ML20101A629
| ML20101A629 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 12/31/1990 |
| From: | NORMANDEAU ASSOCIATES, INC. |
| To: | |
| Shared Package | |
| ML20101A628 | List: |
| References | |
| NUDOCS 9204290272 | |
| Download: ML20101A629 (507) | |
Text
{{#Wiki_filter:_ _ _ _ _ _ _ _ _ _ - _ _ _ - FEABROOK ENVIRONNENTAL STUDIES, 1990 A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS IN THE HAMPTON-SEABROOK AREA DURING THE 0? ERAT 10N OF SEABROOK STATION TECHNICAI. REPORT XXII-II a Preparnd for a PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE NEW HAMPSHIRE YANKEE DIVISION P.O. Box 100 Seabrook Station Seabrook, New Hampshire Prepared by NORMANDEAU ASSOCIATES INC. 25 Nashua Road Bedford, New Hampshire 03110-5500 R-12341.03 November 1991 i 9204290272 920419 ' PDR ADOCK 05000443 R PDn j
. .. .. - - . ~ .- . ~. .
TABIE OF CONTENTS PAGE 7 1.0 EXECUTIVE
SUMMARY
. . . , . . . . . . .. , . . . . . . . . 1 1.1 -INTRODUCTION
. . . . . . . . . . . . . .. . . . . . 1 !
1.2 INTAKE MONITORING . . . . . . . . . . . . . . . . . . . . . 2 , 1.3 DISCHARGE-MONITORING . . .. . . . .. . . ... . . . 4 , L 1.'3.1 Discharge Plume Monitoring . . . . . . . . . . . 41 < 1.3.2 Benthic Monitoring . . . . . . . . . . . .. . . . 7 1.3.3 Estuarine Monitoring . . . . . . . . . . . .. . . .3
~2.0. DISCUSSION . . . . . . . . . . . . . . . .. . . . . . .. 11
2.1 INTRODUCTION
-. . . . . . . . . . . . . . . . . . . . . . 11
'~"
2.1.1- General Perspective .. . . . . . . . . .. . . . 2.1.2 -Sources of' Baseline Variability . . . . . . . . . 13 - [ 2.1.3 LImpact Assessment . . . . .,. . . . . . . . . . 16 ,
- 2.~ 1. 4 Sampling Location. , . . . . . . . . . . . .. . 18 .
2.2= INTAKE AREA MONITORING
. . . . . . . . . . . ., . . . 27 2.2.3 Plankton . . . . . . . . . . . . . . . .. . . . . 27 ' +
t 2.2.1.1 Entrainment. . . . .. . , . . . ., . . 27
~ 2. 2.1.2 - Community Structure . . . . . . . .. . . 33~ $
2.2.1.3 ' Selected Species . . . .. . . . . . . . 41 2.2.2'Finf1hh . _ . . . .. . . . . . . . . . . . . . . . . 46 , 2.2.2.1 -Impingement . . . . . . . . . . . . . . . 46-2.-2,2.2 Pelagic Species . . . . . . . . . ., . . 50 2.2.2.3 LDemersal Species . . . . . . . . . .. . 55 2.3 DISCHARGE AREA MONITORING , . . .. . . . . . . . . . . 58 12.3.1 Plume Studies. . . . . . . . . ., . . ... . . 58 2.3.1.1 Discharge-Plumo Zone -
. . . . . . . . . . 15 8
'2.3.1'.2L Intertidal / Shallow Subtidal Zone . . . . 71
- 2. 3 =.1. 3 Estuarine Zone . . . . . . . . . . . 80 K
fit
r: r PAGE 2.3.2 Benthic Horitoring . . . . . . . . . . . . . . . . 91 2.3.2.1 Macroalgae and Macrofauna . . . . . . . . 91 2.3.2.2 Demersal Fish . . . . . . . . . . . . . 95 2.3.2.3 Epibenthic Crustacea . . . . . . . . . 100
- 3.0 RESULTS . . . . . . . . , . . . . . . . . . . . . . . . . . . 103 3.1 PLANKTON AND WATER QUALITY PARAMETE3S . . . . . . . . . . 103 -
3.1.1 Water Quality Parameters-Seasonal Cycles and Trends . . . . . . . . . . . . . . . . . . . . 103 3 1.2 Phytoplankton . . . . . . . . . . . . . . . . . 114 3.1.2.1 Total Community . . . . . . . . . . . . 114 3.1.2.2 Selected Species . . . . . . . . . . 128' 3.1.3 Microzooplankton . . . . . . . . . . . . . . . 136 3.1.3.1 Total Community . . . .. . . . . . . . . 136
.3.1.3.2 Selected Species . . . . . . . . . . . . 142 3.3 4 Bivcive Larvae . . . . . . . , , , . . . . . . . . 155 3.1.4.1 Community Structure . . . . . . . . . . . 155 3.1.4.2 Selected Species . . . . . . . . . . . 163 3.1.5 Macrozooplankton . . . . . . . . . . . . . . . . . 167 3.1.5.1 Community Structure . . . . . . . . . . ~167 3.1.5.2 Selected Species . . . . . . . . . . . . 182 3.2 FINFISH . . . . . . . . . . . . . . . . . . . . . . . 191 3.2.1 Ichthyoplankton . . . . . . . , . . . . . . . . . 191 3.2.1.1 Co.nmunity . . . . . . . . . . . . . . 191 3.2.1.2 Entrainment . . . . . . . . . . . . . . 208
- , 3. 2.1. 3 Selected Species . . . . , . . . . . . 210 3.2.2. Adult Finfish . . . . . . . . 227 3.2.2.1 Community . . . . . . . . . . . . . . . . 227 + 3.2.2.2 Impingement . . . . . . . . . . . . . . . -248 3.2.2.3 Selected Species . . . . . . . . . . . 250 i. 1 t 17 4 94 q -
. . . . .. _ =. _ . . . ~ _ .
=
- I PAbi !
.- 3.3 BENTH0S . . . . . . . . . . . . . . . . . . . . . . . . . '278
- 3. 3.1' ' Estuarine Benthos . . . . . , . . . . . . . . . . 278 3.3.1.1 Physical Environment . . . . . . . . . . 278 3.3.1.2 Macrofauna . . . . . . . . . . . . . . . 2B4 3.3.2 Marine Macroalgae . . . . . . . . . . . . . . . 298 3.3.2.1 Macroalgal Community . . . . . . . . . . 298 3.3.2.2 Selected Species . . . . . . . . . . . 321 3.3.3 -Marine Macrofauna' . . . . . . . . . . . . . . 323 3.3.3.1 Horizontal Ledge Communities (Destructive Monitoring Program) . . . . . . . . . . . 323 3.3.3.2 -Intertidal Communities (Non-destructive Monitoring Program) . . . . . . . . . . . 342 3.3.3.3 Subtidal Fouling Community (Bottom Panel ~
-Program) . . . . . . . . . . . . . . . . 346 3.3.3.4' Modfolus codlolus Communities (Subtidal Transect Program) . . . . . . . 348 3.3.4 Surface Fouling Panels'. . . . . . . . . . . . . . 349 p
3.3.4,1 Seasonal Settlement Patterns . . . . . . 351 3.3.4.2 Patterns of Community Development . . . . 369 3.3.5 " Selected Benthic Species , . . . . . . . . . . 380 3.3.3.1 ' Myt111dae . . . . . . . . . . . . . . . 380 3.3.5.2 Nucella lapillus . . . . . . . . . . , 388 ? 3.3.5.3 Asteriidao . . . . . . . . . . . . . . . 388 3.3.5.4 fontogeneia inerais . . . . . . . . . . . 390 3.3.5.5 Jessa marmorata . . . . . . . . . . . . . 391 -
--3.3.S.6 Ampithoe rubricata . . . . . . . , . .
_392
- 3. 3. 5 '. 7 Strongylacentrotus droebachlensis . . . . 393 3.3.6 .Epibenthic Crustacea . . . . . . . . . . . . . . . 394 .
. 3.3.6.1 .American Lobsters (Somarus americanus) . 394' 3.3.6.2. Jonah Crab (Cancer bores 1/s) and-Rock-Crab-(Cancer 1rroratus) . . . . . . 409
- 3. 3. 7. Nya arenaria (Soft'-shell Clam) . . . . . . . . . 415 L
3.3.7.1 Larvae . . . . . . . . . . . . . . . . 415 3;3.7.2 Reproductive Patterns . . . . . . . . . 418' y
, n ~- n - e m- s - - u, , p.,n -rw s- %
a w s y
i- . PAGE 3.3.7.31 Hampton Harbor and Regional Population Studies . . . . . . . . . . . 418 " 3.3.7.4 Effects of Predation, Perturbation and Disease on Harvestable Clam Resources . . 427
! 3.3.7.5 Harvestable Clams . . . . . . . . . . . . 436
'4. 0 _ METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 4.1 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . 449 4.2 COMMUNITY STRUCTURE . . . . . . . . . . . . . . . . . . 451 L
4.2.1 Numerical Classification . . . . . . .
. . . . . . 451
! 4.2.2 Multivariate Analysis of Variance . . . . . . . . 455 L' 4.2.3 -Other Community Methods . . . . . . . . . . . . . 456 g 4.? SELECTED SPECIES / PARAMETERS . . . . . . . . . . . . . . . 457 4.3.1 Analysis of Variancs (ANOVA) . . . . . . . . . . . 458 4.3.2- Multiple Comparisons . . . . . . . . . . . . . . 466
=5.0 LITERATURE' CITED . . . . . . . . . . . . . . . . . . . . . . 469
[3 !i l.- [
+
vi I - , --w - -..
< s +e
I k LIST OF FIGURES PAGE ; l
-2.1-1. Schematic of tources and levels of variability in Seabrook ll Environmental Studies . ., . . . . . . . . . . . . . . . 14- )
2,1-2. Sequence of events for determining if there are environ- l mental changes due to the operation of Seabrook Station . 19 l l . -2,1-3. Plankton and water quality sampling stations . . . . . . . 2e p 2.1-4 Finfish samp1'ing stations' . . . . . . . . . . . . . . . . 21 l 2.1-5. Benthic marine sampling st ations . . . . . . . . . 23 2.1-6. Hampton-Seabrook estuary temperature / salinity , sof t-shell
-clam Mya arenaria and green crab Carcinus caenas uampling
-stations . . . . . . . . . . . . . . . . . . . . . . . 24 12.1
- 7. - Locations of lobster and rock crab trapping areas . . . . 25 2.1-8. Sampling sites for Nya arenarla spat , , . . . . . . . . -26 i .
; Months of occurrence and log (x+1) neau abundance (no./m3 )
[ :2.2.1. in preoperational years and 1990 for seasonal groups formed by numerical classification of the microzooplerkton , and bivalvo larvae collections . . . . . . . . . . . . . 34 2.2-2. Months of occurrance and dog-(x+1) mean abundance,(no./
/0003 ) in preoperational years and 1990 for_ seasonal groups formed. by numerical l tlassification of- the holo-and- meroplar.kton and tychoplankton species 'of ~ macro- -
zooplankton collections . . . . . . . . .. , . . . . . 35 , 2 .' 2 -3 . - Mcsths of occurrence and log (x+1) mean ' abundance (no./- 3 1000 m ) in preoperational years and 1990- for seasonal
- groups formed-by numerical classification fof 'finfist eggscand larvae . . . . . . . . . . . . . . . . . . . . . 36 {
2.2-4. Mean' log (x+1) abandance and 95% confidence interval, and percent composition for selected species of phytoplankton (thousands of celln/ liter) and microzooplankton (no./m ) 3 at Station'P2, 1978-1984 and-1990 '. . . . . . . . . . . . - 43-
-2.2-5. Mean log (x+1) abundance and 95% confidence interval, and i- - percent: composition for selected species of bivalve larvae (no./m 3) and macrozooplankton (no./1000 m ),3 - 1978-1989 and -
~
a 1990 at Station P2 . . . . . . . . . . . . . . . . . . . . -44 vil d
l l V PAGE 2.2-6. Mean log (xtl) abundance (no./1000 m i) nnd 95% confidence interval, and percent composition for nelectad species of flah larvae 1975-1989 and 1990 at Station P2 . . . . . . 47 2.2-7. Flow ratt (million gallons per day) of circulating water system and impingement o1 finfish during 1990 . . . . . . 49 2.2-8. Seasonal and annua. changes in composition and abandance of the pelagic fish community, based on esteh per unit effort averagad over gill wat Stations 1, G2, and G3, ~
'976-1989 and 1990
. . . . . . . . . . . . 51 2.2-9. Mean log (xvi) abundence (catch par unit effort) and Sit confidence intervals, and percent cog os? tion fo. 3 elected species of finh, 1978 1989 and 1990 . . . . . . . 54 2.3-1. Monthly mean surf ace and bottora temperatures at nearfic1d i Station P2, and 95% con 51dence intervals dortag troopera-tional peciod and in 1990, and maan monthly surf ace ten.-
perature r2 intake, discharge, und farfield stations . . 59 , 2.3-2. Preoperational nican and 95% confidence limitu, 1990 mean for teuperature (*C), salinity (ppt), dissolved oxygrn (mg/1), and nutrients (pg/1) at St ation P2 . . . . . . 62 2.3-3. Monthly mean and 95% confidence intervals of total phyto-plankton und relative abundance of the major phytoplankton groups during the preoperational period (1978-1984) and nonthly acan .tn 1990 with and without Colontal Cycnophyceae . . . . . . . . . . . 64 e 2.3-4. Precperational mean (1975-19d9)(r.c./1000 m , lobs +er lar-vae; catch por 15-trap effort adulc lobsters and crabs) and 05% confidence limits and 1993 sean for lobster lar-vae, adult lobsters and crabs at the discharge site . . . 69 1,3-5. Season al patt erns of set t'.ement and growth of fouling crganisma during the preoperat ional period and in 1990 as indicated by noncolonial abundance, species richness, and biomass from monthly sequential pancis set at discharge Station B19 . . . . . . . . . . . 71 2.3-6. Seanenal groups formed by numerical classification of log (:r+1) noncolonial abundances from thort-term surface panels f rom Station B19 collected frem 19,o-1984 and July 1906-December 1990 . . . . 73 vili i V Y .u. _n .
, . . . . . . . ~ ~ . . -. - -. - . . . -
a PAGE l I i 2.3-7. Similarity and abundance or bfomsas of macroalgae and l ti macrofauna' species assemblages in 1990 compared to the l preoperational years . . . . .- . . . . . . . . . . -. . . . 75 .
-2.3-8. Nearfield (Sta. 31MLW & B17) annual variability (95% con-fidence limits) of log (x41) biomass (g/m )8 or abundance (no./me )Jand percent composition for selected intertidal and shallow subtical species of algae (triannual collec-tionS) and benthon (August only) during the preoperational period and in 1990 . . -. - . -. . . . . . . . . . . . . . . . 78 2,3~9. Monthly means and 95% confidence limits for seawater sur-
'l' face temperature end salinity taken at low tido in Drowns River over the entire study period (May 1979-December 1990) and in 1990, and precipitation measured in Boston, MA, t' rom 1978-1990 . . . ,. . . . . . . . . . . . . . . . . 81 2.3-10. Annaal. geometric mean density (au./m 8) and mean number of l taxa-perLatation of estuarine benthos (1978-1984; 1986- - 1990), -and annual mean salinity (1980-1984; 1986-1990), at Browns River . . . . . . . . . . . . . . . . . . . . .- . . 84 _ 2.3-11. Seasonal and r-aual changes in composition and abundancn > of _ the estuarine fish community, based on catch per unit-I effort aversged over beach. seine Stations Si, S2 and 53, during'the prooperational period (1976-1984 and 1987-1989) and in 1990 . . . . . . . . . . . . . . . . . . . . . . 85
.2.3-12. Annual log (x+1) mean density (number per square foot) of
-ypung-of-the-year (1-5 mm), spat:(13-25 mm), juvenije (26-50 mm)f and adult _ (>50 mm) Mr.s Jrenerlo 'at. Hampton-Seabrook HarborLFlct I from 1974-1990 . . . . . . . . . , . . . . 88
- 2.3-13. Number of adult clam licenses issued;- the adult clam s standing c;op (bushe'Is).- 3.?71-1990r and. green crab catch in fail, 1381-1990 in Haupton-Seah7cok Harbor , . . . . . . 90 l2.3-14. ~ Preoperational mean. (1978-1939) and 95%-confidence limits and 1990 maan of log (x+1) abundsnee (no./n2 ) and parcent composition for oelected benthic species at midedepth nearfield stat' ion. . . . . . . . . . . . . .- . . . . . . . 94
-2.3-15. Total annual and monthly catch of demersal syncies at Stations 11 and T3 combined _and Station 12 during de pre-operatiot.al: period _(1976-1989) and in 1990 . . . . . . . . 97 IX
_i ,a -y y -4,, 4
< ri. ,
I i l l PAGE I 2.3-16. -Seasonal and annual changes in relative abundance of the I demersal fish community, based on mean catch per unit i ef fort at otter t rawl Station T2 during the preoperntional 'l period (1976-1969) and in 1990 , , . . . . . . . . . . . 98 ! 2,3-17. Size class distribution of lobsters and catches of legal and sublegal-sized lobsters at the discharge station, 1975-1940 . . . . . . . . . . . . . . . . . . . . , , . . . . 102 3.1.1-1. Piriace and bottom teaiperature (*C) at nearfield Station P2, monthly means and 95% confidence intervals over all yeers, 1978-1989 and monthly means at Stations P2, P3 and P7 in 1990. . . , , . . . . . . . . . . . , , , . . . . . 104 3.1.1-2. Comparison of monthly averaged continuous temperature ('C) data collected at discharge (DS) and farfield (T7) sta-- tions during commercial operation, August-December 1990 , 108 3.1.1-3. -Monthly mean dif f erence and 95% confidence If mits between surf ace and bottom temperatures -('C) at nearfield Station P2 over all-years from 1978-1989 and monthly means in 1990 . . . . . . . . . . . . . . . . . . . , 109 d 3.1.1-4.. Surface and bottom salinity (ppt) at nearfield Station P2, monthly _ means and 95% confidence intervals over all years, 1978-1989, and monthly means for 1990 . . . . . . . . . , 111 3.1.1-5=. Surface and bottom dissolved oxygen (mg/L) at nearfield Station.P2, nenthly means and 95% confidence intervals over:all yearn,. 1978-1989, and monthly means.for 1990 , . 112 3.1.1-6. Surface orthophosphate and total phosphorus (pg P/L) at _ nearfield Station P2, monthly means and 95% confidence intervels over all years'from 1978-1984 and 1986-1989, and-4 monthly means for 1990 . 113 3.1.1-7, Surf ace nitrite-nitrogen and nitrate-nitrogen (pg N/L) at nearflold Starica P2, monthly means and 95%_ confidence ink tvals over a11; years from 1978-1984 and 1986-1969, and montuly means for 199'J . ._ . . . . . . . . . . . . . . . 115 3.1.1-8, Surface ammonia-nitrogen (pg N/h) at nearfield Station.P2, monthly means and 95% confidence intervals over all years from'197L 1984 and 1986-1989,. and monthly-ocans for 1990 . 115 1 X
. .__.-m:-___.____.-__m_m..-. _ _ _ _ .----
PAGE
- 3.1.2-1. Log (x+1) abundance (no./1) of total phytoplankton at nearfield Station P2; monthly means and 95% confidence inters als over all preoperational years (1978-1984) and monthly means with and without colonial Cyanophyceae for 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . 117 3.1.2-2. Seasonal succession of the major phytoplankton groups (percent composition) during the preoperational years (1978-1984) at nearfield Station P2 . . . . . . . , . . 122 3.1.2-3. Seasonal succession of the major phytoplankton groups (percent composition) during 1990, all taxa and excluding colonial Cyanophyceae at nearfield Station P2 . . . . . . 124 3.1.2-4. Mean monthly chlorophyll a rencentrations and 95% confi-dence intervals over all pceoperational years (1978-1984) and monthly means in 1990 at nearfield Station P2 . . . 129 3.1.2-5. Mean and 95% confidence intervals of weekly paralytic shellfish poisoning (PSP) toxicity levels in #ycilus edulis in Hampton Harbor over all preoperational years (1978-1984) and mean IcVels in 1990 . . . . . . . . . 131 3.1,2-6. Log (x&l) abundance (no./1) skeletonema costatue at near-field-Station P2; monthly means and 95% confidence inter-vals over all preoperational years (1978-1984) and monthly means for 1990 . . . . . . . . . . . . . . 133 3.1.3-1. Dendrogram formed by numerical classification of log (x+1) -
3 transformed microzooplankton abundances (No/m ) at Sea-brook nearfield Station P2, 1978-1984, July-December 1986, and April-December 1990 . . . . . . . . . . . . . . . 137 3.1.3-2. Seasonal groups formed by numerical classification of 3 log (x+1) transformed microzooplankton abundances (no./m ) at Seabrook nearfield Station P2, 1978-1984 July-December 1986, and April-December 1990 . . . . . . . . . . . . . 139 3.1.3-3. Log (x+1) abundance (no./m3 ) of Eurytencra sp. cope-
> podites and Eurysonora herdmani adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2 . . . . . . . . . . . . . . . . . . 145 3.1.3-4. Log (x+1) ebundance (no./m3) of Pseudoculanus/calanus sp.
naup111 and Pseudocalanus sp. copepodites and adults; menchly ceans and 95% confidence intarvals over all pre-operational years (1978-1984 and 1986) and mont'uly means for 1990 at nearlield Station P2 . . . . . . . . . . 150 xi !
1 l PAGE , l 3 _- 3,1.3-5. Log (x+1) abundance' (no./m ) of Oithona sp. nauplii, copepodites and adults; monthly means and 95% confidence .
^
Intervals over all preoperational years (1978-1984-and 1986) and monthly means for 1990 at nearfield Station P2 . 153 1 3.1.6-1. Dendrogram formed by normal classification of weekly , ( April-October) bivalve larvae log (x+1) transformed l abundances (no./m 3 ) at Seabrook nearfield Station P2, ' 1982-1984 and 1986-1990 . . . . . . . . . . . . . . . .. 156 i 3.1.4-2. Seasonal groups formed by numerical classification of Icg - (x+1) transformed bivalve collections from nearfield ? Station P2, 1982-1984 and 1986-1990 . . . . . .- . . . .. 157 , 3 3.1.4-3. Weekly means log (x+1) abundance (no./m ) of bivalve larva; and 95% confidence intervals over all preopera-tional_ years 1978-1989-and weekly means for 1990 at . nearfield Station P2 . . . . . . . . . . . . .. 159 3.1.5-1. Dendrogram formed by numerical classification of coiiec- . tions of holo- and meroplanktonic species of macrozoo-plankton monthly mean log (x+1) transformed abundances . (no./1000 m3 ) at nearfield Station P2, - 1978-1984 and 1986-1990 . . . . . . . . . . . . . . . . . . . . . . .. 170 i 3.1.5-2. Seasonal grouos formed by numerical classification of log ' (x+1) transformed holo- and moroplankton abundances- i (monthly mean) from macrozooplankton collections at j nearfield Station P2, ~ 1978-1984 and 1986-1990 . . . . . . 171 i l_ 3.1.5-3. 'Dendrogram formed by numerical classification of collec- - tions. cf monthly mean log (x+1) transformed tychoplankton 3 - abundances (no./1000 m ) from macrozooplankton collec-tions at-nearfield Station P2, 1978-1984-and 1986-1990 . 175 i j 3.1.5-4. Seasonal groups formed by numerical. classification of log. (x+1) transformed tychoplankton abundances (monthly mean) from macrozooplankt.on collections at nearfield Ftation P2, 1978-1984 and 1986-1990_. . . . . . . . . . . . .. 176
- 3.1.5-5. Log (x'1) abundance (no./1000 m3 )- of Calanus finmarchleus j
_copepodites and adults; monthly means and 95% confidence . Intervals over all preoperational years (1978-1984, 1986-- 1989) and monthly means for 1990 at-nearfield Station P21 184 i' 'i J
- ]
xii .,
.. . . . + - . .- . . . . -. . -. _
PAGE 3.1.5-6. Log (x+1) abundance (no./1000 m3 ) of Carcinus caenas 1ersne and Crangon septenspinosa zoeas and post larvae; monthly means and 95% confidence intervals over all preoperational years (1978-1984, 1986-1989)- and monthly means for 1990 at nearfield Station P2 . , . . . . . . . 187 3.3.5-7. Log (x+1) abundance (not/1000 m3 ) of Neomysis americana; monthly means and 95% confidente intervals over all preoperational years (1978-1984, 1986-1989) and monthly means for 1990 and mean percent composition of Neocy.31s amer!cana lifesteges over all preoperational years (1976-1984, 1986-1989) and for 1990 at nearfield Station P2 . . 189 3.2.1-1. Dendrogram formed by normal classification of conthly 3 abundances (log (x+1) transformed number per 1000 m ) of fish eggs at Seabrook nearfield Stations P2 and P3, January 1976-December 1990 . ... . . . . . . . . . . 192
- 3. 2.1 -- 2. . Temporal occurrence pattern of seasonal assemblages of fish eggs collected at Seabrock nearfield Stations P2 and P3 during January 1976 through December 1990 . . . . 194 3.2.1-3. Dendrogram formed by normal. classification of monthly L abundances (log (x+1) trsnsformed nuober per 1000 m3 ) of l fish larvae at Seabrook nearfield Stations P2 and P3, '
l- July 1975-December 1990 . . .............. . 197 3.2.1-4. Temporal occurrence pattern of seasonal assemblages of fish la;-vae collected at Seabrook nearfield Stations P2 L and.P3 during-July 1975 through Decea.ber 1990 . . . . . . 199 L L 3.2.1-5. - Log (x+1) abundance (no./1000 m3 ) of American san'd lance [ end winter flounder larvae; monthly means and 95% confi-Geace intervals over all preoperational years . (1975-1969) and monthly means for 1990 at nearfield Stations P2-and P3 . . . . . . . . ... . . . . . . . . . . . . 215
- 3. 2.-1-6. Log (x+1) abundance (no./10003 m ) of yellowtail flounder and Atlantic cod larvae; monthly means and 95% confidence k intervals over all preoperational years (1975-1989) and p monthly means for 1990 at nearfield Stations P2 and P3 . 220 3
l 3.2.1-7. Iog (x+1) abundance (no./1000 m ) of Atlantic mackerel ! and cunner larvae; monthly means and 95% confidence intervals over al1 preoperational yearn (1975-1989) and l-l monthly means for 1990 at nearfield Stations P2 and P3. . 222 x11.1 - d ----s* g P
b
.l PAGE d i
3 3.2.1-8. Log (x+1) abundance (no./1000 m ) of hake and Atlantic herring larvae: monthly means and 95% confidence intervals over all preoperational years (1975-1989) and monthly maans for 1990 at nearfield Stations P2 and P3 . 224 I 3.2.1-9. Log (x+1) abundance (no./1000 3m ) of pollock larvae; monthly means and 95% confidence intervals over all a preoperational years (1975-1989) and monthly means for l 4- 1990 at nearf.ield Statione P2 and P3 . . . . . . . . . . 226 : V i 3.2.2-1. Annual total catch per unit effort (number per 24-hour ' set of one net, surface or bottom) in gill nets by sta-tion and mean of stations, 1976-1990 . . . . . . . . . . 228 i 3.2.2-2. Annual total catch per unit effort (aean number per 10-minute tow) in otter trawls by st.ation and mean of sta-tions, 1976-1990 . . . . . . . . . . . . . . . . . . . 237 3.2.2-3. Annual total catch per unit effort (mean number per seine haul) 2n beach seines by station and mean of stations 1976-1984, 1987, 1988, 1989, and 1990 . . . . . . . . 243 3.2.2-4. Number-of fish impinged at Seabrook Station during 1990 l for various size classes of most abundant species .. . . . 251 3.2;2-5. Log (x+1) catch per . unit ef fort (one 24-hr. set) for ! Atlantic herring and pollock; monthly means and 95% !- confidence intervals over-all preoperational years (1976-1989) and monthly means for 1990-averaged.over gill net Stations G1, G2 and G3 . . . . . . . . . . . . . . . . 253
'3.2.2-6. - Log (x+1) catch per unit effort (one 24-hr. set) for Atlantic mackerel; monthly means and 95% confidence intervals over all preoperational years (1976-1989) and 3
monthly means for 1990 averaged over gill not Stations G1, G2 and G3 . . . . . . . . . . . . . . . . . . . . . 259
. 3.2.2-7. Log-(x+1) catch per' unit effort (one tow) for Atlantic
- cod; monthly maans:and 95% confidence intervals over all
, preoperational years (1976-1989) and monthly means for .
- 1990 from otter trawl Stations:T1, T2, and T3 . . . . . . 260 i7 3.2.2-8. Iag (x+1) catch per unit effort.(one tow) for hakes; monthly means ~ and 95% confidence intervals over all preoperational-years (1976-1989) and monthly means for l > 1990-from otter trawl Stations T1, T2, and T3 . . . . . . 263 E i l
xiv i [_ ~ g v-pr . - p ,n-, -- .,,rw. ~
, . .. ._ .- . . . . ~_
PAGE _z_ -3.2.2-9. LLog (x+1) catch per unit' ef fort (one tow) for yellowtail flounder; monthly means.and 95% confidence intervals over all preoperational years (1976-1989) and monthly means 1 for 1990 from otter trawl Stations T1, T2. and T3 . . .. 265 3.2.2-10. Log (x+1) catch per_ unit effort (one tow) for winter flounder; monthly means and 95% confidnnce intervals over , p all preoperational years (1976-1989) and monthly means for 1990 from otter trawl Stations T1, T2, and T3 . ... 266
~
3.2.2-11. Log (x+1) catch per unit ef fort (one. haul) for winter flounder; conthly means and 95% confidence intervals over all preoperational years (1976-1984, 1987-1989) and monthly means for 1990 averaged-over beach seine Stations S1, S2 and S3 . . . .-. . . . . . . . . . .. . . .... 268 3.2.2-12. Iog (x+1) catch per unit effort (one tow)-for refnbow smelt; monthly means and 95% confidence intervals over all-_preoperational years (1976-1989) and monthly means
.for 1990 from otter trawl Stations T1, T2, and T3 . .. . 270 3.2.2-13. - Log (x+1) catch per unit ef fort (one haul) for rainbow smelt; monthly means and 95% confidence intervals over L all preoperational-years (1976-1984, 1987-1989), and L monthly means for 1990 averaged over beach seine Stati3r L S1, S2 and S3 . . . . . . . . . . . . . . . . .. . .. .
272 3.2.2-14. Log _ (x+1) catch per unit effort (one haul) for Atlantic silverside; aonthly.means and 95% confidence intervals Lgg over all preoperational_ years (1976-1984, 1987-1989) and ; { monthly means for 1990 averaged over beach seine Stations L SitHS2 and S3'. . . . . . . . . . . . . .. . . . . ... 273 3.3.1-1. -Monthly means and 95% confidence _ limits for precipitation h measured in- Boston, MA, from '1978-1990_ and surface salin - 3 ity and temperature taken at low tide in Browns River L +over thefentire_ study period (May 1979-December 1990) and l_ in 1990 . .- . . . . . . . . . . . . . . . ... . . . . 280
=
- .313.1-2; Total montnly outfal1~(millions of gallons por month) from the Seabrook Settling Basin into Browns River from
- October
- 1978 through December 1990- . ... . .. . . . . 283 "3.3.1-3. . Yearly means and 95% confidence limits for_the 1o3 (x+1) density (no./m') of-macrofauna and mean number of taxa L per'5/16 m2 collected at subtidal estuarine stations ll sampled three' times per year from 1978 through-1990' l (excluding 1985) . . . . . . . . . . . . . . . . . .. 288 l
l-l. I: xV i.
/- ! - .- .. . _ . . . _ , ._ ., . . . _
. - . . . - - - - ._ - . _ . .-- . ~.
f PAGE 3.3.1-4. Yactly means and 95% confidence limits for the log (x+1) density (no./m') of macrofeuna and mean number of taxa per 5/16 m# collected at intertidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985) . . . . . . . . . . . . . . . . . . . . 289 3 3.1-5. Yearly means and 95% confidence limits for the log (x+1) Jensity (no./n') of Hediste diversicolor and Capite11a capitata collected at subtidal estuarine stations samcled three times per year from 1978 through 1990 . . . . . . 294 3.3.1-6. Yearly means ar.d 95% confidence limits for the log (x41) density (no./m') of Rediste diversicolor and Capite11a capitata collected at intertidal estuarine stations sampled three times per year from 1978 through 1990 (excluding 1985) . . . . . . . . . . . . . . . . . . . . 295 3.3.2.1. Preoperational (through 1969) median and range and 1990
.value of number of taxe collected in triannual general collections at Stations B1HSL, B1MLM, B17, B19, B31 (1978-1990), B5MSL, BLMLV, B35 (1982-1990), t.nd annual collections at F16 (1980-1984; 1986-1990), B13, B04 (1978-1984; 1986-1990) and (1979-1984; 1986-1990) . . . . 299 3.3.2-2. Nean number of taxa (per 1/16 m'), total biomass (g/m')
and 95% confidence limits of macroalgae collected at intertidal and subtidal stations during the preopora-tional period (see Figure 3.2.2-1 for years sampled) and in 1990 . . . . . . . . . . . . . . . . . . . . . , . 301 i 3.3.?-3; Annual mean biomass (g/m t
) and 95% confidence limits for macroalgae collected in August at selected nearfield benthic stations , . . . . . . . . . . . . . . . . . 305 3.3.2-4. . Relative abundance (% biomass) of dominant nacroalgee at marina benthic stations in August for the preoperational period (see. Figure 3.3.2.1 for dates) and 1990 . . . . . 307 3 '. 3. 2 -5 . .Dandrogram formed by numerical classification of August collections _of marine benthic algae,- 1978-1990 . . . . . 310 3.3.2-6. Precoerational means and 95% confidence limits of abun-danc'e of kelps (no./100 n2 ), (Bli: 1978-1989; B35: 1982-1989) and percent frequencies and 95% confidence limits of doninant understory algae (B17: 1981-1989; B35: 1982-1989) and 1990 means, collected triannually in the shal-
' low and mid-depth subtidal zones . . . . . . . . . . . 315 xv1
PAGE 3.3.2-7. Mean percent frequency anF 95% confidence limits of fucold algae at two fixed transect sites in the mean sea level zone for the preoperational period (1983-1989) and mean percent frequency in 1990 . . . . . . . . . . . . . 320 3.3,2-8. - Annual mean abundance (no./100 m') and 95% confidence interval for Laelnarla saccharina at Station Bl? (1979- l 1990) and B35 (1982-1990) . . . . . . . . . . . . . . . . 322
]
3.3.2-9. Annual mean biomass (g/m') and 95% confidence intervals I of Chondrus crispus collected in May, August and November 1 at Stations B1MLW, B17: 1978-1990; B5MLW, B35: 1982-1990 324 . 3.3.2-10. Mean biomass (g/m') and 95% confidence limits of Chondrus crispus at selected stations in May, August and November. Stations B1MLW, B17: - 1978-1989 and 1990; Stations B5MLW, B35:-1982-1989 and 1990 . . . . . . . . . . . . . . . . . 326 3,3.3-1. Mean number of taxa (per 1/16 m2 ) and log (x+1) mean density-(no./m') and 95% confidence limits of macrof auna
- collected in August during the preoperational period (1978-1989) and in 1990 at intertidal and subtidal ben-thic stations . . . . . . . . . . . . . . . . . . . . . . 328 Annual mean number of.noncolonial macrofaunal taxa (per
~
l: 3.3.3-2. 1/16 m') collected 'in August at intertidal Stations B1MLW
~
L and-B5MLW and shallow subtidal Stations B17 and B35 from
- 1978-1990 . . . . . . . . . . . . . . . . . . . . . . . 331 3.3.3-3. Annual.means and 95% confidence limits for the log (x+1) density (no./m') of macrofauna collected in August at nearfield Stations B2MLV (intertidal) and B17 (shallow
=subtidal)Lfrom 1978-1990 . . . . . . . . . . . . . . . 332 e
'3.3.3-4.--Annual mean number of noncolonial macrofaunal taxa (per 1/16m t
) collected in August at mid-depth Stations- B16, .
