ML20042E842
| ML20042E842 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/30/1989 |
| From: | NORMANDEAU ASSOCIATES, INC. |
| To: | |
| Shared Package | |
| ML20042E838 | List: |
| References | |
| XX-II, NUDOCS 9005030208 | |
| Download: ML20042E842 (379) | |
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'SEABROOK ENVIRONMENTAL STUDIES, 1988. !
A CHARACTERIZATION OF BASEl.INE CONDITIONS !
, IN THE HAMPTON-SEABROOK AREA, 1975-1988. ,
A PREOPERATIONAL STUDY FOR SEABROOK STATION TECHNICAL REPORT XX-II [ 1
?
I Prepared for NEW HAMPSHIRE YANKEE DIVISION PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE P.O. Box 700 , Seabrook Station Seabrook. New Hampshire j t Prepared by ; i NORHANDEAU ASSOCIATES INC. 25 Nashua Road i Bedford, New Hampshire 03102 , R-IJ73 September 1989 900500h>208 900430 ' "8
- 7 PDR ADOCK 03000443 R PDC
TAB 1.E OF CONTENTS PAGE 1.0 EXECUTIVE SUNHARY . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . 1 1.2 INTAKE MONITORING. . . . .. .............. 2 1.3 DISCHARGE MONITORING . . . .......... .... 4 1.3.1 Discharge Plume Monitoring. ........... 4 1.3.2 Benthic Monitoring. . . . . . . . . . . . . . . . 5 1.3.3 Estuarine Honitoring. . ............. 7 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 HONITORING . . . . . .......... , 15 2.2.1 Plankton. . . . .. ............... 15 2.2.1.1 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 Honitoring. ............... 57 2.3.2.1 Macroalgae and Macrofauna. ....... 57 2.3.2.2 Demersal Fish. . . ........... 62 2.3.2.3 Epibenthic Crustacea . . .,...... 67 111
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y I l l PAGE i 3.0 RESULTS . . ......................... 71 3.1 PLANKTON AND WATIR QUALITY PARAMETIRS. . . .. . . ... 71 3.1.1 Water Quality Parameters Seasonal Cycles and Trends. ..................... 71 3.1.2 Bivalvia Veliger Larvae . . . .. . . . . . ... 83 i a 3.1.2.1 Community. . . . . . . . . . . .. .. . 83 , 3.1.2.2 Sclected Species . . .. . . . . . .. . 87
^
3.1.3 Macrozooplankton. . . . . . . . . . . . . . . . . 89 3.1.3.1 Community Structure. . . . . . . . . .. 89 3.1.3.2 Selected Species . . . . . . .. . . . . 98 3.2 FINFISH, ........................ 106 3.2.1 Ichthyoplankton . . . . . . . . . . . . . . . . . 106 3.2.1.1 Total Community. . . . . . .. . . .. . 106 I 3.2.1.2 Selected Species . . . .. . . . .. . . 122 , 3.2.2 Adult Finfish . . . . . . . . . . . . . . . . . . 135 , 3.2.2.1 Total Community. . . . . . . . . ... . 135 3.2.2,2 Selected Species . . . . . . . . . . . . 153 3.2.3 Finfish Appendix Table. . . . . . .. . . .. . . 171 3.3 BENTHOS. . . . . . . . . . . . . . . . . . . . . . . . . 176 3.3.1 Estuarine Benthon . . . . . . . . , . . . . . .. 176 3.3.1.1 Physical Environment . . . . .. . . . . 176 3.3.1.2 Macrofauna . . . . . . . . . . . . . . . 182 3.3.2 Marine Macroalgae . . . . . . . . . . . . . . . . 198 3.3.2.1 Macroalgal Community . . . . . . . . .. 198 , 3.3.2.2 Selected Species . . . . . . . . . . . . 215 5 i iv
PAGE 3.3 3 Marine Macrofauna . . . . . . . . . . . . . . . . 221 3.3.3.1 Hard substrate Community . . . . . . . . 221 3.3.3.2 Intertidal Communities (Non-destructive Monitoring Program). . . . . . . . . . . 232 3.3.3.3 Subtidal'Touling Community . . . . . . . 235 3.3.3.4 Modlolus nodfolus Community. . . . . . . 237 3.3.4 Surface Touling Panels. .. . . . . . . . . . . . 239 3.3.4.1 Seasonal Settlement Patterns . . . . . . 239 3.3.4.2 Patterns of Community Development. . . . 244 3.3.5 Selected Benthic Species. . . . . . . . . . .. . .- 253 3.3.5.1 Mytilidae. . . . . . . . . . . . . . . . 253 3.3.5.2 Huce))s lapillus . . . . . . . . .. . . 260 3.3.5.3 Asterfidae . . . . . . . . . . . . . . . 261 3.3.5.4 Pontogenela inermis. . . . . . . .. . . 262 3.3.5.5 Jassa falcata. . . . . . . . . . . . . . 263 3.3.5.6 Ampithoe rubr/cate . . . . . . . . . . . 264 3.3.5.7 Strongylocentrotus droebachlensis. . . . 266 3.3.6 Epibenthic Crustacea. .; . . ... . . . . . . . . . 268 3.3.6.1 American Lobsters (#omarus americanus) . 268 3.3.6.2 Rock Crab (Cancer frroratus) and Jonah Crab (Cancer borealls) . . . . . . 279 I 3.3.7 Nya arenarla (Soft-shell Clam). . . . . . . . . . 286 3.3.7.1 Larvae . . . . . . . . . . . . . . . . . 286 3.3.7.2 Reproductive Patterns. . . . . . . . . . 290 3.3.7.3 llampton Harbor and Regional Popula- t tion Studies . . . . . .. . . . . . . . 291 3.3.8 Benthos Appendix Tables . . . . . . . . . . ., . 314 4.0 METHODS . . .. .. . . . . . . . . . . . . . . . . . . . . . 328 4.1 GENERAL. . . . . . . . . . . . . . . . . . . . . . . . . 328 4.2 COMMUNITY STRUCTURE. . . . . . . . . . . . . . . . . . . 338 4.3 SELECTED SPECIES / PARAMETERS. . . . . . . . . . . . . . . 342 5.0 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . 350 v j l I I
l
!.IST OF FIGURES PAGE ;
1 2.1 1. Schematic of sources and levels of variability in i Seabrook Environmental Studies . . . . . . . . . . . . . 11 2.2-1. Dates of occurrence and mean abundance (excluding rare j' taxa) for seasonal groups formed gy numerical classifi~ cationofmicrozooplankgon(No./m, 1978 1984), macro-zooplagkton (No./1000 m , 1978-1984), fisheggsjNo./ 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+1) abundance for selected , species of phytoplanktog (thousarids of cells / liter) and ; microzooplankton (No./m ), 1978-1984 . . . . . . . . . . 21 2.2-3, Percent composition, seasonal vs. annual variability (standard deviation) of log (x+1) abundance, and 2" "th" , ofpeakabundanceforlobsterlarvae(No.f)1000m)and and macro-selected zooplanktonspecies (No./1000of bivg)ive m , . . larvae (No./m
. . . .. . . . . . . . . . 22 1
2.2-4. Percent composition, seasonal vs. annual variability (Standarddeviatin) f I g (x+1) abundance (No./1000 m ), and months of peak abundance for selected species of fish larvae, 1975-1988. . . . . .. . . . . . . . . . 23 2.2-5. Seasonal and annual changes in composition and abundance of the pologic fish community, based on catch per unit effort at gill not Stations G1, 02, and G3 combined, 1976-1985. . . . .... . . . . . . . . . . . , . . . . 27 2.2-6. Percent composition, seasonal vs. annual variability , (standard deviation) of log (x+1) abundance (catch per unit effort), and months of peak abundance for selected species of fish, 1976-1988 . . . . .. . . . . . . . . . 29 2.3-1. Seasonal vs. annual variability (standard deviation) and months of peak values for temperature ('C), salinity (ppt), dissolved oxygen (mg/1), and nutrients (pg/1) . . 34 2.3-2. Monthly mean and 95'r, confidence limits for surface and bottom temperature ('C), surface salinity (ppt), and surface dissolved oxygen (mg/1) at Station p2 over all ' years (1978-1988) and monthly means for 1988 . . . . . . 35 vi
PAGE 2.3 3. Annual settlement periods, abundance and survival of major taxa bared on examination of sequentially-exposed panels at neartic1d Stations B04 and B19 ... . . . . . . 39 2.3-4. Depth and abundance characterisations of species assem-blages identified by disc 31minant analysis of August collections of algae 2 (g/m f dominant taxa) and marine benthos (No./m of dominant taxe) during 1978 1988 . . . 41 2.3 5. Percent composition (based on biomass) by station for dominant macroalgae species at marine benthic stations in August, 1978 1988 . ... .. . . . . . . . . . ... 42 2.3-6. Percent composition and nearfield (Sta. B1HLW & B17) vs. f arfield (Sta. B5HLW & B35) annual variability (standard deviation) of log (x+1) abundance for selected inter-tidal and shallow subtidal species of algae and benthos, 1978 1988. ............. .. . . . . . ... 46 2.3-7. Monthly means and 95% confidence limits for seawater surf ace temperature and salinity taken at low tide in Brown's River over the entire study period (Hay 1979-December 1988) and monthly means for 1988. . . . . ... 48 2.3 8. Annual geometric mean density (No./m 2) and mean number of taxa per station of estuarine benthos (1978-19848 1986 1988), and annual mean salinity (1980-1984; 1986-1988), at Brown's River and llampton liarbor . . . .. . . 51 2.3 9. Seasonal and annual changes in composition and abundance of the estuarine fish community, based on catch per unit l effort at beach seine Stations S1, S2 and S3 combined, 1976-1984 and 1987-1988. . , . . . . . . .. . .. . . 52 l 2.3-10. Percent composition by station for abundant species of fish collected in beach seines, all years combined, 1976-1984 and 1987-1988. . . .. . . . . . . .. .... 54 2.3 11. Annual geans and 95% confidence limits of densities (No./ft ) of #re arenarla young-of-the year and spat in llampton Seabrook on Flat 1. . . . . . . . ... .... 56 2.3-12. Number of adult clam licenses issued and the adult clam standing crop (bushels), llampton-Seabrook liarbor,1971-1988 . . . . . . . . . . . . . . . . . . . . . . .... 58 2.3-13 Percent composition and nearfield (Sta B19) vs. far-field (Sta. B31) annual variability (standard deviation) of log (x+1) abundance for selected mid depth benthic species, 1978-1988 . . . . . . . . . .. . . . . . . . . 61 vil 1 I
.. -. . . . . . _ . --_ ---- ~
PAGE 2.3 14. Seasonal and annual changes in composition and abundance of the demersal fish community, based on catch per unit ef fort at otter trawl Stations T1 and T3 combined,1976-1988 . . . . ..... . ........ . .. . . . .. 64 2.3 15. Percent composition by station for abundant species of fish collected in otter trawls, all years combined, 1976 1988. . ..... . ... . . . . . . . .. . . .. 66 2.3 16. Seasonal vs. annual variability (standard deviation) and months of peak abundance (catch per 15-trap effort) for adult lobsters and crabs at the discharge site,1975- ; 1988 . . . . . .... . ... . . .. . . . . . . . .. 68 2.3 17. A. comparlons of legal and sub-legal sir.ed catch and B. size class distribution (carapace length) of Nomarus : americanus at the discharge site, 1975 1988. .. . . . . 70 3.1.1-1. Monthly mean temperature at Station P2, all years' scoan l and 95% confidence interval for 1978 1988 and monthly mean for 1988 for surf ace and bottom . . . . . . . . . . 72 3.1.1-2. Differences between surf ace and bottom temperatures taken semi tnonthly at Station P2,19781988. . . . . .. 73 3.1.1 3. Surf ace salinity and bottom salinity at nearfield Sta-tion P2, monthly means and 95% confidence intervals over all years, 1978 1988, and monthly means for 1988 . . .. 76 3.1.1-4. Dissolved oxygen at nearfield Station P2, monthly means and 95% confidence intervals over all years, 1978-1988, and monthly means for 1988 for surface and bottom. . .. 77 , 3.1.1-5. Orthophosphate and total phosphorus at nearfield Station P2, monthly means and 95% confidence intervals over all years from 1978 1984 and 1986-1988, and monthly means for 1988 . . ..... . ....... . . . . . . . . . 78 3.1.1 6. Nitrite-nitrogen and nitrate-nitrogen concentrations at nearfield Station P2, monthly means and 95% confidence intervals over all years from 1978 1984 and 1986 1988, and monthly means for 1988 . ..... . . . . . . . . . 79 3.1.1-7. Ammonia concentrations at nearfield Station P2, monthly means and 95% confidence intervals over all years from ! 19 78-1984 and 19861988, and monthly means for 1988. . . 80 ! vili
PAGE: 3.1.2-1. Weekly mean abundance and 95% confidence intervals for bivalve larvae at nearfield Station P2,1978-1988. Years enumerated: (a) 1976 1988; (b) 1978 1984, 1986-1988; (c) 1979-1984, 1986 1988 . . . . . . .... . . . 85 3.1.3 1. bog (x41) abundance per 1000 cubic meters for Calanus
//nmatch/cus copepodites and adults; monthly mean and 95% confidence interval over all years 1978 1984, 1986-1988 and monthly means for 1988. . . . . . .... . . . 100 3.1.3-2. log (x41) abundance per 1000 cubic meters for Care /nus ,
maenas larvae and Crangon septemspinosa zoese and post larvae; monthly mean and 95% confidence interval over all years 1978-1984, 1986 1988 and monthly means for 1988 . . . . . . . . . ....... . . . . . . . . . . 103 3.1.3 3. 1.og (x41) abundance per 1000 cubic eneters for #comys/s amer /cana; monthly mean and 95% confidence interval over all yearn 1978-1984, 1986 1988 and monthly tonans for 1988 and mean percent composition of Neomys/s amer /cana lifestagos over all years 1978 1984, 1986 1988 at near-field Station P2 . . . ...... . . . . .... . . . 105 3.2.1-1, Hean and 95% confidence limits over all years and 1988 values, by gonth, for log (x41) transformed abundances (No./1000 m ) for American sand lance and winter floun-der larvae at Stations P2 and P3, July 1975 through , December 1988. . . . ......... . . ... . . .. 124 3.2.1-2. Mean and 95% confidence limits over all years and 1988 values, by gonth, for log (x41) transformed abundances (No./1000 m ) for yellowtail flounder and Atlantic cod larvan Stations P2 and P3, July 1975 through December l 1988 . . .. . . . . ........ . . . ... . . . . 128 3.2.1-3. Mean and 95% confidence limits over all years and 1988 values, by gonth, for log (x+1) transformed abundances (No./1000 m ) for Atlantic mackerel and cunner larvae at Stations P2 and P3, July 1975 through December 1988. . . 130 3.2.1-4. Mean and 95% confidence limits over all years and 1988 - values, by genth, for log (x+1) transformed abundances (No./1000 m ) for hake and Atlantic herring larvae at Stations P2 and P3. July 1975 through December 1988. . . 132 fx
PAGC 3.2.1 5. Mean and 95% confidence limits over all years and 1988 values, by gonth, for log (x+1) transformed abundances (No./1000 m ) for pollock larvae at Stations P2 and P3, July 1975 through December 1988. . . . . . . . .. . .. 134 3.2.2 1. Catch per unit effort (mean number per 10 minute tow) of all species collected in otter trawls by year, and all stations combined, 1976 1988 . . . . . . . . . . . . . . 136 3.2.2 2. Catch per unit effort (number per 24-hour set of one not, surface or bottom) of all species combined in gill nets by year, and all stations combined, 1976 1988. . . .. 141 3.2.2-3. Catch per unit effort (mean number por seine haul) of all species collected in beach seinen by year, station and all stations combined, 1976-1984, 1987 and 1988. .. 149 3.2.2 4. Mean and 95% confidence limits over all years and 1988 values, by month, for log (x+1) transformed catch per unit effort (one 24 hr. set) fo: Atlantic herring and pollock at combined gill net Stations G1, G2 and G3 from 1976-1988. . . . . . . . . . . . . . . . . . .. . . .. 155 3.2.2-5. Mean and 95% confidence limits over all years, and 1988 I values, by month, for log (x+1) transformed catch per unit effort (one 24-hr. set for gill nets, one 10-min. tow for otter trawl) for Atlantic niackerel at combined gill net Stations G1, G2 and G3 and Atlantic cod at otter trawl Station T1, 1976 1988. . . .. . . .. ... 159 3.2.2 6. Mean and 95% confidence limits over all years, and 1988 values, by month, for log (x+1) transformed catch por ) unit effort (one 10-min. tow) for hakes and yellowtail flounder at otter trawl Station T1, 1976 1988. . . . . . 162 3.2.2 7. Mean and 95% confidence limits over all years, and 1988 values, by month, for log (x+1) transformed catch per unit effort (ons 10 min. tow for otter trawls and one haul for beach seines) for winter flounder at otter trawl Station T1 1976-1988 and combined bear' seine Sta-tions S1, S2 and S3 1976-1984, 1987 and 1965 . .. . .. 165 3.2.2-8. Mean and 95% confidence limits over all years and 1988 values, by month, for log (x+1) transformed catch per unit effort-(one 10 min. tow for otter trawl and one haul for beach seines) for rainbow smelt at otter trawl Station T1 1976-1988 and combined beach seine Stations S1, S2, and S3 1976-1984, 1987 and 1988. .. . .. . . . 167 x 4
r 4 PAGE 3.2.2-9. Mean and 95% confidence limits over all years, and 1988 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, 1987 and 1988. . . . . . . . ....... 169 7 3.3.1-1. Monthly means and 95% confidence limits for seawater , surface temperature and salinity taken at low tide in Brown's River over the entire study period (Hay 1979-December 1988) and monthly incans for 1988. ....... 178 ; 3.3.1-2. Yearlymeanang)95%confidencelimitsforthelog(x+1) dentity (No./ni of macrof auna and number of tas.a col-t lected at subtidal estuarine stations sampled three times per year from 1978 through 1988 (excluding 1985) .- 191 ' 3.3.1-3. Yearlymeaneng95%confidencelimitsforthelog(x+1) density (No./m ) of macrofauna and number of taxa col- - 1ected at intertidal estuarine strtions sampled three times per year from 1978 through 1988 (excluding 1985) . 192 3.3.1 4. Yearly moan and 95% confidence limits for the log (x+1) , density of Herels diversicolor and Capite))a capitata collected at subtidal estuarine stations sampled three - times per year from 1978 througn 1988 (excluding 1985) . 195 3.3.1-5. Yearly innan and 95% confidence limits for the log (x+1) l density of Nerels diversicolor and Capite11a capitata collected at intertidal estuarine stations sampled three times per year from 1978 through 1988 (excluding 1985) , 196 3.3.2-1. Median and range of macroalgae taxa collected in'tri-annual general collections at Stations B1MSb, B1HLW, B17, B19, B31 (1978-1988), B5HSL, B5HLW, B35 (1982-1988), B16 (1980-1984; 1986 1988) and B13, B04, (1978-1984; 1986 1988), B34 (1979-1984; 1986-1988) . .. 199 3.3.2-2. A. Number of taxa and B. mean (g/m2) and 95% confidence intervals biomass at intertidal and subtidal benthic stations in August over all years. . . . . .. ..... 201 3.3.2-3. Mean biomass (gms/m ) and 95% confidence limits for macroalgae collected in August at selected nearfleid , benthic stations . ................... 202 3.3.2-4. Relative abundance (% biomass) of dominant inacroalgae at ! marine bonthic stations in August for A. llistorical Period and D. 1988 only. .. . . . . . . . ... .... 203 x1
PAGE 3.3.2-5. A. Mean and 95% confidence interval of A. log No./100 m 2 of kelps (B17: 1978-1988; B35: 1982-1988) and B. Percent frequencies and 95% confidence interval of dominant understory algae (B17: 1981-1988; B35: 1982-1988) col-Iceted triannually in the shallow and mid-depth subtidal zone . . . . . ..................... 210 3.3.2-6. Mean percent frequency and 95% confidence interval of fucold algae at two fixed transact sites in the mean sea level zone (1983 1988) . ................ 214 2 3.3.2-7. Annual mean abundance (No./100 m ) and 95% confidence interval for La=/narla sacchar /na at Station B17 (1979-1988) and B35 (1992-1988). ............... 216 3.3.2-8. Mean biomass (gm/m ) and 95% confidence limits of Chondrus crispus at selected stations in May, August and
, November. Stations.B17, B1MLW: 1978-1988; Stations B35, l B5MLV: 1982-1988). ................... 219 l 2
3.3.2-9. Annual mean biomass (sm/m ) and 95% confidence intervals of Chondrus cr/spus in August at Stations B1MLW, B17 (1978 1988) and B5MLW, B35 (1982-1988) . ........ 220 i 3.3.3-1. Number of taxa and overall abundance (No./m2 ) in August over all years (1978-1988, Stations B1MLW, B17, B19, B31; 1982-1988 B5MLW, B35; 1979-1984,1986-1988, B34; 1978 1984, 1986-1988, B13, B04; 1980-1984, 1986-1988, B16) at intertidal and subtidal benthic stations . . . . 222 2 3.3.3-2. Annual mean abundance (No./m ) and 95% confidence Ifmits for macrof auna collected in August for nearfield Sta-tions B1MLW (intertidal) and B17 (shallow subtidal). . . 224 3.3.3-3. Annual number of taxa (per 5/16 m2 ) collected in August at intertidal Stations 81MLW and B5MLW and shallow sub-tidal Stations B17 and B35 . . . . ... . . . . . . . . 225 3.3.3 4. Annual number of taxa (per 5/16 m2 ) collected in August at Stations B16, B19, and B31 (mid-depth); and Stations B04, B13, and B34 (deep) . ............... 226 + 2 3.3.3-5. Annual mean abundance (No./m ) and 95% confidence limits for macrof auna collected in August for nearfield Sta-tions B19 and B16 (mid-depth) and B04 (deep) . . . . . . 228 xii i
l PAGE i 3.3.4-1. Faunal richness (number of different taxa in two repli- , cates) in 1988 compared to mean species richness and l ' 195% confidenca limits from 1978-1988 on short term ' j panels . . . . . . . .................. 240 l l 3.3.4 2. Log (x+1) abundance in 1988 compared to mean log (x+1) , l abundance (195% confidence limits) from 1978-1988 for l non-colonial fauna on short term panels. . . .. . . . . 242 l 3.3.4-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed i panels at nearfield Stations B04 and B19 . . . . .. . . 247 3.3.5-1. Yearlymeanang)95%confidencelimitsforthelog(x+1) density (No./m of Amplthoe rubricata sampled triannu-ally in May, August, and November from 1978 through 1988. (Il5MLW sampled from 1982-1988.) . . . . . . . . . 265 3.3.6-1. Weekly mean log (x+1) abundance (No./1000 2m ) of lobster larvae at Station P2, 1978-1988, all years' mean and 95% confidence interval and 1988. (No data collected January 1985-June 1986). ........... . . . . . 270 3.3.6 2. Corparisons of legal and sub-legal sized catch of Konsrus amer /canus at the discharge site, 1975-1988. . . 277 3.3.6-3. Size-class distribution (carapace length) of Romarus americanus at the discharge site, 1975-1988. . . . . . . 280 3.3.6-4. Summary of female lobster catch data at the discharge site, 1974-1988. . . . . . . . . . . . . . . . . . . . . 281 l 3.3.6 5. MonthlymeanIgg(x+1)densityand95%confidenceinter-vols (No./1000 ) of Cancer spp larvae at Station P2, 1978 1988 and monthly mean for 1988. (No data collee-I ted January 1985-June 1986). . .. . . . . . . . . . . . 283 l 3.3.7-1. Weekly log (x41) abundance por cubic meter of Mya arenarla larvae at Station P2, 1978-1988, all years' l mean and 95% confidence interval and weekly mean for 1988 . . . . . . . . .......... . . . . . . . . 287 3.3.7-2. Log (x+1) abundance per cubic meter of Nya arenarla veligers at nearfield Station P2, discharge Station PS, f arfield Station P7 and llampton liarbor Station P1,1982-1988 . . . . . . . . . ... ....... . . . . . . . 288 2 3.3.7-3. Abundanco (No./ft ) of 2-mm size classes of Nya arenarla in llampton Seabrook liarbor during early fall, 1974-1988. 292 xili
PAGE 3.3.7-4. Annual mean density (number per square foot) and 95% confidence limits of young-of-the-year #yd drenarla (1-5 mm) at Hasipton-Seabrook Harbor, 1974-1988 . . . . . 296 3.3.7 5. Mean and 95% confidence limits of #ya arenarla spat (shell length $12 mm) densities (No./ft') at two nor-thern New England estuaries, 1976 through 1984 and 1986 through 1988 . . . . . .. .. . . .. . . . . . . . . . 298 3.3.7-6. Means and 95% confidence limits of spat, juvenile and adult log (x+1) densities at Flat 1, Hampton Seabrook Harbor, 1974 through 1988. . .. . . . . . . . . . . . . 299 3.3.7-7. Means and 95% confidence limits of spat, juvenile and l adult log (x+1) densities at Flat 2, Hampton-Seabrook Harbor, 1974 through 1988. . . . . . . . . . . . . . . . 300 3.3.7-8. Means and 95% confidence limits of spat, juvenile and adult log (x+1) densities at Flat 4. Hampton-Seabrook Harbor, 1974 through 1988. . . . . . . . . . . . . . . . 301 ,. 3.3.7-9. Fall mean catch per unit effort for green crabs (Care /nus maenas) in Hampton-Seabrook Harbor and its I relationship to minimum winter temperature, 1978-1988. . 305 l 3.3.7-10. Number of adult clam licenses issued and the adult clam standing crop (bushels) Hampton Seabrook Harbor, 1971-1988 . . . . . . . . ... . . . . . . . . . . . . . . . 309 4.1-1. plankton sampling stations . . . . . . . . . . . . . . . 329 l 4.1-2. Finfish sampling stations. . . . . . . . . . . . . . . . 330 , 4.1-3. Benthic marine algae and macrofauna sampling stations. . -332 4.1 4 Hampton Seabrook Estuary temperature / salinity, soft-shell clam (#ra arenarla) and green crab (Carcinus maenas) sampling stations. . . . . . . . . . . . . . . . 334 4.1 5. Locations of lobster and rock crab trapping areas. . . . 335 4.1-6. Sampling sites for Nay arenarla spat . . . . . . . . . . 336 xiv
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 1986 through 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, Hid-Depth and Bottom Nets Vere Sampled, 1980 Through 1988. . 32 2.3-1. Selected Benthic Species and Rationale for Selection . . 44 2.3-2. Summary of Similarities in Abundance, Blomass, Fre-quency, or Length Among Years and Between Stations for Selected Hacrofaunal and Hacroalgal Species at Inter-tidal 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 ' Hid-Depth Zone . . . . . . .. . . . . . . . .. . . . . 60 3.1.1-1. Annual Heans and Coef ficients of Variation of Water Quality Parameters Heasured During Plankton Cruises at Nearfield Station P2, 1978-1984 and 1986-1988. . . . . . 82 3.1.2 1. Overall Percent Composition of Bivalve Veliger Larvae in 76-pm Net Tows at Stations P1, P2, and P7 from Mid-April Through October, 1982-1988 . . . . . . . . . . . . . . . 84 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 1988 . . . . . . . . . . . . . . 90 3.1.3-2. Mean Abundance and Percent Frequency of Occurrence of Dominant Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Hacrozooplankton Collections at Nearfleid Station P2, 1978-1984, in Comparison to 1986 (July December), 1987 (January-December) and 1988 . 91 (January-December) as Classified by Discriminant Analysis . . . . . . . . . . . . . . . . . . . . . . . . XV
I PAGE 3.1.3-3. . Comparison of Percent Composition, Rank and Percent Frequency of Occurrence of Dominant Species in Macro-zooplankton Collections Among Stations P2, P5 and P7, January-December 1988. . . . . . . . . . . . . . . . . 96 3.1.3 4. Sunuoary of 1988 Biweekly Abundance Comparisons Between Stations Made Using Wilcoxon's Two Sample Test . ... 97 3.1.3-5. Annual Geometric Mean Abundance (No./1000m3 ) and Upper and Lower 95% Confidence Limits of Selected Species of Macrozooplankton at Seabrook Hearfield Statfor. P2, 1978-1984, and 1987 1988 . . .. . . . . . . . . . . . . 99 3.1.3-6. Results of One-Way Analysis of Variance Among Years for Selected Species of Macrozooplankton at Nearfield Station P2, 1978 1984, and 1987-1988 . . . ...... 101 , i 3.2.1-1. Distribution Among Weeks and Among Seasonal Assembla-ges of Samples of Fish Eggs Collected at Nearfield Station P2 During January 1976 Thiough December 1988 . 107 3.2.1-2. Distribution Among Weeks and Amorg Seasonal Assembla-ges of Samples of Fish Larvae P.llected at Nearfield Station P2 During Ja.it.u2; 'Mo Through December 1988 . 114 3.2.1-3. Comparison of Percent Abundance and Peircent Frequency of Fish Egg Collections at Nearfield (P2), Farfield (P7), and Discharge (PS) Stations During 1988. .. . . 120 3.2.1 4. Comparison of Percent Abundance and Percent Frequency of Fish Larvae Collections at Nearfield (P2), Farfield (P7) and Discharge (PS) Stations During 1988. Only Common Species are Listed (Percent Frequency at Least 10% at One or More Stations) . . . . . . . ...... 121 3.2.1-5. Geomet51"M**" f 8*** a f P**k Ab""d*"** (N"*ber per 1000 m ) by Year of Selected Fish Species Larvae at Station P2, July 1975 Through December 1988. . .... 125 3.2.1-6. f Results Log (x+1)of One-way Abundances Transformed Analysis of(No./1000VariancemAmons)Y**'* of Selected Species During Selected Months, July 1975 Through December 1988 . . . . . . . . , . ...... 126 xvi
PAGE 3.2.2 1. Percent Composition by Year and All Years Combined for the M 1ve Most Abundant Species in Otter Trawls During 1976 through 1988 at Stations T1, T2 and T3 Combined . . 137 3.2.2-2. Percent Composition by Station cf Abundant Species Col-lected in Otter Trewis, All Years Combined (1976 1988) , 139 3.2.2-3. Percent Composition by Year and All Years Combined for the Ten Host Abundant Spacies in Gill Net Samples During 1976 through 1988 at Stations G1, G2 and G3 Combined . . 142 3.2.2 4. Percent Composition by Station of Abundant Species Col-1ected in Gill Nets, All Years and Depths Combined (1976 1988). ............. . . . . . . . . . 145 3.2.2+$. Percei;t Composition of Dominant Gill Not Species Accord-ing to Depth (Surface and Off bottom), All Years Com-bined (1976 1988). . . . . . . . . . . . . . . . . . .. 146 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 1988.
. 148 3.2.2-7. Percent Composition by Year for the Ten Most Abundant Species Collected in Beach Seines During 1976 through 1988 (excluding 1985 and 1986) at Stations S1, S2 and S3 Combined. ........... . . . . . .. . . . . 150 3.2.2 8. Percent Composition by Station of Abundant Species Col-1ected in Beach Seines, All Years Combined, April through November (1976 1984, 1987 and 1988). . . . . . . 152 3.2.2*9. Annual Geometric Hean CPUE for Selected Finfish Species. 156 3.2.2-10. Results of One Way Analysis of Variance Among Years of Log (x+1) Transformed Catch per Unit Effort for Selected Finfish Species for all Gill Net Stations Combined During 1976-1988 . . . . . . . . . . . . . . . . . . . . 157 I 3.2.2-11. Results of One Vay Analysis of Variance Among Years of Log (x+1) Transformed Catch per Unit Effort for Selected Finfish Species at Otter Trawl Station T1, During 1976-1988 . . . . . . . . . . . . . . . . . . . . . . . . . . 161 3.2.2-12. Results of One Way Analysis of Variance Among Years of Log (x+1) Transformed Catch per Unit Effort for Selected Finfish Species-for all Beach Seine Stations Combined During 1976-1984, 1987 and 1988. . . . . . . . . . . . . 166 xvii l
PAGE 3.3.1-1 Hean Monthly Seawater Surface Temperature ('C) and Sa-linity (ppt) Taken in Brown's River and Hampton Harbor at High and Low Tide, May 1979 December 1988 . . . . . . 177 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 1988 and 30-year Normals. . . . . . . . . . . . . . . . . . . . . . . . . 180 3.3.1 3 Hean Number of Taxa and the Geometric Hean Density (No./m') for Each Year and Overall Years With 95% Confi-dence Limits for Estuarine Stations at Brown's River (3) and Hill Creek (9) Sainpled From 1978 Through 1988 (excluding 1985) . . . . . . . . . . . . . . . . . . . 183 , 3.3.1 4 Results of One way Analysis of Variance Among Years for the Mean Number of Taxa and Log (x+1) Transformed Den-sity (no/m') of the Host Abundant Estuarine Species and the Total Abundances of Macrofauna Collected at. Estu-arine Stations from 1978 Through 1988 (Excluding 1985) . 185 3.3.2 1 Summary of Spatial Associations Identified From Numerical Classification (1978 1984) and Verified with Discriminant Analysis-(1978-1988) of Benthic Macroalgao Samples Collected in August. . . . . . . . . . . . . . . 205 3.3.2-2 Probability of 1978 1988 Hacroalgao Sample Membership in Each Station Group Verified by Discriminant Function Analysis of 1978-1988 August Benthic Data. . . . . . . . 208 " 3.3.2-3 Results of Significance Tests on Macrealgae Selected Species, Chondrus crispus and Laminarla saccharina . . . 217 3.3.3 1 Station Groups Defined by Numerical Classification and Verified by Discriminant Analysis of Non colonial Hacro-fauna Collected at Intertidal and Subtidal Benthic Sta-tions, August 1978-1988. . . . . . . . . . . . . . . . . 230 3.3.3 2 Median and Range of Percent Frequencies of the Dominant Fauna at Bare Rock, Fucold 1. edge and Chondrus zone Intertidal Sites at Stations B1 (Outer Sunk Rocks) and B5 (Rye Ledge) Honitored Nondestructively. . . . . . . . 233 3.3.3-3 Estimated Density (per 1/4 m8 ) of Selected Sessile Taxa i on Triannual (4 Honths' Exposure) liard Substrate Bottom ! Panels . . . . . . . . . . . . . . . . . . . . . . . . . 236 3.3.3 4 Annual Mean Density (Per 1/4 m') and 95% Confidence In-terval of Nodlolus modfolus Observed at Subtidal Tran-sect Stations, 1980-1988 . . . . . . . . . . . . . . . . 238 xv111 i 1
l PACE 3.3.4 1 Dry Weight (g/ Panel) Biomass on Short-Term Surface i Fouling Panels by Year, Station and Month. . . . . . . . 243 3.3.4-2 Differences Observed on 1987 Nearfield Short-Term Panels t Compared to Baseline Period (1978-1987), and to Far-field Stations . .. . . . . . . . . . . . . . . . . . . 245 r 3.3.4-3 Dry Weight (g/ Panel) Biomass on Monthly Sequential Surface Fouling Panels by Year, Station and Month. . . . 250 3.3.4-4 Laminarla sp. Counts on Monthly Sequential Surface Fouling Panels by Area, Station, Year and Month. . . . . 252 3.3.5 1 Annual Goometric Hean of the Abundance (No./m') of Selected Benthic Species Sampled Triannually in May, August, and November from 1978 through 1988. . . . . . 254 3.3.5-2 Results of One Way Analysis of Variance Among-Years for' the Icg (x+1) Transformed Density (No./m') of Selected Benthic Species Sampled from 1978 or 1982 through 1988 . 255 3.3.5-3 Annual Hnan Length (mm) and the 95% Confidence Interval (C1) for Selected Benthic Species Sampled Triannually in May, August, and November at Selected Benthic Stations from 1982 through 1988 . . . . . . . . . . . . . . . . . . 259 3.3.6-1 Percent Composition of Lobster Larvae Stages at Stations P2, P5 and P7, 1978-1988. . . . . . . . . . . . 269 3.3.6 2 Summary of Total Lobster Cotch Per Trip Effort, by Month and Year, at the Discharge Site from 1974 through 1988 . . . . . . . . . .. . . . . . . . . .. . . . . . 274 l 3.3.6-3 Results of One way ANOVA at the Discharge Site for Lobster (N. americanus), Jonah Crab (C. borealls) and Rock Crab (C. Arroratus) . . . . . . . . . . . . . . . . 275 3.3.6-4 Paired t-test Comparisons of the Discharge Site (L1) and the Fairfield Station (L7) for Lobster (#, americanus), Jonah Crab (C. borealls) and Rock Crab (C. Irroratus), 1982-1988. . . . . . . . . . . . . . . . . . . . . . . . 275 3.3.6-5 Summary of Legal Lobster Catch at the Discharge Site from 1974 Through 1988 . . . . . . . . . . . . . . . . . 278 2.2.6-6. Comparison of Crab Catch Statistics of Jonah Crab (Cancer borealls) and Rock Crab (Cancer irroratus) at the Discharge Site and Rye Ledge, 1982-1988. . . . . . . 284 XIX
PAGE 3.3.7-1 Average Catch per Unit Effort, Percent Female, and Percent Gravid Females for Carcinus maenas Collected at Estuarine Stations from 1977 1988. . .- . . . . . . . . . 304 3.3.7-2 Estimated Distribution (Percent of. Total) of Clam Diggers by flat at llampton Harbor, Spring 1980 through Fall 1988. ... . .. . .. . . . . . . . . . . . . . . 307 3.3.7 3 Summary of Standing Crop Estimates of Adult #ra arenarla in llampton liarbor,1967 through 1988 . . . . . . . . . . 311 3.3.7-4 Distribution (Percent of Total Standing Crop) of liarvestable Clams by Flat at flampton liarbor,1979 through 1988 . . . . . . . . . . . . . . . . . . . . . . 313 4.1-1 Benthic Algae and Hacrofauna Station Iccations and Do-scriptions . . . . . . . ... . . . . . . . . . . . . . 331 4.2-1 Summary of Community Analyses. . . . . . . . . . . . . . 339 I 4.3 1 Analysis of Temporal and Spatial Patterns in Selected Taxa and Parameters: Methods and Data Calculations. . . 343 XX
LIST OT APPENDIX TABLES PAGE f
-3.2.1-1 Finfish Species Composition by Life Stage and Gear, July 1975 December 1988. . . . . . . . . . . . . . . . . 171 3.3.1-1 Month Monthly Seawater Surface Temperature ('C) and Salinity (ppt) Taken in Brown's River and Hampton Harbor, May 1979 - December 1987 . . . . . . . . . . . . 314 3.3.2-1 A Comparison of Sparsaly Occurring Macroalgae Taxa in August Benthic Destructive Samples, 1978-1984 and 1978-1988. . . . . . . . .. . . . . . . . . . . . . . . 315 3.3.2 2 Sparsely Occurring (< 5% frequency of occurrence)
Hacroalgae Taxa in August Benthic Destructive Saeples, 1978-1987. . . . . . . . . . . . . . . . . . . . . . . . 316 3.3.3 1 Species Used in Discriminant Analysis of Benthic Hacrofauna . . . . . , . . . . . . . . . . . . '. . . . . 319 3.3.4-1 Number (mean per two replicates) of Selected Non-Colonial Species Occurring on Sho:t term Touling Pancis by Month. Station, and Year. . . . . . . . . . . . . . . 320 3.3.7-1 Summary of Mya arenarla Population Densities from Annual Fall Surveys in Hampton-Seabrook Harbor, 1971 through 1988 . . . . . . . . . . . . . . . . . . . . . . 325 i l l l l l \ xxi 2
1.0 EXECUTIVE SUNNARY
1.1 INTRODUCTION
Seabrook Environmental' Studies began in 1969 to monitor the bal- I anced indigenous marine communities in preparation for assessing the effects of Seabrook Station operation. As plant operation has not yet begun, the , t study is in the preoperational or baseline monitoring phase. : The purpose of the 1988 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 1987 Seabrook Baseline Report) summarized information collected through 1987, i This report updaten those results with one additional year of data. ! The optimal design of an impact assessment study ensures that a po-tential impact is delineated from naturally-occurring variability. The Sea-brook Honitoring Program accomplishes this by (1) collecting data before and durJng operation to provide a " temporal" reference, and by (2) monitoring areas 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 program focuses on the most variable aspect. For example, the species distributions of plankton and pelagic fish change radi-cally from coason to seasen, but are generally similar within the study area. i 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 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 ;
s 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'intoko effects.- During the' study, both the number 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 predic-table from year to year,-reflecting'the population dynamics of the dominant copepods and the spring and summer reproductive $ctivities 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 predom-inance 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 larvao in late winter and summer. Most of tho' 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, althou"h no power or heated discharge were produced. 'As expected, entrainment remples collected in the last half of 1986 and the first half of 1987 had epecies 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 of Jchthyoplankton entrainment sampics was lower because of the less inten-l 2 1
-sive (i.e., shorter) sampling effort. Density levels of bivalve larvaa were similar to those offshore except during peak abundance periods, when en-trained densities were lower.
Potential intake effects on the pelagic fish cemmunity 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 was the most important; from September to April, it has made up from 65-93% of the total gill net catch. The variability in total fish catches was directly related to year-to-year variations in Atlan-tic herring catches. Another important consideration in intake effects is the depth distribution of the pelagic fish. Atlantic menhaden was the only species that was consistently more abundant in the mid-depth-area, where intake structures are located, than they were at the surface or at the bottom. Ilowever, this species was only slightly more abundant at mid-depth than at the surface and accounted for only 2% of all pelagic fish in the study area. Other species, such as Atlantic mackerel and Atlantic whiting, were occasionally more abundant in the mid-depth area. These species may-potentially be more susceptible than other pelagic fish to intake effects. Benthic-oriented (domersel) fish also may be affected by the intakes if (1) they make excursions off the bottom in search of food and/or (2) they per-ceive the intake structures as protective or food-bearing habitat. The characteristics of the demersal fish communities-in the study area are discussed in the discharge monitoring section (1.3). 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. Based on moni-toring through 1987, projections indicate that approximately 0.02 fish per million gallons of cooling water flow (1 fish /50 million gallons) will be impinged at Seabrook Station. These s'tudies 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 subsequently impinged upon the travelling screens. 3
1.3 DISCHARGE HONITORING 1.3.1 Discherme Plume Monitorinr. 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, nhyto-
~f plankton, and lobster larvae have been monitored primarily for determining potential discharge plume effects. Water quality parameters have histor-ically shown distinct seasonal potterns that were important in driving-biological cycles. Surface and bottom temperatures reached their lowest' l 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 differences in surface water runoff. Nutrients-had f somewhat erratic seasonal cycles, but were generally lowest 4.n summer and L highest in fall and winter. In general, the predictability of seasonal { patterns and low year-to year variability of most of the water quality- I parameters enhances their suitability for impact assessment. The phytoplankton comtounity has shown the most seasonal and annual variability of any of the species assemblages monitiored. Species composition 2 during peak periods varied from year to year. However, total phytoplankton abundance and chlorophyll a were relatively similar among years'and showed'a-predictable seasonal cycle. Increases in irradiance typically initiated the spring bloom; densities usually decreased upon the decline in nitrogen-nutrients, coincident with thermocline development. Densities usually showed ano.ther increase in late-summer or fall. The phytoplankter Conyaulax sp. ; produces paralytic shellfish poisoning, or red tide in this and other coastal areas. This organism usually reached toxic levels (as measured in Nytflus edu11s meat) in May or June in Hampton Harbor, closing flats to bivalve i shellfish fishing for a period of one to seven weeks each year. 4 i
bobster larvae (Stages 1-IV) have a strictly surface orientation, in coastal New llampshire, 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 sur. gests that waters off flampton-Seabrook may be too cold for local production of lobster larvae, and those collected off llampton-Seabrook may 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 f rom year to year. Recruitment and settling activity was low in winter and spring but intensi-fled from summer through fall. The intertidal and shallow subtidal area near Sunk Rocks is outside the immediate plumn 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 stabic parameter. 1.3.2 Benthic Honitorina 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 commun-ities have been small in comparison to variations with depth and substrate. The species compos (tion was highly predictable and distinct for each depth 5
zone. Individual macrofauna species showed significant differences among ! years in their annual abundance levels. Length measurements were not as i 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-j i 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 I 1985.- The demersal fish. species composition basically changed twice por year, from a winter assemblage, when rainbow smelt were- abundant, to an - ei extended summer assemblage (April-November), when hakes and longhorn sculpin were abundant. Othur 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. l i Because of its commercial importance,- the American' lobster was i monitored in the discharge area. Seasonal patterns in catches wore 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 1 varjation 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~ i have been of legal size under the old law were protected from harvest until I their next molt. Total and legal-sized catches of lobster in 1988 have. increased from 1987 levels, which were the lowest of any year during the 1975-1988 study period. 4
}
6 q
1.3.3 EstuarInc Monitoring Although.the likelihood of a cooling water system operational impact on the Hampton Seabrook estuary is low, temperature, salinity, ben-thos, fish, and the sof t-shell clam were all monitored in the . estuary because of the importence and sensitivity of this area. l Temperature and salinity both showed regular seasonal cycles. Maximum temperatures usually occurred in July 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 . , l low precipitation levels and highest discharge volumes of tunnel dewatering q through the Seabrook settling basin. By 1986, salinity levels had returned a { to pre-1980 levels. The estuarine benthic community was highly variable-in species composition and abundance, but predominantly composed of surface and subeurface deposit-feeding polychaetes. The number of species, total abun- , 4 dance, and abundance of some of the dominant species increased during the j period when salinity levels were higher than average, but have returned to the levels observed prior to the tunnel dewatering discharge, i 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. Yocng-of-the-year and yearling rainbow smelt were occa-sionally 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
-nearly 90% during their most 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. 7 j
The species of greatest concern in the Hampton Seabrook estuary is , the soft-shell clam. Density levels of spat, juveniles,-and adults have been i' monitored in the estuary for 18 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 ensure high 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 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.spatialls in 1980 and 1981. Light spatialls from 1982-1988- in~ combination with an increase in predation accounted for a precipitous decline in standing stock since 1983 and ensure l that densities of harvestable clams will remain low for several more years. In addition, neoplasia, a cell growth disease fatal to clams, has been i detected from clams in Hampton estuary. This may also be' contributing to the j decline of harvestable. clams. Experimenta1l seeding of clam spat has been conducted in Hampton Harbor by the State of New Hampshire in one flat area; the possibility of augmenting the Nya population artificially must be fac- ; tored into the monitoring program.
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1 l q 2.0 DISCU,SSION ;
2.1 INTRODUCTION
2.1.1 General Perspective
-Environmental studies for Seabrook Station began in 1969 and i focused on plant design and siting questions. -Once these questions were ;
resolved, a monitoring program was designed which has examined the' structure;
- I of all the major biological communities as well,as the distribution, abun . ,
dance, 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 per'iod. This report focuses on data collected since 1976 for fisheries studies and since 1976 for plankton and benthos studies as these years have maintained a con-sistent sampling design.- The purpose of that report is twofold: (1) to update results of. the preoperational baseline monitoring program, summarized in NAI (1988b),
- with one additional year of data, and (2) provide a perspective cui 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. *
-r ll 2.1.2 . Sources of Baseline Variability i l
l The optimal design of an impact study has four prerequisites that l snsure that c 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 vorjables; (3) monitoring before the potential impact occurs to provide a 9 t' l'
-l 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 prerequisites.- l l
A basic assumption was that there are two major-sources of natural-ly-occurring variability: (1)-that which occurs among'different areas or stations, i.e., spatial, and.(2) that which. varies in time, from daily to- j 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 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 han 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' s seasonal and spatial differences.- Therefore, these studies make' frequent.(at
~
least monthly) collections in the area of the discharge as well as! farfield-areas to the north and south. Because the estuary is an aquatic nursery aren I l 1. and recreationally-important clam flat, baseline collections monitoring l seasonal and annual patterns were also made there for operational-phase l comparison. l Biological variability can be measured on two levels: species and community. A species' abundance, recruitment, size and/or growth are impor- < tant for understanding operational impact, if any. For this reason, th'ese parameters were monitored for selected species from each community type. Specins were chosen for more intensive study based on their commercial or i 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 10
SOURCE 2 OF VARIATILITY TEup0RAL PREOPERATIONAL OPERATIONAL 3>
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m, , -. i LEVELS OF VARIABILITY \ t SPECIES ASSEMBLAGE l h 5 1 1 i 4 DOMINANTS NONDOMINANTS MULTNARIATE NUMERICAL CLASSIFICATION i ANALYSIS DISCRIMINANT FUNCTION ANALYSIS SELECTED SPECIES
,i UNNARIATE ANOVA I
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ANALYSIS NONPARAMETRIC ANALOGUE Figure 2.1-1. Schematic of sources and levels of variability in Scabrook Environmental Studies. Seabrook Baseline Report,1988. I 11
single species; therefcze, the natural variation in community structure was monitored at regular tM intervals, determined by early studies to be sufficient for this pun,sse. s Appropriate statistical methods must be used in conjunction with a ! well planned experimental design-in order to determine the sources and 4 magnitude of variability. Annual and spatial verlability'in species abun-dance and size were tested by using analysis of variance or nonparametric l analysis which will provide a means of evaluating the statistical signifi-cance of changes in the operational period. Spatial, seasonal, and annual LI verjations in community structure were ass'ssed e first with numerica1lclassi-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 methode discussed above has its ultimate focus on the sources of'poten- l 1 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 _.I might be affected by more than one aspect of the cooling water system; l however, the focus here is on t?.e aspect of main concern. In general, intake (pumped) entrainment and impingement would potentially affect mainly plankton i communities, including fish' eggs and larvae, and pelagic fish. If they l occur, thermal effects from the discharge (e.g. plume entrainment) would most likely affect nearshore surface water quality, phytoplankton, and intertidal i 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 l 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 a, 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
'l TABLE 2.1-1.
