ML20151L977
| ML20151L977 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/30/1987 |
| From: | NORMANDEAU ASSOCIATES, INC. |
| To: | |
| Shared Package | |
| ML20151L940 | List: |
| References | |
| NUDOCS 8804220207 | |
| Download: ML20151L977 (420) | |
Text
{{#Wiki_filter:__ t f I i ATTACHMENT 1 i i SEABROOK ENVIRONMEWAL SETDIES, 1986. A CHARACTERIZATION OF BASELINE CONDITIONS IN THE HAMPTON-SEABROOK AREA, 1975-1986. i A PREOPERATIONAL STUDY FOR SEABROOK STATION TECHNICAL REPORT XVIII-II Prepared for NEW HAMPSHIRE YANKEE DIVISION PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE P.O. Box 700 Seabrook Station Seabrook, New Hampshire Prepared by NORMANDEAU ASSOCIATES, INC. j 25 Nashua Road Bedford, New Hampshire 03102 R-310 September 1987 8804220207 880408 PDR ADOCK 05000443 C_ _ fit _feltfe _ ---___ ________--___ _ _
TABLE OF CONTENTS PAGE
1.0 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . 1
1.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . I 1.2 INTAKE MONITORING . . . . . ... . . . . . . . . . . 2 1.3 DISCRARGE MONITORING. . . . . . . . . . . . . . . . 3 1.3.1 Discharge Plume Monitoring . . . . . . . . . 3 1.3.2 Benthic Monitoring . . . . . . . . . . .. . 5 1.3.3 Estuarine Monitoring . . . . . . . . . . . . 6 2.0 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . 9 l 2.1.1 General Perspective. . . . . . . . . . . . . 9 2.1.2 Sources of Baseline Variability. . . . . . . 9 2.2 INTAKE AREA MONITORING. . . . . . . . . . . . . . . 15 2.2.1 Plankton . . . . . . . . . . . . . . . . . . 15 2.2.1.1 Community Structure . . . . . . . . 15 2.2.1.2 Selected Species. . . . . . . . . . 20 2.2.1.3 Spatial Variability . . . . . . . . 24 2.2.2 Pelagic Fish . . . . . . . . . . . . . . . . 24 1 2.2.2.1 Temporal. . . . . . . . . . . . . . 24 2.2.2.2 Spatial . . . . . . . . . . . . . . 29 2.3 DISCHARGE AREA MONITORING . . . . . . . . . . . . . 32 2.3.1 Plume St'idies. . . . . . . . . . . . . . . . 32 1 2.3.1.1 Discharge Plume Zone. . . . . . . . 32 2.3.1.2 Intertidal / Shallow Subtidal Zone. . 39 2.3.1.3 Estuarine Zone. . . . . . . . . . . 46 2.3.2 Benthic Monitoring . . . . . . . . . . . . . 57 2.3.2.1 Macroalgae and Macrofauna . . . . . 57 2.3.2.2 Demersal Fish . . . . . . . . . . . 61 2.3.2.3 Epibenthic Crustacea. . . . . . . . 65 111
i PAGE 3.0 RESULTS. . .. . . . . . . . . ........ ..... 69 3.1 PLANKTON AND WATER QUALITY PARAMETERS . . . .... 69 3.1.1 Water Quality Parameters-Seasonal Cycles and Trends . . . . . . ........ . .... 69 3.1.2 Phytoplankton. . . .. .. ..... .... 80 3.1.2.1 Total Community . ..... .... 80 3.1.2.2 Selected Species. ..... .... 90 3.1.3 Microzooplankton . .. .. .. .. . .... 94 3.1.3.1 Total Community . . . . . . . . . . 94 3.1.3.2 Selected Species. .... .... . 105 3.1.4 Macrozooplankton . . ........ .... 117 3.1.4.1 Community Structure . ..... .. 117 3.1.4.2 l Selected Species. ....... .. 128 3.2 FINFISH , . . . . . . . . . . . . . . . . . . . . . 146 3.2.1 Ichthyoplankton. . ............. 146 i 3.2.1.1 Total Community . . ........ 146 I 3.2.1.2 Selected Species. ......... 166 l 3.2.2 Adult Finfish . . . . . . . . . . . .... 180 3.2.2.1 Total Community . ......... 180 3.2.2.2 Selected Species. . ... . .... 198 l 1 i 3.3 BENTH0S . . . . . . . . . .. .... ....... 219 { ( 3.3.1 Estuarine Benthos. ..... .. .. .... 219 3.3.1.1 Physical Environment. ....... 219 3.3.1.2 Macrofauna. . . . ......... 226 3.3.2 Marine Macroalgam. ... ....... ... 236 3.3.2.1 Macroalgal Community. ....... 236 3.3.2.2 Selected Species. ......... 252 iv
1[ 4 PAGE / 3.3.3 Marine Macrofauna. . . . . .. .... ... 256 3.3.3.1 General . . . . . . . . . . . . . . 256 3.3.3.2 Macrofaunal Community . ... ... 258 3.3.4 Surface Fouling Panels . . . . . .. .. .. 274 3.3.4.1 Seasonal Settlement Patterns. ... "274 3.3.4.2 Patterns of Community Development . 281 3.3.5 Selected Benthic Species . . ... .... . 284 3.3.5.1 Mytilidae . .. . . .. ..... . 284 3.3.5.2 Nucella lapillus. . . . . .. .. . 292 3.3.5.3 Asteriidae. . . . . . ... . .. . 294 3.3.5.4 Pontogenela Inerml . . .. . .. . 295 3.3.5.5 Jossa falcata . . .. . . .... . 296 3.3.5.6 Amptthee ru b r ic a t a . . . . . ... . 298 3.3.5.7 Strongylocentrotus drorbachtensis . 299 3.3.6 Epibenthic Crustacea . . . . . .. ... .. 300 3.3.6.1 American Lobsters (Nomarus ame ricanus) . . . . . . . . . ... 300 3.3.6.2 Rock Grab (Cancer feroratus) and Jonah Crab (Cance r bo realis). ... 314 3.3.7 My arenaria (Sof t-shell Clam) . . .. ... 318 3.3.7.1 Larvae. . . . . . . . .. . .... 318 3.3.7.2 Reproductive Patterns . .. . ... 320 3.3.7.3 Hampton Harbor and Regional Popula-tion Studies. . . . . ...... . 323 4.0 METHODS. . . .. . . . . . . . .. . . ..... ... 371 4.1 GENERAL . . . . . . . . . .. . . . . ... . ... 371 4.2 COMMUNITY STRUCTURE . . . . . . . . . . . . . .. . 379 4.3 SELECTED SPECIES / PARAMETERS . . . . ..... . .. 383 5.0 LITERA1VRE CITED . . . . . . . . .. . . .... ... . 390 v \. _
J 7 l LIST OF FIGURES PAGE 2.1.1. Schematic of sources and levels of variability in Seabrook Environmental Studies. .......... 11 2.2-1. Dates of occurrence and mean abundance of seasonal groups formed by numerical classification 3 (1978-1984) of A. tiicrozoop , macrozooplankton(No./1000m}ankton(No./m)andB.
), and discriminant 3
analysis (1976-1986) of C. fi h eggs (No./1000m ), 5 and D. fish larvae (No./1000m ) collections . . . . 16 2.2-2. Percent composition, seasonal peak, and overall mean and standard deviation of microzooplankton and macrozooplankton selected species (A= adult, C=copepodite, L= larvae, N=nauplius) 1978-1984 . . . 21 2.2-3. Fercent composition, seasonal peak, and overall seasonal mean and standard deviation of bivalve ; larvae (1978-1986) and fish larvae (1976-1986) selected species. . . . . . . ........... 22 2.2-4. Percent composition of six dominant species collected by gill net and total catch per unit effort A. by year and B. by month at combined j stations G1, G2, and G3 from 1976-1986. . . . . . . 26
~
2.2-5. Percent composition, seasonal peak, annual mean
- CPUE and standard deviation of dominant pelagic and demersal fish from 1976-1986. ........... 28 2.2-6. Percent composition of five most abundant fish collected in gill nets (all dates, surface and bottom combir.ed) from 1976 through 1986 . . . . . . 30 2.3-1. Summary of maximum and minimum seasonal values for ,
selected water quality and plankton parameters and I overall mean and standard deviation for Skele tenema ' ecstatum (cells / liter) and lobster larvae (No./1000m8 ). . . . . . . . . ........... 33 2.3-2. Monthly mean surface and bottcm temperature ('C), ) surface salinity (ppt), and surface dissolved oxygen ' (eg/1) at station P2 for each year and over all ! years (1978-1986, except temperature, 1978-1984 and l August December 1986) . . . . ........... 34 i l l vi
i l l l PAGE 2.3-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially- ; exposed panels at nearfield Stations 4 and 19 . . . 38 2.3-4. Year-to-year variations in community structure as shown by discriminant analysis of August , callections from 1978-1986 of A. algae and B. non-colonial macrofauna . . . . . . . . . . . . . . . . 40 2.3-5. Overall mean (No./m8 or gm/m 8), standard deviation, and percent composition of selected benthic macrofaunal and macroalgal species collected triannually at Nearfield and Farfield intertidal (1MLW, SMLW) and subtidal (17, 35) Stations from 1978 (Nearfield) or 1982 (Farfield) through 1986. . 44 2.3-6. Mean monthly salinity (ppt) and temperature ('C) in Hampton Harbor at high tide from 1978-1986. . . . . 47 2.3-7. Annual mean density (No./m 8
), and total number of taxa (No./5/16m ) for Hampton Harbor and Brown's 8
River from 1978-85 and 1986, and averge annual salinity (ppt) for Brown's River at low tide from 1980-1986 . . . . . . . . . . . . . . . . . . . .. 49 2.3-8. Percent composition of six dominant species collected by beach seine and total catch per unit effort A. by year and B. month at combined stations l S1, S2 and S3 from 1976-1984. . . . . . . . . . .. 51 2.3-9. Percent composition of four most abundant fish per station ecliected in Beach Seines (all dates combined) from 1976 through 1984. . . . . . . .. . 52 ] 2.3-10. limits of young-of-Annual the-yearmeans and spat and 95% confidence,8) densities (ft of Mya arenaria at Hampton-Seabrook, 1974 or 1976-1986. . . . . .. 55 2.3-11. Number of adult clam licenses issued and the adult J clam standing crop (bushels). Hampton Harbor, 1971-1986. . . . . . . . . . . . . . . . . . . . . . . . 56 < 2.3-12. Overall mean (No./m 8
) and standard deviation of selected benthic species collected triannually at Nearfield (19) and Farfield (31) Stations from
- 1978 through 1986 . . . . . . . . . . . . . . . .. 60 1
I l vii l l i
PAGE 2.3-13. Percent composition of six dominant species collected by otter trawl and total catch per unit effort A. by year and B. by month at combined Stations T1, T2, and T3 from 1976-1986. . . . . . . 62 2.3-14. Percent composition of six most abundant fish collected in otter trawls (all dates combined) from 1976 through 1986 . .. ... ...... . . . . . 64 2.3-15. Seasonal peak catch and overall mean CPUE and standard deviation of Rock crab, Jonah crab, and
'American lobster; Annuel mean CPUE of total and legal-sized lobster . .. . .... . . . . . . . 66 2.3-16. Size-class distribution of Nomarus omsef eanus at the discharge station, 1975-1966. . . . . . . . . . 68 3.1.1-1. Monthly mean temperature at continuous monitoring ,
Station ID (nearfield) for each year and over all years from 1976-1984 and Aug-Dec 1986 for A. surface and B. bottom . . . . ... . . . .. . . . 71 3.1.1-2. Differences between surface and bottom temperatures taken semi-monthly at Station P2. . . . . .. . . . 73 3.1.1-3. Monthly mean salinity at nearfield Station P2 for each year and over all years from 1978 throvgh 1986 for A. surface and B. bottom. ... . . . . . . . . 73 3.1.1-4. Monthly mean dissolved oxygen at nearfield .ceation P2 for each year and over all years from V/78-1986 for A. surface and B. bottom. ... . . . . . . . . 76 3.1.1-5. Monthly mean concentrations at nearfield Station P2 for each year and over all years from 1978-1984 and July through December 1986 for A. orthophosphate and B. total phosphorus . . . . ..... . . . . . 77 3.1.1-6. Monthly mean concentrations at nearfield Station P2 i for each year and over all years from 1978-1984 and l July through December 1986 for A. nitrite-nitrogen and B. nitrate-nitrogen . . . ..... . .. . . . 78 3.1.1-7. Monthly mean ammonia concentrations at nearfield Station P2 for each year and over all years from 1978-1984 (excluding 1982) and July-December 1986 . 79 3.1.2-1. Total mean abundance of whole water phytoplankton in surface waters at Station P2, 1978-1984 and July-December 1986. . . .. . ... . . . . . . . . 81 viii ) l l 1
1 1 l PAGE 3.1.2-2. Biomass (Chlorophyll a) at Station P2, 1977-1984 and July December 1986. . . .. . . . . . . .. . . 89 3.1.2-3. PSP toxicity levels in Myt tius edults from Hampton x Harbor Estuary, NH and Essex Estuary, MA. Data courtssy of: New Hampshire Division of Public Haalt a and Massachusetts Dapartment of Public Hea'.th, Lawrence Experimental Station . . . ... . 91 3.1.2-4. Monthly mean abundance (log x+1 cells per liter) of Skeletonoma costatum at nearfield Station P2 for each year and over all years from 1978-1984 and July-December 1986. . . . . . . . . . . . . . .. . 92 3.1. 3.1. Weekly occurrence of bivalve veliger larvae at Station P2 from mid April through October from 1978 through 1986. . . . . . . . . . . . . . . . . . .. 104 3 3.1.3-2. Monthly mean abundance (log x+1/m ) for each year and over all years at nearfield Station P2, 1978-1984 and Jul-Dec 1986, for A. Eurytemore sp. copepodites and B. Eurytemera herdmant adults . .. 109 3 3.1.3-3. Monthly mean abundance (log x+1/m ) for each year and over all years at nearfield Station P2, 1978-1984 and Jul-Dec 1986, for A. Pseudoccianus/ Calanus sp. nauplit, B. Pseudocolanus sp. copepodites, and C. Pseudocolanus sp. adults. ... 112 3 3.1.3-4. Monthly mean abundance (log x+1/m ) for each year and over all years at nearfield Station P2, i 1978-1984 end Jul-Dec 1986, for A. OttAono sp. nauplii, B. OttAono sp. copepodites and C. Otthona sp. adults. . . . . . . . . . .. . . . . . .... 114 3.1.3-5. Weekly mean abundance of Myttlus edults larvae at nearfield Stat!on P2 for each year and over all years, 1978 through 1986. . . . . . . . . . .... 116 3 3.1.4-1. Monthly mean abundance (log x+1/1000m ) for each year and over all years at nearfield Station P2 from 1978-1984 and July-December 1986 for A. Calanus fInmarcAlcus copepodites and B. Calanus finmareAlcus sdults . . . .. . . . . . . . .... 130 3 3.1.4-2. Monthly mean abundance (log x+1/1000m ) for each year and over all years at nearfield Station P2 from 1978-1984 and July-December 1986 for A. Carcinus mornas larvae and B. Crangon septemspinoso zoese and post larvae . . . . . . . . . . . .... 131 l ix i 1
PAGE 3 , 3.1.4-3. A. Monthly mean abundance (log x+1/1000m ) of Naomysis americana (lifestages combined) for each year and over all years and B. Mean percent composition of #eomys ts americana lifestages over all years at nearfield Station P2 from 1978-1984 and July-December 1986. . . . . . . . . . ..... 134 3.2.1-1. Occurrence by month of larvae of selected species of fish at neurfield Stations P3 and P2 during the eleven year period 1976-1986. . . . . . .... .. 168 3.2.1-2. Log (x+1) monthly abundances and overall monthly means for A. American sand lance and B. winter flounder larvae collected at nearfield Stations P2 and P3 during July 1985 through December 1986 . . . 170 3.2.1-3. Log (x+1) monthly abundances and overall monthly means for A. yellowtail flounder and B. Atlantic cod larvae collected at nearfiele Stations P2 and P3 during July 1975 through Decerber 1986 . . ... 174 3.2.1-4. Log (x+1) monthly abundances and overall monthly means for A. Atlantic mackerel and B. cunner larvae collected at nearfield Stations P2 and P3 during July 1975 through December 1986 . . . . .. .. .. 176 3.2.1-5. Log (x+1) monthly abundances and overall monthly means for A. hake and B. Atlar. tic herring larvae collected at nearfield Stations P2 and P3 during July 1975 through December 1986 . . . . ...... 178 3.2.1-6. Log (x+1) monthly abundance and overall monthly means for pollock larvae collected at nearfield Stations P2 and P3 during July 1975 through December 1986 . . . . . . . . . . . . . .... .. 179 3.2.2-1. Catch per unit effort (mean number per 10 minute tow) of all species collected in otter trawls by year, station and all stations combined, 1976-1986. 181 3.2.2-2. Catch per unit effort (number per 24-hour set of one net, surface or bottom) of all species collected in gill nets by year, station and all stations combined, 1976-1986. ., . . . ... . .. 187 3.2.2-3. Catch per unit effort (mean number per' seine haul) of a;1 species collected in beach seines by year, j station and all stations combined, 1976-1984 and July-November 1986. . . . . . . . . . . .. . ... 194 l x
PAGE 3.2.2-4. Monthly mean log-transformed (x+1) catch per unit effort (1 24 hr. set) for each year and over all years for A. Atlantic herring and B. pollock at combined gill not stations G1, G2 and G3 from 1976 through 1986. . . .. . . . . . . . . . . . . . . . 200 3.2.2-5. Monthly mean log-transformed (x+1) catch per unit effort (1 24-hr. set for gill nets, 4 replicate tows for otter trawl) for each year and over all years for A. Atlantic mackerel at combined gill net Stations G1, G2 and G3 and B. Atlantic cod at otter trawl Station T2 from 1976 through 1986 . . . .. . 203 3.2.2-6. Monthly mean log-transformed (x+1) catch per unit effort (4 replicate tows for otter trawl) for each year and over all years for A. Hakes at Station T2 and B. Yellowtail flounder at Station T2 from 1976 through 1986. . . .. . . . . . . . . . . . . . . . 206 3.2.2-7. Monthly mean log-transformed (x+1) catch per unit effort (4 replicate tows for otter trawl, 2 hauls for beach seine) for each year and over all years for winter flounder at A. otter trawl Station T2 from 1976 through 1986 and B. combined beach seine Stations S1, S2 and S3 from 1976 through 1984 and 1986. . . . . . . ... . . . . . . . . . . . . . . 208 3.2.2-8. Monthly mean log-transformed (x+1) catch per unit i effort (4 replicate tows for otter trawl, 2 hauls j for beach seine) for each year and over all years l for rainbow smelt at A. otter trawl Station T2 from 1976 through 1986 and B. combined beach seine ; Stations S1, S2 and S3 from 1976 through 1984 and i 1986. . . . . . . . . .. . . . . . . . . . . . . . 210 l 1 3.2.2-9. Monthly mean log-transformed (x+1) catch per unit effort (2 heuls) for each year and over all years for Atlantic silversides at combined beach seine Stations S1, S2 and S3 from 1976 through 1984 and , 1986. . . . . . . ... . . . . . . . . . . . . . . 213 3.3.1-1. Mean monthly salinity (ppt) and temperature ('C) in Brown's River at low tide from 1978-1986. . . . . . 221 3.3.1-2. Discharge from the Seabrook Settling Basin from i 1978-1986 in millions of gallons per day (GPD). . . 224 3.3.1-3. Mean monthly salinity (ppt) and temperature ('C) in Hampton Harbor at low tide from 1978-1986 . . . . . 225 xi
l l l l l i i PAGE 3.3.1-4. Number of individuals per sq. meter collected at subtidal and intertidal estuarine stations sampled three times per year from 1978-1984 and 1986. . . . 230 3.3.1-5. Number of taxa collected at subtidal and intertidal estuarine stations sampled three times per year from 1978-1984 and 1986 . . . . . . . . . . . . . . 232 3.3.1-6. Mean abundance of the important species at subtidal estuarine stations sampled three times per year from 1978-1984 and 1986. . . . . . . ... . . . . . . . 233 3.3.1-7. Mean abundance of the important species at intertidal estuarine stations sampled three times per year from 1978-1984 and 1986. . . . . . . . . . . . . . . . . 234 3.3.2-1. Number of macroalgae species in general collections at each marine benthic station for 1978-1984 (median and range) and 1985 and 1986 (number collected each year) . . . . . . . . . . . . . . . . . . . . . . . 238 3.3.2-2. Number of macroalgae taxa and mean biomass (gms/m') taken during August from 1978-1984 and in 1985/1986 at marine benthic stations. . . .. . . . . . . . . 239 3.3.2-3. Relative abundance (biomass) of dominant macroalgae at marine benthic stations in August 1978-1984. . . 241 3.3.2-4. Summary of spatial associations identified from numerical classification (Bray-Curtis similarity) of benthic macroalgae collected in August 1978-4 1984. . ... . . . . . . . . . .. . . . . . . . . 244 3.3.2-5. Occurrence and peak biomass of the common and abundant macroalgae species over the range of benthic stations sampled in August 1978-1984. . . . 245 3.3.2-6. Macroalgae community analysis: consistency of year-to-year classification of historical (1978- , 1986) August benthic samples into baseline groups, ' based on discriminant function analysis . . . . . . 246 ; 3.3.2-7. Density of kelps (counts) and of dominant understcry algae (% frequencies) in the shallow and i mid-depth subtidal zone 1981-1984 and 1985-1986 i (zero values not shown) . . . . ... . . . . . . . 249 3.3.2-8. Mean biomass (gm/m 8
) and 95% confidence limits of Chondrus crispus at selected stations in May,
! August and November 1978-1984, 1985 and 1986. . . . 255 l l xii I
i PAGE 3.3.3-1. Number of species and abundance at intertidal and subtidal benthic stations . . . . . . . . . . . . . 259 3.3.4-1. 1986 faunal richness (number'of differ *nt taxa over 2 replicates) compared to mean species richness and il standard deviation from 1978-1984 on short term panels. . . . . . . . . . . . . . . . . . . . . . . 275 3.3.4-2. 1986 species abundance (log x+1) compared to mean species abundance (log x+1; 195% confidence limits) from 1978-1984 for non-colonial fauna on short-term panels . . . . . . . . . . . . . . . . . . . . . . . 277 3.3.4-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19 . . . 282 3.3.6-1. Square root projection of lobster larvae mean densities (No./1000m') at Station P2 1978-1986. . . 302 3.3.6-2. Comparisons of legal and sub-legal sized catch of Nomarus americanus at the discharge site 1975-1986. 310 3.3.6-3. Size-class distribution of Romarus amerleanus at the discharge station 1975-1986 . . . . . . . . . . 312 3.3.6-4. Summary of female lobster catch data at the discharge station (L1) 1974-1986. . . . . . . . . . 313 3.3.6-5. Monthly mean abundance of Cancer sp. larvae at Station P2 1978-1984, and July through December 1986. . . . . . . . . . . . . . . . . . . . . . . . 315 3.3.7-1. Square root projections of mean densities (m' ) of umboned M. arencefe valigers sampled at Station P2 1978-1986 . . . . . . . . . . . . . . . . . . . . . 319 3.3.7-2. Log (x+1) densities of Mye arenaria veligers at nearfield Station P2, discharge Station PS, farfield Station P7 and Hampton Harbor Station P1 1982-1986 . . . . . . . . . . . . . . . . . . . . 321 3.3.7-3. Size class distribution of Mya arenaria in Hampton-Seabrook Harbor during early fall 1974-1986 . . . . 324 xiii
PAGE 3.3.7-4. Means and 95% confidence limits of young-of-the-year Mya arenaria (1-Sam) at Hampton-Seabrook 1975-1986. . . ........... . .. . . . . . . . 326 3.3.7-5. Mean and 95% confidence limits of M. arenaria spat (shell length 512mm) densities (ft'8) at'two Northern New England estuaries 1976 through 1984 and 1986. . . ..... ........ ... . . . 328 3.3.7-6. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 1, Hampton-Seabrook Harbor, 1976 through 1986'. . . . ......... 329 3.3.7-7. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 2, Hampton-Seabrook Harbor, 1974 through 1986 . .. .... ...... 330 3.3.7-8. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 4, Hampton-Seabrook Harbor, 1976 through 1986 . ... .. . . . . . . . 331 3.3.7-9. Seasonal mean catch per unit effort for green crabs (Careinus maenos) in Hampton-Seabrook Harbor and its relationship to minimum winter temperature, 1978-1986 . .. . ... ........... . . . 335 3.3.7-10. Number of adult clam licenses issued and the adult clam standing crop (bushels), Hampton Harbor, 1971-1986 . . ..... . ........ . . . . . 339 4.1-1. Plankton sampling stations. .. .. .. . . . . . . 372 4.1.2. Finfish sampling stations . .. . ......... 373 4.1-3. Benthic sampling stations and lobster / crab trapping areas . .. ., .... . .... ......... 375 4.1-4. Estuarine benthic transect locations and Mya arenaria survey flats . .............. 377 l l l i l xiv
]
t' LIST OF TABLES i PAGE 2.1-1. Summary of Biological Communities and Species : j 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 Fntrainment Samples at Seabrook Station from July 28 Through December 30, 1986. .. . ... . . .. . . .. ...... . 19 2.2-2. Summary of Nearfield/Farfield (P2 vs. P7) Spatial Differences in Plankton Communities and Celected Species . . .. . .. . . . . . . . . . .... .. 25 2.2-3. Catch Per Unit Effort by Depth for the Dominant l Gill Net Species Over All Stations and Dates When Surface, Mid and Bottom Nets Were Sampled, 1980 Through 1986. .. .. . . . . . . .. . . . .. . . 31 2.3-1. Selected Benthic Species and Rationale for Selection . . . . .. . . . . . . .. .. .... . 42 2.3-2. Summary of Similarities in Abundance, Biomass, Frequency, or Length Among Years and Between Stations for Selected Macrofaunal and Macroalgal Species at Intertidal and Shallow Subtidal Depths . 43 4
2.3-3. Summary of Similarities in Abundance or Length Among Years and Between Stations for Selected l Species in the Mid-Depth Zone . . . . . . . .... 59 1 3.1.1-1. Qualitative Observations of Seasonal Cycles and l Long-Tere Trends of Water Quality Parameters at the i Nearfield Station (P2) Measured from July 1977 Through December 1986 . . .. .. .. ... . ... 70 3.1.1-2. Annual Means and Coefficients of Variation of Water j Quality Parameters Measured During Plankton Cruises l 1 at nearfield Station P2, 1978-1984 and July-December 1986 . . ... . . . . . . . .. . . ... 72 3.1.2-1. Annual Percent Composition (21.0%) of whole water Phytoplankton in Surface Waters at the Nearfield l Station P2, 1978-1984 . . ... . . ........ 83 l I i l i l I xv 1 I
PAGE 3.1.2-2. Occurrence of Dominant Phytoplankton Taxa in Surface Waters at the Nearfield Station P2, 1980-1984 and Jul-Dec 1986 . . . . . . . . . . . . . . . 84 3.1.2-3. Annual Percent Composition (21%) and Frequency of Occurrence of Vhole Water Phytoplankton in Surface Waters at Stations P2, P5 and P7, July December 1986. . . . . . . . . . . . . . . . . . . . . . . . 88 3.2.1-4. Peak Fall Abundances of Skeletonema costatum in Surface Waters at Station P2, 1978-1986 . . . . . . 93 3.2.1-5. Seasonal Mean Abundances of Skeletonema costatum at Stations P2 and PS, July-December, 1986. . . . . . . 93 3.1.3.1. Seasonal Groups Formed by Normal Numerical Classification of Bray-Curtis Similatity Values Among Microzooplankton Collections from Nearfield Station P2, 1978-1984 . . . . . . . . . . . . . . . 95 3.1.3-2. Dominant Species Occurring in Seasonal Groups Formed by Normal Classification of Microzcoplankton Collections Averaged Over Depth at Nearfield Station P2 from 1978-1984 . . . . . . . . . . . . . 97 3.1.3-3. Percent Composition and Frequency of Occurrence of Dominant Species in Microzooplankton Collections Between Stations P2, PS and P7, July-December 1986. 101 3.1.3-4. Overall Percent Composition of Bivalvia Veliger Larvae in 76p Net Tows at Stations P2 and P7 from Mid-April Through October 1982-1986 . . . . . . . . 103 3.1.3-5. Analysis of Variance Comparison of Mean Total Bivalve Larvae Abundance Anong All Plankton Stations (P1, P2, PS and P7) July 1-October 28, 1986. . . . . . . . . . . . . . . . . . . . . . . . 106 3.1.3-6. Comparison of Weekly Abundances (m'3) of Dominant Bivalve Larvae Taxa at Nearfield (P2) and Entrainment (E1) Stations from July 28 Through October 28, 1986. . . . . . . . . . . . . . . . . . 107 3.1.3-7. Annual Mean Abugdance (Based on Surface and Bottem Averages; no./m ) and Standard Deviation of . Selected Species of Microzooplankton at Seabrook Nearfield Station (P2). . . . . . . . . . . . . . . 110 i xva
PAGE 3.1.3-8. Comparison of Myttlus edults Larval Abundance (m' ) Sampled on the Same Date at Entrainment Station (E1) and Nearfield Station (P2) . . . . . . . . . . 3.1.4-1. Seasonal Groups Formed by Normal Classification of Macrozooplankton Collections at Nearfield Station P2 1978-1984 in Comparison to 1986 Estimates. . . . 120 3 3.1.4-2. Semiannual Mean Abundance (No./1000 ) of Dominant Macrozooplankton Species, July-December 1986. . . . 124 3.1.4-3. Comparison of Percent Composition (and Percent Frequency of Occurrence) of Species in Macrozoo-plankton Collections Between Stations P2, PS and P7, July-December 1986. . .. .. . . . . . . . . . 125 3.1.4-4. Comparison of Rank (and Percent Frequency of Occurrence) of Dominant Species in Macrozooplankton Collections Between Stations P2, PS and P7 July-December 1986 . . . . . . . . . . . . . . . . . . . 126 3 3.1.4-5. Annual Mean Abundance (No./1000m ) and Standard Deviation of Selected Species of Macrozooplankton at Seabrook Nearfield Station (P2). . . . . . . . . 129 3.2.1-1. Finfish Species Compositon by Life Stage and Gear Type, July 1975 December 1986 . . . . . . . . . . . 147 3.2.1-2. Distribution Among Dates and Among Seasonal Assemblages of Samples of Fish Eggs Collected at Nearfield Stations P2 and P3 During July 1985 Through December 1986 . . . . .. . . . . . . . . . 152 1 3.2.1-3. Distribution Among Dates and Among Seasonal Asceablages of Samples of Fish Larvae Collected at Naerfield Stations P2 and P3 During July 1975 Through December 1986 . . .. .... . . . . . . . 157 3.2.1-4. Comparison of Percent Abundance and Percent ! Frequency of Fish Egg Collections at Nearfield ) l (P2), Farfield (P7), and Discharge (P5) Stations : During 1986. All Species Which Were Collected in ]) the Egg Stage Are Listed. . . . . . . . . . . . . . 160 3.2.1-5 Comparison of Percent Abundance and Percent Frequency for Larval Fish Species at Nearfield (P2), Farfield (P7) and Discharge (PS) Stations During 1986. Species I Listed are Considered Common in Overall Station ' Abundance . ...... . .. ... . . . .. . . . 161 1 xvii
l l l l PAGE 3.2.1-6 Summary of Monthly Flow Data in Millions of Gallons per day (mad) through the Seabrook Circulating Water System, June December 1986. . . . ...... ... 163 , 3.2.1-7 Ichthyoplankton Sampling Dates at Entrainment Station (E1) and Nearfield Station (P2), July 31 through December 22, 1986 . . . . . . . .... .. 164 3 3.2.1-8 Mean Abundance (#/1000m ) of Fish Eggs per Month at Stations El and P2. . . . ... . .. .. .. ... 165 3 3.2.1-9 Mean Abundance (#/1000m ) of Fish Larvas per Month at Stations El and P2. . . . . .. ... ... . . .. 167 3.2.1-10 Seasonal Means (Peak Periods) of Untransformed and3 Log (x+1) Transformed Abundance (Number per 1000 m ) by Year of Selected Fish Species Larvae at Station P2, July 1975 through December 1986 . . ..... . 171 3.2.1-11 Analysis of Variance Comparison of Log (x+1) Trans-i formed Yearly Mean Abundances for Selected Months by Year, July 1975 through December 1986 . ... ... 172 3.2.2-1 Total Percent Composition by Year and All Years Combined for the Twelve Most Abundant Species in Otter Trawls During 1976 through 1986 at Stations , T1, T2 and T3 Combined. . . . . . . . . . . . . . 183 3.2.2-2 Total Percent Composition by Station of Abundant j Species Collected in Otter Trawls, All Years Combined , (1976-1986) . . . . . . . . .. . ... . . ... 185 i 3.2.2-3 Total Percent Composition by Year and All Years Combined for the Ten Most Abundant Species la Gill i Net Samples During 1976 through 1986 at Stations G1, G2 and C3 Combined. . .. . . .... ...... 188 3.2.2-4 Total Percent Composition by Station of Abundant Species Collected in Gill Nets, All Years and Depths , Combined (1976-1986). . . .. . . . . ....... 190 j j 3.2.2-5 Total Percent Composition of Dominant Gill Net Species l l According to Depth (Surface and Off-bottom), All Years l Combined (1976-1986). . . . .. ..... ...... 191 J j j l XVili 1
PAGE 3.2.2-6 Catch Per Unit Effort by Depth for the Dominant Gill Net Species over All Stations and Dates When Surface, Mid and Bottom Nets were Sampled,1980 through 1986 . 193 3.2.2-7 Total Percent Composition by Year for the Ten Most Abundant Species Collected in Beach Seines During 1976 through 1986 (not collected in 1985) at Stations S1, S2 and S3 Combinea. . . . . . . . . . . . . . . . 195 3.2.2-8 Total Percent Composition by Station of Abundant Species Collected in Beach Seines, All Years Combined, July through November (1976-1984, 1986) . . . . . . . 197 3.2.2-9 Annual Mean CPUE for Selected Finfish Species . . . . 201 3.2.2 10 Comparison of Log (x+1) Transformed Catch Per Unit Ef fort by Year and Station Utilizing a Two-way Analysis of Variance for Selected Finfish Species Collected in Otter Trawls from 1976 through 1986 . . . . . . . . . 205 3.3.1-1 Annual Mean Temperature ('C) and Salinity (ppt) from Brown's River and Hampton Harbor from 1980-1986 . . . 220 3.3.1-2 Monthly Total Precipitation in Inches (Vater Equivalent in Inches) Boston, MA. . . . . . . . . . . . . . . . . 222 3.3.1-3 Mean Density (No. Per Sq. Meter) for Each Year and Over All Years for Selected Variables Collected from Estuarine Benthic Stations 3, 9, 3MLV, and 9MLV from 1978 through 1986 (excluding 1985). . . . . . . . . . 228 3.3.1-4 Results of a Two-Vay ANOVA Model for Selected Biological Variables Sampled at Estuarine Benthic Stations from 1978-1984 and in 1986 . . . . . . . . . 229 3.3.2-1 Relative Abundance of Dominant Macroalgae at Marine Benthic Stations in August of 1985 and 1986 . . . . . 242 3.3.2-2 Seasonal and Yearly Mean Abundance and Percent Cover of Laminaria saccherina from Transect Studies in the Shallow Subtidal Zone . . . . . . . . . . . . . . . . 253 3.3.2-3 Results of Significance Test on Macroalgae Selected Species, Chondrus crispus and Laminaria saccharina. . 254 xix
l l PAGE ! 8 3.3.2-4 Hean Biomass (3/m ) and Standard Deviation (SD) of ; Chondrus erlapus at Benthic Stations 17, 35,1MLW, and l l SMLW in August from 1978 to 1986. . . . . . . .... 257 l 3.3.3-1 Station Groups Defined by Discriminant Analysis of Non-colonial Macrofauna Collected by Intertidal and Subtidal Benthic Stations, August 1978-1986 . . . . . 263 3.3.3-2 Median and Range of Percent Frequencies of the Dominant Fauna at Bare Rock and Fucoid Ledge Intertidal Mean Sea Level Sites at Stations 1 (Outer Sunk Rocks) and 5 (Rye Ledge) Monitored Nondestructive from 1982-1986 267 l l 3.3.3-3 Percent Frequency of the Dominant Fauna at Intertidal l Mean Low Water Sites at Stations 1 (Outer Sunk Rocks) and 5 (Rye Ledge) Monitored Nondestructively in 1985 and 1986. . . . . . . . . . . . . . . . . . . . ... 269 3.3.3-4 Estimated Density (per 1/4 m8 ) of Selected Sessile Taxa on Triannual (4 Months' Exposure) Hard-Substrate Bottom Panels . . . . . . . . . . . .... 271 l 3.3.3-5 Annual Mean Density (Per 1/4 m8 ) and Standard Deviation of Modfolus medfolus observed at Subtidal Transect Stations, 1980-1986 . . . . . . . . . . . . . . ... 273 3.3.4-1 Dry Weight (gms/ Panel) Biomass on Short-Term Surface c Fouling Panels. . . . . . . . . . . . . . . . . ... 278 l 2 3.3.4-2 Unusual Differences on 1986 Short-Term Panels (Summer / Fall Only) Compared to the Baseline Period j (1978-1984 Except Station 34 Which was 1982-1984). . 279 l
\
3.3.4-3 Dry Weight (ges/ Panel) Biomass on Monthly Sequential Surface Fouling Panels. . . . . . . . . . . . ... . 283 1 3.3.4-4 Laminario sp. Counts on Monthly Sequential Surface Fouling Fanels. . . . . . . . . . . . . . . . .... 285 3.3.5-1 Annual Mean and Standard Deviation of Abundance I (No./m8 ) Sampled Triannually in May, August, and November at Selected Benthic Stations . . . . .... 286 3.3.5-2 Results from ANOVA Models and Comparison Procedures for Abundance (No, per sq. Meter) for Selected Species Sampled Triannually in May, August, and November at Selected Benthic Stations . . . . . . . . . . ... . 289 XX i l
PAGE P i 3.3.5-3 Annual Mean Length (mm) and Standard Deviation for Selected Benthic Species Sampled Triannually in May, August, and November at Selected Benthic Stations . . 291 3.3.5-4 Results of 2-way ANOVA Models and Comparison
- Procedures for Length (mm) of Selected Species '
Sampled Triannually in May, August, and November from 1982-1986 at Selected Benthic Stations. . . . . . . . 293 3.3.6-1 Percent Composition of Lobster Larvae Stages at i Stations P2, P5 and P7, 1978-1986 . . . . . . . . . . 301 3.3.6-2 Summary of Total Lobster Catch Per Trip Effort, by Month and Year, at the Discharge Site (L1) from 1975 through 1986 . . . . . . . . . . . . . . . . . . 306 3.3.6-3 Results of One way and Two-way ANOVA Models for Lobster
- (Homarus americanus), Jonah Crab (Cancer borealis) and j Rock Crab (Cancer trroratus) from the Discharge i Station . ............ . . . . . . . . . . 307 j 3.3.6-4 Comparison of Female Crab Catch Statistics of Jonah 7 Crab (Cancer borealis) and Rock Crab (Cancer Irroratus) at the Discharge Site and Rye Ledge, 1982-1986. . . . 316 ;
3.3.7-1 Average Catch per Unit Effort, Sex Ratio, and Percent Gravid Females for Caretnus meenas Collected at ; Estuarine Stations from 1977-1986 . . . . . . . . . . 334 3.3.7-2 Estimated Distribution (% of Total) of Clam Diggers by Flat at Hampton Harbor, Spring 1980 through Fall 1986 337 1 3.3.7-3 Summary of Standing Crop Estimates of Adult Nya j l arenaria in Hampton Harbor,1967 through 1986 . . . . 341 l s i 3.3.7-4 Distribution (% of Total Standing Crop) of Harvestable
- Clams by Flat at Hampton Harbor, 1979 through 1986. . 342 1
4.1-1 Ber.thic Station Locations and Descriptions. . . . . . 374 l 4.2-1 Summary of Community Analysis . . . . . . . . . . . . 380 4.3-1 Analysis of Temporal and Spatial Patterns in Selected Taxa and Parameters: Methods and Data Calculations . 384 I t i XXi 4
l LIST OF APPENDIX FIGURES l 0 PAGE 3.1.1-1. Weekly means of average daily temperatures at the nearfield continuous monitoring Station ID, 1976-1984, and August-December 1986. . . . . . . . . . . 136 3.2.2-1. Monthly mean log-transformed (x+1) catch per unit effort (4 replicate tows for otter trawl) for each year and over all years for Atlantic cod at A. Station T1 and B. Station T3 from 1976 through 1986. . . . .. .... . . . . . . . . . . . . .. 214. 3.2.2-2. Monthly mean log transformed (x+1) catch per unit effort (4 replicate tows for otter trawl) for each year and over all years for winter flounder at A. Station T1 and B. Station T3 from 1976 through 1986. . . . .. . . .. . . . . . . . . . . . . . . 215 3.3.1-1. Mean monthly salinity (ppt) and temperature ('C) in Brown's River at high tide from 1978-1986 . . . .. 344 3.3.1-2. Mean monthly salinity (ppt) and temperature ('C) in Hampton Harbor at high tide from 1978-1986. . ... 345 i i' I l i I l I i l j xxii
LIST OF APPENDIX TABLES PAGE 3.2.2-1 Least Square Means Evaluation of Year / Station Inter-actions on Log (X+1) Transformed CPUE for Atlantic Cod from 1976 through 1986, at Stations T1, T2 and T3. . . . . . . ... .... . . . . . . . . . . . . . 216 3.2.2-2 Least Square Means Evaluation of Year / Station Inter-actions on Log (X+1) Transformed CPUE for Yellowtail Flounder from 1976 through 1986 at Station T1, T2 and T3 . . . . ... . .... . . . . . . . . . . . . . 217 3.2.2-3 Least Square Means Evaluation of Year / Station Inter-actions on Log (X+1) Transformed CPUE for Winter Flounder from 1976 through 1986 at Station T1, T2 and T3 . . . . . .. . . . . . . . . . . . . . . . . . . 210 3.3.2-1 Macroalgae Species Recorded in General Collections from Benthic Stations Sampled from 1978 to 1984 (a,b).. . . . 346 3.3.2-2 A. Percent Frequency and B. Porcent Cover per 0.25 m2 og Perennial and Annual Macroalgae Species at Fixed Inter-tidal Non-destructive Sites. . . . . . . . . . . . . . . 350 , I 3.3.3-1 Species Used in Discriminant Analysis of Benthic Macrofauna . . ... . . . . . . . . . . . . . . . . . . 353 3.3.4-1 Number (mean per 2 replicates) of Mytilidae Occurring on Short-term Fouling Panels for Each Study Year . . . . 354 l 3.3.4-2 Number (mean per 2 replicates) of Jassa f alcata Occurring j on Short-term Fouling Panels for Each Study Year . . . . 355 l 3.3.4-3 Number (mean per 2 replicates) of #fatella sp. Occurring on Short-term Fouling Panels for Each Study Year . . . . 356 3.*.4-4 a Percent Frequency Cover (mean per 2 replicates) of Diatoms Occurring on Short-term Fouling Panels for Each Study Year . . ... . ... . . . . . . . . . . . . . . 357 3.3.4 5 Number (mean per 2 replicates) of Balanus sp. Occurring on Short-term Fouling Panels for Each Study Year . . . . 358 3.3.4-6 Number (mean per 2 replicates) of Anemia sp. Occurring on Short-term Fouling Panels for Each Study Year . . . . 359 xxiii
. - . - = - - . . . . . . . .= ..
I i l i l I' t ( l ! PAGE l 3.3.4-7 Percent Frequency Count (mean per 2 replicates) of Tubulerie sp. Occurring on Short-term Fouling Panels for Each Study Year. . . . ...........,... 360 j 3.3.4 8 Number (mean per 2 replicates) of Leevnd vinete sp, , Occurring on Short-tern Fouling Panels for Each Study 1 Year . . . . . . . . . . ...........>..... 361 , I 3.3.4-9 Number (mean per 2 replicates) of #udibreneAle sp. ; Occurring on Short-term Fouling Panels for Each Study Year . . . . . . . . . . . . . . . . . . . . . . . . . . 362 , 3.3.4-10 Number (mean per 2 replicates) of Pentotente inermis Occurring on Short-term Fouling Panels for Each Study ; Year . . . . . . . . . . . . . . . . . . . . . . . . . . 365 , 3.3.4-11 Number (mean per 2 replicates) of Strentplecentretus ! dreebe6?lensis on Short term Touling Panels for Each , Study Year . ... . . . .. . ............. 364 3.3.4-12 Number (mean per 2 replicates) of Asteriidae occurring ! on Short-term Fouling Panels for Each Study Year . . . . 365 , 3.3.4-13 Percent Frequency Cover (mean per 2 replicates) of Obei to app. Occurring on Short-term Fouling Panels l for Each Study Year. . . . . . . . . . . . . . . . . . . 366 3.3.6-1 Summary of Legal Lobster Catch at the Discharge Site from 1974 through 1086 . ................ 367 : 1 3.3.7-1 Sununary of Mye arenario Population Densities from i Annual Fall Surveys in Hampton-Seabrook Harbor, 1971 through 1986 . . .. ... ........ ,..... 368 xxiv
1.0 EXEClTTIVE
SUMMARY
1.1 INTRODUCTION
Seabrook Environmental Studies began in 1969 to monitor the balanced indigenous marine communities in preparation for assessing the effects of the station operation on them. As plant operation has not yet begun, the study is in the preoperational or baseline monitoring phase. The of the 1986 Seabrook Baseline Report is to define the sources an- .sa itudes of naturally-occurring variability in the physical and biological environment around Seabrook Station. A previcits report (NAI 1985b) summarized information collected through 1984 This report updates those results with two add' :nnal years of data. The optimal design of an impact as.wssment study ensures that a potential impact is delineated from naturally occurring variability. The Seabrook Monitoring Program accomplishes this by 1) collecting data before and during operation to provide a "temporal control", and by 2) monitoring areas of potential impact as well as areas unaffected by impact to provide a "spatial control". In each biological community, the experimental design of the program focuses on the most variable aspect. For example, the species distributions of plankton and pelagic fish change radically from season to season, but are similar throughout the coastal area. The sampling program collected data at least twice monthly to monitor seasonal trends in abundance at a nearfield and farfield area. For benthic macrofauna and macroalgae, seasonality is less of an issue in comparison to the marked changes in species composition with depth. Benthic collections were made in the predominant substrate type, horizontal hard bottom ledge, along nearfield and f arfield transects at regular depth intervals. The f.merican lobster, soft-shell clam, and certain fish are of particular concern because of their commercial or recreational importance. Data on 1
l I all life stages of these species were collected. The discussion of variability focuses on the source of potential impact (intake, discharge) and the biological community or physical parameter most likely to be affected. 1.2 INTAKE MONITORING The goal of intake monitoring is to provide information on the number and type of organisms entrained by the Seabrook Station cooling water system. Zooplankton, ichthyoplankton, and demersal fish are the organisms which have the greatest potential for exposure to intake effects. During the study, both the number and type of entrainable organisms varied dramaticelly among seasons. The microzooplankton cor;munity shif ted 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 thermal regime. Macrozooplankton assemblages were highly predictable from year-to-year, reflecting the population dynamics of the dominant copepods and the spring and summer reproductive activities of benthic fauna. Seasonal patterns of the bivalve larvae (including mussel and soft shell clam larvae) and the fish egg and larvae species assemblages were the result l of spawning activitiss of the adults. Species composition reflected the predominance of one or two species which were present during a discrete time period. Fish eggs were most abundant in spring and summer, bivalve larvae in summer and fall, and fish larvae in late winter and summer. Most of the species represented in the zooplankton were widely distributed throughout the Gulf of Maine; thus entrainment losses can be l l replenished by the nearshore population. TVo species with local adult l populations contributing to the larval pool, cunner and soft-shell clam, had widespread nearshore larval populations which lessen potential entrainment impact. 2
l l Beginning in June 1986, Seabrook Station operated its cooling water system, although no power or heated discharge were produced. As expected, entrainment samples collected in the last half of 1986 for fish egg, larvae, and bivalve larvae had species distributions similar to samples collected offshore. Density levels for most of the entrained fish eggs and larvae were lower because of the less intensive sampling effort. Density levels of bivalve larvae were similar to those offshore except during peak periods, when entrained densities were lower. Potential intake effects on the pelagic fish community will be apparent from studying the seasonal and annual movements of the six most-abundant species which together constitute over 90% of the popula-tion. Of these, Atlantic herring is the most important; from September to April, it makes up from 60-90% of the total gill net catch. The variability in overall catches was directly related to year-to-year variations in Atlantic herring catches. Another important consideration in intake effects is the depth distribution of the pelagic fish. Atlantic menhaden and occasionally Atlantic mackerel were most abundant in the mid-depth area, where Ontake structures are located. These species may potentially be more susceptible than other pelagic fish to intake effects. 1.3 DISCHARGE MONITORING 1.3.1 Discharge Plume Monitoring As the discharge plutne 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 wate. quality, phytoplankton, and lobster larvae will be monitored primarily for discharge plume effecte. Water quality parameters showed distinct seasonal patterns that were important in driving biological cycles. 3 l
Surface and bottom temperatures reached their lowest points from January through March, then steadily increased from August to October before beginning their fall decline. Dissolved oxygan had a seasonal pattern that was inversely related to temperature, with peak values in late winter and lowest values in fall. Year-to-year differences were low. Salinity values were fairly stable, but highest in winter and lowest in spring, a result of high runoff. Nutrients had somewhat erratic sea-sonal cycles, but were generally lowest in summer and highest in fall and winter. In general, the predictability of seasonal patterns and low year-to-year variability of most of the water quality parameters enhanced their suitability for impact assessment. The phytoplankto: community has shown the most seasonal and annual variability of any of the species assemblages monitored. Species composition during peak periods varied from year to year. However, total phytoplankton 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 another increase in late-summer or fall. One phytoplankter in particular, Confoulax sp., produces paralytic shellfish poisoning, or red tide. This organism usually reached toxic levels (as measured in Mytilus adults meat) in May or June in Hampton Harbor, closing flats to bivalve shellfish fishing for a period of 1-7 weeks each year. l l Lobster larvae (Stages I-IV) have a strictly surfa e orienta-tion. In coastal New Hampshira, successful recruitment of Inrvae is the single biggest factor in determining the level of adult catches. All stages were rare in the study area, generally occurring from June to October, with highest densities from late June through late August. Evidence suggests that waters off Hampton-Seabrook may be too cold for local production of lobster larvae, and those collected off Hampton-Seabrook actually originate from the Gulf of Maine and Georges Bank. 4
Subsurface fouling panels, located three meters below the surface, can be placed in the inner and outer discharge plume area to show impact on timing, type, and abundances of settling benthic organ-isms. Benthic recruitment and community development showed a seasonal pattern that was highly consistent from year to year. Recruitment and settling activity was low in winter and spring but intensified from summer through fall. The intertidal and shallow subtidal area near the Sunk Rocks is outside the immediate plume area but might be exposed to smaller elevations in temperature. Species composition of benthic macroalgae , and macrofaunal communities in the intertidal and shallow subtidal areas changed with depth and substrate, but was highly similar among years. Individual species showed significant variations in recruitment levels frem year-to-year and among stations; however, length measurements of macrofauna were a more stable parameter. 1.3.2 Benthic Menitoring The mid-depth and deep subtidal areas are monitored to determine if any discharge impacts result from increased detritus levels. Year-to-year differences in the macroalgae and macrofaunal communities were small in comparison to variations with depth and substrate. The species composition was highly predictable and distinct for each depth zone. Although individual macrofauna species were highly variable in their annual abundance levels, these differences were not usually significant. Length measurements were not as variable as abundances and showed no differences among years. Demersal fish which inhabit or feed in the discharge area are important because of their predominance in the food chain as well as for their commercial value. Six taxa constituted over 80% of the total otter trawl catch. Long term trends in total catch were evident, as 5
I l catches in 1980 and 1981 were almost twice catches during the lowest
)
years, 1977 and 1985. The demersal fish species composition basically changed twice per year, from a winter assemblage, when rainbow smelt were abundant, to an extended summer assemblage (April-November), when-hakes and longhorn sculpin were abundant. Other dominants such as yellowtail and winter flounder were present year-round. Most of the-fish captured, with the exception of hakes and winter flounder, were juvenileo. Because of its commercial importance, the American lobster was monitored in the discharge area. Seasonal patterns in catches were similar from year-to-year, and were affected by bottom temperatures, which influenced molting and activity levels. Catches usually increased to a peak in August or September, then declined. Decreases in catches in 1984 and 1985 of legal-sized lobsters, a primary concern to lobstermen, were a result of natural variation in combination with the ef fects of the change in the legal-size limit instituted in 1984 by the State of New Hampshire. Lobsters which would have been legal sized under the old law were protected from harvest until their next molt. Based on data from this study, there is some indication that the catches of legal-sized lobster were beginning to recover in 1986. 1.3.3 Estuarine Monitoring The likelihood of an operational impact in Hampton-Seabrook estuary is low; however, temperature, salinity, benthos, fish, and the soft-shell clam were all monitored. Temperature and salinity both showed regular seasonal cycles. Maximum temperatures usually occurred in August with minima in January or February. Salinity levels had a less distinct pattern, but were usually lowest in spring, a result of increased runoff, and highest in 6
summer. Salinity levels in Erown's River were high from 1980-1982, coincident with low precipitation levels and highest discharge volumes from the Seabrook settling basin. By 1986, salinity levels had returned to pre-1980 levels. The estuarine benthic community was highly variable in species composition and abundance, but predominantly composed of surface and subsurface deposit-feeding polychaetes. The number of species, total abundance, and abundance of some of the dominant species increased during the period when salinity levels were higher than average, but have returned to the levels observed prior to the settling basin discharge. Estuarine fish included both anadromous species as well as residents. Alewives and blueback herring pass into the estuary in spring, travelling upriver to spawn. Catch levels were affected by year class strength as well as water temperature and water level, which were influenced by rainfall and resulting runoff. Young-of-the-year and yearling rainbow smelt were occasionally and erratically caught in the estuary, but never constituted a substantial portion of the total catch. The predominant resident species was Atlantic silverside, which made up over two-thirds of the total catch and over 90% during their most abundant period, August through November. Variations in abundance of this species was the single most-important factor in year-to-year changes in total catch. The most important species of concern in Hampton-Seabrook estuary is the soft-shell clam. Density levels of spat, juveniles, and adults have been monitored in the estuary for 16 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 protection 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 har-7
l
\
vestable clams in 1980-82. Increased levels of predation ~ prevented' recruitment of the highly successful spatfalls in 1980 and 1981. Light spatfalls from 1982-1986 in combination with an increase in predation accounted for a precipitous decline in standing stock since 1983 and ensure that densities of harvestable clams will remain low for several more years. In addition, neoplasia, a cell growth' disease fatal to clamo, has been detected from clams in Hampton estuary. This may also be contributing to the decline of harvestable clams. l 8
2.0 DISCUSSION
2.1 INTRODUCTION
2.1.1 General Perspectiva Environmental studies for Seabrook Station were begun in 1969 and focused on plant design and siting questions. Once these questions were resolved, a monitoring program was designed which has examined the structure of all the major biological communities as.well as the distri-bution, abundance, and size of selected species within each community. The goal has been to assess the temporal (seasonal and yearly) and spa-tial (nearfield and farfield) variability which has occurred during the baseline period. This report focuses on data collected since 1976 for fisheries studies and since 1978 for plankton and benthos studies as these years have maintained a consistent sampling design. The purpose of this report is twofold: 1) to update results of the preoperational baseline monitoring program, summarized in NAI (1985b) with two additional years of data, and 2) provide a perspective on the sources and magnitude of naturally-occurring variability against which impact assessment will be made. Variability is important because it is the issue on which sampling design is focused and can be a major impediment to meaningful impact assessment. Therefore it is discussed first. 2.1.2 Sources of Baseline Variability The optimal design of an impact study has four prerequisites that ensure that a potential impact is delineated from any naturally-occurring variability (Green 1979): 1) knowledge of the type, time and l place of potential impact; 2) measurement of relevant environmental and j biological variables; 3) monitoring before the potential impact occurs 9
to provide a temporal control; 4) monitoring in an area unaffected by impact to serve as a spatial control The experimental design of the Seabrook Environmental Program was structured to meet these prerequisites. A basic assumption was that thero are two major sources of naturally-occurring variability: 1) that which occurs among different areas or stations, i.e., spatial, and 2) that which varies in time, from daily to weekly, monthly or annually. In the experimental design and analysis, we focused on the major cource of variability in each commun-ity type and then determined the magnitude of variability in cach com-munity (Figure 2.1-1). In certain communities, particularly planktonic, where circulation patterns provide a similar habitat throughout the area, spatial variability was low in comparison to seasonal. The study design therefore focuses on frequent sampling to monitor seasonal trends at only one nea-field and one farfield station. In other communities, particularly benthic, spatial variability has been higher than seasonal. Benthic sampling design has focused on the dominant substrate type in the discharge area, horizontal hard-bottom ledge, with paired nearfield and farfield stations representing the major depth zones. Finfish catches have shown both seasonal and spatial differences. Therefore, these studies make frequent (at least monthly) collections in the area of the discharge as well as farfield areas to the north and south. Because the estuary is an aquatic nursery area and recreationally-important clam flat, baseline collections monitoring seasonal and annual patterns were also made there for operational phase comparison. i Biological variability can be measured on two levels; species and community. A species' abundance, recruitment, size and/or growth j are important for understanding operational impact, if any. For this l l reason, these parameters were monitored for selected species from each community type. Species were chosen for more intensive study based on their commercial or numerical importance, sensitivity to temperature, potential as a nuisance organism, and habitat preference. Overall com- ) 10 l
-y - , e * , , . .
I SOURCES OF VARIABILITY TEMPORAL RIOPERATIONAL DPELATIONAL 5 e e P A ', T f I e A i L e 1 s, yea rs
'. ! !...ll l
\ weets/renths i l l l .*. b; l .
\
LEVELS OF VARIABILITY I 58tC!ts AsstFn ASI [ j t.onoceina nts
! W inants -
multiva-iate heeried classi'it.ation analysis Discriminant func-ion analysis selectee
$DeCiel univeriate Time series analysis ANOVA l l
Figure 2.1.1. Schematic of sources and levels of variability in Seabrook Environmental Studies. Seabrook Baseline Report, 1986. 11 4 e r -mm- ,,r-w- ge vp .m q ,, -- 4v--,--v --.,-n-, - - - - - - , - - - - --
.ww* ---v~
munity structure, e.g., the number and type of species, total abundance and/or the dominance structure, may also be affected by plant operation I in a way not detectable by monitoring single species; therefore, the natural variation in community structure was monitored at regular time intervals, determined by early studies to be suf ficient for this purpose. Appropriate statistical methods must be used in conjunction ; with a well-planned experimental design in order to determine the l l sources and magnitude of variability. Annual and spatial variability in species abundance and size were tested by 2 sing analysis of variance or nonparametric analysis which will provide a means of evaluating the statistical significance of changes in the operational period. Spatial, j seasonal, and annual variations in community structure were assessed j i first with numerical classification and then with discriminant analysis. j Discriminant analysis provides a set of criteria using the baseline col-l 1ections against which operational phase collectiers may be compared. l l Identification of the sources and levels of var!. ability util- j izing the methods discussed above has its ultimate focus on the sources of potential influence from plant operation, and the sensitivity of a community or parameter to that influence (Table 2.1-1). Naturally, a l community or species might bs affected by more than one aspect of the l cooling water system (CWS); however, the focus here is on the aspect of 1 l main concern. In general, intake (pumped) entrainment and 4mpingement 1 would potentially affect mainly plankton communities, including fish j l l eggs and larvae, and pelagic fish. If they occur, thermal effects from i the discharge (e.g. plume entrainment) would most likely affect near-1 l shore surface water quality, phytoplankton, and intertidal and shallow subtidal benthos. Although no effects are anticipated in the estuary from the offshore discharge, fish and soft-shell clam populations have l been monitored in that area to provide a baseline for operational phase comparisons. Bottom-dwelling _rganisms, including macrofauna, macro-l algae, epibenthic crustaceans, and demersal fish, may be influenced by l 12 i 1
)
I l \ l TABLE 2.1-1.
SUMMARY
OF BIOLOGICAL COMMUNITIES AND SPECIES MONITORED ) FOR EACH POTENTIAL IMPACT TYPE. SEABROOK BASELINE l REPORT, 1986. LEVEL MONITORED SELECTED MONITORING SPECIES / AREA IMPACT TYPE SAMPLE TYPE COMMUNITY PARAMETERS l Intake Entrainment Microzooplankton x x Macrozooplankton x x Fish eggs x Fish larvae x x Soft-shell clam larvae x concer crab larvae x Impingement Pelagic fish x x Discharge Thermal Plume Nearshore water i 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 macroalgae x x Bottom fouling community x Demersal fish x x Lobster adults x Cancer crab adults x l Estuary Cumulative Sources Estuarine temperature x Soft-shell clam I spat and adults x Estuarine fish x x l 13 l l l e-- ; e-- - - - -~ - - - - - - ---, - ,e+y, ,,e e-e, --m-- a e----m- *
- 4 --a -Lt 4 4 4 detritus potentially arising from moribund entrained plankton which.is discharged with the cooling water. A previous impact assessment (NAI 1977e) has shown that the balanced indigenous community in the Seabrook study area should not be adversely influenced by the above factors. Results from the biological communities, species and environmental Parameters sampled will be discussed in light of the feature of the CWS which would have the greatest potential for affecting them. l l 14
_ - .~~_ i l l l l 2.2 INTAKE AREA MONITORING 2.2.1 Plankton 2.2.1.1 Community Structure An estimation of.the number and type of plankton species affected by plant operation will depend on 1) the time of year, and 2) the degree of yearly variability. Results from the community analysis give an indication of the number and type of species present (and thus entrainable) at any one point in time. These provide a multivariate "template" against which seasonal assemblages during plant operation may be compared. The selected species analysis enables a more precise estimate of the entrainable density for key species by examining their annual and seasonal variability. Knowledge of the among-year variabil-ity however, can increase confidence in estimates of impact made from entrainment samples taken in a single season and year. All of the planktonic communities had species assemblages that changed with season during the baseline period (Figure 2.2-1). These ) groups were differentiated primarily on the distribution and abundance ! of dominant species; however, the relative abundance or even absence of other species was also a factor. The type of species entrained will depend on the seasonal assemblage present at the time. Historically, macrozooplankton assemblages have been distinct and consistent, showing high predictability from year-to-year. Macrozooplankton assemblages reflected mainly the population dynamics of the dominant copepods with reproductive activities of benthic organisms affecting spring and summer species composition. In the last half of 1986, macrozooplankton assem-blages were similar to previous years with one exception: historically, summer and fall collections have been characterized by high densities of the cladoceran Podon sp., while in 1986, densities of this species were uncharacteristically low. At the same time, fall densities of all life-15
A. MICR0Z00 PLANKTON (No./m )
, I,l.I,i.i.I,Ia I,io i .Ie
.O.
V g U n . U 3 KEY B. MACR 0Z00 PLANKTON (No./1000m ) a l,l.ln } l4 l4 la l,le l lo i SEASONAL GROUP ABUNDANCE w O 10-100 O2o2-2o0o
. t SEASONAL GROUP MORE
, PROMINENT IN 1985/198 1001-10000 3
C. FISH EGGS (No./1000m ) 10.001-100,000 a i , l.la l.l4 lJ la l,Io l le o
. p p .
-*~A
~
> 100.000 V
t
$-1 1 p l DATES OF OCCURREN3 4
3 D. FISH LARVAE (No./1000m ) l
. l,i Ia I i,I Ia I,l l.lo C ,n V A I
O
.h O .
A v l U i c : O : I Figure 2.2-1. Dates of occurrence and mean abundance of seasonal groups formed b numerical classification (1978-1984) of A. microzooplankton (No./m ) and B. macrozooplankton (No./1000m 3 ), and discriminant analysis (1976-1986) of C. fish eggs (No./1000m3), and D. fish larvae (No./1000m3 ) ' collections. Seabrook Baseline Report, 1986. 16
stages of the mysid Neomysis americana were higher than previously recorded. Microzooplankton and planktonic fish eggs had several over-lapping groups in spring and summer, indicative of both some year-to-year changes in community structure as well as a variable "transition period" in the late summer assemblage (Figure 2.2-1). In the last six months of 1986, the microzooplankton community shifted from one domin-ated by copepods (at the beginning of sampling in July), to one domin-ated by bivalve larvae (in fall) to the typical winter tintinnid com-munity. This was a slightly different pattern from previous years. Fish egg collections in 1985 and 1986 were highly similar to previous years in their species composition and density, particularly in spring and summer when cunner and hake eggs were most abundant. In fall and winter, when egg densities were low and more sporadic in their occurrence, species composition differed slightly from the majority of previous years. Two assemblages which historically had been rare occurred more frequently in 1985 and 1986 (Figure 2.2-1). 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 l flounder and seasnail) and summer-fall (mackerel and cunner). Varia-tions in density of the major taxa, especially during transition periods, caused small changes in species composition leading to the forma- I tion of overlapping "subgroups". Seasonal patterns observed in 1985 and 1986 were highly similar to previous years (Figure 2.2-1). The effects of plant operation will also depend on seasonal variations in density. In most months, macrozooplankton densities have historically 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 (through 1984) and planktonic fish egg assemblages (through 1986), on the other hand, had 17
their greatest concentration in the spring and summer, when bivalve larvae and copepod nauplii (microzooplankton), and cunner eggs (fish eggs), were dominant, and group densities were three orders of magnitude higher than in winter (Figure 2.2-1). Similarly, fish larvae were most abundant in late winter, when sand lance predominated, and summer, when Atlantic mackerel and cunner prede.iinated. The level of entrainment for these as semblages will 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 Haine in either nearshore regions or open water. Two groups, bivalve larvae and cunner larvae, have 1ccai 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 in a test mode; no power or heated ; discharge were produced. The entrained fish egg, larvae, and bivalve larvae communities were similar to those collected offshore, although the smaller sample volumes and less-frequent sample collection in the plant produced some expected differences. The top-ranked entrained fish egg and larvae species were similar to those from offshore collections; however, the abundance and total number of taxa were lower, due to the less-intensive sampling effort (Table 2.2-1). The only exception was Atlantic herring larvae, which were occasionally more dense in entrain-ment samples. Entrained bivalve larvae species were similar to those collected of fshore; however, unlike the ichthyoplankton, densities were very similar to those in offshore samples. When samples from the same day were compared, no significant diffa.rences in density were detected. 18
TABLE 2.2-1. COMPARISON OF DENSITIES OF TOP-RANKED FISH EGG, FISH LARVAE, AND BIVALVE LARVAE TAXA COLLECTED OFFSHORE AT STATION P2 AND IN ENTRAINMENT SAMPLES AT SEABROOK STATION FROM JULY 28 THROUGH DECEMBER 30, 1986. SEABROOK BASELINE REPORT, 1986. DENSITY" DOMINANT SPECIES ENTRAINED (E1) 0FFSHORE (P2) Fish eggs" Cunner /yellowtail 260 1428 Rockling/ hake 88 206 Hake 28 985 Windowpane 33 81 Pollock 21 6 Atlantic cod 17 125 Fish larvae" l Atlantic herring 228 196 Pollock 3 3 Cunner <1 6 Bivalve larvae b Hodlotus modtolus 4489 4189 Heteranomia squamula 2633 2831 1 Myttius edults 672 656 i Hya arenaria 40 56 3 a = No./1000 m 3 b = No./m c = Average of monthly averages coreputed to compensate for unequal numbers of samples 19
2.2.1.2 Selected Species Nine species with various lifestages from the pelagic zooplank-ton communities were designated as selected species. The existence of seven to nine years of preoperational data allows an estimation of sea-sonal and annual variability. These species exhibited different degrees of numerical importance; their relative contributions to their respec-tive communities are shown in Figure 2.2-2. The zooplankton selected species (including various life-stages) historically have constituted less than 40% of the overall abundances (Figure 2.2-2). In both the microzooplankton and macrozoo-plankton assemblages, other copepods typically have made a large contribution to overall abundances. In the microzooplankton, unidenti-fled copepod nauplii and copepodites have been extremely abundant. In the macrozooplankton, copepods other than the selected species have historically been dominant over the year; however, the noncopepod selected species have been dominants in certain seasons. All of the zooplankton selected species reached peak abundance in spring and summer, with the exception of Neomys is ama rteana, which has' been most abundant in winter / spring. Seasonal patterns and abundance levels of microzooplankton and macrozooplankton observed in the selected species during the last half of 1986 were similar to those observed from 1978-1984 with one exception: abundance levels of Neomysis amerleana were much higher than previous years. Selected species of fish larvae predominated in every season, constituting 75% of the total abundance overall (Figure 2.2-3). Gene-rally, each of the species was present only for a brief time period that was fairly consistent from year-to-year. Some slight shifts in seasonal peaks occurred in 1985 and 1986 in comparison to previous years. For example, yellowtail flounder in 1985 and cod in 1986 had somewhat abbreviated peak occurrences; in 1986, cod larvae occurred somewhat later, while yellowtail occurred somewhat earlier. 20
MICR0 ZOOPLANKTON SEASONAt V11ARIlllY ANNUAL VARIA81LliY 100 -
~ Furgtenirim hhmi A.
40- etter O ! r.nu furyt-m sp C. ' l 35 - Q1 Iwem Awal< mum sp. A. k Oir W sp. A.
- ,5 - : = :
g , 3 TsewA wsfa* rue sp. C. O 3 piths sp. C. 15 - -
\ ,
Of f ho' era sp. N. , , , 10 , . , W T4*wAwfanun/cala.eue N. , , l_ _ l _ l _ l _ l _ l.-._l _ l _ l _ g - l l 1 J J J 5 0 10 100 1.000 10.000 f camp. F M A M A 3 seasonal peak Annual i. 50 (no /m ) MACR 0 ZOOPLANKTON 100 - --- - ---- -- etier 0 emp e,ptaaempieerwa t . l l
- l 50- ' Catanun fiorvsrchirun A. ,
N - A 0
- 40 -- '
Carvinus penense L. l l n ,' cara u. ri mer hic. . c. l l f 30 -
=
$ 20 -
.\ ca rve sp. t. l l
, . , . _ _ = l l
,0 t 7- .
I J
,_,_,_,_,_,_,_,_,_,_N F M A M .I .I A 5 0 0 0 10 100 1.000 10.000 100,000
- Seasonal peak Annual i. 50 (no/1000n3)
Figure 2.2-2. Percent composition, seasonal peak, and overall mean and standard deviation of microzooplankton and macrozoop?ankton selected species (A= adult, C= cope-podite, L= larvae, N=naupilus) 1978-1984. Seabrook Baseline Report, 1986.
l BIVALVE LARVAE SEASONAL VARIABILITY AMONG-YEAR VARIABILITY
, 100 - l 2
i th 75 - # v E 50 - , #va arenarfa mmme l : l u E 25 - , nytilus edulis m l : : l l l l l l l l l l l l l l : l l J F M A M J J A S 0 N D 0 10 100 1000 10.000 SEASONAL PEAK ANNUAL i. 5.0. (No./m ) FISH LARVAE SEASONAL VARIABILITY AMONG-VEAR VARIABILITY gon _ other um pollock amme
- l 80 - 4
' I m - sand lance ; ; ' ~ mummmmum W. flounder l : l 60 -
w
$ czr:x$ - Cd " l ; l 5 -
E rackerel - - - a 40 -
/
p yellowtall l : l ,
,f l
" cunner um l :
20 -
/
hake l : a l h - axxxxzs g erring l ; s l i l e I l 'e i l l l i l i 's i cb. J F M A M J J A 5 0 N O O 10 100 1000 10.000 3 SEASONAL PEAK ANNUAL 1. S.D. (No./100(n ) Figure 2.2-3. Percent composition, seasonal peak, and overall seasonal mean and standard da.viation of bivalve larvae (1978-1986) and fish larvae (1976-1986) selected species. Seabrook Baseline Report, 1986. 22
1 Most of plankton selected species showed year-to-year differ-ences in abundance. For the microzooplankton and macrozooplankton, these were low-to-moderate, as reflected in the historically-calculated variance estimates (Figure 2.2-2) and percent change detectable values (NAI 1985b). Ichthyoplankton egg and larval annual densities were more variable, reflecting spawning success of the adult fish (Figure 2.2-3). Despite these fluctuations only three of the nine selected fish larvae species showed significant differences among years. These analyses indicate the species composition of entrained organisms may be fairly consistent over the years, although the actual number of organisms entrained will be more variable. Bivalve larvae studies were carried out in the intake area to address questions related to the potential reduction in Mya arenaria i larvae due to entrainment. Local current regimes and length of time spent in the plankton imply that nearshore Mya larvae populations origi-nate from spawning adult populations in local and more southern estuaries, e.g., Hampton-Seabrook, Merrimack River and Essex, Massachusetts (NAI i 1982b). Spawning adults have been observed in Hampton Harbor and Plum Island Sound (a farfield site) typically from June through September, but as early as April and as late as the end of October in some years. Although larvae were observed throughout the spawning period, peak densities usually did not occur until August or September (Figure 2.2-3); secondary peaks also occurred in May or June in some years. Therefore, the magnitude of entrainment will depend on the time of year as well as the overall annual abundance in that particular year. High annual variability (Figure 2.2-3) was indicative of the year-to-year variations in the occurrence of hva larvae as well as its patchy distri-bution. Initial entrainment samples collected during the period of peak Mya larvae densities were similar in magnitude to those collected off-shore (Table 2.2-1). However, because larval densities in the nearshore area have shown no correlation with spat settlement densities (Section 2.3.1.3), entrainment estimates cannot be used to determine the impact of plant operation on the Hampton Harbor adult clam population. 23
2.2.1.3 Spatial Variability An optimal impact assessment design (Green 1979) has been used for intake monitoring where comparisons of nearfield and farfield samples in both the preoperational and operational periods will be made. A determination of the similarity of nearfield and farfield plankton com-munities must be made in order to ascertain the suitability of the far-field station as a "control" area. Previous analyses of the microzoo-plankton, macrozooplankton, and fish eg3 and larval communities showed that differences among seasons and even dates were greater than those between nearfield and farfield stations (Table 2.2-2). Examination of data collected in 1985 (when available) and 1986 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, hypoplanktonic species, i.e. those which dwell just above bottom, including peracarids, Pontogenela inermis, Neomysis ame r ic ana, and Diastylis sp., were more abundant at the nearfield intake station, probably because of the increased complexity of the substrate, cobble and sands, in comparison to the more-uniform sandy bottom at the farfield station (Table 2.2-2). Spatial differences were also observed historically between intake and discharge (P5) stations for some of the hypoplankters. In addition, rockling/ hake eggs and Atlantic mackerel were more abundant at the nearfield station. Thus, impact analysis for some selected species will have to focus on temporal comparison within stations. 2.2.2 Pelagic Fish 2.2.2.1 Temporal By studying the six dominant pelagic species collected in gill nets, which together make up over 90% of the population (Figure 2.2-4), the effects of plant operations on fish populations in the study area 24
TABLE 2.2-2.
