ML20083A964
| ML20083A964 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 12/31/1993 |
| From: | NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | |
| Shared Package | |
| ML20083A950 | List: |
| References | |
| NUDOCS 9505110212 | |
| Download: ML20083A964 (636) | |
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, ? I I 4-9505110212 950424 ('" PDR ADOCK 05000443 l R PDR y j l P
l l I I SEABROOK ENVIRONhENTAL STUDIES,1993 , A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS IN TIE HAMMON-SEABROOK AREA DURING TIE OPERATION OF SEABROOK STATION , Prepared for I NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station Seabrook, New Hampshire 03874 I Prepared by I NORMANDEAU ASSOCIATES 25 Nashua Road Bedford, New Ilampshire 03110-5500 and NORTIIEAST UTILITES CORPORATE AND ENVIRONMENTAL AFFAIRS I Millstone Station Environmental Laboratory P.O. BOX 128 Waterford, Connecticut 06385 I I I I : 1
I I TABLE OF CONTENTS I SECTION 1.0 - EXECUTIVE
SUMMARY
SECTION 2.0 - WATER QUALITY SECTION 3.0 - PIIYTOPLANKTON SECTION 4.0 - ZOOPLANKTON I SECTION 5.0 - FISil SECrlON 6.0 - MARINE MACROBENTHOS SECriON 2.0. SURrACe PANELS g SE.CTION 8.0 - EPIDENTHIC CRUSTACEA I SECTION 9.0 - ESTUARINE BENTh0S SECTION 10.0 - SOFT SHELL CLAM (MYA ARENARIA) I I - I I I I I
1 1 TABLE OF CONTENTS I I PAGE I I I 1.0 EXECUTIVE S UM M ARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 LIST OF FIGURES . . . . . . . . . . . . . ..................................1-11 LIST OF TABLES . . . .............................................1.ii 1.1 APPROACH ................. ...................................1-1 I 1.2 STUDY PERIODS . . . . . . . . . . . . . . . . . . . . ..... .. ..... .......... ... 1-4 1.3
SUMMARY
OF FINDINGS . . . . . . . . . . . . ....................... .....14 1.4 LITERATURE CITED .................. ......................... 1-14 n I I I I I : I l I I 1-i l l 1 I ! l
[] LIST OF FIGURES I: I PAGE l-1. Sequence of events for detennining if there are envimnmental changes due to the operation of Seabrock Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1-2. Average daily power level at Seabmok Station during 1993 . . . . . . . . . . . . . . . . . . . . . 1 -5 I I I LIST OF TABLES l-1.
SUMMARY
OF BIOLOGICAL COhth1 UNITIES AND TAXA MONITORED FOR EACH POTENTIAL IMPACT TYPE . . . . . ....... .... ................. 1-3 1-2. MONTHLY CllARACTERISTICS OF SEABROOK STATION OPERATION FOR THE PERIOD 1990 THROUGH 1993 ................ .................. 1-5 I I I I I' l -n. . I E'
=
I EXECUTIVE
SUMMARY
1.0 EXECUTIVE
SUMMARY
location within the water column, the intake is also expected to have only a locr.lized effect. This is characterized by the entrainment and impingement I 1.1 APPROACII Environmental monitoring studies were conducted sampling programs. I to determine whether the operation of Seabrook Station had an effect on the " Balanced Indigenous Populations of Fish, Shellfish and Wildlife" in the nearfield coastal A basic assumption in the monitoring program is that there are two major sources of naturally-occurnng variability: (1) that which occurs among different areas waters of New Hampshire. A biological monitoring or stations, i.e., spatial, and (2) that which varies in program established under the National Pollutant time, from daily to weekly, monthly or annually, i.e., Discharge Elimination System (NPDES) pennit, jointly temporal. In the experimental design and analysis, the issued by the Environmental Protection Agency and Seabrook Environmental Program has focused on the the state of New llampshire, fonns the framework for major source of variability in each community type study, and then determined the magnitude of variability in exh community. The frequency and spatial distribution in order to determine whether the operation of of the sampling effon were determined based on the Seabrook Station affected the aquatic biota, a systematic greatest sources of vadability for each parameter (NAl approach of impact assessment was utilized. This 1991). approach incorporated both temporal and spatial components for each biological community evaluated Biological variability was measured on two levels: I (Figure 1-1). Potential operational effects could be ruled out if: (1) results from the operational period species and community (Table 1-1). A species' abundance, recruitment, size and/or growth are ! were similar to previous (preoperational) years, given important for understanding operational impact, if any, I the natum! variability in the system, or (2) differences within the operational pedod were observed in both should changes occur in these parameters between stations or over time. These pammeters were monitored ! I nearfield and fadield areas. In addition.other potential sources of change have ven investigated before the conclusions specified within this report were drawn. for selected species from each community type. Selected species were chosen for more intensive study based on either their commercial or numerical l j
)
I This study design was modeled after objectives discussed by Green (1979), which have been described importance, sensitivity to temperature, potential as a nuisance organism, or habitat preference. Overall community structure of the biota, e.g., the number and l previously in more detail (NAI 1991). type of species, total abundance and/or the dominance l The validity of the impact assessment model is based structure, was also reviewed to determine plant impact, on compadsons between nearfield stations within the if any, for those not detected by monitoring individual inf!uence of Seabrook Station and outside its influence species. Trends in these parameters were reviewed at farfield stations. Modeling studies, as well as against the natural vadation in community structure. operational validation clearly indicates this to be tnie I for thermal effects in relation to the thermal plume. The extent of a +3 'F(1.7 C) isotherm has been shown A previous Summary Report (NAl 1977) concluded that the balanced indigenous community in the Seabrook l to cover a relatively small 32-acre surface area study area should not be adversely influenced by loss I (Padmanabhan and llecker 1991). Due to the buoyant nature of the thermal discharge, temperature differences of individuals due to entrapment in the Circulating Water Systmn (CWS), exposure to the thermal plume, do not extend below the thermocline. Due to its or exposure to increased particulate material (dead 11 I
7 0 o EXECUTIVE
SUMMARY
SEOUENCE OF EVENTS I FOR DETERMidlNG IF THERE ARE ENVIRONMENTAL CHANGES DUE TO OPERABON OF SEABROOK STATION I is Operational Period similar to YES m No previous years impact at nearfield station
?
I Operational Period nearfield YES No similar to impact farfield
?
t NO Observed I i I changes related to NO m No plant Impact operation
?
/"" I Operational Impact Figure 1 1 Sequence of events for determining if there are environmental I
l changes due to the operation of Seabrook Station. Seabrook Operational Report,1993. 1-2 I
L, EXECUTIVE
SUMMARY
l TADLE 11.
SUMMARY
OF BIOLOGICAL COMMUNITIES AND TAXA MONITORED FOR EACII POTENTIAL IMPACT TYPE ! SEABROOK OPERATIONAL REPORT,1993. I I LEVEL 110NITORED l SELECED l MONITORING SPECIES / , AREA IMPACT TYPE SAMPLE TYPE COMMUNITY PARAMETERS l I L Intake Entrainment Micruzooplankton x x Macrozooplankton : x ; { Fish eggs Fish larvae x x x Soft-shell clam larvae x Cancer crab larvae x Impingement Juvenile / Adult fish x x { Lobster adults x Discharge Thennal Plume Nearshore water p quality x L Phytoplankton x x Lobster larvae x Intertidal / shallow subtidal macroalgae [ and macrofauna x x Subsurface fouling { Turbidity community Mid-depth /dcep x x (Detrital Rain) macrofauna and h macroalgae x x Bottom fouling community x Demersal fish x x Lobster adults x Cancer crab adults x Estuary Cumulative Estuarine temperature x Sources Soft-shell clam spat and adults x Estuarine fish x x l-3
O O EXECUTIVE
SUMMARY
organisms) settling from the discharge. The current to address the question of operational effects. study continues to focus on the likely sources of potential influence from plant operation, and the Commercial operation or Seabrook Station began sensitivity of a community or parameter to that intermittently in July and August 1990, and continued influence within the framework of natural variability for periods of approximately three weeks in September (Table 1-1). A community or species within the study and October. Therefore, August 1990 is considered area might be affected by more than one aspect of the the beginning of the operational period for the pwposes CWS. Results from this monitoring pmgram will be of this envimnmental assessment. After operation at discussed in light of that aspect of the cooling water 100% for less than a week at the beginning and end g system that has the greatest potential for affecting that of November, the plant operated nearly continuously 3 particular component of the biological community. from December 1990 through July 1991 when it was Entrainment and impingement were addressed tiuough shut down for routine maintenance. Resumption of g l in-plant monitoring of the organisms entrapped in the full power operation began again in October 1991 and 3 l CWS. continued duough a second maintenance outage in late i September 1992. Full power operation began again
'Ihe effects on the balanced indigenous populations in November 1992 and has continued with only minor of aquatic biota in the vicinity of the CWS intake and interruptions tiuoughout 1993 (Figure 1-2). Monthly
- discharge stmetures were evaluated tiuough continued characteristics of the Ctreulating Water System operation l monitoring at sampling stations established during the throughout 1990,1991.1992 and 1993, are presented preoperational period, with statistical comparison of in Table 1-2.
the results at both the community and the species levels.
'Ihe null hypothesis in all tests is that there has been no change in community structure or selected species 1.3
SUMMARY
OF FINDINGS abundance or biomass that is restricted to the nearfield area. This in tum would indicate, based on the Water Ouality approach opdined in Figure 1-1, that the balanced indigenous populations nave been maintained. Water quality parameters were collected to aid in interpretin.c information obtained from the biological
- monitoring piogram, as well as to determine whether g 1.2 STUDY PERIODS the operation of the Seabrook Station Circulating Water 3 l System had a measurable effect on the physical or Environmental studies for Seabrook Station began chemical characteristics of the water column. Water g in 1969 and focused on plant design and siting quality samples were obtained within the vicinity of 5 questions. Once these questions were resolved, a Seabrook'r. intake and discharge structures, and at
, monitonng program was designed to assess the temporal farfield locations outside of the influence of operation. l (seasonal and yeady) and spatial (nearfield and farfield) Measured parameters included temperature, salinity, variability during the preoperational period as a baseline dissolved oxygen, and nutrients (total phosphorus, against which conditions during station operation could orthophosphate, nitrate, nitrite, and ammonia). be evaluated. 'Ihis report focuses on the preoperational l data collected from 1976 tiuough 1989 for fisheries Potential impacts related to the operation of Seabrook studies and from 1978 through 1989 for most plankton Station include: (1) temperature changes resulting from and benthic studies; during these years sampling design the discharge of a heated cooling water from the Station had consistently focused on providing the background condensers, (2) the discharge of chlorine (sodium 1 l-4 I I.
EXECUTIVE SUhth1ARY lI
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Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 1993 l Figure 1-2 Average Daily Power Level at Seabrook Station during 1993 Seabrook Operational Report,1993. j I TAllLE l-2. 510NTIILY CIIARACTERISTICS OF SEAllROOK STATION OPERATION FOR TIIE PERIOD 1990 TIIROUGli 1993 SEAllROOK OPERATIONAL REPORT,1993 j DAYS OF CIRCULATING WATER AVERAGE DAILY um ! SYSTEM OPERATION FLOW (mgd) MONTil 1990 1991 1992 1993 1990 1991 1992 1993 Ju 31 31 31 31 324 SM 585 587 Feb 28 28 29 28 5 64 580 578 587 hbr 31 31 31 563 580 581 580 I 31 Am 30 30 30 30 563 581 576 579 hby 31 31 31 31 562 581 581 582 Jun 30 30 30 30 563 578 593 582 Jul 31 31 31 31 582 535 593 578 I Aug Sep Oct Nov 31 30 31 30 21 26 31 30 31 29 24 30 31 30 31 30 588 588 590 590 253 257 552 590 583 314 159 SGS 579 574 574 612 Dec 31 31 31 31 589 591 563 608 W 1-5 I
E U EXECUTIVE
SUMMARY
hypochlorite) utilized to prevent the settlement and analyzed. There were significant spatial and temporal accumulation of biological fouling organisms within differences for all nutrient parameters monitored, the Circulating Water System, and (3) associated however, these were consistent with preoperationa E changes related to the addition of moribund entrained characteristics and not attributed to the operation of E phytoplankton to the nearshore marine environment. Seabrook Station. This is based on the consistency of spatial trends between the two periods, as well as Annual average surface temperatures during 1993 the similarity of seasonal pattems across the years. were warmer at each station when compared to recent preoperational years (1987-1989) but were similar to Most water quality parameters showed a distinct the average temperatures over all preoperational years. seasonal cycle that was consistent throughout the This reflects a cooling trend observed in 1992 and 1993 monitoring period. Significant differences among years compared to 1991, when the average annual surface were typical, reflecting high year-to-year variability. temperature at the intake and discharge station was Increases or decreases in all parameters were consistent the highest of record during the fifteen year study between nearfield and farfield stations, indicating that period. Significant spatial differences in the annual the chemical and physical environments in the study mean surface temperature between the tlure monitoring area are dominated by larger regional trends. These locations were identified during 1993. Although appear unrelated to the operation of Seabrook Station. between-period and among-station differences were significant for both surface and bottom temperatures, t!e differences in surface and bottom water temperatures Phytopiankton g between tie preoperational and operational periods were E consistent at all three stations. The phytoplankton monitoring program was initiated to identify seasonal, annual, and spatial trends in the Seasonal panems of surface and bottom salinity were phytoplankton community and to detemline if the similar between preoperational and operational periods; operation of Seabrook Station had a measurable effect however,1993 annual mean salinities at each station on this community. The purpose of the monitoring decreased by approxime.tely 1.5-1.6 ppt compared to prugram is to determine if the balanced indigenous the preoperational means. 1993 bottom salinities phytoplankton community in the Scabrook area has declined by 1.3-1.4 ppt. Over both the preoperational been adversely influenced, within the framework of and operational periods, mean surface salinities have natural variability, by exposure to the thent.al plume. been similar among the tluce stations while mean Specific aspects of the community evaluated included bottom salinities have been higher at the farfield station. phytoplankton (taxa 210 pm in size) abundance and species composition; ultraplankton (taxa < 10 pm in Surface and bottom dissolved oxygen concentrations size) abundance and species composition; community exhibited a seasonal pattem in 1993 similar to previous standing crop as measured by chloruphyll a concentra-years. Differences in annual mean surface and bottom tions; abundance of selected species (Skeleronema dissolved oxygen concentrations were small. costarum); and toxicity levels of paralytic shellfish g Preoperational concentrations were slightly, but poison (PSP, as measured by concentrations of 3 significantly higher, this probably conesponds to cooler Alexandrium spp. in the tissue of the mussel Afytilus preoperational temperatures. edulis) in the llampton-Seabmok area and at farfield g stations. E Nutrient concentrations in 1993 showed both spatial and temporal differences for each of the five parameters 1-6 5
1 I i I l EXECUTIVE
SUMMARY
Monthly abundances of phytoplankton during 1993 among taxa with respect to cell size and chlorophyll and the operational period were within the 95% a content. Preoperational and operational chlorophyll g confidence intervals established for the preoperational a concentrations followed a pattem similar to that of 3 period for most months. On avenge, diatoms phytoplankton abundances during the same periods. (Bacillariophyceae) dominated the phytoplankton assemblage during 10 of 12 months during the Skeletonema costatum was chosen as a selected .I operational period, while the yellow-green alga species because of its historic omnipresence and Phaeocystispouchetri dominated during the remainder overwhelming dominance during much of the year. I of the months. This pattem of seasonal succession in phytoplankton is well documented in other northem During the operational period both spring and fall peaks were larger but followed the same general pattem as temperate waters. Phytoplankton abundances at the the preoperational period. In 1993, S. costatum intake station showed large shifts from year to year abundances generally followed historic pattems, except throughout the operational and preoperational periods. in January when mean abundances were higher than The geometric mean abundance in 1993 (104.400 those typically observed and April mean abundances cells /L) was the lowest of the operational period and were lower. lower than in five of the seven preoperational years. Preoperational geometric mean abundances were similar During the preoperational period, paralytic shellfish between the discharge station and intake monitoring poison (PSP) toxicity levels, commonly known as red locations; however, they were higher than those at the tide, were above the detection limit in tissue of the m northem station. In general, abundances at each station mussel Myrilar edulis and above the closure limit during were higher during the operational period, although the late spring, early summer, and late summer. In 3 1993 abundances were similar to the prroperational. 1991, only two occurrences of PSP above the detection I Overall, tie abundances of the 15 numerically important taxa were not different among the stations in 1993. limit were recorded. PSP was not detected during 1992. In 1993, PSP was detected above the closure level in May and June. Red tide events in New Hampshire I Monthly Log (x+ 1) mean ultraplankton abundances were similar at all stations in 1993 and exhibited a weak seasonal pattem at each station. Annual mean geometric coincided with those in adjacent states. There were no outbreaks of red tide that were restricted to New Hampshire. I abundances were similar among the three stations throughout the operational period. Ultraplankton Zooplankton assemblages were also similar among the three stations in 1993. As in 1991 and 1992. Cyanophyceae were overwhelmingly dominant and followed a similar pattem Three components of the zooplankton community, of occurrence at each station. microzooplankton, bivalve larvae, and macruzooplankton, were sampled separately to identify During both the preoperational and operational spatial and temporal trends at both the conununity and periods, monthly arithmetic mean total chlorophyll a species level. Initial monitoring characterized the concentrations exhibited an early spring peak. Monthly source and magnitude of variation in the zooplankton mean operational concentrations were lower than community and provided data for comparison to that preoperational concentrations in all months. On an obtained during the operational period. The zooplankton ,I annual basis, chlorophyll a concentrations and community is currently evaluated to detemline whether l phytoplankton abundances appear to be inversely entrainment within tre Circulating Water System (CWS) l related. This difference is likely due to differences of Seabrook Station has had a measurable effect on 1-7 I
O O EXECUTIVE
SUMMARY
the community or any species. The entrainment of period than the recent preoperational period at all three bivalve larvae within the CWS has also been evaluated, stations,likely the result of high abundances in 1993. Since the operation of Seabrook Station, Plankton that spend all or a portion of theirlife in ' microzooplankton species composition continued to the water column (holo- and meroplankton) were found resemble the historical pattems. While the abundances to be similar to those in other portions of the Gulf of g of some taxa were different between the operational Maine. The seasonal change in the holo- and 3 and preoperational periods, these differences were meruplankton community composition at both nearfield generally consistent between stations. Patterns of and farfield stations was found to be consistent during g seasonal variation recorded during the operational years the past six years. 5 (1991-1993) for the selected micruzooplankton species were generally similar to those observed during the Tychoplankton are those plankton that inhabit both preoperationalperiod. Operationaldifferences,if they the substrate and the water colunm as a result of occurred, were observed at both nearfield and farfield excursions related to light, lunar cyc!c, storm events, stations. reproduction or nonspecific aggregation. This community exhibited greater spatial variability than The species composition of bivalve larvae during either the holo- or meroplankton community. Seasonal the operational and preoperational periods was similar changes in species composition were generally similar to previous years. Community stmeture was not between the operational and preoperational periods. significantly different among the near'icid and farfield Substrate differences between the nearfield and farfield stations tiuuughout t'te study; however, it was statioru account for some of the variability observed significantly different i t all three stations (combined) in the tychoplankton assemblages. during the operatior,al period compared to the preoperational (198P 1989). liigher abundance of Differences between the spatial and temporal almost all taxa acc( unted for the difference. components of the macrozooplankton assemblages have been consistent. Abundance differences between the Entrainment collections provide a measure of the preoperational and operational periods have occurred actual number of organisms directly affected by Station at both the nearfield and farfield stations. Spatial entrainment. Monthly entramment of all taxa was less patterns for other species (tychoplankton) have been in 1991 and 1992 in comparison to 1990 and 1993. similar both in the preoperational and operational Reduced CWS flaw during outage periods in the periods. summer when larvae typically resch their peak abundance levels in the local coastal waters may have 'There has essentially been no change in the led to reduced entrainment in 1991 and 1992. abundances or seasonality in most of the Abundances of Afytilas edulis larvae in bivalve larvae macruzooplankton selected species. With the exception collections from all stations in 1991 and 1992 were of Canatus finmarchicus copepodites, average also reduced when compared to 1990 and 1993, abundances of all selected species of macruzooplankton contributing to reductions in entrainment. Entrairunent were not significantly different from the recent within the CWS has not affected bivalve larvae preoperational period. abundance. 'Ihe seasonal pattem of the bivalve larvae g Afytilus edulis in the operational period was similar 3 to recent preoperational years. Af. edulis larvae were significantly more abundant during the operational 1-8 E a
i I J l EXECUTIVE
SUMMARY
I I i 1 Fish Population entramment samples and were also dominant in offshore collections during 1993. Entrainment oflarvae in 1993 Finfish studies at Serbrook Station began in 1975 was within the range of earlier years. I to investigate all life stages of fish, including ichthyoplankton (eggs and larvac), juveniles, and adults. Adult pelagic fish were dominated by the Atlantic Potential impacts of Seabrook Station operation on local herring Atlantic mackerel, alewife, rainbow smelt,and I populations include the entramment of eggs and larvac through the Circulating Water System and the Atlantic cod. In general catch per unit effort (CPUE) followed similar trends during the 18-year sampling impingement oflarger specimens on travelling screens pcdod. The spiny dogfish has become increasingly within the Circulating Water pumphouse. Local abundant during the operational period, increasing distribution could also potentially be affected by the continuously since the 1960s. Together with skates, I thermal plume, with some eggs and larvae being subjected to thermal shock due to plume entrainment upon discharge from the system diffusers. The main spiny dogfish now compose about 75% of the fish biomass of the Georges Bank. objective of the finfish studies is to assess whether the The geometric mean CPUE of demersal fish at all operation of Seabrook Station since 1990 nas had any stations combined in 1993 increased over 1992, but measurable effect on the nearshore fish population. was the second lowest since sampling began in 1976. Catches of nearly all species declined from Ichthyoplankton analysis focused on seasonal preoperational to the operational period, particularly , assemblages of both eggs and larvae, as well as on for the yellowtail flounder. Differences in CPUE and the collection of selected larval species. Consistent species composition were apparent among stations. temporal (among months and years) and spatial (among This may be due to the fact that the bottom at the stations) egg and larval assemblages identified through discharge station is located in shallow water off the b. the monitoring programs suggest that the operation mouth of Hampton-Seabrook liarbor where tle substrate of Seabrook Station has not altered the seasonal has a tendency to be inundated with drift algae. He spawning time nor the distribution of eggs in the farfield stations were located in deeper water with I Hampton-Seabrook area. Although the temporal occunence of fish larvac, both monthly and annually, sandier bottoms. was found not to be as consistent as for eggs, spatial The geometric mean CPUE for demersal estuanne I pammeters were consistent. Monthly observations at all three stations dudng each year were grouped together fish caught at all stations during 1993 incre,1 sed from 1992 and decreased for pelagic species. Catches and the three stations were very similar within the same generally were smaller during 1987-1993 compared year and month. Temporal changes in assemblage to 1976-1984. Average catches were less for the abundances were consistent at all three stations. operational period than observed during the preoperational, however, this declining trend began ! During 1993, monitoring revealed that 13 egg and in advance of Station opemtion. De Atlantic silverside 20 larval taxa were entrained within the Circulating has dominated catches in all years sampled. Winter ; Water System. Total annual estimates of entrainment flounder killifishes (mummichog and striped killifish), l were 315.6 million eggs and l26.1 millionlarvae. The ninespine stickleback, and rainbow smelt also total egg entrainment in 1993 was the lowest since the contributed to the catch. Trends in the CPUE were Station began operation, even though the annual found to be due to fluctuations in catch of the dominant condenser water volume was the greatest. Taxa species, Atlantic silverside. entrained in 1993 have dominated previous year's 1-9
n 0 EXECUTIVE
SUMMARY
During 1993 an estimated 1174 fish were impinged differences exist among communities at sites within on the travelling screens at Seabrook Station. Since the llampton-Seabrook area that can be attributed to the Station began Circulating Water System operation, the operation of Seabrook Station. Potential impacts a total of 3,866 fish and 42 American lobsters have include temperaturt-related community alteration to E E been reported. During the 4-year operational period, areas direedy exposed to the thermal discharge plume. winter flounder, pollock, windowpane. lumpfish, This would occur at sites in the upper portion of the longhom sculpin, sea raven, and Atlantic silverside water column due to the buoyant nature of a thermal have made up 61% of the estimated impingemenL plume. Thermal impacts are unlikely in deeper areas; however, increased turbidity resulting from the transpon The design of the Seabrook Station offshore intake of suspended solids and entrained organisms could with a mid-water depth intake fitted with a velocity increase shading and sedimentation. cap has clearly resulted in minimal numbers of fish being impinged when compared to other coastal sited Studies were implemented to identify plant and animal power plants. Estimates ofimpingement indicate that species occupying nearby intertidal and subtidal rock the operation of the Seabrook Circulating Water System surfaces and at those at farfield controllocations. The is presenting a negligible impact on local populations. studies also describe temporal and spatial pattems of species occurrence, identify physical and biological A number of differences were found between the factors that induce variability in these communities, preoperational and operational periods for fish and relate these to the operation of Seabrook Station. assemblages in general, and for most selected species in panicular. In nearly all cases where differences were found, abundance during the operational period was Potential Thermal Plume Effects significantly lower than during the preoperational period. However, in many instances, the declines began in the flydrodynamic modeling and subsequent field studies early or mid-1980s. Several of the decreases reflect indicated that benthic locations experienced either no long-term declining trends of overexploited commercial temperature increase at intenidal sites, or increases of fishes, including Atlantic cod, winter flounder, and <1 F at shallow subtidal sites (Padmanabhan and yellowtail flounder. liccker 1991). Analysis of the overallintertidal benthic community structure indicated that the nearfield mactualgal and macrofaunal communities have changed Marine Macrobenthos little since operation of Seabrook Station began. In high, mid, and low intenidal areas, frequency of The predominant benthic marine habitat within the occunence of dominant taxa, including bamacles, snails, vicinity of Seabrock Station's intake and discharge mussels, fucoids, and Chondrus crispus, generally is rocky substrate in the form ofledge and boulders. remained consistent over the preoperational and These rocky surfaces suppon rich and diverse operational periods. communities of attached plants and animals g (macrobenthos). Because these hard-bottom Abundance patterns of selected dominant intenidal 3 communities are ecologically important, and are taxa indicated that of the four taxa studied, only one potentially vulnerable to localized coastal antiuopogenic (the amphipod Ampirhoe rubricata) was significantly g impacts, studies of these communi:ies have been an different between nearfield and farfield stations during 5 impodant pan of the ecological monitoring program. operation. Nucella lapillus, and Mytilidae had The program has been designed to determine whether significandy lower abundances while Chandrus crispus 1-10 E
e I EXECUTIVE
SUMMARY
had higher biomass during the operational period; Two taxa. laninaria digitata and Modiolus modiolus, however, this occurred at both the neadictd and farfield exhibited area-wide decreases during the operational stations. Ampithoc rubricata abundance revealed period. Anotherkelp,Laninariasaccharina, exhibited significant decreases in the nearfield and increases in consistent patterns of occunence over both periods, the farfield: however, these shifts occurred prior to as did the green sea urchin Strongyiocentrotus I Station operation. For the shallow subtidal benthic communities, no droebachiemis. liigh densities of adult green sea urchin were found in both nearfield and farfield transect areas in 1993. A significant decrease in the abundance of changes have occurred that can be related to the the amphipod, Pontogencia inermis, was detected during operation of Seabrook Station. Numerical classification the operational period at only the farfield station. of macroalgal and macrofaunal data revealed no Nearfield abundance of P. Inermis was comparable ; substantive changes in species composition or overall to the preoperational period. Mytilids wem significantly community structure. Abundances of selected taxa more abundant during the operational period at the were consistent between nearfield and farfield stations nearfield station, no significant difference was observed over both the preoperational and operational periods at the farfield station. for Chondrus crispus, laminaria saccharina, and Jassa marmorata. Two other taxa, Asteriidae and Mytilidae, Measurement of the deep water macrobenthic I exhibited preoperational to operational period shifts only at the farfield station. A significant reduction communities and assessment of the overall community stmeture revealed that nearfield and farfield communities have remained stable over the I in abundance of Laminaria digitata was observed at the nearfield station during operation, but had begun in advance of operation. A similar, but statistically preoperational and operational periods. An increase in the total faunal density was observed at the intake g I significant decline was observed at near and farfield mid-depth stations. station during the operational period. Overall, the macrobenthic communities appear unaffected by Station operation Potential Turbidity Effects Surface Panels Assessments of community parameters and overall community stmeture indicate no changes in the nearfield The surface fouling panels program was designed mid-depth community during the operation of Seabrook to study settlement patiems and community development Station. Significant decreases in both measures of in the discharge plume and in farfield areas. Panels community abundance (total algal biomass and total provide information on the temporal sequence of faunal density) were observed at the mid-depth intake sett!cment activity, as well as on species growth and I station during the operational years, while consistent levels were observed at both the nearfield and farfield patterns of community development. stations over the entire study period, liigh similarity Seasonal cycles in faunal richness, as observed on in annual collections within depth zone were short-term (monthly) panels, were similar in 1993 and characterized for the overall faunal ard algal community during the operational period to the operational trend. structure at mid-depth sites. No substantive changes The average number of taxa was higher during the in community composition have occurred in the mid- operational period than during the preoperational depth zone. average at all monitoring locations. Total mean abundance at all stations in 1993 exceeded all previous l-11 I
mu 5' EXECUTIVE
SUMMARY
operational years. However there were no significant than average, indicate a nearfield-farfield difference differences between the nearfield and farfield stations, that was similar to previous years. Historically, Mytilidae (mainly Myritus edulis) was Total biomass was higher at the mid-depth nearfield , the most dominant noncolonial taxon. In 1993, the station during the operational period, while other seasonal recmitment pattem for Mytilidae during 1993, stations showed no significant change. g closely followed the operational and preoperational g, trends at all monitoring stations. The amphipod lassa marmorata is a common fouling organism. In 1993, Enibenthic Crustacea g; J. marmorata abundances were low throughout the year m_ at nearfield stations, except for a late summer increase. The objective of the epibenthic crustrea monitoring which closely follows the established seasonal pattem program was to determine the monthly, spatial, and for the operational and preoperational periods. annual trends in larval density and catch per unit effort Abundances were lower during the operational period (CPUE) for juvenile and adult stages of American l but not significantly different between the nearfield lobster (Homarus americanus), Jonah crab (Cancer l and farfield deep stations. The hydroid Tubularia sp. borealis) and rock crab (Cancer irroratus). Analyses ) is a dense summer colonizer that can provide a substrate were done to detennine if the discharge from Seabrook and food source to epifaunal taxa. The operational Station had any measurable effect on these species. ; mean percent frequency was significantly lower than during the preoperational mean at all monitoring Annual mean densities of lobster larvae continued , stations. the trends observed in 1991 and 1992. Lobsterlarvac densities during 1993 were higher than during the 1 Seasonal patterns of abundance of the community preoperational period (1988-1989) at each station. dominants observed on monthly sequential panels in Average larval densities during the diree year 1993 were similar to those observed during the operational period were significantly higher than the I preoperational period in most cases. 'Ihe mean numbers average densities during the preoperational period. of non-colonial taxa identified in 1993 and the There were no significant differences among the three operational period, were greater than the preoperational stations during the 1988-1993 monitoring period, mean at all for stations. Monthly trends were found to be similar to those g observed in previous years. Increases in densities 5
'Ihe community settling and developing on surface during 1993 were due mainly to increases in Stage I panels has shown predictable seasonal pattems and Stage IV larvae, historically the most numerous throughout the study, as evidenced both by measures of the four stages. Stage IV larvae are hypothesized of community structure (biomass, abundance, and to originate, at least in part, offshore in the wann number of taxa) and by abundance or percent frequency southwestem waters of the Gulf of Maine and Georges of occurrence of dominant taxa. Most measures showed Bank.
significant differences between operational and preoperational periods, a reflection of year-to-year The 1993 CPUE for adult lobster was lower than i variability in recruitment. These differences were that during the operational period (1991-1993) at both consistent among nearfield and farfield Stations. One nearfield and farfield stations. This decline, however, exception is the increase of Mytilidae at the nearfield was greater at the farfield station. The monthly trend mid-depth station whereas numbers decreased at its of CPUE in 1993 was similar to that observed during farfield counterpart. These numbers, although higher the preoperational period. Legal sized lobsters were 1-12 E a
I EXECUTIVE
SUMMARY
I 6% of the total catch at the nearfield station and 3% at the farfield station, slightly lower than the operation of Seabmok Station. I preoperational averages of 8% and 7% respectively. In 1993, one lobster was impinged in the Station's The mean monthly salinity at low tide in Browns River during 1993 ranged fmm 17.9 ppt in March to 29.5 ppt in August, a pattem similar to long-term Circulating Water System. Four were impinged in averages. The monthly mnge in llampton liarbor was 1990,29 in 1991, and 6 in 1992. somewhat smaller, 20.8 in April to 29.7 in July. Salinities at both Browns River and liampton liarbor Cancer spp. larvae had slightly higher peak period were consistently lower at low tide than at high tide. abundances in 1993 than during the preoperational Seasonal pattems of salinity corresponded to variations period at all stations. The avemge density during the in precipitation. Mean monthly precipitation was three year operational period was significantly higher highest in April, similar to previous years. than the preoperational average for each station. The 1993 mean CPUE for Jonah cob at the nearfield station Mean monthly temperatums at Bmwns River at low was higher than the preoperational average. In contrast, tide during 1993 ranged from a low of 0.0 *C in that at the farfield station declined and was lower than January to a high of 27.0 *C in July. Temperature the preoperational average. Trends in mean CPUE ranges in llampton liarbor were smaller (0.3 *C in I during the operational period also differed between the nearfield and farfield stations. The 1993 rock crab February to 19.8 *C in August). At both sites the monthly water temperatures during 1993 were similar to the monthly values reported since 1979. I CPUE at the nearfield and farfield stations decreased from the high catches observed in 1992, but were still above the preoperational average. Differences between The general macrobenthic community structures at both , I stations were significant, with more crabs occurring at the nearfield station. Rock crabs have been less prevalent than their congener in the study area, probably nearfield (Browns River) and farfield (Mill Creek) stations in the vicinity of Seabrook Station were typical for East Coast estuarine areas with fine-grained because of their preference for sandy substrate. sediments. Species abundances and dominance in the estuary are generally controlled by the physical environment, and the most numerous species are those Estuarine Benthos that tolerate fluctuating water temperatures and salinity and a changing sedimentary envirorunent. Total Environmental studies conducted in llampton liarbor macrofaunal density averaged 4062 individuals /m2 since 1978 have included monitoring of the physical at all sites during 1993, and was within the range of parameters (temperature and salinity), fish populations, densities reported since 1978. benthic macrofauna, and juvenile and adult soft-shell clams (Mya arenaria). Current estuarine monitoring Densities of the opponunistic sedentary bottom feeders efforts are directed to identify potential effects from Capitella capitara and Rediste diversicolor increased at all sites from 1992 to 1993, and the density of I cither the Settling Basin discharge or Seabrook Station operation. The objectives of the estuarine benthos studies are to characterize the macrofaunal communitie<. Streblospio benedicti at Browns River also increased in 1993. These changes were probably related to I in the llampton estuary in terms of abundance arid species composition, to identify spatial and tempor:1 pattems in community structure and abundance, and higher than average precipitation which resuspends sediment in the estuary. In the study area, although the densities of some species increased in 1993 relative to assess whether observed changes are related to the to 1992, densities of the dominant species were within 1-13 I
[] t U EXECUTIVE
SUMMARY
I the density ranges that have been reported since 1978. the operational means at all flats. Adult clam densities increases were observed at both the nearfield and increased significantly at the southem flat; however, farfield stations. no significant differ:nces occurred at others. In 1993, the density of seed clams in the nearfield Soft-Shell Clam area (llampton Harbor) was the highest since the study began in 1987. In the farfield area (Plum Island Sound)
'Ihe objectives of the soft-shell clam (Afya arenaria) in 1993, density increased only slightly over 1992 monitoring programs are to determine the spatial and levels. g temporal pattem of abundance of various life stages W '
of Afya arenaria in the vicinity of Ilampton Ilarbor. Clams in Hampton Harbor have historically been Pelagic life stages may be subject to impacts from subjected to predation from green crabs (Carcinus l Seabrook Station operation due to entrainment into maenas) and human clam digging. hican densities of the Circulating Water System. Benthic stages (after green crabs during the 1991-1993 operational period settlement to the bottom) in the Hampton-Seabrook were lower than preoperational densities for most of estuary may be subject to impacts from discharges from the year. Recreational clam digging on Hampton the Station Settling Basin. Nearfield / farfield liarbor flats has not been permitted by the New comparisons of clam densities are also made between Hampshire Department of Health and Human Services Hampton Harbor and a nearby estuary. Plum Island since April 1989 due to coliform contamination. Sound, Ipswich MA. Afya arenaria larvae occured most weeks from May 1.4 1,lTERATURE CITED through October during the preoperational years. Peak abundances in 1993 were seen in September and October and were above the preoperational average. Green, R.H. 1979. Sampling design and statistical However, the overall operational mean larval abundance methods for environmental biologists. John Wiley g, at all three stations was significantly less than the and Sons, N.Y. 257 pp. g preoperational means, yet was consistent at both nearfield and farfield stations. Normandeau Associates Inc. (NAI) 1977. Summary E document: assessment of anticipated impacts of E in 1993, average density of young-of-year (1-5 mm construction and operation of Seabrook Station on size class) clams was slightly higher than the the estuarine, coastal and offshore waters of preoperational averages at all three flats. Densities Hampton-Seabrook, New Hampshire, in 1993 were higher than for the previous two years. Trends in spat (6-25 mm size class) clams indicate the 1991. Seabrook Environmental Studies, survival of young-of-year that have overwintered. 1990. A characterization of environmer.tal conditions During 1993, recruitment into this size class increased in the Hampton-Seabrook area during the opemtion over the previous year at each flat, but remained below of Seabrook Station. Tech. Rep. XX11 ll. the preoperational mean at all three flats. Mean densities of juvenile (26-50 mm size class) clams in Padmanabhan M. and Hecker, G.E. 1991. 1993 remained lower than the preoperational means Comparative Evaluation of Hydraulic Model and and have been declining since the late 1980s. Adults Field 'Ihermal Plume Data. Scabrook Nuc! car Power (>50 mm size class) in 1993 had densities similar to Station. Alden Research Laboratory, Inc. 1-14 5 5
I 1 TABLE OF CONTENTS I , PAGE I 2.0 WATER QUALITY
SUMMARY
. . . . . ... ... . . .. .. . .. .. .. . ..... . ... . 2-ii :
LIST OF FIGURES . .. .. .. . . ... ... . .. .. . . .. . 2-iii LIST OF TABLES . ... .. .. . . ..... . ... ..... .. . 2-iv
2.1 INTRODUCTION
. . . . . . .. . . ..... . . . ..... ..... 2-1 ,
2.2 METHODS . . . . ... .. . .... .... ..... . . ... . . 2*I 2.2.1 Field Methods . . . . ... . .. .... . . ..... .. 2-1 I 2.2.2 2.2.3 Laboratory Methods . . . . Analytical Methods .... .
. 2-3 2-3 l
t RESULTS . 2-4 I 2.3 ... .. . . .... .. ... . . f 2.3.1 Physical Environment . . . . .. . .. .. .. .... .. . 2-4 2.3.2 Nutrients . .. .... .. .. . . . ... . . . . . 2-2 0 I 2.4 DISCUSSION ... .. . . . . .. .. . .. .... 2-23 t r
2.5 REFERENCES
CITED . .. . . . . . . .. . .. .. .. .. . . . 2-23 ! I I I I I 2-i I I
m E l'
SUMMARY
Most water quality parameters showed a distinct seasonal cycle that was consistent throughout the monitoring program. Signi6 cant differences among years were typical, redecting high year-to > car variability. Surface and bottom temperatures showed a significant increase during the operational period at Stations P2, PS, and P7. Surface and bottom salinities showed a signi0 cant decrease at each station over the same period, along with surface dissolved oxygen concentrations. Ilottom dissolved oxygen concentrations remained similar to preoperational E levels. Operational surface nitrite, ammonia, and orthophosphate concentrations also remained similar to 3 preoperational levels. Increases or decreases in all parameters were consistent between nearfield and farneld areas, indicating that the chemical and physical environments in the study area are dominated by larger regional trends. No localized effects due to the operation of Seabrook Station were observed. __ I I I, I I I I I I I 2-ii I E im l
~
l [ LIST OF FIGURES l I PAGE Water quality sampling stations 2-2 2 1. . . . 2 2. Surface and bottom temperature ( C) at nearfield Station P2, monthly means and 95% confidence intervals over the preoperational pcriod (1979-1989) and the operational period (1991-1993), and monthly means of surface and bottom temperature at Stations P2, PS. and P7 in 1993 . 2-5
- - i 2-3. Time-series of annual means and 95% confidence intervals of surface and bottom temperatures at Stations P2, P5 and P7,1979-1993 .. .. . . . . .. . ... . . .. 2-8 ;
( I l l 2-4. Monthly mean difference and 95% confidence intervals between surface and bottom temperatures ( C) at Stations P2, PS, and P7 for the preoperational (1979-1989) period and rnonthly means for the operational period (1991-1993) and 1993 . . 2-12 2-5. Comparison of monthly averaged continuous temperature ( C) data collected at the surface at discharge (DS) and farfield (T7) stations during commercial operation, August 1990-December 1993 2-14 I Surface and bottom salinity (ppt) and dissolved oxygen (mg/L) at nearfield Station P2, monthly I l 2-6. means and 95% confidence intervals for the preoperational period (1979-1989) and monthly means for the operational period (1991-1993) and 1993 . 2-17 2-7. Time-series of annual means and 95% confidence intervals of surface and bottom salinity (ppt) at Stations P2, P5, and P7,1979-1993 .
. 2-19 l
2-8. Surface orthophosphate and total phosphorus concentrations ( g P/L) at nearfield Station P2, monthly l a means and 95% coifidence intervals for the preoperational period (1979-1984 and 1987-1989). 2-21 l and monthly means for the operational period (1991-1993) and 1993 2-9. Surface nitrite-nitrogen, nitrate-nitrogen and ammonia-nitrogen concentrations ( g N/L)atnearfield Station P2, nwnthly means and 95% confidence inter"als for the preoperational period (1979-1984 l and 1987-1989), and monthly means for the operational period (1991-1993) and 1993 2-22 1 I l 2-iii
O E E LIST OF TABL,ES PAGE I 2-1. ANNUAL MEANS AND COEFFICIENTS OF VARIATION (CV,%) AND AVERAGE MINIMA AND MAXIMA FOR WATER QUALITY PARAMETERS MEASURED DURING PLANKTON CRUISES AT STATIONS P2, PS, P7 OVER PREOPERATIONAL AND OPERATIONAL (1991-1993) YEARS AND THE ANNUAL MEAN, MINIMUM AND MAXIMUM IN 1993 ... . 2-6 2-2. RESULTS OF ANALYSIS OF VARIANCE COMPARING WATER QUALITY CHARACTERISTlCS AMONG STAllONS P2, PS, AND P7 DURING RECENT PREOPERATIONAL YEARS (1987-1989) AND OPERATIONAL (1991-1993) YEARS .. . . . 2-9 2-3. ANNUAL MEAN SURFACE TEMPERATURES
- AND COEFFICIENTS OF VARI ATION (CV,%)
AT STATIONS DS AND T7 DURING OPERATIONAL MONITORING CONDUCTED BY YAEC. SEABROOK OPERATIONAL REPORT,1993 .. . . ... . . 2 13 2-4. MONTHLY MEAN TEMPERATURES ( C) AND TEMPERATURE DIFFERENCES (AT, C) g BETWEEN DISCHARGE (DS) AND FARFIELD (T7) STATIONS AT THE SURFACE, AND g NEARFIELD(ID) AND FARFIELD(T7)3TATIONS ATSURFACE,MID-DEPTH (8.5 m) AND BOTTOM (16.2 m) DEPTHS COLLECTED FROM CONTINUOUSLY-MONITORED TEMPERATURE SENSORS, JULY 1990-DECEMBER 1993 . . . . . . 2-15 2-5.
SUMMARY
OF POTENTIAL EFFECTS OF SEABROOK STATION ON AMBIENT WATER QUALITY. SEABROOK OPERATIONAL REPORT,1993 . . . . . 2-24 I I I E I I I 2-iv I
I WATER OUALITY 2.0 WATER QUALITY of chlorine. To date residual levels of chlorine at the diffusers have been below detection limits. , I
2.1 INTRODUCTION
Water quality parameters were collected to aid in 2.2 METIIODS I interpreting information obtained from the biological monitoring program and to determine whether the operation of the Seabrook Station Circulating Water 2.2.1 Field Methods I System has had a measurable effect on the physical and chemical characteristics of the water column. To provide information on the physical environment, water Near-surface (-l m) water samples for nutrient analysis were collected during daylight hours using a General Oceanics* 8-L water sampler from the intake quality samples were collected in the icinity of the (Station P2,16.8 m depth, MLW), discharge (Station Seabrook Station intake and discharge, as well as at PS,16 m depth, MLW), and farfield (P7,18.3 m depth, a farfield location outside of the influence of Station MLW) sampling locations (Figure 2-1). Nutrient operation. Parameters measured included temperature, sampling commenced at Stations P2 and PS in 1978 salinity, dissolved oxygen, and nutrients. Potential and at Station P7 in 1982. Sampling continued until impacts related to the cooling water system include 1981 at P5 and until 1984 at P2 and P7. Sampling I both that of temperature, through the discharge of a heated effluent from the condensers, and the application resumed at all three stations in July 1986, and continued to the present. Water samples were taken once in of sodium hypochlorite as a biofouling c ontrol measure. January, February., and December and twice monthly I from March through November, in conjunction with Seabrook Station em ploys a once-through Circulating the phytoplankton and raicrozooplankton sampling, I Water System. Ambient ocean water is drawn into the system from approximately 7,000 feet offshore through three intake structures and retumed through and within 24 hours of the weekly macrozooplankton and ichthyoplankton sampling. a multiport diffuser system approximately 5,500 feet Temperature, dissolved oxygen, and salinity offshore. All discharges are controlled under the measurements began in 1979 at Stations P2 and P5, Station's National Pollutant Discharge and Elimination and in 1982 at Station P7. Sampling at P2 and P7 System (NPDES) Permit issued by the State of New continued to the present; sampling at P5 was interrupted Hampshire and the Environmental Protection Agency from January 1982 until July 1986, but was sampled (EPA). This permit specifies that the temperature rise concurrently with P2 and P7 from July 1986 until the shall not exceed 5 F (3"C) within the nearfield jet present. At all stations, temperature and salinity profiles mixing region. This applies at the surface of the were taken four times per month during January through receiving waters within 300 feet of the submerged December with a Beckman# Thermistor Salinometer diffuser in the direction of discharge. (through March 1989) or a YSl* (Model 33) S-C-T Meter (1990 to 1993) within 24 hours of the weekly Seabrook Station utilizes continuous low level macrozooplankton and ichthyoplankton sampling. Full chlorination in the Circulating and Service Water temperature, salinity, and dissolved oxygen profiles e Systems to control biofouling. Information is gathered are reported in appendix tables contained in data through the Chlorine Minimization Program. which summary reports prepared in conjunction with the assesses the effectiveness of chlorine application in baseline (preoperational) and operational reports. Only preventing biofouling w hile utilizing the least amount surface and bottom temperature, salinity, and dissolved oxygen values are reported here. Duplicate dissolved 2-1 1
E RYE LEDOE t =6 e HEAD ' O o .5 1 Nautical Mile 2 Kilometers p FARFIELD AREA o 1 .. SCALE CONTOUR DEPTH IN METERS GREAT BOARS , l g HEAD , 2 HAMPTON us p 3 BEACH
.n I c
BROWNS Riva g P1 Intake * *. a OOTa f
'o 7 "Sg;'o l SEABROOK STATION fy g M. goS Discharge ,
HAVPTON g ,' SEABROOK SUNK HARBOR ROCKS! U SEABROOK "
\
~ :- n LEGEND I
O = water quality stations n ., = continuous temperature recorders g I i Figure 2-1. Water quality sampling stations. Seabrook Operational Report,1993. l 2-2 5 m
~ p L WATER OUALITY F oxygen samples were also collected at near surface Among-year and between-period trends were and near bottom (2 m above bottom) depths, and were evaluated using annual or period (preoperational, opera-L fixed in the field with manganese sulfate and alkaline tion) means. Annual means of 1993 collections were iodide-azide. Additionally, operational continuous calculated as the arithmetic mean of all observations temperature data from the discharge (Station DS), within the year. The means of preoperational and nearfield (Station ID) and farfield (Station T7) areas operational collections were calculated as arithmetic were collected and provided by Yankee Atomic Electric means of annual means over all years within each ( Company (YAEC) as pan of their NPDES permit compliance program (Figure 2-1). period, which varied among stations and parameters. The precision of the mean was described by its coefficient of variation. The preoperational periods for the different analyses are listed on the appropriate 2.2.2 Laboratorv Methods tables and figures; in all cases the operational period consists of collections from 1991-1993. Collections Water quality samples were analyzed for five from 1990 were not included in these analyses since nutrients (total phosphorus, onhophosphate, nitrate, the year was divided between the preoperational and nitrite, and ammonia) using a Technicon@ Autoanalyzer operational periods, and the inclusion of panial years
!! system. All analyses were performed according to in each period would bias the means.
EPA Methods for Chemical Analyses of Water and Wastes (USEPA 1979)and Standard Methods (APHA Operational /preoperational and nearfield/farfield 1989). differences in monthly means were evaluated using a multi-way analysis of variance procedure (ANOVA), which was designed to specifically test for potential 2.2.3 Analvtical Methods impacts of plant operation. Main efTects included PREOP-OP (preoperational and operational periods). Results from these collection efforts were used to YEAR, MON IB, and STATION. An interaction term, describe the seasonal, temporal, and spatial character- PREOP-OP X STATION, was also specified in order istics of the water column within the nearshore waters to determine if changes in spatial relationships coincided off Seabrook Station. Analyses used data from all with the start of plant operation. This ANOVA model stations, but focused on Station P2 since it was sampled was more conservative (more likely to detect significant ; for a longer period of time than Stations P5 and P7. differencer) than alternative models that treat some Any values that were less than the detection limits w ere sources of variation, such as YEAR, as random assigned a value equal to one-half of the detection limit variables. The preoperational period for each analysis for computational purposes (Gilbert 1987). Seasonal was specified as 1987-1989, which was the period [ trends were analyzed using monthly arithmetic mean during which all three stations were sampled temperatures and dissolved oxy gen, salinity, and nutrient concurrently (thus maintaining a balanced model concentrations. Monthly means for the preoperational design). These results were evaluated in conjunction and operational periods were calculated from the with means calculated over all available preoperational monthly arithmetic means for each year within each years to help distinguish between recent trends and period, resulting in a sample size equal to the number long-tenn trends. ofyears in each penod. Monthly means for 1993 were calculated as the arithmetic average of all samples taken within a gisen month. 2-3 L----------------------------------_-___-__
y am E' WATER OUALITY 2.3 RESULTS the preoperational and operational periods (OP> PREOP; Table 2-2). 2.3.1 Physical Environment g As noted for surface temperatures, monthly mean g Temperature bottom temperatures at each station were generally cooler during the winter and warmer during the summer Monthly mean surface water temperatures at Station in 1993 compared to preoperational monthly mean P2 followed a similar seasonal pattern during both the temperatures (Figure 2-2). This is reflected in the wider preoperational and operational periods (Figure 2-2). range of temperatures observed in 1993 compared to In 1993 specifically, surface temperatures were coolest the average range of temperatures recorded during the . , , in February (2 C cooler than in January), then warmed preoperational period (Table 2-1). Average annual by approximately 2 C by the end of April. Tempera- bottom temperatures were warmer at Station P5 tures warmed by 7 C between April and May (the compared to P2 and P7, as in the preoperational period. largest consecutive monthly difference observed during Annual mean temperatures were cooler at each station the year), then continued to warm steadily (1.5 C to in 1993 compared to preoperational mean temperatures. ' 3.5 *C per month) through August, when the annual maximum occurred. Temperatures then cooled by 4.5*C Alt! ough between-period (OP> PREOP) and among-by the end of September, and continued to cool by station differences were significant for both surface about 3 C per month through December. and bottom temperatures, the difTerences in surface and bottom water temperatures between the preopera-Monthly mean surface temperatures recorded in 1993 tional and operational periods were consistent at all at Station P2 were generally cooler during winter three stations (i.e., no significant interaction term; Table months and warmer during summer months compared 2-2). E to preoperational monthly means (all years; Figure 3 2-2). This is reDected in the range of temperatures Monthly mean differences between surface and recorded during 1993, which was wider at each station bottom temperatures (surface - bottom; Figure 2-4) E compared to the r -rage minimum and maximum indicated that the water column at each station was 5 temperatures os er the preoperational period (Table 2-1). essentially isothermal ( AT = -1 C to + 1 C) during seven Surface temperatures in 1993 at Stations PS and P7 of twelve months, during both operational and i followed the same seasonal pattern observed at P2; preoperational periods. A weak temperature stratification 1 temperatures were warmer at Station P5 than at P2 began to develop in May, with a aT of approximately and P7, as in the preoperational period (Table 2-1). 4 C. Maximum surface-bottom differences of 6-7 C occurred in July or August. Temperature differences Average annual surface temperatures in 1993 were then began to decline to approximately 3-4'C by warmer at each station compared to recent preopera- September. The water column retumed to isothermal i tional years (1987-1989), but were similar to average conditions by late October. Throughout 1993, average temperatures over all preoperational years (Table 2- 1 ). surface-bottom temperature differences were generally ) I This reflects a cooling trend observed in 1992 and 1993 larpr than during the preoperational period, but compared to 1991, when the average annual surface exceeded upper 95% confidence limits of preoperational j temperature at P2 was the highest recorded during the means only in March (all stations). May (P2 and P7). g fifteen year study period (Figure 2-3). There were and in August at P7 and in September at P2. g significant differences in annual mean surface temperatures among stations (P5>P2>P7) and between
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r ... s o o i i i e i e i iiie i e i e i e a a e e i e i JAN PES MAA APit MAY LN A't. AUG SEP OCT NOV DEC JAN FES MAA AMt MAY L'N A1 AUC SEP OCT NOW DEC MONTH MONTH 1 Figure 2 2. Surface and bottom temperature ('C) at nearfic!d Station P2, monthly means and 95% confidence intervals over the preoperational period (1979-1989) and the operational period (1991-1993), and monthly means of surface and bottom temperature at Stations P2, PS, and P7 in 1993. Seabrook Operational Report.1993. 2-5
TAllLE 2-1. ANNUAL MEANS AND COEFFICIENTS OF VAltlATION (CV,%) AND AVERAGE MINIMA AND MAXIMA FOR WATElt QUALITY PAllAMETEllS MEASUllED DUltlNG PLANKTON CitUISES AT STATIONS P2, PS, P7 OVEll PitEOPEllATIONAL" AND OPEllATIONAL(1991-1993) YEAltS, AND Tile ANNUAL MEAN, MINIMUM AND MAXIMUM IN 1993. SEAllitOOK OPEllATIONAL ltEPOllT,1993. PREOPER A~IION AI. AI.1, Y EARS" RECENT YEARSb OPERATION AL 1993 PAR AM EI ER I CV MIN MAX u CV MIN MAX x CV MIN MAX i MIN MAX TEMPER AltlRE (*C) Surface P2 9.13 7.99 1.54 18.45 8 99 2.97 1.23 18.53 9.34 6.46 1.80 18.90 9.11 0.00 19.20 P5 9.53 5.59 2.01 18.53 9.15 3.73 1.13 18.13 9.61 5.29 1.90 19.23 9.33 0.10 19.70 P7 8.73 6.26 1.39 18.00 8.84 3.61 0.93 18.20 9.16 5.80 1.87 18.57 8.92 0.20 19.70 Bottom P2 7.13 8.84 1.72 14.35 6 57 2.70 1.13 14 00 7.30 8.85 2.03 14.80 6 61 0.10 15.50 P5 7.05 8.23 2.22 14.12 6.65 3.71 1.10 13 60 7.45 7.87 2.07 14.23 6.84 0.00 13.20 P7 6.85 9.30 1.55 13.61 6.44 3.07 1.03 13.90 7.16 8.17 1.90 13.60 6.62 0 20 13.30 7e S AI INil Y (ppt) Sur f. ice P2 31.59 1.35 28.42 33.32 31.57 1.12 26.90 33.37 30.57 2.08 27.32 32.56 29.95 25.16 32.54 P5 31 61 0.91 28.16 33.70 31.50 1.06 25.50 34.36 30.48 1.91 25.18 32.53 29.94 25.40 32.34 P7 31.53 1.36 26 69 33.58 31.39 1 04 24.97 33.54 30.51 2.04 27.01 32 64 29.86 25.20 32.75 llottom P2 32.18 0.84 30 63 33.52 32.07 0.94 30.10 33.73 31 09 1.37 28.31 32.57 .30.79 28.45 32.54 PS 32.24 0.71 31.00 33.47 32.13 0.71 30.50 33.57 31.09 1.67 26.52 32.56 30.72 26.88 32.44 P7 32 23 0.83 30.51 33.52 32.18 0 82 30.47 33 63 31.24 1.83 28 08 33.21 30.74 27.43 32.65 ! Dl%OINED OXYGEN tmg/L) Surface 9.69 3.14 7.39 12.45 9 71 0.95 7.40 12.27 9.61 1.03 7.47 11.87 9.64 7.00 11.60 P2 9.71 3.92 7.64 11.64 9.73 0.98 7.57 12.33 9.68 1.22 7.50 12.03 9.72 7.00 11.60 , P5 9 66 0.95 7.28 12.65 9.70 1.26 7 43 12.23 9.57 1.08 7.53 I l .73 9 60 7.30 11.50 i P7 llotlOm P2 9.19 4.58 6.59 12 03 9.22 4.22 6.60 11.73 9.24 3.19 6.67 11.73 9.33 6.00 11.60 l ps 9.2 I 5.20 6.73 11.19 9.20 4.45 6.77 I1.87 9.29 2.44 6.70 I l .73 9.33 7.10 11.50 P7 9 09 2.50 6.10 12.50 9.12 4.40 6.43 I l .70 9.18 2.47 6.77 Ii 67 9 29 6.80 11.50 l (Collfilltictl) N MM MM M M M MM M M W MM M g 3 gg
' g pg g g g g g g - g- g g gng ~g g g :-
TAllLE 2-1. (Continued) PhEOPElt ATION Al. l All Y EA RS* ItECENT YEAltSb OPEltATIONAL 1993 1 Pall A M EI Elt I CV MIN MAX T CV MIN MAN I CV MIN MAX I MIN MAX SilRFACE NtflRIENTS (ppl) Or% phosphate 12.95 27.38 2.40 27.10 14.91 14.67 2.83 32.00 14.46 7.92 3.83 31.17 15.75 3.50 32.00 P2 12.10 22.70 1.93 34.86 14.57 12.22 2.33 37.67 14.28 7.81 3.67 28.33 15.15 2.00 30.00 P5 15.91 10.18 2.25 32 83 15.57 11.36 2.50 33.67 14.82 5.23 5.17 31 67 15.70 5.50 29.00 P7 Total Phosphorus P2 2184 18.76 9.05 51.95 29.18 11.83 11.67 53.33 26.42 7.70 15.50 53.67 26.18 12.00 43.00 P5 27.46 22.56 10 07 56 86 29.72 5.90 16,67 56.67 26.34 13.57 15.17 47.00 26.18 9.50 44.50 P7 29.11 12.22 11.33 56 83 30.97 13.18 13.33 60.00 26.86 10.11 12.50 49.67 26.95 15.50 44.50 Nitrite to P2 2.05 30 87 0 55 5.50 2.05 16.16 0.50 6.00 2.20 10.13 0.67 6.33 2.28 0.50 6.00 b P5 2.14 25.95 0.57 6 29 1.96 13.62 0.50 6.67 1.82 8.52 0.67 5.17 1.73 0.50 6.50 P7 1.90 32.32 0.50 5.75 2.17 17.51 0.50 7.33 2.30 4.26 0.67 6.83 2.33 0.50 7.00 Nitrate P2 40.00 20.87 5.50 156.50 44.03 24.48 5.00 170.00 40.54 20.64 3.33 145 00 46.38 2.50 160.00 P5 39.84 19.94 5.71 150 00 42.19 26.19 5.00 163.33 37.88 31.98 3.33 140 00 44.00 2.50 160.00 P7 42.06 24.42 5.00 157.83 47.44 22.45 5.00 166.67 42.37 17.83 3.33 155 00 49.25 2.50 160.00 Ammonia' P2 6.42 10.65 5.00 20.00 -- -- -- - 6.92 58.83 3.33 20.00 l 1.00 2.50 30.00 P5 6 07 24.96 5.00 12.50 .. - -- -- 6.36 59.46 3.33 13.33 10.50 2.50 20 00 1 P7 7.57 18.77 5.00 25.00 -. - -- -- 7.40 50.36 3.33 20.00 11.25 2.50 30.00 i
'Mean of annual means, minima and maxima for preoperational years:
\ Vater tjuality parameters: P2 = 1979-1989 Nutrients: P2 = 1978-1984,1987-1989 P5 = 1979-1981,1987-1989 P5 = 1978-1981,1987-1989 P7 = 1982-1989 P7 = 1982-1984,1987-1989 l
b l987-1989, preoperational period specified in ANOV A (Tabic 2-2), mean of annual means.
'llecause analytical methods for ammonia changed in April 1988, preoperational period for ammonia is April 1988 - December 1989.
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2-8 E 5 m
U W l TABLE 2-2. RESULTS OF ANALYSIS OF VARIANCE COMPARING WATER QUALITY CilARACTERISTICS AMONG STATIONS P2, PS, AND P7 DURING RECENT PREOPERATIONAL YEARS (1987-1989) AND GPFRATIONAL (1991-1993) YEARS. SEABROOK OPERATIONAL REPORT,1993. SOURCE OF MULTIPLE PARAMETER VARIATION" DF MS F COMPARISONS" (ranked in decreasing order) l i 16. .1 287.87' " OP> PREOP Surface Temperature PREOP-OP > ' YEAR (PREOP-OP)d 4 7.73 132.79 "
- MONTil (YEAR)* 66 78.96 1355.97' "
r 2 2.49 42.78 "
- P5>P2>P7 STATION PREOP-OP X STATION 8 2 0.10 1.72 NS ERROR 140 0.06 llottom Temperature PREOP-OP I 42.66 486.31 "
- OP> PREOP YEAR (PREOP-OP) 4 8.76 99.91* "
MONTil (YEAR) 66 28 47 324.57' " y STAllON 2 1.11 12.67 " ' P5>P2>P7
& 0.03 0.37 NS PREUP-OP X STATION 2 ERROR 140 0.09 Suil~ ace Salinity PREOP-OP 1 44.80 503.69 " ' PREOP >OP YEAR (PREOP-OP) 4 10.81 121.56 " '
MONTil (YEAR) 66 4.84 54.37' " STATION 2 0.34 3.87* P2 P5 P7 PREOP.OP X STATION 2 0.13 1.43 NS ERROR 140 0 09 I Ilottom Salinity PREOP-OP I 51.77 1022.62* " PREOP >OP YEAR (PREOP-OP, 4 5.75 113.49* " MONTil (YEAR) 66 1.42 28.04 "
- STATION 2 0.38 7.41 " ' P7>P5 P2 PREOP-OP X STATIO.4 2 0.03 0.64 NS ERROR 140 0.05 (continued)
_____-_x_-_-_______-____----._-_- _ _ _ _ _ _ .
TAllI.E 2-2 (Continued) SOUllCE OF MULTIPLE PAR A M ETElt VA RI ATION' DF MS F COMPARISONS h (ranised in decreasing order) Surface lhssohed PR EOP-OP 1 1.09 62.56 " ' PREOP >OP Osygen YEAR (PREOP-OP) 4 0.41 23.58 " ' MONTil (YEA R) 66 2.84 163.24* " SIAllON 2 0.09 4.92 " PS P2 P7 PREOP-OP X STATION 2 0.03 1.62 NS ERROR 140 0 02 Ilottom Dissolved PREOP-OP I <0 01 021NS Oxygen YEAR (PREOP-OP) 4 3.93 184.47 "
- MON 111 (YEAR) 66 4.59 215.33' "
STATION 2 0.19 8 87' " PS P2>P7 PREOP-OP X STAllON 2 0.02 1.06 NS o ERROR 140 0.02 5 Orthophosphate PR EOP-OP i 10 89 3.71 NS YEAR (PREOP-OP) 4 79.11 26.93* " MONill(YEAR) 66 206.54 70.31 "
- S TA llON 2 5.89 2.01 NS PREOP-OP X STATION 2 1.22 0.41 NS ERROR 140 2.94 lotal Phosphorus PR EOP-OP I $91.38 25.27' " PREOP 2OP YEAR (PREOP-OP) 4 361.23 15.44* "
MON I'll (YEAR) 65 325.02 13.89' " STATION 2 28.84 1.23 NS PREOP-OP X STATION 2 24.52 1.05 NS ERROR 138 23.40 Nitrate PREOP-OP 1 1464.84 34.84* " PREOP >OP YEAR (PREOP-OP) 4 4030.32 95.87' " MONTil (YEAR) 66 9711.81 231 02 " ' STAllON 2 289.52 6.89 " P7 P2 P5 PREOP-OP X STATION 2 3 67 0.09 NS ERROR 140 42 04 (continued) I! WW W m M M M M M M M m> M M m W p m3
' "W M~N'W W W M M M M M M M M M W~M. W [ TAHLE 2-2 (Continued) SOUllCE OF MULTIPLE PAllAM ETEll VARIATION' DF MS F COMPAltlSONSh (ranked in decreasing order) Nitrite PREOP-OP I 0.13 0.31 NS YE/.R (PREOP-OP) 4 2.00 4 93 " ' MONTil (YEAR) 66 7.83 19.28 " ' STATION ' l.77 4.37' P7 P2>P5 PREOP-OP X STATION 2 0 SI 1.26 NS ERROR 140 0.41 Ammonia PREOP-OP I 8.10 2.21 N S YEAR (PREOP-OP) 3 412.94 112.64* " MONTil (YEAR) 52 32.86 8.96 " ' STATION 2 20.29 5.53 " (Non-est.)' PREOP-OP X STATION 2 1.54 0.42 NS
';3 ERROR I10 3.67 C
'llased on averaged monthly collections for all parameters b
Preoperational years. 1987-1989 at each station for all parameters eu.ept ammonia, which was April 1988 through December 1989
'Preoperational versus operational period, regardless of station d Year nested within preoperational and operational periods, regardless of station (Month nested within year nested within preoperational and operational periods, regardless of station
' Station P2 versus PS versus P7, regardless of year 8 interaction between main effects
Underlining indicates no significant difference based on a test of lij LSMEAN(i)=LSMEAN(j)
'Too few preoperational data available to compute the LSMEANS for STATION NS = not significant (p 2 0 05)
' = significant (0 05 2 p>0 01)
" = highly significant (0.012 p >0.001)
"' = very highly significant (0 0012 p)
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l Figure 2 4. Monthly mean difference and 95% confidence intervals between surface and bottom l temperatures (*C) at Stations P2, P5, and 17 for the preoperational period and l monthly means for the operational period (19791989) and 1993. Seabrook Operanonal Report,1993. 2-12 l E se
I WATER OUALITY Continuous surface temperatures recorded at Stations Salinity DS (discharge) and T7 (fartield) by YAEC in 1993 I showed a similar seasonal pattern as temperatures recorded at the plankton stations, including a distinct August peak (Figure 2-5). The annual mean Monthiy average surface 21inities followed a distinct seasonal pattern (Figure 2-6) that was related to freshwater influx and precipitation, air temperatures I temperature at DS decreased since 1991 (Table 2-3). With the exception of May, July and August, monthly mean temperatures at DS were cooler than during and winds, and tides and currents. Several major freshwater sources influence salinities observed in the nearshore area off Hampton Harbor, including the previous years (Table 2-4). Penobscot and Kennebec Rivers in Maine, the Piscataqua River in New Hampshire and the Merrimack At T7, temperatures during most months were cooler River in Massachusetts. Salinities were typically highest in 1993 than in 1991 and 1990, but were warmer during during the colder months due to low temperatures and most months compared to 1992 (Table 2-4). Compared low precipitation and runoff. Salinities declined to to earlier operational years, temperatures in October their lowest levels of the year when freshwater influx I through December in 1993 were particularly warm, especially in comparison to coincident temperatures reached its peak level in the spring, due to spring storms combined with snow melt. Bottom salinitiesexhibited a similar but less pronounced seasonal pattem. Waters I observed at the plankton stations in 1993 (Figure 2-2 and Table 2-4). This, combined with the relatively within the study area are relatively shallow, thus storms cool temperatures observed at DS during these months and strong currents can, at times, affect the entire water in 1993, resulted in a shift in the monthly average AT column (N Al 1979). However, bottom waters in 1993 I from typically positive values (DS > T7) to relatively large negative values (DS < T7). This shift appears generally exhibited a more stable temperature and salinity structure compared to surface waters, i.e., I unusual compared to results from 1990-1992. although the temperatures observed at T7 in 1993 were similar to average temperatures recorded during the early years temperature and salinity changed at a faster rate and to a larger degree over the course of the year in surface waters when compared to bottom waters. I of preopera'ional monitoring (1975-1977; N A1 1979). Average monthly AT values showed full compliance with the station's NPDES permit. TABLE 2-3. ANNUAL 31EAN SURFACE TEMPERATURES' AND COEFFICIENTS OF VARIATION (CV,%) AT STATIONS DS AND T7 DURING l OPERATIONAL MONITORING CONDUCTED BY YAEC. SEABROOK OPERATIONAL REPORT,1993. l STATION DS STATION T7 YEAR MEAN CV MEAN CV 1991 10.55 38.85 9.88 48.10 1992 9.44 41.92 8~2 54.57 ! 1993 9 17 53.34 8.61 57.44
'mean of monthly means; n=l: in 1991 and 1993; n=11 in 1992.
I 2-13 I
a E I I Stations DS (Discharge) & T7 (Farfield) I 20 - ------- m r7 I 18 -
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5 2- \, t 0 i i iii ia iie i i i i i ii iiiiiiiiiiii ie i i i iiiiiii l ASOND JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND 5 1990 1991 1992 1993 l ! I Figure 2-5. Comparison of monthly averaged continuous temperature ('Ci data collected at the surface at discharge (DS) and farfield (T7) stations during commercial operation, August 1990-December 1993. Seabrook Operational Report,1993. V \ E l I E l 2-14 W a ' a l
m M M M M M M M M Mi M M MM M M M M M TAllLE 2-4. MONTilLY MEAN TEMPERATUllES (*C) AND TEMPEllATUllE DIFFERENCES (AT,'C) BETWEEN DISCllAltGE (DS) AND FARFIELD (T7) STATIONS AT Tile SURFACE, AND NEAltFIELD (ID) AND FAltFIELD (T7) STATIONS AT SUltFACE, MID-DEPTil (8.5 m) AND llOTTOM (16.7 m) DEPTilS COLLECTED FROM CONTINUOUSLY-MONITOllED TEMPERATURE SENSollS, .lUI.Y 1990-DECEMllEll 1993. SEAllROOK OPEllATIONAL REPORT, 1993-1990 1991 1992 1993 MONTil DS T7 AT DS T7 AT DS T7 AT DS T7 AT DISCil AltGE - FARFIELD (SUllFACE) JAN --* -- -- 6.47 4.71 1.76 6.02 4.32 1.70 5.69 3.80 1.89 Fell -- -- -- 5.38 4.17 1.21 4.74 2.92 1.82 3.52 1.38 2.14 M Alt -- -- - 5.11 3.78 1.33 4.94 3.16 1.78 3.26 1.63 1.63 A Pit -- -- -- 6.99 6.37 0.62 5.93 4.26 1.67 5.04 4.44 0.60 MAy -- -- -- 10.43 10.21 0.22 10.52 10.32 0.20 10.74 10.02 0.72 JUN -- -- -- 13.8I I3.70 0.11 11.94 I l.84 0.10 11.65 10.53 1.12 JUl. I4.54 14.63 -0.08 I4.58 15.02 -0.44 13.81 14.I6 -0.35 15.92 14.54 1.39 AUG* 18.16 18.36 -0.20 16.86 17.06 -0.20 15.61 14.69 0.92 18.77 16.69 2.08 SEP 16.31 16.09 0.22 15.66 15.69 -0.03 14.03 12.69 1.34 11.62 12.19 -0.57 o OCi I3.04 l 2. I I 0.93 11.87 11.68 0.19 -- -- -- 10.13 11.27 -1.14 NOV 10.24 9.44 0.80 11.00 9.33 1.67 9.01 7.59 1.42 8.03 9.33 -1.30
.L Dl!C 8.91 7.32 1.59 8.45 6.81 1.64 7.32 5.61 1.71 5.64 7.55 -1.91 1990 1991 1992 1993 T7 AT ID T7 AT ID T7 AT ID' T7 AT MONTil ID NEARFIEl.D - FARFIELD (SUltFACE)
JAN -- -- -- 4.63 4.72 -0.09 4.08 4.32 -0.24 3.64 3.80 -0.16 FED -- -- -- 4.24 4.14 0.10 2.81 2.84 -0.03 1.35 1 50 -0.15 MAR -- -- -- 3.95 3.77 0. I 8 -- 3.I 7 - 1.37 1.78 -0.41 APR -- - -- 6.36 6.21 0.15 -- 4.98 -- 3.90 4.44 -0.54 MAY -- -- -- 10.29 10.21 0.08 9.55 10.33 -0.78 9.06 10.02 -0.96 JUN -- -- -- 13.78 13.70 0.08 11.56 11.84 -0.28 9.62 10.53 -0.91 JUI. 14.69 14.63 0.07 15.12 15.02 0.10 14.24 14.21 0.03 AUG 18.11 18.11 0.01 16 70 16.57 0.13 -- 11.70 -- DECOMMISSIONED SEP 16.22 16.06 0.16 15.34 15.38 -0.04 12.21 12.76 -0.55 OCT 13.17 12.98 0.19 11.58 11.68 -0.10 -- -- -- NOV 9.38 9.39 -0.02 9.16 9.34 -0.18 7.43 7.61 -0.18 DEC 7.37 7.34 0.03 6.59 6.81 -0.22 5.26 5.61 -0.35 (continued)
-3 TAllLE 2-4. (Continued) 1990 1991 1992 1993 MONTil ID T7 AT ID T7 AT ID T7 AT ID' T7' AT NEARFiliLD - FARFIELD (MID-DEPTil)
JAN -- -- -- 4.83 5.00 -0.17 4.44 4.70 -0.26 3.86 4.03 -0.17 Fell -- -- - 4.19 4 31 -0.12 3.00 -- -- 1.31 1.58 -0.27 MAR -- -- -- 3.53 3.64 -0. I 1 3.01 -- -
- 1. I4 1.40 -0.26 APR -- -- -- 5.36 5.44 -0.08 4.63 -- --
3.53 3.75 -0.22 MAY -- -- -- 8.11 8.39 -0.28 8.12 8.13 -0.01 7.31 7.42 -0.11 JUN -- -- - 11.19 11.46 -0.27 9.63 9.79 -0.16 9.16 8.99 0.17 JUI. I1.76 11.50 0.26 11.24 l 1.74 -0.50 10.93 11.31 -0.38 AUG 14.81 15.42 -0.61 14.96 14.88 0.08 12.09 12.39 -0.30 DECOMMISSIONED SEP 14.06 13.94 0. I2 13.74 13.87 -0.13 11.09 11.40 -0.3 I OCT 11.92 11.85 0.07 10.94 11.14 -0.20 -- -- - NOV 9.42 9.53 -0.11 9.41 9.58 -0.17 7.63 7.68 -0.05 DEC 7.47 7.57 -0.11 6.86 7.11 -0.25 5.54 5.83 -0.29 1990 1991 1992 1993 MONTil ID T7 AT ID T7 AT ID T7 AT ID' T7* AT NEARFIELD - FAltFIELD (llOTTOM) JAN -- -- -- 5.I 4 5.74 -0.60 4. I6 4.34 -0.I8 4.I5 -- Fell -- -- -- 4.19 4.81 -0.62 2.98 3.06 -0.08 1.55 -- MAR -- -- -- 3.39 3.87 -0.48 3.09 3.I 2 -0.03 0.82 0.84 -0.02 Apg -. -- -- 4.83 5. I 3 -0.30 4.29 4.26 0.03 3. I 8 -- MAY -- -- -- 6.32 6.67 -0.35 6.19 6.09 0.10 5.77 -- JUN -- -- -- 9.15 9.46 -0.31 8.04 7.96 0.08 7.61 -- JUl. 9.08 9.62 -0.54 9.01 9.34 -0.33 8.65 8.5 I 0.I4 AUG 13.26 13.14 0.12 13.08 12.92 0.16 10.08 9.77 0.31 DECOMMISSIONED SEP 12.14 12.31 -0.17 11.89 l 1.99 -0.10 9.79 9.68 0.11 OCT I1.03 11.17 -0.14 10.28 10.37 -0.09 -- -- -- NOV 9.49 9.91 -0.42 9.40 -- -- 8.62 8.83 -0.21 DEC 7.43 7.96 -0.53 6.93 -- -- 5.76 - --
' Commercial operation began in August,1990.
- Data either not collected, or an equipment l'ailure occurred.
'lD (surface, mid. depth, bottom) and T7 (mid-depth and bottom) sensors deconunissioned July 1,1993.
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E O O WATER OUALITY Although seasonal pattems of surface and bottom of the Gulf of Maine become available, this phenome. salinity were similar between preoperational and non will be examined further. operational periods,1993 annual mean surface salinities at each station decreased by approximately 1.5-1.6 ppt compared to preoperational means, and 1993 bottom Dissolved Oxveen salinities declined by approximately 1.3-1.4 ppt (Table g 2-1). Differences between operational and preopera- Surface and bottom dissolved oxygen concentrations 3 tional salinities were significant (Table 2-2). Over both exhibited a seasonal pattem in 1993 similarto prev ious the preoperational (all years and recent years) and years (Figure 2-6). Dissolved oxygen concentrations g operational periods, mean surface salinities have been were highest during the cooler winter months, and 5 similar amorig the three stations while mean bottom peaked in late winter (February and March); concentra-salinities have been higher at Station P7 than at PS tions were lowest during the summer months when l and P2. These relationships have remained consistent temperatures reached the annual maximum (Figure 2-2). W regardless of operational status of Seabrook Station Operational and 1993 mean surface concentrations were (Table 2-2). within preoperational 95% confidence limits during all months; mean bottom concentrations in 1993 were Examination of long tenn trends in annual mean greater than preoperational confidence limits in July salinities (Figure 2-7) revealed that the decline in and August only, and were lower than preoperational salinity began between 1988 and 1989 at all stations confidence limits in October, and at both depths. A similar phenomenon was observed at the Maine Department of Marine Resources Although preoperational-operational differences in West Boothbay Harbor long term environmental annual mean surface dissolved oxygen concentrations monitoring station. This station is fairly comparable were small (s0.13 mg/L. Table 2-1), preoperational E to the Seabrook plankton stations; although in a more concentrations were significantly greater than g protected location, there is relatively little freshwater operational concentrations (Table 2-2), corresponding input to the harbor. Long term (1966-1985) annual to coo!er preoperational temperatures and warmer g mean surface salinities (taken at -5.5 feet MLW) at operational temperatures. Differences in annual mean 3 the West Boothbay Harbor station ranged between 30 bottom concentrations between preoperational and and 32 ppt (MDMR 1987), and in recent years annual operational periods were even smaller (< 0.9 mg/L), g mean salinity has declined from 30.7 ppt in 1990 to and were not significant (Table 2-2). W 29.2 ppt in 1993 (MDMR 1991,1992,1993,1994). Station differences in dissolved oxygen concentrations The reason for the decline in Seabrook salinities were significant across all years at both depths (Table remains unexplained, and probably reflects a 2-2). Concentrations were similar between Stations combination of several factors, including climatological P2 and P5 at both depths. Concentrations were similar conditions and general circulation partems in the Gulf between P2 and P7 at the surface, but concentrations of Maine. Instrumentation error may have been a at P7 were significantly less than at P5 at the surface contributing factor to the observed differences. The and less than P5 and P2 at bottom depths. The YS! meter used through 1993 produced readings within interaction term, howev er, was not significant at either its stated specifications ( 6.5%) but were approximately depth (Table 2-2)- E I ppt lower than duplicate samples analyzed in the g laboratory. As additional data from the Seabrook studies and other insestigations in the nearshore area 2-18 5 i.e
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us 30.0 - ,, 29.5 - 29.5 - 29 0 - 29 0 - 18 8 28 5 , , , , , , , ,,,,,,,, e a . . > > . >>>>>iii 79 80 31 n n p 13 M 37 58 99 90 91 ' 92 93 79 30 81 82 D p L5 M 57 88 39 90 91 92 93 YEAR YEAR Figure 2-7. Time-senes of annual means and 95% confidence intervals of surface and bottom salinity (ppt) at Stations P2. PS, and P7,1979-1993. Seabrook Operational Report.1993. 2-19
C_ O~ WATER OUALITY 2.3.2 Nutrients not significant, nor was the interaction of the main effects (Table 2-2). Phosphorus Species Monthly mean surface orthophosphate concentrations Nitrocen Species followed a distinct seasonal pattern in 1993 that was g typical of earlier years (Figure 2-8). Concentrations Nitrate concentrations exhibited the same strong a were highest during late-fall to late-winter, and lowest seasonality observed in phosphorus concentrations during summer months. This pattem, typical of (Figure 2-9). Monthly mean concentrations in 1993 nutrients in nonhern temperate waters in general, is closely tracked preoperational means during spring _ caused largely by the uptake of phosphorus during the through fall, but were higher in January, February and warmer months by primary producers (Section 3.0). March. Only the February mean concentration exceeded the upper 95% confidence inten al of the preoperational Orthophosphate concentrations during January, mean. Although the annual mean concentrations February, September and December in 1993 exceeded observed in 1993 were higher than during the period preoperational upper 95% confidence limits, but were 1987-1989 (Table 2-1), the preoperational mean over similar to preoperational monthly means during all other all three stations was still significant!y greater than the months. Operational-preoperational(recent years) mean operational mean (Table 2-2). Station differences were differences ranged from 0.25 to o.75 mg/L (Table 2-1), also significant over all years (P7 > PS), but the and were not statistically significant (PREOP-OP term, interaction between main effects was not. Table 2-2). Differences between stations.during both Nitrite concentrations exhibited a weaker, but still periods, were also not significant, nor was the interaction of main effects (PREOP-OP X STATION, significant (Table 2-2) monthly (seasonal) pattern E Table 2-2). compared to other nutrients (F:gure 2-9). Over the 3 whole year, monthly mean concentrations in 1993 were Trends in total phosphorus and onhophosphate variable, and exceeded preoperational upper 95% confi- g concentrations w ere sim ilar on a seasonal basis (Figure dence limits in some months and were less than W 2-8). Monthly mean total phosphorus concentrations preoperational lower 95% con 0dences limits in cthers. observed in 1993 fell within the 95% confidence limits Operational and preoperational annual mean concentra- g tions were not significantly different (Tables 2-1 and W of preoperational monthly means in all months except August, when the 1993 monthly mean exceeded the 2-2). Differences between stations were significant preoperational August upper confidence limit. over the period 19871993 (Table 2-2) with P7 and Operational mean concentrations were significantly P2 > PS. As with other nutrients, the interaction term (approximately 3 mg/L) lower than preoperational r.iean was not significant. concentrations (Table 2-1; Table 2-2). Although ammonia concentrations did not show the During all operational years, total phosphorus distinct seasonality observed in other nutrients, monthly concentrations differed on an annual basis by less than differences were significant over all years from 1987-1 mg/L among the three stations (Table 2-1). Across 1993 (Figure 2-9 and Table 2 2). Monthly mean concentrations in 1993 were higher than preoperatio.. I all preoperational years, among-station differences as E g large as 3 mpL were observed. Oser the period of monthly means in all months except July and October 1987-1993. however. differences among stations were by as much as 25 pg/L,. In spite of the large differences between 1993 and preoperational means (roughly 1 2-20 5
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- Preopernuonal penod for ammonia is April 1988 Decernber 1989. confidence intervals not calculated for this penod. 2 Figure 2 9. Surface nitrite-nitrogen, nitrate-nitrogen and ammonia nitrogen concentrations
( g N/L) at nearfield Station P2, monthly means and 95% confidence intervals for the preoperational penod (1979 1984 and 1987 1989), and monthly means for the operational period (1991 1993) and 1993. Seabrook Operational Report,1993. 2-22 5
I WATER OUALITY I g/L at each station; Table 2- 1 ), operational-preopera- In spite of several preoperational-operational tional differences over all stations were not significant differences in the water quality parameters (Table 2-5), (Table 2-2). This difference is due in large part to there is currently no evidence to indicate any significant -3 change in water quality caused by the operation of the the fact that ammonia was not detected during any previous operational month except August in 1992 (NAl Seabrook Station cooling water system. This is based on the consistency of spatial trends between the two I 1993). periods, as well as the similarity of seasonal pattems across the years. l 2.4 DISCUSSION Water quality information collected during 1993
2.5 REFERENCES
CITED showed a moderately well-mixed water column at each
.I station through most of the year. Although surface- APHA (American Public Health Association).1989.