SUMMARY
OF BIOLOGICAL COHHUNITIES AND SPECIES HONITORED
, FOR EACH POTENTIAL IMPACT TYPE. SEABROOK BASELINE REPORT, 1988.
i-LEVEL HONITORED SELECTED MONITORING SPECIES /- AREA IMPACT TYPE SAMPLE TYPE COHHUNITY PARAMETERS-Intake Entrainment Microzooplankton x x Macrozooplankton x x Fish eggs x Fish larvae x x Soft-shell clam larvae x Cancer crab larvae x Impingement Pelagic fish x x Discharge Thermal Plume Nearshore water quality x Phytoplankton. x x Lobster larvae x Intertidal / shallow subtidal macroalgae and macrofauna x -x Subsurface fouling community x x Plume ' Discharge Mid-depth / deep macrofauna and m.acroalgae x x Bottom. fouling community x Demersal fish x x Lobster adults x . Cancer crab adults x Estuary Cumulative Sources Estuarine temperature x Soft-shell clam spot and adults x Estuarine fish x x 13 l
h J. l= L 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, i 1 l
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n 2.2 JN1AKE AREA HONITORING 2.2.1 j'lankton 2.2.1.1 pommunitY Structure - l 1 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 vultivariate " template" against which seasonal assemblages during plant operation may be compared. The ' j i selected species analysis enables a more precise estimate of the entraineble j density for key species by examining their annual and seasonal variability. ' Knowledge of the within year and among-year variability allows for more y reliable estimates of impact to be made than if entrainment samples were I 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 I were dif ferentiated 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 will depend on the seasonal assemblage present at the time. Hacrozooplankton assemblagen have been distinct and consistent, showing high predictability from year-to-year._ Hacrozooplankton essembleges reflected mainly the population dynamics of the dominant copepods with reproductive activities of benthic organisms af fecting spring and summer ' species composition. In 1988, 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 finstarchicus in summer both showed reduced 1 importance in the macrozooplankton communities sampled in 1987 and 1988. Centropages haniacus, typically an estuarine species, had increased importance - in 1987 and 1988. j 15 l 1
8 l MICROZOOPLANKTON (N3./m ) } . . i e i i i i. i i i J 1 e I a I a I a l J l J l a i s I e I e i e
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FISH LARVAE (No./1000m3 ) 4 lr Ia Ia i a lJ lJ la ls Ie llo n / l O . l n V (_) 3 . O . n . ev : : U O : 6--C . Figure 2.2-1, Dates of occurrence and mean abundance (excluding rare taxa) for seasonal groups formed by numerical classification of micre cooplankton (No./m3 , 1978 1984), macrozooplankton (No./1000 m 3,1978 1984), fish eggs (No./1000 m 3,1976-1984), and fish larvae (No./1000 m 3,19761984) collections. Seabrook Baseline Report,1988. j 16
I l : Hicrozooplankton and planktonic fish eggs had several overlapping groups in spring and summer, indicative of both some year-to year changes in l community structure as well as a variable " transition period" in the late l summer assemblage (Figure 2.2-1). The microzooplankton community typically { shifted from one characterized by rotifers in the spring, bivalve larvae in the summer, copepods in the fall, and tintinnids in the winter (NAI 1987b). ! Fish egg collections in 1988 were generally similar to previous years in their species composition and density. In 1988, as observed in 1987, two previously minor assemblages of late summer and fall species were more j important than in previous years. This may be a result of the change in j classification method from cluster analysis to discriminant analysis. Although species composition and abundances did not appear to differ substan- ! tially 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, sna11 fishes, 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 1988 were similar to previous years (Figute 2.2-1). 1 The effects of plant operation will also depend on seasonal varia-tions in density. In most months, macrozooplankton densities have histori-cally been over 100,000/1000 m3 (Figure 2.2-1). The level of entrainment will be fairly consistent, although different species will be involved in ! each season. Microzooplankton and planktonic fish egg assemblages, on the other hand, had their greatest concentration in the spring and summer, when bivalve larvae and copepod nauplii (microzooplankton), and cunner eggs (fish 3 eggs), were dominant, and group densities were three orders of magnitude i 17
I l-higher than in winter (rigure 2.2-1). Similarly, fish larvao were most abundant in late winter, when sand lance predominated, and summer, when . cunner predominated. The level of entrainment for these assemblages will I vary more dramatically between seasons in comparison to the macrozooplankton [ 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. 'No groups, bivalve larvae j 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, although no power or heated discharge were produced. ! Entrainment samples were collected through July 1987. Since that time, the ! circulating water system has not been operating at a frequency or capacity. { sufficient to warrant further sampling. Initial sampling of. entrained fish l 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 exp6cted differences. 3 The top-ranked entrained fish egg and larvae species were similar to those i from offshore collections (Tabic 2.2-1); however, the total number of taxa was lower, due to the less-intensive sampling effort. Abundances of most of ; i the dominant species were lower in entrainment sampics than in offshore ! namples, in come 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 -i 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 I to those collected offshoro; 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
t TABl.E 2.2-1. COMPARISON OF DENSITIES OF TOP RANKED FISH EGO, FISil LARVAE, AND BIVALVE LARVAE TAXA COLLECTED OFFSil0RE AT STATION P2 AND IN ENTRAINHENT SAMPLES AT SEABROOK STATION FROM JULY 1986 THROUGil JUNE 1987. SEABROOK BASELINE REPORT, 1988. DENSITY
- l-DOMINANT SPECIES ENTRAINED (E1) 0FFSHORE (P2) i l'
l Fish eggs" Cunner /yellowtail flounder 169 3390 Atlantic mackerel 107 1790 l' Rockling/ hake 88 142 j Atlantic cod / haddock / witch 1 flounder 73 102 i American plaice 55 14 !; Windowpano 43 .232 ! Ilake 15 539 Pollock 12 4 l Fourbeard rockling' 9 228 1
'l Fish larvae" Atlantic herring 127 110 i Seasnail 23 33 .
American sand lance 17 56- I Grubby 5 2 0 l Rock gunnel 5 2 ! l Winter flounder 5 20 l American plaico 4 5 l Bivalve larvao b Hodlolus modlolus 3480 3910 i Reteranomia squamula 2520 2930 Hyt))us edu))s 523 646 , Nya arenaria 44 65
."No./1000 m :
No./m~ Average of monthly averages computed to compensate for unequal numbers of samples
-l I
19 l i 1
2.2.1.2 , Selected Species
~
Twelve species with various lifestages from the pelagic zooplankton and phytoplankton communities were' designated as selected species.- The existence of seven to eleven years of preoperational data allows' en estima-tion of seasonal and annual variability. These species exhibited different degrees of numerical importance; their relative contributions to their respective communities are shown in Figures 2.2-2 and 2.2-3.. y The zooplankton selected species (including various lifestages) { historically'have constituted less than 40% of the overall abundances (Fig- ! ures 2.2-2 and 2.2-3). In both the microzooplankton and macrozooplankton' l assemblages, other copopods typicallyjhave-made a large contribution to l overall abundances. In the microzooplankton, unidentified copepod nauplil and copepodites have been extremely abundant. In the macrozooplankton, , copepods other than the selected species have historically been dominant if ! averaged-over the year; however, the noncopepod selected species have been b dominants in certain seasons. All of the zooplankton selected species i reached peak abundance in spring and-summer, with the exception of Neomysis americana, which has been most abundant'in winter / spring. ' i One or another selected species of fish larvae predominated in , every season, constituting 80% of the total abundance overall (Figure 2.2-4). 1 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 i 1988 was consistent with previous years, with only minor variations. Yellow- ' tail flounder reached peak abundance in August in 1988, two months later than !
- usual, llakes, on the other hand, attained highest abundances in June, two months earlier than usual. 'i The plankton selected species showed varying degrees of year-to-1, year differences in abundance. For the phytoplankton and microzooplankton, amcag-year and within-year (seasonal) variations were about the same (Figure ,
( 20 :
~
PEAK SEASON e pa u mo m s i,,
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TEMPORAL VARIABILITY 4-
. mk "
" Inonth m 3- oniy U" o" g : .. no g :
no 3 2- . . on " g : on '. l 1 a U" a Auowouomas(n u) l o AMoNG YEARS (n = 7 or 8) 'l o i 40 IMPORTANCE ! z ' B
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i . . . i i . . i I< > I I I I ( ll $ [] w 1 0 {ItII1.II u 1 Figure 2.2 2. Percent composition, seasonal vs. annual variability (standard deviation) oflog s (x+1) abundance for selected species oiphytoplankton (thousands of cells / liter) and microzooplankton (No./m 3),1978-1984. Seabrook Baseline Report,1988, 1 21 '
-l
PEAK SEASON -a nAxnoms 12 - 10 - l da i E . 3 !
'j 2- I
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i TEMPORAL VARIABILITY U $ N ds* *n'."i '*lill 6- o e AMONG WEEKS (n.26) j
& AMONG WEEKS (n.20)4 l
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j o- - r""" P o , Figure 2.2 abundance,
- 3. Percent andcomposition, seasonal months of peak abundance vs. annual for lobster variability larvae (No/1000 m ,(standard selected deviation) species of bivalve larvae (No/m 3) and macrozooplankton (No. /1000 m 3 ). Seabrook Baseline Report,1988.
22 i
i PEAK SEASON - g pgag ogrs, 12- ,, .. m 10 - 8' 7.y- A 6- ? "? o , 9.
%; 443 A.;
3 4 2-0 TEMPORAL VARIABILITY a-m AMONG MONTHS (n 12) . w o AMONG YEARS (n=13 or 14) 0 - g 2 o . 5
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Figure 2.2 4 Percent composition, seasonal vs. annual variability (standard deviation) of log (x+1) - abundance (No./1000 m 3), and inonths of peak abundance for selected species of fish . , larvae, 1975-1988. Seabrook Baseline Report,1988. 23 l
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 I high variation among as well as within years. In addition #eomys/s amorf-cana and Calanus //nmarch/cus adults showed significant differences among i years. For the latter species, 1988 abundances were significantly lower than
-all'other years. Only two of the nine selected fish larvae. species showed afsnificant differences among years. These analyses indicate that the actual number of organisms entrained could vary widely, particularly among seasons.
.i Bivalve larvae studies were carried out in the intake area to address questions related to the potential reduction in abundances of Nya
{ arenarda larvae because of entrainment. Local current regimes and length of I time spent in the plankton imply that' nearshore Nya larvae populations origi- I nate from spawning adult populations in local and more southern estuaries, s e.g. , llampton-Seabrook, Herrimack River and Essex, Massachusetts (NAI .1982b). Spawning adults have been observed in 1(ampton 11 arbor and Plum Island Sound (a farfield site) typically from June through September, but as early as April and as late as the end of Octotar in some years. Although' larvae were i observed throughout the spawning period, peak densities usually did not occur. ! until August or September (Figure 2.2-3); secondary peaks also occurred in l May or June in some years, including 1988. Therefore, the' magnitude of- ! entrainment will depend on the time of year as well as the overall annual abundance in that.particular year. Initial (1986-1987) entrainment samples collected during the period of peak Nya larvae densities were similar in magnitude to those collected offshore (Table 2.2-1): liowever, because larval densities in the nearshore area have shown no correlation with spat settle- 1 ment densities (Section 2.3.1.3), entrainment estimates cannot be used to i determine the impact of plant operation on the llampton liarbor adult clam population. j 24 1 l l J.
2.2.1.3 Epatial 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 larva communities showed that differences among seasons and even i dates within season were greater than those between nearfield and farfield stations (Table 2.2-2). Examination of data collected in 1988 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, three taxa, Neomysis americana, Pontogenela jnerals, ,and Olastylls sp., were substantially more abundant at the nearfield intake station. Ilowever, in 1988, the dif ferences were significant only for Diastylis sp. Thin pattern may be due to a more complex substrate, cobble and sands, at the-nearfield station in comparison to the more uniform sandy bottom at the farfield station. All three are tychoplanktonic and are thus closely associated with the substrate. Spatial differences were also observed between intake (P2) and discharge (PS) stations for those three ' taxa. Station differences among fish eggs or larvae were negligible. Thus, with the exception of certain tychoplanktonic taxa, the farfield plankton station will provide an effective spatial control uhen examining post-operational plankton communities for possible impacts of Seabrook Station.
}
2.2.2 Pelagic Fish 3 2.2.2.1 Temporal By studying the six dominant species collected in gill nets, which together make up 92% of the population (Figure 2.2-5), any significant effects of plant operations on pelagic fish populations in the study area 25
e
~!
TABLE 2.2-2, ' SUHHARY OF NEARFIELD/FARFIELD (P2.YS. P7) SPATIAL DIFFERENCES IN PLANKTON CONNUNITIES AND SELECTED SPECIES. SEABROOK BASELINE REPORT, 1988. l < i e t CONNUNITY DIFFERENCE BETWEEN P2 AND P7 i Hierozooplankton
-Community None Selected specler 'None-Bivalve Larvae Community None' j Selected species None Hacrozooplankton Community None Selected species Tychoplankters (Pontogenola inermis, Diastylls sp.*, Neomysts americana) P2>P7 Ichthyoplankton Egg .
Community . None Selected species None Ichthyoplankton Larvae Community None Selected species None-Differences were significant in 1988. I 1 26
q q SEASONAL VARIATION i so - i 20 - 10 = 0 , , , ., , , , , , , , , JAN FEB MAR APR MAY JUN ~JUL AUG MiP OCT PO/. CEC 100 - .
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l.. ?? E Atlantiowhlung .j _. & !I .' -- t N * + r. . .. :J B Atlantic herring 0 - JAN ' FEB MAR APR MAY ' JUN : JUL AUG- SEP OCT PD/-' _DEC ' ANNUAL VARIATION 30 - 20 - t 10 - i 0 , 3 , , ,; , , , , , , , , 1976 !s7/ 1978 1979 1980 1981 1982 1983 1984-1985 1986 1987 1988 j l 100
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i n .g . 45, 64. L u.: .. .a. , . , ., ; 4. ;.) y . . :. . : a 4 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987.1988 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 01, G2, and G3 combined, 1976-1988. Seabrook Baseline Report,1988. q I 27
J
.i i
should be visible. The distribution of pelagic fish varied seasonally; two
- main seasonal groups of species, summer and winter,'were identified from .i numerical classification results (NAI 1982c). From September through April,
. j Atlantic herring constituted from 65% 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 2.2-5). 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 I 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 1988, when total I catches were at their lowest levels since the inception of the study, Atlan-tic herring constituted only' 26-52% of the total catch (Figuro~ 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 Ilampton-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 embayments11n spring.(Bigelow and Schroeder 1953). ' l The seasonal variability of the pelagic fish was much greater.than ' annual variability, as demonstrated by comparing the among-month variability i to th,e among-year variability (Figure 2,2-6). Most of the selected species had their peak abundance.during a short but distinct: period of time (Figures 2.2-5 and 2.2-6). Although seasonal fluctuations were variable among years, they were more predictable than variations in annual catch. The number of 3
. individuals that will be impinged by the plant intake would therefore be expected to vary-substantially among seasons and, to a lesser extent, among years. Because of the variability of pelagic fish abundances, predicting abundances with high statistical precision may be difficult.
l 28
l PEAK SEASON O PtAk nowtHs
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TEMPORAL VARIABILITY ! 8' s (n 12. exoopt n.8 for Atlantic ellverside)
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20 0 . PmmaRFEl. . iA I ll . ll . l Figure 2.2 6. Percent composition, seasonal vs. annual variability (standard deviation) of log (x+1) abundance (catch per unit effort), and months of peak abundance for selected species L of fish, 1976-1988. Seabrook Baseline Report,1988. , 29
'5
Since the Circulating Water System began testing its operation in 1985, fish entrained within the system and subsequently impinged upon the travelling screens have been collected by Seabrook Station personnel to determine operational impact. Initial estimates indicate that only one fish will be impinged per 50 elllion 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 (#rorocephalus menaeus, 21%), snailfishes (L/ parts sp., 21%), and longhorn sculpin (# porocephalus occodecesspinosus 11%). During a seven-month period of Station operation in 1986, 1212 individuals 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 1987 resulted in a total of 502 individuals representing 21 species becoming impinged upon the travelling screens. Of these, longhorn sculpin, winter flounder (Pseudopleuronectes amer /canus), and \ windowpane made up 22%,14%, and 13% respectively, of those impinged. The absence of pelagic species from entne.nment collections suggests that the intake caps are performing as designed, minimizing entrapment. The species entrained are mainly demersal species and probably use the discharge for cover. As the CVS operated intermittently and only at low capacities in 1988, no fish data were collected. Operation of the Circulating Water System, in terms of both the number of pumps and whether the system operatid ; at all, varied throughout the four-year period. Data obtained during full system operation will be reviewed along with thoce 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 30 .
)
1
~
taxa were very similar among stations, although catches were approximately a third lower at the southern station G1 (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, $ m above bottom in 17 m of cater. 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 2.2-3). However, this species was ' enly slightly more abundant at mid depth, and it only accounted for 2% of the pelagic fish in the study area. Atlantic whiting and pollock, and to a ; lesser extent alewife, were most abundant near the bottom. Atlantic herring, 3 Atlantic mackerel and blueback herring were most abundant on the surface (Table 2.2-3). 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 1988, on those dates when all depths were sampled, Atlantic whiting and Atlantic msekerel had highest catches in mid-water (NAI 1989), suggesting that certain 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 , carlier results and the rationale for mid water placement of the intakes (NAI 1975a). Furthermore, entrapment data to date indicate that pelagic fish are not being encountered on the CWS screens in substantial numbers. l l L I 1 31 I
TABLE 2.2-3. CATCHPERUNITEFFORT"BkDEPTHFORTHEDOMINANTOILL NET SPECIES OVER ALL STATIONS AND DATES WHEN SURFACE, HID-DEPTH AND BOTTON NETS WERE SAMPLED, 1980 THROUGH 1988. SEABROOK BASELINE REPORT, 1988. CATCH PER UNIT EFFORT SPECIES SURFACE HID DEPTH BOTT0H Atlantic herring 7.0 , 3.8 2.5 Atlantic whit'ng 0.2 0.7 0.8 Atlantic mackerel 1.0 0.8 0.6 Pollock 0.2 0.1 1.1 Alewife (0.1 <0.1 0.2 Bluoback herring 1.0 0.4. 0. 6' r At lantic menhaden 0.6 0.8 0.2 , Rainbow smelt <0.1 <0.1 0.1 l number per one 24-hour set of one net (surface, mid-depth or bottom) i b 32 s
2.3 plSCHARGE AREA MONITORING 2.3.1 Plume Studies 2.3.1.1 Discherme Plume tone Because the discharge plume's largest exposure will be to surface and near-surface waters, the primary focus in this section will be 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 patt erns that were important in driving biological cycles. Surface and bottom t emperatures reached their lowest poJnts 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 (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 temperatures. , The annual mean surface and bottom temperatures in 1938 were lower than average temperatures over all years from October through December (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 1988, seasonal patterns were similar to previous years, though bottom dissolved oxygen values from September through November were lower than the average. Surface salinity values were highest in winter and lowest in spring, a result of increased runoff. In 1988, salinities were similar to previous years (Figure 2.3-2). 33
PEAK SEASON g ,g ,,g,,,, 12 - g m j i { 10 E E 6 - o , , ER i i Ne i E i
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i i i { TEMPORAL VARIABILITY 26 , , e Auowauosms(n.tr> 20 0 AMoNo YEARS (n.8 to it) I l l w 15 , ' o 3 : 10 , , , fu g ,," ' l
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lig o so M h B 0 . . - ' ask E iI s i i s s 5 : a i Figure 2.31. Seasonal vs. annual variability (standard deviation) and months of peak values for temperature ('C), salinity (ppt), dissolved oxygen (mg/1), and nutnents (f g5) . (For salinity, total phosphorus, nitrate, and ammonia values, multiply by 10.) Seabrook Baseline Report,1988. 34 ! I
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tees i 28 . . . . . . . . . . . . 2 6 . 4 JAN FEB MAR M'R MAYJUN JUL AUG SEP OCT rOf EC JAN FEB MAR APR MAYJUN JUL MJG SEP OCT IOf CEC MONTH MONTH i Figure 2.3-2. Monstrly mean and 95% confidence limits for surface and bonora temperature (* C), surface ' salinity (ppt), and surface dissolved oxygen (ag/1) at Station P2 over all years (1978-1988) and monthly means for 1988 Scabrook Baseline Report.1988. -
Nitrogen and phosphorus nutrients had more erratic cycles than temperature, salinity, and dissolved oxygen, but generally had lowest levels in summer and highost in fall and winter (Figure 2.3 1). Values in 1988 followed the patterns observed in previoos years except for unusually high values of orthophosphate in February and (with total phosphate) December. Nitrite was higher than average in February and November, and nitrate was exceptionally low in December. 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 operational imp; cts. The phytoplankton community has shown the most seasonal and annual variability of any species assemblage. Seasonal assemblages have changed rapJdly and frequently, diminishing the suitability of the community for short-term impact assessment (NA1 1985b). Some elements of the phytoplankton community were relatively stable and predictable. For example, ' total phyto-plankton abundae.ca was generally similar among years, with a predictable seasonal cycle that was closely tracked by biomass (chlorophyll a). In-creases 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 watera thereby limiting growth of spring dominants. The phytoplankton in 1986 was unusual in that there was an uncharacteristic July peak caused by bluegreens and Leptocy1/n-dricus. Phytoplankton assemblages from 1978 to 1980 were similar, based on the predominance of Skeletonema costatum, Rhizosolenia de11catula, and Phaeocystis pouchectl, while from 1981 through 1984, only Skeleconema costa-tun and Chaetoceros spp. were consistent dominants. In the latter half of 1986, Skeletonoma continued to predominate, along with the above-mentioned 36 lI
i l { bluegreens. No phytoplankton collections were made in 1987 or 1988; detailed # results from previous studies are presented in NAI 1985b and 1987b and not reiterated in the results section (3.0) of this report. l No spatial differences have been observed in the phytoplankton com- ! cmdty either between intake (P2) and f arfield (P7) areas or between intake 1 (P2) and discharge (PS) areas (NAI 1985b, 1987b). t ! Skeletonema costatum was chosen as the selected phytoplankton species because of its consistent predominance. Generally, there was a major 4 peak in late summer or fall (Figure 2.2-2)-and in some years there was also a smaller peak in the spring (NA1 1981f, 1982a) or winter (NAI 1980c, 1983a). Because of highly variable peak abundances, no significant differences were r detected among years (NAI 1987b). Furthermore, intake and discharge denci-ties were statistically similar (NA1 1987b). Simultaneous nearfield/fatfield comparisons of total phytoplankton abundances and Skeletonoma costatum may be the most consistent parameters for monitoring' primary producers in the ! discharge plume area. L Paralytic shellfish poisoning (PSP) levels in Nytllus edu1/s, as ceasured by the Stats, of New Hampshire and Hassachusetts Department of Public f l Health, has exceeded maximum levels allowable for human consumption every l year from 1972 through 1986, and again in 1988, usually for a period of 1-7 weeks (NAI 1987b; 1989). PSP toxicity levels in 1987 in Hampton Harbor cussels were below the detection limit throughout the April-December monitor-ing season (NAI 1988a). in 1972, toxic levels were present in Hampton Harbor for a period of 16 weeks. Although Hampton Harbor flats have been closed l Gach summer since 1976 to sof t-shell clam diggers for s.onservation reasons, high PSP levels caused the closure of the harbor to all bivalve shellfish digging for several weeks each sammer as well. Peak values in most years (including 1988) occurred in May or June, coinciding in Hampton Harbor and the farfield area, Essex, MA (through 1984, when data from both sites were collected). The maximum value recorded since 1972 was 8398 pg PSP per 100 g test (80 pg is considered the maximum toxicity level acceptable for human. consumption). 37
Of the shellfish in the area with planktonic lifestages (Cancer crabs, lobster, and soft-shell clam larvae), only lobster larvae Stages 1-1V have strictly a surface orientation, typically found in the top few centi-meters of water. The seasonality and variability of Cancer sp. larvae and Nya arenarla larvae were discussed in the intake area monitoring section. Successful recruitment of lobster larvae is the biggest factor in determining 4 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 Haine and Georges Bank (Harding et al. 1983) and are driven into the area by a combination of winds and nontidal currents (Grabe et rl. 1983). Temperatures in the study area are not warm enough to allow plaiAtonic 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 1988, lobster larvae first appeared in mid July, somewhat later than previous years. Maximum densities have occurred over an 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 (Tigure 2.2-3). In 1988 densities were similar to previous years. Stage 1 and IV larvae have predominated, and stage II and 111 have been extremely rare. Densities at the farfield station (P7) were consistently higher than at the intake station from 1982-1987, but in 1988 were for the first time lower than those at Station P2. Discharge area (P5) densities in the last half of 1986 and in 1988 were consistently higher than those at the intake area. l 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 levels while monthly sequential panels, exposed for 1-12 months (Figure 2.3-3), show the dovelopment of the fouling community. Biomass, density, and number of species showed patterns that were highly consistent from year-to-year and between nnarfield and farfield areas, reflecting the increase in 1 38
-i
_ _ _ _ _ __ _ _ - _ - - _ _ _ , i 1 STATION B04 STATION 819 i JfIAIJJ&808D JfI&RJJA808D gggg gge, 3m ...... . .. . . . .. .g . . .g efttliest lest .ma m.*< Mll$l 3tg3 ...... .. g 3g 3 ...... . . .g 3g64
..... 63 1964 ...
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im _ Im _ __num I g ep, jg ... ............... giet,lla sp. 1981 a. a.aamm a.ana. J jgg3 ... u . .. . .......u... tge3 . . . . . .. . .. . .g . . .g l 3ted ................. 3tet .. .. .... .gg . . .g l Ige 6' aM 1906' M l jwt - .................. 3w1 _ ...g............... , ! Iges . . .. . . . .g . . .g aus _.. m ! l Jgg jalg,!) 1981 g .anM (gtti falteta 1981 .a an gfla.S 3t 3 ... . . . . . .. . g It 3 ......g @l[jf tw4 ... . .g tut . .g.. .......g l} 3mi 3m' ... sus ..ggggg im ...... ......g l1ll1; 3teg . . . . . . . . . 3teg ............_... Dedibreechte le annana . bodibreachio lyst ma.g* . 3tg3 . . . . . . . . . . . . . . . 3u3 .....". ..............".." 39:4 ..._...... 3w4 . . . . . . . . . . . . . . . 3th' ..._....a..... 3m' ......... i Ital ............... 3t:1 . . . . . . . . . . . . . . . . . . I I 3ges - _ . . . . . . . . . . . . . . . Iges :.. l l h>tlette sp. Igt! """ Int,[ttij sp. 1982 a.,4(Ill'.al!!! i im ... pl. . . . . . 3. ...g...... i 3gst ...... 1964 . . . . . . l U. . . ! 3m' ...... 3teg e . . . , , . . . , j l l Igli M "5 3ge1 E g.allaan Iges ...g g Q'. . . 3ges . . .g . . .]l.. . . . . . ggill ep, 1982 a.EM p> ells sp. 1982 g . M l.a g Im q............ leg) ...... g......... im - . . .g . . . . . .._g . . . im .._.g............ 1906' g ............ Ige 6' g. . .. im .g...... im _gg . . .g . . . . . . 3tes a.
.... 4 3tes g . . .. . . . . .
Balanes sp. , 1961 ." mana n. Salette op. 1962 .aaaaaaa ana". 3m ...... g ... g ...... 3tt3 .... . .M 9.. . Ell . . .. .. 3ted ......_............ 3t64 . . . . . . . . . -- g . . .g. . . 3te6' ............... Ige 6' ...g............ Iw? a. GEM.aa.M Iw) g.a".EDRTEUQll 3tes ....- 3ges - ......'..........
- present ... 1 25% fregeener N 26 75 E 76 100
'No feeling panels placed or collected free Jantary 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 B04 and B19. Seabrook Baseline Report.1988. j i
39
._ - - en .- W ---T -P w-
M settling activity in summer and fall. The individual sacroinvertebrate taxa also had a predictable seasonal pattern. Only a few showed heavy recruitment before June (Balanus sp. in April). In 1988, the overall patterns were similar to previous years. However, biomass values on short-term panels at B04 B34, and B19 and at all stations for monthly sequentials were much higher than in most past years, due in part to dense Tubularla spp, settle-ment and the presence of large mytilids. Tubularla did not appear on short-term panels at B31 in'1988. Surface panels thould prove to be an effective monitoring tool for benthic settlement activity, particularly when compared to farfield stations, 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 (HSL and MLW) and shallow subtidal (-4.6 m) stations which are representative of the area were monitored on Outer Sunk Rocks (nearfield) and at Rye Ledge (far+ field). Benthic algae and macroinvertebrate collections taken annually (August) at Stations B1HLW and B5MLW (intertidal) and Stations B17 and B35 (shallow subtidal) 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 ststion (Sections 3.3.2 and 3.3.3). In 1988, macrofaunal and macros 1 gal collections were similar to those in previous years (the same species assemblages that were i present at each station in previous years were found in 1988). The assem-bleges 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 their dominant species (Figure 2.3-5). Abundance levels of the macroalgae and macrofaunal community were highest in the intertidal zone, and decreased with increasing depth (Figure 2.3-4). i 5 40 I \
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6 5 3 1 2 4 BENTHIC SPECIES ASSEMBLAGE Figure 2.3-4. Depth and abundance characterizations of species assenblages identified by discriminant analysis of August collections of algae (g/m3 of dominant taxa) and marine benthos (No./m 2 of dominant taxa) during 19781988. Seabrook Baseline Report.1988. 41 j
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DN 884 i i i i , , , Mt.W 5 9 ' 12 ' 18 21 ' DEPTH (m) l l 1 , , Figure 2.3 5. Percent composition (based on biomass) by station for dominant macroalgae species ! at marine benthic stations in August,19781988. Seabrook Baseline Report,1988. !
\. 42
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\g-
Colonial macrofaunal assemblages were somewhat less predictable from year to-year (NA1 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-t blages of colonial macrof aunal spectee were unique and unrelated to any other assemblages. Fourteen benthic species were selected for more intensive moni-toring because of their trophic position, abundance and commercial or recrea-tional value (Table 2.3-1). Parameters monitored included abundance (all taxa), size (fauna only), and reproduction'(epibenthic crustaceans). All , life stages of the commercially important species were studied. Some of those taxa were monitored in the Sunk Rocks area while others were examined as part of the discharge or estuarine studies. Algal selected species had highly consistent biomass or abundance levr.la among years, with differences between nearfield and farfield ststions Jbserved in one of the three species tested. The algal dominant Chondrus crispre had low annual variability, with no significant differences in biomass ai..ing years from 1982 1988 in the intertidal zone and 1978-1988 in the shallow subtidal zone (Table 2.3-2). Intertidal biomass values of Chondrus were significantly higher in the intertidal and shallow subtidal l nearfield areas in comparison to farfield areas (Figure 2.3 6, Table 2,3 2). l Donsities of the dominant kelp, Lan/narla saccharina showed no differenets ' cmong 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 dif ferences in annual abun. dance were found among years for all 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 1968. The amphipod Arp/choc rubricata, once one of the 43
f. TABII 2.3 1. SELECTED BENTHIC SPECIES AND RATIONALE FOR SEIICTION. SEABROOK BASELINE REPORT,1988. SPECIES (COMMON NAME) LIFESTACE" RATIONALE Macroal ma_e_ Laminarla sacchar /na A Habitat (canopy) forming primary (kelp) producer Chondrus crispus A H6bitat (understory)-iceming (Irish moss) primary producer; sporelings may be heat sensitive E sthic Invertebrates Ampfehoe rubr/cata JA Intertidel/ shallow subtidal (emphipod) community dominant Jassa falcata JA Intertidal / shallow subtidal (amphipod) community dominant pontogene/a /nermis JA Subtidal, ubiquitous community 3 (amphipod) dominant Nucella Japl11us JA A major intertidal predator of (dog velk) Nyt/ Jus edulls Asteriidae J Predator, community dominant (starfish) Strongylocentrotus J,A Potentially destructive ! droebrachlensis herbivore (green sea urchin) ppminant Bivalves
#rtflus edu11s L,S.A Habitat former; spat may be heat (blue mussel) 3 sensitive i Nya arenarla L,S.A Recreational estuarine species; (soft-shell clam) larvao entrainable Epfbenthic Crustaceans Carcinus maenas L.A A major predator of soft-shell (green crab) clam spat Cancer borea11s L,J,A Important predator and prey (Jonah crab)
Cancer irroratus L,J,A Important predator and prey (rock crab) Komarus amer /canus L,J,A Commercial species; lartos plume-(American lobster) entrainable
'A = adult; J = Juvenile; L = Larvae; S = Spot i
4 44 i i
TABLE 2.3-2. SUNHARY OF SIMIIARITIES" IN ABUNDANCE, BIOMASS, FREQUENCY, OR LENGTH AMONG YEARS AND BETUEEN STATIONS FOR SELECTED MACROTAUNAL AND MACROALCAL SPECIES AT INTERTIDAL AND WHALLOW SUBTIDAL DEPTHS. SEABROOK j BASELINE REPORT, 1988. AMONG YEARS NEARFIELD VS. FARFIELD SIMI!AR DISSIMIIAR Similar Nucella lap))]us (L) Ampithoe rubricata (L) Jassa falcata (shallow Mytilidae (challow sub-subtidal (L) tidal) (A) Nytilidae (MLW, shallow tidal)(L) l Laminarla saccharina (A) I' Dissimilar Jassa falcata (shallow subtidal) (A) Chondrus crAspus (B) Ampfthoe rubricata (A) (MLW, shallow subtidal) Nucella lapillus (A) Asteriidae (L) Asteriidae (A) Mytilidae (MLW) ( A)
#Results from ANOVAs, paired t-tests, or Wilcoxon's summed ranks tests (A) = abundance (L) = length '
(B) = biomass Station differences tested through 1986 (NAI 1987b) for macrofauna 4 45
TEMPORAL AND SPATIAL VARIABILITY - 6 3 AMON3YEAPIB,NUM sLD (nell #kO9Pt he10 tof faminaria, and he$ lor Asf9tildee ) e AMONG Yr#tt,FAftFIELD (he?) 6- lg a. 4- .. I hk E 2-Ii, , 1-
. lE "
o 0- , , IMPORTANCE 60-e l g 40 - g a h
~
J Q SHALLOWSUBTIDAL D INTERTIDAL. o kj
$ 20 - .f dj j 0 , , , , ,,,,,
1 11 1 lill 1 I gl11l1 1l I11ji 1 l i il i I
- Abundance is NoJm' except for Chondrus, which is g/m' .
Figure 2.3 6. Percent composition and nearfield (Sta BlMLW & B17) vs. farfield (Sta. B5MLW & B35) annual variability (standard deviation) of log (x+1) abundance for selected intertidal and shallow subtidal species of algae and benthos,19781988. Seabrook Baseline Report,1988. 46
i intertidal dominants, steadily declined in abundance from 1982 through 1987. In 1988, A. rubr/cata continued to show below-average abundances at both intertidal stations. llowever, abundances increased noticeably at the far-field shallow water and mid depth stations. Abundances of Jassa falcata at shallow subtidal stations were the lowest recorded since the program began in 1978. 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. Lengths observed in 1988 were similar to previous years with two exceptions. Specimens of the gastropod Nucella Jap /11us and Amp /thoe rubr/cata were unusually large in 1988 compared to previous years at the nearfield station (B1HIN). 2.3.1.3 Estuarine Zone Environmental studies in llampton llarbor estuary include monitoring , phytical parametern (temperature and salinity), fish populations, benthic ' cacrofauna, and juvenile and adult soft-shell clams (#ra arenarla). One of the main environmental issues in the llampton-Seabrook estuary related to plant operation is whether the of fshore intake and discharge will impact the cdult clam population in llampton llarbor. The probability of impact from the l most-likely source, entrainment of Nya larvae, is small (NA1 197'/c); this is discussed in Section 2.2.2. Natural variability of juvenile and adult Jya crenarls will be discussed in this section. Temperature and salinity, monitored in llampton liarbor and Brown's l River since 1978, provide valuable information for interpreting biological phenomena. Maximum temperatures usually occurred in July, with minima in January or February (Figure 2.3-7); 1988 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 e 47 i
Salinity l .. 25 - % ,.
"A. " s.,,7-
,/
+
. , ' . > L .'^, (4
,o . .
1 i .
/- , / ..
3 l
< 10 -
# l DVE W MLAN
- ... .. iw 5-0 , , , , , , , , , , , ,-
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT t<W 000 MONTH I Temperature i 25 - ' a i 20 - r',,.......-.. g . .. b l . , i 15 - / 'g
. l ..
4 E 10
.'/'. ",. N "
5-
\
... . 1960
.' . \,, ;
l Z. '\ 0- ' JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N:N DED MONTH . Figure 2.3 7. Monthly means and 95% confidence limits for seawater surface temperature and salinity- J taken at low tide in Brown's River over the entire study period (May 1979 December 1988) and monthly means for 1988. Seabrook Baseline Report,1988. 48 \ i
melting snow, caused severe flooding in New Hampshire and Haine (NA1 1988b). 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 drop-pod, with higher variability, from 1983 1987, when discharge volumes de-creased and precipitation returned to pre-1980 levels. Salinity levels in 1988 were apparently unaffected by lower total precipitation than in previous years. Months in which precipitation was exceptionally low (April, June, August October, December) were interspersed with months of extremely high j rainfall (July, November) (Table 3.3.1 2) and lower-than average salinity l 1evn1s (rigure 2.3 7). Hempton Harbor salinities, which were not as suscep-tibic to these influences because of the influx of a large volume of offshore waters, showed higher salinity and lower year-to-year variability than Brovn's River. The benthic macrofaunal community in Hill Creek (Station 9) and Brown's River (Station 3) was typical of New England estuaries. The spacies composition was also consistent with that from other estuaries on the t. . Coast (k'atling 1975: McCall 1977; k'hitlatch 1977; Santos and Simon 1980). Surface and subsurface deposit feeders predominated, including opportunistic polychactes st.ch as Streblosplo benedict) and Capitella capitata, with suopension feeders and omnivores forming an important component (NA! 1985b). The most numerous species inhabiting estuaries are those which are resistant cnd resilient to the natural changes in the physical environment, such as fluctuating temperature, salinity, dissolved oxygen, and sediment grain size. In Hill Creek and Brown's River, the biological parameters measured were highly variable seasonally and annually which is typical of this physi-cally heterogeneous habitat; total density, numbers of taxa, and all of the 1 dominant species tested showed significant differences among years and i between stations. Some of this variability was related to changes in salin- I ity. The combination of lower precipitation and higher levels of discharge i 9 49 I
- n.
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 Streblosplo benedletl and Capite11a espleats 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 parameters dropped to their lowest point in 1984; however, they had returned to pre 1980 levels by 1986. The exceptionally low numbers of taxa and total abundance noted in 1987, probably resulting from exceedingly low salinities during spring runoff, returned to more typical levels in 1988 (Figure 2.3 8). 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 constituent of the demersal fish community at the entrance to the estuary (T2), composing 19% of the total catch (Table 3.2.2-2). Significant differences in annual catch (NA1 1988b) have made this station more difficult for monitoring. Catches at T1 were more stable, showing no significant differences among years (Section 3.2.2), but were a smaller component (5%) of the overall community. The absence of smelt in trawls from April through November reflects their movement further ' offshore. 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 9), but no one age group (based on length frequency) has been consistently dominant (NAI 1985b). Rainbow smelt have never comprised a substantial portion of annual seine catches, and over all years (1976-1984 and 1987-1988) averaged less than 3% of the total catch. Catches in 1988 were an order of magnitude lower than the historical average (see Section 3.2.2). River herring, which includes alewife and blueback herring, were monitored both in the Taylor River and in llampton Harbor from 1980 to 1984. The size and length of the river herring "run" was shown to be variable, with 50 ,
ESTUARINE BENTHOS 10000 - - 60 9000= ***... 40
, , * . * * . /,*. , ,
M g 8000 - /*,/. ., .,'., e* -30 h
, / , j
%.., / ',
' ., ,/* .
8 I 4000 - - 20 2000 " Destry -10 q
. ... .. NUMBER OF TAXA .
O i . . . , . . . . . 0 1978 1970 1980 1981 1982 1983 1984 1986 1987 1988 YEAR SALINITY 32 - 30 - [ 1
$ 28 -
n. L 20 - no date 24 , , , , , , , , , , 1978 1979 1980 1981 1982 1983 1984 1986 1987 1968 YEAR Figure 2.3 8. Annual geometric mean density (Nodm 2) and mean number of taxa per station of estuarine benthos (19781984; 19861988), and annual mean salinity (19801984; 19861988), at Brown's River and Hampton Harbor. Seabrook Baseline Report.1988.
$1 i
SEASONAL VARIATION 400 - 300 - g 5 5 I I E I E M MAY JUN JUL- A3 GIF CCT 90/ 100-to - B . winter flounder 30 - I D Atlantic herring O tainbow smelt 40 - Mp g pollock g Fundulus sp. O . r; .
. D AtlanHe silverside
$ 20 -
0 N5llP/I//// - _ , , , : . w,;._h
, , , , i i , ,
APR MAY JUN JUL M*3 SEP OCT 10f 400-ANNUAL VARIATION 200 - U 0 , , , , , , , , , , , 1976 1977 1978 1979 1980 1981 1982 1983 1984 1987 1988 100* [. 80f . go . ~~~'"" B winter Rounder I i
. D Atlantic herring B rainbow smelt 40
- E pollock B Fundulus sp.
p 20 O Atlantic silversido 0-1976 1977 1978 1979 1980 1981 1982 1983 1984' 1987 1988 j I 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 St. S2 and S3 combined,19761984 and 19871988. Seabrook Baseline Report,1988. I 52 i
the number of days that fish were observed passing the Taylor River ladder ' ranging from 31 (1982) to 47 (1981) (NA1 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 durjng 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 tater temperature and level which were in turn influenced by rainf all and the resulting runoff. Alewives and bluebacks combined was the third most abun-dant taxon caught in beach seines at both Brown's River (S2) and Hampton River (S1)(Figure 2.3-10); however, this was caused by large but infrequent catches at these stations. In the estuary as a whole, these species constitu-ted only about 5% of the total catch (1978-1988). No alewifes were caught in the estuary in 1988. 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 (ages 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. Annual catches were significantly different among years, and catches in 1987 and 1988 were the lowest recorded since the program began (see Section 3.2.2). The dominant resident species in the estuary was Atlantic silver-I side, which typically composed 67% of seine catches during the baseline period (1976 1988)(Figure 2.3 10) and nearly 90% within their period of greatest abundance, 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 recruitment (NAI 1985b). Among-month l variability exceeded annual variability because of the seasonal movements of l the estuarine population (Figure 2.2-6). The year-to-year variation in silverside catch was the main cause of the observed variation in the total cnnual catch in beach seines for all species combined. Total catches were high from 1976-1981 (200-360 fish / haul) and much lower from 1982-1988 (60-115 fish / haul) (Figure 2.3-9). 53
- - y
I so .
% B bluebeckhening 1
l!
;l B rainbow smelt a
60 -
$$k
<gp:png:
#A g g Ayantichening 4
I u$
~ n;g:6 0ll e
[kfIk me v i E ^" *IC'"** * *"
- h g n I.
; NJ p
G alewife a 40 -
, tp I E pollock
&# t i l
V I J i T D mummichog n ; 20 - __; ; E Asantooliverside [ t a
'm,- .
() T . c Q 9 m b. s1 s2 s3 STATION Figure 2.310. Percent composition by station for abundant species of fish collected in beach seines, all years combined,19761984 and 19871988. Seabrook Baseline Report,1988. - 54 l
Since the Hampton Scabrook estuary contains the majority of New Hampshire's stock of the recreationally important species #pa arenarla, an extensive sampling program (15 years) has been undertaken in order to charac-terize 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 Censities appear to bear no. relationship to the abundance or periodicity of #ra larvae in the nearshore waters (NAI 1982c). It would appear that #rt. veliger behavior (i.e. their " readiness" or competency to , I settle) combined with the timing of favorable currents may be more important to settlement success than sheer numbers of larvac in the water column. Such conditions apparently existed in 1976, 1977, 1980, 1981 and 1984 when high young-of-the year spat densities indicated successful recruitment at Flat 1 (Figure 2.3-11) and other flats. The 1976 year class in particular provided . cn Jmportant and rojuvenating recruitment to the local population as shown by l the high densitjes of spat clams in 1977 and 1978 (Figure 2.3-11). Continued low densities of spot from 1983 through 1988 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 Nya depends on both the level of predation from its two main predators, the green crab and human clam diggers, and the absent.e 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 1983-1988 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-table clams, causing additional mortality to unharvested 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 e 55 s
FLAT 1 Young .of. Year (15 mm) s.0 - 2.5 - k 2.0 - .. lE p 1.5 -
'l
+ .
5 i 1.0 - .. i' 8E aK < <. o o 0.5 - "
.. .. i ,
[
, 4.
0.0 - , , , , , , , , , , , i i , , ; j 74 76 76 77 78 79 80 81 82 83 84 86 86 87 88 ! YEAR . i a Spat (13 25 mm', t.0 - ..
)
1 1.5 - g g , o E p<E I 1.0 -
$,l ,
~
s8g .. u . o.s -
. i, o.0 - ,
W W m. T I 1974 1975 1976 1977 1978 1979 1980 1981 1982 1963 1984 1986 1986 1987 1946 YEAR Figure 2.311. Annual means and 95% confidence limits of densities (No/ft 2) of Mya arenarla young of the year and spat in Hampton Seabrook on Flat 1. Seabrook Baseline Report,1988, i 56
)
t
- r , , >w - - - , ,n-, , . , , - -
i decline in 1987 and continued to fall in 1988 (Figure 2.3-12). The standing stock has declined precipitously from 1983 through 1987, lagging trends in digging activity by one year (Figure 2.3-12). In 1988, the decline of adult standing stock leveled off while the number of adult licenses continued to decrease. Finally, the presence of disease may add to the effects of preda-tion. Neoplasia, a cell growth disease fatal to Nya, has been detected in 3 27% of the #ra from Hampton Harbor Flats 1 and 2; no incidence of this disease has been found at Flat 4 (Hillman 1986, 1987). 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. One of these factors is clam seeding by the State of New Hamp- , shire. Seeding activities during 1987 and 1988 in tids1 creeks running into Hampton Harbor have yet to enhance 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 Renthic Honitoring 2.3.2.1 Macroalgae and Hacrofauna 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 cf 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 organ-isms sensitive to the increased detritus resulting from moribund entrained crganisms. Mid-depth and deep (10-20 m) benthic communities, including macro-l algae, macrofauna, and bottom panels, were sampled to monitor the preopera-tional benthic community. Year to year variations in community structure l 57 l C
decline in 1987 and continued to fall in 1988 (Figure 2.3-12). The standing stock has declined precipitously from 1983 through 1987, lagging trends in digging activity by one year (Figure 2.3-12). In 1988, the decline of adult standing stock leveled off while the number of adult licenses continued to decrease. Finally, the presence of disease may add to the effects of preda-tion. Neoplasia, a cell growth disease fatal to Nyo, has been detected in 3-27% of the Nya from Hampton Harbor Flats 1 and 2; no incidence of this dicease has been found at Flat 4 (Hillman 1986, 1987). The ability to assess impact in adult clams in Hampton estuary will lk depend on close monitoring of all of the factors _important to recruitment and' predation. One of these factors is clam seeding by the State of New Hamp-shire. Seeding activities during 1987 and 1988 in tidal creeks running into Hampton Harbor have yet to enhance spat densities. Thus, it appears that predation levels and disease are currently the most important factors in determining the standing crop of hersestable clams. 2.3.2 Benthic Honitoring 2.3.2.1 Haeroalgae and Hacrofauna 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 manifest ed 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 organ-isms sensitive to the increased detritus resulting from moribund entrained organisms. Mid-depth and deep (10-20 m) benthic communities, including macro-algas, macrofauna, and bottom panels, were sampled to monitor the preopera-tional benthic community. Year-to year variations in community structure 57 3 i
q a 1sooo - - 1
... .. UCENBES e ,. 4
}t
\
loooo -
\ g
= \
i g ; ;l ' '. . .... -
> \t l ,
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/
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\ . : t :
t l l tg .i ,
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0 e i e i i i i . . . . , , . , , , , , t 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 - ) o YEAR i
'i Figure 2.3-12. Number of adult clam licenses issued and the adult clam standing crop (bushels). -
Hampton Scabrook Harbor. 1971-1988. Seabrook Baseline Report,1988. 58 ll
i were small in con';.erison to variations related to depth and substrate. The i macroalgae community saa highly similar among years, although less so than in ! the intertidal and stallow subtidal areas. Species composition of sample collections in the trid-depth and deep subtidal areas during 1988 were similar to those taken at the same station in previous years (Figure 2.3-4 and , Section 3.3.2). The distinction between mid-depth and deep communities was less clear-cut for macrofauna, where group membership varied from year to , year. However, all 1988 collections at the six mid-depth and deep stations had species assemblages which resembled the majority of those in previous years (Figure 2.3-4 and Section 3.3.3). Colonial macrofaunal 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 amphipod Pontogenela inermis was the only macrofouna species that did not vary significantly in abundance among years. There was rela-tively luw variance in abundance among years for most of the benthic species (Figur6 2.3-13), compared to some of the more variable plankton species assemblages. Length measurements were a stable parameter; no differences. nmong years were detected (Table 2.3-3). Few nearfield/farfield differences were noted in the mid-depth / deep regiten. In the macrofaunal and macroalgae community, all farfield stations were omre similar to their nearfield counterparts than any other areas, irdicating their suitability as " reference" areas (NAI 1987b). Collections ! made in 1988 in all cases were most similar to the majority-of collections from previous years at the same depth stratum (Sections 3.3.2, 3.3.3; Figure 2.3-4). All nearfield lengths were statistically similar to those from thu farfield area (Table 2.3-3). Juveniles of the green sea urchin was the only species that showed no difference in abundance between nearfield and farfield stations (Table 2.3-3). The only irregularity in spatial distribution was in the macroalgae and macrof aunal community structure at mid-depth Statio i B16. l. 59
)
J: TABLE 2.3-3.
SUMMARY
OF SIMILARITIES IN ABUNDANCE OR LENGTH AMONG
. YEARS AND BETWEEN STATIONS FOR SELECTED SPECIES IN THE HID-DEPTH ZONE. SEABROOK BASELINE REPORT, 1988.
-=
AMONG YEARS" - NEARFIELD VS. !
- FARFIELD - SIMILAR DISSIMILAR- '!
i Similar S. droebachiensis=(L) -Jonah crab
~Pontogenela inermis (L) S. droebachiensis (A)'
Mytilidae (L) Dissimilar Pontogenela inermis (A)l Rock crab Lobster Winter flounder- i Hakes Rainbow smelt Yellowtail flounder j Atlantic cod Hytilidae (A) 't Hodlolus modiolus 1 (
"Results of ANOVAs, paired t-tests, or Wilcoxon's summed ranks tests. -
Abundance or catch unless otherwise noted. I (L) = Iength'
)
(A) = abundance ' i i
.1 l
60 lpY . . . . .
TEMPORAL and SPATIAL-VARIABILITY 6-3 AMONGYEARS,NEARF1 ELD (n.11 except n.9 for Modiolus ) o AMONG YEARS,FARFIE.D (n.11 exoppt n=9 for Modiolus )
~
o j ll a q 3 '1
<- 1 2 . g b -
f 3 ,, I 0 l lMPORTANCE l 80 - ! i 60 - s . Elf 3, 1 0 a!h hkh M. h bh i N/A
. i
'l I jiI 11 I ll Il Il !
i la& }il h5 i i Figure 2.3-13. Percent composition and nearfield (Sta. B19) vs. farfield (Sta B31) annual variability (standard deviation) oflog (x+1) abundance for selected mid depth benthic species, 1978-1988.' Seabrook Baseline Report,1988. 61
'l 1
Community composition of the macroalgae was a mixture of shallow-water (5 m) and mid-depth species at this station (Figure 2.3-5). The macrofaunal , community in most years was more similar to shallow subtidal stations than , f those in its own depth zone. The predominance of very flat, horizontal ledge l at this station caused increased amounts of algae and correspondingly higher abundances of herbivores.
'i L
i Because of apparent year-to year stability in the annual community structure, the once per-year August sampling provides a good baseline for monitoring potential changes in total 1 numbers of taxa or individuals. , Community structure analysis provides a simultaneous view of species numbers, '{ abundance, diversity and dominance, and whether changes -occur at a particular ! i' place or time.. Results also indicate that abundance or size patterns-of a certain species in the study area are predictable and changes, if they occur, j could be evaluated with these taxa. ' l i 2.3.2.2 Demersal Fish i
~
Demersal fish which inhabit or feed in the nearshore area are j important not only because of their predominance in the food chain but also l because of their commercial value. As would be expected with any bottom- i oriented species, the nearshore population of demersal fish show spatial differences associated with substrate and location relative to Hampton Harbor. Previous reports have focused on trends in fish abundances at the i more nearshore discharge station (T2), located off the mouth of Hampton Inlet, llowever, this station is heavily 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 effec- l tiveness and even prohibited trawling activities in some months. For this ' reason, collections from the other two trawl stations (T1 and T3) are more. representative of the demersal fish community, and therefore are the focus of-this discussion. ij 1 62
Six taxa composed close to 80% of total nearshore otter trawl catches both across months and years (Figure 2.3-14). Effects, or lack I j thereof, should be evident from following the distribution of these six taxa, l although the total number of taxa as wall as rare and infrequently-occurring ! species have also been monitored. Numerical classification of 1978-1982 data I 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 1 population in summor. The overall community dominants, yellowtail and winter flounder, provided some temporal stability to this demersal community (Figure 2.3-14). I,ong-term trends were also evident. Total catches increased from i 1977 to 1980 and 1981, then steadily declined from 1981 through 1985, and generally increased through 1988 (Figure 2.3-14). Seasonally, catches were lower in winter (December through April)(Figure 2.3-14). Variations in catch of dominant species from year to year were lower than seasonal variations for , species showing sensonal movements (rainbow smelt, hakes)(Figure 2.2-6). Fluctuations in relative abundance also occurred. Longhorn sculpin once accounted for as much as 30% of the total catch in 1984, but from 1986 to 1988 accounted for 10-12% (Figure 2.3-14). ' Rainbow smelt have increased in i relative abundance in 1987 and 1988 to the highest recorded levels. Yellow-tail flounder and hakes also showed dramatic changes in relative abundance from year to year. The age structure of the fish populations is also a factor con-tributing to abundance variability. -Based on 1983 and 1984 length-frequency i data and age-size information from the literature, the dominant age group collected at the nearfield trawl station (T2) was as follows: I SPECIES DOMINANT AGE GROUP RECRUITMENT EVIDENT 7" Atlantic cod Age one and two yes Hakes Several yes Yellowtail flounder Youn A-the-year yes Winter flounder S e ve r.'1 yes Rainbow smelt YovCrof-th e-year yes a From presence of young-of-the-year or yearlings during certain seasons (NAI 1985b) 63
t.. SEASONAL VARIATION 100 - l 50 - o
.t 4 i 0 . , , , ,
' JAN - FEB MAR APR MAY JUN JUL AG SEP OCT PO/ EC
100 - 80 - _'
.)
