ML20138F500
| ML20138F500 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 12/31/1995 |
| From: | NORMANDEAU ASSOCIATES, INC. |
| To: | |
| Shared Package | |
| ML20138F373 | List: |
| References | |
| NUDOCS 9705050415 | |
| Download: ML20138F500 (300) | |
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4 O SEABROOK STATION 1995 ENVIRONMENTAL STUDIES IN THE HAMPTON-SEABROOK AREA A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS DURING THE OPERATION OF SEABROOK STATION
- Prepared for f
- NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station l Seabrook,New Hampshire 03874
- Prepared by NORMANDEAU ASSOCIATES 25 Nashua Road Bedford,New Hampshire 03310-5500 O
b Critical reviews of this report were provided by: THE SEABROOK STATION ECOLOGICAL ADVISORY COMMITTEE: I Dr. John Tietjen, Chairman (City University of New York) Dr. W. Huntting Howell (University of New Hampshire) Dr. Bernard McAlice (University of Maine) Dr. Saul Saila (emeritus, University of Rhode Island) Dr. Robert Wilce (emeritus, University of Massachusetts) NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services ; Aquatic Services Branch Waterford, Connecticut 06385-0128 August 1996 O Printed at Seabrook Station i
1 f TABLE OF CONTENTS 1
- SECTION 1.0 - EXECUTIVE
SUMMARY
l SECTION 2.0 - WATER QUALITY i ! SECTION 3.0 - PHYTOPLANKTON 1 SECTION 4.0 - ZOOPLANKTON SECTION 5.0 - FISH SECTION 6.0 - MARINE MACROBENTHOS O SECTION 7.0 - SURFACE PANELS SECTION 8.0 - EPIBENTHIC CRUSTACEA SECTION 9.0 SOFT-SHELL CLAM (MYA ARENARIA) O
1 1.0 EXECUTIVE
SUMMARY
l l g TABLE OF CONTENTS v
- PAGE I i
- 1.0 EXECUTIVE
SUMMARY
1 r s I l LIST OF FIGURES . . . . . . . . . . . . . . ........ ....................... . . . . ii LIST OF TABLES . . . . . . . . . . . . . . . ........ ........ ........... .. . . . . . . ii 1.1 APPROACH ....... .... .. ..... ,,,,,,,,,,,,,,,,,,,,,,,, y ; i 1.2 STUDY PERIODS . . . . . . . ........ ........................,,,,,, 4 i j 1.3
SUMMARY
OF FINDINGS ... ... .... ... .......... .. ... 5 t 4 i 1.4 LITERATURE CITED . . . . . . . ..... ...... . ..... ......... .... 16 1
- I i
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l 1.0 EXECUTIVE
SUMMARY
LIST OF FIGURES PAGE 1-1. Sequence of events for determining if there are environmental changes due to the operation of Seabrook Station. . . . . . . . . .. ....... .. . .... .... 2 1-2. Average Daily Power Level at Seabrook Station during 1995. ... .. .. . .... 6 LIST OF TABLES 1-1. Summary of Biological Communities and Taxa Monitored for Each Potential Impact Type. Seabrook Operational Report,1995. . . . . . . . . . . ... ... ..... .... .. 3 1-2. Monthly Characteristics of Seabrook Station Operation for the Period 1990 Through 1995. 0 Seabrook Onerational Report,1995 . . . . . .. ..... ......... ......... . 6 1 0 1-il
1.0 EXECUTIVE
SUMMARY
~
i ( 1.1 APPROACH C} (Padmanabhan and Hecker 1991). Because ofits mid-water location, temperature differences do not Environmental monitoring studies were conducted extend below the thermocline. Due to its location to determine whether Seabrook Station, which within the water column, the intake is also ex- l became operational in August of 1990, had an pected to have only a localized effect. This is effect on the " Balanced Indigenous Populations of characterized by the entrainment and impingement Fish, Shellfish and Wildlife" in the nearfield sampling programs. coastal waters of New Hampshire. A biological monitoring program established under the National A basic assumption in the monitoring program is Pollutant Discharge Elimination System (NPDES) that there are two major sources of narral-occur-permit, jointly issued by the Environmental Protec- ring variability: (1) that which occurs among tion Agency and the state of New Hampshire, different areas or stations, i.e., spatial, and (2) that forms the framework for study. which varies in time, from daily to weekly, monthly or annually, i.e., temporal. In the experi-A systematic approach of impact assessment was mental design and analysis, the Seabrook Environ-used to determine whether the operation of Sea- mental program has focused on the major source brook Station has affected the aquatic biota. This of variability in each community type and then approach incorporated both temporal and spatial determined the magnitude of variability in each components for each biological community evalu- community. The frequency and spatial distribution ated (Figure 1-1). Potential operational effects of the sampling effort were determined based on could be ruled out if: (1) results from the opera- the greatest sources of variability for each parame-tional period were similar to previous ter (NAI 1991). (preoperational) years, given the natural variability in the system, or (2) differences within the opera- Biological variability was measured on two levels: tional period were observed in both nearfield and species and community (Table 1-1). A species' farfield areas. In addition, other potential sources abundance, recruitment, size and growth are of change have been investigated before the con- important for understanding operational impact, if clusiont specified within this report were drawn, any, should changes occur in these parameters 4 This study design was nodeled after objectives between stations or over time. These parameters discussed by Green (1979), which have been were monitored for selected species from each described previously in more detail (NAI 1991). community type. Selected species were chosen for more intensive study based on either their commer-The validity of the impact assessment model is cial or numerical importance, sensitivity to temper-based on comparisons between nearfield stations ature, potential as a nuisance organism, or habitat within the influence of Seabrook Station and at preference. Overall community structure of the farfield stations beyond its influence. Modeling biota, e.g., the number and type of species, total studies, as well as operational validation, clearly abundance and the dominance structure, was also indicate this to be true for thermal effects in rela- reviewed to determine potential plant impact. tion to the thermal plume. The extent of a +3 F Trends in these parameters were reviewed against p V (1.7'C) isotherm has been shown to cover a the natural variation in community structure. relatively small 32-acre surface area 1-1
l SEQUENCE OF EVENTS FOR DETERMINING IF THERE ARE ENVIRONMENTAL CHANGES DUE TO OPERATION OF SEABROOK STATION is Operational Period 1
'similar to YES No impact l previous years j at nearfield station
?
NO Operational Period nearfield YES p No similar to impact farfield 7 NO O Observed changes related to NO p No plant impact operation
?
YES Y Operational Impact l l Figure 1-1. Sequence of events for determining if there are environmental changes due to the operation of Seabrook Station. Seabrook Operational Report,1995. 1-2
1.0 EXECUTIVE
SUMMARY
f') Table 1-1. Summary of Biological Communities and Taxa Monitored for Each Potential Impact Type. Seabrook Operational Report,1995. Level Monitored Selected Monitoring Species / Area Impact Type Sample Type Community Parameters Intake Entrainment Microzooplankton x x
- Macrozooplankton x x Fish eggs x Fish larvae x x Soft-shell clam larvae x x Cancer crab larvae x x
- ' Impingement Juvenile / Adult fish x x I Mter Mults x
, Discharge Thermal Plume Nearshore water quality x Phytoplankton x x Lobster larvae x Intertidal / shallow subtidal macroalgae and macrofauna x x Subsurface fM.ing Communit'y x x p)
(# Turbidity (Detrital Rain) Mid-depth /ceep macrofauna and 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 A previous Summary Report (NAl 1977) con- A community or species within the study area cluded that the balanced indigenous community in might be affected by mcre than one aspect of the q the Seabrook study area should not be adversely CWS. Results from this monitoring program will , influenced by loss of individuals due to entrapment be discussed in light of that aspect of the cooling in the Circulating Water System (CWS), exposure water system that has the greatest potential for J to the thermal plume, or exposure to incremsl affecting that particular component of the biologi-particulate material (dead organisms) settling from cal community. Entrainment and impingement are the discharge. The current study continues to addressed through in-plant monitoring of the focus on the likely sources of potential influence organisms entrapped in the CWS. from plant operation, and the sensitivity of a
/7 community or parameter to that influence within The effects on me balanced indigenous populations i U the framework of natural variability (Table 1-1). of aquatic biota in ticinity of the CWS intake 1-3
1.0 EXECUTIVE
SUMMARY
and discharge structures were evaluated through operational periods regardless of other sources of continued monitoring at sampling stations estab- variation such as Station. A significant Preop-Op lished during the preoperational period, with term does not indicate a plant impact, but rather an statistical comparison of the results at both the area-wide trend at both the nearfield and farfield community and the species levels. The null hv- areas, where the farfield area is presumably pothesis in all tests is that there has been no c.hange beyond the influence of the plant. The Station in community structure or selected species abun- term contains levels for each sampling station. dance or biomass that is restricted to the nearfield This term compares data collected from the sam-area. This ir turn would indicate, based on the pling stations tiaughout the study period, both approach outlined in Figure 1-1, that the balanced preoperational and operational periods. A signifi-indigenous populations have not been affected. cant Station term indicates a difference between the Analysis of variance (ANOVA) was an important nearfield and farfield areas; by itself it does not statistical methrd used in the Seabrook environ- suggest a plant effect because the data s1.an both mental Studies Monitoring Program to determine the preoperational and operational periods. whether the operation of Seabrook Station has had any adverse effects on the local marine balanced The Preop-Op X Station term (interaction term) indigenous populations. The ANOVA model used was the most important term in the analysis, as it in the monitoring program was based on Green's alone could indicate potential plant impact. The (1979) Before-After, Control-Impact (BACI) interaction term would be significant if a signifi-principles. In the BACI model, samples are rwn cant difference occurred during the opoational both before and after the potential effect, W o period that was restricted to only one of the areas both control and impact areas. In the Seabrook (nearfield or farfield). The remaining terms, Year Monitoring Program, the Befce After terms (Preop-Op) and Month (Year), were nested terms are represented data collected uaring the that explained some of the temporal variation in the preoperational and operational time periods, and data and improved the fit of the model. The error the Contrc'. and Impact terms are represented by term included all the variation not explained by the . data collected in rearfield and farfield n The model. advantage of th- ~ ACI model is t% potential l impacts are indicatu de signlhcance of the 1.2 STUDY PERIODS l interaction term of time (t bre-After) and loca- I tion (Control-Impact). Environmental studies for Seabrook Station began in 1%9 and focused on plant design and siting The specific ANOVA model used was a random- questions. Once these questions were resolved, a ized block design developed by Dr. Roger Green monitoring program was designed to assess the of the University of Waterloo, Ontario, with the temporal (seasonal and yearly) and spatial following terms as sources of variation: Preop- (nearfield and farfield) variability during the l Op, Station, Preop-Op X Station, Year (Preop- preoperational period as a hseline against which Op), Time (Year), (e.g., week or month) and conditions during r,ation operation could be evalu-Error. The term Preop-Op had two levels: ated. This report focuses on the preoperational preoperational and operational. This term com- data collected from 1976 through 1989 for fisheries pares data collected during the preoperational to studies and nun 1978 through 1989 for most 1-4
i 1.0 EXECUTIVE
SUMMARY
plankton and benthic studies. During these years, discharge structures, and at farfield locations a consistent sampling regime and the addition of a outside of the influence of operation. Measured farfield station provided the background to address parameters included temperature, salinity, dis-the question of operational effects. solved oxygen, and nutrients (total phosphorus, orthophosphate, nitrate, nitrite, and ammonia). Commercial operation of Seabrook Station began intermittently in July and August 1990, and contin- Potential impacts related to the operation of Sea-ued for periods of approximately three weeks in brook Station include: (1) temperature changes September and October. Therefore, August 1990 resulting from the discharge of a heated cooling is considered the beginning of the operational water from the Station condensers, (2) the dis-period for the purposes of this environmental charge of chlorine (sodium hypochlorite) used to assessment. After operation at 100% for less than prevent the settlement and accumulation of biologi-a week at the beginning and end of November, the cal fouling orgamsm within the Circulating Water plant operated nearly continuously from December System, and (3) associated changes related to the 1990 through July 1991 when it was shut down for addition of moribund entrained plankton to the routine maintenance. Resumption of full power nearshore marine environment. operation began again in October 1991 and contin-ued through a second maintenance outage in late The annual mean surface and bottom temperatures September 1992. Full power operation began were significa.ntly warmer during the operational p again in November 1992 and continued with only period, but these differences were consistent at all minor interruptions throughout 1993. In 1994 the stations. There were also significant differences plant was operational from January through early among stations that were consistent between the April, and August through December (Figure 1-2). preoperational and operational periods. This The plant continued at full operation in 1995 consistency between periods and among stations except for short outages in June and November indicated that the operation of Seabrook Station has (Figure 1-2). Monthly characteristics of the not significantly affected surface or bottom water Circhtng Water System operation throughout temperatures in the study area. Mean surface and 1990-1995 are presented in Table 1-2. bottom water temperatures increased in 1995 compared to 1994, contunung a trend that began in 1.3
SUMMARY
OF FINDINGS 1993. Water O==H*v Seasonal patterns of mean surface and bottom salinity were similar between preoperational and Water quality parameters were collected to aid in operational periods. There were no significant interpreting information obtained from the biologi- differences between the preoperational and opera-cal monitoring program, as well as to determine tional periods for surface salinity, but bottom whether the operation of the Seabrook Station salinity was significantly higher during the Circulating Water System had a measurable effect preoperational period. These trends were consis-on the physical or chemical characteristics of the tent among stations, indicating that the operation of O water column. Water quality samples were ob- Seabrook Station has had no effect on salinity, in tamed wahm the vicinity of Seabrook's intake and 1995, surface and bottom salinity increased at all 1-5
1.0 EXECUTIVE
SUMMARY
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sw 4 m>~.pw+ ., wt 0 L, ? . ,- As. h$Ml %& ex u ;~ m.p w.> un r m = m au n. ma = acr a c.c Figure 1-2. Average daily power level at Seabrook Station during 1995. Seabrook Operational Repon,1995. O Table 1-2. Monthly Characteristics of Seabrook Operation for the Period 1990 Through 1995. Seabrook Operational Report,1995. l Days of Cire+ing Water ! : Average Daily System Operations ~ . Flow (mad)'
- Mouth - 1990 Q c- .1992" !1993 19941995 ' ':1990 ' 1991 ~- 1992 ' 1993.. 21994 1.1995 Jan 31 31 31 31 31 31 324 584 585 587 566 576 Feb 28 28 29 28 28 28 564 580 578 587 589 572 Mar 31 31 31 31 31 31 563 580 581 580 573 572 Apr 30 30 30 30 30 30 563 581 576 579 352 573 May 31 31 31 31 24 31 562 581 581 582 188 625 Jun 30 30 30 30 25 30 563 578 593 582 171 662 Jul 31 31 31 31 31 31 582 535 593 578 331 685 Aug 31 21 31 31 31 31 588 253 583 579 681 687 Sep 30 26 29 30 30 30 588 257 314 574 6% 686 Oct 31 31 24 31 31 31 590 552 159 574 690 685 Nov 30 30 30 30 30 21 590 590 566 612 692 287 Dec 31 31 31 31 31 31 589 591 563 608 628 486 1-6
1.0 EXECUTIVE
SUMMARY
O stations, but was within the range of previous Phtoniankton () years. The phytoplankton monitoring program was initi-Surface and bottom dissolved oxygen concentra- ated to identify seasonal, annual, and spatial trends tions exhibited a seasonal pattern in 1995 that was in the phytoplankton community and to determine similar to previous years. Average surface and if the operation of Seabrook Station had a measur-bottom dissolved oxygen concentrations decreased able effect on this community. The purpose of the signifbntly between the preoperational and opera- monitoring program was to determine if the bal-tional periods, but the magnitude of the decrease anced indigenous phytoplankton community in the was similar at both the nearfield and farfield Seabrook area has been adversely influenced, stations. In 1995, surface dissolved oxygen con- within the framework of natural variability, by centrations were slightly lower than 1994, and exposure to the thermal plume. Specific aspects of bottom dissolved oxygen concentrations were the community evaluated included phytoplankton slightly higher or the same. (taxa a10 m in size) abundance and species composition; community standing crop as mea-There were no significant differences between the sured by chlorophyll a concentrations; abundance preoperational and operational periods for nitrate, of selected species (Skeletonema costatum); and orthri$phe, and total phosphate. Nitrite and toxicity levels of paralytic shellfish poison (PSP), ammonia concentrations were significantly higher as measured in the tissue of the mussel Mytilus during the operational period. However, these edulis in the Hampton-Seabrook area. V differences were consistent between the nearfield and farfield stations, and not attributed to the Monthly abundances of phytoplankton during 1995 operation of Seabrook Station. This is based on and the operational period showed seasonal pat-the consistency of spatial trends between the two terns that were similar to previous years. On periods, as well as the similarity of seasonal average, diatoms (Bacillariophyceae) dominated patterns across the years. The maximum concen- the phytoplankton assemblage during January trations of nitrate, nitrite, and ammonia in 1995 through February and June through December were the highest observed during the study period. during the operational period, while the yellow-green alga Phaeocystis pouchetti dominated during Most water quality parameters showed a distinct March and April. This pattern of seasonal'succes-seasonal cycle that was consistent throughout the sion in phytoplankton is well documented in other ; monitoring period. Significant differences among northern temperate waters. Phytoplankton abun-years were typical, reflecting high year-to-year dances at the intake station varied by more than an variability. Increases or decreases in all parame- order of magnitude throughout the preoperational ters were consistent between nearfield and farfield and operational periods. The geometric mean stations, indicating that the chemical and physical abundance in 1995 was lower than the operational environments in the study area are dominated by mean, but higher than the preoperational mean at larger regional trends. These appear unrelated to each station. Significant differences in the operation of Seabrook Station. phytoplankton abundance between stations were cor.sistent between the preoperational and opera-( 1-7
1 1 1.0 EXECUTIVE
SUMMARY
l l tional periods, indicating no effect due to station During the preoperational period, paralytic shell-operation. fish poison (PSP) toxicity levels, commonly known as red tide, were above the detection limit in tissue l During both the preoperational and operational of the mussel Mytilus edulis and above the closure periods, monthly arithmetic mean total chlorophyll limit during the late spring, early summer, and late a concentrations exhibited an early spring peak. summer. In 1991, only two occurrences of PSP There were no significant differences in chloro- above the detection limit were recorded. PSP was phyll a concentrations between the preoperational not detected during 1992. In 1993 and 1994 PSP and operational periods, but there were significant was detected above the closure level in May and differences among stations. These station differ- June, and July. PSP was detected in 1995 on three ences were consistent between periods, indicating occasions in late May. PSP events in New Hamp-no effect due to station operation. On an annual shire coincided with those in adjacent states. basis, there appeared to be no relationship between There were no outbreaks of PSP that were re-chlorophyll a concentrations and phytoplankton stricted to New Hampshire, consistent with recent abundances. The lack of a trend is likely due to research pointing to a non-local origin. differences among taxa with respect to cell size and chlorophyll a content. Seasonally, Zooplankton preoperational and operational chlorophyll a concentrations followed a pattern similar to that of Three components of the zooplankton community, phytoplankton abundances during the same peri- microzooplankton, bivalve larvae, and ods. macrozooplankton, were sampled separately to identify spatial and temporal trends at both the Skeletonema costatum was chosen as a selected coman: sty and species level. Initial monitoring species because of its historic omnipresence and characterized the source and magnitude of varia-overwhehning dominance during much of the year tions in abundance and species composition in the Ahmbe of S. costatum was significantly 12;her zooplankton community and provided a template during the operational period, and thero were no for comparison to data obtained during the opera-significant differences between stations. These tional period. The zooplankton community is differences among stations were consistent between currently evaluated to determine whether entrain-the preoperational and operational periods and ment within the Circulating Water System (CWS) were not due to the operation of Seabrook Station, of Seabrook Station has had a measurable effect on Durmg the operational period, both spring and fall the community or any species. The entrainment of peaks were larger than the preoperational period bivalve larvae within the CWS has also been but followed the same general pattern. In 1995, S. evaluated. costatum abundances generally followed historic patterns, except in April and September when Microzooplankton species composition during the mean abundances were higher than those typically operational period continued to resemble the observed and in July and August when mean historicalpauerns. While the abundances of some abundances were lower. taxa were different between the operational and preoperational periods, these differences were generally consistent between stations. Patterns of 1-8
1.0 EXECUTIVE
SUMMARY
n . seasonal variation recorded during the operational are much lower than predicted. In addition, the years (1991-1995) for the selected microzoo- cooling water system pumping rates are lower than plankton species were generally similar to those predicter' Mr one-unit operation. Predictions of observed duri'g the preoperational period. Opera- larval blue mussel entrainment were within the
- tional differences, if they occurred, were observed range of actual annual entrainment.
at both nearfleld and farfield stations. The community of pimkton that spend all of their The species composition of bivalve larvae and life in the water column (holo- and meroplankton) seasonal appearances of dominant species were were similar to those reported from other portions similar between the operational and preoperational of the Gulf of Maine. The seasonal change in the periods. Two taxa, Hiatella sp. and Solenidae, holo- and meroplankton community composition at showed trends among stations that differed between both nearfield and farfield stations has been consis-the preoperational and operational periods. For tent during the past six years. However, the both of these taxa, annual means exhibited similar abundances of many of the dominant species were . trends at each station. The significant interaction elevated in the operational period compared to the l term is probably not biologically meaningful. preoperational period. Increased abundances I occurred at all three stations, suggesting an area-Entrainment collections provide a measure of the wide change. Comparisons of annual means actual number of organisms directly affected by showed these differences to be slight.
) ,q Station entrainment. The species composition of , U the bivalve larvae entrainment community was Tychoplankton are those plankton that inhabit both similar to previous years with Mytilus edulis the the substrate and the water column as a result of most numerous species entrained. The number of excursions related to light, lunar cycle, storm bivalve larvae entrained in 1995 was 50% higher events, reproduction or nonspecific aggregation.
1 than any previous year, a result of two factors. Tychoplankton exhibited greater spatial variability Seabrook Station operated almost continuously than either the holo- or meroplankton. Seasonal l l throughout the year with the exception of two short changes in species composition were generally T outages, increasing the opportunity for entrain- similar between the operational and preoperational ment. In addition, offshore densities of M. edulis periods. Substrate differences between the were extremely high in 1995, contributing to the nearfield and farfield stations account for some of relatively high entrainment levels. Entrainment the variability observed in the tychoplankton within the CWS has not affected the balanced assemblages. irAigenous bivalve larvae community based on data from 1990-1095. The seasonal pattern of the Differences between the spatial and temporal bivalve la4vae Myrilus edulis during the operational components of the tychoplankton assemblages have period was similar to recent preoperational years, been consistent throughout the study. Abundance differences between the preoperational ani opera-Predicted levels of entrainment of soft-shell clam tional periods have occurred at both the nearfield (NAI 1977) were much higher than actual entrain- and farfield stations. Spatial patterns of ment levels for two reasons Esti nates were based tychoplankton have been similar both in the k on unusually high larval abundaaces; current levels preoperational and operational periods. 1-9
1.0 EXECUTIVE SUbfMARY There has essentially been no change in the abun- Among the selected larval species, changes in dances or seasonality in most of the macrozoo- density were consistent between the preoperational plankton selected species. Changes in abundances and operational periods at all stations, indicating no between the preoperational and operational periods effect due to the operation of Seabrook Station. were consistent at all stations. Entrainment of eggs and larvae in 1995 was Fish Population slightly lower than the 1993 estimate, the only other year with sampling throughout the year and Finfish studies at Seabrook Station began in 1975 no extended outages. Entrainment of eggs in 1995 to investigate all life stages of fish, including was lower than the 1990 through 1993 estimates, ichthyoplankton (eggs and larvae), juveniles, and and entrainment oflarvae was lower than the 1991 adults. Potential impacts of Seabrook Station and 1993 estinntes. Taxa entrained in 1995, and operation on local populations include the entrain- their relative abun< lances were also similar to ment of eggs and larvae through the Circulating 1993, the only other comparable year. Water System and the impingement of larger specimens on travelling screens within the Circu- Actual entramment of eggs and larvae at Seabrook lating Water pumphouse. Local distribution could Station was lower than predictions of entrainment also potentially be affected by the thermal plume, made in the 1970s (NAI 1977), which were based with some eggs and larvae being subjected to on peak egg and larval densities in the nearfield thermal shock due to plume entrainment upon area and the maximum pumping rate for one unit discharge from the system diffusers. The main at Seabrook Station. Offshore egg and larval objective of the finfish studies is to assess whether densities in the nearfield area in the 1970s were the operation of Seabrook Station has had any much higher than densities in entrainment samples, measurable effect on the nearshore fish population. in part a result of the midwater intake location, and actual pumping rates were slightly lower than Ichthyoplankton analyses focused on seasonal predicted pumping rates, resulting in lower en-assemblages of both eggs and larvae, as well as on trainment than expected. the collection of selected larval species. Consistent , temporal (among months and ym) and spatial In the pelagic fish community, Atlantic herring, (among stations) egg and ' larval assemblages blueback herring, silver hake and pollock were identified through the monitoring programs suggest dominant during the preoperational period. During that the operation of Seabrook Station has not the operational period, Atlantic herring, pollock, altered the seasonal spawmng time nor the distribu- Atlantic mackerel and spiny dogfish were domi-tion of eggs in the Hampton-Seabrook area. nant. The change in the species composition of Although the temporal occurrence of fish larvae, dominant pelagic fish reflected larger changes in both monthly and annually, was less consiaent than the pelagic fish community in the Gulf of Maine. for eggs, spatial parameters were consistent. Atlantic herring and Atlantic mackerel biomass Ichthyoplankton composition at all three stations have increased greatly in the Gulf of Maine and was very similar within each year and month. Georges Bank. Spiny dogfish, together with Temporal changes in assemblage abundances were skates, now compose about 75% of the fish bio-consistent at all three stations. mass of the Georges Bank (NOAA 1995). 1-10
1.0 EXECUTIVE
SUMMARY
l The geometric mean CPUE of demersal fish at all became operational and probably is not due to stations combined in 1995 decreased compared to plant operation. 1994 and was the lowest since sampling began in 1976. Dominant demersal fish in the operational During 1995 an estimated 15,910 fish,16 lobsters period were longhorn sculpin, winter fbunder, and six seals were impinged on the travelling yellowtail flounder and skates. Catches cf nearly screens at Seabrook Station. In October 1994, all species declined from the preoperational to the Seabrook Station identified the fact that it had not operational period, particularly for the yellowtail accurately counted the number of small fish im-Gourxler. Changes in CPUE of adult fish between pinged on Seabrook Station's travelling screens the preoperational and operational periods were prior to the fourth quarter of 1994. Therefore, consistent at all stations with the exception of 1995 is the first year of accurate impingement rainbow smelt, winter flounder, and yellowtail estimates. Grubby was the most common fish flounder. The decrease in winter flounder abun- impinged, followed by hake spp., Atlantic silver-dance at the nearfield station began prior to plant side and American sand lance. operation. Similar decreases in rainbow smelt CPUE at the nearfield station were also observed The design of the Seabrook Station offshore intake in the preoperational period. Yellowtail flounder with a mid-water intake fitted with a velocity cap CPUE decreased slightly more at the farfield has resulted in fewer numbers of fish being im-station (TI) than the other stations. Therefore, it pinged when compared to other coastal power p is not likely that these decreases in CPUE were plants. due to the operation of Seabrook Station. A number of differences were found between the The geometric mean CPUE for estuarine fish preoperational and operational periods for adult caught at all stations during 1995 increased slightly fish assemblages in general, and for most selected from the average in 1994. Catches generally were species in particular. In nearly all cases where smaller during 1987-1995 compared to 1976-1984. differences were found, abundance during the Average catches were less for the operational operational period was significantly lower than period than observed during the preoperational during the preoperational period. However, in period. However, this declining trend began in many instances, the declines began in the early or advance of station operation. The Atlantic silver- mid-1980s. Several of the decreases reflect long-side dominated catches in all years sampled. term declining trends of overexploited commercial Winter flounder, killifishes (mummichog and fishes, including Atlantic cod, winte; flounder, and striped killifish), ninespine stickleback, and rain- yellowtail flounder. bow smelt also contributed to the catch. Trends in the CPUE paralleled fluctuations in catch of the Marine Macrobenthos dominant species, Atlantic silverside. The predominant benthic marine habitat within the Winter flounder CPUE decreased at all stations, vicinity of Seabrook Station's intake and discharge
- but the decrease was greatest at Station S3. This is rocky substrate in the form of ledge and boul-
'N decline began in the mid 1980s before the station ders. These rocky surfaces support diverse com-(b munities of attached plants and animals (macro-1-11
1,0 EXECUTIVE
SUMMARY
benthos). Because these hard-bottom communities the farfield station for algae, and the nearfield l are ecologically important, and are potentially station for fauna. Total biomass of algae in the l vulnerable to localized coastal anthropogenic intertidal zone decreased between periods at the impacts, studies of these communities have been an nearfield station, but was unchanged at the farfield important part of the ecological monitoring pro- station. In the shallow subtidal zone, the number gram. The progren has been designed to deter- of faunal taxa decreased significantly at the mine whether dif'erences exist among communities nearfield station but was unchanged at the farfield at sites within the Hampton-Seabrook area that can statien. These differing trends between stations be attributed to the operation of Seabrook Station. and operational periods were attributed to either Potential impacts include temperature-related trends that began in the preoperational period, or community alteration to areas directly exposed to short-term fluctuations in otherwise generally the thermal discharge plume. This would occur at consistent relationships. shallow subtidal sites due to the buoyant nature of a thermal plume. Thermal impacts are unlikely in Of the selected algae studied in these .'.ones, Chon- ! deeper areas; however, increased turbidity result- drus crispus, Ascophyllum nodosum, and Fucus ing from the transport of suspended solids and resiculosis, all showed inconsistency cmong sta-entrained organisms could increase turbidity and tions between periods. These changes all began sedimentation, during the preoperational period and we e appar-ently unrelated to station operation. Of the se-Studies were implemented to identify plant and lected faunal species only Ampithoe rubricata, animal species occupying nearby intertidal and showed inconsistency among stations between the subtidal rock surfaces and at those at farfield two periods. As with the algal selected species, controllocations. The studies also describe tempo- these shifts in abundance among stations began in ral and spatial patterns of species occurrence, the operational period and were apparently unre-identify physical and biological factors that induce lated to station operation. variability in these communities, and relate these to the operation of Seabrook Station. In the shallow subtidal benthic communities, no changes have occurred that can be related to the Potential ThermM Plume Effects operation of Seabrook Station. Numerical classifi-cation of macroalgal and macrofaunal collections Hydrodynamic modeling and subsequent field revealed no substantive changes in species compo-studies indicated that intertidal benthic locations sition or overall community structure. The inun-experienced no temperature increase; shallow ber of faunal taxa decreased significantly between subtidal sites experienced increases of < 1 F periods at the nearfield station but was unchanged (Padmanabhan and Hecker 1991). Overall, inter- at the farfield station. This trend appeared to start tidal benthic community parameters (biomass, in the preoperational period and was not related to number of taxa, etc.) and community structure the operation of Seabrook Station. Among the 1 indicated few changes in nearfield intertidal or selected species, only the alga Iominaria digitata shallow subddal communities. Number of algal exhibited differing trends among station between ; and faunal taxa in the intertidal zone decreased periods. These differences among stations ap- I between periods and the decrease was greatest at . I 1-12 l I I
i I 1.0 EXECUTIVE
SUMMARY
peared to reflect a short-term cyclical pattern Of the six selected taxa, only two, Laminaria , rather than a station impact. digitata and L. saccharina exhibited decreases ) between periods that were not consistent between I Potential Turbidity Effects stations. Density of L. digitata decreased signifi-cantly at both stations between periods but the Assessments of community parameiers and overall decrease was greater at the nearfield station. l community structure indicated few changes in the Density of L. saccharina decreased significantly nearfield mid-depth community du mg the opera- between periods at the nearfield station but was j tion of S eabrook Station. Tiime were few signifi- unchanged at the farfield station. For both these cant dih'erences in measures of community struc- species the declines appeared to have begun in the ture between the preoperational and operational preoperational period and are not due to the opera-periods for the mid-depth macroalgae or tion of Seabrook Station. Densities of selected macrofauna communities. High similarity in macrofauna, Pontogencia inermis, Modiolus annual collections within the mid-depth zone was modiolus, Mytilidae, and Strongylocentrotus characteristic for the overall faunal and algal droebachiensis, were not significantly different l community structure. The number of macroalgal between the preoperational and operational peri- l taxa in the mid-depth zone differed among station ods. ; betweenperiods. The number of taxa collected at each station was highly variable from year to year, Collections in the deep water macmbenthic com- l f, and not clearly related to station operation. Total munities and assessment of the overall community l Q density of macrofauna decreased significantly at the mid-depth stations between periods at the intake structure revealed that nearfield and farfield communities have remained stable over the station, but was unchanged at the discharge and preoperational and operational periods. Overall, farfield stations. At the deep stations, density of the macrobenthic communities appear unaffected macrofauna increased significantly between periods by station operation. at the discharge station and was unchanged at the other two stations. In both of these cases, each Surface Panels station showed very similar trends among years and the differing trends between the preoperational The surface fouling panels program was designed and operational periods appeared to be due to to study settlement patterns and community devel-natural variation. opment in the discharge plume and in farfield areas. Panels provide information on the temporal The nearfield discharge community structure in sequence of settlement activity, as well as on < 1995 was not typical. Algal biomass, total faunal species growth and patterns of community develop-density, number of faunal taxa, and densities of the ment. dominant faunal taxa (Mytilidae, Pontogencia inermis,locuna vmaa, and Anomia sp.) decreased The settlement of the fouling community was l in 1995, creating a " low density" assemblage monitored through the short term panels program, similar to that collected in 1978 and 1979. where panels are exposed for one month each p month of the year. Settlement of fouling organ-b isms on short term panels did not appear to be l l 1-13
1.0 EXECUTIVE
SUMMARY
affected by plant operation. Trends between 'Ihe community settling and developing on surface stations were similar throughout the study period panels has shown predictable seasonal patterns for number of taxa, and biomass of the fouling throughout the study, as evidenced both by mea-community. Total abundance and Mytilidae sures of community structure (biomass, abun-abundance on short term panels increased between dance, and number of taxa) and by abundance or the preoperational and operational periods to a percent frequency of occurrence of dominant taxa. greater extent at the nearfield station. On an Few measures showed significant differences annual basis, there has been a pattern of fluctuating between operational and preoperational periods, abundances over a three- to four-year period that and these differences were consistent among is apparently related to Mytilidae abundance. nearfield and farfield stations, with the exception Both total and Mytilidae abundances in 1994 and of total abundance and Mytilidae abundance on 1995 were lower than 1993 suggesting that this short-term panels, and the number of taxa on the pattern is being repeated in the operational period, year-end monthly sequential panels. and is not indicative of plant effects. Similarly, there was no apparent effect due to plant operation Epibenthic Crustacea on the settlement of selected species Jassa marmorata and Tubularia sp. The objective of the epibenthic crustacea monitor-ing program was to deternune the seasonal, spatial, Fouling conununity development was assessed and annual trends in larval density and catch per through a monthly egndal panel program where unit effort (CPUE) for juvenile and adult stages of panels were exposed for increasing periods of time American lobster (Bomarus americanus), Jonah ranging from 1 to 12 months. Seasonal patterns of crab (Cancn borealis) and rock crab (Cancer development were similar between the irroratus). Analyses were done to determine if the preoperational and operational periods. Average discharge from Seabrook Station had any measur-annual biomass on monthly sequential panels was able effect on these species. sinnlar between the preoperational and operational perioc's at all stations. For the year-end panels Annual mean densities of lobster larvae in 1995 exposed for 12 months, biomass and abundance continued the trends observed in 1991 through were similar between the preoperational and 1994. Lobster larvae densities during 1995 were operational periods at both nearfield and farfield higher than durmg the preoperational period (1988-stations. The number of taxa increased at the 1989) at Station PS, and lower at Stations P2 and nearfield station between the preoperational and P7. Average larval densities during the four-year cperational periods, but there was no difference at operational period were significantly higher than the farfield station. the average densities during the preoperational period. There were no significant differences In 1994 and 1995, panels were also exposed for among the three stations during the 1988-1995 three, six, nine and 12 month periods. Results monitoring period. Monthly trends were similar to from these quarterly panels were similar to the those observed in previous years. Increasesin mornhly -mial panels for parameters that were densities during 1995 were due mainly to increases comparable between the two programs. in Stage IV larvae, historically the most numerous of the four stages. Stage IV larvae are hypothe-
-14
1.0 EXECUTIVE
SUMMARY
l sized to originate, at least in part, offshore in the warm southwestern waters of the Gulf of Maine farfield station, but there was no significant differ-
)
ence at the nearfield station. The reduction in and Georges Bank. CPUE at the farfield station began in the preoperational period and was nct due to the The 1995 CPUE for adult lobster was higher than operation of Seabrook Station. The relationship in the preoperational and operational means, and was rock crab CPUE between stations was consistent I the highest observed during the entire s:udy period. between the preoperational and operational peri- l CPUE declined between the preoperational and ods, indicating no effects due to Seabrook Staticn. l operational periods, but the decline was signifi- Rock crabs have been less prevalent than Jonah I cantly greater at the farfield station. The decline crabs throughout the study area, probably because I in lobster abundance in the study area parallels an of their preference for samiy substrata, which are l overall decline in lobster abundance in the Gulf of rare in the study area. l Maine (NOAA 1995). The monthly trend of CPUE in 1995 was similar to that observed during Soft-Shell Chm the preoperational period. Legal-sized lobsters in 1995 were 4% of the total catch at both the The objectives of the soft-shell clam (Mya nearfield and farfield stations, slightly lower than arenaria) monitoring programs are to determine the preoperational averages of 8% and 7% respec- the spatial and temporal pattern of abundance of tively. The decrease in the percentage of legal- various life stages of Mya arenaria in the vicinity A sized lobsters in the operational period is likely due of Hampton Harbor. Pelagic life stages may be U to the increases in the legal-size limit, as it oc- subject to impacts from Seabrook Station operation curred equally on both nearfield and farfield due to entrainment into the Circulating Water stations. System. Benthic stages (after settlement to the bottom) in the Hampton-Seabrook estuary may In 1995,16 lobsters were impinged in the Station's have been subject to impacts from discharges from Circulating Water System. Four were impinged in the Station's Setthng Basin, which were eliminated 1990, 29 in 1991, 6 in 1992, one in 1993, and 31 in 1994. Nearfield/farfield comparisons of clam in 1994. The current level of impingement does densities are also made between Hampton Harbor not pose a serious threat to the indigenous popula- and a nearby estuary, Plum Island Sound, Ipswich, tion. MA. Cancer spp. larvae had higher abundances in 1995 Mya arenaria larvae occurred most weeks from than during the preoperational and operational May through October during the preoperational per ods at all stations. The average density during years. Peak abundances in 1995 were in Septem-the five year operational period was significantly ber and were similar to the preoperational average. higher than the preoperational average. The 1995 The overall operational mean larval abundance at mean CPUE for both Jonah crab and rock crab all three stations was significantly lower than the I was lower than the preoperational and operational preoperationalmeans at both nearfield and farfield l periods at both the nearfield and farfield stations. stations. O CPUE for Jonah crabs decreased between the preoperational and operational periods at the I 1-15 l
1.0 EXECUTIVE SUMALARY Mean density in 1995 of young-of-the-year (1-5 It is difficult to attribute the differing trends in mm) clams on each of the three flats was less than mean YOY, spat, juvenile and adult clam densities the preoperational mean and either less than or to the operation of Seabrook Station. The two similar to the operational mean density. Spat (6-25 possible impacts of station operation include mm) density in 1995 was lower than preoperational entrainment of larvae (see bivalve larvae sum-and operational mean densities. Juvenile (26-50 mary) and the discharge from the settling basin. mm) mean density in 1995 was higher than the Larval density was significantly lower during the preoperational and operational mean densities. operationalperiod. Since the decrease occurred at Adult (> 50 mm) mean density in 1995 was great- all three stations, it is unrelated to entrainment. In er than the operational and preoperational mean addition, densities of larvae appear unrelated to densities at Flats 1 and 2, and greater than preop- sets of YOY. Therefore, entrainment of larvae crational density at Flat 4. The Preop-Op X Area into the cooling water system of the plant has had interaction term was significant for all benthic no apparent effect on larval densities or YOY clam lifestages, which indicated differing trends between density. The discharge of the settling basin ceased the preoperational and operational periods among in April of 1994, and is not likely to have affected flats. Young-of-the year and spat densities de- clam densities in 1995. The differences in clam creased significantly during the operational period density were probably due to a wide variety of at Flats 2 and 4. No changes occurred at Flat 1. physical a*xt biological variables that include Juvenile densities decreased significantly during the recreational harvesting and the presence of neopla-operational period at Flats 4 and 1, and there were sia. no changes at Flat 2. Adult densities increased significantly between periods at Flat 4, decreased 1.4 LITERATURE CITED at Flat 2, and were not dif.'erent at Flat 1. Green, R.H.1979. Sampling design and statisti-In 1995, the mean density of seed clams (1-12 cal methods for environmental biologists. mm) in Hampton Harbor (nearfield area) was J hn Wiley and Sons, N.Y. 257 pp, similar to the operational mean and lower than the NOAA.1995. Status of the fishery resources of preoperational mean. Densities of reed clams in the northeastern United States for 1994. 1995 in Plum Island Sound (farfield area) were NOAA Tech. Memo. NMFS-NE-108. 140 p. lower than the preoperational and operational mean. Densities were significantly higher at the Normandeau Associates Inc. (NAI).1977. Sum- ,, mary document: assessment of anticipated farfield station during both periods. This consis-impacts of construction and operation of Sea-tency across periods and stations suggests that brook Station on the estuarine, coastal and settlement has been unaffected by Seabrook Sta- offshore waters of Hampton-Seabrook, New tion. Hampshire. 1991. Seabrook Environmental Sarcomatous neoplasia is a lethal form of leukemia Studies,1990. A characterization of environ-t in soft-shell clam. Neoplasia was prevalent at mental conditions in the Hampton-Scabrook Flats 1 and 2 and absent from Flat 4 ia 1986 and area during the operation of Seabrook Station. 1987. By 1995 neoplasia was present at all three Tech Rep. XXII-II. flats. 1-16
1.0 EXECUTIVE
SUMMARY
l i 4 Padmanabhan M. and Hecker, G.E. 1991. Com-
- ( ]
7 parative Evaluation of Hydraulic Model and Field Thermal Plume Data, Seabrook Nuclear j Power Station. Alden Research Laboratory, Inc. 1 1 i 1 k i ! l 1 \ I 1 4 J 1
+ I i l
] l i l l 1 a O 1-17
2.0 WATER QUALITY
=- /\ TABLE OF CONTENTS V
PAGE 2.0 WATERQUALITY 1
SUMMARY
. . . . .. . . .. . 2-ii
. LIST OF FIGURES . . . . .. . 2-iii i LIST OF TABLES . . .. .. . . .. 2-iv l
2.1 INTRODUCTION
. .... . . . 2-1
' 1 1
2.2 METHODS . . .. . . .. . 2-1 i 2.2.1 Field Methods .. . .. . . . ... . 21 2.2.2 Laboratory Methods . ... . . ... 2-3 1 ,' 2.2.3 Analytical Methods . .. . . .. . .. 2-3 2.3 RESULTS . . . ... .. . . . 2-4 2.3.1 Offshore Water Quality . . . . 2-4 2.3.1.1 PhysicalEnvironment .. . . .. ... . 2-4 2.3.1.2 Nutrients . . . 2-20 2.3.2 Estuanne Water Quality . . . .. . . 2-23 2.4 DISCUSSION . . . . . . . . .. . 2-27
2.5 REFERENCES
CITED .. . . 2-29 v . 2-i
2.0 WATER QUALITY
SUMMARY
Water quality measurements collected in 1995 were similar to those in previous years. On average, air temper-atures in 1995 were warmer than previous years, resulting in higher than average annual water temperatures, and lower than average annual dissolved oxygen levels. Salinity levels in 1995 were similar to previous years. Nutrient levels in 1995 showed a similar pattern to previous years, but annual means were higher than previously observed. There were significant differences between the preoperational and operational periods for surface and bottom water temperature and dissolved oxygen, bottom salinity, and surface nitrite and ammonia. Small but significant differences were observed among stations for surface and bottom temperature, salinity, dissolved oxygen, and surface nitrate and nitrite. The relationships among stations were consistent between the preoperational and operational periods, and were not due to the operation of Seabrook Station. O O 2-ii
2.0 WATER QUALITY 7 LIST OF FIGURES [O ' PAGE 2-1. Water quality sampling stations . . . .. . .. 2-2 2-2. Surface and bottom temperature ( C) at nearfield Station P2, monthly means and 95% mn%nce intervals over the preoperational period (1979-1989) and the operational period (1991-1995), and monthly means of surface and bottom temperature at Stations P2, P5, and P7 in 1995 . . . . . .. 2-6 2-3. Time-series of annual means and 95% confidence intervals and annual muuma and maxima of surface and bottom temperatures at Stations P2, P5 and P7,1979-1995 . . .. 2-12 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 monthly means for the operational period (1991-199.5) and 1995 2-14 l 2-5. Comparison of monthly averaged continuous temperature ( C) data collected at the surface l at discharge (DS) and farfield (T7) stations during commercial operation, August 1990-December 1995. . . . . . . . . . .. .... . .. . 2-16 V 2-6. Surface aad bottom salinity (ppt) and dissolved oxygen (mg/L) at nearfield Station P2, monthly means and 95% mnhner int:rvals for the preoperational period (1979-1989) and monthly means for the operational period (1991-1995) and 1995 .. .. . 2-17 2-7. Time-series of annual means and 95% confidence intervals of surface and bottom salinity (ppt) at Stations P2, PS, and P7,1979-1995 . . . ... . ... . 2-19 2-8. Surface orthophosphate and total phosphorus cornusaiions (pg P/L) at nearfield Station P2, monthly means and 95% confidence intervals for the preoperational period (1979-1984 and 1987-1989), and monthly means for the operational period (1991-1995) and 1995 . 2-21 2-9. Surface nitrite-nitrogen, nitrate-nitrogen and ammonia-nitrogen concentrations (pg N/L) at nearfield Station P2, monthly means and 95% confidence intervals for the preoperational period (1979-1984 and 1987-1989), and monthly means for the operational period (1991-1995) and 1995 . . .. .... . . . . .. . .. . . 2-22 2-10. Monthly mer.s and 95% confidence limits for temperature measured at low and high tides in Hampton Harbor from May 1979-December 1995 and monthly means in 1995 . . 2-24 1 q Q 2-11. Monthly means and 95% confidence limits for salinity measured at low and high tides in Hampton Harbor from May 1979-December 1995 and monthly means in 1995 .. 2-26 2-iii i
2.0 WATER QUALITY LIST OF TABLES 1 PAGE 2-1. Annual Means and Coefficients of Variation (CV,%) and Minima and Maxuna for Water Quality Parameters Measured Durmg Plankton Cruises at Stations P2, P5, P7 over ! Preoperational and Operational (1991-1995) Years, and the Annual Mean, Minimum and ) Maximum in 1995 . 2-7 j 2-2. Results of Analysis of Variance Comparing Water Quality Charactenstics among Stations P2, PS, and P7 Dunng Recent Preoperational Years (1987-1989) and Operational (1991-1995) Years . 29 2 3. Annual Mean Surface Temperatures (*C) and Coefficients of Variation (CV,%) at Stations DS and T7 Dunng Operr.tional Monitoring Conducted by YAEC 2-15 2-4. Monthly Mean Surface Temperatures ('C) and Temperature Differences (AT, C) Between Discharge (DS) and Farfield (T7) Stations Collected from Continuously Monitored Temperature Sensors, July 1990-December 1995 . . , 2-16 2-5. Annual Mean and 95% Confidence Limits for Temperature ('C) and Salinity (PPT) Taken at Both High and Low Slack Tide in Hampton Harbor from 1980-1995 . 2-25 2-6. Summary of Potential Effects of Seabrook Station on Ambient Water Quality. Seabrook Operational Report,1995 . . . . . . 2 28 l 1 0 2-iv ) I
2.0 WATER QUALITY [] V
2.1 INTRODUCTION
(NPDES) Permit issued by the State of New Hampshire and the Environmental Protection Water quality data were collected to aid in Agency (EPA). This permit specifies that the interpreting information obtained from the average monthly temperature rise shall not exceed biological monitoring program and to determine 5 *F (3 C) within the nearfield jet mixing region. whether the operation of the Seabrook Station This applies at the surface of the receiving waters Circulating Water System has had a measurable within 300 feet of the submerged diffuser in the effect on the physical and chemical characteristics of direction of discharge. the water column. To provide information on the physical environment, water quality samples were Seabrook Station uses continuous low level collected in the vicinity of the Seabrook Station chlorination in the circulating and service water intake and discharge, as well as at a farfield location systems to control biofouling. Irdonnation was outside of the influence of Station operation. gathered through the Chlorine Minimization Parameters measured included temperature, salinity, Program, which assessed the effectiveness of dissolved oxygen, and nutrients. Potential impacts chlorine application in preventing biofouling while j related to the cooling water system include both that utilizing the least amount of chlorine. Residual of temperature, through the discharge of a heated levels of chlorine at the diffusers, when measured, efIluent from the condensers, and the application of have been below detection limits. sodium hypochlorite as a biofouling control j n measure. In addition to the offshore sampling, 2.2 METHODS () temperature and salinity were recorded weekly at high and low slack tides in Hampton Harbor. These 2.2.1 Field Methods estuarine samples were historically taken in ! conjunction with sampling of estuarme benthos, to Near-surface (-l m) water samples for nutrient j monitor any potential impacts to the estuary analysis were collected during daylight hours using I resulting from the discharge of wastewater from a General Oceanics' 8-L water sampler from the Seabrook Station's settling ponds. Discharges into intake (Station P2,16.8 m depth, MLW), discharge the estuary through these ponds ended in 1994. (Station P5,16 m depth, MLW), and farfield (P7, , Although all sampling has been eliminated in 18.3 m depth, MLW) sampling locations (Figure 2-l Browns River, temperature and salinity monitoring 1). Nutrient sampling commenced at Stations P2 at the Hampton Harbor station (Figure 2-1) and P5 in 1978 and at Station P7 in 1982. continued in 1995. Sampling emnM until 1981 at PS and until 1984 at P2 and P7. Sampling resumed at all three Seabrook Station employs a once-through stations in July 1986, and continued to the present. circulating water system. Ambient ocean water is Water samples were taken once in January, I I drawn into the system from approximately 7,000 February, and December and twice monthly from feet offshore through three intake structures and March through November, in conjunction with the i discharged to the ocean through a multiport diffuser phytoplankton and microzooplankton sampling, and system approximately 5,500 feet o1Tshore. All within 24 hours of the weekly macrozooplankton ) p discharges are controlled under the Station's and ichthyoplankton sampimg. l National Pollutant Discharge Elimination System l 2-1 1 j
l N I RYE LEDGE f O LITTLE BOARS HEAD D 0 .5 1 Nautical Mile 0 1 I 2 Kilometers $ FARFIELD AREA SCALE CONTOUR DEPTH IN METERS o GREAT BOARS HEAD , HAMPTON ,e BEACH
# 17 BROWNS .
RIVER P1 Intake *** D 6_ NEARFIELD OUTER Y~:eID ARE/. SEABROOK DS p: o ON g Discharge HAMPTON ' SEABROOK SUNK HARBOR ROCKS O
\ SEABROOK BEACH
\_
LEGEND l 0 = water quality stations e = continuous temperature ne nitoring stations , Figure 2-1. Water quality sampling stations. Seabroot Operational Report,1995. l l 2-2 l
2.0 WATER QUALITY ( ') Temhcature, dissolved oxygen, and salinity Analyses of Water and Wastes (USEPA 1979) and meaiements began in 1979 at Stations P2 and P5, Standard Methods (APHA 1989). and in 1982 at Station P7. Sampling at P2 and P7 continued to the present; sampling at P5 was inter- 2.2.3 Analytical Methods rupted from January 1982 until July 1986, but was sampled concurrently with P2 and P7 from July Results from these collection efforts were used to 1986 until the present. At all stations, temperature describe the seasonal, temporal, and spatial i and salinity profiles were taken in 2 m increments characteristics of the water column within the four times per month during January through nearshore waters off Seabrook Station and in the December with a Beckman* Thermistor Salinometer Hampton-Seabrook estuary. Offshore water quality (through March 1989) or a YSI* (Model 33) S-C-T analyses used data from all stations, but focused on Meter within 24 hours of the weekly macro- Station P2 since it was sampled for a longer period zooplankton and ichthyoplankton sampling. of time than Stations P5 and P7. Any values that Begmmng m 1995, salinity samples were collected were less than the detection limits were assigned a at near-surface (-l m) and near-bottom (+1 m) value equal to one-half of the detection limit for depths. Collections were made in wax-sealed glass computational purposes (Gilbert 1987). For both bottles and analyzed in the lab using a YSI Model offshore and estuanne stations, seasonal trends were 34 S-C-T Meter. Dunng 1995, field temperatures analyzed using monthly arithmetic mean tempera-continued to be collected using a YSI Model 33 S- tures and salinity, and (for offshore stations) C-T Meter. Duplicate dissolved oxygen samples nutrient and dissolved cxygen concentrations. v were also collected at near-surface ( l m) and near- Monthly means for the preoperational and bottom (1 m above bottom) depths. Samples were operational periods were calculated from the fixed in the field with manganese sulfate and monthly arithmetic means for each year within each alkaline iodide-azide, and analyzed by titration period, resulting in a sample size equal to the within eight hours of collection. Additionally, number ofyears in each period. Monthly means for continuous temperature data from the discharge 1995 were calculated as the arithmetic average of (Station DS), nearfield (Station ID) and farfield all samples taken withm a given month. (Station T7) areas were collected begmnmg in August 1990 by Ocean Surveys Inc. (OSI) as part of Among-year and between-period trends were Seabrook Station's NPDES permit compliance evaluated using annual or period (preoperational, program (Figure 2-1). The results of this operation) means. Annual means of 1995 collec-monitoring are included in this section. tions were calculated as the arithmetic mean of all observations within the year. The means of 2.2.2 Laboratory Methods preoperational and operational collections were calculated as arithmetic means of annual means over Water quality samples were analyred for five all years within each period, which varied among nutrients (total phosphorus, orthophosphate, nitrate, stations and parameters. The precision of the mean aitrite, and ammonia) using a Technicon* was described by its coefficient of variation (Sokal Autoanalyzer Il system. All analyses were and Rohlf 1981). Prwpuadonal periods for the dif- [ ( performed accordmg to EPA Methods for Chemical ferent analyses are listed on the appropriate tables 2-3
2.0 WATER QUALITY and figures; in all cases, the operational period maintaining a balanced model design). These consisted of collections from 1991-1995. Collec- results were evaluated in conjunction with means tions from 1990 were not included in these analyses calculated over all available preoperational years to since the year was divided between the help distinguish between recent trends and long- I preoperational and operational periods, and .the term trends. inclusion of partial years in each period would bias the means. 23 RESULTS l 1 Operational /preoperational and nearfield/farfield 23.1 Offshore Water Ouality j differences in monthly means for offshore water , quality parameters were evaluated using a multi-way 23.1.1 Physical Environment ) analysis of variance procedure (ANOVA), . ing a before-after-control-impact (BACI) desigt itest Climate for potential impacts of plant operation. A fixed-effects ANOVA model was used to test the null The weather in 1995 was unusual in terms of both i hypothesis that spatial and temporal values during temperature patterns and precipitation (Boston the preoperational and operational pedods were not Globe 1996 and Portland Press Herald 1996). Air significantly (p>0.05) different. The data collected temperatures were above average and precipitation for the ANOVAs met the criteria of a Before- was below average. Mean monthly air temperatures After/ Control-Impact (BACI) sampling design in Boston in 1995 deviated from the long-term discussed by Stewart-Oaten et al. (1986), where averages by about 1"F or more in all months except sampling was conducted prior to and during plant March. Differences from the long-term monthly operation and sampling station locations included means ranged from -3.4 to +6 F. Temperatures both potentially impacted and noc-impacted sites. were below average in February, April, May, l The ANOVA was a two-way factorial with nested September and November, and above average in effects that provided a direct test for the temporal- January, June, September, October and December. : by-spatialinteraction. The main effects were period Portland did not experience the extended late winter- ) (Preop-Op) and station (Station); the interaction early spring period of below-average temperatures term (Preop-Op X Station) was also included in the that Boston did, but temperatures during most of the model. Nested temporal effects were years within remainder of the year followed similar pattems to operational period (Year (Preop-Op)) and months Boston. Both Boston and Portland experienced the l within year (Month (Year)), which were added to year's coldest day in February and the hottest day in l reduce the unexplained variance, and thus, increased July. ) the sensitivity of the F-test. For both nested tem s, variation was partitioned without regard to station Precipitation was below average in 1995 both in (stations combined). The final variance not Boston and Portland. After above-average accounted for by the above explicit sources of precipitation in January, both areas experienced variation constituted the Error term. The preopera- below-average precipitation during most months tional period for each analysis was specified as through August. After an average September, 1987-1989, which was the period during which all precipitation was notably above average during three stations were sampled concurrently (thus October and November. Both areas received record 2-4
2.0 WATER QUALITY A
/ snowfallsin December 1995. In Boston,1995 was Surface temperatures at Stations PS (discharge) and the 24th driest year in 125 years. P7 (farfield) were similar during 1995 (Figure 2-2),
f with annual means differing by 0.3 *C or less (Table T*=aarature 2-1). Surface temperatures at PS and P7 have shown long term increases similar to that observed Monthly mean surface water temperatures at Station at Station P2, as indicated by the significant Preop-P2 followed a similar seasonal pattern during both Op difference in the ANOVA results (Table 2-2). the preoperational and operational periods (Figure Although temperature differences between stations 2 2). In 1995, monthly mean surface temperatures have been relatively . mall, particularly during the wae coldest in Febmary and March, and warmed by operational period, these differences were only 1.1*C in April (Figure 2-2). Monthly mean signibnt Arithmetic means over all years indicate surface temperatures increased another 4 C drring that temperatures differed only by 0.2 C to 0.4 C, May, then climbed another 7'C during June, and with temperatures at P5 the wrrrnest and those at P7 remamed atjust under 17 *C in July. Monthly mean coolest. Thi: releionship was consistent in both the temperature peaked in August at 18.8'C. Mean properatiomi eid operational periods, and tWures were still at nearly 9 C in November, thercfore the Preop Op X Station interaction term then dropped to 5.5'C in December. The single was not significant (Table 2-2). warmest surface temperature wasurement in 1995, 20.4*C, occurred on July 25, and was the warmest As noted for surface temperatures, bottom temperature recorded since monitoring began at p) ( Station P2 in 1979 (but only 0. l *C warmer than the temperatures at Station P2 in 1995 werc, generally warmer than preoperational temperatures (Figure 2-1994 maximum temperature). The coolest 2). Operational monthly mean temperatures were temperature for the year,2.3*C, was recorded on also generally warmer than preoperational March 13, and was the warmest annual nummum temperatures. Bottom temperatures in 1995 were . temperature on record for Station P2. smular among the three stations, (Figure 2-2, Table 2-1). Annual mean temperatures for both 1995 and Monthly mean surface temperatures at Station P2 in the operational period were warmer at each station 1995 were higher than preoperational means in all compared to the preoperational period. Bottom twelve months, and higher than preoperational water temperatures at each station have increased upper 95% confidence limits in all months except since 1993, similar to surface temperatures (Figure April, May, November, and December (Figure 2-2). 2-3). Operational mean temperatures were also warmer than preoperational means (all years) in all months ANOVA model results for bottom temperatures except April. Mean annual su-L m water were similar to results for surface temperatures. temperature at P2 in 1995 was 1.6*C wiu mer than The long term increase in temperatures since 1987 the preoperational mean, and the operational annual was reflected by the significant Preop-Op term. mean was 0.5'C warmer thari the preoperational Station differences were significant, and arithmetic mean (Table 2-1). means indicate that, over all years, bottom water temperatures at P5 have been warmer than at P2 and G 2-5
S#mJnWe Bern. Hake Pmopadond 3 Papsalonel Oprand ---- Opsalond g m a r jf. ,}s~4 g m a 15 / ,, ' 'Rs j, 15 g ,1, ' h ,g1 4R\
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/ Preop Year (Preop)* 6 9.76 172.47* "
Month (Year)* 88 84.66 149635 "
- Station' 2 2.66 46.98 "
- P5>P2>P7 Preop-Op X Stations 2 0.04 0.73 NS Error 188 0.06 Bottom Temperature Preop-Op 1 86.84 106933* " Op> Preop Year (Preop) 6 936 115.28 "
- Month (Year) 88 33.69 414.80* "
Station 2 135 16.64* " PS>P2>P7 Preop-Op X Station 2 0.05 0.57 NS w Error 188 0.08 6 Surface Salinity Preop-Op 1 <0.01 0.01NS Year (Preop-Op) 6 637 82.29* *
- Month (Year) 88 4.63 59.85 "
- Station 2 031 3.99* E225P7 Preop-Op X Station 2 0.23 2.99 NS Error 188 0.08 Bottom Salinity Preop-Op 1 0.52 10.97 " Preop >Op Year (Preop) 6 3.86 81.04 * *
- Month (Year) 88 1.63 3434"*
Station 2 0.~3 6.07 *
- P7>ELEZ Preop-Op X Station 2 0.04 0.84 NS Error 188 0.05 (continued)
Tcble 2-2 (Continued) MULTIPLE SOURCE OF COMPARISONS' PARAMETER VARIATION" DF- MS F (ranked in decreasing order) Surface Dissobed Preop-Op 1 2.78 171.88 "
- Preop >Op Oxygen Year (Preop) 6 0.51 31.31 "
- Month (Year) 88 3.02 186.55***
Station 2 0.1 I 6.78*
- P5>E2 EZ Preop-Op X Station 2 0.04 2.44 NS Error 188 0.02 Bottom Dissohed Preop-Op I 1.28 50.51 "
- Preop >Op Oxygen Year (Preop) 6 3.44 135.21 "
- Month (Year) 88 5.00 196.70 "
- Station 2 0.33 12.90 "
- PS>P2>P7 Preop-Op X Station 2 0.07 2.76 NS Error 188 Orthophosphate Preop-Op 1 6.93 1.26 NS 9
L Year (Preop-Op) 6 148.88 27.13 "
- Month (Year) 88 237.51 4 3.2 8* *
- Station 2 13.32 2.43 NS Preop-Op X Station 2 0.31 0.06 NS Error 188 Total Phosphorus Preop-Op i 51.07 1.42 NS Year (Preop-Op) 6 1987.32 55.15 * *
- Month (Year) 87 393.65 10.92 * *
- Station 2 65.92 1.83 NS Prt4-Op X Station 2 22.20 0.62 NS Error 187 36.04 Nitrate Preop-Op I 194.44 2.32 NS Year (Preop-Op) 6 4013.64 47.92* *
- Month (Year) 88 10886.83 129.97* "
Station 2 547.46 6.54 " El.El>P5 Preop-Op X Station 2 119.69 1.43 NS Error 188 83.76 (continued)
O O O Tcble 2-2 (Continued) MULTIPLE '
~- SOURCE OF ' COMPARISONS
- PARAMETER VARIATION
- DF MS - F (ranked la decreasing order)
Nitnte Preop-Op 1 165 6.26* Op>Prrop Year (Preop-Op) 6 3.M 6.72"
- Month (Year) 88 7.82 13.41 * *
- Station 2 2.58 4.43* P7>P2 P5 Preop-Op X Station 2 0.65 1.12 NS Error 188 0.58 Ammonia Preop-Op I 348.13 39.57 "
- Op> Preop Year (Preop-Op) 5 1235.37 140.41 "
- Month (Year) 74 78.15 8.88 * "
Station 2 18.27 2.08 NS Preop-Op X Station 2 3.52 0.40 NS Error 158 8.80 g *Besed on averaged monthly collections for all parameters NS = not significant (p 2 0.05) J *Preoperationalyears: 1987-1989 at each station for all parameters except ammonia, * = significant(0.05 2 p>0.01)
~
which was April 1988 through December 1989 " = highly significant (0.012 p >0.001)
*** = very highly significant (0.001 > p)
Preoperational versus operational period, regardless of station ; dYear 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 of3 rar
' Interaction beturen main effects
" Underlining indicates no significant difference based on a test of H,: LSMEAN(i)=LSMEAN(j). Waller-Duncan multiple means comparison test used for significant main effects.
LS Means used for significant interaction terms. i 4
P2 SURFACE P3 BOTTOM 25 25
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g i, q l $~ n_ i l o?3 'W n 80 m 82 83 84 85 M 87 8B 5 90 9192 93 M 95 W 80 m 82 83 84 85 86 87 88 W 90 m 92 93 M 95 YEAR M P5 SURFACE P5 BOTTOM 25 25 20 g 20-d15 15 \ I 10 s _ k -s _- ' 10 j p, sg'& ~- Ef % M 80 8182 83 84 85 W 87 88 5 90 9192 93 M 95 WAR i 'm 3 80 m 82 83 84 85 86 87 88 5 90 9192 93 94 95 YEAR P7 SUHFACE g g 25 3 6 20 5
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3 I ~~ 1 0 N n 80 8182 83 84 85 86 87 88 W 90 9192 93 94 95 gg gggg p gg YEAR Figure 2-3. Time-series of annual means and 95% confidence inten als and annual minima and manma of surface and bottom temperatures at Stations P2, PS, and P7,1979-1995. Seabrook Operational Report,1995. 2-12
2.0 WATER QUALITY O t a P7. This relationship has remained constant 1995 (Table 2-4). At T7 the annual mean also between the preoperational and operational increased from 8.3 'C to 9.7 C. Monthly periods, as reflected in the non-significant Preop- temperatures measured in 1995 at both T7 and DS Op X Station interaction term (Table 2-2). were generally warmer than, or similar to monthly temperatures from previous years. Monthly mean differences between surface and bottom temperatures (surface - bottom: Figure 2-4) Monthly temperatures at DS were generally 1-2 'C indicated that the water column at each station was warmer than at T7 during all months except June essentially isothermal (AT = -1 C to +1*C) through August. In June and July, DS was about during six to seven of twelve months, during both 1 *C cooler, and temperatures were almost , operational and preoperational periods. identical in August (Table 2-3). These average j Temperature stratification began to develop at each monthly T values (DS-T7) showed full compliance j station by May in 1995, with AT values of about with the Station's NPDES permit, which has been l 2 C. At Station P2 in 1995, the maximum AT the case throughout the operational period. j occurred in June, with a surface-bottom difference of 7.3"C. A smaller peak occurred again in SnWtv August, with a difference of 6.7'C. At Stations P2 and P5, a small peak occurred in June, with Monthly average surface salinities at P2 followed differences of 5.9-6.5'C respectively, but a distinct seasonal pattern (Figure 2-6) that was n maximum AT occurred in August, when related to freshwater influx and precipitation, air U temperature differences where about 7.0-7.2 C temperatures and winds, and tides and currents, respectively. Temperature dif- ferences then Several major freshwater sources influenced began to decline to approximately 3-4*C by salinities in the nearshore area off Hampton September. The water column again became Harbor, including the Androscoggin and Kennebec isothermal by late October. Preoperational and Rivers in Maine (Franks and Anderson 1992), the j operational mean values indicated that the AT peak Piscataqua River in New Hampshire and the typically occurred in July or August at each station Merrimack River in Massachusetts (NAl 1977). (Figure 2-4), thus the occurrence of maximum AT Salinities were typically highest during the colder in June at P2 in 1995 was unusual. The maximum months due to low precipitation and runoff. AT at all stations in 1995 was unusually high Salinities declined to their lowest levels of the year (about 7-8 *C) as maxunum values are typically on when freshwater influx reached its peak level in the order of 5.5 C to 6.5'C. the spring, due to spring storms combined with snow melt. Bottom salinities exhibited a similar Continuous surface temperatures recorded at but less pronounced seasonal pattern. Waters Stations DS (discharge) and T7 (farfield) in 1995 within the study area are relatively shallow, thus showed similar a seasonal pattern as temperatures storms and strong currents can, at times, affect the recorded at the water quality stations including a entire water column (NAI 1979). However, distinct peak in August that was approximately 2 bottom waters in 1995 generally exhibited more .
'C warmer than in 1994 at both stations (Table 2- stable temperature and salinity levels over the year 3, Figure 2-5,). The annual mean temperature at compared to surface waters, i.e., temperature and DS increased from 9.4 C in 1994 to 10.4 *C in salinity changed at a faster rate and to a larger 9
2-13
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JAN PEB W APR MAY JUN JUL AUG SEP OCT NOV DEC uCNm Figure 2-4 Monthly mean difference and 95% confidence intervals between surface and bottom temperatures (*C) at Stations P2, PS, and P7 for the preoperational period (1979-1989) and monthly means for the operational period (1991-1995) and 1995. Seabrook Operational Report,1995. 2-14
( V U . b h ; Table 2-3. Monthly Mean Surface Temperatures (*C) and Temperature Differences (AT,*C) Between Discharge (DS) and Farfield (T7) Stations Collected from Continuously-Monitored Temperature Sensors, July 1990-December 1995. Seabrook Operational Repert,1995. 1991' 1992 1993 1994* 1995 1990 MONTH DS T7 AT DS T7 AT DS T7 AP DS T7 AT* DS T7 AT* DS T7 AP
-* 6.47 4.71 1.76 6.02 432 1.70 5.69 3.80 1.89 4.I; 2.57 1.55 637 4.66 1.72 JAN - -
538 4.17 1.21 4.74 2.92 1.82 3.52 138 2.14 2.27 132 0.91 5.41 3.54 1.86 FEB - - - 5.11 3.78 133 4.94 3.16 1.78 3.26 1.63 1.63 2.69 1.73 0.96 4.67 3.23 1.44 MAR - - - 6.99 637 0.62 5.93 4.26 1.67 5.04 4.44 0.60 - - - 6.86 533 1.53 APR - - - 10.43 10.21 0.22 10.52 1032 0.20 10.74 10.02 0.72 - - - 9.56 8.20 137 MAY - - - ",. JUN - - - 13.81 13.70 0.11 11.94 11.84 0.10 11.65 10.53 1.12 - - - 13.63 15.58 -1.94 JUL 14.54 14.63 -0.08 14.58 15.02 0.44 13.81 14.16 -035 15.92 14.5', 139 - - - 14.76 15.48 -0.73 AUG" 18.16 1836 -0.20 16.86 17.06 -0.20 15.61 14.69 0.92 18.77 16.69 2.08 15.44 15.53 -0.09 17.40 17.71 -031 SEP 1631 16.09 0.22 15.66 15.69 -0.03 14.03 12.69 134 11.62 12.19 -0.57 1633 15.47 0.86 15.93 15.28 0.64 OCT 13.04 12.11 0.93 11.87 11.68 0.19 - - - 10.13 11.27 -1.14 13.94 12.69 1.25 14.27 13.08 1.18 9.44 0.80 11.00 933 1.67 9.01 7.59 1.42 8.03 933 -130 11.77 1037 1.40 9.17 9.11 0.M NOV 10.24 8.91 732 1.59 8.45 6.81 1.64 732 5.61 1.71 5.64 7.55 -1.91 8.74 6.90 1.84 6.76 5.53 1.23 DEC
' Commercial operation began in Au8ust,1990.
- Data either not collected, or an 4 --
c .. . : failure occuned.
'AT = Surface dischar8e - surface farfield temperatures ('C)
*Seabrook Station was omine April-July.
NOTE ID (surface, mid-depth, bottom) and T7 (mid-depth and bottom) sensors decommissioned July 1,1933. See 1993 Seabrook Operational Report for data summary
2.0 WATER QUALITY m Stations DS (Discharge) & T7 (Farfield) O 20 h -
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g, ASONDJFMAMJJASONDJFMAMJJASONOJPMAMJJASONDJFMAMJJASONOJFMAMJJASONO 1990 1991 1992 1993 1994 1995
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Figure 2-5. Comparison of monthly averaged contmuous temperature ('C) data collected at the surface i at discharge (DS) and farfield (T7) stations durmg commercial operation, August 1990-December 1995. Seabrook Operational Report,1995. 1 Table 2-4. Annual Mean Surface Temperatures (*C)* and Coefficients of Variation l (CVS) at Stations DS and T7 During Operational Monitoring Conducted by YAEC. Seabrook Operational Report,1995.
~ ,
' STATION DS . . STATION T7 YEAR ICV :MEAN- :CV 1991 10.6 38.9 9.9 48.1 1992 9.4 41.9 8.3 54.6 1993 9.2 53.3 8.6 57.4 1994 9.4 61.6 8.3 72.4 1995 10.4 43.6 9.7 55.4
'mean of monthly means; n=12 in 1991,1993 and 1995; n=11 in 1992; n=8 in 1994. O 2-16
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g, l 7 _ _ _. pW 7 ___. Opsmond 6, 6 M RB W APR lMt M R AUG SEP OCT D DEC M FEB MAR APR IMY JUN R AUG SEP OCT U DEC WON 1H MONTH i i I l I i Figure 2-6. Surface and bottom salinity (ppt) and dissolved oxygen (mg/L) at nearfield Station P2, l monthly means and 95% ennMmee intervals for the preoperational period (1979-1989) and monthly means for the operational period (1991-1995) and 1995. Seabrook Operational Report,1995. O l 2-17
2.0 WATER QUALITY degree from month to month in surface waters in recent years annual mean salinity has declined when compared to bottom waiers. from 30.7 ppt in 1990 to 29.2 ppt in 1993 (MDMR 1991, 1992, 1993, 1994). Boothbay harbor Seasonal patterns of surface and bottom salinity salinities rebounded slightly in 1994 and 1995, to were similar between preoperational and an annual mean of 30.3 ppt (MDMR 1995; 19%). operational periods. Surface salinities measured at Station P2 in 1995 were below preoperational and Dissolved Oxvnen operational means for the months of January through March, and were similar to the Surface and bottom dissolved oxygen preoperational and operational monthly means for concentrations at P2 exhibited a seasonal pattern in the rest of the year except for November (Figure 1995 similar to nrevious years (Figure 2-6). 2-6). Bottom salinity followed a similar pattern, Dissolved oxygn centrations were highest during except monthly variability was less than surface the cooler winter nionths, and peaked in late winter salinity (Figure 2-6). Differences between (February and March); concentrations were lowest operational and preoperational surface salinities from August through October when temperatures (Table 2-1) were not significant, but there were reached the annual maximum (Figure 2-2) Surface significant differences among stations (Table 2-2). dissolved oxygen concentrations at Station P2 in Bottom salinities were significantly higher during 1995 were lower than preoperational monthly the preoperational period, and there were means throughout the year except in December, significant differences among stations (Table 2-2). Monthly means in February through April, June, and August through November in 1995 were at or The Preop-Op X Station term was not significant below the lower 95% confidence limit for for both surface and bottom salinities. This preoperational means. Similar results were indicates that differences in salinity among stations observed for bottom dissolved oxygen were consistent between the preoperational and concentrations at Station P2 in 1995. Ahhough operational periods, and the operation of Seabrook dissolved oxygen concentrations in 1995 were
)
Station has not affected salinity, lower on average than in previous years, they were I within the range of values observed in the past Long-term annual salinity exhibited a general (Table 2-1). downward trend during the study period at all stations and at both depths (Figure 2-7). A similar The overall significant decline in surface and trend was observed at the Maine Department of bottom dissolved oxygen concentrations was about Marine Resources West Boothbay Harbor long- 0.1 to 0.2 mg/L (Preop-Op term of ANOVA I term environmental monitoring station, suggesting model, Table 2-2) and is a reflection of the overall l a regional trend. This station is fairly comparable significant increases in temperature over the years. I to the Seabrook water quality stations; although in Differences among the three stations over all years a more protected location, there is relatively little were significant for both surface and bottom freshwater input to the harbor. Long tenn (1966- concentrations. The interaction term (Preop-Op X 1985) annual mean surface salinities (taken at -5.5 Station) for both surface and bottom dissolved feet MLW) at the West Boothbay Harbor station oxygen was not significant. ranged between 30 and 32 ppt (MDMR 1987), and 2-18
l Swhoe.Smim P2 nn*=% P2 as ns. 1 no no n as ms - I d g8 /\ -
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l lu no lu no l a3- as . 3D BD . Eh. as. l M M 8182 m M 85 M 87 m M 90 m 92 M N 95 3 80 8182 E N 85 86 87 E M 90 5 92 93 W 95 YEAR M i Safam Station Ps Bonom, Statim Ps as ns no ab 15 ms -
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5 80 8182 D N 85 M 87 M M 90 m 92 93 W 95 3 2 8182 83 N 85 M 87 M M 90 9192 93 M 95 YEAR M i Sudace, Statim PT Botun,Stahm P7 ns 335 no- no 15 m3
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_u s '\/' N/ u ns- ms no no as 35 30 SD 35 25. 3 80 8182 D N 85 M 87 M M 90 m 92 93 N 95 W 80 8182 83 N 85 86 87 E M 90 9192 93 M 95 YEAR YEAR i
- n,
() Figure 2-7. Time-series of annual means and 95% confidence intervals of surface and bottom salinity at Stations P2, PS, and P7,1979-1995. Seabrook Operational Report,1995. 2-19
2.0 WATER QUALITY 2.3.1.2 Nutrients October), and exceeded the preoperational upper confidence limits in all other months. Both the Phosphorus Species operational and 1995 annual mean concentrations were higher than preoperational means (all years Monthly mean surface orthophosphate concen- and recent years) at all three stations (Table 2-1). trations in 1995 at P2 exceeded the preoperational However, there were no significant differences and operational monthly means in January, between operational and preoperational mean February, April, August, September and concentrations (Table 2-2). November, resulting in a seasonal pattern that was slightly different from earlier years (Figure 2-8). Operational mean total phosphorus concentrations While concentrations were usually lowest from differed by no more than 1.4 pgP/L among the May to September during the preoperational and three stations (Table 21). Among-station operational periods, an abbreviated period of low differences were as large as 3.3 pgP/L during the concentrations from May through July was preoperational period. Over the period of 1987-observed in 1995. A pattern of highest 1995, differences among the stations were not orthophosphate concentrations during late fall significant, nor was the interaction of the main through late winter and lowest concentrations effects (Preop-Op X Station, Table 2-2). during the summer is typical of northern temperate waters in general and is largely associated with the Nitrogen Snecies seasonal nutrient requirements of the primary producers (Section 3.0). Nitrate concentrations at P2 exhibited strong seasonality in 1995 typical of pattems obsened in Annual mean orthophosphate concentrations in previous years (Figure 2-9). Monthly mean 1995 were approximately 3.1-5.6 pgP/L higher concentrations in 1995 were within the 95% than preoperational (all years and recent years) cnnh limits of the preoperational period during means (Table 2-1). Operational period mean six manths (March, May, June, August, September, concentra- tions were 0.2-0.3 gP/L lower than and October), and exceeded the upper confidence recent preoperational years (Table 2-1), but these limits of the preoperational means in the remauung differences were not statistically significant (Preop- months. The annual mean concentration observed Op term, Table 2-2). Differences between stations in 1995 was higher than during the recent (both periods combined) were also not significant, preoperational period (1987-1989) at each station nor was the interaction of main effects (Preop-Op (Table 2-1). The maximum nitrate concentrations X Station term, Table 2-2). at each station in 1995 were the highest observed in the time series (Table 21). Over the entire Seasonal patterns in total phosphorus in 1995 operational period, means at Stations P5 and P7 generally followed the pattern observed in previous were lower than recent preoperational years, while years (Figure 2-8) except that concentrations were the mean at Station P2 was higher than recent higher in 1995. Monthly mean total phosphorus preoperational years (Table 2-1). There were no concentrations observed in 1995 fell within the significant differences between periods, and 95% confidence limits of preoperational monthly concentrations at Stations P7 and P2 were signifi-means during only three months (May, July, and 2-20
t 1 2.0 WATER QUALITY 4 O k-) ore w menh=a yo
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\
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m , N ,, , p,'
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e \ / ' iso f / 7 _\p', ', 1 i ^ 10 o JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NCN DEC MONTH l i I Figure 2-8. Surface orthophosphate and total phosphorus concentrations (pg P/L) at Station P2, ( monthly means and 95 % confidence intervals for the preoperational period (1979-1984 and
\ 1987-1989), and monthly means for the operational period (1991-1995) and 1995. Seabrook Operational Report,1995.
2-21
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D JAN PTB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 2-9. Surface nitrate-nitrogen, nitrite-nitrogen and ammonia-nitrogen concentrations ( pg N/L) at nearfield Station P2, monthly means and 95% confidence intervals for the preoperational period (1979-1984 and 1987 1989), and monthly means for the operational period (1991-1995) and 1995. Seabrook Operational Report,1995. 2-22
1 2.0 WATER QUALHY l cantly higher than PS (Table 2-2). The interaction Temperature between main effects was not significant. Both low and high tide temperature in 1995 Nitrite concentrations at P2 exhibited a similar followed the same seasonal patterns obsened monthly pattem to nitrate both in the long-term and previously (Figure 2-10). Monthly mean low-tide in 1995 (Figure 2-9). Monthly mean concentrations temperatures were highest in August at 18.9 C and ! in 1995 exceeded the preoperational upper 95% lowest in January at 1.l*C. Across the year, low confidence limits in several months (March, July, tide temperatures exceeded the 95% confidence and November) and fell below the lower 95% limits of the long-term means during January, June, . confidence limits in August and September. The July, and August, but the annual mean was similar maximum nitrite concentration in 1995 (20.5 to the long-term mean (Table 2-5). Annual mean pgN/L, Station P7) was the highest observed in the low-tide temperature from 1980-1995 ranged from . time series for any station (Table 2-1). The 9.l to ll.l *C, averaging 10.I'C. operational annual mean concentration of nitrite was
- significantly higher than the preoperational mean. High-tide tuumahues in 1995 were also highest in Station differences were small but significant over August (16.9*C) and were lowest in February l
all years (Table 2-2). The interaction of Preop-Op (2.4 C). Monthly mean high-tide temperatures in X Station was not significant. 1995 exceeded the 95% confidence limits of the 16-year monthly means during January, June, August, n As in previous years, ammonia concentrations did September and October, resulting in an annual
'h not exhibit a strong seasonal trend (Figure 2-9).
Monthly mean concentrations in 1995 were higher temperature value that was 0.6'C above the mean ! (Table 2-5). than the preoperational mean in all months except January and July. The maximum ammonia Annual mean high-tide temperature was consistently concentration in 1995 at each station were higher lower than low-tide temperature, ranging from 8.6 to than any previously observed (Table 2-1). 10.1 C during the study period, and averaging Operational mean concentrations were significantly 9.3*C (Table 2-5). Temperature was more variable , higher than preoperational concentrations (Tables 2- among months at low tide than high tide in 1995, I and 2-2). There were no significant differences reflecting a pattern consistent with the long-term among stations and the Preop-Op X Station average conditions. l interaction term was not significant (Table 2-2). 1 Sahnity I 2.3.2 Estuarine Water Ouality 1 Salinity in Hampton Harbor at low tide and high tide
)
Monthly averages of surface water salinity and in 1995 exhibited similar monthly patterns to ! temperature at high and low slack tides in Hampton previous years (Figure 2-11). Salinity at low tide in Harbor were used to examine seasonal and annual 1995 was highest in the late summer and early fall, patterns of these parameters in the Hampton- Although the monthly pattem was similar, annual Seabrook estuary. mean low tide salinity in 1995 was the third highest O 2-23 1
2.0 WATER QUALITY l Lo no. 25 gg y,,,, i. 20 e is l l10 $ o !
-5 i JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC I MONTH l I
i High Tide as ,,y,,,, 3. 1 no a ,, .... 10
\ l kf 6. ..
0
-6 ,
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC I MONm Figure 2-10. Monthly means and 95% confidence limits for temperature measured at low and high tides in Hampton Harbor from May 1979 - December 1995 and monthly means in 1995, Seabrook Operational Report,1995. 2-24
O O O Table 2-5. Annual Mean" and 95% CL6 for Temperature ( C) and Salinity (PPT) Taken at Both High and Low Slack Tide in Hampton Harbor from 1980-1995. Scabrook Operational Report,1995. LOW TIDE HIGH TIDE YEAR TEMPERATURE . SALINITY TEMPERATURE SALINITY 1980 9.6 i 4.4 29.9 i 1.4 9.1 i 3.6 32.0 i 0.5 1981 10.1 i 4.4 28.9 i 1.1 9.3 i 3.8 31.5 i 0.4 1982 10.2 i 4.1 27.3 i 1.5 9.2 1 3.5 31.2 i 0.6 1983 10.4 i 4.3 25.5 1 2.4 9.9 i 3.4 30.1 i 0.9 1984 10.4 i 4.1 25.8 i 2.3 9.4 i 3.1 30.2 i 0.9 1985 10.6 i 4.2 29.1 i 1.0 10.1 i 3.3 32.2 i 0.3 1986 10.0 i 3.9 27.7 i 1.3 9.4 i 3.0 31.5 i 0.4 1987 10.0 i 4.3 27.5 i 2.2 8.9 i 3.5 30.7 i 0.9 1988 9.7 i 3.9 27.8 i 1.0 9.2 i 3.3 31.3 i 0.4 1989 10.2 i 4.4 28.0 i 1.2 9.2 i 3.3 31.4 i 0.7 1990 10.3 i 4.3 27.2 i 1.2 9.7 i 3.6 31.3 i 0.6 1991 11.1 i 4.0 28.0 i 0.9 9.8 i 3.1 30.9 i 0.4 1992 9.1 i 4.0 27.2 i 1.6 9.7 i 2.9 29.4 i 1.6 1993 9.5 i 4.4 26.8 i 1.9 8.7 i 3.5 29.5 i 1.1 1994 9.8 i 4.6 27.8 i 1.9 9.1 i 3.7 30.9 i 0.8 1995 10.2 i 4.3 28.7 i 1.4 9.9 i 3.4 31.5 i 0.2 OVERALIf 10.1 i 0.9 27.7 i 0.4 9.3 1 0.7 31.0 i 0.2
- Annual mean=mean of 12 monthly means
- Confidence limits expressed as half the confidence interval.
- Overall mean=mean of annual means.
l
J l l l 2.0 WATER QUALITY l O
#'_ _ As Years im sa
... .......... , i q..
i 1
} 29 ,J ,
' 'J .
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se 2o I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONm Hich Tide _ _ _ All Ye.ars 3 a _" e. - i
; l 1 I
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n 2 I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Monm i l l Figure 2-11. Monthly means and 95 % confidence limits for mahnity measured at low and high tides in Hampton Harbor from May 1979 - December 1995 and monthly means in 1995. Seabrook ' Operational Report,1995. I 2-26
2.0 WATER QUALITY r recorded since 1980 (Table 2-5). Salinity at low (", concentrations (0.1 to 0.2 mg/L) was very small, tide in 1995 exceeded the historical upper 95% and not likely to affect balanced indigenous confidence limits in April through October. populations or aquatic organisms. Salinity at high tide showed less variability than Water quality measurements have generally low tide salinity (Figure 2-11). Historically, high remained similar among the three stations. Small tide salinity was lowest in March through June, but but significant station differences were detected in I in 1995 there was very little monthly variability. surface and bottom temperatures, salinity, and High tide salinity was the fourth highest recorded dissolved oxygen, and in surface nitrate and nitrite since 1980 (Table 2-5) and exceeded the upper concentrations. In each case, however, these 95% confidence limits for the months of March differences were consistent between the through July and October, preoperational and operational periods, and were l not due to the operation of Seabrook Station. 2.4 DISCUSSION Historic high levels of nitrate, nitrite and ammonia l The seasonal cycles of all 1995 water quality were observed in 1995, and the 1995 nitrate and parameters were consistent with those of ammonia means were higher than the preopera-preoperational years. Air temperature can directly tional and operational means at each station. In affect water temperature and indirectly mediate e dissolved oxygen through water temperature, while temperate waters nitrogen levels are usually highest ( precipitation can affect salinity. In 1995, air in the spring and fall and very low during the temperature was generally warmer than average, summer (Parsons et al.1977). The high levels of and precipitation was below average. Consistent nitrate in 1995 occurred in March and November with air temperature, surface and bottom monthly and may be examples ofisolated short term highs. mean intake station water temperatures in 1995 The highest levels of nitrite and ammonia occurred were warmer than both the preoperational and in July and June when they should be near their operational mean water temperatures, continuing annual lows. These high levels may represent a a trend that started in the recent operational years. release of nutrients following a die off of phyto-Surface and bottom water temperatures in the plankton, or a release of organic nitrogen com-operational period were significantly warmer than pounds from zooplankton (Parsons et al.1977). the preoperational period at all stations (NAI 1995, NAI and NUS 1994, NAI 1993). Surface The results of the analyses of water quality dissolved oxygen was significantly lower at all parameters highlight the cyclical and variable nature stations in the operational period, probably due to of these parameters Preoperational and operational increased water temperatures. The significant pattems for all parameters were consistent (Table 2-differences in water temperature and dissolved 6). Overall, no locahzed effects to water quality due oxygen between the preoperational and operational to the operation of Seabrook Station were observed. periods were observed at all stations and were probably due to an area-wide warming trend, and not due to the operation of Seabrook Station. The magnitude of the decrease in dissolved oxygen 2-27
2.0 WATER QUALITY O Table 2-6. Summary of Potential Effects of Seabrook Station on Ambient Water Quality. Seabrook Operational Report,1995. OPERATIONAL. PERIOD SPATIAL TRENDS SIMILAR TO RELENT PRE- CONSISTENT WITH PARAMETER DEPTH OPERATIONAL PERIOD?' PREVIOUS YEARS 6 Temperature surface Op> Preop yes bottom Op> Preop yes Salinity surface yes yes bottom Preop >Op yes Dissolved oxygen surface Preop >Op yes bottom Preop >Op yes Nitrate surface yes yes Nitrite surface Op> Preop yes Ammonia surface Op> Preop yes Onhophosphate surface yes yes Totalphosphate surface yes yes ' based on ANOVA for 1987-1995, when all 3 stations were sampled concurrently 6 PREOP-OP X STATION term in ANOVA model O 2-28 ) l 1
i 1 l 2.0 WATER QUALITY ( , (g)
2.5 REFERENCES
CITED waters; Hampton-Seabrook, NH. Prepared for l Public Senice Co. of New Hampshire. APHA (American Public Health Association). 1989. Standard methods for the examination of 1979. Annual Summary Repon for i water and wastewater,17th edition. 1977 Hydrographic Studies off Hampton Beach, New Hampshire. Tech. Rep. X-I. Boston Globe. 1996. Boston's daily temperatures Papaational Ecol. Monit. Stud. for Seabrook Station. for 1995 - A month-by-month report. January 1996. 1993. Seabrook Emironmental Franks, P.J.S. and D.M. Anderson. 1992. Along-Studies, 1992. A characterization shore tran:: port of a toxic phytoplankton bloom emimnmental conditions in the Hampton-in a buoyancy current: Alexandrium tamarense Seabrook area during the operation of Seabrook in the GulfofMaine. Marine Biology 112(153 Station. Tech. Rep. XIV-1. 164). 1995. Seabrook Station 1994 Gilbert, Richard O. 1987. Statistical methods for Emironmental Studies in the Hampton environmental pollution monitoring. Van Seabrook Area. A Characterization of Nostrand Reinhold Co. Inc., New York. Environmental Conditions During the l Operation of Seabrook Station. Prepared for Mame Department of Marine Resources (MDMR). North Atlantic Energy Service Corporation. 1991. Boothbay Harbor Environmental Data,
. 1990. West Boothbay Harbor, Maine. Normandeau Associates (NAI) and Nonteast Utilities Corporate and Environmental Af fairs 1992. Boothbay Harbor Emiron- (NUS). 1994. Seabrook Emironmetal Studies,1993. A Characterization of Environ-mental Data,1991. West Boothbay Harbor, ,
Maine' mental Conditions m the Hampton-Seabrook Area During the Operation of Seabrook Station. 1993. Boothbay Harbor Emiron- Prepared for North Atlantic Energy Senice mental Data,1992. West Boothbay Harbor, Corporation. Maine' Parsons, T.R., M. Takaheshi, and B. Hargrave. i 1994. Boothbay Harbor Emiron- 1977. Biological Oceanographic Processes, mental Data,1993. West Boothbay Harbor, 2nd ed. Pergammon Press,New York. 332 p. Portland Press Herald. 1996. 1995 Portland 1995. Boothbay Harbor Environ- weathu wTap up. January 1996. I mental Data,1994. West Boothbay Harbor' Maine' S Lal, R.R. and F.J. Rohlf. 1981. Biometry. W.H. l Freeman and Co., San Francisco, CA 859 p. 1996. Boothbay Harbor Environ-mental Data,1995. West Boothbay Harbor, Stewan-Oaten, A., W.M. Murdoch, and KR. l Maine. Parker,1986. Emironmentalimpact assess-l ment: "pseudoreplication in time?" Ecology, 67:929-940. Normandeau Associates (NAI).1977. Summary I)v,m nt Assessment of anticipated impacts p of construction and operation of Seabrook USEPA (United States Emironmental Protection Agency).1979. Methods for chemical analyses i d Station on the estuarine, coastal and offshore of water and wastes. EPA-600/4-79 020. EMSL, Cincinnati, OH. 2-29 l
3.0 PHJTOPLANKTON O TABLE OF CONTENTS O PAGE 3.0 PHYTOPLANKTON
SUMMARY
. . .................................... . . . . . . . . . . . . . . . . . 3 -ii LIST OF FIGURES . . . . . .. . . . . . . . . . . . . . . . . . . . . . . ..... ......