B19, and B31 and deep _ Stations B04, B13 and B34.from 1978-1990- . . . . . . . . . . . . . . . . . .. . . . . . . . 335 3.3.3-5. ' Annual means and' 95%1 confidence . limits for -the logL (x+1) . s density -(no./m') of macrof auna collected in August at nearfield Stations B19 and B16 (mid-depth and B04 (deep)
- from 1978-1990 . . . . .. . . . . . . . . . . . . . . . .336 3.3.3-6. Dendrogram of normal classification of annual macrofaunal log (x+1)- densities- (no./m') taken in August at all near-field and farfield stations from 1978-1990 . . . . . . 340 l
c. xvii
-f
_ _ . _ _ 2 .. _ ___ ___ _.. __#_ _ - , - - - _ , _ -
r; 9PAGE
~
3.3.3-7. Annual mean density (no, per 0.2; _ square meter) and.95% confidence interval of Modlolus nodlolus observed by divers triannually at subtidal transect stations from 1980-1990 . . . . . . . . . . . . ............ 350 3.3.4-1. Faunal' richness (number of noncolonial faunal taxa on two replicate panels) in-1990 compared to mean faunal rich-ness and 95% confidence limits on short term panels during preoperational period (B19, B31, and B04-from 1978-1984 and July 1986-1989 and B34 from 1982-1984 and July 1986-1989) . . . . . . . . . . . . . . .... . 352 3.3.4-2. Log (x+1) abundance (no./ panel) in 1990 compared to mean l log (x+1) abundance and 95% confidence limits in .1990 and preoperational period (1978-1984 and July 1986-1989, B34 ll l initiated in 1982) for noncolonial f auna on short term panels . . . . . . . . . . . . . ............ 357
- 3.3.4-3. Biomass (g/ panel) in -1990 compared to mean biomass and 95% confidence limits at Stations B04, B19, and B31 from 1980-19o4 and July 1986-1989 and B34 from 1982-1984 and July 1986-1989 on short-term panels . . . . , ...... 359 l' ' 3.3.4-4. Dendrogram formed by numerical classification of noncolo-nial organisms collected'from monthly short-term surface
[l l fouling panels-set at nearfield Station B19, 1976-1984 t [ and 1986-1990 . . . . . . ... . . . . . . . . . . . .{. 362 l - 3.3.4-5. Seasonal groups formed by numerical classif.ication of log b (x+1) noncolonial abundances from-short-term surface K panels from Station B19 collected from 1978-1984 and July L 1986-December 1990. . . . . . . ... . . . . . . . . . 363 % Log abundance _(no. per panel) or. monthly mean percent-p . 3.3.4-6. } frequancy of Mytilidao, ~Jassa carnorata, Balanus sp. and
- L Tabularla sp. on short-term surf ace panels at Statior.s R B04'and:B19 in 1990 compared to ma.an abundance or percent '
R - frequency'and 95% confidence limits during the preopera- $b *icnal period _(1982-1984 and July 1986-December.1989) .
. . 366 Ly - = .
?P -3.3.4-7. :
.Biomaas (g/ panel) in 1990 compared to mean biomass and
- 95% confidence!11mits during the preoperational' period (Stations B04, B19, and B31_from December 1978-1984 and Jdly 1986-1989-and B34 from.1982-1984 and: July 1986-1989)
.tra monthly-sequential: panels . . . . . . . . . . . . 370 m
xviii
. # v --' q 48%ry-Iw W -?--u'-4-'M '7'*
. - _ ._ _ ._ _ . . ._ _. _ m ,
f PAGE 3.3.4-6. Monthly mean percent frequency or log transformed abun-dance (no per panel) on monthly sequential surface panels for Mytilidae, Jassa marmorata, Balanus sp. Tubularla sp. and-Laminarla sp. at Stations B04 and B19 in 1990, compared to mean and 95% confidence limits during
-preoperational period (1982-1984 and July 1986-December 1989) . . . . . . . . . . . . . . . . . . . . 374 3.3.4-9. Mann length of Mytilidae and Jassa rarmorata collected form monthly sequential surface panels in 1990, compared ,
to mean and 95% confidence limits during preoperational J period (1982-1989) . . . . . . . .. . . . . . . . . . . 378 : 3.3.5-1. Yearly means and 95% confidence limits for the log (x+1) density (no./m2 ) of Asteriidae and Mytilidae from Sta-tions B17 and B35 sampled three times per year from 1978 through 1990 . . . . . . . . . . . . . . . . . . . . . 386 3.3.5-2. Mean' length of Mytilidae and Jassa marmorata collected from monthly sequential surface panels in 1990, compared to mean and 95% confidence limits during preoperational period (1982-1989) . . . . . . . . . . . . . . . . . . . 989 Weekly mean long . (x+1) density (no./1000 2m ) of lobster 3.3.6-1. . larvae at Station P2 in 1990 compared to all years' mean and 95% confidence interval during the preoperational period (1978-1989)~ . . . . . . . . . . . . . . . . . . . 397 3.3.6-2. Comparisono of Icgal and sub-legal sized catch of Nomarts americanus at the discharge site, Station L1, 1975-1990 . 406
. 3.3.6-3. Size-class-distribution (carapace length) of Fomarus americanus at the discharge site, Station L1, 1975-1990.. 407
. 3.3.6-4. Summary of. female lobster catch-data at the discharge site,: Station L1,-1974-1990,. . . . . . . . . . . . . . . 408 Monthly mean log-(x+1) density and 95% confidence inter-
~
.3.3.6-5.
vals (no./1000 m 3) of Cancer spp. larvae at- Station P2, . " 1978-1989* and monthly mean for: 1990 . . . . . . . . . 410 3.3.7-1. Weekly log (x+1) density-(no. per cubic meter) of'Mya arenarla larvae at Station P2 in 1990, compared to all yearsmean and 95% confidence interval during the pre-
~
operational period-(1978-1989) . . . . . . . . . . . . . 416
~
XIX
l PAGE 3.3.7-2, Annual log (x+1) mean density (number per square foot) of young-of-the-year (1-5 mm), spat (13-25 mm), juvenile (26-50 mm), and adult (>50 mm) Mya arenaria at Hampton-Seabrcok Harbor Flat 1 from 1974-1990 . . . . . . . . 420 3.3.7-3. Annual log (x+1) mean density (number per square foot) and 95% confidence limits of young-of-the-year Mya arenarle spat (1-5 mm) at Hampton-Seabrook Harbor, 1974-1990 . . . . . . . . . . . . . . . . 421 3.3.1-4. Mean and 95% confidence limits of Mya arenaria spat (shell length 512 mm) densities (no/f t') at two northern New England estuaries, 1976 through 1984 and 1986 through 1990 . . . . . . . . . . . . . . . . . . 423 3.3.7-5. Means and 95% confidence limits of Mya arenarla spat, juvenile and adult log (x+1) densities at Flat 1, Hamp-ton-Seabrook Harbor, 1974 through 1990 . . . . . . 424 3.3.7-6. Means and 95% confidence limits of Mya arenaria spat, juvenile and adult log (x+1) densities at Flat 2, Hamp-ton-Seabrook Harbor, 1974 through 1990 . . . . . . . 425 3.3.7-7. Means and 95% confidence limits of Mya arenarle spat, juvenile and adult Icg (x+1) densities at Flat 4, Hampton-Seabrook Harbor, 1974 through 1990 . . . . . . 426 3.3.7-8. Morahly means and catch per unit effort (log (x+1)) and 95% confidence intervals for total green crabs (Carcinus maenas) and ovigerous green crabs collected at estuarine stations from preoperational years (1983-1989) compared to monthly means in 1990 . . . . . . . . . . . . . . 429 3.3.7-9. Fall (October-December) mean catch per unit effort for green crabs (Carcinus maenas) in Hampton-Seabrook Harbor and its relationship to minimum winter temperature, 1978-1990 . . . . . . . . . . . . . . . . . . . . . . . 430 3.3.7-10. Number of adult clam licenses issued and the estimated adult clam standing crop (bushels), in Hampton-Seabrook Harbor, 1971-1990 . . . . . . . . . . . . . . . 435 XX I
.c
-LIST-OF TABI.ES PAGE 2.1-1. Number lof Days of Operation and Average Daily Flow of ;
Seabrook Station Circulating Water System in 1990. . . . 17 2.1-2. Summary of Biological Communities and Taxa Monitored for Each Potential Impact Type. . . . . . . . . . . . . 16 I
-2.1-3. Benthic Algae and Macrofauna Station Locations and j Descriptions . . . . . ..... . . . . . . . . . . . . 22 2.2-1. Comparison of Geometric Mean Abundances of Top-Ranked Fish Egg, Fish Larvae, and Bivalve Larvae Taxa Collected Offshore at Station P2 and in Entrainment Samples at Seabrook Station from June through December 1990. . . . . 29 2.2-2. Estimated Number of Bivalve Larvae (in billions / month)
; Entrained-by the Cooling Vater System at Seabrook Station During June-October 1990 .. . . . . . . . . , . . . . . 31 2.2-3. Monthly-Estimated Numbers of Fish Eggs and Larvae (in millions) Entrained-by the Cooling Water Syst- at Sea-brook Station During June-December 1990 . . . . . . . 32 2,2-4. Summary of Nearfield/Farfield (P2, P5 vs. P7) by"
<- Differences in Plankton Communities and Selected Species in 1990 . . . . ... . . . . . . . . . . . . . .38 2.2-5. Comparison of 1990 Abundances of Selected Microzooplankton, Bivalve Larvae, Hacrozooplankton and Ichthyoplankton:Lervae, Taxa . . . . . . . . . . . . 45 2.2-6. Comparison of 1990 Abundances of Selected Pelagic Finfish Species . . . . ....... . . . . . . . . . 52 2.2-7. Catch Per Unit Effort by Depth for the Dominant Gill Net Species Over All Stations and Dates When Surface Mid-Depth and Bottom Nets were Sampled, Preoperational Years (1980 through 1989) and 1990_ . . . . . . . . . . . . . . 56 2.3-1. . Monthly Mean Temperatures ('C) and Temperature Differ-ences Between Discharge (DS) and Farfield (T7) at- the Suface, and Nearfield (ID) and Farfield (T7) Stationa.at Surface, Mid-Depth (8.5 m)-and Bottom (16.2 m) Depths Collt :ed from Continuously Monitored Temperature Sensors . . . . . . . . .. . . . . . . . . . . . . . . 61 xxt
( - - _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ ___ _ _ _ _ _ _ __ PAGE 2.3-2. Summary of Differences in Community Parameters Measured at Intertidal, Shallow Subtidal, Mid-Depth, and Deep Benthic Stations and in the Surf ace Fouling Community . . 72 Selected Benthic Species and Rationale for Selection 2.3-3. . 77 2.3-4. Comparison of 1990 Abundances or Biomass Levels of Selected Intertidal and Shalloc Subtidal - Macroalgae and Macrofaunal Taxa . . . . . . . 79 2.3-5. Summary of Similarities of Abundances of Selected Taxa in Mid-Depth Regions in 1950 Compared with Previous Years 94 3.1.1.1. Annual Means and Coefficients of Variation for Water Quality Parameters Measured During Plankton Cruises at Nearfield Station P2, 1978-1990. Seabrook Operational Report, 1990 . . . . . . . . . 106 3.1.1.2. Results of Analysis of 5/ariance of Water Temperatures Compared Among Stations P2, P5, and P7 in 1990 and Among Years at Station P2 From 1978-1990 and Comparisons of Salinity, Dissolved Oxygen and Fitrients Among Stations in 1990 . . . . . . . . . . . . . . . . . . . . . 107 3.1.2-1. Percent Composition of Species by Year for Phytoplankton Data. Data is Subset fc; 1990 Operational Period August-December . . . . . . . . . . . . . ... . . 119 3.1.2-2. Preoperational and Operational Geometric Mean Abundance and Confidence Interval for Phytoplankton Taxa Occurring Between August and December at Station P2 . .. . . . 120 3.1.2-3. Relative Abundance (%) of Phytoplankton Species occurring in Frequencies of 1% or Greater During August-December of the Preoperational Years (1978-1986) and 1990. Seabrook Operational Report, 1990 . . . . . . . . . . . . . 126 3.1.2-4. Results of Multivariate Anslysis of Variance (MANOVA) Comparing Phytoplankton Community Structure at Stations P2, PS and Station P7 Durin: 1990 . . . . . . , . . . . 127 3.1.2-5. Correlation Coefficients Chlorophyll a Concentrations at Stations P2, P5, and F" - 1990 . . . . . . . 130 3.1.2-6. Peak Fall Abundances of Skeletonema costatus in Surface
' daters at the Nearfield Station P2 During Preoperational i Years (1978-1984, 1986) and 1990 . . . . . . . . 134 xxii
i l PAGE 3.1.2 7. Results of Analysis of Variance Compering Nearfield (Sta-tiens P2 and PS) and Farfield (Station P7) SAeletonema costatum Abundances During Preoperational Years (1978-1985) and 1990 and Stations P2, P5 and P7 During 1990. 135 3.1. 3- 1. Geometric Heans of Microzooplankton Abundance (No./m3 ), 95% Confidence Limits, and Number of Samples for Dominant Taxa Occurring in Seasonal Cluster Groups identified by Numerical Classification of Collections at Nearfield Station P2, 1978-1985, July-Decembec 1986, and April-December 1990. . . 138 3.1.3-2. Results of Multivariate Analysis of Variance Conparing Microzooplankton Community Structure at Stations ??, P5, and P7 in 1990. . . . . . . . . . . . . . . . . . . . . . 143 3.1.3-3. Geometric Mecn (No/m I
) by Year, P. ratier.a1 Mean and 95% Confidence Limits and Operational Year Hean (1990) of balented Microzooplankton Species at Station P2 (April-December). . . . . . . . . . . . .... . . . . . . 146 3.1.3-4. Results of the TVo-Way Analyris of Variance of log (x+1)
Transformed Density (No/m5 ) Among Prooperational Years (1982-1984 & 1986) and Operational Year (1990), Area (Nearfield vs. Parfield) and Their Interactions for Selected Microzoeplankton Species. . . . . . . . . . . 148 3.1.4-1. Geometric 11ean Abundance (Hc/m 5
), 95% Confidence Limits of Dominent Taxa, and Number of Samples Occurring in Seasonal Groups Formed by Numerical Classification of Bivalve Larvae Collections at Nearfield Stacion P2, 1982-1984 and 1986-1989 in Comparisoa to 1990 . . . . . . 158 3.1.4-2. Results of Multivariatn Analysis of Variance (MANOVA)
Comparing Bivalve Larvae Community Structure at Stations P1, P2, P5 and P7, April atober 1990. . . . . . . . . . 162 3.1.*-3. Monthly Geometric Mean of Density (no. per cubic m::er) of Bivalve Larvae f rom Entraio acnt and Offshore (P2) Collections During June-Decent:r . . ...... . . . . 164 3.1.4-4. Estimatsd Number of Bivalve Larvue (in billions / month) Entenirs by the Cooling Water System at Seabrook Stction During ine October 1990 . . . . . ,......... 16a 3.1.4-5. Renults o ' Ana' lysis of Variance Comparing Nearfield (Sta-tions P2 and PS) and Farfield (Station P7) Vcekly #rrilus ovu11s abundences During Preoperational (1978-1989) and Opera;' :1 (1990) Periods . . . . . . . . . . . . . . . 168 xxiii
. - - - - . ~ . - . - _ - . _ .- - - - - . - ----- - - - .- - . - - -
O PACC l 3 3.1.5-1. Geometric Hean Abundance (No/1000 m ) and 95% Confidence l Limits of Dominant 11o10- and Heroplanktonic Taxa Occur- i ring in Seasonal Groups Formed by Numerical Classifica- 1 tion of Hacrozooplankton Collections (monthly means) at , Nearfield Station P2, 1978-1984 and 1986-1990. . . . . 172 S 3.1.5 2. Geometric Mean Abundance (No/1000 m ) and 95% Confidenco Limits of Dominant Tychoplanktonic Taxa Occurring in ! Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections (monthly means) at Nearfield
- Station P2, 1978-1984 and 1946-1990. . . . . . . . . . 177 i t
3.1.5-3, Results of Multivariate Analysis-of Variance Comparing ' Hacrozooplankton Community Structure at Stations P2, PS and P7 in 1990. . . . . . . . . . . . . . . . . . . . . 181 ; i 3.1.5-4. Annual Geometric Hean Abundance (No/1000 mS ) and Upper and Lower 95% Confidence Limits of Selected Species of Macrozooplankton at Seabrook Nearfield Station F2 During
- Preoperational Years (1978-1984 and 1987-1989) and Geo- e
,' metric Hean Abundance in 1990. . . . . . . . . . . . . 183 3.1.5-5. Results of Analysis of Variant:e Comparing Nearfield (Sta-tions P2 and PS) and Farfield (Station P7) Abundances of ; Selected. Species of Macrozooplenkton During Preopera-tional (1978-1989) and Operational (1990) Periods. . . 185 3.2.1-1. Faunal Characterization of Seasonal Groups Formed by Numerical Classification of_ Samples of Fish Eggs Collect-ed at Seabrook Nearfield Stations P2 and P3 During Janu-ary 1976 Through December 1990. . . . . . . . . . . . 193 3.2.1-2. Faunal Characterization of Seasonai Groups Formed by. Numerical Classification of Samples of Fish I,arvan Col-1ected at Seabrook Nearfield Stations P2. and P3 During July 1975 Through December 1990. . . . . . . . . . . . . 198 3.2.1-3. Comparison of Percent Abundance and Percent Frequency of 2 Fish Egg Collections at Intake (P2), Farfield (P7) and
- Discharge (PS) Statione During January - December 1990 . '203 i e 3.2.1-4. Comparison of Percent Abundance and Percent Frequency of Flah Egg Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During the First Five Months of Commercial Operation (Augutt-December 1990) . . . . . . . 204 3.2.1-5. Results.of Multivariate Analysis of Variance Tests'for Difference'Among Stations in Communities of Fish Eggs and Larvae During Preoperational and Operational Periods in 1990 . . . . . . . . . . . . . . . . . . . . . - , . . . 205 -
xxiv !
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. . ,.w::--.- .s c-.t-., , , . . .m,w,,w.,e,y m.m,, ,,,,..w. . w-,emm-,_ - - , . ~ y..,.--,mcmy..w-- 1sw v.m- ,y,.www.-,-wy,,v7, .a
. . . _ . . _ . - . _ _ . _ _ _ _ . _ . _ _. - ~ _ _ . _ . _ . _ _ . . . . _ . . . . _ . _ _ __
PAGE 3.2.1-6. Comparison of Percent Abundance and Percent Frequency of Fish Larvan Collections at intake (P2), Farfield (P7) and Discharge (PS) Stations During January-December 1990 . . 206 1.2.1-7. Comparison of Percent Abundance and Percent Frequency of . Fish Larvae Collections at Intake (P2), Farfield (P7) and Discharge (PS) Stations During the First Five Months of Commercial Operation (August-Deuember, 1990) . . . . . . 207 3.2.1-8. Monthly Geometric Moon of Density (por 1000 cubic meters) of Entrained Fish Eggs from Entrainment and Offshore (P2) Collections During June December 1990 . . . . . . . . . 209 3.2.1-9. Monthly Geometric Hoan of Density (per 1000 cubic meters) of Entrained Fish Larvae from Entrainment and Offshore (P2) Collections During June-December 1990 . . . . . . . 211 3.2.1-10. Monthly Estimated Numbers of Fish Eggs (in millions) Entrained by the Cooling Water System at Seabrook Station During June-December 1990 . . . . . . . . . . . . . . . 212 3.2.1-11. Monthly Estimated Numbers of Fish Larvae (in millions) Entrained by the Cooling Vater System at Seabrook Station During June-December-1990 . 713 3 2.1-12. Geometric Hean of Season of Peak Abundance (number per 8 1000 m ) by' Year, Preoperational Mean (Proop.), and Operatior.a1 Year (1990) of Selected Fish Species Larvae at Station P2, July 1975 Through Decembnr 1990 . . . . . - 216 . 3.2.1-13. Results of Analysis of Variance of Log (x+1) Transformed Abundances (no/1000 sm ) of Selected Specien of Ichthyo-plankton Larvae During Months of Peak Abundance for the
. Years 1962-1984, 1986-1990 . . . . . . . . . . . . . . . .210 3.2.2-1 Percent Composition by Year All Preoperational Years Combined, and 1990 for the Ten Host Abundant Species'in Gill Net-Samples from 1976 Through.1990 at Stations 01, G2, and G3 Combined . . . . . . . . . . . . , , . . . . . 229 3.2.2-2. Percent Composition by Station of Abundant Species Col-1ected in Gill Nets, All Preoperational Yours (1976-1989) t -and.1990, Depths Combined . . . . . . . . . . . . . . . . . 232 3.2.2-3. Percent ' Composition of Dominant Gill Net Species Accord-L - - ing to Depth (surface and off-bottom), All Preoperational Years Combined (1976-1989) and 1990 . . . . . . . . . . . 1 234 XXV
-:--_.._____-4a __r * -m_---._--s,.,--w-.,e a-r r+* - - - 4*a -ww^rwi=1+ e-e----qm-r-e_m- e&, 4+-. ira-.w - en-w y wW**- -=4(w-' y%.s- p. ,p g----'7'-twry-r-i-rg y-v gs yy y -v g
. . - . . . - . . - - - - . . . . . - -. - - - - . - .. _ . - - - ~ . - . _ . - -
PAGE 3.2.2-4. Catch Per Unit Effort by Depth for the Dominant Gill Net Species Over All Stations and Dates When Surface Hid-Depth and Bottom Nets Vere Sampled, Preoperational Years (1980 through 1989) and 1990 . . . . . . . . . . . . . . 236 3,2.2-5. Percent Composition by Year, All Preoperational Years Combined, and 1990 for the Twelve Most Abundant Taxa in ' Otter Trawls, 1976 1hrough 1990 at Stations Ti, T2 and T3 Combined . . . . . . . . . . . . . . . . . . .. . . 239 i 3.2.2-6. Percent Composition by Station of Abundant Species Col- , lected in Otter Trawls, All Preoperational Years Combined (1976-1989) and 1990 . . . . . . . . . . . . . . . . 242 3.2.2-7. Percent Composition By Year, All Preoperational Years Combined, and 1990 for the Ten Mast Abundant Specios Collected in Beach Seines (excluding 1985 and 1986) at Stationa S1, S2 and S3-Combined . . . . . . . . . . . . . 245 3.2.2-8. Mean Percent Composition By Station of Abundant Species
- Collected in Bosch Seines Over All Preoperational Years Combined (1976-1984, 1987-1989) and in 1990, April Through November . . . . . . . . . . . . . . . . . . . . 247 7 3.2.2-9. Number of Fish 1mpinged at the Seabrook Station by Month and Species During 1990 . . . . . . . . . . . . . . . . . 249 3.2.2-10. Annual Geometric Hean CPUE for Selected Finfish Species for the Preoperational Period (1976-1989), Their Confi-dence Limits, and 1990 Data . . . . . . . . . . . . . . 254 3.2.2-11. Results of Analysis of Variance Between Preoperational Years (1976-1989) and 1990 for Selected Finfish Species at All Gill Net Stations Combined . . . . . . . . . . . 257 3.2.2-12. Resulte of Two-Vay Analysis of Variance Among Stations (T1, T2, and T3), Preep9 rational (1976-1989) and Opera- ,
tional (1990) Year and Their Interactions of Log (x+1) , Transformed catch Per Unit Effort f or Selected Finfish , From Otter Trawls . . . . . . . . . . . . . . . . . . . . 262 3.2.2-13. Results of One-way Analysis of Variance Between Preopera-tional Years (1976-1989) and the Operational Yent (1990) for Selected Finfish Species for All Lear.h Seine Stations , Combined . . . . . . , . . . . . . . . . . . . . . . . 269 3.3.1-1. Total Precipitntion (water equivalent in inches) by Month and Year Taken at logan International Airport, Boston, liA From January 1978 - December 1990 and 30-year Normals . . 279 t xxvi
, ,-...r - ,
PAGE l 3.3.1-2. Mean Number of Taxa and the Geometric Mean (No./m') Derisity for Each Year and Overall Years With 95% Confi-dence Limits From Estuarine Stations at Browna River (3) and Mill Creek (9) Sampled From 1978 Through 1990 (ex- ; cluding 1985) . . . ...... . ... . . . . . . . . . 285 3.3.1-3. Results of One-Way Analysis of Variance Among Years for the Mean Number of Taxa (per 5/16 me ) and Log (x+1) Transformoj Density (No./m') of the Most Abundant Estun-tine Species and the Total Densf".y of Macrofauna Collect-ed at Estuatine Stations from 1978 Through 1990 (exclud-ing 1985) . . ...... . . . . . . . . . . . . . . . 290 3.3.2-1. Results of Analysis of Variance of Number of Taxa (por 1/Iri m') and Total Biomass (g per m 8) of Maceoalgae Collected in August at Intertidal, Shallow Subtidal, and Deep Stations Pairs, 1978-1990 . . . ,. . . .. . . . . 303 3.3.2-2. Summary _of Spatial Associations identified From Numerical Classification (1978-1990) of Benthic Macroalgae Samples Collected in August ... . . . . . . . . . . . . . . . . 311 4 3.3.0 3. kesults of Nonparametric One-Vay ANOVA Compating Numbers of Four Kelp Species and Percent Frequencies of Three Understory Algao Taxa in 1990 (October only and all months) to Values From 1981-1989- . . .. . . . . . . . . 316 2 n.2-4 R>sultu of Analysis of Variance of Chondrus crispus Biomass (g/m') Comparing Collections in 1990 at Intertid-r al and Shallow Subtidal Station Pairs With Biomass From 1978-1989 . ........ . ... . . . . . . . . . .325 3.3.3-1 Results of Analysis of Variance of Number of T4.xa (per 1/16 c 8) and Total Density (per m') of Hacrof atnia Col-lected .in August at Intertidal.. Shallow Subtidal, and Deep Station Groups, 1978-1990 ..... .. . .. .. 329 3.3.3-2. Station Groups Formed by' Cluster Analysis With Preopers- > tional and Operational (1990) Geometric Mean Density 195% CI for Abundant Macrofaunal Taxa (noncolonial) Collected - Annually in /.ugust From 1978 Through 1990 . . . . . . . . 338 3.3.3-3. Median and Range of Percent Frequencies of the Dominant , Fauna et Bare. Rock, Fucoid Led p , and Chondrus Zone , l = 1ntertidal Sites at Stations B1 (Outer Sunk Rocks) and B5 l~ (Rye Ledge) Manitored Nondestructively From 1982-1989 (Preop) and 1990 .......... . . . . . . . . . 364 l l xxvii L
i f PAPE 3.3.3-4. E.stimated Density (per 1/4 m') af ter Four Months' y.xpo-sure of Selected Sessile Taxa on Hard-hubstrate Bottom Panels at Stations B19 and B31 Sampled Triannually . (April, August. December) From 1981-1969 and in 1990 . . 347 3.3.4-1. Results of Analysis of Variance Comparing Monthly Number < of Taxa, Noncolonial Abundance Total Bionssa, and Se-1ected Species Abundance of Percent Frequency on Short Term Panels at Mid Depth (B19, 831) and Deep (B04,1134) Station Pairs From 1978-1990 . . . . . . . . . . . . . . 353 3.3.C-2. Annual Geometric Mean Abundance and Ovoin11 Goornetric Mean and 95% Confidence 1,imits for Mytilidae Spat and j Jassa s.sroorata Collected Monthly on Short Term Paneln From 1978-1989 and in 1990 (excluding 1985 and January-June 1986) , , . . . . . . . . . . . . . , , . . 360 3.3.4-3. Geometric Mean Abtutdance (No./ panel) and 957. Cond.idencu Limits of Dominant Noncoh nial Taxa Occurring in Sensc;nal Groups Fomed by Numerical Classification of Monthly Short-Term Surfsce Panels Set at Discharge Station B19 From 1978-1990 . . . . . . . . . . . . . . . . 3c4 3.3.t 4. ANOVA Rosalts Compat ing Monthly Sequential Biomass at Mid-Depth (319, 831) and Deep (B04, D34) St ation Pairs From 1978-1990 . . . . . . . . . . . . . . . . 371 3.3.4 5. Anr.ual Meen and Overall Mean Dry Weight Pioraass, Noncolo-nial Number of Taxa, Abundance, and Laminario sp. Counts , on Surface Fouling Paneln Submerged for One Year at Stations B19, B21. B04, and B34 During the PreoperatAonal
*eriod (1962-1984 and 1986-1989) and in 1990 . , .. . . 373 2
3.3.5-1. Annual Geomatric Mean Density (No./m ) of Selected llen-thic Species Sampled Triannually in May, August, and November Free 1978 Thrungh 1990 . . . . . . . . . . . 382 3.3.5-2. Reruits of Two-Way Analyses of Variance Comparing log-Transformed Densities of Selected Denthic Species at Near- and Farfjeld Stat ion Pairs (1MLV/5MLM, B17/B35, B19/E11) During Preoperctional (through 1989) and Opera-tional (1990) Periods . . . . . . . . . . . . . . . . 383 3 3.5-3. Annus1 Mcan Length (mm) 6nd 951 Confidence Intervkl for Selected Benthic Speciss Dampled Triannually in May, August, and November et Salected Benthic Stations From 1982 1hroug,it 1900 . . . . . . . . . . . - . . . . 38i i
'Yvili - - _ _ _ _ _ _ , ]
PAGE 3.3.6 1. Number, Percent Composition and Mean Density of Lobster Larvao by Lifestago at Stat ions P2, PS and P7, 1978-1990 395 3.3.6 2. Results of Analysis of Variattcc Comparing Densities of Lobeter Larvae Collected at Intake, Discharge, and ) Farfield Stations, and Catches of Total and Legal Sized j Lobsters, Jonah Crab, and Rock Crab at the Discharge St ation nr.d kye Ledge . . . . . . . . . . . . . 399 3.3.6-3. Monthly. Annual, and Preoperational Mean and Upper and Lower 95*. Confide.nce 1,imit s of Total and Legal-Size LoLatet Catch Per Trip Effort at the Discharge Site From 1975-1990 . . . . . . . . . . . . . . . 403 3.3.6-4. Comparison of Catch Per Unit Effort of Jonah Crab and Rock Crab at the Discharge Site and Rye Ledge, 1982-1969 and 1999 . . . . . . . . . . . . . . . . . . . 411 3.3.6-5. Annual and Monthly Mean Catch Per Unit Effort and 9:% Confidence Intervcis of Jonah ani Rock Crati Females and Ovigorous remales at the Discharge Site From 1982-1989 and 1990 . . . . . . . . . . . . . . . . . . . 414 l 'l4.7-1. Results of Analysis of Variance Cettparing Mrs Arnt.arla t Larval, Spat, Juvenile and Adult Abundancen During Preoperational and Operational Periods . . . . . 417 3.3.7-2. Estimated Distribution (percent of total) of Clam Diggers by Flat at flampton llarbor. Spring 1980 'l'hrough Fall 1990 433 3.3.7-3. Summary of Standtag Crop Estimates of Adult #ra arenarja in !!ampton !! arbor, 19671hrough 1990 . . . , , . . 437 3.3.7-4. D!.stribution (percent of total stand'.ng crop) of liarvest-able Clams by f lat at liarepton liarbor, 1979 Through 1990 441 4.2-1. Summary of Communities and Methods Vaed in Numerical Classification . . . . . . . . . . . . . . 452 4,2-2. Summary of Communities and Methods Used in Multivariate Analysis of Varianco . . . . . . . . . . . . . . . . 454 $ y 4.3-1. Selected Taxa and Part. meters Used in Analysis of Variance or Nonparametric Analogue . . . . . . . . . . . . . . . 460 xxix
I LIST OF APPENDIX TABl.ES PAGE 3.2.1-1. Finfish Species Composition by Life 5 tag,e and Gear, July 1975-December 1990 . . . . . . . . . . . . . . . . . . . 274 3.3.1-1 Henn Monthly Seawater Surface Tempercture ('C) and Salin-ity (ppt) Taken in Browns River and llampton Harbor at High and Low Tide, May 1979-December 1990 . . . . . . .. 440 3.3.1-2 Annual Hean Vith 95% CL for Temperature ('C) and Salinity (ppt) Taken at Both liigh and Low Slack Tide Frota Browns River and Hampton Hsrbor From 1980-1990 . . . . . . . . 441 3.3.2-1. A Comparison of Sparsely occurring Macroalgao Taxa in August Benthic 9estructive Samples, 1978-1989 and 1990 . 442 , 3.3.2-2. Median and Range of Percent Cover and Percent Frequency of Perennial and Annual Hacroalgao Species per 0.25 m* at. Fixed Intertidal Non-Destructive Sites During the Pre-operational Period (1982-1989) and in 1990 . . . . . . . 443 3.3.7-1. Sumtoary of Mya arenaria Population Densities f rom Annual Fall Surveys in Hampton-Sentrcok liarbor, 1971 'larough 1990 . . . . . . . . . . . . . . . . . . . . . . . .. 445
- -. ~ . . . - - . - - -- - . - . - - . - . - - - _ - - . . . . . .
1.0 EXECUTIVE
SUMMARY
I 1.1 ~INTRODUCIIDH , Seabrook Environmental Studies began in 1969 to monitor the balanced indigenous marine communities in preparation for assessing the ef fects of Seabrook Station Oper ation, plant operation began on July 23, 1990. Seabrook Station operated at full power internittently in August, for 2-3 weeks / month from September-November, then continuously in December. The purpose of this first operational report is to document i the impact of operation, if any, on the balanced indigenous population of shellfish, fish and wildlife in the waters in and around Seabrook s Station's intake and discharge. The optimal design of an impact assess-ment study ensures that a potential impact in delineated from naturally-securring variability. The Seabrook Monitoring program accomplishes this by (1) collecting data before and during operation to provide a
" temporal" reference, and by (2) monitoring arcs of potential impact as well as areas outside the influence he thermal plume to provide a " spatial" reference.-
In each biological community, the experimental design of the monitoring program focuses on its most variable aspect. For example, the species. distributions of plankton and pelagic fish change radically from season to season, but are generally similar within the study area. b The sampling program collected data at Icast monthly to monitor seasonal trends-in abundance at-a nearfield and fartield area. For benthic macrofauna and macroalgae, seasonality tends to be less of an issue in comparison to the marked changes in species composition with depth and substrate. Benthic collections were made'in the predominant substrate type, horizontal ~hard bottom ledge, along nearfield and farfield transects st regular depth intervals. The American lobster, soft-shell clam end certain fish are of particular concern because of their commarcial or recreational importance. Data on all life stages of these species were collected. 1
i i
- l Evaluation of the potent ial for impacts from Seabrook Station took place in a systematic stepwise fashion. Information collected during 1990, particularly during the operational period (August-Decem-ber) was compared to the historical data base. Potential operational effects could be ruled out if any of the following criteria were met: l i
- 1) Biological patterns observed in 1990 were similar to previous years at the neartic1d statfor.s.