1
} gmm -
gl i
; O Auenuecod- ;
,,,,,,,,,--a 40 - a wwwmnew t
. g tonghomacuph .
s u g ! f4g$!g)jf,gll m., g% g 20 - B J m enand-
; m .
#r .o -w Rai ., W 0 , . , ,.
, , i i i
-{
JAN FEB MAR' APR ' MAY JUN 'JUL' AG SEP OCT PO/ EC' ! ANNUAL VARIATION -, 150 - 100 - E .
- b. 1 i 50 -
i O , , , , , 76 77 78 79 80 81- 82 83 84 85 86 '87 88 -l 100 - d
$ 80 -
%we.wed%,,,,,,p
,e 80 -
. I h.
a m.m.n ,
= O Austuiccod ;
g winiwsounsw. 40 - " 5 n ionohom .<uwn u - g hains i g 20 - gpjg I B N ""ad" RERR 76 77 78 79 80 81 82 83 -84 85 86 87 88 i 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 T1 and T3 combined 1976-1988. Seabmok Baseline Report,1988, i 64 ! I il
i As with most of the fish sampled in this study, the majority of fish col-1ected 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 an important consideration with demersal fish. Farfield stations T1 and.T3 were similar in overall catch per unit - effort and relatively similar in species percent composition, although long- ! horn sculpin were more important at T3, while yellowtail flounder were more i important at T1 (Figure 2.3-15). The nearfield station-(T2) was unique, with .i total CPUE (averaged over all' years) 40% lower than at farfield stations. This may be due in part to decreased efficiency from accumulated drift algae ! and interference from lobster traps. Winter flounder and rainbow smelt f (together) composed 45% of the overall catch at T2, compared with 9-11% 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 debris, and T2 is mainly sand, with high currents caused by a 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 spo-cies.
All of the selected demersal fish monitored have shown signifi-cantly different abundances (CPUE) among stations, and three of the five specisa 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 1.ccause of among-year variability. Knowledge of the age-structure of the ,apulation 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 i 1 1 65
- -- --- a:&
I. 100 ~ rirer;> a ,e;<; s, efeoooo;+ Ofj! !j'! f!fff!!
;i !
- i! ijil::::!!
.:s :- :s O others
.. . . ~
'l
, .n E E skates 60 - N
/
@ _ D Atlanticcod f O !
, E ralnbowsmelt U
40 - G l wiriter flounder .
, D - longhorn sculpin i; j D hakes:
4 20 - [ j O yellowtall flounder' ~ I ares!I
,. 5$$$ _
Ti T2 T3 4 STATION l J Figure 2.315. Percent composition by station for abundant species of fish collected in otter trawls, all years combined, 1976 1988. Seabrook Baseline Report,1988.
}
66
r a potential sublethal effects. Results for the first three years of life, when impact effects would be most pronounced, can be summarized as follows: 1 SPECIES l GROWTH CUNNER WINTER FLOUNDE_R I 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. 1 l 2.3.2.3 Ep1 benthic Crustacea i Because of its commercial importance, t.he American lobster has been studied in all of its life stages for 10-15 years. Average annual catches of !. adult lobsters _were fairly stable, varying less than the average monthly catch (Figure 2.3-16), with no significant differences (Table 2.3-3). ' Catches in 1988 increased from their low point in 1987 to a value similar to q the all-years' average. Variations In catches of legal-sized lobsters, a primary concern to lobstermen, were a result of natural variation combined ! with the effects of the increase in the legal size' limit. Following the increase in the legal size limit in 1984 (from 31/8" [79.4 mm) to 3 3/16" [81.0 mm)), catches of legal-sized lobsters remained relatively stable through 1986. However, the proportion of legal-sized lobsters decreased slightly, from an average of 14% (1975-1983) to 7-11% (1984-1986). Studies-by New Hampshire Fish and Game Department noted a 33% decrease in legal-sized catches in 1984. Six percent of the decrease was attributed to the increase i .in size limit and the remainder to low annual catches recorded throughout New -England (Grout et al. 1989). Legal-sized catches dropped to a low point of 67 ____ _ J
'l 1
PEAK SEASON ,,,,,,,,,,, 1 12 - 10
-0 i
E
- m a 4-1 2- 1 0 , , , ,
4.. TEMPORAL VARIABILITY 20 m AMONGMONns (n=6 Jun-Nov) ' 0 AMON3 YEARS (n=14 for lobsters, n=7 for crabs) l 15 - - m - z l 10 - 11 " - 'd D = g- l ll 0- 4 i 6- . o t 5
- y c .
l ~.}s' 1, 0 1 y _ i
= l 1
i; . . 3 Figure 2.316. Seasonal vs. annual variability (standard deviation) and months of peak abundance-(catch per 15 trap effort) for adult lobsters and crabs at the discharge site,1975-1988. 1 (For CPUE of totallobsters, multiply by 10.) Seabrook Baseline Report,1988. l 68
3 per 15 traps in 1987 (7%), reflecting the decrease in total catch (Figure ! 2.3-17). Average legal-sized lobster catches in 1988 increased, as did their proportions, but remained lower than pre 1984 levels. ' Size-class distribution data show an unexplained long-term trend. t , Catches of lobsters measuring 54-67 mm have substantially decreased from !; 1975-1979 levels,'and lobsters measuring less than 54 mm have nearly disap-' l peared (Figure 2.3-17). At the same time, two-year old lobsters (67-79 mm)
]
have dramatically increased from 1975-1979 levels, despite apparent decreases I in the preceding generation. This may indicate increased survival of smaller t size class or immigration of larger (67-79 mm) lobsters. 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 (L1).. Annual catches of other epibenthic crustaceans, Jonah crab end 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 before reaching record high levels in 1988 (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 I the farfield station. ' i 69
-i
4 A. Logal and Subologol Catch 0s . too a - sataca - j g 80 {I' 76 76 77 78 79 80 81 82 83 84 85 86 87 88 i B. Size Class Distribution : 100
- a. so s e .
3 > 105 mm Y . I2. <
$ 12.2 75 76 77 78 79 80 61 82 83 84 '86' 86 87 88 YEAR l
( arapIce1 ngth) H marus amer can at e d scharge fte,1975-1 88. - Seabrook Baseline Report,1988.
.1'
l 3.0 RESULTS 3.1 ELANKTON 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 and 1988 there was no additional sampling for.
.l phytoplankton or microzooplankton. ' Results of those two programs were j i
updated and presented in detail in a previous baseline report (NAI.'1987b)'and are not repeated here. The plankton and water l quality programs presented.in j thir 1988 baseline report are those for which sampling was conducted during 1988: water quality (Section 3.1.1), bivalve larva'e (3.1.2), and macro-
]
zoopinnkton (3.1.3). The cummulative results for all plankton programs,
.l including phytoplankton and microzooplankton, are discussed in Section 2.0.
_f 3.1.1 t'nter Quality Parameters-Seasonal CYeles and Trends - 1
-i Three physical (temperature, salinity and dissolved oxygen) and five chemical (orthophosphate, total phosphorus, nitrite, nitrate and ammo-nia) parameters were examined over a 11-year period to' assess their temporal i variability. Generally, parameters exhibited annual cycles with one or two i
-p peaks; ommonia showed no distinct pattern (Figures 3.1.1-1 through 3.1.1-7).
i Water temperature was monitored in the nearfield both continuously (Station ID, 1978-1986, NAI 1987b) and periodically during the semimonthly-plankton cruises (Station P2 1978-1988). 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 1979-1984, and surface temperatures followed the same general annual cycle, with temperature peaks lagging irradiance peaks by one month (NAI 1985b). Bottom temperatures (depth 16 meters at MLW) showed truncated peaks which legged one to three 71
_. . -. . . . . - . . - ~. _ . . - . - . . - . . . . . . . . .. . s I Surface l 20 - a
.h *
.,- i 16 - '
(.. , .
., 'b.,
w . / ',
. r
' .. , ,[
lo - "
\'
4 . g ' ' t { .
~
. p. 6 OVERALL MEN 4
.,*..*$- L 0 , , , , , ,. , , , , , ,
JAN RB MAR APR ' - M AY JUN . jut AUG SEP ' 0CT . .MN (E MONTH. 1! t Bottom ! 20 - !
- . g 15 -
2,
'. 1 m . . . ..
g ( .- i? ,o : A..- . rm. : p ,: ' ovamtuEm
... .. seee JAN FEB MkR A[H MkY JbN JbL AbG P O h N h (dC MONTH Figure 3.1.1-1. Monthly mean temperature at Station P2, all years' mean and 95% confidence i
interval for 19781988 and monthly mean for 1988 for surface and bottom. Seabrook Baseline Report,1988. 72 5
.___1___..___________1______
1978 h 6-j 4- - 2 .. fl o.; _m - m - -. _ _ - 2 . . . . . . . . , , , , , , . . . . . , r . , , 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1-2 1 2 i JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ; 1 1979 . 6 6- i. 2 . 4-
.n:_
g _ 2 , . . . . . . . . . . . . . . . . . . . . . . . i 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 12 1 2 1 2-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
*~ i 1980 >
b8 ! t- . - i
,, % 2- -
.i 7 g, _ _ _ _ _ .
E T4 ___ _
-2 '. . . . . . . . . . . . . . . . . . . , , , . .
1 2 1 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 1981
;; s.
G. g 4- - h* o 0 mE
^
ul_
-mg-9' 2 . . . . , , . , , , , , , , , , , , , , , , , ,.
1 2 1 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 Figure 3.1.1-2. Differences between surface and bottom temperatures taken semi monthly at Station P2,1978-1988. Seabrook Baseline Report,1988. 73
i a-
. 1982-O 6-4 9 g 2- 4 5 ;
6 o- 0 m=m -
-m En -
Em - I 2 , . ,i i . .,,,,,..... .....
~
I 1 2' 1 2 1 - 2 1 2 1'2 1. 2 1'2 1 2 12 1 2 12 . 1 2 1 JAN FEB ' MAR APR MAY JUN JUL AUG SEP OCT NOV DEC I
~1
*~
1983 l 6-6- -i 2-
]
ga _- _ - _- - .; .E > m 2 . . . , , , , , , . , , , , ,. , ,,,..,,, ! 1 2 1 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 l i 8- ~ 1984 ' G 6-4 ~. O 0 E q _EE E ^ 2 , . . . , , , , , , , . , , , . . , , , . . , , . 1 2 1 2 1 2 1 2 1 2 1 2-1 2 1~2 1~2 1 2 1.2 1 2 JAN FE8 MAR APR MAY JUN JUL . AUG SEP OCT NOV DEC 8' 1985 6 2., 6= W . j 2- _m_. 'E a ~ a_- __ 1 2 , . . . . , , , , , . , , , . , , . . .. , , , . 1 2 1 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 1
Figure 3.1.1-2. (Continued) 74 i-j\.i-
1 1986 6 6- <. l 4 h . - g 2-o _ _ _a E mm E g- 4 g 2 . , , , , , , , , , , , , , , , , , , , , , , , 1 2 1 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 f 8-1987 { O 6- ' l t.,,, ' 4- '
, .i '( 2-u__
aB 2 o , 4 , , , , , , , , , 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 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 8-1988 E , y 4 ", ~~. h 2-f o EB m a mm _ _ _ 2 , , , , , , , , , , , , , , , , , , , , , , , , 1 2 1 2 1 2 1 2 1 21 P 1 2 1 2 1 2 1 2 1 2 1 2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Figure 3.1.1-2. (Continued) . 75 l l
'E
-Surface Salinity '
u- .
?
ss - . .. -
" ~
~ .... . . . .s. . 4 lu- y. '... ..'
- . t p
A, _-y/ .. so - ..
. t
" I so -
3 : 28 - , , , , , , , , , , , , $ JAN RB MAR APR MAY JUN Jul. AUG SEP OCT 70/ . OED !
, i MONTH -
Bottom Salinity u-g 33 - , 4 g , m '
% .. .. K,,e "**** ..
32 -
.........:... .A m -.., -
m .. w
- 0. 31 - .. t g WEWMW l so -
- 4 29 ., , , , , , , , , , , ,
JAN RB MAR -APR MAY - JUN' jut. AUG SEP - OCT N'N DEC MONTH 1 Figure 3.1.1-3. Surface salinity and bottom salinity at nearfield Station P2, monthly means and 95% confidence intervals over all years,19781988, and monthly means for 1988. Seabrook Baseline Report,1988. 76
, - - _ _ . . _ - . . _ ~ _ _ . _ _ _ _ . _
Surface Dissolved Oxygen 32 -i 11 - . ON EN -
. ..... .%- ... .. ,,e, 10 - ., .
I l
% Q. . g4:..
l
- e. ./ ,
7- ! i . i 6 , , , , , , , , , , , ,. JAN FEB _ MAR APR MAY JUN JUL ALO . SEP OCT _ NOV - DED ; MONTH l i Bottom Dissolved Oxygen 12 -
, 'r 11 - ",, '
OVEML MEAN
", " \
... .. iese 10 - -
i g .. g g. N
.,b . . . . ,
j E,g .
-i e- !
y j , a . E . j 7- %.. '~. ...... i 6 , , , , , , , , ,. , , , JAN FEB MAR APR MAY JUN JUL AUG SEP' OCT PD/ ED MOMH Figure 3.1.1-4. Dissolved oxygen at nearfield Station P2, monthly means and 95% confidence intervals over all years,19781988, and monthly means for 1988 for surface and bottom. Seabrook Baseline Report,1988. , 77
Orthophosphate
. 30 - .
jg OVERALLMEAN
. .. ' ./ .
- j. ' . . ., ....... jose s, ,, !
\ -
y% l . .< . 10 -
.-I N "
E ' 1 0 . \ l. < . g
'< / . ,
-{
deteetion- ->- i limit o , , , , , i i , , i i i j JAN FEB MAR APR MAY JUN. JUL AUG-SEP OCT NW ' DEC MONTH ; Total Phosphorus .I 60 - E w -
%~
f OVERALt.MEAN ./ 40 - "".'
, ... ..- 1988 ! .l g '
'l
../ Y 4
W'.. .:..'.'
~
30 '
. . .. -l f.f.
. .. 1 t
/ .
eo . Q..,.7......,,..-)f. . . . . , detection---* 10 - limit . O iii,iiii, .. JAN FEB MAR APR MAY JUN JUL AJG SEP OCT NCN [E MOtrTH Figure 3.1.1-5. Orthophosphate and total phosphorus at nearfield Station P2, monthly means and 95% confidence intervals over all years from 19781984 and 19861988, and monthly means for 1988. Seabrook Baseline Report,1988. 3 78
Nitrate-Nitrogen 160 - .. j 140 - *
.,- -l E '
120 - E, - a 10o . \ OVE N .MEAN j k' ... .. 1e so . \, ,
\. . .
m-I
)
i
\
-l \. -'
/
'\. .
j. 20 - .
\'
.' .. .. m.I... .. /.. *.
as;gjpn - - q o . . . . . . . . . . . . JAN FEB MAR APR MAY JUN JUL 'AUG' SEP OCT- NCN EC ! MONTH -! Nitrite-Nitrogen l 6-i E . ' 6- ,.a. s
. i
/a,.\
g ig . .. . . io - . 4- -- a.
\
\
6 ..
/ .
E 2- " s ' g..
,/.. .. ..
k d3tection% 1- ' limit .. *.,* ,r/ o . . . . . . . . . . .. . JAN FEB MAR APR- MAY JUN JUL . KG SEP OCT NCN 'EC-MONTH Figure 31.1-6. Nitrite. nitrogen and nitrate. nitrogen concentrations at nearfield Station P2, monthly means and 95% confidence intervals over all years from 19781984 and 19861988, and monthly means for 1988. Seabrook Baseline Report,1988. 79
Ammonia .. 120 - - 1 r 110 - *
+
100 - : .. 90 - o m u u.ane m t 1 y \: --
.. ,see "
g- 80 - s :. er 70 us a.
- i. .. .
-e lE -
80 - i' 4 . g 50 - 3 ,\
~
g O E
- e. / \ -
N N ; 2 30 - -*-
- t 20 - .
detection > 10 - *
- limit ,
- . . m .
. ... ,.. ~~~ ** , . .
I 3 E E I I g a g. g y JAN FEB MAR APR MAY JUN: JUL ~AUG JSEP :OCT PEN IID .i , Figure 3.1.1-7. Ammonia concentrations at nearfield Station P2, monthly means and 95% confidence intervals 'i over all years from 1978 1984 and 1986-1988, ai monthly means for 1988. Seabrook -t Baseline Report 1988.- ..
- . . .. . . _ ~__ - _ _ _ _ _ _
months behind surface peaks. From 1978 through 1988, the temperature peak occurred in July and August at the surface and from August to October at the bottom at Station P2 (Figure 3.1.1-1). Bottom temperatures were similar to ; h surface temperatures October through April (Figures 3.1.1-1, 3.1.1-2). Minor temperature inversions occurred each year during winter months (Figure 3.1.1-2). Annual mean surface temperature at P2 in 1988 was lower than all previous years except 1978 (Table 3.1.1-1). Annual mean bottom temperature l in 1988 was the third lowest observed since 1978. The thermocline, typically l 1 }- established from May through September, was strongest in August seven of the { y . ten years, and in late June and early July the other four years (Figure 3.1.1-2). In 1979, 1980 and 19.83, a substantial but temporary breakdown of. the thermocline occurred in midsummer. Low surface and bottom annual mean temperatures reflect significantly lower temperatures September through December. 4 y other water quality parameters were monitored at Station P2'and ;. 1 Station P7 during fortnightly plankton cruises. Salinity concentrations were (s. highest in December and January, reaching it,vels of >33 ppt, though in 1988
- g. peak salinities occurred in November and December at the bottom (32.8 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, 1987a). ( Spring salinity concentrations typically reached lows of 28-31 ppt. Bottom [ . salinity exhibited the same seasonal pattern as the surface, but showed less-f}4 variation within and among years (Figure 3.1.1-3). Annual mean salinities in 1988 for both surface and-bottom were typical of previous years (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 y"'
dissolved oxygen values in 1988 were similar to previous years, though some-what depressed in February, October and December. Bottom dissolved oxygen values in 1988 were lower than normal in February, April, and September 1 81
TABLE 3.1.1-3. AISEtfAL DEADES A)G CXEFFICIDffS OF VARIATION OF ltATER etfALITY PARARETERS 1EASUltED DtIRING Pt.AfetTUlf CIEUISES AT DEARFIEIR STATI0pt P2,1978-1984 ADE) 1986-1988. SEA 8 ROOK BAvf 78E REPORT,1988. AISEUAL DEAN I A)W COEFFICIENT OF VARIATIOft1 PARAMETER 1978 1979 1980 1981 1982 1983 ~1984 1985- 1986 1987 1988 Temperature l'C) . surface 8.37 8.76 8.76 8.72 8.88 9.58 8.94 -9.73 9.31 9.12 8.55 - t66.93) E57.85) t57.86) E63.34) t53.02) t53.74) t55.72) t54.55) t49.57)' E57.80) t60.23) botton 6.61 6.36 7.05 7.37 7.36 7.32 6.93 8.03- 7.58 4.39 6.46 155.62) (47.96) (52.76) (59.11) (46.03) 144.43) (45.04) (47.81) (40.42) 845.95) E45.36) - Salinity Eppt) surface 31.68 31.82- 32.17 31.89 31.84 31.04 30.68 32.15 31.68 30.65 31.74 i3.33) i3.84) i2.64) (Z.16) i3.47) t4.39) f4.93) I2.26). I2.44) t6.76) t2.36) botton 32.24 32.47 32.42 32.32 32.41 31.92 31.77' 32.50 32.20 31.48 32.26 t1.65) (2.77) 11.52) (1.41) 12.01) 12.12) 11.83) 82.54) (1.77) 12.66) -(1.40) Dissolved Oxygen Emg/l) $ surface 10.28 i10.80) 10.02 i13.39) 10.27 I11.17) 9.90 i12.70) 9.60 i11.15) 9.48 (7.73) 10.01 (12.06) 9.67 i10.42) 9.88 i11.03). 9.89 I9.92) 9.72" (11.01) botton 10.07 9.69 9.85 9.43 9.25 8.98 -9.32 9.17 8.96- 9.73 9.07 I8.86) i14.67) (14.28) i17.90). I16.17) t11.99) i13.56) t15.56) i13.52) i11.44) t 16.54 ) Orthophosphate 9.58 9.75 10.12 11.82 17.02 19.23 14.29 - - 18.08 16.80 tpg/1) 129.99) (52.59) 176.10) 130.83). 155.54) 144.47) (56.06) - -- 145.25) (45.24) Total phosphorus 32.50 15.12. 31.96 22.50 24.61 -25.83 24.17 .- -
- 33.36 28.80 tpp/1) t40.09) t63.09) I77.68) E33.93) t28.66) t35.05) t40.43)- - -
t40.30) t34.03) Nitrite 2.12 1.71 '3.17 2.92 2.30 2.05 1.02 - -- 1.48 2.50 spg/1) (46.11) (66.58) (59.59) (53.13) (68.34) 154.34) (98.08) - - t 98.00) E60.43) Nitrate 52.08 38.33 48.33- 45.42 37.17 51.83 36.75 -- -- *' 44.42 '49.50 tpg/l) i116.61) i101.24) '(111.88) t94.41) t137.89) i106.62) t 117.47) -- - t132.17) i111.111
-Ammonia 51.46 47.42 104.17 36.25 <30.00* 27.32 16.57 - --
- 53.33 20.30 app /11 (120.96)' ' (42.931 848.731- 864.733 1- (115.96) (70.82).. - ~, 161.54) (145.32)
*Below detection limitz (30 pg/1) of methods used in 1982.-
b*:ct measured in 1955. dMeasured July through December 1986 only. Collected one meter below surface.
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through December. Maximum orthophosphate and nitrate concentrations occurred in winter (Figures 3.1.1-5 and 3.1.1-6); while minima occurred in summer. Total phosphorous and nitrite showed fall, winter and occasional spring peaks (Figures 3.1.1-5 and 3.1.1-6). Ammonia maxima usually occurred in fall or spring. In 1980, when ammonia concentrations were exceptionally high through-out the year, the peak occurred in July (Figure 3.1.1-7). Orthophosphate and total phosphorus concentrations in 1988 varied somewhat from baseline conditions. Orthophosphate concentrations in 1988 were highest in winter with higher than normal values in February, June, September, October and December. Orthophosphate levels in May were abnor-mally low (Figure 3.1.1-5). Total phosphorus concentrations in 1988 were highest in winter, with higher than normal concentrations in June, July and December. Nitrite concentrations in 1988 were higher than normal in January, February and November and lower than normal in September (Figure 3.1.1-6). Nitrate levels were typical of past years with much lower than normal concen-trations in December (Figure 3.1.1-6). Ammonia concentrations in 1988 were elevated in January and lower than normal in June and September through December. 3.1.2 Bivalvia Veliger Larvae 3.1.2.1 Community Bivalve veliger larvae were identified and enumerated from oblique tows of 76-pm mesh nets from April through October 1976-1988 at one or more of the Stations P1, P2, PS, and P7 (see Section 3.3.7.1 for Nya arenarlo results and Figure 4.1-1 for station locations). Myellus edulls was clearly the dominant species, while Neteranomia squamula, Niatella sp., Solenidae and Modlolus modlolus were secondary dominants (Table 3.1.2-1). Nistella sp. was present April through October, with highest abundances usually occurring in June (Figure 3.1.2-1). Nyt11us edu11s, Nya truncata and Solonidae were usually present by mid to late May. Nytilus 83 i I l l
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MAY a4l1 2 JUN. a4l1 2 3 4l1 e a 4,,,,,l1 l1 2 a4 2 a4 JUL AUG SEP OCT Figure 3.1.21 Weekly mean abundance and 95% confidence intervals for bivalve larvae at nearfield Station P2,19781988. Years enumerated: (a) 19761988;(b) 19781984,19861988; ; (c) 19791984,19861988. Seabrook Baseline Report,1988, i 1 85 l
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edulls peaked primarily in June and July and Nya truncata in la: May. s Solenidae peaked in June and late September to early October, po.41bly due to dif ferential spawning of the three component species (Ensis directus, S111gua costata, Sillque squana). Noteranomia squamula was usually present by early June, with highest abundances July through September. Modfolus modlolus was usually present by mid June and has been highly variable in terms of peak abundance, with peaks occurring from July through October. Splsu14 solldts-slaa and Nacoma balthica usually were not observed until July and August, respectively; these taxa peaked in late summer or fall. Placopecten magel-Janicus was present sporadically throughout the sampling period, with no f clear seasonal peak. In general, larval peak abundances and periods of [ occurrenc+ in 1988 were comparable to previous years with some exceptions. In 1988, Splsula solldissima peaked in early July, slightly earlier than u:ual and Noteranomia squamula was significantly more abundant in June and , July than in previous years. i Station P1 (Hampton Harbor), added to the sampling program in 1986, and the three offshore statione (P5 (discharge), added to the sampling program in 1986 and 1988; P2 (nearfield, intake), and p7 (farfield)) all ! displayed similar patterns of species composition and abundance (NAI 1987a; 1989). EC rainment samples were collected within Seabrook Station (E1) July through .'ecember 1986 and April through June 1987 and results reported in an earlier riport (NAI 1988b). 4 3.1.2.2 Selected Soecies Mya arenarla This species is discussed in Section 3.3.7.
\
87 WM
Nytflus edy))s Ubboned veligera of #ptflus edults 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'C (Podniesinski and McAlice 1986). Spawning of N. edu//s in Long Island Sound wan found to be asynchronous ooth within and among local popula-tions end.to occur over a two to three month period (roll 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 spawn-ing events (Newell et al. 1982). Therefore it is. probable, based on the reproductive behavior of N. edulls, that recruitment of larvae to the plank-ton of New Hampshire coastal watere 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 L 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 (Payne 1976). These factors suggest that planktonic recruitment to the study ~ area was intermit-i j tent and prolonged, and that duration of planktonic life varied over the sampling program as temperature conditions changed. Highest abundances of Nytllus edu11s larvae usually occurred , between early June and early July (Figure 3.1.2-1), although in 1980-1982 abundances in late August, September or October were as high as in early 3 summer (NA1 1981f, 1982a, 1983a). Peak abundances ranged from-6 x 10 /m in 3 1982 to 3.3 x 10 /m in 1979 (NA1 1987b). The difficulty in assessing the l 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 another, even during peak months, varied by zero to three orders of magnitude (NAl-1981c, 1984a). 88
Although variability was high among years, overall spatial vari-ability was low. Historically (1982-1984), no significant differences had been found between Stations P2 and P7 when weekly abundances were ranked (NA1 1985b). 3.1.3 Macrozoonlankton 3.1.3.1 Commug{ty_ Structure Lem_ poral Patterns llistorical analysis (1978-1984) of the macrozooplankton assemblage at the nearfield Station P2 showed seasonal changes that were greatly influ-enced by the population dynamics of dor..inant copepods Contropages typicus and Calanus (lomarchleus. Other taxa, particularly meroplankton, exerted short-term influences, especially during the spring and summer (NAI 1985b). His-torjeal seasonal assemblages (1978-1984) established by numerical classi-ficat.lon on the basis of similarities in species composition were verified by discriminant analysis, and in turn used to evaluate 1986, 1987, and 1988 1 collecG ans. 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 1986, 1987, and 1988 assemblages to previous years, i Winter abundances typically have been low, with the population com-posed mainly of copepods Centropages typicus (Groups 1 and 2) and #etr/dla sp. (Group 2 only)(Tables 3.1.3-1, 2). Winter abundances of C. typicus in 1987 and 1988 were an order of magnitude lower than previous years. In 1986, j 1987, and 1988, winter abundances of copepods Tortanus discaudatus and Temora long/cornis 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 this time I 89 { _ _ _ _ _ _ _ _ ._ a
h T M E 3.3.5-3. SEASONAL SHOUP5 FOWED BY WISERICAf. CLASS 3F2CATICIt OF gyrenannoyggtTUlf CDL12CT3045 FEDR IEEAFIE18 STAT 3ON %
- 1978-1994 AIS SY DISCREGIMfff AleALYSIS OF CDL2.ECT39N5 FMNI JULY 1996-SEG99ER 1988. wamamse amL3pg m 3ggs, SAMPL3 sus PER300 CaowP J' F It A Of J J A S S N -D 3234 3234. 3234 3234 3234 3234 3234 3234- 3234 3234 3234 3234 I late Fall-Ninter B983 2SS9 8 8
' 84 323S 394 83C3 A at 48 C4 8 l C C t Ninter 1980-1982 0 0e 3930 3 3 e9 t t e 3 1ste Winter-Early Spring 2- 4393 9898 48 e 4 82e e30 3 C33 3 2 2 2 4 4 4 8 8 B C C l 4 Spring 39 9999 C3 303 t 4 I e 8 ~C O C 1 5 Late Spriny-Early Summer 2S S98e 294 9 3 9393 4ec a S 324 'A3 23B B3 4 C C B C. ' 4 Summer 898 0889 3993 43A O3 3393 9323 AB t3 4tst t34 A A A3 4 A , S C B A B C 8 C i C 7 Fall C - 8e92 SS99 834 9 93 3239 3 3 39 3 43 4 C t 4 A B 4 A C C C B C year (1978-1994) . ."4 by Imot digits 1986*As 39879 s 1988=C w , ,-e, -g - y .,,ev. . , . , , yw y , m, -. a__.. _ _ _ _ _ _ _ _, _ _ _ _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ , _ _ _ _ _ , , . , _ ._ _ _ , . _ _ _ _ _ __ _ _
y N O) IR TE AB CM IE TC IE . SD Q 0500000 S - 1E 0200000 07070 030 AY IR R 1 11111 06060 1 1 1 030 1 1 CA F U 8 LN 8 AA 9 3 CJ 1 e 0000000 I R( f f A0 e 0000000 00000 00000 000 010 41 91533 72591 E7 I 8 E01 I 3 41 18 1 4 302 2< 0 9 7 U9 / 4 22 1 4 N1 f 5 3 Y , B) R DE EBM I 4 0300000 RE E 0300000 00000 000 OC . 1I I 1 11111 00000 000 FE8 F 11111 111 D8 S 9 7 PY1 8 UL 9 OUT 1 m 0000000 00000 RJR f f 0 0800000 000 G(O A0 7 44318 00000 000 09051 058 L4E F E01 I 1 31136 5 2 411 2 h8R / 21 4 N9 f 3 1 O S AOI 1 N. ) ETL S NS E
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result in a tremendous influx of Cirripedia nauplit and cyprids, which dis-
- tinguish this assemblage (group 3). Copepods Centropages typicus and Calanus i finnarchleus have also been dominant components of this' assemblage histor1-cally (Tables 3.1.3-1,2). The late winter-early spring assemblage in both 1987 and 1988 was similar to previous yeats with the exception of C. typicus cbundance levels, which were two orders of magnitude lower than the 1978-84 cverage (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 1988a). This may have affected C. typfeus densities, as its reported salinity preference is above 30 ppt (Gosner 1971). No such reduction in salinity occurred in 1988, however, so there is no simplo explanation for the low abundance of C. typicus in March and April.
In most years, spring collections were marked by a transitional cssemblage (group 4), composed mainly of Calanus finmarchicus along with other microcrustaceans (Centropages typicus, Hetridia sp., Evadne sp. and l Temora longicornis), the holoplanktonic molluse Limacine retroversa, and I larvacean Olkopleura sp. (Table 3.1.3-2). The transitional period in 1987 consisted only of early May collections, coinciding with continued low sur-face salinity (NAI 1988b: Figure 3.1.1-3). Mean group densities of dominant taxa in 1987 were all an order of magnitude lower than those observed his- ' torically (1978-1984)(Table 3.3.1-2). In 1988, most of the historical dominants reached abundances similar to 1078-1984 levels, with the continued l cxception of C. typicus, as well as L. retroversa and Hutridle sp. l 1, ate spring-carly summer (late Hay-July) conditions showed rapidly increasing surface temperatures along with stabilir.ation of the thermocline (Figures 3.1.1-1, 3.1.1-2). Calanu.r //nmarchleus was typically the dominant organism during this time period, which along with the larval decapods, suphausiids and small copepods formed the basis of group 5 (Table 3.1.3-2). Average group abundances of Heerldla sp. and Centropages typicus were an order of magnitude lower in 1988 than 1978-1984-densities, although tempera-tures, salinity, and dissolved oxygen were typical of previous years. ) 93 A
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 f/nmarchicus and Centropages typicus reached peak or near-peak abundances at this time, while abundance levels of other copepods decreased. Heroplank-tonic larval stages of decapods Cancer sp. , Carc/nus maenas and Crangon septenspinosa, and cladoceran todon sp. all reached peak abundance during this period. The summer assemblage in 1988 was similar to previous years, with one exception. Mean densities of Calanos finmarch/cus, an oceanic spe-cies (Gosner 1971), in group 6 were lower than those observed historically (1978-1984). The fall macrozooplankton assemblegn (group 7) coincided with 3 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 i abundantly, with Podon sp. a secondary dominant in the group, 1988 collet.- tions in group 7 had a similar species composition (Table 3.1.3-2). The estuarine copepod Centropages hamatus, historically not an important com- f ponent of this group, had fall densities in both 1987 and 1988 that were an order of magnitude higher than those observed historically (Table 3.1.3-2). 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 1ervae studies suggest. that areas at similar depths and dis-tances from shore (such as P2 and PS) have similar spacies composition (NAI 1977a). Thus no spatial differences in the mero- or holo planktonic macro-l zooplankton abundances, percent composition, or rank would be expected among j Stations P2, P5 or P7 This has been confirmed in examinations of the annual l 94 \
\ !
l} - . -
peicent composition, percent frequency and rank dominance scores (RDS) of
-doninant species followed by nonparametric testing of apparent differences (NA1 1985b, 1987b). Spatial differences in community structure would be indicated by significant differences in abundance for the majority of the component species.
Species composition of holoplankton and eneroplankton was similar among the three stations in 1988 as well. Percent composition gives an idea of how relative annual abundance of spe'cies compares among the three sta-tions. Copepod Centropages typicus and Cirripedia contributed the two highest percent compositions at P2 and P5. C. typlcus was the ove. whelming dominant at P7, with Cancer sp. larval stages achieving the second highest percent composition (Table 3.1.3-3). 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 indicatica of how fre-q u ntly a taxon han been a dominant. Copepod Temora long/cornis was the top ra.tking species at all three stations (Table 3.1.3-3). The second ranking species differed among stations, C. //nmarchleus at P2, Pseudocalanus sp. at P5 and Centropages hamatus at P7; all ranked within the top ten at each sta-tion. None of the holoplanktonic or meroplanktonic species tested exhibited signifcant differences in abundances between stations (Table 3.1.3 4). Tycho- and hypoplanktonic species, on the other hand, are often otrongly associated with particular substrate types. Substrate type and complexity, along with proximity to Hampton Seabrook estuary, may account for come of the differences observed among tychoplankters. Historically, Neo-tysis americana, Pontogenela inermis, and Diastylls sp. had higher abundances ct P2 where substrate is sand and cobble than at P7, the station f arthest to the north where the substrate is mainly sand (NAI 1985b). A similar trend was confirmed in 1988, although differences were very highly significant only for in.astylls sp. (the number of tests performed necessitates a raore strin-gent significance level to avoid a type I error in assessing differences in cverall community structure) (Table 3.3.1-4). At Station PS, where substrate i is largely ledge outcrop and cobble, 1988 densities of N. amer /cana, 95 s
TABIZ 3.1.3-3. COMPARISON OF PERCENT COMPOSITION, RANK
- AND PERCENT FREQUENCY OF OCCURRENCE OF DOMINANT SPECIES IN MACROZOOPIMITON COLIECTIONS ANONG STATIONS P2, PS, AND P7, JANUARY-DECEMBER 1988. OEABROOK BASELINE REPORT, 1988.
PERCENT PERCENT COMPOSITION RANK
- FREQUENCY OF OCCURRENCE TAXA P2 P5 P7 P2 F5 P7 P2 F5 P7 Centropages typicus 20.7 28.3 52.8 9 8 8 83 79 79 Cirripedia 18.9 29.2 3.7 40 35 37.5 38 46 42 Oikopleurs sp. 12.9 8.0 5.0 14 13 12 83 79 79 Cancer sp. 10.0 5.5 7.8 24 24 21 63 58 63 Calanus finnarchicus '8.8 11.8 6.8 2 3 3.5 96 92 92 Podon sp. 3.8 1.4 1.9 17 17 16 75 75 67 y Eualus prisiolus 3.2 1.9 3.1 3 4 3.5 100 100 96 Centropages heestus 2.7 1.7 1.5 8 7 2 83 83 96 Tesora longicornis 2.6 2.2 3.0 1 1 1 100 100 96 Centropages sp. 2.2 2.3 1.9 16 18 14 79 67 71 Carcinus saenas- 1.6 0.5 2.1 34 25 29 50 58 46 Pseudocalanus sp. 0.8 0.7 1.2 4 2 6 96 100 88 Sagitta elegans 0.3 C.2 0.4 5 6 5 100 92 100 Crangon septeespinosa 0.9 0.3 0.9 6 5 7 96 100 SS Pontogeneia inerais D.05 0.03 0.03 7 10.5 13 100 96 88 Necarysis americans 0.4 0.1 0.1 10 15 17 92 88 75 Evadne sp. 1.7 1.1 1.7 12 9 9 83 83 83 Oedicerotidae 0.4 0.2 0.04 19 10.5 20 83 96 75 Tortanus discaudatus 1.1 'O . 4 1.1 11 19 10 83 67 79 Diasytylis sp. 0.05 0.01 0.01 13 21 26 96 79 67
- simple rank based on Rank Dominance Score (see Methods, Section 4.0) b species included were those comprising >2.07. of the mean sacrozooplankton assemblage annual abundance at any station or ranking among the top-10 taxa based on Rank Dominance Score (RDS) at any station.
Dissrylis sp. included because of station differences observed in 1987 abundances (NAI 1988b).
4 e i TABLE 3.1.3-4.
SUMMARY
OF 1988 BIWEEKLY ABUNDANCE COMPARISONS BETWEEN STATIONS NADE USING WILCOXON'S TWO SAMPLE TEST. SEABROOK BASELINE REPORT, 1988. TEST PARAMETER TESTED P v. P5 P2 v. P7 PS v. P7 l Holoplankters Calanus finmarchlcus NS NS NS Centropages typicus NS NS , NS . Tortanus discaudatus NS NS NS Olhopleura sp. NS NS NS i Herc plankters Cesngon septemspinosa NS NS NS -
'Cas:inus maenas NS NS NS Cirripedia NS NS NS Can:er sp. NS NS NS Tychoplankters '
Neosyris americana P2>PS** P2>Pl** NS l'ontogenela inarxis P2>PS* P2>P7* NS Dedicerotidae NS NS P5>P7* i Dlastylls sp. P2>PS** P2>P7*** P5>P7* Other l Total Abundance NS NS NS I
*significant at 0.01<pf0.05
**significant at 0.001<p50.01 '
C**significant at p50.001 Because of the increased probability of a type I error (falsely accepting a difference as significant) when making numerous pairwise tests, only very highly significant results (p<0.001) are considered different. In terms of . community differences, only a-large number of significant differencas in species abundances between stations should be interpreted as indicating a truo difference. s s 97 s ,
.\ l e
P, P. /nermis and Olsstylls sp. were lower :than at p2 liat did not meet signiff-cance level criteria. Amphipods in the family Oedicerotidae showed no signi-ficant differences in 1988 abundances among the three stations. 3.1.3.2- 1 elected foecies
, Calenus finmarchicus Over the length of this study (1978-1984, 1987-1988) Calanus
//nmarch/cus has been a dominant species in the macrozooplankton assemblage (Table 3.1.3-2). Illstorically, copepodites exhibited greater abundances than adults, a trend which continued in 1988 (Table 3.1.3-5). The major ~ peak in 3 c.-:popodite and adult ab'undance usually occurred April through September. Low abundances, especially of copepodites, occurred during winter (Figure 1
3.1.3-1). In 1988 copepodites exhibited generally typical abundances year round (Figure 3.1.3-1. Table 3.1.3-6). During six months, intermitter.tly throughout 1988, abundances of adults were substantially lower than the his-torical pattern (and outside the 95% confidence limits), resviting in the lowest recorded annual abundance (Table 3.1.3 5)(Figure 3.1.3 1). ' Comparison of semi-monthly abundances of adults over all years by ANOVA indicated significant annual differences (Table 3.1.3-6).' Differences are difficult'to 1 interpret, however, since the multiple comparison test resulted in a contin- ) unm'of years rather than distinct separationn (Tabic 3.1.3-6). A more detniled description of the life history of Calanus //nmarchicus and other selected species is available in the 1984 baseline report (NAI 1984). ' l 1 A comparison of semi-menthly. abundance among stations in 1988 indicated no significant difference (Table 3.1.3-4). Local hydrographic conditions and organism behavior are such that holoplankton populations I appear homogeneous across stations. ' 98 a,
,-
- il
TABLE 3.1.3-5. ANNUAL GEOMETRIC MEAN ABUNDANCE (No./1000 m ) AND UPPER AND LOWER 95% CONFIDENCE LIMITS OF SEIECTED SPECIES OF MACROZOOPIANKTON AT SEABROOK NEAR-FIEIR STATION P2,1978-1984 AND 1987-1988. SEABROOK BASELINE REPORT, 1988. SPECIES /LIFESTAGES 1978 1979 1980 1981 1982 1983 1984 1987 1988 Calanus finnarchicus MEAN 8,999 6,614 19,753 13,159 4,756 12,634 8,819 8,555 6,479 copepodites UCL 51,614 29,219 90,884 53,896 33,342 51,546 59,076 44,336 29,107 LCL 1,568 1,496 4,293 3,212 668 3,' ' 1,316 1,650 1,442 Cs/snus finnarchicus MEAN 767 129 338 116 186 555 518 160 58 adults UCL 4,644 722 898 834 1,366 2,668 1,840 1,370 407 LCL 126 22 127 15 25 115 145 18 7 o Carcinus esenas MEAN 41 22 42 40 40 93 64 62 56
- 406 276 573 592 512 1,394 722 904 990 1arvae UCL LCL 3 1 2 2 2 5 5 3 2 Crangon septeaspinosa MEAN 404 342 152 157 425 547 319 360 474 Zoese and postlarvae UCL 3,002 2,573 1,222 1,464 2,538 2,760 1,595 1,771 2,388 LCL 54 45 18 16 71 108 63 72 94
#eomysis seericans MEAN 154 40 252 400 651 494 758 258 220 all lifestages UCL 521 195 1,288 2,104 2,052 1,688 2,047 783 887 ICL 45 8 49 75- 206 144 280 84 54 4
CALANUS FINMARCHICUS COPEPODITES e-6*
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JAN h MkR A[yt Mky h J)L Aha h h g h l l 1 l l l l l 4 Figure 3.1.31 Log (x+1) abundance per 1000 cubic meters for Calanusfinmarchicus copepodites ( and adults; monthly mean and 95% confidence interval over all years 19781984, i 19861988 and monthly meant for 1988. Seabrook Baseline Report,1988. I 1 100
- - - , - - . - f
TAB E 3.1.3-6. RESULTS OF OIEE-VAY ANALYSIS OF VARIANCE" AMONG YEARS F05t SEMCTED SPECIES OF MACROZOOPIANKTON AT NEARFIEID STATION F2,1978-1984 AND 1987-1988. SEABROOK BASELINE REPORT,1988. SOURCE'OF SPECIES VARIATION df SS F MULTIPLE COMPARISONS Calanus finsarchicas YEARS 8 8.72 0.73NS copepodites ERROR 201 298.43 TOTAL 209 307.14 Calanus finearchicus YEARS 8 32.72 2.18** 78 83 84 80 82 81 87 79 88 adults tRROR 201 377.53
- TOTAL 209 410.25 S
Carcinus --Jenas YEARS 8 4.09 0.18NS larvae ERROR 201 576.95 - TUTAL 209 581.04 Crangon septeaspinoss TEARS 8 7.77 0.62NS zoese and postlarvae ERROR 201 316.88
'IUT.C 209 324.65 Neosysis americana TEARS 8 27.92 3.10** 84 82 83 81 87 88 80 78 79 r--- all lifestages ERROR 201 226.27'
'IUTAL '209 254.18
~.
- Based on semi-monthly sampling periods NS = Not significant (p > 0.05)
* = Significant (0.05 2 p > U.01) f W
** = Highly significant (0.012 p 2 0.001)
*** = Very highly significant (p 2 0.001)
*%i,,,
_ - . . - . - - - - - --------.m.a- --
i CLEC/Dus veenaE Carcinus maenas larvae first occurred in May and were present through December (Figure 3.1.3-2). Larvae were most abundent between June and September and declined sharply in abundance during October in most years. Seasonal aspecte of larval development are detailed in annual data reports (e.g., NA1 1989) and are summarized here. Stage I soeae were abundant fror. mid-June to early September, following peak abundances of gravid females in Hampton Harbor (see Section 3.3.7). In 1988, zoea I and zoea II were most abundant in late _ June and late July, zoea III were numerous in August and zoea IV and megalopa were most abundant in. August through early September. The extended period of abundance for all lifestages suggests that' spawning and recruitment from local and regional adult populations is asynchronous. Abundances of theso larval stages at Station P2 have been similar over the years studied (Table 3.1.3-6). Abundances of Carc/nus maenas larvae were similar at all stations in 1988 (Table 3.1.3-4). Since adults are common in-shore near all three stations and hydrographic conditions typically do not separate stations, this observation was expected. i Crannon septeespinosa Spawning in Crangon septemsp/nosa typically commenced in April with zoese and post-larvae abundant through November (Figure 3.1.3 2). Although larvae, including zoose I, were present year round, peak abundances in June through September were two to three orders of magnitude higher than abundan-ces observed November through Hay. In 1988, peak abundances July.through September were typical of previous years. Overall, annual mean ebundance for 1988 was well within the range of this study, 1978-1984, 1987-1988 (Table 3.1.3-5). A comparison of e.mai-monthly mean abundances indicated no signi-ficant difference among years for Crangon larvae and post-larvae (Table 3.1.3-6). There was no significant difference in Crangon abund6c c autween stations in 1988 (Tsble 3.1.3-4). 102
CARCINUS MAENAS 6-
.--+ ALL YLMS MtAN
$- ... .. 1eos MEM Ig
.,,N.
3- ,*.,' 8i a- . 1-
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- w. _
f.;; 0 -- . . . . u i . . . . . . JAN HB WAR APR WAY JUN M ALO EP 0:T W GD CRANGON SEPTEMSPlNOSA ( 6-6- E , E 4 ,..*., ..
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JAN RB WAR APR WAY JUN R ALO EP OCT W GC Figure 3.1.3 2. Log (x+1) abundance per 1000 cubic meters for Carcinus maenas larvae and , Crangon septemspinosa aoeae and post larvae; monthly mean and 95% confidence ' interval over all years 19781984.19861988 and monthly means for 1988. Seabrook Baseline Report.1988. 1 103 i j f i
a, Neomysts americana Neomysis amer / cans was present year round in the macror.ooplankton but was most abundant September through April (Figure 3.1.3-3). The annual cycle was slightly bimodal, with depressed abundances May through August. Lifestages of Neomysis amer /cana have historically exhibited distinct sea-sonal patterns (NAI 1985b). Immature and mature individuals were most abun-dant in winter while ovitsrous and larvigerous females were most abundant in April. Juveniles were most numerous in late spring and fall (Figure 3.1.3 3). In 1987, unusually low abundances were observed in September and October, largely due to lower than normal numbers of juveniles and immature adults (NAI 1988a). Early in 1988, abundances continued to be depressed relative to historical observations, perhaps due to the reduced availability of juveniles to be recruited into later lifestages. A multiple comparison of I semi monthly Neomysis abundances indicated that there were significant differences among certain baseline years (Table 3.1.3 6). Distinctions were not clear-cut, with the exception that 1979 was significantly lower than all other years except 1978. In 1988, Neomysts mean abundance was not unusual, ranking sixth among the nine years involved in this study. 1 in 1988, as in previous years, Neomysts americana was more abundant ' at Station P2 than at Station P7 (Table 3.1.3-4). As noted in previous base-line reports (NAI 1985b, NAI 1987b), this difference may be related to the different types of substrate underlying each station. Recruitment from nearby Hampton Harbor may also have contributed to high abundances at Station P2. Unlike 1987, Neomys/s abundances at Station P5 wers lower than at Station P2 (Table 3.1.3-4). Abundances were similar at ftacions PS and P7. i 104 V \ El l
I NEOMYSIS AMERICANA
-g.
-o-- 4.t Yt ARs WLAN
... .. seesutAN 4 ..
D lll*:: 6 gg p m,
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O i i i . i i . . . . , , JAN FEB MAR APR MAY JUN JUL A33 SEP CCT 70/ DEC D omhous&LARNRous a ut D nmAtuRtat 5 A M NLE 100= - M < c . I 60 = h t 40 - 20 : o= 9 -W- ' JAN FEB MAR APR MAY JUN JUL AUG SEP OCT W/ DEC Figure 3.1.3 3. Log (x+1) abundance per 1000 cubic meters for Neomysis americana; monthly mean and 95% confidence interval over all years 1978 1984.19861988 and monthly means for 1988 and mean percent composition of Neomysts americana lifestages over all years 19781984.19861988 at nearfield Station P2. Seabrook Baseline Report.1988. 105 i j
3.2 FIKFISH 3.2.1 1chthroplankton 3.2.1.1 Iotal Community Hearfield (P2) ichthyoplankton data collected from 1976 through 1988 were examined for temporal (seasonal and year-to-year) patterns in species assemblages by discriminant analysis. Species composition and - frequency of oc arr. .ce at the f arfield station (P7) and at the discharge station (PS) were compared to data from P2'to detect any differences in ichthyoplankton communities among the sampling areas. Common names recognized by the American Fisheries Society (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 1988 in the Seabrook ichthyoplankton and adult finfish programs are listed with their relative abundances by gear type in Appendix Table 3.2.1-1. One newly-recorded specjes was encountered during the 1988 surveys, striped mullet (#ugf1 cephalus), which was captured by beach seining. Temporal Patterns of Nearfield Fish Era Assemblames Numerical classification of 1976 1984 data had shown that the species composition of fish eggs was highly seasonal in nature, with dif-forent species occurring at different times of the year and generally the samo seasonal succession repeating each year (NAI 1985b). The basic pattern over the 1976-1984 baseline period was summarir.ed by nine groups of samples. l 1 each characterized by a particular assemblage of species occurring at a particular time of year (Table 3.2.1-1).
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TASCI 3.Z.1-1. (Continued) DISTRIBUTIOpt OF SAMPLES EEtBETRIC JAff FEB MAR APR MAY JUll JUL AlfG SEP OCT IIOV DEC AS50 BtAGE 12M 1234 1Z34 IZ34 1Z34 1ZM 1Z34 1Z34 1Z34 1Z34 IZ34 1Z34 DtDt1MAffT FI5BE EGCS 9EAft DEIE5]' E35./1000 m )
- 4. SPRDIs 967 81CD Conner /yellowtail floender Z690 Conner / A98 3C Atlantic mackerel 1210 yellowtail- BIO 2D
, mackerel D24 4 3A A
- 3a B 4C C AD D B
W C o CD D
- 5. Ste9ER 9680-7868 7160 74 Conner /yellowtail fleesuger ette Conner / 3793 3971 9D71 Nake Z830 yellowtail- OM 4093 09 hake Z48 A104 4 3A B33) D 48 D*4 AD AB ,
B Im D
- 4. StWWER A 2C2B 3882 832 Make 339e Nake-conner / C C AC AZ33 ZA Conner #f ellowtail flounder 737 yellowtail A BMA A Nindourane Z18 C %A Ab BO CD-Icentinmed)
l TABLE 3.2.1-1. (Continued) DISTRIBUTIOff DF SAplPtIS GEOPETRIC JAM FEB ltAR APR FIAY JUN JIJL AUG SEP OCT MDY DEC IEAft DENS 12 % It% 1234 IZ34 12 % 1Z34 1Z34 12 % 1Z34 12 % 12 % IZM DOPtI9848tr FISH EGCS (MO./1000 m ) ASSEleLACE C 0996 M3 Make 210
- 7. SUP9ER-FALL D 3130 9CC Foerbeerd reckling ZS Make-48AI 1 Atlantic whiting ZZ rockling-whiting B B3 3 D C4 4 A C B
- 8. StSWER-FALL C 4 C4DC AC Make/fourbeerd reckling M Make/ 8 C B Mindowpape 18 o
reckling- D D windowpane
- 9. FALL A AD A 7343 AACD Atlantic cod 20 Cod- BA4 05 Atlantie whiting 6 whiting- DBA DC Make 5 hake DB Foerbeerd reckling 2 C
Within each month, Meek 1 = detes 1-8, 9 teak 2 = dates 9-15, Meek 3 = dates M-Z3, and Meek 4 = dates 24-31. b Assigrunent of samples from 1976 through 1984 to assemblages was based on numerical c3assification. Samples from 1985 through 1988 were classified into the 1976-1984 assemblages by discriminant fonctions. c Each symbol represents a single sampling dates symbol = last digit of collection year for samples from 1976-1984, A31985, B=1986 C=1987. D*1998. For example, samples collected the first week of January idetes 1-81 were classified as containing the Fall-Minter-Cod-Pollock egg assemblage in the years 1977,1982,19M,1986, and 1988, and containing the Minter-Spring-Plaice-Cod egg assemblage in the years 1980 and 1981. Taxa whose geometric mean densities were at least 5% of the total of all taxa analyzed. e Based on 1976-1984 samples.