4 . . . . . . . . . 3-iii LIST OF TABLES . . . . . . . . . . . . . . . . . . . . .... .........................3-iv LIST OF APPENDIX TAB LES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-iv 3.1 INTROD U CTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 3-1 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 3.3 RESULTS .............. ...................... ........ . 3-5
\
3.3.1 Total Conununity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3.3.1.1 Phytoplankton .......... .... . ..... ... ... ... .. ... . 3-5 3.3.1.2 Chlorophyll a Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . 3-13 3.3.2 Selected Species . . . . . . . ....... ........ ............ 3-15 3.3.3 PSP Levels . . . ................... ................. 3-16 3.4 DISCUSSION . . ....... ................................. 3-16 3.4.1 Community Interactions . . . . . . . . . . . . . ..... ........... 3-16 i 3.4.2 Effects of Plant Operation . . . . . . . . . . . . . . . . . . . . . . ..... .. 3-18 ) i
3.5 REFERENCES
CITED . . . . ....... ....... ............ .. . 3-19 i 1 J f i% 1 3-i
3.0 PHYTOPLANKTON
SUMMARY
The phytoplankton community historically has been highly variable in species composition and abundance. This variability has continued during the operational period. Taxa of the class Bacillariophyceae (diatoms) dominated the community numerically throughout most of the preoperational and operational periods and in 1995. In some years, e.g.,1992, the Prymnesiophyceae taxon Phaeocystis pouchetii was dominant because of its spring bloom. Such shifts in community dominance between diatoms and P. pouchetii were also observed during several preoperational years. Total community abundance and abundance of the selected species (the diatom Skeletonema costatum ) varied from year-to-year during the study period. Community composition during the operational period was generally similar to that observed historically. Chlorophyll a concentrations were also variable from year-to-year, but were independent of phytoplankton abundances. For example, during 1992 the increase in phytoplankton abundance without a corresponding increase in chlorophyll a concentration was likely due to the exceptionally high numbers of Phaeocystis pouchetii, a small-celled form. Any differences in community composition or chlorophyll a concentrations observed during the operational periods occurred at both the nearfield and farfield stations. The ANOVA model comparing nearfield and farfield phytoplankton assemblages showed that total abundance increased in the operational period. Abundances were different between stations, but these differences were consistent between the preoperational and operational periods. Similar results were observed in the ANOVA model comparing nearfield and farfield abundances of Skeletonema costatum. Operational abundances were greater than preoperational abundances for both models (P2 versus P7 and P2 versus PS), and station differences were consistent between the preoperational and operational periods. For chlorophyll a concentrations, there was no significant difference between preoperational (1987-1989) and operational periods, , although there were differences among stations. In all cases, the interaction between time and space (Preop-Op X Station term) was not significant, indicating no impact due to the operation of Seabrook Station. O 3-ii
3.0 PHYTOPLANKTON LIST OF FIGURES 3-1. Phytoplankton sampling stations. . . . ... .. .... .... ... ... . .. . . 3-2 3-2. Monthly mean log (x+ 1) total abundance (no./L) of phytoplankton at nearfield Station P2, monthly means and 95% confidence intervals over all preoperational years (1978-1984), and monthly means over operational years (1991-1995) and in 1995. . . . . . . . . .... . . .. ... .. ...... ...... ... . 3-6 3-3. Percent composition of major phytoplankton groups at Station P2 over all preoperational (1978-1964) and operational years (1991-1995) and in 1995. . . . . ..... 3-7
'3-4. Geometric mean abundances (x 10' cells /L) and 95% confidence intervals of annual assemblages, and percent composition of four selected phytoplankton groups at Station P2 during each year of the preoperational and operational periods. . . . . . ... .. ....... ......... .. . .. .. . ..... . 3-9 3-5. (a) Mean monthly chlorophyll a concentrations and 95 % confidence intervals at p(-/
Station P2 over preoperational years (1979-1989) and monthly means over operational years (1991-1995) and 1995; (b) mean monthly chlorophcll a concentrations and phytoplankton log (x+ 1) abundances during the pm perational and operational periods. . . . . . . . . . . . . . . .. ............. .. ..... . . 3-14 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- i 1984) and monthly means for the operational period (1991-1995) and 1995. . . . .... . 3-15 , I 3-7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor, mean and 95 % confidence intervals over preoperational years , 1 (1983-1989) and monthly means during operational years (1991-1995) and in : 1995. Data provided by the State of New Hampshire. . . . . ...... . ... .. .. 3-17 i
/ \- l 3 iii l
3,0 PHYTOPIANKTON 1 LIST OF TABLES 1 3-1. Summary of Methods Used in Evaluation of the Phytoplankton Community. ... . .. 3-3 l I 3-2. Geometric Mean Abundance (X 10* Cells /1) of Phytoplzakton (210gm) and Skeletonema Costatum, and Mean Chlorophyll a Concentrations (Mg/m') and Coefficient of Variation (Cv,%) for the Preoperational and Operational (1991-1995) Periods, and 1995 Geometric Means. . . . . ... ... ...... .. ... . 3-8 3-3. Arithmetic Mean Abundance (X 10' Cells /1) and Percent Composition of Dominant Phytoplankton Taxa During the Preoperational Period (1978-1984), Operational Period (1991-1995), and 1995 at Nearfield Station P2. . . ..... ..... . 3-10 3-4. Results of Analysis of Variance Comparing Abundances of Total Phytoplankton, Skeletonema Costatum, and Chlorophyll a Concentrations among Stations P2, P5 and P7 During Preoperational and Operational (1991-1995) Periods. . . . . . . . . . ...... 3-12 3-5. Phytoplankton (210 Mm) Species Composition by Station in 1995. ................ 3-13 3-6. Summary of Potential Effects (Based on Anova) of Operation of Seabrook Station on the Phytoplankton Community. . . . . . . . . . . . . . . . . . .. ................. 3-17 LIST OF APPENDIX TABLES 3-1. A Checklist of Phytoplankton Taxa Cited in this Report . . . . . . . . . . . . . . ...... .. 3-20 O 3-iv
2,0 PHYTOPLANKTON
/G t
3.1 INTRODUCTION
1990. These collections continued on this schedule through December 1995. From each whole water The phytoplankton monitoring program was initi- collection, two one-quart (0.946 L) jars containing ated to identify wasonal, annual, and spatial trends 10 mL of a modified Lugol's iodine fixative were 4 in the phytoplankton community, and to determine filled for phytoplankton taxonomic analyses and if the balanced indigenous phytoplankton commu- one gallon (3.785 L) was reserved for chlorophyll nity in the Seabrook area has been adversely a analyses. Weekly paralytic shellfish poison influenced (within the framework of natural vari- (PSP) toxicity levels from mussels collected in ability) by exposure to the thermal plume. Specific Hampton Harbor were provided by the State of aspects of the community evaluated have included New Hampshire. phytoplankton (taxa 2 10 m in size) abundance and species composition; ultraplankton (taxa < 10 3.2.2 Laboratory Methods m in size) abundance and species composition; community standing crop as measured by chloro- Phytoplankton samples were prepared for analysis phyll a concentrations; abundance of the selected following the steps outlined in NAI (1991). One species Skeletonema costatum, and toxicity levels randomly-selected replicate from each station and of paralytic shellfish poison (PSP) as measured in sample period was analyzed for all taxa and a the tissue of the mussel Mytilus edulis in the second replicate was analyzed for the selected Hampton-Seabrook area. In previous years species Skeletonema costatum only. Two 0.1-mL p ultraplankton taxa were identified and enumerated, subsamples from each replicate were withdrawn V Results had limited accuracy because of the small and placed in Palmer-Maloney nanoplankton size and colonial habits of these organisms. There- counting chambers. For those replicates selected fore enumeration of ultraplankton was eliminated for taxonomic analyses, the entire contents of the from the program in 1995. chamber were enumerated and identified to the lowest possible taxonomic level, usually species. 3.2 METHODS Procedures for preparation of chlorophyll a water 3.2.1 Meld Methods samples followed steps outlined in NAI (1991). Following the extraction of the plant pigment, Near-surface (-1 tr.) water samples for fluorescence was determined and chlorophyll a phytoplankton and chlorophyll a analyses were concentrations ( g/L) were computed. ] collected during daylight hours at Stations P2 (in-take), PS (discharge) and P7 (farfield) (Figure 3-1) 3.2.3 Anivtical Methods using an 8-L Niskin bottle. Collections were taken once per month in January, February and Decem- Seasonal abundance patterns vi the phytoplankton i ber, and twice monthly from March through No- assemblages during the preoperational and opera-vember. Sampling occurred at Station P2 from tional periods were compared graphically using log 1978-1984; from 1978-1981 at Station PS: and (x+1)-transformed monthly mean abundances for from 1982-1984 at Station P7. Chlorophyll a col- the total phytoplankton community and the selected lections resumed at all three stations in July 1986 species (Skeletonema costatum; Table 3-1). The
' and phytoplankton collections resumed in April dinoflagellate Oxytorum sp. was moved from the 3-1
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= phytoplankton stations O
Figure 3-1. Phytoplankton sampling stations. Seabrook Operational Repon,1995. 1 3-2
p p g-) V V V Table 3-1. Summary of Methods Used in Evaluation of the Phytoplankton Community. Seabrook Operational Report,1995. DATES USED DATA SOURCE OF ANALYSIS ' TAXA- STATIONS IN ANALYSIS" CIIARACTERISTICS VARIATION PHYTOPLANKTON Percent Composition All P2 1978-1984; Monthly and annual - 1991-1995 arithmetic mean abundances P2,P5,P7 1995 Monthly arithmetic mean - abundances Abundance All P2,P5,P7 1978-1984; Monthly log (x+1) and - 1991-1995 - mual geometric mean e 2undances Skeletonema costatum P2 1978-1984; Monthly log (x+1) and - 1991-1995 annual geometric mean abundances MANOVA 16 dominants P2,P5,P7 1995 Monthly log (x+1) mean Station abundances; species <l% of total abundance notincluded ANOVA All P2,P7 1982-1984; Monthly log (x+1) mean Preop-Op, Year, 1991-1995 abundances Month, Station Skeletonema costatum P2,P7 1982-1984; Monthly log (x+1) mean Prcop-Op, Year, 199l-1995 abundances Month, Station P2,PS 1979-1981; Monthlylog(x+1) mean Preop-Op, Year, 1991-1995 abundances Month, Station (continued)
Table 3-1. (Continued) DATES USED DATA SOURCE OF ANALYSIS TAXA STATIONS IN ANALYSIS
- CIIARACTERISTICS VARIATION CIILOROPHYLL a Concentration - P2 1978-1989; Monthly arithmetic mean -
1991-1995 concentrations P2,P5,P7 1978-1984; Annual arithmetic mean -- 1987-1989; concentrations 1991-1995 ANOVA -- P2,P5,P7 1987-1989; Monthly arithmetic mean Prcop-Op, Year, 1991-1995 concentrations Month, Station L PSP TOXICITY -- - 1983-1989; Weekly arithmetic mean -- 1991-1995 concentrations
'PREOPERATIONAL PERIOD:
! A. PHYTOPLANKTON B. CHLOROPilYLL a P2 = 1978-1984 P2 = 1978-1984,1987-1989 P5 = 1978-1981 P5 = 1978-1981,1987-1989 l P7 = 1982-1984 P7 = 1982-1984,1987-1989 OPERATIONAL PERIOD: 1991-1995, all stations and parameters 1 l l O O O
3.0 PHYTOPLANKTON
,m
( ) uhraplankton group to the phytoplankton group in (Preop-Op)) and months within year (Month 19% based on new information concerning the size (Year)), which were added to reduce the unex-range of the genus. Slight changes in plained variance, and thus, increase the sensitivity preoperational mean abundances resulted (NAl of the F-test. For both nested terms, variation was
- 1995). The log (x+1) transformation was per- partitioned without regard to station (stations formed on the sample period mean prior to calcu- combined). The final variance not accounted for lating monthly means. Temporal (preoperational- by the above explicit sources of variation consti-operational) patterns in species abundances were tuted the Error term. The preoperational period evaluated using geome ric means and community for each analysis was specified as the period during composition was evaluated by examining the which at least one nearfield and one farfield station l percent composition of dominant (> 1%) taxa. were sampled concurrently (thus maintaining a Chlorophyll a temporal and spatial comparisons balanced model design). Preoperational periods were based on untransformed monthly and yearly for each analysis are listed on the appropriate arithmetic mean concentrations. The similarity figures and tables. For all preoperational compari-among the three stations with respect to species sons, the focus was on intake Station P2 because it composition of the dominant phytoplankton taxa had the longest time series. In all cases the opera-was evaluated statistically using a multivariate tional period evaluated in this report includes col-analysis of variance procedure (MANOVA, Harris lections from 1991-1995. Finally, weekly mean 1985). Operational /preoperational and nearfield/ PSP toxicity levels were arithmetically averaged farfield differences in total abundances of S. over the preoperational and operational periods and V costarum and phytoplankton and mean chlorophyll presented graphically.
a concentrations were evthated using a multi-way analysis of variance procedure (ANOVA, SAS 3.3 RESULTS Institute, Inc.1985). A fixed effects ANOVA model was used to test the null hypothesis that 3.3.1 Total Cammunity spatial and temporal abundances during the preoperational and operational periods were not 3.3.1.1 Phytophnkton significantly (p>0.05) different. The data col-lected for the ANOVAs met the criteria of a Seasonal Trends at Station P2 Before-After/ Control-Impact (BACl) sampling design discussed by Stewart-Oaten et al. (1986), Operational monthly mean phytoplankton abun-where sampling was conducted prior to and during dances at Station P2 were within preoperational plant operation and sampling station locations 95% confidence limits during all months other than included both potentially impacted and non-im- April, when the operational mean exceeded the pacted sites. The ANOVA was a two-way facto- upper preoperational confidence limit (Figure 3-2). rial with nested effects that provided a direct test Monthly mean abundances at P2 in 1995 varied for the temporal-by-spatial interaction. The main about the preoperational means, exceeding upper effects were period (Preop-Op) and station (Sta- confidence limits in April, May and June, then l tion); the interaction term (Preop-Op X Station) falling below lower confidence limits in July and i was also included in the model. Nested temporal October. During each period, two peaks in abun-
\
effects were years within operational period (Year l 3-5
3.0 PHYTOPLANKTON Total Abundance of Phytoplankton e.s p,,,p,,,,,,n,, opersoonai 6.o !\
/ q k / \ / yr g ss ~....\ / . .\ %
g ~)f .\
/. g %.
y s.o g 4.s \/ (f/ f 1 8' [ 4.o 3.5 3.o JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MoNN Figure 3-2. Monthly mean log (X + 1) total abundance (no./L) of phytoplankton at nearfield Statien P2, monthly means and 95% confidence intervals over all preoperational vers (1978-1984), and monthly means over operational years (1991-1995) and 1995. Seabrook Operational Report,1995. dance were evident, one during late spring-early in each month during the preoperational period, sununer and the second during early fall. and typically accounted for similar small percent-ages during the operational period, with sorae The most recognizable characteristic of the exceptions. For example, dinoflagellates ac-phytoplankton community offshore of the counted for 33% of the individuals in May opera-Hampton-Seabrook estuary is the dominance by tional collections, and more than 15% of the total diatoms (Bacillariophyceae) during most of the individuals during several months in 1995. The 4 year. Diatoms accounted for over 90% of the total Cryptophyceae taxa were small contributors to the l community during most months in both the overall assemblage during both the preoperational preoperational and operational periods (Figure 3- and operational periods, but accounted for 35% of 3). The occasional overwhehning dominance by the individuals collected during July in 1995. In the Prymnesiophyceae taxon Phaeocystis pouchetil general, the seasonal pattern of major during the early spring, typically March-May, phytoplankton group abundance observed offshore marked the only periods of dominance by a group of Hampton Harbor was typical of northern tem-other than diatoms. Dinophyceae (dinoflagellate) perate coastal waters (Cadde and Hegeman 1986; j taxa were a relatively small component of the Peperzak 1993). Specifically, this pattern was phytoplankton community (generally less than 5 %) characterized by annual dominance by diatoms, 3-6
Preoperational (1978-1984) E3iiis x .EE5 N-(Ns) eo
.o yo i
.o
.o 40
.o ao io
- - - ,,,.,u~ m - - oor ~ov .
oTM@L.o- oT E87M8 Teii?"
,---~ E 8F~M "*"^" -
Operational (1991-1995)
~
9E2 - E2E g g EJ2J
~
" @ iiWii
- M To
.o
.o
(^\ to uom ) c"A*vM@h.o,---
-~
W E 87Mo",-,woeilt" E 8F~"o',i;be'26"^" 1995
.o =
g - === g e g ag g j
.o To l.o * ~
ans 4o . L
.o io
- ---.,u~ m .u. . oor ~c,v o g"d^ y@g_ E87Mo"-, woe"i?" E 8F~ W e,m"^"
l l Figure 3-3. Percent composition of major phytoplankton groups at Station P2 over all preoperational l (1978-1984) and operational years (1991-1995) and in 1995. Seabrook Operational s Report,1995. i 3-7 1
3.0 PHYTOPLANKTON which were most abundant in the spring and fall. Just as diatoms have been dominant on a seasonal Abundances of all phytoplankton were relatively basis, they have been dominant on an annual basis low during the summer. during most years at Station P2 (Figure 3-4). The most prevalent diatom form has historically been Temooral Trends at Station P2 Skeletonema costatum. The diatoms, including Skeletonema costatum, accounted for approxi-Phytoplankton abundances at Station P2 shifted mately 78% of the preoperational assemblage, markedly from year-to-year throughout the study 70% of the operational assemblage, and 91% of period (Figure 3-4). On average, total annual the assemblage in 1995 (Table 3-3). Skeletonema community abundances were greater during the costatum alone accounted for 35 % of the operational period compared to the preoperational preoperationalassemblage,26% of the operational average (Table 3-2). Annual abundance at P2 assemblage, and 30% of the assemblage in 1995, during 1995 was also higher than the During some years (1981,1983 and 1992), preoperational period mean, but relatively low Phaeocystis pouchetii was the dominant taxon, compared to other operational years,1992 and while in other years (1982,1984,1991,1993 and 1994 in particular (Figure 3 4). 1995), this species was absent from the assemblage (Figure 3-4). Table 3-2. Geometric Mean Abundance (X 104 Cells /l) of Phytoplankton (210 m) and Skeletonema Costatum, and Mean Chlorophyll a Concentrations (Mg/m') and Coefficient of Variation (Cv,%) for The Preoperational and Operational (1991-1995) Periods, and g ' 1995 Geometric Means. Seabrook Operational Report,1995. PREOPERATIONAL OPERATIONAL 1995 STATION i' CY* (YEARS)* i* CV i PHYTOPLANKTON P2 11.9 4.9 (78-84) 18.1 3.5 14.2 P5 12.6 4.0 (78-81) 20.9 4.3 13.1 P7 9.9 4.3 (82-84) 16.4 3.3 12.6 SKELETONEhfA COSTATUbi P2 0.2 45.1 (78-84) 0.7 33.1 0.3 P5 0.1 69.0 (78-81) 0.5 35.9 0.3 P7 0.2 32.6 (82-84) 0.4 40.4 0.1 CHLOROPHYLL a P2 0.78 68.1 (87-89) 0.81 76.8 0.86 P5 0.88 70.8 (87-89) 0.84 71.0 0.90 P7 0.75 63.4 (87-89) 0.80 64.1 0.91 'Mean of annual means. . 6 CV = coefficient of variation. l
- () = preoperational years.
i l 3-8 l 1
1 !O - i" l l Preoperational Operational l 70 i s e l l j a l ! hso b l l '*/ , 78 79 80 81 82 83 84 91 92 93 94 95 i i i 4 i ll'l so 20 1o l C~) t$i ". 29 s oa.n $ "E l Figure 3-4. Geometric mean abundances (x 104 cells /L) and 95% confidence inten ab of annual assemblages, and percent composition of four selected phpoplankton T groupings at Station P2 during each year of the preoperational and operational 1, periods. Seabrook Operational Report,1995. 39
Tcble 3-3. Arithmetic Mean Abundance (X 10* Cells /l) and Percent Colnposition of Dominant Phytoplankton Taxa During The Preoperational Period (1978-1984), Operational Period (1991-1995), and 1995 at Nearneld Station P2. Seabrook Operational Report,1995. PREOPERATIONAL OPERATIONAL 1995
-PERCENT PERCENT PERCENT CIASS TAXON ABUNDANCE
- COMPOSITION ABUNDANCE
- COMPOSITION ABUNDANCE' COMPOSITION Dinophyceae Prorocentrum micans 0.8 1.1 0.1 0.2 <0.1 <0.1 Osyroxum sp. <0.1 <0.1 1.6 3.0 0.4 0.8 Gymnodinium,Cyodinium 03 0.4 03 0.5 1.0 2.0 Cryptophytene Cryptomonas sp. <0.1 <0.1 1.0 1.9 I4 2.9 Prymnesiophyceae Phaencystispoucherii 11.8 17.1 113 20.7 <0.1 <0.1 Bacillariophyceae Haci11ariophyceae 0.8 1.1 1.0 1.8 0.8 1.6 Asterionella glacialis <0.1 c0.1 1.2 23 <0.1 <0.1 g Cerataalma bergonii 0.9 1.4 0.1 0.2 0.0 0.0
- Chaetoceros debihs 2I 3.1 03 0.6 02 0.4 O Chaetoceros decipiens *01 <01 05 09 <0.1 <D. I Chaeroceros sociali, 6.5 9.4 2.1 3.9 3.2 6.7 Chaetoceros sp. 1.2 1.7 1.6 2.9 0.8 1.6 Cylindrotheca closterium 'O I #0 I 08 I5 07 I .4 Leptocyhndrus danicus 0A 06 29 53 03 0.7 Leptocylindrus minimus IO I5 6I II I I8 I 37 9 Niaschia sp. 3.2 4.6 1.9 3.5 0.4 0.9 Rhizosolenia delicatulafragulissima 99 IA# I7 3I I5 3I Skeletonema costatum 2Aa 35 A IAI 25 7 IA3 30 0 Thalassionema niuschioides I I9 20 36 09 20 Thala.esiosira sp.
l.9 2.7 2.1 3.8 2.0 42
'Mean sbundance over all year (s) in cach period and in 1995; taxa accounting for <1% of total abundance in each time period not presented, therefore percent composition as shown does not sum to 100.
l l e e e
I 3.0 PH1TOPLANKTON Phytoplankton community composition is inher- Spatial Trends ently variable from year-to-year. This is evident in the relative importance of different taxa during Phytoplankton abundance and community composi-each period during this study. Skeletonema tion were evaluated in the nearfield (Stations P2 costatum was the dominant taxon during nearly and PS) and farfield (Station P7) areas to deter-every year of this study (Figure 3-4), but the mine whether historical spatial relationships were l relative abundance of other dominants varied over maintained during the operational period. time (Table 3-3). Second to Skeletonema costatum Preoperational geometric mean abundances at j (35%) in dominance during the preoperational Stations P2 (1978-1984) and PS (1978-1981: Table ! - period was Phaeocystis pouchetil (17 %), followed 3-2), were similar and higher than abundances at l by the diatom Rhizosolenia delicatula/fragilissima P7 (1982-1984). Abundances at each station were
- (14 %). Another diatom, Chaetoceros socialis, higher during the operational period and in 1995 followed, accounting for 9% of the total. Only compared to the preoperational period. Analysis 4 nine other taxa individually accounted for 1% or of variance comparing nearfield (P2) and farfield !
more of the preoperational assemblage for a total (P7) phytoplankton abundances confirms the of 13 taxa. During the operational period,15 taxa overall increase in abundance during the opera-individually accounted for 1% or more of the tional period (Table 3-4). Although the Station
- assemblage, led by Skeletonema costatum (26%), term in the ANOVA model was significant, the l
Phaeocystis pouchetii (21 %), and Leptocylindrus interaction term (Preop-Op X Station) was not ! p minimus (11%). During the preoperational period, significant, suggesting that the operation of Sea-Leptocylindrus minimus accounted for only 2% of brook Station has had no effect on phytoplankton 4 the assemblage. Similarly, Rhizosolenia abundances. delicatula/fmgilissima, third most abundant during the preoperational period, accounted for only 3% Species composition was similar among the three of the operational assemblage. Eleven taxa each stations in 1995 (Table 3-5). Leptocylindrus , accounted for 1% or more of the 1995 assemblage. minimus and Skeletonema costatum were the top For the first time since this program began, neither two dominants at each station, followed by ] Steletonema nor Phaeocystis were most dominant. Chaetoceros socialis. Sixteen taxa representing 3 i Leptocylindrus minimus accounted for 38% of the four classes each accounted for 1% or more of the l
)
i assemblage, a percent composicion much higher assemblage at at least one of the three stations. All ' than during the preoperational period (1.5%). but four of these taxa (Phaeocystis pouchetii, Skeletonema accounted for 30% in 1995, while Gymnodinium /Gyrodinium, Dinophyceae, and
! Phaeocystis was absent altogether. Cryptomonas sp.) were diatoms.
All remaining taxa other than diatoms and Over all three stations combined in 1995, fifteen Phaeocystis pouchetii (Prorocentrum micans, taxa cach accounted for 1% or more of the assem-Oxytoxum sp. and Gymnodinium /Gyrodinium of the blage (Table 3-5). The abundances of these fifteen Dinophyceae, and the Cryptophycaean taxa were not significantly different among the Cryptomonas sp.) accounted individually for less three stations in 1995 (p = 0.71, Wilkes' Lambda
; than 2% of the preoperational assemblage,6% of as computed by MANOVA).
the operational and 1995 assemblages (Table 3-3).
3-l' I
3.0 PHYTOPLANKTON l Table 3-4. Results of Analysis of Variance Comparing Abundances Of Total Phytoplankton,Skeletonema Costatum, and Chlorophyll a Concentrations h among Stations P2, P5 and P7During Preoperational and Operational (1991-1995) Periods. Seabrook Operational Report,1995. SOURCE OF VARIATION df MS F MULTIPLE COMPARISONS PIIYTOPLANIGON: P2 VS P7 (PREOP = 1982-1984; OP = 1991-1995)* 6 Preop-Op 1 1.09 34.93* " Op> Preop Year (Preop-Op)* 6 1.00 3 2.27 * *
- Month (Year)d 88 0.59 19.09' *
- Station 1 0.17 5.61* P2>P7 Preop-Op X Station' 1 0.03 0.86 NS Error 94 0.03 CHLOROPIIYLL a: P2, PS, P7 (PREOP = 1987-1989; OP = 1991-1995)*
Preop-Op' 1 0.02 0.33 NS Year (Preop-Op)* 6 1.09 19.52* " ; Month (Year)d 88 0.84 15.06* " i I Station 2 0.17 3.07* P1E2 P7 Preop-Op X Station' 2 0.06 1.03 NS Error 188 0.06 SKELETONEMA COSTA TUM: P2 VS. P7 (PREOP = 1982-1984; OP = 1991-1995)* Preop-Op' 1 6.73 32.80 "
- Op> Preop Year (Preop-Op)* 6 2.62 12.78 * *
- Month (Year)d 88 3.05 14.87 "
- Station 1 1.03 5.03* P2>P7 Preop-Op X Station
- 1 0.39 1.89 NS Error 94 0.20 j SKELETONEMA COSTA TUM: P2 VS. PS (PREOP = 1979-1981; OP = 1991-1995)*
6 Preop-Op 1 9.96 32.66* " Op> Preop Year (Preop-Op)* 6 1.80 5.66* *
- Month (Year)d 87 4.41 13.85 "
- Station 1 0.97 3.04 NS Preop-Op X Station' 1 0.07 0.22 NS Error 93 0.32
'ANOVA based on mean of twice-monthly collec- dMonth nested within year regardless of station or tions Mar-Nov and monthly collections Dec-Feb; year.
only years when collections at these stations were ' Interaction between main effects. concurrent are included; analyses include only years when all 12 months were sampled. NS = not significant (p 2 0.05)
'Preoperational versus operational period regardless * = significant (0.05 > p 2 0.01) of station. " = highly significant (0.012 p >0.001) ' Year, regardless of period. *" = very highly significant (0.0012 p) 3-12
1 3.0 PHITOPLANKTON l i O 1 Table 3-5. Phytoplankton (210pm) S ecies Composition by Stationin 1995. Seabrook Operational Report,199 . 1 CLASS TAXA P2 PS P7 PHYTOPLANKTON' Cryptophyceae Cryptomonas sp. 2.9 3.1 1.8 , Dinophyceae Dinophyceaed 0.7 1.1 1.0 Gymnodinium /Gyrodinium 2.0 l.8 3.0 Bacillariophyceae Bacillariophyceae 1.6 1.6 1.7 Chaetoceros debilis 0.4 0.4 3.2 Chaetoceros socialis 6.7 6.9 11.0 Chaeroceros sp. 1.6 2. 2.7 Cylindrotheca closterium 1.4 1.3 1.4 Leptocylindrus danicus' O.7 0.6 1.1 Leptocylindrus minimus 37.9 32.0 30.3 l Nitzschia sp. 0.9 1.3 1.5 Rhizosolenia delicatula/ 3.1 3.2 1.0 fragilissima , Skeletonema costatum 30.0 33.7 22.3 l Thalassionema ' p nitzschloides 2.0 1.9 1.8 e 1 Thalasslostra sp. 4.2 4.2 5.0 V Prymnesiophyceae Phaeocystispouchetti <0.1 0.2 6.8
' Presents only taxa accounting for 21% of total abundance j 6 Excluded from MANOVA 3.3.1.2 Chlorophyll a Concentrations During both the preoperational and operational 3.5 times greater than the preoperational mean, but periods, monthly arithmetic mean total chlorophyll was lower than preoperational means in all other a concentrations at P2 exhibited an early spring months. Monthly mean concentrations in 1995 peak, mid-summer decline, and another peak in were lower than preoperationallower 95% confi-fall (Figure 3-5). Monthly mean operational dence limits from June through December.
chlorophyll a concentrations were lower than preoperational mean concentrations (based on all Arithmetic mean chlorophyll a concentrations were preoperational years) in all months except January, similar between the recent preoperational (1987-and lower than preoperational lower 95% confi- 1989) and operational periods (Table 3-2). The dence intervals from June through August, and ANOVA results confirm that chlorophyll a concen- [J1 October through December (Figure 3-5). In 1995 the mean concentration at P2 in January was over trations from the two periods were not significantly different (Preop-Op term, Table 3-4). 3 13
c.
'" Chl:rophylle
--- w ~
y ..ej g 4.o; I "' s sg
\
~~\
I aoj ss o N -
. _ -N
\
d [... i.e
,n
~~~u
~ ._
os m.m.3 4 - - %z w AU. s. _ _
- b. Abundance Preoperational Years
- Chlorophyil a eo a.o
/ g.s i ..e 40
/- -
p% /
/
- s
\
\ 3.0 m.s % % /
/ g a.o j
' \ 1.s g ..e ,- N g y 3.o 1.o
/
1.s 1.0 c.s ob
- - - .,uge o s.P Oct NO, o.c Operational Years e.o a.o s.t y sa f e.s I 4.s 4D a.o s.s s.o S.s len y an s ,/\ 7
,/ % % 1.o n N' N / / \
1.s g { 12 \ --- - N o.s o.s oD o.o JAN PED MAM APR MAY JUN JUL AUG P OC"i NOV D.O i l Figure 3-5. (a) Mean monthly chlorophyll a concentrations and 95% confidence inten als at Station P2 over preoperational years (1979-1989) and monthly means over operational years (1991 1995) and 1995; (b) mean monthly chlorophyll a concentrations and phytoplankton log (x+1) abundances during the preoperational and operational periods. Seabrook Operational Report,1995. 3-14
4 3.0 PHYTOPLANKTON ( Abundance of Skeletonema costatum Q,) * . _ .- _"" g:::=
- -- im
{6
- A
/ %. \ j .. k* -
--- -- t .\ _yT Q ., 3
[ ,- & ./- , V . .... s, j N'i 1
\
\<
/
.f
( ,J o JAN FEB MAR APR MAY .AJN .AA. AUG SEP OCT NCN DEC MONTH Figure 3-6. Log (X + 1) abundance (no./L) of Skeletonoma costatum at nearfield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means for the operational period (1991-1995) and 1995. Seabrook Operational Report,1995. The ANOVA model detected it significant difier- effect on chlorophyll a concentrations (NAl 1992) ence in chlorophyll a con:,entress among the since it is a small-celled taxon (Lee 1980). Despite three stations (Table 3 4). During bmh periods, these differences, there is evidence of a relation-f] concentrations were highest at P5 and lowest at P7 ship between chlorophyll a concentrations and V (Table 3-2). In 1995, concentrations were lowest phytoplankton abundances in the comparison of l at P2 and slightly higher at P ' and PS. Overall, seasonal patterns. Preoperational and operational l there was no significant ineractior between chlorophyll a concentrations followed a pattern l l preoperational or operationrJ period ind station similar to that of phytoplankton abundances during (Preop-Op X % den ter:a, Table 3-4). indicating the same periods (Figure 3-5). that the operation of Seabrook Statior has had no effect on chlorophyll a concentratiorv in the study 3.3.2 Selected Species crea. Skeletonema costatum was chosen as a selected
)
On an annual basis, chlorophyll a concentrations species because of its historic omnipresence and and phytoplankton abundances appear not to be overwhelming dominance during much of the year. always directly related. The differences observed At Station P2, peak abundances generally occurred in trends between phytoplankton abundances and in the spring and fall during the preoperational i chlorophyll a concentrations were likely due to period (Figure 3-6). The operational time series differences among dominant taxa with respect to exhibited a similar seasonal pattern, although cell size and chlorophyll a content. For example, abundances were generally higher than during the the unusually high annual mean phytoplankton preoperational period. Operational means ex-abundance in 1992 was influenced by high abun- ceeded preoperational uppu 95% confidence limits
, dances of Phaeocystis pouchettil on several dates in January through June, and September through (Figure 34). While P. pouchetil had a large effect December. In 1995, monthly Skeletonema abun-on phytoplankton abundances, it had only a minor dances followed the same historic seasonal pattern, 3 15
1 3.0 PHYTOPLANKTON but fluctuated over a much wider range than 7). PSP toxicity was rarely detected during the preoperational means. Monthly means in 1995 operational period, however. During the first two l exceeded preoperational upper 95% confidence years of the operational period, the State of New limits in April, May, June and September, and Hampshire recorded two occurrences of PSP levels were lower than preoperational lower 95% confi- above the detection limit, both in 1991 (NAI 1992, dence limits in July and August (Figure 3-6). 1993), and during 1993 and 1994 PSP occurrences ) were recorded only during May and early June Skeletonema abundances were evaluated in two (NAl and NUS 1994, NAl 1995; Figure 3-7). separate ANOVA tests since Stations PS and P7 PSP was detected on three occasions in late May were not ampled concurrently during the in1995, but levels were below closure limits each ; preoperational period (Table 3-2). For both tests time. PSP levels were below detection limits on l (P2 versus P7 and P2 versus PS), operational all other sampling dates in 1995. Despite PSP abundances were significantly greater than levels being below closure limits, the New Hamp-preoperational abundances (Table 3-4). This shire Division of Health and Human Services difference is apparent in geometric means as well closed the flats to harvesting on May 25, 1993. ] (Table 3-2). A significant difference in abundance PSP levels had risen over the three previous j was detected between P2 and P7. Geometric sampling dates, and clam flat closures had been means also indicated that P2 had slightly higher implemented along the Maine coast in previous abundances than P7, particularly during opera- weeks. Flats were reopened on June 6,1995. The tional years (Table 3-2). The interaction between widespread occurrence of PSP toxicity in the period and station for the P2-P7 model was not coastal areas of northern New England (NAI significant; suggesting that station operation has not 1993), and the occurrence of high PSP levels in the affected Reletonema abundances at Stations P2 preoperational period, indicates that the occurrence and P7. of PSP toxicity in the study area was unrelated to the operation of Seabrook Station. Operational period abundances of Reletonema were significantly higher than preoperational 3.4 DISCUSSION abundances at Stations P2 and P5 (Table 3-2). Station differences were not significant in the P2- 3.4.1 Cammunity Interactions P5 model, nor was the interaction term (Table 3-4), indicating no effect due to the operation of The operation of Seabrook Station has had no Seabrook Station, demonstrable effect on the phytoplankton comm-unity (Table 3-6). Seasonal patterns of total 3.3.3 PSP Levels abundance, chlorophyll a concentrations, and the occurrence of dominant taxa in the phytoplankton
. During the preoperational period, average weekly assemblage established in the preoperational period PSP toxicity levels were above the detection limit have remained unchanged over the operational I I
of 44 pg PSP /100 g tissue of the mussel Mytilar period (Figures 3-2, 3-3, 3-4). The phytoplankton edulis and periodically above the closure limit then assemblage was dominated by diatoms (Bacillario-in effect (80 pg PSP /100 g tissue) during the late phyceae) both annually and seasonally during both spring, early summer and late summer (Figure 3- periods. In some years, however, the Prymnesio-3-16
3.0 PHYTOPLANKTON
.=
-. TM. 4
.m l
l= b l l_-
- -& 2 i APR MAY JUN JUL SEP OCT NCN DEC Figure 3-7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in HamptonHarbor, l mean and 95% confidence intervals over preoperational years (1983-1989) andmonthly means l during operationalyears (1991-1995) and in 1995. Data provided by the State of New Hampshire.
Seabrook Operational Report,1995. O Table 3-6. Summary of Potential Effects (Based on Anova) of Operation of Seabrook Station on the Phytoplankton Community. Seabrook Operational Report, 1995. DIFFERENCES BETWEEN OP-ERATIONAL AND PRE-OPERATIONAL PERIOD SIM- OPERATIONAL PERIODS ILARTO PREOPERATIONAL CONSISTENT AMONG STA-COM.MUNITY A*ITRIBUTE PERIOD? TIONS? Phytoplankton Op> Preop yes Skeletonema costatum Op> Preop yes Chlorophyll a Op= Preop yes O 3-17
3.0 PHYTOPLANKTON phyceae species Phaeocystis pouchetii accounted no impact to the phytoplankton community due to for as high a proportion of the total individuals at the operation of Seabrook Station. each station as did total diatoms (Figure 3-3). On average, P. pouchetii composed a greater propor- Only minor occurrences of PSP toxicity have been tion of the operational assemblage (21 %) than the documented in the study area during the opera-preoperational assemblage (17%; Table 3-3), tional period. The occurrence of PSP toxicity in primarily due to its high abundances during the this portion of the Gulf of Maine was first docu-spring of 1992 and 1994. With the exception of mented in 1972 (NAI 1985), possibly as the result Phaeocystispouchetii, the community composition of the transport of the PSP-producing changed little between the preoperational and dinoflagellate Alexandrium spp. (formerly called operational periods (Figure 3-3). On a year-to- Gonyaular sp.) from the Bay of Fundy following year basis, however, assemblages differed consid- Hurricane Carrie (Franks and Anderson 1992a). etably. For this reason, the phytoplankton study With few exceptions, PSP has been recorded sea-included an analysis of parameters that were sonally in this region of the western Gulf of Maine expected to be more predictable indicators of ever since, although not always at toxic levels. It community status than species composition, such as is currently thought that Alexandrium spp. blooms the abundance of the selected species (Skeletonema are transported to this region on coastally-trapped costatum), or total biomass as estimated by chloro- buoyant plumes derived from the Androscoggin phyll a concentrations. The ANOVA model and/or Kennebec Rivers in Maine (Franks and An-comparing nearfield and farfield phytoplankton derson 1992a). This theory is consistent with the assemblages showed that average total abundance generally observed north-to-south seasonal pro-increased between the preoperational and opera- gression of occurrence of this dinoflagellate and tional periods, and that there were differences the PSP levels (Franks and Anderson 1992b). between stations over all years (Table 3-4). These 1.ocal sources of dinoflagellates may also contrib-differences were consistent between the ute to the blooms as well. Thus, occurrences of preoperetional and operational periods. PSP toxicity in New Hampshire have been associ-ated with larger regional occurrences in southern Similar results were observed in the ANOVA Maine and northern Massachusetts, and are not a models comparing nearfield and farfield abun- result of the operation of Seabrook Station. dances of Skeletonema costatum. Average opera-tional abundances were greater than preoperational 3.4.2 Effects of Plant Operation abundances for both models (P2 versus P7 and P2 versus PS), and differences in abundance between The phytoplankton community exhibited high ! stadons were consistent between the preoperational variability both temporally and spatially during the and o,wational periods. There was no significant entire study period. The high variability in abun-differexe between preoperational (1987-1989) and dance levels and community structure from year- I operational chlorophyll a concentrations, although to-year was due to the influence of both physical there y ere differences among stations (Table 3-2). and chemical factors, some cyclical and some In all cases, the interaction between Preop-Op and transitory, and to the rapid turnover rate of phyto- l Station (Table 3-4) was not significant, indicating plankton populations. Thus, it has been difficult to 3-18 l
3,0 PHYTOPLANKTON succinctly describe the long-term temporal commu- 1992. Seabrook Environmental (oV) nity structure (NAI 1985). However, all docu. Studies,1991. A characterization of environ-mented characteristics of the phytoplankton com- mental conditions in the Hampton-Seabrook
... area during the operation of Seabrook Station.
munity in the vicimty of Seabrook Station indicate Tech. Rep. XXIII-1. thst the community changes that have occurred over time, occurred at all three stations. There- 1993. Seabrook Environmental j fore there is no evidence indicating that the opera. Studies, 1992. A characterization tion of Seabrook Station had a demonstrable effect envir amental conditions in the Hampton-Seabrook area during the operation of Sea-on any aspect of the local phytoplankton commu-brook Station. Tech. Rep. XIV-I. mty. 1995. Seabrook Station 1994 Envi- : ronmental Studies in the Hampton Seabrook
3.5 REFERENCES
CITED Area. A Characterization of Environmental Conditions During the Operation of Seabrook Station. Prepared for North Atlantic Energy ) Cadee, G.C. and J. Hegeman. 1986. Seasonal ' Service Corporation. and annual variation in Phaeocystis pouchetit. (Haptophyceae) in the westernmost inlet of the Normandeau Associates (NAI) and Northeast Wadden Sea during the 1973 to 1985 period. Utilities Corporate and Environmental Affairs Neth. J. Sea Res. 20(1):29-36. 1994. Seabrook Environmental (NUS). Studies,1993. A characterization of Environ- ' Franks, P.J.S. and D.M. Anderson. 1992a. mental Conditions in the Hampton-Seabrook Alongshore transport of a toxic phytoplankton ! Area during the Operation of Seabrook Sta-bloom in a buoyant current: Alexandrium tam-tion. Prepared for North Atlantic Energy I arense in the Gulf of Maine. Mar. Biol. Service Corporation. 112:153-164. Peperzak, Imuis. 1993. Daily irradiance governs Franks P.J.S. and D.M. Anderson. 1992b.
, growth rate and colony formation of Toxic phytoplankton blooms m the southwest-Phaemstis (Prymnesiophyceae). J. Plank.
ern Gulf of Mame: testing hypotheses of Res. 15(7):809-821. I physical control using historical data. Mar. l Biol.112:165-174. SAS Institute Inc. 1985. SAS User's Guide: Statistics, Version 5 edition. SAS Inst., Inc. Harris, R.J. 1985. A primer of multivariate Cary, N.C. 956 pp. statistics. Acad. Press,'Orlando. 575 pp. Stewart-Oaten, A., W.M. Murdoch and K.R. lee, R.E.1980. Phycology. Cambridge Univer- Parker.1986. Environmental impact assess-sity Press, New York. 478 pp. ment: "Pseudoreplication" in time? Ecology. Normandeau AssociatesInc.1985. Seabrook En- I vironmentalStudies,1984. A characterization of baseline conditions in the Hampton-Sea-brook Area, 1975-1984. Tech. Rep. XVI-II. 1991. Seabrook Environmental Studies. 1990 Data Report. Tech. Report XXII-I. , 1 3-19 1 j I
3.0 PHYTOPLANKTON APPENDIX TABLE 3-1. CIIECKLIST OF PIIYTOPLANKTON TAXA CITED LN THIS REPORT. SEABROOK OPERATIONAL REPORT, 1995. BACILLARIOPHYCEAE Asterionella glacialis Castracane (syn. A. japonica Cleve) Cerataulina bergonii H. P6tagal10 Chaetoceros debilis Cleve Chaetoceros decepiens C1 eve Chaetoceros socialis Lauder Cylindrotheca closterium (Ehrenberg) Reimann. and Lewin Leptocylindrus danicus Cleve Leptocylindrus minimus Gran Nituchia sp. Rhizosolenia delicatula Cleve Rhizosoleniafragilissima Bergon Skeletonema costatum (Greville) Cleve Thalassionema nitzschioides Hustedt Thalassiosira sp. CRYPTOPHYCEAE Cryptomonas sp. Chroomonas sp. DINOPHYCEAE Oxytoxum sp. Prorocentrum micans Ehrenberg Gymnodinium Stein Gyrodinium Kofold and Swezy PRYMNESIOPHYCEAE Phaeocystis pouchettii (Hariot) Lagerheim i l O 3-20
4.0 ZOOPLANKTON ( TABLE OF CONTENTS ( PAGE 4.0 ZOOPLANKTON
SUMMARY
. . . . . . . . . . . .. ..... ......... .. . ..... . . .. .. .. . 4-iii LIST OF FIGURES ............... ........... . . ...... .... . . . . . iv LIST OF TABLES ............ ........ . .... .. ... . . . . . . . . . . . . vi
4.1 INTRODUCTION
...... . . .. ..... ...... . .... ...... 4-1 4.2 METHODS . . . .. . . ... ........ .. .. . . .. . ... .. 4-1 i 4.2.1 Field Methods . ..... .. . .... .. . . . ........... . 4-1 4.2.1.1 Microzooplankton . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 4- 1 4.2.1.2 Bivalve Larvae ........... ... . ... . .. . . . . . 4- 1 4.2.1.3 Bivalve Larvae Entrainment . . . . . . . . . . . .. ............ 4-1 4.2.1.4 Macrozooplankton ........... ........ .. .......43 o
o Q) 4.2.2 Laboratory Methods . ..... ............... ....... ..... .. 4-3 4.2.2.1 Microzooplankton . . . . .... ....... . . . . . . . ... ... 4-3 4.2.2.2 Bivalve Larvae . ............ ................ .. 4-4 4.2.2.3 Macrozooplankton . . .......... ... . .... . ........ 4-4 4.2.3 Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 4-4 4.2.3.1 Communities . . . . ........................... .... 4-4 4.2.3.2 Selected Species . . . . ............... .. ..... ...... 4-8 4.3 RESULTS. ........... ................ ....... . . . . . . . . . . . 4-8 4.3.1 Microzooplankton . . ....... . ....... ..... . . . . . . . . . . . . . . 4-8 4.3.1.1 Community Structure . . ... .. .......... ....... .. 4-8 4.3.1.2 Selected Species . . . . . . . . . . . . . . . . . . . . . . . .......... . 4-10 4.3.2 Bivalve Larvae . . . . . . ... ........................ ...... 4-19 4.3.2.1 Community Structure ........................... . . . 4-19 4.3.2.2 Selected Species . . . . . . . ...... .. .. ..... ........ 4-26 4.3.2.3 Entrainment ................... .. . ......... 4-27 I 4-i i
4.0 ZOOPIANKTON
~ c e.
A h %A a.e 4.3.3 Macrozooplankton . . . . . . . . ........... .... .. . . . . . . 4-30 4.3.3.1 Community Structure . . ... .. ............. . . 4-30 l 4.3.3.2 Selected Species . . . . . . . . . . . . ..... .. ... . . . . 4-37 l l 4.4 DISCUSSION . . . . . . . . .... ... ... .... . . ....... . . . . . 4-44 s 4.4.1 Community . . . . . . . . . .. ....... ... .. . . ... .. 4-44 4.4.2 Selected Species . . ....... .... . .... . ....... . . . . 4-49 4 1
4.5 REFERENCES
CITED . .. . . .... . . . ...... . .. . .. . 4-50 ' O i O 4-ii
4.0 ZOOPLANKTON hv
SUMMARY
Microzooplankton have historically shown a distinct seasonal pattern that relates to changing abundances of dominant taxa, Pseudoazlanus sp., Oithona sp., bivalve larvae, and copepod nauplii. Seasonal patterns during the operational period were generally similar to those observed during the preoperational period. No significant differences in community composidon were detected among stations. Abundances of some key taxa showed significant differences operationally. These include Eurytemora sp., copepodites and adults, Pseudocolanus/Calanus sp. nauplii and adults, and Oithona sp. copepodites and adults. Oithona sp. copepodites were more abundant at the nearfield station (P2) than at the farfield station (P7). No differences were related to the operation of Seabrook Station. 1 he umboned bivalve larval assemblage is defined by varying abundances of dominants such as Hiatella sp., { Mytilus edulis, and Anomia squamula. Seasonal appearances of dominant species were similar to previous I years. However, preoperational and operational differences in community structure were not consistent among stations. Abundances of Solenidae decreased at Station P2 and P5 but remained unchanged at P7. He increase in abundance of Riatella sp. during the operational period was significantly greater at Station P2 compared to P5 and P7. Other changes that were consistent among stations were the decreased abundances of five taxa: Modiolus modiolus, Spisula solidissuna, Mya arenaria, Mya inmcata and Macoma balthica. This consistency suggests an area-wide trend unrelated to the operation of Seabrook Station. A complete year of entramment sampling in 1995 indicated that the timing of peak densities and the species composition in the entrained community were similar to previous years, although the overall total numbers of larvae entrained were much higher than all previous years. His is a result of higher than average densities of M. edulis larvae combined with a slight increase in the cooling water volume. The offshore community has remained relatively stable over time. There is no evidence that entrainment has resulted in decreased numbers of bivalve larvae in offshore waters. The macrozooplankton community is composed of a true planktonic component (defined as holo /mero-plankton) including the copepods Calanusfinmarchicus, Centropages typicus, Pseudocalanus sp., and Temora longicornis, along with larval stages of decapods and barnacles. Amphipods, cumaceans, and mysids occasionally venture into the water column, forming the tychoplanktonic component. The assemblage of species changed seasonally, and, for the most part, has been consistent throughout the study period. However, abundances of many taxa, including some of the dominants, were elevated during the operational period. For the holo /meroplankton, increased abundances generally occurred at all three stations, suggesting an area-wide change. Tychoplankton have historically shown nearfield-farfield differences that are related to variations in substrate. These spatial differences have been consistent during both preoperational and operational periods. No changes in the macrozooplankton community have been observed that could be related to the operation of Seabrook Station. nl I V 4-iii
4.0 ZOOPLANKTON LIST OF FIGURES PAGE 4-1. Plankton and entrainment sampling stations . . ........... ......... .. 4-2 l 4-2. Dendrogram and sea',onal groups formed by numerical classification of logio (x+1) transformed microzooplankton abundances (no./m') at net.rfield Station P2,1978-1984, July-December 1986, April 1990-December 1995 . . . . . ............ ... . 4-9 l l 4-3. Logia (x+ 1) abundance (no./m') of Eurytemora sp. copepodites and Eurytemora herdmani adults, monthly means and 95% confidence intervals for the preoperational period l (1978-1984), the operational period (1991-1995), and 1995 at nearfield Station P2, and l preoperational and operational monthly abundances at nearfield Station P2 and farfield Station P7 . . ...... ....... ........ .. .......... .. ... . 4-13 4-4. logio(x+1) abundance (no./m') of Oithona sp. nauplii, Pseudocalanus sp. and Oithona sp. copepodites and adults, monthly means and 95% confidence intervals for the preoperational period (1978-1984), the operational period (1991-1995), and 1995 at nearfield Station P2 . . . . . . . . . . . . . . . . . . . . . . . . .................. 4-18 4-5. Dendrogram and seasonal groups formed by numerical classification of logia (x+1) O transformed bivalve larvae abundances (half monthly means; no./m') at Seabrook intake i (P2), discharge (PS) and farfield (P7) stations, April-October, 1988-1995 ........ 4-20 l l i
- 44. A comparison of the mean logia (x+ 1) abundance (no./m') among Stations P2, PS, and i P7 during the preoperational (1988-1989) and operational (1991-1995) periods when the l interaction term (Preop-Op X Area) of the ANOVA model is significant for Hiatella sp. l and Solenidae . . . . . . . . . . ................................... . 4-23 I 4-7. Tune series of monthly mean logio (x+ 1) abundances of Hiatella sp. and Solenidae,1988-1995. Seabrook Operational Report,1995 . . . . . . . . ............ ..... . 4-25 4-8. Weekly mean logia (x+1) abundance (no./m') of Myrilus edulis larvae at Station P2 l during preoperational years (1978-1989, including 95 % confidence intervals, and weekly means in the operational period (1991-1995) and in 1995 .............. . . 4-26 4-9. Volume of cooling water pumped during the months sampled for bivalve larvae and total number of bivalve larvae (x109 entrained by Seabrook Station, 1990-1995 .. . 4-29 0
4-iv
4.0 ZOOPLANKTON I ) PAGE LJ 4-10. Dendrogram and seasonal groups formed by numerical classification of mean monthly logio (x + 1) transformed abundances (no./1000 m') of holo- and meroplanktonic species of macrozooplankton at intake Station P2, discharge Station P5 and farfield Station P7, 1986-1995 . . . . . . . . .... ............. .... .. ............. 4-31 4-11. Dendrogram and seasonal groups formed by numerical classification of mean monthly logia (x+1) transformed abundances (no./1000 m') of tychoplanktonic species of macrozooplankton at intake Station P2, discharge Station P5 and farfield Station P7, 1986-1995 . . . . . . . . ......... ........ .. ........ .. . . . . . . 4-34 4-12. Logio (x+ 1) abundance (no./1000 m') of Calanusfinmarchicus copepodites and adults and Carcinus maenas larvae; monthly means and 95% confidence intervals over all preoperational years (1978-1984,1986-1989) and monthly means for the operational period (1991-1995) and 1995 at intake Station P2 . . . . . . ... .......... .. 4-38 4-13. Preoperational and operational monthly mean logio (x + 1) abundance (no./1000 m') of adult Calanusfinmarchicus at the intake station (P2) and the control site (P7) . . . . . 4-41 4-14. Logio(x+ 1) abundance (no./1000 m') of Crangon septemrpinosa (zoea and post larvae) and Neomysis americana (all lifestages); monthly means and 95% confidence intervals over all preoperational years (1978-1984,1986-1989) and monthly means for the operational period (1991-1995) and 1995; and mean percent composition of Neomysis americana lifestages over all preoperational years (1978-1984,1986-1989) and for the 1 operational period (1991-1995) at intake Station P2 . . . . . . . . . . . . . . . . . . . . . . . 4-43 l I i s f ) LJ 4-v
1 1 1 4.0 ZOOPLANKTON l 1 LIST OF TABLES PAGE 4-1. Summary of Methods Used in Numerical Classification and Multivariate Analysis of Variance of Zooplankton Communities, and Analysis of Variance of Zooplankton Selected Species ............ ..... . ............ . ... ...... ... . 4-6 l l 4-2. Geometric Means of Microzooplankton Abundance (No./m'),95% Confidence Limits, and Number of Samples for Dommant Taxa Occurring in Seasonal Cluster Groups Identi-fled by Numerical Classification of Collections at Nearfield Station P2,1978-84, July-d- ) ecember 1986, April-december 1990,1991-95 .........................4-11 4-3. Geometric Mean Density (No./m') and the Coefficient of Variation (Cv,%) of Selected Microzooplankton Species at Stations P2, P5, and P7 for Preoperational and Operational Periods and 1995 . . . . . . . . . . . . . . . . . ........... . -. . . . . . . . . . . . . . 4 - 14 4-4. Results of the Analysis of Variance oflogio (X+1) Transformed Density (No./m') of Selected Microzooplankton Species among Preoperational Years (1982-84) and Opera-tional Years (1991-95) and Nearfield (Station P2) Vs. Farfield (Station P7) Areas . . . 4-15 4-5. Geometric Mean Abundance (No./m'), and the 95 % Confidence Limits of Dominant Taxa and Number of Collections Occurnng in Seasonal Groups Formed by Numerical Classifi-cation of Bivalve Larvae Collections at Intake (P2), Discharge (P5) and Farfield (P7) Stations, 1988-1995 . . . . . . . . . . . . . . . ............................4-21 4-6. Geometric Mean Abundance (No./m') with Coefficient of Variation (Cv) for Mytilus Edulis Larvae at Stations P2, P5 and P7 Durmg the Preoperational Years and Operational Years (1991-1995) and the 1995 Mean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24 4-7. Results of Analysis of Vanance Comparing Intake (P2), Discharge (PS) and Farfield (P7) Weekly Logio (X+1) Transformed Abundances of Mytilus Edulis, Niatella Sp. And Solenidae larvae During Preoperational (1988-1989) and Operational (1991-1995) Periods . . . . . . . . ........ ........... ..... ......... . . . . . . 4-27 4-8. Esumated Number of Bivalve larvae Entrained (X109 by The Cooling Water System at Seabrook Station From he Third Week in April Through he Fourth Week of October, 1995........ ............ ................................4-28 9 4-si
4.0 ZOOPLANKTON PAGE L 4-9. Gcometric Mean Abundance (NoJ1000m') And 95% Confidence Limits of Dominant Holo- And Meroplanktonic Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections (Monthly Means) at Intake Station P2, Discharge Station P5 And Farfield Station P7,1987-1995 . . . . . . . . . . . . . . . . . . 4-32 4-10. Geometric Mean Abundance (No./1000m') And 95% Confidence Limits of Dominant Tychoplanktonic Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collection' (Monthly Means) at Intake Station P2, Discharge Station P5 And Farfield Station P7,1987-1995 . . . . . . . . . . . . . . . . . . . . . . . . . 4 -3 5 4-11. Geometric Mean Abundance (NoJ1000 M') And Coefficient of Variation of Selected Macrozooplankton Species at Stations P2, P5, And P7 During Preoperational And Operational Years (1991-1995), And 1995 . . . . . . . . . .. .......... . . . . 4-39 4-12. Results of Analysis of Variance Comparing Logw (X+1) Transformed Abundances of l Selected Macrozooplankton Species From Stations P2, PS, And P7 During Preoperational (1987-1989) And Operational (1991-1995) Periods .............. . . . . . . . 4-40 O 4-13. Summary of Potential Effects (Based on Numerical Classification And Manova Results) of Operation of Seabrook Station Intake on 'Ihe Indigenous Zooplankton Communities 4-45 l 4-14. Summary of Potential Effects (Based on Anova Results) of Operation of Seabrook Station j Intake on Abundances of Selected Indigenous Zooplankton Species . . . . . . . . . . . . . 4-49 i LIST OF APPENDIX TABLES 4-1. List of Zooplankton Taxa Cited in This Report . ....... ... .... ..... . 4-53 4-vii
4.0 ZOOPIANKTON
4.1 INTRODUCTION
seawater to within 15 cm of the top of the net. Pumping time was recorded to calculate volume
'Ihree components of the rooplankton commu- filtered based on predetermined pumping rates.
nity, microzooplankton, bivalve larvae and Volume filtered generally averaged 150 liters. macrozooplankton, sere sampled separately to Microzooplankton were rinsed from the nets into identify spatial and temporal trends at both the sample containers after puttping and were pre-community and species level. One station outside served in borax-buffered 3 % formalin. the area most likely to be affected by plant opera-tion was selected as a farfHd site. Initial 4.2.1.2 Bivalve Larvae monitoring characterized the source and magni-tude of variation in each zooplankton community The spatial and temporal distributions of 12 taxa and provided a data base for comparing opera- of umboned bivalve larvae were monitored using tional monitoring. Current trends in zooplankton a 0.5-m diameter,0.076-mm mesh net. Samples population dynamics w:re evaluated to determine were collected weekly from mid-April through whether entrainment in Seabrook Station's cool- October at Hampton Harbor (P1), and at Stations ing water system has had a measurable effect on P2, P5 and P7 (Figure 4-1). Sampling began at the community or any individual species. In Station P2 in July 1976. Farfield Station P7 was addition, entrainment of bivalve larvae in the added to the program in 1982, and Station P1 was plant's cooling water system was estimated. added in July 1986. Samples were collected at Station P5 from July-December 1986 and April 4.2 METHODS 1988 through October 1995. Two simultaneous two-minute oblique tows were usually taken at 4.2.1 Field Methods each station. In cases when net "ere clogged, vertical tows were taken. Volume filtered gener-4.2.1.1 Microzooplankton ally averaged 9 m' for oblique tows and 3 m' for venical tows. The volume of water filtered was i Microzooplankton were sampled twice a month recorded with a General Oceanics* flowmeter. l from March-November and monthly in Upon recovery, net contents were preserved with I December-February at intake (Station P2), dis- 1-2% borax-buffered formali- (with sugar added i charge (Station PS) and farfield (Station P7) areas to enhance color preservation) and refrigerated. (Figure 4-1). Sampling at all three stations occurred from July through December M86 and 4.2.1.3 Bivalve Larvae Entrainment from April 1990 through December 1995. In addition, Station P2 was sampled from h.auary Bivalve larvae entrainment sampling has been 1978 through December 1984 and Station P7 conducted up to four times a month by NAESCO from January 1982 through December 1984. personnel within the circulating water pumphouse Four replicate samples were collected by pump at on-site at Seabrook Station from July 1986 to both I m below the surface and 2 m above the June 1987 and from June 1990 to October 1995. bottom at each station on each sampling date. Three replicates were collected during the day on Discharge from the pump was directed into a each sampling date. Sampling dates coincided 0.076-mm mesh plankton net (12 cm diameter) with offshore bivalve larvae sampling whenever I set into a specially-designed stand filled with possible. Entrainment sampling was not conduc-44
N RYE LEDGE O LITTLE o ... BOARS Y HEAD 0 .5 1 Nautical Mile 0 1 2 Kilometers y FARFIELD AREA SCALE CONTOUR DEPTH -- IN METERS o GREATBOARS - V HEAD HAMPTON ,o BEACH BROWNS RIVER Y P1 Intake ***E E1 Discharge - [ O OUTER
~
NEARFIELD O ..-
.. AREA SEABROOK Qv STATION fy g (h.,
HAMPTON SE.tBROOK HARBOR SUNK l ROCKS l @
%~ SEABROOK
%, BEACH LEGEND
= Zooplankton stations E = bivalve larvae stations E1 = Seabrook Entrainment Station
/~N U Figure 4-1. Plankton and entrainment sampling stations. Seabrook Operational Report,1995. 4-2
4.0 ZOOPLANKTON ted on several scheduled sampling dates, how- Macrozooplankton collections were made at night ever, due to either station outages or sampling two times per month, concurrent with equipment problems. Scheduled station outages ichthyoplankton sampling. On each date, four occurred from August through November 1991, replicate oblique tows were made with 1-m September through October 1992, and April diameter 0.505-mm mesh nets at each station. through August 1994. No bivalve larvae entrain- The nets were set off the stern and towed for 10 ment samples were collected in 1994 due to the minutes while varying the boat speed, causing the scheduled outage, equipment being out-of-service net to sink to approximately 2 m off the bottom and personnel scheduling conflicts. Samples were and to rise to the surface at least twice during the collected weekly in 1995 from the third week in tow. When nets became clogged due to plankton April through the fourth week in October. blooms, tows were shortened to 5 minutes. The volume filtered, determined with a General Samples were taken using a double barrel collec- Oceanics* digital flowmeter, generally averaged tion system. A 0.076-mm mesh plankton net was 500 m' for 10-minute tows and 200 ni for 5-suspended in a 30-gallon drum which, in turn, minute tows. Upon retrieval, each net was rinsed was suspended in a 55-gallon drum. Water and the contents preserved in 6 % buffered forma-diverted from the cooling water system entered lin. the 55-gallon drum from the bottom and over-flowed the 30-gallon drum into the plankton net. 4.2.2 Laboratory Methods After passing through the net, the water dis-charged through the bottom of both drums. 'Ihe 4.2.2.1 Microzoonlankton water supply was adjusted to maintain three to six inches of water above the plankton net at all Two replicates from each depth and station on all times. After the water was drained from the sample dates were analyzed for microzoo- plank-system, the sample contents were consolidated ton; the remaining two replicates were archived and preserved with 1 % buffered formalin. Three and stored as " contingency" samples. Samples replicate samples were collected on each sampling were concentrated or diluted to a known volume date. The volume filtered was measured with an that provided an optimal working number of in-line flowmeter and averaged approximately 7 organisms (ca. 200 per 1-m! subsample). Each m2 per replicate. sample was agitated with a calibrated bulb pipette to distribute the contents homogeneously. A 1-ml 4.2.1.4 Macrozoonlankton subsample was removed, placed in a Sedgewick-Rafter cell and examined under a compound Macrozooplankton were collected from July 1986 microscope using magnifications of 40X to 200X. through December 1995 at Stations P2, P5, and All microzooplankton taxa present in the P7 (Figure 4-1). Station P2 was also sampled subsample (generally, all taxa smaller than adult from January '1978 through December 1984, Calanusfinmarchicus, <4.0 mm) were counted Station P5 from January 1978 through December and identified. Most copepods were identified to 1981, and Station P7 from January 1982 through developmental stages, e.g., nauplii, copepodites December 1984. or adults (copepodite 6). Two subsamples were O 4-3
4.0 ZOOPLANKTON analyzed for each replicate. Individual abun- developmental stage. After enumeration, dances for all taxa (no./m') were computed for subsamples were recombined with the sample, each subsample and then averaged to provide mean abundances per taxon for each replicate. To enumerate rarer copepods (Anomalocera opalus, Caligus sp., Candacia armata, Euchaeta 4.2.2.2 Bivalve Larvae sp . , Harpacticoida, Monstrillidae and Rhincalanus nasutus) and the remaining macro-Each bivalve larvae sample collected at each zooplankton, the sample was placed in a Folsom station was analyzed. When the total umboned plankton splitter and serially split into fractions larvae collected ranged from 1-300, the entire that provided counts of at least 30 individuals of sample was processed. Samples were split when each dominant macrozooplankton taxon (as the total umboned bivalve larvae count exceeded defined in NAI 1984a). A maxunum of 100 ml of 300 specimens and two subsample fractions were settled plankton was analyzed. Macrozoo-examined with a dissecting scope. Umboned plankton taxa were enumerated by species using larvae were identified from an established species a dissectmg microscope at magnifications between list and enumerated. Specimens of other species 6X and 150X. Selected species (Cancer sp., were enumerated as Bivalvia. Subsamples (when Carcinus maenas, Crangon septemspinosa, and present) were averaged for each tow. Samples Neomysis americana) were identified to detailed collected in 1985 were analyzed for Mytilus developmental stage. Splits were recombined edulis and Mya arenaria only. upon completion. O 4.2.2.3 Macrozoonlankton For each sample type, species counts were con-verted to density by multiplying each species' Macrozooplankton were analyzed from three of count by the appropriate scaling ratio (the propor-the four tows (randomly selected) at each station. tion of the sample analyzed for each particular Copepods were analyzed by concentrating or organism) and dividing by the volume of water diluting the sample to a known volume from tiltered during field collection. Micro-which a subsample of approximately 150 cope- zooplankton and bivalve larvae abundances were pods per 1 ml could be obtained. The sample was reported as no./m'; macrozooplankton abun-agitated with a Stempel pipette to homogeneously dances were reported as no./1000 m$. distribute the contents and 1 ml was removed and examined under a dissecting microscope. 4.2.3 Analvtical Mghods Subsampling continued until at least 30 of the dominant copepod taxa and 150 total copepods 4.2.3.1 Communities were counted. if an even distribution of cope-pods could not be attained, the sample was seri- Community structure of .he microzooplankton, ally split using a Folsom plankton splitter. bivalve larvae, and marrozooplankton compo-Cyclopoids and copepodites of smaller calanoid nents of the zooplanktoa community was evalu-species (which were not efficiently collected in ated by numerical classification, multivariate the macrozooplankton samples) were not included analysis of variance (MANOVA), and qualitative in the copepod counts. The selected species comparison of loga abundances or geometric Calanusfinmarchicus was identified to detailed means for periods (operational, preoperational 4-4
4.0 ZOOPLANKTON and 1995, Table 4-1). De macrozooplanLon groups were characterized by the mean abundance community includes numerous species that exhibit of the dominant taxa. Communities during the ! one of three basic life history strategies. De operational period (August 1990-December 1995) holoplankton species (e.g., copepods) are plank- were judged to be similar to previous years if tonic essembHy throughout their entire life cycle. collections were placed in the same group as the Meroplankton includes species that spend a majority of collections taken at the same time l distinct portion of their life cycle in the plankton during previous years. A potential impact was I (e.g., larvae of benthic invertebrates). Species suggested if community differences occurred that alternate between association with the sub- solely during the operational period and were strate and rising into the water column on a regu- restricted to either the nearfield or the farfield lar basis are called tychoplankton (e.g., mysids), area. This situation would initiate additional i Because of these behavioral differences, as well as investigations. If community differences oc- l large differences in abundances, macrozooplank- curred at both nearfield and farfield stations, they ton species were categorized into holo / were assumed to be part of an area-wide trend, meroplanktonic species or tychoplanktonic spe- and unrelated to plant operation. cies prior to statistical analysis. The same types of analyses were performed on each group of Multivariate analysis of variance (MANOVA, species. Harris 1985) was the statistical test used to assess simultaneously the differences in abundance Temporal and spatial changes in the community between periods (preoperational and operational), structure of microzooplankton, bivalve larvae, stations (nearfield and farfield), years and months and the two components of macrozooplankton (for microzooplankton and macrozooplankton) or j were evaluated using numerical classification weeks (for bivalve larvae, Table 4-1). The techniques (Boesch 1977). This technique forms interaction term (Station X Period)'was used to l groups of stations and/or sampling periods based determine if there was an impact from plant l on similarity levels calculated for all possible operation for bivalve larvae and macro- l combinations of stations / sampling periods and the zooplankton. When a significant interaction term species that occur there. He Bray-Curtis similar- occurred, a fixed-effects ANOVA model (dis-ity index (Clifford and Stephenson 1975, Boesch cussed below) was applied to abundances of each 1977) was used. Values of the indices ranged dominant taxon individually to elucidate factors from 0 for absolute dissimilarity to I for absolute contributing to the significance. Microzoo- l similarity. He classification groups were formed plankton collections from 1995 were tested only l using the unweighted pair-group method to determine station differences. Historically, (UPGMA: Sneath and Sokal 1973). Results were there have been few differences in planktonic ! simplified by combining the entities based on species assemblages among nearfield intake and their similarity levels, determined by both the discharge and farfield stations. Continuation of within-group and between-group similarity val- this trend during plant operation would suggest ues. Results were presented graphically by that there were no effects from plant operation on dendrograms, which show the within-group these commanities. Probabilities associated with similarity and the between-group similarity (value the Wilks' 12mbda test statistic (SAS 1985) were . at which a group links to another group). The reported. Abundance data from each individual 4-5
O- O O Tcble 4-1. Summary of Methods Used in Numerical Classification and Multivariate Analysis of Variance of Zooplankton Communities, and Analysis of Variance of Zooplankton Selected Species. Seabrook Operational Report,1995. , l SOURCE OF VARIATION DATES USED DATA CHARACTERISTICS' IN (M)ANOVA - ANALYSIS TAXON LIFESTAGE STATIONS IN ANALYSIS MICROZOOPLANKTON MANOVA 32 dominants - P2 1995 log (x+1) transformation of Station P5 each " replicate" sample, x of P7 surface and bottom; species excluded with freqta:ncy ofoc-currence <20% ANOVA Selected species: Eurytemora sp. C' P2 1982-1984; Monthly mean, surface, Preop-Op, Year, Eurytemorn hen /mani A P7 1991-1995 and bottom Month, Station and Interaction Pseudocalanus.Calanus N Tctms Pseudocalanus sp. C,A P Oithona sp. N.C.A cs Numerial 35 dominants - P2 1978-1984, Irg (x+1) transformation of - classification 7/86-12/86 each individual (replicate) 4/90-12/95 sample,iof surface and bottom; species excluded with frequency ofoccurrence <10% , I BIVALVE LARVAE MANOVA All taxa except Bivalvia - P2 1988-1995* Log (x+1) transformation of Preop-Op, Station, PS individual (replicate) sample, Year, Week P7 then weekly means computed ANOVA Selected species: - P2 1988-1995* Same as above Preop-Op. Station, Afytilus edulis P5 Year, Week P7 . Numerical All taxa except Bivalvia - P2 1988-1995' Log (x+1) transforamtion of -- classification PS each individual (replicate) P7 sample, half-monthly means calculated from weekly E (Continued)
Tcble 4-1. (Continued)
- SOURCE OF VARIATION DATES USED DATA CHARACTERISTICS
- IN (M)ANOVA ANALYSIS TAXON- . LIFESTAGE STATIONS INANALYSIS MACROZOOPLANKTON Numerical -
P2 1986-1995 Monthly x. - classification Tycho: P5 Tychoplankton: taxa occumng 22 dominants' P7 in 25% ofP2 preoperational sampics except Mysidacea and Amphipoda. Ilolo/mero: IIolo/mero: deleted taxa occur-50 dominants
- ring in s5% of P2 preoperational samples and Ilimdinea and Polychaeta.
MANOVA Tycho: - P2 1987-1995' Sample period x sampled twice Preop-Op, Station, 22 dominants' P5 per month. Year, Month P7 Tychoplankton: taxa occumng e 9 in 25% ofP2 preoperational samples except Mysidacca and Amphipoda. IIolo/mero: Holo /mero: deleted taxa occur-50 dominants
- nngin s5% ofP2 preoperational samples and Himdinea and Polychaeta.
ANOVA Selected species: Calanusfinmarchicus C.A' P2 1987-1995* Sample period x, Preop-Op, Station, Cancer sp.' L PS sampled twice per Year, Month Carrinus meanas* L P7 month Cntngon septemspinosa L Neomysis americana AlI
'All data log (x+1) transformed unless otherwise noted 'C = copepodite; A = adult; N = nauplii; L = larvae 'l990 excluded 'Ilyperiidae removed, Mysis stenolepis added to list in 1994. 'llydrozoa, Gastropoda, Hyperiidae added to list; Eualus sp., Lebbeus sp. and Spirontocaris sp. lumped together as Hippolytidae in 1994. ' Cancer spp. discussed in Section 8.0 'Carcinus maenas larvae are essentially absent for 7 of 12 months, therefore a peak period of June-October only was analyzed.
O O O
l l 4.0 ZOOPLANKTON g (replicate) sample was log, (x + 1) transformed temporal effects were years within operational V prior to use in the MANOVA model in order to ' period (Year (Preop-Op)) and months or weeks more closely approximate the normal distribution. within year (Month (Year) or Week (Year)), which were added to reduce the unexplained Untransformed densities of bivalve larvae in variance, and thus, increase the sensitivity of the entrainment samples were multiplied by Ac F-test. For both nested terms, variation was ' month's average daily volume pumped through partitioned without regard to station (stations the circulating water system, and by the number combined). The final variance not accounted for of days represented by each sampling date, and by the above explicit sources of variation consti-then summed within month to estimate the num- tuted the error term. The preoperational period ber of bivalve larvae entrained by Seabrook for each analysis was specified as the period Station on a monthly basis. during which all three stations were sampled ) concurrently (thus maintaining a balanced model I 4.2.3.2 Selected Snecies design). As collections from 1990 occurred I during the transition from preoperational to l Biologically important or numerically dominant operational periods, they were excluded from the taxa were selected for further investigation (Table analysis. Some species (e.g. all bivalve larvae, 4-1). The operational, preoperational, and 1995 Carcmus maenas) were seasonally abundant (peak geometric means and coefficients of variation periods), often rare or absent at other times of the (Sokal and Rohlf 1981) were tabulated. Monthly year. Data from only the peak periods were used i O logia (x+1) means and their 95% confidence in analysis of variance and to compute opera-V limits for the preoperational period and were tional, preoperational, and 1995 geomen . means ; compared graphically to the monthly means for for those species. 1995 and the operational period to provide a l visual estimate of their magnitude and seasonal- 4.3 RESULTS ity. A fixed effects ANOVA model was used to test the null hypothesis that spatial and temporal 4.3.1 Microzoonlankton logio transformed abundances during the preoperational and operational periods were not 4.3.1.1 Community Structure significantly (p>0.05) different. De data col-lected for the ANOVAs met the criteria of a Temooral Characteristics l Before-After/ Control-Impact (BACI) sampling design discussed by Stewart-Oaten et. al. (1986), Temporal variability in species abundances and where sampling was conducted prior to and taxonomic composition of the nearshore during plant operation and sampling station microzooplankton community (surface and bot-locations included both potentially impacted and tom samples averaged) at Station P2 for all pre-l non-impacted sites. The ANOVA was a two-way operational and operational collections was i factorial with nested effects that provided a direct examined using numerical classification. He test for the temporal-by-spatial interaction. 'Ihe groups of collection dates formed by numerical main effects were period (Preop-Op) and station classification exhibited a relatively consistent (Station); the interaction term (Preop-Op X seasonal pattern (Figure 4-2). He microzoo-Station) was also included in the model. Nested plankton community was dominated by three 4-8 (
l l h 02 -
.c . , -
y Numbe ersempi Betwous Group Sadency o4-o5 -
~
"i l , _. f N b to k/, /
J // / / O E Croup 1 [ M _g. E croup 2 k \\h . [ 199I hb,i ll E CROUP 3 1990 g\\\\\\\\\gg-g encyP . 1986 E CROUP 5 1984 W k E CROUP 6 Q CROUP 7 1983
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l i NOT SAMPQD 1982 h
==l-] 7 981 1980 llll :
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1978 llll 3 ', J F M A M J J A 3 o y (p Figure 4-2. Dendrogram and seasonal groups formed by numerical classification oflog3, i (x+1) transformed microzooplankton abundances (no/m') at nearfield , Station P2,1978-1984, July-December 1986, April 1990-December 1995. 2 Seabrook Operational Report,1995. I 49 l
1 l 4.0 ZOOPLANKTON l (O groups and four taxa (Figure 4-2, Table 4-2). during the operational period, one month or Groups 3,4 and 5 together accounted for 92% of earlier than during the preoperational period. l all collection dates and covered every tr.onth of l the year. All three groups were dominated by (in The relative abundance of three of the dominant rank order) Oithona sp., Copepoda nauplii, micro _ , ankton taxa, Oithona sp., Copepoda Pseudocalanus/Calanus nauplii and nauplii and Pseudocalanus sp., was similar in the Pseudocalanus sp. Abundances were greatest in operational and preoperational periods in each of the spring and summer (Group 4), declined the three major seasonal groups (Groups 3,4 and through the late summer and fall (Group 5) to low 5; Table 4-2). Pseudocalanus/Calanus nauplii abundances in winter and spring (Group 3), declined in the operational period in Groups 3, 4 and 5. I Sporadic episodes oflow abundances of the four dominant microzooplankton taxa, usually occur- Snatial Patterns 1 ring in the period October through March, re-sulted in the formation of four small groups Spatial variation in the microzooplankton commu-(Groups 1, 2, 6, 7). Occasional " blooms" of nity structure was examined separately for both l Tintinnidae occurred from late October to Janu- the preoperational and operational periods. I ary (Group 1). Reduced abundances of Copepoda Preoperational comparisons of total micro- l nauplii and Pseudocalanus/Calanus nauplii zooplankton densities revealed no significant formed a group frequently occurring in the cooler differences between Stations P2 and P7 (NAI
.O months, December to February (Group 2). Iow 1985). Similarly,1995 abundances of the 32 U abundances and great variability define two dominant taxa were not significantly different l infrequently occurring groups in the winter among the three stations when tested with months, one dominated by Foraminiferida and MANOVA (Wilks' Lambda =0.24, F=1.01, Copepoda nauplii (Group 6), the other by p>0.48), as was found in previous operational Oithona sp. and Cirripedia larvae (Group 7). years (NAI 1991b,1992a,1993a,1995a; NAI :
and NUS 1994). l The seasonal succession of the groups followed a consistent pattern in both operational and 4.3.1.2 Selected Soecies preoperational periods. All groups were repre-sented in both operational and preoperational The copepods Pseudocalanus sp. and Oithona sp. periods. Seasonally, the occurrence of groups in were selected for further analysis in the the operational period corresponded well (within microzooplankton program because of their a sample period) with collections in the numerical dominance. Their abundance and preoperational period, with some exceptions trophic level make them important members of (Figure 4-2). Groups more characteristic of the the marine food web throughout the Gulf of I winter months occurred in late September 1991 Maine and nearby Atlantic Shelf waters (Sherman (Group 2) and early October 1992 (Group 3). 1966, Tremblay and Roff 1983, Davis 1984, The two occurrences of Group 6 in the opera- Anderson 1990). The third selected species, tional period have been earlier than the single Eurytemom herdmani, although not dominant, O occurrence in 1984. He transition from Group has been reported to be an abundant coastal cope-(U 4 to Group 5 occurred more frequently in July pod in the northern region of the western Atlantic 4 10 l l
Tcble 4-2 Geometric Means cf Microzoopl:nkton Abund:nce (N:Jm'),957o Confidezce Limits, cnd N;mber 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 1990,1991-95. Seabrook Operational Report,1995. GROUPNOj PREOPERATIONAL PERIOD OPERATIONAL PERIOD NAME DOMINANT SIMILARITY. TAXA * .N LCL MEAN UCL N LCL MEAN UCL 1 Tintinnidae 4 63 2005 62805 2 0 6421 9.2x10" Fall / Winter Oirhona sp. 22 228 2233 0 130 47662 (0.61/0.55) 2 Oirhona sp. 4 321 636 1262 6 127 571 2557 Fall /%rmter Foraminiferida 8 220 5720 3 21 132 (0.61/0.60) Copepoda nauplii 9 112 1250 62 229 836 Microsetella norvegica 9 83 719 6 92 1320 PseudocalanusCalanus sp.nauplii 11 70 426 5 13 30 Pseudocolanus sp. 7 108 1425 23 85 313 3 Oirhona sp. 40 484 701 1015 29 807 1145 1624 3 Winter / Spring Copepoda nauplii 345 457 605 602 820 1118 4 (0.64/0.60) PseudocalanusCalanus nauplii 276 400 581 105 190 343 Pseudocalanus sp. 98 148 224 84 128 104 4 Oithona sp. 54 3031 3929 5094 23 4603 6244 8469 Spring / Summer Copepoda nauplii 2612 3469 4607 4205 5702 7733 (0.65/0 64) PseudocalanusCalanus nauplii 1234 1673 2268 290 574 1136 Pseudocolanus sp. 548 776 1096 256 517 1042 Bivalvia veliger larvac 478 745 1160 206 531 1366 Oirhona sp. 61 1545 1999 2586 50 2334 3049 3983 5 Copepoda nauplii 808 1082 1449 1084 1392 1788 LateSummer/ Fall PseudocalanusCalanus nauplii 585 759 986 139 214 328 (0.660.64) Pseudocalanus sp. 247 344 480 229 325 463 6 Foraminiferida 1 - 95 - 2 0 52 8.1 x10' Winter Copepoda nauplii - 28 - 0 34 2.1 x10' (0.66/0 60) Oithona sp. - 18 - 0 170 26386 Tintinnidae - 15 - 0 36 6168 Microsetella norvegica - 2 - 0 66 5823 7 Oirhona sp. 2 6 223 7538 1 - 197 - Winter Cirripedia larvae 0 84 7.8x10' - 172 - (0.71/0.60) PseudocolanusCalanus nauplii 0 61 7.4 x10' - 34 - Copepoda nauplii 0 31 1054 - 26 - Microsetella norvegica 0 9 718 - 41 - Polychaeta larvae 0 13 6.7x10' - 39 -
'within group similanty/between group similarity a compnsing > 5% of total group abundance in either preoperational or operational O
4.0 ZOOPLANKTON (Katona 1971). Lifestages of these taxa were years (Table 4-3, NAI 1991b). ANOVA results identified whenever possible to develop an under- indicated that Eurytemora sp. copepodite abun-standing of the dynamics of population recruit- dances during the operational period were signifi-ment cycles. In some cases, however, the possi- cantly lower than densities from recent preopera-ble presence of congeneric species made it im- tional years, but there were no significant dif-possible to routinely identify all lifestages to ferences between stations (Table 4-4). 'Ihe species level. Station P5 was not included in the interaction term (Preop-Op X Station) was not analysis of selected species because a complete significant, indicating that the decrease in abun-year of preoperational data was not collected. dance which occurred between the operational and preoperational periods was similar at both the Ergytemore sp. intake (P2) and control (P7) stations, and no effect could be attributed to the operation of Earlier studies indicated that Eurytemora sp. Seabrook Station. mp. podite and E. herdmani adult populations in Hampton Harbor and the nearfield Station P2 The abundance of Eurytemora herdmani adults underwent similar seasonal cycles, but during the during the operational period followed the same spring the population density in the estuary was general seasonal pattern as described for Eury- ) much higher than at the nearfield station (NAI temora sp. copepodites with the exception that a 1978, 1979). These observations suggested that fall E. herdmani adult peak was not detected in recruitment to the coastal population may be sup- either the preoperational or operational years, nor plemented by the estuarine population. was it observed in 1995 (Figure 4-3). Mean abundances in summer during the operational Eurytemora sp. copepodite monthly mean densi- period were reduced from the peak abundances ties for the operational period and 1995 failed to observed in the preoperational period at both the exhibit the mid-summer density peak that has nearfield (P2) and farfield (P7) stations, indicat-bwn observed in the preoperational years (1978- ing a regional effect (Figure 4-3). In 1995, mean 1984) and were well below the preoperational abundance of E. herdmani adults was similar to average densities for June and July (Figure 4-3). operational abundances, and lower than the mean After August, operational mean densities, while preoperational abundance (Table 4-3). The mean variable, were within the range observed during abundances of E. herdmani adults during the the preoperational period. However, mean oper- operational period were significantly lower than ational densities displayed a spring peak that was the mean abundances for the preoperational years, somewhat lower than the preoperational summer but there were no significant differences between peak, and a fall peak that was comparable to the the stations (Table 4-4). The interaction term fall peak in preoperational years. The operational (Preop-Op X Station) was not significant, indicat-pattern of seasonal occurrence was similar at ing no effect due to station operation. Stations P2 and P7 (Figure 4-3). Abundance peaked in the late summer and in December Pseudocalanus up. during 1995. The 1995 annual geometric mean for Eurytemora sp. copepodites at Station P2 was Historically, Pseudocalanus/Calanus sp. nauplii below the overall mean and below the mean were present in large numbers throughout the values for individual years for the preoperational year at Station P2, and were among the numeri-4-12
i Eurytemora sp. Eurytemora herdmant l Copepodites Adults l 44 44
- pgy
... , . . . e, u _ . _ . u _. .
Iu Iu ju fu tu Lu u - u u - U J..'. t ,.i ,Q 22-f - 1 Eurytemora sp. Eurytemora herdmant
, Preoperational ,
Preoperational
-n -n
--v - - -n
$u Su a. lu -
,, lu ,
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,- '. u : '.
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Eurytemora sp. Eurytemora herdmani Operational Operational ; Q Q lu 1u ! Iu Iu 1u Iu m l u i
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N" ~~~~' Figure 4-3. logic (x+1) abundance (nolm') ofEurytemora sp. copepodites and Eurytemora herdmani adults, monthly means e.nd 95% confidence intervals for the preoperational period (1978-1984), the operational period (1991-1995), and 1995 at nearfield Station P2, and preoperational and operational monthly abundances at nearfield Station P2 and farfield Station P7. Seabrook Operational Report,1995. 4-13
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y p g
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V - V Table 4-3. Geometric Mean Density (NoJm') and the Coefficient of Variation (CV,%) of Selected Microzooplankton Species at Stations P2, PS, and P7 for Preoperational and Operational Periods and 1995. Seabrook Operational Report,1995. PREOPERATIONAL OPERATIONAL 12P_5 SPECIES /LIFESTAGE - STATION MEAN~ CV MEAN* CV MEAN Eurytemora sp. P2 4 35.1 1 20.I 1 copepodites P5 - - 1 22.2 1 P7 4 56.4 1 40.2 1 Eurytemora herdmani P2 2 50.2 1 33.8 1 adults P5 - - 1 25 9 1 P7 3 51.2 1 37.8 i Pseudocalanus/Calanus sp. P2 593 7.5 l58 8.5 100 t nauplii P5 -- - 117 4.5 104 % P7 499 11.2 139 4.5 129 Pseudocalanus sp. P2 223 8.6 153 7.9 81 copepodites P5 - - 137 6.7 107 P7 193 14.0 159 3.8 173 Pseudocalanus sp. P2 23 17.4 15 18.4 7 adults P5 - - 13 20.9 5 P7 25 16.4 14 15.6 8 Oithona sp. P2 465 11.7 500 6.0 568 nauplii P5 - - 541 5.2 783 P7 403 15.1 460 6.5 596 Oithona sp. P2 490 10.1 649 4.7 465 copepodites P5 - - 611 6.3 537 , P7 299 20.1 581 3.6 462 Oithona sp. P2 107 13.5 178 5.5 165 adults PS - - 165 7.8 150 P7 98 23.9 161 5.9 188 6 ationalyears: P2 = 1973-84 P5 = not sampled P7 = 1982-84. Mean of annual means. ational years = 1991-95; 1990 n, ot sampled dunng, January through March, data not included. s can of annual means. l
-2 w- _ . . _- _ _ _ . _ _ - . _ _ _ _ _ _ _ _ . _ . _ . _ _ _ . . _ _ _ _ _ _ _ - _ . . _
Table 4-4. Results of the Analysis of Variance of Logi,(X+1) Transformed Density (NoJm') of Selected Microzooplankton Species among Preoperational Years (1982-84) and Operational Years (1991-95) and Nearfield (Station P2) Vs. Farfield (Station P7) Areas. Seabrook Operational Report,1995. SOURCE OF SPECIES / LIFESTAGE : . VARIATION * ' df MS F MULTIPLE COMPARISONS
- Enrytemora sp. Preop-Op 1 8.28 37.26* *
- Preop >Op copepodite Year (Preop-Op) 6 1.86 8.39"*
Month (Year X Preop-Op) 88 0.74 3.35"* Station 1 0.09 0.39 NS Preop-Op X Station 1 0.36 1.61 NS Error 236 0.22 Eurytemora herdmani Preop-Op 1 8.31 44.35 "
- Preop >Op adult Year (Preop-Op) 6 1.48 7.91"*
Month (Year X Preop-Op) 38 0.75 4.00*" Station 1 0.34 1.83 NS Preop-Op X Station 1 0.19 1.02 NS Error 236 0.19 G Pseudocalanus/Calanus Preop-Op 1 20.55 89.10 "
- Preop >0p sp. nauplii Year (Preop-Op) 6 1.57 6.79"*
Month (Year X Preop-Op) 88 1.42 6.17 *" Station 1 0.15 0.67 NS Preop-Op X Station 1 0.03 0.11 NS Error 236 0.23 Pseudocalanus sp. Preop-Op 1 0.96 3.68 NS copepodite Year (Preop-Op) 6 1.12 4.32"* Month (Year X Preop-Op) 88 1.17 4.49"* Station 1 0.00 0.00 NS Preop-Op X Station 1 0.04 0.17 NS Error 236 0.26 Pseudocalanus sp. Preop-Op 1 3.55 13.02* " Preop >Op adult Year (Preop-Op) 6 2.05 7.52*" Month (Year X Preop-Op) 88 1.35 4.94 *" Station 1 0.00 0.01 NS Preop-Op X Station 1 0.00 0.00 NS Error 236 0.27 (Contin
p J p v (~)/ Table 4-4. (Continued) SOURCE OF-SPECIES / LIFESTAGE - ' VARIATION
- df- MS J F MULTIPLE COMPARISONS
- Oithona sp. Preop-Op 1 0.07 0.34 NS nauplii Year (Preop-Op) 6 2.68 13.10* **
Month (Year X Preop-Op) 88 0.% 4.70"* Station 1 0.49 2.39 NS Preop-Op X Station 1 0.03 0.16 NS Error 236 0.20 Oithona sp. Preop-Op 1 4.29 25.97 "
- Preop <Op '
copepodite Year (Preop-Op) 6 2.59 15.69 "
- Month (Year X Preop-Op) 88 1.22 7.40"*
Station 1 0.69 4.15* P2>P7 ' Preop-Op X Station 1 0.10 0.63 NS Error 236 0,17 + Oithona sp. Preop-Op 1 2.62 13.07 "
- Preop <Op adult Year (Preop-Op) 6 2.96 14.77* "
Month (Year X Preop-Op) 88 1.24 6.19'" Station 1 0.37 1.85 NS Preop-Op X Station 1 0.02 0.12 NS . Error 236 0.20 NS = Not Significant (P> 0.05)
= Significant (0.05 2 P >0.01)
** = Highly Significant (0.012 P > 0.001)
*" = Very Highly 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 Station = nearfield vs. farfield stations Preop-Op X Station = interaction ofmain effects 6Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for significant interaction terms.
4.0 ZOOPLANKTON cally dominant taxa composing the microzoo- tional period and 1995 generally exhibited the plankton community in most seasons (Table 4-2). same seasonal pattern of abundance as during the Seasonal peak abundance occurred during July preoperational period (Figure 4-4), although during preoperational years, and in April and abundances in June were higher in tne opera-from July to September during the operational tional period and in 1995. Average operational period (Figure 4-4). The 1995 abundances densities of Oithona sp. nauplii were not signifi-peaked somewhat earlier than both preoperational cantly different from the preoperational (1982-and operational averages. Mean densities for the 1984) mean and there were no significant differ-operational period were significantly lower than ences between stations (Table 4-4). He interac-the preoperational mean at both stations (Tables tion term (Preop-Op X Station) was not signifi-4-3,4-4). However, the differences between cant, indicating no effect due to station operation periods were consistent between the nearfield and (Table 4-4). farfield areas, indicating an area-wide decrease rather than a localized plant effect. Oithona sp. copepodites also followed the same general pattern of seasonal abundances during the Pseudocalanus sp. copepodites and adults were operational period and in 1995 that was evident also present throughout the year, with peak abun- during the preoperational period (Figure 4-4). dances of copepodites occurnng from May to July The 1995 geometric mean density at Station P2 and adults from June to September (Figure 4-4). was lower than the means for the preoperational Operational monthly mean abundances of and operational periods (Table 4-3). During the copepodites were lower than the preoperational operational period, geometric mean density was abundance in July and near the preoperational significantly larger than during the preoperational averages for the remainder of the year. In 1995, period, and mean density at Station P2 was large reductions in abundance of both copepodites significantly larger than at Station P7 (Table 4-4). and adults occurred in January, July, and Novem- The Preep-Op X Station interaction term was not ber. The mean densities of copepodites during the significant, indicating that the relationship be-operational period were not significantly different tween stations was consistent between the from the preoperational (1982-1984) means but preoperational and operational periods and there the mean densities of adults were significantly was no effect due to the operation of Seabrook lower in the operational period (Tables 4-3, 4-4). Station. The interaction term (Preop-Op X Station) was not significant for either lifestage, indicating no Lowest abundances of adult Oithona sp. during effect due to plant operation. the preoperational period occurred in late winter. Abundances peaked from July through September Oithona sg before decreasing to moderate levels in the fall. Dunng the operational period and in 1995 abun-All Oithona sp. (mostly Oithona similis) life dances peaked in June and September. Abun-stages were present year-round and together dances remained high in October before decreas-constituted the most abundant microzooplankton ing to preoperational levels. Geometric mean taxon throughout the preoperational and opera- abundances for adults at Stations P2 and P7 for tional periods (Tables 4-2 and 4-3). Oithona sp. 1995 were higher than the means for all preop-nauplii densities at Station P2 during the opera- erational years (Table 4-3). Operational densities 4-17
1
,s Pseudocalanus/Calanus Oithona sP. 1 1 Nauplii Nauplii (s u
,,,, u _ , , , ,
i i a .. u . . ,3
* / ]
u /
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- /\
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7
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;u 7' \ '\\ ,u
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H"u \ g" u m = = = w m a = w ocr a ese m sus = = w a a a se,ocr u ese uowm uowm Pseudocalanus sp. Oithona sp. Copepodites Copepodites a 4J _ m,,,
... ... m ,,,
u _ . . = u _ . g e j....... Eu bhkk h g;u/ v u lu u .- 4f %
,s
.l v @/N %t l \
g" g"
) u i
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m ris = m - m a a act - one m ,a = = = m a = = ocr - one nowm now Pseudocalanus sp. Oithona sp. Adults Adults a _ , , , , u _ , , , , u . u _ . Iu Iu . 1- 1- / 's & A.q.. . tu 1u y' y 1 1u .- Q lu 4%,. i !u ' EI'I ,u N. >.rc [# ' ' yu w'agdf
.f..W
\/ \v=3 \ ,,
ju i %-*
/
m en m a uw m a aus au ocr e ese a sus m a = m a a se act a osc mowm uowm Figure 4 4. Logio(x+1) abundance (no/m') of Oithona sp. nauplii, Pseudocalanus sp. and Oithona sp. copepodites and adults, monthly means and 95% confidence intervals for the preoperational period (1978-1984), the operational period (1991-1995), and 1995 at nearfield Station P2. Sesbrook OperationalReport,1995. v 6 4-18
a 4.0 ZOOPLANKTON of Oithona sp. adults were significantly greater in historically. This assemblage occurred once in the operational period (1982-1984, Table 4-4). 1995, at Station P7 in late April. He transition No significant differences were detected between to the late spring assemblage (Group 2), which stations, and the interaction term (Preop-Op X typically occurred in early to late May, was Station) was not significant, indicating no effect marked by peak densities of Hiatella sp., the due to station operation. earliest spawner, along with moderate densities of Mya truncata. Peak mean densities of Af. edulis, 4.3.2 Bivalve Larvae Anomia squamula, and Niatella sp. typified the early summer assemblages (Group 3), which most 4.3.2.1 CDmmunity Structure often occurred throughout June, but occasionally occurred as early as late May, and in 1995 lasted Patterns of abundance of the umboned bivalve into early July at Stations P2 and P7. Although larvae assemblage were enmined using numerical the Group 3 assemblage occurred during both classification to address whether there were periods, the mean abundance of each of the three differences among stations (spatial patterns) or dominant taxa increased substantially during the between the preoperational and operational operational period (Table 4-5). Group 3 was periods (temporal patterns). This aggregation of followed by a period oflow-to-moderate densities meroplanktonic species exhibited strong seasonal of bivalve larvae (Group 4) that occurred from patterns that were generally consistent among late summer through late fall, and included years and stations (Figure 4-5). Mean abun- moderate abundances of Anomia squamula, dances were grouped seasonally, falling into one Afodiolus modiolus, and Afytilus edulis. Abun-of six distinct groups. He seasonal structure of dances of each of the Group 4 dominants de-the community reflected the timing of recruitment creased during the operational period. Late of different taxa as well as their abundance (Table summer or fall collections throughout the study 4-5). period have occasionally contained exceptionally low densities of bivalve larvae, including Anomia Temooral Patterns squamula, Mytilus edulis and Afodiolus modiolus (Group 5). Afya arenaria and Solenidae were The bivalve larvae assemblage showed predictable also present, again in relatively low numbers. seasonal changes that were generally consistent Preoperational-operational differences in abun-among years. Most operational period collections dance showed no consistent pattern for each of (beginning August 1990) were classified into the Group 5 dominants. groups that occurred preoperationally (Figure 4-5 and Table 4-5). Early spring collections (Group Group 5 occurred as early as late July, and as late
- 1) were characterized by low densities of a single as early October. These periods were followed taxon, Riatella sp., and typically occurred in late by an increase in densities of the dominants and April through early May. In 1994, early spring a return to the typical late summer fall assem-collections were similar to previous years in that blage (Group 4). No single group characterized only one taxon, Riatella sp., was present. How- the bivalve larvae assemblage from August-ever, densities were two orders of magnitude October every year, although the Group 4 assem-higher than typical of Group 1, resulting in a blage occurred most commonly during this period unique assemblage (Group la) not observed (Figure 4-5).
4-19
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- o,;
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van A W ,' wwwN, AW,%%,N, i g i j i 1 l 1 Apr May l Jun 1 Jul Aug Sep I Oct j MONTH l l l Group 2. Early Spring, Q Group 3. Early Summer fllf:$i Group 5. Summer /F,all IAw Hiatella sp. Densitie: Low Densiues Groep la . Early Spring,
,s Group 4 1. ate Summer / Fall lu l Ungrouped High Riatella sp. Densities (P7.1. ate April,1993)
M Groep 2 Late Spring Figure 4-5. Dendrogram and seasonal groups formed by numerical classification oflogio (x+1) transformed bivalve larvae abundances (half-monthly means; nolm') at Seabrook intake (P2), discharge (PS) and farfield (P7) stations, April-October, 1988-1995. Seabrook Operational Report,1995. 4-20
i ! Table 4-5. Geometric Mean Abundance (NoJm'), and the 95% Confidence Limits of Dominant Taxa and Number of Collections Occurring in Seasonal Groups Formed by Numerical Classification of Bivalve Larvae Collections at Intake (P2), Discharge (PS) and Farfield (P7) Stations,1988-1995. Seabrook Operational Report,1995. GROUP NOJ NAME SIMILARITY
- DOMINANTTAXA6 PREOPERATIONAL YEARS
- OPERATIONAL YEARS' N* LCL MEAN UCL N d LCL MEAN UCL 1 Iliatella sp. 18 28.0 39.3 55.2 14 28.7 53.8 100.1 (0 ,
I a* Iliatella sp. - - - - 6 717.2 1914.4 5107.4 ( 4 9 2 Iliatella sp. 9 631.5 1315.9 2740.9 24 450.5 610.8 827.8 t S Affa truncata 55.9 111.9 223.1 6.7 11.4 I 8.8 h
~
3 Afytilus edulis 17 2878.7 5367.I 10,005.8 29 5,710.0 11,270.2 22,243.6 Early Summer Anomia squamula 50.7 131.7 340.0 598.4 1,296.1 2,806 9 (0.75/0.63) Iliatella sp. I147.8 1 % 4.9 3,362.9 1917.2 3,494.6 6,369.4 4 Anomia squamula 48 544.6 872.2 1,396 0 133 425.6 536.7 676.7 Late Summer / Fall Afodiolus modiolus 191.9 299.8 468.0 25.5 37.2 54.3 (0 68/0.63) Afvtilus edulis 325.5 640.9 1261.0 332.2 451.3 613.0 5 Anomia squamula 7 12.7 27.3 57.7 6 19.1 41.5 88.9 Fall AIyrilus edulis 10.1 22.0 46.5 4.7 13.3 34.7 (0.61/0.63) Afodiolus modiolus 3.1 13.6 51.3 0.3 0.8 1.4 Atya annaria 0.5 3.0 9.6 1.6 9.3 40.3 Solenidae 0.0 08 2.2 0.4 7.7 53.1 Un IIiatella sp. - - - - 1 -- 2.5 -
'(within-group similarity /betwum-group similarity)
- those taxa contnbuting 25% of total group abundance in either preoperational or operational period collections
- preoperational = April 1988-July 1990; operational = August 1990-October 1995
' 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)
' occurred in 1994 and 1995 only O O O
4.0 ZOOPLANKTON 4 I m In 1995, the typical early spring assemblage annual means of Solenidae were generally similar (Group 1) occurred only in late April at Stations among the three stations, indicating that the signifi-P2 and P5. Higher-than-average densities of cant Preop-Op X Station interaction term was not Hiatella sp. (Group la) occurred only at P7 in likely biologically meaningful. late April. As the bivalve larvae spawning season progressed, the assemblage changed from the Spatial Patterns early spring assemblage (Group 2) to the early summer in late May and early June (Group 3). Distribution of bivalve larvae in marine waters was By late July a transition to the typical late related to several factors: distribution of spawning summer-fall community -(Group 4) was observed adults, length of larval existence and local hydro-at Stations P2 and P7. This transition occurred at graphic conditions. The dominant bivalve larvae Station P5 in early July. There were no occur- collected in coastal waters of New Hampshire were rences of Group 5 in 1995, species whose adults were widely distributed along the New England coastline. Duration of larval Multivariate analysis of the community indicated stage is dependent on temperature, but may be as that differences between the preoperational and long as six weeks (Bayne 1%5,1976; Jury et al. operational periods (Wilks' Lambda =0.36, 1994). The local hydrography is dominated by F=55.7, p=0.0001) were not consistent among tidal and long-shore currents (NAI 1980). Stations stations (Preop-Op X Station: Wilks' P2, PS and P7 are located in waters of similar Lambda =0.90, F= 1.72, p =0.02). Five species depth (Figure 4-1) with no physical barriers be-(Modiolus modiolus, Spisula solidissima, Mya tween them. These conditions tended to create a arenaria, Mya truncata and Macoma balthica) spatially homogeneous bivalve larvae community. decreased in abundance durtng the operational It was not unexpected, then, that the species com-period at all three stations. Two species, Mytilus edulis and Hiatella sp., increased in abundance .
