 NS 35 7 NS NS 1987 NS 20 23 NS NS All Flais 1971 54 54 92 7.7 2.7 1972 54 54 130 6.2 2.2 1973 i1 56 47 2.8 1.0 1974 177 57 2 2.2 1.5 1975 157 53 21 .0.4 0.6 1976 174 62 4.21 .>0.1 0.2 1977 193 47 207 >0.1 >0.1 1978 204 45 123 6.3 >0.1-1979 200 59 49 22.3 0.3 1980 175 115 115 20.6 1.5 1981 125 125 252 19.1 1.6 1982 95 125 17 6.7 1.5 1983 185 140 24 5.9 2.3 1984 185 150 46 .1.7 1.3 1985 193 179 12 0.8 1.1 1986 166 179 9 0.2 0.5 1987 165 -140 11 0.1 0.2 1 i .346

4.0 METHODS

4.1 GENERAL Prior to 1975, the Seabrook Environmental Program involved studies of specific sites (e.g., the estuary, the discharge area, the intake area) or specific species (e.g., Mya arenaria) in order to (1) characterize their physical and/or biological environment'and (2) assess impact of proposed plant design. The results of these studies were reviewed and discussed during the Environmental Protection Agency's hearings on Seabrook Station s open cycle cooling-water system (NAI 1977e; EPA 1977).Since July 1975, the focus of the program has been to provide preoperational characterization of the environment in potentially impacted areas. Field and laboratory methods that were used for data collected during 1980 through 1987 were thoroughly described in the data reports for those years (NAI 1981c, 1981f, 1982a, 1982b, 1983a, 1984a, 1985a, 1986, 1987a, 1988). Methods used prior to 1980 were summarized and explained in detail in previous annual reports for Seabrook Environmental Studies (NAI 1976a, 1976b, 1977a, 1977b, 1977c, 1977d, 1978a, 1978b, 1979a, 1979b, 1979c, 1979d, 1979e, 1979f, 1980a, 1980b, 1980c, 1981a, 1981b, 1981c, 1981d, 1981e, i981f).Plankton studies have been based on samples collected in the nearfield (intake) area and a farfield area (Rye Ledge) located beyond the influence of the Station's operation. In July 1986, sampling at a third station (P5) was resumed in the vicinity of the discharge (Figure 4.1-1); preoperational samp-ling had been conducted at P5 for various plankton programs from July 1977 through December 1981. Fish were sampled offshore by bottom trawls and gill nets near the discharge area and at two farfield sites, and by seining at three locations in the Hampton-Seabrook estuary (Figure 4.1-2). Marine algae and benthos were collected by divers at a series of stations stratified by depth near the intake/discharge area and in a farfield area (Table 4.1-1,.-Figure 4.1-3). Benthos in soft substrates were sampled along two transects in the estuary (Figure 4.1-4). Lobster (llomarus americanus), rock crab 347 .ý -...- .:.1 .:.." ..1 'ROCROO 0 .Arge FJ AREA STATION .NN. > ....SEABROOK EBO HARBOR EBO BEACH.5 1 NAUTICAL MILE..0 2 KILOMETERS SAUISBUIRY SCALE BEACH CONTOUR DEPTH IN METERS, U -microzooplanikon, bivalve larvae and water quality stations = macrozooplankton and ichthyoplankton stations/7 -lobster larvae stations Figure.4.1-1. Plankton sampling stations. Seabrook Baseline Report, 1987 348 , o/ ., i""............".. .FARFIELD AREA BOARS HEAD* , ~~~.. '..... ;.... ..,. ..T3 GREAT 9 BOARS 18-HEAD NG3a M ................ " HAMPTON BEACH .Intake.M...13ROWNS RIVER S2 .._...... ".. ... :, ."....NEARFiR.D AREA SEABROOK 0SNo Dcha U"'.- °c , " .Discharge..... STATION _R.. .. i:, .'.. :.ii.i:*".. ..HAMPTON.SEABROOK ERO HARBOR EABTO0..... .£ BEACH .T.'G1..o 1NAU* ".: 0 .1 NAK.1". ... .. .0 2 Kit j T1 SCALE TAHi.CONTOUR DEPTH IN METE.I T = Otter Trawls N S =Seine Hauls. G Gill Nits 0 Figure 4.1-2. .Finfish sampling stations. Seabrook Baseline Report, 1987.349 I. -I.TABLE 4.1-1.BENTHIC ALGAE AND MACROFAUNA STATION LOCATIONS AND DESCRIPTIONS. SEABROOK BASELINE REPORT, 1987.r DEPTHa'b LOCATION APPROXIMATE COMPOSITION m ft STATION LONGITUDE LATITUDE. OF HARD SUBSTRATES .4.6 4.6 9.4 9.4 12.2 18.3 18.9 21.0 0.3 1.3 15 17 70047'37'" 15 35c 70046"07'" 31 3 1c 70047'37" 31 16 700471031' 40 19 70047'13"? 60 13 70046'58i 62 4 70045'59 69 34. 70047'04".42054'00 42057'22?? 42058'04?? 42054'.16?? 42053'40" 42053'54'? 42053'23?? 42054'23?? 42053'56?? 42053'506? 42058' 19" Algae covered ledge (95%) and crustose covered ledge (5%)Algae covered ledge (85%)and. boulders (15%)Algae covered rocks (30%) mussel beds (60%)and cobble (10%)Algae covered ledge (75%)and mussel beds (25%)Algae covered ledge and boulders (60%) and mussel beds (40%)Algae covered ledge and boulders (40%) mussel beds (55%) and cobble (5%)Mussel beds (70%) and algae covered ledge (30%)Mussel beds (60%) and algae covered ledge and boulders (40%)Algae covered ledge (90%) mussel bed (10%)Algae covered ledge (100%)f 17 1 1MLW 4 lMSL 1 5MLWc 70047'41?? 70047'46?? 70045'36"' Ii 0.3 Algae covered ledge and boulder (90%)mussel bed (10%)1.3 4 5MSLc .70045'44" 42058' 12" Algae covered ledge (100%)a b depth below mean low depth above mean low Cfarfield stations water, subtidal stations water, intertidal stations 350

algae and macrofauna

.surface panels = both Figure 4.1-3. Benthic marine algae and macrofauna sampling stations. Seabrook Baseline Report, 1987.351 I..0*o Intake Discharge 1.New Hampshire -.-Massachusetts 05 1KILOMETER O = Clam Rats U = Green Crab Trap Stations= Benthic Transects HH -B = Estuanne Salinities Figure 4.1-4. Hampton-Seabrook Estuary temperature/salinity, soft-shell clam (Mya arenaria), benthic transects and green crab (Carcinus maenas) sampling stations. Seabrook Baseline Report,1987. 352{'1 i (Cancer irroratus), Jonah crab (C. borealis) and green crab (Carcinus maenas)were collected in traps (Figures 4.1-4, 4.1-5). Soft-shell clams-(mya arenaria) were dug from five flats in the estuary (Figure 4.1-4), with farfield spat stations in Ipswich,-MA. and Ogunquit, ME (through 1984 only.)(Figure 4.1-6).A complete assessment of preoperational conditions was made in the 1984 Seabrook Baseline Report. The 1986 Baseline Report built on conclusions made in that report, updating results with two additional years of data for those programs which had been maintained without-interruption. This 19.87.Baseline Report adds another full year of preoperational data, further characterizing the natural biota of the area. Similar analytical methods, utilizing the entire historical data base, have been used wherever possible to maintain consistency. Changes in a few of the programs in 1987 did occur. The continuous offshore monitoring program for temperature and salinity, and the phyto-plankton and microzooplankton programs were discontinued. Refer to the 1986 Baseline Report for the results of those programs. The ichthyoplankton and bivalve larvae enftrainment collections were discontinued after June 1987, because most of the latter half of the year there were not enough circulating water pumps operating to allow operation of the entrainment sampling system.This report summarizes the results of the entrainment program until sampling/was discontinued. Over the several years of this study there were some instances in which some sample types were collected for only part of a year, or discon-tinued for a whole year, due to program modifications (particularly in 1985 and 1986). This report does not include data from partial sampling years if.they erroneously influence sample statistics. For example, annual means of macrozooplankton selected species were not calculated for 1986 because samples were not collected from January through June *in that year (TablO 3.1.3-6). However, these data could-be used in discriminant analysis since samples are partitioned seasonally (Table 3.1.3-1). Data not presented in a 353

Figure 4.1-5. Locations of lobster and rock crab trapping areas. Seabrook Baseline Report, 1987.354 STUDY SITES Figure 4.1-6. Sampling sites for Mya arenaria spat. Seabrook Baseline Report, 1987.355 table or figure means that they were either not collected or were incomplete

• for that period.As in previous bas'eline reports, preoperational conditions in the Hampton-Seabrook area were examined in this report at the community and.species levels, both useful indicators of environmental change. Community structure and its variation, in time and/or space.have been investigated in previous reports using numerical classification.

Results presented in the 1984 Baseline Report form the basis against which future results (both.preoperational and operational) will be compared. The 1985 through 1987 ..species assemblages were compared to those observed through 1984 either by using discriminant analysis or.by using a variety of.ranking techniques. Abundance of various key species (of numerical or commercial importance) previously identified as "selected species" were compared temporally or spatially using analysis of variance (ANOVA) or non-parametric techniques. in several cases, the size or growth of a selected species was examined in addition to abundance in order to provide a basis for detecting potential sublethal effects. These methods are effective in describing general pat-terns and magnitudes of variability that'have occurred during the preopera-tional period. Once plant operation begins, population levels will be statistically compared to spatial and temporal patterns observed during the baseline period, and significant changes will be identified if they occur.For these comparisons, an analysis may.focus on a single species or several species grouped together. in a higher taxonomic category. Components of and rationales for species "complexes" were'discussed in the 1984 Data Report (NAI 1985a). .4.2 COMMUNITY STRUCTURE Techniques utilized for analysis of both spatial and temporal .aspects of community structure are outlined in Table 4.2-1.356 TABLE 4.Z-1.

SUMMARY

OF COMMUNITY ANALYSES. SEABROOK BASELINE REPORTS, 1987.PURPOSE ANALYTICAL COMMUNITY OF ANALYSIS METHOD STATIONS DATES DATA CHARACTERISTICS a Macrozooplankton (505 micron net)Spatial comparison Temporal comparison Spatial comparison Temporal comparison Percent composition, percent fre-quency Discriminant Analysis Percent composition, percent frequency Abundance Discriminant Analysis P2, PS, P7 1/87 -IZ/87 P2 1/78-12/84, 7/86-12/87 Fish Eggs (505 micron net)P2, P5, P7 1/87 -22/87 Mean of 3. replicate tows; all taxa included Hilcoxon's summed rank test for selected species Mean of 3 tows/date; excluded taxa with percent frequency <3X plus 9 general taxa out'of 125 Mean of two tows; all taxa included Mean of 4 tows/date (Jan 76-Feb 83, except for non-selected species Jan-Dec 821 1 tow); 2 tows (Mar 83-Dec 87)excluded taxa with total percent composition <0.1 (5 out of 16 taxa); excluded 26 sampling periods with <20 eggs in all replicates tW P2, El P2 7/86 -6/87 1/76-12/87 Fish larvae (505 micron net)Spatial comparison Temporal comparison ,Spatial and temporal comparison Percent com-position, percent frequency Abundance Discriminant Analysis PZ, PS, P7 1/87-12/87 Mean of two tows5 taxa with percent frequency> 10% included PZ, El P2 7/86-6/87 1/76-12/87 Demersal fish (otter trawl)Catch statistics Percent composition. T1, T2, 13 1/76-12/87 Replicates treated as for eggs; excluded species with total percent composition <0.1 or frequency of occurrence <5. (27 out of 47 taxa); excluded 29 sampling periods with<20 larvae in all replicates CPUi = /10 min tow; no transformation; all species combined by station, '76 -'86 PERCENT, a) Dominant species grouped by year ('76 -'87) over all stations b) Dominent species grouped by station, all years combined (continued) TABLE 4.2-1. (Continued) tn 00 PURPOSE ANALYTICAL a COMMUNITY OF ANALYSIS METHOD STATIONS DATES DATA CHARACTERISTICS Pelagic fish Spatial and Catch G1, GZ, G3 1/76 -1Z/87 CPUE = /24 hr. set; no transformation;(gill net) temporal statistics a) depths (surface and buttom) and all comparisons species combined b) surface, mid, bottom nets, Feb, Jun, Oct. '80 -'87 combined Percent PERCENT:.. composition a) Dominant species, surface and bottom and all stations combined by year,'76 -'87 b) Dominant species, surface and bottom separate, all stations and years combined c) Dominant species surface and bottom combined, grouped by station, all years combined Estuarine fish Spatial and Catch S1, S2, S3 7/76- 11/84 CPUE /haul; total catch by year and (beach seine), temporal statistics 4/87 -11/87 station for all species combined *Percent 7/76 -11/84 PERCENT-composition 4/87 -11/87 a) Dominant species grouped by year 1976-1984 and 1987 all stations combined b) Dominant species by station, all years combined.Benthic Macroalgae Temporal/ Discriminant 4,34,13,16 August Mean of replicates (airlift) spatial Analysis 19,31,1MLW 1978- 1987' Replicates separate; biomass log 17,35,SMLN (x + 1).transformed; all species included Marine Benthic Temporal/ Discriminant 17,19,31, Aug 1978-1987 Mean of replicates; excluded non-Macrofauna Spatial Analysis IMLN colonial species with <25 occur-(airlift) 34 Aug 1980-1984; rences or <150 individuals in 1986-1987 sample, based on 1978-84 data.4,16,13 Aug 1978-1984;Stepwise discriminant analysis 1986-1987 to reduce species to 32. 1978-1984 35,5MLW Aug 1982-1987 samples in groups according to numerical classification results;1985-1987 samples placed in groups based on depth.a All data log (x +1) transformed unless otherwise noted Discriminant Analvsis The purpose of the discriminant analysis is to provide a means of characterizing or classifying new data with respect to historical (baseline) trends in community structure. It is a multivariate statistical technique that provides a quantitative evaluation of results-of other classification analyses such as cluster analysis as well as a set of multivariate criteria that may be utilized'to classify new data (Cooley and Lohnesv1971). Discriminant analysis (SAS 1985a) develops a classification cri-terion for samples using a measure of distance between groups.. Initially, samples are placed in groups either by simple examination or by an analysis such as numerical classification. The discriminant analysis produces weighting coefficients (linear discriminant function coefficients) that identify the variables (in this case, abundance or biomass of different species) which contribute most to differentiation of:the preassigned groups.The analysis then evaluates the samples based on these criteria and calcu-lates a probability of membership in each group.Classification of new data with respect to-historical (baseline). data can also be accomplished with discriminant analysis (Cooley and Lohnes 1971). This method was extensively discussed in NAI (1984b). Using the spatial and/or temporal groups defined for the historical baseline period (through 1984), a set of multivariate criteria are developed which are then used to classify new data (in this case, 1985-1987). Probability levels associated with group membership are also calculated. In this way, spatial and/or temporal assemblages which occurred in 1985-1987 are quantitatively compared to those described for previous years.Data from each major community (macrozooplankton, fish eggs, fish larvae, algae, and marine benthos) were prepared in a similar fashion to that done for the -1984 Baseline Report community analysis prior to running the discriminant analysis.- Details of the criteria used in eliminating rare species and-sparse samples are shown in Table 4.2-1. Baseline collections 359 (through 1984) were placed in groups identified by the results of the multi-year cluster analysis (NAI 1985b). Discriminant analysis evaluated the species/collection matrix, reassigned the collections to the baseline groups, and calculated the probability level associated with group membership. A few differences in classification that arose between the two methods may be.because discriminant analysis places less weight on abundant species than cluster analysis does.. Discriminant analysis'might characterize a group by ephemeral, nondominant species whereas cluster analysis might characterize the same group by its dominants. In one case (subtidal benthos), the classification variables (species) outnumbered the samples being classified. A stepwise discriminant analysis was first performed to eliminate species that do not contribute to the discriminatory power of the model (SAS 1985a). The discriminant analysis used the resulting reduced species list to classify the historical data. The 1985-1987 data were then tested using the multivariate criteria developed for the. historical data.Ranking Methods Rank dominance scores (RDS) were calculated for macrozooplankton abundances. The scores were calculated by ranking taxa by abundance within samples in descending order, summing across all samples, and standardizing the scores against the theoretical maximum.. The following formula was used: RDS lO0.x sum of ranks for ÷ theoretical maximum all species sum of ranks over all samples This rank thus reflects both abundance and frequency of occurrence. Spatial analysis of plankton and finfish data included ranking by percent composition. Percents were based on total abundances over the entire *period being analyzed (January-December 1987). Apparent differences in ranks 360 (either RDS or percent) among macrozooplankton taxa were examined with a Wilcoxon's two-sample test (Sokal and Rohif 1969; equivalent to.Wilcoxon's sum of ranks test, SAS 1985a).4.3 SELECTED SPECIES/PARAMETERS Temporal and spatial differences for the selected species and water quality parameters were quantitatively evaluated for the preoperational period: Analytical techniques used. in this evaluation are delineated in Table 4.3-1. Many of the selected species and physical/chemical parameters monitored in the Hampton-Seabrook area show year-to-year differences that are part of.natural environmental variability. These among-year differences were assessed using analysis of'variance or non-parametric techniques. Most of the organisms and physical/chemical parameters show seasonal patterns as well. These within-year patterns are shown graphically in plots of the mean over all years for each month. The monthly means are typically 10glo (x + 1)transformed before plotting.For many of the data sets, this year's tables comparing organism abundances among years or months show geometric means and confidence limits.These are calculated by (1) log (x+l) transforming the data, (2) calculating the mean and confidence limits of the transformed data, and (3) back-transforming to the original units. Geometric means are generally somewhat lower than arithmetic means (averages of untransformed data), with the difference between the two means being greater in data sets exhibiting a high degree of variability. An outlier in adata set, such as an unusually high abundance in a single sample., will have less influence on a geometric mean than on an arithmetic mean. Thus a geometric mean is, in effect, a weighted mean, in which extreme values are given less weight than are typical values.For data sets that require logarithmic transformation for statistical anal-ysis, the geometric means faithfully portray the relationships within the data (among years, for example), whereas arithmetic means would sometimes show a different pattern.than that detected by the analysis.361 TABLE 4.3-1. ANALYSIS OF TEMPORAL AND SPATIAL PATTERNS IN SELECTED TAXA AND PARAMETERS: METHODS AND DATA CALCULATIONS. SEABROOK BASELINE REPORT, 1987.PURPOSE OF STA- DATES USED a METHOD PARANETER/TAXON, LIFESTAGE ANALYSIS TIONS IN ANALYSIS DATA MANIPULATIONS Estuarine Strebiospio benedicti spatial compari- 3, 9; -1978-1987 x per sample period, log (x+l)Benthos Capitella capitata sons of seasonal 3MLH, (except abundance, paired t-test Oligochaeta abundances 9MLH; 1985)Mya arenaria Nereis diversicolor Caulleriella sp. B Total abundance No. of taxa Macrozooplankton Calanus finmarchicus spatial compari- P2, P7; 1/87-12/87 R per sample.period; Hilcoxon'.s copepodites ' son P2, PS; summed ranks test; RDS, percent Calanus finmarchicus adults PS, P7; composition Carcinus maenas larvae Crangon septemspinosa larvae Diastylis sp.Pontogeneia inermis Neomysis americana Oedicerotidae Cirripedia Temora longicornis Total abundance continued ON rC1. TABLE 4.3-1. (continued) PURPOSE OF STA- DATES USED METHOD PARAMETER/TAXON,.LIFESTAGE ANALYSIS TIONS IN ANALYSIS DATA MANIPULATIONS b PZ Ichthyoplankton Winter flounder larvae Yellowtail flounder larvae American sand lance larvae Atlantic cod larvae Pollock larvae Atlantic mackerel larvae Hake larvae Atlantic herring larvae Cunner-larvae Temporal compar-ison among years in season of highest density 7/75-12/87. selected months Log (X+1) mean abundance per sample period for months which together comprised over 900 of the total annual abundance, 1-way ANOVA, Waller-Duncan k-ratio +-test W'Demersal fish Winter flounder temporal TI, 1/76-1Z/87 CPUE (no. per haul), 1-way (Otter trawl) Yellowtail flounder ANOVA, Waller-Duncan Atlantic cod k-katio t-test Hakes Rainbow smelt Pelagic fish Atlantic herring temporal all sta- 1/76-1Z/87 CPUE (no. per 24-hr set) 1-way (Gill net) Pollock tions ANOVA, Waller-Duncan k-ratio Atlantic mackerel combined t-test Esturine fish Winter flounder temporal' all sta- 1/76-12/84 CPUE (no. per seine trawl) 1-way (Beach seine) Rainbow smelt tions 1/87-12/87 ANOVA, Waller-Duncan k-ratio Atlantic silverside combined t-test continued TABLE 4.3-1. (continued) PURPOSE OF. STA- DATES USED METHOD. PARAMETER/TAXON, LIFESTAGE ANALYSIS TIONS IN ANALYSIS DATA MANIPULATIONSa Marine Benthic Selected Species Ampithoe rubricata, Nucella lapillus, Mytillidae spat temporal and spatial compari-son of abundance Jassa falcata, Mytilidae spat Asteriidae Pontogeneia inermis, Mytilidae spat, o Strongylocentrotus X-1 droebachiensis 1MLN 5MLW 17 35 17 35 19,31 5/78-11/87 abundance averaged over 5/82-11/87 replicates, 3 dates per year, 1-way ANOVA among years Waller-Duncan K-ratio t-test 5/78-11/87 5/81-11/87 5/82-11/87 5/78-11/87 Ampithoe rubricata, Nucella:lapillus,' Mytilidae spat Jassa falcata, Mytilidae spat, Asteriidae Pontogeneia inermis,*Mytilidae spat, Strongylocentrotus droebachiensis Modiolus modiolus temporal and spatial compari-son of length 1MLW,SMLW 5/82-11/87 Mean and confidence interval 5/82-11/87 calculated for each.year and at nearfield and farfield station pairs 17,35 5/82-11/87 5/82-11/87 19,31 spatial temporal 19,31 19,31 1980-1987 mean per sample period, Nilcoxon~s 198071987 summed ranks test, Kruskal-Nallis test continued 0 TABLE 4.3-1. (continued) PURPOSE OF STA- DATES USED a METHOD PARAMETER/TAXON, LIFESTAGE ANALYSIS TIONS IN ANALYSIS DATA MANIPULATIONS Epibenthic Homarus americanus temporal Li 7/75-11/87 mean CPUE (per 15 traps) per month, crustaceans Cancer irroratus no transformation, Cancer borealis 1-way ANOVA, year, month Homarus americanus spatial Li, L7 6/82-11/87 mean CPUE (per 15 traps:) per month, Cancer borealis no transformation,. Cancer irroratus paired t-test, stations Benthic Laminaria saccharina spatial and 17, 35 1982-1987 mean number per sample period, macroalgae temporal Hilcoxon's paired ranks Chondrus crispus spatial and 17, 35 1982-1987 mean biomass, per sample period, temporal IMLN, log (x+l) transformation, 51LW 1-way ANOVA, years Paired t-test stations Cr%a 1W (X+I) transformation unless otherwise stated for ANOVA.Ichthyoplanktont Station P3. collections made from 7/75-6/775 P2 from 7/77-1Z/86. Differences in substrate, water mass movement, temperature, light penetration,, depth, food availability, reproductive success or all of these.can cause variation in species abundance and growth among stations or areas. h As part of our experimental design, farfield statibns beyond the influence of potential impact were established as "control" stations in areas as similar as possible to the nearfield areas. Any change observed during the opera-tional phase at nearfield stations can be compared with these farfield areas to ascertain whether the change is occurring throughout the coastal area or just at the nearfield area. To evaluate spatial differences in the selected spec ies, a'paired t-test (nearfield vs. farfield stations) or the corres-ponding non-parametric test, the Wilcoxon signed ranks test, was used. -Analysis of Variance (ANOVA) ..Analysis of variance was used to evaluate spatial or temporal variability in both abundance and length of selected species. Analysis of variance is a statistical technique which subdividesthe total variability into portions attributable to different sources (Lentner 1972). In this study, the major sources of variability were (1)'spatial, among stations or areas within stations, (2) temporal, among years, seasons, or sampling dates, and (3) residual, any variability not explainable by the first two sources..The actual analysis of variance differed according to design of the partic-ular study type, but all sought to disprove the null hypothesis that the.means of one or more populations were statistically equivalent. Annual variability was generally evaluated by a one-way analysis of variance among years at a nearfield station. In some data sets that have been shown in previous baseline reports to exhibit no differences among stations (e.g., pelagic fish), or if stations are of essentially equal distance from the intake and discharge locations (e.g., estuarine fishes), data from all stations were combined. For demersal fish, the station nearest the discharge (T2) had several missing data points, so another stationS(Tl)- was used for the among-year ANOVA. For those data sets thatexhibit-a high-366 degree of within-year variability because of seasonal fluctuations (e.g., fish larvae), a subset of the data was chosen to representthe peak period,.and samples from that period in each of the years were used in the analysis.In some cases the reduced data set still had a fairly high within-year variability, but this approach resulted in. significance tests that compared favorably with two-way ANOVA designs (month x year) in terms of power, and avoided the possibility of difficult-to-interpret interaction terms which could hamper the ability to address the effect of primary interest (years).Spatial comparisons were analyzed in some cases with a paired t-test. This is equivalent to a two-way ANOVA without replication, in which the second factor is blocks of time (i.e.,,dates) in which pairs of stations, nearfield and farfield, were sampled. *This design removes the among-date, variability that is common to both stations, providing greater discriminating power than if a one-way ANOVA (or the equivalent unpaired t-test) were used..Analysis of variance and related parametric techniques make the following assumptions: (1) all samples are randomly collected, (2) samples come from a normally-distributed population, (3) error terms are normally and independently distributed, and (4) variances of samples are equal or homo-geneous (Sokal and Rohlf 1969). Random and independent collection of samples is a function of experimental design. Normality of data was tested using the Kolomogorov-Smirnov test when sample size was greater than 50 and the Shapiro-Wilk statistic when sample size was 50 or less (SAS1985b). Homo-geneity of variances~was tested using the F-max test (Sokal and Rohlf 1969).If one or both of these two assumptions was not met, the data were trans-formed and re-evaluated. In most cases, transformation of the data improved the distribution sufficiently to allow the use of analysis of variance.Logarithmic transformations were performed by adding 1 to the data used in the analysis (either for a replicate or average of replicates; see Table 4.3-1) and taking the base-10 logarithm. Square root transformations were accomplished simply by taking the square root of the data. Where sample sizes were unequal, a general linear model was used for the ANOVA (SAS 1985a).367 Multiple Comparisons If a significant difference among means was discovered using analysis of variance, The Waller-Duncan k-ratio t-test was used to test which means or groups of means were significantly different from each other. This test is less conservative than several other commonly used multiple compari-sons tests (i.e., more likely to find significant differences between means).It was selected because more conservative tests failed in several cases to detect any significantdifferences among means even when the overall F-test of the ANOVA was highly significant. Several types of non-parametric tests of significance were also used. Differences in-ranks were assessed by using the Wilcoxon two-sample test (Sokal and Rohlf 1969; equivalent to Wilcoxon's sum of rank test., SAS 1985a) or the Kruskal-Wallis test (Sokal and Rohlf 1969). Wilcoxon' s two-sampie test is a ranking procedure by which two samples of unequal size can be compared. All data are ranked, then ranks are summed within samples. The differences between the summed ranks are compared using the Mann-Whitney U statistic when the larger sample size is 20 or Student's t .value when sample size is > 20. The Kruskal-Wallis test'was used as a non-parametric alternative to one-way ANOVA to test among-year differences or among-station differences. This procedure ranks all pooled data, then sums ranks within a group and compares differences using an H-statistic, distributed approxi-mately as chi square (Sokal and Rohlf 1969)../1 368

5.0 LITERATURE

CITED Abbott, T.R. 1974..- American seashells. Van Nostrand Reinhold Co. New York, NY. 663 pp.Ayer, W.C. 1968. Soft-shell clam population study in Hampton-Seabrook Harbor, New Hampshire. New Hampshire Fish and Game Dept 39pp.Bayne, B.LT 1965. Growth and the delay'of metamorphosis of the larvae, of .ytilus edilus (L). Ophelia 2:1-47.1976. The biology of mussel larvae. Chap. 4 In B.L. Bayne (ed.) Marine mussels: *their ecology and physiology. IBP 10.Cambridge Univ. Press. pp. 81-120.Bigelow, H.B., and W.C. Schroeder. 1953. Fishes of the Gulf of Maine.U.S. Fish Wildl. Serv., Fish. Bull. 53(74,):1-577. Bigford, T.E. 1979. Synopsis of biological data onthe rock crab,.Cancer irroratus Say. NOAA Tech. Rep. NMFS Circ. 426. May, 1979.Bousfield, E.L.! 1973. Shallow water gammaridean Amphipoda of New England. Comstock Publishing, Ithaca, NY 312 pp..Breen, P.A., and K..H. Mann. 1976. Changing lobster abundance and destruction of kelp beds by sea urchins. Mar. Biol. 34:137-142. Briscoe, C.S., and K.P. Sebens. 1988. Omnivory in Strongylocentrotus droebachiensis (MUller) (Echinodermata:Echinoidea): predation on subtidal mussels. J. Exp. Mar. Biol. Ecol. 115:1-24.Brousseau, D.J. 1978. Population dynamics of the soft-shell clam Mya arenaria. Mar.: Biol. 50:63-71.Campbell, A. 1986. Migratory movements of ovigerous lobsters, !fomarus americanus, tagged off Grand Manan, eastern Canada. Can. J. Fish.Aquat. Sci. 43:2197-2205. Cooley, W.W., and P.R. Lohnes. .1971. Multivariate data analysis. Wiley and Sons, Inc., New York.Dalley, E.L., and G.H. Winters. 1987. Early life history of sand lance (Aimodytes) with evidence of spawningof A. dubius in Fortune Bay, Newfoundland. Fish. Bull., U.S. 85(3):631-641. Dow, R. 1969. Cyclic and geographic-trends in seawater temperature and abundance of American lobster. Science 164:1060-1063. 369 1972. Fluctuations in Gulf of Maine sea temperature and specific molluscan abundance. J. Cons. Int. Explor. Mer 34(3):532-534. Ennis, G. 1984. Small-scale movements of the American lobster, fomarus americanus. Trans. Amer. Fish. Soc.- Vol. 113:336-338. ., EPA, 1977. Testimony submitted in the supplementary adjudicatory hearing on remand. NPDES Permit Application No. NH 0020338.Faber, D.J. 1976. Identification of four northern blennioid fish larvae in the Canadian Atlantic Ocean.(Stichaeridae, Lumpenidae). J. Fish. Res.Bd. Canada 33(8):1798-1802. Farley, C.A., S.A. Otto, and C.L. Reinisch. 1986. New occurrence of epizootic sarcoma in Chesapeake Bay soft shell clams, Mya arenaria. K Fish. Bull.,. U.S.. 84(4):851-857. Fell, P.E., and A.M. Balsamo. 1985. Recruitment of Mytilus edulis L. in the Thames estuary, with evidence for differences in the time of maximal settling along the Connecticut shore. Estuaries 8:68-75.Flowers, J.M., and S.B. Saila. 1972. An analysis of temperature effects on the inshore lobster fishery. J. Fish. Res. Bd. Canada 29:1221-1225. Fogarty, M.J.,. and R. Lawton. 1983. An overview of larval American lobster, Ilomarus americanus, sampling programs in New England during 1974-79. pp 9-14. In M.J. Fogarty (ed.) Distribution and relative, abundance of American lobster, flomarus americanus, larvae: New England investiga-tions during 1974-1979. NOAA. Tech. Rept. NMFS SSRF-775. " Glude, John B. 1954. Survival of soft-shell clams, Mya arenaria, buried at various depths. Maine Dept. Seas & Shore. Fish. Res. Bull. 22.Gosner, K.L. 1971. Guide to identification of marine and estuarine invertebrates. John Wiley and Sons Inc., New York, NY 693 pp.1978. A Field Guide to the Atlantic seashore. Houghton Mifflin Co., Boston, MA. 329 pp.Grabe, S.A., J.W. Shipman, and W.S. Bosworth. 1983. Lobster larvae studies in New Hampshire. pp. 53-57 In M.J. Fogarty (ed.) Distribution and relative abundance of American lobster, Homarus americanus, Larvae: New England Investigations during 1974-1979. NOAA. Tech. Rept. NMFS SSRF-775.Green, J. 1969. The biology of estuarine animals. Univ. of Wash. Press, Seattle, WA. 401 pp.Green, R.H. 1979. Sampling design and statistical'methods for environmental biologists. John Wiley and Sons, N.Y. 257 pp.370 Harding, G.C., K.F. Drinkwater, and W.P. Vass. 1983. Factors influencing the size of American lobster (Jiomarus americanus) stocks along the Atlantic coast of Nova Scotia, Gulf of St. Lawrence, and Gulf of Maine: a new synthesis. Can. J. Fish. Aquat. Sci. 40:168-184. Harding, G.C., and R.W. Trites. 1988. Dispersal of Flomarus americanus larvae in the Gulf of Maine from Brown's Bank. Can. J. Fish. Aquat.Sci. 45:416-425. Hillman, R.E. 1986. -Summary report on determination of neoplasia in soft-shell clams, Mya arenaria, near the Seabrook Nuclear Plant. Batelle study no. N-0954-9901 to YAEC. 6 pp.1987. Final report on determination of neoplasia in soft-shell clams. Mya arenaria near the Seabrook Nuclear Plant. Batelle study no.N-0954-9901 to YAEC. 7 pp.Jefferies,. H.P. 1966. Partitioning of the estuarine environment by two species of Cancer. Ecology 47(3):477-481. Kendall, A.W., Jr., and N.A. Naplin. 1981. Diel-depth distribution of summer ichthyoplankton in the Middle Atlantic Bight. Fish. Bull, U.S. 79(4):705-726. Larson, B.R., R.L. Vadas, and M. Keser. 1980. Feeding and nutrition ecology of the green sea urchin, Strongylocentrotus droebachiensis in Maine, U.S.A. Mar. Biol. 59:49-62.Lund, W.A., and L.L. Stewart. 1970. Abundance and distribution of larval lobsters, ffomarus americanus, off the coast of southern New England.Proc. Natl. Shellfish. Assoc. 60:40-49.. Mann, K.H., L.C. Wright, B.E. Welsford, and E. Hatfield. 1984. Responses of the sea urchin Strongylocentrotus droebachiensis (O.F. Muller) to water-borne stimuli from potential predators and potential food algae.J. Exp. Mar. Biol. Ecol. 79:233-244. Mathieson, A.C., and E.J. Hehre. 1986. A synopsis of New Hampshire seaweeds. Rhodora 88:1-139.McCall, P.L. 1977. Community patterns and adaptive strategies of the infaunal benthos of Long Island Sound. J. Mar. Res. 35:221-266. McLeese, D., and D.G. Wilder. 1958. The activity and catchability of the lobster (ffomarus americanus) in relation to temperature. J. Fish.Res.- Bd. Canada 15:1345-1354. 371 Menge, B.A. 1978. Predation intensity in a rocky intertidal community. Relation between predator foraging activity and environmental harshness. Oecologia 34:1-16.National Climatic Data Center. 1987. Local climatological data for Boston, MA, monthly summary, January-December. Nat. Env. Satellite. Data and Info. Serv. Fed. Bldg., Asheville, NC.New Hampshire Fish and Game Department. 1974. Investigation of American lobsters (ffomarus americanus) in New Hampshire coastal waters. Project No. 3-155-R.Newell, R.I.E.,. T.J. Hilbish, R.K. Koehn, and C.J. Newell. 1982. Temporal variation in the reproductive cycle of Mytilus edulis L. (Bivalvia, Mytilidae) from localities on the east coast of the United States.Biol. Bull. 162:299-310. New England Fishery Management Council. 1983. Final environmental impact statement and regulatory impact review for the American Lobster Fishery Management Plan. March 1983.Ni, I.H. 1981a. Separation .of sharp-beaked redfish, Sebastes fasciatus and S. mentella, from northeastern Grand Bank by the morphology of extrinsic gasbladder musculature. J. Northwest Atl. Fish. Sci. 2:7-12.1981b. Numerical classification of sharp-beaked redfishes, Sebastes mentella and S. fasciatus, from northeastern Grand Bank. Can.'J. Fish. Aquat. Sci. 38(8):873-879. Normandeau Associates, Inc. 1975a. Vertical distribution and abundance of finfish in the area of the proposed Seabrook Station intake.Technical Report VI-2.1975b. Studies of American lobster (Jiomarus americanus) catches in the vicinity of Hampton Beach, New Hampshire. Technical Report VI-4..1976a. Spatial and temporal distribution of the-larvae of the soft-shelled clam, Mya arenaria, in New Hampshire coastal waters, 1975.Technical Report VI-10.1976b. Studies on the soft-shelled clam, Mya arenaria, in the Hampton-Seabrook estuary, New Hampshire. Technical Report VII-l.1977a. Studies on the soft-shelled clam, Mya arenaria, in the vicinity of Hampton-Seabrook estuary, New Hampshire. 1976 Technical Report VII-3.1977b. Seabrook Environmental Studies, 1977. Finfish ecology investigations in Hampton-Seabrook estuary and adjoining coastal waters.1975-1976 Technical Report VII-4.372 1977c. Seabrook.Environmental Studies, 1975-1976. Monitoring of plankton and related physical-chemical factors. Technical Report VII-5.* 1977d. Seabrook benthic report. Technical Report VII-6.1977e. Summary document: Assessment of anticipated impacts of construction and operation of Seabrook Station on the estuarine, coastal and offshore waters of Hampton-Seabrook,.New Hampshire. .1978a. Seabrook Ecological Studies, 1976-1977. Studies on the soft-shelled clam, Kya arenaria, in the vicinity of Hampton-Seabrook estuary, New Hampshire. Technical Report VIII-2.1978b. Seabrook Environmental Studies, 1976-1977. Monitoring of plankton and related physical-chemical factors. Technical Report VIII-3.1979a. Seabrook Environmental Studies, 1978. Finfish ecology investigations inHamptbn-Seabrook estuary and'adjoining coastal waters, 1976-1977. Technical Report VIII-.4.1979b.. Seabrook Environmental Studies, July through December 1977. Plankton. Technical Report IX-l.1979c. Seabrook Ecological Studies, July through December 1977.Finfish. Technical Report IX-2.1979d. Seabrook Ecological Studies, July through December 1977.Benthic. Technical Report IX-3.1979e. Seabrook Ecological Studies, 1976-1977. Seabrook benthic report. Technical Report VIII-5..1 979f. Soft-shell clam, Mya arenaria, study. Technical Report X-3.1980a. Seabrook Ecological Studies, January through December 1978. Finfish'ecological investigations in Hampton-Seabrook estuary and adjoining coastal waters. Technical Report X-4.1980b. SeabrookEnvironmental Studies. 1978 Seabrook benthic report. Technical Report X-7.1 1980c. Seabrook Ecological Studies, January through December 1978. Plankton.. Technical Report X-5.1980d. Annual summary report for 1978 hydrographic'studies off Hampton Beach, New Hampshire.. Preoperational ecological monitoring studies for Seabrook Station. Technical Repbrt X-2..373 1981a. Soft-shell clam; Mya arenaria, study. Technical Report XI-I.1981b. Seabrook Environmental Studies, 1979. Finfish ecology investigations in Hampton-Seabrook estuary'and adjoining coastal waters.Technical Report XI-2._1981c.. Seabrook Environmental Studies, 1980. Soft-shell clam, Mya arenaria, study. Technical Report XII-1.1981d. Seabrook plankton studies, January through December 1979. Technical Report XI-3.1981e. Seabrook Environmental Studies. 1979 Seabrook benthic report. Technical Report XI-5.1981f. Seabrook Environmental Studies. 1980 data report.Technical Report XII-2._ 1982a. Seabrook Environmental Studies. 1981 data report.Technical Report XIII-I._ 1982b. Seabrook Environmental Studies, 1981. Soft-shell' clam, Mya arenaria, study. Technical Report XIII-II..1982c. Seabrook Environmental Studies, 1981. A charac-terization of baseline conditions in Hampton-Seabrook area, 1975-1981. A preoperational study for Seabrook Station. Technical Report XIII-3.1983a. Seabrook Environmental Studies. 1982 data report.Technical Report XIV-I...1983b. Seabrook Environmental Studies, 1982. A character-ization of baseline conditions in the Hampton-Seabrook area, 1975-1982. A preoperational study for Seabrook Station. Technical Report XIV-II.1984a. Seabrook Environmental Studies. 1983 data report.Technical Report XV-1.1984b. Seabrook Environmental Studies, 1983. A charac-terization of baseline conditions in Hampton-Seabrook area, 1975-1983. A preoperational study for Seabrook Station. Technical Report XV-II.1985a.. Seabrook Environmental Studies. 1984 data report.Technical Report.XVI-i. 1985b. Seabrook'Environmental Studies, 1984. A charac-terization of baseline conditions in the Hampton-Seabrook Area, 1975-1984. Technical Report XVI-II.374 1986. Seabrook Environmental Studies. 1985 data report.1987a. Seabrook Environmental Studies. 1986 data report.1987bi Seabrook Environmental Studies. 1986. A charac-terization of baseline conditions in the Hampton-Seabrook area.1975-1986. A preoperational study for Seabrook Station. Technical Report XVIII-II..1988. Seabrook Environmental Studies; 1987 data report.Oprandy, J.J., P.W. Chang, A.D. Promovost, K.R. Cooper, R.S. Brown, and V.J.Yates. 1981. Isolation of a viral agent causing hematopoietic neoplasia in the soft-shell clam, Mya arenaria. J. Invert. Pathol.38:45-51.Perry, A.G. 1985. Impact evaluation of the increase in minimum carapace length on the New Hampshire lobster fishery. New Hampshire Fish and Game Dept.Pettibone, M.H. 1963. Marine polychaete worms of the New England region.Bull. U.S. Nat. Mus. 227(1):1-356. Podniesinski, G.S. 1986. Aspects of the early life history of the blue.mussel Mytilus edulis L. MS Thesis, Univ. Maine, 62 pp., and B.J. McAlice. 1986. Seasonality of blue mussel, Mytilus edulis L., larvae in the Damariscotta River estuary, Maine, 1969-1977. -Fish. Bull., U.S. 84:995-1001. Reinisch, C.L., A.M. Charles, and A.M. Stone. 1984. Epizootic neoplasia in soft-shell clams collected from New Bedford Harbor. Hazardous Waste 1:73-81.Richards, R.A., J.S. Cobb, and M.J. Fogarty. 1983. Effects of behavioral interactions on the catchability of American lobster, Ilomarus americanus, and two species of Cancer crab.- Fish. Bull., U.S.81(1):51-60. Robins,,C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. 1980. A list of common and scientificnames of fishes from the United States and Canada. 4th ed. Amer. Fish. Soc. Special Pub. .12. 174 pp.Ropes, J.W. 1969. The feeding habits of the green crab Carcinus maenas (L.)U.S. Fish Wildl. Serv. Fish Bull. 67:i83-203. SAS Institute, Inc. .1985a. SAS User's Guide: Statistics, version 5 edition. SAS Institute, Inc., Cary, N.C. 956 pp..1985b.. SAS User's Guide: Basics, version 5 edition. SAS'Institute, Inc., Cary, N.C. 923pp.375 Santos, S.L., and J.L. Simon. 1980. Response of soft-bottom benthos to annual catastrophic disturbance in a South Florida.estuary. Mar.Ecol. Prog. Ser.. 3(4):347-356. Sherman, K., and R.D. Lewis. .1967. Seasonal occurrence-of larval lobsters in coastal waters of central Maine.* Proc. Nat. Shellfish. Assoc.57:27-30.Sokal, R.R., and F.J. Rohlf. 1969. Biometry. W.H. Freeman and Co., San Francisco. xxi + 776 pp.South, G.R., and I. Tittley. 1986. A checklist and distributional index of the benthic marine algae of the North Atlantic Ocean. Huntsman Marine Laboratory, New Brunswick, Canada. 76 pp.Suchanek, T.H. i978. The ecology of Mytilus edulis L. in exposed rocky intertidal communities. J. Exp. Mar. Biol. Ecol. 31:105-120. Taylor, W. R. 1962. Marine algae of the northeastern coast of North America. The University of Michigan Press, Ann Arbor Press.509 pp.Watling, L. 1975. Analysis of structural variations in a shallow estuarine deposit-feeding community. J. Exp. Mar. Biol. Ecol.19:275-313., Welch, W.R. 1969. Changes in abundance of the green crab, Carcinus maenas (L.) in relation to recent temperature changes. U.S. Fish Wildl. Serv. Fish. Bull. 67:337-345. ., and L.V. Churchill, 1983. Status of green crabs in Maine.Reference Research Doc 83/21. Maine Dept. ofMarineResources.. Whitlach, R.B. 1977. Seasonal changes in the-community structure of the macrobenthos inhabiting the intertidal sand and mud flats of Barnstable Harbor, MA. Biol. Bull. 152:275-294. Witman, J.D. 1985. Refuges, biological disturbance, and rocky subtidal community structure in New England. Ecol. Monog. 55(4):421-445. 376 SEABROOK STATION 1990 ENVIRONMENTAL STUDIES INRTHE HAMPTON-SEABROOK AREA I,.A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS New Hamnpshiire ~iket NORMANDEAU ASSOCIA TES ENVIRONMENTAL CONSULTANTS SEABROOK ENVIRONMENTAL STUDIES, 1990.A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS IN THE HAMPTON-SEABROOK AREA DURING THE OPERATION OF SEABROOK STATION TECHNICAL REPORT XXII-II Prepared for PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE NEW HAMPSHIRE YANKEE DIVISION P.O. Box 700 Seabrook Station Seabrook, New Hampshire Prepared by NORMANDEAU ASSOCIATES INC.25 Nashua Road Bedford, New Hampshire 03110-5500 R-12341.03 November 1991 TABLE OF CONTENTS PAGE 1.0 EXECUTIVE

SUMMARY

... ............. ... ... .1 

1.1 INTRODUCTION

... ................... .......... ..1.2 INTAKE MONITORING ............ .......... 2 1.3 DISCHARGE MONITORING ...... ............... .... 4 1.3-.1 Discharge Plume Monitoring. ............ 4 1.3.2 Benthic Monitoring ..... ....... ......... ....... 7 1.3.3 Estuarine Monitoring. ........ ........... 8 2.0 DISCUSSION .i. ......................................... 11

2.1 INTRODUCTION

....... ............... ....i.2.1.1 General Perspective ......... .... .... 11 2.1.2 *Sources of Baseline Variability ............... 13 2.1.3 Impact Assessment ..... ...... ...... ..16 2.1.4 Sampling Location ........... ........ 18 2.2 INTAKE AREA MONITORING* ................27 2.2.1 Plankton ....................................... 27 2.2.1.1 Entrainment .......... .......... .27 2.2.1.2 Community Structure ...... .....33 2.2.1.3 Selected Species ...... ....... '41 2.2.2 Finfish ....... ....... ........ ...... 46 2.2.2.1 Impingement ............ ..46 2.2.2.2 Pelagic Species..... ...... ....... 50 2.2.2.3 Demersal Species ... ..... .......... ... 55 2.3 DISCHARGE AREA MONITORING ........ ... ........ ... 58 2.3.1 Plume Studies .................................. 58 2.3.1.1 Discharge Plume Zone ................. 58 2.3.1.2 Intertidal/Shallow Subtidal Zone .... 71 2.3.1.3 Estuarine Zone ....................... 80 iii

• PAGE 2.3.2 Benthic Monitoring

....... ....... ..91 2.3.2.1 Macroalgae and Macrofauna 91 2.3.2.2 Demersal Fish ......................... 95 2.3.2.3 Epibenthic Crustacea .. ....... .100 3.0 RESULTS ...... ............ ............. ...... 103 3. 1 PLANKTON AND WATER QUALITY PARAMETERS ..... ......... ...103 3.1.1 Water Quality Parameters-Seasonal Cycles and Trends ..... ............. .. .... ...... 103 3.1.2 Phytoplankton ..... ....... ... ........ 114 3.1.2.1 Total Community ..... ............. ...114 3.1.2.2 Selected Species .......... .... .... 128 3.1.3 Microzooplankton............................. .136 3.1.3.1 Total Community ............. ........ 136 3.1.3.2 Selected Species ......... ........ 142 3.1.4 Bivalve Larvae .... ........... .... ......155 3.1.4.1 Community Structure ............... .. 155 3.1.4.2 Selected Species: .. .. ....... .....163.3.1.5 Macrozooplankton ............. ........... 167 3..1.5.1 Community Structure ........... ... .. 167 3.1.5.2 Selected Species .... ..... ...182 3.2 FINFISH ................. ....................... ..191 3.2.1 .Ichthyoplankton ........ .........191 3.2.1.1 Community ....... .................. 191 3.2.1.2 Entrainment .......... ...208 3.2.1.3 Selected Species .... ........ .... 210 3.2.2 Adult Finfish .........227 3.2.2.1 Community ..... ..... ..... ..... 227, 3.2.2.2* Impingement .......... ............. 248.W 3.2.2.3 Selected Species ............. ....... 250 iv 0 PAGE 3.3 BENTHOS .......... .............. ...278 3.3.1 Estuarine Benthos .......... ... .... .... ... 278 3.3.1.1 Physical Environment ... ........... .. 278 3.3.1.2 Macrofauna ....... ...... ...... .. 284 3.3.2 Marine Macroalgae ....... ....... ..... ...298 3.3.2.1 Macroalgal Community ........ ...... 298 3.3.2.2 Selected Species.... ..321 3.3.3 Marine Macrofauna ............... ........ 323 3.3.3.1 Horizontal Ledge Communities (Destructive Monitoring Program) ..... ... .... .... 323 3.3.3.2 Intertidal Communities (Non-destructive Monitoring Program) ....... .......... 342 3.3.3.3 Subtidal.Fouling Community, (Bottom Panel Program) .... ...... ... ........346 3.3.3.4 Modiolus modiolus Communities (Subtidal Transect Program) ......... 348 3.3.4 Surface Fouling Panels ......................... 349 3.3.4.1 Seasonal Settlement Patterns .. ....... ..351 3.3.4.2 Patterns of Community Development ..... 369 3.3.5 Selected Benthic Species ............. 380 3.3.5.1 Mytilidae ............... .....380 3.3.5.2 Nucella lapillus ........ ........... 388 3.3.5.3 Asteriidae ...............388 3.3.5.4 Pontogeneia inermis ... ...... .. .390 3.3.5.5 Jassa marmorata.................. 391 3.3.5.6 Ampithoe rubricata ................... 392 3.3.5.17 -Strongylocentrotus droebachiensis ....393 3.3.6 Epibenthic Crustacea .......................... 394 3.3.6.1 American Lobsters (lomarus americanus) 394 3.3.6.2 Jonah Crab (Cancer borealis) and Rock Crab (Cancer irroratus) ...... 409 3.3.7ý Kya arenaria (Soft-shell Clam) ........... 415:3.3.7.1 Larvae ......... ....... ..... ... 415 0 3.3.7.2 Reproductive Patterns .......... ..... 418 v PAGE 3.3.7.3 Hampton Harbor and Regional Population Studies ......... .....418 3.3.7.4 Effects of Predation, Perturbation and Disease on Harvestable Clam Resources 427 3.3.7.5 Harvestable Clams ................. ... 436 4.0 METHODS ...... ... ..... ........ ....... ..449 4.1 GENERAL ...... ..... ..... .... ....449 4.2 COMMUNITY STRUCTURE ......... .......... .......... 451 4.2.1 Numerical Classification. ...................... 451 4.2.2 Multivariate Analysis of Variance ...... ...... 455 4.2.3 Other Community Methods ............. 456 4.3 SELECTED SPECIES/PARAMETERS .......................... 457 4.3.1 Analysis of Variance (ANOVA) I....... .... 458 4.3.2 Multiple Comparisons.. ...... ........... 466 5.0 LITERATURE CITED ............... ..... ............... 469 vi LIST OF FIGURES PAGE 2.1-1. Schematic of sources and levels of variability in Seabrook Environmental Studies .-....... .............. 14 2.1-2. Sequence of eventsq for determining if there ,are' environ-mental changes due to the operation of Seabrook Station 19 2.1-3. Plankton and water quality sampling stations. ............ 20 2.1-4. Finfish sampling stations ............................ 21 2.1-5. Benthic marine sampling stations'. ... .. ... .....23 2.1-6. Hampton-Seabrook estuary temperature/salinity, soft-shell clam tya arenaria and green crab Carcinus maenas sampling stations .................... ........ ...24 2.1-7. Locations of lobster and rock crab trapping areas ....25 2.1-8. Sampling sites for iya arenaria spat .......... .26 2.2.1. Months of occurrence and log (x+l) mean abundance (no./m 3)in preoperational years and 1990 for seasonal groups formed by numerical classification of the microzooplankton and bivalve larvae collections .. ................ 34 2.2-2. Months of occurrence and log (x+l) mean abundance (no./10003) in preoperational years and 1990 for seasonal groups formed by numerical classification of the.holo-and meroplankton and tychoplankton species of macro-zooplankton collections ................ .. 35 2.2-3. Months of occurrence and log (x+l) mean abundance (no./1000 mi 3) in preoperational years and 1990 for seasonal groups formed by numerical classification of finfish eggsand larvae ..... ......... ....... 36 2.2-4. Mean log (x+l) abundance and 95% confidence interval, and percent composition. for selected species of phytoplankton (thousands of cells/liter) and microzooplankton (no./m 3)at Station P2, 1978-1984 and 1990 ...... 43 2.2-5. Mean log (x+l) abundance and 95% confidence interval, and percent composition for selected species of bivalve larvae (no./m 3) and macrozooplankton (no./1000 m 3), 1978-1989 and 1990 at Station P2 .......... ................ ....44 vii PAGE 2.2-6. Mean log (x-l) abundance (no./1000 m 3) and 95% confidence interval, and percent composition for selected species of fish larvae 1975-1989 and 1990 at Station P2 ... ......47 2.2-7. Flow rate (million gallons per day) of circulating water system and impingement of finfish during 1990 49 2.2-8. Seasonal and annual changes in composition and abundance of the pelagic fish community, based. on catch per unit effort averaged over gill net Stations 1, G2, and G3, 1976-1989 and 1990. .................... 51 2.2-9. Mean log (x+l) abundance (catch per unit effort) and 95%confidence intervals, and percent composition for selected species of fish, 1978-1989 and 1990 ........... ...... 54 2.3-1. Monthly mean surface and bottom temperatures at nearfield Station P2, and 95% confidence intervals during preopera-tional period and in 1990, and mean monthly surface tem-perature at intake, discharge, and farfield stations ....59 2.3-2. Preoperational mean and 95% confidence limits, 1990 mean for temperature (0 C), salinity (ppt), dissolved oxygen (mg/l), and nutrients (pg/l) at Station P2 ............ 62 2.3-3. Monthly mean and 95% confidence intervals of total phyto-plankton and relative abundance of the major phytoplankton groups during the preoperational period (1978-1984) and monthly mean in 1990 with and without Colonial...Cyanophyceae. .. ....... .. ....... ...... .. ............... 64 2.3-4. Preoperational mean (1975-1989)(no./i000 m2, lobster lar-vae; catch per 15-trap effort adult lobsters and crabs)and 95% confidence limits and 1990 mean for lobsterlar-vae, adult lobsters and crabs at the discharge site ... 69 2.3-5. Seasonal patterns of settlement and growth of fouling organisms during the preoperational period and in 1990 as indicated by nbncolonial abundance, species richness, and biomass from monthly sequential panels set at discharge-Station B19 ....................................

• .*.*.*...71 2.3-6. Seasonal groups formed by numerical classification of log (x+l) noncolonial abundances from short-term surface panels from Station B19 collected from 1978-1984 and July 1986-December 1990 ...... ...... ....... ..... .73 Viii PAGE 2.3-7. Similarity and abundance or biomass of macroalgae and macrofauna species assemblages in 1990 compared to the preoperational*years

................... 75 2.3-8. Nearfield.(Sta. B1MLW & B17) annual variability (95% con-fidence limits) of log (x4-l) biomass (g/m 2).or abundance (no./m 2) and percent composition for, selected intertidal and shallow subtidal species of algae (triannual collec-tions) and benthos (August only) during the preoperational period and in 1990 ..................... 78 2.3-9. Monthly means and 95% confidence limits for seawater sur-face temperature and salinity taken at low tide in Browns River over the entire study period (May 1979-December 1990) and in 1990, and precipitation measured in Boston, MA, from 1978-1990 ........ ... 81 2.3-10. Annual geometric mean density (no./m?) and mean number of taxa per station of estuarine benthos (1978-1984; 1986-_1990), and annual mean salinity (1980-1984; 1986-1990), at Browns River...... ............ 84 2.3-11. Seasonal and annual changes in composition and abundance of the estuarine fish community, based on catch per unit effort averaged, over beach seine Stations S1, S2 and S3, during the preoperational period (1976-1984 and 198.7-1989) and in 1990 ....... ................ ........85 2.3-12. Annual log (x+l) mean density (number per square foot) of" young-of-the-year (1-5 mm), spat (13-25 mm), juvenile .(ý26-50 mm) and adult (>50 mm) Mya arenaria at Hampton-Seabrook Harbor Flat I from 1974-1990.. .............. ... 88 2.3-13. Number of adult 'clam licenses issued, the adult clam standing crop (bushels), 1971-1990, and'green crab catch in fall, 1981-1990 in Hampton-Seabrook Harbor 90 2.3-14. Preoperational mean (1978-1989) and 95% confidence limits and 1990 mean bf log (x+l) abundance (no./m 2) and percent composition for selected benthic species at mid-depth nearfield station ................. .... 94 2.3-15. Total annual and monthly catch of demersal species at, Stations Tl and T3 combined and Station T2 during the pre-operational period (1976-1989) and in 1990 ....i..... 97 ix PAGE 2.3-16. Seasonal and annual changes in relative abundance of the demersal fish community, based on mean catch per-unit effort at otter trawl Station T2 during the preoperational, period (1976-1989) and in 1990 ...... ................ 98 2.3-17. Size class distribution of'lobsters and catches of legal:,and sublegal-sized lobsters at-the discharge station, 1975-1990 ............ ............ .....102 3.1.1-1. Surface and bottom temperature (°C):at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989 and monthly means at Stations P23 P5, and P7 in 1990.: ... .......... .... ....104 3.1.1-2. Comparison of monthly averaged continuous temperature (OC)data collected at discharge (DS) and farfield (T7) sta-tions during commercial operation, August-December 1990 108 3.1.1-3. Monthly mean difference and 95% confidence limits between surface and bottom temperatures (0 C) at nearfield Station P2 over all years from 1978-1989 and monthly means in 1990 .. ........................... 109 3.1.1-4. Surface and bottom salinity (ppt) at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989, and monthly means for 1990.: ill 3.1.1-5. Surface and bottom dissolved oxygen (mg/L) at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989, and monthly means for 1990 112 3.1.1-6. Surface orthophosphate and total phosphorus (jig P/L) at nearfield Station'P2, monthly means and 95% confidence intervals over all;years from 1978-1984 and 1986-1989, and-monthly meansifor 1990 ..... 113 3.1.1-7. Surface nitrite-nitrogen-and nitrate-nitrogen (pg N/L) at nearfield Station P2, monthly means and 95% confidence intervals over all years from 1978-1984 and 1986-1989, and monthly means for 1990 ..... .... ....... .... 115 .3.1.1-8. Surface ammonia-nitrogen (pg N/L) at nearfield Station P2, monthly-means and 95% confidence-intervals over all years from 1978-1984 and 1986-1989, and monthly means for 1990 116 x PAGE 3.1.2-1. Log (x+l) abundance (no./1) of total phytoplankton at nearfield Station P2, monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means with and without colonial Cyanophyceae for 1990 ............................................. ..117 3.1.2-2. Seasonal succession of the major phytoplankton groups (percent composition) during the preoperational years (1978-1984) at nearfield Station P2 ............. ...122 3.1.2-3. Seasonal succession of the major phytoplankton groups (percent composition) during 1990, all taxa and excluding colonial Cyanophyceae at nearfield Station P2 .......124 3.1.2-4. Mean monthly chlorophyll a concentrations and 95% confi-dence intervals over all preoperational years (1978-1984) and monthly means in 1990 at nearfield StationP2 ... .129 3.1.2-5. Mean and 95% confidence intervals of weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor over all preoperational years (1978-1984) and mean levels in 1990 ....... ....... 131 3.1.2-6. Log-,(x+l) abundance (no./l) Skeletonema costatum at near-field Station P2; monthly means and 95% confidence inter-vals over all preoperational years (1978-1984) and monthly means ,for 1990. .... .... ... ....... .... .133 3.1.3-1. Dendrogram formed by numerical classification of log (x+l)transformed microzooplankton abundances (No/m 3) at Sea-brook nearfield Station P2, 1978-1984, July-December 1986, and April-December 1990 ................. 137 3.1.3-2. Seasonal groups formed by numerical classification of log (x+l) transformed microzooplankton abundances (no./m 3) at Seabrook nearfield Station P2, 1978-1984, July-December 1986, and April-December 1990 .................. .... 139 3.1.3-3. Log (x+l) abundance (no./m 3) of Eurytemora sp. cope-podites and Eurytemora herdmani adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2 ...... .... ..145 3.1.3-4". 'Log (x+l) abundance (no./m 3) of Pseudocalanus/Calanus sp.nauplii and Pseudocalanus sp. copepodites.and adults;monthly means and 95% confidence. intervals over all pre-operational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2 ..... ............. ...150 xi PAGE 3.1.3-5. Log (x+l) abundance (no./m 3) of Oithona sp. nauplil, copepodites and adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2 153 3.1.4-1. Dendrogram formed by normal classification of weekly (April-October) bivalve larvae log (x+l)-transformed abundances (no./m 3) at Seabrook nearfield Station P2, 1982-1984. and 1986-1990 ... .. .... ....... 156 3.1.4-2. Seasonal groups formed by numerical classification of log (x+l) transformed bivalve collections from -nearfield Station P2, 1982-1984 and 1986-1990.. .....157 3.1.4-3. Weekly means log (x+l) abundance (no./m 3) of bivalve larva; and 95% confidence intervals over all preopera-tional years 1978-1989 .and weekly means for 1990 at.nearfield Station P2 ................... 159 3.1.5-1. Dendrogram formed by numerical classification of collec-tions of hol0- and meroplanktonic species of macrozoo-plankton monthly mean log (x+l) transformed abundances (no./1000 mi 3) at nearfielc Station P2, 1978-1984 and 1986-1990 ..... ....... .. .....170......t .. ....3.1.5-2. Seasonal groups formed by numerical classification of log.(x+l) transformed holo- and meroplankton abundances (monthly mean) from macrozooplankton collections at nearfield Station P2, 1978-1984 and 1986-1990 .......... 171 3.1.5-3. Dendrogram formed by numerical classification of collec-tions of monthly mean log (x+l) transformed tychoplankton abundances (no./1000 mi 3) from macrozooplankton collec-tions at nearfield Station P2, 1978-1984 and 1986-1990 175 3.1.5-4. Seasonal groups formed by numerical classification of log (x+l) transformed tychoplankton abundances (monthly mean)from macrozooplankton collections at nearfield Station P2, 1978-1984-and 1986-1990 176 3.1.5-5. Log (x+l) abundance (no./1000i m 3) of Calanus finmarchicus copepodites and adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984, 1986-1989) and m6hthly means for 1990 at nearfield Station P2 184 xii PAGE 3.1.5-6. Log (x+l) abundance'(no./1000mi

3) of Carcinus maenas, larvae and Crangon septemspinosa zoeae and post larvae;monthly means and 95% confidence intervals over all preoperational years (1978-1984,'1986-1989) and monthly means for 1990 at nearfield Station P2.......

........ 187 3.1.5-7. Log (X+l) abundance (n0./1000 M 3) of Neomysis americana; monthly means and 95% confidence intervals over all preoperational years (1978-1984, 1986-1989) and monthly means for 1990 and mean percent composition of Neomysis americana lifestages over all preoperational years (1978-1984, 1986-1989) and for 1990 at'nearfield Station P2 .189 3.2.1-1. Dendrogram formed by normal classification of monthly abundances (log (x+l) transformednumber per 1000 mi 3) of fish eggs at Seabrook nearfield Stations P2 and P3, January 1976-December 1990 ............ .... 192 3.2.1-2. Temporal occurrence-pattern of seasonal assemblages of fish eggs collected at'Seabrook nearfield Stations P2 and P3 during January 1976 through December 1990 ....194 3.2.1-3.' Dendrogram formed by normal classification of monthly abundances (log (x+l) transformed number per 1000 mi 3) of fish larvae at Seabrook nearfield Stations P2 and-P3, July 1975-December 1990 .......... ........... 197 3.2.1-4. Temporal occurrence patternof seasonal assemblages of fish larvae collected at Seabrook nearfield Stations P2 and P3 during July 1975 through December 1990 ........ 199 3.2.1-5. Log (x+1):abundance (no./1000 mi 3) of American sand lance and winter flounder larvae; monthly means and 95% confi-dence intervals over all preoperational years (1975-1989) and monthly means for' 1990 at nearfield Stations P2 and P3 ......... ............. .. .... ...... 215 3.2.1-6.* Log*(x+l) abundance (no./1000 mi 3) 'of yellowtail flounder and Atlantic cod larvae; monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990"at nearfield Stations P2 and P3 220.3.2.1-7. Log (x+l) abundance (no./1000 m 3) of Atlantic mackerel and cunner larvae; monthly means and 95%,confidence intervals'over all preoperational years (1975-1989) and monthly. means for 1990 at nearfield Stations P2 and P3. 222 xiii PAGE 3.2.1-8. Log (x+l).abundance (no./1000 ,m 3) of hake and Atlantic herring larvae; monthly means .and 95% confidence intervals.over all preoperational years (,1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3 224 3.2.1-9. Log (x+l) abundance (no./1000 m 3) of pollock larvae;monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3 .. ..... ... ...... 226 3.2.2-1. Annual total catch per unit effort (number per 24-hour set'of one net, surface or bottom) in gill nets by sta-tion and mean of stations, 1976-1990 ".228 3.2.2-2. Annual total catch per unit effort (mean number per 10-.minute tow).in otter trawls by station and mean of sta-tions, 1976-1990 237 3.2.2-3. Annual total catch per-unit effort (mean number per seine haul) in beach seines, by station and mean of stations 1976-1984, 1987, 1988, 1989,. and 1990 .. ...... ....243 3.2.2-4. Number of fish impinged at Seabrook Station during 1990 for various size classes of most abundant species ....251 3.2.2-5. Log (x+l) catch per unit effort (one 24-hr. set) for Atlantic herring and pollock; monthly means and 95% t confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 averaged over.gill net Stations GI, G2 and G3 ........ ......... 253 3.2.2-6. Log (x+!) catch per unit effort (one 24-hr. set) for Atlantic.mackerel; monthly means and 95% confidence intervals over-all preoperational years (1976-1989) and monthly means for 1990 averaged over gill net Stations GI, G2 and G3 ... ... ..259 3.2.2-7. Log (X+I) catch per unit effort (one tow) for Atlantic cod; monthly 'means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations..Ti, T2, and T3 ........ 260 3.2.2-8. Log (x+l) catch per unit effort (one tow) for hakes;monthly means and 95% confidence intervals over all preoperational years (1976-1989) and-monthly means for 1990 from otter trawl Stations Tl, T2, and T3 263 .xiv PAGE 3.2. 2!9.3.2.2-10.3.2.2-11.3.2.2-12.3.2.2-13.3.2.2-14.Log (x+1) catch per unit effort (one tow) for yellowtail flounder; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from.otter-tr-awl Stations Ti, T2, and T3 ....Log (x+l) catch per unit effort (one tow) for winter flounder; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations :TI, T2, and T3 Log (x+l) catch per unit effort (one haul) for winter flounder; monthly means and 95% confidence intervals over'all preoperational years (1976-1984, 1987-1989) and monthly means. for 1990 averaged over beach seine Stations S1,5$2 and S3. .... ................. ....Log:. (x+l) catch per unit effort (one tow) for rainbow smelt; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations T1, T2, and T3 ...Log (x+1) catch per unit effort (one haul) for rainbow smelt; monthly means and 95% confidence intervals over all preoperational years (1976-1984, 1987-1989), and monthly means for 1990 averaged over beachseine Stations SI, S2 and S3 '... ...... .........Log (x+l). catch per unit effort (one haul) for Atlantic silverside; monthly means and 95% confidence intervals'- over all preoperational.years (1976-1984, 1987-1989) and monthly means for 1990 averaged over beach seine Stations , S1, S2 and S3.. .......... .... ..... .......265 266 268 270 272 273 280 283 288 3.3.1-1. Monthly-means and 95% confidence limits for precipitation

measured in Boston, MA, from 1978-1990 and surface salin-ity and temperature taken at low tide in Browns River over the entire study period (May 1979-December 1990) and in 1990 ...................

..... ........... 3.3.1-2.Total monthly outfall (millions of gallons per month)from the Seabrook Settling Basin into Browns River from October 1978 through December 1990 .....3.3.1-3. Yearly means and 95% confidence limits for the log (x+l)density (no./m 2) of macrofauna and'mean number-of taxa per 5/16 m 2 collected at subtidal estuarine stations sampled three times per year from 1978 through 1990', (excluding 1985) .................. ...xv PAGE 3.3.1-4. Yearly means and 95%*confidence limits for the log (x+l)density (no./m 2) of macrofauna and mean number of taxa per 5/16,m 2 collected at intertidal estuarine stations sampledthree times per year from 1978 through;1990 (excluding 1985). ............ ............. .... ..289, 3.3.i-5.ý Yearly means and 95% confidence limits for the. log-I(x-l),. .-density (no./m 2),of fediste diversicolorand Capitella capitata collected at subtidal estuarine stations sampled three times per year from 1978 through 1990 .......... 294 3.3.1-6. Yearly'means and 95% confidence limits-for the log.(x+l)density (no./m 2) of Hediste diversicolor and-Capitella capitata collected at intertidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985) ............................... ...295 3.3.2.1. Preoperational (through 1989) median and range and 1990 value of number of taxa collected in triannual general collections at Stations B1MSL,'BlMLW, B17, B19, B31 (1978-1990), B5MSL, B5MLW, B35 (1982-1990), and annual collections at B16 (1980-1984; 1986-1990), B13, B04 (1978-1984; 1986-1990) and (1979-1984;' 1986-1990) ...299 3.3.2-2. Mean number of taxa (per 1/16ým 2), total-biomass. (g/m?)and 95% confidence limits of macroalgae collected at intertidal and subtidal stations during the preopera-. tional period (see Figure 3.2.2-1 for.years sampled) and in 1990 .......... .. .. ...... 301*3.3.2-3. Annual mean biomass (gim 2) and 95% confidence limits for macroalgae collected in August at selected nearfLeld benthic stations .... ...... ................ ........ 305 3.3.2-4. Relative abundance (% biomass) of dominant macroalgae at marine benthic stations in August for. the preoperational. period (see Figure 3.3.2.lfor dates) and 1990 ..... .. 307 3.3.2-5., Dendrogram formed by numerical classification of August collections of marine benthic algae, 1978-1990... .....310"'.3.3.2-6. Preoperational means and 95% confidence limits of abun-dance of kelps (no./100 m 2), (B17: 1978-1989; B35: 1982-1989).and percent frequencies and 95% confidence limits of dominant understory algae (B17: 1981-1989; B35: 1982-1989) and 1990-means, collected triannually in the shal-low and mid-depth subtidal zones .. ... ..... .315*xvi PAGE 3.3.2-7. Mean percent frequency and 95% confidence limits of fucoid algae at two fixed transect sites in the mean sea level zone for the preoperational period (1983-1989) and mean percent frequency in 1990.. ........ .. .... 320 3.3.2-8. Annual mean abundance (no./100 mi 2) and 95% confidence interval for Laminaria saccharina at Station B17 (1979-1990) and B35 (1982-1990).................322 3.3.2-9. Annual mean biomass (g/m 2) and 95% confidence intervals of Chondrus crispus collected in May, August and November at Stations BlMLW, B17: 1978-1990; B5MLW, B35: 1982-1990 324 3.3.2-10. Mean biomass (g/m 2)4and 95% confidence limits of Chondrus crispus at selected stations in May, August and November.Stations B1MLW, B17: 1978-1989 and 1990; Stations B5MLW, B35: 1982-1989 and 1990 ........ ..... .....326 3.3.3-1. Mean number of taxa (per 1/16 m 2) and log (x+l) mean density (no./m 2) and 95% confidence limits of macrofauna collected in August during the preoperational period (1978-1989) and in 1990 at intertidal and subtidal ben-thic stations ............. ........ ........ 328 3.3.3-2. Annual mean number of noncolonial macrofaunal taxa (per 1/16 m2) collected in August at intertidal Stations B1MLW and B5MLW and shallow subtidal Stations B17 and B35 from 1978-1990 .... ........ .......... ........... .331 3.3.3-3. Annual means and 95% confidence limits for the log (x+l)density (no./mW) of macrofauna collected in August at nearfield Stations B1MLW (intertidal) and B17 (shallow subtidal) from 1978-1990 .................. 332 3.3.3-4. Annual mean number of noncolonial macrofaunal taxa (per 1/16m 2) collected in August at mid-depth Stations B16, B19, and B31 and deep Stations B04, B13 and B34 from 1978-1990 ............. ....... .....335 3.3.3-5. Annual means and 95% confidence limits for the log (x+l)density (no./m 2) of macrofauna collected in August at nearfield Stations B19 and B16 (mid-depth and'B04 (deep)from 1978-1990.... ..... ... .... ........ 336 3.3.3-6. Dendrogram of normal classification of annual macrofaunal log (x+l) densities (no./m 2) taken in August at all near-field and farfield stations from 1978-1990 ........ .340 xvii PAGE 3.3.3-7. Annual mean density (no. per 0.25 square meter) and 95%confidence interval of:Modiolus modiolus observed by divers triannually at subtidal transect stations.from 1980-1990 ....... "... .... ...350 3.3.4-1. Faunal richness (number of noncolonial faunal taxa on two replicate panels) in 1990 compared to mean faunal rich-ness and 95% confidence limits ofi.short term panels during-preoperational period (B19, B31, and B04 from 1978-1984 and July 1986-1989 and B34 from 1982-1984 and July.1986-1989)................ ............. 352 3.3.4-2. Log (x+l) abundance (no./panel) in 1990 compared to mean log (x+l) abundance and 95%,confidence limitslin 1990 and preoperational period (1978-1984 and July 1986-1989, B34 initiated in.1982) for noncolonial fauna on short term panels.. ...... .. ..35............357 3.3.4-3. Biomass (g/panel) in 1990 compared to mean biomass and 95% confidence limits at Stations B04, B19, and B31 from 1980-1984 and:July.1986-1989 and B34 from 1982-1984 and July 1986-1989 on short-term panels .......... .... ..359 3.3.4-4. Dendrogram formed by numerical classification of noncolo--nial organisms collected from monthly short-term surface fouling panels set at nearfield Station B19, 1978-1984 and 1986-1990 ...... ........................ 362 3.3.4-5. Seasonal groups formed by numerical classification of log (X+l) noncolonial abundances from short-term surface panels from Station B19 collected from.1978-1984 and July 1986-December. 1990. 363 3.3.4-6. Log abundance (no. per panel) or monthly mean percent frequency of Mytilidae, Jassa marmorata, Balanus sp. and Tubularia sp. on short-term surface panels at Stations B04 and B19 in 1990 compared to mean abundance or percent frequency and 95% confidence limits during the preopera-tional period (1982-1984 and July 1986-December 1989) 366 3.3.4-7. Biomass (g/panel) in 1990 compared to mean biomass and 95% confidence during thepreoperational period (Stations B04, B19, and B31 from December 1978-1984 and July 1986-1989 and B34 from 1982-1984 and July 1986-1989) on monthly-sequential panels .. .*.............370 xviii - PAGE 3.3.4-8. Monthly mean percent frequency-or log transformed abun-dance (no. per panel) on monthly sequential surface panels for Mytilidae, Jassa marmorata, Balanus'sp. Tubularia sp. and Laminaria sp. at Stations B04 and B19 in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1984 and July 1986-ýDecember 1989) .. .. .. .... ...... ... ... 374 3.3.4-9. Mean length of Mytilidae and Jassa marmorata collected form monthly sequential surface panels in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1989) ..... ... ... ..... ..... 378 3.3.5-1. Yearly means and 95% confidence limits for the log (x+il)density (no./m 2) of Asteriidae and Mytilidae from Sta-tions B17 and B35 sampled three times per year from 1978 through 1990 .... ........ .. ........... .... 386 3.3.5-2. Mean length of Mytilidae and Jassa marmorata collected from monthly sequential surface panels in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1989) ....... ....... ... ......389 3.3.6-1. Weekly mean long (x+l) density (no./1000 m 2) o f lobster larvae at Station P2 in 1990 compared to all years' mean and 95% confidence interval during the preoperational period (1978-1989).... ................ .....397 3.3.6-2. Comparisons of legal and'sub-legal sized catch of flomnarus americanus at the discharge site, Station Ll, 1975-19901. 406 3.3.6-3. Size-class distribution (carapace length) of Ilomarus americanus at the discharge site, *Station Li, 1975-1990 .407 3.3.6-4. Summary of female lobster catch data at the discharge site, Station L1, 1974-1990 ........... .......... .. 408 3.3.6-5. Monthly mean log (x+l) density and 95% confidence inter-vals (no./1000 m 3) of Cancer spp. larvae at Station P2, 1978-1989' and monthly mean for 1990 410 3.3.7-1. Weekly.log (x+l) density (no. per cubic meter) of Mya arenaria larvae at Station P2 in 1990, compared to all years' mean and 95% confidence interval during the pre-operational period (1978-1989) .............. 416 xix PAGE 3.3.7-2. Annual log (x+l) mean density (number per square foot) of young-of-the-year (1-5 mm), spat (13-25 mm), juvenile (26-50.mm), and adult (>50 mm) Mya arenaria at Hampton-Seabrook Harbor Flat 1 from 1974-1990. .......... 3.3.7-3. Annual log (x+l) mean density (number per square foot)and 95% confidence limits of young-of-the-yearMya arenaria spat (1-5 mm) at Hampton-Seabrook Harbor,.1974-1990. ....... ........ .. .............3.3.7-4. Mean and 95% confidence limits of Mya arenaria spat (shell length <12 mm) densities (no/ft 2) at two northern New England estuaries, 1976 through 1984 and 1986 through 1990 ... ... ...... .... ..420 421*423 I 3.3.7-5. Means and 95% confidence limits of Mya juvenile and adult log (x+l) densities ton-Seabrook Harbor, 1974 through 1990 3.3.7-6. Means and 95% confidence limits of iya juvenile and adult log (x+l) densities ton-Seabrook Harbor, 1974 through 1990 arenaria spat, at Flat 1, Hamp-arenaria spat, at Flat 2, Hamp-424*1 3.3.7-7. Means and 95% confidence limits of Pya arenaria spat, juvenile and adult log (x+l) densities at Flat 4, Hampton-Seabrook Harbor, 19.74 through 1990 3.3.7-8. Monthly means and catch per-unit effort [log (x+l)] and 95% confidence intervals for total green crabs (Carcinus maenas) and ovigerous green crabs collected at estuarine stations from preoperational years (1983-1989) compared to monthly means in 1990 ......... ..3.3.7-9. Fall (October-December) mean catch per unit effort for green crabs (Carcinus maenas) in Hampton-Seabrook Harbor and its relationship to minimum winteritemperature, 1978-1990 ............. ...... ............. 425 426 429 I 3.3.7-10.Number of adult clam licenses issued and the estimated adult clam standing crop (bushels), in Hampton-Seabrook Harbor, 1971-1990 ....... .............. .... ......430 435 xx LIST OF TABLES PAGE 2.1-1. Number of Days of Operation and Average Daily Flow of Seabrook Station Circulating Water System in 1990. ...17 2.1-2. Summary of Biological Communities and Taxa Monitored for Each Potential Impact Type. ......... ..... 16 2.1-3. Benthic Algae and Macrofauna Station Locations and Descriptions ....... ......... .............. 22 2.2-1. Comparison'of Geometric Mean Abundances of Top-Ranked Fish Egg, Fish Larvae, and Bivalve Larvae Taxa Collected Offshore at Station P2 and in Entrainment Samples at Seabrook Station from June through December 1990 ........ 29 2.2-2. Estimated Number of Bivalve Larvae (in billions/month) Entrained by the Cooling Water System at Seabrook Station During June-October 1990 ....................... 31 2.2-3. Monthly Estimated Numbers of Fish Eggs and Larvae (in millions') Entrained by the Cooling Water System at Sea-brook Station During June-December 1990 32 2.2-4. Summary of Nearfield/Farfield (P2, P5 vs. P7) Spatial Differences in Plankton Communities and Selected Species in 1990 .............. ...... ....... .38 2.2-5. Comparison' of 1990 Abundances of Selected Microzooplankton, Bivalve Larvae, Macrozooplankton and Ichthyoplankton Larvae, Taxa ' .... .45 2.2-6. Comparison of 1990 Abundances of Selected Pelagic Finfish Species .... ..... .... .............. ..... .52 2.2-7. Catch Per Unit Effort by Depth for the Dominant Gill Net Species Over "All Stations and Dates When Surface Mid7 Depth and Bottom Nets were Sampled, Preoperational Years (1980 through 1989) and 1990 ................ 56 2.3-1. Monthly Mean Temperatures (°C) and Temperature Differ-ences Between Discharge (DS) and Farfield (T7) at the Suface, and Nearfield (ID) and Farfield (T7) Stations at Surface, Mid-Depth (8.5,m) and Bottom (16.2 m) Depths-'Collected from Continuously Monitored Temperature Sensors ..... ..... ...... .............. .... .. 61 xxi PAGE 2.3-2. Summary of Differences in Community Parameters Measured at Intertidal, Shallow Subtidal, Mid-Depth,-and Deep Benthic Stations and in the Surface Fouling Community. 72 2.3-3. Selected Benthic Species and Rationale for Selection 77 2.3-4. Comparison of 1990 Abundances or Biomass Levels of Selected Intertidal and Shallow Subtidal Macroalgae and'Macrofaunal Taxa ......... ........79 2.3-5. Summary of Similarities of Abundances of Selected Taxa in Mid-Depth Regions in 1990 Compared with Previous Years 94 3.1.1.1. Annual Means and Coefficients of Variation for Water Quality Parameters Measured During Plankton Cruises at Nearfield Station P2, 1978-1990. Seabrook Operational Report, 1990..... ... ....... ...... .... ...... 106.3.1.1.2.: Results of Analysis of Variance of Water Temperatures Compared Among Stations P2, P5, and P7 in 1990 and Among Years at Station P2. From 1978-1990 'and Comparisons of Salinity, Dissolved Oxygen and Nutrients Among Stations in 1990 ..... ... ..... .... ... ...... .....107 3.1.2-1. Percent Composition of Species by Year for Phytoplankton Data. Data is Subset for 1990 Operational Period August-December .......... .... ......... ....... .... ....119 3.1.2-2. Preoperational and Operational Geometric Mean Abundance and Confidence Interval for Phytoplankton Taxa Occurring Between August and December at Station P2 ..... ........ 120 3.1.2-73. Relative Abundance (%) of Phytoplankton Species Occurring in Frequencies of 1% or Greater During August-December of the Preoperational Years (1978-1986) and 1990. Seabrook Operational Report, '1990 .... ........ ..... .. 126 3.1.2-4. Results~of Multivariate Analysis of Variance (MANOVA)Comparing Phytoplankton Community Structure at Stations P2, P5 and Station P7 During 1990.... ..... ....127'3.1.2-5. Correlation Coefficients for.Chlorophyll a Concentrations.at Stations P2, P5, and P7 in 1990 .......... .... ... 130 3.1.2-6. Peak Fall Abundances of Skeletonema costatum in Surface Waters at the Nearfield Station P2 During Preoperational, Years (1978-1984, 1986) and 1990 ..... .. ...134 xxii PAGE 3.1.2-7. Results of Analysis of Variance Comparing Nearfield (Sta-tions P2 and P5) and Farfield (Station P7) Skeletonema costatum Abundances During Preoperational Years.(1978-1986) and 1990 and Stations P2, P5 and P7 During 1990. 135 3.1.3-1. Geometric Means of Microzooplankton Abundance (No./m 3), 95%Confidence Limits,'and Number of Samples for Dominant Taxa Occurring in Seasonal Cluster Groups Identified by Numerical Classification of Collections at Nearfield Station P2, 1978-1985, July-December 1986, and April-December 1990. .138 3.1.3-2. Results of Multivariate Analysis of Variance Comparing Microzooplankton Community Structure at Stations P2, P5, and P7 in 1990 ...... .... ..... ............... .... 143 3.1.3-3. Geometric Mean (No/im 3) by Year, Preoperational Mean and 95% Confidence Limits and Operational Year Mean (1990) of Selected Microzooplankton Species at Station P2 (April-December). ........... ..... ........ ....... 146 3.1.3-4. Results of the Two-Way Analysis of Variance of Log (x+l)Transformed Density (No/m 3) Among Preoperational Years (1982-1984 & 1986) and Operational Year (1990), Area (Nearfieldvs. Farfield) and Their Interactions for Selected Microzooplankton Species. .......... .148.3.1.4-1. Geometric Mean Abundance (No/mi 3), 95%'Confidence Limits of Dominant Taxa, and Number of Samples Occurring in Seasonal Groups Formed by Numerical Classification of Bivalve Larvae Collections at Nearfield Station P2, 1982-1984 and 1986-1989 in Comparison to 1990 ............. 158 3.1.4-2. Results of Multivariate Analysis of Variance (MANOVA)Comparing Bivalve Larvae Community Structure at Stations P1, P2, P5 and P7, April-October 1990.. .............. 162 3.1.4-3. Monthly Geometric Mean of Density (no. per cubic meter)of Bivalve Larvae from Entrainment and Offshore (P2)Collections During June-December ............ 164 3.1.4-4. Estimated Number ofBivalve Larvae (in billions/month) Entrained by the Cooling Water System at Seabrook Station During June-October 1990 ........... ...... .165 3.1.4-5. Results of Analysis of Variance Comparing Nearfield (Sta-tions P2 and P5) and Farfield (Station P7) Weekly Mytilus edulis Abundances During Preoperational (1978-198.9) and Operational (1990) Periods ... ..... ................. 168 xxiii PAGE 3.1.5-1. Geometric Mean Abundance (No/1000 mi 3) and 95% Confidence Limits of Dominant Holo- and Meroplanktonic Taxa Occur-ring in Seasonal Groups Formed by Numerical Classifica-w tion of Macrozooplankton Collections (.monthly means) at Nearfield Station P2, 1978-1984 and 1986-1990 ..... 172 3.1.5-2. Geometric Mean Abundance (No/1000 m 3) and 95% Confidence Limits of Dominant Tychoplanktonic Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections (monthly means) at Nearfield Station P2,, 1978-1984 and 1986-1990. ... ........... .177 3.1.5-3.- Results of Multivariate Analysis of Variance Comparing Macrozooplankton Community. Structure at Stations P2, P5 and P7 in 1990. .......... .. .........181 3.1.5-4. Annual Geometric Mean Abundance (No/1000 M 3) and Upper and Lower 95% Confidence Limits of Selected Species of Macrozooplankton at Seabrook Nearfield Station P2 During Preoperational Years (1978-1984 and 1987-1989) and Geo-metric Mean Abundance in 1990. ... ........ .. 183 3.1.5-5. Results of Analysis of Variance Comparing Nearfield (Sta-tions P2 and P5) and Farfield (Station P7) Abundances of Selected Species of Macrozooplankton During Preopera-tional (1978-1989) and Operational (1990) Periods. 185 .3.2.1-1. Faunal Characterization of Seasonal Groups Formed by Numerical Classification of Samples of Fish Eggs Collect-ed at Seabrook Nearfield Stations P2 and P3 During Janu-ary 1976 Through December 1990. ........ .... ...... .193 3.2.1-2. Faunal Characterization of Seasonal Groups Formed by Numerical Classification of Samples of Fish Larvae Col-lected at Seabrook Nearfield Stations P2 and P3 During July 1975 Through December 1990. .......... ...198 3.2.1-3. Comparison of Percent Abundance and Percent. Frequency of Fish Egg Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During January -December 1990 203 3.2.1-4. Comparison of Percent Abundance and Percent Frequency of Fish Egg Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During the First Five Months of Commercial Operation (August-December 1990) ........204 3.2.1-5.. Results of Multivariate Analysis of Variance Tests for Difference Among Stations in Communities of Fish Eggs and Larvae During Preoperational and Operational Periods in 1990 .. ..................... ............ ... 205 xxiv PAGE 3.2.1-6. Comparison of Percent Abundance and Percent Frequency of Fish Larvae Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During January-December 1990 206 3.2.1-7.Comparison of Percent Abundance and Percent Frequency of Fish Larvae Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During~the First Five Months of, Commercial Operation (August-December, 1990)3.2.1-8. Monthly Geometric Mean of Density (per 1000 cubic meters)of Entrained Fish Eggs from Entrainment and Offshore (P2)Collections During June-December 1990 ..... .......... 3.2.1-9. Monthly Geometric Mean of Density (per 1000 cubic meters)of Entrained Fish Larvae from Entrainment and Offshore (P2) Collections During June-December 1990 .......207 209 211 3.2.1-10.3.2.1-11.3.2. i-12.3.2.1-13.Monthly Estimated Numbers of Fish Eggs (in millions)Entrained by the Cooling Water System at Seabrook. Station During June-December 1990......... .......... ....Monthly Estimated Numbers of Fish Larvae (in millions)Entrained by theCooling Water System at Seabrook.Station During June-December 1990 ... .....Geometric Mean of Season of Peak Abundance (number per 1000 m 3) by Year, Preoperational Mean (Preop.), and Operational Year (1990) of Selected Fish Species Larvae at Station P2' July 1975 Through December 1990 Results of Analysis of Variance of Log (x l) Transformed Abundances (no/1000 m 3) of Selected Species of Ichthyo-plankton Larvae During Months of Peak Abundance for the.Years 1982-1984, 1986-1990 .......... ..212 213 216 218 229 232 234 3.2.2-1 Percent Composition by Year, All.Preoperational Years Combined, and 1990 for the Ten Most Abundant Species in Gill Net Samples fromi 1976 Through 1990 at Stations Gl, G2, and G3 Combined. ..... ............. 3.2.2-2. Percent Composition by Station of Abundant Species Col-lected in Gill Nets, AllPreoperational Years (1976-1989) and 1990, Depths Combined ... .... .. .... ........3.2.2-3. Percent Composition of Dominant Gill Net Species Accord-ing to D epth:(surface and off-bottom), All Preoperational Years Combined (1976-1989) and 1990 .... ... .......... xxv PAGE 3.2.2-4. Catch Per Unit Effort by Depth for the Dominant Gill Net Species Over All Stations and Dates When Surface.Mid-Depth and Bottom Nets Were Sampled, Preoperational Years (1980 through 1989) and 1990... ........... 3.2.2-5. Percent Composition by Year, All Preoperational Years Combined, and 1990 for the Twelve Most Abundant Taxa in Otter Trawls, 1976 Through 1990 at Stations Tl, T2 and T3 Combined ................... ............. 3.2.2-6. Percent Composition by Station of Abundant Species Col-lected in Otter Trawls, All Preoperational Years Combined (1976-1989) and 1990 .236 3.2.2-7.Percent Composition by Year, AlllPreoperational Years Combined, and 1990 for the Ten Most Abundant Species Collected in Beach Seines (excluding 1985 and 1986) at Stations SI, S2 and S3 Combined,......... 239 242 245 247 249 3.2.2-8. Mean Percent Composition By Station of Abundant Species Collected in Beach Seines Over All Preoperational Years Combined (1976-1984, 1987-1989) and in 1990, April, Through November. ..... .3.2.2-9. Number of Fish Impinged at the Seabrook Station by Month and Species During 1990. ..................... 3.2.2-10.3.2.2-11.3. 2.2-12.3.2.2-13.Annual Geometric Mean CPUE for Selected Finfish Species for the Preoperational Period (1976-1989), Their Confi-dence Limits, and 1990 Data ...... ..... ... ....Results of Analysis of Variance Between Preoperational Years (1976-1989).and 1990 for Selected Finfish Species at All Gill Net Stations Combined.............. ....Results of Two-Way Analysis of Variance Among Stations (Ti, T2, and T3), Preoperational (1976-1989) and Opera-tional (1990) Year and Their Interactions of Log (x+l)Transformed Catch Per Unit Effort For Selected Finfish From Otter Trawls ................... .Results of One-way Analysis of Variance Between Preopera-tional Years (1976-1989) and the Operational Year (1990)for Selected Finfish Species for All Beach Seine Stations Combined-...

• .. -.....................

254 257 262 269 279 3.3.1-1. Total Precipitation (water equivalent in inches) by Month and Year Taken at Logan International Airport, Boston, MA From January 1978,- December 1990 and 30-year Normals .xxvi PAGE 3.3.1-2. Mean Number of Taxa and the Geometric Mean (No./m 2)Density for Each Year and Overall.Years With 95% Confi-dence Limits From Estuarine Stations at Browns River (3)and Mill Creek (9)'Sampled From 1978 Through 1990 (ex-cluding 1985)... ...... .... ...... ......... 285 3.3.1-3. Results of One-Way Analysis of Variance Among Years for the Mean Number of Taxa (per 5/16 m 2) and Log (x+l)Transformed Density (No.,/mz) of the Most Abundant Estua-rine Species and the Total Density of Macrofauna Collect-ed at Estuarine Stations From 1978 Through 1990 (exclud-in 195 290.ing 1985)........"........."' .".."..................29 3.3.2-1ý Results of Analysis of Variance of Number of Taxa (per 1/16 m 2) and Total Biomass (g per mi 2) of Macroalgae Collected in August at Intertidal, Shallow Subtidal, and Deep Stations Pairs, -1978-1990 ............. .....303 3.3.2-2. Summary~of Spatial Associations Identified From Numerical Classification (1978-1990),of Benthic Macroalgae Samples Collected in August .. ... ...... ..... ... 311 3.3.2-3. Results of Nonparametric One-Way ANOVA.Comparing Numbers of Four Kelp Species-and Percent Frequencies of Three Understory Algae Taxa in 1990 (October only and all months) to Values From 1981-1989. ... ...... .......... 316 3.3.2-4. Results of Analysis of:Variance of Chondrus crispus Biomass (g/m 2) Comparing Collections in 1990 at Intertid-al and Shallow Subtidal Station Pairs With Biomass. From 1978-1989 ..... ......." .....................

• .325 3.3.3-1. Results of Analysis of Variance of Number of Taxa (per 1/16mz) iand Total Density .(per m 2) of Macrofauna Col-lected in August at Intertidal, Shallow Subtidal, and Deep Station Groups, 1978-1990

......... ........... .. 329 3.3.3-2. Station Groups Formed by Cluster Analysis With Preopera-tional and Operational (1990) Geometric Mean Density +/-95%CI for-Abundant Macrofaunal Taxa (noncolonial) Collected Annually in August From 1978 Through 1990 ........ 338 3.3.3-3. Median and Range of Percent Frequencies of the Dominant Fauna at BareRock, Fucoid Ledge, and Chondrus Zone Intertidal Sites at Stations Bi (Outer Sunk Rocks) and B5 (Rye Ledge) Monitored.Nondestructively From 1982-1989 (Preop) and 1990 ................ 344.xxvii PAGE 3.3.3-4.. Estimated Density (per 1/4 m 2) after Four Months' Expo-sure of Selected Sessile Taxa on Hard-Substrate Bottom*Panels at Stations B19 and B31 Sampled Triannually (April, August, December) From 1981-1989 and in.1990 347 3.3.4-1. Results of Analysis of Variance Comparing'Monthly Number.of Taxa, Noncolonial Abundance, Total Biomass, and Se-lected Species Abundance of Percent Frequency on Short Term Panels at Mid-Depth (B19, B31) and"Deep (B04, B34)Stati6nPairs From 1978-1990 ...-. ....-... ....353 3.3.4-2. Annual 'Geometric Mean Abundance and Overall. Geometric Mean and 95% Confidence Limits for Mytilidae Spat.and Jassa marmorata Collected Monthly on Short-Term Panels'From 1978-1989 and in 1990 (excluding 1985 and January-June 1986) ... .. .. ....... ...... ......... 360.3.3.4-3. Geometric Mean Abundance (No./panel) and 95%.Confidence.Limits of Dominant Noncolonial Taxa Occurring in Seasonal Groups 'Formed by Numerical Classification of.Monthly ' Short-Term Surface Panels Set at Discharge Station B19 From 1978-1990. ........ ..... ..... .. ......364 3.3.4-4. ANOVA Results Comparing Monthly Sequential Biomass. at*Mid-Depth (B19, B31) and Deep (B04, _B34.) Station Pairs From".1978-1990 ... ... ..... ........ ..... 371 3.3.4-5. Annual Mean and Overall Mean Dry Weight Biomass, Noncolo.-nial Number of Taxa,' Abundance, and Laminaria sp.. Counts Sonsurface Fouling Paneis"Submerged for. One Year at Stations B19, B31, B04, and B34 During the Preoperational Period (1982-1984 and 1986-1989) and in 1990* ... ....373 3.3.5-1. Annual Geometric Mean Density (N6./m 2) of Selected Ben-, thic Species Sampled Triannually in May, August, and November From 1978 Through 1990 .. .... ... .....382 3.3.5-2. Results of Two-Way Analyses of Variance Comparing Log-Transformed Densities of Selected Benthic Species at Near-_ and FarfieldStation Pairs (lMLW/5MLW, B17/B35,'".B19/B31) During Preoperational (through 1989) and Opera-tional (1990) Periods .......... ....383 3.3.5-3. Annual Mean Length (mm) and 95% Confidence Interval for.Selected Benthic Species Sampled Triannually ,in May, August, and November"at Selected Benthic Stations From 1982 Through 1990.. ........ .e .....".. .. ........ 387 xxviii PAGE 3.3.6-1. Number, Percent Composition and Mean Density of Lobster Larvae by Lifestage at Stations P2, P5 and P7, 1978-1990 395 3.3.6-2. Results of Analysis of Variance Comparing'Densities of Lobster Larvae Collected at Intake, Discharge, and Farfield Stations, and Catches of Total and Legal Sized Lobsters, Jonah Crab, and Rock Crab at the Discharge Station and Rye Ledge ... ........ ....... .......... 399 3.3.6-3. Monthly, Annual, and Preoperational Mean and Upper and Lower 95% Confidence-Limits of Total and Legal-Size .,Lobster Catch Per Trip Effort at the Discharge Site From 1975-1990 ........ ................ 403 3.3.6-4. Comparison of Catch Per Unit Effort of Jonah Crab and Rock Crab at the Discharge Site and Rye Ledge,: 1982-1989 and 1990 .....*.*.*.*.. .. ... .. ..... .... 411 3.3.6-5. Annual and Monthly Mean Catch Per Unit Effort and-95%Confidence Intervals of Jonah and Rock Crab Females and Ovigerous Females at the Discharge Site From 1982-1989 and 1990 ..... ." " ." " " ...." " " ......... 414 3.3.7-1. Results of Analysis of Variance Comparing Mya Arenaria Larval,- Spat, Juvenile and Adult Abundances During Preoperational and Operational Periods .......... .417.3.3.7-2. EstimatedDistribution (percent of total) of Clam Diggers by Flat at Hampton Harbor, Spring 1980 Through Fall 1990 433 3.3.7-3. Summary of Standing Crop Estimates of Adult Mya arenaria in Hampton Harbor, 1967 Through 1990 437 3.3.7-4. Distribution (percent of total standing crop) of Harvest-able Clams by Flat at Hampton Harbor, 1979- Through 1990 441 4.2-1. Summary of Communities and Methods Used in Numerical Classification .............. ..... ............. .. 452 4.2-2. Summary of Communities and Methods Used in Multivariate Analysis of Variance .... ...... ..... ......... .. 454 4.3-1. Selected Taxa and Parameters Used in Analysis of Variance or Nonparametric Analogue ......... ....... ..... .460 xxix LIST OF APPENDIX TABLES PAGE 3.2.1-1. Finfish Species Composition by Life Stage-and Gear, July 1975-December 1990 ........ ..........274 3.3.1-1 Mean Monthly Seawater Surface Temperature (0 C) and Salin-ity (ppt) Taken in Browns River and Hampton Harbor at-High and Low Tide, May 1979-December 1990 ......... 440 3.3.1-2 Annual Mean With 95% CL for Temperature (°C) and Salinity (ppt) Taken at Both High. and Low Slack Tide From Browns River and Hampton Harbor From 1980-1990 ............... .441 3.3.2-1. A Comparison of.Sparsely Occurring Macroalgae Taxa in August Benthic Destructive Samples, 1978-1989 and 1990 442 3.3.2-2.* Median and Range of Percent Cover and Percent Frequency of Perennial and Annual MacrOalgae Species per 0.25 m 2 at Fixed Intertidal Non-Destructive Sites During the Pre-operational Period (1982-1989) and in 1990 ... ...... ... 443Summary of Mya arenaria Population Densities from Annual Fall Surveys in Hampton-Seabrook Harbor, 1971 Through 1990 ............ .... ........ ........... 445 xxx.