I 5 Two of the groups (8 and 9) had lower within-group similarity values (NAl 1985b) and lower numbers of samples than the other 5:ven groups. They were characterized by relatively low abundances of a few species that occurred during the fall (NAI 1987b). Discriminant analysis was used to classify the fish egg data from 1985-1988 according to their faunal similarity to the assemblages previously identified from the 1976-1984 data, to detect any differences among years in the time of year the various assemblages appeared. The results also provide a measure of the ability of this method to recognize the faunal assembleges identifjed by numerical classification. This is accomplished by examining the degree to which the samples from 1976-1984 were classified into the same groups to which they had originally been assigned. 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 219 samples (89.5%) to the same group as that assigned by the cluster analysis. The groupings of samples recog-nized by discriminant anelysis can be categorized seasonally as late fall-early winter (Group 1), winter-early .pring (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 s amples 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) ap-peered in 1988 from November through early January, simfiar to the time period during which it occurred in most of the previous years. 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 ($ 0.3 per 1000 m ). The second seasonal group, a winter-early spring plalce and cod / haddock assemblage, occurred in late March and early April in 1988. In previous years most February and early March samples were also classified 110
into Group 2 by both clrster anLlysis and discriminant analysis. Many of the late winter samples in 1988 were excluded from the analysis because of low densities. Pollock eggs were replaced by American plaice eggs in most years es a dominant species during this seasonal period, i The spring plaice-cunner /yellowtail assemblage (Group 3) was pre- __ sent in late April and early May during 1988, similar to previous years. This group was characterized by an increase in the number of abundont spe-cies. In 1988, fourbeard rockling was also an abundant species (101 per 1000 3 m ), in addition to American plalce, cunner /yellowtail flounder, and Atlantic cod / haddock eggs, the typical dominants at this time of year (NAI 1989). 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 spawn-l ing until June (Bigelow and Schroeder 1953).
=]
~
The spring cunner /yellowtail flounder-mackerel assemblage (Group - 4), was present the last three weeks of May and in three of four weeks of l June in 1988, which was similar to the previous baseline summary period (1976 through 1984). It exhibited high abundances of cunner /yellowtail flounder and mackerel eggs. Fourbeard rockling and windowpane eggs were also abun-dant. i A very abundant summer cunner-hake assemblage composed 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. In - 1988 it occurred frem mid-June through mid-August. Cunner /yellowtail floun-der 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 cunner spawn during the summer (NAI 1983b). Windowpane, Atlantic mackerel, fourbeard rockling, and Atlantic whiting eggs were also abundant in this seasonal group. 111 j L - W
I 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, primarily in August. Only four of those nine years were represented (1978, 1982, 1983 and 1984), with the majority of samples coming from the latter three years. During 1988, only the eggs collected in the third week of August were classified into this assemblage. This group, 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 windowpane eggs. Other species also exhibited a decline from early summer abundances. The seventh seasonal group, a late summer-early fall hake-rockling-whiting assemblage, was composed of samples collect ! from September to mid-October during the 1976-1984 baseline summary period. The only years not repienented in this assemblage were 1977 and 1982. During 1988, this assem-blage occurred during late August through the end of September. Hake, although diminished in abundance in comparison to its density in Group 6 samples, still dominated egg collections. During 1988, as in the past, other species continued their gradual seasonal decline (NAI 1989). 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. Three sampling dates in 1988 were clas-sified with this group. A small group of fall samples composed Group 9. This assemblage was characterized by low to moderate densities of Atlantic cod eggs, along with modest numbers of eggs of species that are primarily late summer spawn-ers: hake, Atlantic whiting, and fourbeard rockling. The samples from early October through the fourth week in November in 1988 were classified with this group. 112 l' .
1 I i Overall, the classification of the 1988 samples of fish eggs by discriminant analysis followed a similar seasonal pattern compared with both numerical and discriminant classifications of samples from previous years, Two minor groups (8 and 9), consisting of late summer and fall samples, have assumed greater importance during the 1985-1988 period than was true during 1976-1984. Atlantic herring, American sand lance, and winter flounder, which are important components of the larval assembleges discussed-below, do not
-appear in the baseline analysis of fish eggs because these species have demersal rather than buoyant eggs. These eggs are rar if, if ever, collected in oblique tows through the water column.
{ Temporal Patterns of Neartic1d Larval Fish Assemblames Numerical classification analysis of-fish larve c.bundanceu at the nearfield station (P2) during the period 1976-1984 revealed the samn 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 1985-1988 samples into one of nine seasonal assemblages (T6ble 3.2.1-2). The first major group, fall-winter,-consisted of two' larval essem-blages (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,1986a, 'l987a).
'During 1988 the occurrence of the Group 1 assemblage was similar to past years, extending from late h tober through the end of November. Group 2 (late fall-early winter) was dominated by pollock as well as Atlantic her-ring, with.the latter displaying decreased abundance from the collections ?
113
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TABLE 3.2.1-2 DISTRIBtfTItNt 199058B SEEKS ABC ARENIC SEASINEAL ASSEFBLAGES OF SAMPLES 0* TISM LAltVAE COL 12CTED AT IEAEFIEID STATIOft P2' DifftING JANtfARY 1976 THROtfGft DECE7mER 1988. 96ABSOOK BASEL15E REPoirr,1988. _ DISTRIBtfTION OF SAftP125 sEmerRIC JAN FEB MAE APB MAY JUN JUL AUG SEP GCT- IEDY DEC PEAft DEMS ASSDSLAGE 1234 1234 1234 Ic34 1134 1234 1234 1234 1234 1234 1234 -1234 DtNtDenstr FISH LARVAE E150./2000 m ) 4496 724A B B Atlantic trerring 192
- 1. FALL C Herrins BA02 13AB C.
B13 348C : 26 4Dcn 4A AD BB C CC L D H 2. FALL-NDifER 7AA - 4A 069. 8797 b11cet 19
$ Pollock- IBB A90 .3032 Atlantic herring' It' herring 'A B12 41A3 Atlantic cod .3 B C 3 A484 D 4 DA A BD C
99? so ' 8 48 2 1208 American send lance , :199
- 3. MINTER Sand 300 14 lave:- CD4 2D DA A S B C D D'
- 4. WINTER- '2 3' (DC 7- C4- A Asnerican send lance 1 le C Atlantic cod ' 1 SPRDIG C (D
.Sami Snailfishes (Liparis spp.) 1 lance - cod -
(continued)'
j1
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C ]m 1
= 5 0 5 7 5 S 5 1 3 rt 0 2 4 2 4 7 9 S4 4 3 eD0 4 1 7 2 4
mD1/. ef t s A 0 1 M (1 I ..) P p - P p s s ) E s s d A e i e T c r i r g s R n a a n a p p n .g. i A. i t 1 l i ri y e l n n L eL n c k i o R d t d ( ai ct c S n n m a ei i I al s u sh l rh
.F s e e o e s p w nh l h d T
f n n s f sd n r c f a ui i e a ai A E cgf rf t c r et i l el ai eb n D rk i t i i r n r a f N e c a n ad e n ul E D m o n i n a m o ot A R S M S I A t CF A
~
C 4 E 3 D2 1 7 4 0 3 M,1 2 T 4 C3 O 2 1 P 4 1 E 3 C S 2 9 3 A C 1 7 3 4 C S G 4
~
E U 3 0 3 C D L A 2 6 7 9 3 4 P 1 8 3 4 D M A 7 9 0 3 4 C D S L 4 8 1 3 4 C D U 3 F J 2 9 4 6 8 7 9 0 2 3 4 D 0 1 3 A BC O 1 2 9 7 3 4 A N O t 2 4 4 A 8 I 1 3 89 4 A 5 D 0 3 D 3 C T 3 2 6 7 9 1 2 3 4 A C U B I 1 89 1 2 3 4 A BGD R Y 4 7 6 0 4 A QCD T A 3 S H2 1 6 8 9 9 0 1 32 43 A3 B4 CA DB CD I 4 D 7 0 3 B D R 4 8 8 9 3 A D P 3 9 0 81 2 3 4 D 6 A 2 8 3 1 7 9 0 1 2 3 4 CD R 4 83 4 A BC D A 3 6 9 0 1 2 3 4 BCD M21 1 2 3 A BC D 8 3 4 A B C D B 4 '6 9 O 2 3 4 A
) E 3 1 4 A D F 2 0 3 B d 1 C e
u n N 4 i A 3 2 t J2 ' n o C (
. - i 2
ee c n n n - h 1 E - a e r s g 2 G R G l g ei - n A EN G rd f R ri 3 L T I d k N e nl E el N R n I t ui I n k E B R n o a Tn c L B D S I P a W SS m. P i l n SM f s U u o S C r A S . . T A 5 6 7 wHw .
- :.. - .~ .,.g.
s .
- ' * - -- * * ' M*^ '
"#~~~ '
. : - .~ x
-O . i'..^ ~~' 'L --
s TABLE 3.2.1-Z. (Continued) C DISTRIBtfrION OF SAMPLES GEGETRIC JAN FEB MAR APR MAY JUL AUG SEP OCT 380 7 DEC IEAft DEBES ASSE39fEIE 1234 1234 1234 1234 1234 1Z34 ~,JUN1234 1234 1234 1Z34 1Z34.IZ34 DOMINANT./ISH LARVAE END./1000 m ). D C AB' A151 EEMO Ctanner 32
- 8. St99tER ,
Cunner DB B2AA A C AC 'D1 G C DA BZ 0 96 83A Fourbeerd rockling 22
- 9. SUf9ER-F LL Rockling ,
4 2 23 1C Mindowpene 4 36 3- Mitch fleender 3. p H AA C Make '2 m C Conner 12 Nithin each month, Maek 1 = dates 1-8, Meek 2 m dates 9-15, Meek' 3 = dates 16-23, and Neek 4 = dates 24-31. 7( b
- Assignment of samples from 1976 through 1994 to sesemblages was based on numerical classification. Samples frts 1985 therigh 1988 were classified into the 1976-1984 assemblages by discriminant functions. -
c l Each symbol represents a single sampling. dates - symbol = last digit of collection year for. samples from 1976-1984, A=1985,' B=198 , C=1987, D=1988. For example, samples collected in the first week of January idates 1-8) were classified as containing the Fall-Minter-Pollock-Nerting larval assemblage in the years 1977, 1981, 1985, 1986,'and 1988, and containing the
- Ninter-Sand Lance larval assemblage in the years 1982 and 1987.
d Taxa whose geometric mean densities were at least 5% of the total of all taxa analyrad. Based on 1976-1984 samples. I 5
#9- "O"- '# ' " " ^ ' ' "' -
's-i='- "--#'-P---"'
,gg,.. .g . , ,
-s +-m's-r#. .= m
earlier in the fall. December and early January collections from 1988 were ! classified with Group 2, consistent with the temporal occurrence of this ' assemblage in previous years. i 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 3 lance'(199 per 1000 m ) and relatively low numbers of a number of other win- 1 ter species (5 6 per 1000 m 3). This assemblage usually occurred from early. 1 January, or earlier in some years, to mid-February, or later in some years'. i Five samples from 1988 were classified with this group. The Group 4 assem- , blage 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 j sand lance still being the dominant species. One sample from 198'8 was classified into this group. Group 5 consisted of a large number of late 4 winter and early spring samples characterized by high densities of American s, 3 Jance (425 per 1000 m ) and moderate densities of rock gunnel (47 per 3 1000 m ) and snailfishes (25 per 1000 m , primarily Liparts cohent). This larval assemblage was generally present from mid-February to late April. , Seven dates from mid-February to late April in 1988 were classified with-Group 5. A spring larval assemblage was usually present during Hay and June in 1976-1984 These samples composed the third major. seasonal group, Group i
- 6. The spring group, as in previous years, was characterized in 1988 by Jnoderate numbers of w. int.er flounder, snailfishes (primarily Liparts atlanti- ,
cus), radiated shanny, and American plaice larvae (NAI 1989). This assem-blage was present from late April to late June in 1988. < 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 117
__________________ _ . - _ - - - - - - ~
l 1 1 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. l Group 9 consists of late summer and early fall samples characterized by a fourbeard rockling larval assemblage. Besides modest numbers of rockling, a' , i few other'apecies'were occasionally important in these samples (windowpane, .I witch flounder, hake,; cunner), although both densities of larvae;and numbers. I of species were characteristically. low. This was also a relatively'small ; group'in 1976-1984 (n=14):that received several additions in 1985-1988 (n=10). f In general, the results of the 1988 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 1985-1988 samples followed a similar. seasonal pattern to those from the earlier years. In most cases , s where the two methods differed, the samples in question had relatively;1ow , numbers of larvae. For example, Group 8 was originally-a small group (only a seven samples in the nine year period 1976-1984), but in the last four years an additional 18 samples have been classified here by the discriminant function analysis, including five from 1988. 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 diiferentiating among groups, :; whereas the Bray-Curtis similarity.index used in the cluster analysis of the
- f
- 1976-1984 data is strongly influenced by abundance, and thus places greater emphasis on the dominant species.
'1 l
l l 118 1 T ' m .
Spatial Patterns of Fish Emms and Larvae I 1 Spatial comparison of abundance and species composition from the { nearlield and farfield stations was previously done usir.g r.smerical classi- i. fication for both fish eggs and larvae. Spatial (statien) differences were found to be less important than short-term temporal differences (NAI 1983b, 1984b). f,caples cdliected on the esme (. ate at different stations (nearfield
.)
and farfield)-more likely resembled each other than if collected one to two ! weeks apart at the same station. This similarity in species composition and- I abundance between nearfield and farfield sites was consistent with the known . extent of water mass movements in the study area. During 1988, 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 j (Tables 3.2.1-3 and 3.2.1-4). i 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 l 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 periodt dominated by longshore flow. The distance from NearfJeld Station Y2 to PL (1-1/2 miles) or to P7 (3-1/2 miles)'is relatively short. Considering that, for example, a water msss 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 densisties and species composition do.not differ among stations, and data from 1988 are very similar - i among stations (Tables 3.2.1-3 and 3.2.1-4) no further analysis wea con-
- ducted, i
119
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- t. u. s. Ra. g g-g . E-- E
- E< s. t. - 2 8 n. 8 8 gW $< ddjdddd did'dddd4fddd4 A l sgg ___._____________________
f ; im.,l ll.ill i_l. ______. _ _ _ _ _ _ _i ll _ _i v_ 120
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--+
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" -- + m.- z zmsz a. rm s =. x =. r. a.- n sr zu m 2 u.= n, ms z z s n .2u s
- 8. sd -4dididd dddidd:ddid idisidd Ec,I l, rlg i ,
c aqa_ _ _r.,_._._ _ _ _ _ _ _ _ _ y _ ; _a. lle l g. < _ _ . _ _ _ ; _ u _s e .s .. p _m .; t, e s. am . m.-: .
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-3.2.1.1 Selected Spectre Larvae. of nine fish species wore selected for a detailed analysis.. 1 y of their within-year and among-year patterns of abundance because of their- i i numerical dominance or importance as a recreational or commercial: species, j Analyses were based on a series of monthly means= for Nearfield Station P2 samples collected from July _-1975 through-December-1987. These monthly means- 'i i were.av, re ss of two to four tows on one to four dates within each month. g! 3 Each of the nine species displayed distinct seasonali patterns of-abundance. 'While fish larvae were present,in every month, the larvae of each ,
;l species exhibited a sharply defined period of only a few months' duration in j 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 fm aach species (NAI 1983b). To reduce overall variability and improve statistical power, or ability to detect significant year-to-year differences-in abundance, seasonal d q mean abundances-(and upper _and lower confidence limits) were calculated using q data only from sampling periods which encompassed the seasonal peak in larval j abundance. These select periods included the' season of maximum yearly ! i abundance and approximately 90%-of total yearly catch for'each species. j 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-1)uncan K-ratio t-test for multiple comparisons. Because sampling was ititiated in July in 1975, that year was only , included in the analysis of variance for those taxa whose peak season occur-red after that time: hake, Atlantic herring, and pollock. The analysis of , pollock data excludes 1988 because the peak season extends into-January and ij February of the following year, and 1989 data are not inclu6 3 in this- l baseline report.
.i.
-l i
i 122 I
i, American Sand Lance American sand lance larvae continued to exhibit a December _through July presence with peak abundance occurring from January through April 1 (Figure'3.2.1-1). In 1988, abundances were slightly higher than normal in l-May but decreased through June, dropping to zero in July. This broad peak l 1 was due primarily to two factors: an extended hatching period and a long j planktonic stage for larvae (Bigelow and Schroeder 1953). Sand lance, the- l l most abundant species over all years, has been highly variable ranging from i 3 35.0/1000 m in 1977 to 447.7 in 1982 (Table 3.2.1-5). Abundance for 1988 (139.7 larvae /1000 3m ) was slightly below the overall mean for the fourteen years of the study. Using the peak season data, a one-way analysis of I variance showed no significant difference among years for log ' (x + 1) transformed abundances (Table 3.2.1-6). Winter Flounde_r Winter flounder larvas, the fourth most.' abundant (over all years) of the nine selected species, were usually present from March through Septem-ber, with the highest concentrations occurring in April through July (Figure 3.2.1-1). Very few specimens were encountered-in March, August and Septem-ber. In 1988, abundances followed the same general pattern as'in previous years. Abundances of wint.n 11ourder larvae, relatively consistent in earlier years (1976-1978), decreased from 17.5 larvae per 1000 cubic meters 3 (1978) to an all-time low in 1981 (2.9 larvae /1000 m ). Abundance increased during the next four years to the highest value (22.41arvae/1000 m3 ) recor-ded. Since that time, abundance has decreased in both 1986 and 1987 (Table ' 3.2.1-5). Abundance in 1988 increased slightly (17.2 larvae /1000 m ) over ! last_ year's mean and was just slightly higher than the overall mean for the study. A one-way analysis of variance of the peak month log-transformed
- abundances showed no significant difference among years (Table 3.2.1-6).
f 123 : l i f
y American sand irnca - ~ - 4 g -
- - OVERALL MEAN 8*
ug. ... .. 3goe o'_ ~ 2- .. , , ' *., j Eh~ s U '
\.g.
1- '
.J v-
'l I
I o, , , , , , ,
.N, ,
-JAN' FEB MAR APR MAY JUN JUL-AUG SEP .07 to/ DEC ;
MONTH
-)
winter flounder 4- ;
^
- ,t 0:
ke 3-OVERALL MEAN
@EJ ,
.m n '2 - '\, ,
pa ' ,.
+3 .
50 *
~*. .
gg i- / . J ,-
./ ., j
/ '.
/ ..
O 3 , , , , , , , , , , ,
~'
JAN FEB MAR APR MAY JUN JUL AUG' SEP . OCT 10/ ' (EC l MONTH i Figure 3.2.1-1. Mean and 95% confidence limits over all years and 1988 values, by month, i for log (x+1) transformed abundanc.s. (No. /1000 m 3 ) for American sand - lance and winter flounder larvae at Stations P2 and P3, July 1975 thrm, b December 1988. Seabrook Baseline Report,1988. i 124
-e' ' L..-..,
l a W 3 TA811 3.2.1-5. GEOPEYRIC IEAlt CF iraam% OF PEAK A8tBEMXE flR9BER PER 1000 ft J BY YEAR OF SE12CTED FISR SPECIES LARTAE AT FirAT100t P2, jut.Y 1975 Titm0ppi DECEBEIER 1988. SEABRotK PJ3ELIIE REPORT,1988.
]' )
CIIIFIDEICE SPECIES tand YEAR .OTER-alt.. LIMIT l months includedI 1975 1976 1977 1978 1979 1980 1981 '1982 1983 19fM - 1985 1986 1987 1988 IE4A 1AleER tlPPER American sr.nd lance - 352.9 35.0 384.0 203.2 219.7' 213.7' 447.7 e5.0 73.8 71.5. 314.8 87.9 139.7 146.1 .02.7 207.6 IJan-Apr) Minter 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 14.2 9.7 20.5 tApr-Ju!)
.6 Yellowtail flounder - 3.7 20.1 4.1 12.4 6.5 -1.3 0.3 43' 2.9 2.2 5.3 1.7 2.8 3.5 Z.4 4.9 iPlay-Aug ) _
t.
- p. .
- / ;<
N Atlantic cod - 4.7 9.4 . 16.1 1.2 3.4 9.9 2.8 7.8 2.1 1.3 1.6 0.6 1*- 2.3 1.4 - 3.2 t.n iApr-JulI ,
~
5.1' 13.1
^
Atlantic M erel- - t.6 5.4' .Z.3 8.0 24.2 12.4' 4.3 12.0 8.4 11.7 12.5 8.5 4.0 8.2 (Pay-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 48.5 30.7 76.4 g iJune-Sep) , Make 6.5 ' 'C. 4.2 2.7 8.2 5.4 ' 5.9 ' 2.4 10.4 7.8 10.0 0.1 3. 2 ' 3.9 k.3 2.6 4.8 tJul-Sep) - 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 30.4 '20.0 .45.8 toet-Dec) b Pollock 12.2 27.7 F.1 1.9 49.2 7.3 4.0 . 2.1 3.4 22.7 13.8 1.2 5.8 - 6.8 4.7 9.8 (Nov-Feb) - g - 4 .- Sampling at P2 bomen in July 1975,' excluding part of annual peak. jf - b Yearly me n not competed for pollock in 1988 beenese January and February 1999 data were mot available. si E' /
,. /' 4*
^ ~~ ~' ' ~
.a., ~s..- ~.wn&w., ' " ~ " ' - -' - ' " * ' ' ~ " ^ * ' ' * ' ' ' ' ^ ' ~ " ^ " "
~ . - ^'Q',_
.C TASLE 3.2.1-6 RESULTS OF ONE-MAY AftALYSIS OF VARIAPT AMDMG YFfJtS OF 1)DG EX+1) TRAJESFORf1ED A34HWiJECLS 1300./1008a i OF SEECITD SPECIES
'RDIG SEECTED MENtDts, JUI.Y 1975 THROUGH DECDBER 1988. SEABROOK BASE 1.IptE ltiPORT, 1988.
SPEC.TS Iand SOURCE OF months included 1 VARIATION df 25 F Mug,Typty cggpm ( American sar,d lance Years 12 11.44 1.24 1Jan-AP r Errcr 121 93.35 I-
; Total 133 104.8L2 Ninter flounder Years 12 4.91 0.45 tApr-Jull Error 132 119.63 Total 144 124.54 /
i Yellowtail flounder Years 12 10.11 1.57
, tMay-Aug) Error 135 72.31 Total 147 82 A2
. Atlantic cod Years 12 11.15 2.45 " 78 31 77 76 80 82 e4 83 Ts6 8", 7? 88 (37 tAPr-Jul) Errer 132 50.01 -
Total 1% 61.17 -
=__
u
<r.
Atlantic mackerel Years 12 7.07 0.44 tMay-Augi Error 1=5 ISO.66 Total 147 18'i.75 Cunner Years 12 ).80 1.34 3 tJune-Sep1 Error 132 179.4c Total 144 201 20 Hake Years 13 10.65 1.03 t Jol-SeP t Error 98 77. F. Total 111 68.59 E Atlantic herring Years IS 17.1r- 1.77 tOct-D*c> Error 92 68.3* Total les 85.50 Pollock Yeaes !! 17.82 5.2c " 79 74 84 85 75 80 87 77 81 83 82 ',15 86 eMov-Feb1 Errer 116 59.86 Total 128 79. 2 Its a not significant tp>0.05)
* = signif acant t 0.05>p>0.GI )
## highly significant 10.01>p>c.001 )
* * = very highly significant tp50.001)
- - -. .. u 'dii
Yellowtail Flounder Yellowtail flounder larvao normally occurred from May through September, with peak abundances occurring from May through August. In recent years there have been an increasing number of larvao present in April, but in 19h no larvae were caught during this month (Figure 3.2.1-2). In 1988 the larvae followed the general pattern of abundance in May and June but were well below the mean value for July. Abundances for August on the other hand were well above the overall nican. Yellowtail flounder, like most of the selected species, has been highly variable from year to year (Table 3.2.1-5). Starting with the highest value in 1977 (20.1 larvae /1000 m ) abundances generally decreased to the lowest value in 1982 (0.3 1arvae/1000 m ) and then were relatively consistent and moderate through 1988. Abundanme in 1988 (2.8 larvae /1000 m ) wan slightly below the overall yearly geometric mean of 3.6 1ervan per 3000 cubic meters. The one-way analysis of variance to test overall yearly differences in log-transformed means was not significant
~
(Table 3.2.1-6). 1 Atlantic Cod Atlantic cod larvae typically exhibited a bimodal distribution with one peak lasting from November through January (ltte 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 1988, . however the April through July peak was not av strong as usual, continuing the trend noticed in 1987. Seasonal geometric mean abundance for Atlantic i 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 1988, spring Atlantic cod larvae (1.1 larvae /1000 m) increastd slightly over 1987 abundanc the lowest (0.6 larvae /1000 m ) in the thirtnen years of the study, thus continuirg the trend of decreasing 4 a and below-aversgo nbundance levels which began in 1982 (Table 3.2.1-5). A l- 127
- h. .
,. _. y .
_.- .- ; y
yGilowtail flound3r 2.0 - { ovmu.usm m . ....... im- [ 1.6 -
/.
lie o 1.o - / a
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t
'8 aeh 0.5
,./ .[ k .
- 1. .
0.0
%^ i 1JAN FEB. MAR APR MAY JUN JUL AJG *EP. OCT PO/ - DEC MONTH
. Atlantic cod 2.0 -
OVERALL MEM
, . . . . .. . . i m o-E g- 1.5 -
Ew gg ga zo 1.0-
- N QQ AO
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4
/
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/
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.<. JAN FEB MAR APR MAY JUN 'JUL AUG SEP OCT NW OED
,m- MONTH L y : '
~
4 t 4
- 0 s, ,,
,D' <
s . , i l + Figure 3.2.12.forMean and 95% confidence limits over m allforyears and 1p)S8 values, by L m I.f a log (x+1) transfortaed abundances (No. /1000 yellowtall DounderJ y, t " lll "* yJ and Atlantic cod larvae at Stations P2 and P3; July 1975 through December 1988. Seabmok Baseline Report,1988. ]; - i, E.'a. o, ' c '
., .q.
l'L ' h ] \\
, l
[ }i I g(I d i 128
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v i lk 1 1 one-way analysis of variance among years found the differencan to be highly significant (Table'3.2.1-6). The Duncan-Waller multiple coruparison test shows that the abundances in 1977, 1978, and 1981 were significantly higher ); . than in 1979, 1987 and 1988. ' l 1 l Atlantic a Mackerel: i d Atlantic mackerel larvae exhibited a May througl. August pattern of occurrence for all years combined, with peak l abundances ocr.urring 'in July. . q No larvae found in October through April (Fip;ure 3.2.1-3). .In 1988, mackerel larvae followed the yearly trend except for. May and' August, when abundances were much larger than the ov$rall mean. ; Seasonal mean abundances for mack-i erel larvan were variable throughoutlthe. study period'but have be'en decreas-- 1 ing since 1986 (from 12.5 to 4.0 larvae /1000 m 3 ).. The highest value occurred 1 i 3
.in 1980 (24.2' larvae />1000 m ) with the average over all years,of 9.0 larvae. .i per 1000 cubic meters A cr.e-way analysis of variance found no'significant difference arsong years.
d
- Cunn u j l
i'
- q.
Curner larvao were present throughout June through September, n1Nsing a pattern of occurrence similar to mackerel larvae. Cunner larvae peaked historically during July and: August and usually disappeared by.0ctobdr (Fir,ure 3.2.1-3).. 1,aruni abundance in 1988. continued to follow the yearly trend, but values 'for July land August were much larger than:the overall mean, creating an even larger' peak than usual. The unusually high peak was the , rer, ult of the- 1argeishundance .of cunuer larvae caudh't in July 19fF3 (4437/1000 -j 3 m ). This species alone account.nd for 53% of all'the larvae caught. in 1986 E. ?(NAI 1989). Seaso ial ae.sn abundances for' cunne : larvae havelheea highly P i.. vat:inble' throughout the put fourteen yenrs (Table 3.2.1-3), with 1987i . i 3 tahlbitir.F theihighkst abund us,ce (255.2 larvae /1000 m ) during this petiod. a i ; I , <
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? [ _... > u 0-i i i i i i i . .. .. , i JAN FEB MAR APR MAY JUN Jul. AUG - SEP OCT '70/ CEC ! MONTH 1 l Figure 3.2.13. Mean and 95% confidence limits over all years and 1988 values, by month,- - I- for log (x+1) transformed abundances (No. /1000 m 3 ) for Atlantic mackerel " and cunner larvae at Stations P2 and P3, July 1975 through December 1988. Seabrook Baseline Report,1988. , 130
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Cunner larvae were the second most abundant of the nine selected species in
-1988. The one-way analysis of variance showed no significant differenco among the years. ;
Hakes-1 Hake larvae, like mackerel and cunner, were confined to e cela- 1 J tively short. period of occurrence. llistorically, they have increased through_ -j June and July reaking in August and September, decreasing in' October,'and ! almost disappearing in November (Figure 3.2.1-4)'. In 1988, larvae followed the June through November pattern of abundecco, except abundances in July and l August . wore- higher than the overall means i a those .u.ths. In addition, 1 Septembe'r and October abundance levels were m M 16wer than-the means for -! those months. Abundances'in 1988 for the month of July were the largest they-have ever been since the start of sampling in 1975 (monthly mean of' 291 - 3 3 larvae /1000 m ). Seasonal mean abundanc.e was relatively consistent' among years, with the highest' abundance occurring in 1983 (10.4 larvae /1000 m ; Table 3.2.1-5). The abundance in 1986 (0.1 larvae /1000 m3 ) was the lowest value in the past thirteen years. Abundance in 1988 was slightly higher (3.9 [ 3 larvan/1000 m ) than 1937 values, but was still below the overall mean of 4.3 larvae per 1000 cubic meters. A one way analysis of variance showed no significant difterence among yearly means. I Atlantic Herrina Atlantic herring . larvae typically occurred from November to June and were rare for the remainder of the year (Figure 3.2.1-4). Abundances : were low-to-medium'from January through May, and peak values occurred from October through Decemb4c. In 1988, herring followed.a pattern similar to that in previous years except that January, April, May, and. August abundances , were higher and February and March were lower than their overall monthly 7 131
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i 1 ,. l means. As most of the other selected species, herring larvae have a highly variable seasonal mean abundance (Table 3.2.1-5). The highest abundances occurred in 1975 and 1976 (197 and 145 larvae /10003m respectively), the 3 lowest in 1978 (2.1 larvae / 1000 m ), a"eraging 31.4' larvae per 1000 cubic i meters over all years. In 1988, the geometric mean abundance (26.6 1arvoe/ ! 3 , 1000 m ) was very similar to the 1987 abundance (28.8 larvae /1000 m3) and was slightly below the'overall mean. A one-way analysis of variance testing the differerees among years was not too significant (Table 3.2.1-6). ! Pollock l Pollock larvae exhibited an abundance pattern similar to that of horring larvae, with large abundances-in November through February and gradually decreasing abundances from March through June (Figure 3.2.1-5). During July through October few if any larvae were present. Pollock larvae in 1988 were absent from March through August and were more abundant than
-usual in October. Seasonal peak abundances for pollock were highly variable ,
from year to year (Table 3.2.1-5), with increasing abundances followed by two or three years of decreasing abundances. In 1988, the seasonal mean was not computed for pollock because its period of peak abundance extends into 1989. However, abundances in 1987 (which include samples collected in 1988) showed a marked increase over values in 1986 (from 1.2 to 5.8 larvae /1000 m ) but were still below the overall mean of 6.8 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 3.2.1-6). The Waller-Duncan multiple comparison test of the yearly means showed five overlapping groups of years, complicating the interpretation of among year patterns. However, , the three most abundant years (1976, 1979, and 1984) had significantly higher densities than the three lowest years (1978, 1982, and 1986). 133 l
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3.2.2 Adult Finfish
- 3. 2. .t .1 Total Community Temporal Patterns in the Demersal Fish Community Otter trawl catch por unit of effort (CPUE) for all stations and species ccabined during the 1976 through 1988 period rose from 50 fish / ten-f minute tow (fish / tow) in 1977 to a peak of 95 fish / tow in 1980 and 1981 !
i (Figure 3.2.2-1). CPUE subsequently declined through 1985 when an average of 43 fish / tow were collected. The CPUE increased to 59 fish / tow in 1988, indicating an increase from the low abundances recorded in 1985. Changes in the annual composition of the demersal fish community were examined by comparing percent composition of the dominant trawl species. Six taxe 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 (19-36%) 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 has not risen above 20 parcent for the last three years (1986-1988). Hake species (red, white and spotted hake) and longhorn sculpin were ranked second in trawl collections and comprised 14% 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 accounted for an increasingly larger percent of the catch from 1976 (5%) through 1984 (27%), but for the past three years (1986-1988), thuir percent contribution to the total catch fell back to j pre-1979 levels (<t2%). 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 in 1988 (9%) was l i 135
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TABLE 3.2.2-1. PERCBtr GMPOSIT1tBE BY YEAR AfD ALL YEAltS QNSIDED FOR THE 118ELVE HOST ABWBAffT 57ECIES III INTER TRANL5 DURING 1976 THROUGIt 1988 AT STATIONS T1, T2 AIO T3 QNSTIED. SEABIt00K BASELDE REPORT. 1988. PERCENT CIMPOSITION ALL YEAR 5
; -1976 1977 1978 1979 1980 1981 1982 1983 19t% 1985 1986 1987 1988 CINBIIED Yellowtail flounder 36 29 21 34 33 28 22 19 18 27 20 19 20 26 Make species
- 18 30 21 8 8 14 19 10 13 15 14 10 8 14 Longhorn sculpin 5 '8 9 12 15 17 16 24 27 22 9 9 11 14 Winter flounder 5 8 10 7 12 15 9 8 7 9 10 V
11 9 9
$ Atlantic cod 4 3 13 14 9 6 7- 8 5 3 3 6 9 7
' Rainbow smelt 13 3 10 .7 4 6 5 9 .6 1 3 15 IS 8 Skate species 3 5 2 2 2 2 3 7 8 11 14 11 9 5
, Atlantic whiting 6 3 4 2 '1 3 4 1 1 1 8 1 2 3 Ocean poet 2 4 .4 2 1 2 2 3 5 3 3 3 2 3 Pollock <1 <1' <1 4 7 2- 1 2 <1 <1 2 <1 <1 2 Nindovrane Z Z -1 . ' <1 3 2 2 5 6 5 7 8 8 3 Maddock 3 2 <1 3 4 ' <1 2- 1 <1 <1 <1 <1 <1 2 Other species 3 3 5 2 1 3 8 3 3 4 8 5 5 3 i Number of other species (25) 122) 126) (25) 122) 127) 128) (26) 126) (20) (21) (25) (27) (47)
"ir b ludas red, white, and spotted hakes' incluoes mig, little, and thorny skates
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a i equal to the thirteen-year average. Rainbow smelt, the fifth ranked taxon, fluctuated between 18% (1988) and.1% (1985) of the total ennual catch, averaging 8% over all years. Percent composition in 1988 (18%) and:1987 (15%) were the highest during the study period. 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 (13% and 14%, 'I respectively), and lowest in 1977, 1985 and 1986 (3% each year). The percent 1 contribution increased to 9% in 1988, the highest level since 1980. I The number of fish species (species richness) collected annually in otter trawls ranged from 36 to 44 and totaled 60 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 l 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.
- Spatial Patterns in the Demersal Fish Community Mean annual catch per unit of effort was similar at the offshore l
stations (T1 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 generally followed the same long-term abundance pattern. As discussed previously, CPUE for all stations combined was low in 1977, peaked in 1980 and 1981', declined to lowest levels in 1985, and began to gradually increase through 1988. > Otter trawl catches at the offshore stations (T1 and T3) were dominated by yellowtail flounder, hakes, and longhorn sculpin (Table l 3.2.2-2). Collectively, these species comprised over 65% of:the catch at l l 138
1 TABLE 3.2.2-2. PERCENT COMPOSITION BY STATION'0F ABUNDANT SPECIES ~ COLLECTED IN OTTER' TRAWLS, ALL YEARS CONDINED , (1976-1988). SEABROOK BASELINE REPORT, 1988. PERCENT COMPOSITION SPECIES- T1 T2 T3 :] " :-i Yellowtail flounder 38 14 21 !! Hake species a 16 10 ,15 .
.)
q Ionghorn sculpin 11 5' 21
.l Atlantic cod 5 5 10 ,)
Rainbow smelt '5 19 4 _{ Winter flounder 6 26 5. Atlantic whiting 4 1 3 Windowpane 4 4 3 b i Skate. species 4 ~; 2 8 l 1 l Pollock 1 7 1 j Ocean pout 1 3 4.. - Haddock 1 <1 3 Other species 4 4 -2
.f i i l Number of other species (42) (33) (38); j t i " includes red, white, and spotted hakes j includes big, little, and thorny skates q i
p s 139 .l ! ,) l T/
l l Station T1 and 57% at T3 for all years combined. Of lesser importance at , . . these stations were Atlantic cod Atlantic whiting and skates. The most l notable difference in percent composition between Stations T1 and T3 was that cod, skates, and ocean pout comprised a larger percentage of the total catch I at Station T3. This.and other smaller differences in species composition L > between Stations T1 and T3 may be attributable to different 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 (NAIr1988). I Yellowtail flounder prefer any sandy bottom, while cod prefer a cobble and shell debris habitat (Bigelow and Schroeder 1953). Otter trawl catches at j i the nearshore station (T2) were dominated by' winter flounder,' rainbow smelt, yellowtail flounder and hakes, comprising 69% of the catch for all years combined. Ilake, yellowtail flounder, and longhorn sculpin comprised a much j smaller percentage at Station T2 than at Stations T1 and T3 while the oppo- i site was true of winter flounder, rainbow smelt and pollock.
~I i
l Temporal Patterns in the Pelastic Fish Community ! 1 , l 'l Catch per unit of effort (one 24-hour set) for all species collected in gill nets combined for all species showed a pattern somewhat- 3 CPUE rose'to a peak in 1980-
~
similar to otter trawl catches (Figure 3.2.2-2). l of 29 fish / net and subsequently declined to lowest levels in 1985 of 3 fish / net. CPUE remained low in 1988 and was virtually identical to levels-encountered in 1984 through 1987. 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 -! c ranged from 3.to 16 with the exception of the 1980 peak. In addition,.the :
- gill net peak catch occurred only during.1980,'wh11e the trawl peak spanned ,
both 1980 and 1981. The high 1980 CPUE for gill nets was'due to unusually i high catches of Atlantic herring and pollock (NAI 1981e). -' Atlantic herring ranked first in gill not collections during every ! year sampled, comprising from 26 to 82 percent of the total annual catch and averaging 63 percent for all years combined (Table 3.2.2-3). The percent 140 3
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d 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, and all stations combined 1976-1988. '
Seabrook Baseline Report,1988. 4 r, e., y p, m.,- ,,rw, , ,..,--s --w.. ,w.3 : -- g 9 ,.,.,-~~.~,,..-,-y
,3..,rr,-..-. , ,.-r '~ ~ ~ - - . + 4 [' '- ,,,y _ _ _ _ _ _ , _ . . _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ , . __
TABLE 3.2.2-3. PERGIff CXRFO5TICII BY YEAR AIS ALL YEARS CINEDED FOR TME TEN HOST -aarr SPECIES Bt GILL IET Safft25 DURING 1976 THROUGIf 1988 AT STATICIES G1, GZ AND G3 COFBINED. SEABROOK BASELDE ItEPORT,1988. t PEltCENT CtMPOSITION ALL YEAR 5 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 ONSDED Atlantic herring 53 48 74 80 82 45 63 48 26 26 34 52 33 ' 43 Atlantic whiting 17 21 2 4 6 5 7 1 5' 1 5 1 1 8 Blueback herring 5 11 14 2 2 2- 10 11 9 10 15 16 II 8 , Pollock 6 3 1 2 5 18 3 13 to' 22 18 6 13 6 Atlantic mackerel - 12 7 '2 2 2- ' 14 5 5 6' 10 3 7 22 5 Alewife '1 2 2 <3 <1 2 2 5 5 6 4 2 6. 2 Atlantic menhaden <1 3 <1 2 1 <1 1 6 5 4 4 2 1 2 Hake species
- 2 2 1 1 <1 4 7 2 1 '1 2 <1 5- 1 Rainbow smelt 1 1 1 1 <1' <1 <1 1 6 2 4 3 1 1 Atlantic cod -1
~
1 <1 l' <1 <1 2 2 3 1 2 2 2 1 Other species 2 <1 2 4 <1 8 6 .7 18 16 13 4 5 4 Number of other species. (10) (16) (14) (13) (13) (19) (21) (18) (20) (14). (14) 19 ) ' '(10) (38)
" includes red, white and spotted hake c .- ..,%.. ..,.~.,, -y ,.w- , , sa -w, +- ,w*-. . , . w
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cal in percent composition to Atlantic herring in the off-bottom nets (NAI 1989). 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 species that 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 ,~ :< ace and off-bottom gill net collections, Atlantic herring and Atlantic mackerel were f more abundant in surface nets than in off-bottom nets. .Blueback herring were more abundant in surface nets, least abundant in mid-water nets, and inter-mediate in abundance in off-bottom nets. Atlantic whiting, pollock, alewife and rainbow smelt were most abundant in bottom nets. In 1988, for those dates when all three nets were fished, Atlantic whiting and Atlantic mackerel were most abundant in the mid-water nets and least abundant in the off-bottom nets. Since all three nets were fished only three times during the year and since surface nets generally showed a higher abundance than off-bottom nets throughout the rest of the year, the higher mid-water not ebundance is probably due to chance. Temporal Patterns in the Estuarine Community 2 er. Catch per unit of effort for seins 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 1988 (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 cach year (Table 3.2.2-7). The percent contribution of silversides to the total annual seine catch ranged from 47 to 88 percent annually. Atlantic silverside contributed 52 percent of the total annual catch in 1988, somewhat lower than the average for all years combined (67%). Ninespine stickleback, the second most abundant species, accounted for 37 percent of the catch from 147
- s. - i
~;
-b TABLE 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 BOTTON NETS WERE SAMPLED, 1980.THROUGH 1988. SEA, BROOK BASELINE REPORT, 1988.
CATCH PER UNIT EFFORT ., : SPECIES SURFACE HID-DEPTH BOTTOH; Atlantic horring= 7.0 3.8 2.5 h Atlantic whiting 0.2 0.7 0.8 Atlantic mackerel 1.0 0.8 0.6 L Pollock 0.2 0.1 l'.1 Alewife *
<0.1 <0.1 0.2 Blueback herring 1.0 0.4 0.6 Atlantic menhaden 0.6 0.8 0.2 Rainbow smelt <0.1 <0.1- 0.1-number por one 24-hour set of one net (surf ace, mid-depth or bottom)'
I i
. l.
I i i 148
l l j i t-TABLE 3.2.2-4. PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES I COLIECTED IN GILL NETS, ALL YEARS AND DEPTHS COMBINED (1976-1988). SEABROOK. BASELINE REPORT, 1988. l l PERCENT COMPOSITION SPECIES G1 G2 G3 - 4 s Atlantic herring 61 69 58 Atlantic whiting 8 6 9- , Blueback herring 6 6 10 ; Atlantic mackerel 5 4 6 Pollock 6 5 6 i Hake species a 2 1 1 , Atlantic menhaden 2 1 2 Alewife 2 2 2 i Rainbow smelt 1 1 1 Longhorn sculpin 1 l' <1 Atlantic cod 1 1 1 Bluefish 1 1 <1 All other species 2 2 3 ; Number of other species (26) (29) (25)-
" includes red, white and spotted hakes i
4 i 4 145
R TABLE-3.2.2-5. PERCENT COMPOSITION OF DOMINANT GILL NET SPECIES-ACCORDING TO DEPTH (SURFACE AND OFF-BOTT0H),~ ALL YEARS-COMBINED (1976-1988). SEABROOK BASELINE REPORT, 1988. t PERCENT COMPOSITION SPECIES SURFACE' 0FF-BOTTOM Atlantic herring 69 55-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 1 a Hake species -<1 3 i Other species ~2 8
" includes red, white, and spotted hakes !
-i L
l. l l 146
cont ribution 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,-
- 1986, and 1988 (26, 26 34 and 33%, respectively). During all other years,.
Atlantic herring ranged from 44 to 63% of the total annual catch. In 1988 I the percent of total annual catch for Atlantic herring (33%) decreased j substantially from the 1987 percentage (52%) and was half the 13 year average. [ l (63%). Atlantic whiting, blueback herring, pollock, and Atlantic mackerel collectively comprised 27. percent of the gill net catch for all. years.com-bined. These taxa were fairly consistently ranked among the top five domi-nant taxa during the 13-year period. Atlantic mackerel, which ranked second in percent comporition for 1988, was 22 percent of the total annual catch, ; the highest level during the 13 year period. Blueback herring, which ranked-second in 1987, decreased to 11 percent of the gill not catch and ranked , fourth in 1988. Lower ranked taxa (e.g., alewife, Atlantic menhaden, hakes,- 'l rainbow smelt and Atlantic cod) comprised a more important portion of the total annual catch during 1984, 1985 and 1986 when catch' abundances were l below normal and Atlantic herring accounted for-a smaller percentage of the ! l total annual catch. In 1988, these species also comprised a more important l-portion of the total annual catch, with hakes showing the largest increase in l percent composition 'of these five species, increasing from less than one percent to five percent of the total catch. Species richness ranged from 19 l l to.31 species annually and totaled 47 for all years combined. In 1988,
. species richness was 20, one of the lower numbers in the past 13 years . ;
(1976-1988). No long-term trend of increasing or decreasing species richness w:s evident. j 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 surka samples, while Atlantic herring were more numerous in winter catches. In 1988, Atlantic mackerel were also caught in October and Novem- q bar, usually characterized as " winter" months. However, the number of fish 143
r
)
i -caught atlthis time was only half the, number # caught during the " summer" > months. Blueback herring and pollock sho*ed inconsistent seasonal differen-ces in abundance from 1976 through 1988. spatial Patterns in the Pelanic Fish' Community
~
fr Mean annual catch per unit of. effort'at the three gill net Stations G1,'G2 and G3 showed similar. fluctuations across years (Figure 3.2.2-2). Mean annual CPUE peaked in 1980 for all stations combined. This psak was l more evident at Stations G2 and G3 than at' Station G1. CPUE for 1978 at G1 i was slightly higher than the 1980 value at G1. Percent composition for the I dominant species in gill not collections was similar'among stations (Table 3.2.2-4). Atlantic herring was the dominant species at each gill not sta-tion, accounting for.58 to 69 percent of the total catch for all years combined. Blueback herring composed 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 (Table 3.2.2-5). 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 composed a larger percent i of the catch in the off-bottom nets. Atlantic menhaden and alewives accoun-- ted for a similcr percentage in both surface and off-bottom nets. Trends in 1988 were similar to those encountered during the past twelve years,.except for two species. Percent composition for Atlantic mackerel was only slightly-less than Atlantic herring in the surface nets and pollock was almost identi-144 i
J' 700 -
---- ' STAT 10N S1
-.... STATION S2 600 - :
- - - - - - STATION S3 2 >- :; Al.LSTATIONS CX)MONED et 500-O .
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us : . t- Mn- : z -
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IM - s s' .,:. - s .... v.'.~~. . o . . . . . . .. . , , , 76 ' 77. 78 79 80 81 82 83 84 87 88 YEAR' L t
, Figure 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 1976-1984,1987 and 1988.
Seabrook Baseline Report,1988.' O e e w .+ nn ,m n- -,y,,, w m-+- n( w- amv, --m<-r- n-y -_,__n__ _ _ _ _ _ _ _ _ _ _ _ _ ,,_ .n ,,,, y ,-.n-
TABLE 3.2.2-7. PERMIET CENEPG51TItNE BY YEAR FOR THE TEft WOST ASINe/ JET SPECIES CDt.f.ECTED IN BEAct SEIBE5 DURING 1976 THROtfligt 1988 IENCLISING 1985 Age 1986) AT STATIONS 51, 52 Ale 53 ONSIDED. SEABIt00K BASELIBE REPOIrr,1988. ;j Pelt Itr CINfPOSITI0ft ALL YEAlt5 1976 1977 1978 1979 1980 1981 1982 1983 1984 1987 1988 CENBIDED Atlantic silverside 73 55 75 60 48 88 57 47 48 56 52 67 Fondulos species
- 15 23 5 3 4 2 10 8 7 3 4 8 Pollock 1 <1 1 8 '21' <1 7 5 2 1 <1 4-Alewife <1 1 <1 18 <1 <1 C1 1 1 <1 0 3 Rainbow smelt 4 5 <1 5 <1 2 5 4 9 8 <1 3 American sand lance 2 9 8 <1 <1 .<1 8 2 <1 0 Z 3 Atlantic herring <1 <1 5 1 4 .'4 <1 7 8 2 <1 2 Minespine sticklebeck 1 4 1' <3 <1' 1 2 7 16 22 37 3 Winter flounder 1 2 2 2 3 1 6 3 3 .2' 1 2 Blueback herring <1 <1 1 1 <1 <1 <1 14 -<1- 0 1 2 Other species 2 <1 - 1 1 <1 1 .4 3 6 4 t 2 Blumoer of other species III) (17) . (14) (12)' 19) (121 (12) '113) (14) .(12) 17) (34)
' includes mum cmi hogs and striped killifish 4
,.iy ,e.g ,
.a - _. .
3,, .. 3: - y - , . , , -
...,,y-. .-yg ., c'., ,,.m.
1 beach seines in 1988. This species has been steadily increasing in percent l l couposition since 1980 when it accounted for less than one percent of the total catch. Also important numerically were Fundulus species (primarily mummichog), which consistently accounted for more than one percent of the catch (1-23% annually). This species ranked among the top five dominant taxa in all years and ranked third in percent composition in 1988. Many species f collected in seines fluctuated from year to year in their ranking and often j comprised less than 1% of the total annual catch. The total number of species collected per year ranged from 17 in 1988 to 27 in 1977. Data for the estuarine fish community for the years of 1985 and 1986 were not included i 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), i Seasonal.ity 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 s cimilar seasonal changes in their fish assemblages. Catches in the spring. were usually characterized by low abundance, and species composition in early cummer was highly variable among years. The most distinct group eas the late summer-fall assemblage, which occurred yearly from. August-November, and in j l which Atlantic silverside was the overwhelming dominant (NAI 1984b). SA atial 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 f 3.2.2-3). During 1982 through 1987, 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 composing 55 and 66% of the total catch (respectively) for all l 151 W
TABLE'3.2.2-8. PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN BEACH SEINES, ALL YEARS COMBINED, APRIL' THROUGH NOVEMBER (1976-1984, 1987 AND 1988). SEADROOK l BASELINE REPORT, 1988.