. stations (Figure 4-5). During 90% of the sampling during the operational period at each station. .
periods, assemblages at all three stations were Hiatella sp. and Solenidae were responsible for the . . sumlar, and were grouped together; assemblages significant Preop-Op X Station interaction term
. at nearfield Stations P2 and P5 were grouped (Figure 4-6; Table 4-6). Densities of Hiatella sp.
together 97% of the time. increased during the operational period at each of the three stations, but this increase was significant In 1995 the three stations were placed in the same only at Station P2. Annual time series plots of auna g mg g a sam g Ped Hiatella sp. indicate that the three stations gener-except for late April, late May and early July ally exhibited the same trends m. density over all
. (Figure 4-5). The assemblage from the earliest years (Figure 4-7). Therefore, the sa.graficant samples (late April 1995) at Station P7 (farfield)
Preop-Op X Station term does not likely reflect a was not similar to any other group due to extreme-meaningful biolog.ical difference. ly high numbers of Hiatella sp. (Group la). By early May 1995, the numbers of Hiatella sp. Operational densities of Solenidae remained similar decreased, making the P7 assemblage similar to to preoperational densities at Stations P2 and P7, [ but declined s.ignificantly at Station P5 (Table 4-6). that at P2 and P5, the late spring assemblage (d (Group 2). In late May, Group 2 persisted at Sta-As noted for Hiatella sp. annual means, trends m. 4-22
4.0 ZOOPIANKTON Hiatella sp. an = = = et 1.8 P7 1.8 k 1 .4 1.2 1.0 0.8 P 0 88 0.4 0.2 0.0 m.on-sww ep w PERIOD Solenidae 2* = = = p2
........ p.
3 -.- --- ~ er 1.8 k,.
,, ........._~ D "'"
_ n. _ 1.0 0.8 e
*0 .6 h 0.<
0.2 0.0 ProopwmW Openmond eenco Figure 4-6. A comparison of the mean logio(x+ 1) abundance (no./m3 ) among Stations P2, PS, and P7 during the preoperational (1988-1989) and operational (1991-1995) periods when the interaction term (Preop-Op X Area) of the ANOVA model was significant for Riatella sp. and Solenidae . Seabrook Operational Report,1995. 4 23
- 4.0 ZOOPLANKTON O T 6>e 4 ne it r^ irsis erv ri ce ce-a ri 1 < *e (e2). aisch r e <rs) and Farfield (P7) Weekly Loga (X+1) Transformed Abundances of Mytilus Edulis, Hiatella Sp. And Solenidae Larvae During Pre-Opera-tional (1988-1989) and Operational (1991-1995) Periods. Seabrook Operational Report,1995.
' SOURCE OF SPECIES VARIATION df MS F MULTIPLE COMPARISONS 1 Myrilus edulis Preop-Op' 1 1.54 11.07 * *
- Op> Preop Station 2 0.32 2.30 NS
, Year (Preop-Op) 5 16.27 116.81***
Week (Year X Preop-Op) 170 5.71 41.03 * *
- Preop-Op X Station 2 0.10 0.72 NS Error 349 0.14 1 Riatella sp. Preop-Op' 1 3.30 14.48 * *
- l Station 2 0.12 0.53 l Year (Preop-Op) 5 3.04 13.35 " * ,
Week (Year X Preop-Op) 170 4.34 19.09* *
- l Preop-Op X Station 2 0.78 3.43* P2On P2Pr PSPr P7Pr P50p P70p i Error 349 0.23 I Solenidae Preop-Op' 1 1.27 6.86*
- Station 2 0.36 1.95 Year (Preop-Op) 5 1.52 8.19 * *
- Week (Year X Preop-Op) 170 2.73 14.72* *
- Preop-Op X Station 2 0.57 3.07* P2On P2Pr PSOo P70n P7Pr PSPr Error 349 0.19 NS= Not Significant (P> 0.05)
*= Significant (0.05 a P >0.01)
**= Highly Significant (0.01 a P > 0.001)
*** = Very Highly 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 Week (Year X Preop-Op)= week nested within year Preop-Op X Area = interaction of main effects <
Station X Year (Preop-Op)= interaction of station and year nested within preoperational and operational period. O v 4-24
l 4.0 ZOOPLANKTON j 1 l
- a. Hiatella sp.
3.0 g i P2 l
+ - -*- - + PS l l i *--* ~ P7
'T
-g 2.5 I i
I I
- = I , I o i.. , s .i k 20 '
,, ,- ;-$l'L'2 E /;S I sN-
,f '
l
? I i 1.5 ,-
l l l l l l I I i 1.0 I I P l i
+ i i E I 1 i o.5 Preoperanonal ! ! Operational I 1 1 I l l l o.o I 88 89 90 91 92 93 94 95 YEAR
- b. Solenidae 1
3.0 i i - - - P2 I I
-- . pS l l -*- ~ ~ P7
? 2.5 l 1 -
li l l 2.0 a i I i
,,,,,,,, l l ,-
11.5 _ 1.0 T
%p'" C-i i l l I l o.5 Prooperanonal l t operstkmal I
I I o.o ' ' 88 89 90 91 92 9' 3 94 95 YEAR Figure 4-7. Time series of monthly mean logw(x+1) abundances of Hiatella sp. and Solenidae,1988-1995 (data between the two dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 4-25
4.0 ZOOPLANKTON tion P7 while Stations P2 and P5 were charac-by (' could decrease the standing stock of harvestable high abundances of Mytilus edulis (Group 3, early clams (Section 10.0). Mytilus edulis, the edible summer). Early July 1995 was the only other time blue mussel, has been the most abundant species period when all three stations were not placed in encountered in bivalve larvae investigations and is the same faunal grouping. The early summer the dominant species in the surrounding shallow-faunal group occurred at Stations P2 and P7 while water hard-substrate benthic community (Section the late summer / fall faunal group, characterized by 7.0). Temporal and spatial patterns of both species high abundances of Anomia squamula (Group 4) were examined to evaluate whether there was occurred at Station P5. The consistency of faunal evidence of impacts induced by operation of groups among nearfield and farfield stations indi- Seabrook Station. cated that the operation of Seabrook Station has not affected the bivalve larvae community composi- Mva arenaria , tion. ! This species is discussed in detail in Section 10.0. I 4.3.2.2 Selected Snecies ) I Mvtilus edulis Mya arenaria was identified as a selected species because of the interest in recreational (locally) and Abundances of Mytilus edulis peaked in June at commercial (regionally) harvesting of adults and Station P2 during the preoperational and opera-n the concern that impacts to the larval population tional periods (Figure 4-8). Blue mussellarvae i k.) ! l SA
= 1ges 1
d
,/.,,Q. . l
{ 4.s / s* A 34
/ ... 1 l
1 L , b i*"
==
2.o l. j' gj ' y /4 WQ l 5
/
14
/
- 4. /N
/y c.o 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 Apr May Jun Jul Aug Sep Oct p Figure 4-8. Weekly mean logw(x+1) abundance (no./m') of Mytilis edulis larvae at Station P2 during i.y preoperational years (1978-1989), including 95% confidence intervals, and weekly means in the operational period (1991-1995) and in 1995. Seabrook Operational Report,1995.
4-26 l 1
4.0 ZOOPLANKTON l l l l remained relatively abundant through the end of The annual abundances at both nearfield and sampling in October. Monthly abundances in 1995 farfield stations during 1995 were higher than the I nereased sharply in early June and reached peak preoperational abundances for the third year in a abundances in late June, with a general decrease row (Table 4-7; NAI and NUS 1994; NA11995a). afterwards. During June and July of 1995, densi- The average operational abundances at all three j ties generally exceeded the upper 95 % confidence stations were significantly higher than recent limits of both the preoperational and operational preoperational (1988-1989) abundances although j weekly averages. station differences were not significant (Table 4-6). l Table 4-7. Geometric Mean Abundance (No./m') with Coefficient of Variation (Cv) for Mytilus Edulis Larvae at Stations P2, P5 and P7 During the Preoperational and Operational (1991-1995) Years and the 1995 Mean. Seabrook Operational Report 1995.
' PREOPERATIONAL OPERATIONAL 1995 STATION - YEAR. MEAN* CV- MEAN* CV MEAN P2 1982-1989 232.4 18.5 215.8 21.0 332.0 P5 1988-1989 184.2 18.0 189.1 16.0 275.1 P7 1982-1984, 250.1 13.2 225.4 20.0 330.4 1986-1989 'mean of annual means The interaction term (Preop-Op X Station) was not December in 1994 (no entrainment samples were significant, suggesting that the plant had no effect collected in 1994). The total number of bivalve on the abundance of Mytilus edulis larvae. larvae entrained in 1995 (27,326.5x10'; Table 4-
- 8) was over 50% higher than the previous high of 4.3.2.3 Entrainment 18,189.8x10', which occurred in 1993 (NAI and NUS 1994). In general, the numbers of all en-The effects of operation of Seabrook Station on trained taxa have increased over time (Figure 4-9).
bivalve larvae were monitored primarily through The high numbers of bivalve larvae entrained in entrainment sampling and secondarily through 1995 may be due to the relatively large amount of comparisons of both community and species larvae available offshore, as reflected in the ex-abundance characteristics between the tremely high Mytilus edulis densities in 1995 preoperational and operational periods. Several (Table 4-7 ), in combination with the slightly scheduled plant shutdowns have occurred during greater amount of water pumped through the the operational period: carly August through cooling water system during the peak season of November 1991: September and October 1993; bivalve larvae abundance (June and July). In all and January through April and October through years, the most abundantly entrained organism was 4-27
. = _ . .. _.
O O O Table 4-8. Estimated Number of Bivalve Larvae Entrained (X 10') by the Cooling Water System at Seabrook Station from the Third Week in April Through the Fourth Week of October,1995. Seabrook Operational Report,1995.
-APR MAY- JUN. JUL J-A U G SEP OCT TOTAL' .%
SPECIES Bivalvia 0.5 15.7 380.2 383.3 10.2 3.9 1.4 795.1 2.91 Anomia squamula 0.0 25.8 1,488.2 5,061.6 2,144.2 152.8 33.3 8,905.9 32.59 Hiatella sp. 2.2 202.0 1,158.3 1,157.6 71.5 2.8 3.7 2,598.2 9.51 Macoma balthica 0.0 0.0 0.0 1.6 0.0 0.2 0.1 -2.0 0.01 Modiolus modiolous 0.0 0.3 350.8 142.8 31.2 0.7 20.7 546.4 2.00 h Myaarenaria 0.0 0.0 0.0 0.0 2.2 2.1 0.0 4.3 0.02 Mya truncata 0.0 4.2 5.7 3.7 13.8 0.0 0.2 27.6 0.10 Myrilus edulis 0.2 70.4 3,022.7 9,519.7 580.5 21.6 16.0 13,231.0 48.42 Placopecten magellanicus 0.0 0.0 3.8 1.9 0.1 0.0 0.5 - 6.2 0.02 Solenidae 0.0 2.4 857.9 226.9 2.5 2.0 0.7 1,092.3 4.00 Spisula solidissima 0.0 0.0 0.0 86.8 17.4 6.7 1.6 112.5 0.41 Teredo navalis 0.0 0.0 0.0 4.5 0.4 0.0 0.0 4.8 0.02 TOTAL 2.9 320.7 7,267.5 16,590.4 . 2,873.8 193.0 78.2 27,326.5 100.00'
% of TOTAL <0.01 1.2 26.6 60.7 10.5 0.7 0.3
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- not sampled 4 Mytilis edulis Anomie squamula Iliatella sp. other Figure 4-9. Volume of cooling water pumped during the months sampled for bivalve larvae and total number of bivalve larvae (x109) entrained by Scabrook Station, 1990-1995. Seabrook Operational Report,1995.
O O O
4.0 ZOOPIANKTON M. edulis. Sinularly, in 1995, M. edulis accounted The Holo- and Mercolankton Assemblage for 48.4% of the total number of organisms en-trained, while Anomia squamula accounted for The distinct seasonal patterns of the holo- and 32.6% and Hiatella sp. 9.5% (Figure 4-9). meroplar.kton previously observed were again evident when 1995 collections were included in Numbers of larvae entrained generally reflected the numerical classification (Figure 4-10; Table the numbers present in the natural environment. 4-9). Groups 1,5,6,7, and 8 formed a distinct In all years, entrainment was highest in June or succession of seasonal groups and together, July, reflecting the natural peak in bivalve larval included 95% of the collections. Temora abundance observed nearshore. However, the longicornis, Sagitta elegans and Centropages species composition in offshore and entrainment IJPicus dominated periods of low abundance in samples was not always the same. For example, late fall and early winter (Group 1). Pseudo. Mytilus edulis larvae were most abundant offshore calanus sp., Tortanus discaudatus and Larvacea during mid-June through late July (Figure 4-8), the (formerly referred to as Oilepleura sp.) were co-
- same period during which the number entrained dominant at this time. Late winter and early washighest(Table 4-8). Anomiasquamulalarvae, spring (Group 5) collections were dominated by however, were most abundant in entrainment Cirripedia. Calanusfinmarchicus and Larvacea samples in July and August, but were most abun- were also abundant in late winter and early dant offshore in June, spring. Late spring (Group 6) collections were dominated by C.finmarchicus, whose abundance was an order of magnitude greater than the co-4.3.3 Macrozooolankton dominants Evadne sp. and Eualus pusiolus.
4.3.3.1 Community Structure Summer (Group 7) collections were dominated by C. typicus, C.finmarchicus, and Cancer sp.; E. pusiolus and T. longicornis were also abundant in Preoperational analysis (1978-1984 and 1986-1989) of the macrozooplankton assemblage at the summer. Most meroplanktonic species, though nearfield Station P2 showed seasonal changes that n t dominant, reached their peak abundances during summer months. C. typicus, Centropages were greatly influenced by the population dynam-hamatus, and Centropages sp. copepodites were ics of the dommant copepods Centropages typicus dommant in fall (Group 8). 'Ihe seasonal shift in and Calanusfinmarchicus (NAI 1990b). Other dominance among Cirripedia, C. finmarchicus taxa, particularly meroplanktonic species, exerted and C. typicus observed m 1987 through 1995 short-term influences, especially during the spring and summer (NAl 1985). Because of their was consistent with patterns observed historically lower abundances, seasonal patterns of (NAI 1990b). In addition to the major groups, three groups occurred sporadically. A few of the tychoplanktonic species (e.g., mysids, amphipods winter months (Group 2) in 1993 and 1994 were and cumaceans) were not well documented by dominated by T. longicornis, Sagitta elegans and numerical classification of the entire macrozoo-T. discaudatus. T. longicornis and S. elegans plankton assemblage. To identify seasonal pat-dominated February collections in 1990 (Group terns more clearly, the tychoplankton assemblage 3). C.finmarchicus with Cirripedia dominated n was analyzed separately from the mero- and March and April samples in 1989 (Group 4). () holoplankton. 4-30
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I 1986 -- - - P, _ _ _ _ _ _ _ _ _- . l, - JANj FEBl MAR l APRlMAYl JUN JULl AUGl SEPlOCT NOvl DEC MONTH . Figure 4-10. Dendrogram and seasonal groups formed by numerical classification of mean monthly log,o(x+1) transformed abundances (no/1000 m') of holo- and meroplanktonic species of macrozooplankton at intake Station P2, discharge Station P5 and farfield Station P7, 1986-1995. Seabrook Operational Report,1995. 4-31
O O O Table 4-9. Geometric Mean Abundance (NoJ1000m') and 95% Confidence Limits of Dominant 11010- and Meroplanktonic Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections (Monthly Means) at Intake Station P2, Discharge Station PS and Farfield Station P7,1986-1995. Seabrook Operaponal Report,1995. GROUP' DOMINANT SPECIES
- PREOPERATIONAL YEARS' OPERATIONAL YEARS' N LCL MEAN UCL N LCL' MEAN UCL 1 Temora longicornis 36 1932 2884 4304 42 728 1145 1800 Late Fall /Early Winter Sagitta elegans 873 1322 2003 ~739 994 1337 (0.64/0.63) Centropages typicus 565 1206 2573 1058 1800 3060 Pseudocalanus sp. 401 701 1222 166 287 496 Torranus discaudatus 216 495 1131 402 702 1223 Larvacca 73 164 367 174 331 632 2 Temora longicornis -- not represented - 9 693 2391 8245 Winter Sagitta elegans 1645 2331 3303 (0.70/0.63) Torranus discaudatus 1030 2035 4018 3 Temora longicornis 3 3226 28662 254624 - not represented -
P February 1990 Sagitta elegans 6896 20601 61540 M (0.80/0.60) 4 Calanusfinmarchicus 6 4390 7900 14217 - not represented - Spring 1989 Cirripedia 893 3550 14100 (0.68/0.59) 5 Cirripedia 12 20260 51170 129237 24 49997 114469 262075 Late Winter / Ear Spring Calanusfinmarchicus 4761 16060 54165 3273 9247 26127 (0.68/0.5 Larvacca 1906 4562 10913 7249 11818 19267 6 Calanusfinmarchicus 30 42197 57527 78424 30 73954 113173 173191 Late Spring Eualus pusiolus 3386 4844 6932 1786 2650 3932 (0.70/0.62) Evadne sp. 2358 4491 8552 9819 15317 23894 7 Centropages typicus 39 17875 37103 77012 51 43935 70788 114052 Sununer Calanusfinmarchicus 20821 36214 62988 11233 22572 45356 (0.67/0.62) Cancer sp. 14019 24401 42471 26280 37556 54531 Eualuspusiolus 3421 6602 12741 3703 6195 10364 Temoralongicornis 1210 2695 5997 8652 13148 19981 8 Cratropages typicus 21 29419 52173 92524 39 35749 62230 108324 Fall Centropages hamatus 2307 4594 9147 122 281 64I (0.68/0.58) Centropages sp. copepodite 2409 4337 7810 814 1603 3158
*(within-group similarity /between group similarity) 6t hose taxa contributing 25% of total group abundance in either preoperational or operational periods *preoperational period = January 1986-July 1990; operational period = August 1990-December 1995
i 4.0 ZOOPLANKTON The seasonal succession of groups formed by The Tychoolankton Assemblace numerical classification of holo- and mero-plankton during the operational period differed Seasonal variation in the tychoplankton species from the preoperational period by the absence of composition was influenced mostly by variations Groups 3 and 4 and the appearance of Group 2, in abundance of the nearly omnipresent dominant all of which were infrequently occurring groups. taxa Neomysis americana, Oedicerotidae and Each resulted from large reductions of some of Pontogencia inennis and by the presence of the the dommant taxa typical for the season (Table 4- seasonal dominant Mysis mixta (Figure 4-11; 9). April collections were more consistent during Table 4-10). Two seasonal groups (Groups I the operational period, represented solely by and 2) encompassed 83% of the collections of the Group 5, in contrast to the preoperational period, tychoplankton (%% of P2 and PS collections). A where April collections were variable (Figure 4- community dominated by high abundances of N. 10). 'Ihe most abundant taxa in their seasons, americana occurred in every year from June Cirripedia, Calanus finmarchicus and through February (Group 1). Group 1 included Centropages typicus, each increased in the opera- every collection at the intake station (P2) except tional period (Table 4-9) and each group experi- for September 1995, most discharge station (P5) enced some change in rank order of the co-domi- collections and almost half of the farfield station nant taxa. Significant differences in community (P7) collections. The amphipods Pontogencia composition between operational and preopera- inermis and oedicerotids were also abundant in tional periods were also detected by MANOVA Group 1 as were harpacticoids and the cuncan (Wilks'l.ambda = 0.17, F = 39.09, p=0.0001). Diastylis sp. M. mixta replaced N. americana as tt: overwhelming dominant in late wimer and Previous analyses have suggested that there are early spring (Group 2). N. americana, P. inermis no spatial differences in holo- and meroplanktonic and Diastylis sp. occurred in moderate st>un-assemblages in the study area'(NAI 1991b). dances at this time. Periods of moderate abun-Numerical classification of holo- and dances of N. americana and reduced abundances meroplanktonic abundances from 1986-1995 of amphipods were common at station P5 and P7, revealed no spatial differences in community especially in the fall and winter (Group 4), composition among Stations P2, P5 and P7 Frequently occurring episodes of low (Figure 4-10). Collections from all stations were tychoplankton abundance resulted in the forma-grouped together within each month. Although tion of seven small groups. 'Ihese episodes were , species composition was similar among stations rare at the nearfield stations (P2 and PS), ac- I when analyzed by numerical classification, differ- counting for only 1% of the collections (Groups ences in abundances among stations were detected 3 and 5). Episodes oflow abundance occurred in by MANOVA (Wilks' Lunbda = 0.54, F = 23% of Station P7 collections and resulted in the 2.94, p=0.0001). Differences in community formadon of five groups (Groups 6,7,8, 9 and composition among stations were consistent 10) composed entirely of Station P7 samples. between the preoperational and operational I periods (MANOVA testing Preop-Op X Station: Spatial differences were clearly indicated by Wilks' I2mbda = 0.82, F = 0.85, p=0.85). numerical classification. i : species composition 4-33
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Table 4-10. Geometric Mean Abundance (No./1000m') and 95% Confidence Limits of Dominant Tychoplanktonic Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections (Monthly Means) at Station P2, Discharge Station P5 and Farfield Station P7,1986-1995. Seabrook Operational Report,1995. GROUP' DOMINANT SPECIES
- PREOPERATIONAL YEARS' . OPERATIONAL YEARS' N LCL MEAN UCL N LCL MEAN~ UCL 1 Neomysis americana 80 140 250 445 116 115 153 204 Summer / Fall / Winter Oedicerotidae 44 67 104 36 50 70 (0.53/0.51) Pontogenciainermis 35 49 68 31 42 57 Diastylis sp. 21 30 43 24 32 42 Harpacticoida 8 11 16 26 35 48 2 Mysis mixta 39 84 226 605 50 144 274 522 Late Winter / Spring Neomysis americana 22 42 82 17 29 49 p (0.55/0.51) Pontogencia inermis 15 23 35 21 33 54 g Diastylis sp. 7 I3 23 13 21 33 3 Neomysis americana 2 0 28 69942 - not represented -
PS/P7 June 1987 Ischyrocerus anguipes 0 27 11001 (0.74/0.46) Corophium sp. I 9 45 Pontogencia inermis 0 6 67988 4 Neomysis americana 16 20 46 104 12 19 45 107 PS/P7 Fall / Winter Oedicerotidae 4 9 20 2 5 8 (0.52/0.46) 5 Neomysis americana 2 0 4 23 10 2 5 12 Summer / Fall Pontogencia inermis 0 3 1742 1 2 5 (0.48/0.44 Harpacticoida 0 2 1666 2 9 34 Calliopius laeviuseulus 0 1 271 0 l 2 Ischyrocerus anguipes - - - 0 1 2 ( d)
O O O Table 4-10. (Continued)
. GROUP'l - DOMINANT SPECIES". PREOPERATIONAL YEARS' OPERATIONAL YEARS'
.N LCL MEAN: lUCL- N -- - LCL : l MEAN UCL 6 Pontagencia inermis 1 -
6 - 1 - 3 - P7 February, April Harpacticoida - 5 - - 1 - (0.51/0.440 Diastylis sp. - 2 - - 2 - Ischyrocerus anguipes - 2 - - - - Mysis mixta - 1 - - 3 - Pseudoleptocuma minor - - - - 9 -
' Neomysis americana - - - -
3 - 7 Oediwviidae 4 0 8 73 2 0 23 10 x 10' P7 Summer Harpacticoida 2 7 18 0 6 1961 (0.51/0.40) Pontogenciainermis 0 2 13 0 1 620 i p 8 Neomysis americana 2 0 22 2.0 x 10' 1 - 19 - g P7 Miscellaneous Jassa marmorata 0 0.1 6 - 2 - (0.54/0.30) Gammarus lawrencianus 0 l 4 - 2 - 9 Diastylis sp. -not represented - 2 0 2 110 P7 Dec 1990-1an 1991 Erythrops erytkropththalma 1 2 4 (0.61/0.30) Oedicerotidae 1 1 1 Neomysis americana o I l4 Leuconidae 0 0.4 6 1n Calliopiuslaeviusculus 1 - 1 - 1 - 0.5 - P7 June Mancocuma stellifera - 0.4 - - - - (0.35/0.06) Harpacticoida - - - - 0.5 - Neomysis americana - - - - 0.4 -
*(within-group similarity /between group similarity) 'those taxa contributing 25% of total group abundance in either preoperational or operational periods *preoperational period = January 1986-July 1990; operational period = August 1990-December 1995
l 1 4.0 ZOOPLANKTON j at the farfield site (P7) differed from either of the 4.3.3.2 Selected Soecies nearfield stations (P2 and PS) on 39% of the collection dates (Figure 4-11). Five of the groups Calanus finmarchicus formed by numerical classification were unique to Station P7 and a sixth group (Group 5) was Average monthly Calanus finmarchicus composed mostly of farfield collections. Differ- copepodite abundances at Station P2 exhibited a ences between the two nearfield stations were less broad spring through summer peak apparent. The intake site (P2) was grouped preoperationally (Figure 4-12). Operational separately from the discharge station (P5) on 10% abundances followed a similar pattern, although of the collection dates. Significant spatial differ- abundances were slightly lower in March and ences in community composition were also de- slightly higher in May. Abundances in 1995 tected by MANOVA (Wilks' Lambda = 0.35, F showed a similar monthly pattern as previous
= 14.21, p=0.0001). years.
Despite similar densities of the dominant taxa and At all stations, the annual geometric mean abun-a consistent seasonal pattern of the three major dances were higher in 1995 than in the opera-groups (1, 2 and 4), differences between the tional and preoperational (all years) periods operational and preoperational periods in the (Table 4-11). Abundances in the operational appearance of some of the minor groups were period were significantly higher than in the recent indicated by numerical classification. He opera- (1987-1989) preoperational period (Table 4-12). tional period differed by the absence of Group 3, The nearfield stations (P2 and PS) had signifi-and the appearance of Group 9; each group cantly greater abundances than the farfield station occurred only once. During the operational (P7). Increases in abundance from the recent period, Group 2 collections extended into June at preoperational period (1987-1989) to the opera-the nearfield stations, later than was typically tional period were consistent among stations, observed during the preoperational period. Both indicated by a non-significant interaction term nearfield stations experienced low abundances in (Preop-Op X Station). September 1995 (Figure 4-11). Significant differences between the operational and he monthly mean abundance of Calanusfinmar-preoperational periods were detected by chicus adults (copepodite 6) during all MANOVA (Wilks' Lambda = 0.73, F = 7.67, preoperational years showed a peak period occur-p=0.0001). Changes from the preoperational to ring in winter and a larger peak occurring June operational periods were consistent among sta- through September (Figure 4-12). During the tions, indicated by a non-significant interaction operational period, a small peak occurred in term (MANOVA testing Preop X Station: Wilks' January and larger peaks occurred in April and lambda = 0.88, F = 1.36, p=0.07). August. The change in the annual cycle was consistent at both Stations P2 and P7 (Figure 4-13). Abundances in 1995 followed operational trends except for August, when adult Calanus l finmarchicus were present in low abundances. l 4-37
l Celanusfinmarchicus
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NCN DEC Figure 4-12. Logdx+1) abundance (nol1000 m') of Calanusfnmarchicus copepodites and adults and p Carcinus maenas larvae; mor thly means and 95% confidence intervals over all preoperational y years (1978-1984; 1986-1989) and monthly means for the operational period (1991-1995) and 1995 at intake Station P2. Seabrook Operational Report,1995. 4-38
Table 4-11. Geometric Mean Abundance (No./1000 m') and Cocificient of Variation of Selected Macrozooplankton Species at Stations P2, P5, and P7 During Preoperational and Operational Years (1991-1995), and 1995. Seabrook Operational Report,1995. PREOPERATIONAL OPERATIONAL 1995 SPECIES /LIFESTAGE STATION MEAN* CV- MEAN' CV MEAN (peak period) Calanusfinmarchicus P2 4153 6.39 4044 3.08 4294 copepodites P5 5713 6.99 5446 3.14 6911 (January-December) P7 2594 7.19 2518 4.43 2974 Calanusfinmarchicus P2 36 26.52 17 18.84 9 x adults PS 26 28.88 23 19.03 15 I (January-December) P7 29 28.96 9 26.42 4 Carcinus maenas P2 3509 6.73 4775 13.62 7565 larvac P5 3615 12.92 5981 11.79 11632 (June-September) P7 4251 6.24 3773 11.34 8095 Crangon septemspinosa P2 257 3.66 237 7.67 303 zceae and postlarvae PS 233 6.72 204 10.36 248 (January-December) P7 161 10.42 109 12.13 231 Neomysis americana P2 151 18.94 183 7.45 200 alllifestages P5 45 30.73 61 13.11 100 (January-December) P7 43 22.03 22 16.59 22
' Years sampled:
Prcoperational: P2 = 1978-1984,1987-1989 P5 = 1987-1989 P7 = 1982-1984,1987-1989 Mean of annual means 6Mean of annual means, 1991-1995 O O O
O O O Table 4-12. Results of Analysis of Variance Comparing Log 3, (X+1) Transformed Abundances of Selected Macrozooplankton Species from Stations P2, P5, and P7 During Preoperational (1987-1989) and Operational (1991-1995) Periods. Seabrook Operational Report,1995. SPECIES * - SOURCE"~ " d.f. MS ' 1F' MULTIPLE COMPARISONS' Calanusfinmarchicus P 1 3.18 5.51
- Op> Preop copepodites -Op)* 6 1.31 2.26 *
(January-December) Mon )* 88 10.88 18.82 *** Station [ 2 3.30 5.70 *
- P2 P5 > P7 Preop-Op X Station
- 2 0.23 0.40 NS Error 470 0.58 Calanusjinmarchicus P 1 0.15 0.18 NS adults Y reop-O 6 5.40 6.33 "*
(January-Dwnber) Station Mon (Year) p) 88 6.01 7.05 "* 2 3.91 4.59
- PS P2 P7 Preop-Op X Station 2 0.43 0.50 NS Error 470 0.85 Carcinus maenas P p 1 0.07 0.11 NS larvae Yea reop-O 6 3.19 4.95 "*
(June-September) Mon Station (Year) p) 24 2.78 4.31 " * .* 2 0.33 0.51 NS k Preop-Op X Station 2 0.16 0.25 NS Error 156 0.65 Crangon septemspinosa P p i 0.12 0.40 NS zoeae and st larvac reop-O 6 2.22 7.05 *" (January- . ber) Mon Station (Year) p) 88 8.53 27.06 "
- 2 5.25 16.67 "
- P2 P5 > P7 Preop-Op X Station 2 0.12 0.39 NS Error 470 0.32 Neomysis americana P I 0.14 0.25 NS alllifestages Y reop-O 6 6.6I i1.70 ' "
(January-December) Station Mon (Year) p) 88 2.53 4.47 "* 2 37.49 66.35 * " P2 > P5 > P7 Preop-Op X Station 2 0.06 0.11 NS Error 470 0.57
' Based on twice monthly sampling periods. 6 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 (1991-1995) periods, regardless of station; 1987-1989 reficcts the period of time that all three stations were sampled coincidentally. ' Year nested within preoperational and operational periods, regardless of station. ' Month nested within year, regardless of station. ' Station P2 vs. station PS vs. station P7, regardless ofyear.
- Interaction between main effects.
NS = Not siptificant (p >0.05)
* = Si ificant(0.05 2 p >0.0l)
" = H significant (0.012 p >0.001)
"* = V ighly significant (0.0012 p)
' Ranked in decreasing order. Underlines indicate no significant difTerence in least-squares means (a s .05).
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,l 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NCN DEC MONTH Operational Period 3.0 m P2
. . . p7 2.5 2.0 g .
~ ~ * ' ..
'g
/x 1.5- ,
\
\ \
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JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NCN DEC < uonts Figure 4-13. Preoperational and operational monthly mean logdx + 1) abundance (no./ 1000 m') of adult Calanus finmarchicus at the intake station, P2, and the control site, P7. Seabrook Operational Report,1995. 4-41
l I 4.0 ZOOPLANKTON l O The abundance of adult Calanusjinmarchicus in Cranron seotemsninosa 1995 was lower than during the preoperational (all years) and operational periods (Table 4-11). Peak mean abundance of the zoea and post-larvae i Differences between the recent preoperational of the sand shrimp Crangon septemspinosa oc- l (1987-1989) and operational periods were not curred from June through September during all significant (Table 4-12). Significant spatial preoperational years (Figure 4-14). Abundances differences occurred; abundances at the discharge steadily decreased to a low in February. station (PS) were significantly higher than those Operational mean abundances were similar to the i at the control site (P7). The interaction term preoperational period, although September abun- l (Preop-Op X Station) was not significant indicat- dances were lower. Abundances in 1995 were ing that differences between stations P5 and P7 considerably higher than previous years from were consistent between periods. February to April, and lower from September to December. Carcinus maenas Annual . geometric means of Crangon Green crab (Carcinus maenas) larvae (zoea and septemspinosa larvae in 1995 were higher than megalopa) first appeared in May during the during the preoperational (all years) and opera-preoperational years, with peak abundances tional periods (Table 4-11). 'Ihere were no occurring from June through September, then significant differences between the recent l steadily declining until the larvae disappeared preoperational (1987-1989) and operational from collections in February (Figure 4-12). periods (Table 4-12). Average abundances at the Operational monthly mean abundances of green nearfield stations were significantly higher than at crab larvae were almost identical to pre- the farfield station. Differences in abundance ) operational abundances. The seasonal pattern in among stations were consistent between opera-1995 was similar to previous years, although tional status periods (Table 4-12) indicating a abundances were generally higher from May broadscale trend not due to the operation of through August. Seabrook Station. Peak period mean abundances in 1995 were Neomysis amerimna considerably higher than in the preoperational l and operational periods (Table 4-11). Differences Monthly geometric mean abundances of Neomysts in abundance among stations and between the americana (all lifestages combined) during the preoperational and operational periods were not preoperational period were lowest in May and significant when tested by ANOVA (Table 4-12). June. Abundances generally increased through The interaction term (Preop-Op X Station) was the summer to a broad peak lasting through fall not significant, indicating no effect on the larvae and winter (Figure 4-14). Abundances in the of Corcmus maenas due to operation of Seabrook operational period generally followed a similar Station. pattern, although abundances were reduced in March. Abundances in 1995 followed the opera-n tional pattern. (v) 4-42
Crangon septemspinos2 e_ ,,,,o,.
- 7 ,,2lll r'
g* . ? . . . .'
~' '
r e 1
- g. ,,-
N
=' -= =%. ._
l
,:~..
,e / ., '
\.
'y '-
M'[/ ,/
'N. ,
i rum uan AP, MAY JUN JUL. M SEP OCT NCN Ot!C Neomysis americana
= "aag::
n-
/ 6 - pw M ['N'
N
/ J.
Z. ~ f [ N' O u _ _ _ _ _ _ e _ Neomysis americana W1 l-OP "8iaal so $ - 2 20 10 M P'EB h4AR APR h4AY JUN JUL. AUG SEP OCY1" NCM DEC C Juverine E em Female. sestf 4 a come.e. s "*%" "*.' Figure 4-14. Logw(x+1) abundance (no11000 m') of Crangon septemspinosa (zoca and post larvae) i and Neomysis americana (all lifestages); monthly means and 95% confidence intervals j over all preoperational years (1978-1984; 1986-1989) and monthly means for the operational period (1991-1995) and 1995; and mean percent composition ofNeomnis americana lifestages over all preoperational years (1978 1984; 1986-1989) and for the operational period (1991-1995) at intake Station P2. Seabrook Operational Report,1995. 4-43 I l
4.0 ZOOPLANKTON The average annual abundance in 1995 was dances in 1993 and 1904. Late September higher than in previous years at the nearfield through early November was a period of consid-stations (Table 4-11). There were no significant etable volatility in the microzooplankton commu-differences in abundances between the recent nity in both operational and preoperational peri-preoperat%nal (1987-1969) and operational ods and corresponds with the breakdown of the periods (Table 4-12). Significant station differ- summer thermocline. In 1991 and 1992, commu-ences occurred; abundances at the intake station nities differed from the typical fall community (P2) were greater than the discharge station (P5). (Group 5) primarily in reduced abundances of the Abundances at the farfield station (P7) were dominant taxa and by reduced abundances of { significantly less than the nearfield stations. He members of the genus Centropages, especially in interaction term (Preop-Op X Station) was not the surface waters (NAI 1992b, NAI 1993b). significant indicating no effect from operation of These effects were sporadic in both operational the Seabrook Station on the abundance of and preoperational periods indicating natural ! Neomysis americana (Table 4-12). processes and not effects from plant operation. ) The long term trend of reduced occurrence of the he relative abundance of the individual lifestages spring and summer community (Group 4) in early (Figure 4-14) at Station P2 suggested that summet appears to have begun in the latter part Neomysis americana produces two generations of the preoperational period and should not be per year, similar to the life cycle described by attributed to plant operation. Mauchline (1980) and observed by Wigley and
-( Burns (1971) on Georges Bank. Although small The microzooplankton community at the intake differences in the relative abundance of the non- station (P2) has never been shown to be signifi-adult stages were apparent in March, the same life cantly different from the other stations, including cycle appeared in both preoperational and opera- the control station (P7) when tested by tional periods indicating that Seabrook Station has MANOVA, indicating no effect from operational not affected the life cycle of Neomysis americana. of Seabrook Station on the microzooplankton community (Table 4-13).
4.4 DISCUSSION Bivalve Larvae 4.4.1 Community Varying aburidances of Hiatella sp., Mytilus Microzoonlankton edulis and Anomia squamula defined most sea-sonal groups identified by the community analy-Since Seabrook Station began commercial opera- sis. The species composition during the opera-tion, community composition has continued to tional period was generally similar to previous resemble the historical patterns; however, results years according to numerical classification tech-of numerical classification indicate a few differ- niques (Table 4-13). One exception was the ences during the operational period. Communi- occurrence of higher-than-average densities of ties atypical of the preoperational period occurred Hiatella sp., which occurred at both nearfield and in wmter and in late summer or early fall. Colder farfield stations in 1994 and at the farfield station (7) than normal winter temperatures at this time may in 1995. Community stmeture in the operational have reduced copepod reproduction and abun- period, according to MANOVA results, was sig-4-44
4.0 ZOOPLANKTON Table 4-13. Summary of Potential Effects (Based on Numerical Classification and Manova Results) of Operation of Seabrook Station Intake on the Indige-h nous Zooplankton Communities. Seabrook Operational Report,1995. DIFFERENCES BETWEEN OPERATIONAL OPERATIONAL AND PERIOD SIMILARTO ' PREOPERATIONAL COMMUNITY ATTRIBUTE' PREOPERATIONAL PERIODS CONSISTENT PERIOD? - AMONG STATIONS? MICROZOOPLANKTON Community Structure yes' yes Abundances no, variable among taxa6 yes BIVALVE LARVAE Community structure yes, with one exception
- yes Abundances Op> Preop
- yes Solenidae no P2, P7: Op= Preop P5: Op< Preop Hiatella sp. no P2 Op> Preop P5, P7 Op= Preop MACROZOOPLANKTON Holo /meroplankton Seasonal occurrence yes yes Abundances Op> Preop yes 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 i
I O l ! 4-45 i
4.0 ZOOPLANKTON IO nificantly different when compared to the recent Although Seabrook Station operated its circulating preoperational period (1988-89). Despite similar water system at varying levels since 1985, no
- hydrographic conditions, differences were not power or heated discharge were produced tmtil consistent among stations. Two taxa were respon- August of 1990. Entrainment collections provide sible for the observed differences. Solenidae a measure of the actual number of organisms density decreased significantly during the opera- directly affected by plant entrainment. Three taxa, tional period at Station P5, but remained un- Mytilus edulis (blue mussel), Anomia squamula and changed at Stations P2 and P7. Densities of Hiatella sp., accounted for more than 85% of the Hiatella sp. increased at all three stations, but the bivalve larvae entrained each year (Figure 4-9).
increases were significant only at Station P2. These Monthly entrainment of all taxa was less in 1991 differences are not suspected to be a result of and 1992 in comparison to 1990 and 1993 and was entrainment, because densities increased at the highest in 1995 (Figure 4-9). Offshore densities of intake station. Furthermore, other taxa abundant M. edulis were extremely high in 1995, contribut-during the same time period (e.g., Mya truncata, ing to the relatively high entrainment levels. Mytilus edulis) did not show a similar pattern. Reduced abundances in 1991 and 1992 contributed ! Since there was no change at the intake station, nor to lower entrainment levels. Although total en- i its farfield counterpart, these changes were not trainment has increased over time, there has been I related to the operation of Seabrook Station. no apparent effect on the offshcre bivalve larvae community as indicated by the relatively stable I
,3 Entrainment community compo'ition s and general increase in densities (Table 4-5) between the preoperational The focus of monitoring plankton in the intake area and operational periods.
was to evaluate the effect of entrainment of organ-isms by the circulatmg water system on community Approximately 41 x 10' soft-shell clam larvae were structure and population levels in the nearfield predicted to be entrained at one unit of Seabrook area. Due to the lumted control of their horizontal Station in one year (NAI 1977). This estimate was l movements and often broad vertical distribution in based on a 113 day season of larval abundance, a the water column, most types of planktonic organ- pumping rate of 2.33 x 106 nl/ day (one unit isms could be exposed to entrainment. Estimates operating at 100% capacity) and an estimated of total monthly levels of entrainment were com- 3 density of 158 larvae /m based on field sampling . puted (Figure 4-9; Table 4-8) to quantify losses of conducted in 1976. Actual entrainment totals, bivalve larvae. Conununity structure and abun- which ranged from 0.2 x 10' in 1992 to 22.5 x 10' dances of selected species in the nearfield area in 1993, were much lower than predicted due to during commercial operation were compared to reduced cooling water system pumping rates, and historical conditions and to farfield conditions, lower than predicted larval clam densities. The These comparisons addressed the question of actual average pumping rate of 1.97 x 106 m'/ day whether the balanced, indigenous planktonic during the April-throughOctober bivalve entrain-populations within the study area have been af- ment season was approximately 15% lower than fected by the plant intake during the commercial the predicted pumping rate due to outages (see Q Q ,i operation to date. Table 1-2). Similarly, actual densities oflarval 4-46
4.0 ZOOPLANKTON 1 1 l soft shell clams in entrainment samples ranged Maine (Sherman 1966). In the study area, cope-3 from 1.8/m in 1991 (NAl 1992a) to 32.3/m' in pods predominate. The dominant species in the I 1995, lower than predicted. study area, Calanus finmarchicus, Centropages l typicus, Pseudocalanus sp. and Temora longicornis l The decrease between predicted soft-shell clam were the dominant copepods in the Gulf of Maine ) densities and actual densities in entrainment sam- and nearby Scotian Shelf and Georges Bank, ples may be due to the location in the water col- occurrmg in a seasonal pattern similar to the study umn where the samples were collected. The 1976 area (Anderson 1990, Kane 1993, Sameoto and bivalve larvae samples were collected using Herman 1992., Tremblay and Roff 1983). The oblique tows that sampled the entire water column, seasonal occurrence of the other groups was also while entrainment samples were drawn from the shnilar to other observations in the Gulf of Maine center of the water column. Soft shell clam larvae (Sherman 1966). were more numerous in the upper portions of the water column (NAl 1974), which were sampled by Community composition of the holo- and the oblique tows. Natural variability may also meroplankton was generally similar throughout the have contributed to the difference. The predicted study period (Table 4-13). The species assemblage entrainment of soft-shell clam larvae (NAI 1977) from late spring through fall during the operational was a worst-case prediction based on one year period was consistent with the preoperational (1976) of relatively-high larval clam abundance. period. Community composition exhibited the greatest variation among years during the period The predicted entrainment of Afytilus edulis at one February through April in the recent unit of Seabrook Station operating at 100% capac- preoperational period and in February and March , ity was approximately 900 x 10' annually (NAI in the operational period. This period corresponds 1977). This level of entrainment was expected to to the lowest annual temperatures and the period of have negligible impacts on local population of M. greatest variability in salinity in the study area edulis due to its high reproductive capacity. Actual (Section 2.3.1). Large scale reductions of domi-entrainment of M. edulis ranged from 13,231 x 10' nant taxa, Centropages typicus in February (NAI in 1995 to 122 x 10' in 1992. The predicted 1991a,1994,1995b) and Cirripedia and Larvacea entrainment of M. edulis is within the range of in March and April (NAl 1990a) occurred sporadi-actual entrainment because the densities used in the cally. These reductions in abundance occurred estimate were similar to the actual entrained both operationally and preoperationally and oc-densities. Entrainment of M. edulis larvae at curred concurrently at the control site (P7) indicat-Seabrook Station appears to have had no effect on ing causative agents other than operation of Sea-local populations of M. edulis monitored through brook Station. Community composition showed no the marine macrobenthos program (Section 6.0). variation in April during the operational period, but this was also consistent between nearfield Holo- and Meroplanktonic Macrozooplankton stations (P2 and PS) and the control site (P7) indicating effects other than plant operation. The holo- and meroplanktonic component of the macrozooplankton conununity in the study area The abundance of holo- and meroplankton was was similar to the other portions of the Gulf of higher during the operational period than the recent 4-47 l
)
4.0 ZOOPLANKTON (1987-1989) preoperational years (Table 4-13). factors as light, lunar cycle, storm events, repro-Interannual variations of orders of magnitude are . duction and nonspecific aggregation (Mauchline l common among copepods on Georges Bank (Kane 1980). These factors can influence apparent ) 1993). Studies have shown both the timing and the abundance dramatically. magnitude of the spring copepod bloom may be related to water temperature. In the presence of Frequent occurrences of low abundance at the high phytoplankton abundance, cold water temper- farfield station resulted in the appearance of a large atures can delay the initiation of egg production number of dissimilar communities occurring either and reduce the quantity of eggs produced by sporadically or infrequently. The heterogeneous Calanusfinmarchicus (Plourde and Runge 1988). nature of the tychoplankton community at Station i Low temperatures can also reduce growth rates P7 indicated a weak seasonal pattern both opera- I and delay the development of larger copepodites tionally and preoperationally. The intermittent (Anderson 1990). Mean annual temperatures were nature of the groups formed by numerical classifi-higher in the operational period (Section 2.3.1). cation obscured any operational and preoperational differences that may have occurred at Station P7. MANOVA results indicated significant station The operational period was similar to the differences. Spatial variation may be related to preoperational period in the nearfield area, with food supply. The phytoplankton standing crop, as the exception of September 1995, a period of very measured by chlorophyll a, was significantly low abundance (Table 4-13). f greater at Station PS (Section 3.3.1). Abundances at Station P5 may also have been influenced by the Substrate differences between nearfield and I Hampton-Seabrook estuary's plume (NAl 1980). farfield sites may be responsible for differences in tychoplankton abundance between the sites. Abundances of holo- and meroplankton increased Tychoplankton species such as mysids (Wigley and since Seabrook Station began operation in 1990. Burns 1971; Pezzak and Corey 1979; Mauer and )
'Ihe magmtude of the increase was almost identical Wigley 1982), amphipods (Bousfield 1973) and at each station. Differences in the succession of cumaceans (Watling 1979) have substrate prefer-seasonal communities were limited to two episodes ences. A relatively homogeneous substrate of sand in winter and occurred concurrently at the exists at the farfield area, with only a few, distant nearfield and farfield stations, indicating that the rockledges. In contrast, the nearfield substrate is holo- and meroplankton community was influenced heterogeneous. Station P2 is sand and hard sand by the broadscale effects such as climate and not with nurr.erous nearby rock ledges. Station PS is by plant operation, sand and rock ledge with considerable amounts of algae. The heterogeneous nature of the nearfield Tychonianhante Macrazannla=han stations may have increased the abundance of various tychoplankton by supplying more diverse The tychoplanktonic community, composed of habitat. Many amphipods such as Pontogencia species that inhabit both the substrate and the water inermis are associated with submerged plants and column, exhibited greater spatial variability than algae. Higher concentrations of macroalgae in the (3 the holo- and meroplanktonic community. Excur- nearfield area may provide additional habitat for O sions into the plankton can be related to such some amphipods and increase their abundance.
4-48
4.0 ZOOPLANKTON Differences in tychoplankton abundance between lifestages of Oithona sp. and Pseudocalanus sp. the nearfield and farfield areas was most likely due was generally similar in the operational period, to differences in habitat and not to the operation of significant changes in abundance occurred. Both Seabrook Station. lifestages of Eurytemora sp. experienced large decreases in abundance operationally and the 4.4.2 Selected Species seasonal cycle changed dramatically, with stable or reduced abundance instead of a peak occurring Microzooplankton in summer. Nauplii and adults of Pseudocalanus sp. and Oithona sp. copepodites and adults also Differences in the operational period were detected had significant changes in abundance during the for all three microzooplankton selected species operational period. Similar changes in abundance (Table 4-14). Although the annual cycle of the occurred at each station in the operational period Table 4-14. Suinnlary of Potential Effects (Based on Anova Results) of Operation of Seabrook Station Intake on Abundances of Selected Indigenous Zooplankton Species. Seabrook Operational Report,1995. DIFFEIULNCES BETMTEN OPERATIONAL . OPERATIONAL AND PLANKTON . PERIOD SIMILAR TO PREOPERATIONAL PERIODS SELECTED SPECIES PREOPERATIONAL' CONSISTENT AMONG AND LIFESTAGES PERIOD? STATIONS? MICROZOOPLANKTON Eurytemora sp. copepodites Preop > Op yes E. herdmani adults Preop > Op yes Pseudocalanus/Calanus nauplii Preop >Op yes Pseudocalanus sp. copepodites yes yes adults Preop >Op yes Oithona sp. nauplii yes yes copepodites Preop <Op yes aduhs Preop <Op yes BIVALVE LARVAE Mytilus edulis larvae yes yes MACROZOOPLANKTON Calanusfinmarchicus copepodites Preop <Op yes adults yes yes Crangon septemspinosa larvae yes yes Carcinus maenas larvae yes yes Neomysis americana yes yes
'recent preoperational years: 1982-1984 for microzooplankton,1988-1989 for bivalve larvae and 19871989 for macrozooplankton.
4 49
i l 4.0 ZOOPLANKTON \ (3 for each species, indicating effects unrelated to Significant differences among stations were the operation of Seabrook Station. detected for Calanus fnmarchicus, Crangon septemspinosa and Neomysis americana, in all Bivalve Larvae cases, differences in abundances among stations were similar in both the preoperational and Umboned larvae of Mytilus edulis have been operational periods, indicating no effect from generally present in the water column during all operation of Seabrook Station on these three months sampled, but were most abundant from species. June through August. Their protracted presence was probably due to spawning patterns and the
4.5 REFERENCES
CITED duration of larvae life. In Long Island Sound, spawning occurred over a two-to-three month Anderson, J.T. 1990. Seasonal development of period and was asynchronous among local popu. invertebrate zooplankton on Flemish Cap. l lations (Fell and Balsamo 1985). Larval develop- Mar. Ecol. Progr. Ser. 67:127-1409. ment requires three to five weeks (Bayne 1976), Bayne, B.L. 1965. Growth and the delay of and metamorphosis can be delayed up to 40 days metamorphosis of the larvae of Mytilus edulis , until suitable settling conditions are encountered (L.) Ophelia 2:1-47. l (Bayne 1%5). He seasonal pattern of M. edulis larvae in the operational period was similar to . 1976. The biology of mussel larvae. Chap. 4 in Bayne, B.L., ed. Marm, e recent preoperational years. Average abundances Mussels: Their Ecology and Physiology. O O of M. edulis larvae were significantly higher IBP 10. Cambridge Univ. Press. pp. 81-120. dunng the operational period at all stations (Table 4-14). Boesch, D.F. 1977. Application of numerical classification in ecological investigations of water pollution. U.S. Environmental Protec-Macrozoonlankton tion Agency, Ecological Research Report Agency, Ecol. Res. Rep.,114 pp. Of the four selected species, differences between the recent preoperational and operational periods Bousfield, E.L. 1973. Shallow-water were detected only for Calanus finmarchicus Gammaridean Amphipoda of New England. Comstock Pub. Assoc. (Cornell University (Table 4-14). Abundances of the copepodite Press; Ithaca, NY and lendon 312 pp. stages in the recent preoperational period (1987-1989) were apparently lower than in the earlier Clifford, H.T., and W. Stephenson. 1975. An (1978-1984) preoperational period. Annual introduction to numerical classification, geometric means for all preoperational periods Academic Press, New York. 229 pp. were similar to operational years (Table 4-11). Davis, C.S. 1984. Interaction of a copepod The increase in abundance during the operational population with the mean circulation of period was similar among stations. He seasonal Georges Bank. J. Mar Res. 42:573-590. cycle of adult Colanusfinmarchicus from Febru-ary through July was generally delayed one Fell, P.E. and A.M. Balsamo. 1985. Recruit-ment of Mytilus edulis L. m the Thames month during the operational period at Stations Estuary, with evidence for differences in the () V P2 and P7. time of maximal settling along the Connecti-cut shore. Estuaries 8:68-75. 4-50
4.0 ZOOPLANKTON Harris, R.J. 1985. A primer of multivariate 1979. Seabrook Environmental l statistics. Orlando: Acad. Press. 575 p. Studies, July through December 1977. I Plankton. Tech. Rep. IX-1. i Jury, S.H., J.D. Field, S.L. Stone, D.M. Nelson, i and M.E. Monaco. 1994. Distribution and 1980. Annual summary report for i abundance of fishes and invertebrates in 1978 hydrographic studies off Hampton North Atlantic estuaries. ELMR Rep. No. Beach, New Hampshire. Preoperational
- 13. NOAA/NOS Strategic Env. Assessments ecological monitoring studies for Seabrook Div., Silver Spring, MD. 221. p. Station. Tech. Rep. X-2.
Kane, J. 1993. Variability of Zooplankton .1984a. Seabrook Environmental Biomass and Dominant Species Abundance on Studies.1983 data report. Tech. Rep. XV-Georges Bank, 1977-1986. Fishery Bull. I. 91:464-474. 1984b. Seabrook Environmental Katona, S.K. 1971 'Ibe developmental stages of Studies,1983. A characterization of baseline Eurytemora afinis Poppe,1880 (Copepoda, conditions in the Hampton-Seabrook Area, Calanoida) raised in laboratory cultures, 1975-1983. Tech. Rep. XV-II. including a comparison with the larvae of Eurytemora americana Williams,1906, and 1985. Seabrook Environmental Eurytemora herdmani Rompson and Scott, Studies,1984. A characterization of baseline 1897. Crustaceana 21:5-20. conditions in the Hampton-Seabrook Area, 1975-1984. Tech. Rep. XVI-II. Mauchline, J. 1980. The Biology of Mysids: Part I, in he Biology of Mysids and Euphau- .1990a. Seabrook Environmental siids. Adv. Mar. Biol. 18:3-372. Studies. 1989 Data Report. Tech. Rep. XXI-1. Maurer, D. and R.L. Wigley. 1982. Distribu-tion and ecology of mysids in Cape Cod Bay, .1990b. Seabrook Environmental MA. Biol. Bull. 163:477-491. Studies.1989. A characterization of base-line conditions in the Hampton-Seabrook Normandeau Associates Inc.1974. The impact area. 1975-1989. A preoperational study of entrainment by the Seabrook Station. for Seabrook Station. Tech. Rep. XXI-II. Prepared for Public Service Company of New Hampshire. .1991a. Seabrook Environmental Studies,1990 data report. Tech. Rep. XXII-
. 1977. Summary Document: As- 1.
sessment of Anticipated Impacts of Construc-tion and Operation of Seabrook Station on the .1991b. Seabrook Environmental Estuarine, Coastal and Offshore Waters Studies,1990. A charactenzation of environ-Hampton-Seabrook, New Hampshire. Pre- mental conditions in the Hampton-Seabrook pared for Public Service Company of New area during the operation of Seabrook Sta-Hampshire. tion. Tech. Rep. XXII-II.
. 1978. Seabrook Environmental .1992a. Seabrook Environmental Studies, 1976-1977. Monitoring of plankton Studies,1991. A characterization of environ-and related physical-chemical factors. Tech, mental conditions in the Hampton-Seabrook Rep. VIII-3. area during the operation of Seabrook Sta-tion. Tech. Rep. XXIII-I.
4-51
4.0 ZOOPLANKTON (m') .1992b. Seabrook Environmental Studies. 1991 Data. Unpub. Data Tab. Sameoto, D.D. and A.W. Herman. 1992. Effect of the outflow from the Gulf of St. Lawrence on Nova Scotia shelf zooplankton. Can. J.
. 1993a. Seabrook Environmental Fish. Aquat. Sci. 49:857-869.
Studies,1992. A charactenzation of environ-mental conditions in the Hampton-Seabrook Sherman, K. 1%6. Seasonal and areal distribu-area during the operation of Seabrook Sta- tion of Gulf of Maine coastal zooplankton, tion. Tech. Rep. XXIV-1. 1%3. ICNAF Special Publ. No. 6. pp. 611-623.
.1993b. Seabrook Environmental Studies. 1992 Data. Unpub. Data Tab. Sneath, P.H.A., and R.R. Sokal. 1973. Numeri-cal taxonomy. He principles and practice of
. 1994. Seabrook Environmental numerical classification. W.H. Freeman Co.,
Studies. 1993 Data. Unpub. Data Tab. San Francisco. 573 pp.
. 1995a. Seabrook Station 1994 Sokal, R.R. and F.J. Rohlf. 1981. Biometry.
Environmental Studies in the Hampton-Sea- W.H. Freeman and Co., San Francisco, CA. brook Area. A Characterization of Environ- 859 p. mental Conditions in the Hampton-Seabrook Area during the Operation of Seabrook Sta- Stewart-Oaten, A., W.M. Murdoch, and K.R. tion. Prepared for North Atlantic Energy Parker.1986. Environmental impact assess-Service Corporation. ment: "pseudoreplication in time?" Ecology, 67:929-940. 1995b. Seabrook Environmental (-I Studies. 1994 Data. Unpub. Data Tab. Tremblay, M.J. and J.C. Roff. 1983. Commu-nity gradients in the Scotian shelf zooplank-Normandeau Associates (NAI) and Northeast ton. Can. J. Fish. Aquatic. Sci. 40:598-Utilities Corporate and Environmental Affairs 611.36 (NUS). 1994. Seabrook Environmental Studies, 1993. A Characterization of Watling, L.1979. Marine flora and fauna of the Environmental Conditions in the Hampton- Northeastern United States. Crustacea: Seabrook Area during the Operation of Sea- Cumacea. NOAA Tech. Rep. NMFS Circu-brook Station. Prepared for North Atlantic lar 423. 23 p. Energy Service Corporation. Wigley, R.L. and B.R. Burns. 1971. Distribu-Pezzack, D.S. and S. Corey. 1979. ne life tion and biology of mysids (Crustacea, history and distribution of Neomysis ameri- Mysidacea) from the Atlantic Coast of the j cana (Smith) (Crustacea, Mysidacea) in United States in the NMFS Woods Hole Passamaquoddy Bay. Can. J. Zool. 57:785- collection. Fish. Bull. 69(4):717-746 793. I Plourde, S. and J.A. Runge. 1993. Reproduc-tion of the Planktonic Copepod Calanus finmarchicus in the Lower St. Lawrence Estuary: Relation to the Cycle of Phytoplankton Production and Evidence for a Calanus pump. Mar. Ecol. Progr. Ser. 102:217-227. w) l 4-52
4.0 ZOOPLANKTON Appendix Table 4-1. List of Zooplankton Taxa Cited in this Report. Seabrook Operational Report,1995. h Protozoa Foraminiferida Tintinnidae Hydrozoa Rotifera Mollusca Bivalvia Anomia squamula Linnaeus Hiatella Bosc 1801 Macoma balthica Linnaeus 1758 Modiolus modiolus Linnaeus 1758 Mya arenaria Linnaeus 1758 Mya truncata Linnaeus 1758 Mytilus edulis Linnaeus 1758 Placopecten magellanicus (Gmelin 1791) Solenidae Spisula solidissima (Dillwyn 1817) Teredo namlis Linnaeus 1758 Gastropoda Polychaeta j Hirundinea Arthropoda Branchiopoda Evadne 1.nv6n Copepoda Acania Dana 1846 Anomalocera opalus Penell 1976 Calanus Leach Calanusfinmarchicus (Gunnerus 1765) Caligus Mditer 1785 Candacia armata (Boeck 1872) Centropages hamatus (Lilljeborg 1853) Centropages Kroyer 1849 Centropages typicus Kreyer 1849 Euchaeta Philippi 1843 Eurytemora herdmani Thompson and Scott 1897 Eurytemora Giesbrecht 1881 Harpacticoida Microsetella norvegica (Boeck) 4 53
4.0 ZOOPLANKTON APPENDIX TABLE 4-1. (Continued) Monstrillidae Oithona Baird 1843 Oithona similis Claus 1866 Pseudocalanus Boeck 1872 Rhincalanus nasutus Giesbrecht 1892 Temora longicornis (MGller 1785) Tonanus discaudatus (nompson and Scott 1897) Cirripedia Malacostraca Mysidacea Erythrops erythrophthalma (G6es 1864) Mysis mixta (Lilljeborg 1852) Mysis stenolepis S.I. Smith Neomysis americana (S.I. Smith 1873) Cumacea Diastylis Say Ixuconidae Mancocuma stellifera Zimmer 1943 Pseudoleptocuma minor (Calman 1912) [ Amphipoda Calliopius laeviusculus (Kreyer) 1838 Corophium Milne-Edwards Gammarcus lawrencianus Bousfield 1956 Hyperiidae Ischyrocerus anguipes Kreyer 1838 Jassa marmorata Holmes 1903 Oedicerotidae Pontogencia inermis (Kreyer 1842) Decapoda Cancer Linnaeus Carcinus maenas (Linnaeus 1758) Crangon septemspinosa Say 1818 Eualuspuslotus (Kreyer 1841) Eualus Railwitz 1892 lebbeus White 1847 j Hippolytidae Spirontocaris Bate 1888 j l Chaetognatha Sagitta elegans Verrill 1873 Chordata 12rvacea (previous to 1994, identified as Oikopleura Mertens) O 4-54 i
5.0 FISH m (G) TABLE OF CONTFNfS PAGE i
SUMMARY
. . . . . . . .... . . .... . . .... . . .. .. .. .. . . . . iii LIST OF FIGURES . . . . ........ ......... . ..... .. . .... .......... iv LIST OF TABLES . .............. . .. . .. ................ .. . . . . . . vii LIST OF APPENDIX TABLES . . . . ... .. . ................ ... . . . . . . ix 5.0 FISH 4
5.1 INTRODUCTION
. . . ....... ... .. ...... . ... . .. . 5-1 5.2 METHODS . . . . . . . . . .. ... ....... .. . . ........ 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
/'~T 5
d 5.2.2 Adult Fish . . . . . . . 5.2.2.1 Pelagic Fishes . . .
. 5-4 5-4 1
5.2.2.2 Demersal Fishes . . . . . ...................... ..... . 5-4 5.2.2.3 Estuarine Fishes . . . . . . . . . . ............. . . . . . 5-4 5.2.2.4 Impingement ... . ........ ..... . ............... 5-6 5.2.3 Analytical Methods . . . . . . . .... ....... ... .... .. . ... 5-6 5.3 RESULTS AND DISCUSSION . . . . . . . . . ........ ........... .. 5-8 5.3.1 Ichthyoplankton Assemblages . . . . . ........................ . 5-8 5.3.1.1 Offshore Samples . . . . ...... ................ .... 5-8 5.3.1.2 Entrainment ........ ... .. . . .......... ...... 5-15 5.3.2 Adult Fish Assemblages . . . .... .. . . . ... .. . . . . 5-21 5.3.2.1 Pelagic Fishes . . . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . . . 5-21 5.3.2.2 Demersal Fishes . . ...... . ...... ...... . ...... . 5-25 5.3.2.3 Estuarine Fishes . . . . . . . . . ........ ... ... ... .. . 5-26 5.3.2.4 Impingement .......... ... ........... .. ..... .. 5-30 (~ s 5-i
S.0 FISH PAGE 5.3.3 Selected Species . . . ... .... .. . . . .. . . 5-36 5.3.3.1 Atlantic Herring . . .. . . .. . .. . . . ... .. . 5-36 5.3.3.2 Rainbow Smelt ... ... .... .. . .... . 5-41 5.3.3.3 Atlantic Cod . . . . .... ............. .. ..... . . . 5-45 5.3.3.4 Pollock ....... . ... ..... . . .. . . ..... . 5-50 5.3.3.5 Hakes . . . . . . . . .. . . ........ . 5-51 5.3.3.6 Atlantic Silverside . .. ... ..... ... .. . 5-55 5.3.3.7 Cunner . .... ....... ........... . . .... . 5-58 5.3.3.8 American Sand Lance . . ........ . . . . .. .. . 5-65 5.3.3.9 Atlantic Mackerel . . .. ..... .. ...... .. . 5-65 5.3.3.10 Winter Flounder . . . . ... . ... . .. ....... . 5-69 5.3.3.11 Yellowtail Flounder . . . . . ... .. . . . 5-76 5.4 EFFECTS OF SEABROOK STATION OPERATION . .. . ............. 5-80
5.5 REFERENCES
CITED . . . . .... . . .. .. .. ..... .. . .. 5-86 i i 1 l l O 5-ii
S.O FISH [3
SUMMARY
C/ Fish of the Hampton-Seabrook area have been sampled rince 1975 to assess potential impacts associated with , the construction and operation of Seabrook Station on lod fish assemblages. Effects include the entrainment of fish eggs and larvae and the impingement ofjuvenile and adult fish at the station intake; entrainment of fish i eggs and larvae into and the avoidance by large fish of the offshore discharge thermal plume; and, through 1994, effects related to the discharge of the plant settling basin into the Browns River within the Hampton-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 significantly I different for rainbow smelt and yellowtail flounder in the trawl, and winter flounder in the trawl and seme, l but the trends in CPUE differed among stations between the preoperational and operational periods. However, I these differing trends appeared to start in the preoperational period for yellowuil flounder and winter flounder, and are probably not due to the operation of Seabrook Station. It is unlikely that the operation of Seabrook Station affected rainbow smelt CPUE because they are primarily estuarine and nearshore fish and are not exposed to significant impingement or entrainment. hnpingement in 1995 was an estimated 15,932 fish, lobsters and seals. In comparison to other New England power plants with marine intakes, Seabrook Station entrains relatively few fish eggs and larvae and impinges fewerjuvenile and adult fish. Because the settling basin no longer is discharged into the Browns River, this j 'Q effluent has been eliminated 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 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 Hampton-Seabrook area. O 5-iii
5.0 FISH LIST OF FIGURES PAGE 5-1. Ichthyoplankton and adult fish sampling stations . ..... ...... ....... ... 5-2 5-2. Dendrogram and temporal / spatial occurrence pattern of fish egg assemblages formed by numerical classification of ichthyoplankton samples (monthly means of log (x+ 1) transformed ( number per 1000 m') at Seabrook intake (P2), discharge (P5), and farfield (P7) stations, July 1986-December 1995 . . . . ......... . . ...... . ..... . ....... . 5-10 i l 5-3. Dendrogram and temporal / spatial occurrence pattern of fish larvae assemblages formed by numerical classification of ichthyoplankton samples (monthly means of log (x + 1) transformed number per 1000 m') at Seabrook intake (P2), discharge (PS), and farfield (P7) stations, July 1986-December 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... ... .... 5-13 5-4. Total monthly cooling water system flow and estimated numbers of fish eggs and larvae entrained during 1995. . . . . . . . . . . . . ................. .... ..... . 5-20 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, 1976-1995 . ........... 5-23 5-6. Annual mean geometric mean catch of all species combined per unit effort (number per 10-min tow) in trawl samples by station and the mean of all stations, 1976-1995 . . .... . 5-25 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, 1976-1995 ..... .... ... . 5-28 5-8. Annual geometric catch of Atlantic herring per unit effort in ichthyoplankton (number per ; 1000 cubic meters) and gill net (number per 24-h set) samples by station and the mean of all l stations, 1975- 1995 . . . . . . . . . . . . . . . . . . . . . . ........... ....... . . 5-39 , I 5-9. Annual geometric mean catch of rainbow smelt per unit effort in trawl (number per 10-min tow) and seine (number per haul) samples by station and the mean of all stations, 1986-1995 I (data between two vertical dashed lines were excluded from the ANOVA model) . . . . . . 5-43 5-10. A comparison among stations of the mean logm (x+ 1) CPUE (number per 10-minute tow) j of rainbow smeh caught by trawl during ttle preoperational (November 1975-July 1990) and operational (November 1990 July 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-15) . . . . . ........ .. ..... ... . 5-45 5-iv
5.0 FISH . PAGE O) L 5-11. Annual geometric mean catch of Atlantic cod per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-min tow) samples by station and the mean of all stations, 1976-1995 ........ ... . ....... ................ . . 5-48 5-12. Annual geometric mean catch of pollock per unit effort in ichthyoplankton (number per 1000 > cubic meters) and gill net (number per 24-h set) samples by station and the mean of all 1 stations, 1975-1995 (data between the two vertical dashed lines were excluded from the l ANOVA model) . . . . . . . ................ ....... ... ...... . . 5-53 I 1 l 1 5-13. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per 1000 ; cubic meters) and trawl (number per 10-min tow) samples by station and the mean of all stations, 1976-1995 (data between the two vertical dashed lines were excluded from the
)
ANOVA model) ... .. ..... ................... . . . . . . . . . . . . . . 5-56 5-14. Annual geometric mean cabh of Atlantic silverside per unit effort in seine (number per haul) samples by station and the mean of all stations, 1976-1995 (data between the two vertical dashed lines were excluded from the ANOVA model) . . . . . . . .............. . 5-59 c- i 5-15. Annual geometric mean catch of cunner per unit effort in ichthyoplankton (number per 1000 cubic meters) samples by station and the mean of all stations, 1975-1995 (data between the two vertical dashed lines were excluded from the ANOVA model) ............ .. 5-62
; 5-16. Annual geometric mean catch of American sand lance per unit effort in ichthyoplankton (number per 1000 cubic meters) samples by station and the mean of all stations, 1976-1995 . . .. ............. ... ....... ........ ... .... 5-65 5-17. Annual geometric mean catch of Atlantic mackerel per unit effort in ichthyoplankton (number per 1000 cubic meters) and gill net (nmnber per 24-h set) samples by station and the mean of all stations,1975-1995 (data between the two vertical dashed lines were excluded from the ANOVA model) . . . . . . . . . . . . . . . . . . . . . . . . . . ... ...... . ...... . 5-68 5-18. Annual geometric mean catch of winter flounder per unit effort in ichthyoplankton (number per 1000 cubic meters), trawl (number per 10-min tow), and seine (number per haul) samples by station and the mean of all stations, 1975-1995 (data between the two vertical dashed lines cre excluded from ANOVA model) . . . . . . . . . . . . ............., .. ..... 5-72 O
5-v
5.0 FISH PAGE 5-19. A comparison among stations of the mean logw (x+ 1) CPUE (number per 10-minute tow) of winter flounder caught by trawl during the preoperational (November 1975-July 1990) and operational (November 1990-July 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-23) . . . . . . .......... . . . 5-74 5-20. A comparison among stations of the mean logw(x+ 1) CPUE (number per haul) of winter flounder caught by seine during the preoperational (April 1976-November 1984; April 1986-November 1989) and operational (April 1991-November 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-23). Seabrook Operational Report,1995. .. ............ . . . ... . .. .... 5-75 5-21. Annual geometric mean catch of yellowtail flounder per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-min tow) samples by station and the mean of all stations,1976-1995 (data between the two vertical dashed lines were excluded from the ANOVA model) . . ........... ......... . .. . ...... . . . 5-78 5-22. A comparison among stations of the mean logw(x+ 1) CPUE (number per 10-minute tow) of yellowtail flounder caught by trawl during the preoperational (November 1975-July 1990) and operational (November 1990-July 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-24). ... ....... . .... ... ... 5-80 0 5-vi
5.0 FISH O g LIST OF TABLES PAGE 5-1. Description of Finfish Sampling Stations ...... . . .... ...... ....... . 5-5 5-2. Selected Finfishes and Sampling Programs That Contributed Abundance Data for Species-specific Analyses . .. . . ..... ............ . . . .. . ........ 5-7 1 1 5-3. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish ; Eggs Collected at Seabrook Intake (P2) Discharge (P5), and Farfield (P7) Stations During July 1986 Through December 1995 .
... .... .. .............. ... 5-11 5-4. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish
^ I Larvae Collected at Seabrook Intake (P2), Discharge (PS), and Farfield (P7) Stations During July 1986 Through December 1995 . . . ......... . ........ .... ... ... 5-14 i 5-5. Monthly Estimated Numbers of Fish Eggs and Larvae Entrained (X 106 ) by the Cooling Water System at Seabrook Station from Early January Through Early April and from Mid-
- O september Through December 1995 . . . . . . . . . . ......................... 5-16 I 0
5-6. Annual Estimated Numbers of Fish Eggs and Larvae Entrained (X106 ) by the Cooling Water l System at Seabrook Station from June 1990 Through December 1995 . . ............ 5-18 j 6 5-7. Comparison of Entrainment Estimates (X 10 ) for Selected Taxa at Selected New England Power Plants with Marine Intakes from 1990 Through 1995 . . . . . . . . . . ......... 5-22 5-8. Geometric Mean Catch per Unit Effort (Number per 24-h Set, Surface and Bottom) with ' Coefficient of Variation (Cv) by Station (G1, G2, and G3) and All Stations Combined for Abundant Species Collected by Gill Net During the Preoperational and Operational Periods and the 1995 Mean . . . . . ..... .............. ....... .......... 5-24 5-9. Geometric Mean Catch per Unit Effort (Number per 10-min Tow) with Coefficient of Variation (Cv) by Station (T1, T2, and T3) and All Stations Combined for Abundant Species Collected by Otter Trawl During the Preoperational and Operational Periods and the 1995 Mean........................................ .............. 5-27 5-10. Geometric Mean Catch per Unit Effort (Number per Standard Haul) with Coefficient of Variation (Cv) by Station (S1, S2, and S3) and All Stations Combined for Abundant Species O Collected by Seine During the Preoperational and Operational Periods and the 1995 M ean . . . . . . . . . . . . . . . . . . . . . . ..................... ........... 5-29 5-vii
5.0 FISH PAGE 5-11. Species Composition and Total Number of Finfish, American Lobster and Seals Impinged at Seabrook Station by Month During 1995 .... ............... ......... . 5-31 5-12. Comparison of Fish Impingement Estimates at Selected New England Power Plants with Marine lntakes . . . . . . . . . . . . . . . ... . . ... . ....... . . . .... 5-34 S 5-13. Geometric Mean Catch per Unit Effort (Number per 1000 M ) with Coefficient of Variation (Cv) by Station (P2, PS, and P7) and All Stations Combined for Selected Larval Species Collected in Ichthyoplankton Samples During the Preoperational and Operational Periods and in 1995 . . . . .... .. ..... .... .... . . .... . ........ .. 5-38 5-14. Results of Analysis of Variance for Atlantic Herring Densities by Sampling Program . . . . 5-40 5-15. Results of Analysis of Variance for Rainbow Smelt Densities by Sampling Program .... 5-44 5-16. Results of Analysis of Variance for Atlantic Cod Densities by Sampling Program . . . .. 5-49 5-17. Results of Analysis of Variance for Pollock Densities by Sampling Program ......... 5-52 5-18. Results of Analysis of Variance for Hake Densities by Sampling Program .... ...... 5-57 5-19. Results of Analysis of Variance for Atlantic Silverside Densities by Sampling Program . . 5-60 5-20. Results of Analysis of Variance for Cunner Densities by Sampling Program . . . .. .... 5-63 5-21. Results of Analysis of Variance for American Sand Lance Densities by Sampling Program . 5-66 5-22. Results of Analysis of Variance for Atlantic Mackerel Densities by Sampling Program . . . 5-70 5-23 Results of Analysis of Variance for Winter Flounder Densities by Sampling Program . . . . 5-73 5-24. Results of Analysis of Variance for Yellowtail Flounder Densities by Sampling Program .. 5-79 5-25. Summary of Potennal Effects of the Operation of Seabrook Station on the Ichthyoplankton5-82 Assemblages and Selected Fish Taxa . . ...... . . ..... .... ... . . 5-82 5-26. Actual and Predicted Entrainment of Selected Fish Eggs and Larvae at Seabrook Station, and a 5-85 Comparison of Peak Densities in 1973-1976 with the Operational Period (1991-1995).
.......... .. ... .. . . .. ... ... . . ...... 5-85 5-viii
S.O FISH n LIST OF APPENDIX FIGURES PAGE 5-1. Total monthly cooling water system flow and estimated numbers of fish eggs and larvae entrained during August 1990 - December 1994 . . . . . . . . . . ... ........... . . 97 LIST OF APPENDIX TABLES 5-1. Finfish Species Composition by Life Stage and Gear, July 1975-december 1995 ....... 5-98 5-2. Subsetting Criteria Used in Analyses of Variance for the Selected Finfish Species . . . . . . 5-101 ; 5-3. Species Composition and Annual Totals of Finfish, American Lobster and Seals Impinged at 'y Seabrook Station During 1994 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 102 l O V 5-ix
5.0 FISH
5.1 INTRODUCTION
their relative abundance in collections from July 1975 through December 1995 by various Finfish studies at Seabrook Station began in July ichthyoplankton and adult finfish sampling 1975 and have included investigations of all life programs are given in Appendix Table 5-1. Both stages of fish, including ichthyoplankton (eggs and the common and scientific names in that table larvae), juveniles, and adults. The initial follow Robins et al. (1991) and common names are objectives of these studies were to determine the used throughout this report. seasonal, annual, and spatial trends in abundance and distribution of fish in the nearshore waters off 5.2 ME1110DS Hampton and Seabrook, NH to establish baseline = data suitable for assessing the effects of future 5.2.1 Ichthvophnkton plant operation. In addition, the nearshore fish populations in the Hampton-Seabrook estuary were 5.2.1.1 Offshore Samnling exammed to determine if there was any measurable effect due to the construction of Seabrook Station Ichthyoplankton sampling for Seabrook Station has and the discharge from the on-site settling basin been conducted since July 1975. Several imo the Browns River, which ended in April 1994. modifications to the sampling methodology and The station began commercial operation in August collection frequencies were made as the nature of 1990. Potential impacts of plant operation on local the ichthyoplankton community and its natural fishes include entrainment of eggs and larvae variability became better understood (NAl 1993). through the condenser cooling water system and Station P2 (nearfield site for the Seabrook intakes) impingement of larger specimens on traveling has been sampled consistently since the start of the screens within the circulating water pumphouse. program (Figure 5-1). Station P5 (nearfield site Also, local distribution of fishes could be affected for the Seabrook discharge) was sampled from July by the thermal plume, and some eggs and larvae 1975 through December 1981 and from July 1986 could be subjected to thermal shock due to plume through December 1995. Station P7 (farfield entrainment following the discharge of condenser station located about 7 km north of the nearfield cooling water from the diffuser system. stations), representing a non-impacted or control site, was sampled from January 1982 through l At present, the main objective of the finfish studies December 1985 and from January 1986 through l at Seabrook Station is to assess whether power December 1995. Through June 1977, collections plant operation since 1990 has had any measurable were taken monthly at each station sampled. effect on the nearshore fish populations. The Subsequently, a second monthly sampling period following report first presents general information was added in February through August and in on each finfish collection program and then December. Beginnmg in January 1979, all months provides more detailed analyses for those fish were sampled twice. Starting in March 1983, species selected because of their dominance in the sample collection was increased to the current Hampton and Seabrook area or their commercial frequency of four times per month at each station or recreational importance. A list of all taxa and sampled. l O' 5-1
RYE LEDGE O N G l uTTd
) BOARS HEAD f py 0 .5 1 Nautical Mile FARFIELD AREA 0
1 2 Kilometers g ,, _ , SCALE .Q ; CONTOUR DEPTH ! !! IN METERS , 0 ! ,
/
GREAT BOARS l g T3 HEAD , HAMPTON n BEACH
\ G3 BROWNS
/'=
~
RIVER g3 intake,,, t NEARFIELD S2 ,. 1
- 0. UTER g.r:- AREA' '
SEABROOK g 1
\' Discharge STATION Jj's3 IN [R, . 6h ,
- HAMPTON { fN SEABROOK SUNK Le < / 's HARBOR ROCKS ji T2 r'* ,
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c, 4G1 I SEABROOK . ,, , l
's BEACH , i ,
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i ! T1 SAUSBURY BEACH L LEGEND P = IchthyoplanktonTows i T = Otter Trawls . 1 G = Gill Nets i E S = Seine Hauls b b Figure 5-1 Ichthyoplankton and adult fish sampling stations. Seabrook Operational Report,1995. 1 5-2
5.0 FISH On each sampling date and at each station, four Simultaneous replicate samples were taken using samples were collected at night from July 1975 three double-barrel collection devices. In each, a , l through December 1993. Beginning in January 0.505-mm mesh plankton net was suspended in a I 1994, two tows were collected on each of the four 30-gal drum which, in turn, was suspended within sampling periods each month. Oblique tows were a 55-gal drum. Water diverted from the cooling-made using paired 1-m diameter,0.505-mm mesh water system entered each 55-gal drum from the j nets. Each net, weighted with an 8-kg depressor, bottom, overflowed into the 30-gal drum, passed was set off the stern and towed for 10 min while through the plankton net, and was discharged varying the boat speed, with the nets sinking to through the bottom of both drums. The water approximately 2 m off the bottom and rising supply was adjusted to maintain approximately 8 to obliquely to the surface at least twice during the 15 cm of water above the plankton nets at all tow. A standard 10-min tow was occasionally times. Following sampling, water was drained reduced to a 5-min tow to minimize net clogging from the system and the contents of each net due to high plankton density. The volume filtered, consolidated, and preserved with 5% buffered calculated using data from a calibrated General formalin. The volume filtered was measured with Oceanics* flowmeter mounted in each net mouth, an in-line flowmeter and averaged approximately averaged approximately 500 m' for 10-min tows 100 m' per replicate. The three simultaneuos and approximately 250 m' for 5-min tows. Upon replicates were summed into one sample during retrieval, each net was washed down from mouth analysis. to codend and the contents preserved in 5% formalin buffered with borax. 5.2.1.3 Laboratorv Methods 5.2.1.2 Entrainment Sampling Prior to March 1983, all four offshore ichthyoplankton samples per date and station were Ichthyoplankton entrainment sampling was analyzed, except from January through December conducted up to four times a month by NAESCO 1982, when only one sample per date and station biologists within the circulating water pumphouse was completely analyzed; only selected taxa were on-site at Seabrook Station from July 1986 through counted from the remaining three samples. June 1987 and June 1990 through December 1995. Beginning in March 1983, only two of the four Sampling dates coincided with offshore ichthyopla- offshore samples (one from each pair; Section nkton sampling whenever possible. Three 5.2.1.1) were analyzed from each station for each replicate samples were collected during the day on sampling date; the remaining two were held as each sampling date. The entrainment data contingency samples. Starting in January 1994, discussed in this report are only those for the only one of the two or four tows was analyzed per operational period of 1990 through 1995. date and station, with the remaining tows held as contingency samples. Seabrook Station's fourth Refueling Outage took place between November 19 and November Samples were subsampled with a Folsom plankton 27, 1995. Ichthyoplankton entraimnent samples splitter and sorted for fish eggs and larvae using a were not taken when there was no flow in the dissecting microscope. Successive aliquots were cooling water system. analyzed until a minimum of 200 eggs and 100 5-3
S.0 FISH larvae were sorted or until 200-400 mL settled 5.2.2.2 Demersal Fishes plankton volume was sorted. All eggs and larvae were identified to the lowest practical taxon 'Ihe inshore demersal fish assemblage was sampled (usually species) and counted. In some instances monthly beginning ir, July 1975 by otter trawl at when eggs were difficult to identify to species due night at one nearfield station, T2, and two farfield to their stage of development, they were grouped stations, T1 and T3 (Figure 5-1; Table 5-1). Four i with eggs of similar appearance (e.g., cunner, replicate tows were made at each station once per , tautog, and yellowtail flounder were grouped as month. Beginning in January 1985, sampling cunner /yellowtail flounder eggs; Atlantic cod, frequency was increased to twice per month and haddock, and witch flounder as Atlantic the number of replicate tows was reduced to two. cod / haddock; and hake species and fourbeard Sampling was conducted with a 9.8-m shrimp otter rockling as fourbeard rockling/ hake). The trawl (3.8-cm nylon stretch mesh body; 3.2-cm notochord lengths of at least 20 larvae per sample stretch mesh trawl bag; 1.3-cm stretch mesh (if present) were measured to the nearest 0.5 mm codend liner). The net was towed at approximate- , for selected taxa, which included Atlantic herring, ly 1 m seed for 10 min, with successive tows taken I Atlantic cod, pollock, hakes, cunner, Atlantic in opposite directions. The volume of drift algae mackerel, American sand lance, winter flounder, caught in the trawl was also recorded. It was not and yellowtail flounder. Entrainment samples always possible to collect samples at Station T2, were processed in a similar manner, particularly from August through October, due io j g the presence of commercial lobster gear; the () 5.2.2 Adult Fish frequency of missed samples has increased since 1983. In 1995 no samples were collected at 5.2.2.1 Pelwie Fishes Station T2 in August, September and October. Fish collected were identified to their lowest Beginnmg in July 1975, gill net arrays were set practical taxon (usually species), and measured to for two consecutive 24-h periods twice each month the nearest 2 cm. at Stations G1 (farfield), G2 (nearfield), and G3 l (farfield) to sample the pelagic fish assemblage 5.2.2.3 Estuarine Fishes (Figure 5-1; Table 5-1). Starting in July 1986, sampling was reduced to once per month. Nets Seine samples were taken monthly from April to were 30.5 m x 3.7 m and comprised four panels November at Stations S1, S2, and S3, beginning in having stretch mesh dimensions of 2.5 cm, 5.1 cm, July 1975 (Figure 5-1; Table 5-1). No samples 10.2 cm, and 15.2 cm. One net array consisting of were collected in 1985 or from April through June surface and near-bottom nets was set at each of 1986. Duplicate daytime hauls were taken into station. All nets were set perpendicular to the the tidal current at each station with a 30.5 m x 2.4 isobath (Figure 5-1). All nets were attached m bag seine. The nylon bag was 4.3 m x 2.4 m between permanent moorings and tended daily by with 1.4-cm stretch mesh, and each wing was 13.1 SCUBA divers. Fish collected were identified to m x 2.4 m with 2.5-cm stretch mesh. Fish their lowest practical taxon (usually species), and collected were identified to their lowest practical ( measured to the nearest 2 cm. taxon (usually species), and measured to the nearest 2 cm. 5-4
1 l i 5,0 FISH l Table 5-1. Description of Finfish Sampling Stations, Seabrook Operational Report,1995. g' l STATION DEPTH BOTTOM TYPE REMARKS i l BEACil SEINE S1 0-2 m sand Affected by tidal currents; approximately 300 m l upriver from Hampton Beach Marina S2 0-1 m sand Affected by tidal currents; approximately 200 m upstream from the mouth of the Browns River j 1 S3 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, appmximately 2 km south of the discharge G2 17 m sand Seaward ofInner Sunk Rocks, approximately 250 m southwest of the discharge G3 17 m rock, cobble Offshore from Great Boars Head, approximately 2.5 km north of the discharge OTTER TRAWL 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 15-17 m sand; drift algae 100 m from Inner Sunk Rocks, approximately with shell debris I km 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 with shell debris 4 km north of the discharge; just seaward of a cobble area (rocks 15 50 cm in diameter) O 5-5
5.0 FISH > O 5.2.2.4 Impingement uated on the basis of whether samples from the operational period were grouped differently by the Fish impinged at Seabrook Station were collected analysis than were the preoperational samples. by NAESCO biologists after being washed from the 0.375-in mesh traveling screens within the Multivariate analysis of variance (MANOVA; circulating water pumphouse. Traveling screens Harris 1985) was used to indicate whether fish egg were generally washed weekly (R. Sher, and larval assemblages had differed significantly (p NAESCO, pers. comm.) and impinged fish were $_0.05) between preoperational and operational sluiced into a collection basket. Fish from weekly periods. Logigx+1) transformed sample densities collections were separated from debris, placed in (number per 1000 m') were used. The analysis dated plastic bags, and frozen. On a periodic was restricted to collections from July 1986 basis, samples were thawed, identified to species, through December 1995, the common period of and counted by NAESCO biologists. Impingement sampling at Stations P2, PS, and P7, and the taxa collections were noted as total counts per species included were the same as those analyzed by by month. In addition, the number of fish numerical classification. The data used were the
- impinged per billion gallons of cooling water was mean oflogdx+1) sample densities for individual calculated. sampling dates and stations. The model design was a three-way factorial with nested effects. The 5.2.3 Analveal Methods main effects were period (preoperational and operational), station, and month nested within Ichthyoplankton assemblages were investigated year; interactions among these main effects were using multivanate rnunerical classification methods included in the model. The nested effect was years to detennine whether species composition changed within period. Type III sums of squares and tests between the preoperational period (July 1990 and of hypothesis were used for the analyses and the earlier) and the operational period (August 1990 rationale for their use was the same as that used and later). The Bray-Curtis similarity index for analysis of variance, discussed below. The (Clifford and Stephenson 1975) was used with the Wilks' lambda statistic (Wilks 1932; Morrison unweighted pair-group clustering method (Sneath 1976) was used to determine if the taxa assemblag-and Sokal 1973) Logm(x+ 1) transformed sample es in the preoperational and operational periods densities (number per 1000 m') of eggs and larvae were significantly different. For the purpose of were analyzed separately. The data sets were power plant impact assessment, sources of reduced by averaging dates within month variation of primary concern were the period (transformed data); including only the more (preoperational or operational) and the period by abundant taxa; and limiting the analysis to data station. interaction.
collected since July 1986, when all three stations of concern (P2, P5, and P7) were sampled. Rare Total ichthyoplankton entrainment was estimated taxa were excluded on the basis of percent- by calculating the arithmetic mean density for each composition (less than 0.1 % of the untransformed sampling week, multiplying by the monthly data) or frequency of occurrence in samples (less average of the daily cooling water volume, and
/ than 5%). The resulting dendrograms were eval- multiplying the mean density by the number days 5-6
5.0 FISH in the sampling week. These weekly estimates all stations combined to examine for trends in were summed for a monthly estimate, and monthly annual abundance. Geometric means were estimates were summed for the annual estimate., computed by logm(x+ 1) transformation of individual sample abundance indices, which were From the 88 species collected over the years,11 number per 1000 m' for ichthyoplankton, and taxa were selected for detailed analyses of catch-per-unit-effort (CPUE) for juvenile and adult abundance and distribution and for an assessment fish. CPUE was defined as the number per 24-h ofimpact by Seabrook Station (Appendix Table 5- set for the gill net, number per 10-min tow for the 1, Table 5-2). These selected species were trawl, and number per standard haul for the seine. numerically dominant in one or more sampling A transformed mean was calculated for each year programs, are important members of the finfish and for combined years (e.g., preoperational and fauna of the Gulf of Maine, and most have operationalperiods). The coefficients of variation recreational or commercial importance. Other (CV) of the mean of annual means (Sokal and species predommant in various sampling programs Rohlf 1981) in the logarithmic scale were also were noted when they occurred. The selected computed. The annual and combined geometric taxa, listed in Table 5-2 by sampling program, means are presented as back-transformed values. were individually evaluated for temporal and Some life stages are seasonal, so the data used to spatial changes in abundance between the compute the geometric means for some species preoperational and operational periods. Geometric were restricted to periods of primary occurrence; means were compared among the preoperational, when trimmed data were used, it is noted in the operational, and 1995 periods for each station and text, figure, or table. l Table 5-2. Selected Finfishes and Sampling Programs That Contributed Abundance Data for Species-Specific Analyses. Seabrook Operational Report,1995. SELECTED SPECIES PREDOMINANT SAMPLING PROGRAMS Atlantic herring ichthyoplankton, gill net Rainbow smelt otter trawl, beach seine Atlantic cod ichthyoplankton , otter trawl Pollock ichthyoplankton, gill net Hakes ichthyoplankton, otter trawl Atlantic silverside beach seine Cunner ichthyoplankton American sand lance ichthyoplankton Atlantic mackerel ichthyoplankton, gill net Winter flounder ichthyoplankton, otter trawl, beach seine Yellowtail flounder ichthyoplankton, otter trawl 5-7
S.0 FISH O g A fixed effects model ANOVA was used to test samples were logm(CPUE + 1) transformed for the null hypothesis that spatial and temporal each individual collection. For larvae, the abundances during the preoperational and transformed mean density of replicate samples was operational periods were not significantly (p > used for data up through 1993 (no replicates were 0.05) different. The data collected for the analyzed in 1994 and 1995). ANOVAs met the criteria of a Before-After/ Control-Impact (BACl) sampling design 5.3 RESULTS AND DISCUSSION discussed by Stewart-Oaten et. al. (1986), where sampling was conducted prior to and during plant 5.3.1 Ichthyoplankton Assemblages operation and sampling station locations included both potentially impacted and non-impacted sites. The analyses for the ichthyoplankton program The ANOVA was a two-way factorial with nested focused on seasonal assemblages of both eggs and effects that provided a direct test for the temporal- larvae, as well as on larvae of individual selected by-spatial interaction. The main effects were taxa (Table 5-2). Selected taxa are discussed in period (Preop-Op) and station (Station); the Section 5.3.3, in relation to juvenile and adult interaction term (Preop-Op X Station) was also stages collected in other sampling programs. In included in the model. Nested temporal effects the assemblage analyses, additional taxa were were years within operational period (Year (Preop- included to better represent the ichthyoplankton Op)) and months within year (Month (Year)), community in the Hampton-Seabrook area. p which were added to reduce the unexplained V variance, and thus, increased the sensitivity of the 5.3.1.1 Offshore Samples F-test. For both nested terms, variation was parti-tioned without regard to station (stations The seasonal assemblages of ichthyoplankton were combined). The final variance not accounted for examined using multivariate numerical classi-by the above explicit sources of variation fication (cluster analysis). These analyses were constituted the error term. conducted to determine if the operation of Seabrook Station had altered either the seasonal The 1990 sampling year was classified as either occurrence or the spatial distribution of fish eggs preoperational, operational, or was excluded from and larvae in the Hampton-Seabrook area. the analysis for a species, depending on seasonal Evaluation of spatial patterns compared the pattern of occurrence of each species or times of distribution of ichthyoplankton among intake (P2), sample collection (Appendix Table 5-2), and is discharge (PS), and farfield (P7) Stations before noted as such on the ANOVA tables. For larvae, and after Seabrook Station operation. Typically, the data were restricted to the period July 1986 ichthyoplankton taxa occur during distinct seasons through December 1995, and for selected taxa and periods of frequent occurrence, which are collected by gill net, trawl, and seine, the data used relatively consistent from year to year. The data were from July 1975 through December 1995. examined were collected from July 1986 through For trawl data, the months of August through December 1995, when all three Stations (P2, PS, October were excluded from the ANOVA because arxl P7) were sampled. The preoperational period O of reduced sampling effort at Station T2. The data extended through July 1990 and the operational used in the analyses of gill net, trawl, and seine period began in August 1990. Several of the egg 5-8
5.0 FISH taxa were grouped, because during early develop- spawning seasons of these three species. Egg mental stages it was difficult to distinguish among abundances in Group 2, termed the winter group, some species (e.g. Atlantic cod, haddock, and were relatively low for the two dominant taxa, witch flounder; cunner, yellowtail flounder, and Atlantic cod / haddock and American plaice, during tautog; fourbeard rockling and hakes). Larvae both preoperational cnd operational periods. This were generally identified to species, except that winter group consisted primarily of monthly hake (Urop/tycis sp.) was not identified to species. collections from January and February. Group 3, it is not known whether the hake larvae comprised termed late winter, primarily including March more than one species (red hake, white hake, and collections, had the same two dominant taxa as the spotted hake have all been collected by the previous group but in somewhat higher densities. Seabrook otter trawl program as adults). Group 4, termed early spring, consisted mostly of April collections. Dominant taxa in the early Eleven egg taxa were analyzed (excluding rare spring group were American plaice and Atlantic taxa) and the subsequent numerical classification cod / haddock (both in greater abundance than in analysis resulted in eight groups (Figure 5-2). A Group 2 and Group 3 collections), with the total of 326 monthly " collections" were used for addition of fourbeard rockling eggs. Group 4 the cluster analysis, with each collection being a collections during the operational period had higher monthly average of samples at one station. Each American plaice and lower fourbeard rockling of the 326 monthly collections analyzed fell within densities than during the preoperational period, one of the eight groups. The eight groups formed two major categories, which corresponded to Group 5, termed the spring group, was found annual periods of cold and warm water during the beginning of the warmer water season temperatares. Groups 1-4 were found during and consisted of May collections exclusively for all periods of cooler water temperatures (November years. The dommant taxa were more diverse than through April) and Groups 5-8 were taken during for the four previous groups and included eggs of the warmer period (May through October). There cunner /yellowtail flounder, fourbeard rockling was no apparent difference in these two categories (most abundant during the preoperational period), between preoperational and operational periods. American plaice, and Atlantic mackerel (most abundant during the operational period). Group 6, Group 1, termed late fall /early winter, represented termed the summer grouping, consisted of all of the beginning of the cooler water period and the June and July collections and some of the consisted primarily of November, December, and August collections. This group was less diverse, January collections. Atlantic cod and pollock were with only cunner /yellowtail flounder as dominants. the dominant taxa in this group (Table 5-3). The This taxon exhibited fairly similar abundance in the operational geometric means for both species were preoperational and the operational periods. Group lower than the preoperational means. Although ' 7 consisted of late summer /early fall collections, eggs of Atlantic cod, haddock, and witch flounder during August and September. The dominant taxa could not usually be identified to species except in this group were fairly diverse, probably due to during their late embryonic stage (Brander and a general decline in egg abundance during this Hurley 1992), Atlantic cod eggs could be identified period. The season represented by Group 8 was during this period on the basis of the known fall and collections occurred exclusively in Octo-5-9 l l
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[d formed oflog (x+1)by numerical transformed numberclassification per 1000 m at Seabrook ofichthyop)lankton intake (P2), discharge samples (monthly me (PS), and farfield (P7) stations, July 1986-December 1995. Seabrook Operational Report,1995. 5-10
Table 5-3. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish Eggs Co'lected at Seabrook Intake (P2), Discharge (P5), and Farfield (P7) Stations During July 1986 Through December 1995." Seabrook Operational Report,1995. NUMBER OF SAMPLES AND DENSITY (EGGS /1000 m*/ PREOPERATIONAL PERIOD' OPERATIONAL PERIOD
- GROUP DOMINANT TAXA' n LCL MEAN UCL n LCL MEAN UCL l-Late Fall /Early Winter Atlantic cod 34 39 58 85 40 21 28 38 (0.68/0.49)6 Pollock 5 7 10 1 2 3 2-Winter Atlantic cod / haddock 12 4 5 7 14 3 4 6 (0.70/0.62) American plaice <1 1 1 <1 <1 <1 3-Late Winter Atlantic cod / haddock 7 4 7 12 12 3 6 10 (0.72/0.62) American plaice 2 3 3 3 4 6 4-Early Spring American plaice 15 22 38 64 18 36 64 112 (0.52/0.37) Atlantic cod / haddock 7 15 30 15 22 33 y Fourbeard rockling 4 8 16 <1 <1 <1
= 5-S ' / 12 175 293 488 15 121 250 517 (0.f3 6) Cunnerdellowtail Fourbe drockling flounder 77 235 715 5 13 31 American plaice 54 73 97 36 59 95 Atlantic mackerel 18 37 77 88 202 460 6-Summer Cunner /yellowtail flounder 29 7620 11700 17900 38 7650 10800 15200 (0.73/0.64) 7-Late Summer /Early Fall Fourbeard rockling/ hake 22 177 316 565 28 170 242 346 (0.70/0.64) Hake 141 211 315 146 229 359 Windo ane 58 79 108 74 109 159 Cunn ellowtail flounder 25 63 157 20 47 109 8-Fall Silver hake 12 7 19 50 18 4 8 15 (0.57/0.41) Hake 8 18 36 3 5 6 Atlantic cod / haddock 10 17 28 1 3 6 Fourbeard rockling/ hake 7 14 29 5 8 12 Fourbeard rockling 3 6 11 1 2 3
*Each " sample" consisted of the average of tows within date and dates within month at one station.