SUMMARY
OF NEARFIELD/FARFIELD (P2 VS. P7) SPATIAL DIFFERENCES IN PLANKTON COMMUNITIES AND SELECTED SPECIES. SEABROOK BASELINE REPORT, 1986. COMMUNITY DIFFERENCE BEWEEN P2 AND P7 Microzooplankton Community None Selected species None Bivalve Larvae Community None Selected species None Macrozooplankton Community None Selected species hypoplankters (Pontogeneta inermis, Neomys is ame ricana, Diastylls sp.) P2>P7 (1982-84;1986) Ichthyoplankton Egg Community None Selected species Rockling/ hake P2>P7 Ichthyoplankton Larvae Community None Selected species Atlantic mackerel P2>P7 25
1986 1985-
/ '
/ .
1 1984- 4 - 1983- - 1982 ATLANTIC HERRING _ OTHER 1981- BLUESACK HERR!NG
~
e 1980- ATLANT!c MACKratt - 5 1979- MENHADEN . 1978-1977- 3ggggycl - 1VHIT!.NG 1976 , , , . : . . . 20 40 60 80 1000 8 16 24 30 DEC B. i NOV. _
~
ATLANTIC Ma.CKEREl. SEP. etutBACK HEkRlt;G _ AUG- - 5 JUL- 9.ifANif@ltifh , qg OTHER , g s r JUtt- gg ggiogg - POLLOCK i:AY- - APR- - ATLANTIC HERRING / _ l FEB- - JAN , , , , 20 40 60 80 100 0 $ l'6 2'4 32 PERCEf1T COMPOSITION CPUE Figure 2.2-4 Percent composition of six dominant species collected by gill net and total catch per unit effort A. by year and B. by month at combined stations G1, G2, and G3 from 1976-1986. Seabrook Baseline Report, 1986. 26
i I should be visible. The distribution of pelagic fish varied seasonally; two main seasonal groups of species, summer and winter, were identified from numerical classification results (NAI 1982c). From September to April, Atlantic herring constituted from 60% to over 90% 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 2.2-4). Pollock (predominantly age-two l fish (NAI 1985b)) is a local resident which also made up a greater proportion of the pelagic nearshore community during summer. In every year, Atlantic herring was the overall dominant pelagic fish in the area; however, it exhibited large annual abundance differences that were reflected in the annual percent composition (Figure 2.2-4). When catch per unit effort (CPUE) peaked in the study area in 1980, Atlantic herring composed 80% of the total catch. From 1984 through 1986, when total catches had reached their lowest point since the inception of the study, Atlantic herring constituted only 25-33% of the total catch (Figure 2.2-4). The slight upturn in total catch in 1986 was caused by a slight increase in Atlantic herring catches. Atlantic herring are known to show high variability in catches spatially as well as seasonally and annually (Bigelow and Schroeder 1953). Most of the fish collected off Hampton-Seabrook were yearlings, particularly in the spring (NAI 1985b). Little is known ab3ut the habits of yearling herring, except that they seek out the warm waters of embayments in spring (Bigelow and Schroeder 1953). t Inconsistency in seasonal patterns adds to the overall variabil-ity in pelagic fish distribution. Each of the selected species appeared for a short but distinct period of time (Figures 2.2-4, 5). However, these seasonal fluctuations were variable among years, compounding the high annual variability, as evidented by high coefficients of variation j (approximately 150-250% for the three selected species). This was parti:ularly important for Atlantic herring, whose abundance was the single biggest determinant of overall catch levels (Figures 2.2-4, 5). l l 1 27 l l
l l l l l PELAGIC FISH SEASONAL VARIAB.LITY AMONG-YEAR VARIABILITY , i g 100 - other E / 75 - - pollock M v E 50 - e \
$ Atlantic mackerel -
H c 25 - Atlantic herring ,
/ - . : .
l . l l l l , l l ; l l l l l l 1 J F M A M J J A $ 0 N O O 10 20 30 COMP. SEASONAL PEAK ANNUAL x.5.D. CPUE DEMERSAL FISH SEASONAL VARIABILITY AMONG-YEAR VARIABILITY 100 - other
! rainbow Smelt -. l :
b BO - winter flounder (no seasonal peak)
/ : ,
v 60 - E r p , - Atlantic cod -
- l Mw 40 -
hale b : l 20 - c - yellowtail flounder == : l k 8 I I I e i A t i I t_ j I 1 i
) kM M bhk5 hN b b 10 20 3O SEASONAL PEAK ANNUAL I, 5.0.
CPUE I Figure 2.2-5. Percent composition, seasonal peak, annual mean CPUE and standard I deviation of dominant pelagic and demersal fish from 1976-1986, i seabrook Baseline Report, 1986. l l 28 i i
The number of individuals potentially affected by plant operation could vary substantially between seasons and years. That is, it is known when species occurred and what the relative seasonal patterns of abundance were, but predicting abundances with high statistical precision would be difficult. 2.2.2.2 Spatial Areal differene.es will be less important than teeporal dif-ferences in evaluating potential plant effects. The pelagic fish moved throughout the study area and were not associated with any one habitat. Relative abundances of the five most-abundant taxa were quite similar among stations, although catches were approximately 25% lower at the southern station G1 (Figure 2.2-6). Differences in the vertical distri-bution of these species may be important, however, because the intake structures are located at mid-depth, 9m below MLV. Only one species, Atlantic menhaden, was slightly more abundant at the intake (mid-water) depth during the months sampled; however, this species was not among the most abundant pelagic fish in the study area (Table 2.2-3). Two taxa, Atlantic whiting and pollock, were most abundant near the bottom, while Atlantic herring, mackerel and blueback herring were most abundant on the surface (Table 2.2-3). These species may be less vulnerable to intake effects. In 1986, for the first time since 1980 Atlantic mackerel had highest catches in mid-depth nets, suggesting that they could occasionally be more prone to intake effects. Thesa results indi-cated that the most abundant and frequentia-occurring pelagic species did not show a preference for mid-depth distribution, verifying earlier results and rationale for mid-water placement of the intakes (NAI 1975a). 29
l l
>f rd G3 (MEAN CPUE=11.2)
EE .d% x % ... ....
>9 'Y'
- ad a d (12.0%) (9.0%) !
;;\ j $;g,y \,. [j.'y ;) '~~"""
[;@ -- (5 ). (5.0%) :
. ,. .f: y,
, .s ....,,s.. ,.
- 2' .,'
. . .. ..g. . . . . ( ) ,;, 9,,f",
SCALE (6. 0%) /-:d'. .
" \
' j '
;, g g .
- ..,;>;,s,. /
$y@?F ;,"-
w
.W,. / p. . .hi .
. . ,,i
/c (10.0%) gt
. .g L ia*
L (58.0%)
. .y v.
- l.r6>rj33 y -s o c ,,...... . .. .
SEABROC GTA7my ,p ' -.! .**> r....... s G2 (MEAN CPUE=12.2) 11"U" '(.' lay i (9.0%) (6.0%)
~,A. 1 e.
- 5.0%
\ j (4.0%) .'k m....g g -@
\m :m. n .m" (6.0%) 1 -
w. G1 (MEAN CPUE=8.9) (13.0%) (8.0%) ( 6. 0*. ) ( 70. 0'. ) (5.0%) GILL NET (G1, 2,3) (6.0%)
- ATLANTIC HERRING
f'[~ K 'lF' ;
ATLANTIC WHITING l i BLUEBACK HERRING
./ ATLANTIC MACKEREL (62.00 yi POLLOCK OTHERS Figure 2.2-6. Percent composition of five most abiindant fish collected in Gill Nets (all dates, surface and bottom combined) from 1976 through l 1986. Seabrook Baseline Report, 1986. '
30 1 1
a TABLE 1.2-3. CATCH PER UNIT EFFORT BY DEPTH FOR THE DOMINANT GILL NET SPECIES OVER ALL STATIONS AND DATES WHEN SURFACE, MID AND BOTTOM NETS VERE SAMPLED, 1980 THROUGH 1986. SEABRC0K BASELINE REPORT, 1986. DEPTH SURFACE MID BOTTOM SPECIES CPUE CPUE CPUE Atlantic herring 7.0 3.7 2.3 Atlantic whiting 0.2 0.6 0.6 Atlantic mackerel 0.7 0.5 0.4 Pollock 0.1 0.1 1.2 Alewife <0.1 <0.1 <0.1 Blueback herring 1.0 0.4 0.6 Atlantic menhaden 0.7 0.9 0.2 Rainbow smelt <0.1 <0.1 0.1 a Number per one 24 hour set of one net (surface, mid or bottom). l l 1 31 , I l
l l 2.3 DISCHARGE AREA MONITORING l 2.3.1 Plume Studies 2.3.1.1 Discherme Plume Zone I Because the disch1rge plume's largest exposure will be to sur-f ace and near-surface waters, the primary focus in this section will be l on parameters or organisms in this part of the water column, namely phytoplankton, lobster larvae, and nearfield water quality parameters. Other organisms, such as pelagic fish and ichthyoplankton will, of course, have some exposure to the discharge plume, but it is assumed that entrainment and/or impingement are the more important issues for these organisms. The water quality parameters measured showed distinct seasonal I patterns that were important in driving biological cycles. Surface and bottom tumperatures reached their lowest points from January through March, then steadily increased from April to August; temperatures were generall:r highest from August to October before beginning their fall l 1 decline ' Figures 2.3-1, 2). Surface temperatures had a more exaggerated i seasonal cycle in comparison to bottom temperatures, with higher spring and summor temperatures. Annual mean temperatures in 1985 &nd, to a-lesser eatent in 1986, (collected on a semimonthly basis) were higher j than previous years, reflecting high summer temperatures in 1985 and a l warm winter and spring in 1986. Continuously-monitored temperatures in the lattee half of 1986 closely followed seasonal patterns from previous years (Fig ure 2.3-2). l l
.iurface 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, 2). In 1985 and 1986, seasonal patterns were similar to previous years, but most monthly values were lower than the average. Surface salinity values were highest in winter and lowest l
l l i ! 32 1
I PLANKTON AMONG. YEAR VARIABILITY SEASONAL PEAK N/A PSP emme lobster larvae l _ a enemuMD Skeletonema costatum
' l l l l l l l l l l l l .' l 100 1000 10,000 100.000 J F M A M J J A S 0 N D 10 MONTH DENSITY (No./1000n OR CELL 5/ LITER)
WATER QUALITY SEASONAL MAXIMUM & MINIMUM nitrate ammanuens X X X X nitrite X X X X - total phosphorus X X -
= MAXIMUM VALUES orthophoschate "
"
- X X X = MINIM.IM VALUES bottom dissolved oxygen X X X surface dissolved oxyeen ;
X X*X X , bottom salinity amum X X X emme surface salinity a= X X X - bottom temperature X X X I surface te+eerature X X X
! l l
$ I ! i 5 I i I
J F M A M J J A S 0 N D 1 l MONTH Figure 2.3-1. Summary of maximum and minimum seasonal values for selected water quality and plankton parameters and overall mean and standard deviation for Skeletonema costatum (cells / liter) and lobster larvae (No./1000m3). Seabrook Baseline Report, 1986 33 1 1 I
. .: 80iiON . Att vtARs* MEAm.197s-19e4
*f SURFACE .. j
"; 1[WERATURE , ; TE WERATURE I}: /h* [j
. w-.s _: .
h!;# : "} i-!
- i i
\.
N.
!-i
- :i !/;/:. !
M -
's .
- N:
i/- :
.i . .! .
. . .i . i . .
i.i N i p i :
- i. i N : . .
.., v... us, .w, n, .
SURFACE D.O. *n55 o'an es a
.! SURFACE SALINITY !
.-s- . nas w
s-
. .. . ;! . . . /. [ - au n=s waa. m.-ee l . . :. . :. .
- :g.- :. : .
.. - v. -.. . .
. .. j %. : :
,+
- . -j. ,
.1
.7 . ' ,,
....f
~. .
, _./__ : -
; .!; .j . %,. :
l .
, .eg x,N; .
- - .1 .
'm ..' :. , : .
l- ::
- l '
, 1 . .
l
.i. y../N.r .
a.. l
- i : .
l . ..; Figure 2.3-2. Monthly mean surface and bottom temperature-(*C)', surface salinity (ppt), and surface dissolved oxygen (mg/1) at station P2 for each year and over all years. (1978-1986, except temperature,'1978-1984 and August-December, 1986). Seabrook Baseline Report, 1986.
in spring, a result of increased runoff. In 1985, salinities were higher than the average in the first half of the year (Figure 2.3-2) as a result of low precipitation levels (see Section 3.3.1). Nitrogen and phosphorus nutrients had more erratic cycles than temperature, but generally had lowest levels in summer and highest in fall and winter (Figure 2.3-1). Values in the latter half of 1986 were similar except for August, when levels of all nutrients were the highest ever recorded for that month. The predictability of seasonal patterns and low year-to-year variability of most of the water quality parameters enhanced their suit-ability for impact assessment. Furthermore, they will provide informa-tion which can assist in separating natural biological variability from impact. Historically the phytoplankton community has shown the most l seasonal and annual variability of any species assemblage. Seasonal assemblages have changed rapidly and frequently, diminishing the suit-ability of the community for short-term impact assessment (NAI 1985b). Some elements of the phytoplankton community were relatively stable and predictable. For example, total phytoplankton abundance was generally similar among years, with a predictable seasonal cycle that was closely tracked by biomass (chlorophyll c). Increases in irradiance typically initiated the spring bloom, and although the species composition varied ; from year-to-year, centric diatoms typically were among the first to j appear. Densities usually diminished when nitrogen-nutrients declined and the thermocline developed. Thermal stratification prevents the replenishment of nutrients from deeper waters thereby limiting growth of spring dominants. 1986 was unusual in that there was an uncharacteris-tic July peak caused by bluegreens and Leptocylindricus. Phytoplankton assemblages from 1978 to 1980 were similar, based on the predominance of Skeletonoma costatum, Rhttosolento delicatulo, and Phaeocyttis pouchetti, 35
l while from 1981 through 1984, only Skele tonema co statum and Chae tece ro s spp. were consistent dominants. In the latter half of 1986, Skeleton,ma continued to predominate, along with the above-mentioned bluegreens. 1 No spatial differences were observed in the phytoplankton com-
]
munity either between intake (P2) and farfield (P7) areas (1982-1984;- July-Dec., 1986) or between intake (P2) and discharge (PS) areas (July-December, 1986). Skeletonema costatum was chosen as the selected phytoplankton species because of its consistent predominance. Generally, there was a small spring peak and a major peak in late summer or fall (Figure 2.3-1). Despite highly-variable peak abundances, no significant dif-ferences were detected among years. Fall densities in 1986 were among the highest obscrved since 1978, but still within the range of previous years. Furthermore, intake and discharge dens.ities were statistically , similar. Simultaneous nearfield/farfield comparisons of total phyto-plankton abundances and Skeletonema costetum ray be the most consistent parameters for monitoring primary producers in the discharge plume area. Paralytic shellfish poisoning levels in nyt tlus edults, as measured by the State of New Hampshire and Massachusetts Department of Public Health, has exceeded maximum levels allowable for human consumption every year since 1972, usually for a period of 1-7 week. In 1972, toxic levels were present in Hampton Harbor for a period of 16 weeks. Although Hampton Harbor flats have been closed each summer since 1976 to soft-shell clam diggers, high PSP levels caused the closure of the harbor to all bivalve shellfish digging for several weeks each summer. Peak values occurred in May or June (Figure 2.3-1) coinciding in Hampton Harbor and the farfield area Essex, MA. The maximum value { recorded since 1972 was 8398 MgPSP/100g meat. Peak levels in 1985 were moderate while 1986 peak levels were the highest since 1981. Of the shellffsh in the area with planktonic lifestages (Cancer crab, lobster and soft-shell clam larvae), only lobster larvae 36
Stages I-IV have strictly a surface orientation, typically found in the top few centimeters of water. The seasonality and variability of Cancer sp. larvae and Mya arenarla larvae were discussed in the intake area monitoring section. Successful recruitment of lobster larvae is the biggest factor in the determining the level of adult lobster catches (Harding et al. 1983). Lobster larvae collected off Hampton-Seabrook actually originate from warm waters in the Gulf of Maine and Georges Bank (Harding et al.1983) and are driven into the area by a combination of winds and nontidal currents (Grabe e t al.1983). Temperatures in the study area are not warm enough to allow planktonic development (Harding et al. 1983), reinforcipp 'a fact that this area is probably not important in the p.sdus 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 2.3-1). In 1985 and 1986, 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 under 3 per 1000 cubic meters (Figure 2.3-1). In 1985 and 1986 densities were low in comparison to previous years. Stage I and IV larvae have predominated, and stage II and III were extremely rare. Densities at the farfield station (P7) were consistently higher than at the nearfield station from 1982-1986. Discharge area (PS) densities in the last half of 1986 were intermediate between the nearfield and farfield areas. Subsurface (-3m) "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 substrates. 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 development of the fouling community. The amount of biomass, density, and species richness showed 37
STATION 4 STATION 19 l isp:awas!6i itjj;{stal.tr lyit i=isiwjftis:* j<isi 1 I i
. 1984 m , len6 M l 198. .. - ... M i
19 6.s
* - * * = = 6 -
; 1983 - C
- 1983 - *6 l d ' 9 ,; ~.- E 199: *-= MC 1 l l 1986 =
- h 1986 h - F
- 1984 *--
~
1984 }2 3 1983 - -
- 1983
}2 I 1982 - 5 198. l
; 1986 == =-- ; 1986 --==*====**=
w u i 1984 ===. N 1
- 1984 * * - = = = =C
% i a
1983 == N g e 1983 --* N m k 1982 2 - k 1982 {
"""2 l
1986 -. j 1986 *= { 198 . = = = - = = = { 194. == = == 1,n a 1,n a q
} 198: -
} 1,8: - - -_ . . . -
l
& 1986 - 2 1986
*
- I 196. . 196. -[-
2 E 1993 M l 4 E 1983 - [ a 19:: - g 198: - --C
~ *- 1 g 1986 _ g 1986 _
194 - = .[ 1984 -O -
- un - _m -
19n - .- 198* N 198: C. _ ~ l I - l g 1986 - g 1 88
. 1984 -.=
l *
. 1984
- -l l 1983 - [---=
l -
! 1983 M [-- I l 198: - - 2 198:
l l g 1916 - g 1916 -= 3 1984 .- .. I 198.
-I 19n -
t .9n .... E 198
- C - = f 198 -
I g 1986 1986 . .. 1986 == ==
]
- 198a I *
- l
- 1983 s 1983 i 198: -- i 198: I l
,_ cresent 1 25 % frecuen:y 7 26-50 C 51 75 m 7e.ioo N.B.1986 s8mples not collected prior to July Figure 2.3-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 1. and 19. Seabrook baseline Report, 1986.
38
patterns that were highly consistent from year-to-year and between nearfield and farfield areas, reflecting the increase in settling activity in summer and fall. The individual sacroinvertebrate taxa also l had a predictable seasonal pattern. Only a few showed her.vy recruitment before June (Balanus sp. In April and #f atella sp. in early summer). In the latter half nf 1986, small differences were noted in the densities of some of the key species (see Section 3.3.4) but overall patterns tiere similar to previous years. Surface panels should 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 Another area outside of the immediate surface plume area that is being monitored for potential plume effects is the Sunk Rocks. Intertidal (HSL and MLW) and shallow subtidal (-4.6m) stations which are representative of the area were monitored on the Outer Sunk Rocks (nearfield) and at Rye Ledge (farfield). Benthic algae and macro-invertebrate collections taken annually (August) at Stations 1HLW and SHLW (intertidal) and Stations 17 and 35 (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 sta-tion was grouped (by discriminant analysis) with the majority of those collected in other years at the same station (Figure 2.3-4). In 1985 and 1986, macrofaunci and macroalgal assemblages were similar to those in previous years with the exception of one intertidal replicate algae sample, which had very low biomass levels (Figure 2.3-4). Colonial macrofaunal assemblages were somewhat less predictable froe year-to-year (NAI 1985b). Intertidal colonial assemblages were distinct in their specias composition, but those from shallow subtidal areas in most years were similar to those from mid-depth areas. In several years,*assem- , blages of colonial macrofaunal species were unique and unrelated to any l other assemblages, 1 j I 39
l A. MACR 0 ALGAE smioH mi.,u .. .n. . 4...,in . .... in ..., ..., 88 sutw 0000O D D it gCOOOO as 00000 to 000000 D Dp ai ggOOOOO to ggoOOOO is D D 0000000 pOOOOOO p 4 34 0000000 D YE AR-TO-YE AR V A Al Astlif Y B. NONCOLONIAL MACROFAUNA
- T ATION bi.riW al th. hew .WJ J.pih 0000 rock 800090099 f.re tutw ggOOOOO sutw oocco 37 00000 as 00000 to 99999 0 35 gOOOOOO O 3, 0000000 o is 00 00 0000 4 0000000 0 34 000 O 00 O YE AR=TO=YE AR Y ARI AstLITY KEY: 00 = ALL OR SOME SAMPLES FROM A GIVEN YEAR CLASSIFIED CONSISTENTLY WITH BASEllNE GROUPS D = SOME SAMPLES FROM A GIVEN YEAR NOT CLASSIFIED CONSISTENTLY WITH BASELINE GROUPS 9 = SAMPLES CLASS!FIED OUTSIDE DEPTH GROUP APPROPRIATE FOR STATION
= 1 YEAR'S COLLECTIONS I CLE Figure 2.3-4 Year-to-year variations in community structure as shown by discriminant analysis of August collections from 1978-1986 of A. algae and B. non-colonial macrofauna. Seabrook Baseline Report, 1986.
40
Fourteen benthic species were selected for more intensive moni-toring because of their trophic position, abundance and commercial or recreational value (Table 2.3-1). Parameters monitored included abund-ance (all taxa), size (fauna only), and reproduction (epibenthic crusta-ce ans) . All life stages of the commercially-important species were studied. Some of these taxa were monitored in the Sunk Rocks . area while others were examined as part of the discharge or estuarine studies. Algal selected species had highly consistent biomass or abund-l ance levels among years, with differences between nearfield and farfield stations observed in the shallow subtidal but not the intertidal. The algal dominant Chondrus crispus had low annual variability, with no significant differences in biomass among years from 1982-1986 in the intertidal zone and 1978-86 in the shallow subtidal zone (Table 2.3-2). Intertidal biomass values of Chondrus were similar between nearfield and farfield areas, but spatial differences were detected in the shallow subtidal zone (Figure 2.3-5 Table 2.3-2). Densities of the dominant kelp, laminoria saccherina showed no differences among years or between nearfield/farfield stations in the shallow subtidal (Table 2.3-2). j l Spatial heterogeneity and variations in recruitment success ! caused a high degree of variability in abundance of macrofaunal taxa (Figure 2.3-5). Significant differences in annual abundance were found j among years for most of the taxa, and nearfield and farfield stations were almost always significantly different (Table 2.3-2). For these j species, impact assessment will be most effective when the preopera-tional period is compared to the operational period within a given sta-tion. Some differences in the historically-observed trends were noted j in 1985 and 1986. Ampf thee rubricato, once one of the intertidal dominants, continued its steady decline in abundance first noticed in 1982; in 1986, no A. rubricata were collected at Station SMLW, and few were collected at Station 1MLW. Intertidal Mytilidae abundances in 1986 l were the highest observed except for 1982 at Station 1MLW, whereas 1985 abundances were the lowest observed except for 1982 at Station SMLW. In l l 41 1
._. __ _ -~ _ _
TABLE 2.3-1. SELECTED BEhTHIC SPECIES AND RATIONALE FOR SELECTION. SEABROOK BASELINE REPORT, 1986. SPECIES (COMMON NAME) LIFESTAGE RATIONALE Macroalaae Laminaria saccharina A Habitat (canopy)-forming primary (kelp) producer Chondrus crispus A Habitat (understory)-forming l (Irish moss) primary producer; sporelings may be heat sensitive Benthic Invertebrates Anc i the e avbricata JA Intertidal / shallow subtidal (amphipod) community dominant Jassa falcata J.A Intertidal / shallow subtidal (amphipod) community dominant Pontogene,a ine rmi J,A Subtidal, ubiquitous community (amphipod) dominant l Nucella lapillus JA A major intertidal predator of ? (dog welh) Nytilus edulis Asteriidas J Predator, commun'*y dominant (starfish) Strongylocentrotus 3,A droebrachtensis Potentially destructive (sea urchin) herbivore l 1 l pominant eivalves l Mytilus edults L,S.A Habitat former; spat may be heat I (blue mussel) sensitive Mya arenario L S.A Recreational estuarine species; (soft-shell clam) Larvas entrainable l l Epibenthic Crustaceans Carefnus meenas LA A major predator of soft-shell (green crab) clam spat Cancer borealis L,J.A Important predator an.1 prey l (Jonah crab) Concer irroratus L,J,A Important predator and prey l (rock crab) l Nomarus americanus L,J A Commercial species; Larvae plume (American lobster) entrainable "A = adult; J = Juvenile; L = Larvae; S = Spat l 42 l l
TABLE 2.3-2.
SUMMARY
OF SIMILARITIES" IN ABUNDANCE, BI0HASS, FREQUENCY, OR LENGTH AMCNG YEARS AND BEWEEN STATIONS FOR SELECTED MACROFAUNAL AND MACROALGAL SPECIES AT INI'ERTIDAL AND - SHALLOW SUBTIDAL DEPTHS. YEARS SIMILAR DISSIMILAR S Nuce!!a lapt!!us (L) Amp tthor rubricata (L) I Jossa falcata (shallow sub- Mytilidae (shallow subtidal, M tidal, panels)(L) panels)(A) S I Mytilidae (MLW, shallow sub- Mytilidae (panels)(L) T L tidal)(L) Jassa faleota (panels)(A) A A Chondrus crispus (MLV)(B) T R Laminaria sacchartna (A) I O D N I S S S Jassa falcata (shallow sub- Amp f thee rubricata (A) I tidal)(A) Nucella lapillus (A) M Asteriidae (L) Asteriidae (A) I Chonde:s ertspus (B)(shallow Mytilidae (MLW)(A) ' L subtidal) A R
"Results from 2-way ANOVAs or Wilcoxon's summed ranks tests l (A) = abundance '
(L) = length (B) = biomass l 43
i 4 SHALLOW SUBTIDAL Other [ Mytilidae l
- l 75 - p.__________________________.o._.4 5
Aste*iidae E 50 - l 0 l ,
; s________________3 0
g Jassa falcata l 0 j
- p_ __ _ _ ___ _ _ _ _ _ _ _ _ _ _.o..a 0 , : l l l l I 100.000 O 10 100 1000 10.000 COMP.
2 DENSITY (No./m ) l INTERTIDAL Other 100 ~ Nucetta lapillus l . 75 - p _ -o. .l E Mytilidae 8 b 50 - l 0 l v g 6- - - o- -i u ) Aerittee rubricata l 0 l ) p._________o.__., 0 l l l l l l l 0 100 1000 10,000 100.000 CN. 10 f 2 i OEN$1TY(No./m) l KEY
- : i AND S.O., NEARFIELD F- --o- - -i FARFIELD 2
Figure 2.3-5. Overall mean (No./m2 or gm/m ), standard deviation, and percent composition of selected benthic macrofaunal and macroalgal species collected triannually at Nearfield and Farfield intertidal (1EW, SEW) and subtidal (17, 35) Stations from 1978 (Nearfield) or 1982 (Farfield) through 1986. Seabrook Baseline Report, 1986, 44
i Al.GAE taminaria saccharina(*%) 5 (t/m2)
> - -4= -4 i
Chondrus crispus (= %) (gel /m2) F--o-i chondrus crispus (MLW) W (ges/m2) F-o-4 l l l 0 10 100 1000 , L 2 810t'A55, (gm/m2) OR NtNBER (m ) 1 N i 1 i l Figure 2.3-5. (Continued) 45 l J
the shallow subtidal, mytilid abundances were relatively high in 1986 while 1985 abundances were the lowest observed. Abundances of other 1 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. Only Ampfthee rubricata showed a difference in length in 1985 in comparison to pre-vious years. No young-of-the-year Ampithee were collected in 1985 or 1986 (NAI 1986, 1987). 2.3.1.3 Estuarine Zone Environmental studies in Hampton Harbor estuary include monitoring physical parameters (temperature and salinity), fish populations, benthic macrofauna, and juvenile and adult soft-shell clams (Mya arenaria). One of the main environmental issues in the l Hampton-Seabrook estuary related to plant operatien is whether the offshore intake and discharge will impact the adult clam population in Hampton Harbor. The probability of impact from the most-likely source, entrainment of Mya larvae, is small (NAI 19778); this is discussed in Section 2.2.2. Natural variability of juvenile and adult Mya arenaria will be discussed in this section. l Temperature and salinity, monitored in Hampton Harbor and f Brown's River since 1978, provide valuable information for interpreting I biological phenomena. Maximum temperatures usually occurred in August, 1 I with minima in January or February (Figure 2.3-6); 1985 and 1986 were no exceptions to this pattern. Salinity levels had a less distinct l seasonal cycle than temperatures, but were usually lowest in spring, coincident with increased runoff. In Brown's River, average annual salinity values remained high for a three-year period from 1980-1982, l coinciding with low precipitation and highest discharge volumes from the I settling basin. This was the period when the maximum dewatering of the 46
2 1 SALINITY l
. . . . 8
. / ; / :. f
- i. .
.N
.i t ' ' '
w .
, K.y! . .
t u . } . . I r
; w m ms .a w a m .n en = nc ;
an
- 1. 6. ET . = 1.A$7 O! GIT OF j SA,9LE YEAA* ,
T! TEMPERATURE , . l
, - = ALL YEAR'S FE AN
. l/.
l , i. . i
.e
- u . .
- i. . . ;
. i ,
l i l . . . i . l .! . 4 3 i a
!./'
e i 1 e i _ .. w m = .a .. m = .n e
== .
Figure 2.3-6. Mean monthly salinity (ppt) and temperature ('C) in j Hampton Harbor at high tide from 1978-1986. Seabrook i Baseline Report. 1986, i i 1 1 47 1 4 l
l l l l l l l i l cooling tunnels took place, and the salinit_v of the settling pond's i discharge water was relatively high. Salinity levels dropped, with fewer fluctuations, from 1983-1986, when discharge volumes decreased and
- precipitation returned to pre-1980 levels. Hampton Harbor salinities, l which were not as susceptible to these influences because of the influx !
l_ of a large volume of offshore waters,-showed higher salinity and lower l l year-to-year variability than Brawn's River. The benthic macrofaunal community in M11'1 Creek (Station 9)- and Brown's River (Station 3) was typical of New England estuaries. The species composition was also consistent with that from other estuaries on the East Coast (McCall 1977; Watling 1975; Santos and Simon 1980; Whitlatch 1977). Surface and subsurface deposit feeders predominated, including opportunistic polychaetes such as Streblesplo benedtett and Capitella capitata, with suspension feeders and omnivores forming an important component (NAI 198Sb). The most numerous species inhabiting ! estuaries are those which are resistant and resilient to the natural changes in the physical environment, such as fluctuating temperature, i salinity, dissolved oxygen, and sediment grain size. In Mill Creek and Brown's River, the biological parameters measured were highly variable seasonally and annually which is typical of this physically heterogeneous habitat; total density, numbers of taxa, and all of the dominant species tested showed significant differences among years and between stations. Some of this variability was related to changes in salinity. The combination of lower precipita-tion and higher levels of discharge from the settling basin from 1980 to 1982 apparently caused higher and less-variable salinities in Brown's River. At the same time, total abundance and number of taxa increased, along with densities of Streblosple benedict o and Capitella capitata at that site (Figure 2.3-7). Higher salinity levels probably enhanced :he habitat for more stenohaline species, and at the same time, opportunistic j i polychaetes invaded the changing habitat. Following an increase in j l l l 48 l j
10 -
# - 25 9- 1 8- / N
< ad 7- ,x \ - 23 g / ' 3 / / b t' / \ s' y r
\
\ ,
o
$ 5- \/ - 21 $
$ x i 3
4- %
+
1 G
$ 3-x
[e - 19 2-1- - 17 0 i i , , , , , , i 1978 79 80 81 82 83 84 85 86 YEAR KEY x x = SALINITY
- = TOTAL DENSITY o- - - - - - -o = NUMBER OF TAXA
\
Figure 2.3-7. Annual mean density (No./m ),and total number of taxa (No./ 5/16m') for Hampton Harbor and Brown's River from 1978-85 and 1986, and average annual salinity (ppt) for Brown's River at low tide f rom 1980-1986. Seabrook Baseline Report, 1986. 1 49 l
n 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. , f Important estuarine fish include both diadromous species as well as residents. Three anadromous fish pass into the estuary: rain-bow smelt in wintor and alewives and blueback herring ("river herring") : in spring, travelling to upper reaches of local rivers to spawn. Rain-bow smelt were caught at the entrance to the estuary (Station T2) from December through March or April (see adult fish section 3.2.2). Abund-ances were significantly different among years, causing moderate base-line variability, making the detection of minor population changes unlikely. In spring and summer, sparse and erratic numbers of young-of-the-year and yearling smelt have been caught in beach seines (Figure 2.3-8), but no one age group (based on length-frequency) has been con-sistently dominant (NAI 1985b). Rainbow smelt have never comprised a substantial portion of annual seine catches, and over all years (1976-1984) averaged only 3% of the total catch. Catches in 1986 (July through November) were much lower than average. ! River herring, which includes alewife and blueback herring, ; u were monitored both in the Taylor River and in Hampton Harbor from 1980 to 1984. The size and length of the river herring "run" was shown to be variable, with the number of days that fish were observed passing the Taylor River ladder ranging from 31 (1982) to 47 (1981) (NA! 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). i Their staff removed fish from the ladder during peak periods to stock other water bodies. Changes in the run size were affected by year class l strength. Periodicity of the run was affected by water temperature and level which were in turn influenced by rainfall and the resulting run-off, Alewives and bluebacks were each the third most abundant species caught in beach seines in the Browns River (S2) and Hampton River (S1), respectively (Figure 2.3-9); however, this was caused by large but i 50
BEACH SEINE 1 1984 q A. , 3,.n7 I ~ 1983 - Wima FLC9HDER MUPMICHOG j - i 1982 - + 1981 -
** I' 33 I" 3 DE POLLOCK a: 1980.- .
5 '
* '1979 - ,' -
ATLANTIC -
- 1978 - HERRIMc !
I OTHER 1977 - . 1976 20 40 60 80 100 100 200 300 400 NOV B.
~
OCT - ATLANTIC sttytRstet j l SEP - l AUG - . l is OTHER , l Jy( - ..
.........m. .
((:- $ YI.CH0G 2 ATMNTIC f.V ggggi% 1 JUN . s POLLOCK / RAINBOW MAY - smetT
!: WINTER. . . . . . .
APR , i *"I , , , , 20 40 60 80 100 250 500 7501000 PERCENT COMPOSITION TOTAL CPUE l Figure 2.3-8. Percent composition of six dominant species collected by beach seine i and total catch per unit effort A. by year and B. month at combined j stations S1, S2 and S3 from 1976-1984. Seabrook Baseline Report, 1986. j ! 51
l I
-= x q;f S1 (Mean CPUE=137.3)
-.. n u..i (10.05>
j (' 05) p%g__ {il S - ... .. . a.or.)
), / o_--
T,1,o h SCkLE ' " , (14.0%) [
- "t','::L"'
j
- .J g ,
/ WW . If
!jf ,S
( .. ., s " di MY.Y;l 5-(gq v- @u M%eWh'.rd-m:%
-x. u _ ,,uy w , ,,.. -
p _N
%,k "a *
& ~,, '
- e# : Q N .i rg,pogg.g
,s m,...,*....
L 52 (Mean CPUE=201.9) ET ATION - b ,, V ,,,,, ['.g.Th',,,gy[ \$N,
M d
?
~h"jb "i
$\ ( n.ev' '
Mh
' y' c - s "ES:N a_. .,2 .s N "
N k 3E-YEd1.Y\
~
s
%2 p.cz)j, tF i
=ML i \
W.t"' N] .t- S n:. w, n, .: n .nu i ETCE
_s_iW
~ . _ O . _M
- d_ ,<sm,
\ " 'I
-.: 5M.55N'l S3 (Mean CPUE=267.2)
[i1..
??[iD/
- p =quy (o.cx)
' NY+'EN?'
- o s.e:>
m' M '
<s es) /. N-RT3 pus; - "$N p.er.)%hr-- %
-am-w mx re- ATLANTIC SILVERSIDE a
7 5'g, MUMMICH0G v 6 m w e i-s -m,, .sn ! ' _r.. . - =_mw-SAND LANCE
=w,n=-
1-
- - - - cr __ -_
BLUEBACK HERRING we.rernv (7s.es) ATLANTIC HERRING N*M' y... POLLOCK
$ ALEWIFE MWINTERFLOUNDER RAINBOW SMELT I IOTHERS Figure 2.3-9. Percer.: composition of four most abundant fish per station collected in Beach Seines (all dates combined) from 1976 through 198!..
Seabrock Easeline Report, 1986. 52 l
I l infrequent catches at these stations. In the estuary as a whole, these species constituted less than 5% of the total catch (1978-1984). Another species which uses the estuary is winter flounder. This species undergoes onshore / offshore migration, depending on the time of year (Bigelow and Schroeder 19.*3). Juveniles (age one and two, based on length-frequency analysis) were nie main constituent in the estuary, ' primarily collected during the sprits and summer (NAI 1985b). Recruitment was evident by the occurrence of young-of-the-year size classes. Total catches were somewhat variable, and catches in 1986 were lower than average (see Section 3.2.2). The dominant resident species in the estuary was Atlantic silverside, which typically comprised 67% of seine catches during the baseline period (1976-1984) and 90% within their abundant period, August to November (Figure 2.3-8). The population was composed primarily of yearling fish but the occurrence of young-of-the-year size classes in l spring indicated recruitment (NAI 1985b). Variability in total seine
- j catch has been the result of high variability in catches of Atlantic silverside; catches were high from 1976-1981 (200-360 fish / haul) and much lower from 1982 - 1986 (60-100 fish / haul).
Since the Hampton-Seabrook estuary contains the majority of New Hampshire's stock of the recreationally-important species, Mya arenaria, an extensive sampling program (over 12 years) was undertaken in order to characterize the natural variability in densities of all : lifestages. Of the potential impact types, larval stages will be most susceptible to intake effects and therefore are discussed in that sec- l tion (Section 2.2.1). Spat settlement densities appear to bear no rela-l tionship to the abundance or periodicity of Mya larvae in the nearshore waters (NAI 1982c). It would appear that Mya veliger behavior (i.e. ! their "readiness" or competency to settle) combined with the timing of favorable currents may be more important to settlement success than i ) 53
I I sheer numbers of larvas in the water column. Such conditions apparently ' existed in 1976 1977, 1980, 1981 and 1984 when young-of-the-year spat densities were highest at flat 1 (Figure 2.3-10) and other flats. The 1976 year class in particular provided an important and rejuvenating recruitment to the local population as shown by the high densities of 13-25 mm class in 1977 and 1978 (Figure 2.3-10). Continued low ~ C densities of spat from 1983 through 1986 at flat 1 (Figure'2.3-10) and j other flats suggest that the standing crop of adults will remain low for at least another 3-4 years. Once settled, survival of young-of-the year Mya depends on both the level of predation from its two main predators, the green crab and human clam diggers, and the absence of diseases such as neoplasia. . Despite relatively heavy densities of young-of-the year in 1980, 1981, l and 1984 on Flat 1, recruitment to yearling class was minimal (Figure { 2.3-10). This pattern was replicated throughout the estuary. Predation l by green crabs, whose densities began to increase in 1980 and from l 1983-1986 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 harvestable class, causing mortality to adults as well as spat and juveniles by disturbance. Digging activity has declined sharply from 1982 to 1985 with a small increase in 1986 as clam diggers switched to other flats in an effort to harvest class. The i standing stock has declined precipitously since 1983, lagging trends in ) digging activity by one year (Figure 2.3-11). Finally, the presence of disease may add to the effects of predation. Neoplasia, a cell growth disease fatal to Mya, has been detected in 3-27% of the Mye from Hampton Harbor flats 1 and 2; no incidence of this disease was found at flat 4 (Hillman 1986, 1987). The ability to assess impact in adult class in Hampton estuary will depend on close monitoring of all of the factora important to recruitment and predation. Clam seeding by the State of New Hampshire during 1987 in tidal creeks running into Hampton Harbor may enhance spat 54 i j
FLAT 1_ YOUNG-OF-YEAR (1-Smm) 500 - f 100 - d w 50 - g .. l p 10 - ,, 5 5- .. 1 4+ 1974 75 76 77 78 79 80 81 82 83 84 85 86 YEAR FLAT 1 . SPAT (13-25mm) 100 - N ! 'e C 10 - ! 1 4 g i
+ . . i A i
l I I I I I I I I I I I j 1976 77 78 79 80 81 82 83 84 85 86 l YEAR l l 1 1 Figure 2.3-10. Annual ceans and 95% confidence limits of young-of-the-year and spat densities (ft-2) of Nya arenaria at Hampton-Seabrook, 1974 or 1976-1986. Seabrook Baseline Report, 1986. 55 i
1 l i 14 - . l 13 - \ p 12 --20t\ 's l
'\
/
\ l
' \
_ 11 - \ / \ / \
\
E \ / t \ # \ E + 10 - t t I \ f \
\ s#
\/ \
l
- e -
-15 g
g
' \
\
= G\ I \ Q\ \ /\ l \ I S- < / \ l C e o
\
\ /
/ \
g l 1, = ~. = t , I \ c ' ~ \r
\ s I \
- = s/ \ I i g o 6 p
\\ l l i b i- 5 \ g \
E 5
\
I tl \
\ '
\
=
, l s 8 \
\
f s s E l \ j 2--5 \ l s
\ l s
\
2- \ , I l
\
;- ',,'s'
, i . . . , , , , . , , , , ,
c-1571 72 73 74 75 76 77 7E 79 80 8; B2 E3 S 85 Si j YEAR )l l ADULT CLAM LICENS t 1 ADULT CLAM STANDING CROP ; i
- : DIGGER TRIPS Figure 2.3-11. Number of adult clam licenses issued and the adult cla: standing crop (bushels), Hampton Harbor, 1971-1986. Seabrook Easeline Report, 1986.
56
densities, but the ultimate effect on harvestable clams depends on predation levels and disease. 2.3.2 Benthic Monitorina 2.3.2.1 Macroalnae and Macrofauna Monitoring of the benthic organisms (macroinvertebrates, algae, demersal fish, and epibenthic crustaceans) was established to determine the extent of change (if any) to the community structure in this zone as a result of plant operation. Changes could be manifested by 1) the enhancement of detritivores and suspension feeders, 2) the increased attraction of benthic feeders caused by 1ccally-increased food supply, and/or 3) impact on organisms sensitive to the increased detritus resulting from moribund entrained organisms. Mid depth and deep (10 20 m) benthic communities, including 1 macroalgae, macrofauna, and bottom panels, were sampled to moniter the l preoperational benthic community. Year-to-year variations in community structure were small in comparison to variations with depth and sub-strate. The macroalgae community was highly similar among years, although less so than in the intertidal and shallow subtidal areas. Species composition of 95% of the 195 replicate samples in the mid-depth and deep subtidal areas were similar to those taken at the same station in previous years (Figure 2.3-4). The same was true for macrof auna, where only five of the 43 annual collections at the six mid-depth and deep stations (12%) had species assemblages which differed from previous years (Figure 2.3-4). Colonial macrofaunal assemblages in the mid-depth and deep areas differed from year-to year, and did not show r distinct association with depth (NAI 1985b). Patterns in abundance and size distribution in selected benthic species were only slightly less predictable than species 57
assemblage characteristics. Over three quarters of the species-station combinations showed no significant differences in size or abundance among years (Table 2.3-3). Although there was high variance in abund-ance over all years for most of the species (Figure 2.3-12), these dif-ferences were not significant for most of the species tested (Table 2.3-3). Length measurements were a more stable parameter; no dif-ferences among years were detected (Table 2.3-3). Few nearfield/farfield differences were noted in the mid-depth / deep region. In the macrofaunal and macroalgae community, all farfield stations were more similar to their nearfield counterparts than any other areas, indicating their suitability as "control" areas (Figure 2.3-4). Collections made in 1985 and 1986 in all cases were most similar to the majority of collections from previous years at the same strata (Figure .1.3-4). Most nearfleid annual abundances and all near-field lengths were statistically similar to those from the farfield area (Table 2.3-3). The only irregularity in spatial distributions was in the macroalgae and macrofaunal community structure at mid-depth Station 16, which was more similar to shallow subtidal stations than those in its own depth zone. The predominance of algae-covered ledge at this sta-tion caused increased amounts of algae and correspondingly higher abund-ances of herbivores. Because of apparent year-to-year stability in the annual com-munity structure demonstrated above, the once-per-year August sampling provides a good baseline for monitoring potential changes in total num-bers of taxa or individuals. Community structure analysis provides a simultaneous view of species numbers, abundance, diversity and domin-ance, and if changes occur at a particular place or time. Results also indicate that certain species in the study area, because their abundance or size patterns, are predictable and changes, if they occur, could be evaluated with these taxa. 58
TABLE 2.3-3.
SUMMARY
OF SIMILARITIES
- IN ABUNDANCE OR LENGTH.AMONG YEARS AND BEWEEN STATIONS FOR SELECTED SPECIES IN THE MID-DEPTH ZONE.
YEARS SIMILAR DISSIMILAR S S. droebachtensis (A, L) . Jonah crab I Pontogeneta inermis (L) Modtolus modtolus M Mytilidae (L) S I T L A A , T R I O N S D I S Pontogeneta inermis (A) Lobster S Rock crab I Winter flounder M Yellowtail I Hakes L Atlantic cod A Rainbow smelt R Mytilidae (A)
"Results of 2-way ANOVAs or Wilcoxon's summed ranks test.
Abundance or catch unless otherwise noted. (L) = length (A) = abundance l l 59 l 1
Modiolus modiolus H F--o--I other Mytilidae
\ '
75.- p___________-____________o.__; O S. droebachlensis 8 h50- l : 3 _____________4 u t Pontogenela inetrels 25 - l : l F _ _ _ _ _ _ _ _ _ _ _. _ _ __ _ _ .o. _ a o l l ; ; g COMP. 0 10 100 1000 10.000 DENSITY
- KEY l : : x and S.D., Nearfield F _ _ _ o.. _ _ .4 Farfield
- a. No./m2 except Modlolus, per 1/4 m .
2 Figure 2.3-12. Overall mean (No./m ) and standard deviation of selected benthic species collected triannually at Nearfield (19) and Farfield (31) Stations from 1978 through 1986. Sea-brook Baseline Report, 1986. 60
2.3.2.2 Demersal Fish Demersal fish which inhabit or feed in the discharge area are important not only because of their predominance in the food chain but also because of their commercial value. Six taxa comprise close to 80% of total otter trawl catches both across months and years (Figure 2.3-13). Effects, or lack thereof, should be evident from following the distribution of these six taxa, although the total number of taxa as well as rare and infrequently-occurring species have also been monitored. Numerical classification of 1978-1982 data identified two basic seasonal groups: "winter" (December-March) and an extended "summer" period (April-November) (NAI 1983b). These two periods were evident from monthly relative abundances (Figure 2.3-13) which show rainbow smelt were prominent mainly in winter, and hakes (red, white and spotted) and longhorn sculpin composed a greater proportion of the demersal population in summer. The overall community dominants, yellowtail and winter flounder, provided some temporal stability to this demersal community (Figure 2.3-13). Long-term trends were also evident; total catches were highest in 1980 and 1981 when catch per unit effort was almost twice as high as the CPUE in 1977 and 1985 (Figure 2.3-13), , 4 the two lowest years. Total catches steadily declined from 1981 through 1985, then increased slightly in 1986 at T1 and T3. Annual catches in 1985 and/or 1986 represent some of the lowest catches recorded for all of the selected demersal species. Variations in catch from year-to-year are reflected in the high variance estimates (Figure 2.2 6), partic-ularly in yellowtail flounder and hakes, which together usually contributed over 40% to the total catch (Figure 2.3-13). Longhorn sculpin once accounted for an much as 27% of the total catch in 1984, I but in 1986 accounted for less than 10% (Figure 2.3-13). The age structure of the fish populations is also a factor con-tributing to abundance variability. Based on 1983 and 1984 length-frequency data and age-size information from the literature, the domin-ant age group collected at the nearfield trawl station (T2) was as follows: l l 61 l l
OTTER TRAWL 1986 NN l A. N ( 1985- s RAINBOW SMELT - 1984- ,
/
LONG- ' 1983- HORN ; SCULPIN 1982-
~ ~
N,, - 1981- ' ' mu
" WINTER f YELLOWTAIL WM FLOUNDER E 1980- FLOUNDER ig 7 OTHER -
w y 3'"
'~:-(
1979- C00 e .
.3 1978- Ny d -
bdKhg-s-
.- o 1977_ .
.~' )'
1976 i i i . i i i i 20 40 60 80 100 0 20 40 60 80 100 DEC y B. 7 NOV - _
'O h OCT - ; A? !i ~id -
n3 w ' l-SEP -
.W% .:l$,(1; '
, l
.ygg '
AUG - oTHER [ JUL - J LONG- - h JUN - N
%?ll$??
~i h b s$tSIN I '
I l'
~
9 YELLOWTAIL '/c 6'W ' , MAY - FLOUNDER k /> , l
'4! C00 l
l APR - - m l MAR - + M af I 4 iWINTER 1 t-FEB - :rLOUNDEp GRAINBOWg
-w~7'
, % 3SMILT tg JAN , , , , , , , ,
20 40 60 80 1000 20 40 60 80 100 PERCENT COMPOSITION TOTAL CPUE Figure 2.3-13. Percent composition of six dominant species collected by otter trawl. and total catch per unit effort A. by year and B. by month at com-bined stations T1, T2, and T3 from 1976-1986. Seabrook Baseline Report, 1986. 62
RECRUITMENT SPECIES DOMINANT AVE GROUP EVIDENT?a Atlantic cod Age one and two yes Hakes Several yes Yellowtail flounder Young-of-the-year yes Winter flounder Several. yes Rainbow smelt Young-of-the-year yes "From presence of young-of-the-year or yearlings during certain seasons (NAI 1985b) As with most of the fish sampled in this study, tnt. 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 another important consideration in demersal fish. Farfield stations T1 and T3 were similar in overall catch per unit effort and relatively similar in species percent composi- ; tion, although the relative contribution of sculpins and yellowtail flounder war reversed at the two stations (Figure 2.3-14). The nearfield l station was most unique, with total CPUE (averaged over all years) being 40% lower than at farfield stations. Winter flounder and rainbow smelt (together) comprised 43% of the overall catch at T2, compared with 7-10% at the farfield stations. Most of the differences in total catch and l 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, although mainly sand, has high currents, often resulting in a great deal of drift algae. The nearfield station is also located off the mouth of Hampton inlet and is influenced by tidal flow from the estuary. Thus, operational comparisons will have to focus on relative changes at a given station in species composition and the absolute abundance of selected species. 63
1
" N'{*
%y'/')y
,f
#?
my .
'[
~'
K ' (-g
,, S""*** T3 (MEAN CPUE=74.2)
$;e -
,,,,,,y.. ' ~.no n.- ,. , ,.j ,.;.. j,: ,.. .
pyEj s g. 23.0% ,.,. ., . .il. . .g;; . (22.0%)
@py - .
. :li
, iAi.U.,. ::
.: c':;:lI!.!!!!.'*.I.!l:..'
?AL ? , .~..~... n .., '::-
J:::f.::.::i:y;i)l i:::;?.'?
! , ,.....n,. R 7!!!.
r:: :,1-.l.l". /- SCALE (3.0%) A-) - (4.0%) , n..,'.. .. :
- 1 s -' g ,'
bjn . :: p . n... . @ ,,
./.:*/.:*
(10.0%) **;** M (16.0%) y" ,
,?
N 619
~
1
. .. ,h-
"'"*y N,,.
gd . . (22.0%) SEABROO ?"'L "" siAr\O w & , . :*::5 s g5*~~'" T2 (MEAN CPUE=44.9) y "." *:. , ,,y
.r .. ! :,
.:: (l3.0%)
h."ar -
@N (23.0%)
- .::.li.i::!7l:::...
p .
- !:.:l!::;:i:.;.
N N !.i$::i:p!!!:::;'(:(:y!
.A .
- / .l : - l (10.0%)
' C,d 51 9; ll::?l://,
. :.p. . .:
.n.....,E g excuietm i.,eru n u.
c
,. ez (5.0%)
(15.0%) lg,9;,~v , .. . . 7-
< 'W:# ! N,~,O ,,...
**c, >' '.,, ,~ V T1 (MEAN CPUE=75.9) G %r ' - - !
'N,.N'].)!w',
U ",'.<. ,d', ,t,e/,,,y,
',?,%-lM,, p"
. . .. . ..., P,a
" ' ' u,%'P' ,'l,',D'#
~
(l6.0%) .. :-l:7. '.:ff.L,
..:.*in): /
(gg,ogy
. . i . .:
(5.0%) : :. ." :iii
. ,l :[. . ." c:' :}(40.0%)
'i.i YELLOWTAIL FLOUNDER (5.0%). f;)'.E',-l,,g,... ;.;;.*;
HAKES (5.0%) + LONGHORN SCULPIN
. fgg ,
s *:' ATLANTIC C00 l
%g .
J
"%[
L WINTER FLOUNDER 1,,c, (12.0%) " RAINB0W SMELT
.s
.:n. OTHERS (17.0%)
Figure 2.3-14. Percent composition of six most abundant fish collected in otter trawls (all dates combined) from 1976 through 1986. Seabrook Baseline Report, 1986. 64
l
'I All of the selected demersal fish monitored have shown signifi-cantly different abundances (CPUE) over both time and space, implying that determination of "control" conditions is difficult. For almost all of these taxa, precision in impact assessment is only moderate because of among-year variability. Knowledge of the age-structure of the popula-tion and use of age and growth parameters (NAI 1985b) can improve the ability to detect impac.ts.
Age and growth parameters for two species, cunner (1983-1984) and winter flounder (1982-1984), abundant in the nearfield discharge area were measured to provide additional precision to the catch estimates and a view of potential sublethal effects. Results for the first three years of life, when impact effects would be most pronounced, can be summarized as follows: SPECIES GROWTH CUNNER WINTER FLOUNDER Sexes different? yes no Year classes different? yes yes (age 1 & 2 only) Percent change detectable 2-5% 3 - 4% Thus, depending on the species, sex and year class dif ferences will have l to be considered when making impact assessment. However, variability of ) age and growth statistics was low, giving better precision than abundance estimates. I 2.3.2.3 Epibenthic Crustacea Because of its corrnercial importance, the American lobster has been studied in all of its life stages for 9-13 years. Average annual catches of all lobsters ranged from 47 to 92 at the discharge zone, and averaged 65 per 15-trap effort (Figure 2.3-15). Catches were significantly greater from 1983 to 1985, while catches in 1986 declined l 65
SEASONAL PEAK AMONG-YEAR VARIABILITY 30 60 90 i f I I I I 1986 - Rock crab
~ I
- I 1984- ; '
1982 - < u , Jonah crab 2 as _ : : : 1980-3O
~ ~
}o
, 1978 -
\ American lobster . - -
legal total 1976 - g g m : : - - - o e 1974 -
' l i i l i I I I I I I I l J J J A S 0 N D 0 10 100 30 60 90 MONTH OVERALL - CPUE AND S.D. ANNUAL CATCH
@ = not sampled (15-trip effort) (15-trip effort)
Figure 2.3-15. Seasonal peak catch and overall mean CPUE and standard deviation of Rock crab, Jonah crab, and American lobster; Annual mean CPUE of total and legal-sized lobster. Seabrook Baseline Report, 1986.
l slightly. Variations in catches of legal-sized lobsters, a primary concern to lobstermen, were a result of natural variation combined with the effects of the change in the legal size limit. Catches ranged from 7 to 10 per 15-trap effort, and, although the variability was lower than that for total catches (Figure 2.3-15), this represented a substantial difference (43%) to a commercial lobsterman. Catches in the 76.2 mm (3.0 in) size class, lobsters which are approximately two years old, have been steadily increasing through 1985 despite decreased catches in the smaller size classes (one-year old lobsters)(Figure 2.3-16). In 1984, the legal size limit was increased by the State of New Hampshire from 3 1/8" (79.4 mm) to 3 3/16" (81.0 mm), and catches of legal-sized lobsters decreased to their lowest point in 1984 and 1985. A number of adults which would have been of legal size under the old law were not harvested, causing increased catches through 1985 in the 88.9 mm (3.5 in) size class, which now contained both legal and sublegal sizes. A decrease in catches in 1986 in the 88.9 mm size class may have been linked to lower catches in the 69.5 mm size class in 1985. Lcbsters have shown consistent seasonal patterns, with catches highest from August through October. Catches to the north (L7) have been consistently higher than at the discharge (L1). Annual catches of other epibenthic crustaceans, Jonah crab and rock crab, were somewhat variable (Figurn 2.3-15). Both species had increasing catches from 1982 through 1985, then slight decreases in 1986. Catches of Jonah crab were generally highest in August or September (Figure 2.5-15), 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 sf railar between nearfield and farfield stations. 67
0 1 N i a l N a: N . a: N a: N i i N a: N a: N i a= N n- N a: N L N e= N a N a: N ;E , == N e= N 0- N a: N si l
<b_- N ca -N a- N a- N !! l cn- bs N o- N 0- N a- N !! '
N ee b- = N a. N n~ N a N ! a: Nrs- 'tess= N a- N 0- N a N , 3Na N m- %= N a- N a- N ay !! !
!! N a- N m. N e= N ca. N a- N~ i ". l
- 1 N 0- Ne N a- N a- N o~a si i i
N a: Ne= N a- N m- N'r is aN 0- %= N a- N a. i . :. 5 N! a. Nam N a N*; !! N s= Nm= N a- ~! si E
@= N2= Nd! i E
Ts= %= 5 $ i M= Nd i-
=
hR , E E 5 e 68
l l l 3.0 RESULTS , 1 3.1 PLANKTON AND WATER QUALITY PARAMETERS 3.1.1 Water Quality Parameters-Seasonal Cycles and Trends Three physical and five chemical parameters were examined over a nine-to-eleven year period to assess their temporal va. lability. Generally, parameters exhibited annual cycles with one or two peaks; ammonia showed no distinct pattern (Table 3.1.1-1) Water temperature was monitored in the nearfield both contin-uously (Station ID) and periodically during the semimonthly plankton cruises (Station P2). Monthly mean values derived from both sampling methods were similar (NAI 1980c,d; 1981f; 1982a; 1984a; 1985a). Con-tinuous temperature data were not available for January 1985 through July 1986. Irradiance values, collected 1979-1984, and surface tempera-tures followed the same general annual cycle, with temperature peaks lagging irradianen peaks by one month (NAI 1985b). Bottom temperatures showed truncated peaks which legged one to three months behind surface peaks. From 1978 through 1986, the temperature peak occurred in July and August at the surface and from August to October at the bottom at , 1 both discreet (Station P2) and continuous (Station ID) monitoring J stations (Figure 3.1.1-1, Appendix Figure 3.1.1-1). Bottom temperatures were similar to surface temperatures January through April and October j through December. Annual mean temperatures for both surface and bottom (Station P2) in 1985 and 1986 were higher than most previous years (Table 3.1.1-2). The elevated annual mean temperatures reflect higher-than-normal values in the summer of 1985 and January through April in 1986 (NAI 1985a; 1986a). The thermocline, typically established from ) May through September, was strongest in August six of the nine years and ) in late June and early July the remaining three years (Figgre 3.1.1-2). In 1979, 1980 and 1983, a substantial but temporary breakdown of the thermocline occurred in mid-summer. ) 1 69
i 1 TABLE 3.1.1-1. QUALITATIVE OBSERVATIONS OF SEASONAL. CYCLES AND LONG-TERM TRENDS OF WATER QUALITY PARAMETERS AT THE: NEARFIELD STATION (P2) MEASURED FROM JULY.1977 THROUGH DECEMBER 1986. SEABROOK BASELINE REPORT, 1986. SEASONAL PEAK PARAMETER CYCLE LONG-TERM TREND VALUES Temperature Annual Surface-increasing trend July-August (1978-1985) Bottom-increasing trend August-(1978-1985) October Salinity Annual Surface-decreasing trend November-(1980-1984) January Bottom-decreasing trend November- l (1983-1984) February Dissolved Annual Surface-no discernable trend March-April . Oxygen Bottom-no discernable trend January-April
)
j a Orthophosphate Annual Increasing trend December-(Polymodal (1978-1983) February 1982) i a ! Total Annual or No discernable trend' November- l Phosphorus bimodal April,-but ; fairly uniform
)
Nitrite- Asmual Decreasing trend January-Nitrogen" (1980-1984) April, September-December Nitrate- Annual No discernable trend September-Nitrogen
- March Ammonia-a None Decreasing trend Spring, Nitrogen (1980-1984) summer or fall a
Measured July 1977 - December 1984 and July - December 1986. 70
- =. .
l l I e is e f
"i A. Surface i i "i ' / ;. i
. s 2 % 4 i 7 N g*
54
- 3 6
7 a. 4 e % $ II e 2 4 0 4 1
- 1
( 12 *\ G l 9 a e in e 9 i ! 9 C le
- 3 6 s
5 g
.9* 5 E 8 3 8* 4
! O
& I 4 S F*
0
$*3
- 6
.1 1
- 8 e
ge e t 0 4 e* 3 4 1 3 5* * *
- 7, 8 [0 t
- t 7 1 9 0*
I 8
.i e
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .my. . . . . . . . . . . . . . . . . . . . . .AUG
. . . . . . . $(P
. . . .' . . . .OCf
. . . . . . . mov
. . . . . . . .Of. C. . . . . . . . . . . . . . . . . . . . .
JA4 fit ma app Joe JUL peon t a 8.9 ETC.
- LAST DIGIT Or $AwPLE YEAR; M!$$lhG POINTS DUE TO u} w tatAppins vAttes
,, ! B. Bottom
...n... 1986 u .I 91 1
-*-
- Att YEAR $' MEAN . 1978 64 14 e i i ne b 0 i I
( 12
- 5 ,, j i !.-.->
(~j '/i ,\ , i .i
!/! '
\
;/- 'N.
? .> i S 8 g n
9 5* s s O
. .e D ,.
i a .
,'II, N I.
i* 9 e i e D .i
.1 ..................................................................................................
JAA fil mA APA mi jut JWL AWG S(P Oct sov HC IMIN l i Figure 3.1.1-1. Monthly mean temperature at continuous monitoring Station ID l (nearfield) for each year and over all years from 1976-1984 and Aug-Dec 1986 for A. Surface and B. Bottom. Seabrook Baseline Report, 1986. 71
- ., ,--e .--.i--. , , , _ y ,- - - - - , ,w-..- - mw w w g -+w4
J TABLE 3.1.1-2. ANNUAL MEANS AND COEFFICIENTS Of VARIATION of WATER QUALITY PARAMETERS MEASURED DURING PLANKTON CRUISES AT l NEARFIELD STATION P2 1978-1984 AND JULY-DECEMBE R 1986. SEABROOK BASELINE REPORT. 1986. l l 1978 1979 1980 1981 1982 1983 1984 1985 1986 5 5 5 5 5 5 E E 5 PARAMETER (CV) (CV) (CV) (CV) (CV) (CV) (CV) (CV) (CV) Temperature ( *C) i surrace 8.37 8.76 8.76 8.72 8.88 9.58 8.94 9.73 9.31 y (66.93) (57.85) (57.86 (63.34) (53.02) (53.74) (55.72) (54.55) (49.57) i bottom 6.61 6.36 1.05 7.37 7.36 7.12 6.93' 8.03 7.56 (55.62) (47.96) (52.76) (59.11) (46.03) (44.43) (45.04) (47.81) (40.42) Salinity (ppt) surface 31.68 31.82 32.17 31.89 31.84 31.04 30.68 32.15 31.68 . (3.33) (3.84) (2.64) (2.16) (3.47) (4.39) (4.93) (2.26) (2.44); j bottom 32.24 32.47 32.42 32.32 32.41 31.92 31.77 32.50 32.20 (1.65) (2.77) (1.52) (1.41) (2.01) (2 12) (1.83) (1.54) (1.77) t
-a Dissolved Oxygen (mg/l)
DJ su rface 10.28 10.02 10.27 9.90 9.60 9.48 10.01 9.67 9.88 (10.80) (13.39) (11.17) (12.70) 11.15) (7.73)- (12.06) (10.42) (11.03) botton 10.07 9.69 9.85 9.43 9.25 8.98 9.32 9.17 8.96 ! (8.86) (14.67). (14.28) (17.90) (16.17) (11.99) (13.56) (15.36) (13.521 b c Orthophosphate 9.58 9.75 10.12 11.82 17.02 19.23 14.29 -- (pg/8) (29.99) (52.59) (76.10) (30.83) (55.54) (44.47) (56.06) -- -- b c Total phosphorus 32.50 15.12 31.96 22.50 24.61 25.83 24.17 -- -- +
*pg/I) (40.09) (63.09) (77.68) (33.93) -(28.66) (35.05) -(40.43) -- --
b- c Mitrite 2.12 1.11 3.17 2.92 2.30 2.05 1.02 -- (pg/I) (46.11) (66.58) (59.59) (53.13) (68.34) (54.34) (98.08) -- -- b c Nitrate 52.08 38.33. 48.33 45.42 37.17 51.83 36.75 -- -- (pg/I) (116.61) (101.24) (111.88) (94.41) (137.89) (106.62) (117.47) . -- -- a_ b c Ammonia 51.46 47.42 104.17 36.25 <30.00 27.32 16.57 -- -- 4 (pg/13 (120.96) (42.93) (48.73) (64.73) -- (115.96) (70.82) -- -- Below detection limits (30 pg/I) of methods used in 1982. 1 6 4 Not measured in 1985. + c 4 Measured July through December 1986 only. 1
l l l 8.0 - 6.0 - 1986 2. s.0-6.0-1985 "c o- _ _h i a.0-6.C-C 0 - s.c-e .c- [ c c-d~ - ~7 - s . c-6.0-4.J- [ - 1982
*c
- 2. 0-g.
./ pg . . h-W M e.c-6.e-4.0-1981 2.c-c o
~ '
/ '= /^ E s .c-
- 6. 0- f l
**** c e
o m
. . L m /h_ _ -
- 8. c=
O *
- c ~ *-
8.0-6 . 0-o c * . <////. m **L v J F M A H J I J I A I S 0 N D
- from continuous monitorin9 station ID Figure 3.1.1-2. Differences between surf ace and bottom temperatures taken semi-monthly at Station P2. Seabrook Baseline Report, 1986.
73
1 l
'1 l
Other water quality parameters were monitored during fort- l nightly plankton cruises. Salinity concentrations were highest in December and January, reaching levels of >33 ppt, though in 1985 peak salinities occurred in February (33.5 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. Salinity concentrations typically reached spring lows of 28-31 ppt; the lowest observed surface salinity (24.7 ppt) occurred in June 1984. Bottom salinity exhibited the same seasonal pattern as the surface, but showed less variation within and among years (Figure 3.1.1-3). Annual mean salinities in 1985 for both surface and bottom were among the highest recorded in this study, reflecting above average , salinities February through June (Table 3.1.1-2, Figure 3.1.1-3.'. Annual mean salinities in 1986 were comparable to previous years (Table i 3.1.1-2). Dissolved oxygen peaks occurred February through April in surface waters and January through April near bottom. Dissolved oxygen-nadirs varied from August to November near the surface and September to November near the bottom (Figure 3.1.1-4). Bottom dissolved oxygen values in 1986 were lower than the all-years' monthly average throughout the whole year (Figu'. 3.1.1-4) and were reflected in the lowest annual mean observed (Table 3.1.1-2). Maximum orthophosphate and nitrate concentrations occurred in winter (Figures 3.1.1-5 and 3.1.1-6); nitrate was consistently lowest in midsummer. Total phosphorous and nitrite showed fall, winter and occasional spring peaks (Figures 3.1.1-5 and 3.1.1-6). Ammonia maxima usually occurred in fall or spring. In 1980, when ammonia concentrations were exceptionally high throughout the year, the peak occurred in July (Figure 3.1.1-7). Nutrient data (orthophosphate, total phosphorus, nitrate, nitrite, ammonia) were not collected in 1985 and only from July through December in 1986. On the dates sampled in 1986, none of the chemical parameters differed greatly from previous baseline data for the same period (Figure 3.1.1-5, 3.1.1-6, 3.1.1-7). 74
.. .. ! A. SURFACE SALINITY n.S 9
i S . S r
$ 3.0 + 3 o 9,'s i S . .
4 t' e
.e,Af n.S .
, ; , , s s
.s
\
- a. n... 5 e i s
. , . s
. , S . S 4--- -
S I i 3 S f 4 P SI.S
- 1 p S 3
t a 3 m 9 4 3 1 31. 0 + t 0 f / 9 3 S'
\* #
o e W 6 % 3 v # ,6 s so.S *
, ,Q, 4 D 4 10.0
- 4 2
1 4 2 29.S
- 9 3 3 29.0
- 29.0
+...e........s........e........s........e.......4........s........s........s........s........s........e...
e Jat fft maa APR MAv JV4 JUL AUG s[F OCT NOV OtC 993R1N
,,,,, i B. BOTTOM SALINITY l 9 l l l 13.30 * '
1 3 3 2 33.25
- l iO $ S & I i 1 l l
I l ll.00 * &, 9 9 4 4 1 0 R 32.75
- g i I 9 S / % S S 4 0 8 0 5 / % 3 a
/ %
j 32.50 * '6 -g I f
# 4 '6 s #
, ,\
*\
S , je- .< $ 1 17.21 * \ p n \ $ l 2 / .* l 0 e S & # 3 U $ # s 32. 00 + s e o 3 o o # ,a# 3 4 a 0 % .4#' 4 i %6" g,9 gig, e LA$f $lgif CF 1AWt( f(AA; I 3 # 9 9 S milllas poian 04 79
,,, g l g g Odetapenas gatL45 g g g g g ***4 *+ +
- lle6 3
,,.,, . ---.m..,.
2 3 4 31.00
- e 3
30.75.*...................................................................................................... Jaa tre man Apa nar Jun Jut auc sgP ccf nov OCC M04iM Figure 3.1.1-3. Monthly mean salinity at nearfield Station P2 for each year and over all years from 1978 through 1986 for A. surface and B. bottom. Seabrook Baseline Report, 1986. 7S
A.: SURFACE D.0. I 1f.0 9 0 . 9 4
. 0 1 ,' t
,# 0 II.$ .
S\
<* - s, .- ' . i ,
g % # % 4 11.0 ) 9 %
. \
u 8 , S' \ 0 t \ '8 0
' g.
L 4 3 e t t .... . j i si 9 1 0 * , S 4 10.0 9
/ ,%s,1 0 9
M. .
. s, ,
- 9. . . ,
, 9 .
0, ,, 9 , ,
! '** '. 'N :
s,,, . , - ., .
..s . i i
a t 0 t 4.0 4 9 l Jail Its man Are MAf Jun JUL AUC St r Oct mov OCC feOIIf M is.0 .i B. BOTTOM D.0* 8. 9. etc. . LAST O!G!f 0F SA"PLE YEAR MISSIM POINTS OUE TO OVERLAPP]NG V M ES
, O. , _ . _ . m v uRs . .
8 *
, ._ _ _ _ _ . 1966 a s si.0 - i 0. % ,N* 9
- 10. . .
ls A S s, s
~~ .. ..', ~,N '
O
! .0.0 ! . , s 'i
. l .<'
':, ,NN.
s 9 A 9.9 s t 4 m l g 3 5 a 4 ($ ' 5 t 9.0 1 .'s % g t ) 1 m [ 1 9 4 4.) .s 3 's 5 0 S p i l 4's 9
/
! .0 's.* N , ,. j l .' , , , - .,- , ,, i ,
j , i - 7.0 S 9 l t 2 6.S .i 4.0
...................................................................................e.....................
JAa f(B MAA AFA RA f JUN JUL AUG $(P OCI NOV DEC nonin Figure 3.1.1-4 Monthly mean dissolved oxygen at Nearfield Station P2 for each year and over all years from 1978-1986 for A. surface and B. bottom. Seabrook Baseline Report, 1986. 76 e.-p. e- -
-.-.e . , ,, , , , , , ,,,...,r-, - - - , - . . . - - . v a-.c, e<a
l l I i A. ORTH 0 PHOSPHATE 8
- 3. .
l3
,r .
I , , , I 2 4 C ,. .l . . o G j -, . l c 3 -1
; l.