- 2) Biological trends in 1990 offfered from previous years, but were consistent in both nearfield and farfield areas , t 4 suggesting an area + wide phenomenon. ;
The evaluation of potential impacts focudes on the most likely source (intake, discharge). 1.2 - IlfrAKE . MONITOR,lHQ , The goal of inteko monitoring is to demonstrate that entrain-ment and impingement have not had an adverse affect on the blota. Seabrook Station ecploys a midwater intake, located 5 m above the bottom in 17 m of water. Zooplankton, jchthyoplankton, and finfish would be the organisms with the greatest potential for entrainment and impinge- t
- ment. Year-to-year variability of organisms, nlong with their seasonal fluctuations, ano location in the water column affect the number of entrained / impinged organirms.
in plant collection of ent.-ained ichthyoplankton and bivalve larvae allows an estimation of the numeer of these groups that are ent rained. Species composition of'the entrained fish and bivalve larvae
- was similar to that collected in offshore-tows. Numbers of entrained fish eggs and larvae were lower than would be expected based on esti-mates from offshore samples; certain taxa may avoid entrainment basnd on-their preferred location in the vater. column.
l , 2
}
- w-w r- y ,e- s.-, r-vvv--,
I Entrainment has had no demonstratable effect on the plankton communities at the intake station. Macrozooplankton, bivalve larvae, j and ichthyoplankton egg and larvae communities at the intake station were similar to previous years in terms of species composition and abundance. Species composition of the microzooplankton community from mid-September to December in 1990 was unusual in comparison to collec-tions made from 1978-84 and 1986, when microzooplankton were last , collected. However, community composition was similar at all three sta-tions, suggesting that this difference was not restricted to the nearfield area. Similarly, community composition in 1990 of holo- and meroplankton,- and bivalve and -ichthyoplankton larvae was statistically similar at the intake, discharge, and farfield areas. Tychoplankton, species that are associated with the substrate during most of theit life - but occasionally venture into the water column, continued to show nearfield-farfield spatial differences because of their affinity vith
- the bottom substrate. Some of the ichthyoplankton egg taxa also showed -
spatial differences,-but in 1990 these were evident only during tha *
-preoperational period. Most taxa did act exhibit-reduced densities at the intake, indicating that there was no relationship to plant opera- .
tion. The number of adult fish lost from impingement has been low. ( In 1990, a total of 499 finfish and 4 lobsters were impinged. Demersal species, including lumpfish, pollock, longhorn sculpin, and windowpane were the most numerous spacles impinged. Lumpfish-in particular tends to be associated with rocky areas or other structures; the intake-ctructure may provide attractive habitat for this species. -Pelagic species, even those that preferred the mid-water zone, v3ro rarely impinged. 'l Trends in the adult finfish community were examined in light
'of'the combined effects of egg'and larval entrainment and adult-impinge-
~
- f. - mont. Because of the widespread movements of pelagic fish,f there is no-
- valid reference area. Impact assessment _ instead focuses '<n. a comparison of trends in 1990 to previous years. Two pelagic species showed catch 9
I m._...m=_.___._..._...__.~...__ _ _ . _ . - . _ _ _ _ , _ _ _ _ _ . __- . . - - - _ . .
I differences in 1990, but these differences appeared to be unrelated to plant operation. Catches of Atlantic mackerel were significantly higher in 1990 than previous years. As high catches were observed beginning in June, this differnnce appears to be unrelated to plant operation. Atlantic herring catches were substantially lower throughout 1990 continuing a trend of decreasing abundance, first noted in 1988. Diminishing catches of Atlantic herring have been observed both locally and regionally (NOAA 1991a). Aside from these two species, the pelagic fish community showed no differences in species distribution and abundance from previous years, 1.3 DISCHARGE lQF.1TORING 1.3.1 Discharge P1rme Monitoring Potential impacts in the discharge plume are related to the threat of exposure to elevated temperature in surface and near-surface waters. Surface-dwelling organisms, phytoplankton and lobster larvae, are those most likely to be entrained in the discharge plume. Water temperatures at the plankton intake station in June and August-December were higher in 1990 than, on average, previous years. However, given the natural variability in water temperatures, temperatures throughout 1990 at the intake were statistically similar to previous years; furthermore there were no differences in water temperatures among the intake, discharge, and farfield stations. Continuously-monitored surface temperatures at the discharge were similai to a fartic1d reference station during the first two months of operation. The average monthly difference was less than 0.22'C. From August-December, dis-charge temperatures averaged 0.8-1.6'C higher on a monthly bas!s than those at the farfield ststion. The phytoplankton species assemblage has histo *ically shown , little stability in terms of densjty level, community structure, and seasonal patterns. Collections in 1990, resumed af t er a three year 4 l
l l hiatus, were markedly different than previous' years. Total abundances at all-three stations were consistently higher in 1990 when compared to 3 the previous years average. Colonial Cyanophyceae (blue-green algae) ' predominated _during most of 1990 at f atake, discharge, and farfield , station. As these organisms were present prior to plaat start-up, appear to be widespread in the Gulf of Maine (Balch et al.1991), and < occurred at both nearfield and farfield areas, their occurrence appears , unrelated to plant operation. Aside from the colonial cyanophytes, the remaining taxa showed seasonal trends and abundance levels that wero similar to previous years.. Of particular concern lo the phytoplankter Conysular sp., >
. which produces paralytic shellfish poisoning (PSP), or red tide in this ,
and other coastal areas. This organism usually reached toAic levels (as measured in Nytllus edults meat by the State of New Hampshire) in May or
- June in Hampton Harbor, causing closure of flats to bivalve shellfish
- fishing for a period of one to seven weeks each year. In 1990, toxic i- levels of PSP.were recorded in late May through June in Hampton Farbor ,
at levels generally much lower than those obs'erved prior to 1990. Lobster larvae (Stages 1-IV) have a strictly surface orienta-
- tion. In coastal New Hampshire, successful recruitkant of larvas is the
~
single biggest-factor in determining the level of adult catches. All stages were rare in the study aren, generally occurring from June to October, with highest denalties from late Jane =through late August, i-
; Evidence'auggests that waters off Hampton-Seabrook may be too cold for local production ofilobster larvae, and those' collected off Hampton-Seabrook'may actually'ori tjnate from elsewhere 1w the Gulf of Maine and-from Georges Bank. In 1990, unusually large numbers of Stage I lobster
- larvac were caught in July Lfollowed by exceptionally large numbers of Stage IV: larvas in' August. These unusual aggregations may have bean assoc a ei t d with areas-of water mass convergence, where lobster larvae [
- have been fSown to accumulate. Higher-than-average surface temperatures may also have contributed to higher numbers of lobster larvas.
As high 5: y y rN-~ 4 -rw w ,s -v --, t- <<xum -- - - - - --r , e- , - - - - - v ,1 - ~ - , - -4 N"
I 4 numbers of :arvae were found at both nearfield and f arfield areas.pr(o to plant start u}, these avents are not related to plant operation. Subsurface fouling panels, located three meters below the surface, placed in the discharge plume area show the timing, type, and abundances of settling benthia. organisms. Benthic recruitment and community development have shown a seasonal pattern that has been highly consistent from year to year. Historically, recruitment and sett1 ment activities have been low in winter and spring but Intensified from summer through fall. Seasonal patterns on surface pancis in 1990 were similar to previous years. Differences occurred in the settlement level; abundance, biomass, and taxa richness (short-term panels) were higher than previous years, whereas community development (monthly sequential) biomasn was lower. As these differences occurred at both nearfield and farifeld areas, they are most likely unrelated to plant
- operation.
The intertidt; and shallow subtidal area near bunk Rocks is o outside the. innediate plume area, but might be exposed to slight ,eleva-, i tions in temperature. Species composition of benthic macroalgao'h51 1. macrofounal communities in the intertidal and shallow subtidal areas changed with-depth and substrate, but was hfghly similar among years. Community composition of intertidal and shallow subtidal macroalgae a.nd intertidal macrofauna in 1990 was similar to previous years. The shallow subtidal mecrofuana assemblage in 1990 was more similar to rid-depth assemblages than to shallow subtidal assemblages from previous years. .High numbers of the barnacle Balanus cronatus contribated te the observed differences. Individual species showed significant variations in recruitment levels from year to year-and among stationn. As the plant operated for only a few days before collect. ions for benthic community analysis were made', it is unlikely that there are any plant-relatad differences. Differences either occurred at both nearfield and farfield stations or were not restricted to the operation-l al period with-the exception of one case. Mytilidae at the nearfield 1 l 6 P
= - E ,.y. ,. =,w,<w -v---- , - < - +
w shallow subtidal station were significantly higher in abondance than previous yearn. As this result relies on only one collection (November) it cannot be definitively related to plant operation. L 1.3.2 ILtnihis.Jonit odn3 i The mid-depth and deep nubtidal areas were monitored to L determine if, daring operation of the circulating water system dis- .. - charge, any discharge impacts resulted from increased detritus levels. Year-to-year differences in the macroalga9 and macrof aunni communities have been small in comparison to variations with depth and substrate, t The species composition was high1, predictable and distinct for each ' depth rene. Senthic community collections in 1990 were similar to previous years. Since they were collected af ter only fout days of coumercial power generator, no differences were expected. Indiv!. dual macrofauna specias historically have shown significant difference: among years in their utnuel abundance levels. Only one taxon, Mytilidae, {~ showed n difference in 1990 that was restricted to the nearfield mid-depth station. However, increased abundance levels occurreo throughout the year and were not restricted to the operational ,neriod. The demersal fish community cooid be susceptible to a number of plent-related effects, including larval entrainment, adult impinge-ment, and detrital effects on their primary food resource, benthic macrofauna. Because of distinct differances between the nearfield and farfield stations, potential plant effects were investigated separately for the two steas. While large num5ers of commercial lobster traps have prevented sampling the nearfield station in Septenber and October, U- makinc impact assessment during those months difficult; seasonal move-ments of the dominant speclec, which composed nearly 8u% of the total
*- catch, were found to be similar in 1990 to previous years. bower catches of Atlantic cod and hakes !n 1990 caused decreases in total catch. As diminished catches of theco species occurred prior to plant operation, they are unrelated to plant operation.
s 7
. . ~ _. _ _ _ _ _ _ _ _ __. _ .__ _.. . _ . - .._ . _ _ _ . _ _ . ... ._. _ ._. _ . __
\
Because of its commercial im;ortance, the American lobster was ; monitored _in the discharge area. Seasonal patterns in cat ches have been ! similar from year l~ year, affected by bottom tenperatures that influ-encel molting and activity levels. Catches usually increased to a peak ' in August or September, then declined. Monthly Icbster catches were ; consistently higher than eterage in 1990 at both dischrrge and farfield
- - stations, reflecting trends observed throughout New England (NOAA ?
1991b). Since 1984, annual mean catch per unit effort of legal-L4 sed , lobsters has been.below the )6 year average except in 1486 This apparent decline, a primary concern to lotstermen, war, a resalt of r.atural variation in ' combination with the ef fects of the changes in the legal size limit instituted in.1984, 1989, and 1990 by the State of New Many lobsters that would have been of Icgal size under the Hampanire. old law were protected from harvest until their next molt. Toe increase in legal size in 1990 reduced catches to approximately 3% of the total cctch, the lowest level observed since the beginning or the study. Jonah and rock crabs are two other important et,15enthic predatorr._ Jonah crebs exhibited lower tatches st the dischstgo area in 1990; however, these differences were first observed prior to plant operation and thus a;, pear unrelated. Rock crabs have shown large fluctuations in annual catches. liigher-than-average catches in 1990 u . vere due-to large catches from June _through August at both the dischar ou area and Ryo. Ledge. There van no evidence of plant-induced = effects. ' n l 1,3.3 Ettuarine MonitorJ,gg i 1 l: Although the likniihood of a rooling water system operational impact on the-Hampton-Seabrook_ estuary is low, temperature,_ salinity, L -benthos, fish, and the suft-shell clam were all monitored in tha estuary, q Temperature and ratinity both showed regular seasonal cycles. , L ' Maximum temperatures unually occurred 'in July with minima in January or 8 l
* -=ww..r4.r--.-...b-..v- ...<,,m_r,.r-r ,,,,,,.n&wv- ,r, .,.,,c. , . . - e, , - - . c_
' February. Saljnity levels had a less distjuct pattern, but were usually lowest in pring, a result of increased runoff, and highest in summer.
Salinity levels in Browns River were high from 1980-1982, coincident with low precipitation Icvels and highest discharge voltats of tut.nel dowatering through the Seabrook settling basin, which terminated in 1983. By 1986, salfuity levels had returned to pre-1980 levels where they have remained af.nce. The estuarine centhic community was highly variable in species comp 7sition and abundance, but predominantly composed of surface and subsurface deposit-feeding polychaeres. The number of species, total abundance, and abundance of some et the dominant species increased _during the period when salinity levels were higher than average, but have returned to the levels observed prior to the tw.nel desstering discharge; no substantial changes to the b9nthic commanit'J were ovident in 1990. Estuarine fish ircluded anadromous species as well as re:f-
- dan.ts . Alewives and blueback herr!ng pass into the estuary.in spring, c
travelling upriver to spawn. Catch levels were affected by yeat closs strength as well es 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 ceught in the estuary..but historicelly have never constituted a anbatantial porrion o# the total catch. In'1990, smelt' composed 35% of_the total catch, the result of large numbers cf smelt in May and August. The predominant' zrnsident species has'baen Atlantic bilverside, which made up over two-thirds of the total catch and.nearly 90% during their most abundant period, August through November. Variations in abundance of this specius was the single most important factor in year-to year changes in total catch. Abundance of Atlantic silverside was lower 1.n 1990 than average, continuing _the trend of decreased abundances first observed in 1982. The species of greatest concern in the Hampton-Seabrook estuary is the soft-shell clem. - Density lev 31s of spat, juveniles,
-and/or adults have been monitored in the estuary since 1969. Densities 9
, . _ _ - . ~ . . - - . - . . _ - . - - - , - . - - . - _ _ _ _ . _ - - . - . - - _ .
I of harvestable clams depend on a set of complex, interacting conditions. i' A successful set of spat is crucial, but this factor alone does not ensure high densities of harvestanle clams. Once settled, survival of 3 young-of-the-year clams depends on protection from its two main preda- , tors, green crats and humans, as well as from disease. In 1976, a large j I spatfall throughout the estuary result ed in high densities of harvest-able clama in 1980-1982. Increased levels of predation prevented recruitment of the highly successful spatfalls in 1980 and 1981. Light-spatialls from 1982-1988 in combination with an increase in predation ; have accounted for a precipitous decline in standing stock since 1983. In addition, neoplasia, a cell growth disease fatal to clams, has been [ detected f rom clams In llampton estuary. This may also have contributed ; } to the decline of harvestable clams. Experimental seeding cf clam spat I has been conducted in Hampton liurbor in 1987 an-1 1988 by the State of j New llampshire in one flat area was not successful. However, the possibility of augmenting the Nya population artificially must be fac- ; tored late the monitoring program. Young-of-the-year settlement increased _in 1989 and again in 1990. Survival of the-1989 year class at Flats 1 and 2 was evidenced by increased yearling densities. This may l in part be due to decreased green crab catches and reductions in digging activities. ! , 1 f L L j 10
m _ _. __ . .__. - _. - __ ... _ ._ .. _ __ _ _ _ - .. . . _ _ _ _ ___ _ _ i i 1 2.0 DISCtWSION 21 INTRODUCTION 4
- 2.1.1 General Perspectlym Environmental studies for Seabrook Station began in 1969 and 1 focused on plant design and siting questions. Once these queations were ;
resolved, a monitoring program was designed which has examined the ' structure of all the major biological communities as well as the distri-bucion, abundance, and size of selected species within each community. The goal was to ansess the temporal (scasonal and yearly) and spatial (nearfield and farfield) variability that had occurred during thn !
; preoperational period. This report focusca on data collected since 1976
'for fisheries studies and since 1978 for plankton and benthos studies as these yearn signify the beginning of a consfrtent preoperational -
. campling1 design.
Seabrook Station operation began interr.ittently in July and , August, and continued for periods of approximately three weeks in September and October. After operation'at 100% for:less than a week at the beginning and end of flovember, the plant operated continuously for-the month of' December (Table 2.1-1). Although the plant was not 8enerating power t hroughout 1990, the circulating water system was i active throughout the.twel"c-month perJod. ; The period beginning in August 1990 is cons.fdered the begin-ning of'the operational period for the purposes of the environmental >
.ansessment of plant-related effects. Previous reports provided a '
perspective on the sourcen and n.agnitude of the naturally-occurring variability.against which environmental: conditions during operation - i would be compared. Identification'of the Invel of var' lability, both - spatial and temporal has been a critical component of this program, one which was a major fociis for sampling design. The degree of variability has.important implications for impact assessment. The rationale for 11 E- - .v.
, - 4 gy-.y ,_ca. -m--w., v6 ,- - , ,-,y- Eo.4. ---. _
r
-TABLE 2,1-1. NUMBER OF DAYS OF OPERATION AND AVERAGE DAILY FLOW OF SEAPROOK STATION CIRCULATING WATFR SYSTEM IN 1990. '
SEABROOK OPERATIONAL REPORT, 1990. DATES OF DAYS OF CIRCULATit1G 100% POWER NUtIBEis or VATER SYSTEM AVERAGE DA]LY MO.4TH GCNERATION PAYF OPERATION FIDW (mgd) Jan D 31 324 Feb 0 28 564 Mar 0 31 563 Apr 0 30 563 May 0 31 562 June 0 30 563 Jul 23-26 4 31 582 Aug 7-12 6 31 588 16-22 7 27-31 5 . Sep 1-19 19 30 588 Oct 4-27 24 31 590 Nov 5-9 5 30 590 25-30' 6 Dec- 1-31 31 31 589 I n b f ., 12 l
focusing on specific sources of variability for each component of the monitoring program is discussed in the following section. 2.1.2' Rolirces of B.nc11pt_Nerlabl111y The_ optimal design of an impact study has four prerequisites
-that ensure that a potential impact is delineated from any naturally-occurring- tariability (Greer.1979): (1) knowledge of the type, time and
-placa cf potential impact; (2) measurement of relevant environmental and biologleal variaba(n; t!) moritoring before the potential impact occurs to provide ~a temporal control; (*) mo-ltoring in an aren vnaffected by impact'to serve as a spatial control. The experinental design of the Seabrook Environmental Program was structured to meet these prerequi- ,
sites. ,< + A basic assumption was that there are two major sources of naturally-occurring variability: '(1) that which occura among dit'ferent ! areas or stations, 1;e., spatial, and (2) that which varies in time, 7
. from daily to weekly, monthly _or, annually. In the experimental design i and analysis, these studics focused on the major source of sariability
- in each' communit.y type and then determined the magnitude of variabill'.y 5 inLeach community ('rigure 2.~1-1). In certain aommunities.,particularly- j
-planktonic, where circulation patterns provide a similar habitat throughout the area, spatial. variability was found to be low in compari- _
- son'to seasonal. *lhe study design therefore focuscs on frequent -
aampling to monitor seasonal trends generally at only one farfield and one nr.two nearfield stations- . In other communities,..particularly benthic, rpatial variability has been higher than seasonal variability. _
. Benthic sampling design has focused on the dominant. substrate type in the, discharge area, horizontal hard-bottom lodge, with paired neatfield
'and farfield stations representing the major depth zones. Fin fish -- -
catches have shown both~ seasonal-and spatial differences. Therefore,- , these. studies make1 frequent (at least monthly) collections in the aren
.'of the discharge as well as farfield areas to the north and south.
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= Me Of A%YSIS NONPARAMETRIC ANALOGUE Figure 2.1 1 Schernatic of sources and levels of variability in Seabrook Environmental Studies.
Seabrook Operational Report,1990. 14 1
1 Because the estuary is an aquatic nursery area and recreationally-important clam flat, baseline collections monitoring seasonal and annual patterns were also made there for operational phase comparison. Biological variability can be measured on two levels: specfes and community. A. species' abundance, recruitment, size and/or growth are important for understanding operational impact, if any. For this I reason, = these parameters were monit ored for selected specins f rora each community type. Species were chosen for more intensive study based on :
- their commercial or numerical importance, sensitivity to temperature potential as a nuis6nce organism, and habitat preference. In some i.
cases, a selected species actual?y encompassed a complex of species grouped together in a_highnr phylogenetic category. Components of and J rationale for, species " complexes" were discussed in the 1984 Data Report (NAI 1985a). Overall community structure, e.g., the number and type of species, total abundance and/or-the dominance structure, may also be ' affected-by plant operation in a way not detectable by monitorin.g singlo ; 4 species; therefore, the natural variation in community structurn was monitored at the regular-time intervals determinnd by early sttui.f es to Ibe sufficient for.this purpose.
- Appropriate st atistical methods must be used in conjuncticn ,
with a well planned- experimental. lesign in order to determine tho -j
- sources and magnitude of variability. Temporal (annual).and spotfal ;
variability in species abundance and size were tested by using analysis ; of variance or nonparametric analysis that provide a means of evaluating , the statistical- significance of changes --in the 'operat ionn) period; i Spatial, seasonal, and annual variations in community structure worn j assessed with numerical classifJcation or multivariate analysis of variance. Specific statistical oesigns are described in the Methods [
-- (. S ec t ion , 4 . 0 ) .
4 Identification of the sources and levels of variabill'ty ut.it- - izing-the' methods discussed above has its ultimate focus on the sources , of potential influence fr m plant operation, and the sensitivity of a 15
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1 i n e community or parameter to that influence (Table 2.1-2). Naturally, a community or species might be af fected by more than one aspect of the , cooling water system; however, the focus here is on the aspect of main ; concern. In general, intake (pumped) entrainment and impingement would potentially affect mainly plankton communities, including fish eggs and larvae, and juvenile and adult fish. I f they occur, thermal effects from the discharge (e.g. plume entrainment) would most likely affect , neershore surface watnr quality, phytoplankton, lobster larvac, and intertidal and shallow subtidal benthos. Although no ef fect s are anticipated An the estuary from the offshore discharge, fish and soft- ' shell clam populations have been monitored in that area to provide a baseline for operational phase comparisons. Bottom-dwelling organisms, , including macrofauna, macroalgae, epibenthic crustaccors, and demersal , fish, may be . influenced.by detritus potentially arising from moribund ! entrained plankton that ir, discharged with the cooling water . A ; previous impact assessment (NAl 1977e) has shown that the balanced indigenous community in the Seabrook study area should not be adversely influenced by the above factors. Results from the biological communi- , ties, species and environmental paremeters sampled will be discussed in light of the feature of the cooling water system that has the greatest pottsntial for affecting them. . t 2.1.3 Im2A93 ld;11amAt, r The purpose of this report is to assess the impacts of the first several months of commercial operation of Seabrook Station on tho ; aquatic biota of coastal waters of New llampshire. Two impacts of con-
~cern, entrainment ond impingement, were addressed ~with in-plant monitor-ing of- the organisms entrapped in the circulating water syst em (CWS).
The effects on.the. balanced. . indigenous population of aquatic biota in the waters in the' vicinity of-the CVS intake and discharge structures E - worn evaluated through contir ued monitoring ut the stations established , during the' preoperational per'iod and statist ical comparisor, of the re-sults on both the community and the species levels. 16 u F m- e r-,,,,mimre--=----h-ww-.rw -,m -w,..-rnrv ,eer- e-r m m _.a .,-e,,...r',- ,4 -*-. w..
. . . _ - . - ~. . - . _ - . . . . - - . - - - . _ - - . - . . . -
TADI.E 2,1-2.
SUMMARY
OF DIOLOGICAL COHHUNITIES AND TAXA HONITORED l FOR EACH POTENTIAL IMPACT TYPE. ' SEABROOK OPERATIONAL, REPORT, 1990. 1.EVEL HONITORLD SELECTED HONITORING SPECIES / AREA IMPACT TYPE SAMPLE TYPE COMMUNITY PARAHETERS Intake Entrainment Microzooplankton x x Hacrozooplankton x x Tish eggs 'x Fish larvae x x Soft-shell clam larvae x Cancer crab larvae x
'mpingement Juvenile / Adult fish x x l Discharge Thermal Plume- Noarshore water '
quality x
.Phytoplankton x- x ,
, Lobster larvae x Intertidal / shallow subtidal macroalgae and macrofauna x x Subsurface fouling community x x Detrital Rain Hid-depth / deep macrofauna and macroalgae x x Bottom fouling community x Demersal fish x x
.Lebster adults x 7 Cancer crab adults x
' Estuary Cumulative
-Ecurces Estuarine temperntura x
Soft-shell clam spat and adults x Estuarine fish x x 3 17 _ - ., - .-... -- - . , . _ . . . ~ - . - . . . . . . . - . . . .
l l / l The ability to determine whether operation of Seabrook Station has affected the " balanced, indigenous population" is dependent upon a systematic approach to impact assessment incorporating both temporal and spatial components (rigure 2.1-2). potent tal operational ef fects could be ruled out if . 1990 results were similar to previous years or 2) 1990 differencet< were observed in both nearfield and farfield areas. In addition, other potential sources of change were investigated before i concluding that plant operation af fected the aquatic biota. 2.1.4 SampRng 1.ncatinn i Plankton and water quality studies have been based on samples collected in the nearfield (intake) area and a f arfield aren (Rye bcdge) located beyond the influence of the Stat ion's operation. In July 1986 ; sampling at a third station (PS) was resumed in the vicinity of the discharge (Figure 2.1-3); preoperational sampling had been conducted at ; P5 for various -planktcn progrnms from July 1977 through December 1981. fI D- . In addition, bivalve larvae were collected from llampton liarbor (PI) starting in-July 1986. Entrainment sampling was resumed in June 1990 for bivalve larvae and ichthycplankton. Fish were sampled offshore by bottom trawls and gill nets near the discharge area and at two farric1d t sites, and by seining at three locationn in the llampton-Scabrook estuary (Figure 2.1-4). Marine algae and benthos unre collected by divers at a series of stations stratified by depth near the intake / discharge area and in a farfield area (Table 2.1 3, Figure 2.1-5). Benthos in soft substrate was sampled along two transects in the estuary (Figure 2.1-6). , Lobster (Howarus americanus), rock crab (Cancer Jrroratus), Jonah crab
. (C. borealls) and green crab (Carcinus caenns) were collected in traps _.
(Figures 2.1-6, 2.1-7). Soft-shell clams (Nya arenaria) were dug from-five flats in the estuary (two flats were dug only for spat starting in
. 1985)' (Figure 2.1-6), with farfield spat stations in Ipswich, MA and in
. 0gunquit,- ME (through 1984 only) (Figure 2.1-8).
18 t,+,-.,.e,w..we%w.,e.. y-, ~ w , , , m.,.u...._,. ,..r m.m. , , , , , . . _ _ . , , . . , . . _ . . . ..,.,..%4,., .#,,em...-,r_.,mp.,Wn. .-% .-.per v c.www
t SEQUENCE OF EVENTS FOR DETERMINING IF THERE ARE ENVIRONMENTAL CHANGES DUE TO OPERATION OF SEABROOK STATION is 1900 si_mtlar to YES W previous years at nearfield
> impact station
?
s NO 1990 nearfield similar to YES m No F farfield impact
?:
NO 4 Observed changes NO N0 related to plant
> Impact operation
?
YES Y i Op6 rational impact
-a 4
4 Figure 2.12. Sequence of events for determining if there are environmental changes due to the operation of Scabrook Station. Seabrook Operational Report,1990. 19 a:-- ; . ,.+- . .. .-...--.-,.----.--,---..:-.,,-.,-,.,,,--, . . - . , . -- , _ - -
N
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l 'W::: =@ T_. x - t r. I \ ,/ , se o 6 1 NALITCAL MILE l \*/ 8 O 1 i i 2 K!LOMETERS SCALE SAL 158t'Ar 8r.ACil CONTOUR DE PTH IN METER $ 5 . bivalve lanae and water qua.fty $!gcr$ . ichtnyoplankton, phytoplankton and Zooplankton sta ms e - continuous temperature s:ations E1 . Seabrook Entreinrnent Stron h . lotster latvaa sta:ms Figure 2.1-3. Plankton and water quality sarnpling stations. Seabrook Operational Report,1990. 20
fyYELEDGE
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- T . 0t's Trawis is S . see.e Iws -a . G1 Nes Figure 2.1-4. Finfish sampling stations. Scabrook Opuational Report,1990.
21
-TABl.E 2.1-3. BENTilIC ALCAE AND HACROFAUNA STATION 1,0 CATIONS AND DESCRIPTIONS. SEADR00X OPERATIONAL REPORT,-1990.
D2PTH"' LOCATION APPROXIHATE COMPOSITION m - f t. STATION LONGITUDE LATITUDE OF llARD SUBSTRATES-4.6 15' -B17 706 47'37" 42'54'00" Algae covered ledge (95%) and crustose , covered ledge (5%) 4.6- 15 B35' 70'46'07" 42'57'22" Algae covered Indge (85%) ' and boulders (15%)- 9.4 31 B31" 70'45'29" 42'58'04" Algae covered rocks (30%) mussel beds (60%) and cobble (10%) L4 31 B16 70'47'03" 42'54'.16" Alpae covered ledge (75%) and mussel beds (25%) , 12,2 40 B19 70'47'13" 42'33'40" Algae covered ledge and boulders (60%) and mussel beds (40%) t 18.3 60 B13 70'46'58" 42'53'54" Algae covered ledge and boulders (40%) mussel L beds (55%) and cobbin (5%) 18.9 '62 B04- 70'45'59" 42'53'23" Mussel beds (70%) and-algae covered lodge (30%) . 21.0 69- -B34 ' 70'44'06" 42*57'23" Mussel beds (60%)'and algae covered ledge and boulders (40%)
- 0. 3 1 BINLV 70'47'41" 42'53'56" Algae covered ledge (90%) mussel beds-(101) 1.3- 4 B1MSL 70'47'46" 42*53'50" Algae covered )cdge (100%)
n.3. 1 B 5 M UJ* ' 70*45'36" 42'58'19" Algae cove. rad ledge and boulders (90%) mussel beds (10%) 1.3l 4 B5MSL' '/c ' 4 5 ' 44" 42'58'12" Algae covered ledge (100%' -
" approximate _ depth be'Iow mean-low water, subtidal stations .
c' approximate depth above meci Iow water, intertidal stat ions farfield stations 22
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" CONTOUR DEPTH IN METERS SAIJ58t/RY #E4cu r i . - -s, o . n- n . a .a Figure 2.1-5. Benthic marine sampling stations. Seabrook Operational Report,1990.
23
f zy'l
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$ = Cam Rats E . Green Crat Traps @ BR = Escanto Temperavelhfme5 Figure 2,1-6. Hampton. Seabrook estuary temperature / salinity, soft-shell clam Mya arenaria arid green crab Carcinus maenas sampling stanons. Seabrook Operational Report,1990. <
24
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Figure 2.1-7. Locations of lobster and rock crab trapping areas. Seabrook Operational Report,1990. 25
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[3 - study sites i I l Figun: 2.1-8. Sampling sites for Mya arenaria spat. Seabrook Operational Report,1990. I 26
. - - - . - . .. . - - .- . - - - ~- . .. . ~
2.2 INTAKE AlWA_ lids 110AlEQ 2.2.1 E.lanhLun The focus of monitoring plankton in the_ intake area was to evaluate the offect of entrainment on community structure and population levels. Due to their limited control of horizontal movements and broad vertical distribution in the water column, all types of planktonic organisms could'be exposed to entrainment. Data on actual levels of entrainment are presented to quantify losses to the bivalve larvae and icthyoplankton communities and individual species. Comparisons of community structure and abundances of selected species in the near field area during the period of commercial power generation (August December 1030) were made to both the farfield area in 1990 end the nearfield and farfield areas historically. Thesc comparisons address the question of whether the balanced, indignnous population has been af fected by thra commercial operation of the plant. An estimation of the number and type of plankton species affected by plant operation depends on (1) the time of year, and (2) the degree of yearly variability. Results from the community analysis give an indication of.the number and type of species present (and thus entrainable) at any particular time of voor. The selected species analysis enables a more precise estimate of the ent rainable density for key species by examining their annual and seasonal variability.
-Knowledge of the within-year and among-year variability allows for more reliable _ estimates of impact than relying on samples taken in a single serson and year.
2.2.1.1 ERLT11nsmit U Beginning in 1985, Seabrook Station operated its circ ulating water cooling system, although no power or hented discharge were produced until 1990. Entrainment samples were collected through June . 1987. Since that time until 1990, the circulating water system had nr,t 27
, . . , . . _ _ . . . _ . . _ . _ .- . ~ _ _ - _ _ , < . _ _ _ .
-been operat'ing at a-frequency or capacity sufficient to warrant further
~
sampling. Entralnment sampling was reinitiated in June 1990 for both
. bivalve-larvae-and lchthyoplanktou.
Fish' egg, larvac, and bivalve larvae communities entrained during the July 1986-June 1987 period were similar to those collected offshore, although the smaller sample volumes and less-frequent rample collection its the ~ plant . produced some expected ' dif ferences . The top-ranked entrained fish egg and larvae and bivalve larvae' species were similar t:o those from offshora collections (NAT 1990b). Abundances of most of the dominant species of eggs were Jower in entrainment samples than in of tshore samples, in some esses substantially so, due to the diff erent depths represented by the two types of samples. The dept h
- j. distribution of ichthyoplankton is typically uneven, particularly-for eggs of someispecies, which are heavily concentrated near the surface or the bottom thus making them'less susceptible to entrainment. Abundances
, of fish .arvae and bivalve larvae were similar in in-plant and offshore collections Jn 1985 - 1986 .(NA1 1990b). c The resultsiof; the in-plant sampling in 1990: confirmed observations made previously. Generally the relative abundance of both 3 ichtnyoplankton and bivalve larvae was similar betteen of fshore (Station L P2) and in-plant (entrainment) samples (Table 2 2-1), while several l' species of fish eggs were less abundant in the in plant samples. Cunner larvae (not a dominant in'prevfous comparisons) were much less-abundant ; in the in plant samples, reflectin'g~this species' preference 'for;the
- near-surface waters as
- demonstrated in dici studies of vertical strati-
-fication (NAI'1981b, 1981f). Abundances of_ bivalve larvae inLin-plant Esamples averaged about 30% higher than in of fshore samples,- with f -differences species! specific-(Table 2.2-1). Although species were' '
- w. .
! ranked the same in in-plant and offshore collections, NeteranocIn ' squamula, Madiolus modiolus and R.intello-rp. oppenrod to be moce commonly entrained, indicating that larvae of these tar,a are not. distributed homogeneously -in the water colu nn. In general, however, the species composition of the plankton likely =to-be entrained in Seabrook p 28 -
COMPARISON OF GEONETRIC HEAN APUNDANCES OF TABLE 2,2-1. ~ TOP-RANKED FISl! EGG, FIS!! 14RVAE, AND BIVALVE LARVAE TAXA COLIECTED OFFSli0kE AT STATION P2 AND IN ENTRAINMENT SAMPLES AT SEABROOK STATION FROM JUNE TilROUGil. DECEMBER 1990. -SBABROOK OPERATIONAL REPORT, 1990. ABUNDANCE" DOMINANT SPECIES- ENTRAINED (E1) 0FFS110RE (P2) Fish eggs b
-Cunner /yellowtail flounder 51 444 Rockling/ hake 44 247 Windowpane 43 170 llake 35 491 Atlantic cod / haddock / witch flounder 27 17 Atlantic mackerel 12 26 Atlantic whiting 8 11 Fourbeard rockliag 7 9 Fish larvae b-Cunner- 9 178 Tourbeard rockling 6 2% !