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dGeometric mean and lower (LCL) and upper (UCL) 95% confidence limits.
'Preoperational = July 1986 - July 1990; Operational = August 1990 - December 1995.
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i 5.0 FISH i {,,) ber. Some of the dominant egg taxa in Group 8 monthly observation (Station P2, October 1992) l were also dominants in Group 7 but the densities did not cluster within any of the seven groups. I were much lower in Group 8. Preoperational and Similar to the egg collection data, two major operational period densities in Group 8 were categories were evident, with collections in Groups generally a little lower in the operational period 1-4 occurring primarily during the cooler water than in the preoperational period, temperature period (generally November through May) and collections in Groups 5-7 during the ; Time of year was the only factor that corresponded warmer period (generally June through October). ) with the cluster groups, which were formed by the Group 1, termed late fall, included all November I analysis on the basis of similar species composition and December collections and a few October and and abundance. Every one of the eight groups January collections (Figure 5-3). Larval Atlantic I contained collections from only one season of the herring was the most abundant species during this year. In contrast, there was a very even period, and there was a decrease in its abundance distribution of stations and of years within each of from the preoperational to the operational period the groups. Most importantly, both the (Table 5-4). Group 2, termed early winter, was assemblages present and their season of occurrence more diverse and generally comprised January were consistent between the preoperational and collections. American sand lance was most operational periods. dominant, with the remaining predominant taxa (Atlantic herring, gulf snailfish, and pollock) found p The consistency of assemblages of fish eggs both at lower abundances. There were no apparent h temporally (among both months and years) and spatially (among stations) suggested that operation differences between preoperational and operational geometric means for any of these taxa. American of Seabrook Station has not altered the spatial or sand lance larvae again dominated in Group 3, temporal distribution of eggs in the Hampton- termed late winter /carly spring. The period of Seabrook area. The spatial stability was occurrence for collections of this group was demonstrated by the fact that for 93% of the relatively long, generally from February through months in which all three stations were represented March and sometimes April. The geometric mean in the analysis, all three stations were classified abundance of American sand lance was higher in into the same group. This spatial similarity was the operational period and abundance of rock further supported by the resuhs of MANOVA, for gunnelwas fairly similar between periods. Group which a significant difference was found between 4 occurred during spring and comprised May and the preoperational and operational periods sometimes April collections for all years. The (p<0.001), but the interaction was clearly not Atlanuc seasnail and American sand lance were the significant (p = 0.77). This indicated that the most abundant larvae in this, the most diverse of temporal changes in assemblage abundance the seven groups. Abundance of snailfish larvae occurred concurrently at all three stations, decreased from the preoperational to the including the farfield Station (P7), the control area. operational period, but the other species were generally collected in comparable densities before Twenty-two larval taxa were selected for and after Seabrook Station began operation. numerical classification analysis, which resulted in O) \ v seven cluster groups (Figure 5-3). Only one 5-12
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O O O Table 5-4. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish Larvae Collected at Seabrook Intake (P2), Discharge (P5), and Farfield (P7) Stations During July 1986 Through December 1995." Seabrook Operational Report,1995. NUMBER OF SAMPLES AND DENSITY (LARVAE /1000 m')' - PREOPERATIONAL PERIOD' OPERATIONAL PERIOIY GROUP DOMINANT TAXA' n LCL : MEAN UCL- a LCL' MEAN UCL I-Late Fall Atlantic herring 27 24 41 70 37 12 17 24 (0.50/0.18)6 Pollock 2 3 4 <1 1 1 2-Early Winter American sand lance 14 12 24 48 14 15 30 57 (0.52/0.43) Atlantic herring 2 4 8 1 2 4 Gulfsnailfish 2 4 6 1 3 6 Pollock 1 3 8 1 2 3 3-Late Winter /Early American sand lance 27 215 295 404 36 294 372 470 Rock gunnel 23 34 51 25 39 63 4-Spring Atlantic seasnail 19 20 39 75 24 12 19 30 (0.58/0.47) American sand lance 18 30 49 22 34 50 t ? Winter flounder 2 5 11 1 2 3 I Gmbby 3 5 8 3 5 7 Radiated shanny 2 5 10 1 3 6 Gulfsnailfish 2 4 7 1 1 2 Rock gunnel 2 3 6 1 2 3 5-Late Spring /Early Cunner 27 40 94 218 30 18 51 141 Summer Fourbeard rockling 28 50 88 20 34 57 (0.60/0.44) Atlantic mackerel 15 27 46 19 37 70 Radiated shanny 17 26 40 23 32 45 Winter flounder 8 14 26 7 11 17 6-Late Summer Cunner 15 101 201 399 29 137 323 756 (0.59/0.44 Fourbeard rockling 28 62 134 23 37 59 Hake 4 7 12 7 16 34 7-Late Summer /Early Fourbeard rockling I8 2 4 6 24 2 3 5 Fall Atlantic herring 1 4 12 1 1 2 (0.36/0.28) Cunner 1 2 4 <1 1 1 Silver hake <1 1 2 1 2 3 Windowpane 1 I 2 1 1 1 Hake 1 1 1 <1 1 2 "Each " sample" consisted of the average of tows within date and dates within month at one station.
(Within p/between group similanty).
Thmew preoperational geometric mean densities together accounted for 290% of the sum of the preoperational geometric mean densities of all taxa within the group dGeometric mean and lower (LCL) and upper (UCL) 95% confidence limits.
'Preoperational = July 1986 - July 1990; Operational = August 1990 - December 1995.
S.0 FISH Group 5 collections occurred primarily during the was also supported by the results of MANOVA, late spring and early summer (June and July), where the preoperational-operational term was representing the first of the warm water groups. significant (p<0.001), but the interaction was The geometric means for the dominant species in clearly not significant (p>0.99). These results this group (cunner, fourbeard rockling, and irxiicated that the temporal changes in assemblage Atlantic mackerel) were fairly comparable between abundance were consistent at all three stations, the preoperational and operational periods. The including the farfield Station P7, located well annual seasonal patterns of occurrence for Groups outside the zone of thermalinfluence of Seabrook 6 and 7 were less consistent than for the other Station. groups. Although Group 6 was not present every year, cunner and fourbeard rockling larvae 5.3.1.2 Entrainment dominated this group during late summer (August and September). When present, collections at all One of the most direct measures of potential three stations were generally grouped together impact of Seabrook Station on the local fish l (ucept September 1995). In Group 6, density assemblages is the number of eggs and larvae differences were not substannally different between entrained through the condenser cooling water j the operational period and the preoperational system. During 1995,18 egg and 21 larval taxa l period. Group 7 was termed late summer /early were collected in entramment samples (Table 5-5). fall, and included collections from August through Total estimates of entrainment were 255.6 million October. Three of the six dominant taxa were also eggs and 145.3 million larvae for the year. These l present in the previous group, but they were numbers are comparable to the 1993 estimates collected at much lower densities in the Group 7 (Table 5-6), the only other year in which sampling samples. In two years,1986 and 1992, no samples was corxiucted for a full 12 months (Table 5-6 and were classified with Group 6. This indicates lower Appendix Figure 5-1). In 1990-1992, which were than usual densities of larvae in August and only partial years of sampling, egg entrainment September for those two years. As the low was much higher than in 1995 and larvae densities occurred equally in preoperational and entrainment was comparable. operational periods, they were not related to plant operation. Atlantic mackerel, Atlantic cod / haddock / witch flounder, and fourbeard rockling/ hake were the As was the case with eggs, the cluster groups most numerous taxa entrained in 1995 (Figure 5-based on larval species composition and abundance 4). These three taxa have consistently been among were strongly related to season but were the dominant eggs entrained by Seabrook Station independent of station, year, and operational (Table 5-6). Cunner /yellowtail flounder eggs had status. In 96% of the months in which all three been among the top two taxa in 1990-1993 but stations were represented in the analysis, all three ranked only sixth in 1995. Atlantic seasnail, stations were grouped in the same chister. This grubby, and rock gunnel were the three most high degree of similarity among nearfield (P2 and abundant species of larvae identified from P5) and farfield (P7) collections was as true during entrainment samples in 1995, consistent with their the operational period as it was during the dominance among larvae entrained in previous preoperational period. Similarity among stations years (Table 5-6). Larval entrainment data for 5-15
Q (v; (3 v i Table 5-5. Monthly Estimated Numbers of Fish Eggs and Larvae (In Millions) Entrained by the Cooling Water System at Seabrook Station During January Through December 1995. Seabrook Operational Report, 1995. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL , t EGGS American plaice 0.0 0.0 1.0 1.2 5.3 6.7 0.6 0.0 0.0 0.0 0.0 0.0 14.8 Atlantic cod 0.2 < 0.1 0.2 0.0 0.0 0.9 0.0 0.0 0.0 0.0 0.2 0.6 2.2 Atlantic cod / haddock 0.0 0.2 0.4 0.3 0.0 0.0 1.4 0.0 0.0 0.0 0.0 0.0 2.2 i Atlantic cod / witch flounder 0.0 0.0 0.0 < 0.1 3.1 26.4 2.5 0.4 0.2 0.0 0.0 0.0 32.6 Atlantic mackerel 0.0 0.0 0.0 0.0 3.9 70.1 0.5 0.0 0.0 0.0 0.0 0.0 74.5 Atlantic menhaden 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.0 0.0 0.2
- v. Cod family 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 < 0.1 0.1 0.2 L
- Cunner /yellowtail flounder 0.0 0.0 0.0 0.1 1.1 8.6 7.3 1.4 0.1 0.0 0.0 0.0 18.6 Cusk 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 Fourbeard rockling 0.0 0.0 0.0 < 0.1 0.1 0.7 0.1 1.6 1.6 0.0 0.0 0.0 4.2 11ake 0.0 0.0 0.0 0.0 0.1 0.2 0.3 3.0 21.4 0.1 0.0 0.0 25.1 Hake /fourbeard rockling 0.0 0.0 0.1 0.4 4.0 2.1 2.6 6.0 12.2 0.1 0.0 0.0 27.5 l
Lumpfish 0.6 < 0.1 0.0 4.1 1.0 0.2 0.1 0.0 0.0 0.0 0.0 0.0 6.0 Po!!ock < 0.1 < 0.1 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.4 l I Silver hake 0.0 0.0 0.0 0.0 0.0 0.3 0.6 3.3 18.1 0.1 0.0 0.0 22.5 Unidentified < 0.1 0.0 0.0 0.2 0.3 2.5 0.9 0.5 1.4 0.0 0.1 0.3 6.4 Windowpane 0.0 0.0 0.0 0.0 1.4 6.7 5.6 1.8 1.6 0.2 0.0 0.0 17.4 Witch flounder 0.0 0.0 0.0 0.0 0.0 0.1 0.4 0.1 0.0 0.0 0.0 0.0 0.7 Yellowtail flounder 0.0 0.0 0.2 0.0 . 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 TOTAL 0.8 0.2 2.3 6.4 20.3 125.9 23.0 ' 18.1 56.7 0.5 0.3 1.2 255.6 (continued)
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5.0 FISH I Table 5-6. Annual Estimated Numbers of Fish Eggs and Larvae Entrained (X10') by The Cooling Water System at Seabrook Station from June 1990 Through December 1995. Seabrook Operational Report,1995. TAXON 1990' '1991 6 1992* 19938 1994* '1995 TE&S Atlantic mackerel 518.8 673.1 4563 112.9 0.0 74.5 hou"nj 'I 490.4 716 3 198.6 58.4 0.0 18.6 o$ dock / witch 29.1 74.5 39.5 503 1.0 34.8 flounder ky h, !!4.2 35.1 50.6 32.7 1.7 27.5 Wm' dowpane 36.4 19.9 22.5 29.1 0.1 17.4 American plaice 2.6 21.0 523 19.5 0.4 14.8 Lumpfish 0.0 0.0 0.0 9.5 0.1 6.0 Fourbeard rockling 7.4 43 0.8 1.4 0.2 4.2 Unidentified 0.0 2.0 0.0 0.8 0.2 6.4 Silver hake 11.4 0.0 0.1 0.4 0.4 22.5 Pollock 0.0 1.0 0.4 0.2 0.1 0.4 Hake 373 2.6 0.0 0.2 0.6 25.1
, Atlantic menhaden 0.0 0.5 1.4 0.1 0.0 0.2 l Cusk 0.1 0.5 0.0 0.1 0.0 0.2 Tautog 0.0 0.2 0.0 0.0 0.0 0.0 Atlantic cod 0.0 0.0 0.0 0.0 0.0 2.2 Atlantic cod'pollock 0.0 0.0 00 0.0 0.0 0.2 Witch flounder 0.0 0.0 0.0 0.0 0.0 0.7 Yellowtail flounder 0.0 0.0 0.0 0.0 0.0 0.2 Total :1247,7 1551.0 822.6 315.6 4.7 255.6 L
5-18 (continued)
i 1 5.0 FISH Table 5-6. (Continued) TAXON. 1990'. 1991* 1992' 1993' 1994'- 1995 LARVAE Atlantic acasnail 11.6 16.0 31.5 64.4 0.0 26.5 Grubby 0.0 22.4 18.9 13.8 4.9 17.4 American sand lance 0.0 37.3 18.1 12.0 8.3 9.5 Atlantic herring 0.7 0.5 4.9 9.6 0.1 11.2 Rock gunnel 0.0 51.1 45.3 5.7 11.0 15.6 Unidentified 0.7 2.1 1.4 5.6 0.6 30.4 Cunner 42.7 <0.1 0.0 4.7 0.1 4.4 Winter flounder 3.2 9.0 6.2 2.9 0.0 8.0 Gulfsnail5sh 0.1 2.8 1.9 2.6 3.5 0.2 Fourbeard rockling 37.9 0.5 0.1 2.2 0.0 3.9 American plaice 0.4 1.0 0.8 0.7 0.0 7.9 Longhorn sculpin 0.0 0.6 0.6 0.4 0.3 0.4 Moustache sculpin 0.0 0.1 0.3 0.4 2.2 0.0 Lump 6ch 0.6 0.1 0.1 0.2 0.0 0.6 Unidentified snail 6sh 0.1 0.3 0.0 0.2 0.0 0.0 Shorthorn sculpin 0.0 0.2 0.6 0.2 0.1 0.5 Radiated shanny 4.8 3.1 1.1 01 0.0 2.1 Atlantic cod 0.7 1.5 0.4 0.1 0.0 2.3 Silver hake 7.7 0.0 0.0 0.1 0.0 0.9 Windowpane 3.8 <0.1 0.1 0.1 0.1 2.0 Hake 4.8 0.0 0.0 0.1 0.0 0.7 Atlantic mackerel 0.2 4.7 0.0 0.0 0.0 0.0 Yellowtail flounder 0.1 0.3 0.1 0.0 0.0 0.1 Alligatorfish 0.0 0.1 0.2 0.0 0.2 0.3 Wrymouth 0.0 0.1 0.0 0.0 0.0 0.0 Witch flounder 0.3 0.0 0.0 0.0 0.0 0.0 Tautog 0.3 0.0 0.0 0.0 0.0 0.0 Pollock 0.2 0.0 0.1 0.0 0.0 0.0 Fourspot flounder 0.2 0.0 0.0 0.0 0.0 0.0 Rainbow smelt 02 0.0 0.1 0.0 0.0 0.0 Goose 6sh 0.1 0.0 0.0 0.0 0.0 0.0 Atlantie menhaden 0.1 0.0 0.0 0.0 0.0 0.0 Red 6sh 0.0 0.0 0.4 0.0 <0.1 0.0 Haddock 0.0 0.0 0.1 0.0 0.0 0.0 UnidentiSed sculpin 0.0 0.0 0.1 0.0 0.0 0.fi Butter 6sh 0.0 0.0 0.0 0.0 0.0 03 Total 121.5 -153.8 133.1 126.2. 31.2 145.3 'From NA!(1991) Represents only 7 months, August- December. 'From NA!(1992). Represents only 8 months, January July, December. 'From NA!(1993). Represents only 8 months, January August.
- From NAl and NUS (1994) Represents only 8 months, January August.
'From NAl(1995). Represents only 8 months, January March, September - December. ; 1 5-19
1 , Plant flow v b '* ts l~ .: n-1
- g. so i
a p M A M J J A S O N O uonm
- 340 Eggs 120 100 O
h* b* f) h "O g p u A M M J UM J A S O N D Attarvtic cod Q EW Camder O ss - - M* ea nou=., = = - - { L Larvae m
! 3 E !E _sm J P M A M J J A S O N D CU a :~ -lo O I DQrutatry Q Mook gunnel mM sm M sa o.,-.
k Figure 5-4. Total monthly cooling water system flow and estimated numbers of fish eggs and lan'ae entrained during 1995. Seabrook Operational Report,1995. 5-20
S.0 FISH 1995 differed from earlier data in the high 5.3.2 Adult Fish Assemblaces proportion of larvae that were unidentifiable due to damage (21%). Differences in entrainment 5.3.2.1 Pelanic Fishes between larval and egg stages of the same taxa in the same year are due to varying susceptibility of The pelagic fish assemblage was sampled using a the two developmental stages to entrainment. gill net array at three stations (Figure 5-1). Among the dominant larval species entrained are Geometric mean CPUE (catch per 24-hour set) of several that have demersal or adhesive eggs, which all fish caught at all three stations combined for are not susceptible to entrainment, including 1995 was 1.2, a decrease from a mean of 2.1 in Atlantic seasnail, grubby, American sand lance, 1994, and the lowest observed during the study i Atlanne herring, rock gunnel, winter flounder, and period (Figure 5-5). Despite the record low, gulf snailfish. One exception to this pattern is CPUE in 1995 was generally similar to annual lumpfish eggs, which have been entrained by means since 1982 (Figure 5-5). Largest catches Seabrook Station on several occasions despite were made during the first five full years of being demersal and adhesive. It may be possible sampling (i.e., 1976-80). The catch in 1995 was that clusters oflumpfish eggs attached to the intake dominated by Atlantic mackerel, pollock, and structure were dislodged by currents. Behavioral blueback herring (Table 5-8). characteristics of some larvae may reduce larval entrainment for some taxa that have high egg In general, CPUE at the three gill net stations entrainment. For instance, hake and fourbeard followed similar trends during the 19-year period j rockling larvae are surface oriented (Hermes 1985) of sampling (Figure 5-5), as did the catch of the j and may not be susceptible to the mid-water most numerous species (Table 5-8). Slightly j intakes. The rapid larval development of Atlantic higher catches were made at G1, the southernmost mackerel may enable them to develop a relatively station, particularly during the first few years of 4 high swimming speed (Ware and Lambert 1985) sampling. Catch during the preoperational period and, thus, may be able to avoid entrainment. (1976-89) was dominated by Atlantic herring, blueback herring, silver hake, pollock, and Annual Seabrook Station entrainment estimates for Atlantic mackerel (Table 5-8). For the operational the selected taxa since 1990 were compared to period (1991-95), most of the catch was made up l estimates from two other New England power of Atlantic herring, pollock, and Atlantic l plants, Pilgrim and Millstone Stations (Table 5-7). mackerel. O Except for Atlantic seasnail larvae, annual entrainment estimates for Seabrook Station had The spiny dogfish has become increasingly l similar annual estimates or were considerably less abundant during the operational period, with a 1 than at the other two power plants. geometric mean CPUE of 0.1, which is approxi- l mately five times the CPUE determined for the j preoperational period. However, CPUE in 1993 ! through 1995 ( < 0.1 - 0.1) has decreased showinHy since the record high CPUE of 0.4 in 1992 (NA11993). The abundance of spiny dogfish ; in the Gulf of Maine has increased continuously i 1 5-21
O O O Table 5-7. Comparison of Entrainment Estimates (X 10') for Selected Taxa at Selected New England Power Plants with Marine Intakes from 1990 Through 1995. Seabrook Operational Report,1995. TAXON SEABROOK PILGRIM
- MILLSTONE
- Cunner /ycilowtail flounde/tautog eggs' 0'-716 860-4122 2,736-5,750 Atlantic mackereleggs- 0'-673 337-2066 -
Atlantic herringlarvac <l'-l 1 1-18 - Cunnerlarvae O'-43 4-323 - d Grubbylarvae 5'-22 7-44 34-76 Atlantic seasnaillarvac* 2-11 u O'-64 - b Rock gunnellarvac 6-51 7-62 - American sand lancelarvae 8'-37 23-459 7-77 Atlantic mackerellarvae 0-5 3-66 - Winter flounderlarvae O'-9 9-21 45-514
*MRI(1991,1992,1993b,1994,1995); 1990-1999 Ope Cod Bay.
6NUSCO (1994a,1994b,1995); eggs-1990-1993, .xubby and American sand lance larvac-1990-1994; winter flounder larvae 1990-1995; Long Island Sound.
*Seabrook-cunner /ycilowtail flounder; Pilgrim-cunner /tautog/ycIlowtail flounder; Millstone-cunner dSeabrook and Millstone-grubby; Pilgrim-grubby and other sculpins. *Scabrook-Atlantic seasnail; Pilgrim-Atlantic seasnail and other snailfishes.
hwest estimate occurred in a year when samples are lacking in some or all of the months when this taxon normally would be entrained (estimate for 1990 was not included for those taxa usually present before June, when the entrainment sampling program was begun).
. . _ _ _ -- - - - _ . - - - _ _ - - _ _ _ - . _ _ _ _ . _ _ - _ . - - - - - . . _ _ _ --n.- .. - - _ - , __ _ _ _ _ . _ _ . _ _ . . _ _ - _ _ . _ _ _ - . _ _ _ _ . . _ . - _ . _ _ - _ _ . - _ . . _ . - _ , _ _ _
5.0 FISH Gill net
" 8 ---
m i ....... m
*-+-+ ME 16 l
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,r i i k to /
\' Preoperauonal l Operatonal sa \ l h8 N s
\
i I 4 \ _ 3' ,, l
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s _ __ -. O ! 75 78 77 78 79 80 81 82 83 84 85 80 87 88 89 90 91 92 93 94 95 veAn I 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, 1976-1995. I I l Ol 5-23
S.0 FISH 73 Table 5-8. Geometric Mean Catch per Unit Effort (Number per 24-h Set, Surface V and Bottom) with CoefHelent of Variation (CV) by Station (G1, G2, and G3) and All Stations Combined for Abundant Species Collected by Gill Net During the Preoperational and Operational Periods and the 1995 Mean. Seabrook Operational Report,1995. PREOPERATIONAL PERIOD" 1995* OPERATIONAL SPECIES STATION MEAN CV MEAN MEAN CV Atlantic hening G1 1.0 18 <0.1 0.3 27 G2 1.1 20 <0.1 0.2 28 G3 1.2 21 0.1 0.4 19 All Stations 1.1 19 0.1 0.3 21 Atlantic mackerel G1 0.2 16 0.2 0.3 21 G2 0.2 15 0.2 0.3 32 G3 0.3 16 0.2 0.3 17 All Stations 0.2 15 0.2 0.3 21 Pollock G1 0.2 17 0.1 0.2 18 G2 0.3 10 0.3 0.3 14 G3 0.3 13 0.2 0.2 16 All Stations 0.3 9 0.2 0.3 13 Spiny dogfish G1 <0.1 45 0.0 0.1 68 G2 <0.1 35 <0.1 0.1 37 G3 <0.1 27 0.1 0.2 43 All Stations <0.1 30 0.1 0.1 42 Silverhake G1 0.2 34 0.0 <0.1 52 G2 0.3 35 0.0 <0. I 80 G3 0.3 31 0.0 0.1 39 All Stations 0.3 33 0.0 <0.1 53 Blueback herring G1 0.2 17 0.2 0.1 20 G2 0.3 18 0.2 0.1 19 G3 0.3 24 0.3 0.1 30 All Stations 0.3 18 0.2 0.1 17 Alewife G1 0.1 17 0.1 0.1 25 G2 0.1 14 0.1 0.1 26 G3 0.1 21 0.1 0.1 44 All Stations 0.1 14 0.1 0.1 29 Rainbow smelt G1 <0.1 26 0.1 0.1 40 G2 0.1 21 0.2 0.1 36 G3 0.1 21 0.1 0.1 40 All Stations 0.1 18 0.1 0.1 31 Atlantic cod G1 0.1 18 0.0 <0.1 77 G2 <0.1 22 0.0 <0.1 61 G3 0.1 13 <0.1 <0.1 100 All Stations 0.1 13 <0.1 4.1 58 Other species G1 0.4 9 0.2 0.3 14 G2 0.4 11 0.3 0.3 19 D3 0.3 12 0.2 0.2 26 All S'.ations 0.4 10 0.2 0.2 16 / 'Preoperational: 1976-1989- geometric mean of annual means.
, ' Operational: 1991 1995 geometric mean of annual means.
k/ " Geometric mean of the 1995 data. 5-24
l 1 l l 5.0 FISH since the 1960s, and together with skates now on the traveling screens since 1990. The makes up about 75% of the fish biomass on increasein spiny dogfish biomass during the Georges Bank (NOAA 1995). The index of spiny operational period has taken place concurrently I dogfish and skate abundance on Georges Bank and with decreases in groundfish stocks in a large the Gulf of Maine has decreased in recent years region of the Northwest Atlantic Ocean (NOAA reflectmg a stabilization of stock sizes, particularly 1995) and is not related to Seabrook Station I for spiny dogfish (NOAA 1995). The decrease in operation. spiny dogfish abundance in the Gulf of Maine and i Georges Bank is apparent in the gill net data in the 5.3.2.2 Demersal Fishes I form of decreased CPUE from 1993 though 1995. A 9.8-m otter trawl was used at three stations in the Gulf of Maine, the spiny dogfish is primarily (Figure 5-1) to determine the abundance and found inshore during summer. It preys upon distribution of demersal fishes. Geometric mean Atlantic herring, Atlantic cod, Atlantic mackerel, CPUE(catch per 10-minute tow) of fish caught at and American sand lance, among other species all stations combined in 1995 was 8.4, a decrease (NOAA 1993). Because female spiny dogfish bear from the CPUE of 12.9 in 1994, and the lowest live young that are relatively large and well- CPUE recorded since year-round sampling began developed, no specimens have been entrained at in 1976 (Figure 5-6). The trawl CPUE peaked in Seabrook Station and only five have been impinged 1980 (78.6) and 1981 (77.6), primarily due to Trawl O! im i ___ i ....... .n r2
'\ T3
\
l N MEAN g 80 / \ l
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I I i . . I O. ' 75 76 77 78 79 80 81 82 83 84 86 86 87 88 89 90 91 92 93 94 95 YEAR Figure 5-6. Annual geometric mean catch of all species combined per unit effort (number per 10-min tow) in trawl samples by station and the mean of all stations. 1976-1995. Seabrook Operational Report,1995. 5 25
5.0 FISH O large catches of yellowtail flounder. In 1995, period were not used in any of the ANOVAs for catch was dominated by longhorn sculpin, winter selected species collected by trawl sampling flounder, yellowtail flounder, skates, and (Section 5.3.3). For other months during the past windowpane (Table 5-9). 18 years, a few collections were missed at T2, but overall trawl sampling effort at T2 was 82% of Catch of nearly all species in the study area that at T1 or T3. declined from the preoperational to the operational period, particularly for the yellowtail flounder 5.3.2.3 Estuarine Fishes (CPUE of 9.3 and 1.9, respectively). Other species with decreased CPUE included longhorn Sampling for estuarine fishes was conducted at sculpin (4.1, 3.0), winter flounder (3.5. 2.8), three stations within the estuary of Hampton-hakes (3.2,1.0), Atlantic cod (1.8, 0.6), and Seabrook Harbor (Figure 5-1) using e 30.5-m windowpane (1.3,0.9). The CPUE of skates (1.9, seine. Geometric mean CPUE (catch per haul) for 1.8) and pollock (0.4, 0.4) was similar in both the all fish caught at all stations during 1995 was 14.9, preoperational and operational periods. As noted a slight increase in catch from 1994 (CPUE of previously, groundfish stocks have all decreased in 13.1; Figure 5-7). Overall, seine catches generally the Northwest Atlantic, except for skate which is were smaller (5.6-24.1) during 1987-95 than they currently very high in this area (NOAA 1995). were during 1976-84, when annual CPUE ranged from 22.7 to 59.1; no seine sampl!ng took place in Differences in CPUE and species composition 1985 or April through June of 1986. The catch of U were apparent among the stations. The bottom at most fishes by seine decreased from the nearfield Station T2, located in shallow (15-17 m) preoperational to the operational period (Table 5- I water off the mouth of Hampton-Seabrook Harbor, 10). Atlantic silverside has dominated the seine was occasionally inundated with drift algae. catch in all years sampled. Winter flounder, Stations T1 and T3 are in deeper water (20-28 and killifish (mummichog or striped killifish), 22-30 m, respectively) and have sandy bottoms. ninespine stickleback, and rairlow smelt also CPUE of all species combined was consistently contributed frequently to the catch during both the lower at T2 than at T1 and T3, which tended to preoperational and operational periods. No have similar catches (Figure 5-6). Catch at T2 rainbow smelt were captured in 1995. was dominated by winter flounder, whereas yellowtail flounder (preoperational period) and Catch by station showed considerable variation longhorn sculpin (operational period) were most over the years. In 1995, CPUE was highest at common at T1 and T3. However, station to station Station S1, due to large catches of Atlantic comparisons are limited by the inability to sample silverside. Station S3, located near the mouth of by trawl at Station T2 during many sampling trips, the estuary, had peak catches in 1976,1979, and i particularly from August through October, when 1990, but its CPUE has been generally close to the catches tend to be largest. Because largest catches three-station mean since 1991. Station S1, located were often made during late summer and early farthest from the mouth, had relatively low CPUE fall, this may have biased interstation comparisons, during the earliest years of sampling, and tended to (G which used the entire database. Because of this approximate the overall mean in more recent years \ potential bias, data from the August-October and in 1995. CPUE at S2, located closest to 5-26
1 5.0 FISH Table 5-9. Geometric Mean Catch per Unit Effort (Number per 10-min Tow) with Coefficient of Variation (CV) by Station (T1, T2, and T3) and All gj i Stations Combined for Abundant Species Collected by Otter Trawl i During the Preoperational and Operational Periods and the 1995 Mean. l Seabrook Operational Report,1995. j l PREOPERATIONAL 1995* OPERATIONAL PERIOD' PERIOD * , SPECIES STATION MEAN CV MEAN MEAN CV l Yellowtail flounder :] 20.j g 2 g3 All tations . 4 'l '9
. 1 12 < b$ 2 All stations 4. h 2.9 kb 4 1
- h k 0: : 2$
All stations 3: 5 : : 8 l
- 4 ':1 1 8:6 4:1 li AU;aem }:1 ! 8:1 1:8 is
. !k < b: !
All stations 1:h ll Ob b:6 4h b ! < : h6 All st tions f9 1:3 1:8 f0
* "r*"* '
g 4:8
!g 4:
bj9 g::! 2 All stanons !'h
. ! 0h f Rainbow smelt 9 0.4 g.j 8 All stations 1.1 . bl4 -- n 82 g <8:3 8: ;
All s tions b:8 6 0:l b; p8 h <b: <b: h j All stations 0.7 l4 b.'4 b:4 !f
* " ** 5
- } j8 8:h 8: lj l All tauons l3: 1 0.2 0 h0
<b: b:0 h AU stations b:2 hh <h'!. <0l $h
**"Pe*i" F 9 4:1 h All s tions 1:l
- 4 5 8j b l i
'Preoperational: 1976-1989; geometric mean of annual means.
Treometric mean of the 1995 data. l
' Operational: 1991 1995; geometne mean of annual means. ! %y include red hake, white hake, spotted hake, or more than one of these species.
5-27
5.0 FISH t ex i Seine V 1= i i ___a
.......s2 l ~ Uem
=
l i l
@ so ,
l- a /N i l , l ar. '~s,I \ m .j-* , , l
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/ / \ f /
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.O V 7s 7e 77 78 7e ao 85 ee ss 84 as se 87 as se so es 82 es e4 es YEM 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 1976-1995. Seabrook Operational Report,1995. O G 5-28
5.0 FISH 1 1 Table 5-10. Geometric Mean Catch per Unit Effort (Number per Standard Haul) With Coefficient of Variation (CV) by Station (S1, S2, and S3) and All Stations Combined for Abundant Species Collected by Seine During hl l The Preoperational and Operational Periods and the 1995 Mean. ' Seabrook Operational Report,1995. PREOPERATIONAL 1995* OPERATIONAL PERIOD' PERIOD' I SPECIES SrATION MEAN _ CV MEAN MEAN CV Atlantic silverside S1 7.2 7 !!.8 4.6 15 S2 6.8 6 5.6 4.0 11 S3 6.7 10 4.5 4.0 8 All stanons 6.9 7 6.7 4.2 8 Winter flounder S1 0.9 11 0.6 0.5 31 S2 1.0 14 0.0 0.3 62 S3 3.2 9 1.0 1.0 9 All stanons 1.5 8 0.5 0.5 10 Killifishes SI 1.1 10 2.7 1.1 35 S2 1.2 19 0.1 0.2 63 S3 < 0.1 27 0.0 < 0.1 100 All stanons 0.7 13 0.6 0.4 26 Ninespine stickleback S1 0.7 20 0.5 0.3 27 S2 0.8 28 0.0 0.1 S3 0.8 24 0.1 0.2 34 All stanons 0.8 20 0.2 0.2 24 Rainbow smelt SI 0.1 41 0.0 0.1 57 S2 0.2 31 0.0 0.2 47 S3 0.7 21 0.0 0.4 43 All stations 0.3 16 0.0 0.2 37 American sand lance SI 0.1 44 0.3 0.2 26 S2 0.2 48 0.1 0.I 8i S3 0.1 28 0.1 0.3 73 All stations 0.1 28 0.2 0.2 24 Pollock S1 0.1 40 0.0 < 0.1 61 S2 0.2 40 0.0 < 0.1 100 S3 0.4 36 0.0 0.1 62 All stanons 0.2 35 0.0 < 0.1 52 Blueback hemng S1 0.2 29 0.2 0.2 39 S2 0.1 36 0.0 0.1 100 S3 0.1 38 0.0 < 0.1 100 All stations 0.1 29 0.1 0.1 41 Atlanac herring S1 0.1 59 0.2 0.1 46 S2 0.3 27 0.0 0.1 69 S3 0.1 24 0.0 0.1 67 All stations 0.2 19 < 0.1 0.1 38 Alewife S1 0.1 38 0.1 < 0.1 43
$2 0.1 49 0.0 0.0 -
S3 0.1 31 0.0 < 0.1 100 All statioru 0.1 33 < 0.1 < 0.1 27 Other species S1 0.8 14 1.2 0.5 34 l S2 1.1 8 0.4 0.6 34 S3 1.5 12 1.1 1.1 16 All stations I.1 9 0.9 0.7 19 'Preoperational: 1976-1989; geometric mean of annual means. Wometric mean of the 1995 data. , ' Operational: 1991 1995 geometric mean of annual means. j O 5-29
5.0 FISH O Seabrook Station, had the largest CPUE in 1993 (15,932) was lower than in 1994 (19,221; t] and was similar to the three-station average in Appendix Table 5-3). During this two-year 1995. Trends in CPUE were mostly due to the period Atlantic silverside was the most numerous fluctuations in catch of the dominant species, fish impinged (6,%9), followed by grubby (5,010), Atlantic silverside. Winter flounder and rainbow hake sp. (5,019), windowpane (2,606), and winter smelt were most common at S3, whereas killifish flounder (2,580). These five species represented were most abundant at S1 and S2, with few taken 63% of the total estimated impingement at at S3, likely due to salinity and temperature Seabrook Station (Appendix Table 5-3). preferences. The majority of the Atlantic silverside impinge-5.3.2.4 Impingement ment occurred during the winter. This fish is extremely numerous in New England estuaries and Seabrook Station operated throughout 1995, with is found occasionally in otter trawls and rarely in monthly average circulating water flow ranging gill net samples (Appendix Table 5-1). Atlantic from 287 to 687 million gallons / day (Table 5-11). silverside leave estuaries in the winter as During 1995, an estimated 15,932 fish, American temperatures drop and overwinter in waters less lobster, and seals were impinged (Table 5-11). than 40 m deep (Conover and Murawski 1982). Most (42%) fish were collected in February, These fish were probably impinged during their followed by December (14%) and October (12%). winter offshore movement. Impingement in the fall and winter usually () increased due to northeast storms (NAI and NUS In 1995, the first full year of accurate impingement 1994). data, grubby were the most numerous fish impinged, followed by hake sp., Atlantic Accurate counts of impingement have been made silverside, American sand lance, and rock gunnel. at Seabrook Station since October 1994 (NAI Grubby were most common in impingement 1995). Prior to that time impingement samples samples during January through March and were soned by plant personnel and small fish were December (Table 5-11). Grubby were not not completely removed from impingement common in trawl samples at any time during the debris, resulting in underestimates due to the year and their abundance in impingement samples incomplete sorting. Starting in October 1994, durmg the winter may be related to storm activity. NAESCO biologists were responsible for the sorting of samples and identification of fishes, and As with grubby and Atlantic silverside, American impingement estimates are believed to be more sand lance were most common in impingement accurate since that time. Impingement estimates in samples during January through Msren and last quarter of 1994 and all of 1995 are December 1995 (Table 5-11). The abundance of substanually higher than previous years, primarily these species in the winter months may be related due to the increased efficiency of sample sorting to an offshore movement through the intake area as j rather than a genuine increase in impingement. nearshore water cools, and increased storm activity that appears to make fish more vulnerable to l Despite the increased efficiency of sample sorting, impingement. I the total number of organisms impinged in 1995 5-30
Table 5-11. Species Composition and Total Number of Finfish, American Lobster and Seals Impinged at Seabrook Station by Month During 1995". Seabrook Operational Report 1995. Species January February . March April - May June July August Septernber October November December Total Percent Grubby 145 892 875 84 13 10 5 7 0 10 2 372 2415 15.2 IIake sp. 25 424 9 2 0 0 4 7 236 800 268 422 2197 13.8 Atlantic silverside 90 1077 75 0 0 0 0 0 5 0 4 370 1621 10.2 American sand lance 43 1078 44 3 0 0 0 0 0 0 0 156 1324 8.3 Rock gunnel 16 21 151 751 55 13 4 92 42 119 28 6 1298 8.1 Winter flounder 22 967 69 6 7 0 0 3 0 0 4 93 1171 7.3 Yellowtail flounder 17 1066 58 2 0 0 0 3 0 0 2 I 1849 7.2 Windowpane 16 539 48 0 5 2 0 12 26 207 25 63 943 5.9 Pollock 2 'O I 1 0 156 43 7 % 120 11 462 899 5.6 Northern pipensh 3 0 1 116 26 4 0 6 61 281 66 15 579 3.6 Cunner 0 2 6 3 28 51 23 79 75 61 8 6 342 2.1 Iterring family I 3 2 0 5 0 0 13 51 138 10 8 231 1.4 Rainbow smelt 12 151 16 0 0 0 4 4 8 18 0 0 213 1.3 Lumprish 0 38 24 35 20 43 17 12 I O O O 190 1.2 Longhorn sculpin 7 102 0 0 9 1 0 2 0 18 2 24 165 1.0 Seasnait sp. I 54 29 1 0 0 0 0 3 26 21 30 165 1.0 Skate sp. 17 74 9 0 2 I I 8 1 3 6 35 157 1.0 Shorthorn sculpin 2 68 19 33 12 5 10 0 5 0 0 2 156 1.0 Threespine stickleback 4 77 23 0 0 0 0 0 0 0 17 34 155 1.0 Sea raven 3 3 1 3 6 12 12 24 19 21 4 17 125 0.8 Atlantic cod 7 6 5 4 41 5 3 3 3 16 0 26 119 0.7 Radiated shanny 0 54 17 9 5 0 0 0 0 0 0 7 92 06 Silver hake 0 0 0 0 0 0 0 0 0 , 25 15 l 9 49 0.3 (continu
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1 l 5.0 FISH Hakes were identified to the species level starting Several hundred Atlantic herring larvae were in July 1995 and comprise primarily red and white observed in screen wash debris on April 3,1995 hake. To maintain the same level of taxonomic during an impingement assessment. These larvae consister.cy throughout the year, red and white were approximately 1-2 cm in length. Other hake were pooled into the " hake sp." category. observations of fish larvae were made during the Based on the known depth distribution of these year; however, data regarding fish larvae observed fishes, the species composition in trawl catches, during impingement assessments are not included and impingement samples after June, the majority in the impingement monitoring program. Station of the hakes impinged were probably red hake, impacts to fish larvae are assessed by the which tend to be more common in inshore waters entrainment sampling program. Fish larvae would than white hake (Musick 1974). Impingement of not normally be observed in impingement samples hakes was highest in September through because they are too small to be impinged by the December, and February (Table 5-11). Red hake traveling screens (3/8" mesh). However, when spawn in the Gulf of Maine at temperatures seaweed accumulates on the traveling screens, this between 5 and 10*C in the fall and winter at depths condition can allow fish larvae to be collected on less than 55 m (Musick 1974). Juvenile red hake the screens along with the seaweed. are common in inshore waters, including shallower harbors and bays (Bigelow and Schroeder 1953). The number of fish impinged annually at Seabrook By autumn immature fish move to deeper waters as Station may be compared to collections or annual temperatures fall below 4*C. Impingement of estimates made at other large power plants in New hakes at Seabrook Station may occur as juveniles England with marine intakes (Table 5-12). From begin to move offshore past the intakes in the November 1972 through October 1977, nearly colder months. 300,000 fish weighing 3,040 kg were collected in I 215 24-h samples of impingement at the Maine 1 Impingement of rock gunnel was also highest Yankee Nuclear Generating Station (Evans 1978). i during the winter months, but was more consistent The mean number of fish collected each year was each month compared to the other commonly approximately 60,000 fish during this period, with impinged fish (Table 5-11). Rock gunnel prefer an average of 1,395 fish impinged per sampling gravelly or stony substrate, including shell beds, day. Most fish were collected from November and are not common on muddy bottoms (Bigelow through April, when water temperatures were less and Schroeder 1953). The intake structure and than 10*C Sticklebacks (four species), smooth associated rip-rap and mussel shell beds may flounder, alewife, rainbow smelt, Atlantic l provide a locahzed habitat for this fish, resulting in menhaden, winter flounder, and white perch j relatively consistent monthly impingement. dominated impingement samples, indicative of this power plant's location within the Sheepscot River With the exception of Atlantic silverside, the estuary. No lobster were impinged at Maine majority of the fishes impinged were demersal. Yankee, Few pelagic fishes such as Atlantic herring, Atlantic mackerel, alewife, and blueback herring At Pilgrim Nuclear Power Station, sited on are impinged as Seabrook Station, even though the Massachusetts Bay, an estimated annual average of plant draws water from mid-depths. 20,029 fish (adjusted for 100% plant operation) l 5-33
p em V U bm Table 5-12. Comparison of Fish Impingement Estimates at Selected New England Power Plants with Marine Intakes. Seabrook Operational Report,1995. SOURCE RA*IED NOMINAL COOLING YEARS MEAN RANGE FOR MEAN WATER CAPACITY WATER FLOW OF ANNUAL CV ANNUAL NUMBER STATION BODY (Mwe) (ni'esec*) STUDY IMPINGEMENT (%) ESTIMATES PER DAY REFERENCE Seabrook Gulf of Maine 1,150 31.5 1995' 15,932' 15932 44 - Maine Yankee Montsweag Bay 855 26.6 1972-77 59,999' 34 31,246-73,420" 1,395 Evans (1978) Pilgrim Massachusetts Bay 670 20.3 1974-94 20.029* 115 1,143-87,752' 55 Anderson (1995) Erayton Point 1-3 Mount IIope Bay 1,150 39.0 1972-92 54,433 136 15,957-359,394 I18 MRI(1993s) Brayton Point 4 Mount llope Bay 460 16.4 1984-85 - - 1,479-18,095 - LMS (1987) 25,927' d Millstone 2 Imng Island Sound 870 34.6 1976-87 59 8,560-60,410 71 NUSCO (1988) Y 65,927* 214 8,560-511,387* 181 Impingement counts prior to October 1994 were underestimated.
- Collected in sampling only, not a calculated annual estimate (11.8% of the total days were sampled).
Estimates adjusted assuming 100% station operation.
- Excluding an estimated 480,000 American sand lance taken on July 18,1984.
Including the sand lance mass impingement episode,
- 5.0 FISH l
was calculated for a 20-yr period (Anderson 1995; largest annual total was 60,410 and the annual i Table 5-12). The mean impingement rate was 55 mean impingement was 25,927 (71 fish per day). I I fish per day. During this period, catch was Impingement samples at Millstone Unit 2 were dominated mostly by Atlantic silverside, with dominated by winter flounder, anchovies, grubby, rainbow smelt, herrings, and cunner occasionally silversides, and Atlantic tomcod. Annual j abundant in samples. In 1994, 97 American impingement estimates for American lobster I lobster were collected, giving an estimated total ranged from 261 to 1,167, with an annual mean of impingement of 1,152 lobster for 100% station 634 (CV = 14%). operation, which was a higher estimate than for l most other years of Pilgrim Station operation Impingement estimates at Seabrook Station were I (Anderson 1995). apparently less than those at comparable electrical generating stations in New England. Impingement In 21 years of study, the average number of fish at a power plant does not reflect absolute fish impinged annually was 54,433 at the Brayton Point abundance near the station, but is related to the l Station (Units 1-3), located on Mount Hope Bay in susceptibility of a species to entrapment, intake ) Massachusetts (MRI 1993a; Table 5-12). Atlantic design and location, plant operating characteristics, menhaden, winter flounder, Atlantic silverside, environmental variables (e.g., water temperature, hogchoker, alewife, silver hake, and threespine wave height, wind direction and velocity), and i 1 stickleback were most often impinged. Fish were time of day (Landry and Strawn 1974; Grimes j impinged at an average rate of 118 per day. In a 1975; Lifton and Storr 1978). The design of ) study to determine the effectiveness of angled Seabrook Station offshore intake with a mid-water screens at Brayton Point Unit 4 (LMS 1987), total entrance and a velocity cap located in a relatively numbers of fish collected on the screens were open water body has apparently been successful at 18,095 in 1985 and 1,449 in 1986. These numbers reducing the impingement of fish and lobster. from the angled screen study represented fish Except for pollock and Atlantic silverside, the fish actually collected and no annual estimates were most often impinged are demersal species. This determined in this study. Bay anchovy made up indicates that some features of the intake, as well most (77%) of the catch in 1985; Atlantic sil- as fish behavior and distribution, allow for the verside, northern pipefish, winter flounder, entrapment of bottom-dwelling species under butterfish, and tautog were also relatively certain conditions. The magnitude of impingement common. at Seabrook Station appears to be affected primanly by storms, parucularly northeasters (NAI Impingement sampling was conducted from 1976 1993). A similar phenomenon was noted at through 1987 at Millstone Nuclear Power Station Millstone Nuclear Power Station, where large Unit 2, located on Long Island Sound (NUSCO winter flounder impingement episodes were found 1988). Annual impingement estimates for fish to be related to a combination of high sustained ranged 8,560 to 511,387 (Table 5-12). The wind and low water temperatures (NUSCO 1987). highest estimate, however, was skewed by a Storm events have also increased impingement at single-day catch of approximately 480,000 other estuarine (Thomas and Miller 1976) and American sandlance. Excluding this catch, the freshwater (Lifton and Storr 1978) power plants. 5-35
5.0 FISH I,,T Impingement of Seals tidal or current), with demersal adhesive eggs deposited on marine vegetation or substrata free In addition to the fishes, six seals, probably harbor from silting (Haegele and Schweigert 1985). A seals, were impinged in 1995. This is the same major spawning area and source of larvae in the number as impinged in 1994, and an increase over western Gulf of Maine is Jeffreys Ledge ; 1993 when one seal was impinged. The population (Townsend 1992), although other banks and ledges of harbor seals in New England is increasing, in this area are also used (Boyar et al.1971). which may account for the increase in seal Other major spawning grounds include Georges impingement. A recent study showed that the Bank and coastal areas of central and eastern i population of harbor seals in southern Maine and ' Maine and Nova Scotia (Sinclair and lies 1985). New Hampshire (Isle of Shoals to Pemaquid Point) has nearly doubled since 1986 (Kenney and Gilbert Currently, the median age and size of maturity for 1994). Harbor seals migrate to the warmer waters U.S. coastal Atlantic herring is about 3 years and of Massachusetts, Rhode Island and New York in 25 cm (O'Brien et al.1993); all fish become l the fall, returning to northern waters in April mature by age-5 (NOAA 1993). Most spawning in i (Payne and Selzer 1989 cited in Gilbert 1994). the western Gulf of Maine occurs during Increased number of seals passing through New September and October (Lazzari and Stevenson Hampshire waters increase the probability of 1993). The early life history of Atlantic herring is contact with the intake structure. somewhat unique among other northern temperate
, fishes in that the larval stage is up to eight months
) 5.3.3 Selected Species old before metamorphosis to a juvenile phase (Sinclair and Tremblay 1984). Larvae hatched 5.3.3.1 Atlantic Herrine early in the season grow faster than those hatched late (Jones 1985). Larval mortality is generally The Atlantic herring ranges in the Northwest highest in fall, low in winter, and increases again Atlantic Ocean from western Greenland to Cape in spring (Graham et al.1972). Larvae tend to Hatteras (Scott and Scott 1988). Separate drift or disperse from offshore spawning grounds spawning aggregations associated with particular into coastal bays and estuaries for further develop-geographic areas in the Gulf of Maine have been ment and transformation to the juvenile phase of recognized (Anthony and Boyar 1%8; Iles and life. After metamorphosis, juveniles remain in Sinclair 1982; Sinclair and lies 1985) and tagging coastal waters during summer. Adults tend to be studies have shown high (> 90%) homing fidelity found in specific summer feeding areas that are of spawning herring (Wheeler and Winters 1984). located near tidally-induced temperature fronts, However, a lack of evidence exists for where plankton productivity is high, and they biochemical, genetic, and morphometric overwinter after spawning in areas with slower differentiation among these spawning groups currents than found elsewhere in the Gulf of Maine (Kornfield and Bogdanowicz 1987; Safford and (Sinclair and lies 1985).
Booke 1992), indicating that there is enough gene flow to prevent the evolution of genetically distinct Graham (1982) hypothesized that year-class stocks. Atlantic herring spawning grounds are strength was determined by a density-dependent (] V typically located in high energy environments (i.e., mortality phase in fall and a density-independent 5-36
l 5.0 FISH phase in winter, both of which may be affected by Atlantic herring eggs have not been identified in j the time of spawning and larval distribution any ichthyoplankton collections for Seabrook i following hatching and dispersion. However, Station studies, probably because they are demersal herring recruitment is a complex interaction among and adhesive. The larval stage was prevalent and many critical factors, which may differ from year typically occurred during an extended period from to year (Campbell and Graham 1991). A series of October through May. Peak abundance was found successive cohorts in space and time may help to during the fall spawning season, from October limit intraspecific competition and mortality through December (NAI 1993). Larval densities (Lambert 1984; Lambert and Ware 1984; in 1995 were the highest observed during the Rosenberg and Doyle 1986). An inverse operational period (Table 5-13; Figure 5-8). A relationship was found between year-class strength large decline occurred during the preoperational and temperature during the late larval and early period at all three ichthyoplankton stations during juvenile phases (Anthony and Fogarty 1985). the late 1970s and again during a similar period in Survival may be related to the rate at which the 1980s, prior to the operation of Seabrook temperature decreases in winter as well as to the Station (Figure 5-8). Since 1989, annual absolute minimum temperatures (Graham et al. abundance has remained relatively stable. Larval 1990). Low temperatures may also indirectly density in the operational period was significantly increase starvation and vulnerability to predation. lower than in the preoperational period (Table 5-Pedersen (1994) found that survival and larval 14), primarily due to declines in density that be'gan length was related to changes in food availability. during the preoperational period. During the Larvae exposed to varying prey abundance grew period when all three stations were sampled (1986-less and had lower survival than larvae exposed to 94), similar densities were collected at the three a continuously high ration. stations. This was substantiated by the ANOVA results, which showed no significant differences Abundance and landings of Atlantic herring have detected among stations (Table 5-14). fluctuated considerably over the past 35 years (NOAA 1995). During this period, the fishery in As pelagic fish, large juvenile and adult Atlantic Maine has also changed from predominantly fixed herring were collected during Seabrook Station gear to almost all mobile gear in recent years, due studies primarily by gill net. Catches were highest to the decreased availability of fish in nearshore in spring and fall, with few taken during July and areas. The Atlantic herring fishery on Georges August (NAI 1993). Abundance of Atlantic hening Bank peaked at 373,600 metric tons in 1960, but was extremely variable in the later 1970s and has collapsed to 43,500 metric tons in 1976. Recent been relatively stable since 1981. Annual uxhcations are that the population on Georges Bank abundance was highest in 1976 through 1979, and is recovering (Stephenson and Kornfield 1990; remamed at relatively low levels from 1981 through Smith and Morse 1993). Present biomass levels the present (Figure 5-8). The high abundance in the have not exceeded pre-collapse levels, but without early preoperational period is reflected in the an offshore fishery to provide long-term catch ANOVA results where CPUE in the preoperational data, present estimates of stock levels, although period was significantly higher than the operational large, are imprecise (NOAA 1995). period (Table 5-14). The Preop-Op X Station in-5-37
S.0 FISH m Table 5-13. Geometric Mean Catch per Unit Effort (Number per 1000 m') with Coefficient of Variation (CV) by Station (P2, PS, and P7) and All Stations Combined for Selected Lan'al S)3ecies Collected in Ichthyoplankton Samples During the Preoperational and Operational Periods and in 1995. Seabrook Operational Report,1995. PREOPERATIONAL PERIOD * . 1995* OPERATIONAL PERIOD
- SPECIES STATION MEAN CV MEAN MEAN - CV American sand lance P2 159.6 14 89.2 123.5 14 (Jan-Apr) P5 225.4 14 141.7 186.4 14 P7 106.0 16 92.7 119.6 16 l All stations 162.5 13 105.4 140.1 13 l l
Winter flounder P2 12.1 19 3.5 5.4 19 (Apr-Jul) P5 10.5 18 6.5 6.4 9 P7 8.0 25 1.8 2.3 45 All stations 10.8 18 3.5 4.4 10 Atlantic cod P2 2.5 63 0.5 0.7 58 , (Apr-Jul) P5 2.4 80 1.1 0.9 $6 I P7 1.0 73 0.5 0.6 24 All stations 2.3 63 0.7 0.7 45 Yellowtail flounder P2 3.4 50 1.5 1.5 57 (May-Aug) P5 5.0 32 1.8 1.9 50 P7 2.9 44 0.7 1.5 36 All stations 3.8 39 1.3 1.6 40 Atlantic mackerel P2 6.9 31 12.0 7.0 46 (May-Aug) P5 6.8 50 8.8 5.4 43 P7 5.9 21 12.0 7.2 41 All stations 6.9 32 10.8 6.5 43 Cunner P2 48.5 22 441.4 76.7 38 (Jun-Sept) P5 55.0 29 308.2 58.6 36 P7 59.0 23 163.0 74.4 32 All stations 48.8 23 281.0 68.6 35 Haked P2 3.9 43 123.7 3.3 75 (Jul-Sept) P5 3.1 50 17.6 3.8 76 P7 3.9 48 5.4 3.6 80 All stations 4.0 39 10.7 3.6 73 Atlantic herring P2 29.0 34 17.2 7.8 34 (Oct-Dec) P5 28.8 40 17.4 9.8 22 P7 33.2 22 30.8 11.0 30 All stations 29.2 32 21.0 9.4 26 Pollock P2 6.3 50 0.4* 0.8 28 (Nov-Feb) P5 8.2 52 0.2 1.1 50 P7 2.4 50 0.2 0.6 55 All stations 6.8 49 0.2 0.8 41
- Preoperational: July 1975-July 1990 (in some years not all three
- May include red hake, white hake, spotted hake, or more than one
[3 ( stations were sampled); geometric mean of annual means.
- Geometric mean of the 1995 data.
of these species.
' Annual geometric mean for pollock in 1995 includes November
' Operational: August 1990-December 1995; geometric mean of through December of 1994, and January through February 1995.
annual means. 5-38
i 5.0 FISH Ichthyoplankton Oct - Dec 200 ____.p, l .. ....ps s
\ l ~ Oem 1e0 - ~ l
\ l i 140 l
g er.operationai i i operationes 8 120 l 9 l i
@ 100 l 80 l
. I
/\ l l 80 ,V
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75 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 S3 94 95 vem Gill net 7 i 1 m c2 8 c3 8 I I I 5 t l 4 . g l
. /<x s i 3 g Preoperatonal l Operabonal
\, i h2 s l
1 r.
\'
l I
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75 78 77 78 79 80 81 82 83 84 85 80 87 88 89 90 91 92 93 94 95 vse Figure 5-8. Annual geometric mean catch of Atlantic herring per unit effort in ichthyoplankton number per 1000 cubic meters) and gill net (number per 24-h set) samples by station and the mean of all stations, 1975 1995. 5-39
m p d ) b Table 5-14. Results of Analysis of Variance for Atlantic Herring Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM / . SOURCE OF VARIATION df- MS F - MULTIPLE COMPARISONS MONTHS USED OF ADJUSTED MEANS8 Ichthyoplankton Preop-Op* 1 2239 56.02 "
- Op< Preop (Oct.-Dec.) Year (Preop Opf 8 3.85 922* "
(1986-1995) Month (Yearf 20 3.67 9.79"* d Station 2 035 0.83 NS Preop-Op X Station' 2 0.17 0.41 NS Error 311 0.42 Gillnet Preopop' 1 635 17537"* Op< Preop (Sep.-May) Year (Preop-Op) 18 1.55 42.74 " * (1976-1995) Month (Year) 159 031 8.43 * " Station 2 0.10 2.59 NS Preop Op X Station 2 0.02 0.49 NS ' Error 354 0.04
- Preop-Op compares 1990-1995 to 1986-1989 regardless of station. NS= Not significant (p>0.05)
- Year nested within preoperational and operational periods regardless of station. *
= Significant (0.05> p>0.01) ' Month nested within Year. " - liighly significant (0.0l > p>0.001)
- Stations regardless ofyear or period. "* - Very highly signifkant (0.00l > p)
- Interaction of the two main efTects, Preop-Op and Station.
'Preopop compares 1990-1995 to 1976-1990, regardless of station.
- Waller-Duncan multiple means comparison test used for significant main efTects. LS Means used for interaction term.
G
5.0 FISH teraction tems was not significant indicating that all appear to be less available to the nearshore fixed three stations showed similar trends among years gear fishery along the coast of Maine (NOAA and abundance was not affected by the operation of 1995). The recovery on Georges Bank appears to Seabrook Station (Table 5-14; Figure 5-8). be related to the lack of commercial fishing pressure in recent years (NOAA 1993). The stock Atlantic herring, alewife, and blueback herring may have re-established itself from a remnant make up the taxonomic category " herring family" population of fish that remained on the bank in the impingement assessment (Table 5-11). (Stephenson and Kornfield 1990) or by Based on the temporal distribution of herrings, recolonization from other spawning grounds off Atlantic herring were likely to have been the Southern New England (Smith and Morse 1993). primary species impinged in the first half of the year. An estimated 231 herring were impinged at 5.3.3.2 Rainbow Smelt ] I Seabrook Station in 1995. Even if all of these are assumed to have been Atlantic herring, the loss of The anadromous rainbow smelt occurs from 231 fish is not likely to affect the Atlantic herring Labrador to New Jersey (Scott and Crossman resource in the study area. 1973). It serves as forage for fish, birds, and seals j and supports minor sport and commercial fisheries Entrainment and impingement of Atlantic herring in New England and Canada. A small(maximum appeared to have a small effect on local size of about 35 cm) pelagic schooling species, it l populations. Atlantic herring accounted for is readily available for sampling because it is j slightly less than 10% of larvae identified in mostly found in shallow, coastal waters. Adults l entrainment samples in 1995, with an estimated begin to mature at ages 1 and 2 and live about five total of 11.2 million entrained (Table 5-5); years (Murawski and Cole 1978, Lawton et al. j however entrainment of Atlantic herring larvae is 1990). Adults enter estuaries in fall and winter I a relatively small impact given that these larvae are and spawn in spring after ascending brooks or likely drawn from the progeny of large spawning streams to the head of tide. Spawning usually groups in the Gulf of Maine that disperse widely peaks with the bimonthly spring tides (Buckley throughout the area over the course of a lengthy 1989). Fecundity ranges from approximately larval developmental period. 1000-73,000 eggs per female (Clayton 1976, ll Lawton et al.1990). Spawning in the Jones River, The ANOVA interaction terms for both the MA commenced when water temperature was ichthyoplankton and gill net programs were not about 4*C (Lawton et al.1990). Most of the significant, which indicated that the operation of spawners in this river were age-2 and the abun-Seabrook Station has not affected the local dance of this age-class considerably affected abundance or distribution of Atlantic herring. spawning stock size. Eggs range in size from 0.9-Even though the Georges Bank-Gulf of Maine 1.2 mm, and attach to rocks, gravel, vegetation, or herring biomass has increased in recent years to each other (Bigelow atxl Schroeder 1953). Larvae relatively high levels (NOAA 1995), recovery has hatch at about 5 mm in length and grow to about not yet occurred in the Hampton-Seabrook area to 63 mm by November (Scott and Scott 1988). former levels of abundance. This is probably a Larvae hatch at night (24-hour periodicity) coast-wide phenomenon, as Atlantic herring also independent of water temperature or stream 5-41
5.0 FISH p) hydrodynamics and are carried down to estuaries, resulting from larger-than-average adult spawning as no larvae are retained on the spawning grounds stocks of the previous year. Historically most (Ouellet and Dodson 1985a, b). In the St. rainbow smelt were taken at S3, although none Lawrence River, smelt larvae are mostly found in were captured at any station in 1995. There were the maximum turbidity zone of that estuary no significant differences in seine catches between (Laprise and Dodson 1989; Dodson et al.1989). the preoperational and operational periods (Table 5-15), probably due to the high variability in Stocks of rainbow smelt are localized to some CPUE during the preoperational period, and the extent, which would be important for impact interaction term was not significant. assessment. Although adults of three geographical groups of rainbow smelt in estuarine waters of The results from the ANOVA indicated that trawl Quebec did not home to specific spawning rivers catches varied significantly among stations between (Frechet et al.1983), nor did fish among three the preoperational and operational periods, different streams of the Parker River, MA estuary resulting in a significant Preop-Op X Station (Murawski et al. 1980), other isolating interaction term (Table 5-15). CPUE decreased mechanisms apparently limit gene flow. A between the preoperational and operational periods probable means is the ability of larvae to retain at all stations, but the decrease was greatest at themselves in estuarine areas by using active Station T2 (Figure 5-10). Mean CPUE was vertical migration in relation to tides (Ouellet and highest at Stadon T2 during the preoperational Dodson 1985a, Laprise and Dodson 1989). period, but d2 ring the (prational period CPUE d was lowest at T2 (Figure 5-10). Near Seabrook Station, rainbow smelt were collected by otter trawl mostly from December There are no apparent reasons for the more through April (NAI 1993), which corresponds to pronounced decrease in CPUE of rainbow smelt at the winter-spring spawning run. The annual T2 between the preoperational and operational geometric mean CPUE peaked in 1989 in the late periods. No trends were evident at any of the preoperational period, and has steadily declined stations during the preoperational period that could throughout the operational period (Figure 5-9). confound the analysis, as shown by the non-Catches were generally highest and most variable significant Year X Station interaction term for the at Station T2, off the mouth of Hampton-Seabrook preoperational period only (Table 5-15). The Harbor. Stations generally showed similar trends preoperational mean at T2 was higher than at the in CPUE, especially after 1985. other stations because it was strongly influenced by high annual means during 1978,1981,1983, and The annual geometric mean CPUE for seine 1988, which were followed by large declines. A sampling was also highly variable, especially at sharp decline in rainbow smelt CPUE at Station T2 Station S3 (Figure 5-9). The largest annual seine began in 1989 prior to the beginning of plant CPUE values occurred in 1979 and 1990, one year operation. The current low CPUE in the after cyclical peaks were observed in trawl operational period at Station T2 is similar to those catches. As seine sampling occurs from April at the other stations and may be a reflection of the p b) through November, these catches may have high natural variability. corresponded to increased numbers of age-1 fish 5-42
5.0 FISH Trawl 5.5 1 ___ n 1 ....... T2 5.0 T3 f
- MEAN g
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Operational g . 1.0 '/ N,/Ng \ \i 0.5 / N N. 0.0 75 76 77 78 79 80 81 82 63 84 85 80 87 68 89 90 91 92 93 94 95 vem Seine 4.5 i i _ i i ........, I i 33 4.0 I
--.-* MEAN l
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O.6 Not Sampled g a, ~~ % . ~ _ n -- -- ...- l - 75 7e n 7e 79 ao et at as a4 e5 es e7 as se no ei a2 as e4 es vem Figure 5-9. Annual geometric mean catch of rainbow smelt per unit effort in trawl (number per 10-min tow) and seine (number per haul) samples by station and the mean of all stations, 1986-1995 (data between two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 5-43
-~
,y G J w i Table 5-15. Results of Analysis of Variance for Rainbow Smelt Densities by Sampling Program.
Seabrook Operational Report,1995. PROGRAM / . . . MULTIPLE COMPARISONS MONTHS USED SOURCE OF VARIATION df MS ' F OF ADJUSTED MEANS8 Seine Preop-Op* 1 0.06 0.95 NS (Apr-Nov) Year (Preop-Op) 16 0.12 1.73* (1976-1995) Month (Year) 123 0.09 1.40* Station 2 0.61 9.21 "
- Non-est Preop-Op X Station 2 0.15 2.29 NS S3 S2.E.L Dror 278 0.07 Trawl Preop-Op* 1 732 94.25 "
- Op< Preop (Nov-May) Year (Preop Op)* 18 0.69 8.83 * * *
(1975-1995) Month (Year)* 120 0.53 6.80"
- Station' 2 034 436* T2>TI>T3 w Preopop X Station' 2 0.40 5.11 " 2 Pre IPre 3 Pre 10o 200 300 g Error 274 0.08 Trawl Year 14 0.80 835'"
(Nov-May Month (Year) 90 0.66 6.93 * " Preop only) Station 2 1A6 15.23* " Year X Station 28 0.07 0.71 Error 179 0.10
- Preop-Op compares 1990-1995 to 1976-1984 and 1986-1989) regardless of station.
- Preo@ compares 1990-1995 to 1986-1990 regardless of station. NS - Not significant (p>0.05)
- Year nested 'vithin preoperational and operational periods regardless of station. = Significant (0.05> p>0.01)
- Month nested within Year. " - Highly significant (0.012 p>0.001)
' Stations regardless of year or period. "* - Very highly significant (0.001 ap)
' Interaction of the two main effects, Prrop-Op and Station. -
Duncan-Walter multiple means comparison test used for significant main effects. LS Means used for interaction term. i 1
5.0 FISH 1.0 y
. - - + T2 0.9 -*- -* -* T3 1
0.8 k 0.7 [g 0.6 * .. s ' . ,, .... E05 .. ,, g_ ~s~ .. 0.3 0.2
~%'~(..
0.1 0.0 Preop- m a w op-mow PERIOD Figure 5-10. A comparison among stations of the mean loggX+ 1) CPUE (number per 10 minute tow) of rainbow smelt caught by trawl during the preoperational(November 1975 - May 1990) and operational (November 1990 - May 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-15). Seabrook Operational Report,1995. The abundance of rainbow smelt is potentially likely to significantly affect population levels of influenced through impingement and entrainment. rainbow smelt. It is unlikely that operation of Rainbow smelt spawn in the estuary, and the Seabrook Station has affected rainbow smelt adhesive eggs remain in the estuary and are not abundance because rainbow smelt are primarily an subject to entrainment. Beause of the behavior estuarine or nearshore fish, adults and larvae have and specific life history of the rainbow smelt, no not been numerous in impingement or entrainment eggs and few larvae (0.03% of all larvae in all samples, and the estuarine seine sampling did not offshore samples) have been collected in the indicate any plant impact. ichthyoplankton sampling program. Larvae also are primarily estuarine and are not subject to a 5.3.3.3 Atlantic Cod large degree of entrainment through the offshore intakes. Larvae have only been collected in The Atlantic cod is found in the Northwest Atlantic entrainment samples in 1990 and 1992, accounting Ocean from Greenland to Cape Hatteras and is one for a total entrainment estimate of about 300,000 of the most important commercial and recreational larvae since the beginmng of plant operation (Table fishes of the United States. The highly predatory, 5-6). An estimated 213 rainbow smelt were omnivorous cod can commonly achieve a length of impinged in 1995 (Appendix Table 5-2). These 130 cm, a weight of up to 25-35 kg, and can live low levels of impingement and entrainment are not 20 years or more. However, smaller (50-60 cm, 5-45
l 5.0 FISH C '\ Q 1.1-2.3 kg, age 2-6) are more typically caught by the fisheries (Bigelow and Schroeder 1953; Scott 1988; Lough and Potter 1993). Vertical (Lough and Potter 1993) and horizontal (Suthers and Frank and Scott 1988; NOAA 1995). The Atlantic cod is 1989) movements become less extensive with age a cool-water fish, and is found and spawns at and larger (> 20 mm) pelagic juveniles occur at
- temperatures from about -1 to 10'C; distribution is greater depths than larvae. By summer, juveniles also influenced by time of year, geographical 40 mm or larger make the transition from a pelagic location, and fish size Dean 1964; Scott and Scott to a demersal habitat. This transition can occur 1988: Branden and Hurley 1992). Many separate over a relatively large size range (40-100 mm) groups spawning at different locations have been over a 1-2 month period and even demersal noted in the northwest Atlantic, but for manage- juveniles may move 3-5 m off the bottom at night ment purposes two stocks (Gulf of Maine, and (Lough and Potter 1993).
Georges Bank and South) are recognized in U.S. waters (NOAA 1993). Spatial distribution also changes with age, as cod of ages 1-2,3, and 4+ in Southern New England Atlantic cod mature between ages 2 and 4, with and on Georges Bank were distributed at different age and size of 50% maturity of 2.1-2.3 years and depths during spring (Wigley and Serchuk 1992). 32-36 cm for Gulf of Maine fish (O'Brien et al. Seasonal distribution shifts are likely associated 1993). Fecurdity can be quite high, with 0.2 to 12 with water temperature. Suthers and Frank (1989) million eggs spawned per female (Powles 1958). noted that nearshore waters of Nova Scotia fm Spawmng can take place from late fall through contained high densities of young cod and may spring, but typically peaks in late winter and early serve as an important nursery area for fish spring (O'Brien et al.1993). In the northwest originating from offshore spawning sites.
- Atlantic, spawning takes place on the continental shelf in areas where eggs and larvae are likely to The success of cod year-classes in the Northwest be retained on the shelf (Hutchings et al.1993). Atlantic Ocean exhibit periodicities of 10 to 20 The timing of cod spawning varied among years, years, and there was little evidence that the annual l and could be accelerated by exposure to warm reproductive output of adult spawners was i
slope waters or delayed by exposure to cold shelf significantly related to year-class success (Koslow water (Hutchings and Myers 1994). Older and Silvert 1987). Year-class success tended to be individuals of both sexes initiated and completed statistically associated with large-scale j spawmng later, and spawneci for a longer period of meteorological patterns. Campana et al. (1989) time, than younger individuals (Hutchings and also did not find evidence that cod year-class i I Myers 1993). The 1.2-1.6-mm diameter egg is strength was related to egg or larval abundance, pelagic. In well-mixed waters the eggs and larvae but was related to abundance of both pelagic and are distributed throughout the water column demersaljuveniles. Sources of mortality were not (Imugh and Potter 1993). However, when lengths identified, but the mortality between the larval and reach 6 to 8 mm, larvae develop a diel behavior, juvenile stages was inversely correlated to year-During the day, larvae are found predominantly class strength. Timing of local physical and near the bottom and at night from mid-depths to biological events were thought to be imputant for )
, O the surface in unstratified waters and at the recruitment success. Brander and Hurley (1992) thennocline in stratified waters (Perry and Nielsen found that cod spawning during spring moved 5-46
5.0 FISH progressively later from southwest to northeast in Atlantic cod larvae typically exhibited a bimodal Nova Scotia waters and matched peak abundance annual occurrence, with one peak from November of the copepod Calanusfinmarchicus, through February and a second, larger peak from April through July (NA1 1993). To compare Because of its long history of exploitation, fishing abundances among years and stations, only data mortality has also played a key role in determining from April through July were used. There was a Atlantic cod abundance. Annual sport and decrease in larval densities during the 1970s, but commercial landings for the Gulf of Maine annual abundances have remained relatively stable averaged about 13,600 metric tons during 1974-83 and very similar at all stations from 1982 to the and 12,500 metric tons for 1984-89, but rose to present (Figure 5-11). This decrease in 18,700 metric tons in 1990 and to a record 20,300 abundance, although not statistically significant metric tons in 1991 (NOAA 1995). Landings (Table 5-16), was evident in the comparison of decreased 11,900 metric tons in 1992 and 11,000 preoperational and operational geometric means metric tons in 1993. The catch in 1993 was (Table 5-13), but the decline occurred about 10 dominated by the weak 1990 year-class and years before plant operation. The Preop-Op X survivors of the strong 1987 year-class. Station term was not significant, indicating that Recruitment since 1988 has been average or below trends among station were consistent between the average and spawmng stock biomass is expected to preoperational and operational periods, and there remain at record low levels. Because of declining was no effect due to Seabrook Station. stock biomass and continued high rates of fishing, the Gulf of Maine Atlantic cod stock is considered At Seabrook Station, larger Atlantic cod were overexploited (NOAA 1995), taken year-round by the trawl sampling program, but consistent with their annual movements, Atlantic cod eggs in ichthyoplankton collections catches were highest in spring and fall and lowest were usually grouped as Atlantic cod / haddock in summer (NAI 1993). Annual geometric mean because it was difficult to distinguish between these CPUE was nearly always greater at the two two species; this aggregation also included witch farfield stations (particularly T3) than at the flounder eggs. These taxa have been dominant nearfield Station T2 (Figure 5-11). This was during the winter and early spring (Table 5-3). attributed to differences in habitat between T2 and Examination of larval data since July 1975 the other stations (NAI 1993). Overall, cod indicated that the percent composition among all abundance was relatively stable from 1978-83 and larvae collected was 0.42% for Atlantic cod, then decreased. An increase in numbers followed 0.02% for haddock, and 0.90% for witch flounder. until a peak was reached in 1988, perhaps due to Assuming a relatively similar hatching rate, it the contribution of the strong 1987 year-class. would appear that Atlantic cod and witch flounder Abundance then declined abruptly to very low eggs p.redominated in this egg group. Atlantic cod levels, particularly in 1992. However, a large eggs have also been dominant in the late fall and increase in abundance occurred in 1993, especially early winter (Table 5-3), before the spawning at T3, but abundance at T2 remained depressed. seasons of haddock and witch flounder (Bigelow In 1994 and 1995 abundances decreased sharply and Schroeder 1953). from the 1993 peak at Stations T1 and T3, and re-5-47
5.0 FISH
/"g
'Q Ichthyoplankton Apr Jul l
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. . . . ., ... ..... ...... ,.......-Q 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR Figure 5-11. Annual geometric mean catch of Atlantic cod per unit effort in ichthyoplankton ,
O V (number per1000 cubic meters) and trawl (number per 10-min tow) samples by ) station and the mean of all stations,19761994. Seabrook Operational Report,1995. 5-48
Table 5-16. Results of Analysis of Variance for Atlantic Cod Densities by Sampling Program. Seabrook Operational Report,1995.
. PROGRAM / - SOURCE OF VARIATION df. MS 'F MULTIPLE COMPARISONS MONTHS USED : OF ADJUSTED MEANS*
Ichthyoplankton Preop-Op' I 0.53 3.64 NS (Apr-Jul) Year (Preop-Opf 7 0.49 3.3 5 * * (1987-1995) Month (Year)* 27 0.63 4.33 "
- Station
- 2 0.17 1.16 NS Preop-Op X Station' 2 0.05 0.33 NS Error 374 0.15 Trawl Preop-Op' 1 7.86 141.46* " Op< Preop (Nov-Jul) Year (Preop-Op) 18 1.14 20.53 " *
(1975-1995) Month (Year) 160 0.16 2.90 * " Station 2 3.97 71.49' " T3>TI>T2 [ e Preop-Op X Station 2 0.16 2.88 NS Error 354 0.05
- Preop-Op compares 1991-1995 to 1987-1990 regardless of station. NS -Not signincant(p>0.05)
- Year nested within preoperational and operational periods regardless of station. * -Signifteant(0.052p>0.01)
- Month nested within Year. " = Ilighly signincant (0.01 ap>0.001) d Stations regardless ofyear or period. "*- Very highly significant (0.001)p)
' Interaction of the two main effects, Preop Op and Station. ' Preop-Op compares 1990-1995 to 1975-1990 regardless of station.
- Waller-Duncan multiple means comparison test used for significant main efTects. LS Means used for interaction term.
O O O
1 I 5.0 FISH mained low at T2. In agreement with this recent cod in the Gulf of Maine. Furthermore, year-class trend, CPUE in the operational period was success was apparently related to luge region ' vide significantly lower than the preoperational period events affecting survival of pelagic and demersal (Table 5-16). This decline occurred at all stations juveniles. j as indicated by the non-significant Preop-Op X l Station interaction term and was not due to the 5.3.3.4 Pollock operation of Seabrook Station. Bottom water 1 temperatures during the operational period The pollock is one of the most pelagic of all the ; increased steadily since 1990 and were gadids and is often found in large schools. It is a I significantly higher during the operational period at cool-water species, preferring water temperatures l all stations (see Section 2.0 - Water Quality). of 7.2-8.6'C and is not found in waters exceeding l Bottom water emperatures in 1995 were higher 18.3'C (Scott and Scott 1988). Pollock may reach l than both ue preoperational and operational a length of 107 cm and a weight of 32 kg. Found averages. Water temperature may have affected from southwest Greenland to Cape Lookout, NC ; inshore abundances, especially if the temperature (Bigelow and Schroeder 1953), it is most abundant at the nearfield station, even if not raised by station on the Scotian Shelf and in the Gulf of Maine operation, was above the preferred range for (NOAA 1993). Adults move into the southwestern Atlantic cod. Gulf of Maine in fall or early winter to spawn, which mostly occurs from November through O It is very likely that decreases in cod abundance February (Colton et al.1979). The median age b are due to regional declines in Atlantic cod and size of maturity for female pollock is two abundance and possibly due to a naturally- years and 39.1 cm (O'Brien et al.1993). Typical occurrmg increase in temperature. These changes of codfishes, the pollock is highly fecund with an have no relation to the operation of Seabrook average production of 225,000 eggs and with a Station. ANOVA results indicated that catch during 10.7-kg female capable of spawning over 4 million I the operational period was significantly less than eggs (Bigelow and Schroeder 1953). The pelagic during the preoperational period, and there were egg is 1.04-1.20 mm in diameter (Markle and ! no significant differences in larval density between Frost 1985) and newly-hatched larvae are 3-4 mm periods (Table 5-16). Given the reported in length (Fahay 1983). First-year growth is rapid decreases in the Gulf of Maine stock and continued and young can often be very abundant along Gulf low recruitment reported by NOAA (1995), this of Maine coastal beaches (MacDonald et al.1984), j was not unexpected for the trawl data. The rocky subtidal areas (Ojeda and
Dearborn 1990),
1 ANOVA interaction terms for both trawl and and apparently even use tide pools as a nursery ichthyoplankton data were not significant, (Moring 1990). Young grow rapidly and by fall indicating a similar pattern in unual abundance at can achieve lengths of 215 mm (Ojeda and all stations during both the preoperational and Dearborn 1990) before they move offshore for the operational periods. An estimated 119 Atlantic cod winter, were impinged at Seabrook Station in 1995 (Table 5-11). Egg and, in particular, larval entrainment Combined U.S. recreational and U.S. and has been relatively low (Table 5-6), given the high Canadian commercial landings for the Scotian L 1 fecundity and source population size of Atlantic Shelf, Gulf of Maine, and Georges Bank regions i 5-50 l
l l l l 5.0 FISH l l l increased from a yearly average of about 46,400 showed no significant differences between metric tons in 1974-83 to 68,500 metric tons by preoperational and operational periods (Table 5- l 1986 (NOAA 1995). Based on National Marine 17). ] Fisheries Service trawl surveys, biomass of pollock l in the Gulf of Maine and on Georges Bank has No changes in abundance or distribution can be decreased sharply during the 1980s from a peak in attributed to station operation. The interaction the late 1970s and has remained relatively low in terms for both gill net and ichthyoplankton recent years although an increase was observed in sampling were not significant, suggesting that plant 1993. During this period, the catch of pollock was operation has not affected abundance. Relatively ) dominated by several moderately strong year- few eggs and larvae were entrained (Table 5-6). classes that occurred every three to four years, Entrainment losses of pollock eggs and larvae at including those from 1975,1979, and 1982. More Seabrook Station from 1990 to 1994 were recently, the 1987 and 1988 year-classes appeared estimated to result in the annual loss of less than 10 to be above the long-term mean. The 1989-91 equivalent adults annually (Saila et al.1995). l year-classes, however, are below average in Entrainment of eggs and larvae in 1995 were abundance. The pollock stock is considered by within the range of previous years, and the number NOAA (1995) to be fully expbited. of equivalent adults lost would be similar to the annual estimate of Salla et al. (1995). Pollock Pollock eggs and larvae were collected in relatively ranked ninth among fishes impinged at Seabrook low densities (Tables 5-3 and 5-4). Larval pollock Station in 1995, with estimated total of 899 fish abundance generally peaked during November (Table 5-11). It is likely that the catch of juvenile l through February (NAI 1993). There was a and adult pollock near Seabrook Station reflects significant decline in the geometric mean density natural variability in annual abundance patterns of between the preoperational and operational the Gulf of Maine stock. periods, with large anmial fluctuations occurring during the preoperational period (Tables 5-13, 5- 5.3.3.5 Hakes 17; Figure 5-12). Larval densities were significantly lower at the farfield Station P7. Three species of hake (genus Urophycis) are found in the Gulf of Maine: red hake, white hake, and Pollock have been collected by gill net near spotted hake. The spotted hake, however, is Seabrook Station from spring through fall and apparently quite rare in this area (Bigelow and were generally absent in winter (NA1 1993). Schroeder 1953; Scott and Scott 1988) and is not Annual geometric mean CPUE varied considerably important to the fisheries. For these reasons, it from year to year, with no single station producing will not be discussed below. Both the red and consistently high or low catches (Figure 5-12). white hakes are common in the Northwestern Fluctuations observed may have corresponded to Atlantic Ocean, particularly on sandy or muddy the successive presence of fish from dominant and grounds off Northern New England. They most weat year-classes reported by NOAA (1995). commonly co-occur in the Gulf of Maine (Musick Catch decreased slightly in 1995 compared to 1994 1974). Similar in appearance and in many aspects and 1993, but was comparable to 1992 and 1991. of their biology, other features differ considerably. However, the ANOVA for gill net catch CPUE The red hake is found in more shallow waters of 5-51
O O O Table 5-17. Results of Analysis of Variance for Pollock Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM / - SOURCE OF VARIATION . df MS' F MULTIPLE COMPARISONS MONTHS USED OF ADJUSTED MEANP Ichthyoplankton Preo@' I 8.51 57.73 "
- Op< Preop '
(Nov-Feb) Year (Preop-Op)* 7 2.15 14.59 " * (1986-1995) Month (Year)' 27 0.86 5.80*" " Station
- 2 0.46 3.10* MI2 P7 Preop-Op X Station' 2 0.02 0.12 NS Error 377 0.15 Gill Net Preop-Op' I <0.01 0.09 NS (Apr-Dec) Year (Preop-Op) 17 0.06 4.63 " *
(1976-1995) Month (Year) 151 0.05 4.09"* Station 2 0.08 6.41" G2G3OI y Preop-Op X Station 2 0.01 0.42 NS
$ Error 336 0.01
- Preop-Op compares 1990-1994 to 1986-1990 regardless of station. NS = Not significant (p>0.05)
- Year nested within preoperational and operational periods regardless of station. * = Significant (0.052p>0.01)
- Month nested within Year. " = Ilighly significant (0.012 p>0.001)
' Stations regardless oryear or period. "*= Very highly significant (0.0012 p)
' Interaction of the two main effects, Preop-Op and Station.
' Preop-Op compares 1991-1995 to 1975-1989 regardless of station.
8 Waller-Duncan multiple means compatien test used for significant main effects. LS Means used for interaction term. l L
I 1 5.0 FISH Ichthyoplankton Nov-Feb 100 i _ _ . e2 i ......,8 I P7 l m MEAN l
$= l 9= l l=
l -ai
~~
l B w ., l E n l 40 'l\ os i l M- \ l
? -
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75 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 YEAR Gill net 0.7 i 1 --- g3 l l ......' G2
. I I c3 0.8 1
,, I I l l g 0.5 i Pr w e a l I Operational
- B 4 l l ,
#I h 0.4 , I I l\
, j
, i\
g
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i\
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l l l 1 - I \ k 0.3 ' t. ' \ , / i 1,- / 5 I i I s l'
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02 /\ l 'l \ / sl' I
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' \ f / \ / /
\ /
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\/ \ l l I I 0.0 I 75 78 77 78 79 80 81 82 33 84 BG 88 87 88 89 90 91 92 93 94 95 YEAR l l
i Figure 5-12. Annual geometric mean catch of pollock per unit effort in ichthyoplankton (number per 1000 cubic meters) and gill net (number per 24-h set) samples by station and the mean of all stations, 19751995 (data between the two vertical dashed lines were l excluded from the ANOVA model). Seabrook Operational Report,1995. O)' 5-53
5.0 FISH t , /~ l (]T the inner continental shelf, predominantly in depths of 73 to 126 m (Musick 1974). It occurs in water hake are inquihne and live within the mantle cavity of the sea scallop (Placopectin magellanicus) until temperatures of 5 to 12*C, but apparently prefers they outgrow this commensal host (Steiner et al. a range of 8-10*C and avoids waters colder than 1982; Garman 1983; Luczkovitch 1991). Other 4*C, In the Gulf of Maine, red hake are found red hake, however, find shelter under shell or inshore for spawning, but disperse offshore other bottom structures (Steiner et al.1982). followmg spawrung Except for young, most white hake are typically found in deeper (200-1,000 m) Based on the depth distribution of the red and water than red hake and are considered to be white hake, red hake is probably the most common inhabitants of the outer shelf and continental slope. hake in the study area. Commercial fishing land-Temperature preferences (5-11*C), however, are ings of red hake in the Gulf of Maine and from the similar to that of the red hake. Current estimates northern Georges Bank are currently very low (< of median size and age of maturity for females are 1,000 metric tons), with an average of only 2,000 26.9 cm (1.8 years) for red hake and 35.1 cm (1.4 metric tons landed over the period of 1974-93 years) for white hake (O'Brien et al.1993). Maxi- (NOAA 1995). The NMFS trawl survey index mum size of the white hake is 135 cm, much showed an increasing trend in abundance from the larger than the maximum of 50 cm for the red mid-1970s to a peak in 1989; indices decreased in hake (NOAA 1995). 1990 through 1993, but remained near the long-term average. Although year-classes produced q The white hake is highly fecund with a 70-cm since 1985 were termed moderate in strength, i V female producing 4 million eggs and a 90-cm fish NOAA (1995) concluded that the red hake is un-l about 15 million (Scott and Scott 1988). Most derexploited and could sustain much higher white hake spawning occurs in spring on the catches. In contrast, although taken primarily in continental slope south of the Scotian Shelf and non-directed fisheries, white hake landings in the I Georges Bank, and off Southern New England Gulf of Maine (primarily from the western portion) I (Fahay and Able 1989; Comyns and Grant 1993). are currently high, being exceeded only by those l Red hake spawn mostly during summer and fall in for the Atlantic cod (NOAA 1995). Previous land- 1 i mid-shelf areas. Eggs of both species are pelagic ings peaked at 7,500 metric tons in 1984, declined l and are similar in size (range of 0.63-0.97 mm; to 5,500 metric tons in 1990, but recently in- l Fahay 1983; Markle and Frost 1985). Newly- creased to an historic high of 9,600 metric tons in hatched larvae of both hakes are neustonic 1992, and 9,100 metric tons in 1993. NMFS trawl i (Hermes 1985) and even juveniles remain pelagic survey indices have fluctuated considerably, but in-j for a considerable time, until 25-30 mm for the red dications are that abundance increased in 1991 and l hake (Steiner and Olla 1985) and 50-80 mm for the 1992. NOAA (1995) concluded that, on the basis white hake (Markle et al.1982). Growth of young of the stability of stock biomass since 1981, the is rapid and can average about 1 mm/ day (Fahay white hake is fully exploited and can sustain annual and Able 1989). Larger juveniles of both species commercial landings of about 7,700 metric tons. tend to be found closer to shore. White hake This species may be overharvested if landings juveniles recruit inshore in June and July (Fahay (such as those in 1992 and 1993) begin to continu-
; and Able 1989) and red hake from September to ally exceed this level. The recreational landings of ' December (Steiner et al.1982). Many young red both hakes in the Gulf of Maine are insignificant.
l 5-54 l l l
5.0 FISH Hake eggs collected in ichthyoplankton samples are Seabrook Station from 1990 to 1994 were difficult to distinguish from fourbeard rockling estimated to result in the loss of less than 1,000 eggs during early development and, therefore, at equivalent adults, assuming that red hake were the times were grouped as fourbeard rockling/ hake. predominant species entrained (Saila et al.1995). Hake and fourbeard rockling/ hake eggs were the Entrainment of hake eggs and larvae in 1995 were predominant eggs collected during the late summer within the range of previous years and probably and early fail (Table 5-3). Hake larvae generally would result in the loss of less than 1,000 peaked during July through September (NAI equivalent adults. The highest entrainment 1993). During the preoperational period, catch estimates occurred in 1990, the year when larvae remained relatively stable; catch was more variable were most abundant (Table 5-6; Figure 5-13). An during station operation, with the largest annual estimated 2,197 hakes were impinged at Seabrook mean in 1990, although data from this year were Station in 1995 (Table 5-11). excluded from the ANOVA. larval density during 1992 and 1993 were among the years of lowest The ANOVA detected significantly larger abundance (Figure 5-13). In 1994, larval density preoperational abuadances than operational ab-increased to the third highest recorded and undances for trawl catches (Table 5-18). decreased slightly in 1995. Densities during the However, the interaction term was not significant, operational period were not significantly different suggesting there were no plant effects. The from the preoperational period due to the recent apparent trend in abundance as measured by trawl increases in 1994 and 1995. CPUE at Seabrook Station differs from the trend in indices reported by NOAA (1995) for these Hake have been taken year-round in trawl species. Since 1976, the NOAA research trawl sampling, but peak catches were made from June index for red hake has fluctuated considerably, but through October, with a sharp decrease occurring with an increasing trend (NOAA 1995). in November (NAI 1993). Generally, catches at Commerciallandings have remamed uniformly low the nearfield Station T2 were smaller than at T1 or throughout this period. White hake have fluctuated T3 and trends were consistent within the without a long-term trend, but increases have l preoperational and operational periods (Figure 5- occurred since 1989 in both the trawl survey index 13). As for the Atlantic cod, the area near T2 may and in landings. Some unknown factors may be not be a preferred habitat for hake. Geometric reducing hake abundance in the Hampton-Seabrook mean CPUEs were highest in 1977,1978, and area, but it is very unlikely that the operation of 1981. Since then, a general decreasing trend has Seabrook Station has affected the hakes, as the been observed with smaller peaks seen every three local decline began in the early 1980s and occurred to four years. CPUE for 1992 through 1995 were consistently at all stations. In addition, failing to the lowest of the time-series. distinguish among the hake species may have I confounded these analyses. Losses due to plant operation did not appear to affect local populations. Entrainment estimates for 5.3.3.6 Atlantic Silverside hake eggs and larvac during 1995 were the second highest since Seabrook Station began operation. The Atlantic silverside is a small, short-lived Entrainment losses of hake eggs and larvae at schooling Osh that is ecologically important as a l 5-55
5,0 FISH O' D Ichthyoplankton Jul-Sep
= , i
___m ,
,, ; , j .......g ll lI l l --
8co lll Ea ll l l 4o ll l 11 8 ** l , m= - l, %,.- B** l: a B gn 1: Ia .. bIl i Qx I ., Q \ 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR
- c. Trawl
( 8 i ___ I ...... .m r2 I T3 7 js l N MEAN
/ \
- I
/ \
l 6 / \ \
\ \ l f g
\ Prooperational Operational g j g l 5 \ / \ I ' '
!! \ '
/ l
@4 g / j\ l g \/ / \ js I
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\
l
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. \
.- \-s 3
., . j., _
N
.,' s l
- o. ' ~ :.,
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR Figure 5-13. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per cubic meters) and trawl (number per 10-min tow) samples by station and the mean of all stations, 1976-1995 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 5-56
Table 5-18. Results of Analysis of Variance for Hake" Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAMJ SOURCE OF VARIATION df- MS F MULTIPLE COMPARISONS . MONTHS USED OF ADJUSTED MEANS* Ichthyoplankton Preop-Op* 1 0.74 1.48 NS (Jul-Sep) Year (Preop-Op)* 7 5.55 11.07 " * (1986-1995) Month (Year)* 18 2.70 538*** Station
- 2 037 0.75 NS Preop-Op X Station' 2 0.17 033 NS Error 292 0.50 Trawl Preopop8 1 5.58 108.85 "
- Op< Preop (Nov-Jul) Year (Preop-Op) 18 032 6.18 * "
w (1976-1995) Month (Year) 160 0.46 8.87 "
- 6 Station 2 0.82 15.98 "
- TI>T3>T2 Preop-Op X Station 2 0.10 1.95 NS Error 354 0.05
- May include red hake, white hake, spotted hake, or more than one of these species.
- Preop-Op compares 1991-1995 to 1986-1989 regardless of station. * - Significant (0.052p>0.0l)
' Year nested within preoperational and operational periods regardless of station. " - Ilighly significant (0.0 l a p>0.001)
- Month nested within Year. '"= Very highly significant (0.0012p)
- Stations regardless ofyear or period.
' Interaction of the two main efTects, Preop-Op and Station.
- Preop-Op compares 1990-1995 to 1976-1990 regardless of station.
- Waller-Duncan multiple means comparison test used for significant main c!fects. LS Means used for interaction term.