'l PERCENT COMPOSITION SPECIES S1 S2 S3 Atlantic silverside 65 55 77 ,
Fundulus species" 13 15 _ <1 i American sand' lance 3 3 2 Blueback herring 6 <1 1-Ninespino stickleback 5 2 3 ; Atlantic herring 2 5 1 Winter flounder 1 1 3 Pollock 1 6 5 Gasterosteus species 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). 1. a includes mummicho8 and striped killifish includes threespine and blackspotted sticklebacks l l l' 152
l i I I years combined and rundulus sp. composing 13% and 15%, respectively. These stations were distinguished from each other and from Station S3 by a rela-tively high proportion of blueback herring at Station S1 (6%) and alewife at j Station S2 (10%). Atlantic silverside comprised a larger percentage of the catch at Station S3 (77%) than at Stations S1 and S2, and mummichogs ac-l l counted for a much smaller percentage (<1%). Because of its proximity to the harbor mouth, salinity readinge were higher at Station S3 than at SI-and S2 l (NAI 1981b). 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 S1 or S2 (1% for each s ta t. ion) . Station S3 was also distinguished by a higher species richness (37) than at S2 (31) and S1 (34). In 1988, percent composition for Atlantic silversides and ninospine stickleback were virtually identical for Stations S1 and S2 (NAI 1989). This was due to the large number of ninespine stickle-backs caught during 1988 (1,088), the majority were collected at Si and S2, t I 3.2.2.2 Selected Species i l 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 l commercial or sport fisheries. The nine species selected and their primary collection methods were: l 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 153 b
> Y ... l y
i. Comparison of yearly mean catches per unit of effort revealed trends in population size, while_ comparison of monthly mean catches per unit of effort provided additional information on seasonal cycles. Seasonal and annual _ variability were then'used to axamine spatial and temporal diffsrences for each 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 1984 Baseline Report (NAI 1985b). Pelagic Species-Atlantic lierring [ Atlantic herring were typically collected in high numbers during the spring and fall (Figure 3.2.2-4), with gill not CPUE values greatest March through May and October through December. In 1988, monthly catches were similar.to the overall mean except in March when CPUE was higher than the overall mean and in April and September when CPUE was lower than the overall mean. No fish were caught during the months of January and February. Annual geometric mean CPUE of Atlantic herring rose from 1976 (3'.~1 fish / net) through 1978 (4.5 fish /not) and then generally declined to the lowest levels observed during the program-(0.5 in 1984 and-1985; Table 3.2'.2-9). Annual mean CPUE increased slightly in 1986 and 1987 (0.6 and 1.0 respectively) but L then decreased again_in 1988 (0.7). Values for the past eight years.were-below the , aver. age mean,for all years (1.6). A one-way analysis of variance
~n . .r .
showed highly significant differences in the'y's'arly log-transformed mean CPUE (Table 3.2.2-10). The Waller-Duncan K-ratio t-test'for multiple comparison showed that 1978, the year with the_ largest CPUE, was significantly different from 1984-1988. 154
\
4
o J j Atlantic Herring 1.4- . ovEnAu.MEAN l 1.2 - .....i I w .. l 1.0 - -
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l . 0.0 e i e i i e i a i i JAN FEB MAR APR MAY- JUN , JUL AUG SEP OCT NOV . DEC ! MONTH E Pollock
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... .. Iges i O
ww 3
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t.. O.0 i i e i i i e i e i e i JAN FEB . MAR APR MAY JUN JUL AUG SEP OCT NOV.DEC i l MONTH Figure 3.2.2-4 Mean and 95% confidence limits over all years and 1988 values, by m wh, for log (x+1) transfonned catch per unit effort (one 24.hr. set) for Atlai.c.c herring and pollock at combined gill net Stations G1, G2 and G3 from 1976-1988. Seabrook Baseline Report,1988, i 155 11.. a
i TABEI 3.2.2-9. 4'am8a' WERETRIC IEAE DUE FOR ELECTED FIFISt SPrm. SEABROCK RN TIE REPORT,1988. ; TEAe OggrEIEst! - SEAN SWre DrfEB9at SPfrIES STATICIf 1974 3977 3978 1984 1980 19e! 1982 19e3 1984 1995 1986 - 1987 390s ALL TEAe5 8.eIES eppte ' Ngater T3 3.27 3.13 2.82 2.53 5.32 4.43 4.39 3.39 2.73 3.24 4.68 4.99 4.43 3.40 3.20 4.e5 ' floender 72 3.79 4.57 7.18 8.9e 17.49 37.30 9.55 7.72 5.50 5 45 3.71 4.3t 4.36 4.93 5.s7 8.15 73 3.32 1.72 3.20 2.08 5.13 4.11 E.75 2.52 2.26 1.as - '2.56 4.47 2.99 t.se t.25 3.ee 73-73 1.94 3.04 4.es 3.74 7.95 7.et 4.97 3.96 3.28 2.86 3.44 4.75, 3.96 4.e7 3.45 4.53 s3-33 1.54 f.9e 2.34 3.e3 4.43 f.3e f.=7 1.44 : 2.u n5* ro* e.e9 e.75 2.nz 1.M t.51 Te11eetail 73 33.50 26.34 30.as 33.34 44.88 40.47 22.13 to.e3 35.73 14.82 34.53 13.36 16.49 22.18 19.e9 34.73 fleender T2 4.23 t.5e 1.78 4.75 7.05 4.67 5.2e f.62 3.03 2.92 ' 3.e3 2.42 2.23 3.30 2.52 3.7e T3 20.57 - 32.50 13.12 21.82 27.4e 17.9e '2e.31 8.27 7.46 a.4e 4.33 7.53 8.45 31.44 10.4e 13.e1 73-73 34.71 9.98 8.23 15.53 20.97 15.46 30.79 a.25 5.45 - 7.44 ' 5.72 6.9 7.99 9.93 a.93 10.se Make species 73 6.77 7.57 6.63 3.02 4.49 7.27 6.43 3.4e 3.63 3.29 4.39 3.22 4.20 ' 4.79 3.4e 6.35 T2 3.91 3.es 3.17 3.07 f.11 3.6s 2.32 3.39 E.40 1.03 2.36 3.30 2.57 2.04 1.Se 2.58 T3 4.32 4.4e - 5.50 3.49 3.83 S.85 5.93 3.43 3.57 3.43 3.24 3.69 2.e5 4.30 3.De 5.53 73-73 3.% '5.39 4.92 2.55 3.35 6.25 4.55 2.95 3.15 2.54 3.42 2.80 3.05 3.64 2.87 4.55
=!
Atlantic eed 71 1.83 3.26 3.77 4.94 4.42 4.3e 3.96 3.9e E.It e.94 1.03 2.16 3.92. ' Z.52 . 2.09 - 2.9e H T2 0.33 0.30 3.3e 2.00 1.47 1.50 3.75 e.31 c.4e e.it e.55 9.73 0.43 e.94 9.44 1.es T3 3.87 3.47 9.M '6.29 :8.43 5.9s 4.67 4.29 . 3.33 0.90 3.55 3.59 e.98 4 21 3.46 5.09 [ T3-73 1.48 0.93 3.91 - 3.80 4.05 3.52 3.26 3.22 1.7e 0.61 0.99 3.94 E.43 2.24 1.9e 2.or mainhoe smelt 73 1.se 0.71 3.67 1.23 1.90 1.30 0.92 ,. 1.41 c.39 c.3e e.43 2.30 2.29 1.17 9.et 1.41 : 72 2.26 8.94 '4.63 1.75 1.6e 1.48 1.21 - 2.99 .1.49 c.44 . 1.M 3.28 4.7e 2.02 1.45 . 2.75 T3 1.59 e.74 1.15 1.e7 0.se 4.44 e.72 0.37 ' O.4e 0.37 e.30 1.93 1.44 0.18 9.52 1.09 T3-73 3.90 . c.79 t.19 1.33 1.12 - 3.20 'O.94 3.17 8.96 0.43 c.66 1.97 2.33 ' 1.25 0.89 3.44 53-33 1.06 c.47 e.99 1.05 0.05 e.72 0.7e 0.59 1.36 M5 2D - e.Se e.es 9.53 0.32 0.77 Attentic C3-83 ' 3.07 ' 3.32 4.53 2.22 3.54 1.4e ' 2.41
- 1.53 0.53 0.47 9.62 2.95 9.49 1.40 3.22 2.05 berrine
'1 Attentic S3-83 0.54 e.48 0.2e e.12 0.33 f.47 e.2% 0.32 0.17 c.24 . c.13 e.22 0.53 9.3e . 9.22 , 0.39 eacherel Pollock G3-C3 8.32 - - e.34 ._9.13 . e.17 . 0.01 0.7% - 0.17 0.54 9.34 0.43 0.57 e.te e.42 e.39 0.30 . e es Atlantic - $343 24.37 13.47 23.5e 22.34 36.05 S.32 7.30 silverside 29.97 5.00 9.78 3t5 2D 5.31 12.49 7.34 /20.82~~ .!
al UTTEe 1RAHL 179 meno catch pee tee per meath at each stettee and eene et all stettees. Sill SET IG p mean estch per 24 heer set af either leoel geerface er betten t per month, e meno for all stations. SEDES ES S mema entch per heel per meethe a mens for all statieas. . . .* hl Otter Troel (T b mean of ISS menthes Gill IIst (Cl mean of 343 esothes Seises IS3 meen et se meethe. c B M5 e met mampled d l ID e Insuff acaent date for campartoon with previsee years G April .3eme est semptedt '
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TABLE 3.2.2-10. RESUt.TS OF INE-ItAY ANALYSIS OF YARIAMM APEBIG YEAlt5 0F LOG f x+1) TRAM 5FOIBED CA10E PER Ulf17 EFFORT FOR SELECTED FINFISIt SPECIES FOR ALL CILL IET STATI0 pts CINEDEED DURING 1976-1988.' SEABit00K maw, Tw IEPORT,1988. 50tMICE OF SPECIES VARIATIOft df SS F PfULTIPLE CXNIPARISONS Atlantic herring Years It 5.58 2.82 " 78 80 77 76 79 83 82 81 87 88 86 84 85 142 23.42 Total 154 29.00 Atlantic mackerel Years - It ' O.35 0.86 Error 14Z 4.74 Total 154 5.09 Pollock . Years 12 0.63 1.95* 80 81 86 83. 85 88 84 77 76 87- 82 79 78 c- Error 142 3.80 'i t.n w Total 154 4.42 MS = not significant ip > 0.05) -
* = significant 13.05 2 p > 3.01)
** = highly significant 10.07 2 p > 0.001)
- *** = very highly significaet er S 0.001) l l
i l l i i I I I l
.._.a_ _ ._. . _ < . - _ . _ _ _ _ - - . - . - ~ < - ~ ~ - . - - - 2- :-~-<-~~--b- C-- - - - - - - ~- - - ~ ' '
- b Pollock t
Pollock gill net catches were highest during late spring and late ; fall, and lowest during winter (Figure 3.2.2-4). The.high catches in the-spring and late fall reflected the inshore-offshore movement pollock undergo each year. 'CPUE for August and October in 1988 were higher than_the overall' mean CPUE and values for December were lower than normal. Annual'mean CPUE (all stations' combined) for pollock varied from 0.1 to 0.8 fish / net and i averaged 0.4 fish /not over all years (Table 3.2.2-9). The 1988 mean CPUE of 0.4 fish / net was average for the study period. A one-way analysis of vari- [ ance showed's significant- difference in the log-transformed CPUE among years 4 (Table.3.2.2-10). Waller-Duncan's multiple comparison revealed that 1987, > 1982, 1979, and 1978, the years with the lowest CPUE, were'significantly { dif ferent from 1980, the year with the highes,t CPUE. , F Atlantic Hackerel Atlantic mackerol were present in gill' net collections primarily from June to November with low or zero CPUE December through May (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:Novem- i ber. In' 1988. CPUE for the months of June, August, October, November, and-December were'all above the overall mean, reflecting the greater percent composition of mackerel in the 1988 gill nets'(Table 3.~2.2-3). Catches for mackerel were variable over the years, with mean CPUE' ranging from 0.1 to 0.6 fish / net, and averaging 0.3 fjsh/ net (Table 3.2.2-9). In 1988, CPUE as 0.5
' fish / net, the second highest value during the 13-year study. The one-way analysis of variance showed no significant differences among yearly means of -
log-transformed data (Table 3.2.2-10). l l I 158
\ \ \ -
Atlantic Mackerel : ll 1.0 - s > 0.8 - !* OYERAU.MEAN ,
... .. 1980
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... .. ,see j 0.8 -
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00 . . . . . . . . . . . . . JAN FEB MAR APR MAY JUN jut. AUG SEP OCT NOV DEC MONTH . k Figure 3.2.2 5. Mean and 95% confidence limits over all years and.1988 values, by month, ' for log (x+1) transformed catch per unit effort (one 24-hr. set for gill nets, one .i 10-min, tow for oter trawl) for Atlantic mackerel at combined gill net Stations . l' G1, G2 and G3 and Atlantic cod at otter trawl Station T1,19761988. Seabrook Baseline Report,1988. 159
~ , , , , -
~v..
o i Demersal Species j i Atlantic Cod Atlantic cod were usually present in otter trawl catches throughout the year, with the highest catch per unit of ef fort (CPUE) in April and May [ and lowest CPUE in July through October-(Figure 3.2.2-5). The 1988 monthly.
- t
~ CPUE at T1 followed the same general pattern as in other years except for the months of _ March, Hay, August, and November when CPUE was below the mean.
l_ 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.1985b).. The annual i mean CPUE (geometric mean averaged over'the three stations) for cod rose from 3 1 0.9 fish / tow in 1977 to greater than 3.7 fish / tow from 1978 through 1980 . l (Tabin 3.2.2-9). Hean CPUE gradually declined from.1981 through 1985, with the lowest level recorded during 1965 (0.6 fish / tow). 'However, mean CPUE increased in 1986,- 1987 and.1988 (1.0, 1.9 and 2.6 fish / tow,~respectively), 4 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 T1 from May through November, and in low numbers from December through April (Figure 3.2.2-6). Hake CPUE increased slowly in March through May, reaching a peak in June through October and then decreased through the winter months. In 1988, mean CPUE followed this general trend; however,' the catch in December was much higher than usual and catches from May through August were lower than the mean CPUE for all years. Annual mean CPUE (all' 1 l I 160
TABLE 3.2.2-11. RESULTS OF OBE-9tAY AftALYSIS OF YARIANCE ABENG YEAltS OF LDC f x*11 TRAlt5FOWED CATCN PER tlIIIT EFFORT FOR SEIECTED FIFISIt SPECIES AT OTTER TRAlfL STAT 10ft T1 DURING 1976-1988. SEABit00K BASELI9E ItEPORT.1988. 50tMICE OF SPECIES VARIATIOpt df SS F MULTIPLE CINIPARISOptS Winter flounder Years 12 2.45 4.39 81 80 ST 88 86 82 83 85 77 78 M 79 76 Error. 143 7.21 i Total 155 9.86 i Yellowtail floonder Years 12 4.38 6.24 80 81 '79 76 77- 82 78 83 88 84 85 86 87 Error 143 8.IS Total 155 12.73 w e l
~
Makes Years 12 2.01 0.48 j Error 143 50.22 Total 155 52.22 ' www Atlantic cod Years 12 4.02 3.25 80 81 79 83 82 78 87 .. 84 88 76 77 86 85 Error 143 14.76 Total 155 18.78 Rainbow smelt Years 12 2.06 0.65 Error 143 37.83 Total 155 39.89 MS = not significant ty > 0.059
* = significant t 0.051 p > 0.011.
*e = hiehly significant 8 0.01 2 y > 0.001)
*** = very highly significant t p 5 0.001)
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- JUL AVG SEP OCT NOV DEC l
MONTH Yellowtail Flounder l 1.8 - 1.6 - " - fu f
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'5'.5** OVEMLL MEAN
':- 0.6- ... .. 1ees a~;3 '
o.4 - o.2 - 00 . . . .i . . . . . . . . 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 1988 values, by month, for log (x+1) transfonnet. catch per unit effort (one 10-min. tow) for hakes and yellowtail flounder at otter trawl Station TI, 1976 1988. Seabrook Baseline Report,1988. 9 162
three stations combined) ranged from 6.2 fish / tow in 1981 to 2.5 fish / tow in 1985, averaging 3.6 fish / tow overall (Table 3.2.2-9). In 1988, mean CPUE (3.1 fish / tow) was lower than the 13-year mean. The results of a one-way analysis of variance showed no significant differences in catch among years , (Table 3.2.2-11). ; Yellowtail Flounder Yellowtail flounder were collected year round in otter trawls at Station T1 (Figure 3.2.2-6), with monthly CPUE varying very little throughout-- % 3 the year. In 1988, CPUE for yellowtail was below the mean CPUE for January - through June and above the mean CPUE for' August and September. Seasonal differences were unimportant at Station T3 (NA1 1986b). Analysis of length-frequency data from previous years showed that while fish of all ages were collected, the majority were young-of-the-year fish (<18 cm). These fish were most abundant during November through March. Annual mean CPUE (all three stations combined) ranged from 21.0 fish / tow in 1980 to 5.7 fish / tow in 1984 and 1986. In 1988, CPUE increased slightly (8.0 fish / tow) but was still below the over-all year mean of 9.8 fish / tow (Table 3.2.2-9). Mean CPUE'was greatest at Station T1 (22.2 fish / tow), intermediate at Station T3 (11.6 , fish / tow) and lowest at Station T2 (2.5 fish / tow). The one-way analysis of variance among years was very highly significant, and Waller-Duncan's multi-ple comparison of yearly means showed six overlapping groups with the 1984-1988 CPUE significantly lower than the CPUE for 1976-1977 and 1979-1981 (Table 3.2.2-10). Demersal and Estuarine Species Winter Flounder Winter flounder were present in otter trawl collections year-round, though not always at all tnree stations (NA1 1988b). No distinct seasonal trend was apparent at Station T1, except mean CPUE was highest in May through 163
N k August (Figure 3.2.2-7). In~1988, CPUE for January was well below the overall mean, while CPUE for April through July,, September and December were. ! all higher.than the overall mean. Annual mean CPUE (all three stations combined) increased from a low of 1.9 fish / tow in 1976 to 8.0 fish / tow in 1980, averaging 4.1 fish / tow over the 13-year period (Table 3.2.2-9). Annual mean CPUE declined from 1982-through 1985 but was about average over the past E three years, ranging from 3.6 to 4.8 fish / tow. Mean CPUE values were highest- ! at T2 (6.9 fash/ tow) followed by Station T1 (3.6 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
=r catches showed 1976 was significantly differers from 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 1988, monthly mean CPUE was much lower than
-average for all months except April, September, and November.- These low .
values contributed to the record low annual mean CPUE of 0.8 fish per tow in l 1988. Annual mean CPUE (all three otations combined) ranged from 0.8 fish /- tow in 1988 to 4.4 fish / tow in 1980, with an average of 2.1 fish / tow (Table . v 3.2.2-9). A one-way analysis of variance among years was very highly signi-ficnnt, and the multiple comparisons of yearly catches showed 1978 and 1988 to be significantly lower than all'other 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. 3 i i- s Rainbow smelt Rainbow smelt were collected in otter trawls primarily during December through March (Figure 3.2.2-8). In 1988, monthly mean CPUE followed this same pattern except catches in February, March, and December were higher l
-than normal. Annual mean CPUE (all three stations combined) ranged from 2.3 fish / tow in 1988 to 0.4 fish / tow in 1985, averaging 1.2 fish / tow overall 164 1 1
1
i i l Winter Flounder (trawls) l t 1.. - 1 2.2 oneuim ;
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o.s - y .. g; a 0.2 - 0.0 , , , , , , , , , , , , ! JAN FEB MAR APR MAY JUN' JUL MIA SEP OCT f(N CEC l , MONTH i Winter Flounder (seines) 1.0 - OVERALL MEAN
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V o.0 -- , , , , , , , , APR MAY JUN JUL AUG - SEP OCT NOV' MONTH i Figure 3.2.2 7. Mean and 95% confidence limits over all years. and 1988 values, by month, for log (x+1) transformed catch Ar unit effort (one 10-min, tow for otter ; trawls and one haul for beach se nes) for winter flounder at otter trawl Station Tl 19761988 and combined beach seine Stations S1, S2 and S319761984, 1967 and1988. Seabrook Baseline Report,1988, i 165 3
,- p , , - - - - - - - - . 4,-- -, , u. - - - ,
TASt.E 3.2.Z-12. 1ESWE.75 SF SIE-StALY mtv515 OF YARIAIICE ARDIIG YEAft5 (F LDS f x*Il TRefE5FBIWED Ot10t PER WIIIT EF94WT FOR SEIECTED FIFIst SPECIES FOR ALL SEACM SEDE STATICIts QWEBDED DURDIE 1976-1994,1967 AIB 1988. SEA 8300K BASELDE REPORT,1988. SOURCE OF
; SPECIES YARIATICII of SS F Hut.TIPtZ C2pEPalmsm Ninter floomter Yeers 30 1.91 4.53 80 79 77 82 81 78 Error 77 94 76 83 87 88 3.24 Total 87 5.15 Itainbow smelt Years le 3.95 1.18 g Erro; 77 6.83 e Total 87 7.88 e
Atlantic silversi.ies Years le 4.20 0.40 Error 77 80.33 Total 87 84.53 M5 = not significant tr > 0.06.1
- e significant (0.05 2 r > 0.01)
** = highly significant iS.91 2 y > 9.9013
***
- very highly significent tr $ 9.901) 1
. d i ___ _ _ -. _ m __ __ _ _ _ _ _ _ _ _ _ _.
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o , ,, E o.6 = a f ^ o.4-o.2 - 0.0 , , , , NH MAY JUN JUL AUG SEP OCT NOV MONTH Figure 3.2.2 8.for Mean and 95% log (x+1) transformed confidence catch limits per unit overe ortall(one gears and tow 10 min. 1988 forvalues, otter by month, trawl and one haul for beach seines) for rainbow smelt at otter trawl Station Tl 1976 1988 and combined beach seine Stations S1, S2 and S319761984,1987 and 1988. Seabrook Baseline Report,1988, 1 167 .
i l (Table 3.2.2 9). In.1988, mean CPUE (2.3 fish / tow) rose to its highest value since the study began in 1976. Mean CPUE was greatest at Station T2 (2.0 ) i fish / tow) followed by Station T1 (1.2 fish / tow) and Station T3 (0.8 fish / ' tow). Results of a one way analysis of variance showed no significant f differences in catch among years (Table 3.2.2-11). Rainbow smelt were also prevalent in beach seine collections in the Hampton Seabrook estuary. Historically, monthly CPUE was variable with large catches possible any time during the eight month sampling period except for April (Figure 3.2.2-8). In 1988 fish were only caught in June and August. l Annual mean CPUE (all three stations combined) ranged from <0.1 fish / seine in 1980 to 1.1 fish /scine in 1976 and 1984, averaging 0.5 fish / seine (Table 3.2.2-9). In 1988, mean CPUE decreased from the 1987 value to the second l lowest value during the past thirteen years (0.1 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 S1 (0.1 fish / tows NAI 1989). A one-way analysis of variance of the yearly log transformed CPUE showed no significant difference among years (Table 3.2.2-12), i Estuarine Species > Atlantic Silverside i 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 1988 followed this general pattern, except that values for April were much higher than the overall mean and July, i August, and October were much lower than the overall mean. These low values i are most likely due to the fact that this species tends to move in large schools, and samples are collected only once a month, thus decreasing the i l l 168
Atlantic Silverside
- t. -
- 2.6 - ..
2.4 - .. 2.2 - 2.0 -
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, ' ' . , ,' . . , . . * * , ,l .
y j . 1.6 - o ' E 1.4-I Y' 1.2 - f
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1.0 - OVEML MEM 0.8 -
... .. im o.e -
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i i i , , , , APR MAY JUN JUL AUG SEP OCT NOV MONTH 1 Figure 3.2.2 9, Mean and 95% confidence limits over all years, and 1988 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 St. S2 and S319761964 1987 and 1988. Seabrook Baseline Report,1988. 169 i
, , ,,. .~ , , . - - , , . - . . . . - - . , , . . -
. . - - - .r e. ~ _ , . ,
i l i chances of encountering the fish. The catches were highly variable through-out the years with annual mean CPUE ranging from 5.8 to 24.4 fish / haul and - averaging 12.5 fish / haul over all years (Table 3.2.2-9). The high variabil-ity 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). P l t I
+
l l . 170
i
- APPENDIX TABLE 3.2.1-1. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND l
GEAR JULY 1975 DECEMBER 1988. SEABROOK ' BASELINE REPORT, 1983. l ICHTHYO- ADULT AND JUVE.
, PLANKTON NILE FINFISH TOWS ,
CILL SCIENTIFIC NAME" COMMON NAME" ECUS LARVAE TRAWLS NETS SEINES , t Acipenser oxyrhynchus Atlantic sturgeon R . Alosa aestivalls blueback herring - R C C Alosa mediocris hickory shad - R Alosa pseudoharongus aleutie - 0 0 0 Alosa sap /d/ss/ma American shed - R 0 0 Aloss sp. R - - Amecdytes amer /canus American sand lance A 0 R 0 Anathiches lupus Atlantic volitish R Anchoa hopsetus striped anchovy R > Angt111e rostrata American eel C R Apeltes quadracus fourspine stickleback R Archosargus l probatocephalus sheepshead R Aspidophoroldes monopterygius alligatorfish C 0 Brevoortia tyrannus Atlantic menhaden 0 0 0 R Brorme brosmo cusk 0 0 , Ctrant hippos crevalle Jack R Ccntropristis striata black sea bass R. R Conger oceanicus conger eel R Clupea harengus harengus Atlantic herring C 0 A 0 Cryptacanthodes caculatus wrymouth 0 R Cyclopterus lumpus lumpfish C R R R Enchelyopus cimbrius fourbeard rockling C C 0 yundulut sp.
- mummichog* C Ccdvs vorhua Atlantic cod -
C C 0 R (continued) 171
l P APPENDIX TABLE 3.2.1-1. (Continued) ; ICHTHYO- ADULT AND JUVE-PIANKTON NILE FINFISH TOWS GILL 4 SCIENTIFIC NAME" COHHON NAME" EGGS IARVAE TRAWI.S NETS SEINES Gadus /Melanogrammus Atlantic cod / haddock C - * - Gasterosteus sp.0 stickleback d y y n Glyptocephalus cynoglossus uitch flounder C C 0 , Hemitriptcrus amer /canus sea raven 0 0 0 R i Hipieglossoides platessoldes American plalce C C 0 Hippogicssus , hippoglossus Atlantic halibut R Labridae/4/manda cunner /yeglowtail flounder A - - - - L/manda terrug/nes yellowtail flounder - C A R R Llopsetta putnami smooth flounder R R C L/parls atlant/cus seasnail R C - - Lipar/s cohenf guli snallfish C - - L/ par /s sp.' snallfish' R - 0 tophlus americanus goosoftsh R 0 0 R Luepenus Jampretdeformis E snakeblenny 0 R Lumpenus maculatus daubed shanny R R-Macrozoarces amer /canus ocean pout 0 C R Helanogrammus negle//nus haddock - 0 C R
- en/dla mentdla Atlantic silverside O R A Menticirthus saracills northern kingfish R Nerlucclus bilinearls Atlantic whiting C C C C R 1
(continued) 172
APPENDIX TABLE 3.2.1-1. (Continued) 1 ICHTHYO- ADULT AND JUVE- , PLANKTON NILE FINFISH TOWS GILL ! SCIENTIFIC NAME" CONHON NAME" EGGS IARVAE TRAWLS NETS SEINES ' Kicrogadus toscod Atlantic tomcod R R 0 t Norono americans white perch R j Norone saxat))]s striped bass R R Hugil cephalus Striped mullet R' I Mustelus canis smooth dogfish R , Hyoxocephals senaeus grubby C 0 R 0 Myoxocephalus b oct odecessp/nosus longhorn sculpin C A 0 R Hyowocephalus scorplus shorthorn sculpin 0 0 R R Odontaspis taurus sand tiger R Oncorhynchus kisutch coho salmon R R Osmerus mordax rainbow smelt C C 0 C Parallchthys dentatus summer flounder R Paralichthys oblongus toutspot flounder 0 0 C R Peprllus triacanthus butteriksh 0 0 R 0 R l Petromyron marinus sea lamprey R Y Pholls gunnellus rock gunnel C 0 R R ' 1 Po))achlus virens pollock C C C C 0 Pomatomus saltatrix blueitsh o O Prionotus caro 11nus northern seatobin - - 0 R Prionotus evolans striped searobin - - R Prionotus sp. searobin .0 R - - - Pseudopleuronectes ; americanus winter flounder C C 0 C-rungitius pungitius ninespine stickleback C Raje sp,I skate i C R Salvo galidneri rainbow trout R (continued) l 173
- l i
APPENDIX TABLE 3.2.1 1. (Continued)
- ICHTHYO- ADULT AND JUVE- i PLARKTON NILE FINFISH l TOWS GILL :
I SCIENTIFIC NAME" COMMON NAME" EGGS LARVAE TRAWLS NETS SEINES Salmo trutta brown trout 0 ; Salvellnus fontinalis brook trout R Scomber japonicus chub mackerel R Scorber scombrus Atlantic mackerel , A A R C R Scophthalmus aquosus windowpane C C C R 0 Sebastes sp.3 redfish 0 Sphoeroides maculatus northern puffer R R Squalus acanthias spiny dostish R 0 c Stenotonrus chrysops scup R 0 R Stichaeus punctatus Arctic shanny 0 , Syngnathus fuscus northern pipetish C 0 R 0 Tsutoga onitis tautog - C R Tautogolabrus adspersus cunner - A 0 0 R Torpedo nobillana Atlantic torpedo R l Triglops murray1 moustache sculpin 0 R Ulvaria subbifurcate radiated shanny C 0 Urophycis sp.k k hake A C A 0 C l Footnotes: See next page. 174 : 5
l I APPEND 1X TABLE 3.2.1 1. (Continued) Footnotes:
- " Names are according to Robins et #1. (1M O) unless otherwise noted. Taxa usually identified to a different level r.re not included in this list to avoid ;
duplication (e.g., Gadidae, Enchelyopu:./Urophyc/s, Hyoxocephalus sp., Urophycis . chuss, etc.) b occurrence of each species is indicated by its' relative abundance or frequency of occurrence for each lifestage or gear type: ' A = abundant (210% of total catch over all years) i C = common (occurring in 210% of samples but < 10% of total catch) 0 = occasional (occurring in < 10 and 2 1% of samples) R = rare (occurring in < 1% of samples)
- = not usually identified to this taxonomic level at this lifestage "Predominantly yundulus heteroc11 tis, mummichog, but may include a small number of Fundulus majalls, striped killifish.
d Two species of Casterosteus have been identified from seine samples: C. aculeatus, threespine stickleback; and G. wheatland/, blackspotted stickleback (both occurring commonly).
'Nay also includo a small number of tautog.
I Three species of b/ parts have been identified from trawl samples l L. atlanticus, b. cohen /, and L. Inquillnus (inquiline snailfish). 8 Spelling after Faber (1976), h Previously called silver hake (NA1 1982a); Atlantic whiting was recommended by Kendall and Naplin (19811707). I Four species of Raja have been identified from trawl samples: R. redlata, thorny skate (common); R. erinacea, little skate (common); R. ocellata, winter ' skate (occasional); and R. erlanteria, clearnose skate (rare). d Previously called S. mar /nus. Recently S. siente114 and S. faselatus have also been reported to occur in the northwest Atlantic (Ni 1981a; 1981b). Sebastes in coastal New Hampshire waters are probably S. fasclatus (Dr. Bruce B. Collette, U.S. National Museum, pers, comm. April 1982), but larval descriptions are insufficient to allow distinction among the three specios, b'hreespeciesofurophyc/shavebeenidentifiedfromtrawlsamples: v. chuss, red hake (common); U. tenuls, white hake (common); and v. regla, spotted hake (rare). 175 I
I 3.3 BERTil0S 3.3.1 Estuarine Benthos 3.3.1.1 Physical Environment i 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 llampton !! arbor station is a control station away ' from the influence of the outfall (Figure 4.1 4). Iow tido collections in Brown's River represent the occurrence of the most extreme enviro'nmental conditions of the stations sampled, because the water is less influenced by-tidal influx of sea water. The outfall from the Seebrook Station settling basin naually contained discharge from the station's sewage treatment plant and runoff from rainfall, and its volume usually averaged much less than onn , million gallons per day. During the years of tunnel dewatering from November 1979 through November 1983 (NA1 1988biFigure 3.3.1-1), the outfall became saline, containing mostly offhsore sea water with salinities of approximately 31 ppt. Volume of saline discharge was highest from November 1979 through December 1982, reaching about two million gallons per day. In 1983 it diminished to about 1.5 million gallons per day. Mean monthly salinity at low tide in Brown's River ranged from . 17.5 1 3.3 ppt in March to 25.3 i 1.4 ppt in August during the ten-year study period (Table 3.3.1-1, Figure 3.3.1-1). In 1988, monthly salinities I were outside the 95% confidence limits of the ten-year averages.for five out of 12 months (Figure 3.3.1-1). The annual mean salinity for 1988 was 20.5 ' ppt, only slightly below the average for the study period (Appendix Table 3.3.1-1). Rainfall during 1988 totaled 34.8 inches, the lowest value since 176
6 TABLE 3.3.11. EAN NVPHLY SEAWATER SURFACE TEMPERATURE ('C) AC SALINITY (ppt) TAKEN IN BROWN'S RIVER AC BANPTON RARBOR At H10H AC IN flDE, MAY 1979 . DECEGER 1988. SBABROOK BASELINE REPORT,1988. l
. . I I BROWN'S RIVEk i RANPTON RARBOR I ,
l 3.....................'..........................................I l 1 1 810B I la i B10H I la i i l g...............+...............+...............+...............l ITEMPERATURE I EAN I Cl i NEAN I Cl I NEAN i Cl l EAN I Cl l 1....................+...............+.......+.......+.......+.......+.......I IJAN I 1.21 1.11 1.01 0.71 2.41 0.41 1.01- 0.61 IFEB l 1.51 1.0! 1.91 1.01 2.41 0.81 1,71 0.61 lHAR I 3.8! 0.81 4.81 0.51 3.71 0.51 4.11 0.71 IAPR 1 7.11 0.71 9.61 0.81 6.31 0.81 8.21 0.61 INAY l 13lt 1.61 14.51 0.91 10.11 0.51 12.61 0.71 IJUN I 16.01 1.01 19.31 1.01 13.41 0.71 16.21 0.81 IJUL I 18.21 1,01 21.51 0.91 15.81 0.?! .38.31 0.81 lAUG I 18.81 0.91 20.91 1,31 16.81 0.81 18.71 0.91 ISEP 1 15.91 0.81 18.01 1.01 14.61 0.91 16.21 0.8! IOCT I 12.01 1.01 12.01 1.21 12.11 0.81 12,01 0.91 IWV I 8.11 0.81 7.21 -1,41 9.11 0.71 8.21 1.01 IDEC I 4.71 1.11 2.61 0.81 5.41 0.71 3.81 0.71 i I I BROWN'SRIVER I BANPTONBARBOR I ; I l....................................................................................... I I RICH I la l RICH I IM i l l....................................................................................... ISALINITY l EAN l Cl 1 EAN l Cl i EAN I Cl i EAN I Cl i 1............+...........................................+.......... ..........+..........+..........l IJAN I 31.51 0.91 23.51 2.61 32.11 0.61 28.51 1.71 IFEB ! 29.41 2.31 19.21 3.61 31.61 0.71 27.41 2,51 INAR I 28,81 1.81 17.5! 3.31 31.11 0.91 25.11 2.11 lAPR I 26.71 2.91 17.81 4.01 30.11 1,61 24.61 '3.41 INAY l 29.01 1,51 20.11 2.91 30.01 0.91 26.61 1,71 i IJUN I 29.11 1.71 21.21 2.91 30,41 0.91 27.61 2,11 IJUL I 30.11 1.01 24.01 1.71 31.01 0.51 28.81 0.81 i IAUG l 30.31 0.51 25.31 1,41 31.31 0.41 29.71 0.61 ISEP 1 30.51 1.0! 24.41 2.41 31.51 0.31 29.61 0.91 10CT I 30.51 0.81 23,71 1.31 31.61 0.31 29.31 0.71 INOV l 30.01 1,41 20.61 3.11 31.8) 0.41 28.11 1.41 IDEC 1 30.4! 1,81 20.61 3.61 '31.81 0.61 27.71 2.21 l 177
i Salinity 30 - ;
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5*. 0 , . .... . . - .i i - i i i i JAN FEB MAR APR MAY JUN JUL AUG SEP OCT W DEC MONTH t Temperature : 25 - . i-
,,,, 20 -
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P l " t 15 - / \' t .
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'g 0 i i . . . . - i i ii i JAN FEB MAR APR MAY JUN JUL AUG SEP OCT W OEC ,
MORTH Figure 3.3.1 1. Monthly means and 95% confidence limits for seawater surface temperature and salinity taken at low tide in Brown's River over the entire study period (May 1979 December 1988) and monthly means for 1988. Seabrook Baseline Report,1988. 178 k
- ,a < - . .
, , _ _%,-_., .. . _.. . - . , m
1980, and was well below the 30-year normal (Table 3.3.1-2). In contrast, 1987 rainfall was above average, and the monthly rainfall during April reached a 30-year maximum (National Climatic Data Center 1988), causing flood waters to reach a 10-year high in'many New Hampshire areas. The mean monthly salinity at high tide in Brown's River ranged from 26.7 1 2.9 ppt in April to 31.5 1 0.9 ppt in January during the ten year study period (Table 3.3.1-1). High tido salinity was always higher than low tide salinity due to the influx of more saline water from Hampton Harbor into Brown's River. At the control station in Hampton Harbor, the mean monthly low tide salinity during the ten-year study period ranged from 24.6 1 3.4 , ppt in April to 29.7 i 0.6 ppt in August (Table 3.3.1-1). The mean monthly high tido salinity ranged from 30.0 1 0.9 ppt in May to 32.1 1 0.6 ppt in January, very similar to offshore, coastal salinities. The salinity in Hampton Harbor was always higher than in Brown's River due to its proximity $ to the harbor inlet. At the control station in Hampton Harbor, there was an inverse relationship between annual precipitation and the annual salinity for every year of the study period (NAI 1988b: Figure 3.3.1-2). Brown's River calinity followed the same inverse relationship with precipitation except for 1981 and 1984, which are the years which mark the peak and end of tunnel dewatering which caused an increase in the salinity of the effluent. In 1981, peak volumes of saline effluent were reached and the annual salinity in Brown's River increased 0.4 ppt, while it dropped 1 ppt at the control in Hampton Harbor. In 1984, the effluent returned to a low volume of fresh water, and the annual salinity in Brown's River dropped 1.3 ppt, while it . rcse 0.3 ppt in Hampton llarbor. Since the annual salinity changes were small ' (+0.4 ppt.in 1981 and -1.3 ppt in 1984), it is difficult to differentiate natural variation from the salinity differential caused by tunnel dewatering (NAl 1988b). 179 -
TABLE 3.3.1-2. TOTAL PECIPITATIolt (NATER EetfITAIBFT IN INCMES) BY DIGIFFN AfD YEAR TABLEN AT 1AGAff INTEFMTIoIIAL AIRPOKT, BOSTON, MA FRtNf JAfRfARY 1978 - DECBSER 1988* Ale 30-YEAR IWI9tALS. SEABRooK BASELIIE REPORT,1988. I I YEAR I l I I I I 30-YR I I I I I I I I I I I III-TEAR I Incemt.- I noiseAL g , I 1978 I '1979 1 19eo I 1981 1 19st I 19e3 1 19e* I 19e5 l 19e6 I 1987 I 19e8 IA9ERAGE I g i I I I I I I i 1 1 I I I I I IJAn i 3.991 a.121 *10.551 e.741 c.951 4.691 5.c31 2.311 1.1z1 3.421 7.rst t.5et 4.z58 IFEB I 3.7el 2.878 3.441 c.881 6.651 5.o01 2.661, 7.811 1.83I Z.838 c.721 3.933 3.511 IrtAR I 4.131 2.441 3.031 5.371 c.4zl 2.171 9.72I 2.r91 6.sti 3.4rl 4.271 3.528 3.971 IAPR I 3.731 1.791 3.191 4.368 3.141 3.421 6.861 # 4.43' 1.628 1.59I 9.46l 1.471 3.761 letAY .I 3.521 4.501 4.24I 2.308 1.171 2.5sl z.941 8.771 3.361 1.31I 1.751 r.861 ' 3.zSI
$ IJun I z.9zi 1.531 o.ast 3.osi 1.651 *13.20I 1.071 3.061 3.948 7.74I 2.628 1.291 3.641 IJut. I z.681 '2.481 z.34I 2.zal 3.478 4.22I 1.073 4.431 3.511 3.961 -c.azi 7.628 3.191 lAUG l 3.68l 4.621 5.o2l 1.Ml 1.e4] 2.228 3.28I 1.6el 6.671 3.328 2.931 1.111 3.038 IsEP I 3.41I 1.301 3.41I o.821 2.541 1.578 1.061 1.221 3.ool 1.08I 7.Z91 1.Z91 2.251 locr I 3.361 3.131 3.14I 4.141 3.431 3.191 3.741 5.181 1.65i 3.r71 z.731 1.4el 3.2o1 Inov I 4.z11 + 211 3.298 3.ekt 4.7sl 3.4t1 *a.89I 1.681 6.01I 6.391 3.491 6.57I 4.52I IDEC 'I 4.461 3.631 '1.421 8.978 6.271 1.Z78 4.94l 2.931 1.21l 6.38I = 2.121 1.02l 2.921 lAssRfALI 43.811 37.64l 44.171 29.391 35.711 44.61I 53.60! So.24I 36.591 44.335 45.481 34.781 41.508
" Source Motional Climatic Data Center, 1988. Local climetological data, monthly swumery. ?-__., -
M A ., Federal Building. Astwille, North Carolina. 3 5sormals are based on the 1951-1980 record period. Source, motional Climatie Dete Center, 1988. Iment c1A=etoleyte=1 date, annual summary with comparative data Federal Building Ashville, hrth Caroline.
*ftenth maximum since 1951. Source, National Climatie Data Center,1988.
Mean monthly temperature at low tide in Brown's River ranged from 1.0 1 0.7'C in January to 21.5 1 0.9'C in July during the ten year study period (Table 3.3.1-1, Figure 3.3.1-1). In 1988, average monthly temperatures were within the 95% confidence limits of the ten-year monthly averages (Figure 3.3.1-1). The mean average yearly temperature was 10.6'O for Brown's River in 1988, slightly cooler than the ten year average (Appendix Table 3.3.1-1). In llampton liarbor, average monthly temperatures at low tide ranged from 1.0 1 0.6'C in January to 18.710.9'C in August during the ten year study period (Table 3.3.1-1). }lampton liarbor water at low tide was slightly warmer than lirown's River in November, December, January and colder during the rest of the year. The annual mean low tido temperature in llampton 11 arbor in 1988 was 9.7'C, slightly below the ten-year average of 10.1*C (Appendix Table 3.3.1-1). In 1988, monthly temperatures in Brown's River w2re close to the nine year average (Figure 3,3.1-1), and llampton liarbor temperatures followed the same trend. ; l Sediment Yearly and seasonal differences in sediment collected in 1978-198t Indicated estuarine sodiments were very patchy with spatial vari-cbility often exceeding annual variability (NAI 1985b). Yearly averages at subtidal stations (3 & 9) showed the median grain size was in the fine send range, which was usually poorly sorted with organic carbon ranging from 0.97 to 2.08% (NAI 1985b). The yearly averages for intertidal stations (3MLV cnd 9MLW) showed the median grain size varied from fine sand to silt, which was often very poorly sorted. The percentage of organic carbon was higher than at intertidal stations and ranged from 1.56 to 5.86% (NAI 1985b). S:diment parameters during the 1980 1982 period were apparently within the range of natural variation, and did not noticeably change during the peak dischnrge period, caused by tunnel dewatering. 181
l 1 i 3.3.1.2 Haerofauna i Subtidal and intertidal estuarine benthic communities in Brown's River (St.ations 3 and 3MIM) and Mill Creek (Stations' 9 and 9MIM) were typical for quiet, tidal creeks with fine-grained sediments, where average monthly salinity ranged from 18 ppt to 25 ppt (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 Streblosplo ; benedletl was the most abundant species in the estuary, and comprised between 5 and 19% of the macrofaunal community at each staMon. 011gochaeta and Cap /tella capitata ranked accond and third, respectively, in overall abundance. The clam worm, Nerels d/ vers / color, was very abundant inter-tidally in Brown's River. The soft-shelled clam, Nya arenaria, was also ; present in substantial numbers at all sampling locations (Tabla 3.3.1-3), Total abundance of organisms (number /m') showed year-to year variations that appear to be related to area-wide environmental trends. Subtidal stations in Brown's River (Station 3) and a control station in Mill Creek (Station 9) have highly significant differences in abundances among years, with 1980,1981, _ and 1982 grouping with the years of highest - abundance and 1984, 1986, and 1987 grouping with years of the lowest abun-dance at both stations (Table 3.3.1-4). Differences among years were less pronounced at intertidal stations; however, the 1980 through 1982 period included years of high abundance, and 1987 was the year of lowest abundance at both stations (Table 3.3.1-4). The period of 1980-1982 was the period of lower precipitation, higher salinity and the highest discharge flow from the settling basin into Brown's River. The years 1983 and 1984 were the years of lower salinities, higher precipitation (Table 3.3.1-2), and the highest tem-peratures for the study period (Appendix Table 3.3.1 1). Through 1984, total abundance at all four stations had declined to the lowest values recorded since sampling began. In 1986, the total abundance (2980/m') recovered and was close to the abundance in the pre-outfall period, 1978 and 1979 (3514/m' and 4099/m', respectively; Table 3.3.1-3). In 1987, total abundance reached I . . 182 i
TMBtf 3.3.1-3. PEAff NINOBER OF TAXA AfD THE GEtWETRIC PEAff DDESITT INo./m2) FOR EAct TEAR AfD 09 ERAT 1 YEAks NIIM 95Z (MNF1BEBIE L1ptITS FRENI ESTUARDE STAT 1tBE5 AT BRONN'S RIVER 4 3) AfD fff11 CREEK 19) SArtPLED FRtft 1978 T1tHOUWI 1988 (UCLW1351985). SEABROOK BASELDE HEPORT,1988. 1978 1979 1980 1981 19*2 1983 1984 1986 1987 1988 ALI. Yeasts STATION PEAft LOIER UPPER 90o. of Taxa 3 35 41 38 42 47 32 27 38 33 38 37 34 to 9 26 34 47 44 34 36 21 36 Z1 27 33 29 36 j 3ptUt 28 37 31 38 35 Z8 18 32 23 31 30 27 33 9FtLN 28 35 35 41 3(, 33 21 36 16 29 31 28 34 I ffEAN 29 37 38 41 38 32 ZZ 35 23 31 33 31 34 Total Atendance 3 3170 4416 4978 5340 9331 e 12 % 1182 1198 3472 2999 2183 4119 9 3619 2209 14,767 11,277 4335 *i'*- 620 2819 726 4764 3311 2092 5242 3rtut 4760 6134 5695 6833 80ZZ 2723 2187 5632 17Z7 3936 4236 3233 5550 9Pfut 3120 451Z 6947 1Z 189 11,383 11,151 5131 4203 653 6115 5147 3358 7889 PEAft 3514 4099 7344 8424 7796 4364 1715 Z980 995 4467 3834 3191 4411 Streblospio 3 367 123 193 525 1964 55Z Z39 99 64 550 273 170 439 benedicti 9 106 26 2396 525 81 538 16 161 49 744 166 71 386 3rtut 439 505 1910 928 3584 5Z5 535 1421 316 1306 811 524 1t55 9PIUt 566 434 Sa6 2700 Z354 3Z15 1560 1t99 11 7% 725 352 1492 PEAN 314 163 684 912 925 842 242 415 58 794 404 291 Set Oli techaeta 3 24Z 270 204 651 2189 556 225 95 133 768 M4 214 554 9 16 100 2910 969 1958 1603 162 528 131 27Z 346 177 677 3PIUt 87 186 318 320 350 292 382 968 215 322 291 185 456 9Plut 574 010 1967 861 565 2877 572 742 161 351 664 379 1165 PEAN 119 253 6 71 446 823 931 198 437 157 392 390 298 509 Capite11a capitata 3 II
.3 123 473 889 ZI6 66 73 57 105 let 59 ret 9 238 29 2453 277 291 376 Z8 808 113 1530 271 145 505 3Pfut 17 t? 138 2% 540 208 124 197 26 44 94 56 140 9Pfut 279 45 125 320 276 800 303 234 19 1968 210 124 357 FEAft 60 40 269 318 443 341 91 2Z8 42 299 156 117 207 tcentimmed9
'l
TAD 12 3.3.3-3. tContinued)
- 1978 1979 1990 1981 1982 1983 1996 1986 1987 1988 alt. Yeasts STATICII IEAN IDIER UPPER Mereis diversicolor 3 83 172 158 352 452 45 50 52 43 128 399 74 16e 9 23 29 41 205 41 7 7 43 2 33 23 23 41 -
3Mut 800 1343 1169 1613 975 220 296 987 358 523 631 390 3023 9 nut 370 164 303 241 135 57 533 294 6 29 300 54 177 PEAN 325 383 367 410 223 45 89 143 38 90 113 8% 156 Cau11eriella Sp. B 3 330 221 835 1 2 3 12 9 1 3C. 22 8 58 9 10 40 46 29% 136 35 7 10 3 36 25 II $7 3Mut 106 174 607 3 23 5% 44 255 S7 2** 81 41 342 9Mut 8 298 48 43 2634 278 325 307 3 21 78 29 298 PEAN 42 347 183 17 64 37 34 53 5 54 43 28 47 y* M arenaria 3 49 358 92 383 332 75 31 21 30 12 58 37 91 9 265- 4t7 199 246 348 368 157 34 53 83 348 94 231 3 nut 306 224 26 379 117 103 tt 13 27 12 5t 29 9t snut 300 328 62 400 141 70 86 23 73 39 88 54 143 PEAft 118 265 8% 237 334 98 55 19 42 26 79 62 393 '
" Yearly mean number of taxa = moon of three seesm1 totals twhere seasonal total = total enenber in all five 1/16 m replict.tes combinedI
' b Yearly mean density = meen of three seasonal meses Iwhere seasonal meen = mean of five replicates) All years mean = mean of 30 soesonal means t3 seasons x 30 yearsI i t
- , , ~ . , ,- r -- ~-
. , - ,. y . , , e -, - - ~ , . - - + , - - - , - - - . _ _ _ - _-,
, - + - + . - .
ax-.- a _ - , . . , - - - , - - m. a
'l I
l E . I Il 's a s a a a a a l s = = . a = , e U e 2 8 e $ e Q $
$ l e 8 e 8 G $ 8 e i . . . e e e , :
I, l s. e : e a a
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,i e = : : i e s .