Atlantic seasnail 6 { Hake 2 Windowpane 2 4 1
.. Radiated shanny 2 3 j Winter flounder, 2 2 i Atlantic whiting 1 7 J
-Atlantic mackerel <1 i
- B1 valve larvae
- Hytilus edulis 3621 3442 Reteranonia squamula 2633 1649 Mcdlolus modlolus 120 275 Rintella sp. 594 245 Hya arenerla 9 11
- Based'only on periods when entrainment and offshere samples were collected within several days of each other
.D
- No/Ig00m#
*No./m i
i
~
29
. - -. . .. .. . - - . - - ~ - . . .- .. - ~ .a- .
- n> ,
Station's circulating water system was similar to the of fshore environ-ment as measured:by plankton sampling. Therefore,' offshore sampling tb 'results can be;used to give a rough estimation of species composition and abundance likely to be entrained. An estimate of the total number of bivalve larvae and ichthyo- , plankton entrained during the period of in-plant sampling in 1990.is reported in Tables 2.2-2 and 2.2-3, Bivalve larvae entrainment was highest in June and July. Nytflus edulis was the predominant species u subject to entrainment, along with hadiolus-codiolus and Feteranosia squacula. -Fish egg entrainment was highest in June and July; over 80% , b of the eggs were Atlantic mackerel and cunner /yellowtail flounder. Larval-losses were heaviest from August to October, and the majority were cunner, fourbeard rockling, Atlantic seasnail, and Atlantic whiting. Slightly less than 1,250 million fish. eggs and. 222 million fish larvae were estimated to be entrained from June to December in-1990. Entrainment. losses estimated from in plant collections wero m:ech lower than the estimates: presented in the Summary Document (NAI .1977e), , even when adjusted for-the partial year of sampling and the use of only one unit instead-of two. .The annual loss of_ Atlant:1c mackere'l was [ _ originally estimated to be 8.8' billion eggs, or.4.4; billion _for 1 onit. If the 6-month estimate obtained for Atlantic macker21'(518.8 million) , in 1990-is doubled, it:is still much lower than the original estimate, Similarly, original estimates for winter flounder (0.158 billion),
. Atlantic mackerel-(2.26 billion) and Atlantic menhaden Inrvae (0.331 n:lllion), are all 1-4 orders of magnitude higher than the fpreliminary estimates obtained in 1990'(Table 2.2 2). The.entrainment loss origi--
nally estimated for soft-shell clam, 83 billion _ larvae per year (NAI: 1977e)'Js en order of magnitude higher than the 8.1 bil.11on estimated j from_l'990 in plant collections duringLthe period of maximum abundance I (Tabl~e 2.2-2). i~ 4 30
~ , c- . - - ;-..
.+
TABLE'2.2-2. ESTIMATED NUMBER OF BIVALVE LARVAE (in. billions / month) ENTRA'NED I BY THE COOLING WATER SYSTEM AT SEABROOK-STATION DURING JUNE-0CTOBER 1990. SEABROOK OPERATIONAL REPORT, 1990. SPECIES 'JUN JUI. .AUG SEP OCT Nytilus edulis 733.8 2,922.9 178.7 '131.3 24.6 Modiolus modiolus 151.8 421.2 19.6 309.I 17.O Placopecten magellanicus .0 0.4' O O.2 <0.1 Seteranomia squacula 130.6 915.8 301.0 320.5 23.S Spisuls solidissima 25.0 27.6 4.1 9.9 2.4 '. ^Nya arenaria 1.3 2.4 0.1 1,8 2.5 Mya truncata 5.1 243.3 0.2 0.1 0.3 Eiste11a sp. 232.4 594.4 24.6 22.5 2.7 2 Macoma balthica 0 26.4 0 0.1 0 Bivalvia '22.9 114.0 11.0 5.2 2.1 Teredo navelis 0 0. <0.1 0 0 Solenidae 28.7 27.4 3.6 0.8 0.6 TOTAL 1,331.6 5,295.8 543.0 793.2 75.0
TABLE 2.2-3. MONTHLY ESTIMATED NUMBERS OF FISH EGGS AND LARVAE (IN HILL 10NS) ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK STATICN DURINO JUNE-DECEMBER 1990. SEABROOK OPERATIONAL REPORT, 1990. TAXON JUN JUL AUC SEP OCT NOV DEC EXE4 Atlantic mackerel 499.1 19.1 0.6 0 0 0 0 Cunner /Yellowtail flounder 380.4 105.0 4.7 0.2 0.1 0 0 Rockling/ hake 86.1 10.2 15,4 1.6 0.7 0.2 0 Hake 6.2 10.9 17.6 2.2 0.4 0 0 Windowpane 13.5 10.0 8.8 4.0 0.1 0 0 Cod / witch flounder. 16.3 5.3 2.2 1.3 0.7 0.4 0 Atlantic whiting 1.5 3.6 1.5 2.7 2.0 0.1 0 Fourbeard rockling 4.2 0.7 1,7 0.7 0.1 0 0 Arerican plaice 2,3 0.3 0 0 0 0 0 Atlantic cod 0 0.2 0.4 0 0 0.9 1.0 Vitch flounder 0 0 0.1 0.3 0 0 0 Cusk 0 0.1 0 0 0 0 0 LAILE Cunnar 0 0.1 -31.7 10.2 0.7 0 0 Fourbeard rockling 1.9 0.1 16.5 11.7 7.7 0 0 ' Atlantic seasnail 8.6 2.9 0.1 0 0 0 0 Atlantic whitfug 0 0 0.3 4.4 3.0 0 0 1 Radiated shanny 4.6 0.'1 0.1 0 0 0 0 _ Hake. O r.1 1.4 2,0 1.3 0 0 Windowpane 0 0.1 0.7 2.0 1.0 0 0 Winter flounder 2.9 0.3 0 0 0 0 0
' Atlantic herring 0 0 0 0 0 0.1 0.6 Unidentified 0 0 0.3 0.3 0.1 0 0
. Lumpfish 0.6 0 0 0 0 0 0 Atlantic cod 0.5 0 0 0.1 0.1 0 0
$ American plaica 0.3 0.1 0 0 0 0 0 Witch floundar 0 0 0.3 0 0 0 0 Teutog 0 0 0.1 0.1 0.1 0 0 Atlantic mackerel 0.2 0 0 0 0 0 0
.Pollock 0 0 0 0 0 0 0.2 Fourspot flounder 0 0 0 0.1 0.1 0 0 Rainbow smelt 0.2' 0' 0 -0 0 0 0 Gulf snailfish 0.1 0 0 0 0 0 0 Goosefish 0 0 0.1 0 0 0 0 Atlantic menhaden 0 0 0.1 0 0 0 0 Yellowtail flounder 0.1 0 0 0 0 0 0 Snalifish 0.1 0 0 0 0 0 0 32 l
l i _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ . ___________...________________________________._________.________U
~
h?- , l c JThe question ofEwhether the entrainment of these and other planktonic organisms has affected the balanced. indigenous population is , addressed in-the following sections on community structure (Section
-2,2.1.2) and selected species (Section 2.2.1.3).
C 2.2.1.2> Communit'v St ructur_e - lhe' purpose off examining Lthe community structure of entrain-
~
ab?e plankton is to determine whether operation of Seabrook Station has had an effect on the balanced indigenous population of planktonic organisms; -Potential operational effects could be ruled out if the 1990 community'was similar at the nearfield to previous yearsi or if 1990
-differences were consistent throughout the area as' demonstrated by MANOVA.' . Community composition.in 1990 was compared to previous years using: numerical classification. The community composition was consid-ered unchanged if. collections at-the nearfield station in 1990 in a Eparticular' season.were.similarJto'the majority of samples from the some p 'seeson from previous years,-causing the analysis to group them together.
~
, All of:the planktonic communities discussed in this section
- had speciesl asseinblages thatc changed with season during the baseline
- period:(Figures 2 2-1, 2.2-2,'and 2.2-3h These groups were differenti-at ed-primarily on the distribution and abundance of :dominent species; howeser,-.the' relative' abundance or even absence of other species was-
.also3a factori The species entrained depend on the seasonal assemblage fpresent at-the time.
t MIS.E23Q991anktga Microzooplankton exhibited several overlapping groups in
= spring cnd summer, indicative of both some year-to year changes in.
community structure as well es 4 variable " transition period" in the late summer assemblage (Figure 2.2-1); The life cycles'of the copepods : 01thona sp._ and Pseudocalanus sp greatly' influenced the structure of 33
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. .i. ::d;i; 70,. hdhS$$SS$iN: ' ~. 5 . ,[w.'.7d"I(T;d.s.;;s:d#i'd,- i'. -:. h 3
" ',*[y' 7s rSw :.:;:: :.':: dm>s&w JANi JEB* uAR 4 APR i MAV JUN I
JUL- AUGI SEP OCT' NOV DEC 4= W 0 o 1
-x 3- zo 1 85 2- :
Io I I f PAEop - b .3 [ O'- o 1990
=m-
,O '
q- < 0 ' ' ' ' 4 1 3 5 6 7 '8 -9.' i 3 '2 GROUP
?
Figure 2.2 3. -Months of occurrence and log (x+1) mean abundance (no./1000 m)) in j . preoperational years and 1990 for seasonal groups formed by numerical' s classification of finfish eggs and larvae. Seabrook Operational Report,1990 36 \:
, . . . . - - . - _ -._,.,,m.. - , _ . , , . _ . - .
. - _ . .. - . ~ . - . .. ...
l l .- :the microzooplankton community.- Other taxa, such as cirripedia larvae (spring), bivalve larvae (summer, f all) anu tintinnids ( f all, winter) j characterized the community seasonally. From April through mid-Septem- I ber 1990, the microzooplankton community exhibited a seasonal progres-
,sion siellar to that observed between 1978 and 1986. During-the remainder of 1990 most taxa were present at similar levels to previous years, although low numbers of bivalve larvae and the presence of g - rotifers and #1erosecella norvegica in the fall made 1990 unusual, leading to the formation of a new group (6). As there were no signifi-ca-t differences in community structure between the nearfield and farfit1d stations in .'990 (Table 2.2-4), _this transttion in community
, structure is unlikely to be related to the operation of -Scabrook Station. During 199u there were no discernible impscts to the microzoo-plankton coe:munity in terms of' species composition or abundance-due to en t ra inrc.cnt . l~ Bivalve Latygg i; Seasonal variations in bivalve larvac community structure at nearfield Station P2 were consistent among years, including 1990 (Figure. 2.2-1). Riatella'sp., Mytilus edulis-and Heteranomia squamula vere regular dominants characterizing the seasonnt groups. Other species were typically abundant for shorter periods. c The similarity of the suc'ession of-taxa between 1990 and , preoperational periods indicates that entrainment of bivalvo larvae has not1 altered ~the composition of this assemblage in the vicinity of the plant. A comparison cf epecies composition throughout 1990 among
- nearfield Stations P2 and PS and farfield Station P5 further confirmed Ethis conclusion (Table 2.2-4). There were n6 significant differences 1
-among these stations.
S i 37
- -u m- ~ , , , ., r m u
E T/ ALE 2,2-4.
SUMMARY
OF NEARFIELD/FARFIELD (P2, P5 VS. P7) SPATIAL DIFFEF:NCES IN PLARKTON COMMUNITIES AND SELECTED SPECIES IN:1990. SEABROOK OPERATIONAL REPORT, 1990. F COMMUNITY DJTFERENCE BETWEEN NEARFIELD (P2 AND PS) AND FARFIELD-(P7) ,
/
Microzooplankton-Community Neno Selected species Ne,e B1velve Larvae Cc n.aun ity - None Selsc*ed species. None Hrerozvoplankton Community Holoplankton/meroplankton - nono Tychoplankton; nearfield
> farfield Selected specier Neomysis americava P2 > PS, P7 Ichthyoplankton Egg Community Necrfield > farfield Ichthyoplankton Larvae-Community Nune Selected species None h
L I-38 u . L
r s REI.sragp10.nki on In the past, the seasonal patterns of the macrozooplankton assemblage have been consistent (Figure 2.2-2), reflecting, primarily, 'i the population dynamics of the dominant copepod species (holoplankton) modified by seasonal presence of larvae of bonthic organisms (meroplank-ton)(NA1.1990b). The interannual-variabliity in seasonal patterns of tychoplankton (texa whose behavior includes movement between the sub-strate and the water column on a regular basis) was examined separately i for this analysis (Figure 2.2-2). Holo- and meroplanktonic components of macrozooplankton assemblages have been distinct and consistent, show-ing high predictabi?fty free year-to-year. beasonal succession of holo-
- and meroplani-ton assemblages in 1990 exhibited the same pattern observed in previous years. The copepoda Calanus fin,rarchicus and Cent ropages typicus were consistently among the dominants. The greatest variability among years in terms of associations of species was evident in Febcuary end April. Variation in February could be due to relatively low abun-dances. The combined effects of freshwatnr flow and solar warming may affect the timing of the transition from winter to spring biological conditions, causing biological conditions in April to be unpredictable.
Although b th the holoplanktor.ic and meroplanktonic cor:ponents of the macrocooplankton arn susceptible to entrainment, there is no indication that theso portions of the community have been significantly impacted. _ Community. structure and abundance were simila- at Station P2 in 1990 both to previous yents and to the farfield area (Station p7). Seasonal succession of tychopicnkten species has shown greater variability than the_ holo- and moroplankton. With the exceptica of-early spring and mid-summer, tychoplankton species composition has not
- been highly predictable and could resemble any of three or four patterns (Figure 2.2-2). However, it is highly likely that at any time of the year, either Neonysis americans or Pontageneln incrmis or both species ,
i- will be'a dominant. Seasonal changes in communit y structure largeiy reflected changes in abundance of these two species. April 1990 was a 3? 4 e
4 ungrouped, distinguished by unusually high abundances of Nysis mixta and i Cammarus laurencianus and seasonally typical abundances of other taxa. Despite a' highly variable seasonal succession of tychoplank-ton,-it is evident _that species composition in 1990 resembled that previously observed at Station P2, Comparisors to-the farfield area confirmed previously noted-(NAI 1990b) differences between the areas. i.e., that abundances of tychoplankton were greater in the nearfield than the farfield (Table 2.2-4). This pattern had been attributed to the more complex substrate of cobble and sand at the nearfield station compared to the uniformly sandy bottom at.the farfield station. There is no indication that the tychoplankton assemblage has been affected by operation of the plant's circulating water system. l Ichthvoulankton (Fish Eggs and 1,arvae') Fish egg assemblages in most months showed a predictable seasonal progression. There are two periods during the year (January- ] February and' October) when it would be difficult to predict the plank-tonic fish egg community structure due to the high degree of variability among years (Figure 2.2-3). Seasonal succession of planktonic fish egg species composition and abundance in 1990 followed patterns previously observed and was most similar to the most recent preoperational' years. Althocgh spatial differences had not previously been investigated, there were differences in spatial distr"'ution of fish eggs in 1990 when i considering the entire year, while comparison omong stations during-the ; period of commercial operation (August-December)' revealed no significant differences (Table 2.2-4). Differences were limited to a number of taxa that typically-occur in the first half of the year. ' Abundances tended I to 'be higher in:the nearflaid than the farfield, further suggesting they were not related to entrainment. Since the nearfield assemblage was similar;in 1990 to preoperational years and species-specific vertical - distribution of fish eggs tends to reduce their susceptibility to i 40 j l I l l i' . , .
, f. -, . _m . .m _ _ ___ . . . . . _ ~ ._. . _ - .. [ _- I H l
'l 1entrainment, it'in unlikely-that this difierence among stations is-
' attributable 4to'opecation of Seabrook Stationi I S-asonal assemblages of fish larvac could be divided 'into six Laajor types based-on their dominent taxa:
fall-(predominated by
' Atlantic herring); late fall-early winter (pollock, American sand lance,
. Atlantic herring), vinter-spring ( American sand lance)r spring (winter
. flounder, snailfishes, radiated shanny, American plalce and American sand lance), late spring-early eummer ( Atlantic mackerel, cunner.-and
- fourbeard rockling) and late summer (cunner and fourboard rockling).
Variations: in density of the major taxa, especia11y'during transition periods-(primarily November, December and January), caused small changes-
- In species' composition leading to the formation of overlapping "sub-groups". During most of 1990, seasonal patterns were similar to previous years (Figure 2,2-3). November and December 1990 collections were unusual =in that they were represented by relstively low 9bundances of Atlantic horring, pollock and Accrican sand lance larvae, resembling only December 1989 among the praoperational collactions.
The 1990,3chthyoplankton community at Station P2 uAs compared- . to Stations P5'and P'l encompassing both thn entire year and the August- _ December period _ representing commercial operation of the plant. In both g .; cases,uthe nearffeld.and farfield communities were statistically similar (Table'2J2-4), indicating that'the low abundances observed in November and December were not restricted to the intake - area but were widespread. Thus, it is unlikely that these biological conditions reflected impacts
; due.to e-trainment of finfish larvar.
i> . 2,2.1.3, ? arJ..est_caLApecies a ,. Eleven species with various 1Lfestages-Irom1the pelagic , zooplankton communit.ies were designated.-as selected species. The existence of seven to twelve years of preoperational data allows an estimation of seasonal and annual variability. These species 1 exhibited , 41
- . - _ _ .__ - _.___ . _ m ..%._. , _. m , , _
I n
'different degrees of numerical importance; their relative contributions to their respective coinmunities are shown in rigores 2 ?-4 and 2 2-5.
The zooplankton selected species-(including various life-stages) historically have constituted less than 40T of the overall abundances (Figures 2.2-4 and 2.2-5). In both the microzooplankton and inacrozooplankton assemblages,- other copepods typically have made as large or larger a.contributicu to overall' abundances. In the microzoo-plankton, copepod nauplii and copopoditov (unspeciated) have been extremely abundant. In the macrozooplankton, copepods other.than the-selected species have historically been dominant it averaged over the year; however, the noncopepod selected species have been dominants in certain seasons. All of the zooplankton selected species reached peak abundance in spring nr.d summer, with the exception of Neomysis americana, which has been most abundant in fall through early spring. Abundances of zooplankton selected species in 1990 were evaluated in relation to the preoperational years in both nearfield (Stations P2_and PS) and farfield (Station P7) using analysis of L variance (Table 2.2-5). -Both the entire year and the operational period from August through December were tested. It was typically the case that differences in abundances occurred between preoperational years as a whole and 1990. These differences, however, were not restricted:to l. L the nearfield area or to the period or commercial operation (August I through December). Thus, there is.no evidence through this initial l period that. commercial operation of the plant has significantly impacted populations of the zooplankton in the study area. 1 Two species of bivalves were a' Iso examined for trends in their larval stages (Figure 2.2-5, Table 2.2-5). Peak abundances of Myrilus - 1 edu11s have h.1storica11y.oecurred in early summer while #ra arenarla.
)
Isr/ae have typically peaked in the August through September period.
- M. edu11s has osually dominated the bivalve larvae' collections and did'
.j so c omin in 1990. N. arenarla makes only a minor contribution to the !
tctal abundance of bivalve larvae (Figure 2.2-5). Abundances in the 1 42 l I
f
- 3oi g <m1mT_:
t C : N na e
- gQ ga 0~
0 3E -[. o2 5 a, - 4 O E C N u, o A : D =O N . U O B -* : A
- m. .O G
- O .
=
L O
, s 2
. -0 O o . _ ,
- 3O pn <G NT(C3am3oO g,
D l C - g, N O I , T I S O g, P M O C j An
? l
/.
- Wy > gy g, hy ll l8
[$g 1[ k-i qu t l .;, lI.' 4- Ij ,j1} ~ l
;r>
,- m
, ~ '
a /i .
.s p
- ts si p p- p po D n t s s l
up t s s ESE r e m e au rd nu s s s t sN ap st ad s at s nt u at o i TI rd o i mia laa a n us n? u n s nU n opo nu od CC toa ss t mpo en cs ado s lat oB h D ht ep ha EE ty a ou a lu t LP ioo eop tap it io C n ES nc t y r o r ud m dn ua c9 o p cd oa O Oc S S - E uc Er o ea s d uCo d u h PC o e s s P P 3ed;; gbh~ teOD 1 r ,4o)nmM+-[ecSgc,o CD" ,u$ nod @aD$ 5n %* Sa moMg:-
) s ooO 1* a
's 9
- o" v<go_e<0 E _,D$c % p y M$5o c eb"$ge~o Uo.
9-QN!e6D o]c~o!o^
- OOM oU ^bAB w
- oy poh Ua"o8OW O3,$ ODE ygoQ.~ee9 2
bW
- z..
3 1
% COMPOSIT!ON LOG ABUNDANCE 8 8- 8 8 3
~
. SELECTED o 8 o - u w - os c BP EC1ES . e i e . - n - n 8 ' ' ' ' ' '
% i o { .
Mya arenaria ,' ) - g 4 tarvee -- y e O to 5 o V
"'W Og E' gg -',,
C,,, a,a8 B uD Mytilus edutis )> m <
$y]w y fatvao
, &.gq@
' aern% g?Arr r A,.3LewfurfRY= m
.,5,l$q%fjdnL T
- pr o Eaq C g
~~ $ +9 Q. E to RB,SO 3E
{- @ g g Cancor sp. larvas @ , Q e ac mo a m
~ o O c. -,-
- e q a u
$ "~I5 OO M o .
b 2 OE "w Carcinus maenas ~
!arvae
~
O
'B@E DO*D E" '
5 kgRy yg Crangon septesnspinosa - . o W gy q -g m<o L %, 3 larvae . t? c<D oc o o.
*p@ l H g7o a Neomys.is , g ay americana
-.m oo g e
$b2 y A sa Catanus et
" 3 *_ finntorcNcus o
$U$
g,a
. copepodites 1].~:lb ..f j?{Q,.
E E.M E Calanus H hQ - tinrnarchicus - a&;tts l o x-
TABLE 2.2-5. CGhPARISON OF 1990 ABUNDANCES" 0F SELECTED HICR0300 PLANKTON, B1 VALVE IARVAE, MACROZOOPIANKTON AND ICHTilYOPIANKTON LARVAE, TAXA. SEABROOK OPERATIONAL REPORT 1990. RESTRICTED RESTRICTED TO TO OPERATIONAL 1990 SIMILAR 1990 DIFFERENT NEARFIELD? PERIOD 7 Eurytenora herdmani Eurytewora sp. no no adults copepodite Pseudocalanus/Calanus sp. nauplii 01thana sp. usuplii Pseudocalanus sp. no no copedodites Oithona sp. to no copepodites 01thona sp. adultn no no Hyt arenaria larvae Lalanus finnarchicus no no copepodites Hytilus edulis lar- C. finmarchicus no no vae adults American sand lance Crangon septenspirosa no no larvoe post larvae , Atlantic cod larvae Neomysis americana no no Vinter flounder lar- no no Atlantic mackerel vae , larvae Yellowtail flounder no no larvae Cunner larvae no no Hake larvae no no Atlantic herring no yen larvae ,
" Abundances of microzooplankton, bivalve larvae and macrozooplankton taxa were compared over the entire year and during the August through December operational period. Abundances of ichthyoplankton larvae were compared during their individual peak periods. Only Atlantic herring larvae peaks entirely within the August through December period.
45 ; l
nearlield (Intake and discharge; stations) were statistically similar to the farfield during both plant operation and preoperational periods. Neither species appears to have been impacted by commercial-operation of the plant. As a group, the selected species of fish larvae composed 80% of the total abundance and at least one species peaked in each season (Figure 2.2-6). Generally, each of the species was present for a brief but fairly consistent time period each year. Timing of abundance peaks in 1990 was consistent with previous years. Abundances of several species differed significantly from preoperational years (Tabic 2.2-5). Winter flounder, yellowtail flounder, and Atlantic herring larvan were less abundant in 1990 than in previous years, Cunner and hake larvae, on the other hand, were more abundant in 1990. None of these dif-ferencec~in abundance was restricted to the nearfield area. Of the ichthyoplankton selected species, only Atlantic herring had its peak abundances-oaring the August through December-period corresponding to commercial operatifon of the plant. Abundances of this L -species-during_its peak were significantly lower than the mean of pre-operational _ years. - Ilowever , abundances were statistically similar
<between the nearfield and farfield areas throughout the preoperational and operational periods. The general trends of reduced larval abun-
_ dances in 1987-1989, coupled with reduced adult catches locally and regionally, indicate that reduced abundances of this species in 1990 were.not-due-to commercial operation of_the plant. x II 2.2;2 Ein11ah o 2.2.2.1 Imninnement Operation of the circulating water system,_in terms of both 7the number of pumps and whether.the_ system operated at all, has varied s.ince operat. ion of the circulating water system began in 1985. Fish entrained within the system and subsequently impinged upon the 46 lc L l~
1 1 Tcmparal Varirbility - 4
)
;,,m- 5 0 1990 O
. ..o
-o
.N: .2- 0
-4 c- ..
gJ r
- m. .
. L 1<- . ll o
j' o o 1
] . }. ~O O t
o
- Relative Abundance so -
m
-D~ N r ..k -
.Ow
_ Q
- so -
We
$Nhi
;f*&
z .in,!
.s-x
).- o
.O
[t f.. f '
$o.
a m- &
;': g..
E it >$t s o -> :; c4 r3 @y j ;;a 10 - j!$$ M W % di LW g Q;$e; 4
. m, , ,
ML W -- we r-- R m, o c, ,
- 1, -s p to3- Ej
-v ..
g 5- 34-
- 1
.o$ jy j[ -{g -_ j. _8 j E
-g- .i j.
x -- .J< g
~{$w%- e
-m w
. .g 3 _-
E
-o Figure 2.2 6.- Mean log (x+1) abundance i species (no./1600 of fishlarvaem2)1975and 1989 95% confiden
- and percent composition for seier and 1990 at Station P2. Seabrook Operational Repon,1990.
-47
l i l l l 1 R i traveling screens-have been~ collected oy Seabrook Station personnel to determine operational impact. Initial estimates provided by station personnel-based on 1985 data indicated that only one fish would be impinged per 50 million gallons of cooling water flow. During-a five-- month period in. 1985, 970 individuals, representing 32 species, were collected from the circulating water system. These were dominated by grubby (#roxocephalus senaeus, 21%), snailfishes (Liparis sp., 21%), and j
- longhorn sculpin (#roxocephalus octodocesspinosus, 11%). During a seven-month period of circulating water system operation in 1986, 1212 individuals representing 35 species were collected. -These were dominat-ed by gruboy (28%)i windowpane (Scophthalmus aquosus, 12%), and longhorn sculpin (9%). The intake structure was clnaned of fouling organisms in 1986 and, subsequently, has been inspected annually to control biologi-cal growth. Intermittent operation of the circulating water system during 1987 resulted in a total impingement of 502 fish representing 21 species. Of these, longhorn sculpin, winter flounder (Pseudopleuro-
.nectos anericanus), and windowpane.made up 22%, 14%, and 13%, respec-tively, of those impinged. As the CWS operated intermittently and only
-at low capacities in 1988 and in 1989, fish impingement data were not collected.
The circulating water system operated regularly during 1990 (Figure 2.2-7). Over the entire year, 499 finfish, representing 31 species, were impinged (Results Section.2.2). This represents an impingement rate of less than one fish per 500 million gallons of cooling; water flow or 1.4~ fish.per day. In a'ddition, four lobsters were-impinged. Lumpfish (Cyclopterus lumpus) and pollock (Fellachlus virens) each represented 14% of the total finfish impinged, longhorn sculpin represented 13% and windowpano, 10% of the total. Impingement was highest in May-June when lumpfish, windovpano and cunner (Tautogolabrus Ladspersus):werec the most frequently impinged species Land November-December when pollock, longhorn sculpin, herring (unspecified) and L wir.dowpane were caught. As in previous years, few pelagic species or i individuals of pelagic species were impinged. Pollock was the primary exception, . reflecting its tendency to be mori abundant near the bottom.
~
48 y
=~ . -_ _
,. ----e - - a
!KC -
o .- W
~
g-
= ,
3 m mo-1 100 - 1 1 o . . . . . . . . . . . . JAN RB MAR APR MAY JUN JUL AUG SEP CUT PG C(C MONTH 1 100 - I 902 I j ni 70 - l z l c w: i oa "i tC W 40 . Jo= x- - r,
- .x,
* ~,
n-10 JAN RB MAR APR MAY JUN JUL AU3 EEP CC'T PG IIC MONTH
.00 -
00 A
'- so 2
,E','*', M B ,'%,'b,:,',
w ro . e &~,; g& . .
,,,,::,, . gjgp __
- . a w ,,
- ,, , a w,,n 2 w- ,y,;s, ;
, :, , ,y qqe.x -
a paa g , , , ;., ,, , z r- ,,,, a v.9-a .~'aa
- o. ,
m/ v - ,, , ' '
,,' ' ',' :g, I J D ando*Panc iQ,g "V s
l.{ g 1""* 40 - #o- . .w _1, m on ,,, o .: , T. Illlllipin .g d lipu:na_ JAN RB MAR APR MAY JUN JUL ALO EEP OCT 7W IE f.ONTH I Figure 2.2 7. Flow rate (million gallons per day) of circulating water system and impingement of finfish during 1990. Seabrook Operational Report,1990. b 49
The low abundance of pelagic species f rom impingement collect lons suggests that the intake caps are performing as designed, minimizing entrapeent. The species impinged are mainly demersal species; it is likely they are aceking cover at the intake structures, tht- increasing tho' likelihood of swimming or being drawn into the intake tunnels. Impingement of even demersal species is low considering the overall impingement rate of 1.4 fish por day observed in 1990. 2.2.2.2 Peluk_jp.nlis Taken together, the six dominant finfish species collected in gill nets have averaged 85% of the population (Figure 2.2-8). Fffects of plant eperations on_pelagle fish populations in the study arco should be visible by studying these species. The distribution of pelagic fish varied seasonally; two main seasonal groups of species, summer and winter, were identified in earlier studies utilizing numerical classiff-cation techniques (NA1 1982c). Prior to 1990, from September through April, Atlantic herring constituted riom 64% to 93% of gill net catches, whale in summer months (May-August'), other migratory species such as Atlantic whiting (formerly known as silver hake) and Atlantic mackerel predominated (Figure 2.2-8). Pollock .(predominantly ago-two fish { NA! 1985b))-is-a-local resident that also made up a greater proportion of the pelagic nearshore community during summer. <; No finfish were caught in gill nets in the early months of 1990, reflecting the sharp decline in the Atlantic-herring population observed locally (Figure 2.2-8; Table 2,2 6) and regionally (NOAA 1991a). Catches of Atlantic herring were again low in the fall of 1990. resulting in_relatively low total catches. As a resuit, relative contribution-of the ceptured population was made up to a greater degree by other' species. Pollock and Atlantic mackerel made up the majority of
-the catches between May and July.- Atlantic thiting, typically abundant fra ' June through August, was barely present~ in 1990. In August, spiny __
dogfish (Squalus acantblas) made up 80% of the catch. Butterfish 50
Seasonst Varlation oc
. - . - arce
....... 1993 w 20 -
E u so e -. . . . . N **...,,,.... "*..
- 3 , , ,.w.t ; , , , , 7_ qn " .
AN FG LMR APR M.AY JUN JR At.G EP CCT tm (10 Prooperational 1CC
- ak (gy] *z M D Attantic hemng 9) pyQV o;AylQ:,1;J'
&(yf y c
m Anante wneng O Mar R;. v i aw f :+ twenack nemr9 y y , ; pj :v ,p,,,,, y- - 9 punge m,en,,e 8 MMhd%;;
- ap p ' ,og.'..Q w *,' AM- O ponock p Auntnmennaaen g_ ,,,,, .
.f7'/' /
, e n !! *.! ( -
JAN FG MAA APH MAY JUN JW AUG EP OCT tm 01E l 1 33 1990 x < O 60 -
,'s
.'s's s /^.
swsV., s's' ' O A;antc hemng
;g , :
"~ '
O Atanto wnmng 2 #O',,'c'',,
?,',
.' , < O NuebacK hemng 3 "~ f %
8 5,['l/ '< J ' ' ' ' '2' ' ' O Atan0c nuckerel 20 ll/ h',? , 0 ' X S ': D P
- ck
, ,'/,'/ /,','//,', O Atante n'enhacen CPUE
- 0
,J
. . i i
i h = i w i
, M V '?????-
i i i JAN FG MAR APR MAY JUN JW AUG EP CCT tm (IC MONTH 4 Annual Variation 30 = 20 - b so . o . . i i i i i i T i i i . . . 76 77 78 79 80 at 82 83 84 85 86 87 88 89 90 1@ - 2 Cs -- [+' g 8 Spgmq w, t ggg , , w q ,e m 83 , 4 g iy. ,, O Atantc hemng 2 < j @ y;1/4
- u ,
97- 4 At: ante whrting a u. . , g:- .
,, muecack namng
'[ <
7 7
/. ' f/// p ,(. O At'anticmackerel 8
N*+ i i i . YbMI..._ . i i i _i NhT1TI i . i D ^" ***'"**o 76 77 78 79 80 81 82 83 84 05 86 87 68 89 90 YEAR Figure 2.2 8. Seasonal and annual changes in composition and abundance of the pelagic fish community, based on catch per unit effort averaged over gill net Stations G1, 02, and G3,19761989 and 1990. Seabrook Operational Report,1990. 51
- w, , ~. ., # .,,._,+v- ..w-. .,w.,,.,-,..-.,....w.,-,, .-m..--.m , - . . . . . ,,m._.-m-m - - , - - . .
.. , . - . - . . . .. ~ ~. . .~ - . . . ~
c : TABLE 2.2-6 COMPARISON OF 1990 AliUNDANCES" 0F SELECTED PE1AGIC FINFISil- S PECIES . SEABROOK OPERATIONAL REPORT 1940. -i 1990 1990 . r SIMIlAR DIFFERENT COMMENT. , Pollock Atlantic herring
- Lower throughout- l' 1990; doctmented regfonal decline Atlantic nackerel
- liigher in 1990
- Abundances were coropared over the entire year without dist.inguishing .
stations. ; h n l i 1 4 1 P 4 3 5 e I l l
-i i
52 -! 1 i a [ ,- + -, ,.w< v m.e-,< ., ,-e.-
,. gw,, , , . . , .....-,,,.,.o% ,,r,,,..wm..,.,,,q y.e-, 3,. , p. ..r,-wp v'y.-% ., -w +y<i 4
(Peprljus t rincanthus) and blnefish (Pomatomus snit atr1x) p edoninated in September, a period of below-average catches. In the fall, when Atlantic herring have usually been most abundant, Atlantic mackerel, blueback herring and Atlantic whiting composed the majority of the catch. Total catch in this period in 1990 was below average. Differ-ences in community structure in 1990 can be attributed to regional changes in species populations (NOAA 1991a) . In every year, Atlantic herring has been thn everall domiria:
-pelagic fish in the area; however, it exhibited large annual abundance differences that were reflected in the annual percent composition (Figure 2.2-8). When catch per unit effort (CPUE) peaked in the study area in 1980, Atlantic herring composed 82% of the total catch. From
--1984 through 1989, eben total catches were at their lowest levels since the inception of tne study, Atlantic herring constituted only 26-61% of the total catch (ligure 2.2-8). In 1990, Atlantic herring constituted only 3%'of the pelagic fish collected, apparently reflecting a broad-scale trend (NOAA 1991ai. Atlantic herring are known'to shop high vari-ability in catches spatially es well as seasonally and annually (Bigelow and Schroeder 1953). Most of the fish collected of f 11ampton-Seabrook were yearlings, partjeularly those captured in the spring (NAl 198Sb),
Little is known about the habits of yearling herring, except that they seek out7ths warm waters of embayments in spring (Bigelow and Schroeder 1953),
-The seasonal-variability of 'the. pelagic fish was found to be greater than annual variability (NAI 1990b). .Most of the selected pelagic apecies had their peak abundance during a short but distinct '
~
period of time (Figures 2.2-8 and 2.2-9). Generally, variability nmong. years has been low. The number of individuals that could be exposed to-
- -intake effects :(impingement) would therefore be expected t o vary substantially among seasons and, to a lesser extent, among years, Areal differences are less important than temporal differences -In evaluating potential plant effects on pelagic fishes. Because of 53 6
_ _= . - _ - . _ .= _ _ _ . .. . ~ . _. . _ _ . . - Tcmporal Vcriablilty c.o-
. mece o 1990 ts-W !