1.0 EXECUTIVE

SUMMARY

1.1 INTRODUCTION

Seabrook Environimental Studies began in 1969 to monitor the balanced indigenous marine communities in preparation for assessing the effects of Seabrook Station Operation. Plant operation began on July 23, 1990. Seabrook Station operated at full power intermittently in August, for 2-3 weeks/month from September-November, then continuously in December.The purpose of this first operational report is to document the impact of operation, .if any, on the balanced indigenous population of shellfish, fish, and wildlife in the waters in and around Seabrook Station's intake and discharge. The optimal design of an impact assess-ment study ensures that a potential-impact is delineated from naturally-occurring variability. The Seabrook Monitoring Program accomplishes this by (1) collecting data before and during operation to provide a"temporal" reference, and by (2) monitoring area of potential impact as well as areas outside the influence of the thermal plume to provide a"spatial." reference. In each biological community, the experimental design of the monitoring program focuses on its most variable aspect. For example, the species distributions of plankton and pelagic fish change radically from season to season, but are generally similar within the study area.The sampling program collected data at least monthly to monitor seasonal trends in abundance at a nearfield and farfield area. For benthic macrofauna and macroalgae, seasonality tends to be less of an issue in comparison to the marked changes in species composition with depth and substrate. Benthic collections were made in the predominant substrate type, horizontal hard bottom ledge, along nearfield and farfield transects at regular depth intervals.. The Americanjlobster, soft-shell clam, and certain fish are of particular concern because of their commercial or recreational importance. Data on all life stages of these species were collected.. 1 Evaluation of the potential for impacts from Seabrook Station took place in a systematic stepwise fashion. Information collected during 1990, particularly during the operational period.(August-Decem-ber) was compared to the historical data base. Potential operational effects could be ruled out if any of the following criteria were met: 1) Biological patterns observed in 1990 were similar to-previous years at the nearfieldstations.

2) Biological trends in 1990 differed from previous years, but were consistent in both.nearfield and farfield areas, suggesting an area-wide phenomenon.

The evaluation of potential impacts focuses on the most likely source (intake, discharge).

1.2 INTAKE

MONITORING The goal of intake monitoring is to demonstrate that entrain-ment and impingement have not had an adverse effect on the biota.Seabrook Station employs a midwater intake, located 5 m above the bottom in 17 m of water. Zooplankton, ichthyoplankton, and finfish would be the organisms with the greatest potential for entrainment and impinge-ment. Year-to-year variability of organisms, along with their seasonal fluctuations, and location in the water column'affect the number of entrained/impinged'organisms.. In-plant collection of entrained ichthyoplankton and bivalve larvae allows an estimation of the number of these groups that are entrained. Species composition of the entrained fish and bivalve larvae was similar to that collected in offshore tows. Numbers of entrained. fish eggs and larvae were lower than would be expected based on esti-mates.from offshore samples; certain taxa may, avoid entrainment based on their preferred location in the water column.2 Entrainment has had no demonstratable effect on the plankton communities at the intake station. Macrozooplankton, bivalve larvae, and ichthyoplankton egg and larvae communities at the intake station were similar to previous years in terms of species composition and abundance'. Species composition, of the microzooplankton community from mid-September to December in 1990 was unusual *in comparison to collec-tions made from 1978-84 and 1986, when microzooplankton were last collected. However, community composition Was similar; at all three sta-tions, suggesting.that this difference was not restricted to the nearfield area. Similarly, community composition in 1.990 of holo- and meroplankton, and bivalve and ichthyoplankton larvae was statistically similar at the intake, discharge, and farfield areas. Tychoplankton, species that are associated with the substrateduring most of their life but occasionally venture into the water column, continued to show nearfield-farfield spatial differences because of their affinity with the bottom substrate. Some of the ichthyoplankton egg taxa also showed spatial differences, but in 1990 these were evident only during the preoperational period. Most taxa did not exhibit reduced densities at the intake, indicating that there was no relationship to plant opera-tion.The number of adult fish lost from impingement has been low.In 1990, a total of 499 finfish and 4 lobsters were impinged. Demersal.species, including lumpfish, pollock, longhorn sculpin, and windowpane were the most numerous species impinged. Lumpfish in particular tends to be associated with rocky areas or other structures; the intake structure. may provide attractive habitat for this species. Pelagic species, even those-that preferred the mid-water zone, were rarely impinged.Trends in the adult finfish community were examined in light of the combined effects of egg and larval entrainment and adult, impinge-ment. Because, of the widespread movements of pelagic fish, there is no valid reference area. Impact assessment instead focuses on a comparison of trends in 1990 to previous years. Two pelagic species-showed

catch 3 differences in 1990, but these differences appeared to be unrelated to plant operation.

Catches of Atlantic mackerel were significantly higher in 1990 than previous years.' As high catches were observed beginning in June, this difference appears to be unrelated to plant operation.. Atlantic herring catches were substantially lower throughout 1990.continuing a trend of decreasing abundance, first noted in 1988.Diminishing catches of Atlantic herring have been observed both locally and regionally (NOAA 1991a). Aside from these two species, the pelagic fish community showed no differences in species distribution and abundance from previous years..1.3 DISCHARGE MONITORING

1.3.1. Discharge

Plume Monitoring Potential impacts in the discharge plume are related to the threat of exposure, .to elevated temperature in surface and near-surface waters. Surface-dwelling organisms, phytoplankton and lobster larvae, are those most likely to be entrained in the discharge plume. Water.temperatures at the plankton intake station in June and August-December were higher..in 1990 than, on average, previous years. However, given the natural variability in water temperatures, temperatures throughout 1990 at the.-intake were statistically similar to previous years;furthermore, there were no differences in water temperatures among. the intake, discharge, and farfield stations. Continuously-monitored surface temperatures at the discharge were similar to a farfield.reference station during the first .two months of operation. The average monthly difference was less than 0.22 0 C. From August-December, dis-charge temperatures averaged 0.8-1.6 0 C higher on a monthly.basis than those at the farfield station. ..The phytoplankton species assemblage has historically shown little stability in terms of density .level, community structure, and seasonal patterns. Collections in 1990, resumed after a three-year 4 hiatus,. were markedly different than previous years. Total abundances at-all three stations were consistently higher in 1990 when compared.to'. the.'previous years' average. Colonial Cyanophyceae (blue-green. algae).predominated during most of 1990 at intake, discharge, and farfield station. As these organisms were present prior to plant start-up, appear to be widespread inthe Gulf of Maine (Balch et al. .1991), and occurred'at both nearfield and farfield areas .their occurrence appears>unrelated to plant operation. Aside from the colonial cyanophytes, the remaining taxa showed seasonal trends and abundance levels that were similar to previous years.Of particular concern is the phytoplankter Gonyaulax sp., which produces paralytic shellfish poisoning (PSP), or'red tide in this and other coastal areas. This organism usually reached toxic levels (as measured in Mytilus edulis meat by the State of New Hampshire) in May or June in Hampton Harbor, causing closure of flats to bivalve shellfish fishing for a period of one to seven weeks each year. In 1990, toxic levels of PSP were recorded in late May through June in Hampton Harbor at levels~generally much lower than those observed prior to 199*0.Lobster larvae (Stages I-IV) have a strictly surface orienta-tion." In coastal New Hampshire, successful recruitment of larvae is the single biggest factor in determining the level of adult catches; 'All stages were rare in the study area, generally occurring from June to October, with highest densities from late June through late August.Evidence suggests that waters off Hampton-Seabrook may be too cold for local production of lobster larvae, and those collected off Hampton-Seabrook may actually originate from elsewhere in the Gulf of Maine and from Georges Bank. In 1990, unusually large numbers of Stage I lobster larvae were caught in July, followed by exceptionally large numbers of Stage IV larvae in August. These unusual aggregations may have been associated'with areas of water mass convergence, where lobster larvae have been known to accumulate. Higher-than-average surface temperatures may also have contributed to higher numbers of lobster larvas., As high 5 numbers of larvae were found at both nearfield and farfield areas prior to plant start-up, these events are not related to plant operation. Subsurface fouling panels, located three meters below the.surface, placed in the discharge plume.area show the timing, type, and abundances of settling benthic organisms. Benthic recruitment and community. development have shown a seasonal pattern that has been.highly consistent from year to year. Historically, recruitment and settlment activities have been low in winter and spring but intensified from summer through fall. Seasonal patterns on surface panels in 1990 were similar to previous years. Differences occurred in-the settlement level; abundance, biomass, and taxa richness (short-term panels) were--higher than previous years, whereas community development (monthly sequential) biomass was lower. As these differences occurred at both nearfield and farfield.areas, they are most likely unrelated to plant operation. The intertidal and shallow subtidal area near Sunk Rocks is outside the immediate plume area, but might be exposed to slight eleva-tions in temperature. Species composition of benthic macroalgae and macrofaunal communities in the intertidal and shallow subtidal areas changed with depth and substrate, but was highly similar among years.Community composition of intertidal and shallow subtidal macroalgae and intertidal macrofauna in 1990 was similar to previous years. The shallow subtidal macrofuana assemblage in 1990 was more similar to mid-depth assemblages than.to shallow.subtidal assemblages from previous.years. High numbers of the barnacle Balanus crenatus contributed to. the observed differences. Individual species showed significant variations in recruitment levels from year to year and among stations., As the plant operated for only a few days before collections for benthic community analysis were ipade, it is unlikely that there are any plant-related differences. -Differences either occurred at both nearfield and farfield stations or were not restricted to the.operation-al period, with the exception of one case. Mytilidae at the nearfield 6 shallow subtidal station were significantly higher in abundance than previous years. As this result relies on only one collection (November) it cannot be definitively related to plant operation.

1.3.2 Benthic

Monitoring The mid-depth and deep subtidal areas were monitored to determine if, during operation of*the circulatingwater system dis-charge, any discharge impacts resulted from increased detritus levels.Year-to-year differences in the macroalgaeandmacrofaunal communities have been small in comparison to variations with depth and substrate... The species composition was highly predictable and distinct for. each depth zone. Benthic community collections in 1990 were similar to previous years. Since they were collected after only four days. of commercial power generator, no differences-were expected. Individual macrofauna species historically have shown significant differences among years in theirannual abundance levels. Only one taxon, Mytilidae, showed a difference in 1990 that was restricted to the nearfield mid-depth station. However, increased abundance levels occurred throughout the year and were not restricted to the operational period.The demersal. fish community could be susceptible to a number of plant-related effects, including larval entrainment, adult impinge-ment, and detrital effects on their primary food resource, benthic macrofauna. Because of distinct differences between the nearfield and farfield stations, potential plant effects were investigated separately for the two areas. While large numbers of commercial lobster traps have prevented sampling the nearfield station in September and'October, making impact assessment during those months difficult; seasonal move-ments of the dominant species, which composed nearly 80% of the total catch, were found to be similar in 1990 to. previous years. Lower catches of Atlantic cod and hakes in 1990 caused decreases in total catch. As diminished catches of these species occurred prior to plant operation, they are unrelated to plant operation. 7

• Because of. its commercial importance, the.American-lobster was monitored in the discharge area. Seasonal patterns in catches have been similar from year to year, affected by bottomtemperatures that influ-enced molting and activity levels. Catches usually increased-to a peak in August or September, then declined.

Monthly lobster catches were consistently higher than average in 1990 at both discharge and farfield stations, reflecting trends observed throughout New England (NOAA 1991b). Since 1984, annual mean catch per unit effort of legal-sized lobsters has been below the 16-year average except in 1986. This apparent decline, a primary concern to lobstermen, was a result of natural variation in combination with the effects of the changes .in the legal size- limit instituted in 1984,. 1989, and 1990 by the. State of New Hampshire-. Many lobsters that would have been of:legal size under the old law were-protected from harvest until their next molt. The increase in legal *size in 1990 reduced catches to approximately 3%'of the total catch, the lowest level observedsince the-beginning of the study.Jonah and rock crabs are two other important epibenthic predators. Jonah crabs exhibited lower catches at the discharge area in 1990; however, these differences were first observed.prior to plant operation and thus appear unrelated. Rock crabs have shown large fluctuations inannual catches. Higher-than-average catches in 1990 1 were due to large catches from June through August at both the discharge area and Rye Ledge. There was no'evidence of plant-induced effects.1.3.3 Estuarine Monitoring Although the. likelihood of a cooling water system operational impact on the Hampton-Seabrook estuary is low, temperature, salinity, benthos, fish, and the soft-shell clam were all monitored in the estuary.Temperature and salinity both showed regular seasonal cycles.Maximum temperatures usually occurred in July with minima in January or,*8 February. Salinity levels had a less distinct pattern, but were usually lowest. in spring,! a result of increased runoff, and highest in'summer. Salinity levels in Browns River were high from 1980-1982, coincident-with low precipitation levels and highest discharge volumes of tunnel.dewatering through the Seabrook settling basin, which terminated..in 1983. By 1986, salinity levels had returned to pre-1980 levels where they have, remained since. The estuarine benthic. community was highly.variable in species composition and abundance, but predominantly composed of surface and subsurface deposit-feeding polychaetes. The number of speci es, total abundance, and abundance of some of.,the dominant species increased during the period when, salinity levels were higher than average,* but have returned to the levels observed prior to the tunnel dewatering discharge; no substantial changes to the benthic.community" were evident in 1990.Estuarine fish included anadromous species as well as resi-.dents. Alewives and blueback herring pass into the estuary in spring, travelling upriver to. spawn.. Catch levels were affected by year class strength as well as water temperature and water level, which were influenced by rainfall and resulting runoff. Young-of-the-year and yearling rainbow smelt were occasionally and erratically caught in the estuary,,but historically have never constituted a substantial portion of the total catch. In 1990, smelt composed 35% of the total catch, the result of large numbers of smelt in May and August. The predominant. resident.species has been Atlantic silverside, which made up over two-thirds of the total catch and nearly 90% during theirmost abundant period, August through November. -Variations in abundance of this species was the single most 'important factor in year-to-year changes in total catch. Abundance of Atlantic silverside was lower in 1990 than average, continuing the trend of decreased abundances first observed in 1982.-The species of greatest concern in the Hampton-Seabrook estuary is the 'soft-shell clam. Density levels of spat, juveniles,' and/or adults have been monitored in the estuary since 1969. Densities 9 of harvestable clams depend on a set of complex, interacting conditions. A successful set of spat is crucial, but this factor alone'does not.!ensure high densities of harvestable clams. Once settled, survival of young-of-the-year-clams depends on protection from its two main preda-tors, green crabs and humans,-1as well as from disease. In.1976, a large spatfall throughout the estuary resulted in high'densities of harvest-ableclams in 1980-1982. Increased levels of predation.prevented recruitmenrt::of the highly successful spatfalls in 1980 and 1981. Light spatfalls from 1982-1988 in combination with an increase in predation have accounted for a precipitous. decline,"i ri-standing stock since 1983.'In addition, neoplasia, a cell growth disease fatal to clams, has been detected from clams in Hampton estuary. This may also have contributed to thedecline of harvestable clams. 'Experimental seeding of clam spat has been conducted in Hampton Harbor in 1987 and 1988 by the State'of New Hampshire in one flat area was not successful. However, the possibility of augmenting the Mya population 'artificially must be fac-*tored into the monitoring program. Young-of-the-year 'settlement increased in 1989 and again in 1990. Survival of the'1989 year class' at Flats 1 and 2 was evidenced by increased yearling densities. This may in 'part be due to decreased green crab catches and reductions in digging activities. 10

2.0 DISCUSSION

2.1 INTRODUCTION

2.1.1 General

Perspective.Environmental studies for Seabrook Station began in 1969 and focused on plant design and siting questions. Once these questions were resolved, a monitoring program was designed which has examined the structure of all the major biological communities as well as the distri-bution, abundance, and size of selected species within, each community. The goal was to assess the temporal (seasonal and yearly) and spatial.(nearfield and farfield) variability that had occurred duringithe preoperational period. This report focuses on data collected since 1976 for fisheries studies and since 1978 for plankton and benthos studies as these years signify the beginning of a consistent preoperational sampling design..Seabrook Station operation began intermittently in July and August, and continued for periods of approximately three weeks in September and October. After operation at 100% for less than a week at the beginning and end of November, the plant operated continuously for the month of December (Table 2.1-1). Although the plant was not generating power throughout 1990, the circulating water system was active throughout the twelve-month period.The period beginning in August 1990 is considered the begin-ning of the operational period for the purposes of the environmental assessment of plant-related effects. Previous reports provided a perspective on the sources and magnitude of the naturally-occurring variability against which environmental conditions during operation would be compared. Identification of the level of variability, both spatial and temporal has been a critical component of this program, one which was a major focus for sampling design. The degree of variability has important implications for impact assessment. The rationale for.11 TABLE 2.1-1. NUMBER OF DAYS OF OPERATION AND AVERAGE DAILY FLOW OF SEABROOK STATION CIRCULATING WATER SYSTEM IN 1990.SEABROOK OPERATIONAL REPORT, 1990.DATES OF DAYS OF CIRCULATING 100%-POWER NUMBER. OF WATER SYSTEM- ':AVERAGE DAILY MONTH GENERATION DAYS' OPERATION FLOW (mgd)Jan 0 31 324 Feb 0 28, 564 Mar 0 .31 563 Apr 0 30 563 May 0 31 562 June 0 30 563 Jul 23-26 4 31 582 Aug 7-12 6 31 588 16-22 7 27-31 5 Sep 1-19 19 30 588 Oct 4-27 24 31 590 Nov 5-9 5 30 590 25-30 6 Dec 1-31 31 "31 589 I 12 focusing on specific sources of variability for each component of the monitoring program is-discussed in the following section.2.1.2 Sources of Baseline Variability The optimal design of animpact study has four prerequisites that ensure that a potentialimpact is delineated from any naturally-occurring variability (Green. 1979): (1) knowledge'of the type, time and place of potential impact; (2) measurement of relevant environmental and biological vdaiables; (3) monitoring before the potential impact occurs to provide a temporal control; (4) monitoring in an area unaffected by impact to serve as a spatial control.* The experimental design of the Seabrook Environmental Program was structured to meet these prerequi-sites.A basic assumption was that there are two major sources of naturally-occurring variability: (1) that which occurs among different areas or stations, i.e.,. spatial, and (2) that which varies intime, from daily to weekly, monthly or annually. In the experimental design and analysis, these studies focused on the major source of variability in each community type and then determined the magnitude of variability in each community (Figure 2.1-1). In certain communities, particularly planktonic, where circulation patterns provide.a similar habitat throughout the area, spatial variability was found to be low in compari-son to seasonal. The study design therefore focuses on frequent sampling to monitor seasonal trends generally at only one farfield and one or two nearfield stations. In other-cOmmunities, particularly benthic, spatial variability has been higherthan seasonal variability. Benthic sampling design has focused on the dominant substrate type in the discharge area,.horizontal hard-bottom ledge, with paired nearfield*and farfield stations representing the major depth zones. Finfish catches have shown both seasonal and spatial differences. Therefore, these studies make frequent (at least monthly) collections in the area of thedischarge as well as farfield areas to the north and south.13 SOURCES OF VARIABILITY TEMPORAL PREOPERATIONAL OPERATIONAL I--CI,.0-J M z LL.............................. .................................. ....... .......................... ......................... I ................................... ................. ....... .......................... .................................. ........ ......................... .................................. ........................... ................... .... ............................. LEVELS OF VARIABILITY SPECIES ASSEMBLAGE MULTIVARIATE 7->ANALYSIS UNIVARIATE NUMERICAL CLASSIFICATION ANOVA or NONPARAMETRIC ANALOGUE I ANALYSIS Figure 2.1-1. Schematic of sources and levels of variability in Seabrook Environmental Studies.Seabrook Operational Report, 1990.14 Because the estuary is an aquatic nursery area and recreationally-important clam flat, baseline collections monitoring seasonal and annual patterns were also made there for operational phase comparison. Biological variability can be.measured on two levels: species and community... A species' abundance, recruitment, size and/or growth are important for understanding operational, impact, if any. For this reason, these parameters were monitored for selected species from each community type. Species were chosen for more -intensive study based on their commercial or numerical importance, sensitivity to temperature, potential as a nuisance organism, and habitat preference. In some cases,.a selected species actually encompassed a complex of species grouped.together in a higher phylogenetic category.. Components of and rationale for species 'complexes" were discussed.in the 1984 Data Report (NAI 1985a). Overall community structure, e.g., the number and type of species, total abundance and/or the dominance structure, may also be affected by plant operation in a way not detectable by monitoring single species; therefore, the natural variation in community. structure was monitored atthe regular time intervals determined by early studies to be sufficient for this purpose.Appropriate statistical methods must be used in conjunction with a well-planned experimental design in order to determine the sources and magnitude of variability. Temporal (annual) and spatial variability in species abundance and size were tested by using analysis of variance or nonparametric analysis that provide a'means of evaluating the statistical significance of changes in the operational period.Spatial, seasonal, and annual variations in community structure were assessed with numerical classification or multivariate analysis of variance. Specific statistical designs are described in the Methods (Section 4.0).Identification of the sources and .levels of variability util-izing the methods discussed above has.its'ultimate focus'on the sources of potential influence from plant operation, and the sensitivity of a 15 community or parameter to that influence (Table 2.1-2). Naturally, a community or:species might be affected by more than one aspect of the cooling water system; however, the focus here is on the aspect of main concern. In general, intake (pumped) entrainment and impingement would potentially affect mainly plankton communities, including fish eggs and larvae, and juvenile and adult fish. If they occur, thermal effects from the discharge (e.g. plume entrainment) would most likely affect nearshore surface water quality, phytoplankton, lobster larvae, and intertidal and shallow subtidal benthos. Although no effects are anticipated in the estuary from the offshore discharge, fish and soft-shell clam populations have been monitored in that area to provide a baseline for operational phase comparisons. Bottom-dwelling organisms,-including macrofauna, macroalgae, epibenthic crustaceans, and demersal fish, may be influenced by detritus potentially arising from moribund entrained plankton that is discharged with the cooling water. A previous impact assessment (NAI 1977e) has *shown that the balanced indigenous community in the Seabrook-study area should not be adversely influenced by the above factors. Results from the biological communi--ties, species and environmental parameters sampled will be discussed in light of the feature of the cooling water, system that has the greatest potential for affecting them.2.1.3 Impact Assessment The purpose of this.report is to assess the impacts of the.first several months of commercial operation of Seabrook Station on the aquatic biota of coastal waters of New Hampshire. Two impacts of con-cern, entrainment and-impingement, were addressed with in-plant monitor-ing-of the organisms entrapped in the circulating water system (CWS).The effects on the balanced, indigenous population of aquatic biota in the waters in the vicinity of the CWS intake and discharge structures were evaluated through continued monitoring at the stations established during the preoperational period and statistical comparison of the re-sults on both the community and the species levels.16 TABLE 2.1-2.

SUMMARY

OF BIOLOGICAL COMMUNITIES AND TAXA MONITORED FOR EACH POTENTIAL IMPACT TYPE.SEABROOK OPERATIONAL REPORT, 1990.LEVEL MONITORED SELECTED MONITORING SPECIES/AREA IMPACT TYPE SAMPLE TYPE COMMUNITY PARAMETERS Intake Entrainment Impingement Thermal Plume Discharge Microzooplankton Macrozooplankton Fish eggs Fish larvae Soft-shell clam larvae Cancer crab larvae Juvenile/Adult fish Nearshore water quality Phytoplankton Lobster larvae Intertidal/shallow subtidal macroalgae and macrofauna Subsurface 'fouling community Mid-depth/deep macrofauna and*macroalgae Bottom fouling community Demersal fish Lobster adults Cancer crab adults Estuarine temperature Soft-shell clam spat and adults Estuarine fish x x x x x x x x x x x x x x x x x x x Detrital Rain Cumulative Sources x x x x x x.x x x x Estuary x 17 The ability to determine whether operation of Seabrook Station.has affected the "balanced, indigenous population" is dependent upon a systematic approach to impact assessment incorporating both temporal and spatial components (Figure 2.1-2). Potential operational effects could, be ruled out if 1) 1990 results were similar to previous years or 2)1990 differences were observed in both nearfield and farfield areas. In addition, other potential sources of change were investigated before concluding that plant operation affected'the aquatic biota.2.1.4 Sampling Location Plankton and water quality studies have been based on samples collected in the nearfield (intake) area and a farfield area (Rye Ledge)located beyond the influence of the Station's operation. In July 1986, sampling at a third station (P5) was resumed in the vicinity of the discharge (Figure 2.1-3); preoperational sampling had been conducted at P5 for various plankton.programs from July 1977 through December 1981.In addition, bivalve larvae were collected from Hampton Harbor.(Pl) starting in July 1986. Entrainment sampling was resumed in June 1990 for bivalve larvae and ichthyoplankton. Fish were sampled offshore by bottom trawls and gill nets near the discharge area and at two farfield sites, and by seining at three. locations in the Hampton-Seabrook estuary (Figure 2.1-4). Marine algae and benthos were collected by divers at a series of stations stratifiedby depth near the intake/discharge area and in a farfield area (Table 2.1-3, Figure 2.1-5). Benthos in soft substrate was sampled along two transects in the estuary-(Figure 2.1-6).Lobster (Ifomarus americanus), rock crab (Cancer irroratus), Jonah crab (C.-borealis) and green crab (Carcinus maenas) were'collected in traps (Figures-2.1-6, 2.1-7). Soft-shell clams, (Mya arenaria) were dug from five flats in the estuary (two flats were dug only for spat starting in 1985) (Figure 2.1-6), with farfield spat stations in Ipswich, MA and in Ogunquit, ME (through 1984 only) (Figure 2.1-8).18 SEQUENCE .OF EVENTS FOR DETERMINING IF THERE ARE ENVIRONMENTAL CHANGES DUE TO OPERATION OF SEABROOK STATION 1990 .:.." similar to s previous .year .sYE at nearfield apc station./.. NO 1990 nearfield YES similar to Observed changes N1 related to NO-INo* plant L Im YES Oprtioal Figure 2.1-2. Sequence of events for determining if there are environmental changes due to the operation of Seabrook Station. Seabrook Operational Report, 1990.19 I .N r\? RYELEDG L/7TLE BOARS HEAD *.: 0.5 18 E4D....... .FARFIELD AREA 37 37 I'I.GREAT BOARS H K.E1 STATION HAMPTON SEABROOK HARBOR N" , -.SEABROOK BEACH ISBURY BEACH LUV iii .Oshargeýý'VR \ODS...4..NEANR FELD AREA.-9 18 18 18 0 1 NAUTICAL MILE 0 1 .2 KILOMETERS SCALE CONTOUR DEPTH IN METERS* = bivalve larvae and water quality stations = ichthyoplankton, phytoplankton and zooplankton stations/2 = lobster larvae stations 0 =.continuous temperature stations E1 -Seabrook Entrainment Station Figure 2.1-3. Plankton and water quality sampling stations. Seabrook Operational Report, 1990.20 I, 0 T =Otter Trawls M S =Seine Hauls -G =Gill Nets Figure 2.1-4. Finfish sampling stations. Seabrook Operational Report, 1990.21 J J TABLE 2.1-3. BENTHIC ALGAE AND MACROFAUNA STATION LOCATIONS AND DESCRIPTIONS.- SEABROOK OPERATIONAL REPORT, 1990.DEPTHa'b LOCATION. APPROXIMATE COMPOSITION m ft STATION LONGITUDE LATITUDE OF HARD SUBSTRATES I 4.6: 15. B17 70047'37"? 4.6 15 B 3 5c 70046'07'tf 9.4 31 B31C 70045'29'9.4 31 B16 70047'03" 12.2 40 B19 70047'13"' 18.3 18.9 21.0 0.3 1.3 0.3 1.3 60 B13 70046'58"' 42054'00"' 42057'22'" 42058'04" 42054'16" 42053'40?? 42053'54"1 4"2053'2311 42057123" 4*2053,56"' 42053'501' 42058'19?? 42058' 12"'Algae *civered ledge (95%) 'and crustose ove'red ledge (5%)Algae 'overed 'ledge (85%)and bouilders (15%)Algae covered rocks (30%) mussel beds (60%)and cobble (10%)Algae covered ledge (75%)and mussel beds (25%)Algae covered ledge and boulders (60%) and mussel .beds. (40%)Algae covered ledge and ,boulders (40%) mussel" beds (55%) and cobble (5%):,.Mussel beds (70%) and algae covered ledge (30%)Mussel beds (.60%) and algae covered ledge and boulders (40%.).Algae covered ledge (90%) mussel beds (10%)Algae covered ledge (100%)Algae covered ledge and boulders (90%)mussel beds (10%)Algae coveredledge (100%)I//{62 B04 70045'59"? 69 B 3 4 c 70044106?? 1 B1MLW 70047'41.? 4 BIMSL 70047'46f'. 1 B5MLWc 70045'36 4- B5MSLc 70045'44'"**a bapproximate ,approxima t e depth below mean low depth above mean low water, subtidal stations water, intertidal stations rarrieid stations 22 LITTLE BOARS .. FARFIELD AREA HEAD.0 9 18 GREAT BOAMSHEAD 37 37.Intake°B.13 I OUTER SEABROOK STATION HAMPTON SEABROOK HARBOR\-~R1MSL-' .NEARFIELD.-AREA B19 Discharge BEABROOK SALISBURY BEACH 18i.9 18 0 .5 1 NAUTICAL MILE 0 2' KILOMETERS SCALE CONTOUR DEPTH IN METERS M = benthic samples 0 = sudace panels F`9 =both LA Figure 2.1-5. Benthic marine sampling stations. 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2.2 INTAKE

AREA MONITORING 2.2.1 Plankton-The focus of monitoring plankton in the intake area was to evaluate the effect of entrainment on community structure and population levels. Due to their limited control of horizontal movements and. broad vertical distribution in the water column, all types of planktonic organisms could be exposed to entrainment. Data on actual levels of entrainment are presented to quantify losses to the bivalve larvae and icthyoplankton communities and individual species. Comparisons of community structure and abundances of selected species in the nearfield area during the period of-commercial power generation (August-December 1990) were made toboth the farfield area in 1990 and the nearfield and farfield areas historically. These comparisons address the question of whether the balanced, indigenous population has been affected by the commercial operation of the plant.An estimation of the number and type of plankton species affected by plant operation depends on (1) the time of year, and (2) the degree of yearly variability. Results from the community analysis give an indication of the number and type of species present (and thus entrainable) at any particular time of year.. The selected species analysis enables a more precise estimate of the entrainable density for key species by examining their annual and seasonal variability. Knowledge of the within-year and among-year. variability allows for more reliable estimates of impact than relying on samples taken in a single season and year.2.2.1'.1 Entrainment Beginning in 1985, Seabrook Station operated its circulating water cooling system, although no power or heated discharge were produced'until 1990. Entrainment samples were collected through June 1987. Since that time until 1990, the circulating water system had not 27 been operating at a frequency or capacity sufficient to warrant further sampling. Entrainment sampling was reinitiated in June 1990 for both bivalve larvae and ichthyoplankton. Fish egg, larvae, and bivalve larvae communities entrained during the July 1986-June 1987 period were similar to those collected offshore, although the smaller sample volumes and less-frequent sample collection in the plant produced some expected differences. The top-ranked entrained fish egg and larvae and bivalve larvae species were similar to those from offshore collections (NAI 1990b). Abundances of most of the dominant species of eggs were lower in entrainment samples than in offshore samples, in some cases substantially so, due to the different depths represented by the two types of samples. The depth distribution of ichthyoplankton is typically uneven, particularly for eggs of some species, which are heavily concentrated near the surface or the bottom thus making them less susceptible to entrainment. Abundances of fish larvae and bivalve larvae were similar in in-plant and offshore collections in 1985-1986 (NAI 1990b).The results of the in-plant sampling in 1990 confirmed observations made previously. Generally the relative abundance of both ichthyoplankton and bivalve larvae was similar between offshore (Station P2) and in-plant (entrainment) samples (Table 2.2-1), while several species of fish eggs were less abundant in the in-plant samples. Cunner larvae (not a dominant in previous comparisons) were much less abundant in the in-plant samples, reflecting this species' preference forthe near-surface waters as demonstrated in diel studies of vertical strati-fication (NAI 1981b, 198lf). Abundances of bivalve larvae in in-plant samples averaged about 30% higher than in offshore samples, with differences species specific (Table 2.2-17) Although species were ranked the same in in-plant and offshore collections, Jieteranomia squamu=a, Modiolus modiolus and Hiatella sp. appeared to be more commonly entrained, indicating that larvae of these taxa are not distributed homogeneously in the water column. In general, however, the species composition of the plankton likely to be entrained in Seabrook 28 TABLE 2.2-1. COMPARISON OF GEOMETRIC MEAN ABUNDANCES OF TOP-RANKED FISH EGG, FISH LARVAE, AND BIVALVE LARVAE TAXA COLLECTED OFFSHORE AT STATION P2 AND IN ENTRAINMENT SAMPLES*AT SEABROOK STATION FROM JUNE THROUGH DECEMBER 1990. SEABROOK OPERATIONAL, REPORT, 1990.ABUNDANCEa DOMINANT SPECIES ENTRAINED (El) OFFSHORE (P2)Fish eggsb Cunner/yellowtail flounder 51 :444 Rockling/hake 44 247<Windowpane 43 170 Hake 35 491 Atlantic cod/haddock/witch flounder 27 17 Atlantic mackerel 12 26 Atlantic whiting 8 11 Fourbeard rockling 7 9 Fish larvaeb Cunner 9 178 Fourbeard rockling .6 25 Atlantic seasnail 6 1 Hake 2 13 Windowpane 2 4 Radiated shanny 2 3 Winter flounder 2 2 Atlantic whiting 1 7 Atlantic mackerel <1 5 Bivalve larvaeC Iytilus edulis 3621 3442 Ifeteranomia squaMul8 2633 1649 Modiolus modiolus 720 275 Iliatelia sp. 594 245 Iya arenaria 99 11 aBased only on periods when entrainment and offshore samples were collected uithin several days of each other bNo./1 9 00 m'No./m 29 Station's circulating water system.was similar to the offshore environ-ment as measured by plankton sampling. Therefore, offshore sampling results can be used to give a rough estimation of species composition and abundance likely to be entrained. An estimate of the total number of bivalve larvae and ichthyo-plankton entrained during the period of in-plant Sampling in 1990 is reported in Tables 2.2-2 and 2.2-3. Bivalve.'larvae entrainment was highest in June and July. Mytilus edulis was the predominant species subject to entrainment, along with Modiolus modiolus and Ifeteranomia squamula.. Fish egg entrainment was highest in June and July; over 80%of the eggs were Atlantic mackerel and cunner/yellowtail flounder.Larval losses were heaviest from August to October, and the majority were cunner, fourbeard rockling, Atlantic seasnail, and Atlantic whiting.Slightly less than 1,250 million fish eggs and 122 million fish larvae were estimated to be entrained from June to December in 1990. Entrainment losses estimated from in-plant collections were much lower than the estimates presented in the Summary Document (NAI 1977e), even when adjusted for the partial year of sampling and the use of only one unit instead of two. The annual loss of Atlantic mackerel was 7 originally estimated to be 8.8 billion eggs, or 4.4 billion for 1 unit.If the 6-month estimate obtained for Atlantic mackerel (518.8 million)in 1990 is doubled, it is still, much lower than the original, estimate.Similarly, original estimates for winter flounder (0.158 billion), Atlantic mackerel (2.26 billion) and Atlantic menhaden-larvae (0.331 million), are all 1-4 orders of magnitude higher than.the preliminary estimates obtained in 1990 (Table 2.2-2). The entrainment loss origi-nally estimated for soft-shell clam, 83 billion larvae per year (NAI 1977e) is an order of magnitude higher than the 8.1 billion estimated from* 1990 in-plant collections during the period of maximum abundance (Table 2.2-2).30 '7-TABLE 2.2-2.ESTIMATED NUMBER OF BIVALVE LARVAE (in billions/month) ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK STATION DURING JUNE-OCTOBER 1990.SEABROOK OPERATIONAL REPORT, 1990.SPECIES JUN JUL AUG SEP OCT Mytilus edulis 733.8 *2,922.9 178.7 131.3 24.6 Modiolus modliolus 151.8 421.2 19.6 300.1 17.0 Placopecten magellanicus 0 0.4 0 0.2 <0.1 fleteranomia squamula 130.6 915.8 301.0 320.5 23.5 Spisula solidissima 25.0 27.6 4.1 9.9 2.4 Mya arenaria 1.3 2.4 0.1 2.5. 1.8 Mya truncata 5.1 243.3 0.2 0.1 0.3 iiatella sp. 232.4 594.4 24.6 22.5 2.7 Macoma balthica 0 26.4 0 0.1 0 Bivalvia 22.9 114.0 11.0 5.2 2.1 TeredO navalis 0 0 <0.1 .0 0 Solenidae 28.7 27.4 3.6 0. 8 0.6 TOTAL 1,331.6 5,295.8 543.0 793.2 75.0 TABLE 2.2-3.MONTHLY ESTIMATED NUMBERS OF FISH EGGS AND LARVAE (IN MILLIONS) ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK STATION DURING JUNE-DECEMBER 1990.SEABROOK OPERATIONAL REPORT, 1990.TAXON JUN JUL AUG SEP OCT NOV DEC Atlantic mackerel Cunner/Yellowtail flounder Rockling/hake Hake Windowpane Cod/witch flounder Atlantic whiting Fourbeard rockling American plaice Atlantic cod Witch flounder Cusk Larvae Cunner Fourbeard rockling Atlantic seasnail Atlantic whiting Radiated shanny Hake Windowpane Winter flounder Atlantic herring Unidentified Lumpfish Atlantic cod American plaice Witch flounder*Tautog Atlantic mackerel Pollock Fourspot flounder Rainbow smelt Gulf snailfish Goosefish Atlantic menhaden Yellowtail flounder.Snailfish 499. 1 380.4 86.1 6.2 13.5 19.1 0.6 0 0 0 -0 105.0 10.2 10.9 10.0 4.7 15.4 17,6 8.8 0.2 1.6 2.2 4.0 0.1 0.7 0.4 0.1 0 0.2 0 0 16.3 5.3 2.2 1.3 0.7 0.4 1.5 3.6 1.5 2.7 2.0 0.:1 0 0 0 0 0 0 0 0 1.0 0 0.4.2 2.3 0 0.0 0.7 0.3 0.2 0O 0.1 1.7 0 0.4 0.1 0 0.7 0 0 0.3 0 0.1 0 0 0 0 0 0 0.9" 0 0 0 0.1 31.7 10.2 0.7 0 0 1.9.8.6 0 4.6 0 0 2.9 0 0 0.6 0.5 0.3 0 0 0.2*0 0 0.2 0.1 0 0 0.1 0.1 0.1 2.9 0.1 0.1 0.1 0.3 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 16.5 0.1 0. 3 0.1 1.4 0.7 0 0 0.3 0 0 0 0.3 0.1 0 0 0 0 0 0.1 0.1 0 0 11.7 0 4.4 0 2.0 2.0 0 0" 0.3 0 0.1 0 0 0.1 0 0 0.1 0 0 0 0 0.0 7.7 0 3.0 0 1.3 1.0 0 0 0.1 0 0.1 0-0 0.1 0 0 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 0 0 0 0 0*0 0 0 0 0 0 0 0 0.6 0 0 0 0 0 0 0 0.2 0 0 0 0 0 0 0*!.F 0 0 32 The question of whether the entrainment of these and other planktonic organisms has affected the balanced indigenous population is addressed in following sections on community structure (Section: 2.2.1.2).and selected-species (Section 2.2.1.3).2.2.1.2 Community Structure The purpose of examining the community structure of entrain-able plankton is to determine.whether operation of Seabrook Station has had an effect on the balanced indigenous population of planktonic organisms. Potential operational effects could be ruled out if the 1990 community was similar at the nearfield to previous years, or if 1990-differences were consistent throughout the area as demonstrated by MANOVA. Community composition in 1990 was compared to previous years using numerical classification. The community composition was consid-ered unchanged if collections at the nearfield station in 1990 in a particular season were similar to the majority of samples from the same season from previous years, causing the analysis to group them together.All of the planktonic communities discussed in this section had species, as'semblages that changed with season during the baseline period. (Figures 2.2-1, 2.2-2, and 2.2-3). Thesegroups were differenti-ated primarily on the distribution and abundance of dominant species;however, the relative abundance or even absence of other species was also a factor. The species entrained depend on the seasonal assemblage present at the time.Hicrozooplankton Ilicrozooplankton exhibited several overlapping groups in spring and summer, indicative of both some year-to-year changes in community structure as.well as a variable "transition period" in the late summer assemblage (Figure 2.2-1). The life cycles of the copepods Oithona sp. and Pseudocalanus sp. greatly influenced the structure of 33 Microzooplanktofn 19904 86 84-J 83 4 z o 82 L.j 81 0 80 1a s'NEW I , -Group 1 D -Group 2* [] Group 3] -Group 4]U -Group 5= -Group 6-no sample w z On'j 7 4-3-2-I 0 t 0=0 I" x0 I PREOP 0 1990 1 0 1 2 3 1 4 86 GROUP Bivalve Larvae.......... 1 01 z 0 LIJU w Oa-00Z 89 88 87 86 84 83 82 5-4 3 2-1-0-I Group I= -Group 2 F]-Group 3 , Group 4 E -no sample U

• ungrouped i PREOP 0 1990 10 Z0.1 KO K 1 2 I GROQUP 4 3 Figure 2.2-1.Months of occurrence and log (x+1) mean abundance (no./m 3) in preoperational years and 1990 for seasonal groups formed by numerical classification of the microzooplankton and bivalve larvae collections.

Seabrook Operational. Report, 1990.34 Holo-/Meroplankton 1,00 z 0 CLU 0 LU 89 88 87 86 84 83 82 81 80 79 78 El El.*LII= Group I-Group 2-Group 3 Group 4-Group 5.Group 6-no sample LU z 04C 00 M=J C3 5 3-2-1-w0 0 0 x'IPREO P 0 1990 0 2 3 4 56 GROUP, Tychoplankton 1990 1 -',..., z 0 LU LU (L U LU 0 z 00-j Z M] -Group I]- Group 2 E -Group 3] -Group 4]. Group 5 D -Group 6--Group 7'Group 8]= Group g D -no sample U -ungrOuped PREoP a 1990.6 5 4 3 2 1 0 10O b I 10 1o 10 I GROUP Figure 2.2-2. Months of occurrence and log (x+l) mean abundance (no./1000 M 3) in preoperational years and 1990 for seasonal groups formed by numerical classification of the holo- and meroplankton and tychoplankton species of macrozooplankton collections. Seahrook Operational Report, 1990.35 Eggs 7 =_ ... ...,. ..........................~ ~ ~ ~ ~ ~ ... 8."..'." ' " .. :: W--~~~~ ~~ ...".....:.::::::.. .oj ... -.... ..::.ii4iiiiiii "' 80 ".. .. " : I ii.il...i......-~ ~~ ~ ...... ..-....=-... ... .U"X-Group I-Group 2-Group 3-Group 4-Group 5-Group 8-Group 7-Group 8-Group 9-no sample* ungrouped e excluded due to low counts 1 5 LU ( 4 z 03 farfieldi Neomysis americana P2 > P5, P7 Nearfield > farfield None None I!38 Hacrozooplankton In the past, the seasonal patterns of the macrozooplankton assemblage have been consistent (Figure 2.2-2), reflecting, primarily, the population dynamics of the dominant copepod species (holoplankton) modified by seasonal presence of larvae of benthic organisms (meroplank-ton)(NAI 1990b). The interannual variability in seasonal patterns of tychoplankton (taxa whose behavior includes movement between the sub-strate and the water column on a regular basis) was examined separately for this analysis (Figure 2.2-2). Holo- and meroplanktonic components of.macrozooplankton assemblages have been distinct and consistent, show-ing high predictability from year-to-year. Seasonal succession of holo-and meroplankton assemblages in 1990 exhibited the same pattern observed in previous years. The copepods Calanus finmarchicus and Centropages typicus were consistently among the dominants. The greatest variability among years in terms of associations of species was evident in February and April. Variation in February could be due to relatively low abun-dances. The combined effects of freshwater flow and solar warming may affect the timing of the transition from winter to spring biological conditions, causing biological conditions in April to be unpredictable. Although both the holoplanktonic and meroplanktonic components of the macrozooplankton are susceptible to entrainment, there is no indication that these portions of the community have been significantly impacted.Community structure and abundance were similar at Station P2 in 1990 both to previous years,.and to the farfield area (Station P7).Seasonal succession of tychoplankton species has shown greater variability than the holo- and meroplankton. With the exception of early spring and mid-summer, tychoplankton species composition has not been highly predictable and could resemble any of three or four patterns (Figure 2.2-2). However, it is highly likely that at any time of the year, either Neomysis americana or Pontegeneia inermis or both species will be a dominant. Seasonal changes in community structure largely reflected changes in abundance of these two species. April 1990 was 39 ungrouped, distinguished by unusually high abundances of Mysis mixta and Gammarus lawrenclanus and seasonally typical abundances of other taxa.Despite a highly variable seasonal succession of tychoplank-ton, it is evident that species composition in 1990 resembled that previously observed at Station P2. Comparisons to the farfield area confirmed previously noted (NAI 1990b) differences between the areas, i.e., that abundances of tychoplankton were greater in the nearfield thanthe farfield (Table 2.2-4). This. pattern had been attributed to the more complex substrate of cobble and sand at thenearfield station compared to the uniformly sandy bottom at the-farfield station. There is no indication that the tychoplankton assemblage has been affected by operation of the'plant's circulating water system.Ichthyoplankton (Fish Eggs and Larvae)Fish egg assemblages in most months showed a-predictable seasonal progression. There are' two periods during the year.(January-February and October) when it would be difficult to predict the plank-tonic fish egg community. structure due to'the high. degree of variability among years (Figure 2.2-3). Seasonal'succession of planktonic fish egg species composition and abundance in 1990 followed patterns previously observed and was most similar to the most recent preoperational years.Although spatial differences had not previously'been investigated, there were differences in spatial distribution of fish eggs in 1990 when considering the entire year, while comparison"among stations during the period of commercial operation (August-December) revealed no significant differencbs (Table 2.2-4). Differences were limited to a number of.taxa.that typically occur in the first half of the year.. Abundances tended to be higher in the nearfield than the. farfield," further suggesting they were not related to entrainment. ýSince the nearfield assemblage was similar 'in 1990 to preoperational years and species-specific vertical distribution of fish eggs tends to reduce their susceptibility to 40 entrainment, it is unlikely that this differenceý among stations is attributable to operation of Seabrook Station.Seasonal assemblages of fish larvae could be divided into six major types based on their dominant taxa: fall (predominated by Atlantic herring), late fall-early winter (pollock,. American sand lance, Atlantic herring), winter-spring (American sand lance), spring (winter flounder, snailfishes,radiated shanny, American plaide andAmerican sand lance), late spring-early summer (Atlantic mackerel, cunner and fourbeard rockling)- and late summer (cunner and fourbeard rockling). Variations in density of the major taxa, especially during transition periods. (primarily November, December and January), caused small changes in species composition leading to the formation of overlapping "sub-.groups". During most of 1990, seasonal patterns were similar to previous years (Figure 2.2-3). November and December 1990 collections were unusual in that they were represented by relatively low abundances of Atlantic herring, pollock and American sand lance larvae, resembling only December 1989 among the preoperational collections. The 1990 ichthyoplankton community at Station P2 was compared to Stations P5 and P7 encompassing both the entire year and the August-December period representing commercial operation of the plant. In both cases, the nearfield and farfield communities were statistically similar (Table 2.2-4), indicating that the low abundances observed in November and December were not restricted to the intake.area but were widespread. Thus, it is unlikely that these biological conditions reflected impacts due to entrainment of finfish larvae..2.2.1.3 Selected Species Eleven species with various lifestages from the pelagic zooplankton communities were designated as selected species. The existence of seven to twelve. years'of preoperational data allows an estimation of seasonal and annual.-variability. These species exhibited 41 different degrees of numerical importance; their relative contributions to their respective communities are shown in Figures 2.2-4 and 2.2-5.The zooplankton selected species (including various life-, stages) historically have constituted less than 40% of the overall abundances (Figures 2.2-4 and 2.2-5). In both the microzooplankton and, macrozooplankton assemblages, other copepods typically have made as large or larger a contribution to overall abundances. In the microzoo-plankton, copepod nauplii and copepodites (unspeciated) have extremely abundant. In the macrozo6plankton, copepods other than the selected species have historically been dominant if averaged over the year; however, the noncopepod selected species have been dominants in certain seasons. All of the zooplankton selected species reached peak*abundance in spring and summer, with the exception of Neomysis americana, which has been most abundant infall through early spring.Abundances of zooplankton selected species in 1990 were evaluated in relation to the preoperational years in both nearfield (Stations P2 and PS) and farfield (Station P7) using analysis of variance (Table 2.2-5). Both the entire year and the operational period from August through December were tested. It was typically the case that'differences in abundances occurred between preoperational years as a whole and 1990.. These differences, however, were not 'restricted to the nearfield areaor to the period of commercial operation (August through December).. Thus, there is no evidence through this initial period that commercial operation of the plant has significantly impacted populations of the zooplankton in~the study area.Two species of bivalves were also examined for trends in their larval stages (Figure 2.2,5, Table 2.2-5)." Peak abundances of lytilus edulis have historically occurred in early summer while Mya arenaria larvae have typically peaked in the August through September period.M. edulis has usually dominated the bivalve larvae collections and did so again in 1990.' M; arenaria makes only a minor contribution to the total abundance of bivalve larvae (Figure 2.2-5).: Abundances in the'42 Temporal Variability 5-4-a PREOP (n= 12)o 1990 (n'14 or 15)I.0 w z z o0 0-J I f 0 I 0 °0 2-10 10 lo 0------- T- I I Relative Abundance 40-3 PREOP B.1990 z 0 0 0 0o 30 20 10O KLKF F-Q. Z:= L C CL0- a) C aw &w wc .7O ~ C U1 =3 o W.. 0zC -i w 03 "'D =3 C 0 E0 C Z Co C r CD -r- C Uj E 2 0 20.Figure 2.2-4. Mean log (x+l) abundance and 95% confidence interval, and percent composition for selected species of phytoplankton (cells/liter) and microzooplankton (no./m3) at Station P2, 1978-1984 and 1990.Seabrook Operational Report, 1990.43 Temporal Variability

• PRECP (n=12)o 1990 (n=10 or 12)LU z z 0 wJ 5-4-3-2-0 I 0 0 T0 I 0 I I 10 0 I1 0 Relative Abundance z 0 0 0.60-50 30" 20-13 PREOP 0 1990 I.1 1:3 05 w W-J a-LU Cn C', 7L-~SCD Ca Ca Ca I~CD iCU 0>cO (a-0 (D CO 0*-A. -Ca.0 CU>CE ýtn.Cd) CD a)E ZCO Cu 0 C0 Ca cc Figure 2.2-5. Mean log (x+l) abundance and 95% confidence interval, and percent composition for selected species of bivalve larvae (n6./m3) and-macrozooplankton (no./1000 m3),1978-1989 and 1990 at Station P2.Seabrook Operational Report,: 1990.44 TABLE 2.2-5. COMPARISON OF 1990 ABUNDANCESa OF SELECTED MICROZOOPLANKTON, BIVALVELARVAE, MACROZOOPLANKTON-AND ICHTHYOPLANKTON LARVAE, TAXA.SEABROOK OPERATIONAL REPORT 1990.RESTRICTED RESTRICTED TO TO OPERATIONAL

1990 SIMILAR .1990 DIFFERENT NEARFIELD?

PERIOD?Eurytemora herdmani Eurytemora.sp. -no no adults copepodite Pseudocalanus/Calanus* .sp. nauplii Oithona sp. nauplii Pseudocalanus sp. no. no copedodites.. Oithona sp. no no copepodites. Oithona sp. adults no, no Mya arenaria larvae, Calanus finnarchicus no no copepodites Mytilus edulis lar- C finmarchicus no no vae adults American sand lance Crangon septemspirosa no no larvae.; post larvae Atlantic cod larvae " Ne6mysis americana no no Winter flounder lar- no no Atlantic mackerel vae larvae YellOwtail flounder no no.. larvae Cunner larvae no no Hake larvae no no Atlantic herring no yes* larvae'Abundances of microzooplankt.on, bivalve larvae and macrozooplankton taxa were compared over the entire year and during the August through December operational period. Abundances of ichthyoplankton larvae were compared during their individual peak periods. Only Atlantic herring larvae peaks entirely within the August through December period.45 nearfield (intake and. discharge stations) were statistically similar to the farfield during both plant operation and preoperational periods.Neither species appears.to have been impacted by commercial operation..of the plant.As a group, the selected species of fish larvae composed.80%

• of the total abundance and. at least one species peaked in each season (Figure 2.2-6). Generally, each of the species was present for a-brief but fairly-consistent time period each year.. Timing of abundance peaks in 1990.was consistent with previous years. ..Abundances of several species differed significantly from preoperational.

years (Table 2.2-5).Winte6r flounder; yellowtail flounder, and Atlantic herring larvae were less abundant in 1990 than in previous years. Cunner and hake larvae, on the other hand, were more abundant in 1990. None of- these dif-ferences in abundance was restricted to the nearfield area.Of the ichthyoplankton selected species, only Atlantic herring had its peak abundances during the August through December period..corresponding to. commercial operation of the plant.. Abundances of this speciesduring its peak were significantly-lower than the mean of pre-operational years. However, abundances were statistically similar, between the nearfield and farfield areas throughout the preoperational and operational periods. The general trends of reduced larval abun-dances in 1987-1989, coupled with reduced-adult catches locally and regionally' indicate that reduced abundances of this species in'1990 were not.due to commercial operation of the plant...2.2.2 Finfish.2.2.2.1 Impingement Operation of the circulating water system, in terms of both the number of pumps and whether the system operated at all, has varied since operation of the circulating water system began in 1985. Fish entrained within the system and subsequently impinged upon the 46 Temporal Variability 0 z z n, 0-j 3-2-0 t 0 a PREOP o 1990 I 0 I 0.0 I I I.0 0 0 I Relative Abundance 40 13PREOP 1] 1990 z 0 0 0 C., 30 20 30 0--J 0-Lw CU -r Ca C.2wci0 .2 0. <E.Figure 2.2-6. Mean log (x+l) abundance (no./1000 M 3) and 95% confidence interval, and percent composition for selected species of fish larvae 1975-1989 and 1990 at Station P2. Seabrook Operational Report, 1990.47 traveling screens have been collected by Seabrook Station. personnel to determine operational impact. Initial estimates provided by station personnel based on 1985 data indicated that only one fish would be impinged per 50 million gallons of cooling water flow. During a five-month period in 1985, 970.individuals, representing 32 species, were collected from the circulating water system. These were dominated by grubby (Myoxocephalus aenaeus, 21%), snailfishes (Liparis.sp., 21%), and longhorn sculpin (Myoxocephalus octodecemspinosus:, 11%). During a seven-month period of circulating water system operation in 1986, 1212 individuals representing 35 species were collected. Thesewere dominat-ed by grubby (28%),,windowpane (Scophthalmus aquosus, 12%), and longhorn sculpin (9%)ý. The intake structure was cleaned of fouling organisms in 1986 and, subsequently, has been inspected.annually to control biologi-cal growth. Intermittent operation of the circulating water system during 1987 resulted in a total impingement of 502 fish representing 21 species. Of these, longhorn sculpin, winter flounder (Pseudopleuro-nectes americanus), and windowpane made up 22%, 14%, and 13%, respec-tively, of those impinged. As the CWS operated intermittently and only at low capacities in 1988 and in 1989, fish impingement data were not collected.' The circulating water system operated regularly during 1990 (Figure 2.2-7). Overthe entire year, 499 finfish, representing 31.species, were impinged (Results Section 2.2). This represents an impingement rate of less than one fish per 500 million gallons of cooling water flow or 1.4 fish per day. In addition, four lobsters were impinged. Lumpfish (Cyclopterus lumpus)'and pollock (Pollachius virens)each represented 14% of the total finfish impinged. Longhorn sculpin represented 13% and windowpane, 10% of the total. Impingement was highest in May-June when lumpfish, windowpane and cunner (Tautogolabrus adspersus). were the most frequently impinged species and November-December when pollock, longhorn sculpin,,herring (unspecified) and windowpane were caught. As in previous years, few pelagic species or individuals of pelagic species were.impinged. Pollock was the primary exception, reflecting its tendency to be most abundant near the bottom,.48 600-500-o400 300 0-j 200-100-0 I I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP COT NOV CEC MONTH U.z U-00= Uj Z n-, wCL z 0 0 0.0 I-)100-90-80-70-60-5o-40-30-20-10-0-100-0o-80 60-s0-40 20 .0-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH....... longhom sculpin E3 windowpane

• El herring.. sea raven JAN MA P A UOnrer JAN FEB MAR APR MAY. JUN JUL AUG SEP CCT .,NOV C MONTH Figure 2.2-7. Flow rate (million gallons per day) of circulating water system and impingement of finfish during 1990. Seabrook Operational Reportj 1990.49 The low abundance of pelagic species from impingement collections suggests that the intake caps are performing as *designed, minimizing entrapment.

The species impinged are mainly demersal species; it is-.,.likely they are seeking cover at the intake structures, thus increasing the likelihood of swimming or being drawn into the intake tunnels.Impingement of even demersal species is low considering the overall j impingement rate of 1.4 fish per day.observed in 1990.2.2.2.2 Pelagic Species Taken together, the six dominant finfish species collected in gill nets have averaged 85% of the population (Figure 2.2-8). Effects of plant operations on pelagic fish populations in the study area should be visible by studying these species. The distribution of pelagic fish varied seasonally;. two main seasonal groups of species, summer and*winter, were identified in earlier studies utilizing numerical classifi-cation techniques (NAI 1982c). Prior to 1990, from September through April, Atlantic herring constituted from .64% to 93% of gill net catches, while in summer months (May-August), other.migratory. species such as Atlantic whiting (formerly-known as silver hake) and Atlantic mackerel.predominated (Figure 2.2-8). Pollock (predominantly age-two fish [NAI 1985b]) is a local resident that also made up a greater proportion of the pelagic nearshore community during summer.No finfish were caught in gill nets in the early months of 1990, refldecting the sharp decline' in the Atlantic herring population observed locally (Figure 2;2-8; Table 2.2-6) and regionally (NOAA 1991a). Catches of Atlantic herring were again low in the fall of 1990, resulting in~relatively low total catches. As a result, relative contribution of the captured population was made up to a greater degree by other species.. Pollock and Atlantic mackerel made up the majority-of the catches between May and July. Atlantic whiting, typically abundant from June through August, was barely present in 1990. In August, spiny dogfish (Squalus acanthias) made up 80% of the catch. Butterfish-50 Seasonal Variation w D.0 30-20-10--PEOP.1990 0 J I I I I5 I I .I I i I JAN FEB 'MAR APR MAY JUN JUL AUG SEP CCT NOV CM Preoperational z 0 0 0-0 3.)O 10o-80-60-40-20-0-JAN R1 MAR APR MAY JUN JUL AUG SEP OCT NOV CM* Atlantic herring o3 Atlantic whiting.J bluebacK herring O Atlantic mackerel UD pollock gg Atlantic menhaden E3 Atlantic herring[I Atlantic whiting E3 blueback herring E] Atlantic mackerel[D pollock Eg AtIanticmenhaden 100-1 1990 z 0 0 I--0 0 0I 80 60 40 20 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV E MONTH Annual Variation wU a-0 30-.20 0 I I I I I I I I II 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 z 0 0 0 O)100-60-40-20-0 76 77 78 79 80 81 82 83 84 85 86 87 -88 89 90 YEAR E2 Atlantic herring D : Atlantic whiting EZ blueback herring UO Atlantic mackerel ED pollock 19 Atlantic menhaden Figure 2.2-8. Seasonal and annual changes in composition and abundance of the pelagic fish.community, based on catch per unit effort averaged over gill net Stations Gi, G2, and G3, 1976-1989 and 1990. Seabrook Operational Report, 1990.51 TABLE 2.2-6. COMPARISON OF 1990 ABUNDANCESa OF SELECTED PELAGIC FINFISH SPECIES. SEABROOK OPERATIONAL REPORT 1990.1990' 1990 SIMILAR DIFFERENT COMMENT Pollock Atlantic herring. 7. Lower throughout 1990; documented. regional decline Atlantic mackerel Higher in 1990'Abundances were compared over the entire stations.year without distinguishing 52 (Peprilus triacanthus) and bluefish (Pomatomus saltatrix) predominated in September, a period of below-average catches. In the fall, when Atlantic herring-have usually been most abundant, Atlantic mackerel, blueback herring and Atlantic whiting composed the majority of the catch. Total catch in this period in 1990 was below average. Differ-.ences in community structure in 1990 can be attributed to regional changes in species populations (NOAA 1991a).In every year, Atlantic herring has been the overall dominant pelagic fish in the area; however, it exhibited large annual abundance differences that werereflected in the annual percent composition.(Figure 2.2-8). When catch per unit effort (CPUE) peaked in the study area in 1980, Atlantic herring composed 82% of the total catch. From 1984 through 1989, when total catches were at their lowest levels since the inception of the study, Atlantic herring constituted only 26-61% of.the total catch (Figure 2.2-8). In 1990, Atlantic herring constituted only 3% of the pelagic fish collected, apparently reflecting a broad-'scale trend (NOAA 1991a). Atlantic herring are known to show high vari-ability in. catches spatially as well'as seasonally and annually (Bigelow and Schroeder 1953). Most of the fish collected off Hampt6n-Seabrook were yearlings, particularly those captured in the spring (NAI i985b).Little is known about the habits of yearling herring, except that they seek out the warm waters of embayments in spring (Bigelow and Schroeder 1953).The seasonal variability of the pelagic fish was found tq_.be greater than annual variability (NAI 1990b). Most of the'selected pelagic species had their peak abundance during a short but distinct period of time (Figures 2.2-8 and 2.2-9). Generally, variability.among years has been low. The number of individuals that could be exposed to intake effects (impingement) would therefore be expected to vary substantially among seasons and, to a lesser, extent, among years.Areal differences are less important than temporal differences in evaluating potential plant effects on pelagic fishes. Because of 53 2.0-Temporal Variability

• PREOP o 1990 1.5-W z 0.0 2-U 0 r 1.0-0.5 Io 10: T I'Ck 0 0 0 0 0 0.0 Relative Abundance 80 60 PELAGIC SPECIES (Gill Nets, PREOP)PELAGIC SPECIES (Gill Nets, 1990)f ESTUARINE SPECIES (Seines, PREOP)-ESTUARINE SPECIES (Seines, 1.990)D EMERSAL SPECIES (Trawls, PREOP)DEMERSAL SPECIES (Trawls, 1990)0 0 0~40 20 r 0L 0.-J a-wU W en 003 ~ ~ ý (D~. C ~ -- -.0 0~o _0. i-C Ct: 0 *- (a.~ E 0. c raC >..--aJ .0 CL C: Figure 2.2-9. Mean log (x+1) abundance (catch per unit effort);and 95% confidence intervals, and percent composition for selected species of fish, 1976-1989 and 1990.Seabrook Operational Report, 1990.54 their high degree of mobility, pelagic fish were not observed to be associated with any one habitat. As expected, relative abundances of the five most abundant taxa were very similar among stations, although catches tended to be lower at the southern station Gi (Section 3.2.2).Differences in the vertical distribution of these species may be important, however, because the intake structures are located at mid-depth, 5 m above bottom in 17 m of water. Historically, only one of the eight most abundant species, Atlantic menhaden, was consistently more abundant at the intake (mid-water) depth during the months sampled than at surface and bottom (Table 2.2-7). However, this species was only slightly more abundant at mid-depth than at the surface, and it only accounted for 2% of the pelagic fish in the study area. Atlantic whiting and pollock, and to a lesser extent alewife and rainbow smelt, were most abundant near the bottom. Atlantic herring, Atlantic mackerel and blueback herring were most abundant on the surface (Table 2.2-7)..These species may be less vulnerable to -intake effects. Despite historical trends, certain species occasionally had higher catches in the mid-depth area than in surface or bottom depths. In 1990, on those dates when all depths were sampled, alewife catches were highest in mid-water gill nets and catches of Atlantic mackerel in mid-water netslwere higher in 1990 than any other species (Table 2.2-7), suggesting that these and other species could occasionally be more vulnerable to intake effects. However, these results indicated that the most abundant and frequently-occurring pelagic species did not show a preference for mid-depth distribution, verifying earlier results and the rationale-for mid-water placement of the intakes (NAI 1975a).. Furthermore, in-plant collections of finfish to date indicate that pelagic fish are not being encountered on the .circulating water system screens in substantial numbers.2.2.2.3 Demersal Species The primary focus for assessment of operational effects of Seabrook Station on demersal finfish has been the impact of detrital 55 TABLE 2.2-7.CATCH PER UNIT EFFORTa BY DEPTH FOR THE DOMINANT'GILL NET SPECIES OVER ALL STATIONS AND DATES WHEN SURFACE MID-DEPTH AND BOTTOMNETS WERE SAMPLED, PREOPERATIONAL YEARS (1980 THROUGH 1989)AND 1990. SEABROOK OPERATIONAL REPORT, 1990.DEPTH SURFACE MID-DEPTH BOTTOM PREOP. PREOP. PREOP.SPECIES YEARS 1990 YEARS 1990 YEARS 1990 Atlantic herring 5.3 0.1 2.9 0.1; 1.9 0.1 Atlantic whiting 0.2 0.6 0.5 0.4 0.7 0.5 Atlantic mackerel 1.0 4.3 0.9 2.2 0.5 1.7 Pollock 0.2 0.0 0.2 0.0 1.2 4.4 Alewife 0.1 0.1 0.1 0.2 0.2 0.2 Blueback herring 0.8 0.3 0.3 0.2 0.5 0.1 Atlantic menhaden 0-.6 0.5 0.7 0.6 0.2 0.0 Rainbow smelt <0.1 0.0 <0.1 0.0 0.1 0.1 a number per one 24-houi' set of one net (surface,, mid-depth or bottom)o-,

rain. This is discussed in Section However, impingement.studies have shown that certain species of demersal fish are susceptible to impingement. The low rate of impingement suggests that'any changes to the demersal finfish community should not be attributable to impinge-ment during plant operation. Of the demersal fish species impinged most frequently, abundances of several (winter flounder,; Atlantic cod and hake)' were examined by analysis of variance (reported in Section 2.3.2.2). There were no changes observed in catches of winter flounder in 1990 *compared to preoperational years. Hakes and Atlantic cod were both relatively less abundant in 19.90 but this.occurred in both near-field and farfield areas and so is not attributable to impingement. One of the most frequently impinged species, lumpfish (Cyclopterus lumpus), has not been caught routinely during the study.Although demersal, it tends to be associated with rocky areas or other structures rather than the open bottom. Thus the intake structures may provide attractive habitat for this species. Impingement of lumpfish was highly seasonal, occurring primarily in May and June (Figure 2.2-7).Most individuals were adults. The seasonality of impingement could be related to post-spawning movements (peak abundances of larvae occurred in May and June, NAI 1991). Thus the species appears to be less susceptible to impingement before or during its spawning period than after. Although a portion of the adult population may be lost through impingement, their spawning potential will have been realized, prevent-.ing magnified losses in future year-classes. 57

2.3 DISCHARGE

AREA MONITORING

2.3.1 Plume

Studies 2.3.1.1 Discharge Plume Zone Because the discharge plume's largest exposure will be to surface and near-surface waters, the primary focus in this section will be on parameters or organisms in this part of the water. column, namely phytoplankton, lobster larvae, and nearfield water quality parameters. Other organisms, such as pelagic fish and ichthyoplankton will, of course, have some exposure to the discharge plume, but it is assumed that entrainment and/or impingement are the more important issues for these organisms.. Water temperatures have shown distinct seasonal patterns that were important in driving biological cycles. Historically, surface and bottom temperatures, measured on a weekly basis and averaged monthly, reached their lowest points from January through March, then steadily increased from April to August; temperatures were generally highest from July to September (surface) or October (bottom) before beginning their-fall decline (Figure 2.3-1). Surface temperatures had a more exaggerat-ed seasonal cycle in comparison to bottom temperatures, with higher spring and summer temperatures. Surface and bottom temperatures throughout the Hampton Seabrook area were higher than average in 1990 in June and from August to December (Figure 2.3-1). However, average monthly temperatures were statistically similar to previous .yearsý, and no differences were detected among intake, discharge, and farfield areas in 1990 (Figure 2.3-1, Results Section 3.1.1). These results indicate that the higher'temperatures observed in 1990 were within the range of natural variabil-ity. Effects of plant operation on average monthly surface and bottom temperatures at Station P2 were not discernible. 58 Surface, Intake LU w LU I-w: C-20-15-.10-5-PE-OP... .. 0 I I a i I I i JAN FEB MAR i I * .g .I I I I I .. APR MAY JUN JUL AUG SEP CCT NOV CM MONTH 0~w 20-15-10-5 Bottom, Intake PRE-P 1990 0-T I I I I I I I JAN F MAR APR MAY JUN JUL AL.G SEP OCT MONTH NOV Surface, 1990 IL M wU 20-15-10-5-INTAKE (P2)....... DISCHARGE (P5)------- FARF1ELD (P7)n. I JAN F MAR APR MAY JUN ý JUL MONTH A i i .i i AUG SEP OCT NOV CE:C Figure 2.3-1. Monthly mean surface and bottom temperatures at nearfield Station P2, and 95% confidence intervals during preoperational period and in 1990, and mean monthly surface temperature at intake, discharge, and farfield stations.Seabrook Operational Report, 1990.59 Temperature differences were noted in the continuously monitored temperature data supplied by YAEC. No consistent-differences were observed in monthly averages of daily surface temperatures between the discharge station (DS, Figure 2.1-3) and farfield station T7 in July, August, and September; the average monthly differences were less than 0.22 0 C. From 0ctober-December, surface temperatures at the discharge station -averaged 0.8-l.6 0 C higher than those that the farfield station (T7)(Table 2.3-1, Figure 2.3-2). At Station ID the nearfield station midway between the intake and discharge (Figure 21.1-3), average surface monthly temperatures were within 0.2 0 C of temperatures at farfield Station T7. Mid-depth and bottom temperatures at this near-field station were at most 0.30 higher than those at *the farfield station; in most'months, temperatures were actually higher at the farfield station (Table 2.3-1).Historically, surface salinity values have been highest in winter and lowest in spring, a result of increased runoff. In 1990, salinity was lower than average from June-December (See Results Figure 3.1.1-4). Higher-than-average rainfall in April, May, August and October (Section 3.3.1) may have contributed to lower-than-average salinity in those months. However, the annual mean salinity in, 1990 was similar to previous years (Figure 2.3.2).Surface dissolved oxygen has had a seasonal pattern inversely related to temperature, with peak values in late winter and lowest values in fall. In 1990; seasonal patterns were similar to previous years, although values, in September were lower than the average (See Section 3.1.1).Nitrogen and phosphorus nutrients had more erratic cycles than temperature, salinity, and dissolved oxygen, but generally had lowest levels in summer and highest in fall and winter. Seasonal patterns and annual mean values of total phosphorus and orthophosphate in' 1990 were slightly higher than previous years (Figure 2.3-2).. Nitrite concentra-tions were unusual in 1990 in that they were much higher than average in 60 0 TABLE 2.3-1.MONTHLY MEAN TEMPERATURES (0 C) AND TEMPERATURE DIFFERENCES BETWEEN DISCHARGE (DS) AND FARFIELD (T7) AT THE SURFACE, AND NEARFIELD (ID) AND FARFIELD (T7) STATIONS AT SURFACE, MID-DEPTH (.8.5 m) AND BOTTOM (16.2 m) DEPTHS COLLECTED FROM CONTINUOUSLY MONITORED TEMPERATURE SENSORS.ý SEABROOK OPERATIONAL REPORT, 1990.DS-T7 ID-T7 ID-T7 ID-T7 SURFACE SURFACE MID-DEPTH BOTTOM MONTH DS T7 DELTA ID T7 DELTA ID T7 DELTA ID T7 DELTA T, T T T JUL 14.54 14.63 -0.08 14.69 14.63 0.07 11.76 11.50 0.26 9.08 9.62 -0.54 AUG 18.16 18.36 -0.20 18.11 18.11 0.01 14.81 15.42 -0.61 13.26 13.14 0.12 SEP 16.31 16.09 0.22 16.22 16.06 0.16 14.06 13.94 0.12 12.14 12.31 -0.17 OCT 13.04 12.11 0.93 13.17 12.98 0.19 11.92 11.85 0.07 11.03 11.17 -0.14 NOV 10.24 9.44 0.80 9.38. 9.39 -0.02 .9.42 9.53 -0.11 9.49 9.91 -0.42 DEC 8.91 7.32 .1.59 7.37 7.34 0.03 .7.47 7.57 -0.11 7.43 7.96 -0.53 ON 20-18-16 12-Temporal Variability

• PREOP (n=12)0 1990 0 I w-1 10-10 0 10 8-0 t 0 6-I 4-I N0 a 0-0 0 21I 0 0 CD 0~E a, ER 0 Z!0.E a, C-E 0 E C-0~0d*0 CD o0~'D>wEM wa Cd r-~0 0 to 2-0~0 C_-al Ea~0 o o ,t-EC a For salinity, total phosphorus, nitrate, and.ammonia values, niultiply by 10.Figure 2.3-2. Preoperational mean and 95% confidence limits, and 1990 mean for temperature.

(0 C), salinity (ppt), dissolved oxygen (mg/1), and nutrients (ughl) at Station P2.Seabrook Operational Report, 1990. February, May, and October, but lower than average in July and August (See Results, Figure 3.1.1-7). The seasonal pattern of nitrate values was similar to previous years although concentrations were higher than average from January-May (See Results, Figure 3.1.1-7). Ammonia levels were below the detection limit of lOpg/l during most.of 1990 (See Results, Figure 3.1.1-8). The annual average for nitrate and nitrite.values in 1990 was higher than previous years, whereas ammonia was lower than average (Figure 2.3-2). These differences, however, were not statistically significant. The phytoplankton community has shown the most seasonal and annual variability of any species assemblage studied in this program.Seasonal assemblages have changed rapidly and frequently, diminishing the suitability of the community for short-term impact assessment (NAI 1985b). Some elements of the phytoplankton community, however, have been relAtively stable and predictable.. Historically, total phyto-plankton abundance has shown a predictable seasonal cycle,. although abundance levelsvaried as much as two orders of magnitude among years (Figure 2.3-3). The spring bloom was typically initiated by increases.in irradiance, and although the species composition Varied from year-to-year, centric diatoms typically were. among the first to appear (NAI 1985b). Abundances usually diminished with the depletion of growth-limiting nutrients (primarily nitrogen); development of the thermocline appeared to prevent the replenishment of nutrients from deeper waters.and thus limit growth of spring dominants. A second (fall) peak usually-occurred, coincident with the dissipation of the thermocline, which acted to replenish the nutrient-supply in surface waters.. In 1990, total abundance displayed atypicalspring peak, but no fallpeak was observed (Figure 2.3-3). Total abundances were higher thIan average in most months, and highly correlated among nearfield, intake and dis-charge, and farfield stations. This suggests that observed trends in phytoplankton abundance occurred on an area-wide basis.Phytoplankton assemblages from 1978 to 1980 were similar, based on the predominance of Skeletonema costatum, RhizosolenI8 63 Total Abundance Relative Abundance, Preoperatlonal 0 8.0 7.5-. PREOP---6--- 1990, including colonial Cyanophyceae ... 1990, excluding colonial Cyanophyceae w z 0-1 0 7.0-6.5 -6.0 -5.5 -5.0 -4.5 4.0-3.5 0-*-z 0 Fp F5 0 (-0 z 0 IX a-JAN FEB MAR APR MAY JUN, JUL AUG MONTH Relative Abundance, 1990 I I I I SEP OCT NOV [D MONTH* or-ER ( Includes specaes Iromn all groups occurng lose than 1%)o

• ANTHOP-fCEAE

[ DI'JOPICEAE E3 BACILLARIOPHYCEAE o3 CRYPTOPHYCEAE 0 CYANOPHYICEAE Relative Abundance, 1990 Excluding Colonial Cyanophyceae i.z 0 0.0 z LU 9X 100-80-60 20'V I V I I K'1/o/z 0/1 0 0 0 0 Ur F-Cz 100 0 r///1 I I I I , JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DW6 MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEz MONTH Figure 2.3-3.Monthly mean and 95% confidence intervals of total phytoplankton and relative.abundance of the major phytoplankton groups during the preoperational period (1978-1984) and monthly mean in 1990 withand without Colonial Cyanophyceae. Seabrook Operational Report, 1990. delicatula, and Phaeocystis pouchetti, while from 19.81 through 1984, only S. costatum and Chaetoceros spp. were consistent dominants. The phytoplankton in 1986 was unusual in that there was an uncharacteristic July peak caused by bluegreens and Leptocylindricus spp. In the latter half of 1986, S. costatum and bluegreens predominated. No phytoplankton collections were made from 1987-1989.' In 1990,. colonial cyanophyceae (bluegreens) replaced diatoms (particularly S. costatum, but also Lepto-cylindricus minimus and Nitzchia delicatissima) as the overwhelming dominants (Figure 2.3-3). Diatoms appeared in significant numbers only in June and October. Other species displayed seasonal trends that were similar to previous years. Phacocystis pouchetti and Chroormonas sp.exhibited spring blooms, followed by filamentous and unicellular green algae.The reason for the predominance of cyanophytes in 1990 is not known, but it may reflect a:Gulfwide phenomenon. Abundances as high as 7 .X-107 cells/l were observed in the central Gulf of. Maine in the summer of 1988 and 1989 (Balch et al. 1991). High. abundances of cyanophyceae have been linked to persistent vertical stratification, organic and inorganic nutrient enrichment, increased temperatures, and high amounts of photosynthetically-active radiation (Paerl 1988).' Although nutrients were higher than average prior to the first collection of phytoplankton in April, temperatures were within the range~of previous years, with no evidence of extraordinary stratification. Thus there is no obvious physical or chemical occurrence in 1990 that can be linked to the abundance of cyanophytes. Cyanophyceae -in some cases exhibit certain characteristics, such as high motility and production of resting cells (akinetes), that can provide them a competitive advantage (enabling them to bloom) over other groups of phytoplankton (Paerl 1988). Blooms of.colonial cyano-phytes have been cited. as causing oxygen depletion, diminished water quality, increased turbidity, reduction of benthic flora and fauna due 65 to .alterations in sediment conditions and reduction of the natural phytoplankton populations (Paerl 1988). These changes were not apparent in the study area.Although abundances of colonial cyanophytes represented 66% of the total phytoplankton abundance from August to December 1990 (Table 3.1.2-1), abundances of most other dominant taxa were within the 95%confidence intervals of historical abundances (Results Table .3.1.12-2), suggesting'that the phytoplankton assemblage has not been markedly altered. Number of taxa was similar to previous observations in all depth zones. There were no dramatic changes in the zooplankton or benthic communities that could be linked, to the increased numbers of cyanophytes. In 1990, as seen historically, no spatial differences were observed in the phytoplankton community either between intake (P2) and.farfield (P7),areas or between intake (P2) and discharge (P5) areas (NAI 1985b, 1987b). In 1990, total abundances and chlorophyll a values-were 'highly correlated among all three stations. Multivariate analysis of variance showed no significant differences among stations for the., dominant taxa.Skeletonema costatum was chosen as the selected phytoplankton species because of its consistent predominance during the baseline period. Historically, there has been a major-peak in late summer or fall (see Results Figure 3.2.1-6) and in some years there'was also a smaller peak in the spring (NAI 1981f, 1982a) or winter (NAI 1980c, 1983a). The characteristic fall peak was absent at all stations in 1990, causing significantly lower densities-during the operational period. Because of highly-variable'peak abundances, significant differences were detected among years and months although intake and discharge and farfield densities, were statistically similar.The phytoplankton species assemblage has shown little stabili-ty in terms of density level, community structure, or seasonal patterns.66 At best, only general trends are predictable, such as the occurrence of a spring peak. The seasonal species assemblage has changed markedly from year to year. 1990 was no exception to this pattern, with changes more marked than those noted in earlier years. There were no changes in community structure or abundances that were unique to the discharge or intake stations. Although differences in.1990 were more dramatic during the August-December time period, differences occurred throughout the year and do not appear to be related to plant operation. Paralytic shellfish poisoning (PSP) is caused by high numbers of the diatom, Gonyaulax sp. PSP levels in Mytilus edulis, as measured by the State of New Hampshire and Massachusetts Department of Public Health (reported through 1984 only), have exceeded maximum levels allowable for human consumption every year from 1972 through 1989.(except 1987), usually for a period of 1-7 weeks (NAI 1987b; 1989a, 1990a). In 1972, toxic levels were present in Hampton Harbor for a period of 16 weeks. Although Hampton Harbor flats have-been closed each summer since 1976 to soft-shell clam diggers for conservation reasons, high PSP levels have caused the closure of the harbor to all bivalve shellfish digging for several weeks.each summer as well. Peak values in.most years occurred in May or June, coinciding in Hampton Harbor and the farfield area, Essex, MA (through 1984, when data from both'sites were collected). In 1990, elevated levels of PSP were recorded in late May through June, similar to previous years at levels generally lower than previous years (See Results, Figure 3.1.2-5).Of the shellfish in the area with planktonic lifestages (Can-cer crabs, lobster, and. soft-shell clams), only lobster larvae Stages I-IV have strictly a surface orientation, typically found in the top few centimeters of water. The seasonality and variability of Cancer sp.larvae and Mya arenaria.larvae were discussed in the intake area monitoring section. Successful recruitment of lobster larvae is the biggest factor in determining the level of adult lobster catches in subsequent years (Harding et al. 1983). Lobster larvae collected off Hampton-Seabrook probably originate from warm waters in the Gulf of 67 Maine and Georges Bank. (Harding et al. 1983) and are driven *into the*area by a combination of winds and nontidal currents (Grabe et al.1983). Temperatures in the study area are typically not warm enough to allow planktonic development (Harding et al.-1983), reinforcing the idea that this area is probably not important in the production of lobster larvae. Lobster larvae, which were rare.throughout the study area, have typically been recorded from the first week in June to the second week in October, with peaks frequently occurring in the mid-summer months (Figure 2.3-4 and Results Figure 3.3.6-1). In 1990, lobster larvae first appeared in early June, at all three stations, similar to previous years. Maximum abundances have occurred over an eight-week period between late June and late August, .during the period of maximum surface temperatures. Historically, abundances of all life stages have been.very low, averaging <2 per 1000 square meters (Figure 2.3-4). From 1978-1989, stage I and IV larvae have predominated, and stage II and III have-been extremely rare. Densities at both the farfield station (P7)and discharge station (P5) were usually higher than at the intake-station (P2). In 1990, an unusually large catch of Stage I lobster larvae occurred in July, over 10/1000 mi 2 at all three stations, followed by an exceptionally large catch of over 60/1000 m 2 Stage IV larvae in August. Higher than average surface water.temperatures throughout the Hampton-Seabrook area may have.enhanced the survival of lobster larvae.In addition, unusually large aggregations of lobster larvae have been associated with convergence areas or shallow sea fronts, .where different water masses meet. These areas are the result of wind-induced down-welling coupled with influences of tides and river discharges, which form visible accumulations of. foam .and debris (Cobb 1983). It's uncertain whether the large numbers of lobster larvae were caused by higher temperatures or convergence of water masses. However, since the timing of these incidents occurred at both near- and farfield areas, it;is unlikely that these were related to plant operation. Subsurface (-3 m) "fouling" panels placed in. the projected inner and-outer discharge plume area and at farfield areas, show. the types', timing and abundances of shallow subtidal organisms that can 68 jl 20 -Temporal Variability. PREOP YEARS 0 1990 15 -1 0 I ULL z D a 10 0 I I 5-0 0 0 I U Cu-D O 2u.0-.0-o3.0 Ca-0-D Cu For CPUE of total lobsters, multiply by 10.Figure 2.3-4. Preoperational mean (1975-1989) (no./1000 tn 2 lobster larvae; catchper 15-trap effort adult lobsters and crabs) and 95% confidence limits and 1990 mean for lobster larvae, adult lobsters and crabs at the discharge site. Seabrook Operational Report, 1990. settle on bare substrates. Short-term panels, exposed for one month, allow estimation of recruitment levels while monthly sequential panels, exposed for 1-12 months, show the development of the fouling community (Figure 2.3-5)....Total biomass, abundance of noncolonial fauna, and richness of faunal taxa showed seasonal patterns that were highly consistent from year-to-year and between nearfield and farfield areas, reflecting the increase in settling activity in summer and fall. The development of the fouling community in 1990 followed the basic seasonal progression observed in previous-years although several differences are notable. Recruitment abundances, taxa richness, and biomass (panels'located at inner plume stations only) measured on short term panels were significantly higher in 1990 than previous years, whereas community.development biomass (monthly sequential panels) was lower (Figure 2.3-5;Table 2.3-2). Changes in the settling population were due to increased numbers of mytilids, which increased biomass as well as provided additional substrate for other organisms. As these differences occurred at both nearfield and farfield areas,.and began before plant start-up, they are unrelated to plant operation. The species assemblage colonizing fouling panels at the*discharge station has shown seasonal changes that were relatively consis-tent from year to year, particularly from June to December. In 1990, the settling community at the discharge station in the latter half of the year was similar to those of previous years (Figure 2.3-6).2.3.1.2 Intertidal/Shallow Subtidal Zone-An area outside of the immediate surface plume area that is-being monitored for potential plume effects is Sunk Rocks. Intertidal (MSL and MLW) and shallow subtidal (-4.6 m) stations'that are represen-tative of the area were monitored on Outer Sunk R6cks (nearfield) and at a reference area at Rye Ledge. Community comparisons have historically focused on August collections when all organisms are identified and enumerated. Operational impact assessment in 1990 for the benthic 70 Short Term Species Richness Short Term Abundance 30 6-0 z D M 51 -PEO 251- ----- 1990 4-3-2-1-4'S '4 x I-0 z 20-15-10-5-0.0 I I. I I I I I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV C MONTH JAN FEB MAR APR MAY JUN JUL AUG S OCT NOV CM MONTH Short Term Biomass Monthly Sequential Biomass 12 PRE. ..... 1990-J z 4 EL 0 M)z 4 IL 0 Fn 1000 900 800 700 600 500 400 300 200 100 0 PREOP 1990 4 2 0 JAN FEB MAR APR MAY. JUN JUL AUG SEP OCT NOV CM JAN FE3 MAR APR MAY JUN JUL AUG SEP OCT N MONTH MONTH Figure 2.3-5. Seasonal patterns of settlement and growth of fduling organisms during the preoperational period and in 1990 as indicated by noncolonial abundance, species rictiness, and biomass from monthly sequential panels set at discharge Station B19. Seabrook Operational. Report, 1990. TABLE 2.3-2.

SUMMARY

OF DIFFERENCES IN COMMUNITY PARAMETERS MEASURED AT INTERTIDAL, SUBTIDAL, MID-DEPTH, AND DEEP BENTHIC STATIONS AND IN THE SURFACE FOULING COMMUNITY. SEABROOK OPERATIONAL REPORT, 1990 SHALLOW 1990.SIMILAR? .1990 DIFFERENT?. NEARFIELD, FARFIELD ZONE STATIONS GROUP3 PARAMETERb GROUP2 PARAMETERb SIMILAR?Intertidal. Sunk Rocks Algae .Richness No Farfield Biomass No Fauna Richness No Abundance No Shallow Sunk Rocks Algae Richness subtidal Farfield Biomass Fauna Richness Abundance Mid-depth Intake Algae Richness, Algae Richness No Discharge intake discharge, Farfield farfield Biomass, Biomass, Yes discharge intake, farfield Fauna Richness, Fauna Richness No intake Abundance Yes Deep Intake Algae Richness Algae Biomass No Discharge Biomass, discharge Farfield intake Fauna Richness Fauna Abundance Yes Surface Discharge, ST Biomass ST Richness No Fouling inner plume outer plume, Abundance No Community. outer plume; farfield Biomass, Farfield inner plume, No outer plume, Yes nearfield MS Biomass No'Algae = macroalgae;: Fauna = macrofauna; ST = short term bRichness = number of taxa; Biomass = total biomass, all of organisms panels; MS = monthly. sequential panels taxa combined; Abundance = total number 1990 1989 1988 1987 1986 CC 1984 LU>- 1983 1982 1981 1980 1979 1978 SEASONAL GROUP-Group I[I1 -Group 2 EL -Group 3-Group 4 J -Group 5-Group 6-Group 7-Group 8 W -Group 9 S- Group 10~H -Group 11 S -Group 12 F -no sample MONTH Figure 2.3-6. Seasonal groups formed by numerical classification of log (x+l) noncolonial abundances from short-term surface panels from Station B 19 collected from 1978-1984. and July 1986-December 1990. Seabrook Operational Report, 1990. community utilizes data collected after limited commercial operation ,(Table 2.1-1). Any. differences observed'in 1990 are, therefore, unlikely to be.related to plant operation. Benthic community structure within the intertidal/shallow subtidal area was assessed in several ways. The number of species (richness) and total abundance.or biomass estimates obtained in 1990'were statisticallycompared topreviousyears. Potential operational] effects could be ruled out if 1990 results were similar to previous years, 1990 differences were consistent throughout the area (i.e., at nearfield and farfield station pairs), or results in 1990 in the.nearfield area were similar to previous years even though they may not have been similar at the farfield area. Community composition in 1990 was compared to previous years using.numerical classification. The community composition was considered unchanged if collections in 1990 at a particular. station were similar to the majority of samples from the same station from previous years, causing the analysis to group them together., The community parameters met the criteria established for demonstrating no operational impact. Although macrofauna. and.macroalgae tara richness and abundance or biomass at intertidal stations showed differences in 1990, these differences occurred at both nearfield and farfield areas (Table 2.3-2)' Macrofaunal and macroalgae community. parameters at shallow subtidal stations were statistically similar to previous years.Benthic algae, and macroinvertebrate collections taken annually in August at Stations B1MLW and B5MLW (intertidal) and Stations B17 and,, B35 (shallow subtidal) have exhibited species assemblages that were consistent'and highly similar from year to year at each station (Figure 2.3-7). Each annual'collection'at a station was grouped (by numerical classification) with the majority of those collected in other years at the same station (Results Sections 3.3.2 and 3.3.3). In 1990, community composition of intertidal and shallow subtidal macroalgae collections 74 Macroilgae INTERTIDAL I SHALLOW I MID-DEPTH DEEP 5 17. 35 .16 1 19 0 31 1 1 4 1 34 1 9 9 0 ..........._.1 z'0 ujwU 0 tu 71 3.5 w) 3.0 0 ' 2.5-Jz C:3< 2.0 1.5 0 o000O000 00 o o 0 0 0 0 0 o o 0 0o o0 o o o o o 00 Oo oo 000 o0 o 0 o o o o 0 o ,o oo o oo oc 0 000000 o o DO o D .=-oo o*o oa o Oo o 0. .. o0 0 o 0o oo 0 Go oo 0 0 oo 0o l o.o..g go a 00 0 go go 0 go 00 0 0. 00 0 10 46.10 0.6 0 0........... ............ ........... ............ ........... ........................................................................................... ............... .......................................................................................................Group 1 I- = Group 2= -Group 3-=Group 4= Group S= Group6-not sampled PREOP 0 1990 I 1 I w 3E z0 0 10 1 0 0 I I 0 6 5 2 GROUP Macrofau na INTERTIDAL I I 5 SHALLOW 17 I 35 MID-DEPTH 16 1 19 1 31 I DEEP 13 i 4 1 34 1-I I ... ~ -I I 1990 :: .0 0 X , * , * *_J z 0 (n or.u e0 89 88 87.86 85 84 83 82 81 80 79 78= Group I.I = Group 2.-"Group 3-Group 4-Group 5-Group 6 LI -not sampled 5.5 LU 0 5.0 01(. 4.5..Z 4.0II Fu 3.53-.Figure 2.3-7.0 I 0 1 -t0 I PREOP 0 1990 I 10 3E II 2-I 6 GROUP3 I 2 Similarity and abundance or biomass of macroalgae and macrofauna species assemblages in 1990 compared to the preoperational years. Seabrook Operational Report, 1990.75 and intertidal macrofauna collections was similar to previous years.For the first time since 1978, the shallow subtidal macrofaunal assem-blage atthe nearfield station (B17) was more similar in 1990 to mid-depth regions than to previous shallow subtidal collections. High numbers of Balanus crenatus probably contributed to the similarity ofthis station to mid-depth areas. Macrofauna density levels in, intertidal and shallow subtidal groups in 1990 were higher than previous years, due to increased mytilid density, which occurred at nearfield and farfield areas. Algae biomass in the shallow subtidal area in 1990 was similar to the preoperational mean. However, the intertidal group biomass in 1990. was lower than the historical average, due to decreased amounts of Chondrus crispus. This difference was observed at the reference station as well as the nearfield station.Fourteen benthic taxa were selected for more intensive moni-toring because of their trophic position, abundance and commercial or recreational value (Table 2.3-3). *Parameters monitored included abundance (all taxa), size (fauna only), and reproductive status (epibenthic crustaceans). All life stages'of the commercially-important taxa-were studied. Some of these taxa were monitored in the Sunk Rocks area while others were examined as part of the discharge or estuarine studies. .Algal selected species showed no evidence of operational impact. Biomass of the dominant algae Chondrus crispus in 1990 in the shallow subtidal zone was similar to previous years (Figure 2.3-8). In the intertidal zone, biomass was lower in October at both stations (Table 2.3-4). This resulted in lower relative abundance in 1990 than previous years (Figure 2.3-8).. Quantitative counts of the dominant kelp, Laminaria saccharina, were much lower than recorded in previous years at the nearfield station.. However, lower, counts were also recorded in April and July, prior to the operational period (Table-4) "..76 TABLE 2.3-3. SELECTED BENTHIC SPECIES AND RATIONALE FOR SELECTION. SEABROOK OPERATIONAL REPORT, 1990.SPECIES (COMMON NAME) LIFESTAGE a RATIONALE Macroalgae Laminaria saccharina (kelp)Chondrus crispus (Irish moss)Benthic Invertebrates Zmpithoe rubricata (amphipod) Jassa marmorata (amphipod) Pontogeneia inermis (amphipod) Nucella lapillus (dog welk)Asteriidae (starfish) Strongylocentrotus droebrachiensis (green sea urchin)Dominant Bivalves Mytilus edulis (blue mussel)Mya arenaria (soft-shell clam)Epibenthic Crustaceans Carcinus maenas (green crab)Cancer borealis (Jonah crab)Cancer irroratus (rock crab)Homarus americanus (American lobster).A A J, A J, A J, A J, A J J,A L,S,A L,S,A Habitat (canopy)-forming primary producer Habitat (understory)-forming primary producer; spore-lings may be heat sensitive Intertidal/shallow subtidal community dominant (formerly) Intertidal/shallow subtidal community dominant Subtidal, ubiquitous community dominant A major intertidal predator of ,Mytilus edulis Predator, community dominant Potentially destructive herbivore Habitat former; spat may be heat sensitive Recreational estuarine species;larvae entrainable A major predator of soft-shell clam spat Important predator and prey Important predator and prey Commercial species; larvae plume-entrainable L,J,A L,J,A L,J,A L,J,A aA = adult; J = Juvenile; L = Larvae; S Spat 77 Annual Variability 6-a PREOP(n=12 except 0 1990 n=9 for Asteriidae 5-w Q-z z C, 0-j Ca 4-0 3E 0 3 I 0 0 0 2-0 I 0 Relative Abundance 80 70 13 PREOP EO 1990 60 z 0 F-0 0Q 0 C.50 40 30 20 10 a-J a.wo (CD a) 23U.-Do 0 C Ca-j Cu-Ca C I)CL Ca CD*0 2 z E Ca-u-3 Ca 0 cc J-_'a a Abundance is no/m 2 except for Chondrus, which is g/m 2.Figure 2.3-8. Nearfield (Sta. BIMLW & B17) annual variability (95% confidence limits) of log (x+ 1) biomass (g/m 2) or abundance (no./m 2) and percent composition for selected intertidal and shallow subtidal species of algae (triannual collections) and benthos (August only) during the preoperational period and in 1990. Seabrook Operational Report, 1990.78 TABLE 2.3L4.COMPARISON OF 1990 ABUNDANCES OR BIOMASS LEVELS OF SELECTED INTERTIDAL AND SHALLOW SUBTIDAL MACROALGAE AND MACROFAUNAL TAXA.SEABROOK OPERATIONAL REPORT, 1990.RESTRICTED RESTRICTED TO TO OPERATIONAL 1990 SIMILARa 1990 DIFFERENTa NEARFIELD? PERIOD?-Chondrus crispus (S) Ampithoe rubricata (I) .ys, .no Jassa marmorata Asteriidae (S) no no (ST,M;ST,D) Jassa marmorata (S) no no Mytilidae (I) no no (S) yes yes (ST,M) no N/A (ST,D) yes N/A.Nucella lapillus (I). no no Chondrus crispus (I) no yes Laminaria saccharina yes no aBased on results of Analysis of Variance or tests.Wilcoxan's Summed Ranks ST,M =ST, D Intertidal Shallow subtidal Short-term panels, Short-term panels, mid-depth deep 79 Differences in 1990 for the majority of macrofauna species occurred either at both nearfield and farfield stations, or were not restricted to the operational period (November), suggesting that they were not related to plant operation (Table 2.3-4). In one instance, one taxon did not meet these criteria. Mytilidae collected in the shallow subtidal zone occurred in significantly higher densities at the near- .field station in November. Since this result is based on only one sample during the operational -eriod, additional information will be necessary to evaluate potential operational effects.2.3.1.3 Estuarine Zone Environmental studies in Hampton Harbor estuary include monitoring physical parameters (temperature and salinity), fish popula-tions, benthic macrofauna, and juvenile and adult soft-shell clams (Pya arenaria). The estuary has been monitored to determine the effects,,if any, of the settling pond discharge since 1978. This included any.possible effects of tunnel dewatering, which added large volumes of ocean water to Browns River through 1983. Current estuarine.monitoring 1 .efforts are conducted to identify any potential effects from either settling pond discharge or Seabrook Station operation.. One of the main environmental issues in the Hampton-Seabrook estuary related to plant operation is whether the offshore intake and discharge will impact the adult clam population in Hampton Harbor. The probability of impact from the most-likely source, entrainment of Mya larvae, is small (NAI 1977e);this is discussed in Section 2.2.2. Effects on juvenile and adult Mya are evaluated by comparing population estimates developed for 1990 with those from previous years.Temperature and salinity, monitored in Hampton Harbor and Browns River since 1978, provide valuable information, for interpreting biological phenomena.. Maximum temperatures usually occurred in July, with minima in January or February (Figure 2.3-9). Temperatures, generally followed this pattern in 1990 but were higher than average in 80 Temperature CU LU CL 30 25 20 15 10 5 0 JAN ,FE MAR APR MAY JUN JUL AUG SEP OCT NOV Cm MONTH Salinity z 0 CL 30 25 20 15 10 5* 10-8 , 6 4-2-a-OVERALL MEAN........ 1990 I i[ I ..I I I I JAN FEB MAR APR MAY JUN JUL MONTH AUG SEP T .NOV

• D, Precipitation OVERALL MEAN 1990 I~~ I ~ I I-I I I I I I I I JAN FEB MAR APR MAY JUN JUL MONTH I I I I I AUG S SEP OCT NOV CEr Figure 2.3-9. Monthly means and 95% confidence limits for seawater surface temperature and salinity taken at low tide in Browns River over the entire study period (May 1979-December 1989) and in 1990, and precipitation measured in Boston, MA, from 1978-1990.