.--- 4 e l' s / 's
,3 ! .
- I s , - .
t,
/ s i \ ,
I i s> ,, a l,,
.N.i
/. \. ,/ : ,
'j ,N s
- :*), -; y:
,1
, , o , . .
=
i. l , s , t 0
. .I. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jaa f(S MA. AP. RAF JWE JUL AUG &lP OCT NOV .(C Monie i s.t.
'=*
- 8. TOTAL PHOSPHORUS .u. . .i..t. . ci,t or ...,i. ,..ri
- a. . ac. ... i. .r.
l i.,,as v.to..
---- 1, .
l - . - . .u ,..,.. . , w s.1su
- I g to .i O
G. . A R. . . S.
- f ,
. 3
.o . . 5 . g i i 3
/\ . ,
i l1 * *
,' N i N j / .\'j / , ','. !
>v *
- l '%. ,
N '
/
+' V N+
,o . . .!./ ,
I' , , %;%/-; : *
- i. .
F , Jag f(B RA. AP. MAY JW4 JUL Av. St P OCl 40 f .( C fGs,N Figure 3.1.1-5. Monthly mean concentrations at nearfield Station P2 for each year and over all years from 1978-1984 and July through December, 1986 for A. Orthophosphate and B. Total phosphorus. Seabrook Baseline Report, 1986. i 77
m , - _ - . . _ - . . _ _m _ . . . . .- , A. NITRITE-NITROGEN 4 I C 3 a e e t o3e G a a 6 5.3 o g I 15
/ %\ 7 0
/ \ i 1----1 .
e 4 7 i
/0 %
.\ !. \
t 5* 3 3 4 i N. $/; . l l- \g. / i s y [g 3 i 3 8* S % 9l 4 z I I
*l \ yl \
V ne 3 3
;x*fi 1 9 3 9 9 9 2
'g g9 0 g 4 4 4 4 0 4 4 e 4 4 0*
Jan f(t maa are mar Jun JWL auc ' sir CCf now NC noniu 8.9. etc.
- 1ast digit of sample year;
=$astas patata *== te ever-140
- B. NITRATE-NITR0 GEN 1apping values 4 -.-- . 19 8 6 gg .
-*- = all years' mean. 1974 1984 3 a 140
- I 3 8 9 C 4 a e o are e i G
a e a a M s sou s
- a e
,P l /4
. i a a 60
- 9 /
t I i e / 9 i / g 6 a 6e . # 4 9 fg
. /
,N'.
- A
/
/
/
e
/ \ /
' 9 \g 20 e
, j a j e a j
. . . . . ,/ . - . . .
- % .-;' ;A.v' . l Jan ris man are mar Jve Jvt ago ser cCf sov HC Moein l Figure 3.1.1-6. Monthly mean concentrations at nearfield Station P2 for each year and over all years from 1978-1984 and July through December, 1986 for A. Nitrite-nitrogen ,
and B. Nitrate-nitrogen. Seabrook Baseline Report, l 1986. 78
1 I I I I 2'20 + 1 l I 225 + o l I i 200 + 1 a j ... . . . ...t ..... ., . ,,. ...r.
, missing potata due to overlapping values
* -
- all yeara* eean enreuen Isee 9
a iso . A l 0 M l S l 125 + P I , E I n R 6 l l l L 100 + l /
/\ 'N 1 1 0 1 O O l / \ o I I \
l [ 15 + / 9 \ l R l 9 f 6 3 9 l I I G /
- 9\ o l
I ' - I
\
5 il 1
*y ;x. 9 e
)
N. l 2, I
./* 9 a 4
x' 3 8 m
-/
' -6 1
N, g
\ 4 i
6 l 1 1 4 3 3 3 4 14 4 3 g g
\
\6 , ', 3 0+ 2 2 2 2 2 2 2 2 2 2 2 2 l
i l l l
............+.................+...................................,..._____,________,________,________,___
1 l JAN ((8 MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH f L Figure 3.1.1-7. Monthly mean ammonia concentrations at nearfield Station P2 for each year and over all years from 1978-1984(excluding 1982) and July-December, 1986. Seabrook Baseline Report, 1986.
. _ _ _ _ _ _ _ _ _ _ _m___.-_-_____ _ _ _ _ _ . - _ _ _ _ _ _ _ . _ _ _ _ _ . _ _ _ --- - - _ _ . _ _ _ _ _ _ . _ . _ _ _ _ _ _ , __ _- --- __
3.1.2 Phytoplankton 3.1.2.1 Total Community Temporal Characteristics: 1978-1986 The high variability in comrunity composition from year to year, due both to the influence of physical and chemical factors, some cyclical and some transitory, and to the rapid turnover rate of phyto-plankton populations, makes it diffi ult to succinctly describe the long-term temporal community structure. However, no significant dif-ferences in total monthly abundance (all species combined) between years were revealed for the period 1978-1984 (NAI 1985b). Seasonally, total phytoplankton abundance generally exhibited a bimodal annual cycle with spring and fall maxima and summer and winter minima (Figure 3.1.2-1). Notable exceptions were in 1984, when a large bloom of diatoms and dinoflagellates created ar. uncharacteristic June peak (NAI 1985a), and in 1986, when, in addition to the usual September peak, there was a peak in late July created by colonial bluegreens and faptocylindrus minimus (NAI 1987). The increase in surface irradiance that occurred in February through April seems to be the most important influence on the initiation of the spring bloom. In 1984, however, a large phytoplankton bloom occurred while daily irradiance was at its low winter levels. In al) other years for which irradiance and phytoplank-ton data are available, the spring bloom occurred after daily irradiance had increased to greater than 300 Langleys per day (NAI 1985b). In mest years, the initial bloom occurred before the water column was stabilized by thermal stratification. By midsummer, when surface nutrients may have been depleted due to algal consumption and a strong thermocline may have restricted the supply of nutrients from deeper waters to the surface, algal abundance declined, r,ising again in late summer as the 80
D N 0 t a
.S s
.A r
.J 8 'O ee 1
' t n ai
.J 9 1 l
wl M 'O 68 e es
.A 'S 1 9 ca M
aB A f F 'J rk uo
.J sor D 'D nb i a N 'N ' e nS 0 'O o t
'S I
.S k .
'A n6
.A a8 _
.J 0 'J l 9 p1
.J9 8 'J o t ,
1
'N yr
.M he 4
.A 'A 8 pb 9 m
.M 'M1 re _
.F F ec ,
t e J aD
.J D 'D w-y ,
el
.N N l u oJ 0 'O h wd
.S S n
'A f a
.A o V
.J9
.M J
9 7 1 W ' J
'J9
'M 3
R 1 e8 c9 n1 a-4 d8 A n7 _
.A u9 M 'M _
b1 . a 6
- , .rJ 'f ,8 _
J n29 _
. aP1
'0 e
.O N 'N mnot ,
li r I' 0 0 at o t ap 5 '$ ot e A TSR
.A J87 'J 2 .
' R 9 J91 1
.J 1 M 'M 2 .
LJ . A A 1 - g
.M 3
.F
. e _
J 3 r u .
, - - , 7 g 0 0 0 0 0 0 0 0 0 0 0 0 i 0 0 0 0 0 0 0 0 0 0 0 0 F 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 O 0 1 0 0 0 0 1 0 0 0 O 1 m
0, 0 0 1 0 0 0 i 0 0 1 0 0 1 0 1 0 1 . 1 1 cg5) c eaun N E3dU m o o
i i thermocline began to dissipate (Figures 3.1.1-2 and 3.1.2-1). The late i summer bloom in 1981 was an exception; it commenced in the presence of a fairly strong thermocline. In any given year a small number of taxa accounted for over 90% of total abundance, but relative abundances of component taxa have undergone considerable annual variation (Table 3.1.2-1). For example, although Skeletonema costatum has ranked among the dominant four taxa during all years, its relative contribution to the total phytoplankton community has ranged from 3% (1983) to 78% (1980) of total cell abundance. Phaeocystis pouchetil comprised 5-10% of total annual abundance from 1978 through 1981 and 58% in 1983, but was absent from 1982 and 1984 collections. Based on overall relative abundance, it appears that phytoplankton assemblages for the years 1978-1980 were more similar to each other than to those of subsequent years in that Skeletonoma costatum, Rhizosolenta dellcatula and Phaeocystis pouchetti combined were the overwhelming dominants in the earlier years. From 1981 through 1984 Skeletonema costatum and Chaetocaros spp, were the only taxa that consistently appearred among the dominants (>1% composi-tion)(Table 3.1.2-1). Phytoplankton species succession followed in some respects the patterns described by Margalef (1958, northwest coast of Spain) and Lillick (1940, Gulf of Maine) who held that nutrient supply is the main determinant of succession and that temperature is important only insofar ; as it works to enhance or restrict nutrient supplies within thermal ! strata. Margalef proposed the following typical progression: 1) small-celled species in the spring, capable of rapid division due to a high surface area-to-volume ratio, succeeded by 2) larger flagellates and diatoms with a lower turnover rate, followed by 3) large motile forms (flagellates and dinoflagellates) during the period of highest thermal stratification (Margalef 1958). Observations of phytoplankton in New Hampshire coastal waters during the study period revealed similar successional stages (Table 3.1.2-2). 82
. _ _ . _ _ _ _ _ m. .
I 4 1 TABLE 3.1.2-1. ANNUAL PERCI NI COMPOSillON ( >1.0%) Of Witol l WATER PlfYTOPLANKTON IN SURFACE WATERS AT 1810 NEARFIELD STATION P2, 1918-1984. SEAHROOK BASEt.INE REPORT, 1986. SPECIES 1978 1919 1980 1981 1982 1983 1984 SAe/econema costatum 43.9 10.1 77.9 T.2 30.6 3.0 33.2 Rhizosofenia delicatula 16.6 58.7 6.1 1.5 1.4 Phaeocystis pouchetii 9.1 10.4 4.5 T.9 57.5 Thalassionema nitzschioides 6.9 1.7 1.4 6.2 Mitzschia delicatissimm 8.8 1,7 1.0 28.8 1.4 Bac i l la riophyceae 4.4 1.5 2.5 Pleurosigma angulatum 1.4 Mitzschia seriata 1.2 1.2 9.1 Flagellates 6.7 9.6 23.4 4.8 Chroomonas sp. 2.6 2.8 co toglenales 2.5 La Unicellular alga 1.5 Dinophycese 1.5 2.0 Gyrodineum sp. 1.1
!=nrocentrum micans 6.3 Peridinium sp. 1.8 Heterocapsa triquetra 1.1 Cyanodinium sp. 2.3 Cerataulina bergonii 3.2 1.0 2.6 Chaetoceros debilis 5.2 17.6 Chaetoceros socialis 33.3 Chaetoceros sp. 2.5 2.1 1.0 2.5 Leptocylindrus minimus 4.5 7.8 2.1 ,
leptocylindrus danicus 1.9 Rhizosofenia fragilissima 12.9 2.1 Rhizosofenia sp. 1.0 Thalassiosira sp. 3.4 2.8 6.7 - 1.1 Cyanophyceae 4.5 Colonial Cyanophyceae 1.5 11.0 Percent of total cells 94.9% 96.7% 95.8% 92.0% 95.6% 93.4% 96.0% Numbe r of taxa >1.0% 7 10 7 17 11 9 11 Total number or taxa 76 64 50 99 77 81 90 i i i ?> t
4 _ C 3 123 3 123 1 _ E D 2 6 as O f 4
) -
1 - d 4 e 88 r4 2 236 3 6 u 9 2is 4 as in 1 V 3 2 t
- O n 0 N 2 3 36 6 o 8 1 C 9 1 14 0 ts
( 1
, 84 236 3 46 2 2 P T 3 214 2 C
N O 2 36 3 6 6 O s s I 1 1 i 01a T A 6 T 4 36 S 2 P 3 i s is D E L S 2 03 O 16 6 E 2 2 I 1 24 la 2 F R 2 A 4 36 23 E N G 3 is U 2 E A 2 1236 i i 6 T 1 0r4 0 T A l a 36 3 6 S L 3 2 4 in t f U f J 2 36 36 l A 1 2 2#4 04 W F . ft 3 3 C6 4 A8 N 3 ' s 28 4 2 2 I9 U R1 J 2 0 U 13s S , 1 34 2 i I NR IPO is 2 3 AI Y 3 23a 8 is 2 4 XR A A M 2 0 0 0 TE N 1 24 is 1 2 2 84 1 NI Ot 3 3 Ti 8 4 3 KS NA R 3 4 O 0 r4 4 AB P 3 3 L A 2 3 2 2 PK OO 1 1 i4 1 si 4 IO VR 3 l iH 4 3 3 PA E R 3 8 4 0 4 04 0 4 a S A 12 T M 2 3 2 23 123 N A . 1 4 4 4 4 N) Ib M( 4 2 2 2 O6 D8 B 3 t o 4 1 14 De 9 E F1 f 2 3 O3 0 0 O 3 4 O C 1 EE CD 4 N- f EL RU N 3 4 284 24 2 RJ A d U J 2 3 013 O CD c1 CN OA o K s s t
. E u i t 2 I e t . l e
- W e a L p a a h 2 a t L p t . i c e s A s s S p c u 1 c o F i T p o o s p p y c / J r N s s
3 h e C r e A s p e. a N i s N s s s E e o m e I s I o o i s L D t i e c R o a M r r t a B NS a r n y PS / i O e e sy on A UI l o h SI $ h D c c T ON l la t p /N s c o o c m RA e l e o RA A s G t t e e o o o
- N g i l n TN / z N c RI a c e a I I A t I 3 a n r AM l a k y NM h i R h h h h EO f R S C I O T M P C C P C YD WD S g
A c 4 C 3 2 - E D 2 046 6 0 - 1 4 3 6 26 V 3 2 O 6 N 2 3 1 4 0 4 6 3 T 3 a s 4 C 3 3 O 2 o 0 1 0 t 8 4 6 P 3 2 2 2 E S 2 3 16 0 84 1 4 e 1 8 l 8: 3 6 26 ic C 3 8s d e U . A 2 13 1236 r e - p 1 8: 04 s r e n 4 3 6 e r L 3 4 23 23 4 e U t J 2 3 6 t e 1 012 2 0 1 h e s 4 3 h s itr - N 3 2 t e - U e n J 2 O 0 w - s o 1 123a t d e 4 l t Y 3 3 itn A d e M 2 e d s i 1 1 r 9, e de p 3 s e -
#4 g 4 n F s i
R 3 s ie P tp y c m a e A 2 e d p s s 1 1 e h d c 4 e a 4 e k aF e ltn n e R 3 e w A e M 2 1 e : id n 3 e , 7 . m e 1 lt 6 8 6 l. s e 9 9 e tt i t 4 t 4 e p e ey s e eb n s a , H 3 1 e u d 9 8 d e I e s J. = 91 e F 2 t y l n r 3 c s 1 e e , e re ews k 0 e 8 s e e e 9 e - 4 p J w 5 s r ; ( e t N 3 s o S rI e p a t. A h - e . 1 J 2 01 13 . 9 y d C 89 5 . e 1 h 8 s ry e lp S u e e 19 a n r n d it l a s i K h i = 6g o t f . t n f p d 2 d e o w . p e et k t m e h c p s t p e s -, ( S s s s g cew e e T n . 1 s n a t 2 N s i p t u S a ae i v 3 e ,
. Ae u s s A a r I am md s ae t
e 4 t a 4 2 N e t s F ia d M ii ei e m t e e
- a c i a nl n A ns no l l
ic t4 2 eM e a at i D NS eu i N es oi a e m e s e s d y e 6 O c r ia n l t l I li ih i o t a f e c. 1 D y t hc e AI M sc oa y c M O ol sc si ss t p t t d e 4 a g* l -
. h i ci l e s e 3 R p r sl o RA oi o D og az e e 3 senm .
7 m t ze s I N zl t za l t r ss u at op t wa E M r n td o MI ie p 1 . i r ai t s e F. sa t M i e i z MM hd e 1 hf hn e r y e= 8 U p C M i UO R l A R T F n h r M9G aCd e A S h SD I S e b e d I R
The spring bloom was initiated by different taxa fron, year to year. Centric diatoms (esp. Thalassiostra spp., Chaeteceros spp., and Skeletonema costatum) were most often among the first to appear in high densities. Small flagellates and colonial bluegreen algae (Cyanophyceae) were also t>ong the spring dominants. Large vernal blooms of Phaeo-cystis pouchettti occurred in five of s'even years. Bv midsummer, dinoflagellates appeared in high numbers. Diatoms (particular1:' Sk e le t o nemar Rhizossienta, Leptocylindrus and Mitzschta) retched their highest densities in the fall, and were the most important winter group in all years. The dominance patterns of the summer and fall of 1986 were similar to those of other years, except that colonial bluegreens maintained unusually high abundances and Skele tonema and Leptocylindrus showed uncharacteristic July peaks (Table 3.1.2-2; NAI 1980c, 1981d, 1982a, 1983a, 1984a, 1985a, 1987). There was a fairly strong inverse relationship between nitro-gen, particularly in the form of nitrate, and phytoplankton abundance in most years, including 1986 (Figures 3.1.1-6 and 3.1.2-1). In 1980, however, when nitrate was present in average concentrations but ammonia levels were very high (Figure 3.1.1-7), algal abundance and total nitrogen rose and fell simultaneously throughout the year. The phos-phorus cycle bore no such recognizable relationship to phytoplankton 1 abundance in any year (Figures 3.1.1-S and 3.1.2-1), suggesting that ) phosphorus was usually not limiting in these waters. This corroborates the results of other studies (Bigelow, Lillick and Sears 1939; Redfield Smith and Ketchum 1937) which have shown that nitrate, not phosphorus, is the main limiting nutrient in the Gulf of Maine. l l l Nearfield and Farfield Assem~olares: 1982 - 1986 ' Total monthly phytoplankton abundance at Stations P2 and P7 showed a statistically significant (a=.05) correlation between stations during the period 1982-1986. Abundances at P2 and PS, July-Decembe r 86 l
m - f 1986, were likewise significantly correlated. Percent composition and frequency of occurrence of most dominant r,pecies has been similar in the nearfield and the farfield (Table 3.1.2-3; NAI 1985b). , A large bloom of Chasteceros soef alls in mid-June 1984 and occasional blooms of colonial bluegreens in 1986 reduced the apparent similarity between stations in those years. The general problem of patchy distribution of phytoplankton populations is magnified in the case of colonial species like Chaetoceros soe f alls or colonial blue-greens which may form colonies of hundreds or thousands of cells. In the process of subsampling, the random inclusion or exclusion of even a single such colony may result in apparent density differences of tens of thousands when expanded to number of cells per liter. Chlorophyll a: 1977 - 1986 The annual biomass (chlorophyll a) cycle generally followed the total phytoplankton abundance cycle, although the magnitudes of coincident changes were frequently not comparable (Figure 3.1.2-1 and 3.1.2-2). Biomass deviated conspicuously from abundance trends on a few occasions. For instance, the two highest chlorophyll a peaks recorded during the seven-year period of observation occurred in 1980, at times of only moderate-to-low overall phytoplankton abundance. Annual differ-ences in chlorophyll a levels appeared to bear some relationship to ammonia concentrations. The numerous and high bicmass peaks in 1980 were coincident with high ammonia concentrations in that year (Figures 3.1.1-7 and 3.1.2-2). Blomass measurements from 1982 through 1986, on the other hand, were comparatively low with reduced seasonal peaks; ammonia concentrations during that period were the lowest for the eight years of record. ! There was no significant (a=.05) difference in chlorophyll a j concentrations between Stations P2 and P7, 1982-1984, nor between l Stations P2, P5 ar.d P7 in 1986, i 87 I
i I i r TABLE 3.1.2-3. ANNUAL PERCENI COMPOSITION (>1%) AND FRIQUENCY OF OCCURHf NCE OF WHOLE WATER PHYTOPLANMTON IN SURFACE WATERS AT STATIONS P2, P5 AND P7, JULY-DI Cf MBER. 1986. SEABROOK BASELINE REPORT. '766. t PERCENT COMPOSIT ION PERCENT FREQUENCY OF OCCURRENCE P2 PS P7 P2 PS P7 SAeteroness costJtus 34 36 37 95 95 100 Cyanophyceae; colonial 33 16 2 77 TT 55 tcptocylindrus mininus 10 12 19 95 100 91 '7 Mhizosofenia fragilissins T 9 13 64 68 68 flagellates 5 8 12 100 100 100 Mitzschis delicatissima 3 3 3 73 91 71 Merisnopedia sp. 1 4 3 14 9 9 Dinophyceae 1 2 2 100 95 95 Thalassiosirs sp. 1 2 2 59 45 41 Centrales 1 2 2 100 1n0 100 os Cheetoceros sp. 1 2 1 64 59 59 0* Thalassionens nitzschioides 1 1 1 64 55 59 Centr / tractus sp. <1 <1 1 68~ 86 73 Total mean abundance (in 1000's of cells / liter) 2367 1707 1300 1
- _ . _ _ . - _ _ _ _ _ _ _ . _ _ _ _ . - _ _ _ - . _ _ - - - - - - - - _ - - . _ _ - - _ - - _ _ - _ - - . __ -w . _ - , ,n u . ,
l l 1l 6 5 6 6 8 5 91 5 3 6 h 6 A 3 K 1 3 9 1 d d - A y I l 3 u I 5 J 5 d 8 n 5 5 a 3 3 8 4 . 3 9 1 86 k 98
.k 1 9 b 1 I 7
'J I
7 , 5 9t E 1 r U
, p o
5 2 e
'J 2 H PR 9
3 [E 1 ne A on i i E tl i U ae t s b S a E B U t ak 5 o .
) o 3
J 3 4 1 ar _. k b _ k l a _ M l e . i yS _ _ IJ h d p 5 o . _ 5 r6 . g 5 o8 _ 5 l 9 0 h1 _ [J 1 3 9 C ( , - r - se - Y b sb am N me oc i i e 0 BD 5 5 9 . 3 7 3 9 2
) 5 1
3 'A 2 m k
/ 1 g i
( m lJ b 3 i e a b r l
'5 5
u g l 3 81 i y ) 91 F h M p k o h r h o l h bb C h 1 1 5 9 A 1 3 5 0 5 0 b 2 2 1 1
~t T E
PSP Levels Gonyaulax sp. has been recorded at Station P2 on only six occasions (June 1978, May and June 1979, July and September 1982 and June 1984,), with highest densities recorded in 1984. This species is of interest because it can cause paralytic shellfish poisoning (PSP). PSP toxicity levels-in Myttlus edults, as measured by New Hantpshire and Massachusetts' public health offices, were compared between Hampton Harbor, NH and Essex Estuary, MA from 1972 through 1986 (Figure 3.1.2-3). The maximum toxicity level acceptable for human consumption was exceeded during most years for a period of one to seven weeks in Loth locations. In 1972, toxic levels of PSP were present at Hampton Harbor for 16 weeks from July through October. Peak values usually coincided in the two estuaries and have generally occurred in May or June since 1974. PSP levels were higher in Hampton Harbor than in Essax Estuary from 1981 through 1986. Peak levels in 1986 in Hampton Harbor were the highest since 1981; Essex peaks were not particularly high that year. 3.1.2.2 Selected Species Skeletonema costatum was chosen as a selected species because of its omnipresence and its dominance during much of the year. Skeletonema abundances during the study period were slightly bimodal in nature, showing a small peak in the spring (varying year to year from l February to May) and a major peak in the late summer or fall (varying from August to October) (Figure 3.1.2-4). Maximum densities during the late summer / fall bloom were highly variable among years, ranging from less than 0.1 million cells / liter (August 1983) to over 8.0 million cells / liter (September 1986) (Table 3.1.2-4). However, a Friedman's l l l 90 l l
4mo 7 A iq 8198g ---- ESSE X ,MA. 54m g g) . .-s AMrires, et.lt. J ltAMPION.N.II. 8'# l l s 700 E5st x, m,q ti [ 6sn ll j llI g 500 7 iI 88 6'- 400 I II I Ii et 300, gg
& ,j g 2m. iL ,, ll
$ '*-o .l.
a n_-----.,. - -, ! i - - - -) -
. f - -. - - - _
p JJA n JA B AnJ A 4'N'bl 9'F'n A'n'/IA'[/EOl B','n' n'E/EA'/EEel p' y 'E m se J'J'a'5'O'Ee l t' F'n' A'n'(( A'S'O'e[8' 1972 1973 1974 1975 1976 1977 1978 { 3 4000' O t ain. 1
. SM-u g 800 o
w R im. (M) . 500. 400 300 ; 200. a[e
- -~
, 4~ T *~ T -_- ~'T -'T ! %~-~ % M - ~ - ---
t----- 1-- aVnYn's'/n's'o'n'e4.'e'n'nV//n'.'/n'el.','nTaV//n's'in' 4.WNJ'.77sW@'n7n'//a'n'a'n' 18a'n'n'//a'n'O'n'n D's 'n'n'n'a'J'n's'o'e'el n 'n'n'n'a'a'n's'a'n'c 1981 19G2 19R3 1984 1985 1986 1979 1960 Figure 3.1.2-3. PSP toxicity levels in Mytilus edulis
- f rom Harmpton Harbor Estuary, N.H. and Essex Estuary, HA. Data courtesy of: New Hampshire Division of Public Health and Massachusetts Department of Public Health, Lawrence Experimental Station. Seabrook Baseline Report, 1986.
i *r5r levels measured la sova arenaria only, Essen Estuary, for else following perioJan June 11 24, Aug 26-sep 3,1985; June 1-July 22,19tl6.
.- ,- ., . ., ._- -- - - . . .- . ~. - - . .I i
10000000 + 1
$u00000 + lt I /\
l /0 \ 8 0 I \ 0 1000000 + / g 3 j 2 g 8 I g 4 500000 + 0 I g i / 9 s I % / % 8 9 1 3 4s s "N N l 2 0 % / I c 50000 + \ / s 9 f l \ / \ L l \ / 4s O
, 8 I b 2p* \ 2 s 10000 + 8
- 4 s l 2 SOOO + 4 2 9 4
I 8 2 8 I ND P I O 2 3. k l 9 9 1 8 0 3 1000 +
- 3 0
- 8 t I 1 8 4 e i 1500 + 9 4 N I i 1
[ l n 1 3 300 + 1 OU
- O 8.9 ETC.
- tA5T OtGIT or 5mett TEAR; MIS 5inG POInis DUE 10 onat ArrinG vAtut5 l
. 10 + - - _ . 3986 i S+ -* - = Att TEAfts* man. 1978-84 8 1 I r 1 4 0+ 8 0 j .....................................__,....._..+.____ _,_ ....._ ..... __,___............ _ ......__ ...
! JAff FEB HAR APR HAY JUN JUL AUG SEP OCT Isov DEC Hotelse l
J a j Figure 3.1.2-4. Monthly mean abundance (log x+1 cells per liter) of Skelefonenu
; costatwn at nearfield Station P2.for each year and over all years from 1978-1984 and July-December 1986. Seabrook Baseline Report, 1986.
i _ _ _ _ _ _ - _ _ . - _ _ _ _ _ _ _ _ _= _ ____
c TABLE 3.1.2-4. PEAK FALL ABUNDANCES OF SKELETONEMA COSTATun IN SURFACE WATERS AT STATION P2, 1978-1986. SEABROOK BASELINE REPORT, 1986. Month of Mean Abundance in Cells / Liter Maximum Occurrence 1978 1979 1980 1981 1982' 1983 1984 1986 6 4 August 1.2x10 8.7x10 6 September 6 5 2.5x10 2.2x10 9.2x10 3 4.5x106 8.7x10 6 October 2.2x10
- test of monthly Skeletenema abundances revealed no significant differ- ,
ences (a=.05) among years, 1978-1984. A spatial comparison of seasone.1 SAele tonema abundance in the nearfield and farfield showed no signifi-cant differences between stations in any season for the period 1978-1984 (NAI 1985b). Likewise, seasonal Skele tonema abundances at PS were not , significantly different from those at P2 in 1986 (Table 3.1.2-5). TABLE 3.1.2-5. SEASONAL MEAN ABUNDANCES OF SKELETONEMA COSTATUM AT STATIONS P2 AND PS, JULY-DECEMBER, 1986. SEABROOK BASELINE REPORT, 1986. ; P2 P5 SIGNIF. _a _ X SD X SD Jul-Sep 1519.9 3528.0 1370.9 3003.6 NS Oct-Dec 101.4 151.8 59.1 100.5 NS i Mean abundances in 1000's of cells / liter NS = no significant difference (a=.05) between stations as determined by ANOVA. 93 I i
l l 1 l l l I l 3.1.3 Microzooplankton l 3.1.3.1 Total Community Seasonal Characteristics, Temporal variability in the nearshore surface microzooplankt.on community (surface and bottom collections combined) for the period 1978-1984 was exa91ned using cluster analysis. Normal numerical clan-sification divided semi-monthly abundances into 11 seasonal groups (Table 3.1.3-1). Results suggested that there was very little variation in the seasonal cycle among the years studied in terms of species composition, but that numerical dominance sometimes shifted (Table I 3.1.3-2). The greatest variation occurred from late spring through summer, causing the formation of subgroups within Group 4. This high variability was associated with higher productivity in comparison to r other seasons, both in terms of magnitude of abundances and num'aer of 1 taxa attaining high abundances. Although secsonal groups rarely included "outlying" collections (i.e., collections separated from the rest of the group by more than two weeks), there was considerable overlap of sampling periods encompassed by consecutive collection J groups. In general, the seasonal groups based on species abandances l encompassed collection periods with similar temperature regimes, partic- l ularly with respect to the position and intensity of the annual therm- i ocline (Tabis 3.1.3-2). 1 Seasonal patterns in the microzooplankton assemb1pge were i delineated by channes both in total abundance and in dominance structure (Table 3.1.3-2). Lifestages of the copepods orthena sp. ar.d Pseudocalanus sp. were abundant in virtually every seasonal group. Wint+r microzoo- 1 I plankton assemblages (Groups 1 and 2) were generally charapterized by ' few taxa and mode rate abundances (Table 3.1.3-2) except w!!en tintinnids ] 4 pulsed and abunAi nces rose (the high abundance in Group 1, represents a high count from a single collection date). Inthesprins/(Groups 3and l 1
/
I l 94 < l 1
. l , " . - P 6
8 G9 4 N1 _ O C 3 d . M , ( e AT D 2 u R n SO 1 i - EP t UE n LR 4 o 7 A c VE V 3 - N O r YI N 2 - TL , . IE 1 RS AA , LB 4 I , MK T 3 IO C SO O 2 R SB 1
. I A TE 1 RS 4 U 2 C P 3
- . E 1
Y4 S 2 . A8 R9 1 B1 F8 4 O7 9 9 C 3 N1 U - O A 2 8 I , m T2 1 0 94 AP . C IN 4 3 8 IO Il L 3 0 914 Sl U SA J 2 8 AT LS 1 0 914 C D LL 4 0 3 _ A[ N 894 1 IClF U 3 RR J 2 0 EA ME 1 4 9 823 1 < UN _ N M 4 8O _ LO _ AR Y 3 4 9 3 ._ MF A _ R M 2 83 9O _ OS _ NN 1 14 02 O YI BT 4 893 C . DE R 3 2 014 EL P ML A 2 2 83 9 RO OC 1 4 01 F - N SO 4 8913 PT UK R 3 04 892 ON A RA GL M 2 3 1 _ P 1 94 . LO _ AO NI 4 2 _ OO SR B 3 1 _ AC E EI T 2 8O3 SM 1 _ 1 4 _ 3 N 3 24 A C _ 1 J 2 9 3 3 1 b ) E ) f . L K 5 / - r ) ) B E - ) r ) 8 0 e 0 C A E 2 3 e 2 4 8 m 4 ,44 _ u - T W ( ( t ( ( 9 ) s ( 98( 7 5 n S 0 10f u 3 793 5 6 i 6 A 7 8 - CS 7 D 917 ~ 1 r 2r 3Wg, n/ 4g. n/ 4r7. e/. C 4 y / 4r1 e- ,/ - e / e/ Pt 4 Pt6 Pei0 Pi3 Pn8A u Pl35 Pm816 u Un 6 Oi Un6 Oi Utr7 Oap Ur7 Op. Um74 Oa .( Ur87 Oa9 Us787 Ou99 RW RW RLS RS RS R[1 RS11 C C C C C C C
,u s
j'
TABLE 3.1.3-1. (Continued) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC WEEK 1234 1 234 1234 1 234 1234 1234 1 234 1 234 1 234 1 234 1 234 1 234 GROUP 4E 1 2 Late Spring 1981, 1982
.80/.72(4C,D)
CaoUP 4r o 9 9 9 9 Late Summer / [arly f all 1979
.74/.71(4C-E)
GROUP 5A 232 ) 81 804 , Late Summer 2 2 23 3 3 3
.70/.69(58) 3 3 4 l ,
't e
GROUP $8 0 8 8382 8809 809 falI 1 0 0 1 9212 1 i .72/.69(5A1 1 2 0 43 2 ' 4 4 1 3 4 UNGROUPED 8 4 2 2 O l a I = dates 1-8, 2 = dates 9-15, 3 = dates 16-23, 4 = dates 24-31 b within-group Bray-Curtis similarity value/between-group Bray-Curtis simila ri ty (closest group) c 8,9,0,1,2,3,4 = last digit or sampling year l l l l
TABLE 3.1.3-2. DOMINANT SPECl[S OCCURRING IN ST ASONAL CROUPS FORMED IW NORMAL. CLAS$1FICAT ION Of MICROIOOPLANKION COttfCIIONS AVERAGED OVin OLPIO AI NEARflLLD STAllON P2 FROM 191E-19884 S[Af1 ROOK OASILIN[ REPORT, 1986. SAMPL E ,, a % b c CROUP DOMINANI IAXA (GROUP) y f it! Q. TEMPERA 10RE CH.ARACTERISTICS 1 lintinnidae (C) 8600 100 no st ra t i rica t ion, ve ry low WINILR Copepoda nauplius (A) 184 00 100 temperatures Oithona sp. (A) 900 100 AT (-0.1 ) - (-0.8 )oC, dec rea s i ng tempora I Iy
? Oithona sp. (A) 1000 100 no stratirication, tempe ra tu re WINIIR Cirripedia (0) 800 100 reaches nadir AT o.1-1.4 0C, f l uc tua t i ng tempo ra l l y ist4 00 8ts
$ 3 t All Rotifera (D)
Oithona sp. (A) 2300 100 initiation of' thermal stra ti rica t ion WINIER/ Pseudoca/ anus /Cs/ anus sp. nauptius (A) 1800 100 A T O.0-84 .60C, SPRING Copepoda naupliass ( A) 1400 100 inc rea s i ng tempora l ly 1A 4 Oithona sp. (A) 8000 100 developing thermocline SPRING Copepoda natsplius ( A) 7900 100 Ai 0.1-7.10 C, Bivalvia ve l ige r la rva (A) 5700 100 inc rea s ing tempora l ly Rotifera (D) Sf400 83 rseudocalanus/Calanus sp. naveIius (A) 4300 100 Pseudcca/ anus sp. (A) 1700 100 Polychaeta l a rva ( IS ) 1600 100 fan Bivalvia veliger larva (A) 39800 100 strong thermocli.a, surface peak SUMMin pseudocatanus/Catanus sp. nauplius ( A) 10800 100 AT 1.1-1.40C, 1980 Copepoda nauplius (A) 8100 100 increasing tempora l ly
- Pseudocalanus sp. (A} 6100 100 Oithona sp. (A) $300 100 fvadno sp. ([) 1100 100 isC Copepoda naisplius ( A) 22100 100 mode ra te to os t rc.ngest the rmoc l ine I AI.1 Y Oithona sp. (A) $700 II)O di 1.1-7.16 C, tempora r i ly SUM *HR furytemors sp. copepodite (C) 2700 83 dissipates in July due to rising 1983 Acartis sp. copepodite (D) 2200 100 bottom temperatures pseudocs/ anus sp. (A) 1800 100 rseudocs/ Anus /Catanus sp. nauplius ( A) 1100 100 1vadne sp. ([} 1300 100 femora longicornis (B) 1200 100
TABLE 3.1.3-2 (continued). SAMPLE _a x
% b ITMPERATURE CHARACTERISTICS c
GROUP DOMINANT IAXA (CROUP) F RE Q. 4D Divalvis veliger la rva (A) 18900 100 bottom temperature continues to SUMMER
- Oighons sp. (A) 1700 100 i nc rea se whi le inc rea se in 1918-1919, Copepoda nauplius ( A) 6TOO 100 surface slacks orr, surface 1981, 198's Pseudocs/snus/Catsnus sp. naupl ius ( A) 4500 100 peak (most years) rseudocsisnus sp. (A) 4000 100 lintinnidae (C) 3800 94 AT O.1-T.9 0C, increasing Gastropoda veliger la rva (B) 1900 100 then decreasing temporally fysdne sp. (E) 1300 1m) 4L Tintinnidae (C) 32000 100 weak thermocline IATE O/thonA sp. (A) 7400 100 '
sprit 4G rseudocstanus/Catsnus sp. nauplius ( A) 3600 100 af 2.0-4.2 0C, increasing 1981, pseudocs/snus sp. (A) 1500 1(X) tempo ra l ly 1982 Copepoda nauplius ( A) 1(WV) 100 q, oo 4T Olghons sp. (A) 1900 1(N) wea k the rmocl i ne (ARLY Copepoda napplius ( A) 2900 1(X) F Al l Pseudocs/snus/Cs/sous sp. napplius (A) 2600 100 A T O.8-7.10C, decreasing 1979 rseudocs/snus sp. (A) 1400 100 tempo ra l ly 5A Oighons sp. (A) 6600 100 thermocline starting to degrade, IATE rseudocatsnus/Catsnus sp. nauplius ( A) 4100 100 curf ace temperatures declining,
$UMMER Copepoda nauplius ( A) 3800 100 bottom temperatures variable rscudocsisnus sp. (A) 2900 1t10 (peak, some years)
Bivalvia veliger la rva ( A) 2500 100 AT (-0.1)-8.50C, decreasing Tenora longicornis (D) 900 95 temporally
$n O/thons sp. (A) 2600 100 thermocline completely broken FALL Copepoda nauplius (A) 2000 100 down, both surface and bottos Tintinnidae (C) 1500 94 temperatures continue to de-Pseudocs/snus/Csfsnus sp. nauplius (A) 1100 1DO cline, bot tom peak ( some years)
AI (0.01-4.20C, decrea sing tempo ra l ly a 3 sean abundance (no./m ) in sample group b pe rcen t f requency or occurrence in sample group C based on continuous temperature records at nearfield station ID
4A), population densities of the dominant copepods (althone sp., Psesdocolanus sp., Pseudocolanus/Calanus sp. nauplii, Copepoda nauplii) increased substantially. Spawning by benthic species introduced large numbers of planktonic larvae into the assemblage during this period, and rotifer production was also high. Abundances of the entire microzoo-plankton assemblage peaked during the summer (Groups 4B,C D.E and SA) when copepod productivity was at its highest and benthic species (particularly bivalves and gastropods) continued to contribute large numbers of individuals to the meroplankton. The large number of taxa contributing to the summer assemblage may have made the summer variabil-ity among years more apparent than variability during other seasons. In summer 1980 (Group 4B) Pseudocolanus/Calanus sp. nauplii, Pseudecolanus sp. and Bivalvia veligers were particularly abundant. In early summer , 1983 (Group 4C) copepoda nauplii predominated; by late summer Otthona sp. became dominant. Bivalve veligers were dominant in late summer of 1986. The dominant copepods continued to maintain moderate populations through the fall while most other taxa declined to nondominant status. Tintinnid abundance patterns were extremely variable year-to-year, and often served to upset the general dominance patterns described above. Tintinnids occurred in very high densities in 1981, 1982 and 1986 with dominating peaks between June and January. In summary, the microzooplankton community structure was generally consistent throughout the period of study, with the greatest annual variability evident d, ring the summer when both abundance and I i number of abundant species was highest. The community structure was l l influenced primarily by the dynamics of the of thona sp. and Pseudoealanus sp. populations and by the production of early lifestages (nauplii) of other copepods. Other taxa exerted only ephemeral influence en commun-ity structure. 99
+-e tr n-m- -
m , pr-- e - -.: -T-
Spatial Patterns of Microzooplankton Abundances The microzooplankton community was sampled in two dimensions, horizontal (stations) and vertical (depths). Numerical classification i of the 1982 surface collections indicated that horizontal differences were negligible (NAI 1983b). Species assemblages from Stations P2 and P7 were similar on all dates for the period 1978-1984 except for l November 15, 1982, which was a transitional period between the two fall groups (NAI 1983b). Both' species composition and seasonal patterns were similar between the two stations. Percent composition and frequency of ' occurrences of dominant species in 1986 collections were also similar between Stations P2, PS and P7 (Table 3.1.3-3). Monthly total abundances for 1982-1984 were not significantly different between stations P2 and P7 (NAI 1985b). Some taxa exhibited apparently large differences in rank (Gastropoda veligers) or percent composition (Rotifera, Bivalvia veliger larvae) between stations, but abundances were not significantly different. 1 r The microzooplankton community exhibited more variability in the vertical dimension than in the horizontal (NAI 1985b). Total' abundances in surface and bottom collections (1982-1984) were statis-tically similar (NAI 1985b); therefore, only abundances of taxa which exhibited apparently large differences in rank between depths (Poly-chaeta larvae, Microsotella norvegica, Pseudocalanus sp. female, Acart ta sp. copepodites, Centrepages sp. copepodites) or in percent composition (Bivalvia veligers, Copepoda naup111, Rotifera) were compared. Of l l these, polychaete larvae, Mterosetella nervatica and Pseudocolonus sp. l females were significantly more abundant in bottom collections, while Centropages sp. copepodites and Copepoda nauplii were significantly more I abundant near the surface (NAI 1985b). Acartta sp. copepodites and rotifers were distributed similarly at the depths sampled. Bivalve valigers exhibited a tendency toward a greater abundance near the bottom, but the difference was not significant (NAI 1985b). In 1986, 1 they tended to be more abundant near the surface. Many species of j 100
a-- _ TABLE 3.1.3-3. PERCENT COMPOSITION AND FREQUENCY OF OCCURRENCE OF DOMINA!E SPECIES IN MICROZOOPLANKIT)N COLLECTIONS BE'IVEEN STATIONS P2, P5 AND P7, JULY-DECEMBER, 1986. SEABROOK BASELINE REPORT, 1986. PERCENT COMPOSITION PERCE!E FREQUENCY OF OCCURRENCE (n=22) SURFACE BOTTOM SURFACE BOTTOM P2 PS P7 P2 PS P7 P2 PS P7 P2 PS P7 Tintinnidae 30 29 37 11 26 14 82 64 82 100 95 86 Copepoda nauplius 19 16 18 13 10 8 100 100 100 100 100 100 Bivalvia veliger larvae 6 9 4 24 30 29 91 86 86 95 77 95 Oithona sp. nauplius 13 15 11 8 3 4 100 100 100 95 95 95 { Oithona sp. copepodite 10 12 11 13 4 6 100 100 100 100 100 100 Pseudocalanus/Calanus sp. nauplius 10 8 7 7 7 4 100 100 100 100 95 100 Pseudocalanus sp. copepodite 5 3 4 3 4 4 95 100 91 100 95 100 Oithona sp. female 2 2 2 4 1 1 95 100 100 95 100 95 Pseudocalanus sp. female 2 1 2 2 2 1 64 64 55 73 68 95 Gastropoda veliger larva <1 <1 <1 2 1 8 45 41 50 82 82 86 i Centropames sp. copepodite 2 2 1 <1 <1 <1 59 59 64 27 45 36 Microsetella norverica <1 <1 <1 4 1 5 41 64 64 86 95 91 Bryozoa cyphonautes <1 1 <1 2 3 1 55 50 73 55 64 45 Opishtobranchia veliger larva <1 <1 <1 1 1 5 45 32 27 86 64 77 Polychaeta larva <1 <1 <1 1 1 4 18 32 23 86 68 91 Acartis sp. copepodite 1 <1 <1 1 <1 1 50 36 73 73 50 68 Total,mean abundance in 1000 s per cubic meter 32.3 46.5 42.5 21.9 20.5 21.4
bivalve veligers do exhibit ontogenetic changes in depth preference (Bayne 1963; Buyanovskii and Kulikova 1985; Carriker 1951; Verwey 1966), but the effect would tend to be masked in this study by the combining of species and lifestages during laboratory analysis. Bivalvia Veliner Larvae All bivalve veliger larvae were enumerated from pumped samples collected from April through October (see Section 3.3.7.1 for Mya arenaria results). Mytilus adults was clearly the dominant species, while Heteronomia squamula, Hlatella sp. and Modtelus modtetus were secondary dominants (Table 3.1.3-4). ,
#tatella sp. was present throughout the April through October period, with highest abundances usually occurring in June (Figure 3.1.3-1). Myt flus edults, Solenidae and Mya truncate were usually present by mid- to late May. Myt tius edults and Hya truncata peaked primarily in June or July. Solenidae peaks were noted in June, late August and October, possibly due to differential spawning of the three component species (Ensis directuso Sillqua costates S!!!qua squama).
i
#eteranomia squamula was usually present by early June, with highest abundances in either mid-August or mid-September. Mediolus mediolus was usually present by mid-June and has been highly variable in terms of peak abundance, with peaks in early June (1978) and in early October (1986), though most often in late August or early September. Spfsula solidissima and Macoma bolthlee did not appear consistently until July and August, respectively; these taxa peaked in late summer or fall. I l
Ploeopecten magellanicus was present sporadically throughout the l sampling period, with no clear seasonal peak. In general, larval peak abundances and periods of occurrence in 1986 were comparable to previous years with some exceptions. In 1986, Mytflus edulis peaked in early June, slightly earlier than usual and Macoma balthfea larvae were not observed (NAI 1986). 102 i
l l l TABLE 3.1.3-4. OVERALL PERCEhT COMPOSITION OF BIVALVIA VELI 0ER LARVAE IN 769 NET TOWS AT STATIONS P2 AND P7 FROM MID-APRIL THROUGH OCTOBER, 1982-1986 . SEABROOK BASELINE REPORT, 1986. l 1982 1983 1984 1986 SPECIES P2 P7 P2 P7 P2 P7 P2 P7 Mytilus edulis 44 54 59 47 77 83 61 54 Reteranonia squanula 21 14 4 17 4 3 12 15 Nistella sp. 9 8 17 13 8 6 10 9 j Modiolus codiolus 9 3 14 18 7 3 13 18 Spisula solidissima 6 8 1 1 1 <1 <1 1 Solenidae 3 4 3 2 2 2 1 2 Nya arenaria 4 5 1 <1 <1 <1 <1 <1 - Other Bivalvia 2 2 1 1 1 1 1 2 i 1 Mya truncata 1 1 <1 <1 <1 <1 <1 <1 Nacome balchica <1 <1 <1 <1 <1 <1 0 0 Placopecten magellanicus <1 <1 <1 <1 <1 <1 <1 <1 i Teredo navalis 0 0 0 0 0 <1 <1 <1 , 1
*0nly Mytilus edulis and Mya arenaria were enumerated in 1985.
b Formerly referred to as Anomia sp. f ( i i 103 I
- ~ m niatella sp.b SCALE
-, s .
x s Mytilus edulis W 1-108642 NO. YEARS PRESENT b C3 Modiolus modiolus -
' 2 .g PERIOD OF PEAK ABUNDANCE Heteranomia squamula l 2 OR MORE YEARS 4
s . - b Solenidae N I - F
- a. 1976-1986
- b. 1978-1984, 1986 E h r- ,
g Mya truncatal' g c. 1979-1984,1986 b f~ ' ' Placopecten magellanicus Ql ' L_. I
~
Spisula so11dissima' E Macoma balthica' ' I liII IIl 1lI il IIil lill I Ii1 I l 34123412341234123412341234 APR MAY JUNE JULY AUG SEPT OCT Figure 3.1.3-1. Weekly occurrence of bivalve veliger larvae at Station P2 fro:n mid-April through October from 1978 through 1986. Scabrook Baseline Report, 1986.
Stations added in 1986, P1 (Hampton Harbor) and PS (dis-charge), were not significantly different in mean total abundance from each other or from Stations P2 and P7 (Table 3.1.3-5). Also, in 1986 entrainment samples were collected within the Seabrook Station from late July through December. A comparison of weekly average abundances of the dominant bivalve larvae taxa showed that weekly occurrences of entrained larvae and offshore tows coincided, and overall abundances were similar (Table 3.1.3-6). When larvae were abundant (>1000/m-3), entrained densities differed greatly from those offshore. As only four of the sample dates coincided between the two programs, the observed differ-ences were probably due to normal day-to-day variations in density compounded by small-scale patchiness. 3.1.3.2 Selected Species The copepods Pseudocolanus sp. and ofthona sp. were selected for special analysis because of their dominant roles in the community. Their abundance and low trophic position make them important members of the marine food web. Eurytemore herdmant has been reported to be an abundant coastal copepod in the northern region of the western Atlantic (Katona 1971) and as such may be particularly sensitive to perturbations in the local temperature regime. Lifestages of these taxa were identi-fled to develop an understanding of cycles of recruitment. In some cases, the possible presence of cogeneric species made it impossible to routinely identify all lifestages to species. However.-information on these lifestages is included to present as complete a picture as possi-ble. Temporal (seasonal and annual) and spatial (horizontal and verti-cal) variability of these species was examined. Although some vertical differences did exist, temporel characteristics are described for surface and bottom collections combined. Spatial comparisons examined surface and bottom abundances separately. In addition to the selected species from microzooplankton tows, the bivalve Myttlus edults, one of 105
b W 1 TABLE 3.1.3-5. ANALYSIS OF VARIANCE COMPARISON OF MEAN TOTAL BIVALVE ! LARVAE ABUNDANCE AMONG ALL PLANKTON STATIONS (P1, P2, l PS AND P7) JULY 1 - OCTOBER 28, 1986. SEABROOK BASELINE REPORT 1986. SOURCE DF F-VALUE r STATION 3 0.46 NS ERROR 68 TOTAL 71 NS = Not significant l i l l 1 106 1
TABLE 3.1.5-6. CIMPARISON OF MEKLY memAntgs gyg'38 OF DOMIMANT SIVALTE LARVtE TAXA AT EARFIEID (P2 B AIS DETRAIBSGrr IEll STATIONS FRGE JULY 28 TM80UEst OCTtBER 28, 1986. SEA 8 ROOK 8ASELIE REPORT,1966. DATE MONTM JULY AUGUST SEPTDBER OCTtBER ALL MEEK 4 1 2 3 4 1 2 3 4 1 2 3 4* TANOtt STAT 1000 Mytilus edulis P2 50 29 396 31 461 310 709 2581 396 3815 181 35 89 333 El N 383 216 182 447 353 492 493 1427 5032 130 196 807 P2 1 <3 6 45 71 303 865 5987 4116 52207 726 86 72 5033 Modiolus medieL --'~ 77 671 763 445 614 1107 18875 38727 729 409 5118 El 5 N 152 e Meteranomia P2 61 20 752 252 2630 1985 14236 6273 350 10227 482 26 3769 1718 3842 941 4451 19358 8400 1060 1874 3458 90 24 4058 $ squamula El 146 N Niatella sr. P2 2 2 83 112 130 162 93 488 13 1 5 90 El 13 N 7 76 139 42 165 89 855 940 18 1 186 g arenaria P2 2 1 68 5 16 17 78 389 60 12 1 <1 78 El N 1 30 7.21 127 459 56 70 hanoftwosamplingdates All a mean of all dates Na not collected
t l the most abundant species encountered both in the bivalve larvae collec-tions and as an adult in the benthic collections, is discussed in terms of its temporal and spatial patterns of abundance. Eurytemore 80 Both Eurytemera sp. copepodites and E. Aerdmant adults have exhibited a high degree of variability in their annual means due to the extreme seasonality of the population (NAI 1985b). Eurytemera sp. copepodites were present in low numbers year-round, generally exhibiting short-term peak abundances in early or mid-summer. An additional-late fall peak was recorded in 1978, 1983 and 1986 (Figure 3.1.3-2). E. Aerdmant adults occurred in lower numbers than the copepodites and, contrary to observations from near Boston (Katona 1971), were essen-tially absert from the plankton from December through April (Figure 3.1.3-2, Taale 3.1.3-7). Eurytemore sp. copepodites and E. Aerdment ; j adults exhibited similar patterns of spatial distribution. Both were more abundant in bottom than surface collections, but abundances at nearfield Station P2 and farfield Station P7, 1978-1984 (NAI 1985b), and at P2 and discharge Station PS in 1986, were not significantly different l (a=0.05). , Earlier studies indicated that Eurytemera sp. copepodites and l E. Aerdment adult populations in Hampton Harbor and Nearfield Station P2 l underwent similar seasonal cycles, but during the spring the estuarine population was larger than the coastal populations by up to 1.5 orders of magnitude (NAI 1978b; 1979b). These observations suggest that recruitment to the coastal population may be dependent upon the estua- ] rine population. Other likely sources of recruitment in the spring are a maturation of and subsequent reproduction by overwintering copepodites (as suggested by Figure 3.1.3-2) and hatching of diapause (overwinter-ing) eggs. Although temperature conditions in the spring would result I in slow maturation, reproduction is possible (Corkett and McLaren 1970; i I 108 j l l
I i
- . i 4.9 tit.
- LAst 01G1T 0F $#9 t6 YtAR .
g M115tha POINTS DUt 70
- wou e e s OVILLAPPih; VAut5 1N6
~*-
- Au ttAts' MCAA THNU IM4 A. Copepodites j s o l
i , l
/, . ,/ . i 6 4 I I p 3 E 4 9 %
a too + 4 / P $
,#i
- I .
I i 0 W ' . de { e e C. i
*****a *
/
/s 3
'\ . p r s
*/t /
g \ i,
- i , .
,4 t
n s
\ t 60
% e S S t 1
1 ,e
. . . t, . ,-
t ,' .
\ g
+
I ew*..9.........*........9........4...................................2.........(.........................9... e Jan ett mas att we goe Jwt awG MP 048 nov HC - t acon t e f 6 4 i two
. B. Adults
- See
- 3 l 4 4 4
0 t t I m 4
* . i 8 Se
- e a
4 l
. i i i
(
,e*#. 's 4
. ., <> i 6
- 4 9
- g ,/ l C 4 J l # 6 a O t / 9 1
N r, . 8 i i . 9 s#s W 9 9
.s' *
/
6.D0.e..e.........a........4........3.........e.................................4........4.......9........9... apa 6(P DCf nov 0(C e das fit staa stav Jwn Jwt awG mein Figure 3.1.3-2 Monthly mean abundance (log x+1/m ) for each year and over all years at nearfield Station P2, 1978-1984 and Jul-Dec 1986 for 9 A. Eurytemora sp. copepodites and B, Eurytemora herdmani adults. Seabrook, Baseline Report. 1986. 109
3 FABtf 3.1.3 7. ANNUAL MEAN A809tDANCE (BASID Oft SURFACE AND 80110M AVERACES; NO./m ) AND STA800ARD DEVIAT8001 OF SELECTED SPECl[S OF HICROIOOPLARATOM AT Sf ABROOK NEARFl[tO STATIO90 (P2). SEA 8 ROOK BASE 1.196E REPORT. 1986. YEAR SPECl[S/LfffSTAGE 1978 19T9 1980 1981 1982 1983 1984 furytenors sp. 2 390 89 of 78 19 444 53 copepodites (SD) (1114) (13T) (133) (75) (34) (1209) (131) fu.ytenors herdasni 5 36 30 14 70 8 126 101 adisl ts (SD) (86) (66) (130) (98) (19) (245) (311) rseudocalsnus/Cassnus sp. E 2557 2350 2676 2130 2964 1920 1343 naarpl i i (50) (PT32) (2115) 13386) (2410) (3914) (2661) (1192) i 1162 1942 1253 1050 1329 1280 533 U o rsetxfocs/snus sp. copepodites (50) (983) (2876) (168T) (1830) (1420) (2026) (623) rseudocs/snut sp. E 127 280 291 234 350 266 101 adastts (50) (172) (451) (4??) (351) ($78) (452) (184) O/thons sp. E 1905 3682 I?60 2043 2515 1850 1018 naisp s I I (SD) (1684) (3491) (1063) (1594) (2689) '(?O38) (1367) Olthons sp. i 1577 3230 1218 923 1809 1537 627 copepodites (SD) (1324) (3326) (857) (494) (1583) (1646) (623) O/thons sp. i 234 442 327 440 492 446 173 edeelts (50) (211) (4TF) (243) (376) (302) (524) (153) Mytilus edutis E 4876 20389 2871 10115 1389 2279 6081 esmhoned ve l i9e rs (50) (18837) (63894) (3896) (14195) (2022) (5590) (9529) Jame-J uly 5 16320 7128T 6988 23896 2451 5667 13506 (SD) (17542) (110542) (49?3) (16057) (2447) (7065) (14494) s Based on oblique tows, eld-April throp9 t i October
McLaren and Corkett 1981). Spring-hatching diapause eggs have been , reported for both furytemore affinis (Grice and Marcus 1981) and I. am ricana (Marcus 1984) so it is a reasonable hypothesis that this is a recruitment strategy utilized by E. Aerdment. r i 1 Eseudocolanus so. 1 Pseudecelanus/Calanus sp. nauplif were present year-round ) (Figure 3.1.3-3) and were among the numerical dominants of the microzoo-j plankton community in all seasons except winter (Table 3.1.3-2). They attained their maximum abundance in early to mid-summer. Pseudocalanus sp. copepodites and adults (Figure 3.1.3-3) were also present throughout the year and occurred in peak abundances July through August. The copepodites were generally about one order of magnitude more abundant , 4 than the adults. The fall decline in abundances was most dramatic in l the adults, suggesting that overwintering by adults is not an important , } strategy for spring recruitment. Both nauplii and copepodites are l capable of undergoing a winter reduction of metabolic rate and develop-
- ment, renewing growth at the onset of suitable photoperiodic conditions [
] (Grice and Marcus 1981; Corkett and McLaren 1978). This enables I j Pseudocolanus sp. to take immediate advantage of optimal environmental , a conditions (food supply, temperature) for population growth. Both of these lifestages maintain substantial populations during the winter in l this area. Seasonal abundance patterns for all lifestages for the l 3 period July through December 1986, were similar to those of preceding i years. i 2 l 4 I There appeared to be no long-term trends in any of the life-l stages of Pseudocalanus sp. (or Pseudocalanus/Colanus sp.) examined in
- this study. Annual mean abundances were similar among yeara, 1978-1984; i they reached their lowest level in 1984 (Table 3.1.3-7). There were no i significant differences in horizontal distribution in any lifestage; l
\
9 111
. _ _ __ _ _ . - - . . _ ~ . _ .-.
A nauplii l . .
!/-)^ \, .
~
. I j ,, ,
./
.%!p, I . ./' .
' st',%
- s . t ,.
* \1 1 . . .
B.coperodites
- l .
]
./j/.>1~.l%.
i . - ' l/,/- A' -l.' 2'N 1
- i iNV t
'..,n:.. m ::;ne s a ,ca, i**
- Oy:Aa 901c5 M TC P;1114.plu i Autt g . --. . i n g ,
' =* * . 4 ttats' . tan THty 1984, eggen l.
man ' C. adults '
. 4
/ . N, t
. / ',s- t*\s.'t, .
i -
,/8 l
- \
g- . . , ,
.\' .
4
. --t -
. .. :1 l
I
+
h
- t'! ,
. 's .
i 1 . Figure 3.1.3-3 Monthly mean abundance (log x+1/m3) for each year and over all years at nearfield Station /2, 1978-1984 and Jul-Dec 1986, for A. Facudocalar.as/Cakmus sp. nauplii, B. Facudecak:as sp. copepodites, and C. Faer4docalanus sp. adults. Seabrook Baseline ; Report, 1986 , l 112
r t vertical distribution, however, varied among the lifestages (NAI 1985b, ; 1987). Pseudocolonus/calanus sp. nauplit occurred in similar abundances in surface and bottom collections; Pseudocolonus sp. copepodites and adults were more abundant in bottom waters (NAI 1985b, 1987). In 1986, 1 however, copepodites were considerably more abundant in surfsco waters; adults appeared in similar numbers in surface and bottom collections ~ (NAI 1987). > Oithena so. Oithona sp. lifestages were present year-round and were always among the most abundant microzooplankton taxa (Table 3.1.3 2). Nauplii ;
; a;.d copepodites occurred at similar levels of abundance; with adults 1
somewhat less abundant (Figure 3.1.3-4, Table 3.1.3-7). The timing of
; peak densities of nauplii was extremely variable among years, occurring !
I anytime between May and Decembar. Nauplit abundances were ordinarily i l depressed during winter and early spring, but densities only varied by 1.5 orders of magnitude between peak and nadir. Annual mean abundances . of nauplii suggested that this lifestage fluctuated on a several-year cycle (Table 3.1.3-7). Copepodites maintained high population levels between May and November, with peak levels attained July through j September. Oithona sp. adults exhibited the same general pattern of , seasonality as other lifestages but maintained a relatively smaller j 1 overwintering population than those of immature stages. Annual peaks of
! adults occurred between June and September. The degree of variability '
f i among annual means in adults was smaller than in the other lifestages ; suggesting that the size of the adult population is not greatly influenced by the typical higher variations in annual productivity and l mortality of the early lifestages. The seasonal patterns observed in the Seabrook area concur with descriptions of Oithone simills population dynamics in the Gulf of Maine (Fish 1936). - 1 ! l l \ 113
1 A. Nauplii ., , i
...-3 s.s .
*N -l/.N
'N.'
il i * [- .
'Q, i
- t. '
/. -
. :\' .' 1.
- i. IA, .
1 . 1 . goes i,
- B. Copepodites ? ----4, ,
,.g I * '
-% ;\. - I. '\, .
t4 i
~ g\i * '-
./- .
i *
~ V' .
t.) (TC. . LAST atstT Cr sasett ?tAA; riss!m3 70tNTS DUt *0 s OvtPtJ77tnG YALLT5
,, -...IM6
= *. . ALL vtAts iEAn THRU 1984
; '\
/.
- C. Adults
. 1
,/.h.'.-
't.
li
* / ' i.
\
. V. .
/ 1 'i
.,/ . \ *.
g . .
/p.- i i.
t/, -
'X. i i
\.'/ -
'?
i
. 4 l '
... ,. ... .. .T-Monthly mean abundance (log x+1/m 3 ) for each year and over Figure 3.1.3-4.
all years at nearfield Station P2, 1978-1984 and Jul-Dec 1986, for A. Olthona sp. nauplii, B. Olthona sp. copepodites and C. Olthona sp. adults. Seabrook Baseline Report, 1986. 114
As with the other selected copepod species, abundances of each lifestage of Otthona sp. were similar at Stations P2 and P7,1978-1984, (NAI 1985b), and at Stations P2 and PS in 1986. Otthona sp. nauplii and copepodites were more abundant in surface waters than in bottom waters; adults were distributed similarly between depths (NAI 1985b). Mytllus edults Umboned veligers of Myttlus edulis were usually present by mid- to late May (Figure 3.1.3-5). Once present, they occurred consis-tently throughout the sampling program. The protracted presence of larvae was due to recruitment patterns and duration of larval life-stages. Major spawning events in Gulf of Maine mussel populations may be limited to temperatures above 10-12*C (Podniesinski and McAlice 1986). Spawning of M. edults in Long Island Sound was found to be asynchronous both within and among local populations and to occur over a two to three month period (Fell and Belsamo 1985). Spawning of some Long Island Sound mussel populations was also restricted by limited food availability for most of the year, resulting in sporadic spawning events (Newell et al. 1962). Therefore it is probable, based o.i M. edulls' reproductive behavior, that recruitment of larvae to the plankton of New Hampshire coastal waters occurred throughout much of the sampling program. Recruitment from non-local sources was probable, as water masses may move large distances over the three to five weeks required for larval development at ambient temperatures (Bayne 1976). Delay of metamorphosis until suitable settlement conditions are encountered can prolong planktonic existence for up to 40 days, depending on tecperature (Bayne 1976). These factors suggest that planktonic recruitment to the study area was intermittent but prolonged, and duration of planktonic life varied over the sampling program as temperature conditions changed. 115
8,9 [TC.
- L AST DIGIT OF SAMPLE VEAR ,
t ArtnossI I MISSING POINTS DUE TO OVER-
! l LAPPING VALUCS '
l l ----
- 1986 l 5,5 +
I -*- = ALL YEAR $* IE AN
- t\
I 9 5.o e I% 9 1 5% i s 6 a 4.5 e f
- g *'-
8I 3 4 s 4 4 8 I 6 11 6 I l 's s2a 1 o I 4.0 e / 5 4 i
!. i
- 5 ft 5 0 g
g $ *
.f O 4 2 81 *g* 2 >
I 3 0 51 2 9 9 0 6 CE 3.5 e / 8 3 g 5 3\ 1
- sg
'g W
Q-l I i
/
5 5 2 3 8 4 \* 1 2
*b6d I 9
w o 3.0 I e f I g I 3 5\* 5 0
- f 9 1# f g go g
l O 4 2 8 5\ f 3 Z
<t i 5 3 1 2 4 \1* 26 '),' \
- e 2.5 e g si 3 3 g
2 6 f6 6-4 6 3 s g3 9 .,
$ 1 g 0
2 k, t 'g 2 s > l,,
'O 3 8 2 2 =
s. 3 0
< 8 l'
,$ % 4 1 4 O 2.0
- I 5 \ 1 1
6 O 1 1 9 ? \ 11 % 1 5 5 8 1 4 / J 6 % o I / l Ig / i 1 I 's '6a 3 %# 6 4 8 5 % / V
- t.5 e I I e i 1 8 . 8 2 8 9 8 5 ,
1.0 +
- 2 8 8
1 f a I s l 5 5 0.5
- f f 0 5 1 / 3 I i 5 3 ,,6 2 5 2 n.o e =-*-* 5 4 4 4 4
------..e....... ...+...+.....--e---*---e.--e...e-..............e---o- -o---*---o---+--.e--.e ..e_..+.... --+---+-..+- ..--.
I 2 3 4 9 2 3 4 9 2 3 4 1 2 3 4 4 2 3 4 1 2 3 4 3 2 3 4 APRIt. PIAY JUNE .tOL Y AlfGtfS t MPIftmiR OCl014 R Figure 3.1.3-5. Weekly mean' abundance of Mytilus edulis larvae at nearfield Station P2 for each year and over all years, 1978 through 1986. Seabrook Baseline Report, 1986
Highest abundances of Mytilus adults larvae usually occurred between early June and early July, elthough in 1980-1982 abundances in late August, September or October were as high as in early summer. Peak abundances ranged from 6x10 m3 -3 (1982) to 3.3 x 10 m5 -3 (1979). The difficulty in assessing the variability in this population is probably compounded by patchiness caused by discontinuous recruitment both spatially and temporally (Podniesinski 1986; Bayne 1976). Collections taken within several days of one another, even during peak months, varied by zero to three orders of magnitude (NAI 1981c, 1984a). In 1986, bivalve larvae were collected within the Seabrook Station in order to estimate larval entrainment. Offshore and entrained densities over all dates were similar (Table 3.1.3-6). However, in some weeks densities between the two types of samples were quite different, a result of small-scale spatial and temporal variations. A comparison of M. edults abundances in entrainment and Station P2 (intake) samples collected on the same date were not significantly different (Table 3.1.3-8). Although variability was high among years, overall spatial variability was low. Historically (1982-1984), no significant differ-ences had been found between Stations P2 and P7 when weekly abundances were ranked (NAI 1985b). 3.1.4 Macrozooplankton 3.1.4.1 Community Structure i l T mporal Patterns of Macrozooplankton Assemblages Historically, the macrozooplankton assemblage (1978-1984) l showed seasonal changes that were heavily influenced by the population i
\
dynamics of copepods Centropages typicus and Calanus finmarchicus, with l l 117 l 1
l l TABLE 3.1.3-8. COMPARISON OF NYTILUS EDULIS LARVAL ABUNDANCE (M' ) SAMPLED ON THE SAME DATE AT ENTRAINMENT STATION (E1) AND NEARFIELD STATION (P2). SEABROOK BASELINE REPORT ~ 1986. STATIONS DATE E l' P2 August 11 383 396 September 02 447 310 September 29 1427 396 October 14 130 181 5= 596.8 5=320.8 SD = 570.17 SD = 101.61 MEAN NYTILUS EDULIS LARVAL ABUNDANCES AT STATIONS El AND P2 WERE NOT SIGNIFICANTLY DIFFERENT (a=.05). l l 1 118 1
other taxa exerting short-term influences, particularly during spring and summer (NAI 1985b). In the last half of 1986, when macrozoopisnkton sampling was re-initiated, seasonal succession of the macrozooplankton community in the nearfield area (Station P2) exhibited trends similar to those identified during the 1978-84 baseline period (NAI 1985b). Winter abundances have been typically low, when the population , was comprised mainly of copepods (Groups 1 and 2, Table 3.1.4-1). During spring warming, when the thermocline was formed, benthic and plankton reproductive activity increased, as evidenced by a tremendous influx of cirripede larvae and increases in the dominant copepods (Group 3, Table 3.1.4-1). In most years, a tiansitional period (represented by Group 4) occurred between early spring and late spring, marked by increased densities of Me tridia sp. , Limac ina re trove rsar Tomo ra lo ng ic o rn is, and Evadne sp. Early summer populations have been typified by substantial populations of Calanus finmarchicus (Group 5), along with increased densities of larval decapods and euphausiids (Table 3.1.4-1). Warming waters and a stabilized thermocline enhanced benthic reproductive activity. In 1986, July samples were similar to early summer (Group 5) assemblages, with Calanus finmarchleus predominating (Table 3.1.4-1). During the summer period of peak maximum temperatures and maximum thermocline (July - early September), populations of Catanus finmarchicus attained peak abundances and Centropage s typicus occurred at near-peak levels, typifying the historically-observed summer assem-blage (Group 6, Table 3.1.4-1). The meroplanktonic larval stages of Cancer sp. , Carcinus maenas, and Crangon septomspinosa also attained peak abundance levels during this period. In 1986, the holoplanktonic cladoceren Podon sp. , exhibiting uncharacteristically low abundance, was undetected during August and September (NAI 1987). With the exception of Podon sp., species patterns were consistent with previously-summarized baseline conditions. 119
IABLE 3.1.4-1 SEASONAL CROUPS FORMED BY NORMAL CLASSI F ICAT ION OF MACROl00PL ANKION COLLECT IONS AT NEARf f ELD STATION P2 1978-1984 - , IN COMPARISON TO 1986 [SilHAILS. SEAHROOK BASILINI RfPORT, 1986. 1978-1984- 1986 CROUP SPECIES X FREQ. X FREQ. 3 3
. 8/1000m f/1000m 1 Winter 1918-1919 Centropages typicus 20800 95 Late fall 1982 1983 Cirripedia larva 3700 33 2400 100 *
- Winter 1983, 1984 PseudoCalanus sp.
Sagitta elegans 2200 100 Neomysis americana 1900 100 Metridia sp. 35100 100 *
- 2 Winter 1980-1982 Centropages typicus 18900 100 Limacina retroversa 13600 93 Pseudocalanus sp. 1900 93 Centropages sp. copepodite 4100 93 (cmora longicornis 3200 86 Catanus finmarchicus '3100 100 Neomysis americana 2400 100 D' Sagitta elegans 3 2300 100 Tortanus viscaudatus 2100 100
{$ O/Aopleura sp. 2100 100 100 - *
- 3 Late Winter- Ci rriped ia . la rva 292000 Early Spring Centropages typicus 72200 93 Calanus finearchicus $4100 100 OiAppleurs sp. 21100 93 Pseudocalanus sp. 9900 100 212000 100 *
- 4 Spring Catanus finmarchicus Limacina retroversa 36500 92 O/Aopleurs sp. 29700 100 Centropages typicus 23800 92 Metridia sp. 21500 83 fvadne sp. 19100 100 femora longicornis 15000 83'
$ Late Sprin9- Catanus finnarchicus 101000 ton Early Summer Euatus pusfolus 37000 100 Metridia sp. 30900 96 Meganyctlphanes norvegica 29000 88 Cancer sp. 26600 100 lortanus discaudatus 15300 96 Centropages typicus 14000 80 l 12 Oikopleura sp.