O O O
5.0 FISH /m consumer of zooplankton and as prey for many mm able to survive the winter (Conover and Ross larger fishes and birds (Bengston et al.1987). 1982; Conover 1992). Found in bays, salt marshes, and estuaries from the Gulf of St. Lawrence to northern Florida, the Atlantic silverside have been only numerous in the Gulf of Maine is near the northern end of its range seine sampling program and were taken throughout (Conover 1992). Most Atlantic silverside complete the August through November sampling season their life cycle within one year and, typically, few (NAI 1993). Most of these fish were likely young- l older fish are found in the population. Spawning of-the-year. Geometric mean CPUE was highest begins at about 9-12'C, which restricts spawning from 1976 through 1981, whereupon catch to May through July in northern areas (Conover decreased. Since then, CPUE has fluctuated and Ross 1982; Jessop 1983; Conover and Kynard around a lower and more consistent average level 1984). Fecundity within a Massachusetts to the present (Figure 5-14). Catch at each station population ranged from 4,725 to 13,525 eggs per tended to follow similar patterns, with the female (Conover 1979). These eggs may be exceptions of Stations S2 in 1993 and S1 in 1995. released during at least four separate periods of CPUE was significantly lower during the ripening and spawning. Spawning occurs during operational period and there were no significant j daylight, coincides with dates of full and new differences among stations (Table 5-19). The i moons and is apparently synchronized with tides Preop-Op X Station interaction term was not (Conover and Kynard 1984). The adhesive eggs significant, indicating that the relationship in p are laid in shallow water on vegetation. Gender of CPUE among stations was consistent between the V Atlantic silverside is determined largely by water preoperational and operational periods, and the temperature during larval development (Conover operation of Seabrook Station did not affect and Kynard 1981; Conover and Fleisher 1986). Atlantic silverside abundance. However, this mechamsm may not be as important for northern populations because of the temporally An estimated 1,621 Atlantic silverside were reduced spawning season in more northern waters impinged in 1995 (Table 5-11). No eggs or larvae (Conover 1992). Larvae are planktonic, but were entrained (Table 5-6). The discharge from remain near the spawning areas. Growth of young the Seabrook Station settling basin no longer enters is fast and mean lengths can exceed 90 mm by Hampton-Seabrook Harbor and, therefore, is no November (Conover 1979). As the lower lethal longer a potential impact to resident marine biota. temperature for Atlantic silverside is about 1-2*C As few Atlantic silverside have been harmed by (Hoff and Westman 1%6; Conover and Murawski station operation to date and because the decline in 1982), inshore distribution in northern areas is seine CPUE occurred before plant start-up, it is limited in winter. Atlantic silverside undertake an reasonable to assume that the continued operation offshore migration in winter to inner continental of Seabrook Station has not affected this species. shelf waters, with most fish caught within 40 km of the shore and at depths less than 50 m (Conover 5.3.3.7 Cunner and Murawski 1982). It is during this period that high (up to 99%) overwintering mortality typically The cunner, found from Newfoundland to ,y occurs, with apparently mostly fish larger than 80 Chesapeake Bay (Scott and Scott 1988), is one of (d 5-58
5.0 FISH l Seine 25 i i _ _ _ 3, I l ... __.s2 l I S3 l l ~"
= l l
. i i I I ti:
Preoperatonal Operatonal g l l g" - l i l I
@ . p I I
." \ l l
10 s l l [
/ \ i i f l1 /
h .\/ .t 5
.., . . . .! ; , s
/
~.
t Not Sampled l l l ' ^Y I I ! o 75 78 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEm Figure 5-14. Annual geometric mean catch of Atlantic silverside per unit effort in seine (number per haul) samples by station and the mean of all stations, 1976-1995 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. t O 5-59 l l
Table 5-19. Results of Analysis of Variance for Atlantic Silverside Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM / SOURCE OF VARIATION dr MS F MULTIPLE COMPARISONS
- MONTHS USED OF ADJUSTED MEANS' -
Seine Preop-Op' I 2.86 2221 "
- Op<Preep (Apr-Nov) Year (Preop-Op)* 16 0.89 6.93 * "
(1976-1995) Month (Year)* 123 2.20 17.11* " Station
- 2 0.05 0.39 NS Preop-Op X Station' 2 0.01 0.06 NS .'
Error 278 0.13
- Preop-Op compares 1991-1995 to 1976-1984 and 1986-1989 regardless of station. NS - Not significant(p>0.05)
- Year nested within preoperational and operational periods regardless of station. * - Significant (0.052 p>0.01)
,
- Month nested within Year. " = Ilighly significant (0.01 ap>0.001) d g Stations regardless of year or period.
- Interaction of the two main efrects, Preopop and Station.
*"- Very highly significant (0.001 ap)
'Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for interaction term.
5.0 FISH the most common fishes in the Gulf of Maine 3 mm in length and settle into preferred habitats (Bigelow and Schroeder 1953). A small fish when 8 to 9 mm long. residing in inshore waters, few cunner measure over 31 cm, although fish as large as 38 cm are Presently, cunner have no commercial value, occasionally taken in deeper waters (Johansen although large quantities were apparently landed 1925; Bigelow and Schroeder 1953). Most cunner during the late 1800s and early 1900s (Bigelow and are closely associated with structural habitats, such Schroeder 1953). Although the cunner is not as rocks, tidepools, shellfish beds, pilings, primarily sought after, numerous fish are caught eelgrass, and macroalgae. Cunner exhibit both by recreational fishermen throughout New diel and seasonal behavior in that they remain England. Because of its restricted inshore habitats under cover and become quiescent at night and and the lack of landings data, no large-area, long-torpid in winter (Olla et al. 1975, 1979). In fall, term abundance indices are available for the 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 eggs and larvae were dominant in the 1979). Although generally remaining within 2 m ichthyoplankton program (Tables 5-3 and 5-4), of territorial shelters, some cunner will move to Cunner eggs were grouped with yellowtail flounder seasonally transitory habitats (e.g., mussel beds, (cunner /yellowtail flounder). This group also macroalgae) after emerging from winter shelter included tautog eggs, although tautog adults were when spring water temperatures reach 5 or 6*C probably not abundant in the Hampton-Seabrook (Olla et al. 1975, 1979). Cunner reach maturity at area, which is located near the northern end of 70-90 mm and at age-1 or 2, depending upon their distributional range (Bigelow and Schroeder latitude and corresponding length of the growing 1953). Tautog have only accounted for 0.04% of season (Johansen 1925; Dew 1976; Pottle and ne larvae collected since July 1975. A Green 1979). Cunner are serial spawners; pairs comparison of cunner and yellowtail flounder spawn within male territories, or aggregations of larval abundance indicated that most of the eggs in fish spawn together during late afternoon or early the cunner /yellowtail flounder group were cunner, evening (Pottle and Green 1979). The assuming a relatively sinular hatching rate between reproductive season lasts from May through the two species (Table 5-13). The annual September, with peak spawning observed by Dew abundance of cunner larvae has greatly fluctuated (1976) during June in Fishers Island Sound. Eggs from year to year, but similar annual densities are pelagic and range from 0.75 to 1.03 mm in occurred at all stations, with the exception of 1994 diameter (Wheatland 1956); average size of eggs and 1995 (Figure 5-15). In 1995, mean density of decreases over the season with increasing water cunner larvae was the highest observed and was temperature (Richards 1959; Williams 1967). much greater than both the preoperational and Wilhams et al. (1973) reported that only about 5 % operational mean densities (Table 5-13; Figure 5-of cunner eggs survived to hatching and speculated 15). However, the results of the ANOVA that predation, particularly by etenophores, was indicated that during the period when all three responsible for the losses. Eggs hatch in 3 d at stations were sampled and cunner larvae were water temperatures of 12.8-18.3*C (Bigelow and present, there were no significant differences Schroeder 1953). Newly-hatched larvae are 2 to between the preoperational and operational 5-61
5.0 FISH l Ch Ichthyoplankton i () 4*o - - - p2 Jun-Sep ' 8 i ,
.......p3 i
<= -L lli ,
I l I B** l l l g= a* i l l l l l g l g i i: f I l7 5 em l\ Ij . { !
@ 1so pr.op.r.cono,
%' g\ op rm ; /
l 100 , ('
\ I 50,
\
g /li l\
- ~
-x l l i
O 1 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR Figure 5-15. Annual geometric mean catch of cunner per unit effort in ichthyoplankton (number q per 1000 cubic meters) samples by station and the mean of all stations, 1975-1995 l 4 data between the two vettical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. periods, or among stations (Table 5-20). Cunner /- Relatively few cunner have been taken by otter yellowtail flounder egg entrainment in 1995 was trawl. gill net, or seine. Most occurrences were estimated at 18.6 million, ranking fourth among recorded from April through November, which taxa of eggs. Except for 1995, this group has likely corresponds to the period of greatest cunner ranked first or second each year that entrainment activity in New Hampshire waters. An estimated sampling was conducted during the summer season 342 cunner were impinged at Seabrook Station of high abundance (Table 5-6). Larval entrainment during 1995, despite the potential of the offshore since 1990 has ranged from 0 to 14.7 million. The intake structure to attract cunner (Table 5-11). large difference between egg and larval entrainment estimates can largely be attributed to 5.3.3.8 American Sand T.ance the high mortality during the egg stage (Williams et al.1973). Recent 24-hour diel studies have Both the American sand lance (Ammodytes indicated that most of the egg mortality occurs americanus) and the northern sand lance (A. shortly after spawning (NUSCO 1994a). Also, the dubius) may be taken inshore in the Gulf of Maine lack of sampling in August and September of 1991, (Winters and Dalley 1988; Nizinski et al.1990). in September of 1992, and in April-September of However, the latter species is more cammon in 1994 contributed to the low entrainment estimates deeper, offshore waters and al! sand lance tQ for cunner larvae. collected in Seabrook Station studi:s are referred 5-62 l l
Table 5-20. Results of Analysis of Variance for Cunner Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM / SOURCE OF VARIATION di MS F MULTIPLE COMPARISONS MONTHS USED OF ADJUSTED MEANS Ichthyoplankton Preop-Op' 1 2.78 3.75 NS (Jun-Sep) Year (Preop-Opf 6 14.60 19.72 " * (1987-1995) Month (Year)' 24 13.01 17.56 "
- Station
- 2 0.18 025 NS Preop-Op X Station' 2 0.23 0.31 NS Error 347 0.74
- Preop-Op compares 1991-1995 to 1987-1989 regardless of station. NS -Not significant(p405)
- Year nested within preoperational and operational periods regardless of station. * - Significant (0.052p>0 01)
- Month nested within Year. " - Ilighly significant (0 01 a p>0.001)
' Stations regardless of year or period. "* = Very highly significant (0.0012 p)
[ w
- Interaction of the two main efTects, Preopop and Station.
O O O
.- - =
5.0 FISH l
) to as the American sand lance. This species is ichthyoplankton samples because they are demersal found from Labrador to Chesapeake Bay (Richards and adhesive. Larvae generally occurred from 1982; Nizinski et al.1990) and in the Gulf of December through June or July, with peak I 4
Maine is usually found in depths of 6 to 20 m abundances present during January through April I (Meyer et al.1979). Found in schools ranging (NAI 1993). Larval abundances in the Hampton- I from hundreds to tens of thousands, sand lance are Seabrook area have declined since the early 1980s, an important trophic link between zooplankton and but appear to be increasing in the operational larger fishes, birds, and marine mammals (Reay period from 1991 through 1994 and then decreased ( 1970; Meyer et al.1979; Overholtz and Nicolas at all stations in 1995 (Figure 5-16). The decline ' l 1979; Payne et al.1986; Gilman 1994). since the 1980s was also apparent in other areas of the Northwest Atlantic Ocean. Larval densities in Sand lance can live up to nine years, but Long Island Sound over a 32-year period (1951-populations are dominated by the first three age 83) were highest in 1965-66 and 1978-79, with the . groups (Reay 1970). American sand lance can latter years corresponding with a peak observed mature at age-1 at sizes of 90 to 115 mm (Richards throughout the entire range of American sand lance { 1982). Maximum size commonly observed is (Monteleone et al.1987). Similarly, larval sand about 23-24 cm (Meyer et al.1979; Richards lance densities were very high in Niantic Bay, CT l 1982). An 18-cm female American sand lance is from 1977 through 1981, with present densities an capable of producing 23,000 eggs (Westin et al. order of magnitude lower (NUSCO 1994a). p 1979). Spawning occurs in inshore waters from Nizinski et al. (1990) also reported a peak in sand ) (,) November through March with a peak in lance abundance throughout the Northwest Atlantic December and January. Eggs are demersal and in 1981, with numbers declining since then. Sand adhesive, forming clumps, with sizes ranging from lance abundance was noted to be inversely 1 0.67 to 1.03 mm (Williams et al.1964; Smigielski correlated with that of Atlantic herring and Atlantic d et al.1984). Embryonic development is lengthy, mackerel (Sherman et al.1981; Nizinski et al. resulting in a well-developed larva of about 6 mm 1990). Sand lance likely increased in abundance, ) in length at hatching. Larvae have ample replacing their herring and mackerel competitors, endogenous energy reserves and can survive long which had been reduced by overfishing in the periods without food (Buckley et al. 1984; 1970s (Sherman et al.1981). In more recent ! Monteleone and Peterson 1986). Larval years, Atlantic mackerel, which can prey heavily j development is also lengthy, with metamorphosis upon sand lance (Monteleone et al.1987), have l occumng at sizes of 29-35 mm in 131 days at 4*C become very abundant as sand lance abundance I and 102 days at 7'C (Smigielski et al.1984). This decreased. Another factor noted to affect sand long period of development results in larvae being lance reproduction and recruitment is water dispersed widely over continental shelf areas temperature, as Monteleone et al. (1987) suggested (Richards and Kendall 1973), even though most that warm December temperatures were associated spawning occurs inshore. with low larval densities. l l American sand lance was the dominant larval taxon Larval sand lance abundance in 1995 was lower ! O b collected in the ichthyoplankton program (Tables than the preoperational and operational period j 5-4 and 5-13). Its eggs have not been collected in averages (Table 5-13; Figure 5-16). Annual l l 5-64 i
5.0 FISH Ichthyoplankton Jan Apr 900 i __ _ P2 i .......p3 800 f, .-
- MEAN
.. l B~- . l
@ eco '
I h , Proopwamnal l Opwawnal B" l E.
. /\ l
!\
^
l 8-\.,l\ ' j\ l b 200 \,
\
..?l
. . . ~:
~~~ ' *!
I j \.,.+1r. 1 v '"
. . .,.} '.
'* \ \'
i > s O 78 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 veAn Figure 5-16. Annual geometric mean catch of American sand lance per unit effort in ichthyoplankton (number per 1000 cubic meters) samples by station and the mean of all stations, 1976-1995 Seabrook OperationalReport,1995. geometric means have increased steadily since 1979, and 1981. Several hundred or more sand . 1991, but declined in 1995 (Figure 5-16). The lance were occasionally taken by seine, but most Preop-Op X Station interaction term was not catches were small and occurred infrequently. significant, indicating that the relationship among Again, abundance was highest during the late crions was consistent between the preoperational 1970s. An estimated 1,324 fish were impinged at and operational periods, and there was no effect Seabrook Station in 1995 (Table 5-11). due to the operation of Seabrook Station (Table 5-21). American sarel lance larvae were a dominant 5.3.3.9 Atlantic Mackerel species in entrainment collections during 1991-95 (Table 5-6); their absence in entrainment samples The Atlantic mackerel is a strongly schooling fish l 1 during 1900 can be attributed to the start of found from Labrador to Cape Lookout, NC that sampling in June, which was after their season of prefers a temperature range of 9 to 12*C (Scott occurrence. and Scott 1988). The median size of maturity for mackerel is about 26 cm, at approximately age-2 ) Very few American sand lance have been taken by (O'Brien et al.1993). Atlantic mackerel exhibit a l Seabrook Station adult fish sampling programs. A distinct pattern of extensive annual movements; .l few fish were taken sporadically by otter trawl, fish can migrate in excess of 2,200 km (Parsons mostly during January through March in 1978, and Moores 1974). Atlantic mackerel overwinter 5-65
O O O Table 5-21. Results of Analysis of Variance for American Sand Lance Densities by Sampling Program. Seabrook Operational Report,1995.
. PROGRAM / SOURCE OF VARIATION dr- MS F -- MULTIPLE COMPARISONS MON'I HS USED OF ADJUSTED MEANS -
Ichthyoplankton Preop-Op' 1 1.39 2.82 NS (Jan-Apr) Year (Preop-Op)* 7 1.50 3.04 " (1987-1995) Menth (Year)" 27 4.43 8.98 "* Station
- 2 2.88 S.84 " P112 P7 Preop-Op X Station' 2 0.78 1.57 NS Error 365 0.49
- Preopop compares 1991-1995 to 1987-1990 regardless of station. NS = Not significant(p>0.05)
- Year nested within preoperational and operational periods regardless of station. * = Significant(0.052p>0.01) vi ' Month nested within Year. " = Ilighly significant (0.012 p>0.001) h
- Stations regardless ofyear or period.
- Interaction of the two main effects, Preop-Op and Station.
*"= Very highly significant (0.0012 p) 'Waller-Duncan multiple means comparison used for significant main effects. LS means used for interaction term.
{ i l {
5.0 FISH offshore along the edge of the continental shelf 1950; Ware and Lambert 1985, D' Amours et al. (Ware and Lambert 1985) and, in spring, move 1990). inshore. Temperature is apparently one of the dominant factors influencing the spring distribution Presently, biomass of the Atlantic mackerel stock and rate of northward migration of Atlantic is very high (NOAA 1995). Although two mackerel (Overholtz et al.1991). Two separate spawning contingents exist, the species is managed spawning components of Atlantic mackerel have as a single stock. Mackerel in the Gulf of Maine been recogmzed (Sette 1950; Berrien 1978; Morse are primarily landed from May through November 1980). One group spawns progressively northward by both sport and commercial fisheries. Landings from mid-April through June in the Mid-Atlantic from the U.S. (about one-third of the total) and Bight and the other spawns in the Gulf of St. Canada peaked at 400,000 metric tons in 1973 and Lawrence from late May to mid-August; peak decreased to about 30,000 metric tons during the spawning occurs at about 13'C (Ware and late 1970s, as apparently weak year-classes were Lambert 1985). Ware (1977) and Lambert and found from 1975 through 1980. Catches then Ware (1984) suggested that the Atlantic mackerel increased steadily to 82,700 metric tons in 1988, spawning season is relatively short and coincides but declined again to 32,100 metric tons in 1993; with peak copepod biomass. Spawning stock size a very strong year-class was produced in 1982 and appears to exert little influence on recruitment, relatively good ones in 1984-88. With current except at very low levels, and environmental spawning stock biomass estimated to exceed 2 factors likely have a major effect on successful million metric tons, catches can be increased reproduction (Anderson 1979). After spawning, substantially without affecting the spawning stock the southern contingent moves into coastal areas of (NOAA 1995). the Gulf of Maine and the northern group remains in Canarlian waters during summer and fall. Atlantic mackerel was the second-most abundant egg taxon collected in the ichthyoplankton program Female Atlantic mackerel are serial spawners and (19.6% of all eggs in all offshore samples). The release five to seven successive batches of eggs; larvae were very abundant in ichthyoplankton fecundity ranges from 285,000 to almost 2 million collections (19.3% of all larvae in all offshore eggs per female (Morse 1980). The 1.1 to 1.3-mm samples), but were not dominant in entrainment eggs hatch in 5 to 7 days. Eggs are distributed samples (Tables 5-5 and 5-6). Larvae typically near the surface, with 85% or more concentrated occurred from May through August (NAI 1993) within the uppermost 15 m (Ware and Lambert and larval abundance in 1995 was greater than the 1985; deLafontaine and Gascon 1989; D' Amours preoperational and operational period averages and Gregoire 1991). The hatched larvae are 3 mm (Table 5-13). Annual larval abundances in length, grow rapidly, and develop a streamlined fluctuated, with a peak at Station P5 in 1981 form early in life that enables relatively high (Figure 5-17). During the period when all three swimming speeds (Ware and Lambert 1985). stations were sampled (1986-95), similar densities Young from both spawning contingents reach an were found at all stations, except for 1991. The average size of about 200 mm in late fall, even results from the ANOVA indicated no significant though their growing seasons differ in length (Sette difference among stations or between preopera-5-67
5.0 FISH b%- )\. ( 45 Ichthyoplankton i May-Aug Z.- .Q
~ UeAn l
I p 35 ' l l 30 lA i Y I!\ Q ** ,\l lII \
,T Preopwatonal g 20 lf i O penmonal
/.\ y 1
1 15 \ g
\
h fr f W 1o
./ \
s
~
x,' s i / 5 . ^' . 1/ \' V l
- /-
l l I O ' 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR j l l l l A A.ll net
) 0.8 _ _ _ _
g, a2 i i i i 4 o3 I I - l 0.7 *-+--* MEAN l l l i 1 i . l l . 0.8 l l 1 1 I l l
/ '. l l -
05 Preoperamd l l / : l E i l l @ o.4 .
;l I [/
i 5 '
/
6 o.s t
- 4. ~1 I.% I IS
'1 l/Q 02 k '
Q. ,, ' lj [l [ ' V. o.i \ ,,, , 2 i N' V is v i i i y operanw 0.0 I I 75 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 i YeAn Figure 5-17. Annual geometric mean catch of Atlantic mackerel per unit effort in ichthyoplankton (number per 1000 cubic meters) and gill net (number per 24-h set) samples by G station and the mean of all stations, 1975-1995 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 5-68
5.0 FISH tional and operational periods; the interaction term 5.3.3.10 Winter Flounder was not significant (Table 5-22). The winter flounder ranges from Labrador to Atlantic mackerel juveniles and adults were Georgia (Scott and Scott 1988), but is most collected by gill net in the Seabrook station area common from Nova Scotia to New Jersey from June through November (NAI 1993). Annual (Perlmutter 1947). Populations of winter flounder geometric mean CPUE reflected trends noted by are composed of reproductively isolated fish that NOAA (1995), with peak abundance observed in spawn in specific estuaries or coastal embayments the mid-1970s that decreased by about two-thirds (Lobell 1939; Perlmutter 1947; Saila 1961; during the early 1980s (Figure 5-17). Beginning in NUSCO 1994b). North of Cape Cod, movements 1988, an overall increasing trend was found, but of winter flounder are generally localized and geometric means have fluctuated sharply from year confined to inshore waters (Howe and Coates to year. Results of the ANOVA indicated that 1975). McCracken (1963) reported that winter CPUE during the operational period was flounder prefer temperatures of 12-15'C and, significantly greater than the preoperational period except for spawning, will move to remain within (Table 5-22). There were no significant that range. However, others (Kennedy and Steele differences among stations (Table 5-22) and trends 1971; Van Guelpen and Davis 1979) noted that in abundance among stations appeared similar movements for feeding and to avoid turbulence and within the preoperational and operational periods ice also affect distribution of northerly populations (Figure 5-17). The interaction term was not and Olla et al. (1%9) reported observing adult fish significant, indicating that the operation of in waters as warm as 22.5'C. Young-of-the-year Seabrook Station did not affect the abundance or are typically found in shallow estuarine waters and distribution of Atlantic mackerel. can withstand temperatures of 30 to 32.4'C (Pearcy 1962, Everich and Gonzalez 1977). No Atlantic mackerel were impinged at Seabrook Station in 1995 (Table 5-11). Large numbers of Adults enter inshore spawning areas in fall or early eggs were entramed and mackerel eggs ranked first winter and spawn in late winter or early spring. or second in annual entrainment estimates since Winter flounder in the Gulf of Maine mature at an 1990 (Table 5-6). However, relatively few (04.7 average age of 3.4 years and at a length of 27.6 million) larvae were entrained each year. As em for males and 29.7 cm for females (O'Brien et previously discussed in the entrainment section, al. 1993). Average fecundity is about 500,000 this may have been related to the rapid eggs per female (Bigelow and Schroeder 1953), developmental rate of Atlantic mackerel, which with a maximum as much as 3.3 million for a large results in larger larvae that can avoid the intake. fish (Topp 1%8). Eggs (0.71-0.96 mm) are Atlantic mackerel biomass is currently very high adhesive and demersal (Fahay 1983). Winter and only an insignificant fraction of the egg flounder embryos develop under a relatively wide production of this highly fecund fish is entrained at range of temperature and salinity conditions, with the plant. highest viable hatch reported at 3*C over a salinity range of 15 to 35 (Rogers 1976). Because winter flounder spawn during periods of low water temperature, larval development is relatively slow 5-69
( C') v J Table 5-22. Results of Analysis of Variance for Atlantic Mackerel Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM / SOURCE OF VARIATION ' df MS F - MULTIPLE COMPARISONS MONTHS USED c ~ OF ADJUSTED MEANSE ' Ichthyoplankton PreopOp' 1 0.72 0.82 NS (May-Aug) Year (Preop-Opf 7 4.95 5.65 "
- l (1985-1995) Month (Year)5 26 9.36 10.69' " l Station
- 2 0.13 0.15 NS Preopop X Station' 2 -0.16 0.18 NS Error 377 0.88 Gill Net Preop-Op' 1 0.21 13.82 " Op> Preop (Nov-Jul) Year (Preop-Op) . I7 0.17 11.20 " '
(1975-1995) Month (Year) 94 0.10 6.59"
- w Station 2 0.03 2.06 NS in Preopop X Station 2 <0.01 0.19 NS C
Error 222 0.01
- Preop-Op compares 1991-1995 to 1987-1990 regardless ofstation.; 1990 was NS = Not significant (pW.05) treated as a preoperational year (May-July only- August 1990 data were * = Significant(0.05 p>0.01) excluded from the analysis). " - Ilighly significant (0.012 p > 0.001)
- Year nested within preoperational and operational periods regardless of station.
***= Very highly significant (0.0012p)
- Month nested within Year.
- Stations regardless of year or period.
' Interaction of the two main efTects, Preopop and Station.
' Preop-Op compares 1991-1995 to 1975-1989.
8 Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for interaction term. '
5.0 FISH and can take up to two months to complete. has declined at all three stations since the mid-Larvae flushed out of estuarine nursery areas are 1980s. Larger annual geometric means were believed to have lowered potential for survival and usually found at P2 than at P5 or P7, although in everrmal recruitment to adult stocks (Pearcy 1962 1995 larval abundance was lowest at Station P2 Smith et al.1975; Crawford 1990). Overall (Table 5-13, Figure 5-18). Mean larval density in mortality of larvae can exceed 99% (Pearcy 1%2). 1995 (all stations combined) decreased compared Young are common in inshore shallows, where to 1994 and ended a modest positive trend that they remain until fall, undertaking little movement started after 1991. There was a significant away from where they settled (Saucerman and difference in larval abundance between the Deegan 1991). preoperational and operational periods and larval densities were significantly higher at Stations P2 Based on numerous meristic and tagging studies and P5 than P7 (Table 5-23). The interaction term conducted for assessment and management was not significant, suggesting that the operation of purposes, winter flounder have been divided into Seabrook Station has not affected the abundance of three groups: Gulf of Maine, Southern New winter flounder larvae in the Hampton-Seabrook England and Middle-Atlantic, and Georges Bank area. (NOAA 1995). Commercial landings of winter flounder from the Gulf of Maine were relatively Winter flounder were taken year-round by otter stable at around 1,000 metric tons per year from trawl at all stations, but occurred most commonly 1961 through 1977, but tripled to about 3,000 from May through October (NA1 1993). metric tons in 1982. Recreational 1andings in some Geometric mean CPUE peaked in 1980 and 1981, years exceeded those of the commercial fishery primarily because of high catches made at the (NOAA 1995). Since 1983, a downward trend nearfield Station T2 (Figure 5-18). Winter was observed in landmgs with a record low of only flounder were considerably more abundant at T2 700 metric tons taken in 1993. Bottom trawl than at T1 or T3 until 1986, when annual mean survey data from the Massachusetts Division of CPUE became more similar. CPUE at T3 was Marine Fisheries spring survey also showed a generally lowest of all these three stations during declining trend since 1983 (NOAA 1995). Lowest the 1970s and 1980s, but catches have become values were observed during 1988-93. Continued more similar to those at T1 and T2 since 1990. low landings and trawl catch indices were CPUE at T2 was the lowest of the three stations in indications that winter flounder in the Gulf of 1992 through 1995. This decrease may be related, Maine have been overexploited (NOAA 1995) and in part, to the inability since 1986 to sample at T2 the stock likely needs rebuilding before yields can on many scheduled dates during August through be sustained or increased. October, months in which winter flounder are most abundant, due to the presence of lobster sampling Larval winter flounder were collected in the gear in the T2 sampling area. However, decreased ichthyoplankton program (Table 5-3), but eggs abundance was also observed in the other months were absent because they are demersal and used in the .ANOVA model. adhesive. Larvae typically occurred in the Hampton-Seabrook area during April through July Geometric mean CPUE for all three stations (NA1 1993). Larval winter flounder abundance combined was highest in 1980 and 1981, and then 5-71
l l t g Ichthyoplankton g Apr.Jul ____.
,s s --
/ \
M / g i ..... T
/ 's x,-\
t 5a , 1 i ,e
/
N
\
5 ' p ,/ : s \. - \, s.i : \ \ ... \ s \/ \/ \\ \ s . s l 5, /
'\; j %.p,/gg' -\ - --
- e. - _ ._ --
n n n n n .o m m u u er = = .o m u u mm Trawl
= _ . _ _ n
....... o u .\ _J
/ \t u i
! : \ l,. ! \ E ,. I \ l f3 E - w V l*
- g
, , ,e s
\
..' .. ,, . q .< -\ ,.." s
,/ s_ / ,
O n = n n n .o u - u = ., .o = = ~ ma Seine . . . . ... .= l I
- g. l
$ l E4 ;
E
- g. -
g, i,
/
. . . . .'\' '
\, ' ,A[W.-?..y/ ..
V(, w= A.~ -~4.,- . . _ O
',/-
l [ t n r. n n n .o m a ~ u er = ' .o m = ~ N l l Figure 5-18. Annual geometric mean catch of winter flounder per unit effort in ichthyoplankton (number i N per 1000 cubic meters), trawl (number per 10-min tow), and seine (number per haul) samples i by station and the mean of all stations,1975-1995 (data between the two dashed lines were i ! excluded from the ANOVA model). Seabrook Operational Report,1995. j 1 5 72 1 l i i
Table 5-23. ReSults of Analysis of Variance for Winter Flounder Densities by Sampling Program. Seabrook Operational Report,1995. PROGRAM /. SOURCE OF VARIATION dr.. MS- F MULTIPLE COMPARISONS MONTHS USED OF ADJUSTED MEANS' ichthyoplankton Preop-Op' I 5.03 12.42 " Op< Preop (Apr-Jul) Year (Preop-Op)* 7 0.83 2.04* (1987-1995) Month (Year)' 27 4.51 11.14 "
- Station
- 2 2.93 723 " E2.Ej. P7 Preogwp X Station' 2 0.42 1.04 NS Error 374 0.40 Trawl Preopop' I 225 39.28 "
- Op< Preop (Nov-Jul) Year (Preop-Op) 18 0.49 8.51 * "
(1975-1995) Month (Year) 160 0.16 2.82"* Station 2 0.95 16.59' " T2>TI>T3 Preop-Op X Station 2 1.57 2732 "
- 2 Pre 1 Pre 100 3 00 3 Pre 2008 Error 354 0.06 Trawl Year 14 0.53 10.81* "
tp (Nov-Jul) Month (Year) 120 0.13 2.58'" d (1976-1989 Station 2 4.83 97.63 "
- Preop only) Year X Station 28 0.16 3.28"*
Error 239 0.05 Seine Preop-Op* 1 3.87 73.80 "
- Op< Preop (Apr-Nov) Year (PreW) 16 0.24 4.65'"
(1976-1995) Month (Year) 123 0.09 1.64 " Station 2 2.17 41.53 "
- S3E1.S2 Preop-Op X Station 2 0.28 533" 3 Pre 2 Pre 3001 Pre 1 On 2 On Error 278 0.05 Seine Year 12 031 6.94 " *
(Apr-Nov Month (Year) 88 0.09 2.08"
- Preop only) Station 2 3.51 78.55 "
- Year X Station 24 0.11 2.40"
- Error 176 0.04
- Preop-Op compares 1991-1995 to 1987-1990 regardless of station. NS = Not significant (p>0.05)
- Year nested within preoperational and operational periods regardless of station. * = Signifcant 0.052p>0.01)
- Month nested within Year. " = liig!Q sign (ificant (0.012 p>0.001)
- Stations regardless of year or p.enod. *"= Ve'v highly significant (0.0012 p)
' Interaction of the two main eilects, Preop-Op and Station. ' Preop-Op compares 1990-1995 to 1975-lWU Underhning signifies no nignificant difTerences among least square means at ps0.05
- Preopop compares 1991-1995 to 1976-1984 and 1986-1989.
' Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for interaction term.
O O O
i l 5.0 FISH l
; decreased to a low in 1985 (Figure 5-18). CPUE pact stations in the period prior to plant start-up remained relatively stable from 1985 through may lead to misleading significance. Since the 1991. In 1995, CPUE was lowest in the time differences in CPUE among stations observed series. The interaction term (Preop-Op X Station) between the preoperational and operational periods was significant, primarily due to a large decrease were also observed within the preoperational in CPUE at Station T2 between the preoperational period alone, they probably were not caused by the I and operational periods (Figure 5-19). Closer operation of Seabrook Station. Furthermore, at examination of CPUE trends at Station T2 least one farfield Station (TI) exhibited the same indicates that CPUE began to decrease during the decreasing trends between the preoperational and preoperational period (Figure 5-18). To further operational periods as the nearfield Station (T2).
quanufy this decrease, an ANOVA was calculated to investigate the relationship between Year and Smaller winter flounder (juveniles through age-2; Station within the preoperational period (Table 5- NAI 1993) were collected in the Hampton-23). The interaction term for Year and Station Seabrook Harbor by seine throughout the April-was significant, which indicates that the stations November sampling period. Annual geometric exhibited differing trends in CPUE within the mean CPUE was consistently higher at Station S3, preoperational period. Smith et al. (1993) states located nearest to the mouth of the estuary, and that differences in trends between control and im- generally lowest at S1, farthest inland (Figure 5-l 10 V ; - . a ", r 0.9 -*- *
- 13 0.8 *-
~~.
0.7 ..,, 0.6 ..,,
@ 0.s -
y ._ _ - _ - - - - - - - - :~ .; g 0.4 hM I 0.2 l 0.1 0.0 l Prooperatonal operatenal emoo Figure 5-19. A comparison among stations of the mean logm(X+ 1) CPUE (number per 10-minute tow) of winter flounder caught by trawl during the preoperational (November 1975-July 1990) and operational (November 1990 - July 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model(Table 5-23). Seabrook Operational Report,1995. l,sI v 5-74
5,0 FISH 18). The pattern of annual abundance was the early preoperational period. This relative l somewhat similar to that of the trawl samples in stability in CPUE at Station S1, and large that CPUE peaked in 1980 (one year earlier than decreases at S2 and S3 was indicated by the for the catch by trawl) and thereafter decreased. significant interaction term for the ANOVA Abundance has remained at relatively consistent calculated only for the preoperational period levels since 1987. (Table 5-23). The differing trends among stations is not likely due to the operation of Seabrook Results of the ANOVA for seine CPUE indicated Station because it began during the preoperational that the relationship of CPUE among stations period. differed significantly between the preoperational l and operational periods, resulting in a significant Annual entrainment estimates for 1990-95 ranged interaction term for the fixed effects model(Table from 0 to 9.0 million (Table 5-6). These totals, 5-23). CPUE at all stations decreased significantly however, are much less than those of other large between the preoperational and operational New England power plants. Annual larval winter i periods, but the decrease was least at Station S1 flounder entrainment at Pilgrim Nuclear Power (Figure 5-20). CPUE at Stations S2 and S3 was Station in Massachusetts ranged from almost 5 to highest during 1977 through 1983, but began to 21 million during 1988-94 (MRI 1995). Similarly, decrease and approach the CPUE at Station S1 by entrainment was much higher at the three-unit 1987. After 1987, CPUE generally remained Millstone Nuclear Power Station, where annual lowest at Station S1, but the difference between S1 totals for 1976-95 were from 45 to 514 million and the other stations was not as great as during larvae (NUSCO 1995). Entrainment of winter i 1.0 g
,, C_7 E o.e 0.7 goe ~.
@ o.s N x g
g o.4
'~~s N g *%
g o.3 .... '- o.e O.1 '** 0.0 Proopersoonal Operadonal emoo Figure 5-20. A comparison among stations of the mean logio(x+1) CPUE (number per haul) of winter flounder caught by seine during the preoperational (April 1976-November 1984; April 1986-November 1989) and operational (April 1991-November 1995) periods for the significant interation term (Preop-Op X Station) of the ANOVA model (Table 5-23 ). Seabrook Operational Report,1995. 5-75
a -- -- ,,----w 5.0 FISH 1 g) /~' flounder egg and larvae at Seabrook Station from flounder prefer coarser sand and gravel bottom 1990 to 1994 were estimated to result in the loss of sediments than those preferred by other flounders i less than 4,500 equivalent adults annually (Saila et of the Northwestern Atlantic Ocean (Scott 1982b) al.1995). Entrainment of winter flounder larvae and are found mostly in depths of 37 to 91 m (Scott in 1995 was within the range of previous years, and Scott 1988). Individuals apparently maintain I and probably would result in the loss of less than generaPy similar depths between seasons while 4,500 equivalent adults. tolerating a wide range of temperatures and salinities (Scott 1982a; Murawski and Finn 1988; In 1995, an estimated 1,171 winter flounder were Perry and Smith 1994). Some limited seasonal impinged at Seabrook Station. This annual movements, however, do occur, with fish moving l impingement is considerably less than the number to shallower waters in spring and into deeper l of winter flounder taken each year at several other waters during fall and early winter. New England power plants. During 1972-92, l annualimpingement of winter flounder at Brayton Median age of maturity for female yellowtail Point Station in Massachusetts ranged from 859 to flounder is age-2, at a size of approximately 26 cm l 23,452 individuals (mean of 7,925; MRI 1993a). (O'Brien et al.1993). Fecundity can range from Annual impingement totals from 1976 through 350,000 to 4.57 million eggs per female (Pitt 1987 at Millstone Nuclear Power Station Unit 2 in 1971). Adults spawn in the western Gulf of Maine Connecticut were from 624 to 10,077 (annual from March through September (Fahay 1983). O mean of 3,484; NUSCO 1988). Most spawning was observed by Smith et al. (1975) to occur at 4 to 9'C. Eggs (0.8-0.9 mm in Abundance of winter flounder throughout the Gulf diameter) are deposited at or near the bottom, but of Maine has decreased in recent years to historic are pelagic and hatch in five days at temperatures lows (NOAA 1995), likely due to overfishing. of 10-11.1*C. Larvae are 2 to 3.5 mm in length This has been reflected by the reductions in catch at hatching (Fahay 1983). Greatest concentrations of winter flounder in Seabrook Station monitoring of pelagic larvae are found in water temperatures studies. The persistently lower abundance at of 4.1-9.9'C (Smith et al.1975). Larvae exhibit nearfield Station T2 since 1991, compared to the pronounced diel vertical movements and are found preoperational period, is unexplained. Although near the surface at night and at depths of 20 m or beginmng before plant operation in the mid-1980s, so during the day, regardless of thermal gradients this change bears close monitoring to determine if (Smith et al.1978). Ascent and descent occur at Seabrook Station has contributed to a distributional sunset and sunnse, respectively, with amplitude of change following the 1990 start-up. movement increasing with larval size. Larvae metamorphose and become demersal at about 11 to 5.3.3.11 Yellowtail Flounder 16 mm in length (Fahay 1983), although fish as large as 20 mm may still ascend to the surface The yellowtail flounder is found from southern (Smith et al.1978). Labrador to Chesapeake Bay (Scott and Scott 1988), but its center of abundance is the western Three discrete groups of yellowtail flounder are O Gulf of Maine and Southern New England (Bigelow and Schroeder 1953). Yellowtail managed in U.S. waters, including Southern New England, Georges Bank, and Cape Cod (NOAA 5-76
5.0 FISH 1995). All of these stocks are considered to be The yellowtail flounder is taken year-round in the overexploited. Abundance was relatively high in Seabrook Station study area and in former years the early 1980s, but subsequently declined due to was one of the most abundant fishes taken by otter overfishing. After several years of low abun- trawl sampling (Table 5-9). Recently, however, it dance, a relatively strong 1987 year-class produced was most common only from May through October within all three stock areas resulted in an increase (NAI 1993). To a large degree, annual mean in commercial landings in 1990. However, the CPUE by otter trawl (Figure 5-21) mirrored that increase was short-lived as the stocks were rapidly of commercial landmgs reported by NOAA (1995). fished down again and current abundance is at very Trawl CPUE peaked in the early 1980s and subse-low levels. quently decreased to a lower, but relatively stable level, until a slight increase was seen in 1989, Yellowtail flounder eggs were grouped as perhaps due to the relatively strong 1987 year-cunner /yellowtail flounder because it was difficult class. CPUE then steadily decreased to near zero to dioinguish between these two species; this group in 1992, rebounded slightly in 1993, and declined , would also include tautog eggs, if present. The again in 1994 and 1995. cunner /yellowtad flounder taxon was the dominant egg collected during both the preoperational and Catches have been consistently highest at farfield operational periods (Table 5-3). Larvae were less Station T1 and lowest at nearfield Station T2 abundant, probably because the egg group throughout the 20-year period; CPUE at T3 tended consisted primarily of cunner, as previously to approximate the overall mean (Tables 5-13; mentioned (Section 5.3.3.7). Yellowtail flounder Figure 5-21). This pattern of abundance may were among the commonly occurring larval taxa reflect habitat preferences of the yellowtail selected for numerical classification analysis, but flounder in the Hampton-Seabrook study area. they were not among the dominant taxa of any of Yellowtail flounder trends in CPUE were the seasonal groups (Table 5-4). The annual significantly different among stations between the geometric mean of yellowtail flounder larvae preoperational and operational periods, resulting in decreased from a high in 1977 to the lowest in the a significant interaction tenn (Table 5-24). The time series in 1982. Since 1982, larval density has decline in CPUE between the preoperational and remained relatively low with peaks occurring in operational periods was virtually identical at all 1983,1987 and 1993 (Figure 5-21). Larval stations, but was slightly greater at Station T1 density in 1995 was lower than the preoperational (Figure 5-22). mean and simdar to the operational mean (Table 5-13). Results from the ANOVA indicated there was in 1995,1,149 yellowtail flounder were impinged no significant difference detected between the at Seabrook Station (Table 5-11). Prior to 1994, preoperational and operational periods or among the cunner /yellowtail flounder group has been stations (Table 5-24). 'In addition, the interaction consistently ranked first or second among egg taxa term was not significant, suggesting that the entrained at Seabrook Station, with annual totals ! operation of Seabrook Station has not ahered the ranging from 58.4 to 716.3 million (Table 5-6). abundance of yellowtail flounder larvae in the No entrainment of the cunner /yellowtail flounder Hampton-Seabrook area. group was estimated for 1994 because of lack of 5-77
5.0 FISH A Ichthyoplankton (v) 22 May-Aug l
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o 1 i ........... 75 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 vwn I Figure 5-21. Annual geometric mean catch of yellowtail flounder per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-min tow) samples bystation and the mean of all stations, 1975-1995 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. J 5-78 ; 1
Table 5-24. Results of Analysis of Variance for Yellowtail F10pnder Densitics by Sampling Program. Seabrook Operational Repert,1995. PROGRAM / SOURCE OF VARIATION df MS F MULTIPLE COMPARISONS MONTHS USED OF ADJUSTED MEANS' lehthyoplankton Preop-Op' 1 0 68 2.09 NS (May-Aug) Year (Preop Opf 6 1.46 4.46 " (1987-1995) Month (Year)* 24 232 7.1 l '" Station' 2 021 0.64 NS Preop Op X Station' 2 0.20 0.61 NS Error 344 033 Trawl Preop Op' I 35.53 457.42* " Op< Preop (Nov-Jul) Year (Preop-Op) 18 0.76 9.83 * " (1975-1995) Month (Year) 160 0.09 1.13 NS Station 2 12.68 163.22* " TI>T3>T2 Pr% X Station 2 0.27 3.45* 1 Pre 3 Pre 10p 2 Pre 30p 20p Error 354 0.08 ta h5 Trawl Year 14 0.79 10.05* " (NovJul, Month (Year) 120 0.08 1.01 NS Preop only) Station 2 16.80 214.78 "
- Year X Station 28 0.14 1.78*
Error 239 0.08
- Preop Op compares 1991-1995 to 1987-1989 regardless of station. NS -Not significant(p>0.05)
- Year r.csted within preoperational and operational periods regardless of station. * = Significant(0.05)p>0.0I)
- Month nested within Year. " - Ifighly significant (0 Ol a p>0.001)
- Stations regardless ofyear or period. '"= Very highly significant (0.001 ap)
- Interaction of the two main efTects, Preop-Op and Station.
'Preo@ compares 1990-1995 to 1975-1990.
Waller-Duncan multiple means comparison test used for significant main elTects. LS Means used for interaction term. O O O
i 5.0 FISH f \ 1.5 i... "
,,, 1,
-- Ta 1.2 1.1 1.0 N ,,,
gas 's as N. g "0.6 g 7
'N N a5 ,,
N a4 "- ,,,, as . . , 0.2 '- , 0.1 00 moweans owmns ' PmOD o Figure 5-22. A comparison among stations of the mean logio(X+ 1) CPUE (number per 10-minute tow) of Q yellowtail flounder caught by trawl during the preoperational (November 1975-July 1990) and operational (November 1990 - July 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-24). Seabrook Operational Report,1995. sampling due to an extended plant outage and other 5.4 EFFECTS OF SEABROOK STATION i factors during the period of highest density. The OPERATION I estimated entrainment in 1995 was 18.6 million eggs. It is likely that this group is composed The fish community in the Hampton-Seabrook area mostly of cunner, as relatively few yellowtail was sampled to determine if the operation of l l flounder larvae (overall and relative to cunner) Seabrook Station has had any discernible effects on have been identified in entrainment samples. The fish abundance or distribution. Potential impacts yellowtail flounder has been severely reduced in of station operation included the entrainment of abundance by overfishing throughout its range, and fish eggs and larvae and impingement of juvenile l catch near Seabrook Station reflected this decline. and adult fish at the plant intake; entrainment of l No change in this simation can be expected without fish eggs and larvae into and avoidance by larger l a Wantial reduction in fishing effort and several fish of the offshore discharge thermal plume; and l years ofimproved recruitment (NOAA 1995). No effects through 1 April 1994 of the discharge of the i significant effects resulted from the operation of plant settling basin into the Browns River within Seabrook Station. the Hampton-Seabrook estuary. 5-80
5.0 FISH There were significant differences between periods remained essentially stable since the early 1980s, for many demersal fishes (Table 5-25). However, after decreasing from a relatively high peak in the in many instances, the declines began in the early late 1970s. It is unknown why abundance has not to mid-1980s, well before Seabrook Station began increased further in the study area, although it may operation. Several of the decreases seen in the be related to aspects of Atlantic herring stock Hampton-Seabrook area simply reflect long-term structure and recruitment in the Gulf of Maine. declining trends of overexploited commercial Low abundance of Atlantic herring in nearshore fishes, such as Atlantic cod and hake spp. areas appears to be a coast-wide phenomenon as Decreases in these and other important New herring have become less available to the inshore England groundfishes, such as haddock, have fixed-gear fishery on the coast of Maine (NOAA resulted in large increases in biomass of skates and 1995). For the past three years, abundance of the spiny dogfish. Increase of the latter was also Atlantic mackerel has increased near Seabrook reflected by increased catches by gill net near Station, as it has throughout the northwest Atlantic Seabrook Station in recent years. The current low (NOAA 1995). Pollock abundance near Seabrook population levet for the selected demersal fishes is Station has been relatively stable in recent years. most likely due to commercial overfishing and not The pollock stock in the Gulf of Maine is consid-due to the operation of Seabrook Station, because ered fully exploited and the spawning stock bio-the decline in abundance generally began in the mass increased slightly since 1991 (NOAA 1995). mid-1980s, before the Station went on-line. The abundance trends for demersal fish off the Among the estuarine fish community there were no j Hampton-Seabrook area are in general agreement significant differences in CPUE between the with trends observed by the National Marine preoperational and operational periods for rainbow Fisberies Service in their annual groundfish stock smelt. This small, short-lived species appeared to assessment surveys (NOAA 1995). Regional exhibit variable and, perhaps, periodic patterns of abundance of both red and white hakes is now annual abundance. It is unlikely that the discharge increasing, but trawl survey indices reported by of Seabrook Station would have significantly NOAA (1995) show erratic changes, likely due to affected rainbow smelt given their early life history varying year-class strength from year to year. The in estuaries distant from the cooling water five-year operational time series in some cases discharge and intake. CPUE of Atlantic silverside may not be sufficient to differentiate fluctuations in was significantly greater during the preoperational year-class strength from longer-term changes in period. However, annual mean CPUE has been abundance. increasing in the operational period since 1992. Atlantic silverside was the third most numerous Few pelagic fishes showed significant differences fish impinged in 1995, and impingement between the preoperational and operational monitoring in future years will continue to periods. Pelagic fishes in the Gulf of Maine have document in-plant losses of this species. Any not been subjected to as much commercial hypothesized effects due to the settling basin exploitation as demersal fishes. Abundance of discharge into th: Browns River are no longer Atlantic herring is presently increasing in the applicable, as this discharge was re-routed through Northwest Atlantic Ocean, particularly on Georges the circulating water system in April 1994. Bank. CPUE in the Hampton-Seabrook area has 5-81
5.0 FISH () g Table 5-25. Summary of Potential Effects of the Operation o'f Seabrook Station on the Ichthyoylankton Assemblages and Selected Fish Taxa. Seabrook Operationa Report,1995. PREOPERATIONAll
- OPERATIONALPERIOD OPERATIONAL SIMILAR TO DIFFERENCES RECENT ABUNDANCE SAMPLING PREOPERATIONAL ' CONSISTENT AMONG TREND IN THE GULF OF - STATUS OF KPECIES PROGRAM PERIOD ** STATIONS 7* ' MAINF' FISdFJtY' Fish sgg assemblages ichthyoplankton seasonal occunence Op=Preep yes abundance variable among taxa yes Fish larvae assemblages ichthyoplankton seasonal occurrence Op= Preop yes abwulance vanable among taxa yes Atlantic hemng ichthyoplankton Op< Preop yes gill net Op@rcop yes increasing underexploited Rainbow smelt traw! Op@rcop no unknown lightly to seine Op= Preop yes unexploited Atlanus cod ichthyoplankton Op= Preop yes trawl Op@rcop yes decreasing overexploited v
Pollock ichthyoplankton Op4: mop yes gill net Op= Preop yes stable fully exploited llaku ichthyoplankton Op=Proop yes red hake; increasing undesexploited trawl Op@reop yes white hake: increasing fully exploited l l Atlantic silverside seine Op@rcop yes unknown unexploited i Cunner ichthyoplankton Op= Preop yes unknown unexploited American sand lance ichthyoplankton Op= Preop yes decreasing in 1980s unexploited now stable (7) Atlantic mackerel ichthyoplankton Op= Preop yes gill net Op>?reop yes increasing underexploited Wmter flomuler ichtlyfoplankton Op@rcop yes trawl Op@rcop no decreasing overexploited seine Op@rcop no Yellowtail flounder ichthyoplankton Op= Preop yes trawl Op@rcop no decrouing overexploited [
- Based on results of numencat classificauon for assemblages and ANOVA for selected taxa.
- Based on Preop Op X Station interaction tenn from the MANOVA for anaemblages and ANOVA fw selected taxa.
- For commercial species, from NOAA (1995).
5-82
5.0 FISH l l The ANOVA interaction term was significant only stations, and probably due to commercial for winter flounder in trawl and seine samples, and overfishing. ; yellowtail flounder and rainbow smelt in trawl samples, suggesting further investigation into a Abundance of rainbow smelt in the trawl decreased potential effect of Seabrook Station operation between the preoperational and operational periods (Table 5-25). Winter flounder abundance at at all stations, but the decrease was greatest at nearfield Station T2 was higher than the farfield Station T2. The decrease at Station T2 began in Stations T1 and T3 during the preoperational 1989 before Seabrook Station became operational. period and lower in the operational period. Large changes in CPUE of rainbow smelt at resulting in a significant Preop X Station interac- Station T2 appear to be a natural feature of the tion term. However, abundance at Station T2 population dynamics of this species in the study began to drop significantly during the preopera- area, because they had occurred during the tional period, indicating that the change in winter preoperational period. There are no apparent flounder abundance between the preoperational and reasons why the plant should be affecting rainbow operational periods began prior to the start-up of smelt abundance. Very few eggs and larvae have Seabrook Station. Furthermore a significant been entrained at the station because rainbow smelt decrease in CPUE occurred at farfield Station T1 spawn in the estuary and the eggs and larvae are as well as the nearfield Station T2. The reasons beyond the influence of the intakes of the plant. It for this are unknown, but could be related to is unhkely that the discharge from the settling basin natural changes in the local environmental or to the Browns River affected rainbow smelt physical conditions. abundance because it stopped in April 1994. Rainbow smelt appear to be exposed to CPUE of winter flounder taken by the seine impingement primarily in the winter (Table 5-11). decreased significantly between the preoperational An estimated 213 rainbow smelt were impinged at and operational periods at all stations, but the Seabrook Station in 1995. Assuming 1995 was decrease was greatest at Station S3. However, representative of the operational period, similar to trawl CPUE, this decrease began during approximately 1,300 rainbow smelt may have been the preoperational period and probably is not due impinged since 1990. It appears unlikely that such to the operation of Seabrook Station. a short exposure to impingement, with apparently small numbers of smelt impinged, could CPUE for yellowtail flounder decreased at all sta- significantly affect abundance in the entire study tions between the preoperational and operational area. periods, but the decrease was slightly greater at T1. 'Ihe significant interaction term for yellowtail Compared to other New England marine power flounder is probably biologically insignificant and plants, Seabrook Station entrains relatively few fish not due to the operation of Seabrook Station. eggs or larvae and apparently impinges very few Although there was a differing trend in CPUE juvenile and adult fish. The location and design of among stations within the preoperational period, the offshore intakes have worked as expected in the decline in CPUE between the preoperational reducing these impacts. In fact, most of the and operational periods was very similar among impingement that does occur is not of pelagic fish, 5-83 I I i
5.0 FISH but demersal fish that predominantly encounter the period was 80.7/1000 m' (Table 5-26). Similarly [] intake during storm events. the predicted egg and larval densities for rainbow smelt, Atlantic menhaden, pollock, and Atlantic Predictions of the amount of fish eggs and larvae mackerel were much higher than the actual that could potentially be entrained into the cooling densities for the same months during the water system of Seabrook Station were made for operational period. rainbow smelt, winter flounder, Atlantic menhaden, pollock and Atlantic mackerel (NAI Densities of ichthyoplankton in entrainment 1977). These fishes were identified as samples were lower than densities in Representative Important Species (RIS) by EPA ichthyoplankton samples collected at the same time Region 1 in the late 1970s, based on their (NAI 1990), primarily due to differential depth l commercial and recreational importance. distributions for eggs and larvae. Fish eggs that Predictions of entrainment were developed from contain large oil globules such as Atlantic mackerel densities of ichthyoplankton observed in 1973 tend to found near the surface (Kendall and Naplin through 1976 and a pumping rate for one unit 1981) and will likely be less abundant in operating at 100% theoretical capacity. These entrainment samples that are collected from water worst case entrainment estimates of eggs and withdrawn near the middle of the water column. larvae were much higher than the actual I Some latval fish such as Atlantic mackerel tend to entrainment from 1990 through 1995 (Table 5-26). be found closer to the surface as they mature (Ware and Lambert 1985), while winter flounder () The predicted entrainment was much higher than larvae become more benthic as they mature actual entrainment because the predictions were (Pearcy 1%2). Larvae that orient to either the based on the highest single monthly densities in surface or bottom will likely occur in lower ; ichthyoplankton samples observed between 1973 densities in entrainment samples drawn from the j
- and 1976, which were higher than densities during middle of the water column. j the operational period, densities in ichthyoplankton samples were higher than those found in Finally, the predicted entrainment estimate l entrainment samples because the entire range of assumed that the plant would be operating at 100% j
. the water column ws sampled, and the predicted capacity all the time. There were periodic outages pumping rates (one unit) were slightly higher than during the operational period, along with minor the actual pumping rates at Seabrook Station. fluctuations in pumping rates that resulted in average annual daily flows that were slightly less Use of the highest monthly densities resulted in a than the maximum flow of 2.33 x 10' m' for one worst-case estimate of entrainment because it unit used in the predictions (see Table 1-2). assumed that the highest observed densities will be present for the entire larval season. For example, In conclusion, little impact to fishes can be the 1977 prediction assumed that the peak winter attributed to Seabrook Station operation. Most of flounder density of 610/1000 m' observed in June the selected species are from very large and highly of 1973 was representative of a 56-day larval fecund stocks spawning throughout the Gulf of A season. Actual arithmetic mean winter flounder Maine. Others, such as the rainbow smelt and larval density for June during the operational Atlantic silverside, spawn in estuaries away from 5-84
Table 5-26. Actual and Predicted Entrainment of Selected Fish Eggs and Larvac at Seabrook Station, and a Comparison of Peak Densities in 1973-1976 with the Operational Period (1991-1995). Seabrook Operational Report,1995. NUMBER ENTRAINED (x 10*) . PEAK DENSITY MEAN DENSITY (no/1000 m') (noJ1000m') LIFE STAGE SPECIES 1991 1992 1993 1994 1995 PREDICTED - 1973-1976 1991-1995 EGGS Atlantic menhaden 0.5 1.4 0.1 0.0 0.2 133 1,900 16 Pollock 0.0 0.1 0.0 0.0 0.4 133 780 5 Atlantic mackerel 673.1 456.3 112.9 0.0 74.5 2,655 37,600 12,500 LARVAE Rainbow smelt 0.0 0.1 0.0 0.0 0.0 5.5 60 0.5 Winter flounder 9.0 6.2 2.9 0.0 8.0 79.0 610 80.7 $ Atlantic menhaden 0.0 0.0 0.0 0.0 0.0 165.5 2,170 0.0 Pollock 0.0 0.1 0.0 0.0 0.0 62.0 500 4.8 Atlantic mackerel 4.7 0.0 0.0 0.0 0.0 1,130 15,500 247.2 O O O
1 1 5.0 FISH
/ the plant intake and have egg or larval life stages region. Can. J. Fish. Aquat. Sci. 42(Suppl.
that are largely maintained in inshore areas. 1): 158-173. Atlantic cod, winter flounder, and yellowtail Bengston, D.A., R.C. Barkman, and W.J. Berry, flounder continue to be overexploited by 1987. Relationships between maternal size, commercial fisheries and their stocks are presently egg diameter, time of spawning season, declining. Other fishes, such as Atlantic mackerel, temperature, and length at hatch of Atlantic were overfished and now have recovered. Catch silverside, Menidia menidia. J. Fish. Biol. 31: of all the selected species in the Hampton-Seabrook 697-704. area simply reflect long-term, regional trends. Berrien, P.L.1978. Eggs and larvae of Scomber Furthermore, the influence of regional scombrus and Scomberjaponicus in continental environmental factors and interspecific interactions shelf waters between Massachusetts and (e.g., American sand lance-Atlantic mackerel) Florida. Fish. Bull., U.S. 76: 95-114. introduces complexities in any evaluation. Because i Bigelow, H.B., and W.C. Schroeder. 1953. ' of the apparently small numbers of fish of all life Fishes of the Gulf of Maine. U.S. Fish. stages directly removed by the plant and the Wildl. Serv. Fish. Bull. 53:1-577. , concurrent changes in abundance at both nearfield i and farfield stations in nearly every instance, the Boyar, H.C., R.R. Marak, F.E. Perkins, and ) operation of Seabrook Station does not appear to R.A. Clifford.1971. Seasonal distribution of
. larval herring, Clupea harengus harengus 1 have affected the balanced indigenous populattom Linnaeus, in Georges Bank-Gulf of Maine g of fish in the Hampton-Seabrook area. area, 1%2-70. Int. Comm. Northw. At!. {
1 Q
5.5 REFERENCES
CITED Fish., Res. Doc. 71/100. 11 pp. Brander, K. , and P.C. Hurley. 1992. Distribution of early-stage Atlantic cod (Gadus Anderson, E.M. 1979. Assessment of the morhua), haddock (Melangrammus Northwest Atlantic mackerel, Scomber aeglefinus), and witch flounder (Glypto-scombrus, stock. NOAA Tech. Rep. NMFS cephalus cynoglossus) eggs on the Scotian ISSRF-732.13 pp. Shelf: a reappraisal of evidence on the coupling of cod spawning and plankton Anderson, R.D. 1995. Impingement of
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]
Saila, S.B., E. Lorda, D. Miller, R. Sher, W. harengus) populations and match-mismatch ; Howell.1995. Equivalent adult estimates for theory. Can. J. Fish. Aquat. Sci. 41: 1055- l egg, larval, and juvenile fish losses at 1065. i Seabrook Staiton. Prepared for Northeast l (di Utilities. Smigielski, A.S., T.A. Halavik, L.J. Buckley, S.M. Drew, and G.C. Laurence. 1984. 5-94 l l
5.0 FISH Spawtung, embryo development and growth of Stephenson, R.L., and I. Kornfield. 1990. the American sand lance Ammodytes Reappearance of spawning Atlantic herring americanus in the laboratory. Mar. Ecol. (Clupedurrengur harengus) on Georges Bank: Prog. Ser. 14: 287-292. population resurgence not recolonization. Can. J. Fish. Aquat. Sci. 47: 1060-1064. Smith, E.P., D.R. Orvos, and J. Cairns, Jr. 1993. Impact assessment using the before- Stewart-Oaten, A., W.W. Murdoch, and K.E. after-control-impact (BACI) model: concerns Parker.1986. Environmentalimpact assess-and comments. Can. J. Fish. Aquat. Sci. ment: "psuedoreplication" in time? Ecology 50:627-637. 67: 929-940. Smith, W. G., and W. W. Morse. 1993. Larval Suthers, I.M., and K.T. Frank. 1989. Inter-distribution patterns: early signals for the col- annual distributions of larval and pelagic lapse / recovery of Atlantic herring Clupea juvenile cod (Gadus morhua) in southwestern harengus in the Georges Bank area. Fish. Nova Scotia determined with two different Bull., U.S 91: 338-347. gear types. Can. J. Fish. Aquat. Sci. 46: 591-602. Smith, W.G., J.D. Sibunka, and A. Wells. 1975. Seasonal distributions of larval flatfishes Thomas, D.L., and G.J. Miller. 1976. (Pleuronectiformes) on the continental shelf Impingement at Oyster Creek Generating l between Cape Cod, Massachusetts and Cape Station, Forked River, New Jersey, from l Lookout, North Carolina, 1%5-1966. NOAA September to December 1975. Pages 317-341 l Tech. Rep. NMFS SSRF-691. 68 pp. in L.D. Jensen, ed. Third national workshop I on entrainment and impingement. Ecological 1978. Diel movements of larval yellowtail Analysts, Melville, NY. flounder, Limanda ferruginea, determined from discrete depth sampling. Fish. Bull., Topp, R.W. 1968. An estimate of fecundity of U.S. 76: 167-177. the winter flounder, Pseudopleuronectes americanus. J. Fish. Res. Board Can. 25: Sneath, P.H. A., and R.R. Sokal. 1973. 1299-1302. i Numerical taxonomy. The principles and practice of numerical classification. W.H. Townsend, D.W. 1992. Ecology of larval herring Freeman Co., San Francisco. 573 pp, in relation to the oceanography of the Gulf of Maine. J. Plankton Res. 14: 467-493. Sokal, R.R., and F.J. Rohlf. 1981. Biometry. W.H. Freeman and Company, San Francisco. Van Guelpen, L., and C.C. Davis. 1979. 775 pp. Seasonal movements of the winter flounder, Pseudopleuronectes americanus, in two Steiner, W.W., J.J. Luczkovich, and B.L. Olla. contrasting inshore locations in Newfoundland.
-1982. Activity, shelter usage, growth and Trans. Am. Fish. Soc. 108: 26-37.
recruitment of juvenile red hake Urophycis chuss. Mar. Ecol. Prog. Ser. 7: 125-135. Ware, D.M. 1977. Spawning time and egg size of Atlantic mackerel, Scomber scombrus, in
, and B. Olla. 1985. Behavorial responses of relation to the plankton. J. Fish. Res. Board prejuvenile red hake, Urophycis chuss, to Can. 34: 2308-2315.
experimental thermoclines. Envir. Biol. Fish. 14: 167-173. , and T. C. Lambert. 1985. Early life history of Atlantic mackerel (Scomberscombrus)in 5-95
1 i 5.0 FISH / the southern Gulf of St. Lawrence. Can. J. Newfoundland waters with a review of species k Fish. Aquat. Sci. 42: 577-592. designations in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 45: 515-529. Westin, D.T., K.L Abernethy, I.E. Meller, and B.A. Rogers.1979. Some aspects of biology of the American sand lance, Ammodytes americanur. Trans. Am. Fish. Soc. 108: 328-331. Wheatland, S.B.1956. Oceanography of Long Island Sound. 1952-1954. II. Pelagic fish eggs and larvae. Bull. Bingham Oceanogr. Coll. 15: 234-314. Wheeler, J.P., and G.H. Winters 1984. Homing of Atlantic herring in Newfoundland waters as indicated by tagging data. Can. J. Fish. Aquat. Sci. 41: 108-117. j Wigley, S.E., and F.M. Serchuk. 1992. Spatial and temporal distribution of juvenile Atlantic cod Gadus morhua in the Georges Bank-Southern New England region. Fish. Bull., p U.S. 90: 599-606. V Wilks, S.S. 1932. Certain generalizations in the analysis of variance. Biometrika 24: 471-494. Williams, G.C.1%7. Identification and seasonal size changes of eggs of the labrid fishes, Tautogolabrus adspersus and Tautoga onitis, of Long Island Sound Copeia 1%7: 452-453.
. S.W. Richards, and E.G. Farnworth. 1964.
Eggs of Ammodytes hexapterus from Long Island, New York. Copeia 1964: 242-243.
, D.C. Williams, and R.J. Miller. 1973. l Mortality rates of planktonic eggs of the I cunner, Tautogolabrus adspersus (Walbaum),
in Long Island Sound. Pages 181-195 in A. Pacheco, ed. Proceedings of a workshop on 1 egg, larval and juvenile stages of fish in Atlantic coast estuaries. Nat. Mar. Fish. Serv., Mid. Atl Coast. Fish. Ctr. Tech. Pub. No.1. I [ Winters, G.H., and E.L. Dalley. 1988. Meristic L composition of sand lance (Ammodytes spp.) in 5-%
. . . _ . _ _ . _ . . _ . . . . _ . _ _ _m. _ - . . . . . .. . . - _ _ - _ . . _ ~. .. _ _.
Plant Flow 9e-80 : y -_ . -_ ___ Mg 50 - 30 1
, n-1 *iii.... ...i .ii ii ii ..... i ii .iii ..... . i w A 5OND 3 P 15 AMJ JASOND J FMAM3 3 A3OND I FMAMJ J A 3OND 2 PMAMJ JA5OND 1990 1991 1992 1993 1994
- Eggs im-120s -
se 1000 - 8 300 - E 600 -
'g -
'"i _ **** _ rq _ ******
iiii A5OND JPMAMJ JA3OND
. . . .ii i i JPMAMJ JA3OND l9.'.m _.. .. *. *. i i i . .
JPMAMJ JA3OND
. . i i . .
. . .....i 3 FMAMJ JA30ND i .
, 1996 1991 1992 1993 1994 b ' Atleeile aneckeret, E Commer/Yellowisit floender E Oiher eggs Larvae * *** **'nP led y so-s, .50-
% m. l .
8 =- ? k :: I : -l l i.a s 5 3d/ iiiii
- P.1 . e E****
ie i i i i a i e iii _ 5 hm iie ie i i i i i e i
- * *
- m an n .
i i i e iiie i i e i I n PI *ER****** e i iii iiiiii APOND I FMAMJ 3A5OND J PMAM3 3A5OND I PMAM3 3A$0ND 3 PMAM3 3A5OND 1990 1991 1992 1993 1994 O Rock summel E Anmerican saadlance , Grubby Aslamais sessaeil b Cuaner E Fourbeard rockinas
- act assapled Appendix Figure 5-1. Total monthly cooling water system flow and estimated numbers of fish eggs and larvae entrained during August 1990 - December 1994. Seabrook Operational Report,1995.
e e O
5.0 FISH (O
'j Appendix Table 5-1.
Finfish Species Composition by Life Stage and Gear, July 1975 - December 1995. Seabrook Operational Report,1995. ICHTHYOPLANKTON ADULT AND JUVENILE - TOWS FLNFISH SCIENTIFICNAME COMMON EGGS GILL NAME . LARVAE TRAWLS -NETS SEINES AcIpenser oxyrhynchus Atlantic sturgeon R* Alosa aestivahs blueback herring - R C C Alosa mediocris hickory shad - R Alosapseudoharengus nlewife - 0 0 0 Alosa sapidissima Amencan shnd - R O O Alosa sp. river herring R - - - Ammodytes amencanus American sand lance A O R O Anarhuchaslupus Atlantic wollfnah R R Anchoa hepsetus striped anchovy R Angusila rostrata American eel C R Apeltes quadracus toutspine stickleback R Archosargusprobatocephalus sheepshead R Aspidophoroides monopterygzus niligatorfish C O Brevoorna tyrannus Atlantic menbaden O O R O R Brosme brosme cusk O O Caranz hippos crevnllejack n Centropnsns striata black ses bass R R Conger oceamcus conger eel R ( Clupea harengus Atlantic herring C O A O Cryptacanthodes maculatus wrymouth o R Cyclopterus tumpus lumplish C R R R Encholyopus cumbnus fourbeard rockling C C O Fundulus sp.' killiftsh C Gadus morhua Atlantic cod - C C O R Gadus:Melanogrammus Atlantic codhnddock C - - - - Gasterostems sp 8 stickleback R R C Glyptocephalus cynoglossus witch flounder C C O Hemstrtprerus amencanus sea raven O C O R Hsppoglossosdesplatessondes American plaice C C O Hippoglossus hippoglossur Atlantic hnlibut R Labridne/Pleuronectes gunner /yellowtail A - - - - l Lupans atlanncus Atlantic sensnail R C - - - 4 pans cohent gulfsnailfish C - - - Liparts sp ' snailfish R - O Lophsus amencanus goosefish R O O R Lumpenus lumpretaeformas snakeblenny 0 R Lumpenus maculatus daubed shanny R R Macrosoarces amencanus ocean pout O C R Melanogrammus aeglefinus haddock - O C R Menidia memdia Atlantic silverside R O R A Menacarrhus saxanks northern kingfish R l Merluccsus bahneans silver hnke C C C C R Microgadus tomcod Atlantic torncod R R O \ Morons amencana white perch R Morone saxanks striped bass R R 5-98 (continued)
\
1 1 5.0 FISH Appendix Table 5-1. (Continued) h ICHTHYOPLANKTON ADULT AND JUVENILE TOWS FINFISH GILL EGGS LARVAE TRAWLS NETS SELNES SCIENTIFIC NAME COMMON NAME stnped mullet R Magsicephalus smooth dogfish R Mustelus cams grubby C O R O Myoxocephalus cenaeus longham sculpin C A O R Myoxocephalus octodecemspanosus shorthorn sculpin C 0 R R M>oxocephalus scorpaus sand tiger R Odontaspus taurus coho sahnon R R Oncorhynchus ktsurch g Oncorhynchus mykiss rasnbow trout rainbow arnett O C O C Osmerus mordax Parahchthys dentatus summer flounder R R Parahchthys oblongus f'outspot flounder O O C R butterfish O O R O R Pepnlus tnacanthus Petromyzon mannus sea lamprey R rock gunnel C O R R Phohs gunnellus winter flounder C C O C Pleuronectes amencanus Pleuronectesferrugineus yellowtail flounder - C A R R Pleuronectesputnami smoothilounder R R C Pollachius mrens pollock C C C C 0 Pomatomus saltatrix bluefish o O Pnonotus carohnus northem searobin - - C R Pnonotus evolans striped scarobin - - R Pnonotus sp. searobin O R - - - Pungstius pungstius ninespine stickleback c Raja sp 8 skate C R Salmo truna brown ttout O brook trout R Salvehnusfontmahs Scomberjapomcus chub mackersl R Scomber scombrus Atlantic mackerel A A R C R Scophthalmus aquosus wh-kuya C C C, R O Sebastes sp? redfish O Sphoeroudes maculatus northern putfer R R Squalus acanthras spiny dogfish R C Stenotomus chrysops scup R O R Stichaeus punctatus Arctic shanny O Syngnathusfuscus northem pipefish C O R O Tautoga omtis tautog - O R Tautogolabrus adspersus cunner - A O R Torpedo nobehana Atlantic torpedo R Tnglops marrayt moustache sculpin O R Ulwarra subbtfurcata radiated shanny C O Urophycis sp! hale C C A O C O 5-99 (continued)
5.0 FISH m' ! (U) Appendix Table 5-1. (Continued) Footnotes Names are according to Robins et al. (1991). Taxa usually identified to a different level are not included in this list to avoid duplication (e.g., Gadidae, Enchelyopuslurophysis,M>uxocephalus sp., Urophycis chuss). Occurrence of each species is indicated by its relative aburulance or frequency of occurrence for each life stage or gear type: A = abundant (a 10% of total catch over all years) C = common (occumng in a 10% of samples but <10% of total catch) O = occasional (occumng in <10% and a 1% of samples) R = rare (occurring in <!% of samples)
- = not usually identified to this taxonomic level at this hfe stage Predonunantly Fundulus heterochris, mummichog, but may include a small number ofFundulus majabs, striped killifish.
Two species of Gasterosteus have beca identified from seine samples: G. aculeatus, threespine stickleback; and G. wheatlandi, blackspotted stickleback (both occumng commonly). May also include a small number of tautog. 11ree species ofLipans have been identified from trawl samples: L atlanticus, Atlantic seasnail, L coheni, gulf snailfish; and L inquilinus, inquiline snailfish 8 Four species ofRaja have been idenufied from trawl samples: R radiata, thorny skate (common);R ennacea, little skate (common); R. ocellata, winter skate (occasional); and R. eglantena, clearnose skate (rare). Sebastes norwgicus, golden redfish; S. mentella, deepwater redfish; and S. fasciatus, Acadian redfish, have been reported to occur in the northwest Atlantic. Sebastes in meeal New Harrplure waters are probably Sfasciana (Dr. Bnn B. Collette, U.S. National Museum, pers. comm. April 1982), but larval descriptions are insufficient to allow distinction among the three species. 1hree species of Urophycis have been identified from trawl samples: U. chuss, red hake (common); U. tenues, white hake (common); and U. regra, spotted hake (rare). O 1 4 1 I l l /~N () 5-100
Appendix Table 5-2. Subsetting Criteria Used in Analyses of Variance for the Selected Finfish Species. Seabrook Operation Report,1995. SPECIES GEAR SEASON PREOPERATIONAL ' OPERATIONAL POOLING DELETIONS Atlantic cod Trawl Nov-Jul 1975-1990 1990-1995 Nov-Dec with Nov-Dec 1995 following year Atlantic cod Ichthyo Apr-Jul 1987-1990 1991-1995 None None Atlantic herring Gill net Sep-May 1976-1990 1990-1995 Sep-Dec with Sep-Dec 1995 followmg year Atlantic herring Ichthyo Oct-Dec 1986-1989 1990-1995 None None Atlantic silverside Seine Apr-Nov 1976-1984;1986-1989 1991-1995 None 1990 Atlantic mackerel Gill net Jun-Nov 1976-1989 1991-1995 None 1990 Atlantic mackerel Ichthyo May-Aug 1987-1990 1991-1995 None Aug 1990 Atlantic sand lance Ichthyo Jan-Apr 1987-1990 1991-1995 None None Cunner Ichthyo Jun-Sep 1987-1989 1991-1995 None 1990 L Hakes Trawl Nov-Jul 1976-1990 1990-1995 Nov-Dec with Nov-Dec 1995 3 following year Hakes Ichthyo Jul-Sep 1986-1989 1991-1995 None 1990 Policck Gill net Apr-Dec 1976-1989 1991-1995 None 1990 Pollock Ichthyo Nov-Feb 1986-1989 1990-1994 Jan-Feb with 1995 previous year Rainbow smelt Trawl Nov-May 1975-1990 1990-1995 Nov-Dec with Nov-Dec 1995 following year Rainbow smelt Seine Apr-Nov 1976-1984;1986-1989 1991-1995 Nonc 1990 Winter flounder Trawl Nov-Jul 1975-1990 1990-1995 Nov-Dec with Nov-Dec 1995 following year Winter flounder Seine Apr-Nov 1976-1984; 1986-1989 1991-1995 None 1990 Winter flounder Ichthyo Apr-Jul 1987-1990 1991-1995 None None Yellowtail flounder Trawl Nov-Jul 1975-1995 1990-1995 Nov-Dec with Nov-Dec 1995 following year Yellowtail flounder Ichthyo May-Aug 1987-1990 1991-1995 None Aug 1990 0 0 0 ---
5.0 FISH th Appendix Table 5-3. Species Composition, Annual Totals, and Two-year Total of Finfish, American Lobster and Seals Impinged at Seabrook I Station During 1994 and 1995. Seabrook Operational Report, 1995'. 1 l SPECIES 1994 1995 TOTAL. i Atlantic silverside 5348 1621 6%9 l Grubby 2678 2415 5093 ;
- Hakes 2822 2188 5010 ;
Winter flounder 1435 1171 2606 Pollock 1681 899 2580 American sand lance 1215 1324 2539 Windowpane 980 943 1923 Rock gunnel 494 1298 1792 Yellowtail flounder 0 1149 1149 Northern pipefish 188 579 767 Rainbow smelt 545 213 758 Herrings 514 231 745 j Cunner 32 342 374 Lumpfish 182 190 372 Skates 190 157 347 Snailfishes 180 165 345 Threespine stickleback 67 155 222 Sculp 20 Atlantic cod 58 119 177 Longhorn sculpin 105 165 175 Shorthorn sculpin 14 156 170 Radiated shanny 0 92 92 Flounders 77 3 80 Wrymouth 55 9 64 American lobster 31 16 47 5-102 (continued) i
5.0 FISH Appendix Table 5-3. (Continued) g SPECIES 1994 1995 TOTAL Unidentified 6 40 46 Silver hake 0 49 49 Red hake 1 16 17 Butterfish 3 14 17 Goosefish 3 13 16 Planehead filefish 0 15 15 Scup 0 14 14 Blueback herring 13 0 13 Seal 6 6 12 White hake 1 7 8 Alewife 0 8 8 Atlantic menhaden 0 7 7 Fourbeard rockling 0 6 6 4 Ocean pout 0 6 6 American eel 0 5 5 l Killifish 4 0 4 I Striped bass 0 4 4 Black sea bass 0 3 3 Atlantic moonfish 0 3 3 Fourspot flounder 2 1 3 l Summer flounder 3 0 3 Atlantic wolffish 0 2 2 Spiny dogfish 1 0 1 Haddock 0 1 1 Atlantic torpedo 0 1 1 Atlantic tomcod 1 0 1
' Impingement data prior to October 1994 was underestimated.
O 5-103
6.0 MARINE MACROBENTHOS
-.s
( TABLE OF CONTENTS G'; PAGE 6.0 MARINE MACROBENTHOS
SUMMARY
. ........................ . ... . ..... ..... . .. . 6-il LIST OF FIGURES . . . . . . . . . . . . . . . . .. .. .......... .... ........ . . iii LIST OF TABLES . . . .... . . . . .. .. . . .... ... .... . vi LIST OF APPENDIX TABLE .. . . . .... ... . ....... . viii
6.1 INTRODUCTION
.. . ..... ...... . . . . ... .... 6-1 6.2 METHODS . . . . .... .. .. ... .. .. .. . .... 6-2 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 Destructive Monitoring Program: Community Analyses ... ... . 6-4 1 6.2.3.2 Destructive Monitoring Program: Selected Species Analyses . . . .... 6-7 6.2.3.3 Non-Destructive Monitoring Program: Selected Species Analyses ... . 6-7
/m\ ' 1 V 6.3 RESULTS AND DISCUSSION . . .. ... ... ............. . . . .. .. 6-8 6.3.1 Marine Macroalgae . . . . . . . .... .... ...... . . ..... . .. .. 6-8 6.3.1.1 Horizontal Ledge Con:munities . . . . . . . . . . . . . ....... .. . .. 6-8 1 6.3.1.2 Selected Species ...... ... ........... .... ........ . 6-25 j 6.3.1.3 Non-Destructive Monitoring Program . .. ................. 6-25 ) 6.3.2 Marine Macrofauna ............ . . ............ .. ..... 6-47 6.3.2.1 Horizontal Ledge Communities . ....... ........ . . . . . . 6-47 6.3.2.2 Selected Benthic Species . . . . . . . . . . . .. .... . .. .. . 6-65 1
6.4 CONCLUSION
S
. . ........... ........ ... .. .... .. .. 6-76 6.4.1 Introduction .. ... .. ............. .................. . 6-76 6.4.2 Evaluation of Potential Thermal Plume Effects on Intertidal / Shallow Subtidal Benthic Communities . . . . . .... .. ............. .. .......... .. 6-76 6.4.3 Evaluation of Potential Turbidity Effects on the Mid-Depth / Deep Benthic Communities . . . . . . . . . . . . . . . . . . . . . . . . . . .................. 6-80 6.4.4 Overall Effect of Seabrook Operation on the Local Marine Macrobenthos ... . 6-82 fm
6.5 REFERENCES
CITED . . . .... .... .... .... .. .. . . .... 6-82 6-i
6.0 MARINE MACROBENTHOS
SUMMARY
Submerg-d rock surfaces in the vicinity of Seabrook Station intake and discharge structures support rich and diverse communities of attached algae and animals (macrobenthos). An extensive monitoring program combining destructive and non-destructive techniques was implemented in 1978 to assess the potential population and community level effects 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 thermal discharge plume, most likely affecting intertidal and shallow subtidal communities, and those associated with increased turbidity and sedimentation from transport of suspended solids and entrained organisms to deeper water communities near the discharge. Thermal impacts to macroalgae, such as shifts in atim_x or occurrence of typically cold-water or warm-water species (i.e., decreases or increases, respectively), were not evident (all zones combined; destructive samples). Although some typically wann water taxa occurred for the first time during the operational period, some cold water taxa increased in frequency of occurrence, and other wac water taxa dureased in frequency of occurrence, over the same time interval. Overall, community parameters (b; lass, number of taxa, etc.) and analyses of community structure (numerical classification), as measured through destructive sampling, indicated few changes in nearfield intertidal or shallow subtidal algal and faunal communities. Of the selected taxa studied in the intertidal zone, percent frequency of occurrence of Ascophyllum nodosum increased slightly but significantly in the nearfield area during the operational period, while Fucus vesiculosus declined significantly in the same zone. In the shallow subtidal zone, only Laminaria digitata densities in the nearfield area declined significantly during the operational period. These trends began in recent preoperational years and their continuation is attributed to natural cycles in environmental or climatic processes rather than to plant operation. Only one intertidal faunal taxon, Ampithoe rubricata, exhibited a shift in abundance between periods, ard this occurred only in the farfield area. Impacts associated with increased turbidity, such as shifts in community dominance to species tolerant of increases in shadmg, 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 consistency of nearfield and farfield algal and faunal 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. None of the selected faunal taxa in the mid-depth zone showed significant changes in abundance between periods. Densities oflanmana digitata declined at both nearfield and farfield mid-depth stations during the operational period (a trend that began in late preoperational years). Ioninaria saccharina densities have also declined, but only in the nearfield area. This decline may be due to the susceptibility of these plants to removal during major storm events (e.g. Hurricane Bob in 1991). None of the above-mentioned shifts represents a change beyond what would be expected from the inherent natural variability of balanced indigenous communities, and no evidence exists to suggest that thermal or turbidity-related impacts have occurred to local macrobenthic communities since Seabrook Station began operation in 1990. 6-ii
6.0 MARINE MACROBENTHOS O O LIST OF FIGURES I PAGE l l 6-1. Marine benthic sampling stations . . . . . . ... .. . ...... .... .... 6-3 4 6-2. Median number and range of unique macroalgal taxa collected in the intertidal and l subtidal zones during the preoperational and operational periods (calculated from ; annual totals) and the 1995 total number of unique taxa . . . . . . . . . . . ...... 6-10 l 6-3. Comparisen between stations for number of macroalgal taxa (per 0.0625 m2 ) in the intertidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA I model . ..... . ..... ...... ......... . .............. . .. 6-14 ) 6-4. Comparison among stations for number of macroalgal taxa (per 0.0625 m2 ) in the
! mid-depth zone during the preoperational (1980-1984; 1986-1989) and operational !
(1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . . . .. . ............. ... ....... .. .. ... .. 6-15 6-5. Comparison between stations for annual mean total macroalgal biomass (g per m2 ) in the intertidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . . . . . . ................. .................... 6-17
- 64. Dendrogram and station groups formed by numerical classification of August collections of marine benthic algae, 1978-1995 . . . . . . . . . . . . . . .... .... . . 6-19 6-7. Comparison between stations for annual mean total Chondrus crispus biomass (g per 2
m ) in the intertidal zone dtuing the preoperational (1982-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . . . . . . . . . . . . . . ...............................6-28 i 2 6-8. Comparison between stations for mean number of holdfasts /100m of the kelp Iommana digitata in the shallow subtidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . . . . . . . . . ........ ............ . . 6-36 l o , e 6-iii
i 6.0 MARINE MACROBENTHOS l PAGE 2 6-9. Comparison between stations for mean number of holdfasts /100m of the kelp Iominaria digitata in the mid-depth subtidal zone during the preoperational (1978-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model .... .............. ............. 6-37 2 6-10. Comparison between stations for mean number of holdfasts /100m of the kelp Iommaria saccharina in the middepth subtidal zone during the preoperational (1978-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model ... . .. .. . . . . ..... ... 6-38 6-11. Comparison between stations for annual mean percent frequency of occurrence of the fucoid Ascophyllum nodosum in the intertidal zone during the preoperational (1983-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . . . . . . . . . . . . . . . . . . . . . . . .... 6-41 6-12. Comparison between stations for annual mean percent frequency of occurrence of the fucoid Fucus vesiculosus in the intertidal zone during the preoperational (1983-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . ............. ........... 6-42 6-13. Comparisons between intertidal stations of mean number of taxa (per 0.0625 m') during the preoperational (1982-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of macrofaunal species (per 0.0625 m2 ) at intertidal stations,1982-1995 . ................. ............................ ... . 6-49 6-14. Comparisons between shallow subtidal stations of mean number of taxa (per 0.0625 m 2) during the preoperational (1982-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of macrofaunal species (per 0.0625 m2 ) at shallow subtidal stations, 1982-1995 ........ ..... .... . . .... .............. 6-52 6-15. Comparisons between mid4epth stations of mean logm (x + 1) density of macrofauna during the preoperational (1981-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean logw(x+ 1) density of macrofauna at mid-depth stations, 1981-1995 ...... ... 6-54 O 6-iv
6.0 MARINE MACROBENTHOS O V PAGE 6-16. Comparisons between deep subtidal stations of mean logio(x+1) density of macrofauna during the preoperational (1979-1989) and operational 6 990-1995) periods for the significant interaction term (Preop-Op X Station) of the i. NOVA model, and annual mean logio(x+ 1) density of macrofauna at deep subtidal stations, 1979-1995 . .... ... ........... . ...... ........ .... . .. 6-55 6-17. Dendrogram and station groups by year formed by numerical classification of August collections of marine macrofauna, 1978-1995 ....................... ... 6-57 6-18. Comparisons between intertidal stations of mean logio(x+ 1) of Ampithoe rubricata during the preoperational (1978-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 6-17) . . . . . . . . . . . . . . . . . . . . ... ............ . . . . . . . . . . . 6-74 O I 6-v
6.0 MARINE MACROBENTHOS 4 LIST OF TABLES 4 PAGE 6-1. Selected Benthic Taxa And Parameters Used in Anova Tests . . . . . . . . . . ...... .. 6-5 6-2. Arithmetic Means And Coefficients of Variation (CV, %) For Number of Algal Taxa And Total Algal Biomass at Various Depths And Stations During 1995 And During The Preoperational And Operational Periods . . . . . . ...... .... .. ...... 6 11 2 6-3. Analysis of Variance Results For Number of Macroalgal Taxa (Per 0.0625 m ) And 2 Total Macroalgal Biomass (g per m ) Collected in Destructive Samples at Intertidal, Shallow Subtidal, Mid-Depth Subtidal, And Deep Stations During Preoperational And Operational Years . . . . . ........ ...... ............ ........ 6-12
- 64. Summary of Spatial Associations Identified From Numerical Classification of Benthic Macroalgae Samples Collected in August Destructive Sampling (1978-1995) . . . . . . . . . 6-20 6-5. A Comparison of Percent Frequency of Occurrence of Rarely Found Species (Overall Frequency of Occurrence <4%) in August Destructive Sampling During Preoperational (1978-1989) And Operational (1990-1995) Periods And Over All Years (1978-1995) . . . . . . . . . . . . ....... . ................... .. 6-23 6-6. Arithmetic Means And Coefficients of Variation (CV,%) For Chondrus Crispus Biomass (g/m') Collected in Triannual (May, August, November) Destructive Samples in The Intertidal And Shallow Subtidal Zones During 1995 And During The Preoperational And Operational Periods . ....... ... ................ 6-26 2
6-7. Analysis of Variance Resuhs For Oendius Crispus Biomass (g/m ) at Intertidal And Shallow Subtidal Station Pairs For The Preoperational (1982-1989) And Operational (1991-1995) Periods . . . . . . . . . .......... .. ................. .. 6-27 6-8. Preoperational And Operational Means And Coefficients of Variation (CV,%), And 1995 Means For Densities of Kelp Species (#/100 m2 ) And Percent Frequency of Occurrence of Understory Species And Five Fucoid Species . . . . . . . . . ........ 6-29 2 6-9. Analysis of Variance Results For Number of Kelps /100 m And % Frequency of Occurrence of Urxierstory Species And Fucoids as Measured in The Non-Destructive Mordtormg Program . ...... ............ .... ................ 6-32 l O , 6-vi
6.0 MARINE MACROBENTHOS \
\
b) (./ PAGE 6 10. Percent Cover And Percent Frequency of Ocarrence of Dominant Perennial And Annual Macroalgal Species at Fixed Intertidai Non-Destructive Sites During The Preoperational And Operational Periods And h m3 . . . . . ......... ........ 6-44 6-11. Preoperational And Operational Arithmetic Means And Coefficients of Variation (CV,%) And 1995 Means of The Number of Taxa Collected, And Geometric Mean i Densities and Coefficients of Variation For Non-Colonial Macrofauna Collected in August at Intertidal, Shallow Subtidal, Mid-Dept'a And Deep Stations . .. ........ 6-48 6-12. Analysis of Variance Results For Number of Macrofaunal Taxa (Per 0.0625 m2 ) And l 2 Total Macrofaunal Density (Per m ) Collected in August at Intertidal (1982-1995) And Shallow (1982-1995), Mid-Depth (1980-1984; 1986-1995), And Deer Subtidal Stations (1979-1984; 1986-1995) ............. .... ............. 6-50 I 6-13. Station Groups Formed by Cluster Analysis with Preoperational wxi Operational 1 (1990-1995) Geometric Mean Density and 95% Confidence Limits of Dominant l Macrofauna Taxa (Non-Colonial) Collected Annually in August from 1978 Through I g 1995 .................... ..................... . . . . . . . . . 6-5 8 O 6-14. Percent Cover and Percent Frequency of Occurrence of Dominant Macrofauna at i 1 Fixed Intertidal Non-Destructive Sites During the Preoperational and Operational i Periods and in 1995 . . . . . . . . . . . . . . . . . . . . . . . . . ..... ... ........ 6-60 l l 6-15. Estimated Density (per 0.25 m2) and Coefficient of Variation (CV,%) of Selected i I Sessile Taxa on Hard-Substrate Bottom Panels Exposed for Four Months at Stations l B19 and B31 Sampled Triannually (April, August, December) from 1981-1995 (except 1985) . . . . . . . . . . . . ................ .................. 6-64 I 2 6-16. Geometric Mean Densities (No./m ) and Coefficients of Variation (CV,%) of Selected Benthic Macrofauna Species Collected During Preoperational and Oper-ational Periods and During 1995. ............... .............. ... 6-66 ' l 6-17. Analysis of Variance Results Comparing Log-Transformed Densities of Selected i Benthic Taxa Collected in May, August and November at Near- and Farfield Station Pairs During Preoperational (1978 - 1989) and Operational (1991 - 1995) Periods .... 6-67 A 'U 6-vii
6.0 MARINE MACROBENTHOS PAGE 6-18. Annual Mean Lengths (mm) and Coefficients of Variation (CV.%) of Selected Benthic Species Collected at Nearfield-Farfield Station Pairs During the Preoperational and Operational Periods and in 1995 . . . . . . .... ......... . 6-71 6-19. Mean Densities (per m2) and Range of Adult Sea Urchins Observed in Subtidal Transects During Preoperational (1985-1989) and Operational (1991-1995) Periods and During l995 . . . . . . . . . . ................... .. .... .. . 6-75 6-20. Summary of Evaluation of Potential Thetmal Plume Effects on Benthic Communities in the Vicinity of Seabrook Station . ... ......... . ............, . 6-77 6-21. Summary of Evaluation of Potential Thermal Plume Effects on Representative 6-78 ( Important Benthic Taxa in the Vicinity of Seabrook Station . .. ..... . . l 6-22. Summary of EvrJuation of Potential'Ibrbidity Effects on Benthic Communities in the l Vicinity of Seabrook Station . . . . . . . . . . . . . . . . ................. .... 6-81 6-23. Summary of Evaluation of Potential Turbidity Effects on Representative Important Benthic Taxa in the Vicinity of Seabrook Station . . . . . . . . . . . . . . . . ......... 6-81 LIST OF APPENDIX TABLES l 6-1. Marine Macrobenthos Sampling History . . . . . . . . . . . . . . . . . . . .......... 6-87 6-2. Nomenclatural Authorities for Macrofaunal Taxa Cited in the Marine Macrobenthos Section .............................. ...... ...... . .. 6-88 6-3. The Occurrence of Macroalgae from General Collections and Destructive Sampling at All Subtidal and Intertidal Destructive Stations, 1978-1995 . . . . . . . . . . . . . . . . . 6-89 O 6-viii
1 6.0 MARINE MACROBENTHOS
6.1 INTRODUCTION
Chapman 1973), but is also present subtidally (Hiscock and Mitchell 1980; Sebens 1985). These The predominant benthic marine habitat in the patterns of community organization are the result vicinity of Seabrook Station intake and discharge of a variety of interacting physical (e.g., desicca-structures is rocky substratum, primarily in the tion, water movement, temperature and light) and form of bedrock ledge and boulders. These rock biological (e.g., herbivory, predation, recruitment, surfaces support diverse communities of attached inter- and intraspecific competition for space) plants and animals that are important in coastal mecharusms, which vary over spatial and temporal ecosystems. In fact, hard-bottom coastal commu- scales. nities are among the most productive regions in the world (Mann 1973). This diversity and productiv. Because coastal hard-bottom communities are ity is accomplished through modification of the ecologically important, are well documented as typically two-dimensional substratum by the at- effective integrators of environmental conditions, tached plants and animals to create a multi-tiered and are potentially vulnerable to localized anthro-community that increases the number of biological pagenic impacts, studies of these communities are niches. part of ecological monitoring programs associated with coastal nuclear power plants (Vadas et al. One of the most productive features of the shore 1976; Wilce et al.1978; Osman et al.1981; and near-shore biota in the Gulf of Maine is an Schroetcr et al.1993; BECO 1994; NUSCO extensive canopy of brown macroalgae. 1994). Similarly, Seabrook Station marine Q Rockweeds (fucoids) inhabit intertidal areas macrobenthos studies are part of an extensive (Menge 1976; Topinka et al.1981; Keser and environmental monitoring program whose primary Larson 1984), while kelp inhabit subtidal areas objective is to determine whether differences that (Sebens 1986; Witman 1987). Understory layers exist among communities at nearfield and farfield generally occur beneath these canopies and contain sites in the Hampton-Seabrook area can be attrib-secondary levels of folius and filamentous algae uted to power plant construction and operation. and upright attached macroinvertebrates over a Potential impacts on the local macrobenthos from layer of encrustmg algal and faunal species, which Seabrook Station operation include direct exposure occupy much of the remaining primary rock sur- to the thermal discharge plume, most likely at sites faces (Menge 1976; Sebens 1985; Ojeda and Dear- in the upper portion of the water column (intertidal born 1989). Also, many niches created in and and shallow subtidal zones). Thennal impacts are around these attached biota are occupied by mobile unlikely in deeper areas. However, increased predator and herbivore species such as fish, snails, turbidity in discharge water resulting from trans-sea urchins, starfish, and amphipods (Menge 1979, port of suspended solids and entrained organisms 1983; Ojeda and
Dearborn 1991),
could increase shading and the rate of sedimenta-tion. To assess these potential impacts, studies Another important aspect of fucoid and kelp were implemented to identify the attached plant assemblages is the distmet zonation pattern exhibit- and ammal species occupying nearby intertidal and l ed by the biota, which throughout the North Atlan- subtidal rock surfaces, to describe temporal and tic is most obvious in the intertidal zone spatial panerns of occurrence of tnese species, and k- (Stephenson and Stephenson 1949; Lewis 1964; to identify physical and biological factors that l l 6-1
6.0 MARINE MACROBENTHOS affect variability in rocky intertidal and subtidal addition, observations were recorded from the communities. mean low water and mean sea level areas (includ-ing tide pools) in the intertidal zone. 6.2 METHODS Beginning in 1982, two intertidal stations that 6.2.1 Field Methods encompass the low to high tide levels (referred to as B1MSL and B5MSL; Fig. 6-1) were evaluated Quantitative (destructive) macrofaunal and non-destructively during April, July and Decem-macroalgal samples were collected three times ber. Observations were made at permanently annually (May, August, November) at six benthic marked 0.25 m2 quadrats at three tidal levels: the stations (Fig. 6-1); three nearfield-farfield station bare rock zone (approximate mean high water or pairs were established at lower intertidal (approxi- upper intertidal), the predominantly fucoid-covered mate mean low water: BIMLW, B5MLW), zone (mean sea level or mid-intertidal), and the shallow subtidal (4-5 m; B17, B35) and mid-depth Chondrus crispitr-covered zone (approximate mean (9-12 m; B19 B31) zones. Four additional sta- low water or lower intertidal). Percent cover of tions were sampled in August only: one mid-depth fucoid algae and percent frequency of occurrence intake station (B16) and three deep water (18-21 of several intertidal species were estimated and m) stations (nearfield-B13 and BM, and farfield- recorded according to an established species list. B34). 'lhis sampling program began in 1978 with This list inclu% several perennial and annual algal four nearfield stations (B1, BN, B13, and B19) species, gastrg. As (Acmaca testudinalis, Littorina and one farfield station (B31). Nearfield station spp. and Nucella lapillus), barnacles and B17 was added to the study in 1979, and nearfield Mytilidae. General observations for the entire station B16 was added in 1980. Subsequently, sampling area were recorded and photographs three farfield stations were added, one in 1980 were taken of each sampling quadrat within each (B34) and two in 1982 (B35 and B5). Station tidal zone. Frequency of occurrence of fucoid sampling histories are summarized in Appendix algae was also recorded along a 9.5 m transect line Table 6-1. (NAI 1991a). Epifauna and epiflora were removed by scraping Non<lestructive subtidal transects were established 2 from five randomly selected 0.0625 m areas on in 1978 to monitor larger macroinvertebrates and rock surfaces. Subtidal collections were drawn macroalgae that were not adequately represented in through a diver-operated airlift into a 0.79 mm destructive samples. Six randomly placed replicate mesh bag, placed in a labeled plastic bag, brought 1 m x 7 m band-transects were sun' eyed at to the surface and sent to the laboratory for preser- nearfield-farfield station pairs in the shallow vation and processing (NAI 1991a). Intertidal subtidal (B17, B35) atxt mid-depth (B19, B31) coBections followed a similar procedure, excluding zones in April, July and October. Percent fre-the use of an airlift. quency of occurrence was recorded for dominant "understory" macroalgae (Chondrus crispus, A comprehensive record of all visible algal species Phyllophora/Coccotylus spp. and Ptilota serrata). (" general algae") was made in conjunction with Counts of Modiolus modiolus, Strongylocentotus destructive sampling at each sampling station. In droebachiensis and the kelp species Laminaria 6-2
i N RYELEDGE j
,/ N IB5MLW \ IB5MSL o ',.. .1831 V Lh7LE !.FARFIELD '
J BOARS ' AREA-HEAD lB351 0 .5 1 Nautical Mile ") , 18341 0 k Kilometers SCALE CONTOUR DEPTH IN METERS b GREATBOARS HUD , HAMPTON in EEACH BROWNS -
'"'" '.=* ibis 1 1813I IB1MLw I NEARFIELD
~
-;; OUTER p g AREA SEABROOK B1MSLi i
STATION vB1e h IN R. s..::
'\J HAMPTON ..Disch%IB04 I SEABROOK SUNK i HARBOR ROCKS !
f i
%, SEABROOK ,
I
% BEACH ,
'\,v / .