Seabrook Operational Report, 1990.81 July-August and again in October-November. Salinity had a less distinct seasonal cyclethan did temperature, but was usually lowest in spring, coincident with increased runoff. Heavy rains in April and May 9f 1990, and again in October, led to lower-than-average salinities during these months (Results, Section 3.3.1, Figure 2.3-9). In Browns River, average annual salinity values remained high for a three-year period from 1980-1982, coinciding with low precipitation and highest discharge'Volumes from the settling basin. This was the period when the maximum de-watering of the cooling tunnels took place, and the salinity of the settling pond's discharge water was relatively high, approximately 25 ppt. After discharge volumes decreased in 1983 and precipitation returned to pre-1980 levels, salinitylevels dropped, averaging 18-20 ppt.through 1990. Hampton Harbor salinities, which were not as suscep-tible to these influences because of the influx of a large volume of offshore waters, showed higher salinity and lower year-to-year variabil-ity than Browns River.The-benthic macrofaunal community in Mill Creek (Station 9)and Browns River. (Station 3) was typical of New England estuaries. The species composition was also consistent with that from other estuaries on the East Coast (Watling 1975; McCall 1977; Whitlatch 1977; Santos and Simon 1980). Surface and subsurface deposit feeders predominated, including opportunistic polychaetes such as Streblospio benedicti and Capitella capitata, with suspension feeders and omnivores forming an important component. The most numerous species inhabiting estuaries are those'that are resistant and resilient to the natural changes in the physical environment, such as fluctuating.temperature, salinity, dissolved oxygen, and sediment grain size.In Mill Creek and Browns River, the biological parameters measured were highly variable seasonally and annually, ,with total abundance, numbers of taxa, and most of the dominant species signifi-cantly different among years and between stations. This is typical of this physically heterogeneous habitat. Some of this-variability was related to changes in salinity. -The combination of lower precipitation 82 and higher levels of discharge from the settling basin from 1980 to 1982 apparently caused higher and less-variable salinities in Browns River.At the same time, total abundance and number of taxa increased (Figure 2.3-10), along with densities of Streblospio benedicti and Capitella capitata at that site.' Higher salinity levels probably enhanced the habitat for more stenohaline species, and at the same time, opportunis-tic polychaetes invaded the changing habitat. Following an increase in precipitation and decrease in discharge volumes, these parameters dropped to their lowest point in 1984; however, they had returned to pre-1980 levels by 1986. Since that time, species richness and total density have been Variable, in part attributable to periods of low salinity caused by heavy precipitation and runoff, especially during recruitment periods (Figure 2.3-10). In 1990, salinity was lower than-average and was associated with lower numbers of taxa. Total density in 1990 was similar to previous years.Important estuarine fish include both diadromous species as well as residents. Three anadromous fish species occur seasonally in the estuary: rainbow smelt in winter, and alewives and blueback herring (."river herring") travelling to upper reaches of local rivers to spawn in the spring. Rainbow.smelt were an important but highly variable (both seasonally and annually) constituent of the demersal fish communi-ty at the entrance to the estuary (T2), composing approximately 20% of the total catch historically and in 1990 (see Section 2.3.2.2). The absence of smelt in trawls from April through November reflects their movement farther offshore. Historically, in spring and summer, sparse and erratic numbers of young-of-the-year and yearling smelt have been caught in the estuary (Figure 2.3-11),. but no one age group (based on length-frequency) has been consistently dominant'(NAI 1985b). Since 1976, rainbow smelt have never composed asubstantial portion of annual seine catches, averaging only 3%'of the total catch (Figure 2.3-11). In 1990, high numbers of rainbow smelt moved 'into the estuary in May and again in August, leading to higher-than-average total catches and relative abundances in these months (Figure 2.3-11). Average smelt catches in 1990 were the highest observed to date, composing 35% of the 83 Estuarine Benthos>-Fn z w-a~10000 8000 6000-4000-2000"'I* 4* C I 5'I,-... O O-40 x-30 U.0-20 M-2 z-10.0.-.50-DENSITY NUMBEROFTAXA n-I -~ *.m m i .! i I .m m i

• m i ý78 79 80 81 82 83 84 86 87 88 89 90 YEAR Salinity, I-o,.a-~t 30-28 26 24-22-20-18-no data 16.4 .-.7 I 8 8 8
• 8 4
• I i I I 78 79 80 81 82 83. 84, 86 , 87 , 88 -89 90 YEAR Figure 2.3-10. Annual geometric mean density (no./m 2) and mean number Of taxa per station of estuarine benthos (1978-1984; 1986-1990), and annual mean salinity (1980-1984; 1986-1990), at Browns River. Seabrook Operational Report, 1990.84 "

W D-C.800 -600-400-200-0 Seasonal Variation-PREOP........ 1990 .*, ", -* #sS * 'q S "S.S .t ,°a a I I APR MAY JUN JUL AUG SEP OCT NOV ioo -1 Preoperatlonal z 0 r--CD 0 0 NOV winter flounder Atlantic herring rainbow smelt z 0 0~0 C)-100-80-60-40-20 0-1990 E] pollock Fundulus sp.El Atlantic silverside APR MAY JUN JUL AUG SEP OCT NOV MONTH Annual Variation 400-200-uLJ 0.C)0 I7 I. I I I I I I8 I I I I I 76 77 78 79 '80 81 82 83 84 87 88 89 .90 z 0 0 0.0 C.-100 80 60 40.20..0 03 0r El winter flounder Atlanti6 herring rainbow smelt pollock Fundulus sp.Atlantic silverside 76 77 .78 79 80 81 :82 83 84 YEAR 87 88, 89 90 Figure 2.3-11.Seasonal and annual changes in composition and total abundance of the estuarine fish community, based on catch per unit effort averaged over beach seine Stations S1, S2 and S3, during the preoperational period (1976-1984 and 1987-1989) and in 1990. Seabrook Operational Report, 1990.85 total catch (Figure 2.2-6, 2.3-11). Since increased abundances of smelt were for the most part due to higher catches prior to commercial operation, they are not related to plant operation. River herring (Alosa spp.,), which. includes alewife and blueback herring, occasionally appeared in large numbers in Hampton Harbor,. especially at the Browns River Station. In the Taylor' River, the size of the river .herring run has been variable, depending on year class strength, whereas the timing of the ruun depended'on water tempera-ture and 'level,. which in turn was influenced by rainfall and runoff (NAI 1985b). 'In the estuarine sampling program, these species 'constituted only about 5% of the total catch"(1978-1989). No alewives or blueback herring were caught in the estuary if 1989. In 1990, blueback herring were caught in low numbers'in the estuary in the fall, but no alewives were collected (see Results Section :3.2.2).Another species that uses the estuary is winter flounder.This species undergoes onshore/offshore migration, depending on the time of year (Bigelow and Schroeder 1953) Juveniles (ages one~and two, based on length-frequency analysis) have been the main constituent in ' 'the estuary, primarily collected during the spring and summer (NAI 1985b).* Recruitment was evident by the occurrence of young-of-the-year size classes. 'Winter flounder have composed only a small portion of the estuarine fish assemblage, averaging only 2% since 1.976 (Figure '2.3-11).Their relative abundance was highest in April, when total catch is low-est. In 1990, winter flounder catches were lower than average through-out the year (see Section:3.2.2). ¶The dominant resident species in the estuary has historically been Atlantic silverside, which typically composed from just under 50%to nearly 90% of seine catches during the baseline period (1976-1989) during their period of greatest abundance, August to November (Figure 2.3-11). This trend continued in 1990, with one exception. High '.rainbow smelt catches in August reduced the relative importance (percent composition) of silversides. The population historically has been 86 composed primarily of yearling fish but- the occurrence of young-of-the-year size classes in spring has indicated recruitment (NAI 1985b).. The year-to-year variation in silverside catch has been the main cause of the observed variation in the total annual catch in beach seines for all species combined. Total catches were high from 1976-1981 (200-360 fish/haul) and much lower from 19.82-1989.(40-115.fish/haul) (Figure 2.3-11). Inceased total catch in 1990 was in largepart due to increased numbers of silversides in comparison to. 1989 levels. .However, given the high annual variability in silverside catches, 1990 were statistically similar to previous years levels, although lower than average (See Results, Section 3.2.2).Since the Hampton-Seabrook estuary contains the majority of New Hampshire's stock of the recreationally-important species Mya arenaria, an extensive sampling program (initiated in 1969) has been un-dertaken in order to characterize the natural variability in the popula-tion for all lifestages. Of the potential impact types, larval stages will be most susceptible to intake effects and therefore are discussed in that section (Section 2.2.1). Spat settlement densities appear to bear no relationship to the abundance or periodicity of Mya larvae in the nearshore-waters (NAI 1982b). It would appear that Mya veliger behavior (i.e. their "readiniess" or competency to settle) combined with the timing of favorable currents may be more important to settlement success than sheer numbers of larvae in the water column. Such condi-tions apparently existed in 1975, 1976, 1977, 1980, 1981 and 1984 when high young-of-the-year spat densities indicated successful recruitment at Flat 1 (Figure 2.3-12) and other flats. The 1976 year class in par-ticular provided an important and rejuvenating recruitment to the local population as shown by the high densities of 13-25 mm (yearling and older) spat clams in 1977 and 1978 (Figure 2.3-12). In 1989, young of the.year settlement densities throughout Hampton. Harbor were again high-er than previous levels. This level of settlement was sustained into 1990 at Flats 2 and 4 and showed further increases at Flat 1 (Figure 2.3-12). Survival of the 1989 year class at Flats 1 and 2 is suggested by increased densities of the 13.25 mm spat in 1990.87 co0 czl Figure 2.3-12.Annual log (x+l) mean density (number per square foot) of youngý-of-the-year (1-5 mm), spat (13-25 mm), juvenile (26-50 mm) and adult (>50 mm) Mya arenaria at Hampton- Seabrook Harbor Flat 1 from 1974-1990. Seabrook Operational Report, 1990. Once settled, survival of young-of-the year Iya depends on both the level of predation from its two main predators, the green crab and human clam diggers, and the absence, Of diseases such as neoplasia. Despite relatively heavy densities of young-of-the year in 1980,-1981, and 1984 on Flat 1, recruitment to yearling clams was minimal (Figure 2.3-12). This pattern was replicated throughout the estuary. Predation bygreen crabs, whose densities began to increase in 1980 and from 1983-1989 remained much higher than previous years, may have virtually eliminated the first and second year-class (Figure 2.3-13). Dramatical-ly decreased green crab catches in 1990 may have enhanced the survival of spat and juveniles, in part contributing to increased'densities at Flat 1 (spat only) and Flat 4 (spat and juveniles)(Figures 2.3-12,13). Human predation is also an important factor in the level of harvestable clams, and causes additional mortality to unharvested adults as well as spat and juveniles by disturbance. Digging activity declined sharply from 1982 to 1985 with a small'increase in 1986 as clam diggers switched among the flats within the estuary in an effort to harvest clams. Digging activity resumed its decline in 1987 and continued to fall through 1989, when flats were closed due to coliform contamination (Figure 2.3-13). The standing stock had declined precipitously from 1983 through 1987, lagging trends in digging activity by one year. In 1988, the decline of adult standing stock leveled off while the number of adult licenses continued to decrease. Harvestable clam densities began to increase at Flat 4 following closure of all of the flats to any digging activities, while standing stock at the other flats remained unchanged. However, for the entire area, harvestable clams have increased steadily since 1987, most likely due to the reduced digging pressure along with reduced numbers of. green crabs.Finally, the presence of disease has an undetermined effect on Mya recruitment and survival. Neoplasia, a cell growth disease fatal to Mya, was detected at Hampton Harbor Flats 1 and 2 in-studies conducted.in 198,6 and 1987 (Hillman 1986, 1987). Presence of neoplasia in 1987 coincided with dramatic decreases in juvenile and adult densities at.89 --- --LICENSES-*-o- 13 GREEN CRAB CATCH 14000 BUSHELS OF CLAMS 140 a " 12wO0 "- -°° "; ,120; i 0 10000 " 100/ * .I/"i z I U) : ~' .w , O .. t o 800 .I:80, (.* .0.LU '/ 4 0 Sb. It-JJ D C* 0 , 4000 b 1 ,-40 2000 "20 71 72 73 74 75 7778798081828384858687. 888990.YEAR Flats Closed Figure 2.3-13. Number of adult clam licenses issued, the adult clam standing crop (bushels), 197 1-1990, and green crab catch in fall, 1981-1990 in Hampton-Seabrook Harbor. Seabrook Operational Report, 1990. Flats 1 and 2, while Flat 4 densities, where no neoplasia were found, remained unchanged. The magnitude of the effect of this disease on the clam population is unknown.Increases in young-of-the-year recruitment in 1990, along with continued survival of yearling spat, suggest that there are no adverse effects from plant operation, including settling pond discharge or off-shore entrainment. The ability to assess impact in adult clams in Hamp-ton estuary will depend on close monitoring of all of the factors impor-tant to recruitment and predation. One of these factors is clam seeding by the State of New Hampshire. Seeding activities during 1987.and 1988 on Hampton Harbor tidal flats did not result in measurably increased spat densities. Thus, it appears that.predation levels and disease are currently the most important factors in determining the standing crop of harvestable clams.2.3.2 Benthic Monitoring 2.3.2.1 Macroalgae and Macrofauna Monitoring of the benthic organisms (macroinvertebrates, al-gae, demersal fish, and epibenthic crustaceans) was established to de-termine the extent of change (if any) to the community structure in this zone as a result of plant operation. Changes could be manifested by (1)the enhancement of detritivores and suspension feeders, (2) the in -creased attraction of benthic feeders caused by locally-increased food supply, and/or (3) impact on organisms sensitive to the increased detri-tus resulting from moribund entrained organisms. Mid-depth and deep (10-20 m) benthic communities, including macroalgae, macrofauna, and bottom panels, were sampled to monitor the preoperational benthic community. Year-to-year variations in community structure were small in comparison to variations related to depth-and substrate. The macroalgae community was highly similar among years, although less so than in the intertidal and shallow subtidal areas.91 Species composition of collections in the mid-depth and deep subtidal areas during 1990 was similar to those taken at the same station in previous years (Figure 2.3-7 and Section 3.3.2).. In 1990, plant start-up began less than a week before macroalgae and macrofaunal community. collections were made. Thus, 1990 collections are not expected to show changes resulting from plant operation. Species composition of the macroalgae community in mid-depth and deep areas was similar to previ6us'years (Figure 2.3-7). Total biomass of the mid-depth station groups in 1990 was similar to previous years. Deep discharge (B04) and farfield (B34) group biomass was lower in 1990 than in previous years, whereas deep intake (B13) station biomass was higher than previous years (Figure 2.3-7). 'Macrofauna community composition at mid-depth station in 1990 , was similar in mid-depth regions to previous years; the assemblage at deep stations was similar to the assemblage collected in the last 2-3 years (Figure 2.3-7). Heavy Balanus crefiatus.sets have differentiated '_the deep stations in recent years from the. deep water assemblage collected prior to 1988. Station group densities in 1990 were similar to previous years'.Other community parameters underscored the stability of the benthic community. The majority of changes noted in .1990 occurred at both nearfield and farfield areas. Taxa richness of both algae and macrofauna in 1990 was statistically similar to previous years at the mid-depth intake station and deep areas. Differences in macrofaunal and macroalgae taxa richness at the mid-depth discharge station were also observed in the farfield area (Table 2.3-2).Patterns in abundance and size distribution in selected benthic species were only slightly less predictable than community characteristics. Historically, abundances have varied among years and between nearfield and farfield stations (NAT 1990b). 1990 abundances of two taxa, amphipod Pontogeneia inermis and mussel Modiolus modiolus, 92 were similar to previous years (Figure 2.3-14). Abundances of mytilids were higher in 1990 at-the discharge station, and lower at the farfield station,-.whereas green sea urchins were more abundant in 1990 at both nearfield and farfield areas (Table 2.3-5, Figure 2.3-14). However, these differences occurred before plant operation began, and thus appear to be part of the natural variability among years. In particular, green sea urchin densities showed evidence of a long term cycle. 1990-densities, although higher than 1988 and 1989 densities, were lower than the preoperational average (see Results, Section 3.3.5).Length measurements have historically been a stable indicator of population recruitment and growth, showing low variability among years. Mytilids were larger than average at the discharge station, but within the range of previous years. Amphipod Pontogeneiainermis and the green sea urchin were similar in size to previous years (see Section 3.3.5).2.3.2.2 Demersal Fish Demersal fish that inhabit or feed in the nearshore area are important not only because of their predominance in the food chain but also because of their commercial value. As would be expected with any bottom-oriented species, the nearshore population of demersal fish show spatial differences associated with substrate and location relative to Hampton Harbor. Of the farfield stations, Tl has a sandy bottom and T3 has sand mixed with cobble and shell debris. The nearshore discharge station T2 is mainlylsand. Station T2, located off the mouth of Hampton Inlet, is influenced by tidal flow from the estuary, which often causes the accumulation of drift algae. The algae, combined with heavy lobster fishing in the area, has decreased gear effectiveness and has even prevented trawling activities in some months. For this reason, poten-tial effects of operation are investigated separately for the nearshore Station T2 and the more distant stations (T1 and T3), which are similar and thus combined for this assessment. 93 Annual Variability 4-3-, PREOP (n=12 except n=10 forModiolus) 0 1990 0 I w U-, z 0_j 1 0 2-1-1 0 I (.0 0 Relative Abundance z 0 0 0 0 0 50 40 30 20 OPREOP ol 1990 10 0 N/A I = I ... ...... i I I LU l LU wj.: a-Co a E CU 0 O'Co En U) 0'0.0 ": ZE CE oa)CD'0Ez0 az-o) E Ua, C a-a- 0 CD(N/A Percent composition not computed in instances where only a single species is collected. Figure 2.3-14. Preoperational mean (1978-1989) and 95% confidence limits and 1990 mean of log (x+1) abundance (no./m2) and percent composition for selected benthic species at mid-depth nearfield station. Seabrook Operational Report, 1990.94 TABLE 2.3-5.

SUMMARY

OF SIMILARITIES OF ABUNDANCES OF SELECTED TAXA IN MID-DEPTH REGIONS IN 1990 COMPARED WITH PRE-VIOUS YEARS. SEABROOK OPERATIONAL REPORT, 1990.RESTRICTED SIMILAR TO TREND AT OPERATIONAL 1990 SIMILARa 1990 DIFFERENT 9 NF/FFa. PERIODa Pontogeneia inermis Mytilidae no no, Modiolus modiolus Strongylocentrotus yes no* .droebachiensis Rainbow smelt Atlantic cod yes no Winter flounder Hakes yes no Yellowtail flounder yes no Lobster (total.catch) yes no Lobster (legal-sized) yes no Rock crab yes no Jonah crab no no'Based on results of ranks tests.Analysis of Variance or Wilcoxon's summed 95 Total catches in the demersal fish community showedevidence of a. multiple-year cycle. Total catches steadily increased from 1977-1981, declined from 1981 through 1985, generally increased through 1988, and decreased in 1990 (Figure 2.3-15). Catches from August-December, the period of operation in,1990, paralleled the trends for the entire year. Thus the decrease in total catch in 1990 wasnot restricted to the operational period. Seasonally, catches were usually lowest from January.through March or April, but the occasional appearance of rainbow smelt increased total winter catches as occurred at T2 in 1990. Total catch was highest in summer and, fall at T1 and T3, and somewhat earlier at T2 (Figure 2.3-15). Seasonal patterns of total catch in 1990 were similar at Tl and T3, but catches were lower than average at these stations. The seasonal pattern of total catch at T2 was slightly different in 1990 from previous. years. Catches were lower than average from March through June, then increased due to high catches of winter flounder. Large numbers of lobster traps prevented trawling at T2 in September and October.Historically, six taxa composed close to 80% of total near-shore otter trawl catches both across months and years (Figure 2.3-16).The spatial, seasonal, and annual variability of these dominant species had a strong influence on the community structure. The relative importance of dominant species often showed year-to-year fluctuations (Figure 2.3-16). Proportions-of hakes, Atlantic cod, and rainbow smelt varied by five to tenfold among years. Yellowtail flounder and winter flounder were more stable constituents, with lower year-to-year vari-ability. In 1990, hakes and cod had lower relative abundance than any previous year. Catches, of these species throughout 1990 were signifi-cantly lower than all previous years-at all three stations (Figure 2.2-6; Table 2.3-5). Rainbow smelt catches were higher than average in.1990 but statistically similar to previous years. Skates were also relative-ly more abundant, on average, than in previous years.The demersal fish community at T2 changed with the seasonal movements of the dominant species. The presence of rainbow smelt and, 96 Annual Catch 120.120 -STATIONS T-1, T3 80-60.I- 40 ., -* *0 I- 20 76 77 78 79 80 .81 82 83 84 85 86 87 88 89 90 Annual Catch,. August-December -STATIONS "/1,T3.p 100 loo* I- 80-0 2O 0-60 0'- 40 -, 40. *...*..K.. -,, .." " .*...o.- .. "-..76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Monthly Catch, Stations T1, T3 100-"" 80- ....... 1990 I--60 .z 0. ... ..... :.... .... " Z 40 %LU 20'0 .I I I I I I I I ~ I I JAN FEB MAR APR MAY JUN JUL, AUG OCP OT NOV DM Monthly Catch, Station T2 100-S .80 ........ 1990 60-Z 40-20 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV cm MONTH Figure 2.3-15. Total annual and monthly catch of demersal species at Stations Ti and T3 combined and Station T2 during the preoperational period (1976-1989) and in 1990. Seabrook Operational Report, 1990.97 z 0 i---0 0.0'3 Annual Variation 100 Stations T1, T3.80 60-40" 20-0 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 ,oo-1 Station T2 z 0 C,, 0 C-O 0 O.80-60-40-20-0 I*, skates 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Seasonal Variation Preoperational, O z 0 a-0 0 10o-80 40-20-0-E2 rainbow smelt-Atlantic cod 9 winter flounder 5 longhorn sculpin.([r hakes Ml Yellowtail flounder 1.f J F JAN FB MAR *APR MAY JUN JUL AUGl SEP OCT NOV rE 1990 100-z 80 0 Cn 60-0-0.o 40-20-0 NO TRAWLS JAN FEB MAR APR MAY JUN JUL -AUG SEP OCT NOV DL 1 MONTH Figure 2.3-16. Seasonal and annual changes in relative abundance of the demersal fish community, based on mean catch per unit effort at otter trawl*Station T2 during the preoperational period (1976-1989) and in 1990. Seabrook Operational Report, 1990.98 to a lesser extent yellowtail flounder, in winter (December-March) differentiated the community from the remainder of the year, when hakes (red, white, and spotted) predominated (Figure 2.3-16).The age structure of the fish population can also be a factor contributing to abundance variability. Based on 1983 and 1984 length-frequency data and age-size information from the literature, the dominant age group collected at the nearfield trawl station (T2) was determined. As with most of the pelagic and estuarine fish collected in this study, the majority of fish collected.with otter trawls were juveniles. Yellowtail flounder and rainbow smelt were predominantly young-of-the-year, whereas the majority of Atlantic cod were ages one and two. Only hakes and winter flounder had no dominant age class, although presence of young-of-the-year for these as well as the other taxa indicated the timing of recruitment. Knowledge of the age struc-ture of the population and use of age and growth parameters (NAI 1985b)can be used to better understand spatial and temporal changes in the*demersal fish population. Spatial differences are an important consideration with demersal fish. Historically, farfield Stations Tl and T3 have been similar in overall catch per unit effort (NAI 1990b). Communities have been dominated by the same species, although longhorn sculpin were more important at T3, while yellowtail flounder were more important at TT (Section 3.2.2.1). The nearfield station (T2) was unique, with total CPUE (averaged over all:years) reaching only 60% of that at farfield stations (Figure 2.3-15). This may be due in part to decreased sampling efficiency from accumulated drift. algae and-interference from lobster traps. Historically, winter flounder and rainbow smelt (together) composed 45% of the overall'catch at T2, compared with 11-12% at the..farfield stations (Figure 2.3-16). These species were relatively more abundant at the farfield stations in 1990 (15-19%) than previous years, but their relative abundance remained less than half that at T2 in 1990 (45%). Most of the differences in total catch and species composition 99 can be attributable to the previously mentioned differences in substrate and location with respect to Hampton Harbor..., Changes in the demersal fish community in 1990 were mainly the result of significantly decreased abundances of Atlantic cod and hakes.This. is consistent with historical trends, as demersal fish catches have shown substantial variations among years. Since catches of these species were diminished throughout the year at all three stations, the differences appear unrelated to plant operation., 2.3.2.3 Epibenthic Crustacea Because of its commercial importance, all life stages of the American lobster have been studied over the last 12-16 years. Annual catches of adult lobsters ("Total catch") averaged between 46 and 93 per year for a 15-1trap fishing effort. Catches were highest during late summer and fall, from August-November. Seasonal trends of lobster catches in 1990 were similar to previous years, but monthly catches were consistently higher than average at both nearfield and farfield stations (Section 3.3.6). Higher than average bottom temperatures may, in part, be responsible for higher catches. Temperature acts not only to incre-ase activity (and .thus the likelihood of being caught [Dow i969.]) but also affects seasonal.movements (Campbell 1985).. Increased lobster catches were reported in 1990 both in New Hampshire and.throughout New " England (NOAA 1991b). Variations in catches of legal-sized lobsters, a primary concern to lobstermen, were a result of natural. variation com-bined with the effects of increases in the legal size limit in 1984, 1989, and 1990. Effects of the first increase in the legal size limit in 1984 (from 3 1/8" [79.4 mm] to 3 3/16" [81.0 mm]), reduced the pro-portion of legal-sized lobsters-from an average of 14% (1975-1983) to 8%(1984-1988). A second increase in the legal size limit (to 3 7/32"[81.8 mm]) in 1989 coincided with a 50% decrease in legal catches to 5%of total catch. The increase in legal size in 1990 to 3 1/4 in (82.6 mm) further reduced legal catches to 3% of the total catch.100 " Size class distributions reflect changes in the legal *size limits. Since 1981, 67-79 mm lobsters have-predominated in trap catches. Numbers of lobsters measuring 79-92 mm, as well as their proportions, were higher in 1990 than in 1984-1989, which in turn were higher than previous years. This probably reflects the increased protection from fishing pressure caused by size limit changes (Figure 2.3-17).Jonah (Cancer borealis) and rock (C. irroratus) crabs are col-lected along with lobsters in the trapping program. Jonah crab catches have shown an increasing trend. Catches at the discharge area were higher from 1985-1987 than previous years; in 1988 and 1989, annual catches surpassed all previous years. 1990 catches, however, were lower than the past two years, but higher than the average for the study period (1982-1990; Figure 2.3-16). Increased catches occurred in July and August. Jonah crab catches at Rye ledge in 1990 were lower than average in all months that collections were made, but within the range of previous years. Although Jonah crabs were statistically different in 1990.only at the discharge area, differences were first observed prior to plant start-up. Thus, 1990 differences are unrelated to plant opera-tion.Rock crabs are less prevalent than their congener in the study.area, probably because of their preference for sandy substrate (Jefferies 1966). Catches in 1989 were the highest observed to date, at both the discharge area and Rye Ledge. In 1990, catches were still higher than average at both stations (Figure 2.3-4), but were lower than the peak catches observed during the previous year. 'Higher than average catches in 1989 and'1990 were due to large catches from June through August.101 " ] Size-class 0.F-0-0.C-, I-.Ct., 90 80 70 60-50 40-30 20 10 ssi sss sss sss sss m ss, ss,P/7 FEE 7 4-"-"I"'I F1s1:*.M > 105 mm 9 92-105 mm] .79-92mm Eo '67 -79 mm 54 --67 mm[ <54mmfI*** --'. I I .I 1 11W,','A V 75 76 77 78 *79 80 81 82 83 84 85 86 87 88 89 90 YEAR Legals and Sublegals E SUB-t.2GAL 100-a: I-U, w.L I-UJ 80-60-40 20 w 1j 1 fI I.- II 1.11 1.07. I 1.5% 6 157. 12% 11 10% 11 7% II 8% I 10% f 7% II 9% I II % II i i I I I I 1 T 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 YEAR Figure 2.3-17. Size class distribution of lobsters and catches of legal and sublegal-sized lobsters at the discharge station; 1975-1990. Seabrook Operational Report, 1990.102.

3.0 RESULTS

3.1 PLANKTON AND WATER QUALITY PARAMETERS Plankton and water quality programs of the Seabrook environ-mental studies have included water quality sampling, phytoplankton, microzooplankton, bivalve larvae, and macrozooplankton. The plankton and water quality programs presented in this 1990 operational report are those for which sampling was conducted during 1990: water quality (Section 3.1.1), phytoplankton (3.1.2), microzooplankton (3.1.3), bivalve larvae (3.1.4), and macrozooplankton (3.1.5). Results from entrainment sampling for bivalve larvae are also presented.

3.1.1 Water

Quality Parameters-Seasonal Cycles and Trends Three physical (temperature, salinity and dissolved oxygen)and five, chemical (orthophosphate, total phosphorus, nitrite-nitrogen, nitrate-nitrogen and ammonia-nitrogen) parameters .were monitored over a 13-year period to assess their temporal variability. A farfield station (P7) was- added in 1982 to provide a reference area. With the exception of ammonia, parameters exhibited cycles with one or two peaks annually.Water temperature was monitored in the nearfield both contin-uously and from discrete samples collected weekly. twice-weekly, or monthly during the plankton cruises. Historically, monthly mean values derived from.both sampling methods have been similar (NAI 1980c,. 1980d, 1981f, 1982a, 1984a, 1985a). Surface water temperatures were strongly influenced by solar irradiation, with temperature peaks lagging.irradiance peaks by one month (NAI 1985b). Bottom temperatures (depth 16 meters at MLW) showed truncated peaks which lagged one to three months.behind surface peaks. Since 1978, highest temperatures at Station P2 have occurred in July or August at the surface, and from August to October at the bottom (Figure 3.1.1-1). In 1990, peak surface and bottom temperatures occurred in August and were above the preoperat-. ional average. Surface and bottom water temperatures.remained above 103 Surface, Intake 20-n I- 10-wU 0U P1990.... 1990 U II I I I I I I I JAN FE MAR APR MAY JUN. JUL AUG S OCT NOV DEC, MONTH Bottom, Intake a: w.I.--20-15-10 P1EOP-... .1990 0 I I I I I I I I I , I I .4 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Surface, 1990 20-o-15-I.U 10-w LU 0 INTAKE (P2)....... DISCHARGE (PS)....... FARFIELD (P7)I I I I I I I I I a I I .I I I I I I JAN FEB MAR APR MAY JUN JUL AUGi SE OCT NOV DEC MONTH Figure 3.1.1-1. Surface and bottom temperature (CC) at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989 and monthly means at Stations P2, P5, and P7 in 1990. Seabrook Operational Report, 1990..1 04 average for the remainder of the year (Figure 3.1.1-1) resulting in annual mean temperatures that were higher than the preoperational average (Table 3.1.1-1). However, 1990 nearfield-temperatures were statistically similar to previous years for both the entire year and during the operational period (August-December; Table 3.1.1-2).In 1990, temperatures were monitored at the-intake (P2),ýdischarge (P5), and farfield stations (P7). Monthly mean surface temperatures were statistically similar at all three stations both for the entire year and for the operational period (Table 3.1.1-2) There were no discernible differences in seasonal patterns among the three stations (Figure 3.1.1-1).Continuous temperature data were provided by:YAEC from stations located near the intake (T7) and discharge (DS) areas. Monthly averages of daily surface temperatures at the discharge station (Figure 3.1.1-2) were similar to those at intake station T7 in July, August, and September. From October-December, surface temperatures at the discharge station averaged 0.8-1.60C higher than those at station T7 (Figure 3.1.1-2)... Temperature differences between surface and bottom waters show the seasonal trend in development and dissipation of the thermocline. Historically, vertical temperature differences were minimal (<10) from January through March and November-December (Figure 3.1.1-3). Vertical temperature differences have been most pronounced (at least 3 0 C) from May through October. Thermocline development in 1990 was similar to previous years, although temperature differences were less than the preoperational average from June through September. Thermocline.dissipation in 1990 during the operational period (August-December) was similar to previous years.Other water quality parameters were also monitored at Station P2, P5 and P7 during fortnightly plankton cruises. As in previous 105 I TABLE 3.1.1-1.ANNqAL MEANS AND COEFFICIENTS OF VARIATION FOR WATER QUALITY PARAMETERS MEASURED zw n xm ,,r n l -i In UA ] ) ~t17 t' niTD "" N ( T 'I DI' '-1.I" T]DURING PLANKTON CRUISES AT ANNUAL MEAN (AND COEFFICIENT OF VARIATION) PARAMETER 197.8 1979 1980 1981 1982 1983 1984 i985 1986 1987 1988 1989 PREOP .1990 Temperature ("C)surface 8.37 8.76 8.76 8.72 8.88 9.58 8.94 9.73 9.31 9.12 8.55 8.87 8.86 9.52 (66.9i3) (57.85) (57.86) (63.34) (53.02) (53.74) (55.72) (54.55) (49.57.) (57.80) (60.23) (62.74) (56.45) (59.32)bottom 6.61 6.36 7.05 7.37 *7.36 7.32 6.93 8.03 7.58 6.39 *6.46 6.54 6.92 7.97 (55.62) (47.96) (52.76) (59.11) (46.03) (44.43) (45.04) (47.81) (40.42) (45.95) (45.36) (56.56) (47.91) (54.23)Salinity (ppt)surface 31.68 31.82 32.17 31.89 31.84 31.04 30.68 32.15 31.68 30.65 31.74 31.48"` 31.57- 31.09 (3.33) (3.84) (2.64) (2.16) (3.47) (4.39) (4.93) (2.26)1 (2.44) (6.76) (2.36) (3.56) (3.89) (4.44)bottom 32.24 32.47 32.42 32.32 -32.41 .31.92 31.77 32.50 32.20 31.48 32:26 32.12 32.18 .31.86 (1.65) (2.77) (1.52) (1.41) (2.01) (2.12) (1.83) (1.54) (1.77) (2.66) (1.40) (1.83) (0.11) (3.01)Dissolved Oxygen (mg/1) -surface 10.28 10.02 10.27 9.90 9.60 9.48 10.01 9.67 9.88 9.89 9.72 9.72 9.87 *9.67 (10.80) (13.39) (11.17) (12.70) (11.15) .(7.73)-(12.06) (10.42).'(11,03) (9.92) (11.01) (10.73) (10.86) (12.16)bottom 10.07 9.69 9.85 9.43 9.25 8.98 9.-32 9.17 8.96. 9.73 9.07 9.07. 9.37* 9.11'(8.86) (14.67) (14.28) (17.90) (16.17) (11.99) (13.56) (15.36) (13.52) (11.64) (16.54) (14.60) (f4.11) (15.82)Orthophosphated 9.58 9.75 10.12 11.82 17.02 19.23 14.29 -_ b -- c 18.08 16.80 .14.08 13.93. 15.42,* (pg/i) (29.99) (52.59) (76.10) (30.83) (55.54) (44.47) (56.06) -- -- (45.25) (45.24) (60.89) (55.11) (59.48)Total phosphorusd 32.50 15.12 31.96 22.50 24.61 -25.83 24.117 -. b -c 33.36 28.80 27.92 26.70" 29.17 (9g/i) (40.09) (63.09) (77.68) (.33.93) (28.66) (35.05) (40.43) -- -- (40.30) (34.03) (36.99) (48.50) (34.16)Nitrited 2.12 1.71 3.17 2.92 2.30 2.05 1.02 -- b 1.48 2.50 1.67' 2.17 2.96'(Pg/i) (46.11)-(66.58) (59.59) (53.13) (68.34) (54.34) (98.08) .. (98.00) (60.43)-(81.24) (68.42) (80.08)Nitrated 52.08 38.33 48.33 45.42 37.17 51.83 36.75 _. b 44.42 49.50 67.62 45.16 73.33 (pg/i) (116,61)(101.24)(111.88) (94.41)(137.89)(106.62)(117.47) .... (132.17)(111.11)(100.99)(112.71) -(85.28)Ammoniad 51.46 47.42 104.17 36.25 <30.00a 27.32 16.57 b C 53.33 20.30. <10 39.26 <10 (pg/l) (120.96) (42.93) (48.73) (64.73) -- (115.96) (70.82) -- (61.541)(145.32) -- (105.70) (56.86)*0 0N Below detection limits (30 pg/l) of metho Not measured in 1-985.-dMeasured July through December 1986 only.Collected one meter below surface.ds used in 1982. TABLE 3.1.1-2. RESULTS OF ANALYSIS OF VARIANCE OF WATER TEMPERATURESCOMPARED AMONG STATIONS. P2, P5, AND P7 IN 1990 AND AMONG YEARS AT STATION P2 FROM 1978-1990 AND COMPARISONS OF SALINITY, DISSOLVED OXYGEN AND NUTRIENTS AMONG STATIONS IN 1990. SEABROOK OPERATIONAL REPORT, 1990.JANUARY-DECEMBER AUGUST-DECEMBER PARAMETER DEPTH SOURCE df SS F df SS F Temperature Surface Station 2 1.88 0.97 NS 2 0.87 0.98 NS'Bottom Station 2 0.07 0.99 NS 2 0.48 0.97 NS Surface Year 12 30.95 1.00 NS 12 38.25 0.99 NS Bottom *Year 12 48.86 0.98 NS 12 59.61 0.74 NS Salinity Surface. Station 2 .0.27 0.05 NS 2 0.36 0.06 NS Bottom ..Station 2 1.41 0.31 NS .2 3.29 0.49 NS:Dissolved oxygen- Surface Station 2 0.26. 0.10 NS 2 0.17 0.31 NS Bottom Station 2 0.98 0.23 NS -2 1.00 0.59 NS Surface Year 13 8.32 0.53 NS 13 6.39 1.09 NS Bottom Year 13 19.30 0.83 NS 13 14.72 1.53 NS Orthophosphate Surface Station 2 <0.01 0.20 NS 2 <0.01 0.10 NS Total phosphate Surface Station 2 <0.01 0.64 NS 2 0 0.00 NS'Nitrite Surface Station 2 <0.01 0.23 NS 2 <0.01 0.48 NS Nitrate Surface Station 2 <0.01 0.12,NS 2 <0.01 0.06 NS Ammonia Surface Station 2 <0.01 1.10 NS 2 <0.01 0.92 NS NS = Not Significant (p>0.05)df = degrees of freedom SS = sum of squares, Stations DS & T7 20-18-16-14-12 CU w Cw w 10-8-4-2-DS (discharge) "'-'""-. T7 (farfieid) (3 ALG I SEP OCT NOV I MONTH Figure 3.1.1-2. Comparison of monthly averaged continuous temperature Q'C) data collected at discharge (DS) and farfield (T7) stations during commercial operation, August-December 1990. Seabrook Operational Report, 1990..108 7-.. E=P 5-4-w w I.l 3-2-1--1 JAN FE I I I I I , FEB MAR APR MAY "JUN JUL AUG SEP COT NOVJ ~ r'MONTH Figure 3.1.1 i-3.Monthly mean difference and 95% confidence limits between surface and bottom temperatures (CC) at nearfield Station P2 over all years from 1978-1989 and monthly means in 1990. Seabrook Operational Report, 1990.109 years, surface salinities in 1990 began to'decline in February (Figure 3;1.1-4). Lowsalinity levels usually occurred in"April or May, but were not observed until June in 1990, when surface salinity was well below the preoperational average. This maybe attributable to above average precipitation for April.and.May (Section 3.3.1). The low surface .salinity observed in June was followed by a small increase in July and then dropped sharply in August (Figure 3.3.1-3), coincident with higher-than-average.precipitation in July and August (Section 3.3.1). The August salinity was the lowest ever observed for this month at Station P2. Surface salinities then steadily climbed through the remainder of the year, but continued to be slightly below the preoperational average. Annual fluctuations in bottom salinities followed roughly the same pattern as surface salinities, although the magnitude of differences was not as pronounced. The annual mean surface and bottom salinities were below the preoperational average for the thirteen-year period, but within the range .of annual means. No signifi-cant differences in salinity occurred among Stations P2, P5 and P7 in 1990 (Table 3.1.1-2).Historically, surface and bottom dissolved oxygen peaked in late winter (February-April) and decreased to lowest levels in fall (August-November) (Figure 3.1.1-5)). Seasonal trends in.1990 were similar, although the fall nadir in September was lower than the preoperational average. Dissolved oxygen patterns were similar at Stations P2, P5 and P7 as evidenced by the results of analysis of variance (Table 3.1.1-2).Historically, orthophosphate and total phosphate did not show evidence of a strong seasonal cycle. Values were lowest in summer, (May-September), during the presence of the thermocline (Figure 3.1.1-6). The seasonal variation of orthophosphate and total phosphorous in, 1990 was comparable to previous years, although values above and below the preoperational average were observed. No spatial differences'-were found for.either parameter in 1990.(Table 3.1.1-2).. Peaks in ortho-110 Surface Salinity PRE1 P 19 l90 34-33 a z Cn I--D: 0. I-,.32-30-29 28 i I I i i i i J J i i i i JAN FEB MAR APR MAY JUN JUL AUG SEP WCT NOV DMC MONTH Bottom Salinity-- PREOP...... -1990 C z U, 0<C"I-0.34-33-32 31 30 29-...28.1 i I S I I I JAN FEB MAR ----APR' MAY JUN.J I i I I I.JUL AUG SEP OCT NOV DEC MONTH Figure 3.1.1-4. Surface and bottom salinity (ppt)at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989, and monthly means for 1990. Seabrook Operational Report, 1990.1i1 Surface Dissolved Oxygen M L.0.U,.-I 12-.11 10-9-8-7-PRE OP 1990 6 I S S S S S S I S I S S JAN FEB MAR APR MAY JUN JUL. AUG SEP OCT NOV DEC MONTH Bottom Dissolved Oxygen w W.(I)12-11 10 7-I-PREOP-. .--- 1990 r.. .. .. .* S I , I I I S S I I I JAN FEB MAR APR MAY JUN.. JUL AUG SEP OCT NOV DEC MONTH Figure 3.1.1-5. Surface and bottom dissolved oxygen (mg/L) at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1989, and monthly means for 1990. Seabrook Operational Report, 1990.112 Orthophosphate x LU LU C, 0 60-50-40-30-20-10-PREOP 1990 detection -limit 0 I I I I I I I I JAN FEB MAR .APR MAY JUN JUL AUG I I -I I~SEP. OCT N?'V, DE MONTH Total -Phosphorus -PREOP 1990 60-50-LU-40 cn 30 20-0 00 5 lo-detection '-'limit 0 Figure 3.1.1-6. Surf me&and I I £ I , I I I I I " " I I I JAN FEB MAR APR- MAY JUN JUL AUG SEP OCT NWV DEC MONTH ace orthophosphate and total phosphorus (ug P/L) at nearfield Station P2, monthly ns and 95% confidence intervals over all years from 1978-1984 and 1986-1989, monthly means for 1990. Seabrook Operational Report, 1990.113 phosphate concentration in 1990 occurred in February and April, and were consistently above the preoperational average from September through December. Values for orthophosphatein March, May and June 1990 were somewhat lower than the mean for previous years. Concentrations of total phosphate for the year stayed generally within the 95% confidence limits, but were elevated in October and November (Figure 3.1.1-6).!- Nitrate levels at station P2 have historically shown a strong seasonal cycle. Values typically steadily decreased from January to May, remained low through September, then steadily increased for the remainder of the year. The seasonal nitrate cycle in .1990 approximated the preoperational average, With the yearly low occurring in June.However, higher-than-average nitrate values were observed from January through May, and in September and October. Ammonia and nitrite levels historically have not shown a strong seasonal pattern. Nitrite values fluctuated widely in 1990, and higher-than-average values were observed in February, May and October (Figure 3.1.1-7). In 1990, ammonia concentrations were below the analytical detection limit (10 pg/1) for seven months of the year (January through March, June through August and November) and below the preoperational average during the remaining months (Figure 3.1.1-8). Concentrations of all nitrogen nutrients were similar among Stations P2, P5 and P7 in 1990 (Table 3.1.1-2).3.1.2 Phytoplankton 3.1.2.1 Total Community Temporal Characteristics During the preoperational years, mean total phytoplankton abundance exhibited a bimodal annual cycle with spring and fall maxima and summer and winter minima: (Figure 3.1.2-1; refer to Figure 3.1.2-1-of NAI 1985b). In 1990, the spring peak occurred in June, one month'later than in preoperational years, and a fall peak was not observed at all.Total abundance was higher in 1990 than during the preoperational 114. Nitrate-Nitrogen P2EOP 2001 ... .. g0*1 80 160 0~cc 140 120 100 80 60 40 a detection --limit 20 JAN. FEB MAR APR MAY JUN JUL ALG SEP OCT NOV DEC.MONTH Nitrite-Nitrogen -- PREOP.1990.IJ v-ILl a-Cn 0 detection a limit 10-9-8-7-6-4-3-2 1-S *I t I I .I I I I I I I I JAN FEB. MAR APR MAY JUN JUL AUG SEP OCT NOV CEEC MONTH a For the purpose of calculating monthly means, data points reported as'below detection limit' were given a value of one-half the detection limit.Figure 3.1.1-7. Surface nitrite-nitrogen and nitrate-nitrogen (xig N/L)at nearfield, Station P2, monthly means and 95% confidence intervals over all years from 1978-1984 and 1986-1989, and monthly means for 1990. Seabrook Operational Report, 1990.115 Ammonia 120 110 100_90 I-rfr cc a 0 cc 80 70 60 40 HT 20 , detection a 10" --- --- -- -- I a I I Ii I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP CXT NV DEC MONTH a For the purpose of calculating monthly means, data points reported as'below detection limit* were given a value of one-half the'.detection limit.Figure 3.1.1-8.. Surface ammonia-nitrogen (ug NIL) at nearfield Station P2, monthly means and 95%confidence intervals over all years from 1978-1984 and 1986-1989, and monthly means for 1990. Seabrook Operational Report; 1990. -PREOP 8.0 -7.8 -.1990, including colonial Cyanophyceae -1990, excluding colonial Cyanophyceae 7.6 -7.4 7.2-7.0 -6.8 -6.4-6.2 -6.0 -LU z 0-j 0 i.5 0 5.8 -5.6 -5.4 -5.2 -5.0 4.8 -4.6 -4.4 -4.2.-4.0 -3.8 -3.6 I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DL MONTH Figure 3.1.2-1. Log (x+1) abundance (no.11) of total phytoplankton at nearfield Station P2;monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means with and without colonial Cyanophyceae for 1990. Seabrook Operational Report, 1990.117 period, with 1990.monthly total abundance values generally above the upper-bound of preoperational 95%,.confidence intervals (Figure 3.1.2-1).For the months of August through December, the number of species composing 1% or more of total abundance varied from only five in 1990 to as many as fourteen in i981 (Table 3.1.2-1). Skeletonema costatum was consistently dominant in the preoperational period,.accounting for approximately 10-90% of the phytoplankton assemblage during these years. In 1990,.however, Skeletonema costatum composed less than'l% of the total assemblage. Colonial Cyanophyceae'replaced Skeletonema costatum as the most abundant taxon in 1990, accounting for 66% of the assemblage, Colonial Cyanophyceae were absent from preopera-.tional samples between 1978 and 1983, and accounted for less than 0.1%.of the assemblage in 1984, buf contributed 13% of the total abundance in 1986. -Other species that were dominant in some years during the preoperational period include flagellate algae (54% in 1983), and Rhizosolenia delicatula (69% in ,1979), while in 1990, unicellular and flagellate algae, filamentous Cyanophyceae, and Chroomonas sp. were all abundant, each accounting for more than 1% of total.abundance. The mean abundances of taxa dominant in 1990 are generally quite different compared to preoperational years. In 1990, five taxa each comprised greater than 1% of the total abundance. These taxa were, as noted above: colonial Cyanophyceae, unicellular algae, flagellated V algae, filamentous Cyanophyceae, and Chroomonas sp. (a cryptophyte). Mean abundances of each of these taxa during August-December in pre-operational years were at least two. orders of magnitude lower'than during the same months -in 1990 (Table 3.1.2-2), and in each case, the lower 95% confidence level for the 1990 means were above the upper bound of the preoperational 95% confidence levels. Confidence intervals of 1990 abundances of other relatively abundant taxa generally overlapped confidence intervals for the preoperational.periods,. This indicates that abundances in 1990 for these taxa were within the previously.observed range of naturalvariability. 118 TABLE 3.1.2-1. PERCENT COMPOSITION OF SPECIES BY YEAR FOR PHYTOPLANKTON DATA DATA' IS SUBSET FOR 1990 OPERATIONAL PERIOD *AUGUST -DECEMBER.SEABROOK OPERATIONAL REPORT, 1990.kO CYANOPHYCEAE;COLONIAL ALGA; UNICELLULAR CYANOPHYCEAE

FILAMENTOUS IALGA; FLAGELLATE ICHROOMONAS SP.SKELETONEMA COSTATUM

PROROCENTRUM MICANS.LEPTOCYLINDRUS DANICUS ILEPTOCYLINDRUS MINIMUS BACILLARIOPHYCEAE ICENTRALES 1PENNALES RHIZOSOLENIA DELICATULA IPERIDINIUM SP.INAVICULA SP.ITHALASSIONEMA NITZSCHIOIDES ICHAETOCEROS SP.NITZSCHIA DELICATISSIMA 1GYMNODINIUM SP.EUGLENALES INITZSCHIA SERIATA 1RHIZOSOLENIA FRAGILISSIMA IMERISMOPEDIA SP.--ITHALASSIOSIRA SP.IDINOPHYCEAE INITZSCHIA LONGISSIMA IRHIZOSOLENIA SP.ICERATAULINA BERGONII.ICERATIUM FURCA RHIZOSOLENIA STOLTERFOTHII ASTERIONELLA GLACIALIS IGYRODINIUM SP.1CYANOPHYCEAE ITHALASSIONEMA SP.PHAEOCYSTIS POUCHETII PLEUROSIGMA ANGULATUM IALL 65.751 19.70 8.181 2.56i 1.89 0.561 0.38: 0.13[0.121 0.071 0.061.0.041 0.031 0.021 0.021 0.021 0.011 0.01'0.011 0.001 0.001 99.561 13.461.0. 05 1 3.28 1 66.221 0.031 0.041 2.091 0.031 1.081 0.171 0.27.1 0.541 0.821 1.381 0.031 6.191 1.351 1.311 1.041 0.061 0.011 0.001 99. 45 1 0.02*0.00 0.02 4.19 72.53 0.14 4.24 3.07 0.01 0.26 0.15 0.69 0.001 0..011.0.541 0.851 0.691 I 0.021 0.971 1.221 1 0.961 3 *231 0.121.0.001 5.70.1 0.011 0: 001 0.001 P9.651 1.I171 0.01n 54.271 10.151 0..091 0.581 0;431 6.291 0.851 2.321 0.781 1.621 0.791 0.051 0.301 0.101 7.991 1.081 4.211 0.151 0.011 1.161 0.821 1.68 0.32 0.05 97.27 15.31 4.63 48.64 0..36 13.38 1.73 0.01 0.19 10.64 0.92 0.28 0.01 0.51 0.40 0..00 0.04 0.08 0.06 1.08 0.45.0.13 0.00 0.05 0.05 98.93 1.141 7.671 0.081 28.851 0.781 1.471 0.791.1.371 1.231 0.011 0.371 1.321 19.861 1.281 2.401 0.531 9.921 I 1.401 0. 181 0.221 0.011 0.011 0.971*I, 0.o00 0.501 13.591 2.431 I 98.371 1.118, 0.22'88.40,'0.06'0.52'3.60'0.00 2.02'0.14'0.801 0.011 1.33'0.091.0.39'0'. 00 0.00'0.141 0.. 01'98. 921 0.031 68 761 0.141 0.02 0.03 0.71 0.02.1.32 0.07 0.06 0.03 0.02 1.23 7.45 1.69 99.40 1 90 1 86 1 84 1 83 1 82 1 81 1 80 1-4-- --------------

+---------.-----4----4---.~---+ 79 1 78 I----+-----II 0.041 0.071 0.021.0.391 62.611 7.361 0.041 i.3.91 22.15 0.00 8.54 0.05 1. 05 0.01 0.03 0.02 1.07 0.03 0.16 0.01 0.00 99.73 9 TABLE 3.1.2-2. PREOPERATIONAL AND OPERATIONAL GEOMETRIC MEAN ABUNDANCEa AND CONFIDENCE INTERVAL FOR PHYTOPLANKTON TAXA OCCURRING BETWEEN AUGUST AND DECEMBER AT STATION P2.SEABROOK OPERATIONAL REPORT, 1990.PREOPERAýIONAL I SPECIES. YEARS 1990 C SPECIES .X, ' CI X CI " Cyanophyceae; colonial-0.64 0.52 6.63 0.14 Alga, unicellular, 1.21 0.53 5-.78 0.77 Cyanophyceae; filamentous 0.13 0.19 4.89 1.14 Alga, flagellate 3.35 0.68 5.00 0.58.Chroomonas sp. 1.36 .0.53 4.83 0.69 Skeletonema costatum 4.71 0.38 3.22 2.42 Rhizosolenia fragilissima 1.76 0.68.Leptocylindrus mninimus 2.01 0.69 2.82 .2.14 SNitzschia delicatissima 2.38 0.63 1.22 2.09 Merismopedia sp. 0.21 0.31 Thalassiosira sp. 2.33 0.59 Centrales 1.43 0.61 3.55 0.40 Dinophyceae .* 2.07 0.62 Chaetoceros sp. 2.47 0.52 0.71 1.97 Thalassionema nitzschioides 2.94 0.58 .94 2.21.Cerataulina bergonii 0.99 0.51 Leptocylindrus danicus 0.66 0.45 1.71 2.91 Nitzschia seriata 2.15 0.60 0.60 1.66 Rhizosolenia delicatula j 3.04 0.65 0.78 2.16: Asterionella glacialis 0.95. 0.47 Pennales 1.22 0.52 2.24 2.54 Rhizosolenia stolterfothii 0.44- 0.35 Navicula sp. 0.60 0.37 3 ' .09 0.16 Bacillariophyceae 2.96 0.42 3.48 0.64 Rhizoselenia sp. 0.89 0.44 Euglenales 1.57 '0.52 1.67 1.90 Cyanophyceae 0.66 0.52 Thalassionema sp. 0.49 0.40 Gymnodinium sp. 0.56 0.44 1.24 2.10 Gyenodinium sp. ** Peridinium sp. '1.03 0.47 1.93 2.23 , Ceratium furca 1.00 0.43'Prorocentrum micans 2.29 0.51 3.40 2.43 Phaeocystis pouchetii 0.27 .Pleurosigma angulatum 1.2 .0.351,-..! ... ..1.22 " 0 .51 Gyrodinium sp.Nitzschia longissima 2.27 ..0!.48'Log transformed means and 95% confidence intervals in cells/liter. bSample size.= 40 (five months by eight years)'.cSample size 5 120 Just as total abundance was shown to vary over the year in Figure 3.1.2-1, the relative abundance of individual taxa also varies throughout the year.' During the preoperational period, phytoplankton species succession generally followed patterns described by Margalef (1958, northwest coast of Spain) and Lillick (1940, Gulf of Maine cited in NAI 1985b). Both studies demonstrated that nutrient supply was the main determinant of succession and that temperature was important insofar as it worked to enhance or restrict nutrient supplies within thermal strata (NAI 1985b). Margalef (1958) proposed the following seasonal cycle of taxa replacement within the community:

1) small-celled species in the spring, capable of rapid division due to a high surface area-to-volume ratio, succeeded by 2) larger flagellates and diatoms with a lower turnover.rate, followed by 3) large motile 'forms (flagellates and dinoflagellates) during the period of highest thermal stratification..

Succession of phytoplankton assemblages during the preopera-tional period at the Seabrook sampling locations was similar to that.described by Marga lef (Figure 3.1.2-2; NAI 1985b). The spring bloom during the preoperational period was initiated by different taxa from year to year; centric~diatoms (Bacillariophyceae, especially Thalassio-sira 'sp., Chaetoceros sp., and Skeletonema cOstatUrn) were most often the first to appear in high densities (see Table 3.1.2-2 of NAI 1985b).Small flagellates and colonial blue-gre.en algae were also among the spring dominants. Large vernal blooms.of Phaeocystis pouchetii (a member of the Xanthophyceae group, or yellow-brown algae) occurred in., five of the seven preoperational years. By midsummer, dinoflagellates (Dinophyceae) appeared in high numbers. Diatoms (Bacillariophyceae) reached their highest densities in the fall due largely to blooms.of Skeletonema costatum and other diatoms. Overall, during the preopera-tional period diatoms were the most abundant group from August through the winter until.February, The Xanthophyceae (Phaeockstis pouchetii) were most abundant in the spring, while during summer all groups were well represented. -121 100 90 80 Z 70 0 ca 60 0 C.o 50 I--z w 40 30 20 10 0 , ~, ~, -\ ~~~4'-I---I'I, I I I I I I I I I I I I'-I I-.,\ % 'III III II-II,-III..' ' \.I-I ,. -\ S.III, S. S.I.S.III.S. S.S S.-II.\*S. S.III.'S.'1~'I.S.I--.~S. '. ~III.'S.'I-I.S.I--.'S.I-.S.'II.S.'II,'S.'III.S. S.S.I IIIS.I,,,'S.'I,,, S.'-'II-~S. S.S.'I'-,'S.II'S.'III,'S.'I-I I I S. S.S.I-,, S. S.S.'III S. S.S.'I-I'I,,'S.-I S.-I-I'-I,S.S.1.-I, S.-III S. S..S.1111 S.-I-I S.I S.-I,, S.-, III S.III S., I 1-.~'S.',. I.,, S.I!(includes species fiom all groups* OTB occuring less than 1%)O XANTHOPHYCEAE [ DINOPHYCEAE 12 El BACILLARIOPHYCEAE CRYPTOPHYCEAE

• CHLROPHYCEAE 0 CYANOPHYCEAE JAN FM MAR APR MAY JUN JUL , I I SEP OCT NDV M MONTH.Figure 3.1.2-2. Seasonal succession of the major phytoplankton groups (percent composition) during the preoperational years (1978-1984) at nearfield Station P2. Seabrook Operational Report, 1990.

Based on yearly mean abundance, colonial Cyanophyceae added substantially to the total abundance and were the overwhelmingly dominant taxon in 1990 (Table 3.l.2-i),-perhaps reflecting a regional pattern. In transects across the Gulf of Maine Balch et al. (1991)observed abundances of cyanophyceae ranging from 2 -7 x 107 cells/i in the summer of 1988 and i989. High densities of colonial cyanophytes have been reported in several other areas of New England: Woods Hole Harbor at 2x10 6-3.,6x10 8 cells/i (Waterbury,Oet al. 1979); Narragansett Bay at.106 cells/i; Rhode Island shelf at 3x10 5 cells/i and Georges Bank at 108 cells/i (Johnson and Sieburth 1979); Montsweag Bay ME at 1.6xI0 5 cells/l (McAlice and Jones 1978). Only McAlice and Jones (1978)reported the relationship of the cyanophyte to the rest of the phyto-plankton assemblage. The cyanophyte bloom lasted for several months.'in Montsweag Bay, ME (McAlice and Jones 1978). The colonial cyanophyte (reported as Microcystis sp.). dominated that phytoplankton assemblage, but co-occurred with a typical and diverse, group of other phytoplankton species. Similarly, the phytoplankton assemblage, excluding colonial Cyanophyceae, observed in 1990 in the coastal waters of New Hampshire resembled the preoperational assemblage in terms of abundance and species composition (Figure 3.1.2-3).Phaeocystis pouchetii exhibited a spring bloom in 1990, as was observed in previous years. Later in the spring the Chlorophyceae (green algae, here consisting of filamentous and unicellular taxa)appeared, and remained one of the dominant groups for the rest of the year. Cryptophyceae (flagellated algae, consisting primarily of Chroomonas sp.) and filamentous Cyanophyceae (in addition to colonial taxa) were also abundant in the summer. Unlike the preoperational period, where diatoms were an important group for most of the year, they composed a substantial proportion of the assemblage only in June (primarily Leptocylindrus minimus and Nitzschia delicatissima) and in October (Skeletonema costatum) and to a lesser degree-in July and December. The appearance of large numbers of Skeletonema costatum in the fail was, however,, characteristic of the preoperational period.123 I All Taxa 100 90 80 z in 0 I-.O 0~I-z LJ LU I.70 60, 50 40 30 20 M , OTHER (includes species from all groups occuring less than 1%)E]XANHOPH-YCE D INOPHYCEAE SBACILLARlIOPH 03 CRYPTO-{YCE M3 cHOIRO-f'CE 13 CYANOPHYCEA AE YCEAE AE 10 0 JAN FEB MAR APR MAY JUN JUL AUG SEP CCT NOV MONTH Excluding Colonial Cyanophyceae z 0, 0 0.0 z LUI CL)100 90 80 70 60 50 40 30 20 11 11 .1 0.... ........ ....... .. .M% Jim AP MYJU JLAU EPOC OVC[]03[]OTHER (includes species from all groups occuring less than 1%)XANTHOPHYCEAE DINOPHYCEAE BACILLARIOPHYCEAE CRYPTOPY'-CEAE CH.LOROPHYCEAE CYANOPHYCEAE I 10 0 MONTH*Figure 3.1.2-3. Seasonal succession of the major phytoplankton groups (percent composition) during 1990, all taxa and excluding colonial Cyanophyceae at nearfield Station P2. Seabrook Operational Report, 1990.124 Nearfield and Farfield Assemblages Percent composition and frequency of occurrence.of most'dominant species have been similar in the nearfield and the farfleld, for both the preoperational and operational periods (Table 3.1.2-3).Historical analyses of the correlations in total abundances between stations have shown that there is a strong correlation (r > 0.800)between stations P2 and P7 (NAI 1985b). For the period of April through December 1990, total phytoplankton abundance showed a significant* correlation (r > 0.700) at alpha = 0.05 between stations P2 and P5, and between P5 and P7. The correlation of total abundance between stations P2 and P7 was also significant, although not as strong as the other two comparisons (r = 0.544).Differences in individual taxon abundances between stations during 1990 were also analyzed using a multivariate analysis of variance procedure (MANOVA) (Table*3.1.2-4). The following taxa were selected for inclusion in the analysis: colonial Cyanophyceae; filamentous Cyanophyceae; Chlorophyceae; Chroomonas sp.; Leptocylindrus.minimus; Phaeocystis pouchetii; Nitzschia delicatissima; and Skeletonema costatum. These were the dominant taxa (relative abundance greater than 1%) for the period of April to December. Phaeocystis pouchetii and Chlorophyceae species represented less than 1% of total abundance between August and December and therefore were.not tested. For both the April to December and August to December periods, no significant-differences in abundances among.the three stations were detected.Chlorophyll a Concentrations Chlorophyll a concentrations may, in general, be used as a measure of phytoplankton standing crop, although the issue is complicat-ed by the varying amounts of chlorophyll a contained in different phytoplankton species. During the preoperational period, chlorophyll a concentrations showed a bimodal pattern, with peaks in spring andfall 125 TABLE 3.1. 2-3. RELATIVE ABUNDANCE (M) OF PTOPLANMON SPECIES OCCURRING IN FREQUENCIES OF 1% OR GREATER DURING THE PREOPERATIONAL YEARS (1978-1986) AND 1990. SEABROOK OPERATIONAL REPORT, 1990.AUGUST -DECE1BER OF 1978 1979 1980 .1981 1982 1983 1984 1 1986 1990 SPECIES P2 P5 P2 P5 P2 P5 P2 P5 P2 P7 P2 P7 P2 P7 P2 P5 P7 Pý P5 P7 Cyanophyceae; filamentous .8 2 5 Bacillariophyceae

• 4 2 <1 <1 1 1 2 3 Nitzschia delicatissima 1 1 20 29 1 1 1 1 1 Nitzschia iongissima 1 1 1 12 Rhizosolenia delicatula 22 25 69 63 4ý 5 1 2 3 1 1 SkeletoaeMa costatum 63 66 10 14 88 79 29 3 49 28 10 4 72 58 66 63 .64 Thalassionema nitzschioides 8 6 2 5 11 18 2 1 <1 1 <1 1 Gyrodinium.sp.

1 1 Nitzschia seriata 1 1 1 2.' <1 1 2 Phaeocystis pouchetii 7 9 Pleurosigma angulatum

• 2 2 Prorocentrum micans 7 8 1 <1 Alga; flagellate

1. 5 8 12 15 17 54 61 4 7 3 5 8 3' .3 3 Chroomonas sp. , i 5* 4 2 2 2 Alga; unicellular 1 "2 ... 1 20. 18 17 Ceratium, furca 1 Chaetoceros sp.

• 1 1 1 1 1 1 1 1 1 1 Cyanophyceae 14 10 <1 Euglenales

..2 8 <1 4 Gymnodinium sp." 1 3 Leptocylindrus minimus 1 1 13 21 1 3 3 2 2 2 Peridinium sp. 1 1 Rhizosolenia fragilissima 10 10 8 3 1 1 6 7 12 Thalassionema sp. .2 1 Thalassiosira sp. 1 1 1 1 1 1 1 2 2 Rhizosolenia sp. .1.Asterionella gilacialis 2 6 Centrales .6 9 1 1 1 2 Cerataulina bergonii-1 6 9 Dinophyceae 4 .3 3 6 1 1 2 Nfavicula sp. 1 1 Pennales Rhizosolenia stolterfothii i 1 Leptocylindrus danicus 4 5 Oscillatoria sp -3 Meriscopedia sp. 1 3 2 Cyanophyceae; colonial 13 12 1 66 72 70 Chaetoceros danicus i TABLE 3.1.2-4. RESULTS OF MULTIVARIATE ANALYSIS OF VARIANCE (MANOVA)COMPARING PHYTOPLANKTON COMMUNITY STRUCTURE AT STATIONS P2, P5 AND STATION P7 DURING 1990..SEABROOK OPERATIONAL REPORT, 1990.NO.OF NO. OF SPECIESa STATIONS PERIOD STATISTIC df F 8 3 Apr-Dec Wilk's criterion 16,50 0.52 NS Pillai's trace .16;52 0.52 NS Hotelling-Lawley trace 16,48 0.53 NS 8 3 Aug-Dec Wilk's criterion 12,22 0.74'NS Pillai's trace 12,24 0.71 NS Hotelling-Lawley trace 12,20 0.77 NS'Analysis included these numerically dominant taxa: Cyanophyceae, colonial Cyanophyceae, filamentous Chlorophyceae-. Chroomonas sp.Leptocylindrus minimus Phaeocystis pouchetii Nitzschia delicatissima Skeletonema costatum 127 (Figure 3.1.2-4). Concentrations followed a somewhat different pattern in 1990, although spring and fall peaks are apparent. The two highest concentrations were observed in March and in November; smaller peaks were apparent in May-June and in September, as occurred during the.preoperational period. Chlorophyll a concentrations were consistently higher in the preoperational period than in 1990, although 1990 concen-trations were contained within the wide preoperational confidence intervals. These differences in concentrations may reflect the domi-nance of Bacillariophyceae:during the preoperational period, and the dominance of Cyanophyceae which contain less chlorophyll, in 1990.Chlorophyll a concentrations in 1990 were similar among the three.stations, as indicated by moderate to high correlation coeffi-cients (Table 3.1.2-5).PSP Levels PSP toxicity levels in Mytilus edulis, as provided by the State of New Hampshire, have shown a strong seasonal pattern of extreme values occurring during the late spring and early summer during the preoperational period (Figure 3.1.2-5). The preoperational data also show a small peak in toxicity levels occurring in August. In 1990, elevated PSP levels were recorded in late May through June, although these levels were generally much lower than those observed prior to 1 1990.3.1.2.2 Selected Species Skeletonema costatum was chosen as a selected species because of its historic omnipresence and overwhelming dominance during much of the year. During the preoperational. period, abundances were slightly bimodal in nature, showing a small peak in the spring (varying from year-to-year from February to May) and a major peak in. the late summer 128 5.0-4.5-4.0-.3.5-3.0 -1990 z 0 z 5E 0 E 0~2.5-2.0-1.5-1.0-0.5-0.0*..7 a -at -SF 5'i "t~~~I~~~~~~ I -I I I I.= g I I I i JAN FEB i i i MAR APR MAY JUN i .M I I !8Z JUL AUG SEP OCT NOV. MEC MONTH Figure 3.1.2-4. Mean monthly chlorophyll a concentrations and 95% confidence intervals over all preoperational years (1978-1984) and monthly means in 1990 at nearfield Station P2. Seabrook Operational Report, 1990.129 TABLE 3.1.2-5. CORRELATION COEFFICIENTS FOR CHLOROPHYLL a CONCENTRATIONS AT. STATIONS P2, P5, AND P7 IN 1990. SEABROOK OPERATIONAL REPORT,1990. P5 P7 P2 0.9113 0.7831 P5 0.7162 All correlations statistically significant at alpha 0.05;coefficients (r) of 0.600-0.800 indicate moderate correlation and coefficients greater than 0.800 indicate high correlation. 130 1300 0 -PREOP 1200 1100 1000 900---'0-- 1990 800-LI-J1 700--600 500 U, 400-300-200 I1 2 3 41 1 A3 4I 2 1 2 U I3 4 1 23 41 1 2 3 4I 1 2C3 4 1 1 2 3 4 1 2 APR AY JUN JUL AG SEP OCT NOV DI Figure 3.1.2-5. Mean and 95% confidence intervals of weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor over all preoperational years(1978-1984) and mean levels4in 1990. Seabrook Operational Report, 1990.3~ 4 or fall (varying from August to October). This pattern was somewhat different in 1990 (Figure 3.1.2-6 and Table 3.1.2-6). A large peak in abundance was observed in*June; in October, the peak was very consistentt with historical trends. An analysis of variance procedure (ANOVA) was structured to examine the following characteristics of Skeletoneina costatum abundances during the preoperational and operational periods: a) Preop-Op tests differences in abundances between the preoperational and operational periods, regardless of station, and will detect whether operational

• period falls within historical variability.;

b) Station tests differences in abundances among Stations P2,,P5 and P7, regardless of sample date, and will detect whether there has been a consistent relationship in abundances spatially; c) Year (Preop-Op) tests differences in abundances among..years nested within preoperational and operational peri-ods, regardless of station, and will detect whether any year or years are unique;d) Month (Preop-Op) tests differences in abundances among months nested within preoperational and operational periods, regardless of station, and will detect whether there is a consistent seasonal pattern; and.e) Preop-Op X Station tests differences in abundances be-tween the main effects of preoperational and operational periods and station and will detect whether the relation-ship in abundance among stations has been consistent between preoperational and operational periods.These results are summarized in Table 3.1.2-7. During the April to December period, significant differences in Skeletonema costatum abundances were shown to exist between the preoperational years and 1990 (Preop-Op), among years (Year (Preop-Op), and among months (Month (Preop-0p)). For the August to December period, a significant difference was shown to exist between preoperational and operational abundances (which is noted in Figure 3.1.2-6), and significant differ-ences were again noted among years and among months. No differences in abundances were apparent among stations in either the April-December or August-December time frame. The relationship among stations in terms of 132 6.5 6.0 5.5 1990 z 4.0 z S" 3.5 -.., 3.0 .2.5 2.0 1.5 1.0- .I I *JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV MC MONTH Figure 3.1.2-6. Log (x+l) abundance (no.11) Skeletonema costatum at nearfield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means for 1990. Seabrook Operational Report, 1990.133 TABLE 3.1.2-6.PEAK FALL ABUNDANCES OF SKELETONEMA COSTATUM IN -SURFACE WATERS AT THE NEARFIELD STATION P2 DURING PREOPERATIONAL YEARS (1978-1984, 1986) AND 1990.SEABROOK OPERATIONAL REPORT, 1990.MONTH OF MEAN ABUNDANCE IN CELLS/LITER MAXIMUM OCCURRENCE 1978 1979 1980 1981 1982 1983 1984 1986 1990 August 2.4x10 6_ 1.2x10 5 September 2.7xi0 5 2.2x10 6 9.2x10 5 4.5xi0 6 8.7x10 6 October' 2.6x100 1.3x10 5.LS TABLE 3.1.2-7..RESULTS OF ANALYSIS OF VARIANCE3 COMPARING NEARFIELD (STATIONS P2 AND P5) AND FARFIELD (STATION P7) SKELETONEMA COSTATUM ABUNDANCES DURING-PREOPERATIONAL YEARS (1978-1986) AND 1990 AND STATIONS P2, P5 AND P7 DURING 1990.SEABROOK OPERATIONAL REPORT, 1990.APRIL -DECEMBER AUGUSTb -,DECEMBER SOURCE OF VARIATION df. SS F df SS F A. SPATIOTEMPORALýVARIATION, 1978-1986 AND 1990 Preop-Op' 1 7.79 6.96** 1 16.22 14.59***Stationd 2 4.49 2.01 NS 2 1.48 0.67 NS-Year (Preop-Op)e 7 26.51. 3.38** 7 18.11 2.33*Month (Preop-Op)f 16 98.77 5.51*** 8 37.94. 4.26***Preop-Op X Stations 2 1.00 0.44 NS 2 0.24 0.11 NS Error 165 153.44 75 83.40 B. SPATIAL VARIATION, 1990 Stationh 2 1.97 0.57 NS 2 0.87. 0.28 NS Error 24 41.55 12 18.83 Ln aBased on twice monthly sampling periods.bCommercial operation began in August 1990.CPreoperational (1978-1986) versus operational period, regardless of area.dStation P2 versus Station P5 versus Station P7, regardless of sample date.'Year nested within preoperational and operational periods, regardless of area.fMonth nested within preoperational and operational periods, regardless of area.glnteraction between the main effects of sample period and station.hStation P2 versus P5 versus P7, regardless of sample period.NS = not significant (p>0.05)*= significant (0.05->p>0.01)

• • = highly significant

.(00l_>p20.001) very highly significant (0.001->p) abundance of S. costatum did not vary between preoperational years and 1990 (Table 3.1.2-7, Preop-Op X Station).An additional analysis was cons.ructed to evaluate the differences in abundances among Stations P2, P5, and P7 in 1990, with.all dates pooled. No significant differences in abundances either during the entire year or the August-December operational period were detected (Table 3.1.2-7).3.1.3 Microzooplankton 3.1.3.1 Total Community Seasonal Characteristics Temporal variability in species abundances and taxonomic composition of the nearshore microzooplankton community (surface and bottom samples combined) at Station P2 (Figure 2.1-2) for all pre-operational (197871984 and 1986) and operational (1990) collections was examined using cluster analysis.. Numerical classification grouped.individual sampling dates into six major groups that corresponded with the seasonal cycle (Figure 3.1.3-1). Comparison of the specific dates.included within each cluster group -indicated that there were moderate differences among years.. The most pronounced variation occurred during late-summer and fall of preoperational years where cluster groups, included a number of "outlying collections" (i.e., a collection date separated by more than two weeks from the rest of the seasonal group), (Figure 3.1.3-2). Collections from 1990 generally clustered into groups containing corresponding dates from the preoperational period, although the fall/winter collections were identified as a separate cluster group from preoperational dates. Preoperational and operational periods were similar in the rank order of numerically dominant taxa identified from each cluster group (Table 3.1.3-1); these taxa accountedfor at least.80% of the total mean abundance within each cluster. Differences among groups, in large measure, were attributed to seasonal Variability in the 136 -. ... ........oO °.. .............o'o o',.. .....-.. ....... ..°O° Oo o*°, .°° ° , .°° °. ° -°o .'. ........° °.°-.. .............O° ° ° , ° -° , ' ° ° ° ° ° .* ° ° °.. o. .............. .. .....°O °° -, ° ' ° ° °* * ° -° o o ° ....°° ..o ......°° ° * ° * .* .. ... .. * ... ..°. ° ° ..° , ...... ..o- -.o.. ....." -..............o* -, , , ,. °. '. ° '** ° o. ..........-.°,-. ..-.. ................o...° o , , *

• o *.. .,,......, ,. .. ...- , * , .. -. .-.-. ...o-. .....,o, ........... .., * .., * .* * ., ...........* .., ..., ZbeI iSpring/Summer

rZ, > to withi group : LUJ/511-simlartylarity

'L b no. of samples ~ '~ .v',- '" -;'-, d-' ,, -', ,.7,- -" ~~1\ \- o \ _ -'/, I'/tween group '. ...-' -..,/---, ', :::,f-,j 0 0 5 samples Z 110 Group 4 Late Summer 0 00 00 0 0 00 00 0 0:00 0 0 0 0O ° ° o 0o oo00 00o0 o o 0o oo%o o o oaoo o o -O oO o o o a oo o -o ooc o oo o oo ooo o oo o o o..,o.o o o.o..o ..oooCo ooo o~ooO.oo o o ooo.o .o 0oo 0 0000.0. 0.0%. 00 00 0.0.000'0 000 0000 oo o oo. o oo .o

• oO o oo ~oo o o..o oo= o*°o o o o ° O°° oOoo. .o° o%0 o ooo oooo o ooo oo o o o oo o oo.0.00° .°0.0° 00 0 0 0 ..00. .Go 000o00 o 0 0 0o0 0 oooooooo ,°o :ooo 0 0 0 0 *0 o 00~~o :oo o 0 oo o o 0 o° o Oo o oo6oooo 0 Fall/Wlnter o ooo0. oo o o o o o oO..OooO 0 0oI. o o o ooo o oo
• oo
• o o o O o .o oo'0 0 o o~o o° o 0 ..0 0 0 oo .0 oo .0o microzooplanto abudace (o° oo m 3) at ok° neroldSaioo2 i o o o o o o ooo o_ oo .7. o oo o.0.5 0.6 0.7 0.8 0.9 1.0'. ~BRAY-CURTIS SIMILARITY' Figure 3.1.3-1. Den~drogram formed by numerical classification of log (x+ 1) transformed microzooplankton abundances (no ./M 3 ) at Seabrook nearfield Station P2, 1978-1984, July -December 1986, and April-December 1990. Seabrook Operational Report, 1990.137 TABLE 3.1.3-1.GEOMETRIC MEANS OF MICROZOOPLANKTON ABUNDANCE (NO.fm 3), 95% CONFIDENCE LIMITS, AND.NUMBER OF SAMPLES FOR DOMINANT TAXA OCCURRING IN SEASONAL CLUSTER GROUPS IDENTIFIED BY NUMERICAL CLASSIFICATION OF COLLECTIONS AT-NEARFIELD STATION P2, 1978 -1985, JULY -DECEMBER 1986, AND APRIL -DECEMBER 1990.SEABROOK OPERATIONAL REPORT, 1990.Co 1978-1984, 1986 1990 DOMINANT LOWER UPPER GROUP TAXA C.L. MEAN C.L. MEAN N 1. Winter Copepoda nauplii 124.75 252.1- 508.40 13 .. ..(0.59/0.56)'

Ouibona SOp. 177.65 361.9 736.13 ... ..* Pseudocaanus sp. 57.30 121.7 257.29 .. ..Pseudocalanus/yralanus nauplii 96.'64 220.1 499.55 ... ..2. t Sr.ng 0 Cirripedia larvae " 130.33 2ý4.8 353.47 36 q.2 Cqpppoda naup v0 .17 8 3.0 123Z-63 Oiboga sp. 974.97 1391.6 1986.0ý 1382.6 Polycnaeta larvae. 180.15 248.5 31.2.4 Pseudocalanus s 27.22 323.5 48340 .0 Pseudocalanus/lalanus nauplii 541.79 802.2 1187.43. 18.7 3. er Bivalvia veliger larvae 1768.55 2966.0 4973.92 48 499.7 4~u.ýWuf5 Cotepocia naupiai 3530.56 4922.6 6863.21 9665.3 OIThona sp. 5203.95 6434.9 7957.01 17510.2 Pseudocalanus s-o. 1438.74 1980.0 2724.87 509.4 Pseudocalanus/lalanus nauplii 2252.00 3087:8 4233.69 1301.8 4. Lat Summer .Bivalvia veliger larvae 210.25 467.2 1036.79 13 862 5 (0.69/0.68) Co epoda naupl1i 109 .87 2406.7 5308.35 7 3 Oitona s. .2957..31 5219.6 921 .79 .069.8 Pseudocalanus sp. 1105.19 1934.7 48 .42 5g.7 Pseudocq]anqs/C'a~anus nauplii 1272.29 2403.2 438.73 .7246.9 Terora longicornis .87.37 -.235.5 631.92 914.0 5. fal.Nngv Bivalvaa veliger larvae 132.95 20 314.40 48 not repre-Co o a nauplii449 117 163098 sente Oitgona sp. 1 46.20 2146.7 2799.23 q Pseudoca anus sp. " 75.78 376.3 513.46 Pseudocalanus/Calanus nauplii 79.3 7 0.3 6 998. 3 Tintinnidae 71.85 154.1 329.35 6. Fall/Winter '90 Centropages sp ,.copepodites not represented 181.6 5 (0.72/0.68) Copepoda =auplii 1349 Microseteyla norvegica 16229.Oithona §p. -2239.O0 tseudoca lFalas n. .227 22 Pseudocalanus/Lalanus nauplii 30.99 Rotifera 13.9 Tintinnidae 2 0.3 b2within group fmilarity/between group similarity no samples co lected on these dates 1984 oOo 0 Group 1~~,-l a oo -0 o o o °o....-, a 0 -, °o 0000oo0oo o oo0 o oa o Group2 1983 -'... """' "'o 0.. 0 000000*............-...-.....-.-.-. " ,oo oo " o o ° o o o = .o- o.o .., ..--.... ......o. °° °o 0°oo r u-oo o ooo oo= ;'Z* o o o o o a o o>" _ 0 000 00 0 Group 4 1 000 ...... ....00o .:0 0o00 o00 1981 """' " "o o 0 o o Group 5 00 .*, * , °° -'.' '. .* ',' * ' " o 0 00 00 00 00 oo .O .o o ° o Oo0O* ., ,. -, ...*, .*,,. **.'... .o'. .o .oo .00.00 oo 0 0 0 00 0 18 000 o 0 o o 0o -.*o o0Oo O Group 6 00 o o o 0 o oo oooo ao. ooo o o~o L o .o o 1979° .,.'.. -'," o o o oo o "---'1 no sample.Sjj \S _, -o O o0 .0°.°.=o,°,','°, /0 0 0 0 o0o o oo 19789 "....2'.i .,0 0 oO O o:,r0 .......z M MRMY J UN JUL AUG SEP OCT NOV0 MONTH Figure 3.1.3-2. Seasonal groups formied by numerical classification of log.(x+1) transformed microzooplankton abundances (no.1m.) at Seabrook nearfield Station P2, 1978-1984, July-December 1986, and April-December 1990. Seabrook Operational Report, 1990. abundances of these dominant taxa. Seasonal groups identified by cluster analysis generally encompassedcollection periods with similar temperature regimes., particularly with respect to the depth and intensi-ty of the thermocline (NAI 1985b).Within-cluster group similarities were fairly high (0.587 -0.723) indicating that the microzooplankton community structure was fairly constant among the dates comprising each group (Figure 3.1.3-1).Between-group similarities were also reasonable high (0.556 -0.677) due to the consistent occurrence and relatively.high densities throughout much of the year of the same dominant taxa (i.e., Copepoda nauplii, Qithona sp., Pseudocalanus sp., and Pseudocalanus/Calanus nauplii; Table 3.1.3-1).As noted above, seasonal patterns in the microzooplankton community structure were largely delineated by changes in both total abundance and.the dominance structure of numerically important taxa.Lifestages of the copepods Oithona sp. and Pseudocalanus sp., and Pseudocalanus/Calanus'nauplii were the most abundant organisms in virtually every cluster group during both pre-operational and operation-al periods (Table 3.1.3-1). The winter microzooplankton (Group 1) was characterized by fewer dominant taxa with moderate abundances. In the late winter through early summer (Groups 2 and 3), population densities of copepods (Oithona sp., Pseudocalanus sp., Pseudocalanus/Calanus nauplii, and Copepoda nauplil) increased substantially. Abundances of the microzooplankton assemblage peaked during the summer (Groups 3 and 4) when copepod densities were at their highest and benthic species (particularly bivalves),contributed large numbers of individuals to the meroplankton.. Among-year differences in the dates assigned to cluster groups 3, 4 and-5 (summer-fall) were more apparent than for the other seasons because of the large number of dominant taxa with highly.variable densities (Figure 3.1.3-2). The dominant, copepods continued to maintain moderate populations throughout the fall and into winter (Groups 5 and 6) while densities of most other. taxa declined. The fall of 1990 (Group 6) differed from earlier years in the subdominance of 140 rotifers, Microsetella norVegica and Centropages'sp. copopodites in addition to the typical fall dominants (Table 3. 1.3-1). The between.group similarity of 0.68-between groups 5 and 6 is a.relatively high value indicating that distinctions between the two groups are subtle.'In summary, the microzooplankton community structure at Station P2 has been fairly consistent throughout this' study, with the greatest annual variability evident during the summer and fall when both abundances and number of dominant species were highest. Although the microzooplankton community varied in the fall of 1990 frompreopera-tional years, the. differences were due to increased abundances of several taxa while the typical species maintained their'predominance. There were no other differences noted'between pre-operational and operational periods. The community structure was influenced primarily by the population dynamics of the copepods Qithona sp. and Pseudocalanus sp. and by the'production of early lifestages (nauplius larvae) of other copepods. Other taxa (including Polychaeta, Bivalvia, and Tintinnidae) exerted'less influence on overall community structure.-Spatial Patterns of Microzooplankton Abundances Spatial variation (i.e., among-stations differences) in the microzooplankton community structure was examined separately for both the preoperational and operational periods, *with abundances averaged'over depth. -Comparison of total microzooplankton densities from 1982 to 1984 using Wilcoxon's two-sample test (Sokal and Rohlf 1969)'revealed no significant differences between Stations'P2 and P7 (NAI 1985b).Although some numerically important taxa exhibited large differences in rank order or percent composition between stations, their individual' abundances were also not significantly different (NAI 1985b).A multivariate analysis of'variance (MANOVA) was performed using the'April-December 1990 abundances of34; numerically important141 taxa from Station P2, P5, and P7. Species composition and abundances were not significantly different among these stations (Table.3.1.3-2). In summary, statistical evaluation of the spatial variationin microzooplankton community structure, as measured by abundance data among sampling stations, found no significant differenc e.s either during preoperational years or during.1990.. 3.1.3.2 Selected Species The copepods Pseudocalanus sp. and Olthona sp. were selected for in-depth analysis in the microzooplankton program because of their dominant roles in the community. Their abundance and low trophic level make them important members of the marine food web. Eurytemora herdmani has been reported to be an abundant coastal copepod in the northern region of the western Atlantic (Katona 1971.) and.as such, may be particularly-sensitive to perturbations in the local temperature regime.Lifestages of these taxa were identified whenever possible to develop an understanding of the dynamics of population recruitment cycles. In some cases, however, the possible presence of congeneric species made it.impossible to routinely identify all lifestages to species. level.Nevertheless, information on.lifestages of these genera. is included in this report to present as complete a picture as possible. Temporal (seasonal and annual) and spatial (horizontal and vertical),variability of the above-mentioned species is characterized. Even-though some vertical, differences in abundancedid exist, temporal characteristics are described for surface and bottom collections combined.Eurvtemora sp. , During the preoperational period, Eurytemora sp. copepodites at Station P2. were present in low~numbers for most.of the year, general-ly exhibiting short-term peak abundances.in early to mid-summer (Figure: 142 TABLE 3.1.3-2. RESULTS OF MULTIVARIATE ANALYSIS OF VARIANCE COMPARING MICROZOOPLANKTON COMMUNITY STRUCTURE AT STATIONS P2, P5, AND P7 IN 1990. SEABROOK OPERATIONAL REPORT, 1990.NUMBER NUMBER OF OF SPECIES STATIONS STATISTIC df F 34 3 Wilk's criterion 68,30 0.6880 NS Pillai's. trace 68,32 0.6714 NS Hotelling-Lawley's 68,28 0.7092 NS trace NS =.Not significant 0 143 3.1.3-3). An additional smaller fall peak was often recorded, especial-ly in 1983 (NAI 1984b), when the highest annual mean abundance for copepodites was recorded (Table 3.1.3-3). Annual geometric means ranged from 1.7 copepodites/m 3 in 1982 to 16.6 copepodites/m 3 in 1983, averag-ing 6.1 copepodites/m 3 during the preoperational period (1978-1984).. E. herdmani adults typically occurred, in lower numbers.than copepodites and were almost absent from the.plankton samples at Station P2 from December through April during the preoperational years (Figure 3.1.3-3).. Peak abundances occurred during one or more months from May through September and usually coincided with peak copepodite abundances. Annual geometric, means were highly variable ranging from 0.9 adults/m 3 in 19 79 and 1982 to 10.5 adults/m 3 in 1983, and averaged 3.1 adults/M 3 over the preoperational period (Table 3.1.3-3).Earlier studies indicated that Eurytemora sp. copepodite and E. herdmani adult populations in Hampton Harbor and the Nearfield Station P2, underwent similar seasonal cycles, but during the spring the estuarine population was much larger (NAI 1978b, 1979b). These observa-tions suggest that recruitment to the coastal population may be supple-mented by the estuarine population. Other sources of recruitment in the spring might be maturation of, and subsequent reproduction of, overwint-ering copepodites (Figure-3.1.3-3) or hatching of diapause (overwinter-ing) eggs.In 1990, Eurytemora sp. copepodite densities did not exhibit the historic early to mid-summer peak and were well below the preoperat-ional average from May through August (Figure 3.1.3-3). However, a late fall peak was evident and was slightly higher than the mean for the preoperational years. The' 1990 geometric annual mean for copepodites (2.5/m 3) was below the overall mean for the preoperational years but was within the range of mean values for individual years (Table 3.1.3-3).: E. herdmsni adults followed the same general seasonal trend in 1990 as during the preoperational years. Values were lower than.the preoperati-onal mean in July and greater than the preoperational mean in August, 144 : Eurytemora sp..Copepodites 2.5 2.0'-PREOP....... 1990 ILl 0--Z2<CDE z (5-00 1.5 1.0 0.0 JAN FEB MAR APR. MAY JUN JUL AUG SEP OCT NOV DEC MONTH Eurytemora herdmani Adults wi oz 0 0 2.5 2.0 1.5 1.0 0.5 0.0-PREOP....... 1990 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DI-C MONTH Figure 3.1.3-3.Log (x+1) abundance (no./m 3) of Eurytemora sp. copepodites and Eurytemora herdmani adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2.Seabrook Operational Report, 1990.145, TABLE 3.1.3-3. GEOMETRIC MEAN (NO/M 3) BY YEAR, PREOPERATIONAL MEAN AND 95% CONFIDENCE LIMITS AND OPERATIONAL YEAR MEAN (1990) OF SELECTED MICROZOOPLANKTON SPECIES AT STATION P2 (APRIL-DECEMBER). SEABROOK OPERATIONAL REPORT, 1990.PREOPERATIONAL YEARS YEAR. UPPER LOWER CONFIDENCE. CONFIDENCE SPECIES/LIFESTAGE 1978 1979 1980 1981 1982 1983 1984 MEAN LIMIT LIMIT 1990 Eurytecora sp.copedodites 4.0 6.1 9.7 10.6 1.7 16.6.. 3.2 6.1 -12.0 2.8 2.5 Eurytemora herdmani..adults 1.3 0.9 4.9 7.0 .,0.9 10.5 3.1 3.1 7.0 1.1 3.0-Pseudocalamus/Calanus sp. ....832.3 1209.0 789.1 1068.2 1577.3 520.5 365.9 822.7 1307.7 517.5 274.3* nauplii Pseudocalanus sp.copepodites 396.5 453.2, 177.6 260.0 645.4 336.7 167.1 314.2 496.5 198.7 148.9 Pseudocalanus sp.adults 22.4 33.7 23.7 22.2 72.8 37.7 12.-0 28.0 46.8 16.6 15.8 Oirhona sp.nauplii

• 401.6 993.4 301.6 1122.4 1482.5 775.2 292.4 643.1 1188.3 347.8 562.7 Oithona sp.copepodites 662.9 1798.3 614.5 651.0 1263*.3 755.1 301.9 753.2 1274.0 445.1 .1069.4 Oitbona sp.adults 71.2 151.2 134.8 263.4 330.3 225.0 69.3 153.3, 270.1 86.8 76.5 I-.-7 -7.