13700 l 96 Sagitta elegans 9100 l (Continued)
I TABLE 3.1.4-1 (Continued) 1978-1984 1986 CROUP SPECIES _X 3 FREQ.. _X 3 FREQ. I/1000m I/1000m 263000 61400 . 6 Summer Centropages typicus 100 100 Catanus l'inmarchicus . 206000 100 258100 100 Cancer sp. zoca & snega lopa 78700 100 136000 100 rodon sp. 54900 97 500 40 Centropages sp. copepodite 17200 85 5600 100 Eualus pusiolus 13000 100 '62000 100 i Carcinus maenas zoca & megalopa 11800 100 58600 100-Crangon septemspinosa 9900 100 35100 100 u" 7 Fast Centropages typicus 145000 100 '141000 100 e rodon sp. 13500 100 400 80 l l Data for this season not inciesded because several months ir. the seasonal grouping were not sampled, i 4 i I Y i i < i a
---- * --_r _ __ _ -e -
-,- v w
Following thermocline degradation and breakdown from late September through November (fall), the copepod Centropages typicus typically predominated in the Group 7 assemblage, with cladoceran Fodon sp. a secondary dominant (Table 3.1.4-1). In 1986, C. typicus had similar fall dansities to those observed historically. The hypoplank-tonic mysid, Neomys ts americana, usually predominant in winter, co-dominated with Centropages typicus throu<hout the fall. Mean abundances of Neomysts rose well above the range of variability exhibited during the 1978-84 period (NAI 1985b). However, Podon sp., continued a trend of low abundance observed during the summer (Table 3.1.4-1). While this isolated event was inconsistent with the overall trend of Podon's predominance, the low abundances fell within the range of variability exhibited by this species over the 1978-84 period (e.g., October-November 1980; NAI 1981f). However, the unusually high abundance of #,omysts differentiated fall 1986 collections from the typical Group 7 assemblage (i.e. , Centropages/Podon) characteristic of the historically-observed fall period. Relatively low abundances of meroplankters in the fall corres-ponded to average conditions previously summarized (NAI 1985b). Since the data year ended December 31, the winter sampling effort in 1986 was too short to clearly discern what appeared to be a Group 2 assemblage; however, the absence of Cirripedia larvae differentiated it from the other historically-observed winter assemblage (Group 1). In summary, the macrozooplankton assemblages identified during the last six months of 1986 were characteristic of average conditions as described in the 1978-1984 baseline report. With the exception of Neomysis, the abundances of dominant species fell within the range of previously-reported values. 122
i l Spatial Patterns of Macrozooplankton Assemblames The spatial distributions of most holo- and aeroplanktonic species in the study crea were governed primarily by local currents. Hydrographic studies have indicated that, in terms of-salinity and temperature, nearfield Station P2 and farfield Station P7 were not discrete (NAI 1985b). Primarily because of proximity, longshore posi-tion, and siting along approximately the same isobath, the discharge station P5 would not be expected to differ from Station P2. No signifi-cant differences had been found in rank or relative abundances of holo-or meroplanktonic species collected at Stations P2 and P7 (NAI 1985b). A comparison of mean abundances, percent composition, and rank dominance scores (RDS) for selected dominant species in 1986 (July-Docember only) illustrated the same overall patterns of distribution among stations - Although percent composition, mean abundances,
~
(Tables 3.1.4-2,3,4). and percent frequency appeared more variable for meroplanktonic species than holoplanktonic forms, non-parametric statistical tests indicated that no significant differences in abundances existed between any station pairs for selected meroplankters (Table 3.1.4-2). This agrees well with previous studies on bivalve larvae which established that longshore distribution was more similar than onshore-offshore distribu-tion (NAI 1977a). l Tycho- and hypoplanktonic species, on the other hand, are l often strongly associated with particular substrate types,'and hence, l may exhibit localized distribution. Substrate near Station P2 consists ! of cobble and sands, substrate near Station P5 is largely ledge outcrop and cobble, and substrate at Station P7 is sand. Overall hypoplankton species composition among all stations was similar. However, signifi-cant differences in abundance were encountered among stations for some hypoplanktonic species (Tables 3.1.4-2). Hypoplankters, Diastylls sp. and Pontogene la inermis showed significantly (P = .05) greater abund-ances at Station P2 as compared to Station P7 in 1986 (July-December), as they did during a similar comparison during the 1982-84 period (NAI 123 ! 1
.. _ _ _ . _ . _~ ._ .. . . _ . . _ .
'l l
l l TABLE 5.1.4-2. SEMIANNUAL MEAN ABUNDANCE (NO./1000 m )u0F DOMINANT 8 I MACROZ00 PLANKTON SPECIES, JULY - DECEMBER, '1986. I SEA 3R00K BASELINE REPORT, 1986.- P2. PS - P7 Centropages typicus 87879 120566 99165 Calanus finmarchicus: 108652 216283 152029 Cancer sp.a 56809 16365 67433 Neomysis americana # 37267 7978' 7137 Eualus pusiolus 25893 9079 40094-a Carcinus maenas 24842 7220 28275 Crangon septemspinosa 16608 2?65 11230 Diastylis sp." 457 136 138 Pontogeneia inermis # 370 293 128 Sagitta elegans 1100 872 1625 l a Results of comparison of semimonthly abundances by Wilcoxon's two sample test, i a = 0.05: Cancer sp. P2=P5=P7 , Carcinus maenas P2=P5=P7 Crangon septemspinosa P2=P5=P7 Diastylis sp. P2>PS P2>P7 Pf=P7 Neomysis americana P2=P5=P7 Pontogenela inermis P2=PS P2>P7 PS=P7 l I
\
124
TABLE 3.1.4-3. COMPARISON OF PERCENT COMPOSITION (AND PERCENT FREQUENCY OF OCCURRENCE) 0F SPECIES IN MACR 0 ZOOPLANKTON COLLECTIONS BETVEEN STATIONS P2, PS AND P7, JULY - DECEMBER 1986.
'SEABROOK BASELINE REPORT, 1986.
P2 P5 P7 Calanus finmarchicus 26.2(100) 49.5(100) 30.8(100) Centropages typicus 21.2(100) 27.6(100) 20.1(100) Cancer sp. 13.7 (83) 3.7(100) 13.6 (92) Neomysis americana 9.0(100) 1.8(100) 1.4 (92) I Eualus pusiolus 6.2(100) 2.1(100) 8.1(100) Carcinus maenas 6.0 (83) 1.7 (92) 5.7(100) Crangon septemspinoss 4.0(100) 0.7(100) 2.3(100) Temora longicornis 3.3 (83) 3.0(100) 1.7 (92) Centropages sp. 1.7 (92) 2.9 (83) 1.6 (83) 1 l
#eganyctiphancs norvegica 1.5 (67) 0.9 (83) 3.6 (67)
Obelia sp. 1.0 (33) 0.1 (33) 0.3 (8) I Eimacina retroversa 0.8 (25) 0.1 (33) 0.2 (8) ! l Phialidium sp. 0.7 (75) 0.5 (83) 2.5(100) Escuna vincta 0.7 (92) 2.1 (92) 1.5 (83) Centropages hamatus 0.7 (92) 0.3 (75) 1.7 (83) 125
TABLE 3.1.4-4. COMPARISON OF RANK (a)(AND PERCENT FREQUENCY OF OCCURRENCE).0F DOMINAhT SPECIES IN MACR 0200 PLANKTON COLLECTIONS BE'IVEEN STATIONS P2, P5 and P7 JULY - DECEMBER 1986. SEABROOK BASELINE REPORT, 1986. P2 P5 P7 Centropages typicus 1(100) 1(100)- 1(100) Calanus finmarchicus 2(100) 2(100) 2(100) Neomysis americana 3(100) 5(100) .10 (92) Crangon septemspinoss 4(100) :4(100) 3(100) Sagitta elegans 5(100) 6(100) 7(100) Centropages sp. 6 (92), 10 (83) 13 (83) Eualus pusiolus 7(100) 7/8(100) 5/6(100)- Centropages hamatus 8 (92) 16/17 (75). 11 (83) Diastylis sp. 9(100) 15 (92) 17'(83) Temoro longicornis 10 (83) 3(100) 5/6 (92) Oedicerotidae 11(100) 14 (92) 16 (92) Pontogeneia inermis 12(100) 16/17 (92) 21~(75) Carcinus maenas 13 (83) 11 (92) 4(100) Cancer sp. 14 (83) 7/8(100) 8-(92) Escuna vincta 15 (92) 12 (92) 15 (83) Pseudocalanus sp. 16 (83) 9 (92) 9 (92) (a) Based on Rank Dominance Scores. l 126 , i l
198Sb). Historically, (1978-1984) Neomysis densities had been signifi-cantly more abundant at P2 in comparison to P7 (NAI 1985b); although densities in the last half of 1986 were more than five times greater at P2, this difference was not significant. As this species is a winter dominant, a complete year of data might provide more similar results to those observed historically. Some differences in abundance were also noted between near-field (P2) and discharge (PS) stations. During the six-month period in 1986, P2 mean densities of Diastylls also significantly greater than at Station PS. Differences between P2 and P5 were not significant for Pontogeneta or Neomysis, although Neomysts mean densities at P2 were more than four times greater than at PS. A comparison of abundance between these two locations from 1978-1981, the last time when both stations were sampled, revealed findings comparable to those observed in 1986. Overall abundances of Neomys ti and Diastylis were significantly (P=.05) greater at the intake (P2) in comparison to the discharge (PS) based on a Wilcoxon's Paired Ranks test. Densities of Pontogenela inermis were not significantly different between intake and discharge areas. Although the plant's circulating water system was operating in a test mode in the latter half of 1986, the non-thermal discharge apparently had no effect on the previously-observed trends. Instead, the differences appeared related to these species' preference for a different bottom habitat. The future elucidation of plant operating effects on these species using only spatial comparisons would be difficult, given these differences. 127
r 3.1.4.2 Selected Species Calanus finmarchleus During 1986, as in the 1978-1984 baseline summary, Calanus finmarch f eus was a dominant specios in the macrozooplankton assemblage (Table 3.1.4-3 and 3.1.4-4). Historically, copepodites exhibited greater abundances than adults, a trend which also occurred in the last I half of 1986 (Table 3.1.4-5). The major peak in abundance of copepo-dites and adults historically occurred in the summer; data collected in j the last half of 1986 supported this result (Figures 3.1.4-1A and 3.1.4-1B). Adults were undetected during November and December in 1986, while copepodites were uncommon. Overall abundance and temporal pat-terns in 1986 were typical of previous baseline observations. A comparison of mean semi-annual abundances among Stations P2, PS and P7 in 1986 did not suggest differences due to factors other than natural variability and patchiness (Table 3.1.4-2). Local hydrographic conditions and organism behavior are such that stations do not host independent populations. Carcinus moenas Carefnus maenas was a predominant member of the Group 6 summer assemblage with peak densities from May through August (Table 3.1.4-1). Carcinus maenas larvae were already present during the initial sampling in July 1986 with peak abundance occurring in July and September (Figure 3.1.4-2A). Analysis of the semi-monthly data indicated that the September peak was greater than that in July; this was not evident from the monthly mean data (NAI 1987). Both peaks consisted predominantly of Stage I and II zoea. Although no larvae were collected at Station P2 in December of 1986 as they had been in all previous years, Station P5 and P7 data indicated larval presence at that time. Semi-annual mean 128
3 IABLE 3.1.4-5. ANNUAL MEAN ABUNDANCE (no./1000 m ) AND STANDARD DEVIAI10N OF SELECTED SPECIES Of MACROZOOPLANKTON AT SEABROOK NEARFIELD STAil0N (P2). SEABROOK BASEllHE REPORT, 1986. 4 1 I YEAR , 1978 1979 1980 1981 1982 1983 198h 1986 SPECIES /LIFESTAGE E 89588 36708 117382 75538 79381 46661 81788 105413 Catanus finearchicus (171491) copepodites (SD) (153895) (61403) (167203) (160288) (204308) .(50487) (114214) E $536 1065 825 804 2641 2301 4208 1390 Catanus finnarchicus adults (SD) (9535) (2110) (1118) (1084) (5868)- (3301) (11651) (3105) O i 1511 1905 3753 5253 5025 6627 2263 24544 carcinus maenas (43743) la rvae (SD) (2776) (3372) (6704) (13098) (14216) (11285) (3897) Crangon septemspinosa i 4880 4109 2326 2557 4815 3402 2125 16554 rocae + postla rvao (SD) (6751) (5890) (4426) (3870) (8078) ($520) (3263) (29518) pcomysis americans i 723 374 1554 1716 2094 1836 2159 37158 all tirestages (50) (1327) (820) (1996) (2140) (3608) (2790) (3805) (51504) 1986 data represent only the period from July - December.
}
4
_ . _ ~ ._ _ _ .- .~ . . . . . . .
"""* ! A. Copepodites- '~
' k(V
\
*/'\
4 taoun o s t, ) n . Sorm .e e N . 1 9 \3 4. 9 7 \ h 0 e 9
- 9- g 3 1 g) e t e \
l'a* ; _ \ t t! N- .. . a i e e \e' g o
. , - - 1 o
- e e s
- o sow . o c
; $a *
- l. .N;
' \
a
\i C \s e :\
t i e j g a 5 . So
- 3 to.*...................................................................................
Jan rce ma 4 *e nav sum Jut ave sce oct nov cre Mo4TM wono ! 8.9 ETC.
- LAST O! GIT OF $A# Lt YEAR B* Adults *
"!55 "3 '" NE T0 "U-LAPP!N3 VALUES e
----
- 1%6 ,
~*- l 10000
- ALL YEAR $' MEAN.- 1978 1984 I e 3 4 I i / ag
%.o
- e t /
4 s o _d t
\
i e ee 3 . . .
\ .
3 u i e a e \
= i
., i -g
! tooo l m i o . j \! o
\
\-
m! 8 a
- o .
o too
- a 3-
- ! / h-*[.
3 ek
.1 ,
j j I 2 1 c e l 9 t 1 2 ' I
-c e . !'
, a
! .. . \ l
! \.
5 5.!
\
o..* \
....................................1..........................*..............'.t.........L.....9....
Jat (El nas are u, Jkt Jui Avc 8tr oCT how ott monfn 3 Figure 3.1.4-1. Monthly mean abundance (log x+1/1000m ) for each year and over all years-at nearfield Station P2 from 1978-1984 and July-December, 1986 for A. Calanus'finmatchicus copepodttes and B. Calanus finmarchicus adults. Seabrook Baseline Report, 1986. 130.
1000ac o
.I A Sen ! A P
/\
\ 8.9 ETC. . LAsi ClGli or SAMPLE YEAR i / g- MISSING P0thil Ot/t TO OVER.
O 3 \ (APPING VAlt($' s \ /
. .. 1986 i- ,
A. Cardnus maenas jyl -.- . n t vt us' O Is7s.lseA I\
.t t .I \
. O \ \
i \ l ,w . s a ' l \
; $a * \
a
\
3
- 0 f N.
100
- 3 g 9
e l \
\.
t t 10
- I
\
,E t 0
. . \ .,
O O -, \'e. 2 9 N. . . , 0.0 ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
\
JAN fit NAA Are MAT J Wh JUL AUG SEP OCT h0V OCC seonty 10000C + f I f B. Crang:n septemspinosa y / ,\ s N
- 8 a \
/ s
' " ' * / ' \
i e I I. !/ \ 5000
- 1 3
!#, g 0 : \
i . O \ l 2000 ! : . O \
.i g ,
gn ( 1 k A 2 1
\
0 8 0 0 3 % 4 2 9 0 100
- 1 \
i
- 0 g g
,0 s .
0 9 \1 9 a
. . .* i 3
t S 1 1 1 10 *
- 0
.S
,1 O N *8 9
1 i S I I
- 0. 0 *
...1........1....... 0......... ....................... .................................... ...........
JAh F[s RAA A rt mav JW4 JUL AWC $EP OCT 40v OCC nomf u 3 Figure 3.1.4-2. Monthly mean abundance (log x+1/1000m ) for each year and over all years at nearfield Station P2 from 1978-1984 and July-December, 1986 for A. Carcinus maenas larvae and B. Crangon septemspinosa zoeae and post larvae. Seabrook Baseline Report, 1986. 131
l abundances exceeded those outlined in the 1978-1984 baseline (. 3.1.4-5). A comparison of monthly mean abundances over all sampling years shows above-average abu' n dances during 1986 (Figure 3.1.4-2A). Although mean abundances of Carefnus moenas larvae were nuch lower at Station PS than at Stations P2 and P7 in 1986, this difference was not significant (Table 3.1.4-2). . The presence of Stage I zoea throughout the 1986 sampling period supports the earlier hypothesis of a protracted breeding period (NAI 1985b), although megalopae continued to occur only between July and October. Cranton septomspinosa Peak abundances of Crangon septemspinosa zoeal and postlarval stages during 1978-1984 typically occurred from June through September (Figure 3.1.4-2B). In the last half of 1986, peak abundances during July and September, and post-peak abundances in October exceeded all earlier estimates. Annual mean abundance estimates from 1978-1984 were much lower than the semi-annual mean for 1986 (Table 3.1.4-5). Even if no larvae were detected during the first half of 1986, the estimated annual mean would still have surpassed the highest previous annual estimate nearly twofold. Although mean abundances in 1986 of Crangon larvae and post-larvae at Station PS were much lower than at Stations P2 and P7, this difference was not significant (Table 3.1.4-2). 132
1 l Neomysts amerleana Historically, Naomysis americana was present year-round, but was most abundant between September and April (Figure 3.1.4-3A). Mean monthly abundances of Naomysis americana during the last half of 1986 exceeded all previous monthly means observed during the 1978-1984 baseline period, except for the month of August (Figure 3.1.4-3A). During 1986, peak abundance occurred in November, similar te peak observations in several previous years. As would be expected, the semi-annual mean abundance varied from one to two orders of magnitude greater than all previous annual means (Table 3.1.4-5). The 1986
#eomysis americana population represented an extreme shif t from the small annual variability of total abundance described for the species in previous reports (NAI 1985b). Further, Neomysts was the second-most abundant species observed at Station P2 from October through December, i
following only the copepod Centropages typteus/Centropages sp. Although semi-annual abundances observed at Stations P5 and F7 (Table 3.1.4-2) likawise exceeded previous annual observations at Station P2 (Table 3.1.4-5), they were still lower than abundances at Station P2 (Table , 1 3.1.4-4). The reason for the station differences may be related to bottom sediment type as discussed previously. I l Lifestages of Naomysis americana historically exhibited I distinct seasonal patterns (NAI 1985b). Immature and mature individuals I were most abundant in winter, while ovigerous and larvigerous females were most abundant in April. Juveniles were most numerous in late spring and fall. The relative contribution of the various lifestages of l
#compris amerteana to the population structure during any given month in i the last half of 1986 continued to reflect average patterns observed throughout the 1978-1984 baseline period (Figure 3.1.4-3B). An excep- l tion for the period existed from September to October when a high proportion of immatures in September were replaced by younger juvenile stages in October without evidence of a pre-existing spawning adult i 133
100000c + 8.9 ETC.
- LAST OlGIT Cr 5AM LE YEA 8 l M155th~ P01hi$ DUE TO OVER-I LAP 91N3 VALLES
! ___. . ise6 's iooooo -.- . Au v E*Rs ' men, 1978-1984
/
,- 's\
/ g t
l A. / s
/
,oew
' j , w!' '
' f I / o ,
n i o
\ / i ! icoo . o ! .
- m;s j ;N/'
N
\
'/' ;
a .
\,
i l' - - o
'oo ; , .-
v So a f N ., i . , c . , , . o io
- o 9
,j ,
l l
"'...;......g.......g................f.......!......7........................g......7.........
pont> g* 78 78 78- 78 78 78 too- - N 86 84 86 84 86 84 86 84 86 H 86 g, a Vj; / ,' g: - fj .:;
* = '
,l. ,
5, 60 -
'l
~
i , , ; Q . .. . 4 F M A P J J .A. 5 0 h 0 m -
, . = .<
5 ~ E 5 I 3 4 5 $ % Figure 3.1.4-3. A. Monthly mean abundance (log x+1/100m ) of A'somysis americana (lifestages combin. ;) fer each year and over all years and B. Mean percent composition of #comysis americana lifestages over all years at nearfield Station P2 from 1978-1984 and July-December, 1986. Seabrook Baseline Report, 1986. 134
I population. The anomaly suggests either recruitment or emigration may have occurred, or the adult mysids may occur in areas not sampled with gear deployed in this study. I l l l l l 135
I\ s D: e> Wr- = C',X3 53; [s'77 7Z . .$ ld LN'M 3. N S.N"- gh. ld I f7s'77 D
. g'.
.c e -
u6 S (( s .\ 's\3 s5?,13 N': (( (/s'
'. 7 s'/712 7 ~/ /3', "j *"
f( lTi F I. 4 \T s5'5T OC~ 27_ f. 7 s'72 D' N#.$ I 'Ci s\1 53 0; --)
- f/ 7 f//7/ Dr~
rz C/s'/7 /r '., eoA [)_ h TV s%',13 CN YT sT9,13 N 3.. NX
?,.
** t_ l' r'~/ 77 '_ 7 s'27 77* *- S '-* O u c f.,
<( 11 .O .3 63 'N N Cs M Vs si'5A \;~
i5'. 5.T N N.: 5 *(
/
'D // ?Zs'7/ /~e!-
f Ts T.' LE 7. / s'77 p u o .o (vL EX O5 3.~N TT CT',X3 02 g,. Lbe [7.' .7s 7~/ 77 7_ 7 s' 7 '7 /3 / ,1~ *. g'. W* 8 Ld "33 " CC C5 TT'O .T 'N~\ iT i5',$1 SX~ 0 ~' Ld f ~'72 '4 f ' ~/ i E' / /. '. /-'/ s> '// / ~,5
'2"' -
= "a o,, u
(( IX s33 M Cs d',\3 5\~ ' . (( 47/ #1. //s'// /~L- '. O tr. I s32.D 5T \S's V\ N.T - E7._. ' // /2s' / .~/ /2 *
" ~/~ ' l.1 (/s'/7 77/ I
3 d-6'VIT X O% 3. \ ST L3 Y \l\ l s3.5 M YT s5'.1 '\ sS',\h
\ 3..
OC - 5 f~/'T/ El {/s' / l/ / ,'
~ "hwm
[$ Ltj IW V1T1332.M h T. .\ TA O% D N.'i s5' s\ \ W [d 7 'U // {/ /// /2 " M 4M
- O Ci CS'. .\ 33 34 d ll '7/ -,O' 22 //s' / '/ /T,1 k ~ ti 4
0"
- 15. 5 5D3.3 A'3 15 i V1 07 X3 53 i\',13 Vi s' i ' \\ .\ N~ ."I 53:
b p' E7/1/. '/s'/2 D
' ,' ' ' . 'E. 4 {/s'11 /Z.
~
'I
$ "cep'
, *e Ch V\ \\ m Dit i%',53 > 3: -
- O l'~i / /E !7s' 7 ~r / i'
-~
eoo Lti in o ss nn3.5 xs rs (s<ssux~;5 Ld ci i zz r,7 .> ff. //c72 ,r -. ; "! 24 {ls'/1 / ~,1 h #* S f [33 D E'i s. 5 ,A3 .\ 3J /\>r3 l 1/.7 / t.1 9 m u 'O (s] I l .' D Vt iX?.X3 N 3J L.3
% nr /Zs' 7.7 /Z eoo "
< { g, Is32.D EE 75'<hT OC- '
<f O li/ /_ 'I.'Z / / ,5~
~ R~
> 0A
(( o., g s 6.s 3.' 3.~.\ \.S. s. 5 ?.N3 5 32 I.D \T s\'.N\ \ J; .3 ([hOsI'. F' E EZs'l / /Z (4, r. 7 s'77y-,"#~ ."3 ~
"$[
% ,4 m Ci (5' \N~ Cs'// r< -
ou o ld e. I ssds ,13 \\ 13: . , . ld E. rz2 e /- ,, ce-5' [ s5'.\\ \_V ~' ~ - - [Is'71.f~2 --
"Oj$
R s\'sh\ Vi [{ /Zs' / '/ / ,I ** g m
<( CT i '. ? 13 \3:~ <( [ 2 ~s'/21Z- W "O -c M C' %X ls'/7T/ U*C g L' ,.NT A\ n '{ l' / ~/ /'s j x u"
j W3 sX IN N.X..
}- i r/ /Z 55.
~
.x 9 . s o u
- p \T- .J p '<.. e e co O.
M $ k, .'!! M [ bh $$~E Ltj i\ x '.; ltJ r/ < - L \2 - V /s: d L \\ g bd l' '/ ,I
~
g( d S" V. I \.1N
\3:
5 [f
/ 4? &
'> ~> -
1 \m4- r/ f3' ' l\ .\ M'y I/ /~/E .$
- -- -. .- - -- - . -. .. - .- . - -. -- o 4
(4 O O O 't- N O C O t H O cl O O e 4 of O W 6 4 e1 0 w n e3 s- s- ,- ,- s- cg n r- s- ,- r s- ,4 Ea.
.M e4 0 503t<l 33UWGdELL 3 5 0 3 00 33 U W O d1.lt "8 o
C. O. 4*.
16f P" If I N/ Ag /f= m A A P'"" "'?" P h A & f""* m A "T" t t m f'"= VV C. rs L I M V C. N Mu ". C.tVI P C. NM i t ) N C*_
- 977 - S UR C'AC E 22 4 I I W
i i g as I t ,.
- l
- 16 Y l n Ye 's C *'
4 i r, / A + 4 i _ dr // _n I & I VR VViV/i// __ l u 12 ,, ,-,,,,,,,.,r , W I f) I GG .m If") C7fdide')IM)4))didi/ld;dM.;/)C]3 tJs)lL!;p;;;;j;;) ;>1 ~.,.j rj s AV f,/ddfiddl Q ,?, P f t (?f (({/
,W)/d 6/ ff f fff f f f(ddV): //1dddbdd, A/f'/dfddd
\
r,c < r. c n r .r.< r.r.< 1 < r < r < < -r <,c r. < .orr:r r r y,c, f l g s i V// i,-,.// A V. /,/ .
--2,,,V'//VV//////,//A//d,/////M
, ,._e, - ,,, ,, ,
_t n 7 m/v/V/////V/VW/V'//////Y//' /VVY/V/V// l
. '/ 3 )W//'/V>>'//// //VD/'/s)// /)/J'/V //////) l
/*
- f////f,/ Vf//f//f/* /f//// // / /// /ff/ff'?f q c'r'rEr'Nr"r r'bbe tn Y r$rb N Vrbe :rbNekrYEYrbrbb Arbb lr Er?rYr5rkrb e
.; ; r: u A: u J J: A: :: 0 Ni :1
',*/E EK S 1 4/P'" P""l / t s/ A \ /f" R A /s r"* "T" F & a f""% P m A
- I emf VV C.C f\ L.4 M V C. N MO C. A C"IVI F C. N M i t_/ N C.,
'977 - EQUOM 22 ' I i
20 I t 30 . . O 16 M ' C .A I l
' l v .
b 12 , w i m m i l CJ 3 s- Is'd_ UO OCe ese, 4 c: ch. Wa, L Li i '- Muk k i i 1 l6 g g 8 (M_ ,ts hhq,I.l s s s 's .l iddsl ss.
. 'sA,sls.l. l~l.
I l c, 7 SN NNvwNN:vs:s vN s N N 35 sin N N:YN l t
- . , _ . % ,N ,.Jw s.s N N w s N s.N s s s v s:w w N w 3 s _ i G V
. _ , . N N , N N N j'. N s c ,NNNN N.NNNN N N . w i N. N . N. N . N 7=, N .
mNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN1 4 ' y. ' : W y, ' ::_v:' :_L': ': LL W : ,-? ' 9 _mNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNI s_ _.sNssAss
, wss:ss Nsss w s wsNNvsw w ssw w '
ss - m s.s s u w s/s.s. w s. w s.s s.s s s s s s.s s w N s.s w s s w g , SNiNR_~ J.K >.L ',) N%,',Isi.ShhO.NKh.9,,M,NW,hl ,4,M,N'!h3 ! a r u A: u a a A: 23 c u, :::
'*!E EM S APPENDIX FIGURE 3.1.1-1. (Continued) 137
00:?Q TX C777 72 - t 0.' 'i s V5 -
'Zi'1777-ld ld 5.OOM
?O S\
M ,. L{ C7s'77 /2"-
/. Z s'77 //- h, (L, 13,Q2
- 5. 4 .. .' ?G \\
-)
-g
(( CZ EC C72'77 /Z - I N100 ?O M - F EZ CZs'77 /75- _ J cs s1 O li 113. 0g. .-Q
?s s LT M ..
7 _ in- Zz EL' LE e7czy CZa'1712- " 2.z [_ lXX X 3.G.'M V5 L _. ZZ r. 71'77 /7
<( CD?U .\ LOO.?O \\ 8(
< EZ ?Zs'77 27 tv IGXA 13.\'? 2G Y\ - ,_
pg DE37 L2 7Z t Z .s' Z2 /.2-LL [G' VX X3.QO M SN -O LL G7C' .M r. Z 1'77 /Z ") g [5 G'.U 55 f-d rz (7s'7 y jg"- bd 1VY G5.XT S3.00Ms n O.' Vs bd 0 73' r{ r. 7 /77 17 . [{ l'X N'.\5 51.00.M XX - " (( FM" .> Z/ fZs' 7 '/ fD"- " l XXWG' X1 53 .'Q M fR/ 22 ?2/77 >DS O X\ L'- O KA S *.OO.
' )_
~~ h3 AAW t('C U XYOO.X. s M
.L'J2Q X.\ -
'3 d-IZZ r/L LC' ZZ C> ZZ CZj'/77Z C/s'7/ /g" -
[d [.l [^ AA G G'.XN 1100M h X.\ W.Wi KX X .1 GO2G 5\ M '. [d }i Erz7_ PLZ/ M CZ/// // C /. s' /17/.." b~ b: 4 L WGX3 13 O 2G H ~ i b-' C. C> 72 J71 /3".4 F- ',. Z g' r,y. n: ELXCC'il 51 OD' 2G si r b r y_2'fyyz 3 [X CC .U 53 ( 2G X:5 - U} . U! bd vi LEE' C CD 11 5100Jui
.X5 53 G'O2Q O M ii h
i.,3 Ed O' Tr rZ CZ 777 C.{ ?>_ CZj'71 7Z-G
/.Z hw
/n
\> l co
(>n I O Il X 3:002G X\ > Cr ry3'7y77- a
<( g, CCD D 13:V 15 51Q2 2D SX
.. D 2d S.\ "
<{ its t CZ//2 /L U_ CZj'71 /:Z
^C 5
L (_ Z T71 /2-" ."' p (( o; CD:G1 T3'M LT - ' (f_b. O' $ E.3 5 .052G H L7_Z. CZs'7 / c Ed ,- E ..032G V1 ,. Ed if J77 r /s/ lj' /777 y 13 PO2GXY ; 3 - LGO2Ci M i CZ ?77 22 -- o 5'(
< E02G V5 CG YT -
<{ L'// /Z P717 u
h M -*
-Q E711 -Q
)- h 15 )_ .
y_ J M i _J v $F.
- T
~
r/ - Ed - Ed t - m 3 - ld - " ld yz05-. [ w n:
* > ES -
'> IX -
5 Irz- :) O FTX -
-: E/ /5 r7/r.z"-:;
r rCs M
._ . . . - . _. _ _ _ . - - - - _. _ - -. - _ _ -4; . _ . . _ . _ __ _- -_-_... ._. _ -_~ ,
o to e 4 o- o o e + n o n n o e. e + n o.. io o 4 o o E n - .- .- - l N q . .- .. r z sa.3 Da 4
-c 3 EBREKI 33HMGdEll O 5DFFX13311MGatti .
% A f F f" t / 1 V A% /P" & A A r'" ~ r" 6 ARPR A*I 4 % '""
V V C., C rN L_ i MVCNXuC I C svi F C. NM i L/NC 19"9 - SUROCE 20 . i t . r, + 16 , I vP/,.M a I ,
,a 1 ffpi, i I r9%'JrreyWG I 14
?! Pr b
% ' f) f r M jfif;f. H f f.r G f f)e _
4 i F,7i,q,d,f.,/ ,if,/irGW /le'r,W i f 30 w < _///V//////Vv/Vd//d/A//n/?nn >
% / /// /'//'/'// /////Y'/'/// / /'/'/ ////
'n ////////////////////////////r i d s n I PWW/WWV/M/WW/W' / / '/' //WV/WV/W'/V/V7 i Q * , r.n ct, .r.r c rr.r.r.r.r r.</.w e.r/ t.7( ~ r v.r .
4 I n f, fNTI")fIf h f) f) f f$')* f$d '$d'$ '/ '
, k'M.
Jn_ TPir'[rNY'" _nn/4/ /MUrY'.'. nn ykM nn n/
'Ju.k.Nr'i/ ihr'/irjrJ'D'n./h':/rjkj'/)
r"
/i "t/ i 2
1////n //////f//f////////////f//////////ff/////
///// e,/// N///N////H//// N/N H N // H/////// r i !
-2 J1 71 f.-i t Ai Mi J1 J1 A1 31 01 Ni 01 WEEKS infr-r- /. v ^se-mA A r- rx e n r- m A , i r. -
V / C. C rN. L_ t M V C. N Mu C. 1 C. IV I .' ' C N M a L / N C.
".9'79 - 90HOM 22 .
. 4 10 t i ga i
! l O $$
41 i C e4 4 I b 12 w I m I Q; 3
' s'e _t c i
., s41 e, n, - 1 5 g
, i.W.
.s '.h C. Ced C%".b.,L.k.C..r s
I g ,
- c. i :w S., NNNNNNNN NNN NwN.NNvw% i
,i i N,NNSSNNiNisNNN.3 N N-N .WNNNsNN '
g:: 0 . c., s ,. , . , , .,v
.s s s , . . , , , . s. s . . s s. . s
. . n 1 N_ _ NNNNNNNNNNNNNN NNN NNNNNNNN NN I A ':. J :::::: '- : ' '- : ': ': '. ' ' . ' . '- :: , 2 , ':, .
i NNm mM NNNNNNNNNNNNNNNNN NNN NNNNNNNN NN l
' s N%
N mCNN kN'N(s'NA NNN N N's s'NAi! NNN \ s.N' N'N GN1 NN' i v uss v -s ss N s ssvsss ssvsss Ns vN vsv vvv svvss' ss
.U.(.,'.s.(. ,'_i,tC._,,,.,.'U,(l'J,(V, . . 4_ ,1_
_, . , W t t
- . 4.( ,h,, , gig,rg,(,r,, ( . . , , L,t,, ,tu.( i.ti.r to,l LtL1 I
. , ,14. ,. ,1 , ,li,ng o .i .
. . . .,1 . .
1 g Ji 71 M1 Ai M1 Ji J1 Ai 31 01 N1 Oi
'.*/E EK S APPENDIX FIGURE 3.1.1-1. (Continued) 139
% A f F" f"" t *I %.s A\ / f" r"% A #S f" "f'* P k A f"i f" R A T 1 i f'
v v C. C 6 L. i m v C. NMu C., i C. s vi F C. Nm i U N's f"C. ] 7 950 - St.'R8 ACE 22 i
+
1 1 20 1 1 15 a n - 1 i f_m'fm LF) I o 3g A t 76/Adm a C .a s nrv/V//A n s
% s nVd///AA?A d_m t M l VVVWW/MWWWirrA'/,W l b 12 - , , , , , , , , , , , , , . -
w CLJ CU)8 u,/'J')' A#sy's;)l/MAJ _ i
% .n
- U G'"J.J 23'Jf;A> hj 22Juuu +
d ** s _f;tJf)\)6sJU! JiJfit)8JI)))!)l)IJen I b ' r-{.b*Vb)VA'$ VJEOUYlbOU7 g 3 i nYwryMrry::'wrMddtMtMC i
?. ,
- r ? V V + #:Y 'if Vl?tY V;Yl/s/VViti'VVlftfirifVVVi_ f P "
+_ nv ri r.<.r.rr.n.r;.r.n < sr.r.r s + r < < < :<. v. rs n r r. .r rs._ .
tVn V//VVV//AA/d/V/VVAVAA/AVVAV///AA 1 4 _ . , -
.....,,,,,_,,,,2 . ._ ., . _..,,,_
t//vn n v/ /v/v vWV V'/V V/V / //// A/ A'/VA ////// /n f
+ T/ / s./ 7 m) } }} }-))>/) s /d s's)'//> s /J })///} /c/JJ//) f n s erm sss s ss s.svsjs sps s ssp s/ s ssw s si svisi sv s
N#fY,Ur$8e5HrE E e'rbrYrNNA YbMb5NbAbd/A r l n l 'b'kh/?e'e'?N'e'l' e r r e r Ji F1 M1 At M1 J1 J1 Ai 31 C1 N1 D1 WEC<S P""" A / P"" r"% A ss f'" *T* f" k A f""% P" R A *T 1 P"% f" tvA/ C. C. P" fd L.Y m%v C. N mu C. 1 C. iv e F C. n m a" fU N C.
1950 - 9070M 22 f a 20 1 0
<a r
- , i o ,s ' '
V t i O' 5 c; 4 ,' m. w NN , s c 12 - s
, ,,T_
w i "N O trath, WyWW 8 g ,,
' e Ous.W d 6 it t i I L1 i l i
- s t n _D.C.lsLisD D LUiiLh.IW
.s - s s - .. s s y 1
s % =d. r A O1n u 5 g . , ww:e vwv3 N wwNe3 , i
- -i.
- 5 ,
m N e N N s .s,,,,..,
,,,v ,c,,,,..,,,.,,.ss,,
, N N W ,,.,,3,,,,,,,,,yy G N:n Wn % ,,5_
_. NNNNNNNNNNNNNNNNN NNNNNNNNNNNN9 I m- l
, ., g gg;g i _9NNNNNNNNNNNNNNNNNNN NNNNNNNNNNNNNN l NNN_
w w: _ -. Nss.w.rssN xeww(w ww wwwwws'W WVv0! s :w s se s, s.s ~ s.wss s's.w ss N s s swN ses. sis s.s ws s A s s s. . .
+
Wq
, , ,', ,u, ,m.e. , u, t ,ueA hv mm,, ,\u.. im .o. N:veumt ,u,v. .u,u u,slu, m,, ,1J. ,,slL,1's,la,l : 1 2 m , . , - , i O
i i i 1 i i i J1 71 M1 A1 ::1 Ji Ji A1 si ci N1 Ci
'.'.'E EX S APPENDIX FIGURE 3.1.1-1. (Continued) 140
% A / f"" f""* l / 6 N/ A% / l'" N n /'N f"" P f"" k J R " N A Tl t m f""
V V C. C. r\ L , i M V C. N M J C., a C.IVII"'C.R M i U N C. 1981 - S U R 5"AC E
.m.
t 1 20 18 i
' O U
m 16 o [ vin /en
, <./ n i C ., n ws// 7//// '
% ? M4//4 MMM//n i Y l V/V// *////// 1 D 12 7,~e,, e ,,, <r<<<rr w % .m i V/y')V}tAff) tidi}f)/)% b is_,t;DriJ *;> > 2;;,- , t C I)\ YI)f } }l)l)/) l)'); / s )')t))Q.w W9dD,J9999'/,J 99999)99999 A 5 i - i c 8 - ,4, 1 t (1(f f)fH V/fif'/t'M&sM
, ,AMmMhWAWA 3 7 (fr'V 16M'N&Ma"1 d W ?/ff n
t u 5 & f_r.( f,r.c r r;r pt:r.f r_rs cr(ar r f .* I f f. c f f,r f m 4 I
, f,/ , /,- /,/ /.;,.,_- , , , , , , , , _- , , , , ,
/ ? / / Y,Vy V,d, /?//////////////7m '
l -/ V//V/VVW//VVV// ' VV//Y'/V/AA///////I
/
'O wr 7 ') / //'/s W W )f?'/ V ) / / '}JV/Vs// ))) } } s') // / l
'/ /// t/1/ J O / J J ' / /
o ' l --- VhW;/}/ /HVA AV.OAM'*///'//JJ'}%/.A,M (AN/W,// / #}/ / // /// ///4MA/l49 ! . J r: :: A: t,1 J1 J1 At s1 Ci N: 01 WEEKS
% A # f"" A / P"" f"""
- f"'" k Af A*I I R f" v v C. C.*""r I( tL_Y s\v C." R AN r G C. i C. i v i r"'% f"" RC. m M i u n C."
<ea, :snrrey I '
00 i I
., . i
- i i i i O 16 ^
A i ,' . C 4 N N 4
% N N n i Q l N9'Q NMNm 6 u 12 s,s =s o, W I I % ., i e_m%I _N. NNu.WN- .. m x . $ l bbbbbbbb[bIbbIbNL., l c a -
- m"""' - ' 'n -
g i NRNN bl93NbhNNNgNNNNNNWNN . .NbNNNiNN.O biW t.J WN NW:P t
,,, I N.4N5 , I p 6 ; ggg,3g,y,y,y,m ,y,y s,yg,yg,w ,,y,y ,
I r9NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN l 4 ..^ f ' X '? N'3N 'f,%NNN'.9 / '?.'? ?.' v ' tN
- l mNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNi A*- MkWWWWWNWWWWWNNWWWWWMNNWWWWWW I 2 'y i
%WNNN NNN NN N WN i NN N NNN N NWNM M NN kNNNgNAN Nk -
I o , ,k,,-, ., f,,,k . ,Njk,\\,INNk,INNk,k,k,ikik,l,Q,k,'k,N.'k. s ,'y,k,']k,klk,A. ,lk. ,N,ik,
-. m , .
2
, ,, , , ., m 1 ,m, .. ,
J1 71 M1 Ai i<t i di J1 Ai 31 C1 N1 D1 WEEMS l APPENDIX FIGURE 3.1.1-1. (Contir.ued) ! 1 I 141
~
k5', 5'\ VX- l?. 7J77 // - isY',5% \ ~'. . C7s'77 /Z-- Ld (l' [5 rct Ci st'su si',D NN o W .. Ld (t, r/ C' t7 C7 J7/ /7 7Z r7J77 f/ 'n t, Ct sY',NT NT 77 '7c77 /7 - TE NX',D VX- 5".) 77 f. Z s'77 //
-)
- g. _ 13 L'h's t t1 33 VC (v',nXV LS',AT Y\-.', -)
p_ ti // G"'/ I. T C7s'7/ / rr cz.'77 f/~~f- 0 rr c7,'77 r/ ,
'( $~,E ( V'. l '. 5\
~/3' u
[5 1'\'%% % sT',D IsVDh 52t sY',1% VX \N- .( E
'4' G_/
7 r.7 .E cz/Z27% C7s' 7/ /_Y - t LL [5 s .K3 33 C- L' V '. .N T \X - o,. O LI,i ' to H :M:ME3M to 'J 38E M EfMF
\'% - y C' 72 f7.'/ / 77-G 103 '\ CE LX',U Ed 7Z F7;/:/
'5 11.5 9VW s5',\T V\ '5 T'/ -
fh $ fC*i.T \ I~ fh y I 7) l / C-
.'. OA SS .sr 33 CC si' 1A \N *~
- c. .*t7 i~ T'> E/ r.7 i // rz C7s'/7 e~/ -Q k'-~ d C1 \ \. S5 J.('3 ~5 h (5'sN 5 \.X .I h E- [7-d' I,/. -
0: [\ Y1's .l.5 3h 1E Ci', A .\T _X F- r/ / Z/. CZ/ // /Z -
-* I I1 sM 3% CC s1',A3 U.V. L' Ce gz ezc yy- C!
Ld in i sr34 a ss',x s xx-. ;5 Ld a, g c,-zz e/.. ,f ,j/. e - ; li I II sr 3-s CE CX: il LX u fE CZ/ // /.Z u (>n l [ sr T3 VX iX ,N\ \X :: C3 t/ l' r ~.E Czs'// L'/- ':: cw
<( q IT33.G CX'.D H- '
<( N I"}' ZZ ?ZJ'7/ 7Z- ^ d e l? 33 G C5:,5 \
%X-G c C/ CL/// /L-G '8
(( o, ir v CC C5'.NT \ ~;- (( ce C/ ZZ_ C/. C7;'77/Z :3 Ed . d.D. bh CC N si',NS
- s. l. ',13 % ld ""
[ '/.'/7 7/ CE '. I s'7/ /r/ c:
'y (5XL C5',%\ \X- ,f y i CZs'// 77 y
- C5',15 YT "
[s"/7 7Z -' o
<( s'.51 \X. <{ :17 /z- o v
E .T \X - F7 r/ L3 \.X
- E'/
F.Z-Q
)- 55 \ _\ --Q L\ VX-
)- t//Z F /~Z -
-l 1. w ,.
J t< z- .. 2 N 1 .U -
-8 u.Z - .
1 NX - r f2 f - Ld is u- Ld v/ rZ
- L G
^
ls' /11./ -
.bd b M
-- (( lt) E/ 7_Z- (( w
> s u r gy
/2.- x
*> L KN- *
- -)
3
~
F. 3 MN E7 /_Z - l'\} H -G Is'/7./.Z G ss. 04 n d OW e-e t r1 v- w- e O, - S O 't MO t4 n o e e t r1
<t v- r e- e-OW v-H 4 H O $
7 w A O SB3D3 3311MOdlill O TD3EFJ 3311MOdilill
s a s r- r i / i v A s f r- m A /s r- -T r 6 4 m r- N A *T"t 6 h P" V V C. C. tN, L. I M V C. N Mu C. 1 C.,ivit" C.N M iL./N C. 1953 - SUqract 22 , , 20 i i I ' 18 ou
, i a 3.
an [!~099 nr.r.au.w. n i e i VA mV/VVrv//V V i t C .a s mu w 12 i I n~u-wwwwn. . mn~n i d ,, , s ww w .s,s a,v.nups,p,r,no.1, sy>wy ,. < a - , > ;us, , _,d,3 3 >> >,> ,m > > > s >> >9 Mh9h. 9 u99Mh9999%Mh9 I
,i m . __ dPe$MfYddNA$.NIdMNAAAAAAAfi2AA2 h _ l v u. r.,;rw n , r r,. , < m, ~ -n w. .~ ,.~ ,
c - , , . , t VV m VWVMVVWWVWMVVWWVWVtv'VM/M l ' 4 :: . . ,
'::: ' /' r ::: ' ',': :,': . ': ':.'.', ::::: '-:::. ' :
t VVe m I 1,/ N e s} _ JHAV' /A ' ,V'NVVVVVHV/'NWH//// ANN /Hf l e9VHV / 'N J h'/ W's ','s*/ 'h*/'/h'.//'N A'nh h')V'sh f e
'H/Y)?J M /H2/V'r//V o l 'A4/AWR'//V' 4 e W WW WWM w'/V'///1////1//1/ Of////////WWWZws%x/WZOZev J1 F1 M1 A1 M1 J1 J1 A1 S1 01 N1 01 wrexs WEEKLY AVERAGE TEMPERATURE 4ees - eo m e 22 1 1
I i 20 i i gn '
'~ l 4 U 18 l M i i C 4 i
5 '
- 4 g i _f53
~~
t , W GG
.o .
NN9D Lsssss&L~sNk% I I C1' '"' [ [
' ' . , . ~-''''''''''- T l C 5 -
NN NN iN r,ND :N NN 'NNNNN5 g, e ' N, , n 6 NNNNNN 4 NN. . n i A
~
i . , , ,,, . w.w .s 3 s ,ww , .x w y 3.s s w w s. , , v 't '..u u . ,.,, I I NN MNm9NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNI I s ':. _' '.': ' ' ': ' : :, - ::: ':: ': ' ':: .':: ':: ', ' l 1NN_~m n9NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN! l y . IvsNvvs.sNssNsvsssNss-s.ssNs.sys-ss.ssssssss'ss-sssssvsss kNN s_ at:Qs N N'N N N W Y N N NNN N s% N NN NN'N N N N'N'NNNN NN'NNN'M bNN N SS NSNbNNNN NNNNkbNNkNNb , N - n ! NNN]NN NNh-J1 T1
- A1 !.11 J* J1 A. . v. . . . w.
WEEKS APPENDIX FIGURE 3.1.1-1. (continued) 143
C [5',53 53 ~ [ /7s'77 E/ - E CX2,53 3X- CC r/s'7777-ld C/- [d Es ( 5 'i,13 53;"
,53 OC g'.
C2 / 7s'77 ((T E5 lZI r/s'77/sb o, (( W l k CC L5',53 3*K -) L Z' r7s'77Ag' - 77 7. 7 s'/7 A .) p_ 1 33 t, Ti iS'>53 Y\ EX i1',13h-L3 Sh CL C5',X3 3';- I.,
')
L 13 G2 77 f. 7 ;'77 )g['- l Ed Efd '77 //- ,. <( l @ B: [. O Sh,. N : iS',5 C5' 5 $3:- *~ 3%- f.
<(
C/ ~)
- [K' /7 '_7 ;'/7 gE ZT !7s 777~ ~'- 2 -
T !. . M' t x 3 wC 65?,1 LXr ss 3t o 3X - ,, T L?'i [2. N 22 rZ;' m nl,' 71 /7;'Z7: eiv77 Z7'7 2- , _ E sM3NTC EX' ,53 8 22 -o [y I iU_dTC C5',X3 3,l w 1K-- -' 7Z r. 7 J'I71 _- (( LM%3YC i1',13 3 (( -[2/ f7s'/7 ( , Q,7%-,' [ TX.W.7. M C5',53 l /Z 77s'77/_sfn 5_ fa.T5 VI:s33 33TC C5',X3 5 .E _,' Z/ FZj'Z714-
- - 1XC3 55 55.W ~\STs (51,1335.A- \ ~~ 1.T~C Z I. ?2s'Z7 I7-t z r<n>/sw'q
[d y L S
;'ba:'Li iS'W33 5 rs m 3ast ts: s3 YI sX',15 M~ . - [d 3,: 0%p' cc LZ r7 'Z7 s..v 4 c F n,;
tr 85 32 3 '.,xi i11.55 3& 15 .W 3bSi C51,11 31- V I. - 6 zz !. z -' L *1>~1 EL EZ;'77TZ-
-a E'W 33 UC EX:.13 33 01 Ce CE. EZ;'7777- "I ld m II.J033YE CiLX13.3~~ '; dj [d m i77 c7, 77 yf _ ;' gj ll..33 33. VT ii!,11 3X- w ()r) g CE CZ;' /_77s. w o
(>#1 I IN CQ C X .',13 3X- > LC ELL' Z2 17- : * (( ,e I W S1 C5'sl M3C-4 El. C Z 'J'/7 2~ 2s[-
^ "
li'53 %% C51,53 3X YX- _", <( O L' CE LL;'Z2 L
-G ],
[ e,a c3' CX',X3 [( ce IC21'77 C. [5 ,53 &~ 4 C/s'/~1 - c bd - L 5 3.13 3X C C X ? .13 3X ,_
. [d
IG'221 _- ,. E;'I77 y 5 - lCS2,13 3._X 2 2 L'/ T/ ~# o <( C,13 YX. <( (Z77 _- o v l' 13 5X~ 17 777-g<,55 q. . " gy yj '~ 13 %_Y~4 }- E7Z I . )E l 5X-NX- N 127 i ?~j% i V- tt. s~ .a ~.." _Y 17 7 72 gy .e .0 ~. g33 [d L3 L. s [d [2 rj/- 2~. t 3:N C7 / - bd E3.'\; g7 [d (/ / -[ w 5 E. N U a: " = D '> BM '> r1'-
.Q;-
c II-/ S 11 3 - c',1m '; zi __- '; . u. x n o e e +- n.- o e e t o o n o o, . e + n o.- e e t a o "@, n a - .. n n .- .. .- w 0. k O S:ORBG 33HWOd131 0 5 B 3 03 33 U W O d131
l WEEKLY AVERAGE TEMPERATURE AUGUST-DECEMBER, 1986 SURFACE 18 , 17 7 l 16 -! 7
! / / / >
. l 14 f j f j __
v i
/ / / / / -
/ / 7 i
'? / / / /,
f / - C l / , l E 10
, / / / / / / / , / , - .
' / ' '
I b l / / j / j / / l '/ } w 8 l / ' ' / ' '
~
6 4
' /
/ / '
' l / / / l l
1 l
/ , / ,
// / , l/ //l / , , I
', / / / / / l/ / I / / /
, /
0 iiiiiiiiiiiiiii,iiiiii Al S1 01 N1 D1 WEEKS WEEKLY AVERAGE TEMPERATURE AUGUST-DECEMBER, 1986 BOTTOM 18 I i 1 g 16 . , , 1 N l
~
u ' "" ~ 12
- N O
l_F l W i \ s '- N QN \ l 30 g\
$ l g \N
\ g\ g \ i m s N N \ - i 3 '
N ' 5 i \ g\ \ N xs g ._ i g , N x s N < N mi y I \ \ g\ s N g\ g N \ N Il w 4 1 \ \ . \ s N \ . \ g\ g N\N N l
- N '
N 6 N g g g l \ \ \ \ - \ '
\ \ \ '\ - \I 2 N N w > x x s i
! \ \ \ \ \ \ N \ \\ \ l
< \ \ \ < \ \ ,
0 _, 4 i I i i i i i i i i i i i i i i 4 4 4 I 4 A1 51 01 wttts N1 01 : Appendix Figure 3.1.1-1. (Continued) 14.* l
1 l l 3.2 FINFISH 3.2.1 Ichthyoolankton 3.2.1.1 Total Community Nearfield (P2) ichthyoplankton data collected from 1978 through 1986 was examined for temporal (seasonal and year-to-year)- patterns in species assemblages by discriminant analysis. Farfield (P7) data was collected historically and during 1986 and compared to P2 for similarities in species composition and frequency. Species composition at the dir. charge station (PS), collected only from July-December 1986, was compared to that at P2. Common names recognized by the American Fisheries Society (Rebins et al. 1980) are used for fish species in the text. The common and scientific naneu for every species collected from 1975 to 1986 in the Seabrook ichthyoplankton and adult finfish programs are listed with their relative abundances by gear type in Table 3.2.1-1. No newly-recorded species were encountered during either the 1985 or 1986 sur-veys. Temporal Patterns of Nearfield Fish Enz Assemblames Numerical classification of historical data (1975-84) had shown that the species composition of fish eggs was highly seasonal in nature, with different species occurring at different times of the year and generally the same seasonal succession repeating year after year (NAI 1985b). The basic pattern over the 1975-1984 baseline period was summarized by seven major seasonal groups of samples, each characterized by a particular assemblage of species (Table 3.2.1-2). Eight samples from the 1984 classification had previously been left as "ungrouped"; in 146
l f TABLE'3.2.1-1. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND GEAR TYPE, JULY 1975-DECEMBER 1986. SEABROOK BASELINE REPORT, 1986. t ICHTHY 0- ADULT AND JUVE-PLANhTON NILE FIhTISH TOWS , a a GILL-SCIEhTIFIC NAME COMMON NAME EGGS LARVAE TRAWLS NETS SEINES Acipenser oxyrhynchus Atlantic sturgeon R R C C Alosa aestivalis blueback herring Alosa mediocris hickory shad R Alosa pseudoberengus alewlie 0 0 0 Alosa sapidissies American shad R 0 0 Accody:es americanus American sand lance A 0 R 0 Anarbichas lupus Atlantic volffish R f Anchos hepsetus striped anchovy R Anguilla rostra:a American eel C R Apel:es quadracus toutspine stickleback R i Archosargus proba:ocephalus sheepshead R Aspidophoroides monop:erygius alligatorfish C 0 ! Brevoor:da tyrannus Atlantic menhaden 0 0 0 R r Brosee brosee cusk 0 0 Caranx hippos crevalle )ack R Cancropristis s:riera black sea bass R R Conger oceanicus conger eel R Clupea harengus harengus Atlantic herring C 0 A 0 l 1 Cryp:acan:hodes escu14:us wrymouth R , Cyclop:erus lucpus lumptish o O R R Enchelyopus ciebrius tourbeard rockling C C 0 Fundulus sp.* mummichog* . C l Cadus eorhua Atlantic cod - C C 0 R l centanuec 1 J 147 _ - . _ - .. - _- _ _ . _ . _ . - . - - . _ . , _ - - . _ _ . _ , . . ~ . _
I 1 TABLE 3.2.1-1. (Continued) ICHTHYO- ADULT AND'JUVE-- PLANKTON NILE FINFISH TOWS
- a. a GILL SCIENTIFIC NAME COMMON NAME EGGS LARVAE TRAVLS NETS SE1NES
-- ~
Gadus /Melanogrammus Atlantic cod / haddock C - - 0 0 Gasterosteus sp. stickleback R C Glyptocephalus cynoglossus witch flounder C C 0 Hemitripterus americanus sea raven 0 C 0 R Hippoglossoides platessoides American plaice C C 0 Hippoglossus hippoglossus Atlantic halibut R j Labridae/Limanda cunner /yellowtail flounder
- A - - - - I Limanda ferruginea yellowtail flounder - C A R 0 Liopsetta putnami smooth flounder R R C Liparis atlanticus seasnail 'C - - -
Liparis coheni gulf snailfish C -- - - I Liparis sp. snailfish - 0 , Lophius americanus goosefish 0 0 R Lumpenus j 14mprecaeformis 8 snakeblenny 0 R Lumpenus maculatus daubed shanny E R Macrozoarces americanus ocean pout O C R Melanogrammus seglefinus haddock - 0 C R Menidia menidia Atlantic silverside O R A Menticirrhus i saxatilis northern kingfish R Merluccius bilinearis Atlantic whiting C C C C R continued 148 l l l
TABLE 3.2.1-1. (Continued)
- ICHTHYO- ADULT AND JUVE-PLANKTON NILE FIhTISH TOVS a a GILL SCIENTIFIC NAME COMMON NAME EGGS LARVAE TRAVLS NETS SEINES Ricrogadus :oncod Atlantic tomcod R 0 Horone americana white perch R Horone saxatilis striped boss R R Mustelus canis smooth dogfish R Gyoxocephalus senaeus grubby C 0 R 0 Hyoxocephalus occodecenspinosus longhorn sculpin C A 0 R #roxocephalus scorpius shorthorn sculpin 0 0 R R i Odontaspis taurus sand tiger R Oncorhynchus kisurch coho salmon R R Osmerus nordax rainbou smelt 0 C 0 C Paralich:hys oblongus toutspot flounder R C Pepriles triacanthus butterfish 0 0 R 0 R Perromyzon carinus sea lamprey R Pholis gunnellus rock gunnel C 0 F R Pollachius rirens pollock C C C C 0 Poca:ocus sal:a:rix bluefish 0 K Prionotus carolinus northern searobin R 0 R Prionotus evolans striped searobin R Pseudopleuronectes americanus winter flounder C C 0 C Pungitius pungi:ius ninespine stickleback C Raja eglsn=eria clearnose skate R Raja erinaces little skate C R #aja banoculata big skate O R Raja radiata thorny skate C Saleo gairdneri rainbow trout 0 continued 149
l TABLE 3.2.1-1. (Continued) ICHTHYO- ADULT AND JUVE-PLANKTON NILE FINFISH TOWS a a GILL , SCIENTIFIC NA!!E C0?1?l0N NA!!E EGGS LARVAE TRAVLS NETS SEINES i
?
l l Salmo trut s brown trout 0 Salvelinus fontirslis brook trout R Scomber japonicus chub mackerel R Scoeber scombrus Atlantic mackerel A A R C R Sce;hthalmus aquosus uindoupane C C C R 0 Sebssees sp.i redfish 0 Sphoeroides esculsius northern puffer R R Squalus scen: hiss spiny dogfish R R S:enotomus chrysops scup R 0 R S:fchseus punc:stus Arctic shanny R Syngnathus fuscus northern pipefish C 0 R 0 740 togs oni:is . O tautog R 74u:ogolabrus adspersus cunner - A 0 0 R Torpedo nobilians Atlantic torpedo R Triglops curray moustache sculpin T R Ulvaris subbifurcs:s radiated shanny C 0 l Urophycis sp.3 hake d A C A 0 C 1 I Footnotes: See next page. I i 1 150 l
TABII 3.0.1-1. (Continued) Footnotes ONames are according to Robins et al. (1980) unless otherwise noted. Taxa usually identified to a different level are not included in this list to avoid duplication (e.g., Gadidae, Enchelyopus/Urophycis, 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 (310% of total catch over all years) C = common (occurring in 310% of samples but <10% of total catch) 0 = occasional (occurring in <10 and 31% of samples) R = rare (occurring in <1'. of samples)
- = not usually identified to this taxonomic level at this lifestage "Predominantly fundulus he:eroclitis, mummichog, but may include a small number of fundulus hajalas, striped killifish.
C. aculeatus, bwespeciesofCasteros:eushavebeenidentifiedfromseinesamples: threespine stickleback; and C. whes Jandi, blackspotted stickleback (both occurring commonly).
'May also include a small number of tautog.
I a:Janricus, Three species of Liparis have been identified from trawl samples: L. cohen 2, and L. inquilanus (inquiline snailfish). OSpelling after Tabe: (1976). f 1 F'Previously called silver hake (NAI, 1962a); Atlantic whiting was recommended bv l Kendall and Naplin (1951:707).
)
Previously called S. caranus. Recently S. men:ella and S. fasciatus have also ; been reported to occur n the northwest Atlantic (Ni, 1981a; 1981b). Sebas:es ' in coastal New Hampshire waters are probably S. fasciatus (Dr. Bruce B. Collette, U.S. National Museum, pers. come. April 1982), but larval descriptions are insufficient te allow distinction among the three species. U chuss, 37nree species of Orophycis have been identified from trawl samples: red hake (common); v. :enuis, white hake (common); and v. regia, spotted hake (rare). l l I l l 151 l l
TACIE 3.2.1e2. D8518t18U18081 AMOseG DATES A%D AMOMG SEASOseAL ASSEMBLACES OF SAMPLES OF FISH ECCS COLLECTED AT NEARFIELD STATIONS P2 AleD P3 DURING JULY 1975 THROUGH DECEMBER 1936. SEABROOK BASELINE REPORT, 1966. see een a,e etet see see men se e me ese se s a .me e ee . 4 esesent er4 eaae eaeo ease eae= aaae eae= =2se eaae eeaa ease eaae eis= esesomes esse ens senese e* eoeo e, e aaaa ce eeis.o.ee.,
..seen e
- r. 9 .s .e ea e 9e s
e.ee a .. ai=a
=n seeses.se res eec see e.9.e Os.#
rara .e e9== a esse .s ess s s en e e 99 s
- r. useeer-sea seo e e -
ea e :eea e:oe 9*ea ae o ame<8een eseere eu e.s.ee.e..emer 06 e : es=s s ae eas as e.ee es eeste-. ee.. ,s esse een s e .9 esen r a e aee e e .e e e
- s. a no.we4ee. sse* =e meer se Cee e,.a pesos.
.ee ses ese ee reen tee,sese e, 929..s 58 .
ye s teme t e . 99 e4 Caethoceost R7e.3 eB e eeartoece roeheseg 4 ef,F e t R e
- e. speeeg a Caseess/yeeeeeees Feeeeeet seeFs e t- - e/ 9s4 4e assemees mesteeee rg es.F yee w ete- aee e someteefe rechstag teSS .e m6eseg ee7 e mesessen pestee toe.:
9e F ea a ee e W # U. PJ ee ee 3 sem aae aae Casemea/yeeeeeeeee reeeeeeef 2sse9 e casesioe/ 933e 4eee eeFe F 4 neae eens.S
,ee eeee e t t, ss94 9ee9 9 8e acessees eesteeee. gese e a o. Fes eIs % 9 easte teg/ mete 24fe e ee 99e f e aa e e4 ee
- 6. Sammer aaa eteeeme/ a t Fe sE s E58 eense Stee e yee eeeee e s e a367 e Cameneteet esess e s # e Post. s a e4 Aa Weesoupeste f eessesse 486. e e
7, feee seee-whJ e eme ee9e e4 mote es9 e t9ae e se come se ehe e ses se . S seae 4 aos 6 8 esmerhose a 79. e e et 9 eeustseeed eteeeeeg te%. e e a e
- e. Summese =f eeee e ee,e ee
-o no e e ae emett emem ess.t meeeeeeese e e -
4 7.e eene == e as emes se ans t ees 3.e
- s. e ss e-eeeeee aseeesse ese e a e r aa aa assesses see een P eeo e st eeme 6s emen tog so.e 3 s eo*e 8. e ee aeereseed <=b o see =.S e
ee e e., e-e. 3 e soees e-es, o e mese, so-se, e e e e so-se e , _ _ _ _ _ _ _ ._.______.._M'u u tM N.O r it h i 36 . _ .__ . ..m - .
I 1 order to classify all baseline data, these samples have'been assigned to two loosely defined groups (8 and 9) which were characterized by rela-tively low abundances of a few species which occurred during the fall and winter. J j Discriminant analysis agreed fairly well with numerical l-classification analysis in the recognition of the nine seasonal assen-blages of eggs. Twenty-two of the 217 samples (10.1%) were reclassified by discriminant analysis, i.e. assigned to a group different from that assigned by the cluster analysis. The asasonal groupings of saeples included late fall-early winter (Group 1), winter-narly spring (Group 2), spring (Groups 3 and 4), summer (Groups 5 and 6), fall (Group 7), late summer-early fall (Group 8), and fall--winter (Group 9). d The late fall-early winter, cod-pollock (Group 1) assemblage appeared in the 1985-1986 season from November until .early yebruary, l similar to the 1975-1984 baseline summary observations. The Group 1 assemblage .in 1985-1986 was characterized by moderate nuebers of Atlantic cod and pollock aggs, with very low abundances of other species. The second seasonal group, a winter-early spring plaice and ] cod / haddock assemblage, in 1986 succeeded the first group in February, ; which was typical of the baseline years' pattern. However in 1985, this assemblage which usually appeared in January or February and lasted only l until mid-April, appeared in March and persisted into May. Abundances of pollock eggs declined dramatically during this seasonal period. ! . t i The spring plaice-cunner /yellowtail assemblage (Group 3) was j present from the beginning of April to the middle of May during 1978 ' through 1984. During 1985, this assemblage was absent, and it occurred from only late April to early May in 1986. This group was characterized I by an increase in the number of abundant species. In 1986, American l l plaice was the most abundant species, followed by fourbeard rockling, I
! 153
I cunner /yellowtail flounder, and Atlantic cod / haddock eggs. Most of the j cunner /yellowtail flounder eggs at this time of year, while not identi- j fled to species, are assumed to be yellowtail-flounder since this species begins spawning in March, while cunner do not typically begin spawning unt;il June (Bigolow and Schroeder 1953). The spring cunner /yellowtail. flounder-mackerel assemblage (Group 4), had a relatively short duration in 1985 and 1986, which was characteristic of the previous 1975 through 1984 baseline summary period. During 1985 and 1986, the Group 4 assemblage occurred from the second week in May to early June. It exhibited high abundances of j cunner /yellowtail flounder and mackerel eggs. Fourbeard rockling, windowpane flounder, and American plaice eggs were also abundant.
- A very abundant summer cunner-hake assemblage comprised the f
fifth group. Generally, the Group 5 assemblage occurred from early June -; to late August or September. The 1985 and 1986 occurrence was detected I from mid-June to mid-July. Cunner /yellowtail flounder and hake eggs ! dominated egg collections during this period. Most of the eggs identi- i fled as cunner /yellowtail are believed to be cunner at this time of year . (NAI 1983b). Atlantic mackerel, fourbeard rockling/ hake, and windowpane , flounder were also abundant in this seasonal group. Atlantic whiting occurred in moderate to low abundances (NAI 1987), i A second sususer group (Group 6) was a hake-cunner /yellowtail I flounder assemblage. During the 1975-1984 summary baseline period, this assemblage occurred from early July to mid-September. Only four years (1978,1982,1983 and 1984) were represented, with the majority of ; samples coming from the latter three years. During 1985, this assen- ! 1 blage first appeared in late June but was consistently present only from ! August to mid-September. In 1986, the assemblage occurred from late ; July to late August. This assemblage, which temporally overlapped the ; I t f t i 154 i
fifth group, was differentiated from Group S by its low cunner / yellowtail abundances. This assemblage was further characterized by moderate numbers of windowpane flounder eggs. Other species also exhibited a decline from early summer abundances. The seventh seasonal group, a late summer-early fall hake-whiting assemblage, was composed of samples collected from September to mid-October during the 1975-1984 baseline summary period. The only years not represented in this assemblage were 1977 and 1982. During 1985, this assemblage occurred only during the latter part of September, while it occurred throughout September in 1986. Hake, although dimin-ished in abundance in comparison to its association with the Group 6 assemblage, still dominated egg collections. During 1985, as in the past, other species continued their gradual seasonal decline (NAI 1986). But in 1986, hake shared dominance with fourbeard rockling. Atlantic whiting was relatively uncommon in 1985 and 1986, unlike previous years. An atypical summer-fall group (8), represented by only six samples, temporally overlapped Groups 6 and 7. This assemblage con-sisted of the same taxa occurring in Groups 6 and 7, but all except rock 11ng/ hake had lower densities. Another fall-winter seasonal group occurred predominantly in 1983 and 1986, with only a single collection in 1977. The Group 9 assemblage was largely a composite of species from the fall Group 7 and winter Group 1, with the exception of an occasional abundance of cod / witch flounder (NA1 1987). A Group 9 assemblage was also distinguished during the winter of 1985, when Atlantic cod presence dominated the samples (NAI 1987). In summary, discriminant analysis placed 1985 and 1986 species assemblages into groups previously identified with numerical classifica-tion. The 1985 and 1986 species assemblages generally compared posi-155
.. - . - - . ~ =. l tively with those from previous years, with the exception of increas-ingly sore importance being assigned to two previously-minor groups now presented as Groups 6 and 9 during the fall and winter. 1 Atlantic herring,'American sand lance, and winter flounder, which were important components of the larval assemblages discussed below, were omitted from the historical baseline analysis of fish eggs because these species have demersal rather than buoyant eggs. Histor-ically, their eggs have not been frequently collected in oblique tows through the water column. Temporal Patterns of Nearfield Larval Fish Assemblages, l Numerical classification analysis of fish larvae abundances at the nearfield station (P2) during the baseline period, 1975-1984, revealed the high degree of seasonality observed among eggs (NAI 1985b). The seasonal succession of larval assemblages can be summarized by four major groups, f all-winter, winter-spring, spring, and r,ummer, each containing from one to three subgroups (Table 3.2.1-3). Discriminant analysis placed the 1985-1986 data into the following nine seasonal subgroupings. ) The first major group, fall-winter, consisted of two subgroups (1 and 2), each dominated by Atlantic herring larvae. Atlantic herring larvae were most abundant in subgroup 1 from early October to mid- l November. Only a few other species were present in very low abundances during this period (NAI 1985b; NAI 1986; NAI 1987). The second winter subgroup in 1985 1986 was dominated by pollock, with Atlantic herring displaying decreased abundance from the earlier collections. During the 1975-1984 historical period, pollock and Atlantic herring alternated as the dominant and subdominant species. Previously, Subgroup 2 occurred from mid November to early January for most years, but during 1985 it extended into early Fabruary and in 1986 it extended into mid-January, 156
s 5 e S e * *. ** . **- *. *t t .. t I* g si 31. E.. 1 [2] - = : 25 g. g :; x m II " i I i
- j ::
a
-=
li i i
- j-2
.t..;i 3
i g r m. : -::: r . o w
!!.5 .g p .
n i. 2 : - lig .g d :
- 13 l:e i s il..: : .I 8
we <C > (> a.- . . == a. ...... ~ : ?2 . . .... - y . .. .... I-og I. ed. .. x< i. a.. . g= . .. . ... 3g .. e . i eg . -. .. - ow . .. .. ..
<a .. .. .. t
, f.. .. ... .
.. J. ,
- z. . .....
wm C. . .... . .i 2 pe (.. .. ......
;E
- a. -. . .. ;, ,
tw . ... .. .- - ga g. ..... - ;2
, 3
. . ......~...
*o ...-.. :I.
e- .
- s. .......
[q3 . . . . .... ,1 2 ,-
<= . .. . ...
- e: --- -
, e. ... .
.-[2
<c 3g .....
......... . ;}{
,, i... ..... ,. .
a.= ..... . 4: -. g ., . ........ .,- g ,,
. ...... . t :,
8_g . .,- .. . .. , i t _o ,e.1. n, 3 ,
-< . . a , .3 m -~
oc I . 2 83
.g l
.4, ,.
I rr T 5, . . .] .
-g
*j-j
- a g,
- i. e. ,- :] 13 1 1.3
...its L
- 1. a sa . ; a . a .-
b. 1 W i b
< 1 .um 157 <
I
i l American sand lance larvas dominated the second major seasonal group, winter-spring. This grouping contained three subgroups (3, 4 and
- 5) which were distinguished primarily by high, moderate, or low numbers of sand lance larvae. In subgroup 3, sand lance larvae were very abundant and rock gunnel larvae were modestly abundant from mid-February to the end of April. This sand lance-rock gunnel assemblage comprised the majority of samples, both historically and in 1985 and 1986, within the winter-spring group. Subgroup 4, a secondary sand lance-pollock assemblage characterized by high pollock and moderate sand lance abundances, was evident from late January to early February during 1985 and 1986, and reoccurred in mid-April 1986. This was somewhat shorter than the December to mid-February presence between 1976 and 1984. The third subgroup during the winter-spring period, Subgroup 5, occurred only in early May 1985 and in mid-February 1986. Previously, only four atypical samplos from 1977 to 1984 were classified in this group, with low densities of sand lance larvae and little else.