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" U I O o.o Relative Abundance 60 - ("] PELAGIC SPEclER (G.it Ness. PREOP)
O PEL4cic ST'EclES (G,t! Nett.1960} ESTUARINE SPECit$ tseines. PREOP) ESTUARINE SPECiEG (Ss,.. 6 199-a DEMERSAL $PECIES (Tran*a. PREOP) OEME RSAL $PEC:ES (Trewis,19x) 60 z 9 . b un O 43 g W! O o -
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Figure 2.2 9, Mean log (x+1) abundance (catch per unit effort) and 95% confidence intervalc, l and percent composition for selected species of fish, 19761989 and 1990. Secbrook Operational Report,1990. , 54 j w - - - - , , , . - , - ,- - .e--
their high degree of snobility, pelagic fish were not observed to be associated with any one habitat. As expected, relative abundances of the five most abundsnt taxa were very similar among stations, although catchet tended to be lower at the southern station G1 (Section 3.2.2). Dif ferences in the vertical distributien of these species may be important. however, because the intoke st ructures are located at mid-depth, 5 m above bottom in 17 m of water. llistorically, only one of the elght most abundant species. Atlantic menhaden, was consistently more abundant at the intake (mid water) depth during the w nths sampled than at surface and bottom (Table 2.2-7). Ilowever, this species was only slightly more abundant at mid-depth than at the surface, and it only accounted for 21 of the pelagic fish in the study area. Atlantic whiting and pollock, and to a lesser extent alewife and rainbow smelt, were most abundant near the bottom. Atlantic horring, Atlantic mackerel and blueback herring were tnost abundant on the surf ace (Table 2.2-7). These species may be less vulnerable to intake cliects. Despite historical trends, certain species occasionally nad higher catches in the. mid depth area <han in sutisce or bottom depths. In 1990, on those datas when all depths were campled, alewife catches were highest in mid-water gill nets and catches of Atlantic mackerel in mid-wat er nets wars h10 her in 1990 than any other spouies (Tabic 2.2-7), suggesting that these and other species could occasicnally no more vulnerabic to intake effectw. However , these results indicated that the most abundant and frequently occurring pelegic species did not show a preference for mid-depth distribution, verif3 ng earlier results and the rationale for mid-1 wster placement of the intakes (NAI 197Sa). Furthermore, in-plant cojiections of finfish to date indicate that pelagic fish are not being encountered on the circulating water system screens la substantial numbers. 2.2.2.3 DamtIfiAl_hac.icA The primary focus for assessment of operational effects of Seabrook Station on demersal finfish has been the impact of detrital 55
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.,/.N F3 MAR APR MAY ."LN JUL ALG R? CCT NCV E ucNTH Figure 2.31. Monthly mean surface and bottom temperatures at nearfield Station P2, and 95 le confidence intervals during preoperational period and in 1990, and mean monthly surface temperature at intake, discharge, and farfield stations.
Seabrook Operational Report,1990. , 59 j E
l l l l l Toeperature ditferences were not ed in t he continuously *@ monitored temperature data supplied by YAEC No consistent d i f f e r encere l were observed in monthly averages of daily surface temperatures between t he discharge st ation (DS, Figure 2.1-3) and farfield station T7 in ) July, August, and September; the average monthly differences were less than 0.22'C. Frem October December, surface temperatures at the discharge station averaged 0.8-1.6'C higher than those that the farfinld station (T7)(Table 2.3-1, Figure 2,3-2). At Station ID the nearfield stat ion midway bett.een the intake and discharge (Figure 2.1-3), average sur f r a monthly temperatures we-e wit hin 0. 2'C of t emperat urns at farfield Station T7. Mid-depth and bottom temperatures at this nonr-field station were at most 0.3' highet t han t hose at the farfield station; in most mont.hs, temperatures were actually hinner at the farfield station (Tabla 2.3-1).
!!i s t o r i c a l l y , sur f ace salinit y values have been highest in winter and lowest in spr ir.g. a result of increased tonoff. In 1990, salinity was lower than average trom June-December (See Results Figure 3.1.1-4). lii ghe r - t h a n - ave r a ge rainfall in April, May, August and October (Section 3.3.1) may have contributed to iower-thaa-averagej s
salinity in those monthr.. llowever, the annual meno sa!! nit y in 1%0 was similar to previous years (Figue 2.3.2). Surface dissolved oxygen has had a seasonal pattern inversely related to temperature, with peak values in Int e wint er and lowes t values in fall. In 1990, seasonal patterrs were similar to previous years, although values in September were !ower than the average (Sre Sectton 3.1.1). Nit rogen and phospherus nut rients had more erratic cycles than temperature, salinity, and disrolved oxyg,en, but generally had lowest levolm in summer and highest in fall and winter. Seasonal patterns and annual mean values of total phosphorus and orthopho_.phate in 1990 were slightly higher than previous yearr (Figute 2.3-2). Nitrite concentra-tions were unusual la 1990 in that they were much higher than average in 60
rain. This is discussed in Section 2.3.2.2. However, impingement studies have shovn that certain species of demersal fish are susceptible to icpingement. The low rate of impingement sut, gests that any thonges to the d+mersal finfish community should not be attributable to impinge-ment during plant operation. Of the demersal fin!. species impinged most frequently, abundances of several (winter flounder, Atlantic cod and hake) were examined by analysis of variance (reported in Sectit 2.3.2.2). There were no changes observed in catches of winter flounder in 1990 compared to pccuperationsi years. Hakes and Atlantic cod were _ both reintively less abundant in 1990 but this occurred in both near-field and farfield areas and so is not attributable to lapingement. One of the most fregnently impinged species, lumpfish (Cyclopterus lurpus), has not been caught routinely during thn study. Although deme.rsol, it t9nds to be associated with rocky areas or other structures rather than the open bottom. Thus the intate structures may provide attractive habitat for this species. Impingement et lumpfish was highly seasonal, occurring primarily in May and June (Figure 2.2-7). Most individuals were adults. The seasonality of impingement could be related to post-spawning movements (peak abundances of larvae occurred in May and June, NAl 1991). Thus the species appears to be less susceptible to impingement before or during its spawning period than afte - Although a portion of the adult population may be lost through impingement, their spawning potential will have been realized, prevent-ing magnified losses in future year-classes. 51
t a 2.3 DISCllAIEfMal0J11TDRUig < 2.3.1 Plume Studin 2.3.1.1 DischarreJJnas_Ja.9 Because the discharge plume's largest exposure will be to surface and near-surface waters, the primary focus in this section will be on parameters or organisms in this part of the water column, namely phytoplankton, lobster larvae, and nearfield water quality paramet ers.
~
Other organistns, such as pelagic fish and ichthyoplankton will, of course, have some exposure to the discharge plumn, but it is assumed that entrainment and/or impingement are the more important issues for these organisms. Water-temperatures have shown distinct seasonal patterns that were important in driving biological cycles. llistorically, surface and bottom temparatures, measured on a weekly basis and averaged monthly, reachou their lowest points from January through March, then steadily increased from April to August; temperatures were genera?ly highest from July to September (surface) or Octobir (bottom) before beginning their fall decline (Figure 2.3-1). Surf ace t emper atures had a more exaggerat-ed seasonal cycle in comparison to bottom tamperatures, with higher spring and summer temperatures. Surface and bottom tempstatures throughout the llampton Seabrook area were higher than average in 1990 in June and from August to Decernbor (rigure 2.3-1). lioweve r , average monthly teroperntures were statistically similar to previous years, and no differences were detected among intake, discharge, and farfield areas in 1990 (Figure 2.3-1, Results Section 3.1.1). These resuits indicate that the higher temperaturca cbserved in 1990 were within the range of natural variabil-ity. Eficcts of plant operation on average monthly surface and bottom temperatures at Station P2 were not discernible. 58 m________________. __ __
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__ . _ ._..m _ _ _ . _ _ _ _ _ _ . _ . - - - - - . _ - . _ . _ . . _ . _ Tebrusry, May, and October, but lower than average in July and August (See Results, FJgure.3.1.1-7). The seasonal patt-rn of nitrate valuns was similar.to previous years although concentrations were higher than average from January-May (See Results, Figure 3.1.1-7). Ammonia levels were below t.he detection limit of 10pg/l during most. of 1990 (Sco Results, Figure 3.1.1-8). The annual average for nit rate and nit rite values in ~ 1990 was higher than previous years, whereas ammonia was lower than' average (Figure 2.3-2). These dif ferences, however, were not , statistical.ly significant. e j The phytoplankton community has shown the most seasonal and annual variabilicy of any species assemblage studied in this program. Seasonal assemblages have changed rapidly and frequent.ly, diminishing-the suitability of the community for short-term Impact assessment (NAl j 1985b). Some elements of the phytoplankton community, however, have been relatively stable and predictable. llistorically, total phyto-plankton abundance has shown a predictable seasonal cycle, although r j abundance levels _ varied as much as two orders of magnitude among years (Figure 2.3-3). The spring bloom was typically initiated by increases in irradiance, and although the spacies composition varied from year-to-year, centric diatoms typically were among the first to appear (NAI 1985b). Abundances usua))y diminished with the deplot.f on of growth-- limiting nutrients (primarily nitrogen); developmant of the thermoclin
- appeared to prevent the replenishment of nutrients from deeper waters and thus 11mit growth of spring dominants. A second (fall) peak usually occurred, coincident with the dissipation of the thermocline, which acted to replenish the nutrient supply in surface waters. In 1990, ,
total-abundance displayed a typical spring peak, but no fall peak was
. observed (Figure 2.3-3). Total abundances were higher than average in most months, and higbly correlated -among nearfield,-intake and dis-
. charge, and farfir,1d stations. This suggests that observed trends in L ,phytoplankton abundance oer'irred on an arca-wide basis, i
L ! Phytoplankton assemblages from 1978 to 1950 were similar, based on the predominance of Skeletonemn costatum, Rhlicsolenia 63 l 1
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delicatula, and Phaeocystis pouchetti, while f rom 1981 through 1984, only S. costatum and Chaetocaros spp. wure consistent dominants. The phytopinnkton in-1986 vss unusual in that there was an uncharacteristic July peak caused by bluegreens_and Leptocylindricus spp. In the latter half of 1986, S. costatum and bluegreens predominated. No phytoplankton collections were made from 1987-1989. In 1990, colonial cyanophyceae , (bluegroans) replaced diatoms (particularly S. co.statum, but also Lepto-cylindricus 2inimus and Nitzchia delicatisalma) as the overwhelming dominants (Figure 2.3-3). Diatoms appeared in significant numbers only in Jur.e and October. Other species displayed seasonal trends that were similar to previous years. Thacocystis pouchetti and Chroononas sp. exhibited spring blooms, followed by filamentous and unicellular green algae. The ressen for the predominance of cyanophytes in 1990 is nat ; . known, but it may reflect a Gulfwide phenomenon. Abundances an high as 7 x 107 cells /1 were observad in the central Gulf of Maine in the summer of 1988 and 1989 (Balch at al, 1991). liigh abundances of cyanophyceae _ have been linked to persistent vertical stratification, organic and . Inorganic nutrient enrichment, increased temperatures, and high amounts of photosynthetically-active radiation (Paer1 1988). Although nutrients were higher than average prior to the first collection of phytoplankton in April, temperatures were within the range of. previous years, with no evidence of extraordinary stratification. Thus there is no obvious physical or chemical occurrence in 1990 that can be linked to the abundance of cyanophytes. Cyanophyceae in some-cases exhibit certain. characteristics, such as high motility and production of resting cells (akinetes), that . can provide thea a competitive advantage (enabling them to bloom) over otherfgroups of phytoplankton (Paer1 1988). Blooms of_ colonial cyano - ,_ phytes have been cited as-causing oxygen depletion,' diminished water quality, increased turbidity, reduction of benthic flora and fauna due . f-65
.au
_ . - - -~ - -.. . . - ... _ - ._.-. _ .. _ . __~ _ - .- -. . I to siterations in sediment conditio.as and reductinn of the natural phytoplankton populat,lons (Pr.erl 1988). Theae changes were not apparent in the study area. i l Although' abundances of colonial cyanophytes represented 66% of ! the total phytoplankton abundance from August to December 1990 (Table , 3.3.2-1), sbundances of most ather dominant taxa were within the 951 confidence intervals of historical abundances (Results Table 3.1.2-2), suggesting that the phytoplankton assemblage has not been marked 1v ; altered. Number of_ taxa was similar to previous observations in all > depth zonas. There were_no dramatic changes in the r.ooplankton or < benthic communities thct could be linked to tho increased numbers of , l cyanophytes. , In 1990, es seen historically, no spatial differences were observed in the phytoplankton community either between intake (P2) and farfield (P7) areas or between intake (P2) and discharge (PS) areas (NA1 . 1985b, 1987b). In 1990, total abundances and chlorophyll a valuer, were highly correlated among all three stations. Multivariate analysis of variece showed no significant differences among stations for the 1 dominant texa. Skeletonoma costatum was chosen as the selected phytoplankton species. because of its consistent predominnnce during the baseline period, llistorically, there has been a major peak in late sunner or fall (see Results Figure 3,2.1-6) and in some years there was also a smaller peak in the spring (NAI 1981f,- 1982a) or winter (NA1 1980c, 1983a). The characteristic fall peak was absent at'all stations.in 1990,_ causing significantly lower densities during the operational period. Because of highly-variable peak abundances, significant differences were-detected among years and monthsLalthough intake and- J !~ ' discharge and farfield densities were statistically similar. The phytoplankton species assemblage has shown little stabili-ty in terms of density level, community structure, or seasonal patterr.s. 66
.9 l - . , , . - . , . . _ . . _ ...- _ ,, - __ . .--._c_._.u--__._ _.____;___;,~_-_
~ _ . . . . ~ - . . - - - - . . - - . _ _ -- - - _ _ . . - - -
i At best, only general trends are predictable, such as the occurrenca of a apring peak. The seasonal species assemblage has changed markedly from year to year. 1.990 was no exception to this pattern, with whangen more marked than those noted in earlier years. There were no changen in community structure or abundances that were unique to the discharge or intake stations. Although differences in 1990 were more dramatic during the August
- December time period, differences occurr ed throughout the .
year and do not appear to be reisted to plant operation. 4 Paralytic shellfish poisoning (PSP) is caused by high numbers .; of the diatom, Conraular sp. PSP levels in Ny+11es edu11s, as messured '
~by the Sta+.e of New Hampshire and Massachusetts Department of Public-Health (reported through 1984 only), have exceeded maximum levels allowable for hume consumption every year from 1972 through 1989 (except 1987), usually for a period of 1-7 weeks (NA1 1987b; 1989a, ,
1990s). In 1972, toxic Isvols were present in Hampton Harbor for a. l. period of 16 weeks. Although Hampton Harbor f2ats have been closed each summor since 1976 to soft-shell clam diggers for conservation reasons, high PSP levels have caused the closure of the harbor to a'1 bivalve , shellfish digging for several weeks each summer as well. Peak values-in most years occurred in May or June, coinciding in Hampton Harbor and the r , farfield-area, Essor., MA (through 1984, when data from both sites were collected). lIn 1990, elevated levels of PSP.were recorded in late May through June, similar to previous years at levels generally lower than previous years (See Results Figure 3.1.2-5). U 'Of the' shellfish in the area with planktonic lifestages (Can-
- car crabs, lobster, and soft-shell clams), only lobster larvae Stages I-
, IV have strictly a surf ace orientation, typically found in the top few centimeters of water. The seasonality and variability of Cancer sp. larvae _and Nya arenarla larvan were discussed in the intake area' monitoring section. Successlui recruitment of lobster larvae is the f biggest factor in determining the. level of adult lobster catches-in subsequent years (Harding et al. 1983). Icbster larvae collected off Hampton-Seabrook probably originate from warm waters in the Gulf of i 67 m
l l l l l i Maine and Georges Bank (Harding et al. 1983) and are driven into the area by a combination of winds and nontidal currents (Grabe et al. 1983). Temperatures in the study area are typically not warm enough to f allow planktonic development (Harding et al. 1983), reinforcing the idea that thia area is probably not important in the production of lobster larvae. Lobster larvae, which were rare throughout the study area, have , typically been recorded from the first week in June to the second week I in October, with peaks frequently occurring in the mid-summer months (Figure 2.3-4 and Resulta Figure 3.3.6-1). In 1990, lobster larva; first appeared in early June, at all three stations, similar to provious years. 'faximum abundances have occurred over an eight-week period between late June and late August, during the period of msximum surface n temperatures. Historically, abundances of all life stageu have been
. Very low, averaging <2 per 1000 square meters (Figure 2.3-4). From 197d-1989, stage I and IV larvas have predominated, and stage II and III have been extremely rare. . Densities at both the farfield station (P7) and discharge station (PS) were usually higher than at the intake 4 station (P2). In 1990,.an unusually large catch of Stage I lobster larvae occurred in July, over 10/1000 m 8 at all three stations, followed i by an'excepttonally large catch of over 60/1000 m8 Stage IV larvae in August. Higher than average surface water temperaturer throughout the ,
Hampton-Seabrook area may have enhanced the survival of lobster larvae. In addition, unusually large aggregations of lobster larvae have been 1 associrted with convergence areas'or shallow sea' fronts, where different water masses meet. These ureas are the result of wind-induced down- i welling coupled with influences of tides and river discharges, which form visible necumulations-of foam and debris (Cobb 1983). 'It's ; uncertain whether the large numbers of lobster larvae were caused by higher temperatures or convergence of water masses. However, since the a timing of these incidents occurred at both near- and farfield areas,-it is unlikely that these were related to plant operation. l L . i Subsurface (-3 m) " fouling" panels placed in the projected inner and outer discharge plume area and at farfield areas, show the types, timing and abundcnces of shallow subtidal organisms that can 68
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sett le on bare substrates. Short-term panels, exposed for one month, allot estimation of recruitment levels while monthly sequential panels, exposed for 1-12 months, show the development of the fouling community (Figure 2.3-5). Total biomass, abundance of noncolonial fauna, and richness of faunal taxa shoved seasonal patterns that were highly consistent from year-to-year and between nearfield and forfield areas, reflecting the increase in settling activity in summer and fall. 7te , development of the fouling community in 1990 followed the basic seasonal progression observed in prbvious years although several differences are notabic. Recruitment abundances, taxa richness, and biomass (panels locatel at inner plume stations only) measured on short term panels vere significantly higher in 1990 than previous years, whetcas community development biomass (monthly sequential panels) was lower (Figure 2.3-$; Table 2.3-2). Changes in the sett ling population were due to increased numbers of mytilids, which increased biomass as well as provided additional substrate for other organisms. As those differences occurred at both voarfield and farfield arcat, and began before plant start-up, they are unrelated to plant operation. The species assemblage colonizing fouling panels at the dircharge station has shown seasonel changes that were relatively , consis-tent frem year to year, particularly from June to December, in 1990, the r.sttling community at the discharge station in the latter half i of the year was similar to those of previous years (Figure 2.3-6).
-2.3.1.2 Int ert idal/Shn11oduktidal,lang An tran outside of the immediate surface plume area that is
- s-
- nitored for potential plume effects is Funk Rocks. Intertirial 1:
L u V. ad MhW) and shallow subtidal (-4.6 m) stations that are represen-tative of the area were monitored on Outer Sunk Rocks (nearfield) and at a reference area at Rye Ledge. Community comparisons have historically l focused on August collections when all organisms are identified and enumernted 9erational impact assessment in 1990 for the benthic i 70 t
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d TABLE 2.3-2.
SUMMARY
OF DIFFERENCES IN COMMUNITY PARAMETERS MEASURED AT INTERTIDAL, SRALLOW
..SUBTIDAL, MID-DEPTH, AND DEEP BENTHIC STATIONS AND IN THE SURFACE FOULING COMMUNITY. SEABROOK OPERATIONAL REPOPT,1990 1990 SIMI1 ART 1990 DIFFERENT!
NEARFIELD, i FARFIELD-b b SIMIIART GROUP" PARAMETER GROUP
- PARAMETER ZONE STATIONS Algae Richness No Intertidal Sunk Rocks Biomass No Farfield Richness No Fauna Abundance No Shallow Sunk Rocks Algae Richness subtidal Farfield Biomass Fauna Richness Abundance Algae Richness No Mid-depth Intake Algae Richness, discharge, u Discharge intake
" farfield Fartield Biomass, Biomass, Yes discharge intake, farfield Richness, Fauna Richness No Fauna Yes intake Abundance l Richness Algae Biomass No Deep . Intake Algae discharge {
Discharge Biomiss, Farffeld intake { Richness Fauna Abundance les Fauna ST Richness No Surface Discharge ST Biomass No inner plume outer plume, Abundance Fouling- farfield Biomass, Community outer plume; inner plume, No Farfield- outer plume, Yes nearfield MS Biomass No
- Algae = macroalgae; Fauna = macrofauna; ST = short term panels; MS = monthly sequential panels Nichness = number .of taxa; Biomass = total biomass, all taxa combined; Abundance = total number of organisms N ---
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community utilizes data collected af ter limited commercial operation (Table 2.1-1). Any differences observed in 1990 are, therefore, unlikely to be related to plant operation. Benthic community structure within the intertidal / shallow subtidal area was assessed in several ways. The number of species (richness) and total abundance or biomass estimates obtained in 1990 were statistically compared to previous years. Potential operational effects could be ruled out if 1993 results were similar to previous years,1990 dif ferences were consistent throughout the area (i.e. , at nearfield and farfield station pairs), or resultr in 1990 in the nearfield area.wcre similar to previous years even though they may not have been similar at the farfield area. Community composition in 1990
-was compared-to previous years using numerical classification. The ,
community composition was considered unchanged if collections in 1990 at a particular station were similar to the majority of samples from the same-station from previous years, causing the analysis to group them together. The community parameters met the critoria established for demonstrating no. operational impact. Although macrofauna and macroalgan taxa richness and abundance or biomass at intertidal stations showed differences in,1990, these differences occurred at both nearfield and farfield areas (Table 2.3-2), Macrof aunal and macroalgae community parameters at shallow subtidal stations were statistically similar to previous years, Benthic algae and mactninvertebrate collections taken annually
-in August at Stations B1MLW and B5HLW (intertidal) and Stations B17 and s; - B35 -(shallow subtidal) have exhibited species assemblages that were consistent and highly similar-from year to. year at each station (Figure 2.3-7). Each annual collection at a station was grouped (by numerical classification) with the majority of those collected in other years at the same station (Results Sections 3.3.2 and 3.3.3). In 1990, community F ' composition of intertidal and shallow subtidal macroalgae collections 74
^
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m-as. ." 30- ' ' ' ' ' e s 4 3 i 3 : CROUP Figure 2.3 7. Similarity and at;undance or biomass of macroalgae and macrofauna species assemblages in 1990 compared to the preoperational years Seabrook Operational Report,1990. 75
,..,4a-. .r.... ,..,,,.r,-g .-,--v,-. .,-,,-er,,e-- e-,,:-yw,--e-.rwv,-w-,%+-.,--ww,,,,.-w..e., ---.----,,,.,w-,,,,--, v-,-w-,,i.,,v,-,,,,..-i-+,.e. ,,,,w--a-,+re-e,-. w,--,sw.
s.___._.. _ _ _ _ . . _ _ _ _ _ . _ _ _ _ l l l and intertidal macrofauna collections was similar to previous yesix. l l For the first tir. since 1978, the shallow subtidal macrofaunal assem- I blage at the nearfield station (B17) was more similar in 1990 to mid- j depth regions than to previous shallow subtidal collections. High ] numbers of Balanus crenatus probably contributed to the similarity ofthis station to mid-depth areas. Hacrofauna density levels in I intertidal and challow subtidal groups in 1990 were higher than previous l years, due to increased mytilid density, which occurred at nearfield and farfield areas. Algae biomass in the shallow subtidal area in 1990 was similar to the_preoperational mean. Stowever, the intertidal group biomass in 3990 was lower than the historical average, due to decreased i l amounts of Chondrus crispus. This difference was observed at the reference station as well as the nearfield station. i Fourteen benthic taxa were selected for more intensive moni- ! toring because of their trophic position, abundance and commercial or , recreational value (Table 2,3-3). Paramotors monitored included abundance (all taxa), size (fauna only), and reproductive status , (epibenthic crustaceans). All life stages of the commercially-important i taxa were studied. Some of these taxa were monitored in the Sunk Rocks area while others were examined as part of the discharge or estuarine 3 studies. Algal selected species showed no evidence of operational i impact. Biomass of the dcminant algao Chondrus crispus in 1990 in the shallow subtidal zone was similar to previous years (Figure 2.3-8). In l the intertidal zone, biomass was lower in October at both stations (Table 2.-3-4). This resulted in lower relative abunf~ :e in 1990 than I L previous-years (Figure 2.3-8). Quantitative counts of the dominant help, l.an/narla saccharina, were much lower than recorded in previous , years'at the_nearfield station. However, lower- counts were - also recorded in April and July, prior to the operational period (Table: , 2.3-4). t 76 i
- 2. . _ .-. . . - . _ _ _ - . _ -._a,___. :_ ,._. -. . _ _ _ . ,~.__u.,._a,___a_.-_.
I TABLE 2.3-3, SElICTED-BENTilIC SPECIES AND RATIONALE FOR SELECTION. ! SEABROOK OPERATIONAL REPORT, 1990. l SPECIES (COMMON NAhE) LIFESTAGE" RATIONALE Macroalgae faminarla saccharina A liabitat (canopy)-forming primary (kelp) producer l Chondrus crispus A Habitas (understory)-forming , (Irish moss) primary producer; spore-lings may be heat sensitive
]!rnth:u InvArteb. 331 ,
Anpithoe rubrica, J,A Intertidal / shallow subtidal L (amphipod) community dominsnt (formerly) l Jassa marmorata JA Intertidal / shallow subtidal (amphipod) community dominant Pontogenels inermis JA Subtidal, ub1quitous community (amphipod) dominant Nucella lapillus JA A major intortidal predator of (dog velk) Hytilus edulis Asteriidae J Predator, community dominant (starfish) Strongylocentrotus J,A potentially destrt,ctive
- droebrachlensis herbivore (green sea urchin)
L Dominant-Bive1vos Nytllus edulls L,S,A Habitat former; spat may te heat (blue musse') sensitive l- Nya arenaria L,S.A Recreational estuarine species; l (soft-shell clam? larvae entrainable ! Enibenthic Cr15taceans Carcinus caenas ' , J,A A major predatcr of soft-shell j (green crab) clam spat Cance* borealis L,J,A Important predator and prey i (Jonah crab) Cancer 1rroratus L,J,A Important predator and prey l (rock crab) . Romarus aesticam:s L,3,A Commercial species; larvae (American lobster)- plume-entrainable a A u- adult; J = Juvenile; L = Larvae; S n Spat. i l l l l 77 L- !=
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pgg g. o 5 C1 9 - e 3 us on $-O o. 3 8 ja tot j u-on " Jassa marmofeta~~ % O 5 CT 5' E D 8 D D. O shailow subtidal n o OO D- ~ 55 pc$B. O *h ~ e -- g[ cx t=e
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TABLE- 2.3-4. COMPARISON OF 1990 ABUNDANCES OR BICMASS LEVELS l OF SELECTED INTERTIDAL AND SilAI. LOW SUBTIDAL I MACROAI, GAL AND MACROYAUNAL TAXA. i SEABROOK UPERATIONAL REPORT, 1990. RESTRICTED RESTRICTED TO TO OPERATIORAL 1990 SIMILAR* 1990 DIFFhRENT* NEARFIELD7 PERIODf- I Chondrus crispus (S) Amp 1thoe rubricata (I) yes no Jassa marmorata Asteriidae (S) no no (ST., M; ST, D) Jossa marmorata (S) no no Hytilidae (I) no no (S) yes yes (ST,M) no N/A (ST,D) yes N/A Nucella lapillus (I) no no Chondrus crispus (1) no yes Laninarla saccharian yes no
- Based on results of Analysis of Variance or Wilcoxan's Summed Ranks tests.
'I = Intertidal S = ShallowLaubtidal ST,M = Short-term panels, mid-depth ST,D = Short-term panels,- deep ,
i: i l '. 79
Dif ferences in 1990 for the majorit y of macrof auna species occurred either at both nearfield and farfield stations, or were not restricted to the operational period (November), suggesting that they were not related to plant operation (Table 2.3-4). In one instance, one taxon did not meet these criteria. Mytilidae collected in the shallow subtidal zone occurred in significantly higher densities at the near-field station in November. Since this result is based on only one sample du-ing the operational period, additional information will be necessary to evalusto potential operational effects. 2.3.1.3 Estaarine Zone Environmental studies in Hampton Harbor estuary include monitoring physical parameters (temperature and salinity), fish popula-tions, benthic macrofauna, and juvenile and adult soft-shell clams (#ro arenaria). The estuary has been monitored to determine the effects, if any, of the settling pond discharge since 1978. This included any possible effects of tunnel dewatering, which added large volumes of ocean water to Browns River through 1983. Current estuarine monitoring efforts are conducted to identify any potential effects from either settling pond discharge or Seabrook Station aperation. One of the main environmental issues in the Hampton-Seabrook estuary related to plant operation is whether the offshore intake and discharge will impact the adult clam population in Hampton Harbor. The probability of impact from the mosc likely source, entrainment of #ya larvae, is small (NAI 1977e); this is discussed in Section 2.2.2. Effects on juvenile and adult Nya are evaluated by comparing population estimates developed for 1990 with those from previous years. ; b Temperature and salinity, monitored in Hampton Harbor and Browns River since 1978, provide valuable information for interpreting i biological phenomena, Maximum temperatures usually occurred in July, l with minima in January or February (Figure P . 3-9). Temperatures generally followed this pattern in 1990 but wert higher than average in 80 l l
Temperature 307-G 25 b
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O 3 , , 3 , i i i i 4 i i JAN R3 MAR APH A,W JUN fJL AUG SEP CCT POV 3C MONTH Figure 2.3-9. Monthly means and 95c/c confidence limits for senwater surface temperature and salinity taken at low tide in Browns River over the entire study period (May 1979-December 1989) and in 1990, and precipitation measured in Boston, MA, from 1978-1990. Seabrook Operational Report,1990. 81
.-.. . .~ , .. - -. -- . .. .. _._ - . _ _ - . - - - .
j l l l l i July August.and'again in Octcber-November. Salinity had a less distinct seasonal cycle than did temperature, but was usually lowest in spring, coincident with increased runoff. Heavy rains in April and May of-1990, and againt in-October. led to lower-than-average salinities during these months (Results, Section 3.3.1, Figure 2.3-9). In Browns River, average annual salinity values remained high for a three-year period from 1980-1982, coinciding with low precipitatica and highest discharge volumes l i from the settling basin. 'This was the period when the mailmum de- ; watering of the cooling tunnels took place, and the salinity of the settling pond's discharge water was relatively high, approximately 25
. ppt. After discharge volumes decreased in 1983 and precipitation j returned to pre-1980 Icvels, salinity levels dropped, averaging 18-20 ,
ppt through'1990. Hampton Harbor salinities, which were not as suscep- I tible to these influences because of the influx of a large volume of of fshore waters, showed higher salinity and lower year-to-year variabil-ity than Browns Rivet. The benthic macrofaunal community in Mill Creek (Station 9) and Browns River '(Station 3) was typical of New England estuaries. The l species composition was also consistent with that from other estuaries ' on the East Coast (Watling 1975; McCall 1977; Whitlatch 1977; Santos and Simon 1980). Surface and subsurface deposit-feeders predominated, including opportunistic polychaetes such as Streblosplo benedicci and
.Capite11a capftsta, with suspension feeders and omnivores forming an important component. The most numerous species inhabiting estuaries-are those that are resistant and resilient-to the natural changes in the physical environment,'such as fluctuating temperature,-salinity, ,
dissolved oxygen, and sediment grait size.
.)
.In Mill Creek and Browns River, the biological parameters l( measured were highly variable seasonally and annually, with total abundance, numbers-of t'axa, and most af the dominant species signifi-
! car.tly different among years and between stations. This ic typical of this physically heterogeneous habitat. Some of this variability was related to changes in salinity. The combination of lower precipitation 82
- ~ . . _ . - , ._ - - --
r and higher levels of discharge f rom the settling basin f rom 1980 to 1982 apparently caused higher and less-variable salinities in Browns River. At the same time, total abundance and number et taxa increased (Figure 2.3-10), along with densities of St reblospio benedictl and Capite11a cap!! ara at that site. Higher salinity levele probably enhanced the habitat for more stenohaline species, and at the same time, opportunis-tic polychaetes invaded the changlug habitat. Following an increase in precipitation and decrease in discharge volumes, these parameters dropped to their lowest point in 1984; howeeer, they had returneu to pre-1980 levels by 1986. Since that time, si,ecies richness and total density have been variable, in part attributable to periods of low salinity caused by heavy precipitation and runoff, especially during a recruitment periods (Figure 2.3-10). In 1990, salinity was lower then average and was associated with lower numbers of taxa. Total density in 1990 was similar to previous years. Important estuarine fish include both diadromous rpecies as well as residents. Three ansdromous fish spacies occur seasonally in the estuary: rainbow smelt in winter, and alewives and blueback herring (" river herring") travelling to upper reaches of local rivers to spawn in the spring. Rainbow suelt were an important but highly variable 3 (both seasonally and annually) constituent of the demersal fish communi-ty at the entrance to the estuary (T2), composing approximately 20% of the total catch bistorically and in 1990 (see Section 2.3.2.2). The absence of smelt in trawls from April through November reflects their movement farther offshore. Historically, in spring and summer, sparse end erratic numbers of young-of the-year and yearling smelt have been caught in the estuary (Figure 2.3-11), but no one age group (based on length-frequency) has been consistently dominaat (NAI 1985b). Since 1976, rainbow smelt have never composed a substantial portion of annual seine catches, averaging only 3% of the total catch (Figure 2.3-11). In 1990, high numbers of rainbow smelt moved into the estuary in May and again in. August, leading co higher-than-average total catches and relative abundances in these months (Figure 2.3-11'). Average smelt catches in 1990 were the highest observed to date, composing 35% of the 83
Estuarine Benthos 10000 - - 50 8000 - " ..,* -so X
;1
- . W 5 ,
O Z - g
- Cr.
W W
'O 4000 - - 20 ca 2
D Z , 2000 - De6TY "O
... .. NUMBER OF TAXA 0 i i , i . . . , , , . . 0 78 74 80 81 82 83 84 86 87 88 89 90 i
YEAR Salinity. 30 - 28 -
- l. 28 -
24 .- c.
- Q.
22 - 20 - 18 - no data 16 i i i i i . . . . . . i 78 79 80 81 82 83 84 86 87 . 88 89 90 YEAR Figure 2.3-10. Annual geometric mean density (no/m 2) and mean number of taxa per station of estuarine benthos (19781984; 1986-1990), and annual mean salinity (1980
-1984; 1986-1990), at Browns River. Seabrook Operational Report.1990.
l 84 l
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...... 1993 .
soo . !