October, and December (Figure 3.1.3-3). The geometric annual mean in 1990 was virtually identical to the geometric mean for all preoperatio-nal years (Table 3.1.3-3).Results of the two-way ANOVA on Eurytemora copepodites showed that differences in abundances between 1990 and the preoperational years were very significant for the April through December collections (Table 3.1.3-4, Preop-Op). Although abundances in 1990 were significantly lower than preoperational densities, the area (nearfieldvsfarfield) and interaction terms Were not significant, indicating densities were generally lower throughout the area. Differences in annual and seasonal densities were also significant (Table'3.1.3-4, year (Preop-Op) and month (Year (Preop-Op)) indicating high variability among years and months. Results of the two-way ANOVA on E. herdmani adult densities during April through December were not significant for either temporal or spatial effects.During the months of plant operation (August through December)the results of the ANOVA on Eurytemora copepodite and adult densities were not significant for either temporal or spatial effects or their interactions. This indicates that the population in the vicinity of the intake was not quantitatively different from the one in the farfield area.Pseudocalanus sp.Historically,-Pseudocalanus/Calanus sp. nauplii were present year-round at Station P2 (Figure 3.1.3-4), and were among the numerical dominants of the microzooplankton community in all seasons except winter (Table 3.1.3-1). Seasonal peak abundance was attained during mid-summer. Annual geometric means at Station P2 ranged during the preoper-ational period from 366 nauplii/m 3 in 1984 to 1577 nauplii/m 3 in 1982, and averaged 823 nauplii/m 3 (Table 3.1.3-3). Pseudocalanus sp. cope-podites and adults were also present throughout the year with peak 147 TABLE 3.1.3-4.RESULTS OF THE TWO-WAY ANALYSIS OF VARIANCE OF LOG (X+l) TRANSFORMED DENSITY (NO/m 3)AMONG PREOPERATIONAL YEARS (1982-1984 & 1986) AND OPERATIONAL YEAR (1990), AREA.(NEARFIELD VS. FARFIELD) AND THEIR INTERACTIONS FOR SELECTED MICROZOOPLANKTON SPECIES. SEABROOK OPERATIONAL REPORT, 1990.SPECIES/ SOURCE OF APRIL -.DECEMBER AUGUST -DECEMBER LIFESTAGE, VARIATIONa df SS F df SS F Eurytemora sp. Preop-Op 1 4.09 14.49*** 1 0.34 1.25-NS copepodite Year (Preop-Op) 3 14.27 16.84*** 3 10.75 13.12***Month (Year (Preop-Op)) 37 47.40 4,54*** 20 25:48 4.67***Area 1 0.43 1.53 NS 1 0.92 3.36 NS Preop-Op X Area 1 0.03 0.09 NS 1 0.13 0.48 NS Error .142 40.10,, 81 22.12 Eurytemora herdmani Preop-Op 1 0.54 2.29 NS 1 0.37 1.52 NS adult Year (Preop-Op) .3 11.52 16.33*** 3 4.32 5.99***Month (Year (Preop-Op)) 37 47.39. 5.45*** 20 15.76 3.27***Area 1 0.23 0.99 NS 1 0.54 2.23 NS Preop-Op.X Area 1 <0.01 0.01 NS 1 0.08 0,34 NS Error 142 33.38. 81 19.51 Pseudocalanus/Calanus Preop-Op .1 6.10. 2 9..94*** 1l- 8.40 40.66***sp. nauplii Year (Preop-Op) 3 6.86 11.22*** 3 0.90 1.45 NS Month (Year (Preop-Qp)) 37 36.58 4.85*** 20 14.48 3.50***.Area 1 1 0.03. 0.15 NS 1 0.08 0.38 NS Preop-Op X Area 1 0.20 .0.98 NS 1 0.22 1.05 NS.Error 142 28.96 81 16.74 Pseudocalanus sp. Preop-Op 1 8.59 41.54*** 1 2.63 12.18"**copepodite Year. (Preop-Op) 3 6.67 10.75*** .3 1..25 1.93 NS Month.(Year (Preop-Op)) 37 37.67 4.93*** 20 9.35 2.17"*Area 1 0.05 0.25 NS 1 0.13. 0;61 NS Preop-Op X Area 1 0.08 0.41 NS 1 0.02 0.08 NS Error 142 .29.35 81 17.46 Pseudocalanus sp. Preop-Op 1 .13.21 43.38*** 1 5.43 18.96***adult Year (Preop-Op) 3 7.54 .9.20**. 3 0.66 0.77 NS Month (Year (Preop-Op)) 37 53.20 5.27*** 20 26.68 4.66***Area 1 0.19 0.70 NS 1 0.20 0.71 NS Preop-Op X Area 1 0.17 0.63 NS 1 0.14 0.50 NS Error 142 38.78 81 23.20 (continued). ..T I TV TABLE 3.1.3-4.(Continued) SPECIES/ SOURCE OF APRIL -DECEMBER AUGUST -DECEMBER LIFESTAGE VARIATION3 df SS F df SS F Cithona sp.. Preop-Op 1 0.14 0.81 NS 1 0.74 4.72*nauplii Year (Preop-Op) 3 9.07 18.09*** 3 1.54. 3.28*Month (Year (Preop-Op)) 37 27.42 4.43*** 20 10.54 3.36***Area 1 0.23 1.37 NS 1 0.09 0.56 NS Preop-Op X Area 1 0.02 0.14 NS 1 0.14 0.89 NS Error 142 23.76 81 12.70 Oithona sp. Preop-Op 1 1.17 8.50** 1 0.05 0.40 NS copepodite Year (Preop-Op) 3 10.74 25.96*** 3 2.54 6.80***Month (Year (Preop-Op)) 37 35.86 7.03*** 20 5.42 2.17**Area 1 0.12 0.86 NS, 1 0.04 0.33 NS Preop-Op X Area 1 0.08 0.56 NS 1 0.0.9 .0.69 NS Error 142 19.57 81 10.10 Oithona sp. Preop-Op 1 7.40 37.96*** 1 10.25 83.25***adult Year (Preop-Op) 3 10.73 18.34-** 3 1.83 4.95**Month (Year (Preop-Op)) 37 34.93 4.84*** 20 10.19 4.14***Area 1 .0.15 0.79 NS 1 <0.01 0.01 NS Preop-Op X Area 1 <0.01 0.02 NS 1 0.02 0.19 NS Error "'42 27.69 81 37.06\fl NS** ==Not Significant (P> 0.05)Significant (0.05 -P >0.01)Highly Significant (0.01 P > 0.001)Very Highly Significant (P 0.001)* Preo Year (Preop:Month (Year (Preop-p-Op.= preoperational period vs. operational period, regardless of area-Op).= year nested within preoperational and operational periods, regardless. of area Op)) = month nested within year nested within preoperational and operational periods, regardless of area Area = interaction of main effects Area = nearfield vs. farfield stations Preop-Op X " Pseudocalanus/Calanus sp.Nauplii z 00-.S.4.0 3.5 3.0 2.5 2.07 1.5 1.0-0.5 0.0' I I I I JAN FB MAR APR MAY Pseudocalanus sp.Copepodites. JUN JUL AUG SEP OCT NOV .EC MONTH 4.0-z 00*~-j a 3.5 .3.0 2.5 2.0 1.5 1.0-- PRE OP 1990 0.5 -0.0.._I I I I I I JAN FEB MAR APR MAY JUN JUL MONTH Pseudocalanus sp.Adults PREOP,....... 1990 I I I i -I AUG SESP OCT NOV MEC wI Z~~og z1~4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 -/0.0-I I I I I -I I I I I *JAN FE MAR APR MAY JUN JUL AUG SEP OCr NOV DEL MONTH t Figure 3.1.3-4.Log (x+l) abundance (no./m 3) of Pseudocalanus/Calanus sp. nauplii and Pseudocalanus sp. copepodites and adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990.at nearfield Station P2. Seabrook Operational Report, 1990.150 abundances occurring in mid-summer (Figure 3.1.3-4). Copepodites were generally about one order of magnitude more abundant .than the adults.Annual geometric mean.abundances of copepodites'and adults were also variable during the preoperational years (Table 3.1.3-3). Abundances-of both lifestages were at a minimum in 1984 (167 copepods/m 3 and 12 adults/m3) and at a maximum in 1982 (645 copepodites/m 3 and 73 adults/mi 3).In 1990, the seasonal abundances of Pseudocalanus/Calanus sp.nauplii at Station P2 were more variable than during the preoperational years (Figure 3.1.3-4). Values were considerably below average for May, August through October, and December. Pseudocalanus sp. copepodite seasonal abundances were also variable during 1990 with values below average in April through, June, September, and December. Adult Pseudo-calanus sp. followed the same seasonal trend present during the pre-operational years; Values were slightly below the mean for May through August, and November, and were much lower than the mean during Septem-ber. The geometric mean abundances.for nauplii and copepodites in 1990 were well below both the means and ranges reported during the preoperat-ional period (Table 3.1.3-3). The 1990 geometric mean for adults was also below the overall mean for the preoperational period but was within the range of individual mean values for that period.Results of the two-way ANOVA for April through December found temporal differences to besignificant for all three lifestages (Table 3.1.3-4, Preop-Op). Although operational densities were lower than preoperational densities, the area and interaction terms were not significant, indicating 1990 densities were generally lower than previous years at all stations. Differences in abundances-among years and among months were also significant (Table 3.1.3-4), year (Preop-Op) and month (Year (Preop-0p)), similar to observations made in previous years (NAI 1990b)'.During the operational period (August-December), each life-stage of Pseudocalanus sp. showed significant differences .in the " 151 temporal effects (Table 3.1.3-4, Preop-Op) but no significant difference in the area or among year interaction terms. Month within year densi-ties (month (Year (Preop-Op)) term) were significantly different for Pseudocalanus/Calanus nauplii and Pseudocalanus copepodite and adult lifestages. Oithona sp.All Oithona sp. lifestages were present year-round and were the most abundant microzooplankton taxa throughout most of the year during the preoperational period (Table 3.1.3-1). Nauplii and cope-podites occurred at similar levels of abundance, while adults were only slightly less abundant (Figure 3.1.3-5).- Peak density for nauplii during the preoperational years extended from May through September. Densities were depressed during the winter and early spring, although they varied by only one order of magnitude compared to the peak months.The annual geometric means for nauplii during the preoperational years were highly variable, ranging from 292 nauplii/m 3 in 1984 to 1482 nauplii/m3 in 1982 (Table 3.1.3-3). During the preoperational period, copepodites maintained high population levels between May and November (Figure 3.1.3-5). Peak abundance was attained in July through September with decreasing values during the winter months. Annual geometric mean abundance at Station P2 ranged from 302 copepodites/m 3 in 1984 to 1798 copepodites/m 3 in 1979, averaging 753 copepodites/m 3 over all preopera-tional years (Table 3.1.313). Cithona sp.:adults exhibited the same general pattern of-seasonality as other lifestages, but maintained a relatively smaller overwintering population than did immature.stages. The time of peak abundance for adults .during the preoperational period occurred between Juneand September. The-annual geometric means during the preoperational years ranged from 69 adults/m 3 to 330 adults/m 3" In 1990, Oithona sp. nauplii generally exhibited the same seasonal pattern of abundance as during the preoperational periodb, except abundances were greater than average during June and lower than 152 Qithona sp.Nauplii z 52 4.0 -3.5 3.0 2.5 2.0 1.5 1.0 0.5, 0.0 PREOP....... 1990 I I I JAN FB MAR Oithona sp.Copepodites I .I ..I I APR MAY JUN JUL MONTH I , I I I I-AUG SEP CCT NOV. I:1 z C,-00 z_5 4.0 -3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0-. PREOP------- 1990 I I I I I I I I I I .I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV Dr, MONTH O"thona sp.Adults LU zo 5.4.0 -3.5 3.0 2.5 2.0-1.5 1.0 0.5 0.0 PRE OP-. 1990-I I .1. I I I~ I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV CE.MONTH, Figure 3.1.3-5. Log (x+1) abundance (no./m 3) of Oithonasp. nauplii, copepodites and adults;monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2.Seabrook Operational Report, 1990.153 average during September (Figure 3.1.3-5). The annual geometric mean for 1990 at Station P2 was slightly lower than the overall preopera-tional mean but was within the range of individual mean values recorded during those years (Table 3.1.3-3). Oithona sp. copepodites also followed the same pattern of seasonal abundances in 1990 that was evident during the preoperational period. However, abundances for June, July, and-November were. larger than normal (Figure 3.1.3-5). The geometric mean for copepodites in 1990 was larger than the overall mean for the preoperational period and five of the seven preoperational years (Table 3.1.3-3),. Seasonal abundance of Oithona-sp: adults in 1990 was, highly variable, contrasting sharply with preoperational data (Figure 3.1.3-5). Adult abundance was larger than normal for June and much lower than normal for August through October. Geometric mean abundance for 1990 was lower than the mean for all preoperational years but was within-the range of individual mean values for those years. r During the April through December period, the results of the two-way ANOVA found temporal differences in the abundances of Qithona sp. copepodites and adults to be significant (Table 3.1.3-4, Preop-Op). Area and interaction terms were not significant, indicating-that differences in densities in 1990 occurred areawide for these two lifestages. Oithona sp. nauplii densities for both temporal and spatial effects and their interactions were not significant. Differences among years and among months were significant for abundances of all three lifestages of Oithon8 sp. during the April through December period.These results indicate highly variable annual and seasonal abundances. During the period of plant operation (August through Decem-ber), temporal differences in Oitbona sp. nauplii and adult densities were significant (Table 3.1.3-4 Preop-Op). Although areawide densities*in 1990 were significantly different fr.om the preoperational period, the lack of significance in the area and interaction terms indicate no differences in the nearfield and farfield areas both before and during plant operation. Temporal and spatial effects and their interactions were not significant for'Oithona sp. copepodites. The seasonal-and 154 annual variability in abundances of all lifestages evident in the April-December period was also apparent in the August-December comparisons (Table 3.1.3-4, year (Preop-0p); month (Year (Preop-Op)).

3.1.4 Bivalve

Larvae 3.1.4.1 Community Structure Temporal Patterns The bivalve larvae assemblage exhibited strong seasonal patterns that were generally consistent among years and represented seasonal fluctuations in abundance of the dominant taxa.. Numerical classification of weekly collections resulted in four distinct seasonal groups (Figures 3.1.4-I, 3.1.4-2). Species composition in all collec-tions from 1990 was similar to that observed in previous years within each time frame (Figure 3.1.4-2).The spring period (Group 1) encompassed most collections in April and May (Figure 3.1.4-2). Although eight taxa were present at some point in during this period, Hiatella sp. dominated (Table 3.1.4-1;Figure 3.1.4-3) contributing 97% of the mean total abundance. Variabili-ty in abundance of Hiatella sp. coupled with the intermittent occurrence of other taxa resulted in a relatively low within-group similarity. (0.44). However, its similarity to other collections was only 0.23, clearly distinct.The late spring period (Group 2) included most collections from late. May through June (Figure 3.1.4-2). The within-group similari-ty. was a moderately high 0.63 (Table 3.1.4-1). The species composition of these collections was most closely related to Groups 3 and 4 (simi-larity of 0.55). Total abundance of bivalve larvae was higher during these months than at other times during the year, as indicated by the 155 within group si m'i a r ity sno. of samples L-b ewen group 0Gru 1 similarity 5 samples roup I E 1 0 Spring...... ..-.., ,.................,.......o o o .......o ° .....° * °.. .....o ............o ......° ......°..... ° .Gr ° o u 2 ..o Lat Sp ig :: ... ...* ° ° o * ....* ° °. ....... .°. o........° ° ° ° ° ° .... o* 1 ,-. .... .......... ..11 " 1\ ' _l -, -\I' "It- l.,... ..... ;-.. .... -; , ..-.. <...Group................ ..~~~.. ......> .- *,, .*.,./ , u%-.. .', -" ,' -S u -ii"...-.. .- -.-.-.'- 111..7F ,u-groudsamproupl e Fiue314-.Dnrgrmfrebolclely ( -ummOer) b P 1 2 9 a -2 Repo rt, 199 0.6_0.7 0-8'0.9 1.0- .BR<Y-CTI '" ~ ~ ~ i Inroe samplesI \ /1lFigur -idrg r fome bynr a lssfcto f eky(pi -Otbr bivlve larva log trasfome abundance ".-.M" at Seabrook ma--i,, Stto P2 1,982-1984 an 196190 Seabroo Opeatina Report ', 199 ..,t:-:'156 W= Group 1= Group 2 LII=.Group 3= Group 4= no sample u = ungrouped H_.urI MONTH a more than one collection within week Figure 3.1.4-2. Seasonal groups formed by numerical classification of log (x+l) transformed bivalve collections from nearfield Station P2, 1982-1984 and 1986-1990. Seabrook Operational Report, 1990. 0 TABLE 3.1.4-1.GEOMETRIC MEAN ABUNDANCE (no./m 3), 95% CONFIDENCE LIMITS OF DOMINANT TAXA, AND NUMBER OF SAMPLES OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF BIVALVE LARVAE COLLECTIONS AT NEARFIELD STATION P2, 1982-1984 AND 1986-1989 IN COMPARISON. TO 1990. SEABROOK OPERATIONAL REPORT, 1990.H0 1982-1984 AND 1986-1989 1990 LOWER UPPER LOWER UPPER GROUP SPECIES N. C.L. MEAN C.L. N C.L. MEAN C.L.1 Spring ffiatella sp. 32 39.42 83.7 176.49 5 8.68 54.2 314.48 (.44/.23)3 2 Late Spring Hiatella sp. 38 1316;26 2021.1 3103.03 6 885.13 2546.7 7323"57 (.63/.55) Mytilus edulis 637.67 1776.2 4944.09 60.30 1130.0 2 20865.81 Solenidat 79.89 147.2 270.50 29.13 160.3 862.61 Sffeteranomia squamula 14.52 36.5 89.76 2.30 61.7 1189.21 Mya truncata 14.05 31.2 67.92: 143.57 .307.0 655.41 Modiolus modiolus 2.58 7.8 20.54 -0.01 23.2 594.64 3 Summer-Fall Mytilus edulis 98 463.23 676.1 986.58 17 787.89 ý2136.4 5790.29 (.68/.60) Heteranomia squamula 440.02 623.5 883.39.. 857.73 1662.8 3222.54 Modiolus modiolus 134.68 205.3 .312.75 101.56 339.1 1126.88* Spisula solidissima .33.26 .49.2 .72.68 56.04 125.5 279.42 , iatella sp. 28.55 43.8 67.01 43.11 151.8 528.61 Solenidae 24.72 35.9 51.84 9.06 25.0 73.60 Mya arenaria 11.31 17.3 26.13 3.39 11.9 37.12 4 Summer Heteranomia squamula 18 32.45 53.2 86.69 not represented (.69j.57) Mytilus edulis 27.24 45.5 75.71 a(within group similarity/between group similarity) Heteranomia squamula (b)z 00*Lu a ~z E 00~Lu C.)-ze Lu z2 0~5, 4 3 2, 1, 0 5-4-4-3 2 1-0-5 4 3 2 0 PREOP 1990 Hiatella sp. (b)Macoma balthica (c)-PREOP 1990 I I I I I I ~I1 ~ I AP 1 APR 2 3 MAY I I I I 12 3 JUN 41 1 2J3 JUL; 1; l2A3 AUG.4 2 3 SEP I I I I a 41 1 2 3 4 OCT Modiolus modiolus (b)Years enumerated: (a) 1976-1990; (b) 1978-1984, 1986-1990; (c) 1979-1984, 1986-1990. Figure 3.1.4-3. Weekly means log (x+l) abundance (no./m 3) of bivalve larvae; and 95%confidence intervals .over all preoperational years 1978-1989 and weekly means for 1990 at nearfield Station P2." Seabrook Operational Report, 1990.159 Mya tru ncata (b)Z z.=0 00-LU 0Z z 00 5 4 3 2 1 0-5-4-3-2-.1-0 5-4-3--PREOP...,... 1990 MAY OCT Mytillis edulls (a)Placopecten magellanicus (b)uJ 02 z co -.-< M 0200 zI.<3 0 PREOP....... 1-990 2 123 4 1 2 3 41 1 2 3 41 1 2 3 4 1 2 3 4 1 2 3 4 APR MAY JUN JUL AUG SEP OCT Solenidae (b)F Spisula solidissima (c)PREOP 19.0 4 3 2 1 0 MAY JUN JUL SEP OCT Figure 3.1.4-3. (Cqptinued). 160 abundance of the dominant taxa. Iliatella sp., Mytilus edulis, Solenidae and Mya-truncata abundances all peaked during this period (Figure 3.1.4-3).Most summer and fall collections were closely linked in Group 3 (within group similarity 0.68, Table 3.1.4-1). Although mean total abundance was lower than in Group' 2, more taxa were numerically dormant.ffeteranomia squamula, Modiolus modiolus and. Mya arenaria peaked during this period (Figures 3.1.4-3, and Results Section 3.3.7). All collec-tions after the first week in July 1990 were associated with this group (Figure 3.1.4-2).A number of summer collections exhibited relatively low abundances of bivalve larvae, particularly during 1984, 1986, 1987 and, 1988. These collections were segregated into Group 4 (within group similarity =0.69; Table 3.1.4-i), and were most closely related to Group 3 (Figure 3.1.4-1). Jleteranomia squamula and Mytilus edulis were the dominant species during this period. No collections from 1990 were included in this group.Spatial Patterns In previous years, .species composition in the bivalve larvae community has been.similar among Stations Pl, P2, P5 and P7 (NAI 1990b).Multivariate analysis of variance confirmed there were no significant differences in species composition among stations in 1990 (Table 3.1.4-2). This result was expected due to the combination of hydrographical and biological characteristics present. The-magnitude of tidal and longshore currents measured in the area is sufficient to transport aýwater mass about two nautical miles in one tidal cycle, or 5-15 miles in one day during periods dominated by longshore flow (NAI 1990b). The relative].y long .planktonic existence (4-6 weeks) of bivalve larvae serves as a dispersal mechanism for these species. Larvae can be transported great distances from the parent population. 161 TABLE 3.1.4-2.RESULTS.OF MULTIVARIATE ANALYSIS OF VARIANCE (MANOVA)COMPARING BIVALVE LARVAE COMMUNITY STRUCTURE AT STATIONS P1, P2, P5 AND P7, APRIL-OCTOBER 1990.SEABROOK OPERATIONAL REPORT, 1990.NO. OF NO. OF SPECIES STATIONS STATISTIC df F 11 4 Wilk's Criterion 33,210 1.22 NS Pillai's Trace 33,219 1.20. NS Hotelling-Lawley Trace 33,209 1.24 NS I.162 The maximum distance between the offshore stations (P2, P5 and P7; Figure 2.1-3) is about five miles; within that distance a water mass could move within a day during periods dominated by longshore flow.Station PI, in Hampton Harbor, would not be directly affected by longshore currents, but it is strongly-influenced by tidal currents;Located about 1.5 miles from Stations P2 and P5, PI is probably subject to essentially the same water masses due to tidalflow in and out of the Harbor except when there is significantly higher freshwater flows from the Blackwater Creek and Taylor River.Entrainment Entrainment samples were collected June through October, usually on the same days as the offshore and harbor collections. The entrained community structure was similar to'that occurring offshore (Table 3.1.4-3). Mytilus edulis and Heteranomia squamula were most dominant, together comprising over 55% of the total assemblage at each station. Total abundances were higher in entrainment collections than offshore (Station P2), probably reflecting the tendency of bivalve larvae to concentrate well below the surface.Entrainment losses were estimated for June through October based on total cooling water system daily flow and the observed bivalve larvae densities in entrained samples (Table 3.1.4-4). Highest entrain-ment losses were incurred in July, primarily affecting Mytilus edulis, ffeteranomia squamula and Iliatella sp.larvae. 3.1.4.2 Selected Species Mya arenaria This species is discussed in Section 3.3.7.163 TABLE 3.1.4-3. MONTHLY GEOMETRIC MEAN OF DENSITY (NO. PER CUBIC METER) OF BIVALVE LARVAE FROM ENTRAINMENT AND OFFSHORE (P2) COLLECTIONS DURING JUNE-DECEMBER 1990. SEABROOK OPERATIONAL REPORT 1990.ENTRAINKENT i JUN iJUL AUG 1 SEP I OCT .--------------------- +----------+-------------------------

---

i + -IBIVALVIA.

..306: 10061 911 531 391 IHETERANOMIA SQUAMULA 9341 9312: 30631 17841 3431 1HIATELLA SP. .39501 50931 1771 1661 481{MACOMA BALTHICA 0 O1 51 O.1 I. O1 INODIOLUS MODIOLUS 9761 36571 100: 13051 1371 1NYA ARENARIA .221 121 11 121 .391 IMYA TRUNCATA .691 8451 1! 0! .61 INYTILUS EDULIS 1 92411 216321 20441 11301 4511 IPLACOPECTEN HAGELLANICUS O1 01 1 0! 11 11 ISOLENIDAE .4101 2911 281 31 141 1SPISULA SOLIDISSIMA i 371 521 411 681 511:TEREDO NAVALIS i o0l 01 01 01 01 OFFSHOREa " JUN 1 JUL 1 AUG : SEP 1 OCT--------------------- + ---------- +----------+----------+----------"--- IBIVALVIA 1821 3731 181 2081 1011 IHETERANOMIA SQUAMULA 4521 37531 7991 35271 9501 IHIATELLA SP. 1 .44071 18491 16i 2631 531 INACOMA BALTHICA 1 {01 01 .01 21. 01 1MODIOLUS MODIOLUS 1 3481 13181 14: 16931 2271 IMYA ARENARIA i 321 131 O1 1141 31: 1MYA TRUNCATA .. .4801 -661 01 O 01.IMYTILUS EDULIS 1 98331 218741 7661 33661 5871 IPLACOPECTEN MAGELLANICUS 1 11 0: O1 11i O0 ISOLENIDAE i 6551 181i 1! 361 791 ISPISULA SOLIDISSIMA 1 01 310: 301 6681 1101 ITEREDO NAVALIS 1 0 0! 01 11 i 0 OP2 means based only on dates with a corresponding entrainment collection. 164 TABLE 3.1.4-4.ESTIMATED NUMBER OF BIVALVE LARVAE (in billions/month) ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK-STATION DURING JUNE-OCTOBER 1990.SEABROOK OPERATIONAL REPORT, 1990.SPECIES JUN JUL AUG SEP OCT ilytilus edulls 733.8 2,922.9 178.7 131.3 24.6I ,Modiolus modiolus 151.8 421.2 19.6. 300.1 1.7.0 Placopecten mag6llanicus 0 0.4 0 0.2 <0.1 ffeteranomia squamula 130.6 915.8 301.0 320.5 23.5..Spisula solidissima 25.0 27.6 4.1 9.9 2.4 Mya.arenara. 1.3 2.4 0.1 2.5. 1.8.Mya truncata 5.1 243.3 0.2 0. 0.3I'ifiatella sp! 232.4 594.4 24.6 22.5 2.7 Macoma balthica 0 -26.4 0- 0.1 0 Bivalvia. 22.9 1-14.0 11.0 5.2 2.1 Teredo navalis 0 0 <0.1 0 0 Solenidae " 28.7 27.4 3.6 0.8 0.6 TOTAL 1,331.6 -5,295.8 543.0 793.2 75.0.1.-n Wzlvtlus edulis Umboned veligers of Mytilus edulis were usually present by mid- to late May (Figure-3.1.4-3). Once present, they occurred consis-tently throughout the sampling program.ý -The protractled presence of larvae was due to recruitment patterns and duration of larval life-.stages. Major spawning events in Gulf of Maine mussel populations may be limited to temperatures above 10-120C (Podniesinski and McAlice 1986). Spawning of.M. edulis. in Long Island Sound was found to be asynchronous both within and among local populations and to occur over a two to three month period (Fell and Balsamo 1985). Spawning of some Long Island Sound mussel populations was also restricted by limited food availability for most of the year, resulting in spor-adic spawning events (Newell et al. 1982). Therefore it is probable, based on the reproduc-tive behavior of M. edulis, that recruitment of larvae to the plankton of.New Hampshire coastal waters occurred intermittently throughout much of the sampling program. Recruitment from non-local sources was also probable, as water masses may move large distances over the three to*five weeks required for larval development at ambient temperatures (Bayne 1976). Delay of metamorphosis until suitable settlement condi-tions are encountered can prolong planktonic existence for up to 40, days, depending on temperature (Bayne 1976)., These factors suggest that planktonic recruitment to the study area was intermittent and prolonged, and that duration of planktonic life varied over the-sampling program as temperature conditions, changed.Highest abundances of Mytilus edulis larvae have historically (1976-1989) occurred between, early June and'early July (Figure 3.1.4-3),.although in 1980-1982 and in 1990 abundances in late August, September or, October were as high as in early summer (NAI 1981f, ý1982a, 1983a, 1990a). Peak abundances ranged froms6 x .10 3/m 3 in 1982 to 3.3 x 105/m 3*in 1979 and 1989 (NAI 1987b, 1990a). The difficulty in assessing the variability in this population is probably compounded by patchiness caused by discontinuous recruitment both spatially and temporally (Bayne 1976; Podniesinski 1986). Collections taken within several days of one 166 another, even during months of peak abundance, varied by zero to three orders of magnitude (NAI 1981c, 1984a).Although temporal variability was high, as indicated by significant differences among years (Table 3.1.4-5; Year (Preop-Op)), overall spatial variability was low (Table.3.1.4-5; Area) when tested by ANOVA for both April to October and August to October 1990 collections. The lack of a significant interaction between main effects (Area X Preop-Op).indicated that throughout the 1990 collections, abundance of Mytilus.edulis larvae in the nearfield during 1990 were not significant-ly different from those in preoperational years and in the farfield area.3.1.5 Macrozooplankton-3.1.5.1 Community Structure Temporal Patterns The macrozooplankton community is comprised of numerous species that exhibit three basic life history strategies. The holo-plankton species, e.g. copepods, are planktonic essentially throughout their entire life cycle. Meroplankton includes species that spend a distinct portion 'of their lifecycle in the plankton, e.g. larvae of.benthic invertebrates. Species that alternate between association with the substrate and rising into the water column on-a regular basis are called tychoplankton, e.g. mysids.Historical analysis (1978-1984 and 1986-1989) of the macrozoo-plankton assemblage at the nearfield Station P2 showed seasonal changes that were greatly influenced by the population dynamics of the dominant copepods Centropages typicus and Calanus finmarchicus (NAI 1990b).Other taxa, particularly meroplanktonic species, exerted short-term influences, especially during the spring and summer (NAI i985b).Because of their lower abundances, seasonal patterns of tychoplanktonic 167 TABLE 3.1.4-5.N RESULTS OF ANALYSIS OF VARIANCE COMPARING NEARFIELD (STATIONS P2 AND P5) AND FARFIELD (STATION. P7) WEEKLY MYTILUS EDULIS ABUNDANCES- DURING PREOPERATIONAL (1978-1989) AND OPERATIONALb (1990) PERIODS. SEABROOK OPERATIONAL REPORT, 1990.APRIL-OCTOBER AUGUST-OCTOBER SOURCE OF VARIATION df SS F df .SS F Preop-0pc 1 0.14 0.21 NS 1 1.48 2.32 NS Year (Preop-0p)d 6 1.97 0.49 NS 6 10.65 2.79**Week.,(Preop-Op X Year)e 24 7.09 0.44 NS 24 13.57 0.89 NS Areaf 1 0.10 0.14 NS 1 0.04, 0.06 NS Area X Preop-Opg 1 0.31 0.47 NS 1 0.08 0.13 NS Error 492 304.92 -- 193 122.86'Based. on weekly sampling periods bCommercial operation began in August 1990' CPreoperational (1978-1989) versus operationalperiod, regardless of area--dyear nested within preoperationalad operational periods, regardless of. area eWeek nested within year nested within preoperational and operational periods, regardless of area fNearfield area = Stations P2 and P5; Farfield area = Station P7, regardless of year or period'gnteraction between/main effects NS.,= Not significant .(p>0.05)= Significant (0.05_>p>001)

• • Highly significant:(0.01_>p_>0.001)

Very highly significant (0.001_>p) species, e.g., mysids, amphipods and cumaceans, were not well documented by numerical classification of the entire macrozooplankton assemblage. To more clearly identify seasonal'patterns of this valuablle finfish food resource, the tychoplankton was, analyzed separately from the mero- and holoplankton. In the holo- and meroplankton assemblage there were four major seasonal groups (Figures 3.1..5-1 and 3.1.5-2) that encompassed the same time frame in most years (Groups 2, 4, 5 and 6). Two smaller groups (Groups 1 and 3) reflected occasional differences from the predominant patterns of species composition. The seasonal groups were distinct;within-group similarities ranged from 0.56 to 0.78and between-group similarities ranged from 0.43 to 0.68 (Figure 3.1.5-1; Table 3.1.5-1).Early months in 1978 and 1979 exhibited similar species composition, forming the small"winter group, Group 1. Dominated by copepods, abundances in this group were low (Table 3.1.5-1). During most years.the holoplanktonic and meroplanktonic constituents were similar in February, March and April, forming winter Group 2 (Figure 3.1.5-2).. Cirripedia larvae predominated, coinciding with the onset of vernal warming and initiation of thermocline formation (Figure 3.1.1-2).Copepods, particularly Calanus finmarchicus, Pseudocalanus sp. and Centropages typicus were abundant, as was the chaetognath Sagltta elegans. In 1990, March. and April collections were associated with Group 2..April has been shown to be a transitional period in the macrozooplankton, perhaps due to the combined effects of seasonal warming and highly variable freshwater influence (Section 3.1.1).Community.structure is not highly predictable as it has varied over the years. In most years, including 1990, it resembled the winter, assem-blage defining Group 2. In several years, the number of dominant taxa was smaller than in Group 2 although total abundances were higher.Spring Group 3 encompassed only March and April in several years (Figure 3.1.5-2). During these periods Calanus finmarchicus and Cirripedia 169 be........... Late Spring-Summer .. .u,-- "-.-.--.--.---.--.-.-..-.-

-Group 5 ,.,,> ,:.,-A-- .,

' ..,.La e ..mme.. .,'--.9.:... --withi group ' Y ' .Ie* " i; ',- 'etween group similarity , 10)[ no. of-6 0 samples -alWne 0V z w itT I , g I 0.4 0.5 0.6 .0.7 0.8 0.9 1.0~BRAY-CURTIS SIMILARITY Figure 3.1.5-1. Dendrogram formed by numerical classification of collections of halo- and meroplanktonic species of m acrozooplankton monthly mean log (x+l1)transformed abundances (no./1000 mn') at nearfield Station P2, 1978-1984*and 1986-1990. Seabrook Operational Report, 1990..0 170 0 cc ox all-o0 0 -- o 200 0 o"ooo~ '2 7 7&'°°~~~~ ..° .° ........ ... .......... "°"" ooo~ ~ "o * ' * * ....................S0 .......-.. ........ ..,.°OoO.°.o. .° ., ............ ......-.007 T °O oo°O ... ..... ..... .........'":' " 'G °o o o ....,. ,o ...-.-.- ... .... ..oc o o o o o I~ o~ o.o o ......................... L,,,'-..' -"..._... "" "..........* ---.-.-................... ? -, o o 0 .... ....., ..D 0°0, °I.' .° .°. '. .°°- ..,° .. ..... .° °. ° .°20 000 o'~~/.~~~ ~ ~ .. .00 0 0 0 ..2 .c 0 00 ...... ... ....~~ ~ ~ .% ..- ..............° ....° ...° °.°. .-. ........* .* * * ' °' -* ..°.°°.°,. .°°. .°. ° .....° .....o° ...00 000 ..... .................... o.o o ..... ..... ... .....°°°-°0 ..° ..-. .0 0 00 ..° .... *,:::: oo~~~ ~ .oo ..." " '" '" " *'°' " "" ' *'-- ..........,. ..... °.oi i i i ii0:-= Group 1= Group 2 S= Group 3 S= Group 4= Group 5 S= *Group 6 I= no sample H 2-1........... MONTH Figure 3.1.5-2. Seasonal groups formed by numerical classification of log (x+1) transformed holo-andrrieroplankton abundances (monthly mean) from macrozooplankton collections at nearfield Station P2, 1978-1984 and 1986-1990. Seabrook Operational Report, 1990. TABLE 3.i.5-1.GEOMETRIC MEAN ABUNDANCE (No./1000 m 3) AND 95Z CONFIDENCE LIMITS OF DOMINANT' HOLO- AND MEROPLANKTONIC TAXA OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS (MONTHLY MEANS) AT NEARFIELD STATION P2, 1978-1984 AND 1986-1990. SEABROOKOPERATIONAL REPORT, 1990.PREOPERATIONAL YEARS (1978.-1984;1986-1989) OPERATIONAL YEARS (1990)LONER UPPER.GROUP SPECIES N C.L. X C.L. N 1 .Calanus finmar-hicus 3 11 793 50,601. 0 Winter Ceniropaqes 35 493 6,875 (.0.56/0.43) Tortanus discaudatus .<1 307 74,182 Pseudocalanus sp. 62 295 1,398 Sagitta eleqgans -1 Z24 13,078,085 2 Cirripedia Z2 3,502 11,398 37,090,. 2 134,378 Hinter-Early Calanus finmarchicus 1,859 3,673 7,257 7,759 Spring PseucKocalanus sp. 1,757 3,345 6,366 6,084 (0.60/0.55) Cent+/-opaqes. tvpicus 449 1,049 2,448- 396§;@itt ejeans .345 784 1,780 2,707 Temora lonLicornis 126 389 1,201 16,134 Evadne sp. 10 34.. 116 13,207 3 Calanus finmarchicus 6 25,387 69,290 189,114 0 Spring Cirripedia 830 25,656 791,768 (0.65/0.63) Oikopleura sp. 496 6,079 74,403 Evadne sp. 1,485 5,279 18,762.: 4 Calanus fiinmarchicus 39 68,471 98,477 141,632 4 135,190 Late Spring- Cancer sp. ara 10,882 Z2,329 45,816 7,771 Summer Eualus pusiolus 7,767 12,080 18,788 6,321 (0.70-0.68) Temora oni2o~is 3,862 6,134 9,743 15,745*enr -gp; tvpicus 1,502 4,999 16,633 11,046 Css m_ S, emspinosa 3,242 .4,694 6,797 1,467 Ps lans Sp. 2,841 4,054 5,785 4,354 Meganyctiphanes norvenica 813 2,317 6,602 35,130 Metridia sp. 1,186 2,522 5,363 12,088 5 Centr-opaqs toicu 14 :77,467 163,246 344,008 1,377,271 Late Summer Calanus finmarchicus 2 28,929 .62,761 136,155 3,152.(0.72/0.68) Cancer sp. larvae 6,063 15,199 38,098,- 18,561septemspinosa 5,907 9,807 16,279 4,152 Centropages sp< copepodites 720 3,899 21,092 65,081 6- Centropaes tpicus 42 14,079 26,262 48,989 5 2,036 Fall-Hinter Cet ropaqs sp. copepodites 668 1,503, 3,379. 161 (0.78/0.64) Centr-oaqes hamatus 456 1,102 2 2,662 335 Temora lonqicornis 478 1,034- 2,230 1,929 Calanus finmarchicus 628 996 .1,579 3Z5elegans 443. 751 1,274 1,104 Pseucpl alanus sp. 395 749 1,421 66 0ikopleura sp. 23 59 14&. 540 Tortanus discaudatus 268 561 1,169 276 Eva&be sp. 14 35 86 155'dominant taxa are those whose abundance is ZZ of the group geometric mean in either the preoperational or the operational years larvae were the overwhelming dominants (Table 3.1.5-1). The larvacean Oikopleura sp.. and the cladoceran Evadne sp. were also abundant (Table 3.1.5-1). April 1988 was associated with late spring-summer Group 4.The holoplankton and meroplankton community structure was similar in most years from May through August (Group 4). Many species achieved high abundances (Table 3.1.5-1). Larvae'of crustaceans (e.g.Cancer sp., Eualus pusiolus and Crangon septemspinosa) and euphausiids (Meganyctiphanes.norvegica) were generally abundant. The copepods Calanus finmarchicus, Temora longicornis, Pseudocalanus sp. and Metridia sp. typically reached their highest abundances during this part of the year. May through August collections from 1990 were similar to this group.September was a distinct period (Group 5) in most years (Figure 3.1.5-2). Generally, September marks the period of highest bottom temperature and the beginning of the breakdown in the thermal stratification (Figure.3.1.i-3). Centropages typicus reached its annual peak abundance during this period. Copepodite densities of this genus also peaked. Abundances of Calanus finmarchicus and Cancer sp. larvae were similar to the previous summer months (Table 3.1.5-1). Crangon septemspinosa, predominantly immature stages, typically peaked in abundance in September. Species composition in September 1990 was similar to other years comprising Group 5, although abundance of Calanus finmarchicus was unusually low.With the reduction of spawning 'activity as coastal.waters cooled in the fall (Section 3.1.1), meroplanktonic species became less predominant components of the macrozooplankton assemblage (Table 3.1.5-1). Total abundances declined despite the continued presence of most species as dominant taxa. This assemblage (Group 6) characterized the period from October through January of most years (Figures 3.1.5-1 and 3.1.5-2). Centropages typicus continued t0 dominate, exceeding the abundance of other taxa by an order of magnitude. Centropages sp.copepodites, Centropages hamatus, Temora longkcornis and Calanus 173 finmarchicus occurred as secondary dominants. January, February and October through December 1990 collections were similar to the Group 6 assemblage, although Oikopleura sp. was unusually abundant in the 1990-collections (Table 3.1.5-1).. In summary, the copepods Calanus finmarchicus and Centropages weretypicus were consistently among the dominants of the seasonal groups formed by numerical classification,.C. finmarchicus usually ranking first or second in abundance. Many other species exhibited high abundances seasonally, but were generally limited to dominance during one or two seasonal groups (Table 3.1.5-1). Seasonal patterns of abundance and species composition in 1990 were-similar to previous years.'Although seasonality was evident in the assemblage of tycho-planktonic species (Figures 3.1.5-3 and 3.1.5-4), 'separation of seasonal groups was less distinct than in the holoplankton-meroplankton assem-blage. Between group similarities were close to within group similari-ties and each group was added successively with lower similarities Figure 3.1.5-3). This may result from the fact that twenty of the*twenty-two species used in the analysis were present essentially year-round occurring in each of the four major seasonal groups (Groups 1, 2, 7 and 8; Table 3.1.5-2). .Total abundances were two or more orders of magnitude lower than holo- and meroplankton abundances. Two. species (Neomysis americana and Pontogenela inermis) were each ranked among the three most abundant species in eight out of nine groups. Distinctions between groups of tychoplankton assemblages were generally based on moderate changes in abundances rather than dramatic changes in species composition. Four major seasonal groups encompassed most of the collections (Figures 3.1.5-3 and 3.1.5-4). Winter (January through March) months were generally similar (Group i). Neomysis americana,-Diastylis sp. and Pontogeneia inermis predominated in both. preoperational and 1990 collections (Table 3..1.5-2). .174

• ungrouped sample ...-j* ..-.........

..Group I- 0-~WinterO Late Group 4 Late Sp-rinSrng E "----.'...'" roup 3 Late Sprifig..J

__ __7 7Gr 3c Group 6 9Spring...'r

.0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 BRAY-CURTIS SIMILARITY Figure 3. 1.5-3. Dendrogram formed by numerical classification of collections of monthly mean log (x+l)transformed tychoplankton abundances (no./1000 M 3) from macrozooplankton collections at nearfield Station P2, 1978-1984 and 1986-1990. Seabrook Operational Report, 1990.175

" * ::.'o.. ',',""" ... -/ c !;~ = Group 1° j Group4I 19.87 X..000 00 ,:: __ : * *= Group 2 003 ..... ~~'~*~=Gop 1986= Group 3 1982* -- -o,, ,"- s\ "' .-* Group 5..-,.;.. ,,,, ,,. =~- I ~Gou.8 -: '. :.:-:.= Group 9.".".""..."...........

.1980'-' ~ -:::::::i U = ungrouped--1 9 8 1' .; .' .' .'o.G o u 1979"...:*

.,'1978 JAN FEB MAR APR MAY JUN JUL .AUG SEP OCT NOV DEC* MONTH Figure 3.1.5-4. Seasonal groups formed .by numerical classification of log (x+l) transformed tychoplannkton abundances (monthly mean) from macrozooplankton collections at nearfield Station P2, 1978-1984 and 1986-1990. Seabrook Operational Report, 1990.--.. FT V TABLE 3.1.5-2. GEOMETRIC MEAN ABUNDANCE (No./1000 m') AND 95Z CONFIDENCE LIMITS OF DOMINANT' TYCHOPLANKTONIC TAXA OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS (MONTHLY MEANS) AT. NEARFIELD STATION P2, 1978-1984 AND 1986-1990. SEABROOK OPERATIONAL REPORT, 1990.PREOPERATIONAL YEARS (1978-198451986-1989) OPERATIONAL YEARS (1990)LOWER UPPER GROUP SPECIES N C.L. X C.L. N x 1 americana 33 305 655 .1,402 3 2,299 Winter iasty-lis sp. 125 .197 310 85 (0.64/0.61) ooe a inermis 75 114 174 65 Oedicerotidae 28 44 67 52 Mv mixta 10 37 133 40 PS zTe-p-ocumia minor 23. 35 52 22 2

• mixta 20 205 630. 1,936 1 8,204 Spring F -- americana 75 152 308 129 (0.61/0.59) ontoieneia inernis 41 71 120 159*Dza-s-lIS sp- 15 27 47 88 Harpacticoida 9: 21 44 9 3 Oedicerotidae 3 1 73 3,082 0 Late Spring Pont qeeia inermis -1 39 6,262 (0.59/0.51) t americana 2 18 110 iastvyis sp. <1 14 202 IMschvraerus anquioes 1 12 88 Garm__rus lawrenc ianus -1 7 155 4 Oedicerotidae 3 30 3512 397,640 1 .432 Late Spring ameýricana 27 594 12,561 226.(0.72-0.61) 19 471 11,072 837 Gammarus lawrencianus 1 <1 4 98 5 Hyperiidae 2 -1 .216 1,170,067 0 Miscellaneous Pcgnjggnia inermis- -1 50 3,24Z,874 (0.56/0.45)

Neomysis americana -1 16 305,023 Jassa marmorata -1 8 6,408 6 ontooeneia inermis 2 8 23 59 0 Spring anquipes .-1. 19 16,392 (0-5' sp. -1 5 31,107 aripac icoida -1 4. 510,993 Dalis sp. -1 4 5. OxlO9 Ganna ruslawrencianus <0 1 4 7 i~s americana 33 91 168 311 2114 Summer ono la inermis 73 95 123 398 10.67/0.64) Diasty-is 64 94 137 87 Oedzoe 44 90 182 73 Harpacticoida 35 58 99 234 Unciola irrorata 7 12 20 30 8 si. americant 22.. 2,651: 5,133 9,936 4 3,647 Fall a s sp. 1 147 234 373 233 (0.69/0.64) Poa inermis 120 204 345 160 Pseudolevtocan-a minor .92 149 239 74 9 eNeom"Vsis americana 8 101 362 1,293 0 Late Fall Dialis sp. 6 13 .28 (0.54/0.51) Hyperiidae 1 8 52'dominant taxa are those whose abundance is k 2Z of the group geometric mean in either the preoperational or the operational years The mysid Mysis mixta has typically been most abundant in the spring in coastal waters of New Hampshire (Grabe and Hatch 1982) prior to its offshore migration. M. mixta dominated in the spring (Group 2)while Neomysis americana and Pontogeneia inermis continued to occur as subdominants (Table 3.1.5-2). Although the April 1990 collections were not clearly associated with a seasonal group this may be the result of unusually high abundance of Mysis mixta (2.4 x 10 5/1000m 3) and Gammarus lawrencianus (4.3 x 10 4/1000m 3) (NAI 1991) rather than the absence 'or reduced abundance of key species.During the preoperational period, several other assemblages, (representing Groups 3, 4, 5 and 6) have characterized the late spring period. Mysis mixta was not among the dominants in any of these groups, although Neomysis americana or Pontogeneia inermis was (Table 3.1.5-2).The amphipod family Oedicerotidae.dominated Groups 3 and 4. Subdomina-nts included other amphipod species, generally atypical of the major seasonal groups. The June 1990 assemblage was most similar to Group 4 (Figure 3.1.5-4)"' July, August and. generally September were similar (Group 7)among years (Figure 3.1.5-4). Neomysis americ'ana., Pontogeneia inermis and Diastylis. sp. were again dominants (Table 3.1.5-2). The occurrence of Oedicerotidae, harpacticoid copepods and the amphipod Unciola, irrorata as subdominants distinguished-this group. The tychoplankton assemblage occurring in July and August. 1990 was similar to preoperatio-nal collections included in this group.Neomysis americana generally reached'its highest abundances in the fall (Table 3.1".5-2), distinguishing Group 8. Fall months of most years, with the exception of 1978, 1979, 1981 and 1987, were represented in Group 8. Abundances of N. americana have been found to'be signifi-*cantly different among years (Section 3.1.3.2), With 1978, 1979 and 1987 exhibiting lower abundances than other years (NAI 1990b). Overall 178 abundances, as well as N. americana.abundances,, were low in some years, distinguishing a second fall assemblage: (Group 9) of tychoplankters (Table 3.1.5-2).In summary, seasonal groups 1,2, 7 and 8 encompassed more than 85% of the preoperational collections and 83% of 1990 collections. Most tychoplanktonic species were present year-round. Neomysis americana,. Diastylis sp. and Pontogeneia inermis were frequently-among the dominan-ts. Moderate changes in abundance of these taxa, rather than dramaticýchanges in species composition distinguished groups in general, with the exception of spring Group2 when Mysis mixta dominated. Most collec-tions in 1990 were similar to the major seasonal groups. April 1990 was unusual in not-showing high similarity to other spring collections but this may have been due to unusually high abundances of Mysis mixta and Gammarus lawrencianus. June 1990 was similar to a small group that encompassed several historical collections. Spatial Patterns The spatial distribution of most holo- and meroplanktonic. species in the study area is governed primarily by local currents.Hydrographic studies of temperature and salinity have shown that nearfield Station P2, and farfield Station P7 are exposed to the same water mass (NAI 1985b). Furthermore, bivalve larvae studies suggest that areas at similar depths and distances from shore (suchas P2 and P5) have similar species composition (NAI 1977a). Thus no spatial differences in the rneroz or holoplanktonic macrozooplankton abundances, percent composition, or rank would be. expected among Stations P2, P5 or P7. This has previously been confirmed in examinations of the annual percent composition, percent frequency and rank dominance scores (RDS)of dominant species with nonparametric tests (NAI 1985b, 1989b).A multivariate analysis of variance (MANOVA) comparing semi-monthly species composition, including mer.o-, holo- and tychoplankton 179 taxa indicated that there-were some significant species differences among Stations P2, P5 and P7 in 1990 (Table 3.1.5-3). ANOVAs comparing abundances of individual species were utilized to identify'where the differences in community structure occurred. The ANOVAs revealed no.significant spatial differences in any holoplanktonic or meroplanktonic species. However, of the nine tychoplankt'onic species tested, eight exhibited distinct spatial patterns of distribution (Table 3.1.5-3).Generally, abundances were similar at Stations P2 and 'P5 and were significantly -lower at Station P7. These differences, were apparently large enough to influence the results of the MANOVA.Tychoplanktonic species are often strongly associated with particular substrate types. Substrate type and complexity, along with proximity to Hampton-Seabrook estuary, may account for some of the differences observed among tychoplankters. Historically, Neomysis americana, Pontogenei8 inermis, and Diastylis sp. have had.higher abundances at P2 where substrate is sand and cobble than at P7 where the substrate is mainly sand (NAI 1985b, 1988b, 1989b). At Station P5, where substrate is largely ledge outcrop and cobble, densities of Diastylis sp. have been significantly lower than at P2 (NAI 1988b, 1989b). Amphipods-in the family Oedicerotidae continued to be more abundant at Stations P2 and P5 than P7 (Table 3.1.5-3; NAI 1.988b, 1989b).- Of the tychoplanktonic species tested, only Mysis mixta did not differ in abundance among stations. This may be attributable to the extreme seasonality (complete absence during much of the year) of this species, overriding the effects of any substrate preference. MANOVA was not conducted on the August-December operational period' in 1990. To properly evaluate community structure 'it is impor-tant to include all dominant taxa.. Unfortunately, the constraints of the MANOVA require that the number of samples tested be greater than.the number of tAxa. Because of the complexity of the macrozooplankton assemblage it was not realistic to reduce the species tested to meet this requirement. However, abundance patterns of the selected.species.were individually tested using analysis of variance (Section 3.1.5.2).180 II TABLE 3.1.5-3.RESULTS OF MULTIVARIATE ANALYSIS OF VARIANCE COMPARING MACROZOOPLANKTON COMMUNITY STRUCTURE AT STATIONS P2, P5 AND P7 IN 1990. SEABROOK OPERATIONAL REPORT, 1990.MULTIVARIATE (MANOVA) TESTS NUMBER OF TAXA NUMBER OF STATIONS STATISTIC df F 46 3 Wilks' criterion 92,48 2.30***Pillai's' trace 92,50 2.22**Hotelling-Lawley trace 92,46 2.38***TAXA SHOWING MULTIPLE SPATIAL DIFFERENCESa COMPARISONb 1 Harpacticoida P2 P5 P7 Diastylis sp. P2 P5 P7 Pseudoleptocuma minor P2 P5 P7.Gammarus lawrencianus P2 P5 P7 Oedicerotidae P2 P5 P7 Pontogeneia inermis P2 P5 P7 Unciola irrorata P2 P5 P7 Neomysis americana P2 P5 P7'based on one-way analysis of variance bstations listed in order of decreasing abundance; stations connected by line were not significantly different from each other.NS Not significant

• Significant at 0.05_>p>0.01
  • = Highly significant at 0.01_>p>0.O01 Very highly significant at 0.O01->p 3.1.5.2 Selected Species Calanus finmarchicus Over the length of this study 1978-1984, 1987-1990)

Calanus finmarchicus has been a dominant species in the macrozooplankton assemblage (Table 3.1.5-1). Historically, althoughuboth lifestages usually occurred yearround, copepodites exhibited greater abundances than adults, a trend which continued in 1990 (Table 3.1.5-4). The major peak in copepodite abundance usually occurred April through September. Low abundances of copepodites occurredduring winter (Figure 3.1.5-5).Analysis of variance confirmed a strong seasonality in copepodite abundance (Table 3.1.5-5; Month (Year (Preop-Op))). In 1990 copepodites exhibited typical abundances during March through July but midwinter and..late summer-fall (August through November) abundances were substantially* lower than the historical average, as indicated by a significant Preop-Op term (Figure 3.1.5-5; Table 3.1.5-5). Although this same pattern of relatively low summer and fall abundances was observed in 1989, mean abundance in 1989 was not significantly different than earlier years (NAI 1990b). The annual abundance of copepodites in 1990 was lower than., any previously, reported value (Table 3.1.5-4), contributing to a significant difference among years (Table 3.1.5-5; Year* (Preop-0p)) and between 1990 and the preoperational years (Preop-Op). Calanus finmarchicus adults tended to peak in the summer months (June through September, Figure 3.1.5-5), declining to lowest abundances in November and December. The general of the seasonal pattern.was confirmed with analysis of variance which showed significant differences among months (Table .3.1.5-5). Abundances of adults in 1990 were below the confidence limits of the preoperational mean'during April through July as well as*September and October.(Figure 3.1.5-5), result-ing in a significantly lower annual abundance (Tables 3.1.5-4,5). In 1989, monthly abundances of adults had been unusually low in September through November but at typical levels the rest of the.year. A more 182 TABLE 3.1.5-4. ANNUAL GEOMETRIC MEAN ABUNDANCE (No./1000 m3) AND UPPER AND LOWER 95% CONFIDENCE LIMITS OF SELECTED SPECIES 'OF MACROZOOPLANKTON AT SEABROOK NEARFIELD STATION P2 DURING PREOPERATIONAL YEARS (1978-1984 AND 198711989)a AND GEOMETRIC MEAN ABUNDANCE IN 1990.SEABROOK OPERATIONAL REPORT, 1990.MEAN VALUES PREOPERATIONAL YEARS 1990 SPECIES/LIFESTAGES 1978 1979 1980 1981 1982. 1983 1984 1987 1988 1989 LCL x UCL x Calanus finmarchicus 8,999 6,614. 19,753 13,159 4,756 12,634 8,819 8,555 6,479 5,396 6,344. 8,689 11,900 3,994 copepodites Calanus finmarchicus 767 129 338 116 186 555. 518 160 58 96 115 213 .392 35 adults Carcinus.maenas 41 22 42 40 .40 93 64 62 56 44 36 47 62 65 Slarvae Crangon septemspinosa 404 342 152 157 425 547 319 360 474 345 241 328. 446 203.Zoeae and postlarvae Neomysis americana 154 40 252 400 651 494 758 258 220 1,835 159 332 693 972 all lifestages al986 sampling took place only from July-December and this is not included in annual X computation. 0O LO Calanus finmarchicus Copepodites 6-1 0 PREOP....... 1990 Zo is~-5-4-3-A-U I I J I I I I I .U A I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT ~NOV E MONTH Adults 6 5/LU C Z a 00 4 3 j 2 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV i MONTH Figure 3.1'.5-5. Log (x+l) abundance (no./1000 M 3) of Calanusfinmarchicus copepodites and adults; monthly means and 95% confidence.intervals over all preoperational years (1978-1984, 1986-1989) and monthly means for 1990 at nearfield Station P2. Seabrook Operational Report, 1990.184" TABLE 3.1.5-5.RESULTS OF.ANALYSIS OF VARIANCE 8 COMPARING NEARFIELD (STATIONS P2 AND P5) AND FARFIELD (STATION P7) ABUNDANCES OF SELECTED'SPECIES OF HACROZOOPLANKTON DURING PREOPERATIONA1(1978-1989) AND OPERATIONAL (1990) PERIODS.SEABROOK OPERATIONAL .REPORT. 1990.'JANUARY-DECEMBER AUGUSTb- DECEMBER SOURCE OF SPECIES VARIATION df SS F. df SS Calanus finmarchicus Preop-Opc 1 11.46 22.05A** 1 17.58, 25.39***copepodites Year (Preop-Op)d 6 18.13 5.8l]** 6 24.52 5.90***Montl (Year (Preop-Op))e 82 647.95 15.21*** 32 237.78 10.73"**Area, 1 0.96 1.85 NS 1 0.54 0.78 NS Preop-Op X Area5 1 0.08 0.15 NS 1 0.33 0.48 NS.Error 376 195.38 168 116.37 Calanus finmarchicus Preop-Op 1 39.86 39.93"** 1 21.81 24.39***adults Year (Preop-Op) 6 58.82 9.82*** 6 33.67 6.28***Month (Year.(Preop-Op)) 82 525.41 6.42*** 32 369.01 12.90-**Area 1 3.33 3.33 NS 1 0.76 0.85 NS Preop-Op X Area 1 0.40 0.40 NS 1 0.09 0.10 NS Error 376 375.33 168 150.20 Carcinus maenas Preop-Op 1 3.37 11.26"** 1 0.08 0.27 NS larvae Year (Preop-Op) 6 59.89 33.32*h* 6 9.90 5.62***Month (Year (Preop-Op)) 82 1173.71 47.78***. 32 346.98 36.97*A*Area 1 0.15 0.52 NS 1 0.23 0.77"NS Preop-Op X Area 1 0.01 0.03 NS 1 0.20 0.69 NS Error 376 112.63 168 49.28 Crangon septemspinosa Preop-Op 1 15.02 54.37*** , 3.67 15.03"**zoeae and post larvae Year (Preop-Op) 6 23.48 14.17"** 6 4.86 3.31"*Month (Year (Preop-Op))

• 82 538.70 .23.79***

32 164.80 21.07***Area 1. 1.68 6.08* 1 0.47 1.93 NS Preop-Op X Area 1 0.03 0.10 NS 1 0.20 0.80 NS Error. 376 103.84 168 41.07 Neomysis americana Preop-Op

• 1 6.53 10.45"* 1 0.62 1.03 NS all lifestages Year (Preop-Op) 6 83.41 22.24*** 6 71.72 19.80***Month (Year (Preop-Op))

82 242.68 4.73*** 32 94.01 4.87***Area 1 26.27 42.05*** 1 8.21 13.60***Preop-Op X Area .1 1.90 3.03 NS 1 <0.01 0.00 NS Error 376 235.04 168 101.41 k-O bbased on twice monthly sampling periods ,commercial operation beg an in August 1990 dpreoperational (1978-19 9) versus operational period, regardless of area_~year nested within preoperational and operational periods, regardless of area emonth nested within year nested within preoperational and operational periods, regardless of area .nearfield area = Stations P2 and P5; -arfield area Station P7, refardless of year or period ginteraction between main effects NS = not significant (->0.05)= significant 0.052:p>0.01) = hihl si nificant

• • Very ig.h1y significant (D.0012p) detailed description of the life history of Calanus finmarchicus and other selected species is available in the.1984 baseline report (NAI 1985b).Previously, the.lifestages were combined to assess spatial distribution.

In both 1989 and 1990, abundances were. similar at Stations P2, P5 and P7 (NAI 1990b). Analysis of variance was performed on both copepodites and adults to ascertain whether the relationship of their abundances in the nearfield area (Stations P2 and P5) to those in the farfield varied between preoperational and operational periods j-(Preop-Op X Area). Despite differences among years for both copepodites and adults, the spatial relationship did not change between the opera-tional and preoperational periods for either the January through December' time frame or the August through December time frame (Table 3.1.5-5).Carcinus maenas In 1990, Carcinus maenas larvae exhibited the same seasonal pattern of abundance observed historically, first occurring in May and persisting.through December (Figure 3.1.5-6). Larvae were most abundant between June and September. and declined sharply in abundance during October in 1990 as in previous years. Seasonal aspects of larval development are detailed in annual data reports (e.g., NAI 1990a) and are summarized here. Stage I zoeae were abundant in June and July. In 1990, zoeae Stages II, ilI and IV were most abundant in September. Megalopa were most abundant in August. The extended period of abundance for zoeaI, II and III suggests that spawning and recruitment from local and regional adult populations is asynchronous. Annual abundances of these larval stages at Station P2 in 1990 were lower than preoperation-ally.(Tables 3.1.5-4, -5; Preop-Op). Abundances during the August through December period of commercial operation in 1990 were similar to the preoperational mean from the same period.186 Carcinus maenas 6 1PRE0OP 5 ° ..... 1990 0 ZC3-00 4 3 2 0 JAN FEB MAR APR. MAY JUN JUL AUG SEP OCT NOV -DET C MONTH Crangon septemspinosa C)0-j.6-5-4-3 2--.o- PREOP 1990 1 0.1 I I I I I I I -I. I I I I JAN FEB MAR :-APR MAY JUN JUL AUG SEP OCT NOV 7E=MONTH Figure 3.1.5-6. Log (x+l) abundance (no./1000 M 3) of Carcinus maenas larvae and Crangon septemspinosa zoeae and post larvae; monthly means and 95% confidence intervals over all preoperational years (1978-1984, 1986-1989) and monthly means for 1990 at nearfield Station P2. Seabrook Operational Report,. 1990.187 Neither spatial nor temporal differences of Carcinus maenas larval abundances had been evident in previous years (NAI 1990b), since adults are common in-shore near all three stations and hydrographic' conditions typically do not separate plankton stations (NAI:1985b). Abundances in the nearfield during the period of commercial operation (August through December 1990) were statistically similar to those in the farfield during the same period and to both nearfield and farf-i eld abundances in the preoperational years (Table 3.1.5-5).. Crangon septemspinosa,.. Spawning in Crangon septemspinosa typically commenced in " April, with zoeae and post-larvae abundant through November (Figure 3.1.5-6). Although larvae, including zoea'I, were present year round, peak abundances in June through September were usually two to three orders of magnitude higher than abundances observed November through April. In 1990, winter, spring and fall abundances were typical of previous years.but abundances in July and August were about an order of magnitude lower.than occurred previously. Although annual mean abun-dance at Station P2 for 1990 was within the range of this study (Table 3.1.5-4), abundance was significantly lower in 1990 than the preoperati- -onal mean across the whole year (January through December; Table 3.1.5-5, Preop-Op). A comparison of semi-monthly mean abundances of Crangon larvae and post-larvae indicated no significant change in the relation-ship of nearfield and farfield abundances between preoperational years and 1990 throughout the year or during the August through December period (Table 3.1.5-5; Preop-Op X Area). No spatial-or temporal differenc~s have been observed in the past (NAI 1990b).Neomvsis americana Neomysis americana has been present year round in the macro-zooplankton but was usually-most abundant from September through April (Figure 3.1.5-7). Generally, the annual cycle was slightly bimodal, 188 Z0 nJo 0'*0 5-.4-3-2-.1-Neomysis americana-o-- PRE OP....... 1990 0 I I I I I I I I.JAN FEB MAR APR MAY JUN JUL AUG SEP OCT 'NOV DC MONTH El OVIGEROUS & LARVIGEROUS ... ADULT E0 IMMATURE ADULT* JUVENILE PREOP 90 1990 I--z ILl C.)(Ll w.80 70 60 50 40 30-20 ,oiii 0 , 0 JAN FEB MAR APR MAY JUN JUL OCT MONTH Figure 3.1.5-7. Log (x+1) abundance (no./1000 M 3) of Neomysis americana; monthly means and 95% confidence interval over all preoperational years (1978-1984, 1986-1989) and monthly means for 1990 and mean percent composition of Neomysis americana lifestages over all preoperational years (1978-1984, 1986-1989) and for 1990 at nearfield Station P2. Seabrook Operational Report, 1990.189 with lowest abundances May through August. The elevated abundancesý observed in 1989 (NAI 1990b) continued into the early part of 1990, contributing to the significantly higher annual mean-in 1990 than in preoperational years (Tables 3.1.5-4,5; Preop-Op). From March through the end of 1990, abundances were similar to the mean of the preoperati-onal period. Abundances in August-December 1990 were similar to the same months in preoperational years (Table 3.1.51-5) Lifestages of N.americana have historically exhibited distinct seasonal patterns (NAI 1985b). Juveniles were most numerous in late spring and fall (Figure 3.1.5-7). Immature mysids were most prevalent from late fall through winter. Mature individuals were most abundant in winter with a second-ary peak in the summer, while ovigerous and larvigerous females were most abundant in April and July. All lifestages generally followed these patterns in 1990.Spatial differences in abundance of Neomysis americana have been detected in the past and occurred-again in 1990.(NAI 1990b; Tables 3.1.5-3,5). Spatial differences were attributed both to substrate conditions and distance to Hampton Harbor.. However, when abundances in the nearfield area as a whole (i.,e. Stations P2 and P5) were compared to those in the far'field (Station P7)-between operational and pre-operational periods, no significant changes in'the spatial distribution of N. americana were observed (Table-3.1.5-5, Preop-Op X Area).190

3.2 FINFISH

Common names recognized by the American Fisheries Society (Robins et al. 1991) are used for fish taxa. The common and scientific names for every *taxon collected from 1975 through 1990 in the Seabrook ichthyoplankton and adult finfish programs are listed with their relative abundances by gear type in Appendix Table 3.2.1-1. No species new to the Seabrook program were encountered during tht 1990 surveys.3.2.1 Ichthyo-plankton 3.2.1.1 Community The nearfield ichthyoplankton community has been examined in annual baseline reports using numerical classification (NAI 1982c, I983b, 1984b, 1985b) and discriminant analysis (NAI 1987b, 1988b, 1989b, -1990b). Species composition of both eggs and larvae exhibited distinct seasonal changes, which were consistent among years. For this first operational report, numerical classification (cluster analysis).was used to examine how well the 1990 community fit *the patterns observed in previous years..Temporal Patterns of Nearfield Fish Egg Assemblages Numerical classification of monthly fish egg abundances showed the species composition to be highly seasonal in nature, with different taxa occurring at different times of the year and the same seasonal succession repeating year after year. The basic pattern over the period 1976 through 1990.can be summarized by nine seasonal groups of samples, each characterized by a particular assemblage of taxa (Figure 3.2.1-1i and Table 3.2.1-1).Group 1 occurred in the -fall of most years, primarily during November (Figure 3.2.1-2), and.was dominated by Atlantic cod eggs, with 191 I['I r- within group' imilarity 4 .of samples-between group similarity 10 .5 samples" " ~0'0" Group 1 all Group 2..:::Late Fall/Early Winter":':i ..... .. ..... ---.- * * °... ° ' oo. o. .+/-..... ...*... .. .* * *** 3 > ruLate Winter.e-'," Grouip 5 Early Spring.77GY S rn C0 uJ U-0 z....=_ .. " n _I Lo °°0%Groupo6 ,o. o.O Late Sprong/Earmy Summer -o o oo 0*. -............ ............................................................................ Group 8 i())-((:::::::::(.............. ....._I-.............................................................................." ." *'" : :"Group 9 Early Fall...................

---

I I 0I.0.1 0.2 0.3 0.4 0.5 I I 0 l 0.5 0.6' 0.7 0.8 0.9 1.0 BRAY-CURTIS SIMILARITY Figure 3.2.1-I..Dendrogram formed by normal classification of monthly abundances (log (x+l)transformed number per 1000 M 3) of fish eggs at Seabrook nearfield Stations P2 and P3, January 1976-December 1990. Seabrook Operational Report,'1990. 192 I TABLE 3.2.1-1.FAUNAL CHARACTERIZATION OF SEASONAL GROUPS FORNED BY NUMERICAL CLASSIFICATION OF SAMPLES OF FISH EGGS COLLECTED AT SEABROOK NEARFIELD STATIONS.P2 AND P3 DURING JANUARY 1976 THROUGH DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990.NO. OF SAMPLESb. DENSITY (NO./1OO0m 3)d PREOP. YEARS 1990 PREOP.SAMPLE GROUPa YEARS 1990 DOMINANT FISH EGGSc MEAN LCL UCL MEAN GrouD 1 9 1 Atlantic cod/haddock 154 90 263 166 Fall 0.72/0.64 Group 2 Late fall-early winter 0.68/0.64 Group 3 Winter 0.64/0.49 Group 4 Late winter 0.76/0.58 Group 5 Early spring 0.63/0.58 Group 6 Spring 0.74/0.65 Group 7 Late spring-early summer 0.71/0.65 Group 8 Summer 0.59/0.57 Group 9'Early fall 0.45/0.36 27 2 Atlantic cod/haddock Pollock 63.'46 11 2 Atlantic cod/haddock American plaice 22 .0 Atlantic cod/haddock American plaice 11 I American plaice Atlantic cod/haddock Fourbeard rockling 14 1 Cunner/yellowtail flounder Atlantic mackerel'Fourbeard rockling American plaice 25 2 Cunner/yellowtail: flounder Atlantic mackerel 8 4 42 27 6 1 42 36 122 17 21 95 78 13 8 88 89 63 8 10.I 61 57 302 51 48 745'153.107 62 14 85 507 782 529 1160 643 331 283 172 103 119 2390 1060 672 35 2 Hake Cunner/yellowtail flounder Windowpane 8 1 Hake Atlantic cod Atlantic whiting Fourbeard rockling Fourbeard rockling/hake 21200 14000 32000 3500 1700 7230 1570 972 2530'316 '118 845 94' 51 171 15 7 32 12 2 49 10 2 41 5 1 17 3 <1 12 2440 470'105 51100 20600 1530 213 290 7 38 43 1 14 aThe predominant season of occurrence is listed for each group, along with the within-group and the b among-group similarities. Each monthly "sample" included in the analysis consists of the average of tows within date and dates within month..C Taxa listed as dominants are those whose geometric mean densities together account for >90% of the sum of the geometric mean densities' of all taxa within the group.Densities shown are geometric mean and corresponding lower 95% confidence limit (LCL) and upper 95%confidence limit (UCL) among the samples within the group.Table 3.2.1-1.193

• - 0 S-0...... .........

........ .1990 ~'.7 '* 0 0a*~\ / 00 001, 1989 \' L, "" "~oo%1988 o::* .. .* ....h .~ .oo'o.*°00000 .......o.. .1988 ::::: :::: ::: ) , ..................................... ........ ., ... .. -..s... -.0o. 0.. ..... -Group.., ... ..- 0.-o Group I*~~~~~~ \ *o*°°°.*...........o°*

• • oo *.... oo*.....*...
    • °,o.19 87 r;'.'.'.'.'." o ...... ....... ..... ...........

.......................... 6 0-00.0 00 :: : :. ...".. "j" -Group 2 I. 0/ 00. ..... .::::00:::::::0:::::::::: °° °" '" " -Group4 1986 o. ....G p ...... .A. ..Group4..." C: .............. A .". .Group 3* -o a A ...ln.f 1980 ".. ... o. o.'. ... .Gro 1985a o ..... ...-a 0.......................... .......... ...........00000. ..0 = unGrouped* * ......... .....exlude.du> 1984 o= = = ,= =,,,= ,= o.;:..:.:.....................u. o , .....................i.ii i i i i i i ....o.iiiiiiiiiiiIiii:i.... -i ii -i -.Groop. .1983 .0000 000 A A " J F MAR............. AR M JN JL AG S O .C...T.... NO ................................

u ro pe 19782 o o o oo o nea7feld Sation P2.ad.P3.uringJanuay 197 throgh Deembe 190 earo Operational.'. l Report,.19

90. ...........

..~ ~~ o o o .. .. ..::::::to ow c u 1981 o" 198 ne il Sttin P2 an P3 duin January. 196thog Deeme .90 .eabroo Opraioa Re o, .1990.op If no other taxon making an important contribution. Late fall-early winter collections (Group 2) were characterized bythe co-dominance of Atlantic cod eggs and pollock eggs. This assemblage was always present in December, sometimes appearing as early as November, and often persisting through January.The next seasonal assemblage to appear was Atlantic cod/haddock and American plaice, characterizing both Groups 3 and 4. These two groups had similar dominant taxa, but different abundances. In Group 4 collections, egg densities were roughly an order of magnitude greater than in Group 3. Nearfield fish egg samples were-classified as either Group 3 or Group 4 from January or February through March or occasionally April.Most April collections were classified as Group 5 (except for three years .in which Group 4 persisted through April). In addition to the continued importance of Atlantic cod/haddock, these samples featured an increase in the abundance of American plaice eggs and also the first appearance of substantial numbers of fourbeard rockling eggs.The next group, Group 6, was seasonally the most consistent of all groups. It included only the month of May in every year (Figure 3.2.1-2). Group 6 was characterized by a fish egg assemblage of increased abundance and increased diversity. Four taxa shared the dominance: cunner/yellowtail flounder, Atlantic mackerel, fourbeard rockling, and American plaice.A late spring-early summer assemblage (Group 7) appeared each year in June, often continued through July, and twice extended into August.: Abundances of the two dominant taxa were much higher than in May (Group 6): Atlantic mackerel and particularly cunner/yellowtail flounder.Group 8 consisted of mid-summer to late summer: collections, occasionally including samples as late as October. These were 195 characterized by.hake eggs, cunner/yellowtail flounder (much less abundant than. in Group 7, butstill important), :and windowpane. October was a transitional month. The majority of October samples were classified in a separate group, Group 9, but in some years they were classified into Groups 1, 2, or 8. The Group 9 samples exhibited relatively low densities compared to the other eight groups, reflecting the low level of spawning activity typical for:the early-fall. This assemblage included hake, Atlantic whiting, and ,fourbeard rockling eggs, as well as some early Atlantic cod. eggs.Species assemblages occurring in 1990 were consistent with'those observed in previous-years (Figure 3.2.1-2). Collections of fish eggs during the first half-year of commercial operation of Seabrook Station were classified in a similar pattern to those from 1976-1989. The only exception was the absence of Group-'4 samples in 1990, an indication that the abundances of the winter Atlantic cod/haddock and.American plaice assemblage were lower than in most previous years. No group 4 samples were observed in 1985, 1988, and 1989.Temporal Patterns of Nearfield Fish Larvae-Assemblages

• Numerical classification of monthly fish larvae abundances revealed a degree of seasonality similar to that observed in the analysis of the fish egg community.

Seasonal assemblages of fish larvae'were identified on the basis of sample groups that consistently included only collections from a particular time of year regardless of which year they were from. Nine sample groups were identified as representative of the seasonal progression of species assemblages (Figure 3.2.1-3 and Table 3.2.. 1-2)..Group 1 'consisted of fall samples, primarily-during October, and November (Figure'3.2.l-4). The dominant fish larvae during this, period were Atlantic herring. In the late.fall and early winter,. the 196 within group similarity fno. of s be,..en group similarity ... .aamples Group I 10 10E samples.. ..-... ..: .- --......- -..-.- ." t::--:-': Group 2 -::::::: '"Late Fall/Early Winter "'*Group 3 Late Fall L, U Group 4 Winter; ~Group 5 Late nter ar y p. v JI, U-J 0~cc Lu Ca----------------............'.',Group 6 Spring-------------..........-, .Group 7 LB100pringir-arlyounimer, 0oo 0 0 0 0 0 0 0 -- 0 0 0 --G 0 o 0 0 0 0- 0o -a 0 0 0 0 0 o 0 0 0 0.o.-.. .a o a °a°oleo o Oo ooo o :o o oýo o.0 0. 0 0 0 0** 0 .00 00 00 00 00 0o o0 00000 .00 ;0000 c000 o 0 .000000 0 0 00 , 000-000000000000000000 0o 0 0 .0 oo. -o. 0000 0 0 0 0 00 0 G -' 0 0'.0 .0 0 0 .0 o 000000o0 0 0 0 0 roup 0 0 0 o00 Late Summer °o. o .o o'.. o o. o o

• o o o o o o 000 00 0 0 0 0 0 0 0 000 000 000 0, 0*00 00 000.-o0 0o 0 0 0 0 0 00 -o0.0 0 °0 0. 0 0 0 o 000 .° -oO I *0*'* oo. oo o oo .- 0 oo o o oo----- --------------

i Group 9 Late Summer 0.1 0.2 0.3 0.4 I I I I I 0.5 -0.6 0.7 0.8 0.9 1.0 BRAY-CURTIS SIMILARITY Figure 3.2.1-3. Dendrogram formed by normal classification of monthly abundances (log (x+l)transformed number per 1000 m 3) of fish larvae at Seabrook nearfield Stations P2 and P3, July 1975-December-1990. Seabrook Operational Report, 1990.197 TABLE 3.2.1-2.FAUNAL CHARACTERIZATION OF SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF SAMPLES OF FISH LARVAE COLLECTED AT SEABROOK NEARFIELD STATIONS P2 AND P3 DURING JULY 1975 THROUGH DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990./i NO. OF SAMPLESb .DENSITY (NO./lOOOm 3 d PREOP. YEARS 1990 PREOP.. 1990 DOMINANT FISH LARVAEc SAMPLE GROUJP YEARS MEAN LCL UCL MEAN.Group 1 27 0 Atlantic herring 156 94 257-Fall 0.58/0.43 Group 2 -15 .0 Pollock 55 28 108 Late.fall-. American sand lance 15 4. 49 -early winter ..Atlantic herring 12 6 22 -0.63/0.43 Group. 3 1 2 Atlantic herring 13 -3 Late fall 0.50/0.39 Group 4 4 1 Amerfcan sand lance 28 10 75 7 Winter Snailfishes 3 0 30 11 0.62/0.45 Group 5 44 4 American sand lance 412 277 611 425 Late winter- Rock gunnel 38 22 67 72 early spring 0.56/0.45 Group 6 15 0 .Snailfishes' 149 87 254 Spring Winter flounder .85 52 140 -0.67/0.47 Radiated shanny 55 32 94 American plaice. 42 16 107 American sand lance 35 17 72 Group 7 26 2 Atlantic mackerel 147 55 393 1150 Late spring- Cunner 121 40 359 437 early summer Fourbeard rockling .107 58 197 51 0.53/0.47. Radiated shanny 77 50 120 45 Witch flounder .29 15 57. <1 Winter flounder 26 11 63 71 American plaice 18 10 32 23 Group 8 34 3 Cunner 79 33 186 .183 Late summer Fourbeard rockling 30 16 55 54 0.40/0.30 Hake 15 7 31 68 Atlantic whiting 11 5 24 49 Windowpane 8 5 12, 16 Group 9 2 0 Cunner 4 0 1530 Late summer Radiated shanny 3 0 40 -0.65/0.22 Windowpane 1 0 10 .-Fourbeard rockling <1 .0 2 -Footnotes: For each group is listed the predominant season of its occurrence, the within-group similarity, and b the among-group similarity. b Each monthly "sample" included in the analysis consists of the average of tows within date and dates within month.CTaxa listed as dominants are those whose geometric mean densities together account for >90% of the d sum of the geometric mean densities of all taxa within the group.Densities shown are geometric mean and corresponding lower 95% confidence limit (LCL) and upper 95%confidence limit (UCL) among the samples within the group.t~198 4 u'-Group 1 D -Group 2= Group 3= Group 4= Group 5-Group 6= Group 7" .G roup 8= Group 9 1.E -no sample X .excluded due to low, counts MONTH Figure 3.2.1-4. Temporal occurrence pattern of seasonal assemblages of fish larvae collected at Seabrook nearfield Stations P2 and P3 during July 1975 through December 1990.Seabrook Operational Report, 1990. abundance of Atlantic herring larvae was generally lower,;and pollock and American sand lance larvae became prevalent (Group 2). Three monthly collections at this time of year segregated into a separate group, Group 3, characterized by similarly reduced Atlantic herring densities as in Group 2, but lacking the pollock.and American sand lance.(December 1989 and.November and December 1990)...Another small group, Group 4, consisted of:a few winter ,collections dominated:by American sand lance and snail fishes. Most of.the winter samples, as well as some early spring.coll:ections, were.classified as Group 5. American sand lance.larvae also. dominated this group, although their abundances were substantially higher than.in Group,..4. Group 5 was also characterized by increased abundances of. rock gunnel larvae.This group containedthe May',samples.from.every year but 1989" a Iand 1990. .The June and July samples from almost every year were'.classified together as a group (Group 7). This late spring-early summer group was characterized by even greater diversity than was Group 6, with seven species occurring in substantial abundance (Table 3.2.1-2). The-three most abundant species were Atlantic mackerel, cunner; and four-beard rockling.". Group 8 was primarily a late summer feature, extending into October in some years. cunner and fourbe.ard rockling continued their importance into this period, :and were joined as dominant species by hake, Atlantic whiting, and windowpane. Two-'additional later summer samples (September 1978 and September 1986) were classified as a distinct group, Group 9. These were characterized primarily by low abundances (Table 3.2.1-2).The 1990 collections generally agreed withthe pattern of seasonal progression of larva.l assemblages observed .in previous years.In 1990, however, none of the samples from the fall and early winter were classified with Group 1 or Group 2 as they had been in most 200 previous years. .Instead, November and.December 1990 were grouped with the December 1989 collection (Group 3), an indication of lower-than-normal abundances of Atlantic herring, American sand lance, and pollock larvae at this time of the year in 1989 and 1990. No 1990 sample was classified into Group ý6. The grouping of the May 1990 sample with Group 5 indicated that-the late winter-early spring American sand-lance assem-blage persisted into.May just before the appearance of. the late-spring and early summer Atlantic mackerel and cunner assemblage. This pattern also occurred in .1989.Spatial Patterns of Fish Eggs and Larvae Spatial comparison of abundance and species composition from the nearfield and farfield stations was previously done using numerical classification of the 1982 and 1983 collections for both fish eggs and larvae (NAI.1983b, .1984b). Spatial (station) differences were found to be less important than short-term temporal differences. Samples collected on the same date at different stations (nearfield and far-field) more likely resembled each other than if collected one to two weeks apart at the same station..This similarity in species composition and abundance between nearfield and farfield sites was consistent with the known extent'of water mass movements in the study area. Tidal currents and longshore (northward and southward) currents in the study area are typically in the range of 0.2 to 0.6 knots about 75% of the time (NAI 1980d).Currents of this magnitude would transport a water mass about.two nautical miles during a single tidal excursion, or about 5-15 miles in 24 hours during periods *dominated by longshore flow. The distance from Station P2 to P5 (1-1/2 miles) or to *P7 (3-1/2 miles) is relatively short. Considering that, for example, a water mass sampled at Station P2 could very possibly have been located at Station P7 a few hours before sampling, the assumption (for the purpose of statistical analysis 201 of spatial effects) that these locations are distinct from each other in terms of plankton is not always. met..'Despite this possibility of exchange of plankton-bearing water masses among the stations, the 1990 ichthyoplankton data were analyzed in an attempt to test for'differences in communities of fish eggs and larvae among intake; discharge, and farfield stations. These'analyses were conducted for two different time frames: the entire year (January-December) and just the period of commercial operation (August-December). The taxonomic composition of fish eggs based on relative abundance appeared to be similar among stations both for the whole year (Table 3.2.1-3) and for the period after commercial operation commenced at Seabrook Station (Table 3.2.1-4). Multivariate analysis of variance results indicated, however, that fish egg abundances did differ signifi-cantly among stations during the year as a whole (Table 3.2.1-5). For individual taxa, there.were some significant differences among the three stations.in the log(x+l)transformed densities for 1990 (Table 3.2.1-5).Station P2 had fewer fourbeard rockling eggs than P5, while P5 had more cunner/ yellowtail flounder eggs than both P2 and P7. In the farfield area (P7) there were fewer rockling/hake and'windowpaneeggs than at either nearfield station, and fewer cod/haddock eggs than at P5. The , analysis did not indicate any station differences in fish egg composi-tion during operational months.The percent composition of species for fish larvae was also similar among stations for all of 1990 (Table 3.2.1-6) and for the.operational months (Tabje 3.2.1-7). Multivariate analysis of dominant taxa did not indicate any difference among stations either during plant.operation or for the January-December period (Table 3.2.1-5).202 TABLE 3.2.1-3. COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF FISH EGG COLLECTIONS AT INTAKE (P2) FARFIELD (P7) AND DISCHARGE (P5). STATIONS DURING JANUARY -DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990.i P2 1P5.1I ---------- +--------------------------+------------------------- 1 PERCENT 1 PERCENT : PERCENT I PERCENT 1 PERCENT 1 PERCENT 1!ABUNDANCE !FREQUENCY !ABUNDANCE

FREQUENCY

!ABUNDANCE !FREQUENCY

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.------------.------------

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+------------.--------- IFOURBEARD ROCKLING 0.611 37.501 0.651 43.751 1.191 50.001 IROCKLING/HAKE i 2.941 43,751 4.361 35.421 3.731 39.581 ICOD/WITCH FLOUNDER 0.351 41.67: 0.351 35.421, 0.561 45ý831-!ATLANTIC COD .0.191 39.581 0.211 '33.331 0.211 37.501!ATLANTIC COD/HADDOCK 0.011 14.581 0.011 14.581 0.051 16.671!WITCH FLOUNDER '<0.011 4.171 <O.Oi 4.171 0,021 8.33:!AMERICAN PLAICE 1 0.121 29.171 0.161 33.331 0.251 27.081 lCUNNER/YELLOWTAIL FLOUNDER! 59.851 39.581 48.631 43.751 ,59.701 41.671 1YELLOWTAIL FLOUNDER 1 0.031 4.171 0.031 .6.251 0.021 8.331 HADDOCK i 1.0.00! 0.001 <0.011 6.251 <0.011 10.421 ,ATLANTIC WHITING I 0 .621 27.081 1.251 22.921 .. 1.001 27.081!POLLOCK i 0.011 12.501 0.011 12.501 0.021 16.671!NORTHERN SEA ROBIN i <O.Ol 2.081 0.00: .0.001 0.001. 0.001 IATLANTIC MACKEREL 1 23.211 20.831 37.331 22.921 25.561 22.921!WINDOWPANE 1.341 43.751 0.691 39.581 1.551 41.671!HAKE i 10.721 35.420 6.331 35.421 6.13: 35.421 203 TABLE 3.2.1-4. COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF FISH EGG COLLECTIONS AT INTAKE (P2), FARFIELD (P7) AND DISCHARGE (PS) STATIONS DURING THE FIRST FIYE MONTHS OF COMMERCIAL OPERATION (AUGUST-DECEMBER 1990). SEABROOK OPERATIONAL REPORT, 1990.------------------------------------ +------- 7 ------------------- 4------------------------- P2 P7 ,P5 I PERCENT 1 PERCENT PERCENT 1 PERCENT 1 PERCENT 1 PERCENT.-.!ABUNDANCE !FREQUENCY !ABUNDANCE !FREQUENCY !ABUNDANCE !FREQUENCY -- --.-...--- ".--77 ---------------------- 7- -- .------------.-------------.

FOURBEARD ROCKLING 1 0.431 30.001 0.501 35.001 0.521 50.00: IROCKLING/HAKE 17.471 60.001 9.57: 50.00i 18.91: 55.001!COD/WITCH FLOUNDER 0.461 ' 40.001 0.441 40.001 1.00; 45.001!ATLANTIC COD 2.421 40.001 4.091,' 40.001 2.041 40.001!WITCH FLOUNDER i 0.01! 5.001 0.021 5.00! * <O.Oi .5.001!CUNNER/YELLOWTAIL FLOUNDER!

30.381 35.001 38.311 45.001 27.471 40.001!ATLANTIC WHITING 1 7.89: 40.001, 19.691 25.001 6.611 40.001 PIOLLOCK

• 0.101 10.001 0.061. 10.001 0.081 10.001 1SEAROBIN i <0.011 5.001 0.001 0.001 0.001 0.001!ATLANTIC MACKEREL O.00 0.001 0.00i 0.001 0.141. 5.001!WINDOWPANE 5.251 '50.001 2.891: 40.001 .7.031 45.001!HAKE 35.591 50.001 24.441 45.001 36.201 55.001* .....................................................................---. ....................'204 TABLE 3.2.-1-5.

RESULTS OF MULTIVARIATE ANALYSIS OF VARIANCE TESTS FOR DIFFERENCE AMONG STATIONS IN COMMUNITIES OF FISH EGGS AND LARVAE DURING PREOPERATIONAL AND OPERATIONAL PERIODS IN 1990.SEABROOK OPERATIONAL REPORT, 1990.UNIVARIATE ANOVAsd NUMBER OF INDEPENDENT TOTAL LIFE TAXA VARIABLES NO. OF.STAGE PERIOD (DEPENDENT (NUMBER OF OBS. CRITERIONb df F-VALUEc TAXON COMPARISONS VARIABLES) LEVELS)" Eggs Jan-Dec 11 Station (3) 114 Wilks 22,128 2.63*** Fourbeard Date (38) Pillai 22,130 2.64*** rockling P5>P2 Hotelling 22,126 2.62*** Rockling/hake P2=P5>P7 Cod/haddock. P5>P7 Cunner/yellow. tail flounder P5>P7=P2,. Windowpane a P2=P>P7*""Six olter taxa no differences Eggs Aug-Dec. 10 Station (3) 57 Wilks. 20,54 1.46 NS Date (19) Pillai 20,56 1.50 NS Hotelling 20,52 1.42 NS Larvae Jan-Dec 19 Station (3) 108 Wilks 38,104 1.46 NS Date (36). Pillai 38,106 1.41 NS Hotelling 38,102 1.51 NS Larvae Aug-Dec 11 Station (3) 30 Wilks 22,16 0.69 NS.Date (10) Pillai. 22,18 0.73 NS Hotelling .22,14 0.64 NS U-, CDý_n Analyses excluded those dates on which the average dehsity for all three stations was <20/100m 3.Criteria: Wilks' criterion, Pillai'-s trace, and Hotelling-Lawley trace.¢ Significance levels: NS p>0.05,

• 0.05 >p>0.01, ** 0.01 > p>0.O01, **A p<0.001..d If the MANOVA was significant, univariate ANOVAs were performed on individual taxa. ANOVAs with effects were followed by Wa1ler-Duncan K-ratio multiple comparisons test at. =0.05.significant station TABLE 3.2.1-6. COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF FISH LARVAE COLLECTIONS AT INTAKE (P2) FARFIELD (P7) AND DISCHARGE (PS) STATIONS DURING JANUARY-DECEMBER, 1990. SEABAOOK OPERATIONAL REPORT, 1990., 1 P7 P, P5 i-------------

--- ------------- +-------------------- TAXA 1 PERCENT PERCENT ' PERCENT 1 PERCENT PERCENT PERCENT I ABUNDANCE !FREQUENCY IABUNDANCE !FREQUENCY !ABUNDANCE !FREQUENCY I I ---------+------------+------------------------------------------------- ýAMERICAN SAND LANCE 1 15.821 52.081 17.79: 43.751 21.831 47.921!AMERICAN EEL 0.031 8.331 0.011 6.251 0.011 4.171!ALLIGATOR-FISH 1 0.171 18.751 1.341 25.001 0.111 20.831:ATLANTIC HERRING , 0.081 33.331 0.241 37.501 0.231 37.501 ILUMPFISH 0.011 .8.331 0.011 10.421 0.011 8.331!FOURBEARD ROCKLING 1.391 41.671 2.391 37.501 2.701 43.75i!ATLANTIC COD 0.05: 18.751. 0.021 14,581 0.051 20.831!WITCH FLOUNDER 1 0.161 10.421 0.161 10.421 0.061 12.501.AMERICAN PLAICE i 0.301 18.751 0.241 20.831 0.581 25.001 1YELLOWTAIL FLOUNDER i 0.041

• 14.581 0.051 14.581 0.071 14.581 ,ATLANTIC SEASNAIL I d941 29.17i 0.301 29.171 0.381 27.081 GULF SNAiLFISH 0.881 43.751 2.01: 41.671 0.591 39.581!ATLANTIC WHITING i .2.60: 22.921 6.26: 18.751 2.361 .22.921!GRUBBY
• 0.471 25.001 1.19: 27.081 0.281 16.671!LONGHORN SCULPIN 0.081 22.921 0.18i 22.921 0.061 18.751!SHORTHORN SCULPIN 1 0.09: 12.501 0.141 16.671 0.031 8.331!RAINBOW SMELT '0.011 4,171 0.011 8.331 <O.Oli0 4.171 IFOURSPOT FLOUNDER 0:091 8.331 0.081 10.42: 0.091 10.421!ROCK GUNNEL 2.781 37.501 5.011 29.171 1.601. 27.081!POLLOCK i 0.041 20.831 0.031 14.58: 0.041 25.001!WINTER FLOUNDER i .1.071 18.751 0.231 14.581 0.621 22.921 IATLANTIC MACKEREL 1 32.361 14.581 22,681 16.671 21.351 16.671!WINDOWPANE

1. 0'631 22.92: 0.37; .20.831 0.631 25.001 1TAUTOG 0.09i 8.331 0,101 6.251 0.091 8.331 ICUNNER. 36.621 31.251 34.491 31.251 43.531 29.171!RADIATED SHANNY 1 0.481 20.831 0.331 25.001 0.361 18.751:HAKE .. .1 2.401 .22.921 4.171 25.001 2.021 22:921 common taxa are listed (percent frequency at least 5% at one or more stations).Table 3.2.1-6.206 TABLE 3.2.1-7. COMPARISON OF PERCENT ABUNDANCE AND PERCENT FREQUENCY OF FISH LARYAE COLLECTIONS AT INTAKE (P2). FARFIELD (P7) AND DISCHARGE (P5) STATIONS DURING'THE FIRST FIYE MONTHS OF COMMERCIAL OPERATION (AUGUST-DECEMBER, 1990). SEABROOK OPERATIONAL REPORT, 1990.-P2 , P7 .i. P5 .---- -- ---- -- --- ;.. ... ...--- ---- -- -- ------!,PERCENT 1 PERCENT 1 PERCENT 1 PERCENT 1 PERCENT 1 PERCENT 1 S!.ABUNDANCE IFREQUENCY IABUNDANCE

!FREQUENCY !ABUNDANCE !FREQUENCY ........ .---------.---------- 4----------4----------

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+----------+-----------. AMERICAN SAND LANCE i -<0.011 5.001 0.021 10.00i 0.021 10.001 1ALLIGATORFISH 1 0.131 10.001 0.001 0.001 0.001 O.OO0 IATLANTIC HERRING i 0.171 50.001 0.371 45.001 0.231 55.001 LUNPFISH .0.01 0.001 0.021 10.00i 0,001 0.001 IFOURBEARD ROCKLING 2.471 55.001 4.331 50.001 4,411 60.001!ATLANTIC COD 0.011 10.00; 0.001 0.001 <0.011 10.00;!WITCH FLOUNDER 0.401 20.001 0.371 15.001 0.051 20,001 1GOOSEFISH 0.00; 0.001 0.051 10.001 0.031 10.001!ATLANTIC WHITING 1 6.801 ' 50.001 14.971 35.001 4.841 30.001 IFOURSPOT FLOUNDER 1 0.231 20.001 0.191 25.001 0.181 20.001 IBUTTERFISH 1 0,041 5.001 0.091 10.001 0.021 5.001:POLLOCK 1 0.031 25.001 0.011 .5.001 0.041 25.001!ATLANTIC MACKEREL i 0.261 5.001 0.401 10.001 .0.361 10.001!WINDOWPANE 1 1.461 40.001 0.691 40.001 1.121 -45.00V 1TAUTOG 1 0.251 20,001 0.241 15*001 0.191 20.001 ICUNNER 1 81.581 40.001 68.361 40.001 83.911 40.001 IHAKE i 5.861 45.001 9.711 45.001 4.151 45.001 207 3.2.1.2: Entrainment Seabrook .StationIs Circulating Water. System was in operation throughout 1990, with 'average daily flows of 531 million gallons per day (MGD) during;the preoperationalýperiod (January-July) and 589 MGD during* the commercial operational period (August-December)(.Table!2.1-1).,Entrainment samples were collected June-December, usually on the same.days that the nearfield and farfield ichthyoplankton samples were collected at stations P2, P5,.andP7. Fish egg taxa in entrainment samples had similar species composition to those in offshore nearfield collections collected during the same week (Table 3'2.1-8)". Atlantic mackerel, hake, cod/witch flounder, rockling/hake, cunner/yellowtail flounder, and. windowpane were the six most abundant taxa in the in-plant and offshore samples. In general, mean abundances

at nearfield Station P2 exceeded those observed-in entrainment samples, oftenby as much as an order of magnitude.

Species such as Atlantic mackerel, windowpane, hake, and fourbeard. rockling, which have large oil globules, exhibit characteristics similar to other buoyant species in the middle Atlantic bight (Kendall and Naplin 1981) in that they tend 'to be found more often at surface depths.Because of this tendency to concentrate near the surface, eggs of these species were less abundant in. the entrainment samples than in the oblique offshore tows, because the plant intake draws water from well below the surface. Cunner/yellowtail flounder eggs were approximately 20 times higher in abundance in offshore samples than in entrainment samples. Although this species lacks an oil globule, previous studies (NAI 1981b,. 1981f) have shown.that this species is present in much greater abundances in middle and surface depths. Species such as Atlantic cod/witch .flounder, which lack oil, may be less buoyant and therefore more abundant in the bottom portions of the water column, thus, accounting for the occasionally higher abundances observed in in-plant samples compared with offshore samples.208 TABLE 3.2.1-8. MONTHLY GEOMETRIC MEAN OF DENSITY (PER 1000 CUBIC METERS) OF iNTRAiNED FISH EGGS FROM ENTRAINMENT AND OFFSHORE (P2) COLLECTIONS DURING JUNE-DECEMBER 1990.SEABROOK OPERATIONAL REPORT,. 1990.I ENTRAINMENT iJUN IJULI [ AUG 1 SEP.: OCT 1 NOYV DEC--------------------- +----------+----------+----r-------------------7--------+-------------- ICUSK TFOURBEARDROCKLINGI (ROCKLING/HAKE '!COD/WITCH FLOUNDER.ATLANTIC COD!WITCH FLOUNDER!AMERICAN PLAICE!CUNNER/YELLOWTAIL FLOUNDER!ATLANTIC WHITING!ATLANTIC MACKEREL!WINDOWPANE !HAKE* I M!? I .I I .191 31 241 10: i 1301 851 1691 23: 9i 1 2391 601 291 10: 151 i 21 11, i 231 i I <l1 31 221 31 i l 1 1 11211 10361 451 21.. I 121 51i 51 61 31 , 1 14571 1071 11 1 1 1421 .1231 1121 421 1 501 881 1951 291 i i 141 i A i .1JUN f JUL AUG I SEP ' OCT 1 NOV 1DEC , SOFFSHORE

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"" MEAN 1 M EAN 1 MEAN 1 MEAN MEANI MEAN I MEAN 1------ -- ------.. .--. .. .. ..-- '---- -- -------'-'-'-- ....+- .. .. --- -- -- .. .. .---------------

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+1FOURBEARD ROCKLING .5101 5.1 11 181 31 i i 1ROKLING/HAKE i 11591 660: 14291 2711 1! 1 i COD/WITCH FLOUNDER 1 421 2091 41 51 1061 " i!ATLANTIC COD ] 1 1 3141 4381 IWITCH FLOUNDER i 1i 1 1i i i!AMERICAN PLAICE 21 i i i. 1 i ICUNNER/YELLOWTAIL FLOUNDER 1 196201 200711 12251 61 1 ATLANTIC WHITING 31 371 21 4331 .i ATLANTIC MACKEREL 140971 9931 * " i" WINDOW PANE 10011 7991 4251 1871 "!HAKE .2101 112671 34711 5071 11 1 aIncludes only collections corresponding to dates when entrainment samples were collected. 209 Entrained

fish larvae also followed trends in species composi-tion similar to those observed in the-offshore nearfield station collections (Table 3.2.1-9).