Standard methods for the examination of water and bottom differences were present at times during the year, a strong ;tratification that would block the cycling wastewater,17th edition. of nutrients between surface and bottom waters did not develop at any time. Temperatures were generally Gilbert, Richard O. 1987. Statistical methods for cooler compared to earlier operational years, although environmental pollution monitoring. VanNostrand over the operational period as a whole, temperatures Reinhold Co. Inc., New York. were still warmer compared to the preoperational I surface and bottom mean temperatures. Salinities were significantly lower during the operational period Maine Department of Marine Resources. Boothbay Harbor Environmental Data,1990. West Boothbay Harbor, Maine. 1991. compared to the preoperational period, although long term trends indicate that the decline began in the late I 1980s. Monitoring data collected by the MDMR in 1992. Boothbay Harbor Environmental West Boothbay Harbor, Maine suggest that these Data,1991. West Boothbay Harbor, Maine. I temperature and salinity trends may be typical of the nearshore Gulf of Maine region. However, the change 1993. BoothbayHarbor Environmental in instrumentation in 1990 may have contributed to Data,1992. West Boothbay Harbor, Maine. ; I the observed decline in salinity. Surface dissolved 1994. Boothbay Harbor Environmental oxygen concentrations decreased during the operational Data,1993. West Boothbay Harbor, Maine. I period in response to warmer surface temperatures, w hile operational bottom dissolved oxygen concentra-tions remained similar to preoperational concentrations. Normandeau Associates Inc. (NAI). 1979. Annual in both cases, station differences were consistent over Summary Report for 1977 Hydrographic Studies time, indicating that there was no effect due to plant off Hampton Beach, New Hampshire. Tech. Rep. 1 operation. Nutrient concentrations showed both X-I. Preoperational Ecol. Monit. Stud. for Seabrook temporal and spatial differences, but for each of the Station. five analyzed, the interaction term in the ANOVA model was not significant, indicatirg that observed USEPA (United States Environmental Protection results were not influenced by the operate of %bmnk Agency). 1979. Methods for chemical analyses of water and wastes. EPA-600/4-79-020. EMSL, Station. Cincinnati, OH. 2-23 I
O' O WATER OUALITY TABLE :-5. SUhB1ARY OF POTENTIAL EFFECTS OF SEABROOK STATION ON AMBIENT WATER QUALITY. SEABROOK OPERATIONAL REPORT,1993. OPERATIONAL PERIOD SPATIAL TRENDS Il l l SDIILAR TO RECENT PRE- CONSISTENT WITH b DEPTH OPERATIONAL PERIOD?a PREVIOUS YEARS PARAMETER surface Op> Preop yes Temperature bottom Op> Preop yes surface Preop >Op yes Salinity bottom Preop >Op yes surface Preop >Op yes Dissolved oxygen bottom yes yes surface yes yes Nitrite surface Preop >Op yes Nitrate surface yes yes Ammonia surface yes yes Orthophosphate su face Preop >Op yes Total phosphate I
- based on ANOVA for 1987-1993, when all 3 stations were sampled concurrently bPREOP-OP X STATION term in ANOVA model E
I I I I. I E
- .s
I . I TABLE OF CONTENTS I i PAGE I 3.0 PHYTOPLANKTON
SUMMARY
. . . . .. . .... . . . . . . 3-ii 3-iii i
LIST OF ?IGURES . .. . .. . . . . LIST OF TABLES .. .. .
. .. .. . . 3-iv I LIST OF APPENDIX TABLES . .. .. ... . . . . . . . . 3-iv
3.1 INTRODUCTION
.. .. .. . .. . . . 3-1 t
3.2 METHODS. . . . ... . . . . . . 3-1 3.2.1 Field Methods . . ... . .. . 3-1 3.2.2 Laboratory Methods . . . . . . 3-1 , 3.2.3 Analytical Methods . . . . . . 3-1 1 3.3 RESULTS . . . . . . 3-3 Total Community 33 l I 3.3.1 . ... ,... . . . . . . . l l 3.3.1.1 Phytoplankton . . . 3-3 3.3.1.2 Ultraplankton . . . . 3-13 . 4 3.3.1.3 Chlorophyll a Concentrations 3-13 3-15 l 3.3.2 Selected Species . . . . 3-17 I 3.3.3 PSP Levels l l 3.4 DISCUSSION . 3-17 3.4.1 Community Interactions .... 3 17 3.4.2 Effects of Plant Operation . . . 3-18
3.5 REFERENCES
CITED . . . . .
. . 3-19 I !
I l I I 3-i I
O O' I
SUMMARY
I The phytoplankton community continued to show variability in abundance and community structure during the operational period. Tau of the class Hacillariophyceae (diatoms) generally dominated the community numerically, although in 1992 the Prymnesiophycea Phaeocy3tispouchetii was dominant. Such shifts between diatoms and Phaeocystis were observed during the preoperational period. Total community abundance and abundance of g the selected species (the diatom Skeletonema costatum) increased significantly during the operational period, 3 although chlorophyll a concentrations decreased significantly over the same period. This increase in abundance without a corresponding increase in chlorophyll a concentrations was likely due the high numbers of Phaeocystis g pouchetii, a small-celled form, which was present in exceptionally high numbers in 1992. The phytoplankton 3 community historically has been highly variable in species composition and abundance. This trend has continued during the operational period. I I I I I I' I I I I 3-ii I E
u
. . LIST OF FIGURES .
[: PAGE [.. 1. Phytoplankton sampling stations . . . ......... ............. ......... . . . : 3-2 3-2. Monthly mean Log (x+1) total abundance (no/L) of phytoplankton (;t10 m) at nearfield Station P2, monthly means and 95% confidence intervals over all preoperational years (1978-1984), and monthly means over operational years (1991-1993); and percent composition by major division 3-6 for preoperational and operational periods . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 3-3. Geometric mean abundances (x 10' cells /L) and 95% confidence intervals of annual assemblages, and percent composition of four selected phytoplankton groupings at Station P2 during each year 3-9 of the preoperational and operational periods ...... ..... . ..... ....... ..... 3-4. Monthly mean Log (x+1) total abundance of ultraplankton (<10 m) at Station P2. PS and P7 during
. . ...... .............................. .. 3-9 1993 ..... ..... . .
3-5. Mean monthly chlorophyll a concentrations and 95% confidence intervals at Station P2 over . preoperational years ( 1979- 1989) and monthly means over operational years (199 l- 1993); and mean monthly chlorophyll a concentrations and phytoplankton Log (4+1) abundances during the
.............. 3-14
. preoperational and operational periods . . . . ... . . . ............
3-6. Log (x+1) abundance (no/L) of Skeletonema costatum at nearfield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means for the operational period (1991-1993) and 1993 . .. .. . ..... .. ....... .. .. . 3-16 3-7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor, mean and 95% confidence intervals over preoperational years (1983-1989) and operational years (1991-1993). Data provided by the State of New Hampshire . . . ... . ..... . . . 3-16 L 3-iii
t Q, LJ I LIST OF TABLES PAGE 3-1.
SUMMARY
OF METHODS USED IN EVALUATION OF THE PHYTOPLANKTON COMMUNITY , . . .. .. .... . . . . . . 3-4 3-2. GEOMETRIC MEAN ABUNDANCE (x 10' cells /L) OF PHYTOPLANKTON (210pm) AND SKELETONEMA COSTATUM AND CHLOROPHYLL a CONCENTRATIONS (mg/m') AND COEFFICIENT OF VARIATION (CV,%) FOR THE PREOPERATIONAL AND OPERATIONAL (1991-1993) PERIODS, AND 1993 GEOMETRIC MEANS . .. . 3-7 3-3. ARITHMETIC MEAN ABUNDANCE (x 10' cells /L) AND PERCENT COMPOSITION OF DOMINANT PHYTOPLANKTON TAXA DURING THE PREOPERATIONAL PERIOD (1978-1984), OPERATIONAL PERIOD (1991-1993), AND 1993 AT NEARFIELD STATION P2 ... . 3-10 3-4. RESULTS OF ANALYSIS OF VARIANCE COMPARING ABUNDANCES OF TOTAL PHYTOPLANKTON, ULTRAPLANKTON AND SKELETONEMA COSTA TUM. AND CHLOROPHYLL a CONCENTRATIONS AMONG STATIONS P2, PS AND P7 DURING E PREOPERATIONAL AND OPERATIONAL (1991-1993) PERIODS . .. . . . 3-11 5 3-5. 1993 PHYTOPLANKTON(210 m) ANDULTRAPLANKTON(<10 m)SPECIESCOMPOSITION BY STATION . . . . . .... . . . . 3-12 3-6. GEOMETRIC MEAN ABUNDANCE (10' CELLS /L) AND COEFFICIENT OF VARIATION (CV, %) OF ULTRAPLANKTON AT STATIONS P2, PS AND P7 DURING THE OPERATIONAL PERIOD . . . ... 3-13 3-7.
SUMMARY
OF POTENTI AL EFFECTS (BASED ON ANOVA) OF OPERATION OF SEABROOK STATION ON THE PHYTOPLANKTON COMMUNITY . 3-17 I I LIST OF APPENDIX TABLES l 3-1. A CHECKLIST OF PHYTOPLANKTON TAXA CITED IN THIS REPORT . . 3-20 l l I' 3-iv 5 is
-PHYTOPLANKTON 3.0 PHYTOPLANKTON 10 mL of a modified Lugol's iodine fixative were filled for phytoplankton taxonomic analyses and one gallon
3.1 INTRODUCTION
(3.785 L) was reserved for chlorophyll a analyses. Weekly paralytic shellfish poisoning (PSP) toxicity He phytoplankton monitoring program was initiated levels from mussels collected in Hampton Harbor were _;~ to identify seasonal, annual, and spatial trends in the provided by the State of New Hampshire. phytoplankton community to determine if the operation - of Seabrook Station had a measurable effect on the community. The purpose of the monitoring program 3.2.2 Laboratory Methods is to determine if the balanced indigenous phytoplankton community in the Seabrook area has been adversely Phytoplankton samples were prepared for analysis influenced, within the framework of natural variability, following the steps outlined in NAl (1991). One , by exposure to the thermal plume. Specific aspects randomly-selected replicate from each station and of the community evaluated included phytoplankton sample period was analyzed for all taxa and a second (taxa 2 10 pm in size) abundance and species replicate was analyzed for Skeletonema costatum only. composition; ultraplankton (taxa < 10 m in size) Two 0.1-mL subsamples from each replicate were abundance and species composition; community standing withdrawn and placed in Palmer-Maloney nanoplankton ! crop as measured by chlorophyll a concentrations; counting chambers. For those replicates selected for . abundance of the selected species (Skeletonema taxonomic analyses, the entire contents of the chamber costatum); and toxicity levels of paralytic shellfish were enumerated and identified to the lowest practical > poison (PSP, as measured by concentrations of Alex- taxon. andnum spp in the tissue of the mussel Myrilur edulis) , in the Hampton-Seabrook area. Procedures for preparation of chlorophyll a water , samples followed NAl(1991). Following the extraction of the plant pigment, fluorescence was determined and 3.2 METHODS chlorophyll a and phaeophytin concentrations (pg/L) were computed separately. 3.2.1 Field Methods Near. surface (-I m) water samples for phytoplankton 3.2.3 Analytical Methods and chlorophyll a analyses were collected during daylight hours at Stations P2 (intake). PS (discharge) Members of the phytoplankton community were and P7 (farfield) (Figure 3-1) using an 8-L Niskin classified into two size fractions as defined by Marshall bottle. Collections were taken once per month in and Cohen (1983): ultraplankton (<10 m) and phytoplankton(210 m). Thesegroupswereanalyzed , January, February and December, and twice monthly from March through November. Sampling occurred separately. During the earlier years of the Seabrook at Station P2 from 1978-1984; from 1978-1981 at program, ultraplankton forms were only partially , Station P5; and from 1982-1984 at Station P7. identified (the picoplankton size fraction, or forms <2.0 Chlorophyll a collections resumed at all three stations m in size, were generally not identified). Beginning in July 1986 and phytoplankton collections resumed in the mid-1980s, an effort to identify these smaller in April 1990. These collections continued on this forms was initiated throughout the scientific community schedule through December 1993. From each whole (Stockner 1988). This effort plus use of an improved water collection, two one-quart (0.946 L) jars containing identification technique (phase contrast microscopy) 3-I l
C O N "'*** l 5 J. o
- I-LRTLE
^
~
BOARS > HEAD .-
'.. - . ].
0 .5 1 Nautical Mile , 9 , , FARFIELD l 0 1 2 Kilometers AREA = SCALE '-,~~' CONTOUR DEPTH IN METERS ., o
^
GREAT BOARS , HEAD , HAMPTON ~ ( se lq BEACH
+ . ~.
BROWNS RIVER
\ Dischar ger'
.;-. OUTERf,l gggg SEABROOK STATION 'uf HAMPTON ' a _ , ,7 _l M SEABROOK SUNK -
HARBOR ROCKS __
~~ :hABROOK s .
's, BEACH ,
\
I LEGEND
= phytoplankton stations l I I
I I Egure 3-1. Phytoplankton sampling stations. Seabrook Operational Report,1993. 3-2 E a
f PHYTOPLANKTON h
- was undertaken on this project when phytoplankton preoperational comparisons, the focus was on intaxe cnumeration was re-initiated in 1990. These issues Station P2 due to the greater number of years of data f collection. In all cases the operational pericd evaluated and their impacts on ultraplankton enumerrion were in this report includes collections from 1991-1993.
j- discussed in more detail in NAl (1992b). Since the ( ultraplankton have been enumerated in greater detail during the operational period than during the Weekly mean PSP toxicity levels were arithmetically preoperational period, an impact assessment that relies averageci over the preoperational and operational periods on comparisons between the two periods was not and examined graphically. appropriate. Therefore, analyses focused only on near6cid-far6 eld comparisons during the operational period. 3.3 RESULTS Seasonal abundance patterns of the phytoplankton 3.3.1 Total Community assemblages during the preoperational and operational periods were compared graphically using Log (x+1)- 3.3.1.1 Phytoplankton transformed monthly mean abundances for ultraplank-ton, total phytoplankton and the selected species (Skel- Seasonal Trends at Station P2 clonema costatum; Table 3-1). The Log (x+1) trans-formation was performed on the sample period mean, Monthly abundances during 1993 and the operational prior to calculating monthly means. Temporal (pre- period were within the 95% conGdence intervals operational-operational) patterns in species abundances established for the preoperational period with the were evaluated using geometric means and community exception of January and September (1993 only, Figure composition was evaluated by examining the percent 3-2). The increased abundances in January during the composition of dominant (>l%) taxa. Chlorophyll a operational period consist largely of high counts of temporal and seasonal comparisons were based on chain forming centric diatoms and unicellular alga (NAl untransformed monthly and yearly arithmetic mean 1994). Seasonally, during both preoperational and concentrations. The similarity among the three stations operational periods, the most distinct period of peak with respect to species composition of the dominant abundance occurred in the fall (October) with a smaller phytoplankton taxa was evaluated statistically using secondary increase in early summer (May-June). a multivariate analysis of variance procedure (MANOVA,11arris 1985). Operational /preoperational On average, diatoms (Bacillariophyceae) dominated and near6 eld /farfield differences in total abundances the phytoplankton assemblage during 10 of 12 months ofS. costatum and phytoplankton and mean chiarophyll during the preoperational period, while the Prymnesio-a concentrations were evaluated using a mu:ti-way phyceae taxon Phaeocystis pouchetii dominated during analysis of variance procedure ( ANOVA, SAS '.nstitute, April and May and composed a minor portion of the Inc.1985). The ANOVA model was more conservative assemblage in August (Figure 3-2). This pattern of (more likely to detect signi6 cant differences) than seasonal succession in phytoplankton is well document-l alternative models that treat some sources of vanation cd in other northern temperate coastal waters (Cadee suchasYearasrandom variables. An ANOVA model and IIcgeman 1986; Peperzak 1993). Other groups, was run on ultraplankton abundances as well. but primarily the dinonagellates (Dinophyceae), were included only Year, Month and Station as sources of present in low numbers throughout the summer during variation. Preoperational periods for each analysis are the preoperational period. Seasonal successionduring listed on the appropriate figures and tables. For all the operational period showed a similar pattern, with 3-3
TAllLE 3-1. SUMMAltY OF METilODS USED IN EVALUATION OF Tile PilYTOPLANKTON COMMUNITY. SEAllitOOK OPEllATIONAL ltEPOllT,1993. DATES USED DATA SOUltCE OF ANALYSIS TAXA STATIONS IN ANALYSIS
- CllAllACTEltlSTICS VAltIATION PilY~IOPl.ANKTON Percent Composition All P2 1978-1984; Monthly and annual -
1991-1993 arithmetic mean abund aes P2,P5,P7 1993 Monthly arithmetic mean -- abundances Abundance All P2,P5,P7 1978-1984; Monthly log (x+ 1) and -- 1991-1993 annual geometric mean abundances -- L SAe/etonema co3tatum P2 1978-1984; Monthly log (x+1) and 1991-1993 annual geometric mean abundances MANOVA 15 dominants P2,P5,P7 1993 Monthly log (x+ 1) mean Station abundances; species <l% of tota' abundance not included ANOVA All P2,P7 1982-1984; Monthly log (x+1) mean Preop-Op, Year, 1991-1993 abundances Month, Station Skeletonema costatum P2,P7 1982-1984; Monthly log (x+ 1) mean Preop-Op, Year, 1991-1993 abundances Month, Station P2,P5 1979-1981; Monthly log (x+ 1) mean Preop-Op, Year, 1991-1993 abundances Month, Station M M M M M M M M M M M M M M M M d""YI EE
TAllLE 3-1. (Continued) DATES USED DATA SOURCE OF l ANALYSIS TAXA STATIONS IN ANALYSIS' CllARACTERISTICS VAltlATION ! l Ul!!RAPLANKTON Percent Composition All P2,PS P7 1993 Monthly arithmetic mean - abundances Abundance All P2,P5,P7 1991-1993 Monthly log (x+1) and - annual geometric mean abundances All P2,P5,P7 1991-1993 Monthly log (x+ 1) mean Year, Month, ANOVA abundances Station Y Clli.OROPilYLL a P2 1979-1989; Monthly aritlunctic mean - Concentration -- 1991-1993 concentrations l P2,P5,P7 1978-1984; Annual arithmetic mean -- 1987-1989; concentrations 1991-1993 P2,P5,P7 1987-1989; Monthly arithmetic mean Preop-Op, Year, ANOVA -- 1991-1993 concentrations Month, Station
-- 1983-1989; Weekly arithmetic mean --
PSP TOXICITY -- 1991-1993 concentrations
'PREOPERATIONAL PEIUOD: B. CllLOROPilYLL
- A. PilYTOPl.ANKTON P2 = 1978-1984, 1987-1989 P2 = 1978-1984 P5 = 1978-1981, 1987-1989 P5 = 1978-1981 P7 = 1982-1984, 1987-1989 P7 = 1982-1984 OPERATIONAL PERIOD: 1991-1993, all stations and parameters
L,. r7 u Phytoplankton: Total Abundance 4.5 - :- - E
.......... op.,m .:
; g
,,, --.-- 1993 e3 f k, W .
/ s.
V ss-s ....... ...- - .... g y Y,N, je s B , }<
>g s
' r,
%..,a f
. %; q','
>~.
w 4.5 - i s 2 H =
; 40-Y
'"',s, 3.3 - 3:0 i i . . . i i i i i i i FEB MAR APR MAY JUN jut. AUG $EP OCr NOV DEC JAN MONTH I Phytoplankton: Preoperational Percent Composition (1978-1984)
'" = = = - = = = = = m m =
's's',
i's',' 's 's ',, !s'/ :::::: 's',f s !s ',', s's's' 's's's fs's', s's's' 's ',' c 's 's ', r 80 - ',f s's' 's's's !s's :::::, 's',', !s'6 s's's' 's','s f6!, s's's' 's's's
!/6 //s' ?,! 6 6!,,' 's ' / s f//,
d i '//s !s's tt ; '.!./r 's'/s 2 '../6,'s' '//s /// :: ' :::::: !/6 s'// '//r !//, ,f// '//c '//,
'//,
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so ,. '//s' s's' '//s "
,// :: :: ::tt:0 f/6 n!/ '//s f/6 o!// '//c s '//s !!/ :::::: :::::: !/6 //s' '//s ?6!, ///
///
'//c '//,
f//, 2 #- i'/s' '//,, !,!? :::::: :::tt //6 ,f / / 'J/s f/6 '//c i'/s' 's'/s /// :::::: ::::: !/6 //s' *//s !/6 ///
///
'//c '//,
'//,
9" 10 ' /,f s' '//, !!/ :::::; t tttt !/6 /// '//s !/6 '//c
# '//s' '//s /// ::::: ::::: m
'/6 /// M 4r
=
f/6
, '//c
$, .. , . , . m
'//,
M M' ', ' /, ,' //. ??'??? i i i . . . i i i e i i JAN IT.B MAR APR MAY JUN JUI. AUG SEP OCr NOV DEC MONTH Phytoplankton: Operational Percent Composition (1991-1993) t n - rry r 7r m r- r rr m r, m rr, ,,,
*//, ?//, M % ?//, /// '//E '//s *// '/// //s ?//
Z '
. '/ /, :: ;;; ::: :: .'//, /// '//l '//. *// */// '//s ?,'/
go , '//, ?// P. //, ?/,', :::::: ::: :: ?//< /// '/// '//. '//
'//
'///
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'//s
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be ?//, ::: ; :: ? ' ?//. /// ','// '//. 60 - 'w//, ,w, :::::: ::::g f,t ppf ffj spp, spp ffj 'w//s , pff
'2 W,
.W. :::: : ' :::: W, /// W/ .Ws W '/// Ws ?//
x e- w, .W. :::::: :::::: -
/// ws w. W /// Ws ?//
g W, .W. :::: ' :::::: /// Wi W.
'/// Ws w,
,W w, 3, , . :::::: :::::: /// , /,. w. ///
jfj w,
?//
pff p 20 - w, yj,\ ;;;;;; ::: :: fff M s - ss3 W. n
... ?//. ::t::: ::tt:0 y,,,, 3'.' M.. 9// @
i i e i i i e i i a i i IT.B MAR APR MAY JUN JUL AUG SEP OCr NOV DEC JAN MONTH g B.ca.nopay== cy... pay. . [ chino,ny -- D opny . E chrv acav= = m prymn ony . E crra'ararc - l Figure 3-2, Monthly mean log (x+1) total abundance (no/L)of phytoplankton (210 m) at nearfield Station P2, monthly means and 95% confidence intervals over all preoperational years (1978-1984), and monthly means over operational years (1991-1993); and percent composition by major division for preoperational and operational periods. Seabmok E Operational Report,1993. 5 3-6 5 E
1 PHYTOPLANKTON L' l diatoms dominant in all months except March and April, age the operational geometric mean abundance ( 166,400 ( cells /L) was higher than the preoperational mean L when P. poucherii was dominant. The dominance of abundance (l 19,000 cells /L; Table 3-2). This was due P. pouchetii in operational averages was due to the extremely high numbers encountered in 1992 (an in large part to the high annual mean abundance during (- average ofover 3 million cells /L over the four sample 1992 (334,800 cells /L), which was higher than in any dates on which it was present; NAl 1993a). This is individual preoperational year (Figure 3-3). The in contrast to a nearly complete absence of P. pouchetii geometric mean abundance in 1993 (104,400 cells /L) was the lowest of the operational period (Table 3-2), in 1991 (NAl 1992b) and 1993 (NAl 1994). and lower than in five of the seven preoperational years (Figure 3-3). Amone-Year Trends at Station P2 Based on historical data, the annual phytoplankton Phytoplankton abundances at Station P2 showed large community at Station P2 can be divided into four major shifts from year-to-year throughout both the preopera- components: Skeletonemacostatum(Bacillariophyceae), tional and operational periods (Figure 3-3). Although all other diatom taxa, Phaeocystis pouchetii, and all some preoperational years had higher annual geometric remaining taxa. Although these groupings are descrip-mean abundances than some operational years, on aver- tive of both the preoperational and operational periods, l TABLE 3-2. GEOMETRIC MEAN ABUNDANCE (x 10* cells /L) OF PHYTOPLANKTON .' ( 2: 10pm) AND SKELETONEMA COSTATUM, AND CHLOROPHYLL a CONCENTRATIONS (mg/m') AND COEFFICIENTOF VARIATION (CV,%) FOR T f THE PREOPERATIONAL AND OPERATIONAL (1991-1993) PERIODS, AND 1993 GECMETRIC MEANS, SEABROOK OPERATIONAL REPORT,1993. PREOPERATIONAL OPERATIONAL 1993 STATION I* CV (YEARS)* I* CV I PHYTOPLANKTON ' P2 11.86 4.79 (78-84) 16.64 5.13 10.44 P5 12.60 3.97 (78-81) 22.36 5.54 13.13 P7 9.94 4.32 (82-84) 13.72 3.99 8.31 SKELETONEM4 COSTA TUM P2 0.23 44.23 (78-84) 0.77 33.56 0.43 P5 0.11 68.95 (78-81) 0.53 41.21 0.21 P7 0.24 36.95 (82-84) 0.46 41.07 0.18 CHLOROPHYLLa P2 0.78 68.13 (87-89) 0.72 57.62 0.52 P5 0.88 70.81 (87-89) 0.78 62.67 0.55 P7 0.75 63.38 (87-89) 0.72 58.58 0.48
'Mean of annual means.
*( ) = preoperational years.
3-7
O. O, PITYTOPLANKTON the relative importance of each group or species, as All remaining species accounted for 5-6% of both well as individual abundances, varied considerably on the preoperational and operational assemblages and a year-to-year basis (Figure 3-3). 1% of the 1993 assemblage (Table 3-3). Prorocentrum , micans (Dinophycea) accounted for slightly more than Diatoms (including Skeletonema costatum) as a group 1% of the preoperational assemblage, and Cryptomonar composed approximately 77% of the preoperational sp. (Cryptophyceae) accounted for about 2% of the assemblage (532,000 celis/L),60% of the operational operational and 1993 assemblages. All other taxa assemblage (329,400 cells /L), and 93% of the 1993 composed less than 1% of total abundance over both assemblage (273,500 cells /L; Table 3-3). Skeletonema periods and in 1993 (Table 3-3). costatum alone accounted for 35% of the preoperational assemblage,22% of the operational assemblage, and 23% of the 1993 assemblage. Within the preoperational Spatial Trends period, the relative abundance of Skeletonema costatum varied from 5% in 1983 to 80% of total abundance Phytoplankton abundance and community composi- g in 1980 (Figure 3-3). Within the operational period, tion were evaluated in the near6 eld (Stations P2 and g the relative abundance o fSkeletonema costatum varied P5) and far6 eld (Station P7) areas to determine whether from 17% in 1991 (N Al 1992b) to 26% in 1993. The historical spatial relationships were maintained during g remaining diatom taxa accounted for 42% (288,400 the operational period. Preoperational geometric mean 5 cells /L) of the preoperational assemblage (Table 3-3), abundances were similar between Stations P2 (1978-ranging from 16-17% in 1980 and 1983 to 70% in 1979 1984) and P5 (1978-198I; Table 3-2), while (Figure 3-3). abundances at Station P2 were higher than abundances at P7 (1978-1982). Abundances at each station were Diatom taxa other than Skeletonema costatum that higher during the operational period compared to the were important during the preoperational period were preoperational period, although 1993 abundances w ere Chaetoceros spp. and Rhi:osolenia delicatula/ siinitar to preoperational abundances. Spatial fragdissima(each at 14% over the period; Table 3-3). differences during the operational period paralleled These taxa were less important during the operational those that existed during d < preoperational period period and in 1993 (approximately 7% during both (Table 3-2). periods). The two Leptocylindrus taxa combined were more abundant in the operational period and in 1993 Operational abundances were signi6cantly greater (13- 15%) compared to the preoperational period ( 1.5%). than preoperational ( 1982- 1984) abundances over Sta- g Asterionella glacialis was present in 1993 and composed tions P2 and P7 combined (Table 3-4). In addition, g 21% of the assemblage. This species, however, did abundances among individual years, months, and not occur above 1% of total abundance during any other between the two stations (P2 > P7) were signi6cantly g year. different (Table 3-4). However, these differences were 5 consistent regardlessofoperationalstatus,asindicated Phaeocystis pouchetii abundances varied over a wide by the non-signi6 cant interaction term, indicating no range during the preoperational period, ranging from apparent effect on abundances due to the operation less than 1% in 1982 and 1984 to 76% in 1983 (Figure of Seabrook Station. 3-3). Although this species accounted for 33% (181.300 cells /L) of the operational assemblage, it accounted Groups of taxa or individual taxa composed similar for less than 1% of the 1991 and 1993 assemblages proportions of the total assemblage among the three (Figure 3-3). stations in 1993 (Table 3-5). Diatoms as a group com- , 3-8 E
=
t w
.) -g' -
33 ., ('
>0 -
a 2s 4 E~ 20 - 13 - 10 - [ s 3= 0 U 1978 1979 1980 1981 1982 1983 1984 1991 1992 1993 PREOPERATIONAL YEARS OPERATIONAL YEARS g 80 aae 3 , T gg;g 3 70 - we . - - - - h
. g ,, # 6f V: .
.' W .' y
*f - TV .L '. M i My $p*$
s; 50 -
@Mr SY*,
2 N g 30 ~" a!^6 n m .h? 1%$
%d &d Tu $l5 rt @ ., $
0*~"h 8 Wg T@ #%V . N ; 58 % Wi; " $$ 20 spM- . 10 ~ cy' r-9 r, p++ N~ ^ ^ wr ~ -*nt +n a',','. 'M ^
=-
# . . . i . .
a 4 a 1981 1982 1983 1984 1991 1992 1993 1978 1979 1980 PREOPERATIONAL YEARS OPERATIONAL YEARS 0 Bacillatiophycesc ;; Skeletonema cestatum Phaeocystis pouchetii
@ Other Figure 3 3. Geomen.; taean abundances (x 10' cells /L) and 95% confidence intervals of annual assemblage, and percent composition of four selected phytoplankton groupings at Sta* ion P2 during each year of the preoperational and operational periods. Seabrook *.
Operational Repert,1993. (- [ Ultraplankton: Total Abundance ( y w 8.0 - saa n g 7.3 ., . ...... ... Staum P5 z .......... simum n
- a
- m. 7.0 -
<u . x.-::: ~v.. . . .. . . . . . ...... ~~~
rs -
'^
. ~ ~' - , ,f ' ' -
,, A. 3 ... . .
x- .. s.O - [ "
- 5.3 -
9
*' i . .
5.0 . . . . . i 1 i [ JAN FEB MAR APR MAY JUN It*l. At U SEP OCT NOV DEC MONTH Figute 3-1. Monthly mean log (x+1) total abundance of ultrrplankton (<10pm) at Stations P2, P5 and P7 dunng 1993. Seabrook Operational Repo't.1993. 3-9
T ADLE 3 3. ARITIIMETIC MEAN ADUNDANCE (a 10' cells /LJ Aht) PERCENT COMPOSITION OF DOMINANT PilYTOPLANKTON TAXA DURING Tile PREOPERATIONAL PERIOD (1978-19841 OPERATION AL PERIOD (1991-1993), AND 1993 AT NEARFIELD STATION P2. SEADROOK OPERATION AL REPORT.1993. PRIOPERATIONAL OPERATIONAL 1993 PERCENT PERCENT PERCENT CLASS TAXON ABUNDANCE
- COMPOSITION ABUNDANCE
- COMPOSITION ADUNDANCE* COMPOSITION Dmophneae frurocentrum neecons 0 79 1.15 0 18 <l 00 <0 01 < l 00 Cryptophyceae Crjpac=unas spp <0 05 < l 00 1 10 2 02 0 69 2.35 Prymnesiophyceae riscucistes pouchere, 11 80 17 09 18 13 33 34 0 03 < 100 Bacillarwaphycese Daciliariophgeae 0 77 1.11 0 92 1 69 0 57 I 94 Asterronella glacsohs 0 05 < l .00 2 07 3 80 6 20 21 01 Ceronaufma bergom: 0 95 1.39 0 00 <l 00 0 00 0 00 Chaeroceros debdis 2.12 3 08 0 33 < l .00 0 ris < l 00 Chaeroceros decepiens 0 02 <lM 0 60 1.10 006 1.22 g
s Chaeroceros sorsahs 6 50 9 45 1.28 2.35 0 "s4 1.16 1 19 1 74 l.87 3 45 r.23 4 19
$ Chueroceros spp 0 07 <l .00 0 82 1.51 0 85 2 88 C3/adrotheca classer...
Leprocstmdrus damcus 0 40 <l 00 3.70 6 80 3 37 II 44 Lepsocyhndrus mmimus 1 00 1 46 3.54 6 51 1.22 4.15 Net:schea spp 3.20 4 65 2 41 4 43 2 56 8 69 Routzusolema dehcarula'frogshssmea 9 89 1438 1 72 3 17 I .S 5 $.2$ SAelesenema costarum 2435 35 41 18.96 21 99 7 62 25.82 Thalasssonema marschnoides 1.33 1 94 0 94 1 73 0 64 2.17 Thalassrosera spp I 89 2.74 I II 2 04 0 84 2 85
*Mean 6+ lance over all yearts) in each persod, specms accountmg fa cl% of total abundance not presented, therefore percent compositum as showr +e sum to 100 M M M M M M M M M M M M ME
PHYTOPLANKTON
. TABLE 3-4. RESULTS OF ANALYSIS OF VARIANCE COMPARING ABUNDANCES l OF TOTAL PHYTOPLANKTON, ULTRAPLANKTON AND SKELETONEMA i
{ CMTA7TM, AND CHIDROPHYLL a CONCENI' RATIONS AMONG STA'I1ONS P2, P5 AND P7 DURING PREOPERATIONAL AND OPERATIONAL r (1991-1993) PERIODS. SEABROOK OPERATIONAL REPORT,1993. L
- MULTIPLE df MS F COMPARISONS
{ SOURCE OF VARIATION PHYTOPLANKTON: P2 VS P7 (PREOP = 1982-1984; OP = 1991-1993)* Preo Op' 1 0.69 27.96 "
- Op> Preop I.. Yea Preop-Op 4 1.36 54.71 ' " 1 L- Mont 66 0.59 24.04 " * <
Station Preop-Op X Station' (Yearf )* 1 I 0.26
<0.01 10.57 "
0.00 NS P2>P7 Error 70 0.02 CHLOROPHYLL a: P2, PS, P7 (PREOP = 1987-1989; OP = 1991-1993)* Preop-Op' I 0.23 4.53
- Preop >Op Year (Preop-Op)* 4 1.13 22.39 * "
Month (Year)' 66 0.61 11.97 "
- Station 2 0.19 3.74
- P5>fif.7 l Preop-Op X Station' 2 0.02 0.46 NS i Error 140 0.05 SKELETONEMA COSTA TUM: P2 VS. P7 (PREOP = 1982-1984; OP = 1991-1993)* j Preo Op' 1 4.96 11.10 " Op> Preop I
Yea Preop-Op)* 4 3.31 7.42 '" Mont (Year)d 66 2.89 6.4 8 * " Station 1 0.71 1.60 NS Preop-Op X Station' 1 0.23 0.52 NS Error 70 0.45 SKELETONEMA COSTA TUM: P2 VS. PS (PREOP = 1979-1981; OP = 1991-1993)' 19.54 "
- Op> Preop l Preop-Op' I 9.26 Year (Preop-Op)' 4 2.76 5.82 * *
- Month (Year)d 65 5.05 10.65 * "
Station i 1.07 2.25 NS Preop-Op X Station' I <0.01 0.02 NS Error 69 0.47 ULTRAPLANKTON: P2, PS, P7 (Operational period only, 1991-1993) Year 2 0.37 9.52 *" 93 91>92 Month (Year / 33 0.43 11.10 * " { Station Year X Station' Error 2 4 66 0.03 0.08 0.04 0.79 NS 2.14 NS
'ANOVA based on mean of twice-monthly collections Mar-Nov and monthl'v collections Dec-Feb; only years when coflections at these stations were concurrent are included; analyses include only years when all 12 months were sampled.
'Preoperational versus operatinral period regardless of station.
' Year, regardless of preop-op.
dMonth nested within year regardless of station or year. I
' Interaction between mam effects.
NS = not significant (p 2 0.05)
" = hichly sigm,0.05 > p 20.01)* = significant ( ficant10.012 p >0.001)
"* = very~ highly significant (0.0012 p) 3-11
O O PHYTOPLANKTON TABLE 3-5. 1993 PHYTOPLANKTON (210pm) AND ULTRAPLANKTON (<10 m) SPECIES COMPOSITION BY STATION. SEABROOK OPERATIONAL REPORT,1993. CLASS TAXA P2 PS P7 PHYTOPLANKTON* Cryptophyceae Cryptomonas sp. 2.35 1.88 2.56 Chroomonas sp. 3.73 2.59 2.62 Bacillariophyce Asterionella glacialis 21.01 23.89 25.85 Bacillariophyceae 1.94 2.75 2.51 Chaetoceros debilis < l .00 l.04 < l .00 l Chaetaceros decipiens l .22 < l .00 2.99 E Chaeroceros socialis 1.I6 2.25 1.46 Chaetoceros sp. 4.19 3.40 3.38 g Cylindrotheca closterium 2.88 2.95 2.73 g Leptocylindrus danicus 11.44 10.27 8.'i5 Leptocylindrus mmimus 4.15 7.98 o.55 Nitzschia sp. 8.69 8.19 6.93 Rhi:osolenia delicatula/fragilissima 5.25 4.F2 6.70 Skeletonema costatum 25.82 2'.01 21.29 Thalassionema nit:schioides 2. l 7 2.39 1.93 Thalassiosira spp. 2.85 .).44 2.24 ULTRAPLANKTON' t Chlorophyceae Alga; Flagellate 2.97 2.18 2.22 Alga; Unicellular 18.96 20.19 20.02 Dinophyceae Oxytorum sp. 0.63 0.50 0.45 Cyanophyceae Cyanophyceae; Total' 73.71 74.54 74.69
' Presents only taxa accounting for 21% of total abundance "All ultraplankton taxa presented
, ' Includes colonials and filamentous forms posed 93-94% of total abundance at each station. debilis occurred only at Station PS, while Chaetoceros Cryptomonas sp. was the only other taxon present at decipiens occurred at P2 and P7 but not at P5 (Table any station in amounts greater than 1% of the total, 3-5). Overall, the abundances of the 15 numerically B composing approximately 2 to 2.5% of total abundance. important taxa (Table 3-3) were not significantly 3 ( A similar assemblage was present at each station in different among the three stations in 1993 (p = 0.35, ! 1993. The only differences were that Chaetoceros Wilkes' Lambda as computed by the MANOVA). l l 3-12 I E
I PHYTOPLANKTON l Ultraniankton For reasons discussed in Section 3.2.3, it was not 3.3.1.2 possible to test preoperational-operational differences in the ultraplankton community. However, the lack l I Monthly Log (x+ 1 ) mean ultraplankton abundances at Stations P2, P5, and P7 were similar in 1993, and exhibited a weak seasonal pattern at each station (Figure of nearfield-fardeld difTerences in the ultraplankton assemblage indicates that there was no effect caused 3-4). Annual geometric mean abundances were similar by Seabrook Station. among the three stations throughout the operational period (Table 3-6). Abundances were lowest in 1992 at each station, a trend that was opposite that in 3.3.1.3 Chloronhvil a Coneentrations phytoplankton abundances (Table 3-2). A one-way analysis of variance (ANOVA) confirmed that During both the preoperational and operational ultraplankton abundances were not significantly different periods, monthly arithmetic mean total chlorophyll a among the three stations during the operational period concentrations exhibited an early spring peak, mid-sum-(Table 3-4), and that abundances in 1991 and 1993 mer decline, and late fall peak. Monthly mean opera-were significantly greater than abundances in 1992. tional concentrations were lower than preoperational l concentrations in all months, and below the lower 95% l The ultraplankton assemblage was similar among confidence limits of the preoperational means in June, the three stations in 1993 (Table 3-5). As in 199I and October and November (Figure 3-5). The 1993 monthly I 1992, Cyanophyceae were overwhelmingly dominant mean concentrations were less than preoperational lower at each station (approximately 75% of the assemblage), 95% confidence limits in February, June. October, and followed a similar seaso .al pattern of occurrence November and December, j at each station (NAl 1992a,1993a,1994). I l TABLE 3-6. GEO31ETRIC 51EAN ABUNDANCE (10' CELLS /L) AND COEFFICIENT OF VARIATION (CV, %) OF ULTRAPLANKTON AT STATIONS P2, PS AND P7 E g DURING TiiE OPERATIONAL PERIOD. SEABROOK OPERATIONAL REPORT,1993. l STATION l P2 PS P7 YEAR SIEAN CV 31EAN CV S1EAN CV f 199l* 355.93 6.04 293.91 7.15 294.88 5.59 1992* 188.42 8.90 190.37 8.45 284.92 8.21 l 4.06 339.1I 2.94 1993* 288.88 2.91 380.22 I OP MEAN* 268.58 2.19 277.09 2.36 305.42 0.62
' Annual means me means of monthly means. n = 12.
" Operational means are means of annual means. n = 3.
l 3-13 l
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! Figure 3-5. Mean monthly chlorophyll q con:entrations and 95% confidence intervals at Station P2 over preoperational years (1979 1989) and monthly means over operational years E (1991 1993); and mean monthly chlorophyll a concentrations and phytoplankton log 3 (x+1) abundances dunng the preoperational and operational periods. Seabrook Operational Repon.1993. 3-14 g
+ E l PHYTOPLANKTON , [ l Chlorophyll a concentrations at each station declined 3.3.2 Selected Species
- h. slightly (by 0.03 to 0.1 mg/m') during the operational period (Table 3-2). Over the three stations combined, Skeletonema costatum was chosen as a selected operational mearmoncentrations were significantly lower species because of its historic omnipresence and p overwhelming dominance during much of the year, L than preoperational means (Tabie 3-4). Throughout the entire study, chlorophyll a concentrations were At Station P2, peak abundances generally occurred in higher at Station P5 than at Stations P2 and P7, and the spring and fall during the preoperational period differences between P2 and P7 were not significant (Figure 3-6). During the operational period both the (Tables 3-2 and 3-4). Since the relationship of spring and fall peaks were larger but followed the same general seasonal pattem of the preoperational period. .i chlorophyll a concentrations among the stations remained the same during both the preoperational and Operational mean abundances were higher than operational periods, the interaction between the main preoperational means in all months except September, and exceeded preoperational upper 95% confidence
{ effects of operational status and str.cien was not sig-nificant (Table 3-4). limits during January and April. In 1993,S. costatum l abundances generally followed historical patterns, except On an annual basis, chlorophyll 2 corcentrations that the January mean abundance was higher than and phytoplankton abundances appear to be inversely typically observed, and the April mean abundance was related, rather than directly related as expected. much lower than typically observed. A small August Chlorophyll a concentrations declined between the peak was also present in 1993 (Figure 3-6). preoperational and operational periods at each station, while phytoplankton abundances increased (Table 3-2). Like phytoplankton abundances, abundances of ,, The decline in chlorophyll a concentrations was Skeletonema costatum increased during the operational statistically significant. The differences observed in period at each station (Table 3-2). S. costatum trends between phytoplankton abundances and abundances were evaluated in two separate ANOVA chlorophyll a concentrations were likely due to tests since all three stations were not sampled differences among taxa with respect to cell size and concurrently during the preoperational period chlorophyll a content. For example, during 1992 (particularly Stations P5 and P7; Table 3-2). For both phytoplankton abundances were higher than during tests (P2 versus P7 and P2 versus PS), operational abun-any other year of the study, primarily due to the dances were significantly greater than preoperational presence of Phaeocystispouchetii on only a few dates abundances, and there were significant differences (Figure 3 3). While P. pouchetii had a large effect among individual years and among months (Table 3-4). on phytoplankton abundances, it had only a minor effect No differences in abundances were detected between on chlorophyll a concentrations (NAl 1992b) since the nearfield (Station P2) and the far6 eld (Station P7) it is a small-celled taxon (Lee 1980). Evidence for areas or between Stations P2 and P5 in the nearfield the relationship between chlorophyll a concentrations area. The interaction of main effects was not significant and phytoplankton abundances exists in the comparison for either pairing, thus preoperational-operational of seasonal patterns. Preoperational and operational differences were unrelated to the operation of Seabrook chlorophyll a concentrations followed a pattern similar Station (Table 3-4). b to that of phytoplankton abundances during the same periods (Figure 3-5). 3-15
O
, Skeletonema costatum: Aburdanc2 0 8.0 - 7 ,
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.......... opersuonal N --o-- 1993 6.0 - J M )\ N
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" 4 4 . I . . i e i i i i 3 JAN FEB MAR APR MAY AJN JUI. AtJo SEP OCr NOV DEC MONTH Figure 3-6. Log (x+1) abundance (no./L) of Skeletonema costanun at neadield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means for the operational period (1991 1993) and 1993. Seabrook Operational Report,1993.
PSP Toxicity Levels
,w - 7 ,
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i i i i i i s -y ;, e - --( i i i i i i . .. i i i i i i f 5 i i i i i i i 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 MAY JUN JL'L AUG SEP OCT NOV DEC APR WEEK / MONTH C.L = closure level of 80 ng PSPn00 g meat D L = method deteccan tirrut of 44 PSP /100 mg mesi No PSP detected in 1992 Figure 3 7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mynlus edulis in Hampton Harbor, meais and 95% confidence intervals over preoperational years (1983-1989) and operational years (1991-1993). Data provided by the State of New Hampshire. Seabrook Operational Report.1993. 3-16 5 a
1 PHYTOPLANKTON l assemblage were similar between the preoperational l 3.3.3 PSP Levels [ PSP toxicity leve!s were above the detection limit and operational periods, although phytoplankton abundances increased significantly during the of44 g PS P/100 g tissue of the mussel Mytilus edulis operational period (Table 3-7). The phytoplankton [ and above the closure limit of 80 pg PSP /100 g tissue during the late spring, early summer and late summer assemblage was dominated by diatoms (Bacillario-phyceae) both annually and seasonally during both during the preoperational period (Figure 3-7). PSP periods. In some years, however, the Prymnesiophyceae toxicity was rarely detected during the operational species Phaeocystis pouchetii accounted for as high period, however. In 1991, the State of New Hampshire a proportion of the community at each station as did recorded only two occurrences of PSP levels above total diatoms (Figure 3-3). On average, P. poucherii p composed a greater proportion of the operational L' the detection limit, and these measured only 45 g/ 100 g (NAl 1992b). No PSP toxicity was detected assemblage (33%) than the preoperational assemblage in 1992 (NAl 1993b). In 1993. PSP levels registered (17%; Table 3-3), due sole ly to its presence during above the 80 pg/100 g tissue closure level in May and the spring of 1992. With the exception of P. pouchetii, June. The widespread occurrence of PSP toxicity in the group of taxa that accounted for the majority of the coastal areas of northern New England (NAl 1993b) the community changed little between the preoperational indicates that the occurrence of PSP toxicity in the and operational periods (Figure 3-3). On a year-to-year project area was unrelated to the operation of Seabrook basis, however, assemblages differed considerably. Station. For this reason, the phytoplankton study included an j analysis of parameters that were expected to be more predictable indicators of community status than species DISCUSSION composition, such as the abundance of the selected ( 3.4 species (Skelefonema costatum), or total biomass as j estimated by chlorophyll a concentrations. Like total l 3.4.1 Community Interactions ( The seasonal pattems of total abundance and the phytoplankton abundance, the annual mean abundance ofS. costatum increased during the operationai period. occurrence of dominant taxa in the phytoplankton Seasonal patterns between the two periods remained l j TABLE 3-7.
SUMMARY
OF POTENTIAL EFFECTS (BASED ON ANOVA) OF OPERATION OF SEABROOK STATION ON THE PHYTOPLANKTON COMMUNITY. SEABROOK i' OPERATIONAL REPORT,1993. [ OPERATIONAL PERIOD DIFFERENCES BETWEEN OPERATIONAL AND PRE-SIMILAR TO PREOPERA- OPERATIONAL PERIODS [ COMMUNITY ATTRIBUTE TIONAL PERIOD? CONSISTENT AMONG STATIONS? Phytoplankton Op> Preop yes ( Skeletonema costatum Op> Preop yes i Chlorophyll a Preop >Op yes 3-I7 I
O O PHYTOPLANKTON similar, and no nearfield/farfield differences in abun- 1992a). With few exceptions, PSP has been recorded dance were detected (Table 3-4). Although annual seasonally in this region of the western Gulf of Maine ever since, although not always at toxic levels. It is mean chlorophyll a concentrations declined significantly 5 during the operational period, on a monthly basis currently thought that Alexandrium spp. blooms are 3 chorophyll a concentrations did closely track transported to this region on coastally-trapped buoyant phytoplankton abundance. The overall increase in plumes derived from the Androscoggin and/or Kennebec phytoplankton abundance without a corresponding Rivers (Maine)(Franks and Anderson 1992a). This increase in chlorophyll a concentrations may be due theory is consistent with the generally observed north-to the large number of small P. poucherii cells in 1992 to-south seasonal progression of occurrence of this dino-collections. Dagellate and the PSP levels (Franks and Anderson 1992b). Local sources of dino0agellates may also There were no significant interactions between contribute to the blooms as well. Thus, occurrences operational status and station for total phytoplankton of PSP toxicity in New Hampshire have been associated abundance, Skeletonema costatum abundance, or with larger regional occurrences in southem Maine and chlorophyll a concentrations (Table 34). This indicates northern Massachusetts, and are not a localized , that the operation of Seabrook Station has had no occurrence. measurable effect on these aspects of the phytoplankton community. 3.4.2 Effects of Plant Operation ne focus of the investigation of the ultraplankton assemblage was an examination of nearfield-farfield Be phytoplankton community varied both temporally differences during the operational period, as identifi- and spatially during the whole of the study period. cation techniques and information availability The high variability in density levels and community E substantially im proved after preoperational collections structure from year-to-year was due to the inDuence E ended in 1984. During 1993, the ultraplankton of both physical and chemical factors, some cyclical assemblage w as domimted by Cyanophyceae, particular- and some transitory, and to the rapid tumover rate of ly colonials (Table 3-5). Percent composition of each phytoplankton populations. Thus,it has been difficult of the ultraplankton taxa, and the seasonal occurrences to succinctly describe the long-term temporal of total abundances, were similar among the three sta- community structure (NAl 1985). However, all tions. Other studies conducted in the Gulf of Maine documented characteristics of the phytoplankton indicated that these forms were prominent throughout community in the vicinity of Seabrook Station indicate the region during both the preoperational and that, although some community changes occurred over operational periods (Shapiro and Haugen 1988; Haugen time, these changes occurred at all three stations. In 1991). some cases (i.e. the apparent increase of certain Cyanophyceae forms), these changes w ere widely docu-Only minor occurrences of PSP toxicity have been mented in the Gulf of Maine. Therefore there is no documented in the study area during the operational evidence indicating that the operation of Seabrook E period. The occurrence of PSP toxicity in this portion Station had a measurable or detrimental effect on any g of the Gulf of Maine was Orst documented in 1972 aspect of the local phytoplankton community. (N Al 1985), possibly as the result of the transpon of g the PSP-producing dinonagellate Alexandrium spp 3 (formerly called Gonyaular sp.) from the Bay of Fundy following Hurricane Carrie (Franks and Anderson 3-18 5 m
PHYTOPLANKTON 3.5 ' REFERENCES CITED .1993b. Seabrook Environmental Studies, 1992. A characterization environmental conditions ( in the Hampton-Seabrook area during the operation Cad 6e, G.C. and J. Hegeman. 1986. Seasonal and of Seabrook Station. Tech. Rep. XIV-1. annual variation in Phaeocystispouchetii(Haptophy-( ceae) in the westemmost inlet of the Wadden Sm during the 1973 to 1985 period. Neth. J. Sea Res.
.1994. Seabrook Environmental Studies.
Unpub.1993 Data. 20(1):29-36. Franks, P.J.S. and D.M. Anderson.1992a. Alongshore Peperzak, Louis. 1993. Daily irradiance governs gr wth rate and colony formation of Phaeocystis ; transport of a toxic phytoplankton bloom in a (Prymnesiophyceae). J. Plank. Res. 15(7):809-821. buoyant current: Alexandrium tamarense in the Gulf j ( of Maine. Mar. Biol. I12:153-164. .. SA$ insnrute Inc.1985. SAS User's Guide: Statistics, Version 5 edition. SAS inst.,Inc. Cary, N.C. 956 j Franks, P.J.S. and D.M. Anderson. 1992b. Toxic PP- l phytoplankton blooms in the southwestem Gulf of Maine: testing hypotheses of physical control using . Shapiro, L.P. and E. M. Haugen. 1988. Seasonal historical data. Mar. Biol. I12:165-174. distnbution and temperature tolerance ofSprechococ. cus in Boothbay Harbor, Maine. Estuar. Coast. Shelf Harris, R.J.1985. A primer of multivariate statistics. Sci. 26:517:525. Acad. Press, Orlando. 575 pp. Stockner, J.G.1988. Phototrophic picoplankton: an Haugen, E.1991. Unpublished phytoplankton data ( filed with MWRA, Deer Island otTshore outfall overview from marine and freshwater ecosystems. Limn 1. Oceanogr. 33:765-775. monitoring studies,1990. Lee, R.E.1980. Phycology. Cambridge University Press, New York. 478 pp. ( Marshall, H.G. and M.S. Cohen.1983. Distribution and composition of phytoplankton in nonheastern coastal waters of the United States. Estuar. Coast. l and Shelf Sci. 17:119-131. l { Normandeau Associates Inc. 1985. Seabrook Environmental Studies,1984. A characterization r L of baseline conditions in the Hampton-Seabrook Area,1975-1984. Tech. Rep. XVI-il. 1991. Seabrook Environmental St>: dies. ( 1990 Data Report. Tech. Repon XXII-1. 1992a Seabrook Environmental Studies. ( Unpubl.1991 Data. 1992b Seabrook Environmental Studies, f 1991. A characterization ofenvironmentalconditions in the Hampton-Seabrook area during the operation of Seabrook Station. Tech. Rep. XXill-l. 1993a. Seabrook Environmental Studies. Unpubl.1992 Data. 3-19
O_ a~ PHYTOPLANKTON APPENDIX TABLE 3-1. CHECKLIST OF PHYTOPLANKTON TAXA CITED IN THIS REPORT. SEABROOK OPERATIONAL REPORT,1993. BACILLARIOPHYCEAE Asterionella glacialis Castracane (syn. A. japonica Cleve) Cerataulina bergonil H. Peragallo Chaetoceros debilis Cleve Chaetoceros decepiens Cleve Chaetoceros socialis Lauder - Cylindrotheca closterium (Ehrenberg) Reimann. and Lewin g Leptocylindrus danicus C1 eve l Leptocylindrus minimus Gran Nit:schia sp. Rhi:osolenia delicatula Cieve l E Rhi:osoleniafragilissima Bergon Skeletonema costatum (Greville) Cleve Thalassionema nit:schioides Hustedt Thalassiosira sp. l CRYPTOPHYCEAE Cryptomonas sp. Chroomonas sp. DINOPHYCEAE Oxytorum sp. Prorocentrum micans Ehrenberg PRYMNESIOPHYCEAE Phaeocystis pouchettii (Hariot) Lagerheim I I I 3-20 I _1
1 TABLE OF CONTENTS PAGE P 4.0 ZOOPLANKTON
SUMMARY
. . . . . . . .. . ..... .. . . .. . 4-ii LIST OF FIGURES . .. . . .. . . .... .. . . . 4 iii LIST OF TABLES .. . . ... .. . .. .. . . . . 4-v INTRODUCTION . . . . . . .. 4-1 4.1 .. . . . .. .
4.2 METHODS . . . .. .... .. .. . . . . . . . . . 4-1 4.2.1 Field Methods . . . . . .. 4-1 4.2.1.1 Microzooplankton 4-1 I 4.2.1.2 Bivalve Larvae . . . . . . .. 4-1 4.2.1.3 Entrainment .. .. . . . 4-1 4.2.1.4 Macrozooplankton . . . . 4-3 1 4.2.2 Laboratory Methods . . ... . . . 3
,. 4-3 4.2.2.1 Microzooplankton . . . . . .
4-3 I 4.2.2.2 Bivalve Larvae ... . .. .. .. .. . . ... 4.2.2.3 Macrozooplankton .. ... . .. .. . 4-4 4.2.3 Analytical Methods . . .. . . . . . .. ... 4-4 I 4.2.3.1 4.2.3.2 Communities Selected Species
. . . 4-4 4-7 4.3 RESULTS . . . . . .. .. . . .... 4-8 4.3.1 Microzooplankton . . . . . . . .. . .. 4-8 4.3.1.1 Community Structure . 4-8 I
4.3.1.2 Selected Species .. .. . . .. . .. .... . . 4-12 4.3.2 Bivalve Larvae . . . . . . ... . . . 4-19 4.3.2.1 Community Structure . .. ... . , . ... 4-19 4.3.2.2 Selected Species . . . ... . . . . . 4-22 4.3.2.3 Entrainment . . . . 4-25 4.3.3 Macrozooplankton . . 4 25 4.3.3.1 Community Structure 4 25 4.3.3.2 Selected Species . . . 4-36 I 4.4 DISCUSSION .
.. 4-42 4.4.1 Community . . 4-42 4.4.2 Selected Species . 4-46
4.5 REFERENCES
CITED . 4-48 I 4-i I
O E I
SUMMARY
Microzooplank:an have historically shown distinct seasonal changes that relate to changing abundances g of dominant taxa, including copepods Pseudocalanus sp. and Oithona sp., bivalve larvae, and copepod nauplii. g Seasonal patterns during the operational period were similar to those observed during the preoperational period, although abundances of some key species showed significant differences. 'Ihese include Eurytemora sp., Pseudocala-nus/Calanus nauplii, and Oithona copepodites and adults. No differences in abundance were obsened between near6 eld and far6 eld areas, indicating that there is no evidence of an effect related to Seabrook Station. The umboned bivalve larval assemblage is defined by varying abundances of dominants such as #iatella sp., Myrdus edulis, and <fnomia squamula. Seasonal appearances of dominant species were similar to previous years. Ilowever, average abundances for many of the species during the operational period were elevated in comparison to the preoperational average. Since increased abundances occurred at both nearfield and far6 eld stations, they suggest an areawide trend unrelated to the operation of Scabrook Station. The level of entrainment of bivalve larvae changes with the abundance of larvae in the surrounding waters. Entrainment in 1993 was higher than the previous two years because of increased numbers of larvae in the study area and continuous plant operation (and thus larval entrainment) during peak periods (July through September). There is no evidence that larval entrainment has resulted in decreased numbers of bivalve larvae in coastal waters. He macrozooplantkon community is composed of a true planktonic component (defined as holo /meroplankton) g including copepods Calanusjinmarchicus, Centropages typicus, Pseudocalanus sp., and Temora longicornis, g along with lanal stages of decapods and barnacles. Amphipods, cumaceans, and mysids occasionally venture into the water column, fonning what is de6ned as the tychoplanktonic component. The assemblage of species changes seasonally, and, for the most part, has been consistent throughout the study period. Ilowever, abundances of many of the dominants were elevated during the operational period when compared to the preoperational period. For the holo /mehoplankton, increased abundances occurred at all three stations, suggesting an arcawide change. Tychoplankton have historically shown near6 eld-far6 eld differences that are related to variations in substrate. These spatial difTerences have been consistent during both preoperational and operational periods. No changes in the macrozooplankton community have been obser ed that could be related to the operation of Seabrook Station. I I I 4-ii ini
I : I LIST OF FIGURES I PAGE 4-1. Plankton and entrainment sampling stations . . . 4-2
~
4-2. Dendrogram and seasonal groups fonned by numerical classification of log (x+1) transformed micrczooplankton abundances (no/m') at nearfield Station P2.1978-1984, I 4-3. July-December 1986, April 1990-December 1993 Log (x+ 1 ) abundance (noim') of Eurgemora sp. copepodites and Eurgemora herdmani
. . 4-9 I adults, Pseudocalanus/Calanus sp. nauplii. and Pseudocalanus sp. copepodites and adults; monthly means and 95% confidence intenals over all preoperational years (1978-1984 and 1986) and monthly means for 1993 and operational period at nearfield Station P2 . 4-13 4-4. Log (x+ 1 ) abundance (nolm') 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 1993 and operational period at nearfield Station P2 4-18 4-5. Dendrogram and seasonal groups formed by numerical classification of bivalve larvae log (x+1) transformed abundances (half monthly merns; nolm') at Seabrook intake I 4-6.
(P2), dischcrge (PS) and farfield (P7) stations, April-October, 1988-1993 Weekly mean log (x+1) abundance (no/m') of Mvrilus edulis larvae at Station P2
. . 4-20 I during preoperational years (1978-1989, including 95% confidence intervals), and weekly means in the operational period (1991-1993) and in 1993 4-23 Volume of cooling water pumped during the months sampled for bivalve larvae and I
4-7. total number of bivalve larvae (x10') entrained by Seabrook Station, 1990-1993 . 4-27 4-8. Dendrogram and seasonal groups formed by numerical classification of mean monthly log (x+ 1) transformed abundances (noll 000 m') of holo- and meroplanktonic species of macrozooplankton at intake Station P2, discharge Station P5 and farfield Station P7,1988-1993 . . .. 4-28 4-9. Dendrogram and seasonal groups formed by numerical classification of mean monthly log (x+ 1 ) transformed abundances (no11000 m') of tychoplanktonic species of macrozoo-plankton at intake Station P2, discharge Station PS and farfield Station P7, I 4-10. 1988-1993 Log ( ;+1) abundance (no11000 m') of Calanusfinmarchicus copepodites and adults 4 33 I and Carcinus moenas larvae; monthly means and 95% confidence intervals over all preoperational years (1978-1984,1986-1989) and monthly means for the operational period (1991-1993) and 1993 at intake Station P2 4-37 I I l 4-iii I 1
O O I; PAGE , 4-11. Log (x+ 1) abundance (no11000 m') of Crangon septemspinoso(zoca and post larvae) and Neomysis americana (all lifutages); monthly means and 95% confidence intervals over all preoperational years (19781984,1986-1989) and monthly means for the operational period (19?l 1993) and 1993; and mean percent composition ofNeomysis americana lifestages over all preoperational years (1978-1984,1986-1989) and for !
, .. . 4-41 the operational period (1991-1993) at intake Station P2 , . . . ..
I E I I: i I' I I~ E I-I I 4-iv 1 u
i I LIST OF TABLES , PAGE
SUMMARY
OF METHODS USED IN NUMERICAL CLASSIFICATION AND MULTIVARIATE I 4-1. ANALYSIS OF VARIANCE OF ZOOPLANKTON COMMUNITIES, AND ANALYSIS OF VARIANCE OF ZOOPLANKTON SELECTED SPECIES ... . .... . 45 4-2. GEOMETR1C MEANS OF M1CROZOOPLANKTON ABUNDANCE (Na/m'),95% CONFlDENCE 1 LIMITS, AND NUMBER OF SAMPLES FOR DOMINANT TAXA OCCURRING IN SEASONAL CLUSTER GROUPS IDENTIFIED BY NUMERICAL CLASSIFICATION OF COLLECTIONS AT NEARFIELD STATION P2,1978-84, JULY-DECEMBER 1986, APRIL-DECEMBER 1990, I 1991-93 .. . . . .. . . . .. .. .. .. 4-10 4-3. GEOMETRIC MEAN DENSITY (No/m') AND THE COEFFICIENT OF VARIATION (CV,%) I OF SELECTED MICROZOOPLANKTON SPECIES AT STATIONS P2, PS, AND P7 FOR PREOPERATIONAL AND OPERATIONAL PERIODS AND 1993 . .. . . . 4-14 r i 4-4. RESULTS OF THE ANALYSIS OF VARIANCE OF LOG (X+1) TRANSFORMED DENSITY (NoJm') OF SELECTED MICROZOOPLANKTON SPECIES AMONG PREOPERATIONAL YEARS (1982-84) ANDOPERATIONALYEARS(199193) ANDNEARFIELD(STATION P2)
. . . .. 4-15 i
VS. FARFIELD (STATION P7) AREAS . . 4-5. GEOMETRIC MEAN ABUNDANCE (Nolm'), AND THE 95% CONFIDENCE LIMITS OF DOMIN ANT TAXA AND NUMBER OF COLLECTIONS OCCURRING IN SEASONAL GROUPS i FORMED BY NUMERICAL CLASSIFICATION OF BlVALVE LARVAE COLLECTIONS AT INTAKE (P2), DISCHARGE (PS) AND FARFIELD (P7) STATIONS, 1988-1993 . . . 4-21 4-6. GEOMETRIC MEAN ABUNDANCE (Nodm') AND UPPER AND LOWER 95% CONFIDENCE LIMITS OF ACTILUSEDULIS LARVAE AT STATIONS P2, PS AND P7 DUlGNG PREOP-1 ERATIONAL YEARS AND GEOMETRIC MEAN ABUNDANCE DURING THE OPERATIONAL PERIOD (1991-1993) AND 1993 . . . . . .. . 4 24 I 4-7. RESULTS OF ANALYSIS OF VARIANCE COMPARING INTAKE (P2). DISCHARGE (PS) AND FARFIELD (P7) WEEKLY ABUNDANCES OF ACTILUSL'DULIS DURING PREOPER-4-24 ATION AL (1988-1989) AND OPERATIONAL (1991-1993) PERIODS . . 4-8. ESTIMATED NUMBER OF BlVALVE LARVAE (X10') ENTRAINED BY THE COOLING WATER SYSTEM AT SEABROOK STATION FROM THIRD WEEK IN APRIL THROUGH I 4-9. FOURTH WEEK OF OCTOBER 1993 GEOMETRIC MEAN ABUNDANCE (No11000m') AND 95% CONFIDENCE LIMITS OF
. . . 4 26 DOMIN ANT HOLO- AND MEROPLANKTONIC TAXA OCCURRING IN SEASONAL GROUPS 8 FORMED BY NUMERICAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS (MONTHLY MEANS) AT INTAKE STATION P2. DISCHARGE STATION PS AND FARFIELD
;-29 STATION P7.1988-1993 I
I 4-v I
0 0 PAGE i I 410. GEOMETRIC MEAN ABUNDANCE (No11000m') AND 95% CONFIDENCE LIMITS OF DOMIN ANT TYCHOPLANKTONIC TAXA OCCURRING IN SEASON AL GROUPS FORMED l BY NUMERICAL CLASSIFICAllON OF MACROZOOPLANKTON COLLECTIONS (MONTHLY E MEANS) AT INTAKE STATION P2, DISCHARGE STATION PS AND FARFIELD STATION P7.1988-1993 . . .... ... . . 4-34 4-11. GEOMETRIC MEAN ABUNDANCE (Noll000 m') AND COEFFICIENT OF VARIATION OF SELECTED MACROZOOPLANKTON SPECIES AT STATIONS P2, P5, AND P7 DURING PREOPERATIONAL AND OPERATIONAL YEARS (1991-1993), AND 1993 4 39 412. RESULTS OF ANALYSIS OF VARIANCE COMPARING ABUNDANCES OF SELECTED M ACROZOOPLANKTON SPECIES FROM STATIONS P2, PS, AND P7 DURING PREOPERA-TIONAL (1987-1989) AND OPERATIONAL (1991 1993) PERIODS . 4-40 4-13.
SUMMARY
OF POTENTI AL EFFECTS (BASED ON NUMERICAL CLASSIFICATlON AND MANOVA RESULTS)OF OPERATION OF SEABROOK STATION INTAKE ON THE INDIG-4-43 l y ENOUS ZOOPLANKTON COMMUNITIES . . . . . 414.
SUMMARY
OF POTENTIAL EFFECTS (BASED ON ANOVA RESULTS) OF OPERATION OF SEABROOK STATION INTAKE ON ABUNDANCES OF SELECTED INDIGENOUS ZOOPLANKTON SPECIES . . . . . . . . . 4-47 APPENDIX TABLE 4-1. LIST OF ZOOPLANKTON TAXA CITED IN THIS REPORT 4-51 I t i I I I 4-vi I E a
v 'I ZOOPLANKTON I 4.0 . ZOOPLANKTON was recorded to calculate volume filtered based on predetermined pumping rates. Volume filtered averaged I
4.1 INTRODUCTION
Three components of the zooplankton community, 125 liters and ranged from 105 235 liters (NAl 1991a). Microzooplankton were rinsed from the nets into sample containers after pumping and were preserved in borax-microzooplankton, bivalve larvae and macrozooplank- buffered 3% formalin, ton. were sampled separately to identify spatial and temporal trends at both the community and species I level. One station outside the area most likely to be affected by plant operation was selected as a farfield site. Initial monitoring characterized the source and 4.2.1.2 Bivalve Lanne The spatial and temporal distributions of 12 taxa I magnitude of variation in each zooplankton community and provided a base of data for comparing operational of umboned bivalve larvae were monitored using a 0.5-m diameter,0.076-mm mesh net. Samples were ' monitoring. Current trends in zooplankton population collected weekly from mid-April through October at I' dynamics were evaluated to determine whether entrainment in Seabrook Station's cooling system intake Hampton Harbor (P1) and at Stations P2, P5 and P7 (Figure 4-1). Sampling began at Station P2 in July I has had a measurable effect on the community or any 1976. Farfield Station P7 was added to the program individual species. In addition, entrainment of bivalve in 1982, and Station P1 was added in July 1986. larvae in the plant's cooling water system was Samples were collected at Station P5 from July-I estimated. December 1986 and April 1988 through October 1993. Two simultaneous two-minute oblique tows were usually taken at each station. In cases when nets were 4.2 METITODS clogged, vertical tows were taken. Volume filtered
= ranged from 6-13 m' and averaged 9 m' for oblique 4.2.1 Field Methods tows, and ranged from 2-5 m' and averaged 3 m' for vertical tows (NAl 1991a). The volume of water i- 4.2.1.1 Microrooplankton filtered was recorded with a General Oceanics*
flownter. Upon recovery, net contents were preserved I Microzooplankton were sampled twice a month from March-November and monthly in Decem ber-Febn.ary with 1-2% borax-buffered formalin (with sugar added to enhance color preservation) and refrigerated. at intake (Station P2), discharpe (Station PS) and I farfield (Station P7) areas (Figure 4-1). Sampling at all three stations occurred from July through December 4.2.1.3 Entrainment 1986 and from April 1990 through December 1993. I In addition, Station P2 was sampled from January 1978 through December 1984 and Station P7 from January Bivalve larvae entrainment sampling was conducted up to four times a month by N AESCO personnel within I 1982 through December 1984. Four replicate samples were collected by pump at both I m below the surface and 2 m above the bottom at each station on each the circulating water pumphouse on. site at Seabrook Station from July 1986-June 1987 and June 1990-October 1993. Three replicates were collected during I sampling date. Discharge from the pumps was directed mto a 0.076-mm mesh plankton net (12 cm diameter) set into a specially-designed stand filled with seawater each sampling date. Sampling dates coincided with offshore bivalve larvae sampling whenever possible. Entrainment sampling was not conducted on several l to within 15 cm of the top of the net. Pumping time scheduled sampling dates however, due to either station l 4-1 l l
O N RYE UDGE N ' J n I
~~V '
Y"n HEAD 8- 0 0 .5 1 Nautical Mile 0 1 2 Kilometers g FARFIELD AREA SCALE "In?#s" GREAT BOARS - l' ' HEAD , HAMPTON - % re BEACH BROWNS - b /g *
\ P1 Intake ***O
\ Discharge-N k, /OUTERj'
^'
g AREA SEABROOKNO V = STATION J . ,- HAMPTON SEABROOK SUNK l HARBOR ROCKS 0 %, SEABROOK \, . .
%, BEACH
)(
LEGEND
= zooplankton stations O = bivalve larvae stations E1 = Seabrook Entrainment Station Figure 41. Plankton and entrainment sampling stations. Seabrook I
Operational Report,1993. 4-2 8 m
L.; ZOOPLANKTON r
~ outages or sampling equipment problems. Scheduled (averaged 166 m') for 5-minute tows (NAl 1991a).
.- stationoutagesoccurred from August-November 1991 Upon retrieval, each net was rinsed and the contents and September-October 1992. preserved in 6% buffered formalin.
- Samples were taken using a double barrel collection system. A 0.076-mm mesh plankton net was suspended 4.2.2 Laboraton Methods
. in a 30-gallon drum which, in tum, was suspended in 4.2.2.1 Microrooplankton a 55-gallon drum. Water diverted from the cooling water system entered the 55-gallon drum from the j bottom and overflowed the 30-gallon drum into the Two replicates from each depth and station on all plankton net. After passing through the net, the water sample dates were analyzed for microzooplankton; the ,
discharged through the bottom of both drums. The remaining two replicates were archived and stored as ! water supply was adjusted to maintain three to six " contingency" samples. The sample was concentrated inches of water above the plankton net at all times. or diluted to a known volume that provided an optimal One double drum collector was operated at a time. working number of organisms (ca. 200 per 1-ml After the water was drained from the sys:em, the subsample). Each sample was agitated with a calibrated contents of the four nets were consolidated and placed bulb pipette to distribute the contents homogeneously, in one samplejar with 1% buffered formalin. The A l-ml subsample was removed, placed in a Sedgewick-Rafter cell and examined under a compound microscope ; volume filtered was measured with an in-line flowmeter and averaged approximately 7 m' per replicate. using magnifications of 40X to 200X. All microzoo- -l plankton taxa present in the subsample (generally, all taxa smaller than adult Calanusfinmarchicus: <4.0 j] 4.2.1.4 Macrorooplankton mm) were counted and identified. Most copepods were j identified to developmental stages, e.g., nauplii, j copepodites or adults (copepodite 6). Two subsamples { Macrozooplankton were collected from July 1986 through December 1993 at Stations P2, P5, and P7 were analyzed for each replicate. Individual abundances (Figure 4-1). Station P2 was also sampled from January for all taxa (no/m') were computed for each subsample 1978 through December 1984. Station P7 was also and then averaged to provide mean abundances per > sampled from January 1982 through December 1984. taxon for each replicate. b Macrozooplankton collections were made at night I four times per month, concurrent with ichthyoplankton 4.2.2.2 Hivalve Lanae ( sampling. On each date, four replicate oblique tows were made with 1-m diameter 0.505-mm mesh nets . Each bivalve larvae sample collected at each station at each station. The nets were set off the stern and was analyzed. When the total umboned larvae collected towed for 10 minutes while varying the boat speed, ranged from 1-300, the entire sample was processed. causing the net to sink to approximately 2 m off the Samples were split when the total umboned bivalve bottom and to rise to the surface at least twice during larvae count exceeded 300 specimens and two the tow. When nets became clogged due to plankton subsample fractions were examined with a dissecting blooms. tows were shortened to 5 minutes. The volume scope. Umboned larvae were ilentified from an filtered, determined with a General Oceanics* digital established species list and enumerated. Specimens flowmeter, ranged from 408-567 m' (averaged 494 of other species were enumerated as Bivalvia. m') for 10-minute tows, and ranged from 109-280 m 2 Subsamples (when present) were averaged for each 4-3
O n U ZOOPLANKTON tow, Samples collected in 1985 were snalyzed for For each sample type, species counts were converted Mrtilus edulis and Mya crenaria only. to density by multiplying each species' count by the appropriate scaling ratio (the proportion of the sample g analyzed for each particular organism) and dividing g 4.2.2.3 Maeroioonla nkton by the volume of water 61tered during 6 eld collection. Microzooplankton and bivalve lanae abundances were E Macrozooplankton were analyzed from three of the reported as no/mh macrozooplankton abundances were 5 four tows (randomly selected) at each station for two reported as no11000 m'. of the foui sampling periods each month (usually alternating weeks). Copepods were analyzed by concentrating or diluting the sample to a known volume 4.2.3 Analytical Methods from which a subsample of approximately 150 copepods l 85 per i mi could be attained. The sample was agitated 4.2.3.1 Communities with a Stempel aipette to homogeneously distribute the contents ane .I was removed and examined under Community structure of the microzooplankton, a dissectingmi . cope. Subsampling continued until bivalve larvae, and macrozooplankton components of at least 30 of the dominant copepod taxon and 150 the zooplankton community was evaluated by numerical tctal copepods were counted. If an even distribution classification, multivariate analysis of variance of ccpepods could not be attained, the sample was (MANOVA), and qualitative comparison of log serially split using a Fcisom plankton splitter. abundances or geometrie means for periods (operational, g Cyclopoids and copepodites of smaller calanoid species preoperational and 1993)(Table 4-1). The macrozoop- g (which were not ef6ciently collected in the macrozoo- lankton community includes numerous species that plankton samples) were not included in the copepod exhibit one of three basic life history strategies. The g counts. For the selected species Calanusfinmarchicus, holoplankton species, e.g. copepods, are planktonic g both lifestage and sex were identified. After essentially throughout their entire life cycle. enumeration, subsamples were recombined with the Meroplankton includes species that spend a distinct sample. portion of their life cycle in the plankton, e.g. larvae of benthic invertebrates. Species that alternate between To enumerate rarer copepod s (A nomalocera opalus, association with the substrate and rising into the water Caligus sp., Candocia armata. Euchaeta sp., column on a regular basis are called tychoplankton, Harpacticoida. Monstrillidae and Rhincalanus narutus) e.g. mysids. Because of these behavioral differences, and the remaining macrozooplankton, the sample was as well as large differences in abundances, macrozoo-placed in a Folsom plankton splitter and serially split plankton species were categorized into holo /meroplank-into fractions that provided counts of at least 30 tonic species or tychoplanktonic species prior to individuals ofcach dominant macrozooplankton taxon statistical analysis. The same types of analyses were (as defir'ed in NAl 1984). A naximum of 100 mi of
. performed on each group of species.
settled plankton was analyzed. Macrozooplank1on taxa rg were enumerated by species using a dissecting Temporal and spatial changes in the community g microscope at magni 6 cations between 6x and 150x. structure of microzooplankton, bivalve larvae, and the Selected species (Cancer sp., Carcinus maenas, two components of macrozooplankton were evaluated g Crangon septenupmosa. and Neomrsis americana) were using numerical classi6 cation techniques (Boesch 1977). g identi6ed to detailed developmental stage (lifestage This technique forms groups of stations and/or sampling and/or sex). Splits were recombined upon completion. periods based on similarity levels calculated for all 6 R 4-4 5 i.e
- .- - .. . - . . m TABLE 4-1.
SUMMARY
OF METilODS USED IN NUMERICAL CLASSIFICATION AND MULTIVARIATE ANALYSIS OF VARIANCE OF ZOOPLANKTON COMMUNITIES, AND ANALYSIS OF VARIANCE OF ZOOPLANKTON SELECTED SPECIES. SEABROOK OPERATIONAL REPORT,1993. SOURCE OF DATES tlSED DATA VARIATION IN TAXON LIFESTAGE STATIONS IN ANALYSIS CIIARACTERISTICS* (M)ANOVA ANALYSIS j MRROZ(X)pl.ANKTON Station 29 dominants -- P2 1993 Log (x + 1) transformation _of l' MANOVA each " replicate" sample, x of PS P7 surface and bottom; species excluded with frequency of occurrence <20% ANOVA Selected species: C' P2 1982-1984; Monthly mean, surface, Preop-Op, Year, ! Ertrytemora sp. Month, Station Eurytemora herdmani t. P7 1991-1993 and bottom PseudocalarrusiCalanus N rscudocalarms sp. C.A o Ostfrorra sp. N.C.A O. P2 1978-1984, Log (x+1) transformation of - Numerial 35 dominants - I 7/86-12/86 each individual (replicate) l classification 4/90-12/93 sample, x of surface and bottom; species excluded with frequency of occurrence <7% B1 VALVE LARVAE P2 1988-1993* Log (x+1) transformation of Preop-Op, Station, MANOVA All taxa except Bivalvia -- P5 mdividual (replicate) sample, Year Week P7 then weekly means computed Selected species: - P2 1988-1993' Same as above Preop-Op, Station, ANOVA Year Week Afytilus edul?s P5 P7 All taxa except Bivalvia - P2 1988-1993* Log (x+1) transforamtion of - Numerical each individual (replicate) PS classification sample, half-monthly means P7 I calculated from weekly x (continued)
- =_ . -__ - n_
TAHLE 4-1. (Continued) SOURCE OF DATES USED DATA VARIATION IN ANALYSIS TAXON LIFESTAGE STATIONS IN ANALYSIS CllARACTERISTICS* (M)ANOVA MACROBX) PLANKTON Numerica! -- P2 1988-1993 Monthly x. _ classifica: ion Tycho: P5 Tychoplankton: used all taxa 22 dominants P7 except Mysidacea and Amphi-poda. Ilolo/mero: llelo/mero: deleted taxa oc. 50 dominants curring in s5% of samples and general taxa. MANOVA Tycho: - P2 1988-1993c Sample period x sampled Preop-Op, Station, 22 dominants P5 twice per month. Year, Month P7 Tychoplankton: used all taxa llolo/mero: except Mysidacea and Amphi-o 50 s'ominants poda
& Ilolo/mero: deleted taxa oc-curring in 55% of samples and general taxa.