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~~
ggg ___n gyn ~-- a~~ --~ -~ 5ll v ee ne ee ee ee - ee ne ee l,ll
,, g*l s,u s,a, ,,a ,a. w w w w- !!! l, - - 1 i - - 1 I lm_}! i -
o ia b t a I d " j 185
TABEE 3.3.1-4 (Continood) SOURCE 8F STATItSt VARIATION M SS F W.E N 5treblospio benedicti 3 Years 9 4.03 1.91 M5 82 83 88 81 78 M 80 79 86 87 Error 20 4.70 Total 29 8.73 9 Years 9 12.86 1.90 M5 80 88 83 81 M 78 82 87 79 86 Error 20 15.04 Total 29 27.90 3MUt Years 9 2.64 1.22 M5 82 86 88 80 81 86 83 79 78 87 Error 20 4.82 Total 29 7.46 9Mut Years 9 13.55 4.42ee 83 81 - 82 84 86 88 78 80 79 87 e Error 20 4.81 M e Total 29 20.36 Oligochaeta 3 Yeers 9 4.44 2.26 M5 82 88 81 83 79 78 86 88 87 86 Error 20 4.37 Total 29 8.81-9 Years 9 12.20 5.05 s se 83 82 81 86 88 86 87 79 7s Error to 5.37 Total 29 17.57 DK3? Years 9 2.86 0.69 M5 86 86 82 88 81 8e 83 87 79 75 Error 20 6.05 Total ~ 29 7 ,91 9NUC Years 9 2.81 0.65 MS 83 80 81 79 86 78 84 82 88 87 Errer 20 * . 54 Total 29 12.35 tcontinuedI
TABLE 3.3.1-4. (Continued) SOHCE OF STAT 10st VARIAT2006 df SS F MULTIPLE CIBIPARISDN5 Capite11e capitata 3 Yeers 9 7.39 2.22 M5 82 83 83 80 88 86 M 79 87 78 Error to 7.38 Total 29 14.77 9 Years 9 11.19 6.2388* 80 88 86 8% 82 81 78 87 79 M Error to 3.99 Total 29 15.18 DItJ8 Years 9 6.55 3.50** 82 81 83 86 se M 88 79 87 78 Error 20 4.16 Total 29 10.71 w m 9PEJi Yeere 9
" 7.35 4.54e= 88 83 81 M 78 82 86 80 79 87 Error 20 3.60 Total 29 10.94 feeris diversiecler 3 Years 9 3.69 4.88== 82 81 79 80 88 78 Error 86 M 83 87 to 2.05 Total 29 5.74 9 Yeers 9 6.96 3.49e= 81 86 82 80 88 79 78 84 83 87 Error 20 4.43 Total 29 11.38 NEM Yeers 9 3.41 1.33 M5 81 79 80 86 Error 20 82 78 88 M 83 87 5.70 Total 29 9.11 9PEJt Years 9 7.62 3.36** M 81 86 78 79 82 8e 83 88 87 Errer to 5.06 Total 29 12.65 feentiewed)
. - . . . . . . , . . _ _ , . _ _ __.. _ . , ~ .
t TABt.E 3.3.1-4. t Continued ) SotM E Or STATIOpt VARIATIOlt of SS F MtfLTIFLE N M arenerie 3 Yeere 9 4.14 Z.52* 81 79 82 80 83 78 M 87 M 88 ' Error to 3.65 Total 29 7.79 s 9 Years 9 3.22 1.56 M5 79 80 78 81 83 86 82 M 87 86 Error to 4.58 Total 29 7.80 DR.M Years 9 5.95 1.97 M5 79 81 82 78 83 87 88 86 86 88 Error 20 6.70 Total 29 12.64
- c. 9Mut Years 9 4.7% Z.35 MS 81 79 82 78 86 87 83 88 88 g Error 20 4.48 86 Total 29 9.21 Caelleriella sr. 8 3 Years 9 26.90 7.52=== 80 78 79 88 m 86 83 82 87 81 Error 20 7.95 Total Ze 34.85 9 Years 9 9.99 1.31 M5 81 Et 88 79 83 88 86 78 M 37 I Error 20 15.42 Total 29 24.51 DEN Years 9 18.37 2.89* 80 86 as 79 78 87 83 86 82 81 Error 20 7.97 Total 29 18.34 9MUt Yeers 9 21.86 3.12* 82 M 86 79 83 80 81 88 78 87 Error 20 15.54 Total 29 37.38 feontinued)
- , - . . - .- . . . . . _ . . . _....,,..e _ -, . -. . . , _ _ , _ _ _ _ _ _ _ . _ _ _ _ . . . ~ . _ _ - . . .
e TAStf 3.3.1-4. tContinuedi SDWWE OF STAT 10R YARIAT10st df 35 F M CW FARISDIES Spio setene 3 Yemes 9 E.94 1.43 St5 88 87 82 81 M 83 M 88 79 78 Error 29 3.18 Total 29 S.22 9 Years 9 13.24 2.62* 82 88 80 82 86 79 78 83 37 34 Error 20 11.21 Total 29 24.45 Dfut Years 9 4.22 1.34 ft5 86 86 87 79 se 33 78 31 gg gg < Error 29 7.00 Total 29 11.21 es op e 9PUt Years 9 5.46 1.32 pts 81 86 79 78 82 se 38 83 et 37 Error to 9.18 Total 29 14.6
- MS = not significant tr>C.95)
* = significent 10.952y>9.91)
** = highly significant 19.912p>O.901)
*** = very highly significant Ep29.901)
Since the F value is MS, years are .gu M in order of decreasing abondence, and not greeped.
.. . .m -.- - . , , . . _ ,. .. . . , _ _ . _ _ . . _ _. _ . _ _ _ . .
i all time lows at three of the four sttr:!ons (Figures 3.3.1-2, 3). Extremely j low salinities in April, May and Septentier, 1987 may have affected recruit- ! ment rate (NA1 1988b). Total abundances through 1987 showed no significant differences between corresponding subt:!dal and intertidal station pairs (NA1 1988btTable L 3.1-4). In 1988, a yett of ~1ow rainfall and nearly average ! annual salinity, total overall abundance had nearly quadrupled the 1987 all-time low, and a very sharp increase in total abundance occurred at all r four stations (Table 3.3.1-3), reflecting values'similar to those collected early in the program. The mean number of taxa collected annually at all stations com-bined ranged from 16 to 47 during the ten-year study period (Table 3.3.1-3). Annual changes in the number of taxa were generally similar at all four stations for most of the study period. During the 1980-1983 period of relatively high salinities and increased discharge into Brown's River, the pattern did not persist; however, variations were slight and within the range of natural variation (Figures 3.3.1-2, 3.3.1-3). Highly significant dif-ferences were found among all stations except the Brown's River rubtidal station (Table 3.3.1-4). Mean number of taxa collected in 1984 and 1987 ranked among the lowest two or three years of the study period at every station sampled (i.e., both nearfield and " reference" stations). The years 1980, 1981, and usually 1982 ranked among the top five years at every station (Table 3.3.1-4). The seasonal cycle at each of the four stations showed that the highest number of taxa usually occurred in August or Hay, 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. Subtidal stations in Brown's River showed a signiff-cantly higher number of taxa (through 1987) than Hill Creek. However, the I l intertidal stations were not significantly difierent (NAI 198Bb: Table I
- 3.3.1-4).
The annual trend in the number of taxa seems to show a rela-tionship with the mean annual salinity. Decreases in numbers of taxa at i ! I
\
190 j G
Subtidal Station 3 Subtidal Station 3 l 6- Total Abundance 60 - 70 - ) 6- ,, ; 60 - > o ,,
.. .. .. 50 - :
g ,
/
l4 l
,, ( "j/ /Y v 80 "
N t 20 - ' 2- , 10 - 1 , i i , , , ,,,, 0 , ,,,,,,,,, . l 1978 1979 1080 1981 1982 1983 1984 1968 1081 1988 1978197019801981 198219831964198C 19871988 YEAR YEAR Subtidal Station 9 Subtidal Station 9 80 - 6- Total Abundance < ..
.. 70 -
6* '
. 60 - .
l < ' p., 50 - ,, 4- .
" ~~""
g 40 - , , l r s ' 8 g 3-30 - [ . 20 - ,, . , 2- ,
.. 10 -
l i i , s ,,,, 0- , ,,,,,,,,, 19781979 19801981198219831984198819871988 1978 1979 1980 1981 1982 1983 1964 1968 1987 1984 YEAR YEAR Figure 3.3.12. Yearly mean and 95% confidence limits for the log (x+1) density (No./m 2)of macrofauna and number of taxa collected at subtidal estuarine stations sampled three times per year from 1978 through 1988 (excluding 1985), Seabrook Baseline Report,1988, 191
- , - , , , .- ,e.w-- g v-.,,.
i l l i Intertidal Station 3MLW Intertidal Station 3MLW 6- Total bundance 70 -
)
60 - i 6- , )
,, ,. 60 -
.. ,, h ,
" 40 -
l4- .
,, -l\ s / I ,
/\ \
N/ g- ..
.. ": l l20-
- 2- ,
10 - - l 1 i i i . . i i i . . O i , , , . ,,,,, . 1978 107910801981198219831984198810871988 19781970 19801981198219831984198619871986 . i
- YEAR YEAR Intertidal Station 9MLW Intertidal Station 9MLW 6- TotalAbundance 70 -
l . l - 60 - T 6- ,
, 50 ..
l T Y < '- '- 4- r p 40 - j/ , .
~
/g ,.
i $ "
\
l 0 3-
<- 30 -
1 cJ , 20 - m 2- m 10 - , ,, 1 i i i i i i i i , 0 , , , , , ,,,,, 1 1978197910801981198219831084198610871988 19781970 19801981198219831984198610871989 YEAR YEAR ] Figure 3.3.13. Yearly mean and 95% confidence limits for the log (x+1) density
; (No./m 2 ) of macrofauna and number of taxa collected at intertidal estuarine stations sampled three times per yent from 1978 through 1988 (excluding 1985). Seabrook Baseline Report,1988. S 192 i
most stations in 1983 and 1984 coincided with high spring rainfall and low l salinity (NA1 1987b: Tables 3.3.1-1,2). A similar pattern was noted in 1987 l when rainfall in April reached a 30 year high for that month (National 1 Climatic Data Center 1988). In 1988, when rainfall was well below average, the mean taxa at each station showed substantial increases over the 1987 ' lows , at all four stations (Figures 3.3.1-2,3). Streblosplo benodlett is a cosmopolitan opportunistic polychaete (Grassle and Grassle 1974), and one of the first to colonize after a portur-bation 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: Figures 3.3.1-6,7). No significant differences in abundances (through 1987) were found between Brown's River and Hill Creek stations with a paired t-test (NAI 1988b: Table 3.3.1-4). However, intertidal stations had significantly higher abundance than subtidal stations (NAI 1988b: Table 3.3.1-4). No significant differences among years occurred except at the subtidal station in Mill Creek (Table 3.3.1-4). The most consistent trend among stations was that the years 1979, l'984, and 1987 had below average densities. Those years had above average rainf all,~ and one month from each year had a 30-year maximum monthly rainfall (Table 3.3.1-2). The dramatic overall population decrease seen in 1987 was followed by an increase of an order of magnitude in 1988 (Table 3.3.1-3). The class Oligochaeta was very abundant in the estuary. 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. No significant differences in abundances (through 1987) were found between Brown's River and Hill Creek stations with a paired t-test (NAI 1988b: Table 3.3.1-3). No significant differences occurred among years, except at the subtidal station in Hill Creek. When examining the yearly abundance, population fluctuations were not consistent among stations except in 1981, 193 i
L which was a year of relatively high abundance ranking among' the top five and 1978 and 1984 which had relatively low abundance, ranking among the bottom o five.: 1- , L The opportunistic polychaete Cap /tella cap /tata was abundant at. i both intertidal and subtidal stations and no significant differences were found between abundances in Brown's River and Mill Creek through 1987 (NAI. 1988b: Table 3.3.1-4). Highly significant differences were foundi among years s at a11' stations except the subtidal station in Brown's River'(Table 3.3.1-4). ! Following the very low population levels in 1987 at'all stations, populations increased greatly in 1988, particularly in Hill Creek (Figure 3.3.1-4,5 and > Table 3.3.1-3). Cau11erfella sp. B is a polychete that was occasionally abundant in q
- the estuary. Its annual.goometric mean density at all stations ranged from '
5/m' in 1987 to 183/m8 in 1980 (Table 3.3.1-3). It rarely' sustained densi-ties of over 100/m' for more than'three consecutivo years, and in 1987 it.had i annual densities of less than 10-at three of the four estuarine stations (Table 3.3.1-3). In 1988, densities greatly increased in Brown's River,'but- 1 Significant differences among
~
only very slightly increased in Mill Creek. q years occurred at all stations except the subtidal station in Mill. Creek. Relatively low population densities occurred at all.four stations in 1987,. I and 1980 ranked among the top three years at three of the four stations , (Table 3.3.1-4). The clam worm, Nerels diversicolor, is a highly euryhaline species which is common where there is a mixture of fresh and salt water ! (Pettibone 1963). Both intertidal and subtidal stations at Brown's River had significantly higher densities than stations of comparable depth at Hill Creek (NAI 1988b: Table 3.3.1-4). Intertidal stations had higher densities' than subtidal stations (Table 3.3.1-3), as expected,1:ince the species is primarily intertidal (Pettibone 1963). Highly significant differences among ,, years occurred at all stations except the intertidal station in Brown's River, where Nerels is most common (Table 3.3.1-4). Densities of Nerels were-194
^i
- SUBTIDAL STATION 3 SUBTIDAL STATION 3 i s- s
't 1 Nerels Capitella' ;
4 6-l .. 1 .. 7 4- . j
/ Ii ' . . .
l 7
-h!'
Ej l j/ \
/ \
1- a- / l 0-1 l . 1978 1979 1980 198119821983198419861087 1988 f- 1978197919801981 198219831084198619871988 YEAR YEAR f
~t
-\
c SUBTIDAL STATION 9- SUBTIDAL STATION 9 6- 6-Nerels Capitella 4- s-3- . 4- . l
.. . 2 '
" E ..
g s-g
.a 2-
, s. /\ ' .
.a 1-
- y. ,, 2-
[ 0 . . . . .. . 1 . . , , , , , 1978197919f 01981198219831984198619871988 1978197919801981198219831984198610871988 -I YEAR YEAR Figure 3.3.14. Yearly mean and 95% confidence limits for the log (x+1) density of . Nerels diversicolor andCapitella capitata collected at subtidal estuarine stations sampled three times per year from 1978 through 1988 (excluding 1985). Seabroc.i P eline Report,1988. 195
l' i g i L q L . INTERTIDAL STATION 3MLW INTERTlDAL STATION 3MLW - , ,=
- 5. Nerels 6- .
l ,, ,, . Capitella-1 \ 4 , ,, 6-
, 1 3 / '"""-' N 4- -
' ~
O ,,
- g. .
i 8- . .- .. d
/\ N ". ' '
f 1- 2- i 7 .
/
o i , , i . , , , , 1 i i i ,, i 197819791980198;19821983198419881987 1988 1978197919801981 198219831984 198819871988, 1 YEAR YEAR INTERTIDAL STATION 9MLW INTERTIDAL STATION 9MLW - ) 6- 6- '! Nereis Capitella 4- 5-
'; l 3- i ' '
4-2- b ' ' 3-
.J
., J
,\
/, -
1- , ,, I / 2- , t h . . 0 i
, , , , , , , , , 1 , , , , ,. , ,
1978 1979 1980198'.1982'.9831984 198819871988 1978 1979 19801981198219831984198619871988 4 YEAR YEAR Figure 3.3.1-5. Nere Yearlb mean andnnd diversicolor 95% confidence Capitella capitata limits for theatlog collected (x+1) estuarine. intertidal density of stations sampled three times per year from 1978 through 1988 (excluding 1985). Seabrook Baseline Report,1988. 196 1
L* , 1 I i j I lowest in 1987 at all four stations (Figures 3.3.1-4, 5). Tha year 1988 5 ranks among the top two years for highest density at all four stations (Table' 3.3.1-4). Nya arenarla, the soft-shelled clam, has important commercial and recreational value in the study area. When intertidal and subtidal station ! pairs in Brown's River and Hill Creek were tested with a paired t-test, densities in Hill Creek were found to be significantly higher (NAI 1988bt Table 3.3.1-4). Significant differences among years were found at two out of four stations. Abundances were low from 1986 through 1988 at all four .j stations, and highest in 1979 and 1981 at all stations (Tables 3.3.1-3,4). J In Hampton Harbor, the green crab, Carcinus maenas is an important predator ofLNya, and its abundance may affect the success of recently-settled young (Section 3.3.7). All-time low abundances in 1986 at all four stations , coincided with high catches of green crab in Hampton Harbor (Figure 3.3.7-9). However, this relationship did not hold true for'all years. ) i I In summary, changes throughout the estuary occurred.in total cbundance, number of taxa, and abundance of the most dominant species, i, As these changes were not site-specific, and tended to occur at Brown's River cnd 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, not just the outfall into the settling pond. 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 in_both Brown's River and Mill Creek. Increases in the settling basin discharge volume l probably acted in conjunction with 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. By 1988, when rainfall was below everage, densities of all selected species except Nya substantially in- ' creased, as did the total abundance and number of taxa.
197 l
li
.3 i
I 3.3.2 Marine Haeroalmae. 1 3.3.2.1 Macroalmal Community - r Species Collections .I General algae collections represent the maximum number of species at a station. As no new species were collected in 1988, the numb'er of;spe - + cies collected at all stations'in this program remains at the 1967 level of-123 (NA1 1988b). Over half-(52%) of these taxa were red algae (Rhodophyta), , withtheremainderdividedalmostevenlybetweenbrownalgae-(Phaeophyta)(and. f green algae (Chlorophyta)(25% and 23%, respectively; NAI 1988b). This proportion is typical for the New Hampshire coast (Mathieson and Hehre 1986). l Spatially, the highest number of taxa. collected through'ut o the his- ., torJcal period wero in the mean low water (MLW) zone (a median of 50 at Sta - i tion DSMLW); numbers decreased with increasing depth, with the fewest species I collected at the deepest stations (Figure 3.3.2-1). The lower numbers at-the deep stations are due to several factors: lower light, lower. temperatures, fewer annual species-and a less-intensive sampling effort (once per year); there
'. 8 have also been fewer collections at Station B16. Number of species col- :
lected also decreased with increasing elevation from MLW (e.g., at the HSL stations). This is consistent with.other New Hampshire studies (Mathieson a et al. 1981). For the most part, the numbers of taxa collected at nearfield and farrield stations from 1978 to 1988 were similar. Exceptions-were the MLW zone where more taxa were recorded at Rye Ledge (B5MLW) than at the Outer Sunk Rocks (B1HLW) and the mid-depth zone where fewer taxa were recorded at the station near the intake (Station B16) than at the discharge and farfield I stations (B19 and B31). Numbers of taxa collected-in-1988 were within the !! range collected over the prior baseline period (1978-1987). However, the number of taxa collected at three stations in 1988 (B5MLW, B16, and B34) equalled the lowest recorded values at those stations. i 1 198 j l l
I i 70 -' $ MEDIAN ! 65 .'. RANGE '
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- AUGUST ONLY r i
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~
STATIONS
-i I
i 1 Figure 3.3.21. Median and rarige of macroalgae taxa collected in triannual general-- collections at Stations B1MSL, B1MLW, B17, B19, B31 (1978 1988), i B5MSL, B5MLW, B35 (1982-1988), B16 (19801984: 19861988) and B13, B04 (1978-1984; 1986-1988), B34 (1979-1984; 19861988). Seabrook Baseline Report,1988, 199 e
i l
)
Annual Biomass Collections l' The effect of depth on light quality and quantity is reflected in 1 the total biomass of macroalgae and the number of. taxa collected at the hard substrate (algal-covered _ rock and ledge) stations sampled from 1978 through 1988_(Figure 3.3.2-2). The numbers of taxa recorded were greatest at'the intertidal (MLW) sites, decreased to 21-25 taxa as depth increased to about: , l 9.5 m, then declined to.approximately 16 as depth increased to 20 ni. Numbers of taxa were similar between nearfield and farfield stations except at the. farfield intertidal station (B5HLW),. where seven more taxa were collected. Biomass values were highest at the intertidal and shallow subtidal stations, [ then declined as depths increased from_9.5 to 20 m. Biomass values were gen- s erally similar between nearfield and farfield stations.except at mid-depth stations. There, mean biomass values at Nearfield Station B19 (Discharge) were substantially lower (and outside the range of 95% confidence limits) than the Farfield Station B31 (Rye Ledge). Nearfield Station B16-(Intake) had biomass values that were intermediate between shallow subtidal and the other mid-depth stations. There is extensive flat ledge at this. station s which provides ideal substrate for dense algae cover. A temporal presentation of annual'(August) algae biomass levels at' the nearfield stations indicated no consistent among-year trends (Figure , 3.3.2-3). At the intertidal Sunk Rocks site (B1MLW), mean biomass was lower . during the 1978-1981 period than during the 1982-1986 period. In 1988, mean-biomass returned to previous levels from a 1987 low. Most of this increase ' I was due to increases in Chondrus crispus (see Section 3.2.2). At the shallow ; subtidal (B17), mid-depth (B19) and' deep (B04) nearfield stations there was some variability among years but it was relatively minor and there were no- ; among-year trends evident. Blomass' levels in 1988 were similar to previous years. The depth differences among benthic stations were also reflected in the relative abundance (biomass) of the seven taxa that were dominent during the baseline period (Figure 3.3.2-4). Ptilota serrate was dominant at the 200
'I A. I so < 1 l
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N O"
% 4.8m 4.6m Depth (m) below MLW g I 9.5m ?
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I 1000 3 , m . i 9.4m f ' Depth (m) below MLW fi , s.sm 5" - lg . i < ,, r.a3 . 13.7m m i i a e. . b .1s.sm 19.7m 1s.7m - eramm
~ E! n B1 LW B5htW Bk7 .Bh5' 816 - B31 B9 B3 B04 B34
' STATION Figure 3.3.2 2. A. Number of taxa and B. mean biomass (g/m 2) and 95% confidence intervals at intertidal and subtidal benthic stations in August over all years (see Table 3.2.2-1 for number of years sampled). Seabrook Baseline Report,1988.
201
Station Station . B1MLW - 317 se - ga . ,. w-m: ' E anoc - g soon . Isoo - teoo .' . g ,, 1E " .. g so. a to ; , 1200-
$1200{
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g 1000 - - 1000 - "% %" eno . \"/ . E g .' s . . Ig " ggson-e soo - , m- EE m2 son: . ano: . o . . ..,,,. . o . . . . ...... 19781979196019611982196319641985198619871968 1978 1979 1980 1961 1962 1983 1964 1965 1966 1967 100 YEAR' YEAR Station Station B04 ,on . B19 soo. E E 800 - soo - .. w w - s a ' l
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a m ' IB . n N/ " ' 5a. g 200 - g 200 - ' g als E .
- f. g .
o - i i.. i... . o .. . . . ..i,... 1978 1979198019811082198319841985196819871086 19781079198o19811962198319641985106610671968 . YEAR YEAR I Figure 3.3.2-3. Mean biomass (gms/m2) and 95% confidence limits for macroalgae collected in August at selected nearfield benthic stations (note differences in scale). Seabrook Baseline Report.1988. 202 l i ..
l A. HISTORICAL PERIOD !
'"~ n
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$ IQ M 'N' N': 'N' ':
R ,,,, :, ,, N % i ' D Ptilota serrata l g g so . N !{l[ j(( 3:{j{ j((((;
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,:: , ; ::::: :;$ E Corainnaomcinans r g :::::
' 'N' :::$ ::::: E Phycodrysrubens
.. , . E Cystocionium purpureum -
O Chondruscrispus I 40 - , N: ,j::f: 5 Mastocarpus stellatus j E OtherTaxa
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IE , , B1MLW B5MLW 817 8 35 816 831 B19 BIS BN BM STATION B. 1988 15 - - ,, ,,e ,,, , i
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,J
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W4 mu ,,,,,,, l_ si stw esktw s17 sis sts s's1 eis als a64 and l STATION Figure 3.3.2 4. Relative abundance (% biomass) of dominant macroalgae at marine benthic ! stations in August for A. Historical Period (see Table 3.3.2-1 for dates) and B.1988 only. Seabrook Baseline Report,1988, 203
'l d
L
' deepest (20 m) Stations B04 and B34. 'Phy11ophora spp.'(P. truncata and P.
pseudoceranoldes) were most abundant at mid-depth' Stations B19_and to a lesser extent B31, as well-as deep Station B13. -Chondrus crispus was domi-
~
nant' in the shallow subtidal and intertidal. #astocarpus stellatus was 1 restricted to the intertidal zone. ; Some differences occurred between nearfield stations and their' farfield counterparts. Station B5MLW had a larger proportion of N. stellatus
~ and correspondingly smaller proportions of Chondrus crispus in comparison.to Station B1MLW. This trend was~less evident in 1988, as percentages of N. ;
stellatus were low at both stations (Figure.3.2.2-4). At shallow subtidal stations, Farfield Station B35 had higher percentages of Phy11ophora spp.,: Corallina officinalls, and Cystoclonium purpureum when compared to Station I D17, where the overwhelming dominant was Chondrus crispus. ' Percentages in 1988 differed from previous years at B35 because of dramatically higher values for Cystoclonlur purpureum (23%). Farfield Station B31 was typified l by three dominants, Phy))ophora spp., Coraillna officina11s, and Chondrus crispus; whereas at Nearfield Station B19, Phy11ophora spp, was the over-whelming dominant and Phycodrys rubens occurred as a subdominant. . Deep stations differed mainly in the presence of C.'officinalis as a subdominant l at the Nearfield Station (B04). i E Community Analysis ;
- Station differences in the macroalgae
- community were caused by the -j 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). These associations were verified by discriminant function analysis of collections.for the entire baseline period
.(1978-1988; Table 3.3.2-1). Although several taxa had been found across all l depths, most species had one or two depth zones within which they reached
! peak biomass (NAI 1985b); it was the unique association of species' biomasses i 204
'1
5 TABLE-3.3.2-1.
SUMMARY
OF SPATIAL ASSOCIATIONS IDENTIFIED FROH
. NUMERICAL CLASSIFICATION ' (1978-1984) AND' VERIFIED WITH DISCRININANT ANALYSIS (1978-1988) 0F BENTHIC MACROALGAE SAMPLES COLLECTED IN AUGUST. SEABROOK BASELINE REPORT, 1988.
a HEAN HEAN BIONASS
- GROUP STA- DEPTH GROUP NO. TIONS (m) YEARS INCLUDED DOMINANT TAXA (g/m')'
1 .B13 18.3' -1978-1984;- .Phy11ophora spp. .66.68. 1986-1988- -Pt/lota serrata 11.90-
'Phycodrys rubens 6.21.
~Polysiphonia- ?
urcoolata : 3'.16 ' Scagella corallina 3.12- 'l
.L' 2 B04 19.7 1978-1984; .Ptilota serrata 65.66 1986-1988 Phyllophora spp. 9.32 B34 1979-1984; Corallins' 1986-1988 officinalls 7.26 Scagella corallina 1.22 Phycodrys rubens. 1'.01 :
3 B19 11.6 1978-1988 Phy11ophora spp. 208.25 1 B31 1978-1988 Corallina , B16 1984 'off/cInalls 56.20
.Chondrus crispus' 55.30 Phycodtys rubens 39.31 Callophyllis.
cristata 12.22 Ptllota serrata 11.86 4 B16 9.4 1980-1983; Phy11ophora spp. 424.88 1986-1988 Phycodrys rubens 201.98 Cystoclonjun purpureun 54.39 i Chondrus crispus 51.19 i Ceramlum rubrun 41.44 Callophyllis
, cristata 34.05 continued
\ 205
i I
~
L '= . . .
+
TABLE 3.3.2-1. (Continued) i 1, 1 NEAN" . HEAN: BIONASSL c GROUP 'STA- DEPTH GROUP
- l. NO. .TIONS (m) ' YEARS INCLUDED DOMINANT TAXA ' ( g/m' ).
?
5 B17 4.6 -1978-1988 Chondrus crispus 778.96; ; B35 1982-1988- Phy11ophora sp.- -208.24 i ~ Ceranlun rubrun~ 67 59 Corallina officinalls 51.12' Cystoclonjun .; purpureun _ 49.53 6 B1HLW ' HLW 1978-1988 . Chondrus crispus 1025.84
. B5MLW ' MLW 1982-1988 #astocarpus -l sec11atus 218.56 Corallina ;
officinalis 54.94 Ceranlun rubrun 2.68 Porphyra , leucosticta -0.87 ?
"1978-1988 period (Stations B1MLW, B17,'B19, B31:-1978-1988; Stations B5HLW, B35: 1982-1988;- Station B16: 1980-1984, 1986-1988; Stations.B13, l B04: 1978-1984, 1986-1988; B34: 1979-1984, 1986-1988) i l
l t k
'i 206
that resulted in a different community structure in each depth zone. Within eac'h depth zone, the paired nearfield and farfield stations were most similar
- to each other-(Table 3.3.2-1).
Differences in community structure at the different station groups were typified by differences in the biomass of dominant species. Intertidal and shallow subtidal areas (Groups 5 and 6) were characterized by large amounts of Chondrus crispus (Table 3.3.2-1). The areas were differentiated by the presence of Phy11ophora spp. as a subdominant in the shallow subtidal area while Nestocarpus stellatus appeared as a subdominant in the intertidal-area. Phy11ophora spp. were predominant at mid-depth areas-(Groups 3 and'4) and deep Station B13 (Group 1). Large amounts of Phycodrys rubens and. pre-sence of two typically shallow subtidal species as subdominants (Cystoclonlum purpureve, Ceramium rubrum) distinguished Station B16 (Group 4 except in 1984) from the other mid-depth stations. The community at Station B13 (Group l 1) vas a transition zone between mid-depth areas, as indicated by the predom-inance of Phy11ophora spp., and deep areas, suggested-by the presence of Pelloca serrata. At this depth (18 m), the shallow subtidal and intertidal opecies had disappeared from the community. Areas sampled at 20 m depth,'the deepest areas sampled in the study (Group 2), showed a community where Pellota serrata predominated, and Phy11ophora spp. was.less important than in cha11ower areas. Species assemblages identified by discriminant analysis were iden-tical to those identified for the baseline period by cluster analysis. Sam-ples collected from 1985-1988 were placed in the same group as the majority of samples from previous years, verifying the similarity in species .composi-tion (Table 3.3.2-2). 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' biomasses has been very consistent. The degree of differences at the species level is examined for two dominant macroalgae species in the " selected species" section which follows. 207
--g
t 1 TABLE 3.3.2-2. PROBABILITY OF 1978-1988 NACROALGAE-SAMPLE HEMBERSHIP IN EACH STATION GROUP VERIFIED BY DISCRIMINANT FUNCTION ANALYSIS'0F 1978-1988 AUGUST BENTHIC DATA. SEABROOK BASELINE REPORT, 1988.- h DISCRIMINANT FUNCTION GROUP
'ASSIGNEDSgNPLE i GROUP 1 2 ,3 4 5- 6- t f
I i b 1 100 0 0 0 0 0 (10) ' Ji 2 0 100 0- 0 0' 0 (19) . 3 0 0 100 0 0 0- . (23) 4 0 0 0 100 0 0. (7) 5 0 0 0 0 100 0-(18) _ 6- 0 0 0 'O O 100 (18) I , l "See Table 3.3.2-1, 1978-1984 samples assigned based on results of l b eluster analysis l 100 = sample percent probability of group membership (10) = number of samples per group i i 1 l 'h ( 208 w
4
- In order to monitor the algal community for new or infrequently I
occurring species which might bloom to " nuisance" levels, the rarer species occurrences were also examined. Twenty-seven taxa occurred sparsely (less than 1.7% frequency in the biomass collections, the level used historically; (NAl 1985b) from 1978 to 1988 (Appendix Table 3.3.2-1). Fif teen of these have historically been sparse taxa, occurring in similarly low frequencies during the 1978-1984 period (NAI 1985b). As these taxa have exhibited no change in f requency, they can be considered typical " sparsely occurring" taxa. Two taxa, Polysiphonia nigrescens and Porphyra umb111 calls, that were classified as " sparsely distributed" based on low numbers of occurrences from 1978-1984 (NAI 1985b) have substantially increased their frequency of occur-rence in the last four years. Both taxa have been collected in previous-studies of the New llampshire nearshore coast and estuaries (Mathieson and Hohre 1986). Eleven taxa are new occurrences in destructive sampics collec-ted since 1984, although most had been collected in the general algae collec-tions prior to 1984. These most probably represent rare taxa in the study l-crea. However, species moving into'the area in increasing frequencies would l show n similar pattern. Continued monitoring of the sparsely-occurring taxa ( will enable us to detect changes in their distribution. The only unusual oc-l currence reported to date was Bonnemaisonia haml/ era which was now to biomass collections in-1986 (Stations B5MLW, B31 and B35), and occurred again'in 1987 (B17) and 1988 (B5MIM, B35). This species, typical of southern Massachusetts sad Long Island (Taylor 1952), has been recorded in coastal New llampshire and Great Bay (Mathieson and llehre 1986), but not at offshore sites in this study prior to 1986. The recent occurrence may have been related to the naturally increased water temperatures in the nearshore area in 1985 and 1986. Kelp Transect Survey Spatial differences in kelp species abundance appear primarily attributable to depth differences. Laminaria saccharina was most abundant at the shallower stations (Figure 3.3.2-5). Laminarla digitata and Alarla 209
Ao Kelps J Shallow Mid4epth
3 l i
=- a w a tste I
. a. *
- sin 1r -
a w*mo l o wame 8
'I T- '
t- g 1-i
..] .
o
" "' n '
, , , o il 11 li 11 si11li11 B. Understory algae Shallow Mid depth 80 - 80 -
'3 0 *
- mtD '
E W# #I U '***d N63 - 60 - so - 8 l e 40 - *I l 40 - E T._. U
- o . _I., ,o . T. ) _T 0- - -
T o- -- - -- l. Il f* II l} $* t? II 3 Figure 3.3.2 5. A. Mean and 95% confidence interval of A, log No/100 m 2 of kelps (B17: 19781988; B35: 19821988) and B.- Percent frequencies and 95% confidence . Interval of dominant understory algae (B17: 1981-1988; B35: 1982-1988) collected triannually in the shallow and mid depth subtidal zone. Seabrook Baseline Repon,1988. l 210
.- . . . . .. ._ . __l
l esculenta reached maximum abundance in the study area at farfield Station B31 (9.4 m below MLW), whereas Agarum cr/brosum's greatest abundance was at Sta-tion B19 (discharge, 13.7 m below MLW). Substantial spatial differences between nearfield and farfield mid-depth stations (B19 and B31), were found for some species; b. digitata, L. saccharina, and Alarla esculenta were more abundant (and outside the 95% confidence limits) at Farfield Station B31 (Figure 3.3.2-5). Abundances recorded in 1988 followed similar spe.tial patterns to historical (1978-1988) occurrences (NAI 1989). In several cases, abundance levels in 1988 differed from the historical average. Numbers of L. saccharina at the mid-depth stations (B19, B31) and L. digitata , at the shallow subtidal stations (B17, B35) and B31 in 1988 were lower than j the historical average (and outside the 95% confidence limits)(Figure l 3.3.2-5, NA1 1989). Numbers of A. cribrosum and L. digitata at B19 were higher than the historical average (and outside the 95% confidence limits). l No consistent seasonal variation in abundance was observed for any species of kelp, probably because " juvenile" (<15 cm) plants were not enu-c merated; these plants are difficult to e'curstely count in situ because of l their small size and high density (NAI 1984a, 1985b). Seasonal veriation in l biomass was reflected in growth studies conducted prior to 1965; growth l closely followed the solar irradiance and nutrient cycles (NAI 1985b). Stand density, which is controlled by substrate availability, recruitment and envi-ronmental conditions (e.g. storm disruption), showed some variability among years. Kelps, particularly Laminarla species, are quick-growing, opportunis-tic plants. Consequently, 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 under-otory algae that were dominant at transect sites (Figure 3.3.2-5), showed differences among depths that were similar to those observed from biomass collections (Figuro 3.3.2-4). Chondrus crispus occurred more frequently in the shallow subtidal zone whereas Phy11ophora spp and Pellota serrate were 211
)
^?
encouritered more frequently in the mid-depth zone. Pellota serrata occurred as frequently as Phy11ophora spp at Station B19 cven though it was not at.
~its peak biomass (Figure 3.3.2-4). Fellota serrata was significantly lower and Chondrus crispus significantly higher at Station B31 (which is 9.5 m deep) than at Station B19-(13.7 m deep), as evidenced by mean values outside the 95% confidence limits (Figure 3.2.2-5). Patterns shown by the 1988 fro-quencies of occurrence were within the range observed historically,'with one exception: Pellota serrata continued to show fewer occurrences at Station t B19 and B31.than.in past years (NAI 1989). 1988 values for P. serraca at B31 1 remained at the lowest recorded value for the-third year in a row (NAI 1989; l 1988b). * - ,I_ritertidal Communities (Nondestructive Monitorina Pronram) .
In situ counts of macroalgae-in fixed quadrats at the intertidal ,
. .t stations (Stations B1 and B5) were conducted at various locations-in the ;
i intertidal zone on bare ledge, and Chondrus- and fucoid-covered' ledge habi- i tats. These quadrats were set up in order to monitor a fixed location thus i
.a eliminating small-scale spatial variability and focusing on temporal varia- 1 tion. Appendix Table 3.3.2-2 shows the occurrence of the more commonly-occurring species. Since the areas have unique characteristics, eac'h-l will be described in turn. I
- The Bare Ledge Site, at the upper edge of the mid-tidal zone was ;
characteristic of " bare" ledge in the area, that is, ledge not continuously ; covered by macroalgae. Although highly seasonably variable, barnacles have q been common in this quadrat (see Section'3.3.3 for faunal coverage). During j the spring the annual greens, Urospora pencilliformis and Ulothrix flacca (at-both stations), and the red algae, Bangla fuscopurpurea (Station BS), were ; the most frequently occurring species (Appendix Table 3.3.2-2). Small, imma-
) . ture perennial Fucus spp. plants have also been found in this habitat in all j seasons; although they occurred frequently, their percent cover was usually I 212 !
l l less than 15%. Variability in the seasonal occurrence of these species is
~
l apparently not related to any seasonal or yearly trend but likely to plant i loss and slow regrowth. Algae settlement and growth are controlled by bal- , ancing the opportunity for settling on available space versus the effects of predation. Spatially, the bare rock quadrats have been generally similar, although temporal variations in Tucus spp. appeared spatially independent (NAI 1988b). The more persistent red algae, Porphyra sp. was unique to B1, while B. /uscopurpurea was unique to B5 (in these fixed quadrats). Results from 1988 observations (NAI 1989) were similar to previous years. The Fucold Ledge Site, in the mid-tide zone, is situated in the area of maximum fucold algae cover. The perennial, Fucus spp., has been the major taxon within the quadrats, (mainly T. ves/culosus, with some F. disti-cus v. edentatus) although some Ascophyllum nodosum (Station B5) have been recorded (Appendix Table 3.3.2-2). These fucolds were quite persistent and frequently occurring, although relatively low (<40%) coverages have been recorded at times. 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 at Station B1 only). Trends observed in 1988 (NAI 1989) were similar to those from previous years. l t Fixed line transects have also been surveyed in the mid-tide zone from 1983 to 1988 to quantify the areal coverage of the fucold algae. In the fixed areas studied, the percent frequency of occurrence of Ascophy11um nodosum was one-third higher at B5 but within the 95% confidence limits (Figure 3.3.2-6). Fucus resiculosus was almost twice as frequent at the nearfield station (B1) than at the farfield station (BS)(Figure 3.2.2-6). Some F. distichus var. edentatus was also recorded at B1, but none at the farfield site (B5). The quadrat in the MLW (mean low water) zone is situated in the area of maximum red algae cover. Chondrus crispus and Hastocarpus stellatus dominated this zone; together they typically covered 80 to 100% of the sub-213 f
100 - 100 - 100-
. 2ccophyllum , Fucus . Fucus distichus 1 nodosum vesiculosis . var.'edentatus- ,
80 - 80 - 80 -
,f-e e . L
,. -?
60 - 60 - 60 - W
- l r w i
$ ; 40 - 40 - 40 -
p ; 1 i . 1 20 - 20 - 20 - l l . 0-1 81MSL B5MSL 0 B1MSL e 1 .. BSMSL 0-B1MSL B5MSL-I i t i l' STATION I' L c l t= .t i Figure 3.3.2 6. Mean percent frequency and 95% confidence interval of fuce a algae at two i fixed transect sites in the mean sea level zone (1983-1988). Seabrook Baseline Repon,1988. b 214 i
- . - - - --r -r *--**~'~~
strate (NAI 1988b). Spatially, the frequency of occurrences at the two stations' quadrats were generally similar for these two dominants although l there has tended to be a greater frequency of C. crispus at B5. Other spatial differences included the occurrence of understory taxa Fucus spp., which was persistent only at B1, and Core 11/na o///cInalls, which was persistent only at B5; small scale vertical differences between stations likely contributed to these species occurrence differences. Observations made in 1988 were similar to those from previous years. 3.3.2.2 Selected Species haminarla sacchar /no s Laminarla 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 variability in the amount of Cubstrate available for settlement combined with the contagious (clumped) distribution of those plants. At Station B17, the highest annual mean densi-ties were recorded in 1979 (979 plants /100 m'), decreased to 285 plants /100 l m' in 1982, and remained at that approximate level through 1988 (Figure 3.3.2-7). The most precipitous change in density occurred between April and July 1982 with an 85% drop in density (NAI 1983b). There had been a very large and dense stand of kelps in the western portion of this station which has diminished since 1979; this has contributed to changes observed in 1982. L -It can be hypothesized that due to scouring from the storm of 1978 larger amounts of substrate became available for Laminarla settlement, which resulted in higher densities in 1979; over time these stands may have dimin-1shed to a more " typical" level (as in 1982) as substrate became recovered with understory algae. Over the last seven years (1982-1988) when both near-field and farfield stations were monitored, however, annual differences were not significant (Table 3.3.2-3). Average numbers of plants per quadrat were olmilar between the nearfield (B17) and farfield (B35) stations over the 215
Nearfield (B17) 2400 - 22m; E 8*0 '. 18o0 , 1 a 1800 - E 12x , .. -
=8 t a= -
g ,
<g soo , .. .. -
l); m 4-soo . doo *
=
1
/
~
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i 0- . . . i i i 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 -i YEAR- !
}
-l Farfield (B35) 2400 -
2200 , - E w 2000 - b '**'. a tem - g 1400 - g 12 : .. . WO -
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*8 -
am ' .
@5
- s Ib aoo ,
4m - jy #\ 200 5
~
3 .. o i i . . i 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 , i YEAR i Figure 3.3.2-7. Annual mean abundance (No./100 m 2 ) and 95% confidence interval for Laminaria saccharina at Station B17 (1979-1988) and B35 (1982-1988). Seabrook Easeline Report,1988, 216 l l
d TABLE 3.3.2-3. RESULTS OF SIGNIFICANCE TESTS ON KACR0 ALGAE SELECTED SPECIES, CRCHDRUS CRISPUS AND LAMINARIA SACCHARINA. SEABROOK BASELINE REPORT, 1988. A. C#0NORUS CRISPUS BIONASS (g/m*) - Temporal (Year) Comparisons (1978-1988): one-way ANOVA of Log (x+1) means STATION df SS F VALUE SIGNIFICANCE" i B1MLW 10 0.573 1.77 N . S ,- i B17 10 0.328 0.60 N.S. 4
-l I
Spatial (Station) Comparisons-(1982-1988): Paired t test of sample means 1 STATIONS t SIGNIFICANCE COMPARISON j B1MLW vs. B5MLW 3.00 ** Nearfield greater B17 vs. B35- 3.18 ** Nearfield greater l
-B. LAMINARIA SACCHARINA DENSITIES (NO./m*)
Temporal (Year) Comparisons (1982-1988): Wilcoxon's Ranks Test i STATIONS VARIABLE SIGNIFICANCE ' I B17 and B35 . years N.S. 'I combined (1982-1988) ; i Spatial (Station) Comparisons (1982-1988): W11coxon's Ranks Test STATIONS VARIABLE SIGNIFICANCE !
-t B17 vs. B35 stations N.S.
Seasonalbomparison(1982-1988): Wilcoxon's Ranks Test STATIONS VARIABLE SIGNIFICANCE B17 and B35 seasons N.S. ' combined ( Apr, Jul, Aug) C "N.S. = Not significant
* = Significant at p < .05
** = Significant at p < .01 217
4 entire 1982-1988 period -(Table 3.3.2-3), but the kelp beds were t v > , evenly distributed at Station B17 than at Station B35 (NAI 1985b), evidently because of differences in.available substrate. There were no ! t significant differences among the three seasons sampled (April, July, : August)(Table 3.3.2-3). l Chondrus crispus Chondrus crispus '(Irish moss) was the dominant understory . :f algal species in the lower intertidal and shallow subtidal zones near. the Sunk Rocks (see Community Analysis.section). Destructive samples j were collected in'May, August,.and November from'1978 to 1988 (1982 to 1988 for Stations B35 and B5MLW); maximum. biomass typically occurred in
' August at all stations-(Figure 3.3.2-8). Minimum values generally.
occurred in May at subtidal-stations and in fall at intertidal stations. However, confidence limits (calculated for:1978-88) implied a signifi-cant difference between. minimum and maximum seasonal biomass only at Station B17. Blomass values from.1988 generally differed very little from the historical data (NAI 1989). At the shallow subtidal. stations, ; biomass.in.1988 was noticeably (about 50%)'h'gher i in May collections and 50% lower in November than in previous years (NAI 1989). These data-
-continued to add to the natural variability of the baseline data at this .;
station. August biomass values at Station B17 ranged from less than 400 g/m* in 1982 to over 900 g/m' in 1986 (Figure-3.3.2-9). Because of this high variation, differences in annual biomass were not significant (Table 3.3.2-3). However, overal1~ biomass at Station B17 was signifi-- cantly higher than that at Station B35 (Table 3.3.2-3). Peak biomass at '! Station B1MLW was recorded in 1984, its minimum in 1978. No'significant differances among years were detected (Table 3.3.2-3). Values'in 1988 I were only slightly less than that of the peak year (NAI 1989). Biomass , at B1MLW was statistically higher (at p <.01) than the farfield-station (Table 3.3.2-3). 218 4; f
Q i 1400 - [ , 5 MAY
-~
1200 - B mousr O foeEER l 1000 - r 5
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-= 1 e
e s= 400 - y o l 200 - i + c O- -- I ~-- B1MLW- 85 MLW B17. B35 , i i STATION I i
-1 l Figure 3.3.2-8. Mean biomass (gm/m 2 ) and 95% confidence limits of Chondras crispas at selected stations 4
in May, August and November. Stations B17, B1MLW: 1978-1988; Stations B35. B5MLW:
~ 1982-1988. Scabrook Baseline Report,1988.
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YEAR YEAR d 1
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YEAR YEAR I Figure 3.3.2 9 Annual mean biomass (g/m 2 ) and 95% confidence intervals of Chondrus crispus i in August at Stations BIMLW, B17 (19781988) and B5MLW, B35 (19821988).
- Seabrook Baseline Report,1988. ;
220 i
3.3.3 }Larine Macrof auna 3.3.3.1 Mard substrate Community General Studies of the macrofaunal invertebrates off Hampton Beach, New Hampshire since 1978 have focused on the horizontal algae covered rock / ledge habitat in four depth zones: intertidal (MLV and HSL), 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 farfield counterparts near Rye Lodge 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 com-munity (see Section 3.3.4 also).
} Lumbers of Taxa and Total Abundance Numbers of taxa and total abundance have been used to monitor spa-tial and temporal trends in the macrofaunal community. These parameters, nessured in August, have shown broadscale changes in relation to depth. The l number of taxa generally increased with increasing depth, and neerfield sta- ,
tions 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), nainly due to decreased numbers of mytilids (see Section 3.3.5). Total abundance in the intertidal area far exceeded that of sub-tidal depths (Figure 3.3.3-1). The total number of taxa (collected over the i cntire study period) at nearfield and farfield intertidal stations was lower than that at subtidal counterparts. Nearfield Station B1MLW had higher num-221 U
NUMBER OF TAXA .; E
^
STATION OVERALL ABUNDANCE n0000 i 200000 + g 180000 l a 140=0
$ 120000 100000 N
.i -
I 40000
* '~
0 - - BiblWB5dLW B17 Bh6 816 Bh1 B19 B13 B04 sh4 STATION
- IN81988, Stations 1 17 B1 B3 ; 9821788,B M B 5; ,
1 16 at tertdk1 d sub ida n c ta lon's abrook Baseline Report,1988. 222
bers of taxa and total abundance (which was outside the 95% confidence inter-val) than its f arfield counterpart, Station B5MIM (Figure 3.3.3-1). The pre-sence of boulders at the farfield site may decrease available habitat space, in turn decreasing the total abundance and number of taxa. The 1988 abun-dance Itvels at B1MIM continued to decrease from the extremely high levels recorded in 1986 to the lowest levels recorded to date (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 1988 recovered from the 1987 low value to levels similar to previous years at both stations (Figure 3.3.3 3). The shallow subtidal stations (5 m), Stations B17 (discharge) and B35 (f arfield), had higher numbers of taxa than their intertidal nearfield and f arfield counterparts but lower numbers than mid depth and deep areas (Figure 3.3.3 1). The nearfield station had a higher number of taxa (238 for the entire study period) in comparison to the farfield area (199). Over-all abundance was lower at the nearfield station but within 95% confidence intervals (Figure 3.3.3 1). Number of taxa increased to levels similar to previous years in 1988 (Figure 3.3.3-3). Total abundance in 1988 increased slightly from the low value in 1987 (Figure 3.3.3-2). I Results from mid-depth (9-12 m) stations, Stations B16 (intake), B31 (farfield), and B19 (discharge), reinforced the finding of increased numbers of taxa and decreased abundances with increased depth. Numbers of l taxa were consistently higher and similar to those at deep stations at Station B19 (Figure 3.3.3 1), where algae covered ledge predominates and tussel beds comprise 25-40% of the habitat. In comparison, numbers of taxa were much lower at Station B31, which was predominantly composed of mussel beds (60%) with cobble and algae-covered rocks also present (Table 4.1-1). Numbers of taxa at Station B16, similar in depth to Station B31 and in substrate to Station B19, were intermediate between these other mid-depth stations. Numbers of taxa in 1988 at all three stations recovered from the low levels encountered in 1987 (Figure 3.3.3 4). Abundance levels averaged over all years at Station B16 were higher than at Station B31 which in turn 223
INTERTIDAL (B1MLW) 1000000 - 900000 000000 - f 700000 =
- t Wg . !
i 500000 - t O 400000 - 5 - - 1 ej 4-
.00000-l 200000 - \'- "
f 100000 - - , 0 , , , , , , , , ; l 1978 1979 1980 1981 1982 1983 1984 1986 1986 1987 1988 i YEAR l l 1 SHALLOW SUBTIDAL (B17) 100000- < 90000 - m 80000 - w . I b 7o000 - E < 60000 - ly
< 60000 -
e , , g,g q 40000 -
~ "
/ g .. ,,
*** N
"/.
- 10000- .
O i i i i i i i , , 1978 1979 1980 1981 1982 1983 1984 1986 1988 1987 1988 YEAR Figure 3.3.3 2. Annual mean abundance (No./m 2) and 95% confidence limits for macrofauna collected in August for nearfield Stations B1MLW (intertidal) and B17 (shallow subtidal.i. Seabrook Baseline Report,1988. l 224 i l l 1
i i h INTERTIDAL i j 20 - l 1(,0 - **\ i
\ .\.,
e
, .0 - s .
., i
. \ ,. . . ,... ,,..* )
.0 -
l i 40 - i 6 B1MLW (nearfiskf) 20 * ....... 36MLW (terieskf) 0- . . . . . . . . . . . 1978 1979 1980 1981 1982 1983 1984 1986 1986 1987 1988 YEAR l SHALLOW SUBTIDAL ! 140 - [ 120 - 100 .....'"" . . , ,/ *.,, ... g . . g 80 - ' . , ,/ 60 - l 40 - I 817 (neerfleki) 20 - ... .. 33s (tar 16s6d) O i . i i . . . . . . . 1978 1979 1980 1981 1982 1983 1984 1986 1986 1987 1988 YEAR Figure 3.3.3 3. Annual number of taxa (per $/16 m 2) collected in August at intertidal Stations , B1MLW and B5MLW and shallow subtidal Stations B17 and B35. Seabrook Baseline Repon,1988, i 225
MID-DEPTH I 190
- 160 -
i r { 1ai 120 -. A - g ,a ,
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YEAR ! DEEP ' 180 - 160-( . u 1a:
- h ........