Abundances of entrained andioffshore larvae were comparable for several species, but Atlantic whiting, Atlantic mackerel, cunner, and hake larvae had higher abundances at the offshore nearfield station than at the entrainment station. The variety of depths sampled might explain the larger abundances for the offshore oblique tows at*Station P2 (the cooling water intake is 5 m above the bottom in 17 m of water). In a few cases, abundances of entrained larvae were an order of magnitude higher than in offshore samples, such as Atlantic seasnail in June and July.Total entrainment was estimated for both eggs and larvae for, June-December on the basis of observed densities in entrainment samples and the total cooling water flow, (Table 3.2.1-10 and 3.2.1-11).. Atlantic mackerel and cunner/yellowtail'flounder were the egg taxa entrained in the greatest quantities. The greatest entrainment losses.among larvae were those for fourbeard rockling and cunner.The high degree of similarity of the 1990 fish eggs and larvae communities to those observed in previous years and the similar species composition at nearfield and farfield stations both indicate that ichthyoplankton losses due to entrainment have had a negligible effect on the ichthyoplankton in the nearfield area.3.2.1.3 Selected Species Larvae of nine fish species were selected for a detailed analysis of their within-year and among-year patterns of abundance because of their numerical dominance or importance as a recreational or commercial species. Each of the nine species displayed distinct seasonal patterns of abundance. While fish larvae were present in every.month, the larvae of each species exhibited a sharply defined period-of. peak abundance of only a few months' duration. Fish larvae in other 210 TABLE 3.2.1-9. MONTHLY GEOMETRIC MEAN OF DENSITY (PER 1000 CUBIC METERS) OF ENTRAINED FISH LARVAE FROM ENTRAINMENT AND OFFSHORE (P2) COLLECTIONS DURING JUNE-DECEMBER 1990.:SEABRO{OK OPERATIONAL REPORT, 1990.ENTRAINMENT I JUN I JUIL AUG I SEP I OCT I NOY I DEC i ----------

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4----------+----------4-'--------------4--- 4-------!ATLANTIC HERRING i 1 1 .1 31 10O ILU ,FFISH i 21 F I IFOURBEARD ROCKLING -1 31 1 831 371 , 1ATLANTIC.COD i 51 i Ii IWITCH FLOUNDER 1 1 21 1 1 AMERICAN PLAICE 31 1 v -IYELLOWTAIL FLOUNDER i 1 1 I IATLANTIC.SEASNAýL 1 1241 151J 1.. 1 1.IGULF SNAILFISH 1 II f ' l 1 1..ISNAILFISH I1 i 1 i!ATLANTIC WHITING 1 i i 31 41 " i!RAINBOW SMELT 1I i 1 1 1!UNIDENTIFIED .1 21 21 , i IFOURSPOT FLOUNDER 1 1 1 Ii 1!POLLOCK 1 1 -1 31!WINTER FLOUNDER 46: 31 ' 1 ,!ATLANTIC.MACKEREL 1 21 1 ; 1 ,!WINDOWPANE 1! 61 231 'ITAUTOG. 1 1 1 11 1CUNNER 1 11, 3831 631 1'!RADIATED SHANNY 501 Ii 11 i '!HAKE. Ii 101 51 .. .1.{ JUN 1' JUL { AUG 1 SEP 1 OCT 1 NOV 1 DEC i OFFSHORE 8 + ------------ +----------+----------+------------------------------ I 1 MEAN. I MEAN I MEAN I MEAN .1 MEAN I MEAN I MEAN f I------------- 4-+------------------+----------+----------+----------+

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+!ATLANTIC SILVERSIDE 1 31 1 1!ALLIGATOR FISH .i 4: .i!ATLANTIC HERRING .i A1 11 241 -1 21 ILUMPFISH i Ii .1 1 IFOURBEARD ROCKLING , 381 561 251 1301 i I IATLANTIC COD i 41 .{. Ii!WITCH FLOUNDER 1 11- I 321!AMERICAN PLAICE 31 31 1.1YELLOWTAIL FLOUNDER i 3: 1: 21 i!ATLANTIC SEASNAIL 1 131 21 1 1. 1!SILVER HAKE .i .841 337: .!UNIDENTIFIED i 2 61 51 41 1 IFOURSPOT FLOUNDER .. 11 161.IBUTTERFISH -21 IPOLLTK I 1 21!NORTHERN SEAROBIN 1 I .1 I IWINTER FLOUNDER 1 251 51 1 ,!ATLANTIC MACKEREL 1 371 471 21 1 ..!WINDOWPANE .i 81 1 1121 1!NORTHERN PIPEFISH 1 11 Ii 1 " 1TAUTOG i 1 -1 51 .31 1 CUNNER , 131 .6221 56021 7631 1 1 IRADIATEDSHANNY , 531 141. 1 1 1 IHAKE " .1 61 4171 891 '.Includes only collections corresponding to dates when entrainment samples were collected. 211 TABLE 3.2.1-10. MONTHLY ESTIMATED NUMBERS OF FISH EGGS, (IN MILLIONS) ENTRAINED BY THE, COOLING WATER SYSTEM AT SEABROOK STATION DURING JUNE-DECEMBER 1990.SEABROOK OPERATIONAL REPORT, 1990.TAXON Atlantic mackerel Cunner/yellowtail flounder Rockl ing/hake Hake Windowpane Cod/witch flounder Atlantic whiting JUN 499.1 380.4 JUi 19.1 105.0 AUG 0.6 4.7 SEP 0 0.2 86 6 13 16 1.1 10.2 .15.4 1.6.2 10.9 17.6 2.2.5 10.0 "8.8 4.0.3 5.3 2.2 1.3.5 3.6 1.5 2.7.2 0.7 1.7 0.7.3 0.3 0 0 0 0.2 0.4 0 0 0 0.1 0.3 0 0.1 0 0 OCT 0 0,1 0.7 0.4 0.1 0.7 2.0.0,1 0 0 0 0 NOV 0 0 0.2 0 0.4 0.1 0 0 0.9 0%DEC.0.0 0 0 0 0 0 0 1.0 0 0 Fourbeard rockling American plaice Atlantic cod Witch flounder 4 2 Cusk 212 TABLE 3.2.1-11. MONTHLY ESTIMATED NUMBERS OF FISH LARVAE (IN MILLIONS) ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK STATION DURING JUNE-DECEMBER 1990.SEABROOK OPERATIONAL REPORT, 1990.TAXON JUN JUL AUG SEP OCT NOV DEC Cunner 0 0.1 31.7 10.2 0.7 0 0 Fourbeard rockling 1.9 0.1 16.5 I1.7 7.7 0 0 Atlantic seasnail 8.6 2.9 0.1 0 0 0 0 Atlantic whiting 0 0 0.3 1 4.4 3.0 0 0 Radiated shanny 4.6 0.1 0.1 0 0 0 0 Hake 0 0.1 1.4 :2.0 1.3 0 0 Windowpane 0 0.1 0.7 2,0 1.0 0 0 Winter flounder 2.9 0.3 0 0 0 0 0 Atlantic herring 0 0 0 0 0 0.1 0.6 Unidentified 0 0 0.3 0.3 0.1 0 0 Lumpfish 0.6 0 0 0 0 0 0 Atlantic cod 0.5 0. 0 0.1 0.1 0 0 American plaice 0.3 0.1 -0 0 0 0 0 Witch flounder 0 0 0.3 0 0 0 0 Tautog 0 0 0.1 0.1 0.1 0 0 Atlantic mackerel 0.2 0 0 0 0 0 0 Pollock 0 0 0 0 01 0 0.2 Fourspot flounder 0 0 0 0.1 0.1 0 0 Rainbow smelt 0.2 0 0 0 .0 0 0 Gulf snailfish 0.1 0 0 0 0 0 0 Goosefish 0 0 0.1 0 0 0 0 Atlantic menhaden. 0 0 0.1 0 0 0 0 Yellowtail flounder O.1 0 0 0 0 0 0 Snailfish 0.1 0 0 0 0 0 0 2"13 months were typically much less abundant or. absent from samples. These seasonal fluctuations were the primary reason for the high within-year variability (NAI 1983b).Two-way analyses of variance (ANOVAs).were used to test the.statistical significance of temporal (preoperational vs. 1990) and spatial (nearfield vs. farfield areas), differences in log (x+l) trans-*formed densities. Because sampling at both the nearfield and farfield areas was initiated'in January of 1982, only data collected since, that.time were included.in the two-way ANOVAs ANOVAs focussed on the period of peak-abundance for each species identified in the historical data.Of the selected species, only Atlantic herring abundance typically peaks between August and December, the period of commercial operation in 1990.Pollock peak abundances occur in winter, from November or December through February. This report presents annual abundances from November 1989 through February 1990. Information on'pollock during the operational period will be' presented in the 1991 Operational Report..I.American Sand Lance Historically, American sand lance larvae were present in collections at Station P2 from October through July with peak abundances occurring from January through April. (Figure 3.2.1-5). In 1990, abundances were slightly higher than normal in March, and lower than, normal in January and December with no larvae caught during July through November. This broad peak was due primarily to two factors: an extended hatching period (Richards 1982) and a long planktonic stage for larvae (Bigelow and Schroeder 1953). American sand lance was the most abundant species over all years at. Station P2, ranging from 35.0/1000 m 3 in 1977 to 447.7/1000m 3 in 1982 (Table 3.2.1-12). Abundance for 1990 (163.3'larvae/1000 mi 3) was slightly higher than the overall mean for the preoperational period (147.9 'larvae/1000i 3). Combining nearfield and 214

• American Sand Lance, PREOP 1990 LU0 0 E Z~(0 zI.3 2 1 0 JAN FEB MAR APR MAY JUN JUL ALUG SEP OCT NOV D MONTH Winter Flounder 4 PREOP W C a E Z~C,..no1..3 2 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOYV C MONTH Figure 3.2.1-5.Log (x+l) abundance (no./1000 M 3) of American sand lance and winter flounder larvae; monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3. Seabrook Operational Report, 1990.: 215 TABLE 3.2.1-12.

GEMTRIC ,MAN OF SEASON OF PEAK ABUNDANCE (NUMBER PER 1000 M 3) BY YEAR, PREOPERATIONAL MEAN (PREOP.), AND OPERATIONAL YEAX (1990) OF SELECTED FISR SPECIES LARVAE AT STATION P2, JULY 1975 THROUGH DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990.CONFIDENCE OPERATIONAL

SPECIES (and YEAR PREOP. LDIIT YEAI Wnths included) 1975 1976 1977 1978 1979 1980 1981 1982 .1983 1984. 1985 1986 1987 1988 1989 MEAN LOWER UPPER 1990 American sand lance -2 352.9 35.0 384.0. 203.2 219.7 213.7 447.7 95.0 73.8 71.5 314.8 87.9 139.7 168.0 147.9 106.5 205.3 163.9 (Jan-Apr)Winter flounder 12.5 10.4 17.5 7.9 9.5 2.9 12.4 14.4 19.7 22.4 19.1 15.4 17.2 12.4 14.0 9.7 19.9 5.7 (Apr-Jul)Yellowtail flounder 3.7 20.1 4.1 12.4 6.5 1.3 0.3 4.3 2.9 2.2 5.3 1.7 2.8 0.7 3.1 2.2 4.3 0.7 Atlantic cod 4.7 9.4 16.1 1.2 3.4 9.9 2.8 1.8 2.1 1.3 1.6 0.6 1.1 0.1 2.0 1.4 2.8 0.7 o * (Apr-Jul) Atlantic mackerel 2.6 5.4 2.3 8.0 24.2 12.4 4.3 12.0 8.4 11.7 12.5 8.5 4.0 2.0 7.3 4.6 11.3 5.9 (May-Aug)Cunner -21.1 224.5 30.3 46.1 97.7 29.1 22.6 97.9 22.7 40.7 12.4 255.2 .49.4 59.9 49.6 32.3 75.8 274.0 (June-Sep)

Hake 6.5 0.5 4.2 2.7 8.2 5.4 5.9 2.4 10.4 7.8 10.0 0.1 3.2 3.9 2.3 4.1 2.5 6.3 60.9 (Ju17Sep)Atlantic herring 197.0 144.7 16.1 2.1 7.4 34.0 50.0 62.7 9.3 40.3 21.5 126.7 28.8 26.6 8.7 26.9 18.1 39.6 2.1 (Oct-Dec)Pollock 12.2 27.7 5.1 19 49.2 7.3 4.0 2.1 3.4 22.7 13.8 1.2 5.8 4.4 0.6 6.6 4.7 9.1 .b (Nov-Feb)b Sampling at P2 began in July 1975, excluding part of annual peak.Yearly mean not computed for pollock in 1990 because January and February 1991 data were not available. 7_11 T_ farfield collections, the two-way ANOVA showed that abundances of larvae of this species were not significantly different in 1990 than the mean'of historical abundances (Table 3.2.1-13; Preop-Op). As discussed.in regard to the ichthyoplankton community, the nearfield and farfield areas are linked hydrographically. Abundances of American sand lance larvae were similar in these areas (Table 3.2.1-13; Area). The interac-tion between temporal (Preop-Op) and spatial (Area) factors indicated that mean abundance of American sand lance larvae in 1990 in the nearfield was similar to.mean abundance in both the nearfield and farfield in preoperational years and in the farfield in 1990 (Table 3.2.1-13). Annual differences in American sand lance densities were highly significant (Table 3.2.1-13; year (Preop-Op)), indicating a high variability from year to year.Winter Flounder Winter flounder larvae, the fourth most abundant (over all preoperational years) of the nine selected species, were usually present from April through August, with the highest concentrations occurring in May and June (Figure 3.2.1-5). Few or no specimens were encountered in January through March and September through December. In 1990, abun-dances followed the same general pattern as in-previous years, but the.concentration of winter flounder larvae was lower than average in April" and May, and greater than average in July. Abundances of winter flounder larvae, relatively consistent in earlier years (1976-1978), decreased .from 17.5 larvae/1000 m 3 (1978) to an all-time low of 2.9 larvae/1000 m 3 in 1981 (Table 3.2.1-12). Abundance increased during the next four years to the highest value recorded, 22.4 larvae/1000 m 3 (1985). Since that time, a general trend of.decreasing abundance was observed. Despite the annual variability in the abundance of winter flounder larvae, there were~no statistically significant differences among.years (Table 3;2.1-13, year (Preop-Op)). However, the reduced number of winter flounder larvae occurring in 1990 (5.7 larvae/i000m3' was statistically significant at both nearfield and farfield areas.217 TABLE 3.2.1-13. RESULTS OF ANALYSIS OF VARIANCE OF LOG (x+l) TRANSFORMED ABUNDANCES (no/O00 03) OF SELECTED SPECIES OF ICHTHYOPLANKTON LARVAE DURING MONTHS OF PEAK ABUNDANCE FOR THE YEARS 1982-1984, 1986-1990. SEABROOK OPERATIONAL REPORT, 1990.SPECIES SOURCE OF (PEAK PERIOD) VARIATION 3 df SS F MULTIPLE COMPARISONS. American sand lance (Jan-Apr)Winter flounder (Apr-Jul)Yellowtail flounder (May-Aug)Atlantic cod (Apr-Jul)Atlantic mackerel (May-Aug)Cunner (Jun-Sep)Hake (Jul-Sep)Atlantic herring (Oct-Dec) .Preop-,Op Area Preop-Op X Area Year (Preop-Op) Error Preop-Op Area Preop-Op X Area Year (Preop-Op) Error Preop-Op Area Preop-Op X Area Year (Preop-Op) Error Preop-Op.Area +Preop-Op X Area Year (Preop-Op) Error* Preop-Op Area Preop-Op X.Area Year (Preop-Op) Error Preop-Op Area Preop-Op X Area Year (Preop-Op) Error Preop-Op Area.Preop-Op X Area Year (Preop-Op) Error Preop-Op Area Preop-Op X Area Year (Preop-Op) Error Year Error 1 1 1 6 266 1 1 1 6 286 1 l 1 6 302 6 1 1 6 286 1 1 1 6 302 1 1 1 6 306:1 1 6 230 1 I 6 225<0.01 2.71 0.86 13.44 202.90 8.60 2.70 0.71 1.04 220.29 3.03<0.01 0.47 7.84 137.75 0.81 0.17 0.32 7.71 59.96 0.01 0.03 0.01 10.47 400.28 12.51 0.01*0.01.42.21" 423.77 23.91 0.05 0.21 14.02 180,20 22.55<0,01.<0:01 21.00 157.77 0.00 NS 3.40 NS 1.09 NS 2.94**11.34'**3.57 NS 0.94 NS 0.23 NS 6.42*0.00 NS 1.00 NS 2.87**3.48 NS 0.73 NS 1.39 NS 6.13***0.01 NS 0.31 NS 0.01 NS 1.32 NS 8.38**, 0.01 NS 0.01 NS 5.08***29,05***0.05 NS.0.25 NS 2.98**29.14**0.00 NS 0.00 NS 4.99***10.50i**.1.t Pollock (Nov-Feb)14 56.53 330 126.88 7975 85 76 84180 87-77 81 88 83 78 82 86 89 I aPreog-Op = temporal variation (preoperational years vs. operational year)=rea nearfield vs. farfield Preop-Op X Area = interaction between main effects-Year (PreopýO )= year nested within preoperational and operationalperiods, regardless of area S= not significant (p>0.05) o=* significant (0.05ýp>0.01) =**= highly siqnificant ((0.012 >0.001)very highly significant (pKO.O0l)218 Yellowtail Flounder Yellowtail flounder larvae at nearfield Station P2 normally occurred from May through September, with peak abundances occurring in June and July (Figure 3.2.1-6). In recent years there has been an increasing number of.larvae present in April, but in 1990 there was no evidence ofthis. Larvae'were present only during the months of May through July and September in 1990. Yellowtail flounder abundances have shown significant diff erences among years. (Table 3.2.1-12). Abundance was highest in 1977 (20;1 larvae/1000 mi 3) then generally decreased to the lowest value in 1982 .(0.3 larvae/1000 mi 3). Since that time abun-dances have remained relatively consistent and moderate through 1988.Abundances in 1989 and 1990 at Station P2 *reached the second lowest value recorded during the years of study (0.7 larvae/1000 m 3). *This contributed to significantly lower abundances in 1990 in comparison to previous years at both nearfield and farfield stations (Table 3.2.1-13).' Abundances were statistically similar at both stations throughout the study period.Atlantic Cod Atlantic cod larvae typically exhibited a bimodal distribution with one peak lasting from November through January (late fall-winter) and the other (usually stronger) peak in April through July (spring-early summer, Figure 3.2.1-6). Very few cod larvae were caught in 1990 with abundances below normal for May and no larvae present in February through April, July through October, and December. Geometric mean peak-season abundance for Atlantic cod includes only the spring-early summer.peak, which represents the higher abundances and longer period of'occurrence in comparison to the late fall-winter peak. Abundance increased in early years, reaching a peak in 1978 of 16.1 larvae/1000 m 3 (Table 3.211-12). Abundances were low during the next two.years and then rose again in 1981. A trend of decreasing and below-average abundances began in 1982 and has continued through 1990. The geometric mean for 1990 (0.7 larvae/1000 mi 3).rose slight-ly from 1989 (0.1 219 Yellowtail Flounder 2.0-1 -PREOP'--1990 1.8 1.6 we 0:E Zo zc 00_-1.4 1.2 1.0 0.8 0.6 0.4 0.2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV [EC MONTH Atlantic Cod 2.0 n -PREOP-- --1990 w (0 E 00 (0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2, 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N0V E-C MONTH Figure 3.2.1-6. Log (x+l) abundance (no./1000 M 3) of yellowtail flounder and Atlantic cod larvae; monthly means and 95% confidence intervals, over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3.Seabrook Operational Report, 1990...220 -' .larvae/1000 mi 3), the lowest abundance during the preoperational period, but was still well below the mean abundance for that period (2.0 larvae/1000 m3n). Abundances in 1990 were statistically similar to previous years at both nearfield and farfield stations (Table 3.2.,1-13). Atlantic Mackerel Atlantic mackerel larvae have historically exhibited a May through September pattern of occurrence , with the highest monthly average occurring in July. No larvae were found in January through April, October and December (Figure 3.2.1-7). In 1990, mackerel larvae followed the historical seasonal pattern of occurrence, except that July and August had above normal abundances and no larvae were caught in May or September.. Mean abundances for mackerel larvae during the peak season of May-August have been variable throughout the study period and had been decreasing from 1986 through 1989(from 12'5 to 2.0 larvae/1000 m 3)(Table 3.2.1-12). Abundance for 1990 (5.9 larvae/lO00 m at Station P2) increased slightly over 1989 abundance; however 19.90 abundances at P2 and P7 were statistically similar to previous years (Table 3.2.1-13). Cunner cunner larvae were present throughout June through October, showing a pattern of occurrence similar-to mackerel larvae but generally a little later. Cunner larvae have historically peaked during July and.August and usually disappeared by October'(Figure 3.2.1-7). Larval abundance in 1990 continued to follow the seasonal pattern observed.in previous years,.but values for June, August, and. September were much larger than the preoperational mean. Mean peak season abundances for cunner larvae have shown significant differences among the, preoperatio-nal years (Table 3.2.1-12) with 1987 exhibiting the highest abundance (255.2 larvae/1000 M 3) during that time. Cunner larvae have ranked.*among the top three in abundance throughout all years of the study period except 1986. In 1990 cunner larvae ranked first in abundance 221 Atlantic Mackerel.PREOP 1990 0 CoQ 00(1.-j 3 2 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Cunner 4-PREOP 1990 Za, z'0**3 2 1 0 JAN FEB MAR APR MAY JUN JUL~MONT"H AUG SEP OCT NOV CPO Figure 3.2.1-7. Log (x+l) abundance (no./1000 m 3)'of Atlantic mackerel and cunner larvae;monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3.Seabrook Operational Report, 1990.222 with 274 larvae/1000 mi 3.At both nearfield and farfield stations, 1990.abundances were significantly higher than preoperational years (Table 3.2.1-13)..Hake Historically, hake 'larvae, like mackerel and cunner, were.confined to-a relatively short period of occurrence. Abundances were at or near zero from January to May, increased in June and July peaking in August and September, decreasing in'October, and negligible in November and-December (Figure 3.2.1-8). In 1990, larvae were only present from July through October, with values during these months much higher than average. Yearly peak season abundance at Station P2 during the preoper-.ational years-did not rise above 10.4 larvae/1000 mi 3 (Table 3.2.1-12). During the operational year, the abundance*of hake larvae (60.9/1000 mi 3)was significantly higher than in any of the preoperational years which averaged (4.1/i000 mi 3):.Atlantic Herring Atlantic herring larvae typically occurred from October..through May and were rare for the remainder of the year (Figure 3.2.1-.'8). Abundances were usually highest from October through-December with peak values occurring in November. In 1990, herring followed *the same seasonal pattern; however, abundances for most of the season were much lowerthan the mean for ,the preoperational period. "As is the case with most of the other selected species, herring/larvae have had a highly variable yearly peak-season abundance at Station P2 during the preopera-tional years (Table 3.2.1-12). Abundances ranged from 145 larvae/1000. m 3 in 197.6 to 2.1 larvae/1000 m 3 in 1978. In 1990, mean abundance (2.1 larvae/1000 m 3) was substantially lower than the overall mean (26.9 larvae/1000 m 3). and all.:preoperational years except 1978..223 Hake-PREOP-....... 1990<a,.Dao 0wa~<.~~1 0 JAN FEB MAR. APR MAY. JUN JUL AUG SEP OCT NOV DEC MONTH Atlantic Herring 3 -1. PREOP------ -1990 Z0 wog.40-2 1 0 JAN FEB MAR, APR MAY JUN; JUL AUG SEP : OCT, NOVC. DEC'MONTH Figure 3.2.1-8. Log (x+1) abundance (no./1000 m3) of hake and Atlantic herring larvae;monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2 and P3.Seabrook Operational Report, 1990.224 NAtlantic herring was the only larvae species with its peak period of abundance during the period of 100% plant operation (August-December). 1990 abundances were significantly lower than previous years at bothnearfield and farfield stations (Preop-Op term; Table 3.2.1-13). However, there has been a general decline in abundance of Atlantic herring larvae since 1986 in the nearfield area (Table 3.2.1-12). Adult Atlantic herring catches in both the, study area (NAT 1990b) and the Gulf of Maine (NOAA 1991a) have been low in recent years indicating a possible reduction in the number of spawning individuals and the resulting number of larvae.Pollock Pollock larvae also exhibited a fall-winter pattern of occurrence, but briefer than that of herring larvae. Large abundances occurred in November through February and few or no larvae were caught from March through October (Figure 3.2.1-9). Pollock larvae were absent in February, March and July through October 1990. They were also less abundant'than normal in November and December. ':Peak seasonal abundances for pollock were highly variable during the preoperational years (Table 3.2.1-12) with the highest abundance occurring in1979 (49.2 larvae/lO00 m ). In 1990,. the seasonal me'anwas not computed for pollock because its period of peak abundance extends into 1991, For this reason, an ANOVA design testing among-years differences was used to be consistent withthe previous year's results (NAT 1990b).. However, mean abundance in 1989 (which includes samples collected in early 1990) was the lowest recorded for any of the preoperational years (0.6 larvae/i000 m 3) and was well below the overall mean of 6.9 larvae per 1000 cubic meters.Annual-abundances were significantly different among years (Table 3.2.1-13). The multiple comparison test showed eight overlapping groups of years, making interpretation of among-year patterns very complicated. Although the late 1989-early 1990 abundances were the lowest among all years, -they were not significantly lower than those in 1978, 1982, 1983 or 1986.225 I Pollock 2.0 PREOP 1990 C,)E Zu 00_5 S 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0.I -1:* S.JAN FEB MAR APR MAY :JUN JUL AUG SEP OCT T NOV CeO 1..MONTH Figure 3.2.1-9. Log (x+1) abundance (no./1000 in 3) of pollock larvae; monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly means for 1990 at nearfield Stations P2.and P3. Seabrook Operational Report, 1990..226:

3.2.2 Adult

Finfish 3.2.2.1 -Community Inter-Annual Patterns in the Pelagic Fish Community Mean catch per-unit of effort (CPUE: catch/24-hour set) for gill nets (all stations combined) rose .to a peak of 29 fish/net in 1980 then declined to 6 fish/net in 1981, remaining at low levels through'1989 (Figure 3.2.2-1). CPUE remained low in 1990 (3 fish/net) and-was virtually' identical to levels encountered in 1984 through 1989. The high CPUE in 1980 was due to unusually high catches o'f Atlantic herring and pollock (NAI 1981e). Commercial landings for Atlantic herring in the western"Gulf of Maine also reached a maximum in 1980 (NOAA .1989)indicating a large, widespread population. The low CPUE in 1990 reflects a continuation of the-low and generally decreasing trend in CPUE that started in 1981 and appears to be due to the regional decline in herring abundance (NOAA 1991a).Atlantic herring were the most abundant species in gill net collections during every preoperational year sampled, comprising from 26 to 82 percent of the total annual catch and averaging 63 percent for all preoperational years combined (Table 3.2.2-1). The percent contribution of Atlantic herring to the annual gill net catch was highest in,1978, 1979 and 1980(74, 80, and 82%) and lowest in 1984, 1985, 1986, and 1988 (26, 26, 34, and 33%). During all other years, Atlantic herring ranged from 45 to 63% of the total annual catch. In 1990, Atlantic herring formed only 3% of the total catch, a substantial decrease from previous years. This low percentage is a result of abnormally low catches of Atlantic herring and higher than average catches of Atlantic mackerel (see Section 3.2.2-3).. Atlantic whiting, blueback herring, pollock, and Atlantic mackerel collectively composed 27 percent of the gill net catch for all preoperational years combined. In the years when Atlantic herring 227 50 --" STATION GI------- .STATION G2-STATION G3 40.-.

• STATIONS AVERAGED 0 IL-IL 30- , I JJ ' *-z U 20--,- ........0- I I " i I l I I I -I I I I I .. 1 76 77 78 79 80 81 82 83, 84 85 86 87 88 89 90.YEAR Figure 3.2.2-1. Annual total catch per unit effort (number per 24-hour set of one net, surface or bottom) in gill nets by station and mean of stations,.

1976-1990. Seabrook Operational Report, 1990.Ii ..- .I TABLE 3.2.2-1. PERCENT COMPOSITION BY YEAR, ALL PREOPERATIONAL YEARS COMBINED, AND 1990 FOR THE TEN MOST ABUNDANT SPECIES IN GILL NET SAMPLES FROM 1976 THROUGH 1990 AT STATIONS GI, G2, AND G3 COMBINED. SEABROOK OPERATIONAL REPORT, 1990.YEAR ALL PREOP.YEARS 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 COMBINED 1990 Atlantic herring 53 48 74 80 82 45 63 48 26 26 34 52 33 61 63 3 Atlantic whiting 17 21 2 4 6 5 7 1 5 1 1 5 1 .1 8 5 Blueback herring 5 11 14 2 2 2 10., 11 9 10 .15 16 11 7 8 5 Pollock 6 3 1 2 5 18 3 13 10 22 18 6 13 10 :6 23 Atlantic mackerel 12 7 2 2 2 14 5 5 6 10 3 7 22 6 5 37 Alewife 1 2 2 <1 <1 2 2 5 5 6 4. 2 6 1 2 1 Atlantic menhaden <1 3 <1 2 1 <1 1 6 5 4 4 2 1 2 2 2 Hake speciesa 2 2 1 i. <1 4 1 1 7 2 .2 <1 5" <1 1 1.Rainbow smelt 1- 1 1 1 <1. <1 <1 1 6 2 4 3 1 1 .1 1i 1 Atlanticlcod 1 1 <1 1 <1 <1 2 2 3 1 2 2 2 1 1 <1 Other species 2 <1 2 4. <1 8. 6 7 18 16 13 4 5. 10 4 22 Total number of species 19 26 23 22 21 29 29 24 30. 23 23 19 20 24 24 20 aincludes red, white and spotted hake. accounted for less than 50 percent of the total annual catch, these four species comprised from 30 to 47 percent of the total catch. These taxa have consistently rankedamong the five most abundant taxa during, the 14-year preoperational sampling period. In 1990, these four taxa-com-bined accounted.for 70% of the total catch. Atlantic mackerel, the most abundant of these, comprised 37% of the total catch. This percentage was much higher than any of the preoperational years and the mean of all years. Catches of Atlantic mackerel were atypically high in.June and July in 1990 (NAI 1991), accounting for the higher-than-normal percent composition. Atlantic mackerel stocks have, been increasing in recent years throughout the Gulf of Maine and the Northwest Atlantic (NOAA 1991a)..Pollock ranked second in. relative abundance in 1990, compris-ing 23 percent of the total catch, which is considerably larger than the mean of 6% for all preoperational years (Table 3.2.2-1). This change was. due to a decrease in the relative abundance of Atlantic herring.Atlantic whiting and blueback herring both ranked third *in abundance, each contributing.5% to the total catch. Values for these taxa in 199.0 were similar to values during the preoperational years.Less abundant-taxa (e.g., alewife, .Atlantic menhaden, hakes, rainbow smelt and Atlantic cod) composed a larger portion of the total annual catch during '1984; 1985, 1986 and 1988, when catches were below normal and Atlantic herring were relatively less abundant. In 1990, these taxa formed a smaller percentage.of the-catch despite the low abundance of Atlantic herring. However, "other" species accounted for a greater proportion of the catch in 1990 (22%) than during the preopera-tional years, primarily due to large numbers of spiny'dogfish Squalus acanthus (12% of the 1990 catch) and butterfish Peprilus triacanthus (7%of the catch). During.the preoperational. period,.spiny, dogfish and butterfish accounted for. no more than 7% and 5%.of the catch in any given year.230 Average species richness for the preoperational period was 24, ranging from 19 to 30 species annually. Forty-five species were collected during all preoperational years combined. Species richness in 1990 (20 species) was within the rangefor previous years but slightly below the average for the preoperational period. No long-term trend of increasing or decreasing species richness was evident.Seasonality of the pelagic species assemblage has been analyzed in previous reports (NAI 1982c,.1983b). Two distinct sample groups were-observed based on abundances of the dominant species:'summer" (June-August) and ",winter" (September-May). ,Atlantic mackerel and Atlantic whiting were more abundant in summer-samples, while Atlantic herring were more numerous in winter catches. In recent years, Atlantic mackerel have been caught in increasing numbers in October and November. In 1990, Atlantic mackerel continued this trend but were much more numerous during the summer months. Catches for Atlantic herring were so low that no seasonality could be detected. The other dominant species continued to exhibit their historical seasonal differences. Blueback herring and pollock showed inconsistent seasonal differences in abundance from 1976 through 1990.Spatial Patterns in the Pelagic Fish Community. Mean annual catch per unit of effort at the three gill net Stations G1, G2, and G3 showed similar fluctuations among years (Figure 3.2.2-1). Mean annual CPUE peaked in 1980 for all stations combined.'This peak was more evident at Stations G2 and G3, where Atlantic herring comprised

a. greater portion of the catch, than at Station GI (NAi 1981A). Since 1980, CPUE at each gill- net station has fluctuated within a narrow range.Percent composition for the dominant species in gill net collections was similar among stations during the preoperational years (Table 3.2.2-2).

Atlantic herring was the dominant species at each gill net station, accounting for 58 to 68 percent of the total catch for all 231 K TABLE. 3.2.2-2.PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN GILL NETS, ALL PREOPERATIONAL YEARS (1976-1989) AND 1990, DEPTHS COMBINED.SEABROOK OPERATIONAL REPORT, 1990.STATION GI G2 G3 PREOP. PREOP. PREOP.SPECIES YEARS 1990 YEARS 1990 YEARS 1990 Atlantic herring 61 2 68 2 58 *4 Atlantic whiting 8 3 6 9 9 3 Blueback herring 6. 3 6 6 10 6 Atlantic mackerel 6 41 4 45 6 26 Pollock 6 6 6 20 6 44 Hake speciesa 2 1 1 2 1 0 Atlantic menhaden 2 4 1 1 2 "0 Alewife 2 2 2 2 2 1 Rainbow smelt 1 0 1 2 -1 " 0 Longhorn sculpin 1 1 1 0 <1 1 Atlantic cod 1 1 1 1 1 0 Bluefish 1 1 01 <1 4 All 'other species 3 35. 2 10 3 11 Total number of species .17 14 18 14 18 14 aincludes red, white, and spotted hakes. preoperational years combined. Blueback herring comprised a slightly.larger percentage. of the total catch at Station G3 (10%) than at Station Gl or Station G2 (6% at each station). Atlantic whiting, Atlantic mackerel, and pollock were also numerically important at each station, each comprising from 4 to 9 percent of the catch at the three stations for all years combined. Percent composition for Atlantic herring, although similar among stations, was very low in 1990. These results are coincidental with low commercial landings in the Gulf of Maine fishery in recent years, suggesting a regional decline in herring abundance (NOAA 1991a). In 1990, Atlantic mackerel was the most abundant species at Stations GI and.G2 and ranked second at G3, while pollock was the most abundant species at G3 and ranked second at G2.. At'Station Gl, pollock comprised similar percentages during 1990 and the preoperational years. Percent composition for the remaining species was similar among stations with one exception. "Other" species accounted for 35 percent of the catch at Gi. Spiny dogfish and butterfish comprised 25 percent and 10 percent respectively of the catch and were*the only two "other" species.Depth differences in species composition were examined by comparing percent composition in surface nets to that in off-bottom nets (3 m above the bottom) for all years combined (Table 3.2.2-3). Histori-cally, Atlantic herring was the dominant species in collections at both depths, with a slightly higher percent composition in surface nets compared to off-bottom nets. The proportions of blueback herring and Atlantic mackerel were also higher in surface nets during the preopera-tional years. Atlantic whiting, pollock, and hakes composed a larger percentage of the catch in the off-bottom nets. Atlantic menhaden and alewives accounted for a similar percentage in both surface and off-, bottom nets. During 1990, Atlantic herring formed similar percentages in surface and off-bottom nets, However, percent composition was much, lower than during the preoperational years. Atlantic mackerel were dominant and most abundant in the surface nets while pollock were dominant and most abundant in the off-bottom nets. These species.233 PERCENT COMPOSITION OF DOMINANT GILL NET SPECIES ACCORDING TO DEPTH (SURFACE AND OFF-BOTTOM), ALL PREOPERATIONAL YEARS COMBINED (1976-1989) AND 1990. SEABROOK OPERATIONAL REPORT, 1990. .TABLE 3.2.2-3.DEPTH SURFACE OFF-BOTTOM SPECIES PREOP. YEARS 1990 PREOP. YEARS, 19901:'.Atlantic herring Blueback herring Atlantic mackerel Atlantic whiting Atlantic menhaden Alewife Pollock Rainbow smelt Hake speciesa Other.species 69 10 7 5 2 2.1<1 3.9 9 59 4 4 1 0 0 21 55ý5 3 11 1 1 12 3 8 4"1" 16 5 0 2 45 1.2 24 aincludes red, white, and spotted hakes I 234 accounted for much higher percentages in 1990 than during the preopera-. tional years as discussed above. Blueback herring.and Atlantic menhaden accounted for higher percentages in the surface nets. Atlantic whit-..ings, alewives, rainbow smelts and hakes all had similar percentages in surface and off-bottom nets.Since 1980, mid-water nets have been set in addition to the surface and off-bottom nets during February, June, and October. Compar-ison of CPUE among surface', mid-water, and off-bottom nets on dates when all three nets were fished revealed'that Atlantic menhaden was the only,.species that was slightly more abundant in mid-water catches than in surface and off-bottom catches during the preoperational period and 1990 (Table 3.2.2-4). As observed with the regular surface and off-bottom gill net collections (Table 3.2.2-3), Atlantic herring and Atlantic mackerel were more abundant in surface nets and least abundant in off-bottom nets:' Bluebackherring were most abundant in surface nets.and least abundant in mid-water nets. Atlantic. whiting, pollock, alewife and rainbow smelt were most abundant in bottom nets. In 1990, for those dates when all three nets were fished, Atlantic menhaden was more abun-dant in the surface and mid-water nets. Atlantic mackerel were more abundant in the surface nets and pollock were more abundant in the offf-bottom nets. Atlantic herring, Atlantic whiting,'alewives, and blueback herring were similarly abundant in surface, mid and off-bottom nets.Rainbow smelt were only caught in off-bottom nets.Inter-Annual Patterns in the Demersal Fish Community Otter trawl catch per unit of effort for all stations and species combined during the 1976 through 1989 period rose from 50 fish/ten minute tow (fish/tow) in 1977 to a peak of 95 fish/tow in 1980 and 1981 (Figure 3.2.2-2)' CPUE subsequently declined to a s:econd low point in 1985 when an average of 43 fish/tow were collected. CPUE grad-.ually increased to 61 fish/tow in 1989 but declined to 49 fish/tow in 1990.235 TABLE 3.2.2-4.CATCH PER UNIT EFFORT 9 BY DEPTHFOR THE DOMINANT GILL NET SPECIES OVER ALL STATIONS AND'-DATES WHEN SURFACE MID-DEPTH AND BOTTOM NETS WERE SAMPLED, PREOPERATIONAL YEARS (1980 THROUGH 1989) AND 1990. SEABROOK OPERATIONAL REPORT, 1990.DEPTH SURFACE MID-DEPTH BOTTOM PREOP. PREOP. " .PREOP.SPECIE.S YEARS 1990 YEARS 1990 YEARS 1990 Atlantic herring 5.3 0.1 2.9 0.1 1.9 0.1 Atlantic whiting 0.2 0.6 0.5 0.4 .0.7 0.5 Atlantic mackerel 1.0 4.3 0.9 2.2 0.5 1.7 Pollock 0.2 0.0 0.2 0.0 1.2 4.4 Alewife 0.1 0.1 0.1 0.2 0.2 0.2 Blueback herring 0.8 0.3 0.3 Q0.2 0.5 0.1 At lantic menhaden .0.6 -0.5 0.7 0.6.7 0.2 0.0;Rainbow smelt <0.1 0.0. <0.1 0.0 0.1 0.1 wx.anumber per one 24-hour set of one net (surface, mid-depth, or bottom) 0 U-ILL L-w F--z a--U* ' ,* -120-,110-100-90-80-70-60 50,-STATION T3 STATIONS AVERAGED STATION T1....... STATION T2 a N).4V.40-30 ,* % .--I 20.1 I I I I I I I I I I I I I I I 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR a In most years sampling was curtailed at station T2 during September and October due to presence of lobster gear.Figure 3.2.2-2. Annual total catch per unit effort (mean number per 10-minute tow) in otter. trawls by station and mean of stations, 1976-1990. Seabrook Operational Report, 1990. The number of fish species (species richness) collected annually in otter trawls ranged from 32 in 1985 to 40 in 1982 and totaled 56 for all preoperational years combined (Table 3.2.2-5).Changes in the annual composition of the demersal fish community were:examined by comparing percent composition of the dominant trawl species.Six taxa accounted for nearly 80 percent of the trawl catch abundance.for all preoperational~years combined (Table 3.2.2-5). Yellowtail. flounder composed the largest percentage of the annual *catch (19-36%). in all years.except 1983. and 1984, when it ranked secondto longhorn sculpin. The percentage of yellowtail flounder in trawl collections.consistently declined from 1980 until 1984 when that species represented only 18 percent of the total annual catch. The percent contribution of.yellowtail flounder increased to 27 percent in 1985.ending a five-year: decline in.relative contribution, but was less than 20 percent for the next three years (1986-1988). The percent composit.ion of yellowtail flounder increased to 30% -in 1989 and was 27%. in 1990, values slightlyýlarger than the average for the preoperational (1976-1989) period..Longhorn sculpin was the second most abundant demersal species in trawl collections, composing 14% of the catch for all years combined'(Table 3.2.2-5).. Longhorn sculpins accounted for an increasingly larger portion of the catch from 1976 (5%) through 1984 (27%) but .their'contribution to the total *catch fell back.to pre-1979 levels, ranging 'from 9 to 11%, from 1986 through.1989. Relative abundance in 1990 was 15t..Hake species (red, white and spotted hake) were the third most abundant group of demersal fishes in the trawl catches. The annual relative contribution of hake species was variable, ranging from 8 to 30% during the preoperational period (Table 3.2.2-5). Hakes composed 8% of the total catch in 1988 and 1989 and 5% in 1990, which is below the average percent composition (13%) in preoperational years.Historically, winter flounder ranked fourth in relative abundance averaging (10%), contributing from 5 to 15% of the total.238

• V -~ -~0 TABLE 3.2ý2-5. PERCENT COMPOSITION BYYEAR, ALL, PREOPERATIONAL YEARS COMBINED, AND 1990 FOR THE TWELVE MOST ABUNDANT TAXA IN OTTER.TRAWLS, 1976 THROUGH 1990 AT STATIONS TI, T 2 a AND T3 COMBINED.

SEABROOK OPERATIONAL REPORT, 1990.YEAR ALL PREOP YEARS 1976 1977 1978 .1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 COMBINED' 1990 Yellowtail flounder Longhorn sculpin Hake speciesb Winter flounder Rainbow smelt Atlantic .cod Skate speciesc Atlantic whiting Ocean pout Pollock Windowpane Haddock Other species 36 29 21 34 33 28. 22 19 18 27 20 19 20 30 5: 8 9 12 15 .17 16 24 27 22 .9 "9 11 10 18 30 21 8 8 14 .19 10 13 15 14 10 '8 8 5 8 10 7 12 15 9 8 7 9 10. 11 9 .11 13 3 10 7 4 6 5 9 6 1 3 15 18 .19 4 3 13 14 9 6 7 8 5 3 .3 6 9 1 3 5 2 2 2 2 3 7 8 11 14 11 9 9 5 3 4 2 1 3 4 1 1 1. 8 1 1 1 2 4 4 2 1 2 2 .3 5 3 3 3 2 2<1 <1 <1 .4 7 2 1 2 <1 <1 .2 <1 <i I 2 2 i <1 3 2. 2 5 6 5 7 8 8 5 3 2 <1 3 4 <1 2 1 <1 <1 <1 <1 <1 0 4 4 5 2 1 3 8 3 3 4 8 5 5 3 26 27 14 15 13 5 10 11 8 11 7 1 5 11 3 1 3 3 2 4 4 7 1 0 4 ~3 Total number of species 37 34 38 37 34 39 40 38. 38 32 37 39 38 56 , 39 39 aIn most years sampling was curtailed at -Station T2 during September and October due to presence of lobster gear.bincludes red, white, and spotted hakes cincludes big, little, and thorny skates annual catch (Table 3.2.2-5). Winter flounder formed 11% of the total catch in 1989 and 1990 and have consistently formed 9 to 11% of the total annual catch since 1985.Rainbow smelt formed 11% of the.total annual catch in 1990, slightly more than the 8% contribution for all years combined (Table 3.2.2-5). The relative contribution of rainbow smelt to the total catch has been highly variable, ranging from I to 19% and has increased by as much as-12% in one year.' The percent composition.in 1990:'(11%) was 4 higher than the average for the preoperational period but represented a decline from 1987-1989 values.Atlantic cod was the sixth most common species based on all preoperational years (7%) but formed.a minor portion *(l%)of the 1989 and 1990 catches (Table 3.2.2-5). The relative abundanceof Atlantic cod has been highly variable as evidenced by increases from 3% in 1977 to 13% in 1978 and decreases from 9% in 1988 to.1% in 1989. Lower abundance of juvenile/adults was coincidental with lower abundance of Atlantic cod larvae in recent years (see previous section).Skates (big,. little, and thorny skates) were relatively uncommon in trawl catches from 1976 through 1982, but have formed from 7 to 14% of the total demersal catch since 1983 (Table 3.2.2-5). Since 1985-, skates have composed, on average, 11% of the total annual catch, including 9% in 1988 and 1989 and 11% in 1990.Spatial Patterns in the Demersal Fish Community Mean annual catch per unit of effort was 'similar at the offshore stations (Ti and T3), while CPUE at the shallower nearshore station (T2) was much lower (Figure.3.2.2-2).. Trawls are generally not*.fished at Station T2 during September and October. due'to the high density of lobster gear in the station area; These two months are typically a period of high abundance for demersal species and the lack 240 of data could be biasing the results to a lower mean CPUE at Station T2.In addition, the accumulation of drift algae decreased gear effective-' ness. Otter trawl catches *at the offshore stations (Ti and T3) were dominated by yellowtail flounder, hakes, and longhorn sculpin (Table'3.2.2-6). Collectively, these species comPrised 64% of the catch at Station T1 and 57% at T3 for all years combined during the preopera-tional period. Atlantic cod, Atlantic whiting, and skates were less common at.these stations. The most notable difference in species composition between Stations Ti and T3 was'that Atlantic cod, skates, and ocean pout comprised a larger percentage of. the total catch at Station T3. This, and other small differences in species composition. between Stations Ti and T3, may be related to differences in-bottom sub-strates'. Station T1 has a sandy bottom, while the bottom substrate at Station T3 is sand, littered with small cobble and shell debris.Yellowtail flounder prefer any sandy bottom, but cod prefer a cobble and shell debris habitat (Bigelow and Schroeder 1953).Otter trawl catches at the nearshore station (T2) were domi-nated by winter flounder, rainbow smelt, yellowtail flounder, and hakes, contributing 68% of-the catch for all years-combined. Relative abun-dances of hakes, yellowtail flounder, and longhorn sculpin were lower at Station T2 than at Stations T1 and T3, while the opposite was true of winter flounder,-rainbow smelt, and pollock.Percent composition results for 1990 were somewhat different than previous years at a ll stations. Hakes and Atlantic cod formed a smaller portion of the 1990 .catches.. White skates and windowpane were proportionally more common in 1990 (Table 3.2.2-6).., Inter-annual Patterns in the Estuarine Fish Community Catch per unit of effort for all-seine stations within the Hampton/Seabro0k estuary-'ranged from 41 to 362 fish/haul (Figure 3.2.2-3). Seine CPUE values were lower from 1982 through 1989 (41 to 114 241 0 TABLE 3.2.2-6.PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN OTTER TRAWLS, ALL PREOPERATIONAL YEARS 'COMBINED (1976-1989) AND 1990..SEABROOK OPERATIONAL REPORT, 1990.STATION TI T28 .T3 PREOP. PREOP. PREOP.SPECIES YEARS 1990 YEARS 1990 YEARS 1990*Yellowtail f ounder 38 35 14 14 21 23 Hake species 15 7 9. 4. 15 3 Longhorn sculpin. 11 11 5 5 21 27 Atlantic cod 5 1 5 1 10 1*Rainbow smelt 6 7 19 21 6 11.I Winter flounder 6 8 26 24 5 8 Atlantic whiting 3 1 1 <1 3 1 Windowpane -4 11 4 5 3 "4.Skate speciesc 4 .12 2 4 8 13 Pollock .1 5 7 9 1 1 Ocean pout 1 <1 3 5 4 5 Haddock 1 <1 0 2 0 Other species 5 2" 5 .8 3 3 Total number of species 30 ..29 23 21 28 28 aIn most years. sampling was curtailed at Station band October due to presence of lobster gear.bincludes red, white, and spotted hakes cincludes big, little, and thorny.skates T2 during September 700 I-cc 0 ILL IL w w C.C.I.100, STATION S1 STATION S2 STATION S3 STATIONS AVERAGED* -*1*--CCC. ** --* 1%* C.* *. C* -C 75 76 77 78, 79 80 81 82 83 84 87 88 89 90 YEAR Figure 3.2.2-3. Annual total catch per unit effort (mean numberper seine haul) in beach seines by station and mean of stations 1976-1984, 1987, 1988, 1989, and 1990. Seabrook Operational Report, 1990. fish/haul) than during.the period.1976 through 1981 (200 to 362 fish/haul). Annual variations.in beach seine CPUE were influenced primarily by annual catches of the Atlantic silverside, which was the most abundant species in seine collections each year (Table 3.2.2-7).In 1990, CPUE for all stations combined increased to 208 fish per haul., andwas primarily influenced by the large catches of rainbow smelt..The relative contribution of silversides to the total annual seine catch ranged from 47 to 88% during the preoperational period and remained relatively steady from 1982 to 1989. Atlantic silverside" contributed only 41 percent of the total annual catch in 1990, lower than any of the previous years and the average over preoperational years.(66%). Rainbow smelt ranked second in relative abundance in 1990,.accounting for 35% of the total catch. During the preoperational period, percent composition for this species ranged from one to nine'percent of the total catch. Fundulus spp. (primarily mummichog) ranked third in relative abundance in 1990 (9%), slightly higher than the overall mean for the previous years but within the range for those,-.years. Abundance for ninespine stickleback, highly variable during preoperational years, ranked fourth in 1990. Many of the other species fluctuated from year to year in their ranking, often comprising less than 1% of the total annual seine catch during the previous period. In'1990, means for these other species were similar to means for the previous years except that no alewife were caught in beach seines in 1990.The total number of species collected ranged from 16 in 1988 and 1989 to 27 in 1977 and averaged 21. In 1990, a total of 21 species was caught in the beach seines.Seasonality of the estuarine fish community was analyzed previously using numerical classification (NAI1983b, .1984b). The.estuarine community was highly seasonal in all years, and all three, seine stations exhibited similar seasonal changes intheir fish assem-blages. Catches in the spring were usually characterized by.low 244 0 ..... -w O O..TABLE 3.2.2-7. PERCENT COMPOSITION BY YEAR ALL PREOPERATIONAL YEARS COMBINED AND 1990 FOR THE TEN MOST .ABUNDANT SPECIES COLLECTED IN BEACH SEINES (EXCLUDING 1985 AND i986) AT STATIONS S1, S2 AND S3 COMBINED. SEABROOK OPERATIONAL REPORT. 1990.YEAR ALL PREOP.YEARS 1976 1977 1978 1979 1980 1981 1982 1983 1984 1987 -1988 1989 COMBINED 1990 Atlantic silverside 73 55 75 60 68 88 57 47 48 56 52 55 66 41 Fundulus speciesa 15 23 5 3 4 2 10 8 7 3 4 24 8 9 Pollock I (.I 1. 8 21 -<1 7 5 1 2 <1 0 5 <1 Alewife <1 1 <1 18 <1 <1 I " I. <1 0 0 .4 0 Rainbow smelt 4 5 .<1 5 <1 2 5 '4 9 8 <1 2 3 35 American sand lance 2 9 8 <1 <1 <1 8 2 <3 0 2 <1 3 4 Atlantic herring <1 <i 5 1 4 4 <Q 7 8 2 <1 2 3 <1I Ninespine stickleback 1 4 1 Q< <1 1 2 7 16 22 37 4 3 8 Winter flounder 1 2 2 2 3 1 6 3 3 2 1 5 2 1 Blueback herring <1 <1 I I <1 <1. <1 14 <1 0 1 0 " <1 Other species 2 <1 1 I <1 1 4 3 6 4 2. 8 2 .1 Total number of species, .11 17 14 22 9 12 12 13 14 12 7 9 i3 12 aincludes mummichogs and striped killifish r')U1 abundance, and species composition in early summer was highly variable among years. The most distinct group was the late summer-fallassem-blage, which occurred yearly from August-November, and in which Atlantic silverside was the dominant taxon (NAI 1984b). With the. exception of..the unusually high catches of rainbow smelt at Station S3, species composition and relative abundance were similar in 1.990 to the previous years.Spatial Patterns in the Estuarine Fish Community Mean annual catch per unit of effort during the period 1976.through 1981 was usually highest at Station S3 and lowest at Station Sl-(Figure 3.2.2-3). From 1982 throughf1984 and 1987, when catches were smallrelative to earlier years, mean annual CPUE was similar among the three stations. In 1988 and 1989, Station S1 had the highest CPUE among the three stations but total CPUE remained low. in 1990, CPUE was highest.at. Station S3 and was a result of unusually high catches of rainbow smelt (Table 3.2.2-8).Stations S1 and S2 were similar'during the 1976-1989 period in their overall species composition, with Atlantic silversides composing 53 and 66 percent and Fundulus spp. composing 14 and 15 percent of the.total catch for all years combined (Table 3.2.2-8). These stations were distinguished at that time from'each other and from Station S3 by a., higher proportion of blueback herring at Station Sl (3%) and alewife at Station S2 (10%). Atlantic silverside comprised a larger percentage of the catch at Station S3 (76%) than at Stations SI and S2, and Fundulus spp. accounted for a much smaller. percentage (<1%).: Because of its proximity to the-harbor mouth, salinity was higher at Station S3 than at S1 and S2 (NAI- 1981b). Fundulus spp. prefer.a more brackish environ-ment, explaining the larger numbers caught at S1 and S2 than at S3.Rainbow smelt, a species which prefers a more saline environment, " accounted forta larger percentage of the catch at Station S3 (6%) than 246 '7 TABLE 3.2.2-8.MEAN PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN:BEACH SEINES OVER-ALL PREOPERATIONAL YEARS:COMBINED (1976-1984, 1987-1989) AND IN-1990, APRIL THROUGH NOVEMBER. SEABROOK OPERATIONAL REPORT, 1990.STATION Si S2 S3 PREOP. PREOP. PREOP.SPECIES "YEARS 1990 YEARS 1990 YEARS 1990 Atlantic silverside 66 66 53. 26 76 ,39 Fundulus speciesa 14 5 15 69 "<1 <1.American. sand lance 4 25 3 .:<1 2 <1 Blueback herring 3 1 <1 <. 1 <1ýNinespine stickleback 5 2. 2 1 4 .11 Atlantic herring 2 <1 6. 0 <1 Winter flounder 1 <1 1 .2 3 <1 Pollock b 1 0 7 0 5 0 Gasterosteus species 1 1. 1 1 1 <1 Alewife 1 0 10 <1 0 Rainbow smelt 1 <1 1 <1 6 .49 Smooth flounder <1 0 <1 0 <1I 0* All other species <1 <1 <1 <1 <1 <1 Total number1 1 19 or species 13 10 14 12 17 19., 4-1 aincludes mummichog and striped killifish bincludes threespine and blackspotted sticklebacks at either Station Si or S2 (1% for each station). Station S3 was also distinguished'by greater species richness (36) than Stations S2 (32) and S1 (29).In 1990, Atlantic silverside was, the most abundant species at Station Si Fundulus species were the most abundant taxa and comprised a much greater percentage of the total catch at Station. S2,, while rainbow smelt was the most abundant species and. comprised a greater percentage.of the total catch at Station S3. Additional station, differences were reflected in the higher relative abundances of American sand lance at Station Sl and of ninespine sticklebacks at Station , Pollock and alewife, normally present at Station S2, were.not caught at any.station during 1990. Percentages for the remainder of the species.caught in'1990 were similar to those during the preoperational years.-Spatial differences in the estuarine fish community in 1990 were caused by extremely large catches of American sand lance in July at Station S1, and Fundulus species at Station S2 and rainbow smelt at Station S3 in August (NAI 1991). .3.2.2.2 Impingement A total of 499 fishes were impinged at the Seabrook Station duringý 1990 (Table 3.2.2-9). Impingement was greatest during May, June, November, and December. Lumpfish, pollock, longhorn sculpin, window-pane, herrings (Clupeidae.), and seaeraven each formed more than.5% of the total.number of fish that were impinged.. With the exception of.herrings -and pollock, each..of these are demersal species. 'Lumpfish, windowpane, and searaven were the most.common fishes impinged during..May. and June.. Pollock, longhorn sculpin, windowpane,-and herrings were the most common species impinged in November and December. Fish between," 15 and 45 cm were the most commonly impinged among most species although:4:' 248

0.0 TABLE

3.2.2-9.NUMBER OF FISH.IMPINGED AT THE SEABROOK SEABROOK OPERATIONAL REPORT, 1990.STATION BY MONTH AND SPECIES DURING 1990.N)SPECIES JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL PERCENT Lumpfish 1 4 8 10 38 5 1 2 69 13.8 Pollock *6 23 11 24 5 69 13.8 Longhorn sculpin 1 2 2 4 1 2 3 2 21 29 67 13.4 Windowpane 3 11 11 2 .3 ý3 9 10 52 .10.4 Herring spp. 1 4 .6 2 6 .1. 9 12 3 44 8.8 Sea raven 1 7 12 2 1 5 38 7.6 Cunner 1 .1 6 6 4. 1 1 1i 21 .4.2 Winter flounder 8 1 1 .1 2 5 18, 3.6 Cod 3 5 2 3 2 3 18 3.6 Hake spp. 1 1 4 3 2 5 16 3.2 Rock gunnel 4 1 1 3 4 1 14 2.8 Grubby 4 2. 1 1 1 1 1 11 2.2 Sea robin 2 1 3 3 1 10 2.0 Clearnose skate 4 1 1 6 1.2 Little skate 1 3. 2 6 1.2 Wrymouth 1 " 4 4 5 1.0 Shorthorn sculpin 2 1 1 4 08'Unknown 1 3 4 0.8 Radiated shanny 1 3 4 0.8 Mackerel 4 4 0.8 Smooth flounder 3 3 0.6 Tautogf. .1 3 .6 Sand. lance 3 3 0.6 Fourspot flounder 1 1 2 0.4 Goosefish 1 1 0.2 White perch 1 1 0.2 Lamprey eel

• 1 1 0.2 Ocean pout 1 1 0.2 American eel 1 1- 0.2 Toadfish 1 1 0.2 Striped anchovy 1 1 0.2.Spiny dogfish 1 1 0.2 All species 0 25 10 34 62 88 17 27 36 35 83 72 499 100.0 pollock, windowpane, herrings, cunner, winter flounder, hakes, rock gunnel, and grubby less than 15 cm were also relatively common (Figure 3.2.2-4).Each of. the most common species impinged (except lumpfish) was also relatively abundant in otter trawl, gill net, or beach seine samples during 1990 and most are demersal species. Adult lumpfish are not particularly vulnerable to otter trawls, gill nets,-or seines and this probably explains their absencefrom'the fisheries surveys.However, it appears that lumpfish are.relativelyabundant near the.intake structure as evidenced.by the impingement data. Most of the impinged lumpfish were found in May or June and most were adults (Table 3.2.2-9; Figure 3.2.2-4).

This seasonal periodicity could be related to" post-spawning movements by adults such that they are more vulnerable to impingement than during the spawning period (April-May; Bigelow and Schroeder 1953).3.2.2.3 Selected Species General.Seasonal, inter-annual, and spatial variations in abundance were analyzed for nine selected species. Selection of species was based on two criteria:

1) high abundance in at least one life stage and gear type; and 2). importance in local commercial or sport fisheries.

The nine species selected and their primary collection methods were: Species. Gear Type Atlantic herring.

• gill nets* Atlantic mackerel
• gill nets Pollock gill nets Atlantic cod otter trawl Hakes (red, white and spotted) otter.trawl Yellowtail flounder otter trawl Winter flounder .* otter trawl and beach seine Rainbow smelt otter trawl and'beach seine Atlantic silverside beach seine.250 -

7 7 T.I 80-I M 75-90 CM cc I-0 70 60 50 40 30 20 10 II I11 if'I I1 I II 0 0]03 60-75 CM.45-60 CM[3.. 30-45 CM 15L30 CM 0-15 CM 11 I II I Ii k I II It I II=::::=:::==:=1 II II 0-75.>CL = w E 0 M,:-C r- C- cc 0 Ci)CC t0-05 C.o.0-o SPECIES Figure 3.2.2-4. Number of fish impinged at Seabrook Station during 1990 for various size classes of most abundant species. Seabrook Operational Report, 1990, Analysis of variance was used to statistically test the differences in catch per unit of effort (CPUE) for selected gill net, otter trawl, and beach seine species. Data were log (x+l).transformed prior to analysis. For all species, a nested ANOVA was run with month.nested within year and operational status, and year nested within operational status. For speciescollected in gill nets or beach seines, the mean CPUE for the preoperational period and 1990 were also compared.Otter trawl species were. subjected to a-factorial design with interac-tion comparing the effect of operational status and station on mean CPUE.Comparison of yearly mean catch per unit of effort revealed'general patterns in population size, while comparison of monthly mean catch per unit of effort provided information on seasonal cycles.'Statistical analysis of the seasonal and annual differences showed they were highly variable for almost all of the selected species. Size-structure of fish populations also yields important information on age classes that use the area and-supplies information on recruitment patterns; this information was examined thoroughly in the i984 Baseline Report (NAI 1985b).Pelagic Species Atlantic Herring Atlantic herring were typically most abundant during the spring and fall (Figure 3.2.2-5), with gill net CPUE values greatest during March through May and October through December. In 1990, catches were zero or much lower than the overall mean for all months except July. The annual geometric mean CPUE of Atlantic herring rose from 3.1 fish/net in 1976 to 4.5 fish/net in 1978. and then generally declined to the lowest levels observed during the program (0.5 in 1984 and 1985;Table 3.2.2-10). Annual mean CPUE increased slightly in 1986 and 1987 (0.6 and 1.0) but then decreased slightly in 1988 (0.7) and again in 252 Atlantic Herring LU 0.wJ JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Pollock 1.2- -PREOP... 1990 1.0 tU a-0-j 0.8 0.6 , , 0.4 0.2 0.0 JAN FEB *MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-5. Log (x+l) catch per unit effort (one 24-hr. set) for Atlantic herring and pollock;monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 averaged over gill net Stations Gl, G2 and G3. Seabrook Operational Report, 1990.253 TABLE 3.2.2-20. ANNUAL GEOMETRIC MEAN' CPUE POP, SELECTED FINFISH SPECIES FOR TEE PREOPERATIONAL PERIOD (1976-1989). THEIR CONFIDENCE LIMITS, AND 1990 DATA. SEABROOK OPERATIONAL REPORT, 1990.YEAR MEA1( OVER CONFIDENCE ALL PREOP. LIMITS SPECIES STATION 1976 1977 1978 1979 1980 1981 1982 1983 2984 2985 2986 1987 2988 1989 YEARS, LOWER UPPER 1990 Atlantic G1-G3 3.07 3.32 4.51 2.22 3.54 1.40 1.41 1.51 0.53 0.47 0.62 1.05 0.69 0.52 1.51 1.15 1.92 0.07 herring ." Pollock GI-G3 0.32 0.34 0.13 0.17 0.82 0.74 0.17 0.54 0.34 0.43 0.57 0.20 0.42 0.27 0.38 0.30 0.4 0.29 Atlantic GI-G3 0.56 0.48 0.20 0.12 0.33 0.47 0.24 0.32 0.17 0.24 0.13 0.22 0.53 0.16 0.29 0.21 0.37 0.64:mackerel Atlantic cod TI 1.83 1.26 3.77 4.04' 4.42 4.30 3.96 3.98 2.11 0.94 1.03 2.16 1.92 0.67 2.33 1.94 2.77 0.28 T2 0.33 0.30 1.30 2.00 -1.47 1.50 1.75 0.81 0.60 0.14 0.55 0.71 0.41 0.21 0.79 0.60 1.01 0.20 T3 3.07 1.47 9.74 6.29 8.63 5.98 4.67 6.29 3.33 0.90 1.55 3.59 8.98 0.73 3.82 3.14 .4.61 0.43 TI-T3 1.48 0.93 3.91 3.80". 4.05 3.52 3.26 3.22 1.78 0.61 0.99 1.94 2.61 .0.56 2.08 1.77 2.43 0.31 Bake species TI 6.77 7.57 6.63 3.82 4.49 7.27 6.43 3.48 3.61 3.20 4.19 3.22 4.20 3.47 4.68 3.65 5.95 2.55 T2 1.91 3.08 3:17 1.07 2.11 3.68 2.32 1.39 2.40 1.01. 2.36: .1.38 1.57 1.41 1.99 1.55 2.51 1.05 T3 *4.32 6.48 5.50 3.49 3.81 8.85 5.93 3.4] 3.57 3.43 3.24 .3.69 2.85 .2.14 4.11 .3.19 5.23 1.03 Ti-T3 3.94 5.39 4.92 2.55 3.35 6.25 4.55 2.95 3.15 2.54 3.42 2.80 3.05 2.54 3.55 2.83 4.40 1.54 Yellovtail TI 33.50 26.34 18.88 33.54 44.88 40.47 22.33 18.03 25.73 14.82 24.51 13.36 16.49 24.52 22.34 20.13 24.80 18.13 flounder. T2 4.21 2.58 1.78 4.73 7.05 4.67 5.28 2.62 1.03 2.91 1.83 2.62 2.23 7.82 3.30 2.70 4.00 2.92 T3 20.57 12.50 13.12 21.82 27.68 17,98 10.31 8.27 7.66 8.40 4.83 7.53 8.65 10.92 21.58 10.42 12.86 9,55 TI-T3 14.71 9.98 8.21 15.53 20.97 15.46 10.79 8.25 5.65 7.64 5.72 6.84 7.99 13.43 10.05 9.18 11.00 9.07 Winter TI 1.27 .3.11 2.82 2.53 5.32 6.43 4.39 3.39 2.71 3.24 4.60 .4.99. 4.61 6.31 3.76 3.34 4.21 4.49 flounder T2 3.79 4.87 7.18 8.90 17.49 17.10 9.55 7.72 5.50 5.65 3.71 4.32 4.36 6.34 6.89 5.87 8.06 6.60 T3 , 1.32. 1.72 3.20 , 2.08 5.13 .4.1) 2.75 .: 2.52 2.26 1.08. 2.56 4.47 2.89 2.52 2.60 -2.25 2.98 2.75 TI-T3 1.94 3.04 4.08 3.76 7.95 7.82 4.97 3.96 3.28 2.86 3.64 4.75 3.96 4.68 4.11 3.71 4.55 4.29 S]-S3 1.54 2.98 2.36 3.83 4.41 2.38 2.47 1.44 2.16 NSc IDd 0.89 0.75 1.23 2.03 1.71 2.39 0.72 (continued) Ll 3 TABLE 3.2.2-10. (Continued) YEAR .MEA1 OVER CONFIDENCE ALL PREOP. LIMITS SPECIES STATION 1976 2977 2978 1979 1980 1981 2982 1923 1984 1985 1986 1987 1988 1989 YEARS LOWER UPPER 1990 Rainbow smelt TI 1.88 0.71 .2.67 1.23 1.00 2.10 0.92 1.42 0.89 0.30, 0.63 2.30 2.20 2.61 1.25 0.88 1.70 1.37 T2 2.26 0.94 , 4.63 1.73 1.60 2.48 1.21 2.89 1.69 0.64 .1.34 3.28 4.70 4.55 2.14 1.56 2.85 3;18 T3 1.59 0.74 1.15 1.07 0.80 0.44 0.72 0.37 0.48 0.37 0.38- 1.03 1.64 2.94 0.89 0.60 1.23 1.12 TI-T3 1.90 0.79 2.29 1.33 2.11- 1.20 0.94 1.17 0.96 0.43- 0.66 .1.97 2:33 2.90 1.33 0.97 1.74 1.57 SI-S3 1.06 0.67 0.09 1.05 0.05 0.72 0.70 0.59 1.06 NS ID 0.30 0.08 0.21 0.50 0.31 0.72 1.29 Atlantic SI-$3 24.37 13.47 23.58 22.36 16.05 19.97 5.80 9.78 8.32 NS ID 7.30 5.31 4.08 11.44 6.91 -]8.54 5.94 silverside a) OTTER TRAWL (T) mean catch per tow per. month at each station and mean of all stations.GILL NET (G) mean catch per 24 hour set of either level (surface or bottom) per month, a meanfor all stations.SEINES (S) mean catch per haul per month, a mean for all stations.b) Otter Trawl (T) mean of 168 months *except T2 meanof 158 months; Gill Net (G) mean of 167 months; Seines (S) mean of 96 months.c) NS -not sampled * -, d) ID -Insufficient data for comparison with previous years (April -June not sampled) 1989'(0.5). Mean CPUE for. 1990 was much lower than any of the preopera-tional years. Analysis of variance showed that the difference between preoperational and 1990 means was highly significant (Table 3.2.2-11)and that the preoperational mean was greater than the 1990-mean (Table 3.2.2-10). Atlantic herring monthly CPUE in 1990 (Figure 3.2.2-5) for most of the year was much lower than the preoperational mean or was zero. A similar pattern was observed in each of the past four years and lower than normal annual geometric means have-also been recorded for the past six years (1984-1989; Table 3.2.2-10). These results suggest a trend of decreasing monthly and yearly means that has continued into 1990 and is coincidental with decreasing Atlantic herring catches from the commercial fishery along the Maine coast and the western Gulf of Maine (NOAA 1991a).Pollock Pollock gill net catches were highest during late spring and late fall, and lowest during winter (Figure 3.2.2-5). The high catches.in the spring and late fall reflected annual onshore and offshore movements. CPUE for April,.May, and September through December in 1990 were lower than the overall mean CPUE for the preoperational period. No pollock were caught during the months of January through April, November and December. Annual mean CPUE (all stations combined) for pollock varied from 0.1 to 0.8 fish/net and averaged 0.4 fish/net over all preoperational years (Table 3.2.2-10). The 1990 mean CPUE of 0.3 fish/net was similar to the mean in 1989 and slightly lower than the preoperational mean. Results of the analysis of variance on differences between preoperational and operational years were not significant (Table 3.2.2-11). 256 TABLE 3.2.2-11. RESULTS OF ANALYSIS OF VARIANCE BETWEEN PREOPERATIONAL YEARS (1976-1989) AND 1990 FOR SELECTED FINFISH SPECIES AT ALL GILL NET STATIONS COMBINED.SEABROOK OPERATIONAL REPORT, 1990.SOURCE, OF SPECIES VARIATIONa df SSFb Atlantic Preop-Op 1 2.06 *49.75***-herring Year (Preop-Op) ' 11 12.98 28.53***Month (Year (Preop-op)) 142 43.63 7.43***Error 487 20.15 Pollock Preop-Op 1 .0.01 0.70 NS.Year (Preop-Op) 11 0.75 4.21**Month (Year (Preop-Op)) 142 5.65 2.46***Error 487 7.88 Atlantic Preop-Op 1 0.28 24.08***mackerel Year (Preop-Op) 11 0.62 4.86***Month (Year (Preop-Op)) 142 10.08 6.15***Error 487 5.62 8 Pre-Op = Preoperational period vs. 1990.Year (Preop-Op) = Year nested within preoperational and periods..operational Month (Year (Preop-Op)) = Month nested within year nested within preoperational and operational periods.bNS not significant (p>0.05)* = significant (0.05>p>0.01)

• • = highly significant (0.01p>O.l001)
• =very highly significant (p50.001)257 Atlantic Mackerel Historically,.

Atlantic mackerel were present in gill net* collections primarily from June to November with low or zero CPUE from December through May (Figure 3.2.2-6). Following a gradual increase in abundance in June, monthly mean CPUE leveled off and remained at.stable levels through November. In 1990, CPUE was above the preoperational mean during June, July and October and was zero in August. Catches for mackerel were variable over the years, with mean CPUE ranging 'from 0.1 to 0.6 fish/net, and averaging 0.3 fish/net (Table-3.2.,2-10). In 1990, CPUE was 0.6 fish/net, significantly larger than both the overall V preoperational mean' and any of the preoperational years (Table 3.2.2-11). Analysis of variance showed a highly significant difference between preoperational and 1990 means (Table 3.2.2-11) with the 1990 mean exceeding that of the preoperational period.Demersal Species Atlantic Cod During 1990, Atlantic cod were present in otter trawl catches from March through July and September through December (Figure 3.2.2-7).Monthly mean CPUE in 1990 were generally lower than the overall mean for the preoperational period ('1976-1989') at Stations Tl and T3.. Monthly mean CPUE at Station T2 in 1990 were also typically lower than the preoperational mean except during May, June, and July.The annual mean CPUE (geometric mean averaged over the three stations). rose from 0.9 fish/tow in 1977 to greater than 3.8 fish/tow from 1978 through 1980 (Table 3.2.2-10). Annual mean CPUE declined gradually from 1981 to 0.6 fish/tow in 1985. The annual mean CPUE rebounded from 1986 through 1988 but declined' to 0:6 fish/tow in 1989.The 1990 annual mean CPUE of 0.3 fish/tow is the lowest value observed during the study period. The annual mean CPUE at each station in 1990 258 Atlantic Mackerel 1.2 1.0 0.8-PREOP---- -1. ~9W w D.0-o 0.6 I T 0.4 0.2 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-6.Log (x+1) catch per unit effort (one 24-hr. set) for Atlantic mackerel; monthly means'and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 averaged over gill net Stations G1, G2 and G3.Seabrook Operational Report, 1990.259 Station T1-PREOP 1990 D,.CL 0.j 1.4 -1.2-1.0-0.8-0.6-0.4-0.2-0.0 i 1111 p I I I I .I * ,I I I " JAN FEB APR MAY JUN JUL AUG SEP OCT NOV DEC-MONTH Station T2 0.0j 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0-PREOP 1990 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station T3 PRE OP....... 1990 0.C.)0 0_j 1.4-1.2 1.0-0.8-0-.6-0.4-0.2.-0.0~~0---.............

• i I I I I I -l -I .4 I i .I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-7. Log (x+ 1) catch per unit effort (on:e tow) for Atlantic cod; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations Ti, T2 and T3. Seabrook Operational Report, 1990.260 was considerably lower than the overall mean for the preoperational.,.

period and was most.pronounced at Stations Ti and-T3, indicated by a significant interaction between station and'Preop-Op variables.in the ANOVA (Table 3.2.2-10). Annual mean CPUE was greater during preopera-tional years.at all stations; however, the difference between preopera-tional and 1990CPUE was less at Station T2 than at Stations Ti and T3 (Table 3.2.2-12). Hakes Hakes were generally present in otter trawl catches throughout the year during 1990 (Figure 3.2.2-8). Peak abundance generally occurred during May, June, and July but each station showed a secondary peak during autumn. Monthly mean CPUE during 1990 were generally lower.than the overall mean for the preoperational period at Station T3.Monthly mean CPUE at Stations T1 and T2 in 1990 were also typically lower than the preoperational mean; however, during February and Decem-ber, 1990 values exceeded the preoperational mean at Station T2.The annual geometric mean CPUE (averaged over all stations)fluctuated within a narrow range between. 1976 and 1989, with the maximum of 6.3 fish/tow recorded in 1981 and the minimum of 2.5 fish/tow recorded in 1985 and again in 1989 (Table 3.2.2-10). Annual mean CPUE in 1990 was lower than the preoperational.mean at all stations, with the largest differences. at Stations:Tl and T3. These results indicate that abundance of hakes was low at'all stations during 1990. Analysis of variance indicated that a significant interaction between st'ation and operational status affected the annual mean. CPUE for hakes. Mean CPUE was greater during preoperational years at all stations, but the difference between preoperational and 1990 CPUE was smaller at Station Tl and T2 than at Station T3 (Table 3.2.2-12). 261 ON TABLE 3.2.2-12. RESULTS OF TWO-WAY ANALYSIS OF VARIANCE AMONG STATIONS (TI, T2, AND T3), PREOPERATIONAL (1976-1989) AND OPERATIONAL (1990) YEAR AND THEIR INTERACTIONS OF LOG (x+l) TRANSFORMED CATCH PER UNIT EFFORT FOR SELECTED FINFISH FROM OTTER TRAWLS.SEABROOK OPERATIONAL REPORT, 1990.SOURCE OF INTERACTION TERMS SPECIES VARIATION8 df SS Fb STATION PERIOD N_ MEAN Atlantic Station 2 2.06 16.47*** TI Op. 20 0.081 cod Preop-Op .1 7.20 108.33*** Ti Preop.. 177 0.475 Year (Preop-Op) 13 15.81 19.43*** T2 Op. 19 0.069 Month (Year (Preop-Op)) 135 26.72 3.16*** T2 Preop. 172 0.214 Preop-Op X Station 2 1.16 9.42*** T3 Op. .20 0.125*Error 419 26.23 T3 Preop. 177 0.633 Hake Station 2 2.15 15.41*** Ti Op. .2Q 0. 4ý'4 Preop-Op 1 2.39. 34.16*** Ti Preop. .17 0.607 Year (Preop-Op) 13 4.72 5.18*** T2 Op. 19 0.254 Month (Year (Preop-Op)) 135 96.10 10.15** T2 Preop.. 172 0.3.9 Preop-Op X Station 2 0.49 3.52* T3 Op. 20 0.209 Error 419 29.39 T3 Preop. 177 0.5-25 Rainbow Station 2 1.28 7.09**smelt .Preop-Op 1 0.06 0.14 NS Year (Preop-Op) 13 8.92 7.60**Month (Year (Preop-Op)) 135 115.54 9.48***Preop-Op X.Station 2 0.01 0.06 NS Error 419 37.83 Yellowtail Station 2 17.46 91.83"**" flounder Preop-Op 1 0.54 5.57** Year (Preop-Op) 13 11.43 9.35ý**Month (Year (Preop-Op)) .135 15.33 1.21 NS Preop-Op X Station 2 0.05 0.25. NS Error ..419 39.42 Winter Station 2 3.12 23.18***flounder Preop-Op 1 0.12 0.04 NS Year (Preop-Op) 13 7.46 8.34***Month (Year (Preop-Op)) 135 24.16 2.60***'Preop-Op X Station 2 0.05 0.40 NS Error 419 28.82'Station: Tl vs. T2 vs. T3 regardless of year or month; Preop-Op = preoperational period vs. 1990;Year'(Preop-Op) = year nested, within preoperational-and operational periods, regardless of area;Month. (Year (Preop-Op)) = month nested within year nested within Preop-Op reagardless of station;Preop-Op X Station = interaction of main effects lNS = not significant (p>0.05)* = significant (0.05->p>0.01)

• =highly significant (0.01>p>0.001)

S.very highly significant (p50.O01)-~ ---_ -~.1. Station Ti 0.0 0.-J 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0*1.6 1.4-1.2-1.0.0.8-0.6-0.4-0.2-0.0-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH, Station T2-. PREOP 1990 JAN FEB MAR APR MAY DEC MONTH Station T3 a,.0..1 1.6 1.4'1.2 1.0'0.8..0.6 0.4'0.2 0.0-JAN FF-B MAR APR MAY. JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-8. Log (x+1) catch per unit effort (one tow) for hakes; monthly means and 95%confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations T1, T2 and T3. Seabrook Operational Report, 1990.263 Yellowtail Flounder Yellowtail flounder were collected throughout 1990 in otter.trawls and there was limited variation among the months at each of the stations (Figure 3.2.2-9). Monthly mean CPUE during 1990 at-Stations.T1 and T2 were generally similar to. the overall mean for the preoperational period exceptaduring April, November, and December. Monthly mean CPUE at Station T3 in 1990 were generally lower than the preoperational mean from January through May but similar to the preoperational mean during the remaining months.The annual geometric mean CPUE for yellowtail flounder (averaged over all stations) ranged from 5.7 fish/tow in 1984 and 1986 to 21.0 fish/tow in 1980. Annual mean CPUE in 1990 (9.1 fish/tow) was slightly lower than the overall mean of 10.1 fish/tow (Table 3.2.2-10). The 1990 annual mean CPUE at Stations T1 and T3 were less than the lower limit of the 95% confidence intervalfor the overall mean; however, the annual mean at Station T2 (2.9 fish/tow) was within the 95% confidence interval for the overall mean. Analysis of variance indicated that annual mean CPUE for yellowtail flounder were significantly greater at Stations T1 and T3 than at Station T2 (Table 3.2.2-12). Also, annual mean CPUE was significantly larger during the preoperational period at all stations. These results indicate that abundance of yellowtail flounder is typically lower at Station T2 regardless of plant.operation-alstatus and that during 1990 (the first year-of plant operation), abundance of yellowtail flounder was 'lower than the mean of the preoper-ational period at each 'station.Demersal and Estuarine Species Winter Flounder Winter- flounder were collected in .otter trawls throughout 1990 (Figure 3.2.2-10). Monthly'mean CPUE during 1990 were generally similar to or greater than the overall mean for the preoperational period at 264 Station T1 Cil 0-J 1.8-1.6 1.4-1.2-1.0" 0.8 0.6 -0.4 -0.2-0.0-- PREOP 1990 JAN FEB MAR Station T2-- PREOP 1990 1 I I "I APR MAY -JUN JUL MONTH I I I I r i i i i AUG SEP OCT NOV i DEC 0.C, 0._j 1.8-1.47 1.2-1.0-0.8-0.6 -0.4 0.2" 0.0 1.8-1.6-1.4-1.2-1.0-0.8-0.6-0.4-0.2-0.0.I I I I I I I JAN FEB MAR APR MAY JUN JUL MONTH i I OCT INO I AUG SEP OCT NOV DEC Station T3 PREOP....... 1990 I I 1 TV~ I 1 I I I I

• I I I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH I Figure 3.2.2-9. Log (x+l) catch per unit effort (one tow) for yellowtail flounder; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations TI, T2 and T3. Seabrook Operational Report, 1990.265

.U 0-J 1.4.1.2-1.0-0.8-0.6-0.4-Station T1-PREOP 1990.0.2.0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station T2-PREOP 1990.ILl 0.0-J 1.6.-1.4-1.2 1.0-0.8" 0.6 0.4.-0.2 0.0 I. I I I I 1I I

• I I I I -JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station T3-- PREOP 1990" ILU 0n.0-j 1.6-1.4 -1.2 1.0 -0.8.-0.6-0.4-0.2 -0.0*I I I I I *~I *l I I £JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-10.

Log (x+1) catch per unit effort (one tow) for winter flounder; monthly means:*.-and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations Ti, T2 and T3. Seabrook Operational Report, 1990.266 each station. However the 1990 mean CPUE was less than the lower limit of the 95% confidence interval for the overall mean during at .least one month at each station. The highest monthly mean CPUE occurred during June or July at each station.Annual geometric mean CPUE (averaged over all stations) ranged from 1.9 fish/tow in 1976 to 8.0 fish/tow in 1980 and has been relative-ly stable since 1.986 (Table 3.2.2-10). Annual mean CPUE for 1990 at.each station was slightly higher than the overall mean for the preopera-tional period.. However, there were significant differences in annual mean CPUE among the three stations (Table 3.2.2-12). Winter flounder were also collected in beach seines during 1990 from May through November (Figure 3.2.2-11). Monthly mean CPUE during 1990 were less than the lower limit of the 95% confidence interval for the overall mean except during July, October, and November.Analysis of variance indicated a significant difference between mean CPUE for the preoperational period and 1990 (Table 3.2.2-13), with the mean for 1990 (0.7 fish/haul).less than the preoperational mean (2.0 fish/haul; ,Table 3.2.2-10). Rainbow Smelt Rainbow smelt were typically, most abundant in otter trawls from January through March (through April at Station T2) and in December (Figure 3.2.2-12). During these months, mean CPUE in. 1990 were general-ly equal to or greater than the overall mean for the preoperational period.The annual geometric mean CPUE. for rainbow smelt (averaged.over all stations) ranged from 0.4 fish/tow in 1985 to 2.9 fish/tow in 1989 (Table 3.2.2-10). The 1990 value .(1.6 fish/tow) was slightly greater than the mean for the preoperational period.. During 1990 the annual mean CPUE also exceeded the overall mean CPUE at each station and at Station T2. was greater than the upper limit of the 95% confidence -267 Winter Flounder 1.2-1.0-0.8--PREOP 1990 LIJ 0.-j 0.6-0.47 0.2-0.0* P.'a I I I I I JAN FEB MAR APR MAY i I I I .I I IDJUL AUG SEP' OCT. NOV .DEC MONTH Figure 3.2.2-1 1.Log (x+1) catch per unit effort (one haul) for winter flounder; monthly means and 95 % confidence intervals over all preoperational years (1976-1984, 1987-1989) and monthly means for 1990 averaged over beach seine Stations S1, S2 and S3. Seabrook Operational Report, 1990.268 : TABLE 3.2.2-13. RESULTS OF ONE-WAY ANALYSIS OF VARIANCE BETWEEN PREOPERATIONAL YEARS (1976-1989) AND THE OPERATIONAL YEAR (1990) FOR SELECTED FINFISH SPECIES FOR ALL BEACH SEINE STATIONS COMBINED.SEABROOK OPERATIONAL REPORT, 1990..-SOURCE OF SPECIES VARIATION* df SS Fb Winter Preop-Op 1 0.33 7.02*flounder Year (Preop-Op) 11 2.01 3.85***Month (Year (Preop-Op)) 91 5.55 1.29 NS Error 61 2.89 Rainbow Preop-Op 1 0.36 6.68*smelt Year (Preop-Op). 11 1.10 1.86 NS Month (Year (Preop-Op)) 91 8.08 1..65*..Error 61 3.28 Atlantic Preop-Op 1i 0.,24 1.40 NS.silverside Year (Preop-Op) 11 6.32 3.41***Month (Year (Preop-Op)) 91 131.64 8.58***Error 61 10.28 aPreop-Op = Preoperational period vs. 1990.Year (Preop-Op) = Year nested within preoperational and operatioi periods.Month (Year (Preop-Op)) = Month nested within year nested within pereoperational and operational periods.bNS = not significant (p>0.05)* = significant (O.05!p>O.Ol) = highly significant (O.01p>O.O01) = very highly significant (pO.O01)nal 269 Station T1.Il 0_J 1.6 1.4 1.2 1.0 0.8 0.6-PREOP....... .1990 0.2 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station T2 IL 0'-j 1.6 1.4 1.0 0.8.0.6 0.4 0.2'-- PREOP 1990 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station T3 1.6, 1.4-1.2'1.0.0.8.0.6'0.4" 0.2, PREOP 1990 I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-12. Log (x+l) catch per unit effort (one tow) for rainbow smelt; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations TI, T2 and T3. Seabrook Operational Report, 1990.270 interval for the overall mean. Analysis of variance Indicated that.annual mean CPUE for rainbow smelt was significantly greater at Station T2 that at Stations Tl or T3 (Table 3.2.2-12). However, there was no difference between preoperational and 1990 CPUE at any of the stations-Rainbow smelt were present in beach seine collections from April through November (excluding June)' during 1990 (Figure 3.2.2-13). Annual mean CPUE averaged over all stations for the preoperati6nal period was 0.5 fish/haul with a low of 0.1 fish/haul recorded in 1980 and 1988. The 1990 mean CPUE of 1.3 fish/haul was substantially higher than the overall mean for the preoperational period and therefore is in general agreement with the otter trawl results.Atlantic Silverside Throughout the preoperational period, Atlantic silversides were most abundant in beach seine collections from August through.November and this pattern was repeated in 1990 (Figure 3.2.2-14). The annual geometric mean CPUE ranged from 4.1 fish per haul in 1989 to 24.4 fish/haul in 1976, averaging 11.4 fish/haul throughout the preoperatio-nal period. (Table 3.2.2-10). The 1990 CPUE of 5.9 fish/haul was not significantly different from the preoperational mean (Table 3.2.2-13). Atlantic silverside CPUE have remained relatively low since a sharp.decline in 1982.The catches were highly variable over the years with annual mean CPUE ranging from 4,.1 to 24.4 fish/haul and averaging 11.4 fish/haul over all years (Table 3.2.2-9). The high variability is most likely due to the fact that.this species tends to move in large schools, and samples are collected only once a month. As a result, the chances-of encountering this species can vary greatly. The annual geometric mean for 1989 was 4.1 fish per haul, slightly lower than the mean for 1988 (5.3 fish/haul) and the lowest value for the fourteen years of this study. Results of the one-way analysis of variance were not significant (Table 3.2.2-12). 271 Rainbow Smelt 2.8-2.6 --PREOP....... 1990 2.4 -2.2-2.0-1.8 -UJ ILl 0.., 1.64 1.4-I ** I I.1.2 -1.0 -0.8-0.4-0.2-0.0 i I T ---------- r-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-13. Log (x+l) catch per unit effort (one haul) for rainbow smelt; monthly means and 95% confidence intervals over all preoperational years (1976-1984, 1987-1989) and monthly means for 1990 averaged over beach seine Stations S1, S2 and S3. Seabrook Operational Report, 1990, 272 Atlantic Silverside 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4-PREOP....... 1990 Uj 0 0-1 1.2 1.0 0.6 0.4, 0.2'JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.2.2-14.Log (x+l) catch per unit effort (one haul) for Atlantic silverside; monthly means and 95% confidence intervals over all preoperational years (1976-1984, 1987-1989) and monthly means fQr 1990 averaged over beach seine Stations S1, S2 and S3. Seabrook Operational Report, 1990.273 APPENDIX TABLE 3.2.1-1. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND GEAR, JULY 1975-DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990.ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAMEa COMMON NAMEa EGGS LARVAE TRAWLS NETS SEINES Acipenser oxyrhynchus Alosa aestivalis Alosa nediocris Alosa pseudoharengus.Alosa sapidissima Alosa sp.Ammodytes americanus Anarhichas lupus Anchoa hepsetus Anguilla rostrata Apeltes quadracus Archosargus probatocephalus Aspidophoroides sonopterygius Brevoortia tyrannus Brosme brosme Caranx.hippos Centropristis striata, Conger. oceanicus Clupea harengus'Cryptacanthodes maculatus Cyclopterus lumpus Enchelyopus cimbrius Fundulus sp.'Gadus morhua Gadus/Ilelanogrammus Gasterosteus sp.d Glyptocephalus cynoglossus ifemitripterus americanus Atlantic sturgeon blueback herring.hickory shad alewife American shad American sand lance Atlantic wolffish striped anchovy American eel fourspine stickleback sheepshead alligatorfish Atlantic menhaden cusk crevalle jack .black sea bass conger eel Atlantic herring wrymouth lumpfish fourbeard rockling mummichogc Atlantic cod lAtlantic cod/haddock sticklebackd witch flounder sea raven Rb R C R O 0 R 0 O R R R A C 0 0 0 R R If C C 0 0 R R 0 0 0 0 R<R R , R R C 0 C C C 0 A 0 R R 0 C R R R C C R 0 C R C C C 0 0 C. 0 R (Continued) 274 APPENDIX TABLE 3.2.1-1.(Continued) ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAMEa COMMON NAME 9 EGGS LARVAE TRAWLS NETS SEINES Ilippoglossoides platessoides hippoglossus h ippoglossus Labridae/Pleuronectes Liparis atlanticus Liparis coheni Liparis sp.f Lophius americanus Lumpenus lampretaeformisg Lumpenus maculatus Macrozoarces americanus Melanogrammus aeglefinus Menidia menidia Menticirrhus saxatilis lerluccius bilinearis Iicrogadus tomcod Morone americana Morone saxatilis Mugil cephalus Mustelus canis Myoxocephalus aenaeus Myoxocephalus octodecemspinosus Myoxocephalus scorpius Odontaspis taurus Oncorhynchus kisutch Oncorhynchus mykiss Osmerus mordax Paralichthys dentatus American plaice Atlantic halibut cunner/yellowtail flounder'Atlantic seasnail gulf snailfish snailfishf goosefish snakeblenny daubed shanny ocean pout haddock Atlantic silverside northern kingfish Atlantic whitingh Atlantic tomcod'white perch striped bass striped mullet smooth dogfish grubby longhorn sculpin shorthorn sculpin sand tiger coho salmon rainbow trout rainbow smelt summer flounder C C 0 R A R R R C.C 0 0 R 0 0 0 R R R C R 0 C C R C C 0 C R R R A R C R 0 R R R R R 0. R 0 R R C C A 0 C R 0 R R R- R R 0. C C (Continued) 275 APPENDIX TABLE 3.2.1-1. (Continued) ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS GILL SCIENTIFIC NAMEa COMMON NAME 8 EGGS LARVAE TRAWLS NETS SEINES Paralichthys oblongus Peprilus triacanthus Petromyzon marinus Pholls gunnellus Pleuronecte$ americanus* Pleuronectes. ferrugineusJ Pleuronectes putnamik Pollachius virens Pomatomus saltatrix Prionotus carolinus Prionotus evolans Prionotus sp.Pungitius pungitius Raja sp.1 Salmo trutta Salvelinus fontinalis Scomber japonicus Scomber scombrus Scophthalmus aquosus Sebastes sp.m Sphoeroides maculatus Squalus acanthias Stenotomus chrysops Stfchaeus punctatus Syngnathus fuscus Tautoga onitis Tautogolabrus adspersus Torpedo nobiliana Triglops murrayi Ulvaria subbifurcata Urophycis sp.n fourspot flounder.butterfish sea lamprey, rock gunnel winter flounder yellowtail flounder smooth flounder pollock bluefish northern searobin striped searobin searobin ninespine stickleback skate 1 brown trout brook trout.chub mackerel Atlantic mackerel windowpane iredfish northern puffer.spiny dogfish scup Arctic shanny northern pipefish*.tautog cunner Atlantic torpedo-.moustache sculpin radiated shanny haken.R 0 0 0 C R R 0 R 0 -R C C R C C 0 R C A 0 R R R C R C 0 0 R C C 0 0 R R C C R 0 R A.C A C 0 R C R R 0 R C R R 0 R 0 R R 0 C-C-A 0 C A C 0 R R 0 0 R R 0 A 0 C Footnotes: See next page.276 APPENDIX TABLE 3.2.1-1. (Continued) Footnotes: aNames are. according to Robins et al. (1991) unless otherwise noted. Taxa usually identified to a different level are not included in this list to avoid.duplication (e.g., Gadidae, Enchelyopus/Urophycis, Myoxocephalus sp., Urophycis chuss, etc.)bOccurrence of each species is indicated by its relative abundance or frequency of occurrence for each lifestage or gear type: A = abundant (2 10% of total catch.over all years)C = common (occurring in 10% of samples but.< 10% of total catch)O = occasional (occurring in < 10 and a .1% of samples)R = rare (occurring in < 1% of samples)-=,not usually identified to this taxonomic-level at this lifestage'Predominantly Fundulus heteroclitis, mummichog, but may include .a small number of Fundulus majalis, striped killifish. dTwo species of Gasterosteus have been identified from seine samples:'G. aculeatus, threespine stickleback; and G. wheatlandi, blackspotted stickleback (both occurring commonly). eMay also include a small number of tautog.fThree species of Liparis have been identified from trawl. samples: L. atlanticus., L.. coheni, and L. inquilinus (inquiline snailfish). 9Spelling after.Faber (1976).hpreviously called silver hake; Atlantic whiting was recommended by Kendall and Naplin (1981:707). iformerly Pseudopleuronectes americanus iformerly Limanda ferruginea kformerly Liopsetta putnami IFour species of Raja have been identified from trawl samples.: R. radiata, thorny skate (common);.R. erinacea, little skate (common); R. ocellata, winter skate (occasional); and R. eglanteria, clearnose skate (rare).mPreviously called S. marinus. Recently S. mentella and S.. fasciatus have also been reported to occur in the northwest Atlantic.(Ni 1981a; 1981b). Sebastes in-coastal New Hampshire waters are probably S. fasciatus (Dr. Bruce B. Collette, U.S. National Museum, pers. comm. April 1982), but larval descriptions are insufficient to allow distinction among the three species."Three species of Urophycis havebeen identified from trawl samples: U. chuss, red hake (common); U. tenuis, white hake (common); and U. regia, spotted hake i(rare).277

3.3 BENTHOS

3.3.1 Estuarine

Benthos 3.3.1.1 Physical Environment Salinity and Temperature Weekly measurements of surface water salinity and temperature at high and low slack tides in Browns River and Hampton Harbor and daily rainfall data from Logan Airport, 'Boston; MA (National Climatic Data Center, 1990) were used..to investigate annual and monthly patterns. The Browns River salinity station is a nearfield station just downstream from the benthic transect, and about,0.5 km downstream from the settling basin outfall; the Hampton Harbor station is afarfield station away from the influence of that outfall.(Figure 2.1-6),. The most.extreme environmental conditions at.the stations sampled occur at low tide in Browns River,. because the water is less influenced by the tidal influx of sea water. Those conditions are most likely to influence the structure of the estuarine benthic communities. Precipitation (rain and melted snow.and ice) is.measured-daily by the National Climatic Data Center at Logan Airport, Boston, Massa-chusetts (Table 3.3.1-1), and has a relatively high annual variation. The thirteen-year average and 95% confidence interval for the stu'dy period from 1978-1990 was41.96 +/- 4.09 inches per year. Precipitation' that was below-the lower 95% confidence limit occurred in 1978, 1980, 1981, 1985, and 1988. Rainfall that was above the 95% confidence limit occurred in 1983, 1984,-and 1990. Rainfall in'1990 was especially high in October (when 3.34 inches fell on-October 14), fol1ow ed by August, April, and May (National Climatic Data Center 1990, Figure 3.3.1-1).Mean monthly salinity and 95% confidence interval, 1979-1990,. at low tide in Browns River ranged from 17.0 +/- 3.4 ppt in April. to 25.1+ 1.3 ppt in August (Appendix Table 3.3.1-1, Figure 3.3.1-1). In 1990, monthly salinities were below the 95% confidence limits- of the mean for 278 TABLE 3.3.1-1. TOTAL PRECIPITATION (WATER EQUIVALENT IN INCHES) BY MONTH AND YEAR TAKEN AT LOGAN INTERNATIONAL AIRPORT.BOSTON, MAa FROM JANUARY 1978 -DECEMBER 1990 AND 30-YEAR NORMALSb. SEABROOK OPERATIONAL REPORT, 1990.TIME PERIOD----------------------------------------------------

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30-YR. 1 1. :13 YR.i 1NORMAL 1 1978 :1979 1980 1981 1982 1 1983 1 1984, 1985 1 1986 1987 1988 1 1989 1990 :'MEAN!JAN 3.991 8.12: 10.55; 0.74: 0.95: 4.69: 5.03: 2.31: 1.121 .3.42: 7.281 2.50: 0.61: 3.78: 3.93ý!FEB 3.70:. 2.87: 3.46: 0.88: 6.65: 2.66: 5.00 7.81: 1.831 2.83: 0.72: 3.93: 2.51: 3.60! 3.44::MAR 4.13: 2.46: 3.03: 5.37: 0.62: 2.17: 9.72: 6.82: 2.29: 3.42: 4.27: 3.52: 3.07: 1.7)1 3.73::APR 3.73: 1.79: 3.19: 4.36: 3.14: 3.42: 6.86: 4.43: 1.62? 1.59: .9.46: 1.47: 3.58: 5.94: 3.91::MAY 3.52: 4.50: 4.24: 2.30: 1.171 2.58: 2.94: 8.77: 3.36: 1.31: 1.75: 2.86: 3.54: 6.53: 3.53:!JUN 2.92: 1.531 0.86: 3.05: 1.65: 13.20: 1.07 3.06: 3.94: 7.74: 2.62: 1*29: 2.84: 0.69: 3.35: 1JUL 2.68: 1.48: 2.36: 2.20: 3.47: 4.22: 1-.07; 4.43: 3.511 3.96: 0.82: 7.62: ý5.091 4.08: 3.41:ýAUG 3.68: 4.62: 5.02: 1.551 1.04: 2.22; 3.28: 1.60: 6.67: 3.321 2.931 1.11f 5.92: 6.57: 3.53::SEP 3.41: 1.30: 3.61: 0.82: 2.54: 1.57: 1.061 1.22: 3.00: 1.08: 7.29: 1.29: 4.61: 1.67: 2.39::OCT 1 3.36: 3.13: .3.14: 4.14: 3.43: 3.19: 3.74: 5.18: 1.65: 3*27: 2.73: 1.60; 5.71: 7.36: 3.711:NOV 4.21: 2.211, 3.29: 3.011 4.78: 3.42: 8.89: 1.68: 6.39: 6.01: +3.49: 6.57: 4.13: 1.39: 4,25::DEC : 4.48: 3.63: 1.42: 0.97: 6.27: 1.27: 4.94: 2.93: 1.211 6.38: 2.12: 1.02: 0.811 3.18: 2.78::ANNUAL: 43.81: 37.641 44.17: 29.39: 35.71: 44.61: 53.60: 50.24: 36.59: 44.33: 45.48: 34.78: 42.42: 46.50: 41.96::YEARS RANKED IN ASCENDING ORDER .:YEAR 1 80 88 81 85 78 89 79 86 82 87 90 84 83 : PRECIPI-::TATION : 29 35 36 37 38 42 44 44 45 45 47 50 54:----------------------------------------------------------------------------

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I.Source: National Climatic Data Center, 1990. Local climatological data, monthly summary.January-December, Federal Building, Asbville, NC.bNormals are based on the 1951-1980 record period. Source: National Climatic Data Center, 1989. Local climatological data, annual summary with comparative data, Boston, MA.Federal Building, Ashville, NC.OMonthly maximum since 1951. -Source: National Climatic Data Center, 1989. Precipitation 4-C z 0 I-I-0.10-8-6 4 2-0 OVERALL MEAN....... 1990 I I I -I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV EL MONTH Salinity a p* .0.I-Z-J"C 30-25-20-15-10-5-OVERALL MEAN....... 1990 0 I I I I I I I I I I II JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH a Temperature. Lii I-"C w 0~w I-30 25 20 15 10 5 0 JAN FEB MAR APR MAY JUN JUL AUG SEP CCT NOV C MONTH a not sampled during January and February 1990.Figure 3.3.1-1. Monthly means and 95% confidence limits for precipitation measured in Boston, MA, from 1978-1990 and surface salinity and temperature taken at low tide in Browns River over the entire study period (May 1979-December 1990) and in 1990. Seabrook Operational Report, 1990.280" five out of ten months (Figure 3.3.1-1). Low tide salinity in Browns River tended to have an inverse relationship with monthly precipitation.(Figure 3.3.1-1).The mean monthly salinity and 95% confidence interval at high tide in Browns River ranged from 27.1 +/- 2.3 ppt.in April to 31.5 +/- 0.8 ppt in January during the study period (Appendix Table 3.3.1-1). High'tide salinity was always higher and less variable than low tide salinity due to the influx of more saline water from Hampton Harbor into Browns River.At the Hampton Harbor station, the mean monthly low. tide salinity and 95% confidence interval during the study period ranged from 24.5. +/- 2.7 ppt in April to 29.6 +/- 0.7 ppt in September (Appendix Table 3.3.1-1). The mean monthly high tide salinity and 95% confidence interval ranged.from 30.0 +/- 0.8 ppt in May to 32.2 +/- 0.5 ppt in January;very similar to offshore, coastal salinities. The salinity in Hampton Harbor was always higher and less variable than in BrownsRiver due to its proximity to the harbor inlet. Thelow tide eleven-year average and 95% confidence interval was 27.7 +/- 0.5 ppt (Appendix Table 3.3.1-2).-Mean salinity fell below the 95% confidence limit of the overall mean in 1983, 1984, and 1990, and coincided with years of above average precipi-tation. Years of high salinity (above 28.2 ppt, the upper confidence limit of the overall mean) included 1980, 1981, and 1985., and coincided with years *of low precipitation, except for 1988 which had salinity within the 95% confidence interval and below average precipitation. The overall mean monthly temperature and 95% confidence interval at low tide in Browns River ranged from 1.0 +/- 0.6 0 C in January to 22.1 +/-l1.1 0 C in-July during the study period (Appendix Table 3.3.1-1, Figure 3.3.1-1). In 1990, average monthly temperatures were above the 95% confidence limits of the averages for seven out of the 10 months sampled (Figure 3.3.1-1).281 In Hampton Harbor, the overall average monthly'temperatures and 95% confidence

• intervals at low tide ranged from 1.0 +/- 0.5 0 C in January to 18.8 +/- 0.7 0 C in August during the study period (Appendix Table 3.3.1-1).