ANOVA Selected species: Calanus finmarchicus C,A* P2 1988-1993* Sample period x, Preop-Op, Station. Cancer sp
- L PS sampled twice per Year, Month Carcimes mcanar L P7 month Crangon septemspinosa L Neomysis amer,cana All
'All data log (e l} transformed unless otherwise noted
'C = coperodite; A = adult; N = nauplii; L = larvae
*1990 excluded
' Cancer spp discussed in Section 8.0
'Carcim,5 macnar larvae are essentially absent for 7 of 12 months, therefore a peak period of June-Octohr only was analyred GB M M M M M M MM M M M' MM M M M M MN
Eu ZOOPLANKTON possible combinations of stations / sampling periods and on these co.nmunities. Probabilities associated with the Wilks' Lambda test statistic (SAS 1985) were ( the species that occur there. The Bray-Curtis similarity
. index (Clifford and Stephenson 1975, Boesch 1977) reported. Abundance data from each individual was used. Values of the indices ranged from 0 for (replicate) sample was log (x+1) transformed prior to absolutedissimilarityto 1 forabsolutesimilarity. The use in the MANOVA model in order to more closely b.
classification groups were formed from arithmetic approximate the normal distribution. averages by the unweighted pair-group method (UPGMA: Sneath and Sokal 1973). Results were Untransformed densities of bivalve larvae in entrain-simplified by combining the entities based on their ment samples were multiplied by the month's average similarity levels, determined by both the within-group daily volume pumped through the circulating water . and between-group similarity values. Results were system, and by the number of days represented by each presented graphically by dendrograms, which show sampling date, and then summed within month to the within-group similarity value and the between-group estimate the number of bivalve larvae entrained by similarity (value at which a group links to another Seabrook Station on a monthly basis, group). The groups were characterized by the mean abundance o.'the dominant taxa. Communities during { the operational period ( August 1990-December 1993) 4.2.3.2 Selected Species were judged to be similar to previous years if collections were placed in the same group as the Biologically important or numerically dominant taxa majority of collections taken at the same time during were selected for further investigation (Table 41). The operational, preoperational, and 1993 geometric ! previous years. A potential impact was suggested if community differences occurred solely during the means and coefficients of variation were tabulated. [ Monthly log (x+1) means and 95% confidence limits operational period and were restricted to either the near-field or the farfield area. This situation would initiate for the preoperational and operational periods, and 1993 additional investigations. If community differences were compared graphically to provide a visual estimate occurred at both nearfield and farfield stations, they of their magnitude and seasonalitv. Finally, an analysis were assumed to be pan of an area-wide trend, and of variance (ANOVA) was used on log (x+1) unrelated to plant operation. transformed data to evaluate the plant impact by comparison of preoperational and operational means Multivariate analysis of variance (MANOVA, Harris among nearfield and farfield stations. All sources of 1985) was the statistical test used to assess simulta- variation in the analysis of variance model were neously the differences in abundance between periods assumed to be fixed. This was a conservative model, (preoperational and operational), stations (nearfield more likely to detect significant differences than rtd farfield), years and weeks (Table 4-1). The alternate models that assume some of the sources of interaction term (Station X Period) was used to variation were random. When the F value was determine if there was an impact from plant operation significant (Ps0.05) for the interaction term or class ( for bivalve larvae and macrozooplankton. Microzoo- variable (Station or Preop-Op), the least squares means plankton data from 1993 were tested only to determine procedure (SAS 1985) was used to evaluate differences station differences. Historically, there have been few among means. Collections from all three stations intake differences m planktonic species assemblages among (P2) discharge (PS) and farfield (P7) were used in the nearfield intake and discharge and farfield stations. analysis where the preoperational database was Continuation of the trend during plant operation would sufficient. Some species (e.g. all bivalve larvae, suggest that there were no effects of plant operation Carcmus macnas) were common only during part of 4-7
I O 0 7,00 PLANKTON I the year (peak periods). Data from the peak periods (Group 5), numbers of bivalve veligers diminished (<5% E were used in analysis of variance and to compute of total group abundance) and numbers of Oithono sp., y Pseudocalanus sp. lifestages, and copepod nauplii operational, preoperational, and 1993 geometric means. decreased. The summer / fall and miscellaneousgroups l (Groups 6 and 7) did not differ appreciably from the M RESULTS other collection dates with respect to those taxa that 4.3 were numerically important. The ungrouped sample 4.3.1 Microroonlankton mean was taken in late May 1982 and had very high abundances of Oithona sp. and Acartia sp., and 4.3.1.1 Community Structure Polychaeta larvae and Rotifera were common. Temporal Characteristics Comparison of the specific sampling periods included within the major cluster groups indicated that . Temporal variability in species abundances and differences among years were generally moderate. taxonomic composition of the nearshore microzooplank- Collectionsfrom the operational period w ere generally ton community (surface and bottom samples averaged) placed into groups containing corresponding dates from at Station P2 for all preoperational and operational the preoperational period, although some collections from summer / fall 1990 and 1991 with lower-than-typical collections was examined using numerical classification. E-q Collections were grouped into five major groups that abundances were identified as a separate group (Group corresponded with the annual seasonal progression of 6)(Figure 4-2). Preoperational and operational periods dominant species and two smaller groups (one collection were similar in the rank order of numerically dominant date was ungrouped; Figure 4-2). The major seasonal taxa identified from each cluster group (Table 4-2). patterns in the microzooplankton community structure Differences among groups, in large measure, were were largely delineated by changes in both total attributed to seasonal variability in the abundances of abundance and the dominance structure ofnumerically these dominant taxa. For example, the fall assemblage important taxa. The copepods Onhona sp. and (Group 5) in 1993 persisted into January, which also Pseudocolane sp., and Pseudocalanus/Calane nauplii occurred in 1978 and 1981. Seasonal groups idectified were the most abundant organisms in virtually every by numerical classification generally encompassed seasonal group during both preoperational and collection periods with similar temperature regimes, operational periods (Table 4-2). Early winter samples particularly with respect to the depth and intensity of (Group 1) were characterized by low abundances of the thermocline (NAl 1985, NAl 1991b). all taxa including Oithona sp. and Copepoda nauplii during both periods (preoperational and operational). Increased numbers of these taxa and the appearance Spatial Patterns of Cirripedia larvae marked the appearance of the g winter / spring assemblage (Group 2). The spring Spatial variation in the microzooplankton community B assemblage (Group 3) was characterized by increased structure was examined separately for both the preopera-abundance of Copepoda napplii and the presence of tional and operational periods. Historical comparisons low densities ofAcarrio sp. an d bivalve veliger larvae. of total microzooplankton densities revealed .w The late spring / summer asserr olage (Group 4) had peak significant differences between Stations P2 and Ph abundances of Onhona sp., Copepoda nauplii. although some numerically important taxa exhibited Pseudocalanus/Calanus aauplii. Pseudocalanus sp., large differences in rank order or percent composition and bivalve veliger larvae. In the fall assemblage between stations,their individual abundances were not 4-8 I W 5
E i
-sowcrwn
--W+W/y:.mf$sgmzt Group 1. Early Winter g;
~
,....... widun group sunilanry ungrot ped a
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A i ' J l J lA l l 'O l lD 5 8 8 N MONTil Figure 4-2. Dendrogram and seasonal groups formed by numencal classification oflog (x+1) transformed microzooplankton abundances (no/m') at nearfield l Station P2,19781984. July-December 1986. April 1990-December 1993. Seabrook Operational Repon.1993. 4-9 I i l
TAllLE 4-2. GEOMETRIC MEANS OF MICROZOOPLANKTON AllUNDANCE (NoJm'),95"A CONFIDENCE LIMITS, AND NUMilER OF SAMPLES FOR DOMINANT TAXA OCCURRING IN SEASONAL CLUSTER GROUPS IDENTIFIED llY NUMERICAL CLASSIFICATION OF COLLECTIONS AT NEARFIELD STATION P2,1978-84, JULY-DECEMilElt 1986, APRIL DECEMllER 1990, 1991-93. SEAtlROOK OPERATIONAL REPORT,1993. GROUP NO./ DOMINANT PREOPERATIONAL PERIOD OPERATIONAL PERIOD NAME TAXA
- FIMILARITY LCL MEAN UCL N N LCL MEAN UCL 1 Copepeda nauplii 12 66.2 126 240.1 4 4.3 65 813.0 Early Winter (hrhona sp. 99.4 218 477.1 21.8 292 3755.3 (0.58/0 55) Pscrulocalanus sp. 28.3 64 143.3 28.8 95 309.4 Pscrnlocalanus/Calanus nauplii 32.8 72 158.3 0.3 16 235.7 Tintinnidae 10.0 83 643.1 3.9 21 100.9 Foraminiferida 5.7 14 33.5 7.5 40 204.1
[ 2 Cirripedia larvac 24 48.7 105 223.6 8 48.5 231 1084.2 o Winter / Spring Copepoda nauplii 323.0 506 793.8 334.4 567 959.2 (0.67/0.65) Oithona sp. 539.0 923 1581.4 340.3 1025 3081.8 Pecudocolanut sp. 108.4 197 357.9 35.9 77 163.8 Pscenlocalanut/Calanus nauplii 423.6 654 1008.5 46.6 114 278.9 3 Copepoda nauplii 20 612.1 1089 1936.0 12 1363.9 1901 2650.6 Spring Oirhona sp. 565.9 1075 2042.0 1381.4 2167 3400.2 (0.68/0 65) Pscrulocalanus sp. 87.0 180 370.2 165.8 357 768.6 Pscrulocalanut/Calanus nauplii 230.1 451 883.7 165.6 508 1551.9 4 Divalvia religer larvae 64 479.6 736 1128.7 26 204.5 422 870.3 Spring / Summer Copepoda nauptii 2313.0 3098 4149.1 2872.3 3953 5440.3 (0.66/0.64) Oithona sp. 3447.2 4194 5102.8 5356.1 6960 9043.5 Pseudocalanus sp. 561.0 769 1054.5 293.7 557 1055.2 Pscinlocolanus/Calanus nauplii 1264.9 1654 2162.4 350.4 612 1069.9 M e M M M M M M M M W W M M M M e M.timgg
- - - ~ .
3 TAHLE 4-2. (Continued) GROUP NO.I DOMINANT PREOPERATIONAL PERIOD OPERATIONAL PERIOD NAME TAXA
- SIMILARITV N LCL MEAN UCL N LCL MEAN UCL 5 Copepoda nauplii 44 437.5 614 860.4 13 417.5 612- 897.2 Fall Oithenta sp. 1001.6 1323 1748.6 1019.6 1515 2249.8 Pscraloca/ anus sp. 146.9 221 332.3 145.4 220 334.0 (0.66/0.65)
Psernlocalanus/Calanrix nauplii 345.2 482 673.2 47.3- 117 289.4 Tintinnidae 30.1 71 165.7 47.4 287 1710.9 , l 6 Hivalvia veliger larvae not represented 5 31.8 142' 625.7 l Summer / Fall Copepoda nauplii 263.1 508 980.2 ' .l (0.74/0.65) Oithona sp. 506.7 1092 2353.9 -l Pscralmitmero sp. 36.4 114 352.4 l b 7 Bivalvia veliger larvae 1 -- 1180 - 3 17.4 ~ .405 8954.9 Misc. Copepoda nauplii -- 2344 -- 300.6 1834 i i 158.8 Oithona sp. -- 670 - 48.1 2383 115710.4 (0.69/0.63) Pscialocalanus sp. -- 1I24 -- 0.0 69 25648.9 rserelocalanus/Calanus sp. -- 1019 -- 0.0 60 114672.6
'within group sim;larity/between group similarity
- taxa comprising >, 5% of total group abundance in either preoperational or operational period
O O ZOOPLANKTON significantly different, and confidence intervals of the (overwintering) eggs (Grice and Marcus 1981, Marcus preoperational and operational abundances generally 1984). overlapped (NAl 1985). Similarly,1993 abundances of the 29 dominant taxa were not significantly difTerent Eurytemora sp. copepodite monthly mean densities among the three stations when tested with M ANOVA for the operational period and 1993 failed to exhibit (Wilks' Lambda 4.33, F=0.74, p>F4.87), as was found the mid-summer density peak that has been observed in previous years (NAl 1991b,1992,1993b). in the preoperational years (1982-1984) and were well below the preoperational average density from June through October (Figure 4-3). However, mean oper- g 4.3.1.2 Selected Species ational densities displayed (I) a late-spring peak that 5 was comparable in magnitude to the preoperational The copepods Pseudoca/ anus sp. and Oithona sp. mid-summer peak, and (2) a fall peak that was E were selected for further analysis in the microzooplank- comparable to the fall peak in preoperational years. E ton program because of their numerical dominance. Abundance peaked only in the fall during 1993. The neir abundance and trophic level make them important operational and 1993 annual geometric means for I members of the marine food web throughout the Gulf Eurytemora sp. copepodites at Station P2 were below E5 of Maine and nearby Atlantic Shelf waters (Sherman the overall mean for the preoperational years (Table 1966,Tremblay and Roff 1983, Davis 1984, Anderson 4-3), but were within the range of mean values for 1990). The third selected species, Eurytemora herd- individual years (NAl 1991b). ANOVA results mani, although not dominant, has been reported to be indicated that Eurytemora sp. copepodite abundances an abundant coastal copepod in the northern region during the operational period were significantly lower of the western Atlantic (Katona 1971). Lifestages of than densities from recent preoperational years (Table these taxa were identified w henever possible to deselop 4-4). De differences were consistent between stations, an understanding of the dynamics of population indicating they occurred arcawide, and were not a recruitment cycles. In some cases, however, the localized effect of plant operation. Significant possible presence of congeneric species made it im- differences were also noted among years and months. E possible to routinely identify all lifestages to species Average densities at Station P2 were not significantly g level. different from those at Station P7. Temporal changes in the abundance of Eurytemora Eurrtemora sp. hen /mani adults during the operational period followed the same general seasonal pattern as described for Eury-Earlier studies indicated that Eurytemora sp. temora sp. copepodites with the exception that a fall , copepodite and E. herdmam adult populations in peak was not detected in E. hen /mani adult abundances i f lampton liarbor and the nearfield Station P2 undern ent in either the preoperational or operadonal years (Figure similar seasonal cycles, but during the spring the 4-3). The mean abundances of E. herdmani adults population density in the estuary was much higher than during the operational period and 1993 were below the nearfield population density (NAl 1978, 1979). the mean densities for the preoperational years (Table These observations suggest that recruitment to the 4-3), and the mean operational density of E. herdmani coastal population may be supplemented by the cstuarine adults was found to be significantly lower than the population. Other sources of recruitment in the spring preoperational mean (Table 4-4). Ilowever, the might be maturation of, and subsequent reproduction difTerences were consistent between the nearfield and of, overw intering copepodites or hatching of diapause farfield areas, indicating an areawide decrease, not a 4 12 E i I
i 1 g Ecrytem:rs sp. Errytem:ra hsrdmazi i Copepodites Adults , 40- - -_, 4.0 - %,,a g, .......... %,,,g 3,, ,
.......... %w
--4-- tw3 ...o_- iw3 U U T 3.0 -
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'......._...._.._.b
', , , , , , , 00 , 2, ',_ ,T, h, ,#,% , ./ , -L,.
x, i 40 , , JAN FIB MARAPRMAYJUN JUL AUO SEP OCrNOVDEC JAN FT.B MARAPRMAYJUN JLt AUG sEP OCTNOVDEC MONTH MONTH Pseudocalanus/Calanus Nauplii I 4.0 - 35-
~~**~~
Preoperunenal op,,,,a I"3 e'+ I'^ I r T ' I bz:r 3.0 - y i u- - I ' if[ n.
*- ' " ' 1. ' -
T
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%r i 40 i a e ia a a a i e i i JAN FEBMARAPRMAYJUN JLL At% sEP OCTNOVDEC MONTH Pseudocalanus sp. Pseudocalanus sp.
Copepodites Adults 40- 40- p,,op,,,,a
-- ------- Opmaana
- u. ,o -9 u_ -- --
im w Qg_ 30~ f . f,
- 1 r,
w Q2 z- _ 3A ~
,i E z-ga u- .- ,.3.2.,- T r,T s. , - ,
g ga u- ,, , ,
,i
' ^
w 2.0 - #.. ,' 8,2w 2.0 - '-
.T " 'h .- b1 e' ., . ,
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--.-- im x, 00 i i i i i i i i i i i i OS iiil i i e i i e i i JAN FT_B MARAPRMAYJUN JUL AtlC SEP OCTNOVDEC 1AN FEB MARAPRMAYJUN JLt AUG sEP OCTNOVDEC MONTH MONTH I Figure 4-3. Log (x+1) abundance (no/m') of Eurytemora sp. copepodites and Eurytemora herdmani adults, PseudocalanustCalanus sp. nauplii, and Pseudocalanus sp.
copepodites and adults; monthly means and 95% confidence intervals over all preoperational years (1978-1984 and 1986) and monthly means for 1993 and operational penod at nearfield Station P2. Seabrook Operational Report.1993. I 4-13 I
l TAllLE 4-3. GEOMETillC MEAN DENSITY (No/m') AND Tile COEFFICIENT OF VARI ATION (CV,%) OF SELECTED MICROZOOPLANKTON SPECIES AT STATIONS P2, PS, AND P7 FOR PREOPERATIONAL AND OPERATIONAL PERIODS AND 1993. SEAUROOK OPERATIONAL REPORT,1993. l l PREOPERATIONAL OPERATIONAL 1993 SPECIES /LIFESTAGE STATION MEAN CV MEAN' CV MEAN Enrireniora sp. P2 4 35.1 1 16.6 I copepodites P5 -- -- 1 29.4 I P7 4 56.4 1 52.4 <l Enrttentora herdmani P2 2 50.2 1 44.4 <1 adults P5 -- -- 1 35.5 <l P7 3 51.2 1 53.0 cl Beudocolanut/Calannr sp. P2 593 7.5 187 9.I 284 nauplii P5 -- -- 133 3.2 136 7 P7 499 11.2 144 6.2 186 7 ncudocolanus sp. P2 223 8.6 179 5.1 243 i 152 8.2 103 copepodites P5 -- - ! 193 14.0 156 5.2 118 I P7 I l &cudocolanus sp. P2 23 17.4 19 14.4 32 5 adults PS -- -- 18 9.8 21 P7 25 16.4 19 7.1 16 (hihona sp. P2 465 11.7 539 7.1 531 nauplii P5 -- - 558 2.9 505 P7 403 15.1 465 8.0 384 (hrhona sp. P2 490 10.1 779 3.6 64i copepodites PS -- -- 746 6.0 480 P7 299 20.1 643 3.8 533 (hrhona sp. P2 107 13.5 188 7.4 188 adults PS -- -- 178 10.5 132 P7 98 23.9 158 7.9 164
'Preoperational years: P2 = 1978-84, P5 = not sampled, P7 = 1982-84. Mean of annual means.
' Operational yests = 1991-93; 1990 not sampled during January through March, data not included.
Mean of annual means. M M M M M M M M M M M M M m M m a m 33
- M M P ..
- T N J
TABLE 4-4. RESULTS OF Tile ANALYSIS OF VARIANCE OF LOG (X+1) TRANSFORMEI) DENSITY : (Nolm') OF SELECTED MICROZOOPLANKTON SPECIES AMONG PREOPERATIONAL. YEARS (1982-84) AND OPERATIONAL YEARS (1991-93) AND NEARFIELD (STATION P2) VS. FARFIELD (STATION P7) AREAS. SEABROOK OPERATIONAL REPORT,1993, t
.l SPECIES / SOURCE OF LIFESTAGE VARIATION * .df MS F MULTIPLE COMPARISONS * - ;
1 Eurrtemara sp. Preo Op I 5.81 22.52* " Op<Preep copepodite Yea Preop-Op) 4 2.76 10.69' " Mont (Year X Preop-Op) 66 0.82 3.17"
- Area 1 0.04 0.16 NS Preop-Op X Area 1 0.35 1.35 NS Error 176 0.26 o Eurrtenmra Ircrdniani Preo Op I 7.14 38.77* " Op< Preop -
adult Yea Preop-Op) 4 2.17 1 1.81 * * *
- v. Monti (Year X Preop-Op)- 66 0.84 4.5 8"
- Area 1 0.31 1.70 NS Preop-Op X Area 1 0.12 0.68 NS Error 176 .0.18 Pscrulaca/ anus /Ca/ anus Preop-Op .1- 13.75 55.32 "
- Op< Preop sp. nauplii Year (Preop-Op) 4 2.17 8.74 "
- Month (Year X Preop-Op) 66' l.33 5.3 5"*
Area 1 0.36 1.44 NS Preop-Op X Area 1 0.15 0.62 NS Error 176 0.25 Pseudocolanus sp. Preo Op . I' O.42 1.59 NS
. copepodite Yea Preop-Op) 4 1.52 5.81 "
- Mont (Year X Preop-Op) 66 1.07 4.08* "
- Area 1 0.12 0.45 NS Preop-Op X Area 1 0.02 0.08 NS Enor 176 - 0.26 '
Pseudocalanus sp. Op . I- 0.58 . 2.14 NS : adult Preop Year (Preop-Op) 4 1.95 7.15"*l _ Month (Year X Preop-Op) 66 1.33 4.86"
- Area I. 0.00 0.00 NS Preop-Op X Area 1- 0.00 0.00 NS Error 176 0.27'
- (contmued)
- a . - n- .__ _
TAllLE 4-4. (Continued) SPECIES / SOURCE OF LIFESTAGE VARIATION' df MS F MULTIPLE COM PARISONS* (firhona sp. Preop-Op I 0.14 0.74 NS nauplii 4 3.76 19.44* " Year Month(Preop-Op) (Year X Preop-Op)66 0.91 4.69 "
- Area 1 0.60 3.10 NS Preop-Op X Area 1 0.00 0.00 NS Error 176 0.19
(>ithona sp. Preop-Op i 5.33 33.71* " Op>Preep copepodite 4 3.60 22.75 * *
- Year Month(Preop-Op)
(Year X Preop-Op) 66 1.20 7.5 8 '" Area 1 0.88 5.59' P2>P7 Preop-Op X Area 1 0.01 0.05 NS Error 176 0.16 i
; (>ithona sp. Preop-Op 1 2.29 12.14* " Op> Preop adult 4 4.42 23.47 " '
Year Month(Preop-Op)Freop-Op) (Year X 66 1.19 6.3 4 * " Area 1 0.53 2.81 NS Preop-Op X Area I <0.00 0.01 NS Error 176 0.19 NS = Not Significant (P> 0.05)
= Significant (0.05 2 P >0.01)
" = liighlv Significant (0.012 P > 0.001)
"* = Very liigfily Significant (P s 0.001)
- Preop-Op = preoperational period vs. operational period, regardless of area Year (Preop-Op) = year nested within preoperational and operational periods, regardless of area Month (Year X Preop Op) = month nested within year Area = nearfield vs. farfield stations Preop-Op X Area = interaction of main effects
*Least squares means compared with a paired t-test M M M M- M M M M M M M M M M M M e M m3
ZOOPLANKTON localized plant effect. Significant differences were were present year-round and together constituted one of the most abundant microzooplankton taxa throughout { noted among years and months. the preoperational and operational periods (Tables 4-2 l and 4 3). Oithona sp. nauplii densities at Station P2 Picudoca/ anus sn. during the operational period and 1993 generally exhib-ited the same seasonal pattern of abundance as during l Historically, Pseudoca/ anus /Calanus sp. nauplii were the preoperational period (Figure 4-4). The 1993 present year-round at Station P2 in large numbers monthly geometric means for P2 were about equal to (Figure 4-3), and were among the numerically dominant or higher than the overall (1978 1984) preoperational i taxa composing the microzooplankton community in mean except in February and April. Average most seasons (Table 4-2). Seasonal peak abundance operational densities were slightly higher when occurred during mid-summer during preoperational compared to the preoperational (1982-1984) mean years and in 1993, and slightly later during the (Table 4-3), but the difference was not significant l opera'.ional period (Figure 4 3). The 1993 abundances (Table 4-4). Mean densities at the near6 eld and farfield l were much lower than the preoperational averages from stations showed similar trends between the preopera- j January - March. Mean densities for the operational tional(1982 1984) and operational periods, indicating l period were signi0cantly lower than the preoperational the slight increase was areawide, not ic,calized in the mean at both stations (Tables 4-3,4-4). However, the vicinity of the plant (Table 4-4). Significant differences differences between periods were consistent between were noted among years and months, but not between the nearfield and farfield areas, indicating an areawide stations, decrease rather than a localized plant effect. Differences among months and years were significant, while spatial Oithona sp. copepodites also followed the same differences were not significant. general pattern of seasonal abundances during the opera-tional period and 1993 that was evident during the pre-Pseudocalanus sp. copepodites and adults were also operational period (Figure 4-4). The operational and present throughout the year, with peak abundances 1993 geometric means for copepodites at Stations P2 occurring from mid-summer through fall (Figure 4-3). and P7 were considerably larger than the means for j Monthly mean abundances in 1993 were lower than the preoperational period (Table 4-3). Operational the preoperational average in spring and higher than densities were significantly larger than those during average from May- July and in September. The mean the preoperational (1982-1984) period when stations densities of both copepodites and adults during the were averaged (Table 4-4). Differences among years operational period were not significantly different from and months were also significant. The density of the preoperational (1982- 1984) means (Tables 4-3,4-4). copepodites at Station P2 over all sampling dates was Differences between periods at the nearfield and far0 eld significantly greater than at Station P7 (Table 4-4). stations were consistent, indicating no effect due to Mean densities at the nearfield and farfield stations plant operation occurred. Significant differences were showed similar increases between the preoperational notd aniong years and months, but not between (1982-1984) and operational periods, indicating the sta3 ort increase was areawide, not localized in the vicinity of the plant (Table 4-4). Seasonal fluctuations in abundance of Oithona sp. Ofhona so. adults during the operational period and 1993 were All Oithona sp. (mostly Oithona similis) lifestages similar to those observed during the preoperational 4-17
Olthona sp. Olth2xs sp. Nauplii c0Pepodites 4.0 - 4.0 3.3 -
# se 3.5 - ,
.>k
, ' , . ' t . . .*.~ k , . - - -pt %
3.0 - ,j % \ .,a j 3.0 -- o j;I % !i "- 21 !z ? I4,'7 u- ,
/
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r
< , o <a i 1.5 - (; # '
1.5 - ' d- 1.0 - ._.i 1.0 - @ml , __
.......... %w _
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- - .o - - 1993
--.o-- 1993 00 ... " i . . i i i i e i i i .
JAN FEBMARAPRMAYJt.N NL AUG SEP OCrNOVDEC JAN FEB MARAPRMAYJLN Jti AUG SEP OCTNOVDEC MONTH MONTH Oithona sp. I Adults 40- WE u- --.o.- 3,,3
,s a
#n ., ,. 3,-
<- u- n g8 a m to-i, w 1 1.N%q 31: i.5 -
e .:; S..F , ' yf . '.d... I cc ' '- 411.0- s 8
'tf 0.5 -
" i i i i i i i i e i ii JAN FEB MARAPRMAY AN NL AUG SEP oCTNOVDEC MONTH I
I I Figure 4-4. Log (x+1) abundance (no./m') of Oirhona sp. nauplii, copepodites and adults; monthly means and 95% confidence intervals over all preoperanona! yean (19781984 and 1986) and monthly means for 1993 and operational period at g nearfield Station P2, Seabrook Operational Report.1993. g 4-18 5
\ ZOOPLANKTON ,_ I period (Figure 4-4). Geometric mean abundance for preoperationally (Figure 4-5 and Tab'e 4-5). Early edults at Station P2 for the operational years and 1993 spring collections (Group 1) were characterized by low ;
- were slightly higher than the mean for all preoperational densities of only a single species, Hiatella sp. The f-- years (Table 4-3). Mean operational densities of transition to the late spring assemblage (Group 2) was !
, Oithona sp. adults were signi6cantly greater than the marked by peak densities of Hiatella sp., the earliest recent preoperational (1982-1984) means at both spawner, along with moderate densities of Afvrilus l f near6 eld and farneld stations. Mean densities at the edulis, Afya truncata and Solenidae. Peak mean l near6 eld and farfield stations showed similar increases densities of Af edulis, Anomia squamula, and Afodiolus between the preoperational (1982- 1984) and operational modiolus typified one of the two summer / fall j [ periods, indicating the increase was areawide, not assemblages, Group 3. This assemblage was followed j i localized in the vicinity of the plant (Table 4-4). by a period of low-to-moderate densities of bivalve I - Differences among years and months were also larvae (Group 4) that occurred in July or August. In significant. No significant differences were detected most years, including 1993, a second peak of Af edulis, between stations. A. squamula and Af modiolus led to the recurrence I of the summer / fall assemblage (Group 3) in late summer or fall, which was often again followed by low to 4.3.2 Hivalve Larvae moderate densities of larvae, primarily A. squamula, i Af edulis and Af modiolus(Group 4). No single group 4.3.2.1 Community Structure characterized the bivalve larvae assemblage from August-October every year. The bivalve larvae Patterns of abundance of the umboned bivalve larvae assemblage during the operational period (beginning assemblage were examined using numerical ciassifica- in August 1990) was similar to previous years. tion to address whether there were differences among stations (spatial patterns) or between the preoperational in 1993 the early spring assemblage (Group 1) and operational periods (temporal patterns). This aggre- characterized most stationsin late April and early May I gation of meroplanktonic species exhibited strong sea- (Figure 4-5). During late May, as the spawning season i sonal patterns that were generally consistent among progressed, the late spring community (Group 2) char-years and stations, especially for the early spring and acterized all stations. During June and early July, the spring groups (Figure 4-5). Mean abundances were high density summer / fall assemblage (Group 3) grouped seasonally, falling into one of four distinct characterized all stations. From late July through groups. The seasonal structure of the community re- August, most stations were characterized by low density j l flected recruitment of different taxa and their abundance summer / fall assemblage (Group 4). During September, (Table 4-5). the high density assemblage (Group 3) recurred, and i during October densities declined and Group 4 again I characterized all stations. Temnoral Patterns During the operational period (1990-93) geometric The bivalve larvae assemblage showed predictable mean densities in the two summer / fall assemblages I seasonal changesthat were generally consistent among (Groups 3 and 4) were somewhat higher than years No unusual assemblages (groups) of bivalve preoperational densities (Table 4-5). Operational larvae have occurred during the operation of Seabrook densities in the late spring assemblage (Group 2) were Station, as evidenced by the classi6 cation of all the lower than preoperational densities for all dominant operational period collections into groups that occurred taxa. Multivariate analysis indicated that operational 4 19
q Ls Ungrouped. Early Spring 1993 ;))
...... wnhin smup q.., ;._ g,=.g smularuy
.M:;TPgmey?
M$ymrtObir Group 1. Early Spring
% , W*9YS* E
,-@p a c a. of samples . ;ic p "OC m m ys 4 ....... bes=cen gmup semilsray ,. ,. ,. ,. ,. ,. ,. ,. ,. C#'uE2
- SE'i"E
* *#*'l * * *
- no. of samples :::. ::. :.-
I Group 3 Early Summer / Fall E w,v,v,v,v, I
# # //1 //f f f /
7
/ / / //# # # # # /
/ / / # # # # # # # #
# $ / / / / / ff f 4 f 1 / / / / f f f b s % /./ % s% % ss%
p;4;+</;4:4; G,oup 4 - t i. summ.rer.ii
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a 6 I i e 0.2 0.4 0.6 0.8 1.0 0.0 BRAY CURTIF SD11LARITY
' , W ,' --
p2 .- eqm -
,.,. p;pp, pp',
ypp,' 1993 P5 pypp s s s yff, p1 u , .f.
,. ppy,s . pppy, p2 y;c *::::::. ????, r //V//v?/V// <
' ~5~~~~
1991 P5~ *
"Di.E.E.!.* , , ,*.****.'
p p'p'p'p ' 5 '~ 5'~'~ 5 5 ' Y '~'pppppppppfy, *c
,. , , p""") Group t P_ ~C ,.,.,.f ,. - - {ffffss ' ypppppps Y,Y,Y?.
g 4
? ...... . .a.*: # s/Y/#
s s s ,' a P2 as '/// '. s ss ssss
'//////c w C Group 2 1991 P5- A ,ff.W --
s e:s':/./.e s .s . r. py- 4: ,, s s 's'/. ,', / #. . c n
& O*
p2 1e= ::,
.. $$ I p7 Va',';;f y?/ y M p2 a.ow ::.
^' '''' 8"
?/'s'; / ,' V' F' V' '/
1988 IE o'n' wr~r.' 97- t ~xrc . .. ppppppppy APR l MAY l JUN l Rh, l Abc l Sk.P l ocT i MONTH Figure 4-5. Dendrogram and seasonal groups formed by numerical classification of bivalve larvae log (x+1) transformed abundances (half monthly means; nodm') at Seabrook l intake (P2), discharge (PS) and farneld (P7) stations, April-October, 1988-1993. ' Seabrook Operational Report,1993. 4-20 E s ;
TAHLE 4-5. GEOMETRIC MEAN ABUNDANCE (Nolm'), AND Tile 95% CONFIDENCE LIMITS OF DOMINANT TAXA AND NUMBER OF' COLLECTIONS OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF BlVALVE LARVAE COLLECTIONS AT INTAKE (P2), DISCII ARGE (PS) AND FARFIELD (P7) STATIONS, 1988-1993. SEABROOK OPERATIONAL REPORT,1993. GROUP NO1 DOMINANT TAXA
- PREOPERAT!ONAL YEARS' OPERATIONAL YEARS
- NAME SIMILARITV' N' LCL X UCL N LCL X UCL 1 IliarcIla sp. 18 28 39 55 II 20 44 92 Early spring (b.64/0.44) 2 Iliarella sp. 9 632 1316 2741 17 434- 650 974 Late spring Afyn truncata 56 112 223 .5 10 19 7 69 Solenidae 38 51 8 13 23 U (0.68/0.44) 70 2 g4 Afytilus edulis lI 28 5 3 Afytdus edidis 55 1103 1912 3315 48 1553 2455 3879 Summer / Fall Anomia squamula 364 621 1061 579 972 1630 f Afodiolus modiolus 200 309 477 102 186 339 I (0.64/0.54)
Iliatella sp. 95 185 360 164 293 522 Afyn arenaria 8 12 19 2 4 7 4 Anomia squamula 17 50 96 181 58 184 240' 312 Summer / Fall Afodiolus modiolus 15 29 56 5 7 10 l Afyfilus cdulis 23 39 65 97 153 242 (0.63/0.54 Afyn arenaria 5 10 19 6 9 13 Spisula solidissima 5 8 13 10 14 20 Ungrouped IliarcIla sp. -- -- - -- I - 2 - (--I.13)
*those taxa contributing ;tS% of total group abundance in either preoperational or operational period collections
'preoperational = April 1988-October 1989; operational = August 1990-October 1993
'(within-group similarity /between-group similarity)
*N = number of half-monthly means calculated from weekly means (first half-month includes weeks beginning with days 1-15; second half with days 16-31)
---J-_______-____-_---_---___________ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _
O O ZOOPLANKTON densities were significantly different than densities in was similar (Group 4). Multivariate analysis of variance 1988 and 1989 (Wilks' Lambda =0.30. F-50.6, indicated there were no significant differences among p=0.0001); these difTerences were consistent among the three stations during the preoperational (1988,1989) stations (Preop-Op X Station: Wilks' Lambda =0.88, and operational (1991,1992, and 1993 ) years (Wilkes' F= 1.47. p=0.08). Lambda =0.91, F=0.99, p=0.48). I Spatial Patterns 4.3.2.2 Selected Species Mya arenaria was identified as a selected species E Distribution of bivalve larvae in marine waters was related to several factors: distribution of spawning because of the interest in recreational (locally) and com-adults, length of larval existence and local hydrographic mercial (regionally) harvesting of adults and the concern conditions. The dominant bivalve larvae collected in that impacts to the larval population could decrease coastal waters of New Hampshire were species whose the standing stock of harvestable clams (Section 10.0). g adults were widely distributed along the New England Mrtilus edulis has been the most abundant species g coastline. Duration of larval stage is dependent on encountered in bivalve larvae investigations. Teiaporal temperature, but may be as long as six weeks (Bayne and spatial patterns of both species were examined to 1965,1976; Jury et al.1994). The local hydrography evaluate whether there was evidence ofimpacts induced is dominated by tidal and longshore currents (NAl by operation of Seabrook Station. 1980). Stations P2, PS and P7 are located in waters of similar depth (Figure 4-1) with no physical barriers between them. These conditions tended to create a Mra arenaria spatially homogenous bivalve larvae community, it was not unexpected, then, that the species composition This species is discussed in detail in Section 10.0. was usually similar at each of the three stations (Figure 4-5). During 90% of the sampling periods, assemblages at all three stations were similar, and were grouped Mtilus edulis together; assemblages at nearfield Stations P2 and P5 were grouped together 100% of the time. In 1993. Abundances or Mytilus edulis peaked in mid-June the assemblage from the earliest samples taken (late at Station P2 during the preoperational and operational April 1993) at Station P7 (farfield) was not similar periods and during 1993, and remained relatively g' to any other group because only extremely low numbers abundant through the end of sampling in October 3 of Hiatella sp. were present. By early May 1993, the (Figure 4-6). Monthly abundances in 1993 were usually P7 assemblage was similar to that at P2 and P5 and higher than the average operational and preoperational g placed in the early spring assemblage (Group 1). abundances, and were generally above the upper 95% e confidence limit of preoperational means after the third The only other sampling period in 1993 where all week of June. The 1993 peak abundance (in late June) three stations were not placed in the same faunal group was greater than the preoperational peak by more than occurred in late August. Collections from Station P7 an order of magnitude. (farfield) were placed in Group 3. the high density summer / fall assemblage, while collections at Stations The annual abundances at both nearfield and P2 and P5 (nearfield) were placed in Group 4. By farfield stations during 1993 were more than double early September, the assemblage at all three stations the operational and preoperational abundances (Table 4-22 I.
~
f '.. {.. (l ! h t Mytilus edulis
.......... ww 3
--o-- 1993 _, k '
y 'E , _ .. '. ~ .o 9 j
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APR MAY JUN JUL AUG SEP OCT NOV 2 MONTH / WEEK Figure 4-6. Weekly mean log (x+1) abundance (no./m') of Mysilus edulis larvae at Station P2 during preoperational years (1978 1989, including 95% confidence intervals), and weekly means in the operational period (1991 1993) and in 1993. Seabrook OperationalReport.1993. E_ 4-23
Oi 0 ZOOPLANKTON 4-6). Mytilid abundances had been low at all stations significant during the period when collections were in 1992 (N Al 1993b). but the average operational abun-made at all three stations, although differences among dances at all three stations were not significantly years and months were significant. The interaction g different than recent preoperational (1988-1989) term (Preop-Op X Station) was not significant, 3 suggesting that the plant had no effect on the abundance abundances (Table 4-7). Station difTerences were not of Mytilus edulis larvac. TABLE 4-6. GEOMETRIC MEAN ABUNDANCE (No./m') AND UPPER AND LOWER 95% CONFIDENCE LIMITS OF M}TILUS EDULIS LARVAE AT STATIONS P2, P5 AND P7 DURING PREOPERATIONAL YEARS AND GEOMETRIC MEAN E ABUNDANCE DURING TIIE OPERATIONAL PERIOD (1991-1993) AND 1993. 3 SEABROOK OPERATIONAL REPORT,1993. PREOPERATIONAL OPERATIONAL 1993 CV MEAN' CV MEAN STATION P2 YEAR 1982-1989 MEAN* 232.4 18.52 149.0 8.50 417.7 I P5 1988-1989 184.2 18.00 146.1 .4.89 305.4 P7 1982-1984 250.1 13.22 162.4 27.27 487.6 1986-1989 I 'mean of annual means I TABLE 4-7. RESULTS OF ANALYSIS OF VARIANCE COMPARING INTAKE (P2), DISCilARGE (PS) AND FARFIELD (P7) WEEKLY ABUNDANCES OF M}TILUS EDULIS DURING PREOPERATIONAL(1988-1989) AND OPERATIONAL (1991-1993) PERIODS. SEABROOK OPERATIONAL REPORT,1993. SOURCE OF MULTIPLE E VARIATION MS F COMPARISONS g< df Preop-Op 1 0.02 0.12 NS g Station 2 0.20 1.49 NS g Year (Preop-Op) 3 23.73 181.14* " Week (Preop X Year) 122 5.31 40.57 "
- Preop-Op X Station 2 0.08 0.60 NS Error 244 0.13 I
4 24 5
I ZOOPLANKTON I 4.3.2.3 Entrainmeni in all years, entrainment was highest in J une or J uly, reDecting the natural peak in bivalve larval abundance The effects of operation of Seabrook Station on observed nearshore. Entrainment appeared to be hivalve larvae were monitored primarily through substantiallylower in 1991 than during 1990 and 1993 entrainment sampling and secondarily through compar- (N Al 1991 b), largely as a result of a four-month plant isons of both community and species abundance shutdown, which resulted in reduced entrainment of characteristics between the preoperational and dominants Afyrilus edulis. Hiatella sp. and Anomia operational periods. The estimated total number of squamula (Figure 4-7). I larvae entrained in the cooling water system in 1993 is presented in Table 4-8. In 1993, entrainment samples were collected from the third week in April through 4.3.3 Macroroonlankton I October. No samples were taken during scheduled or unscheouled plant shutdowns. Scheduled plant 4.3.3.1 Community Structure shutdowns occurred from early August through E November 1991 and in September and October 1992. Historical analysis (1978-1984 and 1986-1989) of 3 The total number of bivalve larvae entrained in 1993 the macrozooplankton assemblage at the near6 eld was greater than in 1991 and 1992 (Figure 4-7) due Station P2 showed seasonal changes that were greatly 'I to the above average abundance of some species such as Afvtilus edulis and Anomiasquamula in the natural influenced by the population dynamics of the dominant copepods Centropages tspicta and Calanusfmmarchicus environment. Also, in 1993 samples were collected (NAl 1990). Other taxa. particularly meroplanktonic throughout the period when bivalve larvae were species, exerted short-term influences, especially during typically abundant (July - September), since there were the spring and summer (N Al 1985). Because of their no plant shutdowns. In 1993 Afvtilus edulis accounted lower abundances, seasonal pattems of tychoplanktonic for 55% of the total bivalve larvae entrained, while species, e.g., mysids amphipods and cumaceans, were Anomia squamula accounted for 22%, Hiatella sp. for not well documented by numerical classification of 13% and Afodiolus modiolus for 7% (Table 4-8). Most the entire macrozooplankton assemblage. To identify larvae were entrained during June (22%), July (39%), seasonal pattems more clearly, the tychoplankton August (17%) and September (18%), and less than 5 assemblage was analyzed separately from the mero-I % of the total was collected in late April, May and October. and holoplankton. Numbers of larvae entrained reflect the numbers The Holo- and Meroplankton Assemblace present in the natural environment. For example, The distinct seasonal patterns of the holo- and I Afvtilus edulis larvae were very abundant in 1993 from late June through the third week of July (Figure 4-6). That penod of peak abundance is reflected in the high meroplankton previously observed were again evident when 1993 collections were included in the numerical I numbers entrained in July (Figure 4-7, Table 4-8). An early fall (September) peak in bivalve larvae entrainment in 1993 was due to high numbers of classification (Figure 4-8, Table 4-9). Groups 2,4, 5,6 and 7 were represented by at least one month in every year and, together included 92% of the Anomia squamula and other bivah es, primarily Afodio- collections. Temora longicornis and Sagitta elegans lus modiolus (Table 4-8). Hearclla sp., an early spawn- dominated some winter collections in 1990 and 1993 er, was most abundant in entrainment samples in June (Group 1). Winter and early spring (Group 2) and July. collections were dominated by Cirripedia. Copepods 4-25 I
TAllLE 4-8. ESTIMATED NUMBER OF BlVALVE LARVAE (X10') ENTRAINED BY Tile COOLING WATEll SYSTEM AT SEABROOK STATION FROM TIIIRD WEEK IN APRIL TIIROUGli FOURTil WEEK OF OCTOBER 1993. SEAHROOK OPERATIONAL REPORT 1993. SPECIES APR MAY JUN JUL AUG SEP OCT TO:AL! % Alttilus cdulis <0.1 0.1 2254.0 5387.5 1497.3 661.9 249.9 10050.7 l 55.2 i Al,nliotros nuntiolus 0.0 <0.1 0.5 7.5 452.0 752.6 71.3 1283.9 l 7.1 I 0.0 <0.1 8.5 7.9 0.2 0.2 <0.1 0.1 l'htcopecten vnagelhnricus 16.9 l i Anonria squanrula 0.0 0.1 378.3 707.0 767.1 1717.4 353.0 3922.7 l 21.6 o i 0.0 0.0 0.0 l I .0 6.4 13.4 17.7 0.3 ch Spistula soli,lissinia 48.5 l I Alur arenaria 0.0 0.0 0.6 1.8 2.2 0.7 17.2 22.5 l 0.1 1 Aint truncata 0.0 <0.1 1.5 0.0 0.2 0.0 0.4 2.1 l <0.1 I l //iarcl/a sp. < 0.1 6.7 1126.3 917.2 271.0 79.8 4.5 2405.5 i 13.2 i I l Alaconta balthica 0.0 <0.1 0.1 0.0 0.0 0.0 0.1 0.2 l <0.1 l l <0.1 <0.1 82.9 109.1 57.3 57.5 27.4 1.8
- Bivalvia 334.3 l l l Solenidae 0.0 0.1 54.5 23.7 2.4 3.4 18.4 102.5 0.6 l l
- I TOTAL <0.1 6.9 3907.1 7172.8 3056.1 3286.9 760.0 18189.8 l
_________=_ - - - -_ _ - - - = = - - - - - - __ - - - - -- __1____
% OF TOTAL <0.1 <0.1 21.5 39.4 16.8 18.1 4.0 I
W M. W W M M EB
, w I
! Cooli:g Wcter P;mped
~
, f [* v f W*
s ., e0 - E% 2E $0 - E ax y j a0-l I I T 30 - o ZE l '3 m 2 - 2e U d 10 - ! o MAY EN R AUG APR MAY NN APR MAY AN JUL AUG SEP OCT AN JUL AUG SEP OCr 1991 1992 1993 1990 l YEAR / MONTH
- no samples coucaed
)
Bivalve Larvae l I 3 [4, 4 ,
, -- J W -
z
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E h_Vn - = m ,'s' A r !l! 20a0 - .er [ 4,% l h G 4~ C ' y ' f g . .
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AN EL AUG SEP OCT MAY AN JUL AUG APR MAY NN APR MAY NN NL AUG SEP OCr 1990 1991 1992 1993 YEAR / MONTH
- not sampled j 0 Mytilis edslas & Anomia squamula O Hiate:La sp. D other 1 Figure 4 7. Volume of cooling water pumped during the months sampled for bivalve larvae and total number of bivalve larvae (x10') entrained by Seabrook Stanon,1990-1993. Seabrook Operational Repon,1993.
4-27
O
,..... wiusm group
~i' M~I* ' ' '^' ""' Group 1. Winter ]
l sundanay _ .;.;.;.;. .;.;.;.;.; no. of samples
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......- between group similanty :,f y y y y y Y X X X' Group 3. Spring 1989
- Group 4 Late Spring Group 5 - Summer I
, /
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,j : Group 7- Late Fall /Estly Winter i
1 4 4 4 1 0.0 0.0 0. 4 0.6 0.8 10 BRAY-CL'RTIS SIMILARITY I 1993 n- ;m .s~. P5_ , . ;j eg :,:.:.: a.gg ;. i;:
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JAN l FEB l MAR l ApR l MAY l EN l EL l AUG l SEP l OCT l Nov l DEC M! ! MONTH I ' Figure 4-8. Dendrogram and seasonal groups fo:Tned by numencal classification of mean monthly log (x+1) transformed abundances (no11000 m') of holo- and meroplanktonic species of macrozooplankton at iatake Station P2. discharge Station PS and farfield Station P7, . j
- 1988-1993. Seabrook Operational Repon,1993.
I' 4-28 l 5
=
l l
m v TAllLE 4-9. GEOMETRIC MEAN ABUNDANCE (NoJ1000m') AND 95% CONFIDENCE LIMITS OF DOMINANT IIOLO- AND MEROPLANKTONICTAXA OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MACRO 7,00 PLANKTON COLLECTIONS (MONTHLY MEANS) AT INTAKE STATION P2, DISCIIARGE STATION PS AND FARFIELD STATION P7,1988-1993. SEAHROOK OPERATIONAL REPORT,1993. 1 GROUP' DOMINANT SPECIES
- PREOPERATIONAL YEARS
- OPERATIONAL YEARS' n LCL i UCL n' LCL i. UCL 1 Teniora longicornis 3 3225.6 28662 254623.8 9 211.0 996 4694.6-Winter Sagitta c/cgans 6896.1 20601 61540.4 1249.4 2148 3691.0 l 0.9 32 575.3 141.1 653 3007.3 l (0.60/0.55) Tortonus cliscarnIntus 6.7 32 142.3 205.1 412 826.5 Calanusfinnrarchicus 2 Cirripedia 12 3692.4 8431 19250.6 18 28329.0 66603 _156587.8 Winter.Early Spring Tcmora longicornis 2086.9 4065 7918.8 152.2 664 2882.9 L (0.67/0.57) Calanusfinmarchicus 1242.9 27II 59I I.7 694.0 3540 18044.1 Pseudocalanus sp. 964.9 1867 3610.3 872.8 1867 3992.1 405.6 1336 4394.3 204.9 417 -848,1 Sagitta c/cgans OiAopleura sp. 78.8 501 3157.0 10933.7 19232 33826.6 6 4389.6 7900 14217.1 not represented 3 Calanusfinmarchicus Spring 1989 Cirripedia 893.3 3550 14099.8 (0.66/0.57) 4 Calanusfinmarchicus 24 38253.0 56059 82153.I 18 81399.9 I44009 254774.3 late Spring Eualus pusiolus 3658.0 5598 8565.7 1301.0 1973 2992.9 Temora longicornis 2484.6 4636 8650.6 1495.5 3141 6596.5 (0.71/0.64)
Enuhre sp. 2065.7 4599 10235.6- 7818.8 13368 22853.8 5 Calanusfnmarchicus 15 17993.5 45735 116242.9 24 31328.7 46367 68623.1 Summer Cancer sp. 15783.8 37088 87I46.1 50310.2 67553 90706.6 Centropages typicus 2302.6 12059 63134.9 12601.4 24904 49214.9 (0.67/0.64) Eualus pusiolus 4806.1 11499 27509.2 6008.2 10977 20054.3 Tcmora longicornis 853.0 278I 9062.3 6424.4 II752 2I495.7 (continued) ~
~- - A _ _ _ _ __ _ _ ___. _ _______ _ _________ _ __ _ ______ ____ _ _ _ _ _ _
TABLE 4-9. (Continued) GROUP' '? MINANT SPECIES' PREOPERATIONAL YEARS' OPERATIONAL YEARS' n LCL T UCL n LCL T UCL 6 Centropages typicus 15 26201.3 54321 112620.3 36 29091.7 52548 94917.6 Fall Centropages sp. 2563.3 5334 11099.1 546.8 l170 2501.4 (0.66/0.6I) 7 Centropages typicus 18 1423.4 2802 5514.9 18 2204.3 3545 _5700.5 I. ate Fall- Temora longicornis 1468.7 2446 4073.3 397.6 770 I490.5 liarly Winter Centropages hamatus 611.4 II02 1985.7 2.7 14 56.9 (0.66/0.61) Sagitta elegans 521.5 876 1472.7 517.5 882 1503.8
,, Pse ulocalanus sp. 398.8 791 1568.0 69.4 171 421.5 d, Torranus discaudatus 87.5 324 1191.7 201.7 525 1363.8 Dikopleura sp. 183.9 463 1163.7 186.3 425 967.6
'(within. group similarity /between group similarity)
*those taxa contributing 25% of total group abundance in either preoperational or operational periods
'preoperational period = January 1988-July 1990; operational period = August 1990-December 1993 M M M M M M M M M M M M M M M M M EE
.e . _ _ _ _ - _ - _ _ - -
- ,m
I i l ZOOPLANKTON l ( T. longicornis. Calanusfinmarchicus. Pseudocalanus dominant during this time. This pattern, although i abbreviated, was aiso observed in February 1990. A l h sp.) S elegans and Oikopleura sp. were also abundant in winter and early .;pring. C fnmarchicus with slightly delayed Cirripedia peak combined with low Cirripedia dominated March and April samples in 1989 copepod abundances and sustained high abundance of (Group 3). Late spring (Group 4) collections were S elegans extended the winter community (Group 1) dominated by C.fnmarchicus, whose abundance was into March 1993 (NAl 1994). The delay of the spring an order of magnitude greater than the co-dominants Cirripedia and Calanusfnmarchicus peaks, the low T. longicornis, Evadne sp. and Eualus pusiolus. abundance of C. Opicus, and the longevity of the winter Summer (Group 5) collections were dominated by group may have been the result of the lower than Cancersp.and C.fnmarchicus. Centropagestypicus, normal water temperatures during the winter of 1993 E. pusio/us and T. longicornis were also abundant in (Section 2.3.1). l I summer. Most meroplanktonic species (e.g., Carcinus Group abundances were generally similar between I maenas. Sec. 4.3.3.2), though not dominant, reached their peak abundances during summer months. C. operational and preoperational periods with three typicus and Centropages sp. copepodites were dominant exceptions. Winter (Group 1) abundance was lower in fall (Group 6). C. typicus also dominated late fall in the operatienal period due primarily to low , and early winter (Group 7) periods when other abundances of Temora longicomis and Sagitta elegans. copepods, S elegans and Oikapleura sp. were relatively Abundances of Cirripedia and Oikopleura sp. in winter and early spring (Group 2) were substantially higher j abundant. during the operational period than the preoperational The seasonal shift in dominance among Cirripedia, period. Late spring (Group 4) abundance was higher ~ Calanutfnmarchicus and Centropages typicus observed in the operational period due mostly to higher in 1988 through 1993 was consistent with pr.ttems ob- abundance of Calanusfnmarchicus. Geometric mean served historically (NAl 1990). The seasonal shifts abundances were generally higher in the operational in dominance observed among the copepods C. years of 1991-1993 than in the preoperational period fnmarchicus C. typicus and to a lesser extent, of 1988-1989 and the operational status was significant-Pseudocalanus sp. were consistent with other ly different (p=0.0001) in the MANOVA. Of the the observations for the Gulf of Maine (Sherman et al. 50 taxa included in the MANOVA, 26 exhibited 1988). significantly higher abundance in the operational period while only 6 taxa were lower in abundance (individual Species composition of holo- and meroplankton dur- species differences determined by ANOVA). Of the ing the operation of Seabrook Station was generally 13 taxa that dominated the holo- and meroplankton similar to the preoperational period examined. during various parts of the annual cycle, seven (T longi-liowever, the period from December 1992 through cornis. Centropages typicus. Oikopleura sp., Cirripedia, March 1993 was atypical of previous years (Figure C.finmarchicus. Concer sp. and Tartanus discaudatus) 4-8). The fall dominant Centropages typicus typically reached higher abundances in the operational period declined in abundance each December, but remained than in the recent preoperational period (1988-1989). a dominant in the low abundance winter assemblage. Only Centropages hamatus declined in abundance. However, in December 1992, C npicus continued to S elegans Pseudocalanus sp., Evadne sp., Centropages occur m high abundance. then virtually disappeared sp. copepodites and Eualus pusio/us were similar in in Ja:,uary 1993 (NAl 1994). Winter 1993 was abundance between the two time periods. Although p L dominated by species Sagitta elegans. Oikopleura sp. differences in the operational and preoperational periods and Torranus discaudatus, which normally were co- were detected, a similar shift was detected at all stations 4-31
n LJ [] ZOOPLANKTON (M ANOVA testing Preop-Op X Station, p=0.97) grouped togetner within each month. Although species indicating a broad scale trend. Increases of holo- and composition was similar among stations, differences meroplankton in the operational perbd could be in individual species abundances were detected by attributed to a number of environmentu factors such MANOVA (p=0.0001). For those species, abundances as changes in temperature, reduced abundances of were generally higher at near6 eld stations. This was ichthyoplankton predators and recruitment of the case for Calanusfinmarchicus (see also Sec. 4.3.3.2) macrozooplankton from other areas (Meise-Munns et and Temora longicomis, the two numerically dominant al 1990; Kane 1993). Small but signi0 cant broadscale taxa from 1988-1993. Differences could be related g increases in temperature have been detected in the to spatial differences in water quality parameters or 3 operational period, primarily 1991 and 1992 (Section phytoplankton abundance. Temperature, for example, 2.3.1 ). The abundance ofichthyoplankton, w hich feed was higher in the nearfield area than far6 eld in both g on macrozooplankton, has declined in the operational near-surface and near-bottom waters and dissolved 5 period (Section 5.3.1). Copepod abundance in the Gulf oxygen was higher in near-bottom waters, while bottom of Maine has been increasing (Jossi and Goulet 1993) salinity was higher in the farDeld waters (Section 2.3.1). and New Hampshire coastal waters may be experiencing The larger sized phytoplankton (>10 m), the major some of this increase. Calanurfinmarchicur was report- food source for many zooplankton, have been more ed to base exhibited an increasing trend in the North- abundant in the near0 eld area (Section 3.3.1.1). west Atlantic over the past 30 years (Sherman 1991). Jossi(1991) reported that total copepod abundances in the Gulf of Maine were higher in 1990 than in the The Tvehoplankton Assemblace previous decade. Seasonal variation in the tychoplankton species Previous analyses have suggested that there are no composition was influenced mostly by the nearly spatial differences in holo- and meroplanktonic omnipresent dominant taxa Neomysis americana, assemblagesin the study area (N A! 1991 b). The geog- Oedicerotidae and Pontogencia inermis and by the g raphy of coasta! New England helps to create the seasonally dominant Afrsis mixta (Figure 4-9; Table 5 hydrographic conditions of the Gulf of Maine. There 4-10). Three seasonal groups encompassed 76% of are no major land barriers between the Bay of Fundy the collections of the tychoplankton (93% of P2 and B and Cape Cod that would divert coastal currents P5 collections). High abundances of X americana 3 offshore, although several embayments can affect local dominated fall and winter collections (Group 1). M conditions. This condition promotes a circulation pat- mixta replaced K americana as the overwhelming tern that allows widespread dispersal of planktonic dominant in late winter and early spring (Group 4). organisms, particularly holoplankton and those mero- A transition period between spring and summer planktonic specieswith extended larval existence. The assemblagestypically occurreu in May and June. This distances among Stations P2, P5 and P7 are small period coincides with the offshorc migration ofM mzxta relative to the area from which holo- and meroplank- juveniles, which has been linked to surface water tonic organisms could be recruited (via current trans- temperatures approaching 12 C and the onset of thermal port) to coastal New Hampshire. stratification (Grabe and Hatch 1982). This period was charreterized by two com m unities; one dom inated Numerical classincation of holo- and meroplanktonic by low abundances of Af mixta (Group 5), the other abundances in 1988-1993 revealed no spatial differences by moderate numbers of P. inermes.1schyrocerus in commumty composition among Stations P2, P5 and angwpes and X americana (Group 6) at the nearfield P7 (Figure 4-8). Collections from all stations were Stations P2 and PS. Community composition at P7 4-32 g
=
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U JAN l FIB l MAR l APR \ MAY k JUN k JUI. l AUG k sEP l OCT k Nov l DEC , MoSTH Figure 4 9 Dendrogram and seasonal groups fonned by numental classificauon of mean 2 monthly log (x+1) transfonned abundances (no/1000 m ) of tychoplanktonic species of macmzooplankton at intake Stauon P2. discharge Station PS and I farield Station P7.1988-1993. Seabrook Operanonal Report.1993. 4-33
TAllLE 4-10. GEOMETitIC MEAN AIIUNDANCE (NoJ1000m') AND 95% CONFIDENCE LIMITS OF DOMINANT TYCllOPLANKTONIC TAXA OCCURRING IN SEASONAL GROUPS FORMED BY NUMERICAL CLASSIFICATION OF MACROZOOPLANKTON COLLECTIONS (MONTIILY MEANS) AT INTAKE STATION P2, DISCIIARGE STATION P5 AND FARFIELD STATION P7,1988-1993. SEAHROOK OPERATIONAL REPORT,1993. (;ROUP' DOMINANT SPECIES $ PREOPERATIONAL YEARS' OPEllATION AL YEARS' n LCL T UCI, n LCL T UCL I Neonersis americana 34 107.6 230 491.1 46 146.4 219 326.6 Fall / Winter Pontogencia inermis 17.9 28 42.9 23.4 37 59.3 (0.59/0.58) Diastriis sp. 14.0 25 42.9 21.3 31 43.6 Oedicerotidae 9.7 16 25.4 13.4 19 26.8 l 2 Neomrsis americana II 55.9 I45 375.9 7 19.8 64 203.8 o P7 Fall / Winter Oedicerotidae 1.4 6 18.8 1.1 4 11.2 d, (0.53/0.44) u 3 Diattylis sp not represented 2 0.0 2 109.6 P7 Winter Erythrops erythrophthalma 0.6 2 3.5 (0.62/0.33) Oedicerotidae 0.9 1 1.3 Neomrsis americana 0.0 1 14.4 Ilyperiidae 0.0 1 12.3 4 Afrsis mixta 21 282.7 989 3451.8 22 354.3 863 2101.7
- 1. ate Winter / Spring (0.59/0.57) 5 Afrsis mista 3 0.0 8 241.9 6 2.5 12 50.1 Winter / Spring Pontogencia incrmis 1.1 4 11.7 1.9 5 10.0 (0.51/0.42) liarpacticoida 0.0 2 20.5 0.2 3 10.0 Diastylis sp. 0.6 2 4.8 0.6 3 8.5 Ischtrocerns anguipes 0.5 2 3.9 0.1 2 6.9 Oedicerotidae 0.0 2 165.2 0.0 1 6.3 Neomysis americana 0.0 1 12.0 1.6 5 12.1 (continued) 1 W W M M M M M M M M M M M M M M M EM
L 1 - U R W D f M
. 1: ,
TAllLE 4-10. (Continued) GROUI" DOMINANT SPECIES
- PREOPERATIONAL YEARS' OPERATIONAL YEARS' n LCL T -UCL n LCL i UCL.
DJ 6 Neonrysis americana 5 21.4 -153 1060.8 4 0.1 15 219.8 Nearfield Spring Pontogencia inermis 6.5 116 1834.1 5.0 120 2420.5 (0.59/0.57) hclerrocerus anguipes 3.8 16 61.7 62.7 132 ' 276.1 Afyfis mista 0.9 7 57.9 0.3 -63 ~-3197.2 .! Diasrylis sp. 2.2 12 54.7 5.3 22 84.2 -l 7 Neomysis americana 1 - 4 - 3 I .6 - 3 - 5.4 P7 SpringIFall Gammarus lawrencianus - 1 -- 0.0 <l 1.2 (0.51/0.39) Oedicerotidae - -- 1 -- 0.4 1 3.2 e- Ilarpacticoida - <l - 0.0 2 -17.5 0., Pontogeneia inermis - 0 -- 0.0 2 12.6 i
- ischyrocerus an - 0 --
0.3 1 3.5 Corophium sp. guipes - 0 - - - 0.0 1 29.5 ~ 1 8 Oedicerotidae 13 111.8 324 934.1 27 80.6 <200 494.0 i Summer Pontogencia inermis 76.5 140 257.3 34.5 67 - 127.4 liarpacticoida 18.2 44 105.0 72.6 -123 208.5 (0.61/0.58) 10.5 41 153.3 27.0 55 112.7 Neomysis americana 9 liarpacticoida 3 1.2 5 17.9 2 0.0 -6 1961.5 0.0 4 53.4' 1.0x10' . P7 Summer Oedicerotidae O.0 23 (0.48/0.39) Calliopius Ineviusculus 0.0 1 16.8 0.0 <l 78.7 Pontogencia inermis 0.0 1 8.3 0.0 - .1 620.1 10 Pontogeneia inermis . 1 - 6 -- 4 0.0 4 34.9 Summer / Fall Ilypenidae - - 6 -- 16.9 121 '827.0 liarpacticoida - 3 - 0.8 10 70.3-(0.52/0.44) 0.8 20 Neomysis americana -- 3 --
'236.1 Calliopius laeviusculus - 1 --
0.2 2 5.6 Oedicerotidae - 0 - 0.0 9~ 526.7
- witliin-group similarity /between group similarity)
*(those taxa contributing 25% of total group abundance in either preoperational or operational periods
'preoperational period = January 1988-July 1990; operational pened = August 1990-December 1993
O O ZOOPLANKTON w as highly variable during this period. Oedicerotidae (92% of collections Figure 4-9). The assemblage at became the dominant taxon in summer collections. Station P7 was distinct from that at the near6 eld stations Harpacticoida. P. ine, mis and X americana were also in 60% of the collections. Despite the differences at abundant in summer (Group 8). Episodes of low Station P7, farfield communities parallelled the nearSeld iychoplankion abundance, panicularly at Station P7 progression of dominant taxa from Neomysis americana from June to October resulted in the formation of N the fall and winter (Groups 1.2) to Mvsis mixta in g several small groups (Groups 7,9 and 10) represented the spring (Groups 4.5) to the amphipods in summer 3 by diverse amphipod assemblages. Tychoplankton were (Groups 8,9,10). The greatest similarity between also present in very low numbers in December 1990 nearfield and farneld stations occurred during the Msis g and January 1991 (Group 3). Moderate abundances mixta peak in March and April and again in August 5 of N americana and reduced abundances of amphipods when amphipods dominated. Although Station P7 and the cumacean Diastylis sp. formed a fall and early pencrally exhibited similar seasonal patterns to Stations winter group unique to Station P7 (Group 2) which P2 and P5, abundances of dominant taxa, particularly was concurrent with the dominance by N americana Pontogencia inermis and Oedicerotidae, were lower, at the nearfield stations, resulting in the formation of four groups (2,3,7, and
- 9) composed solely of farfield collections. Resultsof Near0 eld collections in 1993 followed the same numerical classification w ere substantiated by pattern as observed in the recent preoperational years MANOVA, which indicated that there were significant (Figure 4-9; Table 4-10). At Station P7,1993 seasonal differences among stations in species composition assemblages were generally typical of those observed (p=0.0001). Tychoplanktonic species are often strongly during the preoperational period except during the fall, associated with particular substrate types. Substrate w hen higher than average abundances of Diastvlis sp. type and complexity, along with proximity to Hampton-and Pontogencia mermis (N Al 1994) caused the Station Seabrook estuary, may account for some of the g P7 collections to be grouped with near6 eld collections. differences observed amongtychoplankters. Neomysis 3 americana. Pontogeneia mermis, and Oedicerotidae Seasonal patterns of the tychoplankton assemblage have higher abundances in the heterogeneous sand and g were similar between Stations P2 and P5 during rock ledge substrate in the nearfield area than at Station 5 preoperational and operational periods throughout most P7, where the substrate is mainly sand.
of the year (Figure 4-9). There was little consistency among years at Station P7, partially an anifact of the relatively Iv,v abundances at this station. MANOVA 4.3.3.2 Selected Species results indicated that differences in abundance between preoperational( 1988- 1989 ) and operational ( 1991 - 1993 ) Calanus finmarcliicus periods existed (p=0.0001), with abundances higher during operational years than in recent preoperational As in previous years, Calanusfinmarchicus, particu-years. His shift occurred in both near0 eld and farfield larly the copepodite lifestage, was a dominant stations (Figure 4-9. Preop-Op X Station, p=0.78), macrozooplankton species, as observed in the indicating a broadscale trend. community assessment (Table 4-9). Both copepodites and adults are usually present throughout the year. Differences between the ncarfield and farfield areas Average monthly copepodite abundances at Station E in tychoplankton assemblages from 1988 through 1993 P2 have historically exhibited a broad spring-to-fall 3 w ere apparent from numerical classification. Collections peak (Figure 4-10t Operational and 1993 abundances from Stations P2 and P5 were usually grouped together followed a similar pattern, with slightly more exag-4-36 E
(; Cala cs fizmarchic:s L Copepodites
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- Carcinus maenas Larvae 6- P- p- .nu
. .......... op., .a
{ 5- --o-- 1993 tv-....- ;...... - ; .. . w a .. o t x2 :s
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i, .- ..,. x. 0 I' i i i MAY i i na. e i AL;G SEP i OCT i NOV i DEC i JAN FEB MAR APR JUN MONTH Figure 4-10. Log (x+1) abundance (no/1000 m 2) of Calanusfinmarchicus copepodites and adults and Carcmus maenas larvae: monthly means and 95% confidence intervals over all preoperational years (1978 1984,1986-1989) and monthly means for the operational period (1991 1993) and 1993 at intake Station P2. Seabrook Operational Report.1993. 4-37
n LJ C ZOOPLANKTON gerated scasonal extremes. Operational or 1993 monthly signincantly among years, months and stations, but mean copepodite abundances exceeded the upper 95% this was not related to the operation of Seabrook confidence limit of preoperational means in April, May, Station, as indicated by the nonsignificant interaction June, and November, and were less than the lower 95% term (Table 4-12). confidence limit of preoperational means during February, March and December (Figure 4-10). Carcinus maenas Copepodite mean abundance was significantly higher during the operational period than the preoperational As in previous years, monthly mean abundances period (Tables 4-11,4-12). In recent years (1987-1989 of larvae of the green crab Carcinus maenas in 1993 show a strong seasonal pattern at Station P2, with peak and 199l-1993), average abundances at Stations P2 B and P5 have been similar (Table 4-12). Average abundances occurring during the late spring through 3 abundances at Station P5 were signi0cantly greater early fall (Figure 4-10). The timing and abundance than at Station P7. Average abundances at Station P2 of green crab larvae were very similar during both the g were not significantly different from Station P7, These preoperational and operational periods, although 5 differences have been consistent regardless of operational monthly mean abundances exceeded the operational status, as indicated by the nonsigni0 cant upper 95% confidence limit of preoperational means interaction term (Table 4-12), and do not indicate any in May, June, and July, efTect due to plant operation. Signi0 cant differences were also noted among years and months. Over all preoperational years and operational years, average peak period abundances have been similar at 1 l Adult copepod abundance does not show as clear both nearfield and farfield stations (Table 4-12), and a seasonal pattern as the copepodites (Figure 4-10). have increased between preoperational and operational Monthly mean adult abundances in 1993 were highest periods (Table 4-11). This increase, however, was not in April and lowest in June. Monthly mean adult signincant, and there is no indication of any effect due ! abundances during the operational period exceeded to plant operation based on the nonsignificant interaction the upper 95% cun.;dence interval of preoperational term (Table 4-12). Signi0 cant differences were noted monthly means in April and November, and were less among months. g than the lower 95% confidence interval of preopera- g tional monthly means in February and June. Crancon septemspinosa Mean adult abundances at Stations P2 and P7 declined slightly between the preoperational period As in previous years, monthly mean abundances (all years) and the operational period, while abundances of the zoeae and post-larvae of sand shrimp, Crangon at Station P5 increased slightly(Table 4-11). Average septemspinosa, in 1993 showed a peak over a broad adult abundance at Station P5 and Station P2 were not period between late spring and early fall (Figure 4-11). l significantly different. Average abundances at Station Operational monthly means were higher than the upper P5 were significantly different from Station P7. 95% confidence limit of preoperational means in March, Abundances at Station P2 and P7 were not significantly April and May. In September, however, the operational different from each other(Table 4-12). Average adult mean abundance was lower than the 95% confidence abundances have not changed signincantly between limit of the preoperational mean (Figure 4-11). the recent (1987-1989) preoperational period and the operational period (Table 4 12). Abundances differed 4-38 g
=
M r D U n O O M M M TABLE 4-11. GEOMETRIC MEAN ABUNDANCE (NoJ1000 m') AND COEFFICIENT OF VARIATION OF SELECTED MACROZOOPLANKTON SPECIES AT STATIONS P2, PS, AND P7 DURING PREOPERATIONAL AND OPERATIONAL YEARS (1991-1993), AND 1993. SEABROOK OPERATIONAL REPORT,1993. - PREOPERATIONAL OPERATIONAL 1993 SPECIES /LIFESTAGE STATION T' CV ? CV T (pcak period) i s l P2 4,153 6.39 4.324 3.54 5,747 Calanntfinnrarchicus copepodites PS 5,713 6.99 5,605 2.93 5,887 3 (January-December) P7 2,594 7.19 2,810 3.70 3,591 l Calanusfinnrarchicus P2 36 26.52 26 7.61 33 adults P5 26 28.88 35 10.25 53 ; (January-December) P7 29 28.96 15 6.90 17 ' ( Carcinus niacnar P2 3,506 6.72 8,030 3.59 5,548 7 4 3,613 12.91 8,552 4.64 5,279
$ larvae PS (June-September) P7 4.245 6.24 4,593 8.19 2,6I 7 Crangon tcpremspinosa P2 212 7.95 269 5.66 200 mene and postlarvae PS 170 7.24 264 3.29 295 (January-December) P7 159 10.25 i10 5.27 110 Nennrysis americana P2 151 18.94 153 7.76 114 all lifestages P5 45 30.73 44 _ 11.37 48 (January-December) P7 43 22.03 17 - 11.94 15-
' Years sampled:
Preoperational: P2 = 1978-1984,1987-1989 PS = 1987-1989 P7 = 1982-1984,1987-1989 Mean of annual means
'Mean of annual means, 1991.1992 and 1993
TAllLE 4-12. RESULTS OF ANALYSIS OF VARIANCE COMPARING ABUNDANCES OF SELECTED MACROZOOPLANKTON SPECIES FROM STATIONS P2, PS, AND P7 DURING PREOPERATIONAL(1987-1989) AND OPERATIONAL (1991-1993) PERIODS. SEAHROOK OPERATIONAL REPORT,1993. SPECIES' SOURCE
- d .f. MS F MULTIPLE COMPARISONS
- Calanta finmarchicus copegulites Preo Op' 1 3.67 7.76 " Op> Preop (January-December) Year Preop-Op), 4 1.43 3.03*
Mont 66 11.39 24.11 "
- StationfYear)' 2 2.28 4.82*
- PS P2 P7 Preop-Op X Station' 2 0.10 0.20 NS Error 356 0.47 Preo Op i 2.14 2.36 NS Colanutfinmarchicus 4 4.17 4.60 "
adults Year Preop-Op) (January-December) Mont 66 6.97 7.70 "
- Station (Year) 2 2.87 3.17' PS P2 P7 Preep X Station 2 0.25 0.28 NS Error 356 0.91 Carcinus macnas I 1.38 2.08 NS e- larvae Preop (-Op Year Preop-Op) 4 0 61 0.92 NS L (June-September) Month (Year) 18 1.92 2.89 "
- o Station 2 0.54 0.81 NS Preop X Station 2 0.14 0.21 NS Enor 116 0.66 Crangon septemspinosa Preo Op 1 0.08 0.25 NS rocae and post larvae Year Preop-Op) 4 0.71 2.28 NS (January-December) Mont 66 8.66 27.78 " '
Station (Year) 2 5.08 16.30* " P2 P5>P7 Preop X Station 2 0.34 1.08 NS Error 356 0.31 Ncomrsis americana Preo Op i 2.21 3.81 NS all lifestages Year Preop-Op) 4 8.11 13.97' " (January-December) Mont 66 2.69 4.64 * *
- Station (Year) 2 31.28 53.91 "
- P2>P5>P7 Preop X Station 2 0.01 0.01 NS Error 356 0.58
' Based on twice monthly sampling periods.
- Commercial operation began in August 1990; 1990 data left out of analysis to keep a balanced design in the ANOVA procedure. 'Preoperational (1987-1989) versus operational (1991-1993) periods, regardless of station; 1987-1989 reficcts the riod of time that all three stations were sampled coincidentally. ' Year nested within Nonth nested within year, regardless of station. ' Station P2 vs. station PS vs.
regardless station of year. Pf,reoperational
' interaction and operational between main effects. p NS = Not significant (p >0.05)
* = Significant (0.05 2 p >0.01)
** = liight significant (0.012 p >0.001)
"* = Very ighly significant (0.0012 p)
- Ranked in decreasing or er. Underlines indicate no significant difference in least-squares means (at s .05).
Il M M M M M M M M EE
I l Cr:ng:n septemspi:::s
- 3" Pmopemand g .......... op., g
! % 4- - - * * - - 1993
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@ Ovigerous & Larvigerous C Aduk O imrniair. =r=>4 O Juvenii.
{ Figure 411. Log (x+1) abundance (noJ1000 m)) of Crangon septemspinosa (zoea and post larvae) and Neomysis americana (all lifestages); monthly merns and 95% confidence intervals over all ptroperational years (1978-1984,19861989) and monthly means for the operational period (1991-1993) and 1993; and mean percent composition of Neomysis americana lifestages over all preoperational years (1978 1984,1986-1989) and for the operational period (1991-1993) at intake Station P2. Seabrook Operational Report,1993. 4-41
C C ZOOPLANKTON Abundances have increased slightly between the February. The decline in the relative abundance of preoperational (all years) and operational periods at immature mysids during the early spring was paralleled Stations P2 and P5. ond have decreased slightly at by an increase in the relative abundance of adults. Station P7 (Table 4-il). At all three stations, however, By May, juveniles (sexual organs absent or not abundances have shown no significant difference over differentiated) were alsoabundant. During May,there the recent preoperational period (1987-1993)(Table was a higher percentage of adults, ovigerous and 4-12). Regardless of operational status, abundances larvigerous Neomysis during the operational period than have been similar between Stations P2 and PS, yet during the preoperational period. The opposite was significantly greater than abundances at Station P7 true for juveniles and immature mysids. Differences (Table 4-12). The absence of a significant interaction betw een the two periods were also seen in other months, term indicates that there was no effect due to plant particularly in June, October, and November, but this operation. Abundancesshowedsignificantdifferences was not related to the operation of Seabrook Station, among months. as shown by the nonsignificant interaction term (Table 4-12). Neomrsit americana During the remainder of the year, percent composi-tion of the lifestages was similar between the tw E For the combined lifestages of Neomysis americana periods. Adults and immatures were the most common g (ovigerous and larvigerous females, adults, immature lifestagesduringJulyand August. Juvenilesincreased mysids, and juveniles), monthly mean abundances at between September and October, when they were the g Station P2 during both the preoperational and dominant lifestage. Juveniles began to decline during 3 operational periods showed no consistent seasonal November and December, at which time immature pattern, although there is a tendency towards lower mysids accounted for an increasing proportion of the l abundancesin the summer (Figure 4-11). Abundances total. averaged over all months at Stations P2, PS and P7 have also remained stable between the preoperational l and operational periods, and there have been no 4.4 DISCUSSION signincant preoperational-operational differences observed at all three stations combined (Table 4-12). 4.4.1 Community During both the recent preoperational period and the operational period, abundances of all life stages Microroonlankton combined have been significantly higher at Station P2 than at either Station P5 or P7. Abundances of all life Seasonal patterns of the natural assemblage of miciozooplankton have historically been dominated stages combined were also significantly higher at Station E PS than at Station P7 (Table 4-12). by the population dynamics of the copepods Oithona g sp. and Pseudocalanus sp. and the production of early Although the abundance of the combined lifestages lifestares (nauplius larvae) of other copepods that were g changed relatively httle throughout the year, the preser year round. Seasonally, other taxa such as E individual lifestages showed strong seasonal patterns polychaete larvae, bivalve larvae and tintinnids of occurrence (Figure 4-11). During both the influenced community structure. Since Seabrook Station preoperational and operational periods. immature mysids began commercial operation, species composition (sexual organs difTerentiated but not fully developed) continued to resemble the historical patterns (Table were the most common lifestage during January and 4-13) Although abundances of some taxa were dif-4-42 I.
[L ZOOPLANKTON e TABLE 4-13.
SUMMARY
OF POTENTIAL EFFECTS (BASED ON NUMERICAL L CLASSIFICATION AND MANOVA RESULTS) OF ' OPERATION OF SEABROOK STATION INTAKE ON THE
' INDIGENOUS ZOOPLANKTON COMMUNITIES.
SEABROOK OPERATIONAL REPORT,1993. {. (: DIFFERENCES BETWEEN OPERATIONAL OPERATIONAL AND PERIOD SIMILAR TO PREOPERATIONAL { COMMUNITY ATTRIBUTE PREOPERATIONAL PERIOD? PERIODS CONSISTENT AMONG STATIONS? MICROZOOPLANKTON Community Structure yes' yes yes j Abundances no, variable among taxa * { BlVALVE LARVAE yes' yes j Community structure [ Abundances Op> Preop * ' yes MACROZ00 PLANKTON h" { liolo/merr> plankton Seasonal occurrence yes, except for winter 1993* yes Abundances Op> Preop (most dominant yes taxa)' Tychoplankton Seasonal occurrence yes yes Abundances Op> Preop' yes
' Based on results of numerical classification
' Based on comparisons of group mean abundances
' Based on MANOVA results
[ 4-43 ;
n o C ZOOPLANKTON ferent between the preoperational and operational balanced, indigenous planktonic populations within periods. the differences were usually consistent among the study area have been affected by the plant intake the nearfield and farfield stations. Since the difTerences during the commercial operation to date. occurred areawide, they were not due to the operation of Seabrook Station. Although Seabrook Station operated its circulating water system at varying levels since 1985, no power or heated discharge were produced until August of Ilivalve Larvae 1990. Entrainment collections provide a measure of the actual number of organisms directly affected by Varying abundances of Hiatella sp., Afvtilus edulis plant entrainment. Three taxa, Afvtilus edulis (blue and Anomia squamula de0ned most seasonal groups mussel), Anomia squamula and Hiatella sp., accounted identified by the community analysis. The species for more than 85% of the bivalve larvae entrained each composition during the operational period was similar year (Figure 4-7). Afodiolus modiolm was intermittently to previous ycars according to numerical ciassi6 cation entrained during 1990 and 1991 (NAl 1991b, NAl techniques (Table 4-13). Community structure, 1992) and was common in August and September 1993 according to M ANOVA results, was not significantly (Table 4-8). Monthly entrainment of all taxa was less different among near6 eld and farfield stations in 1991 and 1992 in comparison to 1990 and 1993 g throughout the study period. However, community (Figure 4-7). Reduced CWS flows during outage 3 structure during the operational period at all three periods in summer when larvae typically reach their stations (combined) was signi0cantly different than peak abundance levels in local coastal waters led to g the recent preoperational period (1988-89), due to higher reduced entrainment in 1991 and 1992. Furthermore, E abundances of almost all taxa during the operational abundances of Af. edulis larvae observed in local coastal period (Table 4-5). Entrainment into the circulating waters (P2, P5, P7) in 1991 and 1992 were reduced water system of Seabrook Station is not suspected to when compared to 1990 and 1993 abundances, which have affected bivalve larvae abundance. contributed to lower entrainment levels. I Entrainment IIolo- and Meroplanktonic Macrozooniankton The focus of monitoring plankton in the intake area The holo- and meroplanktonic component of the I was to evaluate the effect of entrainment of organisms macroplankton community in the study area was similar by the circulating water system (CWS) on community to the other portions of the Gulf of Maine (Sherman structure and population levels in the nearfield area. 1966). In the study area, copepods predominate. The Due to the limited control of their horizontal movements dominant species in the study area, Calanusfinmar. E and often broad vertical distribution in the water chicus. Centropages typicus. Pseudocalanus sp. and g column, most types of planktonic organisms could be 7'emora longicornis were the dominant copepods in exposed to entrainment. Estimates of total monthly the Gulf of Maine and nearby Scotian Shelf and g levels of entrainment were computed (Table 4-8) to Georges Bank, occurring in a seasonal panern similar E quantify losses of bivalve larvae. Community structure to the study area (Anderson 1990. Kane 1993, Sameoto and abundances of selected species in the nearfield area and Herman 1992. Tremblay and Rofi 1983). The during commercial operation were compared to seasonal occurrence of the other groups was also similar historical conditions and to farfield conditions. These to other observations in the Gulf of Maine (Sherman comparisons addressed the question of whether the 1966). 4-44 I.