Subgroup 6, a flounder-seasnail assemblage, which lasted from late April to late June-early July in 1985-1986, comprised the spring or third major seasonal group. The 1985-1986 spring group, as in previous years, was characterized by moderate numbers of winter flounder, American plaice and sessnail larvae. An increase in abundance for most other species was also apparent (NAI 1986; NAI 1987). The fourth major seasonal group, summer-fall, consisting of Subgroups 7, 8 and 9, typically lasted from mid-June to mid-October. In 1985, Subgroup 7 was evident from early July to mid-September, but in 1986 it did not occur past mid-August. In August and September 1986, larval abundances were so low that no subgroups were discernible. l Atlantic whiting, fourbeard rockling, witch flounder, Atlantic cod, and ! yellowtail flounder all reached their yearly peak abundance during the l summer-fall period. A second summer-fall assemblage, Subgroup 8, . consisted of low-to-moderate numbers of cunner larvae and low-to- I moderate abundances of other species (NAI 1986; NAI 1987). This i I 158 l
assemblage occurred infrequently (only seven August and September samples were contained in Subgroup 8 from 1975 to 1984), but in 1985 and 1986 this assemblage was much more common, with more than double the number of samples than in previous years. A third summer-fall assemblage (Subgroup 9), occurred sporadically from mid-July to mid-October 1985 and only once in 1986 in August. Typically, moderate abundances of fourbeard rockling and hake characterized this subgroup. But, in 1986 the single sample in this subgroup did not fit the typical species profile, as cunner was more abundant than the observed single rockling larva (NAI 1987). As in the past, most species continued to decline in abundance during this period, providing a distinct break before the beginning of the f all-winter herring assemblage. In general, the results of the 1985-1986 discriminant analysis for ichthyoplankton larvae agreed with previous seasonal and species groupings determined by numerical classification (NAI 1985b). Spatial Patterns of Fish Ear and Larvae Abundances Spatial differences in abundance and species composition from the nearfield and farfield stations were previously compared using numerical classification (NAI 1983b; 1984b) for both fish eggs and larvae. Spatial (station) differences were found to be less important than short-term temporal differences. Samples collected on the same date at different stations (nearfield or farfield) more likely resembled each other than if collected 1-2 weeks apart at the same station. This similarity in species composition and abundance between nearfield and farfield sites was consistent with the known extent of water mass movements in the study area. During 1986, the relative abundance and percent frequency of most taxa in ichthyoplankton samples were very similar between Stations P2 and P7 for both eggs and larvae (Tables 3.2.1-4 and 3.2.1-5). 159
TABLE 3.2.1-4. COMPARISON Of PERCENT ABUNDANCf AND PE RCE NT FREQUINCY 3F f lSH ECC COL LECTIONS AT NEARFIELD (P2). FARFIEL D ( PT) AND DISCHARCE ( PS) STAllONS DURING 1986. ALL SPICl[S WHICH WERE CotLIC?[D IN life [CG STAGE ARE LISTED. SEAHROOA BASIL INE RE PORT , 1986. STAllON P2 STATION P7 SIATION P2 STATION P5 JAN-DEC 1986 JAN-Dtc 1986 JULY-DEC 1986 JUL-DEC 1986 P[RCENT P[RCTNT PERCENT PERCINI P(RCENT PERCENT PERCENT PERCENT SPECif s ABUNDANCE IREQUINCY ABUNDANCE IRfQUENCY ABUNDANCE FREQUENCY ABUNDANCE FREQUENCY Brosse brosse <0.1 4.2 <0.1 8.3 <0.1 8.3 <0.1 4.2 inchelyopus cimbrius 3.8 54.2 6.0 52.1 1.1 58.3 1.4 66.7 Enchelyopus/urophycis 7.4 31.2 2.1 31.2 14.8 54.2 4.1 58.3 Gadidae /Clyptocephstus 1.8 13.3 2.8 31.5 0.7 31.5 0.6 50.0 Cadus/McInnogrammus O.4 25.0 0.3 25.0 -- -- -- -- C2dus morhus 0.9 54.2 1.7 56.2 1.7 50.0 0.9 50.0 Clyptocephalus cynoglossus 0.2 12.5 0.2 16.1 0.1 8.3 0.1 16.7 Hippoglossoides platessoides 0.9 41.7 0.1 31.5 <0.1 4.2 0.1 4.2 tabridae/L/msods 53.6 43.8 54.0 43.8 63.0 50.0 68.3 50.0 L/mands ferrug/nes <0.1 18.8 <0.1 14.6 <0.1 4.2 <0.1 4.2 ,, Merlucclus bilinearls O.4 22.9 1.0 22.9 0.3 33.3 0.1 37.5 m polischlus virens 0.3 35.4 0.6 33.3 0.1 37.5 0.2 41.7 c) Scomber scombrus 17.5 20.8 19.5 22.9 1.3 8.3 2.4 4.2 Scophthalmus aquosus 2.9 45.8 1.6 43.8 2.6 54.2 1.8 58.3 12utogolabrus adspersus 2.7 22.9 4.0 20.8 3.9 29.2 2.9 29.2 urophycis sp. 7.2 41.7 4.8 39.6 10.3 70.8 16.9 66.7
_ _ . _. _ _ _ . .__ . - - _ - . _ _ _ -. _m _ = __ ._- _ _ _ . _ T ARI. E 3.2.1-5. COMPARISON OF PERCENT ABUNDANCE AND PERCINI FRIQUE NCY 50R L ARVAl_ F ISH SPfCIES AT NEARFl[LD ( P2), F ARF l[LD ( PT) ANO i DISCHARCE ( PS) ST AT IONS DURING 1986. SPECIES LIST [D ARE CONS 10fRID COMMON IN OVf RALL ST AT ION A8UMOANCE ( see species Idst in Table 3.2.1-1). SEAHROOK BASE 11NE HIPORT, 1986. STATION P2 STAllON PT STAllON P2 STATION P5 JAN-DEC 1986 JAN-ofC 1986 JUL-Dic 1986 JUL-DEC 1986 PfRCINT PfRCENT PIRCENT PfRCENT PERCENT PERCENT PIRCENT PERCENT ABUNDANCE fRfoutNCY AnUNDANCE FREQu(NCY ABUNDANCE FREQUINCY ABUNDANCE FREQUINCY SPICIIS Aomodytes americanus 36.5 $2.1 38.4 52.1 0.1 16.1 0.5 20.8
== -- --
- Anguilla rostrata <O.1 2.1 <0.1 2.1 -
Aspidophoroides -- monopterygius <0.1 10.4 <0.1 4.2 == -- -- Clupea harengus harengus 8.5 45.8 9.8 41.8 18.9 54.2 38.1 50.0 Cyclopterus luopus <O.1 6.3 <0.1 10.4 <O.1 k.2 0.1 8.3 inchelyopus cimbrius 1.2 33.3 10.5 35.4 14.4 45.8 14.1 50.0 Cadus oorhus O.4 31.5 0.4 39.6 0.3 20.8 0.3 25.0 Clyptocephalus cynoglossus 1.1 14.6 2.7 16.1 2.1 20.8 3.4 29.2 Hippoglossolies platessoides 0.6 29.2 0.1 33.3 0.4 8.3 0.2 8.3
>" timanda ferruginea 1.2 20.8 1.6 14.6 1.1 20.8 <O.1 4.2 liparis atlanticus 1.9 25.0 0.5 18.8 0.3 4.2 0.6 8.3 \
l2 O.3 21.1 0.9 25.0 -- -- -- -- liparis coheni 20.8 t Merlucclus bilinearls 0.3 14.6 0.6 10.4 0.1 29.2 0.3
-- ~~ -- --
Myonocephalus aerseus 0.9 25.0 1.0 25.0 Myonocephalus -- -- -- -- octodecesspinosus O.3 16.1 0.1 10.4 , tholis gunnelius 6.1 27.1 5.5 25.0 -- -- -- Fallachius virens 3.9 33.3 3.8 31.2 0.3 25.0 0.6 29.2
!seudopleuronectes accricanus 2.2 25.0 1.0 22.9 1.5 8.3 0.3 8.3 18.8 13.9 CM.8 43.2 16.7 31.6 16.7 Scomber scombrus 19.4 16.1 0.1 25.0 0.2 25.0
} Scophthaleus aquesus 4.4 16.1 0.8 , Syngnathus fuscus 0.2 14.6 <0.1 18.8 0.1 29.2 <O.1- 25.0
- 6.2 41.1
!autogolabrus adspersus 5.k 29.2 5.4 22.9 12.2 50.0 utvaria subtifurcata 3.3 37.5 2.1 35.4 3.0 31.5 1.6 33.3 urophycis sp. <0.1 6.2 0.1 8.3 <O.1 12.5 0.3 29.2 1
i 1 4
. _.___ _ _.._ . - __m -- . . _ - - . - - , . . . - . _ , , - ,. v --- --.w-- , . - . - - - , . . , , _ , , . _ ___
Relative abundance and percent frequency of eggs between P2 and PS during July-December 1986 were similar for most taxa (Tables 3.2.1-4 and 3.2.1-5). An exception was rockling/ hake eggs, which were relatively more abundant at P2 than P5 or P7, although they occurred slightly more frequently at P5. Most larval species occurred in similar relative abundances and frequencies between P2 and PS. Atlantic herring occurred in greater relative abundance at P5 although percent frequency was slightly less. Atlantic mackerel occurred as frequently at PS as P2, but relative abundance at P2 was greater than at P5 or P7. Entrainment Species Assemblames Although Seabrook Station was not generating power or dis-charging heat in 1986, the circulating water system operated in a test mode from June 7 through the end of the year (Table 3.2.1-6). Flow rates per month averaged between 411 million gallone per day (mgd) and 496 mgd. As a preliminary evaluation of entrainment effects, ichthyoplankton samples were collected periodically in the intake pumphouse (Station E1) from July 31 through December 22, 1986. Generally, entrainment samples were collected within hours of the offshore nearfield collections, but not necessarily synoptically (Table 3.2.1-7). More samples were collected at the nearfield station (21 dates vs. 15) contributing to some observational differences discussed below. Because of equipment restrictions, entrainment pump sarple volumes averaged approximately 100 m3 (as designed) as compared to l 3 approximately 475 m for offshore towed net samples (NAI 1987). Fish egg taxa in entrainment samples followed trends similar to those in offshore nearfield collections (Table 3.2.1-8). Cunner / ! yellowtail flounder, rockling/ hake, windowpane, hake and pollock were the five most abundant taxa in in-plant samples. In general, mean
. abundances and the total number of taxa in the offshore samples exceeded those observed in entrainment samples. However, species not encountered 162
___-_____-_____-__-_-_1
TABLE 3.2.1 6. SU! DIARY OF MONTHLY FLOV DATA IN MILLIONS OF GALLONS PER DAY (egd) THROUGH THE SEABROOK CIRCULATING VATER SYSTEM, JUNE - DECEMBER 1986. SEABROOK BASELINE REPORT, 1986. NO. DAYS RANGE OF DAILY MONTH OPERATING FLOV RATES MEAN FLOV (mgd) (egd) Jun 24 116-499 467 Jul 31 451-499 488 Aug 29 41-509 443 Sep 31 467-499 496 Oct 24 5;-536 411 Nov 30 107-499 471 Dec 30 83-499 478 163
l i 1 l 1 TABLE 3.2.1-7. ICHTHYOPLANKTON SM1PLING DATES AT ENTRAIN!!EST STATION (E1) AND NEARFIELD STATION (P2), JULY 31 THROUGH DECEt!BER 22, 1986. SEABROCK BASELINE REPORT, 1986.
?!ONTHS JUL AUG SEP OCT NOV DEC STATIONS VEEK El P2 El P2 El P2 El P2 El P2 El P2 DATES 1 - 4 9 2 7 7 -
5 - 5 0F 2 11 11 18 9 14 13 11 11 12 11 SMIPLING 3 18 20 23 17 21 20 - 18 22 21 4 31 28 28 26 29 24 - 28 25 25 - 30 - = not st.mpled i i 1 l i I 164
TABLE 3.2.1-8. Mf AN ABUNDANCE (#/lonoms) Or flSH IGGS PfR HONIH Al STAllONS fI and P?. STABROOK BASEL.INE RE POR T. 1986. Jul. AUG ST P OCT NOV OfC E/MONIH TAXON El P2 Il P2 ft P7 [1 P2 [1 l*2 El P2 [1 P2 Cunner /Yellowtail i t oernde r 1552 1611 8 M6? o 96 260 14?8 Rockling/Habe 466 530 58 116 7 400 0 10 88 206 Wi endowpa ne 155 ITT 70 23? ?6 I? O ? 33 61 Habe 34 4003 TO 1415 56 5 086 5 11 0 <1 28 989 Pollock 8 1 5 15 119 21 21 6 Conner 121 161 0 133 20 49 Atlantic cod 2 9 37 537 62 205 17 125 Fourbeard rockling O $? ? 54 43 263 4 18 0 <1 8 65 Atlaestic Macheret 17 0 3 O Cod /W6 tch f loiceder 2 ? O 3 2 88 <1 16 Witch f'lounder ? 4 <1 <1 Atlantic whiting 3 ? 30 0 6 0 <1 <1 7 Tautog 0 29 0 5 Unidentified Species 0 1 0 3 0 <1 0 <1 Yellowtail flounder o a o <1 Cusk o <1 0 <1 Intal Species [ncountered 6 6 7 11 5 9 4 9 2 6 2 2
in entrainment samples were not common at the nearfield station. Larger sample volumes and greater frequency of offshore collections contributed to the increased number of taxa. Entrained fish larvae also followed trends in species compost-tion and abundance as observed in the offshore nearfield station collec-tions (Table 3.2.1-9). Atlantic herring was the most abundantly j entrained larval species. Monthly mean abundances of Atlantic herring were very similar to monthly mean abundances observed at the nearfield station. In comparison to Atlantic herring, other species' larval abundances were low. In order of abundance, pollock, cunner, rockling and radiated shanny comprised the remainder of the top five entrained species. In general, larval mean abundances and the total number of species encountered offshore were greater than those observed in entrainment samples. I l 3.2.1.2 Selected Species Nine larval fish species were selected for a detailed analysis of their within-year and among-year patterns of abundance because of their numarical dominance or importance as a recreati6nal or commercial species. Analyses were based on a series of 132 conzeeutive monthly , i means for nearfield station samples collected from January 1976 through ! December 1986. These monthly means were averages of two to four repli-cate tows and one to four dates within each month. Each of the nine species displayed distinct seasonal patterns of abundance (Figure 3.2.1-1). While the presence of some larvae was noted year-round, the larvae of each species exhibited a sharply defined
- period of only a few months' duration in which their peak abundance occurred. Values in other months were typically much lower and were often zero. These seasonal fluctuations were primarily responsible for 166
IAftlE 3.2.5-9. HIAN AntlNDANCE (#/1000sms) 0F IISH ICitVAL PI R HONill Al STATIONS [1 Atil) P2. SIABROOK BA3EllM REPORI. 1986. JUL AUG St P OCI NOV D[C E/NONTH IAXON [1 P2 Il P? Il PP f1 P2 El P2 [1 P2 f1 P2 Attantic lierring O <1 1039 Is?9 7fs 3 695 als $3 ??8 196 PoIInck T IT 9 3 3 3 Ca enne r 0 16 is 18 <1 ? <1 6 f ossr tica rd rock l ing O 9 3 2 <1 <1 O 12 0 <1 <1 la Radented Shareny ?) 11 2 8s ? ? <1 3 O 2 0 <1 <1 <1 1 I <1 <1 P i rwe f i s ts Sand I arece 2 3 <1 <1 (Jnideritified Species O <l 1 1 0 <1 <1 <3 C <l 2 0 <1 <1 $ Cadidae Conscrish ? <l <1 <1 Seasnail 1 0 <1 o Atlantic Macherel 0 13 0 2 Witch iloiroder O ? O 8 0 2 Wi twf owpasse O $ 0 1 0 <1 0 1 0 <1 0 3 0 <1 0 <1 Atlarit ic Cod 0 <I O 7 0 <1 0 <1 Atlantic Vflitifl9 8 ? O <t A rc t ic Sha nny O <1 0 ? O <1 Habe O <1 0 <1 Yer t i rNt a i l F l osende r lotal Species frw;ountered O T 84 9 4 8 3 8 is 6 3 $
ie. a - e.
- e. - AMIRlCAh 4 SAND LANCE 8; r"" 9 se-WINTIR
.. . FLOUNCER
__r- YELLO 4All
.. FLOUhttR I r L_
ATLANTIC _ h L, _
.- f- _ iTL m !C l" MACKtttL I _,
e ie. ; .. s-e- cussts 4"
': - 'l 7
':: A e- Hart
*: m -- m
, e. _, --
e- w.r--
'" ~
Afi, ANTIC
- n. htRRlhG
. a V- - s. . m 4.. -, r-e-
'," p POLLOCK
*: D '
J F M A M J J A 3 0 N O a.)high pollock abundance in June was due to the presence of a single larva in a split sample, occurance of any occurance of annual abundance l larvae .- peak 1 Figure 3.2.1-1. Occurrence by cronth of larvae of selected species of fish at Near-field Stations P3 and P2 during the eleven-year period 1976-1986. Seabrook Baseline Report, 1986. I 168
1 l the high variances calculated for each species (NAI 1983b). In order to reduce overall variability and improve statistical power, or ability to , detect a significant change in abundance, seasonal mean abundances (and variance) were calculated using data only from sampling periods which encompassed the seasonal peak in larval abundance. These select periods i included the season of maximus yearly abundance and approximately 90% of total yearly catch for each species. Yearly mean abundance patterns from this subset were tested for significant differences among years with a one-way analysis of variance. American Sand Lance f American sand lance larvae continued to exhibit a December ; through July presence with peak abundance occurring from January through April (Figure 3.2.1-1 ed Figure 3.2.1-2A). This broad peak was due to i two factors: an extended hatching period, and a long planktonic period for larvae (Bigelow and Schroeder 1953). ; Mean abundance over selected months in 1985 compared similarly ; to trends exhibited from 1975-1984 (Table 3.2.1-10). Using the peak occurrence data, differences among years in log-transformed mean j abundances were not significant (Table 3.2.1-11). i Winter Flounder Winter flounder larvae were first detected in 1985 in March, i earlier than previous observations which consistently placed the first ) observation during April (Figure 3.2.1-2B). Larvae persisted until July ' of both 1985 and 1986, although they have been previously observed as late as September (Figure 3.2.1-1). Peak abundances occurred in June and May of 1985 and 1986, respectively. The 1985 mean abundance was 169
Ae tonno e 0.9 (TC. e taff 016l? 0F 1Amt 'f at; L 9 I 8!!!!M P0lotl DLt 10 8 g y Ottetataloc vatws 9 1. e IMit 8.
- IM6 l I i
4 1
-e - . u ,tus eta 1000
- I E 9 8
- O O .A 0 R 0 3 g 3 6 g a a e g e
- 6 6
1 2 0,, e. . .! , I 9 3 9 e g 9 0 3 9 6 C 4 3 g A 0 7 0 1 8 7 C- to e 4
- f A a A I
- 1 0 0
- N 9
.e...~....e..........e..........e..........e..........e..........e..........e..........e..........e..........e...........
e. JA4 f ts man are nav JUm JUL AUC $tt CCf n0V DEC f*041 H 8. I i0000 e L 3 L s 1000 e a U " a A 8 A 1 0 6 6 8 A C li 1 4
.S e , ,
C 6 8 m ? t
- 3 i a t 2 0 6 3 4 9 9 0 3 g es 9 9 e
.e................................................................g.......................................................e.
Jat e e e e e fit MAA APA MAY JUN JUL AUC $tP OCT h0V O(C sMin Figure 3.2el-2, Log (x+1)-monthly abundances and overall monteely means for As American sand lance and Be winter flounder-larvae collected at nearfield Stations P2 and P3 during July 1975 through December 1986e Seabrook Baseline Report, 1986e 170
TABLE 3.2.1-10. SEASONAL ME ANS ( PEAK PERIODS) 0F UNIRANSIORMED AND I OG (X+1) TRANSFORMED A8UNDANCE (NUMBER PER 1000 08) BY YEAR OF SELECTED FISit SPECIES l ARVAE AT EIATION P2, JULY 1975 TisROUCH DECEMBER 1986. SEAbROOK BASELINE. REPORT, 1986. OVE rat l. OVERAlt. 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 ' ME A N STANDARD DEVIATION UNIStANSIORMED a b American sand lance - 425.6 979.3 1191.5 651.9 536.2 804.2 1810.8 204.3 360.5 343.0 1261.6 735.9 1545.9 3 Winter riounder - 35.6 46.2 143.3 57.6 135.0 6.9 40.0 182.6 186.5 259.3 76.7 128.9 332.2 2 Yellowtail flounder - 4.9 113.8 18.8 59.5 216.3 3.4 0.9 18.0 20.0 10.2 40.9 41.8 189.1
- Atlantic cod -
7.6 23.8 100.4 2.? 18.7 477.8 7.8 6.6 7.1 3.0 7.4 46.8 352.0 l 382.5 688.8 981.0 7211.3 1 Atlantic mackerel - 9.0 51.9 23.7 24.8 1556.6 9516.7 63.6 291.9 34.4 Cainne r - 133.5 343.7 459.8 957.4 649.4 886.3 880.0 2919.7 451.2 190.1 190.9 821.5 3623.3 Hake 14.3 0.9 46.2 4.6 75.2 67.6 30.4~ 20.6 127.6 193.5 78.8 0.2' 71.2 258.5 Atlantic herrin9 658.6 156.1 354.9 5.2 20.4 193.6 651.6 140.4 32.0 173.4 69.3 392.2 213.4 550.4 Pollock 13.1 32.9 38.7 3.4 159.0 47.9 13.6 6.0 11.4 77.9 137.9 c 59.8 155.1 LOG (X+1) IRANSIORMED to b [3 American sand lance - 2.55 1.56 2.59 2.31 2.34 2.33 2.G5 1.98 1.87 1.86 2.50 2.2- 0.94 F* Winter flounder - 1.13 1.06 1.27 0.95 1.02 0.59 1.13- 1.19 1.32 1.37 1.30 1.17 0.96 Yellowtail riounder - 0.67 1.33 0.71 1.13 4rs 0L7 0.37 0.11 0.73 0.59 .51 .80 0.69 0.78 Atlantic cod - 0.75 1.02 1.23 0.35 0.65 1.04 0.58 0.44 0.49 .35 41 0.59 0.69 Atlantic mackerel - 0.56 0.80 0.52 0.96 1.40 8.13 0.72 1.12 0.97 1.10 1.13 1.00 1.11 Cunner - 1.35 2.35 1.50 1.67 1.99 1.48 1.37 2.00 1.38 1.62 1.13 1.59 1.20 Habe 0.87 0.18 0.72 0.57 0.96 0.80 0.84 0.53 1.06 0.94 1.04 .04 0.74 0.88 Atlantic herring 2.30 2.16 1.23 0.49 0.92 1.54 1.71 1.80 1.01 1.62- 1.35 2.11 1.51 0.91 Pollock 1.12 1.46 0.79 0.47 1.70 0.92 0.70 0.49 0.65 1.38 1.17 c 0.99 0.82 a i Species Season American sand lance January-April Winter riounder April-July Yellowtail flounder May-August Atlantic cod April-July Atlantic mackerel May-August Cunner J une-Sep tembe r 4 Ila ke July-September Atlantic herring Oc tobe r-Decembe r Pollock Novembe r- Feb rua ry b Sa mp l i n9 a t P2 began in July 1975. excluding part or annual peak, c Yea rly mean not computed for pollock in 1986 because Janua ry and Icbruary 198 7 da ta were not ava i lable.
- . . - - - - ~ _ . _ . -. _- -. . _ . . _
TABLE 3.2.1-11. ANALYSIS OF VAllANCE COMPARISON OF LOG (x + 1) TRANSFORMED YEARLY MEAN ABUNDANCES FOR SELECTED MONTHS BY YEAR, JULY 1975 THROUGH DECEMBER 1986. SEABROOK BASELINE REPORT, 1986. ANALYSIS OF VARIANCE PARAMETERS a SOURCE OF DEGREES OF F YEARLY VARIATION FREEDOM DIFFERENCES b American sand lance Model 10 1.22" None Error 94 Total 104 Winter flounder Model 10 0.49 None Error 105 Total 115 Yellowtail Flounder Model 10 1.57 None-Error 105 Total 115 Atlantic Cod Model 10 1.97 78>79,82-86 Error 105 81>79 Total 115 Atlantic mackerel Model 10 0.45" None Error 105 i Total 115 Cunner Model 10 0.85"8 None Error 102 Total 112 8 Hake Model 11 1.25 None Error 76 Total 87 Atlantic herring Model 11 2.18 78<75,76,81,82,84,86 Error 71 75>79,83 Total 82 86>79,83,85 Pollock Model 10 2.41 79>77,78,80-83 Error 86 84>78,81-83 Total 96 85>82 a Least squares mean multiple comparison between. yearly means reported when ANOVA detected significant difference. Years listed are significantly different from each other with a = 0.05 b NS = not significant at a = 0.05, * = significant at a = 0.05 172
l
)
i higher than any other previously-recorded yearly seasonal mean and it continued a trend of increasing seasonal mean abundance after its lowest point in 1981. However, the 1986 larval mean abundance was within the ten year range of variability. Yearly differences in log-transformed mean abundances were not significant (Table 3.2.1-11). Yellowtail Flounder Yellowtail flounder larvae occurred only during June and July 1985 which was consistent with normal periods of peak abundance., although the period of presence has extended from April through November (Figure 3.2.1-1 and 3.2.1-3A). In 1986, larvae occurred from May through August. The seasonal mean abundance in 1985 was lower than that observed in most years from 1975-1984, yet it ranked higher than several earlier observations (Table 3.2.1-10). The 1986 mean approximated average abundances observed from 1975-1984. Overall yearly differences in log-transformed means were not significant (Table 3.2.1-11). Atlantic Cod Atlantic cod larvae occurred sporadically throughout 1985 and 1986, but they tended towards a late fall-winter and spring-early summer bimodal peak occurrenco consistent with earlier observations (Figures 3.2.1-1 and 3.2.1-3B). Spring-early summer larval abundances continued the trend of higher seasonal abundances, while the late-fall 1986 peak was extremely weak. Seasonal mean abundance for Atlantic cod was computed only for the spring-early summer peak, from April to July, due to the higher abundances and the longer period of occurrence in comparison to the fall-winter peak. In 1985 and 1986, spring Atlantic cod larvae continued to exhibit below-average abundance levels which were first noted in 1982 (Table 3.2.1-10), although levels in 1979 173
i l
, A. -)
6.9 ITC. . L Alf 816110F Smf stas; millier. Poisti DUE TO g Ortkarrier. skutt I t ... it...>- 1
, .= *- . ALL TItal' PE M e
8 1000 O D a 8 8 I i a i 9 I > p 1 g I io0 e l l- g. I 8 8 1 7 0 4 .) A 4 ( l :I N .. i ( 10 4 A 7 3 a e 9 t 8 " '
- 6 2
- g g 3 S
- I 1 4 5
^O 3 g 3 0 8
- I 9 9 1.. . .
.............................................A..........3.....................A...... .
....a..................................
Joe ff8 MAA APA MAY Jun JWL AUG 6(P OCT NOW O(C MONIN l B. 10 oo . l 1 i L
- l 8
1
- I .I
. i l
tuno . a v i e i I 8 g 4 8 1 P l
-t 1 8 loo .
l 0 9 1 4 0 F l S 0 g a e # 1-
; ;%! ^
A g A I .4 g 40
- 4 5 $
6 O. n 3 A
' \ N f
/,g[*: e
- f-l .'. . . . . . . .: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................
, :%t . . . . . . . . . . . . . . . . .:. . . . . . . .
Jag fl$ MAA Are may jgg jgg Ayc ggp gg) goy ggg i M04 f M Figure 3.2.1-3. Log (x+1) monthly abundances and ovetull monthly means-for A. yellowtail flounder and B. Atlantic cod larvae collected at nearfield Stations P2 and P3 during July 1975 through December 1986. Seabrook Baseline Report, 1986. 174 l
.. -- . _. _ ~ _ . - -
remained the lowest observed seasonal mean abundance. With the addition of 1985 and 1896 collections, significant differences (a = 0.05) were detected among years (Table 3.2.1-11). A least squares mean (LSM) multiple' comparison, which compensates for unequal cell sizes (SAS 1985a) indicated that log-transformed abundances during some years were significantly higher than others (Table 3.2.1-11). For example, the highest saasonal mean abundance of Atlantic cod larvae occurred in 1978. This seasonal mean was significantly higher than all other means except during the years 1976, 1977, 1980 and 1981. Atlantic Mackerel Atlantic mackerel larvae during 1985 and 1986 continued a trend of occurrence from May to July or August (Figures 3.2.1-1 and 3.2.1-4A). Seasonal mean abundances in 1985 and 1986, while higher than the mean abundances between 1982 and 1984, were considerably lower than the means observed during 1980 and 1981 (Table 3.2.1-10). No signifi-cant differences in log-transformed mean abundances among years were detected (Table 3.2.1-11). l 1 l Cunner i l Cunner larvae continued to follow a similar pattern of occurrence as mackerel larvae. Cunner larvae also continued to peak in July or August and disappear by October (Figures 3.2.1-1 and 3.2.1-4B). Seasonal mean abundances in 1985 ano 1986 were very similar, and were I the lowest seasonal means observed since 1976 (Table 3.2.1-10). No significant differences in log-transformed abundances were detected among years (Table 3.2.1-11). 1 175
I I i ionnon e A. , i
'i 8.9 ETC.
- LAST DIGli 0F SAMPLt Y[ARL
'0000 * . MIS $thG PO!NT5 00E TO O OvtRLAPPING VALU($
e A.
- 19651 B.' ? 1966
, === * - o A(( Y[ AR$ ' ( AN O 9000
- A h-I e a 'O.
-0 3 M
3 900 *- % 8 j e t a f ' 9 4 l 10 * , , , i 6 3 1 1
. .. . . . : , , : :~.
.e.....................e..........e..........e...........................................................................e JAt f(B mas Ata mas Jve Jyt Aug St p eCf 40V MC PetM f H hasutNMJ e Be
$0Guo
- 3 1
9 7 e n
- 3 0 1000 e 0 9 0 0 0 g p-
# 3
$ 1t4
- 3 a 1 9
.4 7 $
4 0 I to e e 3 0 t 8 8 9 7
. e I i .e JAR
...........e.....................e..........e..........e.............................6...........e..........*..........*e IES MAS e
APA MAT JUN JWL AUG SEP GCf h0V MC MD4 f M Figure 3.2el-4e Log (x+1) monthly abundances and overall monthly means for A. Atlantic mackerel and B. cunner larvae collected at near-field Stations P2 and P3 during July 1975 through December, 1986. Seabrook Baseline Report, 1986. 176 4 g .>w-g- ,.sv--s- r , , - , , , - ,.. -,,w , - , --+m-,,wr 4,-e -- m- w,v--,,-, y ~ , ww e-
Hake Hake larvae mean abundances in 1985 were within the range observed from 1975 to 1984, but 1986 abundances were ostensibly absent during the usual July-through-September peak period (Table 3.2.1-10; Figure 3.2.1-5A). Consequently, the few larvae collected in October were responsible for the first denotation of the species seasonal peak mean abundance at that time period (Figure 3.2.1-1), No significant differences in log-transformed mean abundances were detected among years (Table 3.2.1-11). Atlantic Herring During 1985 and 1986, Atlantic herring larvae occurred throughout most of the year except late spring-summer, which was generally consistent with the overall 1975-1984 baseline period (Figures 3.2.1-1 and 3.2.1-5B). Seasonal mean abundances in 1985 and 1986 within the range of variability were observed from 1975 through 1984 (Table 3.2.1-10). Significant differences (a = 0.05) were detected among sample years (Table 3.2.1-11). A LSM multiple comparison revealed significant differences among several years. For example, the 1978 sesonal mean abundance was the lowest recorded and it was significantly lower than those means observed during all years except 1977, 1979, 1980, 1983 and 1985. Pollock Pollock larvae exhibited peak mean seasonal abundances during January 1985 and 1986 (which correspond to 1984 and 1985 seasonal peaks, and are included in the 1984 and 1985 computations of peak mean abundance, respectively) (Figures 3.2.1- 1 and 3.2.1-6). A seasonal 177
.. - =- . . . . . - . . . - .
i 1 1 8,9 ETC.
- LAST O! GIT OF SA"PL[ V[AR; g I M!$$lhG POINTS DUC to inoaa .
OVERLAPP! G VAlt($ A = 1985; 8.
- 1986 '
-* ~
- ALL Y[AR$ ' ME AN -
ion,. 4 e 0 $
. 9 -?
/ e5 1
o o ina A
= s 3
1 1 o 5 io . -
. . N F
f 4 9
- o e e a t e
- i. . . .#* l l .
JA4 ftR MAR APR WAY JtM JUL Arm St # . oC f mov CIC soom1M i 1 inoon .t B. l l I in.wi . e 0 0 e s e i i a e O e inn . A. i - 9 s N 1 A 9 3 3 5 0 9 A a e e t 3 e 0 A 9 le . 9 9 a e i 3
- 4 8 4 9 F 0 9 9 9 Ja= sto == are nav Jve Ja an st e oci nov ote l SO4fM
.i
-Figure 3.2.1-5. Log (x+1) monthly abundances and overall monthly means for A. hake and B. Atlantic herring larvae collected at nearfield Stations P2 and P3 during July, 1975 through December, 1986.
Seabrook Baseline Report, 1986. 178
8.9 ETC.
- LAST DIGIT OF SAPFtt YEAtt MIS $1NG POINTS CLt TO OVERLAPPING YALLt$
im } A. = 19851 8.
- 1986
-*- = ALL YEARS' PEAN t
n '9 0
. 0 A 1 /, 0 0 i 0 100 A I '
u 9 A M i 3 7 8 , 0 0 8 9 8. 3 6 6 2 to . ,A 2 ' A l 6
,2 . .
.l .
6 7 1
, 2.~
9 7 2 4
. .: , : i ~!';N. .
JAN FEB MAA APA MAf JUN JUL. Apo SEP OCT Nov Otc MONin 1 I l i Figure 3.2.1-6. Log (x+1) monthly abundance and overall monthly means for pollock larvae collected at nearfield Stations P2 and P3 during July, 1975 through December, 1986. Seabrook Baseline Report, 1986. 179 4
., _ _ - . . .m__ y _ , - ____...c _ , , , , , . _ _ . _ , . . , . . _ , , , . ..__,c_,,,, . . - , , . . , _ , ,- . . - - -
l i l mean was not computed for 1986 because its period of peak abundance which began in November would continue into 1987 and these data are not reported here. Similarly, 1984 data not previously reported (NAI 1985b) are included herein. The 1984 and 1985 seasonal peak abundances exceeded those observed from 1975 to 1983, with the exception of 1979 (Table 3.2.1-10). The 1985 untransformed seasonal mean represented the second highest mean observed over the baseline period, although the log-transformed means showed a different array of high abundances (Table 3.2.1-10). A significant difference (a = 0.05) was observed among log-transformed annual means. The 1979 seasonal mean abundance was significantly greater than those of 1977, 1978, 1980-1983; while the 1984 and 1985 means were greater than 1978, 1982 and 1983 (Table 3.2.1-11). I 3.2.2 Adult Finfish l 3.2.2.1 Total Community i Temporal Patterns in the Demersal Fish Community Otter trawl catches per unit of effort (CPUE) for all stations and species combined during the 1976 through 1986 period rose from 50 fish / ten minute tow in 1977 to a peak of 95 fish / tow in 1980 and 1981 (Figure 3.2.2-1). CPUE subsequently declined through 1985 when an average of 40 fish / tow were collected. The 1986 CPUE showed a slight increase to 45 fish / tow, possibly signaling an upturn in the long-term downward trend of catch abundance since 1981. Annual means of bottom water temperature, salinity and dissolved oxygen recorded at nearfield Station P2 showed no long-term trends that would explain annual variations in mean annual CPUE (Table 3.1.1.2). 180
e sse .E - - - STATION Tl 8 1
' '\ ---- SIATION T2 i i- ------ STATION T3
.w . g ,(.3 . .. .. . .. . . . . . ,..\
. . . . i, \ All. STATIONS COMBINED g s- .
s i f .% 8!r...f 4 4 9se 0
\.
l ./ \*.~.- c 8 ,// \.~~ 3 ., A I e
- nei . i
/./ \
se I s s
' / 4
\
Ig e s .- - / 7- ~ ~ _ ' ' e i N ' N l \
..s* / -7 , 4 s I
s, / [ s % 3..,**.- a i,. w-
.-. , y s ...
e s * / / s Ni (9 ft l .'**., *
.'*#*%8 / \s 4\
\\ ..* 3*
e '. ,/ N , t t.as .e 4 g
*N.
e, s
/
N s g N N ...*.. ,, I , I i 3 s %1 s 8 I / .. p j \ as % , p s._-- 8
> a *,es .i 4 / 7 T3 #
co , i 2
** a 3 / --_ - 2
\ .3....***
..,3 l ,
s 4 4.s . I
/ N
/
l 2' '\ l
/ '2 Se, i Ps s
. ~
/ N.
I
's, / N, ' y' "2 l % ,, /
%. 7 ri .I 16 is 14 79 nie al 82 83 84 85 86 YI A84 Figure 3.2.2-1. Catch per unit effort (mean number per 10 minute tow) of all species collected in otter trawls by year, station and all-stations combined, 1976-1986. Seabrook Baseline Report, 1986. '
l l l l l Six taxa accounted for nearly 80 percent of the trawl catch abundance for all years combined (Table 3.2.2-1). Yellowtail flounder comprised the largest percentage of the annual catch (20-36%) in all years except 1983 and 1984 when it ranked second below longhorn sculpin. Beginning in 1980,.the percentage of yellowtail flounder in trawl collections consistently declined until 1984 when they represented only 18 percent of the total annual catch. Percent contribution of yellow-tail flounder to the annual catch increased to 27 percent in 1985 ending a 3-year decline, but dropped again in 1986 (20%) to a level approaching the 1984 low. Hake species (red, white and spotted hake) constituted the second-ranked taxon in trawl collections and comprised 15% of the catch for all years combined. Hakes showed no consistent long-term trend of increasing or decreasing rank. Longhorn sculpin also comprised 15% of the catch for all years combined. Longhorn sculpin accounted for an increasingly larger percent of the catch from 1976 (5%) through 1984 (27%), but in 1986, their percent contribution to the total catch fell back to pre-1979 levels (<10%). Winter flounder ranked fourth in percent abundance over all years and comprised 5 to 15% of the catch. The percentage of winter flounder in otter trawl collections during 1985 and 1986 (9% and 10%, respectively) was about average for all years combined. Atlantic cod ranked fifth over all years, and accounted for an average of seven percent of the total catch. Cod percent contribu-tion to the total catch was highest in 1978 and 1979 (14% each year), l l and lowest in 1977, 1985 and 1986 (3% each year). Rainbow smelt, the ' sixth ranked taxon, fluctuated between 13% (1976) and 1% (1985) of the total annual catch and averaged 6% over all years. l The number of fish species (species richness) collected annually in otter trawls ranged from 32 to 40 and totaled 58 for all years combined (Table 3.2.2-1). Species richness oscillated between years of lower numbers of fishes (32-34 species) and years of higher numbers of fishes (37-40 species). l 182 l
IAlltf 3.2.2-1 IOTAl PERCE NT COMPOSillOf4 ilY YEAR AND All YI ARS CottillNI O IOR lif f lutlVE PIOSI AllONDAN I SPfCilS IN 0131H IHAWIS DUNING 1916 IllROUCal 1986 A T SI Allot 45 I I, I2 AfiD 13 COHulfilD. SI AltHOOK llASil lHL f(EPOHl. 1986. VIHClNI COHPOSIIION Al.l. YEAftS 1976 1977 1918 1919 19tto 1983 1982 1983 1988e 1985 19tl6 COHilllef D j Vellovtail f lousede r 36 29 23 34 31 2tl 22 19 18 - 27 20 27 t j liabe species 18 30 19 9 8 14 19 10 13 15 - las l$ j (red, white, spotted) 1 ton 98 orn sculpin S 8 9 13 15 17 16 28s 27 22 9 15 Winter flounder 5 8 9 i 12 IS 9 8 7 9 30 9 g Atlantic cod 4 3 18s 14 9 6 7 8 5 3 3' 7 Rainbow smelt 13 3 188 7 is 6 S 9 7 1 3 6 Skate species 3 $ 2 2 2 2 3 7 8 11 I ts 4 (bi9, little, thorny) Atlantic hisiting 6 3 4 3 3 3 81 1 <3 <l 8 3 l Ocea** pont 2 4 3 2 1 2 2 3 *> 3 3 3 Pollock <1 <3 <l 4 1 2 3 2 <l <1 2 2 ? Windowpane 2 2 1 <1 3 2 2 5 7 5 7 3 Iladdock 3 2 <l 3 4 <l 2 1 <1 <l <1 2 > Other species 3 3 $ 2 3 3 8 3 2 3 7 4 Iotal or ottier species (25) (22) (26) (25) (22) (27) .(28) (26) (26) (20) (24) (46) l
Seasonal changes in the demersal community were examined in past years by numerical classification of the trawl catches (NAI 1982c). This resulted in samples being classified into two major groups, reflect-ing a "winter community" (December through March) and a "summer commun-ity" (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 catches per unit of effort were similar at the offshore stations (T1 and T3), while catches per unit of effort at the shallower naarshore station (T2) were much lower (Figure 3.2.2-1). Despite the dif ferences, mean annual CPUE for the three stations followed the same long-term abundance pattern from 1976 through 1986. As discussed previously, CPUE for all stations was low in 1977, peaked in 1980 and 1981, declined to lowest levels in 1985, and began to increase again in 1986. l Otter trawl catches at the offshore stations (T1 and T3) were dominated by yellowtail flounder, hakes, and longhorn sculpin (Table 3.2.2-2). Collectively, these species comprised over 60% of the catch for all years combined at Stations T1 and T3. Of lesser importance at j these stations were Atlantic cod, Atlantic whiting and skates. The most l i notable difference in percent composition between Stations T1 and T3 was j that yellowtail flounder predominated at Station T1 while longhnrn l sculpin predominated at Station T3. In addition, cod and skates com-prised a larger percentage of the total catch at Station T3. This and other smaller differences in species composition between Stations T1 and T3 may be attributable to different bottom substrates (T1 has a sandy bottom, T3 has sand littered with small cobble and shell debris). Otter trawl catches at the nearshore station (T2) were dominated by winter 184 l
TABLE 3.2. 2-2. TOTAL PERCENT COMPOSITION BY STATION OF ABUNDANT ~ SPECIES COLLECTED IN OITER TRAVLS, ALL YEARS COMBIhTD (1976-1986). SEABROOK BASELINE REPORT. 1986. T1 T2 T3 SPECIES % COMPOSITION % COMPOSITION % COMPOSITION f Yellowtail flounder 38 14 18 Hake sp.a 14 7 15 Longhorn sculpin 15 6 28 Atlantic cod 5 3 9 : Rainbow smelt 4 14 2 Winter flounder 7 30 5 Atlantic whiting 3 1 3 , Windowpane 4 4 3 l Skate sp. 3 2 8 i , t Pollock 1 9 <1 i Ocean peut 1 3 3 Haddock 1 <1 2 i All other species 4 7 3
)
# of other species (34) (25) (28) includes red, white and spotted hakes includes big, little and thorny skates -
185 l
. . , . - . . - . , - _ - . . _ - . - .- ._ . - ~ . . - - - - . - , - - . -- - - - - - . - - - - - - ---
l flounder, yellowtail flounder, rainbow smelt, and pollock. These species comprised 67% of the trawl catch at Station T2 for all years combined. Hake and sculpin comprised a much smaller percentage at Station T2 than at Stations T1 and T3 while the opposite was true of winter flounder, rainbow smelt and pollock. Temporal Patterns in the Pelanic Fish Community Catches per unit of effort for gill nets (one 24-hour set) combined for all species showed a pattern somewhat similar to otter trawl catches (Figure 3.2.2-2). CPUE rose to a peak in 1980 of 29 fish / net and subsequently declined to lowest levels in 1985 of 3 fish / net. The pattern was not as distinctive as with trawls, in that annual CPUE only ranged from 3 to 13 with the exception of the 1980 peak (29). In addition, the gill net peak catch occurred only during 1980, while the trawl peak spanned both 1980 and 1981. The high 1980 CPUE for gill nets was due to record high catches of Atlantic herring and pollock (NAI 1981e). Atlantic herring ranked first in gill net collections during every year sampled, comprising from 25 to 82 percent of the total annual l catch and averaging 64 percent for all years combined (Table 3.2.2-3). The percent contribution of Atlantic herring to the annual gill net i catch was highest in 1978, 1979 and 1980 (74, 80, and 82%, respectively) and lowest in 1984, 1985, and 1986 (26, 25 and 33%, respectively). During all other years, Atlantic herring ranged from 44 to 63% of the total annual catch. Atlantic whiting, blueback herring, pollock, and q Atlantic mackerel collectively comprised 26% of the gill net catch for l all years combined. These taxa were fairly consistently ranked among the top five dominant taxa during the eleven-year period. Lower ranked ! taxa (i.e., alewife, menhaden, hakes, smelt and cod) comprised a more important portion of the total annual catch during 1984, 1985 and 1986 when catch abundances were below normal and Atlantic herring accounted 186
I es e e I i l 7 go . si I /\ --- STATION G1 l ' S --- STATION G2 35 * '
/
\*
.......... STATION G3 i All. STATIONS COMBINED c
A g ,/ \ 4
- l . .3*.
.\.5 s s c so . s. .-
n a = g .f.
,, , ..- o .\
s : .r ' / 4 a 2, . .-
\.
U s l .*
..- ,a s..
= -
s 1
\.
,/ s .
- 2" ; ,,.-
- 1
< , i \. ..s.
e g ; e
. . . ' . . ,."e, , 2 \,
{ ff s 3,..'
, s-
'-2' N 1"
/
f /\
\
\
- 8 N / \ \ a -2s t % /
/
. -2 N ,
,/ g 5 s ~.
\
' \ '
s's %
\,/ g , .,,, ,,,,,3,, ,
/ >
3 - , e Ni ,,, 4:i - -,.........- s 4 ... / 4 g 1 si2 %- - - __, i _- n --- -..-) I n.
.I 16 FF 18 19 no MI
==+------ -.-....-.----.....___.-...
82 83 84 85 86 YE AR , 7 Figure 3.2.2-2. Catch per unit effort (number per 24-hour set of one net, surface or bottom) of all species collected in gill nets by year, station and all stations combined, 1976-1986. Scabrook Baseline Report, 1986. w - - - ~ . n- w--..n,im ---+. v. e - w,
4 1 4 IAnt0 3.2.2-3.
, TOTAL.1976 DURING PERCENI COMPOSITION IllROUCal BYGI, 1986 Ai SIATIOrds YEAR G2 AridAND All VI ARS COMuttat u 5 004 litf litt MOST AllHNOANI SPfCIES IN Cllt NE G3 COilHINID.
SI AllHOOK BASEL. INE ftLPONT. 1966. I Pt f(Cf NI COMPOSIIION 1976 1977 3918 1979 1980 1981 1982 1983
-Al.l. YEAMS 1984 1985 8986 COHolNED Atlantic herring 53 48 74 80 82 45 63 44 26 25 33 64 Atlantic whiting 17 28 2 4 6 5 7 I 5 2 1 8 Dieseback herring 5 Il 14 2 2 2 to 12 9 9 15 '7 Pollock 6 4 2 3 5 18- 4 12 10 22 18 6 Atlantic mackerel 12 7 2 2 2 14 5 5 6 10 5 5 $$ Alewife 1 2 2 <1 <I 2 2 4 5 6 3 2 Atlantic menhaden <1 3 <3 2 <l <l 1 II 5 6 5 2 Ilakes (vrophyc/s sp.) 2 2 <I <a l 4 I I 7 2 2 1 Rainbow smelt I i <3 <l 3 <l <1 1 6 2 4 1 Atlantic cod I <I <l <l <l <l 2 2 3 <l 2 <l Other species 2 <3 3 5 I 8 5 7 18 16
) 12. 3 4 total or other species (10) (16) (14) (13) ~ (13) (19) (21) (18) (20) (14) (14) (37)
i l l for a smaller percentage of the total annual catch. Species richness ranged from 20 to 31 species annually and totaled 47 for all years combined (Table 3.2.2-3). No long-term trend of increasing or decreasing species richness was evident. Seasonality of pelagic species were analyzed in previous reports (NAI 1982c;1983b). Two distinct sample groups were observed based on abundances of the dominant species: "summer" (June-August) and "winter" (September-May). Atlantic mackerel and Atlantic whiting were more abundant in summer samples, while Atlantic herring were more-numerous in winter catches. Blueback herring and pollock showed incon-sistent seasonal differences in abundance. Spatial Patterns in the Pelagic Fish Community i Mean annual catches per unit of effort at gill net Stations G1, G2 and G3 showed similar fluctuations across years (Figure 3.2.2-2). Mean annual CPUE peaked in 1980 at all stations. This peak was more j evident at Stations G2 and G3 than at Station G1. Percent composition i for the dominant species in gill net collections was similar among stations (Table 3.2.2-4). Atlantic herring was the dominant species at each gill net station, accounting for 58 to 70 percent of the total ; 1 catch for all years combined. Also numerically important at each j station were Atlantic whiting, blueback herring, Atlantic mackerel and pollock; each comprising from 4 to 10 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 'l 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 bottom nets. The proportions of blueback herring and Atlantic mackerel were also higher 189 , 1 l l
.i l
l TABLE 3.2.2-4. TOTAL PERCENT C0!! POSITION BY STATION OF ABUNDANT SPECIES COLLECTED IN GILL NETS, ALL YEARS AND DEPTHS C0?!BINED (1976-1986). SEABROOK BASELINE REPORT,.1986. G1 G2 G3 SPECIES % COMPOSITION *. C0t! POSITION % C0t! POSITION Atlantic herring 62 70 58. Atlantic whiting 6 6 9 Blueback herring 6 6 10 Atlantic mackerel 5 4 5 Pollock 6 5 6 Hake sp.* 2 1 <1 ; Atlantic menhaden 2 1 2 r Alewife 2 2 2 Rainbow smelt 1 <1 1 i Longhorn sculpin 1 <1 <1 '
\
Atlantic cod 1 <1 1 Bluefish <1 <1 <1 All other species 3 2 4
# of other species (24) (28) (25)
F
- includes red, white and spotted hakes 4
190 t
- - - -- , ,-n ~ , . - , r.- ,, ,, n., - e
TABLE 3.2.2-5. TOTAL PERCENT COMPOSITION OF DOMINAhT GILL NET SPECIES ACCORDING TO DEPTH (SURFACE AND OFF-BOTTOM). ALL YEARS COMBINED (1976-1986). SEABROOK BASELINE REPORT, 1986. ' SURFACE OFF-BOTTOM SPECIES.- '.COMPOSITION *. COMPOSITION Atlantic herring 69 56 Blueback herring 10 5 Atlantic mackerel 6 3 Atlantic whiting 5 11 ! Atlantic menhaden 2 1 Alewife 2 1 Pollock <1 12 Rainbow smelt <1 1 Hake sp.a <1 3 Other species 4 7 includes red, white and spotted hakes I l l 191 4
1 l l in surface nets. Atlantic whiting, pollock, and hakes comprised a larger percent of the catch in the bottom nets. Atlantic menhaden and alewives accounted for a similar percentage in both surface and off-bottom nets. Since 1980, mid-water nets have been set in addition to the surface and off-bottom nets during February, June and October. Comparison of CPUE among surface, mid-water and off-bottom nets on dates when all three nets were fished revealed that Atlantic menheden was the only species that was more abundant in mid-water catches than in surface or near-bottom catches (Table 3.2.2-6). As was observed with the regular surface and near-bottom gill net collections, Atlantic herring and Atlantic mackerel were most abundant in surface nets and least abundant in bottom nets. Blueback herring were also most abundant in surface nets but were least abundant in mid-water nets, and intermediate in abundance in off-bottom nets. Atlantic whiting, pollock, and rainbow smelt were most abundant in bottom nets. The alewife showed no depth preference, with low CPUE values (<1/ net) at each depth. f Temporal Patterns in the Estuarine Community Catches per unit of effort for seine stations combined for all species ranged from 60 to 362 fish / haul (Figure 3.2.2-3). Seine CPUE values were lower during the period 1982 through 1986 (60 to 110 fish / haul) than during the period 1976 through 1981 (200 to 360 fish / haul). Annual variations in beach seine CPUE were influenced primarily by annual catches of the Atlantic silverside, which was the most abundant , species in seine collections each year (Tablo 3.2.2-7). The percent contribution of silversides to the total annual seine catch ranged from 47 to 88 percent annually. Also important numerically were mummichogs which consistently accounted for more than one percent of the catch (1-23% annually) and ranked among the top five dominant taxa in all years. All other species collected in seines fluctuated from year to year in their ranking and often comprised less than 1% of the total l annual catch. The total number of species collected per year ranged 192
TABLE-3.2.2-6. CATCH PER UNIT EFFORT
- BY DEPTH FOR THE DOMINANT GILL NET SPECIES OVER ALL STATIONS AND DATES VMEN SURFACE, MID AND BO'ITOM NETS WERE SAMPLED,1980 THROUGH 1986.
SEABR00R BASELINE REPORT, 1986. DEPTH SURFACE MID BOTTOM SPECIES CPUE CPUE CPUE Atlantic herring 7.0 3.7 2.3 Atlantic whiting 0.2 0.6 0.8 Atlantic mackerel 0.7 0.3 0.4 Pollock 0.1 0.1 1.2 Alewife <0.1 <0.1 _< 0.1 Blueback hcrring 1.0 0.4 0.6 Atlantic menhaden 0.7 0.9 0.2 Rainbow smelt <0.1 <0.1 0.1 "Number per.one 24 hour set of one net (surface, mid or bottom). 1 l i i 1 193
t I s t I
- 69) + -- - STATION S1 8 3 4
STATION S2 6 .. . .; - ----- - -- - ST AT I ON S3 8 1., ALL STATIONS COPEINED E ~ 5 54:
- t ..
c s .
,- A Seus * .
a . c i 3 se sy, e . ; 3 r s l ,2n n s<ns
- a
- ,7; %, '.~.~...,-
s . o sys e n 8 .
./
- s n 8 .. :7 %\ '
4 3 l . .> e sene *
/ \ ..*.3..-
~
..* e s ..
e : I \' .. s 7,n e 2.-
.s - . .. . .. . .. '3-~,4
. u o s 1 ,
- Q ,, '..~~...3.-
, e4 s p t -
e se rime .I N% 4-7 f 4 \ 4
*- e i N
-e s
/
/ 8-~N '%~-
g s .,,, e s / --. _'s %. , ~ 2 ~. -- 1 s. N / .,.
. 2
,,,,, 8
- N' i f w J. M x'~~. 3h 2- r .5-- - - . -z N
i l 1. # 4 1.3
,n
- I I
-.._________.-_....-- --.--------------+--------------*--------------+--------------*--------------+-----------*-----------+--
-- ,,,_ ,, in i, sie as nr as at as - a6 VI Ah i
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 and July-November, 1986. Seabrook Baseline Report, 1986. i i 1
I Altl E 3.2.?-7. IOTAL PERCENI COMPOSITION IW YEAR FOR THE IIN HOSI Ant!NDANI SPECILS COLLECTED IN BEAClf SEINES DURING 1976 TilROUGH 1986 (NOT COLLICIE D IN 1985) AT STAllONS SI, S2 AND S3 COMBINEO. SEABROOK BASELINE REPORT, 1986. PERCENT COMPOSITION a 1976 1977 1978 1979 1980 1981 1982 1983 1984 1986 Atlantic silversides 73 55 15 60 68 88 57 47 48 47 H ammichogs (/undulus sp. ) 15 23 5 3 4 2 10 8 7 1 Pollock <1 <1 1 8 71 <1 7 5 i O Alewife <1 1 <1 18 <1 <1 1 <1 <1 <1 Rainbow smert 4 5 <1 5 <1 2 5 4 9 1 American sand lance 2 9 3 <1 <1 <1 8 2 <1 O Atlantic herring <1 <1 5 <1 4 4- <1 7 8 <1 Ninespine stickleback 1 4 1 <1 <1 <1 2 7 16 45 Winter flounder <1 2 2 2 3 1 6 3 3 5 filoeback herring <1 <1 <1 1 <1 <1 <1 14 <1 O Other species 3 <1 2 2 <1 ? 4 3 7 1 total or other species (11) (17) (14) (12) (9) (12) (12) (13) (14) (9) a Jeely through November only
l l l l from 19 in 1980 and 1986 to 27 in 1977. The reduced sampling effore in 1986 (no sampling during April, May and June) may have been responsible in part for the low number of species collected in that year. Seasonality of the estuarine fish community was analyzed previously using numerical classification (NAI 1983b; 1984b). The estuarine community was highly seasonal in all years, and all three seine stations exhibited similar seasonal changes in their fish assem-blages. Catches in the spring were usually characterized by low abun-dance. Species composition in early summer was highly variable among years. The most distinct group was the late summer-fall assemblage, which occurred yearly from August-November, and in which Atlantic silverside was the overwhelming dominant (NAI 1984b). Spatial Patterns in the Estuarine Fish Community Mean annual catches per unit of effort during the period 1976 through 1983 were usually highest at Station S3 and lowest at Station S1 (Figure 3.2.2-3). During 1984 and 1986, when catches were small rela-tive to earlier years, mean annual CPUE at each station was comparable. Atlantic silverside was the dominant species at each station (Table 3.2.2-8). Stations S1 and S2 were comparable in their overall species , 1 composition with silversides comprising 72 to 77% of the total catch (respectively) for all years combined (July through November only) and mummichogs (rundulus sp.) comprising 14%. These stations weta distinguished from each other and from Station S3 by a relatively high proportion of blueback herring at Station S1 (7%) and American sand lance at Station S2 (4%). Station S3 yielded a slightly different composition of fishes. Atlantic silversides comprised a larger percen- l tage of the catch at Station S3 (85%) than at Stations S1 and S2, and mummichogs accounted for a much smaller percentage (<1%). Mummichog catches were rare at Station S3 compared to Stations S1 and S2, because they prefer brackish water and tidal creeks (Bigelow and Schroeder 196
TABLE 3.2.2-8. . TOTAL PERCENT COMPOSITION BY STATION OF ABUNDANT SPECIES COLLECTFD IN BEACH SEINES, ALL YEARS COMBINED, JULY THROUGH NOVEMEER (1976-1984, 1986). SEABROOK BASELINE
' REPORT, 1986.
l S 1' S2 S3 SPECIES % COMPOSITION % COMPOSITION '4 COMPOSITION Atlantic silverside 72 '77 85 Fundulus spp. 14 14 <1 American sand lance <1 4~ <1 Blueback herring 7 <1 <1 Ninespine stickleback 3 2 4 Atlantic herring 1 1 <1 Winter flounder 1 1 2 Pollock 0 <1 <1 b <I Casterosceus spp. <3 <l l
~I Alewife <1 <1 <1 Rainbow smelt <1 <1 5 Smooth flounder <1 <1 <1 All other species <1 <1 3
# of other species (18) 0.4) (21) l
- includes mummichogs and striped killifish b
includes threespine and blackspotted sticklebacks 197 l l 1
I 1953). Station S3 was also distinguished from S1 and S2 by c higher proportion of rainbow smelt (S3:5%; S1,S2:<1%) and by a higher species richness (S3 species richness:33; S2 species richness:26; Si species richness:30, for the period July through November only). 3.2.2.2 Selected Species General Species selections for examination of seasonal, annual, and l spatial variations in abundarce were determined by the following two i l criteria: high abundance in at least one life stage and gear type, and importance in local commercial or sport fisheries. The nine species selected and their primary collection methods were: i 1 Species Gear Type I Atlantic herring gill nets l Atlantic mackerel gill nets Pollock gill nets Atlantic cod otter trawl Hakes (red, white and spotted) otter trawl , , Yellowtail flounder otter trawl l Winter flounder otter trawl and beach seine - Rainbow smelt otter trawl and beach seine Atlantic silversides beach seine 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 examine spatial and temporal differences. Size-structure of fish populations also yields important information on age classes that utilize the area and supplies information on recruitment patterns. This information was examined thoroughly in the 1984 Baseline Report (NAI 1985b), and so will not be reported here. I i l 198 l
. . . - . . . = - . ..- . . . ~ .
Pelamic Species Atlantic Herrinz Atlantic herring were typically' collected in highest numbers , during the spring and fall (Figure 3.2.2-4). Gill ~ net CPUE values were ; highest March through-May, and October.through Dacember. Mean annual CPUE of Atlantic herring rose from 1976 (4.7/ net) through 1978 (24.3/ net), leveled off through 1980 (23.5/ net), and then declined through 1985 i (0.9/ net) to the lowest levels observed during the program (Table } 3.2.2-9). The annual mean CPUE' rose slightly in 1986 (1.9/ net) but was I still below pre-1984 levels. Station differences for herring and other ', schooling pelagic species sampled by gill nets were not analyzed for the j present report because of their high degree of mobility and lack of l c 4 consistent otation differences, Pollock l Pollock gill net catches were highest during spring and late fall, and lowest during winter (Figure 3.2.2-4). Summer catches were I generally moderate relative to the spring and late fall, reflecting a ) temporary offshore movement of pollock in response to increasing summer water temperatures. Pollock typically avoid water with temperatures
, higher than 60*F (Bigelow and Schroeder 1953). During early winter as
, inshore water temperatures approach minimal levels, declining pollock catch abundances presumably reflected an offshore movement into the
- higher temperature offshore waters to spr.wn. Annual mean gill net catches per unit of effort for pollock vi.ried from 0.3 to 1.5 fish / net and averaged 0.7 fish / net over all years (Table 3.2.2-9). The 1986 mean CPUE of 1.0 fish / net was slightly greater than the average over all years.
4 u 199 l
- - -- _ _ _ ~.. .,. . _ , . _ _ _ . . _ , _ . , , , - _ _ _ _ . . . , _ . _
1 i
,,, e A. Atlantic Herring
- STATIONS Gl. G2 + G3
'E E SO . ,
-a o .
a > c a 7 8 t 1 .. C 9 ~t' ! a 9. , 9 t
.t ,- .
e s s e e se e r i i-i .
*\
f 9e 9
! ?
't N i f 6 a e
- I 9 a a f 8 e e e e a-y a g ,
e a 4 - 4 a F G e 1 0
.e - ;
t .3
., i I !
i . . . . .. 3 a . 3 4-a t.es..........e..........9......................a...........e.....................4...........9..........a...........S............. au may - avo st e ece. nov Otc Jag ste man sve Jet W IN
*
- LAST 0131T 0F 5 &PLE YtAR FROM 1976 1964 A = 1965e 8 = 1966 MIS $lhG Po!NTS ARE DLt d 'a
- TO OVERLAPPlhG VALLt5
-e- a
. Au VtARS MtAs
" 3 t
.a e
1
,e B. Pollock ,
^
! STATIONS G1, G2 + G3 e i a
I W t -t a 6 0 i e - I s a e !
!, t e e
, .t N *i . .1 %.
- i . . . i t
, 7 6 3 4 4 8 3 e a
$ 7
- e , IN'#I .
t 4 4 4 3 0 4 4 9 9 i eee e a
..e.....................e............................................a......................t..........3...........a...........a..
are
- Jaa fit Man mar Jve JUL avC Stt ett mov Otc a c.
1 .I e ! Figure 3.2.2-4. Monthly mean log-transformed (x+1) cateb per unit effort (1 24-hre set) for each year and over all years for j A Atlantic herring and Be pollock at combined gill net Stations G1, G2 and G3 from 1976 through 1986, J t Seabrook Baseline Report, 1986. j l t l 200 l l l
-. ., , , _ . , , _ _ , _ . _ . _.- _ -_.._._-~-. _ . . . _,. _ . _ , . - - , _ _ r , .
a IABLE 3.2.2-9. f.NNUA1. HEAN CPUF TOR. SELECTED FINI1511 SPfClfS. SEAOROOK BASELINE REPORT, 1986. VfAR OVERALL YEARS b c SPICl[S STATION 1976, 1977 1978 1979 1980 1983 1982 1983 1964 1985 1986 MfAN CV Winter i lounder il 1.61 3.50 2.98 2.88 6.57 1.03 5.06 3.78 2.79 8.24 4 5. f4 3 a.2 s 71.5 12 5.03 6.10 9.71 11.88 21.98 ?8.86 12.57 8.16 6.55 6.17 is.46 11.2 125.5 13 1.61 1.96 3.68 2. f45 6.84 *>.19 3.51 2.96 2.13 1.884 3.37 3.3 89.9 T1-13 2.75 3.88 5.f 5 5.74 11.80 13.69 7.04 84 . 9 7 8.03 8 3.90 4. fs t 6.2 187.5 4 d e St-S3 2.09 3.89 3.35 5.86 6.?! 3.?1 3.77 2.47 3.91 NS ID 3.9 72.6 Yellowtail il 37.62 28.51 23.13 40.57 48.95 51.96 2i.69 4 19.96 16Js9 17.95 15.75 29.6 70.6 flounder 12 5.43 2.75 2.38 6.88 12.51 6.?8 8.91 4.26 1.52 4.41 3.35 5.f4 138.0 13 22.08 12.81 I ts . 93 29.06 30.03 19.86 11.89 9.20 8.73 9.90 5.25 15.8 80.6 11-13 23.71 14.69 13.48 ?*>.50 30.50 ?6.03 15.16 11.14 8.93 10.93 8.40 17.0 10f4 .6 Hake il 16.23 21.36 18.78 4 9.93 9. 684 13.34 17.69 6.58 8.63 7.96 7.90 12.2 123.0 12 8.33 4 5.53 6.31 1.53 88 . 0 8 's.10 fa . 6 3 2. 4 fs 3.a2 1.91 se . 36 4.1 129.6 T3 10.71 17.11 12.98 8.20 8.52 18.98 18.80 4 8.42 8. 084 7.78 4.95 11.3 129.2 11-13 10.42 18s.66 11.35 6.55 7.f 41 1?.68 13.58 5.81 6.83 5.99 5.82 9.2 140.7 11 ?.17 1.68 5.94 7.73 6. 3f4 5.?9 4.11 4 5.59 3.13 1,32 1.32 4.1 1 18s. 3 Atlantic Cod " 12 0.46 0.48 1.92 10.75 2.35 7.f 4 2 3.68 0.91 0.87 0.19 0.76 2.3 125.9 4 O T3 4.20 1.93 17.33 1?.66 15.19 9.40 1.11 7.82 4.21 1.46 2.39 7.6 If40,5 T1-13 2. fs 8 1.36 8.40 14.37 7.96 5.70 5.07 4.77 2.73 1.01 1.53 4.7 192.3 Rainbow Smelt T1 6.72 1.37 5.27 6.65 3. 884 3.95 2.66 4.65 3.33 0. 8:5 1.63 3.7 215.2 12 12.38 2.03 8.87 4.33 4.00 10.58 5.93 9.72 5.92 0.92 3.39 f.' 231.3 13 7.01 1.87 3.88 4 Is . fs 6 2.93 1.59 1.80 0.76 0.99 0. 8s 9 0.67 2. fs 265.0 11-13 8.10 1.76 5.87 5 . 18: 3.59 *a . 3 7
. 1.46 5.08s 3. f:1 0.61 1.81 4.1 251.0 S1-S3 18.71 4 9.40 0.11 16.71 H.06 4.67 P.78 3. f40 9.77 NS ID 6.8 278.1 Atlantic lierring C1-C3 f4.72 6.07 2fs . 25 13.52 73.46 2.69 8.03 4 4.00 1.13 0.87 1.89 7.9 251.4 Atlantic Mackerel GI-G3 0.97 0.83 0.56 0.27 0.58 0.84 0.31 0.85 4 0.25 0.35 0.19 0.5 193.1 Pollock GI-C3 0.57 0.13 4 0 . 384 0.36 1.48 1.08 0.23 1.11 p. is 5 0.75 1.03 0.7 165.5 Atlantic Silverside SI-S3 261.35 108.95 18s6 . 814 252.59 153.22 193.8? 3's . fa9 39.8 4fs 5fs.42 NS ID 134.5 150.2 a) Otter trawl (1); mean catch per tow per month at each statiors. Gill net (G): mean catch per 24 hour set or one level (surf ace or bottom) or one not array (stations averaged). Ileach seine (S): mean catch per hassi per month
(? or 4 hansis per date. 1 or 2 dates per month, s ta t ions avo raged ) . b) Mean of monthly means, N = 132 .'o r i t , 13; 129 fo r 12;1132 for C1-G3; 17 ror SI-S3. Hean c) Coef f icient or Va ria tion - ( Sta nda rd Dev i a t i on x 100) d) NS = Not sampled. e) to - Insterricient data for compa rison wi th previons yra rs.
-t..
I s Atlantic Mackerel-Atlantic mackerel were present in gill not collections pri '
.marily from May to November and were rare in sill not collections from January through Aprili(Figure'3.2.2-5). Following a gradual increase in-
~
CPUE from May;through. July,1 monthly mean CPUE leveled off and remained at rimilar levels'throughout the July through November period.. Annual j mean-CPUE oscillated between 0.2 and'1.0 fish / net, and averaged 0.5 fish / net (Table 3.2.2-9). ' Catches declined from highest levels in 1976. l j to a low in 1979, increased'in 1980.and 1981,.and.once again declined I through 1986 when the lowest annual mean CPUE was recorded.' ; l Demersal Species l Atlantic Cod l
-\
Atlantic cod were present in otter trawl collections-through-out the year, with highest CPUE values occurring in spring and fall (Figure 3.2.2-5). The spring peak appeared to occur slightly earlier at-Station T1 (March-May), followed by Station T2'(April-May), and lastly Station T3 (May-June) (Figure 3.2.2-5 and Appendix Figure 3.'2.2-1). Past years' data have shown the spring peak to be comprised primarily of sexually-immature age one and two cod, while the fall peak consisted of young-of-the-year to at least age five cod (NAI 198Sb). The small spring cod are probably offspring of winter spawners, while the small l i fall cod are likely the product of spring spawners, i Annual mean CPUE (averaged over all three stations) of Atlantic cod rose from a low of 1.4 fish / tow in 1977 to a high of 10.4 fish / tow in 1979, and subsequently declined to 1.0 fish / tow in 1985 (Table 3.2.2-9). In 1986, the annual mean CPUE increased slightly to 1.5 fish / tow. Station mean CPUE of cod was highest at Station T3 (mean i
= 7.6/ tow), intermediate at Station T1 (mean = 4.1/ tow) and lowest at l
202 l 1
-. ., e,-. .-- - . . , - - - , . , - - . _ , _ _ , , , y ,.. - ,___ . - , ,,,-,-ny,--._.-7 - m -,, ,ee.er.,, ,
A. Atlantic mackerel , STATIONS G1, G2 + G3 t -
. .. i
.t a f e t t .
e , l P a t 6 I e 7 . t . .
! j 'N. t ; e .
i . . e . . . . Jag MAS A PG Mat jut JVL .UC StP OCI h0V Df C ff. set t W l l
*
- LA57 DIGIT OF SAMPLE
.. B. Atlantic cod . vtAn raoe 1976 1984 STATION T2 A = 1985. s .1986
-MI$51NG PolNTS AR( Dct
. TO OVERLAPPING VALK$
1 -*-
- ALL Yt AR$' M[Ax a
c A i i c N e e a a u no . 3 , E . l e . 3 4 . p 1 . t . l . . a . y . o i 3
/1
/*/' s i
1
.N./,
. Jaa. ..............re nna . . . . . . . . . . . . . . .Joe Pa n., . . . . . . . . . . . . . .aus avt . . . . . . .up. . . . . . .ocs
. . . . . . . . . . . . . .Mc now ...............
NDa tW Monthly mean 1og-transformed (x+1) estch per unit ef fort
~
Figure 3.2.2-5. (1 24-hr. set'for gill nets, 4 replicate tows for otter trawl) for each year and over all years for A. Atlantic mackerel at combined gill net Stations G1, C2 and G3 and B. Atlantic cod at otter trawl Station. T2 from 1976 through 1986. Seabrook Baseline Report, 1986. 203
i Station T2-(mean = 2.3/ tow).' ~A two-way analysis of variance showed-significant differences in year and station catch data and in year / station interactions (Table 3.2.2-10).-. Evaluation of least squares means for interpretation of significant year / station interactions showed' the occurrence of 14 overlapping year / station groupings _(Appendix Table ' 3.2.2-1). This number of groupings and the' significance of the interaction term means that station differences were not consistent from year to year; the interpretation of results, therefore, would be quite complex. Hakes ~ Hakes, a dominant species group (red, white and spotted hake) during summer, increased in monthly mean CPUE from lowest levels in , January and February to peak levels during June through October, and subsequently declined (Figure 3.2.2-6). Annual mean CPUE (stations , combined) ranged from 5.8 fish / tow in 1983 to 14.7 fish / tow in 1977 and averaged 9.2 fish / tow (Table 3.2.2-9). The 1985 and 1986 CPUE values were at the low end of the range of mean CPUE values in past years. - Results of a two-way ANOVA showed significance in year and station catch data but not in year / station interactions (Table 3.2.2-10). Scheffe's multiple comparison of yearly means showed that differences between annual means of CPUE were generally not significant except that the 1981 mean was significantly different than the 1979 and 1985 means. A multiple comparison of station means revealed that the mean catch per unit of effort was similar at Stations T1 and T3 (mean = 12.2/ tow and 11.3/ tow, respectively) and significantly lower than both of these stations at Station T2 (mean = 4.1/ tow)(Table 3.2.2-10). ; 1 204 J
TABIE 3.2.2-10. COMPARISON Of LOG (X+1) IRANSTORHtD CAICll PER UNil [Ff0RT BY YEAR AND STATION UTillZING A TWO-WAY ANALYSIS Of VARI ANCE FOR S[l_ECTED f lNi lSH SP(CIIS col t f CIED IN OIIIR IRAWts fROM 1916 IllROUCH 1986. SEABROOK HASILINE REPORT, 1986. SOURCE Of DICH[ES Of Nf AN a SPECl[S VARIAllON FRIEDOM SQUARE F VAlUE PR>I MUt i l PL E COM PAR I SON Winter flounder Year 10 3.01 24.fs t 0.OOut**b 81 80 82 78 83 86 79 84 77 85 76 Station 2 21.83 I T 7. fs3 0.0001** Interaction 20 0.31 2.52 0.0002** [rror 1431 0.12 T2>f1>T3 Yellowtail flounder Year 10 3.24 25.41 0.0001** 80 81 79 76 82 77 83 85 78 84 86 Station 2 10.95 555.68 0.0001** I nte ract ion 20 0.35 2.11 0.0001** Ita31 on f r ro r 0.13 11>T3>T2 fla nc s Year 10 1.59 fa.82 0.000l** 83 77 78 82 76 86 80 884 83 79 85 Station 2 12.78 38.83 0.0001** I nte ract ion 20 0.11 0.35 0.996fa(NS) T1=13>f2 frror 18a31 0.33 Atlantic cod Year 10 f.19 4 21.82 0.0001** 80 79 78 83 82 81 84 76 86 77 85 Station 2 18.29 121.35 0.0001** Inte rac t ion 20 0.28 1.88 0.0103** E r ro r 1431 0.15 T3>TI>T2 Rainbow socit Year 10 1.36 5.9fs 0.0001** 78 76 79 83 81 82 80 884 77 86 85 Station 2 6.11 26.95 0.0001** Inte rac t ion 20 0.32 1. f: 1 0.10 lfa ( NS ) T2>T1=T3 E rro r 1431 0.23 a Years and stations are listed in order or decreasing catch abundance Schef fe's multiple compa rison of yea rly and station means. a= from left to right. Yea rs unde r l ined a re not significantly different f rom eacle other a t 0.05. Stations that a re not significantly dif ferent form each other at a = 0.05 a re shown as being equa l . b
**
- Significant at a= 0.05
* = Significant at a= 0.05 3(NS) x Not significant
- 5. .