The temperature range in Hampton Harbor was-not as-great as Browns River, due tO its proximity to the inlet. The low tide eleven-year average temperature and 95%. confidence interval from 1980 to 1990 was 10.1 +/- 1.1%C, which includes all the annual means (Appendix Table 3.3.1-2). Low tide temperatures in 1990 were average, with a yearly mean of 10.3 +/-4.3 0 C.In summary, total annual low tide salinity in Browns River and Hampton Harbor (Appendix Table 3.3.1-2) generally had an inverse relationship to.mean'annual precipitation (Table-3.3.1-1), as would be expected. In 1983 and 1984, when precipitation'was over,50 inches'a year, annual low tide.salinity in both Browns River and Hampton Harbor were at or near all time lows. Likewise in 1980 and 1981, when precipi- .-tation was'very low, annual low tide salinities at both nearfield and farfield stations were at or near all time highs. The years 1983 and 1984 were warm at both stations; however, the coldest years varied from station to station. * *I'-'The outfall from the Seabrook Station settling basin runs into ' 1'Browns River, and usually contains the fresh water discharge from the station's sewage treatment plant-and runoff from rainfall. During the years of intake and discharge tunnel construction from November 1979 through November 1983," the outfall became saline and volume of the.discharge increased (Figure 3.3.1-2). Coincident with the first two'full years of saline discharge (1980, 1981) was a period of low rainfall (Table 3.3.1-1), and above average salinities occurred in both Browns River' and Hampton Harbor (Appendix Table 3.3.1-2), indicating'that,-the salinity increase was area-wide.' Once tunnel construction was completed I in 1983, the discharge from the settling basin diminished to..low levels.,... In 1990., 'the total annual volume of discharge (150 x-10 6 gallons) was greater than the discharge in the preceding year (86 x 106 gallons), but remained low, relative to the entire study period. .282.

• I.1.*150-125 -100-75 25 -0 A\\\\0-a-- \\\*E. .z" 1I I I I I I I I I I I .I .I e I I'I' 1 1" ." I I " I " ' I I I"I I F I O N DJ F M A M J J A D J F M A M J J A S O N DjJ F M A M J J A S o N D J F M A MýJ J A S O N D 1978 1979 " 1980 1981 1982 z U)c~o I-j~w -U) C IM 2-..00 150 125 100 75 50 25 0 1IS0.125.-100-75 -so-50-25-0SALINE OUTFALL DUE TO.TUNNEL CONSTRUCTION

\ \\\ \\ \\ \\-1---I I I I I I I I *I ,I I I I I I I i I 'W I J F M A M J J A S O N 1983 I1'oJ M A M J J A SO N DIJ F M A M J J A S O N D 1985 1986 1984 El I I I I II I A I .I I I I I I I I I I I I I I I I I I II I I I I I I ' I I I I I 1 .....J F MA M J JA.S O N D J D J F MA M J J A S 0 N J F M:A M J.J A S 0 N D 1987 1 " I 188. 1989

• I 1990 Figure 3.3.1-2. Total monthly outfall (millions of gallons per month) from the Seabrook Settling Basin into Browns River from October 1978 through December 1990. Seabrook Operational, Report, 1990.

Sediment Yearly and seasonal differences in sediment collected from 1978-1984 indicated grain size was highly variable among stations, with little year-to-year stability (NAI 1985b). Yearly averages at subtidal stations (3 and 9) showed the median grain size was in the fine sand range,, which was usually poorly sorted with organic carbon ranging from 0.97 to 2.08% (NAI 1985b). The yearly averages for intertidal Stations (3MLW. and 9MLW) showed the median grain size varied from fine sand to silt, which was often very poorly sorted. Thepercentage of organic carbon was higher than at subtidal stations and ranged 'from 1.56 to 5.86% (NAI'.1985b). Sediment parameters during the 1980-1982 period were within the range of natural variation, and did not noticeably change during the period of maximum discharge'(due to tunnel dewatering).from the settling pond.3.3.1.2 Hacrofauna Subtidal and intertidal estuarine benthic communities in Browns River (Stations 3 and 3MLW) and Mill Creek (Stations 9 and 9MLW)were typical for quiet, tidal creeks with fine-grained sediments, where average monthly salinity ranged from about 17 ppt at low tide to 31.5 ppt at high tide (Appendix Table 3.3.1-1). Spatial distribution of organisms was very patchy, and large population fluctuations/occurred seasonally, as is typical in estuarine habitats.. The polychaete Streblospio benedicti was the most abundant species in the estuary, and comprised 6 to 8% of the total density at both intertidal stations, and 14 to 20%,of the total density atboth subtidal stations (Table 3.3.1-2). Oligochaeta'.and Capitella capitata were also present in very high numbers. The clam worm ifediste diversicolor (formerly Nereis diver-sicolor) was very abundant.intertidally in Browns River. The soft--shelled clam, Mya arenaril., was also present in-substantial numbers at all sampling locations, especially Mill Creek (Table 3.3.1-2).284 .-. ...7 TABLE 3.3.1-2. MEAN NUMBER OF TAXAa AND THE GEOMETRIC MEAN DENSITYb (No./m 2) FOR EACH YEAR AND OVERALL YEARS WITH .95%CONFIDENCE. LIMITS FROM ESTUARINE STATIONS AT BROWNS RIVER (3) AND HILL CREEK (9) SAMPLED FROM 1978 THROUGH 1990 (EXCLUDING 1985).c SEABROOK OPERATIONAL REPORT, 1990.ALL YEARS STATION '1978 1979 1980- 1981" 1982 1983 1984 1986 1987 1988 .1989 1990 MEAN UPPER LOWER.Mean No.of Taxa 3 9.3MLW 9MLW MEAN 35 41 26 34 28,. 37 28 35 29 37 38 47 31 35 38 42 44 38 41 41 47 32 .27 .38 33 38 34 36 .21 36 21 27 35 .28 18 32 23 31 36 33 .121. 36 16 29 38 32 22 35 23 31 38 35 .37 39 25 31 32 35 31 28 30 32 29 36 31 34 31 '33 32 34 35 28 28 28 31 Total Density 3 9 3MLW 9MLW MEAN tO 3170 4616 4978 53606 9331 2635 1244 1182 1198 3472 2583 1707 2826 3713 2150 3619 2209 14,767 11,277 .4335 4533 620 2819 726 4764 1878,. 2488 3084. 4599 2068 4260 6136 5695. 6833 8022 2723 2187 5632 1727 3936 6940 1778 4106 5260 3205 3120 4512 6947 12,189 11,383 11,151 .5131 4203 653 6115 7525 3845 5185 7420 3622 3514 4099 7344 8424 7796 4364 1715 2980 995 4467 3990 2321 3691 4339 3139 11 63 123 473', 889 216 66 73 57 105 72 16 .90 161 50 238 29 2453 277 291 .376 28. 808 113 1530 262 259 269 .468 155 17 29 138 244 540 208 124 197 26 46 27 24 76. i22 48 279 45 125 320 276 800 303 234 19 1068 173 466 221 350, 140 60 40. 269 318 443 341 91 228 42 299 98. 84- 142 186 109 Capitella capitata 3 9 3MLW 9MLW MEAN Caulleriella .3 sp.B 9 3MLW 9MLW MEAN ffediste .3 diversicolor 9 3MLW 9MLW MýEAN 330 221- 835 1 2 3 12 9 1 101 10 40 46 .292 136 35 7 10 3 16 106 174 607 3 23 52 44 255 87 .244 8 298 48 43 1634 278 325 307 1 21 42 147 183 17 64 37 34 53 5 54 7 4 80.3 10 6 18 41 4 19 41 28 74 134 8 51 123 9 34 50 8 9 41 21 23 83 172

• 158 352 452 45 50 52 43 128' 52
• 38 94 137 64 21 29 41 205 41 7 7. 43 2 33 .29 8 22 36 13 800 1343 1169 1613 975 220 ,296 987 .150. 523 1235 199 606 941 391 170 164 101 241 135 57 513 184 6 29 93 18 86- 144 51.125 183 167 410 223 45 89 143 18 90 115 33' 102. 137 76 (continued)

TABLE 3.3.1-2. (Continued) 0'0O ALL YEARS STATION 1978 1979 198b 1981 1982 1983 1984 1986 1987 1988 1989 1990 MEAN UPPER LOWER Mya arenaria 3 ' 69 158 92 181 *132 75 31 21 30 12 35 64 56 82 38 9 265 427 299 246 148 168 157 34 53 83 69 208 143 213 95 31ILW 106 224 26 179 117 103 22 13. 27 12 "73 25 50 83 30 9MLW 100 328 62 400 141 70, 86 13 73 39 425 266 110 172 70 MEAN 118 265 82 237 .134 98 55 19 42 26 93 98 82 102 65 Oligochaeta 3 242 270 204 651 2189 556 225 95 133. *768 301 156 319 485 209 9 16 100 2910 969 ... 1058 1603 162 528 131 272 233 260 327 576 186 3MLW 87 186 318 320 350 292 382 968 215 322 409 48 258 399 167 9MLW 574 810 1067 861: 565 2877 572 742 161 351 2888 362 714 1172 435 MEAN- 119 253 671 646 823 931 298 437 157 392 .537 163 372 474 292 Spio setosa 3 38 39 65 155 159 120 113 151 171 244 447 334 133 190 93 9 50 59 .287 346 170 16 3 75 6 315 236 110 69 137 35 3MLW 7 9 8 6 4 8 2 46 25 46 24. 26 12 21 7 9MLW 54 59 43 78 48 30 8 65 2 32 41 117 35 61 20 MEAN 30 33 51 72 51 26 10 76 16 104* 102 103 45 61 33 Streblospio 3 367 123 193 525 1064 552 239 99 '66 550 181 56 231 359 149 benedicti 9 106 26 2396 525 81 538 16 161 49 744 167 400 178 368 86 3MLW 439 505 1010 928 3584 525 535 1421 316 1306 3227 259 827 .1256 545 9MLW 566 434 466 2700 2354 3215 1560 1299 11 744 399 1023 .710 1309 385 MEAN 314 163 684 912 925 .842 242 415 58 794 445 ý278 .395 529 295 ayearly mean number of taxa.,= mean of three seasonal totals (where seasonal total total number in all, five 1/16.m2 breplicates combined)Yearly mean density = mean of three seasonal means (where seasonal mean = mean of five replicates) All years mean = mean of 36 seasonal means (3.seasons x 12 years) Total density of all macrofaunal organisms (number/m 2) showed year-to-year variations during the thirteen-year study period. These variations appear to be related to area-wide environmental trends, since major changes often occurred simultaneously in both Browns River and Mill Creek (Figures 3.3.1-3, 4). Subtidal stations in Browns River.(Station 3) and the reference station inMill Creek (Station 9) had highly significant differences in densities among years; 1980-1981 ranked with years of highest density, and 1984 and 1987 ranked with years of lowest abundance at both.stations according to multiple comparison tests (Table 3.3.1-3). Differences among years were less pronounced at intertidal stations; however, densities were at or near the all time high in 1981 afid at the all time low in 1987 at both stations, (Table 3.3.1-2,3). In 1990, total densities at all stations were lower than average, but within the range of previous years. This trend was more evident at the intertidal stations, as indicated by the multiple comparison test.Precipitation and its effect on salinity in the tidal creeks seems to be an important environmental factor causing area-wide

• changes in total macrofaunal density. In 1980 and 1981, when annual precipita-tion was lowest (Table 3.3.1-1), salinity was, very high (Appendix Table 3.3.1-2), and ,total densities at both subtidal stations (Stations 3 and 9) were very high (Table 3.3.1-3).

In 1984, when annual rainfall was very high and salinities at both stations were very low, total densities at both stations were also very low.. Low densities in 1987 could be accounted for by heavy rainfall in April and September, normally periods of high recruitment. Density variations at intertidal stations appeared to be less associated with fluctuations iff precipitation than at..subtidal stations.The mean number' of taxa collected annually at all four stations ranged from 16 to 47.during the thirteen-year study period (Table 3.3.1-2). Annual variations' in the number of taxa were highly ,significant at all stations except Station 3 (Table 3.3.1-3). Annual changes in the number of taxa were generally similar At all four 2'87 Subtidal Station 3 Total Density Number of Taxa U, z w 0 0 0-'I 6-.5-4-3-2-00, x LL 0 z w 70-60-50 -40 30 80 -T:-1 .I" 9 8 811 82 " 84 86 I I 8 I.78 79 80 81 82 83 84 86 87 88 89 90 78 79 80 81 82 83 84 86 87 88 89 90 YEAR, : YEAR Subtidal Station 9 Total Density Number of Taxa 0 0j 6-5-4-3-2-1*k/x LL 0 0 z 80 60 40 " 30 20 I-! ...." I .I I I I I I I I I I I 78 79 80 81 82 83 84 86 87 88 89 90 78 79 80 81 82 83 84 86 87 88 89 90 YEAR YEAR Figure 3.3.1-3. Yearly means and 95% confidence limits for the log (x+1) density (no./m 2) of macrofauna and mean number of taxa per 5/16m 2 collected at subtidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985). Seabrook Operational Report, 1990.288 Intertidal Station 3MLW Total Density.Number of Taxa 6-5-4-3.-70 -z 0-j 3ý oooooýLL.0 0i z z wi 60-50-40-30-20-10-/~A I I. I I I I I I I I *I.NIN 2-0 I ...........*I I I 1 I 1 I 1 1 1 1 1 1 78 79 80 81 82 83 84 86 87 88 89 90 I I I. i l I ' I l 6 ' 1I 78.79 80 81 82 83 84 86 87 88 89 90 YEAR YEAR Intertidal Station 9MLW Total Density Number of Taxa 6-5-4-3-(, z 0-j lo" K/'1 X I-0 z z O 70 50-40-30 20-10/1 0 I i , I I I I I I i I -I 1 1 78 79 80 81 82 83 84 86 87 88"89-90-II I I I I I I I I I I 78 79 80 81 82 83 84 86 87 88 89 90 YEAR YEAR Figure 3.3.1-4.Yearly means and 95% confidence limits for the log (x+l) density (no./m 2) Of macrofauna and mean number of taxa per 5/16m 2 collected at intertidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985). Seabrook Operational Report, 1990.289 TABLE 3.3.1-3.RESULTS OF ORE-WAY ANALYSIS OF VAIIANCE2 AMONG YEARS FOR THE MEAN NUMBER OF TAXA (per 5/16 r) AnT) LOG (x+l) TRANSFORMED DENSITY (No./,,) OF-THE MOST ABUNDANT ESTUARINE SPECIES AND THE TOTAL DENSITY OF MACROFAUNA COLLECTED AT ESTUARINE STATIONS FROM 1978 THROUGH 1990 (EICLUDING 1985). SEABROOK OPERATIONAL REPORT, 1990.I STATION Fb MULTIPLE COMPAIISONSC -SUBTIDAL STATIONS STATION. Fb MULTIPLE CMIARISONSC -INTERTIDAL STATIONS Number of Taxa 3 2.18 NSd 82 81 79 80: 88 89 86 90 78 87 83 84 3MLW 2.95"*' 81 79 82 86 89 80 88 78 83 90 87 84 9 6.02**" 80 81 83 86 79 82 90 88 78 89 87 84 9MLW 3.07*' 81 90 82 86 80 79 83 88 89 78 84 87 Total Density 3 3.92** 82 81 80 79 88 78 83 89 90 84 87 86 3MLW 2.55* 82 89 81 79 80 86 78 88 83 84 90 87 9 80 81 88. 83 82 78 86 90 79 89 87. 84 9MLW 2.42* 81 82 83 89 80.88 84 79 86 90 78 87 itreloio 3 2.04 NS 82 83 88 81 78 84-80 89 79 86 87 90 3MLW 1.73 NS 82 89 86 88 80 81 84 83 79 78 87 90 n9 1.72 WS 80 88 83 81 90 89 86 78 82 87 79 84 9MLW 3.93"* 83 81 82 84 86 90 88 78 80 79 89 87 Oligochaeta 3 1.94 NS 82 88 81 83 89 79 78 84 80 90 87 86 3MLW 1.09 NS 86 89 84 82 88 81 80 83 87 79 78 .90 9 4.46* 80 83 82 81 86 88 90 89 84 87 79 78 9MLW 0.92 NS 89 83 80 81 79 86 78 84 82 90 88 87 3 2.02 NS 82 81 83 80 88 86 89 84 79 87 90 78 3MLW 3.98 8281 83 86 80 84 88 79 89 87 90 78 9 3.83*** 80 88 86 83 82 81 89 90 78 87 79 84 9MLW 3.88* 88 83 90 81 84 78 82 86 89 80 79 87.(continued) if. T _t TABLE 3.3.1-3. (Continued) STATION Fb MULTIPLE COfPARISONSc " SUBTIDAL STATIONS STATION Fb MULTIPLE CONPAISONSc STATIONSolor 3 2.68* 82. 81 79 180 88 78 86 89 84 83 87 90 3MLW' 1.43 NS 81 79 89 80 86, 82 78 88 84 83 90 87 9 2,.75' 81 86 82 80 88 79 89 78 90 84 83 87 9MLW 3.301* 84 81 86 78 79 82 80 89 83 88 90 87 Mvyarenaria 3 2.47* 81 79 82 80 83 78 90 89 84 87 86 88 3MW 1.81NS 79 81 82 78 93 89 87 80 90 84 86 88.9 1.41NS 79 80 78 81 90 83 84 82 88 89 87 86 9MLW 2.85* 89 81 79 90 82 78 84 87. 83 80 88 86 1Cauleriella 3 7.20*** 80 78 79 88 84 86 89 90 83 82 87 81 3Mg 2.67* 80 86 88 79 78 87 89. 83 84 90 82 .81 sp.9 1.32NS 81 82 80 79 83 88 86 78 84 89 90 87 9MLW 3.71*. 82 84 86 79 83. 80 81 88 90 78 89 87 S setosa 3 2.17 NS 89 90 88 87. 82 81 86 83 84 80 79 78 3MLW 0.96 NS 86 88 90 87 89 79 80 83 78 .81 82 84 9 2.65* 81 88 80 89. 82 90 86 79 78 83 87 84 9MLW 1.32NS 90 81 86 79 78 82 80 89 88 83 84 87 I,..'Degrees of freedom for the model (years).= 11 Degrees :of freedon for the error -24 b NS not significant (p>0.0S)jsignificant (0.05>p>0.01) = highly significant (0;01p>0.00l) = very highly significant (I50.001)'Multiple comparison test is Waller-Duncan K-ratio T test Horizontal lines connect statistically similar years.dSince the F value is NS, years are reported in. order of decreasing abundance stations for most of the study period. Like total density, the number of taxa collected in 1984 and 1987 ranked among.the lowest two or three years of the study period at every station sampled. Number of taxa in 1981 ranked in the highest group at every station with the multiple comparison test (Table 3.3.1-3). The seasonal cycle at each of the four stations showed that the highest number of taxa usually occurred in August or May, and the lowest number :occurred in November, (NAI 1987b).The annual trend in the number of taxa seems to show an inverse relationship with the annual precipitation. This was evident at all four stations., but was more prominent at subtidal stations. In .-1984, the mean number of taxa was at or near the all time low at every station, and 1984 was the second consecutive year of extremely high precipitation (Table 3.3.1-1). A substantial decline in'the number of taxa was also observed in 1987 when rainfall in April reached a 30-year high for that month, and salinity in the second week of April was <2 ppt (NAI 1988a). In 1990, mean number of taxa was similar to past years (within the overall 95% confidence interval) at three out of four L stations; at Station 9MLW the mean was higher than average, but had very, wide confidence limits (Figure 3.3.1-3,4; Table 3.3.1-2).Streblospio benedicti is a cosmopolitan opportunistic poly-chaete (Grassle and Grassle 1974), and one of the first to colonize after a perturbation of the environment (Rhoads et al. 1978). It is the most abundant species in the estuary, and extremely high densities occurred during any season 'at both intertidal and subtidal stations.Such high densities were rarely sustained into the next sampling period, causing tremendous population fluctuations (NAI 1987b). With such high natural variation, no significant differences among years were found except at the intertidal station (9 MLW) in Mill Creek (Table 3.3.1-3).The most consistent trend among'stations was that in general, the densities were well below average in 1987. Extremely high monthly rainfall occurred 'in April 1987 and also inSeptember (Table 3.3.1-1).The dramatic overall population decrease in 1987 was followed by an'increase of an order of magnitude in.1988 at three out of four stations. '292 In 1.983, the inverse relationship between precipitation and population density did'not, hold true. Even though annual rainfall was very high, annual densities were also very high.at.two out of four stations.(Table 3.3.1-2). In 1990, the annual density of S. benedicti was at an all-time low in Browns River (Stations 3 and 3 MLW), but was intermediate in Mill Creek (Stations 9 and 9MLW). Average densities for the study period were similar for. each intertidal and subtidal station pair; the highest densities occurred intertidally (Table 3.3.1-2).The class Oligochaeta is a species complex that is abundant in the estuary.. The seasonal cycle of oligochaetes indicated that peak densities occurred during any season (NAI 1987b), but were not sus-tained. No consistent differences in densities were found between Browns River and.Mill Creek stations (Table 3.3.1-2). No significant differences occurred among years, except at the subtidal station in Mill Creek (Table 3.3.1-3). When examining the.yearly densities, population fluctuations were not consistent, probably because they were represented by more than one species. Oligochaete densities. in 1990 were similar to previous years, except in the Browns River, where they were the lowest recorded to date.The opportunistic polychaete Capitella capitata was common at-both intertidal and subtidal stations and typically showed large annual.population fluctuations. Browns River densities were consistently lower than densities at Mill Creek (Table 3.3.1-2) .Highly significant differences were found among years at all stations except the subtidal station in Browns River (Table 3.3.1-3). Following the very low population levels in 1987 atall stations, populations increased greatly in 1988, particularly-in Mill Creek (Figures 3.3.1-5,6). Densities declined at every station in 1989, and averaged less than 100/mi 2 at both stations in Browns River (Table 3.3.1-2). In 1990, densities in Browns River were very near the all time low (whichoccurred in 1978), but in Mill Creek, they were near-or above average (Tables 3.3.1-2,3). 293 I .Subtidal Station 3 Hediste Capitella 5-6-4-0'-j 3-2-5-4--A C-z C)0 0j r 3-2-/0 , * * * * * , ; * * ," 78 79.80 81 82 83 84 86 87 88 89 90 I I I 79 80 81 83 I I I I I 8 83 84 86 87 88 89 90 78 82 YEAR YEAR Subtidal Station 9 Hediste Capitella 5 4 3 2 6 5 F-z LI.0_j I-U, z 0-J.4 3 2 1 , 1 1 0 78 79 80 81 82 83 84 86.87 88 89 90 YEAR 78 79 80 81 82 83 84 86 87 88 89 90 YEAR Figure 3.3.1-5.Yearly means and 95% confidence limits for the log (x+l)-density (no./m 2).of Hediste diversicolor and Capitella capitata collected at subtidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985). Seabrook Operational Report, 1990.294 Ihtertidal Station 3MLW Hediste Capitella 5 4 6-5-z w 3 2 U).z w 4-3-2-1 0 1 I I, I I I.. .] ..I 78 79 80 81 82 83 84 86 87 88 89 90 78 7 98 I I I I I I I 8 78 7 9 80 81 82 83 84 86 87 88 89"90 YEAR YEAR Intertidal Station 9MLW Hediste Capitella , 5-4-3-2-6-1.I-z 0-j-F/z 0-J.5-4.3-L/I III 0-2-/I , I I I I I I I I I 1 78 79 80 81 82 83 8486 87 88 89 I I I! I" 90 78 79 80 81 82 83 84 86 87 88 89 9"0 YEAR YEAR Figure 3.3.1-6. Yearly means and 95% confidence limits for the log (x+l) density (no./m 2) of Hediste diversicolor and Capitella capitata collected at intertidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985). Seabrook Operational Report, 1990.295 Caulleriella sp. B is a polychete that was occasionally abundant in the estuary. It rarely sustained densities of over 100/M 2 for more than three consecutive years, and in 1987 it had annual densities of less than 10 at three-.of the. four estuarine stations (Table 3.3.1-2). Significant differences among years occurred at all stations except the subtidal station in Mill Creek (Table 3.3.1-3). Relatively low population densities occurred at three out of four stations in 1987,.while 1980 ranked among the top three years at three out of four stations. ..In 1989, densities.declined substantially from the previous year at all four stations, and remained low at all four stations in 1990 (Table 3.3.1-2).The clam worm, flediste diversicolor, is a euryhaline species that is most common intertidally where there is a mixture of fresh and salt water (Pettibone 1963). It is an omnivore, frequently abundant in nutrient rich areas, and has been considered an opportunist and an indicator of pollution (Hull 1987). Both intertidal and subtidal stations at Browns River had substantially higher densities than stations of comparable depth at Mill Creek (Table 3.3.1-2). Intertidal stations had higher densities than subtidal stations (Table 3.3.1-2), particularly Station 3MLW in Browns River. Highly significant differ-ences among years occurred at all stations except Station 3MLW, where ff.diversicolor was most abundant' (Table 3.3.1-3).

• ff. diversicolor abundances at all four stations followed the trend of numbers of taxa, total density, and S.-benedicti and C.capitata abundances; the extremes of population density appeared.inversely related to precipitation, with one exception.

Density was high in 1981 at all four stations, and low in 1987, and was grouped accordingly with multiple comparison tests (Table 3.3.1-3). Low abundances' occurred atthree out of four stations in 1984; however, at Station 9MLW, it reached its highest annual abundance. In 1990, the year with the.third highest rainfall, flediste. populations declined substantially at all stations (Figures 3.3.i-5, 6).296 Mya arenaria, the soft-shelled clam, has important commercial and recreational value within the estuary. Mya spat (<5 mm) and a few yearling clams (512 mm) predominate in estuarine samples. Densities of Mya spat were statistically similar among years at two of the four stations (Table 3.3.1-3); however, densities were usually higher in Mill Creek than in Browns River (Table 3.3.1-2). Mya densities in 1990 in Mill Creek were well above average.In summary, substantial variability has occurred throughout the estuary in total density, number of taxa, and density of the most dominant species. As these changes were not site-specific, and tended to occur simultaneously at Browns River and Mill Creek (except in 1983), they were probably related to area-wide environmental variables such as precipitation and corresponding salinity changes, temperature, and abundance of predators and competitors. The largest population increas-es for most of the estuarine polychaetes, total density, and number of taxa in both Browns River and Mill Creek occurred during the period of low precipitation andhighest salinity (1980-1983). By 1986, physical and biological parameters had returned to the pre-1980 conditions. In 1984 and 1987 the most pronounced drops in density and number of taxa which 6ccurred during the study period seemed to be related.to high precipitation and low salinity. These biological parameters recovered, and approached the average range within one or two years. In 1990, a year of intermediate salinity (although in some months, lower than average) and slightly above average precipitation, densities were typically within normal range, although lower than average.297

3.3.2 Marine

Macroalgae-3.3.2.1 Macroalgal Community Number of Taxa The effect of depth on light quality and quantity is reflected in the diversity (number of taxa), total biomass and species composition of the macroalgae community from hard substrate rock and ledge. The numberof taxa is an important measure of.community diversity. Macro-algae taxa richness is measured two ways. Although a qualitative L measure, the number of taxa from "general collections" represents the maximum number occurring at a station during a given season, depending on the visibility and other factors affecting collection efficiency. The number of taxa collected from destructive samples represents a quantitative measure in a 1/16 m 2 area, and thus-can be statistically tested.A total of 128 taxa has been collected during the preopera-tional study from 1978 through 1989 in general collections (NAI 1990b).No new taxa were collected in 1990. This number includes plants not identifiable to the species level that were placed in genera or higher classifications. Historically, over half (51%) of these taxa were red algae (Rhodophyta), with the remainder divided almost evenly between brown algae (Phaeophyta, 27%) andgreen algae (Chlorophyta, 22%)(NAI 1990b). This proportion is typical for the New Hampshire coast (Mathie-.son and Hehre 1986). In 1990, the proportions were slightly different. More than half of the. species were red algae (57%), more than one quarter brown algae (29%), and the remainder (14%) were green algae (NAI 1991).Spatially, the highest number of taxa collected from general collections throughout the historical period was in the mean low water (MLW) zone (a.median of49 at Station B5MLW); numbers decreased with increasing depth, with the fewest taxa collected at the deepest stations (Figure 3.3.2-1). The lower numbers at the deep 'stations were due to 298 70-65-MEDIAN RANGE a 1990* AUGUSTONLY 4 x I--0 LU z 60-55 50-45-40-35 30 25 20 15 10 51 I i I a I a w I1'lT I]m I 0 I U I I I I I I I I 0 I I B1 MSL B5MSLB1MLWB5MLW B17 B35 216

• B19 INTERTIDAL SHALLOW MID-DEl 2 I 2 I B31 IB1.3* B04*2341 PTH DEEP STATIONS Figure 3.3.2-1.Preoperational (through 1989) median and range and 1990 value of number of taxa collected in triannual general collections at Stations B1MSL, B1MLW, B17 B19, B31 (1978-1990), B5MSL, B5MLW, B35 (1982-1990), and annual collections at B16 (1980-1984; 1986-1990), B13, B04 (1978-1984; 1986-1990) and B34 (1979-1984; 1986-1990).

Seabrook Operational Report, 1990.299 several factors: lower light, lower temperatures, fewer annual taxa and ,a less-intensive sampling effort (once per year). Number of taxa collected also decreased with increasing elevation from MLW (e.g., at the MSL stations). This is consistent with other New Hampshire studies"(Mathieson et al. 1981).In 1990, numbers of taxa from general collections were below the median value for the preoperational period at all stations, although more than half were within the range of previous years. Numbers of taxa in 1990 were the lowest ever recorded at both intertidal MLW stations,, nearfield mid-depth, and farfield deep stations. The 1990 values were within the range of previous years at both of the high intertidal and shallow subtidal stations, and farfield mid-depth and nearfield deep stations. A decrease in the annual number of taxa was first noted in 1989, when the number of taxa at half of the stations was lower than the lowest recorded annual value (NAI 1990b)..For the most part, the numbers of taxa collected at corre-sponding nearfield and farfield stations from 1978 to 1989 were similar.In the intertidal zone, the nearfield station (BlMLW) had fewer taxa at the approximate mean low water mark and a greater number of taxa at mean sea level than.its farfield counterpart at Rye Ledge (B5MLW), a trend that continued in 1990 (Figure 3.3.2-1). In the mid-depth zone, fewer taxa have been recorded throughout the study at the station near the.intake (Station B16) than at the discharge and farfield stations (B19 and B31). This may be due in part to. fewer annual collections at B16 (once per year).than atB19 and B31 (three times per year). In 1990,.the number of taxa was lower at the nearfield mid-depth station (B19)than at the farfield (B31).Numbers of taxa collected quantitatively from destructive. sampling paralleled the trends noted in general collections.. Histori-cally,.the average number of taxaduringthe preoperational period was highest at the farfield intertidal and shallow subtidal stations (Figure 3.3.2-2). Nearfield intertidal and shallow subtidal areas had moderate 300 25 -20 T LU 0 T0 "f1. ..015 0 I I]o To 10 ~o10.z 5-: 0-I I .. p ' 'I ' 1.B1MLW B5MLW B17 B35 B16 B31 B19. B13 B04 B34 INTERTIDAL. SHALLOW MID-DEPTH DEEP DEPTH ZONE& PREOP (nearlield) 0 1990 (nearfield). 1600 0 PREOP (far"ield) 13 1990 (far'ield) 1400 1200T+/- I 1000-I I Co" 0C. 600 400 200 0' *INTERTIDAL J SHALLOW. MID-DEPTH DEEP DEPTH ZONE Figure 3.3.2-2. Mean number of taxa (per 1/16 mi 2), total biomass (g/m 2) and 95% confidence limits of macroalgae collected at intertidal and subtidal stations during the preoperational period (see Figure 3.2.2-1 for years sampled) and in 1990.Seabrook Operational Report, 1990.301 numbers of taxa and deep stations had the lowest numbers of taxa.Numbers of taxa in 1990 showed similar spatial relationships. However, numbers of taxa were significantly lower in the intertidal area in 1990 at both nearfield and farfield stations, although the difference was more pronounced at the farfield station (Table 3.3.2-1; Figure 3.3.2-2.). Significant differences in numbers of taxa were also noted in 1990 at.mid-depth stations. However, trends in 1990 were not similar at all three stations, as indicated by the significance of the Station X Preop-op interaction term (Table 3.3.2-1). At the intake station (B16), numbers of taxa were higher than average, while numbers of taxa were lower at both the discharge. and farfield stations (B19 and B31).Numbers of taxa 3n 1990 were similar to previous years at the shallow subtidal and deep stations.. Total Biomass The effect of light on the quantity of macroalgae was evident from the changes in total biomass with depth. Historically (1978-1989), August total biomass values have been highest in the intertidal areas (Figure 3.3.2-2). In 1990, total biomass values were significantly lower than those observed historically at both nearfield and farfield intertidal stations. This difference was pronounced at the nearfield area, as indicated .by the significant Station-Preop-Op interaction term in the ANOVA (Figures 3.3.2-2,3; Table 3.3.2-1).Shallow subtidal areas also historically had high biomass values. Levels in 1990 were similar to the historical averages-at both stations (Figures 3.3.2-2,3; Table 3.3.2-1). The-intake Station B16 historically has had total biomass levels that were intermediate between shallow subtidal and mid-depth discharge and farfield stations, a trend that continued in 1990. At the discharge mid-depth station, total biomass in 1990 was signigicantly higher than previous years, whereas biomass was lower than previous years at the intake ahd farfield stations. The deepest stations (B04, B13, B34) have historically had 302, __. -1 TABLE 3.3.2-1.RESULTS OF ANALYSIS OF VARIANCE OF NUMBER OF TAXA (per 1/16 m 2) AND TOTAL BIOMASS (g per mi) OF MACROALGAE COLLECTED IN AUGUST AT INTERTIDAL, SHALLOW SUBTIDAL, AND DEEP STATION PAIRS, 1978-1990. SEABROOK OPERATIONAL REPORT, 1990.LW PARAMETER DEPTH ZONE SOURCE OF VARIATION df SS Fe Number of Taxa Intertidal Preop-0a 1 33.1 4.48*Station 1 161.0 21.78-**Year- (Preop-Op) 11 1072.7 13.19**Station X Preop-Opd 1 19.1 2.58 NS Error 91 672.6 Shallow Preop-Op ..1 6.5 1.46 NS Subtidal Station 117.4 26.46***Year (Preop-Op) 11 270.4 5.54***Station X Preop-Op 1 .11 0.25 NS Error .91 403.7'Mid-depth Preop-Op 1 6.0 **3.23 NS Station* 2 .22.8 6.14**Year (Preop-Op) 11 134.2 6.56***Station X Preop-Op 2 18.5 4.98**.Error 158 294.1 Deep Preop-Op 1 0.6 0.58 NS Station 2 3.4 1.57 NS Year (Preop-Op) 10 -- 47.5 4.37***Station X Preop-,Op 2 0.5 0.20 NS Error 159 172.8 (continued) 4 TABLE 3.3.2-1.(Continued) PARAMETER DEPTH ZONE SOURCE OF VARIATION df SS Fe Total Biomass Intertidal Preop 1 977,400.4 12.00***Station 1 37,676.4 0.46 NS Year (Preop) 11 12,685,235.8 14.16***Station X Preop 1 494,681.3 3 6.07*Error 91 7,412,357.0 Shallow Preop 1 7.3 0.00 NS Subtidal Station 1 802.8 0.01 NS.Year (Preop) 11 2,381,208.8

• • 2.66**Station XPreop 1 7,546.9 0.09 NS Error 91 7,413,102.6 Mid-depth Preop 1 53,650.0 1.35 NS Station 2 1,486,648.3 18.75**Year (Preop) 11 1,647,974.4 3.78***Station X Preop 2 214,368.6 2.70 NS Error 158 .6,263,875.5 Deep.. Preop 1 185.4 0.08 NS Station 2 36,710.1 7.86***Year (Preop) 10 59,345.0 2.54**Station X Preop 2 17,370.2 3.72*Error 159 371,397.4 aPreop-Op=

1990 vs. preoperational (1978-1989) period (Stations B1MLW, B17, B19, B31: 1978-1989; Stations B5MLW, B35: 1982-1989; Station B16:: 1980-1984, 1986-1989; Stations B13,B04: 1978-1984, 1986-1989; B34: 1979-19,84, 1986-1989) Stations within depth zone Intertidal: BlI, B51; shallow subtidal: B17, B35; mid-depth: B16, B19, B31; deep: B04, B34, B13 CYearnested within preoperational and operational periods regardless of area dinteraction between main effects eNS = Not significant (p>0.05)* = Significant (0.05>p>0.01) = Highly significant (O.Ol_>p>..001) Very highly significant (p!.O01)~77 Station B1MLW Station B17 E crl 2400 2200-2000-1800 -1600 1400-1200 1000 860 600O 400 0 2400 2200 2000 1800 1600T 1400 1200ý1000 800 600 400 20078 78 79 80 81 .82 83 84 85 86 87.88 89 90 I -I I I I .1 I I I I I I I 78 79 80 81-82 83 84 85 86 87 88 89 90 YEAR Station B19 YEAR Station B04 800 -700-600-0 CF.9 50 400-300-200-100-0 Ez 800 -700 600 5 00 -.400-300-200-100-0.14 78 79 80 81 82 83 84 85 86 87 88 89 90 I ............I I .I I I I I I .I 1 I 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR YEAR Figure 3.3.2-3. Annual mean biomass (g/m 2) and 95% confidence limits for macroalgae collected in August at selected nearfield benthic stations. Seabrook Operational Report, 1990.305 lowest biomass levels. This trend continued in 1990. 'However, total biomass in 1990 was significantly lower than average at both.nearfield discharge and farfield deep stations and higher than average at the deep intake station.Community Analysiis Depth-related differences in species distribution have led to the development of distinct communities at the different depth zones.These communities were evaluated through the use of two techniques: examination of the relative abundance (percent of total biomass) of the seven.most abundant taxa, and utilization of numerical classification. Changes in relative abundahce give an indication of general changes in the dominant taxa.. Numerical.classification quantitatively evaluates similarities in community structure among years using all but the rarest taxa.Depth differences among benthic stations were reflected in changes in the relative abundance of the seven dominant taxa (Figure 3.3.2-4). During the preoperational period, Chondrus crispus was domi-nant in the shallow subtidal and intertidal. lastocarpus. stellatus was restricted to the intertidal zone. Phyilophora spp. (P. truncata and P.pseudoceranoides) were most abundant at mid-depth Stations B19, and to a lesser extent B31 and B16, as well as deep Station B13. Ptilota serrata was dominant at the deepest (18.9, 21.0 m) Stations B04 and B34.Trends in community composition in 1990 weresimilar to previous years, with a few exceptions. In the intertidal zone, the relative importance of Chondus crispus diminished, with a corresponding increase in Mastocarpus stellatus (Figure 3.3.2-4). Percentages of M.stellatus in 1990 at B1IMLW (73%) were six-fold higher thanthe preopera-tional average (11%). The increase in M..stellatus in the farfield intertidal was approximately double the. average of previous years.306 Preoperational Period 100 , R 80 l Ptilota serrata.v Phyllophora spp.z 6 60" e* "'V Corallina officinalis

• E2 Phycodrys rubens.Cystoclonium purpureum w 40 .. Chondrus crispus-Mastocarpus stellatus El Other Taxa ,, 20 , 0-B1MLW B5MLWI B17 835 B16 831 B19 B13 B04 B34 INTERTIDAL SHALLOW MID-DEPTH DEEP STATION 1990 100*~~ %* %,%8 , Ptilota serrata o 0 % Phyllophora spp.%' Corallina officinalis z E2 Phycodrys rubens U Cystoclonium purpureum% % Chondrus crispus> Mastocarpus stellatus...... Other Taxa w 20.0 BIMLWB5MLW B17 B35 B16 831 B19 B13 ý04 834 INTERTIDAL SHALLOW MID-DEPTH DEEP STATION Figure 3.3.2-4. Relative abundance

(% biomass) of dominant macroalgae at marine benthic stations in August for the preoperational period (see Figure 3.3.2-1 for dates)and 1990. Seabrook Operational Report, 1990.307 Proportions of C. crispus also decreased in the shallow subtidal zone at the nearfield station only, coinciding with a corresponding increase in Phyllophora spp. The proportion of CG. crispus also decreased at the farfield mid-depth station (B31), with a corresponding increase in..Corallina officinalis. Changes in C. crispus biomass in 1990 will be further discussed in Section 3.3.2.2.. At the discharge station (Bl9), relative abundance of:Phycodrys rubens-was higher than average, replac-ing Phyllophora. spp. Species composition at.,the remaining stations in 1990 was similar to previous years.Community composition differed in some cases between nearfield stations and their farfield counterparts. Historically, Station B5MLW had a larger proportion of M. stellatus and correspondingly smaller proportions of Chondrus crispus in comparison to Station B1MLW.Increases in M. stellatus at the nearfield area in 1990 reduced this discrepancy (Figure 3.3.2-4). At shallow subtidal stations, farfield Station B35 historically had higher percentages of Phyllophora spp., Corallina officinalis, and Cystocloniumpurpureum when compared to Station B17, where the overwhelming dominant Was Chondrus crispus.Reductions in the proportion of C. crispus in 1990 at the nearfield station increased the similarity of these two stations. Farfield Station B31 was typified by three dominants, Phyllophora spp., Corallina officinalis, and Chondrus:crispus; whereas at nearfieldStationB19, Phyllophora spp. predominated and Phycodrys rubens occurred.as a subdominant. In 1990, relative abundance of C. crispus at B31 was lower than'previous years, and abundance of P. rube'ns was correspondingly higher. Deep stations differed mainly in the presence:,of C. officinalis as a subdominant at the nearfield Station (B04). In 1990, C. officina-]is was relatively less abundant at Station B04 than during the histori-cal period.The focus of the multivariate community analysis was to determine if plant operation had caused changes in the species assem-blages typically found in each depth zone. The algae community in 1990 308 was judged to be similar to previous years if 1990 collections at a given station grouped with the majority of collections from. the pre-operational period. This was true in all cases in.1990.Numerical classification of samples collected from 1978 through 1990 produced results consistent with previous analyses (NAI 1985b, 1990b). Community structure was stable from year-to-year, but changed markedly with depth (Figure: 3.3.2-5). Intertidal, shallow subtidal, mid-depth discharge and farfield (B19, B31), mid-depth intake:(Bl6),:deep intake (B13) and deep discharge and farfield stations had distinct species assemblages. Nearfield stations were more similar to their farfield counterparts than to other areas.Differences in community structure at the different station groups were typified by differences in the biomass of dominant species in each group. Intertidal and shallow subtidal areas (Groups 5 and 6)historically had been characterized by large amounts of Chondrus cr-ispus (Table 3.3.2-2). Although C. crispus biomass was lower'in 1990 than in previous years, it remained a dominant in these areas. Increased biomass of secondary dominants, Phyllophora spp. in the shallow subtidal area and Mastocarpus stellatus in the intertidal area, coincided with reduced biomass of Chondrus. Phyllophora spp. was predominant at mid-depth areas (Groups 3 and 4) and deep intake Station B13 (Group 1).Large amounts of Phycodrys rubens and presence of two typically shallow subtidal species as subdominants (Cystocloniumpurpureum, Cerarnium rubrum) distinguished Station B16 (Group 4 except in 1984) from the other mid-depth stations. With the exception of the decreased impor-tance of C. crispus, 1990 community dominants were similar to previous years. The community at Station B13 (Group .1) has consistently been a transition zone between mid-depth areas, as indicated by the predomi-nance of Phyllophora spp., and deep areas, suggested by the presence of Ptilota serrata. At this depth (18.3 m), the shallow subtidal and intertidal species were not part of the community. This trend continued in 1990, although biomass of Phyllophora in 1990 was lower than the 309 in group imilarity no. of samples between group similarity r"10 U,-j IL 0 z.20.30 .40 .50 .60 .70 .80 BRAY-CURTIS SIMILARITY Figure 3.3.2-5. Dendrogram formed by numerical classification of August collections of marine benthic algae, 1978-1990. Seabrook Operational Report, 1990..90 310- '0 TABLE 3.3.2-2.

SUMMARY

OF SPATIAL ASSOCIATIONS IDENTIFIED FROM NUMERICAL CLASSIFICATION (1978-1990) OF BENTHIC MACROALGAE SAMPLES COLLECTED IN AUGUST. SEABROOK OPERATIONAL REPORT, 1990.to FH WITHIN/ GROUP BIOMASS (g/m 2)MEAN BETWEEN STA- DEPTH GROUP PREOPa 1990 GROUP TIONS (m) YEARS INCLUDED SIMILARITY DOMINANT TAXA MEANb CIb MEAN Deep Intake (1) B13 18.3 1978-1984; .67/.53 Phyllophora spp. 68.85 23.77 118.82 1986-1990 Ptilota serrata 11.54 3.96 9.09 Phycodrys rubens 5.82 2.95 11.04 Polysiphonia urceolata 2.87 3.35 0.06 Scagelia corallina 2.86 2.83 0.70 Deep Discharge/ Farfield (2) B04 18.9- 1978-1984; .68/.53 Ptilota serrate 64.00 18.27 42.39 21.0 1986-1990 Phyllophora spp. 10.97 5.04 7.49 B34 1979-1984; Corallina 1986-1990 officinalis 6.86 3.59 2.13 Scagelia corallina 1.32 1.18 1.01 Phycodrys rubens 1.01 0.40 1.27 Mid-depth Discharge/ Farfield (3) Bi9 9.4- 1978-1990 .69/.64 Phyllophora spp. 207.25 33.13 188.56 B31 .12.2 1978-1990 Chondrus crispus 56.81 30.00 16.13 B16 1984. Corallina officinalis 54.48 21.19 52.80 Phycodrys rubens 37.86 10.81 72.05 Callophyllis cristath 11.42 .3.49 5.04 Ptilota serrata 11.09 .3.82 11.28*(continued) TABLE 3.3.2-2. .(Continued) WITHIN/ GROUP BIOMASS (g/m 2)MEAN BETWEEN STA- DEPTH GROUP PREOPa 1990 GROUP TIONS Cm) YEARS INCLUDED SIMILARITY DOMINANT TAXA MEANb CIb MEAN Mid-depth Intake (4) B16 9.4 1980-1983; .80/.64 Phyllophora spp. 429.87 93.92 369.02 1986-1990 Phycodrys rubens 203.80 72.19 215.46 Chondrus crispus 61.16 33.55 17.60 Cystocloniumr purpureum. 49.39 27.86 28.90 Ceramium rubrum 37.08 23.41 2.21 Callophyllls Shallow q.cristata 32.73 10.02 19.30 Subtidal (5). B17 4.6 1978-1990 .-75/.55 Chondrus crispus 774.22 111.65 544.96 B35 1982-1990 Phyllophora spp. 204.73 61.90 378-61 Ceramium rubrum 69.29 20.72 51.79 Cystoclonium purpureum 56.59 41.12 115.82 Corallina officinalis 51.58 23.24 35.39 Intertidal (6) BIMLW MLW 1978-1990 .68/.33 Chondrus crispus 986.18 189.73' 278.13 B5MLW MLW 1982-1990 mastocarpus stellatus 215.23 108.66 517.71 Corallina officinalis 51.25 31.30 14.13 Ceramium rubrum 2.43 2.24 0.94 aPreop = preoperational, 1978-1989 period (Stations B1MLW, B17, B19, B31: 1978-1989; Stations B5MLW, B35: 1982-1989; Station B16: 1980-1984, 1986-1989;. Stations B13, B04: 1978-1984,' 1986-1989; B34: 1979-1984, 1986-1989) bGeometric mean and 95% confidence interval 7_7. 7T historical average. Areas sampled at 18.9-21 m depth, the deepest areas sampled in the study (Group 2), were characterized by a community where Ptilota serrata predominated, and Phyllophora spp. was less important than-in shallower areas. Deep areas in 1990 had the same dominants as found historically, although average biomass was lower than previous years.In order to monitor the algal community fornew or.infre-quently occurring species that might bloom to "nuisance'.' levels, the occurrence of rare taxa was, also examined. Thirty taxa out of a total of 128 occurred sparsely (less than 1.7% frequency) in the biomass collections. from 1978 to 1989 (Appendix Table 3.3.2-1). Five of these taxa occurred in 1990 in low frequencies. Only one taxon appeared more frequently in 1990 than in previous years.. Bonnemaisonia hamifera, a relatively uncommon taxon that was new to biomass collections in 1986, occurred in small amounts eight times in,1990 at three farfield stations (B5MLW, B35, B31). This species, typical of southern Massachusetts and, Long Island (Taylor 1952), has been recorded in coastal New Hampshire"and Great Bay (Mathieson and Hehre 1986). Its occurrence at offshore sites in this study beginning in 1986 may have been related to the naturally-increased water temperatures in the'nearshore area (NAI 1987a;1988a; 1989a, 1990a). As B. hamifera, which is not considered a nuisance organism, has occurred only at low levels, it does not pose a threat to the established algae community. Kelps and Understorv Species To monitor larger macroinvertebrates and macroalgae that are not adequately represented in destructive samples, transect surveys were performed at shallow and mid-depth stations. Invertebrate results are discussed in Sections 3.3.3.4 and 3.3.5.7. Kelps are important habitat formers that are not collected in destructive samples.. Spatial differ-ences in adultkelp (>15cm) species abundance appear primarily attribut-able to depth differences. Historically, Laminari1a saccharina was most 313 abundant at theshallow subtidal stations (Figure 3.3.2-6). Laminaria digitate and Alaria esculenta reached maximum abundance in the study area at farfield Station B31 (9.4 m below MLW), whereas Agarum cribro-sum's greatest abundance was at Station B19 (discharge, 12;2 m below MLW). -Substantial spatial differences between mid-depth-stations (B19 and B31), were found for some species; L. digitata and Alaria esculenta were more abundant (and outside the 95% confidence limits) at farfield Station B31, whereas A. cribosum was more abundant at the nearfield Station B19 (Figure 3.3.2-6).Spatial trends observed in 1990 were similar to previous years (Figure 3.3.2-6). Mean numbers of A. esculenta and A. cribrosumin 1990'did not differ significantly from previous years at mid-depth stations (Table 3.3.2-3). Abundances of the two Laminaria species in 1990 showed differences from previous years. L. digitata had significantly lower abundances in 1990 (including May, Augustand November samples) at the nearfield shallow subtidal station (B17). and at the farfield mid-depth station (B31) when compared to previous years (Table 3.3.2-3). However, when the operational period (October) was compared to the same period in previous years, no significant differences were detected. Abundances were not significantly different at the other stations. L. saccharina abundances in all months of 1990 were significantly lower than the historical average at the shallow subtidal nearfield station (B17), although October abundances were similar to previous years. Remaining stations showed no change from previous years.No consistent seasonal Variation in abundance was observed for any species of kelp, probably because "juvenile" (<15 cm) plants were not enumerated; these plants are difficult to count accurately in situ because of their small size and high density (NAI 1984a, 1985b).Seasonal variation in biomass was reflected.in growth studies conducted, prior to 1985; growth closely followed the solar irradiance and nutrient.cycles (NAI 1985b). Stand density, which is controlled by substrate availability, recruitment and environmental conditions (e.g. storm disruption), showed some variability among years. Kelps, particularly 314 Kelps Shallow Mid-depth E 0.0 0~900 8OO 700 600-500 400 300" 200-:100.0 03 nearfield (B17)farfield (B35)a 1990 C-0cc_j 900'.'=r=C3 10 800 700-600 600 0 aJ.I go 400 300 200 100 0 Cm Z 0CD 0 Co E S0 a-o cam Understory algae Shallow Mid-depth 80 80 O nearfleld (B17)o farfleld (B35)'a 1990 60 60 nearfield (819)o farfield (B31)* 1990 Z LU 40 z LJJ 0 Lu I -, 40 20 20 O 0.~0 00 CL 0 -x C).cc C0C C 0 =0.0.C r 0 c=* a.Figure 3.3.2-6.Preoperational means, and 95% confidence limits of abundance of kelps (no./100 Mi 2), (B 17: 1978-1989; B35: 1982-1989) and percent frequencies and 95% confidence limits of dominant understory algae (B17: 1981-1989; B35: 1982-1989) and 1990 means, collected triannually in the shallow and mid-depth subtidal zones. Seabrook Operational Report, 1990.315 TABLE 3.3.2-3.RESULTS OF NONPARAMETRIC ONE-WAY ANOVA COMPARING NUMBERS OF FOUR KELP SPECIES AND PERCENT FREQUENCIES OF THREE.UNDERSTORY ALGAE TAXA IN i990 (OCTOBER ONLY AND ALL MONTHS) TO VALUES FROM 1981-1989. SEABROOK OPERATIONAL REPORT, 1990.TAXON .,STATION df Z."OCTOBER ALL MONTHS Alaria esculenta Agarum cribosum Laminaria digitate Laminaria saccharina Chondrus crispus.Phyllophora sp..'Ptilota serrata 19 31 19 31 17 35 19 31 17 35 19 31 17 19 17 19 17 19 l 1 1 1 1 1 1 1 1 1*1 1 1 1 1 .1 1*1-0.00 NS-0.'67 NS 0.67 0.40-0.87-0.19 0.40-1.47-1.45-1.47-1.35 0.13-0.70 1.36 0.18-1.40-0. 70-0.97-0.35 0.35 0.38 0. 00-1.40-1.40 NS NS NS NS NS NS NS NS.NS NS NS NS NS NS NS NS NS NS NS NS NS NS-0.34 NS-0.34 NS:.100NS 0.45 NS-2.43*-0.48 NS 1.61 NS-2.37*-1.95*-1.08 NS-1.45 NS-1.61 NS 0.07 0.92 0.95-1.07-0.87-1.08 0.14 0.21 0.43-0.10-1.14.-1.04 NS NS NS NS NS NS NS NS NS NS.;NS NS probability

• = <.05 316 Laminaria species, are fast-growing, opportunistic plants. Consequent-;

ly, they are among the "pioneer" species that colonize freshly exposed substrate, adding to the year-to-year variability in distribution. Measurements of percent frequency of occurrence of the three understory algae that were dominant at transect sites (Figure 3.3.2-6), showed differences among depths that were similar to those observed from biomass collections (Figure 3.3.2-4). The understory community in the shallow zone historically has been dominated by Chondrus crispus with Phyllophora spp. a secondary dominant. A similar pattern occurred in 1990. Algal frequencies in October, 1990 (the only sampling period during plant operation) at the nearfield Station B17 were not signifi-cantly different from those observed historically (Table 3.3.2-3).Frequencies of C. crispus were lower at the farfield area (B35) in comparison to the nearfield (B17) but were similar for the other two taxa. The understory community at mid-depth stations differed among stations. Phyllophora spp. and Ptilota.serrata predominated at the nearfield station (B19), whereas C. crispus was relatively rare.October frequencies in 19 90 were not significantly different from previous years for any of the taxa (Table 3.3.2-3).' The understory"' community at farfield Station B31 was predominated by;Phyllophora spp., but C. crispus and P. serrata were.also important constituents..Frequencies of.Phy~lophora spp. in 1990 were similar to previous years.Ptilota serrata continued to show fewer occurrences at Station B19.and B31 than in past years, a trend first observed in 1986 (NAI 1990b).Intertidal Communities (Nondestructive Monitoring Program)In situ counts of macroalgae in fixed quadrats at the inter-tidal stations (Bl and B5) were conducted.at locations representing.three tidal elevations between approximate MLW and MHW. 'The three quadrats were situated (from highest to. lowest elevation) on bare ledge, fucoid-covered ledge, and Chondrus-cover.ed ledge. These quadrats were set up to monitor fixed locations; thus eliminating small-scale spatial 317 variability and focusing-on temporal variation. .Appendix Table 3.3.2-2 shows the occurrence Of the more commonly-occurring species.The Bare.Ledge Site, at the upper edge of the mid-tidal zone was characteristic of ledge not continuously covered by macroalgae. Although seasonally high in variability,, barnacles have been common in this quadrat (see Section 3.3.3 for faunal coverage). Historically, during the spring the annual greens, Urospora penicilliformis and Ulothrix flacca (at both stations), and the red alga, Bangia fusco-purpurea (Station B5), were the most frequently occurring species (Appendix Table 3.3.2-2). B. fuscopurpurea has not been observed since.1986. Small, immature perennial Fucus spp. plants (mainly F. vesiculos-is with some F. distichas edentatus) have also been found in this habitat in all seasons; although they occurred frequently, their percent cover was usually 23% or less. Until 1985, the-bare rock quadrats.were spatially similar. In the years since, the Fucus spp. percent cover dropped to less than one percent at Station BI (accompanied by a decrease in Balanus sp.)(NAI 1988b). In contrast, increased amounts of Fucus spp. have appeared at Station B5 during the same time period, resulting in median values for the preoperational period that were >80%.During the spring and summer of 1990, Fucus spp. percent cover in the bare ledge site at Station B5 occurred in amounts greater'than the historical median, but within the ranges established for each season.The more persistent annual red alga, Porphyra spp. continued to be unique to Station B1 during all seasons in frequencies similar to previous years..The Fucoid Ledge Site, in the mid-tide.zone, is situated in the area of maximum fucoid algae cover. The perennial, Fucus spp., has been the dominant taxon within the quadrats, although some Ascophyllum nodosum have been recorded at Station B5 (Appendix Table 3.3.2-2).These fucoids were quite persistent and occurred frequently, although relatively low (<40%) coverages have been bccassionally recorded. The -perennial red algae Chondrus crispus and Mastocarpus stellatus occurred 318 in the understory at both stations.in low amounts (usually <10% frequen-cy); *the latter species was more persistent.. Of the other algae occurring in these quadrats, only Porphyra' sp. and Spongomorpha sp. were common (both at Station Bl. only). With few exceptions, observations recorded during 1990 were similar to recent years and within established ranges.Fixed line transects have also been surveyed in the mid-tide zone since 1983 to quantify the areal-coverage of the fucoid algae.Historically in the fixed areas studied, A. nodosum has occurred more frequently at Station B5 than at Bi. In 1990, the percent frequency of occurrence at both stations was slightly less than 1989 but within the confidence limits established for the preoperational period (Figure.3.3.2-7). Fucus vesiculosus was almost twice as frequent at nearfield Station Bl than at farfield Station B5.. Frequencies recorded in 1989 (NAI 1990b) and 1990 for F. vesiculosis were similar and much lower than the historical mean. F. distichus var. edentatus, historically less frequent than the two-other species, was also recorded at-both stations in 1990. However, since 1989, the percent frequency of occurrence increased nearly twofold at nearfield Station Bl and decreased twofold at farfield Station B5 (NAI 1990b). The .1990 frequencies were outside the 95% confidence limits established for the preoperational period at both-stations for the second consecutiv6 year, suggesting that F.'distichus may be replacing F. vesiculosus within the sample quadrat.The Chondrus zone quadrat in the MLW (mean low water) zone is situated in the area of maximum red algae cover. Chondrus crispus and Mastocarpus stellatus dominated this zone; median percent frequencies exceeded 90% during preoperational period, with no differences noted between the two stations (Appendix Table 3.3.3-2). Spatial differences included the occurrence of understory taxa Fucus spp., which persisted only at Bi, and Corallina officinalis, which was persistent only'at B5.It -is likely that small scale differences in topography between stations contributed to these differences in species distribution. The 1990 319 100, Ascophyllum nodosum 100*8o-Fucus vesiculosis 8o-C.U.60-40 T 80 60 40 T 40-20/ -4 Fucus distichus var. edentatus-0 V'l .20-..0i 0 '-L B1MSL B5MSL B1MSL B5MSL B1MSL B5MSL STATION a 1990 Figure 3.3.2-7. Mean percent frequency and 95% confidence limits of fucoid algae at two fixed transect sites in the mean sea level zone for the preoperational period (1983-1989) and mean percent frequency in 1990. Seabrook Operational Report, 1990.320 observations of perennial algal species showed frequencies similar to the most recent years with two exceptions.: Chondrus crispus at Station B5 in December and Corallina officinalis at Station B5 in April were both observed in amounts greater'than the ranges established historical-ly. Fucus sp., which historically occurred throughout the year at B1, occurred only in July in 1990. Percent frequencies were lower than average, amounting to virtually no cover. The annual red algal genus.Porphyra sp., which usually is observed in low frequencies in summer at Station B1, occurred well above the baseline range.3.3.2.2 Selected Species Lamrinaria saccharina Laininaria saccharina has been one of two dominant canopy-forming kelps in the shallow subtidal zone (1 to 9 m deep) surrounding the Inner and Outer Sunk Rocks. Density varied greatly due to vari-ability in the amount of substrate available for settlement combined with the contagious. distribution of these plants. Numbers of L.saccharina have been affected by storm activities; particularly in 1979 and again in 1982 (NAI 1990b). Since that time, numbers of kelps have.remained similar through 1989 (Figure 3.3.2-8).In 1990, numbers of kelps at the nearfield shallow subtidal were significantly lower than previous years (Table 3.3.'2-3, Figure 3-.3.2-8). This difference, however, was not restricted to the opera-tional period in 1990. Numbers of kelps were not significantly differ-ent in 1990 at the farfield shallow subtidal stations or either of the mid-depth stations.321 Nearfield (B17)0 z CF I~M< Os 2200 2000 1800 1600 1400 1200 1i000 800 600 400 200 0 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Farfield (B35)E zU,< S.1400 1200 1000 800 600 400!200 0 79 80 81 82 83 84 85 86 87 88 89 .9!0'YEAR Figure 3.3.2-8. Annual mean abundance (no./100 m 2) and 95% confidence interval for Laminaria saccharina at Station B17 (1979-1990) and B35 (1982-1990). Seabrook Operational Report, 1990.322* Chondrus crispus Chondrus crispus (Irish moss), a red algae, is common to intertidal and shallow subtidal habitats from Nova Scotia to New Jersey (Taylor. 1952). It was the dominant understory algal species in the lower intertidal and shallow subtidal zones near the Sunk Rocks (see Community Analysis section). C. crispus biomass was higher in the intertidal zone than in the:subtidal zone, and annual differences were more pronounced there (Figure 3.3.2-9).In 1990, intertidal biomass levels were significantly lower than previous years. However, this difference was not restricted to the operational period. (indicated by the similarity of August/November results to results using all three sampling periods) nor was it unique to the nearfield station (indicated by. a non-significant Station term in the ANOVA) (Table 3.3.2-4). Biomass levels were lower than the histori-cal average at both intertidal stations, beginning in May at the near-field station (Figure 3.3.2-10) and November 1989 at the farfield station (NAI 1990b). Typically this species does not exhibit a strong seasonal pattern in the intertidal zone.Shallow subtidal C. crispus exhibited a trend of decreased abundance in May and August 1990 at the-nearfield station (Figure 3.3.2-10). However., biomass during the operational period (August, November)and for the entire year .was not significantly different from the same time period during previous years (Table .3.3.2-4).

3.3.3 Marine

Macrofauna 3.3.3..1 Horizontal Ledge Communities (Destructive Monitoring Program)General Studies since 1978 of the macrofaunal invertebrates off Hampton Beach, New Hampshire have focused on the horizontal algae-323 Intertidal Station BIMLW Station B5MLW E 0~2600-2400-2200-2000-1800-1600-1400-1200-1000-800-600-400-200-0*//2600 2400 2200 2000 1800 1600 0 E 14600 S1200 O 1000 800 600 400 200* 0 4/i I ..I I ....I £78 79 80 81 82 83 84 85 86 87 88 89 90 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR YEAR Subtidal Station B17 Station B35 E Fn 2 2600 2460 2200 2000 1800 1600 1400 1200 1000 800 600.400 200 0 IC, Co,-2600 -2400 2200 2000 1800 1600 1400 1200 1000 800-600-400-200-0 K.'I...... i i 78 79 80 81 82 83 84 85 86 87 88 89 90.78 79 80 81 82.83 84 85 86 87 88"89 90 YEAR.YEAR Figure 3.3.2-9. Annual mean biomass (g/m 2) and 95% confidence intervals of Chondrus crispus collected in May, August and November at Stations B1MLW, B17: 1978-1990; B5MLW, B35: 198241990. Seabrook Operational Report, 1990.324 .1.. .1.TABLE 3.3.2-4.RESULTS OF ANALYSIS OF. VARIANCE OF CHONDRUS CRISPUS BIOMASS. (g/m 2)COMPARING COLLECTIONS IN 1990 AT INTERTIDAL AND SHALLOW SUBTIDAL STATION PAIRS WITH BIOMASS FROM 1978-89.SEABROOK 1 OPERATIONAL REPORT, 1990.SOURCE OF PARAMETER DEPTH ZONE VARIATION df SS Fe.Chondrus Intertidal Preop-Oga 1 665.87 11.89**.crispus AUg., Nov., Station 1 ..48.33 0.86 NS Year .(Preop-Op)c d 11 4,138.15 6.72***Station X Preop-Op d 1 209.85 3.175 NS Error 185 10,359.77 Intertidal Preop-Op 1 1,980.17 38.19***All months Station 1 60.33 1.16 NS* Year (Preop-Op) 11 4,602.99 8.07***Station X Preop-Op 1 360.19 6.95**Error 275 14,258.39 Shallow Preop-Op 1 3.94 0.08 NS subtidal Station 1 171.90 *3.49 NS Aug., Nov. Year (Preop-Op) 11 605.14 1.12 NS Station X Preop-Op 1 82.74 .1.68 NS Error 185 9,100..83 Shallow Preop-Op 1 1.75 0.04 NS subtidal .Station 1 69.34 1.46 NS All months Year (Preop-Op) 11 612.07 1.17 NS Station X Preop-Op 1 153.18 3.22 NS Error 275 13,063.18:Preop-Op = 1990 vs. all previous years, regardless of station Station pairs within a depth zone: intertidal = BIT, B51; shallow subtidal =.B17, B35, regardless of year or period CYear.'nested within preoperational and operational periods regardless of area dInteraction of main effects'NS = Not sigftificant (p>0.05)* = Significant (0.05->p>Oý.01)

• • • Highly- significant (0.01->p>0.001)
• Very ighly significant (p-l001) 1400-1200-0ooo-13 MAY u'E%a, 2 I 800 -1, 600-400 -200-0-B1MLW B5MLW B17 B35 STATION.Figure 3.3.2-10.Mean biomass (g/m 2) and 95% confidence limits of Chondrus crispus at selected stations in May, August and November.

Stations B 1MLW, B17: 1978-1989 and 1990; Stations B5MLW, B35: 1982-1989 and 1990.Seabrook Operational Report, 1990.TT -__ __ covered rock/ledge habitat in near- and farfield areas in four depth zones: Macrofaunal studies include a community analysis of intertidal and subtidal habitats, as'well as a detailed examination of populations of selected species (see Section 3.3.5 also), and an investigation of the near-surface (see Section 3.3.4) and bottom fouling.community. Numbers of Taxa and Total Density Numbers of taxa and total density (number of noncolonial macrofauna/m

2) have been used to monitor spatial and annual, trends in the macrofaunal community.

These parameters have been measured in August beginning in 1978, and have shown broadscale changes in relation to depth. The number of taxa generally increased from intertidal through mid-depth stations, and declined slightly at the deep stations.(Figure 3.3.3-1). The number of taxa ranged from 49 at intertidal Station BIMLW to 70 at mid-depth Station B16 during the baseline period, and no new taxa were collected in 1990. Total density showed a general decrease with increasing depth (Figure 3.3.3-1), mainly due to decreases in Mytilidae (primarily Mytilus edulis)(see Section 3.3.5).In the intertidal area, the habitat at nearfield Station B1MLW was about 90% algae covered ledge and 10% mussel (mytilid) beds.Farfield Station B5MLW was similar, except for the presence of boulders (Table 2.1-2), and it was more protected. The predominant alga was Chondrus crispus (Irish moss)(Figure 3.3.2-4). The number of taxa in 1990 at both intertidal stations .was just slightly lower than the baseline averages, thus the interaction term of the ANOVA model was not significant (Table 3.3.3-1). The baseline mean number of taxa at both stations was very similar (48.9 and 48.3; Figure 3.3.3-1). Although the.1990 mean number of taxa at each station was slightly lower than its corresponding baseline mean, each was well within the range of the preoperational period (Figure 3.3.3-2). The 1990 densities at both stations were above the baseline average at each intertidal station, and approached the all time high density set in 1986 (Figures 3.3.3-1,3). 327 Number of Taxa 110-1 0,*.=E.SL 2 C 90 80-60-50 40-30 20-10-I If ~ If 41 I I I I I B1MLW B5MLW B17 I I I I I I I B35 B16 B31 B19 B13 B04 B34 STATION Total Density=PREOP 6-1 51 v-D Za zCa 4-3-2-1-X.I .al 0 i I I I BIMLW B5MLW B17 I I I I I i I I 835 B16 B31 B19 B13 .B04 B34 STATION Figure 3.3.3-1.Mean number of taxa (per 1/16 Mi 2) and log,(x+l) mean density (no./m 2)and 95% confidence limits of macrofauna collected in August during the preoperational period (1978-1989) and in 1990 at intertidal and subtidal benthic stations. Seabrook Operational Report, 1990.328 TABLE 3.3.3-1.RESULTS OF-ANALYSIS OF VARIANCE OF NUMBER OF TAXA (per 1/16 m?) AND TOTAL DENSITY (per m 2) OF MACROFAUNA COLLECTED IN AUGUST AT INTERTIDAL, SHALLOW SUBTIDAL, AND DEEP STATION GROUPS, 1978-1990. SEABROOK OPERATIONAL REPORT, 1990.0 PARAMETER STATION PAIRS CLASS VARIABLE df SS Fa Number.of Taxa, BlI, B51 Preop-Opb 1 221.8 2.86 NS Stationc 1 46.3 0.60 NS Year (Preop-Op) di 6,371.2 7.47***Station X Preop-Op 1 196.1 2.53 NS Error 91 7,059.5 B17, B35 Preop-Opb 1 205.3 2.38 NS Stationc 1 393.9... 4.56*Year (Preop-Op) 11 2,445.5 2.58**Station X Preop-Opd 1 150.3 1.74 NS Error 91 7,852.5 B19, B31, B16 Preop-0pb 1 2,023.1 15.40***.Stationc 2 .2,378.8 9.05***Year (Preop-Op) d 11 8,889.4 6.15***Station X Preop-Op 2 1)375.3 5.23**Error 158 20,755.1 B04, B34, B13 Preop-Opb 1 340.5 2.40 NS Stationc 2 637.9 2.25 NS Year (Preop-Op) 10 10,678.0 7.53***Station X Preop-Opd 2 128.9 0.45 NS Error .159 22,535.5 (continued) 0 TABLE 3.3.3-1.(Continued) w 0 PARAMETER STATION PAIRS CLASS VARIABLE df SS Fa Total Density BlI, B51 Preop-0pb 1 0.7 11.25**Stationo 1 0.3 4.44*Year (Preop-0p) d 4.7 6.69***Station X Preop-Op 1 0.04 0.62 NS Error .91 5.8 B17, B35 Preop-Opb 1 0.1 2.61 NS Stationo 1 0.1 1.15 NS Year (Preop-Op) d 3.1 5.31***Station X Preop-Opd 1 0.001 0.02 NS Error 91 4.9 B19, B31, B16 Preop-Opb 1 0.002 0.02 NS Stationc 2 0.7 3.21*Year (Preop-Op) 11 9.3 8.02*d Station X Preop-Op 2 1.2 5.77**Error 158 16.7-B04, B34, B13 Preop-0pb 1 0.1 1.48 NS Stationc 2 1.0 5.25**Year (Preop-Op) 10 8.7 9.00***Station X Preop-Opd 2 0.6 3.01*Error .159 15.3 aNS Not significant (p>0.05)* = Significant (0.05->p>0.01).'

• * =Highly significant (0.01->p>.001)

Very highly significant (p<.001)bpreoperational (through 1989) versus operational (1990) period, regardless of station Cnearfield = Stations BII, B17, B19, B16, B04, B13; farfield = Stations BSI, B35, B31, B34,.regardless of year/period dinteraction between main effects* -I ..... .--.- ._} 0 E<I--X a zz 4.-we 100 40-20 -Intertidal B1MLW B5MLW a. J I I I I I I .78 79 80 81 82 83 84 YEAR I I I I I I 85 86 87 88 89 90 v 2 E aSL I-Y 100 60-40-20-Shallow Subtidal B17 B35 0 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Annual mean number of noncolonial macrofauna! taxa (per 1/16 m 2)* collected in August at intertidal Stations B1MLW and B5MLW and shallow subtidal Stations B17 and B35 from 1978-1990. Seabrook .6 Operational Report, 1990.Figure 3.3.3-2.331 Intertidal (BIMLW)a)E 00 I5-S 6.5-6.0 -5.5-5.0.4.5-4.0-3.5 3.0 6.5-6.0-I I I I I I I 1 1 7.8 79 80 81" 82 83 84 85 86 87 88 89 90 YEAR Shallow Subtidal (B17)5.5-1.CD 00 5.0-4.5-4.0-3.5 3.0.I .I I I I I I I I I I I I 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Figure 3.3.3-3. Annual means and 95% confidence limits for the log (x+1) density (no./m2) of macrofauna collected in August at nearfield Stations(intertidal) and B17 (shallow subtidal) from 1978-1990. Seabrook Operational Report, 1990.332 However, the interaction term was not significant, since both near- and farfield.stations had above average densities in 1990 (Table 3.3.3-1).'In the shallow subtidal area (5 m), the habitat at nearfield Station B17 was about 95% algae covered ledge and 5% crustose algae-covered ledge. Farfield.Station B35 was85% algae, covered ledge and 15%boulders. Laminaria saccharine is a canopy-formingkelp occurring at Stations 17 and 35 (Section 3.3.2.2).: The understory during the preoperational period was dominated primarily by Chondrus, with about 10'-20% Phyllophora spp. (Figure 3.3.2-4). The preoperational mean number of taxa at both stations was higher than their intertidal counterparts (Figure 3.3.3-1). Although the 1990 mean number of taxa at each station was higher than the preoperational mean (Figures 3.3.3-1,3), the interaction between the near- and farfield stations was not significant (Table 3.3.3-1). Shallow subtidal total density at both*stations was lower than intertidal stations, but higher than all the deeper stations except for Station B16, the mid-depth station at the.intake (Figure 3.3.3-1). The 1990 annual mean density at each station was slightly higher, but within the 95% confidence.limits of the preoperational mean, and there was no significant interaction between the near- and'farfield stations (Figure 3.3.3-1, Table 3.3.3-1Y)In the mid-depth area (9-12 m), the habitat at nearfield Station B19 (discharge) included algae-covered ledge and boulders and horse mussel beds (40%), ýand its farfield counterpart, B31, had 60%horse mussel beds, algae covered rocks-and about 10% cobble. The nearfield Station B16 (intake) had more similar substrate to the nearfield shallow subtidal station, and was primarily algae-covered ledge with mussel beds (25%) and lacked boulders or cobbles. The algae at all three mid-depth stations was *composed of more species than. the shallower stations, but generally was about.50% Phyllophora spp. (Figure 3.3.2-4). Significant differences in the number of taxa at the three mid-depth stations occurred between 1990 and the baseline period (Table 3.3.3-1). At both the discharge station (B19) and its farfield counter-part (B31), the number of taxa in 1990 showed a large increase (about 20 333 taxa) over the baseline period, while at intake Station B16 the 1990 and preoperational means were nearly the same (Figure 3.3.3-1), thus the interaction among the three stations was signficant (Table 3.3.3-1). In the 1990.operational~period, the number of taxa was at, its all time high at B31, and at. B19 it was exceeded only in 1989 (Figure 3.3.3-4). At the intake, B16, the 1990 mean number of taxa was just slightly lower than the preoperational mean, but well within the 95% confidence limits.The total densities at all three mid-depth stations were intermediate between the intertidal and deep 'areas (Figure 3.3.3-1). -The 1990 " density was higher than the baseline averages at Station B19 (discharge station), but lower at Stations B31 and B16 (intake), and the interac-tion term was significant (Table 3.3.3-1, Figure 3.3.3-1). In 1990, the total density at each.station .had-relatively wide confidence..limits- .(Figure 3.3.3-1) and was higher than the 95% confidence limits of the preoperational mean at Station B19, and lower at Stations B116 and B31..Yet, mean density at each of the three stations was within the range observed during the study period (Figure 3.3.3-5). At Station B19, the mean density was exceeded only bythe density values recorded in 1986.In the deepest area (18-21 m), horse mussel beds comprised over 50% of the substrate at all.three stations;, algae-covered ledge was generally the next most frequent substrate. Boulders (40%) were present at B34 (farfield) and cobbles (5%) were present at B13 (intake). The-discharge (B04) lacked both boulders and cobbles (Table 2.1-3). Algae at Station B13 were predominantly.Phyllophoraspp. (like the mid-depth stations), but at B04 and B34 Ptilota serrata was the numerical dominant (Figure 3.3.2-4). -The 1990 mean number of taxa'at farfield Station B34 was nearly the same as the baseline period, and at B04 and B13, the 1990 means were somewhat higher. (Figure 3.3.3-1). The 1990 means were within the range of the preoperational period at all stations (Figure 3.3.3-4), and the interaction among the three stations was not significant (Table 3.3.3-1). In 1990, the means for total- density were high (above the upper confidence limit of the preoperational mean). at Stations B13:- .(intake) and B34 (farfield), and. just below the preoperational confi-dence limit at B04 (nearfield)(Figure 3.3.3-1). -Thus, the interaction 334 Mid-Depth"Ca go 100-80 -60 40 20 f4,° -*S St -.49 S V B19........ B31 II a =v 78 79 I , I1 80 81 82 83 I 84 YEAR ai I* -I I I 1 I 85 86 87 88 89 90 Deep E 0 0r 100 80 60 40 20* 555* *555 --V B04." ...... 834 0 78 79 80 ,81 82 83 84 85 86 87 88 89 90 YEAR Mid-Depth To Deep E 4--W0 100 -80 60-40-20 0-* 55 V 4* 49"- B13........ B16 I a a a I a a a 78 79 80 81 82 83 84 85 YEAR.8 8 8 I I 86 87 88 89 90 Figure 3.3.3-4.Annual mean number of noncolonial m acrofaunal taxa (per 1/16 m 2 )collected in August at mid-depth Stations B16, B19, and B31 and deep Stations B04, B13 and B34 from 1978-1990. Seabrook Operational Report, 1990.335

• Mid-Depth (B19)00_j0.5.5 -5.0-4.5-4.0-3.5-I 3.0 I I I I I I I 78 79 80 81 82 83 84 85 86 87 88 89. 90 YEAR Mid-Depth (B16)5.5-5.0-E 4.5-cc wU M' =" 4.0-003.-5I-- 3.5 J 3.0 I I a I I I I I 1 i 78 79 80 81 82 _83 84 85 86 87 88 89 90 YEAR I.Deep (B04)5.5 5.0 0>" E 4.5 4.0 0.o-J -- 3.5.3.0 78 79 80 81 82 83 84 85 86 87 88 89 .90 YEAR Figure 3.3.3-5. Annual means and 95% confidence limits for the log (x+l) density (no./m 2) of macrofauna collected in August at nearfield Stations B19 and B16 (mid-depth) and B04 (deep) from 1978-1990.

Seabrook Operational Report, .1990.336 among the three stations was significant (Table 3.3.3-1). Yet, 1990 mean densities at all stations were withinthe range of the baseline period (Figure 3.3.3-5).Community Structure The noncolonial, macrofaunal, hard-bottom community structure at all near- and farfield stations has historically shown changes related to depth (NAI 199bb). Intertidal (B1MLW, B5MLW), shallow subtidal (B17, B35), mid-depth (B16, B19, B31), and deep (B04, B13, B34)areas were distinct in both species distributions and abundances. In most cases, based on the similarity in species composition, the 1990.'collections were placed in the group with the majority, of preoperational collections from the same stationl(Table 3.3.3-2, Figure 3.3.3-6)). The intertidal, shallow subtidal, and mid-depth assemblages showed little year-to-year variation in their community structure. Benthic assem-blages were less stable at deep stations, as evidenced by shifts in group assignment by the cluster analysis.Differences in community structure among stations were indicated by differences in densities of dominant taxa as well as species composition. The cluster analysis used 89 species occurring

• in 6% or more of the samples. Very rare species, occurring in less than 6%(36 out of 562) of the samples, Were not included.