[ ZOOPLANKTON
- w. ,
The seasonal change in the holo- and m:roplankton coastal water masses and shelf water masses. [ __ community composition at both nearfield and farfield stations was consistent during the past six years. Abundance of many holo- and meroplankton species Consistent seasonal changes were observed at Station was higher during the operational period than the recent { P2(nearfield) freca 1978 through 1984 and from 1986 (1988- 1989) preoperational years (Table 4- 13 ). Thirteen of the 50 macrozooplankton taxa, including two seasonal through 1990. In the recent preoperational and operational periods, community composition exhibited dominants, experienced order of magnitude changes { the greatest variation between years during the period from the preoperational to the operational periods. An additional three taxa, including two seasonal February through April. This period corresponds to the lowest annual temperatures and the period of dominants had large increases in abundance. ( greatest variability in salinity in the study area (Section Interannual variations of orders of magnitude are { common among copepods on Georges Bank (Kane 2.3.1 ). 1993). Jossi and Goulet (1993) suggested that there h The community variation in February through April has been a possible general increase in copepod abundance from 1961 through 1989 for the entire Gulf is probably due to combined regional watcr temperature [- and salinity effects. Winter water temperatures may of Maine. Calanusfinmarchicur increased in abundance in all regions except the extreme western portion of be a controlling variable in the composition of the holo-and meroplankton communities. Winter water the Gulf of Maine, which includes coastal New 3 [ temperatures approach threshold limits for some species Hampshire. and small differences from year to year may have significant efTects on community composition during Although holo- and meroplanktonic community a [ this period. The occurrence of Centropages rypicus structure was qualitatively similar among Stations P2, has been associated with surface water temperatures PS, and P7, quantitative examination of abundances of 2.2 to 26.6 C (Grant 1988). Water temperatures indicated that spatial differences occurred, and in fact, in 1993 fell below 2.2 *C for an extended period . persisted from preoperational through operational periods (as evidenced by the MANOVA's significant (Section 2.3.1). These lower than normal water temperatures in 1993 may have reduced the population station term and insignificant i..araction term). Specific of C. typicus resulting in the occurrence of an differences were not clearcut. Fewer than 20% of the anomalous group that was characterized by its usual 50 taxa examined exhibited significant station co-dominants. Studies have shown both the timing differences. Differences may be related to water quality and the magnitude of the spring copepod bloom may characteristics (Section 2.0). Temperature and bottom be related to water temperature. In the presence of dissolved oxygen have been higher in the nearfield (P2 and PS) while bottom salinity has been higher in ( high phytoplankton abundance. cold water temperatures the farfield (P7) (Section 2.0). The proximity of can delay the initiation of egg production and reduce the quantity of eggs produced by Calanusfinmarchicus Stations P2 and PS to Hampton Harbor may partially p (Plourde and Runge 1988). Iow temperatures can also account for water quality pattems. L reduce growth rates and delay the development oflarger copepodites( Anderson 1990). Salinity during the spring bloom may also have accounted for some of the Tvehoplanktonic Macroroonlankton variability in community composition. High variability in salinity among years can be caused by meteorological The tychoplantonic community, composed of species events. Storms can increase run-off and reduce salinity that inhabit both the substrate and the water column, and can also cause mixing between lower salinity exhibited greater spatial variability than the holo- and 4 45
' l l
O n LJ ZOOPLANKTON meroplanktonic community. Excursions into the have differed between the preoperational and operatienal plankton can be related to such factors as light, lunar periods, similar changes have occurred at nearfield and cycle, storm events. reproduction and nonspecific farfield locations. Other species, particularly aggregation (Mauchline 1980). These factors can tychoplankton, have exhibited spatial patterns that have in0uence apparent abundance dramatically. been consistent from preoperational to operational periods. The long-term consistency in distribution g Seasonal changes in species composition w ere similar indicates that operation of Seabrook Station's cooling B between preoperational and operational years, except water system has not affected the macrozooplankton during the fall at Station P7 in 1993. Fall community community. composition at Station P7 has generally varied considerably from year to year, generally due to low abundances found there. Increased abundance of 4.4.2 Selected Species Pontogeneia inermis and Diastvlis sp. (NAl l994) account for the differences in 1993. Microroonlankton Substrate differences between near6 eld and farfield Patterns of seasonal variation recorded during I sites may be responsible for differences in tychoplank- operational years (1991-1993) for the selected on abundance between the sites. Tychoplankton species microzooplankton species were generally similar to such as mysids (Wigley and Burns 1971; Pezzak and patterns observed during the preoperational period at Cory 1979; Mauer and Wigley 1982), amphipods nearfield Station P2 (Figures 4-3, 4-4). ANOVAs g (Bousfield 1973) and cumaceans(Watling 1979)have detected significantly lower operational mean densities 3 substrate preferences. A relatively homogeneous for Eurviemoro sp. copepod ites, Eurytemora sp. adults substrate of sand exists at the farfield area. Rock ledges and PseudocalanuvCo; anus sp. nauplii, and significantly g are few and generally not near the farfield station. higher abundances of Oithona sp. copepodites and adults 5 in contrast, the nearfield substrate is heterogeneous, during station operation. In no case, however was the Station P2 is sand and hard sand with numerous nearby interaction (Preop-Op X Ama) term significant, rock ledges. Station P5 is sand and rock ledge with indicating that the operational differences were observed considerable amounts of algae. The heterogeneous at both nearfield and farfield stations and therefore nature of the nearfield station may have increased the could not be attributed to a plant effect (Table 4-14). abundance of various tychoplankton by supplying more diverse habitat. Many amphipods such as Pontogencia inermis are associated with submerged plants and algae. Rivalve Larvae Higher concentrations of macroalgae in the nearfield area may provide additional habitat for some amphipods Umboned !arvae of Mytilus edulis have been and increase their abundance. Differences in generally present in the water column during all months tychoplankton abundance between the nearfield and sampled, but were most abundant from June through farfield areas may be due to differences in habitat and August. Their protracted presence was probably due g not to the operation of Seabrook Station. to spawning pattems and the duration of larvae life. g in Long Island Sound, spawning occurred over a two-to-While both temporal and spatial differences have three month period and was asynchronous among local g been observed in various components of the macrozoo- populations (Fell and Balsamo 1985). Larval 5 plankton community, these differences have been development requires three to five weeks (Bayne 1976), consistent. Although abundances of a number of species and metamorphosis can be delayed up to 40 days until 4-46 E
=
E ZOOPLANKTON {. TABLE 4-14.
SUMMARY
OF POTENTIAL EFFECTS (BASED ON ANOVA {, RESULTS) OF OPERATION OF SEABROOK STATION INTAKE ON ABUNDANCES OF SELECTED INDIGENOUS ZOOPLANKTON SPECIES. SEABROOK OPERATIONAL REPORT.1993. DIFFERENCES BETWEEN {L OPERATIONAL OPERATIONAL AND PLANKTON PERIOD SIMILAR TO PREOPERATIONAL PERIODS SELECTED SPECIES PREOPERATIONAL' CONSISTENT AMONG h AND LIFESTAGES PERIOD? STATIONS? l MICROZOOPLANKTON Eurytemora sp. copepodites Op< Preop yes {- E. herdmani adults ' Op< Preop yes ! Pseudocalanus/Calanus nauplii Op< Preop yes yes ( Pseudocalanus sp. copepodites adults yes yes yes l L l Oithona sp. nauplii yes yes j copepodites Op> Preop yes ! adults Op> Preop yes ( BIVALVE LARVAE Mytilus edulis larvac Op> Preop yes MACROZOOPLANKTON Calanusfinmarchicus copepodites no yes , adults yes yes l Crangon septemspinosa larvae yes yes i Carcinus maenas larvae yes yes { Neomysis americana yes yes ,
'recent preoperational years: 1982-1984 for microzooplankton, 1988-1989 for bivalve larvae and macrozooplankton
{ suitable settling conditions are encountered (Bayne Macroioonlankton 1965). The seasonal pattern of M cdulis larvae in the operational period was similar to recent preoperational There has essentially been no change in the years. M cdulis larvae were significantly more abundances or seasonality in most of the macrozoo-abundant during the operational period than the recent plankton selected species. With the exception of preoperational period, at all three stations (combined), Calanusfinmarchicus copepodites, average abundances primarily due to increased abundances in most sampling of all selected species during the operational period periods from late June through October in 1993 (Figure were not signi6cantly different from the recent 4-6). These differences occurred at both the far6 eld preoperational period (Table 4-14). One species, and near6 eld stations and it is unlikely that the Neomysis americana, showed significant near6 eld-operation of Seabrook Station was a factor (Table 4-14). farGeld differences during both the preoperational and 4-47
ai Ol ZOOPLANKTON l operational periods. Abundances have remained stable Grabe, S.A. and E.R. Ilatch. 1982. Aspects of the over time, and the re'ationship of abundances between biology of Mnis mitta (Lilljeborg i 852)(Crustacea, the three stations has also remained unchanged. Mysidacea)in New Hampshire coastal waters. Can. J. Zool. 60(6):1275-1281. .
4.5 REFERENCES
CITED Grant, G.C.1988. Seasonal occurrence and dominance of Centropages congeners in the Middle Atlantic Anderson, J.T. 1990. Seasonal development of Bight, USA. 11ydrobiol. 167/168:227-237. invertebrate zooplankton on Flemish Cap. Mar. Ecol. Progr. Ser. 67:127-1409. Grice, G.D. and N.11. Marcus.1981. Dormant eggs of marine copepods. Oceanogr. Mar. Biol. Ann. Bayne, B.L. 1965. Growth and the delay of Rev. 19:125-140. metamorphosis of the larvae of Mrtilus edulis (L.) Ophelia 2:1-47. liarris, R.J.1985. A primer of multivariate statistics. Orlando: Acad Press. 575 p. B 1976. The biology of mussel larvae. Chap. 4 in Bayne, B.L., ed. Marine Mussels: Their Jossi,J.W.1991. Gulf-of-Maine copepods hit I l-year Ecology and Physiology. IUP 10. Cambridge Univ. high. In Northeast Fish. Ctr. End-of-Year Rep. for Press. pp. 81-120. 1990. NOAA-NMFS. Boesch, D.F. 1977. Application of numerical Jossi, J.W. and J.R. Goulet, Jr. 1993. Zooplankton classification in ecological investigetions of water Trends: U.S. Nonheast Shelf Ecosystem and pollution U.S. Environmental Protection Agency, Adjacent Regions Differ from Northeast Atlantic g Ecological Research Report Agency Ecol. Res. Rep., and North Sea. ICES J. Mar. Sci. 50:303-313. E 114 pp. Jury, S.II., .i D Field, S.L. Stone, D.M. Nelson, and Bousfield, E.L.1973. Shallow-water Gammaridean M.E. Monaco.1994. Distribution and abundance Amphipoda of New England. Comstock Pub. Assoc. of fishes and invertebrates in North Atlantic estuaries. (Cornell University Press; Ithaca, NY and London. ELMR Rep. No.13. NOAA/NOS Strategic Env. 312 pp. Asessments Div., Silver Spring, MD. 221 p ClitTord, ll.T., and W. Stephenson.1975. An introduc- Kane, J.1993. Variability of Zooplankton Biomass tion to numerical classification. Academic Press, and Dominant Species Abundance on Georges Bank, New York. 229 pp. 1977-1986. Fishery Bull. 91:464-474. I i Davis, C.S.1984. Interaction of a copepod population Katona, S.K. 1971. The developmental stages of with the mean circulation of Georges Bank. J. Mar. Eurytemora a/Jinis Poppe, 1880 (Copepoda, g Res. 42:573 590. Calanoida) raised in laboratory cultures, including 3 a comparison with the larvae of Eurytemora Fell, P.E. and A.M. Balsamo.1985. Recruitment of americana Williams.1906, and Eurrtemora herdmani Mrtilus edulis L. in the Thames Estuary, with evi- Thompson and Scott,1897. Crustaceana 21:5-20. dence for dilferences in the time of maximal settling along the Connecticut shore. Estuaries 8:68-75. 4-48 I.
I ZOOPLANKTLN Marcus, N.ll.1984. Recruitment of copepod nauplii 1988. Seabrook Environmental Studies. into the plankton: importance of diapause eggs and 1987. A characterization of baseline conditions in the llampton-Seabrook area. 1975-1987. A I benthic processes. Mar. Ecol. Prog. Ser.15:47-54. Mauchline, J.1980. The Biology of Mysids: Part preoperational study for Seabrook Station. Tech. Rep. XIX-II. I, in The Biology of Mysids and Euphausiids. Adv. Mar. Biol. 18:3-372. 1989. Seabrook Environmental Studies. 1988. A characterization of baseline conditions in Maurer D. and R.L.Wigley.1982. Distribution and the llampton-Seabrook area. 1975-1988. A ecology of mysids in Cape Cod Bay, MA. Biol. preoperational study for Seabrook Station. Tech. Bull.163:477-491. Rep. XX-II. I Meise-Munns, C., J. Green, M. Ingham and D. 1990. Seabrook Environmental Studies. Mountain. 1990. Interannual variability in the 1989. A characterization of baseline conditions in copepod populations of Georges Bank and the the llampton-Seabrook area. 1975-1989. A Western Gulf of Maine. Mar. Ecol. Progr. Ser. preoperational study for Seabrook Station. Tech. 65:225-232. Rep. XXI-il. Normandeau AssociatesInc.1978. Seabrook Environ- .1991a. Seabrook Environmental Studies, mental Studies, 1976-1977. Monitoring of plankton 1990 data report. Tech. Rep. XXil-1. I and related physical-chemical factors. Tech. Rep. Vill-3. 1991b. Seabrook Environmental Studies, 1990. Acharacterizationofenvironmentalconditions - 1979. Seabrook Environmental Studies, in the llampton-Seabrook area during the operation July through December 1977. Plankton. Tech. Rep. of Seabrook Station. Tech. Rep. XXil-II. I IX-1. 1980. Annual summary report for 1978
.1992. Seabrook Environmental Studies, 1991. A characterization ofenvironmental conditions hydrographic studies oft llampton Beach, New in the llampton-Seabrook area during the operation l llampshire. Preoperational ecological monitoring of Seabrook Station. Tech. Rep. XXill l. l I
studies for Seabrook Station. Tech. Rep. X-2. 1993a. Seabrook Environmental Studies. 1984. Seabrook Environmental Studies. 1992 Data. Unpub. Data Tab. , 1983 data report. Tech. Rep. XV-1. 1993b. Seabrook Environmental Studies, 1985. Seabrook Environmentd Studies, 1992. Acharacterizationofenvironmentalconditions i 1984. A characterization of baseline conditions in in the llam pton-Seabrook area during the operation E of Seabrook Station. Tech. Rep. XXIV-1. 5 thcIlampton-Seabrook Area,1975-1984. Tech. Rep. XVI-II. 1994. Seabrook Environmental Studies.
.I 1993 Data. Unpub. Data Tab.
I 4-49 I
O C> ZOOPI.ANKTON i Peterson, W.T.1985. Abundance, age structure and Sneath, P.H.A., and R.R. Sokal. 1973. Numerical lll in situ egg production rates of the copepod Ternora taxonomy. The principles and practice of numerical longicornis in Long Island Sound, New York. Bull. classiGcation. W.H. Freeman Co., San Francisco. Mar. Sci. 37(2):726-738. 573 pp. Pezzack, D.S. and S. Corey.1979. The life history Tremblay, M.J. and J.C. Roff. 1983. Community and distribution of Neomysis americana (Smith) gradients in the Scotian shelf zooplankton. Can. (Crustacea, Mysidacca) in Passamaquoddy Bay. J. Fish. Aquatic. Sci. 40:598-611.36 Can. J. Zool. 57:785 793. Watling, L. 1979. Marine Cora and fauna of the Plourde, S. and J. A. Runge.1993. Reproduction of Northeastern United States. Crustacea: Cumacca. the Planktonic Copepod Calanusfinmarchicus in NOAA Tech. Rep. NMFS Circular 423. 23 p. the Lower St. Lawrence Estuary: Relation to the Cycle of Phytoplankton Production and Esidence Wigley, R.L. and B.R. Bums.1971. Distribution and E for a Calanus pump. Mar. Ecol. Progr. Ser. biology of mysids(Crustacea, Mysidacea) frorn the g 102:217-227. Atlantic Coast of the United States in the NMFS Woods 11 ole collection. Fish. Bull. 69(4):717-746 g Sameoto, D.D. and A.W. lierman. 1992. Effect of 5 the outHow from the Gulfor St. Lawrence on Nova Scotia shelf zooplankton. Can. J. Fish. Aquat. Sci. 49:857-869. SAS Institute, Inc. 1985. SAS User's Guide: Statistics, version 5 edition. SAS Ins., Inc., Cary, N.C. 956 pp. Sherman K.1966. Seasonal and areal distribution I of Gulf of Maine coastal zooplankton,1963. ICN AF Special Publ. No. 6. pp. 611-623. l 1991. Northwest / northeast Atlantic g zooplankton show different trends. jn Northeast E Fish. Center End-of-Year Rep.1990. NOAA-NMFS. i Sherman, K., M. Grosslein, D. Mountain, D. Busch, J.O'Reilly and R. Theroux.1988. The continental shelfecosystem off the northeast coast of the United States. Chapter 9, pp. 279-337. In 11. Postma and J.J. Zijlstra, Ecosystems of the World 27. Con?inen-tal Shelves. Elsevier, Amsterdam. I 4-50 as
ZOOPLANKTON APPENDIX TABLE 4-1. LIST OF ZOOPLANKTON TAXA CITED IN THIS REPORT. SEABROOK OPERATIONAL REPORT,1993. Protozoa Foraminiferida Tintinnidae Rotifera Mollusca Bivalvia Anomia squamula Linnaeus l Hiatella Bose 1801 Macoma balthica Linnaeus 1758 Modiolus modiolus Linnaeus 1758 I Mya arenaria Linnaeus 1758 Mya truncata Linnaeus 1758 Mytilus edulis Linnaeus 1758 Placopecten magellanicus (Gmelin 1791) Solenidae Spisula solidissima (Dillwyn 1817) Polychaeta Arthropoda Branchiopoda Evadne Loven . Copepoda Acarria Dana 1846 Anomalocera opalus Penell 1976 Calanusfinmarchicus (Gunnerus 1765) Caligus MQller 1785 Candacia armata (Boeck 1872) Centropages hamatus (Lilljeborg 1853) Centropages Kroyer 1849 Centropages typicus Kroyer 1849 Euchaeta Philippi 1843 i Eurviemora herdmani Thompson and Scott 1897 Eurvremora Giesbrecht 1881 Harpacticoida Monstrillidae Oithona Baird 1843 i Pseudocalanus Boeck 1872 Rhincalanus nasutus Giesbrecht 1892 Temora longicornis (Muller 1785) Tortanus discaudatus (Thompson and Scott 1897) (continued) 4-51
O Ui ZOOPLANKTON APPENDIX TABLE 4-1. (Continued) , Cirripedia Malacostraca Mysidacea ' Erythrops erythrophthalma (Gbes 1864) Mysis mixta (Lilljeborg I852) Neomysis americana (S.I. Smith 1873) l Cumacea m Diastylis Say Amphipoda a Calliopius laeviusculus Kroyer 1838 Corophium Milne-Edwards 1830 l Gammarus lawrencianus Bousticid )956 Hyperiidae Ischyrocerus anguipes Kroyer 1838 Oedicerotidae Pontogencia inermis (Kroyer 1842) g Decapoda Cancer Linnaeus 3 Carcinus moenas (Linnaeus 1758) Crangon septemspinosa Say 1818 Eualus pusiolus (Kroyer 1841) l l Chaetognatha Sagitta elegans Verrill 1873 l Chordata Oikopleura Mertens I I-i I 4-52 l
I TABLE OF CONTENTS
;I PAGE 5.0 FISII S UMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-i ii LIST OF FIGURES . . . . . . ............................................5-iv !g LI ST OF T A B LES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 -vi !E LIST OF APPENDIX TAB LES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-viii
5.1 INTRODUCTION
. . .......... . ...... ... .. ... ............ 5-1 5.2 METiiODS . . . . .. .. . . ... . ....... . ... .... . ... 5-1 5.2.1 Ichthyoplankton . . .. . . . . ..... .. .. ... 5-1 5.2.1.1 Offshore Sampling . . . ..... ..... ....... ....... .. 5-1
- 5.2.1.2 Entrainment . ... ... .. . . .. .. .. ..... 5-3 5.2.1.3 Laboratory Methods . . . ....... . ......... .... ...... 5-3 5.2.2 Adult Fish . . . . . . .................... . .... .... . . . . . . . 5 -4 5.2.2.1 Pelagic Fishes . . . . . .. ....... . .................5-4 5.2.2,2 Dermersal Fishes . . . . . .......... . .... ..........5-4
- 5 5.2.2.3 Estuarine Fishes . . ..... .. . ... . ..... .... ..54 5.2.2.4 Impingement . .. . ... .... ..... . . ... . . . .... 5-6
- I i
5.2.3 Analytical Methods . . .. ....... .... . .. . .. .... .... . 5-6 5.3 RESULTS AND DISCUSSION . .. ... ... . ... ........... 5-8 5.3.1 Ichthyoplankton . . .. . . ........ .. ............... 5-8 5.3.1.1 Seasonal Assemblages . .... ... . . . . .... . . 5-8 5.3.1.2 Entrainment . .... .. . .... . .. ... .. . . 5-17 5.3.2 Adult Fish . . . . . .. . . . 5-21 i I 5.3.2.1 Assemblages . 5.3.2.1.1 5.3.2.1.2 Pelagic Fishes Demersal Fishes . .
. 5 21 5-21 5 21 5.3.2.1.3 Estuarine Fishes 5-26 I
i I 5.3.2.2 Impingement 5-28
]
I S., J
O 3 .! ! i PAGE Il 1 1 l l 5.3.3 Selected Species ................ ............................ 5-31 5.3.3.1 Atlantic herring . . . . . . . . . .. .................. .......... 5-31 5.3.3.2 Rainbow smelt . . ............................ ............ 5-33 5.3.3.3 Atlantic cod . . ... . ..... ............ ..... ,,,...,,,.,,539 5.3.3.4 Pollock . ..... ..... . ........ ......... .... ........ 5-42 5.3.3.5 Hakes ......... ..... ...............................5-44 , 5.3.3.6 Atlantic silverside . ..........................,............5-48 5.3.3.7 Cunner . . . . . . . . .....................................5-53 g' 5.3.3.8 American sand lance . . . . . . . . . . . ..... ............. .. 5-56 3 5.3.3.9 Atlantic m ackerel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 -5 9 5.3.3.10 Winter flounder . . . .. . ...... . .. ..... .... .. 5-61 5.3.3.11 Yellowtail flounder . . . .. ... ... .. .. .... ............ 5-67 5.4 EFFECTS OF SEABROOK STATION OPERATION . 5-71 g,
5.5 REFERENCES
CITED . . . . . . . . .. .......... 5-75 I I I E I 1: E' . I' 5-ii 5 m
SUMMARY
Fish of the llampton-Seabrook area have been sampled since 1976 to assess potential impacts associated with the construction and operation of Seabrook Station on local fish assemblages. Effects include the entrainment of fish eggs and larvae and the impingement of juvenile and adult fish at the station intake; entrainment of fish eggs and larvae into and the avoidance by larger fish of the offshore discharge thermal plume; and effects related to the discharge of the plant settling basin into the Browns River within the llampton-Seabrook estuary. The spatial and temporal abundance of specific fish assemblages were examined along with various life stages of eleven selected fish taxa. Preoperational and operational abundances were compared using multivariate analysis methods for ichthyoplankton assemblages and l analysis of variance (ANOVA) for larval, juvenile, and adult stages of the selected taxa. The sampling scheme used to collect data for the ANOVA was designed to meet the Before-After/ Control-Impact analysis criteria. Although a number of significant differences were found in the abundance of several species between the preoperational and operational periods, nearly all of these differences can be attributed to large scale, regional decreases in abundance, particularly for commercially important fishes. One potential effect was found at a station that could possibly be related to plant operation: a decrease in the l abundance of winter flounder at the nearfield trawl station. Ilowever, this change could be related to naturally occurring environmental factors and not necessarily to plant operation and may bear funher scrutiny during the next few years. In comparison to other large New England power plants with marine intakes, Seabrook Station entrains relatively few fish eggs and larvae and impinges very few juvenile and adult fish. Because the settling basin no longer is discharged into the Browns River, this effluent has been climinated as a potential source of impact. Based on the small numbers of individuals directly removed by station operation, the general lack of significant differences found between the nearfield and farfield t stations, and the large source populations of potentially affected fishes in the Gulf of Maine, the operation of Seabrook Station does not appear to have affected the balanced indigenous populations of fish in the l llampton-Seabrook area. 5-iii
1 nL 1 I i LIST OF FIGURES I PAGE I, 5 1. Ichthyoplankton and adult fish samping stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 5-2. Dendmgram and temporal / spatial occurrence pattem of fish egg assemblages formed by numerical classification of ichthyoplankton samples (monthly means of logio(x+1) transformed number per 1000 m3) at Seabrook intake B (P2), discharge (PS), and farfield (P7) stations, July 1986 December 1993 ........ 5-11 5 5-3. Dendrogram and temporal / spatial occurrence pattern of fish larval assemblages formed by numerical classification of ichthyoplankton samples (monthly means of logio(x+1) transformed number per 1000 m3) at Seabrook intake (P2), discharge (PS), and farfield (P7) stations, July 1986-December 1993 .. ..... 5 14 5-4. Total monthly cooling water system flow and estimated numbers of fish eggs and larvac entrained at Seabrook Station during the operational period . . . . . . . 5 19 5-5. Annual geometric mean catch of all species combined per unit effon (number g per 24-h set) in gill net samples by station and the mean of all stations,1976- g 1993.. . . ....... . . . .. .. .... .... ... ... .. . 5-22 5-6. Annual geometric mean catch of all species combined per unit effon (number per 10-min tow) in trawl samples by station and the mean of all stations,1976-ke l 1993 . . .. ... .. .. . .. . . .. ........ ........ ... 5-24 5-7. Annual geometric mean catch of all species combined per unit effon (number per haul) in seine samples by station and the mean of all stations, 1976-1993 .. ... 5-26 5-8. Annual geometric mean catch of Atlantic herring per unit effon in 3 ichthyoplankton (number per 1000 m3) and gill net (number per 24-h set) g samples by station and the mean of all stations, 1975-1993 (data between the two venical dashed lines were excluoed fmm the ANOVA model) . . .. ... ..... 5-34 _ 5-9. Annual geometric mean catch of rainbow smelt per unit elfon in trawl (number per 10-min tow) and seine (number per haul) samples by station and the mean of all stations, 1976-1993 (data between the two venical dashed lines were excluded from the ANOVA model) . . .. . . ........... . . . 5-37 5-10. Annual geometric mean catch of Atlantic cod per unit effon in ichthyoplankton (number per 1000 m3) and trawl (number per 10-min tow) g samples by station and the mean of all stations, 1975-1993 (data between the g two vertical dashed lines were excluded from the ANOVA model) . ... . . . 5-41 5-11. Annual geometric mean catch of pollock per unit effon in ichthyoplankton j (number per 1000 m3) and gill net (number per 24-h set) samples by station m and the mean of all stations. 1975-1993 (data between the two venical dashed lines were excluded from the ANOVA model) . . . . 5-45 I I 5-iv I l E e
b PAGE 5 12. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per 1000 m3) and trawl (number per 10-min tow) samples by station and the mean of all stations, 1975-1993 (data between the two venical dashed lines were excluded fmm the ANOVA model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-49 5-13. Annual geometric mean catch of Atlantic silverside per unit effon in seine (number per haul) samples by station and the mean of all stations, 1976-1993 (data between the two vertical dashed lines were excluded from the ANOVA m od e l ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5 1 5-14. Annual geometric mean catch of cunner per unit effon in ichthyoplankton (number per 1000 m3) samples by station and the rnean of all stations,1975-1993 (data between the two venical dashed lines were excluded from the ( ANOV A model) . . . . . . . . . . . . . . . . . . .................................554 5-15. Annual geometric mean catch of American sand lance per unit effort in ichthyoplankton (number per 1000 m3) sampics by station and the mean of all stations, 1976 1993 .... . . . .......... ... ... ....... . . . . . . . . . . 5 -5 7 5-16. Annual geometsic mean catch of Atlantic mackerel per unit effort in ichthyoplankton (number per 1000 m3) and gill net (number per 24-h set) samples by station and the mean of all stations, 1975-1993 (data between the two venical dashed lines were excluded from the ANOVA model) . . ............ 5-60 5-17. A comparison among stations of the mean logio(x+1) CPUE (number per 24-h set) of Atlantic mackerel caught by gill net during the preoperational (June 1976-November 1989) and operational (June 1991-November 1993) periods for the significant interaction term (Preop-Op X Station) of the ANOVA 4:{ model (Table 5-22) . . .... ... . ............ .......... ........... 5-63 5-18. Annual geometric mean catch of winter flounder per unit effon in ichthyoplankton (number per 1000 m3), trawl (number per 10-min tow), and j seine (number per haul) samples by station and the mean of all stations,1975- 4 1993 (data between the two venical dashed lines were excluded from the ANOVA model) . . . . . . .. .. . ..... . ............... ........... . 5-64 5 19. A comparison among stations of the mean logio(x+1) CPUE (number per 10- ; min tow) of winter flounder caught by trawl during the preoperational (November 1975-July 1990) and operational (November 1990-July 1993) periods for the significant interaction term (Preop-Op X Station) of the i ANOVA model (Tabic 5-23) . .... . .... ........... ... . 5-67 l r 5-20. Annual geometric mean catch of yellowtail flounder per unit effon in ( ichthyoplankton (number per 1000 m3) and trawl (number per 10-min tow) samples by station and the mean of all stations, 1975-199'i (data between the two venical dashed lines were excluded from the ANOVA model) . . ... ... 5-69 l 5-21. A comparison among stations of the mean logio(x+1) CPUE (number per 10- { min tow) of yellowtail flounder caught by trawl during the preoperational 1 (November 1975. July 1990) and operational (November 1990-July 1993) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-24) . .... ... . ... .. . ... . ..... ... . . . 5 -71 5-v
E; 5l l LIST OF TABLES PAGE 5-1. DESCR'IrrION OF FINFISH SAMPLING STATIONS . . . . . . . . . . . . . . . . . . . . . . . 5-5 5-2. SELECTED FINFISHES AND SAMPLING PROGRAMS THAT m CONTRIBUTED ABUNDANCE DATA FOR SPECIES-SPECIFIC ANALYSES . . . . 5-7 5 3. GEOMETRIC MEAN CATCH PER UNIT EFFORT (NUMBER PER 1000 m3) WITH COEFFICENT OF VARIABILITY (CV) BY STATION (P2, PS, AND P7) AND ALL STATIONS COMBINED FOR SELECTED LARVAL SPECIES COLLECTED IN ICHTilYOPLANKTON SAMPLES DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND IN 1993 ............ 5-9 5-4. GEOMETRIC MEAN DENSITY (NUMBER PER 1000 m3) OF FISH EGGS COLLECTED AT SEABROOK INTAKE (P2), DISCHARGE (PS), AND E FARFIELD (P7) STATIONS FROM JULY 1986 TIIROUGH DECEMBER 5 1993 .... .... ...... ......... ... ...... .. ............. . . 5-12 5-5. GEOMETRIC MEAN DENSITY (NUMBER PER 1000 m3) OF FISH LARVAE COLLECTED AT SEABROOK INTAKE (P2), DISCHARGE (PS). AND FARFIELD (P7) STATIONS FROM JULY 1986 THROUGH DECEMBER 1993. ..... . ......... ......... ....... . . . 5-15 5-6. MONTHLY ESTIMATED NUMBERS OF FISH EGGS AND LARVAE ENTRAINED (x 106) BY THE COOLING WATER SYSTEM AT SEABROOK STATION FROM JANUARY THROUGH DECEMBER 1993 ............. .... 5-18 5-7. ANNUAL ESTIMATED NUMBERS OF FISH EGGS AND LARVAE ENTRAINED (x 106) BY THE COOLING WATER SYSTEM AT SEABROOK STATION FROM JUNE 1990 THROUGH DECEMBER 1993 ..... . ... . 5-20 5-8. COMPARISON OF ENTRAINMENT ESTIMATES (x 106) AT SELECTED NEW ENGLAND POWER PLANTS WITH MARINE INTAKES FROM 1990 m THROUGH 1993. . . ..... .. ... ...... ..... .... .. ..... . 5-22 g 5-9. GEOMETRIC MEAN CATCH PER UNIT EFFORT (NUMBER PER 24-h SET, SURFACE AND BOTTOM) WITH COEFFICIENT OF VARIABILITY (CV) g, BY STATION (G1, G2, AND G3) A.ND ALL STATIONS COMBINED FOR g ABUNDANT SPECIES COLLECTED BY GILL NET DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND Tile 1993 MEAN. . . . . .. . . ... .. . . ... . .. ... . 5-23 5-10. GEOMETRIC MEAN CATCH PER UNIT EFFORT (NUMBER PER 10-min TOW) WITil COEFFICIENT OF VARIABILITY (CV) BY STATION (TI, T2, AND T3) AND ALL STATIONS COMBINED FOR ABUNDANT SPECIES COLLECTED BY OTFER TRAWL DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND THE 1993 MEAN . . . .. .... .. ... . 5-25 I I 5-vi I R
b - . ,
^
Eb l I PAGE 5 11. GEOMETRIC MEAN CATCH PER UNIT EFFORT (NUMBER PER .
- STANDARD HAUL) WITH COEFFICIENT OF VARIABILITY (CV) BY .
STATION (St,' S2, AND S3) AND ALL STATIONS COMBINED FOR hJ ABUNDANT SPECIES COLLECTED BY SEINE DURING THE .. PREOPERATIONAL AND OPERATIONAL PERIODS AND IN 1993 ............'5-27 i h' 12. SPECIES COMPOSITION AND TOTAL NUMBER OF FINFISH AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION BY MONTH l DURING 1993'...................'.................................. 5-29'
'5-13 . ' COMPARISON OF FISH IMPINGEMENT ESTIMATES AT SELECTED - 1 '
NEW ENGLAND POWER PLANTS WITH MARINE INTAKES . . . . . . . . . . . . . . . . 5-30
. Shl4. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC HERRING l DENSITIES BY SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-35 .l 1
. 5-15. RESULTS OF ANALYSIS OF VARIANCE FOR RAINBOW SMELT DENSITIES BY SAMPLING PROG RAM . . . . . . . . . . . . . . . . . . -, . . . . . . . . . . . . . . 5-3 8 l 1
- 5 16. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC COD l DENSITIES B Y S AM PLING PROG RAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 -4 3
- 17. RESULTS OF ANALYSIS OF VARIANCE FOR POLLOCK DENSITIES BY
- S AMPLING PROG RA M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 -4 6 -
5 18. RESULTS OF ANALYSIS OF VARIANCE FOR HAKE DENSITIES BY d S AMPLING PROG RA M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -. . . . . . . . . . 5 -5 0 e 5-19. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC SILVERSIDE DENSITIES BY SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-52 i 5-20. RESULTS OF ANALYSIS OF VARI ANCE FOR CUNNER DENSITIES BY SAM PLING PROG RA M . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................5-55 5 21. RESULTS OF ANALYSIS OF VARIANCE FOR AMERICAN SAND LANCE DENSITIES BY SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 8 5-22. RESULTS OF ANALYSIS OF VARIANCE FOR TLANTIC MACKEREL-DENSITIES BY SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 l [ 5 23. RESULTS OF ANALYSIS OF VARIANCE FOR WINTER FLOUNDER i j r DENSITIES BY S AMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 66 5 24. RESULTS OF ANALYSIS OF VARIANCE FOR YELLOWTAll FLOUNDER DENSITIES BY SAMPLING PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-70 5-25. SUMMAL Y OF POTENTI AL EFFECTS OF THE OPERATION OF SEABROOK STATION ON THE ICHTHYOPLANKTON ASSEMBLAGES AND SELECTED FISH TAXA . . ........ .. . ................. ...... 5-73 i 5-vii
O 5, LIST OF APPENDIX TABLES PAGE 5 1. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND GEAR, JULY > 1975 - DECEM B ER 199 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . 5-86 5-2. S'/ECIES COMPOSITION, ANNUAL TOTALS. AND 4-yr TOTAL OF FINFISH AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION FROM 1990 THROUGH 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-89 5-3. SPECIES COMPOSITION AND CUMULATIVE MONTHLY TOTALS OF FINFISH AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION FROM 1990 TIIROUGH 1993 . . . . ................. .. .... 5-90 I I I I I I I I I I i 5-viii 1' E w <
FISH 5.0 FISH plankton and adult fmfish sampling programs are given in Appendix Table 5-1. Both the common
5.1 INTRODUCTION
and scientific names of fishes found in that table ( follow Robins et al. (1991) and they are used Finfish studies at Seabrook Station began in throughout this report. j July 1975 and have included investigations of all life stages of fish, including ichthyoplankton (eggs , 1 and larvae), juveniles, and adults. The initial 5.2 MET 110DS h objectives of these studies were to determint. th 5.2.1 Icht hynninnkton seasonal, annual, and spatial trends in abundance j I p and distribution of fish in the nearshore waters off i Hampton and Seabrook, Nil to establish baseline 5.2.1.1 Offshore Samoline ; data suitable for assessing the effects of future j i plant operation. In addition, the nearshore fish Ichthyoplankton sampling for Seabrook Station populations in the llampton-Scabrook estuary has been conducted since July 1975, Several were examined to determine if there was any modifications to the sampling methodology and measurable effect due to the construction of collection frequencies were made as the nature of Seabrook Station and the discharge from the the ichthyoplankton community and its natural onsite settling basin into the Browns River. The variability became better understood (NAl 1993). station began commercial operation in August Station P2 (nearfield site for the Seabrook intakes) 1990. Potential impacts of plant operation on has been sampled consistently since the start of the local fishes include entrainment of eggs and larvae progmm (Figure 5-1). Station P5 (nearfield site through the condenser cooling water system and for the Seabrook discharge) was sampled from impingement of larger specimens on traveling July 1975 through December 1981 and from July screens within the circulating water pumphouse. 1986 through December 1993. Station P7 Also, local distribution of fishes could be affected (farfield station located about 7 km north of the by the thermal plume, and some eggs and larvae nearfield stations), representing a non-impacted or could be subjected to thermal shock due to plume control site, was sampled rmm January 1982 entrainment following the discharge of condenser through December 1984 and from January 1986 cooling water from the diffuser system. through December 1993. Through June 1976, { collections were taken monthly at each station l I At present, the main objective of the finfish sampled. Subsequently, a second monthly studies at Seabrook Station is to assess whether sampling period was added to February through station operation since 1990 has had any August and to December. Beginning in January measurable effect on the nearshore fish popu- 1979, all months were sampled twice. Starting in lations. Tbc following report first presents general March 1983, sample collection was increased to informati on on each finfish collection program the current frequency of four times per month at and then provides more detailed analyses for those each station, fish species selected because of their dominance in the Hampton and Seabrook area or their commer- On each sampling date and at each station, four cial or recreational importance. A list of all taxa samples were collected at night. Oblique tows and their relative abundance collected from July were made using paired 1-m diameter,0.505-mm 1975 through December 1993 by various ichthyo- mesh nets. Each net, weighted with an 8-kg 5-1 i
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l: i \ l LEGEND P = IchthyoplanktonTows T = Otter Trawls G = Gill Nets I Figure 5-1. Ichthyoplankton and adult fish sampling stations. Scabrook Operational Report,1993. 5-2 I~
I FISH depressor, was set off the stern and towed for 10 The water supply was adjusted to maintain I min while varying the boat speed, with the nets sinking to approximately 2 m off the bottom and rising obliquely to the surface at least twice during approximately 8 to 15 cm of water above the plankton net at all times. Following sampling, water was drained from the system and the I the tow. A standard 10-min tow was occasionally contents of the nets were consolidated, placed in reduced to a 5-min tow to minimize net clogging one sample jar, and preserved with 5% buffered due to high plankton density. The volume formalin. 'The volume filtered was measured with I filtered, calculated using data from a calibrated General Oceanics* flowmeter mounted in each net an in-line flowmeter and averaged approximately 100 m3 per replicate. Monthly entrainment mouth, averaged approximately 500 m for 10- 3 estimates were determined by calculating the I, min tows and approximately 250 m3 for 5-min arithmetic mean density for each sampling week, tows during 1993. Upon retrieval, each net was multiplying the mean density by the number days I washed down from mouth to codend and the contents preserved in 5% fonnalin buffered with borax. in the sampling week, and by the average daily condenser cooling water volume for the month. These weekly estimates were summed for a I 5.2.1.2 Entrainment monthly estimate. No entrainment estimates were made for the periods of August through November 1991 or September through November 1992, when sampling was suspended due to Ichthyoplankton entrainment sampling was extended plant outages. conducted up to four times a month by NAESCO personnel within the circulating water pumphouse on-site at Seabrook Station from July 1986 5.2.1.3 Laboratory Methods through June 1987 and June 1990 through I December 1993. Sampling dates coincided with offshore ichthyoplankton sampling whenever Prior to March 1983, all four offshore ichthyoplankton samples per date and station were possible. Three replicate samples were collected analyzed, except from January through December I on each sampling date. Entrainment sampling was 1982, when only one sample per date and station not conducted on several scheduled dates, either was completely analyzed; only selected taxa wen: I because of plant outages when sampling could not be conducted, or because of sampling equipment problems. The entrainment data discussed in this counted from the remaining three samples. Beginning in March 1983, only two of the four offshore samples (one from each pair; Section report are only those for the operational period of 5.2.1.1) were analyzed from each station for each 1990-93. sampling date; the remaining two were held as contingency samples. I Samples were taken using a double-barrel collection system. A 0.505 mm mesh plankton Sampics were subsampled with a Folsom net was suspended in a 30-gal drum which, in tum, plankton splitter and sorted for fish eggs and I was suspended within a 55-gal drum. Water divened from the cooling-water system entered the larvae using a dissecting microscope. Successive aliquots were analyzed until a minimum of 200 I 55-gal drum from the bottom, overflowed into the 30-gal drum, passed through the plankton net, and was discharged through the bottom of both drums. eggs and 100 larvac were sorted or until 200-400 mL settled plankton volume was sorted. All eggs and larvac were identified to the lowest practical l l l 5-3 I
Fi 5 FISil I taxon (usually species) and counted. In some 5.2.2.2 Demersal Fishes instances when eggs were difficult to identify to species due to their stage of development, they The inshore demersal fish assemblage was were grouped with eggs of similar appearance sampled monthly beginning in July 1975 by otter g (e.g., cunner, tautog, and yellowtail flounder were trawl at night at one nearfield station. T2, and two g grouped as cunner /yellowtail flounder eggs; farfield stations T1 and T3 (Figure 5-1; Table 5-Atlantic cod, haddock, and witch flounder as 1). Four replicate tows were made at each station g Atlantic cod / haddock; and hake species and once per month. Beginning in January 1985. E fourbeard rockling as hake /fourbeard rockling). sampling frequency was increased to twice per The notochord lengths of at least 20 larvae per month and the number of replicate tows was l sampic (if present) were measured to the nearest reduced to two. Sampling was conducted with a 9 0.5 mm for selected taxa, which included Atlantic 9.8-m shrimp otter trawl (3.8-cm nylon stretch herring, Atlantic cod, pollock, hakes, cunner, mesh body; 3.2-cm stretch mesh trawl bag; 1.3-cm Atlantic mackerel, American sand lance, winter stretch mesh codend liner). The net was towed at flounder, and yellowtail flounder. Entrainment approximately 1 m seed for 10 min, with succes-samples were processed in a similar manner. sive tows taken in opposite directions. The volume of drift algae caught in the trawl was also recorded. It was not always possible to collect g 5.2.2 Adult Fish samples at station T2, particularly from August E through October, due to the presence of 5.2.2.1 Petacic Fishes commercial lobster gear; the frequency of missed samples has increased since 1983. Fish collected E' 3 Beginning in July 1975, gill net arrays were set were identified to their lowest practical taxon for two consecutive 24-h periods twice each month (usually species), measured, and length data were at stations G1 (farfield), G2 (nearfield), and G3 grouped into 2-cm size-classes. (farfield) to sample the pelagic fish assemblage (Figure 5-1; Table 5-1). Starting in July 1986, sampling was reduced to once per month. Nets 5.2.2.3 Estu irine Fishes were 30.5 m x 3.7 m and were comprised of four panels having stretch mesh dimensions of 2.5 cm, Seine samples were taken monthly from April l 5.1 cm,10.2 cm, and 15.2 cm. One net array to November at stations S1, S2, and S3, beginning -) consisting of surface and near-bottom nets was set in July 1975 (Figure 5-1; Table 5-1). No samples ' at each station. All nets were set perpendicular to were collected in 1985 and from April through ; the isobath (Figure 5-1). All nets were attached June of 1986. Duplicate daytime hauls were taken between permanent moorings and tended daily by into the tidal current at each station with a 30.5 m g, SCUBA divers. Fish collected were identified to x 2.4 m bag seine. The nylon bag was 4.3 m x B ; their lowest practical taxon (usually species), 2.4 m with 1.4-cm stretch mesh, and each wing 1 measured, and length data were grouped into 2-cm was 13.1 m x 2.4 m with 2.5-cm stretch mesh, size-classes. Fish collected were identified to their lowest practical taxon (usually species), measured, and length data were grouped into 2-cm size-classes. 5-4 I 5: r ,
g TABLE 51. DESCRIPTION OF FINFISH SAMPLING STATIONS. SEABROOK OPERATIONAL REPORT, 1993. STATION DEPTH BOTTOM TYPE REMARKS REACH SEINE ( StL 0-2 m . sand Affected by tidal currents; approximasely 300 m upriver from Hampton Beach Marina (. Affected by tidal currents; approximately 200 m ( S2 0-1 m sand upstream from the mouth of the Browns Rive 53 0-3 m sand Affected by tidal currents; located in Seabrook Harbor, approximately 300 m from Hampton Harbor Bridge GILL NET - G1 20 m sand Seaward of rocky outcropping off Seabrook, approximately 2 km south of the discharge G2 17 m sand Seaward of Inner Sunk Rocks, approximately 250 m southwest of the discharge G3 17 m rock, cobble Offshore from Great Boers Head, approximately 2.5 km north of the discharge OTTER TRA% L Tl 20-28 m sand Transect begins 0.5 miles southeast of Breaking Rocks Nun.150 200 m from submerged rock outcroppings, approximately 4 km south of the discharge T2 1517 m sand; drift algae 100 m from Inner Sunk Rocks, approximately I km with shell debris south of the discharge; scoured by tidal currents with large quantities of drift algae T3 22-30 m sand; littered Located off Great Boars Head, approximately 4 km - with shell debris north of the discharge;just seaward of a cobble area (rocks 15 50 cm in diameter) 5-5 f. 1 1
O FISH g 5.2.2.4 Imoinnement the preoperational samples. In addition, monthly preoperational and operational means (from Fish impinged at Seabrook Station were transformed data) were compared with t-tests collected after being washed from the 0.125-in (Sokal and Rohlf 1969) for individual taxa within mesh traveling screens within the circulating water each cluster group, under the assumption of g pumphouse. Traveling screens were washed unequal variances. g weekly (K. Dow YAEC, pers. comm.) and impinged fish were sluiced into a collection Multivariate analysis of variance (MANOVA; g basket. Fish from weekly collections were liarris 1985) was used to indicate whether fish egg 5 separated from debris, placed in dated plastic bags, and larval assemblages had differed significantly and frozen. On a periodic basis, samples were (p s 0.05) between preoperational and operational thawed, identified to species, and unted by periods. Logio(x+1) transformed sample densities YAEC personnel. Impingement collections were (number per 1000 m3) were used. The analysis noted as total counts per species by month. In was restricted to collections from July 1986 addition, the number of fish impinged per billion through December 1993, the common period of gallons of cooling water was calculated. sampling at stations P2, PS, and P7, and the taxa included were the same as those analyzed by I numerical classification. The data used were the E 5,2.3 Analytical Methods mean of logio(x+1) sample densities for individual sampling dates and stations. The model design Ichthyoplankton assemblages were investigated was a three-way factorial with nested effects. The using multivariate numerical classification main effects were period (preoperational and E methods to determine whether species composition operational), station, and month; interactions 3 j changed between the preoperational period (July among these main effects were included in the ( 1990 and earlier) and the operational period model. The nested effect was years within period. (August 1990 and later). The Bray-Curtis Type 111 sums of squares and tests of hypothesis similarity index (Clifford and Stephenson 1975) were used for the analyses and the rationale for was used with the unweighted pair-group their use was the same as that used for analysis of clustering method (Sneath and Sokal 1973). variance, discussed below. The Wiiks' lambda ! Logio(x+1) transformed sample densities (number statistic (Wilks 1932; Morrison 1976) was used to 3 per 1000 m ) of eggs and larvae were analyzed determine if the taxa assemblages in the separately. The data sets were reduced by preoperational and operational periods were averaging dates within month (transformed data); significantly different. For the purpose of power g including only the more abundant taxa; and plant impact assessment, sources of variation of g limiting the analysis to data collected since July primary concern were the period and the period 1986, when all three stations of concern (P2, P5, (preoperational or operational) by station g and P7) were sampled. Rare taxa were excluded interaction. 3 on the basis of percent-composition (less than 0.1% of the untransfonned data) or frequency of Of the 76 taxa recorded over the years,11 were occurrence in samples (less than 5%). The selected for detailed analyses of abundance and resulting dendrograms were evaluated on the basis distribution and for an assessment of impact by of whether samples from the operational period Seabrook Station (Table 5 2). These species were were grouped differently by the analysis than were numerically dominant in one or more sampling 5-6 I
=
7.. I l FISH I l " TABLE 5-2. SELECTED FINFISIIES AND SAMPLING PROGRAMS THAT CONTRIBUTED ABUNDANCE DATA FOR SPECIES SPECIFIC ANALYSES. SEABROOK r OPERATIONAL REPORT, 1993. I SELECTED SPECIES PREDOMINANT SAMPLING PROGRAMS l ; Atlantic herring ichthyoplankton, gill net Rainbow smelt otter trawl, beach seine i Atlantic cod ichthyoplankton, otter trawl Pollock ichthyoplankton, gill net ; Hakes ichthyoplankton, otter trawl l Atlantic silverside beach seine [ Cunner ichthyoplankton American sand lance ichthyoplankton Atlantic mackerel ichthyoplankton, gill net f Winter flounder ichthyoplankton, otter trawl, beach seine Yellowtail flounder ichthyoplankton, otter trawl j l l programs, are important members of the finfish 100) in the logarithmic scale were also computed. fauna of the Gulf of Maine, and most have The annual and combined geometric means are ] recreational or commercial importance. Other presented as back-transformed values. Some life I species predominant in various sampling programs were noted when they occurred. The selected taxa, stages are seasonal, so the data used to compute the geometric means for some species were , I listed in Table 5-2 by sampling program, were individually evaluated for temporal and spatial changes in abundance between the preoperational restricted to periods of primary occurrence; when trimmed data were used, it is noted in the text, figure, or table, 4 and operational periods. Geometric means were compared among the preoperational, operational, Analysis of variance (ANOVA) was used to test and 1993 periods for each station and all stations the null hypothesis that spatial and temporal combined to examine for trends in annual abundances during the preoperational and abundance. Geometric means were computed by operational periods were not significantly (p 2 logio(x+1) transformation of individual sample 0.05) different. The data collected for the I abundance indices, which were number per 1000 m3for ichthyoplankton, and catch-per-unit-effort ANOVAs met the criteria of a Before-After / Control-Impact (BACI) sampling design discussed (CPUE) for juvenile and adult fish. CPUE was by Stewart-Oaten et. al. (1986), where sampling I defined as the number per 24-h set for the gill net, number per 10-min tow for the trawl, and number was conducted prior to and during plant operation and sampling station locations included both I per standard haul for the seine. A transformed mean was cniculated for each year and for com-potentially impacted and non-impacted sites. The ANOVA was a two-way factorial with nested effects that provided a direct test for the temporal-( bined years (e.g., preoperational and operational I periods). The coefficients of variability (CV) of the mean of annual means (CV = standard error of by-spatial interaction. The main effects were period (Preop Op) and station (Station); the the mean divided by the mean and multiplied by interaction term (Preop-Op X Station) was also 5-7 I ,
O FISII O included in the model. Nested temporal effects to the period July 1986 through December 1993, I were years within operational period (Year (Preop- and for selected taxa collected by gill net, trawl, g Op)) and months within year (Month (Year)), and seine, the data used were from July 1975 4 which were added to reduce the unexplained through December 1993. For trawl data, the variance, and thus,increa3cd the sensitivity of the months of August through October were excluded F-test. For both nested terms, variation was from the ANOVA because of reduced sampling partitioned without regard to station (stations effort at station T2. The data used in the analyses combined). The final variance not accounted for of gill net, trawl, and seine samples were by the above explicit sources of variation logio(CPUE + 1) transfonned for each individual constituted the Error term. A fixed-effects model collection, but for larvae the mean transformed was assumed with all sources of variation tested density of replicate samples was used. against the mean square error (MSE); therefore, the MSE was the common denominator in the E ratios which determined the F-values. Type 111 5.3 RESULTS AND DISCUSSION E sums of squares and tests of hypotheses were used for the analyses because cells in the factorial 5.3.1 Ichthroolankton design contained unequal observations (unbalanced data). In reviews of ANOVA designs, The analyses for the ichthyoplankton program Freund et al. (1986) and Shaw and Mitchell-Olds focused on seasonal assemblages of both eggs and g (1993) concluded that Type III was the most larvae, as well as on collections of selected larval 5 powerful (i.e., most likely to find a significant taxa (Table 5-3) discussed in Section 5.3.2. The difference) test for factorial designs with results for each of the selected taxa are discussed interactions and unbalanced data. in relation to juvenile and adult stages collected in other sampling programs. In the assemblage For assessing Seabrook Station effects using the analyses, additional taxa were included to better above ANOVA model, the sources of variation of represent the ichthyoplankton community in the primary concem were the Preop-Op main effect 11ampton-Scabrook area, and the Preop-Op X Station interaction. Ilowever, a significant Preop-Op term would not imply power plant effect unless the Preop-Op X Station 5.3.1.1 Seasonal Assemblagg2 E interaction was also significant (Thomas 1977; g Green 1979; Stewart-Oaten et al.1986). Even in The seasonal assemblages of ichthyoplankton the latter case, the interaction would have to be were examined using multivariate numerical further examined to determine if the significance classification (cluster analysis). These analyses was the result of differences between potentially were conducted to determine if the operation of impacted and non-impacted stations. Seabrook Station had altered either the seasonal occurrence or the spatial distribution of fish eggs The 1990 sampling year was classified as either and larvac in the llampton-Scabrook area. More preoperational, operational, or was excluded from specifically, the focus of these analyses was to the analysis for a species, depending on seasonal examine the distribution of ichthyoplankton pattem of occurrence of each species or times of among intake (P2), discharge (PS), and farfield g sample collection, and is noted as such on the (P7) stations before and after Seabrook Station 5 ANOVA tables. For larvac, the data were restricted operation. Typically, ichthyoplankton taxa occur 5-8 s
7 3 TABLE 5-3. GEOMETRIC MEAN CATCH PER UNIT EFFORT (NUMBER PER 1000 us ) WITH (. COEFFICIENT OF VARIABILITY (CV) BY STATION (P2, P5, AND P7) AND ALL STATIONS COMBINED FOR SELECTED LARVAL SPECIES COLLECTED IN ICHTHYOPLANKTON SAMPLES DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND IN 1993. SEABROOK OPERATIONAL REPORT,1993. PREOPERATIONAL PERIOD
- 1993 b OPERATIONAL PERIOD' SPECIES STATION MEAN CV 'MEAN MEAN CV American sand lance P2 148.4 4 191.1 104.8 7 (Jan.Apr) P5 207.4 5 153.4 141.7 2 P7 98.4 6 109.1 90.9 3 All stations 151.4 4 147.3 110.5 4 Winter flounder P2 9.0 9 8.7 7.3 6 (Apr.Jul) P5 7.9 9 6.4 6.8 8 P7 7.3 to 1.7 2.1 13 j 4.6 4.7 'l All stations 8.4 8 5 Atlantic cod P2 3.1 19 1.2 1.7 36 (Apr.Jul) P5 3.0 22 1.0 1.8 47 P7 1.8 28 1.2 1.5 25
[ All stations 3.0 17 1.1 1.7 37 Yellowtail flounder P2 3.4 15 4.2 2.5 28 (May-Aug) P5 3.8 16 5.3 2.8 31 < P7 3.2 19 2.6 2.2 18
)
All stations 3.6 12 3.9 2.5 25 i Atlantic mackerel P2 5.6 12 5.9 7.9 33 (May Aug) P5 6.1 18 5.0 5.6 33. P7 5.9 10 4.6 7.7 32 All stations 5.8 12 5.2 7.0 32 .( Cunner P2 42.5 6 87.7 34.6 28 (Jun. Sept) P5 43.9 9 79.8 31.0 26 P7 50.0 9 95.9 41.7 27 All stations 42.8 6 87.6 35.5 27 d Hakes P2 3.9 12 1.6 1.- 45 (Jul-Sept) P5 3.2 18 1.5 2.1 64 P7 4.3 19 1.3 2.3 81 All stations 4.0 12 1.5 2.0 66 Atlantic herring P2 27.4 9 5.3 6.4 21 { (Oct Dec) P5 27.5 13 7.7 8.2 14 P7 30.3 9 8.9 9.7 16 All stations 27.4 9 7.2 8.0 16 Pollock P2 6.4 14 .* 1.8 4 (Nov.Feb) P5 7.4 16 - 2.2 17 P7 5.4 23 - 1.6 24 All stations 7.0 14 - 1.8 12
'
- Preoperational: July 1975. July 1990; geometric mean of annual geometric means.
b Geometric mean of the 1993 data.
- Operational: August 1990. December 1993; geometric mean of annual geometric means.
d Includes red, white and spotted hakes. Annual geometric mean not computed for pollock in 1993 because January and February 1994 data were not yet available. 5-9
i Ol a, nsu llurley 1992), and based on the frequency of during distinct seasons and periods of frequent occurrence, which are relatively consistent from occurrence in samples, Atlantic cod were probably year to year. The data examined were collected dominant during this period, in addition to some from July 1986 through December 1993, when all pollock eggs. Egg abundances in Group 2, three stations (P2, PS, and P7) were sampled. The termed the winter group, were relatively low for preoperational period extended through July 1990 the two dominant taxa, Atlantic cod / haddock and and the operational period began in August 1990. American plaice, during both preoperational and Several of the egg taxa were grouped, because operational periods and no significant (p > 0.05) during early developmental stages it was difficult differences were detected. This winter group to distinguish among some species (e.g. Atlantic consisted primarily of monthly collections from E cod, haddock, and witch flounder; cunner, January through March; from the frequency of 5 yellowtail flounder, and tautog; fourbeard occurrence in samples where eggs were identified rockling and hakes). Larvac were generally to species, Atlantic cod was dominant. Group 3. E identified to species, except that red, white, and termed early spring, primarily included April 5 spotted hakes were grouped together. collections, having the same dominant taxa of the previous group with the addition of fourbeard Nine egg taxa met the criteria as dominant taxa rockling eggs. There appeared to be a decline in and the subsequent numerical classification fourbcard rockling and an increase in American analysis resulted in eight groups (Figure 5-2). A plaice abundances between preoperational and total of 270 monthly observations were used for operational periods and these differences were the cluster analysis and only two monthly significant (p < 0.02; Table 5-4). observations (station P7, February 1990 and station P7, February 1992) did not fall within any Group 4, termed the mid spring group, was of the eight groups. The eight groups formed two found during the beginning of the warmer water major categories, which corresponded to annual season and consisted of May collections periods of cold and warm water temperatures. exclusively for all years. The dominant taxa were Groups 1-3 were found during periods of cooler more diverse than for the three previous groups g water temperatures (November through April) and and included eggs of cunner /ycilowtail flounder, 5 Groups 4-8 were taken during the warmer period fourbeard rockling (most abund at during the (May through October). There was no difference preoperational period), American plaice, Atlantic in these two categories between preoperational and mackerel (most abundant during the operational . operational periods. Group 1 termed late fall, period), and Atlantic cod / haddock. For fourbeard represented the beginning of the cooler water rockling, Atlantic mackerel, and Atlantic period and consisted primarily of November and cod / haddock the changes were significant (p < December collections. Atlantic cod /pollock was 0.05 ). Group 5 consisted of June collections the only dominant taxon in this group (Table 5- exclusively and was termed the early summer 4). The operational geometric mean for grouping. This group appeared much less diverse, cod /pollock was lower than the preoperational with only cunner /ycIlowtail flounder and Atlantic g mean and the difference was significant (p < 0.05) mackerel as dominant. These two taxa showed an g based on trsults of a t test on monthly means from approximate two-fold increase in abundance from transformed data. Atlantic cod, haddock, and the preoperational to the operational period, but g witch flounder eggs can be identified to species only the cunner /ycllowtail flounder difference was 5 during their late embryonic stage (Brander and significant (p < 0.05). Group 6 was again 5-10 I
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] Not Sampled P2 (s ::M;5s::' .:t; Exct I rom Yb ib $ N IkfNA 5Lik JUL l AUG SEP OCT l NOV l DEC l MONTil Figure 5 2. Dendrogram and temporal / spatial cecurrence pattem of fish egg assemblages forrned by numerical j classification of ichthyoplankton samples (monthly means of logiO(x+1) transformed number per 1000 m3) at Seabrook intake (P2), discharge (P5), and far0cid (P7) stations, July 1986-December 1993. Seabrook Operational Report,1993.
5-11 {
TABLE 5-4. 3 GEOMETRIC MEAN DENSITY (NUMBER PER 1000 m ) OF FISil EGGS COLLECTED AT SEABROOK INTAKE (P2), DISCHARGE (PS), AND FARFIELD (P7) STATIONS FROM JULY 1986 TilROUGII DECEMBER 1993. SEABROOK OPERATIONAL REPORT, 1993. CLUS1FP. ANALYSIS PREOPERATIONAL PERIOD' OPERATIONAL PERIODb GROUPS DOMINANT TAXA' Nd LCL' MEAN UCL N LCL MEAN UCL 1 - Late Fall Atlantic cod /pollock 32 43 62 90 23 22 34 52 (0.72/D.57)f 2 - Winter Atlantic cod / haddock 24 3 5 6 27 3 4 5 (0.67/0.57) American plaice <l 1 1 <1 1 2 3 - Early Spring American plaice 15 21 36 62 9 52 120 274 (0.53/0.38) Atlantic cod / haddock 6 14 28 14 25 43 Fourbeard rockling 3 8 16 <1 <1 g 4 - Mid Spring Cunner /yellowtail flounder 12 156 275 487 9 114 285 711 (0.69/0.55) Fourbeard rockling 67 220 713 2 11 43 Y American plaice 45 63 87 17 33 65 C Atlantic mackerel 16 33 69 293 477 775 Atlantic cod! haddock 19 28 41 3 g 23 5 - Early Summer Cunner /yellowtail flounder 12 5847 9S91 16731 9 13124 19654 29431 (0.79/0.71) Atlantic mackerel 1283 2335 4249 2193 3393 5250 6 - Mid Summer Cunner /ycllowtail flounder 26 1654 3636 7994 21 1974 Fourbeard rockling/ hake 3727 7035 (0.76/0.71) 242 433 774 260 399 612 7 - Late Summer Fourbeard rockling/ hake 16 69 124 221 12 84 164 323 (0.70/0.63) llakes 78 119 182 36 69 132 Windowpane 12 26 54 52 Fourbeard rockling 5 90 156 13 33 2 4 6 Silver hake 4 13 36 91 144 228 8 - Early Fall llakes 9 5 9 15 12 2 3 5 (0.64/0.41) Siber hake 5 7 11 4 Fourbeard rockling 9 19 1 4 8 <1 1 1
- Preoperational = July 1986. July 1990 b Operational = August 1990-December 1993.
e Those whose combined preoperational geometric mean densities accounted for 290% of the sum of the preoperational geometric mean densities of all taxa within the group d N represents the number of momhly means.
- Geometric mean and lower (LCL) and upper (UCL) 95% confidence limits.
f (Within group /between group similarity). ll M M E 'M E 'm M M m m m m M M m W M EB
b FISH { dominated by cunner /yellowtail flounder, with the Twenty-three larval taxa were selected for addition of fourbeard rockling/ hake eggs. The numerical classification analysis, which resulted in season for this gmup was termed mid summer and seven cluster groups (Figure 5-3). Only onc ! occurred exclusively in July and August for all monthly observation (station P2, October 1992) years. All the dominant taxa had similar densities did not cluster within any of the seven groups. j during the preoperational and operational periods Similar to the egg collection data, two major j categories were evident, with collections in Gmups I and no significant (p > 0.05) differences were detected. Group 7 consisted of late summer 1-4 occurring primarily during the cooler water collections, primarily those during September. temperature period (generally November through
'The taxa comprising this group were fairly diverse, May) and collections in Groups 5-7 during the probably due to a general decline in egg warmer period (generally June through October). j abundance during this period. Differences Group 1, termed late fall, included November and between preoperational and operational periods December collections (Table 5-5). Larval Atlantic were significant (p < 0.05) for windowpane, herring was the only dominant species during this fourbeard rockling, and silver hake eggs. The period and there was a significant (p < 0.01) season represented by Group 8 was early fall and decrease in its abundance from the preoperational collections occurred primarily in October. There to the operational period. Group 2, termed early was a significant (p < 0.05) decrease between winter, was more diverse and was generally preoperational and operational periods for hakes comprised of January collections. American sand and fourbeard rockling eggs. lance was most dominant, with the remaining predominant taxa found at lower abundances.
The consistent temporal (among both months There were no apparent differences between and years) and spatial (among stations) preoperational and operational geometric means assemblages suggested that operation of Seabrook for any of these taxa and this was substantiated by Station has not altered the seasonal spawning time result of the t-tests. American sand lance larvac nor the distribution of eggs in the llampton- again dominated in Group 3, termed late Seabrook area. The spatial stability was winter /early spring. The period of occurrence for demonstrated by the fact that about 97% of the collections of this group was relatively long, monthly observations at all three stations during generally from February through April. The each year were found in the same groups. geometric means were similar between Furthermore, about 37 % of the monthly preoperational and operational periods for all taxa, observations at the three stations exhibited a high except the slight decline of gulf snailnsh eggs in degree of similarity for each year and month the operational period was marginally signincant combination. This spatial similarity was further (p = 0.N7). Group 4 occurred during late spring supponed by the results of MANOVA, for which a and was consistently comprised of May collections significant difference was found between the for all years, except for 1993, when this group was preoperational and operational periods (p < 0.01), not present. The Atlantic seasnail was the most but the interaction was clearly not signincant (p > dominant fish in this group and its geometric 0.99). This indicated that the temporal changes in mean, along with that of winter flounder larvae, assemblage abundance occurred concurrently at decreased from the preoperational to the all three stations, including the farfield station operational period, although these declines were (P7), the control area. not significant (p > 0.05). l 5-13
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f:!f;2:l;E:::IAN[iiis'{iiX1i}'kiW[siXi}'ES] Jul [Xiid[TIFl ocr l Nov l o MONTil Figure 5-3. Dendrogram ark! temporal / spatial occurrence pattern of fish larval assemblages formed by numerical classification of ichthyoplankton samples (monthly means of logiO(x+ 1) transformed number per 1000 m3 ) at Scabrook intake (P2), disharge (P5), and farfield (P7) stations, July 1986. December 1993. Seabrook ' Operational Report,1993. l l 5-14 I
=
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l l TABLE 5-5. GEOMETRIC MEAN DENSITY (NUMBER PER 1000 m3 ) OF FISH LARVAE COLLECTED AT SEABROOK INTAKE (P2), DISCHARGE (PS), AND FARTIELD (P7) STATIONS FROM JULY 1986 THROUGH DECEMBER 1993. -SEABROOK OPERATIONAL REPORT, 1993. CLUSTER ANALYSIS PREOPERATIONAL PERIOD
- OPERATIONAL PERIODb GROUPS DOMINANT TAXA' Nd LCL' MEAN UCL N LCL . MEAN - UCL I - Late Fall Atlantic herring 30 27 46 79 26 8 12 19' (0.37/0.17)f 2 - Early Winner American sand lance 14 II 22 44 9 12 23 41-(0.53/0.48) Atlantic herring 2 4 7 <l 2 4 I
Gulf snailfish 2 3 5 2 4 6' i Pollock 1 3 8 1 2 3 3 - Late Winter / American sand lance 34- 136 197 283 30 98 149 224 Early Spring Rock gunnel 13 21 32 8 14 23 u (0.58/0.48) Gulf snailfish 8 10 14 4 6 -9 f Grubby 4 6 10 3 .5 8 u 4 - Late Spring Atlantic snailfish 12 32 68 143 6 11 34 105 (0.63/0.39) American sand lance 9 18 35 4 17 66: Radiated shanny , 10 14 19 7 37 39 Winter flounder 5 10 20 1 5 13 5 - Early Summer Cunner 30 45 101 226 I8 5 18 61 (0.56/0.44) Fourbeard rockling 26 45 .78 14 23 40-Radiated shanny 15 22 -32 21 33 52 Atlantic mackerel 8 16 31 13 36 94-Winter flounder 4 8 15 5 9 17 6 - Late Summer Cunner 12 64 137 292 18 157 401- 1021 (0.62/0.44) Fourbeard rockling 18 48 124 19 30 46 Hakes - 4 7 12 3 12 35 l Silver hake 2 6 14 4 33 34 Witch flounder 2 5 10 1 1 2 Windowpane 2 5 9 2 ~4 9 (continued)
TABLE 5 5. (CONTINUED) PREOPERATIONAL PERIOD
- OPERATIONAL PERIODb GROUP DOMINANT TAXA' Nd LCL' MEAN UCL N LCL MEAN UCL 7 - Late Summer / Cunner 15 1 3 5 15 <1 1 2 Early Fall Fourbeard rockling i 2 5 2 4 6 (0.38/0.30)f Windowpane 1 I 2 <1 3 g Y Atlantic herring <1 1 2 <t g 3 g Silver hake <1 1 2 <l 1 2 Hakes <l 1 1 <1 1 i Witch flounder <1 1 1 <1 3 2
- Preoperational = July 1986-July 1990.
b Operational = August 1990. December 1993. e Those whose ccmbined preoperational geometric mean densities accounted for 290% of the sum of the preoperational geometric mean densities of all taxa within the group. d N represents the number of monthly means.
- Geometric mer.n and lower (LCL) and upper (UCL) 95% confidence limits.
I(Within group /between group similarity). UE E E E E E E E E E E E E E E E E E EE
l FISII Group 5 collections occurred primarily during 5.3.1.2 Entrainment early summer (June and July), the beginning of the warm water groups. The geometric mean for One of the most direct measures of potential cunner, the most dominant species in this group, impact of Seabrook Station on the local fish declined from the preoperational to the assemblages is the number of eggs and larvae operational period and this was significant (p < entrained through the condenser cooling water 0.05). The annual seasonal patterns of occurrence system. During 1993,13 egg and 20 larval taxa for Groups 6 and 7 were less consistent than for were collected in entrainment samples (Table 5-6). the other groups. Although Group 6 was not Total annual estimates of entrainment were 315.6 present every year, cunner and fourbeard rockling million eggs and 126.1 million larvac. The total larvac dominated this group during late summer egg entrainment in 1993 was the lowest since plant ! (August and September). When present, this operation began, even though the annual j group annually occurred together at all three condenser water volume was the greatest (Figure stations. In contrast to Group 5, cunner larvae 5-4). About 90% of the eggs entrained were from l were more abundant during the operational period six taxa: Atlantic mackerel, cunner /ycllowtail than the preoperational period and this increase flounder, Atlantic cod / haddock, hake /fourbeard was significant (p = 0.01). Finally, Group 7 was rockling, windowpane, and American plaice, with termed late summer /carly fall, with most over 50% attributed to Atlantic mackerel and collections from August through October. All but cunner /ycllowtail flounder. Eggs from these taxa one (Atlantic herring) of the seven dominant taxa have also previously dominated entrainment were also present in the previous group, but at samples (Table 5-7) and were also dominant in much lower densities, particularly for cunner and offshore collections during 1993 (Table 5 4). fourbeard rockling larvac. In general, for the months of August and September, Groups 6 and 7 Total larval entrainment in 1993 was within the were mutually exclusive, but there was no apparent range of previous years, even though the 1990 pattern that could be related to plant operation. estimate included only the months of June through December, and in 1991 and 1992, no Although the temporal occurrence of larval entrainment sampling was cm. ducted during a 3-groups, both monthly and annually, was not as to 4-mo period (August or September through consistent as for fish eggs, spatial clustering was November) due to plant outages. The Atlantic consistent. About 99% of the monthly obser- seasnail accounted for over 50% of the 1993 larval vations at all three stations during each year were entrainment estimate. The dominant larval taxon grouped in the same clusters, and in about 44% of entrained was not consistent from year to year, the monthly observations the three stations were with fourbeard rockling predominating in 1990 very similar within the same year and month. and rock gunnel in 1991 and 1992. There was no Similarity among stations was also supported by consistent relationship between larval and egg taxa the results of MANOVA, where the entrained in the same year. This inconsistency was preoperational-operational term was significant (p probably due to varying susceptibility of the two < 0.01), but the interaction was clearly not developmental stages to entrainment. Among the significant (p > 0.99). These results indicated that species entrained that have demersal or adhesive the temporal changes in assemblage abundance eggs, which are not susceptible to entrainment, were consistent at all three stations, including the include the Atlantic seasnail, grubby, American non impacted farfield station (P7). sand lance, Atlantic herring, rock gunnel, winter 5-17
C C I TAllLE 5-6. MONTIILY ESTIMATED NL'MBERS OF FISli EGGS AND LARVAE ENTRAINED (x 10') BY TIIE COOLING WATER SYSTEM AT SEABROOK STATION FROM JANUARY TIIROUGil DECEMBER 1993. SEAllROOK OPERATIONAL REPORT,1993. TAXON Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total % I Atlantic mackerel 0.0 0.0 0.0 0.0 18.4 94.0 0.4 0.1 0.0 0.0 0.0 0.0 112.9 35.8 l Curmer/ycilowtail nounder 0.0 0.0 0.0 0.1 1.6 24.8 5.9 25.9 0.0 0.1 0.0 0.0 58.4 18.5 E Atlantic cod / haddock 0.0 0.0 17.9 0.4 3.0 18.4 7.1 2.3 0.3 0.1 0.1 0.7 50.3 15.9 Ilakes/fourbeard rockling 0.0 0.0 0.0 0.0 0.8 10.2 3.4 10.8 7.5 0.0 0.0 0.0 32.7 10.4 Windowpane 0.0 0.0 0.0 0.0 3.5 9.6 3.2 10.9 1.9 0.0 0.0 0.0 29.1 9.2 American plaice 0.0 0.0 0.0 7.3 6.4 5.7 0.1 0.0 0.0 0.0 0.0 0.0 19.5 6.2 Lumpfish 0.0 0.0 0.0 0.1 7.3 2.0 0.1 0.0 0.0 0.0 0.0 0.0 9.5 3.0 Unidentified 0.0 0.0 0.0 0.0 0.1 0.3 0.1 0.0 0.3 0.0 0.0 0.0 0.8 0.3 Fourbeard rockling 0.0 0.0 0.0 0.0 0.0 0.7 0.2 0.4 0.1 0.0 0.0 0.0 1.4 0.4 Silver hake 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.3 0.0 0.0 0.0 0.0 0.4 0.1 Pollock 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.1 ilakes 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0,0 0.1 0.0 0.0 0.2 0.1 Atlantic menhaden 0.0 0.0 0,0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 Cusk 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 Total 0.0 0.1 17.9 7.9 41.2 165.8 20.7 50.7 10.1 0.3 0.1 0.8 315.6 100.0 LARVAE 5 Atlantic seasnail 0.0 0.3 0.0 2.3 18.6 38.1 4.6 0.5 0.0 0.0 0.0 0.0 64.4 51.1 Grubby 0.1 0.2 0.6 9.0 3.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13.8 10,9 American sand lance 2.8 1.4 0.1 2.9 4.6 0.1 0.0 0.0 0.0 0.0 0.0 0.1 12.0 9.5 Atlantic hening 0.1 0.2 0.0 8.7 0.3 0.0 0.0 0.0 0.0 0.0 0.1 0.2 9.6 7.6 Rock gunnel 0.1 0.7 1.7 1.8 1.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.7 4.5 Unidentified 0.1 0.0 0.5 1.5 1.7 1.3 0.1 0.2 0.0 0.0 0.1 0.0 5.5 4.4 Cunner 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.5 0.2 0.0 0.0 0.0 4.7 3.7 Winter nounder 0.0 0.0 0.0 0.0 0.1 2.5 0.2 0.1 0.0 0.0 0.0 0.0 2.9 2.3 Gulf snailfish 0.6 0.7 0.1 1.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.6 2.1 g Fourbeard rockling 0.0 0.0 0.0 0.0 0.0 0.0 0.1 1.9 0.1 0.0 0.0 0.1 2.2 1.7 g American plaice 0.0 0.0 0.0 0.0 0.3 0.3 0.1 0.0 0.0 0.0 0.0 0.0 0.7 0.6 Longhorn sculpin 0.0 0.3 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.3 Moustache sculpin 0.0 0.1 0.1 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.4 0.3 Lumpfish 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 Snailfishes 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 Shorthorn sculpin 0.0 0.1 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 Radiated shanny 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.2 0.2 Atlantic cod 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.1 Silver hake 0.0 0,0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.1 Windowpane 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.1 g
}{akes 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.1 g Total 3.8 4.0 3.2 27.6 31.0 42.7 5.3 7.6 0.3 0.0 0.2 0.4 126.1 100.0
( 5-18 E
I - k *E80 - Pfar.t Flow 170J r
$al h 50f 40 J
< 30;
$ 204 h l0-
{ hbNb }hbkN 5Ehbhb $hbkb b b I993 1990 1991 1992 1400 - _ Eggs
' ~ g Atlanuc mackerel O Cuncer/Yellowtailflounder O otheressi
{ L F 1000 F 800 - s .: w 0 g a: g2*_ m Not Sampled Nogtled 0 97, , , , , ,75,b,,,*,,,,,7,,,T,,,,, ,T797d7, ,, A SOND J FMAMJ J ASOND J FMAMJ JASOND J FMAMJ JASOND 1990 1991 1992 1993 801 g Attantic wasnail @ Amencan sandlance Q Cunna O Otherlarvae 70 i g Rock gunnel O or=667 8 Fourbeardrockling 5 w 60 .
~
g ai = Q : r['h y 40 i[@ 30 _ g $ . 20 g - m 7 10
- N a Not Sampled Not Sam led d Oj.
4
" - - - - r, i e RGSgh $[$ ____
iSb$$l}FM.M5l SE dbNbflFMdM55 $bNb $FM Ml5 $bNb____ 1990 1991 1992 1993 Figure 5-4. Total monthly cooling water system Dow and estimated numbers of fish eggs and larvae entrained at Seabrook Station during the operational period. Seabrook Operational Report,1993. 5-19
o; u . TABLE 5-7. ANNUAL ESTIMATED NUMBERS OF FISH EGGS AN3 LARVAE ENTRAINE3 (x 10') BY THE COOLING WATER SYSTEM AT SEABROOK STATION FROM JUNE 1990 THROUGH DECEMBER 1993. SEABROOK OPERATIONAL REPORT,1993. - TAXON 1990* 1991 b 1992' 1993 Atlantic mackerel $18.8 490.4 673.1 716.3 456.3 198.6 112.9 58.4 l W Cunner /yellowtail flounder Atlantic cod / haddock 29.1 74.5 39.5 50.3 Hakes /fourbeard rockling 113.6 35.1 50.6 32.7 Windowpane 36.4 19.9 22.5 29.1 American plaice 2.6 21.0 52.3 19.5' Lumpfish 0.0 0.0 0.0 9.5 Fourbeard rockling 7.4 4.3 0.8 1.4 Unidentified 0.0 2.0 0.0 0.8 Silver hake i 1.4 0.0 0.1 0.4 Pollock 0.0 1.0 0.4 0.2 Hakes 37.3 2.6 0.0 0.2 Atlantic menhaden 0.0 0.5 1.4 0.1 Cusk O.1 0.5 0.0 0.1 Total 1247.1 1550.8 822.5 315.6 LARVAE Atlantic sea: nail 11.6 16.0 3.5 64.4 Grubby 0.0 22.4 1.9 13.8 American sand lance 0.0 37.3 18.1 12.0 Atlantic herring 0.7 0.5 4.9 9.6 Rock gunnel 0.0 51.1 45.3 5.7 Unidentified 0.7 2.1 1.4 5.6 Cunner 14.7 <0.1 0.0 4.7 Winter flounder 3.2 9.0 6.2 2.9 Gulf snailGsh 0.1 2.8 1.9 2.6 Fourbeard rockling 37.9 0.5 0.1 2.2 American plaice 0.4 1.0 0.8 0.7 Longhorn sculpin 0.0 0.6 0.6 0.4 Moustache sculpin 0.0 0.1 0.3 0.4 Lumpfish 0.6 0.1 0.1 0.2 Snailfishes 0.1 0.3 0.0 0.2 Shorthorn sculpin 0.0 0.2 0.6 0.2 Radiated shanny 4.8 3.1 1.1 0.2 Atlantic cod 0.7 1.5 0.4 0.1 Silver hake 7.7 0.0 0.0 0.1 Windowpane 3.8 < 0.1 0.1 0.1 Hakes 4.8 0.0 0.0 0.1 Atlantic mackerel 0.2 4.7 0.0 0.0 Yellowtail flounder 0.1 0.3 0.1 0.0 Alligatorfish 0.0 0.1 0.2 0.0 Wrymouth 0.0 0.1 0.0 0.0 Witch flounder 0.3 0.0 0.0 0.0 Tautog 0.3 0.0 0.0 0.0 Pollock 0.2 0.0 0.1 0.0 Fourspot flounder 0.2 0.0 0.0 0.0 Rainbow smelt 0.2 0.0 0.1 0.0 Goosefish 0.1 0.0 0.0 0.0 Atlantic menhaden 0.1 0.0 0.0 0.0 RedGsh 0.0 0.0 0.4 0.0 Haddock 0.0 0.0 0.1 0.0 i Unidentified sculpin 0.0 0.0 0.1 0.0 l Total 93.5 153.8 87.8 126.2 l 6
' From NAl(1991). From NAl (1992).