; ;=; , ,....... w.... *.
g 90 - W
$0 5 - '
B04 (nearnold) ) 90 - """" B34 (farheld) l 0- . . .....,,,, i 1978 1979 1980 1981 1982 1983 1984 1986 1988 1987 1988 YEAR MID DEPTH To DEEP 180 -
. imi g . ... .................
l
- 1:
M-M'
./
- w. -
c l BIS (nearnold) 20 - """" B16 (farteld) 0- i i i i . . . i i i i 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 YEAR i Figure 3.3.3-4. Annual number of taxa (per 5/16 m 3 ) collected in August at Stations B16. B19, and B31 (mid depth); and Stations B04 B13, and B34 (deep). Seabrook Baseline Report.1988. 226
I were higher than at Station B19, because of the varying numbers of mytilids. All were within tho 95% coniidence intervals (Figure 3.3.3 1). Abundance , levels in 1988.at Station B19 increased slightly from the low value recorded i in 1987 (Figure 3.3.3 5). At Station B16, total abundance in 1988 was the highest recorded since sampling began in 1980 (Figure 3.3.3 5). The deepest stations (18 21 m), Stations B04 (discharge), B34 (far-field) and B13 (intake), 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 B13, which has a mixture of algae covered ledge, mussel beds, and cobble, and highest at Station B04, where mussel beds predominate, with some algae covered ledge present. Station B34, slightly deeper at 21 m, has been intermediate in its number of taxa, and is predominantly mussel bed (Figure 3.3.3-1, Table 4.1-1). Numbers of taxa in 1988 increased at B04 and B34; at B34 values were the highest recorded to date (Figure 3.3.3-4). Abundances at the nearfield station (804) were approximately half those at the farfield station (B34) and cutside the 95% confidence limits (Figure 3.3.3-1). The abundance levels in 1988 increased dramatically at Station B04 to the highest level recorded (Figure 3.3.3-5). High numbers of Balanus crenatus (2547/m') contributed to the high overall abundance (NA1 1989). Commuqity Structure The noncolonial, macrofaunal, hard-bottom community structure has historically shown changes related to depth (NAI 1988b). Intertidal, shallow subtidal, mid-depth, and deep areas were distinct in both species distribu-tions and abundancos. The 1988 collections showed highly similar species composition to collections from previous years (Table 3.3.3-1). In most cases, based on the similarity in species composition, the 1988 collections were placed in the group with the majority of historical collections from the same station (Tablo 3.3.3-1). The intertidal and shallow subtidal showed 227 l
MID DEPTH (B19) i 5 h 40000 - : e . .. .. i IE
< E.
0 A 1~ 5" "
..\
1978 1979 1980 1981 1982 1983 1984 1095 1986'1987 1988 j YEAR i i ! MID DEPTH (B16) ,
" 140000 2 '
a '"I " 100000 - UE 80000 -
<D 60000- . .
lk e{ 40000i 20000 . 0 . . . . . . . . i 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 YEAR , 1 DEEP (504) 20000-
@ 18000 -
g ' ' 16000-E 14000 - 12000 - ! w e 10000 -
B1611986,87,88 i Balanes crene+es 1213 O
Miste11a sr. 3199 Amenis sr. ISM Lacone wineta 711 4 BInt 1979-84,87 9 13 Deer /intatee, dis- Ptytilidae 451 834(1979,1981-82,1987) chorpe and forfield 7s,,; , u ia inen ts 407 B13t1987I sid-durth Anceis sr. 548 p19819879 discherpe Asteriidae 353 i Carre11a sorteatrienetis 289 solenes crenetes 319 5 B17f1978-88) 23 Shellee/forfield flyt111dee 3671 835t198t-889 discherpe 1.meone vinets 5722 B1681980-83,86 I mid-derth/intatte ?w;,- _ ze ineemis 3993 i Idotee p~.,^. _ E294 Carre11a septentrionalis 1967
.3 esse falcata 1856 4 B1fEJet 1978-88 9 18 Intertidel/ Deter Mytillene 95195 B5MEJet 1982-88 i Sunk Stocets, Rye Joera merime eas9 IAMApe 3966 #
Tertenza war-4e^' Miste11a sr. 5273 , laceae vincts 4973 Summerelles angelones 3798 anseella larillus 2762 i
- Iso semples collected at Station B36 in 1979 er 19855 Stetiens 95 DEN and B35 in 1978-81s or Stations B16 in 1978,1979 and 1985.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ . __ . .. . . . - . _ . _ . . . . .. _ . . , ~ . _ -~ - ._ .._ ._ _. _ _. _. ._ _
carid crustaceans such as Pontogencia inermis, Capre11a septentrionalls, ido-tes phosphorea, and Jassa falcata (Table 3.3.3-1). Relatively high densities cf the latter two species, along with Call /oplus laev/usculus distinguished the shallow subtidal area from other areas. The addition of 1988 collections did not drastically alter the within group abundance. Species composition at ; Station B16, with depth of 10.7 m, was usually more similar to the shallower Stations B17 and B35 because of the predominance of uniform algae covered ledge, causing increased biomass of algae (see Section 3.3.2). This, in turn, was related to increased numbers of subdominant herbivorous species such as I,acuna v/ncta and 1dotea phosphorca, which increased the similarity of this station's species composition with that of shallow subtidal stations. ' Turthermore, flat ledge at Station B16 (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. , CJstenides granulata and Cerastoderma pinnulatum. 1 l i Hid depth areas were usually characterized by a predominance of ( Hytilidae spat, with other mollusca (e.g. , N/atella sp. and Anomia sp.) and amphipods (e.g., Pontogenela inerals and Capre11a septentrionalis) occurring in high numbers, placing these collections in Group 3 (Table 3.3.3-1). Sta-tions B19, B16 (discharge) and B31 (farfield) in most years were charac-terized by this assemblage, as were deep Station B13 and mid depth Station B16 for approximately a third of their annual collections. The 1988 collec-tions at Stationa B19, B16, and B31 were similar to previous years, and thus placed in the same group. 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 lack of Mytilidae spat, cnd the increased importance of crustaceans and other taxa. These character-istics also occasionally occurred at mid-depth areas (9-14 m), leading to the appearance of collections in these areas in the typically deep station groups. The majority of collections at deep stations (B04, B34, B13) were 231
1 placed in two groups. In some years, peracarids (rontogerefa /ncre/s, l Capre11a septentrions/1s), Asteriidae, and molluses (Anosta sp., Hytilidae) l- were the dominant taxa, forming Group 4 (Table 3.3.3-1). Average abundances of dominants were less than 700/m', giving this group low overall abundance, l No collections in 1988 had species composition that was similar enough to be ' placed in this group. ' l In other years, at Stetions B04 B13, B34 and B19 (1985 only), l Balanus crenatus, along with molluses (Mytilidae, Anomfa sp., and Flate114 sp.) were the most abundant taxa, causing these stations to be distinct from ; other collections, forming Group 2. Collections made at Stations B04, B13, I and B34 in 1988 were placed in this group, in part due to high densities of' U Balanus crenatus (16,493, 16,224 and 2517/m', respectively) (NA1 1989). A , third group (Group 1) of four station collections, including mid-depth B19 and B31 and deep B04 and B34, was formed because they were unlike the other assemblages in having moderate numbers of Mytilidae sp. and Flate11a sp. but . Iow numbers of Balanus spp. No collections from 1988 showed a similar species composition to this group. - l 3.3.3.2 Intertidal Communities _(Non* destructive Monitorinn Pronram) Important species on the fucoid-covered and bare rock ledge habi-tats in the mid tide zone and Chondrus zone habitat at mean low water (HIM) were monitored non destructively at fixed stations on Outer Sunk Rocks (Station B1) and Rye I, edge (Station B5) three times per year. The bare rock l areas supported low percentages of algae such as Porphyra spp, at Station B1 and Tucus spp. mainly at Station B5 (Section 3.3.2). The predominant macro-faunal resident was Balanus spp., which was most common on the bare rock substrate. Frequencies were slightly higher in April following the spring recruitment period, than in July and December (Table 3.3.3-2). Herbivorous gastropods Littorina littorea (mainly at Station B5) and Littorina saxatills (occurring at both stations but restricted to the bere rock zone), were also important constituents of the bare rock community, showing lower frequencies ! 232
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in April than in July or December. Mytilidae spat occurred in low fsequen-cies in July and December. Patterns of faunal distribution in 1988 were siellar to those observed in previous years with one exception. Frequencies of balanus sp. at B1 were low in all three months and similiar to low levels ! noted in 1986 (NA1 1989; 1987a). ! Fucold-covered ledge areas in the mid tide zone were characterized by a heavy cover (over 80%) of the perennial algae Tucus spp. (mainly T. - ves/culosus), with an understory of perennial red algae (#estocarpus stella-tus and, less frequently, Chondrus crispus). Highly-seasonal annual algae occurred in spring or spring and summer, particularly at Station B1 (Section ' 3.3.2). Hytilidae spat was the most common taxon at Station B1, with high ,. percentages during all three sample periods (Table 3.3.3-2). In 1988, frequencies were the lowest recorded in April and July (NAI 1989). Mytilidae usually did not show high frequencies at Station B5. Balanus spp. were also important members of the fucoid ledge community and were more frequently , encountered at Station B5. As on bare rock, frequencies were usually highest in April following spring recruitment and lowest in December. No Balanus were found in April at Station B1 in 1988 (NAI 1989). Nuce11a lapillus , occurred mainly on the algae-covered ledge, most commonly encountered in July in the fucold zone. Other important gastropods were Acmaea testud/nalis and ' Littorina obtusata (most frequent in July and December) and L/ttorina lit-tores (almost exclusively occurring at Station B5). , 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 #astocarpus stellatus. Tucus spp. were also frequently encountered at Station B1 only (Section 3.3.2). , 0f the macrofaunal species that were monitored, Nucella lapillus and Mytilidae spat were the most fre-quently encountered at both stations. At Station B1, Nucella were more abundant in July than in April or December (Table 3.3.3-2). This is consis-tent with other studies which show adult Nucella to be active from May- , through Octobet, while juveniles tend to be active throughout the year (Henge 234
1978). On Rye Ledge (Station B$), Nucella was less-frequently encountered in July, a seasonal pattern that was reversed from its nearfield counterpart. Seasonal movements of Nucella appeared unrelated to those of its main prey, Mytilidae. Nytilidae hed medium-to high frequencies in April and July with
- generally lower percentages in December. No relationship with abundance levels of either species at mean low water or with the fucold community at mean sea level has been noted (NA1 1987b). The gastropod Littorina lletorea "
occurred at only Station BS in high frerjnncies throughout the year. Acmaea testudinalls was enumerated in low-to-moderate frequencies at Station B1 in all years and Station B$ in 1985 and again in 1988 (Table 3.3.3 2). Fre-quencies in December 1988 at Station B1 were the highest ever recorded (81%)(NA1 1989). 3.3.3.3 Subtidal Foulinn Community Data collected from subtidal bottom panels gives information on recruitment of benthic macrofaunal species. Balanus spp. (mainly Balanus crenatus, with somo 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, and densities were lower in August (Table 3.3.3-3). Densities in December were consistently low, as Balanus populations disap-peared as a result of mortality or disturbance. Settlement on the 1988 pancis showed the same pattern. Balanus spp, densities were higher at Station B31 in all years except 1984. Anomia sp. had a pattern of late-summer-fall recruitment. Although low densities of Anomla 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 1988, December densities were the highest ever recorded at Station B19. There were no consistent differences between nearfield and farfield stations. 235
. . . . . . - . - - . . . - -- . - - . . - . - ~ . - ~ .-
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i i l l I 1 Elatella sp., another sessile mollusc, showed highest densities by August collections, with most disappearing from panels by December. Den-sities in 1988 showed a similar seasonal pattern (Table 3.3.3+3). Numbers were generally higher at Station B31 than at Station B19 (1987 was an excep- J tion), a pattern not borne out in benthic collections. Especially high den-sities on bottom panels in 1984 were reflected in higher densities in the bottom samples in 1984 (NAI 1985a). Nytilidae 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 een take place throughout the year. Few of these newly settled mytilida survived through the winter in the natural habitat or on artificial substrate (NAI 1985b). Densities on bottom panels at Station B31 were usually higher than at station B19, a pattern which also occurred in the benthic collections (Section 3.3.5). l 3.3.3.4 Hodfo]us mod /olus Community As part of the subtidal nondestructive program, Nodiolus mod /olus 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 (NAl 1985b). Over the nine-year period 1980-1988, results from a Wilcoxon's signed rank test indicated densities at nearfield Station B19 were significantly higher than at the farfield Station B31 (Table 3.3.3-4). Significant differences were detected among years using a Kruskal-Wallis test (p < 0.001, DF = 8). Densities were highest in 1982 and 1983, averaging over 110/m8 (Table 3.3.3-4). In subsequent years, annual mean density was less than 100/m' at both stations. The 1988 density at Station B31 was lower than the 1980-1988 average, and at Station B19, approximately the same as the all-years average 237
- s- -- 2 - -
1 i l E R : II I 3 31 l R kh 42 9 : M I 5 . al f l R ya ; ll g i ,, .= il
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e (Table 3.3.3 4). Despite year to-year fluctuations in Nod /olus density, the community as a whole is relatively persistent and is an important refuge from large predators for macroinvertebrates. At the 8 m depth off Portsmouth, N.H., Mod /olus beds persisted for over five years. However, survival de-pended on the ability of Modlolus to avoid pnedation by Asteries vulgarls or afslodgement by attached helps, which in turn are regulated by grazing sea urchins (Witman 1985). 3.3.4 Eurf ace roujing Panels The fouling pancis program was designed to study both settlement patterns and community development. The short-term (ST) panels provided in-formation on the temporal sequence of settlement activity, while monthly se-quential (HS) panels provided information on growth and successional patterns of community structure. Surface fouling panels have been collected at nearfield (B04, B19) and farfield (B31, B34) stations since 1978 (except B34; sinc e 1982). Panels were not collected, however, for the period January 1985 through June 1986. Panel collection resumed in July 1986 and continued through December 1988. 3.3.4.1 Eeasonal Settlement Patterns Historically, species richness (number of taxa) on Seabrook short-term surface panels has increased steadily throughout the summer and early fall and decreased in late fall (Figure 3.3.4-1). In 1988, faunal richness inciensed steadily to a peak in September at all stations except B04, which peaked in October, then declined throughout the late fall. The mean number cf taxa in 1988 wan lowest at Stations B04, B19 and B34 in March and at B31 in May (Figure 3.3.4-1). The mean number of taxa in 1988 was highest in September (B19, B31, B34) and October (B04), with values ranging from 13 taxa at Station B31 to 17 taxa at station B34. The mean number of taxa on short-239 i
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ouBWW.L MEM g 2- - 2- a - o . . . . ......... o . JAN RB MAR APR MAY.RM .RA. MS SP OCT POf E JAN RB MAR APR MAY.RM .AA. AUG EP OCT IOf E I 300 NTH MONTH Figure 3.3.4-1. Faunal richness (number of different taxa in two replicates) in 1988 compared to mean species richness and t 95% confidence lin.its from 1978-1988 on short term panels. Scabrook Baseline Report,1988. ~
l term surface panels, over all years, has ranged from a lou of 2 (March, 1 Station B04) to a high of 16 (September, Station B34)(Figure 3.3.41). Fauna ! appearing on the short term panels in 1988 included bivalves, r.mphipods, polychaetes, and colonials; taxonomic groups that have all occurred pre- I viously. Overall, in 1988, species richness at the nearfield Station B04 was slightly lower than at the farfield Station B34, flowever, f aunal richness at the nearfield Station B19 (near the discharge) was slightly higher than the farfield Station B31 (Figure 3.3.4-1). Over the baseline period, the greatest mean species abundance occurred in the summer and declined through the fall at all stations (Figure 3.3.4-2). Stations B04 (nearfield) and B34 (farfield) have followed similar temporal patterns; however, abundances at Station B34 were slightly higher than at Station B04. Species abundance patterns at Station B19 (nearfield) cnd Station B31 (farfield) have remained quite similar in most months. The species abundance values for 1988 were comparable to past years, with a few notable exceptions (Figure 3,3.4-2). In April and May 1988, abundance values et farfield Station B31 were lower than the mean of all years combined, with May showing a dramatic deviation from the overall mean (no noncolonial crganisms were collected). The dry-weight biomass (g/ panel) for short-term panels followed the pattern observed for the seasonal distribution of species density and species richness, llistorically, biomass values have been highest during August, September, and October. Seasonal trends in 1988 were similar to baseline years (Table 3.3.4-1). Stations B19 (nearfield) and B34 (farfield) exhibited notable biomass increases in October, as has occasionally occurred in pre-vious years. !!1gh biomass values in 1988 at these three stations were due to dense Tubularla sp. cob.erage and large Nyt/1/s edu11s individuals (up to 36 mm in length)(NAI 1988a and photographs in project file). l 241
, f I I MEARFIELD s-. s- ' Station 904 Station B19
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Seabrook Baseline Report,1988.
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Several dominant taxa on panels were monitored to determine their : long term recruitment patterns at nearfield (804, B19) and farfield (B31, 834) stations. A summary of notable differences for these species in 1988 compared to the baseline period is shown in Table 3.3.4 2. l i Monthly mean abundances for some of these short-term panels species : are shown for all years sampled in Appendix Table 3.3.4-1. The panels selected species, Mytilidae and Jassa talcata are discussed in Section 3.3-5. - l l 3.3.4 2. fal.1_er,Us of Community _ Development ! Monthly sequential panels measure growth and successione1 patterns of community development. A comparison of the settlement sequence and species survival on nearfield (Stations B04 and B19) monthly sequential panels is shown in Figure 3.3.4-3. Historically, settlement activity has been most intense in the summer months and has continued into fall (Figure 3.3.4-3). In 1988, the phttern of community development on monthly sequential panels was similar to that of previous years. Similar to previous years, settlement density in 1988 was high in summer months, especially for Mytilidae and Obella spp., and persisted throughout the fall. The density and settlement pattern of #1ste11a sp. in 1988 was similar to recent years in which panels were exposed for up to a full year (1982-1984, and 1987). Jassa ( /alcata settlement followed baseline trends, but density at both monthly { sequential Stations B04 and B19 was substantially lower than all previous years. The settlement of the hydroid Tubularla sp. was similar to previous years at both stations, with the exception of recruitment in January and February. Winter settlement in 1988 reflected an unusually protracted recruitment of the 1987 year class. Balanus ap, was present April through i December in 1988 and exhibited similar frequencies at both Stations B04 and 244
I TABIZ 3. 3.4-2. DIFFERENCES OBSERVED ON 1988 NEARFIELD,$HORT-TERM PANELS COMPARED TO BASELINE PERIOD (1978-1987 ) AND TO FARFIELD STATIONS. SEABROOK BASELINE REPORT, 1988. , 8PATIAL TEMPORAL (NEARFIELD VS. FARFIELD (NEARTIELD B19 VS. 831
- SPECIES B04, B19) B04 VS. B34)
Anon /a sp. Station B04 and Station Station B31 1988 abundance B19 abundance lower higher in October vs. than 1987 but compara- Station B19. Station ble to previous base- B04 abundance higher line years in September and Octo-ber than Station B34 : Asteridae Comparable to baseline Station B04 abundance , i higher in October than Station B34. Station B31 abundance higher in July than Station B19 ' Balanus sp. Abundances at Station Station B19 abundance B04 and Station B19 higher in April, May, highest in April and and July vs. Station l May, total abundance B31. Station B34 abun-comparable to baseline dance higher than B04 in May Klatella sp. Station B19 abundance Station B19 abundance comparable to baseline, higher during June Station B04 second low- through August vs. Sta-est annual abundance tion B31. Station B34 observed; Station B04 abundance higher in , lower than most baseline July and August and l years in June, July, lower in September vs. August and higher than Station B04 all other years in July through November Jassa falcata Annual abundances at July thrcugh November both Station B04 and abundance higher at Station B19 the lowest Station B31 vs. Sta- t observed over all years tion B19. July, Sep-tember, and October abundance higher at Station B34 vs. Sta-tion B04 - Lacuna v/ncta Station B19 annual Station B19 abundance abundance comparable higher than Station B31 (continued) 245 5
t TABI.E 3.3.4 2. (Continued)
- SPATIAL '
I TEMPORAL (REARFIEIS VS. FARFIELD (NEARFIELD B19 VS. 831 SPECIES 804, B19) 804 VS. B34) l bacuna vincta to baseline, Station in August. Station B04 l (cont'd. B04 annual abundance abundance higher than lower than most years. Station B34 in August August abundances at l and lower than Station Station.B19 the high- B34 in October and est observed for that November i l month l Hytilidae Station B19 August Station B19 abundance t L abundance second high- higher July through + est observed Station September than B31. t B04 comparable to base- Station B04 abundance ' line years higher in July vs. B34 ' Nudibranchia Abundance at Station B34 much higher in Sep-tomber than at Station B04 l l Pontogenela inermis No differences observed Density low L . l- Strongylocentrotus Density extremely low No differences observed ' droeschlensis Diatoms- No differences observed August percent frequency higher at Station B19 vs. Station B31 Obella spp. No differences observed No differences observed Tubularia sp. Station B19 percent fre- Percent frequency high-quency highest in Aug- est at Station B19 vs. ust, similar to 1978 and Station B31 in August. 1979. Station B04 per- No settlement of cent frequency highest Tubularla sp. occurred in September, similar at Station B31 in 1988, to 1980. 1981, and 1982 liigh percent frequency extends from August through October at Eta- 3 tion B04 and from Sep- t tember through November at Station B34 I s except at Station B34 where panels were first co11ceted in 1982 and from January 1985 through July 1986, where no panels were placed or collected ', 246
1 i i , STATION B04 STATION B19 ! JTN&NJJ&80WD JfMANJJA80ND sytnidae 19u ...... .........N..5nigm nyt m ese tw2 ...... ..... Enguilt *
" . - ." }))lllllg -. "M
_""...... g gg l 19 0 19 0 " iw4 in. _""... ... 19M' 19E' M l 1987 ... lgll...g 1987 ." "._gglgan" 1988 ". 1988 - jl liste11eop. 1982 ... ............... Ilate11aap. 1982 ... ........................ l 19e ... ......g............ 1983 ...........[H...N 1984 ............ ...... 1984 .........llg...g 1986' " M 11 M 1 HilE 1m' fl!I11Ml!!mittl3 . j 3w? _ ......g............ 3w, _ _ ...nlp.............. t ! 1988- "".""Q]h"Q]j 1988 -".ll))illlJll))il]ill$ ! Jessa falcata 1982 llh @]E : 13::falesta 1982 ." """Hlg l}h"?l$ i,o ... _ ...".."..".gi
. g i,o ......gjg ggly 1964 ... - ... g } M jj]f M 1984 ..lU........' l]'l 1%%' -
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" " " " " " M 11110 1988 " " " . " 1988 . " " " " " . ~ " .
Nudibranchia 1*2 . Nudibranchia 1982 """N]h " ". 1983 ...".".."."..".."....".. 19g3 ............... 1984 ... - ...... 1984 ... ... ...... ... 8 1986' ... - ...**....... 19 % ......... 1987 ............... 1987 ............... ... 1988 _ ... ............ 1988 ... _ l Labelariasp. 1982 """ fubularia sp, 1982 n.HTl]H"ll)) 1983 ...
))]. . . . . . 1983 ". [gn""
iwi ...... 3w4 ......g... i i,m ...... im i 1987 '" 1987 lll "[l]h"." ins ...pygjg... 3 ,8 ... ...g...... I - present ." 125% frepeney g2675 76 100 a llo feeling panele placed or collected froa January 1985 through June 19M. Figure 3.3.4 3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations B04 and B19. Seabrook Baseline Report.1988, i 247
i 3 STATION B04 STATION B19 ! JFNANJJA$0ND JFMANJJA$0kD t meilier. In: ".3gm obeisiip. 1982 pga." Inly."3 nu - 3 3 ... ......... 19e ...... g......... i 1984 ---
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1%4 ...... _ ...... _ ...... Iwi . . 39mi _ ............... Im i ...E............ l 1987 "glWHHH"""NM , 1987 M"""Stinizine 1988 _ ...... 1988 - " " " " " " " " " - Nere!! rp. 1982 . Netelssp. 1982 """"""". 19g3 ......"......"..".."....
. 19g3 .....................
1984 - 1984 19g e --""."..".."_" 19m a ,,,",,",," Iw? ..................... Iu? _ .................. i 19e ... _ ... 1,u _ ... _ ... _ ...... Polynoidae 1982 iHl Polynoidae 1982 1983 ". .- 1983 """- , 1984 ... "... 1984 . " _ " " . " " _ . " 8 8 1986 ."-"""""" 19E " " " _ " " " " . 1987 ." 1987 """ , l it88 ... 1933 _ ... ... ...
- present ".1251 ireguency N 26 75 E 76 100 a
no fooling panels placed or collected from Jantary 1985 through Jane 1986, 1 + l l l 1 Figure 3.3.4 3. (Continued) l 248 l
l 1 B19 as in previcus years (except for 1983 and 1987, where colonization was particularly heavy). Nudibranchia were present earlier than usual at Station B04 in 1988, similar to 1987, but summer and fall patterns of settlement and density were similar to all other previous years, as were those of Polynoidae and #erels 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 . f weights has normally occurred from summer into the fall months at all sta- , tions (Table 3.3.4-3). Annual biomass weights in 1988 were comparable to recent baseline years (1983-1986, with thu exception of 1987, which was lower : than previous years). In 1988, the December biomass dry weights at all monthly sequential stations were the highest recorded over all previous baseline years due to high mytilid biomass. Temporal patterns at paired stations (B19 vs B31 and B04 vs B34) were similar in 1988 (Table 3.3.4-3 and photographs in project file). Laminarla spp. sporeling (mostly L. saccharina, but occasionally L. , digitata) settlement on MS panels has been highly variable from year to year, but generally, more Laminarla spp, fronds have been present June through ( September than in other months (Table 3.3.4-4). Settlement was dense April through August 1988, especially at Station B19 and Station B31 (Table 3.3.4-4). Laminarla spp. density at Station B31 through August in 1988 was higher than all previous years. Annual mean counts at Station B34 were notably higher when compared to those at Station B04 in 1988. I i 3.3.5 Selected Benthic Species i 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 station pairs were sam-249 i
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TABt.E 3.3.0-3. (Continued! YEAR 57AT10N J F M A M J J A 5 0 N D e 1984 B19 <0.1 0.1 0.5 0.6 3.1 8.6 17.9 53.0 ' 213.6 666.9 774.9 1117.6 B31 0.1 0.2 1.2 1.9 2.2 20.3 56.6 116.4 199.6 929.6 364.0 773.6 804 <0.1 0.1 0.7 1.2 1.4 2.7 4.8 232.4 343.6 52.5 583.4 1935.5 B34 <0.1 0.2 0.8 1.2 1.1 9.7 15.4 57.5 262.0 349.0 706.2 1264.1 1986 ** B19 33.3 164.3 422.9 931.1 494.7 498.1 B31 22.1 179.3 449.3 857.7 716.8 883.3 , B04 20.8 157.1 357.0 899.0 481.3 1971.3 B34 29.7 123.9 502.3 873.2 576.9 952.6 1987 B19 <0.1 0.7 1.8 0.4 1.8 28.4 131.6 220.0 54.1 90.7 129.7 170.8 u B31 0.1 1.1
. 0. 2 1.3 - 3.3 17.6 88.8 100.1 40.3 73.1 165.3 93.1 B04 <0.1 1.5 2.1 1.5 1.7 21.9 62.9 49.3 60.3 75.5 114.0 85.2 B34 . <0.1 0.6 1.5 1.5 2.1 13.8 62.8 95.2 129.5 170.1 172.9 167.5 1988 B19 <0.1 0.5 0.5 1.1 4.4 14.9 47.1 158.5 312.2 449.4 534.7 1408.1 B31 <0.1 0.3 1.2 3.8 8.1 19.4 47.5 194.4 267.1 476.9 700.7 1711.3 B04 <0.1 0.2 0.7 0.9 . 1.5 6.2 15.8 74.4 329.2 819.3 199.0 1082.7 B34 <0.1 0.3 0.9 1.2 1.4 5.6 15.7 90.9 221.5 514.4 270.0 1716.4
-a b
In 1978, biomass measured only from December monthly sequential panels, Data not available for Janeery 1979. d Panels were not sampled in January 19815 or from Jenwary 1985 through June 1986. Station B34 was first sampled in 1982.
' e December weights in 1983 through 1988 represent means calculated from two replicate panels (10 x 10 cal. ...an,4 - s s. .g m.- ,. . . . . - . . 4y2-w.,,. - e:
9 'ew-,, 7-- g- ~ g m . . , , , . ~q_,
' TAB 1.E 3.3.4-4. I.AffDEARIA SP. CX3UNTS 01819DNTMLY SEGUENTIAL SUPIACE FOULING PAIELS BY AIIEA, STATION, YEAR AIS MONTIt.
SEA 85t00K BASELIBE REPotr,1988. AREA STATION . YEAR APR MAY JUN JUL AUG' SEP OCT HD9 DEC IEAff S.D. MEARFIEID B19 1980 0 0 10 19 10 18 % 23 13.9 31 10.22
.1981 4 13 0 2 0 0 0 0 0 2.1 4.31 1982 53 54 ' 32 116 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 2 6 10.3 10.90
- 1986 8 3 1 3 4 0 3.2 2.79 1987 0 22 69 102 27 176 85 63 97 71.2 52.80 1988 69 68 129 127 97 36 1 0 0 58.6 52.44 FARFIEID B31 1980 0' O -d 22 39 12 79 75- 39 33.3 30.92 1981 4 0 6 19 0 1 0 5 5 4.4 5.98 u 1982 les 98 72 92 104 95 122 103 64 95.3; 17.85 in '1983 0 97 126 143 N 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 1988 48 82.4 57.28 294 .273 293 349 190 70 26 55 ' 56 178.4 127.41 NEARFIEID B04 1980 0 0 18 15 4 4 5 18 29 10.3 10.06 1981 3 1 0 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- 0 0 1.7 3.57 -
1984 2 1 2 0 0 0 0 0 0 0.6 0.88 1986 . 7 0 1 0 .0 0- 1. 3 - 2.80
-1987 0 2 6 0 24 1 2 4' 1 4.7 7.60 l
1988 27. 29 28 16 8 3 0 4 6 13.4 11.77 FARFIELD B34 1982 27 51 46 69 65 50 53 47 65 52.6 12.83 1983 0 8 II 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 23 43 24.6 17.66
~1988 33 15 52 57 36 16 12 12 2 26.1 19.28
- Fronds counted were L. saccharine and occasionally L. digiteta.
e,No panels collected Yren January 1985 through June 198 . d No Imminaria sp. >3 cm tainimum length for counting) present before April. Data missing for Station 31 June 1980.
i pled three times a year: intertidal Stations B1MLW and B5MLW, B17 and B35 at approximately 5 m depth, and Stations B19 and B31 at 9-12 m depth. Selection of taxa was based on abundance, and/or trophic level (Table 2.3-1). Data from fouling panels set 3 m below the water surface at Stations B19 and B31 and exposed for one month intervals from 1978-1988 were compared to benthic data. Numbers of large sea urchins estimated from counts for SCUBA diver transects were noted. 3.3.5.1 Hytilidae Mytilidae, composed primarily of juvenile #rtflus edu11s, was the most abundant taxon at all three nearfield/farfield station pairs. Nytllus edu11s reaches 100 mm in length (Gosner 1978), and is an iniportant prey spe-cies for fish, sea stars, lobster, and gastropods. It clings to hard sub-strate with strong byssal threads, is an important fouling organism, and forms a habitat for many other species. The geometric mean density for the entire 1978-1988 study period was highest intertidally, and generally de- 4 creased with increasing depth (Table 3.3.5-1). The highest density (geomet-ric mean over all years) was 116,198/m' at intertidal Station B1MLW and the lowest was 1680/m 8 at Station B19, 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 with a one-way ANOVA (Table 3.3.5-2) and apparently reflect a high natural variability in primary and secondary recruitment. Abundance was highest in 1985 at both l l cid-depth stations (B19 and B31), but 1985 had nearly the lowest abundance l l ct the shallow subtidal (5-m) stations (B17 and B35) and intertidal stations 253
4 TABLE 3.3.5-1. AIB OAL GED4ETRIC N OF THE ABUIDUICE ObJm') W SELitTED BENTHIC SPECIES SAMPLED TR IN MAY. AtlGUST. A!ID IIOVD!BER FROM 1978 72R00GE 1988. SEABROOK BASELIllE REPORT.1988. OVER ALL YEARS TAIA STA 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 MEAN 12TER LONER Aspithoe rubricata BIEW 518 545 448 343 133 23 9
-b 3 - <1 0 <1 28 51 15 BSEW - - -
88 15 0 0
<1 0 1 2 5 1 B17 0 0 0 191 0 14 4 2 1 0 E6 - 1 2 3 1 0 52 10 6 11- 2 11 7 12 4-B19 - 0 0 0 74 0 9 I 24 7 B31 0 0 0 4 1 3 5 2 147 0 5 8 3 1 2 15 3 5 2 Asteriidae B17 - - -
1738 669 208 392 592 373 448 712 535 662 432 B35 - - - - 630 39 167 198 79 245 338 177 258 121 Jassa falcata B17 1007 884 679 3389 3298 398 660 1622 2166- 1513 261 1083 1467 799 B35 - - - - 5307- 4980 2031 1465 -1387 809 742 1817 2755 1199 Mytilidae- BIEW 161759 116973 70760 130890 253375 60978 78849 63307 196498 B5 M - - - - 42213 126995 154602 116198 142322 94870 60552 73895 57505- 120455 127304 99100 77310- 98216. 60854 B17 1875 8789 1269 2256 3490 963 7980 566 4744- 5171 1226 2477' 3497 1755 B35 - 1565 7328 13416 1055 5294 7981 4539 4385 6409 2999 B19 84 307' 905 2069 1776 1247 -6493 6651 4943- 3521 3668 1680 2480 1137 B31 1437 3338 13422 13650 1687 1095 17842 - 81457- 3995 8000 8194 6299 8877 4469 Nucella lapillus Bl u 1355 2987 3973 1981 -944 -1586 5176 3250 2559 1037 1360 2064 2483 1716 B5EW - - - - 649 783 909 1378 691 1326 746 ' 888 -1121 703 Pontoceneia inerais B19 902' .538 '599 584 762 .562 386 604 908 308 893 608 ~765 484 B31 1% 400 390 649 554 470 512 280 773 105 838 407 537 309 Stronavlocentrotus B19 20 70 152 - 281 - 80 15 29. '188 135 99 oroebachiensis 15 65 100 - 42 B31 .28 60 73 142 71 55'-- . 33 35 - 23 17- 16 40 . -56 29 a n - 9 (3 replicates taken 3 times per year) b - not sampled 4
.-a..
. ~~ , % -
# - - -c.,-,.-~.v.. 3. .a .',., ..
TABLE 3.3.5-2. RESULT 5 0F OBE-40AY ANALY5IS OF VARIANCE ANYEAltS FOR 71tE IAC Ex*1) TRAlt3F0EWED DDt3ITY f sw% ) OF SEIECTED BDt!1 TIC SPECIES SAMPLED FItG1 1978 OR 1982 TNIt0'JCit 1988. SEABit00K BASELIE ItEPORT,1988. SOINIM OF flULTIPLE CINIPARISONS SPECIES STATIcet VARIATION df 35 F AmPhithee rubricata B1Mut Years 10 115.14 20.79e#= 79 78 80 81 82 83 84 85 86 88 87 Error 88 48.73 Total 98 163.87 B5Mut Years 6 31.60 12.7888* 82 83 88 84 86 87 85 Error 56 23.07 - - Total .62 54.67 B17 Years to 45.04 20.08e** 81 83 84 85 86 - 88 80 82 79 87 78 g Error 88 19.74 - - u Total 98 64.78 w B35 Years 6 15.57 5.52*** 83 88 '86 84 85 87 82 Error 56 24.34 . Total 62 41.91, B19 Years le 36.29 10.99=== 81 85 83 87 86 88 84 82 79 80 78 Error 88 29.09 Total 98 65.38 B31 Years 10 40.88 15.49e** 81 ~ 88 84 83 85 87 86 82 - 79 80 78 Error 88 23.22 - Total 98 64.10 f contirmed )
.._m. .~ . ~ . - - . .
_ ~ m>-. .
. , . . , , , ,. . ,. ,_, __ . ,_ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ._ _ l
TAB 12 3.3.5-2. (Continued) SOURCE OF MULTIPLE CIMPARISENE5 SPECIES STATION YARIATICH df SS F Mucella lapilles B1MLN Years 10 5.38 4.51e** m 80 85 79 86 81 - 83 88 78 .87 82
-Error 88 10.50 Total 98 15.88 B5M1Jf Years 6 0.95 0.98 M5 85 87 84 83 88 86 82 Error 56 9.06 Total 62 10.01 Jassa falcata B17 Years 10 11.45 3.22*** 81 82 - 86 85 .87 78 79 80 84 83 88 go Error 88 31.30 y Total 98 42.75 B35 Years 6 6.37 2.33" . 82 83 84 85 86 87 88 Error - 56 25.D Total 62 31.87 ene Asteridae B17 Years '7 4.53 6.39. 81 ' 88 82 85 87. 84 86 83 Error 64 6.48~ -
Total 71 11.01 - B35 Years 6 8.55 4.52 " 82 88 87--.85 84 86 83 Error 56 17.64 Total 62 26.18 Pontogenia inermis B19 Yemes 10 -- 7.46 .1.73 M5 78 88 82 85 .80 81 83 79 84 87 86 -
- Error 88 ~ 37.83 Total 98 45.29
~
B31 Years le 6.45 1.98" 88- 86 '81 82 M- 83 79 80 85 78 87 Error 88 '28.62 Total 98 35.07 (continued) 1
~ --v -- ->_ _ _ - - __ _ : -- N r- ~
r ~ - -~ r ' ~- --'-+A<" N -A- + t- - - a ,s + - 4 m >,- e -
s
~
TABLE 3.3.5-2. tContinued) SOtMCE OF PRfLT77tX CINIPARI501E5 SPECIES STATI0ft VAacIATIOpt df SS F Strongylocentrotus B19 Years le 18.05 2.15 81 85 80 . 87 82 79 84 86 78 83 88 droebachtensis Error 88 73.88 Total 98 91.93 B31 Years 10 7.60 1.65 MS 81 80 82 79 83 85 84 78 86 b 87 88 Error 88 40.45 Total 98 48.05 Mytilidae B1MLN Years 10 3.87 2.23 82 86 78 - 88 81 87 -79 85 84 80 83 Error 88 15.24 Total 98 19.11 N B5MLW Years 6 1.74 1.84 MS 87 86 88 84 83 85 82 - Error 56 8.83 Total 62 10.56 B17 Years 10 13.83 2.94 " 79 84 87 86 82 81 78 80 88 83 85 Error 88 41.37 Total 98 55.20
!)
M B35 Years 6 8.48 4.39 84 87 83 88 82 85 Error 56 18.09 Total 62 26.57 woe B19 Years 10 29.23 3.49 85 84 88 87 81 82 83 86 80 79 78
-Error ~ 88 73.73 .
Total -98 102.97 B31 Years 10 28.04 9.26 85 84 81 80 88 87 86 79 82 78 83 Error 88 26.65 - Total 98 54.69 MS r not significant (p>0.05) e = significant 10.052p>0.01)
** = highly significant t o.012p>0.081 )
e * = very highly significant ty20.001) bS*ince the F value is MS, years are reported in order of decreasing abendence, and not groeped.
( (B1HLW and B5MUW)(Table 3.3.5-2). At the shallow subtidal stations, the abundance was at'the all-time high in 1979 at Station B17, and wcs also very high in 1984 and 1987 at both shallow subtidal stations. The Mytilidae collected usually ranged from less than 1 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 inves- , { tigators (Bayne 1965; Suchanek 1978).. The overall mean length of. intertidal; mytilids was slightly larger than subtidal mytilids, (Table 3.3.5-3), even y though intertidal population densities were much higher than subtidal densi- '! i ties. Hytilid lengths showed no significant differences between nearfield and farfield station pairs when tested with a two-way ANOVA (NAI 1987bt Table- ,; 3.3.5-4). Yearly differences in mean11ength for each of the nearfield/far-field station pairs historically have hot been significant-(NAI 1987b: . Table 3.3.5-4). In 1988, the lengths at the intertidal station pair were about average even though the density had changed from the previous year. At sub- ! tidal station pairs the mean lengths in 1988 were above average, and densi-ties were approximately the same or lower than 1987 densities (Tables 3.3.5-1, 3), indicating slightly below-average recruitment. The level of mytilid recruitment is indicated by the abundance on short term fouling panels set 3 m below the surface at Stations B19 and B31 - and exposed for one month intervals from 1978 through-1988. Recruitment was ~ the highest ever at Station B31 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 low-est with- just under 60 individuals per panel. Abundance in 1988 was below average at.both Stations B19 and B31, respectively. Information from surface ' fouling panels suggests that-some primary or secondary settlement takes place throughout the year, but is heaviest from June through November (Appendix-Table 3.3.4-1). Mytilid lengths at Stations B19 and B31' ranged from <1 mm to' ; 40 mm in 1988 (NAI 1989: Appendix Table 9-7), about the same as previous . 258
, l- -
t il i < l4 I 2 36 32 22 12 21 46 32 84 C 8 3 00 00 00 00 00 00 00 00 - Y 8 A 9 . M 1 t f 99 74 64 25 89 74 51 27 75 N A I E 26 48 44 33 22 32 17 65 22 D 1 1 Y ._ L - L A W . I 36 21 21 1 1 11 64 34 23 5 8 7 C f 8 - - 00 00 00 00 00 00 00 00 A 9 I 1 89 R 1 T , t f 16 85 11 93 80 93 76 77 T A DR E - - 54 33 33 12 12 14 45 11 E O I 1 L P P E MR A S E I 66 22 12 1 2 13 55 32 32 N C S I E L 6 8
-- 02 00 00 00 00 00 00 00 I E 9 C S 1 N
E A 31 41 80 57 31 72 72 55 P B A S E - - 77 44 24 22 24 76 45 11 K I 1 CO I O M R T B l l A I 1 40 22 21 21 21 35 33 46 E E C B S 5 4- 01 00 00 60 00 00 00 00 8 D 9 E . 1 T 8 M 9 51 55 60 44 45 03 38 75 C 8 A I9 E 0 - 70 44 23 22 23 56 55 22 1 1 M 1 1 E S N r C e - R U b OO I 5 89 21 1 1 1 2 11 24 22 32 m F R C -. e
) H 4 1 - 00 00 00 00 00 0e 00 00 v T 9 o I 9 N C 2 1 I 8 M 99 87 47 79 81 11 09 96 77 d 9 A n 3 L 1 E 68 75 43 22 23 22 46 44 11 a A f T f ,
RR t t E R T F s r N I u a 68 74 22 11 11 26 33 53 g e I St C 2 2. . u y f 3 00 03 00 00 00 00 00 00 00 A E 0 8 t C I 9 , a N T 1 y h E A M 75 44 37 52 11 39 32 22 83 a t D T A M I S E 78 51 43 43 22 21 36 55 12 n F I 1 n i N C i O I d C MT d e e r
%N I 35 35 22 1 1 11 12 32 32 r u 5 E C 3. f. u s 9 B 2 00 00 00 00 00 00 00 00 00 s a 8 a e +
E D 9 e m M E 1 m T T M 76 03 35 78 98 02 07 46 87 s C A s l OEL I E I 67 45 33 22 11 22 85 44 11 l a u a A E u d S d i a) i v T v i nA I 34 23. 11 11 11 11 22 11 11 i d a R L C d n
~
t L 00 00 00 00 00 00 00 00 00 n i E A i R R T B f Ea o G N V D V M O A 08 48 29 23 46 47 61 12 99 l l E a r IO I M M 77 56 43 33 22 22 66 55 11 f b e o m A e l l u g s n EA I N h t l O NN NN NN g a L T I LL 1LM LL n t A S T MM 75 75 ! 75 91 MM 91 91 e o U U E A 1S 13 13 !S 13 13 1S 13 13 l t G T d S U AI A S e e h t t c
. i s e f l 3 a s o l ,
- t . n o 5
a e a c a e a c i i u 3 e a t d a l a e a s e a s l w h c s n e 3 A o c i f d a l i y s a = o X h i i i l l g u b n E A T t r b r e a s l l ep i # mr o n t e M B i p u s i t e o o A = A m r t s a t y ca n n r r r E e ol o i t t'd M - T A A J M N P S a - gvm
l-L -{ years. Monthly measurements indicate over 94% of the mytilids measured at ' L each station were 1 mm or less in July, with subsequent monthly growth and L new recruitment evident through December (NAI 1989: Appendix Table 9-7). 3.3.5.2 Nuce))a lapillus l 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). Signifi- r cant differences in abundance between stations'were found between intertidal Stations B1HLW and B5MLW from 1982 through 1986 (NAI"1987b: Table 3.3.5-2). t The overall abundance at Station B1MLW was more than double the overall abun-dance at Station B5HLW (Table 3.3.5-1). Very highly significant differences among the years 1978 through 1986 were found for Station B1MLW with 1984 ' l having the highest abundance and 1987 and .1982 having the lowest abundances # (Table 3.3.5-2). Farfield Station B5MLW was sampled from 1982-1988, and no significant differences were found among years (Table 3.3.5-2), although
- abundance was also lowest in 1982.
m Nucella collected during the entire study period ranged in-length , from about 1-27 mm, and averaged slightly over 6 mm in length at both sta-tions (Table 3.3.5-3). In 1987 and 1988, the mean length _was unusually large i due primarily to the occurrence of substantial numbers of large (14-18 mm) individuals. Large numbers of small Nucella usually occurred in August or September, indicating recruitment occurred at that time'(NAI-1985b). Larger individuals (>10 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 average yearly length ranged from 3.3 mm at Station B1MLW in 1983 to an unusually large 11.9 mm at Station B1MLW in 1987. No significant differences in the yearly mean length (through 1986) were found L between stations or among years (NAI 1987b: Table 3.3.5-4). 260 ,
l 3.3.5.3 Astertidae i i The Aster 11dae ollected are juveniles, too young to be assigned to genera. Two species of both Aster /as and Leptasterfas can occur within the ! study area (Gosner 1978). Aster 11dae are important predators on bivalves, particularly on the recently-settled stages, as well as other molluses and barnacles (Gosner 1978). Very highly significant differences in annual abundances were found I; among years and between stations at subtidal Stations B17 and B35 (Table 3.3.5-2). Annual mean densities were consistently !.igher at Station B35,. leading to an overall average that was three-fold higher at the nearfield otation (Table 3.3.5-1). Very highly significant differences were found , among years at both Stations B17 and B35 when tested with one-way ANOVA. (Table 3.3.5-2). The yearly trend was very similar at both stations: highest abundances occurred in 1981, 1982, and 1988 and lowest abundances i l occurred in 1983, 1984 and 1986 (Tables 3.3.5-1 and 2). 1 L i A successful set of juvenile Aster 11dae occurred in August of 1982 (NA1 1983a), and very little recruitment occurred in 1983 or 1984. In 1985, 1987, and 1988, annual densities were relatively high, indicating successful recruitment. Spatial and temporal changes in abundance and length seem to be related to the recruitment success of each year's cohorts (NAI 1985b). The- ' cverall average length at Station B17 was 5.4 mm 1 0.2, and at Station B35 it was 6.8 mm i 0.3 (Table 3.3.5 3). Yearly mean length of sea stars collected at Station B35 was usually greater than Station B17, 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, with larger sea stars occurring at Station B35 (NAI 1988b). 261 i
i T I A few recently-settled Asteriidae were collected on short term surface fouling panels from 1978 through 1988, 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). F 3.3.5.4 Pontonenelo inermis
- Pontogenelo inermis (maximum length, 11 mm) is a pelsgic, cold i water amphipod (Bousfield 1973), and a dominant species in benthic and 4 macrozooplankton collections (NAI 1985b). It clings to submerged algae from.
the lower' intertidal to depths greater than 10 m (Bousfield 1973). Popula-tion densities were remarkably consistent'from 1978-1988, and no signi-m ficant differences were found among years at Station B19. However yearly-differences were significant at Station B35 with 1988 having the highest density and 1987 the lowest (Table 3.3.5-2). .In 1988, population densities , were well-above average at both stations. Interstation differences were sig-nificant (NAI 1987b: Table 3.3.5-2), and the overall geometric mean abundance
'was from 1.5 times higher at Station B19 than at Station B31 (Table 3.3.5-1). ,,
Historically, ovigerous and brooding females have been collected in low numbers from January through September (NAI-1985b). Recruitment, as'in-dicated 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).. l The overall mean length for the 1982-1988 study period was 5.1 mm at Station B19 and 5.2 mm at Station B31 (Table 3.3.5-3). No significant differences in mean lengths (through 1986) were found between stations or years-(NAI 1987b: 1 Table 3.3.5-4). Average lengths in 1988 were well above the 10 year average at both stations (Table 3.3.5-3) at the same time that population densities were very high. Thus, 1988 was a year of high growth and recruitment for t 1 Pontogenela inermis. ! 262
1 l Pontogeno/a Joermis was common on short term fouling panels at Sta-L tions B19 and B31 from 1979 through 1983, but numbers decreased sharply from 1984 through 1988 (no samples in 1985). Peak abundance usually occurred from April through June, and annual mean abundance was highest in 1981 (Appendix Table 3.3.4-1). By 1987 the average yearly abundance had declined to zero, and remained unchanged in 1988. 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 end wave currents (Bousfield 1973). It is a suspension feeder and also preys on small crustaceans. Significant differences in yearly abundance were found for subtidal Stations B17 and B35 (Table 3.3.5-2), with 1988 having the all-l time lowest recorded density at both stations. The mean geometric density ranged from 261/m' at Station B17 in 1988 to 5307/m 2 at Station B35 in 1982 (Table 3.3.5-1). Most lifestages of Jassa were collected at Station B17 and B35, renging from gravid females to newly-hatched young (NAI 1985b). llistori-cally, gravid females have been 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 cverage length for the 1982-1988 study period was 4.2 mm at Station B17 and ! 3.9 mm at Station D35; interstation differences through 1986 were not signi-l ficant (NAI 1987b: Tables 3.3.5-3, 4). In 1988, the yearly annual mean length at both stations was the largest during the study period (Table 3.3.5-3). The size ranged from about 2 to 8 mm in length at both stations cnd more large specimens were present than collected-in previous years (NAI 1989). Densities on short term fouling panels, exposed for one-month in-tervals, from 1978 through 1988 give an indication of recruitment or settle-ment activ!cy. From 1978-1988, substsntial numbers of young began appearing 263
.. t 5
in July'and continued to-settle through October, and'in some years through December (NAI 1988b:-Appendix Table 9-4). Record high monthly densities oc . curred at Station B31 in 1987 from July through October, peaking in September- ; with 541 individuals per panel. Mytilid spat, which can provide habitat for' , amphipods, were also abundant at that time. In 1988, densities were very low at both stations (Appendix Table 3.3.4-1), as they were for benthic stations. e 3.3.5.6 Ampithoe rubricata ~ c Ampfthoe rubricata (maximum length,- 14-20 mm) is an amphi4tlantic' boreal amphipod which constructs a nest of tubescamong macroalgae (fuccids) and in' mussel beds (Bousfield 1973). It As found in intertidal and' shallow subtidal areas. Yearly densities have fluctuated significant1y'during the study period, and have generally declined from about:1981 through 1987 (Tables 3.3.5-1, 2). The most dramatic decrease in density occurred at intertidal Station B1MLW where densities fell from 518/m8 in 1978 to 0 in 1987, and were <1/m* in 1988 (Figure 3;3.5-1). -In 1988, populations at subtidal farfield stations showed a noticeable increase in abundance. Ampichoe rubricata is a boreal species near-its southern. zoogeographic limit, Long Island Sound'(Bousfield 1973), and it may.have-been affected by increas-- ing annual surface temperatures from 1983 through'1987 (which' approximate intertidal temperatures). Annual mean surface temperatures decreased by 0.6*C in 1988 (Table 3.1.1-1). The decrease in A. rubricata abundances =did , -not appear to be accompanied by increases in any other: similar species. Ovigorous and brooding females were rare, but have been occasion-ally 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 densitios l and larger mean size (NAI 1985b), and the trend continued through 1988. The overall mean length for the 1982 through 1988 study period was 7.0 mm at Sta-f 264
INTERTIDAL INTERTIDAL
,, Station B1MLW .. Station B5MLW s.
a-Ia. l
.g .
g . s a .. , 1- - l
.. i 0 . . . . . . 0 !