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', ', 'h' ', ',' 'k,' '9' ,9* '/ , U * ***' "
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20 = ,,,,,,,,,, s sss p/hijj({ spy (wfk%ya g e:f g-c m Bluftag, sggg%D ' ng. q%4j)A[$$M$h O Atlanticherring hMf r.. ws.mc' * . 0 i , , . . i APR MAY JUN JUL ALO SEP CCT NCY E rainbow trnelt i D pc4ock i 1990 i3 s 2 asqej i Fundulus sp. t o 8o - wg%eggw ep E D Atan:!c siNersde o Go g q yl' gby ,w)Vi?qqgy MNt:Sji I;mch - o do - w gge wa ' m4 a A O " ' >;wS ..a yN6T9 ji-lisdSEh? VMR 20 - R ig!l js n'
# % ;ol;WW tr. ?: 5 e
i , i i APR AMY' JUN JUL ALG SEP CCT PCV uoNm i Annual Variation 4co - m 2 200 - N o - 0 i i. ir - i i i e i i 76 77 78 79 80 S1 82 83 64 87 88 89 90 100 1 5 ao - lllll ,
,s,s' -
ll 0 winter counder h h e- s .-
# D Adante hernng 2 yh [h}$ >
ng JAQ E rainbow smelt
- l. y 40 - [$p$$ 1((j{$hj$$ gNy [ 5%Qg ,gj (jg ;
C pCllock V p 20 - hishit g4686M Engg'df ";pigggghI"[f -[1
- e
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Atlantic sJverside a jfygi7N(y?;gh<Qgyg)jh;g$(jng:gg@p3f w iW-fg a-c NsyNIIj' O . . i e i i i i i i 76 77 78 79 80 81 82 83 84 67 88 89 90 YEAR Figure 2.3-11. Seasonal and annual changes in coraposition and total abundance of the estuarine fish community based on catch per unit effort averaged over beach seine Stations S1. 52 and S3, during the preoperational period (1976-1984 and 1987-1989) and in 1990. Seabrook Operational Report,1990. 83
total' catch (Figure 2.2-6, 2.3-11). Since increased abundances of smelt were.for the.most'part due to higher catches prior to commercial
~
operation, they are not related to plant operation. River herring (Alosa spp.), which includes alewife and blueback herring, occasionally appeared in large numbers in Hampton Harbor, especially at the Browns River Station. In the Taylor F;vor, the size of tho' river herring run has been variable, depending on year claar strength, whereas tl.e timing of the run depended on water tempera-
- ture and level, which in turn was influenced by rainf all and runof f (NAI 1985b). In the estuarine sampling program, these species constituted only abcut 5% of the total catch (1978-1989). No alewives or blueback
- herring were caught in the estuary in 1989. In 1990, blueback herring wera caught in low numbers in the estuary in the fall, but no alewives ,
were enllected (see Results Section 3.2.2). Another species that uses the estuary is winter flounder. This species undergoes onshore / offshore migration, depending on the time
'I of year (Bigelow and Schroeder 1953). Juveniles (ages one and two, based on length-frequency analycis) have been the main constituent in the estuary, primarily collected during the spring and summer (NAI 1985b). Recruitment was evident by the occurrence of young-of-the-year l 1
- size classes. - Winter floander have composed only a small partion of the estuarine. fish assemblage, averaging only 2% since 1976 (Figure 2.3-11).
- Their relative abundance was highest in April, when total catch is low-est. In 1990, winter f1cunder catches were lower than average through- !
1 out the year (see Section 3.2.2). ; The_ dominant resident species in the estuary has historically .) been Atlantic silverside, which typically composed-from just under 50% to~nearly 90% of seine-catches during the baseline period (1976-1989)
-during their period of greatest abundance, August to November (Fit e 2.3-11). This trend continued in 1990. with one exception. High l rainbow smelt catches in-August reduced the relative importance (percent. j composition) of-silversides. The populat ion historically has been 86
I:
- n. ,
l l j i
- composed primarily of yearling fish but the occurrence of young-of-the- ]
year size classes in spring has indicated recruitment (NAI 1985b). The j year-to-year variation in silverside catmh has been the main cause of- i ' the observed variation in the total anr,a. match in beach seines for all , species combined. Total catcher, were high from 1976-1981 (200-360 fish / haul) and much lower.from 1982-1989 (40-115 fish / haul) (Figure 2.3-11). Inceased total catch in 1990 was in large part due to increased numbers of silversides in comparison to 1989 levels. However, given the high'annudl variability in silverside catches, 1990 were statistically
-similar.to previous years levels, although' lower thr.n average (See Results, Section 3.2.2).
Since the Hampton-Seabrook estuary contains the majority of New Hampshire's stock of the recreationally-important species #ra arenaria, an extensive sampling program (initiated in 1969) has been un-dertaken in order to characterize the natural variability in the popula-tion for all lifestages. Of the potential impact types, larval stages will be most susceptible t.2 intake effects and therefore are discussed in that section (Section 2.2.1). Spat settlement densities appear to i bear no relationship to the abundar.cc or periodicity of Nya larvae in the nearshore waters (NAI 1982b). It would. appear that #ra veliger < behavior (i.e. their " readiness" or competency to settle) combined with the timing.of favorable currents may be more important to settlement , success than sheer numbers of larvae in the water column. Such condi- . tions apparently existed in 1975, 1976, 1977, 1980, 1981 and 1984 when high-young-of-the-year spat densities indicated successful tecruitment at-Flat 1 (Figure 2.3-12) and other flats. The 1976 year class in par-
-ticular provided an:important and rejuvenating recruitment to the local population as shown by the high densities of 13-25 mm (yearling and older) spat clams in 1977 and 1978 (Figure 2.3-12). In 1989, young of the year settlement densities.throughout-Hampton Harbor were again high-L er than previous levels. This level of settlement was sustained into
.1990 at Flats-2 and 4 and showed further increases at Flat 1 (Figure
~2.3-12). Survival of the 1989 year class at Flats 1 and 2 is suggested by increased densities of the 13-25 mm spat in 1990.
87
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Once settled, survival of young-of-the year liya depends ou i 'both the level of predation from its two main predators, the green crab and h'rnan clam diggers, and tee absence of diseases such as neoplasia. 4 Despihe'relatisely heavy densities of young-of-the year in 1980, 1981, and 1984 on Flat 1, recruitment to yearling clams was minimal (Figure 2.3-12). This pattern was replicated througheut the estucry. Predation by green crabs, whose densities bege.' to increase in 1980 and from 1983-1989 remained much higher than previous years, may have virtually eliminated the first and second year-class (Figure 2.3-13). Dramatical-ly decreased green crab catches in 1990 may have enhanced the survival j _ of spat. _ and juveniles, in part contrJbuting to increat.ed densities at Flat 1 (spat only) and Flat 4 (spat and juveniles)(Figures 2J3-12,13).
- l. Human predation is also an isoportant factor in the level of L harvestable clams, and causes additional mortality to unharvested adults
.as well as spat and juveniles by disturbance. Digging-activity declined
--s harply from 1982 to 1985 with a small increase in 1986 as clam diggers l-switched.among the flats within the estuary in an effort to harvest-L . class. Digging activity resumed its decline in 1987 and continued t2 l fall through 1989, when flats were closed due to coliform contaminat.on l --
l
'(Figure 2.3-13). The standing stock had declined precipitously from 1983 through 1987, lagging trends in digging _ activity by one year. In-E 1988, the decline of adult standing stock leveled eff while the number of adult licenses continued to decrease. Harvestable clam densities
! -began to inciease at Flat 4 following closure of all of the flats to viy , digging activities, while standing stock at the other. flats remained o- !. unchanged. However, for-the entire area, harvestable clams have L
.increesed steadily since 1987, most likely due to the reduced diggina l'
l pressure alons with reduced numbers of green crabs. Finally, the presence of disease has an undetermined effect on Nya recruitment and nurvival. Neoplania, a cell growth disease fatal to
, #ya, was detected at Hampton Harbor Flats 1 and 2 in studies conducted in 1986:and 1987 (Hillman 1986, 1987). Presence of neoplasia in 1987 coincided. with dramatic decreases in juvenile and adult densitics at 89 l
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u Flats 1 and'2, while Flat 4 densities, where no neoplasia were found, remained-unchanged. The magnitude of the ef fect of this disease on tLe clam population is unknown. I increases-in young-of-the-year recruitment in 1990, along with j J continued survival of yearling spat, suggest that there are no adverse i i effects from plant operation, including settling pond discharge or off- i shore entrainment. The- ability to assess impact in ' adult cisms in Hamp- I ton estuary will depend on close monitoring of all of the f actors impor-tant to recruitment 'and predation. One of these factors is clam seeding
.by the State of.New Hampshire. Seeding act ivities during 1987 and 1988 on Hampton Harbor tidal flats did not result in measurably increased' spat densities. Thus, it appears that predation levels and disease are currently the most important factors in determining the standing crop of harvestable clams.
'2.3.2 Benthic Monitoring 2.3.2.1- Macroalegg_and Macrofau.ng Monitoring of- the benthic organisms (macroinvertebrates, al- ,
gae, demarsal floh, and epibenthic crustaceant) was established to de-termine1the extent of change (if any) to the community structure in this zone as: a tesult of plant operation. Changes could be manifested by (1)- the' enhancement of'detritivorea and suspension feeders, (2) the in- - creased attraction of benthic feeders caused by locally-lucreased food . supply, and/or (3) impact on organisms sensitive to the increased detri-tus resulting-from mor.ibund entrained organisms. Mid depth and-deep (10-20 m) benthic communities, including - macroalgae, macro. fauna, and bottom-panels, were sampled to monitor the preoperational benthic community. Year-to year variations in community structure were small in-ccmparison co variations related to depth and substrate. The macroalgae community was highly similar among years, , although less so than in the intertidal and shallcw subtidal areas. 91 y .
i 1
- Species composition ofLcollections_in the mid-depth and deep subtidal areas during 1990 was similar to those taken at the same station in
-previous years (Figure 2.3-7 and Section 3.3.2). In 1990, plant start-up began less than a week before macroalgae and macrofaunal community
-collections were made. Thus, 1990 collections are not expected to show
. changes resulting_from plant operation.
Species composition of the.macroalgae_ community in mid-depth and deep areas was similar to previous years-(Figure 2.3-7). . Total biomass of the mid-depth station groups in'1990 was similar to previous years. Deep discharge (B04) and farfield (B34) group biomass was lower in 1990 +.h-sn in previous years, whoress deep intake (E13) station biomass was-higher than previous _ years-(Figure 2.3-7). Mr.crofauna community composition at mid-depth station in 1990 was similor-in mid-depth regions to previous. years; the assemblage at deep stations .was similar to= the assemblage collected in the last 2-3 years (Figure 2.3-7). Heavy Balanus crenatus sets have differentiated the deep' stations in recent years from the deep water assemblage collected prior to 1988. Station group densities in 1990-were similar to previous years. Other community parameters underscored the_ stability of the benthic community. The majority of changes noted in 1990 occurred at . both nearfield and'farfield areas. Taxa richness of both algae and
-macrofauna.in 1990 was statistically similar-to previous years at the
, mid-depth intake station and deep areas. Differences in macrofaunal and
.macroalgae taxa richness at the mid-depth discharge station were also observed,in the farfield area (Table 2.3-2).
Patterns in abcndancs and size distribution in selected
' benthic species were-only slightly less predictable than coamunity characteristics. Historically, abundances have varied among years and between nearfield and farfield stations-(NAI 1990b). :1990'aoundances of two t.axa, amphipod Pontogenela'inernis and mussel Modiolus modfolus, 92
F were similar to previous years (Figure 2.'J-14). Abundances of mytilids were higher in 1990 at the discharge station, and lower at the farfield station, whereas green sea urchius were more abundant in 1990 at both nearfield_and farfield areas (Table 2.3-5, Figure 2.3-14). However, these differeaces occurred before plant operation began, and thus appear to be part of the natural variability among years. In particular, green sea urchin densities showed evidence of a long term cycle. 1990 densities 3 although higher than 1988 and 1989 densitics, were lower than the preoperational average (see Results, Section 3.3.5). Length measurements have historically been a stable indicator of population recruitment and growth, showing low variability among _ years. Mytilids were larger than average at the discharge station, but within the range of previous years. Amphipod Pontogenela increis and the green sea urchin were similar in size to previous years (see Section 3.3.5). I L 2.3.2.2 Demersal_Elth Demersal fish that inhabit nr feed in the nearshore area are important not only because of their predominance in the . food chain but also because of their commercial.value. As would be expected with any bottom-oriented species, the nearshore population of demersal fish show spatial differences associated with substrate and location relative to Hampton Harbor. - Of the farfield stations, -T1 has a sandy bottom and T3 has sand mixed with cobble and shell debris. The nearshore discharge station T2 is mainly sand. Ststion T2, located off'the mouth of.Mcmpton Inlet, is influenced by tidal flow from the estuary, which often causes
, the accumulation of drif t algae. The algae, combined with heavy lobster fishing in-the area, has decreased gear effectiveness and-has even I
' prevented trawling activities in some months. For this reason, poton-tial effects of operation are investigated separately-for the nearshore Station T2 and the more distant stat.fons (T1 and T3), which are similar- l l
and thus combined for this assessment, 93 i
Annual Variability a ff' fop (0*12 91 Cept n*10 forModicles ) 4-0 o 1990
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M o- e- g$u g z 2 v I' N/A - Percent comoosition not computed in instances where only a sing!4 species is collected. Figure 2.3-14. Preoperational rnean (1978-1989) and 95% confidence limits and 1990 mean of log (x+1) abundance (no./m2) and percent composition for selected benthic species at mid depth nearfield station. Seabrook Operational Report,1990. 9e
l h TAB 12 2.3-5.
SUMMARY
OF SIMIIARITIES OF ABUNDANCES OF SELECTED TAXA IN MID-DEPTH REGIONS IN 1990 COMPARED WITH PRE-VIOUS YEARS. SEABROOK OPERATIONAL REPORT, 1990. RESTRICTED SIMIIAR TO TREND AT OPERATIONAI. 1990 SIMILAR" 1990 DIFFERENT* NF/FF" PERIOD" Pontogenela inerals hytilidae no no Modiolus codiolus Strongylocentrotus yes no droebachlensis Rainbow smelt Atlantic cod yes no Winter f Munder Hakes yes no Yellowtail flounder yes no Lobster (total catch) yes no Lobster (legal-sized) yes no Rock crab yes no Jonah crab no no
" Based on results of Analysis of Variance or Wilcoxon's summed l ranks tests.
4 95
Total catches in the demersal fish community showed evidence of a multiple-year' cycle. Total catches steadily increased from 1977-1981, declined from 1981 through 1985, generally increased through 1988, and decreased .in 1990 (Figure 2.3-15). Catches from August-December, the period of operation in 1990, paralleled the trends for the entire year. Thus the decrease in total catch in 1990 was not restricted to the operational period. Seasonally, catches were usually lowest from January tnrough March or April, but the occasional appearance of rainbow smelt increased total winter catches as occurred at T2 in 1990. Total catch was highest in summer and fall at T1 and T3, and somewhat earlier at T2 (Figure 2.3-15). Seasonal patterns.of total catch in 1990 were similar at T1 and T3, but catches wer* lower than average at these stations. The seasonal pattern of total catch at T2 was slightly different in 1990 from previous years. Catches were lower than ave: age j from March through-June, then increased due to high catches of winter-flounder. Large numbers of lobster traps prevented trawling at T2 in September and October. F Historically, six taxa composed close to 80% of total near-
.. shore otter trawl catches both across months and years (Figure 2.3-16).
I ~The spatial, sansonal, and annual variability of these dominant _ species had a strong influence on the community structure. The relative importance of dominant' species often showed year-to-year fluctuations
-(Figure 2.3-16). Proporticas of hakes, Atlantic cod, and rainbow smelt f
l varied by five to tenfold among years. Yellowtail flounder and winter flounder were more stable constituents, with'1cuer year-to-year vari-- i ability. In'1990, hakes and cod had lower'relativa. abundance than any previous year. Catches of these species throughout 1990 were signiff-cantly lower than.all previous years at all three stations-(Figure 2.2 - -) i
- 6; Table 2.3-5). Rainbow smelt catches were higher than average in 1990 l but statistically similar to previous years. Skates were also relative-o ;
~1y more abundant, on average, than in previous years. -i
;\
The .demersal fish community at T2 changed with the seasonal ' movements of the. dominant species. The presence of rainbow smelt and, j
-1 L- 96 l
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m . _ . . Annual Catch
' ST ATCNS T1. T3 x 100 -
..*..* $TA1CN T2 u
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s 20 - 0 , . . . . . . . . . . 1 i i i 76 77 78 79 80 81 82 83 84 85 86 87 86 to 90 Annual Catch, A>igust Decernbcr STAT CNS T1.73 120 = ...... STATCN T.
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<0 - .......a.,,...........,*.,,. .'s w
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y ' X 20 - O- , , , . . i ; i i i a 1 JAN RB MAR APR MAY #3 JUL AUG SEP OCT POV CEC MONTH Figure 2.315 Total annual and monthly catch of demersal species at Stations T1 and T3 combined and Station T2 during the preoperational period (19761989) and in 1990. Seabrook Operational Report,1990. 97 1
Annu:1 Varlstlen 100 - Stati;ns T1, T3 g go . - _ _ _ . nzwez@ O $4V 'A
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! o-- , , , , , , , , , , , , i G Atante cod 76 77 76 79 80 81 82 83 84 85 86 87 88 89 90 YEAR Seasonal Variation e ma rounow - 103 - Preoperational 9
~
#* "' Q hakes re a#,;Y,h, g_"_
-r 5 /s, -
$ 20 - j;g g y
- %s@M@,sMW B
' ' , AgaT- "
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, , , , , , , D YeRow1al flounder JAN RB MAA APR. LMY JON JUL AUG SEP CCT NOV TIC toc q 1990
/
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- ~'
NO F@ % k: .@Agp!r9486 , TAAwts catfq, o . . . . . .. i i i JAN R3 MAR APR VAY JUN JUL AUG EP CCT NOV rfC MONTH Figure 2.3-16. Seasonal and annual changes in relative abundance of the demt.rsal fish community, based on mean catch per unit effort at otter trawl Station T2 during the preoperational period (19761989) and in 1990. Seabrook Operational Report,1990. 98
to a lesser extent yellowtail flounder, in winter (December-March) differentiated the community frorn the remainder of the year, when hakes . _(red, white, and spotted) predominated (Figure 2.3-16). The age structure of the-fish population can also be a factor contributing to abundance variability. Based on 1983 and 3904 length- , frequency data and age-size information'from the literature, the dominant age group collected at the nearfield trawl station (T2) was determlued. As with most of the pelagic and estuarine fish collected in , this s.tudy, tho' majority of fish collected with otter trawls were
-juveniles.-Yellowtail flounder and rainbow smelt were predominantly young-of-the-year, whereas the majority of Atlaatic cod were ages one
'and two. Only hakes and winter flounder had no dominant age class, al+. hough presence of young-of-the-year for these as well as the other taxa-indicated the timing of recruitment. Knowledge of the age struc-ture of- the population and use of age and growth parameters (Nh1 1%5b) can be used to better understand spatial and temporal changes in the demersal fish population.
r. Spatial dif ferences are an important consideration with J demersal fish. Historically, farfield Stations T1 and T3 have been similer in overall catch.per unit effort (NA1 1990b). Communities have been dominated by_the same species, although longhorn sculpin were more important-at T3, while yellowtail flounder were more important at T1 (Section 3.2.2.1). The nearfield station (T2) was unique, with total CPUE (averaged over all years) reaching only 60% of that at farfield L . stations 1(Figure 2,3-15). This may be duo in part to decreased sampling efficiency from eccumulated drift alsan and interference from lobster
-traps. " Historically, winter flounder and rainbow smelt'(together)
. composed 45% of the overall catch at T2, compared with 11-12% at the farfield stations (Figure 2.3-16). These species were relatively more abundaat at theff. cield stations in. 1990 (15-19%) than previous years, but their relative abundance remained less than half that at T2 in 1990
.(4$%). Most of the differences in total catch ano species composition 99 5
r
can be attributable to the previously mentioned differences in substrate and location with respect to Hampton Harbor. Changes in the detaersal fish community in 1990 were mainly the result of significantly decreased abundancea of Atlantic cod and hakes. This is consistent with historical trends, as demersal fish catches-have shown substantial vatiations among years. Since catches of these species were diminished throughout the year at all three stations, the differences appear unrelated to plant operation. ; r 2.3.2.3 Enibenthic Crustacea t. i Because of its commercial importance, all life stages of the American lobster have been studied over the last 12-16 years. Annual catches of adult lobsters (" Total catch") averaged between 46 and 93 per year for a 15-trap fishing effort. Catches were highest during late summer and fall,-from August-November. Seasonal trends of lobster L
- catches in 1990 were similar to previous years, but. monthly catches were I consistently higher than average at both nearfield and farfield stations f-(Section 3.3.6). Higher than average bottom _ temperatures may, in part, be responrible for higher catches. Temperature acts not only to incro-asa activity (and thus the likelihood of being cao3ht (Dow 1969]) but t-also affects sessenal moveme.nts (Campbell 1985). Increased lobster catches were reported in 1990 both in New.l!ampshire and throughout New England (NOAA 1991b). . Variations in catches of legel-sized lobsters, a primary concern to lobstermen, were a result of natural variation com-bined with the-effects of increases in ~ the legal size limit in 1984,
;1989,_and 1990. -Effects of the.first increase 1n the legal size limit
~
L in 1984 (from 3 1/8" [79.4 mm) to 3 3/16" [81.0 mm]), reduced the pro-i p portion of legal-s.tzed lobsters frcm an average of 14% (1975-1983)-to 8% (1984-1988). A second-increase .in the legal size limit.(to 3 7/32" , [81.8 mm)) in 1989 coincided with a 50% decrease'in legal catches to 5% (- ' l of, total catch. The increaso in legal size in 1990 to-3 1/4 in (82;6 am) further' reduced legal catches to 3% of the total catch. l' 1 100 L
l 2 Size class distributions reflect changes in the legal size 1 limits. Since 1981, 67-79 mm lobsters have predominated _in trap catches. Numbers of lobsters measuring 79-92 mra, as well as their - proportions, were higher in 1990 than in 1984-1989, which in-turn were higher than previous years. This probably reflects the increased protection from fishing pressure caused by size lirit changes (Figure 2.3-17). Jonah.(Cancer borea115) and rock (C. irroratus) crabs are col-lected along with lobsters in the trapping program. Jonah crab catches have shown an increasing trend. Catches at the discharge area were higher.from 1985-1987 than previous years; in 1988 and 1989, annual catches surpassed all previous years. 1990 catches, however, were lower
- - than the past two. years, but higher than the average for the study period (1982-1990; Figure 2.3-16). Increased catches occurred in, July and August. Jonah crab catches at Rye ledge in 1990 were lower than average in all months thct collections were made, but within the range
[ of-previous years. Althcugh Jonah crabs were statistically different in i l~ i 1990 only at the discharge aren, differences were first observed prior te plant start-up. Thus, 1990 differences are unrelated to plant opera-tion. Rock crabs are less prevalent.than their congener in the study area,.probably because of their preference for sandy substrate (Jef.feries -1966) . Catches in 1989 were the highest observed to date, at
- both-the discharge area and Rye Ledge. In 1990, catches were still' higher than1 average at both stationa (Figure 2.3-4), but were lower than the peak' catches observed during the previous year. Higher than average
[ catches in 1989 and 1990 were due to large catches from June through August. l: l-l 101 l N. ]
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16 % t% 9% t% r- e' .N 83 84 86 67 se 89 Do 75 76 77 70 79 80 al 62 R5 YEAR Figure 2.3-17. Size class distribution oflobsters and catches of legal and sublegal-sized lobsters at the discharge station, 1975-1990. Seabrook Operational Report,1990. , I l 102
3.0 RESUI.TS 3.1 PIANKTON AND )fAIER_ QUALITY PAPXdETQS Plankton and water quality programs of the Scabrook environ- 4 mental studies have included water quality sampling, phytoplankton, microzooplankton, bivalve larvae, and macrozooplankton. The plankt.on and water quality programs presented in this '990 operational report are those for which samplinp. pas conducte,d during 1990: water quality (Section 3.1.1), ' phytoplankton ' (3.1. 2), microzooplankton (3.1. 3), bivalve larvae (3.1.4). and macrozooplankton'(3.1.5). Renults from entrainment sampling for bivalve larvae are also presented, l
-- 3.1.1 ilA1AL.RuAlitJ._fRA01tnA?le.n.qna1 Cyc1es and Trsmis Three physical (temperature, salinity and dissolved oxygen) and five chemical (orthophosphate, total phosphorus, nitrite-nitrogert, nitrate-nitrogen and ammonia-nitrogen) parameters were monitored over a 13 year period to assess their temporal-variability. A farfield station (P7) was_added in 1982 to provide a reference area. With the exception of ammonia, parameters exhibited cycles with one or two peaks. annually.
Water temperature was monitored in the nearfield both contin-uously and-from d1screte samples collected weekly, twice-weekly, or
-monthly during the plankton cruises. llistorically, monthly mean values derived from both sampling methods have been similar (NAi 1980c, 1980d, 'i81f,-19G2a, 1984a, 19859). . Surface yater temperatures were strongly , influenced by solar irradiation, with temperature peaks lagging irradiance peaks bylone. month (NAl 1985b). Bottom temperatures (depth 16 meters at IILW) showed truncated. peaks which logged one to three . months.behind surface peaks. Since 1978, highest temperatures-at ' Station P2 have occurred in July or August at the surface, and from August to October at the bottom (Figure 3.1.1-1), Jn 1990, peak surfaco and bottom temperatures occutred in August and were above the preoperat-ional average. Surface and bottom water temperatured remained above 103
Surfaca, intake co - PA7DP g ... .. 139) ,/ /**.,"*.. ,,* L 16 - T .
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P..... + 0 4 i . .: 4 . i , , . , , JAN RB MAA AP9 MAY JUN s u',. ALG Ep ocT p4;v g MOPITH Surface,1990 20 -
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. . _ _ . _ _ . . . . _ . _ _ _ _ _ _ _ . _ _ . _ . - - - _ . . ....._ _ _.__ _.__.m _ _ . _ _ _
average for the remainder of the year (Tigure 3.1.1-1) resultjug in j annual mean temperatures that were higher than the preoperational average (Table 3.1.1-1). !!owever,1990 near'(eld temperatures were l
-statistically similar to previous years for both the entire year and !
- during the operational pertoi (August-Docember: Tabic 3.1.1 2). ,
i' n 1990, temperatures were monitored at the intake (P2), 1 discharga (P5), and farfleid stations (P7). fionthly mean surface l temperatures worn statistically similar at all three ntations both for , r the entire year and for the operational period (Table 3.1.1 2). There ( were no discernible (lif ferences in seasonal patterns among the thren stations (Figure 3.1.1-1)'. Continuous .wperature data were provided by YAEC f rom , stations located near the intake (T7) and discharge (DS) areas. Monthly r averages of daily surface temperatures at the discharge r.tation (Figure ;
. 3.1.1-2) were similar to those at intake station T7 in July, August, and i September. Trom October December, surfacn temperatures at. the discharge i station averaged 0.8-1.6 % higher than those at stat.fon T7 (Figure -f 3.1.1-2).
Temperature differences between_ surface and bottom watern shou , the'seasonni trend in development and dissipation of the thermoe:ine.
- llis orically, vertical temperature differences were minimal (<1 from -
< January through if arch and Noveaber-December (Figure 3.1.1-3).
Vertical ; temperature differences have been mest pronounced (at least 3'C) from May through October. Thermocline development in 1990 was sImflar to f previ9us years, although temperature differences were less than the pr*. ope ratier:a) average from June through September. Thermocline dissi. ation in 1999 during the operat.ional period ( August-December) was ;
. similar'to-previous years.
Other water-quality paramotors were niso monitored at Station , P2,.P5 and P7 during fortnightly plankton cruises. As in previous i' 105 l 1
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N w e . 6* 4" DS (ctscharge) 2 T7 (!sd.eid) o -- , , . , , AT4 EEP CCT to/ Ett MONTH Figure 3.1.12. Comparison of monthly averaged continuous temperature CC) data collected at discharge (DS) and f arfield (T7) stations during commercial operation. August December 1990. Seabrook Operationt.1 Report,1990, 108 l
. _. ._ _ _ _ __. .._ _ _ . _ _ . = _ . . . _ . . , _ . _ _ _ - . - . _ _ . .
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*g I 4 4 4 h 1 y I 3 uky adN JL ALO SEP OCT fG E MONTH Figure ~2.1.13. Monthly mean difference and 95% confidence Ilmits between surface and bottom temperatures (C) at nearfield Station P2 over all years from 19781989 and monthly means in 1990. - Scabrook Operational Report,1990.
109
~. , ._ , ._ ,
l l l years, surf ace salinit ies in 1990 began to decline in February (Figure ] 3.1 1 4). Low salinity levels usually occurred in Aptil or Hay, but l were not observed until June in 1990, when surfaen aslinity was well below triu preoperational average. This may be attributable to above average precipitation for April and May (Section 3.3.1). The low surface salinity observed in June was followed by a small increase in ' j July and then dropped sharply in August (t1gure 3.3.1-3,5, coincident j
-- with higher-than-avetage precipitation in July v.nd Augi.st (Sect ion 3.3.1). The August salinity was the lowest ever observed for this month at Station P2. Surface salinities then steadily climbed through the
- remainder of the year, but ciet!cu N alightiy below the preopemtional averaga. Annt. s im uL *n bottom salinit ies f followed roughly the same patto e <,, oince se initics, althengh the ;
magnitu.ie of differences was not as pronounced. The annual mean surface and bottom salinities were below the trioperettoral average fcr the thirteen-year period, but witnin the tengn of annuni means. No signiff- l cant differences in salinity occurred among Stations P2, PS and P7 in 1990 (Table 3.1.1-2). Historically, surface and bottom dissolved oxygen peaked in late winter (Februar7-April) and decreased to lowest levels in fall (August-November) (rigure 3.1.1-5). Seasonni ttands in 1990 were similar, although the fall nadir in Septen.ber.wes lower than thn preoperational average. Dissolved oxygen patterns were similar at ; Stations P2, P5 and P7 as evidenced by the results of analysis of , variance (Table 3.1.1-2). liiatorically, orthophosphate and total phosphate did net show
-evidence of.c st rong seasonal cycle. Values were lowest in summer, (May-September), during the presence of the thermoclinn (Figure 3.1.1-
- 6). The seasor.a1 variation of orthophosphate and total phosphorous in 1990 was cornparable to previous years, although values abovn and below the preoperational average were observed. do spatial differences were found for either paramettir in 1990 (Table 3.1.1-2). Peaks in-ortho-l' 110 e--w- ,---+m'.r- , ex-., e-e_-r, -
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fk ., '/ m 30 - ' H CC IL 20 - 20 - , , , i i i , , , , , i JAN - FEB MAR APR MAY JUN JUL AJG SEP CCT PC/ TL MOWH Figure 3..l.1-4. Surf ace and bottom salinity (ppt) at nearfield Station P2. monthly means and 95% conDdence intervals c'ter all yean. 19781989. and monthly means for 1990. l'.eabrook Operational Report.1990. lil
Surface Dissolved Oxygen 12 - 11 - N.$ x .