- From NAl(1993).
5-20 I
f FISH { flounder, and gulf snailfish. Behavioral catches were made at G3, the northernmost station, characteristics of larvae may also reduce their particularly during the first few and the most susceptibility to entrainment. For instance, hake recent years of sampling. Catch during the and fourbeard rockling larvae are surface oriented preoperational period (1976-89) was dominated (Hermes 1985) and may not be susceptible to the by Atlantic herring, blueback herring, silver hake, mid-water intakes. The rapid larval development pollock, and Atlantic mackerel. For the opera-of Atlantic mackerel may enable them to develop tional period (1991-93), most of the catch was a relatively high swimming speed (Ware and made up of Atlantic herring, pollock, Atlantic Lambert 1985) and, thus, may be able to avoid mackerel, and spiny dogfish. entrainment. The spiny dogfish has become increasingly Annual Seabrook Station entrainment estimates abundant during the operational period, with a for the selected taxa were compared to estimates geometric mean CPUE of 0.2, which is approxi- ' from two other New England power plants, Pilgrim mately seven times the CPUE determined for the and Millstone Stations, for 1990 through 1993 preoperational period. However, catch in 1993 (< (Table 5-8). Except for Atlantic seasnail larvae, 0.1) decreased substantially from the CPUE of 0.4 annual entrainment estimates for Seabrook Station determined for 1992 (NAl 1993). Spiny dogfish had similar annual estimates or were considerably have increased continuously since the 1960s, and, less than at the other two power plants. together with skates, now comprise about 75% of the fish biomass on Georges Bank (NFSC 1993). In the Gulf of Maine, the spiny dogfish is 5.3.2 Adult Fish primarily found inshore during summer. It is known to prey upon Atlantic herring, Atlantic cod, 5.3.2.1 Assemblaces Atlantic mackerel, and American sand lance, among other species (NFSC 1993). Because J I 5.3.2.1.1 Pelacie Fishes female spiny dogfish bear live young that are relatively large and well-developed, no specimens The pelagic fish assemblage was sampled using have been entrained at Seabrook Station and only a gill net array at three stations (Figure 5-1), 4 have been impinged on the traveling screens Geometric mean CPUE of all fish caught at all since 1990. The recent increase in spiny dogfish three stations combined for 1993 was 1.8, a biomass has taken place concurrently with ) decreases in groundfish stocks in a large region of I decrease from a mean of 2.7 in 1992, but generally similar to annual means found through- the Northwest Atlantic Ocean (NFSC 1993) and, out the 1980s (Figure 5-5). Largest catches were thus, is not related to Seabrook Station operation. made during the first 5 yr of sampling (i.e.,1976-80). Catch in 1993 was dominated by the Atlantic herring, Atlantic mackerel, alewife, rainbow smelt, 5.3.2.1.2 Demersal Fishes and Atlantic cod (Table 5-9). I A 9.8-m otter trawl was used at three stations in general CPUE at the three gill net stations (Figure 5-1) to determine the abundance and l followed similar trends during the 18-yr period of distribution of demersal fishes. Geometric mean sampling (Figure 5-5), as did the catch of the most CPUE of all fish caught at all stations combined in numerous species (Table 5-9). Slightly higher 1993 was 21.9, an increase over the CPUE of 11.6 5-21
C n v TABLE 5-8. COMPARISON OF ENTRAINMENT ESTIMATES (x 10') AT SELECI'ED NEW ENGLAND POWER PLANTS WITH M ARINE INTAKES FROM 1990 TIIROUGli 1993. SEABROOK OPERATIONAL REPORT,1993. SEaBROOK PILGRIM' MILLSTONE b TAXON Cunner /yellowtail flounder /tautog eggs' 58 716 629-2,609 2,736-4.758 I Atlantic mackerel eggs 113-673 337-1,892 - Atlantic herring larvae 1-10 1-6 - Cunner larvae 0 15 3-134 - Grubby larvae d 2 22 7-44 34-76 E g Atlantic seasnail larvae 4 64 2-9 - Rock gunnellarvae 6 51 7-38 - American sand lance larvae 12-37 23-108 7 61 Atlantic mackerellarvae 05 4-108 - Winter flounder larvae 3-9 7 11 45-514
- MRI (1991,1992,1993b, and 1994); Cape Cod Bay.
6 NUSCO (1994a, b); eggs 19901992, larvae-1990-1993; teng Island Sound.
- Scabrook: ccer/yellowtail; Pilgrim: cunner /tautog/yellowtail flounder; Millstone: cunner.
d Seabrook and Millstone: grubby; Pilgrim: grubby and other sculpins. I GILL NET I ALL SPECIES COMBINED l 20 - W 18-
/ \ { GI
$ 16- / \ l G2 i4 / -- c3 t: ,
\
- a g 12 - ,,
, g ,
MEAN 10 - [ \ { g s. PREOPERAT10NAL f OPERATIONAL
- 5
,)~\-
. =
7 ' d-1 . .
- i n.
,fN 2- . , ,
' 'W.Q _
4 0 . , , , , , . . . . . , i , , , . , 76 77 78 79 80 81 82 83 84 85 16 87 88 89 90 91 92 93 YEAR , Figure 5 5. Annual geometric mean catch of all species combined per unit effort (number per 24-h set)in gill net samples by station and the mean of all stations, 1976-1993. Scabrook Operational Report,1993, l 5-22 E a
i l TABLE 5 9. GFDMETRIC MEAN CATCH PER UNrr EFTORT(NUMBER PER 24h SfT SURFACE AND BolTOM) WrrH COFJFICIENT (W VARfABILITY (CV) BY IrrATlON (G1.G2, AND G3) AND ALL STATIONS COMBINED IUR A BUNDANT SPECIES COLLECTED BY GILL NET.DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND THE 1993 MEAN. SEABROOK OPERATIONAL REIORT,1993. PREOPERAT10NAL PERIOIP 1993b OPERATIONAL PERIOD' SPErIES STATION MEAN CV MEAN MEAN CV Adande herring G1 1.0 18 0.4 0.4 13 G2 1.1 20 0.1 0.3 32 G3 1.2 20 0.4 0.5 5 All Stanms 1.1 19 0.3 0.4 13 . Atlande mackerel GI 0.2 17 0.3 0.2 23 G2 0.2 16 0.5 0.2 47 G3 0.3 16 0.5 0.4 20 All Stanans 0.3 15 0.4 0.3 28 Pulkua GI 0.2 17 0.3 0.2 25 G2 0.3 10 0.3 0.3 11 G3 0.3 13 0.4 0.3 27 All Stauuns 0.3 9 0.4 0.3 18 Spiny dogfish GI <0.1 45 <0.1 0.1 79 G2 <0.1 35 <0.1 0.1 38 G3 <0.1 27 0.1 0.3 54 AU Statums <0.1 30 <0.1 0.2 50 Silver hake GI 0.2 34 <0.1 0.1 69 G2 0.3 36 <0.1 0.1 76 G3 0.3 32 <0.1 0.1 40 AD Staums 0.3 34 <0. t 0.1 59 Blucheck hemng G1 0.2 17 0.1 0.1 36 G2 0.3 18 0.1 0.1 36 G3 0.3 23 0.1 0.1 37 All Stanmi 0.3 18 <0.1 0.1 15 Alewife GI 0.1 17 <0.1 0.1 38 G2 0.1 14 <0.1 0.1 45 G3 0.1 22 0.1 0.1 di Alt c nons a 0.1 15 <0.1 0.1 41 Ramhow smeh G1 <0.1 26 0.2 0.1 68 G2 0.1 21 0.1 <0.1 51 G3 0.1 21 0.2 0.1 50 AH Stauans 0.1 18 0.2 0.1 52 Adantic ccal G1 0.1 17 0.0 <0.1 100 G2 0. I 22 0.0 <0. I 100 G3 0.1 13 0.0 0.0 . All Statumn 0.1 13 0.2 <0.1 100 Other species G1 0.4 9 0.2 0.3 21 G2 0.4 10 0.2 0.3 25 G3 04 11 0.1 0.3 32 All Statum: 0.14 9 0.2 0.3 22 a 1%yer:6 anal: 19761989; ge<wnetnc mean of annual ge(snetric means. b Geomeinc mean of the 1993 data.
- Operauonal: 1991 1993; geometnc mean of annual geomeinc means.
5 23
O O FISII water off the mouth of flampton-Seabrook I determined for 1992, but remaining the second-lowest CPUE since sampling began in 1976 liarbor, was occasionally inundated with drift (Figure 5-6). The trawl CPUE peaked in 1980 algae. Stations T1 and T3 are in deeper (20-28 (78.9) and 1981 (78.2), primarily due to large and 22 30 m, respectively) water and have sandy catches of yellowtail flounder. In 1993, catch was bottoms. CPUE of all species combined was dominated by winter Counder, longhom sculpin, consistently lower at T2 than at T1 and T3. which Atlantic cod, yellowtail flounder, skates, hakes, and tended to have similar catches (Figure 5-6). Catch windowpane (Table 5-10). at T2 was dominated by winter flounder, whereas yellowtail Counder (preoperational period) and Catch of nearly all species declined from the longhorn sculpin (operational period) were most g preoperational to the operational period, common at T1 and T3. However, station to station 5 particularly for the yellowtail flounder (CPUE of comparisons are limited by the inability to sample 9.2 and 1.9, respectively). Other species showing by trawl at T2 during many sa.npling trips, panicu-E decreases included the longhom sculpin (4.1,2.7), larly from August through October, when catches a winter flounder (3.4, 3.1), hakes (3.1,1.3), and tend to be largest. Because largest catches were Atlantic cod (1.9, 0.8). The catch of skates was often made during late summer and early fall, this similar (1.8,1.7) in both periods. As noted may have biased interstation comparisons, which previously, groundfish stocks have all decreased in used the entire database. Because of this potential the Northwest Atlantic and skate biomass is bias, data from the August-October period were currently high in this area (NFSC 1993). not used in the ANOVAs for selected species collected by trawl sampling, which is discussed Differences in CPUE and species composition below. For other months during the past 18 yr, a were apparent among the stations. The bottom at few collections were missed at T2, but overall trawl nearfield station T2, located in shallow (15-17 m) sampling effon at T2 was 92% of that at Tl or T3. TRAWL ALL SPECIES COMilINED PR FOPER ADON Al. ', OPl.R ADON Al.
/ .~ .
g go . / \\ 11 g j. ' % : 12 c: f. t : vo - \ / ~ Ig f T3 g g \ ,/' s '/
. 3 g v -
. \ ~' -
MEAN l 40 - m z m
. , /.
h 20 - (/ O , , , , , , , , , , , , , , , I 76 77 78 79 ko 8I 82 83 E4 85 h6 N7 R8 89 90 91 92 93 YEAR Figure 5-6. Annual geometric mean catch of all species combined per unit elfort (number per 10-min tow) in trawl samples by stauon and the mean of all stations. 1976-1993. Scabnok Operational Report,1993. 5-24 5, e ,
I TABLE 5-10. GEOMITRIC MEAN CATCH PER UNTT EFR)RT(NUMBER PER 10 smia TOW) C ITH COEJTICIEPfr OF VARIABILITY (CV) BY STATION (TI.T2, AND T3) AND ALL STATIONS COMBINED FOR ABUNDANT SPECIES COLLECTFD BY (TrTER TRAWL DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND THE 1993
.I MEAN. SEABROOK OPERATIONAL REPORT,1993.
6 PR FOPFR ATION 41. PFR f 0D* 1993 OPF.R ATION AL PERIOff SPITIES STATION MEAN CV MEAN MEAN CV Yellowtail flounder Tl 19.9 3 5.3 4.4 19 12 2.9 8 0.4 0.4 34 I lemghorn sculpin T3 All Stations T1 10.2 9.2 4.6 5 4 7 2.0 2.2 5.3 1.8 1.9 3.4 28 23 12 T2 1.1 12 0.5 0.4 19
- I T3 All Stations 8.4 4.1 6
7 til 3.4 5.7 2.7 3 8 Wmter flounder Tl 3.1 6 3.8 3.5 11 I T2 T3 All Stations Tl 6.1 2.2 3.4 6 7 5 3.1 3.9 3.6 2.4 3.3 3.1 19 6 10 llakes a 4.2 5 1.5 1.9 14 I T2 T3 All Stauons 1.6 36 3.1 9 5 5 09 0.8 1.0 0.7 1.3 1.3 24 23 18 Atlanuc cod Tl 2.0 10 2.8 0.8 64 I T2 T3 All Statxms 0.7 32 1.9 16 11 11 0.3 59 2.5 0.2 1.4 08 47 N) N) Skates TI 1.7 16 2.0 2.7 17 n .I T3 All Statums 0.5 3.8 1.8 10 9 5 0.4 3.5 1.8 0.2 2.8 1.7 21 18 15 j I Windowpane Tl T2 T3 All Statums 1.9 1.0 1.1 1.3 11 10 13 10 1.8 0.3 0.4 0.8 2.0 0.5 0.6 1.0 11 24 31 18 0 y I Rainbow smelt Tl T2 T3 All Stauons 1.0 20 0.8 1.2 10 14 9 8 0.4 0.6 0.3 0.4 0.4 0.8 0.5
#5 11 31 30 24 I Ocean pout TI T2 T3 All Staums 0.7 06 1.3 09 6
9 6 7 0.2 0.3 0.2 0.2 0.2 0.3 0.3 0.3 17 17 17 12 I Silver hake Tl T2 T3 All Staums 0.9 0.2 0.9 06 16 21 14 15 0.3 0.1 04 0.2 0.4 0.1 0.7 0.4 18 53 16 17 I Pullock Tl T2 T3 0.3 0.7 0.2 17 20 20 0.4 0.3 0.2 0.7 0.5 0.2 33 25 28 All Staum: 0.4 17 0.3 0.5 28 I lladdock Tl U T3 0.2
<0.1 0.5 34 62 27 00' 0.0 0.2
<0.1 0.0 0.1 100 58 I
All Statims 0.2 28 0.1 <0. I 55 Other species Tl 59 2 46 4.2 7 T2 3.5 2 2.0 2.1 10 T3 61 2 4.5 4.2 4 I All Statkms 53
- Preoperauonal: 1976-1989; geornetnc mean of annual getrnetne means.
- Geornetnc mean of the 1993 data 2 40 3.7 6
- Operauonal; 1991 1993 geornetnc mean of annual geometnc means.
'I 8 Includes red, white and spotted hakes.
5-25 I
O E FISil I 5.3.2.1.3 Esttrarine Fishes ninespine stickleback, and rainbow smelt also contributed to the catch. Sampling for estuarine fishes was conducted at three stations within the estuary of Hampton- Catch by station showed considerable variation g Seabrook liarbor (Figme 5-1) using a 30.5-m over the years. Station S3, located near the mouth g seine. Geometric mean CPUE for all fish caught of the estuary, had peak catches in 1976, 1979, at all stations during 1993 was 10.2 and, similar to and 1990, but its CPUE has been generally close g CPUE for the gill ret and otter trawl, reptrsented to the three-station mean since 1991. Station S1, E an increase in catch from 1992 (CPUE of 5.6; located farthest from the mouth, had relatively low Figure 5-7). Overall, seine catches generally were CPUE during the earliest years of sampling, but smaller (5.6-24.1) during 1987-93 than they were tended to approximate the overall mean in more during 1976-84, when annual CPUE ranged from recent years. CPUE at S2, located closest to 22.7 to 59.1; no seine sampling took place in Seabrook Station, had the largest CPUE value in l 1985 or April through June of 1986. The catch 1993. Trends in CPUE were mostly due to the
- of most fishes by seine decreased from the fluctuations in catch of the dominant species, the preoperational to the operational period (Table 5- Atlantic silverside. Winter flounder and rainbow 11). The Atlantic silverside has dominated the smelt were most common at S3, whereas killifish seine catch in all years sampled. Winter flounder, were most abundant at S1, with few taken at S3, killifishes (mummichog and striped killifish), likely due to salinity and temperature preferences.
SEINE I ALL SPECIES COMBINED l 100 - W PREOPERAlloNAl, OPERATloNAL 90 - k \
$ 80 - \
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7 0-j . , 10 - NOT s AM P11.D l , I i l 3 3 I I I I I I i l I I I I I 76 77 78 79 Sn 81 82 83 84 E5 86 87 88 89 90 91 92 93 YEAR Figure 5-7. Annual geometric mean catch of all species combined per unit effort (number per haul) in seine samples by station and the mean of all stations, 1976 1993. Seabrook Operational Report,1993. 5-26 I 5 m
b L TABIE S.I1. GEOMETRIC MEAN CATCH PER UNTT EWORT(NUMBER PER STANDAN MAUL) WTrH COEFMCIENT OF VAR 1ABILrrY BY KTATION (SI,52, AND S3) AND ALL STATIONS COMBINED FOR ABUNDANT SPECIES COLLFfrED (CV) BY SEINE Dl! RING THE PREOPERATIONAL AND OPERATIONAL PERIODS AND THE 1993 MEAN. SEABROOK OPERATIONAL REPORT,1993, 6 OPERATIONAL PERIOD
- t -
PRF. OPERATIONAL PERIOD' 1993 SPErlES STATION MEAN CV MEAN MEAN CV 1 Atlantic silvenide S1 7.7 7 2.2 3.6 19 52 7.3 5 7.3 3.9 18 S3 7.5 8 2.6 - 4.1 15 , All Stations 7.5 6 3.6 3.8 10 ! Winter flounder S1 0.9 1I 0.3 0.3 63 ' S2 1.1 13 1.2 0.4 62 l S3 . 2.9 8 0.9 1.1 9 j All Stations 1.5 9 0.7 0.6 16 - Kilhfishes SI 1.2 9 06 0.9 56 l S2 1.3 18 0.2 0.1 100 -l S3 <0.1 30 0.0 0.0 - i All Sunons 0.7 12 0.3 0.3 50 1 Ninespine stickleback 51 0.8 21 <0.1 0.3 50 S2 0.6 24 0.1 0.1 25 0.0 0.2 77 l S3 06 24 All Stanons 0.7 20 <0.1 0.2 39 f Rainbow smelt S1 0.1 48 0.0 0.1 50 S2 0.1 35 0.7 0.3 . 50 ' S3 0.7 23 0.8 0.4 53 All Stations 0.3 18 0.5 0.2 40 American sand lance S1 0.1 44 0.3 0.3 3 S2 0.2 47 0.8 0.2 100 S3 0.1 27 0.I <0.1 61 All Stations 0.2 26 0.4 0.2 40 Pollock 51 0.1 39 0.1 0.1 50 S2 0.2 39 0.0 <0.1 100 S3 0.4 35 0.0 0.2 51 All Stations 0.2 34 <0.1 0.1 35 Blueback hemng S1 0.2 28 0.2 0.2 58 S2 0.1 35 0.4 0.1 100 S3 0.2 37 0.0 <0.1 100 All Stanons 0. I 28 0.2 0.1 50 Atlanue herring S1 0.1 58 0.1 0.1 62 S2 0.3 27 0.0 0.1 60 S3 0.1 27 0.0 0.1 100 All Stations 0.2 19 <0.1 0.1 52 Alewife 51 0.1 41 0.0 <0.1 54 S2 0.1 49 0.0 0.0 - S3 0.1 33 0.1 <0.1 100 All Stanons 0.1 35 <0.1 <0.1 14 Other species St 0.8 15 0.2 0.2 30 S2 1.1 7 0.5 0.4 29 S3 1.3 10 0.8 0.9 24 All Stanor s 1.1 8 0.5 0.5 27
- Preoperanonal: 1976 1989; geometnc mean of annual geometric means.
- Geometric mean of the 1993 data.
- Operational: 1991 1993; geometric mean of annual geometne means.
5-27
l C E nsu I 5.3.2.2 Imnincement 1977, nearly 300,000 fish weighing 3,040 kg were g collected in 215 24-h samples of impingement at 3 Seabrook Station operated throughout 1993, the Maine Yankee Nuclear Generating Station with average circulating water flow ranging from (Evans 1978). The mean number of fish collected i 571 to 611.8 million gal d (Table 5-12). During each year was approximately 50,000 fish during 1993, an cdmated 1,174 fish and American this period, with an average of 1,395 fish impinged lobster were impinged, the same number as in per sampling day. Most fish were collected from 1992 (Appendix Table 5 2). Most (43%) fish November through April, when water temperatures were collected in December, followed by March were less than 10*C. Sticklebacks (four species), (14%) and April (12%). Most of the smooth flounder, alewife, rainbow smelt, Atlutic impingement in December was associated with an menhaden, winter flounder, and white perch intense coastal nonheastern storm in that month dominated impingement samples, indicative of this (K. Dow, YAEC, pers. comm.). Only 151 power plant's location within the Sheepscot River specimens were impinged from June through estuary. No lobster were impinged at Maine November, with about 25% of the total comprised Yankee. g by Atlantic silverside and winter flounder. The 5 lumpfith, windowpane, sea raven, northern At Pilgrim Nuclear Power Station, sited on pipcGh rainbow smelt, and grubby made up an Massachusetts Bay, an estimated annual average of g additional 47% of the total catch. 18,996 fish (adjusted for 100% plant operation) W was calculated for a 20-yr period (Anderson 1994;
- ht. 1990, when the station began more or less Table 5-13). The mean impingement rate was 52 m.W.ous pumping of seawater, the cumulative fish per day. During this period, catch was impingement totaled 3,866 fish and 42 American dominated mostly by Atlantic silverside, with lobster (Appendix Table 5-2). More than one- rainbow smelt, herrings, and cunner occasionally third of all fish impinged since 1990 were abundant in samples. In 1993, 91 American collected in December (Appendix Table 5-3). lobster were collected, giving an estimated total Very few (6%) fish were impinged in summer impingement of 1,184 lobster for 100% station (June-August). 1)uring the 4-yr operational operation, which was a higher estimate than for period, winter flounder, pollock, windowpane, most other years of Pilgrim Station operation 5
lumpfish, longhom sculpin, sea raven, and Atlantic (Anderson 1994). g silverside made up 61% of the total estimated impingement. Except for pollock and Atlantic In 21 yr of study, an average of 54,433 fish was I silverside, all of these fishes are primarily impinged annually at the Brayton Point Station 5 demersal. In fact, few pelagic fishes, such as (Units 1-3), located on Mount Hope Bay in herrings, Atlantic mackerel, and butterfish, have Massachusetts (MRI 1993a; Table 5-13). Atlantic been impinged at Scabrook Station, even though menhaden, winter flounder, Atlantic silverside, the plant draws water fmm mid-depths. hogchoker, alewife, silver hake, and threespine stickleback were most often impinged. Fish were The number of fish impinged annually at impinged at an average rate of 118 per day. In a Seabrook Station may be compared to collections study to determine the effectiveness of ar.eled or annual estimates made at other large power screens at Brayton Point Unit 4 (LMS 1987), total plants in New England with marine intakes (Table numbers of fish collected on the screens were 5-13). From November 1972 through October 5-28 5 m
i I I i l I l I TABLE 5 12. SPECIES COMPOSITION AND TOTAL NUMBER OF FINFISH AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION BY MONTH DURING 1993. SEABROOK OPERATIONAL REPORT,1993. l I SPECIES JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL PERCENT Atlantic silverside 1 2 2 4 147 156 13.3 Winter flounder 35 12 44 20 1 1 28 141 12.0 Lumprish 8 14 22 17 6 21 23 3 4 118 10.1 Windowpane 10 8 10 9 5 10 2 48 102 8.7
" Sca raven 1 1 1 15 34 7 5 1 14 7 12 98 8.3 Northern pipefish 1 2 80 83 7.1 I Rainbow smelt Grubby Atlantic cod 6
2 5 2 22 5 3 7 2 8 1 2 3 67 38 11 80 67 37 6.8 5.7 3.2 I tenghorn sculpin Skates Righteye flounders 7 2 1 5 4 13 7 19 3 1 1 1 2 4 2 6 26 37 35 32 3.2 3.0 2.7 I Pollock 3 3 1 1 2 1 6 13 2 32 2.7 Shorthorn sculpin 1 2 4 F 4 1 1 2 5 28 2.4 Rock gunnel 1 4 9 8 1 1 1 25 2.1 I IIerrings 1 1 1 2 14 19 1.6 3 17 1.4 ' Threespine stickleback 2 7 5 Cunner 1 8 3 1 13 1.1 Snailfishes 9 3 13 1.1 I 1 Wrymouth 6 1 5 12 1.0 Sculpins 5 2 7 0.6 Sea larnprey 3 3 6 0.5 Tautog 1 1 1 3 0.3 Hakes 3 3 0.3 American sand lance 1 1 1 3 0.3 Red hake 1 1 2 0.2 I- Alewife 1 1 0.1 Scarobin 1 1 0.1 I American plaice Fourspot fk>under American lobster 1 1 1 1 1 1 0.1 0.1 0.1 1UTAL 86 51 164 138 84 38 27 9 2 38 37 500 1174 100.0 CIRCULATING WATER I AVERAGE FLOW (MGD) R ATE (noJ10' gal) 587 587 580 579 582 582 578 579 574 571 612 608 4.73 3.10 9.12 4.84 2.11 1.56 1.51 0.50 0.12 2.15 2.02 26.53 i I 5-29 I
TAllLE 5,13. COMPARISON OF FISil IMPINGEMENT ESTIMATES AT SELECTED NEW ENGLAND POWER PLANTS WITil MARINE INTAKES. SEABROOK OPERATIONAL REPORT,1993. SOURCE RATED NOMINAL COOLING YEARS MEAN RANGE FOR MEAN WATER CAPACITY WATER FLOW OF ANNUAL CV ANNUAL NUMBER STATION BODY (MWe) (m'*see-1) STUDY D1PINGEMENT (%) ESTIMATES PER DAY REFERENCE Seabrook Gulf of Maine 1.150 31.5 1990-93 957 33 499-1,173 2.6 - Maine Yankee Montsweag Bay 855 26.6 1972-77 49,999' 34 31,246-73,420' l.395* Evans (1978)
'$ Pilgrim Massachusetts Bay 670 20.3 1974-93 18,996 6 81 1,143-87,752 6 52" Anderson (1994)
Brayton Point 1-3 Mount Hope Bay 1.150 39.0 1972-92 54,433 136 15,957-359,394 118 MRI (1993a) Brayton Point 4 Mount ilope Bay 460 16.4 1984-85 - 1,479-18.095* - LMS (1987) Millsto.= 2 Long Island Sound 870 34.6 1976-87 25.927' 59 8,560-60,410* 71* NUSCO (1988) 65,927 d 214 8,560-511.387 d 181 d
- Collected in sampling oc.ly, not a calculated annual estimate.
6 Estimates adjusted assuming 100% station operation.
- Excludmg an estimated 480,000 American sand lance taken on July 18, 1984.
d including the sand lance mass impingement episode. m W M M M M M M M M M M M M M M M M ME
h MSH 18,095 in 1985 and 1,449 in 1986. These well as fish behavior and distribution, allow for the numbers represented fish actually collected and entrapment of bottom-dwelling species under no annual estimates were determined in this study. certain conditions. The magnitude of impinge-Bay anchovy comprised most (77%) of the catch ment at Seabrook Station appears to be affected in 1985; Atlantic silverside, northem pipefish, primarily by storms, particularly nonheasters (NAI cinter flounder, butterfish, and tautog were also 1993). A similar phenomenon was noted at relatively common. Millstone Nuclear Power Station, where large winter flounder impingement episodes were found impingement sampling was conducted at to be related to a combination of high sustained Millstone Nuclear Power Station Unit 2, located on wind and low water temperatures (NUSCO 1987). Long Island Sound, from 1976 through 1987 Storm events have also' increased impingement at f other estuarine (Thomas and Miller 1976) and i (NUSCO 1988). Annual impingement estimates for fish ranged from 8,560 to 511.387 (Table 5- freshwater (Lifton and Storr 1978) power plants. 13). The highest estimate, however, was skewed by a single-day catch of approximately 480,000 American sand lance. Excluding this catch, the 5.3.3 Sekcted Snecies largest annual total was 60,410 and the annual [ mean impingement was 25,927 (71 fish per day). 5.3.3.1 Atlantic Herrine impingement samples at Millstone Unit 2 were dominated by winter flounder, anchovies, grubby. The Atlantic herring ranges in the Northwest silversides, and Atlantic tomcod. Annual Atlantic Ocean from westem Greenland to Cape impingement estimates for American lobster Hatteras (Scott and Scott 1988). Separate ranged from 261 to 1,167, with an annual mean of spawning aggregations associated with particular , 634 (CV = 14%). geographic areas in the Gulf of Maine have been recognized (Anthony and Bcyar 1968; lies and ) Impingement estimates at Seabrook Station Sinclair 1982: Sinclair and lies 1985) and tagging were niuch less (s 5%) than those at comparable studies have shown high (> 90%) homing fidelity electrical generating stations in New England, of spawning herring (Wheeler and Winters 1984). Impingement at a power plant does not reflect flowever, a lack of evidence cxists for biochemical, absolute fish abundance near the station, but is genetic, and morphometric differentiation among related to the susceptibility of a species to these spawning groups (Kornfield and entrapment, intake design and location, plant Bogdanowicz 1987: Safford and Booke 1992), operating characteristics, environmental variables indicating that there is enough gene flow to i (e.g., water temperature, wave height, wind prevent the evolution of genetically distinct stocks. direction and velocity), and time of day (Landry Atlantic herring spawning grounds are typically and Strawn 1974; Grimes 1975; Lifton and Storr located in high energy environments (i.e., tidal or 1978). The design of Seabrook Station offshore current), with demersal adhesive eggs deposited on intake with a mid-water entrance and a velocity marine vegetation or substrata free from sitting cap located in a relatively open water body has (llaegele and Schweigert 1985). A major f been successful at reducing the impingement of spawning area and source oflarvae in the westem fish and lobster. Except for pollock and Atlantic Gulf of Maine is Jeffreys Ledge (Townsend 1992), silverside, demersal fish are most often impinged. although other banks and ledges in this area are j This indicates that some features of the intake, as also used (Boyar et al.1971). Other major ( f 5-31
O E FISII I spawning grounds include Georges Bank and during summer. Adults tend to be found in coastal areas of central and eastern Maine and specific summer feeding areas that are located Nova Scotia (Sinclair and Iles 1985). near tidally-induced temperature fronts, where plankton productivity is high, and they overwinter Curn:ntly, the median age and size of maturity after spawning in areas with slower currents than for U.S. coastal Atlantic herring is about 3 yr and found elsewhere in the Gulf of Maine (Sinclair 25 cm (O'Brien et al.1993); all fish become and lies 1985). g' mature by age-5 (NFSC 1993). Maximum size is E about 430 mm and 0.68 kg (Bigelow and Graham (1982) hypothesized that year-class Schroeder 1953). Most spawning in the westem strength was determined by a density-dependent Gulf of Maine occurs during September and mortality phase in fall and a density-independent October (Lazzari and Stevenson 1993). Fecundity phase in winter, both of which may be affected by of fall-spawning Atlantic herring from southwest the time of spawning and larval distribution Nova Scotia ranged from about 50 to 222 following hatching and dispersion. Campbell and thousand eggs (Messich 1976). The early life Graham (1991), however, noted that herring history of Atlantic herring is somewhat unique recruitment is a complex interaction among many g among other northem temperate fishes in that the critical factors, which may differ from year to larval stage is up to 8 mo long before metamor- year. A series of successive cohorts in space and g phosis to a juvenile phase (Sinclair and Tremblay time may help to limit intraspecific competition E 1984). Instead of spawning in spring to coincide and monality (Lambert 1984; Lambert and Ware with increasing water temperature and plankton 1984; Rosenberg and Doyle 1986). An inverse g food resources, fall-spawning herring must deal relationship was found between year-class strength 5 with extremely low winter temperatures and and temperature during the late larval and early minimum plankton abundances (Townsend juvenile phases (Anthony and Fogarty 1985). 1992). The 1.0-l.4-mm eggs hatch in abaut 10- Survival may be related to the rate at which 15 d, when larvae are 4-10 mm (Fahay 1983). temperature decreases in winter as well as to the liatching and larval growth are highly variable absolute minimum temperatures (Graham et al. and depend mostly upon prevailing water 1990). Low temperatures may also indirectly temperatures. Lough et al. (1982) noted tha'. increase starvation and vulnerability to predation. larvae hatching at 5.7 mm grew to 30.9 mm over a 175-d period. Graham and Townsend (1985) Abundance and landings of Atlantic herring reponed mean growth of 0.199 mm d'3 (range of have fluctuated considerably over the past 35 yr g 0.123-0.270) and a monality rate of 2%d'i (0.7- (NFSC 1993). During this period, the fishery in 3 3.1%) for Gulf of Maine larval Atlantic herring. Maine has also changed from predominantly fixed Larvac hatched early in the season grow faster gear to almost all mobile gear in recent years, due g than those hatched late (Jones 1985). Larval to the decreased availability of fish in nearshore 5 mortality is generally highest in fall, low in winter, areas. The Atlantic herring fishery on Georges and increases again in spring (Graham et al. Bank peaked at 373,600 mt in 1960, but collapsed 1972). Larvae tend to drift or disperse from to 43,500 mt in 1976. Recent indications are that offshore spawning grounds into coastal bays and the population on Georges Bank is recovering estuaries for further development and (Stephenson and Kornfield 1990; Smith and transformation to the juvenile phase of life. After Morse 1993). Present biomass may even exceed metamorphosis, juveniles remain in coastal waters pre-collapse levels, but without an offshore fishery 5-32 5 m
L f [- FISH f to pmvide long-term catch data, present estimates area. liowever, as expected, catches among years cf stock levels, although large, are imprecise and months were significantly different. (NFSC 1993). Despite their occurrence in the area of the Atlantic herring eggs have not been identified Seabrook Station intake throughout much of the in any ichthyoplankton collections for Seabrook year, no Atlantic herring have been impinged on Station studies, probably because they are the traveling screens to date (Appendix Table 5-demersal and adhesive. The larval stage was 2). Thus, no direct plant impact to juvenik or prevalent and typically occurred during an adult fish has occurred. The Atlantic herring was extended period from October through May. the fourth-ranked species of entrained larvae in Peak abundance was found during the fall 1993, with an estimated total of 9.6 million (Table . l spawning season, from October through 5-6); this was the largest number entrained since December (NAl 1993). Larval densities in 1993 the beginning of commercial operation (Table 5-were similar to those found during the operational 7). Ilowever, this number is relatively small given period (Table 5-3) and in 1992 (NAl 1993). A that these larvae are likely drawn from the large decline occurred during the preoperational progeny of large spawning groups in the Gulf of period at all three ichthyoplankton stations Maine that disperse widely throughout the area ( (Figure 5-8). There was a noticeable decline in over the course of a lengthy larval developmental annual abundance during the late 1970s and again period. The ANOVA interaction terms for both duririg a similar period in the 1980s, prior to the the ichthyoplankton and gill net programs were , operation of Scabrook Station. Since 1989, not significant, which indicated that the operation annual abundance has remained relatively stable. of Seabrook Station has not affected the local f During the period when all three stations were abundance or distribution of Atlantic herring. \ sampled (1986-93), similar densities were Even though the Georges Bank-Gulf of Maine collected at each station and this was substantiated herring biomass has increased in recent years to j l with the ANOVA results which showed no relatively high levels (NFSC 1993), recovery has significant differences detected among stations not yet occurred in the Hampton-Seabrook area to (Table 5-14). former levels of abundaru. The recovery on Georges Bank appears to be related to Atlantic As pelagic fish,large juvenile and adult Atlantic herring biology and the lack of commercial herring were collected during Seabrook Station fishing pressure in recent years (NFSC 1993). studies primarily by gill net. Catches were highest The stock may have re-established itself from a in spring and fall, with few taken during July and remnant population of fish that remained on the August (NAl 1993). Annual abundance was bank (Stephenson and Kornfield 1990) or by highest in 1976-78, began to decline in 1979 4 0, recolonization from other spawning grounds off I and has remained at a relatively low level from Southern New England (Smith and Morse 1993). 1981 through the present (Figure 5-8). This was reflected by the ANOVA results, showing that the mean catch during the preoperational period was 5.3.3.2 Rainbow smelt significantly greater than the operational period (Table 5-14). No significant differences were The anadromous rainbow smelt occurs from found among stations, indicating relatively Labrador to New Jersey (Scott and Crossman uniform distribution of Atlantic herring in the 1973). It serves as forage for fish, birds, and seals 5-33
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76 77 78 79 20 El 82 83 84 85 86 87 88 89 90 91 92 93 YEAR 3 Figure 5-8. Annual geometric mean catch of Atlantic herring per unit effort in ichthyoplankton (number per 1000 m ) and gill net (number per 24 h set) samples by station and the mean of all stations,1975-1993 (data tetween the two vertical dashed lines were excluded from the ANOVA model). Scabrook Ogerational Repon.1993. l I' 5-34 1 I
;s TABLE 514. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC HERRING DENSITIES BY SAMPLING PROGRAM. SEABROOK-OPERATIONAL REPORT,1993.
PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTHS USED VARIATION df MS F. OF ADJUSTED MEANS Ichthyoplankton Preop-Op' 1 27.15 68.13 " Op< Preop (Oct.-Dec.) Year (Preop-Op)b 6 4.29 10.77 " (1986-1993) Month (Year)* 16 4.07 10.22 ** Stationd 2 0.38 0.95 NS Preop-Op X Station" 2 0.31 0.78 NS Error 248 0.40 ta Gill Net Preop-Opf I 3.33 8444 " Op(Preep - (Sep..May) Year (Preop-Op) 16 1.38 34.89 ** (1975-1993) Month (Year) 139 0.27 6.96 " Station 2 0.10 2.60 NS Preop-Op X Station 2 0.05 1.28 NS Enor 310 0.04
- Preop-Op compares 1990-1993 to 1986-1989 regardless of station. NS= Not significant (p>0.05) -
6
- Year nested within preoperational and operational periods regardless of station. = Significant (0.05W.01)
- Month within year regardless of year, station or period. "= Highly significant (ps0.01) d Stations regardless of year or period.
- Interaction of the two main effects, Preop-Op and Station.
f Preop-Op compares 1991-1993 to all previous years regardless of station. _ . - - _ _ . . . - -. . . - - . - . - . - _ - - - _ - - _ . , _ - . . - - - . . _ - - - - - _- _ _ _ _ ~- _ _ - . - _ . . - _ .-.-,--- _ _. - .-
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U FISi! I and supports minor sport and commercial themselves in estuarine areas by using active fisheries in New England and Canada. A small vertical migration in relation to tides (Ouellet and (maximum size of about 35 cm) pelagic schooling Dodson 1985a; Laprise and Dodson 1989). species, it is readily available for samplirig because g it is mostly found in shallow, coastr,1 waters. Near Seabrook Station, rainbow smelt were 3 Adults begin to mature at ages-1 and 2 and live collected by otter trawl mostly from December above 5 yr (Murawski and Cole 1978; Lawton et through April (NAl 1993), which corresponds to E al.1990). Adults enter estuaries in fall and winter the winter-spring spawning run. The annual E and spawn in spring after ascending brooks or geometric mean CPUE showed some evidence of streams to the head of tide. Fecundity ranges cyclical variation, with the operational period from approximately I to 73 thousand eggs per beginning during a decreasing trend and CPUE in female (Clayton 1976; Lawton et al. 1990). both 1992 and 1993 apparently corresponded to a Spawning in the Jones River, MA commenced period of low abundance (Figure 5-9). Catches when water temperature was about 4*C (Lawton et were greatest at station T2, off the mouth of al.1990). Most of the spawners in this river were Hampton-Scabrook Harbor, and were smaller, but age-2 and the abundance of this age-class relatively similar at Tl and T3. considerably affected spawning stock size. Based on larval production estimates, minimum egg The annual geometric mean CPUE for seine survivorship in the Jones River was 0.06% in sampling also showed some cyclical variation in 1980. Eggs range in size from 0.9-1.2 mm, and abundance (Figure 5-9). The largest annual seine attach to rocks, gravel, vegetation, or each other CPUE values occurred in 1979 and 1990,1 yr (Bigelow and Schroeder 1953). Larvac hatch at after cyclical pe,s ; were observed in trawl catches. about 5 mm in length and grow to about 63 mm As seine sampling occurs from April through by November (Scott and Scott 1988). Larvae November, these catches may have corresponded hatch at night (24-h periodicity) independent of to increased numbers of age 1 Osh resulting from water temperature or stream hydrodynamics and larger-than-average adult spawning stocks of the are carried down to estuaries, as no larvae are previous year. Most rainbow smelt were taken at retained on the spawning grounds (Ouelict and S3, although catches at all three stations in 1993 Dodson 1985a, b). In the St. Lawrence River, showed increases relative to 1991 and 1992. smelt larvac are mostly found in the maximum turbidity zone of that estuary (Laprise and The results from the ANOVA indicated that Dodson 1989; Dodson et al.1989), abundances were significantly greater during the g operational period in comparison to the g Stocks of rainbow smelt are localized to some preoperational period for both the trawl and seine extent, which would be important for impact data (Table 5-15). Given the longer time span of assessment. Although adults of three preoperational sampling and the several peaks of geographical groups of rainbow smelt in estuarine abundance that occurred during this period, this waters of Quebec did not home to specific was not unexpected. The ANOVA interaction spawning rivers (Frechet et al.1983), nor did fish terms for both trawl and seine catches were not among three different streams of the Parker River, significant, indicating that no power plant impact MA estuary (Murawski et al.1980), other isolating has occurred. Because of the behavior and mechanisms apparently limit gene flow. A specific life history of the rainbow smelt, no eggs probable means is the ability of larvae to retain and few larvac (about 3% frequency of occurrence 5-36 I u
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( 5 37
TABLE 5-15. RESULTS OF ANALYSIS OF VARIANCE FOR RAINBOW SMELT DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAMI SOURCE OF MULTIPLE COMPARISONS MONTIIS USED VARIATION df MS F OF ADJUSTED MEANS Trawl Preop-Op* 1 3.38 53.98 ** Op(Preop (Nov..May) Year (Preop-Op)b 16 0.50 7.92 " (1975-1993) Month (Year)* 104 0.18 2.88 " Station d 2 0.02 0.35 NS Preop-Op X Station
- 2 0.11 1.83 NS u Error 238 0.06 Seine Preop-Opf I 4.54 29.70 " Op<Preep
( Apr.-Nov.) Year (Preop-Op) 13 0.63 4.14 " (1976 1993) Month (Year) 105 0.92 6.05 " Station 2 0.04 0.26 NS Preop-Op X Station 2 0.17 1.08 NS Error 236 0.15
- Precpop compares Nov.1990-May 1993 to all previous months / years regardless of station. NS= Not significant (p>0.05) 6
- Year nested within preoperational and operational periods regardless of station. = Significant (0.052p>0.01)
- Month within year regardless of year, station or period. * * = liighly significant (ps0.01) d Stations regardless of year or period.
- Interaction of the two main effects. Preop-Op and Station.
f Preop-Op compares 1991-1993 to 1976-1989 regardless of station. m m m m m m M . m m m m m m 33
b i f L FISH f t m all offshore samples) have been collected in the 12 million eggs spawned per female (Powles ichthyoplankton sampling program. Annual 1958). Spawning can take place from late fall through spring, but typically peaks in late winter 4 entrainment estimates have been very low, with larvae collected only in 1990 and 1992, and early spring (O'Brien et al.1993). The 1.2-accounting for a total entrainment estimate of 1.6-mm diameter egg is pelagic. Newly-hatched about 3,000 larvac since the 'or, ginning of plant larvae are about 4-5 mm in length and growth j [ operation in 1990 (Table 5 'l;. A total of 159 over the first 9 mo averages about 0.21 mm d d rainbow smelt was impinge: during the last 4 yr (Bolz and Lough 1988). In well-mixed waters the (Appendix Table 5 2). Given that so few rainbow eggs and larvae are distributed throughout the smelt have been taken at Seabrook Station and water column (Lough and Potter 1993). liowever, that the abundance in trawl sampling showed when lengths reach 6 to 8 mm, larvae develop a similar pattems in annual CPUE at all stations, it is diel behavior. During the day, larvae are found very unlikely that this species is affected by predominantly near the bottom and at night from Seabrook Station operation. mid-depths to the surface in unstratified waters and at the thermocline in stratified waters (Perry and Nielsen 1988; Lough and Potter 1993). 5.3.3.3 Atlantic cod Vertical (Lough and Potter 1993) and horizontal (Suthers and Frank 1989) movements become less The Atlantic cod is found in the Northwest extensive with age and larger (> 20 mm) pelagic Atlantic Ocean from Greenland to Cape flatteras juveniles occur at greater depths than larvae. By and is one of the most important commercial and summer, juveniles 40 mm or larger make the recreational fishes of the United States. The transition from a pelagic to a demersal habitat. highly predatory, omnivorous cod can commonly This transition can occur over a relatively large achieve a length of 130 cm, a weight of up to 25- size range (40-100 mm) over a 12 mo period and 35 kg, and can live 20 yr or more. Ilowever, even demersal juveniles may move 3-5 m off the smaller (50 60 cm,1.1-2.3 kg, age-2-6) are more bottom at night (Lough and Potter 1993). typically caught by the fisheries (Bigelow and Schroeder 1953, Scott and Scott 1988; NFSC Spatial distribution also changes with age and { 1993). The Atlantic cod is a cool-water fish, and cod of ages 1-2, 3, and 4+ in Southern New is found and spawns at temperatures from about- England and on Georges Bank were reported by 1 to 10*C; distribution is also influenced by time Wigley and Serchuk (1992) to be distributed at of year, geographical location, and fish size (Jean different depths during spring. Seasonal 1964; Scott and Scott 1988; Branden and liurley distribution shifts are likely associated with water 1992). Many separate groups spawning at differ- temperature. Suthers and Frank (1989) noted that ent locations have been noted in the Northwest nearshore waters of Nova Scotia contained high Atlantic, but for management purposes two stocks densities of young cod and may serve as an (Gulf of Maine, and Georges Bank and South) are important nursery area for fish originating from recognized in U.S. waters (NFSC 1993). offshore spawning sites. Atlantic cod mature between ages 2 and 4, with The success of cod year-classes in the Northwest age and size of 50% maturity of 2.12.3 yr and Atlantic Ocean exhibit periodicities of 10 to 20 yr 32-36 cm for Gulf of Maine fish (O'Brien et al. and there was little evidence that the annual j reproductive output of adult spawners was 1993). Fecundity can be quite high, from 0.2 to 5-39
O O FISII I significantly related to year-class success (Koslaw considered overexploited (NFSC 1993). et al.1987). The periodicities observed may correspond to regional physical and biological Atlantic cod eggs in ichthyoplankn. - processes (Koslow 1984). Year-class success collections were grouped as Atlantic cod / haddock g tended to be statistically associated with large-scale because it was difficult to distinguish between 3 meteorclogical patterns. Campana et al. (1989) these two species; this aggregation also included also did not find evidence that cod year-class witch flounder eggs. These taxa have been strength we related to egg or larval abundance. dominant during late fall (Table 5-4; Figure 5-2). Ilowever, abundance of both pelagic and demersal Examination of larval data since July 1975 juveniles did appear to reflect year-class strength. indicated that the frequency of occurrence in Sources of mortality were not identified, but the samples (total of 3,681) of Atlantic cod was 858, monality between the larval and juvenile stages haddock was 56, and witch flounder was 668. was inversely correlated to year-class strength. Assuming a relatively similar hatching rate, it Timing of local physical and biological events would appear that Atlantic cod and witch flouader were thought to be important for recruitment eggs predominated in this egg group. success. Brander and liurley (1992) found that cod spawning during spring moved progressively Atlantic cod larvae typically exhibited a Inter from southwest to nonheast in Nova Scotia bimodal annual occurrence, with one peak from waters and matched peak abundance of the November through February and a second, larger (opepod Calanus finmarchicus. This may be peak from April through July (NAl 1993). To mnsistent with a " match-mismatch" hypothesis compare abundances among years and stations, (Ceshing 1984) for successful reproduction in only data from April through July were used, that cod spawning is coupled with copepod There was a decrease in larva' #nsities during the production, but definitive relationships remain to 1970s, but annual abundanm ' aave remained be demonstrated (Brander and llurley 1992). relatively stable and very similar at all stations from 1980 to the present (Figure 5-10). This Because of its long history of exploitation, decrease in abundance was evident in the fishing monality has also played a key role in comparison of preoperational and operational determining Atlantic cod abundance. Annual geometric means (Table 5-3), but the decline spon and commercial landings for the Gulf of occurred about 10 yr before plant operation. Maine averaged about 15,100 mt during 1972-82 and 13,100 mt for 1983-89, but rose to 18,700 mt At Seabrook Station, larger Atlantic cod were in 1990 and to a record 20,300 mt in 1991 (NFSC taken year-round by the trawl sampling program, 1993). Landings decreased 43% to 11,600 mt in but consistent with their annual movements, 1992, but commercial otter trawl effon remained catches were highest in spring and fall and lowest g at near-record high levels. The catch has been in summer (NAl 1993). Annual geometric mean E dominated by the strong 1987 year-class, which CPUE was nearly always greater at the two farfield accounted for about 55% of the 1992 landings. stations (panicularly T3) than at the nearfield Rtcruitment since 1988 has been average or below station T2 (Figure 5-10). This was attributed to average and spawning stock biomass is expected differences in habitat between T2 and the other to ecmain at record low levels. Because of stations (NAl 1993). Overall, cod abundance was declining stock biomass and continued high rates relatively stable from 1977-83 and then decreased. of fishing, the Gulf of Maine Atlantic cod stock is An increase in numbers followed until a peak was 5-40 I
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, trawl (number per 10-min tow) samples by station and the mean of all stations,1975-1993 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabmok Operational Report.1993.
5-41
Ol 0i FISil reached in 1988, perhaps due to the contribution juveniles. Thus, it is very likely that decreases in l of the strong 1987 year-class. Abundance then abundance and a possible change in local ) declined abruptly to very low levels, particularly in distribution are due to regional declines in Atlantic 1992. However, a large increase in abundance cod abundance and to a naturally-occurring occurred ia 1993, especially at T3, but abundance increase in temperature. These changes have no at T2 remained depressed. Bottom water relation to the operation of Seabrook Station. temperatures during the operational period were significantly higher than during the recent preoperational period at all stations, although 5.3.3.4 Pollock 1993 was generally cooler than 1992 or 1991 (se E Section 2.0 - Water Quality). Water temperature The pollock is one of the most pelagic of all the g may have affected inshore abundances, especially codfishes and is often found in large schools. It is if the temperature at the nearfield station, even if a cool-water species, preferring water temperatures not raised by station operation, was above the of 7.2-8.6*C and is not found in waters exceeding preferred range for Atlantic cod. 18.3*C (Scott and Scott 1988). Pollock may reach a length of 107 cm and a weight of 32 kg. Found An ANOVA applied to Atlantic cod trawl data from southwest Greenland to Cape Lookout, NC indicated that catch during the operational period (Bigelow and Schroeder 1953), it is most abundant was significantly less than during the on the Scotian Shelf and in the Gulf of Maine preoperational period, but for larvae the opposite (NFSC 1993). Adults move into the southwestern was true (Table 5-16). Given the reported Gulf of Maine in fall or early winter to spawn, decreases in the Gulf of Maine stock and which mostly occurs from November through continued low recruitment reported by NFSC February (Colton et al.1979). The median age (1993), this was not unexpected for the trawl data. and size of maturity for female pollock is 2 yr and g The significantly greater operational abundance 39.1 cm (O'Brien et al. 1993). Typical of g of larval cod was due to the restriction of data codfishes, the pollock is highly fecund with an from July 1986 through 1993 for the ANOVA, average production of 225 thousand eggs and with when all three stations were sampled; this short a 10.7-kg female capable of spawning over 4 series showed a slight increase in abundance only million eggs (Bigelow and Schroeder 1953). The during the operational period (Figure 5-10). The pelagic egg is 1.N-1.20 mm in diameter (Markle ANOVA interaction terms for both trawl and and Frost 1985) and newly-hatched larvae are 3-4 ichthyoplankton data were not significant, mm in length (Fahay 1983). First-year growth is indicating a similar pattem in annual abundance at rapid and young can often be very abundant all stations during both the preoperational and along Gulf of Maine coastal beaches (MacDonald operational periods. Only 109 Atlantic cod have et al.1984), rocky subtidal areas (Ojeda and been impinged at Seabrook Station since 1990
Dearbom 1990),
and apparently even use tide (Appendix Table 5-2). Egg and, in particular, pools as a nursery (Moring 1990). Young grow larval entrainment was relatively low (Tables 5-6 rapidly and by fall can achieve lengths of 215 mm and 5-7), given the high fecundity and source (Ojeda and Dearborn 1990) before they move population size of Atlantic cod in the Gulf of offshore for the winter. Maine. Furthermore, year-class success was 5 apparently related to large region-wide events 5 affecting survival of pelagic and demersal 5-42 I E
W W M M m m m m- m a m- g 5 TABLE 5-16. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC COD DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTilS USED VARIATION df MS F OF ADJUSTED MEANS Preop Op' 1 0.52 5.58
- Op> Preop Ichthyoplankton Yeer (Preop-Opf 5 0.53 5.72 "
(Apr.-Jul.) Month (Year)* 21 0.42 4.52 " (1987-1993) Stationd 2 0.15 1.67 NS Preop-Op X Station
- 2 0.01 0.10 NS Error 289 0.09 u
h w Preop-Opf 1 1.05 24.76 " Op< Preop Trawl Year (PreopOp) 16 0.52 12.34 " (Nov.. Jut.) 0.08 Month (Year) 140 1.95 " (1975-1993) 1.32 31.07 ** Station 2 Preop-Op X Station 2 <0.01 0.07 NS Error 308 0.04 NS = Not significant (p>0.05)
- Preop-Op compares 1991 1993 to 1987-1990 regardless of station. * = Significant (0.052p>0.01) 6 Year nested within preoperational and operational periods regardless of station.
- Month within year regardless of year, station or period.
** = Highly significant (ps0.01) d Stations regardless of year or period.
- Interaction of the two main effects, Preop-Op and Station.
r Preop-Op compares Nov.1990-May 1993 to all previous rnonths/ years regardless of station. _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ - - _ - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ - _ _ _ - - - - _ - _ - _ - - - - - __. X * -' n _ ______-
O O FISII Combined U.S. and Canadian landings for the occurred in 1993 relative to 1992 and 1991, Scotian Shelf. Gulf of Maine, and Georges Bank despite estimates of below-average year-classes regions increased from a yearly average of about produced in recent years. 38,200 mt in 1972-76 to 68,500 mt by 1986, with U.S. landings alone in 1986 of 24,500 mt (NFSC The ANOVA for gill net catch data showed no 1993). Recreational landings fluctuated between significant differences between preoperational and 100 and 1.300 mt. Based on NMFS trawl surveys, operational periods (Table 5-17). Ilowever, larval biomass of pollock in the Gulf of Maine and on abundance was significantly greater during the Georges Bank has decreased sharply during the preoperational period. The interaction terms for 1980s from a peak in the late 1970s and has both gill net and ichthyoplankton sampling were remained relatively low in recent years. During not significant, suggesting that plant operation has this period, the catch of pollock was dominated by not affected abundance. Relatively few eggs and several moderately strong year-classes that larvae were entrained (Table 5-7), but the pollock occurred every 3 to 4 yr, including those from ranked second among fishes impinged at 1975,1979, and 1982. More recently, the 1987 Scabrook Station from 1990-93, with a total of and 1988 year-classes appeared to be above the 456 fish (Appendix Table 5-2). Nevertheless, this long-term mean and accounted for about half the is a relatively small number for such a widespread landings in 1992. The 1989-91 year-classes, and abundant species. It is likely that the catch of however, are below average in abundance. The juvenile and adult pollock near Seabrook Station pollock stock is considered by NFSC (1993) to be reflects natural variability in annual abundance fully exploited. patterns of the Gulf of Maine stock. No changes in abundance or distribution can be attributed to Pollock eggs and larvac were collected in station operation. relatively low densities (Tables 5-4 and 5-5). Larval pollock abundance generally peaked during November through February (NAl 1993). 5.3.3.5 llakes 'Ihere was a decline in the geometric mean density between the pre perational and operational Three species of hake (genus Urophycis) are periods, with large annual fluctuations occurring found in the Gulf of Maine: the red hake, white during the preoperational period (Table 5-3; hake, and spotted hake. The spotted hake, Figure 5-11). Except for 1985, annual however, is apparently quite rare in this area abundances have been similar at all stations. (Bigelow and Schroeder 1953; Scott and Scott 1988) and is not important to the fisheries. For Pollock have been collected by gill net near these reasons,it will not be discussed below. Both Seabrook Station from spring through fall and the red and white hakes are common in the were generally absent in winter (NAI 1993). Northwestern Atlantic Ocean, particularly on Annual geometric mean CPUE varied sandy or muddy grounds off Northern New considerably from year to year, with no single England. They most commonly co-occur in the station pmducing consistently high or low catches Gulf of Maine (Musick 1974). Similar in (Figure 5-11). Fluctuations observed may have appearance and in many aspects of their biolooy, corresponded to the successive presence of fish other features differ considerably. Some of the from dominant and weak year-classes reponed by most distinguishing characteristics between these NFSC (1993). Ilowever, an increase in catch two species are in specific geographical 5-44 I 5
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TABLE 5-17. RESULTS OF ANALYSIS OF VARIANCE FOR POLLOCK DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTilS USED VARIATION df MS F OF ADJUSTED MEANS lehthyoplankton Preop Op* 1 5.61 38.55 " Op< Preop (Nov.-Feb.) Year (Preop-Op)b 6 2.09 14.35 " (1986-1993) Month (Year)* 20 0.91 6.27 " ! Stationd 2 0.40 2.76 NS Preop-Op X Station
- 2 <0.01 <0.01 NS u Error 295 0.15 Gill Net Preop-Opf 1 0.03 0.96 NS (Apr..Dec.) Year (Preop Op) 15 0.28 8.99 "
(1976 1993) Month (Year) 136 0.11 3.71 " Station 2 0.12 3.98
- Preop-Op X Station 2 0.08 2.74 NS Error 302 0.03
- Preop-Op compares 19901993 to 1986-1990 regardless of station. NS= Not significant (p>0.05) 6 Year nested within preoperational and operational periods regardless of station. *
= Significant (0.052p>0.01)
- Month within year regardless of year, station or period. * * = liighly significant (ps0.01) d Stations regardless of year or petiod.
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f Preop-Op compares 1991-1993 to 1976-1989 regardless ..f station. M m aB
I FISH I distribution and in size attained. The red hake is Many young red hake are inquiline and live within I found in more shallow waters of the inner continental shelf, predominantly in depths of 73 the mantle cavity of the sea scallop (Placopectin magellanicus) until they outgrow this commensal to 126 m (Musick 1974). It occurs in water host (Steiner et al. 1982; Garman 1983; I temperatures of 5 to 12*C, but apparently prefers a range of 8-10*C and avoids waters colder than Luczkovitch 1991). Other red hake, however, find shelter under shell or other bottom structures 4*C. In the Gulf of Maine, red hake are found (Steiner c' al.1982). I inshore for spawning, but disperse offshore following spawning. Except for young, most Commercial fishing landings of red hake in the white hake are typically found in deeper (200- Gulf of Maine and from the northern Georges 1,000 m) water than red hake and are considered Bank are currently very low (< 1,000 mt), with an to be inhabitants of the outer shelf and continental average of only 1,100 mt landed over the period slope. Temperature preferences (5-ll*C), of 1977-92 (NFSC 1993). The NMFS trawl however, are similar to that of the red hake. survey index showed an increasing trend in Current estimates of median size and age of abundance from the mid-1970s to a peak in 1990; maturity for females are 26.9 cm (1.8 yr) for red indices decreased in 1991 and 1992, but remained hake and 35.1 cm (1.4 yr) for white hake near the long-term average. Although year-classes (O'Brien et al.1993). Maximum size of the white produced since 1985 were termed moderate in I hake is 135 cm, much larger than the maximum of 50 cm for the red hake (NFSC 1993). strength. NFSC (1993) concluded that the red hake is underexploited and could sustain much higher catches. In contrast, although taken l I I The white hake is highly fecund with a 70-cm female producing 4 million eggs and a 90-cm fish primarily in non-directed fisheries, white hake landings in the Gulf of Maine (primarily from the about 15 million (Scott and Scott 1988). Most western portion) are currently high, being white hake spawning occurs in spring on the exceeded only by those for the Atlantic cod continental slope south of the Scotian Shelf and (NFSC 1993). Previous landings peaked at 7,500 l Georges Bank, and off Southern New England mt in 1984, declined to 5,500 mt in 1990, but l (Fahay and Able 1089; Comyns and Grant 1993). recently increased to an historic high of 9,600 mt Red hake spawn mostly during summer and fall in in 1992. NMFS trawl survey indices have mid-shelf areas. Eggs of both species are pelagic fluctuated considerably, but indications are that and are similar in size (range of 0.63-0.97 mm; abundance increased in 1991 and 1992. NFSC Fahay 1983; Markle and Frost 1985). Newly- (1993) concluded that, on the basis of the stability g of stock biomass since 1981, the white hake is E hatched larvae of both hakes are neustonic (liermes 1985) and even juveniles remain pelagic fully exploited and can sustain annual commercial for a considerable time, until 25-30 mm for the landings of about 6,500 mt. This species may be I red hake (Steiner and Olla 1985) and 50-80 mm for the white hake (Markle et al.1982). Growth overharvested if landings (such as those in 1992) begin to continually exceed this level. The d recreational landings of both hakes in the Gulf of I of young is rapid and can average about 1 mm d (Fahay and Able 1989). Larger juveniles of both species tend to be found closer to shore. White Maine are insignificant. l hake juveniles recmit inshore in June and July llake eggs collected in ichthyoplankton samples l (Fahay and Able 1989) and red hake from are difficult to distinguish from fourbeard l September to December (Steiner et al.1982). rockling eggs during early development and, 5-47
a E FISII therefore, at times were grouped as hake /fourbeard index for red hake has fluctuated considerably, E rockling. liake and hake /fourbeard rockling eggs but with an increasing trend (NFSC 1993). g were the predominant eggs collected during the Commercial landings have remained uniformly summer and early fall (Table 5-4). IIake larvae low throughout this period. White hake have g generally peaked during July through September fluctuated without a long-term trend, but recent E (NAI 1993). During the preoperational period, increases have occurred in both the trawl survey catch remained relatively stable; catch was more index and in landings. Some unknown factors l variable during station operation, with the largest may be reducing hake abundance in the um annual mean in 1990 and 1992 and 1993 among flampton-Scabrook area, but it is very unlikely the years of lowest abundance (Figure 5-12). that the operation of Seabrook Station has affected These low abundances in 1991-93 were apparent the hakes as the local decline began in the early in the comparison of preoperational and 1980s and occurred consistently at all stations. In operational geometric means (Table 5-3). addition, combining the catch of all hake species may have confounded these analyses. Ilake have been taken year-round in trawl sampling, but peak catches were made from June through October, with a sharp decrease occurring 5.3.3.6 Atbntic silverside in November (NAl 1993). Generally, catches at g the nearfield station T2 were smaller than at Tl or The Atlantic silverside is a small, short-lived E T3 (Figure 5-12). As for the Atlantic cod, the schooling fish that is ecologically important as a area near T2 may not be a preferred habitat for consumer of zooplankton and as prey for many hake. Geometric mean CPUEs were highest in larger fishes and birds (Bengston et al.1987). 1977,1978, and 1981. Since then, a general Found in bays, salt marshes, and estuaries from the decreasing trend has been observed with smaller Gulf of St. Lawrence to northern Florida, the Gulf peaks seen every 3 to 4 yr. CPUE for both 1992 of Maine is near the northern end of its range and 1993 were the two lowest of the time-series. (Conover 1992). Most Atlantic silverside complete their life cycle within 1 yr and, typically, The ANOVA detected significantly larger few older fish are found in the population, preoperational abundances than operational Spawning begins at about 9-12'C, which restricts it g abundances for both trawl and ichthyoplankton to spawning in May through July in nonhem areas g collections (Table 5-18). Ilowever, the interaction (Conover and Ross 1982; Jessop 1983; Conover tenn was not significant, suggesting there were no and Kynard 1984). Fecundity for a Massachusetts g plant operational cf fccts. Entramment estimates population ranged from 4,725 to 13,525 eggs per E for hake eggs and larvae during 1993 were among female (Conover 1979). These eggs may be the lowest since Seat) rook Station began operation, released during at least four separate periods of with the highest values occurring in 1990, the year ripening and spawning. Spawning occurs during when larvac were most abundant (Tab!c 5-7; daylight, coincides with dates of full and new Figure 5-12). Only 67 hake have been impinged moons and is apparently synchronized with tides at Seabmok Station since 1990 (Appendix Table (Conover and Kynard 1984). The adhesive eggs 5-2). Trends in abundance as measured by trawl are laid in shallow water on vegetation. Gender of CPUE at Seabrook Station apparently differ from Atlantic silverside is determined largely by water
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indices reported by NFSC (1993) for these temperature during larval development (Conover species Since 1976, the NFSC research trawl and Kynard 1981; Conover and Fleisher 1986). 5-48 5 is
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76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 YEAR I I Figure 512. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per 1000 m3) and trawl (number per 10-min tow) samples by station and the mean of all stations 1975-1993 (data between the two vertical dashed lines were excluded from the ANOVA model). Scabrook Operational Report.1993. ; I 5-49 I - _
TABLE 518. RESULTS OF ANALYSIS OF VARIANCE FOR II AKE' DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT, 1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTilS USED VARIATION df MS F OF ADJUSTED MEANS Ichthyoplankton Preop-Opb 1 2.29 6.83 " Op< Preop (Jul..Sep.) Year (Preop-Op)be 5 3.08 9.17 " (1986 1993) Month (Year)d 14 1.85 5.51 " Station' 2 0.27 0.81 NS Preop-Op X Station f 2 0.05 0.14 NS Error 227 0.34 Y 1.82
$ Trawl Preop-Ops Year (Preop Op) 1 16 0.13 47.80 "
3.3 6 *
- Op<Preep (Nov..Jul.)
(1975 1993) Month (Year) 140 0.20 5.13 ** Station 2 0.44 11.46 " Preop-Op X Station 2 0.07 1.74 NS Error 308 0.04
- Ilake = red, white, and spotted hakes. NS= Not significant (p>0.05)
- Preop-Op compares 1991-1993 to 19861989 regardless of station. = Significant (0.05.>.p>0.01)
' Year nested within preoperational and operational periods regardless of station. " = Highly significant (ps0.01) d Month within year regardless of year, station or period.
- Stations regardless of year or period.
t Interaction of the two main efrects. Preop-Op and Station. s Preop-Op compares Nov.1990.Jul.1993 to all previous months / years regardless of station. M M M M M M MM M M M e M M m mm m. 3 3
FISil i Ilowever, this mechanism may not be as imponant Atlantic silverside have been only numerous in I for northern populations because of the temporally reduced spawning season in more the seine sampling pmgram and were taken from August through November (NAI 1993). Most of northern waters (Conover 1992). Larvae are these fish were likely young-of-the-year. I planktonic, but remain near the spawning areas. Growth of young is fast and mean lengths can Geometric mean CPUE were highest from 1976 through 1981, whereupon catch decreased. Since exceed 90 mm by November (Conover 1979). As then, CPUE has fluctuated around a lower and more consistent average level to the present 4 the lower lethal temperature for Atlantic silverside is about 1-2*C (lioff and Westman 1966; Conover (Figure 5-13). Catch at each station tended to I and Murawski 1982), inshore distribution in northem areas is limited in winter. Atlantic silverside undertake an offshore migration in fol low similar patterns, although it varied somewhat more at S2 than at Sl or S3. No significant differences were found among stations winter to inner continental shelf waters, with most or for the interaction term (Table 5-19). The fish caught within 40 km of the shore and at operational period mean was significantly smaller depths less than 50 m (Conover and Murawski than the preoperational mean, likely because of 1982). It is during this period that high (up to the relatively high catches made in 1976-81. Only 99%) overwintering mortality typically occurs, 231 Atlantic silverside have been impinged since with apparently mostly fish larger than 80 mm Seabrook Station began operation (about two-I able to survive the winter (Conover and Ross 1982; Conover 1992). thirds of the total in December 1993; Appendix Table 5-2) and no eggs or larvae were entrained I SEINE 25 - , , SI I $ s 20- g 52 a \ /\ ; ;-- s3 I . at g 15 - \
\ .
!\
.l- \
{
- MEAN b 10-
\ -i/
\ PREoPERAUoNAL OPERATIONAL A. ; ; l
; \
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y l s-2
, ; j '
NoT S AMPLED ; , l 0 , , , , , , , , , , , , , , , , , , 76 77 78 79 80 81 82 83 84 85 h6 87 68 89 90 91 92 93 YEAR Figure 5-13. Annual geometric mean catch of Atlantic silserside per unit effort in seine (number per haul) samples 'I by station and the mean of all stations, 1976-1993 (data betw een the two vertical dashed lines were excluded from the ANOVA model). Scabrook Operational Report,1993. l 'I 5-51 i
TAllLE 519. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC SILVERSIDE DENSITIES BY SAMPLING PROGRAM. SEABROOK OPER ATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTIIS USED VARIATION df MS F OF ADJUSTED MEANS Seine Preop-Op' I 6.12 45.66 ** ON reop P u ( Apr.-Nov.) Year (Preop-Op)6 13 0.90 6.71 " t'n (1976-1993) Month (Year)e 105 1.40 10.45 "
" Stationd 2 0.10 0.75 NS Preop-Op X ',tation* 2 0.02 0.17 NS Error 236 0.13
- Preop-Op compares 1991-1993 to 19761489 regardless of staton. NS= Not significant (p>0.05) b
- Year nested within preoperational and operatsel penods regardless of station. = Significant (0.052p>0.01) c Month within year regardless of year, station or period. " = Highly significant (ps0.01) d Statens regardless of year or period.
- Interaction of the two main effects, Preop-Op and Station.
EM MM M M M M M ,M W MM M W. M MM M es
FISif I (Table 5 7). The discharge from the Seabrook within male territories, or aggregations of fish I Station settling basin no longer enters Hampton-Scabrook Harbor and, therefore, marine biota spawn together during late afternoon or early evening (Pottle and Green 1979). The reproduc-there should no longer be potentially affected by tive season lasts from M;y through September, I it. As few Atlar. tic silverside have been harmed by station operation to date and because the decline with peak spawning observed by Dew (1976) during June in Fishers Island Sound. Eggs are in seine CPUE occurred before plant start-up, it is pelagic and range from 0.75 to 1.03 mm in Is reasonable to assume that the continued operation of Scabrook Station will not have any deleterious diameter (Wheatland 1956); average size of eggs decreases over the season with increasing water effect on this species. temperature (Richards 1959; Williams 1967). I- Williams et al. (1973) reported that only about 5% of cunner eggs survived to hatching and specu-5.3.3.7 Cunner lated that predation, particularly by ctenophores, was responsible for the losses. Eggs hatch in 3 d The cunner, found from Newfoundland to at water temperatures of 12.8-18.3'C (Bigelow Chesapeake Bay (Scott and Scott 1988), is one of and Schroeder 1953). Newly-hatched larvae are 2 the most common fishes in the Gulf of Maine to 3 mm in length and settle into preferred (Bigelow and Schroeder 1953). A small fish habitats when 8 to 9 mm long. I residing in inshore waters, few cunner measure over 31 cm, although fish as large as 38 cm are Presently, cunner have no commercial value, I occasionally taken in deeper waters (Johansen 1925; Bigelow and Schroeder 1953). Most cunner are closely associated with structural although large quantities were apparently landed during the late 1800s and early 1900s (Bigelow and Schroeder 1953). Although the cunner is not g habitats, such as rocks, tidepools, shellfish beds, primarily sought after, numerous fish are caught su pilings, eclgrass, and macroalgae. Fish exhibit by recreational fishermen throughout New both diel and seasonal beh:vior in that they England. Because of its restricted inshore habitats remain under cover and become quiescent at night and the lack of landings data, no large-area, long-and torpid in winter (Olla et al. 1975, 1979). In term abundance indices are available for the fall, when water temperatures fall below about 8'C, cunner. cunner move into cover to overwinter (Green and Farwell 1971; Green 1975; Dew 1976; Olla et al. Cunner (ggs and larvac were dominant in the 1979). Although generally remaining within 2 m ichthyoplankton program (Tables 5-4 and 5-5). I of territorial shelters, some cunner will move to seasonally transitory habitats (e.g., mussel beds, Cunner eggs were grouped with yellowtail flounder (cunner /ycllowtail flounder). This group also included tautog eggs, although tautog adults i macroalgae) after emerging from winter shelter when spring water temperatures reach 5 or 6'C (Olla et al. 1975, 1979). were probably not abundant in the Hampton-Scabrook area, which is located near the northern I Conner reach maturity at small (70-90 mm) sizes and at age-1 or 2 depending upon latitude end of their distributional range (Bigelow and Schroeder 1953). Tautog larvae have only been present in about 3% of the ichthyoplankton and corresponding length of the growing season samples collected since July 1975. A compariton 'I (Johansen 1925; Dew 1976; Pottle and Green of cunner and yellowtail flounder larval 1979). Cunner are serial spawners; pairs spawn abundance indicated that most of the eggs in the 5-53
a FISil l cunner /yellowtail flounder group were cunner, yellowtail flounder egg group was 58.4 million. I assuming a relatively similar hatching rate between Annually, this group has ranked first or second the two species (Table 5-3). The annual since entrainment sampling was started in June abundance of cunner larvae has greatly fluctuated 1990 (Table 5-7). Larval entrainment since 1990 from year to year, but similar annual densitics has ranged from 0 to 14.7 million and the large occurred at all stations since sampling at all three difference between egg and larval entrainment stations began in July 1986 (Figure 5-14). This estimates can be attributed to the high mortality was substantiated by results from ANOVA, where during the egg stage (Williams et al.1973). Also, the nested year term was highly significant and the recent 24-h diel studies have indicated that most station main effect was not significant (Tab!c 5- of the egg mortality occurs shonly after spawning 20). In 1993, larval abundance increased greatly (NUSCO 1994a). ' relative to 1992, when abundance was at an all-time low (Figure 5-14). The 1993 geometric Relatively few cunner have been taken by otter g mean at all stations was larger than both the trawl, gill net, or seine. Most occurrences were 3, preoperational and operational means (Table 5-3). recorded from April through November, which The results of the ANOVA indicated that during likely corresponds to the period of greatest g the period when all three stations were sampled cunner activity in New Hampshire wates. Only W and cunner larvae were present, the operational 49 cunner were impinged at Seabrook Station abundance was significantly lower than abundance during 1990-93, despite the potential of the l during the preoperational period (Table 5-20). offshore intake structure to attract cunner 4 The 1993 entrainment estimate of the cunner / (Appendix Table 5-2). I ICHTHYOPLANKTON JUN-SEP 300 l l P2 P5 250 - e , ;, ;-- P7 2*~ -
- MEAN g ,
PREGPERATIONAL gOPERAT1oNAt. g ,3g _ [" '
/
\
/ , i !\
100 - j / l l
\
\
~
/ -
50 - ,
\
- ', l 3 I I I I I I I I I I I 4 I I I I I I 75 76 77 78 79 80 81 82 83 84 85 86 57 88 89 90 91 92 93 YEAR Figure 5-14 Annual geometric mean catch of cunner per unit effon in ichthyoplankton (number per 1000 m3) samples by station and the mean of all stations, 1975-1993 (data between the two vertical dashed lines were excluded l
y from the ANOVA model). Seabrook Operational Repon,1993. 5-54 I 5 E '
' 7 M M M .Q_ C 1
-l T ABLE S-20. RESULTS OF ANALYSIS OF VARIANCE FOR CUNNER DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT, 1993.
PROGRAM / SOURCE OF MULTIPLE COMPARISONS - MONTIIS USED VARIATION df MS F OF ADJUSTED MEANS i Ichthyoplankton Preop-Op' 1 12.36 19.85 " Op< Preop (Jun.-Sepl Year (Preop Op)b 4 15.03 24.14 " u* Month (Year)' 18 11.36 18.24 " tn (1987-1993)
" Stationd 2 0.27 - 0.44 NS I PreopOp X Station
- 2 0.11 0.17 NS Enor 260 0.62
- Preop-Op compares 1991-1993 to 1987-1989 regardless of station. NS= Not significant (p>0.05) 6 Year nested within preoperational and operational penods regardless of station. = Significant (0.052p>0.01)
- Month within year regardless of year, station or period. " = Highly significant (ps0.01) d Stations regardless of year or penod.
- Interaction of the two rnain effects, PreopOp and Station.
_m__.___________.__ _ m____ mm..._..__.A.._M__m _ _...____..m..m
. - _ _ _ _ . _ _ _ = - -
O FISII g 5.3.3.8 American und lance also lengthy, with metamorphosis occurring at I sizes of 29-35 mm in 131 d at 4*C and 102 d at E Both the American sand lance (Ammodytes 7'C (Smigielski et al.1984). This long period of 5 americanus) and the nonhern sand lance (A. development results in larvae being dispersed dublus) may be taken inshore in the Gulf of widely over continental shelf areas (Richards and Maine (Winters and Dalley 1988; Nizinski et al. Kendall 1973), even though most spawning 1990). However, the latter species is morc occurs inshore. common in deeper, offshore waters and all sand lance collected in Seabrook Station studies are American sand lance larvae was the dominant referred to as the American sand lance. This larval taxon collected in the ichthyoplankton species is found from Labrador to Chesapeake program (Tables 5-3 and 5-5). Their eggs have Bay (Richards 1982; Nizinski et al.1990) and in not been collected in ichthyoplankton samples the Gulf of Maine is usually found in depths of 6 because they are demersal and adhesive. Larvae g to 20 m (Meyer et al.1979). Found in schools generally occurred from December through June 5 ranging from hundreds to tens of thousands, sand or July, with peak abundances present during lances are an important trophic link between January through April (NAl 1993). Larval g zooplankton and larger fishes, birds, and marine abundances in the llampton-Seabrook area have 5 mammals (Reay 1970; Meyer et al. 1979; declined since the early 1980s (Figure 5-15) Overholtz and Nicolas 1979; Payne et al.1986; These declines were also apparent in other meas Gilman 1994). of the Nonhwest Atlantic Ocean. Larval densities in Long Island Sound over a 32-yr period (1951-Sand lance can live up to 9 yr, but populations 83) were highest in 1965-66 and 1978-79, with the latter years corresponding with a peak are dominated by the first three age groups (Reay 1970). American sand lance can mature at age-1 observed throughout the entire range of American at sizes of 90 to 115 mm (Richards 1982). sand lance (Monteleone et al.1987). Similarly, l Maximum size commonly observed is about 23- larval sand lance densities were very high in 24 cm (Meyer et al.1979; Richards 1982). An Niantic Bay, CT from 1977 through 1981, with l g l 18-cm female American sand lance is capable of present densities an order of magnitude lower g producing 23 thousand eggs (Westin et al.1979). (NUSCO 1994a). Nizinski et al. (1990) also Spawning occurs in inshore waters from reported a peak in sand lance abundance g l November through March with a peak in throughout the Nonhwest Atlantic in 1981, with 3 December and January. Sand lance are well- numbers declining since then. Sand lance adapted for winter spawning and embryonic abundance was noted to be inversely correlated development can occur in temperatures as low as with that of Atlantic herring and Atlantic mackerel i 2*C (Buckley et al.1984). Eggs are demersal and (Sherman et al.1981; Nizinski et al.1990). Sand adhesive, forming clumps, wnh sizes ranging from lance likely increased in abundance, replacing 0.67 to 1.03 mm (Williams et al.19M; Smigielski their herring and mackerel competitors, which had et al.1984). Embryonic development is lengthy, been reduced by overfishing in the 1970s resulting in a well-developed larva of about 6 mm (Sherman et al.1981). In more recent years, in length at hatching. Larvae have ample Atlantic mackerel, which can prey heavily upon endogenous energy reserves and can survive long sand lance (Monteleone et al.1997), have become g periods without food (Buckley et al. 1984: very abundant as sand lance abundance 5 Mon & leone et al.1986). Larval development is decreased. Another factor noted to affect sand 5-56 i 5 i.;
n h FISH ^ ICHTHYOPLANKTON JAN-APR sm. . ----- P2 700 - P5 ~ g g; [ '. { - - P7 h - MMN Sm- ! .' l
- i b "" /. .. PFtEOPERATloNAL g f OPERAUoNAL l ', '.',
3m. f., ,
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/ ;.
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Im- . - l ,~__ I6 I7 Is I9 do [1 d2 $3 [4 85 N6 [7 88 $9 N0 Il d2 d3 YEAR f Figure 5-15. Annualp)eometric 1000 m samples by station mean and the mean catch ofstations,1976-1993. of all American sand lance Seabrook per unit Operational effort in ichthyoptankton Report, 1 1993. lance reproduction and recruitment is water 1990 can be attributed to the start of sampling in temperature, as Monteleone et al. (1987) June, which was after their season of occurrence. suggested that warm December temperatures were However, the ANOVA interaction term was not associated with low larval densities. significant, indicating that operation of Seabrook Station did not affect the abundance of larval Larval sand lance abundance in 1993 was American sand lance in the Hampton-Seabrook similar to the average preoperational period, but area. was much lower than during the 1970s and early f 1980s (Table 5-3: Figure 5-15). Annual Very few American sand lance have been taken geometric means have remained relatively stable by Seabrook Station adult fish sampling j' since 1987. The results of the ANOVA indicated programs. A few fish were taken sporadically by i no significant difference between the otter trawl, mostly during January through March ! preoperational and operational periods, but a in 1978,1979, and 1981. Several hundred or significant difference was found among stations more sand lance were occasionally taken by seine, (Table 5-21). The differences detected among but most catches were small and occurred stations can be attributed to a consistently lower infrequently. Again, abundance was highest
' annual abundance at the control station P7 during during the late 1970s. Only 34 fish have been 1987-93. American sand lance larvae dominated impinged at Seabrook Station since 1990 entrainment collections during 1991-93 (Table 5- (Appendix Table 5-2).
7); their absence in entrainment samples during 5-57 i i
TABLE 5-21. RESULTS OF ANALYSIS OF VARIANCE FOR AMERICAN SAND LANCE DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTilS USED VARIATION df MS F OF ADJUSTED MEANS Ichthyoplankton Preop-Op' 1 0.04 0.08 NS w (Jan.- Apr.) Year (Preop-Op)b 5 0.91 1.67 NS
& (1987-1993) Month (Year)c 21 4.11 7.58 "
oo Stationd 2 2.40 4.43
- Preop-Op X Station' 2 0.48 0.89 NS Ermr 283 0.54
- Preop-Op compares 1991-1993 to 1987-1990 regardless of station. NS= Not significant (p>0.05) b Year nested within preoperational and operational periods regardless of station. *
= Significant (0.052p>0.01) e Month within year regardless of year, station or period. * * = liighly significant (ps0.01) d St:6ons regardless of year or perhxt.
- Interaction of the two main eff-cts, Preop-Op and Sta6on.