. . . . . . .. . . .. i' 19781070198019811982198319841986198610871958 19781079198019811982198319641985198619871988 YEAR YEAR i i
~
SUBTIDAL SUBTIDAL 4 Station B19 .. Station B31 a- 3
2-8 a
j
, a ->
1- " 1
,, / ..
g 0 . . 0 ' i i i i i , , { , . , , 19781970198019811982198319841905198610871988 19781979108019811982198319841985108610871988 3 YEAR YEAR Figure 3.3.5 1. Yearly mean and 95% confidence limits for the log (x+1) density (No./m 2) of Ampfthoe rubricata sampled triannually in May August, and November from 1978 through 1988. ( B5MLW sampled from 1982-1988 ). Seabrook Baseline Report,1988. 265 l
{
'I tion B1MLW, and 7.8 mm at Station B5MLW (Table.3.3.5-3), and no significant-difference in the average yearly length through 1986 was found.between sta- ,
tions (NAI 1987b: Table 3.3.5-4). The average yearly length ranged from 6.7 mm at Station B1MLW in 1982, when young were present, to 12.9 mm at Station l B1MLW in 1988, when only one specimen was collected (Table 3.3.5-3). When i mean seasonal lengths were compared with a paired t test, interstation dif-forences were not significant (NAI 1988b). ~ i 3.3.5.7 Strontvlocentrotus droebachlensis Strongylocentrotus droebachlensis, 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 , Laminarla saccharina over other common algal species (Larson et al. 1980; Mann et al. 1984). When the nacroalgal supply is depleted, it will prey on , Nytilus edu1/s (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'significant differences were found between Sta- ;
tions D19 and B31 (NAI 1987b: Table 3.3.5-2) for the 1978-1987 study period when the overall years' mean was 75/m' and 45/m' at each station, respec-- tively. Differences among years were not significant at Station B31, but. were significant at Station B19 when tested with a one-way ANOVA'for the 1978-1988 study period (Table 3.3.5-2). The yearly trend was-similar at both stations, with the highest abundance occurring in 1981, and the lowest in 1988 (Table 3.3.5-1). Most of the individuals collected subtidally were juvenile, mea-suring less than 3 mm in diameter, and recruitment of newly-settled young has historically occurred in August and September (NAI 1985b). The average length for the 1982 through 1988 study pariod was 1.9 mm at both stations
, (Table 3.3.5-3). Neither yearly nor interstation differences in average *
,, 266 l l=
1 l length through 1986 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 Sta-tion B19 in 1985 and in 1988. Very few specimens were collected in 1988, indicating poor recruitment. A few relatively large individuals caused the 1988 annual mean length to be higher than the overall years' average, l In order to account for adult individuals which were too large to l be collected in the destructive program, urchins were enumerated in the sub-tidal transect program done by SCUBA divers. No more than 13 large (> 10 mm) Dea urchins.per year were counted (0.02/m') in three years of sampling (NAI 1986a, 1987a, 1988a), llowever, in 1988 there was an increase to 32, or 0.06/m*. Italf of the urchins were found at Nearfield Station B19; the rest were collected at B17 and B35. None were found at Farfield Station B31 (NAI 1989: Appendix Table 7-10). The extremely low densities of adult urchins in comparison to juveniles indicate that. natural forces are keeping this poten-tial nuisance species under control. l Recently-settled sea urchins occurred occasionally in monthly sam-ples from short term fouling panels set at Stations B19 and B31 during the 10 year study period (Appendix Table 3.3.4-1). Most were collected at Station-B19 from June through September 1981, when the yearly density averaged 1 per panel. The yearly density for all other years including 1988 was_less than one specimen per panel per year. The geometric mean yearly density from bottom samples also reached an all-time high in 1981, at Station B19 (Table 3.3.5-1), and is a reflection of successful recruitment of young-of-the-year. l 267
i 3.3.6 Epibenthic Crustacea 3.3.6.1 American Lobsters (#omarus ' 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') and lowest in 1980 (0.46/1000 m') (Table 1 3.3.6-1). The mean number of lobster larvae caught in 1988 at Station.P2 was slightly below the average of all the other years sampled, but similar to l 1985-1987. The maximum density of lobster larvae usually occurred from July-- through September (Figure 3.3.6-1). During 1988 lobster larvae first ap-peared in early-July at Station P2, a trer.d which was similar to other sampling years, and peaked in early August. At the-farfield sampling site, Station P7. the-density of lobster larvae declined from 1982 through'1984, then steadily increased through-1987, h which had the highest level recorded in this study (Table 3.3.6-1).- In'1988, however, the density of larvae' fell to 0.66/1000m',_the lowest level over the seven years this station has been sampled. Densities were always higher at Station P7 than P2 from 1982-to 1987; this difference was most pronounced in 1985 and 1986, when abundances at Station P7 were more than twice those at < Station P2. In 1988, however, densities at P7 were lower than at P2. Larvao , first appeared at Station'P7 in early May and peaked in late July during 1988. (NA1 1989). In 1986, a third station, PS,-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 and for the entire sampling program in 1988. In 1988, the density observed was 1.34/1000m', the highest density at all three stations. Larvae at Station PS in 1988 first appeared in 1 268
\
k h l TABLE 3.3.6-1. PERCENT COMPOSITION OF LOBSTER LARVAE STAGES AT STATIONS-P2,
- l. PS AND P7, 1978-1988. SEABROOK BASELINE REPORT 1988. t 1
L TOTAL % NO. OF HEAN PERCENT PER STAGE OF LARVAE NO. OF-STA- STAGES COL- LARVAE YEAR TION" I -II III IV I AND IV LECTED' COLLECTED J 1978 P2 10.1 0.0 0.6 89.3- 99.4 169 1.45 , py .. .. .. .. .- NS NS ' 1979 P2 70.8 2.5 1.7 25.0 95.8 120 1.18- 1 p7 .. ... .. .. .. NS NS 't l 1980 P2 86.5 0.0 0.0 13.5 100.0 57 0.46 P7 .. .. .. .. .. Ng Ng I 1981 P2 31.8 1.9 6.5 59.8 91.6 107 0.86 py .. .. .. .. .- 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 l P7 47.5 0.6 3.5- 48.4 95.9 162 1.10 1984 P2 14.6 11.5 21.8 5 2.~ 1 - 66.7 79 0.57 P7 37.2 1.0 2.8 59.0 96.2 101 0.73 l' 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 PS 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 1988 P2 ?.0.3 2.9 5.8 71.0 91.3- 69' O.84 PS 20.4 7.4 13.9 58.3 78.7 108 1.34 , P7 5.9 2.0 -- 92.2 98.1- 51 0.66 0 = In 1986, Station P5 sampled only from July 1 through October 14. b
= R/1000 m' NS = Not sampled 269 e
1 t
; i I
"(,
1.2 - A1.LYEARS MEAN 1.0 - -------- 1988 O ' E w g 0.8-
>- m ,
UI E . , zm :<). 0.6 - - 00 - . . e -
"o -
1
+o no .
M n
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8 n, OW 0.4 - l . [ l\
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. . . . . . . . . . . . . i.' . .
2 3 - 4 1 2 3 2 3: 4 1 '2 3' 2 3 2 3 4 IWAY JUN 4-l-1 JUL AUG. 4l1 . SEP 4l1 OCT
' Figure 3.3.6-1. ' Weekly mean log (x+1) density (No/1000 m 2) oflobsterlarvae at Station P2
_ 1978-1988, all years' mean and 95% confidence interval and 1988. (No data collected in 1982 and January 1985-June 1986). Seabrook Baseline Report.1988. 1
.o.,,, - .m _,m. ,._ -. = _ _ _ _ , _ _ _ _ _ _ _ _ _ _ _ , . -; m- -* -
-w'=*--4 -g ------~i s 4 ,-a' -*"y--..'%- r-~ =-1 r- r.--~. '-
-c. ,y , - r ,..,.y a,._. _
,5 >~m.,ive-<
?
f mid July and peaked in early August, much like Station P2. Larvae were i observed from early July through mid-September matching the pattern at the other two stations in 1986 (NAI 1987a). Historically, Stage I and Jh/ larvae have dominated the collections at both Stations P2 and P7, with few Stage II or III larvae collected (Table i 3.3.6-1). . Stage I larvas dominated the. collections in 1979 and 1980, while L Stage IV- larvae dominated the collections in a11' other years. ' Stage II and III larvao collectively constituted 8.7% or less of the larvae collected for . ' all years except in 1984, when they made up'33% of the total density at . Station P2 (Table 3.3.6-1). In 1988, the pattern at Stations P2 and P7 was similar to previous years; over 90% of the larvae were either Stage I or IV. However at Station P5, 21% of'the larvae were either Stage II or III. - No Stage III-larvae were collected at Station P7 (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 usually first= appeared in late Hay or' June in low numbers at Stations P2.and P7.
l- Peak density of Stage IV larvae varied in occurrence between. July' and August
- (NAI 1988b). The variability in larval density from year to year may be L explained by patchy distribution, which is not revealed by the sampling program (Cobb 1976).
Larval occurrences at all stations in 1988 were generally consis-tent with previous years. A single Stage I larva occurred in mid-June at' P7 but Stage I larvae did not occur at P2 or PS until early August. Stage'IV l larvae appeared at all three stations in mid-July while Stage ,II larvae were first observed in late July or early August (NAI 1989). The occurrence of Stage IV larvae prior to Stage II in 1988 may have been a fortuitous capture. Trends in the occurrence of lobster larvae in this study have' gen-erally agreed with other lobster larvae studies in New England (Sherman and LewJs 1967; Lund and Stewart 1970). An extensive review of New England re-271
1
)
gional-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. 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% i of Stage IV larvae were collected off the New Hampshire coast when winds were on- or along- shore. Air temperature differences betwoon water and land mas-ses, combined with predominantly light westerly summer winds, produced on-- l shore winds during the day and offshore winds at night. In addition, hydro-graphic studies-in the Hampton/Seabrook area indicated a net drift northward l.
, or southward along the New Hampshire coastline. Combined, these two actions suggested that lobster larvae may be 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 al. (1983) supports this explanation. 'They noted that lobster landings for l all regions neighboring on the Gulf of Maine have been very similar since the l mid-1940s, and conclude that a single lobster stock with common recruitment
, exists. They further concluded that warm southwestern waters of the Gulf of Maine and Georges Bank supply the Maine coast and adjoining areas with ad-vanced larval stages, evidenced by a preponderance of Stage IV larvae in the surface waters from southwestern Nova Scotia to Hampton, New Hampshire. A l- recent examination of hydrographic drift studies (Harding and Trites 1988) also supports the suggestion that lobster larvae are carried into the New England region through current transport. The abundance of Stage IV lobster l- . larvae in the present study may occur as a result of such conditions.
272
1 J l Adults ! Adult lobsters (legal and sublegal sizes combined) have been col-1ected in the vicinity of the discharge site (L1) from 1974 to 1988 (Table 3.3.6-2). During that period, the highest monthly catch usually occurred from August through October. Results of a one-way ANOVA confirm that during l the historical period catches in September were highest, followed by catches l in August, October and November, which were sie_ilar. Catches in June and 3 July were-significantly lower than all other months (Table 3.3.6-3). Monthly catch was highest in September during 1988 (Table 3.3.6-2). 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 in 1987 to'92.5 in 1984, but were not significantly different among years (Tables 3.3.6-2, 3). The average yearly catch for 1988 was 65.5 per fifteen-trap trip, similar to several previous years. Among stations, lobster catch was significantly 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 ct the farfield station has been consistent throughout the study since sam-pling at Station L7 was begun in 1982. j- Adult lobster abundances have been related to seawater temperature 1' (McLeese and Wilder .1958, Dow 1969, and Flowers and Salla 1972, NAI 1975b). In the llampton/Seabrook study area, continuous bottoa temperature monitoring , (1978-1984) at Station ID, near the discharge area, was compared to monthly cean lobster. catch. During June, at the discharge station, catch declined as bottom water temperature increased; however, this uns 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*C and lobsters had molted to legal size (NAI 1985b). As 273
L l j
~
TABI.E 3.3.6-2. SUNHARY OF TOTAL LOTJSTER CATCH PER TRIP EFFORT *, BY < d HONTH AND YEAR, AT.THE DISCHARGE SITE FROM 1974 i THROUGH 1988. SEABROOK BASELINE REPORT, 1988. i l-l e r NONTH- 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 66.6- 69.1 63.7 -48.0 54.2-1977 45.8- 32.3 63.5 -67.3 54.5 61.1. 53.71 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- i 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 l' 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 i . 1987 39.5 26.3 33.3 57.2 83.2. 48.2" 46.0 t 1988 41.5 32.8 69,4 98.9 84.5 73.2 65.5 j MONTHLY AVERAGE 40.7 39.6 70.6 86.6 82.4- 70.1 i
" Catch per trip effort = total catch from 15 traps per trip.
/
1 274
1 J 4 TABLE 3.3.6-3. RESULTS OF ONE-WAY ANOVA AT THE DISCHARGE SITE FOR LOBSTER l l. (R. ANERICANUS), J0NAll CRAB (C. BOREALIS) AND ROCK CRAB 1 C. IRRORATUS). SEABROOK BASELINE REPORT, 1988. SOURCE OF HULTIPLE ~ SPECIES VARIATION df as F-VALUE COMPARISONS Lobster Year 13 14033.62 1.51 NS Error 70 50158.42 > Total 83 64182.05 : Month- 5 29261.53 13.07***. 9 10 11 8 6 7 Error 78 34930.52-Total 83 64192.05 Jonah Crab Year 6 678.06 1.99 NS Error 35 1983.12 Total 41 2661.18 Month '5 1258.76' 6.46*** 8 9 7 11.10 6 Error 36 1402.42 Total 41 2661.18 Rock Crab Year 6 70.81 4.74** 85 88 86 84 87 83 82 Error 35 87 15 Total 41 157.96 Month 5 49.02 3.24*. 8 7 11' 6- 10 9 Error 36- 108.94 Total 41 157.96 "8
= Not Significant (p>0.05)
* = significant (0.05>p>0.01)
** = highly significant (0.01>p>0.001)
Q** = very highly significant (p50.001) TABLE 3.3.6-4. PAIRED t-TEST COMPARISONS OF THE DISCHARGE SITE (L1) AND THE FARFIELD STATION (L7) FOR LOBSTER (R. A#ERICANUS), ! JONAH CRAB (C. BOREALIS) AND ROCK CRAB (C. IRRORATUS), 1982-1988. SEABROOK BASELINE REPORT, 1988. CATCH /15 TRAPS MEAN SIGNIFICANT SPECIES L1 L7 DIFFERENCE' n t DIFFERENCES Lobster 65.5 75.6 17.31 42 4.62*** L7 > L1 Jonah Crab 16.6 8.1 1.36 42' 1.60 NE ! Rock Crab 3.2 0.6 1.08 42 4.44*** L1 > L7
= Not Significant; *** p 5 0.001 275
l
]
I i bottom temperatures cooled, catch declined in November, perhaps reflecting
. seasonal inshore movement patterns (Ennis 1984) or decreased activity level. i Lobsters typically show a seasonal migration pattern which is thought to maintain the' population at-the highest local water temperature (Campbell 1986). It is uncertain, however,,whether New Hampshire lobsters undergo L 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, but it was also influenced .,
by other factors such as molting and. food availability (NHFG 1974). s In 1987 and 1988, monthly bottom temperatures at Station P2 in the vicinity of the discharge station were 0.1-2.4% lower than the overall =f monthly'mean for all years from July-through November (see Figure 3.1.1-1). Low catches in 1987 may have resulted from cooler bottom temperatures at the- + discharge station, but similar low temperatures in 1988 were not. correlated ; with similarly reduced catches (Figure 3.3.6-2). Warmer-than-average tempera-tures in spring of 1988 may have increased survival in spring and offset:the ! lower-than-average fall-temperatures (Figure 3.1.1-1). t l Catch per effort of legal-sized lobsters at the discharge station ranged from 3 to 10 individuals per fifteen-trap trip from 1975 through 1988 (Figure 3.3.6-2, Table 3.3.6-5). In 1984,'an increase in the legal size limit for lobsters from 3-1/8" (79.2 mm) to 3-3/16" (80.9 mm) was enacted,- and a number of adults which would have been legal-sized-under-the old size limit, were retained in the sublegal size classes. While annual catches of
~
I legal-sized lobsters remained relatively stable for the first three years following the size change (1984-1986), percentages decreased from an average ~ j of 14% (1975-1983) to 7-11% (1984-86). A study by the New Hampshire Fish and j' Game Department (Grout et al.1989) noted a 33% decrease in legal catches in 1984; however, only 6% of the decrease was due to the change in size limit l and the rest was due to lower than average catches throughout New England. I-In 1988, catches increased from three individuals in 1987 (the lowest average recorded) to nearly six legal-sized individuals per fifteen-trap trip. 276
100
. l 75 76 77 78 79 80 81 82 83 84 85 86 87 88 YEAR v
-..,,,,, .=_wa,,-- . _
_ _ . -_ _ _ _..--,_..__________.__._________m___m_.___m. - _m -
f 6 TABI.E 3.3.6 5.
SUMMARY
OF LEGAI. LOBSTER CATCH" AT THE DISCHARGE SITE FROM 1974 THROUGH 1988. SEA 8 ROOK BASELINE i REPORT, 1968. i NORTH i YEARLY YEAR JUN JUL AUG SEP OCT NOV AVERAGE : 2.0 ' 1988 2.7 7.9 5.5 4.8 11.5 5.7 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 HONTHLY 3.5 5.8 AVERAGE 9.9 8.4 9.0 9.2 ND - No Data
" Catch per trip effort = legal catch from 15 traps por trip.
{ l 278
i Annual size class distributions (Figure 3.3.6 3) indicate that the abundances of lobsters in the 42 54 mm and 54+67 mm size classes have stead-11y 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 (>3 1/8") have had low abundances, particularly up to 1984 when all lobsters in this size : category were classified as legal sized, indicating that commercial fishing in the study area quickly removed the majority of lobsters as they attained minimum legal size. ! In 1988, female lobsters composed $5% of the total catch at the , dische.tge station. This is similar to the 1984-1987 period which ranged from 54 56%. Previous to 1984, females composed nearly 60% of the catch for most years, ranging from 55% in 1981 to 62% in 1978 (Figure 3.3.6 4). Egg bearing female lobsters composed 0.6% of the total catch at the discharge station in 1988. This represented the lowest catch of egg-bearing lobsters since 1977, and was nearly half the 1987 egg bearing catch (Figure 3.3.6-4). Previously, from 1981-1986, egg-bcaring females were ap-proximately 0.7% of the total catch. From 1974-1980, the percent of egg-bearing female lobsters was quite variable ranging from 0.5% in 1977 to 1.5% in 1975. NHFG studies (Perry 1985, McInnes 1986) found that 0.4 and 0.6% of the total lobsters examined during lobster surveys over a two-year period were berried. 3.3.6.2 Jonah Crab (Cancer borealis) and Rock Crab (Cancer 1rroratus) karvac Cancer spp. (Cancer borealis and Cancer Arroratus) larvae generally cxhibited 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, Can e spp. larvae in 1988 were most abundant during 279
i 100 - OX so - g
- a es - ---
I E 92-105m E
. .. e n ,
H 67-Mm i 5 54-67m 20 - l D <se-t r 0 . 1975
- f. 1976 1977 1978 1979 1980 1981 1982
[t _ 1983 f, M> 1994 1995 w. 1995 ' 1987 1988
' T-i T.:hR
~ '
Figure 3.3.6-3. i N meericanar atthedischarge a a ., u. .c.x.>.x.= - _ _ - n.w"- .-n- n ~. w + , - - - --w>~~-. -n.,,,- +uww-= n----~,--w,---,,-----v --.-- n,-.--,- e-,-,...n-e.
e. 64 - - 1.6 r. 62 - .I - % N McA u - 1,4
, %ecosseweresus ,
I e z 60 - " 3 - 1.2 u i. <
< :. .: I. 3 0 :.
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e 58 - i.. :
. %. - 1.0 E_
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52 , , , , , , , ,- , , , , , , , o.4 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 I YEAR Figure 3.3.6-4. Summary of female lobster catch data at the discharge site.1974-1988. Seabrook Baseline Report.1988.
. . . - - - . ~ - , . . - . - . . . . _ - - - . - - - . - - . . .
i l August, similar to most years except in 1981, 1983, and 1987 when density was greatest in July. In 1988, from July through December, the observed pattern j was very similar to previous years, although larval densities were lower from l October through December (rigure 3.3.6-5). l t Adults Adult Jonah crab (C. boreAlls) and rock crab (C. /rrorseus) catches , have been monitored since 1975 at tee discharge site (NA1 1985b). Since 1982, these populations have been monitored at two stations, the discharge site (L1) 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 (Table 3.3.6-3). Average monthly catches por fifteen trap ; trip have ranged from 0.6 to 29.1 at the discharge station and from 1.3 to 31.5 at Rye Ledge from 1982 through 1988 (Table 3.3.6 6). The total annual catch of Jonah crabs increased from 1982 through 1985, and was lower in 1986 and 1987 at both stations. In 1988, the catch reached a.n all time high at the discharge station, but was about average at Rye Ledge (Table 3.3.6 6). Catches of Jonah crab at the discharge site from 1982 through 1987 were not significantly different from year to year. A paired t test compari-son of the discharge site and the farfield station, Rye Ledge, did not indi- i cate a significant difference between the two sites (Table 3.3.6 4). ' Monthly catch of rock crabs has ranged from 0.0 to 6.8 per fifteen- ' trap trip at the discharge station and from 0.0 to 2.9 at Rye ledge from 1962 through 1988 (Table 3.3.6-6). The catch of rock crabs had also been generally increasing from 1982 through 1985, when catches were significuntly higher than all other years; catches then decreased in 1986 and 1987 at the discharge and increased in 1988. At Rye Ledge, rock crab catch has remained stable from 1986 through 1988 (Table 3.3.6-6). Rock crab catches have ; generally been greatest in July or August, and since 1984 have been greatest at the discharge station. , 282
_ _ _ _ _ . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . = _ _ _ . _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6-M1T9W45rMEm r 1 i 5- - 58 " I -
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W . o . . . . . . . . . t JAN RB MAR APR MAY JUN JUL AUG SEP OCT IOf G!C 1 1 MONTH 5 Figure 33.6-5. Monthly mean log (x+1) density and 95% confidence intervals (No11000 m 3 ) of Caecer spp. larvae at station P2.1978-1988 and monthly mean for 1988. (No data , collected January 1985-June 1986). Seabrook Baseline Report.1988.
,g..
" - 9 9 9. " 9*t**** **9.'.**.,
g 9.*99898
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l Rock crab catches at the discharge site varied from year to year. I Morthly catch data was also variable, with catches significantly higher in July and August (Table 3.3.6 3). 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 be- t tween the two species of crabs (Richards et al. 1983). Also, rock crabs pre-fer 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 also been monitored since 1982 (Table 3.3.6 5). The highest proportion of Jonah crab females at the discharge station occurred during September in most years including 1988, 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 proportions 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 low catch comprised of only female crabs (Table 3.3.6 5). Percentages of females in 1987 were higher than most of the previous years' catches. Egg bearing Jonah crabs were most abundant in 1988 at both stations (about 2% 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 1988 at either site, similar to findings from 1982 to 1987 (Table 3.5.6 5). This is as expected, considering the low catches of rock crabs and the low proportion of the popu-lation that would be ovigorous females. 285
i I Width frequency distributions taken in 1985 and 1986 Andicated that male Jonah crabs were slightly larger than females, although ovigerous fe-males were slightly larger than males in 1986 (NAI 1986b, 1987a). This trend generally continued in 1987 and 1988; however, both females and evigerous females were slightly larger than males at the discharge site but at Rye i Ledge, males were slightly larger than females (NA1 1989). Due to low t overall catch, trends in the size class distribution of sock crabs were less apparent. Male rock crabs were generally larger than females (NA1 1989). Gear selectivity had an influence on size distributions reported, since l catches from lobster traps do not include the smaller size classes in the i crab populations. , t 3.3.7 #FA a[enar/d_(Soft shell Clam) 3.3.7.1 Larvae , i Nya arenarla larvae occurred in plankton samples Hay through October from 1978 to 1988 (Figure 3.3.7-1). Each year, maximum abundances were recorded in late summer or early fall, while in many years a secondary e peak also occurred in early summer. Peak densities observed in 1985 (63/m3 ) were the lowest encountered from 1978-1988 (NAI 1986). Peak larval abundan-ces in 1988 (965/m3 ) ranked fourth over the past eleven years, 1978 1988, 1he highest peak abundance was observed in 1982 (1,505/m 3)(NA1 1985b). Peak abundances in 1988 were observed in early October, later than all other years except 1984, which also peaked in early October (Figure 3.3.7-2). Factors influencing the timing and magnitude of the observed pattern of larval abundance are not-fully understood. #. arenarla is known to spawn in the spring at temperatures greater than 4-6'O with summer spawning at 15-18'O (Brosseau 1978). Maximum larval abundances in August and September coincided with water temperatures in Hampton Harbor that regularly exceeded 15-18'C. However, these temperatures also occurred 286
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4 Figure 3.3.7-1. Weekly log (x+1) abundance per cubic meter of Mya arenerfa larvae a h P2,1978-1988, all years' mean and 95% confidence interval and weekly mean for 1988. Seabrook Baseline Report,1988. . 4 6
.- - , - - - . . . s.,_ . .
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- a. Only station P2 was examined forMya veligers in 1985. IJ Figure 3.3.7 2. Log (x+1) abundance per cubic meter of Mya arenarla veligers at nearfield Station P2, discharge Station P5, farfield Station P7 and Hampton Harbor Station Pl.
19821988. a.b.c Seabrook Baseline Report 1988. - 288 .
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Figure 3.3.7 2. (Continued) 289
. - . _ . . , _ . _ , - . - , , _ . _ _ . _ ,. . _ __ , . , . . . . , _ , . _ - . , . . - , . . . , . . + . . . . , , '
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4 h frequently in June and July, which were characterir.ed by much lower larval abundances, suggesting that temperature is a minimum requirement for spawn- ; ing. 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 en-trained larvae significant distances bcfore larval settlement.' The late- ' summer peaks have been observed to be coincident with northward-flowing , currents. 'This implies that these offshore larval peaks hay in part have a more southern estuarine component. Overall, factors controlling the occur-y rence of #. arenarla larvae off Hampton Harbor Beach are complex, the result , of environmental and biological factors including: adult condition at the time of spawning, temperaturS at spawning sites, location of spawning sites relative to prevailing coastal currents, water column stratification and l larval behavior. 4 A comparison of larval densities at nearfield (P2) and farfield (P7) stations indicated similar patterns at the two stations, 1982-1984 and 1986-1988 (Figure 3.3.7 2). Only Station P2 was examined in 1985. Larval densities at Hampton Harbor Station P1, added in July 1986, and Discharge
- Stat.fon P5, added in 1988, were similar to patterns at P2 and P7 (Figure 3.3.7-2).
L 3.3.7.2 Reproductive Patterns
#ra arenarla with developing gonads appeared in the Hampton estuary ,
, in March or early April during most years. 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). 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 1 l 290
I
'before larval occurrence. The peak larval abundance always occurred well I after spawning had commenced, indicating both flampton liarbor and Plum Island l
Sound clams may contribute to the large nearshore larval densities of late summer (NAI 1985b). l l l 3.3.7.3 Ilampton liarbor and Rexional Population Studies
}Lampton liarbor Spatiall The soft-shell clam population has been studied through intensive surveys of spat and adults in llampton liarbor ( Appendix Table 3.3.7-1). These surveye have been supplemented by quantitative studies of regional spatfall in nearby estuaries, where settlement is known to occur. Over a 15-year period, the llampton liarbor population has gone through substantial changes in l Cbundance. The #yn population structure during the 1984-1988 period resem-bled that observed in 1974-1975, suggesting long-term trends based on the i
interaction of spatfall and disturbance, possibly due to natural and human i predation (Figure 3.3.7-3). The continuing decline in juvenile and adult l (>25 mm) clam densities is partially the result of light spatfalls (1982- j 1988). The size distribution in 1974-1975 also indicated a decreasing l Juvenile and adult (>25 mm) population with an absence of any clams <25 mm in l 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 arid 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 j Flat 4. In llampton liarbor, the least-successful recruitment years occurred ! in 1974, 1982, and 1985-1988. I i i 291 l
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m ,, g o.6 - .. u { o.o . . . . . . . . . . . . . . 74 76 76 77 78 78 So 81 82 83 84 86 86 87 88 - l YEAR l Figure 3.3.7-4. Annual mean density (number per square foot) and 95% confidence limits of young of the year Mya arenaria (15 mm) at Hampton Scabrook Harbor, 1974 1988. Seabrook Baseline Report,1988. 296
- - .. - -, , . , - , - . , , ~ . . . - - ,-
i JLeaf onal Spat f all i The regional spatiali 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. Regional spatiall in 1988 showed marked differences between estuaries. Spetta11 at Flat 2, while higher than in 1982 and 1987, was lower than all other years. Flat 4 had the lowest l spatfall yet observed, 1978-1988. Recruitment in Plum Island Sound, unlike Hampton Harbor, was higher than all previous years (1976 '1987) except 1977. ; Yearlina and Aduh Clams Yearling clams (10-12 mm) became numerous in 1977 following the 1976 spatiall and began showing a decline in 1981 at Flat I and 1982 at Flat 2 and Flat 4 (NAI 1982b, NA1 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 (Figures 3.3.1-6, 7, 8). 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 densitico (>50 mm) were recorded in 1980 and have declined from 1983 through 1987. Juvenile densitics remained low in 1988 at Flat 2 but in-creased slightly at Flat I and Flat 4. Adult densities in 1988 were similar to 1987 at Flat 1 and Flat 2, while Flat 4 showed a small increase (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. In 1987 and 1988, attempts by the New Hampshire Fish and Game Department to augment natural recruitment by seeding juvenile clams at Flat 5 have not been successful (Horris 1989). The local 4-H organization is also producing seed clams on a small-scale (30,000 juveniles in 1988) for reseeding Hampton Harbor clam flats. 297
i Hampton Harbor Flat 2 , 4- ! 7= 1 . 3 j g . .. ..
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u u m o o l 3 ,, i g , m o- i , , , , , , , i , a 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 l YEAR Hampton Harbor Flat 4 " 4- ; l A s- .
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.. m 5 . ..
o i i i i i i i i i i .- i i . 1976 1977 1978 1979 1980 1981- 1982 1983 1984 1985 1986 1987 1988 YEAR > l a. Flat 4 not sampled in 1976 and 1977. > Figure 3.3.7 5, Mean and 95% confidence limits of Mya arenaria spat (shelllength 512 mm) , densttles (No./ft 2) at two northern New England estuaries,1976 through 1984 and 1986 through 1988. Seabrook Baseline Report,1988. 298
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- 1. -y y I , , I-o.o . . . . . . . . . . . . . . .
1974 1976 1976 1977 1978 1979 1980 1981 1982 1983 1984 1986 1986 1987 1988 YEAR Figure 3.3.7 8. Means and 95% confidence limits of spat, juvenile and adult log (x+1) densities at Flat 4. Hampton Seabrook Harbor,1974 through 1988. Seabrook Baseline Report.1988. 301 _ _ -- ~ _ . . _ _ _ _ . _ . _ - - -
In order to better understand the patterns of population structure, J 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 i 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 1988, did not warrant a NORMSEP analysis for those years. The 1976 ycar 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 l density data, indicated that the 1980 to 1982 year classes experienced far l greater mortality during the first two years than was observed for the 1976 year class. The higher mortality for year classes 1980 through 1987 (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 1982-1987 appears to have been virtually eliminated by its second year. 1 I Predation and liarvestable Clam Re:ources 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) Nya, and humann who dig adult Nya (>50 mm) but also cause mortality to 1 302 1 l l
i 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 (Care.(nus asenas) is a major predator of Nya, with clams being a major source of food particularly in the fall months (Ropes 1969). Green crab catches in Hampton liarbor 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 1986 appear to have stabilized somewhat at higher densities, with fall abundances fluctuating between 69.3 (1985) and 123.9 (1984) CPUE (catch per unit effort). Green crabs generally feed more actively at temperatures abovo 9'C, and females are more active predators on Nya than males (Ropes 1969). The presence of more females in the catch in llampton liarbor from' July through September (1981-1988) indicated greater predation pressure for the newly-sett led spat in the estuary. Continued high catches of males and females occurred until late November or December when temperatures declined below 7'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 1 season 1978-1988, 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 3.3.7-9); a ! significant correlation (p(0.01) was obtained between fall abundances (time of peak activity), 1980-1988, and the previous winter minimum temperature. Close examination of the yearly data indicated the type of response proposed I by Welch (1969). Followirig the winter of 1979-1980 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 temperaturca in 1983, 1984 and 1986 were associated 303
TABLE 3.3.7 1. AVERAGE CATCH PER UNIT EFFORT", PERCENT FEKnLE, AND PERCERT GRAVID FEKALES FOR CARCINUS #AENAS COLLECTED AT EST0ARINE i STATIONS FROH 1977 1988. SEABROOK BASELINE REPORT, 1988. AVERAGE FECUNDITY , CATCH PER I SAMPLE PERCERT (% GRAVID YEAR PERIOD UNIT EFFORT FEHALE FEKALES) 1977 Oct Dec 17.5 47.4 0.3 : 1978 Apr Jun 7.5 76.7 7.0 t Jul Sep 8.6 56.5 3.2 . Oct-Dec 7.2 56.5 0.5 t 1979 Apr-Jun 6.4 50.0 6.0 , Jul-Sep 6.0 60.0 0.6 Oct-Dec 22.1 60.0 0.0 1980 A 6.7 52.4 8.4 Jbr-Jun l-Sep 15.8 50.0 2.3 Oct-Dec 53.1 66.7 0.0 1981 Apr Jun 39.5 60.0 4.6 , Jul Sep 34.0 67.7 1.6 i Oct Dec 39.4 54.5 0.0 1982 Apr-Jun 37.4 61.5 4.1 Jul-Sep 44.6 80.0 0.8 Oct-Dec 56.1 66.7 0.0 1983 Apr-Jun 47.5 61.5 3.7 Jul-Sep 61.8 66.7 1.0 Oct-Dec 117.4 61.5 <0.1 + 1984 Apr-Jun 84.7 54.5 2.4 Jul Sep 80.6 73.0 1.2 Oct-Dec 123.9 58.3 0.0 1985 Apr Jun 58.3 56.5 3.9 Jul Sep 54.8 68.8 1.0 Oct-Dec 69.3 58.3 0.0 1986 Apr-Jun 52.6 71.4 6.6 Jul-Sep 53.5 73.7 0.7 Oct Dec 113.5 56.5 <0.1 1987 Apr-Jun 62.0 68.2 6.5 , Jul Sep 76.0 73.9 1.1 Oct Dec 70.8 66.4 0.0 1988 Apr Jun 44.7 53.4 6.1 Jul-Sep 87.0 80.4 0.7 Oct-Dec 88.2 58.4 0.0 i
" Number of C. maenas per trap per day, eight " box" traps fishing for 24 hours, twice per month.
304 i
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! 0* , , , .- , , , , , , , 1-1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 ' ! YEAR i l I i i l Ie j !. 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 1988. Seabrook Baseline Report,1988. l l- . } 305
- l. ,
l-1
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. A relatively mild winter in 1988 was followed by a marked increase in fall green crab catches. l The increase in' green crab CPUE, and associated predation'in the l years 1980-1988 ca'n be observed in examination of the 1981-1988 #ya year classes, as estimated by densities of young-of-the-year clams (Figure j 3.3.7-4). The 1981 year class, which was relatively large, showed decreased j 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' I llampton liarbor clam populations, 1983-1988, has been very low, corresponding-to high. green crab abundances'and low spat recruitment.
]
4 Welch and Churchill (1983) reported an increase in near-surface temperature at Boothbay liarbor, Maine in the early 1970s along with an 1 increase in green crab abundance. Although no green' crab or temperature data '! j are available for.11ampton liarbor for this time period, catches from Kittery, Maine,'showad a maximum crab occurrence (1973-1975) corresponding to the ( reduction in younger year classes observed in llampton 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 1 southern Maine coast (Welch and Churchill 1983)-may have also occurred in Hampton liarbor, which may have contributed to the survivorship of the strong ! 1976 and 1977 year classes. { Recreational clam digging on the llampton liarbor 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 ! J
. 1 306
t TABLE 3.3.7-2. ESTIMATED DISTRIBUTION (PERCENT OF TOTAL) 0F CIAH DIGGERS BY FLAT AT HAMPTON HARBOR, SPRING 1980 i THROUGH FALL 1988. SEABROOK BASELINE REPORT, 1988.
- ESTIMATED" ESTINATED TOTAL. NUMBER OF.
FIAT DIOGER BUSHELS SEASON TRIPS HARVESTED > 1- 2 3 4 5' Springc 1980 12.5 17.9. 1.7 52.5 15.4 3,860 1,200-d 2,700* 11.3 18.4 3.3 11.8 840 Fall 1980 55.1
'(
Spring 1981 9.7 15.6 0.8 65.9 7.9
- 12,500 3,900 l
. 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 Fal) 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 Fal) 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 l Fal) 1987 38.8 6.9 0.8 49.8 3.8 1,541 482 1 1 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
" Based prietarily on Friday head counts at time of low slack water; most Saturday counts are assumed from observed Fri: Sat ratio (n=14 pairs)-of b2.24 i SD 0.96; seasonal totals have' approximate error of i 18%
Assumes each clammer takes 10 quarts per trip; 1 bushel = 32 quarts or 3.2 clammer trips d Includes the period 1 January through weekend before Hemorial Day
# Includes the weekend after Labor Day through 31 December Based on average Spring: Fall ratio for 1981 and 1982 (0.68 i SD 0.02) 307 l
l 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 declined further in 1987 and 1988 to the lowest levels observed in the study 1980-1988. The changing pattern of clam abundance on the Hampton Harbor flats is reflected in 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 by one to two years illustrating a typicol 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 d'clining; resources overall, , and particularly at the most accessible area, Flat 4- . As clam densities i continued to sharply decline in 1985 and 1986' digger activity again shifted',- l from Flat 2 and Flat 4 to Flat 1, possibly due to slightly greater densities : at Flat 1. In 1987 and 1988, 80-90% 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 fle.ts;.however, Flat 1 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 Nya arenaria, has been observed in Hampton liarbor Nya populations (Hillman 1986, 1987). A
, virus, similar to the B-type retroviruses, is known to initiate the disease I
in Nya (0prandy et el. 1981). Although the N ectisn has been observed in 308
i 15000 - suses
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0 , , , , i 1971 1972 1973 1974 . 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 i YEAR I Figure 3.3.7-10. Number of adult clam licenses issued and the adult clam standing crop (beshels). Hampton-Seabrook Harbor,1971-1988. Seabrook Baseline Report 19M. 1_ 4
- < . * - ,_..w--- .v- ,.%,- - 6,_. . - - .-. -
.y ,,e, % 3_,_, g_ ,
i i regions of relatively-pristine waters, the rate of infection may also be ! enhanced by pollution-mediated deterioration of the environment (Reinisch et 7 al. 1984). The infection rate in some #ya populations may reach 100 percent .; with 100 percent mortality of infected clams (Farley ec al. 1986).- The incidence of sarcomatous neoplasms in }Iampton Harbor Nya populations was observed. In October 1986 and February 1987 (H111n3an 1986,1987). Neoplastic infections were more prevalant 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 1- and- 2 may'suf fer significant -l disease-related reductions in clam production, llowever, since no historical f data is available on the incidence of neoplasms in Itampton !! arbor clam popu-lation, it is not known if current infection rates are typical or indictative. l of an increasing trend. In 1987 clam flat surveys did indicate, however, j that juvenile and adult densities fell by over 50% at Flat 1 and Flat 2 while j Flat 4 remained unchanged. l l q
}!arvestable Clams j i
The patterns discussed above have resulted in substantial changes .l
. in the number of harvestable clams on the llampton flats (Table 3.3.7-3). The greatest adult standing stock in }!ampton Harbor was reported by Ayer (1968) 'for 1967. Subsequent years indicated a gradual decline in available adult.
blams 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 ]i for the summer (Hemorial Day to Labor Day)'and eliminating digging on Sundays [
-and holidays. Survival of the 1976 year class made a substantial increase in .j 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. l l l 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 310 i-
TABLE 3.3.7-3.
SUMMARY
OF STANDING CROP ESTIHATES OF ADULT" #YA ARENARIA IN HAMPTON HARDOR, 1967 THROUGH 1988. ' SEABROOK BASELINE REPORT, 1988. ESTIMATED NUMBER TOTAL ESTINATED > 0F Tp?"Ita NUMBER'0F DATE PER ACRE OF BUSHELS . November 1967 152 b 23,400 b July 1969 103 15,840 i November 1971 94 13,020 L -November'1972 58 8,920 l November 1973 41 6,310 _.i November 1974 56 8,690 November 1975 29 4,945 ; ( November 1976 11- 1,350 1 November 1977 6 1,060 November 1978 6 940 November 1979 9 1,400 October 1980 54 8,890 October 1981 75 12,400 October 1982 55 9,200 October 1983 78 13,020 October 1984 54 8,821 i November 1985 39 4,015 October 1986 23 2,793 , October 1987 8 976 October 1988 10 1,137 .
"Shell length >50 mm From Ayer.(1966) 1 311 i
'V -;
4 o I in 1980 1984, increased predation <byfgreen crabs, and continued human disturbance. : Although standing crop increased alightly in 1988, signifi- ) cant increases over the'next four years are unlikely, due to poor recruit- : ment in-the 1985-1988 year classes. t 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 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-3.3.7-4).
-In 1987, the percentage of harvestable clams increased at Flat 4, while decreasing at Flat I and Flat 2, reflecting the stabilization of-clam ,
populations at Flat 4 at low levels, while populations on Flat'I and Flat 2 continued to decline (Appendix Table 3.3.7-1). ~In 1988, the distribu - tion of harvestable clams changed little, as Flat 2 dropped slightly,
-Flat 4 increased slightly and Flat I remained unchanged.
s .
?
312
hl i TABLE 3.3.7 4. DISTRIBUTION (PERCENT OF TOTAL STANDING CROP) 0F , llARVESTABLE CLAHS BY FLAT AT HAMPTON HARBOR, 1979 THROUGH 1988. SEABROOK BASELINE REPORT, 1988. 1 (' l l YEAR FLAT l
^
1 2 3 4 5 i l l 1979 33.3' 6.2 2.2 55.7 2.5 i 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 L i 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 ' 1 4 3 313
+ , w
APPENDIX TABLE 3.3.1-1. ANNUAL MEAN" WITH 95% CONFIDENCE LIMITS FOR TEMPERATURE (C) AND SALINITY (PPT) TAKEN AT BOTH HIGH AND LOW SIACK TIDE FROM BROWN'S RIVER AND HAMPTON HARBOR FROM 1980-1988. SEABROOK BASELINE REPORT, 1988.. I I. saoset*5 RIVER I I I I I I um I utest i I I I I I TDfPERATtntE i CL i SALINITY I CL I TDIPERATINtE I C1. . I SALINITY I . C1. - 1 I + + + + + + + - 1 11980 1 10.91 5.21 25.1I 1.91 9.6! 4.41- 31.ol 1.6I 11981 1 10.61 4.4I z5.51 1.61 10.31 4.61 3o.ol 1.71 11962 1 --20.71 4.51 22.s1 1.s1 9.91 4.11 30.ol 1.21-l1983 1 11.91 5.01 19.41 3.61 11.01 4.21 2s.01-- 1.98 11984 I 11.91 5.11 1s.11 3.31 10.6l 3.91 2s.41 1.sl 119e5 1 11.31 5.01 21.71 2.11 10.11 4.41 3o.61 c.71 119e6 l 10.gl 4.s1 zo.4f 3.11 9.gl 4.c4 o.91 11987 I - -1 -l 20.1 2.9I -1 -1 so.rf ts.7 1.91 119es 10.61 5.11 20.51 z.21 10.31 4.01 29.el o.71 i E$ c. loVERAL1'Il 11.31 1.51 z1.51 0.91 lo.zl 1.31 29.61 o.51 I I- nAftPTUt MARBoR _ ! 1 I - ~ - 1 I i 12m i MIsst . 'I I 1 I l l TDfPERAftMtE I CL i SALINITY I CL i TDIPERARMtE I CL 'I SALIMITY l CL I . I + + - ' I 119e0 l 9.61 4.4I .29.91 1.41 9.11 3.61 32.ol o.51 11981- l 10.11 4.41 2s.91- 1.11 9.31 3.si 31.51 o.sl .. 11982 1 10.21 4.11 z7.31 1.51 9.21 3.51 31.21 c.61 ' 119e3 1 10.41 4.31 25.51 z.41 9.91 3.el- 30.11 0.91 119En I 10.41 -4.11 2s.s1- z.31 9.41 3.11-' 33.zl o.91 119e5 1 10.61 4.21 29.11 1.01 10.11 3.3I 32.zl o.31 119e6 l 10.01 3.91 27.71 1.31 9.4I. 3.o1 31.51 o.4I' 119s7 l 10.01 4.31 27.51 2.21 a.91 3.51 30.71 o.91 119es I -9.71 3.91 27.s1 1.o! 9.21 3.31 31.31 0.41 loVERALL i 10.11 1.ZI ~ 27.71 c.51 9.41 1.01 31.28 c.zt.
*b Annual mean' = mean of 12 monthly means', except where footnoted.
Confidence limits expressed as half the confidence interval.
,No data were taken in .3mnuary or February,1987, therefere no annual mean was computed.
No data were taken in February, therefore n =_11 months.
' *Overall mean = mean of los monthly means, except for n '= 107 for Brown's River salinity and n = 96 for Brown's River tempe: ature t1987 excluded entirely 1.
J e APPENDIX TABLE 3.3.2-1. A COMPARI' SON OF SPARSELY OCCURRING MACR 0 ALGAE TAXA IN AUGUST BENTHIC DESTRUCTIVE SAMPLES, 1973-1984 AND 1978-1988. SEABROOK BASELINE REPORT, 1988.
- l 2
TAXA 1978-1984 1978 1988 i Nonostrona oxyspereur; x x Enteromorpha sp. x. x Enteromorphe intestinells. x' x Enteromorpha linza , x x Enteromorpha. prolifera x x Ectocarpus siliculosus x ; Giffordla granulosa x x -( Sphacelarla cirrosa. x x
. Desmarestle viridis x x !,
Petalonla fascia x 7 Scytosiphon lomentarla- x Dumontla contorta x Coranium deslangchampil x x P11ayella littoralis x x Plumaria elegans x Polyslphonla ap. x x
*Polysiphonia denudata x Polysiphonia nigrescens x Polysiphonia harveyl .x Porphyra minista x Porphyra umbilicalls x Gigartinales x x Entocladla viridis 'x x \
Spongonema tomentosum x Cladophora sericea x Spongomorpha spinescens x' x ' Bonnemassonia hamifera x Palmarla palmata x less than 5 occurrences out of 295 samples less than 8 occurrences out of 462 samples
*new to destructive collections since 1984 J
i 315 J
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b APPDEIX TABLE 3.3.2-2. IContinued) i B. PERCDET COVER FUCXIID 12DGE EIt5L) BARE 12DGE Ilent) OIceRUS 2 DIE tIDI)# STATICII APR JU!. DEC APR JUL' DEC APR JUI. DEC 4 i PERDENIAL AtRF Species Focus spp.* B1 median 92 94 70 2 1 <1 22 18 22 irangeI t25-98) (60-100) t25-95) t0-8) ( 0-10 ) t0-40) t4-38) I13-49) t13-38) B5 median ' 92 97- 94- <1 1 IS 0 0 0 trange1 (60-98) t65-200) i2-98) t0-40) (<!-45) (0-80) EO) t0) 10I w
' 00 Ascophy11em nodosima B1 median 0 0 0 0 0 0 0- 0 0 frange) 10) to) (0) 10) to) 10) to) 40) 10) '
B5 median 0 0 0 0 - 0 0 0 0 0 trenge). 40-20) (0-15) 10-5) to) to) to) to) 10) (0)
- Percent fregeeney of faccid algae.is based on presence of holdfasts only Present, % frequency not recorded ,
% frequency recorded using different method in 1982 h quadrat initiated in 1985
- Percent cover of focoi1 algae is based on whole Plant.
... . . . , - ,e~ c.. , __ ._ . . _ . . _ _ . _.-..;
F 1 l l APPENDIX TABLE 3.3.3-1. SPECIES USED-IN DISCRIMINANT ANALYSIS OF BENTHIC MACROFAUNA.- SEABROOX BASELINE REPORT, 1988. i e i Aeginina longicornis Alvania exarata A._ pseudoareolata ,
^Amphlopholls squamata ,
Asabellides oculata 1 Balanus crenatus Callioplus laeviusculus Capre11a linearls' l C. penantis > C. septentrionalis . ) Cerastoderma pinnulatum Dendrodos sp. , Cnathis cerina a Rarmothoe Ambricata Riatolla sp. Ryas coarctatus Idotea phosphorea l Ischyrocerus angulpes ? 1 'Jaera marina
, Jassa falcata. ,
Lacuna vincta Llicorina littorea Mitre 11a para Hya arenaria Nicomache sp. Odostomia dealbsta Onchidoris sp. Ophlopholls aculeata l Phoxochilidium fenovatum l Phoxocephalus holboll l Polydora socialis Thelepus cincinnatus Tonicella marvorea ; Tonicella rubra Strongyloncentrotus droebachiensis I 319
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4 1 , l I l APPENDIX TABLE 3.3.7-1.
SUMMARY
OF #fA ARENARIA POPULATION DENSITIES l FROH ANNUAL FALL SURVEYS IN HAMPTON-SEABROOK :
- l. HARBOR, 1971 THROUGH 1988. SEABROOK BASELINE REPORT, 1988.
NUMBER OF ' l' SAMPLES' NEAN DENSITY (No./ft*) COLLECTED-SPAT JUVENILES ADULTS < L LOCATION YEAR ADULTS SPAT (1 to 25 mm) (26 to 50 mm) (>$0 mm) Flat 1 1971 18 18 48 6.8 2.1 1972 18 18 110 8.1 3.3 1973 36 18 44 ?.5 1.3 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 57 6.2 3.4
- 1905 106 71 5' 1.4 1.6 L 1986 75 70 9 0.2 0.7 1987 70 55 7 0.1 0.2 1988 70 62 3 0.3 0.2 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 . I 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 (continued) 325
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APPENDIX TABLE 3.3.7-1. (Continued)- I NUMBER OF 8 SAMPLES HEAN DENSITY (No./ft )- COLLECTED SPAT . JUVENILES -ADULTS LOCATION YEAR ADULTS SPAT (1 to 25 mm) (26 to 50 mm) (>50 mm) i 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 1 1978 23 6 71 <2.1. 0.1 ,; 1979 12 4 6 1. 0 ' O.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 ' 1986 NS 30 2 NS NS Flat 4 1971 12- 12 106 17.6 2.8-1972 12 12 13B 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 ', l 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 2.3 4 1982 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 3 0.3 0.2 1987 40 20 12 1988 40 28 6 0.9 0.4 4 (continued) )
A 326 J 1
l APPENDIX TABLE 3.3.7-1. (Continued) NUMBER OF ' SAMPLES HEAN DENSITY'(No./ft') COLLECTED SPAT JUVENILES ADULTS LOCATION YEAR- ADULTS. SPAT (1 to 25 mm) (26 to 50 mm) (>50 mm) r
-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 >0.1- > 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 0.1 L 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 All Flats 1971 54 54 92 77 2.7 1972 54 54 130 6.2 '2.2' 1973 111 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 i 1977 193 47 207 >0.1 >0.1 1978 204 45 123 6.3 >0.1 1979 200 59 49 22.3 0.3 1 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' O.8 1.1-4 1986 166 179 9 0.2 0.5 1987 165' 140 11 0.1 0.2 1988 165- 170 3 0.4 0.2 v
327 3
1 I
.4. 0 METHODS '4.1 GENERAL.
Prior to 1975, the Seabrook Environmental'i'rogram. involved studies of specific sites (e.g., the estuary, the discharge area, the intake area) or 1 specific species (e.g. , Nya arenarla) 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 1988 were thoroughly. described in the data reports for those years (NAI 1981c, 1981f, 1982a,.1982b, 1983a, 1984a, 1985a, 1986, 1987a, i 1988a, 1989). Methods used prior to 1980 were summarized and explained in detail in previous annual reports'for Seabrook Environmental Studies (NA1 1976a, 1976b, 1977a, 1977b, 1977c, 1977d, 1978a, 1978b, 1979a, 1979b,' 1979c, 1979d, 1979e, 1979f, 1980s, 1980b, 1980c, 1981a, 1981b, 1981c, 1981d, 1981e, - 1981f). Plankton studies have been based on samples collected-in the near-field (intake) area and a farfield area (Rye Ledge) located beyond'the f influence of the Station's operation. In July 1986, sampling at a third station (PS) was resumed in the vicinity of the. discharge-(Figure 4.1-1); preoperational. sampling had been conducted at PS-for various plankton pro-t grams from July 1977 through December 1981. .In addition, bivalve larvae were collected from Hampton Harbor (P1) starting in July 1986. 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 i 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 328 i s r
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