The most abundant taxon, Mytilidae spat, was ubiquitous, and contributed little to the discrimination among stations. Less-abundant species, such as per-acarids Calliopius laeviusculus, Jassa marmorata (formerly J. falcata), Jaera marina, and gastropod Lacuna vincta, accounted for the majority of the among-station variability. The intertidal habitat (Group 6) was the most distinct (between group similarity of only 0.436) of all areas because of the overwhelming predominance of Mytilidae spat (69,205/M 2 preoperationally) and the presence of species such as Nucella lapillus, Turtonia minuta, 337 TABLE 3.3.3-2.STATION GROUPS FORMED BY CLUSTER ANALYSISa WITH PREOPERATIONAL AND OPERATIONAL (1990) GEOMETRIC MEAR DENSITY +/- 951 CI FOR ABUNDANT MACROPAUNAL TAXA (NON-CLI.i) COLLECTE ANNUALLY IN AUGUST FROM 1978 THROUGH 1990.SEABROOK OPERATIONAL REPORT, 1991.GROUP NO./NAME DOlMINANT PREOPERATIONAL 1990 SIMILAXITyb STATIONS (YEARS) TMX LOWER MEAN UPPER N LOWER MEAN UPPER N Misc. 819 1978) Pontogeneia inermis 9 734 54501 3 0.663/.609, 831 1978) Mytilidae 5 359 21183 834 (1980) Cr. 98 228 532 septenltronalis Hiatela sp. 4 217 8628 Lacuna vincta 23 209 1824 -Sp. 37 187 l928 Asteriidae 65 181 500* 2 0 Historical B04 (1978-84 86-87) Pontoeneia rmis 233 332 474 22 0 SDeep L1 (978-841 -stlerzianae 177. 5 362 l.650/.530 B34 (1979, 81-84, 87) A a sp. 124 202 326 Tnice lla rubra 150 174 203 -Ca re11a l 97 153' 242..septnrionalis Mytilidae 63 116 213 -3 *3 Recent Deep 804 (1988-90) Balanus crenatus 94 3191 10834 13 0 747 4017783-.733/.680 813 1ytilidae 49 1211 2966 3 281 21310 831 (1989) glat sp. .392 823 1726 386 505 660 834 1986, 88-90) Anomla sp. 386 709 .1301 505 936 1734 oeneia inermis 137 293 .627 7 177 4196 ANtereiaae 144 220 337 .86 330 '1253 Achelia sp-inosa 122 217 386 13. 86 521 4 .Mid-depth 316(1980-81, 83-84, Mytilidae. 3474 5966 10245 33 3190 8165 20896.695-.680 86-90 .Pontogeneia inermis 1121 1696 *2565 601 1688 4737 817 (1990) 10 .ria 748 1114 1659 470 1351 3879 819(1979-1990) septentrionalis 831 90) A a sp. 544 789 1143 511 1359 3616"late Slalsp. 447 678 1027 236 , 690 2013 Lacunalvincta 306 427 597 53 816 12358 Asteriia 183 268 391 85 839 8227 (continued) _71-7F H ,-.TABLE 3.3.3-2.. (Continued) GROUP. NO.!NAME DOMINANTC PREOPERATIONAL 1990 SDILIIP b STATION (YEARS)' TAU LOWER MEAN UPPER N LOWER MEAN UPPER N Shallow B16 (1982)' Mytilidae 3128 5112 8353 21 6701'subtidal B17 (1978-89) Lacuna yincta 3512. 5052 7268 12851.745/.574 B35 (1982-90) Idotea phosphorea 1679 2125 2690 2221 Pontogeneia inermis 1320 1987 2991 931 Jassamarmorata .. 1150 1632. 2316 755-509 797 1247 413 septentrionalis Idotea balthica 324 689 1463 4461 Asteriidae .392 599 914 6449.6 2 Intertidal BIMLW (1978-90) Mytilidae 47977 69205 99824 20 148998.693/.436 B5MLW (1982-90) .Jaera marna 2116 3626 6216 1930 Lacuna vincta 2035 3209 5060 2774 Turtonia minuta .1367 2707 5360 6236 Hiatell sp. 1464 2604 4631 1513 Nucella lanillus 925 1501 2432 5304 Gammarellus angulosus 181 572 1803 43 Gammarus oceanicus 241 564 1318 1237 Anomia sp. 373 493 650 1107 aBray Curtis similarity coefficient bw(Sneath and Sokal 1973).within/between group similarity (Clifford and Stephenson 1975) with group average agglomeration for the clustering method within group - no. of :::::::::::::::::::::::::: / :::"""""'"""::::Group 2-between group" :':"" Deep (prior to 1988)::::i~ii similasity: no. of -.-..... -..... -...............* .o10 .De sape Group 4 2-~Mid-depth

.' ..IL 00 00 00 00 0 oo o 00 0010-~o 0 oo 000 000 000 000 00~~Group 4 , 0 0 0 a 9 0 0,a 0 0 0 00 a 000o 0,ShaIntridalutial 00 00 0 00 0 c 00 000 00 0 00 00 00 00 0 0 ... 0 0 0 0 0 0 00 ao 00 o o* 0 *0000000000000 Seabrookc Operationa Report,1990

.0 0 0 00 0 0 00 0 0.3 0. 0.0. .0 c.8 0. 1 oc:% .0 Seabrook~~~~ OpraioalRpot,190 340/I: Jaera marina, and ifyale nilssoni (less common) that are restricted to or most abundant in the intertidal zone (Table 3.3.3-2). Other dominants included the molluscs fliatella sp. spat, and Lacuna vincta, and the amphipod Gammarellus angulosus. Intertidal collections made in 1990 were placed in this group based on similar species composition and abundance. In 1990, densities of mytilid spat, Turtonia minuta, Nucella lapillus, Gammarus oceanicus, and Anomia sp. were more than double the preoperational means (Table 3.3.3-2).The shallow subtidal habitat (Group 5) has included Stations B17 and B35 in most years and Station B16 (mid-depth, intake) in 1982 (Table 3.3.3-2). Mytilidae was still the predominant taxon, although an order of magnitude less abundant than in the intertidal area. Aside from the herbivorous gastropod, Lacuna vincta, and juvenile Asteriidae, dominants were peracarid crustaceans such as Pontogeneia inermis, Caprella septentrionalis, Idotea phosphorea, I. balthica, and Jassa marmorata (formerly J. falcata) (Table 3.3.3-2). Relatively high.densities of the latter three species, along with Calliopius laevius-culus distinguished the shallow subtidal area from other areas.Stations B17 and B35 were placed in this group every year, except in.1990 when B17 was more similar to the mid-depth habitat (Group 4). In, 1990, the number of juvenile Asteriidae at Station B35 increased by an order of magnitude over the preoperational mean, and likewise numbers of I. balthica and L. vincta were very high.Group 4 (the mid-depth stations) was usually characterized by a predominance of Mytilidae spat, and other molluscs (fIiatella sp., Anomia sp. and Lacuna vincta) and amphipods (Pontogeneia inermis and Caprella septentrionalis) that occurred-in high numbers (Table 3.3.3-2).In most years, Stations B31, B19 (discharge) and B16 were characterized by this assemblage. The 1990 collections at all three stations were similar to previous years, and thus placed in. the same group. The shallow subtidal Station B17 also was placed in Group 4 in 1990, due to 341 an'abundance of mytilid spat and Anomia sp., as well as an increase in Balanus crenatus in.1990.Stations with depths greater than 15 m had lower densities of macrofauna (Figure. 3.3.3-1), and formed several loosely-associated deep.station groups (Groups 1, 2 and 3). All differed from shallower stations in the decreasing influence of molluscs, particularly the lack of Mytilidae spat, and the increased importance of crustaceans and other.taxa. These characteristics also occasionally occurred atmid-depth areas (9-14 m), leading to their appearance in the typically deep station groups. The majority of collections at deep stations (B04, B34, B13) were placed in two groups: Group 2 (prior to 1988) and Group 3. In 1990 and recent years, deep stations in Group 3 were characterized by the high abundance of the barnacle, Balanus crenatus, and by molluscs.such as mytilids,,Anomia sp., and Hiatella sp. Most samples from deep stations prior to 1988 (Group 2) lacked an abundance of barnacles, and'were characterized by low numbers of the molluscs Anomia sp.-, Tonicella rubra (red northern chiton) and mytilids. Asteriidae were also present in comparatively high numbers.Group 1 consisted of only three samples, two of which were mid-depth Stations B19 and B31, sampled in 1978, and one deep station.The.group was characterized by relatively, low abundances of the molluscs Mytilidae, fliatella. sp., L. vincta and Anomia sp., and high densities of Pontogeneia inermis. No stations have been similar to Group.1 since 1980.3.3.3.2 Intertidal Communities (Non-destructive Monitoring Program)Important intertidal species from the bare rock habitat (mean.high water zone), the Fucus spp. habitat (mean sea'level zone) and the Chondrus crispus habitat (mean low water zone) were monitored non-destructively at fixed stations on nearfield Outer Sunk Rocks (Station Bl) and farfield Rye Ledge (Station B5) three times per-year. The bare 342 rock areas at approximately mean high water supported low percentages of algae such as Porphyra spp. at intertidal Station Bl and Fucus spp. at farfield Station B5 (Section 3.3*.2). 'The predominant macrofaunal resident was Balanus spp., which was most abundant in the bare rock habitat. Balanus spp.. frequencies at both stations were slightly higher in April following the spring recruitment period,, than in July and December (Table 3.3.3-3). Preoperationally and in .1990, the nearfield station had a lower~frequency of Balanus spp. than the farfield. station.Herbivorous gastropods, Littorlina littorea (mainly at Station B5) and Littorina saxatilis (from both stations, but almost exclusively in the bare rock'zone), were also important constituents of the bare rock community, showing lower frequencies in April than in July or December.Patterns of faunal distribution in 1990 were within.the range of those observed in previous .years,. except for a large set of mytilid *spat at.farfield Station B5 in July, which was not sustained into the following season.Fucoid-covered ledge areas at approximately mean sea level were characterized by a heavy cover (over 80%) of the perennial algae Fucus spp. (mainly F. vesiculosus), with 'an understory of perennial red algae (Mastocarpus stellatus and, less frequently, Chondrus crispus).Highly-seasonal annual algae occurred in spring or spring and summer, particularly at Station Bl (Section 3.3.2). During the preoperational period, Mytilidae~spat was the most common taxon at nearfield Station Bl, with high frequencies during all three sample periods (Table 3.3.3-3.). -Mytilidae usually did not show high frequencies at Station, B5, where Balanus spp. was more common. Mucella lapilius occurred in the fucoid zone and was-more frequent .at Bl. It was most" commonly encountered in July. 'Other common gastropods were Acmaea.*testudinalis, Littorina obtusata and Littorina 7ittorea (almost exclusively occurring, at.:Station BS). Frequencies in 1990 were similar to previous years, except for Littorina obtusata which was more frequent atBl than in previous years in April and December, although it was absent in July-(Table 3.3.3-3).343 TABLE 3.3.3-3. MEDIAN AND RANGE OF PERCENT FREQUENCIESa OF THE DOMINANT FAUNA AT BARE ROCK, FUCOID LEDGE, AND CHONDRUS ZONE INTERTIDAL SITES AT STATIONS BI (OUTER SUNK ROCKS) AND B5 (RYE LEDGE) MONITORED NONDESTRUCTIVELY FROM AND 1990.SEABROOK OPERATIONAL REPORT, 1990.BARE ROCKC FUCOID LEDGE 0 COoNDRUS ZONEc PERIODb APR JUL DEC APR JUL DEC APR JUL DEC Acmaea testudinalis PREOP Bi median 0 0 0 0 6 .13 13 13 13.(range) (0) 10) (0) (0-25) (0-38-) (6-69) (6-38) (O-ZS) (6-81)1990 X freq. 0 0 0 12 12 12 6 19 31 PREOP BE median 0 0 0 6 6. 10 0 .0 0 (range) (0) (0) (0) (0-19) (0-38) (0-38) (0-44) (0-13) (0-25)1990 7 freq. .0" 0 0 12 38 25 12 0 0 Balanus spp. PREOP BI median 61 51 9 10 8 1 0 0 0 (range) (<1-100) {9-88) (0-88) (0-100) (1-38) (0-63) (0-47) (0-4) (0)1990 7 freq. 35 35 V7 19 11 1 7 7 0 PREOP B5 median 89 85 72 31 .23 5 0 0 0 (range) (58-100) (24-100) (5-100) (6-100) (12ý100) (1-88) (0) (0) (0-3)1990 Z freq. 96 88 59 31 21 9 0 0 0 t,, Littorina littorea PREOP 1990 PREOP 1990 BI median (range)Z freq.B5 median (range)7 freq.0 (0).0 (0-6)0 0 (0-13), 0 13 (0-56)25 0 (0-13)6 82 (13-100)88 0*(0)0 10 0-38)25 0 -(0-6)0 53 (13-75)38 0 (0-6).0 9" (0-31)z5 0 (0)19 81 (75-100)94 0 (0-13)25 100 (94-100)100--0 (0-6)19 88 (44-94)75 Littorina obtusata PREOP EB median 0 0 0 3 10 6 0 0 0 (range) (0) (0-19) (0) (0-6) (0-25) (6-19) (0-13) (0-44) (0-13)1990 Z frefq. 0. 0 0 25. 0 Z5 V0 0 6 PREOP B5 median 0 6 0 3 16 7" 0 0 0 (range) (0-6). (0-19) (0-13) (0-25) (0-44) (0-44) (0-13) (0) (0)1990 Z freq. 0 12 6 0 1z 25 lz 0 0 Littorina saxatils PREOP BI median 7 57 16 0 0 0 0 0 0 1990 (range) (0-44) (0-88) (0-88) (0) (0) (0-6) (0) (0) (0)199D 7 freq.. 0 0 12 0. 0 0 0 :0 0 PREOP. 85 median 50 66 75 0 0 0 0 *0 (range).. (0-100) (38-94) (6-100) (0-6) (0) (0-6) (0) (0) (0)1990 Z freq. 100 100 .88 0 0 0 0 0 0 (continued) TT TABLE 3.3.3-3. (Continued) BARE ROCKc FUCOID LEDGEc CHONDJUS ZONEC PERIODb APR JUL DEC APR JUL DEC APR JUL DEC (lytilidae PREOP B1 median 0 8 3 82 76 78 90 89 65 (range. (O-ZO) (0-40) (0-75) (37-1001 (27-100) (43-100) (54-95) (71-95) (15-85)1990 X freq. 0 11 18 73 82 69 55 84 63 PREOP 'B5 median 0 15 33 8 1 5 49 63 26 (range) (0-38) (0-38) (1-75) (2-100) (0-100) (0-100) (10-72) (23-80) (0-49)1990 Y freq. 30 47 26 9 16 8 46 69 15 Nucella lapillus PREOP Bi median 0 0 0 6 100 25 75 100 56 (range) (0) (0) (0-6) (O-ZS) (25-100) (6-50) (13-100) (100) (31-88)1990 Y freq. 0 0 0 6 100 12 12 100 19 PREOP B5 median 0 0 0 0 28 .0 94 38 69 (range) (0-94) (0-44) (0-56) (0) (6-81) (0-6) (75-100) (13-56) (56-81)1990 Y freq. 0 6 0 0 1,9 0 100 75 75 a Method of computing percent frequency varies among species (point-contact method for Nytilidae and Balanus since July 1983, bpercent frequency of occurrence for all other ins ances).PREOP period is 1982-1989, except for Chondrus zone, where sampling began in April, 1985.cBare ledge station is at upper edge of MSL zone, at approximate mean high water. Fucoid station is at approximate mean sea level mark. Chondrus zone station, first sampled in 1985, is at approximate mean low water mark.U-The Chondrus zone, at approximately mean low water, was characterized by rock ledge with a thick cover of red algae, mainly Chohd'eus crispus and Iastocarpus stellatus. -Fucus spp. were a6ltofte-quently encountered at Station B1 only (Section 3.3.2).. Of the macro-faunal species that were monitored, Nucella lapillus and Mytilidae spat were the most frequently encountered at both stations (Table 3.3.3-3).During the preoperational period, Mytilidae had medium-to'-high, frequen-cies in April and July with generally lower percentages in December. At Station Bl, Nucella was more abundant in July than in April or December.This is consistent with other studies which show adult Nucella to be active from May through October, while juveniles tend to be active throughout the year (Menge 1978). On Rye Ledge (Station B5), Nucella was the least frequently encountered in July during the preoperational period. In 1990, frequencies were higher than the median level in all seasons at the farfield station' No relationship between abundance levels of either Mytilidae or Nucella-at mean low water or within the fucoid habitat at mean sea level has been noted (NAI 1987b). The.gastropod, Littorina littorea, occurred in high frequencies-at only Station B5 throughout the year, and was most numerous in the Chondrus zone. In 1990, it occurred with moderate frequencies at B1 also. lAcmaea testudinalis was enumerated in low-to-moderate frequencies in the Chondrus zone at Station B1 in all years and occasionally at"Station B5;frequencies followed the same pattern in 1990.3.3.3.3 Subtidal Fouling Community (Bottom Panel Program)Analysis of subtidal bottom panels at mid-depth Stations B19 and B31 (sampled triannually in April, August, and December) provides information on recruitment of sessile macrofaunal species. Balanus spp.(mainly Balanus crenatus, with some. Balanus balanus) typically settled by April, Recruitment continued in some years'after the April sampling period and densities were higher in the August samples, while in other years April. sampling occurred near the settlement peak (Table 3.3.3-4).By December, densities were consistently low, as Balanus. populations 346 TABLE 3.3.3-4. ESTIMATED DENSITY (PER 1/4 m2i) AFTER FOUR MONTHS' EXPOSURE OF SELECTED SESSILE TAXA ON HARD-SUBSTRATE BOTTOM PANELS AT STATIONS B19 AND B31 SAMPLED TRIANUALLY (APRIL, AUGUSt, DECEMBER) FROM 1981-1989 AND IN 1990. SEABROOK OPERATIONAL REPORT, 1990.PREOP (1981'-1984, 1 9 8 6 b, 1987-1989) 1990 APR AUG DEC APR AUG DEC MEAN SD MEAN SD MEAN SD Balanus spp. Sta. B19 17053 13793 6403 4973 9 13 46366 3350 0 Sta. B31 40962 ZZ611 7917 6166 14 17 53333 700 0 Anomia sp. Sta. B19. <1 <1 31 68 1232 1136 6 1z5 3100 Sta. B31 0 0 36 42 993 1246 6 345 1766 Hiatella sp. Sta. B19 1 2 3966 2595 27 31 0 6117 36 Sta. B33 <1 <1 11659 10594 16 21 12 16304 49 Mytilidae Sta. B19 2 3 367 247 58 57 0 1083 44 Sta. B31 8 11 5035 10054 36 36 20 4786 104 aln 1981 only Balanus spp. and Anomia sp. were counted at Sta. B19. In 1982 only Balanus spp. and Anomia sp. were counted at both stations. In 1983 counts of all four taxa at both stations began. No samples were taken in 1985.1 bonly December collections were made in 1986.W. disappeared due to mortality. In 1990, the Balanus set at both stations was high (above the baseline average) in April, and had. virtually disappeared by December.Anomia sp. was unique among-the sessile taxa that were examined, showing a pattern of late summer-fall recruitment. Although low densities of Anomia sometimes occurred on panels by August, numbers were typically highest in December when abundances of all other sessile taxa was low (Table 3.3.3-4). In 1990, Anomia were very abundant, in comparison to the baseline average in December at both stations, indicating they had a "good" set..Iliatella sp.,. another sessile bivalve, showed highest den-sities by August collections, with most disappearing from panels by December during the baseline period. Densities in 1990 were well above average at both stations and showed a similar seasonal pattern (Table 3.3.3-4).During the preoperational period, Mytilidae spat generally had settled on bottom panels by August, with numbers greatly reduced by December (Table 3.3.3-4). Very high densities occurredin August 1990 at both stations. At B19, densities were at an all time high, and at B31 they were exceeded only in August 1984. Few of the newly-settled mytilids survived to December 1990, however at B31, the December density was above the baseline average.3.3.3.4 Modiolus modiolus Communities (Subtidal Transect Program)Shallow and mid-depth areas are monitored nondestructively to collect additional information on large invertebrates and macroalgae. Kelps and dominant understory algae species are discussed in Section 3.3.2. The green sea urchin, a key predator of kelps, is discussed in Section 3.3.5. As part of this program, Modiolus modiolus populations were enumerated triannually by divers along randomly pre-selected, 348 radiating transects at mid-depth Stations B19 (near the discharge), and its farfield counterpart, B31. No significant differences in Modiolus densities were found between 1990 and the preoperational period (1980-1989) when stations were tested separately with the Wilcoxon Signed Rank Test (at alpha- 0.05). Results using abundances from all three seasons, as well as those from October only (since October 1990 is the only operational collection) are: Wilcoxon' s Signed Rank Z Statistic OCTOBER ALL MONTHS Station 19 1.03 NS 0.51 NS Station 31 0.26 NS 1.13 NS Historically, abundances have been significantly higher at Station B19 than at B31 (NAI 1990b). This trend continued in 1990 (Figure 3.3.3-7), resulting in a significant difference over all years when tested with a Wilcoxon's two sample test (p<0.001). In 1990, the density of Modiolus increased over the previous year at both stations, as populations rebuilt after their 1989 decline (Figure 3.3.3-7). Despite year-to-year fluctuations in Modiolus density, the beds as a whole are relatively persistent, and form an important refuge for macroinvertebrates. As long as Modiolus survives the two main sources of mortality, predation by Asterias vulgaris and dislodgement by attached kelp, it can survive for several decades (Witman 1985).3.3.4 Surface Fouling Panels The surface f6uling panels program was designed to study both settlement patterns and community development in the discharge plume area. Short-term panels, 10 x 10cm plexiglass squares submerged for one month, provided information on the temporal seque .4r f settlement activity, while monthly sequential panels, exposed from one to twelve months' duration, provided information on growth and successional patterns of community structure. 349 Station B19 (Nearfield) E M0 0%0C 160 -150 -140 130 120 110 100 90 80 70 60 50 I ; I a I I I Ii 80 81 82 83 84 85 86 87 88 89 90 YEAR Station B31 (Farfield) E 0 Z.'no 160 150 140 130 120 110 100 90.80 70 60 I 50 80 81 82 83 84 85 86 87 88 89 90 YEAR Figure 3.3.3-7. Annual mean density (no. per 0.25 square meter) and 95% confidence interval of Modiolus modiolus observed by divers triannually at subtidal transect stations from 1980-1990. Seabrook Operational Report, 1990.350 3.3.4.1 Seasonal Settlement Patterns Faunal Richness and Abundance Development of a typical fouling community begins with bacterial invasion, followed by colonization by diatoms and other microorganisms that are apparently prerequisites to recruitment of larvae and spores (Wahl-1989). The intensity of recruitment on short--term panels, measured by the richness and abundance of noncolonial organisms, gives an indication of the potential for fouling community development. Historically, the number of nonncolonial faunal taxa (or faunal richness) settling on short-term (exposed for one month) surface panels has been low from January through April (Figure 3.3.4-1). The number of taxa settling on panels increased dramatically in June, remained relatively high through September, then decreased in the remaining months. Seasonal patterns were similar at all four stations..In 1990, numbers of taxa were exceptionally high (and outside the 95%confidence limits) from June or July through October at all four stations, continuing a trend first observed in 1989 (NAI 1990b).Analysis of Variance results indicate that the numbers of taxa in 1990 were significantly higher than previous years at both nearfield and farfield stations in the mid-depth (B19, B31) and deep (B04, B34)regions (Table 3.3.4-1). Numbers of taxa were similar between the nearfield and farfield station pairs. A variety of organisms including polychaetes, amphipods and molluscs, particularly nudibranchs, were responsible for the increased number of taxa (NAI 1991).Over the baseline period, total abundance (noncolonial taxa only) was low through May, peaked in the summer (July) and declined through the fall at all stations (Figure 3.3.4-2). Seasonal patterns were similar at all stations. Peak abundances on panels located over mid-depth stations (B19, -B31) were slightly higher but within the 95%confidence limits of abundances .at deep stations (B04, B34). In 1990, abundances at all four stations peaked in June and again in September. Abundances from July through September or October were higher than average'at all stations, a result of an exceptionally dense Mytilidae 351 Hearileld Station B04 30-2 x 4.I-l 0 CC W z 30-- PRE OP.25-19 20.ps %.. ... .. ,, 15 10 JAN, I I IA JAN. FEB MAR APR MAY JUN JUL AUG SEP CCT NOV EC~LI 0 cc z 25-20-15-10-5 Station B19 PREOP-.----- 1990 0 MONTH LO 4 I.-M z 30-25-20-15-10-Farfleld Station B34 PREOP 19- .I I I I I I I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV "DE MONTH Station B31-- PREOP 1990* .* '.,.1~. T ~'.4 I--0 zu zo 30-25-20-15-10-5-0.-I I I I I I I I 0 I- I a I I I I -I I I I I.JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DM MONTH I I .I I I I I I I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV (HZ MONTH Figure 3.3.4-1. Faunal richness (number of noncolonial faunal taxa on two replicate panels) in 1990 compared to mean faunal richness and 95% confidence limits on short term panels during preoperational period (B19, B31, and B04 from 1978-1984 and July 1986-1989 and B34 from 1982-1984 and July 1986-1989). Seabrook Operational Report, 1990. '7.7---I 4--.TABLE 3.3.4-i.RESULTS OF ANALYSIS OF VARIANCE COMPARING MONTHLY NUMBER OF TAXA, NONCOLONIAL ABUNDANCE, TOTAL BIOMASS, AND SELECTED SPECIES ABUNDANCE OR PERCENTFREQUENCY ON SHORT TERM PANELS AT MID-DEPTH (B19, B31) AND DEEP (B04, B34) STATION PAIRS FROM 1978-1990. SEABROOK OPERATIONAL REPORT, 1990.LO SOURCE OF PARAMETER STATIONS VARIATION df SS Ff Number of faunal B19, B31 Preop-Og' 1 138.13 24.26***taxa Station 1 0.45. 0.08 NS Year (Preop'0p)c. 10 832.75 14.62***Month (Year X Preop-0p)d 125 7,884.25: 11.08***Preop-Op X Station 1 3.38 0.59 NS Error .133 757.42 B04, B34 Preop-Op 1 21.45***.Station i 112. 07 1.62 NS Year (Preop-Op) 10 8.46 .13.61***Month (Year X Preop-Op) 125 711.04 9.64***Preop-Op X Station 1 6,296.03 0.01 NS Error 88 0.06 459.77 Noncolonial faunal B14, B31 Preop-Op 1 1.25 11.76***abundance Station 1 0.28 "2.67 NS Year (Preop-0p) 10 20.38 19.23***Month (Year X Preop-Op) 125 293.79 22.18***Preop-Op X Station 1 0.00 0.00 NS Error 133 14.09 B04, B34 Preop-Op 1 1.31 14.78***Station 1 0.28 3.19 NS Year (Preop-Op) 10 12.84 14.53***Month (Year X Preop-Op) 125 200.21 18.12***Preop-Op X Station 1 0.23 2.59 NS Error 88 7.78 (continued) TABLE 3.3.4-1. (Continued) U, SOURCE OF PARAMETER STATIONS VARIATION df SS Ff Biomass. B19, B31 Preop-Op 1 5.43 5.38*Station 1 0.43 0.43 NS Year (Preop-Op) 8 18.00 2.23*Month (Year X.Preop-Op) 103 408.96 3.94***Preop-Op) X Station 1 2.37 2.35 NS.Error ill 111.89 B04, B34 Preop-Op 1 0.17 0.15 NS Station 1 0.20 0.19 NS Year (Preop-Op) 8 18.91 2.21*Month (Year X Preop-Op) 103 524.02 4.75***Preop-Op X Station 1 5*05 4.71*Error 88 94.34.Mytilidae B19, B31 Preop-Op 1 1.48 12.32***Station 1 0.22 1.87 NS Year (Preop-Op) 10 20.80 17.36***Month (Year X Preop-Op) 125 350.66 23.42***Preop-Op X Station 1 0.01 0.00 NS Error 133 15.93 B04, B34 Preop-Op 1 1.21 12.65***Station 1 0.40 A4.12*Year (Preop-Op) 10 12.74 13.28***Month (Year X Preop-Op) 125 228.95 19.10"**Preop-Op X Station 1 0.40 4.16*Error 88 8.44 (continued) TABLE 3.3.4-1. (Continued)' -I-.Lw.Ln SOURCE OF PARAMIETER STATIONS VARIATION df SS Jassa marmorata B19, B31 Preop-Op 1. 0.42 3.87 NS Station 1 1.02 9.41**Year (!Preop-Op) ..10 6.45 5.95***Month (Year X Preop-0p) 125 92.21 6.80***Preop-Op X Station , 1 0.39 NS Error 133 14.43 -B04, B34. Preop-Op .1 0.02 0.17 NS Station 1 0.10 0.78 NS Year (Preop-Op) 10 5.43 4.38***Month (Year X Preop-Op) 125 66.02 4.26***Preop-Op X Station 1 0.48 3.8.7 NS Error 88 10.90 Balanus sp. B19, B31 Preop-Op .1 0.35 15.53***Station 1 0.02 0.67.NS Year (Preop-Op). 10 3.46 15.23***Month (Year X Preop-0p) 125 34.05 11.98***Preop-Op X Station 1 0.00 0.04 NS Error 133 3.02 B04, B34 Preop-Op 1 0.02 1.51 NS-,Station 1 0.00 0.19 NS Year (Preop-Op) 10 0.95 7.96***Month (Year X Preop-Op) .125 13.23 8.85***Preop-Op X Station 1 0.00 0.40 NS Error 88 1.05 (continued) TABLE 3.3.4-1. (Continued) SOURCE OF PARAMETER STATIONS VARIATION df SS Ff Tubularia sp. B19, B31 Preop-Op 1 0.02 0.12 NS Station 1 0.10 0.61 NS Year (Preop-Op) 10 9.74 6.19**Month (Year X Preop-Op). 125 95.11 ..84*ýPreop-Op X Station 1 0.08 0.49ýNS Error 133 20.92-B04, B34 Preop-Op .1 0.00 0.05 NS Station 1 .0 00 0.02 NS Year (Preop-Op)

10. 9.74 10.78***Month (Year X Preop-Op) 125 98.57 8.73***Preop-Op X Station 1 0.01 0.09 NS Error 88 7.95 U, oL.Preop.Op = 1990 v. all previous years (1978-84; July 1986-December 1989 except B34, whic* in 1982)..bStation regardless of year or period.-Year nested within preoperational and operational periods regardless of station: dMonth nested within year nested within preoperational and operational.

periods regardless elnteraction of main effects INS = Not significant (.05>p)*= Significant. Highly significant (.O01<p< .01)= VeryHighly Significant (p.O01)hL began of station --T-7--Nearfleld Station B04 6 Station B19 6-1"1 -PREOP 5 -i- -- 1990 5 .-- -PREOP 1990 z 00 z-j..4 3 2 w C)z:30 DC 0~~4 3-:2 1-K1f'I 0 U JAN FEB MAR APR MAY JUN JUL AUG. SEP OCT NOV DEC MONTH I I I .I I I IV I I 1 1I'JAN FR MAR APR MAY JUN, JUL AUG SEP OCT NOV EC MONTH I Farfield Station B34 6 w,-1--PlPREOP j -1990 w uC 0.00:3 n..5 4 3 2 0 0 w 0 z z m S 6-5-4 3-2-1-Station B31 PREOP.......- 1990.0 I I I I I I I I : I ! .1I 1 I I a I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP CCT NOV EEC MONTH MONTH Figure 3.3.4-2.Log (x+l) abundance (no./panel) in 1990 compared to mean log (x+1) abundance and 95% confidence limits. in 1990 and preoperational period (1978-1984 and July 1986-1989, B34 initiated in 1982) for noncolonial fauna on short term panels. Seabrook Operational Report, 1990. settlement. As a result, faunal abundances in 1990 were significantly h iher than.previous years at both nearfield and farfield station pairs-(Table 3.3.-4-1). Biomass Seasonal settling patterns for the entire 'fouling community (motile fauna, colonial organisms, macroalgae) are best demonstrated by changes in biomass. The dry-weight biomass (g/phnel) for short-term panels paralleled the pattern observed for the seasonal distribution of.faunal abundance and richness, although it was compressed into a shorter.period. Historically, biomass values have been highest during August,.September, and October at all stations (NAI 1990b). Seasonal trends in 1990 were similar to baseline years (Figure 3.3.4-3). At the mid-depth stations, peak biomass occurred in September, exceeding previously-observed values.. Biomass values for the entire year were significantly higher than previous years at both nearfield and farfield stations (Table 3.3.4-1). The primary cause was dense growth of the hydroid Tubularia sp. Molluscs including Mytilidae, Anomia sp., Iiatella sp., and predators suchas Asteriidae and nudibranchs,, also contributed to'high. biomass in September (NAI 1991).. At the deep stations, only nearfield station B04 showed a similar pattern in 1990 to the mid-depth stations; biomass values at the farfield station.were similar to previous years. The statistical significance of this result is demon-strated by a p<.05 in the Preop-Op X Station interaction term (Table 3.3.4-1). Decreased biomass is probably due to lower mytilid numbers (Table 3.3.4-2),and reduced Tubularia growth at B34 in comparison to B04. Panel photographs show Tubularia growth interspersed with bare spots at B34 in September, suggesting that grazing-or mechanical disturbance may have caused reduced biomass. The other stations showed a thick cover'of Tubularia sp.358 Nearfield Station B04 12-10-8 CU)6-4-2 0-PRE.......- 199 E0P aaC 12-10-8-6-4-2-Station B19 PREOP 1990 SII 4 a a. ---.I i I I I I I I I 0 m I I= I -I I JAN FEB MAR APR MAY JUN -JUL AUG SEP OCT NOV DEC MONTH I 1 .1 1 1 1 I I I JAN FEB MAR APR MAY JUN JUL AUG SEP MONTH I I I .OCT NOV DEC Farfield Station B34 Station B31 12 10 12 ul-PREOP-----.- 1990-PREOP 1990-86 4 2 0 0 n-C@'Tj 8 6 4 2 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV OW MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV Dr, MONTH Figure 3.3.4-3. Biomass (g/panel) in 1990 compared to mean biomass and 95% confidence limits at Stations B04, B19, and B31 from 1980-1984 and July 1986-1989 and B34,from 1982-1984 and July 1986-1989 on short-term panels. Seabrook Operational Report, 1990. TABLE 3.3.4-2.ANNUAL GEOMETRIC MEAN ABUNDANCE AND OVERALL GEOMETRIC MEAN AND' 95% CONFIDENCE LIMITS FOR MYTILIDAE SPAT AND JASSA MARMORATA COLLECTED MONTHLY ON SHORT-TERM PANELS FROM 1978-1989 AND IN 1990 (EXCLUDING 1985 AND JANUARY-JUNE 1986).SEABROOK OPERATIONAL REPORT, 1990.0'N CD PREOP.a b U L 19 TAXON STATION 1978 1979 1980 1981 1982 1983 1984 1986 1987 1988 1989 x U L 1990 Mytilidae B19 10 30 .76 79 20 20 21 133 17 27 .37 29 46 18. 59 B31 17 45 88 122 22 13 32 147 35 27 37 37 60 23 74 B04 5 18 41 37 13 11 15 48 21 18. 25 .18. 28 12 50 B34 .. ... -..8 15 14 141. 26 16 20 19 32 11 27 Jassa B19 3 2 3 6 5 3 4 4 4 1 3 3 4 2' 1 marmorata 831 3 4 3 3 8 2 5 8 10 2 2 4 5 3 4 B04 1 1 2 4 3 3 6 1 3 .0 5 2 3 2 2 B34.. -... .. .. 2 2 2 2 3 1 4. 2 3 1 3.n = 24 for Annual means and for overall mean 124 (B19, B31), 125 (B04) and 78 (B34)b July-December only 7_1 Community Composition Seasonal changes in the fouling community were further.examined through the use of numerical classification. The focus of this assessment was to determine if the seasonal species assemblages observed in 1990 at the discharge station (B19) were similar to previous years.The similarity levels of the various seasonal groups are displayed in a dendrogram (Figure 3.3.4-4), and the months in each year that compose the groups are shown in Figure 3.3.4-5.Seasonal changes in the noncolonial community structure at B19 parallelled those observed in total biomass and abundance. In winter (January-March,' and, in some years, December) settlement activity on.panels was low. The community was characterized by low densities of mytilids, either as the only dominant organism (Group 3), or in associ-ation with other species such as Anomia sp. (Group 1), the nudibranch Coryphella sp. (Group .2), and amphipod Pontogeneia inermis (Group 4;Table 3.3.4-3). The majority of collections from January through April were typified by this community (Figure 3.3.4-5).In some years, spring settlement of Balanus sp. transformed the typical winter community. In most cases, the spring species assemblage was restricted to low densities of Balanus sp. (Group 9); in one instance, Balanus sp. densities exceeded.500 (Group 7), and in two other collections, Balanus occurred along with Hiatella sp. and amphi-pods Ischyrocerus anguipes and Jassa marmorata (formerly J. falcata;Group 8).A summer community (Group 6), characterized by heavy bivalve settlement, occurred in every year, beginning in June and extending through September or October (Figure 3.3.4-4,5). Abundances of mytilids were exceptionally high, along with Ifiatella sp. and. Anomia sp. (Table 3.3.4-3). The summer community was replaced by a late fall/winter community (Group 5), characterized by moderate densities of Mytilidae 361 ................................. .................................. .................................... .................................. .................................. .................................. .............. -::'::Group 3 X'.............. Winter...... ... ............................. ..................... ..6............... ......................................................cn U)U-0 z l F 0.0 0.2 0.4 0.6 BRAY-CURTIS SIMILARITY 0.8 1.0/Figure 3.3.4-4.Dendrogram formed by numerical classification of noncolonial organisms collected from monthly short-term surface fouling panels set at nearfield Station B19, 1978-1984 and 1986-1990. Seabrook Operational Report, 1990.362 -GroupI......... Group 2 1989 0 "' ' '"" -FT\-G"u'o-o-, -°°, °. .8 Group4........... Group....... ...... ... ..~ ~ -Group 10 1986 -T ".'. " ".rup 1......... ." : Group6 CC 1984 ..... ..... .... i : i.:. Group 7>'= 1983"' "-.Group 8 JAN FM ..MAY JUU.A GSP.0. Group 9 1981 Grup1 198 ..= Group 11 Fiur...4.... Sesoa groups':: fomdGynmeiacasfiaiopflo xl)nnolna auac1979 fr St Group f 1978 and Jul 1 -m 1 er O t l JAN FB MAR-i APR MAY JUN JUL AG EP OCT =NOV DEC- unrpe MONTH Figure 3.3.4-5. Seasonal groups formed by numeric al'classi fi cation of log (x+.l) noncolonial abundances from -short-term surface panels from Station B 19 collected from 1978-1984 and July 1986-December 1990. Seabrook Operational IReport, 1990. TABLE 3.3.4-3. GEOMETRIC MEAN ABUNDANCE (NO./PANEL) AND 95% CONFIDENCE LIMITS OF DOMINANT NONCOLONIAI TAXA OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MONTHLY SHORT-TERY1 SURFACE PANELS SET AT DISCHARGE STATION B19 FROM 1978-1990. SEABROOK OPERATIONAL REPORT, 1990.NUMBER OF WITHIN/BETWEEN PREOPERATIONAL 3 1990 GROUP SAMPLES GROUP DOMINANT x C.I. x NUMBER SEASON PREOP 1990 SIMILARITY TAXA Lb Ub 1- Winter 12 2 0.49/.39 Mytilidae 1.1 .8 1.3 0.5 A-omia sp. .2 0 .4 0.6 2. Winter 2 0 0.57/.39 M3tiidae .5 '-.5r -.....-Corypbella sp. .5 .... --3 Winter/ 16. 0 "..,0.42/.37 MNytilidae 7.0 4.2 11.3 Spring 4. Winter/ 2 0 0.66/.37 Pontogeneia inermis 4.9 .......Spring. Mytilidae 2....5 Fall 32 2 0.56/.47 Mytilidae .42.4 28.9 62.0 "35.6.sse marmorata .6.3 4.4 8.9 4.6 6 Summer .32 7 -.0.54/.47 Mytilidae" 571.0 342.9 950.3' 3395.3"- iatella sp. 25.4 15.0 42.6 .262.5 Anomia sp. 2.6 1.3 4.5 32.7 7. Spring 1 0 0.42/.42 .Balanus sp.. 531.5 --.IMytitidae 52.0 -- --0.8 Late 2 0. 0.61/.40 Hiatella sp. 43.2 .... ..Spring Balanus sp.s 4.7 ... --Iscbyrocerus anguipes 4.5 --Jassa marmorata 4.3 .... .9. Late 9 1 0.38/.17 Balanus sp.. 5.7 2.1 13.4 2.0 Spring 10 Winter 1 0 0.33/.09 Coryphella sp. 1.5 ......11 Winter/ 2 0 0.54/.09 Riatella sp. 0.7 ......Spring 12 lSring 0 2 1.0/.049 Anomia sp. --0.5 b~upper and lower confidence 95% limits included only if n>2 preoperational = 1978-1984 and July 1986-December 1989 LO Oss.1 along with amphipod Jassa marmorata. This community occasionally preceded the period of heavy bivalve settlement as .well (Figure 3.3.4-5).The seasonal progression of the fouling community in 19.90 was in most months similar to previous years. January and February samples were characterized by low densities of mytilids and Anomia sp., making them most similar to Group 1 samples. March and April samples were sparse except for Anomia sp., a situation that had not occurred histori-cally. This led to the formation of Group 12, a group unique to 1990.Species composition from May through December progressed through typical spring (Group 9), summer (Group 6) and fall (Group 5) communities. In these months, species assemblages in 1990 were similar to those most common in previous years (Figure 3.3.4-5)'. Dominant Taxa Several dominant taxa on panels were monitored to determine their long-term recruitment patterns.Mytilidae spat (mainly juvenile MytilUs edulis) was the most abundant noncolonial taxon on short-term panels. Although settlement took place throughout the year, activity was most intense from June through September (Figure 3.3.4-6), coincident with larval availability (Figure 3.1.4-3). Some of this recruitment may also be the result of secondary settlement by juveniles (Bayne 1964). In 1990, as in 1989, Mytilidae spat settled in exceptionally high numbers, peaking in June and again in August-September. The annual average in 1990 was double the average of previous years at B19, B31, and B04 (Table 3.3.4-2).Mytilid abundances in 1990 were significantly higher than previous years at both nearfield and farfield mid-depth stations (Table 3.3.4-1). At the deep stations, mytilid abundances were significantly higher. in 1990 only at the nearfield station B04, demonstrated by the significant 365 Mytilidae Station B04 Station B19 5 w Q-z z D 0_j PREOP-------.. 1990 PREOP 3 2 z z D C, 0_j 4 3 2 0 JAN FE MAR APR MAY JUN JUL AUG SEP CGT NOV Dr, MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV EEB MONTH Jessa marmorata Station B04 Station B19 5 z 4 0 zj 4-3-2--PREOP 1990 uw 0 z z 3 ,4.x C, 0_J PREOP 1990 4 3 2 TiE-T-~L-~ 1 0I I I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV 133 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV Dr, MONTH MONTH Figure 3.3.4-6.Log abundance (no. per panel) or monthly mean percent frequency of Mytilidae, Jassa marmorata, Balanus sp. and Tubulariasp. on short-term surface panels at Stations B04 and B19 in 1990 compared to mean abundance or percent frequency and 95% confidence limits during the preoperational period (1982-1984 and July 1986-December 1989).Seabrook Operational Report, 1990.T 7Th p: __m _.w 0.z z 0_j 4-3-2-1-Balanus sp.Station B04 PRE OP-----.- 1990 5 PREOP 1990 Station B19 z 0-1 4 3 2 I 0 Iý0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV [EE MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV. DEC MONTH 100 90 Tubularla sp.Station B04 PRECP 1990 z I , z a: LL LI.100 90 80 70 s0 50 40 30 20 10 0 Station B19 PREOP.... 1990 30 20 ,10 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV EC MONTH JAN FEB MONTH Figure 3.3.4-6. (Continued) Preop-op-Station interaction term (Tables 3.3.4-1,2). This result is consistent with the biomass results.The amphipod.Jassa marmorata (formerly known as J. falcata) is a common fouling organism. As this species lacks a larval stage, recruitment occurs through dispersal of juveniles pr. adults through the water column. Historically, Jassa appeared on short-term panels throughout. the year, but recruitment was heaviest in the latter half of the year (Figure 3.3.4-6).. Gravid females historically have been most abundant from April through November (NAI 1985b). Seasonal patterns.observed in.1990 at the two nearfieldstations were similar to previous years (Figure 3.3.4-6). Despite lower-than-average peak abundances at the nearfield mid-depth station ('B19), 1990 abundances did not differ significantly from previous years at any of the stations (Table 3.3.4-1).Balanus sp. barnacles are among the first macro-organisms to colonize panels during the year. Settlement of planktonic larvae generally took place in March with barnacles appearing on the April panel collections (Figure 3.3.4-6). Historically, Cirripedia larvae in macrozooplankton tows have been most abundant in March and April (Section 3.1.5). -Peak density levels on panels varied by two orders of magnitude, and in some years Balanus sp. were rare. In 1990, Balanus sp. appeared only in May at B19 (Figure 3.3.4-6). Abundances in 1990 L were significantly lower.than previous years at both mid-depth stations (Table 3.3.4-1). At B04, Balanus sp. occurredin April and June in 1990. Abundances in 1990 were similar to previous years at both deep stations (Table 3.3.4-1).The hydroid Tubularia sp. is a dense summer colonizer. It is important not only because of its voluminous growth habits, which can prevent settlement and growth of other sessile organisms, but also as a substrate for epifaunal taxa. It is a favored prey of carnivores such as nudibranchs. Tubularia typically first appeared'in July or August, reaching peak cover within two months (Figure 3.3.4-6). Percent cover 368 often reached 100% at this time. Cover levels decreased by December.In 1990, Tubularia cover peaked later than usual (September) and was denser than the historical average (Figure 3.3.4-6). However, 1990 Tubularia sp. cover was statistically similar to previous years (Table 3.3.4-1).3.3.4.2 Patterns of Community Development Biomass Monthly sequential panels measure growth and successional patterns of community development. Seasonal patterns of community development are generally reflected in the monthly biomass levels.Historically, biomass values remained low through June, then increased sharply from August through October at all four stations (Figure 3.3.4-.7). The general trend, as indicated by monthly values averaged for the preoperational period, was for biomass levels to continue to increase for the remainder of the year at the farfield stations (B31, B34), while biomass at nearfield stations leveled off or decreased slightly in November before increasing in December (Figure 3.3.4-7). However, peak biomass levels have occurred in October, November or December (NAI 1990b). Subsequent decreases in biomass did not appear to be related to decreased abundance or cover of dominants but instead probably reflected the decreased volume of the community. In 1990, total biomass did not increase as the year progressed but remained depressed in comparison to average values. Levels in 1990 were significantly lower than previous years at all four stations (Table 3.3.4-4). Panel photographs show little evidence of community development, unlike previous years. This suggests that either recruitment did not occur, or immediate grazing or disturbance removed newly-settled species.369 Nearfield Station B04 1000 P19OP.... 1990 O-.800.700.600.500 400 300 200 100 V) -U)'E< C 2 Ca 0 CL ai'a 1000-9w0" 800-]700 -'600 400-300-200-100-o0-: Station B19 PREOP 1990*4* s---~.*I I I I I I I

• I I I *£ -JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV Dr, MONTH JAN FE3 MAR APR MAY JUN JUL AUG SEP OCT NOV MONTH Farfield Station B34 Station 31-1O 0,.C')-L a .1000, 800'700'600'500'400'300 200 100 0-PFEOP 1990 PREOP 1990 C')-.(fl*j O.~.800, 700-600.500.400, 300-200'100, 0 1000 JAN FEB MAR APR MAY JUN JUL AUG. SEP OCT NOV DEC'MONTH.JAN FEB MAR APR MAY.JUN JUL AUG SEP OCT MONTH Figure 3.3.4-7. Biomass (g/panel) in1990 compared to mean biomass and 95% confidence limits during the preoperational period (Stations B04, B 19, and B31 from December 1978-1984 and July 1986-1989 and B34 from 1982-1984 and July 1986-1989) on monthly-sequential panels. Seabrook Operational Report, 1990.77T 71 7 7V TABLE 3.3.4-4.ANOVA RESULTS COMPARING MONTHLY SEQUENTIAL BIOMASS AT MID-DEPTH (B19, B31) AND DEEP (B04, B34) STATION PAIRS FROM 1978-1990.

SEABROOK OPERATIONAL REPORT, 1990.--SOURCE OF STATIONS VARIATION df SS Ff Mid-depth Preop-OQP 1 385,535.1 36.44***B19, B31 Station 1 890.8 0.08 NS Year (Preop-0p)C 10 3,229,896.2 30.53***Month.(Year X Preop-Op)d 113 12,118,677.4 l0.14**Preop-Op X Statione 1 13,442.4 1.27 NS Error 123 1,301,269.1 Deep Preop-0p-1 .528,746.8 56.56**B04, B34 Station 1 2,658.0 0.28 NS Year (Preop-0p) 10 2,953,711.2 -31.60***Month (Year X.Preop-Op) 113 11,264,509.0 10.66***Preop-Op X Station 1 11,540.4 1.23 NS Error .88 822,617.8 aPreop-Op =.ý1990 v. all previous years (1978-84; July 1986-December 1989 except B34, which began in 1982)bStation regardless of year or period'Year nested within preoperational and operational periods regardless of station dMonth nested within year nested within preoperational and.operational periods regardless of station eInteraction of main effects fNS = Not significant (.05>p)SSignificant (.Ol<pS.05) Highly significant Very Highly Significant (p.l001) Annual Community Development Year-to-year differences in community.development were apparent, as indicated by the biomass, number of taxa, and abundance of organisms on surface panels exposed for one year. Biomass, which is a measure of the total.community, occasionally varied by two orders of magnitude among years. (Table 3.3.4-5). 1990 year-end biomass values were the lowest recorded.-to date at all four stations', parallelling, trends observed in the monthly biomass data. However, given the high variability in the data, 1990 values were not found to be. significantly different from previous years. Average values for the preoperational period were similar among stations, although yearly. values often showed an order of magnitude difference among stations. .In 1990, biomass at B19 was more than double that at the other stations.Number of noncolonial taxa was a more stable measure of the community than biomass or abundance, showing lower variability among years and stations. In 1990, the number of taxa was similar to " previous years at .B31, B04, and B34. Number of taxA in 1990 at B19 was significantly higher than previous years (Table 3.3.4-5).Historically, noncolonial abundance has been variable among years and stations. In 1990, noncolonial abundance was statistically.- similar to previous years at all stations, although abundances at B19 were the highest recorded to date (Table 3.3.4-5).Dominant Taxa Seasonal patterns of several species were examined to deter-mine survival after settlement. Historically, mytilid spat first appeared as an important component of the fouling community in June;.The percent frequency of occurrence had reached peak proportions by July or August, (Figure 3.3.4-8) coincident with the peak recruitment levelsýobserved on short-term panels (Figure 3.3.4-6). <Percentages remained high through December, exceeding more than 60% at both stations. While 372 TABLE 3.3.4-5.ANNUAL MEAN AND OVERALL MEAN DRY WEIGHT BIOMASS, NONCOLONIAL NUMBER OF TAXA, ABUNDANCE, AND LAMINARIA SP.COUNTS ON SURFACE FOULING PANELS SUBMERGED FOR ONE YEAR AT STATIONS B19, B31, B04, AND B34 DURING THE PREOPERATIONAL PERIOD (1982-1984 AND 1986-1989) AND IN 1990.. SEABROOK OPERATIONAL REPORT, 1990.-4)PREOPERATIONAL STATION .1982 1983 1984 1986 1987 1988 19.89 MEAN S.D. 1990 BIOMASS B19 133.3 714.9 1,117.6 698.1 170.8 1,408.1 387.4 661.5 476.88 132.8 NS (g/panel)B31 349.6. 397.6 773.6 883.3 93.1 1,711.3 753.8 708.9 523.86 52.1 NS B04 108.6 665.7 1,035.5 1,071.3 85.2 1,082.7 157.0 600.9 .474.66 51.1 NS B34 115.1 821.5 1,266.1 952.6 167.5 1,716.4 723.0 823.2 570.39 60.5 NS NUMBER OF NON- B19 25 14 21 19 19 27 24 21.3 4.42 34*COLONIAL TAXA (No./panel)," 831 26 24 20 33 23 31 24 25.9 4.60 24 NS B04 19 23 17 25 27 26 28 23.6 4.16 24 NS B34 16 27 18 20 24 25 30 22.9 5.05 27 NS NONCOLONIAL B19 2,647 15,197 20,783 14,745 6,148 21,281 16,535 13,905.1 7,046.48 27,625 NS ABUNDANCE (No./panel) B31 1,983 24,127 14,945 31,159. 11,185 58,300 22,074. 21,967.6 18,398.27 23,265 NS B04 3,149 13,805 10,868 , 10,008 .48,310 22,391 27,171 19,386.0 15,063.89 27,024 NS B34 822 ý12,702 11,931 12,532 62,537 21,002 13,026 19,221.7 19,986.38 5,693 NS LAMINARIA SP. B19 51 16 6 0 97 0 0 24.3 36.91 0 NS (No./panel) 831 64 78 13 11 48 56 5 39.3 29.24 4 NS B04 92 .0 0 0 1 6 0 14.1 34.40 2 NS 834 65 0 0 1 43 2 0 15.9 26.83 0 NS*.01<PS.05 when tested with a single sample t-test (Sokol and Rolf 1969.) Mytilldae z W..0 w M II-e0 a Uj wL 0-100 90 80 70 60 50 40 30 20 10 0 Station B19-PREOP....... 1990 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV ECI MONTH JAN FEB MAR APR MAY JUN JUL AUG SP OCT NOV EEC MONTH Jassa marmorata Station B04-PREOP 1990 Station B19 100-90-80-70-100'-PREOP---.--- 1990 C)z a uJJ II-.60 50 40 30 .20 10 0'JAN FEB MAR APR MAY JUN z U.'LU.LL.80.70, 60.50'40, 30, 20'10 0'I I I I I I JUL AUG SEP OCT NOV Dr, Dr, MONTH MONTH Figure 3.3.4-8. Monthly mean percent frequency or log transformed abundance (no. per panel) on monthly sequential surface panels for Mytilidae, Jassa marmorata, Balanus sp., Tubularia sp. and Laminaria sp. at Stations B04 and B 19 in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1984 and July 1986-December 1989). Seabrook Operational Report, 1990.I IT _7 --'- _----

---

--------Balanus sp.Station*B04 Station B19 100-PREOP--.---- 1990 z LL 70 z LUI LU U-.100 90 80 70 60 50 40 30 20 10 0 I PREOP....... 1990 0 AUG SEP OCT NOV CM JAN FEB MAR APR MAY JUN JUL AUG SEP OCT MONTH MONTH LU ,U-j m LU LI-Tubularla sp.Station B04 100-90 -PREO'1990 ..80-70-so-" 40 30" 20 0-=T JAN FEB MAR APR MAY JUN JUL AUG SEP CxT NOV DIr MONTH>-z LU 0 Ll IJ-Station B19 100.go 80 70 60, 50-40, 30-20-10.0.-- PREOP 1990 JAN FE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 3.3.4-8. (Continued)

Laminaria sp.Station B04 Station B19 w 0 z 0 z 0 2.0 1.5 1.0 0.5, 0.0 LU z z 0-j 2.0 1.5 1.0 0.5 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DCr MONTH MONTH Figure 3.3.4-8. (Continued) [ii 717 percentage frequencies remained stable in late summer and fall, mussel growth (as evidenced by larger lengths; Figure 3.3.4-9) contributed to the high biomass levels in the latter part of the year. Mussel growth also decreased available space, crowding out taxa such as Balanus sp.In 1990, seasonal patterns'and frequency levels were similar to previous years at both nearfield stations (Figure 3.3.4-8). Mussel lengths were'smaller than average for mostof the year at both stations (Figure 3.3.4-9). This probably contributed to lower-than-average biomass levels (Figure 3.3.4-7).Historically, the amphipod Jassa marmorata has occurred year-round, but had become an important constituent of the fouling community beginning in June, occurring with frequencies of at least 10% (Figure 3.3.4-8). Overall mean percent frequencies increased in September-October, remained high through December at B04 and-decreased at B19.However, large confidence intervals indicate seasonal patterns were variable among years. Increased frequency of occurrence was most likely related to increased available substrate (as indicated by increased biomass levels), providing increased structural complexity, food, and refuge. In 1990, Jassa appeared at Station B19 in substantial frequen-cies only in November (Figure 3.3.4-8). At Station B04, Jassa occurred later than usual and was encountered frequently only from October to December (Figure 3.3.4-8). The diminished presence of Jassa may be related to decreased Inumbers of Laminaria sp. (Table 3.3.4-5), its preferred substrate on panels. In 1990, during the months when it was present on panels, Jassa lengths were similar to the historical average (Figure 3.3.4-9).Historically, Balanus barnacles typically first appeared on monthly sequential panels in April, as observed on short-term panels (Figure 3.3.4-8).. Percent frequency of occurrence increased in June at both stations. At B19, Balanus percentages stabilized at approximately 20% through.December. Percentages at B04 remained high from June-August, then decreased. However, large confidence intervals around monthly means indicated large differences in seasonal patterns among 377 Station 19 Mytilidae Jassa marmorata E z-j 10 8 7 6 5 4 3 2 1 0-PRE OP-----.- 1990 z LUI-J 10 9 8 7 6 5.4 3 2 1 0 JAN FE MAR APR MAY JUN JUL AUG SEP OCT NOV CEC MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Station 31 Mytilidae Jassa marmorata Co z LU-j z LU-J JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH JAN FE3 MAR APR MAY JUN JUL AUG SEP CCT NOV D3 MONTH Figure 3.3.4-9. Mean length of Mytilidae and Jassa marmorata collected from monthly sequential surface panels in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1989).. Seabrook Operational Report, 1990. years. Decreased frequencies probablyreflected decreases in available space due to growth of other sessile taxa such as mytilids and Laminaria sp. As on short-term panels, Balanus frequencies were lower than average in 1990. Peak abundances (September, B04; July, B19) were later than has been typically observed.Historically, Tubularia sp. has predominated in the latte.r half of the year. Peak frequencies reaching nearly 40% usually occurred in August' at B19 and in September at B04 (Figure' 3.3.4-8); November and December were generally periods of lower frequencies. However, large confidence limits suggest that seasonal patterns were not as consistent as indicated by the preoperational monthly-mean. In 1990, Tubularia sp.occurred mainly in'September and October Peak densities occurred *in September at B04, consistent with previous years. At B19, peak densi3-ties occurred in October, later than observed in-previous years.Tubularia had higher than average peak frequencies in 1990,. paralleling trends observed on short-term panels.Kelp (Laminaria spp., mostlyjuvenile L. saccharine but occasionally L. digitata) are important members of the surface fouling panel community. Generally opportunistic in their settling patterns, kelp sporelings are among the first organisms to colonize new substrate. Once established, they provide habitat and a food source for other fouling organisms. Kelp settlement was highly variable among years. In some years, no juveniles settled on panels while in others, an annual average of up to 97 per panel was attained (Table 3.3.4-5). Numbers were generally higher on panels from mid-depth stations (B19, B31) in comparison to deep stations (B04, B34). In 1990, no Laminaria remained on panels placed at B19 and B34-after a year's exposure. Low numbers were collected at B04 and B31. Numbers ofnLaminarla in 1990 were statistically similar to previous years at all four stations.The seasonal pattern of Laminaria sp. settlement and growth was variable from year to year. Sporelings first appeared from April to July (Figure 3.3.4-8). Peak abundances generally occurred in June or 379 July, and abundances stabilized for the remainder of the year. Numbers of Laminaria and their seasonal occurrence in 1990 were similar to previous"years at B04. AtB19., Laminaria numbers were higher-than. average from May-July in 1990, then decreased sharply in October.3.3.5 Selected Benthic Species Seven macrofaunal taxa from the area of the discharge (near-field) and from a control area off Rye Ledge (farfield).(Table 2.1-2, Figure.2.i-4) were selected for intensive monitoring from intertidal.. Stations. BIMLW and B5MLW, shallow subtidal stations B17 and B35 and mid-depth Stations B19 and B31: Selection of.taxa was based on abundance, and/or trophic level (Table 2.3-3). Sampling~generally took.place in May, August and November. Abundance data.,from short-term fouling panels at Stations B19 and B31 were compared-to benthic:data. Length data for Mytilidae spat and Jassa inarmorata from monthly sequential panels were examined. Numbers of large sea urchins estimated by SCUBA divers from counts on subtidal transects were noted.3.3.5.1 Mytilidae Mytilidae, composed primarily of juvenile Mytilus edulis, was the most abundant taxon at all three nearfield/farfield station pairs.Ilytilus edulis reaches 100 mm in length (Gosner 1978), and is an important prey species for fish, sea stars, lobsters, and gastropods. It clings to hard substrate with strong byssal threads, is an important fouling organism, and forms a habitat for many other species. The geometric mean density for the 1978-1989 preoperational period was over an order of magnitude higher at intertidal stations than subtidal depths (Table 3.3.5-1).Densities in 1990.were higher than baseline averages at both near- and farfield stations in the intertidal and shallow subtidal depth*380 zones, and their interactions were not significant (Table 3.3.5-1,2).. The annual trend at each shallow subtidal station, for example, was roughly similar, with the lowest density in 1985 at both near- and farfield stations, and the highest in 1984 during the 1982-1990 period (Figure 3.3.5-1). However, at the mid-depth station pair, the 1990 density at B31 was below the baseline average, but at B19 (discharge) it was above average, and the interaction was significant. Station B31 was the only station out of the six stations sampled to show a belowaverage density in 1990.The Mytilidae collected usually ranged from less than i mm to 30 mm in length, and averaged between 2 and 3 mm. Many of the smallest mytilids had settled on macroalgae rather than on the bottom or hard substrate, a pattern also observed by other investigators (Bayne 1965;Suchanek 1978). The preoperational mean length of intertidal mytilids was slightly larger than subtidal mytilids (Table 3.3.5-3) although intertidal population densities were much higher than subtidal densi-ties. Yearly differences in mean length for each of the nearfield/far-field station pairs historically have not been significant (NAT 1987b).In 1990, the lengths at all three station pairs were within the range of previous years.The level of mytilid settlement at mid-depth Stations B19 and B31 is indicated by the abundance on subsurface short-term fouling panels (Section 3.3.4). Monthly densities suggest that some primary or secondary settlement takes place throughout the year, but is heaviest from June through November. In 1990, the heaviest sets occurred from., early summer through early fall (Figure 3.3.4-8) and nearly equaled or exceeded any previous all time high. Mytilid lengths at Stations B19 and B3i ranged from <1 mm to 44 mm in 1990 (NAT 1991),.greater than previous years. Monthly measurements indicate 99% of the mytilids measured in June at both stations in 19.90 were I mm or less (NAT 1991).The all years' mean monthly length was about 1.0 mm at both stations in July, indicating settlement of new recruits occurred (Section 3.3.4).From September through December the monthly mean length over all years 381 TABLE 3.3.5-1. ANNUAL GEOMETRIC MEAN DENSITY (NO.I/mn) OF SELECTED BENTHIC SPECIES SAMPLED TRIANNUALLY IN MAY, AUGUST, AND NOVEMBER FROM 1978 THXOUGE 1990. SEABROOK OPERATIONAL REPORT. 1990.--------------------------------------------------------------------------------------------------------------------------------------------------------------------------- SPECIES STA 1978 1979 : 1980 1 1981 : 1982 1 1983' 1984 1985 : 1986 1987 ý 1988 : 1989 1 PREOP m I 990b .+ + + + + ------- -------------------------------------- -- ---- --- --- ------- --- --- ------- ---- -- -------------

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MEAN ! MEAN MEAN ý MEAN MEAN ; MEAN : MEAN MEAN : MEAN : MEAN 1 MEAN : MEAN : LOWER: MEAN ; UPPER :,LOWER : MEAN : UPPER:---------

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7 -- -+---------- .--------- +---------- +--------------+- +.......-

+ -------+--- .------------------------

Mytilidae BIMLW B5MLW B17 B35 B19 B31!Nucella BIIGW:lapillus B5MLW:Asteriidae B17 S : B35 o Pontogeneia B19 linermis B31.Jassa B17 imarmorata 3ýAiMithoe BlMLW 1rubricata B5fLW:Stronqyloce-B19 introtus B31:droebachien-

sis:178931: 135333: 76830: 117038: 217205: 51811: 84696: 63307: 227020: 121566: 140499: 1766761 105260: 123874: 145780: 90590: 1513861 2529821 2098: 166: 1171: 1385:-882.189: 1209: 344:..37: 20:-: 39282: 47738: 78963: 575051 123203: :98711: 85673: 65360: 60128: 72491 : 87397: 90643: 126900:-177659:

8940:. 1674: 1704: 268: 9551 2323:.3501: 12144: 14042: 3492: 3815: 1821: 1832: 561: 715: 617: 429: 510: 458: 907: 727: 2950: 508: 505: 357: 581 173: 279: 53: 66: 89: 3975: 1764: 1695: 1743: 759: 6691 743: 655: 949: 659: 28811 5699: 134: 1361 94: 74;963: 7980: 566: 7328: 13416: 1055: 1247: 6493: 6651: 1095: 17842: 81457: 1568: 5633: 3250: 530: 888! 1378: 208: 392: 592: 39: 167: 198: 562: 386: 604: 470: .512: 280: 398: 660: 1622: 4980:. 2031: 1465:1 36: 9: 3i 20: (Q: o: 15: 29: 188:ý55: 33: 34: 6071 : 8511 7868: 3704: 2347: 824!393: 71: 595: 606: 2047: 1881:<1: 0 : 175: 34: 4214: 1299: 7834:' 3834: 4780: 3471: 6537: 17192: 1166: 1122: 1146: 681: 508: 748:ý299: 284: 280W 9351*174: -862: 841: 326: 946: 9671 o: (1: 0: 21 112: 23: 19: 22: 3714: 4052: 3245: 3261: 1456: 1026: 827: 241: 702: 260: 900: 944 0: II: 26: 31 2090;3514:l 1322: 4513: 1647: 711:.534:-148: 509 : 326: 818!I1187: 13: 2: 51: 22: 2731: 3570:.4667: 6198: 1816: 2495: 5878: 7657: 1928: *2256: 855: 1029: 632: 7481 195: 2561 623: 762: 399: 487: 10341. 13071 1673: 2358: 22: 36: 31 6: 71: 971 30; 40: 2861: 6774: 160411 3211: 55831 9710: 3651: 6568' 118161 792: 15551 3056: 1485: 3361: 76061 891: .141]: 22341 643: .1238: 2382: 761: :16801 3708: 352: 643: 1174: 160: 281: .4941.170: 502: 1479: 771: 1196: 1856: o0 o: Ol 8: 25i 76: 3: 91 27: 7: 20! 521-PREOP = preoperational period = May, August, and November through 1989; LOWER/UPPER --95% (geometric) confidence interval 199O preoperational period = May , August , and November 1990; LOWER/UPPER -95% (geometric) confidence interval T --- 7 TTI .-T--. ;-17 1K TI TABLE 3.3.5-2.RESULTS OF TWO-WAY ANALYSES OF VARIANCE COMPARING LOG-TRANSFORMED DENSITIES OF SELECTED BENTHIC SPECIES AT NEAR- AND FARFIELD STATION PAIRS (IMLW/5MLW, B17/B35, PREOPERATIONAL (THROUGH 1989) AND OPERATIONAL (1990)PERIODS. SEABROOK OPERATIONAL REPORT, 1990.SAMPLED IN SAMPLED IN MAY, AUGUST, NOVEMBER AUGUST. NOVEMBER SOURCE OF SPECIES STATIONS VARIATIONa df SS Fy df SS Fb Mytilidae BImLW Month (Year (Preop-Op)) 26 22.72 8.98*** 13 10.19 7.11***B5MLW Year.(Preop-Op) 11 4.66' 4.35-** 11 9.62 7.93***Station 1 0.64 6.62* 1 0.68 6.15**Preop-Op -1 0.77 7.91" 1 0.48 4.31**Preop-Op X Station 1 0.17 1.74 NS 1 0.10 0.86 NS Error 249 24.24 172 18'.97 B17 .IMonth (Year (Preop-Op)) 26 45.64 7.13"** 13 15.62 5.93***B35 Year (Preop-ýOp) 11 21.01 7.76*** 11 23.99 10.77***Station 1 0.14 0.56 NS 1 0.30 1.47 NS Preop-Op 1 1.72 7.00** 1 1.94 9.56"*Preop-Op X Station 1 0.64 .2.60 NS 1 1.18 5.84*Error .241 59.29 164 33.21 B19 Month (Year (Preop-Op)) 26 36.53 4.07*** 13 15.57 3.52**A B31 Year (Preop-Op) 11 64.73 17.06"** 11 33.45 8.94***Station 1 0.04 0.11 NS 1 0.25 0.74 NS Preop-Op 1 0.00 0.01 NS 1 0.39 1.13 NS Preop-Op X Station 1 9.41 27.27*** 1 5.53 16.25**Error 294 101.41 200 68.05 (continued) TABLE 3.3.5-2. (Continued) SAMPLED IN SAMPLED IN MAY, AUGUST. NOVEMBER AUGUST. NOVEMBER SOURCE OF SPECIES STATIONS VARIATION 2 -FS Nucella lapillus B1MLW Month (Year (Preop-0p)) 26 17.14 5.62-,*" 13 7.06 4.27***B5MLW. Year (Preop-Op) 11 6.46 5.01- i1 8.21 5.87**Station 1 2.94 25.08*** 1 1.42 'Preop-Op 1 1.00 8.14"* 1 1.65 12.98***Preop-Op X Station 1 .0.04 0.37 NS 1 0.05 0.39 NS Error 249 29.21 " 172 21.85 Asteriidae B17 Month (Year (Preop-Op)) 20 21.18 10.17* 1i0 4.07 3.83***B35 Year (Preop-Op) 8 14.68 17.62*** 8 15.81 18.61***Station 1 0.60 5.80* 1 0.34 .3.17 NS Preop-Op 1 9.75 93.63*h 1 13.43 126.41***Preop-Op X Station 1 2.11 20.250 1 2.72 25.57**-Error 205 21.34 140 14.87 Pontogeneia BI9 Month (Year (Preop-op)) 26 28.59 5.36 6 13 19.11 6.97.**inermis B31 Year (Preop-Op) 11 6.74 2.99** 11 6.00 2.58***.Station 1 1.92 .9.37*-* 1 1.65 7.80'Preop-Op 1 0.08 0.41 NS 1 0.03 0.16 NS Preop-Op X Station 1 0.23 1.14 NS 1 0.32 1.54 NS Error 294 60.30 200 42.18 (continued) w cn0 TOO -711 -T .-T-. I -0 TABLE 3.3.5-2. '(Continued) LO 00 Ltn SAM{PLED IN SAMPLED IN MAY. AUGUST. NOVEMBER AUGUST. NOVEMBER SOURCE OF FS SPECIES STATIONS VARIATION df SS df SS Jassa marmorata B17 Month (Year X Preop-Op) 26 23.70 2.50*** 13 10.78 1.81*B35 Year (Preop-Op) 11 16.01 4.00**A 12 16.48 Stationb 1 2.62 7.18-* 1 2.40 5.23*Preop-Ope 1 1.92 1 1.18 2.57 NS-Preop-Op X Stationd 1 0.09 0.25 NS 1 0.27 0.59 NS Error 241 87.76 164 75.33 Ampithoe rubricata B1MLW Month (Year X Preop-Op) 26 33.96 3.23*:. 13 24.48 4;66h**B5MLW Year (Preop-Op) 11 236.02 53.04** 11 169.07 38.00***Station 6 1 13.99 34.59*** 1 16.52 40.84***Preop-Op' 1 9.30 22.99* 1 3.25 8.04**Preop-Op X Stationd 1 12.32 30.46*A, 1 13.65 33.75***Error 249 100.72 172 69.56 Strongylocentrotus B19 Month (Year X Preop-Op) 26 36.50 2.89*-* 13 13.99 2.61l droebachiensis B31 Year (Preop-Op)- 11 39.67 7.42*** 11 32.92 7.27-*Stationb .1 0.05 0.11 NS 1 0.32 0.77 NS Preop-Op' .d .7.07 I4.56***. 1 4.59 11.15*l*Preop-Op X Stationd 1 3.20 6.58* 1 3.80 9.23*!*Error 294 142.88 200 82.34.aNS not significant (p>0.05)* = significant (0.05->p>0.01) = highly significant (0.01np>0.001) = very highly significant (p50.001)bnearfield = Stations 1MLW, B17, and B19; farfield Stations B5MLW, B35, B31, regardless of year/period preoperational (through 1989) versus operational (1990) period, regardless of station interaction between main effects z w.0 C, 0-j 2-3-2-Station B17 Asteriidae 4-3-Mytilidae z 0 c,)0-i 2 f 1 0 I ý:-0 I I I I I I I I I I I 1 1 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR I I1 I , I I I I I -I I 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Station B35 Asteriidae Mytilidae-z 0-j 5-4-3-2-I-.-ILl (3 0 5-4-3-2-1-0-I I I I .I I I 1 1 1 I 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR I I I I I I I I 1 I. 1 1 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Figure 3.3.5-1.Yearly means and 95% confidence limits for the log (xýl) density (no./m 2) of Asteriidae and.Mytilidae from Stations B17 and B35 sampled three times per year from 1978 through 1990. Seabrook Operational Report, 1990.I II TABLE .3.3.5-3. ANNUAL MEAN LENGTH (MM) .,ANT) 95% CONFIDENCE INTERVAL FOR SELECTED BENTHIC SPECIES SAMPLED TRIANNUALLY IN MAY, AUGUST,AND NOVEMBER AT SELECTED BENTHIC STATIONS FROM,1982 THROUGH 1990. SEABROOK-OPERATIONAL REPORT, 1990.:TAXA STATION 1982 1983 1984 1985 1986 '1987 :1988 1989 PRED?. :1990 S--------+-----------+-----------+-----------+-----------+-----------+-----------+-----------+----------

• w .i "'EN~C MEAN : CI :MEAN: CI :MEAN : CI :MEAN; CI :MEAN ; CI.:MEAN : CI :MEAN : CI :MEAN:; CI lfMEAN 1 CI---------- ---- ---- --------- -------------------------------;Mytilidae lMLW 2.7: 0.1: 4.5: 0.2: 2.7: 0.1: 2.6: 0.2: 2.8: 0.1; 3.1: 0.2: 3.2: 0.2:V 3.7: 0.2; 3.2: 0.1; 3.1: 0.1;I5MULW 2.8: OXi 3.2:40.2:

2.9: 0.1: 3.0: 0.11 4.0: 0.2;.3.1: 0.1: 3.5: 0.2: 3.5; 0.1: 3.3k0.1:. 3.5: 0.11 17 1.9: 0. 1. 2.1! OX 2.8: 0.1: 2.4: 0.2: 2.51 0.11 1.9: 0.1: 2.8: 0.1; 2.1: 0.i .2.3k0.1: 2.2: o.1;35: 1.8: 0.i: 2~: .1: OX 3.1: 0.2: 2.4 0.1: 2.7: 0.2: 2.3: OXi 2.9: 0.2: 2.4:* 0.1: .2.5:<0.1: 2.5: 0.1: 19 .2.0: OX1 2.3: 0.1: 2.1: OXi 2.4:.0.21:2.3: o-i: 1.8: OXi 3.7: 0.2: 2.3: 0.2: 2.4 0.1: 3.0: 0.1: 31 :2.2:'0.2: 1.9: 0.X 2X1_ o.i; 3.5: 0.1; 4.11 0.3:,2.0: 0.o1: 2.4: *OXi 4.0: 0.2: 2.8: OXi 2.7 0.2::Nucella 1LW :8.0: 0.3: 3.3: 0.2:.4.0:. 0.2 5.0: 0.3: 7.7: 0.5:11.9: 0.,6:11.5: 0.6: 8.5: 0.4: 6.9: 0.2: 5.4: 0.4: 0-0 :lapillus 5M'UW .:5.7: o.5: '6.2: 0.6: 6.9: 0.6: 6'.3: o.5: 6.2: 0.5ý 4.3: .0.4 7.1: 0.6: 5.2: 0.6: 6.0ý 0.21: 5.9: 0.6::Asteriidae 17 :4.0: 0.3: 5.4: 0.7: *7.8: 0.8: 7.5: 0.4: 7. 3: 0.6; 3.1: .0.3; 4.7: 0.3; 3.2: 0.2; 5.0ý 0.2: 3.3: 0.2: 35 : 5.3: .0.5:11..4: 3.4: 5.7: 0.9:10.1: 1.0:13X1 2.6: 4.6: 0.6: 8.4 0.6: 6.0: 1.0: 6.7: 0.3: 3.0: 0.2:* :Pontogeneia. 19 4A .OS3 5.2 0.3: 4.9: 0.2: 5.3: 0.3ý 4.7: 0.3: 4.7: 0.3: 6.2: 0.3 `5.2: 0.3; 5.1: 0.1: 5.21 0.2::inermis 31 :4.6: 0.2: 5.2: .0.3: .4.6: 0.2: 5..8: 0.3; 5.2: 0.2: 5.6: 0.4: 5.7: 0.2: 5.6: 0.3: 5.3: 0.1: 6.0: --0.4::Jassa .17 :3.3: 0.2: 4.3: 0.2: 4.4: 0.2: 4.5: 0.2: 4.4: 0.2: 3.8: 0.12: 4.6: 0.31 4.1: 0.2: 4.2: 0.1: 3'.9: 0.2 ,mroaa 3 3.5:.0.2: 3.7: 0.2: 3.7: 0.1i 4.5: 0.2: 4.1: 0.2: 3.5: 0.1: 4.4 0.2. 4.2:0239 .240 .:Anmithoe 1¶~W :6.7: 0.3: 7.7: 0.6:.6.9: 1.5:.10.9: 4.1 ,b -:-- : -:12.9; --: :7.0: 0.3: -: -:rubricata 5MLI.W : 7.6: 0.5: 8.5: 0.8: 8.9: -: -: -.- : -6.9: 3 2,,' 8.0,: 1.0: 7.8: 0.4ý 6.1: 0.8;:strongyloce-19 :1.8: 0. 3: 1.8: o.5: 1.7: 0.3: 2.7: 0.4; 1.5: 0.3: 1.7: 0.2: 2.7: 0.8: 1.7: o.s: 1.9: 0-1: 2.0: 0.7::ntrotus 31.' : .I I I I .I I .1 I* .droebachien-II II Ii 1.7: 0.2: 2.3: 0.3: 1.7: 0.21 2.5: 0.6: 1.5,02 .~03 .:04 .:19 ~:oi .:os aMEAN=0SM OF THE LENGTHS OF ALL INDIVIDUALS MEASURED IN MAY, AUGUST, AND NOVEMBER"+ TOTAL NUMBER-OF INDIVIDUALS MEASURED IN THAT YEAR bNONE COLLECTED ranged from about 4-6 mm at both stations (Figure 3.3..5-2), indicating 'that a smaller percentage of new~recruits (1-2 mm) settled,'and second-,ary settlement and growth occurred.3.3.5.2 Nucella lapi.lus Nucella lapillus reaches 51 mm in length (Abbott 1974), and is*.an abundant intertidal gastropod (drill) and an important predator,- particularly on mytilid spat and barnacles (Gosner 1978). It ranges.from eastern Long Island Sound to the Arctic, and also northern Europe (Gosner 1978). When 1990 mean densities were compared to the preopera-tional means at the intertidal station pair, the interaction term was not significant (Table 3.3.5-1,2). The 1990 densities at both stations.were higher than the baseline averages. The nearfield density was .within the range of previous years, and the farfield density was at.the all time high (Table 3.3.5-1), .Nucella collected during 1990 ranged in length :from about.1-27* mm, (NAI 1991) and averaged about 6-7 mm in length at both stations during the preoperational period. In 1990, mean length was below average (about.5.5 mm at both stations), but within the baseline ranges.(Table 3.3..5-3). In 1987 and 1988, the.mean length was unusually large due primarily to the occurrence of substantial numbers of large (14-18 mm) individuals. Previous studies have shown adult snails to be active -only from May through October, retreatinginto crevices in the winter;.while juveniles (2-5 mm) are more evenly dispersed throughout the year (Menge 1978).3.3.5.3 Asteriidae The Asteriidae collected are juveniles, too small to be.assigned to genera. Two species of both Asterias and Leptasterias can 388 T 77 Station 19 Mytilidae PRE OP 1990 Jassa marmorata-PREOP------- 1990 E z-J E I-9 7 6 5 4 3 2 0.JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEM MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT MONTH Station 31 Mytilidae-1990 Jassa marmorata E z LU-j JAN FEB. MAR APR MAY JUN JUL AUG SEP OCZT NOV DEC MONTH MONTH Figure 3.3.5-2.Mean length of Mytilidae and Jassa marmorata collected from monthly sequential surface panels in 1990, compared to.mean and 95% confidence limits during preoperational period (1982-1989). Seabrook Operational Report, 1990. occur within the study area (Gosner 1978). Asteriidae are -important predators on bivalves, particularly on the recently-settled stages, as well as other mollusks and barnacles (Gosner 1978).Asteridae densities'at both near- and farfield stations were higher in 1990 than their baseline averages, but the farfield station had a much greater increase than the nearfield station (Table 3.3.5-1), as indicated by the significant Preop-Op X Station interaction-term (Table 3.3.5-2). As in previous years., differences between stations and among years, were signi ficant, with more sea stars usually occurring at.the nearfield station. The 1990 density reached the all-time high at the farfield station (not sampled in 1981), and was exceeded only by the 1981 density at the nearfield station (Figure 3.3.5-1). The all-time.low densities occurred in 1983 at both stations.The preoperational average length at Station B17 was 5.0 mm, and at Station B35 it was 6.7 mm (Table 3.3.5-3). In 1990, the annual average length was only about 3 mm at both near- and farfield stations, due to large numbers of recently settled juveniles. Over 50% of the specimens collected were 1 mm or less at both stations, and most of these were collected in August (NAI I99i).A few recently-settled Asteriidae were co1lected'on short-term surface fouling panels from 1978( through 1990, and only occurred from July through October. All years except 1981 and 1990 had very low monthly :densities, and averaged less than one specimen per panel per year. In 1990, as in 1981, a heavyset of sea stars (at least 28 per panel) occurred at Station B19 in September. Likewise, September 1990 numbers were somewhat elevated (7 per panel) at.Station B31 (NAI 1991).3.3.5.4 Pontogeneia inermis Pontogeneia inermis (maximum length, 11 mm) is a pelagic, cold, water amphipod (Bousfield 1973), and a dominant species in both benthic 390 and macrozooplankton collections (Section 3.1.5). It clings to sub-merged algae from the lower intertidal to depths greater than 10m (Bousfield 1973). The 1990 densities at. both near- and farfield stations.were close to the baseline averages, and the interaction (Preop-Op X Station) was not significant (Table 3.3.5-1,2).. Differences between stations were significant With the nearfield (B19) having a higher density than-the farfield (B31) in most.years (Table 3.3.5-1).. Substrate preferences may provide an explanation, since P. inermis often.clings to algae and Station B19 is about 60% algae covered and Station B31 has only about 30% coverage (Table 2.1-3).During the preoperational period, ovigerous and brooding females have been collected in low numbers from January through Septem-ber (NAI 1985b). Historically, recruitment, as indicated by a sharp increase in density and increased numbers in the 1 to 3 mm.size class, has taken place between May and July. In fall and winter, abundance decreased, but average size increased as the population grew (NAI 1985b). The overall mean length.for the preoperational period was 5.1 mm at Station B19 and 5.3 mm at Station B31, and the 1990 mean lengths were similar at.the nearfield but larger than average at the farfield (Table 3.3.,5-3). ...3.3.5.5 Jassa marmorata Jassa marmorata (formerly J. falcata) is a tube-building, amphipod, and a dominant fouling organism on hard substrates in areas with strong tidal and wave currents (Bousfield 19.73). It is a suspen-sion feeder and also preys on small crustaceans. ..The..1990 annual densities of Jassa at both stations were lower than the. preoperational means (Tables 3.3.5-1,2').. No significant interaction occurred:between 1990.and baseline averages at the near- farfield station pair (Table 3.3.5-2).391 Most lifestages of Jassa were collected at Stations B17 and B35, ranging from gravid females to newly-hatched young (NAI 1985b). In 1990, no ovigerous specimens occurred in August, although they were taken in May and November. The baseline average length for the-pre-operational period was 4.2mm at Station B17 and 3.9 mm at Station B35.In 1990, the yearly annual mean length'at both stations was similar to the preoperational average (Table 3.3.5-3); and the length ranged from about <1 to 9 mm at both stations. In 1990, about 7% of the specimens were classified as ovigerous or with brood (NAI 1991).Densities on short term fouling panels give an indication of recruitment or settlement activity (Section 3.3.4,. Figure 3.3.4-6).During the preoperational period from 1978-1989, substantial numbers of young began appearing in June or July and continued to settle through October, and in some years through December (Section.3.3.4). The 1990 monthly.pattern was similar to previous years at mid-depth stations, but at Station B19, densities were lower than preoperational monthly means.In 1990, settlement as indicated by the abundance of :1 mm size classes, began in June or July and was heaviest from September through December (NAI .1991). On monthly sequential panels in 1990, average monthly i lengths were about 6-7 mm in late spring, and decreased to about 3 mm by December, indicating recruitment of young had occurred (Figure 3.3.5-2).3.3.5.6' Ampithoe rubricata Ampithoe rubricata (maximum length, 14-20 mm).is an amphi-Atlantic boreal amphipod that constructs a nest of tubes among macro-algae (fucoids) and-in mussel beds (Bousfield 1973). It is. foun d primarily in intertidal areas. Yearly densities have fluctuated significantly during the study period, and have steadily declined'from about 1980 through 1987 (Table 3.3.5-1). The most dramatic decrease in density occurred at intertidal Station BIMLW where densities fell from 344/mr 2 in 1978 to near zero from 1987 through 1990 (Table 3.3.5-1). In 392 1988, populations at the farfield station showed a slight increase in abundance that continued through 1990. Densities in 1990 were lower than average at BIMLW, but higher than average at B5MLW, as reflected by the significant Preop-op X Station interaction (Table 3.3.5-2).Ovigerous and brooding females were rare, but during the preoperational period were collected from April through September (NAI 1985b). The largest numbers of small (1-3 mm) individuals were collect-ed from April through September, suggesting recruitment occurred during this time period. In 1983 and 1984, recruitment appeared depressed, accounting for both lower overall densities and larger mean size (NAI 1985b), and the trend continued through '1990. The overall mean length for the preoperational period was 7.0 mm at Station B1MLW, and 7.8 mm at Station B5MLW (Table 3.3.5-3). In 1990, the average length measured 6.1 mm at B5MLW, and no Ampithoe were present at the nearfield station.3.3.5.7 Strongy1ocentrotus droebachiensis Strongylocentrotus droebachiensis, the green sea urchin, reaches 75 mm in diameter, and is an-important prey species for lob-sters, cod and other fish, and sea stars (Gosner 1978). It is an omnivore, but prefers grazing on Laminarla saccharina over other common algal species (Larson et al. 1980; Mann et al. 1984). -When the macroalgae supply is depleted, it will prey on Mytilus edulis (Briscoe and Sebens 1988). It is subject to population "explosions"' that can.denude large areas of macroalgae, leaving barren rock (Breen and Mann 1976). Although average abundances during the preoperational period at B19 were double those at B31 (Table 3.3.5-1) these inter-station differences are not significant. Density in 1990 was lower at each station, but at the nearfield station, the difference was greater, as indicated by the significant interaction (Table 3.3.5-1,2). The 1990 differences were not restricted to the operational period (August, November). 393 Most of the individuals collected subtidally were juvenile, measuring less than 3 mm in diameter.. Recruitment of newly-settled young through 1984 has historically occurred in August and Septembei (NAI 1985b). The average length. for the 1982 through 1989 pre7 operational period was 1.9 mm at-both stations. 1990 average lengths were 2-2.3 mm (Table 3.3.5-3). The average yearly length ranged from 1.2 mm at Station-B31 in 1989 to 2.7 mm.at Station B19 in 1985 and in 1988..In order to account for adult individuals that were too large to be collected in the benthos sampling program, sea urchins were enumerated by SCUBA divers in the subtidal transect program. No more than a total of 13 large (>10 mm) sea urchins per year were counted (0.02/m 2) in the first three years.of sampling (NAI 1986a, 1987a, 1988a). However, in 1988 there was an~increase to a total of 32 observed (0.06/mi annual density for entire study area), and the in-crease was sustained~through 1989 (NAI1989a,.1990a). The gradual increase continued into 1990, when the annual density for the entire study area was 0.14/m 2 The increase was due to the large number observed in July at farfield Station 35, and was not sustained into the fall (NAI 1991). The extremely low densities of adult urchins in comparison to juveniles indicate that natural forces are keeping this potential nuisance species under control.3.3.6 Epibenthic Crustacea 3.3.6.1 American Lobsters (Homarus americanus) Lobster Larvae Lobster larvae have been relatively rare during the thirteen-year study period at Station P2. Mean density of lobster, larvae at theýintake site was highest in 1978.(I.45/1000 m 2) and lowest in 1980 (0.46/1000 m 2) during the 1978-1989 period (Table 3.3.6-1). The mean number of lobster larvae caught in 1990 (5.04/1000 m 2) at Station P2, 394 TABLE 3.3.6-1.NUMBER, PERCENT COMPOSITION AND MEAN DENSITY OF LOBSTER LARVAE BY LIFESTAGE AT STATIONS P2, P5 AND P7, 1978-1990. SEABROOK OPERATIONAL REPORT, 1990.TOTAL % NO. OF PERCENT PER STAGE OF LARVAE MEAN T STAGES COL- DENSITY 2 YEAR STATIONa II III IV I AND IV LECTED "NO./1000m 1978 P2 10.1 0.0 *0.6 89.3 _99.4 169 1.45 1979 P2 70.8 2.5 1.7 25.0 95.8 120 1.18 1980 P2. 86.5 0.0 0.0 13.5 100.0 57 0.46 1981 P2 31.8 1.9 6.5 59.8 91.6 107 0.86 1982 P2 3.2 .0.0 0.0 96.8 100.0 161 1.17 P7 3.8 0.0 0.5 95.6 99.4 185 1.32 1983 P2 41.4 0.8 4.9 -52.9 94.3 115 0.79 P7 -47.5 0.6% 3.5 48.4 95.9 162 1.10 1984 P2. 14.6 11.5 21.8 52.1 '66.7 79 0.57 P7 37.2 1.0 2.8 59.0 96.2 101 0.73 1985 P2 1.5 2.9 2.9 92.6 94.1 .68 0.85 P7 7.0 2.1 2.1 88.8 95.0 143 1.91 1986 P2 .-. 1.4 98.6 98..6 69 0.84 P5 3.5 .... 96.5 100.0 102 1.79 P7 21.6 -. -78.4 100.0 156. 2.01 1987 P2 13.,0 -.7 1.4 85.5 98.5 69 0.92 P7 7.5 -- -- 92.5 100.0 146 1.94 1988 P2 20.3 2.9 5.8 71.0 91.3 69 0.84 P5 20.4 7.4 13.9 58.3 78.7 108 1.34 P7 5.9 2.0 -- 92.2ý 98.1 51 0.66.1989 P2 8.3 0.0 0.0 91.7 100.0 72 0.91 P5 0.0* 0.0 0.0 100.0 100.0 199 2.48 P7 0.0 0.0 0.0 100.0 100.0 ,85 1.09 1990 P2 16.6 4.1 3.0 76.3 92.9 367 5.04 P5 6*.1 0.7 0.7 92.6 98.7 444 6.44 P7 33.9 1.6 2.5 62.0 95.9 434 5.71 a In 1986, Station P5 sampled only from July 1 through October 14.395 however, was nearly 3.5 times greater. than in 1978. The maximum density-of lobster larvae usually occurred from July-through September (Figure: 3.3.6-1). During 1990, lobster larvae first appeared in late June at Station P2, a trend which was similar to other sampling years, and peaked in early July and again in mid-August.' No larvae were collected after August in 1990 (Figure 3.3.6-I).At the farfield sampling Site, Station P7, the density of lobster larvae declined from 1982 through 1984, then steadily increased through 1986, which up to that year was the highest level recorded in this study (Table 3.3.6-1). In 1988, however, the density of larvae fell to 0.66/1000 in, the lowest level since this station has been sam-pled. Density in 1989 increased to moderate levels of 1.09/1000 mi.However, in 1990, the mean density was 5.71/1000 ml, nearlythree times greater than in 1986. With the exception of 1988, densities have his-torically been higher at Station P7 than P2. This difference was most pronounced in 1985, 1986 and 1987, when abundances at Station P7 were more than twice those at Station P2 .... In 1988, however, densities at P7 were lower than at P2. Mean density in 1990 at Station P7 was greater than that at P2. Larvae first appeared at Station P7 in early June and peaked in early August during 1990. No larvae were collected after August (NAI 1991). -.. j In 1986, P5, located in the vicinity of the discharge struc-ture, was added to the sampling regime. This station was sampled only from July 1 through October 14, 1986 and for the entire sampling program in .1988,-1989 and 1990. In 1990, the density observed was 6.44/1000 m 2 , the highest density at all three stations and the greatest density over all sampling years... Prior to 1990, the highest density of larvae had occurred at Station P5 in 1989 (2.48/1000mW). Lobster larvae were more abundant at Station P5 than at Stations P2 or P7 from 1988 through 1990, three out of the four years Station P5 was sampled. Larvae at Station.P5 in 1990 first appeared in early June and peaked in early August, much like Stations P2 and P7. No larvae were collected after August in 1990 (NAI 1991).396 2.01,-. PREOP 1990+0 00'-S 1.8-1.6-1.4-1.2-1.0-0.6'-0.4-0.21 0.0 1.U.5 9-.,,./ I I I I I I I I 1 2 3 MAY I4 1 1 2 JUl I I 3 4 4"1 1 1 2 3 JUL a 1 2 3-AUG 4 1 2 3 41 SEP 2 3 OCT 4 Figure 3.3.6-1.Weekly mean log (x+l) density (no./1000 M 2) of lobster larvae at Station P2 in 1990 compared to all years' mean and 95 % confidence interval during the preoperational period (1978-1989). Seabrook Operational Report, 1990. Analysis of variance resultsindicate that densities in 1990 were significantly higher than previous. years (Table 3.3.6-2). This.difference was not restricted to the operational period (August-Decem-ber) but occurred during the entire sampling year (May-October), Densi-ties were statistically similar at intake, discharge,.and farfield ar-eas.Historically, Stage I and IV larvae have dominated thecol-lections at both. Stations P2 and P7,. with few StageII or III larvae collected (Table 3.3.6-1). Stage I larvae dominated the collections in 1979 and 1980, while Stage IV.larvae dominated the collections in all ' .other years. ,Stage II and III larvae collectively constituted 8.7% or:less of the larvae collected" for'all years except in 1984, when-.they.made-up 33% and21i% of the.total densities at Stations P2 and'P5, re-spectively (Table 3.3.6-1). In 1989, at Station P2, a few Stage I lar-vae were collected; but more. than 90% of the larvae were Stage IV. At Station P5 and P7, only Stage, IV larvae were- collected (Table 3.3.6-1).lDuring 1990,.:93% or more of the larvae collected were either Stage I or.State IV at all stations. At Station P7, 33% of the larvae were Stage I (Table 3.3.6-1).Generally, lobster larvae densities" have peaked for all years.between late July and mid-August (Figure 3.3.6-1). Stage I larvae usu-ally first appeared in late May or June. in low numbers at Stations P2 and P7. Peak density of Stage IV larvae varied in occurrence between July. and August (NAI 1988b). The variation in larval density between years may be:due, in part, to low larval densities and the patchy dis- .tribution (Cobb 1976)... Seasonal occurrences of lobster larvae Stages I and IV at all stations in 1990 were. generally consistent .with previous years. Stage I..larvae at Station P2 'were first observed in late June,.but. slightly earlier at Stations P5 and P7. Stage-IV larvae appeared at all three stations in late July. Large numbers of Stage I larvae'in early July, particularly at Station P7, and even larger numbers of Stage IV larvae in early August at all'stations resulted in the collection. of 398 S W, TABLE 3.3.6-2. RESULTS OF ANALYSISOFVARIANCE COMPARING DENSITIES OF LOBSTER LARVAE COLLECTED AT INTAKE, DISCHARGE, AND FARFIELD STATIONS, AND CATCHES OF TOTAL AND LEGAL SIZED LOBSTERS, JONAH CRAB, AND ROCK CRAB AT THE DISCHARGE STATION AND RYE LEDGE. SEABROOK OPERATIONAL REPORT, 1990.ALL MONTHS OPERATIONAL MONTHS SOURCE OF SPECIES VARIATION df SSý Fb df SSý Fb MAY -. OCTOBER AUGUST -OCTOBER Lobster larvae Preop-Op 1 0.84 5.81*' 1 0.79 5.088 Station .. 2 0.0008 0.00 NS 2 0.01 0.03 NS Preop-Op X Station 2 0.027 .0.10 NS 2 0.023 0.08 NS Year.(Preop-Op) 1 0.001 0.01 NS- 1 0.43 2.80 NS Error 191 26.81 92 13.51 Lobster larvae Preop-Op 1 0.40 4.21* 1 0.42 4.27*(P2 only) Year (Preop-Op) 11 5.42 5.13"** 11. 5.19 Week (Preop-Op) 40 16.84 4.38*8*h 19 9.24 4.88***Error 320 30.74 162 16.17 JUNE -NOVEMBER AUGUST -NOVEMBER Lobster Preop-Op 1 26,145.10 26.40**- 1 18,415.82 l3.93**, (total catch) Station 1 26,954.22 27.22**, 1 44,110.46 33.36,**A Preop-Op X Station 1 24.50 .0.02 NS 1 286.28 0.22 NS Year (Preop-Op) 7 147,389.09 21.26"** 7 205,119.70 22.16*e*Month (Preop-Op (Year)) 451 1,411,246.34 31.66*.* 27 425,260.84 11.91"**Error 1115 1,104,312.90 721 953,348.19 Lobster Preop 1 1,262.88 104.72"*** 1 1,264.75" 89.93***(legal size) Station 1 1.23 0.10 NS 1 0.33 0.02 NS Preop-Op X Station 1 0.21 0.02 NS 1 1.83 0.13 NS Year (Preop-Op) 7 3,647.79 43.21*** " 7 3,185.51 32.36**-Month (Preop-Op (Year)) 45- 6,965.41 12.83"** ?27 2,-122.52 .5.59**Error 1115 13,459.09 "721 10,154.23 Jonah crab Preop 1 45.98 0.55 NS 1 228.48 2.27 NS Station 1 3,804.06 45.66*** 1 3,589.53 35.60***Preop-Op X Station 1 893.39 10.72"* 1 656.13. 6.51*Year(Preop-Op) 7 .15,301.34 26.24*** 7- 12,778.09 18.11 *ll-Month (Preop-Op (Year)) 45 60,876.31 16.24"** 27 44,784.66, 16;45h*e Error 1094 -91,139.90 712ý 71,787.38 Rock crab Preop 1 599.98 45.90*** 1 4.41 0.54 NS Station .1 15.78 1.21 NS 1 .1 103.02 12.64*Preop-Op X Station 1 32.68 2.50 NS 1 .0.01 0.00 NS Year (Preop-Op) 7 3,169.06 34.64* 7 1,224.04 21..46*',. Month (Preop-Op (Year)) 45 5,057.76 8.60*** 45 2,708.96 12.31"**" Error 1094 14,299.45 712 5,801.84.*Preop-Op = Preoperational period (Lobster Larvae, all stations: 1988, 1989;-P2 only, 1980-1989; Adult lobster a.1982-1989) vs. 1990 regardless of Station or month.Station = Station differences )Lobster Larvae: P2, P5, P7; Adult lobster: Discharge and Rue Ledge) regardless c or period.Preop-Op X Station = Interaction of main effects.Year (Preop-Op)-= Year nested within preoperational and operational periods regardless of year, month or.Station. 11onth (Preo-Op.(Year)) = Month nested within'Preop-Op and Year, regardless of Station.ONS = Not significant

• = Significant (p>O..05)= Highly significant (0.05p>0.01)

AAA= Very Highly Significant (0.oo01p). nd crabs: f year, month 1245 larvae, 3.5 times greater than 1989, the most abundant collection of larvae since all three stations have been collected (Table 3.3.6-1).Eighty-six percent of the larvae collected in 1990 were ob-served-on two dates: July 2 and August 13 (NAI 1991). Unusually large aggregations of lobster larvae have been associated with°convergence areas and sea.fronts (Cobb 1983).. This may.,have been a factor in the large numbers of.larvae ing1990, although no evidence of a convergence area was observed at the time of collection. Warmer than average tem-peratures throughout the study area may also have contributed to large numbers of larvae. -,Figure 3.1.1-1 shows that surface and bottom temper-atures were on average warmer at Station P2 in 1990.compared.to the-1978-1989 period, particularly during June and August and continuing through the end of the year. Since the collection of such large numbers of larvae occurred at all stations on the same dates in July._and August, the seasonally warmed waters of the study area may have provided an optimum condition for larvae. Other *factors such as food availability and light intensity may have also contributed to this occurrence. Stud-ies have also indicated that light intensity may influence lobster lar-vae distribution. Harding et al. (1987) reported that Stage I larvae were photopositively influenced by a maximum light intensity; while Stage IV larvae' appeared to show no significant differences between day and night abundances in offshore waters. The high catches may also have simply been a fortuitous capture of-larvae which despite their relative rarity, have a patchy distribution. In contrast to the above, a New Hampshire Fish and Game study (1991) found few lobst..er larvae in the Piscataqua River-Great Bay estu-arine area north of this study area in 1989 and 1990. The few larvae collectedwere taken during mid-July to mid-August, coinciding with occurrences of larvae for this study.Historically, trends in the occurrence of lobster larvae in this study have generally,'agreed with other lobster larvae studies in 400 New England (Sherman and Lewis 1967; Lund and Stewart 1970). An exten-sive review of New England regional lobster larvae studies (Fogarty and Lawton 1983) indicated that the period of peak abundance coincided with that observed off New Hampshire waters as described by this study. The long-term variability in the predominance of Stage I and Stage IV larvae observed off coastal New Hampshire has also been documented in other New England studies (Fogarty and Lawton 1983). Abundances and occurrence of lobster larvae in inshore areas have been associated with wind direc-tion. Grabe et al. (1983) reported that 67% of Stage IV larvae were collected off the New Hampshire coast when winds were. on- or alongshore. Air temperature differences between water and land masses, combined with predominantly light westerly summer winds, produced onshore winds during the day and offshore winds at night. Inaddition, hydrographic studies in the Hampton/Seabrook area indicated a net drift northward or south-ward along the New Hampshire-coastline. Combined, these two actions suggested that lobster larvae may be moved by nontidal water-mass move-ments into New Hampshire waters and then transport'ed onshore by winds.A synthesis of lobster larvae distribution studies by Harding et al. (1983) supports this explanation. They noted that lobster land-ings for all regions neighboring on the Gulf of Maine have'been very similar since the mid-1940s, and concluded that a single lobster stock'with common recruitment exists. They further concluded that warm south-western waters of the Gulf of Maine and Georges Bank supply the Maine coast and adjoining areas with advanced larval stages, evidenced by'a preponderance of Stage IV larvae in the surface waters *from southwestern Nova Scotia to Hampton, New Hampshire. A recent examination of hydro-graphic drift studies (Harding and Trites 1988) also supports the sug-gestion that lobster larvae are carried into the New England region through current transport. -401 Adults Total lobsters (legal and sublegal sizes combined) have been collected in the vicinity of the discharge site (LI) from 1975 to 1990 (Table 3.3'6-3). During that period, high monthly catches usually oc-curred from August through November. However, catches were usually highest in September and October.. Data from 1945 to 1973- reported by the New England Fishery Management Council (1983) for the Maine lobster .fishery also indicate August, September and October as peak months in lobster abundance. Average yearly catches per fifteen-trap trips at the discharge station ranged from 46.0 to 93.0. The average yearly catch for 1990 was 88.1 per fifteen-trap trip, significantly higher than previous years at both discharge and farfield stations (Table 3.3.6-2). -This is consistent with increased lobster landings reported for New Hampshire as well as the New England region (NOAA 1991b).Among stations, lobster catch was significantly greater at the farfield station (L7) than at the discharge site (LI) (Table 3.3.6-2).The pattern of peak monthly abundances and the greater abundance of lobster catch at the farfield station has been consistent throughout the -study since sampling at Station L7 was begun in 1982.7 Adult lobster abundances.have been related to seawater temper-ature (McLeese and Wilder 195.8, Dow 1969, Flowers, and Saila 1972, and NAI 1975b). Low temperatures act in two ways to reduce lobster catches.Low .winter temperatures may increase mortality of first year juveniles, leading to lower adult catches after a 6 to. 8 year lag period. Low, temperatures in the first half of the year may also affect timing and magnitudeoof molting and decrease catchability,'reducing catches of adult lobsters (Dow 1969).. In the Hampton/Seabrook study area, bottom temperatures, continuously monitored from 1978-1984 near the discharge area, were significantly correlated with lobster catches in only two of the six months'sampled. In June, catch declined as bottom water temper-ature increased, probably caused by the onset of molting, which ' .402. TABLE 3.3.6-3. MONTHLY, ANNUAL. AND PREOPERATIONAL MEAN AND UPPER AND LOWER 95%CONFIDENCE LIMITS OF TOTAL AND LEGAL-SIZE LOBSTER CATCH PER TRIP EFFORT AT THE DISCHARGE SITE FROM 1975-1990 SEABROOK OPERATIONAL REPORT. 1990 TToAL , i MONTH"*I " JI J I I I ".-------------I ---------------------, JUN , JUL , AUG 1 SEP ,. OCT ,.NOV , LOWER! ALL, IUPPER , i------I-------------------------+-----------+ ---+--7----------------. 1PREOP 1975 41.11 42.51 73.91 74.21 71.61 .55.21 55.51 59.91 -'64.31 1976 .35.01 40.71 68.91. 69.81 63.71 48.01 50.51 54.51 58.6: 1977 " 46.11 29.81 63.41 67.31 54.51 61.31 48.61 53.01 57.41 1978 49.71. 35.61 63.41 87.21 79.11 .65.51 57.91 63.21 '68.51 1979 .54.11 57.61 61.51 68.14 69.91 58.81 58.9: 61.51 64.01 1980 33.21 30.21 70.41 59.61 41.51. .43.41 42.81 47.51 52.2.1 1981 38.01 43.31 80.51 94.2: 65.71 .59.31 56.71 62.61 68.61 1982 1 35.71 52.31 83.81 71.71 88.81 79.11 60.61 67.51 74.51 1983 1 49.21 39.91 89.31 128.21 96.31 29.61 59.51 70.01 80.41 1984 1 49.91 28.21 72.11 117.91 146.61 140.51 79.61 93.01 106.41 1985 1 25.41 45.21 81.31 .121.31 131.21 130.41 74.81 .86.61 98.41 1986 1 35.51 42.71 86.01 96.41 86.11 106;01 65.11 73.41 81.61 1987 1 39.51 26.31 33.3: 57.21 83.21 48.1: 38.71 46.01 53.31 1988 1 41.51 32.81 69.41 98.91 84.51 73.21 58.11 65.51 72.81 1989 1 42.41 40.31 46.4: 110.5: 79.01 67.51 55.31 63.71 72.01 LOWER '1 38.91 37.11 :65.91 82;61 -76.2: 64.51 Ii ALL 1 41.11 39.41 69.61 .87.21 81.71 70.21 62.1: 64.11 66.11.UPPER 1 43.31 41.61 73.31 91;81 87.21 75.91 i lOP. 1990 1 63.21 55.61 89.01 .114.71 108.61 101.31 79.21 88.11 97.01 LEGAL-SIZE I MONTH Si ------------------------------------------------