M M M MM M M M M' M M M M 'M M M M M SB
FISH i 5.3.3,9 Athnele mm kerel 1989; D' Amours and Gregoire 1991). The hatched larvae are 3 mm in length, grow rapidly, The Atlantic mackerel is a strongly schooling and develop a streamlined form early in life that fish found from Labrador to Cape Lookout. NC enables relatively high swimming speeds (Ware that prefers a temperature range of 9 to 12*C and Lamben 1985). Larvae are often canni-(Scott and Scott 1988). Maximum size recorded balistic, preying on smaller individuals from
- in recent years has been 47 cm and 1.3 kg (NFSC younger cohorts (Peterson and Ausubel 1984; 1993), but most fish average 32-36 cm (Scott and Ware and Lambert 1985). Young from both l
Scott 1988). The median size of maturity for spawning contingents reach an average size of l mackerel is about 26 cm, at approximately age-2 about 200 mm in late fall, even though their I (O'Brien et al.1993). Atlantic mackerel exhibit a growing seasons differ in length (Sette 1950; Ware distinct pattern of extensive annual movements; and Lambert 1985; D' Amours et al.1990). fish can migrate in excess of 2,200 km (Parsons and Moores 1974). Atlantic mackerel overwinter PresenQ, biomass of the Atlantic mackerel offshore along the edge of the continental shelf stock is very high (NFSC 1993). Although two I (Ware and Lambert 1985) and, in spring, move spawning contingents exist, the species is managed inshore with two separate spawning components as a single stock. Mackerel in the Gulf of Maine recognized (Sette 1950; Berrien 1978; Morse are primarily landed from May through 1980). One group spawns progressively north- November by both spon and commercial fisheries, ward from mid April through June in the Mid- Landings from the U.S. (about one-third of the Atlantic Bight and the other spawns in the Gulf of total) and Canada peaked at 400,000 mt in 1973 i St. Lawrence from late May to mid-August; peak and decreased to about 30,000 mt during the late spawning occurs at about 13'C (Ware and Lambert 1970s, as apparently weak year-classes were f( und I 1985). Ware (1977) and Lambert and Ware from 1975 through 1980. Catches tnen incrersed (1984) suggested that the Atlantic mackerel spawn- steadily to 82,700 mt in 1988, but declined again ing season is relatively short and coincides with to 38,300 mt in 1992; a very strong year class was peak copepod biomass. Spawning stock size prodcced in 1982 and relatively good ones in ( appears to exert little influence on recruitment, 1984 88. With current spawning stock biomass except at very low levels, and environmental fac- estimated to exceed 2 million mt, catches can be tors likely have a major effect on successful repro- increased substantially without affecting the duction (Anderson 1979). After spawning, the spawning stock (NFSC 1993). l southern contingent moves into coastal areas of the Gulf of Maine and the northem group remains Atlantic mackerel eggs were the second-most j in Canadian waters during summer and fall. abundant egg taxon collected in the ichthyo-t plankton program (Table 5-4). The larvae were { Female Atlantic mackerel are serial spawners very abundant in ichthyoplankton collections, but and release five to seven successive batches of were not dominant in entrainment samples (Tables l eggs; fecundity ranges from 285 thousand to 5-6 and 5-7). Larvae typically occurred from f almost 2 million eggs per female (Morse 1980). May through August (NAl 1993) and larval I The L1 to 1.3-mm eggs hatch in 5 to 7 d. Eggs abundance in 1993 was similar to the average are distributed near the surface, with 85% or more preoperational period (Table 5-3). Annual larval concentrated within the uppermost 15 m (Ware abundances fluctuated, with a peak at station P5 in and Lambert 1985; delafontaine and Gascon 1981 (Figure 5-16). Since all three stations were 5 59 i
M 5 ICHTHYOPLANKTOff I MAY-AUG 40 - ' '
..... P2 35 - P5 l 'l c PREOPERAT10NAL l ,' OPERAllONAL '
E 30 - -- P7 . . , h
- MEAN
- lh 25 -
f5 a l l>II' y 20 - l {,/ 5,
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q 0 , , , . , , , , , , , , , , . , , , . 75 76 77 78 79 60 81 82 83 84 15 86 87 88 89 90 91 92 93 YEAR GILL NET I 0.7 -
\ '
OI PREOPERATIONAL OPERATIONAL g 06-
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05- j\ ! ,'. l / MEAN j . . ' .
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l1 0.1 - .- - . j . , b b-I6 Y7 Y8 I9 N0 $1 I2 [3 d4 d5 N6 87 [8 [9 9O 9'1 9'2 9'3 YEAR I Figure 5-16. Annual geometric mean catch of Atlantic mackerel per unit effort in ichthyoplankton (number per 1000 m3) and gill net (number per 24 h set) samples by station and the mean of all stations. 1975-1993 (data between the two vertical dashed lines were excluded from the ANOVA model). Scabrook Operational Repor'. 1993. I: 1 5-60 I:I
*l i
HSH sampled (1986-93), similar densities wem found at the entrainment section, this may have been related all stations, except for 1991. The results from the to the rapid developmental rate of Atlantic ANOVA indicated no significant difference mackerel, which results in larger larvae that can among stations or between preoperational and svoid the intake. Atlantic mackerel biomass is operational periods; the interaction term was not currently very high and only an insignificant significant (Table 5-22). fraction of the egg production of this highly fecund fish is entrained at the plant, making an Atlantic mackerel juveniles and adults were impact highly improbable. collected by gill net in the Seabrook station area {. from June through November (NAI 1993). Annual geometric mean CPUE reflected trends 5.3.3.10 Winter nounder noted by NFSC (1993), with peak abundance observed in the reid-1970s that decreased by The winter flounder ranges from Lat rador to about two-thirds during the early 1980s (Figure 5- Georgia (Scott and Scott 1988), but is most 16). Beginning in 1988, an overall increasing common from Nova Scotia to New Jersey trend was found, but geometric means have (Perlmutter 1947). Maximum size of coastal fish - fluctuated sharply from year to year. Results of is about 45 cm and 1.4 kg (Bigelow and ( the ANOVA showed no difference in catch Schroeder 1953). Populations of winter flounder between the preoperational and operational are composed of reproductively isolated fish that periods, as mackerel are as abundant now as they spawn in specific estuaries or coastal embayments were in the 1970s (Table 5 22). The interaction (Lobell 1939; Perlmutter 1947; Saila 1961; term was significant, however, and a plot of the NUSCO 1994). North of Cape Cod, movements interaction term illustrated the differences in of winter flounder are generally localized and { alnmdance trends between G3 and that for stations confined to inshore waters (flowe and Coates G1 and G2 (Figure 5-17). A multiple comparison 1975). McCracken (1963) reported that winter test indicated that catch at the farfield station G3 flounder prefer temperatures of 12-15*C and, ( during the operational period was significantly except for spawning, will move to remain within greater than that of the other station-period that range. Ilowever, others (Kennedy and Steele combinations. Two relatively large catches of 1971; Van Guelpen and Davis 1979) noted that ( movements for feeding and to avoid turbulence Atlantic mackerel were made at G3 in October 1991 and September 1992, which, in part, could and ice also affect distribution of northerly have accounted for the significant differences populations and Olla et al. (1969) reportcd found. Despite the significant difference in the observing adult fish in waters as warm as 22.5'C. interaction term, it is highly unlikely that the Young-of-the-year are typically found in shallow operation of Seabrook Station affected the estuarine waters and can withstand temperatures of abundance or distribution of the Atlantic 30 to 32.4*C (Pearcy 1962; Everich and Gonzalez mackerel. Only 20 larger fish were impinged at 1977). Seabrook Station since 1990 (Appendix Table 5-2). Large numbers of eggs were entrained and Adults enter inshort spawning areas in fall or mackerel eggs ranked first or second in annual early winter and spawn in late winter or early entrainment estimates since 1990 (Table 5-7). spring. Winter flounder in the Gulf of Maine flowever, relatively few (0-4.7 million) larvae were mature at an average age of 3.4 yr and at a length entrained each year. As previously discussed in of 27.6 cm for males and 29.7 cm for females [ 5-61
~ - - - - - _ _____
TABLE 5-22. RESULTS OF ANALYSIS OF VARIANCE FOR ATLANTIC MACKEREL DENSITIES BY SANfPLING PROGRA31. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COSIPARISONS MONTIIS USED VARIATION df MS F OF ADJUSTED MEANS (Ranked in decreasing order) Ic hthyoplankton Preop-Op* 1 2.30 3.43 NS (May-Aug.) Year (Preop-Op)b 4 7.10 10.60 " (1987 1993) Month (Year)* 18 9.16 13.67 " Station d 2 0.08 0.12 NS Preop-Op X Station' 2 0.28 0.42 NS u Error 260 0.67 Gill Net Preop-Op* 1 <0.01 0.02 Ni (Jun.-Nov.) Year (Preop-Op) 15 0.24 10.15 " (1976 1993) Month (Year) 85 0.10 4.27 " Station 2 0.15 6.35 " Preop-Op X Station 2 0.10 4.12
- 3 Op 3 Pre 2 Pre 1 Pre 1 Oo 2 Dof Error 200 0.02
- Preop-Op compares 1991-1993 to 1987-1989 regardless of station. NS= Not significant (p>0.05) b Year nested within preoperational and operational periods regardless of station. *
= Significant (0.052p>0.01)
- Month within year regardless of year, station or period. "= Ifighly significant (ps0.01) d Stations regardless of year or period.
- Interaction of the two main effects, Preop-Op and Station.
t Underlining signifies no significant differences among least square means at p s 0.05. M M M MM M M M MW WM M M M M M M SR
r i FISH h [ i m
........... l
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--------s y n, . ;
. . . . . c3 7 ;G b 0.2 - .
re- PERIOD os_o Figure 5-17. A comparison among stations of the mean logio(x+1) CPUE (number per 24-h set) of Atlantic mackerel caught by gill net during the preoperational (June 1976-November 1989) and operational (June 1991-November 1993) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-22). Seabrook Operational Report,1993. (O'Brien et al.1993). Average fecundity is about flounder from the Gulf of Maine were relatively 500 thousand eggs per female (Bigelow and stable at around 1,000 mt per year from 1961 Schroeder 1953), with a maximum as much as 3.3 through 1977, but tripled to about 3,000 mt in million for a large fish (Topp 1968). Eggs (0.71- 1982. Recreational landings in some years 0.96~ mm) are adhesive and demersal (Fahay exceeded those of the commercial fishery (NFSC i 1983). Winter flounder embryos develop under a 1993). Since 1983, a downward trend was relatively wide range of temperature and salinity observed in landings with a record low of only conditions, with highest viable hatch reported at 900 mt taken in 1992. Bottom trawl survey data 3*C over a salinity range of 15 to 35% (Rogers from the Massachusetts Division of Marine 1976). Because winter flounder spawn during Fisheries spring survey also showed a declining periods of low water temperature, larval trend since 1983 (NFSC 1993). Lowest values development is relatively slow and can take up to were observed during 1988-92. Continued low 2 mo to complete. Larvae flushed out of estuarine landings and trawl catch indices were indications nursery areas are believed to have lowered that winter flounder in the Gulf of Maine have potential for survival and eventual recruitment to been overexploited (NFSC 1993) and the stock adult stocks (Pearcy 1962; Smith et al.1975; likely needs rebuilding before yields can be Crawford 1990). Overall mortality of larvae can sustained or increased. exceed 99% (Pearcy 1962). Young are common in inshore shallows, where they remain until fall, Larval winter flounder were collected in the undertaking little movement away from where ichthyoplankton program, but eggs were absent they settled (Saucerman and Deegan 1991). because they are demersal and adhesive (Table 5-4). Larvae typically occurred in the llampton-Based on numerous meristic and tagging Seabrook area during April through July (NAI studies conducted for assessment and management 1993). Larval winter flounder abundance has purposes, winter flounder have been divided into declined since the mid-1980s and this was three groups: Gulf of Maine, Southern New apparent at all three stations; larger annual England and Middle Atlantic, and Georges Bank geometric means were usually found at P2 than at (NFSC 1993). Commercial landings of winter P5 or P7 (Figure 5-18). This decline was 5-63
gm wi l ICHTHYOPLANKTON Il APRJUL 25 - ,
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PREOPERAT10NAL ' OPERATIONAL 0 , , , , , , , , , , , , , , , , , , , 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 YEAR TRAWL I ts. , , 16- TI { T2 I4
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NOT SAMPLED T T T 1 T T T T U T E U U T T 3 I E 76 77 7s 79 RO 31 82 83 84 e5 A6 87 Ss 89 90 91 92 93 YEAR Figure 5-18. Annual geometric mean catch of winter flounder per unit effort in ichthyoplankton (number per 1000 m3 ), trawl (number per 10-min tow), and seine (number per haul) samples by station ar.d the mean of all stations, - 1975-1993 (data between the two vertical dashed lines were excluded from the ANOVA model). Scabrook Operational Report.1993. s a
L ( risu L r' substantiated by the results of the ANOVA, which significantly less than that of the preoperational showed significant differences between the period (Table 5-23). The interaction term was preoperational and operational periods, in the also significant and the multiple comparisons test nested year term, and among stations (Table 5- and a plot of abundance by period (Figure 5-19) 23). Although there has been a decline in larval indicated that there was a significant decline of abundance, this was not related to plant operation winter flounder catch at station T2 between the because it occurred at all three stations and the preoperational and operational periods. interaction term in the ANOVA model was not significant. The lower abundance of larvae at Smaller winter flounder (juveniles through age-station P7 may be related to its location, which is 2; NAI 1993) were collected in the Hampton-not near the Hampton-Seabrook estua.y, the likely Seabrook Harbor by seine throughout the April-spawning area for local winter flounder. November sampling period Annual geometric mean CPUE was consistently higher at station S3, The winter flounder was taken year-roimd by located nearest to the moc'h of the estuary, and otter trawl at all stations, but occurred most generally lowest at S1, fa.thest inland (Figure 5-commonly from May through October (NAI 18). The annual pattern of abundance was 1993). Geometric mean CPUE peaked in 1980 somewhat similar to that of the trawl samples in y L and 1981, primarily because of high catches made that CPUE peaked in 1980 (1 yr earlier than for at the nearfield station T2 (Figure 5-18). Winter the catch by trawl) and thereafter decreased. flounder were considerably more abundant at T2 Abundance has remained at relatively consistent than at Tl or T3 until 1986, when annual mean levels since seine sampling resumed in July 1986. CPUE became more similar. CPUE at T3 was Results of the ANOVA for seine data indicated generally lowest of all these three stations during that, similar to trawl data, abundance during the the 1970s and 1980s, but catches have become preoperational period was significantly higher more similar to those at T1 and T2 since 1990. than during the operational period (Table 5-23). CPUE at T2 was the lowest of the three stations in This was not surprising, given the relatively high 1992 and 1993. This decrease may be related, in catches made during the 1970s and early 1980s part, to the inability since 1986 to sample at T2 on and the current depressed state of winter flounder many scheduled dates during August through stocks. The interaction term, however, was not October, months in which winter flounder are significant suggesting that Seabrook Station has most abundant. However, this does not account not affected the abundance or distribution of for decreased abundance observed in other juvenile winter flounder in the Hampton-Scabrook months, the deta for which are used with the estuary. ANOVA model. Annual entrainment estimates for 1990-93 Overall, geometric mean CPUE increased ranged from 2.9 to 9.0 million (Table 5-7). These slightly from a low in 1985 and remained totals, however, are much less than those of other generally stable from 1986 through 1991 (Figure large New England power plants. Annual larval 5-18). A decrease occurn'd in 1992, but catch in winter flounder entrainment at Pilgrim Nuclear 1993 was very similar to that in 1991. Data used Power Station in Massachusetts ranged from for the ANOVA were from November of one year almost 5 to 17.8 million during 1988-93 (MRI through July of the next. Trawl catch of winter 1994). Similarly, entrainment was much higher at flounder during the operational period was the three-unit Millstone Nuclear Power Station. 5-65
TABLE 5 23. RESULTS OF ANALYSIS OF VARIANCE FOR WINTER FLOUNDER DENSITIES IlY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTilS USED VARIATION df MS F OF ADJUSTED MEANS (Ranked in decreasing order) Ichthyoplankton Preop-Op' 1 2.93 8.61 " Op< Preop ( Apr..Jul.) Year (Preop-Op)b 5 0.84 2.47 * (1987-1993) Month (Year)c 21 4.16 12.25 " l Stationd 2 5.31 15.63 " l Preop-Op X Station
- 2 0.69 2.02 NS Error 289 0.34 Trawt Preop-Opf 1 0.39 9.95 " Op< Preop (Nov.-Jul.) Year (Preop-Op) 16 0.24 6.01 "
u (1975 1993) Month (Year) 140 0.09 2.35 " 4 Station 2 0.40 10.28 "
& Preop-Op X Station 2 0.57 14.52 " 2 Pre 1 Pre 10n 3 On 2 On 3 Pres Error 308 0.04 Seine Preop-Oph 1 1.28 9.54 " Op< Preop
( Apr.-Nov.) Year (Preop-Op) 13 0.25 1.85 * (1976 1993) Month (Year) 105 0.32 2.39 " Station 2 0.14 1.03 NS Preop-Op X Station 2 0.11 0.84 NS Error 236 0.13
- Preop-Op compares 1991-1993 to 19871990 regardless of station. NS= Not significant (p>0.05) b
- Year nested within preoperational and operational periods regardless of station. = Significant (0.052p>0.01)
- Month within year regardless of year, station or period. " = Ilighly significant (ps0.01) d Stations regardless of year or period.
I
- Interacton of the two main effects, Preop-Op arwi Station.
f Preop-Op compares Nov.1990.Jul.1993 to all previous months / years regardless of station. a Underlining signifies no significant differences among least square means at p 5 0.05. h Preop-Op compares 19911993 to 19761989 regardless of station. l l l M M M M M M M M M M M W M M M M M m en
k r' nsu L I-
- TI 0 .8 - ...
e & =g ..... ._ . . . . n
.g 0.6 - . . - - - - - - ~ ^^~*
......n 3J
~a ~ 0.4 -
k A 0.2 - 0 , , Preoperadmal operadmal PERIOD Figu c 5-19. A comparison among stations of the mean logiO(x+ 1) CPUE (number per 10-min tow) of winter flounder caught by trawl during the preoperational (November 1975 July 1990) and operational (November 1990-July 1993) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model(Table 5-23). Seabrook Operational Report,1993. annual totals for 1976-93 were from 31.2 to abundance at nearfield station T2 since 1991, 513.9 million larvac (NUSCO 1994b). Ilowever, however, is unexplained. Although perhaps larvae entrained at the offshore intake of beginning before plant operation, this change Seabrook Station were probably flushed from bears funher study to determine if Seabrook estuarine spawning areas. According to Pearcy Station has contributed to a distributional change (1962), Smith et al. (1975), and Crawford (1990), following the 1990 start-up. larvae not retained within estuaries have a lower probability of survival. 5.3.3.11 Yellowtail flounder Since 1990, more winter flourider (484) have been impinged at Seabrook Station than of any The yellowtail flounder is found from southern I other species (Appendix Table 5-2). However, Labrador to Chesapeake Bay (Scott and Scott this 4-yr total is considerable less than the number 1988), but its center of abundance is the western of winter flounder taken each year at several other Gulf of Maine and Southern New England New England power plants. During 1972-92, (Ligelow and Schroeder 1953). It commonly annual impingement of winter flounder at Brayton reaches a length of 47 cm and a weight of 1 kg Point Station in Massachusetts ranged from 859 to (NFSC 1993). Yellowtail flounder prefer coarser 23,452 individuals (mean of 7,925; MRI 1993a). sand and gravel bottom sediments than those Annual impingement totals from 1976 through preferred by other flounders of the Northwestern 1987 at Millstone Nuclear Power Station Unit 2 in Atlantic Ocean (Scott 1982b) and are found Connecticut were from 624 to 10,077 (annual mostly in depths of 37 to 91 m (Scott and Scott mean of 3,484; NUSCO 1988). 1988). Individuals apparently maintain generally similar depths between seasons while tolerating a Abundance of winter flounder throughout the wide range of temperatures and salinities (Scott Gulf of Maine has decreased in recent years to 1982a; Murawski and Finn 1988; Perry and Smith historic lows (NFSC 1993), likely due to 1994). Some limited seasonal movements, overfishing. This has been reflected by the however, do occur, with fish moving to shallower reductions in catch of winter flounder in Seabrook waters in spring and into deeper waters during fall Station monitoring studies. The persistently lower and early winter. 5-67
O FISif g Median age of maturity for female yellowtail group would also include tautog eggs, if present. I flounder is age-2, at a size of approximately 26 The cunner /ycIlowtail flounder taxon was the E cm (O'Brien et al.1993). Fecundity can range dominant eEg collected during both the 5 from 350 thousand to 4.57 million eggs per preoperational and operational periods (Table 5-female (Pitt 1971). Adulis spawn in the westem 4). Larvac were less abundant, probably because Gulf of Maine from March through September the egg group consisted primarily of cunner, as (Fahay 1983). Most spawning was observed by previously mentioned (Section 5.3.3.7). Smith et al. (1975) to occur at 4 to 9'C. Eggs Yellowtail flounder were not among the (0.8-0.9 mm in diameter) are deposited at or near predominant larval taxa selected for numerical the bottom, but are pelagic and hatch in 5 d at classification analysis (Table 5-5). The annual temperatures of 10-ll.l*C. Larvac are 2 to 3.5 geometric mean of yellowtail flounder larvac mm in length at hatching (Fahay 1983). Greatest during 1986-93, when all three stations were concentrations of pelagic larvae are found in water sampled, has remained relatively constant and the g ternperatures of 4.1-9.9'C (Smith et al.1975). annual densities were similar at all stations (Figure g Larvae exhibit pronounced dici vertical move- 5-20). In addition, the 1993 geometric mean was ments and are found near the surface at night and similar to those for both preoperational and g at depths of 20 m or so during the day, regardless operational periods (Table 5-3). This was W of thermal gradients (Smith et al.1978). Ascent substantiated by the results from the ANOVA, and descent occur at sunset and sunrise, where there was no significant difference detected respectively, with amplitude of movement between the preoperational and operational increasing with larval size. Larvae metamorphose periods or among stations (Table 5-24). In and become demersal at about 1I to 16 mm in addition, the interaction term was also not length (Fahay 1983), although fish as large as 20 significant, suggesting that the operation of t mm may still ascend to the surface (Smith et al. Scabrook Station has not altered the abundance of l 1978). yellowtail flounder larvae in the Hampton-l Seabrook area. Three discrete groups of yellowtail flounder are g managed in U.S. waters, including Southem New The yellowtail flounder is taken year-round in g
- England, Georges Bank, and Cape Cod (NFSC the Seabrook Station study area and in fomier i 1993). All of these stocks are considered to be years was one of the most abundant fishes taken g overexploited. Abundance was relatively high in by otter trawl sampling (Table 5-10). Recently, 3 the early 1980s, but subsequently declined due to however, it was most common only from May everfishing. After several years of low abundance, through October (NAl 1993). To a large degree, a relatively strong 1987 year-class produced annual mean CPUE by otter trawl (Figure 5-20)
I within all three stock areas resulted in an increase mirrored that of commercial landings reported by in commercial landings in 1990. Ilowever, the NFSC (1993). Trawl CPUE peaked in the early l increase was short-lived as the stocks were rapidly 1980s and subsequently decreased to a lower, but I fished down again and current abundance is at relatively stable level, until a slight increase was very low levels. seen in 1989, perhaps due to the relatively strong ! 1987 year-class. CPUE then steadily decreased to Yellowtail flounder eggs were grouped as near zero in 1992, before rebounding slightly in cunner /yellowtail flounder because it was difficult 1993. E 3 to distinguish between these two species, this 5-68 s l l
1 ( l ICHTlWOPLANKTON l' MAY-AUG 2 ( 4 Is - , , , , , g 16 - l, P5
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l l : MEAN 5 l - l l A 10 - - PREOPERADONAL l l OPERA 710NAL h m 8-l ', y -l . . o 6_ f l l
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I I I I i i I I I I I 3 B E E 5 I s I 75 76 77 78 79 50 81 82 83 84 85 86 87 88 89 90 91 92 93 YEAR TRAWL j 40 - . . 35 - ,- - ' '. -. l l Tl g ' l l T2 i g 30 - '. - . l l m ', . l '
, ; ;-- T3
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,' ' . . , l OPER ATION AL
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w .* y, N _._ ' v ', 5- . .l , , v. 0 . . , , . , i . . . , , . . . , , i 76 77 78 79 80 si' 82 83 84 85 86 87 88 89 90 91 92 93 YEAR l l l l 1 Figure 5-20. Annual geometric mean catch of yellowtail flounder per unit effort in ichthyoplankton (number per 1000 m3) and trawl (number per 10-min tow) samples by station and the mean of all stations.1975-1993 (data between the two vertical dashed lines were excluded from the ANOV A model). Seabrook Operational Report, 1993. 1 l 5-69 l 1
TABLE S-24. RESULTS OF ANALYSIS OF VARIANCE FOR YELLOWTAIL FLOUNDER DENSITIES BY SAMPLING PROGRAM. SEABROOK OPERATIONAL REPORT,1993. PROGRAM / SOURCE OF MULTIPLE COMPARISONS MONTIIS USED VARIATION df MS F OF ADJUSTED MEANS (Ranked in decreasing order) Ichthyoplankton Preop-Op' 1 0.01 0.G6 NS (May-Aug.) Year (Preop-Op)b 4 1.61 6.43 * * (1987-1993) Month (Year)c 18 2.11 8.46 " Stationd 2 0.12 0.50 NS Preop Op X Station
- 2 0.16 0.65 NS Error 260 0.25 Y
13.66 227.91 " Op(Preop
$ Trawl Preop-Opf Year (Preop-Op) 1 16 0.63 10.43 a (Nov.-Jul.)
(1975-1993) Month (Year) 140 0.06 1.01 NS Station 2 5.45 90.98 " Preop-Op X Station 2 0.29 4.83 *
- 1 Pre 3 Pre 1 On 2 Pre 3 Op 2 Op8 Ermr 308 0.06
- Preop-Op compares 1991-1993 to 1987-1989 regardless of station. NS= Not significant (p>0.05) 6 Year nested within preoperational and operational periods regardless of station. = Significant (0.052p>0.01)
- Month within year regr-dless of year. station or period. " = lii hly E significant (ps0.01) d Stations regardless of year or period.
- Interaction of the two main effects. Preop-Op and Station.
I Preop-Op compares Nov.1990-Jul.1993 to all previous months / years regardless of station. Underlining signifies no significant differences among least square means at p 5 0.05. M M M M M M M M M M M M M M M M M SB
FISH 1.4 - T1 1.2 - j d ., e, . ~.. . . . . n "g j - 0.6 -
*- ....**** ......,. " * ~ . . . . . * ' . . . .
''* -. "*- U g o.4 -
" o.2-Preopchanal opera 6 anal PERIOD
( Figure 5-21. A comparison among stations of the mean loglo(x+1) CPUE (number per 10-min tow) of yellowtail flounder caught by trawl during the preoperational (November 19754uly 1990) and operational (November 19904uly 1993) periods for the significant interaction term (Prcop-Op X Station) of the ANOVA model(Table 5-24). Seabrcx* Operational Report,1993. Catches have been consistently highest at flounder has been severely reduced in abundance farfield station T1 and lowest at nearfield station by overfishing throughout its range, and catch T2 throughout the 18-yr period; CPUE at T3 near Seabrook Station has simply reflected this tended to approximate the overall mean. This decline. Increased abundance and stock pattern of abundance may reflect habitat rebuilding will require a substantial reduction in preferences of the yellowtail flounder in the fishing and several years of improved recruitment flampton-Scabrook study area. The CPUE during (NFSC 1993). the operational period was significantly smaller than during the preoperational period (Table 5-24). Ilowever, this was likely due to the overall 5.4 EFFECTS OF SEABROOK decrease in abundance for this species since the STATION OPERATION early 1980s that resulted from overfishing. The interaction tenn was also significant, but a plot of The fish community in the Hampton-Scabrook the data showed that mans for each station by area was sampled to determine if the operation of period were essentially parallel (Figure 5-21). Scabrook Station has had any discernible effects . I This indicated that the significant difference may on fish abundance or distribution. Fatential have been due to large sample size and the impacts of station operation included the l sensitivity of the ANOVA model, as no plant entrainment of fish eggs and larvae and j effect was evident. Only 11 yellowtail flounder impingement of juvenile and adult fish at the plant i have been impinged at Seabrook Station since intake; entrainment of fish eggs and larvae into 1990 (Appendix Table 5-2). The cunner / and avoidance by larger fish of the offshore j yellowtail flounder group has been consistently discharge thermal plume; and effects of the ; ranked first or second among egg taxa entrained discharge of the plant settling basin into the ; at Seabrook Station, with annual totals ranging Browns River within the llampton-Scabrook ! from 58.4 to 716.3 million (Table 5-7). Ilowever, estuary. Monitoring programs were established it is likely that this group is comprised mostly of that used sampling gear appropriate for several cunner, as relatively few yellowtail flounder larvac specific fish assemblages. Samples were period-(overall and relative to cunner) have been ically taken at fixed stations in nearlicld and identified in entrainment samples. The yellowtail farfield areas relative to the station intake and 5-71
a FISif $ discharge for various periods prior to commence- panicular. In nearly all cases where differences I ment of Seabrook Station commercial operation were found, the abundance during the operational in August 1990 and continuously since then. The period was signincantly lower than during the impacts of impingement and entrainment were preoperational period. However, in many directly estimated from samples taken at the instances, the declines began in the early to mid-station when it operated. 1980s, well before Seabrook Station began operation. Several of the decreases seen in the Assessment of impact was based on an ANOVA Hampton-Seabrook area simply reflect long-term model, primarily used to examine for differences declining trends of overexploited commercial in abundance of selected fishes between the Hshes, including the Atlantic cod, winter nounder, preoperational and operational periods and for the and yellowtail flounder. Decreases in these and consistency of any observed differences between other important New England groundfishes, such these periods among the fixed stations (i.e., the as haddock, have resulted in large increases in g Preop-Op X Station interaction). Data were biomass of skates and spiny dognsh. Increase of 5 selected for the ANOVA taking into account the the latter was also renected by increased catches temporal distribution of a species, its occurrence by gill net near Seabrook sta:!on in recent years, relative to the August 1990 startup, and samples Larger CPUE of both Atlantic cod and pollock missing as a result of temporary cessation of were noted in 1993, 'chich perhaps is a positive monitoring or the inability to sample a station at sign for future increases in the area. Regional certain times of the year. Possible changes in abundance or M:h red and white hakes is now seasonal ichthyoplankton assemblages were also increasing, kt trawl survey indices reported by examined using multivariate analyses. In general. NFSC (1993) show erratic changes, likely due to the species selected for analyses are abundant in varying year-class strength from year to year. A the Gulf of Maine and are important to the trophic longer time-series of operational data at Seabrook g dynamics of this marine ecosystem. Most of these Station may be needed in some cases to discern 3 fishes also have commercial and recreational current abundance trends in the study area. importance for the region. Because fishing can g signincantly alter the abundance, distribution, and For pelagic Gshes, even though abundance of 5 population dynamics of heavily exploited fishes. Atlantic herring is presently increasing in the trends in landings and present status of fishing Nonhwest Atlantic Ocean, panicularly on Georges stocks of these species were also examined to put Bank, CPUE in the Hampton-Scabrook area has into perspective any changes seen in the Seabrook remained essentially stable since the early 1980s, area. Finally, comparisons of entrainment and after decreasing from a relatively high peak in the impingement were made between Seabrook late 1970s. It is unknown why abundance has not Station and those at other large marine power increased funher in the study area, although it plants in New England to illustrate the relatively may be related to aspects of Atlantic herring stock benign impact of Seabrook Station as a result of structure and recruitment in the Gulf of Maine. its intake design and placement. For the past 2 yr, abundance of the Atlantic 5 mackerel has increased near Seabrook Station, as it g As summarized in Table 5-25, a number of has throughout the Northwest Atlantic, but differences were found between the preoperational additional years of operational data may be E and operational periods for Osh assemblages in needed to demonstrate a significant change in 5 general, and for most of the selected species in abundance. 5-72 I 5 wii
4 y t TABLE 5-25. -
SUMMARY
OF PorENTIAL DTEClli OFTHE OPERAT10N OF SEABROOK frrATION ON THE
. ICH1HYOPLANKTON ASSEMBLAGES AND SELFLTED FISH TAKA. SEASROOK OPERATIONAL REPORT,1993.
PREOPERATIONA!/ OPERATIONAL PERIOD ' OPERATIONAL SIMILAR TO DIITERENCES RECENT ABUNDANCE SAMPLING PREOPERATIONAL CONSISTE.VT AMONG TREND IN THE CULF STA1US OF PROGRAM PCRIOD?* STATIONS?" OF MAINE' F1SHERY' SPECIES Fish egg assemblages ichshyoplankton seasonal occurrence Op=Preap yes abundance vanable among taxa ~ yes Fish larvae assemblages ichihyoplankton seasonal occunence Op= Preop yes abundance variable among taxa yes underexploited Atlantic hernng ichthyoplankton OpcPreop yes increasing gill net OpcPreop yes trawl OpcPreop yes unknown hghtly to Rainbow unelt seine Op< Preop yes unexpidsed ichthyoplankton Op> Preop yes decreasing overemploited Atlantic cod trawl Op< Preop yes ichthyoplankton OpcPreop yes stable fully expid:ed d Pollock gill net Op= Preop ye: ichthyoplankton OpcPreop yes red hake: increasing underexploited llakes ~ trawl OpcPreop yes white hake: increasing fully expidted Atlantic sdverside seine OpcPreop yes unknown unexploited Cunner ichthyoplankton Op< Preop ye: unknown unexpidted American sand lance ichthyoplankton Op= Preop yes decreasing in 1980s unempisted now stable (7)
~
' Atlantic mackerel ichthyoplankion Op= Preap yes increasing underesploited gill net Op= Preop no Winter flounder ichthyoplankton Op< Preop yes decreasing overexploited trawl OpcPreop no seine Op<Preep yes Yellowtail flounder ichthyoplankton Op= Preop yes decreasing overesploited trswl Op< Preop no
- Based on results of numerical clanification for assemblages and ANOVA for selected taxa.
- Based on Preop-Op X Stataan interaction term from the MANOVA for assemblages and ANOVA for selected taxa.
' For commercial species, from NFSC (1993).
5-73 {
- r. - -
O O FISII I Two estuarine-dependent fishes, the rainbow offshore intakes has worked as expected in smelt and the Atlantic silverside, also had reducing these impacts. In fact, most of the significant differences in CPUE, with impingement that does occur is not of pelagic fish, preoperational geometric means exceeding those but demersal fish that predominantly encounter g for the operational period. These small, short- the intake during storm events. Numbers g lived species appear to exhibit variable and, impinged were not only low relative to other perhaps, periodic patterns of annual abundance. regional power plants, but also insignificant when g It is unlikely that Seabrook Station would have compared to commercial and recreational W significantly affected these species, given their landings, or even to losses from sampling gear in mode of reproduction and concentration in the study area (NAl 1993). Impingement totals estuaries distant from the plant intake and for each affected species are so low that they cooling-water discharge. Relatively few specimens would not be expected to measurably reduce have been entrained or impinged. Any hypoth- popu.'ation size or affect reproductive capacity of esized effects due to the settling basin discharge local Oshes and the American lobster. into the Browns River will no longer be applicable, as this discharge has been re-routed through the In conclusion, other than a possible circulating water system in April 1994, distributional change for winter flounder, little impact to fishes can be attributed to Seabrook For three species (Atlantic mackerel, gill net; Station operation. Most of the selected species are winter flounder, trawl; yellowtail flounder, trawl), from very large and highly fecund stocks the ANOVA interaction term was significant, spawning throughout the Gulf of Maine. Others, E which suggested a potential effect of Seabrook such as the rainbow smelt, Atlantic silverside, and 3 Station operation. For Atlantic mackerel, the winter flounder, spawn in estuaries away from the greatest difference was an increase in catch at the plant intake and have egg or larval life stages that farfield station G3 during the operational period, are largely maintained in inshore areas. The which was unlikely a result of plant operation. Atlantic cod, winter flounder, and yellowtail Yellowtail flounder, once much more common in flounder continue to be overexploited by trawl catches and with abundance now depressed commercial fisheries and their stocks are presently by overfishing, appears to have decreased declining. Other fishes, such as Atlantic mackerel, similarly at all stations. Winter flounder showed a were overfished and now have recovered. Catch of lower abundance at the nearlicld station T2 than at all the selected species in the Hampton-Seabrook the two farfield stations. The reasons for this are area simply reflect long-term, regional trends. g unknown, but could be related to natural changes Furthermore, the influence of regional environ- g in the local environmental or physical conditions, mental factors and interspecific interactions (e.g., which might not persist very long. Ilowever, it is American sand lance-Atlantic mackerel) I also possible that this distributional change may introduces complexities in any evaluation. E be related, in pan, to station operation and this Because of the relatively small numbers of fish of may bear further scrutiny over the next few years. all life stages directly removed by the plant r,1d the concurTent changes in abundance at both near-Compared to other New England marine power and farfield stations in nearly every instance, the plants, Scaorook Station entrains relatively few operation of Seabrook Station does not appear to fish eggs or larvae and impinges very few juvenile have affected the balanced indigenous populations and adult fish. The location and design of the of fish in the llampton-Seabrook area. , 5-74 I i B a
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Ammodytes americanus from the St. Lawrence River to Chesapeake Bay, 1972-75, including a Scott, J.S.1982a. Depth, temperature and salinity comparison of the Long Island Sound preferences of common fishes of the Scotian postlarvae with Ammodytes dubius. J. Northw. Shelf. J. Northw. Atl. Fish. Sci. 3: 29-40. Atl. Fish. Sci. 3: 93-104. 1982b. Selection of bottom type by
, and A. W. Kendall. 1973. Distri- groundfishes of the Scotian Shelf. Can.J.
bution of sand lance, Ammodytes sp., larvae on Fish. Aquat. Sci. 39: 943-947. the continental shelf from Cape Cod to Cape llatteras from RV Dolphin surveys in 1966. Scott, W.B., and E.J. Crossman. 1973. Freshwater Fish. Bull., U.S. 71: 371-386. lishes of Canada. Bull. Fish. Res. Board. Can. 184. 966 pp. ! Robins, C.R., R.M. Bailey, C.E. Bond, J.R. l Brooker, E.A. Lachner, R.N. Lea, and W.B. and M.G. Scott. 1988. Atlantic i Scott. 1991. A list of common and scientific fishes of Canada. Can. Bull. Fish. Aquat. Sci. names of fishes from the United States and 219. 731 pp. Canada. 5th ed. Am. Fish. Soc. Spec. Pub. No. 20. 183 pp. Sette, O.E. 1950. Biology of the Atlantic .j mackerel (Scomber scombrus) of North Rogers, C.A. 1976. Effects of temperature and America. Pan II - migrations and habits. U.S. salinity on the survival of winter flounder Fish. Wildl. Serv. Fish. Bull. 51: 251-358. embryos. Fish. Bull., U.S. 74: 52-58. Shaw, R.G., and T. Mitchell-Olds. 1993. ANOVA Rosenberg, A. A., and R.W. Doyle. 1986. for unbalanced data: an overview. Ecology 74: Analysing the effect of age structure on stock- 1638-1645. recruitment relationships in herring (Clupea harengus). Can. J. Fish. Aquat. Sci. 43: 674- Sherman, K., C. Jones, L. Sullivan, W. Smith, P. 679. Berrien, and L. Ejsymont. 1981. Congruent shifts in sand cet abundance in westem and Safford, S.E., and 11. Booke. 1992. Lack of castern North Atlantic ecosystems. Nature biochemical genetic and morphometric (London) 291: 486-489. evidence for discrete stocks of northwest Atlantic herring Clupea harengus harengus. Sinclair, M., and T.D. Iles.1985. Atlantic herring j Fish. Bull., U.S. 90: 203-210. (Clupea harengus) distributions in the Gulf of Maine-Scotian Shelf area in relation to Saila, S.B. 1961. A study of winter flounder oceanographic features. Can. J. Fish. Aquat. movements. Limnol. Oceanogr. 6:292-298. Sci. 42:880-887. l 5-83 l \ _ _ _________ -
O O FISII I and M.J. Tremblay. 1984. Timing chuss. Mar. Ecol. Prog. Ser. 7: 125-135. of spawning of Atlantic herring (Clupea harengus harengus) populations and match- - and B. Olla. 1985. Behavorial mismatch theory. Can. J. Fish. Aquat. Sci. 41: responses of prejuvenile red hake, Urophycis g 1055-1065. chuss, to experimental thermoclines. Envir. g Biol. Fish. 14: 167 173. Smigielski, A.S., T.A. lialavik, L.J. Buckley, S.M. E Drew, and G.C. Laurence. 1984. Spawning, Stephenson, R.L., and I. Kornfield. 1990. E embryo development and growth of the R(appearance of spawning Atlantic herring Amerim sand lance Ammodytes americar.us (Clupea harengus harengus) on Georges in the laboratory. Mar. Ecol. Prog. Ser.14: B mk: population resurgence not recolo-287-292. nization. Can. J. Fish. Aquat. Sci. 47: 1060-1(64. Smith, W. G., and W. W. Morse. 1993. Larval distribution patterns: carly signals for the Stewan-Oaten A., W.W. Murdoch, and K.E. collapsc/ recovery of Atlantic herring Clupea Parker. 1986. Environmental impact harengus in the Georges Bank area. Fish. assessment: "psuedoreplication" in time? Bull., U.S 91: 338-347. Ecology 67: 929-940. Smith, W.G., J.D. Sibunka, and A. Wells. 1975. Suthers, I.M., and K.T. Frank. 1989. Inter-annual Seasonal distributions of larval flatfishes distributions of larval and pelagic juvenile cod g (Pleuronectifcrmes) on the continental shelf (Gadus morhua) in southwestern Nova Scotia g between Cape Cod, Massachusetts and Cape detennined with two different gear types. Can. Lookout, North Carolina, 1965-1966. NOAA J. Fish. Aquat. Sci. 46: 591-602. 5 Tech. Rep. NMFS SSRF-691. 68 pp. 5 Thomas, D.L., and G.J. Miller. 1976.
. 1978. Diel movements of larval Impingen:ent at Oyster Creek Generating yellowtail flounder, Limanda ferruginea, Station, Forked River, New Jersey, from determined from discrete depth sampling. September to December 1975. Pages 317-341 Fish. Bull., U.S. 76: 167-177. in L.D. Jensen, ed. Third national workshop ,
on entrainmer.t and impingement. Ecological Sneath, P.ll.A., and R.R. Sokal. 1973. Numerical Analysts, Melville, NY. taxonomy. The principles and practice of numerical classification. W.ll. Freeman Co., Thornas, J.M. 1977. Factors to consider in San Francisco. 573 pp. monitoring programs suggested by statistical g analysis of available data. Pages 243-255 in 3 Sokal, R.R., and F.J. Rohlf. 1969. Biometry. W. Van Winkle, ed. Proceedings .he W.II. Freeman and Company, San Francisco. conference on assessing the effects of power-775 pp. plant-induced mortality on fish populations, Gatlinburg, TN, May 3-6, 1977. Pergamon Steiner, W.W., J.J. Luczkovich, and B.L. Olla. Press, New York. 1 1982. Activity, shelter usage, growth and recruitment of juvenile red hake Urophycis Topp, R.W. 1968. An estimate of fecundity of Il 5-84 5 , 1
I I FISH the winter flounder, Pseudopleuronactes ameri- Southern New England region. Fish. Bull., I canus. 1302. J. Fish. Res. Board Can. 25: 1299- U.S. 90: 599-606. Wilks, S.S. 1932. Certain generalizations in the I Townsend, D.W. 1992. Ecology of larval herring in relation to the oceanography of the Gulf of analysis of variance. Biometrika 24: 471-494. Williams, G.C. 1967. Identification and seasonal I Maine. J. Plankton Res. 14: 467-493. Van Guelpen, L., and C.C. Davis. 1979. Seasonal size changes of eggs of the labrid fishes, Tautogolabrus adspersus and Tautoga onitis, movements of the winter flounder, Pseudo- of Long Island Sound. Copeia 1967: 452-pleuronectes americanus, in two contrasting 453. inshore locations in Newfoundland. Trans. S.W. Richards, and E.G. Farnworth. Am. Fish. Soc. 108: 26-37. 1964, Eggs of Ammodytes hexapterus from Ware, D.M.1977. Spawning time and egg size of Long Island, New York. Copeia 1964: 242-Atlantic mackerel, Scomber scombrus, in 243. relation to the plankton. J. Fish. Res. Board Can. 34: 2308-2315.
. D.C. Williams, and R.J. Miller. 1973.
I . and T. C. Lambert. 1985. Early life Mortality rates of planktonic eggs of the cunner, Tautogolabrus adspersus (Walbaum), ) history of Atlantic mackerel (Scomber in Long Island Sound. Pages 181-195 in A. I scombrus) in the southern Gulf of St. Lawrence. Can. J. Fish. Aquat. Sci. 42: 577-Pacheco, ed. Proceedings of a workshop on egg, larval and juvenile stages of fish in g Atlantic coast estuaries. Nat. Mar. Fish. Serv., I 592. Westin, D.T., K.J. Abemethy, l.E. Meller, and B.A. Mid. Atl Coast. Fish. Ctr. Tech. Pub. No.1. Rogers. 1979. Some aspects of biology of the Winters, G.H., and E.L. Dalley. 1988. Meristic American sand lance, Ammodytes americanus. composition of sand lance (Ammodytes spp.)in Trans. Am. Fish. Soc. 108: 328-331. Newfoundland waters with a review of species designations in the Northwest Atlantic. Can. J. Wheatland, S.B. 1956. Oceanography of Long Fish. Aquat. Sci. 45: 515-529. island Sound. 1952-1954.11. Pelagic fish eggs I and larvae. Bull. Bingham Oceanogr. Coll.15: 234-314. Wheeler, J.P., and G.ll. Winters. 1984. Iloming of Atlantic herring in Newfoundland waters as I indicated by tagging data. Can. J. Fish. Aquat. Sci 41: 108-117. Wigley, S.E., and F.M. Serchuk. 1992. Spatial and temporal distribution of juvenile Atlantic cod Gadus morhua in the Georges Bank-5-85 I
O, rm , LJ APPENDIX TABLE 51. FINFISH SPECIES COMPOSITION BY LIFE STAGE AND GEAR, JULY 1975 - DECEMBER 1993. SEABROOK OPERATIONAL REPORT,1993. ICIITilYOPLANKTON ADULT AND JUVENILE TOWS FINFISil SCIENTIFIC COMMON GILL NAME* NAME' EGGS LARVAE TRAWLS NETS SEINES Acircaser osyrhynchus Atlantic sturgeon Rb Alosa aestivalis blueback herring -- R C C Alosa mediocris hickory shad - R w Alosa pseudoharengus alewile - O O O Alosa sapidissima American shad -- R O O g Alosa spp. river herring Ammodytes americanas American saruf lance R A O R O 5 Anarhichas lupus Atlantic wolifish R Anchoa hepsetus striped anchovy R l Anguilla rostrata Apeltes quadracar American eel fourspine stickleback C R R g' Archosargus probatocephalus sheepshead R Aspidophoroides monopterygius alligatorfish C 0 l Brevoortia tyrannus Atlantic menhaden O O R O R E Brosme brosme cusk O O Carans hippos crevalle jack R Centropristis striata black sea bass R R Conger oceanicns conger eel R Cly>ra harengus Atlantic herring C O A O Cryptacanthodes maculatus wrymoutn O R Cyclopterus luny >us lumpfish C R R R Enchelyopus cimbrius fouthcard rockling C C O Fundulus spp.' killifish C Atlantic cod C C O Gadur morhaa Gadus /Melanogrammus Atlantic cod / haddock C -- -- -- R l 3 Gasterosteus spp.d stick!cback R R C Glyptocephalus cynoglossus witch flounder C C 0 flemitripterus americanus ses raven O C O R liippoglossoides platessoide.r American plaice C C O liippoglossus hippoglossus Atlantic halibut R Labridac/Pleuronectes cunner /yellowtail flounder
- A -- -- -- ~
Liparis atlanticar Atlantic seasnail R C -- -- Liparis coheni gulf snailfish C -- -- -- Liparis spp.' snailfish R -- O Lophius ameritanus goose fish R O O R Lumpenas lumpresarformis snakeblenny 0 R l g Lumpenar maculatus daubed shanny R R Macrozoarces americanus ocean sn>ut O C R Melanogrammus aeglefinus hnddock -- O C R Menidia menidia Atlantic silverside R O R A Menticirrhus saxatilis northern kingfish R Merluccius bilinearis silver hake C C C C R (continued) I 5-86 I 5
t ! APPENDIX TABLE 51. (Continued) ICHTHYOPLANKTON ADULT AND JUVENILE { TOWS FINFISH SCIENTIFIC COMMON GILL NAME' NAME' EGGS LARVAE TRAWLS NETS SEINES h Microgadas somcod Atlantic tomcod R R O ( white perch R L Morone americana striped bass R R Morone saxatitis Mugil cephalus striped millet R smooth dogfish R (. Mustelus canis Myosocephalus aenaeus grubby C O R O b Myosocephalus octodecemspinosus longhorn sculpin C A O R Myoxocephalus scorpius shorthorn sculpin C O R R Odontaspis taurus sand tiger R Oncorhynchus kisurch coho salmon R R Oncorhynchus mykiss rainhow trout R Osmerus mordax rainbow smelt O C O C Paralickshys dentata surnmer flounder R R Paralichthys oblorgus fourspot flounder R O C R Peprilus triacanthus butterfish O O R O R Petromyton marinus sea lamprey R Pholis gunnellar rock gunnel C O R R Pleuronxses americanus winter ik>under C C 0 C Pleuronecsesferruginess yelloweni1 flounder - C A R R Pleuronectes putnami smooth flounder R R C f Pollachius virens pollock C C C C O bluefish O O Pomatomus saltatris Prionotus carolinus northern senrobin - - O R ( n Prionotus evolans striped senrobin - - R \ Prionotus spp. senrobin O R - -- .- Pungitius pungitius ninespine stickleback C Raja spp.8 skate C R Salmo trutta brown trout O brook trout R Salvelinus fonsinalis Scomber japonicus chub mackerel R Scomber scombras Atlantic mackerel A A R C R Scophskalmus aquosus windowpsne C C C R O Jebasses spp.h redfish O Sykorroides maculatus northern putfer R R Squale acanthias spiny dogfish R C Stenotomus chrysops scup R O R Stichaeus punctatus Arctic shnnny O northern pipefish C O R P Syngnathus fuscus Tautoga onitis tautog - C R Tauscgolabens adspersus cunner - A O O R Torpedo nobiliana Atlantic torpedo R Triglops murrayi moustache sculpin O R rndisted shanny C O Ulvaria subbfurcata Urophycis spp) hake A C A O C Footnotes: See nest page. l 5-87 l
O O APPENDIX TAllLE 51. (Continued) Footnotes:
- Names are according to Robins et al. (1991). Taxa usually identified to a different level are twit included in this list to avoid duplication (e g., Gadidae, EnchelyopusIUrophycis, Myosocephalus sp Urophycis chass) b Occurrence of each species is indicated by its relative abundance or frequency of occurrence for each life stage or gear type:
A = abundant (21% of total catch over all years) C = common (occurring in 21% of samples but <lM of total catch) l 3 s O = occasional (occurring in <lM and 21% of samples) R = rare (occurring in <!% of sampics)
-- = not usually identified to this taxonomic level at this life stage
- Predominantly fundulus Arteroclitis, mummichog. but may include a small number of fundulas majalis, striped killifish.
d Two species of Casterostrus have been identified from seine samples: G. aculcatus, threespine stickleback; and G. whcarlandi, blackspotted stickitback (both occurring commonly).
- May also inc'ude 5 nall number of tautog as well as cunner.
f Three species of Liparis have been identified from trawl samples: L. atlanticus, Atlantic seasnail; L coheni, gulf snailfish; and L. inquilinus inquiline snailfish. 8 Four species of Raja have been identified from trawl samples: R. radiata, thorny skate (common); R. trmacra, little skate (common); R. ocellata, winter skate (occasional); and R. rglanteria, clearnose skate (rare). h Srbstries norvrgicus (previously called S. marinus), golden redfish; S. mentella, deepwater redfish; and S.fasciatas. Acadian redfish, have been reported to occur in the northwcw Atlantic. Srbastes in coastal New Hampshire waters are probably S. farciatus (Dr. Ilruce H. Collette. U.S. National Museum, pers. comm. April 1982) but larval descriptions are insufficient to allow distinction anumg the three species. 8 Three species of Urophyris have been identified from trawl samples: U. chuss, red hake (cc,mmon); U. tenuis, white hake (common); and U. regia, spotted hake (rare). I I I I I 5-88 I
J (I L: APPENDIX ; TABLE 5 2. SPECIES COMPOSITION, ANNUAL TOTALS, AND 4-yr TOTAL OF FINFISH AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION FROM 1990 THROUGH 1993, SEABROOK OPERATIONAL REPORT,1993. (t ) SPECIES 1998 1998 1992 1993 TOTAL ! p . Wsuer flounder 18 116 209 14I 484
~
Pollock 69 124 231 32 456
. Windowpane 52 150 96 102 400 Lumpfish 69 93 -29 118 309 fonghorn sculpin 67 54 88 37 246 Searaven 38 42 55 98 233 Atlantic silverside 8 67 156 231 Rainbow smelt 12 67 80 159 Grubby 11 26 54 67 158 Atlantic cod I8 28 26 37 109 102 Little skate 6 96 Shorthorn sculpin 4 47 17 28 96 Herrings 44 8 22 19 93 .; Northern pipefish 6 2 83 91 Rock gunnel 14 11 40 25 90 Skates 48 35 83 Hakes 16 33 15. 3 67
[ Cunner Wrymouth 21 5 2 15 13 16 13 12 49 48 American lobster 4 29 8 1 42 Flounders 7 32 39 28 3 34 (_. ' American sand lance Tautog 3 3 9 9 3 24 Scarobins 10 12 1 1 24 17 23 Threespine stickleback 3 3 3 6 13 22 j f Snailfishes ( Silver hake 22 22 Atlantic mackerel 4 13 3 20 .. Sea lamprey 1 5 3 6 15 I 6 9 15 ( Clearnose skate Unidentified fish 4 4 5 13 Yellow ail flounder iI i1 Sculpins 1 7 8 Fourspot flounder 2 2 1 1 6 [- Ocean pout 1 2 3 6 American eel 1 1 3 5 Radiated shanny 4 1 5 Spiny dogfish 1 2 1 4 Smooth flourwier 3 3 Summer flounder 3 3 Rough scad ' 3 3 Red hake 1 2 3
' Butterfish 2 2 Alewife 1 1 2 Cusk 1 1 2 Wolffish 1 1
[. White perch 1 I American plaice 1 1 Conger eel 1 1 Striped anchovy i 1 Oyster tondfish i I Goosefish 1 1 Scq l 1 Black sea bass 1 I Northern kingfish 1 1 ALL SPECIES 503 1019 1174 1174 3870 5-89
n LJ U' APPENDIX TABLE 5 3. SPECIES COMPOSITION AND CUMULATIVE MONTHLY TOTALS OF FINFISH g AND AMERICAN LOBSTER IMPINGED AT SEABROOK STATION FROM 1990 g THROUGH 1993. SEABROOK OPERATIONAL REPORT,1993. SPECIES JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL l Wmter flounder 51 24 55 31 6 5 21 52 11 228 484 5 Pollock 3 4 2 21 117 26 28 54 52 149 456 Windowpane 19 15 14 44 88 13 2 5 27 32 141 400 Lumprish 11 18 47 49 43 86 34 5 2 2 13 43 14 309 78 246 l 3 Longhorn sculpin 11 3 17 42 21 8 3 5 Sca raven 2 3 8 36 60 26 6 7 3 19 21 42 233 Atlantic silverside 6 5 2 4 2 2 3 207 231 127 159 Rainbow smelt 8 13 2 4 2 1 1 1 6 77 158 l m Grubby 16 14 25 7 4 2 1 1 5 Atlantic cod 1 5 13 16 7 7 3 4 11 8 34 109 Little skate 21 2 7 6 1 7 40 10 8 102 Shorthorn sculpin 6 9 11 14 9 12 20 15 3 1 6 2 1 11 16 7 20 22 96 93 l m Herrings 1 1 2 Northern pipefish 1 2 1 6 81 91 Rock gunnel 4 2 5 20 20 3 3 3 4 3 2 21 90 Skates 12 1 4 1 8 1 8 16 4 8 60 23 83 67 l g Hakes 2 1 1 Cunner 1 2 4 19 14 1 4 1 1 2 49 Wrymouth 9 1 2 1 2 8 1 24 48 American lobster 1 4 1 1 1 5 20 9 42 Flounders 1 3 13 22 39 American sand larice 1 1 1 3 1 27 34 Tautog 1 8 9 1 1 1 1 1 1 24 Scarobins 1 2 5 3 4 8 6 24 23 l g Threespine stickleback 2 7 8 Silver hake 2 11 9 22 Snailfishes 1 9 3 2 1 6 22 Atlantic mackerel 6 5 8 1 20 Clearnose skate 1 4 8 1 1 15 Sea lamprey 4 10 1 15 Unidentified fish 4 1 3 5 13 Yellowtmil flounder 4 6 1 11 8 l g Sculpins 5 2 1 Fourspot flounder 1 2 2 1 6 Ocean pout 3 2 1 6 American eel 3 1 4 5 5 l g Radiated shanny 1 1 Spiny dogfish 2 2 4 Rd hde 1 1 1 3 Rough scad 2 1 3 Smooth flounder 3 3 Summer flounder 3 3 Alewife 1 1 2 Butterfish 2 2 l Cusk 1 I 2 3 l American plaice 1 1 1 1 Black sea bass Conger eel 1 1 Goosefish 1 1 Northern kingfish 1 1 Oyster tondfish 1 1 Scup 1 1 Striped anchovy 1 1 White perch 1 I Wolffish 1 1 ALL SPI'CIES 195 138 250 377 357 326 87 41 105 301 270 1423 3870 I l 5-90 f I
=
l
I l I TABLE OF CONTENTS PAGE 6.0 MARINE MACROBENTHOS
SUMMARY
. . . . . . . . 6-iii I LIST OF FIGURES LIST OF TABLES ,
LIST OF APPENDIX TABLES
. . 6-iv
. 6-v
. . 6-viii I
6.1 INTRODUCTION
. . .. . .... . . . 6-1 6.2 METHODS . .. . . . . . . 62 6.2.1 Field Methods . . . . . .. . . . 6-2 6.2.2 Laboratory Methods . . 6-4 6.2.3 Analytical Methods . . . . .. 6-4 6.2.3.1 Community Methods . 6-4 6.2.3.1 Selected Species . . 6-7 6.3 RESULTS AND DISCUSSION . . . . . . . 6-7 1
6.3.1 Marine Macroalgae 6-7 I 6.3.1.1 Horizontal Ledge Communities 6-7 l 'I 6.3.1.2 Selected Species . . . . . 6 26 i 6.3.2 Marine Macrofauna .. .. . 6-26 l i 6.3.2.1 Horizontal Ledge Communities . . . 6-26 6.3.2.2 Selected Species . . . 6-45
6.4 CONCLUSION
S 6 57 I 6.4.1 Introduction . 6 57 j 6.4.2 Evaluation of Potential Thermal Plume Effects on Intertidal / Shallow
'I Subtidal Benthic Communities 6-58 l
l 6.4.2.1 Background 6-58 6-i I
Ol O PAGE 6.4.2.2 Intenidal Benthic Community . . . ... .. .. . 6-58 6.4.2.3 Shallow Subtidal Benthic Community . . ... 6-60 6.4.3 Evaluation of Potential Turbidity Efrects on Mid-Depth / Deep Benthic Communities 6-61 6.4.3.1 Background .. . .. . 6-61 6.4.3.2 Mid-Depth Benthic Community 6.4.3.3 6-61 g' Deep Benthic Community . . 6-63 3 6.4.4 Overall EfTect of Seabrook Operation on the Local Marine Macrobenthos 6-63
6.5 REFERENCES
CITED . 6-64 I I-I I I I I: 6-u I a
I I
SUMMARY
Submerged rock surfaces in the vicinity of Seabrook Station intake and discharge structures support rich and I diverse communities of attached plants and animals (macrobenthos). An extensive monitoring program was implemented in 1978 to assess the potential population and community level efTects of Seabrook Station operation on this habitat. Studies were designed to monitor two types of potential impacts; those associated with exposure to elevated water temperatures from the discharge thermal plume, most likely afTecting intertidal and shallow subtidal communities, and those associated with increased turbidity and sedimentation from I transport of suspended solids and entrained organisms to deeper water communities near the discharge. Thermal impacts, such as shifts in abundance or occurrence of typically cold-water or warm water species (i e., decreases or increases, respectively), were not evident at nearfield intertidal or shallow subtidal sites. Overall, ccmmunity parameters (biomass, number of taxa, etc.) and analyses of community structure (numerical classification) indicated little change in nearfield intertidal or shallow subtidal communities. Of the selected taxa studied in these zones, only two (the amphipod Ampithoc rubricata and the kelp Laminaria digitata) exhibited significant shifts (decreases) specifically in the nearfield area. In both cases, these trends began in recent preoperational years and their continuation was attributed to natural cycles in environmental or climatic processes rather than to plant operation. Impacts associated with increased turbidity, such as shifts in community dominance to species tolerant ofincreases in shading, sedimentation rates, and organic loading were not evident at mid-depth or deep stations in the nearfield area. Analyses of community parameters and overall structure revealed remarkable consistency of nearfield and farfield communities in both depth zones over both preoperational and operational periods, reflecting the more stable natural environmental conditions characteristic of deeper benthic habitats. This stability was also exhibited by abundance patterns of selected dominant taxa. Only two of the six taxa showed significant changes in abundance during the operational period relative to preoperational abundances; a significant decrease in abundance of the amphipod Pontagencia incrmis was detected, but only at the farfield station, and a significant increase in mussel (Mytilidae) abundance was noted at the nearfield station, with no difference at the farfield station. None of the above-mentioned shifts represents a change beyond what would be expected from the inherent natural variability of balanced indigenous
- g communities, and no evidence exists to suggest that thermal or turbidity-related impacts have occurred to local 5 macrobenthic communities since Seabrook Station began operation in 1990.
I t I I I 6-iii
O E I L!ST OF FIGURES PAGE 6 1. Marine benthic sampling stat ons . ... . . .. .. . 6-3 6-2. Preoperational (through 19P)) median and range, and 1991-1993 values of number of taxa collected in triannual general algae collections at Stations B1MSL, BIMLW, B 17, B 19, B31(1978-1993, B5M S L, B5 MLW, B35 (1982-1993), and annual (August only) collections at Stations marked with ***,i.e., B16 (1980-1984; 1986-1993), Bl3, B04 (19781984; 1986-1993) and B34 (1979-1984; 1986-1993) . . 6-8 6 3. Comparisons among stations of mean total macroalgal biomass during the preoperational (19781989) and operational (1991-1993) periods for depth zones with a significant interaction term (Preop-Op X Station) of the ANOVA model (Table 6-3) ... . .. 6-14
- 64. Dendrogram and station groups formed by numerical classification of August collections of marine benthic algae, 1978-1993 . . . . .. . 6-15 6 5. Comparisons between stations of mean number of macrofaunal taxa during the preoperational (1978-1989) and operational (1990-1993) periods for depth zones with a significant interaction term (Preop-Op X Station) of the ANOVA model (Table 611) . .. .. . 6-31 6 6. Comparisor among stations of mean total macrofaunal density (logiox+1) during the preoperational (1978 1989) and operational (1990-1993) periods for depth zones with a significant interaction term (Preop-Op X Station) of the ANOVA model (Table 6-11) 6-33 6 7. Dendrogram and station groups formed by numerical classification of August collections of marine macrofauna, 1978-1993 . 6-35 6-8. Comparisons between stations of mean density (logi,x+1) of selected macrofaunal taxa during the preoperational (1978-1989) and operational (1991-1993) periods for g depth zones with a significant interaction term (Preop-Op X Station)of the ANOVA g model (Table 6-16) . . 6-50 I
6-iv
$i e i
LIST OF TABLES I PAGE ! 6-1. SELECTED BENTHIC TAXA AND PARAMETERS USED IN ANOVA OR WILCOXON'S SUMMED RANK TEST .. . .. ... . . 6-5 6-2. ARITHMETIC MEANS AND ASSOCIATED VARIABILITY (CV)FOR NUMBER OF ALGAL TAXA, TOTAL ALGAL BIOMASS, AND CHONDRUS CRISPUS I BIOMASS AT VARIOUS DEPTHS AND STATIONS DURING 1993 AND DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS 6-10 6 3. ANALYSIS OF VARIANCE RESULTS FOR NUMBER OF TAXA (per '/,, m2 ) AND TOTAL BIOMASS (g per m 2) OF MACROALGAE COLLECTED IN AUGUST AT INTERTIDAL, SHALLOW SUBTIDAL, AND DEEP STATIONS, . 1978-1993 . . 6-11 I 6-4.
SUMMARY
OF SPATIAL ASSOCIATIONS IDENTIFIED FROM NUMERICAL CLASSIFICATION (19781993) OF BENTHIC MACROALGAL SAMPLES COLLECTED IN AUGUST . . . . . . 6-16 r 6-5. A COMPARISON OF PERCENT FREQUENCY OF OCCURRENCE OF RARELY FOUND (OVERALL FREQUENCY OF OCCURRENCE <4%) SPECIES IN AUGUST DESTRUCTIVE SAMPLING DURING PREOPERATIONAL (1978-1989), OPERATIONAL (1990-1993), AND OVERALL (1978-1993) PERIODS OF SAMPLING . . . . . 6-18 6-6, PREOPERATIONAL AND OPERATIONAL MEANS, AND 95% CONFIDENCE LIMITS, AND 1993 MEANS, AND RESULTS OF WILCOXON'S SUMMED 2 RANKS TEST COMPARING DENSITIES OF FOUR KELP SPECIES (#/100 m ) AND PERCENT FREQUENCIES OF THREE UNDERSTORY TAXA BETWEEN OPERATIONAL AND PREOPERATIONAL PERIODS 6-20 6-7. PERCENT COVER AND PERCENT FREQUENCY OF DOMINANT PERENNIAL AND ANNUAL MACROALGAL SPECIES OCCURRENCE AT FIXED INTERTIDAL NON-DESTRUCTIVE SITES DURING THE PREOPERATIONAL I AND OPERATIONAL PERIOD . 6-22 6-v I
E O PAGE 6 8. PREOPERATIONAL AND OPERATIONAL MEANS WITH 95% CONFIDENCE LIMITS, AND 1993 MEANS, AND RESULTS OF WILCOXON'S SUMMED RANKS TEST COMPARING PERCENT FREQUENCIES OF FUCOID ALGAE AT TWO FIXED TRANSECT SITES IN TliE MEAN SEA LEVEL ZONE BETWEEN PREOPERATIONAL AND OPERATIONAL PERIODS . .. .. . 6 25 6-9. ANALYSIS OF VARIANCE RESULTS OF CHONDRUS CRISPUS BIOMASS (g/m') AT INTERTIDAL AND SHALLOW SUBTIDAL STATION PAIRS FOR TiiE PREOPERATIONAL (1978-1989) AND OPERATIONAL (19911993) PERIODS . ... . . . . . . . . ... 6 27 6 10. PREOPERATIONAL AND OPERATIONAL MEANS (WITli COEFFICIENTS OF VARIABILITY) AND 1993 MEANS OF Tile NUMBER OF TAXA AND GEOMETRIC MEAN DENSITY FOR TOTAL DENSITY (NON-COLONIAL MACROFAUNA) SAMPLED IN AUGUST AT INTERTIDAL, SilALLOW SUBTIDAL, MID-DEPTil AND DEEP STATIONS . ... . .. 6-28 6-11. ANALYSIS OF VARIANCE RESULTS OF NUMBER OF TAXA (per 0.0625 m') AND TOTAL DENSITY (per m') OF MACROFAUNA COLLECTED IN AUGUST AT INTERTIDAL, S11 ALLOW, MID-DEPTil, AND DEEP STATIONS,1978-1993 . . . .. . . . .. 6-29 6 12. STATION GROUPS FORMED BY CLUSTER ANALYSIS WITil PREOPERATIONAL AND OPERATIONAL (1990-1993) GEOMETRIC MEAN DENSITY AND 95% CONFIDENCE LIMITS (LOWER, LCL AND UPPER, UCL) OF ABUNDANT MACROFAUNAL TAXA (NON COLONIAL) COLLECTED ANNUALLY FROM 1978-1993 . . . 6-36 6-13. MEDIAN PERCENT FREQUENCY OF OCCURRENCE BY SEASON AND OVER ALL SEASONS OF Tile DOMINANT FAUNA WITil!N PERMANENT 0.25 m' QUADRATS AT TliE UPPER (BARE ROCK), MID-(FUCOID ZONE), AND LOWER (CHONDRUS ZONE) INTERTIDAL ZONES AT NEARFIELD (OUTER SUNK ROCKS) AND FARFIELD (RYE LEDGE) DURING Tile PREOPERATIONAL AND OPERATIONAL PERIODS, AND MEAN PERCENT FREQUENCY OF OCCURRENCE DURING 1993 6-39 6 14. ESTIMATED DENSITY (per 0.25 m2 ) OF SELECTED SESSILE TAXA ON llARD BOTTOM PANELS EXPOSED FOR FOUR MONTliS AT STATIONS B19 AND B31 SAMPLED TRIANNUALLY (APRIL, AUGUST, DECEMBER) FROM 1981-1993 (EXCEPT 1985 AND 1990) 6-44 6-vi I
I PAGE 2 6-15. GEOMETRIC MEAN DENSITIES (no./m ) OF SELECTED ~ BENTHIC MACROFAUNAL DURIN6 PREOPERATIONAL AND OPERATIONAL PERIODS, AND DURING 1993 . . . ... . . . . . 6-46 6-16. ANALYSIS OF VARIANCE RESULTS COMPARING LOG-TRANSFORMED DENSITIES OF SELECTED BENTHIC TAXA AT NEAR- AND FARFIELD STATION PAIRS (BIMLW/B5MLW, B 17/B35, B19/B31) DURING I PREOPERATIONAL PERIODS . . . (1978 1989) AND OPERATIONAL (1991-1993)
. . . . .. . . . 6-47 6 17. MEAN LENGTH (mm) AND LOWER (LCL) AND UPPER (UCL) 95%
CONFIDENCE LIMITS DURING PREOPERATIONAL AND OPERATIONAL PERIODS, AND MEAN LENGTHS DURING 1993 OF SELECTED BENTHIC SPECIES AT NEARFIELD-FARFIELD STATION PAIRS . . . 6-53 6-18. MEAN DENSITIES (per m2 ) AND RANGE DURING PREOPERATIONAL (1985- ; 1989) AND OPERATIONAL (1991-1993) PERIODS, AND DURING 1993 OF ADULT SEA URCHINS IN SUBTIDAL TRANSECTS . . .. . . 6-57 6-19.
SUMMARY
OF EVALUATION OF POTENTIAL THERMAL PLUME EFFECTS I ON BENTHIC COMMUNITIES IN THE VICINITY OF SEABROOK STATION . . .. . . 6-59 6-20. SUMM ARY OF EVALUATION OF POTENTIAL THERM AL PLUME EFFECTS ON REPRESENTATIVE IMPORTANT BENTHIC TAXA IN THE VICIMITY OF SEABROOK STATION 6-59
)
6-21.
SUMMARY
OF EVALUATION OF POTENTIAL TURBIDITY EFFECTS ON BENTHIC COMMUNITIES IN THE VICINITY OF SEABROOK STATION . 6-62 6-22.
SUMMARY
OF EVALUATION OF POTENTIAL TURBIDITY EFFECTS ON REPRESENTATIVE IMPORTANT BENTHIC TAXA IN THE VICINITY OF SEABROOK STATION 6-62
)
i l I 6-vii I
O O I LIST OF APPENDIX TABLES PAGE 6 1. NOMENCLATURAL AUTHORITIES FOR MACROFAUNAL TAXA CITED IN THE MARINE MACROBENTIiOS SECTION . . .. 6-69 6 2. TIIE OCCURRENCE OF MACROALGAE FROM GENERAL COLLECTIONS AND DESTRUCTIVE SAMPLING AT ALL SUBTIDAL AND INTERTIDAL < STATIONS, 1978 1993 . ..... .. .... . . . . . .. . . 6-70 I I I I I I I I 6--viu I 5 m
I MARINE MACROBENTIIOS I 6.0 MARINE MACROBENTIIOS assemblages is the distinct zonation patterns exhibited by the biota, which throughout the North
6.1 INTRODUCTION
Atlantic are most obvious in the intertidal zone I The predominant benthic marine habitat in the vicinity of Seabrook Station intake and discharge (Stephenson and Stephenson 1949; Lewis 1964; Chapman 1973), but are also apparent subtidally (Hiscock and Mitchell 1980; Sebens 1985). These j i structures is rocky substrata, primarily in the form of bedrock ledge and boulders. These rock surfaces, as with similar habitats in the Gulf of Maine and other patterns of community organization are formed by, and reflect, a variety of interacting physical (e.g., desiccation, water movement, temperature and light) northern temperate coastal areas, support rich and and biological (e.g., herbivory, predation, l diverse communities of attached plants and animals recruitment, inter- and intraspecific competition for g (macrobenthos), which are important and integral space) mechanisms, which vary over spatial and g parts of coastal ecosystems. In fact, hard-bottom temporal scales. coastal communities are among the most productive I l regions in the world (Mann 1973). This diversity and productivity is accomplished modification of the typically two-dimensional through Because these coastal hard-bottom communities are ecologically important, are well documented as effective integrators of environmental conditions, and substratum by the attached plants and animals, i c., are potentially vulnerable to localized coastal habitat-formers that create a multi tiered community anthropogenic impacts, studies of these communities and substantially enhance the number of potential have been and continue to be part of ecological biological niches. monitoring programs associated with coastal nuclear power plants (Vadas et al.1976; Wilce et al.1978; l One of the most obvious and produ:tive features Osman et al.1981; Schroeter et al.1993; BECO of the shore and near-shore biota in the Gulf of 1994; NUSCO 1994). Similarly, Seabrook Station Maine is an extensive canopy of brown macroalgae, marine macrobenthos studies continue to be part of l e g., rockweeds (fucoids) intertidally (Menge 1976; an extensive environmental monitoring program . Topinka et al.1981; Keser and Larson 1984), and whose primary objective is to determine whether ! kelps subtidally (Sebens 1986; Witman 1987). uifferences that exist among communities at sites in Generally, several understory layers occur beneath the Hampton-Seabrook area can be attributed to these canopies, and are comprised of secondary power plant construction and operation. Potential levels of foliose and filamentous algae and upright impacts on the local macrobenthos from Seabrook I l attached m acroinvertebrates over a layer of encrusting algal and faunal species, which occupy Station operation include temperature-related community alteration to areas directly exposed to the much of the remaining primary rock surfaces (Menge discharge thermal plume, most likely sites in the 1976; Sebens 1985; Ojeda and Dearborn 1989). upper portion of the water entumn (intertidal and l Also, many of the niches created in and around this shallow subtidal zones). Thermal impacts are attached biota are occupied by mobile predator and unlikely in deeper areas; however, increased turbidity herbivore species such as fish, snails, sea urchins, in discharge water resulting from transport of starfish, and amphipods (Menge 1979,1983; Ojeda suspended solids and entrained organisms could and Dearborn 1991). increase shading and sedimentation rates. To assess these potential impacts, studies were implemented to Another important aspect of these species identify the attached plant and animal species 6-1
~~ l i Ol MARINE MACROBENTIIOS UI I occupying nearby intertidal and subtidal rock low water and mean sea level areas (including tide surfaces, to describe temporal and spatial patterns of pools) in the intertidal ione. occurrence of these species, to identify physical and biological factors that induce variability in rocky Beginning in 1982, two intertidal stations (BIMSL g' intertidal and subtidal communities, and finally, and B5MSL; Fig. 6-1) were evaluated 3 relate these to Seabrook Station operation to nondestructively during April, July and December. determine impact, should it occur. Observations were made at permanently marked 0.25 m2 quadrats at three tidal levels: bare rock zone (approximately mean high water), predominantly 6.2 METIIODS Fucus spp.-covered zone (mean sea level), and Chondrus crispus-covered zone (approximately mean 6.2.1 Field Methods low water). Percent cover of fucoid algae and percent frequency of occurrence for organisms from Quantitative (destructive) m acrofaunal and an established species list of perennial and annual macroalgal samples were collected three times a year algal species, gastropods (Acmaca testudinalls, g (May, August and November) at six benthic stations Littorina spp. and Nuccl/a lapillus), Balanus spp. and g (Fig. 6-1); three near6cid-far6cid station pairs were Mytilidae were estimated and recorded. General established at lower intertidal (BIMLW, B5MLW), observations for the entire sampling area were shallow subtidal (4-5 m; Bl7, B35) and mid-depth recorded and photographs were taken of each tidal (9-12 m; B19, B31) locations. Four additional zone and each sampling quadrat. Frequency of stations were sampled in August only: one mid depth occurrence of fucoid algae was also recorded along intake station (B16) and three deep water (18-21 m) a 9.5 m transect line (NAl 1991a). stations (nearficid-B13 and B04, and farGeld-B34). This sampling program began in 1978 with Svc Subtidal transects were established in 1978 to near6 eld stations (B1, B04, B13, Bl7 and B19) and monitor larger macroinvertebrates and macroalgae one farGeld station (B31). Near6cid station (B16) that were not adequately represented in destructive was added to the study in 1979. Subsequently, three samples. Six randomly placed replicate 1 m x 7 m farGeld stations were added, one in 1980 (B34) and band-transects were surveyed at nearGeld-farncid two in 1982 (B35 and B5). Epifauna and epinora station pairs in the shallow subtidal (B17, B35) and g were removed by scraping from Gvc randomly mid-depth (B19, B31) zones in April, bly and IN selected 0.0625 m' areas on rock surfaces. Subtidal October. Percent frequency of occurrence was collections were drawn through a diver-operated recorded for dominant "understory" macroalgae airlift into a 0.79 mm mesh bag, placed in a labeled (Chondrus crispus. Phyllophora spp. and Ptilota plastic bag, brought to the surface and sent to the screata), as well as counts of Modiolus modiolus, laboratory for preservation and processing (NAl Strongy/ocentrotus drocbachiensis and all kelps. 1991a). Intertidal collections followed a similar procedure, excluding the use of an airlift. Information on patterns of recruitment and g settlement of sessile benthic organisms was obtained 5 A comprehensive collection of all visible algal from the bottom panels program. Bluestone panels species (" general algae") was made in conjunction (60 cm x 60 cm) were placed 0.5 m oft the bottom with destructive sampling at each sampling station. at Stations B19 and B31, beginning in 1982. In addition, collections were taken from the mean Stations B04 and B34 were added in 1986. Short-6-2 I 5 a
I i RYE LEDGE N !B5MLWl SU 85" 3 g i ugf FAR" RE HEAD iB35! rBY! \
,$ 1 Nautical M'l8 i 2 gnometus SCALE CO"TE N ES
) GREAT BOARS
- HEAD ,
, HAMPTON ,,
). gm BEACH
> ~
( } ag*]5 %\ intake,..jg 1813.] PJEARRELD lB1MLWl AREA [ourER gLetfi Sg%K 1 9f,8 ro* p ~ HAMPTON gygg sFf,B,R,00,K g (g3 I x sw=" & l
~
I
,/
's/
t 1 l SAUSBURY BEACH ( LEGEND i = benthic samples l Figure 6-1. Marine benthic sampling stations. Seabrook Operational Report,1993-6-3
l Ol Vq !l MARINE MACROBENTIIOS 1 term bottom panels were exposed for four months amphipod was determined and the presence of eggs ) during three exposure periods: December-April, or brood was recorded. l April-August, and August December. Long-term bottom panels were exposed for one year, deployed Macroalgae from general collections were l in August and collected in August of the following identified to the lowest practical taxon. The W year. complete macroalgal species list was compiled from both general and destructive collections and included crustose coralline algae, collected only in August.
- 6.2.2 Laboratory Methods All undisturbed bottom panel faces were first All destructive samples were washed over a 1.0 analyzed for Balanus spp. and Spirorbidae, and then mm sieve. Algal species from each sample were scraped to remove sessile bivalves and solitary g identified to the lowest practical taxon, dried for 24 chordates for identification and enumeration. 3 hours at 105'C, and weighed. Only fauna previously liydrozoa, Bryozoa and any abundant algal species designated as selected species were identified and were analyzed only on long-term panels. E counted from May and November macrofaunal 5 samples. Selected species were determined from previous studies to be those species that are the most 6.2.3 Analytical Methods useful as indicators of overall community type in the study area, based on abundance, trophic level, and 6.2.3.1 Community habitat specificity. All faunal species collected in August were identified to the lowest possible taxon; Macroalgal and macrofaunal community analyses non-colonial species were counted and any colonial included numerical classification and analysis of taxa were listed as present. In addition, abundance variance (ANOVA) of community parameters such of spirorbid polychactes at subtidal Stations B19 and as number of taxa and total abundance or biomass B31 was estimated from five subsamples of the alga from August samples (Table 6-1). The ANOVA g Phyllophora spp. design was directed to test for significant Preop-Op 5 X Station interaction; a more detailed description of Life history information was obtained for nine the ANOVA design can be found in NAl(1992). In n.acrofaunal taxa at paired nearfield farfield stations addition, the median percent-frequencies of dominant where they were most abundant. These taxa (and taxa in the intertidal non-destructive program during g their station pairs) were Ampithoe rubricata the operational period were compared to the median 3 (BIMLW/B5MLW), Jassa marmorata (B17/B35), and range from the preoperational period. Total Pontogenet inermis (B19/B31), Cancer irroratus number of algal taxa from general collections during (Bl?/B35), C. borealis (B17/B35), Strongylo- 1991,1992 and 1993 was compared to the median centrotus drobachicnsis (B19/B31), Asteriidae and range from the preoperational period. A (B 17/B35), Nucella lapillus (B I M LW/B 5 M LW), and comparison of macroalgal and macrofaunal Mytilidae (BIMLW/B5MLW, B17/B35, B19/B31) community composition during operational and preoperational periods was carried out using A subsample ofindividuals from each station from numerical classification methods (Boesch 1977).
May, August and November samples was measured Bray-Curtis similarity indices were computed for the to the nearest 0.1 mm and enumerated. Sex of each annual August log-transformed average densities 6-4 E M
- m. - m .
W v m. v w TABLE 6-I, SELECTED CENTHIC TAXA AND PARAMETERS USED IN ANOVA OR WILCOXON'S SUMME3 RANKS TEST. SEABROOK . - OPERATIONAL REPORT,1993. DATA DATA SOURCES OF .. COMMUNITY PARAMETER STATION PERIODS USED CIIARACTERISTICS* VARIATION - IN ANALYSIS IN ANOVAS* Benthic Laminaria saccharina Bl7 1978 - 1993 Mean number per sample Preop-Op* Macroalgae L2minaria digitata B35; 1982 - 1993 period and station, no Ataria esculenta B19,B31 1978 - 1993 transformation. Agarum cribrosum B19,B31 (except 1990) Wilcoxon's summed ranks by station. Chondrus crispus Bl7,B19,B31 1981'- 1993 Mean % frequency per . Preop-Op Phyllophora spp. B35 1982 - 1993 year. No transformation. Ptilota serrata (except 1990) Wilcoxon's summed ' ranks test.