A. Hakes STATION T2 I t 8 3 6 9 6 0 0 m i I e 4 0 a 1 # a 1 4 4 4 C to e e a 7 a e 4 4 1 $ *
- 1 1 C 4 0 9 7 0
. 9 a 1 8
,e i t u i 9 9 0 m 4 + 6 3 %
a t i 1 7 4 9 4 F 7 0 3 8 1 a $ e e f 6 o 5 e e e a a 9 a 4 9 7 3 S
- 6 t*a...........a....
Jag sta
..............7..........................................0....................3..........3..........a man sta war Jun Jut am st e oct mov Of C m tw l e 4
Sa . . #= LA$t 0:31T 08 $ AMPLE B. Yellowta11 flounder vtAR ram 19n.19s4 STATION T2 A . 1985. t = 1966 8 MIS $lkG PolNTS AAI M TO OVERLAPPING VAL),T$ { -*-* ALL vtAR$' FIAN e e , o
.a C 3 3 a 3 3 o C t t 9 0 N 8 6 1 0 9 to e P P G 1 1 g I a a
t 9+t
/ ;
1 6
'/'
I 6 0 0 t , 3 *%. 4 e s f 9 7 4 4 4 4 a F 9 8 7 1 0 a e t a *
- 3 4 4 7 0 3 3 1 a f 6 .
'N ,
1 e s I e s I m e \ Ie....................4..........4..........9.........4.........0.........5...........%...........a.........3............ Jae pte man are mar e Joe Jyt avC Et t
. i CC1 nov OtC p.Ns t n Figure 3.2.2-6. Monthly mean log-transformed (x+1) catch per unit effort (4 replicate tows for otter trawl) for each year '
and over all years for As Hakes at Station T2 and i B. Yellowtail flounder at Station T2 from 1976 1 through 1986. Seabrook Baseline Report, 1986. I l 3 206
]
Yellowtail Flounder Yellowtail flounder were collected in otter trawls year-round (Figure 3.2.2-6). Mean monthly CPUE values at Station T2 were notably reduced during summer compared to the other seasons, while no distinct seasonal variations in mean monthly catches were evident at Stations T1 and T3. Reduced catches at Station T2 during summer may be related to increased water temperatures at this shallow-water station, and perhaps to seasonal changes in substrate composition (e.g., drift algae). Annual mean CPUE averaged over all three stations ranged from a low of 8.4 fish / tow in 1986 to 30.5 fish / tow in 1980, and averaged 17.0 fish / tow overall (Table 3.2.2-9). Mean CPUE was highest at Station T1 (mean = 29.6/ tow), intermediate at Station T3 (mean = 15.8/ tow), and lowest. at Station T2 (mean = 5.4/ tow). Differences among year and station catch data, and interactions between years and stations were found to be significant (Table 3.2.2-10). Evaluation of least squares means for interpretation of significant year / station interactions produce 17 overlapping year / station groups (Appendix Table 3.2.2-2). These differences in year / station groups means that' differences in year I and station catch data are very complex, and difficult to interpret. Demersal and Estuarine Species Winter Flounder Winter flounder were present in otter trawl collections year-round during most years (Figure 3.2.2-7). Distinct seasonal trends were not apparent for winter flounder CPUE values at Stations T1 and T2. However, Station T3 did exhibit higher CPUE values from June through October (Figure 3.2.2-7; Appendix Figure 3.2.2-2). Annual mean CPUE averaged over all three stations increased from a low of 2.8 fish / tow in 1976 to a high of 13.7 fish / tow in 1981, and subsequently declined to , 207
# . LAst DIGIT Of sAMPLt YEAR FROM 1976 1984 A. Winter flounder a . 3,es. s . i,es.
STATION T2 P!ssths Points Art Oct TO OvtitLApp!h3 VALUt3 '.
, - - . Att YE ARs' ME An 100
- m i t
., a Se e e u 9 t C 1 a o-1 e e a u 3 e o. 4 1 9 e t 9 i a t t t 4 a p
.e g a
8
.N! !
,x.
N ., ; t e a t
.x, r . .
a f . a e 9 6 !
# $ "a a e a e t
1 8 9 a- a i 9 e 4 3 L 6 i e.+4..................................................................................................3..........9............ are
. 4 Jae ets was mar Jun svi, auc st e oct nov etc penaIw B. Winter flounder o
- i, STATIONS S1, S2 + S3 ,
e
. .s .
,' e r
# 9
. i i .
t > . i A $* j/\! . . i
,\. .
i e e a 6 4 p 4 1 i i f i n
, N s,
. s 2 y'
'l.,,-,,,'I
. i a 3 S
e i e , e
, s \
Jan its maa are mas Joe su auc ser oct mov etc l
.. i i
Figure 3.2.2-7. Monthly mean log-transformed (x+1) catch per unit effort (4 replicate tows for otter trawl, 2 hauls for beach seine) for each year and ovhr all years for vinter flounder at A. otter trawl Station T2 from 1976 through , 1986 and B combined beach seine Stations S1, S2 and l S3 from 1976 through 1984 and 1986. Seabrook Baseline l Report, 1986. ! 208
3.9 fish / tow in 1985. The annual mean CPUE increased slightly to 4.4 fish / tow in 1986 (Table 3.2.2-9). CPUE values were highest at Station T2 (mean = 11.2/ tow) followed by Station T1 (mean = 4.2/ tow), and Station T3 (mean = 3.3/ tow)(Table 3.2.2-9). Year and station catch data, and interactions between years and stations were found to be significant (Table 3.2.2-10). Evaluation of least squares means for interpretation of significant year / station interactions showed the occurrence of 14 year / station groups, only one of which was non-overlapping and distinct (Station T2 in 1981 and 1980)(Appendix Table 3.2.2-3). Once again, these differences in year / station groups means that year and station differences are very complex and difficult to interpret. Winter flounder were also present in beach seine collections from the Hampton-Seabrook estuary throughout the April-November sampling season (Figure 3.2.2-7). Monthly CPUE varied widely with peaks at various times from May to October. This high variability in monthly catches notwithstanding, annual mean CPUE values were reasonably simi- i lar. Annual mean CPUE ranged from 2.1 to 6.2/ haul, and averaged 3.9/ haul with a coefficient of variation of only 72.6 (Table 3.2.2-9). Seines were not employed in 1985, and insufficient data were collected , in 1986 (not sampled during April, May and June) for direct comparisons with previous years. However, mean monthly CPUE values in 1986 were lower than the monthly means for previous years (Figure 3.2.2-7). Rainbow Smelt Rainbow smelt were collected in otter trawls primarily during winter and early spring (Figure 3.2.2-8). Annual mean CPUE ranged from ) 0.6 to 8.7/ tow and averaged 4.1/ tow (Table 3.2.2-9). Lowest CPUE values occurred in 1977, 1985 and 1986 (0.6-1.8/ tow) and highest values in 1976 and 1978 (5.9-8.7/ tow). Mean CPUE was highest at Station T2 (mean = 209
A. Rainbow smelt ' ' STATION T2 *
- LAST Cla!T or s w Lt
** ' YEAR FROM 1976 1964 A
- 1965. 8 1964 MI55thG P0thT5 ARI DUt m
t to .. 70 OvtRLAnthG VAtuts a
$ - . Au, itARs' mt An
!. . i.
t i e . .- e i..* *%, i . S .' I, .' . 2. 9
. A A A
= . . . .
s s o
- y. '
a
- --- t t-i.
........ ........ . ............ ..... . ......... A......... .................... . ........ . .
e. J i B. Rainbow smelt
. STATIONS $1, $2 + $3
. t a
! i
< i
. le . 3
.i
. . 5 .
3 4
.a ,
i , L ~ 1s; j'
.\ f g h/
, ,,i ~ ~ " .
*:...........................t........t........!.........t.,......!........t........t........t............
Jan f48 mAA APR RAT Jve Jul eeG ti p CLI Nov NC pa3ela Figure 3.2.2 8. Monthly mean log-transf ormed (x+1) c,atch per unit ef f ort (4 replicate tows for otter trawl, 2 hauls for beach j seine) f or each year and over all years f or rainbow j smelt at A. otter trawl Station T2 from 1976 through 1 1986 and B. conbined beach seine Stations S1, S2 and S3 from 1976 through 1984 and 1986. Seabrook Base-line Report, 1986. 210
i 6.3/ tow) followed by Station T1 (mean = 3.7/ tow) and T3 (meen = 2.4/ tow). Results of a two-way ANOVA showed significant differences in catch among 5 years and stations but not in year / station interactions (Table 3.2.2-10). - A multiple comparison of yearly means showed that only the years 1978 and 1985 were significantly distinct. A multiple comparison of station means showed that, the differences in station means were significant
-between Station T2 and the other two stations but not between Stations s
T1 and T3. I Rainbow smelt were also present in beach seine collections taken from April through November in the Hampton-Seabrook estuary (Figure 3.2.2-8). The beach seine program takes place from April through Novembar, and consequently does not provide information on smelt abundances during winter and early spring when they are most numerous in otter trawl collections. Monthly smelt CPUE values were erratic, with large catches (10-100/ haul) occurring at various times during the beach ! seine sampling period. Much of this variability can be attributable to the schooling tendency of rainbow smelt. In spite of the high vari-l ability in monthly CPUE, mean monthly CPUE was reasonably constant from j May through November. On the other hand, variations in mean annual CPUE , I wer e large (Table 3.2.2-9). Mean annual CPUE ranged from 0.1 to i If.7/ haul and aver 0ged 6.8/ haul, with a coefficient of variation of 778.1 (the largest CV for a grand mean, stations averaged). Though no annual mean was calculated for 1986 due to the reduced sampling effort, mean monthly CPUE for Jely through October were below the mean monthly CPUE values (Figure 3.2.2-8). ! l i l l l I i. l 1 211 i
i 1 Estuarine Species Atlantic Silversides Atlantic silversides were present in Hampton-Seabrook estuary beach seine collections throughout the April through November sampling. season. The largest CPUE values for Atlantic silversides usually occurred from August through November (Figuro 3.2.2-9). Silversides were the most abundant species in beach seine samples during this period. Station differences in Atlantic silverside CPUE values were not evident for this schooling, highly mobile species. Annual mean catches of silversides appeared to fall into two groups: 1) 1976-1981, when annual mean catches ranged from 109 to 261.4/ haul and 2) 1982-1984, when annual mean catches ranged from 34.5 to 54.4/ haul. Seine hauls made from July through November 1986 contained low abundances of silversides, suggesting that the trend of low silverside abundances which began in 1982, continued through 1986. Summary of Variability in Finfish Selected Species Overall data characteristics for selected finfish species indicated highly variable catches during the baseline period. Coeffi-cient of variation, a relative measure of variability allowing stand-ardized comparisons among data, ranged from 71 for yellowtail flounder at Station T1 to 426 for Atlantic cod at Station T2 (Table 3.2.2-9). Overall, coefficients of variation were higher for Station T2 catches than for Station T1 or T3 catches for all species, except rainbow smelt. Rainbow smelt variability was slightly higher at Station T3 than Station T1 or T2. Considering all stations and sampling methods, rainbow smelt exhibited the highest degree of variability based on CV values, and yellowtail flounder and winter flounder the lowest. .0ther species were intermediate in variability, with no trends noted within gear type. 212
i 10tMi o 6 I
.I Atlantic silverside 9 I STATIONS S1, 52 + 53 I 6 o i 500 + 6 1
7 1 1 l 8 1 8 i
- O j l e = LAST DIGIT OF SAfst!
l YEAR FM]pt 1976-19R4 9 4 8 7
- 1 3 = 1986 MI55tnG Po!NTS ARE DUE g
TO OVER1APPinG VAttE5 . g . 4 4 l -*~ = ALL YE AR$' *E Ah l II > 100 + 0 \ l l 1 2 3 I \ i M t i 4 f \
\
s 3 / i A I \ N 50 + / I I \ f J \ j 3 N I 4 U l ? g \ f M l \ / 0 Il l \2 / u E l 6 i \/ v R l l 'g W 6' l I r i E 1 l R 10 + l n ! a 1 A i ; u l 1
/
8 -; ! L 5+ I l 1 6 1
- l l I I 9 l I l
6 3 a 9 l l i ! '-; " l l 1 0 2 A s g j i 2 7 o s s , O+ 9 4 NB
.,..+........+........+........+........+........+........+........+........+
MAR APR MAY JUN JUL AUC SEP
.......+........+........+...
OCT NOV DEC JAN f[8 i MONTH f Figure 3.2.2-9. Monthly mean log-transformed (x+1) catch per unit ef fort (2 hauls) for each year and over all years for Atlantic silversides at combined beach seine Stations S1, S2 and ! S3 from 1976 through 1984 and 1986. Seabrook Baseline Report, 1986.
.__--_----__ - - _----__.--____.-----_-_ - -- - - _ _ _ - - - - - - - - --- , w - e - .- --wv-,m-wnw,--- r ~ v
. . LAST DIGli 0F 5AstPLt
. vtaa e i n s.i m A. Atlantic cod *
- I "I ' '
- I "'
STATION T1 P!531N3 POINTS AAI D'T . TO OvtRLAPP!h3 VAtttl g - . - . ALL YEAt$' MEAN
. t i ! .
. i e .
i i u . l .
! t f ; % .'; '
. **1 , .- .
IN. l i .
. /.*/ .
.N.
I
.x,%./
e
. .., . . . . . ... . . . . .. . .. . . ..... . . . . m. . . . . . .. .. . . . . %. . . . . ..R. . . . . u. . ...........
. . . . .ci... ... ... ... .. m. ,. . .. ... ... ... ..we MM . M
! B. Atlantic cod .
STATION T3
- i .
i . .
. i C i 4 .
.. . s
. s .' N I. . .' .
. s
. 1
. , i .
t./ y. i *
,N /:
i i . . , J.a fr...........m..................................................................................................
. . P. n.T 4tMs JM .esG .( . OC, .0v MC sed. i .
i Appendix Figure 3.2.2-1. Monthly mean log-transformed (x+1) catch per unit i effort (4 replicate tows for otter trawl) for ! each year and over all years for Atlantic cod l at A. Station T1 and B. Station T3 from 1976 : through 1986. Seabrook Baseline Report, 1986. -l 214 ,
. . 1
l
. -l A. Winter flounder ;
STATION T1 L
. a 1 .i e i .
. i e
- . ie .
e i i e
, t ,
i
' c.
2
", i e e i e
. . . e a
!. / e* 1 1 !. . t I
. > 1 .
e i , , , . . IN i IN! e
. 3-
. , e e i e e e a 4 6 4
A t . 9 j-f a ' na.........4.............................................................................e................................... 4 .
. et. ma . e. m, so. m avo see oct .ov occ se;i. I .
4 1 e . LAlt DIGIT Cr $so ;[ t YEAR FAQr })76 1984 ,
"
- i A . 1 H S. l . 1966 M:15th3 Po!NTS Ant Det to CVER1487!h3 VAWI5
- * ~ . Au YE AA3 ' PI AA .
s B. Winter flounder : t STATION T3 ! ' . e e i c., ie . e i e 1 4. e .
. i e e
. e. .i . t i e i
e . . .N.
- 1 l
- . . e *%! t ; i
,l i e 1
.e I. e i, 1
1 e e e a . l i
,0 i e e e
. t
. e i . i e e . , . .i i i e . . .
l i ' .I i ! e i , [ s e e . : e , e . i, . a 5 l: ! ie.......................r......................m 4 ,ie m. . ave m ..................................................
.ve u, .c t .
wc i I ma t. - 4. I I
. l i
Appsndix Tigure 3.2.2-2. Monthly mean log-transformed (x+1) catch per unit ef fort i (4 replicate tows for otter travi) for each year ! i and over all years for vinter flounder at A. Station l ! T1 and B. Station T3 from 1976 through 1986. i Seabrook Baseline Report, 1986. ; k 215 6 4
-. .r, ,n,,.., n-, - - - - - - - - - - , - , - - -- - pg.--,.,v+ , - - - - -n - - - - , , -- , y 7,-., - - , - , - . - -, ,
= - - - _ _ _ . . . . . . _ . . _ _ . __. _.......- - . . ~ _ . _ . _ _ ~ - . - _ _ _ = = .
_ ._ . . . _ ~ _ - _ _ . - - . . _ _ . _ = . . _ _ _..
. . ~.
i APPENDIX TABLE 3.2.2-1. LEAST SQUARES M[ANS [ VALUATION OF Y[AR/STAllON INi[RACTIONS 005 LOG (X+1) TRANSFORM [D CPUE FOR Ail _ANitC COO
# ROM 1976 THROUGH 1986 AI STAllONS TI, 12 aruf 13. STABROON BASELINE REPORT, 1986.
i YtAR 1978 1980 1983 1979 1981 1982 1980 1983 1981 1982 1979 1978 1984 1976 1979 1984 1976 STAllON T3 13 T3 T3 33 13 11 il 11 11 11 11 I3 T3 T2 11 T1 I s h YE AM 1979 1984 1976 1980 1982 1981 1977 1986 1977 1918 1983 1986 1985 1985 1986 1984 1977 1976 198$ STATION T2 it il T2 T2 12 13 13 11 T2 12 il T3 il 12 T2 12 T2 12 y NOTE: Years omderlined are not si9nificantly diff'ereret f rom each other at G = 0. 0% Dash line shows overlap in years /stasions between top and bottom portiors of' table. s 9 i l
APPINnix TA8Lt 3.2.2-2. LIAST SQUARES MIANS IVALUATION OF YfAR/STAllON INif RACilONS ON LOG (X+I) IRANSFORMED CPUC FOR Yri.t OWT All - FLOUNDER (ROH 1916 filROUGH 1986 Ai ST Al l Of4S II, 12 AND II. $[ABROOK BASELitif REPORT, 1986. YIAR 1980 ICS1 19T6 1979 1980 1977 1982 1979 1976 1978 1983 1981 1984 1985 1986 1978 1977 1982 STAllON II le il 11 13 Ti 11 13 13 Il II 13 TI II II T3 T3 13 VI AR 1982 1985 1983 1984 1980 1982 1986 1919 12 1981 12 1916 12 1983 12 1985 12 1971 12 1986 12 1978 12 1984 12 STAllON T3 73 13 13 T2 12 T3 92 M M NOft: Years underlined are not significantly dirrerent f rom each other at G= 0.05. Dash line shows overlap in yea rs/ stations betweers top and bottom portiose of table.
APPflec t X T A81 [ 3.2.2 3. LEAST SQUARES ME A815 EVAt oaf TON or YE AR/SI AllON INTERACTIONS 000 LOG (X+1) TRAseSFORt9ED CPUC TOR WINTER FLOUNDER TROM 1976 THROUGH 1986 AT STAllONS TI, T2 AND T3. SIABROOK BAS [l.IllE REPORT, 1986. vt Ast 8948 8900 1982 1983 1979 1978 1984 8988 1985 19848 8977 198th 1986 1982 1986 8981 8976 1983 1986- 1985 19FS SI Al 80et 12 12 I2 12 I2 12 82 il 12 Il 12 Il la It I2 E3 I? It 33 le il to c* co YE Ast 1986 1981 8976 1983 1*e6 1945 1918 19FF 8982 1978 '983 1964 1979 1984 3919 1977 1976 1975 19e5 St Al sose 12 II 12 II f3 ft 13 ft II II II It Il 33 13 53 It is 33 e 19088 : Year s seredert lesse are sect sigeoiricaretly de f rasent feraan eacts astiseer a t e 86.05. taa ste 0 ene shs everlago des yeas s/statioens Apetes togs asses anat tasse goes t iease of Lats t e . m__ _ _ . - _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - . - - - . - . , . . _ _ - _ . _ , , . - - . - - _ , , _ _ _ . . , . -m_-,m. -_ _ - , . . . _ . _ _ _ _ _ - . . _ _ - - _ _
3.3 BENTH0S 3.3.1 Estuarine Benthos 3.3.1.1 Physical Environment Temperature and Salinity Weekly measurements of temperature and salinity at high and low tides in Hampton Harbor and Brown's River were taken to investigate seasonal and annual patterns. The Brown's River site, downstream from Seabrook Station is the most likely area to show effects of the settling basin discharge. Low tide collections represent the most extreme conditions for these parameters, and thus were most affected by environmental conditions. Hampton Harbor temperatures and salinities are tempered by tidal influx, and showed less variation than Brown's River. Thus the Brown's River site at low tide will be the focus of this discussion. However, annual trends were similar at both stations and tides. Salinity values showed evidence of a long-term trend that was related to both precipitation levels and the settling pond discharge. In 1980 and 1981, annual average shlinities were highest (25.1 and 25.5 ppt, respectively), with average monthly salinity rarely dropping below 20 ppt (Table 3.3.1-1, Figure 3.3.1-1). Salinity decreased in 1982-1984, with 1983 and 1984 values the lowest recorded (19.4 and 18.1 ppt, l respectively)(Table 3.3.1-1). The fluctuations in annual salinity corresponded to changes in total annual precipitation. In 1980 and 1981, precipitation was well below average, dropping to 29" and 36", ' respectively, while in 1983 and 1984 it increased to over 50" (Table 3.3.1-2). In 1985 and 1986, precipitation dropped to near-average levels (42"). Acting in conjunction with decreases in annual precipi-tation in 1980-1981 were increases in the volume of settling basin l l l 219 l
. _,m. --...-._..._...__.m- -_ . ________.__--___m -
. _ _ __- m. _ . . .m. _..m. _ _ . _ - . . . . _ . . . _ -.. - -__ -..
d 4
, TA8tE 3.3.1-1 AsseeUAL ME AN i f MPERAT URE ( *C ) AND SAL I N I TY ( PPI ) TROM OROWIt'S RIVER ;
Afe0 NAMPIOtt HARBOR fROM 1980-1986. i 1 BROWN'S RIVER HAMPT0pe HAR804 t.OW ilDE HICH ilDE LOW IIDE HIGH TfDE ftMP SALINifY TEMP SALINITY TIMP SAL I NI TY IIMf' SAtlNifY (*C) (ppt) ('C) (ppt) (*C) (ppt) (*C) { ppt) , l 1980 10.9 25.1 9.6 31.0 9.6 29.9 9.1 32.1 1 1981 10.6 25.5 10.3 30.0 9.3 28.9 9.3 31.5 1982 10.7 22.8 9.9 30.0 10.2 21.3 9.2 31.2 , 1983 11.9 19.4 11.0 28.0 10.4 25.5 9.9 30.1 ea O 1984 11.9 18.1 10.6 28.4 10.4 25.8 9.4 30.2 1985 11.3 21.7 10.1 30.6 10.6 29.1 10.1 12.2 1986 10.3 20.4 9.6 30.2 10.0 2 T. 7 9.4 31.5 l i 4 1 e i i _ _ _ _ __ _ _ _ - _ - _ _ _ _ _ . - - , , ..m. .- ,- . . . . . . , _ _ , ,m .,-._,-.-,c. . ,-,_,,..r,y...-.. _ _ , . - ,,-._.e, -..n ie 3- ., _ ., - ., , ., ,. .
35 0 - 1979 l 1980 1 1981 1 1982 1 1983 i 30.0 - - , Q / -s /\ ,,
/. \
25,0 -
,}
/. , \ '
ys
\ /
(" n \ ' g ("\/ . ..
.\
(
& 20.0 - / -
- ( l f
\ / ) 00NT!v.n g
. BELOW l.
f15.0- / M ' '
/
10.0 - e 5.0 - 0 iiiiigi i ii i i i iii ii iii i,i ii i ii iii i i s ii i ii ii i ii ii ii iii i ii i ii i i J r = A M J J A 5 o n ; J F M A M J J a s o n c J r m A M J J A 5 0 % C J F M A M J J A S O N D J F P A m .' J A 5 0 s ; i 1979 l 1980 1 1981 1 1982 1 1983 I 35 0 " l 1984 1985 1986 I f 1 l i 30.0 - 610NTHLY
\/ MEAN D
25.0 - y , l O 5 20.0 - [" \ N
)5
( STANDARO
' OEY!ATION l CONTINLED I ..
(
..,'/
i p FROMABOYE[ ,
\ ,f ( ,
2 " f.. - z 15.0 - - 3 ,
,)
l"
@ / 1 -
I 10.0 - 5.0 - i 0 iiii,,ii,,,,,iiiiii,,,i iiiiiiiiiiiiii;eii,,iii iiii iiiiii f J F M A MJ J A 5 0 m C J F P A N J J A 5 0 N 0 JF M A M J J A 10 h 0 I i 1984 1 1985 1 1986 l l Figure 3.3.1-1. Monthly mean and standard deviation of Brown's River low tide salinity. Seabrook Baseline Report, 1986. 221
TA3LE 3.3.1-2. MONTHLY TOIAL PRECIPITATION IN INCHES (4ATER (QUIVAlf Ni IN INCitFS)-BOSTON, MA.* SEA 8R00k BASEtt4E REPORT. 1986. MONIHLY ICIALS MONTH 1913 1279 170Q 1981 1982 128) j?$9 1265 J996 JAM 8.12 10.55 0.7% 0.95 4.69 5.03 2.31 1.12 3.42 ft8 2.87 3.46 0.86 6.65 2.66 5.00 7.81 1.83 2.83 MAR 2.46 3.03 5.37 0.62 2.1T 9.72 6.82 2.29 3.42 A PR 1.79 3.19 4.36 3.14 3.42 6.86 4.43 1.62 1.59 MAY 4.50 4.24 2.30 1.11 2.58 2.94 8.77 3.36- 1.31 JuN 1.53 0.86 3.05 1.65 13.20 1.07 3.06 3.94 7.74 J Ut 1.48 2.36 2.20 3.47 4.22 1.07 4.43 3.51 3.96-AUC 4.62 5.02 1.55 1.04 2.22 3.28 1.60 6.67 3.32 J St P 1.30 3.61 0.82 2.54 1.57 1.06 1.22 3.00 1.08 OCT 3.13 3.14 4.1'J 3.43 3.19 3.74 5.18 1.65 3.27 Nov 2.21 3.29 3.01 4.18 3.42 8.89 1.68 6.39 6.01 Of C 3.63 1.42 0.97 6.2T 1.21 4.94 2.93 1.21 6.38 ANWUAL 37.64 44.17 29.39 35.71 44.61 53.60 50.24 36.59 44.33
*Soisrce: National ClimatlC Data Center. 1986.
A I (Figure 3.3.1-2) which contained mostly offshore sea water, with salinities of approximately 31 ppt. During the three-year period of high discharges and low precipitation (1980-1982), salinities rarely fell below 20 ppt and usually ranged from 25 to over 28 ppt. j Seasonni patterns in salinity were similar at both stations and at both tide levels. Levels were highest in August and September ] and lowest from February through April, the period of highest runoff 1
- (Figures 3.3.1-1,3; Appendix Figures 3.3.1-1,2).
I Annual temperatures at low tide in Brown's River were warmar , l from 1983 85 in comparison to previous years, with peak temperatures a usually more than 22'C (Table 3.3.1-1; Figure 3.3.1-1). Average temperatures in 1986 were the coolest recorded, averaging only 10.3*C (Table 3.2.1-1). Annual temperatures at Brown's River high tide and Hampton Harbor (both tides) showed a similar pattern except that there l was less variability among years (Table 3.3.1-1). 4 Seasonal patterns of temperature at both tides and at both ! e stations were similar (Figures 3.3.1-1,3; Appendix Figures 3.3.1-1,2). Temperatures at Brown's River (low tide) were highest in July or August, I and were greater than 20'C ) six of the eight past years. Temperatures ! reached their lowest point in January or ;.bruary, 1 ~ Spatial and tidal differences in temperature and salinity were j predictable. High tide salinities were always higher and less variable because of the influx of more saline water from offshore. High tide temperatures were less extreme than low tide, warmer in winter and i
- cooler in summer. Hampton Harbor salinities were higher and tempera-1 tures were lower than Brown's River because of offshore influences (Figures 3.3.1-1,3; Appendix Figures 3.3.1-1,2).
4 i 223 i
SEABROOK SETTLING POND DISCHARGE APPROX. GALLONS / DAY 5-4- ^*^2' b O b 3~ $
- N.c ~
h E
~
1-o s ej is sijiib A s hi4 a= j j ii6 4 6 Jis A 4j j Ai6 sb jisim)Jii6N 6 l1978 4--- 1979 :t 1980 ::t 1981 :C 1982-
- 5-4-
?
e b 3-s a 9 d 2-r 1-l%u ai a A 4 3 3 A s 6 s 6)i A L AJ j Ai6 4 6 3 i A A A 3 J Aioi 63i Ai AJ J is o a 6 M 1983 C' 1984 % 1985 2% 1986 A Figure 3.3.1-2. Discharge from the Seabrook Settling Basin from 1978-1986 in millions of gallons per day (GFD). Seabrook Baseline Report, 1986. 224
sal.INITY I e e e e . I
'iN! '
- I
.x' ,
\*.s,
- i
, !-; e i e
- s. . .
u . < M
- 3 3
I 1
.I.~....~ . - . . . . . . . . . .
m.....,. n. . . an
=
m res a = . 3 m e e.**t re. 5. 6. Eic. . LAU O! GIT CF TEMPERATURE sAxPLt itAR. is s .
-:- . - . ALL ygAR.$ ggA3 l
" "l is e .
i
- /.:
a I
\! .
j . ii i . - l
- t
- i. e . . ,
I
. . .l , ;
i .. l , si. . !
..m .
- -i
-t $ .
-- - - ~.- . ... _ . . .~. . . _ _
*a m == = . a. m ,,, .n Figure 3.3.1-3. Mean monthly salinity (ppt) and temperature (*C) in Hampton Harbor at low tide from 1978-1986. Seabrook Baseline Report, 1986, 225
o l l l l 1 Sediment j Yearly and seasonal differences in sediment taken from 1978-1984 indicated estuarine sediments were very patchy with spatial vari-ability often exceeding annual variability (NA1 1985b). Yearly averages at subtidal stations (3 & 9) showed grain size was fine sand, which was usually poorly sorted with organic carbon ranging from 0.97 to 2.08% i (NAI 1985b). The yearly averages for intertidal stations (3 HLW & 9 MLW) showed. the grain size varied from fine sand to silt, which was often very poorly sorted. The percentage of organic carbon was higher than at subtidal stations and ranged from 1.56 to 5.86% (NAI 1985b). Although differences in low tide salinity in Brown's River appeared from 1980-1982, sediment parameterc during that period were apparently within the range of natural variation. I 3.3.1.2 Macrofauna l l i The estuarine benthic communities in Brown's River (Station 3) and Hill Creek (Station 9) were not unusual for quiet, tidal creeks with fine-grained sediments, where average conthly salinity ranged from 18 l l ppt to 25 ppt. Spatial distrioution of organisms was very patchy, and large population fluctuations scurred seasonally, as is typical in estuarine habitat. Deposit ar.1 surface deposit feeders predominated, usually composing over 70% of the fauna at Stations 3, 9 and 9MLW (NAI , 1985b). Three taxa comprised the majority of individuals: Streblospio be ne d ic t I , 011gochaeta, and Capitella capitata. The clam worm, Nerois l diversicolor, was very abundant intertidally in Brown's River (Station 3MUW). The sof t-shelled clam, Mya arenerla, was also present in substantial numbers at all sampling locations. Total abundance of organisms (number /m2 ) showed year-to-year variations that were related to long-term environmentui trends. The years of highest abundance were 1980-1982, when the mean annual abund-226
ance ranged from 9405/m to 10063/m 8(Table 3.3.1-3.'. The year of lowest abundance was 1984, averaging only 2442/m". The period of 1980-1982 was the period of lowest precipitation, highest salinity and highest discharge flow from the settling basin into Brown's River. The years 1983 and 1984 were the years of lowest salinities, highest precipitation, and highest temperatures for the study period. By 1986, the total abundance (3649/m') was very similar to abundance in the pre-discharge period, 1978 and 1979 (3964/m 8 and 4690/m , respectively; 8 Table 3.3.1-3). Total abundance of organisms was significantly dif-ferent for both years and stations; however, significant interactions were also present (Table 3.3.1-4). Stations in Mill Creek (9 MLW & 9) had slightly higher average densities for the study period than stations in Brown's River (3 MLW & 3) (Table 3.3.1-3). The seasonal cycle of total abundance showed density was usually highest in May or August at both intertidal and subtidal stations (Figure 3.3.1-4). The usual increase in abundance in spring or summer was probably due to the recruitment of one or more dominant taxa (NAI 1985b). 1984 was the only year when density had no major seasonal peak at any of the four stations. It was also the second consecutive year of very high precipitation (Table 3.3.1-2) and had record low salinities (Figure 3.3.1-1). In 1984, the rainfall during May was double that of any other year, and the salinity was correspondingly low. The average salinity in February and April, 1984 was just over 10 ppt, and in May it was about 15 ppt, the lowest May salinity recorded during the study period (Figure 3.3.1-1). Water temperatures in 1983 and 1984 were also higher than previous years (Figure 3.3.1-1). The low densi-ties observed in Brown's River and Mill Creek in 1984 may have been
)
related to spawning and recruitment failures in 1983 and 1984, caused by more extreme natural conditions. i 1 227
TABLE 3.3.1-3. MEAN DENSI TY (NO. PER SQ. METER) FOR EACll YEAR AND OVER ALL YEARS FOR SELECTED VARIABLES COLLECl[D FROM ESTUARINE BENTHIC STATIONS 3, 9, 3MtW, AND 9MlW IROM 1918 illROUGH 1986 (EXCLUDING 1985).
~
SEABROOK BASELINE REPORT, 1986. VARIAntE STAllON 1978 1919 1980 1981 1982 1983 1984 1986 MEAN Total abundance 3 3492 4931 5818 585T 12050 2958 1346 1217 4709 9 3972 2f62 4 18298 11706 5373 6326 688 2992 6477 - 3MLW 520f4 65: 7019 7201 8283 3091 2581 5643 5695 9MLW 3189 C 8017 12855 18:545 13174 5154 4 1845 8313 NfAN 39684 9788 9405 10063 6387 2442 3649 Total taxa 3 35 48 48 82 6 47 32 27 35 37 9 26 34 4/ 4is 34 36 21 33 34 i I 3Mt w 28 31 31 38 35 28 18 29 30 9MtW 28 35 35 41 36 33 21 32 33 HEAN 29 37 38 41 38 32 22 32 Streblospio benedicti 3 RhD 220 '465 110 152I 622 281 10I 560 9 146 27 4171 1377 169 882 30 - 284 5 1031 3Mtw 533 838 156T 1089 3979 529 821 1518 1809-4 9MLW 61 3 559 1951 3172 4444 3828 4 1649. 1745 2196 MEAN 713 411 2190 1987 2537 1365 695 904 b3 Oligochaeta 3 363 801 4 341 658 3114 850 339 134 7:3 Q$ 9 51 163 4868: 1018 12fa6 2758 11 4 540 135i4 3Mt W 189 276 899 333 382 401 650 979 514 9MLW 578 1167 3286 1010 583 5912 636 8 14 . 1756 MEAN 295 502 23'48 755 1331 2480 455 632' capitet/s espitats 3 37 122 245 521 2395 318 118 91 481 9 277 f4 4 2867 414 3P. 444 51 10894 688 3MLW 57 32 221 326 548 236 155 199 222-9MtW 308 100 253 384 5 287 827 372 331 353 MEAN 170 74 897 417 883 456 174 417
#ercis divers / color 3 84 1 784 198 463 522 75 Sr4 53 203 9 48 39 67 2 184 57 14 7 49 64 3M! W 1643 li25 1596 1667 1120 446 366 1113 1209-9M* d 271 177 159 320. 151 132 708 196 264 MEAN 511 529 505 611 462 167 284 353 Cou//eric//s sp. B 3 397 313 1157 2 12 5 16 20 .240 9 60 53 1845 1423 825 39 18s 18e 322 3MtW 121 650 6's ? 21 50 - 63 62 -335 284 4 9MLW 20 316 353 900 263t4 --130 51's 337 725 MEAN 149 333 576 587 860 209 151 177 nya arenaria 3 92 159 103 266 182 118 33 53. 126 9 271 fa68 650 426 295 173 230 iss 320 3MtW 110 227 35 2t:0 159 193 26 50 130 9Mtw 106 3r:3 69 864 285 91 231 22 201 MEAN 184 5 299 214 384 9 230 144 130 43
TABLE 3.3.1-4. RESULTS OF A 'IVO-WAY ANOVA MODEL FOR SELECTED BIOLOGICAL VARIABLES SAMPLED AT ESTUARINE BENTHIC STATIONS FROM 1978-1984 AND IN 1986. SEABROOK BASELINE REPORT, 1986. a VARIABLE CLASS F-VALUE Total density year 9.71*** station 5.66** year
- station 2.06**
Total taxa year 15.36*** station 6.31** year
- station 1.16 Streblospio benedicti year 2.63*
station 10.38*** year *statien 1.37 011gochaeta year 4.45*** station 3.97** year
- station 1.98* j Capitella capitata yeat 6.97***
station 2.66 year
- station 2.07**
Nereis diversicolor year 5.15**w station 43.97*** ! year
- station 1.18 Cau11eriella sp. B year 2.25*
station 4.65** year
- station 3.15***
Mya arenaria year 6.76***
-station 3.70*
year
- station 0.45
* = significant differences at alpha = .05
** = significant differences at alpha = .01
*** = significant differences at alpha = .001 l
l 229
36' N " SUST!DAL 32,000 - h
$7Ai!ON 3 1\
28.000 - (840.t5 RIVER) /%
--- sT Attoh 9 I I 24,000 - (MILL CR([K) /
6 2c,000 - I 'g 6a I g E d 16,000 - / g ut I \ g12.000- \ s A wn ! \ , \ k/ /\
$ g 6.000 - \
f \
* : "N '
a / g \ E E 4.000 - N
, %' / s s/ '
^% s t / ....__ ^
C i i i e i e i e s a e : i e i i i i a i t// I i HAT AUG CEO MAT AUG C[0 PAY AUG NOV MAY AUG NOV MAY AUG NOV PA) AUG N0Y MA' AUG NOV MAY AUG NOV 1978 1979 1980 1981 1982 1983 1984 1986 SA9 LING DATES 2E,000 - INTERT!DAL A
$ 2A,00c - It $ STATION 3 P;W
- f. '
II'0**I "IVIEl h a 20,000 - EQ - - STATION 9 P;W /
\ I
/ t
\
g k i \ g - 16,000 - (M;LL CRI[K) /g g / g i \ CW / \ / i l \ a s 12,000 - f v' f \ ER ['% .,/ g I \ g Ea 8 *0 - , i i s E E 4, ooc j E :
# N,/' \J
/ L,, \ . ** [.\
/
J l 1 i i i j i i i & l i l i i i i i i I // l I 3 MAY AUG LI MAY AUG C[ PAY AUG NDY MAY AUG N0Y MAY At'a NOV MAY AUG NOV t%Y AUG NOV MAY AUG h0V 1978 1979 1980 1981 19S2 19El 1984 1986 SAMPLING DATES Figure 3.3.1-4, Number of individuals per sq. meter collected at subtidal and intertidal estuarine stations sampled three times per year from 1978-1984 and 1986. Seabrook Easeline Report, 1986. 230
l The mean number of taxa collected annually at all stations combined ranged from 22 taxa in 1984 to 41 in 1981 (Table 3.3.1-3), and significant differences were found among both years and stations (Table 3.3.1-4). The years 1980 through 1982 had the highest' number of taxa collected, while 1978 and 1984 had the lowest number of taxa (Table 3.3.1-3). 3y 1986, the high number of taxa occurring during the 1980-1982 period of high salinity and discharge had returned to approximately the same number as before the period began. The two subtidal stations had a higher number of taxa than the two intertidal stations. The seasonal cycle at each of the four stations showed that the highest number of taxa usually occurred in August or May, and the lowest number occurred in November (Figure 3.3.1-5). The most abundant species in the estuary, the polychaete Streblospio benedicti, exhibited significant differences in abundance among both years and stations (Table 3.3.1-4). The years before and after the period of high salinity and high discharge (1980-1982) had the lowest abundance. All-time high densities were reached in 1981 and 1982 (Table 3.3.1-3), and 1983 was a transitional year with relatively high population densities. When stations were compared, the two intertidal stations had the highest densities, and the two subtidal stations had the lowest densities. The seasonal cycle of S. benedicti indicated that extremely high densities (over 10,000/m2) could occur during any season at both intertidal and subtidal stations. Such high densities were almost never sustained into the next sampling period, causing tremendous population fluctuations (Figures 3.3.1-6,7). S. benedict i is an l opportunistic species (Grassic and Grassle 1974), and one of the first i to colonize af ter a perturbation of the environment (Rhoads e t al. I 1978). i The class 011gochaeta was very abundant in the estuary. Comparisons among years showed the years of highest abundance were 1980-1983 when population densitics ranged from 755/m' in 1981 to 2480/m in 1983 (Table 3.3.1-3). The years of lowest abundance included 8 l 231
-- __ ,~
SUBT10AL STATION 3 70 (EROW':S RIVER) 60 - ---STATION 9 A (MILL CREEK) / \
\
50 / . E 40 -
/ \_ \
- es % - bs A ^ y ,' s, s ' % s, ~ , 30 - , f- - s s @ 20 -
/ N*
5 o 10 - 0 i e 6 i 6 6 i i 6 I I I i l i e i i i l l i I M A 0 M A 0 M A N M A N M A N M A N M A N M A N 1978 1979 1980 1981 1982 1983 1984 1986 SAMPLING DATES l INTERTICAL STATION 3 MLW tstown: R:vtR) 60 " --- SW ON 9 ML'.' (Mllt CR!tr.) 50 s h
~
& y / 40 - j
/'s ,, / (, ,
\' '
30 -
' ' ' ' ~~~'s g' g
,f g ,
20 - E; 10 - r 0 i i 6 4 i 4 a a i 6 6 4 4 6 4 6 i a i 6 6 1// 4 4 M A 0 M A 0 M A N M A N M A N M A N M A N M A N 1978 1979 1980 1981 1982 1983 1984 1986 SAMPLING DATES Figure 3.3.1-5. Number of taxa collected at subtidal and intertidal estuarine stations sampled three times per year from 1978-1984 and 1986. Seabrook Baseline Report, 1986. 232
- =, - z.
- < g -<F
--r- ,-r-4 - .
=,
f
. I t 2 e -< e
- =
.f -
=
=,
l I _ *- M c c-e oe l'-"m E I k ~*- " G 1 -= 2 WI -*E # *
- I ee 6 .
r . . _R .
- ms E w: g.-
ug sc
.e . i
_,~o , .
-= c .g s ~ o oo
.Eo . .- . .y;-*E I -
r .t. co
- -=
=
i ; s _- g - u u .o
-e ' % / ~ ' W .t.
=a 0" 4 4 I g! 2
-a gy Q- **** **...... ,,**\ -*g y 2 0
.3
%i_,- a
.J C-
& M t
A$0 C- / -r- * .
'l J E e Im5 <'%' ' ~1-= 4 H \
l wm
** W \ lb" E o Qm W *.v Q' g m M .*-.,C e
j'-eg W l G CO l s == . .. E- -4 r== i 1
~
3
. 5 .i ,! !
= 1 g
a s g
. [ t
~ E_
t* m Z*/SlynCIAIONI 40 vist.N NY3A .s, /5 % %!A!CN! so V3 M N NY3W M k. u w C 48 C W L
- z. *,,,a, w q 1
1
= <$ .f.
. < y, oG j
_,- g. >, !
*D- s. u, w 6 g
; g b.
. q $
0 4
,e
# '.* - E : E u M s; _x- e pg i e _.-
a g . u o . s :- ,No L' -x a c@ @ s- -
<Kog :2I-:
' >?)-: -<$o N eum o .c o
*=*"""d-
%' - E y
52s a p 5p ( *8
-=
w C ua*
=
. , c. -
. c- .c -J =
~.
\ . ,8W - a G Nd /
e8a ~W ( - g C. .- - - - 3. . - . -=- e e. o a e c-E'-
-:: s / - -
, m Q
w 5 =. = "~-*~* *a" wi.
$ F,,
O nO xMx
/
2g N
~*
,5 ~ 6s .
~*
n 2 ff. e e O
, .\ - . e m
g d, m o m. 3 - e e** o.= -e~ l . f'. M g.* =E W 1-E - M.
< l < .. M o- - a + y-a, e q ,. - ., e e
e -
-.;- o W
~ /
i i a 3 a 666e i. 8 . 4 8 6 4 is4 ai E S . 9 9 9 9 c e 9' 9 9 9 9 9 9
- M 5 5 5 = = 5 5 e 5
~ - c 3_ - . a e. 2 ~ _ ".
Z 8/5WnCIA!0N! 40 k%AN NY3W cafs yc gfg;gg jo v3ggnu sy3a 6 i 233 1 1
e
, . . - ).= g
-x<h
~
e * -a
..y g s =
- i pq b' z ,
. , e e g g *
.. e
.-{ fj' ~- 3
.a e ./ **
. ,=*~'y .g l.
.:" % 5 ~* .* # " W 5 -a an h3h *x e e .f
* *7
. } '**..***.t -<
" C
-e i
I (, ,' .s .. e: '.
.g 64 t:0 gm
; 3 ew
- s. , N O I -a m
*) -E
%..,'--= Em
.f~* E g*
8 O l , 2O o ae
- =z == 4
,.A..- 8= = gd *..******p ,
.,y e g N
...,**....g o, to st Tm s
g'i
. -=eW eJ
= c.
5 ' -=*Wa u-
< - -r g
1
,4 -c c,. u i oe 3 i s
=E om
.J z e.. 1 -*
e r< e u r.- r J i
- J..e .< e m ae a; m .g m
=d /. -r -=e z . .,
e ua MC z S O %j -< t
- s V
2 mu u y ' -r < -c c W * ' e -c. m e -c m ~ C- .c = cv
- c. P.
/[ ' '2 S * "
s "
- u '", ,
2 t h $- E a f c 5 o h !, l { j- C c. c g e g"/ m UCIAICMI .10 32 b d . :u/sw gAICN, Jo gaggn3 g
. u m <:h )
u oeo
- c. w q
-)
G se a 1
- u\
O ou. hb
- .-a, y ,g g l
;_ u J
-=E
[ -( / "" *a ~ ~ .,,,,' ~ ~ . ol
. .x- . .g - O 'O C ;
- s ~s
.s' ,
* *sa' C .G w;
-* p.*
r,a -.ee 's,* /
"< . U c. g C E ml
- I,/ -r" ,
.g .e
*~.... .- - ,' l N n n;
\
. r= =c m m' '
*rm ** C 8
0 e e
.se_ **~ f. - = ,
, s a .w .
I, <e** o' - _ == D C o-
. . . ) ., g - '
,- "E 4 ,o oL.i
.g... f . c ----==***-==
,, a N, c q g g e
c u ,o ; 4
..'*=.**g s \5 N e
o ,
,. ., o Ju o A m =
c
- g gg
'. s ==$w
-t c.
,,,,"== *=.* .
-E g W
c.
\ % (* * , -
,. ...==-==*** . " . 7..#
*a= ,
%g% .
e W <$WJ r e i g
) *=a c.
J %**
,e"> ...***. .t C.
l y)
- I, "E E g .
je
* . s 4..--- ., m J ~) " -r o m 3 $ i; , ".,
j -e e .;_ "4.,.., M 2 "; a J :- E o . sa * ( -r 3 w
-l
" , " , * .*r -
N g m ,'*, s .em i
#r=w e s E Jg ti we g 2" N e , / .,. < ~e
. . e.
#** e Ch ::
o aw . . ' ~
"g O,,.
. t i =g s '. "E p t I
,3., -o O ff
< 's ~*e
.. . , ~
~
> f I * "*
m ,% < c . a r E 9 e m f g E 9 e
$ j E E A f
- 5 N e.
.
- A g*/S"IYOC*AICNI JO V2tWaN NY2W 5 g /$'IY3CIAICNI Jo g3gMON NY2K 234
l 1978 and 1984 when density was 295/m and 4SS/m", respectively. Thus, the years before and after the period of highest salinity and discharge had similarly low densities. Interstation comparisons showed the stations with the highest abundance were Station 9MLW and 9 (Mill Creek) and stations with the lowest abundance were Stations 3 and 3MLM, (Brown's River) (Table 3.3.1-3). The seasonal cycle of oligochaetes indicated that peak densities could occur during any season (Figures 3.3.1-6,7). Densities reached over 6000/m2 occasionally during the study period, but were never sustained into the following season. The opportunistic polychaete Capitella capitata was abundant in the estuary at both intertidal and subtidal stations. The highest population densities occurred in 1980 and 1982, when densities were nearly 900/m" (Table 3.3.1-3). In 1981, however, the dqnsity dropped by about 50%, and avereged 417/m' for the year. It was the only abundant species to show a sizable population decrease in 1981. The years of lowest abundance were 1978, 1979, and 1984, when abundance ranged from 74/m to 174/m2 (Table 3.3.1-3). By 1986, density had increased to 8 417/m2 . Capitella capitata had lower population densities than S. benedtett and 011gochaeta. At intertidal stations, density was about half that of the subtidal stations, and population fluctuations were somewhat damped (Figures 3.3.1-6,7). The remaining selected species include the polychaetes #ereis dtversicolor and Caulteriella sp. B, and the soft-shelled clam, Mya arenarta. Caullertello sp. B and M. arenaria had relatively high abundance from 1980-1982, but had relatively low abundance in 1984, like the other species tested (Table 3.3.1-3). Since this decrease occurred in both Brown's River and Mill Creek, it was probably related to ! area-wide environmental changes such as increased precipitation and temperature (NAI 198Sb). N. divers teolor was the only abundant species , to show a general decline from 1978-1984, but by 1986 the population had l increased substantially. N. diversicolor also had distinct seasonal population fluctuations, which may be related to its unique spawning i i 235 l l l
i behavior (Figures 3.3.1-6,7). Interstation comparisons indicated that N. divers teolor was most abundant intertidally in Brown's River, while Coulteriella sp.B was most abundant intertidally in Mill Creek '(Table 3.3.1-3). M. arenaria was usually more abundant in Mill Creek than Brown's River (Table 3.3.1-3). In. summary, changes throughout the estuary occurred in total abundance, number of taxa, and abundance of most of the dominant species. As these changes were not site-specific, they were probably related to area-wide environmental variables such as precipitation and corresponding salinity changes. Increases in the settling basin discharge volume probably acted in conjunction with low precipitation to increase salinity. By 1986, physical and biological parameters had returned to the pre-1980 conditions. 3.3.2 Marine Macroalgae 3.3.2.1 Macroalgal Community l I Species Collections l From 1978 to 1986, 118 species of macroalgae were recorded from general species collections at 12 benthic stations (Appendix Table 3.3.2-1). As is typical of this region, 52% of these taxa were red algae (Rhodophyta), 26% were brown algae, and 22% were green algae (Mathieson et al. 1981a,b). Four of these species were collected only in 1985 And 1985: Devaleraea remontaceum and Phyllophora traillit, which are red algao; and Pe talonia rosterifolla and Scrop ton k fellmen t i, both brown algae. D. ramentaceum and S. AJellmanit were collected only from tide pools. All four species have been previously collected from the nearshore open coast between Portsmouth and Seabrook, New Hampshire by Mathieson and Hehre (1986). Spatially, the most taxa collected throughout the eight-year period were in the mean low water (MLW) zone 236
(a median of 57 at Station SMLW); numbers decreased with increasing-depth, with the fewest species collected at the deepest stations (Figure 3.3,2-1). Number of species collected also decreased with increasing elevation from MLW (e.g., at the MSL stations). For the most part, the numbers of taxa collected at nearfield and farfield stations from 1978 to 1986 were similar. Exceptions were the MLW zone where more taxa were recorded at Rye Ledge (5MLW) than at the Outer Sunk Rocks (1MLW) and the mid-depth zone where fewer taxa were recorded at the station near the intake (Station 16) than at the far-field station (Station 31). Numbers of taxa collected in 1985 and 1986 were within the range collected over the baseline period (1978-1984) with a few exceptions. The most notable difference was at Station 5MLW in 1985, where 15 taxa were not recorded that had been collected in the historical program. Twelve of these taxa were small annuals and may have been too sparse to be found in 1985 general collections. The remaining three taxa were species only rarely found at this intertidal site anyway. The range of the number of species collected in general collections during the 1978-1984 period is also shown in Figure 3.3.2-1. Not all stations were sampled each year (Appendix Table 3.3.2-1). In lI 1985, only four subtidal and two intertidal stations were sampled- ' whereas eight subtidal and two intertidal stations were sampled in 1986 , 1 (as in the baseline period prior to 1985). l Annual Biomass Collections The effect of depth on light quality and quantity is reflected in the biomass of macroalgae and the number of taxa collected at the hard substrate (algal-covered rock and ledge) stations sempled from 1978 - through 1986 (Figure 3.3.2-2). The numbers of taxa recorded were 237
a o MEDIAN RANGE 62 - . b NUMBER OF SPECIES 60 - O-1985 58 - o-1986 A 56 - c NF = NEARFIELD 54 - FF = FARFIELD ,
~ *'
50 - d SEE APPENDIX TABLE 3.3.2-1
$ FOR PERIODS OF COLLECTION 48 - AT EACH STATION 46 - !
44 42 [ gy l 40 - n --
)
38 36 ho u 34 - MLE " O g 32 - g 30 - u_ 28 - i 26 - Q , m 24 -
- E 22 - O
[k - 5 20 - 3 O 18 - 1 16 - A o a o 14 - , g A 12 - y3t - - 10 - 8- - MSL 6-4- 2-0 , , , , , , , , , , 1 5 17 35 16 19 31 13 4 34 l
.NF' FF NF FF NC NF FF Nr Nr FF INTERTIDAL SHALLOW MID-DEPTH DEEP Figure 3.3.2-1. Number of macroalgae species in general collections at each marine benthic station 8 for 1978-1984 (median and range) and 1985 and 1986 (number collected each year).
Seabrook Baseline Report, 1986. 238
N 50 - 40 - 20 7
- NUMBER OF TAXA h30 0 1985-86, ADDITIONAL TAXA a
7 u.
\\
Q 1978-1984 20 - -
!'- 9 x
\ \x
\ \
\ x \ \
STATION 0- x\s5 \\ L 34
- 4* 13
- L 19 L
31 L 16
- 35
\
L 17
\ k u
1MLW SMLW DEPTH 19.7m 19.7m 18.3m 13.7m 9.5m 9.6m 4.6m 4.6m MLW MLW 10 - - r -r- - - p/ / / / / / /
/ /
/ / / / / / /
I h /
~ /
l / / / / / /
/ /
d~ E bh1 /
/
/
/
/
/
/
/
/
/
/ /
/ /
i-
/
s
/ / / / / /
i: . d / / / / BIOMASS 2 T-1978-1984 o 1985
- 2000 - . 1986
- NOT SAMPLED, 1985 8
NOT PREVIOUSLY RECORDED IN THE BASELINE BIOMASS SAMPLES b 50.ME STATIONS NOT SAMPLED AS EARLY AS 1978; SEE ADP. TABLE 3.3.2-1 Figure 3.3.2-2. Number of macroalgae taxa and mean biomass (gms/m 2 ) taken during August from 1978-1984 and in 1985/1986 at marine benthic stations. Seabrook Baseline Report, 1986. 239
greatest at the intertidal (MLW) sites, declined to 15-20 taxa as depth increased to about 9.5 m, then remained at approximately the same level as depth increased to 20 m. Biomass values were similar at the inter-tidal and shallow subtidal stations, then declined as depth increased to about 18 m, from which point biomass remained relatively level. Numbers of taxa and biomass values were generally similar between nearfield and farfield stations. However, mean biomass at farfield Station 31 (Rye Ledge) was 50% greater than the nearfield Station 19 (Discharge) and 40% less than nearfield Station 16 (Intake). More taxa were recorded in the biomass samples from the farfield intertidal site (5MLW) than from the nearfield station (1MLW). The number of taxa collected at each station during the baseline period increased in 1985 and 1986 at all but two stations (Stations 34 and 4)(Figure 3.3.2-2). Five of these species had not previously been collected at any station during the 1978 to 1984 biomass collections: Scytostphon tomontaria and Spongonoma tomentosum were collected in 1985; Bonnemaisonia hamtfera and Plumeria elegans were collected in 1986; and Polystphonia harveyt was collected both years. Mean annual biomass was greater than baseline (1978-1984) values for . ten of the 16 station / year combinations in 1985 and 1986. The depth differences among benthic stations were also reflected in the relative abundance (biomass) of the six taxa that were dominant during the baseline period (Figure 3.3.2-3). Ptilota serrata was dominant at the deepest stations, Phyllophora spp. (P. truncata and P. pseudocaronoides) were most abundant at mid-depth stations, and Chondrus crispus was dominant in the shallow subtidal and intertidal. Relative abundances for 1985 and 1986 showed this same pattern (Table 3.3.2-1). Three other taxa were frequent sub-dominants. These six dominants combined typically represented more than 90% of the biomass at each station. 240
STATION 13 31,19 16 17,35 1,sstw ASSOCIATION: 4.34 DEPTH: 19.7m 18.3m 11.6m 9.6m 4.6m MLw I I I I I l w/////////////////////////-- - All other species Gigartina stell M ///// Chondrus crispus 100*. -
' ' ' wwhNK s~ ~ -
7s:_ Phycodrys rubens
~-------2 so:- A A Corallina officinalis SCALE 25:-
c-Phyllophora spp.
/////////------
Ptilota serrata l i I I i I DEPTH: 19.;m le.3m 11.6e s,e 4,% rcw Figure 3.3.2-3. Relative abundance (biomass) of dominant macroalgae at marine benthic stations in August,1978-1984. Seabrook Baseline Report, 1986. 241 l
t b TABLE 3.3.2-1. RELATIVE ABUNDANCE OF DOMINANT MACROALCAE AT MARINE HEN 1 HIC STATIONS IN AUGUST OF 1985 AND 1986. SEABROOK BASEllNE REPORT, 1986. HEL AT IVL ABUNDANCE ( PERCENT ) DEEP SIATION INSERilDAL a a a a SPEClES YEAR 4 34 13 19 31 16 17 35 1MLW SMLW Chondrus crispus 1985 -- -- -- 0 45.0 -- 89.3 45.6 84.6 53.0 1986 0.1 0 0 0.4 38.6 3.7 89.8 52.6 62.8 83.5 Corallina officinalis 1985 -- -- -- 9.6 15.3 -- 5.6 2.2 0.3 11.9 1986 16.7 0 <0.1 2.8 20.0 0.1 1.9 5.6 2.3 2.6 Gigartina stellata 1985 -- -- -- 0 0 -- 0 0 14.9 28.7 Yi 0 0 0 0 oa 1986 0 0 0 0 34.8 13.7 thycodrys rubens 1985 -- -- -- 17.7 5.0 -- 0.5 1.2 <0.1 <0.1 1986 0.8 0.3 3.4 22.5 2.5 30.3 0.3 2.0. <0.1 <0.1 Phy!!ophora spp. 1985 -- -- -- 59.4 32.9 -- 2.1 26.8 <0.1 .<0.1 1986 31.7 36.0 88.3 67.0 35.? 59.6 2.2 29.4 <0.1 <0.1 rtilota scerata 1985 -- -- -- 72 0.5 --
<0.1 <0.1- .0 <0.1 1986 47.6 59.1 6.4 3 . .. 0.8 1.0 <0.1 <0.1 0 <0.1 ,
All others 1985 -- -- -- 6.2 2.7 -- 2.4 24.3 0.2 0.4 1986 3.1 4.6 1.9 8.9 P.9 5.5 5.8 10.4 0.1 0.2 a Not sampled in 1985.
~l Community Analysis l l
1 Station differences in the macroalgae community were caused by the depth-related differences in species' relative abundance. n Historically six depth-related station groups had been identified from cluster analysis of August samples (NAI 1985b; Figure 3.3.2-4). Although several taxa had been found across all depths, each species had a depth zone within which it reached peak biomass (Figure 3.3.2-5); it was the unique association of species' biomasses that had caused a dif ferent community structure in each depth zone. Within each depth zone, the paired nearfield and farfield stations were most similar to each other (Figure 3.3.2-4). A discriminant analysis was used to confirm results of the cluster anlaysis and to allow a comparison of the 1985 and 1986 results. Results of the two methods were very similar, with 97% of the 1978-1984 samples (285 of 295) classified similarly. The consistency of occurrence of samples within their baseline group over the 1978-1984 period was quite high (Figure 3.3.2-6). As anticipated, the spatial distribution of macroalgae biomass was very similar between 1985/1986 and the rest of the baseline period. With the exception of the 1985 intertidal samples, all of the intertidal and shallow subtidal samples collected in 1985 and 1986 were classified within their respective baseline depth groups. Most of the "misclassi-fled" samples in the deep water stations (13 and 4/34) were associated with an adjacent depth group. Likewise, all the samples at Station 16 that were "misclassified" had been placed with the Station 19/31 group, which are at a similar depth. There was one 1985 intertidal sample that appeared unique; it was not classified in the "normal" baseline group or even in the adjacent depth group. This sample, from SMLV (Rye Ledge), was charac-243
MACR 0 ALGAE SPATIAL SIMILARITY h . LITTLE RYE - SEABROOK BOAR's .* LEDG l g)
. HEAD ..
h STATION . 90 g
.y 65 HAMPTON ..t.
HARBOR
/'
HA 40N BEACH
'i g 35 5
'1$ 3\
O
- Wd BD BEACH- 65 M-SUNK ROCKt 11
** INTAKE 15 So 16
'O
.S' o
\
"y, DISCHARGE 19
/
l 1E 13 6S FARFIELD
.s' NEARFIELD a VERTICAL NOT TO SCALE b BETWEEN STATION SIMILARITY; ARROWS LINK STATIONS MOST CLOSELY ASSOCIATED.
c IMLW ' = STATION
.68 = WITHIN STATION SIMILARITY Figure 3.3.2-4. Summary of spatial associations
- identified from numerical classification (Bray-Curtis similarity) of benthic macroalgae collected in August, 1978-1984.
Seabrook Baseline Report, 1986. 244
l l l GK0"P: 11 1 III IV V VI 13 19/31 16 17/35 1/! M STATIONS:b A/34 DEPTH: l 9.7 m 16.3m 11.em 9.4m 4.em C SPECIES Rhodophyllis dichotons 6 Ptilots serrats
$ cage]La pylassani Polysiphonia urceolata Antithoenionella floccoss Coralline officinalis neehronopters alata Grenogongrus crenulatus Callophy112s cr2 state Phyllophora spp.
Phycodtys rubens Cystoclon2ue purpureue Cerne2ue rutrur Chaetorcrpha relagensur Chaetorcrpha picquet 2ar:s Cesearestsa aculente Ca12ithorn2cn tetragonue Polyides rotundus Chondrus cr2spus Chaetoeorpha sp. Ahnfelt2s plicata Rhocorels centervo2ces Ulva lectuca Gagertsaa ste))ata Paleerse polenta Polysiphonto flex 2caults Porphyra leucosticto RhasocJonsur tortuosue Polystononia lanosa nonostroes fuscur f. bi"til Leathesas difformis Elechssts fucicola Ectocarpus fasc 2culatus Cladophoto serices
'Kate taxa (less than 5 occuttences ir. '95 samples) net included in this analysis Depth belw &
"Peak biomass bangeofoccurrence Figure 3.3.2-5. Occurrence and peak biomass of the common
- and abundant macroalgae species over the range of benthic stations sampled in August,1978-1984. Seabrook Baseline Report,1986, 245
x T I ea O r O E z SS g O > b 2 e . o=
. O 0 D
. O
*
- a E
w a a u"- O m r - o O O 8 C " 3 u' O o " %%y o E o o a c. a O O w a xno 4 O O c , ,em O O - w a oo O O O C Lc3 o Oe O 5 v G e 2% xmm g OO e $ ,og oa 5 OO < v xRT e g o OO > W s C ? o OO t z e E"8 x " OO d W e *3# 9 E -o OO OO $ g 5 a f, j 0000 a - > mc M< e < co g < r 5 8#J e > o > u-
= 0 E i o " E G EE s ? = 5 m w
< "a<c F%
w = 0 >
- 1 e d 8 L*
a O .o'.exmc. t mD um
- u. a.
D eee c .3
@ Gb w o
O O 5 we de xT t
, O O w 8* d* 3R8 2 O O *E QU 8D' \
j O O 83 ^3 E*" e O O am um ggg OO "< o< u-
"" ^*
O OO %# to o k 2 i l a a -uu ' O O aem , O e . o--
-
- b
4 O O O E O O 248 2 O O 8 OO $ Ji 00 N e O O W R , a a - n - n - - n n p- 2 2 p o
- e n - $
M 246
l 1 terized by very low abundances of Chondrus crispus, Corallina offic tanalis and Phyllophora sp; total'blomass 1*or these three taxa was 5.6 gms/m8 in the sample, compared with the 1982-1986 average of 915.8 gms/m 8 at this station. Historically, these three taxa formed a species group (from inverse classification) that showed highest biomass at the intertidal / shallow subtidal stations and very low biomass in the deep subtidal (NAI 1982b). The very low biomass of these three taxa in the SMLW (1985) sample caused it to be differentiated in the discriminant analysis, making it very uncharacteristic of a typical intertidal sample. Only two taxa in the 1978-1984 period had peak biomass at the deepest stations (Figure 3.3.2-5). From 1978 to 1984, 16 taxa had peak biomass in the intertidal (Stations 1/5 MLW) zone, but in 1985 and 1986 this number was 11 taxa (NAI 1986, 1987), equalling the shallow subtidal zone. From 1978 to 1984 two taxa were restricted to the subtidal zone whereas 15 taxa were restricted to a shallow subtidal or intertidal distribution. Eleven taxa were ubiquitous, found in samples from the entire depth range. In order to monitor the algal community for new or infre-quently occurring species which might b] cam to "nuisance" levels, the ' i rarer species occurrences were also excminad. Sevanteen taxa occurred sparsely in biomass collections from 1978 to 1984 (NAI 1985b) and an additional five in 1985-86 (NAI 1986, 1987). The only unusual occur-rence to date was Bonnemalsenta hamffera which was new to biomass collections in 1986 (Stations SMLW, 31 and 35), and occurred in greater , than 5% of the samples (in 1985-86). This warmer water species has been recorded in Great Bay (Mathieson and Hehre 1986), but not at offshore sites in this study. Its recent occurrence may be related to the increased water temperatures in the nearshore area (see Section 3.1.1). More of the "sparsely occurring" taxa have also been recorded in recent years (NAI 1985b) and may be related to the same cause. . 247
- . . . . . _ _ _ ~ -_ , .- -- -, - - - - . , . - - - .
Kelo Transect Survey Differences in kelp species abundance can be attributed primarily to depth differences. Laminaria saccharina has historically been most abundant at the shallowest stations (Figure 3.3.2-7). Laminaria digitata has been shown to reach maximum abundance at Station 31 (9.4 m below MLW), whereas Agarum ertbrosum's greatest abundance was at Station 19 (13.7 m below MLW). Significant spatial differences were found for some species in the mid-depth zone (Stations 19 and 31) where L. digitata and Alaria esculenta were more abundant in the nearfield (Station 19)(NAI 1985b). Abundances recorded in 1985 and 1986 followed similar spatial patterns to 1978-1984 occurrences, but densities of kelps were lower than past years in several cases (Figure 3.3.2 7). No consistent seasonal variation in abundance was observed for any species of kelp, probably because "juvenile" (<15 cm) plants were not surveyed; these plants are difficult to accurately count in situ because of their small size and high density (NAI 1984a, 1985b). Stand density, which is controlled by substrate availability, recruitment and ) environmental conditions (e.g. storm disruption), showed some variability emong years. Kelps, particularly Laminario species, are quick-growing, opportunistic plants. Consequently, they are among the "pioneer" I species that colonize freshly exposed substrate, adding to the year-to-year variability in distribution. Measurements of percent frequency of occurrence of the three understory algae that were dominant at transect sites during the 1981-1986 period (Figure 3.3.2-7) yielded resulta similar to relative abundance in biomass samples (Figure 3.3.2-3). Chondrus crispus was more frequent in the shallow subtidal zone whereas Phyllophora sp. was encountered more frequently in the mid-depth zone. Ptflota serrata occurred as frequently as Phyllophora sp. at Station 19 even though it was not at its peak biomass (Figure 3.3.2-5). Pt flo ta serrata was significantly lower and Chondrus crispus significantly higher at the 248
tcoo . U..
.. 1e 35 3g 31 T y u ,,; . i N O O g323- '
I g' o I o ,, oo O 18 8 C o T to m Qo I E100- - t o'n 19 i 31 5
- c. .
1 13 1 25 , o 32 - 37, { I SHALLOW o MID DEPTH l ( i= 11.6m) to - ( i= 4.6m) .. I I 4, , f 17 3 l I ,, I i 1
=>'s m e t ,. .: . t vu.5. m e te f31,22 t =' =st i
$ *::=** ' w ts:Arce co'sm ,= g;g33 naconsiu [1gg=2 t'itet*
3ee - n- .. w sc - ou -- u MID JEPTH
$ 7:_ ao ..
g SHALLOW ( i= 11.6m) [v 6:.. gas ( i= 4.6m) -- w I C so . }
.. j Uz i
1 T 311 1 1
'O ~ ""
5 o 3,'
} '
3 si C 1 2T l E so - g 9,
" t 1 o T
-- I 0 1 20 - I 33 0 f 31 0
- r -
. 1 g 17 35 e # .'
es ea -tu~.. c:aa ee:=a -* cata c:r.s n. um2 uma r nr2 a ' STANDARD DEVIATION 0 1985 DENSITY NEARFIELD FARFIELD b STATION 35-
- o MEAN (1981-1984) o 1986 DENSITY 1982-1984 ONLY Figure 3.3.2-7. Density of kelps (counts) and of dominant understory algae
(% frequencies) in the shallow and mid-depth subtidal zone
- 1981-1984 and 1985-1986 (zero values not shown). Seabrook Baseline Report, 1986.
249
i l o l shallower (9.5 m) Station 31 than at Station 19 (13.7 m)(NAI 1985b). Patterns shown by the 1985 and 1986 frequencies of occurrence were similar to those seen during 1981 to 1984, except for Phyllophora sp. , which showed fewer occurrences at both Stations 19 and 31, and Chondrus crispur, which was higher at the farfield station (31) than in past years. Intertidal Fixed Quadrat Surveys In situ counts of macroalgae in fixed quadrats at the inter-tidal stations (Stations 1 and 5) were conducted at mean low water (Site "D") and on bare ledge (Site "C") and fucold-covered ledge (Site "B") habitats at mean sea level. These quadrats were set up in order to , monitor the same exact habittt thus eliminating small-scale spatial l variability and focusing on temporal variation. Appendix Table 3.3.2-2 , shows the occurrence of those species recorded more than once in a quadrat; other less common taxa (i.e., recorded only once in the study I to date), are listed in previous data ports (NAI 1983a, 1984a, 1985a, l 1986, 1987). Since the quadrats (sites) have unique characteristics, ccch will be described in turn, l I l The Bare Ledge Site (C), at the upper edge of the MSL (mean sea level) zone, was characteristic of "bare" ledge in the area, that is, ledge not covered by algae. Although highly seasonably variable, barnacles have been common in this quadrat (see Section 3.3.3 for faunal I coverage). During the spring the annual greens Urospora peneilliformis and Ulothrix flacea (at both stations) and the red algae, Bangia fuseopurpurea (Station SMSL) have been abundant. Small, immature perennial (rueus sp.) plants were clso found in this quadrat; although they occurred frequently, their percent cover was usually less than 10%. , l Temporal variations in these fucoids have been observed ovec one to two year periods (Appendix Table 3.3.2-2). Algae growth and settlement are controlled by balancing the opportunity of settling on available space 250
i I versus the effects of predation. Spatially, the bare rock quadrats have been generally similar, although temporal variations in Tucus sp. appearred spatially independent. The more persistent red, Porphyra sp. was unique to IMSL, while B. fuscopurpurea was unique to SMSL (in the fixed quadrats). The Fucold Ledge Site (B), in the mid MSL zone, is situated in the area of maximum fuccid algas cover. The perennial, rueus ves teulosus, has been the major species, although some T. dist reus v. edentatus and Ascophylum nodusum (Station SMSL) have been found (Appendix Table 3.3.2-2). These taxa were quite persistent, although relatively low (<40%) percent coverages have been recorded at times, e.g., December 1982 (both atations) and winter / spring of 1984-1985 (at 1MSL). The perennial red algae, Chondrus crispus and Gitartina stellata occurred as understory algae at both stations, but in relatively low amounts (usually <10% frequency); the latter species was more persis-tent. Few other algae were common in these quadrats, except Porphyra sp. and Spongomorpha (Station IMSL only). The Mean Low Water Site (D), in the MLW (mean low water) zone, is situated in the area of maximum red algae cover. Chondrus crispus and Gitartina stellata dominated this zone; together they covered nearly 100% of the substrate and have been found in generally equal amounts. Spatially, the two stations' quadrats were similar for the two domin-ants; however, rueus sp. was persistent at 1MSL as overstory, while l Corallina offlefanatts was persistent at SMSL as an understory species. l l 251
3.3.2.2 Selected Species Laminarla sacchartna Laminaria saccherina was the dominant canopy-forming kelp in the shallow subtidal zone (1 to 9 m deep) surrounding the Inner and Outer Sunk Rocks. Average seasonal densities (1979-1986) of adult plants ranged from 1 to 11 plants /m8 at the nearfield Station (17), and average percent cover ranged from 3% to 43% (Table 3.3.2-2). Density varied greatly due to variability in the amount of substrate available for settlement combined with the contagious (clumped) distribution of l these plants. At Station 17, annual mean densities were greatest in 1979 (9.8 plants /m ), decreased to 2.9 plants /m8 in 1982, at.d remained , at that approximate level through 1986. For years when both nearfield and farfield stations were monitored, however, (1982-1986) annual differences were not significant (Table 3.3.2-3). Average numbers of plants per quadrat were similar between the nearfield (17) and farfield (35) stations over the 1982-1986 period (Table 3.3.2-3), but the kelp beds were more evenly distributed at Station 17 than at Station 35 (NAI 1985b), evidently because of differences in available substrate. Chondrus ertsous Chondrus ertspus (Irish moss) was the dominant understory algal species in the lower intertidal and shallow subtidal zones near the Sunk Rocks (see Community Analysis section). Destructive samples were collected in May, August, and November from 1978 to 1986 (1982 to 1986 for Stations 35 and SMLW); maximum biomass occurred in August at all stations with few exceptions (Figure 3.3.2-8). Minimum values generally occurred in May at all stations except at 1MLW, where lowest values were generally found in the fall. However, confidence limits (calculated for 1978-84) implied a signiff. cant difference between j 252
TABLE 3.3.2-2. SEASONAL AND YEARLY MEAN ABUNDANCE AND PERCENT COVER OF LAMINARIA SACCEARINA FROM TRANSECT STUDIES IN THE SHALLOW SUBTIDAL ZONE. SEABROOK' BASELINE REPORT, 1986. 88
#/m8 " *. COVER #/m *. COVER 17 35 17 35 17 35 17 35 1979 A 10.5 35.0 1983 A 0.8 1.0 3.4 4.6 J 8.9 43.0 J 2.2 3.8 12.5 18.1 N 10.0 34.0 9 6.9 2.1 12.6 11.3 x 9.8 37.0 x 3.3 2.3 9.5 11.3 1980 A 7.0 18.0 1984 A 3.1 2.1 9.3 9.1 J 7.0 32.0 J 2.5 2.1 13.3 17.7 N 7.0 37.0 g_ 5.6 1.5 20.3 8.0 x 7.0 29.0 x 3.7 1.9 14.3 11.6 1981 A 7.2 21.3 1985 A 3.4 1.1 15.8 5.4 J 5.2 24.2 J 2.2 2.6 16.4 19.5 N 5.0 19.8 9 2.9 3.0 19.2 6.4 x 5.8 21.8 x 2.8 2.2 17.1 10.4 1982 A 5.9 25.0 1986 A 2.8 7.6 16.5 20.8 J 0.9 6.7 6.0 36.0 J 1.7 1.9 8.0 15.7 9 1.8 4.1 14.0 14.0 O_ 1.7 2.5 7.2 20.2 x 2.9 5.4 15.0 25.0 x 2.1 4.0 10.6 18.9 a
only plants measuring > 15 cm long were counted. b Station 17 = nearfield; Station 35 = farfield. 253
~. .