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JAN- F8 MAR APR MAY JUN JUL /LG SEP OCT 10/ Ctr, MoffrH l l Figure 3.1.15. Surface and bottom dissolved oxygen (mg/L) at nearfield Station P2, monthly meanc and 95% confidence intcrvals over all years, 19781989, and monthly means for 1990. Seabrook Operational Report.1990. l 112
Orthophcsphate so - mew
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Figure 3.1.16. Surface orthophosphate and total phosphorus Oug P/L) at nearfield Station P2, monthly means and 95% confidence intervals over all years from 19781984 and 19861989, and mor.thly means for 1990. Seabrook Operat!onal Report.1990. 113
phosphate concentration in 1990 occurred in February nnd April, and were consistently above the preop? rational average f rom September through December. Values for orthophosphate in !! arch, May and June 1990 were somewhat lower than the mean for previous years. Concentrations of total phosphate for the year staye'l generally within the 95% confidence limits, but were clovated in October and November (ri;,ure 3.1.1-6) . Nitrate levels at station P2 have historically shown a strong seasonal cycle. Values typically steadily decreased from January to MSy, remained low through September, then steadily increased for the remainder of the year. The seasonal nitrate cycle in 1990 approximated the preoperational average, with the party low occurring in June, llowever, higher than-average nitrate values were observed from January l- through May, and in September and October. Ammonia and nitrite leveln historically have not'shown a st.rong seasonal pattern. Nitrite valunn iluctuated widoly in 1990, and higher-than-avernge values were observed in February, May and October (Figure 3.1.1-7). In 1990, ammonia concentrations wars below the analytical detection limit (10 pg/1) for seven months of the year (Janunty through March, June through August and November) and belw the preoperational average during tbn remaining months (rigure 3.1.1-3). Concentrations of all nitrogen nutrients were similar among Stations P2, P5 and P7 in 1990 (Table 3,1,1-2). 3,1.2 Phyton1Anklau 3.1.2.1 IRLAl C.0matuR1.ty Irm,Roral Charag.txtlating i i During the preoperational years, mean total phytoplankton abundance exhibited a. bimodal annuel cycle with spring and fall maxima and summer and winter minima (Figure L 1.2-1; ref er _ to rigure 3.1.2-1 of -
~
NAl;1985b). In 1990,'the spring peak-occorred in June, one month later than in preoperational-years, and a fall peak was-not observed at all. Total abundance was higher in 1990 than during the preoperational 114 l. g _ - . . - _ . , _ . ~ . , _ . . _ . _ . . . . . , _ _ _ . _. _. _. _ ._ -~. _ _ _ _ . _ _ _
Nitrate Nitrogen mw
* . . . . . . 1990 1Bo -
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'a For the puipose of calculating monthly means, data points reported as
'below detection limit' wete ghan a value of one half the detection limit.
l Figure 3.1.1-7. Surface nitrite nitrogen and nitrate nitrogen (pg N/L) at nearfield Station P2 monthly means aac 95% confidence intervals over all years from 19781984 and 19861989, and monthly means for 1990. Seabrook Operational Report 1990. 115
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3.s . .. 3.6 , , , , , , , , , , , , JAN RB MAR APR MAY JUN JUL AUG EP CCT PCV CEC MONTH Figure 3.1.2-1 l.og (x+1) abundance (no./l) of total phytoplankton at nearfield Station P2: monthly means and 95% confidence intervals over all preoperational years (19781984) and monthly means with and without colonial Cyanophyceae for 1990. Seabrook Operational Repon,1990. 117 s re- < . , - , -,-e r-, . _ . . . . . . ._ . , , . -+ -a.-- J
l r period, with 1990 monthly total abundance values generally above the l upper bound of preoperational 95% confidence intervals (Figure 3.1.; ;). i I For the months of August through December, the number of specic5 ' composing 1% or more of total abundance varied from only five in 1990 to as many as fourteen in 1981 (Table 3.1.2-1). SAcletonema costatum was consistently dominant in the preoperational period, accounting for approximately 10-90% of the phytoplankton assembinge during these years. In 1990, bewever, Skeletonema costatem composed less than 1%'of the total assemblage. Colonial Cyanophycene replaced I Skeletonema costatum as the most abundant taxon in 1990, accourting for ; 66% of the assemblage. Colonial Cyanophyceae werc'nbnent from preopera-tional samples between 1978 and 1983, and accounted for less than 0.1% of the assemblage in 1984, but contributed 13% of the total abundnnce in J 1986. 'Other species that were dominant in some years duting the ' preoperational period include flagellate algae (54% in 1903), and Rhizosolenia delicatula (69% in 1979), while in 1990,-unicellular and flagellate algae, filamentous Cyanophyceae, and Chroomonas sp. were all , abundant, each accounting for more ti.an 1% of total abunciance. The mean abundances of taxa dominant in 1990 are generally quite different compared to preoperational yearn, in 1990, five_ taxa cach comprised greater.than 1% of the total abundance. These taxa were, L~ as noted above: colonial Cyanophyceae, unicellular algan, flagellated algae, filamentous Cyanophyceae, and Chroomonas sp. (a cryptophyte). Mean abundances of each of these taxa during August-December in pre-operational years were at least two orders of magnitude lower than during the same months in 1990 (Table 3.1.2-2), and in each case, the lower 95% confidence level for the 1990 means were above the upper bound ' of the preoperational-95% confidence levels. Confidence intervalo of L 1990 abundances of other relatively abundant ~ taxa generally overlapped, confidence intervals for the preoperational periods. This indicates that abundances in 1990 for those taxa were within the previously
. observed rangefoi natural variabilit-l- 118 e
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TAB 12 3.1.2-2. PREOPERATIONAL AND OPERATIONAL GEOMETRIC HEAN ABUNDANCE" AND CONFIDENCE INTERVAL FOR PilYTOPIANKTON TAXA OCCURRING BETWEEN AUGUST AND DECEMBER AT STATION P2. SEABROOK OPERATIONAL REPORT, 1990. PREOPERATIONAL YEARSh 1990" SPECIES R C1 E CI Cyanophyceae; color.lal 0.64 0,52 6.63 0.14 Alge, unicellular 1.21 0.53 5.78 0.77 Cyanophyceae; filamentous 0.13 0.19 4.69 1.14 Alga, flageliste 3.35 0.68 5.00 0.58 Chrooronas sp. 1.36 0.53 4.83 0.69 Skeletonema costatum 4.71 0.38 3.22 2.42 Rhizosolania fragilissima 1.76 0.68 Leptocylindrus minimus 2.01 0.69 2.82 2.14 Nltzschia driicatissima 2.38 0.63 1.22 2.09 Herismopedis sp. 0.21 0.31 Thalasslosira sp. 2,33 0.59 Centrales 1.43 0.61 3.55 0.40 Dinophyceae 2,07 0.62 Chaetoceros sp. 2.47 0.52 0.71 1.97 Thalassionema nitzschioices 2.94 0.58 1.94 2.21 Ceratavlina bergonil 0.99 0.51 Leptocylindrus denicus 0.66 0.45 1.71 2.91 Hit zschia serfsta 2.15 0.60 0.60 1.66 . Rhizosolenia delicatula 3.04 0.65 0.18 2.16 Asterionella glacialis 0 95 0.47 Pennales 1.22 0.52 2.24 2.54 Rhizosolcnia stolterlothfi 0.44 0.35 Novicula sp, 0.60 0.37 3.09 0.16 Bacillarlophycean 2.96 0.42 3.48 0.64 Rhizoselenia sp. 0.89 0.44 Euglenales 1,57 0.52 1.67 1,90 Cyanophycean 0.66 0.52 Thalassionene sp. 0.49 0.40 Cyanodinium sp. 0.56 0.44 1.24 2.10 Peridinium sp. 1.03 0.47 1.93 2.23 Ceratium Jurca l'00 0'43 2*29 3 40 2 43 Prorocentrum micens 0'.51 0.27 0 38 Phaeocystis pouchetil 0'35 0 35 Pleurosigma angulatum 1 22 0'51 Gyrodinium sp, 2'2I 0'48 Nitzschia icngissima
' Log transformed means and 95% confidence intervals in cells /ljter.
b Sample size = 40 (five months by eight years)
*Sanple size = 5 120
l i Just as total abundance was shown to vary over the year in Figure 3.1.2-1, thu relative abundance of individual taxa also varies l throughout the year. During the preoperational period, phytoplankton ' species succession generally followed patterns described by Margalef , (1958, northwest coast of Spain) and Lillick (1940, Gulf of Hafne cited in NA1 1985b). Both Ltudies demonstrated that nutrient supply was the main determinant of succession and that temperature was important insofar as it worked to enhance or restrict nutrient supplies within thormal strata (NAI 1985b). Margalei (1958) proposed the following seasonal cycle of taxa replacement within the community: 1) small-celled species in the spring, capable of rapid division due to a high surface _ area-to-volumefratio, succeeded by 2) larger flagellates tuul diatoms with a-lower turnover rate, followed_by 3) large motilo forms (flagellates and dinoflagellates) during the period of highest thermal stratification. , Succession of phytoplankton ansemblages during thn preopera-tional period at the Seabrook sampling locations was similar to that , described by Margalef (Figure 3.1.2-2; NA1 1985b). 1he spring bloom l
!during the preoperational. period was initiated by'different taxa from year to' year; centric diatoms (Facillariophyceae, especially Thalassio-sfra sp., Chaetaceres sp., and Skeletonoma costatum) were most often the l first to appear in high densities =(sen' Tabic 3.~1.2-2 of NAI'1985b).
Small flagellates and colonial blue-green algae were also among the spring dominants. - Large vernal blooms of_Thaeocysels pouchet/l (a member of the Xanthophyceae group, or yellow-brown algae) occurred in ! five ofLthe seven preoperational years. By midsummor, dinoflagellates- , (Dinophyceae) appeared in high numbers. . Diatoms (Bacillariophyceae) I reached their highest densities in the fall due.largely to blooms-of Skeletonsas costatum and other diatoms. Overall, during the preopera-tlonal period diatoms were the m6st' abundant group from August through the winter until February. The Xanthophyceau (thacocyst/s_pouchettl) - were most abundant in the spring, while during summer all groups were
' well represented.
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. .. _ __ _ _ _ _ . _ _._ _ - _ . . _ _ _ _ . . . _ . ~ _ . . _ . _ _ _ _ _ Based on yearly nican abundance, colecial Cyanophyceae added l substantially to tho total abundance and ware the overwhelmingly dominant taxon in 1990 (Table 3.1.2-1), perhaps reflecting a regional pattarn. In trtmsects across the Gulf of Haine Balch of 41. (1991) cbserved abund uces of cyanophyceae ranging from 2 - 7 x 107 cells /1 in the sunner of 1988 and 1989. High densities, of colonial cyanophytes have been reported in several other arear of New England: Woods Hole Harbor at 2x106 -3.6x10e ce,11s/1 (Waterbury, et al. 1979); Narragansett Bay at 105 cellu/1 Rhodn Island shelf at 3x10 cells 5
/1 and Georges Bank s 5 et lo cells /1 (Johnson and Sieburth 1979); Hontsweng Bay ME at 1.6x10 cells /1 (McAlice and Jones 1978). Only McAlice and Jones (1978) reported the relationship of the cyanophyte to the rest of the phyto-plankten assemblage. The cyanophyte bloom lasted for several months in Montsweag Bay, ME (McAlice and Jones 1978). The colonial cyanophyte (reported as N/crocystis sp.) dominated that phytoplankton' assemblage,
~
but co occurred with a typical-and diverse group of other phytoplankton species. Siellarly, the phytoplankton assemblage, excluding colonial Cyanophyceae, observed in 1990 in the coastal waters of New Hampshire resembled the preoperational asseniblage in terms of abundance and species composition.(Figure 3.1.2 3). Phaeocystis pouchetil exhibited a spring bloom in 1990,-as was observed in previous years. Later in the spring the Chlorophyceae (green algae, here consisting of ftlamentous and unicellular taxa) appe: red, and re.nained one of the dominant groups for the rest of the
.. ye ar. Cryptophyceae (flagellated h!gae, consisting primarily of
~ Chroomonas sp.) and filamentous Cyanophyceae (in addition to colonial taxa) wero alao abundant in the summer. Unlike the preoperational period, where diatoms were an importanc group for most of the year, they composed a substantial proportion of the assemblage only in June
.(primarily Leptocylindrus minimus and Hitzschla delicatissima) and in October (Skeletonema costatum) and to a lesser degree in July and December. The appearance of large numbers of Skeletonoma costatus in the fall was, however, characteristic of the preoperational period.
123
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l
)
l Hudield and Fodf eld Anemhlaan ' Percent composition a frequency of occurrence of most l dominant species have been similar in the nearfield and the farfield, , for both the preoperational and operattonal periods (Table 3.1.2-3). llistorical analyses of the correlationr in total abundances between
-stations have shown that there is a strong correlation (r > 0.800) between stations P2 and P7 (NA1 1985b). For the period of April through December 1990, total phytoplankton ab m dance showed a significant '
correlation (r d' 0.700) at alpha = 0,05 between st.ations P2 and PS, and between PS and P7. The correlation of total abundance between stations P0 and P7 was also significant, although not as strong as, the other .two comparisons . (r = 0.544) . Differences in individual taxen abundances between stations' during 1990 were also analyzed using a multivariate analysis of variance procedure (MANOVA).(Table 3.1.2-4). The following taxa were selected for inclusion in the analysis: colonial Cyanophyceae; filamentous
- Cyanophyceae; Chl >rophycean; Chroomonas sp. ; Leptocylindrus minimus; Phaeocystis pouchetil; Nitzschia delicatissima; and Skeletonema costatum. These were the dominant taxa (relativo abundance greater than 1%) for the_ period of_ April to Unce.mber. Phaeocystis pouchetil and-Chlorophyceae species represented less than 1% of total abundance between August and December and therefore were not tested. For bri.h the >
April to December and August to December periods, no significant , differences-in_ abundances among the three stations were detected. T Citlarophv1LL.Epmer.1Laihna Chlorophyll a concentratlors may, in-general, he used as-a-lz reasure of phytoplankton ' standing crop, although t.he issae is complicat-ed by t.he varying amounts of chlorophyll a contained in dif ferent phytoplankton species. During'the.preoperational period, chlorophyll a ! concentrations showed a bimodal patt ern, with peaks in spring and f all 125
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. TABLE 3.1.2 4._ RESULTS OF HULTIVARIATE ANALYSIS OF VARIANCE (HANOVA) '
COMPARING Pl!YTOPIANKTON COHHUNITY STRUCTURE AT STATIONS P2, PS AND STATION P7 DURING 1990. I SEABROOK OPERATIONAL REPORT,1990. l I NO.0F NO. OF SPECIES * -STATIONS PERIOD STATISTIC df F 8 3 Apr-Dec Wilk's criterion 16,50 0.52 NS P111al's trace 16,$2 0.52 NS Ilotelling-Lawley trace 16,48 0.53 NS 8 3 Aug-Dec Wilk's critorion 12,22 0.74 NS Pillai's trace 12,24 0.71 NS llotcIling-Lawley trace 12,20 0.77 NS
' Analysis included th ese numerically dominant taxa:
Cyanophyceae, colonial Cyanophyceae, filamentous Chlorophyceae Chroononas np Leptocylindrus minimes t . Phaeocystis pouchet1.1 Nitzschia delicatissima i Skeletoneen costatum t >. 8 r r: 127 ; y.-. ,. ny, - - - - r . c.r., r,,.,%.. . - , , . , . . .v-.- ,. c oL ,-. . - , . . - - _-- _. - , _ _ _._. .___ _ _ _ __,____m
i P P (Figure 3.1.2-4). Concentrations followed a somewhat different pattern i
.In 1990, although spring and fall peaks are apparent. The two highest ;
concentrations were observed in March and in November; smaller peaks ,
- were apparent in May-June and in September, as occurred during the p
preoperational period. Chlorophyll a concentrations were consistent.ly higher in the preoperational period than in 1990, although 1990 concon-trations were contained within the wide preoperationel confidence intervals. These differences in concentrations may reflect the domi-
- nance of Bacillariophycese during the preoperat.fonal period, and the dominance of cyannphyceae which contain less chlorophyll, in 1990.
Chlorophyll a concentrations in 1990 were similar among the three stations,_as indicated by moderate to high correlation coeffi-cients (Table 3.1.2-5). t I l'EP Leveln psp toxicity levels in Nytllus edults, as prov[ded by the a State of New l!ampshire, have 'shown a strong seasonal patt ern of extreme values occurring during the late spring and early summer during the preoperational period (Figure 3.1.2-5). The preoperational date also show a small peah in toxicity levels occurring in August. In 1990, elevated psp levels were recorded in late May through June, although-these levels were generally much lower than thosn observed prior to 1990.
'3.1.2.2 Er. leal;i,Sp_q.c.ie.s <
Skeletonema costatum was chosen as_a selected species because , ^ of its historic omnipresence and overwholraing dominance during'much of the year. .During_the preoperational period, abundances were slightly bimodal.in nature,. showing a smal.1 peak in the spring (varying from ryear-to year from February tc May) and a .r.ajor peak in the Inte surtmer 4 128
i 5.0-Pmor M 4.s . ... .. im 4.0 - 3.5 - 3.0 - O P 2.5 - m c-
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JAN EB MAR APR MAY JUN JUL A.O SEP CCi PO/ Tc MONTH Figur: 3.1.2 4. Mean monthly chlorophyll a concentrations and 95% confidence intervals over all preoperational years (19781984) a3d monthly means in 1990 at nearfield Station P2. Seabrook Operationai Report.1990. 129 l
. _ . _ . ~ _ _ . _ _ _ - . . . _ _ . . _ . . _ . . . _ . . . _ _ . . . _ . . _ _ _ . _ ~ - . . . _ _ . . . _ _ . _ . . _ . - . . . . _ . _ . . . - _ _
s TAB 12 3.1.2-$. CORRE!ATION COEFFICIENTS FOR CllLOP.3PilYLL a CONCENT"ATIONS AT STATIONS P2, P5, AND P7 IN 1990. SEABROOK OPERATIONAI, REPORT,1990. i t P5 P7 i P2 0.9113 c.7831 F5 0.7162 111 cottelations statistically significant at alpha = 0.05; coefficients (r) of 0.600-0.800 trulicate moderate correlatfor, and coeff!cients greater than 0.800 indicate high correlation.
+
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-- ^((p *f y ry y h G y' %
100 - - o .,.... . . .r. 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 *2 3 4 1 2 3 4 1 2 3 4 I ? 3 4 NOV DEC AUG SEP OCT I APR MAY t JUN JUL t Figure 3.1.2-5. Mean and 95% confidence intervals of wcekly paralytic shellfish poi:Oning (PSP) toxicity levels in Myrilta edulis ia llampten liarber over all preoperational years (1978-1984) and mean le.'els in 1940 Seabrook Opera:ional Report.1990.
i a or fall (varying from August to October). This pattern was somewhat diftetent in 1990 (Pigure 3.1. 2-f> and Table 3.1.2-6). A large peak in abundance vna observed in June; in October, the peak was very consistent with historical trends. An snaiysis t,f variance procedure ( ANOVA) was st ructured to examine the following charact erirties of sac 1ctonce:n costatum abundances during the preoperational and operational periods: a) Preop Op tents dif f e':ences in abundances between the preonerational and oporational periods, regardle,s of " station, and will detect whether operational period falls within historical variability; b) Station tests difforences in al>undances among Stations P2, P5 and P7, regardless of sample date, end will detect whether there has been a consistent relationship in ' abundances spatially; c) Year (Proop-Op) t ests dif f erences in abundances arr.ang years nested within preoperational and operational peri-ods, regardless of static;n, and will det ert whether any year or years are unique; d) !!onth (Preop-Op) tests J2ffcrences lu abundances among i toonths nested within preoperational and operat ional e periods, regardlers of station, and will detect whether there is a consistent seasonal pattern; and e) Preop-Op X Station tests differeeces in abundancer be- ' tween the main ef fects of preopn;ational and operat ional periods and station and will detect whether the relation-ship in abundance among stat ions has been consistent between preoperat ional and operat ional periods. These results are summarized in Table 3.1.2-7. During the April to December period, significant differences in Skeletonoma costatum abundances were shown to exist between the preoperationni years ano 1990 (Preop-Op), a m- rs (Year (Preop-Op), and smong rnonths (fionth (Preop-Op)) . F the August to Decembtr period, a sia,nificant dif ference was shown to exi.st between preoperat.f onal and operational abundances (which is noted in Figure 3.1.2-6), and significant differ-ences were again noted among years had amon,r, months, No differences in abundances were apparent among stations in either the April-December or August-Docember time frame. he relationship among stations in terms of 132
w > l 6.5 - mw n.0 -
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I O? a 3.0 - ' .. , 2.5 - 2.0-1.5 - 1.0 . i i i . . . . . . . . JAN RS MAR APR MAY JUN JUL AJG SEP GCT FO/ CEC MONTH Figure 3.1.2-6. Log (x+1) abundance (noll) Skeletonema costatum at nearfield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1934) and monthly means for 1990. Seabrook Operational Report.1990. 133
. w- . . ~ ,
=
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'i TABLE 3.1.2-6. PEAK FALL ABUNDANCES OF SKELETONEMA COSTATuff IN SURFACE WATERS AT TIE NEARFIELD STATION P2 DURING PREOPE*tATIONAL YEANS (1978-1984, 1986) AND 1990.
SEABROOK OPERATIONAL REPORT, 1990. l l-l MONTil 0F MEAN ABUNDANCE IN CELLS / LITER rfAXIMUM 1986 1990 1978 1979 1980 1981 1982 1983 1984 OCCURRENCE l August 2.4x10* 1.2x10 6 6 2.7x19 5 2.2x10 6 9.2x10 5 4.5x10 S.7x10' Geptember 1.3x10 5 October 2.6x10 6 _ _._ _ ..x , % ~ w
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Tt 1 i, abundance of S. costatum did not: vary between-preoperational years and 1990.(Table 3.-l.2-7, Preup-Op X Station). An additional analysis was constructed to evaluate the differences in abundances among Stations P2, PS, and P7 in 1990, with all' dates pooled. No significant differences in abundances eithei duilng the entire yest or the August-December operational period were
-detected (Table 3.1.2-7).
I: 3.'l.3 111strzoonlanktna lt k L 3.1.3.1 Total Commun11y it l EcAssng.1 Charaeter111.isa 1 ., i; l Temporal variability in species abundances and taxonomic l composition of the nearshore microzooplankton community (surface and . bottera samples combined)- at Station P2 (Figure-2.1-2) for all pre-operationalL(1978-1984 and 1986) and operational (1990) collections was nxamined using cluster analysis. Numerical--classification grouped L individual sampling dates :into six major: groups that corresponded -with l> p the seasonal: cycle (Figure 3.1.3-1). scomparison of the specific-_ dates 1 included within each. cluster group-indicated that there were' moderate' [ l . differences among years. .The most-pronounced variation' occurred during-
-late-summer and fall of-preoperational-years where. cluster groups'
-included a number of'" outlying collections" (1.e,, a collection date separated by more . than two . weeks -f rom 'the Frest of- the: seasonal group)
[(Figure ~31.3-2). Collections from 1990 generally clustered into groups. l :containing corresponding dates from the preoperational period, although: b 'the fall / winter collections were . identified as a separate cluster group. from preoperational dates. -.Preoperational and: operational periods were
~
.similar in tihe rank order of numerically dominant taxa identified.from each-cluster group (Table'3.1.3-1); these taxa' accounted for at least.
80%lof the total ~mean abundance within each cluster. .Diffe'rences among-groupsy inflarge measure, were attributed to seasonal variability 11. the 136
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0.5 0.6 03 0.8 0.9 1.0 BRAY.CURTIS SEILARIT( l' Figure 3.1.3-1. Dendrogram fonned by numerical classification cf log (ul) transformed microzooplankton abundances (no./m 3) at Seabrook neartield Station P2, 1978-1984, July December 1986, and April December 1990. Seabrook Operational Report,1990. . 137
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'shundances of these dominant taxa. Seasonal groups identifled by I
cluster' analysis generally encompassed collection periods with similar
- temperature regimes, particularly with respect to the depth and intensi- -
~ ty of'the thermocline (NA1 1985b). Within-cluster sroup similarities were fairly high (0.587 - 0.723) indicating that the microzooplankton community structure was fairly constant-among the dates comprising each group (Figure 3.1.3-1). Between group similarities.were also reasonable high (0.556 - 0.677) due to the consjitent occurrence and relatively high densities throughout , , much of the year of the same dominant taxa (i.e., Copepods nauplii, Oithona sp , Pseudacelanus sp., and Pseudocalanus/Calanus nauplit; Table 3 .' I . 3 - 1 ) .
- As noted above, seasonal patterns in the microzooplankton
- community structure were largely delineated by changes in both total
- abundance and the dominance structure of numerically important taxa.
Lifestages of the copepods Olthona sp. and Pseudocalanus'sp., and~ Pseudocalaaus/Calanus naup)ti were'the most abundant organisms in virtually-every cluster group during both pre-operational and operation-al periods (Table 3.1. 3-1). The winter microzooplankton (. Croup 1) was characterized by fewer dominant taxa with moderate abundances. In the l. l late winter throu p early summer (Groups 2 and 3), population densities , p of copepods (Oithoa.3 sp., Pseudocalanus sp.,_Pseudocalanus/Calanus nauplii, and Copepoda nauplii) increased substantially. Abundances of the microzooplankton assemblage peaked during the summer (Groups 3 and l l? 4) when copepod densities wer" at their highest and benthic species h (particularly bivalves) contributed large numbers of individuals to the meroplankton. Among-year differences in the dates assigned to cluster groups 3, 4 and.5-(summer-fall) were more apparent than for the other seasons because of the large number of dominant taxa with highly variable densities (Tigure 3.3.3-2). The dominant copepods continued to maintain moderate populations throughout the fall and into winter l .(Groups 5 and 6) while densities of most other taxa declined. The fall
=of 1990 (Group.6) differed from earlier years in the subdominance of l.
140 l l' h.
1 i , ] rotifers, Microsecolla-norvegica and Centropages sp. copopodites in addition-to the typical fall dominants (Table 3,1.3-1). The between-i group similarity of 0.68 between groups 5 and 6 is a relatively high-4 value' indicating;that distinctions between the two groups are subtle. In summary, the microzooplankton community structure at
- Station P2 has been fairly consistent throughout this study, with the greatest annual variability evident during the summer and fall when both abundances'and number of dominant species were highest. Although the
.microzooplankton community varied in the fall'of 1990 from preopera-tional years, the differences were due to increased abundances of several taxa while the typical species maintained _their predominanen. +
There-were no other differences noted between pre-operational'ard operational periods. The community structure was influenced primarily
~
- by the population dynamics of the copepods Ofthena sp. and Pseudocolanus sp. and by the production of early lifestages (nauplius larvae) of other ,
copepods. Other-. taxa (including Polychaeta, Bivalvia, and Tintinnidae) i exorted-less influence on overall community structurn. Epai,1.qLfgt_ terns of' Hiunmoplankton Ab3ndantaa Spatial variation (i.ec, among-stations differences? In the _m i crozoop l ankton community structure was' examined separately for both the preoperational and operational periods, with abundances averaged
. over-depth. Comparison of total microzooplanhton densities from 1982 to 1984 using Vilcoxon's two-sample test (Sokal and Rohlf 1969) revealed no
- significant differences between Stations P2 and P7 (NA1 1985b).
Although some numerically important taxa exhibited large; differences in
- rank order or percent composition between stations, their individual abundances were also'not significantly_different (NAI 1985b). ,
.I A multivariete analysis of variance -(MANGVA) was performed using the April-December 1990 abundances-of 34 numerically important 141 1
i-1 l I taxa from Station P2,-PS, and P7, = Species composition and abundances were not significantly different among these stations (Tabic 3.1.3-2), Inisummary,. statistical evaluation of the spatial variation in j microzooplankton community structure, as measured by abundance data
.auong sampling statious, found no significant differences either during ,
1 preoperational years or during 1990. 3.1 ~. 3. 2 Selected Soccles 1 The copepods Pseudocolanus sp. and Cithona sp. were selected for_in-depth analysis in the microzooplankton program because of their l t dominant roles in the community. Their abundance and low trophic level make them in.portant members of =the marine' food web. Eurytemors herdman 1 has.been' reported to be an abundant coastal copepod in the northern region _of.'he t westernfAtlantic-(Katona 1971).and as such, may be . particularly. sensitive to perturbations in the local temperature regime.- Lifestages of these taxa were identified whenever possible to develop an understanding of the dynamics of population recruitment cycles. In some cases, however..tlus possible presence of congeneric species made it impossible to routinely identify all lifestages to s.pecies level.
.Nevertheless',,information on lifestages of these genera is included in L
=this. report to present es complete a picture as possible. Temporal
'(seasonal and annual) and spatial'(horizontal and vertical) variability of-the above-mentioned species is~ characterized. F.ven though some vertical differences ~in atundance did exist, temporal. characteristics are-described for: surface and bottom collections combined.
"r : 11 -Eurvtemort.gu i During the preoperational period, Eurytemora sp. copepodites Lat Statio:L P2.were present in low numbers for most of the year, general-ly exhibiting short-term peak abundances in early to mid-summer (Figure 142
~h
- ,+, -,n ,
TABIE 3.1.3-2. RESULTS OF HULTIVARIATE ANALYSIS OF VARIANCE COMPARING ' HICR0ZOOPIANKTON C0KHUNITY STRUCTURE AT STATIONS P2, PS, AND P7.IN 1990. SCADROOK OPERATIONAL REPORT, 1990. NUMBER NUMBER OF OF SPECIES STATIONS STATISTIC df- F 34 3 Wilk's cr.iterion 68,30 0.6880 NS Pillaj's trace 68,32 0.6714 NS Hotelling-Lawley's 68,28 0.7092 NS trace
' NS = Not significant t
L-143
, . ._ __ _ ~ .. __ _. _ .. _ ._ _ __ ______ _ -__-._.__.._._._ _ _.
-3.1.3-3). An additional smaller fall peak was often recorded, especial-ly in 1983 (NAI 1984b), when tha highest annual mean abundance for coperodites was recorded (Table 3.1.3-3). Annual geometric means ranged 3
from 1.7 copepodites/m in 1982 to 16.6 copepodites/m 3in 1983, averag-lug 6,1 copepodites/m3 during the preoperational period (1978-1984).
.E. herdman 1 adults typically occurred in lower numbers than copepodites and were almost absent from the plankton samples at Station p2 from December through April during the preoperational years (Figure 3.1.3-3).
Peak abundances occurred during one or more months from May through I September and usually coincided with peak copepodito abundances. Annual geometric means were highly variable rang,ing from 0.9 adults /m3 in 1979 and 1982 to 10.5 odults/m3 in 1983, and averaged 3.1 adults /m3 over the preoperational period (Table 3.1.3-3). < Earlier studios indicated that Eutytemore sp. copepodite and E. herdmani adult populations in Hampton Harbor and the Nearfiela g Station P2, underwent similar seasonal cycles, but during the spring the estuarine population was much larger (NAI 1978b, 1979b). These observa-tions suggest that recruitment to the coastal population may be supple- + mented by the estuarine population. Other sources of recruitment in the spring might be maturation of, and subsequent reproduction of , overwin.t-ering copepodites (Figure .3.1.3-3) or hatching of diapause (overwinter-ing) oggs. In 1990, Eurytemora sp. copapodite densities did not exhibit tlic historic 'ently to mid-summer peak nnd were well below the preoperat- , Jonal' average _f rom May through August (Figure 3.1. 3-3). However, a late fall peak was evident and was slightly higher than the- mean for the preoperational-years. The 1990 geometric annual mean'for copepodites t f(2.5/m ) vas'below the overall mean for the preoperational years but was 3
- l. within the frange of mean values for individual years (Table 3.1.3-3).
E. hardmani adults followed the same general seasonal trend in 1990 as during the-preoperational years. Values were lower than the preoperati-i anel mean la July and greater than the preoperetional mean in August, l 144 i-~ l
F ~ Eurytemora sp. Copepodites 2.5 - PRE cp - ... .. 1m 2.0 - L NC. z . .
<e 1.5 - .
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% 3 0 $ e
\
0 s l a5 \- 0.5 7 f' I
.t
...,,,,.... ...... ...... .....,, ./ ,
0.0 , , , , , , , , , , 7 JAN FEB MAR APR MAY JUN JUL AEi SFP CCT NCV CEC MONTH =- Eurytemora herdmanl Adults L-
.e PRECF
,a L - 2.0 -
NO
@j 1.5 - p.,
_ os : .
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/
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= - - MONTH
=
E:- Figure 3.1.3 3. Lcg (x+1) abundance (no./m)) of Eurytemora sp. copepodites and Eurytemora herdmaniadults; mor.thly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2. Seabrook Operational Report,1990. 145 i
t_m.. -. . _ . . . . . . . . . _ - - - . . . . . . . . _ . . - - 4 o - m- n. o, e. e e. . h. 4 e. m m
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October, and December (Figure 3.1.3-3). The geometric annual mean in
~
1990 was: virtually identical to the geometric mean for all preoperatio-nal-years:(Table 3,L,3-3). 1 Results of'the two-way ANOVA on Eurytemora copepodites showed that differences in: abundances between 1990 and the preoperational yetts
.wert very significant for the April through December collections (Table -
3;1.3-4; Preop;0p). Although shundances in 1990 were_significantly lows- than preoperational densities, the area (nearfield vs forfield)
~
.and interaction terms were not significant, indicating densit1es were-
-generally lower throughout the area. Differences in annual and seasonal densities were also significant (Table 3.1.3-4, year (Preop-Op). and month (Year (Preop-Op)). indicating high variability among years and months. Results _ of the _ two-way ANOVA on' t, bordrant adult densi+.ies during April through Decembec were not significant for either temporal' or spatial effects.
'During the months of' plant. operation (August _through December) -
the results'of the ANOVA on Eurytenora coperodite and adult densities were not_significant for either. temporal or spatial effect.s or their-
-interactions: .This indicates that.the population in the vicinity of the
-intake was ' not- quantitatively dif ferentl f r'om the one in the farfield area.
Egeudocsigny1_]ip_,, _ Historically,lPseudocalanus/Calanus-sp. nnuplii were present-
-. year-round at Station P2 (Figure 3.li3-4); and were Lamong the numer.ical dominants of 'the microzooplankton' community in all seasons except winter (Table 3.1.3-1). -Seasonal-peak abundance was attained during mid-
- .s umme r . Annual geometr ic means at -Station P2 ranged during the preoper-ationa11 period from 366 nauplii/mlin 1964 to 1577 naup131/m3 in 1982 ,
3 and averaged 823 naup111/m (Table 3.1/3-3). Pseudocolanus sp. coca--
~
_ podites and adults were-also present throughout the year with peak
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d 8'5 a to - 0.5 - o.o . . . . . . . - i . . . i JAN - MB WR- APC MAY JUN JUL AUG SEP- OC*T NOV Ctr - MONTH Pseudocalanus sp. CopeptJdites 4.0 -
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JAN- fEB MAR ' APR ' .mY JUN JUL AUG GEP . OCT NOV. - (IE .- MONTH-
- Figure 3.1.3 4. I.og (x+1) aburidance (no./m3) of Pseudocalanus/Calanus sp. nauplii and Pseudocalanus sp. copepodites and adults; monthly means and 95% confidence intervals over all preoperational years (19781984 and 1986) and monthly means for 1990 at nearfield Station P2. Seabrook Operational Report,1990.
150 i
-._-_-_-.---.L__-__--.______----._.
abundances occurring in mid-summer (Figure 3.1.3-4). Copepodites were generally about one order of magnitude more abundant than the adults. Annual geometric mean abundances of copepodites and adults were also variable during the preoperational years (Table 3.1.3-3). Abundances of both lifestages were at a minimum in 1984 (167 copepods /m' and 12 adults /m3 ) and at a maximum in 1982 (645 copepodites/mi and 73 adults /n*). In 1990, the seasonal abundances of Pseudocalanus/Calanus sp. . _ . nauplil at Station P2 were more variable t han during the preoperational years (Figure 3.1.3-4). Values were considerably below average for May, August through October, and December. Pseudocalanus sp. copepodite seasonal abundances were also variable during 1990 with vclues below average in April through, June, September, and December. Adult Pseudo-calanus sp. followed the same seasonal trend present during the pre- < operational years. Values were slightly below the mean for May through August, and November, and were much lower than the mean during Septem-ber. The geometric maan abundances for nauplit and copepodites in 1990 were well below both the means and range- reported during the preoperat-lonal period (Table 3.1.3-3). The 1990 geometric mean for adults was also below the overall mean for the preoperational period but was within the range of individual mean values for that perior!. Results of the two-way ANOVA for April through December found temporal differences to be significant for all three lifestages (Table 5.1.3-4, Preop-Op). Although operational densities were lower than preoperational densitins, the area and interaction terms were not v significant, indicating 1990 densities were generally lower than previous years at all stations. Differences in abundances among years and among months were also significant (Table 3.1.3-4), year (Preop-Op) and month (Year (Preop-Op)), similar to observations made in previous years (NAI 1990b). During the operational period (August-December), each li fe-stage of Pseudocolanus sp. showed significant differences in the 151
o - temporal effects-(Table 3.1.3-4, Preop-Op) t>nt no significant difference y ~in the-area or among year interaction. terms. Month within year densi-l ties (month (Year (Preop-Op)) term) were significantly dif ferent for l
.Pseudocalanus/Calanus naup)11 and Pseudocalanus copepodite and adult lifestages.
j l (2Rhona spi j l i - All Olthona sp. lifestages were present year-round and were the most abundant microzooplankton taxa throughout most of the year during the preoperational period (Table 3.1.3-1). Nauplii and cope-podites occurred'at similar levels of abundance, while adults were only slightly less abundant (Figure 3.1.3-5), Peak density for nauplii 'l during the preoperational years extended from May through September. ; Densities were depressed during the winter:and early spring, although they varied by only one order of magnitude compared to the peak months. The annual geometric means = for nauplit during the preoperational years were highly variable, ranging from' 292 naupl:11/m3 in 1984 to 1482 h nauplil/m3 in_1982 (Table'3.1.3-3). During the preoperational period, copepodites maintained high population levels between May and November (Figure 3.1.3 5). Peak abundance was attained in July through September J with decreasing values during the winter months. Annual geometric _mean
- 4
-abundance at Statlon P2 ranged from 302-copepodites/m3 in 1984'to11798:
copepodites/m3 ' in 1979, - averaging 753 copepodites/m 3 over all preopera-
-tional-years (Table 3.1.3-3). Oithona sp. adults exhibited the same g eneral pattern of s.easonality as other lifestages, but maintained a-relatively smaller overwintering population than did immature stages.
The time of peak abundance for adults during the preoperational period occurred between June and September. The annual _ geometric means.during the:preoperational _ years ranged from 69 adults /m3 to 330 adults /m 3-L In 1990, 01thona sp. nauplii generally txhibited the same o i seasonal pattern of abundance as during the preoperational period, except abundances were greater than average during June and lower than 152
.olt,* tono sp. . .
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JAN RB MAR APR- LMY ' JUN J'.L AUG SEP CUT NOV DEC l MONTH Olthona sp. . Copepodites 4.0 - . . - - PPEOP ~ a s .- ... .. mo ,
,..'"" . ....,,7 y ,,.
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-- Adults -
en - PRE OP 16 .* ... . 1990
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- - 0.0 .i , i , s i i .. . .. . i iJAN RB . MAR _1 APR - MAY JUN .JUL AUG 'GEP CCT. NOV EC MONTH Figure 3.1.3-5. Log (x+1) abundance (no./m 2) of Oithona sp. nauplil, copepodites an'd adults;
- monthly means and 95% confidence intervals over all preoperational years L
- (1978-1984 and 1986) and monthly means for 1990 at nearfield Station P2.
Seabrook Operational Report,1990.