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+1 JUN 1 JUL 1 AUG.. SEP. ... OT 1 NOV 1 LOWER + ALL .UPPER-i -- --------------- -------- --- ----------------------------------- +1PREOP 1975 1 2.71. 5.41 9;5: 8.01 10.01 10.11 6.61 7.61 8.51 1976 1 3.31 8.91 10.3' 7.51 9.21 10.31 7.41 8.21 9.11 1977 1 .5.91 3.51 13.91 9.91 7.31 9.4: 7.11 8.21 9.31 1978 1 7.11 4.01 13.11 14.51 11.41 9.41 8.81 9.91 11.11.197.9 1 6,11 8.41 8.81 8.81 12.41 i .31 8.51 9.21 9.91 1980 1 3.01 4.51 12.51 7.31 6.31 7.71 .6,01. 7.01 8.0!.1981 1 4,7: 8.91 11.11 12.5: 10.01 10.91 8.31 9.51 10.71 1982 2.11 9.61 9.71. 7.61 10.01 8.51 6.61 8.01 9.31 1983 1 2.51 4.61 10.91 7.01 13.81 4.21. 5.51 6.91 8.41 1984. 1 2.31 1.81 11.01 4.31 10.8: 9.01 5.51 6.91 8.21 1985 1.41 8.61 5.91 7.71 7.81 7.61 5.51 6.51 7.41 1986 1 3.61 6.81 7.11 6.7: 8.91 12.31 6.21 7.21 8.11 i .1987 1 2.01 1.71 4.81 3.31 3.61 3.21 2.51 3.11 3.61 1988 1 2.01. 2.71 7.91 5.51 4.81 11.51 -4.61 5.71 6.7.1 1 1989 1 2,61 2.71 3.31 5.81 3.11 3,.91 2.91 3.51 4.21 LOWER 3.11 4.91 8.71 7231 7.91 8.01 1.ALL 1 3.51 5.51 9.41 7.91 8.6: 8.61 6.91 7.21 7.51 UPPERý 1 4.01 .6.2: 10':11 8.61 9.31 9.21 1!OP 1990 -2.31 1.41 3.41 2.61 3.11 2.31 1.91 2.61 3.21 NOTE: Lower and upper represent the 95% confidence limits around the monthly and yearly mean,.403 would reduce the catchability of lobsters. Peak catch of adult lobsters usually occurred after bottom water temperatures reached approximately 1o 0 C and lobsters had molted to legal size (NAT 19.85b). As bottom temperatures cooled, catch declined in November, perhaps reflecting seasonal inshore movement patterns (Ennis 1984) or decreased activity level.ý Lobsters typically show a seasonal migration pattern which is thought to maintain the'population at the highest local-water tempera-.ture (Campbell .1986).' It is uncertain, however, whether New Hampshire lobsters undergo seasonal migrations (NHFG 1974). The New Hampshire Fish and Game Department conducted similar studies off the New Hampshire coast and concluded that bottom water temperature did affect lobster catch, along with other factors such as molting and food availability (NHFG 1974).Variations in catches of legal-sized lobsters can be related to fluctuations in total catch as. well as changes in the definition of a legal-sized lobster. In 1984, an increase in the legal size limit from 79 mm (3 i/8") to 81 mm was enacted, followed by a second increase to 82 mm (3 7/32") in 1989. Legal size was increased again in 1990 to 83 mm (3 1/4 "). Monthly catches of legal-sized lobsters have ranged from less than 2 to about 14 individuals per 15-trap trip from 1979-1990.(Table 3.3.6-3). Significant differences in annual catches of legal-sized lobsters were detected (Table 3.3.6-2). Total catches of legal-'sized lobsters prior to 1984 were generally higher than those after the i change in legal-size limit (Table 3.3.6-3). The proportion of legal sized lobsters, which averaged 14% of the total catch in 1984, decreased 'slightly after the first change in legal size limit to 7-10%. More dramatic decreases were noted in a study by the New Hampshire Fish and.Game Department (Grout et al. 1989), where legal catches decreased by 33% in 1984. However, only 6% of the decrease was due to the change in'size limit and the rest was due to lower than average catches throughout New England. In that study, percentages of legal-sized-lobsters dropped from 28% of the total catch in the five months prior to the legal size 'change to 18%.in the subsequent two years. In 1989, after the second size limit change, legal size catches decreased to nearly half of the 404 1988 level, and composed only 5% of the total catch. During 1990,. legal size catches were the lowest recorded to date (2.6); only 3% of the total catch were of legal size (Table 3.3.6-3; Figure 3.3.6-2).. Legal catches in 1990 were significantly lower than previous years at both the discharge station and Rye Ledge (Table 3.3.6-2).. Changes in the size class distribution in 1984, 1985, and 1990 show the effects of the changes in legal-size limits.' The 79-92 mm size class was composed solely of legal-sized lobsters prior to 1984, but since that time has contained in part individuals protected by the new legal size limits (Figure 3.3.6-3). Proportions of lobsters measuring.79-92 mm have increased since 1984 from 11% to 17% of the total catch, reflecting an increase in CPUE of this size class from 6.8 to 12.4.These changes suggest that new size limits for fishing have allowed the survival of some of the lobsters in this size class. Since 1987, an increase in the'<54 and 54-67 mm size classes is also evident.Female lobsters made up slightly more than half of the total lobster population. In .1990, female lobsters composed 54% of the total catch at the discharge station. This is similar to the 1984-1989 period which ranged from 54-56%. Prior to 1984,. females composed nearly-60% of the catch for most years, .ranging from 55% in 1981 to 62% in 1978 (Fig-ure 3.3.6-4). NHFG studies found that females constituted 52% of the total legal-sized population (Grout et al. 1989.).Egg-bearing female lobsters represented a small component of the lobster population for 1990; berried females composed 0.6% of the total catch at the .discharge statiori.":The percent of egg-bearing female lobsters has been quite variable, ranging from 0.5% in 1977-to 1.5% in 1975. Changes in legal size limits for fishing do not appear to have affected the proportion of egg-bearing females. NHFG studies (Grout et al. 1989) found that 0.3% of the total lobsters examined during lobster surveys from 1983-1985 were.berried. 405 10 SUB-LEGAL 100 -80 Cr c-It)60 40 C 20 75 15% i 16% 16% 15% 15%76 77 .78 79 80 15% 11 12% /o 10% 1I 7%0 8% 10% gI ° 9%: 81 82 83 84" 85 86 87 88 89* 90*.YEAR*-= Legal size limit changed.Figure 3.3.6-2.Comparisons of legal and sub-legal sized catch of Homarus americanus atthe discharge site, Station LI, 1975-1990. Seabrook Operational Report, 1990.--T -F 100-go-80-_7n --607 F _ ' ..uW 50-rr w a. I.-< 30-0..C0 20.10-, ,.7.,-' .>105 mm 41- -92 105 mm-. 7 -0 921mm S679-792mm --- .4- 67 mm.. <54mm*.......... 6 7677 78 79 80 81 82 83 84 85 86 87 88 89. 90 YEAR Figure 3.3.6-3. Size-class distribution (carapace length) of Homarus americanus at the discharge.site, Station Li, 1975-1990. Seabrook Operational Report, 1990..0" 75 64- % FEMALES IN CATCH 64----.... % EGG BEARING FEMALES-1.6-1.4 62-z (I)-j w L...60-58--1.2-1.0 U)LJ IJ-U..I z LU M 0 C, C,ýj-00 5&.54--0.8-0.6 52.1 1. i-~ I I I I I I I I I I I I I I I ~.4 74 75 76 77 78 79 80 81 82 83" 84 85 86 87 88 89 90 YEAR v Figure 3.3.6-4.Summary of female lobster catch data at the discharge site, Station L1, 1974-1990. Seabrook Operational Report, 1990.F" In 1990, one lobster was impinged in the plant's cooling water system during the months of February, July, August and October No size-class information was obtained. It is possible that these individuals were seeking cover at the intake structure and subsequently became entrained. 3.3.6.2 Jonah Crab (Cancer borealis) and Rock Crab (Cancer irroratus) Larvae Cancer spp. (Cancer borealis and Cancer irroratus) larvae ,generally exhibited a pattern for all sampling years of very low or.-near-zero density from January through April with rapidly increasing numbers in May, reaching peak abundance in August and declining in den-sity from October through December. At plankton Station P2, Cancer spp.larvae in 1990 were most abundant during August, similar to the 1978-'1989 period. In 1990, from September through December, the observed pattern was very similar to previous years (Figure 3.3.6-5), although densities in May, June, November and December were lower.Adults Adult Jonah crab (C. borealis) and rock crab (C. irroratus) catches have been monitored since 1975 at the discharge site (NAI 1985b). Since 1982, these populations have been monitored at two sta-tions, the discharge site (Ll) and at Rye Ledge (L7). Historically, catches of Jonah crabs have been significantly greater in August and September in comparison to all other months sampled (NAI 1990b, Table 3.3.6-4). Average monthly catches per fifteen-trap trip have ranged from 5 to 25 at the discharge station and from 4 to 17 at Rye Ledge from 1982 through 1990 (Table 3.3.6-4). The total annual catch of Jonah crabs increased from 1982 through 1985, and declined from 1986 to 1987.409 IPREOP.... CF) o JL gE-.. -.+0 Wo.'~0 JAN _FEB MAR APR MAY JUN JUL : A/JG SEP ..OCT NOV 131W MONTH.... "" " aExcluding January 1985 through June 1986.Figure 3.3.6-5. *Monthly mean log (x+l) density and 95% confidence intervals (n0./1000 M3) Of'Cancer spp. larvae, at Station P2, 1978-1989 a and monthly mean for 1990.' Seabrook Operational Report, 1990. TABLE 3.3.6-4. COMPARISON OF CATCH PER UNIT EFFORT OF JONAH CRAB AND ROCK CRAB AT THE DISCHARGE SITE AND RYE L.EDGE, 1982-1989 AND 1990., SEABROOK OPERATIONAL REPORT, DISCHARGE STATION iPREOP .OP. .i- ------ ------....---------------------

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1982 1 1983 1 1984 1 1985 1 1986.1 1987.1 1988 1 1989 !LOWER ALL !UPPER 1990 !LOWER 1 ALL ]UPPER------- +------ ..+. ...+-- --..-- -- -.. --- .-------------------------------------------------.------

--- -...--------- JONAH JUN 3.51 2.81 3.61 9.31 7.51 0.61 4.51. 8.91 3.91 5.21 6.61 5.31 1.81 5.31 8;71 JUL : 4.51 6.41 4.51 14.31 9.61 9.21 7.11 32.41 8.51 11.01 13.51 19.91 11.61 19.91 28.21 AUG 5.71.12.11 11.51 26.71 26.61 25.51 29.11 60.81 20.11 24.51 29.01 32.01 20.51 32.01 43.51 SEP 1 8.31 8.41 9.31 11.41 18.51 26.21 28.41 22.81 13.91 16.81 19.71 12.51 8.11 12.51 16.91 OCT 1, 2.71 3.81 7.31 9.71 5.61 2.51 12.11 14.51,. 6.11 7.51 9.01 7.11 4.71 7.11 9.51 1 NOV 1 3.41 1.61 8.91 11.71 6.21 1.41 17.91' 7.81 6.11 7.71 9.21 8.01 6.31 8.01 9.71 LOWER 3.81; 4.81 6.21 11.61 10.41 8.01 13.61 18.21 1 11.31 11.21 1 11.21 .ALL 1 4.81 6.11 7.81 14.01 13.31 11.31 16.61 24.81 1 12.61 1 14.81 1 14.81 1 UPPER 1 5.81 7.31 9.31 16.31 16.21 14.51 19.61 31.41 1 13.81 1 18.41 1 18.41 1:ROCK JUN 1 0.01 0.21 0.91 2.71 2.31 0.21 1.01 2.81 0.91 1.31 1.71 6.71 1.41 6.71 12.11 JUL 1 0.81 0.81 2.61 5.31 3.71 4.21 5.01 9.81 3.01 4.01 5.11 8.81 3.01 8.81 14.51 AUG 1 0.01 1.01 3.41 6.71 3.21 2.51 6.81 15.31 3.51 4.81 6.21 6.21 1.71 6.21 10.61 SEP 1 0.01 0.21 1.51 0.61 1.21 1.21 0:81 4.81 0.71 1.31 1.91 0.91. -0.21 0.91 2.01 OCT 1 0.11 0.01 0.21 3.31 1.71 0.11 0.1 0.81 0.61 0.91 1.21 0.71 0.31 0.71 1.11 NOV 1 0.31 0.11 0.21 5.71 2.21 0.01 3.61 1.21 1.01 1.71 2.41 1.91 0.51 1.91 3.21 LOWER 1. 0.01 0.21 1.11 3.21 1.91 1.01 2.31 3.71 1 2.11 1 2.71 1 2.71 ALL 1 0.21 0,41 1.61 4.11 2.41 1.61 3.21 5.91 1 2.51 1 4.41 1 4.41 UPPER, 1 0.41 0.61 2.01 5.01 3.01 2.21 4.21 8.01 1 2.91 1 6.01 1 6.01 RYE LEDGE PREOP OP OP------------------------------------- I-------------- -- ------I I 1982 1 1983 1 1984 1 1985 1 1986 1 1987 1 1988 1 1989 !LOWER I ALL !UPPER 1 1990 !LOWER I ALL IUPPER i-- ---- .+-+----- +---------------------------

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+ .... ------------- +-+-JONAH JUN 1 5.31 4.41 5.91 .7.71 5.91 1.31 2.11 3.81 3.6: 4.51 5.41 3.21 1.61 3.21 4.81 JUL 1 3.81 11.71 6.41 16.01 8.61 7.71 4.41 16.31 7.81 9.41 11.01 8.41 5.21 8.41 11.71 AUG 1 4.71 13.61 17.91 31.51 7.51 27.41 15.81 24.61 15.21 17.71 20.31 9.61 4.31 9.61 14.81 SEP 1 5.61 9.81 11.41 9.81 11.41 17.91. 10.81 10.11 9.11 10.81 12.61 6.01 2.01 6.01 10.01 OCT 1 3.41 4.11 8.31 7.71 7.41 1.61 9.61 3.51 4.81 5.81 6.81 3.81 2.91 3.81 4.71 NOV 1 4.01 3.01 8.51 13.11 7.31 1.31 5.31 9.31 '5.51 6.61 7.71 3.61 2.41 3.61 4.91 LOWER 1 3.81 6.31 8.41 11*91 6.81 7.21 6.41 8.41 1 8.71 1 .4.5.1 1 4.51 i ALL 1 4.41 8.21 10.21 14.51 8.11 10.11 8.11 11.31 1 9.51 1 5.91 I 5.91 i UPPER 1 5.11 10.11 12.01 17.21 9.41 13.11 9.91 14.21 '1 10.31 1 7.31 1 7.31 i ROCK JUN 1 0.01 0.41 0.21 1.51 0.51 0.11 0.51 12.51 0.91 2.21 3.51 9.91 5.81 9.91 14.01 JUL 1 1.61 0.81 1.71 1.31 2.01 0.81 0.81 11.31 1.41 2.51 3.61 11.21 2.71 11.21 19,71 AUG 1 0.11 1.31 1.41 2.91 0.21 2.31 1.31 8.51 1.51 2.21 2.91 3.41 1.31 3.41 5.61 SEP 1 0.11 0.21 1.61 0.81 0.21 1.21 0.11 1.11 0.41 0.71 1.01 0.31 -0.01 0.31 0.61 OCT 1 0.01 0.01 0.61 1.61 0.51 0.11 0.41 0.71 0.21 0.51 0.81 0.41 0.01 0.41 0.81 NOV 1 0.11 0.21 0.21 1.91 0.01 0.01 0.11 -3.11 0.41 0.81 '1.21' 1.11 0.21 1.11 2.11 LOWER 1 0.01 0.3-1 0.61 1.21 0.31 0.51 0.31 4.31 1 1.21 1 2.81 i 2.81 i ALL 1 0.41" 0.51 1.01 1.71 0.61 0.81 0.61 6.31 1 1.61 1 .4.51 1 4.51 .UPPER 1 0.71 0.81 1.41 2,11 0.91 1.21 0.91 8.41 1 1.91 1 6.31 1 6.31 .NOTE: Lower and upper represent the confidence limits around the monthly and yearly mean.411 - at both stations. In 1988, the catch increased at the'discharge sta-..tion, but was about average at Rye Ledge. For 1989, the yearly average of 24.8 was the highest recorded at the discharge station. during this study. The average catch of 11.3 in 1989 at Rye Ledge was an increase over the previous three years. In 1990, catch declined to 14.8 and 5.9 at the discharge station and Rye Ledge, respectively. Historically, Jonah crabs were significantly higher at the discharge station (12.6) than at Rye Ledge (9.5). In 1990, catches at.the discharge station (14.8) represent an increase over the preopera-tional average, whereas at Rye Ledge, 1990 catches (5.9) were lower than the preoperational average (Table 3.3.6-4). These trends are reflected in a significant interaction (Preop-Op X Station) in the ANOVA result.Differences occurred throughout the 1990 sampling year and were not restricted to the operational period (August-December) (Table 3.3.6-2). ..Average monthly catch of rock crabs has ranged from <1 to 5 per fifteen-trap trip at the discharge station and from <1 to 3 at Rye Ledge from 1982,through 1990 (Table 3.3.6r4). The catch of rock crabs had also been generally increasing from 1982 through 1985, when catches were significantly higher than all other previous years (Table 3.3.6-2);catches then decreased in 1986 and 1987 at the discharge and increased in 1988 and 1989. At Rye Ledge, rock crab. catch has remained stable from 1986 through 1988 (Table 3.3.6-4). During 1989, rock crab monthly catches exceeded all previous, years reaching 15.3 in August at the dis-charge site and 12.5 in June at Rye Ledge. Yearly averages were also greater than previous years, reaching 5.9 at the discharge station and 6.3 at Rye Ledge. As with the Jonah crab, both stations experienced a decline during 1990. ANOVA results indicate 1990 catches were statisti-cally similar during the operational period, when rock crabs are not, very abundant. However, higher-than-average catches in June and July resulted in significant differences between 1990 and preoperational catches at both discharge and Rye Ledge stations (Table 3.3.6-2).412 Total catch of rock crabs has been low at both stations rela-tive to the catch of Jonah crabs; this may be due to intra-specific competition between the two species of crabs (Richards etal. 1983).Also, rock crabs prefer sandy habitat which is available nearthe dis-charge site compared to rocky.habitat located at Rye Ledge preferred by.Jonah crabs (Jefferies 1966; Bigford 1979).The percent of female crabs in the catch has also been moni-tored since 1982 (Table 3.3.6-5). The highest catches of Jonah crab fe-males at the discharge station occurred during August and September in most years, composing from 83% to 96% of the total catch. In 1990,.catches of female crabs were highest in August. Annual mean catch of female Jonah crabs generally increased from 1982 through 1989; in 1990, catches of females decreased but the annual mean was similar to the preoperational average. Trends of female rock crab occurrence were less defined than Jonah crabs due to the low overall catch of rock crabs.Catches of female rock crabs' were generally greatest in the fall, from August-November. Catches of female Jonah crabs in 1990 were higher than the preoperational average from June-August. Egg-bearing Jonah crabs were most abundant in June in 1990 at Rye Ledge (about 17% of the total catch), compared to generally about 2%of the total catch at both stations fromf1982 to 1989 (Table 3.3.6-5,.. NAI 1990b). Ovigerous rock crabs were collected for the first time in 1989 and averaged less than 1% of the catch in 1990. Considering the increased catches of rock.crabs in 1989, greater numbers of ovigerous females were probably available resulting in their first-time capture.However in 1990, although rock crab catch declined, egg-bearing females were collected in June at the discharge station.413 TABLE 3.3.6-5. ANNUAL AND MONTHLY MEAN CATCH PER UNIT EFFORT AND 95%. CONFIDENCE INTERVALS OF JONAH AND ROCK CRAB FEMALES AND OVIGEROUS FEMALES AT THE DISCHARGE SITE WROM I%2-1989 AND 1990.FEMALES i " PREOPERATIONAL , OPERATIONAL i i ------ -- -------------

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i I 1982 i 19831 1984 1 1985 1986 1 1987 1 1988 1 1989 1LOWER 1 ALL IUPPER 1 1990 ILOWERI ALL 1 PPER-------- ----- +- .....-+---- --+---------------- -- .+------ +----- +---+ --+--+--+ ......- --IJONAH JUN 2.01 1.71 1.91 6.01 4.81 0.21 2.41 3.81 2.21 2.91 3.71 2.91- 0.21 2.91 5.61 JUL 1 2.41 4.51 2.51 8.51 6.91 5.81 4.81 19.01 5 31 6.81 8.31 10.91 5.01 10.91 16.81 i AUG 1 4.91 9.01 8.31 21.81 23.81 19.81 24.91 44.01 16.01 '19.41 22.81 23.01 14.81 23.01 31.21 I SEP 7.01 7.81 7.71 10.01. 17.71 22.91 26.31- 19.81 12.41, 15.01 17.71 10.31 5.91 ..10.31 14.71.OCT 2.11 3.31 5,91 .8.31 5.01 2.11 10.61 13.01 5.21 6.51 7.91 5.41 .3.3!,.-..5.41 7.61 NOV 1 2.61 1.31 6.21 8.51 5.01 1.31 14.61 5.01 4.51 5.81 7.11 5.11 3.61 5.11 6.61 LOWER 2.71 3.71 4.31 8.51 8.61 6.11 11.21 12.71 .8.71 1 7.51 1 7.51 ALL 3.61 4.71 5.71 10.61 11.41 8.81 14.01 17.61 i 9.71 1 10.21 1 10.21 i UPPER 1 4.51 5.71 7.01 12.61 14.21 11.61 16.81 22.41 1 10.71 1 12.81 1 12.81 I!ROCK JUN 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.71 -0,11 0.11 0.31 1.61 -0.81 .1.61 4.01 1 JUL 1 0.21 0.11 0.21 0.11 0.01 O081 1.21 3.51 0.11 0.81 1.41 1.11 -0,01 1.11 2.2!i AUG 0.01 0.01 0.31 0.01 0.11 1.01 1.71 5.41 0.51 1.01 1.61 2.81 -0.41 2.81 6.11 SEP 1 0.0.1 0.01 0.21 0.01 0.11 0.31 0.11 0.81 0.11 0.21 0.31 0.11 -0.11 0.11 0.31 i OCT 1 0.01 0.01 0.11 1.91 0.61 0.01. 0.01 0.01 0.11 0.31 0.51 0.21 -0.11 0.21 0.61 i NOV 1 0.01 0.01 0.11 2.61 1.01 0.01 0.01 0.21 0.11 0.51 0.81 0.41 -0.11 0.41 0.81 LOWER 1 -0.01 -0.01 0.11 0.31 0.11 0.21 0.31 0.71 1 0.31 ' 0.41 1 0.41 i ALL 1 0.01 0.01 0.11 0.71 0.21 0.41 0.61 1.81 ; 0.51 i 1.21 1 1.21 i i UPPER 1 0.11 0.01 .21 1.11 0.41 0.61 0.81 2.91 1 0.71 i 1.91 1 1.91 .OVIGEROUS FEMALES ---------I I PREOPERATIONAL .OPERATIONAL I.I ------------------------------------------------ + ------------- i :11982-1-1983-1-1984 1 1985 1 1986 1 1987 1 1988 1 1989 !LOWER I ALL !UPPER 1 1990 !LOWER I ALL IUPPER I +---------------------+... m-4 ------ 4 ------------+-------+----+-.....-+.------+-------+-----------------+----- !JONAH JUN A 0.11 0.01 0.2! 0.21 0.11 0.01 0.51 0.11 0.11 0.11 0.2! 0.1! -0.11 0.11 0.31 i JUL 1 0.01 0.11 0.21 0.01 0.41 0.51 0.21 1.01 0.11 0.31 0.41 0.31 -0.21 0.31 0.91 i AUG 1 0.11 0.21 0.21 0.0.1 0.01 1.21 0.61- 1.91 0.31 0.51 0.81 0.61 0.11 0.61 1.11 SEP 1 0.01 0.01 0.21 0.01 0.01 0.21 -0.01 0.11 0.01 0.11 0.11 0.01 0.01 0.01 0.01 1 OCT 0.01 0. 001 0.01 0.01 0.01 0.01 0.01 O 001 0.01 0.01 0.01 0.01 0.01 0.01 V i NOV 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.31 -0.01 0.01 0.11 '0.01 0.01 0.01 0.01 LOWER 1 -0.01 0.01 0.01 -0.01 -0.01 0.21 0.11 0.31 i 0.11 i 0.11 1 0.11 ;ALL 0.01 0.11 0.11 0.01 0.11 0.41 0.21 0.61 1 0.21 .0.21 .0.21 UPPER 1 0.10 0.01 0.01 0.1. 0.21 0.51 0. 0 0.01 0.31 i 0.31 i 0.31 i:ROCK JUN 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 S JAUG 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.21 -0.01 0. 01 0.01 0.01 0.01. 0.01 0.01 AUG i 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01-0.01 0.01 0.1: 0.01 0.01 0.01 0.01 SSEP 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 i OCT 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 NOV 1 0.01 0.01 0.0O1 0.01 0.01 0.01 0.01. 0.1 .1 0.01 .1 -0.0 1 0.01 41 LOWER 1 0.0 OZ 0.O0 1 O.01 0.01 0.0: 0.01 0.O O.O: 0 : i 0.0: .-i -OO i 7-0.'0i i ALL. 1 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.11 1 0.01 i 0.01 i 0.01 i UPPER 1 0.01 0.01 0.01 0.01 0.01. 0.01 0.01 0.21 1 0.01 1 0.11 i 0.11 !Lower ----Lower -l ---t-of ---------------- I .-_,-_.,_-, .........

---

Lower = Lower limit of 95%.confidence interval.U pp e r = U p pe r l i m i t o f I I I , c o n f i d e n c e i n t e r v a l s ..414 3.3.7 Mya arenaria (Soft-shell Clam)3.3.7.1 Larvae Mya arenaria larvae occurred in plankton samples May through October from 1978 to 1989 at nearfield Station P2 (Figure 3.3.7-1).Each year, maximum abundances were recorded in late summer or early fall, while in many years a secondary peak also occurred in early summer. The lowest peak densities observed in the study occurred in 1985 (63/m3 ) (NAI 1986). Peak larval abundances in 1990 (755/m ) ranked sixth over the past nine years,: 1982-1990 (NAI 1991). The highest peak 3.abundance was observed in 1982 (1,505/m ) (NAI 1985b). Peak abundances in 1990 were observed in September with-lesser peaks in June, July and October (Figure 3.3.7--1). Comparison of 1990 Mye larval abundances with previous years at Station P2, using a one-way ANOVA, revealed no significant differences (Table 3.-3.7-1). Similarly, a two-way nested-ANOVA comparing 1990 Mya arenaria larval abundances with previous years at Nearfield (P2, P5) and Farfield (P7) stations found no significant' spatial differences' (Table 3.3.7-1).Factors influencing the timing and magnitude of the observed pattern of larval abundance are not fully understood. M. arenaria is known to spawn in' the spring at temperatures greater than 4-6 0 C with summer spawning at 15-18 0 C (Brosseau 1978). Maximum larval abundances in August and September coincided with.water 'temperatures in Hampton Harbor that regularly exceeded 15-18 0 C. However, these temperatures also occurred frequently in June and July, which were characterized by much lower larval abundances, suggesting 'that temperature is a minimum requirement for spawning. In addition, recruitment of larvae of non-local origin is likely due 'to currents in the Gulf of Maine, which may move water masses and their entrained larvae significant distances before larval settlement (NAI 1979f). The late-summer peaks have been observed to be coincident with northward-flowing currents. -This implies that these offshore larval peaks may in part have a more southern 415 I-.->-0 Ix 0.0'+'.* *'00 3.0 -2.5-2.07 1.5 1.0 -0.5 0.0-*1990,'IT\-PREOP ON-0.5 , a 1

• 1 1 1 1 .1 v 3 '4; !APR+2 -3 MAY 2 3 JUN 4 1 2 JUL L 2 3 AUG 2 3 SEP 2 a 4 1- 2O 3 1_ OCT 4 4 a No data collected in 2nd week of Oct., 1990.Figure 3.3.771.Weekly log (X+1) density (no. per cubic meter) of Mya arenaria larvae at Station P2 in 1990 compared to all years' mean and 95% confidence interval during the preoperational period (1978-1989).

Seabrook Operational Report, 1990. TABLE 3.3.7-1.RESULTS OF ANALYSIS OF VARIANCEa'b COMPARING HYA ARENARIA LARVAL, SPAT, JUVENILE AND ADULT ABUNDANCES DURING PREOPERATIONALc AND OPERATIONAL PERIODS. SEABROOK OPERATIONAL REPORT, 1990.SOURCE OF APR-OCT AUG-OCTc LIFESTAGE STATION/FLAT VARIATION. df SS F df SS F Mya argnaria P2 Year 12 5.38 0.66 NS larvae Error 299 202.25 Mya arpnaria Nearfield (P2, P5) Preop.Opd 1 0.03 0.04 NS 1 1.37 2.18 NS larvae Farfield (P7) Area f 1 0.09 0.14 NS 1 0.04 0.06 NS Year (Preop-Op)t 7 3.26 0.71 NS 7 10.70 2.43*Week (Preop-Op Year)9 27 7.65 0.43 NS 27 14.91 0.88 NS Preop-Op Area 1 0.32 0.48 NS 1 0.08. 0.13 NS Error 477 312.20 199 125.03 Young ofbyear 1, 2,-4 Preop-Op 1 3.20 6.77**(1-5 mm) Area 2 3.02 3.20*Year (Preop-Op) 15 156.13 22.07"** Preop: Flat 2 = Flat 4 > Flat 1 Preop-Op XArea 2 2.90 3.08* 1990: Flat 2 = Flat 4 Flat 1 Error 1269 825.28 Regional Hampton Harbor Preop-Op 1 0.09 0.13 NS snatfall Plum Island Sound Area 1 3.29 4.73*(I-12 mm)* Year (Preop-Op) 2 1.59 1.14 NS Plum Island > Hampton Harbor Preop-Op X-Area 1 0.25 0.37 NS Error 74 51.45 Hampton Harbor b 1, 2, 4 Preop-Op 1 0.03 0.11 NS spat (13-25 mm) Area 2 8.26 16.43***Year (Preop-Op) 13 .106.49 32.60"** Flat 4 5 Flat 1 = Flat 2 Preop-Op X-Area 2 0.18 0.37 NS Error 923 231.92 Hampton Harbor 1, 2, 4 Preop-Op 1 1.30 6.71"**juveniles and b Area 2 14.25 36;71*A* Preop: Flat 1 = Flat 4 >-Flat 2 adults (226 mm) Year (Preop-Op) 15 192.32 66.06**' 1990: Flat 4 > Flat I > Flat 2 Preop-Op X-Area 2 2.95 7.60**', Error 2275 441.51 4S aLarval. comparisons based on weekly sampling periods, mid-April through October bSpat, juvenile and adult comparisons based on annual.October field surveys CCommercial operation began in August 1990 d 1 9 9 0 versus preoperational period regardless of area. Larval preoperatioial period 1978-1989; spat, juvenile and adult preoperational period 1974-1989 Station or flat,. regardless of year or period Year nested within preoperational and-operational periods, regardless of area NWeek nested within year nested within preoperational and operational periods, hregardless of area Interaction of main effects NS Not significant (p>O.05)Significant (O.05_p>0.Ol) Highly significant (0.01->p>0.001) Very highly significant(0.001_>p) estuarine component. Overall, factors controlling the occurrence of M.arenaria larvae off Hampton Harbor Beach are complex, the result of environmental and biological factors including: adult condition at the time of spawning, temperature at spawning sites, location of spawning sites relative to prevailing coastal currents, water column stratifica-tion and larval behavior.3.3.7.2 .Reproductive Patterns Mya arenaria with developing gonads were collected in the Hampton estuary in March or early April during most years from 1978-1984, the years when Mya reproduction was studied. Ripe individuals-have been observed between the second week in April and the third week in June. In most years, ripe individuals occurred at similar times at both Hampton Harbor and Plum Island Sound, with the exception being 1984 (NAi.1985b).. Theonset of spawning in Hampton Harbor and' Plum Island Sound, as indicated by the gonadal studies, usually occurred following the appearance of larvae in offshore tows, presumably from Mya'populations further south. Only in 1980 and 1981 was spawning detected before'larval occurrence. The peak larval abundance always occurred well after spawning had commenced, suggesting both Hampton Harbor and Plum Island Sound clams may contribute to the large nearshore larval densities.of late summer (NAI 1985b).3.3.7.3 Hampton Harbor and Regional Population Studies Hampton Harbor Spatfall The soft-shell clam population has been studied through intensive surveys of spat and. adults in Hampton Harbor (Appendix Table , 3.3.7-1). These surveys have been supplemented'by quantitative.studies 418 of regional spatfall in nearby estuaries. Over a 17-year period, the Hampton Harbor population has gone through substantial changes in abundance (Figures 3.3.7-2 through 3.3.7-7). The age distribution in 1974-1977 at Flat 1 indicated a declining juvenile and adult (>25 mm)population despite presence of the young-of-the-year (1-5 mm). The Mya population structure during the 1984-1989 period at Flat 1 resembled that observed in i974-1977, suggesting long-term trends based on the interaction of spatfall and'disturbance, possibly due to natural and human predation (Figure 3.3.7-2). The decline in 1983-1988 in juvenile and adult (>25 mm) clam densities at Flat 1 was partially the result of light spatfalis during this period with the exception Of 1984.In 1976, a large spatfall (indicated by young-of-the-year spat) (Figure 3.3.7-3), occurred at all flats, which initiated changes in the population structure during the 1976-1982 period. The 1976 spatfall was the largest observed in the study; however, other important spatfalls (indicated by young-of-the-year) occurred in 1975, 1977, 1980, 1981 and in 1984 (Figure,3.3.7-3). The recruitment (defined as survi-vorship of one-year old clams into the 1,3-25 mm size class) of the 1976 year class was successful on Flat 1 (Figure 3.3.7-2) and Flat 4 (Figure 3.3.7-7), while the 1980 year class and, to a lesser extent, the 1981 year class were successful on all flats (Figures 3.3.7-2, 6, 7). Spat settling in 1984 failed to survive on any flat. Successful recruitment of-light spatfalls have been observed on all flats for the 1987 year.class and on Flat.2 and Flat 4 for the 1988 year class. Poor recruit-ment .and light spatfalls were observed 1974-75, 1982-83 and 1985-86.Spatfall in 1989 was the highest observed since 1984, though still lower than observed historically. Spatfall in 1990 was similar to 1989 at Flats 2 and 4, and was higher at Flat 1 (Figure 3.3 7-3, Appendix Table 3.3.7-1). Analysis of variance results suggest that spatial differences in 1990 differed from previous years (Table 3.3.7-1). Historically, young-of-the-year densities have been lower at. Flat I in comparison to Flats 2 and 4. In 1990,' densities were roughly equivalent. The change in spatial differences in 1990 is reflected in the significant Preop-Op x Area interaction term (Table 3.3.7-1).419 QLU. .00MDI 0 u 0.00 0 S?%3.2 .I ..% ,- ...Figure 3.3.7-2. Annual log (x+I) mean density (number per square foot) of young-of-the-year (1-5.mm), spat (13-25-mm),'juvenile (26-50 mm), and adult (>50 mm) Mya arenarta at Hampton-Seabrook Harbor Flat 1 from 1974-1990. Seabrook Operational Report, 1990.__ ..1 1. T77 i 7_11 7.7

0. C 00 ,.3.0-2.5-2.0-1.5-1. 0-0Z5 Flat 1 111111111" I I n tj -u.l ==74-J-------J--------

J- *I------ J

• I I l " I I J 75 76 77 78 79 80 81 82 83 84. 85 86 87. 88 89 YEAR 0 90 Flat 2 0.;j.S 3.0-2.5 -2.0-1.5-1.0-0.5'-~lj~~I.I ill I I 0.O --T-74 , I 1 i v I I I I i 1 75 76 177 78 79 80 81 82' 83 YEAR 84 85 86 87 88 I I .89 90 Lu w 06 J0S 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Flat .4 I *1 74 75 76 77 78 I I I I I I I 1 1 79 80 81 82 83 84 85 86 87 YEAR 88 i I 89 90 Figure 3.3.7-3. Annual log (x+l) mean density (number per square foot) and 95%confidence limits of young-of-the-year Mya arenaria spat (1-5 mm)at Hampton- Seabrook Harbor,' 1974-1990.

Seabrook Operational Report, 1990.421 Regional Spatfall The regional spatfall study (clams 1-12 mm) verified that the heavy recruitment occurred in 1976 occurred throughout the.region (Figure 3.3.7-4). However, annual densities, including 1990, were statistically similar (Table 3.3.7-1).ý A comparison of spatfall at Hampton Harbor and Plum Island Sound MA indicates that spatfal..ias been significantly higher at Plum Island Sound (Table 3.3.7-1). ANOVA results found no significant difference in spatial spatfall patterns between 1990 and preoperational years (Table 3.3.7-1).Yearling and Adult Clams .L Trends in 13-25 mm yearling clams indicate the survival success of young-of-the-year spat. Yearling clams (10-12 mm) became numerous in 1977 following the 1976 Spatfall and began showing a decline in 1981 at Flat .1 and 1982 at.Flat 2 and Flat 4 (NAI 1982b, NAI 1983a).Since that time, survival of young-of-the-year spat to the 13-25 mm yearling clams has been low until 1990 at Flat 1 (Figures 3.3.7-2,5). Older spat (13-25 mm) densities at Flat 2 showed small increases in 1988-1990 over previous years (Figure 3.3.7-6). At Flat 4, 13-25 mm spat densities were higher in i988 and 1989 in comparison to previous years; in 1990, densities were the highest since 1982. Although annual differences were statistically different, '1990 densities were not significantly different from previous years (Table 3.3.7-1). Densities at Flat 4 over the entire study have been significantly higher than those at Flats 1 and 2 (Table 3.3.7-1).Juveniles (26-50 mm), two to four years old, were relatively scarce from 1976 to 1978, but became abundant from 1979 to .1981 at all three flats (Figures 3.3.7-5, 6, 7). This pattern reflects the growth of the large sets of 1976 and 1977. The:large spat sets of 1980 and 1981 did not result in increased densities of juveniles. 422 Hampton Harbor Flat 2~0*C,.2-J 4.0 -3.5-3.0-2.5-2.0-1.5-1.0-0.5-0.0 I I I I I I I I I I I .....I .I I I I I I I I , i I I 76 77 78 79 80 81 82 83 84 85 86 87 YEAR 88 89 90 Hampton Harbor Flat 4 a 4.0-LU.x U.,- CL 0.J-3.5 3.0-2.5 2.0-1.5-1.0-0.5-I III I I I I I I.I 0.0... .... ...--I I I I i I *76 77 78 79 80 81 82 83 YEAR 8 84 I I I I 85 86 87 88 89 K 90 Plum Island Sound (Ipswich) MA-!+1.N 0 C 4.0-3.5-3.0 2.5-2.0 1.5 1.0-0.5 0.0 I I I I I I I I I I I 1 1 .I I -I I 76 77 78 79 80 81 82 83 YEAR I I I 86 I I I I 84 85 86 .. 87 88 89 90 a. Flat 4 not sampled in 1976'and, 1977.Figure 3.3.7-4.Mean and 95% confidence limits of Mya arenaria spat (shell length -< 12 mm)densities (no./ft 2) at two northern New England estuaries, 1976 through 1984 and 1986 through 1990. Seabrook Operational Report, 1990.423 13-25 mm Spat.2.0 0T I I C'},, 1.0 T '.4. I / ..O. 0.5-0, 0.00.5-eo 11.0r T 8 o.o... ... ..74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR 26-50 mm Juvenile 2.0 -t:0 1.5-S1.0 0 .0 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR 2 > 50rmm Adult 2.0 -[1:0 .5 LU q+.C;0g 0.5-Jo o- I I i I , , .-t 3E 0.0 I I I I I I 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90" YEAR Figure 3.3.7-5. Means and 95% confidence limits of Mya arenaria spat, juvenile and adult log (x+l) densities at Flat 1, Hampton-Seabrook Harbor, 1974 through 1990. Seabrook Operational Report, 1990.424 13-25 mm Spat~0.0.z0 I 0.5 0.0 74 7576- 77 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR 26-50 mm Juvenile t:0 1.L 1.5 -1.0'0.5-I I 0.0 , T , , ? + , r T T T T 4-74 75 76 77 78 79 80 81 82 83 84' 85 86 87 88 89- 90 YEAR -> 50 mm Adult 0 "-..- a.0 -00 1.5-* 1.0-0.5-II'. i~ii~ IT--w 0.0 , T t i l, , , , II 74 75 76 77 78 79 80 81 82 83 84 8586 87 88 89 90 YEAR Figure 3.3.7-6. Means and 95% confidence limits of Mya arenaria spat, juvenile and adult log (x+l) densities at Flat 2, Hampton-Seabrook Harbor, 1974 through 1990. Seabrook Operational Report, 1990.425 13-25 mm Spat LU, a 0 C 2.0-1.5-1.0-0.5-1jJ]ITII 0.01 74 75 76 T-I I I 7 77 I I ..I I I I i I I I i I 78 79 80 81 82 83 84 85 86 87 88 89 90 YEAR 26-50 Juvenile zn LU.0, 2.0 1.5-1.0 0.5-'III I I II I I I III iT 0.0 1 1 " T T I I 74 75 76 77 78 79 I .I I .I , I 80 81 82 83 84 85 86 87 88- 89 90 YEAR> 50 mm Adult~0 S.2.0 2.0-1.5-1.0-0.5-I III I I I 31 0.0 , , , T V , , i , , I , .74 75 76 77 7879 80 81 82 83 84 85 86 87 88 89 90 YEAR Figure 3.3.7-7. Means and 95% confidence limits of Mya arenaria spat, juvenile and adult log (x+1) densities at Flat 4, Hampton-Seabrook Harbor, 1974 through 1990. Seabrook Operational Report, 1990.426 High adult densities (>50 mm) were recorded in 1980 and have declined from 1983 through 1987. The 1980-1982 adult densities reflect-ed the success of the 1976 and 1977 year classes; subsequent decline resulted from the harvesting of these clams and the failure to recruit the spatfalls of 1980, 1981 and 1984 into the juvenile and adult size clams In 1987 and 1988, attempts by the New Hampshire Fish and Game Department to augment natural recruitment by seeding .juvenile clams at Flat 5 were not successful (Morris 1989). The local 4-H organization has also produced seed clams on a small-scale (30,000 juveniles in 1988)for reseeding Hampton Harbor clam flats. Juvenile densities, 1988-1990, remained low at Flat 2, but increased slightly at Flat i and Flat 4.Adult densities at Flat 2 remained relatively unchanged from 1987-1990, while.increasing gradually at Flat l and Flat 4 (Figures 3.3.7-5, 6, and 7).. Differences among flats in juvenile and adult densities in 1990 were not consistent with previous years, -as indicated by a significant interaction between Preop-Op and Area terms in the ANOVA (Table 3.3.7-1). Historically, densities at Flats 1 and 4 were similar and an order of magnitude higher than densities at Flat 2. In 1990, Flat 4 densities were highest, followed by Flat 1; Flat 2 densities were an order of magnitude lower than those at Flats l and 4.. *3.3.7.4 Effects of Predation, Perturbation and Disease on Harvestable Clam Resources Clams in Hampton Harbor are subject to predation pressure from twomajor sources: green crab consumption of spat (1-25 mm) and .juve-nile (26-50 mm) Mya, and humans wholdig adult Mya (>50 mm) and also.cause mortality to smaller clams by disturbing the flat. Sea gulls may also be major predators, as they are commonly observedpicking over clam digger excavations for edible invertebrates, including spat and juvenile.clams. The green crab (Carcinus maenas) is a major predator of Mya, with clams being a major source of food particularly in the fall months (Ropes 1969).- Green crab catches in Hampton Harbor have shown a 427 substantial increase in abundance since 1980 (NAI 1990b). Maximum abundances usually occurred in'the fall, with the highest number;recorded in 1984. Green crab numbers'from 1983 to 1989 appear:to have stabilized somewhat at higher densities (Figure 3.3.7-8), with fall abundances fluctuating between 69.3 (1985) and 123.9 (1984) catch per unit effort (CPUE). The fall 1990 green crab CPUE was the lowest observed since 1981; the April through November catches in-1990 were substantially lower than those. for the same months in previous years, (Figure 3.3.7-9)'. Green crabs generally feed'more actively at temperatures above 9 0 C, .and females are more active predators on'Mya than males (Ropes 196.9). The presence of more females in the catch in Hampton Harb6r'from July through September historically (NAI 1990b) and in 1990 (NAI 1991)'indicated greater predation pressure for the newly-settled spat in the'estuary. Continued high catches of males and femalesoccurred until late November or December, when temperatures declinedbelow 7 0 C and'activity"decreased Welch (1969) and Dow (1972) have shown that green crab abund-ances increased markedly during relativelywarm winters. Seasonal CPUE for green crab from 1978-1989 showed an increase from fall of 1980 through 1984 and again in 1986. The increase in green crab abundance corresponded to elevated winter minimum temperatures observed from 1981-1984 (Figure 3.3.778); a significant'correlation (p45 mm, but also is a source of mortality to spat and juvenile clams due to disturbance. Mortality tolyounger clams (<50 mm) from digging is dependent on the.depth of burial, the size of the clams, the-time Of theyear (Glude 1954), and the substrate (Robinson and Rowell 1990). Glude (1954) found that survival is inversely proportional to depth of burial; the deepest burial tested (13 cm) resulted in the-lowest survival., Clams. 9-20 mm suffered the greatest mortality (51%)with 36-50 mm clams having only 31.5% mortality.' More recently, Robinson and Rowell (1990) have:-suggested that'diggingrelated mortality is usually less than 20%, though actual.mortality rates canvary due to substrate (lower in sandy sediment and higher in clay sediment) and temperature (highest in summer). Field observations indicate thatsubstrate types do vary across Hampton Harbor flats, thus some flats may be more susceptible to digging related mortality thanothers. No data have been collected on the amount of-disturbance caused by digging on the Hampton Harbor flats;however, Flat 1 and Flat 4, with the highest historical usage by clammers, would likely have suffered substantial mortality to-young, clams due to digging.Census figures indicate digging activity tripled from 1980 to 1981 (Table 3.3.7-2). Effort remained high through 1982 before undergo:-ing successive reductions from 1983-1985. Digging activity increased slightly in 1986 over 1985 levels, but remained lower than in previous years, .1082-1984. Digging-activity declined further.from 1987-1989 to the lowest levels observed in the study -since 1980. Hampton Harbor Flats were closed from April 1989 through December 1990 by the New Hampshire Department of Health and Human Services due to coliform contamination. .432 TABLE 3.3.7-2. ESTIMATED DISTRIBUTION (PERCENT OF TOTAL) OF CLAM DIGGERS BY FLAT AT HAMPTON HARBOR, SPRING 1980 THROUGH FALL 1990. SEABROOK OPERATIONAL REPORT, 1990.ESTIMATEDa ESTIMATEDb TOTAL NUMBER OF FLAT DIGGER BUSHELS SEASON, TRIPS HARVESTED 1 .2 2 4 5 Springc 1980 '12.5 17.9 1.7 52.5. 15.4 3,860 1,200 Falld 1980 11.3 18.4 3.3 55.1 11.8 2 , 7 0 0 e 840 Spring 1981 9.7 15.6 .0.8 65.9 7.9 12,500 3,900 Fall 1981 13.9 12.9 0.2 63.8 9.1 7.,060 2,200 Spring 1982 12.6 13.0 0.8 67.1 6.4 10,800. 3,400 Fall 1982 26..6 8.5 0.7 60.7 3.5 9,300 2,900 Spring 1983 30.7 7.1 1.3 58.6 2.2 7,700 2,400 Fall 1983 29.4 14.7 0.5 54.7 0.7 6,690 2,100 Spring 1984 22.1 26.4 0.6 49.9 1.0 6,200 1,950 Fall 1984 26.9 28.9 0.3 43.2 0.8 5,850- 1,830 Spring 1985 51.6 11.3 0.4 36.1 .0.8 6,940 2,169 Fall 1985 63.1 5.0 0.4 31.5 0.0 2,873 898 Spring 1986 59.3 6.4 0.3 33.4 0.6 6,210 1,941 Fall 1986 58.1 6.4 0.4 34.7 0.4 4,713 1,473 Spring 1987 39.4 8.1 1.5 49.0 2.0 1,763 551 Fall 1987 38.8 6.9 0.8 49.8 3.8 1,541 482-Spring 1988 13.2 14.3 3.7 66.4 2.4 574 179 Fall 1988 22.8 10.9 4.2 57.4 4.7 1,386 433 Spring 1989 22.1 10.6 0.0 65.3 2.0 357 112 Fallf 1989 -- --Springg 1990 Fallg 1990 -- -- -- --aBased primarily on Friday head counts at time of low slack water; most Saturday counts are assumed from observed Fri:Sat ratio (n=14 pairs) of'2.24 +/- SD 0.96;. seasonal totals have approximate errorof +/- 18DY bAssumes each clammer takes 10 quarts per trip; 1 bushel = 32 quarts or 3.2 clammer trips dIncludes the period 1 January through weekend before Memorial Day dIncludes the weekend after Labor Day through 31 December fBased on average Spring:Fall ratio for 1981 and 1982 (0.68 +/--SD 0.02)Data collected January -March only. Flats closed April -December.gFlats closed January -December 433 The changing pattern of clam.abundance on the Hampton Harbor flats is reflected inthe number of licenses issued by theState of New Hampshire (Figure 3.3.7-10). Changes in the number of licenses.general-ly lag behind the changes in standing crop by one to two years, illus-trating a typical predator-prey cycle. In 1989,. the number of clam licenses issued did not reflect clam abundance but rather the aborted..harvesting season. With the Hampton Harbor flats closed, the few li-censes issued (lowest in at least twenty years) in 1990 were for digging elsewhere in New Hampshire,*in flats associated with Great Bay and the Piscataqua River.Estuary.- The distribution of clam diggers and therefore, fishing pres-sure, has varied among flats since observations were first recorded in 1980. In 1980 -1983, 50-70% of all clam diggers harvested on Flat 4, where clams were abundant and easily accessible by foot (Table 3.3.7-2).Diggers shifted some of their activity in late 1983 and 1984 from Flat 4 to Flat 2, probably in response to declining resources. overall, particu-larly, at Flat 4.. As clam densities continued to sharply declinein 1985 and 1986 digger activity:again shifted, from Flat 2 and Flat 4 to Flat 1, possibly due to slightly greater densities at. Flat 1. From 1987 -1989, 80-90% of digging activity was confined to Flat l:and Flat 4, which had the highest remaining standing. crop..Effect of Disease on Harvestable Clam Resources .Sarcomatous neoplasia, a lethal form of cancer in lya arenar-ia,' has been observed in. Hampton Harbor Mya populations (Hillman 1986,.1987). A virus,.similar to the B-type retroviruses, is known to initi-.ate the disease in. Mya. (Oprandy et al. .1981).. Although the infection has been observed in regions.of relatively-pristine waters, the rate of infection may also be enhanced by pollution-mediated deterioration of the environment (Reinisch et al. 1984). The infection rate in some Hya'populations may reach 100 percent with 100 percent mortality of'infected clams (Farley et a!. 1986). The incidence of sarcomatous neoplasms in 434 . 7T V 0 14000 12000 10000-8000-6000-8SBL4ES----- LICENJSES z w C.j@5 U, C,q 4000-2000-71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 .86 87 88 890 90 YEAR Figure 3.3.7-10. Number of adult clam licenses issued and the estimated adult clam standing crop (bushels) in Hampton-Seabrook Harbor,, 1971-1990' Seabrook Operational Report, 1990. Hampton Harbor Mya populations was observed in October 1986 and February 1987 (Hillman 1986, 1987). Neoplastic infections were more prevalent in February, reaching 6% at Flat 1 and 27%at Flat 2. Infections were* absent from.Flat

4. Assuming 100 percent mortality of infected clams (Farley et al. 1986), Flats land.2 may suffer significant disease-re-lated reductions in clam production.

However, since no historical data are available on the incidence of neoplasms in Hampton Harbor clam-popu-lation, it is not known if 1986-1987 infection rates are typical or indicative of an increasing trend. In 1987 clam flat surveys did indi-cate, however, that juvenile and adult densities fell by over 50% at Flat 1 and Flat 2 while Flat 4 remained unchanged. 3.3.7.5 Harvestable Clams The patterns discussed above have resulted in substantial changes in the number of harvestable clams on the Hampton flats (Table 3.3.7-3). The greatest adult standing stock in Hampton Harbor was re-.ported by Ayer (1968) for 1967. Subsequent years indicated a gradual decline in available adult clams to a low of six bushels/acre in 1977 and 1978. In 1976, the State of New Hampshire applied more stringent clamming regulations, closing the flats for the.summer (Memorial Day to Labor Day) and. eliminating digging on Sundays and holidays. Survival of the 1976 year class made a substantial increase in the standing crop in 1980, four years-after settlement. The number of harvestable clams.continued to increase in 1981 as more of the 1976 and part of the 1977 year class became harvestable. Through 1984, the number of harvestable bushels had not de-creased substantially. However, in 1985 through 1987, the harvestable standing crop dropped precipitously (Table 3.3.7-3), reflecting poor re-cruitment observed in 1980-1984, increased predation by green crabs, and continued human disturbance. Standing crop increased slightly in 1988, followed by substantial increases in 1989 and 1990, probably due to reduced digging pressure on adult clams as well as decreased disturbance 436 TABLE 3.3.7-3.

SUMMARY

OF STANDING CROP ESTIMATES OF ADULTa fYA ARENARIA IN HAMPTON HARBOR, 1967 THROUGH 1990.SEABROOK OPERATIONAL REPORT, 1990.ESTIMATED NUMBER TOTAL ESTIMATED OF BUSHELS NUMBER OF DATE PER ACRE OF BUSHELS.November 1967 July 1969 November 1971 November 1972 November. 1973 November 1974 November 1975 November 1976 November 1977 November 1978 November 1979 October 1980 October 1981 October 1982 October 1983 October 1984 November 1985.October 1986 October 1987 October 1988 October 1989 October 1990 15 2b 103 94 58.'41 56 29.11 6 6 9 54 75 55 78 54 39 23 8 10 19 57 23,1400b 15,840 13,020 8,920 6,310 8,690 4,945 1,350 1,060 940 1,400 8,890 12,400 9,200 13,020 8,821 4,615 2,793 976 1,137 2,295 6,752 aShell length >50 mm bFrom Ayer (1968)437 and mortality of smaller size classes.. The estimated adult standing-crop of Hampton Harbor flats in 1990 is the fifth highest observed, 1971-1990. The distribution of clams by flat has changed since 1980 when the 1976,year class became harvestable (Table 3.3.7-4). Flat 1 showed a continuous increase in its percentage of.adult clams through 1984, while Flat 4 showed a steady decrease. In 1985 the percentageof harvestable clams decreased on Flat 1 and increased on Flat 4, followed by increases on Flats 1 and 2 and a decrease on Flat.4 during 1986 (Table 3.3.7-4), In 1987, the percentage of harvestable clams increased at Flat.4, while decreasing at Flat 1 and Flat *2, reflecting the stabilization of clam populations at Flat 4 at low levels, while populations on Flat 1 and Flat 2 continued to decline (Appendix Table 3.3.7-1). In 1988, the distribution of harvestable clams changed little, as Flat 2 dropped slightly, Flat 4 increased slightly'and Flat 1 remained unchanged. In 1989 and 1990, the percentage of harvestable clams continued to increase on Flat 4 while decreasing at both Flat 1 and Flat 2.'," I-438 -0 K TABLE 3.3.7-4. DISTRIBUTION (PERCENT OF TOTAL STANDING CROP') OF HARVESTABLE CLAMS BY FLAT AT.HAMPTON HARBOR, 1979 THROUGH 1990. SEABROOK OPERATIONAL REPORT, 1990.YEAR FLAT.1 2 -3 .5 1979 33.3 6.2 2.2 55.7 2.5 1980 45.1 10.5 1.0 39.5 3.9 1981 53.0 7.3 1.5 34.4 3.7 1982 52.2 7.0 1.0 38.4 1.3 1983 62.9 25.6 0.5 10.5 0.5 1984 72.0 13.6 1.9 11.5 0.9 1985 60.2 14.6 NS 25.1 NS 1986 63.0 21.9 NS 15.1 NS 1987 40.0 15.9 NS 44.2 NS 1988 40.9 9.0 NS 50.1 NS 1989 30.1 3.1 NS 66.8 NS 1990 24.6 1.6 NS 73.8 NS NS = not sampled 439 APPENDIX TABLE 3.3.1-1. MEAN MONTHLY SEAWATER SURFACE TEMPERATURE (0 C) AND SALINITY (ppt)TAKEN IN BROWNS RIVER AND HAMPTON HARBOR AT HIGH AND LOW TIDE, MAY 1979 -DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990.!TEMPERATURE BROWNS RIVER .HAMPTON HARBOR------------------------- +------------------ 7 -----7-7-----------------------------I HIGH TIDE 1 LOW TIDE i HIGH TIDE LOW TIDE---------- +-------------

---

+--------------------------+------------------------- 1 MEAN 1 CI MEAN CI 1 MEAN: CI 1 MEAN CI--- -------------------------

---

.------------------------

4 ---------+----------------------- !JAN 1.511 1.21 1.0! 0.61 2.6: .71 : l 1.0: 0.5i!FEB 1.71 1.01 1.8: 0.81 2.5: 0.71 1.71 0.51 IMAR i 4.21 0.9: 5.11 0.6: 3.71 0.41 4.3: 0.61!APR 7.01 0.71 9.61 0,61 6.31 0.61 8.21 0.51!MAY 12.71 1.41 14.51 0.81 9.91 0.51 12.41 0.71:JUN 16.11 0.9: 19.31 0.81 13.51 0.61 16.31 0.71 iJUL 18.31 0.81 22.11 1.11 15.81 0.61 .18.51 0.71!AUG 1 19.11. 0.91 21.21 1.1i 17.01 0.81 18.81 0.71!SEP 1 16.21 0.81 18.01 0.81 14.81 0.81 16.31 0.71 1OCT 11.91 0.81 12.51 1.31 12.01 0.61 12.1: 0.71!NOV i 8.31 0.81 7.61 1.3 ! 9.01 0.61 8.31 0.81!DEC 1 4.51 1.01 2.41 1.01 5.31 0.71 3.51 .0,9i!SALINITY 1 BROWNS RIVER HAMPTON HARBOR i --------------------------------- +----------------------------------- 7------------------I A 1 HIGH TIDE I LOW TIDE 1 HIGH TIDE I LOW TIDE 1 i i ---------- +--------------------------4-------- A ------------------ +------------------------- i MEAN 1 CI MEAN I CI 1 MEAN 1 CI 1 MEAN I CI--------------- f------------+------------+------------+-------------I-------------+------------+------------ (:JAN .31.5i 0.81 23.71 2.31. 32.21 0.51 28.71 141!FEB .1 29.51 2.11 19.31 3.21 31.8i 0.61 27.41 2.01!MAR 29.01 1.41 17.71 2.61 31.31 0.71 25.71 2.01 IAPR 1 27.11 2.3! 17.01 3.41 30.1: 1.31 24.5: 2.71!MAY i 28.71 1.51. 19.11 2.81 30.01 0,81 26.31 1.5:!JUN 1 28.91 1.41 21.11 2.41 30.4: 0.81 27.61 1.7:!JUL 30.11 0.81 23.9: 1.41 31.01 0.41 28.8: 0.71 i!AUG i 30.21 0,51 25.11 1.31 31.3: 0.31 29.5: 0.51!SEP 1 30.71 0.91 24.41 2.01 31.5: 0.21 29.61 0.71 IOCT 30.51 0.61 .22.81 1.71 31.61 0.21 29.01 0.71!NOV 1 29.91 1.21 20.11 2.71 31.71 0.31 27.9! 1.21!DEC i 30.51 1.51 20.4X 3.01 31.8: 0.51 27.71 1.81 440 APPENDIX TABLE 3.3.1-2. ANNUAL MEAN3 WITH 95% CLb FoR TEMPERATURE (°C) AND SALINITY (ppt)TAKEN AT BOTH HIGH AND LOW SLACK TIDE FROM BROWNS RIVER AND HAMPTON HARBOR FROM 1980-1990. SEABROOK OPERATIONAL REPORT, 1990 i BROWNS RIVER I------------I----7------------------------------------------------------

---

I LOW TIDE i HIGH TIDE .-------------------------------

---

i TEMPERATURE 1 CL 1 SALINITY 1 CL TEMPERATURE I CL 1 SALINITY 1 CL----------+ -4.. .- ......-- ----- ---------------- 4 ---- ....... .. .----- ---------+ ---- ---L+ ---:1980 10.91 5.21 25.11 1.91 9.6: 4.41 31.01. 1.61 i1981 10.61 4.41 25.51 1.61. 10.31 4.61 30.O[ 1.71 11982 10.71 4.51 22.81 1.8: 9.91 4.11 30.01 1.21 11983 11.91 .5.01 19.41 3.61 11.01 4.21 28.01 1.91 11984 1 11.91 5.11 18.11 3.3: 10.61 3.91 28.41 1.81.11985 1 11.31 5.01 21.71 2.11 10.11 4.41 30.61 0.71 11986 .10.31 4.81 20.41 3.11 9.61. 4.01 30.21 0.91 11987 -- I 20.11 2.91 -- -i 28.71 1.91 11988 i 10.61 5.11 20.51 2.21 10.31 4.01 29.81 0.71 11989 i 11.51 5.41 20.21 2.51 10.11 3.91 .30.01 0.71 i1990 ---: --i i 1OVERALL[, 11.31 1.41 .21.41 0,81. 10.21 1.1i 29.71 0.41 S I .HAMPTON HARBOR. .I LOW TIDE I HIGH TIDE[I g .............................+1 TEMPERATURE 1 CL .SALINITY .CL 1 TEMPERATURE 1 CL SALINITY CL i---------- -------------- -------------- -------------- -------------.....-- ---------- -------------- -------------- -------------. .11980 1 9.61 4.41 29.91 1.41 9.11 3.61 32.01 0.51 11981 1 10.11 4.41 28.91 1.11 9.31 3.81 31.51 0.41 11982 1.0.21 4.11 27.31 1.51 9.21 3.51 31.21 0.61 11983 1 10.41 4.31 25.51 2.41 9.91 3.41 30.1i 0.91 11984 1 10.41 4.11 25.81 2.31 9.41 3.11 30.21 0.91:1985 " .10.61 4.21 29.11 1.01 10.11 3.31 32.21 0.31 11986 1 1001 3.91 27.71 1.31 9.41 3.01 31.51 0.41 11987 1 10.01 4.31 27.51 2.21 8.91 3.51 30.71 0.91 i1988 1 9.71 3.91 27.81 1.01 9.21 3.31 31.31 0.41 i1989 1 10.21 4.41 28.01 1.21 9.21 3.31 31.41 0.71 11990 i 10.31 4.31 27.21 1.21 9.71 3.61 31.31 ' 0.61 OVERALL 1 10.1i 1.11 27.71 0.51 9.41 0.91 31,21 0.21'Annual mean=mean of 12 monthly means, except where footnoted. bConfidence limits expressed as half the confidence interval.cNo data were taken in February, therefore n=11 months.d Overall mean-mean of monthly means: does not include data from 1987 and 1990 in Browns River (except for salinity-in 1987).441 APPENDIX TABLE 3.3.2-1. A COMPARISON OF SPARSELY OCCURRING TAXA IN AUGUST BENTHIC DESTRUCTIVE 1978-1989 AND 1990.SEABROOK OPERATIONAL-REPORT, 1990.MACROALGAE SAMPLES, TAXA 1978-1989a 1990b monostroma grevillei x monostroma oxyspermum x Enteromorpha sp. X: Enteromorpha intestinalis x Enteromorpha linza x Enteromorpha prolifera x Ectocarpus siliculosus x x Giffordia granulosa x-Sphacelaria cirrosa x x Desmarestia viridis x x Petalonia fascia x x Scytosiphon lomentaria x Dumontia contorta x Ceramium deslongchampii x Pilayella littoralis x Plumaria.,elegans x Polysiphonia sp. x Polysiphonia denudata x Polysiphonia harveyi x Porphyra miniata x x Entocladia viridis x Spongonema tomentosum x Cladophora sericea x Spongomorpha spinescens x Bonnemaisonia hamifera x 0 Palmaria palmata x'less than 9 occurrences out of 512 samples (1.8%)b x occurred once out of 55 samples (1.8%)o 0 occurred eight times out of*55 samples (14.5%)442 4L 4:-APPEN13X TABLE 3.3.2-Z. MEDIAN AID RANGE OF PERCENT COVER'AND PERCENT FREQUENCY OF PERENNIAL AND ANNUAL HACROALjGAE PER 0.n5 M 2 AT FIXED INTERTTMAL NON-DESTRUCTIVE SITES DURING THE PREOPERATIONAL PERIOD (198Z-1989) AND IN 1990.SEABROOK OPERATIONAL REPORT, 1990.PERENNIAL ALGAE BARE LEDGE b FUO LDEbCONDRUS ZN STATION APR JUL DEC APR JUL DEC APR JUL DEC Percent Coverayg Fucus spp.c Bi 1982-89 median 1 <1 <1 93 93 68 25 18 18 ( range) (0-8) (0-10) (0-40) (25-98) (60-100) (25-95) (4-38) (13-69) (0-38)1990 0 4 2 92 0 25 0 0 0 BS 1982-89 median 6 11 23 94 94 93 0 0 0 (range) (0-50) (<1-75) (0-80) (60-98) (65-100) (2-98) (0) (0) (0)1990 18 77. 25 60 65 50- 0 0 0 Percent frequencya,f Fucus spp.c BI 198Z-89 median 6 19 6 94 88 88 13 13 16 (range) (0-81) (0-94) (0-94) (69-100) (75-100) (69-94) (0-44) (2-75) (0-60)1990 0 0 0 .94 100 94 0 6 0 B5 1982-89 median 82 97 100 85 85 91 0 0 0 (range) (0-100) (12-100) (0-100) (62-100) (69-100) (31-100) (0) (0) (0)1990 100 100- 100 88 87 88 ý0 0 .0 Chondrusd B1 1982-89 median 0 0 0 2 1 2 45 .34 45 crispus I 990 (range) (0) (0) (0) (0-8) (0-13) (0-7)3 (20-53) (20-38) (28-53)1990 0 0 0 15 2 3 41 23 53 B5 1982-89 median 0 0 0 <1 <1 0 45 48 41.(range) (0) (0) (0) (0-5) (0-8) (O-Z) (0-72) (41-55) (39-48)1990 0 0 0 0 0 5 so 39 61 Mastocarusd BI 1982-89 median 0 0 0 9 7 13 47 66 48 stel(aru frange) (0) (0) (0) (0-29) (0-19) (0-32) (21-69) (65-71) (32-67)1990 0 0 0 37 19 22 61 59 49 B5 1982-89 median 0 0 0 6 5 10 47 51 44-(range) (0) (0) (0) .(0-15) (0-13) (0-19) (0-53). (41-63) (43-56)1990 0 0 0 10 10 -13 26 63 44+Corallina El 1982-89 median 0 0 0- 0 0 0 0 0 0-officinalis (range) (0) (0) (0) (0) (0) (0) (0) (0) (0)1990 0 0 0. 0 0 0 0'. 0 0 B5 1982-89 median 0 0 0 0 0 0 30 52 .52, (range). (0) (0) (0) (0) (0) (9) (15-57) (33-61) (31-65)1990 0 0 0 0 0 63 40 I contl nued ,1 APPENDIX TABLE 3.3.2-2. (Continued) ANNUAL ALGAE BARE FUCOID LEDEm~ cHONRus ZONEb STATION 'APR JUL DEC APR JUL DEC APR ML DEC Percent Frequencya'f Porphyra sp. .Bi 1982-89 median <1 5 <1 2. 7 <1 0 0. 0 (range) (0-15) (0-78) (0-21) (0-9) (0-17) (0-5) (0) (0-9) (0)1990 1 3 Z 0 5 0 0 .36 0 B5 1982-89 median 0 0 0 0 0 0 0 0 0 (range) (0) (0) (0) (0) (0) (0) (0) (0) (0)1990 0 0 0 0 0 0 0 0 0 Urosp "a B1 1982-89 median 45 .0 0 0 e 0 0 0 0 0 xiformis/ (range) (0-99) (0) (0) (0-Pe) (0) (0). (0) (0) (0)Ulothri flacca 1990 79- 0 0 0 0 0 0 0 0 B5 1982-89 median 73. 0 0 0 0 0 0 0 0 (range) (0-100) (0) 10) (0-5) (0) (0) (0) (0) .(0)1990 0 0 0 0 0 0 0 0 0 BI 1982-89 median 0 0 0' 0 0 0 0 0 0 fuscopurpurea (range) (0) (0) (0) (0) (0) (0) (0) (0) (0)1990 0 0. 0 0 0 0 .0 0 0 B5 1982-89 median 25 0 0 0 0 0 0 0 0 99 (range) (0-100) (0) (0) (0) (0) (0) (0) (0) (0)1990 0 0 0 '0 0 0 0 0 0 t sed on fixed quardrats: re ledge station is at upper edge of HSL zone, at approximate mean high water. Fucoid station is at .approximate cmean sea level mark. Chondrus zone station, first sampled in 1985, is at approximate mean.low water mark.dPercent frequency of fucoid algae is based on presence of holdfasts only.eX frequency recorded using different method in 198Z..fPresent, Z.frequency not recorded.Based on point,contact line sampling.gPercent cover of fucoid algae is based on whole plant. APPENDIX TABLE 3.3.7-1.

SUMMARY

OF MYA ARENARIA POPULATION DENSITIES FROM ANNUAL FALL SURVEYS IN HAMPTON-SEABROOK HARBOR, 1971 THROUGH 1990.SEABROOK OPERATIONAL REPORT, 1990.NUMBER OF SAMPLES MEAN-DENSITY (No.ift 2)COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (I to 25 mm) (26 to 50 mm) (>50 mim)Flat 1 1971 .18 18 48 6.8- 2.1'1972 18 18 110 8.1 3.3 1973 36 18 44 2.5 i.3 1974 64 18 2 3.7 2.1 1975 57 18 31 0.8 1.1 1976 49 18 580 >0.1 0.3 1977 60 14 437 >0.1 0.2 1978 63 14 209. 1.4 >0.1 1979 62 20 40 30.4 0.1 1980 30 20 90 72.0 1.7 1981 25 25 45 44.7 3.7 1982 25 25 6 13.1 2.8 1983 40 40 21 21.1 4.2 1984 40 45 .7 6.2 3:4 1985 106 71 5 1.4 1.6 1986 75 70 9 0.2 047 1987 70 55 7 0.1 0.2 1988 70 62 3 0.3 0.2 1989 65 60 ii 0.8 0.4 1990 65 32 114 0.5 0.8 Flat 2 1971 9 9 91 4.8 3.8 1972 9 9 152 2.2 1.4 1973 18 9 136 3.8 1.1 1974. 25 9 0 1. 3 1.3 1975 25 9 .5 0.0 0.5 1976 19 9 198 >0.1 0.1 1977 33 7 49 0.0 >0.1 1978 29 7 8 3.9 0.2 1979 32 9 31 3.5 0.2 1980 .40 25 253 3.9 2.2.1981 25 25 519 1.0 0.9 1982.. 15 25 7 0.2 0.9 1983 40 25 19 4.4 5.4 1984. 40 25 25 0.9 1.7 1985 51 25 21 >0.1 0.5 1986 53 20 9 >0.1 0.3 1987 55 20 13 >0.1 0.1 1988 55 25 2 >0.1 0.1 1989 80 30 25 0'.1 '0.1 1990 70 25 40 .0.1 0.1 (continued) 445 APPENDIX TABLE 3.3.7-1. (Continued) NUMBER OF SAMPLES MEAN DENSITY (No./ft 2)COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (I to 25 mm) (26 to 50 mm) (>50 mm)Flat 3 1971 6 6 7.4, 4.7 4.6.1972 6 6 39 1.6 0.4 1973 12 6 8 3.6 2.2 1974 16 6 1 0.7 1.5 1975 17 6 1 0.0 0.5 1976 24 5 321 >0.1 0.3 1977 20 6 43 >0.1 >0.1 1978 23 6 71 2.1 0.1 1979 12 .4 6 1.0 0.0.1980 40 ,25 56 0.5 0.4 1981 25 25 51 0.1 0.4 1982 15 25 4 0.2 0.3 1983 40 *25 12 0.1 0.2 1984 40 30 32 0.1 0.4 1985 NS 25 12 NS NS 1986 NS 24 8 NS NS 1987 NS 25 9 NS NS 1988 NS 30 2 NS, NS 1989 NS 21 11 NS NS.C 1990 NS 20 28 NS NS Flat 4 1971 12 12 106 17.6 2.8 1972 12 12 138 10.6 2.3 1973 24 .12 18 3.8 0.6 1974 39 12 3. 2.8 1.7 1975 38 12 39 0.3 0.4 1976 68 18 475 >0.1 >0.1 1977 42 11 245 >0.1 >0.1 1978 51 11 172 16.8 >0.1 1979 66 18 97 36.3 0.6 1980 25 25 96 47.2 3.2 1981 25 -25 236 49.4 2.3ý1982 25 25 24 12.3 2.2 1983 25 25 45 2.8 .1.0 1984. 25 25 82 1.0 0.9 1985 36 25 16 0.3 0.6 1986 38 30 12 0.2 0.2 1987 40 20 12 0.3 0.2 1988 40 28. 6 0.9 0.4 1989 30 21 35' l i 0.7 1990 30 21 97 3.1 2.6 (continued) 0 446 APPENDIX TABLE 3.3.7-1. (Continued) NUMBER OF SAMPLES MEAN DENSITY (No./ft 2)COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR ADULTS SPAT (I to 25 mm) (26 to 50 mm) (>50 mm)Flat 5 1971 9 9 176 1.3 1.6 1972 9 9 196 3.8 2.3 1973 21 11 23 1.0 0.4 1974 33 12 2 >0.1 0.1 1975 20 8 5 0.0 >0.1 1976 14 12 309 0.0 >0.1 1977 38 9 64 >0oi >0.1 1978 38 .7 32 4.8 >0.1 1979 28 8 8. 2.0 >0.1 1980 40 20 65 2.2 *0.8 1981 25 25 409 0.3 0.7 1982 15 25 43 >0.1 0.2 1983 40 25 25 0.0 A0.1 1984 40 25 16 >0.1 0. 1 1985 NS 33 15 NS NS 1986 NS 35 7 NS NS 1987 NS 20 23 NS NS 1988 NS 25 3 NS NS 1989 NS 20 21 NS NS 1990 NS 20 40 NS NS All Flats 1971 54 54 92 7.7 2.7 1972 54 54 130 6.2 2.2 1973 11 56 47 2.8 1.0 1974 177 57 2 2.2 1.5 1975 157 53 21 0.4 0.6 1976 174 62 421 >0.1 0.2 1977 193 47 207 >0.1 >0.1 1978 204 45 123 6.3 >0.1 1979 200 .59 .49- 22.3 0.3 1980 175 115 115 20.6 1.5 1981 125 125 252 19.1 1.6 1982 95 125 17 6.7 1.5 1983 185 140 24 5.9 2.3 1984 185 150 46. 1.7 1.3 1985 193 179 12 0.8 1.1 1986 1.66 179 9 0.2 0.5 1987 165 140 11 0.1 0.2 1988 165 1.70 3 0.4 0.2 1989 175 152 18 0.5 .0.3 1990 165 118 68 0.8 0;8.447

4.0 METHODS

4.1 GENERAL The purpose of this report is to evaluate the effect of Seabrook Station on the balanced, indigenous population of shellfish, fish, and wildlife in the waters in and around the discharge.' Previous reports have documented the natural temporal and spatial variability of communities and selected species. Data collected in 1990, particularly during the months when Seabrook Station was. operational (August-December), were compared to the historical data base. Differences observed in 1990 were further investigated to determine if they were restricted to nearfield areas or occurred only during the period of operation. A change was potentially deemed the result of plant operation only if these criteria were met and then only if other causes were eliminated. The Seabrook Environmental Program has evolved from a series of individual studies to a consistent and highly unified sampling regime. Prior to 1975, the Seabrook Environmental Program involved studies of specific sites (e.g., the estuary, the discharge area, the intake area) or specific species (e.g., ffya arenaria) in order to (1)characterize their physical and/or biological environment and (2) assess impact of proposed plant design. The results of these studies were reviewed and discussed during the Environmental Protection Agency's hearings on Seabrook Station's open cycle cooling-water system (NAI 1977e; EPA 1977).From July 1975 through 1989, the focus of the program has been to provide preoperational characterization of the environment in potentially impacted areas. Field and laboratory methods that were used for data collected during 1980 through 1990 were thoroughly described in the data reports for those years (NAI 1981c, 1981f, 1982a, 1982b, 1983a, 1984a, 1985a, 1986, 1987a, 1988a, 1989a, 1990a, 1991). Methods used prior to 1980 were summarized and explained in detail in previous annual 449 reports for Seabrook Environmental Studies (NAT .1976a, 1976b, 1977a, 1977b, 1977c, 1977d, 19-78a, 1978b, 1979a, 1979b, 1979c, 1979d, 1979e, 1979f, 1980a, 1980b, 1980c, 1981a, 1981b, 1981c, 1981d, 1981'e, 1981f)'.In-depth reports describing baseline conditions were written for data collected through 1981 (NAI 1982c), 1982 (NAI 1983b) and 1983 (NAI 198.4b). A complete assessment of preoperational conditions was made.in the 1984. Seabrook Baseline Report (NAI 1985b)'. Subsequent baseline reports (NAI 1987b, 1988b,. 1989b, 1990b) have built on conclu-sions made in that report, updating results with additional data for those programs which had been maintained without interruption. All studies performed during the 1989 program were continued unchanged in the 1990 program. Phytoplankton and microzooplankton -sampling programs were reinstated in 1990, along with ichthyoplankton and bivalve larvae entrainment collections. Methods and data tables results for the 1,990 program are presented in NAI (1991).Over the several years of this study there were instances in which some sample types were collected for only part of a year, or discontinued for a whole year or years, due to program modifications (particularly in 1985 and.1986). This report does not include data from L partial sampling years if they erroneously influence sample statistics. For example, annual 'means of macrozooplankton selected species have not, been calculated for 1986 because samples were not collected from January through June (a period of peak abundance) in that year. However, these data could be used innumerical classification and analysis of variance since samples are partitioned seasonally. Data not presented in a table or figure-means that they were either-not collected or were incomplete.for that period.As in previous baseline reports, conditions in the Hampton-Seabrook area were examined in this report at and species', levels, both useful indicators of environmental change. Community:, structure and its variation in time and/or space were investigated using 450 numerical classification or multivariate analysis of variance.Abundance of various key species (of numerical or commercial importance) previously identified as "selected species" were compared temporally or spatially using analysis of variance (ANOVA) or non-parametric techniques. In several cases,, the size or growth of a selected species was examined in addition to abundance or biomass in order to provide a basis for detecting potential sublethal effects. Thesemethods

are effective in describing general patterns and magnitudes of variability that have occurred.

Analyses have focused on a single species or several species grouped together in a higher taxonomic category.Components of and rationale for species complexes were discussed in the 1984 Data Report (NAI 1985a).4.2 COMMUNITY STRUCTURE Community analyses included numerical classification (Table 4.2-1), multivariate analysis of variance (Table 4.2-2), and qualitative comparison of the relative abundances of dominant species (adult fin-fish, phytoplankton).

4.2.1 Numerical

Classification Numerical classification (Boesch 1977) was used to examine community structure either spatially (using data collected from different areas), and/or temporally (using data collected over time);comparisons were made.based on species composition. Plankton (bivalve larvae, microzooplankton, macrozooplankton, ichthyoplankton eggs and larvae, and benthos (macroalgae, macrofauna, surface fouling panels)species assemblages were analyzed in this way (Table 4.2-1).The "normal" classification forms groups of stations and/or sampling periods, based on similarity levels calculated for all possible combinations of stations/sampling periods and the species that occur there. Normal classifications were performed.using the Bray-Curtis 451 TABLE 4.2-1.

SUMMARY

OF COMMUNITIES AND METHODS USED IN NUMERICAL CLASSIFICATION. SEABROOK OPERATIONAL REPORT,. 1990.COMMUNITY STATIONS DATES DATA CHARACTERISTICSa Macrozooplankton (505 micron net)Microzooplankton Bivalve larvae Fish eggs (505 micron net)P2 1/78-12/84, 7/86-12/90 P2 1978-1984, 7/86-12/86 4/90-12/90 Monthly x; separated tychoplankton and holo/-meroplankton. Tycho-plankton: used all taxa except Mysidacea and Am-phipoda (22 taxa).Holo/mero: deleted taxa occurring in 5% of sam-ples and general taxa.50 taxa used in analy-sis.x, surface and bottom tows. Taxa excluded with frequency of occur-rence <20% and total abundance <0.1%. 35 taxa used in analysis.x of duplicate tows.Deleted 1 general taxon (Bivalvia). Mean of 4 tows/date (Jan 76-Feb 83, except for non-selected species Jan-Dec 82, ltow); 2.tows (Mar 83-Dec 90);dates averaged'within month; excluded taxa with total percent com-position <0.1% or per-cent frequency <5%;excluded 2 months with<20 eggs. 11 taxa used in analysis P2 P2 Apr-Oct, 1982-1984 1986-1990 1/76-12/90 (continued) 452 . TABLE 4.2-1. (Continued) COMMUNITY STATIONS DATES DATA CHARACTERISTICSa. Fish larvae, P2 1/76-12/90 Data treated as for (505 micron net) eggs; excluded species with total percent com-position <0.1% or fre-quency of occurrence <5%. 21 taxa used in analysis; excluded 3 months with <20 larvae.Benthic macro- B17,B19,B31, 'Aug 1978-1990 Algae: Mean of algae and macro- BlMLW cates; excluded taxa fauna B34 Aug 1980-1984; with <2.0% frequency of 1986-1990 occurrence. 34 taxa B04,B13 Aug 1978-1.984; used in analysi[s. 1986-1990 Square root transforma-B35,B5MLW Aug 1982-1990 tion. Macrofauna: Mean B16 Aug 1979-1984; of replicates; excluded 1986-1990 noncolonial species with 36 occurrences based on 1978-90 data .(6.4%). and all colonials. 89 taxa used in analysis.Short-term sur- B19 1978-1990 Monthly mean abundance face panels of noncolonials. Ex-cluded taxa with <8 occurrences (5%). 20 taxa used in analysis.aAll data log (x+l) transformed unless otherwise noted 453 TABLE 4.2-2.

SUMMARY

OF COMMUNITIES AND METHODS USED IN MULTIVARIATE ANALYSIS OF VARIANCE. SEABROOK OPERATIONAL REPORT, 1990-COMMUNITY STATIONS DATES DATA CHARACTERISTICS 3 Phytoplankton P2,P5,P7 1990 Mean of replicates. Taxa deleted if % comp.<1%. 8 taxa included in analysis.Macrozooplankton P2, P5, P7 1990 Mean of 3 replicate. (505 micron net) tows; excluded taxa with x annual abundance for all 3 stations <20.plus 4 general taxa. All months used in analysis.. Bivalve larvae P1, P2, P5, 1990 Mean of duplicate tows.P7 All taxa included except Bivalvia.Microzooplankton P2, P5, P7 1990 x, surface and bottom tows. Deleted taxa <25%frequency of occurrence (all stations combined). Fish eggs, P2, P5, P7 Aug-Dec. Mean of two tows per Fish larvae 1990; Jan-Dec date. Deleted dates <20 (505 micron net) 1990 eggs or larvae. Taxa Fish larvae deleted if % comp. <0.1%or percent frequency of occurrence <5%.V'All data log (x+.l) transformed unless otherwise noted 454 similarity index '(Clifford and Stephenson, 1975; Boesch, 1977). Values of the indices vary from 0 for absolute dissimilarity to 1 for complete similarity. Samples which-contained very few organisms were excluded from.the analysis because they usually contribute little to the communi-ty description. Rare species,.which.generally have no consistent pattern of occurrence and contribute little information to the overall analysis, were excluded from the classification based on their low frequency of occurrence or low total abundance over the period of study (Table 4.2-1). In all cases, abundance data were or square-root transformed to reduce differences between.large and small values and thus avoid overemphasizing the abundant species. The classification groups were formed from arithmetic aVerages by the unweighted pair -.group method (UPGMA: Sneath and Sokal, 1973). Results were simplified by combining the entities based on their similarity levels, determined by both the within-group andibetween-group similarity values. Results were presented graphically by dendrograms, which show the within-group similarity,.and the similarity levels at which they link to the other *groups. The groups were characterized in terms of the mean abundance of dominant taxa and total abundance (sum of all taxa) during thepreoper-ational period and in 1990. 'Communities in 1990 were judged to be similar to. previous years if:.collections were placed in the group with the majority of seasonal (plankton, surface panels) or station (macro-fauna, macroalgae) collections from'previous.years. A potential impact was suggested if community differences in 1990 occurred solely during the'operational period (August-December) and were-restricted to the nearfield area. This situation would trigger additional investigations.

4.2.2 Multivariate

Analysis of Variance.Multivariate analysis of variance (MANOVA, Harris 1985)_was utilized to assess simultaneously the similarity in abundances.of dominant taxa among nearfield and farfield stations. Historically,. there have been few differences in planktonic species assemblages Ariing nearfield intake, discharge, and farfield stations. Continuation of the 455 preoperational trend in 199.0 during plant operation would suggest that there were no effects of plant operation on these communities. MANOVA was used for the macrozooplankton, bivalve larvae, microzooplankton and fish larvae communities-(Table 4.2-2) Probabilities associated with the Wilks' lambda, Pillai's trace and Hotelling.Lawley trace test statistics are reported (SAS. 1985a)" 4.2.3 Other Community Methods Demersal, pelagic, and estuarine fish communities are composed almost exclusively of a few dominant species, many of which are desig-nated as selected species. Previous use of multivariateanalysessuch as numerical classification indicated that there were two seasonal assemblages (summer and winter), whichchanged based on seasonal movements of the most abundant taxa (NAI 1982c, 1983b). Since that time,.seasonal, annual and spatial changes in the fish community have been:monitored.using relative abundance (percent composition) of -dominant taxa. For demersal and estuarine.fish, spatial differences have been evaluated by comparing relative, abundances among stations both during the preoperational period and in 1990, Historically, pelagic fish have not shown area-wide differences, undoubtedly because of their mobility. Therefore, differences. among stations for the pelagic fish, have not been evaluated. Relative abundances in 1990 for all dominant species of fish were compared to previous years. Differences in 1990 that were outside the range of previous years warranted further scruti-ny, using analyses outlined for selected species (Section 4.3). For demersal fish, potential changes in 1990 at the nearfield station (T2)only; occurring during the operational. period, were examined carefully. Impact assessment for demersal fish is complicated by the difficulty in obtaining trawls at T2 in late: summer because of lobster fishing activities. 456

4.3 SELECTED

SPECIES/PARAHETERS Temporal and spatial. differences for.the selected species and water quality parameters were quantitatively evaluated for the preopera-tional and operational periods. Many of the selected species and physical/chemical parameters monitored in theHampton-Seabrook area have shown year7to-year differences that are part of natural environmental variability. Given this framework, values in 1990 were compared to previous years using analysis of variance or non-parametric techniques. Most of the organisms and physical/chemical parameters show seasonal patterns as well. These within-year patterns are shown graphically in plots of the mean and 95% confidence limits over all preoperational years for each month. Monthly mean values in 1990 were plotted on the same graph-to provide a visual comparison of their magnitude and seasonality.- Many of the tables comparing organism abundances among years or months show geometric means and confidence limits. These are calculated by (1) log (x+l) transforming the data, (2) calculating the mean and confidence limits of the transformed data, and.(3) back-transforming to the original units. Geometric means are, generally somewhat lower than arithmetic means (averages of untransformed data), and the difference between the two means. {§greater in data sets exhibiting a high'degree of variability. An outlier in a data set, such as an unusually high abundance in a single sample, will have less influence on a geometric mean than on an arithmetic mean. Thus a geo-metric mean is, in effect, a weighted mean', in which extreme values are given less weight than are typical values. For data sets-that require*.logarithmic transformation to meet the assumptions of'a normal distribu-.tion for statistical analysis', the geometric means faithfully portray the relationships within the data (among years, for example), whereas arithmetic means would sometimes show a different pattern than that detected by the analysis.. 457 Differences in substrate, water mass.movement, temperature, light penetration, depth, food availability, reproductive success or any combination of these factors can cause variation in species abundance and growth among stations or areas. As part of our experimental design, farfield stations beyond the.influence of potential impact were estAb-lished as "control." stations in areas as similar as possible to the nearfield areas. Any change observed during the operational phase at nearfield stations can be compared with these farfield areas to ascer-tain whether the change is occurring throughout the coastal area or just at the nearfield area. Spatial differences in the selected species were evaluated as part of the ANOVA design, by utilizing a paired t-test (nearfield vs. farfield stations), or the non-parametric Wilcoxon's summed ranks (or "two-sample") test.4.3.1 Analysis of Variance (ANOVA)Analysis of variance was used to evaluate spatial or tempora'l variability in abundance of selected species and. values of water quality ,parameters. Analysis of variance is a statistical technique which sub-divides the total variability into portions attributable to different sources (Lentner 1972). In this study, the major sources of variability have been (1).spatial, amongstations or areas within stations, (2)temporal, among years, seasons, or sampling dates, and (3) residual, any variability not explainable by the first two. sources.The initiation of plant operation introduced a new source of,, potential variation. All ANOVAs sought to test the null hypothesis that values collected in 1990 were statistically

• similarto previous years.An ANOVA design was developed with-the assistance of Dr. Roger Green (University of Western Ontario), using the following variables:

Preop-Op: Partitions data into the operational year (1990)*and all previous years, regardless of station, testing whether the operational observations fall within the historical variability. 458 Year (Preop-Op): Partitions data into years nested within-operational and preoperational periods, regardless of station or sampling period, testing the variability among years.Station or Area: Partitions data.into stations or areas representing nearfield and farfield areas, where applica-, ble, regardless of year or sampling period, testing whether there has been a consistent relationship spatial-ly.Sampling period (Year): For data that show seasonal trends, a variable was included, such as months, weeks, or sampling period nested within .years, testing whether there are significant differences seasonally.. All appropriate class variables were used in the ANOVAs along with the pertinent interactions. The discrete operational period, (August-December) as well as the entire year were analyzed in cases where thespecies'.or parameters' peak period occurred during the operational period, or when seasonality was not pronounced. The beauty of this ANOVA design is that it specifically tests for potential impacts of plant operation. Differences occurring at one of the paired stations would be reflected in a significant result for the Preop-Op Station interaction term (Preop-Op X Station). Significant Preop-Op X Station results were further investigated to determine if the change occurred at the nearfield station (rather than the farfield station) and if changes were restricted to the August-December time period. If these conditions were met, a potential impact was suggested, triggering further investigation. The variables for each selected species or parameters are listed in Table 4.3-1, along with the data manipulations that preceded the analysis.. In some cases, differences in 1990'were evaluated by a one-way analysis of variance among years at a nearfield station or station group. In some data sets that havebeen shown in previous baseline reports to exhibit no differences among stations (e.g., pelagic fish), 459 TABLE 4.3-1. SELECTED TAXA AND PARAMETERS USED IN ANALYSIS OF VARIANCE OR NONPARAMETRIC ANALOGUE. SEABROOK OPERATIONAL REPORT, 1990.-DATES USED DATA SOURCE OF COMMUNITY PARAMETER/TAXON LIFESTAGEa STATIONS IN ANALYSIS CHARACTERISTICSb VARIATIONc Water quality Surface and bottom -- P2 1978-1990.Monthly mean, -Year temperature no transformation Surface, bottom tem- -- P2, PS, P7 1990 Monthly mean, Station perature no transformation Surface, bottom dis- ..P2; P5, P7 1990 x of sample Station solved oxygen; periods, no Surface, bottom salinity; transformation Orthophosphorus, Total phosphorus, nitrate, nitrite, ammonia Phytoplankton Skeletonema costatum P P2, P5, P7 1982-84; Monthly x abundance Preop-Op, Area, 4/86-12/86 Grouped P2, P5 as Month 4/90-12/90. nearfield; P7 Year as farfield P2, P5, P7 1990 x of reps. Station Bivalve larvae Mytilus edulis L. P2 1982-1990 Weekly x, Preop-Op, Area, P7 Group P2, P5 as Year, Week nearfield; P7 as farfield L P2 1978-1990 Weekly x abundance Year Microzooplankton Eurytemora sp. C P2, P7 1982-1984 Mean, surface and Preop-Op, Year, Area Eurytemora berdmani A P5 4/86-12/86 bottom tows (=Station) Pseudocalanus/Calanus N 4/90-12/90 Grouped P2, P5 as Pseudocalanus sp. C,A nearfield; P7 as Oithona sp. N,C,A farfield (continued) 0'ON I. V7. -~ -- - 0- -TABLE 4.3-1. (Continued).-is a'I-.DATES USED DATA SOURCE OF COMKUNITY PARAMETER/TAXON LIFESTAGE 3 STATIONS IN ANALYSIS CHARACTERISTICSb VARIATIONc Macrozooplankton Calanus finmarchicus C,A P2, P7 1982-90 Grouped P5, P2 as Preop-Op,.Area. Cancer sp. L P5 nearfield & P7 as Year Carcinus meanas L farfield.. Mean Month Crangon septemspinosa L abundances per Neotnysis americana All sample period.Ichthyoplankton Winter flounder L P2,P7 7/75-12/90, Mean abundance per Preop-Op, Yellowtail flounder L selected sample period for Year, Station American sand lance L months months which together Atlantic cod L composed over 90% of Atlantic mackerel L the total annual Hake L abundance.Atlantic herring L Pollock L Cunner L Demersal fish Winter flounder J/A Tl, T2 1/76-12/90. x CPUE (no. per haul) Preop-Op, Station, (Otter trawl) Yellowtail flounder J/A T3 per date, all months Month, Year Atlantic cod J/A used in analysis Hakes J/A Rainbow smelt. J/A Pelagicfish Atlantic herring J/A mean of 1/76-12/90 x CPUE (no. per 24- Preop-Op, Month (Gill.net) Pollock J/A all 3 hr set) per date, Year Atlantic mackerel J/A stations surface bottom nets averaged, all months used in analysis (continued) TABLE 4.3-1. (Continued) DATES USED DATA SOURCE OF COMMUNITY" PARAMETER/TAXON LIFESTAGEa STATIONS IN ANALYSIS CHARACTERISTICSb VARIATIONC Estuarine fish Winter flounder J/A mean of 1/76712/84, x CPUE (no. per seine Preop-Op, Year, (Beach seine) Rainbow smelt J/A all 3 1/87-12/90 haul), all months Month Atlantic silverside J/A stations used in analysis Estuarine Streblospio benedicti J/A 3, 9; 1978-1990 Mean per sample Year benthos Capitella capitata J/A 3MLW, (except period; all months Oligochaeta J/A 9MLW; 1985) used in analysis Pya arenaria J/A Nereis diversicolor. J/A Caulleriella sp. B J/A Total abundance --No. of taxa --Benthic Laminaria saccharina B17 1979-1990 Mean number per Preop-Op macroalgae Lawinaria digitata -- B35; 1982-1990 sample period and Alaria esculenta -- B19, B31 1978-1990 station, no trans-Agarum cribosum -- B19, B31 formation. Wilcox-on s summed ranks by station Chondrus crispus -- B17,B19, B31 1981-1990 Mean% frequency per Preop-Op, Station Phyllophora spp. -- B35 1982-1990 year. No transfor-Year Ptilota serrata -- mation. Wilcoxon's summed ranks test.Chondrus crispus -- ,B17, BMIfLW 1978-1990 Mean bi6mass per Preop-Op,. Station, B5MLW, B35 1982-1990 sample period, square Year root transformation Number of taxa -- B1MLW, B5MLW; August, Mean per station and Preop-Op, Station Total Biomass -- B17, B35; 1978-1990 year; no transfor-Year B19, B31, B16 mation (continued) 0-21-p :. I. n-i~-T TABLE 4.3-1. (Continued) DATES USED DATA SOURCE OF COMMUNITY. PARAMETER/TAXON LIFESTAGEa STATIONS IN ANALYSIS CHARACTERISTICSb VARIATIONC Marine'benthos, Ampitboe rubricata, J/A BIMLW, 5/78-11/90 Abundance averaged Preop-Op, Station, selected species Nucella 1apillus, J/A B5MLW 5/82-11/90 over replicates; Year, Month Mytilidae spat J/A 3 dates per year Jassa falcata, J/A B17, 5/78-11/90 Mytilidae spat, J/A B35 5/82-11/90 Asteriidae J/A B17, 5/81-11/90 B35 5/82-11/90 Pontogeneia inermis, J/A B19,B31 5/78-11/90 Mytilidae spat, J/A Strongylocentrotus J/A droebacbiensis Number of taxa, -- Station August, x per year and Preop-Op, Station Total.Abundance -- Groups: 1978-1990 station; No. Year BIMLW, B5MLW; .(see above transformation B17, B35; for years)1B9, B31, B16;B04, B34,B13 Modiolus modiolus J/A B19, B31 1980-1990 Mean per sample Preop-Op period, Wilcoxon's summed ranks test, No transformation (continued) X" O3%wo TABLE 4.3-1. (Continued) DATES USED DATA SOURCE OF COMMUNITY PARAMETER/TAXON LIFESTAGE-STATIONS IN ANALYSIS CHARACTERISTICSb VARIATIN 0.Surface panels,' Number of taxa -- Station pairs: 1978-1984 x per station and Preop-Op,' short-term Noncolonial abundance -- B19, B31; 1985-1990 sampling period. Year Biomass I -_ B04, B34 (B34 initi- All months used 'Month Mytilidae abundance J/A ated in in analysis. Station Jassa marmorata abundance J/A 1982). No transformation Balanus sp. % frequency J/A for No. of taxa, Tubularia sp. % frequency J/A Biomass, Balanus, Tubularia Surface panels, Biomass B19, B31 1978-1984 x per station Preop-Op, monthly sequential 1986-1990 and sampling period. Year, Month,.No transformation. Station* All months used in analysis Biomass, -- B19, B31, BO4, 1982-1984, x per station Preop-Op No. of.taxa,. -- B34 1986-1990 and year.Noncolonial abundance -- Dec. only ."*No transformation Laminaria sp. counts J/A Single sample t-test by station Epibenthic .Homarus americanus L P2, PS, P7 1982-1990 Weekly mean Preop-Op, Year, Week, crustaceans Station L P2 1978-1990 Weekly mean Preop-Op, Year, Week Honarus amfericanus LE, A LI, L7 6/82-11/90 Mean CPUE (per 15 Preop-op,, Station, Cancer borealis A traps) per month, Year, Month Cancer irroratus 'A no transformation, (continued) 0c' TABLE 4.3-1.I -~7 (Continued) DATES USED DATA SOURCE OF COMMUNITY PARAMETER/TAXON LIFESTAGEa STATIONS IN ANALYSIS CHARACTERISTICSb VARIATION 0.Estuarine Nya arenaria J/A Hampton, 1987-1990 Mean per year and Preop-Op, Station, Flats 2 & 4; station. Operational Year Plum Is. Sound (Oct.) data only Y, J/A Hampton 1974-1990 Mean per year and Preop-Op, Station, Flats 1, 2, 4 station. Operational Year S 1976-1990 (Oct.) data only L P2 1978-1990 Mean per week. Year P2, P5, P7 1982-1990 aLife Stages: N = nauplii, C = copepodite, L = larvae, A = adult, All all, J/A = juveniles and adults; LE = legal-sized,.S = spat, by = young-of-year .,log (X+l) transformation unless otherwise.stated. Operational months.(Aug-Dec) and all months in 1990 tested against same time period in previous years unless otherwise noted.Preop-Op= 1990 vs; all previous years.On or if stations are of essentially equal distance from the intake and discharge locations (e.g., estuarine fishes), data from all stations were combined. For those data sets that exhibit a high degree of within-year variability because of seasonal fluctuations (i.e., no.specimens found during certain seasons as, for example, fish larvae), a subset of the data was chosen to represent the peak period, and samples..from that period in each of the years were used in the analysis.Analysis of variance and"related parametric techniques make the following assumptions: (1) all samples are randomly collected, (2)samples come from a normally-distributed population, (3) error terms are normally and independently distributedj and (4) variances of samples are equal or homogeneous (Soka]. and. Rohlf 1969). Random and independent collection of samples' is a function of experimental design. Normality of data was tested using the.Kolomogorov-Smirnov test when sample size was greater than 50 and the Shapiro-Wilk statistic when sample size was 50 or less (SAS 1985b). Homogeneity of variances was tested'using the F-max test (Sokal and Rohlf 1969). :If one or'both of these two assump-tions-was not met, the data were transformed and re-evaluated. In most cases, transformation of the data improved the distribution.sufficiently to allow the use of analysis of variance. Logarithmic.transformations were performed by adding 1 to the data used in the analysis and taking the base-l0 logarithm. Where. sample sizes were unequal, a general linear model was used for the ANOVA (SAS 1985a). [4.3.2 Multiple Comparisons If a'significant difference among means was discovered using analysis of variance, the Waller-Duncan k-ratio t-test was used to test which means or groups of means were significantly different from-each other. This test is less conservative than, several other commonly used multiple comparisons tests (i.e., more likely to find significant differences between means). It was selected because more conservative 466 0 tests failed in several cases to detect any significant differences among means even when the overall F-test of the ANOVA was highly significant. Several types of non-parametric tests of-significance were also used. Differences in ranks were assessed by using the Wilcoxon two-sample test (Sokal and Rohlf 1969; equivalent to.Wilcoxon's sum of, rank test, SAS 1985a) or the Kruskal-Wallis test (Sokal and Rohlf 1969).Wilcoxon's two-sample test is a ranking procedure by which two samples of unequal size can be compared. All data are ranked, then ranks are summed within samples. The differences between the summed.ranks are compared using the Z~statistic. The Kruskal-Wallis test was used as a non-parametric alternative to one-way ANOVA to test among-year differ-ences or among-station differences. This procedure ranks all pooled data, then sums ranks within.a group and compares differences using an H-statistic, distributed approximately as chi square (Sokal and Rohlf* 1969).467

5.0 LITERATURE

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