1 i TABLE 3.3.2-3. RESULTS OF SIGNIFICANCE TEST ON MACROALGAE SELECTED SPECIES, CHONDRUS CRISPUS AND LMINARIA SACCHARlHA. SEABROOK BASELINE REPORT, 1986. A. C#0#DRUS CRISPUS BIOMASS (gms/m8 ) f Temporal Comparison (1978-1986): one-way ANOVA STATION F VALUE SIGNIFICANCE 1MLW 2.89 p<.001 *** 17 2.00 p<.C 5 N.S. Spatial Comparison (1982-1986): two-way ANOVA STATIONS VARIABLE F VALUE SIGNIFICANCE 17 and 35 year 1.51 p<.21 N.S. i station 6.50 P<.02
- interaction 2.25 p<.07 N.S.
1MLW and year 0.43 p<.79 N.S. SMLW station 3.83 p< 06 ',4. S . interaction 0.43 p<.79 N.S. B. LAMINARIA SACCHARINA DENSITIES (#/n') Temporal Comparison (1982-1986): Wilcoxon's Ranks Test STATIONS VARIABLE SIGNIFICANCE 17 and 3 years N.S. ! Spatial Comparison (1982-19861: Wilcoxon's Ranks Test STATIONS VARIABLE ClGNIFICANCE 17 and 35 years N.S. l I l l 254 l I
1800 - 1600 - a 1400 - O 1200 - 3 N d O~ E 1000 - .. .. s -jl g .
-- .. o a f 800 - 4 g c>
~
c -
+
,$ 600 -
- O --
1 oO O -- g y 3 400 - ** a 200.- 0 , , , , , , , , , , ,, my a nov my a my my a nov mv m nov STATIONS: 17 35 IMLW SMLW
- MEAN HONTHLY BIOMASS:
- MEAN MONTilLY BIOMASS AND 95% CONFIDENCE
__ INTERVAL FOR 1978_ O - 1985 1984 a - 1986
- a. STATIONS 35 AND SMLW SAMPLING INITIATED IN 1982.
Figure 3.3.2-8. Mean Biomass (gm/m ) and 957. confidence limits of chondrus crispus at selected stations in May, August and November, 1978-1984a, 1935 and 1986. Seabrook Baseline Report, 1986
1
)
i 1 l minimum and maximum seasonal biomass only at Staticas 17 and 1MLW.- '
~
Biomass values from 1985 and 1986 differed from the historical data in ! several cases. In 1986 at Station 1MLW and in 1985 at Station SMLV, maximum biomass occurred in May, not August. Moreover, at Station SMLW in 1985, minimum biomass occurred in August. At subtidal Station 17, biomass in 1985 and 1986 was noticeably (over 40%) higher in August collections. These data continue to add to the natural. variability of the baseline data. Annual differences in August biomass samples collected between 1978 and 1984 were approximately 220% at Station 17 and 350% at Station 1MLW (Table 3.3.2-4). The highest August biomass was recorded in 1985 at Station 17, the minimum in 1980. Overall biomass at Station 17 was significantly higher than that at Station 35 (Table 3.3.2-3). Peak biomass at Station 1MLW was recorded in 1982, its minimum in 1978; biomass at 1MLW was not statistically different from the farfield station. 3.3.3 Marine Macrofauna 3.3.3.1 General Studies of the macrofaunal invertebrates off Hampton Beach, N11 since 1978 have focused on the horizontal algao-covered ledge habitat in four depth zones: intertidal (MLW), shallow subtidal (4-6 m), mid-depth (9-14 m) and deep (19-21 m). Nearfield stations near the intake and discharge areas have paired farfield cuenterparts near Rye Ledge in the , same depth zone for an optimal impact assessment design (Green 1979). Macrofaunal studies include a community analysis of August collections, an in-depth examination of key species (Section 3.3.5) and an investi-gation of the fouling community (Section 3.3.4). j l i I 4 256 !
8 TABLE 3.3.2-4. MEAN BIOMASS (g/m8 ) AND STANDARD DEVIATION (SD) 0F CEONBRUS CRISPUS AT' BENTHIC STATIONS 17, 35, IMLV, AND SMLV IN AUGUST FROM 1978 TO 1986. SEABROOK BASTLINE REPORT, 1986. SHALLOV SUBTIDAL INTERTIDAL STATION 17 STATION 35 STATION 1 MLW STATION 5 MLW YEAR (NEARFIELD) (FARFIELD) (NEARFIELD) (FARFIELD) MEAN S.D. MEAN S.D. MEAN S.D. MEAN S.D. a 1978 860.3 535.7 NS 459.7 532.9 NS 1979 713.8 301.8 NS 638.6 138.1 NS 1980 574.9 282.4 NS 797.8 262.1 NS 1981 1113.8 384.2 NS 917.3 558.1 NS l l 1982 593.6 194.5 491.9 234.9 1622.9 345.3 1147.4 174.4 j 1983 853.8 243.5 663.4 388.9 1539.6 129,1 994.3 461.8 1984 782.1 251.5 484.7 344.2 1612.4 263.8 457.3 321.7 1985 1272.7 366.2 544.3 428.4 1203.5 179.9 530.9 479.7 1986 1193.3 329.7 523.7 343.2 1154.4 723.1 857.7 258.0 All YEARS x 884.3 541.6 1105.1 797.5 a NS = Not sampled. 257
I l
.i 3.3.3.2 Mscrofaunal Community Numbers of Taxa and Total Abundance The numbers of caxa intertidally were lower than those.in subtidal areas, while densities were higher. Intertidally, numbers of taxa ranged from 78-108 (per S/16 m') at nearfield Station 1MLW and 67-104 at Station SMLV (Figure 3.3.3-1). Numbers of taxa have been consistently higher at the nearfield intertidal station. In 1985, the numbers of taxa were similar to the somewhat depressed levels in 1984, but the number of taxa increased at both stations in 1986. Total annual abundance has been highly variable at both stations, with densities' con-sistently lower at the farfield Station SMLW (Figure 3.3.3-1). The presence of boulders at the farfield station may decrease habitat space, in turn decreasing abundances. While densities in 1985 fell within the range of previous years, 1986 represented a peak year, with total abundance reaching 548,422 8m at Station-1MLW and 171,142/m' at Station SMLW. This increase is due primarily to high numbers of Mytilidae. In August, 1986, a 0.5 mm wash bag was required for sample collection by the New Hampshire Fish and Game Department instead of the 0.79 mm bag used historically. However, sieve size for sample washing did not change. The change in methodology may have contributed te the observed differences in 1986. However, Mytilidae densities remained elevated in November (wh,n the historically-used methodology was .# employed) (NAI ,
1985b, 1987). Therefore, increased densities of Mytilidae probably represent a real phenomenon. In the shallow subtidal area (4-6 m in depth), numbers of taxa were slightly higher in comparison to intertidal areas, while total abundance was lower. Numbers of taxa ranged from 66 per 5/16 m' (Station 35, 1985) to 121 (Station 17, 198C) with no clear station differences (Figure 3.3.3-1). In 1985, numbers of taxa were lower than i previous years, but numbers rebounded in 1986. In fact, the number of ; taxa in 1985 and 1986 at Station 35 represent the lowest and highest li i 1 258 '
1 i
)
i 1 l
~
1986 0//un-////m//u/////u/w/un/,' ,a/ 1985 h,,yg,y,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,y,,,,,' 19ST l,y,y, y,,,,,,,,,,,,,,,,,y,,,,,,,,y,y,,,,,,,,,,,,) 198 c',,,,y,y, ,,,,,, ,,,,, n 198 ' ,y/,,,,,, r y,y ,,,h,,,,,, 198 r,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,//,,,,,,/,,, 1980 w,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1979 y,,,,,-,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,y, 1978 r,,,,, , , , , , , , ,,y ,,,y,, , ,, , , ,, ,,,,y ,,, i i i n nij i i i nni; uni i ig unj jn ;in ij u si i i o nni i i i oni i i n uni s 8 s 2 a 8 8 o g 8g@g o
- o o 8. 8R SPECIES
~
2~ e 5 ' INDIVIDUALS /m# V/A l IPiW $PiW 1986 7,,,,,,y,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 198{ y,,,,,,,,,,,,,,,,,,y,,,,,,,,,,,,,,,,,,,,,, 198? y,,,,,,,, ,,, , , , , ,,,,y ,,, , ,,,,y ,y , ,,y,,,, ,,y ,) 198 ? w' w // , ////////// - - n n////// ' 198?
' ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,-j 198.L v--- //</n - - - - n//// ,, :
1 198o van /-- n/ w n ///- w ///// - > 1979 y,,,,,,., ,, , ,,,,, , , , ,,,,,, ,,, ,,, , , , ,, , , , , , , 1978 c,,,y,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, jit ii j iiii j i i l l i itisiiig i isinug i i14itig i iinuj i i gitiij s 8 s e a 8 g g gg SPECIES
~
2 s8 i 2 m i INDIVIDUALS /m ) 35 17 l l 1 Figure 3.3.3-1. Number of species and abundance at intertidal and subtidal Benthic Stations. Seabrook Baseline Report, 1986. 259
I i f r I 1986 K:.::..... ............. ---- --.-- -..--..-...........a V//////////////////////////////////////////A T// NSSN
) $ 5 5 5 5//)f//)D h b/////
1984 .......... ,..............................................n _ V/////////'Y/////////////////////////////A 1983 DN _ vwm/o///////m//////m///////n 198 (M cm/// /w////m/w//w w w w/////> s 1981 t::::::::::::t:::::::::::::::::::::::::::::... .----- . --- _ I/////////>'//////////////////////////////1
...............................r......- ,
1980 s . .... _ Y///////////////////////////////////A 1979 0:....:...... ..::..................:.:.- - -
--- o
_ E////////////////////////////////////A 1978 e:....... ................................- - a _ Y////////////////////////////////////4 llill j lliI Iill l l lilll] I l l illli l I ( 11ll] I I Illlil i i llilill s 8 s 2 2 8 8 8 8 9 9 9 SPECIES
~
2 2 8
~
INDIVIDUALS /m a M 19 31 16 1986 L..... . . .. .. ............... --. __ _ ............ 9 _ V////////s'////////////// ///////////l
~
M l 1984 f . ....... . . . . . . .. . . . . . . . . . . . . . . . . ................. 4 ! _ U////////////////////////>/////////l 198 .---. -- , _ s//////' ///////////////////////A ' 198 L'. V//////////s '///////////////////////////A mm' 1981 . . . > . . . . . . .... ..i ...-
+
_ V///////////////////////////////////A 198 r///////////////////////////////////A 1979 . ... ................................- ..-- Y/////////;////////////////////////////] 0 1978 V/////////////////////////////////A ll1IIllIlilll([ l I t illlij i i l ililll l 1 l illij i i t illilj i i tillij s- 8 s a e 8 g g. g. SPECIES
~
2 3 8 a ~ INDIVIDUALS /tr VM 4 34 13 a = Stations 16, 4, 34, and i 13 not sampled in 1985. Figure 1.3.3-1. (Continued) 260
. _ _ _ _ . _ . _ _ __ _ __ _.__ _ ___~ _ _ _ _ _ _ _ _ _ _ _ . _ _ _
values recorded. Total abundance mirrored this pattern; at both sta-tions, densities were the lowest recorded while in 1986 they were the highest (Figure 3.3.3-1). Exceptionally high densities of gastropod Locuna vincta along with high densities of Mytilidae contributed to peak 1986 abundance levels. Although use of a 0.5 mm wash bag may have affected 1986 August abundances, numbers of Mytilidae were also at record levels in November (NAI 1985b, 1987). Mid-depth (9-14 m deep) stations continued the trend of increasing numbers of taxa and decreasing abundance with increasing depth. Nurbers of taxa were consistently higher at Stations 19 and 16, where algas-covered ledge predominates and mussel beds comprise 25-40% of the habitat. In comparison, Station 31 was predominantly composed of mussel beds (60%) with cobble and algae-covered rocks also present (Table 4.1-1). Numbers of taxa in 1985 and 1986 were similar to previous years, falling in the range of from 78 per 5/16 m8 (Station 31, 1978) to 162 (Station 16, 1980). Number of individuals has ranged from 5421/m 2 (Station 31, 1983) to 248,699 (Station 31, 1985). Densities at Station 16 were generally higher than at the other mid-depth stations because of the higher numbers of mytilids. Abundance levels in 1985 and 1986 fell within the previous ranges with the exception of Station 31 in 1985, where total abundance was six times higher than the highest previously-recorded level (Figure 3.3.3-1); a result of high Mytilidae l densities. The deepest stations sampled, 4, 34 and 13, where depths ranged from 18-21 meters, had the highest number of taxa and lowest number of individuals of all areas sampled. Numbers of taxa ranged from I 92 per 5/16 m8 (Station 13, 1933) to 144 (Station 34, 1981)(Figure , 3.3.3-1). Since 1981, the number of taxa has consistently been lowest at Station 13, which has a mixture of algae-covered ledge, mussel beds, and cobble, and highest at Station 4, where mussel beds predominate, with some algae-covered ledge present. Station 34 has been intermediate in its number of taxa, and is predominantly mussel bed (Figure 3.3.3-1, 261
Table 4.1-1).- Numbers of taxa in 1986 (1985 data was not collected, see Section 4.0) fell within'the range of previous years. Density levels have shown no consistent spatial differences, ranging from 1712/m 8 (Station 34, 1983) to 24,173 (Station 13, 1986). 1986 values were similar to those of previous years at Stations 4 and 34, while at Station 13, levels were more than double the highest previously-recorded value (Figure 3.3.3-1), a result of large numbers of Balanus crenatus (10,323/m )(NAI, 1987). Macrobenthic Community The noncolonial, macrofaunal, hard-bottom community structure has histcrically shown changes related to depth (NAI 1985b). Intertidal, shallow subtidal, mid-depth, and deep areas were distinct in both species distributions and abundances. 1985 and 1986 collect tons showed highly similar species composition to collections from previous years (Table 3.3.3-1). Historical station associations (1978-84) established by numerical classification on the basis of similarities in species composition, were verified by discriminant analysis, and in turn used to evaluate 1985 and 1986 collections. In all cases, based on the similarity in species composition, new collections were placed in the group with the majority of historical collections from the same station (Table 3.3.3-1). The addition of two years of data caused little change i in the within-group abundance of dominant taxa, underscoring the similarity of 1985 and 1986 to previous years. Differences in community structure among stations are most obvious from differences in densities of dominant taxa; however, it is often the species which are restricted to a certain depth zone which contributed most to the uniqueness of a station. The discriminant analysis relied on only 32 of the original 89 species used in the l cluster analysis to form the station groups (Appendix Table 3.3.3-1). l 1 I l i 262
TABLE 3.3.3-1 STATION GROUPS DEFINED BY DISCRIMINANT ANALYSIS OI NON-COLONIAL MACROIAUNA COLLECT [D AT INTERilDAL AND SunilDAL BE NiillC ST AT IONS, AUGUST 1978-1986. StAHROOK HASILINE REPORI, 1986. WlIHIN-GROUP STAllON S1 HILARITY STATIONS SAMPLLS/ DEPIH/ 2 GROUP LEVEL (YEARS) GROUP SIIL DOMINANT TAXA NO./M 1 0.65 19(1978) 4 Mid-depth - deep / rantogenais inermis 1550.4 31(1978) discharge and Mytilidae 620.8 4(1978) contro1 #iatella sp. 322. ts 34(1980) Asteriidae 244.0 Caprella septentrionalis 242.0 Anomia sp. 234.0
? 0.69 13(1978, 1981-84,86) 9 Deep / discharge Balanus crenatus 334's.4 34(1983-84,86) and control nytilidae 1209.6 Anomia sp. 716.8 Balanus sp. 618.0 lacuna vincta $20.0
#iatellJ sp. 430.0 rantogeneia inermis 314.8 Asteriidae 308.4 3 0.72 10(1979-86) 19 M id-dep th/d i sc ha rge, Nytilidae 19133.6 31(19T9-86) intake, control re.togeneia inermis 1463.5 N 13(1979-80) deep / discharge #istella sp. 1334.0 16(1984) Caprella septentrionalis 1065.2
- 8) Anomia sp. 927.3 Balanus crenatus 154.3 Molgula sp. 583.8 Lacuna vincta 484.2 4 0.73 4(1919-84,86) 10 Deep / discharge fontogencia inermis 572.8 34(1979, 1981-82) and control Caprella sp. 544.6 Asteriidae 316.5 Caprella septentrionalis 290.9 Ratanus crenatus 281.1 Anomia sp. 214.3 Musculus niger 2'34.5
- 0. 14 17(197P-86) 19 Shallow - mid-depth / Mytilidae 9367.0 5 d i scha rge. intake facuna vincta 5285.6 35(1982-86) pontogene/a inermis 4491.0 16(1980-83,86) control
'Caprella septentrionalis 2165.3 Idotea phosphorca 2108.5 Jassa falcata 2098.6 lHlW(1918-86) 14 Intertidal / Outer Mytilidae 107148.6 6 0.72 Sunk Rocks, Rye Jacra marina 8089.4 5HLW(1982-86) f urtonia mirnsta 6193.4 Ledge
#iatella sp. 6281.8 lacuna vincts 51s19. 1 Cammarellus angulosus 4516.7 Oligochaeta 4032.2 Nucella lapillus 3160.0
________ _ ___._.-_m . _ _ _ . _
a The most abundant species (i.e., Mytilidae spat, Pontogeneto inermis, Lacuna vincta, Caprella septentrionalis) were ubiquitous, and contrib-uted little to the discrimination among stations. Less-abundant spe-cies, such as Nucella lapillus, Callioplus larvtusculus, Jossa falcata, Nero is pelagica, Jae ra marina, and Musculus niger, accounted for the majority of the among-station variability. The intertidal habitat (Group 6) was the most distinct of all areas because of the overwhelming predominance of Mytilidae spat (107,149/m') and the presence of species such as Nucella lapillus, Fabricta sabella, Nyale niissont, and Jarra marina which were restricted to that area. Other dominants included molluscs Turton ta minu to, Ntatella sp., and Lacuna vincta. Mytilidae spat were significantly more abundant at Stations 1MLW and SMLW in 1986 in comparison to all previous years .' ept IMLW in 1982 (see Section 3.3.5). In addition, densities of Jc a marina in 1986 were double that of previous years (NAI 1987). Otherwise, densities of dominants were similar to those observed histor-ically (NAI 1985b). Tne shallow subtida! station group (5) has included Station 17 and 35 in all years and Station 16 in 1980-1983 and 1986 (Table 3.3.3-1). l Mytilidae was still the predominant taxon, although less abundant than I in the intertidal area. Aside from gastropod Lacuna vincta, dominants were peracarid crustaceans such as Pontogeneto Inormis, Caprella 1 septentrionalts, Idotea phosporea, and Jassa falcata (Table 3.3.3-1). l l Relatively high densities of the latter two species, along with Calliopius laevtusculus distinguished this area from other areas. The addition of 1985 and 1986 collections did not change the order of the dominant species, nor drastically alter the within-group abundance. However, average group abundance levels of Lacuna vtacta (5286/m') increased in comparison to 1978-84 levels, due to highest recorded densities of this species at Stations 17 and 35 in 1986 (NAI 1985b, 1987). Species composition at Station 16, with depth of 10.7 m, was usually more similar to the shallower Stations 17 and 35 because of the 264
w predominance of uniform algae-covered ledge, causing increased biomass of algae (see Section 3.3.2). This, in turn, increased numbers of subdominant herbivorous species such as Lacuna vineta and Idotea phos-phorea, which increased the similarity of this station's species compo-sition with that of shallow subtidal stations. Furthermore, flat ledge at Station 16 (with. fewer mussel beds and boulders) prevented the accumulation of sediment and detritus, making it less suitable than other mid-depth stations for species which need sof t substrate such as Nichomache sp., Cistentdes granulata and Corastoderma pinnulatum. Mid-depth areas (Group 3) were characterized by a predominance of Mytilidae spat, with other molluscs (e.g., #tatella sp. and Anomia sp.) and amphipods (e.g., Pontogenela Inermis and Caprella septentrionalis) occurring in high numbers (Table 3.3.3-1). Stations 19 and 31 in most years were characterized by this assemblage, along with occasional appearances of deep Station 13 and mid-depth Station 16. 1985 and 1986 collections at Stations 19 and 31 were similar to previous years, and thus placed in the same group. However, the within-group abundance of dominant species showed densities of Mytilidae (19,134/m') and #tatella sp. (1334/m') that were double those observed from 1978-84 (Table 3.3.3-1, NAI 1985b). Mytilidae densities at Station 31 in 1985 reached an all-time high for the entire subtidal region of 234,832/m', which was significantly higher than previous years for the mid-depth areas (see Section 3.3.5). l Stations with depths greater than 15 m formed several loosely- 1 associated deep station groups. All differed from shallower stations in l the decreasing influence of molluscs, particularly the overwhelming I predominance of Mytilidae spat, which were replaced by crustaceans and other taxa. The majority of collections at deep stations (4, 34, 13) were placed in two groups. In some years, at Stations 4 and 34,
)
peracarids (Pontogenela ine rmis, Caprella spp. ) Aster 11dae, and molluses (Anemta sp. , husculus niger) were the dominant taxa forming Group 4 (Table 3.3.3-1). In other years, at Stations 13 and 34, Balanus spp., I 265
1 1 l along with molluscs (Mytilidae, Anomie sp. , Lacuna vineta and #tatella sp.) were the most abundant taxa, causing these stations to be distinct from other collections, forming Group 2. The high within-group abundance of Balanus crenatus is deceptive, however, as it is heavily-influenced by Station 34 in 1984, where Balanus crenatus averaged 12,233/m8 (NAI 1985a), and 1966 et Station 13, where Balanus. averaged 10,323/m' (NAI 1987). A third gtoup of four station collections, including mid-depth 19 and 31 and deep 4 and 34, was formed because they were unlike the or. hor assemblages in having moderate numbers of Mytilidae sp. and #tatella sp. but low numbers of Balanus spp. No collections from 1985 and 1986.showed a similar species composition to this group. Intertidal Bare Rock. Fucoid Ledge, and Chondrus Communities Both algae-covered and bare rock ledge habitats at mean sea level (MSL) and Chondrus zone habitat at mean low water (MLW) were monitored triannually at fixed stations (sampled non-destructively) on Outer Sunk Rocks (Station 1) and Rye Ledge (Station 5)- The bare rock areas supported low percentages of algae such as Porphyra spp at Station 1 and rueus spp at both stations (Section 3.3.2). The predom-inant macrofaunal resident was Balanus spp., which had slightly higher frequencies in April following the spring recruitment period, than in July and December (Table 3.3.3-2). Gastropods Littorina littoren (at Station 1) and Littorina saxatills (at both stations) were also impor-tant constituents of the bare rock community, showing low frequencies in April and higher frequencies in July and December. Mytilidae spat was the only other taxon occurring on bare rock, occurring in low frequen-cies in July and December. Algae-covered ledge areas were characterized by a heavy cover (over 80%) of the perennial algae Tucus spp. (mainly F. ves teuloids), with an understory of perennial red algae (algart ina stellato and Chondrus crispus). Highly-seasonal annual algae occurred in spring or 266
1 Ee qm ,= m == we m C ** C e ~ C e == Ee Q == *= c c m C a m e C- A A a a N .w' CCw CC @e or C* e- CC C* ce @* e P= mN CC CC . Je C w Ne @s - ea = a- Ne @e -e a w w m (o N A O C 4, @ C =, c C w w O.
. A - = w w = o
- w w i mE.
EC wg -h en w "
- u. y u -= ~
=>
,=
C m ,= == * ,= *=
. .J .J == m e o m 6 == @ e e C e *= ~
W J-c( g3 QC C .C me =e MN C C, C- Ae Ce da em CC CC o oa r= s C "e ce wS
. =e = I P= s *= e a w w C CE @ 3 C C C C m C C =
w2 E = N w == == w *.* = =- d Je ( w g e .M
== 8 C> 4 e == a.=
w C = m ,= -= m == at wC g a == C == @ *= @ M C C A a a to CC E A CC CC m- CC Ce CC Ce Ca @A CN Oe CC CC ( - - P= P e ea w - C e a e C *- = t 32 m e .C. w C C C - C (C Ew
==
A
=a
== =. = m UE @
8 CC T g e. u a= *=
== e. == =.
a.= m ~ em == C C C *.= = g > e m e @ -= C C (
** 3 == @ A @ w c, Q m= mm -@ a co Ce mm @@ C: CC Ce c- -- es Ce x w e -e e e C .- : , e w C ee e mm O E
~ C @ C - == 4 w '= C - w
~w ,,
C.
. = =. - .O n .= = L 4C = C Q b (w
2w w 4 D 4y m C w> w
,= ,= == g
== == ** C & *= m C C C - a K w .J Cs e e C ** m C
=w 2 CS
= @=
s Cm a Nm e Ne C O.
=
@ '=
ce e
@ -- m e -e C .C.
OO a w oe O e OC ee O-
-e @m e
t E Z (b - C C == > : O C & O & = .a C w w w - = = w m -- N = c C Q w w w Z = I 4 ( w C d d C t w M'= U
- g *= *= *= m e
wp *.= a 0 C ** == *= == C C *.* g C = == m O O a e C e a C C O A a w= b CO Ca @* Na OC em Oe ON CC Ce a- c- @N CC
=
C 4 = e -a me w Ne C C ea- c
- C 2 b C e -- e e = c e z - - - c,
=
w w w N .N O w M3 = i wM == m G= OM Zw od w ,= ,= ,= a == ,= == ,= m m. m @0 33 CC CC CC CC C@ CC CC CC CC CC C@ C@
,=
CC CC
==
gg m ., Q e@ e@ ee eo e@ em a& mm ee ae ee em 4@ #e @ g is C.@* ** C = C =C =C =C =C =C =C =C =C == =C =C =C pw E e Tm V4 9m Ve Ve 4m t et te Te ts Tm te D4 %4 Ce es. ea m C6 06 c6 @6 06 @6 06 @6 @6 0b
- E- E == E= E -- E= E == Ew E- E -- Ew g6 06 a == E ==
96 a-g6 a =* e=
=M E=
22 e wQ* 6 U-Z e4 C x>C J .,J ) .J .J .J g4
.J J J .J J .J .J J =a w(A M M M M M M M M M M M M M M Q. > 6md E E E E E E E E E E E E E 6C Mz .E -
c - A = c - e n a a - A - e >-.
'C > w 42 h at w = O U @ .J C6 2Ww @O
(*M =b E=( e ME CC C 6y E .J w (wX G
>C w6 2wC C6 (JK oO E UU-
-C((
www w w at t u et 6c
@C EMM eg
( eg % % a C % O % e 2 @C
% w 3 4 % C e b 44 e k % =h N 3 a % e a 4 a w Q t
M
% wo m u a CL sC e e, en een et et c it ae m e C C O
% EC e m % % %
M CC e L % yc 84 L L =% % = 4 O O O - % w M 9 w w w 6b i E w w w
=
w b c ec o t- 4 w ( a: % % % w a y M CC w -4 w E 4t C f. camc. NC Ea 4 267
i l l spring and summer, particularly at Station 1 (Section 3.3.2). Mytilidae spat was the most common taxon at Station 1, with high percentages during all three sample periods (Table 3.3.3-2). Mytilidae did not show high frequencies at Station 5. Balanus spp. was also an important member of the fucoid ledge community, more frequently encountered at Station 5. As on bare rock, frequencies were highest in April following spring recruitment and lowest in December. Nucella lapillus was restricted to the fucoid ledge, most commonly encountered in July. Other important gastropods were Acmaea testudinalls and Littorina obtusata (most frequent in July and December) and Littorina littorea (almost exclusively occurring at Station 5). The intertidal community in the mean low water zone was characterized by rock ledge with a thick cover of red algae, mainly Chondruz crispus and Gigartina stellata. Fucus spp. were also fre-quently encountered at Station 1 only (Section 3.3.2). Of the macro-faunal species that were monitored, Nucella lapillus and Mytilidae spat were the most frequently encountered. At Station 1, Nucella were more abundant in July than in April or December (Table 3.3.3-3). This is consistent with studies which show adult Nucella to be active from May , through October, while juveniles tend to be active throughout the year l (Menge 1978). On Rye Ledge (Station 5), Nueella were less-frequently encountered in July, a seasonal pattern that was reversed from its near-field counterpart. Seasonal movements of Nucella appeared unrelated to those of its main prey, Mytilidae. Mytilidae had medium-to-high fre-quencies in April and July at Station 1; percentages remained high in December in 1986 but decreased sharply in 1985. Mytilidae were not common at Station 5. No relationship with abundance levels of either i species in May, August, and November (collected from destructive samples) or with the fucold coramunity at mean sea level were noted. Another important species in this community was the gastropod Iittorina littorea, which occurred at Station 5 only throughout the year. Acmaea testudinalis was enumerated in low-to-moderate frequencies at Station 1 1 268 ;
)
IABLE 3.3.3-3. PERCENI IREQUENCY OF 181L DOHINANI FAUNA Al INTE HilOAt. Mf AN LOW WATER SITES AT STATIONS 1 (OUTIR SUNK ROCKS) AND 5 (IWF LEDCL) MONIIORID NONDESTRUCTIVELY IN 1985 AND 1986. SEBROOK 15A5fLINE RIPORI, 1986. s SPICIES STATION VIAR A PR I 1. JULY DECIMBER
. - - ~.-
Nucella lapillus 1 Hl W 198's 15.0 100.0 68.8 1986 50.0 100.0 56.3
$ Ht W 1985 l's . H 12.5 81.3 1986 100.0 31.2 68.8 littorina littoren 1 HLW 1985 0 0 0 1986 0 0 0 5 HLW 198'> 100.0 100.0 81.3 1986 81.2 100.0 43.8
- l. sJWAtilis 1 Mtw 1985 0 0 0 1986 0 0 0 5 NtW 1985 0 0 0 1986 0 0 0 I. obtusats 1 HtW 198's 6.1 0 0 9 0 0 0 m 1986 e $HLW 1985 0 0 0 1986 0 0 0 Acanea testudinalis 1 HLW 1985 12.5 12.5 25.0 1986 37.5 6.3 12.5 5 Htw 1985 0 12.5 25.0 1986 0 0 0 BA/ Arnis spp. 1 Mt W 1985 0 0 0 1986 84 6. T 8.0 4 0
$ MtW 1985 o O 2.7
- O O 1986 Fyti/us/Hytilidae 1 HLW 1985 95.3 71.3 14.7 1986 584 . 0 95.3 88s. 7 5 HLW 1985 10.0 23.3 2.7
- 80.0 0 1986 lacuna vincts 1 HLW 1985 -
6.25 - 1986 - - - 5 HLW 1985 - - - 1986 - - - A BA / AfM/s $pp. add Myti/us/Hytllidae measured by polHL Of cutstact.
- data not collected due to tide.
in both years and Station 5 in 1986 only. A heavy set of Balanus spp. occurred in 1986 at Station 1 in April, but numbers dropped in subse-quent collections. Subtidal Foulina Community Data collected from subtidal bottom panels gives information on recruitment of benthic macrofaunal species. Balanus spp. (mainly Balanus crenatus, with some Balanus balanus) typically settled by April. Recruitment continued in some years after the April sampling period so that densities were higher in the August samples, while in other years sampling occurred near the settlement peak, so that densities were lower in August (Table 3.3.3-4). Densities in December were consistently low, as Balanus populations disappeared as a result of mortality or disturb-ance. In 1986, panels collected in December showed this same pattern. Balanus spp. densities were higher at Station 31 in all years except 1984. Anomia sp. had a pattern of late-summer-fall recruitment. Although individuals may have appeared on panels in August, numbers were typically highest by December's collections (Table 3.3.3-4). Similar densities in August and December collections in 1986 suggested an l earlier set than other years. In 1986, December collections showed high ! numbers of Anomia sp. consistent with patterns of previous years. No spatial differences could be detected either from the panels or from bottom collections (NAI 1985b).
#tatella sp., another sessile mollusc, showed highest densi- l l
ties by August collections, with most disappearing from panels by ! December. Densities were low in December, 1986, consistent with pre- i vious years (Table 3.3.3-4). Numbers were higher at Station 31 than at Station 19, a pattern not borne out in the natural environment. High i l 270
2 TABLE 3.3.3-4. ESTIMATED DENSITY (PER 1/4 m ) 0F SELECi[D SESSflE TAXA ON TRI ANNUAL (4 MONTHS' EXPOSURE ) HARD-SUBSTRATE BOTTOM PANELS. SEABROOK BASELINE RE PORI, 1986. a 1981 1982 1983 1984 1966 TAXA APH AUG DEC APR AUG Of C APR AUG DEC APR AUG DEC DEC Ba/ ANUS spp. Sta. 19 7600 7950 1 1600 9250 0 2630 1409 0 25060 12360 25 9 Sta. 31 NS NS MS 82803 13023 26 35100 4304 0 19768 9290 46 9 Anom/s sp. Sta. 19 0 0 278 0 0 991 1 27 0 0 184 195 1017 Sta. 31 MS NS NS O O 1387 0 58 340 0 104 166 450 s
#iatet/A sp. Sta. 19 NS NS NS NS NS NS O 160 2 0 4345 20 4 Sta. 31 MS NS NS NS NS NS 0 1369 2 1 19226 18 25 4
Mytilidae Sta. 19 NS NS MS NS NS NS O 19 19 1 709 80 161 Sta. 31 NS NS NS NS NS NS 0 300 5 21 23018 80 77 I$ ALL YIARS e* APR AUG DEC E SD E SD X SD
#A/ Anus spp. Sta. 19 9224 10818 7742 4610 7 1)
Sta. 31 45890 37873 8872 4375 20 20 Anom/s sp. Sta. 19 0.3 0.5 53 88 49T 476 Sta, 31 0 0 54 52 586 547 N/stetts sp. Sta. 19 0 - 2253 2959 8 11 Sta. 31 0.5 0.7 10?98 1?627 1$ 12 Mytilidae Sta. 19 0.5 0.7 364 488 87 71 Sta. 31 11 15 11659 16064 54 43 4 i NS e Not sampled. a Only December coIIections were made in 1986. ; ] i i
l l t densities on bottom panels in 1984 were reflected in higher densities in the natural environment in 1984 (NAI 1985a). Mytilidae spat generally had settled on bottom panels by August, with numbers diminishing by December (Table 3.3.3-4). Low numbers of mytilids were collected in December 1986. In the natural environment, small mytilids appeared from August througa October, but information from surface fouling panels suggests that settlement can take place throughout the year. Few of these newly-settled mytilids-survived through the winter in the natural habitat or on artificial substrate (NAI 1985b). Densities on bottom panels at Station 31 were usually much higher than at Station 19, a pattern which also occurred in the natural habitat (Section 3.3.5). Mediolus mediolus Community As part of the subtidal nondestructive program, Modlotus mediolus populations were enumerated by divers along random, radiating transects at selected stations. Previous reports have demonstrated that there has been little seasonal variability in density levels (NAI 1985b). No significant differences were detected among nearfield and farfield stations by a Wilcoxon's signed rank test (Table 3.3.3-5). Significant differences were detected among years using a Kruskal-Wallis test. Densities were highest in 1982 and 1983, while densities in 1985 and 1986 at the nearfield Station 19 and 1984-1986 at the farfield station 31 were lower than previous years. Despite year-to-year fluctuations in Medfolus density, the community as a whole can be relatively persistant and is an important refuge from large predators. At the 8 m depth off Portsmouth, N.H., Modletus beds persisted for over 5 years. However, survival depended on the ability of Mediolus to avoid predation by Asteries vulfaris or dislodgement by attached kelps, which in turn are regulated by grazing sea urchins (Witman, 1985). 272
2 1Antf 3.3.3-5. ANNUAL NE AN DI NSI TY (l'I R 1/fs a ) AND ST ANDARD pt VI AT IOff Of NOO/0/uS NOO/Ol&S OBSERVf D AT SUBT IDAl. TRANSECT STATfDNS, 1980-1986. SIAllROOK RASELINE REPORI. 1986. ALL SIATION 19AO 1981 1982 1983 1984 1985 1986 YEARS Nearfield E 91.6 108.3 132.0 111.5 96.9 76.6 90.3 102.1 (19) SD is 8. s p 84.6 59.9 66.2 54.9 46.4 39.3 54.2 Tarfield E 118.7 9 3. fo 121.4 116.4 87.7 93.1 61.5 98.9 (31) SD 48a . 3 5 86 . 3 64.0 50.0 38.1 43.5 41.7 52.1 Station 19 = Station 31 (0= .005) va M 4,ob
3.3.4 Surface Foulina Panels The fouling panels program was designed to study both settle-ment patterns and community development. The short-term (ST) panels provided information on the temporal sequence of settlement activity. Surface fouling panels were not collected from January 1985 through June 1986. Therefore, only six months of addLtional baseline data have been collected since the 1984 Baseline Report. 3.3.4.1 Seasonal Settlement Patterns In general, seasonal settlement patterns have been consistent in terms of species richness (number of taxa) since sampling began on l Seabrook short-term panels. Historically (1978-1984), species richness increased steadily throughout the summer and early fall and decreased in late fall (NAI 1985b). Settlement patterns observed on short-term panels in 1986 were within the range of previous years except in October. During that month, at Stations 4, 19 and 34, the number of species present far exceeded the mean of baseline years combined (1978*1984, except for Station 34, which only included 1982-1984)(Figure 3.3.4-1). The increased number of species included a few individuals each of nudibranchs, bivalves, amphipods, and polychaetes, all species which I have occurred previously on panels. In 1986 the number of species at Nearfield Station 4 were slightly higher than at Farfield Station 34, except in October, when faunal richness was higher at Station 34. Nearfield Station 19 was slightly higher than Farfield Station 31 in terms of species richness, except in August, when Station 19 had a sharp ' drop in the number of species. Over the baseline period, the greatest mean species abundance occurred in the summer and declined steadily through the fall at Near-field Stations 4 and 19 (NAI 1985b). Stations 4 (nearfield) and 34 : (farfield) followed similar temporal patterns; however, abundances at I l 274 I 1
asaanroot gg-t 20- STATION 4 20 STATION 19 / 's 18- [Is. 18- $ e e 's i s t 16- ,' 's 16 -- ,
/ Y, N,l \\
14 - '/ 14
..s . i .
U 12-f.
/m \ (
\ s O 12.
s a
\
s M 10- - ' M 10- 't ' e g_ e g_ g - g - 6- , 6- - 4 q- 4 ,
~
2- 2-0 . . . . . . . . . . 0 . . . . . . . . . . J F M A M J J A S 0 N D J F M A M JJ A S 0 N D MONTHS MONTHS FARFIELD 24-22- j'i, w 20- STATION 34 j I, 20- STATION 31 , , 18- / 'g 18- - 16- - '. 16- g 14 - . .,/ \ 14 - i. O 12- g 12-M 10 - / \ e 10 -- 4 S 8- \ b 8-
'\
6- ) '_ 6- s, 4- ~ C /, , 4-N_ 2- . 2- . 0 . . . . . . . . . . . 0 . . . . . . . . . J F M A M J J A S 0 N D J F M A M J J A S 0 N D MCNTH$ MONTHS
--------- 1986 1978 - 1984 (STATION 34: 1982-1984)
Figure 3.3.4-1. 1986 faunal richness (number of different taxa over 2 replicates) compared to mean specie = richness and 1 standard deviation from 1978-1984 on short term panels. Seabrook Baseline Report, 1986. -. _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ - - - - - _,___=-r--
-- n - - - - -
1 l 1 l i I Station 34 were generally higher, especially,in October and November. The species abundance values for July through December 1986 were similar ! to other years, with a few notable differences (Figure 3.3.4-2). At Stations 19 (nearfield) and 31 (farfield), mean species abundance was , lower in August 1986 compared to other years and substantially higher in October (Station 31) and November (Station 19). These deviations from the historical mean are a reflection specifically of differences in Mytilidae abundances (NAI 1987, 1986, 1985a, 1984a, 1983a). l The dry weight biomass (gms/ panel) for short-term panels generally followed the pattern observed for the seasonal distribution of density and species richness. Historically, biomass weights normally have been highest during August and September (NAI 1985b). Seasonal trends in 1986 were similar to these bsseline years (Table 3.3.4-1). The Nearfield Stations 19 and 4 followed similar seasonal patterns; however, higher biomass weights were observed in 1986 at Station 19 [ during all months except October, when total dry-weight was lower. An exceptionally high weight was obtained in November, 1986 at Station 34 due to dense Tubulario sp. coverage (NAI 1987 and photographs in project l file). Several dominant taxa on panels were monitored to determine their long-term recruitment patterns at nearfield (19, 4) and f arfield (31, 34) stations. A summary of notable differences for each species on - the 1986 short-term panels compared to the baseline period is shown in Table 3.3.4-2. Monthly mean abundancas for these short-term panels species are shown for all years sampled in Appendix Tables 3.3.4-1 ,
- through 3.3.4-13. The panels selected species, Mytilidae, and Jassa 2 f
falcata are discussed in Section 3.3-5. i t s . i 276 l i t
- . ~ - . , - , . _ ,
4.0- 4.0-STATION 4 STATION 19 7x 3. 0 - 7* 3. 0 - .. g . m lh's. x
- f.. s - c--- s
'( N y
- 2. 0 - ] 2.0 - \, g g
o
=
s..
$ N Z .
h, 5 1. 0 - - 5 1.0- 4 E N /,_ N ~ b/ 0 0 . . . . . . . . . . . . . . , , J F M A M J J A S 0 N D J F M A M J J A 5 0 N D MONTH MONTH w u 4.0 - 4.0-
~ STATION 34 :iTATION 31 1
g 3.0 - - l'~. 5 o, 3.0- ./
/
- g i ,
o g- '
's
- 2. 0 - / '\, 2.0-
\
q -
,. x - -
Q f "' s z
/.
2 1. 0 - . S 4 1.0-N. ~ '/ -
-l.
0 . . . . . . , , , 0 . . . . . . . . , J F M A M J J A S 0 N D J F M A M J J AS 0 N D MONTH MONTH
----- 1986 ABUNDANCE 1978-1984 MEAN ABUNDANCE (STATION 34: 1982-1984)
Figure 3.3.4-2. 1986 species abundance (log x + 1) compared to mean species abundance (log x + 1; i95% confidence limits) from 1978-1984 for non-colonial fauna on short-term panels. Seabrook Baseline Report, 1986.
TABLE 3.3.4-1. DRY 'iEIGHT (GMS/ PANEL) BIOMASS ON SHORT-TERM SURFACE FOULING PANELS. SEABROOK BASELINE REPORT. 1986. a 1986 STATION J F M A M J J A S 0 N D 19 .5 .7 1.5 .2 .7 1.1 31 .2 1.7 .8 .7 .2 .1 4 .1 .3 1.0 .8 .2 .1 34 .1 .9 1.1 1.7 4.9 <.1 1984 STATION J F M A M J J A S O N D 19 <.1 <.1 <.1 .1 .2 .1 <.1 .3 1.7 4.3 .8 .1 i 31 .1 .1 <.1 <.1 .5 .1 .8 .1 1.4 .5 .8 .1 l 4 <.1 <.1 <.1 <.1 .3 .3 .1 .5 .2 .2 1.1 .1 34 <.1 <.1 <.1 <.1 .1 .1 <.1 .1 .5 .3 1.2 <.1 1983 l STATION J F M A M J J A S 0 N D 19 .1 .1 .1 .2 .2 .3 .3 .3 2.4 6.8 .1 .1 31 .1 .1 .1 .1 .2 .1 .1 .1 .9 <.1 <.1 .1 4 .1 .1 <.1 .1 <.1 .3 <.1 2.0 1.1 1.1 .3 .1 34 .1 .1 .1 .1 .1 .3 .3 4 2.8 6.3 .5 .3 D 1982 STATION J F M A M J J A S 0 N D 19 <.1 .1 <.1 .2 .4 .1 1.8 1.9 1.9 2.1 .1 .1 l 31 .1 .1 .1 .3 .1 .3 2.6 2.7 2.0 1.9 <.1 .1 4 .1 .1 .1 .3 .1 .1 1.5 2.0 2.3 2.0 .1 .1 34 .1 .2 .1 .2 .2 .2 1.7 1.6 1.9 2.3 .1 .1 1981 l STATION J F M A M J J A S 0 N D
.2 .2 .2 .2 .4 3.2 .3 .2 .2 19 .1 9.0 31 .1 .2 .2 .2 .1 .6 10.9 5.0 .8 .3 .2 4 .1 .1 .2 .2 .2 4 .7 9.5 .6 .3 .5 1980 l STATION J F M A M J J A S O N D l 19 .4 <.1 <.1 .5 4 .5 .8 .5 .9 .9 .5 .8 l
31 .4 *1 . <.1 .7 .4 4 .6 2.2 .6 .6 .6 .5 l 4 .4 <.1 <1 .6 4 .6 .8 .7 1.1 .4 1.2 4 l l a l No fouling panels placed or collected in January 1981, or from January 1985 through June 1986. b Station 34 was first sampled in 1982. 278 l
TABLE 3. 3.4-2. UNUSUAL DIFFERENCES" ON 1986 SHORT-TERM PANELS (SUMMER / FALL ONLY) COMPARED TO THE BASELINE PERIOD (1978-1984, i EXCEPT STATION 34 WHICH WAS 1982-1984). SEABROOK , BASELINE REPORT, 1986. , U SPECIES TEMPORAL (NEARFIELD) SPATIAL , (NEARFIELD VS FARTIELD) Mytilidae Station 19 November Station 19 higher in abundance higher November; Station 31 higher in October.
' Station 34 higher in October and November vs Station 4 Xiatella sp. August abundances l lower compared to baseline '
Jassa falcata Lower densities at Stations 4 and 19 s Balanus sp. Anomia sp. ; i Tubularla sp. Lower at Stations 19 and 4, except 4 in November when percent frequency is higher than baseline period. ! 3 l Lacuna vincto No differences observed Nudibranchia Slightly lower values in 1986 for 19 vs 31 j and 4 vs 34 as com-pared to baseline period. Pontoteneto inermis No differences observed 279
i l a TABLE 3.3.4-2. (Continued) b SPECIES TEMPORAL (NEARFIELD) SPATIAL (NEARFIELD VS FARFIELD) Strongylocentratus No Differences Observed droebachtensis Asteriidae No Differences Observed Obella sp. No Differences Observed Diatoms No Differences Observed
= observational only b
= nearfield vs farfield (19 vs 31; 4 vs 34) 280
3.3.4.2 Patterns of Community Development Monthly sequential (MS) panels measure growth and successional patterns of community development. Historically, settling activity was most intense in the summer months, and continued into the fall (NAI 1985b). In 1986, the pattern of community development on monthly sequential panels was similar to previous years. A comparison of the settlement sequence and survival of species on nearfield (Stations 4 and
- 19) monthly panels is shown in Figure 3.3.4-3. Similar to previous years, settlement density in 1986 was high in the summer months, especially for Mytilidae, #fatalla sp. and Obella spp., and persisted throughout the fall. In 1986, an increase in occurrence of Niatella sp. , and a decrease in occurrence of, Jassa f alcata was noted. The hydroid Tubulario sp. settled later and less densely at Station 19 in 1986 than compared to previous years; settlement at Station 4 was similar to previous years except 1983, when settlement was earlier and more intense. Salonva sp. was a regular colonizer over the six month period sampled in 1986, and was similar in density to 1984 settlement, I but lower than densities in 1983. Nudibranchia, Polynoidae and #ereis )
sp. showed similar summer and fall sett.lement patterns as well as similar densities, compared to other years. Jarra falcata showed the greatest variation among species in 1986, with substantially lower settlement densities than all other years. The patterns of community growth and development are generally reflected in the biomass data from the monthly sequential panels (Table 3.3.4-3). Over the baseline period, a pattern of increased biomass dry-weights occurred from summer into the fall months (NAI 1985b); however, a drop in biomass weight occurred at all stations in November, and peak weight for Station 19 occurred in October, not December. The dry-weights were consistently higher from August through October in 1986 at all stations than in any other years sampled. Nearfield versus farfield ('19 vs 31; 4 vs 34) were similar in 1986 for the six months sampled. 281
l l d 1 STATION 4 STATION 19
'l E l H a l vl ll J la 15 l3 l'. l 0 _
.' I' l*l A l*lJlf l fli lolNl2 l l
1980 M long M j;
. a g 1984 .. - . . . - ,mi 19.
7 -.- --- - ,
; 1983 - .. C >
1981 ^j == 6 E 1962 - [w E 1982 - M*C 1986 h En h 1986 F 4 1986 - -
- 1964 }[
$. 1983 - %~ .
1983 }2 E 1982 = 5 1982
; itse .. . . . . I 1986 - * = = = = =
- w u 3
1984 --- - .
~
19t 4 ----- M 1983 - -- w 2 1983 - - - - .. um { 1982 3 -3 k 1982 P"- M*"-2 j 1986 -.
$ 1966
{ 1964 --- - ** - { 198.
) 1983 $ 1983 -
} 19f: ===
) 1982 -- _-- =
l l h 1986 - h 1986
= 1m --
199 --I 4 1983 M 4 1984 - t-2 2 g 19f2 - g 1982 h-*2 g 1986 [ g 1986 [=== - = 1984 - g -[- 1984 0 1983 -- } O 1983 - C 2 8' o 1982 6 1912 CwZ{ g 1986 -. g 1986 -~ _ l
* * \
, 1984 === . 1984 -[-[- j
{ 1983 M -[- ! 1983 M-[ , i 1982 - ==* 2 1982 2 a 1986 - 1986 s % 2 1984 = = = = 3 1984 1983 ---.- 1983
- -k - - - . . . . i i
2 1982 7- - 2 1982 - i l l 1986 1986 * . -
"l n n 1984 == == 1984 -. 2.-
j 1983 j 1983 2 1992 - - 2 1982 I l present 1 25 t frequency I I 26-50 51-75 E 76-100-Figure 3.3.4-3. Annual settlement periods, abundance and survival of major taxa based on examination of sequentially-exposed panels at nearfield Stations 4 and 19. Seabrook Baseline Report, 1986. 282
TABLE 3.3.4-3. DRY WEIGHT (GMS/ PANEL) BIOMASS ON MONTHLY SEQUENTIAL SURFACE FOULING PANELS. SEABROOK BASELINE REPORT, 1986. s 4. e 1986 STATION J T M .A M J J &' S 0- N C 19 33.3 164.3 422.9 931.1 496.7 698.1 31 *2.1 179.3 469.3 857.7 716.8 481.3 6 20.8 157.3 357.0 (99.0 481.3 1071.3 14 29.7 123.9 502.3' 473.2 578.9 .952.6 s-1944 STAT!0N J T M A -- M J' J A $- 0 N C 19 c.1 .1 .5 .6 3.1 8.6 17.9 53.0 213.6 666.9 776.9 1111.6 31 .2 .2 1.2 ~ 1.9 2.2 20.3 ' 56.6 116.4 199.6 3 66 . 0 929.6 773.6 6 <.1 .1 .7 1.2 1.6 2.7 6.4 52.5 232.6 363.6 583.6 1035.5 36 <.1 .2 .4 1.2 1.1 9.7 15.4 57.5 262.0 369.0 706.2 1166.1 1983 b STATICK J T M A M J J A 8 O N E 19 <.1 .1 .6 .5 .7 18.7 60.5 66.6 87.2 . 327.1 656.2 116.9 31 .1 <.1 .6 .7 2.0 11.0 17.8 52.0 131.6 221.0 160.6- 39*.6 6 <.1 .1 .5 .6 1.1 e.9 7.1 27.6 16 .7 28.0 9.6 e65.7 36 D
<.1 .1 .7 .8 .8- 5.7 10.9 34.5 161.6 106.9 513.8 821.5 1982 STATICH J T M & M J J A $ 0 N D 19 .1 .. 2.6 9.5 1.8 3.5 9.8 20.4 93.6 90.1 161.6 133.3 il .1 .8 1.9 2.6 2.9 7.1 2C.3 33.8 631.3 193.0 276.6 349.6 6 .2 .2 1.6 1.8 5.8 9.1 8.5 60.5 31.5 86.1 73.7 104.6 36* .1 .6 1.1 2.0 .9 6.6 13. 31.2 39.6 75.9 61.3 115.1 1981 STATION J' T M A M J J A 5 0 N D 19 .1 .2 .3 1.3 .6 17.4 26.1 32.3 32.1 34.0 33.7 31 .2 .1 .e 2.1 3.8 20.6 32.3 36.7 113.3 28.6 207.4 4 .1 .2 6 2.7 3.0 13.7 5.2 5.8 56.2 60.1 7C.6 1980 STATION J T M A M J J A $ 0 N D 19 a.1 .* .7 1.8 19.1 130.0 257.2 186.5 221.5 105.9 155.5 261.9 31 <.1 .8 1.9 2.6 6.5 19.5 67.6 55.6 516.9 616.1 342.2 567.9 6 <.1 7 .8 1.3 4.2 86.3 266.0 151.7 173.3 213.9- 52.2 115.5 1979 d
STATION J T M A M J J A 5 0 N D 19 .1 .6 .5 2.0 7.0 52.6 77.5 82.5 96.2 129.9 213.3 31 .2 .6 .6 1.5 4.8 66.6 92.0 205.9 976.9 519.1 643.1
. .1 .6 1.2 2.2 14.5 56. 0 70.1 310.5 689.7 392.3 226.6 i
1978' STATION J T M A M J J A $ 0 N D 19 758.4 31 735.7 4 804.8
'7anels were not sampled in January.19811 or f ree January,1985 through June,1986.
- i. Mean per two repiscate (10 x 10 cm) panels.1.eceeber only.
!~ $tetson 1. was farst sampled in 1982 Casa not available.
"In 1978, blooses sessured only from December monthly sequential panel.
283
- -. . . _ . - - . . _ , - __ _ _ _ . , . _ . _ _ _ . . _ ~ _ _ _ .- _ , _ . .,_
Laminarla sp. spore 11ngs (mostly L. saccharina, but occasionly L. digitata) settlement on MS panels has been highly variable from year to year, but generally, more Laminaria sp. fronds have been present in July, August and September than later in the year (NAI 1985b). Settle-ment was sparse at all stations in 1986, especially at Stations 19 and 31 where higher densities historically occurred (Table 3.3.4-4). For each year, mean abundance at Station 31 far exceeded that for any other station. Nearfield and farfield stations have been somewhat similar (19 vs 31; 4 vs 34) in terms of abundance over the baseline period. Station 19 versus Station 31 similarly exhibited higher abundances during 1982 and 1983; however, values at Station 31 were generally higher, including number of fronds collected in 1986. Station 4 and Station 34 were similar and exhibited higher abundances in 1982 and lower abundances in all other years sampled. 3.3.5 Selected Benthic Species 3.3.5.1 Mytilidae Mytilidae, composed primarily of juvenile Mytilus edults, was the most abundant taxon at all three nearfield/farfield station pairs. l Nyttlus adults reaches up to 100 mm in length (Gosner 1978), and is an important prey species for fish, sea stars, lobster, and gastropods. It clings to hard substrate with strong byssal threads, and is an important- , 1 fouling organism. The densities averaged over the entire study period j were highest intertidally, and generally decreased with increasing depth l (Table 3.3.5-1), a trend also reported in NAI (1985b). Overall densi-ties averaged from 1978 through 1986 ranged from 187,731 per m at intertidal Station 1MLW to 7,024 per m" at Station 19 with a depth of about 10 m. 284
a TABLE 3.3.4-4. LAN/NAR/A SP. COUNTS ON MONillLY SEQUENTIAL SURFACE FOULING PANELS. SEABROOK BASELINE REPORT, 1986. APR MAY JUN JUL AUG SEP OCf NOV DEC MEAN S.D. STATION 19 1980 0 0 10 19 10 18 Ils 23 31 13.9 10.22 1981 4 13 0 2 0 0 0 0 0 2.1 is.31 1982 53 54 32 116 67 68: 84 8 65 51 61.1 23.21 1983 0 10 8 3 3fs 25 38 21 16 17.2 13.35 198f4 9 1 34 10 22 6 84 1 6- 10.3 10.90 c 1986 8 3 1 3 4 0 3.2 2.79 d STATION 31 1980 0 0 -- 22 39 12 79 75 39 33.3 30.92 1981 4 0 6 19 0 1 0 5 5 4. 8s 5.98 190.2 108 98 72 92 104 95 122 103 64 95.3 17.85
- v. 1983 0 97 126 11:3 136 IT5 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 STATION is 1980 0 0 18 15 8 is 5 18 29 10.3 10.06 1981 3 1 0 0 0 0 0 0 0 .4 1.01 1982 48 128 112 76 125 97 69 83 92 92.2 26.48 1983 0 0 0 11 1 1 2 'O O 1.7 3.57 1984 2 1 2 0 0 0 0 0 0 .6 .88 1986 7 0 I o 0 0 1.3 2.80 STATION 34 1982 27 51 46 69 '65 50 53 47 65 52.6 12.83 1983 0 8 11 27 11 1 0 6 0 1.1 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 a f ronds counted were L. Jaccharina and occasionally L. digstata.
b No faminaris sp. >3 cm (minimum eength for cotanting) present herore Aprit. C No panels cJitected f' rom Jantiary 1985 through June 1986. d Data missing for June 1980.
~ . . . . ._. _ _
= . s I ! i
- i
)~ 2 IABtE 3.3.5-1. ANNUAL MEAN AND ST ANDARD Of VI All0N Of ABUNDANCE ( No./m ) SAMPLED 1RIANNUALLY IN MAY, AUGUSi, 1 AND NOVEMBER As SELECTED BEN 1 HIC SfAil0NS. SI ABROOK HASillt:E REPORT, 1986. f i I IAXA STATION OVfRAIL 1978 19/9 1980 1981 + - -3 - - - X SD X SD X SD X SD X SD I Amp /thoe rubricata IMLW 518.5 915.5 1.836.4 204.9 967.1 986,3 803.6 699.9 416.4 404.5 ; SHLW 79.3 204.9 --b -- -- -- -- -- -- --
- Jassa ra/cata 17 2,731.1 3,759.3 1,171.6 730.5 1.162.7 778.8 1.400.9 1,2T7.2 6,12's.4 6,657.7 l
! 35 4.848.4 5,518.2 -- -- -- -- -- -- -- -- , I rantogencia inermis 19 1,815.0 1.539.9 1.815.1 2,045.5 718.2 539.3 901.3 750.6 835.6 662.7 31 811.9 1.332.6 348.4 538.5 528.0 48's.3 624.0 701.7 999.1 947.1-Nucetta tapittus IMI W 3,264.2 3,063.3 1.594.7 891.5 3,194.7 1.263.7 5,104.0- 4.012.9 2,183.1 1,076.2 1,107.6 699.3 -- -- -- -- -- :-- -- SMLW -- l t Asteriidae 17 840.9 1,158.7 -- -- -- -- -- -- 2,497.8 2,148.7 35 344.2 486.0 -- -- -- -- -- -- -- -- h) Strongytocentrocus 19 203.9 193.8 110.2 154.4 211.5 164.1 259.6 181.7 359.1 258.9 !
$& droebachiensis 31 104.1 124.0 48.0 43.1 131.6 133.8 94.2 65.7 186.7' 121.9- l i Mytilidae 1MLW 181.731.2 211.666.0 222.789.3 207.334.3 132.132.6 65.409.2 162,096.0 230,073.6 273.200.0 315.280.2 1 5MLW 91.961.2 66,553.0 -- -- -- -- -- -- -- -- <
, IT 8,253.0 14,186.8 3.962.1 3,584.6 20.343.1 22,545.8 1,831.1 1.527.8 4.940.4 6,149.8 . 13.361.8 21,554.1 -- -- -- --- -- 35 -- -- -- 19 7.024.0 14,319.7 387.6 853.9 1,091.6 1,404.8 2.163.9 3,266.6 4,104.9 5,324.7 31 24.326.7 49,081.5 5,304.9 11.106.4 1,539.6 13,311.9 20.154.7 18.427.3 20,401.8 15,956.0 i
, , , , - ,, . -, -, - - ,m , - . , --L- - . - - - _ _ - - - _
TA8tf 3.3.5-1. (Continued) I TAXA STATION 1982 1983 1984 1985 .1986 ~ t E SD E SD E SD E SD E SD Ampichoo rubricaca 1MLW 392.9 456.6 122.7 167.6 55.1 80.4 10.7 13.9 1.8 5.3 SMLW 288.0 369.1 106.T 152.2 1.8 5.3 0.0 0.0 0.0 0.0. Jassa ra/caca 17 6,344.9 6.159.3 1.589.3 2,236.3 1,123.6 1,072.4 2,513.8 2,162.1 3,148.4 2,394.9 35 8,120.9 6,901.0 6.416.4 5,434.0 2,570.7 1,875.0 2,147.6 1,834.0 4,926.2 7,373.2 foncogencia incrais 19 1,848.9 2,941.4 983.1 1,226.1 114.7 749.3 993.8 1,068.7 1,854.2 2,029.9 31 995.6 1,040.9 P88.9 147.5 1,082.7 1,269.7 453.3 444.9 1,786.7 3,326.6 l Nucc/pa tapitrus 1MLW 1,276.4 752.8 2,304.0 1,800.0 7.032.9 5,605.2 3,895.1 2,735.9 2,792.9 1,021.7-SMLW 1,114.7 131.6 1,180.4 1.032.1 986.1 465.5 1,527.1 646.6 728.9 269.9 Asteriidae 17 794.7 441.9 238.2 119.1 472.9 258.6 625.8 233.4 416.0 187.8 35 906.7 715.7 117.3 132.9 341.3 400.9 252.4- 157.9 103.1 72.9 S$ Strongy/ocentrocus 19 158.2 106.0 60.4 19.5 195.6 228.8 261.3 174.2 218.7 233.4
-a drocbachiensis 31 94.2 72.6 136.9 188.7 92.4 165.5 56.9 40,1 96.0 169.3 +
Mytilidae 1HtW 329.266.8 285.576.8 111,664.0 133,203.3 86,807.1 37,670.2 110,542.2 144,802.0 261,084.4 244,257.9 ' SMLW 81,991.1 86,911.9 65,605.3 24,885.4 115,155.6 91,108.5 69.054.2 43,980.9 128,000.0 47,890.1 17 5.646.2 5,704.7 4,145.8 5,545.6 19.244.4 28,985.6 997.3 743.6 13,166.2 15,111.4 l 35 4.844.4 8,375.1 20,846.2 31,136.0- 22,099.6 24.022.1 1,530.7 1,422.2 -17,491.6 23,001.3 19 4.245.3 7.594.9 1,955.6 1,925.7 13.813.8 17,639.0 16,302.2 22.061.9 19.086.2 25,950.2 31 4,051.6 6,907.2 1,952.e 2,165.9 21.059.6 14,.776.9 128,696.9 91,849.1 9,779.6 14,023.7 a ' n = 9 (3 replicates taken 3 times a year) b
-' = not sampled ll
}
l 4 j I f d
- _m . _ - _ ___.._ _.
l The three nearfield/farfield station pairs were tested l separately for annual (1982-1986) and station differences: Intertidal l Station 1MLW and SMLW, shallow subtidal. Stations 17 and 35 with a depth of about 5 m, and mid-depth subtidal Stations 19 and 31 with a depth of approximately 10 m. Significant dif f erences in annual abundance occur-red among years for each of the three pairs when tested with 2-way ANOVA's (Table 3.3.5-2). During the year 1986, annual abundance was relatively high at all stations, except Station 31, where it was very low (Table 3.3.5-1). Annual densities varied greatly. Similarly, significant differences were found among years for the extended study period (1978-1986) at both nearfield stations tested (Stations 1MLW and 17)(Table 3.3.5-2). The year of lowest abundance at both stations was 1985; however, populations had increased substantially by 1986. Significant interstation differences in abundance occurred for the intertidal and mid-depth stations, but not for shallow subtidal stations when tested with 2-way ANOVA's (Table 3.3.5-2). The overall abundance at the intertidal nearfield station (Station 1MLW) was double that of its farfield counterpart; at the mid-depth farfield control (Station 19) overall abundance was nearly triple that of its nearfield counterpart (Table 3.3.5-1). The Mytilidae collected ranged from 0.3 to 31.8 mm in length, and many of the smallest mytilids had settled on macroalgae rather than on the bottom or hard substrate, a pattern also observed by other investigators (Bayne 1965; Suchanek 1978). Information from surface fouling panels suggests that primary or secondary settlement takes place throughout the year, but is heaviest from June through October (NAI 1985b). Mytilid lengths showed no significant differences between nearfield and farfield station pairs, as found in NAI (1985b). The I overall mean length of intertidal mytilids (about 1 mm) was slightly larger than subtidal mytilids (Table 3.3.5-3), even though intertidal population densities were much higher than subtidal densities. Although yearly differences in mean length for each of the nearfield/farfield 1 288
l l l l TABLE 3.3.5-2. RESULTS FROM ANOVA MODELS AND COMPARISON PROCEDURES FOR ABUNDANCE.(NO. PER SQ METER) FOR SELECTED SPECIES SA'! PLED TRIANNUALLY IN MAY, AUGUST, AND NGVEMBER AT SELECTED' BENTHIC STATIONS. SEABROOK BASELINE REPORT, 1986. TAXA STATION CLASS Fa ,b
'IVO-WAY ANOVA -
Ampithoe rubricata 1MLW, Year 18.67*** 5MLW Station 5.59* Interaction 0.80 Nucella lapillus 1MLW, Year 4.46** SMLW Station 29.40*** Interaction 1,69 Jassa falcata 17,35 Year 2.18 Station 5.89** Interaction 3.11** Asteriidae 17,35 Year 9.03*** Station 22.62*** Interaction 1.71 Ponrogeneia inermis 19.31 Year 0.82 Station 4.39* Interaction 1.02' Strongylocentrotus 19,31 Year 2.75** droebachiensis Station 1.98 Interaction 1.36 Mytilidae 1MLV, Year 3.61** SMLW Station 6.85** Interaction 3.23* Mytilidae 17,35 Year 6.04*** Station 2.00 i Interaction 1.71 Mytilidae 19,31 Year 14.85*** Station 39.69*** Interaction 3.57*** (Continued). 289
TABLE 3.3.5-2. (Continued) TAXA STATION CLASS Fa ,b ONE-VAY ANOVA Acpithoe rubricata 1MLV 13.78*** Nucella lapillus 1MLV 4.45*** Mytilidae IMLW 2.56* 17 2.87** Jassa falcate 17 2.52* l 1 l Results of ASOVA's done on log (a undance + 1) from 3 10 replicate samples taken triannually.