1 i SAUSBURYBE, CH .
)
1 LEGEND l l I = benthic samples l 1 P l Figure 6-1. Marine benthic sampling stations. Seabrook Operational Report,1995. 6-3
6.0 MARINE MACROBENTHOS digitata, L saccharina, Agarum clathratum and taxa (and their station pairs) were Nucella lapillus Alaria esculenta were also made. and Ampithoe rubricata (B1MLW/B5MLW); Cancer irroratus, C. borealis, Jassa marmorata, Information on patterns of recruitment and settle- and Asteriidae (Bl*//B35); Pontogencia inermis ment of sessile benthic organisms was obtained and Strongylocentrotus droebachiensis (B19/B31, l from the bottom panels program. Bluestone panels B17/B35); and Mytilidae (BlMLW/B5MLW, (60 cm x 60 cm) were placed 0.5 m off the bottom B17/B35, B19/B31). at Stations B19 and B31, beginning in 1982. Stations BO4 and B34 were added in 1986. Short- A subsample ofindivxiuals of the above referenced term bottom panels were exposed for four months taxa collected at each station in May, August and during three exposure periods: December-April, November was measured to the nearest 0.1 run April-August, and August-December. Long-term and enumerated. For all amphipods measured, sex bottom panels were exposed for one year, de- was determined and the presence of eggs or brood ployed in August and collected in August of the was recorded. following year. Macroalgae from general collections were identi-6.2.2 Laboratory Methods fied to the lowest practicable taxon. The complete macroalgal species list was compiled from both All destructive samples were washed over a 1.0 general and destructive collections and included mm sieve. Algal species from each sample were crustose coralline algae, collected only in August. identified to the lowest practicable taxon, dried for 24 hours at 105'C, and weighed. Fauna previously All undisturbed bottom panel faces were first designated as selected species were identified and analyzed for Balanus spp. (which includes counted from May and November macrofaunal Semibalanus balanoides) arxi Spirorbidae, and then
)
samples. Selected species were determined from scraped to remove sessile bivalves and solitary previous studies to be those species that are the chordates for identification and enumeration. most useful as indicators of overall community Hydrozoa, Bryozoa and any abundant algal species type in the study area, based on abundance, trophic were analyzed only on long-term panels, level, and habitat specificity. All faunal species collected in August were identified to the lowest 6.2.3 Analvtical Methods j practicable taxon; non-colonial species were I counted and colonial taxa were listed as present. 6.2.3.1 Destructive Monitorine Program: In addition, abundance of spirorbid polychaetes at Community Analyses subudal Stations B19 and B31 was estimated from five subsamples of the algal complex Macroalgal and macrofrunal community aalyses Phyllophora/Coccotylus (formerly Phyllophora included numerical classification and analysis of spp.). variance (ANOVA; detailed below) of community parameters such as number of taxa and total abun-Life history information was obtained for nine dance or biomass from triannual or August-only macrofaunal taxa at paired nearfield-farfield samples (Table 6-1). Operational /preoperational ; stations where they were most abundant. These and nearfield/farfield differences in total abun-6-4
O O O Table 6-1. Selected Benthic Taxa and Parameters Used in Anova Tests. Seabrook Operational Report,1995. DATA ' DATA SOURCE OF
. COMMUNITY ' PARAMETER STATION PERIODS USED - CHARACTERISTICS
- VARIATION IN ANALYSIS IN ANOVAS*
Benthic Laminaria saccharina B17 1979-1989,1991-1995 Mean munber per sample Preop-Op,* Station, Macroalgae Laminaria digitata B35 1982-1989,1991-1995 period and station. Year, Month Alaria esculenta B19,B31 1978-1989,1991-1995 Aganim clathratum Chondnes crispus Bl7,B19,B31 1981-1989,1991-1995 Mean % frequency per year. Prcop-Op, Station, PhyllophoraCoccotylus B35 1982-1989,1991-1995 Mean % frequency per year, Year, Month no transformation. Ptilota serrata Mean % frequency per year. m Chondnis crispus B1MLW, B5MLW 1982-1989,1991-1995 Biomass per sample period Preop-Op. Station, t'n B17,B35 1982-1989,1991-1995 and replicate. Square root Year, Month transformation, shallow subtidal; no transfonnation, intertidal. Number of taxa B1MLW, B5MLW 1982 -1995 Amount or number per sta- Prrop-Op. Station. Total biomass B17.B35 1982- 1995 tion, year and replicate; no Year, Month B16,B19,B31 1980 -1984,1986 -I995 transformation. B04,B34,B13 1979 - 1984,1986 - 1995 Ascophyllum nodosum B1MSL,B5MSL 1983-1989,1991-1995 Mean % frequency per sam- Preop-Op, Station, Fucus vesiculosus pie period and year. Year, Month Fucus distichus spp. edentatus Fucus distichus spp. distichus Fucus sp. (Continued)
Table 6-1. (Continued) DATA DATA SOURCES OF COMMIJNITY PARAMETER STATION PERIODS USED CHARACTERISTICS
- VARIATION IN ANALYSIS IN ANOVAS' Benthic Ampilhoe rwbricata' B1MLW, 1978-1989,1991-1995 Abundance per replicate; Preop-Op, Station.
Macrofauna Nucella lapillus B5MLW 1982-1989,1991-1995 3 dates per year. Year, Month Mytilidae spat Jassa marmoratad B17,B35 1978-1989,1991-1995 Abundance per replicate; Preop-Op, Station, Mytilidae spat 1982-1989,1991-1995 3 dates per year. Year, Month Asteriidae B17,B35 1981-1989,1991-1995 Abundance per replicate; Prety-Op, Station, 1982-1989,1991-1995 3 dates per year. Year, Month Pontogencia inennis' B19,B31 1978-1989,1991-1995 Abundance per replicate; Preop-Op. Station, Mytilidae spat 3 dates per year. Year, Month Stmngylocentmtus dwebachiensis Total density B1MLW, 1982-1995 Amount or number per Preop-Op, Station, Year 9 Number of Taxa B5MLW; 1982 -1995 year, station and repli-
- B17, B35; 1980 - 1984,1986 - 1995 eate; no transformation B1; B19,B31; 1979-1984,1986 -1995 for number of taxa.
B16, B19, B31; B04,B34 B13 Afodiolus modiolus B19,B31 1980 - 1989, Ranked densities; mean Preop-Op, Station. Year, 1991 - 1995 per sample period,no Month tranformation.
- 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; juvenile / adult.
O O O
6.0 MARINE MACROBENTHOS dance or biomass and number of taxa were A comparison of macroalgal and macrofaunal evaluated using a multi-way analysis of variance community composition during operational and procedure (ANOVA, SAS Institute Inc.1985). A preoperational periods was carried out using fixed effects ANOVA model was used to test the numerical classification methods (Boesch 1977). null hypothesis that spatial and temporal abun- Bray-Curtis similarity indices were computed for dances during the preoperational and operational the annual August log-transformed average densi-periods were not significantly (p > 0.05) different. ties (macrofauna) and monthly square-root trans-The data collected for the ANOVAs met the formed average biomass (macroalgae). criteria of a Before After/ Control-Impact (BACI) Macroalgal species with less than 2% frequency of sampling design as discussed by Stewart-Oaten et. occurrence and macrofaunal species with less than al. (1986), where sampling was conducted prior to 6% frequency of occurrence were excluded from and during plant operation, and sampling locations the analysis. In all,34 algal and 93 faunal taxa included both potentially impacted and non-im- were included in the collections for which similar-pacted sites. The ANOVA was a two-way facto- ity indices were computed. The group average 4 rial with nested effects that provided a direct test method (Boesch 1977) was used to classify the . for the temporal-by-spatialinteraction. The main samples into groups or clusters. The actual effects were period (Preop-Op) and station (Sta- computations were carried out by the computer tion); the interaction term (Preop-Op X Station) program EBORDANA (Bloont 1980). was also included in the model. Nested temporal p effects were years within operational period (Year 6.2.3.2 Destructive Monitorine Procram: V (Preop-Op)) and (in some cases) months within Selected Species An=Ivses year (Month (Year)), which were added to reduce the unexplained variance, and thus, increase the Some algal and faunal taxa were selected for more sensitivity of the F-test. For both nested terms, detailed analyses due to their ecological or eco- l variation was partitioned without regard to station nomic importance in the study area. ANOVAs I (stations combined). The final variance not ac- were used to evaluate temporal and spatial differ-counted for by the above explicit sources of varia- ences in algal biomass or faunal abundances ob-tion constituted the Error term. The tained from the destructive monitoring program. preoperational period for each analysis was speci- 1 fied as the period during which at least one 6.2.3.3 Non-Destructive Monitorine Pim-m: nearfield and one farfield station were sampled Selected Snecies Analvses concurrently (thus maintaining a balanced model ) design). Preoperational periods for each analysis Comparisons between preoperational and opera-are listed on the appropriate figures and tables. tional periods were made by means of ANOVA or The Waller-Duncan multiple comparison test was Wilcoxon's summed ranks test (Sokal and Rohlf used to rank the levels of the main effects (Preop- 1969) for several subtidal species (telps and Op, Station) when they were significantly differ- understory algae and associated fauna species) and ent. The LS Means procedure was used to rank for several intertidal species (fucoids and associ-the levels of the interaction term (Preop-Op X ated fauna species). ANOVA models were used to O Station) when it was significant. examine the imeraction between period and station (a 6-7
6.0 MARINE MACROBENTHOS for algal species only, and were structured simi- Ninety-one algal taxa were collected over all larly to those run on collections from the destruc- stations during the 1995 sampling year (Appendix , tive monitoring program. Data transformations Table 6-3); the previous operational high of 80 were performed prior to runnmg ANOVA models taxa occurred in 1991. The highest annual total to ensure that assumptions of normality were met. number of taxa collected during the operational The log (x+ 1) transformation achieved normality period from each of the three major groups, in most cases where untransformed data were non- Chlorophyta, Phaeophyta and Rhodophyta, oc-normal. In the few cases where transformation did curred in 1995 (20, 25 and 46 taxa, respectively). not provide an adequate approximation of normal- The 1995 total ranks third highest over all years ity (typically due to multiple zero values in the data studied, with 95 and % taxa having been collected set), ANOVA models were not run. in 1983 and 1984, respectively (Appendix Table 6-3). Relatively more chlorophycean and 6.3 RESULTS AND DISCUSSION phaeophycean taxa, and relatively fewer rhodophycean taxa were collected in 1995 com-6.3.1 Marine Macro 21ome pared to the average over all 17 years. In 1995, chlorophycean taxa accounteA for 22% of the total, 6.3.1.1 Horizontal Ledne Communities phaeophycean taxa accounted for 27%, and rhodophycean accounted for 51%. The average Number of Taxa composition over all years (excluding 1990) was 20%,26%. and 55%, respectively. There was no Assessment of spatial and temporal patterns in apparent difference between preoperational (1978-number of algal taxa has proven useful as an 1989) and operational (1991-1995) averages (Ap-indicator of impacts associated with several nuclear pendix Table 6-3). power plants in New England (Vadas et al.1976; Wilce et al.1978; Schneider 1981; NUSCO 1994). In general, the assemblage of macroalgal taxa To assess algal community diversity at Seabrook collected over the years at Seabrook sites was very study sites, the number of algal taxa was deter- consistent with other New Hampshire studies mined in two ways. Numbers of taxa from general (Mathieson and Hehre 1986). The floristic affm' ity collections were used to qualitatively characterize ratio (Rhodophyta plus Chlorophyta, divided by the overall floristic composition at a given study Phaeophyta; Cheney 1977 cited in Matheison et site. The destructive sampling program provided al.1991) for the preoperational period was 3.0, quantitative information on algal diversity (i.e., reflecting an assemblage of plants intermediate number of taxa per unit of area), data which are between cold-temperate and warm-temperate more amenable to statistical analysis. A total of affinities, while the ratio for the operational period 143 taxa have been collected from the two pro- (excluding 1990) was slightly lower, at 2.8. The grams during the 17-year study (Appendix Table 6- ratio for 1995 was 2.6, indicating a slightly more 3); only two of these taxa were collected for the cold-temperate assemblage. first time in 1995: Chordaflum and Puncrada plantcginea. The numbers of taxa collected in 1995 at each station were within preoperational ranges at all locations except B17 and B31, where the 1995 6-8
i 6.0 MARINEMACROBENTHOS \ p totals were slightly higher (Figure 6-2). The 1995 means between the two stations did not appear to totals at all stations were also comparable to or reflect a clear biological difference, and the fact : slightly higher than most other operational years. that the greatest change between periods occurred Patterns of number of taxa colketed within each at the farfield station indicates that these differ- ' depth zone were consistent between the ences are not related to station operation. preoperational and operational periods. Over all zones, median preoperational total numbers of taxa The total numbers of taxa collected in the shallow collected were highest in the lower intertidal and subtidal zone at farfield station (B35) were signifi- ! shallow subtidal zones, and generally lowest in the cantly higher than nearfield (B17) totals in the deep subtidal and mid-intertidal zones. Opera- preoperational and operational periods and in 1995 tional median totals followed the same pattern as (Tables 6-2,6-3). The total number of taxa col-preoperational median totals. During the lected over both shallow subtidal stations remained preoperational period, median farfield total num- stable between the preoperational and operational bers of taxa were higher than nearfield totals in the periods as indicated by the non-significant interac-lower intertidal, shallow subtidal, and mid-depth tion term in the ANOVA model(Table 6-3). subtidal zones. Median nearfield totals were higher than farfield totals in the mid-intertidal zone Numbers of taxa in the mid-depth zone showed and the deep subtidal zone. in 1995, this pattern changes among stations and between operational l was slightly different. More taxa were collected at and preoperational periods. Numbers of taxa l p the nearfield shallow subtidal station (46 at B17) collected throughout the study and in 1995 at d than at the farfield station (41 at B35), and more taxa were collected at the deep farfield station (20 farfield mid-depth subtxial station B31 were signif-icantly higher than those collected at either of the l at B34) than at the two nearfield deep stations (17 two nearfield stations (B16 and B19; Tables 6-2, taxa each at B04 and B13). 6-3). Relationships among stations were not consistent between periods, resulting in a signifi-Numher of Tara: Ouantitative Samples cant interaction in the ANOVA results (Preop-Op X Station term, Table 6-3). At station B19, the Quantitative results from the destructive sampling number of taxa collected declined significantly program supported the results from general collec- during the operational period, while there was no tions. Mean numbers of taxa collected at farfield significant difference at B31, and a significant intertidal station B5 were higher than means from increase at B16. High numbers of taxa collected at nearfield station B1 during preoperational and B16 in 1993 and 1995 contributed to the significant operational years and in 1995 (Table 6-2). Num- increase between periods (Figure 6-4). The appar-bers of taxa collected over both stations declined ent decline in the numbar of taxa collected at B19 significantly during the operational period (Preop- during the operational period was due in part to a Op term), but to a slightly greater extent at B5 relatively high peak in 1987, and the subsequent compared to B1, as indicated by a significant decline that started in 1988. The number of taxa Preop-Op X Station interaction term (Table 6-3; collected at B19 began to rebound in 1991, and has Figure 6-3). Annual means for the two stations fluctuated since. Although preoperational totals tracked one another closely throughout the entire exceeded operational totals, the lowest total num- \ study (Figure 6-3). Subtle differences in annual ber of taxa collected at B19 occurred during the 6-9
Intertidal (Triannual) Shallow Subtidal(Triannual)
,m sc
- : : opuescnd O
,6 6a ses g oaa m g) a 50 e oa l] A 8 " "
fe m fe o "e'
" - e 3,
o o .m 3 a m9, o 3 " 20 e 8 m 5
" na , o io u
5 5 0 0 BilASL B5MSL 894W B9Aw Bt7 B35 Mid-Depth Subtidal(Triannual) Deep Subtidal(August only) es : E. preopensc,w soe-e-+ cperskrw eoW Opeasand gA A A 1996 gA A A 1995 50 2 e # 40 m oa # bz " 82 2 "" # m oa E 1z g m o O di o m
'" g
O 116 3 e on m
e . .l^ o 10 10 5 5 o o l m a a m m m I l Figure 6-2. Median number and range of unique macroalgal taxa collected in the intertidal and subtidal zones during the preoperational and operational periods (calculated from annual totals) and the 1995 total number of unique taxa. Seabrook Operational Report,1995. O 6-10
O O O Table 6-2. Arithmetic Means and Coefficients of Variation (CV,%) for Number of Algal Taxa and Total Algal Biomass at Various Depths and Stations'During 1995 and During the Preoperational and Operational Periods. Seabrook Operational Report,1995. ' FREOFERATIONAL* REPORT YEAR OPERATIONAL PERIOD - 1995 FERIOD FARAMETER DEFTH ZONE STATION MEAN - CV~ MEAN . MEAN CV Number of taxa Intertida? B1MLW 15.6 15.8 17.6 153 153 (no. per 0.0625 m') B5MLW 22.2 13.6 21.0 20.0 9.6 Shallow subtida? B17 14.2 13.0 16.8 15.5 7.6 B35 18.1 18.1 21.0 19.1 19.2 Middepth' B16 9.0 83 11.6 9.8 16.1 B19 10.2 13.0 11.0 9.5 14.8 B31 11.1 12.4 15.4 11.5 21.1 Deep
- B04 7.6 10 2 9.2 7.9 11.2 m BI3 7.9 8.9 8.6 8.4 15.5
/ B34 7.7 7.9 10.4 7.9 16.0 r
Total biomass Intertida? B1MLW 1042.7 23.7 868.5 999 2 11.6 (g'm') B5MLW 1034.9 22.9 1124.0 1015.6 80 Shallow subtida? B17 9163 13.2 8673 923.1 11.7 B35 891.4 15.7 707.1 864.9 21.1 Mid4cpth* B16 779.8 28.1 768.7 621.5 22.2 1319 308.6 25.8 214.6 322.1 33.4 B31 471.2 27.5 464.9 3813 17.8 Deep
- B04 99.6 30.1 79.6 91.0 19.8 B13 96 0 32.1 128.2 89.0 $3.7 B34 713 71 3 94.6 49.9 53.5 Statiens B1MLW, D17, B19, B31: 1978 - 1989; Stations B5MLW, D35: 1982 - 1989; Station B16: 1980 - 1989; Station B13, B04: 1978 - 1984,1986 - 1989; B34: 1979 - 1984,1986 - 1989; means of annual means.
' Sampled destructively in May Aupist and November, operational period = 1991-1995.
' Station B16 sampled in August only, so means for each station in this depth zone are August-only; operational period = 1990-1995.
*All stations sampled in August only; operational period 1990-1995.
Table 6-3. Analysis of Variance Results for Number of Macroalgal Taxa (per 0.0625 m2 ) and Total Macroalgal 2 Biomass (g per m ) Collected in Destructive Samples at Intertidal, Shallow Subtidal, Mid-Depth Subtidal, and Deep Stations During Preoperational and Operational Years. Seabrook Operational Report,1995. PARAMETER DEPTH ZONE SOURCE OF - df MS F* MULTIPLE COMPARISON' (STATIONS) VARIATION (Ranked in decreasing order) - Number of Taxa Intertidaf Preop-Op* I 303.71 40.92 * *
- Preop > Op (BIMLW,BSMLW) Stationd 1 2066.41 278.43*** B5 > B1 Year (Preop-Op)* 11 53.36 7.19 * "
Month (Year)' 26 48.21 6.50* Preop-Op X Station' 1 38.48 5.18 * " BSPre > B50p > BlPre > BIOp Error 309 7.42 ? Shallow SubtidaP Preop-Op 1 8.28 1.65 NS G (B17,B35) Station 1 552.99 110.09' " B35 > B17 Year (Preop-Op) 11 44.61 8.88 * *
- Month (Year) 26 21.98 4.38"*
Preop-Op X Station 1 0.31 0.06 NS Error 309 5.02 Mid-depth
- Preop-Op 1 0.91 0.36 NS (B16,B19 B31) Station 2 71.54 28.65 * *
- B31 > B19 B16 Year (Preop-Op) 13 22.14 8.87"*
Preop-Op X Station 2 12.03 4.82 *
- B3100 B31 Pre > B19 Pre B1600 B190p B16 Pre Error 205 2.50 Deep
- Preop-Op 1 4.41 3.14 NS (B(M,B34,B13) Station 2 4.00 2.85 NS Year (Preop-Op) 14 7.38 5.25 * "
Preop-Op X Station 2 0.08 0.05 NS Error 220 1.41 (continued) e O O
a ,
\. ,] N.) %.)
Table 6-3. (Continued) PARAMETER DEPTli ZONE SOURCE OF df MS P . MULTIPLE COMPARISON' (STATIONS) VARIATION (Ranked in decreasing order) Total Biomass Intertidal
- Preop-Op 1 421,365 6.70* Preop > Op (B1MLW,B5MLW) Station 1 396,513 6.31* B1 > B5 Month (Year) 26 793,067 12.61 "
- Year (Preop-Op) 11 620,978 9.88* *
- Preop-Op X Station 1 610,558 9.71 *
- BIPre>BSOo BSPre BION Error 309 62,881 Shallow Subtidal* Preop-Op i 28,843 0.50 NS (B17,B35) Station i 116,299 2.00 NS Month (Year) 26 875,494 15.06* "
Year (Preop-Op) I1 364,848 6.28*" Preop-Op X Station 1 39,173 0.67 NS Error 309 58,120 Mid-Depth
- Preop-Op I 324,542 7.71 " Preop > Op (B16,B19,B31) Station 2 2,793,792 66.38* " B16 > B31 > B19 Year (Preop-Op) 13 131,620 3.13 * *
- 9 g Preop-Op X Station 2 116,253 2.76 NS Error 205 42,089 Deep
- Preop-Op 1 10,041 4.49* Preop > Op (B04,B34,B13) Station 2 28,954 12.94 "
- B04 B13 > B34 Year (Preop-Op) 14 5,350 2.39 *
- Preop-Op X Station 2 962 0.43 NS Error 220 2,238
- Includes all months (May, August, November).
' Includes August only.
- Compares Preop to Op, regardless of station; years included in each station grouping: if all three months used. Op years = 1991-1995; if only August data are used Op years = 1990-1995; Preop years: BIMLW, B5MLW = 1982-1989; B17, B35 = 1982-1989; B16, B14, B31 = 1980-1984,1986-1989; B04, B34, B13 = 1979-1984,1986-1989.
' Stations within depth zone, regardless of year, month or period. ' Year nested within preoperational and operational periods regardless of station. ' Month nested within years, regardless of station. ' Interaction of the two main effects, Preop-Op and Station. *NS = not significant (p>0.05); * = significant (0.052p> 0.01); " = highly significant (0.012p>0.001); *" = very highly significant (O. 0012p). 'Waller-duncan multiple means comparison test used for significant main effects. LS Means used for interaction terrt Underlining indicates no significant difference (as0.05).
6.0 MARINE MACROBENTHOS l Intertidal zone: Number of Taxa E -
. . . . . B1MLWBsutw 18 f, 16 ,,,,__
E ~~~--....,,,"" gu - - - - - . . . . . , , , , , ,,,
@n a \
k 10 t ._ 1 5* b . 4 1 2 0 er opween=> opnamnal PERIOO 20 18 ,#
/'s, I
j l i j l
--- asutw B1MLw Ol
' l l g16 el '~. ,_ l l E _\ l l ga 's ; j
,12 s_ __r I ,0 l l l i p le ! !
b l i 6 l l l l l 1
- 4 l l l l 2 Pr.operwuorw opw.enai l l l 1 0 ' I 82 83 84 85 86 87 86 89 90 91 92 93 94 95 vsAR 2
Figure 6-3 Comparison between stations for number of macroalgal taxa (per 0.0625 m ) n the intertidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for the significant irneraction term (PreopOp X Station) of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report, 1995. 6-14
6.0 MARINE MACROBENTHOS Mid-depth Subtidal Zone: Number of Taxa 12 _________ - -----~~~ to ****--------.......,,,,,,,,----- ~ _.. ...; 9 8 E es Y 6 g . .
- _ . , B1, ,
b l- 2 1 O Prooperabonal Opershonal PERIOD
; 16 B16 1
\d ---
- - B31 B19 l I
/
'd /
l / t 12 A < l f /\ / h 10% ____[ /'~ ,,
\ \' r '
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l
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6 s l l- 2 Prooperational l l l Operational l l O_ l 80 81 82 83 84 85 86 87 88 89 90 9 92 93 94 95 vse Figure 6-4. Comparison among stations for number of macroalgal taxa (per 0.0625 m2) in the mid-depth zone durmg the preoperational (1980-1984; 1986-1989) and operational (19901995) periods ,- p) (" for the significant interaction term (Preop-Op X Station) of the ANOVA model. Seabrook Operational Report,1995. 6-15
6.0 MARINE MACROBENTHOS preoperational period (1989), emphasizing the with a subsequent increase beginning in 1991. The cyclical namre of this measurement of the algal drop in biomass at B1 between 1994 (NAI 1994) community. The numbers of taxa collected at B16 and 1995, when biomass increased at B5, likely over the years has also been quite variable, with an accounts for the significant interaction, and may all-time low occumng in 1991 and an all-time high reflect a short term cycle consistent with occurring soon after in 1995. The fluctuations preoperational fluctuations. observed at each of the mid-depth stations over the years, along with the differences noted between the Mean biomass in 1995 at Station B17 was slightly two nearfield stations, suggest that the observed lower than the preoperational and operational phenomena were unrelated to the operation of means, while in 1995 mean biomass at Station B35 Seabrook Station. was substannally lower. There were no significant differences between stations or periods in mean At each station in 1995, the number of taxa col- total biomass in the shallow subtidal zone (Table 6-lected in the deep subtidal zone in 1995 was higher 2 Table 6-3). Because of this consistency, the than both the preoperational and operational means interaction term in the ANOVA model was not (Table 6-2). ANOVA indicated that there were no significant. significant differences in number of taxa between the preoperational and operational periods, or A decline in mean total biomass occurred at the among stations (Table 6-3). The relationship intake (B16) and farfield (B31) mid-depth stations among stations was consistent between the during the operational period, while mean total preoperational and operational periods as indicated biomass increased at the discharge station (B19; by the non-significant interaction term (Table 6-3). Table 6-2). In 1995, mean biomass was lower than both the preoperational and operational means Total Biomass at Station B19, and lower than the preoperational mean at Stations B16 and B31. Over all three Biomass generally decreased with increasing stations combined, mean biomass declined signifi-depth, similar to patterns observed in the number cantly between the preoperational and operational of taxa collected (Table 6-2). Preoperational mean periods (Table 6-3). During both periods, mean total biomass at the intertidal nearfield station (B1) total biomass was significantly higher at the intake was higher than at the farfield station (BS), but station and lowest at the discharge station, with the then dropped below farfield biomass during the farfield station intermediate. The consistency of operational period and in 1995 (Table 6-2). Mean the relationship among the three stations resulted in total biomass decreased significantly in the a non-significant interaction term (Table 6-3). nearfield area (B1), between the preoperational and operational periods but remained unchanged in in the deep zone, mean biomass in 1995 was lower the farfield area (Table 6-3), resulting in a signifi- than the preoperational and operational means at cant interaction term (Preop-Op X Station; Table Station BN, but higher at Stations B13 and B34 6-3). Nearfield biomass was higher than farfield (Table 6-2). Mean total biomass was significantly biomass during most preoperational years, most higher at the two nearfield stations (BN and B13) notably in 1986 (Figure 6-5). However, a decline compared to the farfield station (B31) during both is evident at both stations between 1982 and 1990, the preoperational and operational periods (Table 6-16
6.0 MARINE MACROBENTHOS T ' Intertidal Zone: Total Biomass 1200 sooo ....................................... . y i 800 i
,a .00
= ewtw
- - - + . + B5MLW l_
1 2oo ; l O Proopwath penco W i 1
"l l l - - - -e' "u 8
s m 1400 , I I
' I l l l i i ;
g 1200 s l l g , e' I I ,
' l (200o
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s I l
== l l l
1 400 I , I I I I
== l l Proopwadonal l l Opwauonal O I I i 82 83 84 85 88 87 88 80 Do 91 92 93 94 95 vsAn Figure 6-5. Comparison between stations for annual mean total macroalgal biomass (g per m2 ) in the intertidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for p the significant interaction term (Preop-Op X Station) of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational !] Report,1995.
l 6-17
6,0 MARINE MACROBENTHOS I 6-3), although biomass over all three stations Collections, from the two shallow subtidal stations declined significantly between periods (Preop-Op (B17 and B35) comprised Group 2 (Table 6-4). In term, Table 6-3). The consistency in mean bio- addition to C. crispus and Phyllophora/Coccotylus mass among the three stations and between the two (the two top dominants), shallow subtidal periods resulted in a non-significant interaction dominants included, in descending order of percent term (Preop-Op X Station term, Table 6-3). of total biomass, Ceramium nodulosum, Cystocloniumpurpureum, and Comilina oDicinalis. Macr =1ont Cammunity Analvsis The biomass of Group 2 as a whole, as well of its component species, changed little during the Multivariate community analysis techniques were operational period (Tables 6-2, 6-3, 6-4). used in this study to quantify the degree of similar-ity among all August macroalgal collections made Groups 3,4 and 5 included only mid-depth stations at the macrobenthic sampling stations since 1978. B16, B19 and B31, respectively. These three In this case,165 station / year collections, repre- stations were segregated from one another by sented by 34 macroalgal taxa, were grouped into significant differences in total biomass (Table 6-3) seven station groups. A power plant-induced as well as differences in species assemblages impact to the macroalgal community could be (Table 64). Ozondms crispus became less impor-inferred from the failure of operational years' tant at B16 compared to the intertidal and shallow collections (1990-1995) at a station to be grouped subtidal zones, dropping to third largest component with collections from preoperational years (1989 of total biomass. Phyllophora/ Coccotylus was the and earlier) at that station. However, all collec- dominant at B16, with a biomass higher than in any tions were invariably grouped by station, with all other group, followed (in descending order) by years (preoperational and operational) included Phycodrys rubens, C. crispus, Cystoclonium (Figure 6-6). Although the dominant taxa at all purpureum, Ceramium nodulosum, and stations were members of the Rhodophyta, each Callophyllis cristata. The biomass of each of the group was distinguished from the others by the top three dominants declined between periods abundance of a characteristic macroalgal species (Table 6-4), as did group biomass overall (Table 6-assemblage. 2) Collections from the intertidal stations (B1MLW Collections at discharge Station B19 comprised and B5MLW) comprised Group 1 (Table 6-4). Group 4. Seven taxa each accounted for more The three dominant taxa in this group (based on than 2% of total group biomass, and included, in percent of total group biomass), in descending descending order (based on the preoperational order, were Chondrus crispus, Mastocarpus period) Phyllophora/Coccotylus, Phycodrys ru-stellatus and Comilma oficinalis. M. stellatus was bens. Corallina oDicinalis, Ptilota serrata, restricted to intertidal collections. Biomass de- Callophyllis cristata, Cystoclonium purpureum, and creased overall in Group 1 between periods (Ta- Membranoptera alata. Increased amounts of M. bles 6-2 and 6-3), ahhough the relative contribution alata during the operational period resulted in its I to total biomass of each of the three major compo- inclusion as a Station B19 dominant for the first l nents of the group remained similar (Table 6-4). time in 1995, although it was present in low l 6-18 1 l
7s o c U b bs
- , - c ,s* w we oi , s t.nty 0.0 -
0.1 - O 20 0.2 - 03 - b 3 0.4 -
.s m
.n 0.5 _
E U g 0.6 - T & 1 G 0.7 _ l 0.8 - q ' l 0.9 -
/ lllN
'/j Enli!iliil!!!
1.0 I i i i i Group I -Intertidal (BIMLW, B5MLW) Group 2 - Shallow Subtidal (BI7, B35) Group 3 - Mid-depth: Farfield (B31) Group 4 - Mid-depth: Intake (BI6) Group 5 - Mid-depth: Discharge (D19) Group 6 -Deep Intake (B13) Group 7 - Deep: Discharge /Farfield (B04, B34) Figure 6-6. Dendrogram and station groups formed by numerical classification of August collections of marine benthic algae, 1978-1995. Seabrook Operational Report,1995.
Table 6-4. Summary of Spatial Associations Identified from Numerical Classification of Benthic Macroalgae Samples Collected in August Destructive Sampling (1978 - 1995). Seabrook Operational Report,1995. GROUP BIOMASS (gh') WITillN/ DEITH BETWEEN PR EOl* OP' ZONE MEAN YEARS GROUP (GROUP) STATION . DEITH(m) INCLUDED SIMILARITY DOMINANT TAXA
- LCL MEAN UCL LCL MEAN UCL Intertidal BIMLW MLW 1978 -1995 0.66/0.33 Chondnes cnspus 7%4 986.2 1175.9 625.1 823.3 1021.6 I B5MLW MLW l982 - I995 Mastocarpus stellatus 106.6 215.2 323.9 61.0 177.4 293.8 Corallina oficina!u 19.9 51.2 82.5 0.9 16.2 31.5 m Shallow B17 4.6 1978- 1995 0.76/0.54 Chondnes enspus 662.6 774.2 885.9 550 8 7551 959.4 Q Subtidal B35 I982 - I995 Phyllophom-Coccotylus 142.8 204.7 266.6 125.9 221.I 316.4 2 Cemmlum .wdulosum 48 6 69.3 90 0 47.8 75.3 102.9 Cystoclonium purpurrum I5.5 56.6 97.7 36.0 71.1 106.1 Corallina oficinalis 28.3 51.6 74.8 23.4 42.7 62.0 Mid-depth B16 9.4 1980 - 1984; 0.79/0.67 PhyllophomCoccotjius 304.6 404.5 504.3 235.3 301.0 366 8 Intake 1986 - 1995 Phyrodrys nabens 117.8 188.9 259.9 71.7 132.9 194.1 3 Chondnas crispus 26.5 57.0 87.4 0.0 43.4 100.5 Cystoclonium purpurrum 18 0 44.5 71.0 0.0 57.3 l25 8 Ceramium nodutosum 14.3 35 0 55.7 0.0 40.2 82.6 Callophyths enstata 23.8 32.5 41.1 16 8 31.2 45.7 (Continued)
O O O
O O O Table 6-4. (Continued) GROUP BIOMASS (ghn') WrrHIN/ DEPTH BETWEEN - -PREOF" OF' ZONE MEAN YEARS GROUP (CROUP) STATION : DEPTH (m) - INCLUDED SIMILARrfY ' DOMINANTTAXA' LCL MEAN1 UCL LCL MEAN -UCL Mid-depth B19 12.2 1978 -1995 0.76/0.67 PhyllophomCoccutylus 163.6 201.9 240.1 102.1 180.9 259.7 Discharge Phycodrys mbens 30.9 50.2 69.5 32.9 84.1 135.3 4 Corallina oficinalis 10.8 15.2 19.6 3.4 6.6 9.8 Ptilota sermta 9.7 16.0 22.3 0.0 18.0 41.2 Callophyllis cristata 6.8 12.5 18.2 6.7 13.4 20.1 Cystoclonium purpureum 1.6 6.0 10.4 2.5 8.6 14.6 Alembmnoptera alata 1.9 4.3 6.8 1.4 6.2 11.0 Mid-depth B31 9.4 1978 - 1995 0.76/0.64 PhyllophomCoccotylus 148.5 213.2 277.8 78.7 140.6 202.5 Farfield Chondms crispus 72.5 114.8 157.1 28.4 94.1 159.8 5 Com/ lina ogicinalis 71.1 97.8 124.5 62.1 84.4 106.7 m Phyrodrys rubens I7.4 22.9 28.4 11.8 27.3 42.8 ' O Callophyllis cristata 5.0 8.7 12.5 0.0 8.6 17.5
~
Alembranoptera alata 2.2 5.3 85 3.0 7.8 12.5 Polysiphonia stricta 01 0.2 0.3 0.0 7.7 24.0 Deep B13 18.3 1978 - 1984; 0.65/0.53 PhyllophomCoccotylus 45.1 68.8 92.6 23.6 69.0 114.5 Intake 1986 - 1995 Ptilota serrata 7.6 11.5 15.5 0.3 6.6 13.0 6 Phycodrys rubens 2.9 5.8 8.8 1.3 5.0 8.8 Polysiphonia stricta 0.0 2.9 6.2 0.0 2.2 5.2 Scageliapylaisaei 0.0 2.9 5.7 0.0 2.7 5.6 Callophyllis cristata 1.2 2.4 3.6 0.6 1.5 2.4 i Deep B04 I8.9 - 21.0 1978 -1984; 0.64/0.53 Ptilota serrata 45.7 64.0 82.3 33.3 45.5 57.6 Discharge / 1986 - 19 % PhyllophomCoccotylus 5.9 11.0 16.0 4.2 10.6 17.0 Farfield B34 1979 -1984; Com/ lina oficinalis 3.3 6.9 10.4 0.3 1.5 2.7 ; 7 1986 - 1995 Scageliapylaisaci 0.1 1.3 2.5 1.7 8.1 14.4 - Phycodrys rubens 0.6 1.0 l.4 0.3 I.5 2.6
' Dominant taxa comprise 2% or more of total biomass in cil.cr or both of the periods (Preop, Op).
' Preop = preoperational penod,1978-1989 (Stations B1MLW, Bl7, B19, B31: 1978 - 1989; Stations B5MLW, B35: 1982-1989; Station B16: 1980 - 1984,1986-l %'9; Stations B13,B04: 1978-1984,1986 - 1989; B34: 1979 -1984,1986-1989).
*Op = operational period, 1990-1995.
1 i 6.0 ALARINE MACROBENTHOS amounts throughout the preoperational period. Group 7 consisted of collections from the two Overall, the operational mean biomass of Group 4 remaining deep stations, B04 (discharge) and B34 was higher than the preoperational mean (Table 6- (farfield) (Table 6-4). Five taxa comprised the i 2), although the biomass of some of the dominants dominants in this group and included in descending ! (Phyllophora/Coccotylus and C. opcinalis) de- order: Ptilota serrata, Phyllophora/Coccotylus, clined during the operational period (Table 6-4). Corallina oficinalis, Scagelia pylaisaci, and The largest increase in biomass during the opera- Phycodrys rubens. Ourall Group 7 biomass tional period was noted for P. rubens; other declined between periods (Table 6-2). Declines dominants changed little between periods. were most apparent for P. serrata and C. opcinalis, while S. pylaisael biomass increased Collections at farfield Station B31 formed Group substantially between periods (Table 6-4).
- 5. Seven species accounted for 2% or more of the total biomass of this assemblage and included, in The community analysis techniques described l
descending order, Phyllophora/Coccotylus, Chon- above used biomass values from a large number of i drus crispus, Corallina ofcinalis, Phycodrys algal taxa (34 out of a total of 79; all those with a j rubens, Callophyllis cristata, Afembranoptera frequency of occurrence in destructive samples of alata, and Polysiphonia stricta. The latter two taxa at least 2% over all depth zones and all years). l were included as dominants at Station B31 for the However, these analyses are influenced most first time during the operational period due to strongly by commonly-found species with high increases in biomass in 1995 (Table 6-4). Total total biomass; small, rarely found taxa contribute biomass of Group 5 decreased between periods little to the Bray-Curtis similarity indices. There-l (Table 6-2), as was reflected in the decline in fore, a further community analysis was performed, l biomass of Phy## ora /Coccotylus, C. opcinalis examining any trends in the occurrence of rarely and C. crispus : aute 6-4). encountered species (frequency of occurrence in august destructive samples less than 4%). Of the l Group 6 consisted of collections from deep intake 39 species that met this criterion in either the station B13. Total biomass was an order of magni- preoperational or operational period or both (Table tude lower in the deep subtidal zone compared to 6-5), eight were found in both preoperational (1989 the shallower zones (Table 6-2). However, several and earlier) and operational (1990-1995) periods, taxa were present that accounted for 2% or more but have decreased in frequency of occurrence in of this group's total biomass: Phyllphoral the operational period (Elachista fucicola, Coccotylus, Ptilota serrata, Phycodrys rubens, Rhodomela confe.'voides, Gymnogongrus Polysiphoma stricta, Scagelia pylaisari (which was crenulatus, Ectocarpus fasciculatus, Leathesia not present in any of the shallower depth zones), difformis, Ulvaria obscura v. blyttii, Cladophora and Callophyllis cristata. Total biomass of Group sericea, Porphyra miniata). Six species were 6 decreased between periods (Table 6-2). Biomass found in both periods, but have become relatively of each of the dominants declined slightly or more frequent since Seabrook Station began opera-showed no change between periods. tion (Bonnemaisonia hamsfera, Desmarestia viridis, O 6-22
6.0 MARINE MACROBENTHOS Table 6-5. A Comparison of Percent Frequency of Occurrence of Rarely Found Species (Overall Frequency of Occurrence <4%) in August Destructive Sampling During Preoperational (1978-1989) and Operational (1990-1995) Periods, and over All Years (1978-1995). Seabrook Operational Report,1995. SPECIES PREOPERATIONAL . OPERATIONAL ALL YEARS Elachistafucicola 6.3 2.7 4.9 Rhodomela confervoides 4.3 3.3 3.9 Gymnogongrus crenulatus 4.1 3.3 3.8 Bonnemaisonia hamifera 1.4 8.7 4.1 Ectocarpusfasciculatus 4.7 0.3 3.1 Polyides rotundus 3.1 3.0 3.1 Desmarestia viridis 0.6 11.0 4.4 Leathesia difformis 2.9 0.3 2.0 Ulvaria obscura v. Blyttil 1.8 0.3 1.2 Cladophora sericea 1.4 1.0 1.2 Petaloniafascia 0.4 2.7 1.2 Porphyra miniata 1.4 0.7 1.1 Afonostroma grevillet 1.6 1.0 Ectocarpus siliculosus 1.0 3.0 1.7 Palmariapalmata 1.4 0.3 1.0 Spongomorpha spinescens 1.0 0.6 Pilayella littoralis 1.0 0.6 Ilincksia y avulosa 0.8 0.5 Sphacelar.o c rrosa 3.6 0.7 0.6 Enteromorpnaprohfera .6 . 0.4 Dumontia contorta .6 0.4 : Ceramium desiongchampit 0.6 0.4 Polysiphonia harveyi 0.6 . 0.4 i Chordariaflagelhformis* O.7 0.2 l Scytosiphon simplicissimus 0.2 0.3 0.2 \ Spongonema tomentosum 0.4 . 0.2 isthmoplea sphaerophora' O.7 0.2 Ulvaria oxysperma 0.2 0.1 Enteromorphaintestinalis 0.2 0.1 Enteromorphalinza 0.2 0.1 Bryopsisplumosa 0.3 0.1 Plumaria elegans 0.2 0.1 \ Polysiphonia denudata 0.2 . 0.1 1 Polysiphonia nigra' O.3 0.1 Entocladia viridis 0.2 0.1 Urosporapencilliformis' O.3 0.1 Sphacelariaplumosa' O.3 0.1 Punctariaplantaginea 0.3 0.1 Pterothamnion plumula 1.3 0.5 f b) * = never observed in August samples, but occasionally observed in May and/or November samples. 6-23
6.0 MARINE MACROBENTHOS Petalonia fascia, Ectocarpus siliculosis, Sphace- If similar trends were observed in the macroalgal laria cirrosa, Scytosiphon simplicimus). Fifteen community near Seabrook Station, it could be species were found , during August in considered evidence of a power plant impact. preoperational years, but have not yet been col- However, of the three rare species that showed lected in the operational period (Monostroma relatively large increases from preoperational to grevillel. Spongomorpha spinescens, Pilayella operational periods, (B. hamtfera, Desmarestia littoralis, Hincksia granulosa, Enteromorpha viridis, and Petaloniafascia (Table 6-5), the latter prohfera, Dumontia contorta, Ceramium two are associated with cold water, and typically deslongchampli, Polysiphonia harveyi, found in late winter /early spring (Taylor 1957). Spongonema tomentosum, Ulvaria oxyspenna, Bonnemaisonia hamiferia is a small, bushy red alga Enteromorpha intestinalis, Enteromorpha lin:a, described by Taylor (1957) as an " exotic" typically Plumaria elegans, Polysiphonia denudata, found off southern Massachusetts and into Long Entocladia viridis); eight species were identified Island Sound B. hamtfera has also been recorded for the first time in August samples after Seabrook from coastal New Hampshire and from Great Bay Station start-up (Chordaria flagelhformis, by Mathieson and Hehre (1986). None of these Isthmoplea sphaerophora, Bryopsis plumosa, taxa are considered nuisance species. Several Polysiphonia nigra, Urospora pencilhfonnis, species showed relatively large decreases in fre-Sphacelaria plumosa, Punctaria plantaginea, quency of occurrence between periods. Elachata Pterothammonplumula). Five of these species (C. fucicola is an intertidal epiphyte found from New flagelhfonnis, I. sphaerophora, P. nigra, U. Jersey to the Lower Saint Lawrence (Villalard-pencilhfonnis, S. plumosa ) were collected during Bohnsack 1995). Leathesia dgormis, descr'ibed the preoperational period in May or November as a summer plant, decreased in frequency of only. None of the 39 rare species was considered occurrence during the operational period. The a major component of the local macroalgal flora filasuntous brown alp Ectocarpus fasciculatus, (average biomass was < 0.10 g/m;), nor were the described by Taylor (1957) as being adapted to reductions or increases in frequency of occurrence warmer waters, also declined in frequency of during the operational period considered to repre- occurrence during the operational period. These sent a significant alteration of the established algal trends are the converse of the expected response to community. a thermal incursion. Trends observed in taxa appearing for the first time in the operational Ano:her monitoring study that evaluated the im- period are less conclusive. Two taxa, Bryopsis pacts nsociated with constmetion and operation of plumosa and Pterothamnion plumula, are warm i a nuclear power plant on the attached macroalgal water forms more typical of southern New Eng-flora (NUSCO 1994) documented that incursion of land and even further south along the Atlantic a thermal effluent to nearby rocky shore sites coast. Punctaria plantaginea is an uncommon j caused an alteration of the algal community at species characteristic of cold water, but is adapt-those sites. Specifically, there was an increased able to warmer waters. In general, the macroalgal ! frequency of occurrence (i.e., extended growing communities in the vicinity of Seabrook Station are season) for species requiring or tolerant of warm typical of those reported elsewhere in northern water, and an absence or reduced frequency of New England (e.g., Mathieson et al. 1981; occurrence for species with cold water affinities. Mathieson and Hehre 1986). No itnpact on these { 6-24 l
6.0 MARINE MACROBENTHOS O communities as a result of construction or opera- cant interaction term may be due to the fact that in tion of the power plant has been observed to date. 1995 mean nearfield biomass dropped well below farfield biomass for the first time. 6.3.1.2 Selected Species Substantial, although somewhat smaller, amounts Chondrus crispus of C. cdspus were found at shallow subtidal stations, with biomass levels often exceeding 400 l 2 low intertidal and shallow subtidal horizontal rock g/m . Nearfield biomass significantly exceeded surfaces in the vicinity of the Seabrook intake and farfield biomass in both periods (Tables 6-6, 6-7). discharge structures support dense stands of the red Mean total biomass was similar at both stations alga Chondrus crispus. The perennial habit of this between periods, and the interaction term of the species allows extensive populations to continue to ANOVA model was not significant. dominate suitable rock surfaces to the exclusion of l most other species. Similar, nearly monospecific 6.3.1.3 Non-Destructive Monitorine Prom-n ) i turfs of C. cdspus are common throughout the North Atlantic (Mathieson and Prince 1973), from Lip 4 New Jersey to southern Labrador (Taylor 1957). ! Owing to its predominance in the Seabrook area, Extensive canopies of ceral kelp species com-C. crispus was selected for further, more detailed monly occur in coastal subtidal zones (4-18 m) in
- f. analyses. C. crispus biomass (g/m 2) at Seabrook the northwestern Atlantic, and can account for up study sites was typically highest at the intertidal to 80% of total algal biomass (Mann 1973). In the sites, at times exceeding 1000 g/m2 (Table 6-6). Gulf of Maine, Ianinaria spp. (mostly L.
Nearfield (B1) mean total biomass was higher than saccharina and L. digitata) are most common in farfield (BS) mean total biomass in both periods, the shallow subtidal zone (4-8 m), while a mixture l although this relationship was reversed in 1995 ofAgarum clathrarum, Ianinada spp and Alana (Table 6-6). Mean total biomass increased be- esculentaare found in deeper zones (Sebens 1986; tween periods in both areas; this increase was Witman 1987; Ojeda and Dearborn 1989). significant only in the nearfield area. This incon-sistency resulted in a significant Preop-Op X A similar distribution of kelp species was found at Station interaction term (Table 6-7). Annual Seabrook study sites during the preoperational and means at both stations have followed a similar operational periods. Laminaria spp. were com-pattern over time, declining through the monly found in both shallow and mid-depth zones preoperational period to a low in 1990 (not in- during the preoperational period (Table 6-8). L. cluded in the ANOVA), then increasing during the saccharina was the dominant kelp species at first few operational years (Figure 6-7). Mean shallow subtidal stations (B17 and B35), with more total biomass was higher at B1 than at B5 in all L. digitata occurring at mid-depth stations (B19 years included in the ANOVA except 1993 (when and B31). Agarum clathratum was dominant at they were approximately equal) and in 1995, when mid-depth stations (particularly at B19). Moderate 2 the farfield mean was approximately 300 g/m (or amounts of Alada esculenta were also observed in Q D 30%) higher than the nearfield mean. The signifi- this zone (Table 6-8). In 1995, L. saccharina 6-25
Table 6-6. Arithmetic Means and Coefficients of Variation (CV,%) for Chondrus Crispus Biomass (g/m 2) Collected in Triannual (May, August, November) Destructive Shmples in the Intertidal and Shallow Subtidal Zones During 1995 and During the Preoperational and Operational Periods. Seabrook Operational Report,1995. PREOPERATIONAIf REPORTYEAR - OPERATIONAL PERIOD 1995 PERIOD PARAMETER DEPTn ZONE - STATION MEAN CV MEAN MEAN -CV Chondrus crispus inomass Intertidal B1MLW 908.7 27.6 711.7 938.4 16.6 (gh') B5MLW 787.8 26.9 1020.1 814.0 21.9 Shallow subtidal Bl7 644.1 18.9 645.2 660.1 14.6 B35 477.3 10.9 25R.I 428 5 39.6 , Years: Station B1MLW: 1978-1989,1991-1995 , Station B5MLW: 1982-1989,1991-1995 O O O
p n V V U Table 6-7. Analysis of Variance Results for Chondrus Crispus Biomass (g/m2 ) at Intertidal and Shallow Subtidal Station Pairs for the Preoperational (1982 - 1989) and Operational (1991 - 1995) Periods. Seabrook Operational Report, 1995.
' MULTIPLE COMPARISON 1 DEP111 ZONE - SOURCE OF ' OF ADJUSTED MEANS*
' TAXON (STATIONS) ' VARIATION df : ~ MS F' (Ranked in decreasing order) -
Chondrus Intertidal' Preop-Op' l 131,945 1.30 NS crispus (n1. B5) Year (Preop-Op)' II 508,745 5.02 *" Month (Year)* 26 655,858 6.47 *" Station' 1 3,698,669 36.50 * *
- Bl>BS m Preop-Op X Station
- I 595,428 5.88
- B1 Pre >BIOp>B50p B5 Pre th Error 309 101,320 Shallow Subtidal' Preop-Op 1 84.52 1.97 NS (B17, B35) Year (Preop-Op) I1 129.46 3.02 * *
- Month (Year) 26 235.47 5.50 "*
Station 1 1,826.67 42.66 * " B17>B35 Preop-Op X Station 1 27.16 0.63 NS Error 309 42.82
' Preop-Op compares 1982 - 1989 to 1991-1995 regardless of station. The years selected are those during which each station within each pairing were sampled. ' Year nested within preoperational and operational periods regardless of station.
- Month (May, August, November) nested within year regardless of year, station or period.
' Station pairs nested within a depth zone: intertidal = B 1MLW, B5MLW; shallow subtidal = B17, B35, regardless of year or period. ' Interaction of the two main effects, Preop-Op and Station.
HS = not significant (p>0.05); * = significant (0.052p>0.01); ** = highly significant (0.0 lap 20.00I); *** = very highly sigmficant (0.001a p).
*Waller-Duncan multiple means comparison test used for significant main eiTects. LS Means used for interaction term. Underlining indicates no significant difference (aso.05).
- Data untransformed.
' Data square-root transformed.
6.0 MARINE MACROBENTHOS Intertidal Zone: Chondrus crispus biomass 1200 1000 i eco - - -- --- --- E euw a em - - - -asutw I_ 200 0-n.op-.tw cm esuco 18m B1MLw l l - - - - esutw iso j l l T 1200 l j ! I
'0*
h ,, j\ - s' E a sw ,-
,- 's / \ ! l e' \ s ,'
r, \ ' ~ l l l , l g em
's
'Nl l \
\ i
\
e' in ' s'
\ l b
'J l 400 I' 1 I I I I 25 ! !
~~ l l -
O I f 82 83 64 85 86 87 88 89 90 91 92 93 94 95 vsAn Figure 6-7. Comparison between stations for annual mean total Chondrus crispus biomass (g per m2 ) in the intertidal zone during the preoperational (1982-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 6-28
O O O Table 6-8. Preoperational and Operation'al Means and Coefficients Of Variation (CV,%), and 1995 Means for 2 Densities of Kelp Species (#/100 m ) and Percent Frequency of Occurrence of Understory Species and Five Fucoid Species." Seabrook Operational Report,1995. PREOPERATIONAlf 1995 OPERATIONAIf ' TAXON- STATION MEAN CV MEAN MEAN CV 2 KELPS (#/100 m ) Laminaria digitata B17 213.9 51.0 65.1 45.4 41.1 B35 155.8 45.5 53.2 118.0 40.2 B19 139.9 65.7 0.8 12.7 78.4 B31 500.2 31.0 33.3 181.2 56.7 Laminaria saccharina B17 415.1 51.8 161.0 300.0 56.6 B35 325.7 42.2 310.2 325.3 28.9 B19 59.1 152.2 0.8 10.8 70.8 B31 95.5 59.1 146.8 87.7 39.2 P Alaria esculenta B19 2.4 307.8 0.0 3.8 129.6
@ B31 75.2 115.8 120 6 74.9 60.8 Agansm clathratum B19 786.6 34.6 996.8 755.3 23.7 B31 366.4 37.0 647.0 469.8 60.5 UNDERSTORY (% FREOUENCY)
Chondnes crispus B17 71.8 7.7 85.0 76.7 10.9 B35 54.1 16.8 58.3 61.3 14.5 B19 4.2 116.0 4.0 5.0 83.0 B31 21.0 42.2 15.0 20.7 3 ! .2 Phyllophom/Coccotylus B17 20.3 36.7 11.7 19.4 41.4 B35 19.9 52.2 17.7 25.3 44.4 B19 34.0 21.3 19.0 30.1 33.3 B31 31.8 25.5 19.3 25.0 27.0 Ptilota serrata B17 0.8 126.9 0.0 0.8 160.2 B35 0.6 122.5 4.3 1.4 124.5 B19 35.6 25.5 61.7 45.4 31.6 B31 13.1 37.8 15.3 14.5 66.8 (continued)
Table 6-8. (Continued) PREOPERATIONAI) 1995' OPERATIONAlf TAXON- STATION MEAN CV MEAN MEAN CV FUCOIDS (% FREOUENCY) Ascophyllum nodosum Bl 32.0 18.8 41.3 39.5 6.9 B5 41.2 21.3 35.7 36.2 7.9 Fucus vesiculosus B1 47.4 49.4 5.7 2.9 66.0 B5 27.0 38.9 15.0 15.6 18.5 Fucus distichus B1 16.2 67.9 20.0 19.I I7.5 subsp. cdentatu, B5 3.6 264.6 3.3 5.9 115.2 Fucus distichus B1 0.0 - 0.7 4.7 162.5 subsp. distichus B5 0.0 - 2.3 3.2 83.5 e Fucus spp. BI 7.6 148.9 44.3 31.9 39.4 B5 0.6 264.6 h (juveniles) 14.0 9.7 43.8
'All taxa recorded along non-destmetive subtidal or intertidal transects in April, July, and October. %ean of annual means. Preop yeers for kelps - Stations B19, B31: 1978-1989; Station B17: 1979-1989; Station B35: 1982-1989; for understory species-Stations B17, B19, B31: 1981-1989; Station 35: 1982-1989; for fucoids - Stations B17 and B35: 1983-1989. *1991-1995. 'n= number of years, both periods combined.
O O O
6.0 MARINE MACROBENTHOS dominated the shallow subtidal as in past years, Laminaria saccharina density at the nearfield while A. clathratum was the overwhelming domi- shallow subtidal station (B17) declined between nant at mid-depth stations. periods (density in 1995 was particularly low). Preoperational, operational, and 1995 densities at Laminaria digitata densities declined substantially the farfield station were similar (Table 6-8). The (79%) at station B17 (nearfield shallow subtidal) overall ANOVA model for L. digitata density in during the operational period, while densities at the shallow subtidal zone was not significant, B35 (farfield) declined moderately (24%; Table 6- therefore a nonparametric test was used to evaluate 8). These differing rates of decline resulted in a differences between periods at each station. significant interaction term in the ANOVA results Wilcoxon summed ranks test revealed no signifi-(Table 6-9). Although densities at the two stations cant differer.ces between preoperational and opera-tracked one another closely during preoperational tional mean densities at B17 (n=16, Z= -1.63, years, a slight downward trend in densities at B17 p > 0.05) and B35 (n= 13, Z =0.39, p2 0.05). is evident throughout the study period, with the steepest declines occurrmg between 1990 and 1992 In the mid-depth subtidal zone, Ianinaria (Figure 6-8). Densities rebounded somewhat saccharina densities declined between periods at beginning in 1993. In 1995, densities at the two both stations (Table 6-8). Densities in 1995 were stations were again similar. Therefore, the inter- below the preoperational and operational means at action may reflect a short term cyclical departure Station B19 (nearfield), but higher than period from the generally close correlation in densities means at Station B31 (farfield). The decline in t g observed during much of the preoperational pe- density between periods at Station B19 coupled riod. with no decrease at Station B31 resulted in a significant Preop-Op X Station term in the Similar results were observed for Laminaria ANOVA results (Table 6-9). Densities of L. digitata in the mid-depth subtidal zone. Densities sacchannabegan to decline at the nearfield station declined substantially at both stations between in the early 1980s before the plant became opera-periods and in 1995 (Table 6-8), but on a percent- tional, and reached the lowest observed levels in age basis, the decline at the nearfield station (B19) 1995 (Figure 6-10). The pattern of decline of L. exceeded that at the nearfield station (B31), result- sacchannam the mid-depth subtidal zone is similar ing in a significant interaction between period and to that for L. digitata. station (Table 6-9; Figure 6-9). Annual means show that densities at the two stations essentially Alaria esculenta densities were low during both converged in 1988, but began to decline and periods in the nearfield area at B19, and none were diverge the following year (Figure 6-9). The collected in 1995. Densities at Station B31 decline at B19 was most severe between 1990 and (far'ield) were similar during both periods, but 1991 and between 1993 and 1994. A study period sustantially (60%) higher than period means in low of less than one holdfast per 100m2 was 1995 (Table 6-8). Densities of A. esculenta were reached in 1995, reflecting a possible operational sig'lificantly higher at Station B31 than at Station impact. B10 during both periods, and therefore the interac-tior. term was not significant (Table 6-9). v 6-31
Table 6-9. Analysis of Variance Results for Number of Kelps /100 m2 and % Frequency of Occurrence of Understory Species and Fucoids as Measured in the Non-Destructive Monitoring Program. Seabrook Operational Report,1995.
' DEPTH ZONE SOURCE OF MULTIPLE COMPARISON' PARAMETER -: ' (STATIONS) VARIATION - tdf MS ' -F* - (Ranked in decreasing order)-
Laminaria digitata' Shallow Subtidal Preop-Op* 1 2.40 31.84 * *
- Preop > Op 2
(#/100m ) (B17,B35) Station
- 1 0.86 11.43** B35 > B17 Year (Preop-Op)* 11 0.12 1.66 NS Month (Year)' 26 0.05 0.65 NS Preop-Op X Station8 1 1.26 16.71 * *
- B17 Pre B35 Pre B350p> B170p Error 36 0.07 m
63 Laminaria digitata' Mid-depth Preop-Op i 16.05 224.21 "
- Preop > Op
" (B19,B31) (#/100m') Station 1 20.18 282.04*** B31 > B19 Year (Preop-Op) 15 0.44 6.16 * *
- Month (Year) 34 0.08 1.12 NS Preop-Op X Station 1 2.45 34.29'*
- B31 Pre > B310p B19 Pre > B190p Error 49 0.07 Laminaria saccharina' Mid-depth Preop-Op 1 2.71 13.85 * *
- Preop > Op 2
(#/100m ) (B19,B31) Station 1 12.38 63.34 * *
- B31 > B19 Year (Preop-Op) 15 0.49 2.53 *
- Month (Year) 34 0.24 1.23 NS Preop-Op X Station 1 1.23 6.32* B31 Pre B310c > B19 Pre > B190p Error 49 0.19 (continued)
O O O
8 o ry b Table 6-9. (Condnued) i DEPTH ZONE - SOURCE OF. MULTIPLE COMPARISON' - PARAMETER. (STATIONS)' . VARIATION _df MS P '(Ranked in decreasing order) Alaria esculenta' Mid-depth Preop-Op 1 0.15 1.04 NS 2 (#/100m ) (B19,B31) Station 1 52.51 351.43*** B31 > B19 Year (Preop-Op) 15 0.23 1.53 NS Month (Year) 34 0.11 0.75 NS l Preop-Op X Station 1 0.02 0.12 NS l Error 49 0.15 Agarum clathrutum' ! Mid-depth Preop-Op 1 0.04 1.82 NS 2 (#/100m ) (B19,B31) Station 1 1.94 81.80 * *
- B19 > B31 Year (Preop-Op) 15 0.21 8.97 * *
- Month (Year) 34 0.03 1.40 NS Preop-Op X Station 1 0.01 0.36 NS Error 49 0.02 Chondrus crispra* Shallow Subtidal Preop-Op 1 728.21 10.08** Op > Preop l
(% frequency) . (B17,B35) Station 1 4576.56 63.34* *
- B17 > B35 l Year (Preop-Op) 11 283.12 3.92* *
- Month (Year) 26 120.69 1.67 NS i Preop-Op X Station 1 3.92 0.05 NS !
Error 36 72.25 Chorufrus crisput Mid-depth Preop-Op 1 <0.01 0.03 NS (% frequency) (B19,B31) Station 1 12.41 119.76*** B31 > B19 l Year (Preop-Op) 12 0.26 2.49* Month (Year) 28 0.09 0.84 NS Preop-Op X Station 1 0.01 0.02 NS Error 40 0.10 i (continued) ,
Table 6-9. (Continued) DEPTH ZONE ' SOURCE OF. MULTIPLE COMPARISON' - PARAMETER (STATIONS) VARIATION df MS . F* (Ranked in decreasing order) Phyllophora/Coccotylus 6 Shallow Subtidal Preop-Op 1 87.52 1.17 NS (% frequency) (B17,B35) Station 1 60.97 0.82 NS Year (Preop-Op) 11 392.73 5.26*** Month (Year) 26 117.21 1.57 NS Preop-Op X Station 1 302.08 4.04 NS Error 36 74.72 Phyllophora/Coccotylus' Mid-depth Preop-Op 1 548.82 6.27* Preop > Op (% frequency) (B19,B31) Station 1 260.51 2.98 NS Year (Preop-Op) 12 242.26 2.77 *
- P Month (Year) 28 101.71 1.16 NS T Preop-Op X Station 1 37.33 0.43 NS Error 40 87.53 Ptilota serrata' Mid-depth Preop-Op 1 0.03 0.99 NS
(% frequency) (B19,B31) Station 1 5.02 181.56*** B19 > B31 Year (Preop-Op) 12 0.14 4.94 * *
- Month (Year) 28 0.05 2.02*
Preop-Op X Station 1 0.04 1.52 NS Error 40 0.03 Ascophyllum nodosum*J Intertidal Preop-Op 1 0.02 1.86 NS (% frequency) (B1,BS) Station 1 0.02 1.88 NS Year (Preop-Op) 10 0.01 1.36 NS Month (Year) 24 0.01 1.22 NS Preop-Op X Station 1 0.08 9.44 *
- B5 Pre BIOp B50p B1 Pre Error 34 0.01 (continu
O O O i Table 6-9. (Continued) ' DEPTH ZONEI ' SOURCE OF; - MULTIPLE COMPARISON' - PARAMETERi ' - (STATIONS)" - VARIATIONi LdfJ :MS? F*1 ' (Ranked in decreasing order)- l l Fucar vesiculosis* Intertidal Preop-Op 1 4.93 97.80* *
- Preop > Op i
(% frequency) (B1,BS) Station 1 0.17 3.42 NS i Year (Preop-Op) 10 0.19 3.69 *
- Month (Year) 23 0.12 2.33* !
Preop-Op X Station 1 1.55 30.74* *
- BIPre > B5 Pre > B50p> BIOp .
Error 28 [ Fucus spp. (juveniles)* Intertidal- Preop-Op 1 2.35 49.01 * ** Op> Preop , (% frequency) (B1,BS) Station 1 1.98 41.33 **
- Bl > B5 !
Year (Preop-Op) 8 0.31 6.57 * *
- Month (Year) 17 0.10 2.06 NS '
Preop-Op X Station 1 0.06 1.29 NS : m Error 16 0.05 + h ' Data log (X+ 1) transformed. ! tntransformed data. [ cCompares preoperational period to operational period, regardless of station; years included in each station-species pairing: all fucoids : (B1,BS) = 1983-1995; all kelps (B17,B35): 1982-1995; all kelps (B19,B31) = 1978-1995; understory species (B17,B35) = 1982-1995; understory species (B19,B31) = 1981-1995; operational period = 1991-1995. ; dStations within depth zone, regardless of year, month or period.
' Year nested within preoperational and operational periods regardless of station. l
' Month (April, July, October) nested within year, regardless of station.
81nteraction of the two main effects, Preop-Op and Station. h NS = not significant (p>0.05); * = significant (0.052p> 0.01); ** = highly significant (0.012p> 0.001); *** = very highly significant (0.0012 p). i Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for interaction term. Underlining ~ [ indicates no significant difference (as0.05). , Dverall model not significant (P = 0.096), but R2 relatively high (R2 = 0.63) { i t k I i i I
1 1 f 6.0 MARINE MACROBENTHOS ; 1 i Shallow Subtidal Zone: Imninaria digitata 3.0 - _ gig ,
..a \
i 2.5 i 1.5 E io 0.5 0.0 Pnsoperational Operauonal PEROD 5 I i g7 l
. . . 333 m l
l i I W 4 l l l 1 I I I l I i a l I a l l E A l l *
.\ . . .__,, .
; i i I, I l I i p+ u l l c aw :
I I o I i 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR 2 Figure 6-8. Comparison between stations for mean number of holdfasts /100 m of the kelp Laminaria digitata in the shallow subtidal zone during the preoperational (1982-1989) and operational (1991- 1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 6-36
6.0 MARINE MACROBENTHOS (. ( v) 3.0 Mid-depth Subtidal Zone: Iominaria digitata
" 'd e.5 2.0 1.5 E
1D 0.5 0.0 F. e ; Operstkanal PEROD O 5 l l _ g,
- - . -.- B31 1 I I I I I I I I i 3 I i y .... ~--........._......._ l l 1 g .....- --.4,,,i, ,, . ,
I I 2 l l . I T I I k I i Prooperaenal l l Operamnal I i o ' ' i 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 vsAn 2 Figure 6-9. Comparisons between stations for mean number of holdfasts /100 m of the kelp Laminaria j digitata in then mid-depth subtidal zone during the preoperational (1978-1989) and j operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) ()
,em of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995.
i 6-37 l 1 i
6.0 MARINEMACROBENTHOS Mid-depth Subtidal Zone: Iaminaria saccharina 3.0j
; g, 2.6
. . . . es,,
2.0 g 14 h '"\ 0.5 0.04--
";-_-panonal PUUOO Operannonal i
1...i E I I l l l l 1 i 3 l i B l 1 I I E ! !
~~"
@ l l l, ..
. -~~., , , , . . . . - . .
l l
\
g,
..,,, ,,,I,.. .
p M. -l l i t Preoperat w 0- l l opwanonal re i 1 78 so ei ! 8 en as u as esruner se es so e, as es u es Figure 6-10. Comparison between stations for mean number of holdf 2 operational (1991-1995) periods p- p
) and tation) for the signific of the ANOVA model(data between the two vertical d ANOVA model). Seabrook OperationalReport,1995 cue .
rom the 6-38 si - - _ - - -
i 6.0 MARINE MACROBENTHOS
]o Mean densities of Agarum clathratum declined slightly between periods at nearfield Station B19, was similar to the preoperational and operational means, but lower at Station B31. The frequency of and increased moderately at farfield Station B31; occurrence of C. crispus ir. the shallow subtidal densities observed in 1995 were substantially zone was significantly higher in the operational higher than either period mean at both stations period (Table 6-9). As is evident in Table 6-8, (Table 6-8). Densities in the nearfield area were nearfield frequencies significantly exceeded higher than those in the farfield area during both farfield frequencies in both periods (Table 6-9).
periods, and the interaction term in the ANOVA The consistency of these relationships resulted in a results was not significant (Table 6-9). non-significant interaction term. In the mid-depth zone, a preoperational-operational difference was ) Understory Mome not detected (Table 6-9). In a reversal of what was seen in the shallow subtidal zone, the frequency of Patterns of occurrence and abundance of some occurrence of C. crispus was greater in the understory species can be influenced by the degree nearfield than in the farfield (Station term, Table of kelp canopy cover (Johnson and Mann 1988). 6-9). Again, the interaction between station and ! l Common understory species in the Seabrook area, period was not significant. l which occur beneath and adjacent to kelp canopies, include the foliose red algae Chondrus crispus, Frequency of occurrence of Phyllophoral l Phyllophora/Coccotylus and Ptilota serrata. Coccotylus in the shallow subtidal and mid-depth n Patterns of distribution of these species in fixed zones in 1995 was lower than both the j () transects were similar to those observed from preoperational and operational means at both I biomass collections (Tables 6-4,6-6). The shallow stations within each depth zone (Table 6-8). subtidal zone (B17/B35) was dominated by exten- There were no significant differences between sive turfs of the perennial red alga C. crispus, with stations observed in either depth zone for the i moderate occurrences of Phyllophora/Coccotylus. frequency of occurrence of Phyllophoral In the mid-depth subtidal zone, Phyllophora/ Coccotylus (Table 6-9). The frequency of occur-Coccorylus and P. serrata were dominant at the rence of this algal complex decreased significantly
- nearfield station (B19), while at the farfield station between the preoperational and operational periods (B31), Phyllophora/Coccotylus was dominant, in the mid<iepth zone, but no significant difference followed by C. crispus; (Table 6-8). was observed in the shallow subtidal zone. The interaction between station and period was not Overall, relationships in patterns of occurrence of significant in either depth zone (Table 6-9).
undersmry taxa between depth zones and between nearfica farfield stations have remained remark- Ptilota serrata occurred infrequently during both ably consistent over the study period. Frequency periods in the nearfield shallow subtidal area of occurrence of Chondrus crispus in 1995 in the (B17), and none were collected in 1995 (Table 6-shallow subtidal zone was higher than both the 8). The frequency of occurrence in the farfield preoperational and operational means at Station area (B35) was also low in both periods, but the 4 B17, and higher than the preoperational mean at 1995 mean was higher than either period mean O Station B35 (Table 6-8). In the mid-depth zone, (Table 6-8). The overall shallow subtidal ANOVA
^
d frequency of occurrence in 1995 at Station B19 model for Ptilota serrata was not significant due to 6-39
I 6.0 MARINE MACROBENTHOS a large proportion of zero values. Wilcoxon tional mean at both Stations B1 and B5 (Table 6-summed ranks test results show no significant 8). Frequency of occurrence decreased substan-difference between operational and preoperational tially between periods at both stations, but to a means at Station B17 (n=14, Z=-0.47, p20.05) greater extent at Station B1 compared to Station and B35 (n=13, Z=0.99, p20.05). The fre- B5. Although the interaction term in the ANOVA quency of occurerence of P. serrata increased results was significant (Table 6-9a), this change in slightly at both mid-depth stations (B19, B31) the relationship between the two stations does not between periods; higher frequencies were observed appear to be related to the operation of Seabrook at both stations in 1995 (Table 6-8). No between- Station. The decline in F. vesiculosis began in the period differences were detected (Table 6-9), preoperational period (1938), and continued into although frequency of occurrence has been consis- the operational period (Figure 6-12). Similar long-tently greater in the nearfield area than in the terrn decline / recovery cycles that were unrelated to farfield area (Table 6-9), which is evident in the power plant operation have been observed in other period means (Table 6-8). There was no signifi- monitoring studies (NUSCO 1996). cant period-station interaction for P. serrata in the mid-depth zone. Fucus distichus subsp. edentatus was a persistent component of the rockweed community at both Fucoids stations, although generally at lower abundance levels than the fucoids discussed above. The Fuccid abundance was monitored in the mid- annual mean in 1995 at B1 was similar to the intertidal zone at B1 and B5 using fixed-line tran- operational mean and higher than the , sects located at mean sea level. Ascophyllum preoperational mean; at B5 the 1995 mean was 1 nafosum was a consistently dominant taxon at both similar to the preoperational mean W lower than i 1 study sites over all years, particularly during the the operational mean (Table 6-8). The overall l l operational period (Table 6-8). Percent frequency ANOVA model for this species was not significant of occurrence in 1995 was higher than the due to a large number of zero values. No signifi-preoperational and operational means at Station cant differences were detected between the B1, but lower than the preoperational mean at preoperational and operational means at B1 (n= 12, ) Station B5 (Table 6-8). Percent frequency of Z = 1.14, p>0.05) or B5 (n= 12, Z=1.63, ) occurrence increased significantly between periods p>0.05) when tested by the Wilcoxon summed l at Station B1, but was not significantly different at ranks test. Fucus distichus subsp. distichus was 1 Station B5, resulting in a significant interaction not collected during the preoperational period; ) term (Table 6-9). Annual means show that the 1995 densities were lower than the operational frequencies of occurrence of A. nodosum in the average (Table 6-8). 'lne increase was significant I nearfield and farfield areas have tracked closely at B1 (n= 12, Z= 3.10, 0.05 > p > 0.01) and B5 throughout the study period, suggesting that the (n= 12, Z=2.61, 0.05 > p > 0.01) when tested with significant interaction term was not indicative of a the Wilcoxon summed ranks test. I power plant impact (Figure 6-11). Juvenile Fucus spp. occurred more frequently at Percent frequency of occurrence of Fucus both B1 and BS in 1995 than during the preopera-vesiculosus in 1995 was lower than the preopera- tional and operational periods (Table 6-8). Mean 6-40
6,0 MAklNE MACROBENTHOS
Intertidal Zone: Ascophyllum nodosum 3.0
_ _ g,y g
. . esu m 2.5 l
2.0 i 1.5 1 g l 7 l a ; 1.0 0.5 0.0 Prwaporaucrul C4mratual PERIOD Os
%j 5 i i - eium l l . . esu m I I I I 4
l l l l 1 I
. i l
l I
- l !
;2 Proopwabonal i
I i Opwahonal l _ _ .....a... . . . = , i i 1 l l l 1 1 I I I I I I o I ! 83 84 85 88 87 88 89 90 91 92 93 94 95 venn Figure 6-11. Companson between stations for annual mean percent frequency of occurrence of the fucoid Ascophyllum nodosum in the intertidal zone during the preoperational (1983-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station)
; of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995.
6-41
6.0 MARINE MACROBENTHOS l IntertidAI Zone; FUCUS VCSiCul0 SUS 3.0 _ _ _ gjutw j
- . . + DSMLW 1 1
25 2.0
$ 'A
*e *~~~~~----..... ...,______
,1.0 0.5 0.0 Proopersuonal Opwatioral PERIOD 5 l l
- B1MLW j l .. . 85utw I I i 1 4
! l l 1 1 l l 1 1 I a l i I i a l l
# l I l l 2 Prooperatonal I I Operanonal
% i f
,).....
l _ , _ . , - - ,l,
.. . t.......
I I I i 6 V i i l 1 0 I I 83 84 85 86 87 88 89 90 91 92 93 94 95 vem Figure 6-12. Comparison between stations for annual mean percent frequency of occurrence of the fucoid Fucus vesiculosus in the intertidal zone during the preoperational (1983-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1995. 6-42
6.0 MARINE MACROBENTHOS O U percent frequencies during the operational period periods; however, heavy sets of fucoid germlings were significantly higher than during the occasionally occurred, resulting in high frequen-preoperational period at both stations, and cies of occurrence in some years (Table 6-10). In nearfield frequencies exceeded farfield frequencies general, fluctuations ir lucoid abundances at B1 during both periods. The interaction between have been high dura' g the preoperational and station and period was not signficant for Fucus operational periods, and likely reflect variability in spp. in the intenidal zone (Table 6-9). recruitment and the conditions for new recruit survival characteristic of the high intertidal (Keser Intertidal Ca==nnides and Larson 1984; NUSCO 1992). This variability is apparent in the frequency of occurrence of Macroalgal species abundance patterns on intertidal fucoids in 1994, when they occupied relatively rock surfaces exhibit striking patterns of zonation, large proportions of the quadrats in April and July which result from factors directly and indirectly (69 and 75%, respectively), but were absent in related to tidal water movement (Lewis 1964; December (NAI 1995). By comparison, no fuc-Chapman 1973; Menge 1976; Lubchenco 1980; oids were found in any months in 1995 (Table 6-Underwood and Denley 1984). Physical stress 10). Frequency of occurrence of fucoids has (e.g., desiccation, temperature extremes) resulting historically been higher at the farfield station (B5); from long exposure times is an important structur- the median has typically exceeded 80%, and has ing mechamsm on macroalgae in the high intenidal been relatively constant seasonally (Table 6-10). g zone (Lewis 1964; Schonbeck and Nonon 1978). Frequencies in 1995 were lower than the Q Other factors related to biological processes, such as grazmg pressure (Cubit 1984; Keser and Larson preoperational and operational medians. 1984) and recruitment (Underwood and Denley The ephemeral green algal association of Urospora 1984; Gaines and Roughgarden 1985; Menge penicilhfonnis/Ulothrixflacca exhibited a consis-1991), can also be seasonally imponant. To tent annual cycle of abundance at both nearfield effectively monitor macroalgal species abundance and farfield stations, occurring only during the in the intertidal zone and characterize these zona- April sampling period in most years in both the tion patterns at each site over time, permanently preoperationalandoperationalperiods. Conditions marked quadrats were established at three tide for establishment and growth of these species on levels and sampled three times annually at high intenidal surfaces are most favorable in late nearfield and farfield sites. winter and early spring. Both physical stress (related to temperature extremes and desiccation) At Seabrook intenidal study sites, much of the high and snail grazing pressure (e.g., by Littorina intertidal zone, denoted as Bare Ledge, consists of littorea and L. saratilis; Keser and Larson 1984) bare rock with seasonal and perennial populations are least intense during this period (Cubit 1984). of fucoids (Fucus spp. and Ascophyllum nodosum), It is not uncommon for these species to be absent and seasonally abundant ephemeral green algal during an entire year. In 1995 these species turfs (mostly an association of Urosporapenicilli- occurred only in December at Station BS, the first formis and Ulothrixflacca). Fucoids were absent time they have occurred in December at either A from sampling quadrats at nearfield station B1 station in any year (Table 6-10). during much of the preoperational and operational l l 6-43 l l
6.0 MARINE MACROBENTHOS Table 6-10. Percent Cover and Percent Frequency of Occurrence
- of Dominant Perennial and Annual Macroalgal Species at Fixed Intertidal Non g,
destructive Sites During the Preoperational and Operational Periods and in 1995. Seabrook Operational Report,1995. TAXA AREA ZONEb (DATA TYPE *) (STATION) APR JUL 'DEC Bare Ledge Fuccid Speciesd (%F) Nearfield (B1) Preoperational' 6 (0-81) 19 (0-94) 6 (0-94) Operational' 0(0-69) 0 (0-75) 12 (0-81) IW5 0 0 0 Farfield (BS) Preoperational 82 (0-100) 97 (12-100) 100 (0-100) Operational 94 (38-94) 100 (31-100) 87 (0-100) Iw5 38 31 0 t f cc ( F) Nearfield (BI) Preoperational 45 (0-99) 0 (0-0) 0 (0-0) Operational 33 (0-55) 0(04) 0 (0-0) IWS 0 0 0 Farfield (BS) Preoperational 73 (0-100) 0 (0-0) 0 (0-0) Operational 13 (0-82) 0 (0-0) 0 (0-64) IW5 0 0 64 Fucoid Ledce Fucoid Species (%C) Nearfield (BI) . Preoperational 93 (25-98) 93 (60-100) 68 (25-95) Operational 80 (45-95) 98 (34-100) 66 (40-78) IWS 64 100 66 Farfield (B5) Preoperational 95 (60-100) 98 (65-100) 95 (80-98) Operational 71 (60-100) 85 (52-100) 95 (70-100) IWS 87 52 70 Fucoid Species (%F) Nearfield (B1) Preoperational 94 (69-100) 88 (75-100) 81 (38-94) Operational 87 (56-100) 100 (81-100) 31 (56-100) IWS 100 100 94 Farfield (BS) Preoperational 85 (62-100) 85 (69-100) 91 (62-100) Operational 87 (75-94) 88 (62-94) 88 (63-88) IWS 81 88 88 O 6-44 (continued)
6.0 MARINE MACROBENTHOS i %J (l Table 6-10. (Continued) TAXA AREA ZONE' (DATA TYPE *) (STATION) . APR JUL DEC Chondrus Zone Chondrus crispus (%F) Nearfield (B1) Preoperational 45 (20-53) 34 (20-38) 45 (28-53) Operational 35 (17-59) 21 (3-37) 38 (25-55) IWS 59 37 55 Farfield (BS) Preoperational 45 (0-72) 48 (41-55) 41 (39-48) Operational 38 (19-58) 33 (15-65) 53 (39-59) IWS 49 33 55 Mastocarpus stellatus (%F) Nearfield (BI) Preoperational 47 (21-69) 66 (65-71) 48 (32-67) Operational 42 (23-49) 55 (16-74) 42 (31-73)
- IW5 31 74 73 Farfield (B5)
, Preoperational 47 (0-53) 51 (41-63) 44 (43-56)
Operational 42(2349) 55 (22-63) 31(21 46) 1W5 31 56 21
- Corallina opicinalis (%F)
Farfield (BS) Preoperational 30 (15-57) 52 (33-61) 52 (31-65) Operational 52 (49-66) 60 (55-68) 65 (45-69) : 1W5 65 61 65 l 1
' Median and range for preoperational and operational periods (based on annual means) and annual mean for 1995.
%are Ledge: approximately mean high water; Fucoid Ledge: a Chondrus Zone:pproximately mean approximately mean lowsea level; water.
- Data Type %F = Percent frequency of occurrence based on int contact line sampling.
%C = Percent coverage of substratum based on txed 0.25 m 2quadrats
' Includes all Fucus spp. and Ascophyllum nodosum. j
'Preoperationalperiod = 1982-1989
' Operational period = 1991-1995 1
I 6-45
6.0 MARINE MACROBENTHOS A distinct horizontal band of fucoids delineates the from 34-48% (Table 6-10). Operational medians mid-intertidal zone (Fucoid Ledge) at Seabrook were lower than preoperational medians at both study sites. Habitat conditions for these species stations in each month, except in December at B5 are ideal in the mid-intertidal, as longer immersion (53 %). Operational medians at B5 were higher time results in a longer period for zygospore than those at B1 during each of the three months settlement (Underwood and Denley 1984), and sampled. Median percent frequency of occurrence 1 reduces physical stress compared to that in the high of C. crispus at nearfield station B1 during each of 1 intenidal; new recruits are able to grow rapidly in the three sample periods in 1995 was higher than this zone and develop physical and chemical during the preoperational period, and represented defenses against gruing (Geisehnan and an all-time high in April and in December (Table McConnell 1981; Lubchenco 1983). Fucoids were 6-10). The seasonal pattern observed in 1995 was, dominant in mid-intertidal quadrats at both however, similar to previous years. Despite the nearfield and farfield stations over the preopera- high frequencies observed in 1995, operational tional period and much of the operational period, medians were still lower than preoperational both in terms of percentage of substratum cover medians in each month. The percent frequencies and percent frequency of occurrence (Table 6-10). of C. crispus at farfield station B5 in 1995 were Percent cover was similar between the nearfield higher than preoperational medians in April and and farfield stations during the preoperational December, but lower in July. The 1995 July period, except in December when percent cover frequency was less than the range observed was lower at the nearfield station. Median percent preoperationally, while the 1995 December cover did not change substantially between the frequency was higher than observed , preoperational and operational periods in any preoperationally. month at either station, except in April at the farfield station (24% decline). Percent cover at the Percent frequencies of occurrence of Mastocarpus fartield station in 1995 was the lowest recorded stellatus in 1995 were higher compared to during any year during August and December preoperational medians at Station B1 in July and (52% and 70% respectively), although the percent December, although operational medians were still frequency of occurrence during these months was lower. Percent frequencies of M. stellatus at typical of past years (Table 6-10). Overall, Station B5 in 1995 were lower than preoperational percent frequency of occurrence was similar and operational medians in April and December. between stations and during both the preoperational In contrast, the July frequency in 1995 was slightly and operational periods. higher than both the preoperational and operational medians (Table 6-10). Operational medians at B5 The low intertidal or Chondrus zone was typically were lower than the minimum preoperational dominated by perennial red algal turfs composed of values only in December, but were within the . Chondrus crispus and Mastocarpus stellatus, range of preoperational values in April and July. which, once established, competitively exclude other algae such as fucoids (Lubchenco 1980). The coralline red alga Corallina oBicinalis can be Preoperational median percent frequencies of a locally abundant understory species in the low occurrence of C. crispus were similar among the intertidal zone. Percent frequency of occurrence 4 three months and between both stations, ranging of this species generally exceeded 30% in all 6-46
6.0 MARINE MACROBENTHOS seasons at farfield station B5 throughout number of taxa collected in 1995 was comparable 4 preoperational and operational years, but was to that collected over the operational period (1990-absent from the nearfield (B1) area throughout our 1995). Fewer taxa were collected at B1MLW than studies (Table 6-10). The frequency of occurrence at B5MLW during the operational period (Table 6-of this species has increased throughout the 11). Overall, the number of taxa collected in the operational period, such that operational medians intertidal zone decreased between periods (Table 6-exceeded preoperational medians in each month. 12). This decrease was most pronounced at Frequencies observed in 1995 met or exceeded BIM'LW, resulting in a significant Preop-Op X maximum preoperational values in each month. Station interaction term for the intertidal station group (Table 6-12, Figure 6-13). In general, both , 6.3.2 Marine Macrofauna stations showed parallel trends among years, with l 5 the decline in the number of taxa collected evident 6.3.2.1 Horimatal Ledne Ca==nnitiec beginning between 1989 and 1990, prior to the 4 start-up of Seabrook Station (Figure 6-13). Total l Numher of Tarn and Total Dancity faunal density at both intertidal stations declined substantially between 1994 (NAI 1995) and 1995 Many attached and slow-moving invertebrate (Table 6-11). However, there was no significant species comprise the marine macrofaunal difference in overall intertidal density between community on local intertidal and subtidal rock periods (Table 6-12). Nearfield densities surfaces. Macrofaunal community parameters significantly exceeded farfield densities over both Q similar to those used for macroalgal monitoring periods, and because of the consistency of these (i.e., number of taxa, total density) have relationships, the interaction term in the ANOVA consistently been monitored as part of Seabrook results was not significant (Table 6-12). studies since 1978, and have proven useful elsewhere for assessing potential ecological Mean numbers of taxa collected at both shallow impacts from coastal nuclear power plants (Osman subtidal stations (B17 and B35) in 1995 (Table 6-et al.1981; NUSCO 1992,1994; BECO 1994). 11) were lower compared to 1994 (NAI 1995) and Overall species richness, as determined by the the operational period (Table 6-11). Over both 2 mean number of taxa per 0.0625 m quadrat, stations combined, however, no significant generally increased with increasing depth, with difference between preoperational and operational lowest numbers of taxa at intertidal stations period means was detected (Table 6-12). (B1MLW and B5MLW) and highest numbers at Significantly more taxa were collected during.the mid-depth (B16, B19, and B31) and deep stations operational period at the nearfield station compared (B04, B13, and B34; Table 6-11). In contrast, to the farfield station (Table 6-12), whereas total faunal density was highest at the intertidal and preoperational means were similar between the two shallow subtidal stations, with lowest densities stations (Table 6-11); this resulted in a signficant observed at the deep subtidal stations, interaction term in the ANOVA results (Table 6-12). The divergence in the numbers of taxa The mean number of taxa collected at the nearfield collected in the shallow subtidal zone began in
'[ intertidal site (B1MLW) in 1995 was the lowest to 1989, prior to the start of plant operation (Figure date (Figure 6-13). At B5MLW (farfield) the 6-14). Total faunal density was reduced in 1995 6-47
l 6.0 MARINE MACROBENTHOS i Table 6-11. Preoperational and Operational Arithmetic Means and Coefficients of Variation (CV,%) and 1995 Means of the Number of Taxa Collected, and h Geometric Mean Densities and Coefficients of Variation for Non-Colonial Macrofauna Collected in August at Intertidal, Shallow Subtidal, Mid-Depth and Deep Stations. Seabrook Operational Report,1995. DEPTH ZONE- STATION PREOPERATIONAL* 1995 OPERATIONALb MEAN CV MEAN MEAN CV MEAN NO. OF TAXA (per 0.0625 m') Intertidal B1MLW 49 18.5 30 37 16.5 B5MLW 48 16.5 41 42 8.6 Shallow subtidal B17 58 11.4 58 63 5.2 B35 55 9.0 46 53 10.8 Mid-depth B16 70 11.8 64 71 10.2 B19 68 18.3 50 68 17.1 B31 51 16.5 45 53 21.4 Deep B04 63 13.8 60 72 21.6 B13 54 13.9 50 56 21.2 B34 64 22.0 55 63 18.1 TOTAL FAUNAL DENSITY (#/m)2 Intertidal BIMLW 122795 5.3 36770 86115 6.9 B5MLW 68684 5.1 19354 68948 6.7 Shallow subtidal B17 23373 4.6 8836 23777 5.7 B35 28372 4.6 14944 29447 7.0 Mid-depth B16 31590 5.9 14971 18181 6.8 B19 12785 6.7 6999 13755 6.8 B31 16240 11.4 9811 14472 4.8 Deep BN 4936 5.7 3352 5554 9.1 B13 6073 10.5 4882 14420 10.5 B34 5523 9.3 3405 6180 8.4 'Preoperational period extends through 1989 (Stations B1MLW, B17, B19, B31: 1978-1989; Stations B5MLW, B35: 1982-1989; Station B16: 1980-1984,1986-1989; Stations B13, BN: 1978-1984,1986-1989; Station B34: 1979-1984,1986-1989). ' Operational period: 1990-1995. O 6-48
6.0 MARINE MACROBENTHOS Intertidal Zone: Number of Taxa
- ~~~~-----.... ,,, ,--*--.....,,
E e-6 k 1 3" 6 10
= . _
O + - + -
- B6MLW Prooperauoral Operational Pmoo O ! _ _ _ _ E',
LJ 7 l i w , l , 1 m - s i s' gm , 's , 's, i N e Ee -
'4is /
\s %,'
8= l 8 I E PreoperatW Operaponal 10 i i o ' 82 83 84 85 86 87 88 89 90 91 92 93 94 95 vsm Figure 6-13. Comparisons between intertidal stations of mean number of taxa (per 0.0625 m2 ) during the preoperational (1982-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and ( annual mean number of macrofaunal species (per 0.0625 m') at intertidal stations, 1982-1995. Seabrook Operational Report,1995. 6-49
Tcble 6-12. Analysis of Variance Results for Number of Macrofaunal Taxa (per 0.0625 m 2) and Total Macrofaunal Density (per m 2) Collected in August at Intertidal (1982-1995) and Shallow (1982-1995), Mid-Depth (1980-1984; 1986-1995), and Deep Subtidal Stations (1979-1984; 1986-1995). Seabrook Operational Report,1995. DEPTH ZONE ~ MULTIPLE COMPARISONS PARAMETER (STATIONS) SOURCE OF VARIATION df. MS P ' (Ranked in decreasing order) Number ofTaxa Intertidal Preop-Op* I 2361.01 35.37' " Preop >Op (BIMLW, Station
- I 39.80 0.60 NS B5MLW) Year (Preop-Op)* 16 44521 6.67"
- Preop-Op X Station
- 1 413.21 6.19' BIPreoc BSPreco B50p BIOp Error 136 66.75 Shallow Subtidal Preop-Op 1 48.52 0.62 NS (B17,B35) Station 1 1327.82 17.00 "
- B17>B35 Year (Preop-Op) 16 212.43 2.72"
- e Preop-Op X Station 1 469.08 6.01* B170p B17Preoo B35Preon B350p 6 Error
~~
136 78 10 O Mid-depth Preop-Op 1 95.84 0.77 NS (B16, B19, B31) Station 2 7547.89 60.59' " B16 B19 B31 Year (Preop-Op) 16 890.25 7.15 "
- Preop-Op X Station 2 30.63 0.25 NS Error 228 124.57 Deep Preop-Op I 626.55 4.58* Op> Preop (B04, B34, B13) Station 2 3152.08 23.09* " B04>B34>B13 Year (Preopop) 15 1387.15 10.13* "
Preop-Op X Station 2 3 % 61 Error 2.90 NS 229 136.94 (Continued) O O O
. -. - . - . . . ~ . _ . - - ----
f O O O Table 6-12. (Continued)
~ DEFntZONE- . . L MULTIPLE COMPARISONS':
PARAMETER _ (STATIONS) SOURCE OF VARIATION - df .MS- F'_ (Ranked in decreasing order) . Total Faunal Intertidal Preop-Op 1 0.23 3.84 NS Density (B1MLW, Station 1 0.99 16.76 * *
- B1MLW>B5MLW B5MLW) Year (Preop.Op) 16 0.59 10.02* "
Preop-Op X Station 1 0.19 3.20 NS Error 136 0.06 Shallow Subtidal Preop Op I <0.01 0.02 NS (Bl7,B35) Station 1 0.29 5.51* B35>B17 Year (Preop-Op) 16 0.40 7.44 "
- Preop-Op X Station I <0.01 <0 01 NS Error 136 0.05
[ Mid-depth Preop-Op I 0.40 3.76 NS
~ (B16, B19, B31) Station 2 1.26 11.83*** B16>B3l>B19 Year (Preog4p) 16 0.79 7.46"'
Preop-Op X Station 2 0.33 3.10* B16 Preop B1600 B31Preon B3100 B1900 B19Preon Error 228 0.11 , Deep Preop-Op I 1.55 16.85 "
- Op> Preop (B04, B34, B13) Station 2 1.43 15.51 "
- Bl3 B34 B04 Year (Preop-Op) 15 1.17 12.68 "
- Preop-Op X Station 2 0.64 7.01 " Bl30p B3400 B 13Preon B04Oo B34Preon B&4Preon Error 229 0.09
' Preop-Op compares pwm.amel to operational p:riod regardless of station. *Nearfeld = Stations BlMLW, B17, B16 B04, B13; farfield - Stations B5MLW, B35, B31, B34, regardless ofyear/ period.
Tear nested within Preoperational and Om.im.: periods regardless of Station. d interaction of the two main effects, Preop-Op and Station.
'NS = not significant (p>0.05),
- significant (0.052 p>0.01); * * - Ifighly significant (0.012 p>0.001); "* - Very highly significant (pso 001).
' Willer-Duncan multiple means comparison test used for significant main effects. LS means used for interaction term. Underlining indicates no signifmant difTerence (aH105).