~
Chondrus crispus Bl7, BIMLW 1978 - 1993 Biomass per sample Preop-Op, B5MLW, B35 1982 - 1991 period and replicate. Station, Year, (except 1990) Square root transform- Month ation, shallow subtidal; no transformation,
& Intertidal Number of taxa BlMLW, B17 Aug,1978 - 1993 Amount per station, year Preop-Op, l
Total biomass B19.B31 and replicate; no Station Year B5MLW, B35 1982 - 1993 transformation. 1978 - 1984, i B13, B04 1986 - 1993 B34 1979 - 1984, 1986 - 1993 Ascophyllum nodosum BIMSL, 1983 - 1993 Mean % frequency per Preop-Op Fucus vesiculosus B5MSL (except 1990) sample period and year; Fucus distichus no transformation. Wil-spp. edentatus coxon's summed ranks Fucus distichus . test by station. spp. distichus Fucus sp. (Continued) -
=. .
TABLE 6-1. (CONTINUED) DATA DATA SOURCES OF COMMUNITY PARAMETER STATION PERIODS USED CllARACTERISTICS* VARIATION IN ANALYSIS IN ANOVAS' Benthic Ampirhoe rubricara d BIMLW, 1978-89,91-93 Abundance per replicate. Preop-Op, Macrofauna Nucella lapsilus B5MLW 19b2-89, 91 -93 3 dates per year. Station, Mytilidae spat Year, Month Jassa marmorata
- B 17, 1978-89, 91-93 Mytilidae spat B35 1982-89, 91-93 Asteriidae B17, 1981-89, 91-93 B35 1982-89, 91-93 Pontogencia inermis' B19 B31 1978-89,91-93 Mytilidae spat Strongylocentrorus Jroebachiensis Total density BlMLW, B5MLW; August, Amount per year, station Preop-Op, B17, B35; 1978 - 1993 and replicate. Station, Year
& B 19, B 31, B16; (see algae B04,B34 B13 for years)
Number of taxa same as above Same as above Number per year, station, Preop-Op, and replicate; no Station, transformation. Year Modiolus modiolus B19,331 1980 - 1989, Mean per sample period, Preop-Op 1991 - 1993 Wilcoxon's summed ranks tests, no transformation.
" Log,,(x+1) transformation unless otherwise stated.
'ANOVAs used except where otherwise noted (e g., Wilcoxon's tests).
- Preop-Op: Preoperational period vs. Operational period.
' Life stages determined: juvtnile/ adult.
E M M MM M M M W M M M M M M M M M RE
MARINE MACROBENTHOS (macrofauna) and square root transformed average 6.3 RESULTS AND DISCUSSION biomass (macroalgae). Macroalgal species with less than 1.2% frequency of occurrence and macrofaunal 6.3.1 Marine Macroniese species with less than 10% frequency of occurrence were excluded from the analysis, in all, 38 algal 6.3.1.1 liorirontal Ledee Communities species and 100 faunal taxa were included in the final data sets for which similarity indices were Number of Tara computed. The group average method (Boesch { 1977) was used to classify the samples into groups Assessment of spatial and temporal patterns in or clusters. The actual computations were carried number of algal taxa has proven useful as an out by the computer program EBORDANA (Bloom indicator of impacts associated with several nuclear 1980). power plants in New England (Vadas et al.1976; Wilce et al.1978; Schneider 1981; NUSCO 1994). To assess algal community diversity at Seabrook 6.2.3.2 Selected Species study sites, number of algal taxa was determined in two ways. Numbers of taxa from general collections C,omparisons between preoperational and were used to qualitatively characterize the overall ope, ational periods were made by means of ANOVA floristic composition at a given study site. The oe Wilcoxon's summed ranks test (Sokal and Rohlf destructive sampling program provided quantitative 19a9) on data for the dominant species listed in information on algal diversity (i.e., number of taxa Table 6-1. ANOVA was used to test for differences per unit of area), data which are more amenable to in abundance or biomass between periods at statistical analysis. In these facets combined, a total nearticid/farfield station pairs. For a description of of 121 taxa has been collected during the 16-year the ANOVA design, refer to NAl (1992). The study (Appendix Table 6-2). adjusted Least Squares Means (LSMEANS, PROC GLM, SAS Institute, Inc.1985) were used in the t-test to evaluate differences when the Preop-Op X Number of Tata: General Collections Station interaction term was significant at cx s 0.05. To further facilitate interpretation of these Seventy-eight algal taxa were collected over the difTerences, the adjusted LS means for operational 1993 sampling year, which was similar to totals from and preoperational periods were plotted by station. previous operational and preoperational years (NAI The Wilcoxon's test was used to test for significant 1992, 1993). No new taxa were added in 1993 to differences in percent-frequency or abundance the overall recorded flora (Appendix Table 6-2). between preoperational and operational periods at Composition of the flora during 1993, based on the / cach station. proportions of the three major taxonomic divisions, was 52% red algae (Rhodophyta), 26% brown (Phacophyta) and 22% green (Chlorophyta). These proportions v a .imilar to other operational years (NAl 1992, h93), to the overall preoperational period (51% reo, 27% brown, 22% green), and consistent with other New Hampshire studies (Mathieson and Hehre 1986). 6-7 L - __ - . l
1 C U 65- INTERTIDAL SHALLOW MID-DEPTH DEEP 60- I 55-a 1991 50- a 1992 o 1993 45- a ,, o a a 40- O a 0 H 35- 0 Y) g 5 30- p 4 ..o a E i , 3 Z 25- . I
..a o ..
O i 20- a , , 2 a , 15- g a a D a 10 5- , , , , , , , , , , , , , 8 t htSL B'.MSL BlWLw B*MLw St7 B35 B16e B19 B31 B83 B04. B34. I Figure 6-2. Preoperational (through 1989) median and range, and 1991-1993 values for number of taxa l m collected in triannual general algae collections at Stations B1MSI, BIMLW, B17, B19, B31 (1978-1993), B5MSL, B5MLW, B35 (1982-1993), and annual (August only) collections at Stations marked with ***, i.e., B16 (1980-1984; 1986-1993), B13, BN (1978-1984; 1986-1993) and B34 (1979-1984; 1986-1993). Seabrook Operational Report,1993. i I 6-8 I. R E
{ MARINE MACRO 7ENTHOS E As with previous operational years, numbers of Number of Taxa: Ouantitative Samoles taxa from general collections in 1993 were within ( the range of annual numbers from preoperational years at most stations (Fig. 6 2). Two stations had Numbers of algal taxa based on August quantitative samples, in general, followed a pattern 1993 totals that were only slightly (by one taxon) similar to that from qualitative sampling. Most taxa outside the preoperational range; those were were typically collected at shallow subtidal and B5MLW (below) and B35 (above). The 1993 totals intertidal stations, with fewer taxa at mid-depth { were also comparable to other operational years, stations and lowest numbers at deep stations (Table 62). Mean numbers of taxa for 1993 were lower Relationships for numbers of taxa among depth than both preoperational and operational means at intertidal stations BIMLW and B5MLW. { zones during 1993 were, in general, consistent with those of previous years (Fig. 6-2). Typically, the Conversely, at all shallow subtidal, mid-depth and most taxa were collected at low intertidal (BIMLW deep stations,1993 means were higher than both ( and B5MLW) and shallow subtidal (B17 and B35) sites, with intermediate numbers at mid depth preoperational and operational means. Although ANOVA results (Table 6-3) indicated some stations (Bl6, B19 and B31), and lowest numbers at significant difTerences between operational periods mid intenidal(B1MSL and B5MSL) and deep (B04, (for the intenidal depth zone) or among stations Bl3 and B34) sites. This zonal pattern was within depth zones (for all except the deep zone), no consistent with studies conducted elsewhere on the significant (ps0.05) preoperational-operational period New Hampshire coastline (Mathieson et al.1981). (Preop-Op) X Station interaction was observed for any zone. Differences within nearfield/farfield station pairs were not apparent at either intenidal level, as the same number of taxa were collected within each pair Total Biomass in 1993 (24 taxa at both MSL sites and 37 taxa at both MLW sites). When differences in number of Total algal biomass (g/m') has exhibited a distinct tr.xa between corresponding stations did occur during pattern over depth zones during 1993, as well as 1993, such as within shallow subtidal, mid-depth and over both preoperational and operational periods, deep station groups, relationships among stations similar to that described previously for number of were consistent with previously observed trends. For taxa (Table 6-2). Biomass in August was
, example,in the mid-depth group, annual totals have consistently highest at shallow subtidal and intertidal typically been lowest at intake station B16, highest stations, and lowest at deep stations. Based on
{ at far6 eld station B31 and intermediate at nearfield station B19, regardless of plant operation status. ANOVA results, total algal biomass during the operational period was significantly less than Similarly, nearfield station B17 (shallow subtidal) biomass during the preoperational period for three of ( generally had fewer taxa than its farfield station counterpan B35. Consistently lower values at Bl6 the four depth zones (intertidal, mid-depth and deep; No significant difference between Table 6-3). p were likely due to less frequent collections at that operational and preoperational periods was detected L site (1/yr) than at B19 and B31 (3/yr). for algal biomass in the shallow subtidal zone, and no significant Preop-Op X Station interaction was apparent. ( 69 E - - - - - - - - - - - - - - - - - - - - - - - - - - - i
TAILE 42. /.RITilSIETIC MEANS AND ASSOCIATED VARIAIILITY (CV) FOR NUMBER OF ALGAL TAXA, TOTAL ALG AL BIONIASS. AND CHONDRUS CRISPUS BIO % LASS AT VA RIOUS DEFTilS AND STATIONS DURING 1993 AND Dl' RING TIIE PREOPERATIONAL AND OPERATIONAL PERIODS. SEABROOK OPERATIONAL REPORT.1993. PREOPERATIONAL* REPORT YEAR OPERATIONAL 1978 - 1989 1993 1991 - 1993 FARAStETER DEPTil ZONE STATIONS RIEAN C%* hlEAN RIEAN CV Number of taxa' intertidal BlktLW l I .0 92 80 93 6.9 (no. per 0 0625 m') B5hiLW l 3.1 7.9 13 0 14 I 46 Shallow subtidal DI7 11 4 44 12 4 II.I 42 B35 15.3 53 16 8 13 4 11.1 htid-depth D19 to 1 3.7 10 8 96 3.9 H31 10 9 33 12.8 10.9 88 D16 90 2.7 11.8 96 8.3 Deep D04 76 3I 80 7.4 4.1 BI3 7.9 2.7 88 78 64 D34 7.7 2.3 78 7.3 3.2 Tetal inomass' Intertidal BlktLW 13005 9.4 863.7 9948 14.7 (gem') D5htLW 1898.0 9.7 967.4 1028 6 5.3 [ Sheilow subtidal Bl7 1208 4 37 1303 9 1233.9 66 cm B35 1170 0 7.5 1032 0 1083 8 66 htid-depth 1319 308 6 7.4 352 8 380.7 l 9.7 B31 4712 7.9 379 4 373.7 8.7 B16 779 8 9.3 5873 549.2 9.5 Deep H04 99.7 9.1 122.7 92 8 11.9 BI3 96 0 9.7 29 6 86 8 313 D34 71 4 22.5 54.7 36 0 21.0 Chondrus ernspus biomass
- Intertidal DikfLW 908 7 80 954.3 989.7 7.4 f (g m') B5htLW 787 8 9.5 966 6
, 752 6 14 6 I Shallow subtidal Bl7 644.1 54 685.2 614.4 5.8 D35 477.3 38 466.4 394 6 96 Kfid. depth B19 16 33.3 0.3 1.4 33 g D3I 98 1 12.4 151.2 120.1 36.5
" Stations DlhtLW, Bl7, D19. B31: 1978 - 1989. Ftations B5htLW B35: 1982 - 1989. Station B16: 1980 - 1989, Station B13. D04: 1978 - 1984,1986 - 1989, B34: 1979 1984, 1986 - 1989. Eleans of annual means.
'CoefTwient of variability of the mean (standard enor of the mean, d;vided by the mean and multiplied by 100).
' August only.
- Sampled three times annua!!y at intertidal shallow and mid-depth subtidal only. Rarely collected at deep stateans.
l$ @M E M M E E Os O N E E
e TACLE 6-3. ANAYSIS OF VARIANCE RESULTS FOR NUMIER OF TAXA (per % ne') AND TOTAL EIOMASS (g per un') OF MACROALCAE COLLECTED IN ' AUGUST AT INTERTIDAL, SHALLOW SUBTIDAL, AND DEEP STATIONS, 1975-1993. SEABROOK OPERATIONAL REPORT,1993. PARAMETER DEPTII ZONE SOURCE OF df MS F* MULTIPLE COMPARISON' (STATIONS) VARIATION (Ranked in deeressing order) Number of intertidal . Preop-Op' 1 26.14 11.41 " Op< Preop Taxa (niut.w. B5MLw) Station
- 1 150.28 65.59 "
Year (Preop-Op)' 14 16.95 7.40 " 0.49 NS -j Preop-Op X Station' I 1.12 Enor 10 2.29
.l Shallow Subtida! Preop-Op I 3.08 1.42 NS j (D17 U35) Station I 41,94 19.34 '
Year (Preop-Op) 14 5.53 2.55 NS l Preop-Op X Station i 136 0.63 NS Enor 10 2.17 I
~
Mid-depth Preop-Op 1 0.02 0 01 NS (nts, n19 n31) Station 2 7.78 6.47 " Year (Preop-Op) 14 2.40 2.00 NS Preop-Op X Station 2 0.99 0.82 NS Error 25 1.20 Deep Preop-Op I 0.16 0.60 NS (D04, B14. Bl3) Station 2 0.43 1.63 NS Year (Preop-Op) 13 0.96 3.63 " Preop-Op X Station 2 <.01 0.20 NS Error 25 0.26-(Continued) ( . .
TABLE 6-3. (CONTINUED) PARAMETER DEPTII ZONE SOURCE OF df MS P MULTIPLE COMPARISON' (STATIONS) VARIATION (Ranked Iri decreasing order) Total Biomass Intertidal Preop-Op I 485,435 6.26
- Op< Preop (DIMLW, B5 MLW) Station 1 470,847 6.07
- Year (Preop-Op) 14 989,173 12.76 "
Preop-Op X Station 1 738,343 9 52 ' BI Pre B5-Op B5-Pre DI-Op Error 118 77,525 Shallow Subtidal Preop-Op I 34,396 0.43 NS (1117, B35) Station i 188,817 2.37 NS Year (Preop-Op) 14 210,193 2.64 " Preop-Op X Station i l11,371 1.40 NS Error 118 79,718 Mid-depth Preop-Op 1 307,475 8.14 " Op< Preop (n16. B19, n31) Station 2 1,547,078 40.98 " Year (Preop-Op) 14 121,416 3.22 " ? Preop-Op X Station 2 323,754 8.57 " Bl6-Pre Bl6-Op B31-Pre B19-Op B31-Op B19-Pre C Error 200 37,756 Deep Preop-Op I 12,015 5.34
- Op< Preop (D04.1334. B13) Station 2 32,128 14.29 "
Year (Preop-Op) 13 5,132 2.29 " Preop-Op X Station 2 3,191 1.42 NS Error 201 2,249
- Preop-Op compare 1978-1989 to 1990-1993 regardless of station.
'Statens within depth zone. ' Year nested within preoperational and operational penods regardless of area.
- Interaction of the two main effects, Preep-Op and Statua
'NS = Not significant (p>0 05) * = Significant (0 052p>0.01). " = Ifighly significant (pso.01). 'Underhning indicates that t-tests showed no significant difTerences (as0.05) among the underimed least squares means.
i MARINE MACROBENTHOS 4
)
A significant Preop-Op X Station interaction was distinguished from the others by the abundance of a detected for intertidal and mid-depth zones (Table 6- characteristic macroalgal species assemblage. For e 3). Total algal biomass at nearfield intertidal station example, the initial separation of collections occurred BlMLW was significantly lower during the at approximately 23% similarity into a group operational period than during the preoperational consisting of all three deep water (18-21 m) stations period, while biomass levels at the farfield intertidal (Fig. 6-4; Cluster 11, Groups 6 rnd 7, stations B04,
. counterpart (B5MLW) were not significantly B34 and B13) and a larger group (Cluster I) different between periods (Fig. 6-3, Table 6-2). For containing all other stations (intertidal, shallow subtidal and mid-depth, Groups 1-5). The deep '
the mid-depth zone station group, operational period total algal biomass was significantly lower than water group was segregated from the other stations on the basis oflow macroalgal biomass (<100 g/m'; preoperational biomass only at intake station B16; comparisons orpreoperational and operational means Table 6-4); it was further divided into Cluster !!a at both the nearfield (B19), and farfield (B31) (Group 6, discharge and farfield deep water stations, stations indicated no significant between-period dominated by Ptilota, with lesser amounts of difference (Fig. 6-3, Table 6-2). Phyllophora and Corallina) and Cluster iib (Group 7, intake deep water station, dominated by As mentioned above, algal biomass in the deep Phyllophora,with smaller contribution by Ptilota and zone was lower during the operational period than Phycodrys). during previous years; however, this trend occurred f consistently at all deep stations (i.e., no significant Among the other Eroupings, the intertidal stations Preop-Op X Station interaction; Table 6-3), (BIMLW and B5MLW) coeprised a discrete entity indicating an area-wide phenomenon, at least in deep (Cluster la; Group 1, within-group similarity 66%),. water. not very similar to the other groups (between-group similarity 32%); the distinguishing characteristics of i this group were high biomass values for Chondrus Macronleal Community Analysis and Afastocarpus (this was the only group that included Afastocarpus), and absence of Phyllophora 1 [ Multivariate community analysis techniques were (Table 6-4). Similarly, the shallow subtidal stations ! used in this study to quantify the degree of similarity (Cluster Ib, Group 2, stations B17 and B35) were among all August collections made at the characterized by high Chondrus and Phyllophora macrobenthic sampling stations since 1978. In this abundance, but very low Phycodrys biomass. The case,145 station / year collections, represented by assemblage at all of the mid-depth stations (Cluster square-root transformed biomass values of 38 Ic, Groups 3,4 and 5; stations B31, B19 and B16, macroalgal taxa, were grouped into clusters respectively) was dominated by Phyllophora (ca. according to Bray-Curtis similarity indices. A power 150-400 g/m', representing 42-65 % of the plant-induced impact to the macroalgal community macroalgal biomass at these sites); each was could be inferred from the failure of recent years' distinguished from the others by the presence and collections at a station (operational collections; 1990- abundance of a suite of other species (Table 6-4). 1993) to cluster with collections from preoperational years (1989 and earlier) at that station. However. The community analysis techniques described collections invariably clustered first by station, then above used biomass values from a large number of by depth zone (Fig. 6-4); each cluster was algal taxa (38 out of a total of 62; all those with an 6-13
O O I I' INTERTIDAL I400 - I
~
^
3:00 BIMLW (Nearfield) p 1000 -
$ 800 -
O E 600 - J
$ 400 - ****
B5MLW (Farfield) 200 - Precperauanal Operanonal MID-DEPTH I I 700 - ' B19 (Nearfield) 600 - ..,
< 500 -
{ .......******---- ----- ..... _ ; B31 (Farfield) E " a 300 -
$ 400
' B16 0 '*"
" 100 - (Inuke)
Pmperadanal Operanonal PERIOD I Figure 6-3. Comparisons among statsons for mean total macroalgal biomass during the preoperational (1978-1989) and operational (1991-1993) periods for depth zones with a significant interaction term (Preop-Op X Station) of the ANOVA model(Table 6-3). Seabrook Operational Report,1993. I I 6-14 g
I MARINE MACROBENTIIOS 0.2 - .Between Group Similarity 0.3 - l l WithinGroup Similarity L + + NumberofSamples g 0.4 - M / )0.5- 0 2 Tb 'IC la Ib Number of Samples Ob- l 8 I
~
h 0.7 - 1 0.8 - , [ Oroup1 h Group 2 ~ Gry 3 ~ Group 4 p5 p6
~
y7 i Gaup l-laustadel(B1MLW. B5MLW) Goup 2-Shauow Subendal(B17. B35)- Gaup 3-Mid-depdt Farrmid(B31) Gaup 4-M44<sepsh: Descharse (B19) Gaup 5-M,4wicpsh: leuke (Bt 6) Gaup Mkep: Farfwid/ Discharge (Bos, B34) Gaup 7-Deepe leiake (Bl3) Figure 6-4. Dendrogram and station groups formed by numerical classification of August collections of marine benthic l l algae,19781993. Seabrook Operational Report,1993. overall frequency of occunence of at least 1.2%). Station start-up. None of the 32 rare species was liowever, by their nature, these analyses are considered a major component of the local 2 influenced most strongly by commonly found species macroalgal flora (average biomass was <0.10 g/m ), with high total biomass; small, rarely found taxa nor were the reductions or increases of occurrence contnbute little to the Bray-Curtis similarity indices. during the operational period considered to represent Therefore, a further community analysis was a significant alteration of the established algal performed, examining rare species (overall frequency community. of occurrence less than 4%). Of the 32 species that met this criterion (Table 6-5), eight were found in Another monitoring study, evaluating the impacts both preoperational (1989 and earlier) and associated with construction and operation of a operational (19901993) periods, but relatively more nuclear power plant on the attached macroalgal flora
&cquently in the preoperational period; five species (NUSCO 1994), documented that incursion of a were found in both periods, but have become thermal effluent to nearby rocky shore sites caused reintively more frequent since Seabrook Station an alteration of the algal community at those sites.
began operation. Sixteen species were found in Specifically, there was an increased frequency of preoperational years, but have not yet been collected occurrence (i c., extended growing season) for in the operational period; only three species have species requiring or tolerant of warm water, and an been identified for the first time since Seabrook absence or reduced frequency of occurrence for 6-15 L _ _ -- _ _
T A BL E 6-4. SU5151ARY OF SPATIAL ASSOCIATIONS IDENTIFIED FRO 51 NU51ERICAL CLASSIFICATION (1978 - 1993) OF BENTillt 51ACROALGAE SA51PLES COLLECTED IN AUGUST SEABROOK OPERATIONAL REPORT,1993. WITI{INI GROUP BIO 51 ASS (g/m') BETWEEN DEPTil 51EAN YEARS GROUP PREOP' O P' ZONE STATION DEPTil (m) INCLUDED SISTILARITY DO511NANT TAXA 51EA N* Cl* SIEAN Cl Intertidal IllMLW ATLW 1978 - 1993 66/.32 Chondrus crispus 986 18 189.73 780 69 307 69 135MLW MLW 1982 - 1993 Afastocarpus stellatus 215 23 108 66 206 36 185 66 Corallina of]icinalis 51 25 31 30 20.29 24.10 Shallow Il17 46 1978 - 1993 .76/.55 Chondrus crispus 774 22 111.65 660.74 194 00 Subtidal 1135 1982 - 1993 Phyllophora spp 204.73 61.90 251 18 136.50 Ceramium rubrum 69 29 20.72 75 44 27 09 Cystoclonium purpureum 56 59 41.12 85.11 $0.14
, Curallma oBicanalis 51.58 23.24 35 02 13.38 h
- Mid-depth il16 94 1980 - 1984; .79/68 Phyllophora spp 404 45 99 80 297 82 II1.18 l Intake 1986 - 1993 Phycodrys rubens 188.86 71.00 119 51 102.17 i Chondrus crispus 56 97 30 43 19 21 40 81 Cystoclonium purpurcum 44.50 26 48 31.98 35 9s Ccmmeum rubrum 34.99 20.70 37 38 75 35 Callophyllis crustata 32 46 8 64 26 55 22.45 (Continued) i M M M M M M M M M M M M M M M M M SM
.. .. . - ~ - - v . . - - , m TABLE 6-4. (CONTINUED)
WITHIN/ - - CROUP BIOMASS (g/m') BETWEEN DEPTil MEAN YEARS GROUP PREOP' OP' ZONE STATION DEPTH (m) INCLUDED SIMILARITY DOMINANT TAXA MEAN' CI' MEAN Cl Mid-depth B19 12.2 1978 - 1993 .77/.68 Phyllophora spp 201.85 38.26 220.53 85.60 Discharge Phycodrys rubens 50.16 19.30 110.71 - 52.% Corallina officinahs 15.17 4.41 6.69 6.19. Callophyllis cristata 12.52 5.71 14.32 .I2.33 Ptilota serrata 16 01 6.33 10.06 8.47 Cystoclonium purpureum 5.97 4.42, 9.02 9.20 .< Mid-depth B31 9.4 1978 - 1993 .80/.64 Phyllophora spp. 209.50 64.66 . 158.77 106.24 Corallina officinalis 96.83 26.70 88.37 33.27
, Farfield Chondrus crispus 113.11 42.26 83.06 100.26 Phycodrys rubens 22.51 5 49 24.45 28.92 l
Deep Intake B13 18.3 1978 - 1984; .65/.53 Phyllophora spp. 68.85 23.77 67.88 - 79.56' 19R6 - 1993 Ptilota serrata l1.54 3.96 6.72' 9.78 Phycodrys rubens 5.82 2.95 4.84 6.% 18.9 - 21.0 1978 - 1984; .67/.53 Ptilota serrata 64.00 18.27 45.54 19,73 Deep B04 Discharge / 1986 - 1993 . Phyllophora spp. 10.97 5.04 8.70 .7.56 B34 1979 - 1984; Corallina officinahs- 6.86 3.59 1.52 1.83 Farfic!d 1986 - 1993
- preop = preoperational, 1978-1989 period (Stations BIMLW, B17, B19, B31: 1978 - 1989; Stations B5MLW, B35: 1982-1989; Station B16: 1980 - 1984, 1986-1989; Stations Bl3, B04: 1978-1984,1986 - 1989; B34: 1979 - 1984, 1986-1989).
'Mean and 95% confidence interval.
*Op = 1990,1991,1992 and 1993.
C TABLE 6-5. A COMPARISON OF PERCENT FREQUENCY OF OCCURRENCE OF RARELY FOUND U (OVERALL FREQUENCY OF OCCURRENCE <4%) SPECIES IN AUGUST DESTRUCTIVE SAMPLING DURING PREOPERATIONAL (1978-1989), OPERATIONAL (1990-1993), AND OVERALL (1978-1993) PERIODS OF SAMPLING. SEABROOK OPERATIONAL REPORT, 1993. g SPECIES PREOPERATIONAL OPERATIONAL OVERALL 5 Ectocarpusfasciculatus 5.5 0.5 3.9 Gymnogongrus crenulatus 4.4 3.0 3.9 Polyides rotundus 4.1 3.0 3.7 Bonnemaisonia hamufera 1.8 6.5 3.3 Desmarestia virdis 0.6 7.0 2.5 Leathesia difformis 3.0 0.5 2.3 Ulvaria obscura (v. blyttii) 2.0 0.5 1.5 Cladophora stricea 1.7 1.0 l.4 Petalonia fascia 0.4 3.5 l.4 Ectocarpus siliculosus 1.2 I.5 1.3 Porphyra miniata i.3 1.0 1.3 Monostroma grevillei 1.7 1.2 Palmaria palmata 1.3 0.9 Pilayella littoralis 1.3 0.9 Spongomorpha spinescens 1.2 0.8 Gsfordia granulosa 1.1 0.7 E ' Sphacelaria carrosa 0.8 0.5 0.6 Polysiphonia harveyi 0.7 0.5 Dumontia contorta 0.6 0.4 Ceramium desiongchampii 0.6 0.4 Enteromorpha prolifera 0.5 0.4 Scytosiphon somentaria 0.3 0.5 0.3 Spongonema tomentosum 0.5 0.3 Chordaria J1agellsformis t.0 0.3 Enteromorpha linsa 0.3 0.2 E Bryopsis plumosa 0.5 0.2 Polysiphonia denudata 03 0.2 isthmoplea sphaerophora 0.5 0.1 Ulvaria oxysperma 0.2 0.1 Enteroor.orpha intestinalis 0.2 0.1 Plumaria elegans 02 0.1 Entocladta virudis 02 0.l l 6-18 I
MARINE MACROBENTIIOS species with cold water afnnities. If similar trends zones, L. saccharina was the dominant kelp species were observed in the macroalgal community near at shallow subtidal stations (B17 and B35), with L Seabrook Station, it could be considered evidence of dominance switching to L. digitata at mid-depth a power plant impact. Ilowever, of the three species stations (B19 and B31). Agarum cribrosum was a that showed significant increases from preoperational codominant at mid-depth stations, where relatively to operational periods (Table 6-5; Bonnemaisonia moderate amounts of Alaria esculenta were also hamifera, from 1.8% of the preoperational observed (Table 6-6). In general, kelp densities (no. collections to 6.5% of the operational period plants /100 m2 ) during 1993 were consistent with collections, Desmarestia viridis, from 0.6 to 7.0%, means from both preoperational and operational and Petalonia fascia, from 0.4 to 3.5%), the latter periods for all species except L. digitata (described two are associated with cold water, and typically below). Although some year-to-year fluctuations in i found in late winter /carly spring (Taylor 1957). abundance have been observed for L. saccharina. A. Leathesia difformis is described as a summer plant, cribrosum and A. esculenta populations, results of p L but decreased in frequency of occurrence from 3.0% Wilcoxon's summed rank tests indicated that overall in the preoperational period to 0.5% in the operational means for these species were not operational period. Both these trends are the significantly difTerent (ps0.05) from corresponding converse of the expected response to a thennal preoperational means (Table 6-6). Mean abundance incursion. The macroalgal community in the vicinity of L. digitata during the operational period was significantly lower than during preoperational years of Seabrook Station is typical of those reported elsewhere in northern New England (e g., Mathieson at three of four sampling sites: nearfield stations B17 et al.1981; Mathieson and Hehre 1986); no impact (shallow subtidal) and B19 (mid-depth), and farfield ~ on this community as a result of construction or mid-depth station B31. The lower operational means operation of the power plant has been observed to at these sites resulted from a general decline in date. abundance of L. digitata that began prior to power plant start up (e g.,1988 at B19,1989 at B17 and Spring 1990 at B31; NAl 1993) and was further Kelo and Understory Species exacerbated by Hurricane Bob in 1991, when large scale removal of several kelp species, particularly L. Extensive canopies of several kelp species digitata at B19, was noted (NAI 1992b). commonly occur in coastal subtidal zones (4-18 m) in the northwestern Atlantic, and can account for up Patterns of occurrence and abundance of some to 80% of total algal biomass (Mann 1973) In the understory species can be influenced by the degree of kelp canopy cover (Johnson and Mann 1988). ( Gulf of Maine, Laminaria spp. (mostly L. saccharina and L. digitata) are most common in the shallow Common understory species in the Scabrook area, subtidal zone (4 8 m), while a mixture of Agarum occurring beneath and adjacent to kelp canopies, crebrosum. Lamona'ia spp. and Alaria esculenta are include the foliose red algae Chondrus crispus, found in deeper zories (Sebens 1986; Witman 1987; Phyllophora spp. and Ptilota serrata. Mean percent Ojeda and
Dearborn 1989). frequencies of occurrence of the three domina;.,
understory algae during 1993, and during A similar distribution of kcip species was found at preoperational and operational periods are presented Seabrook study sites. While Laminaria spp. were in Table 6-6. Patterns of distribution of these commonly found in both shallow and mid-depth species in fixed transects were similar to those 6-19
TABLE 6-6. PREOPERATIONAL AND OPERATIONAL ' ANS AND 95% CONFIDENCE LIMITS, AND 1993 MEANS, AND RESULTS OF WILCOXON'S SUMMED RANKS TEST Ciao'ARING DENSITIES OF FOUR KELP -SPECIES (#/100 in') AND PERCENT FREQUENCIES OF TilREE UNDERSTORY TAXA BETWEEN OPERATIONAL AND PREOPERATIONAL PERIODS. SEABROOK OPERATIONAL REPORT,1993. PREOPERATONAL" 1993 OPERATIONAL" TAXON STATION LCL MEAN UCL MEAN LCL MEAN UCL n r KELPS (#/100 m') Lantinaria digitata B17 141 5 213.9 286 4 36.5 20.1 32 0 43.9 15 -2.4 9
- B35 96 5 155.8 2151 122.2 25.3 131.7 238.2 II -0.51 NS B19 81.5 139.9 198 3 22.2 12.9 19.8 25 8 15 -2.53
- B31 401 6 500.2 598.7 257.0 191.0 252.1 313.2 15 -2.5 3
- Lantinaria saccharina B17 272.5 4151 557.7 508.5 -193.7 336.5 866 7 15 0 00 NS B35 210.9 325.7 440.5 381.0 72.0 288.4 504.8 11 -0.10 NS B19 20 59.1 116.3 18.2 10.1 16.1 22.2 15 -1.51 NS B31 59.6 95.5 131 3 82.5 39 3 73 8 108 0 15 -0.36 NS Alaria esculenta B19 -2.3 2.4 7.2 10.3 -7.4 6.3 20.1 15 1.57 NS es Illi 19.9 75.2 130.5 58 0 -58.2 69.3 196 8 15 0.22 NS h
Aganent cribrosurn B 19 613.5 786 6 959.6 525.0 390.7 641.7 892 6 15 -1.22 NS B31 280.2 366.4 452 6 250.0 213.3 272.2 331.2 15 -0.94 NS UNDERSTORY (% FREQUENCY) Chondnis crispus B17 67.6 71.9 76.2 64.3 54.3 71 8 89.3 12 0 00 NS B35 46.8 54.2 61.7 47.3 30.9 61.2 91 6 11 0.71 NS 1119 0.5 43 8.1 6.0 -5.8 6.7 19.2 12 0 83 NS B31 14.4 21.1 27.8 20.7 13.0 24 8 36 6 12 0.92 NS Phyllophora sp' 1117 14.6 20.4 26.1 17.7 0.8 22.8 44.8 12 0.18 NS B35 11.2 20.0 28.7 30.3 -7.0 28.4 63.9 11 0.92 NS B19 28.6 34.1 39.7 30.7 28.7 36.7 44.6 12 0.28 NS B31 25 6 31 g 38.1 16.7 54 26.4 47.5 12 -0.65 NS Ptilota Serrata B17 0. 0.9 1.7 1.0 -2.5 1.3 5.1 12 0.47 NS B35 0.0 0.6 1.2 0.0 -0.8 0.7 2.I II 0.11 NS B19 28.6 35 6 42 6 33.3 10.4 36.6 62.7 12 0.00 NS B31 9.4 13.2 16.9 60 -17.3 8.9 35.1 12 -1.30 NS
*Mean of annual means. Years for Leips - Stations B17 B19.B31: 1978-1989; Station B35: 1982-1989. For understory species-Stations B17,B19,B31: 1981 1989-*
Station 35: 1982-1989. LCL = lower confidence limit. UCL = upper confidence limit.
'1991-1993.
- Wilcoxon's test: NS = not significant (p>0.05), * = significant (0.052p>0.01), ** = highly significant (ps0.01).
M M M M M M M M M M M M M M M M M M WB
. MARINE MACROBENTHOS d
observed from biomass collections (Table 6-4). The and Denley 1984; Gaines and Roughgarden 1985; shallow subtidal zone (B17/B35) was dominated by Menge 1991), can also be seasonally important. k extensive turfs of the perennial red alga Chondrus At Seabrook intertidal study sites, much of the crispus (ca. 50-70%), with moderate occurrences of Phyllophora spp. (20 30%) Understory dominance . high intertidal zone, denoted as Bare Ledge, consists {' shifted to Phyllophora spp. in the mid-depth zone of bare rock with seasonal and perennial populations (B19/B31; 25-35%), with Piilota serrata as a of Fucus spp., and seasonally abundant ephemeral secondary dominant (10-35%). Relationships in green algal turfs (mostly an association of Urospora pattems of occurrence between depth zones and penicilhformis and Ulothrirflacca). Fucus spp. was-between nearfield-farfield stations have remained absent from sampling quadrats at nearfield station B1 remarkably consistent over the study period; in April and July 1993; however, a heavy set of j operational means were not significantly different Fucus germlings occurred after that time, resulting in from ~ preoperational means for all species, at all high frequency of occurrence (81%) of young p L- stations (Table 6-6). These consistent patterns of fucoids by December (Table 6-7). This annual cycle occurrence are likely due to the perennial habit of of Fucus abundance has been observed consistently each of these species (Taylor 1957), which allows over the operational period (NAl 1992b,1993), and populations to maintain dominance once established. has also been noted during some preoperational years. In general, fluctuations in Fucus abundance at BI have been high over the entire study period, Intertidal Communities (Non-destructive and likely reflect variability in recruitment, and in Monitorine Program) conditions for new recruit survival characteristic of the high intenidal (Keser and Larson 1984; NUSCO Macroalgal species abundance patterns on 1992). Frequency of occurrence of Fucus in the intertidal rock exhibit striking patterns of zonation, high intertidal at farfield station B5 has historically p L which result from factors directly and indirectly (including 1993) been higher than that at B1 (often l related to tidal water movement (Lewis 1964; at levels of 90% or more; Table 6-7), with Chapman 1973; Menge 1976; Lubchenco 1980; populations there often persisting year round. The Undenvood and Denley 1984). To efTectively ephemeral green algal association of Urospora monitor macroalgal species abundance in the penicilbformis/U/othrirflacca exhibited a consistent intertidal zone and characterize these zonation annual cycle of abundance at both neadicld and patterns at each site over time, permanently marked farfield stations, occurring only during the April
.quadrats were established at three tidal levels and sampling period in 1993 and all previous years in sampled three times annually at nearfield and farfield both operational periods. Conditions for sites. establishment and growth of these species on high intertidal surfaces are most favorable in late winter Physical stress (e g., desiccation, temperature and early spring. Both physical stress.(related to extremes) resulting from long emersion time is an temperature extremes and desiccation) and snail important structuring mechanism on macroalgae in grazing pressure (e g., by Littorina littorca and L
{ the high intenidal zone (Lewis 1964; Schonbeck and saxatilis; Keser and Larson 1984) are least intense Norton 1978). Other factors related to biological during this period (Cubit 1984). These stress processes, such as grazing pressure (Cubit 1984; mechanisms appear to be less severe at farfield Keser and Larson 1984) and recruitment (Underwood station B5 than at nearfield B1 (due to site 6-21
O_ O~ TABLE 6-7. PERCENT COVER AND PERCENT FREQUENCY OF DOMINANT PERENNIAL AND ANNUAL MACROALCAL SPECIES OCCURRENCE AT FIXED INTERTIDAL NON- g DESTRUCTIVE SITES DURING TIIE PREOPERATIONAL AND OPERATIONAL PERIOD. 5 SEABROOK OPERATIONAL REPORT,1993. ZONE
- DATA TYPE" STATION PERIOD / APR JUL DEC TAXA (%) YEAR
- Bare Ledgg g Fucus spp. Frequency Nearfield Preoperational 6 19 6 4 (BI) (range) (0-81) (0-94) (0 94)
Operational 0 0 56 1993 0 0 81 Farfield Preoperational (range) 82 97 (12 100) 10 (0-100) 5 g (BS) (0-100) - Operational 94 94 94 1993 94 100 100 Urospora penicsllsformis/ Frequency Nearfield Preoperational 45 0 0 Ulotheix flacca (BI) (range) (0-99) (0) (0) Operational 44 0 0 1993 44 0 0 Farfield Preoperational 73 0 0 (BS) (range) (0-100) (0) (0) Operational 42 0 0 1993 82 0 0 Fucoid Ledge g Fucus spp Cover Nearfield Preoperational 93 93 68 5 (BI) (range) (25-98) (60-100) (25-95) Operational 78 75 .62 1993 45 46 60 Farfield Preoperational 94 94 93 g (BS) (range) (60-98) (65-100) (2-98) g Operational 77 91 93 1993 100 100 94 Frequency Nearfield Preoperational 94 88 88 Fucus spp. (BI) (range) (69-100) (75 100) (69-94) Operational 77 87 81 1993 56 81 100 Farfield Preoperational 85 85 91 (BS) (range) (62 100) (69-100) (31-100) Operational 83 88 86 1993 88 88 88 (Continued) 6-22 I
=
l
r TABLE 6-7. (CONTINUED) PERIOD / APR 'JUL DEC ZONE DATA TYPE STATION TAXA (%) YEAR Chandrus Zone Preoperational 45 34 45 Chondrus crispus Frequency Nearfield ( L (BI) (range) (20 53). (20-38) (28-53) Operational '36 12 35 1993 17 3 43 h Farfield Preoperational 45 48 41 (BS) (range) . (0-72) (41 55) (39-48) Operational 48 60 41 1993 49 55 31 Preoperational 47 66 48 Masrocarpus stellatus Frequency Nearfield (BI) (range) (21-69) - (65-71) (32-67) Operational 35 16 42 1993 38 42 37 { Preoperational 47 51 44 Farfield (BS) (range) (0-53) (41-63) (43-56) Operational 45 47 39 1993 49 55 31
]
Preoperational 0 0 0 Corallina officinalis Frequency Nearfield (range) (0) (0) (0) y (B1) Operational 0 0 0 l 1993 0 0. O Preoperational 30 52 52 Farfield (range) (15-57) (33-61) (31-65) l (BS) Operational 57 61 60 1993- 52 60 65'
' Bare Ledge: approximately mean high water. Fucoid ledge: approximately mean sea level. Chondrus Zone:
approximately mean low water. Data Type (%): Frecuency - percentage of occurrence based on point contact line sampling. 2 Cayn percentage of substratum coverage based on fixed quadrats of 0.25 m .
'Preoperational: 19821989 median and range; Operational: 1991 1993 median; 1993: annual mean.
6-23
1 l o o, 1 Cl MARINE MACROBENTIIOS I' topography and degree of exposure to waves), as percent-frequency levels decreased from 47% to 2%. frequency of occurrence of this green algal No significant difference was detected at B5 for this association was typically higher there in 1993 (82 % species. Fucus distichus sump. edentatus was a vs. 44%) and over the entire preoperational period persistent component of the rockweed community at (medians of 73% vs. 45%; Table 6-7). both stations at lower abundance levels than fucoids discussed above, and these levels remained consistent A distinct horizontal band of rockweeds (Fucus over the entire study period (i.e., no significant spp. and Ascophyllum nodosum) delineates the mid between-period differences were detected). Between-period difTerences in abundance were identified for intertidal zone (Fucoid Ledge) at Seabrook study 5 sites. liabitat conditions for these species are ideal Fucus distichus subsp. distichus, which did not occur 3 in the mid intertidal, as longer immersion time at either study site during preoperational years, but results in a longer period for zygospore settlement established small populations (and significantly I W (cf. Underwood and Denley 1984), and reduces higher levels of occurrence) at both sites during the physical stress compared to that in the high operational period, and persisted through 1993. intertidal; new recruits are able to grow rapidly in Significantly higher frequency of occurrence of this zone and , develop physical and chemical juvenile Fucus sp. was detected at farfield station B5 defenses against grazing (Geisciman and McConnell during the operational period, while no differences 1981; Lubchenco 1983). Fucus spp. was the were observed at nearfield station Bl. dominant taxon in mid intertidal quadrats at both nearfield and farfield stations over the entire study The low intertidal or Chondrus zone was g period (1983-1993), both in terms of percentage of monitored non-destructively in fixed quadrats only at 5 substratum cover and percent-frequency of the mean low water level. These areas are typically occurrence (Table 6-7). In 1993 and during dominated by perennial red algal turfs composed of E preoperational and operational periods, consistently Chondrus crispus and Mastocarpus stellatus, which, W high and comparable levels of abundance of Fucus once established, competitively exclude other algae spp. have been recorded at B1 and B5. such as Fucus spp. (Lubchenco 1980). Overall operational period percent-frequencies for Chondrus Fuccid abundance in the mid intertidal zone at BI and Mastocarpus typically exceeded 30% during g and B5 was also estimated using fixed-line transects most sampling periods, with levels comparable g located at mean sea level. Overall, a consistently between stations and, in most cases, between dominant taxon at both study sites (particularly in preoperational and operational periods (Table 6-7). recent years) was Ascophyllum nodosum. Mean At nearfield station B1, low percent-frequencies were percent-frequencies of occurrence of A. nodosum recorded in 1993 for C. crispur (April and July) and du g 1993 an,d the operational period were for M stellatus (July); however, median percent-comparable at both nearfield and farfield sites, frequencies were generally similar between ranging from 37% to 41% (Table 6-8). Mean preoperational and operational periods. The coralline percent frequency during the operational period was red alga Corallina officinalis can be a locally significantly higher than the preoperational mean at abundant understory species in the low intertidal B1, whereas the period means at B5 were not zone. Percent frequency of occurrence of this g significantly difTerent. A concomitant significant species generally exceeded 30% in all seasons at 3 decrease in abundance of Fucus vesiculosus was farfield station B5 throughout preoperational and observed at BI during operational years, where mean operational years, but was absent from the nearfield 6-24 E r.,
- v. ~
TABLE 6-8. PREOPERATIONAL AND OPE!!ATIONAL MEANS WITH 95% CONFIDENCE LIMITS, AND 1993 MEANS, AND CESULTS OFD WILCOXON'S SUMMED RANKS TEST COMPARING PERCENT FREQUENCIES OF FUCOID ALGAE- AT TWO FIXED TRANSECT SITES IN TIIE MEAN SEA LEVEL ZONE BETWEEN THE PREOPERATIONAL AND OPERATIONAL PERIODS.~ SEABROOK OPERATIONAL REPORT,1993. j PREOPERATONAL* 1993 OPERATIONAL
- 1 TAXON STATION LCL MEAN UCL MEAN LCL MEAN UCL n Z' BI 26.4 32.0 37.6 38.3 34.5 40.1 45.7 10 2.29
- l Ascophyllum nodosurn B5 31.1 41.2 49.4 40.7 27.9 37.0 46.1 10- -0 68 NS f
B1 25.7 47.4 69.0 2.3 -0.5 1.7 3.9 to -2 28
- Fucus resiculosus B5 17.3 27.0 36 6 13.7 5.6 15.4 25.3 10 -1.36 NS B1 6.0 16.2 26.4 17.7 7.1. 18.4 29.7 to 0.91 NS Fucus distichus B5 -51 3.6 12.3 0.7 -16.9 5.6 28.0 10 1.12 NS i subsp. cdentatus BI - 0.0 - 3.3 -16.2 7.4 31.1 to 2.80 " -
{ Fucus distichus
" 11 5 - 0.0 - 2.7 -1.5 4.5 - 10.7 to 2.80 a subsp. distichu, B1 2.9 7.6 18.1 15.7 3.1 23.8 44.5 10 1.60 NS Fucus spp.
B5 -0.9 0.6 2.1 10.7 -3.2 7.7 18.5 - 10 . 2.31 " (juveniles)
'Mean of annual means, 1983-1989; LCL, UCL = upper and twer 95% confidence limits.
"1991-1993.
' Wilcoxon's test: NS = not significant (p>0.05); * = significant (0.052p>0.01); " = highly significant (ps0.01).
i _..__.____,___._____i______1_ _ [___ _ A_g_ _ _ _
O O MARINE MACROBENTIIOS I significant between-period (Preop-Op) difference or (BI) area throughout our studies (Table 6-7). E Preop-Op X Station interaction was detected for 3 shallow subtidal Chondrus biomass, based on 6.3.1.2 Selected Species ANOVA results (Table 6-9). Chondrus crispus 6.3.2 Marine Macrofauna Low intertidal and shallow subtidal horizontal rock surfaces in the vicinity of Seabrook discharge 6.3.2.1 Ilorirontal Ledee Communities and intake support dense stands of the red alga Chondrus crispus. As discussed in the previous Number of Taxa and Total Density section, the tough perennial habit of this species g allows extensive populations to continue to dominate Many attached and slow-moving invenebrate 3 suitable rock surfaces to the exclusion of most other species comprise the marine macrofaunal community species. Similar, nearly monospecine turfs of on local intertidal and subtidal rock surfaces. g Chondrus are common throughout the North Atlantic Macrofaunal community parameters similar to those us (Mathieson and Prince 1973); North American used for macroalgal monitoring (i.e., number of taxa, distribution occurs from New Jersey to southern total density) have consistently been monitored as Labrador (Taylor 1957). Owing to its predominance part of Seabrook studies since 1978, and have proven in the Seabrook area, Chondrus was selected for useful elsewhere for assessing potential ecological further, more detailed analyses. Chondrus biomass impacts from coastal nuclear power plants (Osman et (g/m') at Seabrook study sites was typically highest al. 1981; NUSLO 1992, 1994; BECO 1994). at the intertidal sites, at times approaching 1000 g/m 2 Overall species richness, as determined by the mean g (Table 6 2). During 1993, biomass levels at number of taxa, generally increased with increasing g intertidal stations were similar, although historically, depth, with lowest numbers of taxa at intertidal levels at farGeld station B5MLW have been lower stations (BlMLW and DMLW) and highest than those at nearfield station B1MLW. Operational numbers mid-depth (B16, B19 and B31) and deep mean biomass levels were significantly higher than stations (B04, B13 and B34; Table 6-10). those during the preoperational period (Table 6-9). Conversely, total faunal density decreased with Regardless of these overall between-station and increasing depth, with highest densities at intertidal between-period differences, ANOVA results revealed stations, and lowest densities at deep stations. no significant Preop-Op X Station interaction for intertidal sites, suggesting that any shifts were not Mean numbers of taxa at intertidal sites in 1993 were comparable to those recorded over the related to power plant operation. Substantial, operational period (1990-93), with fewer taxa 5 W although somewhat smaller, amounts of Chondrus were found at shallow subtidal stations, with biomass collected at B1MLW (nearGeld) than at B5MLW levels often exceeding 400 g/m 2 Biomass at (farfield) over that period (Table 6-10). Overall, nearfield station B17 was higher than that at the operational means were significantly lower than corresponding farfield station B35 in 1993; this preoperational means (Table 6-11). This decrease, relationship between stations was consistent with however, was most pronounced at BlMLW, and those observed during both preoperational and resulted in a significant Preop-Op X Station operational periods (Table 6-2). Consequently, no interaction for the intertidal station group (Table 6-6-26
.E 4
v <- rv w c- c- _ _ r w -- w-- w- - -- TABLE 6 9. ANALYSIS OF VARIANCE RESULTS FOR CHONDRUS CRISPUS BIOMASS (g/m') AT INTERTIDAL AND SIIALLOW SUBTIDAL STATION PAIRS FOR TIIE PREOPERATIONAL (1978 - 1989) AND OPERATIONAL (1991 - 1993) PERIODS. SEABROOK OPERATIONAL REPORT,1993. TAXON DEPTil ZONE SOURCE OF df MS F MULTIPLE COMPARISON (STATIONS) VARIATION OF ADJUSTED MEANS* (Ranked In decreasing order) Chondrus Intertidal Preop-Op* I 585,734 5 64
- Op> Preop crispus (Bl. B5) Year (Preop-Op)' 13 1,024,295 9.86 "
Month (Year)* 30 525,298 5 06 " Station' 1 4,328,746 41.66 " Preop-Op X Station
- I 45,215 0.44 NS Error 303 103,898 Shallow Subtidal Preop-Op I 163.5 3.87 NS l (Ul7, B35) Year (Picop-Op) 13 58.4 1.38 NS l
Month (Year) 30 179.3 4.24 " Station I 1129.6 26.73 " m 2.8 0.07 NS L Preop-Op X Station 1
" 42.3 Error 303
' Preop-Op compares 1978 - 1989 to 1990-1993 regardless of station.
' Year nested within preoperational and operational periods regardless of station.
' Month nested within year regardless of year, station or period.
' Station pairs nested within a depth zone: intertidal = BIMLW, B5MLW; shallow subtidal = B17 B35, regardless of year or period.
' Interaction of the two main effects, Preop-Op and Station.
'NS = Not significant (p>0 05); * = Significant (0.054>0.01); " = liighly significant (ps0 01).
'The > or < signs indicate a significant difference between two LS means.
f I
O; ol TABLE 6-10. PREOPERATIONAL AND OPERATIONAL MEANS (WITH COEFFICIENTS OF VARIABILITY), AND 1993 MEANS OF TIIE NUMBER OF TAXA AND GEOMETRIC MEAN E DENSITY FOR TIIE TOTAL DENSITY (NON-COLONIAL MACROFAUNA) SAMPLED IN W AUGUST AT INTERTIDAL, SIIALLOW SUBTIDAL, MID-DEPTII AND DEEP STATIONS. SEABROOK OPERATIONAL REPORT,1993. ' DEPTil ZONE STATION PREOPERATIONAL' 1993 OPERATIONAL
- MEAN CV' MEAN MEAN CV MEAN NO. OF TAXA (per 0.0625 m')
Intertidal B1MLW 48 17.3 35 37 11.5 B5MLW 47 17.6 44 42 10.4 Shallow subtidal B17 56 17.4 65 64 4.3 B35 52 14.3 61 54 10.6 Mid-depth B16 67 15.2 78 70 9.7 B19 64 19.8 71 72 14.2 B31 49 16 2 55 53 24.6 Deep B04 62 17.5 66 67 7.9 Bl3 53 14.7 44 55 25.7 B34 62 25.7 63 60 11.8 TOTAL DENSITY (wm') , Intertidal B1MLW 122795 5.3 66408 87909 6.7 l B5MLW 68684 5.1 126729 93942 4.6 Shallow subtidal B17 23373 4.6 40696 31081 3.5 g B35 28372 4.6 106260 40050 6.6 3 l l Mid-depth B16 31590 5.9 42565 15835 7.5 E W j B19 12424 6.1 24128 16726 7.2 B31 16240 11.4 25593 14878 5.4 Deep B04 4936 5.7 5407 4278 26 Bl3 6073 10.5 29826 12816 7.3 B34 5523 9.3 5145 5131 4.3 l 'Preoperational period extends through 1989 (Stations BlMLW, B17, B19, B31: 1978-1989; Stations B5MLW, B35: I 1982-1989; Station B16: 1980-1984, 1986-1989; Statians B13, B04: 1978-1984, 1986-1989; Station B34: 1979- 3 l 1984,1986 1989).
' Operational period. 1990-1993.
E
' Coefficient of variability of the mean (standard error of the mean divided by the mean and multiplied by 100).
l I I 6-28 I
=
- m. ..
~
ANAYSIS OF VARIANCE RESULTS FOR NUMIER OF TAXA (per 4.0625 ma') AND TOTAL DENSITY (per ma') OF MACROFAUNA', N TAELE 6-11. COLLECTED IN AUGUST AT INTERTIDAL, SHALLOW, MID-DEPTH, AND DEEP SUBTCAL STATIONS, 1978 -.1993.'- SEABROOK OPERATIONAL REPORT,1993. PARAMETER DEPTH ZONE SOURCE OF df MS F* MULTIPLE COMPARISON'- VARIATION (Ranked ist decreasing'erder) (STATIONS) Number of Taxa Intertidal Preop-Op* l' 1416.12 21.17 " Op< Preop (Bt MLw. B5MLW) Station
- I 81.11 1.21 NS Year (Preop-Op)* 14 457.79 6.84 "
Preop-Op X Stationt 1 396.73 5.93
- B t-N B5-N us-op' B1-op Error i18 66.88 Shallow Subtidal Preop-Op 1 509.23 6.64
- Op> Preop (017. B35) Station 1 827.65 10.79 "
Year (Preop-Op) 14 421.24 5.49 " Preop-Op X Station 1 384.48 5.01
- Bt7-op Bl7-N B35-op B35-N .
Error 118 76.69 l ? i 1157.49 9.04 " Op> Preop l @ Mid-depth Preop-Op (B16. B19. B31) Station 2 5682.09 44.37 " Year (Preop-Op) 14 913.94 7.14 " Preop-Op X Station 2 47.03 0.37 NS Error 200 128.06 Deep Preop-Op i 241.09 1.85 NS (004,B34.BI3) Station 2 1623.53 12.44 " Year (Preop-Op) 13 1403.60 10.76 " Preop-Op X Station 2 171.65 1.32 NS Error 201 130.47
' (Continued) .
TABLE 6-11. (CONTINUED) PARAMETER DEPTII ZONE SOURCE OF df MS F* MULTIPLE COMPARISON' (STATIONS) VARIATION (Ranked la decreasing order) Total Density Intertidal Preop-Op I < 01
. 0.05 NS (BIMLw, B5MLw) Station 1 0.31 5.25
- Year (Preop-Op) 14 0.48 8.22 "
Preop-Op X Station 1 0.50 8.40 ' BI-Pre B5-Op Bi-Op B5-Pre Error i18 0.06 Shallow Subtidal Preop-Op 1 0.45 8.33 " Op> Preop (B17, B35) Station 1 0.27 5.11
- Year (Preop-Op) 14 0.30 5.63 "
Preop-Op X Station I < 01. 0.03 NS Error 118 0.05 Mid-depth Preop-Op 1 0.20 2.07 NS p (Bl6, D19, B31) Station 2 0.57 5.85 "
$ Year (Preop-Op) 14 0 84 8.62 "
Preop-Op X Station 2 0.62 6.33 " B16-Pre B19-Op B16-Op B31-Pre B31-Op B19-Pre Error 200 0.10 Deep Preop-Op 1 0.30 3.13 NS (B04. B34. Bl3) Station 2 1.32 13.89 " Year (Preop-Op) 13 0.72 7.59 " Preop-Op X Station 2 0.65 6 82 " Bt34)p B13-Pre B34-Pre B34-Op D04-Pre B044)p Error 201 0.10 y compares 1978 - 1989 to 1990 - 1993 regardless of station.
'Nearfield = S' tiocr BIMLW, B17, B16, B04, B13; farfield = Stations B5MLW, B35, B31 B34, regardless of year / period.
' Year nested within preoperational and operational periods regardless of station.
' Interaction of the two main effects, Preop-op and Station.
- Wilcoxon's test: NS = not significant (p>0.05); * = significant (0.052p>0 01); " = highly significant (ps0.01).
' Underlining indicates that t-tests showed no significant differences (as0.05) among the underlined least squares means. The > cr < signs indicate a significant difference between two LS means.
M M M M M W W m m W W m M M m m m m 33
~ I INTERTIDAL I. l I ' 70 - 65 - 60 2 55-BIMLW W'*dId) h H $0 - E .$ o 45 , 40 - l B5MLW 35 - ~ ~ E*#M) 30 2 25 - 20 , l Preoper:6 mal Oper:6 mal PERIOD 1 , SHALLOW SUBTIDAL g i l I 70 - 65 - 4 rfield) g n H 50 - l $ 45 - I i o 40 2 352 30 ; 25 - B35-(. .. field) f I 20 ' , Preoper:6 mal PERIOD Oper:6 mal I l Figure 6-5. Comparisons between stations of mean number of macrofaunal taxa during the preoperational(19781989) and operational (1990-1993) periods for depth zones with a significant interxtion term (Preop.Op X Station) of the ANOVA model(Table 611). Seabrook Operational Report,1993. 6 31
1 0, Ol MARINE MACROBENTIIOS I 11, Fig. 6-5). This general decrease in number of overall increase m numbers of taxa appeared to be l
=
taxa at BlMLW during operational years was an area-wide phenomenon, as it was observed at all mirrored by a decline in total faunal density at that mid-depth stations (i.e., ANOVa results revealed no site in 1993 and over the operational period (Table signiGeant Preop-Op X Station interaction). 6-10). The opposite trend was apparent at the ANOVA results did identify a significant Preop-Op farGeld station (B5MLW), with densities increasing X Station interaction for total faunal densities at mid-E during the operational period, particularly in 1993. depth stations (Table 6-11), which was attributed to g These opposing trends (Fig. 6-5) resulted in a shifts in density at the intake station B16. Densities signiGcant Preop-Op X Station interaction, based on at nearGeld (B19) and farGeld (B31) stations were B ANOVA results (Table 6-11). generally similar to each other and consistent over 5 preoperational and operational periods (Fig. 6-6). In contrast to between-period difTerences in liowever, at intake station B16, mean density number of taxa at intertidal stations, a significant decreased ca. 50% from the preoperational to the increase in number of taxa for the shallow subtidal operational period (Table 6-10), in spite of a high station group (Bl7 and B35) was apparent during annual mean for the most recent sampling year operational years, compared to previous years (1993). (Tables 6-10 and 6-11). Numbers of taxa in 1993 strongly influenced this overall trend, as they were At deep stations, preoperational, operational and higher than both preoperational and operational 1993 mean numbers of taxa were generally means. The increase in number of taxa during comparable among all stations, with the exception of g operational years was most obvious at the nearGeld a low mean in 1993 at intake station B13, compared a site (B 17). ANOVA revealed that this to preoperational and operational means for that site disproportional increase in number of taxa at B17 (Table 6-10). ANOVA indicated no significant resulted in a signiGennt Preop-Op X Station between-period (Preop-Op) differences and no interaction for the shallow subtidal station group significant Preop-Op X Station interaction for (Table 6-11, Fig. 6-5). Total faunal density for the numbers of taxa at the deep stations. Total faunal overall shallow subtidal station group was also densities at both the nearfic!d and farGeld deep significantly higher during the operational period stations (B04 and B34, respectively) were than during previous years (Tables 6-10 and 6-11). remarkably similar to each other over the entire E 3 This was due, in large part, to the high densities study period, including 1993 (Tabic 6-10). However, recorded at both stations in 1993. The increase in as with the mid-depth station group, shifts in total total density during the operational period was density were apparent in the vicinity of the intakes similar for both stations, and therefore, ANOVA (B13), where a twofold increase in mean total results indicated no signiGeant Preop-Op X Station density was observed during the operational period, interaction (Table 6-11). compared to the preoperational mean. Based on ANOVA results, this increase in total density at B13, Similar to the shallow subtidal group, the mid- coupled with relative consistency at both B04 and depth station group had higher numbers of taxa B34, resulted in a significant Preop-Op X Station during operational years than during preoperational interaction for the deep station group (Table 6-11; g > cars (Tables 6-10 and 6-11) Mean numbers of taxa Fig. 6-6) 3 in 1993 at mid-depth stations were generally consistent with overall operational means. The 6-32
.I
-)
INTERTIDAL' 6-O. L A s.5: B1MLW (Nes h W) 5 .
-S 43 -
4 B5MLW W (ramw) 33
'N
[ 3 Paperadonal Operadonal PERIOD b
.l 6 MID. DEPTH- ,
? B19 I
6 : 2 5.5 - (Nearficid) 5-E u- ... . . . . . . .. . . . . . . . . . . . .
. . . . g>,i o ,,,
d 3.5 -
....... B16(Intake) 4 1
'3 e i
M Pregeradonal Operadonal PERIOD C 4 [ DEEP
= 6-7-
B04
% 5.5 - (Nearfield) 5 B34 b 43
~"**
(Farfield) j c 4- ,,
,............. J 1'--- --..... .... ..........,... gl j
- 4) ,,
3.5 - g 3 , , Preoperancmal Operadonal PERIOD Figure 6-6. Comparisons among stations of mean total macrofaunal density (logio(x+1)) during the preoperational j (1978 1989) and operational (1990-1993) periods for depth rones with a significant interaction term (Preop-Op X Station)of the ANOVA model(Table 6-11). Seabrook Operational Report,1993. 6 33 )
O O MARINE MACROBENTIIOS I Macrofaunal Community Analysis deeper water stations. The noncolonial macrofauna associated with :.ard Collections from the shallow subtidal stations substrata in the vicinity of Seabrook Station (B17 and B35) also comprise a discrete cluster comprise a rich and diverse community; over 400 (Group 2; within-group similarity 68%/ between-taxa have been collected in August destructive group similarity 29%; Fig. 6-7 and Table 6-12). samples since 1978, some with densities of over Mytilidae were also dominant at these stations (ca. 100,000 individuals /m2 . Very few of these animals 5,000-6,000/m 2), but mussel densities were more than are ' habitat formers' (cf. macroalgal section), and an order of magnitude lower than at the intertidal g most are motile; therefore, the faunal species sites. Lacuna vincta was the most abundant species g assemblages are not as distinct as those of the algae, at the shallow subtidal stations, in terms of number However, multivariate m acrofaunal community of individuals (ca. 5,400-10,700/m 2), and became g analyses, similar to those performed on macroalgae, significantly more abundant in the operational period. E facilitate the separation of annual collections at each This small herbivorous snail is a dominant grazer on station into groupings based on Bray-Curtis the kelp Laminaria saccharina, and also feeds on similarity indices, as well as the determination of many other attached and drift algae. Since the food within- and between-group relationships. These resource is quite patchy, the abundance of Lacuna is analyses were applied to log-transformed also variable. Other species abundant at the shallow macrofaunal density data for the top 100 taxa, in subtidal stations (isopods Idotea phosphorca and L terms of frequency of occurrence over the entire balthica, gammaridean amphipods Pontogencia g study period. The groupings of the 145 station / year mermis and Jassa marmorata) exhibited very g collections are illustrated in Figure 6-7. consistent densities between preoperational and operational periods (Table 6-12). E As with the macroalgal collections (Fig. 6-4), the W intertidal stations (BlMLW and B5MLW; Group !) Group 3 includes all collections from station B16 comprise a distinct entity (Fig. 6-7), characterized by (mid-depth intake) and several from station B19 extremely high densities of Mytilidae spat (ca. (mid-depth discharge; termed 'recent*, although 70,000 individuals /m2 ; Tab!c 6-12). These mussels preoperational years 1986 and 1987 are included, accounted for about 70-80% of the individuals while operational year 1990 is not). As reported collected at the intertidal sites; the isopod Jaera earlier, subtidal zonation becomes less distinct with marina, gastropods Lacuna vincta and Nucella increasing depth; as the macroalgae (and associated g lapillus, bivalves Turtonia minuta and Hiatella sp., epifauna) become increasingly patchy, collections y oligochactes, and the am phipod Gammarus oceanicus exhibit less tendency to cluster together and were also commonly found intertidally, but at much stations / depths often overlap. The 95% confidence lower densities; none of these taxa accounted for limits for all numerically dominant taxa (Mytilidae, more than about 5% of the individuals collected. In amphipods Pontogencia inermis. Caprella addition to the high densities of Mytilidae, and the septentrionalis and Caprella sp., molluscs Hiatella presence of primanly intertidal species lacra marma, sp., Lacuna vmeta and Anomia sp. and the Nucella lapillus and Turtoma minuta, this grouping pycnogonid (sea spider) Achelia sp.) overlapped j separated from other clusters because of very low between preoperational and operational periods l densities of the gammaridean amphipod Pontogencia (Table 6-12); however, the wide range of values inermis, which was much more abundant at the indicates a high degree of variability in the data. 6-34 5 e 1 I
? 0.2 - _Betwecn Group Similanty 0.3 - ) l Within Group Sinulanty 5 g0.4-i
*
- Number of Samples f 0.5 -
L E o go 0.6 - F W Number of Samples b 0.7 - m 0.8 - , c . 1 - A~ up I Gryp 2 Ortysp 3 Gryp 4 Gryp 5 l 2-Shadow Subudal Group 3-%d4kpah:1 state /Recent Discharge (86,87,91,9',,93) L Group 4.%44epe:Farfkid.Histonc Discharge 09-85, 8&-90); Deep: Intake (s t ,83,84,8693) Group 5-Deg: Farfield/DischargcAmtake Os,79,80,82) i Edwicpth: Discharge (78) f GROUP Group 2 Group 3 Group 4 Group 5 l Group 1 l I [
- - L /
N 85
/) PREOPERAllONAL 84
( i 81 d/ / r [ [ [ '
/ Not Sampled Not Grouped
[ l
, M ___ }
BlML B 5MLW' B17 B35 ' B16 B19 B31 B13 B34 B04 STATION Figure 6-7, Dendrogram and station groups by year formed by numerical classification of August collections of marine macrofauna,1978-1993. Seabrook Operational Report,1993. 6-35
TAllLE 6-12. STATION GROUPS FORMED BY CLUSTER ANALYSIS WITil PREOPERATIONAL AND OPERATIONAL (1990-1993) GEOMETRIC MEAN DENSITY AND 95% CONFIDENCE LIMITS (LOWER, LCL, AND UPPER, UCL) OF ABUNDANT MACROFAUNAL TAXA (NON-COLONIAL) COLLECTED ANNUALLY IN AUGUST FROM 1978 TIIROUCl{ 1993. SEABROOK OPERATIONAL REPORT,1993. CHOUP NAME/ SIMILARITY DOMINANT N O. LOCATION OVITIIIN/ TAXA PREOPERATIONAL OPERATIONAL HETWEEN GROUP) (STATIONNEA RS) LCL MEAN UCL LCL MEAN UCL I Intertidal / .604/291 Mytilidae 47979 69205 99823 37349 70118 131644 Nearfield Jacra marina 2117 3626 6217 690 1242 2239 (nt utw,1978-93) locuna vincta 2036 3209 5061 2474 3888 6114 Farfield Turtonia minuta 1368 2707 5361 683 1850 5016 (B5BLW; 1982-93) lliatella sp. 1465 2604 4632 297 840 2378 Oligochaeta 1204 2030 3424 182 837 3860 Nucella lapillur 926 1501 2433 530 1437 3901 Gammarus oceanicus 242 564 1320 743 1731 4038 cs ts
* .679/.571 locuna vincta 3762 5379 7695 8182 2 Shallow Subtidal/ 19698 13991 Nearfield Mytilidae 2906 4758 7794 1520 5829 22359 (Bl7,1978-93) Idotta P hosphrea 1696 2166 2768 1603 2136 2850 Farfield Pontogencia inermis 1249 1773 2519 814 1680 3470 (n33; 19s2-93) Jassa marmorata 1098 1572 2255 822 1900 4393 Idorea balthica 509 890 1560 280 659 1552 3 Mid-depth 636/.57: Mytilidae 662 4034 24608 1396 3779 10238 Intake Pontogencia inermis 495 2600 13657 451 1420 4474 (n t 6.1980-93) Caprella septentrionalis 404 1995 9868 1061 2475 5775
'Recent* Discharge focuna vincta 150 601 2412 195 503 1303 (Dl9,1986,1987.199193) Anomia sp. I16 489 2063 121 264 579 Caprella sp. 134 485 1758 594 1011 1726 A.helia spinosa 103 376 1375 532 735 1020 liiatella sp. 94 316 1065 385 609 967 (Continued)
IM M M M M M M M M M M M M M M M M EB
- - m - -
~
TACLE 6-12. (CONTINUED) GROUP NAMEt SIMILARITY DOMINANT (wtTitINr TAXA PREOPERATIONAL - -OPERATIONAL ~ NO. LOCATION (STATION, TEARS) BETWEEN CROtIF) LCL ~ MEAN UCL LCL MEAN 'UCL
.511/.493 Mytilidae 1975 3491 6176 2193- 5587 14238 4 Mid-depth /
Balanus crenatus 535 776 1127 687 1106 1783 llistoric' Discharge Anomia sp. 503 719 1029 224 - 530 1259 (B19,1979-85,1988-90) Iliarella sp. 425 632 942 417 1041 2603 Farfield Pontogencia inermis 324 438 593 ~161 311 605 (B31; 1978 93) Caprella septentrionahs 68 218 711 923 2153 5026 and Deep / Intake - (BI),1981.1983-84,1986-93)
.487/.468 Pontogencia inermis 135 246 452 67 148 330-5 Deep /
Caprella sp. 129 227 405 60 121 - 251-Discharge " Asteriidae 113 191 325 210 297 423 (D04.1978-84,1986-93) Anomia sp. 90 167 313 248 407- '671 Intake Caprella septentrionalis 78 137 244 60 121 250' (BI); 1978,1979,1980,1982) Tonicella rubra 81 127 202 59 85 .125 Farfield Afusculus nir r 63 110 197 86 109 140 (B34,1979-83,1986-93) Mytilidae 57 109 212 68 127 241 Iliarella sp. 47 92 185 50 153 473 Thelepus cincinnatus 9 20 St 132 207 329
.___________n _ -____ ___ - - _ - .
C O MARINE MACROBENTHOS I Since such variability was evident before Seabrook changes to the macrofaunal community have resulted E Station began operation,it was not attributed to the from operation of Seabrook Station. 3 power plant. Similarly, Group 4 represents a relatively Intertidal Communities indistinct assemblage, including all collections from (Non-destructive Monitorine Procram) station B31 (mid-depth far6cid), most collections from stations B19 (mid-depth discharge), most Patterns of faunal abundance on local rocky shores collections from station B13 (deep intake), and even exhibit patterns of zonation similar to those discussed one year from station B34 , the deep farneld site previously for intertidal macroalgae (Lewis 1964; (1984). It should be noted that the slight diiTerence Menge 1976; Underwood and Denley 1984). between the within-group (49%) and between-group Common intertidal fauna occurring in non- g (51%) similarities is an indication that the cluster is destructive sampling quadrats included barnacles, E not well defined, and groupings can be expected to mussels, snt.ils and limpets. Spatial (among zones, change from year to year. Of the numerically between stations) and temporal (among seasons, E dominant taxa in this group (Mytilidae, Anomia sp., between operational perbds) abundance patterns of E Pontogencia inermis, Hiatella sp., Caprella these species for ear 6cid and farfield study sites are septentrionalis, and the barnacle Balanus crenatus), described below. only C. septentrionalis exhibited a significant change in density (from a mean of 218/m' in preoperational Barnacles (especially Semibolanus balanoides) 2 collections to 2,153/m in operational collections; commonly occur on high intertidal (Bare Ledge) Table 6-12). The final major cluster, Group 5, was rock surfaces in the Seabrook area and throughout composed exclusively of deep water collections: all the North Atlantic (Connell 1961; Menge 1976; Grant 1977; Bertness 1989). Although generally E those from station B04 (discharge), almost all those 3 from station C34 (farfield; excluding 1984), and common, intertidal bamacle populations typically several from B13 (intake). These collections were exhibit high seasonal and year-to-year variability characterized by very low densities of all taxa (ca. (Menge 1991; Minchinton and Sheibling 1991; 100-400/m2 ); the bivalves Mytilidae, Anomia sp. and NUSCO 1994); similar temporal variability in Hiatella sp. were particularly scarce, relative to barnacle abundance has been observed in Seabrook densities in shallower water (Table 6-12). No study quadrats (Table 6-13). Barnacle abundances significant changes in density were seen (from (based on percent-frequency of occurrence estimates) g preoperational to operational periods) except for the during April were the lowest recorded during the g tube-building fan worm Thelepus cincinnatus, which operational period for both nearfield and farneld increased from a mean of 20/m2 to over 200/m 2 stations, but frequencies in subsequent months (July g However, this increase was noted at both nearfield and December) were the highest recorded for that B and far6cid stations, and does not appear to represent period, indicating good conditions for settlement and either a major alteration of the macrofaunal growth of barnacles after April. Because year-to-community or a power plant impact. year variability is so high, between period, within station comparisons are best made by examining in general, collections from operational years ranges of annual frequencies. Taking this approach, (1990-93) at each station clustered with at least some operational ranges (both monthly and averages for all of those from preoperational years, indicating that no seasons), although sm aller, fall within preoperational 6-38
.I
E TABLE 6-13. MEDIAN PERCENT FREQUENCY OF OCCURRENCE CY SEASON AND CVER ALL SEASONS OF THE DOMINANT FAUNA WITHIN PERMANENT 0.25 an' QUADRATS AT THE UPPER (BARE ROCK), MID. (FUCOID ZONE), AND LOWER (C#0NDRUS ZONE) f INTERTIDAL ZONES AT NEARFIELD (OUTER SUNK ROCKS) AND FARFIELD (RYE LEDGE) DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS, AND MEAN PERCENT FREQUENCY OF OCCURRENCE DURING 1993. SEABROOK OPERATIONAL REPORT,1993. ( ZONE' STATION PERIODI APR JUL DEC ALL YEAR
- SEASONS
- TAXON Bare Ledne Preoperational 61 51 9 40 Barnacles Nearfield (BI) (range) (4-100) (9-88) (0-88) (0-100)
Operational 41 76 74 68~ (range) (41 51) (46-98) (48-81) (41-98) 1993 41 98 81 73 f Far6 eld Preoperational 89 85 72 82 (BS) (range) (58 100) (24-100) (5-100) (5-100) Operational 70 67 50 58 (range) (36-95) (60-67) (11-54) (11-95) 1993 36 67 54 52 Near6 eld Preoperational 7 57 16 27 Lirrorina saxarilis ' (BI) (range) (0-44) (0-88) (0-88) (0-88) Operational 37 81 75 60 (range) (25-50) (81-100) (0 100) (0100) 1 50 100 100 83 @ 1993 Far6 eld Preoperational 50 66 75 64 l (BS) (range) (0-100) (38-94) (0-100) (0 100) l l Operational 31 50 50 50 (range) (0-81) (6-69) (19-81) (0-81) > j 1993 0 69 81 50 l Fucoid Zong ' Near6 eld Preoperational 82 76 78 79 Mytilidae (BI) (range) (37-100) (27-100) (43100) (27-100) f 83 93 52 70 1 Operational (range) (23-91) (29-99) (19-95) (19-99) 1993 23 29 52 35 Far6 eld Preoperational 8 1 5 5 (BS) (range) (2-100) (0-100) (0-100) (0-100) Operational 9 13 0 8 (range) (5-10) (0-19) (0-11) (0-19) 1993 10 13 0 8 (Continued) 6-39
O O TABLE 613. (CONTINUED) ZONE STATION PZRIOD/ APR JUL DEC ALL g TAXON YEAR SEASONS W Fucoid Zone (continued) Nearfield Preoperational 3 10 6 6 Littonna obtusata (BI) (range) (0-6) (0-25) (6-19) (0 25) Operational 6 6 12 12 (range) (0-6) (0-19) (0 44) (0-44) 1993 0 6 44 17 Farfield Preoperational . 3 16 7 9 (BS) (range) (0-25) (0-44) (0-44) (0-44) Operational 6 31 37 27 (range) (0-12) (25-50) (12-56) (0-56) l 56 37 = 1993 6 50 Chondrus Zone Mytilidae Nearfield Preoperational 90 89 65 81 (BI) (range) (54-95) (71-95) (15-85) (15-95) l Operational 77 76 66 79 5 (range) (67-95) (72-95) (63-93) (63-95) 1993 77 72 66 72 Farfield Preoperational 49 63 26 46 (BS) (range) (10 72) (23-80) (0-49) (0-80) E Operational 21 53 49 41 g (range) (0-57) (27-92) (8-87) (0-92) 1993 57 92 87 79 Nucella lapillus Nearfield Preoperational 75 100 56 77 (BI) (rarge) (13-100) (100) (31-88) (13-100) Operational 25 100 37 61 (range) (19-81) (94-100) (19-69) (19-100) 1993 19 94 69 61 Farfield Preoperational 94 38 69 67 (BS) (range) (75-100) (13-56) (56-81) (13-100) Operational 94 50 31 58 (range) (37-100) (37 94) (19-75) (19-100) 1993 37 94 75 69 (Continued) I I 6-40 I W.
TABLE 6-13. (CONTINUED) PERIODI APR JUL DEC ALL ZONE STATION SEASONS TAXON YEAR _ L Chondrus Zone (continued) 0 0 0 0 Littorina littorea Nearfield Preoperational (range) (0) (0 13) (0-6) (0-13) (BI) { Operational 0 6 12 12 (range) (0-19) (0-25) (12-50) (050) 0 0 50 17 { 1993 81 100 88 90 Farfield Preoperational (range) (75-100) (94-100) (44-94) (44-100) { (BS) Operational (range) 94 (81-100) 100 (100) 62 (9-75) 85 (9-100) J 100 100 75 92 1993 l Preoperational 13 13 13 13 l Aemoso testudinolis Nearfield l (range) (6-38) (0-25) (6-81) (0-81) (BI) Operational 12 12 12 II (range) (0-19) (6-12) (0-81) (0-81) 0 6 81 29 1993 0 0 0 0 Farfield Preoperational (range) (0-44) (0-13) (0-25) (0-44) (BS) . 8 Operational 12 6 6 (range) (6-12) (0-12) (0-44) (0-44) 6 0 44 7 1993 l
' Bare Ledge station is at upper edge of mean sea level (MSL) zone, approximately mean high water. Fucoid Zone station is approximately MSL. Chondrus Zone station is approximately mean low water.1982 - 1989, e Treoperational period extends from l
Operational period extends from 1991 - 1993. I ' Average of three seasonal medians. I I I I I I 6-41 I
O O MARINE MACROBENTIIOS _ ranges with one exception (Bl in July), indicating Frequency of occurrence estimates during 1993 at overall stability of barnacle populations at both nearfield station BI were consistent with those from stations. The herbivorous snail, Littorina saratills, preoperational and operational periods. At the is an important grazer in the high intertidal zone. farfield station (B5), high abundances were observed Abundance of L. saxatilis in the high intertidal was in 1993 and over the operational period, relative to generally lowest in early spring (April; Table 6-13), preoperational years. However, considerable overlap g prosiding a temporal refuge for ephemerK Jgse (see of preoperational and operational ranges was g Table 6-7). As with high intertidal earnacles, apparent for both stations. The carnivorous snail considerable overlap of preoperational and Nucella lapillus commonly preys on mussels and operational ranges of monthly and all-seasons barnacles, and can have considerable influence on estimates of L. saratilis abundance were noted for low intertidal community structure (Connell 1961; both nearfield and farfic!d stations. hienge 1983, 1991; Petraitis 1991). At Seabrook study sites, N. lapillts can be locally abundant, at The dominant faunal taxon in the mid-ir..co..dal times reaching frequency of occurrence levels of (Fucoid) zone has been hiytilidae (primanly the blue 100 % (Table 6-13). Over the entire study, mussel Myrdus edulis), which can continually occurrence of this species has been very consistent, dominate certain rocky shores in New England both between nearfield and farfield stations and E (Lubchenco and hienge 1978; Petraitis 1991) and between periods. Of the herbivorous littorine snails 3 elsewhere in the North Atlantic (Seed 1976). occurring in the Gulf of hiaine, Littorina littorca has hiytilidae were most abundant at the nearfield station the most pronounced efTect on intertidal community (BI), with median percent-frequencies (both structure, particularly in the low intertidal zone preoperational and operational) exceeding 50% for (Lubchenco 1983; Petraitis 1983). In the Scabrook all sampling periods (Table 6-13); somewhat lower study area, L httorca was most common at the abundances were observed at this s'ation in 1993. farfield station (B5), often exceeding 80% frequency The 1993 and period median frequencies wcre all of occurrence during both periods (Table 6-13). less than 13% at farfield station B5, although Frequencies at the nearfield stmion (BI) never considerably higher abundances have been observed exceeded 50% during our studies, and many times, there occasionally. hiussels are typically L. littorea was absent from the study areas. g outcompeted by barnacles at this site (NAI 1993) Abundances of L. littorea at Bl tended to be lower 3 , At both sites, operational ranges generally fall within during the preoperational years (<l3%) than during preoperational ranges. The herbivorous snail the operational period, when the highest monthly Littonna obtusata was a common mid-intertidal estimates were recorded. Another low intertidal resident at both stations. Overall, operational grazer, the limpet Acmaca testudinalis, occurred in abundances have generally been higher than those low to moderate frequencies in most years at during preoperational years, a trend which was nearfield station BI, and occasionally at similar apparent at both nearfield and farfield stations (Table levels at farfield station B5 (Table 6-13). g 6-13). Operational ranges for individual sampling periods g were generally similar to preoperational ranges, and ! liigh mussel abundances were also typical of the preoperational and operational ranges for all seasons low intertidal or Chondrus ione, with only small combined at each station were identical (0-81% at g E l, difTerences between nearfield and farfield stations, B1,0-44% at B5) relative to those in the mid intertidal (Table 6-13) 6-42 i
e MARINE MACROBENTHOS I (- Subtidal Fouline Community (Bottom Panel Anomia spp. (jingle shells), which consistently
- Monitorine Program) have peak settlement during the September to
[ i December exposure period, a period when water Recruitment success and annual patterns of temperatures are rapidly cooling (cf. Fuller 1946). I settlement for sessile macroinvertebrates were Preoperational densities of these bivalves were assessed by the bottom panel study using short term similar between the nearfield and farfield stations exposure periods (three sequential four-month (Table 6-14). Operational densities at the nearfield exposure periods a year). Although the type of station have tended to be higher in April and f.. December than those during the preoperational substratum, length of exposure period and deployment strategies can all influence the patterns period. The 1993 December density estimates at the of community colonization (Zobell and Allen 1935; nearfield station were the highest observed during Fuller 1946; Schoener 1974; Osman 1977; the operational period and were over twice as high 2 Sutherland and Karlson 1977), these factors may be as the operational mean (2600 individuals /0.25 m ) standardized to allow comparisons between nearfield reported last year (NAl 1993). Densities at the and farfield sites during these different periods of the farfield station, though generally lower during the year (January-April, May-August, and September- operational than the preoperational period, have I December). Four-month exposure periods provide remained fairly stable since 1991. the minimum duration for larval stages to settle, Another species of interest is the small crevice-
=
metamorphose, and grow into juveniles or young adults that can be effectively identified. Of the seeking bivalve, Niatella, which has historically organisms collected on these panels, four taxa settled during the August exposure period at both (Balanus, Anomia, Niatella, and Mytilidae) have stations. Settlement has normally been highest in been collected in sufficient frequency and numbers August at the farfield station, where densities in to allow comparisons oflong term trends in densities excess of 10,000 individuals per 0.25 m* were within and between nearfield and farfield stations for commonly reported. This trend changed in 1993, 2 assessing power plant effects (Table 6-14). when only 1,266 individuals per 0.25 m were collected at the farfield station. At the nearfield 2 Subtidal barnacles in the Seabrook area are station, August settlement (5399 individuals /0.25 m ) represented primarily by two species of Balanus was similar to those reported in past years (ranging (mainly B.crenatus, and B. balanus). Peak from 3868 to 7473 individuals /0.25 m' during the settlement usually occurred in early spring, resulting period extending from 1984 to 1993). in highest densities in the April exposure period (Table 614p. 11owever scillement is protracted, and Mytilidae (mostly blue mussel,Mytilus edulis) are variable from yta to year; substantial densities of an important component of the local macrofaunal j tunacles were found in August, and occasionally community, and are discussed in more detail in the
- (ne2 ably in 1993), bamacles recruited to bottom following section. Recruitment to bottom panels pancis in the September-December exposure period. followed a pattern similar to that described for Typically, bamacle densities were higher at the Niatella, i.e., peak recruitment occurred during the farfield station (B31) than at the nearfield station August exposure period and densities were (B19) over both preoperational and operational consistently highest at the farfield station. Similar to periods. recruitment trends for Hiatella, the August 1993 i
recruitment of Mytilidae spat at the farfield station 6-43
'l ABLE 614. ESTIM ATED DENSITY (per 0.25 m's OF SELECTED SESS!LE TAXA ON 11 ADD-SUBSTOATE BOTTOh! PANEIE EXPOSED FOR FOUR &lONTHS AT STATIONS B19 AND B31 SAMPLED TRIANNUALLY (APR!l, AUGUST. DECEMBER) FROM 1981 - 1993 (EXCEPT 1985 AND 1990k SEABROOK OPERATION AL REPORT.