*** -a= .001, ** - a = .01, * - a = .05.
290
TADLE '.3.5-3. ANNUAL MEAN LENGill (mm) AND STANDARD DEVI ATION FOR SELECTED DENTHIC SPECIES SAMPLED TRI ANNUALLY IN MAY, AUGUST, AND NOVEMHER AT SELECTED BENIHIC ST AT IONS.a SEABROOK BASELINE REPORT, 1986. OVERAll 1982 1983 1984 1985 1986 TAXA STA E SD E SD E SD E SD E SD E SD b Ampichoe rubricata 1MLW 7.00 2.52 6.73 2.40 7.75 2.10 6.85 3.25 10.86 3.33 -- -- SMt W 7.82 2.76 7.57 2.87 8.50 2.36 8.90 0.00 -- -- -- -- Jassa (Alcata 17 4.18 1.10 3.35 1.14 4.31 1.00 4.43 0.98 4.54 0.92 4.35 0.98 35 3.84 0.99 3.48 1.22 3.68 0.93 3.74 0.71 4.48 0.76 4.05 0.84 fontogeneis incesis 19 4.87 1.81 4.45 1.72 5.23 2.01 4.90 1.45 5.30 1.83 4.70 1.90 31 5.05 1.38 4.63 1.12 5.24 1.47 4.64 1.44 5.79 1.50 5.11 1.12 Nuce/ts tapittus 1MLW 5.32 4.40 7.95 4.19 3.31 3.96 3.96 2.50 4.98 3.29 7.73 5.48 { SMLW 6.28 5.26 5.73 5.09 6.23 5.29 6.94 5.77 6.30 5.36 6.22 4.67 j Asteriidae 17 6.26 4.75 4.03 3.34 5.40 3.87 7.79 6.06 7.48 4.26 7.32 4.88 l 35 7.04 7.21 5.32 5.16 11.42 13.45 5.69 6.02 10.12 6.23 13.12 9.88
- w u> Strongy/ocentrotus 19 1.98 1.98 1.83 1.21 1.75 1.35 1.70 1.35 2.73 2.70 1.55 1.74
"' drocDschiensis 31 1.92 1.14 1.73 0.72 2.28 1.33 .1.69 0.77 2.48' 1.76 1.48 0.58 Mytilidae 1MLW 3,06 2.07 2.73 1.37 4.51 2.88 2.70 1.51 2.61 2.24 2.84 1.47 5MLW 3.17 1.72 2.78 1.37 3.21 1.95 2.94 1.49 3.00 1.13 4.00 2.18 17 2.33 1.52 1,91 1.40 2.11 1.23 2.84 1.62 2.42 1.74 2.46 1.47 35 2.47 1.70 1.84 1.46 2.14 1.27 3.08 2.07 2.44 1.51 7.73 1.82 19 2.22 1.48 1.97 1.38 2.27 1.46 2.14 1.10 2.38 1.89 ' 32
- 1.44 31 2.82 2.38 2.25 2.35 1.95 1.25 2.05 1.06 3.46 1.55 11 3.64 a
Up to 200 individuals were measured from each sampling period (May, August and November). E= sumJ r__3he length or all indlviduals measu[gd in Maydu_qtMWnd_ November total number or fndividuals measured in that year b
-- = pone collected f
j
1 station pairs were not significant (Table 3.3.5-4), 1986 had slightly larger lengths than most other years at all three station pairs, and the mean densities were also high in 1986 at all three stations. The level of mytilid recruitment as measured by abundance on short term fouling panels set 3 m below the surface at Stations 19 and 31 has varied greatly from 1978 through 1984 and in 1986 (no samples in 1985). Recruitment was the highest in 1981, with a yearly average of 4,082 spat per panel (Appendix Table 3.3.4-1). The next year, 1982, rec.uitment was the lowest with 57 individuals per panel. Densities in 1986 were well below average with 1,386 Individuals per panel. Over 60?. of the mytilids collected at Stations 19 and 31 in 1986 were 3 mm or less in length (NAI 1987). Mytilid lengths at Stations 19 and 31 ranged from <1 mm to 38 mm in 1986 (NAI 1987). 3.3.5.2 Nucella lapillus Nucella lapillus reaches up to 51 mm in length (Abbott 1974), and is an abundant intertidal gastropod and an important predator, particularly on mytilid spat. Significant differences in abundance among years and between stations were found at intertidal Stations 1MLW and SMLW from 1982 through 1986 (Table 3.3.5-2). The highest abundance (7,032 per m8 ) during the 1982 through 1986 study period occurred in 1984 at Station 111LW and the lowest (729 per m2 ) at Station SMLW in 1986 (Table 3.3.5-2). Station 1HLW (overall density = 3,264 per m') had a significantly higher population density than Station SMLW (overall density = 1,108 per m") for the study period (Table 3.3.5-1). Signifi-cant differences among years were also found at Station IMt.V for the extended study period, 1978 through 1986. Again, 1984 had the highest log abundance for the study period, ano 1978 had the lowest abundance. ! 292 l l
. ~ . . .- . . . _ = . . - - .. - - -.
l , TABLE 3.3.5-4. PISULTS OF 2-WAY ANOVA MODELS AND COMPARISON PROCEDURES FOR LENGTH (mm) 0F SELECTED SPECIES SAMPLED TRIANNUALLY IN MAY, AUGUST, AND NOVEMBER-FROM 1982 1986 AT SEIECTID BENTHIC STATIONSa SEABROOK BASELINE REPORT, 1986. TAXA , STATION CLASS F Ampithoe rubricata ,1MLW Year '4.27* SMLW Station 0.26 Interaction 0.00 Nucella lapillus 1MLW Year. 0.75 SMLW Station 0.13 Interaction 1.50 Jassa falcata 17 Year 2.14 35 Station 0.89 Interaction 0.54 Asteriidae 17 Year 2.47 35 Station 10.21** Interaction 0.86 Pontogeneia inermis 19 Year 0.32 31 Station 0.01 Interaction 0.07 Strongylocentrotus 19 Year 1.34 droebachienjis 31 Station 'O.06 Interaction 0.26 Mytilidae 1MLW Year 2.29 SMLW Station 0.07 Interaction 1.99 1 l Mytilidae 17 Year 4.53 35 Station 0.29 Interaction 0.10 Mytilidae 19 Year 2.21 31 Station 3.53 Interaction 1.37 a Mean' lengths from each station and sample period were used for computations of ANOVA's, so that results were not biased by large numbers of newly-recruited individuals. I Significance level: alpha = 0.05* l alpha = 0.01** ; alpha = 0.001*** 293
- . . _ . . . , , __ - , _ . _ , _ . _ _ - - - _ . - - . - , - _ _ . _ _ _ _- __l
Large numbers of small Nucella occurred in August or September, indicating recruitment occurred at that time (NAI 1985b). Larger individuals (10-25 mm) were. collected in most months, but dis-appeared from November 1983 through June 1984. Previous studies have l shown adult snails to be active only from May through October, retreating into crevices in the winter; while juveniles (2-5 mm) are more evenly dispersed throughout the year (Menge 1978). The overall mean length for the 1982 through 1986 study period was 5.3 mm at Station 1MLW, and 6.3 mm at the control (Table 3.3.5-3). The average yearly length ranged from 3.3 mm at Station 1MLW in 1983 to 8.0 mm at Station 1MLW in 1982; years were not significantly different (Table 3.3.5-4). 3.3.5.3 Asteriidae The Asteriidea collected are juveniles, too young to be assigned to genera. TVo species of both Asterias and Zeptasterias can occur within the study area (Gosner 1978). Larger Aster 11dae occasion-ally occurred, but were not sampled because of the difficulty of making statistically-reliable counts in the field. Asteriidae are important predators on bivalves, particularly on the recently-settled stagas, as well as other mollusks, and barnacles (Gosner 1978). Significant differences in annual abundances were found among years and between stations at subtidal Stations 17 and 35, sampled from 1982 through 1986 (Table 3.3.5-2). Station 17 had higher densities during all years except 1982, and average yearly densities there ranged from 238 per m in 1983 to 795 per m' in 1982 (Table 3.3.5-1). At Station 35, average yearly densities ratiged from 103 per m' in 1986 to 907 per m' in 1982. 294
l l l l A successful set of juvenile Asteriidae occurred in August of 1982 (NAI 1983a), and very little recruitment occurred in 1983 (NAI l 198.4a). Spatial and temporal changes in abundance and length seem to be related to the recruitment success of each year's cohort (NAI 1985b). The overall average length at Station 17 was 6.3 mm and at Station 35 was 7.0 mm (Table 3.3.5-3). Yearly mean length of sea stars collected at Station 35 was usually greater from 1382 throu'gh 1986, and the two stations were significantly different according to the results of a 2-way ANOVA (Table 3.3.5-4). The average yearly length ranged from 4.0 mm in 1982 to 7.8 mm in 1984 at Station 17, and from 5.3 mm in 1982 to 13.1 mm in 1986 at Station 35. Although large numbers of small sea stars declined during the study period, years were not significantly different when tested with a 2-way ANOVA (Table 3.3.5-4). A few recently settled Asteriidae were collected on short term surface fouling panels from 1978 through 1984 and in 1986 (no samples in 1985 or first half of 1986). Most were collected in September 1981, at Stations 19 and 31, and annual densities averaged zero from 1982 through 1986 (Appendix Table 3.3.4-12). In 1982, when densities of juvenile asterilds were highest in benthic samples from Stations 17 and 35, asteriids were very rare on the short term fouling panels, j 3.3.5.4 Pontogeneto Inermis \ Pontogeneta inermis (maximum length at maturity, 11 mm) is a pelagic, cold water amphipod (Bousfield 1973), and a dominant species in benthic and macrozooplankton collections (NAI 1985b). It clings to submerged plants and algae from the lower intertidal to depths greater than 10 m (Bousfiald 1973). Population densities were remarkably consistent from 1978-1986, and no significant differences were found among years with 2-way ANOVA's (Table 3.3.5-2). Interstation differ-ences were significunt, and Station 19 had a higher average yearly I 295 ) I 1 I i
l I 1 abundance for the 1978-1986 study period (1,815 per m*) than Station 31, (812 per m 8 )(Table 3.3.5-1). Ovigerous and brooding females were collected in low-numbers from January through September (NAI 1985b). Recruitment, as indicated by a sharp increase in density and increased numbers in the 1 to 3-mm aize class, took place between May and July. In fall and wir.ter abund-ance decreased, but average size increased as the population grew (NAI 1985b). The overall mean length for the 1982-1986 study period was 4.9 mm at Station 19 and 5.1 mm at Station 31 (Table 3.3.5-3) and no significant difference in mean lengths was found between stations (Table 3.3.5-4). The average yearly length ranged from 4.5 mm at Station 19 in 1982 to 5.8 mm at Station 31 in 1985, with no significant difference among years. Pontogencia ine rmis was common on short term fouling panels, particularly at Stations 19 and 31, during the 1978 through 1986 study period (no samples in 1985). Peak abundance usually occurred from April through June, and the year with the highest overall abundance was 1981 (Appendix Table 3.3.4-10). Abundance in 1986 was very low, but since sampling began in July, yearly density values were underestimated. 3.3.5.5 Jossa falcata Jassa falcata (maximum length at maturity, 9 mm) is a tube-building amphipod, and a dominant fouling organism on hard substrates in areas with strong tidal and wave currents (Bousfield 1973). It is a suspension feeder and also preys on small crustaceans. Significant differences among years were found with a one-way ANOVA when comparing yearly abundance at Station 17 during the extended study period from 1978-1986 (Table 3.3.5-2). Densities were below average from 1978 through 1980, and peaked in 1981 and 1982, with population densities 296
l l reaching over 6,000 per m . By 1983, the population declined by about three-fold, and then increased in 1986 to 3,148 per m2 (Table 3.3.5-1). Station 35 had a higher population density of Jessa than Station 17 during all years except 1986. The overall density at Station 35 for the 1982 through 1986 study period averaged 4,848 per m and fluctuated between 2,148 and 8,121 per m 2 (Table 3.3.5-1). At Station 17, the overall yearly density was 2,731 per m 8, and ranged from 1,163 to 6,345 per m8 . Significant differences in abundance were found between subtidal Stations 17 and 35, but not among years; however, the interaction between years and stations was significant (Table 3.3.5-2). Most lifestages of Jossa were collected at Station 17 and 35, ranging from gravid females to newly-hatched young (NAI 1985b). Gravid females were most abundant from April to November, and newly-recruited juveniles measuring 1-2 mm were most abundant in July, and were col-1ected during the remainder of the year (NAI 1985b). The overall average length for the 1982-1986 study period was 4.2 mm at Station 17 and 3.8 mm at Station 35; interstation differences were not significant l (Tables 3.3.5-3,4). Average yearly lengths ranged from 3.4 mm in 1982 at Station 17 to 4.5 mm in 1985 at Station 17 (Table 3.3.5-3), and were not significantly different. Densities on short term fouling panels, exposed for one-month intervals, give an indication of recruitment or settlement activity. From 1978-1984, substantial numbers of new recruits began appearing in j July and continued to settle through October (NAI 1985b). In 1986, settlement was highest in September / October with most Jassa ranging between <1 mm and 3 mm (NAI 1987) at the subtidal Stations 19 and 31. Annual density on panels at Station 31 was nearly double that of Station 19 during 1986. Examination of annual density levels since 1978 showed that 1986 was about average at Station 31 and well below average at 297
l l Station 19 (Appendix Table 3.3.4-2). The years with the highest annual density were 1981 and 1979 and the years with the lowest were 1982, 1986, and 1984. 3.3.5.6 Amptthor rubricata Amp tthoe rubricata (maximum length at maturity,14-20 mm) is an amphi-Atlantic boreal amphipod which constructs a nest among macroalgae (fucoids) and in mussel beds (Bousfield 1973). Average yearly densities have dropped steadily and significantly during the study period (Tables 3.3.5-1,2), and populations at both Stations 1MLW and SMLk had virtually disappeared by 1986. Significant differences were found between stations, with Station 1MLW having much higher densities than the farfield Station SMLW (Table 3.3.5-2). During the extended study period between 1978 and 1986, the average yearly density declined significantly, ranging from 1836 per m in 1978 to two per m* in 1986. Ampfthor rubricato is a boreal species near its southern zoogeographic limit (Long Island Sound) (Bousfield 1973), and it may have been affected by in reasing annual temperatures. Ovigerous and brooding females were rare, but were 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 densities and larger mean size (NAI 1985b), and the trend continued through 1986. The'overall mean length for the 1982 through 1986 study period was 7.0 mm at Station 1MLW, and 7.8 mm at Station 5MLW (Table 3.3.5-3), and no significant difference in the average yearly l 1ength was found between stations (Table 3.3.5-4). The average yearly length ranged from 6.7 mm in 1982, when young were present, to 10.9 mm in 1986, when only a few large specimens were collected. Annual mean l 1engths were significantly different from one another (Tables 3.3.5-3,4). 298 l l
-.- =- -. l This is probably a reflection of the severely diminished juvenile recruitment. 3.3.5.7 Strongylocentro tus droebach ten Is Strongylocentrotus droebach tens is, the green sea urchin, is a large herbivore reaching up to 75 mm in diameter, and is an important prey species for lobster, cod and other fish, and sea stars (Gosner 1978). It is subject to population explosions which can denude large areas of macroalgae, leaving barren rock (Breen and Mann 1976). Average yearly population densities changed significantly from 1978 through 1986, ranging from 48 per m in 1978 at Station 31 to 359 per m' in 1981 at Station 19 (Tables 3.3.5-1,2). No significant differences were found between Stations 19 and 31 (Table 3.3.5-2), where the overall densities for the study period were 204 and 104 per m8 , respectively. Most of the individuals collected subtidally were juvenile, measuring less than 3 mm in diameter, and recruitment of newly-settled young usually occurred in August and September (NAI 1985b). The average length for the 1982 through 1986 study period was 2.0 mm at Station 19 and 1.9 mm at Station 31 (Table 3.3.5-3). Neither yearly nor interstation differences in average length were significant (Table 3.3.5-4), and the average yearly length ranged from 1.5 mm at Station 31 in 1986 to 2.7 mm at Station 19 in 1985. In order to account for adult individuals which were too large to be collected in the destructive program, urchins were enumerated in the subtidal transect program. No more than 10 large (> 10 mm) urchins l per year were counted in the two years of sampling, and none were noted ! at Station 35 (NAI 1986, 1987). Of these, most occurred in April. 299
Recently-settled sea urchins occurred occasionally in monthly samples from short term fouling panels from 1978 through 1984 and in 1986 (Appendix Table 3.3.4-11). Most were collected from June through September 1981, when the yearly density averaged 1 per panel. 3.3.6 Epibenthic Crustacea 3.3.6.1 American Lobsters (#omarus ame rteanus) Lobster Larvae Loster larvae were relatively rare throughout the nine-year study period. The total number of lobster larvae collected annually was lowest in 1980 (57) and highest in 1982 (185) (Table 3.3.6-1). Mean density of lobster larvae at the intake site was highest in 1982 2 2 (1.17/1000 m ) and lowest in 1980 (0.46/1000 m ) (Table 3.3.6-1). The mean number of lobster larvae caught in 1985 and 1986 at Station P2 was l slightly below the average of the other years sampled. The maximum abundance of lobster larvae usually occurred in July or August with additional peaks occurring in September (Figure 3.3.6-1). During 1985 and 1986 lobster larvae first appeared 11. mid-July at Station P2 which was later than most other sampling years. The farfield sampling site, Station P7, was sampled beginning in 1982. The total number of lobster larvae collected at this station 3 fell from 1.32/1000 m in 1982 to the lowest level in 1984 and increased again in 1985 and 1986 to the highest levels ~ recorded in this study (Table 3.3.6-1). Abundances were higher at Station P7 than P2; this difference was most pronounced in 1985 and 1986, when abundances at Station P7 were more than twice those at Station P2. 300
l l TABLE 3.3.6-1 PERCENT COMPOSITION OF 1/)BSTER LARVAE STAGES AT STATIONS P2, P5 AND P7, 1978-1986. SEABROOK BASELINE REPORT, 1986. TOTAL .*.' ' NO.~ OF MEAN PERCENT PER STAGE OF LARVAE NO. OF STA- STAGES COL- LARVAE YEAR TION 1 II III- IV I AND IV' LECTED COLLECTED 1986 P2 -- -- 1.4 98.6 98.6 69 0.34 P5 3.5 -- -- 96.5 100.0 102 1.79 P7 21.6 -- -- 78.4 100.0 156 2.01 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 1984 P2 14.6 11.5 21.8 52.1 66.7 79 0.57 P7 37.2 1.0 2.8 59.0 96.2 101 0.73 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 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 1981 P2 31.8 1.9 6.5 59.8 91.6 .107 0.86 p7 .. .. .. .. .. NS NS 1980 P2 86.5 0.0 0.0 13.5 100.0 57 0.46 py -- -- -- -- -- NS NS l 1979 P2 70.8 2.5 1.7 25.0 95.8 120 1.18 l p7 .. .. .. .. .. NS NS , 1978 P2 10.1 0.0 0.6 89.3 99.4 169 1.45
-- -- -- -- -- NS NS 'i P7 a = Station PS sampled from July 1 through October 14, 1986 b = 5/1000m' NS = Not sampled l
I 301 1
1986 l 1982 l l l V 1981 A A 1985
, -, 1980 l o
1979 19M l 1983 1978
^
MAY JUN JUL AUG SEP OCT MA) JUN JUL AUG SEP OCT nt 2 2 0.25/I00hu 0.50/100nn 2 1.0/100&u Figure 3.3.6-1. Square root projection of lobster larvae mean densities (No./1000m ) o ..n m a -- - _1m s_ _ _ nam 1_ m_m . 3_ , ,um m. m _
~
1 l 1 1 f l In 1986, a third station, PS, was added to the sampling regime, located in the vicinity of the intake structure. This station was sampled from July 1 through October 14, 1986 only. Larval abund-ances were intermediate between abundances at Station P2 and P7 (Table 3.3.6-1). Larvae were observed from early July through mid-September matching the pattern at the other two stations in 1986 (NAI 1987). Historically, Stage I and IV larvae have dominated the collec-tions at both Stations P2 and P7, with few Stage II or III larvae collected (Table 3.3.6-1). Stage I larvae dominated the collections in 1979 and 1980, while Stage IV larvae dominated the collections in all other years. Stage II and III larvae collectively constituted 7% or less of the larvae collected except in 1984, when they made up 33% of the tots 1 abundance at Station P2. In 1985, the majority of lobster larvae were again Stages I and IV at Stations P2 and P7 (Table 3.3.6-1). During 1986, the pattern at Stations PS and P7 was similar to previous years but at Station P2, only Stages III and IV were collected; the majority of larvae were overwhelmingly Stage IV, however. Stage I larvae usually appeared at Station P2 during July with large peaks also occurring in June in 1980 and 1983. Peak abundance of Stage IV larvae varied in occurrence between July and August (NAI 1985b). Stage I larvae first appeared in 1985 in late May at Station P7 (NAI 1986). Stage IV larvae were observed in late July at Stations P2 and P7. Stage IV larvae appeared at all stations and dominated the collections in 1986. Stage I larvae were observed at Station P2 in early June and early July at P5; however, collections did not begin until July at Station PS. At all three stations, Stage IV larvae were first observed in mid-July. Trends in the occurrence of labster larvae in this study have generally agreed with other lobster larvae studies in New England (Sherman and Lewis 1967; Lund and Stewart 1970; for example). Further, an extensive review of New England studies (Fogarty and Lawton 1983) 303
1 l I indicated that the period of peak abundance in the region coincided with that observed off New Hampshire waters, as described by this study. Also, the high predominance of Stage I and Stage IV larvae in this study has been shown to vary from year to year in other New England studies (Fogarty and Lawton 1983). Abundances of inbster larvae have been associated with wind direction. Grabe et al. (1983) reported that 67% of Stage IV larvae were collected off the Eew Hampshire coast when winds cere on- or along-shore. They further suggested that thermal differences between air and land masses, combines with predominantly-westerly summer winds, produced onshore winds durir.g the day and offshore winds at night. In addition, hydrographic studies in the Hampton/Seabrook area indicated a net drift northward or southward along the New Hampshire coastline. Combined, these two actions suggested that lobster larvae were moved by nontidal water mass movements into New Hampshire waters, and were then trans-ported onshore by winds. A synthesis of lobster larvas distribution studies by Harding et al. (1983) supports this hypothesis. They noted that lobster land-ings for all regic i neighboring on the Gulf of Maine have been very similar since the mid-1940s. They interpret this to indicate a single lobster stock with common recruitment. They further concluded that warm southwestern waters of the Gulf of Maine and Georges Bank supply the Maine coast and adjoining areas with advanced larval stages, evidenced by a preponderance of Stage IV larvae in the cooler surface waters from southwestern Nova Scotia to Hampton, New Hampshire. This may explain the abundance of Stage IV lobster larvae in the present study. Adults l Adult lobsters (legal and sublegal sizes combined) have been collected in the vicinity of the discharge site (L1) from 1974 to 1986 1 . 304 f
i (Table 3.3.6-z). During that period, the highest monthly catch occurred during September at least half the time. However, in 1980 and 1982 the greatest catches were in August; in 1979, 1984, and 1985, in October; and in 1986, November. June or July have had the lowest monthly catches (Table 3.3.6-3). Average yearly catches per fifteen-trap trips ranged from 47.3 in 1980 to 92.5 in 1984 (Table 3.3.6-2). Lobster catch abundance was also high in 1985 (86.6), but dropped to average levels in 1986 (66.4). Catch differences observed among years (1982-1986) or months were not consistent between stations, as evidenced by significant interactions in the two-way ANOVA results (Table 3.3.i-3). In most years, annual catches at Rye Ledge were significantly higher than at the discharge site. Similarly, when monthly catches were higher (August, September), these catches were significantly higher at Rye Ledge; in the other months, there were no significant differences between stations. Early summer months (June and July) had significantly lower catches at both stations than all other months (Table 3.3.6-3). Adult lobster abundances have been related to seawater temperature. McLeese and Wilder (1958), Eow (1969) and Flowers and l Salla (1972) have examined this relationship. In the Hampton/Seabrook study area, continuous bottom temperature monitoring (1978-1984) at 1 Station 17, near the discharge area, was con. pared to monthly mean lobster catch. Bottom temperature and lobster catch were positively correlated during the month of June and negatively correlated during November (NAI 1985b). During June, catch declined as bottom temperature increased, probably caused by the onset of molting which would reduce the catch-ability of lobsters. Peak catch of adult lobsters usually occurred after bottom temperatures reached approximately 10'C and lobsters had molted to legal size (NAI 1985b). As bottom temperatures cooled, catch declined in November, perhaps reflecting seasonal inshore movement 305 l 1
t TABLE 3.3.6-2.
SUMMARY
OF IOIAL LOBSTER CAICH PER TRIP EFFORT DY MONill AND VfAR. AI illE DISCilARGE SITE (L1) FROM 1974 IHROUGH 1986. SEABROOK BASELINE REPORI. 1986. YEAR MONIHLY. MONIH 1974 1975 1976 1917 1978 1979 1980 1981 1982 1983 1984 1985 .1986 AVERACE-JtfNE f1.7 4 81.1 4 35.0 84 *> . 8 8.9. T 584 . 1 32.2 38.1 35.7 49.2 89.9 25.3 32.8s 40.8 J U t,Y 51.2 42.5 40.7 32.3 3f4 .8 57.6 30.? 8a 2. 5 52.3 39.9 28.2 85.2 4 37.5 f 1.1 AUGUST 73.6 73.9 68.6 63.5 63.4 61.5 70.3 80.2 83.9 89.3 72.1 81.3 -75.0 73.6 SEPTIMBER 103.0 7f .0 4 69.1 67.3 86.4 62.8 59.7 984 .3 71.7 128.2- 117.9 121.3 86.9 87.9 OCTOntR 78.6 71.6 63.7 54.5 79.1 69.9 41.3 65.6 88.8 96.3 184 6 . 6 131.2 80.5 82.1 1 NOVEMBER 59.7 55.2 48.0 61.1 65.5 58.8 43.4 $9.3 79.1 29.6 140.5 130.4 99.7 71.6 VI Af:LY e AVERACE 68.0 59.7 54.3 53.7 63.2 61.4 47.3 62.84 68.6 72.1 92.5 86.6 66.4 a catch per trip errort = total catch frem 15 traps per trip a s i i 6
--.-- - - - - - - -. -- -- .. - - - . . - --n - , , - .- -,m m , r . _ - - _ _ _ - _ - - _ _ _ .
TABLE 3.3.6-3. RESULTS Of ONE-WAY AND IWO-WAY ANOVA MODllS FOR LOSSIER (#0 NANUS ANIN/CANUS), JONAH CRAD (CANCTR BOREAL /S) AND ROCK CRAB (CANCER /RRORAIUS) IROM THE DI ScilAitGE SI Al lON. S[ AfiftOOK llASELINE REPORT, 1986. SP[CifS VARIAllit df F-VAlut SICNiflCANCE TEST One-Way Test tohster month 5 19.82** Sep Oct Aten Nov Jun Jul yr a r 11 12.82** als 85 83 82 86 78 81 79 75 76 77 Jonah crab month 5 ?6.Ola* i Aug Sep Jul Nov Oct Jain year la 27.10** 85 86 als 83 82 Rock crab montti 5 9.83** Jts t Aug Nov Jun Oct Sep ta C) year is 3 5. lfs *
- 85 86 als 83 82 Iwo-Way Test lobster station 1 2.13" year le 21.03**
station x yea r la 2.85* 82 84 8f4 86 83 85 85 83 82 86
- 1. 7 L7 11 iT L7 I7 L1 L1 L1 Lt station 1 20.81**
month 5 12f.51** t
. station x month 5 6.15** Sep Aug Oct Oct Sep Nov Nov Aug Jul J ur. Jul Jun I/ 1/ ll L1 11 l.1 Ld L1 l. T t/ L1 L1 owe
=w
( Con t i nise<! )
i IABLE 3.3.6-3. (Continued)
. i SPECIES VARIAfttL dr I-VAtUf SIGNIFICANCE TESI Jonah crab station 1 0.00 year 4 27.oS**
station x yea r 4 5. 8 8 *
- 4 85 65 86 Bis 83 86 8's 83 82 82 i
II II tI t7 t7 iT tI t.1 L1 t. 7 sta; ion i O.00 NS mor.th $ 28.0C** Aug Sep Jul Nov Oct Jan station x month 5 0.80 NS o" Rock crab station 1 39.86** 4 oo year fa 37.89"* station x year 4 11.31** 85 86 85 Bis 84 86 83 83 82 82 11 t.1 11 Lt L7 LT 17 L1 L7 L1
^
station 1 38.30** 4 month $ 10.3?'" station x month 5 2.12* Aug Jail Nov Jul Jun Aleg Oct Sep Sep O^t Jun Nov L1 (l 1.1 t. 7 L1 lI tI L1 17 LT L7 t.7 NS - Not significant a - 0.05
** Or 0.01 l
patterns (Ennis 1984) or decreased activity level. Lobsters typically show a seasonal migration pattern which is thought to maintain the population at the highest local watst .:Jperature (Campbell 1986). It is uncertain whether New Hampshire lobsters undergo seasonal migrations (NHFG 1974). Although the relatianship be tween lobster catch and bottom temperature has been shown to be sigt.ificant for some months, the combined effects of molting and other factors such as food availability probably interact, affecting lobster catchability and its relationship to bottom temperature. This conclusion is consistent with results reported earlier (NAI 1975b). Further, the New Hampshire Fish and Game Department conducted similar studies off the New Hampshire coast from 1971 through 1974 and concluded that bottom temperature did affect lobster catch, but was influenced by other factors such as molting (NRFG 1974). Catch per effort of legal-sized lobsters at the discharge station averaged from seven to ten individuals per fifteen-trap trip from 1975 through 1986 (Appendix Table 3.3.6-1). The catch of legal-sized lobsters ranged from seven to ten lobsters until 1981, consti-tuting approximately 12% of the tots 1 catch, but decreased slightly to seven to eight, approximately 10-11% of the total catch during 1982 and 1983. In 1984 at the discharge, despite having the highest yearly mean catches, the legal-sized lobster catch declined to less than seven, approximately 7% of the total catch (Appendix Table 3.3.6-1; Figi.re 3.3.6-2). Legal-sized lobster catch increased slightly to 7.2 (10%) in 1986. Changes since 1984 were probably a result of the increase in the legal size limit for lobsters from 3 1/8" (79.2 mm) to 3 3/16" (80.9 mm) in 1984. Because of the change in the law, a number of adults which would have been legal-sized under the old law, were retained in the
. sublegal size class during 1984 and 1985, molting to legal-sized lob-sters in 1986.
309
i 7ek on. THIP
. ee e.
ee e* ee ee ee
** ee ee
- ee e, ee
** .. e. e.
** ee .. ee e, g ee ee ec. ee ea I ** ** ** ** **
8 ** ** ** ** *) 60 . ea se ee e* .: 3 ee ee eo e. .e g ee ** e, se e, se se e, g ee ee se .6 ee se ee ce ee so . e, e. ee ea ++ ** ee. e, ce e.
- g ee se ** ** ** ee ** ee ee ee .e g ee ee e, e. ee ee se e, es o. ee g ee ee se ee ao se e, ee ee oc ee e.
gn . ee ee se ee ee ee se o. ** e. ee e,. t ** ** ** ** ** ** ** ** ** ** ** **. g ee .. ee ec o. >- os e. ee e. ee se g e, .* ee ee se se ee se ee oc e, c3 3e . ee se ee eo eo ee ee ** ee e, .** ee g ee e, oe ee ee e,
- es ee ea ee va g ee ee ee e. e, ee e- ** ** e, se e+
20 .t ** ee 'e e* ** ** ** *e ** ** ee +e
, .. e. ee .. ee ee ee ee e. ee e, ee
, ee ee ee ee ee ee e+ ee e. e, cc ee g ee eo eo e, se se e, ee ee e+ ee- ee gg io . .. e. .. ee .. e. .* eo .. .. ee e. .. ee e, .e c2 . ** ** ** ** ** ** ** ** ** ** ** ++ ** ** ** ** ** ** ** ** ** ++ e' **-
t ** ** ** ** ** ** ** ** ** ( ' ** ** ** ** ** ** ** ** ** ** ** ** ** ** g ee ee se ee ee se eo eo ee eo se ee ** oc ee se se se .e ee ee oc ee ca
= =--- = .....---.--..............--- --....-------..........
5 s s 5 5 5 5 5 5 5 5 s U U U U U U U U U U -U U 6 S S S S S B R 9 8 8 9 L L L L L L L L L L L L L L L L L L L L L L L L (ta%5 F ~ E E E E F E E f E E E E E E E E E E E E E E
- G G G G G G G G G G G G G G G G G G G G G 6 G G a e a a a a a a a a a a a a a a a a A A .
A 4 e i t L L L L L t L L L L L t t L L L L L L L t t t 19FS 99F6 1977 1978 1979 1980 $984 1982 1989 1984 198S 1986 vfAR
* = CHANGE IN LEGAL SIZE FROM 3 1/8" TO 3 3/16" CARAPACE LENGTH.
Figure 3.3.6-2. Comparisons of legal and sub-legal sized catch of Romarus amer *icanus at the Discharge Site 1975-1986. Seabrook Baseline Report, 1986. a-. ._ - _ _ - _ - _ _ _ _ _ _ - - _ _ _ _ _ . _ _ _ _ _ _ _ _ - - _ - . - _ _' _a w *
- v Te-Y +'w -
._a---- *M-T--' T' _ ww--- _* _ s__
Annual size-class distributions (Figure 3.3.6-3) indicate that the abundances of lobsters in the 50.8 and 63.5 mm size classes have steadily declined since 1975, while catches in size class 76.2 mm (2 5/8"-3 1/8") have increased through 1985. -Size classes from 88.9 to ! 114.3 me have tsd low catch abundances, indicating that commercial fishing in the study area quickly removed the majority of lobsters as they attained minimun legal sita. The increase in catch abundance within size class 80.9 mm from 1984 through 1986 may be attributed to the increase in the legal-size limit implemented by the State of_New Hampshire. Lobsters in this size class, measuring 3 1/8" to 3 3/16" which had been available for harvest through 1983 were now protected until their next molt. New Hampshire inshore lobster landings reported for 1984, the first year the change was enacted, had decreased by nearly twenty-four percent based on information obtained from state-required annual reports. However, adjusting catch for a generally poor catch in the southern Gulf of Maine , in 1985, the actual reduction that was due to the change in size limit f 1 was approximately 13% (Edward Spurr, NHFG, pers. comm.). This resulted r in an estimated 28% loss in total catch weight in 1985 (Perry 1985). Preliminary data reported to the state indicate that the catch weight has recovered in 1986 (Edward Spurr, NHFG, pers, comm.). This agrees , with results from this study, which show an incretse in legal-sized , lobster catches in 1986 to 1983 levels (Appendix Table 3.3.6-1). Fenale lobsters have represented nearly 60% of the total catch for all years at the discharge except in 1983 when a substantial deciaese was reported (NAI 1984b). In 1984 female lobsters returned to I previous levels, approximately 55% of the catch, and remaiaed at that 1 i level in 1983 and 1986. Egg-bearing female lobsters comprised 0.7% of the catch in 1985 and 1986, consistent with previous years' data (Figure l 3.3.6-4). I i 311
- . _ _ _ _ _ _ . ._- . ___._._._~,_ -,_
e
\ a:!
0:l\ a: \ ! N 0: N a- 3
@= \ a- N a: is N 2= N a: N a N :
e= N 0- N a= N W=N N a. N o. N a; x
!s He S- "- -lN e.N 0-N a x ii N 5":vN a-N a~ N aN l?
p Nam =~ N a. N a_ x o. x !! N 3-%= N o_ N xa~ y 0= !! b';0=
~
~
x N a-N == N e. 0= 0: N= = N a. N a. N a~ a_ {i ;! L
!?
>bbo= Ne=
~
N o~ N 2 xf= o- %= N 0- N 2.t i !! N c r= = N a ; Nd
~
ei
" S* N= = N a; _! si N >a - Ne= N9
=
Ec %=
" s 3 hFilisa \'
5 i
- 5
'Nme . -
s y2 l l 312 l i
% FEMALES IN CATCll
----- t EGG BEARING FEMALES 70 i 60 - g -1.5
,/ N s g
\
r \
/\ $'
sa o / \\ G f,0 - \ / \
-1.0 "-
cs o \ # N
\
/ 5 O, z \
/ ^ %. s g s~
u -
\ / s,/[ V< % ~~ -
ce g g \ / a \/
- 2 40 - V -0.58us g
s
==
s<
-0.0 30 -
I [' s l I I l 5 5 I I I I 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 YEAR l Figure 3.3.6-4. Surmary of female lotester cat cli < lata, at tIee Iniscliarge Station (I.1), 1974-1986. Scalirook Baseline l<eport ,1986. i
l
)
l l 3.3.6.2 Rock Crab (Cance r trroratus) and Jonah Crab (Cancer borealls) Larvae Cancer spp. (Cancer borealts and Cancer trroratus) 1arvae generally exhibited a pattern for all sampling years of very low or near-zero abundance from January through April with rapidly increasing numbers in May, reaching peak abundance in August and declining density from October through December. At plankton Station P2, Cancer spp. larvae were most abundant during August, except in'1981 and 1983 when density was greatest in July (Figure 3.3.6-5). In 1986, from July through December, the observed pattern was very similar to previous years. Adults Adult rock crab and Jonah crab catches have been monitored since 1975 at the discharge site (NAI 1985t). Since 1982, these popula-
- tions have been monitored at two stations, the discharge site and at Rye Ledge. Historically, catches of Jonah crabs have been significantly greatest in August, although catches were occasionally higher in September at both stations (Tables 3.3.6-3, 4). Average monthly catches l per fifteen-trap trip have ranged from 1.8 to 26.7 at the discharge station and from 3.0 to 31.5 at Rye Ledge from 1982 through 1986 (Table 3.3.6-3). The total annual catch of Jonah crabs increased from 1982 through 1985, when catches were significantly higher than other years, and declined in 1986 at both stations (Table 3.3.6-3,4).
Catch of rock crabs has ranged from 0.0 to 6.7 per fifteen-trap trip at the discharge station and from 0.0 to 2.9 at Rye ledge from 1982 through 1986. The catch of rock crabs has also bern generally l increasing from 1982 through 1985, when catches were higher than all 314 ,
- C 981 3o V+to
\ d
\
\ - n
\
a j\g -
- 4
\ - V 8 06 1 9O +O 9
\ - N 1
\ - 8
\ - 7 N - 9 .
\ - 16
\ -
I ,8
\ +C 9 fg 92
\ -- o 21 P
\ - ,
\ - nt
\ -
or i o t p 6 - P ae 3 s (29 i +E
- S t R
. - S
\ ;s
.e 4
s - e
\ . w o - t n
\ ,. o n
- ai e - l
\ es 6
7 - ee
\ s, 9
- fG as
. e.
3
? 9 o 4
+l
- A va se - rB
- t e
- a
. ilnu w - l k oa * - o
- pv e - .o 4 ao gg s.
- l pr sb t y o ft
- 6 3 8 29 O il .t s p '
- f.
a
. s p
' s
- r c 3 im1 8' a. -
t eS
- * = -
l i c
- H n
- - O a .
. - - K c6
. - N 8 i? n" .
- o- tJ f
f 9
- s. - o1 s -
e ,
- cr
- ne
- ab
- Y d m -
9 a D +A1 ne f uc
- b e
- aD _
- nh
- ag
- H cu 3 - 3+r
- A aor
- yh
- l t
- h
- t y
- nl
+ A
- R ou -
- H MJ
_ - 5 n _
~9+i
- p 6
3
- t
- 3
- e
- r
- u
- N g o _ n+A i
- J F
I+ I ili + g+ Iiillelel1Ill+- I+1. IIII I+ lilll+Bl+liI:I+ o H n o , n o mw
)
t n i w n (
)
c 0 o o e, B M f 0 5 t o. v u u )O n M f 9 u S I n f t n s o H i s - n a S f j t pwHwI U mO o gg gwa gJm6z t a mHu t
i l i i i N N I e C. C. #. O. C. C. m. C.O. C.O. C.C.O. e #. 4. C. 0 0 0. C. O. O. O. C. C.C.C. o mC=CCCC CCCCCCC e N#CCCCN CCCCOCC C e M % o e O. m e. O. C. C. C.
. C.C. O.O. C.O.O. c ". m. N. O. O. C. C. O.O.O. O. O.C.C*
M w & ON*OCOO OOOOCOO @ N"*OCCC 0000000 cc ce - ~ O O< Cc wK % NU z ae m. =. &. C. C. O. M. C.O. C.O. O.C.O. c O. C. c. a. C. O. M. C.C.O. C.C.C.C. Q wc o ca-NCCN OCCOCCO o *C-NNC* CCOCCCO W O C2 - m-at = M .% < Q w & & , e e O. C. O. C. O. O. N. C.C.C.O.C. O.C. c N.O. C.N. C.C.N. C. C. O. C. C. O. O.
@ NCCCCCC CCCCCCO O Cf"*00" CCOCCCC C - -
c U g e N. C.C.C. O.O.C. C. O. C. O. C. O. C. e =. =. C. C. C. O. C. C. O. O. C. C. C. O. U o *McCOOC C"DCOCCC o M*CCCCC OCCCCCC O. =
- e Oc Z o.
- q. N a. m.N C.C.O.M
. . O. A. C. C. C. C. C. N M. N. m. C. o. *. *. C. O.O.C. C.O.N.
o N=@2CnN C*CCCCm D kGO"Ch> C O O O C C ** a e cAccooNN N o mos3@NN@ NC- N w - e %= %O Mi m m ww e m c. o. m. N. m. N.
. C. =. O. O. O. O. A. e O. N. O. N c. O. C.
. O. C. M . C. O. O. a RZ & ~OENCaC 0700C0= ? OC%AC
- w .47OC*
C D ~ 4%%@cch e b e k C G % *= lc 6 6 z Cc - < %. O 3 3
- u. . c *=. *. O. m C. N. A.
. C.m.m.A.C. O.m. c e. O. @. #. C. O. o. O. A. O. N. O. C. *'..
ar Z
- Cs *NP.m-O@ O 4 C N O O .= 0 =0N4CO4 OOOCOOM M< * #cNCCc4 -ceN = JOCENCC - a ea QC =
- c 4 CQ <w G P
= c %C.4%4CO 0400442 &
cs; z
. . . . . . c P. C. C. ?. C. N. C ". C. 7 0. P. 7. m .
UC w b ea co=%eNe 4ACCCNN
==CCNc%
Ac* o
.=
eO:NrO=. mec?cNN
=ccCNN*
@C@CMOC
<e 2 C C C e O. N. C. C. N . .a C. O. c. e. % C. N. C.
. c C. m. N. C. a e. m.
. O. C. m O. m
. . C. C.
7
- CP ** * > A c a e CCNNc4> m OCmeASC OCMOmCe C
- 4 % C S C C CC m: - a c e3 C o % ~ m C -
C C7 ~ ma N N m I'" e % e. s. . N o. m
. . c. %. O. O. . N. N. e c. N. C. e. g. e. e. N. o. . . e. . . s U..CN & NMacNm:.
== & - COCCCCO & Mmeemmm Ow: COCO V" L y ."- . a =W
- m e 4 C C. &. ~. 3. m. C. . N. &. c. N. C. *. *. c a. c. @. C. C. C. C. #.e.M N.O.N.e. g MO
- 7 N4NCC~4 CC=OOCO 3 cNm>.- cmc 00~O000 m
,= = = - - w -- z.
.G= vL.o c. 3
<> " = : L um -- e < .b. b. n. N. @. b. .' 0 3. b. N. N. m. e C. a. m. a. m. f. C. N. N e. @. @. N. O.
CC
<2 U
=- -
<=
@ M c
- Ch h C % CNm*CC=
.& cco. ccc O--eOcw g
[ E< 02 w U D W e e O w* c m. N. N #. N. N. O.
. %. m.N.c. m.N..a c N. O. c. c. N. .=
. c. c. N. e. c. c. p.%. y
*" O @44*@*2 NeQOMA# @ N@*@Nmg 4M = "N" =* - em --
- e.
- N C .= .= = s g
w .J 9 C E @ @
-< e @. @ . .@ e. C. N. m. M. N. N. N. % . N. M. . S. C. A. #. .m. e.C.N.N.A.C. C. $,
CO m N@@C@Cm Nmm>*NN e ecN"%%c c
,y
- t. -
- e e ONOQCcc a
C-MC 2 O g Ed TwCA=>6 333'4V00 ZJOL>>W ZJOkk>6 TJCAw>w 6 033*gCC =20 97<mw2<QOU
$* < 77<. G24 994Mv24 0:2.w000 C t,
- E E E 97<MO2< g w
w W M w U< >
> w w c W < < > >
0 W < < w
- a >. > h* > >
=. 5 - w a c~
C E z a
< a C c c 8 < = < < < e < u
- - < w w e w < w e U > E > > Q > C > a m
, V E Q g .
A $ W Q
- 4 3
w V C C 2 ;) w C g x ,O a u$
- e -.e e g
316
t other years; catches then decreased in 1986 at both stations (Tables 3.3.6-3,4). Rock crab catcher have generally been greatest in July or August, and since 1984 have been largest at the discharge station. General trends in annual and monthly catches are not consistent between stations, as evidenced by significant interactions in the two-way ANOVA results (Table 3.3.6-4). Total catch of rock crabs has been low rela-tive to catch of Jonah crabs at both stations. Low rock crab catch is perhaps due to the intra-specific competition between the two species of crabs (Richards et al. 1983). Also, rock crabs prefer sandy habitats compared to Jonah crabs (Bigford 1979; Jefferies 1966). Female crab distribution has also been monitored (Table 3.3.6-4). In 1985 and 1986 female Jonan crabs were most abundant at the discharge in September comprising 87.7% in 1985 and 95.6% in 1986 of the total catch. At Rye Ledge, they were also abundant in September 1985, (92.9%) and October 1986 (95.1%). Overall, as a percentage of total catch at both stations, female catch of Jonah crabs sas greater compared i to other years reflecting the general trend of greater catch from 1982 through 1986. Occurrences of female rock crabs were less defined than Jonah crabs due to the low overall catch of rock crabs. In 1985 and 1986, catches of female rock crabs were generally greatest in the fall, but some earlier months had greater percentages due to a low catch comprised of only female crabs (Table 3.3.6-4). Percentages of females in 1985 and 1986 were comparable to previous years' catch figures. Egg-bearing Jonah crabs were less abundant in 1985 and 1986 at both stations, occurrir ; mainly in June or July, generally averaging less than 1% of the total catch at both stations from 1982 to 1986. No ovigerous rock crabs were collected in 1985 or 1986 at either site, similar to findings from 1982 to 1984 (Table 3.3.6-4). In 1985 and 1986, width frequency distributions of male Jonah cr-bs were slightly larger thcn females, althougn ovigerous females were slightly larger than males in 1986 (NAI 1986, 1987). Due to low overall catch, trends in the size class distribution of rock crabs were less i i 317 J
apparent. Male rock crabs were generally larger than females (NAI 1987). Gear selectivity apparently influenced size distributions, since few small crabs were collected. 3.3.7 Mya arenaria (Soft-shell Clam) 3.3.7.1 Larvae Mya arenaria larvae occurred in the plankton from May through November from 1978 to 1986 (Figure 3.3.7-1). Each year, maximum abund-ances were recorded in late summer or early fall, while in many years (1978, 1979, 1980, 1984, 1986) a secondary peak also occurred in early summer. Maximum densities observed in 1985 (63 m' ) were the lowest encountered from 1978-1986. The lata-summer peak (4100 m' ) in 1986 was higher than 1984 or 1985, but much lower than those observed from 1978-1983. Late-summer peaks in 1985 and 1986 occurred from early to mid-September, similar to 1978-1982. Factors influencing the timing and magnitude of the observed pattern of larval abundance are not fully understood. /f. arenaria is known to spawn in the spring at temperatures greater than 4-6*C with summer spawning at 15-18'C (Brosseau 1978). Maximum larval abundances in August and September coincided with water temperatures in Hampton Harbor that regularly exceedM 15-18'C. However, these temperatures also occurred frequently in June and July, which were characterized by much lower larval abundances, suggesting that temperature is a minimum requirement for spawning. In addition, recruitment of larvae of non-local origin is likely due to currents in the Gulf of Maine, which may ) 1 move water masses and their entrained larvas significant distances i before larval settlement. The late-summer peaks hare been observed to be coincident with northward-flowing currents. This implies that these offshore larval peaks may in part have a more southern estuarine compo-nent. Overall, factors controlling the occurrence of A. arenaria lacvae i l 318
1978 1982 1979 1983
- = = c --; -- 2 _
1984 1985
- SCALE 1981 f 1986 r-100 e
-3 =
1000 m'3 8' ' s e a e i . , , , , MAY JUN JUL AUG SEPT OCT NOV MAY JUf! JUL AUG SEPT OCT NOV Figure 3.3.7-1. Square root projections of mean densities (m- ) of umboned H. arenaria veligers, sampled at Station P2, l')78-1986. Scabrook Baseline Report, 1986.
I off Hampton Harbor Beach are complex, the result of environmental and biological factors including: adult condition at the time of spawning, temperature at spawning sites, location of spawning sites relative to prevailing coastal currents, water column stratification and larval behavior. A comparison of larval densities at nearfield (P2) and far-field (P7) stations indicated similar patterns at the two stations, 1982-1984 and 1986 (Figure 3.3.7-2). Only Statior P2 was examined in l in85. In 1986, Hampton Harbor (P1) and discharge (PS) stations, added in July, were also similar to patterns at P2 and P7 (Figure 3.3.7-2). l l 3.3.7.2 Reproductive Patterns , Developing stages in the Mya reproductive cycle in the Hampton ! estuary appeared in March or early April during most years. Ripe 1 individuals were observed between the second week in April and the third week in June. In most years, ripe individuals occurred at similar times at both Hampton 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 appearance of larvae in offshore tows. Only in 1980 and 1981 was ; spawning detected before larval occurrence. The peak larval abundance always occurred well after spawning had commenced, indicatingo'oth Hampton Harbor and Plum Island Sound clams may contribute to the large nearshore 1erval densities of late summer (NAI 1985b). 320
l i 800o-
- m t
e
,ooo l '*):
I <
.+
! c, .
l= i ! l , I< l i8
. l 'i
' d,{
l ,
, i .
j 'I v , l I i
' i ,
lt {
! l l
}
t i f. 4 i ,c- \ Lj! f,, i I t 6 .
) :p l$
i
. ,ti t i, .
3, '1. , .. 1
> [0 :,\, j' ,I .l
, ' 'l\ ? t e
Y
' ' I' J MUb
k 8' IAAT JUN JUL AUG $3D 9003 to0C 7
i I j e ! ,
*: n f,1 ' i
- os, n i gl ij i 8 i j! l 1 , '!! l ll l I I P2 l
ll I. a ! .---- ... p7 Ai { i 3
,jll i l
!, ,, !, i,
'c. l I l I i ! l
' i i
ii t i f s I i ,3 , a ei i i
\I l
\'l s
f
,1 I 'i i i n i- (l ' . \.
toAY JVh JUL AUS SEP OCT inn. Figure 3.3.7-2. Log (x+1) densitien of Mya arenaria veligers at nearfield Station P2, discharge Station PS, farfield Station P7 and Hampton Harbor Station P1, 1982-1986a,b,
- a. Only Station P2 was examined for Mya veligers in 1985. .
- b. Stations PS and P1 were added in June 1986.
321
4 4 100.
- I 10 .
E i
~
O APR MAY JUN JUL AUG SEP OCT 1945 1000. 4
- [ -. p3
! yf!h\
"2 10 0 ]~
'ih\
e P$
---- - P 7 l
j ,
~
l \
\
I \
' flY g \
N . J \ I S ~
\
< l \ 1' l l
-\le t i f
- 'E I hi :
~
l l0 i I :3: ik lij
!\
1
^ E, I \\
\
\ I
~
l \ ,'\1\ ly\ l 'i \\ l I
\g, fl\g't ,
i nl l g;
\\\
y\ J !! \l 1'Y,1 p o . I f I} '/ \j (j i, APM MAy JUN JUL AUG SEP OCT 1966 Figure 3.3.7-2. (continued...) 322 I
. .~ . .
4 3.3.7.3 Hampton Harbor and Regional Population Studies Hampton Harbor Spatfall The soft-shell clam population has been studied through intensive surveys of spat and adults in Hampton Harbor (Appendix Table 3.3.7-1). These surveys have been supplemented by quantitative studies of regional spatfall in nearby estuaries, where settlement is known to occur. Over a 13-year perind,-the Hampton Harbor population has gone through substantial changes in structure. The Mya population structure 1984-1986 resembled that observed in 1974-1975, suggesting long-term trends based on the interaction of spatfall, and natural and human predation (Figure 3.3.7-3). The continuing decline in juvenile and adult (>25 mm) clam densities is partially the result of light spatfalls (1982-1986). The size distribution in 1974-1975 also indicated a decreasing juvenile and adult (>25 mm) population with an absence of any clams between 5-25 mm in 1974 and 1975 except for the young-of-the-year settlement (1-5 mm). In 1976, a large settlement occorred at all flats (Figure 3.3.7-4) which initiated changes in the population during the 1976-1982 period. The current trend of decreasing, low juvenile and adult densities is not likely to be reversed without a significant spatfall. The 1976 spat settlement was the Ir.rgest observed in the l study; however, other important settlements occurred in 1977, 1980, 1981 l and in 1984 (Figure 3.3.7-4). The 1976 recruitment was successful on all flats, while the spatfal) in 1980 and 1981 was most successful on r F1r 2 and in 1984 on Flat 4. In Hampton Harbor, the least-successful , recruitment years occurred in 1974, 1982, 1985 and 1986. l ,I i I 323 1
. isri ,. iere 7.. ..
! b i q i l l ll b
I l l b
...l l 11 NI . ...... i : : i u n..i n i-.: : .n i i...: r.........-
.:.. i .. .. *I .. . li .I. 4 I I!llilt i in.ni n .1 in. ---..t i . r...t....-.. ..... ...
7.. iere iere
,)
I .. .e m.w ll l ,l {,f kr 4, J / j ij ll g Aplf!, d i, m i W , jp
., . t_l l . .. . . .. Il .n.g... !!!ltijill{lf
} Il n nl Inn l} i i ..: . . . . . . . *) . - I . 5 IUH l n t . 1 l-. . . -.. . . . . - . . .. . . - . . . . . . .
,, iere
,. ie90 I
i
' d
'tr
... : ............... ... nu urunun s!!!;!!!!nfl!Iununnnn n i i n .. n i i n .._ .. . ........ i
] m!l l ie,.
i l ll ,1 .i lpl h l>L I n . { ; I l l l n!!,!!!iliidiinnnt Il u i t .... . ....... . .
.. i .............. . ...ilu!ElilE!!Ul!!!!S !!3!!!!Ut4!1Jmunnnn i...................-.......
Figure 3.3.7-3. Size class distribution of A*ga aver.aMa in Harnpton-Seabrook Harbor daring early fall, 1974-1986. Seabrook Baseline Report, 1986. 324
- .... o 0 .. l .0 ..I..Ni I
" ,; * * ' ' 7 "[ ' $'"ek '"" =
.: , lijn..r i .:. r.i.lnn.n111lIli.}.!Ill.i ill.}Illl.i.llin.nm.
. ... - inn.t i i
r , 1
... .Ilu.liilil!!!!i'I!)lIUi}I}}
[ !IIII!Illillunnnn.nn
. ---- -- in . ni 1.. .-........ ' ' ,-
'".""E'" .""
!r"u'"y'"':'"!!'"!!""!'"!""hII.II'I'.d".'!!".T"!P"""
i
.f .
l . l jj} . l l lI ..
... ... l didb i n.,
--a l' L I.lll. bl!!!!il inutne innt.. nr. : .i... ..
= =
I"'!" ' !:" !!"'!!'"T"!!"'!;"'!!".T"."",T"!""k"'!"".!
"!! ' ;; ; v' : .
Figure 3.3.7-3. (co: inued) 325
_. _ _ , . _ _ _ _ . - . _ _ _ . _ . _ _ _ _ _ _ _ _.m__ b J. 500- FLAT 2 500- FLAT 1 y soo. _ 'oo.
., So.
., 50 3 C
~ G * ~*
C so- Q s. f
+4 i i 9974 75 76 FF 78 79 80 89 R2 83 94 SS M 1975 76 FF FS 79 SO S1 32 83 84 95 06 De4R YEAR t
4 FLAT 4 ALL FLATS w
>J
, @ 500-SOO-
^
7 soo.
% soo-D b2 f M-E }
y so. a 80-S- b-
}
}
i I 1974 FS FS FF FS F9 SO Of 82 93 94 85 06 1974 75 F6 FF F8 Fe 20 St 82 S3 34 85 86 i YEAR YEAR i Figure 3.3.7-4 Means and 95% confidence limits of young-of-the-year Mya arenaria (1-Sam) at Hampton-Seabrook, 1975- 1986 Seabrook Baseline Report, 1936 4 1 i _ _ _ _ _ - - - - ~_ -, - . _ _ , . . . < _ . . . . _ _ _ = . _ _ _ _ _ . _ _ _ _ _ _ _
s Regional Spatfall The regional spatfall study verified that the large 1976 recruitment occurred throughout the region (Figure 3.3.7-5). The 1982 year class was larger at Plum Island Sound than at the Hampton Harbor Flats 2 and 4. Overall, 1983 had the lowest abundance of spat in the regional study. In 1986 spatfall was significantly higher at Flat 2 than at Plum Island Sound (Paired t-test, P < 0.05). No significant differences were found between Flat 4 and Flat 2 or Plum Island Sound. Yearling and Adult Clems Yearling clams (10-12 mm) became numerous in 1977 following the 1976 spatfall and began showing a decline in 1981 at Flat I and 1982 at Flat 2 and Flat 4 (Figure 3.3.7-3). Juveniles (26-50 mm) age two to four years old, were relatively scarce from 1976 to 1978, but became abundant from 1979 to 1981 at all three flats. This pattern reflects the growth of the large sets of 1976 and 1977. The large spat sets of 1980 and 1981 did not result in increased densities of juveniles. High I adult densities (>50 mm) were recorded in 1980 and have declined from 1983 through 1986 (Figures 3,3.7-6, 3.3.7-7 and 3.3.7-8). The 1980-1982 densities reflected the success of the 1976 and 1977 year classes; subsequent decline resulted from the harvesting of these clams (see 1 below) and the failure to recruit the spatfalls of 1980, 1981 and 1984 into the juvenile and adult size clams. In order to better understand the patterns of population structure, growth and survivorship of the one-year and older c1.ims, the size-class density distributions were separated into year classes ) utilizing NORMSEP (Hasselblad 1966). This method attempts to fit normal distribution curves to complex frequency dietributions so that the mean j and standard deviation of each cohort can be estimated. A Chi Square ! test was also performed to test the difference between actual and pre-2 327
PLUM IS_AND SOUND (IPSWICH) MA. HAMPTON HAR80R FLAT 2 1000 . _ 1000 - 7 7
% w . .
v 100 - ~~ T 1 + v
>- 100 -
t - - - -
-- 2 ~ ~
s . - N - . . . . . E h 5 10 - 10 - 3 I I I I I I I I I I I I I I I I l l 1 1 1 1976 77 78 79 80 81 82 83 84 85 86 1976 77 78 79 80 81 82 83 84 85 86 HAMPTON HARSOR FLAT 4 M c _ 1000- + 7
>- 100- - - - -
g . . . . - - 8 10- - - I I a i s s : i 1976 77 78 79 80 81 82 83 84 85 86 Figure 3.3.7-5. Mean and 95% confidence limits of If. amnaria spat (shell length 512mm) densities (ft-2) at two Northern New England estuaries, 1976 through 1984 and 1986. Seabrook naseline Report, 1986.
FLAT 1 100 - SPAT (13-25m) N
'a b , ..
D 10 - j .. t . . . . ~ I i i i i i i i i i l 1976 77 78 79 80 81 82 83 84 85 86 100 - N y .. D __ JUVENILE (Shell length 26-50m) D 10 - c .. g ..
+ +
I I I i e i i i l I i 1976 77 78 79 80 81 82 83 84 85 86 l 100 - i m
~
$ 10 -
x ADULT (Shell length >50mm) 2 c 8 6-l l l
+ + +
A 4 1 4 i i e i i 6 i i i 1976 77 78 79 80 81 82 83 84 85 86 Figure 3.3.7-6. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 1, Hampton-Seabrook Harbor, 1076 through 1986. Seabrook Baseline Report, 1980, 329
10< 5- SPAT (SHELL LENGTH 13-25 m) 1-
~ ~
19i4 f5 7'6 i' 78 79 80 il 82 8'3 84 85 8'6 10- [ 5- JUVENILE (SHELL LENGTH 26-50 m) C h ..
$ 1-g ..
u y
- 1 = - = =
1974 75 76 77 78 79 80 81 82 83 84 85 86
- 1 1
10-5- ADULT (SHELL LENGTH > 50 m) 1
.. ..-. -- f 1974 75 76 77 78 7i 8'O 81 82 S'3 64 85 8'6 )
i l l Figure 3.3.7-7. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 2 Hampton-Seabrook Farbor, 1974 through 1986. Seabrook Baseline Report, 1986. 330
FLAT 4 100 -
- SPAT (13-25mm) g x ..
d 10 - .. E .. S .. 1 4 4 i i i i i i i i 6-1976 77 78 79 80 81 82 83 84 85 86 100 - N
'u 5 "
3 10 - } .
. JUVENILE (Shell length 26-50.~0
'G
$ l
. + t 4 i i i i i i 6 e l' i 1976 77 78 79 80 81 82 83 84 85 86 10 -
^
m ADULT (Shell length >50mm) D , l
'O 5~
k
.. \
Y
+
4 a e i 6 4 1 6 i l l 1976 77 78 79 80 81 82 83 84 85 86 l Figure 3.3.7-8. Means and 95% confidence limits of spat, juvenile and adult densities at Flat 4, Hampton-Seabrook Harbor, 1976 through 1986. Seabrook Baseline Report, 1986. 331
-m - - - - - ,n - -, , - -,-,,---,--.-,a -
dicted 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 class in 1985 and 1986 did not warrant a NORMSEP
- analysis for those years. f
; The 1976 year class (Figure 3.3.7-3) was most easily traceable * ' as few juvenile and adult class existed when it entered the population.
By November 1976, the class 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 success-fully, i An examination of survivorship from the NORMSEP analysis of l size density data, indicated that the 1960 to 1982 year classes experi- l enced far greater mortality during the first two years than was observed for the 1976 year class. The higher mortality for year classes 1980 through 1985 corresponded to an increase in density of its main pred- ] ator, the green crab, during this period. Each year class, 1982-1985, ; appears to have been virtually eliminated by its second year (Figure 3.3.7-3). 1 Predation and Earvestable Clam Resources Clams in Hampton Harbor art subject to predatior. pressure from two major sources: green crab consumption of spat (1-25 mm) and juve-nile (26-50 mm) Mya, and humans who dig adult Mya (>50 mm) but also cause mortality to smaller clams by disturbing the flat. A possible third major predator is the seagull, which is commonly observed picking over clamdigger excavations for edible invertebrates, including spat and , juvenile clams. Green crabs (Carefnus maanas) are a major predator of Mya, with clams being a major source of food particularly in the fall 332
months (Ropes 1969). Green crab catches in Hampton Harbor have shown a substantial increase in abundance aince 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 fluctu-ating between 69.4 (1985) and 123.9 (1984) CPUE (catch per unit effort). ; Green crabs generally feed more actively at temperatures above 9'C, and females are more active predators on #pa than males (Ropes 1969). The presence of more females in the catch in Hampton Harbor from July through September (1981-1986) indicated greater predation pressure for the newly-settled spat in the estuary. Continued high catches of males and females occurred until late November or December when tempera-tures declined below 7'C and activity decreased. Welch (1969) and Dow (1972) have shown that steen crab abund-ances increased markedly when winter temperatures were warmer. Green crab CPUE by season 1978-1986, showed an increase from fall of 1980 through 1984. The increase in green crab abundance corresponded to elevated winter minimum temperatures observed from 1981-1984 (Figure L 3.3.7-9); a significant correlation (a = 0.05) was obtained between fall abundances (time of peak activity), 1980-1986, and the previous winter minimum temperature. Close examination of the yearly data indicated the type of response proposed by Welch (1969). Following the winter of 1979-1980 when the temperature minimum was high, the fall crab popula-l tion showed a marked increase (Figure 3.3.7-8). 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 summer-fall of 1981 followed by a moderate increase in summer-fall 1982. Higher minimum winter temperatures in 1983, 1984 and 1986 were associated with a marked rise in fall green crab catches. I i
1 l a TABLE 3.3.7-1. AVERAGE CATCH PER UNIT EFFORT , SEX RATIO. 4 ND PERCENT I GRAVID FEMALES FOR CARCINUS /fAENAS COLLECTED AT ESTUARINE STATIONS fro?' 1977-1986. f>EABR00R BASELINE l REPORT, 1986. AVERAGE FECUNDITY SAMPLE CATCH PER SEX RATIO (*. GRAVID YEAR PERIOD UNIT EFFORT (M:F) FEMALES) 1977 Oct-Dec 17.5 1:0.9 0.3 1978 Jan-Mar 0.1 Females only 0.0 Apr-Jun 7.5 1:3.3 7.0 Jul-Sep 6.6 1:1.5 3.2 Oct-Dec 7.2 1:1.3 0.5 1979 Jan-Mar 0.7 1:1.7 0.0 Apr-Jun 6.4 1:1.0 6.0 Jul-Sep 6.0 1:1.5 0.6 Oct -De c 02.1 1:1.5 0.0 1980 Apr Jun 6.7 1:1.1 8.4 Jul-Sep 15.6 1:1.0 2.3 Oct-Dec 53.1 1:;.0 0.0 l 1981 Apr-Jun 39.5 1:1.5 a.6 I Jul-Sep 34.0 1:2.1 1.6 Oct-Dec 39.4 1:1.0 0.0 ; 1980 Apr-Jun 37.4 1:1.6 4.1 i Jul-Sep 44.6 1:4.0 0.8 1 Oct-Dec 56.1 1:2.0 0.0 l 19ES Apr-Jur 47.5 1:1.6 3.7 l Jul-Sep 61.E 1:2.0 1.0 Oct-Dec 117.4 1:1,6 <0.1 1984 Apr Jun 64.7 1:1.0 2.4 i Jul-Sep 80.6 1:0.7 1.2 Oct Pet 102.9 1:1.4 0.0 1985 Apr-Jun SE.3 1:1.3 3.9 Jul-Sep 54.5 1: .: 1.0 Oct-Dec 69.3 1:1.4 0.0 1966 Apr-Jun $2.6 1:2.5 6.6 Jul-Sep 53.5 1:2.E 0.7 Oct-Dec 113.5 1:1.3 <0.4 a Nu=ber cf C. caenas per trap per day, eigh: "box" traps fishing fer 2e hours, twice per month. b Traps se: in January, February, and March in 1976 aad 1979 only. 334
'd 2.5 y
,x 2.0 hy MINIMUM WINTER ,- 'N -
1.5 3g TEMPERATURE ,M' 'N - 1.0 0#-*
'_x 5k x,s 0.5
, ,,,____x' -
0.0
- -0.5 -
no-C i2. - E iso - 0 S so. -
$ so - GREEN CRAB _
; b w
.o - CATCH i g to -
! 5: 4,o - - l so - _.
- o". 40 - -
l 6 ao - l
< 20 -
1
'* io - /
! o FlB, Ei i n F2 i i i i i R M i i i . . . . . . . . i i i i i i i . i i i i - i i i i 1 s su r s su e s su a s su a s su r s su a s su y s su r s su 0 l l 1978 1979 1980 1981 1982 1983 1984 1985 1986 ( 'l
'Figu re 3. 3. 7 -9. Seasonal mean catch per unit effort for green crabs (Carcinus maenas)
' in llampton-Seabrook liarbor and its relationship to minimum winter temperature, 1978-1986. Seabrook Baseline Repoet, 1986. I i _ _ _ _ _ _ _ _ _
The increase in green crab CPUE, and associated predation in the years 1980-1986 can be observed in examination of the 1981-1986 Mya year classes, as estimated by densities of young-of-the-year clams (Figure 3.3.7-4). The 1981 year class, which was relatively large,
- showed decreased survivorship and substantially-reduced first and second year clams (Figure 3.3.7-3). In 1982, settlement was the poorest since 1974 (Figure 3.3.7-4) and the subsequent mortality, probably related to
! green crab predation, has virtually eliminsted this year class (Figure t 3.3.7-3). Recruitment into Hampton Harbor clam populations, 1983-1986, , l has been insignificant, corresponding to high green crab abundances and low spat recruitment. l l 1 Welch and Churchill (1983) reported the increase in near-surface temperature at Boothbay Harbor, Maine, in the early 1970's along with an increase in greer crab abundance. Although no green crab or temperature data are available for Hampton Harbor for this time period, catches from Kittery, Maine, showed a maximum crab occurrence (1973-1975) corresponding to the reduction in younger year classes observed in Hampton Harbor prior to the 1976 settlement. Subsequent reductions in the reported sea surface temperature and related decreases in green crab abundance and predation along the southern Maine coast (Welch and Churchill 1983) may have also occurred in Hampton Harbor, which may have contributed to the survivorship of the strong 1976 and 1977 year class era. Recreational clam digging on the Hampton Harbor flats is the most significant source of nortality for clams of '45 mm, but also is a sourco of mortality to spat and juvenile clams due to disturbance. Census figures indicate digging activity tripled from 1980 to 1981 (Tatle 3.3.7-2). This level of effort was maintained through 1982 before undergr>1ng successive reductions 1983-1985. Digging activity famreased slightly in 1986 over 1985 levels, but remained lower than in previous yr.ars, 1982-1984 336
TABLE 3.3.7-2. ESTIMATED DISTRIBUTION (*. OF TOTAL) 0F CLAM DIGGERS BY FLAT AT HAMPTON HARBOR, SPRING 1980 THROUGH FALL 1986. SEABROOK BASELINE REPORT, 1986. a b ESTIMATED ESTIMATED TOTAL hu!BER OF DIGGER BUSHELS SEASON FLATS TRIPS HARVESTED 1 2 3 4 5 Spring" 1980 12.5 17.9 1.7 52.5 15.4 3,8t0 1,200 d 2,700* 840 Fali 1980 11.3 18.4 3.3 55.1 11.8 Spring 1981 9.7 15.6 0.8 65.9 7.9 12,500 3,900 Fall 1981 I 13.9 12.9 0.2 63.8 9.1 7.060 2,200 i l Spring 1982 12.6 13.0 0.8 67.1 6.4 10,800 3,400 Fall 1932 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 34.7 0.7 6,090 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 l 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 1 Spring 1986 59.3 6.4 0.3 33.4 0.6 6,210 1,941 ' Fall 1986 58.1 6.4 0.4 34.7 0.4 4,713 1,473
- Based primarily on Friday head counts at time of low slack water; most Saturday counts are assumed from observed Fri: Sat ratio (n=14 pairs) of 2.24 i .96; j seasonal totals have approximate error of f 18'4 l 1
Assumes each clammer takes 10 quarts per trip; 1 bushel = 32 quarts or 3.2 clammer trips "Includes the period 1 January through weekend before Memorial Day d Includes the weekend after Labor Day through 31 December
- Based on average Spring: Fall ratio for 1981 and 1982 (0.68 1 02) 1 337
I 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 one to two years illustrating a typical predator-prey cycle. Diggers shifted some of their activity in late 1983 and l 1984 from Flat 4 to Flat 2 (Table 3.3.7-2), probably in response to l declining resources overall, and particularly at the most accessible area, Flat 4. As clam densities continued to sharply decline in 1985 and 1986 digger activity again shifted, from Flat 2 and Flat 4 to Flat 1, possibly due to slightly graater densities at Flat 1. 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 (5") resulted in the lowest survival. Clams 9-20 mm suffered the greatest mortality (51%) with ; 36-50 mm clams having only 31.5% mortality. No data has been collected on the amount of disturbance caused by digging on the Hampton Harbor flats; hcwever, Flat 1 and Flat 4, with the highest usage by clammers, would likely have suffered substantial mortality to young clams due to digging. i Sarcomatous neoplasia, a lethal form of cancer in Mya arenaria, has been observed in Hampton Harbor Mya populations (Hillman 1986, 1987). A virus, similar to the B-type retroviruses, is known to initiate the disease in Mya (0prandy et al. 1981). The rate of infection may also be enhanced by pollution-mediated deterioration of the environment (Reinisch et al. 1984). The infection rate in some Mya populations may reach 100 percent with 100 percent mortality of infected i clams (Farley et al. 1986). The incidence of sarcomatous neoplasms in Hampton Harbor Mya populations was observed in October 1986 and February 1987 (Hillman 1986, 1987). Neoplastic infections were more prevalant in February, reaching 6% at Flat 1 and 27% at Flat 2. Infections were absent from Flat 4. Assuming 100 percent mortality of infected clams 338
l l 14 - 13 - \ p\
/
12 - \
\
lg\
\ /
/ \
11 -
\ / \
\ /
/ \
, g f \
E \ t \ / \
\
h 10 ' \ s' \ \ 8 i\ i
'/ \
9- s E ~
\\ /\ I \
e g- s
/g i 1 i
/ g ;
M \ / \ i E 7- \ ,' \ g t b s. t g I t 5 \ l s s- \' l i $ I \ m
, I \
\ j s
\ ; \
\
3" \ #
\ # \
\
2- \
\ '
\ ,
. ~~~,_,'
1971 72 73 74 75 76 77 78 79 80 81 82 E3 84 85 SE YEAR ADULT CLAM LICENSES
- - - - - - ADULT CLAM STANDING CROP Figure 3.3.7-10. Number of adult clam licenses issued and the adult clam standing crop (bushels), Hampton Harbor, 1971-1986. Seabrook Baseline i' Report, 1986.
339
percent mortality of infected clams (Farley et al. 1986), Flats 1 and 2 may suffer significant disease-related reductions in clam production. However, since no historical data is available on the incidence of neoplasms in Hampton Harbor clam population, it is not known if current infection rates are typical or indictative of an increasing trend. Harvestable Clams The patterns discussed above have resulted in substantial changes in the number of harvestable clams on the Hampton flats (Table 3.3.7-3). The greatest adult standing stock in Hampton Harbor was reported by Ayer (1968) for 1967. Subsequent years indicated a gradual decline in available adult clams to a low of six bushels / acre in 1978. In 1976, the State of New Hampshire applied more stringent clamming regulations, closing the flats for the summer (Memorial Day to Labor Day) and eliminating digging on Sundays and holidays. Survival of the 1976 year class made a substantial increase in the standing crop in 1980, four years after settlement. The number of harvestable clams continued to increase in 1981 as more of the 1976 and part of the 1977 year class became harvestable. Through 1984, the number of harvestable bushels had not decreased substantially. However, in 1985 and 1986, the harvestable standing crop dropped precipitously (Table 3.3.7-3), reflecting poor recruitment observed in 1980-1983, increased predation by green crabs, and continued human disturbance. Since recruitment has remained low through 1986, the trend of decreasing standing crop will likely continue for at least another three to four years, assuming a successful spatfall in 1987. The distribution of clams by flat has changed since 1980 when the 1976 year class became harvestable (Tables 3.3.7-2, 3.3.7-4). Flat 1 showed a continuous increase in its percentage of adult clams through 340
l l TABLE 3.3.7-3. SUM!1ARY OF STANDING CR0P ESTI?!ATES OF ADULT
- NYA ARENARIA IN HA!!PTON RARBOR.1967 THROUGH 1986. SEABROOK BASELINE REPORT, 1986.
ESTI}!ATED nut!BER TOTAL OF BUSHELS ESTIt!ATED NUr!BER DATE PER ACRE OF BUSHELS b b November 1967 152 23,400 July 1969 103 15,840 3 November 1971 94 13,020 , 56 8,920 I l November 1972 i' November 1973 41 6.310 November 1974 56 E,690 i . November 1975 29 4,945 l November 1976 11 1,350 l ! November 1977 6 1,060 November 1978 I 6 940 i ! Nove=ber 1979 9 1,400 October 1980 54 8,890 October 1961 75 12,400 October 1982 55 9,200 October 1983 78 13,020 October 1984 Se 8,821 November 1965 39 4,615 October 1986 23 2,793
- shell length >50 cm b
free Ayer (1965) 341
TABLE 3.3.7-4. DISTRIBUTION (*. OF TOTAL STANDING CR0P) 0F HARVESTABLE CLAHS BY TLAT AT HAMPTON HARBOR, 1979 THROUGH 1986. SEABROOK BASELINE REPORT, 1936. YEAR FLATS 1 2 3 4 5 1979 33.3 6.2 2.2 55.7 0.5 1980 45.1 10.5 1.0 39.5 3.9 1981 53.0 7.3 1.5 34.4 3.7 1982 52.2 7.0 1.0 38.4 1.3 1983 62.9 25.6 0.5 10.5 0.5 1984 72.0 13.6 1.9 11.5 0.9 1985 60.2 14.6 SS 25.1 SS 1986 63.0 21.9 NS 15.1 SS 2 342 w - - - - - - ,_e -
-, ,e- --
1984, while Flat 4 showed a steady decrease. Flat 4 has been subject to the greatest digging pressure, 1980-1984, because of its accessibility. In 1985 and 1986 the percentage of harvestable class decreased on Flat 1 i and increased on Flat 4, reflecting the shif t in digging activity from Flat 2 and Flat 4 to Flat 1 (Tables 3.3.7-2, 3.3.7-4). The percentage of total standing crop at Flat 2 has increased in relation to Flat 1 and Flat 4, reflecting lighter digging pressure rather than successful recruitment at Flat 2 (Figures 3.3.7-6, 3.3.7-7, 3.3.7-8, Tables 3.3.7-2, 3.3.7-4). L 1 i l 7 l l l l ! l I l l l 1 i
- 343
4 i mmni
- .i SALINITY ~
. .- . . . t
. ! l !/;N l l l.
' *N '
a . . .- 5
. . , i 4
a . . , , I n .
.I. - - - .. - . - --
Jaa F... Sua m. Jge JUL AU. F .f. .U. C m
- 5. 6. (TC. = LAST DIGIT OF SAMPLE YEA).
. re r TEMPERATURE *-e AU, YEAR'$t8EAN u.. I i . . l
"'l ,
/
i.. { 4 u.. l ; i i . j ' I . t l .
. . t l ; Appendix Figure 3.3.1-1. Mean monthly salinity (ppt) and temperature (*c) in J Brown's River at high tide from 1978-1986. Seabrook i Baseline Report, 1986, 1 344 ;
i 1 SALINITY
""'" l .
n .. s n . . e i
*
- L. ! -;
; !/. .
" ,. . . ! ! . ./; ! ! .
'\ . ! .
, N. ,.
1 l
' . . . . . . . . . ~ . . . .+ . - - . ~ ~ . . + -
a re. m am m Jus a ate .r. ett n tre
- 5. 6. ETC. . LAST 0131T OF
!" ! TEMPERATURE i .
, - . Au Yews PEAN
- i. .
. l[
- i. .
. i
- i. . . .
. i
..}}