L
- _____.m_ _______________.________m._..____.__________.____.___________________.___m .___-m __
. _ . < - . - , - m
6.0 MARINE MACROBENTHOS \ l Shallow Subtidal Zone: Number of Taxa 80 1 1 70 l - E 80 g .................................................. s-O li e a
$5 6
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. . . . . B17ms 0
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i m t 8 l 20 Proopera&nal W I 10 l l l 0 82 83 84 85 86 87 88 89 90 91 92 93 94 95 YEAR Figure 6-14. Comparisons between shallow subtidal stations of mean number of taxa (per 0.0625 2 m ) during the preoperational (1982-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of macrofaunal species (per 0.0625 m 2) at shallow subtidal stations, 1982-1995. Seabrook Operational Report,1995. 6-52 I
6.0 MARINE MACROBENTHOS ( from that measured in 1994 (NAI 1995) and lower term appears to be due to natural variability, most than the preoperational and operational period notably at the intake station. means for both shallow subtidal stations, more so in the nearfield area compared to the farfield area 'Ihe numbers of tan collected in the preoperational (Table 6-11). However, faunal densities were and operational periods r.nd in 1995 were generally similar between periods over this depth zone comparable among the deep water stations (B04, (Table 6-12). In both periods, farfield densities B13, and B34)(Table 6-11). The number of taxa exceeded nearfield densities, and because of this collected over the depth zone as a whole increased consistency, the interaction term of the ANOVA significantly between periods (Table 6-12). Over results was not significant (Table 6-12). both periods, the number of taxa collected at the nearfield (discharge) station was highest, and the Mean numbers of taxa collected at the mid-depth number collected at the intake station (B13) reas stations (B16, B19, and B31) were lower in 1995 lowest. As these relationships were consistent in' (Table 6-11) than in 19N (NAI 1995) and less than both periods, the Preop-Op X Station interaction the preoperational and operational period means term was not significant (Table 6-12). Total faunal (Table 6-11). The numbers of taxa collected at densities were similar among the three stations each station were similar between periods (Table during the preoperational period and in 1995, 6-11), and overall there was no significant although the operational period mean density at the difference in the number of taxa collected in this intake station (B13) was substantially higher than n zone between periods (Table 6-12). The numbers preoperational and operational period densities at Q of taxa collected at the intake (B16) and discharge the other two stations (Table 6-11). Although (B19) stations were similar in both periods, and faunal densities at the intake station were higher exceeded those collected at the farfield (B31) than in the nearfield and farfield areas in both station (Tables 6-11, 6-12). Because of the periods, the relatively greater difference among consistency of these relationships, the interaction means in the operational period resulted in a term of the ANOVA results was not significant significant interaction term in the ANOVA results (Table 6-12). Total faunal densities were lower in (Table 6-12). All three stations generally showed 1995 (Table 6-11) than in 1994 (NAI 1995) and parallel trends in annual mean density, especially also lower than preoperational and operational during the operational period and between the period means (Table 6-11) at all mid-depth nearfield and farfield areas (Figure 6-16). This stations. Significant differences among the station suggests the predominance of natural regional means between periods were observed, leading to factors rather than an effet of Seabrook Station. a significant Preop-Op X Station interaction term (Table 6-12). Density significantly decreased at Macrofa==d Ca====ier An=1vsis intake Station B16 between periods, while there were no significant between-period differences at The noncolonial macrofauna associated with hard the discharge (819) and farfield (B31) stations substrata in the vicinity of Seabrook Station (Figure 6-15). Stations showed very similar trends comprise a diverse community. Over 400 taxa among years, particularly the nearfield (dis- have been collected in August destructive samples ]v charge)-farfield pair. The significant interaction since 1978, some with densities of over 100,000 6-53
6.0 MARINE hl4CROBENTHOS Mid-depth Subtidal Zone: Macrofaunal Density 5.0 4.5 W. : =. :-: :-- . : : : --: w.- s vr.-rs vr.-re rv.-vu - . -4 s.5 sO s.O
$ 2.5 2.0 1.5 1 .0 t 0.5
- . gjg 816
*~#
0.0 Preop.muone opermuman PERICO l 6.0 i _ _ _ _ ,io B,, 5.5 - - B31 l l
/ \
f 5.0 / \ l i
"'" ~
/ '
^
~ x_ ,,r ~ , ' ,e \
kN 4,
'Ne ' '
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10 4.0 N'%Njw ,f - g l . g s.s I s.O i g 2.0 ; g I g 1 .5 pr.w.a s operanone l t '."5 0 l l 1 I 0.0 et a2 ea 84 as as av as so ao m e2 83 e4 es wxt Figure 6-15. Compansons between mid-depth stations of mean logw(x+ 1) density of macrofauna during 2e preoperational (1981-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean logdx+1) density of macrofauna at mid-depth stations, 1981-1995. Seabrook i Operational Report,1995. 6-54
1 l
- 6.0 MARINE MACROBENTHOS t
/% i Deep Subtidal Zone: Macrofaunal Density V
5.0 4 .5 f .................................................. 3.5 E o 3.0 a i i A 2.5 2.0 g i.s 1 .0 t 0.5 - - B04
. + . + B13 0.0 Preoperational Opershonal PERIOD 8.0 i B4 iO SE i
I _ _ _ _ ,0,3
- -
- B34
-r l j 5.0 i l ' <s
{ *5 -y l ,- 's, [N - '__,/\ % l e' s
- - N - '
\ '
& 3a l l-l 2.0 l
l 15 Prooperamnal g l Opwahnal 1.0 0.5 l l 0.0 ' 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 YEAR Figure 6-16. Comparisons between deep subtidal stations of mean logm(x+1) density of macrofauna during the preoperational (1979-1989) and operational (1990-1995) ) periods for the significant interaction term (Preop-Op X Station) of the ANOVA I fT d model, and annual mean logw(x+ 1) density of macrofauna at deep subtidal stations, 19791995. Seabrook Operational Report,1995. 1 6-55 i 1
6.0 MARINE MACROBENTHOS l 2 individuals /m . Very few of these animals are Collections from the shallow subtidal stations (B17 j
" habitat formers" (cf. macroalgal section), and and B35) made up a second discrete assemblage, J most are motile. Therefore, the faunal species Group 2 (Figure 6-17 and Table 6-13). Lacuna assemblages are not as distinct as those of the vinctawas the most abundant species at the shallow algae. However, multivariate macrofaunal subtidal stations in terms of number of individuals community analyses, similar to those performed on (ca. 5,000/m 2), and became more abundant in the macroalgae, facilitate the separation of annual operationalperiod. This small herbivorous snail is collections at each station into groupings based on a dominant grazer on the kelp Imninaria Bray-Curtis similarity indices, as well as the sacchanna, and also feeds on many other attached determination of within- and between-group and deift algae. Since the food resource is quite relationships. These analyses were applied to pazhy, the abundance of L. vincta also is variable.
log-transformed macrofaunal geometric mean Mytilidae spat were dominants at these stations (ca. density data for those taxa (94 total) appearing in 3,000-5,000/m 2), but mussel densities were more 50 or more sample replicates over the entire study than an order of magnitude lower than at the period. The groupings of the 165 station / year intertidal stations. Other species abundant at the collections are illustrated in Figure 6-17. shallow subtidal stations (isopods Idotea phosphorea and L balthica, gammaridean As with the macroalgal collections (Figure 6-6), amphipods Pontogencia inermis and Jassa the macrofaunal assemblage at intertidal stations mannomta) exhibited consistent densities between (BIMLW and B5MLW) comprised a distinct entity preoperational and operational periods (Table 6-(Group 1; Figure 6-17), characterized by 13). extremely high densities of mytilid spat (ca. 2 50,000-70,000 individuals /m ; Table 6-13). These Group 3 included all collections from mid-depth mussels accounted for about 65% of the individuals mtake station B16, and most collections from mid-collected at the intertidal sites during the depth discharge station B19 and mid-depth farfield preoperational and operational periods. The station B31 (Table 6-13). Group 3 dominant taxa isopod Jaera marina, gastropods Lacuna vincta included species identified as among the most and Nucella lapillus, bivalves Tunonia minuta and abundant in the other groups. Preoperational and Hiatella sp., oligochaetes, and the amphipod operational period means for the dominant taxa Gammarus oceanicus also were commonly found were quite similar, with considerable overlap in the intertidally, but at much lower deustries. None of 95% confidence intervals of both periods. Mytilids these taxa accounted for more than about 5% of were dominant in Group 3 but Lacuna vincta, the individuals collected. In addition to the high which was dominant in Group 2, was present at densities of Mytilidae, and the presence of the much lower densides. primarily intertidal species Jaera marina, Nucella lapillus and Turtonia minuta, this group separated Group 4 contained recent (1986-95) collections from other groups because of very low densities of from deep intake station B13 and nearly all strictly subtidal species, such as the gammaridean collections from deep discharge station B04 and amphipod Pontogencia ineimis, which was much deep farfield station B34 (Figure 6-17 and more abundant at subtidal stations. Table 6-13). The assemblage was characterized by , 6-56
-C Between Group Sindia.ity C Within Gmup Smilenty 0.0 -
0.1 - d 0.2 - H ** as = pia a b ' 2' 1 c 0.3 -
,g 0.4 -
' m .
.n t
0.0 - I y 0.6 - i
^
8 0.9 - N 1,0 % 1 i i O. i s I Group I Group 2 Group 3 Group 4 Group $ Ungrouped I 2 Group 1. Intertidal. BIMLW (1978-1995); B5MLW (19821995) Group 2. Shallow Subsidal B17 (1978-1989,1991-1995), B3$ (1982-1905) Gruup 3 Shallow Subsidal. B17(1990) ! Mo<hyth B16(19801984,19861995);B19(1979,19811994);B31(1941988,19901995) Group 4.Mid depth B31(1989) Deep 813 (19861995); B04 (194l984,19861995); B34 (1979,1981 1982,1984 1995) Group 3 Md. depth. B19(1978,1980,19951 B31(1978) Deep B13 (1941984); B34 (1980,19831984) j Ungrouped. Deep B04(1978) 95 f////,] g L 94 N 2 !!=== GROUP 1 ! 4 1 93 92 N O h 0: W GROUP 2 l GROUP 3 91 . g so , GROUP 4 gg ; GROUP $ _88_ l l NS I NOT SAMPLED 87 I l NOT GROUPED 86 85 NS NS NS i 82
'97 m 8
l i 81 ::::::: E 80 ::::::: NS NS 7(([jM 79 ::::::: N V//////// s
~
78 ???ii d NS NS B B B B B B B B B B
- 1 5 1 3 1 1 3 1 0 3 M M 7 5 6 9 1 3 4 4 L L W W STATION p)
\.
Figure 6-17. Dendrogram and station groups by year formed by numerical classification of August collections of marine macrofauna,1978-1995. Seabrook Operational Report,1995. 6-57
Tcble 6-13. Station Groups Formed by Cluster Analysis with Preoperational and Operational (1990-1995) Geometric Mean Density and 95% Confidence Limits of Dominant Macrofauna Taxa (Non-Colonial) Collected Annually in August from 1978 Through 1995. Seabrook Operational Report,1995. SIMILARTTY GROUP NAME/ LOCATION (WITHIN/ NO. (STATION / YEARS) - BETWEEN DOMINANT TAXA PREOPERATIONAL OPERATIONAL GROUP) LCL MEAN - UCL LCL MEAN UCL I Inte: tidal 0.70/0.43 Mytilidae 47977 69205 99824 30714 54186 95598 Nearfield (BIMLW; 1978-95) Jarra marina 2116 3626 6216 655 1028 1614 Farfield (B5MLW; 1982-95) Lacuna vincia 2035 3209 5060 2218 3751 6345 Turtonia minuta 1367 2707 5360 722 1455 2928 Hiatella sp. 1464 2604 4631 453 1025 2320 Oligochaeta 1203 2030 3423 224 721 2318 Nucella lapillus 925 1501 2432 865 1653 3158 Gammarus oceanicus 241 564 1319 721 1511 3166 2 Shallow Subtidal O.76/0.58 Lacuna vincta 3761 5379 7694 5448 8046 I1881 ? u Nearfield (Bl7; 1978-89,1991-95) Farfield (B35; 1982-95) Mytilidae 2905 4758 7793 1270 3488 9574 Idoteaphosphorca 1695 2166 2768 1233 1775 2556 00 Pontogencia inennis 1248 1773 2518 1017 1684 2788 Jassa marmorata 1097 1572 2254 513 1246 3024 Idotea halthica 508 890 1559 1% 449 1025 3 Shallow Subtidal 0.70/0.65 Mytilidae 3949 6688 11326 2745 5113 9522 Nearfield (B17; 1990) Pontgencia inermis 1174 1838 2877 859 1359 2148 Mid-Depth Caprella septentrionalis 840 1267 1912 872 1583 2874 Intake (B16; 1980-84,1985 Anomia sp. 580 821 i162 588 853 1237 Discharge (B19; 1979,1981 Hiatella sp. 475 717 1084 312 489 768 Farfield (B31; 1979-88; 19%I 5) Lacuna vincta 328 460 645 601 935 1455 Asteriidae 185 271 397 181 327 590 4 Mid-Depth 0.67/0.65 Pontogencia inermis 219 336 517 162 267 439 Farfie!d (B31; 1989) Anomia sp. 207 332 531 392 581 859 Deep Mytilidae 125 270 585 1% 458 1068 Discharge (B04; 1979-84,1986-95) Asteriidae 179 242 329 251 300 359 Farfield (B34; 1979,1981,1982,1986-95) Caprella septentrionalis 134 198 291 113 172 264 Intake (B13; 1986-95) Hiatella sp. 79 179 403 164 389 924 5 Middepth 0.64/0.63 Pontogencia inermis 195 369 699 N/A 602 N/A Nearfield (B19; 1978,1980,1995) Mytilidae 130 306 719 2624 Farfickl(B31; 1978) Asteriidae 140 226 363 333 Anomia sp. 97 208 444 99 Deep IIiston 'eIntake(B13; 1978-84) Hiatella s . 98 194 380 227 Farfield (B34; 1980,1983,1984) Tonicella' rubra 75 125 210 106 Caprella septentrionalis 62 124 248 1555 O O O
6.0 MARINE MACROBENTHOS (m V) 2 low mean densities (<600/m ) of the dominant Interti<M Ca==imities (Non-Destructive taxa (including Pontogeneia inermis, Mytilidae, Monitorine Proeram) and Anomia sp.) in both preoperational and operational periods. Means and 95% confidence Faunal abundance patterns on local rocky shores intervals were similar for the dominant taxa in both exhibit zonation patterns similar to those discussed periods. previously for intertidal macroalgae (Lewis 1964; Menge 1976, Underwood and Denley 1984). The last clu ter (Group 5) contained historic (1978- Common intertidal fauna occurring in non-
- 84) collections from deep intake station B13, and destructive sampling quadrats included barnacles, a scatter of collections from deep farfield station mussels, snails and limpets. Spatial (among zones, B34 (1980,1991 and 1984), mid-depth nearfield between stations) and temporal (among seasons, station B19 (108,1980, and 1995), and mid-depth between operational periods) abundance patterns of farfield station B31 (1978) (Figure 6-17 and Table these species for nearfield and farfield sample 6-13). With one exception, no collections from the stations are described below.
operational period were present in this cluster. Preoperational period collections were Barnacles (especially Balanus spp. and characterized by low mean densities of the Semibalanus spp.) commonly occur on high dominant taxa (<400/m2 ), w th only relatively intertidal (Bare Ledge) rock surfaces in the small numbers of Mytilidae present. The Seabrook area and throughout the North Atlantic collection at B19 in 1995 contained lower numbers (Connell 1%1; Menge 1976; Grant 1977; Bertness 7q l V of most dominants including mytilids, Pontogencia 1989). Although generally common, intertidal i , inermis, Anomia sp., and Lacuna vincta (NAI barnacle populations typically exhibit high seasonal 1996) making it more similar to the low density and year-to-year variability (Menge 1991; ; I collections from 1978 and 1980. This type of Minchinton and Sheibling 1991; NUSCO 1994); ! assemblage, although unusual, also occurred \ similarly, temporal variability in barnacle preoperationally, and thus is not attributable to frequency of occurrence has been observed in Seabrook Station. Seabrook study quadrats (Table 6-14). Because year-to-year variability is so high, between period In general, macrofaunal collections made at and within station comparisons are best made by stations located in the same depth strata (i.e., examining ranges of annual frequencies. Taking i intertidal, shallow subtidal, etc.) clustered this approach, preoperational and operational together. Secondly, the collections made during measurements were similar at each station, with the operational years (1990-1995) at each station values somewhat higher at farfield station B5MLW were similar enough to be grouped with the compared to nearfield Station BIMLW (Table 6-majority, if not all, of those made in the 14). Measurements made in 1995 indicated lower preoperational years. These are indications that no barnacle densities in all months at B1 and in July j 1 nearfield-farfield or temporal changes to the and December at B5. Similar reductions were l macrofaunal community have resulted from observed during both the preoperational and i operation of Seabrook Station. operational periods. l V 6-59
6.0 MARINE MACROBENTHOS Table 6-14. Percent Cover and Percent Frequency of Occurrence of Dominant Macrofauna at Fixed Intertidal Non-destructive Sites During the h Preoperational and Operational Periods and in 1995. Seabrook Operational Report,1995. ZONE: TAXA 1 AREA APR JUL' DEC
- (DNfA TYPE) (STATION)
Bare Ledge Balanus spp. Nearfield (B1) Preoperational 61 (1-100) 41 (9-79) 9 (0-63) Operational 41 (28-90) 79 (0-98) 48 (1-81) IW5 28 0 1 l Farfield (BS) I Preoperational 89 (58-100) 85 (24-100) 72 (5-88) Operational 92 (36-95) 67 (13-87) 11 (0-54) I 1995 93 13 0 Littonna saxatilis Nearfield (BI) Preoperational 7 (0-44) 57 (0-88) 16 (0-88) Operational 37 (0-56) 81 (0-100) 50 (0-100) 1995 0 0 0 Farfield (BS) Preoperational 50 (0-100) 66 (0-94) 75 (0-100) Operational 25 (0-81) 31 (6-69) 25 (0-81) 1995 0 31 0 Fuccid Ledge Mytilidae Nearfield (B1) Preoperational 72 (2'.-100) 76 (27-100) 78 (43-100) Operational 56 (13-91) 75 (11-99) 58 (19-95) 1995 56 11 58 Farfield (BS) Preoperational 8 (2-100) 1(0-88) 8 (0-100) Operational 9 (5-12) 13 (0-77) 11 (0-63) 1995 12 1 11 Littonna obtusata Nearfield (BI) Preoperational 6 (0-19) 10 (0-25) 6 (0-19) Operational 6 (0-31) 19 (0-62) 12 (0-81) 1995 0 44 6 Farfield (BS) Preoperational 3 (0-50) 16 (0-38) 16 (0-69) Operational 12 (0-25) 38 (25-50) 37 (0-56) 1995 19 44 0 0 6-60 (continued)
6.0 MARINE MACROBENTHOS ( Table 6-14. (Continued) ZONE. TAXA AREA APR JUL DEC (DATA TYPE) (STATION) Chondrus Zone l Mytilidae Nearfield (BI) Preoperational 90 (54-%) 89 (71-95) 65 (15-85) Operational 77 (26-95) 72 (14-95) 63 (48-93) 1995 26 14 48 Farfield (BS) , Preoperational 49 (10-72) 63 (23-80) 26 (0-49) Operational 47 (0-88) 79 (27-92) 43 (8-87) l 1995 88 91 43 Nucella lapillus Nearfield (B1) l Preoperational 75 (13-100) 100 (100-100) 56 (31-88) i Operational 31 (19-81) 100 (94-100) 38 (19-100) 1995 56 100 38 Farfield (BS) Preoperational 94 (75-100) 38 (13-56) 69 (56-81) Operational 94 (37-100) 88 (37-94) 56 (19-94) 1995 100 88 56 Littorina linorea Nearfield (B1) Preoperational 0(0-0) 0 (0-13) 0 (0-6) Operational 0(0-19) 19 (0-38) 12 (0-50) 1995 6 38 12 Farfield (BS) Preoperational 81 (75-100) 100 (94-100) 88 (44-94) Operational 94 (81-100) 100 (94-100) 75 (56-94) 1995 88 94 56 Acmaea testudinalis Nearfield (B1) Precperational 13 (J-38) 13 (0-25) 13 (6-81) Operational 19 (0-44) 12 (6-25) 12 (0-81) 1995 38 19 0 Farfield (B5) Preoperational 0 (0-44) 0 (0-13) 0 (0-25) Operational 12 (6-12) 6 (0-25) 6 (0-44) 1995 12 0 0
/O 6-61
6.0 MARINE MACROBENTHOS The herbivorous snail, Littorina saxatilis, is an differences between nearfield and farfield stations, important grazer in the high intertidal zone. Like relative to those in the mid-intertidal zone (Table barnacles, abundances of L. saratilis displayed 6-14). Frequency of occurrence estimates during great seasonal and annual variability during the 1995 at nearfield station B1 were less than l preoperational and operational periods at both preoperational and operational period medians and stations (Table 6-14). Densities of L. saxatilis were the lowest recorded to date in April and July, were quite low in 1995 at both stations. At the farfield station (BS), aburdances in 1995 were higher than the medians for both operational The dominant faunal taxon in the mid-intertidal and preoperational periods. The carnivorous snail (Fuccid) zone has been Mytilidae (primarily the Nucella lapillus commonly preys on mussels and blue mussel Mytilus edulis), which dominates barnacles, and can have considerable influence on certain rocky shores in New England (Lubchenco low intertidal community structure (Connell 1961; and Menge 1978; Petraitis 1991) and elsewhere in Menge 1983,1991; Petraitis 1991). At Seabrook the North Atlantic (Seed 1976). Mytilidae wen study sites, N lapillus can be locally abundant, at I most abundant at the nearfield station (B1), with times reaching frequency of occurrence levels of percent frequencies (preoperational, operational, 100%, particularly in July (Table 6-14). Over the and 1995) exceeding 50% for all sampling periods entire study, occurrence of this species has been except July 1995 (Table 6-14). The preoperational consistent, both between nearfield and farfield and operational seasonal median frequencies were stations and between periods. all less than 15% at farfield station B5, with , similar values in 1995. Mussels are typically Of the herbivorous littorine snails occurring in the outcompeted by barnacles at this site (NAI 1993). Gulf of Maine, Littorina littorea has the most Operational period ranges generally fell within pronounced effect on intertidal community preoperational period ranges at both stations, with structure, particularly in the low intertidal zone operational period medians slightly lower than (IWhenco 1983; Petraitis 1983). In the Seabrook preoperational period medians in all sampling study area, L. littorca was most common at the periods at nearfield station Bl. farfield station (BS), often exceeding 90% frequency of occurrence during both The herbivorous snail Littorina obtusata is a preoperational and operational periods (Table 6-common mid-intertidal resident at both stations. 14). Frequencies at the nearfield station (B1) Overall, operational frequencies were generally never exceeded 50% during our studies, and many higher than those during preoperational years, a times, L. littorea was absent from the study sites, trend which was rpparent at both nearfield and Percent frequencies of L. littorea at B1 tended to farfield stations (Table 6-14). Frequencies in 1995 be lower during the preoperational years ( < 13 %) were within or exceeded ranges observed during than during the operational period, when the the preoperational period at both stations except in highest monthly estimates were recorded. Another July, where frequencies exceeded the low intertidal grazer, the limpet Acmaca preoperational ranges at both stations, testudinalis, occurred in low to moderate frequencies in most years at nearfield station B1 High mussel abundances were also typical of the and occasionally at farfield station B5 (Table 6-low intertidal or Chondrus zone, with only small 14). Operational period ranges for individual 6-62
- 6. 0 MARINE MACROBENTHOS preoperational and operational ranges for all during the September-December exposure period V seasons combined were identical (0-81 % at B1, 0- (NAl and NUS 1994). Typically, barnacle 44% at B5). densities were higher at the farfield station (B31) than at the nearfield station (B19) over both SubtMM FonHno Community mottom Panel preoperational and operational periods, although Monitoring Program) this relationship was reversed in August 1994 (NAl
) and NUS 1995) and in 1995 (Table 6-15). Recruitment success and annual patterns of settlement for sessile macroinvertebrates were Anomia sp. (jingle shells) consistently display peak 4 assessed by the bottom panel study using short- settlement during the September- December term exposure periods (three sequential four-month exposure period, a period when water exposure periods per year). Although the type of temperatures are rapidly cooling (cf. Fuller 1946). substratum, length of exposure period and Nearfield (B19) densities exceeded farfield (B31) deployment strategies can all influence the patterns densities in both the preoperational and operational of community colonization (Zobell and Allen 1935; periods (Table 6-15). However, this relationship Fuller 1946; Schoener 1974; Osman 1977; was reversed in 1994 (NAI and NUS 1995) and in Sutherland and Karlson 1977), these factors may 1995 (Table 6-15). Anomia sp. densities were be standardized to allow comparisons between higher in the operational period at both stations. nearfield and farfield stations during these different
.s periods of the year (January-April, May-August, Another species of interest is the small crevice-and September-December). Four-month exposure seeking bivalve, Hiatella sp., which historically periods provide sufficient duration for larval stages has settled during the May-August exposure period to settle, metamorphose, and grow into juveniles or at both stations. Settlement has normally been young adults that can be effectively identified. Of highest at the farfield station in both the the organisms collected on these panels, four taxa preoperational and operational periods, where (Balanus spp., Anomia sp., Hiatella sp,,, and densities in excess of 10,000 individuals per 0.25 Mytilidae) have been collected in sufficient m2were commonly reported (Table 6-15). The frequency and numbers to allow comparisons of year 1995 was no exception, with the greatest long-term trends in densities within and between densities measured at the farfield station. Densities nearfield and farfield stations for assessing power were lower than the preoperational and operational plant effects (Table 6-15). averages at both stations.
Subtidal barnacles in the Seabrook area are Mytilidae (mostly blue mussel, Mytiis edulis) are represented primarily by two species, B. crenatus an important component of the local macrofaunal and S. balanoides. Peak settlement usually occurs community, and are discussed in more detail in the in early spring, often resulting in highest densities following section. Recruitment to bottom panels in the January-April exposure period (Table 6-15). followed a pattern similar to that described for However, settlement can be protracted and Hiatella sp., i.e., peak recruitment occurred variable from year to year. For example, C- substantial densities of barnacles were found at both nearfield and farfield stations in August 1995, and in 1993, barnacles recruited to bottom panels 6-63
Table 6-15. Estimated Density (per 0.25 m2 ) and Coefficient of Variation (CV,%) of Selected Sessile Taxa on Hard-Substrate Bottom Panels Exposed for Four Months at Stations B19 and B31 Sampled Triannually (April, August, December) from 1981-1995 (Except 1985). Seabrook Operational Report,1995. APRIL AUCU5T DECEMBER AIL SKASO*IS TAXA STATION PERIOD / YEAR MEAN CV' MEAN CY MEAN CV MEAN CV Baianas spp. Nearfield Precp' 17053 81 6403 78 9 144 7822 110 (B19) Op* 8945 139 11900 61 610 216 7152 122 1995 10 - 10883 - 0 - 3631 173 Farfield Preop 40962 55 7917 78 14 121 16298 133 (B31) Op 14137 79 10650 64 169 125 8319 112 1995 334 - 3433 - 61 - 1276 147 Anomra sp. Nearfield Preop <1 <1 31 219 1232 92 421 167 (B19) Op 53 152 63 87 2186 111 767 217 1995 6 - 44 - 1313 - 454 164 Farfield Preop 0 0 36 117 993 125 343 164
@ (B31) Op 10 80 85 170 1201 103 432 202
[ 1995 22 - 2 - 3195 - 1073 171 Hnatella sp. Nearfield Preep i 200 3966 65 27 115 1331 171 (B19) Op 3 89 5891 75 9 102 1%8 189 1995 3 - 642 - 8 - 218 169 Farfield Preop <l <1 11659 91 16 131 3892 173 (B31) Op 3 80 12379 79 73 185 4152 192 1995 3 - 3766 - 20 - 1263 172 Mytilidae Nearfield Preop 2 150 367 67 58 98 142 139 (B19) Op 64 133 2361 85 44 29 823 189 1995 9 - 1258 - 39 - 435 164 i Farfield Preep 8 138 5035 200 36 100 1693 171 ( (B31) Op 16 141 3338 91 52 76 1135 201 1995 4 - 2147 - 36 - 729 169
- Preop: 1981-1984 (81alames and Anomna, B19); 1982-1984 (Balanas and Anomia, B31); 1983-1984 (Hiatella and Mytillidae, B19 and B31); Dec.1986-1989 (all taxa and stations).
'Op = 1991-95 O O O
6.0 MARINE MACROBENTHOS 8 during the May-August exposure period, with no significant Preop-Op X Station interaction was densities typically higher at the farfield station than detected for the intertidal stations (Table 6-17). : the nearfield station in both the preoperational and I ^ operational periods (Table 6-15). Mytilidae were also among the dominant taxa at t shallow subtidal stations B17 and B35 (Table 6-6.3.2.2 Selected Benthic Species 16). As in the case of the intertidal stations, I
- substantial recent year-to-year variability in mytilid j Mstilida density was observed at the shallow subtidal j stations. Densities higher than preoperational or Representatives of the family Mytilidae (mytilids) operational period means that were observed in '
are common in the North Atlantic, and are 1993 (NAI and NUS 1994) were followed by typically found attached to intertidal and shallow substantial declines in 1994 (NAI 1995) and 1995. subtidal rocky substrata, but are occasionally Although there was no significant difference recorded from deeper water (Seed 1976). observed between the preoperational and ' Important as prey for marine carnivores such as operationalperiods, densities at the farfield station the dogwinkle Nucella lapillus in the intertidal zone (B35) were significantly higher than at the (Menge 1991; Petraitis 1991), and starfish, nearfield station (B17). However, no significant i lobsters, crabs and fish subtidally (Menge 1979; Preop-Op X Station interaction was detected (Table I Witman 1985; Ojeda and
Dearborn 1991),
mytilid 6-17). l shell surfaces and interstices within mytilid ! () aggregates also provide attachment and habitat Mytilids were also abundant at mid-depth stations areas for many algal and faunal species (Dayton B19 and B31, relative to other taxa collected at l 1971; Seed 1976). these locations (Table 6-16). Densities were significantly higher at the farfield station (B31) At Seabrook study sites, Mytilidae (primarily the compared to the nearfield station (B19) and during blue mussel Mytilus edulis) was, by far, the the preoperational period compared to the 2 dominant tarta in terms of density (no./m ) n the operational period (Table 6-17). However, there l intertidal zotw (Stations B1MLW and B5MLW; was no significant Preop-Op X Station interaction Table 6-16). Annual mytilid abundances have (Table 6-17). Densities in 1995 were an order of been variable over the preoperational period (NAI magnitude lower than the preoperational and 1991b), and similar variability has become operational averages at both stations (Table 6-16). apparent over the operational period. High Comparable densities were also observed in 1978 year-to-year variability in mytilid recruitment is and 1979 (NAI 1991b). typical for the Gulf of Maine (Petaitis 1991). For example,1993 mytilid densities were higher than The most common mytilid collected at Seabrook other operational years (NAI and NUS 1994); in study sites, the blue mussel Mytilus edulis, can 1994 (NAl 1995) and 1995 they were generally reach shell lengths up to 100 mm (Gosner 1978). lower. Although preoperational period densities However, most mytilids collected during our study were significantly greater than those measured ranged from 1 to 25 mm, with the majority A operationally and nearfield densities were collected as newly settled spat measuring 2 to 3 b significantly greater than farfield measurements, mm, Mytilids generally have been largest in the ! 6-65
6.0 MARINE MACROBENTHOS I Table 6-16. Geometric Mean Densities (No./m') and Coefficients of Variation (CV,%) of Selected Benthic Macrofauna Species Collected During gl l Preoperational and Operational Periods and During 1995. Seabrook Operational Report,1995. l l TAXON STATION' PREOPERATIONAL6 1995 OPERATIONAL' MEAN CV MEAN MEAN CV Mytilidae B1MLW 121297 8 47586 74563 10 B5MLW 72831 7 6599 33189 13 i B17 2580 18 2539 2372 24 I B35 4449 14 2516 5261 21 B19 1947 23 269 1601 29 ; B31 6196 17 978 4103 12 l l Nucella lapillus B1MLW 1970 11 1830 1429 15 B5MLW 905 10 1337 891 14 ; Asteriidae B17 590 12 817 742 10 B35 184 23 311 183 30 ' Pontogenciainermis B19 604 15 213 449 18 O B31 404 15 311 270 22 Jassa marmorata B17 1045 14 384 798 19 B35 1888 15 1062 2213 13 Ampithoe nebricata B1MLW 19 92 1 2 100 B5MLW 3 125 151 136 11 Strongylocentrotus B19 66 36 91 98 30 droebachiensis B31 31 35 28 40 31 Modiolusmodiolus' B19 100 14 95 16 23 l B31 89 27 52 79 45 'Nearfield = BIMLW, B17, B19, Farfield = B5MLW, B35, B31. , 'Preoperational = mean of annual means,1978-1989 (B1MLW, B17, B19, B31) or 1982-1989 (B5MLW, B35). l ' Operational mean = mean of annual means,1991-1995, for all stations. l ' Arithmetic mean of annual means. Preop = 1980-1989, Op = 1991-1995. i O 6-66
r O O O Table 6-17. Analysis of Variance Results Comparing Log-Transformed Densities of Selected Benthic Taxa Collected in May, August and November at Near- and Farfield Station Pairs During Preoperational (1978 - 1989) and Operational (1991 - 1995) Periods. Seabrook Operational Report,1995. DEPTH ZONE SOURCE OF . MULTIPLE COMPARISONS 6 TAXA" '(STATION) VARIATION df. MS F8 (Ranked in decreasing order) Mytilidae Intertidal Preop-Op* I 6.36 49.72 " Preop >Op (<25 mm) (B1, B5) Year (Preop-Op)* 11 1.69 13.23** Month (Year)d 26 1.16 9.05 " Station
- I 7.44 58.18 " B1MLW>B5MLW Preop-Op X Station' 1 0.28 2.17 NS Error 309 0.13 Shallow Subtids! Preop-Op 1 0.04 0.17 NS (B17, B35) Year (Preop-Op) 11 3.94 14.65**
Month (Year) 26 2.63 9.76 " [ Station 1 6.98 25.92** B35>B17
- Preop-Op X Station 1 0.28 1.05 NS Error 264 0.26 Mid-Depth Preop-Op I 1.71 4.43* Preop >Op (B19, B31) Year (Preop-Op) 15 6.33 16.41**
Month (Year) 34 1.54 3.99 " Station 1 21.29 55.20 " B31>B19 Preop-Op X Station 1 0.26 0.66 NS Error 408 0.39 (continued)
Table 6-17. (Continued) DEPTH ZONE SOURCE OF MULTIPLE COMPARISONSh TAXA * (STATION) VARIATION df MS -P (Ranked in decreasing order) Nucellalapillus Intertidal Preop-Op 1 0.22 1.74 NS (B1MLW, B5MLW) Year (Preop-Op) 11 1.27 10.08 " Month (Year) 26 1.I1 8.81" Station 1 5.36 42.63** B1MLW>B5MLW Preop-Op X Station 1 0.17 1.38 NS Error 309 0.13 Asteriidae Shallow Subtidal Preop-Op 1 0.59 3.79 NS (B17, B35) Year (Preop-Op) 1I 2.83 18.25 " Month (Year) 26 0.88 5.67 " Station 1 22.90 147.42** B17>B35 P Preop-Op X Station 1 0.59 3.81 NS
@ Error 301 0.16 Pontogencia Mid-Depth Preop-Op 1 2.29 10.21** Preop >Op intermis (B19, D31) Year (Preop-Op) 15 0.89 3.98 "
Month (Year) 34 1.45 6.47 " Station 1 4.36 19.41 " B19>B31 Preop-Op X Station 1 0.02 0.07 NS Error 408 0.22 Jassa marmorata Shallow Subtidal Preop-Op 1 0.00 0.01 NS (B17, B35) Year (Preop-Op) 11 2.38 7.41 " Month (Year) 26 1.31 4.07 *
- l Station 1 10.34 32.13* B35>B17 Preop-Op X Station 1 0.72 2.23 NS l Error 301 0.32 (continued) l O O O
% O (d V Q
V Table 6-17. (Continued) DEPTH ZONE : SOURCE OF MULTIPLE COMPARISONSh TAXA" (STATION) -VARIATION - df MS P -(Ranked in decreasinit order) - Ampithoe rubr/cata Intertidal , Preop-Op 1 37.12 97.87** Op> Preop (B1MLW, B5MLW) Year (Preop-Op) 11 7.19 18.96** Month (Year) 26 0.96 2.53 " Station 1 62.95 165.97 " Preop-Op X Station 1 56.50 148.96 " B50p B5 Pre B1 Pre BION Error 309 0.38 Strongylocentrotus Mid-Depth Preop-Op 1 1.98 4.08' Op> Preop droebachiensis (B19, B31) Year (Preop-Op) 15 3.52 7.25 " Month (Year) 34 1.74 3.59 *
- Station i 13.87 28.56 " B19>B31 Preop-Op X Station 1 0.01 0.01 NS
, Error 408 0.49 h Modiolus modiolus Mid-Depth Preop-Op 1 1,002,443.27 40.56 " Preop >Op (adults) (B19, B31) Year (Preop-Op) 13 151,055.34 6.1 1 *
- Month (Year) 30 40,817.81 1.65
- Station 1 10,915.09 0.44 NS Preop-Op X Station 1 16,307.70 0.66 NS Error 1026 24,716.23
'legio (x+1) density, except for M modiolus adults, which were samp!cd semi-quantitatively and therefore rank densities were used.
6 Preop-Op compares 1982-1989 to 1991-1995 regardless ofstation for B1MLW/B5MLW and B17/B35. Preop-Op compares 1978-1989 to 1991-1995 regardless of station for B19/B31. Preop-Op compares 1980-1989 to 1991-1995 regardless of station form modiolus.
- Year nested within Preoperational and Operational periods regardless of Station.
dMonth nested within Year regardless of Station or Period.
' Station pairs nested within a depth zone: Intertidal = nearfield (B IMLW), farfield (B5MLW); Shallow subtidal = nearfield (B 17), farfield (B35);
Mid-depth = nearfield (B 19), farfield (B31); regardless of Year, Station or Penod.
' Interaction of the two main effects, Preop-Op and Station.
HS = not significant (p>0.05); * = significant (0.05>p>0.01); " = highly significant (ps0.0l). j
Waller-Duncan multiple means comparison test used for significant main effects. LS Means used for interaction term. Underlininig indicates no '
significant difference (n=0.05).
6.0 MARINE MACROBENTHOS l intenidal zone, a trend which has been consistent 1991). At Seabrook study sites, N. lapillus , over both periods (Table 6-18). Intenidal mytilids abundances at nearfield station B1MLW were ' l typically have been slightly larger at the farfield significantly higher than abundances at farfield I station (B5MLW) than at the nearfield station Station B5MLW (Tables 6-16 and 6-17). Densities (B1MLW) over both preoperational and in 1995 were close to or exceeded preoperational - operational periods. A similar difference in size and operational period means at both stations, was observed between preoperational and Differences in preoperational and operational l operational periods at both intertidal stations periods were not significant and no significant l (preoperational period slightly larger than Preop-Op X Station interaction was detected (Table operational period). In 1995, mytilids were 6-17). smaller than preoperational and operational averages at both stations. Nucella lapillus shell length measurements from ) intertidal collections were also made as part of the l Mytilids generally were smaller in the subtidal life history studies. N. lapillus can reach lengths zones than in the intertidal zone. Subtidal of up to 51 mm (Abbott 1974), but typically ranged operational period mean lengths were generally from 3-12 mm during this study (NAl 1993). slightly larger compared to preoperational mean Mean length was greater at the nearfield station lengths. However, relatively large numbers of (B1MLW) than at the farfield station (B5MLW) in very small mytilids were collected at mid-depth 1995, a trend observed during the preoperational nearfield station B19 and farfield shallow subtidal and operational periods (Table 6-18). Operational Station B35 in 1995, thereby reducing the and 1995 mean lengths at both stations were below operational period means to less than the the respective preoperational means. l preoperational means. In contrast, relatively large mytilMs viere measured in 1995 at farfield Station Asteriidae B31. This same phenomenon was observed in 1994 (NAI 1995) and is unexplained. During the Asteriidae (sea stars) is another predatory taxon preoperational period, mytilid lengths were smaller that can occur in the low intertidal zone, but is l at the nearfield stations (B17 and B19) than at the most abundant in the shallow subtidat zone. farfield counterparts (B35 and B31). However, Although two genera of starfish occur in the Gulf during the operational period, slightly larger of Maine, Asteriar and Leptasterias (Gosner 1978), mytilids were collected at nearfield station B17 two species of the former, Asteriasforbesii and A. compared to farfield station B35 and nearfield vulgaris, were most commonly collected in this station B19 mytilids were substantially smaller than study. Predation by Asterias spp. on mussels can those measured at farfield station B31. be locally intense, and this feeding activity is believe.1 to have considerable influence on both in-Nucella lavillus tertidal and subtidal community structure (Menge 1979; Sebens 1985). Abundance patterns of The only common intertidal macrofaunal predator Asteriidae in the Seabrook area were examined in in the Seabrook area is the dogwinkle, Nucella detail in the shallow subtidal zone, where they lapillus, preying primarily on mussels and were most abundant Densities in 1995 slightly barnacles (Connell 1%1; Menge 1976; Petrattis exceeded preoperational and operational means at 6-70
6.0 MARINE MACROBENTHOS O T aie 6 ^ > *e te =<6 ca-> o coerrieie ts er v ri tie <cv.*) er Selected Benthic Species Collected at Nearfield-Farfield Station Pairs During the Preoperational and Operational Periods and in 1995. Seabrook Operational Report,1995. PREOPERATIONAL" 1995 OPERATIONAL" TAXON STATION MEAN CV MEAN MEAN CV Mytilidae' B1MLW 3.1 64.7 2.5 3.0 53.0 B5MLW 3.3 53.1 2.4 3.1 58.3 B17 2.3 63.4 2.4 2.5 53.9 B35 2.5 64.8 1.7 2.4 .57.6 B19 2.4 73.7 1.4 1.8 55.8 B31 2.8 77.8 3.4 3.1 70.8 l uucezza tapillus B1MLW 6.9 80.5 6.7 6.2 73.0 B5MLW 6.0 98.5 4.1 5.0 82.0 l lD j V ' Asteriidae B17 5.0 86.0 6.0 5.2 68.5 B35 6.7 98.5 8.1 5.4 93.3 Pontogeneia inermis B19 5.1 39.4 4.7 5.3 32.8 B31 5.3 29.2 5.2 5.4 28.1 Jassa marmorata B17 4.2 26.6 3.8 4.2 28.5 B35 3.9 27.2 4.4 4.0 28.7 Ampithoe rubricata B1MLW 7.0 36.2 - 8.6 42.4 B5MLW 7.8 34.6 7.5 7.3 43.1 Strongylocentrotus B19 1.9 95.2 1.9 2.5 86.5 droebachiensis B31 1.9 56.9 2.2 3.4 131.2 heru.uonal = mean of annual means,1982-1989. Annual mean is sum of lengths of allindividuals collected in May, August, and November divided by the total number of individuals measured.
' Operational = mean of annual means, 1991-1995. ' Individuals measuring >25 nun were excluded.
O 6-71
];
6.0 MARINE MACROBENTHOS , I both stations (Table 6-16). Although densities depth stations, mean lengths were approximately 5 were significantly lower at farfield station B35 mm (Table 6-18). Mean length at farfield station compared to nearfield Station B17, no significant B31 was slightly larger than at nearfield station difference was measured between the B19 in both the preoperational and operational I preoperational and operational periods and no periods and in 1995. Mean length during the significant Preop-Op X Station interaction was operational period was slightly larger than during detected (Table 6-17), the preoperational period at both stations. Mean length in 1995 at station B19 was smaller than the The sizes of Asteriidae collected over the study preoperational and operational averages, period generally have been consistent and the vast coinciding with reduced densities. majority of individuals collected were juveniles (Table 6-18). Larger Asteriidae were collected at Jassa mannorata farfield station B35 during the preoperational period and in the operational period until 1994, The tube-building amphipod Jassa marmorata is a when substantially smaller individuals appeared at common member of the local fouling community, this station (NAI 1995). hi 1995, however, the Populations of this species can dominate prirvary long-term tendency of larger Asteriidae at farfield space on hard surfaces, often outcompeting station B35 was again observed (Table 6-18). encrusting species by forming a mat " complex" composed of numerous tubes made from sediment Pontogencia inermis and detritus (Sebens 1985). Prunarily a suspension feeder (Nair and Anger 1979), J. marmorara also The amphipod Pontogencia inermis is a preys on small crustaceans and ostracods numerically-dominant macrofaunal species in (Bousfield 1973). In the Seabrook study area, J. benthic habitats in the Gulf of Maine, where it marmorata is most abundant and among the clings to submerged algae in the intertidal and dommant taxa at shallow subtidal stations (Table 6-subtidal zones to depths of more than 10 m, and 16). Annual mean densities during 1995 were less can also occur in the water column (Bousfield than preoperational and operational period means 1973). At Seabrook study sites, P. inennis was a at both stations (Table 6-16). No significant dominant taxon at all subtidal stations, but difference between the preoperational and occurred most consistently in the mid-depth zone. operational period means was detected. Although Temporally, mean densities were significantly densities were significantly greater at farfield higher during the preoperational period for both Station B35 compared to nearfield Station B17, no mid-depth locations; spatially, densities were significant Preop-Op X Station interaction was significantly higher at nearfield Station B19 observed (Table 6-17). compared to farfield Station B31 (Table 6-17), despite an observed reversal of this long-term trend Jassa mannorata can reach a maximum length of in 1995 (Table 6-16). No significant Preop-Op X up to 9 mm (Bousfield 1973), and growth rate and Station interaction was detected (Table 6-17). molting frequency of this species is strongly related to temperature (Franz 1989). Lengths of J. Pontogencia inennis can reach lengths of up to 11 mannoratain our study averaged approximately 4 mm (Bousfield 1973); however, at Seabrook mid- mm, with mean lengths slightly higher at the near-6-72 l l
\
l l 6.0 MARINE MACROBENTHOS O V)
- field station (B17) than at the farfield station (B35) during both preoperational and operational periods lengths generally ranged from 7 to 10 mm (Table 6-18), with a variety of size classes observed.
(Table 6-18) and in 1994 (NAI 1995). However, During the preoperational period, mean length was mean length in 1995 was larger than the larger at the farfield station, with the opposite preoperational and operational averages at the observed during the operational period. Mean farfield station, but smaller than period averages at lengths at B1MLW are likely not representative B17 (Table 6-17). because of the low densities of A. rubricata available for measurement. Ampithoe rubricata Stronnlocentrotus droebachiensis Another amphipod occasionally common to benthic habitats in the Seabrook area is Ampithoe The green sea urchin, Strongylocentrotus rubricata. This species is most abundant in the droebachiensis, is well documented as having intertidal zone, bmidmg nests among fucyds and in considerable influence on low intertidal and mussel beds (Bousfield 1973). Occurrence and subtidal community structure (Lubchenco 1980; I abundance patterns of A. rubricata have been Witman 1985; Novaczek and McLachlan 1986; l unpredictable over the entire study period, with Johnson and Mann 1988). Grazing by locally l relatively high densities noted in some years, and dense aggregates of S. droebachiensis in the l absence or near-absence observed in other years. subtidal zone can preferentially eliminate l For example, A. tubricata was the dominant populations of foliose algae (Breen and Mann ( ) intertidal crustacean in 1982, but was rarely 1976; Witman 1985), such as Laminaria collected during the period 1984-89 (NAI 1991b). sacchannaand L. longicneris (Larson et al.1980; Because of this extended period of low abundance, Mann et al.1984). What remains after this severe overall preoperational period mean densities for grazing is a barren ground of primarily crustose this species were low (Table 6-16). This trend of coralline algae. S. droebachiensis is susceptible to low abundance continued through 1992. disease-induced local extinction, allowing foliose Abundance increased in 1993 and 1994 and algae to recolonize denuded areas. Sea urchin declined in 1995 at nearfield Station B1MLW abundance cycles and subsequent habitat (Figure 6-18). However, a dramatic increase in A. modification have been linked to shifts in local rubricata abundance occurred at the farfield station lobster landmgs (Breen and Mann 1976); however, (B5MLW) from 1987-1991 followed by stable this relationship is still unclear and remains a densities through 1995. Continued low densities source of controversy (Einer and Vadas 1990), during operational years at B1MLW and continued high densities at B5MLW for that period, when Sea urchins collected in destructive samples were examined with ANOVA, resulted in a significant small(Table 6-18), and not considered a dominant Preop-Op X Station interaction (Table 6-17, Figure factor in structuring communities at any depth 6-18). zone. Sea urchins were most abundant in the mid-depth zone in both preoperational and operational Ampithoe rubricata reach a maximum size of 20 periods, with higher densities measured at /" mm (Bousfield 1973). Durmg our studies, average nearfield station B19 (Table 6-16). Significant be-6-73
6.0 MARINE MACROBENYdOS Intertidal Zone: Ampithoe n4bricata 3.0 : _ gi asi 2.6 s 20 * ...** g 1.s ,... 1.0
.. -, ..- 1 0.5 0.0 Prooperational Operan6onal l PERIOD 1
1 5 l - gg
. . + usi l
l i d l l 1 1 I T !.- l2 . p,_w ,, gg. ~ . . . . . . * *
- i l
I l -
.. i 0
82 83 84 85 88 87 88 89 90 91 92 93 94 96 veAn Figure 6-18. Compansons between intertidal stations of mean logio(x+ 1) of Ampithoc nebricata during the preoperational(1978-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 6-17). Seabrook Operational Report,1995. 6-74
l 6.0 MARINE MACROBENTHOS O tween-period and between-station differences were detected, ahhough the Preop-Op X Station mean. However, higher densities have been recorded at station B35 and both mid-depth stations interaction term was not significant (Table 6-17). (B19, B31) during the operational period. Most sea urchins collected were juveniles, with Modiolus modiolus mean length approximately 2 mm during the preoperational period at both nearfield and farfield Beds of the northern horse mussel Modiolus stations (Table 6-18). Mean length was somewhat modiolusare often extensive in subtidal habitats in I larger during the operational period, although 1995 the Gulf of Maine, providing additional hard sub-mean length was similar to the preoperational stratum for benthic algae (Sebens 1985), and average. The average length during the shehering a diverse group of invertebrates in operational period and in 1995 at B31 was larger spaces between individual mussels (Witman 1985; than that at B19. Ojeda and Dearborn 1989). Large sea stars l (Asterias spp.) actively prey on M. modiolus, while Densities of adult sea urchins also were estimated another common subudal predator, the omnivorous l during subtidal transect sampling, and have been sea urchin Strongylocentrotus droebachiensis, relatively low since sampling began in 1985 (Table appears to choose foliose macroalgae over M. l 6-19). Annual mean densities during the modiolus (Briscoe and Sebens 1988). Urchin l preoperational period never exceeded 4.0/m2 , and activity may actually enhance M. modiolus were typically <0.5/m2 . At shallow subtidal abundance by grazing kelps off mussels and i Station B17, operational and 1995 means were decreasing the risk of mussel dislodgement low, but within the range of the preoperational (Witman 1987). l l Table 6-19. Mean Densities (Per m 2) and Range of Adult Sea Urchins Observed in l Subtidal Transects During Preoperational (1985-1989) and Operational l (1991-1995) Periods and During 1995. Seabrook Operational Report, 1995. PREOPERATIONAL 1995 OPERATIONAL STATION - MEAN RANGE- MEAN MEAN RANGE. B17 0.29 0.00-3.98 0.01 0.08 0.00-0.93 B35 0.04 0.00-0.19 0.06 0.43 0.00-5.07 B19 0.10 0.00-0.50 0.25 1.90 0.00-10.00 B31 0.05 0.00-0.62 1.97 4.10 0.00-20.36 l ALL STATIONS 0.12 0.00-3.98 0.57 1.63 0.00-20.36 l' 6-75
6.0 MARINE MACROBENTHOS l Mean densities of M. modiolus measured in 1995 Another less cone impact resulting from were higher than preoperational and operational coastal nuclear power f ts is related more to period means at nearfield station B19, with the altered water circulation patterns than to thermal opposite true at farfield station B31 (Table 6-16). incursion. Specifically, the introduction Densities were significantly higher during the (discharge) of turbid water to an area of preoperational period (Table 617). However, no historically lower levels of turbidity decreases light significant difference was detected between penetration and increases sedimentation rates. stations, nor was a significant Preop-Op X Station Sources of this turbidity included suspended interaction observed. inorganic and organic particles from higher energy areas, such as wave-swept shores (Osman et al.
6.4 CONCLUSION
S 1981; NUSCO 1988; Schroeter et al.1993) and increased detrital deposition resulting from 6.4.1 Introduction settlement of entrained organisms. Turbidity impacts would be most pronounced in areas where Thermal and hydrodynamic changes in physical levels of water movement and physical disturbance conditions, created by operation of the Seabrook are low, such as in deeper water. Turbidity effects Station condenser cooling water system, could detrimental to macrobenthic plants and animals potentially affect the Ic, cal hard-bottom included shading or burial, and an increased macrobenthic communities in several ways. The community dominance by suspension-feeding most obvious type of impact is temperature-related organisms and organisms more tolerant of higher community alteration, resulting from direct sedimentation rates (Hiscock and Mitchell 1980; exposure to the discharge thermal plume. This Schroeter et al.1993). type of impact could produce significant changes to nearby attached communities, depending on the Because the type of impact a community is proximity of these habitats to the discharge, and vulnerable to appears to be related to its relative the hydrodynamic characteristics of the thermal position in the water column (i.e., temperature plume itself. These changes are most likely to effects for shallow water sites, turbidity effects at occur in surface and near surface waters, due to deeper water sites), potential impacts associated the buoyant nature of most thermal plumes. Such with construction and operation of Seabrook impacts are well-documented for intertidal and Station on communities in each of these depth shallow subtidal communities during monitoring zones will be examined separately, studies for coastal nuclear power plants elsewhere, l and included elimination or reduced abundance of 6.4.2 Evaluation of Potential Thermal Plume cold-water species, and increased aburglance of Effects on Intertidal / Shallow Subtidal warm-water tolerant and/or opportunistic species, Benthic Communities j leadmg to the development of communities distinct from those seen prior to thermal incursion and Nearfield sampling sites used for the Seabrook from those on nearby unaffected coasts (Vadas et intertidal and shallow subtidal macrobenthos al, 1976; Wilce et al.1976; BECO 1994; studies were selected because they best represent NUSCO 1994). the shallow water communities that are most sus-6-76
6.0 MARINE MACROBENTHOS A l (v) ceptible to incursion by the Seabrook Station thermal discharge plume. Hydrodynamic Intertidal Zone l modeling, conducted prior to plant start-up to Several of the parameters used to evaluate different predict the areal extent of the thermal plume under aspects of the macroalgal and macrofaunal l various meteorological and current regimes, communities showed nearfield-farfield differences indicated that thermal incursion to these sites that were not consistent between periods, although would be minimal, with temperature increases of for both macroalgae and macrofauna, community
< l'F(Teyssarxiier et al.1974). Subsequent field structure has not changed over time (Table 6-20).
studies conducted after Seabrook began The number of algal taxa decreased s:gnificantly commercial operation verified these predictions by between periods in the intertidal zone, to a greater measuring no temperature increases at the extent at the farfield station compared to the intertidal sampling site, and increases of < 1*F at nearfield station. The number of faunal taxa also the shallow subtidal site (Padmanabhan and Hecker decreased between periods, in this case, to a 1991). greater extent in the nearfield area compared to the Table 6-20. Summary of Evaluation of Potential Thermal Plume Effects on Benthic Communities in the Vicinity of Seabrook Station. Seabrook Operational Report,1995. O OPERATIONAL. NEARFIELD-FARFIELD - PERIOD SIMILAR DIFFERENCES i AREA /DEPTII . _ TO PREVIOUS ' CONSISTENT WITH l COMMUNITY ZONE PARAMETER' YEARS?" PREVIOUS YEARS?' j Macroalgae Intertidal No. of taxc No NF: Op< Preop FF: Op<< Preop J Total biomass No NFr Op<<Preor j FF: Op= Preop l Community stmeture Yes Yes Shallow No. of taxa Yes Yes Subtidal Total biomass Yes Yes Community structure Yes Yes Macrofauna Intertidal No. of taxa No NF: Op<< Preop FF: Op< Preop q Total density Yes Yes Community structure Yes Yes I i Shallow No. of taxa No NF: Op> Preop Subtidal FF: Op= Preop Totaldensity Yes Yes Community structure Yes Yes
' Abundance, no. of taxa, biomass, total density, evaluated using ANOVA; community structure evaluated using g numerical classification by year and station.
t j 6 Operational period = 1990-1995 (August only). V 'NF = nearfield; TF = farfield. I 1 6-77 f 1
)
1 6.0 MARINE MACROBENTHOS i farfield area. The numbers of algal taxa collected station between periods (Table 6-20). Patterns of followed very similar temporal patterns at the two annual mean algal biomass at both stations were intertidal stations, declining at both throughout the variable throughout the preoperational period, preoperational period. The decreasing trend in the although both showed an overall decline between number of faunal taxa collected was established in 1982 and 1990, and a subsequent increase through the preoperational period, and continued into the 1994. In 1995, nearfield biomass declined, while operational period, therefore the decline was at the farfield station, biomass continued the unrelated to station operation. Thus trends leading increasing trend apparent at both stations between to the significant interaction term for both algal and 1991 and 1994. Therefore the interaction may faunal species were established prior to station reflect a short-term fluctuation in an otherwise operation. generally consistent relationship. While total faunal density was consistent among There were differing trends between stations in stations and between periods in the intertidal zone, abundances of Ampithoe ntbricata between the algal biomass at the nearfield station declined to a preoperational and operational periods (Table 6-relatively greater degree compared to the farfield 21). However, examination of annual abundances Table 6-21. Summary of Evaluation of Potential Thermal Plume Effects on Representative Important Benthic Taxa in the Vicinity of Seabrook Station. Seabrook Operational Report,1995. h OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES AREA / DEPTH TO PREVIOUS ' ' CONSISTENT WITH COMMUNITY ZONE' SELECTED TAXON YEARS?* PREVIOUS YEARS?' Macroalgae Intertidal Chondrus crispus Yes NF: Op<Proep FF: Op= Preop Ascophyllum nodosum Yes NF: Op> Preop FF: Op= Preop Fucus vesiculosis No NF: Op<< Preop FF: Op< Preop i Fucus spp. (juveniles) No Yes Shallow Subtidal Chondrus crispus Yes Yes Shallow Subtidal Laminaria saccharina Yes Yes Shallow Subtidal Laminaria digitata No NF: Op< Preop FF: Op= Preop Macrofauna Intertidal Ampithoe rubricata No NF: Op= Preop l l FF: Op> Preop Intertidal Nucella lapillus Yes Yes Intertidal Mytilidae Yes Yes , Shallow Subtidal Jassa marmorata Yes Yes Shallow Subtidal Asteriidae Yes Yes Shallow Subtidal Mytilidae Yes Yes 1 ' Conclusions derived from ANOVA or nonparametric analysis for Preoperational versus Operational periods. l 'NF = nearfield, FF = farfield, note that nonparametric tests do not test for significant station differences or ! station-period interactions.. l 6-78
6.0 MARINE MACROBENTHOS
-) revealed that.tliese shifts began prior to station operation. Once dominant at intertidal stations stations and depth zones had similar assemblages with no evidence of differences between prior to 1986, A. rubricata disappeared from both preoperational and operational periods. This stations until recolonization was observed in 1988 suggests that the important structuring mechanisms at the farfield station (NAI 1989). Abundances at creating differences between stations and periods tl.e farfield station increased and leveled-off in the are most likely natural factors that are unrelated to
)
operational period, with some minor recolonization station operation. Consistent with this was the at the nearfield station since 1992. As this cycle of examination of rarely found algal taxa, which local extinction and recolonization began prior to provided no evidence of a proliferation of warm ) IM3, it is not related to operation of Seaback water species, the appearance of nuisance species, Sta.on. Abundances of the remaining two or a decline in cold-water species, indicating that in:cuidal selected faunal species were consistent the thermal plume has had no effect on species among stations and between periods. composition. Three of the four intertidal selected algal species Shallow Subtidal Zone showed some inconsistency among stations between the two periods. Chondrus crispus Relationships among stations for numbers of biormss declined between periods at the nearfield macroalgal taxa collected and total macroalgal station, but remained unchanged at the farfield biomass were consistent between periods in this oq station. This pattern is similar to that seen in total zone (Tables 6-20,6-21). This was true as well
\
() algal biomass, as C. crispus is the dominant for Chorufrus crispus biomass, and all selected species in this zor.e, so discussion of trends in macrofaunal taxa and total faunal density. The annual means for total algal biomass applies to C. number of faunal taxa collected in the nearfield crispus biomass as well. The frequency of area increased between periods, while it remained occurrence of Ascophyllum nodosum in unchanged in the farfield area. These trends were nondestructive intertidal transects increased established prior to station operation. Selected between periods in the nearfield area, while it faunal taxa in the shallow subtidal zone showed no remained unchanged in the farfield area. In significant change in density or mean length contrast, the frequency of occurrence of Fucus between periods. ! vesiculosus declined in the nearfield area between pe'riods, and to a lesser extent in the farfield area. The density of Laminaria digitata declined at the These declines began during the preoperational nearfield station between periods, while density at period, and therefore are unrelated to station the farfield station remained similar. Densities at operation. The frequency of occurrence of the two stations were similar each year in the juvenile fuccids (Fucus spp.) at both stations preoperational period, then diverged beginning in increased between periods such that there was no 1990. In 1993 densities began to coberge, and significant station-period interaction. were similar in 1995. The nearfield-farfield difference in L. dgitata densities observed between Numerical classification of macroalgal and periods may therefore reflect a short-term cyclical macrofaunal biomass and abundance revealed that pattern rather than a station impact. The density of v 6-79
6.0 MARINE MACROBENTHOS Ianmaria saccharina remamed consistent between Mid-Depth Zone stations during both periods. Most aspects of the algal and faunal community 6.4.3 Evaluation of Potential Turbidity Effects remained consistent between periods. Some on the Mid-Denth/ Deep Benthic Commu- differences were, however, apparent (Table 6-22). nities The number of algal taxa collected increased between periods at the intake station, decreased at Nearfield middepth and deep study sites represent the discharge station, and remained unchanged at macrobenthic communities in closest proximity to the farfield station. The numbers of taxa collected the Seabrook Station discharge. However, due to at each station was highly variable from year to their position in the water column (9-21 m) relative year, with no apparent relation to station operation. j to the near-surface thermal plume, temperature Nearfield community structure in 1995 was also effects at these sites are unlikely. Higher not typical. Algal biomass, total faunal density, sedimentation rates resulting from increased levels number of faunal taxa, and densities of the of suspended particles in discharge waters relative dominant faunal taxa (Mytilidae, Pontogencia to the surrounding waters could potentially affect inennis,Iocuna vincta, and Anomia sp.) decreased j nearfield deeper water benthic communities. in 1995, creating a " low density" assemblage Higher sedunentation rates (and impacts to nearby similar to that observed in 1978 and 1979. macrobenthic communities) associated with a thermal effluent have been documented for a Ianinaria saccharina showed a significant ' nuclear power plant in California with a shallow decrease in the nearfield area between periods, but nearshore mtake and a deep offshore discharge not in the farfield area (Table 6-23). Since the ' (Osman et al.1981; Schroeter et al.1993). At the nearfield decrease began prior to plant operation, ; California power plant, fine inorganic sediments the trend is unrelated to Seabrook Station. Density I from nearshore waters where were transported to of Laminaria digitata also showed a significant the deep offshore discharge. The organic decrease between periods, in both the nearfield and l component of these sediments contributed little to farfield areas. The decrease was more precipitous the overall flux of sediments, and no indications of in the nearfield area, and the 1995 density was the organic enrichment were observed at sites near the lowest observed to date. The cause of this is discharge. 'Ihe Seabrook intake is located offshore unknown, but likely is not related to changes in and draws in relatively low turbidity water, similar temperature or sedimentation. The density of to that near the discharge. Therefore, transport of Agarum clathratum, however, increased in the fine inorganic particles is unlikely and any nearfield and farfield areas in 1995. increase in sedimentation would be the result of settlement of organic material from entrained Adult sea urchins (Strongylocentrotus organisms. However, plankton densities are also droebachiensis) proliferated in both the nearfield lower in deeper offshore waters near the intake and farfield areas during the operational period, structure, compared to those in more productive but the increase has been most dramatic in the inshore waters, thereby reducing the likelihood of farfield area. In 1995 urchin densities decreased any organic loading to benthic habitats near the by more than an order of magnitude, likely a result discharge. of harvesting activities. 6-80
i ; l 6.0 MARINE MACROBENTHOS
) Table 6-22. Summary of Evaluation of Potential Turbidity Effects on Benthic )
Communities in the Vicinity of Seabrook Station. Seabrook Operational - Report,1995. OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES
- AREA /DEFIll TO PREVIOUS ' CONSISTENTWITH COMMUNITY - ZONE PARAMETER' YEARS?" PREVIOUS YEARS?'
Macroalgae Mid-depth No. of taxa Yes B16: Op> Preop B19: Op< Preop - B31: Op= Prep l , Total biomass No Yes l Community structure Yes Yes Deep No. of taxa Yes Yes Total biomass No Op< Preop
- Community structure Yes Yes Macrofauna Mid-depth No. of taxa Yes Yes Total density No B16
- Op< Preop l
B19, B31: Op= Preop Community structure No B19: assemblage low density B16, B31: Op= Preop
- Deep No. of taxa Yes Yes Total density No B04: Op=Preep B13: cop B34: = Preop
.; Community structure Yes s
' Abundance, no. of taxa, biomass, and total density evaluated using ANOVA; community structure evaluated using numerical classification by year and station.
i 6 Operational period = 1990-1995 (August only). i 'NF = nearfield; FF = farfield. Table 6-23. Summary of Evaluation of Potential Turbidity Effects on Representative
'Important Benthic Taxa in the Vicinity of Seabrook Station. Seabrook Operational Report,1995.
l
- OPERATIONAL NEARFIELD-FARFIELD :
PERIOD SIMILAR DIFFERENCES j AREA /DEFI11 . TO PREVIOUS CONSISTENT WITH COMMUNITY -ZONE SELECTED TAXON YEARS?' PREVIOUS YEARS?' I Macroalgae Mid-depth Laminaria digitata No NF: Op<< Preop FF: Op< Preop Laminaria saccharina No NF: Op< Preop FF Op= Preop Macrofauna Mid<lepth Pontogencia inermis Yes Yes Modiolus modiolus Yes Yes Mytilidae Yes Yes Strongylocentmtus droebachensis Yes Yes
' Conclusions derived from ANOVA or nonparametric analysis for Preoperational versus , Operational periods.
'NF = nearfield; FF = farfield; note that nonparametric tests do not test for significant station differences or lq station-period interactions.
6-81
6.0 MARINE MACROBENTHOS in summary, changes occurred in the kelp
6.5 REFERENCES
CITED community in both the nearfield and farfield areas. Changes are most pronounced, however, in the Abbott, R.T. 1974. American seashells. 2nd nearfield shallow subtidal and mid-depth areas and ed., Van Nostrand Reinhold, New York. may reflect a potential plant effect, or may be due . BECO (Boston Edison Company). 1994. Benthic to successional changes related to recovery from Algal Monitoring at the Pilgrim Nuclear urchin predation. Because factors causing these Power Station. Pages 1-23 in Marine ecology changes are unclear, but coincide with plant start- studies related to operation of Pilgrim Station. up, the nearfield kelp community should be Semi-Ann. Rep. No. 43. m nitored closely. Bertness, M.D.1989. Intraspecific competition and facilitation in a northern acorn barnacle Deep Subtidal Z .11e 9 population. Ecology 70:257-268. All aspects of the deep subtidal algal and faunal Bloom, S.A. 1980. A package of computer communities remained consistent between the Programs for benthic community analyses. Univ. Florida. preoperational and operational periods, with no indication of changes related to Seabrook Station Boesch, D.F. 1977. Application of numerical operation. classification in ecological investigations of water pollution. U.S. Environmental 6.4.4 Overall Effect of Seabrook Ooeration on Protection Agency, Ecological Research Report Agency, Ecol. Res. Rep. 114 pp. the Local Marine Pg}acrobenthos Bousfield, E.L 1973. Shallow water These extensive monitoring studies have gammaridean Amphipoda of New England. documented that hahW indigenous macrobenthic Comstock Pub., Ithaca, NY. 312 pp. communities continue to occupy intertidal and
. . Breen, P.A., and K.H. Mann. 1976. Changing subtidal rocky habitats m the va. . .cunty of the lobster abundance and destruction of kelp beds Seabrook discharge, with little change beyond that by sea urchins. Mar. Biol. 34:137-142.
expected from natural variability. While some changes have been detected between the Nmnan, A.R.O.1973. A critique of prevailing preoperational and operational periods, most were attitudes towards to control of seaweed zonation on the sea shore. Bot. Mar.16:80-either part of an area-wide trend (occurring at both 82. nearfield and farfield stations), part of an historical trend that began prior to commercial operation of Connell, J.H. 1%1. Effects of competition, Seabrook Station, or restricted to a site (intake) Predation by Thais lapillus, and other factors where little potennal for impact exists. There is no n natural populations of the barnacle Balanus balanoides. Ecol. Monogr. 31:61-104. evidence to suggest that thermal impacts or impacts associated with increased organic loading on the Cubit, J.D. 1984. Herbivory and the seasonal local macrobenthos have occurred since the start- abundance of algae on a high intertidal rocky up of Seabrook Station in 1990. shore. Ecology 65:1904-1917. 6-82
6.0 MARINE MACROBENTHOS O Dayton, P.K. 1971. Competition, disturbance Johnson, C.R., and K.H. Mann. 1988. Diversity, and community orgamzation the provision and patterns of adaptation, and stability of Nova subsequent utilization of space in a rocky Scotian kelp beds. Ecol. Monogr. 58:129-intertidal community. Ecol. Monogr. 41:351- 154. 389. Keser, M., and B.R. Larson. 1984. Colonization Einer, R.W., and R. L. Vadas. 1990. Inference and growth dynamics of three species of in ecology: the sea urchin phenomenon in the Fucus. Mar. Ecol. Prog. Ser. 15:125-134. northwestern Atlantic. Am. Nat.136:108-125. 12rson, B.R., R.L. Vadas, and M. Keser. 1980. Feedmg and nutrition ecology of the 3reen sea Franz, D.R 1989. Population density and urchin, Strongylocentrotus droebachtensis in demography of a fouling community Maine, U.S.A. Mar. Biol. 59:49-62. amphipod. J. Exp. Mar. Biol. Ecol. 125:117-136. Lewis, J.R.1964. The Ecology of Rocky Shores. English Univ. Press, London. 323 pp. Fuller, J.L. 1946. Season of attachment and growth of sedentary marine organisms at Lubchenco, J. 1980. Algal zonation in the New Lamoine, Maine. Ecology 27:150-158. England rocky intertidal community: an experimental analysis. Ecology 61:333-344. Gaines, S., and J. Roughgarden. 1985. Larval settlement rate: a leading determinant of 1983. Linorina and Fucus: effects structure in an ecological community of the of herbivores, substratum heterogeneity, and (q) marme mtertidal zone. Proc. Natl. Acad. Sci. USA 82:3707-3711. ph.nt escapes during succession. Ecology 64:1116-1123. Geiselman, J.A., and O.J. McConnell. 1981. Lubchenco, J., and B.A. Menge. 1978. Polyphenols in brown algae Fucus vesiculosus Community development and persistence in a and Ascophyllum nodosum: chemical defenses low rocky intertidal zone. Ecol. Monogr. against the marine herbivorous snail, Littorina 48:67-94. linorea. J. Chem. Ecol. 7:1115-1133. Mann, K.H. 1973. Seaweeds: their productivity Gosner, K.L.1978. A Field Guide to the Atlantic and strategy for growth. Science 182:975-seashore. Houghton Mifflin Co., Boston. 329 981. PP. Mann, K.H., L.C. Wright, B.E. Welsford, and E. Grant, W.S. 1977. High intertidal community Hatfield.1984. Responses of the sea urchin organization on a rocky intertidal headland in Strongylocentrotus droebachiensis (0.F. Maine, USA. Mar. Biol. 44:15-25. Muller) to waterborne stimuli from potential predators and potential food algae. J. Exp. Hiscock, K., and R. Mitchell. 1980. The Mar. Biol. Ecol. 79:233-244. description and classification of sublittoral epi-benthic ecosystems. Pages 323-370 in J.H. Mathieson, A.C., E.J. Hehre, and N.B. Reynolds. ; Price, D.E.G. Irvine and W.F. Farnham 1981. Investigations of New England marine (eds.) 'lhe Shore Environment, Vol. 2: algae. II: The species composition, Ecosystems. Academic Press, London and distribution and zonation of seaweeds in the New York. 945 pp. Great Bay estuary system and the adjacent i f) U open coast of New Hampshire. Bot. Mar. 24:533-545. 6-83 i
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Mathieson, A.C., and E.J. Hehre. 1986. A mental conditions in the Hampton-Seabrook j synopsis of New Hampshire seaweeds. area during the operation of Seabrook Station. Rhodora 88:1-139. Tech. Rep. XXII-II. 1 Mathieson, A.C., and J.S. Prmee 1973. Ecology 1993. Seabrook Environmental of Orondrus crispus Stackhouse. Pages 53-79 Studies,1992. A characterization of environ-in M.J. Harvey and J. Maclachlan (eds.) mental conditions in the Hampton-Seabrook Chondrus crispus. Nova Scotian Inst. Sci., area during the operation of Seabrook Station. Halifax. Tech. Rep. XXIV-1 Menge, B.A. 1976. Organization of the New 1995. Seabrook Environmental England rocky intertidal community: role of Studies. 1994 Data. Unpublished Data predation, competition, and environmental Tables. heterogeneity. Ecol. Monogr. 46:355-393.
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rocky intertidal community structure. J. Exp. Experimental studies on the life cycle of Jassa Mar. Biol. Ecol. 146:69-100. falcata (Crustacea, Amphipoda). Helgo. Wiss. Meeres. 37:444-452. Minchinton, T.E., and R.E. Scheibling. 1991. The influence of larval supply and settlement Novaczek, I., and J. McLachlan. 1986. on the population structure of barnacles. Recolonization by algae of the sublittoral Ecology 72;1867-1879. habitat of Halifax County, Nova Scotia, i following the demise of sea urchins. Bot. NAI (Normandeau Associates, Inc.). 1989. Mar. 29:69-73. Seabrook Environmental Studies. 1988. A characterf2.ation of baseline conditions in the NUSCO (Northeast Utilities Service Company). Hampton-Seabrook area. 1975-1988. A 1992. Rocky Intertidal Studies. Pages 237-preoperational study for Seabrook Station. 292 in Monitoring the marine environment of Tech. Rep. XX-II. Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut. Ann. Rep., 1991a. Seabrook Environmental 1991. Studies. 1990 Data Report. Tech. Rep. XXII-I. 1994. Rocky Intertidal Studies. Pages 51-79 in Monitoring the marine environ-
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Nuclear Power Station, Waterford, Factors controlling the upper limits of fucoid Connecticut. Ann. Rep.1995. algae on the shore. J. Exp. Mar. Biol. Ecol. 31:303-313. Ojeda, F.P. , and J.H. Dearborn. 1989. Community structure of macroinvertebrates Schroeter, S.C., J.D. Dixon, J Kasteadiek, and inhabiting the rocky subtidal zone in the Gulf R.O. Smith.1993. Detecting the ecological of Maine: seasonal and bathymetric distribu- effects of environmental impacts: a ctse study tion. Mar. Ecol. Prog. Ser. 57:147-161. of kelp forest invertebrates. Ecol. Appl. 3:331-350. 1991. Feeding ecology of benthic mobile predators: experimental analyses of Sebens, K.P. 1985. The ecology of the rocky their influence in rocky subtidal communities subtidal zone. Am. Sci. 73:548-557. ' of the Gulf of Maine. J. Exp. Mar. Biol. Ecol.149:13-44. .1986 Community ecology of vertical walls in the Gulf of Maine. USA: small scale Osman, R.W. 1977. The establishment and processes and alternative community states. development of a marine epifaunal Pages 346-371 in P.G. Moore and R. Seed ; community. Ecol. Monogr. 47:37-63. (eds.). The Ecology of Rocky Coasts. Columbia Univ. Press, New York. l ( ') Osman, R.W., R.W. Day, J.A. Haugsness, J. Deacon, and C. Mann. 1981. The effects of Seed, R. 1976. Ecology. Pages 13-65 in B.L. the San Onofre Nuclear Generating Station on Bayne (ed.), Marine Mussels: Their Ecology sessile invertebrate communities inhabiting and Physiology. Cambridge Univ. Press, ; hard substrata (includmg experimental panels). Cambridge. ) Hard Benthos Project, Marine Science , Institute, University of California, Santa Sokal, R.R., and F.J. Rohlf. 1%9. Biometry. l Barbara. Final Rep., 223 pp. W.H. Freeman and Co., San Francisco. 775 pp-Padmanabhan, M., and G.E. Hecker. 1991. Comparative evaluation of hydraulic model Stephenson, T.A., and A. Stephenson.1949. The , and field thermal plume data, Seabrook universal features of zonation between i Nuclear Power Station. Alden Research tidemarks on rocky coasts. J. Ecol. 38:289-Laboratory, Inc.12 pp. 305. Puraitis, P.S. 1983. Grazing patterns of the Stewart-Oaten, A., W.M. Murdoch, and K.R. I periwmkle and their effect on sessile intertidal Parker.1986. EnvironmentalImpact Assess-organism. Ecology 64422-533. ment: "pseudoreplication in time?" Ecology 67:929-940. Petraitis, P.S.1991. Recruitment of the mussel Mytilus edulis L. on sheltered and exposed Sutherland, J.P., and R.H. Karlson. 1977. shores in Maine, USA. J. Exp. Mar. Biol. Development of stability of the fouling Ecol.147:65-80. community at Beaufort, North Carolina. Ecol. O Monogr. 47:425-446. i 6-85
1 l 6.0 MARINE MACROBENTHOS Taylor, W.R. 1957. Marine algae of the Power Station, 1969-1977. Sum. Rep. Boston ! northeastern coast of North America. Edison Co. l University of Michigan Press, Ann Arbor. I 509 pp. Witman, J.D. 1985. Refuges, biological l disturbance, and rocky subtidal community l Teyssandier, R.G., W.W. Durgin, and G.E. structure in New England. Ecol. Monogr. Hecker. 1974. Hydrothermal studies of 55:421-445. diffuser discharge in the coastal environment: Seabrook Station. Alden Research Laboratory 1987. Subtidal coexistence: storms, Rep. No. 86-124. grazmg, mutualism, and the zonation of kelps and mussels. Ecol. Monogr. 55:421-445. Topinka, J., L. Tucker, and W. Korjeff. 1981. The distribution of fucoid macroalgal biomass Zobell, C.E., and E.C. Allen. 1935. The along the central coast of Maine. Bot. Mar. significance of marine bacteria in fouling of 24:311-319. submerged surfaces. J. Bacter. 29:239-251. Underwood, A.J. 1994. On beyond BACI: Sampling designs that might reliably detect environmental disturbances. Ecological Applications 4(1):3-15. Undeavood, A.J., and E.J. Denley. 1984. Paradigms, explanations and generalizations in models for the structure of intertidal i communities of rocky shores. Pages 151-180 in D.R. Strong, Jr., D. Simberloff, L.G. Abele and A.B. Thistle (eds.), Ecological Communities: Conceptual Issues and the Evidence. Princeton Univ. Press, Princeton N.J. Vadas R.L., M. Keser, and P.C. Rusanowski. 1976. Influence of thermal loading on the ecology of intertidal algae. Pages 202-251 in ! G.W. Ecsh and R.W. MacFarlane (eds.) Thermal Ecology II. ERDA Symp. Ser., Augusta GA. l l Villalard-Bohnsack, M. 1995. Illutrated key to l the Seaweeds of New England. Rhode Island Natural History Survey Cooperative Extension Education Center. University of Rhode Island. Wilce, R.T., J. Foertch, W. Grocki, J. Kilar, H. Levine, and J. Wilce. 1978. Flora: Marine Algal Studies. Pages 307-656 in Benthic , Studies in the Vicinity of Pilgrim Nuclear 6-86
O O O Appendix Table 6-1. Marine Macrobenthos Sampling IIistory. Seabrook Operational Report,1995. SAMPLING - STATIONS' METHOD MONTHS YEARS < FARFIELD STATIONS Intertidal: B5MLW Destructive May, August, November 1982-1995 B5MSL Non-destructive April, July, November 1983-1995 Subtidal: B35 (shallow) Destructive May, August, November 1982-1995 Non-destructive April, July, October 1978-1995 B31 (mid-depth) Destructive May, August, November 1978-1995 P* Non-destructive April July, October 1978-1995 2 Panel Studies Short Term, Long Term' 1982-1995 B34 (deep) Destructive August 1979-1995 Panel Studies Short Term, Long Term' 1986-1995 NEARFIELD STATIONS Intertidal: B1MLW Destructive May, August, November 1982-1995 B1MSL Non-destructive April, July, November 1983-1995 Subtidal: B17 (shallow) Destructive May, August, November 1978-1995 Non-destructive April, July, October 1979-1995 B16 (mid-depth) Destructive August 1980-1984,1986-1995 B19 (mid-depth) Destructive May, August, Novemb:: 1978-1995 Non-destructive April, July, October 1978-1995 B04 (deep) Panel Studies Short Term, Long Term 1982-1995 Destructive August 1978-1995 B13 (deep) Panel Studies Short Term, Long Term 1986-1995 Destructive August 1978-1995
'Short-term panel studies: three exposure periods - December to April, April to August, August to December.
Long-term panel studies: one-year exposure, August to August.
l 6.0 MARINE MACROBENTHOS Appendix Table 6-2. Nomenclatural Authorities for Macrofaunal Taxa Cited in the Marine Macrobenthos Section. Seabrook Operational Report, h 1995. 1 l Mollusca Polyplacopiiora Tonicella rubra (Linnaeus 1767) Gastropoda lecuna vincta (Montagu 1803) Littorina littorea (Linnaeus 1758) Littorina obtusata (Linnaeus 1758) Littorina saxatilis (Olivi 1792) . Nucella lapillus (Linnaeus 1758) Bivalvia Mytilidae Musculus niger (1.E. Gray 1824) Modiolus modiolus (Linnaeus 1758) Anomia sp. Turtonia minuta (Fabricius 1780) Hiatella sp. Annelida Polychaeta Thelepus cincinnatus (Fabricius 1780) Oligochaeta Arthropoda Pantopoda Achelia spinosa (Sthnpson 1853) Crustacea Balanus sp. Balanus crenatus Bruguiere 1789 Idotea balthica (Pallas 1772) Idoteaphosphorea Harget 1873 Jaera marina (Fabricius 1780) Ampithoe rubricata (Montagu 1808) Gammarus oceanicus Segerstrale 1947 Jassa mannorata (Holme 1903) Pontogeneia inermis Kreyer 1842 Caprella sp. Caprella septer.trionalis Kreyer 1838 Echinodermata Echiniodea Strongylocentrotus droebachiensis (Maller 1776) Stelleriodea As'eridae O 6-88
6.0 MARINE MACROBENTHOS l O l
!t] Appendix Table 6-3. The Occurrence of Macroalgae from General Collections and l ; Destructive Sampling At All Subtidal and Intertidal Destructive l Stations, 1978-1995. Seabrook Operational Report,1995. .
1 CHLOROPHYTA I l SPECIES l78l79l80l81l82l83l84l85l86l87l88l89l90l91l92l93l94l95
..............................................................+..+..+..+..+..+..+..+..+..+..+..+..+..+..+..+..+..+..
BLIDINGIA MINIMA (Nuegeli ex Kutz.) Kylin X X X X X X X X BRYOPSIS PLUMOSA (Huds.) C.Agardh X X X l CHAETOMORPHA BRACHYGONA Harv. X X X X X X X X X X X X X X X CHAETOMORPHA LINUM (0.F.M0ll.) K0tz. X X X X X X X X X X X X X X X X X X ' CHAETOMORPHA MELAGONIUM (F. Weber et D.Mohr) K0tz. X X X X X X X X X X X X X X X X X X CHAETOMORPHA PICQUOTIANA Mont, ex K0tz. X X X X X X X X X X X X X X X X X , J CHAETOMORPHA SP. X X X X X X X X X X X X X X X X X X CLADOPHORA REFRACTA (Roth) K0tz. X X X X CLADOPHORA SERICEA (Huds.) K0tz. X X X X X X X X X X X X X X X X X X j CLADOPHORA SP. X f COD 10 LUM PETROCELIDIS Kuck. X X ENTEROMORPHA COMPRESSA (L.) Nees X
)
3 ENTEROMORPHA INTESTINAL!S (L.) Nees X X X X X X X ENTEROMORPHA LINZA (L.) J.Agardh X X X X X X X X X l
- ENTEROMORPHA PROLIFERA (0.F. Mull.) J.Agardi X X X X X X X X ,
I ENTER 0MORPHA SP. X X X X X X MONOSTROMA FUSCUM (Postels et Rupr.) X X X X X l MONOSTROMA GREVILLEI (Thuret) Witt. X X X X X X X X X X X X X X X X I MON 0 STROMA SP. X X X I PROTOMONOSTROMA UNDULATUM (Wittrock) K.L.Vinogr. X X X X X X X X X X X X X X X X X PSELDENDOCLONIUM SUBMARINUM Wille X RHIZOCLON!UM TORTU0 SUM (Dillwyn) K0tz. X X X X X X X X X X X X X X X X X X SPONG0MORPHA ARCTA (Dillwyn) K0tz. X X X X X X X X X X X Og SPONGOMORPHA SP. X ('j SPONG0MORPHA SPINESCENS K0tz. ULOTHRIX FLACCA (Dillwyn) Thuret X X X X X X X X X X X X X X X X X X X j ULOTHRIX SP. X ULVA LACTUCA L.
- X X X X X X X X X X X X X X X X X X ULVARIA OBSCURA V. BLYTTI! (Arasch.) Bliding X X X X X X X X X X X X X X X X X ULVARIA OXYSPERMA (Kuetz.) Bliding X X X X X UR0SPORA PENIC!LLIFORMIS (Roth) Aresch. X X X X X X !
UR0SPORA WORMSKJOLD11 (Mert in Hornem.) Rosenv. X I GROUP TOTAL TAXA 18 17 13 16 20 20 20 16 16 15 14 14 14 15 13 17 14 20 l l l 1 A (d 6-89 1
}
6.0 MARINE MACROBENTHOS Appendix Table 6 3. (Continued) h PHAEOPHYTA SPECIES
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .l78l79l80l81l82l83l84l85l86l87l88l89
. . . . .. . . . . . . . . .l 90 l 91 l 92 AGARUM CLATHRATUM Dumort. X X X X X X X X X X X X X X X X X X ALARIA ESCULENTA (L.) Grev. X X X X X X X X X X X X X X X X X X ASCOPHYLLUM N000 SUM (L.) Le Jolis X X X X- X X X X X X X X X X X X X X CHORDA FILUM (L.) Stackh. X CHORDARIA FLAGELLIFORMIS (0.F.M0ll.) C.Agardh X X X X X X X X X X X X X DESMAREST!A ACULEATA (L.) J.V.Lamour. X X X X X X X X X X X X X X X X X X DESMARESTIA VIRID!$ (0.F. Mall.) J.V.Lamour. X X X X X X X X X X X X X X X X X ECT0 CARPUS FASCICULATUS Harv. X X X X X X X X X X X X ECT0 CARPUS SILICULOSUS (Dillwyn) Lyngb. X X X X X X X X X X X X X X X X ECT0 CARPUS SP. X X ELACHISTA FUCICOLA (Velley) Aresch. X X X X X X X X X X X X X X X X X X FUCUS DISTICHUS SSP. DISTICHUS Powell X X X X X X X X X X X FUCUS DIST!CHUS $$P. EDENTATUS (Bach.Pyl.) Powell X X X X X X X X X X X X X X X X X y FUCUS DISTICHUS SSP. EVANESCENS (C.Agardh) Powell X X X X X X X X X X X X FUCUS SP. X X X X X X X X X X X X X X FUCUS VESICULOSUS L. X X X X X X X X X X X X X X X X X X FUCUS VESICULOSUS VAR. SPIRALIS Farl. X X HINCKSIA GRANULOSA (J.E. Smith) P.C. Silva in P.C. Silva X X ISTHMOPLEA SPHAEROPHORA (Carmich. ex Harv. In Hook) Kjellm. X X X LAMINARIA DIGITATA (Huds.) J.V.Lamour. X X X X X X X X X X X X X X X X X X LAMINARIA SACCHARINA (L.) J.V.Lamour. X X X X X X X X X X X X X X X X X X LAMINAR!A SP. X X X X X X LAMINAR 10COLAX TOMENTOS0! DES (Farl.) Kylin X X LEATHESIA DIFFORMIS (L.) Aresch. X X X X X X X X X X X X X X PETALONIA FASCIA (0.F.M0ll.) Kuntze X X X X X X X X X X X X X X X X PETALONIA ZDSTERIFOLIA (Reinke) Kuntze X PETR00ERMA MACULIFORME (Wollny) Kuck. X PHAEOPHYCEAE X PILAYELLA LITTORALIS (L.) Kjellm. X X X X X X X X X X X X X X X X X PSEUDOLITHODERMA EXTENSUM (P.Crouan et H.Crouan) S.Lund X PUNCTARIA PLANTAGINEA (Roth) Grev. X SACCORMIZA DERMATODEA (Bach.Pyt.) J. Agard X X SCYT0 SIPHON $1MPLICISSIMUS (Clemente) Cremedes X X X X X X X X X X X X X X X X X SORAPION KJELLMANNI (Wille) Rosenv. X SPHACELARIA CIRROSA (Roth) C.Agardh X X X X X X X X X X X SPHACELARIA PLUMOSA Lyngb. X X X X X SPHACELARIA RADICANS (Dillwyn) C. Agard X X X SPONG0 NEMA TOMENTOSUM (Huds.) Katz. X X X X X X X X X X X X X GROUP TOTAL TAXA 19 18 16 20 20 24 25 21 22 21 20 23 23 21 20 20 21 25 G
~
6-90
6.0 MARINE MACROBENTHOS
/%
(J \ Appendix Table 6-3. (Continued) RH000PHYTA SPEC 1ES l78l79
....................................................................l8Dj81l82l83l84l85l86l87l88l89l90l91192l93l94l95 ACROCHAET!UM FLEXU0 SUM Vickers X X X AC*0CHAETIUM SP. X X X AHNFELT!A PLICATA (Huds.) Fries X X X X X X X X X X X X X X X X X X 4
ANTITHAMN10NELLA FLOCCOSA (0 F.MQll.) Whittick X X X X X X X X X X X X X X X X X X AUDOUINELLA DAVIES!! (Dillwyn) Woelk. X X AUDOUINELLA MEMBRANACEA (Magnus) Papenf. X X AUDOUINELLA PURPUREA (Lightf.) Woelk. X X X X AUDOUINELLA SP. X X X BANG!A ATROPURPUREA (Roth) C.Agardh X X X BONNEMAISONIA HAMIFERA Har. X X X X X X X X X X X X X CALLITHAMhl0N SP. X CALLITHAMNION TETRAGONUM (With.) S.F. Gray X X X X X X X X X X X X X X X X X CALLOPHYLLIS CRISTATA (C.Agardh) K0tz. X X X X X X X X X X X X X X X X X X CERAM!UM DESLONGCHAMPl! Chauv. ex Duby X X CERAM!UM NODULOSUM (Lightf.) Ductuzeau X X X X X X X X X X X X X X X X X X CERAT0COLAX HARTZ!! Rosenv. X X X X X X X X X CHONDRIA BAILEVANA (Mont.) Harv. X CHONDRUS CRISPUS Stackh. X X X X X X X X X X X X X X X X X X CHORE 0COLAX POLYSIPHONIAE Reinsch X X X X X X X X X X X CLATHROMORPNUM CIRCUMSCRIPTUM (Str6mf.) Fost. X X X X X X X X X X X X X X X X X CLATHROMORPHUM COMPACTUM (Kjelle.) Fost. X X X X C0CCOTYLUS TRUNCATUS (Pallas) N.J.Wynne et Heine X X X X X X X X X X X X X X X X X X COLACONEMA SECUNDATA X X X CORALLINA 0FFICINALIS L. X X X X X X X X X X X X X X X X X X j f] CYSTOCLONIUM PURPUREUM (Huds.) Batters X X X X X X X X X X X X X X X X X X ( b) DEVALERAEA RAMENTACEA (L.) Guiry DUMONT!A CONTORTA (S.G. Gmelin) Rupr. X X X X X X X X X X X X X X X- X X X X j 1 ERYTHROTRICHIA CARNEA (Dillwyn) J. Agar & X X X X X FIMBRIFOLIUM DICHOTOMUM (Lepechkin) G.I.Hansen l X X X X X X X X X X X X X X X X X X FOSLIELLA FARINOSA (Lamour.) Howe X GIGARTINALES X GLC10$1 PHON 1A CAP!LLARIS (Huds.) Carmich. ex Berk. X X GYMNOGONGRUS CRENULATUS (Turn.) J.Agardh X X X X X X X X X X X X X X X X l HILDENBRANDIA RUBRA (Sommerf.) Menegh. X X X X X X X LEPTOPHYTUM F0ECUNDUM (Kjellm.) Adey X X X X X X X X X X X X X X LEPTOPHYTUM LAEVE (Str6mf.) Adey X X X X X X X X X X X X X X X X X X LEPTOPHYTUM SP. X (CONTINUED) I 6-91
l 6.0 MARINE MACROBENTHOS Appendix Table 6-3. (Continued) g l
""** " "'............................................................................................................ l SPECIES l78l79l80l81l82l83l8,l85l86l87l88l89l90l91l92l93l94l95 LITHOPHYLLUM CORALLINAE (Crouan) Heydr. X X LITHOTHAMNION GLACIALE Kjellm. X X X X X X X X X X X X X X X X X X .