1993. APRIL AUGUST DECEMBER ALL SEASONS TAXON STATION PERIOD / YEAR MEAN CP MEAN CV MEAN CV MEAN CV Nearfield Preop
- 17053 81 6403 78 9 144 7822 110 p,alanus spp.
(B19) Op' 13406 113 8861 73 28 171 7432 92 1993 3433 - 1683 - 83 - 1733 - Farfiekt Preop 40962 55 7917 78 14 121 16298 133 (B31) op 19683 53 10194 53 106 173 9994 98 1993 12650 - 16233 - 317 - 9733 - Nearfield Preop <1 <1 31 219 1232 92 421 167 Anomia spp (D19) Op 85 113 79 90 3905 68 1356 163 1993 8 - 72 - 6516 - 3410 - Farfield Preep 0 0 36 117 993 125 343 164 (113 1) Op 7 71 140 124 5.'7 18 228 121 1993 4 - IB - 498 - 173 - s~ liiatella spp. Nearfield Preop I 200 3966 65 27 IIS 1333 171 (Dl9) op 3 100 5488 38 9 144 1833 173 1993 0 - 5399 - 24 - 1808 - Farfield Preop <l <l 11659 91 16 131 3892 173 (B31) op 3 100 14801 81 114 ISI 4973 373 1993 1 - 1266 - 312 - 526 - Mytilidae Ne field Preop 2 150 367 67 58 98 142 139 (B19) Op 89 121 2951 88 SI 16 1030 161 1993 1 - 2610 - 42 - 884 - Farfield Preop 8 138 5035 200 36 100 1693 171 (B31) Op 24 112 4484 81 59 92 1522 169 1993 0 - 408 - 60 - 156 -
- Preop: 1981 - 1984 (Balanus and Anomu, B19); 1982 - 1984 (Balan=s and Anomu, B31); 1983 - 1984 (Huretto and Mytillufse, B19 and B31); Dec.1986 1989 (a?! taxa and stations).
'Op = 1991 - 1993.
'CoefDcient of variabihty of the mean (standard enor of the mean divided by the mean and multiplied by 100).
UM M M M M M M M W$ M M M M M M SS
I I MARINE MACROBENTIIOS I was depressed by an order of magnitude over that these high densities in 1993, overall mean 4 observed in past years. At the nearfield station, the operational densities have remained significantly 1993 settlement was more consistent with those lower than preoperational densities (ANOVA results; reported for other operational years. A trend for Table 6 16). During 1993 and over both higher densities of mussels on panels during preoperational and operational periods, mytilid operational years, relative to preoperational years, densities (Table 6-16) have been consistently higher I occurred at the nearfield, but not the farfield station. This trend was evident in both the August data and at the nearfield station (BlMLW) than at the farficId station (B5MLW). Because this between-station relationship has been so consistent over the entire I the combined seasonal data. study period (reflecting an arca-wide pattern of recruitment), ANOVA results indicated no significant 6.3.2.2 Selected Benthic Species Preop-Op X Station interaction for intertidal mytilid densities (Table 6-16). Mytilidae Mytilidae were also among the dominant taxa at Representatives of the order Mytilidae (mytilids) snallow subtidal stations, and the high recruitment in are common in the North Atlantic, found attached to 1993 discussed previously for the intertidal zone was I intertidal and shallow subtidal rocky substrata, but occasionally recorded from deeper water (Seed also apparent; mytilid densities in 1993 at shallow subtidal stations w cre considerably higher than either 1976). Important as prey for marine carnivores such preoperational or operational means (Table 6-15). as the dogwinkle Nucclla lapillus in the intertidal As in the intertidal zone, previous operational means zone (Menge 1991; Petraitis 1991), and starfish, had been significantly lower than preoperational lobsters, crabs and fish subtidally (Menge 1979; means (NAl 1993); however, high densities in 1993 Witman 1985; Ojeda and
Dearborn 1991),
mytilid have resulted in no significant between-period shell surfaces and interstices within mytilid difTerences (ANOVA results; Table 6-16). The aggregates also provide attachment and habitat areas dramatic increase in mytilid abundance in 1993 was for many algal and faunal species (Dayton 1971; most pronounced at the farfield station (B35), with 1993 mean density approximately an order of I Seed 1976). magnitude higher than either preoperational or At Seabrook study sites, Mytilidae (primarily the operational mean. Although farfield densities have consistently been higher than those at the nearfield I blue mussel Myrtlus edulis) was, by far, the dominant taxon in terms of density (nolm') in the intertidal zone (Table 615). Annual Mytilidae station (B17) over the entire study period, the greater difference between nearfield and farfield station abundances have been vanable over the means in the operational period (due, in large part, preoperational period (NAI 1991b), and similar to exceptionally high densities at the farfield station variability has become apparent over the operational in 1993) has, based on ANOVA, resulted in a period. High year-to-year variability in mytilid significant Preop-Op X Station interaction for the recruitment is typical for the Gulf of Maine (Petaitis shallow subtidal station pair (Table 6-16, Fig. 6-8). ( 1991). For example, while densities have been low during the operational period in previous years, Mytilids were also abundant at mid-depth stations, relative to preoperational densities,1993 densities relative to other taxa collected at those sites. As were higher than other operational years. In spite of noted in the other depth zones, densities recorded in 6-45 i I l
r_ C n TABLE 6-15. GEOMETRIC MEAN DENSITIES (#/M') OF SELECTED EENTIIIC MACROFAUNAL SPECIES DURING PREOPERATIONAL AND OPERATIONAL PERIODS, AND DURING 1993. SEABROOK OPERATIONAL REPORT,1993. TAXON STATION' PREOPERATIONAL' 1993 OPERATIONAL' MEAN CV* MEAN MEAN CV BIMLW 121297 4.0 113424 87852 7.4 Mytilidae B5MLW 72831 2.8 95743 57606 6.7 B17 2580 10 8 9187 2195 17.5 g B35 4449 9.8 55420 8335 18.9 3 B19 1876 16.0 11413 4644 10.3 B31 6196 14.7 8495 5981 9.9 BIMLW 1970 7.4 1208 947 3.1 Nuccl/a lapillu, B5MLW 905 3.7 773 554 4.6 Asteriidae B17 590 9.0 561 588 5.8 5 B35 184 16.4 81 96 34.4 B19 599 5.6 941 747 8.7 Pontogencia inermis B31 404 8.3 320 259 11.4 Jassa marmorata B17 1045 10.4 1124 1443 4.7 I B35 1888 9.6 4464 3782 2.0 BIMLW 19 88.3 2 1 74.2 Ampithoc rubricata B5MLW 3 117.3 108 144 6.5 B19 65 23.3 156 69 18.1 Strongylacentratus B31 31 28.0 59 31 16.2 droebachicnsis B19 100 22.9 11 79 13.5 Modiolus modiolus e B31 89 30 8 62 68 28.3
'Nearfield = BlMLW, B17, B19 Farfield = B5MLW, B35. B31. *Preoperational = mean of annual means, 1978-1989 (BIMLW, B17, B19. B31) or 1982-1989 (B5MLW, B35). ' Operational mean = mean of annual means, 1991-1993, for all stations. ' Coefficient of variability of the mean (standard error of the mean divided by the mean and multiplied by 100). 'Arithmentic mean of annual means. Preop = 1980-1989, Op = 1991-1993.
I 6-46 I
.E
R R - O M M Q TV, T TABLE 6-16. ANALYSIS OF VARIANCE RESULTS COMPARING LOG-TRANSFORMED DENSITIES OF SELECTED BENTHIC TAXA AT NEAR- AND FARFIELD STATION PAIRS GIMLWIB5MLW,217/B35, D19C31) DURING PREOPERATIONAL (1978 - 1989) AND OPERATIONAL (1991 - 1993) PERIODS. SEABROOK OPERATIONAL REPORT,1993.- SAMPLED IN MAY, AUGUST, NOVEMBER TAXA
- DEPTII ZONE SOURCE OF df MS F* MULTIPLE COMPARISON' (STATION) VARIATION (Ranked in decreasing order)
Mytilidae Intertidal Preop-Op' I 0.88 7.50 " Op< Preop (<25 mm) (Bl B5) Year (Preop-Op)* 13 0.88 7.51 " Month (Year)* 30 0.84 7.13 " Station
- I 2.75 23.39 "
Preop-Op X Station' I 0.05 0.39 NS Error 303 0.12 i Shallow Subtidal Preop-Op 1 0.61 2.18 NS (B 17, B35) Year (Preop-Op) 13 3.64 12.97 " es Month (Year) 30 2.17 7.75 " b Station 1 10.03 35.78 "
~
Preop-Op X Station i 1.87 6.67
- B35-Op B35-Pre B17-Pre B17-Op Error 295 0.28 Mid-Depth Preop-Op i 2.46 6.55
- Op> Preop (B19, B31) Year (Preop-Op) 13 5.42 14.42 "
Month (Year) 30 1.19 3.17 " Station 1 7.06 18.79 " Preop-Op X Station 1 3.03 8 05 " B31-Pre B31-Op B19-Op B19-Pre Error 355 0.38 (Continued) _ . . . _ _ m .. . _-_.-m.. . _ . . _ -_m_.m.. _ _ . ~.m.__ ____.s_._,..-m--.-_.m.___m_ma_._m.m . A
TABLE 6-16. (CONTINUED) SAhlPLED IN h1AY, AUGUST, NOVEh!BER TAXA DEPTII ZONE SOURCE OF df hts F h1ULTIPLE COh1PARISON (STATION) VARIATION (Ranked in decreasing order) Nucella Intenidal Preopop 1 5.18 40.52 " Op< Preop lapillus (HIMLW, B5MLW) Year (Preop-Op) 13 0.55 431" Month (Year) 30 0.97 7.61 " Station 1 4.32 33.79 " Preop-Op X Station 1 0.06 0.47 NS Error 303 0.13 Asteriidae Shallow Subtidal Preop-Op I 1.95 12.94 " Op< Preop (B17, B35) Year (Preop-Op) 13 2.10 13.95 " Month (Year) 30 0.84 5.58 " Station 1 22.86 152.06 " Preop-Op X Station 1 1.84 12.22 " B17-Pre Bl7-Op B35-Pre B35-Op m 0 15 k Error 295 Mid-Depth Preop-Op I 0.16 0.73 NS Pontogencia (D19, B31) Year O'reop-Op) 13 0.95 4.25 " intermes Month (Year) 30 1.16 5.16 " Station 1 7.39 32.96 " Preop-Op X Station 1 I 25 5.60
- B19-Op B19-Pre B31-Pre B31-Op Error 355 0.22 jossa Shallow Subtidal Preop-Op i 2.71 8.96 " Op> Preop marmorata (B17, B35) Year (Preop-Op) 13 1.26 4.04 "
Month (Year) 30 0.79 2.55 " Station 1 7.01 22.48 " Preop-Op X Station 1 0.39 1.26 NS Error 295 0.31 (Continued) M M M M M M M M M EE
M M . M M M M M M M'_ M M M ' TACLE 6-16. (CONTINUED) SAMPLED IN MAY, AUGUST NOVEMBER TAXA DEPTil ZONE SOURCE OF df MS F MULTIPLE COMPARISON (STATION) VARIATION (Ranked in deerca:Ing order) Ampathoe Intertidal Preop-Op 1 0.50 1.31 NS rubricata (B 1, B 5) Year (Preop-Op) 13 18.16 47.21 " Month (Year) 30 1.09 2.38 " Station 1 58.29 151.50 " Station X Preop-Op 1 52.99 137.73 " B5-Op B5-Pre B1-Pre B1-Op Error 303 0.38 Strongylocentrotus Mid-Depth Preop-Op 1 0.01 0 02 NS Jroebachiensis (B 19, B31) Year (Preop-Op) 13 3.51 7.34 " Month (Year) 30 1.75 3.65 " Station 1 8.44 17.65 " Station X Preop-Op I 0.00 0.00 NS p
@, Error 355 0.48 Modiolus Mid-Depth Preop-Op I 672,939 36.21 " Op< Preop modnotus (B 19, B31) Year (Preop-Op) 11 135,019 7.26 "
(adults) Month (Year) 26 34,900 1.88 " Station 1 112 0.01 NS Station X Preop-Op 1 4,286 0.23 NS Error 888 18,585
' Log,(x+1) density, except for M. modiolus adults, which were sampled semi-quantitatively and therefore rank densities were used.
' Preop-Op compares 1978-1989 to 1990-1993 regardless of station.
' Year nested within preoperational and operational periods regardless of station.
' Month nested within year regardless of year, station or period.
' Station pairs nested within a depth zone: Intertidal = nearfield (BIMLW), farfield (B5MLW); Shallow subtidal = nearfield (B17), farfield (B35); Mid-depth =
nearfield (B19), farfield (B31); regard! css of year or period.
' Interaction of the two main effects, Preo-Op and Station.
'NS = not significant (p>0.05); * = significant (0.052p>0.01); " = highly significant (ps0.01).
" Underlining indicates that t-tests showed no significant differences (as0.05) among the underlined least squares means; multiple comparisons listed in decreasing order. The > or < signs indicate a significant difference between two LS means.
n-i LJ l 0l ) MYTILIDAE SHALLOW SUBTIDAL 5-
= l 5
#~5 ~ B17 ,
~
(NearneW) 2 ,_
..........--- ----- --~~~----* ~~*
3- -~~~~ B35 d (F 6cM) c 2.5 - 2 Pmpebsmal opeyga,,j PERIOD I I MID-DEPTH
=
7 4.5 - _ B19 i 4-(NearGeld) h- _ D = IM 3 B31 c 2.5 -
~~*~
e mew) g 2 Preapebdonal Operauonal PERIOD Figure 6 8. Comparisons between stations of mean density (logio(x+1)) of selected macrofaunal taxa during the preoperational (1978-1989) and operational (1991-1993) periods for depth zones with a significant interaction term (Preop-Op X Station) of the ANOVA model (Table 6-18). Seabrook Operational Report,1993. I 6-50 E
b r u ASTERIDAE c SHALLOW SUBTIDAL L 3- _ j E 23 - B17
?.
2-
.................................. $ =6*W) l h E :- B35 (rarr,w) 5 0 0.5 -
i l 0 ' Pregersumal Operduonal i ' \ l I i P. INERMIS L MID. DEPTH 3- { g
,, .................................. g9,,,)
2-1.5 - 1- B31 (Fer6cid) j C 0.5 - 1 I O i Prayeraumal PERIOD Opersumal I l A. RUBRICATA INTERTIDAL 3-2 7 2.5 - BIMLW 5 2 (Near6cW) g .$ .
.... '~
1- " * *
- B5MLW N (Farneld)
O 0.5 - 0 ' Prayeriumal OpeEuonal Figure 6-8. (condnued)
n MARINE M ACROBENTIIOS 1993 were higher than both preoperational and 1993 and during the operational period than during operational means, providing further evidence for preoperational years at both nearfield and far6cid high recruitment in 1993 (Table 6-15). These higher shallow subtidal stations (B17 and B35, 1993 densities contributed to the signi6cantly higher respectively). At near6 eld mid-depth station B19, overall operational mean density, compared to the mytilids were generally smaller during the overall picoperational mean (ANOVA results; Table operational period and during 1993, relative to the 6-16). liigh recruitment in 1993 was most notable preoperational mean. Mytilid lengths at the mid-at the nearfictd station B19, and resulted in a depth farGeld station have been consistent over the relatively higher operational mean at that site, entire study period, including 1993. g compared to the operational mean at the farfield a station (B31). ANOVA results indicated that this shift in the relationship between mytilid densities at Nucella lavillus nearfield and far6cid stations (Fig. 6-8) was significant (i c., a Preop-Op X Station interaction; The only common intertidal predator in the Table 6-16). Seabrook area is the dogwinkle, Nucella lapillus, preying primarily on mussels and barnacles (Connell The most common mytilid collected at Scabrook 1961; Menge 1976; Petraitis 1991). At Seabrook study sites, the blue mussel Mytilus edulis, can reach study sites, N. lapillus abundances at near6cid station lengths up to 100 mm (Gosner 1978). However, BIMLW were nearly twofold higher than most mytilids collected during our study ranged from abundances at the farfield station (B5MLW)in both g 1 to 25 mm, with the majority collected as newly preoperational and operational periods and during E settled spat measuring 2-3 mm. A summary of 1993 (Table 6-15). Densities in 1993 were lower mytilid lengths over preoperational and operational than the preoperational means, and ANOVA results years is presented in Table 6-17. Mytilid lengths indicated that overall means for the operational have generally been greatest in the intertidal zone, a period were significantly lower than the trend which has been consistent over both periods. preoperational mean (Table 6-16). Because the Intertidal mytilids typically have been larger at the relationship between N. lapillus L..sities at neadield farfield station (B5MLW) than at the near6cid and farfield intertidal stations has remained relatively station (BIMLW) over both preoperational and consistent and proportional over the study period, operational periods, with a considerable between- ANOVA results also indicated no significant Preop-station difference noted in 1993 (4.5 mm vs. 3.0 Op X Station interaction. mm). Mytilids w ere slightly larger dunng operational years at both intertidal stations, com pared NuccIla lapillus length measurements were also to preoperational years conducted as part oflife history studies. N. lapillus can reach lengths of up to 51 mm (Abbott 1974), but Mytilids were generally smaller in the subtidal typically ranged from 3-12 mm during this study zones than those in the intertidal, with preoperational (NAl 1993) Average lengths were greater at the means ranging from 2.3 to 2.8 mm. During 1993 near6 eld station (BlMLW) than at the far6 eld and over both operational periods, mytilid lengths station (B5MLW) in 1993, a trend that has been were smaller at the nearfield stations (B17 and B19), observed over preoperational and operational periods than at the farfield counterparts (B35 and B31, (Table 6-17). Operational mean lengths at both respectis ely). Mean mytilid lengths were larger in stations were below the respective preoperational i 6-52 l
= ,
I
j TABLE 6-17. MEAN LENGTH (mm) AND LOWER (LCL) AND UPPER (UCL) 95% CONFIDENCE l LIMITS DURING THE PREOPERATIONAL AND OPERATIONAL PERIODS. AND MEAN l LENGTHS DURING 1993 OF SELECTED BENTHIC SPECIES AT NF.ARFIELD-FARFIELD STATION PAIRS. SEABROOK OPERATIONAL REPORT,1993. PREOPERATONAL' 1993 GPERATIONAL" TAXON STATION LCL MEAN UCL MEAN LCL MEAN UCL , I BIMLW 3.1 3.1 - 3.2 3.0 3.2 3.3 3.4 Mytilidae* 3.3 3.3 4.5 3.4 3.5 3.6 B5MLW 3.2 2.3 2.4 2.6 2.5 2.6 2.7 B17 2.3 2.5 2.5 3.1 2.6 2.7 2.7 B35 2.4 I B19 B31 2.3 2.7 2.4 2.8 2.4 2.9 2.2 2.7 2.0 2.7 2.0 2.7 2.1 2.8 I Nucella lapillus 131MLW B5MLW 6.7 5.8 6.9 60 7.0 6.2 7.9 4.4 6.0 4.9 6.2 5.2 6.5 5.5 4.7 4.7 4.8 5.0 Asteriidae Bl7 4.8 5.0 5.1 6.4 6.7 7.1 7.7 5.7 6.1 66 B35 5.2 5.4 5.5 4 B 19 5.0 5.1 5.3 5.8 Pontogeneia inennis I B31 5.2 5.3 5.4 5.4 5.3 5.4 5.5 i,: 4.2 4.l 4.2 4.4 4.5 Jassa inarrnorata Bl7 4.1 4.2 3.9 4.0 3.5 3.9 4.0 4.1 B35 3.9 a I Arnpithoc rubricata BIMLW B5MLW 6.7 7.4 7.0 7.8 7.3 8.2 6.7 5.9 5.6 6.7 7.2 7.1 8.8 7.4 I Strongylocentrotus B19 1.8 1.9 2.0 1.3 1.4 1.5 1.7 1.8 1.9 2.0 2.1 2.1 2.6 3.1 B31 droebachiensis
'Preoperational = mean of annual means, 1982 1989. Annual mean is sum of lengths of all individuals collected in May, August, and November divided by the total number of individuals measured I ' Operational = mean of annual means, 1991-1993.
' Individuals measuring >25 mm were excluded.
6-53 I
C 0 MARINE MACROBENTif 0S means and their 95% confidence limits. been observed; Asteriidae have generally been larger g at the farneld station (B35; means ra.nging from 3 approximately 6 to 7 mm), while means at nearGeld Asteriidae station B17 are typically smaller (around 5 mm) (Table 6-17). For both stations, operational and Asteriidae (starGsh)is another predatory taxon that preoperational means were similar, with overlapping can occur in the low intertidal zone, but are most 95% confidence limits. abundant in the sha!!ow subtidal. Although two genera of starGsh occur in the Gulf of Maine, Asterias and Leptasterias (Gosner 1978), tu o species Pontoreneia inermis of the former, Asterias forbesti and A. vulgaris are the most common in this study. Predation by The amphipod Pontogencia inermis is a Asterias spp. on mussels can be locally intense, and numerically dominant macrofaunal species in benthic this feeding activity is believed to have considerable habitats in the Gulf of Maine, where it clings to influence on both intertidal and subtidal community submerged algae in the intertidal and subtidal zones structure (Menge 1979; Sebens 1985). Abundance to depths of more than 10 m, and can also occur in patterns of Asteriidae in the Seabrook area were pelagic waters (BousGeld 1973). At Seabrook study examined in detail in the shallow subtidal zone, sites, P. inermis was a dominant taxon at all subtidal where they were most abundant. Over the entire stations, but occurred most consistently in the mid-study period, Asteriidae densities have been highest depth zone. Historically, and during recent years at the nearfield shallow subtidal station (B17), with including 1993, P. inermis densities have been densities consistently approaching 600/m 2 during higher at the nearGeld station (B19) than at the both preoperational and operational periods and farfield station (B31; Table 6-15). Mean densities at during 1993 (Table 6-15). This may be due to B19 have typically been higher during the l higher densities of the prey taxon Mytilidae at that operational period, and in particular during 1993, site. Densities have been more variable at the than during the preoperational period. The opposite g farGeld station (B35) over the study periods; trend was apparent at farfield station B31; the e i operational and 1993 means were approximately half preoperational mean was higher than both 1993 and ) the preoperational mean, resulting in a significant operational means. Based on ANOVA, these shifts 1 decrease in Asteriidae density for the operational in P. inermis densities at mid-depth stations during period at this station, relative to preoperational years the operational period (i.e., increasing densities at the g; (Tab!c 6-16). When examined with ANOVA (Table nearGeld station, decreasing densities at the farGeld 3 j 6-16), this decreasing trend at the farfield station station; Fig. 6-8) resulted in a significant Preop-Op l coupled with relative consistency at the nearfield X Station interaction (Table 6-16). ) station (Fig. 6-8), caused a significant Preop-Op X l Station interaction. Pontogencia inermis can reach lengths of up to 11 l mm (Bousfield 1973); however, at Seabrook mid. The sizes of Asteriidae collected over the study depth stations, average lengths were approximately period have been consistently small, and indicate that 5 mm (Table 6-17). Mean lengths at nearfield (B19) the vast majority of individuals collected were and farfield (B31) stations were similar to each jus eniles. A consistent relationship between other. Although a relatively high mean for 1993 was Asteriidae sizes at nearfield and farfield stations has recorded at B19, preoperational and operational 6-54 W l _____.______________.____________1
MARINE MACROBENTIIOS l l means were comparable, with overlapping 95% to temperature (Franz 1989). Lengths of J. I confidence limits. In 1993, moderate numbers of juveniles measuring 1-3 m m were collected in marmorata in our study averaged approximately 4 mm, with mean lengths slightly higher at the August at both mid-depth stations. In previous I years, most juveniles were collected in May (NAI 1993). Historically, low numbers of reproductive nearfield station (B17) than at the farfield station (B35) over both periods and during 1993 (Table 6-17). Comparisons of preoperational and operational females were collected from January through means revealed little between-period difTerence at I- summer (NAI 1993); however, no reproductive either site. Individuals measuring 1-3 mm were females were collected in 1993 at either B19 or B31 numerous in subtidal samples in August and (NAI 1994). November 1993, consistent with previous years (NAI 1994). No reproductive females were collected in Jassa marmorata 1993 at either B17 or B35 (NAI 1994). The tube-building amphipod Jassa marmorata is a common member of the local fouling community. Amalthoe rubricata I Populations of this species can dominate primary space on hard surfaces, often outcompeting Another amphipod occasionally common to I encrusting species by forming a mat " complex" composed of numerous tubes made from sediment and detritus (Sebens 1985). Primarily a suspension benthic habitats in the Seabrook area is Ampithoc rubricata. This species is most abundant in the intertidal zone, building nests among fucoids and in 4 feeder (Nair and Anger 1979), J. marmorata also mussel beds (Bousfic!d 1973). Occurrence and a preys on small crustaceans and ostracods (Bousfield abundance patterns of A. rubricata have been ; 1973). In the Seabrook study area,J. marmorata is unpredictable over the entire study period, with I most abundant at shallow subtidal stations, where it is among the dominant taxa (Table 6-12). During relatively high densities noted in some years, and absence or near-absence observed in other years. preoperational and operational periods and 1993, J. For example, A. rubricata was the dominant I marmorata mean densities (Table 6-15) were higher at the farfield shallow subtidal station (B35) than at intertidal crustacean in 1982, but was rarely collected during the period 1984-89 (NAI 1991b). Because of the nearfield station (B17). Annual mean densities this extended period of low abundance, overall during 1993 were higher than preoperational means preoperational mean densities for this species were at both stations but most notably at B35, and low (Table 6-15). This trend oflow abundance has consistent with the overall operational means. Based continued through 1990 and all operational years, on ANOVA, operational densities of J. marmorata including 1993, at nearfield station BIMLW. were significantly higher than preoperational How ever, a dramatic increase in A. rubricata densities, and because comparable increases during abundance has occurred at the farfield station the operational period were observed at both (B5MLW) during operational years, a trend which has continued through 1993. I nearfield and farfield stations, no significant Preop-Op X Station interaction was detected (Table 6-16). Continued low densities during operational years at BlMLW and continued high densitics at B5MLW for that period, Jassa marmorata can reach a maximum length of when examined with ANOVA, resulted in a up to 9 mm (Bousfield 1973), and growth rate and significant Preop-Op X Station interaction (Table 6-molting frequency of this species is strongly related 16, Fig. 6-8). 6-55
um MARINE MACROBENTIIOS _ E I Ampithor rubricata can reach a maximum size of Sea urchins collected in destructive samples were 20 mm (BousGeld 1973). During our studies, small (Table 6-17), and not considered a dominant average lengths generally ranged from 7 to 8 mm factor in structuring communities at any depth zone. (Table 6-17), with a variety of size classes observed. Sea urchins were most abunaant in the mid-depth At near0cid station BlMLW, A. rubricata mean zone (Table 6-15), with higher densities at the lengths have been fairly consistent over both periods near6 eld station (B19) than at the farEcid station and during 1993. A. rubricata have generally been (B31). This relationship between stations was smaller during the operational period, including consistent over both periods and during 1993. 1993. This trend may be the result of high Operational mean densities were remarkably similar recruitment observed over recent years at B5MLW to preoperational means at both stations; ANOVA results indicated no significant between-period l
=
(i c., more young individuals). Indeed, moderate numbers of individuals measuring 1-3 mm were difference, and no signincant Preop-Op X Station observed in August at B5MLW, while no juveniles interaction term (Table 6-16). were collected at BIMLW in 1993 (NAI 1994). Ovigerous females have been rare over the study Most sea urchins collected were juveniles with period, and none were collected during the average lengths generally around 2 mm during the operational period, including 1993 (NAI 1994). preoperational period at both nearneld and farfield stations (Table 6-17). During the operational period g and the 1993 sampling year, mean lengths at 3 Stronnlacentrotus droebachiensis nearfield station B19 were smaller than the preoperational mean, while somewhat larger sea The green sea urchin, Strongylocentrotus urchins were collected at the farfield station (B31) droebachiensis, is well documented as having during the operational period than during considerable influence on low intertidal and subtidal preoperational years. community structure (Lubchenco 1980; Witman 1985; Novaczek and McLachlan 1986; Johnson and Densities of adult sea urchins were also estimated Mann 1988). Most common in the subtidal zone, during subtidal transect sampling, and have been grazing by locally dense aggregates of S. relatively low since sampling began in 1985 (Table droebachicnsis can effectively climinate populations 6-18). Annual mean densities during the g of foliose algae (Breen and Mann 1976; Witman preoperational period never exceeded 1.3/m', and E 1985), preferentially Laminaria saccharina and L were typically <0.5/m 2 At shallow subtidal stations, longicruris (Larson et al.1980; Mann et al.1984). operational and 1993 means were within the range What remains after this severe grazing is a barren of preoperational means for both near6 eld and grounds of primarily crustose coralline algae. S. farfield stations (B17 and B35, respectively). droebachiensis is susceptible to disease-induced local Conversely, considerably higher densities have been extinction, allowing foliose algae to recolonize recorded at both mid-depth stations during the denuded areas. Sea urchin abundance cycles and operational period and,in particular,during 1993. In subsequent habitat modification have been linked to fact, the highest densities to date were observed in shifts in local lobster landings (Breen and Mann that depth zone in 1993, exceeding 6 urchins /m2 at 1976), however, this relationship is still unclear and the farGeld station (B31), and 1.3/m2 at the nearfield remains a source of controsersy (Einer and Vadas station (B19). 1990). 6-56 I E a
I MARINE MACR @ BENTHOS I TABLE 6-18. MEAN DENSITIES (PER m') AND RANGE DURING PREOPERATIONAL (1985-1989) AND OPERATIONAL (1991-1993) PERIODS, AND DURING 1993 OF ADULT SEA URCHINS LN SUBTIDAL TRANSECTS. SEABROOK OPERATIONAL REPORT,1993. PREOPERATIONAL 1993 OPERATIONAL STATION MEAN RANGE MEAN MEAN RANCE B 17 - 0.20 0.00-1.30 0.01 0.02 0.01-0 05 B35 0.10 0.00-0.50 0.21 0.07 0.00-0.21 I B19 0.09 0.02-0.20 1.36 0.71 0.01-1.36 0.04 0.00-0.24 6.14 2.07 0.00-6.14 I B31 ALL STATIONS 0.11 0.00-1.30 1.93 0.72 0.00-6.14 Afodiolus modiolus consistent over both periods. Therefore, based on ANOVA results, no significant Preop-Op X Station I Beds of the northern horse mussel Modiolus modiolus are often extensive in subtidal habitats in interaction was detected (Table 6-16). Overalllower densities during the operational period may be due to the Gulf of Maine, providing additional hard removal by storms, similar and perhaps related to , substratum for benthic algae (Sebens 1985), and that previously discussed for kelps (Section 6.3.1.1). g sheltering a diverse group of invertebrates in spaces I between individual mussels (Witman 1985; Ojeda and Dearbom 1989). Large sea stars (Asterias spp.)
6.4 CONCLUSION
S actively prey on Afodiolus, while another common I subtidal predator, the omnivorous sea urchin Strongylocentrotus droebachtensis, appears ta choose 6.4.1 Introduction l foliose macroalgae over Afodiolus (Briscoe and Sebens 1988). Urchin activity may actually enhance Afodiolus abundance by grazing kelps off mussels Thermal and hydrodynamic changes in physical conditions, created by operation of the Seabrook Station condenser cooling water system, could and decreasing the risk of mussel dislodgement potentially impact the local hard-bottom macrobenthic comm mities in several ways. The (Witman 1987). most obvious type of impact is temperature-related I Overall mean densities of Afodiolus during the operational period and during 1993 were lower than community alteration, resulting from direct exposure to the discharge thermal plume. This type ofimpact I mean densities for the preoperational period (Table could produce significant changes to nearby attached 6-15), and the between period (Preop-Op) difference communities, depending on the proximity of these was significant (Table 6-16). However, the habitats to the discharge, and the hydrodynamic relationship between Afodiolus densities at nearfield characteristics of the thermal plume itself. These (B19) and farfield (B31) stations (i.e., higher changes are most likely to occur in surface and near densities at B19 than those at B31) has remained surface waters, due to the buoyant nature of most 6-57
1 mm MARINE MACR 1CBENTIIOS 5 thermal plumes. Such impacts are well-documented I 6.4.2 Evaluation of Potent e* i 'crm al for intertidal and shallow subtidal communities Plume Effects on intt nallow during monitoring studies for coastal nuclear power Subtidal Benthic Communnies plants elsewhere, and include climination or reduced ~ abundance of cold-water species, and increased 6.4.2.1 Backcround abundance of warm-water tolerant and/or opportunistic species, leading to the development of Nearfield sampling sites used for the Seabrook communities distinct from those seen prior to intertidal and shallow subtidal macrobenthos studies thermal incursion and from those on nearby were selected because they occur within, and best unaffected coasts (Vadas et al.1976; Wilce et al. represent, the shallow water communities that are 1976; BECO 1994; NUSCO 1994). most susceptible to incursion by the Seabrook - Station discharge thermal p!we. flydrodynamic Another less common impact resulting from modeling, conducted prior to plant start-up to predict coastal nuclear power plants is related more to the areal extent of the thermal plume under various altered water circulation patterns than to thermal meteorological and current regimes, indicated that incursion. Specifically, the introduction (discharge) thermal incursion to these sites would be minimal, of turbid water to an area of historically lower levels with temperature increases of <l'F (Teyssandier et of turbidity can decrease light penetration and increase sedimentation rates. al.1974). Subsequent field studies, conducted after g Sources of this Seabrook began commercial operation, verified these N turbidity include suspended inorganic and organic predictions by measuring no temperature increases at particles from higher energy areas, such as wave- the intertidal sampling site, and increases of <l'F at swept shores (Osman et al.1981; NUSCO 1988; shallow subtidal site (Padmanabhan and liccker Schrocter et al.1993), and pctentially, increased 1991). detrital deposition resulting from settlement of entrained organisms. Turbidity impacts would be most pronounced in areas where levels of water 6.4.2.2 Intertidal Benthic Community movement and physical disturbance are low, such as E g in deeper water. Turbidity effects detrimental to While several parameters used to evaluate certain macrobenthic plants and animals include shading or burial, and an increased community dominance by aspects of benthic intenidal communities indicated g significant differences between preoperational and 5 suspension-feeding organisms and organisms more operational periods, analyses of overall community tolerant of higher sedimentation rates (iiiscock and structure showed that nearfield macroalgal and Mitchell 1980; Schroeter et al.1993). macrofaunal communities have changed little since Seabrook began operation (Table 6 19). For Because the type of impact a community is example, significant decreases during the operational vulnerable to appears to be related to its relative period at the nearfield station were detected for total position in the water column (i c., temperature effects algal biomass, number of faunal taxa and total faunal for shallow water sites, turbidity efTects at deeper g density, and significant overall decrease in number of E water sites), potential impacts associated with algal taxa was observed at both nearfield and farfield construction and operation of Seabrook Station on Ilowever, numerical classification of communities in each of these depth zones will be stations. g m acroalgal and macrofaunal data, an analysis 5 examined separately and discussed below. technique that incorporates abundances of all 6-58 I 5 m
I TAELE 619.
SUMMARY
OF EVALUATION OF POTENTIAL THERMAL PLUME EFFECTS ON BENTIIIC COMMUNITIES IN TIIE VICLNITY OF SEABROOK STATION. SEABROOK OPERATIONAL REPORT,1993. OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES TO PREVIOUS CONSISTENT WITII I COMMUNITY Macroalgae AREA /DEPTII 7ONE Intertidal PARAMETER' No. of taxa YEARS?' Op< Preop PREVIOUS YEARS?' Yes NF: Op< Preop j Total biomass Op< Preop FF: Op= Preop 5 Community structure Yes Yes Yes Yes Shallow No. of taxa Total biomass Yes Yes subtidal Community structure Yes Yes No. of taxa Op< Preop NF: Op< Preop Macrofauna Intertidal FF: Op= Preop W NF: Op< Preop Total density Yes FF: Op= Preop I Shallow Community structure No. of taxa Yes Op> Preop Yes NF: Op> Preop I subtidal Total density Community structure Op> Preop Yes FF: Op= Preop Yes Yes I ' Abundance, no. of taxa, biomass, total density, evaluated using ANOVA; community structure evaluated using numerical classification by year and station.
' Operational period = 1990-1993 (August only).
'NF = nearfield; FF = farfield.
I, 4 L TABLE 6-20.
SUMMARY
OF EVALUATION OF POTENTIAL TIIERMAL PLUME EFFECTS ON I REPRESENTATIVE IMPORTANT BENTIIIC TAXA IN TIIE VICINITY OF SEABROOK STATION. SEABROOK OPERATIONAL REPORT,1993. OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES I, AR EA/DEPTII TO PREVIOUS CONSISTENT WITII COMMUNITY ZONE SELECTED TAXON . YEARS?' PREVIOUS YEARS?' I Macroalgae Intertidal Chondrus crispus Shallow Subtidal Chondrus crospus Shallow Subtidal Laminaria saccharina Op> Preop Yes Yes Yes Yes Yes NF: Op< Preop i Shallow Subtidal Laminaria dsgitara Op< Preop FF: Op= Preop Ampithoe rubricata Yes NF: Op< Preop Macrofauna Intertidal FF: Op> Preop I-Intertidal Intertidal Nucella lapstlus Mytilidae Shallow Subtidal Jassa marmorata Op< Preop Op< Preop Op> Preop Yes Yes Yes NF: Op= Preop I Shallow Subtidal Asteriidae Op< Preop FF: Op< Preop Shallow Subtidal Mytilidae Yes NF: Op= Preop FF: Op> Preop
'I ' Conclusions derived from analysis of variance or nonparametric analysis for Preoperational versus Operational periods.
%. 'F = nearfield, FF = farfield.
6-59 I
m MARINE MACROBENTUOS 5 I important components of these communities, power plant operation. g revealed that annual collections invariably clustcred 5 by station or depth zone Grst, with no evidence of Operational period shifts in abundance of groupings by preoperational or operational period. Ampithoc rubricata, relative to the preoperational This suggests that the important structuring abundance, were not consistent between stations l a mechanisms creating differences between stations (signi6 cant decrease at the nearneld station, and among years are most likely natural factors significant increase at the far6cid station). However, unrelated to power plant operation. examination of annual abundances revealed that these shifts began before power plant start-up. Once Patterns of abundance and occurrence of g a dominant at intertidal stations prior to 1986, A. 3__ indisidual taxa in the intertidal zone were monitored rubricata disappeared from both stations until in several ways. In high, mid and low intertidal quadrats, frequency of occurrence of dominant taxa, recolonization was observed m 1988 at the farneld g station (NAI 1989). Abundances at the farfield 5 including barnacles, snails, mussels, fucoids and station have continued to increase through 1993, but Chondrus crispus, generally rem ained consistent over no recolonization has occurred at the near6 eld both preoperational and operational periods (Tables station since 1986. Temporally patchy abundances 6-7 and 6-13). Some changes during operational of A. rubricata have been typical of the entire study years were observed in fucoid abundances at period, suggesting that highly unpredictable nearfield fixed transect sites (e . g ., increased environmental / climatic processes, and not power dominance by Ascophyllum nodosum, decreased plant impacts, may have produced local extinction abundance of Fucus vesiculosus) However, since A. and subsequent recolonization. g nodosum is reportedly less tolerant of temperature E increases than is F. vesiculosus (Vadas et al.1976; NUSCO 1994), this change is most likely a natural g 6A.2.3 Shallow Subtidal Benthic Community 5 successional shift, and not a power plant impact. Community parameters used to evaluate shallow Destructive sampling allowed more detailed subtidal benthic communities indicated that ,in most monitoring of abundance patterns of selected cases, no changes have occurred that could be related dominant intertidal taxa. More rigorous statistical to power plant operation (Table 6-19). Only a tests (i c., ANOVA) could be applied to these data to significant change in number of faunal taxa was examine difTerences between preoperational and operational periods and among stations. These detected (increase during the operational period at g the nearfield station, no change at the farfield 3 analyses indicated that, of the four taxa studied, only station). Numerical classification of macroalgal and one (the amphipod Ampithoe rubricata) had macrofaunal data revealed no substantive changes in signi6 cant changes in the relationship between species composition and overall community structure . near6cid and farfield stations during the operational at shallow subtidal stations, with clusters determined period (Table 6-20). For all other selected taxa by station and/or depth zone, rather than by (Chondrus crispus, Nucella lapillus and Mytilidae), preoperational and operational periods. significantly lower abundances were recorded dunng the operational period; howeser, this trend occurred Specific analyses on abundances of selected at both near6 eld and farfield stations for all three of important taxa in the shallow subtidal zone these taxa, indicating area-wide shifts unrelated to (ANOVA) revealed consistent relationships between 6-60 E 5
L MARINE MACROBENTHOS o L near6cid and farGeld stations over both macrobenthic communities in closest proximity to preoperational and operational periods (i.e., no the Seabrook Station discharge. However, due to F' impact) for three of six selected taxa (Chondrus their position in the water column relative to the ' thermal plume (depths 9-21 m), temperature effects crispus, Laminaria saccherina and lassa marmorata; Table 6-20). Of the remaining three selected taxa, at these sites are unlikely. Higher sedimentation two exhibited significant preoperational to rates resulting from increased levels of suspended operational period shifts only at the farfield station particles in discharge waters relative to the (Asteriidae decreased during the operational period, surrounding waters could potentially impact nearneld u Mytilidae increased during that period). These deeper water benthic communities. Higher trends may be related; since Asteriidae prey almost sedimentation rates (and impacts to nearby exclusively on mussels (Menge 1979; Sebens 1985), macrobenthic communities) associated with a thermal l reductions of star 6sh at the farGeld site during the effluent have been documented for a nuclear power j operational period may have enhanced the local plant in California (Osman et al.1981; Schroeter et mussel population. Regardless of this possible al.1993), with the major source of turbidity being relationship, this shift was observed only at the fine inorganic sediments transported from inshore farneld station, and therefore, was not attributable to waters where intakes for the plant were located. The power plant operation. organic component of these sediments contributed little to the overall flux of sediments, and no a A signiGeant reduction in abundance of Laminaria indications of organic enrichment were observed at digitata was observed at the nearfield station during sites near the discharge. The Seabrook intake is the operational period, while farfield abundance located well ofTshore and draws in relatively low .. levels remained relatively consistent. This decline at turbidity water, similar to that near the discharge. g the nearfield station actually began prior to power Therefore, transport of Gne inorganic particles is plant start-up (1989). A similar decline in L unlikely and any increase in sedimentation would be digitata abundance was also observed at both mid- the result of settlement of organic material from depth stations (Table 6-6), indicating an area-wide entrained organisms. However, plankton densities shift in abundance likely relat:d to the susceptibility are also lower in deeper offshore waters near the of this species to removal by storms (Kitching 1937), intake structure, compared to those in more such as Hurricane Bob in 1991, and subsequent productive inshore waters, thereby reducing the natural factors affecting the degree of recolonization, likelihood of any organic loading to benthic habitats such as increased abundance of sea urchins noted in near the discharge. recent years in both near6cid and farfield study areas. 6.4.3.2 Mid-Depth Benthic Community 6.4.3 Evaluation of Potential Turbidity All assessments of community parameters and Effects on the Mid-Depth / Deep overall community structure indicated no changes to Benthic Communities the nearfield mid-depth community during Seabrook operational years (Table 6-21). Signincant decreases 6.4.3.1 Backcround in both measures of community abundance (total algal biomass and total faunal density) were ; NearGeld mid-depth and deep study sites represent observed at the mid-depth intake station during the 6-61 { r ___
C TACLE 6 21.
SUMMARY
OF EVALUATION OF POTENTIAL TURBIDITY EFFECTS ON BENTHIC O COMMUNITIES IN THE VICINITY OF SEABROOK STATION. SEABROOK OPERATIONAL REPORT,1993. OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES AREA / DEPTH TO PREVIOUS CONSISTENT WITH COMMUNITY ZONE PARAMETER
- YEARS?' PREVIOUS YEARS?'
Macroalgae Mid-depth No. of taxa Yes Yes Total biomass Op< Preop Discharge, FF; Op= Preop Intake: Op< Preop Community structure Yes Yes Deep No. of axa Yes Yes 3 Total biomass Op< Preop Yes Community structure Yes Yes E Macrofauna Mid-depth No. of taxa Op> Preop Yes Total density Yes Discharge, FF: Op= Preop ' Intake: Op< Preop Community structure Yes Yes Deep No. of taxa Yes Yes Total density Yes Discharge, FF: Op= Preop Intake: Op> Preop g Community structure Yes Yes g
' Abundance, no. of taxa, biomass, and total density evaluated using ANOVA; community structure evaluated using numerical classification by year and station. ' Operational period = 1990-1993 (August only). 'NF = nearfield; FF = farfield.
TABLE 6-22.
SUMMARY
OF EVALUATION OF POTENTIAL TURBIDITY EFFECTS ON I REPRESENTATIVE IMPORTANT BENTHIC TAXA IN THE VICLNITY OF SEABROOK g STATION. SEABROOK OPERATIONAL REPORT,1993. g l OPERATIONAL NEARFIELD-FARFIELD l PERIOD SIMILAR DIFFERENCES AREA /DEPTli TO PREVIOUS CONSISTENT WITil COMMUNITY ZONE SELECTED TAXON YEARS?' PREVIOUS YEARS?' Macroalgae Mid-depth Laminaria digitara Op< Preop Yes Laminarsa saccharina Yes Yes Macrofnuna Mid-depth Pontogencia inermis Yes NF: Op= Preop l FF: Op< Preop Modiolus modiolus Op< Preop Yes Mytilidae Op> Preop NF: Op> Preop FF; Op= Preop l Strongylocentrotus droebachensis Yes Yes
' Conclusions derived from ANOVA or nonparametric analysis for Preoperational versus Operational periods. 'NF = nearfield; FF = farfield.
I 6-62 I w
MARINE MACROBENTHOS L F L cperational years, while consistent levels for both Nearfield abundances of f. inermis were comparable parameters were observed at nearfield and farfield over both periods. Mytilids were significantly more [ sites over the entire study period. We have no explanation for these shifts at the intake station; abundant during the operational period at the nearfield station, while no significant between-period however, because impacts associated with intakes are change was observed at the farfield station. The greatly minimized by locating these structures well high operational mean at the nearfield station is,in above the bottom, we feel these changes were not large part, due to exceptionally high mytilid densities related to power plant operation. Numerical during a single operational year (1993), when classification characterized overall algal and faunal conditions for recruitment at this station were community structure at mid-depth sites, and revealed apparently near-optimal, but unlikely related to high similarity of annual collections within depth power plant operation. zone, and no evidence of separate groupings based on operational and preoperational periods. In other words, no substantive changes in comm unity 6.4.3.3 Deep Benthic Community j composition have occurred at any mid-depth site ! since Seabrook began commercial operation. Measurement of various aspects of deep water macrobenthic communities (numbers of algal and Detailed analyses of selected mid-depth benthic faunal taxa, total algal biomass and total faunal taxa abundance patterns are summarized in Table 6- density) and assessment of overall community
- 22. Four of the six selected taxa showed no structure (through numerical classification) revealed significant changes over the operational period that that nearfield and farfield communities have would indicate a power plant impact. Two of these remained remarkably stable over both preoperational taxa (Laminaria digitata and Modiolus modiolus, and operational periods (Table 6-21). The only often found attached to each other) exhibited arca- significant between-period shift at deep water wide decreases during the operational period, which stations occurred at the intake station, where an may be related to the susceptibility of these species increase in total faunal density was observed during to removal by storms (Kitching 1937; Witman 1987). the operational period. Overall, deep water Another kelp, Laminaria saccharma exhibited macrobenthic communities in the Seabrook area consistent patterns of occurrence over both periods, appear unafTected by power plant operation.
as did the green sea urchin Strongylocentrotus droebachtensis. Record high densities of adult sea urchins were found in both nearfield and farfield 6.4.4 Overall Effect of Seabrook Operation transect areas in 1993, perhaps indicating area-wide on the Local Marine Macrobenthos movement of this w--i- into the Seabrook area. Such mass migrativ seen observed previously These extensive monitoring studies have at the nearby Isles o O ils (Witman 1985) documented that balanced indigenous macrobenthic communities continue to occupy intertidal and Two other species c- Sited significant changes in subtidal rocky habitats in the vicinity of the patterns of abundance C ring the operational period. Seabrook discharge, with little change beyond that A significant decrease in abundance of the amphipod expected from natural variability. While some Pontogencia mermis was detected during the changes have been detected over the operational operational period, but only at the farfield station. penod, most were either part of an arca-wide trend 6-63
a MARINE MACROBENTIIOS E I (occurring at both near6cid and far6 eld stations), sea urchins. Mar. Biol. 34:137 142. part of an historical trend that began prior to commercial operation of Seabrook, or restricted to a Briscoe, C.S., and K.P. Sebens.1988. Omnivory in site (intake) where little potential for impacts exists. Strongylocentrotus dros bachtensis (Muller) g There is no evidence to suggest that thermal impacts predation on (Echinodermata: Echinoidea): 3 or impacts associated with increased organic loading subtidal mussels. J. Exp. Mar. Biol. Ecol.115:1-on the local macrobenthos have occurred since the 24. start-up of Seabrook Stati-i in 1990. Chapman, A.R.O. 1973. A critique of prevailing attitudes towards to control of seaweed zonation on the sea shore. Bot. Mar. 16:80-82.
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i I APPENDIX TABLE 6-1. NOMENCLATURAL AUTHORITIES FOR MACROFAUNAL TAXA CITED IN TH E MARINE MACROBENTIIOS SECTION. SEABROOK l I OPERATIONAL REPORT,1993. l Mollusca I Polyplacophora j Tonicella rubra (Linnaeus 1767) Gastropoda Lacuna vincta (Montagu 1803) Littorina littorea (Linnaeus 1758) Littorina obtusata (Linnaeus 1758) Littorina saxatilis (Olivi 1792) Nucella lapillus (Linnaeus 1758) E Bivalvia Mytilidae Afusculus niger ().E. Gray l824) i Afodiolus modiolus (Linnaeus 1758) Anomia sp. Turtonia minuta (Fabricius 1780) Hiatella sp. Annelida Polychaeta Thelepus cincinnatus (Fabricius 1780) $ I Oligochaeta Arthropoda Pantopoda I Achelia spinosa (Stimpson 1853) Crustacea Balanus sp. Balanus crenatus Bruguiere 1789 Idotea balthica (Pallas 1772) Idotea phosphorea Hatger 1873 I Jaera marina (Fabricius 1780) Ampithoe rubricata (Montagu 1808) I Gammarus oceanicus Segerstrale 1947 Jassa marmorata (Holme 1903) Pontagencia inermis Kroyer 1842 Caprella sp. Caprella septentrionalis Kroyer 1838 Echinodermata Echiniodea Strongylocentrotus droebachtensis (Maller 1776) I Stelleriodea Asteridae i 6-69 I
I APPENDIX TABLE 6-2. THE OCCURRENCE OF MACR 3 ALGAE FROM TRIANNUAL GENERAL COLLECTIONS AND DESTRUCTIVE SAMPLING AT ALL SUBT!DAL AND INTERT!DAL DESTRUCTIVE STATIONS, 1978-1993. " SEA 3R00K OPERATIONAL RF' ORT, 1993. CHLOROPHYTA l SPECIES l 1978 j 197911980 l 1981 l 198'* ; 1983 j 19E4 ! 1985 l 1986 l 1987 l 1988 l 1989 ( 1990 l 1991 l 1992 l 1993 ' ) j.....................................................+....+....+....+....+....+.........+....+.........+....+..............,,,,,,,,,, lBLIDINGIA MINIMA (Naeg. ex Keutz.) Kylin l X' l X !X X Xl X Xj X f e j lBRYOPSIS PLUMOSA (Hudson) Agardh l l l lX l [ j X X l lCHAETOMORPHA BRACHYGONA Harvey l X l l X Xj X Xj X X X X X X* X X lCHAETOMORPHA LINUM (0.F. Muell.) Kuetz. l X XlX X, X Xl X X j X X X , X X Xl X X i X X X Xt X X X Xj X X X ? X X X X X' lCHAETOMORPHA MELAGONIUM (F. Weber et Mohr) Kuetz. lCHAETOMORPHA PICQUOTIANA Mont. en Kuetz. ) X X{i X X X X X Xj X , X X , X X X X X lCHAETOMORPHA SP. , X XlX X X i X X XlX X X X X X, X Y_ i l 'CLADOPHORA REFRACTA (Roth) Kuetz. .l l l y' , .; ; l lCLADOPHORA SERICEA (Hudson) Kuetz. X Xl' X X X X X XlX X X X X X j X' A IENTEROMORPHA COMPRESSA (L.) Grev. l X g g jENTER0MORPHA INTESTINAL!S (L.) Link X X X X X 2 i ,
'ENTEROMORPHA LINZA (L.) J. Agardh X X X X X X X i g l ;
X
- m ENTEROMORPHA PROLIFERA (0.F. Muell.) J. Agar @ X X X X , X X j Xj '
, X X X Xj X j j i .
i 4 C ENTEROMORPHA SP. , j X X X Xl X ; i ; l
.lMONOSTROMA FUSCUM (Postels et Rupr.) [
X X l X X X X X X X X X' X Xi I x; lMONOSTROMA GREVILLEI (Thuret) Wittr. X X Xl X X X X X X X X X k ; X; X! lMONOSTROMA PULCHRUM Farlow lMONOSTROMA SP. l t X I X , g ; j lPSEUDENDOCLONIUM SUBMARINUA Witte lRHIZOCLONIUM TORTUOSUM (Dillwyn) Kuetz. X X X X X X , X X X' X X X , X Xj T ' kl ISPONGOMORPHA ARCTA (Oillwyn) Kuetz. l X X l X X XlX jk X yi g . l X l 1 l l ;'SPONGOMORPHA SP. l lSPONGOMORPHA SPINESCENS Kuetz. j X l X X X X X X X Xl XlA X XfX X lULOTHRIX FLACCA (Dittwyn) Thuret l X , X l' l i lULOTHRIX SP. l X jutvA LACTuCA L. lX X x, x X X , X x X X X x X X X X lULVARIA OBSCURA V. BLYTTI! (Aresch.) B!iding X X X X X XlX X X X X X X X X lULVARIA OXYSPERMA (Kuetz.) Bliding X X X X ! X lUROSPORA PENICILLIFORMIS (Roth) Aresch. l l l Xl X lX X' X lUROSPORA W(PMSKJOLDll (Mert.) Rosenv. l l l Xl i j j
" Stations B1MLW, M1MSL (general collection only), B17, B19, B31 samled 1979-1993; B5MLW, B5MSL (general collection only), 835 sampled 1982-1995; B16 sampled 1980-1984 and 1986-1993; B13, 804 sampled 1978-1984 and 1986-1993; I B34 sampled 1979-1984 and 1986-1993.
Stations 804, B13, B16, B34 sa mled in August only. O M M M M M M m. W W W :M e emm 33
.mm m . . ~ ~- ~ .
r- r--m . 9 APPENDIX TABLE 6-2. THE OCCURRENCE OF MACROALGAE FRCh GENERAL COLLECTIONS ANo oESTRuCTIVE SAMPLING AT ' ALL SuBTIDAL AND INTERTIoAL DESTRUCTIVE STATIONS. 1978-1993. SEAsROOK OPERATIONAL REPORT, 1993. PHAEOPMTTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , , , , , _ , , , _ , J l 1978 l 1979 ; 1980 j 1981 l 1982 ! 1983 j 1984 l SPECIES
- ........................................................................................11985(1986l1987[1988l1989;1990j1991l199211993j ..........................,............,,,,!
'AGARUM CRI8ROSUM (Mert.) Bory j xi X Xl xj x!xj x; xf xj x' x*-x*
fALARIAEsculENTA(L.)Grenvilte j x[ x , x* xl x, xj Xl x xl x x '! .xl x j xj xj xfxfxlxl x
; xtx; x xj xj x; xl x x x x; x; x' ,
SCOPHitttm N000 sum (L.) teJotis lCHORDARIA FLAGELLIFORMis (Muell.) Agard l xl xl x , x xj xj j xg, x*f glg xlg g;g gy gg xg *I l 10ESMARESTIA ACuLEATA (L.) Lamourous xj x' x, x xl xj x!xj.xj xi x!Lxl xj xl xf x' l joESMAREST A viRiots (Muett.) Lamouroux xl x , ; x ; xl xl xj xl x; x: xl x .xl x x; x , x xi x l'
- x x x!x*
- tCT0 CARPUS FASCICutAtuS Harvey x x x x x;
x- x xlx;t x; x i- k: x ; x; x x' xI-ltCTOCARPuS SiticutcSuS (oittwyn) tyngbye e lECTOCARPuS SP. l , l g a gggy , g g
;ELACntSTA FuCrCola (vetter) Aresch. x x x1x x x l h; x; xl x; x; x:.x, x ! x-l x;
; x x; x; i x' ; '
i xl x* x' puCuS otsfiCHus SSP. o ST:CHus-lFutuS 0iSTICHuS S$P. EDENTATuS (Sach. Pyt.) Powet t l x xl x' x xf x{ x xj.xf'xj xf.xl-x x x '! xx ' x! 1-puCuS o STICHuS SSP. EVANESCENS Agar & l X x x x. Xl xl x l A jxl-xl 'xi j x , x x x 1 l xl x xl xl xi x j .x x j. p l fucus SP. L x; x, xj x x; x x-xi x x x; xt x: x* x* ~ a fucus vEsiCutOSuS t. fucus VES!Cul0 sus V. SPIRALIS L. l l l ll l x x x! l l l t l j-x*
- e lx e i le.
i LGIFFORDIA GRANul0SA (Sm.) Hamet
;ISTHMOPLEA SPHAEROPHORA (Carm. em Harv.) Kjelt. I l l l f fxfx f
' LAMINARIA DIGITATA (Hudson) Lamourous xi x x' xl x x x!xl x xl xl xl x[ xl xl'x
., LAMINARIA SACCHARINA L. Lamouroux x x x xj x x xl xj xf xj xl xj xj xl x'x i LAMINARIA SP.
x l x xl l Xl l xl j j j j
- j .j j jgg LAMINARIOCOLAx TOMENTOSOIDES (Fartow) Kylin f l ll l l j x j x! x x x xj X LLEATHESIA oIFFORMIS-(L.) Aresch.
lPETALONIA FASCIA (Muell.) O. Kuntre l x l x x ' ' x x , x! x
' x f x! xl xl xjx xl j- x *x!xl!-x j x 5 PET ALONIA ZOSTERIFOLIA (Reinke) O. Kuntze j , ,
f l l g e x; } f
- e ! !
LPETRODERMA MACutlFORME (Wottny) Kuck. l 1 , , ' JPILATELLA LITTORALis Kjettman j x x x , x xl x' X! x' x, 4 x xl* x x!x!! l l 8 x l jPSEUDOLITH00ERMA ExTENSUM (P.Crou et H.Crou.) S.Lundl i , I lSACCORMIZA oERMATODEA (8ach. Pyt.) J. Agard I x , f xl j j j f j 5 l j$Cvf0$tPHON LomENTARIA (Lyngbye) Link x; x' xl x; xl-x, xl x l x; x!x xl x x .x f l l l Xl l ; ;
- e e
;SORAPION KJELLMANNI (Witte) Rosensv.
l$PHACELARIA CIRROSA (Roth) Agar & x f' xl x xl xl x' x' j xl f x ! ,; g -f l xl x l .x j j xl ' l l l
- j. ';
l: L LSPHACELARIA PLUMOSA Lyngbye
- .SPHACELAR A RAo CANS (otitwyn) Agard , u x; x; x ; l- ; ; g lSPONG0NtMA TOMENTOSuM ruetzing ; ; l x q x l x; x; x; x; x;
, j x; x; xj x: x;
*name in question
. . l . , _. . . .. . t . y . .
APPENDIX TABLE 6-2. THE OCCURRENCE OF MACROALGAE FROM GENERAL COILECTIONS AND DESTRUCYlvE SAMPLING AT ALL SUSTIDAL AND INTERTIDAL DESTRUCTIVE STATIONS, 1978-1993. SEABRJ0X OPERATIONAL REPORT, 1993. PMODOPNYTA l SPECIES l1978l1979l1980 j . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......... . . . . . . ...... . ..........,....
. . . . . . . . . .!....,....1981 l 1982 l 1953 l 1984,,,j 1985 l 1986 l 1937 ! 198 lACROCHAETIUM FLEXUOSUM* l l l l X l Xl X l" ; l. j j g i jACROCNAETIUM SP. j X l X l l X l l l l g g lAHWFELTIA PLICATA (Hudson) Fries l X j X j Xl X; Xl X l X X XlX Xl X X Xl Xl X lANTITHAMMIONELLA FLOCCOSA (Muell.) Whitt. l X ! Xl X l X Xj X j X X L X , X X Xj X Xl Xj X lAUDOUINELLA DAVIEsti (Dittwyn) Weelk. l j j l l l , j j x; ;
lAUDOUINELLA MEMBRANACEA (Magnus) Papenf. j j j j j l ! l l X' X lX lAUDOUINELLA PURPU'EA (Lightf.) Woelk. l l l l' l j X X l lAUDOUINELLA SP. l l 1 l l f X l BANGlA ATROPURPUREA (Roth) Agar @ l l , l X l X a j g x BONNEMAISONIA HAMIFERA Harlot l X j X X' j j Xl X X X X1 X fX lCALLITHAMNION SP. l l X f -l g ] X Xl X XLM jtALLITHAMMION TETRAGONUM (With.) 5.F. Gray l X X X X X X X M X X, X lCALLOPHYLLIS CRISTATA (Agardh) Xuetz. X X X ' X X X XlX X X , Xj X X X X , X ch jCERAMIUM DESLONGCHAMPIl Chauvin ; Xl X j j L U lCERAM!UM RUBRUM (Hucison) Agardh LM X X X Xj X Xl X X Xl X X X X X X ! N lCERATOCOLAX HARTZ!! Rosenv. XlX X X Xj X Xl X' X , lCHONDRIA BAILEYANA (Mont.) Harvey X ~, j '
; I l lCHONDRUS CRISPUS Stackhouse l XlX X X X X X Xl X u X Xl X X X X ! X !
lCHOREOCOLAX POLYSIPHONIAE Reinsch l X X X lX X XlX X X I lCLATHROMORPHUM CIRCUMSCRIPTUM (Stroemf.) Fostie XlXl X X y X X Xj X X Xj Xll Xy X' X X lCLATHROMORPNUM CCEPACTUM (Xjettm.) Fostie l l X j l j Xj j ! X , lCOLACOhEMA SECUNDATA* XlX j X j j i 1 , , I lCORALLINA 0FFICINALIS L. XlX , X X Xj X X XlX X X X X X ! X ! X lCYSTOCLONIUM PURPUREUM (Hudson) Batters j Xl X j X X l Xl X X Xl X l Xj X X X, X X ! X ! lDERMATOLITHON PUSTULATUM (Lamour.) Fostie l Xl X l X X X X X Xl X Xj X X Xj X X ! X ! lDEVALERAEA RAMENTACEUM (L.) Guiry l l l X X Xl Xl X ! lDuMONTIA CONTORTA (S. Gmelin) Rupr. l l l , x X X Xj X XlX X , X X X'! X lERYTHROTRICHIA CARhEA (Dittwyn) Agardh j X ' Xl l Xi X l ; j i lFIMBRIFOLIUM DICHOTOMUM (Lepechin) G. Hansen l X , X l Xl X X1X X Xl X ., X' X Xl X, X X X lFOSLIELLA FARINOSA (Lamour.) Howe j X ' l 1 j '
;FOSLIELLA LEJOLISil* ! X ,
X XfX lX X X X XlX x lGIGARTINALES I Xl 4 l , s d lGLOIOSIPHONIA CAPILLARIS (Hudson) Carmich. ex Berk. l l X X 4 j j j ( I l lX l lGYMNOGONGRUS CRENULATUS (Turner) J. Agardh X X Xj X Xj X X Xl X 'X X X X lHILDENBRANDI A RUBRA (Sorrnerf.) Mengh l X l X Xl X Xl X ! ! lLEPTOPHYTUM F0ECUNDUM (Xiettman) Adey I X l X X Xl X X X Xj j X X X lLEPTOPHYTUM LAEVE (Stroemf.) Adey lLEPTOPHYTUM SP. l X' X l X X Xl X l 1 X X, l X X j Xg x l t x xlXx X ' x ltITHOPHYLLUM CORALLINAE (Crouan f rat.) Heydr. lX , l Xl l l l l I lLITHOTHAMNION GLACIALE Kjeltman l X X ' Xl X Xj Xl X , X' X Xlx xl xlxl X l lMASTOCARPUS STELLATUS (Stack.) Guiry lX lX X X Xl X XlX Xl Xj X J Xj X , X l X XlXlX " Xl Xj Xj X xl x; y Xj Xl X l X l X lX x x lMEMBRAN0PTERA ALATA (Hudson) Stackhouse ,
*name in question (continued) muu inut aus uns en aus uma num uma sur em mas an e aus um og aus ea t
M M M M M'W W W W M: M M M Mm M W W $ APPENDIX TABLE 6-2. (Continued) RitCX)CPHY T A l SPECIES l1978l1979l1980j1981 l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................................................
. . . . . . . . . '. . . . . . . . + . . . . +. . . .11982 ! 1983 l 1984 l 1985 l 1986 LPALMARIA PALMATA (L.) O. Kuntre l Xl X l X l Xf Xl X X X l X l Xl X l X' Xl Xj Xl X PEYSSONNELIA ROSENV!NGI! Schmitt l X' Xj X X X' X X Xl Xl X Xl X j jX; i
,PHYCODRYS RUBENS (L.) Batters j X Xl X ,
X X X , X Xl X l X 'X X X XlX X lPHYLLOPHORA PSEUDOCERANO! DES (S. Gnelin) Newr. ] X Xl X g X! X Xj X X X' X X X X X X X lPHYLLOPHORA SP. lX Xl Xl X ' X' Xl X X , X X X X' X X X X, jPHYLLOPHCRA TRAILLII Holmes ex Batters. l l i l , X X l lPHYLLOPHORA TRUNCATA (Pallas) A. Zin. lX X' X, X Xl X l Xj X X X X X X X , X X lPHYMATOttTHON LAEVIGATUM (Fostle) Fostie l X X Xj X X X X Xl X X X Xj X lPHYMATOLITHON LENORMAN0!! (Aresch.) Adey lX , X X X X j X X X X X X X X X j X lPHYMATOLITHON RUGULOSUM Adey lX X Xl X X i X X X Xl X j i. X Xj X X X X X ll X j lPLUMARIA ELEGANS (Bonhem.) Schmitz i , jPOLYIDES ROTUNDUS (Hudson) Greville XlX
- XlX X X X i X X X X X l Xl X X X' lPOLYSIPHONIA DENUDATA (Dillwyn) Grev. ex Harvey l l l X .g e e jPOLYSIPHONIA FLEXICAULIS (Harvey) F. Collins X X X l Xj X X X ,X Xj X X X j X X X y lPOLYSIPHONIA HAPVEYI J. Bailey j j X X ,
X ; X Xt X X lX W XlX X X X X X X X X X X X X X lPOLYSIPHONIA LANOSA (L.) Tandy X lPOLYSIPHONIA NIGRA (Hudson) Batters X X X X X X t X X X X X X X X j X X X X X X X X X X lPOLYSIPHONIA N!GRESCENS O & n) Grev. i j jPOLYSIPHONtA SP. l X , lPOLYSIPHONIA URCEOLATA (Lightf. ex Dillwyn) Grev. l X Xj X X Xj Xl X X X X X X, X X X X lPORPHYRA LEUCOSTICiA Thuret ! X j X X Xl Xj X X X ,'X , X X X X X X lPORPHYRA LINEARIS Greville j '
! l X lPORPHYRA MINIATA (Agardh) Agardh lX X X l X Xl X l X X X X X X X X X X lPORPHYRA SP. l l l X' X X l X X lPORPHYEA UMBILICALIS (L.) J. Agerdh l X X X X X j X X X X X X X X X X X lPTILOTA SERRATA Keutzing j X X XlX Xl X X X X l X X X X X X X lRH0DOMELA CONFERVOIDES (Hudson) Silva j X X Xj X X j X X X X X X , X l X X X X lRHODOPHYSEMA ELEGANS (P. Cruan et H. Cruan) P. Dixon j X l Xl X X Xll X j e i lSCAGEllA CORALLINA (Rupe.) Hansen* l X X X j X Xl X X l X X X X o Xl X X X X lTURNERELLA PENNY! IHarvey) Schmitz l X j X l i j j j g g
*name in question 4
l _A
I I TABLE OF CONTENTS i PAGE , B g 7.0 SURFACE PANELS
- m 7-ii
SUMMARY
. .. . 7-iii LIST OF FIGURES
.. 7-iv LIST OF TABLES . .. . . . .
7-1
7.1 INTRODUCTION
f 7-1 7.2 METilODS . ... . . . . .. . l 7-1 7.2.1 Field Methods . . 7-1 7.2.2 Laboratory Methods .. 7-3 l 7.2.3 Analytical Methods . I 7-3 7.3 RESULTS .... . Short-Term Panels .... 7-3 l 7.3.1 .. . Monthly Sequential Panels 7-12 7.3.2 . . l3 . . . . 7-17 j 7.3.3 One Year Panels . .. . . 7-18 7.4 DISCUSSION . . 7-20
7.5 REFERENCES
CITED . . . I I I I I I I 7.i I
- -- E
O E I
SUMMARY
The fouling community settling and developing on surface panels has shown predictable seasonal patterns throughout the study. Most measures of community structure (biomass, abundance, number of taxa) and abundances and frequencies of individual taxa showed significant differences among years, a reflection of year to year variability in recruitment. Measures that indicate fouling community settlement (on panels exposed for one month) and g development (on panels exposed for increasing time periods,1 -12 months) show ed signi0 cant difTerences between g preoperational and operational periods that were consistent between nearfield and farfield stations, suggesting area wide trends. Some parameters measured on the year end fouling community (panels exposed for one year) indicated changes during the operational period that were not consistent between nearfield and farfield areas. E 5 This observation is complicated by the weather-related loss of panels at the nearfield station in 1992, reducing the number of observations during the operational period. These parameters w ill continue to be monitored closely. l l 5 E I I I I I I I I,, Ii
)
I 7-ii I R wq l
L I L F LIST OF FIGURES ? L PAGE r l 7-1. Surface panel sampling stations . .
. 7-2 72 Monthly faunal richness (number of faunal taxa on two replicate panels), abundance, and biomass on short-term panels at nearfield Stations B19 and B04. The operational period (1991-1993) and 1993 compared to the means and 95% confidence limits during the preoperational period (1978-1984 and July 1986-December 1989) . .. . . . . .. . 7-8 7-3. Log abundance (no. per panel) of Mytilidae, and monthly mean percent frequency ofJassa marmorata, -
and Tubularia sp. on short-term panels at Stations B 19 and B04. The operational period (199 l- 1993) and compared to the mean abundance or percent frequency and 95% confidence limits during the L preoperational period (19811984 and July 1986-December 1989) . . . . 7-10 - 7-4. A comparison of the Log (x+ 1) abundance of Mytilidae on short-term panels at the nearfield/farfield middepth station pair (B 19/B31) during the preoperational (1978-1984,1986-1989) and operational (1991-1993) periods when the interaction term (Preop-op X Station) of the ANOVA model was rignificant (Table 7-2) .
.. . 7 11 7-5. Mean biomass (g/ panel) and Mytilidae spat (percent frequency ofoccurrence) during the operational period (1991 1993) and in 1993 compared to mean and 95% confidence limits during the preoperational f period (Stations B19 and B04 from 1978-1984 and July-December 1986-1989) on monthly sequential 7-13 panels . . .
7-6. Monthly mean percent frequency of occurrence on monthly sequential panels for Jassa marmorata. Balanus sp., and Tubularia sp. at Stations B19 and B04 during the operational period (1991-1993) and in 1993, compared to mean and 95% confidence limits during the preoperational period (1982-1984 and July 1986-December 1989) .
.. 7-16
[ m 7-iii
~~ - - - - - - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
a 0' I LIST OF TABLES Il 1 PAGE 7-1. MEANS (PER PANEL) AND COEFFICIENT OF VARIATION (%) FOR SELEC'ED PARAMETERS AND SPECIES ABUNDANCES AT STATIONS B19, B31, 804, AND B34 OVER THE . FREOPERATIONAL AND OPERATIONAL PERIODS (1991-1993), AND 1993 MEANS 74 7 2. RESULTS OF ANALYSIS OF VARIANCE COMPARING MONTHLY TOTAL NUMBER OF El TAXA, NONCOLONIAL FAUNAL ABUNDANCE, TOTAL BIOMASS. AND SELECTED SPECIES 5 ABUNDANCE OR PERCENT FREQUENCY ON SHORT TERM PANELS AT MID-DEPTH (B19, B31) AND DEEP (B04, B34) STATION PAIRS DURING PREOPERATIONAL (19781989) 7-5 AND OPERATIONAL (1991-1993) PERIODS . . . . 7-3. ANOVA RESULTS COMPARING MONTHLY SEQUENTIAL PANEL BIOMASS AT MID-DEI 411 (B19, B31) AND DEEP (B04, B34) STATION PAIRS DURING PREOPERATIONAL (1978-1989) l AND OPERATIONAL (1991-1993) PERIODS . . . . .. .. . 7-14 5 7-4. NEARFIELD/FARFIELD COMPARISON OF ANNUAL MEAN AND STANDARD DEVIATION g OF JASSA MARAf0 RATA AND MYTILIDAE SPAT LENGTHS (mm) FROM MONTHLY g
........ 7-15 SEQUENTIAL PANELS COLLECTED IN 1993 . .. . .
7 5. DRY WE!GHT BIOMASS, NONCOLONIAL NUMBER OF TAXA, ABUNDANCE, AND LAMINARbf SP. COUNTS ON SURFACE FOULING PANELS SUBMERGED FOR ONE YEAR AT STATIONS B19, B31 B04, AND B34. MEAN AND STANDARD DEVIATION FOR THE PREOPERATIONAL PERIOD (1982-1984 AND 1986-1989) AND MEAN FOR 1993 AND THE OPERATIONAL PERIOD (1991-1993) . ... . . .. . 7-17 7-6. SUMM,sRY OF EVALUATION OF DISCHARGE PLUME EFFECTS ON THE FOULING COMMUNITY IN VICINITY OF SEABROOK STATION . . . 7-19 3 l I I I I 7-iv I 3 m
L-L SURFACE PANELS 7.0 SURFACE PANELS panel were collected monthly at each of the four stations. In December, an additional MS panel was [
7.1 INTRODUCTION
collected at each station. r The surface fouling panels program was designed to study both settlement pattems and community devel- 7.2.2 I.ahoratorv Methods opment in the discharge plume area and in correspond-l ing farfield areas. The program is based on the In the laboratory, each panel was dismantled and hypothesis that the balanced indigenous fouling the panel face photographed. The fouling material was community should not be adversely in6uenced due scraped off the wood block and panel support apparatus. and rinsed over a 0.25 mm mesh sieve prior to storage - to exposure to the thermal plume. Short-term panels, submerged for one month, provide information on the or processing. The wood blocks from all MS panels were dried, split, and examined for the presence of [ temporal sequence of settlement activity, while monthly wood-boring organisms. L sequential panels, exposed from one to twelve months, provide information on species growth and pattems of community development. All noncolonial species collected monthly on both f ST replicates and one December MS replicate were identi6ed and enumerated. When high abundances 7.2 METIIODS of Mytilidae. Hiatella sp. and Anomia sp. occurred, organisms were enumerated from subsamples generated 7.2.1 Field Methods using a Folsom plankton splitter (NAl 1990). Colonial animals, diatoms and macroalgae on ST panels were Fouling panels (10.2 cm x 10.2 cm roughened plexi- quantined by determining the percent frequency of glass plates) were collected monthly from January occurrence on the panel face (Mueller-Doinbois and through December at two mid-depth stations (near6 eld Elk nberg 1974; Rastetter and Cooke 1979; N Al 1990). L Co,onial animals, diatoms, and macroalgal species were B19, depth 12.2 m and far6 eld B31, depth 9.4 m) and two deep stations (near6 eld B04, depth 18.9 m and re :orded as P"(present, but not quantified) w hen found p L farfield B34, depth 21 m; Figure 7-1). The designations in the sample, but not directly on the panel face. For mid-depth and deep stations are based on the surface MS panels, the percent frequency of occurrence of to bottom depth in relation to more shallow stations selected dominants (colonial and noncolonial), and F sampled for other programs in this study (i.e., benthos, diatom and macroalgal species were estimated using macroalgae). Panel depths below the water surface the procedure cited above. Counts were estima,ed for ranged from 3 to 6 m depending on the tidal stage. noncolonial species and an abundance class was record-Collections were made at Stations B04, B19 and B31 ed. Abundance classes, assigned I through 5, consist from 1978 to 1984, at Station B34 from 1982 to 1984, of ranges of numbers ofindividuals (1 -10, I l-100, , and at all stations (804, B19,83 I and B34) from July > 10,000). Colonial and noncolonial dominants, diatoms, 1986 through 1993. and macroalgae were recorded as "P"(present, but not quanti 6ed) w hen found in the sample, but not directly Two different panel types were employed at each on the panel face. station: short-term (ST) panels. exposed for one month, and monthly sequential (MS) panels, exposed for Random samples of 2200 Mytilidae and 2 l 00 Jassa p increasing time periods from 1-12 months. Two marmorata Holmes 1903 individuals found on MS L replicate short-term panels and one monthly sequential panels and in the residue were measured and recorded 7-1
E , 5 RYE LEDGE N . J l Ll77 - FARhlELD AREA . I BOARS , HEAD 0 .5 1 Nautical Mlle 0 1 2 Kilometers SCALE ERS l j h GREAT BOARS l l ' HEAD HAMPTON ,, l BEACH BROWNS RIVER
. NEARFIELD
+** Intake AREA '
f OUTER $ G SEABROOK . ~ 1" STATION ..
- Discharge' SEABROOK SUNK HARBOR ROCKS
\ SEABROOK __
% BEACH
{ N / 4
'N / lI SAtiSBURr BEACH
/.
l I LEGEND I o = _ tace p_1, E Figure 7-1. Surface panel sampling stations. Seabrook Operauonal Report.1993. 7-2 5i m
s SURFACE PANELS ~ l in 0.1 mm increments (NAl 1990). AllJ. marmorata t Test l and Mytilidae individuals less than 1.0 mm were recorded as <l.0 mm and estimated at 0.5 m n in Community development was also assessed by calculations of mean lengths. examining biomass, species richness, and abundance on surface panels exposed for one year. A comparison Dry-weight biomass frcts one of each pair of ST was made between preoperational(generally 1982-1984 replicates and all MS panels was determined after and 1986-1989) and operational (1991-1993) periods taxonomic processing by drying all faunal and floral at each station using paired t tests (SAS 1985). Selected l material to a constant weight at 105 C. dominant species (Mytilidae and Jassa marmorata) lengths were also compared using paired I tests to determine if average annual lengths varied between L 7.2.3 Analytical Methods nearfield and far6 eld station pairs in 1993. F L Analysis of Variance 7.3 RESULTS F Recruitment on ST panels, measured by the number of all taxa, the abundance of noncolonial organisms, 7.3.1 Short-Term Panels and biomass, indicated the potential for fouling commu-nity development. Monthly biomass levels on MS Short-term panels provided information on the sea-panels give an indication of observed community devel-}}