~
153
average during September (Figure 3.1.3-5). The annual geometric mean for 1990 at Station P2 was slightly lower than the over 11 preopera-
- tional mean but was within the range of-individual mea.. values recorded during those years (Table 3.1.3-3). Oithona sp. copepodites also followed the same pattern of seasonal abundances in 1990 that was evident! during the preoperational period. llowever, abundances for June, July, and' November were Jarger than normal (Figure 3.1.3-5). The geometric mean for copepodites in 1990 was larger than the overall mean
? for the preoperational period and five of the_reven preoperationni years (Table 3.113-3). Seasonal abundance of Olthona sp. adults in 1990_was highly variable, contrasting sharply with preoperational data (Figure 3.1.3-5). Adult abundsnce was larger than normal for June and much lower than normal _for August through October. Geomntric mean abundance for 1990 was lower than the mean for all preopesationel years but was within the range of individual mean values T- r ther.e ye.ct . During the April through Der:moer perfed, the results of the two-way ANOVA found temporal dif ferences 2n the . abundances of Oithona sp. copepodites and_ adults to be signfliceno (T6Me 3 1. 3-4, preop-Op). Area and interaction terms were not significent, indicating that differences in densities in 1990 occurred 9reawi-le for-these two lifestages. Olthona sp. nauplii censifiles for both temporal and spatial effects 1and their interactions were not r igni fica nt . Differences _among- _ years.and among months _were?signif2 cant for abundances of all-three-i
- 11festages of 01thona sp. during the ' April through December period.
These results indicate highly variab.le annual and seasonal abundances. During the period of--plant operation ( August through Decem- , 1 ber),-temporal differences in'Oltbona sp.~nauplii'and adult densities were sigt,ficant (Table 3.1.3-4-Preop-Op). Although areawide densities-in 1990 wt.e-significantly different from the preoperational period,.tha-Jack of ' significance -in the' area and interaction : terras indicate no - differences in the.nosrfield and-farfield arear both before and during
. plant operation; . Temporal anl spatial effects.and their interactions t-A were not significant for Oithona sp. copepoditer,. The seasonal and 154
~
l. <:6
m, .. . - - - - ~.. . - annual;variabilityLin abun'dancos of'all:- 13festages evident in the April- ':
'T)ecember_ period wastalso apparent-in the Augunt-December comparisons-
-(Table 3nt.3-4, year (Praop-Op); month (Year (Preop-Op)).
3,1.4 Rivalve LaryAq 3.1.4.1 Emaainity l Structurs. i IAmporni Patterns L i The bivalve larvae: assemblage exhibited strong seasonal
- patterns that were generally consistent amang years and represented
= seasonal- fluctuations in abundance' of the dominant taxa. Numerical c classification of weekly collections resulted in four distinct seasonal
. groups (Figures 3.1. 4 - 1, ' 3.1. 4 -2 ) . Species composition in all collec-
[ ltions.from.1990 was similar to that observed in previous years within-e each .thne fr'ame .(Figure 3.1.4-2). ThtJspring' period-(Group 11) encompassed most' collections in
. April _ and_ tiay . (Figure -' 3.1,4-2) . Although night taxa were present at
. .some point in during this period, Biotella sp. ~ dominated. (Table 3.1,4-1; Tigure 3.1.4-3)Leontributing'97% of the mean total abundance. Variabili-
~
ty in. abundance of'#1 stella sps coupled with the intermittent occurrence ; ^
'of other taxa resulted Ja a relatively low within group similarity (0,44); However, its n imilarity to other ' col!ect icus was only 0.23,
- clear ly Ld ist inct.
kk;
=The" late;&pring period (Group 2) included most collections from late Hay through Junng (Figure 3. I'.4-2). lhn_within-group similari-ef; ty .was a moderately h igh 0. 63 - (Table' 3.1.4 -)) . The speclec composition
.;of these- callections was most closely rolated to Groups 3 and 4 (simi-
' ~ larity. nf. 0.55). _ Total alundance of bivalvo-larvac was higher during 'a these months than at other times during the year, as -indicated by the
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The maximum dist ance between the of f r,hore stations (P2, P5 nnd P7; Figuro 2.1-3) is about f iv. 3fles; within that distance a water mass could move within a day during periods dominated by longshore iIow. Station P1, in llampton llartnr, would not be direct ly af f ected by longshore currents, but it it strongly influenced by tidal currents. 1,ocate d about 1.5 miles f rom Stations P2 and PS, Pi is probably subject to essentially the same water masses due to tidnl ilow in and out of the liarbor except when there i t. significantly higher freshwater flows from the Blackwater Creek and Taylor River. fdtlInhlment Entrainment samples were collec t ed June t hr ough Oct obet , U90 filly on the same days as the of f shore e.nd harbor collections. The entrained community structure was similar to that octorring offshore (Table 3.1.4-3). Hytllus edults and Het oranomia squimula were cont dominant, together comprising over 55% of the total assemblage at eacF station. Total abundances were higher in entrainment collections than of fshore (Station P2), probably reflecting the tendency of bivalve larvae to concentrate well below the surface. Entrainment lossen were estimated for June through October based or, total cooling water system daily flow and the observed bivalve larvao densit les in entrained samples (Table 3.1,4-4). liighest entrain-ment losses were incurred in 'uly, primarily affecting Nyfilu.<, edulls, Reteranomic s g.wmula and Hint ella sp. larvac. 3.1.4.2 En.hgigi,1pp_q,ign LLALDDDda This species is discussed in Section 3.3.7. 163
. . _ _ __ _ - _ _ _ _ _ _ _ _ . . - _ _ _ _ _ _ _ _ _ _ ____.._-_._..m , _.____ m. . _ _ _ _ _
TA RE 3 1.4 3. OWTILT CEOMFTRIC KIAN OF CENSITY ( O. FER CUP!C MI IR) 0F M VALYi 1,MYA): Tt0M ENTIAINMI AND fLI P M P A M W 1 R " " I \ !G'.5&WT I Jt'N I JUI, 1 AUG i fEI I OCT
+j....... ............4........(.......6.......4........(........l ; ;
!BlVALV'i I 3061 1006: 91: 53: 33:
IEETEF.WN 771AKJ1.A ! 9341 9312: 3063 17641 30: lHIA1E11A St. ! 3950! 5093! 1771 If.6: (B: W.ACW.A PALTRICA 0: 5 0 If 0:
!MJ01000S C010LUS I ??61 36;71 103: 13051 137:
INYA ARENAM A 1 22l l?' 1: ;21 391 00A TRUKATA ! t>9; 845; 1: 0 f: IMYTILUT Edit!S : 92(11 21632: 20441 1D0: 4511
!Pi ACOTFCTFN MAGE!1ANICUr ! 0: ll 0: 1: il IS01.EMtAE ! 110) 291' 28' 3: 14l ISTISULA SCLil)lSSIMA 1 37: $T 41! (E 51!
!TEREDO NAVAllS ! 0 0: 0: 0: 01 t I JUN JUL 400 SEC 1 OCT 1 1........Off> Hoke *..................... 4........1 ........1 .........! ..... . 4........t
. IBlVA!Nik !!21 3731 IBi 208t 101' IEETERAOMIASQUACLA ! 4521- 3153: 799 35271 950: lFlATELid Sr. ! 44071 1844! 16! 263) 531 tMAC& A BALTEICA 1 O! O! 0: 21 01 IHJ010LUS M0010141S ! 3481 Dl!i 14: 1693; 2211 iMYA ARENARIA 1 32 13: 0! 1141 311
=INYA TRUNCATA i 490: 06: 0: ti! 0l
;HYTli.U' ED'JLIS I 9P11! 21874; 7661 3%6: 587:
!!'!E0fl0 TEN MAGEllANICUS 11 0 0: 13 O!
lSOLEhlht i 655: 181! ;: Ml 101 lF.TISULA SOLIDISSin 1 0: 310: 30: 668: 110: ITEFEr0 MVALIC 1 0; 0: 01 11 O!
*f2 reans band only on dates oth a corrupnding entrmunt collect 100.
k 164
;r ll t ,i !l!tL ;i .
E H T Y T 60154837 1 6 0 C . B . O 470321020200 5 0 21 < 2 7 _ D9 E9 . N1 I AR RE TB hO - ET P - C E 312595151 2 8 2 .
~)O S h- 1000920205G0 3 tE 30 2 2 9 nN 13 3 7 oU mJ - /
sG nN oI iR lU G 76 01126 016 0 lD U . . . i A bN 8901 400401 03 3 O 71 0 2 1 < 4 - nI 1 3 5 iT (A T ES . A 0 .. VK3 RO5 AO1 L 9248643440 4 8 IR U B , J 21 05723464O7 5 EAT 22 1 2 4921 2 9 V. E R ISO 94 9 25 1 2, A P 2 5 VTE IAR B ML FEA OTN N 88 60314 9 7 6 SO U RYI J 31 00515202D8 EST 32 2 1 3 B A 35 3 2 2 MRR UEE 71 1 3, NTP 1 AO DW E K TGO s . ANO u . MIR c ILB i TOA na SOE el a ECS l uc sl ri ueas
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h l
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. e t msac a ae 3
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, ;l
~ _ . _ - . _ _ . - - _ _ . _ - - _ _ _ _ . _ - _ _ _ _ _ _ _ _ - _ _
1 l l gyt11us cdulls Umboned veligers of Nytilus edu11s were ust. ally present by mid- to late May (Figure 3.1.4-3). 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- I stages. Major spawning events in Gulf of Haine mussel populations may be limited to temperatures above 10-12'C (Podniesinski. and McAlice 1986). Spawning of N. edu11s 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 (r lle and Dalsamo 1985). Spawning of some-Long Island Sound mussel populations was also restricted by limited food availability for most of the year, resulting in sporadic spawniiig events . (Newel) et al. 1982). Therefore it is probable, based on the reproduc-tive behavior of N. edulls, that recruitment of larvae to the plankton of New Hampshire coastal waters occurred intermittently throughout much of the sampling program. Recruitment from non-local sources was also proba21e, as water masses may move largo distances over the three to five weeks required for larval development at umbient temperatures (Bayne 1916). Delay cf metamorphosis until suitable settlement condi-tions are encountered can prolong planktonic existence for up to 40 days, depending on temperature (Bayne 1976). These factors suggest that ( planktonic recruitment to the study area was intermittent and prolonged, ( and that duration of planktonic life varied over the sampling program as temperature conditions changed. : Highest abundsnces of #ytilus edu11s larvae have historically (1976-1989) occurred between early June and early July (Figure 3.1,4-3), , although in 1980-1982 and in 1990 abundances in late August, September , l- or October were ar high as in early summer (NAI 1981f, 1982a, 1983a, 3 3 8 3 1990a). Peak abundanc.es ranged from 6 x 10 /m in 1982 to 3,3 x 10 /m in 1979 and 1989.(NAI 1987b, 1990e). The difficulty in assessing the f l-variability in this population.in probably compounded by patchiness caused by discontinuous recruitment both spatia 11,y and temporally (Bayne 1976; Podniesinski 1986). C:>11ections taken within several days of one 166 r
)
l taother, even during months of peak abundance, varied by zero to three orders of magnitude (NAI 1981c,19844). Although teroporal variability was high, nn indicated by significant differences amcas years (Table 3.1.4-5; Year (Proop-Op)), overall spatial varlability was low (Table 3.1.4-5; Area) when tested by ANOVA for both' April to October and August to October 1990 collections. ] The lack of a significant interaction between main effects (Area X l Preop-Op) indicated that throughout the 1990 collections, abundance of Nytllus eduIls larvac'in the'nearfield during 1990 were not significant-ly different from those in preoperational years and in the farfield i area. 3.1. 5 Hagntgoon1rtnkts
- 3.1.5.1 Communi.ty. Eingly.to -
Temocral Pat. terns The macrozooplankton comunity is cornprised of numerous. species that exhibit three basic life history strategies. The holo-l plankton species, e.g. copepods, are planktonic essentially throughout , their entire life cycle. Heroplanktoa includes species that spend a [ distinct 1.ortion of their lifecycle in the plankton, e.g. larvae of l_ benthic invertebrates. Species that alternate between association with p the substrate _and rising into the water column on a regular basis are ca.lled tychoplankton, v.g. mysids. ll Historical analysis (1978-1984 and 1986-1989) of the macrozoo-plankton ascemblage'at the nearfield Station P2 showed seasonal changes o that were greatly influenced by.the populat3on dynamics of the dominant ncpepods Centropages typicus and'Calanus finmarchicus (NAI 1990b).
- j. Other taxa, particularly meroplanktonic species, exerted short-term 1 Influences, especially during the spring and summer (NAI 190Sb).
, Because of their lower abundances, seasonni patterns of tychoplanktonic r i 167
, , - . - - - , . . , _ _ _ __ - ~_ _-______. _
2. E i' TABLE 3.1.4-5. RESULTS OF ANALYSIS OF VARIANCE COMPAKING NEARFIELD (STATIONS P2 AND PS) AND FARFIELD
- (STATION P7) WEEKLY MYTIII1S EDf/I.IS ABUNDANCES
- DURING PRE 0*ERATICML (1978-1989) '
l AND GPERATIONALb (1990) PERIODS. SEABROOK OPERATIONAL REPORT,1990.
- i
- ' APRIL-0CTOBER AUGUST-OCTOBER [
SOURCE OF VARIATION df SS F df SS F- ; i Preop-Op*- 1 0.14 0.21 NS 1 1.48 2.32 NS , l f' Year (Preop-Cp)d 6 1.97 0 49 NS 6 10.65 2.79* Week (Preop-Op X Year)*' 24 7.09 0.44 NS 26 13.57 0.89 NS I Area' 1 0.10 0.14 NS 1 0.04 0.06 NS , t l Area X Preop-OpS 1 0.31 0.47 NS 1 0.06 0.13 NS Error 492 304.92 -- 193 122.8' -- [ i i t
*3ased on weekly sampling periods
*Comercisi operation began in August 1990 f' i: *Preoperational (1978-1989) versus operational period, regardless of area dYear nested within preoperational and operational periods, regardless of area
[
" Week nested within. year nested within preoperational cad operational periods, regardless of area !
'Nearfield area =- Stations P2 rad P5; Farfield area = Station P7, regardless of year or period fu
^
SInteraction b+ tween main effects , i + NS = Not ~ significant (p>0.05) ;
* = Significant (0.052y 0.01)
- ** =' Highly significant (0.012p20.001) ,
*** = Very highly significant (0.0012p) l l
4 f
< _, . .. ~ . .- . . . . .-_.- . ._. _. - _ ...
species, e.g., myrids, amphipuds and cumaceans, were not well dor.umented by numerical classification of the entire macrozooplankton assemblage. To more clearly identify seasonal patterns of thin valuable finfish food resource, the tychot.lankt on was analyzed separately f rom the mero and holoplankton. In the holo- and meroplankton assemblage there were four major seasonal groups (Figures 3.) 5-1 and 3.1.5-2) that encompassed the samn time frame in most years (Groups 2, 4, 5 and 6). Two smaller groups (Groups 1 and 3) reficcted occasional differences from thn predominant patterns of species composition. The seasonal groups were distinct; within-group similarit ies ranged f rom 0.56 to 0. 78 and between-group similarities rangrd f rom 0.43 to 0.68 (Figure 3.1.5 1; Table 3.1.5-1). Early months in 1978 and 1979 exhibited similar species composition, forming the small winter group, Group 1. Dominated by copepods, abundances in this group were low (Table 3.1.5-1). During most years the holoplanktonic and meroplanktonic constituents ware similar in February, tiarch and AprJ1, forming wintar Group 2 (Figure 3.1.3-2). Cirripedia larvae predominated, coinciding with the onsnt of vernal warming and initiation of thermocline formation (Figure 3.1.1-2), Copepods, partIcu1er1y Calanus l'invarchicus, pseudocalenus an. and Centropages typicus were abundant, as was the chnetognath S q ltra elegan.r . In 1990, ?! arch and April collections were associated with Group 2. Apr il has been shown to be a transit ional per iod in the macrozooplankton, perhaps due to the combined of fects of seasonal warming and highly variable freshwater influence (Section 3.1.1). Community structure h not highly predictable as it has varied over the years. In most yeara, including 1990, it resembled the w. inter assem-blage defining Group 2. In severn! years, the number of dominant taxo was smal'er then in Group 2 although totnl abundances were higher. Spring Group 3 encompassed only fiarch and April Jn several years (Figure 3.1.5-2). During these periods Calonus finnnichicus and Cir ripedia 169
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170
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t.. i l' TABLE 3.1.5-1. GEONETRIC MEAN ABUNDANCE 1No./1000 m'l AND 95% CONFIDENCE LIMITS OF DOMINANT
- H01.0- AND MkOPLApeCTUNIC TAX % OCCURRING IN
- SEASONAL' GROUPS FORND BY #C91ERICAL CLASSIFICATION OF P*ACP0ZEEP;.AiETON COLLECT 1t*es EMENTNLY MEA.*tSi AT NEARFIELD STATION P2, 1978-19% AND 1*86-1**0. SEABROOK #ERATIONAL REPORT, 19*0.
4 2 PREOPERATIONAL YEARS 81978-19eres1886-1989) OPERATIONAL YEARS (1*90) d LO4ER UPPER CROUP SPECIES H~ C.L. E C.L. N i 1 CMeus firumerchicus 3 11 7?3 50,601 e s Ninter Senig typicy 35 493 6,875
,'f0.56/0.43) 12enanus gl.sc= O tus <1 337 74,182 Ps_ousocolarm s sp. 62 .295 1,393 negitta elegans -1 224 13.078.035 2 Cirripedia . 22 3,502 11.398 37,090 2 134,378 1,859 3 ,6 73 7,257 7,759
. Hinter-Early C_e.larsas firmerchicus 6,0% 54> ring Pseudocalar.vs sp. 1,757 3,345 6.3% 10.60/0.55)' LEDt roomans M cus 4A9 1,M* 2,448 396 SegitT* 2129mns. 345 7% 1,780 2,707
. Leur2t2 lonascomas 126 389 1,201 16.134 EvodnsLr sp. 10 34 116 13,207 w 25,387 69.2*0 189.114 0 3 (elarnas finnerchicus 6
- y. Soring t0.65/0.63)-
Carrapedte Oikoolours sp. 830
**6 25,656 6,079 791,768 74.403 1,485 5,275 18,762 1_vah 4 68,471 % 477 141,632 4 135,190 4 Colarius finnerchicus 39 10,882 45,816 7,771 Late Sprico- (pager sp. larvae 22.32?
*m Lyelus ousiolus 7,767 12,080 18,786 6.321 3,862 6,134 9.743 15,745 80.70-0.66: ' lainscomis 1,502 4,'*9 16,633 11,046
- en m t micus 6,797 1,667 smoteursonnosa 1,242 4 ,6 *s6 P- = lanus sp. 2,841 4,054 5.785 4,354 i
Pemagnyci wnenes r,orvecies 313 2,317 6,602 35,150 1,136 2,522 5,%3 12,088 teatridte sp. Centraneans tvpacus 14 77,467 163.246 344,008 1 1,377,271 5 Late Smaner. Lalm 11rumorrhacus 28,929 62,761 136,155 3.152 Cancer sp. larvae 6.063 15.1** 38,096 18,561 t0.72/0.66) 16,279 4,152 Crianage septessoituse 5,907 9,807 Tlent- sp. copapodites 720 3,8*9 21,0*2 65,081 Centecomers typacus 42 14.079' 26,262 48,989 5 2,C36
-- 6 Fall-Nintee ( 4 ecesars t sp. copapodites M8 1,503 3,379- 161 10.'78/0.645 Centropees buenhr, 456 1 102 2,u2 335 1,034 2,230 1,929 Tesoes 3onnicornis 478 996 .1,57' 325 h* f aruerchacus
$maat.te elegees 628 643 751 1,2 Ns 1,104 P - A celan_te2 sp. 395 749 1,421 M Oikoolours sp. 23 59 148- MO Tort =nug dis- Atos 268 561 ~.169 276 i 155 Evache sp. 14 35 ' 36 4-
'doeninent taxa are those ashose sensionnce as 22 of the gens gmametric mean in either tFe p .etional oc the vv. .tacrml years 3
m - . . _ . . . _ .. _ _ _ _
- - . . . - . - - - . - . ~ _ . - - - - . - . . _ . . _ - . - - . . .
I larvac were the overwhelming dominantr., (Table 3.1.5-1). The larvacetn , 01kopleurs sp. and the cladoceran Ei'adnn sp. were also abundant. (Table 3.1.5-1). April 1988 was associated with late spring-summer Group 4. The holoplackton and meroplankton community structure was similar in mest years from May through August (Group 4). Many species achieved high abundancea (Table 3.1.5-1). Larvae of crustaceans (e.g. Cancer sp., Eualus puslolus and Crangon septomspinosa) and cuphausilda i (hegany:tlphanes noriegica) were generally abundant. The copopods Calanus finmarchicus, Tomora longicornis, Pseudocalanus sp and Met ridia sp. typically reached their highest abundances during this part of the I year. May through August collections from 1990 were similar to this group. September was a distinct period (Group 5) in most years (Figure 3.1.5-2). Generally, September snarks the period of hightest bottom temperature and'ths beginning of the breakdown in the thermal ! stratification (Figure 3.1.1-3). Centropages typ/cus reached its nnnual peak abundance during this period. Copepodite densities of this gemw . also peaked. . Abundances of Calanus (inmarchicus and Cancer sp. . l.r v::e were similar to the previous summer months (Table 3.1.5-1). - Crango._ ! septomspinosa, predominantly immature stages , typically peaked in
' abundance.In September. Species composition in September 1990 was similar to other years _ comprising Group 5, although abundance of Calanus finmarch/cus was'ununua1ly low.
With the reduction of spawning activity as coastal waters
. cooled in the-fall (Section 3.1.1), meroplanktonic species became less '
. predominant components of the macrozooplankton assemblage (Table 3.1.5-1). Total abundances declined despite the continued presence of most species as dominant taxa. - rhin assemblage (Group 6) characterized the period from October the ugh January of most years-(Figures 3.1'.5-1 and , 3.1.5-2). Centropages typicus continued to dominate, exceeding the abundance of other taxa by an order of magnitude. Centropages sp.
- copepodites, Centropages hamatus, Temora longicornis and Calanus 173
,n. _..,___.n._.-
- - . - _ . - - _ _ - . _ _ _ -- -- - . _ ~
finnarchlcus occurred as secondary dominants. January, February and , October through December 1990 collections were similar to the Group 6
- - assemblage, although Olkopleura sp. was unusually abundant in the 1990 collections (Table 3.1.5-1).
In summary, the copepods Calanus finnarchacus and Centropagos werotypicus were consistently among the dominants of the seasonal groups formed by numatical classification, C, finmarch/cus usually ranking [ ilrat or second.in abundance. Many other species exhibited high abundances seasonally,Lbut were generally limited to dominance during one or two seasonal groups (Table 3.1.5-1). Seasonal pitterns of *
- abundance and species composition in 1990 were similar to previous years. !
i Although seasonality was__ evident-in the assembidge of tycho-planktonic-_speclos (Figures 3.1.5-3 and 3.1.5-4),- separation of scanonal groups was less distinct than in the holoplankton meroplankton assem-blage.. Between group similarities were close to within group similari-ties and each group was added succcasively with lower similnrities 1 Figure 3.1.5-3). This may result from the fact + hat twenty of the i twenty two species used in the analysis weto prement essentially _ year-round occurring in each of the four major seasonal grm'ps (Groups 1, 2 7 and 8;1 Table 3.1.5-2). Total'ahundances were two or more orders of e magnitude lower than holo- and meroplankton abundances. Two species (Neomysis americana and Pontogeneln inermis) were cach ranked among the threo most abundant species in eight out_of ninn groups. Distinct f ons between groups of tychoplankton assemblages were' generally based on moderate changes in abundances rather than dramatic changes in species 1 composition.
~
1Four major _ seasonal groups encompassed most of the collections (Figures 3.1.5-3 and 3.1.5-4). Winter (January:through March) months were generally similar (Group 1). K wysis' americana, Olastylis sp. and Pontogenela inerm/s predominated it .sth preoperational and 1990 collections (Tabin 3.1.5-2). 174 i
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l i TJ@LE 3.1.5-2.' CEOPETRIC NE AN AMUISANCE INo./1r00 s') M 95% CONFIDENCE' LIMITS OF DOMINAPtT* TYCMOPLAPG(TONIC TAX 1 OCCURRANG DI - SEA 5 DEAL GROJPS FDRPE3 CY at.WEUCAL CLASSIf 2COTIDN OF MACRUZOOPLAP8(7CR4 COLLECT 1(MS IN3NTHLY F.A8G) AT PEARTIELD
"- STATION P2,1978-19% AN 1985-1*% SEASROCK OPERATIONAL R90RT,19*0.
9
~ PREOPERATIONAL YEAd (1978-19ee s 1986-1*e9) OPERATIONAL Ys.ARS 81*90 )
LOMER tJP:*E R i GROUP ' SPECIES 39 C.L. .E C.L. N E
~
1 !weeracone 33 305 655 1,402 3 2,2+* Wieder ~ - W sp. 125 1*7 310 85 t o .M/0. 618 cannena iagrul.2 75 114 176 e5 7 Dodsonrot scine 28 *ae 67 52, 10 EAE.13 37 133 43 _ Asolmotc= uma rii.coC 23 35 52 22 sixta' 2 20 205 630 1,93* 1 8,204
'Socing emmericano 75 152 308 12*
10.41/0.59) T w _gg s te Erwcons 4a 71 120 15* 1p2%,13 50. 15 27 47 88 uncoide
- 21 44 9
! 3 Oedioeroti:.5ee 3 1 ?! 3.c82 0 Late Spring Extoasts.1= igermis -I 3* 6,262 80.59/0.51A Venauwsms amoracene 2 18 110 111 sp. <1 14 202 5 rus 3LncrJapes_ 1 12 88 ruz law-tmc m.;rvas -2 7 155 4 Oedicecotidae 3 30 3512 397,MO 1 437 emeiicang
~
Laim Spring 27 5*4 12,561 226
]L-80.72-0.611 canneta 2nereas 19 471 11,072 637 Geommerus lammencsanus -1. <1 * *8 4
a 5 Hypeeiidae 2 -1 216 1,170,047 0 Miscellaneous %toma inonets -1 50 3,242,876 10.56/O.45) Neoemysms asserica_na -1 16 305.023 aas_sa puerwirate -1 8 6,40s 6 toannuia igerwis 2 8 25 59 0 Socing w as ,. 1 1* 16,392 t U.53/0.38 3 g op. -1 5 31,107 rpec accada -1
- 510,*93 Diestvlis sp. -1 4 5.0x10*
Genumerus lawrencianus (C 1 4 7 his seeescone 33 91 16e 311 2 116
%w Nritosamosa mornas 73 95 123 3*s d o.67/D.M ) h+s sp. M **, 137 8' bedacemtidae 64 9C 182 23 Herrectacoadm 35 58 ** 234 IAwllaola irrorsia 7 12' 20 '30 8 Nmouvsis ammeje ge 22 2,651 5,133 *.93. 4 3 M7 Fall Dros tvlis sp 147 234 373 233 10.69/O.64) PantaannoLa $rweistas 120 204 36S 160 F3.uniol-te- manoe *2 1** 239 74
- ammeri, cons e 101 362 1,2*3 0 Laie Fall tas .as sp. e 13 28 80.54/0.513 Hypera aciime 1 8 52
*dominent taica are those whose soundance is t ZZ of the i,srote geommetric aman irs ei6er the petional or the operational m i
i l-
_. _ . . _ . _ . _ , . _ . _ . - . . _ . _ - _ - _ . _ _. _ . _ . _ .___ . _ ._-_..... _ _.~._ _ _ _
-i. l The mysid Nysis eixta has typically been most sundant in the l
spring in coastal waters of New llampshire (Grabe and llatch 1982) prior l to its offshoto migration. N. mixta dominated in the spring (Group 2) while Neonysis anericana and Pontogenola /nermis continued to occur an subdominants (Table 3.1.5-L). Although the April 1990 collections wero ; not clearly associated with a seasonal group this may be the result of l 5 unut lly high abundance of Nysis nixts (2.4 x 10 /1000m ) and 3 Commarus 'l 3 Inwrencianus (4.3 x 10*/1000m ) (FAI 1991) rather than tho absence or reduc.ed abundance of key npecies. During the preot erational period, several other assemblages (representing Groups 3, 4, 5 and 6) have charceterized the late spring > period. Mysis m/xta was not among the dominanta in any of these groups, althaugh Neonysis americana or Pontogennia inernis was (Tahle 3.1.5-2). The amphipod family Dedicerotidae dominated Groups 3 and 4 Subdo'n in a - nts included other amphipod species generally atypical of the major seasonal groups. The June 1990 sssemblage was most similar t'o Group 4 ) I (Figure 3.1.5-4). July, August and generally September were similar (Gioup 7) among years (Figure 3.1.5-4). Neomys/s americana. Pontogencia frermis and Mastrils sp. were again dominants (Table 3.1.5-2). The occurrence ! of Oedicerotidae, harpacticold copopods and the amphipod Unclola irrorata as subdominants distinguished t.his group. The tychoplankton assemblagn occurring in Jult and August 1990 was similar to preoperat20-nal collections included in'this group. I Neocys/s americans generally reached its highest abundances in the fall (Table 3.1.5-2), distinguishing Group 8. Fall n;onths of most _ years, with the exception of 1978, _1979, 1981-and 1987, were represented in Group 8. Abundances of N. amorleans have been_found to be signifi- i ( cently ~ dif forent among years (Section 3.1,3.2), wit h 1978, 1979 and 1987 , l exhibiting lower abundances than other years (NA1 1990b). Overall i 178
,, . , . , - . _ . - . ~ . - . - . . . . . ~ . - . - . - - - - --.. - . - - . _ - - . - . . - -- .. - .-
I abundances, as well as N. americana abundances, were low in some years, dietinguishing a second fall assemblage (Group 9) of tyrhoplankters (Table 3.1.5-2). ] In summary, seasonal groups 1,2, 7 and 8 encorrpssned more than 85% of the preoperational collections and 83% of 1990 collections. Most tychoplanktonic1 species wero- preser,t year-round. Naomysis aver / cans, Dlastylls sp. and Pontogencie inctmla were frequent 1y among the dominan-ts. Moderate changes in abundance of thes9 taxa, rather than dramatic changes in species composition, distinguished groups in general, with the exception of spring Group-2 when tfysis m/xto domina ed. Most colicc-tions in 1990-were ofmilar to the major seasonal groups. April 1990 was t' unusual in not showing high similarity to other spring collections but-this rnay have been due to unusually high abundane.es of tfysis m/xto and 6ammarus laurenclanus. June 1990 was similar to a small group that encompassed several' historical collections. ! i-Santial Patt.nInn The spattel distribution of most holo- and mnroplanktonic species in the study area is go.$erned primarily by local currents. Hydrographie studies of tempersture and salinity.have shown that nearlield Station P2, and farfield Station P7 are exposed to the same I wat.or mass (i:AI 1985b). Furthermore, bivalve larvae studies suggest that areas at sim3 ar 1 depths-and distances from shore (such as P2 and PS) have similar 6pecies compositisn (NAI 1977n). Thus no spatial dif ferences in the saeto- or_ holoplanktonic macrozoopa ankton abundances, ' percent cot, position, or rank would be expected among Stations P2, P5;or P7. <This has previously been confirmed in examinations of the aanual percent composition, percent; frequency and rank dominance scores (RDS) of dominant species with nonparametric test.s (NAI 1985:3, 1989b). A mult.ivariate analysis of variance (IfANOVA) comparing semi-monthly species composition, including mero , lolo- ond tychoplankton 179
.~.,__.-.-,-..a.._...-.--....,.a.-..-_._ _ _ . . . _ . _ . . - - . . - ._ ~_ .
taxa indicated that theic were some significant species dif ferences among Stations P2, PS and P7 in 1990 (Table 3.1.5-3). ANOV/s comparing abundances of individual species were utilized to identify where the differences in community structure occurred. The ANOVAs revealed no significan~c spatini differences in any holoplanktonic or meroplanktonic 4 species. However, of the nine tychoplanktonic species tested, eight exhibited distinct. spatial patterns of distribution (Tabic 3.1.5-3). , Generally, abundancer. were similar at Stations P2 and PS and vote significantly lower at Station P7. These differences were apparently , large enough to influence the results of the MANOVA. Tychoplanktonic species are often st.ongly associated with particular substrate types. Substrate type and complexity, along with proximity to llampton-Seabrook estuary, may account for some of the difforcuces observed among tychoplankters. Historically, Neomysis americana,- Pontop;encia inermis, and Diastylls sp. have had highet abundances'at P2 whare substrate is sand and cobble than at P7 where the substrato is mainly sand (NAl-1985b, 1988b, 1989b), At Station P5, , where subattate in largely ledge outcrop and cobble, densities of Plastylls sp. have boca significantly lower than at P2 (NA1 1968b. . 1969b). Amphipods in the family Oedicerotidae continued to be more abundant at Stations -P2 and P5 than P7 (Tabic 3.1.5-3; NAI 1988b, , 1989b)-. Of the tychoplanktonic species tested, only #rs/s mixte did not differ in abundarcc among stations. 'This may be attributable to the extreme seasonality. (complete abrence during much of the year) of this
- species, overriding the effects of any subntrato preference.
MANOVA was not conducted on the August-December operational period in 1990. To properly evaluate community structure it is impor-tant to include all dominant taxa. Unfortunately, the constraints of
' the MANOVA- require that= the number of samplea _ tested be greator than the number of taxa. Because of the complexity of the macrozooplankton-
. assemblage it was not realistic'to reduce the species tested to meet liowever, abundance patterns of the selected species this requirement.
were individually-tested using analys]s of variance (Section 3.1.5.2), 180
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i aq l 1 3.1.5.2 SDMA.Ltd..JRe.s1RR I C!tlRQuL.fiuRRIChlGR Over the length of this study (1978-1984, 1987-1990) Calanus I finaarch/cus has been a-dominant species in the macrozooplankton ! assernblage (Table 3.1.5 1) . llistorically, although both lifestages I , usunlly occurreo yearround, copepoditon exhibited greater abundances than adults, a trend t<hich cont 8nued in 1990 (Tabin 3il.5 4). The major l ? peak'in copepVito abundance usually occurred April through September. i bow abundeuces of copepodites occurred during winter (rigure 3.1.5-5). l1 Analysis of varianco confirmed a strong seasonality in copepodito I~ abundanca (' table 3.1.5-5; Month (Year (Proep-Op))). In 1990 copepoditen; t -
- exhibited typical abundances during March through July but midwinter and late numor-tall ( August through November) abundances were substantially
. Iowet than tha historical average, as indi.:nted by a significant Proop-Op t erne (Fig re 3.1.5-5; Tabic 3.1. 5-5) . Although this sair.e pattern of relatively low suminr and f all abundances was obtierved in 1989, mean abundance in 1989 was not significantly different than earliar years (NAl 1990b). The annual abundance of copepodites In 1990 was lower thnn ,
any previously reported value (Table 3.1.5 4), contributing to a significant difference among yonts (Table' 3.1.5-5; Year (Preop op)).and L between 1990 and the preoperational years (Proop Op). , ?
? Calanus //mnareb/cits adults Lended to peak in the summer L~ .
months (June through September, Figure 3.1.5-5), declining to lowest abundances in Novet6er and December. The general of the seasonal H L pattern was confirmed _with analysir of variance which showed significant
. differences among months (Table 3.1,5-5). Abundances of adults in 1990
- ' were below the. confidence limitr. of_the.preoperational mean during April c - through July _'as well as September and October (Figure 3.1.$ 5), renult-Ing in a significantly lower ennual abundance (Tchles 3.1.$e4,5). In 1989, monthly-abundances of adults had been unusually low in September through Neverober buti at Oypical levels the rent of the year. A more 182 m
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