MASTOCARPUS STELLATUS (Stackh. In With.) Guiry in Guiry et al. X X X X X X X X X X X X X X X X X X l MEMBRAN0PTERA ALATA (Huds.) Stackh. X X X X X X X X X X X X X X X X X X PALMARIA PALMATA (L.) Kuntze X X X X X X X X X X X X X X X X X X PEYSSONNELIA ROSENVIJGl! F.Schmitz in Rosenv. X X X X X X X X X X X X X X X PHYCODRYS RUBENS (L.) Batters X X X X X X X X X X X X X X X X X X PHYLLOPHORA PSEUDOCERANOIDES (Gmelin) Newr. et A. Taylor X X X X X X X X X X X X X X X X X X PHYLLOPHORA TRAILL1! Holmes X X PHYLLOPHORA/COCCOTYLUS X X X X X X X X X X X X X X X X X X PHYMATOLITHON LAEVIGATUM (Fostle) Fostle X X X X X X X X X X X X X X X PHYMATOLITHON LENORMANDl! (Aresch, in J. Agar & ) Adey X X X X X X X X X X X X X X X X PHYMATOLITHON RUGULOSUM Adey X X X X X X X X X X X PLUMARIA PLUMOSA (Huds.) Kuntze X X X X X X X X PNEOPHYLLUM FRAGILE KQcz. X X X X X X X X X X X POLYIDES ROTUNDUS (Huds.) Grev. X X X X X X X X X X X X X X X X X X POLYSIPHONIA DENUDATA (Dillwyn) Grev. ex Harv. In Hook. X POLYS!PHONIA FLEXICAULIS (Harv.) Collins X X X X X X X X X X X X X X X X X POLYt!PHONIA FUC0! DES (Huds.) Grev. X X X X X X X X X X X X X X X X X X POLYSIPHONIA HARVEY! Bailey X X X X X X X
~
POLYSIPHONIA LANOSA (L.) Tandy X X X X X X X X X X X X X X X X POLYSIPHONIA NIGRA (Huds.) Batters X X X X e X X X X X POLYSIPHONIA SP. X X POLYSIPHONIA STRICTA (Dillwyn) Grev. X X X X X X X X X X X X X X X X X X PORPHYRA LEUCOSTICTA Thur. In Le Jolis X X X X X X X X X X X X X X X X X PORPHYRA LINEARIS Grev. X X PORPHYRA MINIATA (C. Agar &) C.Agardh X X X X X X X X X X X X X X X X X PORPHYRA SP. X X X X X X X l PORPHYRA UMBILICAL!S (L.) J. Agar & X X X X X X X X X X X X X X X X X X PTEROTHAMNION PLUMULA (J.Ellis) Nugeli X PTILOTA SERRATA KQtz. X X X X X X X X X X X X X X X X X X RH0DOMELA CONFERVotDES (Huds.) P.C. Silva X X X X X X X X X X X X X X X X X X RHODOPHYSEMA ELEGANS (P.Crouan et H.Crouan ex J. Agar &) X X X X X X P.S. Dixon SCAGELIA PYLAISAE! (Mont.) M.J.Wynne X X X X k y X X X X X X X X X X X X TITAN 00ERMA PUSTULATUM (J.V.Lamour.) Woelk., Y.M. Chamb. X X X X X X X X X X X X X X X X X TURNERELLA PENNYI (Harv.) F.Schmitz X X GROUP TOTAL TAXA 43 40 42 42 48 51 51 44 47 47 42 47 40 44 43 41 44 46 l0VERALLTOTALTAXA l 80 l 75 l 71 l 78 l 88 l 95 l 96 l 81 l 85 l 83 l 76 l 84 l 77 l 80 l 76 l 78 l 79 l 91 l O 6-92 i
d 7.0 SURFACE PANELS C) r V TABLE OF CONTENTS
- PAGE 7.0 SURFACE PANELS
. SUMM ARY . . . . . . . . . . . . . . . . . . . . . . ..................................7-il I LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-iii LIST OF TABLES . . . . . . . . . . . .........................................7-iv
7.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................7-1 7.2 METIIODS . .................................................7-1 7.2.1 Field Methods . . . . . . . . . . . . . . . . . . ..... ........... ....... 7-1 7.2.2 1.aboatory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 1 7.2.3 Analytical Methods . . . . . . . . . . . . .. . . . . .. . .. .. .. .. ... . . . . . . 7-3 7.3 RESULTS ....... .. .. ... . .. ... ...... ... .... ...... ...... .. ... 7-4 rm
('} 7.3.1 Short-Term Panels . . . . . ...................... ...... .. ... 7.3.2 Monthly Sequential Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4 7-13 7.3.3 Quarterly Sequential Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18 7.3.4 One Year Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-21 7.4 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23
7.5 REFERENCES
CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25 l l 1 ! 1 I v 1 i 1 1 I l l 7-1 ! l l
7.0 SURFACE PANELS
SUMMARY
i l l l l 'Ihe fouling community se'tling and developing on surface panels has shown predictable seasonal patterns throughout the study. Trends observed during the operational and preoperational periods were similar. l Most measures of community structure (biomass, abundance, number of'.axa), and abundam and frequencies of individual taxa indicate fouling community settlement (on panels exposed for one month) and development (on panels exposed for periods of 1-12 months) showed no significant differences between preoperational and operational periods. Some parameters measured on the year-end fouling community (panels exposed i for one year) indicated changes during the operational period that were not consistent between nearfield and l farfield areas. The wood-boring mollusk, Teredo sp. occurred in wood blocks for the first time since 1980, l at both nearfield and farfield stations. 'Ihis organism has been present in the bivalve larvae study each year l since 1984, and adults have been observed on panels during the preoperational period in 1976,1979 and 1980. None of the findings in 1995 or in previous operational years indicate that Seabrook Station operation has any effect on the local fouling community. l I l 9 l l l 9 7-ii
__ _ ~ 7.0 SURFACE PANELS o) LIST OF FIGURES PAGE 7-1. Surface panel sampling stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 7-2 7-2. Monthly number of taxa (on two replicate panels), abundance, and biomass on short-term ) panels at nearfield/ farfield station pair B19 and B31 during the operational period (1991- { 1995) and 1995 compared to the means and 95 % confiderte limits during the preoperational period (1978-1984 and July 1986-December 1989) . . . . . . . . . . . . . . . . . . . . . . . . . 7-5 7-3. A comparison between stations of the logdx + 1) no. per panel total abundance and Mytilidae abundance in short-term panels during the preoperational (1978-1985; 1987-1989) and operational (1991-1995) periods . . . . . . . . . . . . . . ............. ........ 7-10 7-4. Annual geometric total abundance and abundance of Mytilidae on short-term panels at Stations B19 and B31,1978-1995 . ....... ...... .................... 7-11 7-5. Log abundance (no. per panel) of Mytilidae, and Jassa marmorata, and monthly mean I
, percent frequency of Tubularia sp. on short-term panels at Stations B19 and B31 during
( the operational period (1991-1995) and 1995 compared to the mean abundance or percent frequency and 95% confidence limits during the preoperational period (1982-1984 and July 1986-December 19 89) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 12 7-6. Mean biomass (g/ panel) and Mytilidae spat (percent frequency of occurrence) during the operational period (1991-1995) and in 1995 compared to mean and 95 % confidence limits during the preoperational period (Stations B19 and B31 from 1978-1984 and July-December 1986-1989 for biomass and 1987-1989 for Mytilidae) on monthly sequential panels . . . . 7-14 7-7. Monthly mean percent frequency of occurrence for Jassa marmorata, Balanus sp., and Tubularia sp. at Stations B19 and B31 during the operational period (1991-1995) and in 1995, compared to mean and 95 % confidence limits during the preoperational period (1987-1989) on monthly sequential panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... 7-17 7-8. Mean biomass (g/ panel) and Mytilidae spat (percent frequency of occurrence) and 95 % confidence limits (n=3) during 1995 from Stations B19 and B31 on Quarterly Sequential panels compared to the monthly preoperational amans (1987-1989) . . . . . . . . . . . . . . 7-19 7-9. Mean percent frequency ofoccurrence and 95 % confidence limits (n = 3) forlassa marmorata, Balanus sp. and Tubularia sp. at Stations B19 and B31 during 1994 and 1995 compared [_) s.- to the monthly preoperational means (1987-1989) on Quarterly Sequential panels . . . . . 7-20 7 iii
1 7.0 SURFACE PANELS LIST OF TABLES PAGE 7-1. Means (Per Panel) and Coefficient of Variation (%) for Selected Parameters and Species Abundances at Stations B19 and B31 During the Preoperational and Operational Periods (1991-1995), and 1995 Means . . . .. ....... . ............... .... ............... 7-6 7-2. Results of Analysis of Variance Comparing Monthly Total Number of Taxa, Noncolonial Faunal Abundance, Total Biomass, and Selected Species Abundance or Percent Frequency on Short-term Panels at the Mid-depth Station Pair (B19, B31) During Preoperational (1978-1989) and Operational (1991-1995) Periods . . . . . . . . . .................... . 7-7 7-3. Anova Results Comparing Mor:bly Sequential Panel Biomass at the Mid-depth (B19, B31) Station Pair During Preoperational (1978-1989) and Operational (1991-1995) Periods . . 7-15 7-4. Nearfield/farfield Companson of Annual Mean and Standard Error of Mytilidae Spat and Jassa Marmorata Lengths (Mm) from Monthly Sequential Panels Collected in 1995 ... 7-16 7-5. Nearfield/farfield Companson of Annual Mean and Standard Error of Mytilidae Spat and lassa Marmorata Lengths (Mm) from Quarterly Sequential Panels Collected in 1995 . .. 7-21 7-6. Dry Weight Biomass, Noncolonial Number of Taxa, Abundance, and Lammaria Sp. Counts on Surface Fouling Panels Submerged for One Year at Stations B19 and B31. Mean and Standard Deviation for the Preoperational Period (1982-1984 and 1986-1989) and Mean for 1995 and the Operational Period (1991-1995) . . . . . . . . . . . . . . . . . . . . . . . . . 7 -2 2 i 7-7. Summaty of Evaluation of Discharge Plume Effects on the Fouling Community in Vicinity of Seabrook Station . ..... .... .............................. . . 7-24 O' 7-iv
~ ._ ___._ _ __..._.-_.__ _ _ ._._.. __ . _ - _ . _ . _ _ . _ _ _ . _ _ _ _ . _
i i I 7.0 SURFACE PANELS ' l
7.1 INTRODUCTION
1995. Historically, collections were also made at Station B04 from 1978 to 1984 and 1986-1993, and i De surface fouling panels program was designed at Station B34 from 1982-1984 and 1986-1993. to study species settlement patterns and fouling com- Information on these stations is presented in NAI i munity development in the discharge plume area and NUS (1994). and the corresponding farfield area. He main objectives of the panels program were: (1) to nree different exposure strategies were employed describe the temporal patterns of the dominant at each station: short-term (ST) panels, exposed organisms that comprise the fouling community, for one month; monthly sequential (MS) panels, and to determine if any of these organisms have exposed for increasing time periods from 1-12 i
~the ability or potential to affect the operation of months and quarterly sequential (QS) panels exposed Seabrook Station, and (2) to describe the balanced three, six, nine and 12 months. Two replicate short-indigenous fouling community in the vicinity of term panels and one monthly sequential panel were i Seabrook Station and determine if the discharge collected monthly at each of the stations. In addition
. from Seabrook Station has affected this community. to the one MS panel, two QS panels were collected The program is based on the hypothesis that the in March, June, Sapeamher and D-*mhar for a total l local fouling community is not adversely influenced of three panels. In December, an additional MS l
by exposure to the thermal plume. Short-term panel was collected at each station. l panels, submerged for one momh, provided infor- ) mation on the temporal sequence of settlement 7.2.2 Laboratory Methods I activity, while monthly sequential panels, collected after one to twelve months exposure and quarterly In the laboratory, each panel was dismantled and 1 sequential panels collected after three, six, nine and the panel face photographed. Fouling material was
)
~ 12 months, provided information on species growth scraped'off the wood block and panel support )
and patterns of community development. apparatus and rinsed over a 0.25 mm mesh sieve prior to storage or processmg. Wood blocks from 7.2 METHODS all MS and QS panels were dried, split, and l anmined for the presence of wood-boring organ- l 7.2.1 Field Methods isms. l l Fouling panels (10.2 cm x 10.2 cm roughened plexi- All noncolonial species collected monthly on both glass plates, bolted to pine blocks ofequal size) were ST replicates and one D~*mher MS replicate were collected monthly from January through December identified and enumerated. When high abundances at two mid-depth stations (nearfield B19, depth 12.2 of Mytilidae, Riatella sp. and Anomia sp. occurred, m and farfield B31, depth 9.4 m, Figu.c 7-1). De organisms were enumerated from subsamples designation mid-depth was based on the surface to generated using a Folsom plankton splitter (NAI bouom depth in relation to more shallow stations 1990). Colonial animals, diatoms and macroalgae sampled for other programs in this study (i.e., on ST panels were quantified by determining the benthos,macroalgae). Paneldepthsbelowthewater percent frequency of occurrence on the panel face surface ranged from 3 to 6 m dependmg on the tidal (Mueller-Dombois and Ellenberg 1974; Rastetter O stage. Collections were made at Stations B19 and B31 from 1978 to 1984 and from July 1986 through and Cooke 1979; NAI 1990). Colonial animals, diatoms, and macroalgal species were recorded as I 7-1
O N RYE LEDGE f 0 0
+ .5 1
1 Nautical Mile h Kilometers UTTd BOARS HEAD
; FARFIELD AREA SCALE
" ?n"?ls""
o GREAT BOARS HEAD ,
~
yrfs"]\ y b\ b NEARFIELD
** Intake AREA OUTER $ ;
SEABROOK O STATION fy gg h.. yDischarge SLABROOK SUNK HARBOR ROCKS
%% SEABROOK _
BEACH
%/
SAUSBURY BEACH LEGEND
- surface panels Figure 7-1. Surface panel sampling stations. Seabrock Operational Report,1995.
O 7-2
7.0 SURFACE PANELS "P" (present, but not quantified) when found in the Station and Month) were used to compare fouling ; j sample, but not direcdy on the panel face. For MS community settlement patterns (as exemplified by 1 and QS panels, the percent frequency of occurrence number of taxa, total abundance, total biomass and l of selected dominant animals (colonial and non- abundance and size of selected dominant species j colonial), and diatom and macroalgal species was on ST panels) as well as community development
- estimated using the procedure cited above. Counts (biomass, donunant species on MS panels) between
{ wereestimatedfornoncolonialspeciesand recorded preoperational(1978-1984 and 1986-1989 for ST i as an abundance class. Abundance classes, assigned panels and MS biomass, 1987-1989 for other MS i 1 through 5, consist of ranges of numbers of variables) and operational (1991-1995) years at [ individuals (1-10,11-100,101-1,000,1,001-10,000, paired nearfield (B19) and farfield (B31) Stations !- > 10,000, respectively). Colonial and noncolonial (the two preoperational periods, 1978-1984 and dominants, diatoms, and macroalgae were recorded 1987-1989, were treated as one period and were as "P" (present, but not quantified) when found in not statistically compared). Operational /- the sample, but not directly on the panel face. Rese preoperational and nearfield/farfield differences laboratory methods for MS panels were initiated in monthly means for fouling community paramaars in 1987, and abundances of dominant taxa were evaluated using a multi-way analysis of variance procedure ' Random samples of a200 Mytilidae and a 100 Jassa (ANOVA), using a before-after-control-impact i marmosta Holmes 1903 individuals found on MS (BACI) design to test for potential impacts of plant and QS panels and in the residue were measured operation. Afixedeffects ANOVAmodelwasused and recorded in 0.1 mm increments (NAI 1990). to test the null hypothesis that spatial and temporal All J. marmorata and Mytilidae individuals less abimdancae during the preoperational and opera-than 1.0 mm were recorded as <1.0 mm and tional periods were not significantly (p>0.05) mimated at 0.5 mm in calculations of mean lengths. different. De data collected for the ANOVAs met the cntena ofa Before-After/ Control-Impact (BACI) Dry-weight biomass from one of each pair of ST sampliag design discussed by Stewart-Oaten et al. replicates and all MS and QS pancis was determmed (1986), where sampling was conducted prior to and after taxonomic processing by arymg all faunal and durmg plant operation and sampling station locations j floral material to a constant weight at 105'C, includedbothpotentiallyimmenad andnon immerad sites. De ANOVA was a two-way factorial with nested effects that provided a direct test for the 7.2.3 Analvtical Methods temporal-by-spatialinteraction. He main effects were penod (Preop-Op) and station (Station); the Analvais of Variance interaction term (Preop-Op X Station) was also included in the model. Nested temporal effects were Recruitment on ST panels, measured on a monthly years withm operational penod (Year (Preop-Op)) basis by the number of taxa, the abundance of and months within ycar (Month (Year)), which were noncolonial organicmc. and total biomass, indicead added to reduce the unexplained vanance, and thus ; the potential for fouling community development. increased the sensitivity of the F-test. For both
- Monthly biomass levels on MS panels give an nested terms, variation was partitioned without indication of community development. Multiway regard to station (stations combined). De final analyses of variance (variables Preop-Op, Year, variance not accounted for by the above explicit 7-3
l l \ 7.0 SURFACE PANELS sources of variation constituted the Error term. Monthly numbers of taxa during the operational Preoperational periods for each analysis are listed period were generally simdar to the preoperational i
- on the appropriate figures and tables. Log (x+ 1) period, although several months (May, June, l transformed monthly mean values were used in the August, October and November at B19 and June, i l
ANOVAs for ST noncolonial total abundance and August and October through December at B31) all selected taxa abundances (Jassa mannorata and averaged higher than the upper 95 % confidence l Mytilidae), or frequencies of occurrence (Tubularia limitof thepreoperationalmonthlymeans Durmg sp.). Non-tansformed monthly means were used 1995, the monthly number of taxa was often higher in the multiway analyses of variance for ST and than the preoperational period upper confidence l MS biomass and short-term number of taxa. A limit, including April, June and August through significant difference in the interaction (Preop-Op November at B19 and August through December X Station) was investigated by comparing the least at B31. Durmg several months, February at B19, square means with a paired t-test (SAS 1985). and January, Febmary and July at B31, the number i of taxa in 1995 was lower than the lower 95% l LTest confidence limit of the preoperational period. The annual mean number of taxa in 1995, although j Community development was also assessed by higher than either the preoperational or operational examinmg biomass, species richness, and abundance period mean (Table 7-1), was within the range of ) on surface panels exposed for one year. A previously observed values (NAI 1992). Based on comparison was made between preoperational ANOVA, the number of taxa was significantly (generally 1982-1984 and 1986-1989, which was higher during the operational period than the treated as one period) and operational (1991-1995) preoperationalperiod(Table 7-2). ANOVAresults periods at each station using paired t tests (SAS indicated that the number of taxa at B19 was 1985). Selected dominant species (Mytilidae and signhndy higher than the number of taxa at B31 Jassa marmorata) lengths from MS and QS panels (Table 7-2). The interaction term (Preop-Op X were also compared using paired t tests to determme Station) was not significant, indicating that the if average annual lengths varied between the between-station difference occurred during the nearfield and farfield station pair in 1995. preoperational and operational periods, and was unlikely related to plant operation. 7.3 RESULTS Seasonal patterns of faunal abundance for non-7.3.1 Short-Term Panels colonial species at middepth Stations B19 and B31 during the operational years, including 1995, were Short-term panels provided information on the similar to those during preoperational years. seasonal cycles of settlement activity. Seasonal Historically, abundances remainediow from Jam'ary cycles in number of taxa in 1995 and during the to May, increased in June and July, then declined operational period were simdar to the preoperational from August to December (Figure 7-2). Mean trend (Figure 7-2). The number of taxa typically abundances atboth stations during 1995 were greater increased during May and June and remained high than the preoperational and operational period through September at both B19 and B31. In 1995, means, primarily due to the elevated abundances number of taxa remamed high through November during June through November (except July at B31), at both stations, with the exception of July at B31, which were above the preoperational 95 confi-7-4
Number cfTaxa Suon Be Sisson B31 : 2 - p 0,,, song , 2 - pmannamons -Q v 5 mes ,
,e s 85 --
oneasons nas ,s r e, ,,....N,i l.
- 8. /&Q,3 N\
lm 8 ,,
/. J.~-hs jy,rg. ?s ..
4 l. Q l., 4 / S E I 5 m i N, A Zt; f, , O. O M FeB M M M JUN JUL AUG SEP OCT NOV DEC M FEB M APR M JUN JUL AUG SEP OCT W DEC MONTH MOW l Log (x+1) Abundance Suon es Sinnon Bat 5- 5_ g -- w - 3 , -- {4
~- mes ,,
N g4 ~. 1ons As E g '-
.....\ -% 1 % - -.
N '
,\ 3
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h #' M FEB M APR M JUN JLL AUG SEP OCT NCM DEC 8' 0 W9
." -- A M FEB MAR APR MAY .AJN .AJL AUG SEP OCT NOV DEC MONTH MONTH Biomass Stanon Be Staton B31 10 _ 10 _
opsmoond g opensand j g ~* 1996 ig 8
"* IoB5 i ig ii I6 !
I g
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I // '\ ; o. f - 0i ~ M FEB MAR APR M JUN JUL AUG SEP OCT NOV DEC M FEB MAR APR W JUN JUL AUG SEP OCT N0/ DEC MONTH MONTH Figure 7-2. Monthly faunal number of taxa (on two relicate panels), abundance, and biomass on short-term panels at the nearfield/farfield station pair B19 and B31during the operational period (1991-1995) and 1995 compared to the means and 95% cmh limits during the preoperational period (1978-1984; July 1986-December 1989). Seabrook Operational Report,1995. 7-5
________ _ __ ~- . Table 7-1. Means (Per Panel) and Coefficient of Variation (%) for Selected Parameters and Species Abundances at Stations B19 and B31 During the Preoperational' and Operational Periods (1991-1995), and 1995 Means. Seabrook Operational Report,1995. PREOPERATIONAL' 11225. OPERATIONAL PARAMETER / : PANEL"' . . . TAXON -TYPE STATION' MEAN*- CV MEAN* MEAN* CV Total no. of taxa ST B19 11.3 30.4 15.1 13.6 13.3 B31 10.8 25.2 12.3 12.4 4.8 Total noncolonial ST B19 53.7 17.2 101.7 79.5 11.8 abundance B31 69.9 18.2 74.4 67.4 14.1 Total biomass ST B19 0.8 40.8 1.7 0.8 74.5 (g) B31 0.6 67.5 0.9 0.6 54.4 Mytilidae ST B19 30.4 22.6 60.1 45.0 18.8 y B31 39.6 21.1 54.0 39.9 23.5 Jassa mannorata ST B19 3.0 29.0 8.6 2.9 37.9 B31 3.9 30.4 12.1 4.2 41.3 Tubulada spp. ST B19 1.9 51.2 3.6 2.2 21.2 B31 1.1 73.6 3.2 1.0 89.0 Biomass MS B19 207.8 106.6 172.1 197.2 49.3 (g) B31 236.8 90.0 141.1 193.6 36.3 Biomass QS B19 - - 237.8 194.6 - (g) B31 - - 259.6 208.3 -- Total number of taxa QS B19 - - 19.5 20.8 - B31 - - 18.5 17.3 - Laminada sp. QS B19 - - 0 0 - B31 - - 0 0 --
'ST = short term MS = monthly sequential QS = quarterly sequential 6
Preoperational = 1978-1984; Jul 1986-Dec 1989
- Geometric mean for total abundance, Mytilidae, J. marmorata abundance and percent frequency of occurrence for Tubulada sp. Preop.
and Op. means are means of annual means. O O O
O O O Table 7-2. Results of Analysis of Variance Comparing Monthly Total Number of Taxa, Noncolonial Faunal Abundance, Total Biomass, and Selected Species Abundance or Percent Frequency on Short Term Panels at the Mid-depth Station Pair (B19 and B31) During Preoperational (1978-1989) and Operational (1991-1995) Periods. Seabrook Operational Report,1995. i SOURCE OF. MULTIPLE 1 PARAMETER 2 STATIONS ; - VARIATION - : df . S- 'F" : COMPARISONS 8 ' Number of taxa B19,B31 Preop-Op' 1 305.10 47.58 "
- Op> Preop Year (Preop-Op)6 14 128.96 20.1l' "
Month (Year)* 166 86.11 13.43 "
- Station d 1 50.55 7.88 " B19>B31 Preop-Op X Station
- 1 11.12 1.73 NS Error 180 6.41 Noncolonial faunal abundance B19,B31 Preop-Op 1 0.39 4.51* Op> Preop Year (Preop-Op) 14 1.57 18.10 * * *
? " Month (Year) 166 2.43 27.99 "
- Station 1 0.05 0.57 NS Preop-Op X Station 1 0.69 7.97 " B190p B31Preon B3100 B19 Preop Error 180 0.09 Biomass B19,B31 Preop-Op 1 0.43 0.47 NS Year (Preop-Op) 12 2.56 2.79 "
Month (Year) 146 2.79 3.05"* Station 1 3.02 3.30 NS Preop-Op X Station 1 0.01 0.01 NS Error 158 0.92 l Mytilidae B19,B31 Preop-Op I 0.50 4.81* Op> Preop Year (Preop-Op) 14 2.14 20.85 "
- Month (Year X Preop) 166 2.86 27.49* "
( Station 1 0.08 0.79 NS l Preop-Op X Station 1 0.56 5.38* B1900 B31Preon B3100 B19 Preop I Error 180 0.10 (continued) l -_-_ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ - _
Table 7-2. (Continued)
. SOURCE OF : { MULTIPLE -
PARAMETER STATIONS : VARIATION.T dr.- S' P' ~ COMPARISONS
- Jassa marmorata B19,B31 Preop-Op 1 <0.01 0.01 NS Year (Preop-Op) 14 0.87 9.79"
- Month (Year X Preop) 166 0.82 9.18 * "
Station 1 0.92 10.34 " B31>B19 Preop-Op X Station 1 0.05 0.53 NS Error 180 0.09 Tubularia sp. B19,B31 Preop-Op 1 0.01 0.04 NS Year (Preop-Op) 14 0.91 6.32* *
- Month (Year X Preop) 166 0.75 5.23 * "
Station 1 2.06 14.32 "
- B19>B31 Preop-Op X Station 1 0.08 0.53 NS Error 180 0.14 a
so
' Preop-Op = 1991-1995 v. previous years (1978-84; July 1986-December 1989) regardless of station 6 Year nested within preoperational and operational periods regardless of station
' Month nested within year regardless of station dStation regardless ofyear or period
' Interaction between main effects Station and Preop-Op
'NS = Not significant (p>0.05)
* = Significant (0.052p>0.01)
** = Highly significant (.0 lap >0.00l)
*** = Very highly significant (0.00l> p) 8Rankedin decreasing order LS means multiple means test used for significant interaction temi O O O
- 7.0 ' SURFACE PANELS 4
dence limits (Table 7-1, Figure 7-2). ANOVA December values were consistent with operational results indicated that the interaction of the main and preoperational periods. Annual mean biomass effects (Preop-Op X Station) was significant; a for 1995 at both stations was higher than significant increase in abundance between preoperational and operational means (Table 7-1) preoperational and operational periods occurred because of the higher than normal August and
- at Station B19, but there was no significant October peaks observed at both stations. ANOVA !
difference at B31 (Table 7-2, Figure 7-3). results indicated, however, there were no signhat Historically, there has been an increase in total differences for the main effects (Preop-Op and l
- abundances every three to four years (Figure 7-4). Station), and the interaction of the main effects 1 l Dese periodic increases have been observed at both (Preop-Op X Station) was not significant (Table i
stations. Abundances in 1994 and 1995 were lower 7-2). l than in 1993, suggesting that a similar pattern is ,l being repeated in the operational period. The Several dominant taxa on short-term panels were l l significant ANOVA results, which only test monitored to determine their seasonal settlement j operational and preoperational averages, are not patterns. Historically, Mytilidae (mainly Mytilus ! { indicative of plant effects. edulis Linn61758 spat) was the most abundant f l noncolonial taxon. Seasonally, the recruitment Seasonal settling patterns for the entire fouling pattern for Mytilidae during 1995 at Stations B19
. community (motile fauna, colonial organisms, and B31 closely followed the operational and
- macroalgae) were also assessed by examining preoperational seasonal trends (Figure 7-5). I.ow changes in biomass. The 1995 seasonal trend for to moderate settlement occurred from January to l <
- biomass at Station B19 followed a pattern generally May. Settlement increased in June and remained sinularto the preoperational and operationalperiods, high until late fall, following the pattern of larval
{; except that August and October values were availability (Section 4.0). 'Ihe 1995 monthly q unusually high (Figure 7-2). Biomass remained abundances at Station B19 were higher than the j low through July in 1995, peaked in August and operational and preoperational averages durmg July, j October .and then declined steadily through August and October (Figure 7-5). Monthly December. He unusually high biomass values in abunanma at Station B31 in 1995 were higher than August and October 1995 at B19 resulted in an operational and preoperational means durmg June,. j annual mean value that was twice the means of both August and October. Annual mean abundances at i the preoperational or operational periods (Table Stations B19 and B31 in 1995 were higher than their 7-1). respective preoperauonal and operational averages j (Table 7-1). ANOVA results indicated that there At farfield Station B31, the operational period was a significant interacuon between the main effects biomass levels remained low throughout the year. (Preop-Op X Station). Similar to noncolonial Only in November were mean operational period abundance, Mytilidae abundance showed a biomass levels above the 95% confidence levels significant increase between the preoperational and established during the preoperational period. operational periods at B19, but no significant Durmg 1995 at Station B31, biomass levels remamed increase occurred at B31 (Figure 7-3). Mytilidae low through July, peaking in August (4g/ panel) and abundance, a major contributor to the observed remaining at or above preoperational period means trends in total abundance, has undergone a three through October (Figure 7-2). November and 7-9 I l
7.0 SURFACE PANELS Total Abundance gl 2.00 , g3g
........................... - - + - + 831 l 1
1.75 - j g 1.50 1.25 I l 1.co 0.75
)
7 foso l o.25 0.00 Pr.op-m Op-m PEFUOO l 1 1 l 2.00 Mytilidae _ _ g$g g'
.. .. a j 1.75
.............................. ... ........; I 1.so --
1.25 i I 1.00 1 0.75 l 7 ( o.co 0.25 0.00 Prooperathmal OperanoneJ PERCO Figure 7 3. A comparison between stations of the logio(x+1) no per panel total abundance and Mytilidae abundance in short-term panels during the preoperational (1978-1985; 1987-1989) and operational (1991-1995) periods. Seabrcok Operational Report,1995. 7-10
l l i i 7.0 SURFACE PANELS l 1
/~5' t
Total Abundance i LJ i l 220
- 829 l
/, - asi
** /\
l
/ \ 1 180 l \ \
l \ l 1eo i \ \ l \ ?, ; ido l \ is 1
- :, l \, ,
t 120 l \ l\ l
' \
l \ /\' l
/
I'" ./ \ ', i l' '\ l
, eo .: \ \ l ',
~~. 1
\
! \ ? l \
60
/
/ \
' /
/ \\ / \ l
\\ / \
- l ~ '
~,'
l
, \/
- y l
l 206 1 o j i 78 79 80 81 82 83 84 85 88 87 88 89 90 91 02 93 94 05 l yE4a 1 1 l O l Mytilidae -B !
- e'sss ! ) 180 l l
l too i 140 I 12o A l
$ l\ ?,
R 300 / \ !\
=
o
\, l ,
i , , \ ec j l
/ ;
\
\ l l\
/
l l \
\ ~ /
,., '?
' ~
eo
\
o l 78 79 80 81 82 83 84 86 88 87 88 89 90 91 02 93 94 95 YEAR Figure 7-4. Annual geometric total abundance and abundance of Mytilidae on short-term panels at Stations B19 and B31,1978-1995. Seabrook Operationil Repon,1995. 7-11 i
j. Mytilidae Station Big Stadon B31 5 5 g m ---.
*++
w
*++ 1995
,/ \ 1995 j 4 A N
/ \
h/ s I4 /TE'N - qN _
,ff$-['s N ->
^ *'-J' ~27 o/ o JAN FEB MAR APR MAY .LN JJL AUG SEP OCT NOV DEC M FEB M APR MY JLN JUL AUG SEP OCT NOV DEC MON.'H n TH Jassa marmorata etmaan Bs Staban B31 8 5 p Preapendmd
+++
m 1995
---. m
*++ 190s 4
I4
\
3
~ ~ /s l3 / \~ s g: / \ :: / ,.... \
1 , N' 1 g
'-- 'N y
,W_ x2 -/~~~~' ,&<
.mN FEB MAR APR MAY JLN JLL AUG SEP OCT PG DEC M FEB MAR APR EY JLN JUL AUG SEP OCT NOV DEC em uaurH Tubularia sp.
Staban BW Staksi B31 100 ,--- 100 r-+ 3 I 3 90 ---- Open.a. ,8 g 90- - - - Operancrud i n W 1995 fg i &M 1995 { 80 f 80 l n c llj \\ l
\
n m
~
l l \
\
l VN\\ ,n l v-
/N-x.;
\
j, v;\ .l a ?l 20 . N fl M FEB M APR MAY J.N JUL Ab3 SEP OCT tG DEC M FEB MAR Am MY JJN JLL AUG SEP OCT No/ DB: um x NrH Figure 7-5. Log abundance (no. per panel) of Mytilidae and Jassa marmorata end monthly mean percent frequency of Tubularte sp. on short-term panels at nearfield Stations B19 and B31 during the operational period (1991-1995) and 1995 compared to the mean abundance or percent frequency and 95% confidence limits during the preoperational period (1982-1984; July 1986. December 1989). Seabrook Operational Report,1995. l 7-12 l 4 l l
7.0 SURFACE PANELS n to four-year abundance cycle unrelated to plant here was no significant difference for the main operation (Figure 7-4). temporal effect (Preop-Op; Table 7-2). Percent frequency was significantly higher at Station B19 The amphipod Jassa marmorata (formerly known than Station B31 for the entire study period (Table . as 1. falcata and revised by Conlan (1990)) is a 7-2). He interaction of the main effects (Preop-Op 1 common fouling organism (Barnard 1957). This X Station) was not significant indicating no effect species lacks a larval stage, so recruitment oc( urs due to the operation of Seabrook Station (Table 7-2). through dispersal ofjuveniles or adults through the water column (Bousfield 1973). Throughout the 7.3.2 Monthly Seauential Panels study period, J. marmosta abundances at B19 and B31 were low during the early part of the year with Monthly sequential panels provide information on a small late-summer increase (Figure 7-5). This cumulative growth and successional patterns of seasonal recruitment panern also occurred in 1995. development within the fouling community. However, abundances at both stations were above Seasonal patterns of community development were the upper 95 % confidence limits of the assessed by examining monthly biomass levels. preoperational period means from August through At Stations B19 and B31 during the operational and l November. Annual mean abundances in 1995 were preoperational periods, monthly biomass on monthly 1 higher than the preoperational and operational means sequential panels remained low from January to (Table 7-1). Based on ANOVA, there were no June, increasing from July to a peak in late significant differences between the preoperational fall / winter (Figure 7-6). During 1995, biomass and operational periods, but abundances were followed this same general pattern, although Station significantly higher at B31 than B19 (Table 7-2). B31 experienced a slight decline in October. On . Re interaction term was not significant, indicating an annual basis, the 1995 mean biomass at both that the pattern between stations was consistent stations was lower than either preoperational or l between the preoperational and operational periods, operational means (Table 7-1). Historically there l and there was no effect due to the operation of has been high year-to-year variability in mean l Seabrook Station. biomass as is indicated by the high coefficient of variation (CV) at each station during the preopera- l Hydre of the genus Tubularia are dense summer tional period (Table 7-1). Here were no significant colonizers Rey are important as habitat formers differences between the preoperational and and provide a substrate (Field 1982) and food source operational periods, between stations, and no (Clark 1975) for epifaunal taxa. During the significant interaction of these main effects (Table l preoprationalperiod, Tubularia sp. increased rapidly 7-3). beginning in June and reached peak cover in l September (Figure 7-5). Durmg 1995, peak percent Seasonal panerns of abundance of the community cover occurred at both B19 and B31 from August dommants in 1995 were similar to those obsen'ed through October when percent frequencies were during the preoperational period in most cases. 100% and above the upper 95 % confidence limits Mytilidae spat settled heavily on panels in June at ofthepreoperationalyears. Becauseoftheextended both stations (Figure 7-6). Percent frequency of and extremely elevated peak period at both stations, occurrence during 1995 reached high levels in July l 1995 annual means were higher than either that were maintained through December at both preoperational or operational means (Table 7-1). stations. During the operational period Mytilidae 7-13
Biomass station Bts c!ailon B31 G' l' a % m , a ___.w a ___. % J g *++ m5 g. *++ m : I a / { m-a ,+- fag. ,
,. d, l y j' ' ~ ~ ,f. - 1 o) l ,,,,,,-
a y a H] l u
- u. .. .,'; ' /-- 300
- a. .-
'/
.1l'h'
.. , s m
, a 0; -
0; , JAN FEB M M MAY JLN JUL AUG SEP OCT U DEC M FEB M M M JUN JUL AUG SEP OCT U DEC Kymi MONTH r I 1 l Mytilidae Station B19 '1alian B31 2 ap ..g g---' ~ 100
,7 ,;,- ;-- y !
- c. ___.p 1 go ___. p ,/j p c +++ 1995 i \ so
* * ' /
lI i N N ll l ll c C u t
/
- 50 ll ll ll C '
- 4) ll
- C *x !!
l C E # c 10 oi oi N FEB M M N JUN Ju % SEP OCT U DEC M FEB M M M JUN JUL AUG SEP OCT U DEC WONTH MONTH Figure 7-6. Mean biomass (g/ panel) and Mytilidae spat (percent Sequency ofoccurrence) during the operational period (1991-1995) and in 1995 compared to mean and 95% confidence limits during the preoperational period (Stations B19 and B31 from 1978-1984 and July-December 19861989 for biomass and 1987-1989 for Mytilidr) on monthly sequential panels. Seabrook Operational Report,1995. 7-14
p I ip d v C/ Table 7-3. Anova Results Comparing Monthly Sequential Panel Biomass at the -Eid-depth (B19, B31) Station Pair During Preoperational (1978-1989) and Operational (1991-1995) Periods. Seabrook Operational Report,1995. SOURCE OF STATIONS VARIATION df MS- l' Mid-depth Preop-Op' 1 4,756.22 0.42 NS B19,B31 Year (Preop-Op)6 14 276,118.10 24.61 * *
- Station
- I 6,395.16 0.57 NS Month (Year)d 156 129,656.88 11.55* "
y Preop-Op X Station
- 1 38,260.42 3.41 NS Error 170 11,221.74 U
' Preop-Op = 1991-1995 v. previous years (1978-84; July 1986-December 1989) 6 Year nested within preoperational and operational periods regardless of station
' Station regardless of year or period dMonth nested within year regardless of station
' Interaction between main effects NS= Not significant (p>0.05)
* = Significant (0.052p>0.01)
" = Highly significant (0.0la p>0.001)
*" = Very highly significant (0.0912 p)
7.0 SURFACE PANELS monthly percent frequencies of occurrence were lassa mannomta percent frequency at Station B19 , similar to monthly means during the preoperational during the preoperational period was quite variable period. seasonally. This variability has continued throughout the operational period (Figure 7-7). Mytilidae spat measurements from monthly However, in general, frequency of occuiTence at sequential panels in 1995 were compared to B19 has been low from January to June followed determine if mean lengths differed between the by an increase in August through October and a nearfield-farfield station pair. Mytilidae annual slight decrease at the end of the year. Percent mean lengths averaged 3.0 at Station 19 and 2.9 frequency followed this pattern at B19 during the mm at Station 31 in 1995 (Table 7-4), and were operational period, and in 1995. 'Ibe farfield Station not statistically different based on a paired t-test B31 exhibited a more distinct mid-year peak in both (t=0.1, p > 0.9). thepreoperationalandoperationalperiods. In 1995, Table 7-4. Nearfield/farfield Comparison of Annual Mean and Standard Error of Mytilidae Spat and Jassa Marmorata Lengths (Mm) from Monthly Sequential Panels Collected in 1995. Seabrook Operational Report,1995. MYTILIDAE SPAT . JASSA MARMORATA STATION MEAN- STANDARD MEAN -STANDARD LENGTH ERROR- LENGTH- ERROR (mm) ~ (mm) Mid-depth B19 3.0 0.97 3.6 0.48 B31 2.9 0.94 3.5 0.43 l there was little decline in frequency at B31 at the In 1995, Balanus sp. (including Balanus spp. and end of the year. The operational period was simdar Semrbalanus balanoides L.) was first found at Stations ) to the preoperational period although there were B19 and B31 in April, similar to previous years several instances in 1995 (August at B19, (Figure 7-7). Monthly percent frequencies in 1995 l September, November and December at B31) when were high (>60%) at both stations during June percent frequency was above preoperational through August, in contrast to the lower confidencelimits(Figure 7-7). Theaveragelength precru.6eralmonthly means. With few exceptions, of J. mannorata individuals colonizing monthly the operational monthly means at both stations were sequennal panels was 3.6mm at B19 and 3.5mm at greater than the preoperational means but withm the B31 in 1995 (Table 74). A t-test indicated that there established 95% confidence limits. were no significant differences in length between the nearfield (B19) and farf .'i (B31) stations (t = 0.1, During the preoperational period, Tubularia sp. p>0.8). generally first occurred in April at both stations, with 7 16
Jasss marmorata l i swan se swan sai [D m a -v so __-Popsmow
++*
x __% _. e so 1ses a0
** 1ees n b n
/sS.-g 0.1 s
/ w _, , _ , , -
j l*xso so M I
\ \
so M ,l$' m , f I/ ~,s Q5 %
*x a j j fi'
\/
sm? _.
% ---l M FEB WR M M JUN R AUG sEP OCT O DEC M FEB W APR WY JUN R E sEP OCT U DEC uomH WOmH Balanus sp.
s oon as amon est P.opmasonal PW so _ _ _ .
% so ___. %
so
*++ 1ess so
*++ 1ess N N so /,,a-
~.., ,f ~~.
so ,e s
//
so / \ so \ s e / -" s. \ u & '/ t N .. A,
- so j'* $~~':.
i,. *x l ,/ ,/ \j' \ L - 7;i . x. s s = uv s o. ys/
- o:
j < - M FEB WR APR W .1M R AUG IEP OCT NCV DEC M FEB MM APR W AM R AUG IEP OCT 10/ DEC uomH M0mH Tubularia sp. sman em suon sai
- r
- p.op, mow
- . _ . -- op.i--eow
--a }
so
*++
so ___. % so 8 86 so m ines n7 \ l N l n ao l \ ao l*#
*m , , ~ .
/'
/
'i
.~
\
'\ *x M
a y // i..
'h, a -
e s g _
-g? l .. ) **;***%
M FEB MW M W .KM R AUG SEP OCT H DEC M FEB WR APR WY UN R AUG SEP OCT U DE: WONTH MONTH Figure 7-7. Mean percent frequency of occurrence forJassa marmorata, Balanus sp. and Tubularia sp. at Stations B19 and B31 duriag the operational period (1991-1995) and in 1995 compared to means and 95% d ennf!% limits during the preoperational period (1987 1989) on monthly sequential panels. Seabrook Operational Report,1995. 7-17 l l
7.0 SURFACE PANELS the seasonal pattern of occurrence quite variable from The arnmal average biomass in 1995 was higher than year to year, as evidenced by the wide 95% observed for MS panels (Table 7-1) and higher than confidence intervals (Figure 7-7). In 1995, Tubulada in 1994 (NAI 1995). The nearfield and farfield sp. first appeared during the summer at both stations. biomass values were similar in 1995. At B19, frequencies were higher than the preoperational 95% confidence limits during The number of taxa on QS panels in 1995 averaged SeptemberandNovember. AtStationB31,Tubularia 19.5 at Station B19 and 18.5 at Station B31 (Table sp. occurred only in July and October through 7-1), sinular to the number observed in 1994. The December. Durmg the operational period, Tubulada number of taxa on QS panels averaged higher than sp. has occurred later in the year (July at both B19 on ST panels, reflecting the longer exposure period and B31) than during preoperational years. of the QS panels. There were 22 taxa present on the December QS (12-month exposure) panels at both Fifteen specimens of the woodboring " shipworm", stations, compared to 19 at Station B19 in 1994 and Teredo sp., were found on the MS and QS panel 14 at Station B31. '1he increase in number of taxa blocks at Station B19 in October, November and observed in December 1995 compared to 1994 was December and at Station B31 in October and also noted in the long- erm panels (Section 7.3.4). December (NAI 1996). Teredo sp. individuals have been recorded from MS panels several times in the No Zammada sp. blades were collected on QS panels past, at Station B19 in 1976 (NAI 1977) and 1979 in 1995 (Table 7-1), as in 1994. While Laminaria (NAI 1981a) and at Station B31 in 1980 (NAI 1981b). sp. blades were present on the December MS (12-month exposure period) panels at both stations, they 7.3.3 Ouarterlv Seouentin] Panels occurred in relatively low numbers. Quarterly m=W (QS) panels provide additional Seasonal patterns of abundance of dominant animals information on growth and successio::al patterns of on QS panels were examined in 1995. Mytilidae development within the fouling community, and were not present during March but were present through panel replication, allow assessment of within- during the last three quarters with percent frequencies station variability. Comparisons can be made with between 50% and 100% at both stations (Figure 7-8). the preoperational period by using the monthly Seasonal patterns in 1995 were similar to those preoperational mean from the MS panel program observed during the preoperational period. In 1995, for those months sampled in the QS program (Figure Jassa mannorata frequency of occurrence was low 7-7). Quarterly biomass levels were used to assess in March and June, but reached 25 % or higher for patterns of conununity development. the rest of the year at both stations. J. marmorata first appeared in June at both stations and reached During 1995, biomass levels were first measurable a high in September at B19 and in December at B31. in June and increased in September at both Stations Frequencies in September and December 1995 were B19 and B31; biomass continued to increase in higher than the preoperational average at both stations December at B19 while decreasing at B31 (Figure (Figure 7-9). In 1995, Balanus sp. first appeared 7-8). This seasonal trend paralleled those observed and peaked in June at both stations followed by a in ST panels (Figure 7-2) and MS panels (Figure 7-6) decline (Figure 7-9). Peak percent frequencies in both in 1995 and during the preoperational period. 1995 (approximately 35 % at B19 and 55% at B31) 7-18
Biomass . Shdion B19 Station B31 l E e+* Pnop 900
*+* Pnop g ..... g g ..... g
.g -. g 800 000 500
,M 500 j
/~~'
/ j, j***
l MO y /. ".
;'?./-
g 200 u o__
, y ,a
=>
- 200 u
c
/
(?< M JJN SEP DEC M JUN SEP DEC MONTH MONTH Mytilidae Stahon B19 Stadon B31 mg ---- gg 100 r - - - - - - - - - -- m 100 ;
,3 f 'p 90- ---- g / 90 V
eo --. g
.. ,/ , -- . m j -
lo g , l
/.........
10 g , l . i i- \ 50 l
/
/
/ 50
/ :/
/ <
e i m ll Y $ -
.!-li/
$ $ e i:
ll 20 20 if,/ 10 o 10 0 ' < 0 MAR JUN SEP DEC M JUN SEP DEC MONTH MONTH l l 1 l l l i Figure 7-8. Mean biomass (g/ panel) and Mytilidae spat (percent frequency of occurrence) and 95% ennMenca limits (n=3) during 1995 from Stations B19 and B31 on Quarterly Sequential ;
- panels compared to the monthly preoperational means (1987-1984 and 1986-1989 for biomass j
/~T and 1987-1989 for Mytilidae). Seabrook Operational Report,1995. 1 O l l
7-19 ) l i I
Jassa marmorata Staban B19 Station B31 m m p,,,, m g, j 90 .... gg 90 .... gg i l 80 --- 1995 80 - - - 1995 M- M
= {m -
1 so so ,/ ' '__ M /
~~,%w M /
/'
,/ ,/
10 -
/ 1o-
"" " ~~
o 0 M JUN EEP DEC M JLN SEP DEC M0tmi MONTH Balanus sp. Station B19 Station B31 2' *++ Preap # m Preap go- .... gg go. . . . . . gg go - -
- 1995 / So - - 1995 /
70
', \
/ m !. <
,/
l 70 j'
" - ~ ~ ~ -
so. so / ,' e e / ,e . . . .
- 30 p 30 / , ' ~ Q~ ' ~ ~
po l ,' ,/l % ,, '~~ . . - - - . - - - - - 20 i ,' . S S .[ , M JUN SEP DEC M JUN SEP DEC MONTH MONM Tubularia sp. Station B19 Station B31
- m Preap 15 m Pniop 90 ..... gg 90 ..... ga
, _ _. m ,o _ _. 39,3 70 80 80 1
- so so
# 70 ,/ gN, em so 4
20 / %' .-- 20 - Io o -
,/
'NJ <
1o o [" N JUN SEP DEC M JLN SE DEC uomH MONm Figure 7 9 Mean percent frequency of occurrence forJassa marmorata, Balanus sp. and Tubularia sp. at Stations B19 and B31 during 1994 and 1995 compared to the monthly preoperational means and 95% confidence limits (1987-1989) on Quarterly Sequential panels. Seabrook Operational Report,1995. 4 1 7 20 ) 1 1 I
7.0 SURFACE PANELS l fi Q were lower than those observed during 1994 but Mytilidae spat andlassa mannorara measurements higher than during the preoperational period. from QS panels in 1994 were compared to determme Tubulana sp. appeared and peaked in September at ifmeanlengths differed between the nearfield/farfield both Stations B19 (35 %) and B31 (20 %) (Figure 7-9). station pair. Mytilidae annual mean lengths averaged While peak occurrences were higher than observed 4.2 mm at Station B19 and 3.3 mm at Station B31 during the same months preoperationally, they were (Table 7-5). This difference was not significant (t=- lower than the peaks observed on MS panels in 1995 0.32, p > 0.7). Average lengths of J. mannorata (Figure 7-7). The quarterly samplinr, regime misses individuals colonizing QS panels averaged 2.6 mm the mid-summer montic when aie preoperational at Station B31 and 2.8 mm at Station B19. There average has been highest on MS panels (Figure 7-7). was no significant difference in length between the two stations (t=0.30, p > 0.7). Table 7-5. Nearfield/farfield Comparison of Annual Mean and Standard Error of Mytilidae Spat and Jassa Marmorata Lengths (Mm) From Quarterly Sequential Panels Collected in 1995. Seabrook Operational Report,1995. MYTIL1DAE SPAT . JASSA MARMORATA 4 g MEAN LENGTH ' STANDARD MEAN LENGTH : STANDARD STATION ' (mm) ERROR- ERROR () (mm) - B19 4.2 2.23 2.8 0.55 B31 3.3 1.93 2.6 0.55 7.3.4 One Year Panels (Table 7-6). The operational mean was significantly greater than the preoperational mean at Station B19, Community development was also assessed by while there were no significant differences between enmining biomass, species richness (number of taxa) the preoperational and operational means at Station and abundance on surface panels exposed for one B31. The number of noncolonial taxa at B19 was year. Year-end biomass in 1995 at B19 was similar similar to 1994 and, at B31, was double that fcund to the preoperational mean, whereas biomass a: B31 in 1994 (NAI 1995). At both stations, the number was lower than the preoperational mean (Table 7-6). of taxa in 1995 was lower than the average for the The values at both stations were elevated from the operational period (Table 7-6). 1994 operational period lows (NAI 1995). Mean year-end biomass during the operational period was Non-colonial abundance in 1995 was higher than both not significantly different from the preoperational the preoperational and operational mean abundance mean at either Station B19 or B31 (Table 7-6). at B19 (Table 7-6). At B31, abundance in 1995 was higher than the preoperational mean, but similar to The number of noncolonial taxa in 1995 was higher the operational mean. There were no significant
)
than the preoperational mean at Stations B19 and B31 differences between the preoperational and operation-7-21
c __ Table 7-6. Dry Weight Biomass, Noncolonial Number of Taxa, Abundance, and Laminaria Sp. Counts on Surface Fouling Panels Submerged for One Year" at Stations B19 and B31. Mean and Standard Deviation for the Preoperational Period (1982-1984 and 1986-1989) And Mean for 1995, and the Operational Period (1991-1995). Seabrook Operational Report,1995. PREOPERATIONAL .1925 OPERATIONAL
- STATION MEAN S.D. MEAN MEAN S.D.
BIOMASS B19 661.5 476.88 601.2 749.1 NS 506.49 7 (g/ panel) B31 708.9 523.86 437.4 510.0 NS 271.47 NUMBER OF NON- B19 21.3 4.42 24.0 29.5
- 4.80 COLONIAL TAXA (Nolpanel) B31 25.9 4.60 30.0 31.0 NS 11.45 NONCOLONIAL B19 13,905.1 7,046.48 77,209.0 41,Ill.3 NS 34,032.68 ABUNDANCE (Nolpanel) B31 21,967.6 I8,398.27 58,961.0 59,481.8 NS 35,261.04 IAMINARIA SP. 6 B19 24.3 36.91 1.0 0.3 NS 0.50 (Nolpanel)
B31 39.3 29.24 9.0 6.4
- 6.43
- 01<ps.05 when preoperational and operational means tested for equality with a single sample t-test (SAS 1985)
" December MS panel only (one replicate) 6 not determined to species due tojuvenile condition of most plants
'B19:1991,1993-1995; B31:1991-1995. B19 panel lost due to weather O O O
J 7.0 SURFACE PANELS al means at either station. Mean noncolonial (Ou) abundance at the farfield station was higher than at The community settling and developing on surface panels has shown predictable seasonal patterns the nearfield station during the operational period, throughout the study, as evidenced by both measures
- consistent with the relationship between the of community structure (biomass, abundance, and preoperational means. number of taxa) mxt abundance or percent frequency of occurrence of dominant taxa. During 1995, Ianmana sp. blade counts on one-year panels have abundance varied seasonally on ST panels and been low during most years of this study. At biomass varied seasmally on both ST and MS panels. i nearfield Station B19, Ianinaria sp. did not occur Biomass exhibited similar trends at nearfield and durmg three of the seven precperational years (NAI farfield stations on bcnh ST and MS panels. Temporal 1991,1992,1993) and has not occurred during any patterns of total and Mytihda
- (the most abundant 4
operational year until 1995 (Table 7-6). Laminaria taxon) abundance differed signifienntly between the i sp. did occur during each preoperational year and nearfield and farfield stations (Table 7-2, Figure 7-4). early operational years at farfield Station B31, but Historically (Figure 7-3), there has been a pattern was absent during 1993 and 1994 (NAI 1995: NAI offluctuatmg total and Mytilidae abundances repeated and NUS 1994). Differences between operational over a several-year period, suggesting that this j and preoperational means were significant only at difference is not indicative of plant effects. The farfield Station B31. number of taxa on ST panels was higher during the operational period than preoperationally. This lp 7.4 DISCUSSION pattern was consistent between stations and is, l V therefore, not related to the operation of Seabrook The surface panels program was established to Station. In most cases, the operational means closely document the temporal and spatial patterns in the followed the historical patterns established during recruitment and development of the fouling the preoperational period (Table 7-7), ideiting that community and to monitor the effects of Seabrook settlement and development of the local fouling Station's operationonthe community. The character- community remams unaffected by the operation of istics of Seabrook Station's thermal plume have been Seabrook Station. estimated from hydrothermal modeling studies (Teyssandier et al.1974) and confirmed in recent The year-end values for parameters measured for l field studies (Padmanabhan and Heckler 1991). surface panels exposed for twelve months provide Results from field studies generally confirmed initial information on long-term successional development model results, indicating that the discharge plume of the fouling community and reflect cumulative area was relatively small under the conditions tested. effects of biological processes such as recruitment, For example, the isotherm of a surface temperature growth, and competnion. One parameter, number increase of 3*F (1.7'C) covered a relatively small of non-colonial taxa, showed a difference durmg the 32-acre area in the vicinity of the discharge area. operational period that was not consistent between Water temperatures were elevated at most by 2-3 F the nearfield-farfield station pair (Table 7-7). The (under the conditions tested) in the approxunate area mean number of norsolonial taxa was significantly where panels at nearfield Station B19 are deployed. higher at Station B19 (nearfield) during the n ( operational period. Although the number of taxa was ingher at the farfield station, this difference was 1 i 7 23 1
7.0 SURFACE PANELS Table 7-7. Summary of Evaluation of Discharge Plume Effects on the Fouling Communityl in Vicinity of Seabrook Station. Seabrook Operational Report,1995. 4 1
- NEARFIELD--
FARFIELD 1 OPERATIONAL DIFFERENCES ' I DEIrrII PERIOD SIMILARTO . CONSISTENT WITH l COMMUNITY ZONE PARAMETER
- PREVIOUS YEARS? PREVIOUS YEARS?' l Fouling community: Mid-depth Abundance no NF:Op> Preop Settlement
- FF:Op= Preop No. of taxa no yes Biomass yes yes Fouling community: Mid-depth Biomass yes yes l Development-MS' j l
Fouhng community: Mid-depth Abundance yes yes l Development- No. of taxa no NF:Op> Preop : year end* FF:Op= Preop l Biomass yes yes Fouling community: Mid-depth Mytilidae no NF:Op> Preop Settlement' FF:Op= Preop l I Mid-depth Jassa marmorata yes yes , 1 Mid-depth Tubularia sp. yes yes ' Abundance, number of taxa, biomass, total density, and frequency of occurrence evaluated using ANOVA, or t-test l HF = nearfield FF = farfield ! I ' Settlement = short term panels; Development = monthly sequential panels - MS; year end = one year exposure not significant. The same pattern was observed in and the operational periods were significant only at 19% (NAI 1995) and a similar trend was observed the mid-depth farfield Station B31. There is no in 1993 (NAI and NUS 1994), where significant indication that this effect is due to Seabrook Station l differences were noted at both stations. The algal operation, since the decline occurred at both nearfield j species Laminaria sp. was present in 1995 at both and farfield stations and began prior to the operation i stations, although it connnued to occur at low levels, of Seabrook Stanon. i reflecting the declining trend that began during the , preoperationalyears(NAI, 1991, 1992, 1993, 1995 The quarterly sequential panel program was initiated I NAI and NUS 19%). However, the differences in in 1994 to provide information on within-station abundance of faminaria between the preoperational variability of e tement and development. Given , 7-24
i 7.0 SURFACE PANELS the varymg exposure period (3,6,9, and 12 months), (Dow and Baird 1953). The mode of dispersion is the program parallels that of the community through the larval stage; veliger larvae are planktonic development (1-12 months exposure, MS) program. for 2-3 weeks following release from the adult and 7he methodology used is similar to the MS program, can travel in ocean currents frr hundreds of ; relying on percent frequencies for dominant taxa. kilometers (Scheltema 1971; Nair and Saraswathy Quarterly biomass values were similar to those 1971). observed in the MS program in 1995. The atypical fall decrease observed in MS and QS biomass levels Based on the historic documentation of Teredo in in 1994 was not observed in 1995 when biomass the Gulf of Maine by other researchers and in the I returned to a more typical seasonal pattern. Selected Hampton-Seabrook area specifically during species Mytilidae, Balanus sp and Jassa marmomta preoperational study years of these monitoring i collected in the QS program showed similar seasonal studies, and the fact that Teredo sp. was identified j 1 patterns and frequencies to the MS program, as would at both nearfield and farfield stations in 1995, the I be expected. Tubularia sp. frequencies typically most recent occurrence in 1995 QS and MS panels display a seasonal pattern in the MS program that is not indicative of an impact from Seabrook Station is not consistently detected by the QS program. QS operation. l panel analyses demonstrate within-station variability was high for all parameters, a factor which should Overall, results in 1995 agree with those from be taken into account in micrprecation of MS and previous years. There is no evidence that operation O ST results. of Seabrook Station has had an effect on the local fouling community. The occurrence of the slupworm Teredo sp. in 1995 in QS and MS wooden blocks that support surface
7.5 REFERENCES
CITED panels is not unexpected for the Seabrook area. Occasional specimens have been collected previously Barnard, J. Laurens. 1957. Amplupod crustaceans dunng the surface panels study, including 1976 and as fouhng organisms in Los Angeles-Long Beach Harbors, with reference to h innuence of seawater 1979 at Station B19 and 1980 at Station B31 (NAI
.. turbidity. California Department of Fish and Game.
1977,1981a, b). Addtuonally, teredinid veliger Contribution No. 212. Allan Hancock Foundation. larvae have been observed in bivalve larvae samples every year since 1984. Bousfield, E.L.19'13. Shallow-Water Gammandean Amphipoda of New England. Comstock Pub. Teredo navalis is the most common teredimd reported Ithaca, NY. 312 pp. for the Gulf of Maine (Grave 1928; Turner 1966), Clark, K.B. 1975. Nudibranch life cycles in the and is cosmopolitan in its distribution, being found northwest Atlarde and their relationship to the ecol-in most semi-tropical to boreal ocean environments ogyoffoulingcommunities. Helgo. Wiss. Meere. (Gosner 1971). Along the east coast of North 27-28-69. America, it occurs from Newfoundland to Florida Conlan, Kathleen E.1990. Revision of the crustacean (Culliney 1975). While T. navahs is most abundant amphipud genus Jassa Leach (Corophiodea; in temperate and semi-tropical waters south of Cape Isehyroceridae). Can. J. Zool. 68:2031-2075. Cod, periodic cutbreaks have been reported in more f}
' northern boreal waters, including the Gulf of Maine 7-25
7.0 SURFACE PANELS Culliney, J.L. 1975. Comparative larval .1990. Seabrook EnvironmeraalStudies. development of the shipworms Bankia gouldi 1989 Data Report. Tech. Rep. XXI I. and Teredo navalis. Mar. Biol. 29:245-251. 1991. SeabrookEnvironmentalStudies, Dow, R.L. and F.T. Baird, Jr.1953. Methods to 1990. A characterization of environmental reduce borer damage to lobster traps. Tech. conditions in the Hampton-Seabrook area during i Bull. No. 3. Dept. Of Sea and Shore Fisheries. the operation of Seabrook Station. Tech. Rep. l Augusta, Maine. 15 pp. XXII-II. ) Field, B. 1982. Stuctural analysis of fouling 1992. SeabrookEnvironmentalStudies, community development in the Damariscotta 1991. A characterization of environmental i River estuary, Maine. J. Exp. Biol. Ecol. conditions in the Hampton-Seabrook area during 57:25-33. operation of Seabrook Station. Tech. Rep. XXIII-I. Gosner, K.L.1971. Guide to Identification of .1993. SeabrookEnvironmentalStudies, Marine and Estuarine Invertebrates. Wiley- 1992. A characterization of environmental Interscience. John Wiley and Sons, Inc. 693 conditions in the Hampton-Seabrook area during pp. the operation of Seabrook Station. Tech. Rep. XXIV-I. Grave, B.H.1928. Natural history of shipworm, Teredo navalis, at Woods Hole .1995. SeabrookEnvironmentalStudies, Massachusetts. Diol. Bull. Woods Hole 55:260 1994. A characterization of environmental 282. conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Tech. Rep. Mueller-Dombois, D., and H. Ellenberg. 1974. XXV-I. Aims and Methods of Vegetation Ecology. John Wiley & Sons, NY. 547 pp. .1996. SeabrookEnvironmentalStudies, _ 1995 Data. Unpublished data tables. Nair, N.B. and M. Saraswathy.1971. The biology of wood-boring tereduud molluscs. Adv. Normandeau Associates (NAI) and Northeast Utilities Mar. Biol. 9:335 509 Corporate and Environmental Affairs (NUS). 19%. Seabrook Environmental Studies,1993. A Normandeau Associates Inc. 1977. Seabrook Characterization of Environmental Conditions in Benthic Report.1987. Tech. Rep. VII-6. the Hampton-Seabrook Area Durmg the Operation of Seabrook Station. Prepared for North Atlantic
. 1981a. Seabrook Environmental Energy Service Corporation.
Studies.1979 Seabrook Benthic Report. Tech. Rep. XI-5. Padmanabhan, M., and G.E. Hecker. 1991. Comparative evaluation of hydraulic model and
. 1981b. Seabrook Environmental field thermal plume data. Seabrook Nuclear Power Studies. 1980 Data Report. Tech. Rep. XII-2. Station. Alden Res. Lab., Inc. 12 p.
. 1988. Seabrook Environmental Rastetter, E.B., and W.J. Cooke. 1979. Response Studies.1987. A characterization of baseline of marme fouhng communities to sewage abatement I cotuhtions in the Hampton-Seabrook area. 1975- inKaneohe Bay, Oahu, Hawaii. Mar. Biol. 53:271-1987. A preoperational study for Seabrook 280.
Station. Tech Rep. XIX-II. O 7-26 l
l 7.0 SURFACE PANELS SAS Institute, Inc.1985. User's Guide: Statistics, Version 5 Edition. SAS Inst. Inc. Cary, NC 956 pp. Scheltema, R.S. 1971. Dispersal of phytoplanktotrophic shipworm larvae (Bivalvia: Teredinidae) over long distances by ocean currents. Mar. Biol.11:5-11. 4 Stewart-Oaten,A. , W.M. Murdoch and K.R. Parker. 1986. Environmental impact assessment:
"Pseudoreplication in time?. Ecology. 67:920-940.
Teyssandier, R.G., W.W. Durgin, and G.E. Hecker, 1974. Hydrothermal studies ofdiffuser dscharge in the coastal environment: Seabrook Station. Alden Res. Lab. Rep. No. 86-24. Turner, R.D. 1966. A Survey and Illustrated Catalogue of the Teredinidae (Mollusca: Bivalvia). The Museum of Comparative Zoology, Harvard Univ., Cambridge, Mass. . O 265 pp. U i l I l l 1 7-27
8.0 EPIBENTHIC CRUSTACEA 4
- (0s TABLE OF CONTENTS PAGE a
8.0 EPIBENTHIC CRUSTACEA
SUMMARY
. . . . . ... . . .... ......... ..... ......... . . . . . . 8-ii i LIST OF FIGURES . . . . . . . . . . . . . . . . ...... .... ..... .... . . . . . . . . . 8-iii LIST OF TABLES . . ..... ................ ... .. . . . . . . . . . . . . . . . . 8-iv 1'
8.1 INTRODUCTION
. . . ............ .... ........... .... .... 8-1 8.2 METHODS . . . . ................................... ........ 8-1 8.2.1 Field Methods . . . . ....... .. .... ... ..... .. ........ 8-1 8.2.2 Laboratory Methods ..... .. ........ ......... . . . . . . .. .... 8-3
, 8.2.3 Analytical Methods . . . .. .. ........ ........... ... .. ..... 8-3 1, 8.3 RESULTS ...........' ........ ............... .... . . ....... 8-4 i ( 8.3.1 American Lobster . . . . . . . . . . . . . . . . . . . . ....... .. .. . . ... ... 8-4 8.3.2 Jonah and Rock Crabs . ......... ....................... 8-12 8.4 DISCUSSION ............. ... . .. ..... ........ . . . . . . . . . 8- 16 8.4.1 American Lobster . . . . .. ................... . . . . . . . . . . 8- 16 8.4.2 Jonah and Rock Crabs . . . . . . . . . . . . .......... . . . . . . . . . . . . 8- 18 I i
8.5 REFERENCES
CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 18 r
+
8-i
8.0 EPIBENTHIC CRUSTACEA SLSBIARY Epibenthic crustacea in the study area include the American lobster and rock and Jonah crabs, important invertebrate predators in the region. The local lobster population also supports an important commercial fishery. Lobster larvae have historically been relatively rare in the study area, averaging less than I per 1000 square meters. The larvae, predominantly Stage IV, typically had peak abundances in July and August. Larval abundance during the operational period was significantly greater than durmg the preoperational period at all three stations. Adult lobster catches (all sizes) were typically highest from August through November. This seasonal cycle was observed during both the preoperational and operational periods. Total catch in 1995 was the highest observed to date during this study. However, while average CPUE at the nearfield station during the operational period showed no significant difference from that during the preoperational period, CPUE at the farfield station showed a significant decrease. Catches of legal-sized lobsters were significantly lower during the operational period at all stations, likely a result of increases in the legal-size limit. There was no evidence of an effect from Seabrook Station operation. Cancercrab larvae were most abundant in the study area from June through September. Average densities dunng the operational period were significantly higher than the preoperational period at all three stations. Jonah crab densities showed no significant difference at the nearfield station between the preoperational and operational periods, but declined significantly at the farfield station. This decline began during the preoperational period and was not due to the operation of Seabrook Station. Adult rock crabs were less abundant than their congener, likely due to preference for sandy substrate, which is less common in the study area than hard substrate. Rock l crab catches were significantly higher during the operational period at all stations. There was no evidence of an ef'ect of Seabrook Station on local Jonah or rock crab populations. O 8-ii
8.0 EPIBENTHIC CRUSTACEA (q
%j ; LIST OF FIGURES PAGE 8-1. Epibenthic crustacea (American lobster, Jonah and rock crabs) sampling stations. . . . . . . 8-2 8-2. Preoperational mean and 95 % confidence limits and 1995 and operational means of a. weekly 2
density (no./1000m ) of lobster larvae at Station P2, b. lobster larvae density by lifestage at P2, c. monthly CPUE (15 traps) of total (legal and sublegal) lobster at Station L1, and
- d. monthly CPUE (15 traps) of legal-sized lobster at Station L1. ..... ......... . 8-8 8-3. a. Percentage and b. catch (per 15 trap effort) of legal-sized and sublegal-sized lobster at Station L1 and c. size-class distribution at Station L1 from 1975-1995. . . . . . . . . . . . . . 8-9 8-4. A comparison of the mean catch per unit effort (no per 15 traps) for total lobster by station during the preoperational(1982-1984 + 1986-1989) and operational (1991-1995) periods when the interaction term (Preop-Op X Station) of the ANOVA model was significant (Table ;
8-2)............... .............................. . . . . . . . . . . 8-11 l eg 8-5 Annual mean CPUE (no. per 15 traps) for total lobster, 1982-1995 (data between dashed j () lines excluded from ANOVA Model). ................................ . 8-11 8-6. Monthly means ano 95 % confidence intervals of log (x+ 1) density (noJ1000 m) of a. Cancer spp. larvae at Station P2, and monthly mean catch per unit effort (15 traps) of b. Jonah and
- c. rock crabs at Station L1 during the preoperational period (1978-1984 + 1986-1989: larvae, 1975-1984 + 1986-1989: adults) and monthly means during the operational period (1991-1995) and in 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... 8-13 8-7. A comparison of the mean catch per unit effort for Cancer borealis by station during the preoperational (1982-1984; 1986-1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model. . . . . . . . . . . . . . . . . . . . 8-15 8-8. Annual mean CPUE (no. per 15 traps) for Jonah crab, 1982-1995 (data between the two dashed lines excluded from the ANOVA model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15 I
c i kv/ 8-iii
8.0 EPIBENTHIC CRUSTACEA LIST OF TABLES PAGE 8-1. Geometric Mean Abundance (Larvae: Lobster = No./1000 M2 ; Cancer Spp. = No./1000 M') or Arithmetic Mean Catch per Unit Effort (No./15 Traps) and the Coefficient of Variation (Cv,%) of Epibenthic Crustacea at Nearfield (P2, P5, L1) and Farfield (P7, L7) Stations During the Preoperational and Operational Periods and in 1995 . . .. . .... ....... 8-5 8-2. Results of Analysis of Variance Comparing Densities of Lobster and Cancer Spp. Larvae Collected at Intake, Nearfield, and Farfield Stations, and Catches of Total and Legal-sized Lobsters, Jonah Crab, and Rock Crab at the Nearfield and Farfield Stations. ..... .. 8-6 8-3. Number of lobsters Impinged in the Cooling Water System of Seabrook Station During 1990 Through 1995. . . . . . . . . . ... ..... . ..... ... . .... .... 8-12 8-4. Summary of Potential Plant Effects on Abundance of Epibenthic Crustacea. . . . . . . . . 8-17 O l l O 8-iv l
1 8.0 EPIBENTHIC CtUSTACEA h
8.1 INTRODUCTION
the net mouth approximately 0.5 m below the surface. 2 The area sampled averaged about 3732 m (generally 2 The objective of the epibenthic crustacea monitoring ranging from 2874 to 4300 m ), program was to determine the seasonal, spatial, and annual trends in larval density and catch per unit ef. Cancer spp. Larvae (Macrozoonlankton) j fort for the juvenile and adult stages of American l lobster (Homams americanus Milne-Edwards 1837), Cancer spp. larvae (C. borealis and C. irroratus) Jonah crab (Cancer borealis Stimpson 1859), and and other macrozooplankton were sampled four times
)
rock crab (Cancerirroratus Say 1817). Analyses per month from January through December. On each I were done to determine if the discharge from date, four replicate (two paired-sequential) oblique Seabrook Station had any measurable effect on these tows were made at night with 1-m diameter, 0.505-species. The planktonic larval stages of Cancer mm mesh nets at the intake (P2), discharge (PS), l species may potentially be affected by entrainment and farfield (P7) stations (Figure 8-1). Collections within the cooling system of the plant where began in 1978 at Station P2 and in 1982 at Station ; l mechanical damage or temperature increase may P7. Collections at Station P5 occurred from 1978-cause death or stress. Lobster larvae may be 1981, July-December 1986, and from 1987 to the entrained in the buoyant discharge plume, which may present. No collections were made in 1985 at any affect survival, successful molting, and settlement station. The nets with depressors were set off the to the bottom. The benthic (bottom dwelling) stages stern and towed for 10 minutes while varying the n of these crustaceans may be impinged at the intake boat speed, causing the net to sink to approximately () or be subject to possible discharge effects such as increased turbidity. 2 m off the bottom and to rise to the surface at least twice during the tow. If nets became clogged due to plankton blooms, tows were shortened to 6 8.2 METHODS minutes. The volume filtered was deter nined with a General Oceanics* digital flowmeter. Upon re-3.2.1 Field Methods trieval, each net was thoroughly washed down with filtered seawater and the contents preserved in 5-10% Lobster Larvae (Neuston) borax-buffered formalin. To monitor the distribution of American lobster Juveniles and Aduks (Lobster Traps) larvae, neuston samples were collected once a week, during the day, from May through October along American lobster, Jonah crab and rock crab were horseshoe-shaped tows approximately 1/2 mile (800 collected at the nearfield discharge station (L1) and m) long on a side. These tows were centered at the a farfield station located off Rye Ledge (L7) (Figure mtake (P2), discharge (P5), and farfie'd (P7) stations 8-1). Collections. began at Station L1 in 1975 and (Figure 8-1). Collections began in 1978 at Station at Station L7 in 1982. Fifteen 25.4 mm (1 in) mesh P2, in 1982 at Station P7, and in 1988 at Station P5. experimental lobster traps without escape vents were Collections were made with a 1-mm mesh net (1 m retrieved at two<iay intervals, approximately three deep x 2 m wide x 4.5 m long) fitted with a General times per week from June through November. Lob-O Occames* flowmeter and a 40-lb depressor. Thirty ster carapace lengths were recorded in the field to ! mmute surface tows were taken with the bottom of the nearest 1/8 inch. Beginning in 1990, lobsters 8-1
N RYE LEDGE ,..
.!\ .
o .
........ i UTTLE
y '
., '\
1 BOARS , ...\ . .! HEAD ). L7 \ o .5 1 Nautical Mlle . FARFIELD AREA b k Kilometers , SCALE ' CONTOUR DEPTH Il 4 IN METERS , o . GREAT BOARS - - HEAD ' HAM) ')N ,7 ' ' k
, BEAL. I ~. .
j BROWNS - !. . 3 ' RIVER . Intak i
' ** j
,. NEARFIELD AREA QUT2KCf
SEABROOK ("? STATION IN +
, ........~i.disch arge HAMPTON 1 SEABROOK SUNK : l HARBOR ROCKS i L1' l l
\ SEABROOK _,
%% BEACH N/ .
SAUSBURY BEACH ; i LEGEND
= Lobsterlaryae (neuston) maammen P = Jonah and rock crab larvae (macrozooplankton)
L = Lobstertraps (15 traps) Figure 8-1. Epibenthic crustacea (American lobster, Jonah and rock crabs) sampling stations. Seabrook Operational Report,1995. 8-2
K0 EP.TBENTHIC CRUSTACEA measuring greater than 83 mm (3-1/4 in) were spp. larvae to determine differences between the classified as legal. The total numbers of males, fe- average abundances for the operational (1991-1995) males, and egg-beanng femalo were also recorded. and recent preoperational (1988-1989, when all three stations were sampled concurrently) periods at the hnpingement Collections nearfield, intake, and farfield stations. The year 1990 was deleted from the analyses because Seabrook See Section 5.2.2.4 for a description of impingement Stadon became operational in Aug'st of 1990, during collection procedures. the larval and adult sampling season. Monthly geometric means were calculated for lobster larvae 8.2.? Imhoratorv Mahas and for Cancer spp. larvae. The untransformed monthly arithmetic mean CPUE (no. per 15 traps) In the laboratory, lobster larvae (neuston) samples was used for juvenile ard adult lobsters and crabs were nnsed through a 1-mm mesh sieve, and sorted. for the preoperational (1982e 1989) and operational Iobster larvae (Stages I-IV) were enumerated and (1991-1995) periods. e a larvae were released into Hampton Harbor. Those samples that were not processed the day of A fixed effects ANOVA model was used to test collection were preserved in 6% formalin (NAI the null hypothesis that spatial and temporal 1991), differences dunng the preoperational and operational periods were not significantly (ps0.05) different. g Cancer spp. larvae from macrozooplankton samples The data for the ANOVAs met the criteria of a V were analyzed from three of the four tows (randomly selected) at each station for two of the four sampling Before-After/ Control-Impact (BACI)samplingdesign discussed by Stewart-Oaten et al. (1986) where periods each month (usually the first and third weeks). sampling was conducted prior to and during plant in the laboratory, each sample was split with a operation and sampling stations included both Folsom plankton splitter into fractions that provided potentially impacted and non-impacted sites. The counts of at least 30 individual Cancer spp. larvae. ANOVA was a two-way factorial with nested effects A maximum of 100 ml of settled plankton, generally that provided a direct test for the temporal-by-station 1/4 of the original sample volume, was analyzed. interaction. The main effects were period (Preop-Op) Cancer spp. larvae were identified to developmental and station (Station); the interaction term (Preop-Op stage and enumerated (NAI 1991). X Station) was also included in the model. Nested temporal effects were years within operational period In the laboratory, juvenile and adult Cancer spp. were (Year (Preop-Op)) and months within year identified, enumerated and sexed, and the carapace (Month (Year)). These terms were added to reduce width was measured to the nearest millimeter. In the unexplained vanance and increase the sensitivity addition, the number of egg-bearing females was of the F-test. For both nested terms, variation was recorded. partitioned without regard to station (stations combined). The final variance not accounted for 8.2.3 Anahtical Methods by the above explicit sources of variation constnuted the Error term. O An analysis of vanance (SAS 1985) was used on log (x +1) transformed densities oflobster and Cancer i 8-3
LO EPIBENTHIC CRUSTACEA l 8.3 RESULTS The increases in density in 1995 and the operational period, compared to the preoperational period, were , 8,3.1 American Lobster due mainly to increases in Stage IV larvae, histori- I cally the most numerous of tl.e four larval stages l Lobster Larvae (Figure 8-2). Stage I larvae were the second-most abundant in 1995 and during the preoperational and Annual mean lobster larvae densities in 1995 were operational periods. Stage II and Stage III larvae higher than preoperational (1988-1989) densities at have historically been least abundant, and none were each station, continuing the trends observed in 1991 collected in 1995. Stage I lobster larvae predommat-through 1994 (NAI 1992,1993,1995; NAI and NUS ed in the majority of other studies, mainly from 1994). Lobster larvae densities during 1995 were southern New Enghnt as reviewed by Fogarty and lower than operational mean (1991-1995) densities Lawton (1983). Stage IV larvae, however, were at Stations P2 and P7 (Table 8-1). Average larval most numerous in some years in Cape Cod and densities during the five-year operational period were Buzzards Bay, and Long Island Sound (Fogarty and sienificandy higher than the average densities during Lawton 1983), as well as in collections from the coast the preoperational period (Table 8-2). There were of southwestern Nova Scotia to New Hampshire no significant differences among the three stations (Harding et al.1983). These Stage IV larvae, during the 1988-1995 study period. The interaction including those in the study area, are hypothesized term (Preop-Op X Station) was not significant, to originate, at least in part, offshore in the warm inmening increases between the preoperational and waters of the southwestern Gulf of Maine and operational periods were consistent among stations. Georges Bank (Harding et al.1983, Harding and Trites 1988). Monthly trends in 1995 were similar to previous years (Figure 8-2). In 1995, high densities oflobster larvae Total Catch: Leenl- and Subleent-Sized occurred at the nearfield station P2 in June and July, while low densities occurred in May, September and The 1995 total catch per unit effort for lobsters at October. The timing of peak lobster larvae both the nearfield (LI) and farfield (L7) stations was abundance during the preoperational period was higher than the average CPUE for the preoperational consistent with other studies in New England, and operational periods (Table 8-1), and the highest k h% that peak abundances occur sometime from observed durmg the entire study period (Figure 8-3). July through August (Fogarty and Lawton 1983; In 1995, the monthly pattern in total CPUE at L1 NUSCO 1995). Other studies relate first appearance was similar to that observed in the preoperational of. lobster larvae with a surface temperature of and operational periods, with a peak in the late 12.5'C (Harding et al.1983), which typically occurs summer and fall (Figure B-2). However, the in June or July in the study area (Section 2.0). Newly- magnitude of the peaks in CPUE in 1995, especially hatched larvae require a sea water temperature above in the months of August through November, was . 10*C (50*F) to survive (Mariano 1993). Larvae much higher than either the preoperational or spend roughly one month in the water column, operational period means, molting three times before they settle to the bottom. l The frequency of molting atxt growth rate may Monthly variations in lobster catches were due in l increase with temperature (Mariano 1993). part to regional temperature changes. Warmer 8-4
O O O Table 8-1. Geometric Mean Abundance (Larvae: Lobster = NoJ1000 M2; Cancer Spp. = NoJ1000 M') or Arithmetic Mean Catch per Unit Effort (NoJ15 Traps) and the Coefficient of Variation (Cv,%) of Epibenthic Crustacea at Nearfield (P2, PS, L1) and Farfield (P7, L7) Stations During the Preoperational and Operational Periods and in 1995. Seabrook Operational Report,1995. PREOPERATIONAL' 19956 OPERATIONAL
- SPECIES ' STATION ' MEAN CV MEAN MEAN CV (period sampled)
Lobsterlarvae P2 0.4 22.7 0.6 0.9 24.9 (May-Oct) P5 0.4 33.3 0.9 0.8 23.9 P7 0.6 28.0 0.7 1.1 26.0 Lobster total L1 70.7 20.4 112.3 67.8 38.0 (Jun-No'v) L7 87.2 16.9 114.5 68.3 38.2 Lobster, legal L1 6.0 29.6 4.4 2.8 33.1 (Jun-Nov) L7 6.0 37.2 4.8 2.5 55.8 oo Lobster female L1 39.0 19.4 59.1 36.6 36.1
- 6. (Jun-No'v) L7 47.2 17.0 60.3 36.8 36.6 Lobster, e L1 0.6 17.1 0.4 0.5 24.7 (Jun-Nov)gg-bearing L7 0.6 31.8 0.7 0.7 25.5 Cancer spo. larvae P2 9 532.4 5.2 38,780.0 16,330.0 9.6 (May-Sep)" P5 5,063.9 5.6 25,588.3 11 712.9 8.3 P7 8'426.2
, 5.7 20,723.7 14,694.6 , 6.5 Jonah crab, total Li 12.3 52.7 10.2 12.7 21.1 (Jun-Nov) L7 9.4 31.4 3.0 5.4 58.7 Jonah crab, female L1 9.5 50.6 8.7 9.4 14.2 (Jun-Nov) L7 6.7 30.1 1.9 3.4 68.8 Rock crab, total L1 2.4 78.9 1.9 3.1 74.8 (Jun-Nov) L7 1.5 133.5 1.4 2.7 54.3 Rock cra female L1 0.5 119.4 16 1.9 129.4 (Jun-Nov L7 0.3 148.7 14 2.2 139.3 'Preoperational: Lobster larvae from Sta. P2-1978-89; Sta. P5-1988-1989; Sta. P7-1982-89; Cancer spp. larvae from Sta. P2-1978-84,1986-89; Sta. P5-1982-84 + Jul-Dec 1986 + 1987-89; Sta. P71982-84 + 1987-89; all others 1982-89.
6 1995 mean; mean of the total number of samples collected during the period sampled.
- Operational: 1991-95, mean of annual means.
' Sampled year-round but abundance computed for peak period (May - September).
Table 8-2. Results of Analysis of Variance Comparing Densities of Lobster and Cancer Spp. Larvac Collected at Intake, Nearfield, and Farfield Stations, and Catches of Total and Legal-sized Lobsters, Jonah Crab, and Rock Crab at the NearficId and Farlield Stations. Seabrook Operational Report,1995. SOURCE OF SPECIES VARIATION
- df MS P MULTIPLE COMPARISONS' lobsterlarvac Preop-Op 1 1.79 42.59' " Op> Preop (May-Oct) Station 2 0.03 0.48 NS Year (Preop-Op) 5 0.17 3.95 "
Week (Year) 129 0.32 7.68 *" Preop-Op X Station 2 0.07 1.69 NS Error 310 0.04 Lobster Preop-Op 1 34,266.73 42.07 "
- Op< Preop (total catch) Station 1 29,100.33 35.73* " L7>LI (Jun-Nov) Year (Preop-Op) 11 46,624.52 57.25* "
Month (Year) 64 29,137.51 35.78* " Preop-Op X Station 1 22,522.90 27.65* " 7 Pre 1 Pre 7001On . Error 1671 814.46 I:n Lobster Year 7 20,763.41 21.30 " * (total catch, Month (Year) 40 32,780.14 33.64 "
- preoperational Station 1 71,534.44 73.40 "
- period) Year X Station 7 5,812.21 5.96*"
Error 998 974.58 Lobster Preop-Op 1 4,069.98 424.20 "
- Op< Preop (legal size) Station 1 14.81 1.54 NS (Jun-Nov) Year (Preop-Op) 11 390.62 40.71 "
- Month (Year) 64 123.28 12.85 "
Preop-Op X Station 1 25.95 2.70 NS Error 1593 9.59 Cancer spp. Preop-Op 1 3.52 4.89 Op> Preop larvae Station 2 0.76 1.05 NS (May-Sep) Year (Preop-Op) 6 2.I 1 2.94 NS Month (Year) 32 7.15 9.94 NS Preop-Op X Station 2 0.12 0.16 NS Error 193 continued) O O (O
_ _ _ . . -.. . _ _ ._ ___ ~. _ O O O Table 8-2. (Continued) SOURCE OF SPECIES ' ' VARIATION
- df MS P MULTIPLE COMPARISONS *
(ranked in decreasing order) _. Jonah Crab Preop-Op 1 990.91 12.88 "
- Op< Preop (Jun-Nov) Station 1 10,885.09 141.49*** Ll>L7 Year (Preop- p) 11 1,707.82 22.20* "
Month (Year 64 1,143.73 14.87* *
- Preop-Op X tation 1 1,901.01 24.71 "
- 1 On 1 Pre 7 Pre 7 Op Error 1571 76.93 Jonah Crab Year 7 2,187.57 28.36* "
(Preoperational Month (Year) 40 1,411.19 18.30* " period) Station 1 2,180.16 28.27 "
- Year X Station 7 1,098.00 14.24* "
Error 1031 77.12 la - Rock Crab Preop-Op 1 165.15 9.89 " Op> Preop I (Jun-Nov) Station 1 150.72 9.02 " Ll>L7 ' Year (Preop- ) 11 351.76 21.06 "
- Month (Year 64 103.81 6.21"* :
Preop-Op X tation 1 38.76 2.32 NS Error 1570 16.71
- Preop-Op = Preoperational period (Lobster and Cancer spp. larvae, all stations: 1988,1989; Adult lobster and crabs: 1982-1989), Operational period: 1991-95 regardless of station or month.
Station = Station differences (Lobster and Cancer spp. larvac: P2, PS, P7; all others: Discharge (L1) and Rye Ledge (L7)) regardless of year, month or period. Year (Preop-Op) = Year nested within preoperational and operational periods regardless ofyear, month or station. Week (Preop-Op X Year) or Month (Preop-Op X Year) = Week or month nested within interaction of Preop-Op and Year. Preop-Op X Station = Interaction of main effects. Station X Year (Prcop-Op) = Interaction of station and year nested within preoperational and operational period. 6NS = Not significant (p>0.05)
* = Si ificant (0.052 p>0.01) "=H ly sigmficant (0.012 0.001) "*=V HighlySignificant 0.0012p) 'Underlinmg sigmfies no signi icant differences (as0.05) among least squares means with a paired t-test.
Lobster Larvae b. Preoperational and Operational l
- a. Monthly Trends Trends by Stage u am u -~ = *** =
as l" ou A l\ Iam ou
\
u y\ J,-. am u
;Is' / '
d r -- 1 c. 23412341234123412341234 I 8 5 SI
- u. = u **= se or saae Lobster (legal and sublegal)
- c. Totalcatch d. Legal-sized
.__ on w , .
_op ww 9
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s- o-m a an er oCr o a a a aP oCr O m m l 1 1 1 Figure 8-2. Freepdional mean and 95% ennM~a limits and 1995 and operational means of a. weekly , density (nol1000 m') oflobster larvae at Station P2, b. lobster larvae density by lifestage at P2,
- c. monthly CPUE (15 traps) of total (legal and sublegal) lobster at Station L1, and d. monthly CPUE (15 traps) oflegal-med lobster at Station L1. Seabrook Operational Report,1995.
8-8
R.
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Year [ Figure 8-3. a. Percentage and b. catch (per 15 trap effort) oflegal-sized and sublegal-sized lobster at Station L1 '" and c. size-class distribution at Station L1 from 1975 1995 Seabrook Operational Report,1995. 8-9
8.0 EPIBENTHIC CRUSTACEA temperatures, such as those measured in the Lecal-sized Lobster operational period and 1995 (Section 2.0), tend to increase the activhy level of adults, increasing the Dunng 1995, average CPUE of legal-sized lobsters probabilhy of hebg caught (McLeese and Wilder was higher than the operational average but lower 1958, Dow 1%9). In addition, temperature may thanthepreoperationalaverage. Legal-sizedlobsters affect seasonal lobster migrations (Campbell 1986). composed 4% of the average operational total catch In New Hampshire, adult lobsters are thought to move at both the nearfield station and farfield stations, inshore in spring and summer and offshore in fall lower than the preoperational averages of 8% and and winter (NHFG 1992). 7%, respectively (Table 8-1). During the five-year operational period, the average annual catch at both Despite the high catches in 1995, average CPUE stations was significantly lower than the preopera-declined significantly at the farfield station (L7) tional average (Tables 8-1, 8-2) There was no between the preoperational and operational periods, significant difference in CPUE between the nearfield but no significant difference occurred at the nearfield and farfield stations. As the decrease between the station (L1), resulting in a significant Preop-Op X preoperational and operational periods was consistent Station interaction term (Table 8-1; Table 8-2; Figure between stations, there was no significant interaction 8-4). term. The monthly pattern of legal-sized lobster catches in 1995 showed an August peak, similar to The BACI design assumes that stations exhibit the monthly patterns observed dunng the preoperational same trends in CPUE within the preoperational period (Figure 8-2). period. If trends between stations are different prior to plant start-up, the assumption of non-additivity Catches of legal-sized lobsters were affected by is violated and misleading significance may result fisheries regulations and environmental factors such (Smith et al.1993). To test this assumption, an as water temperature. The legal-size limit for lobsters ANOVA was calculated using CPUE only from the was increased in 1984,1989, and in 1990, and is preoperational period (Table 8-2). The significant currendy defined as a carapace length of 83 mm (3-Year X Station term during the preoperational period 1/4 in). Each increase in the legal size proportionally indicated a difference in trends in CPUE between reduced the catch oflegal-sized lobsters (Figure 8-3). stations during the preoperational period. Examina-tion of the annual CPUE time series indicated that Sir ss and Sex Distribution CPUE at the farfield station (L7) did not consistendy parallel that at the nearfield station (L1, Figure 8-5). The majority of lobsters collected at the nearfield CPUE at Station L7 appeared to be decreasing (with station in 1995 were in the 68-79 mm (2-5/8 1/8 the exception of 1990 and 1995) since monitoring in) carapace length size class, as was true in previous began in 1982. The significant Prop-Op X Station years beginnmg in 1981 (Figure 8-3). CPUE in this interaction term probably does not indicate a plant size class was the highest observed to date, for any effect because trends were present in the operational size class, contributing substannally to the high total period, and CPUE at Station L7 appeared to be lobster CPUE. lobsters measuring 5447 mm (2-1/8 - decreasinFbefore the plant became operational. 2-5/8 in) ranked second in abundance in 1995, similar to most previous years. 8-10
I I 4 ! 8.0 EPIBENTHIC CRUSTACEA } l G 100- l 0 . . . . . E'7 90 l
~...'-
} Bs ....,__ l g ao '. !
g . ' ..., 75 70- ' h es I So l . ss I I so 1 Pr + & e Operanonal i I PERIOD Figure 8-4. A comparison of the mean catch per unit effort (no. per 15 traps) for total lobster by station during the preoperational (1982-84; 1986-89) and operational (1991-1995) periods when the interaction , tenn (Preop Op X Station) of the ANOVA model was significant (Table 8-2). Seabrook Operational l Report,1995. l
\ l I
l a= '
........ut7
= : i so .... .... ,,', l v' -
l/ ',j
%e B
A 'l
..= s' e*
y .. l l l 5 30 I '-
,, ..-..... )
g
$5 !i ii lo l l
1 o neee ! ! operabonal 82 as 84 as as a7 as as so 91 92 as 04 es YEAR I Figure 8-5. Annual mean CPUE (no. per 15 traps) for total lobster 1982-1995 (data between the two dashed I l lines excluded from the ANOVA model). Seabrook Operational Report,1995. m U i 8 11 l
8.0 EPIBENTHIC CRUSTACEA In 1995, female lobster catch CPUE averaged 59.1 Impingement at the nearfield station, 53% of the total lobsters collected (Table 8-1). During the preoperational and In 1995,16 lobsters were impinged in the plant's operational periods, the proportion of females were cooling water system (Table 8-3). This is a decrease 55% avd 54%, respectively at the nearfield station, compared to 1994, when 31 lobsters were impinged. Similar proportions were observed at the farfield Rye In previous years impingement ranged from one to Ledge Station both in 1995 (53%) and during both 29 lobsters (Table 8-3), the preoperational and operational periods (54%). NHFG studies found that females were 52% of the 8.3.2 Jonah and Rock Crabs total legal-sized population in the New Hampshire coastal area (Grout et al.1989). Lar ae Egg-bearing female lobsters represented a small Cancerspp. (Cancerborealisand Cancerirroratus) component of the lobster population. In 1995. CPUE larvae had higher peak period abundances in 1995 averaged 0.4 at the nearfield station (L1), represent- than during the preoperational and operational periods ing 0.4% of the total catch. CPUE of egg-bearing at all three stations (Table 8-1). During the five-year females at Rye Ledge (L7) was slightly higher and operational period, the average density was averaged 0.7,0.6% of the total catch (Table 8-1). significantly higher than the preoperational average Duringthe preoperationalperiod, egg-bearing females (Tables 8-1, 8-2). Since the increase occurred at accounted for 0.8% of the total catch at the nearfield both the nearfield and farfield stations, it reflects an station, and 0.7 % at the farfield station. Egg-bearing area-wide increase and is not due to plant operation. females accounted for 0.7% (nearfield) and 1.0% The seasonal trend of occurrence at nearfield Station (farfield) of the total operational period catches. P2 in 1995 and for the operational period was similar NHFG studies (Grout et al.1989) found that 0.4 % to preoperational years. Densities were low from of 911 lobsters examined during lobster surveys of January through April. peaked from May or June New Hampshire coastal waters from 1983-1985 were through September, then decreased from October egg-bearing. through December (Figure 8-6). Densities in 1995 Table 8-3 NumberLobstersImpingedintheCoolingWatersystemofSeabrookStation Dunng 1990 Through 1995. Seabrook Operational Report,1995. YEAR NUMBER OF LOBSTERS IMPINGED 1995 16 1994 31 1993 1 1992 6 1991 29 1990 4 8-12
k
- c. Cancer spp. Larvc3 i
( m g
-\
. - s g, ___s I
; j ,e' \
1 [. i
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\, ,
j / g g f
/ '%,
s, j 2 I 1 . l l <% . 1 o s -_ - ? -
-4
- =. - - - .-- - , o
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i 4 k b. Jonah Crab ;
-:O - ~- =,.s
! = g ,-,- . . .
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, =
o
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- c. Rock Crab
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Figure 8-6. Monthly me== and 95% ennsdence intervals oflogiA+1) density (no11000 m') of
! a. Cancer spp. larvae at Ststion P2, and monthly mean catch per unit effort (15 traps) 4 of b. Jonah and c. Rock crabs at Station L1 during the preoperational period (1978-1984; i 1986-1989: larvac.1975-1984; 1986-1989: adults) and monthly means during the % operational period (1991-1995) and in 1995. Seabrook Operational Report,1995.
8-13 t
8.0 EPIBENTHIC CRUSTACEA were above the upper 95% confidence limit for the operational period, the proportion has varied from preoperational period in May through August. year to year, and averaged 77 % and 71 % at the near-and farfield stations, respectively(Table 8-1). Durmg Total Catch: Juveniles and Adults the operational period,74% of the Jonah crabs at the nearfield station were female, and 63% were The 1995 mean CPUE for Jonah crab (Cancerboreal- female at the farfield station. is) at both nearfield and farfield stations was lower than both the preoperational and operational averages Rock crabs (Cancer irroratus) were less abundant (Table 8-1). Highest catches in 1995 and the than Jonah crabs in the study area (Table 8-1), preoperational and operational periods at the nearfield probably a result of this species' preference for sandy station occurred in August. Monthly mean catches habitat rather than the cobble-rock that predominates l in 1995 were generally below preoperational and in the study area (Jefferies 1966) as well as intra-spe-operational means except October and November cific competition (Richards et al.1983). In 1995, (Figure 8-6), rock crab CPUE at the nearfield and farfield stations decreased from high catches observed in 1992 and
'Ihe nearfield and farfield stations exhibited different 1993 (NAI 1993; NAI and NUS 1994) wi were trends in CPUE between the preoperational and lower than preoperational averages (Table 8-1). In operational periods, resulting in a significant 1995, CPUE of rock crab peaked in July (Figure interaction term (Table 8-2). CPUE decreased 8-6). Average monthly CPUE in the preoperational significantly at the farfield station (L7), but was not period peaked in August, whereas monthly CPUE significantly different at the nearfield station (L1, during the operational period peaked in June and Figure 8-7). Examination of the annual time series generally declined in subsequent months. Average of CPUE at each station indicates that the reduction CPUE during the operational period was significantly in CPUE at the farfield station began in the mid higher than CPUE during the preoperational period, 1980s during the preoperational period (Figure 8-8). and average CPUE at the nearfield station was This is illustrated quantitatively by the significant significantly higher than at the farfield station (Table Year X Station interaction term for an ANOVA 8-2). The differences between the preoperational calculated on!y for the preoperational period (Table and operational periods were consistent at both 8-2). rk significant Year X Station interaction term stations, thus the interaction term was not significant.
during the preoperational period indicates that differing trends in CPUE between stations were Female rock crab CPUE in 1995 was lower than ! present in the preoperational period. Because there operational and preoperational means at both stations. was no change in CPUE at the nearfield station, and Female rock crabs composed approximately 20% the reduction in CPUE at the farfield station began of the average total catch at each station during the prior to plant start-up, there is no effect evidence preoperational period. The proportion wa; 19% of an of Seabrook Station's operation. (nearfield) and 22% (farfield) during the operational period, and 6 % (nearfield) and 14 % (farfield) in 1995 ( Trends in female Jonah crab CPUE paralleled those (Table 8-1). of total catch. Female crab catches in 1995 were i 85% and 63% of the total catches at the nearfield . l and farfield stations, respectively. During the pre-8-14
1 8.0 EPIBENTHIC CRUSTACEA j O 13
^
, ....O 11 10 a
g ..,,,_, g, ..
...'~-
g* , I. 3 2 1 0 W om PmoD Figure 8-7. A comparison of the mean catch per unit effort for Cancerborealis by station during preoperational (1982-1984; 1986-1989) and operational (1991-1995) periods for significant interaction term f)) (Preop-Op X Station) of the ANOVA model Seabrook Operational Report,1995. 26 - 1 I L1 24 l l *-+-* L7 22 l l 20 l 1 18 l i I i 16 I i I I a l g' # 10 ..- .. '- ., l , A 8 l 6 l ' '. rl . l I I 4 l t ' g l l ...* Preoperational l l Operational O 82 83 84 85 B6 87 88 89 90 91 92 93 94 95 YEAR 1 Figure 8-8. Annual mean CPUE (no. per 15 traps) for Jonah crab,1982 1995 (data between the two dashed lines excluded from the ANOVA model). Seabrook Operational Report,1995. ; 8-15
8.0 EPIBENTillC CRUSTACEA 8.4 DISCUSSION prohibiting harvest of egg-bearing females and V-notched females (marked while egg-bearing). Also 8.4.1 American Lobster the minimum legal size has been increased three times during the study period (1975-95). Even so, most Lobster larvae have traditionally been thought of as females that are legal-sized (mimmum carapace length strictly neustonic, although recent research suggests of 83 mm) have not attained sexual maturity (90-100 that they migrate vertically in waters above the mm) in the Gulf of Maine, (NH Fish and Game 1974, thermocline (Harding et al.1987, Boudreau et al. Manano 1993). Despite this fact, these regulations 1991). Lobster larvae could be exposed to the may have contributed to the slight increase in the discharge plume, which could influence larval sur- proportion of egg-bearing females during the vival, molting and successful bottom settlement (Stage operational period and re ,uited in increased numbers IV larvae only). Juvenile lobsters in the study area oflarvae, especially Stage I. As the increase in larvae are recruited from Stage IV larvae (the stage prior occurred at both the nearfield and farfield sites, it to benthic settlement), some of which are believed does not appear to be related to the operation of to originate offshore from w .ters of the southwest Seabrook Station. Gulf of Maine and Georges Bank (Harding et al. 1983). Although the level of juvenile recruitment Bottom-dwelling juvenile and adult lobsters would has been correlated with abundances of Stage IV most likely be susceptible to the potential effects of larvae (Harding et al.1982, Harding et al.1983), plant operation resulting from changes in their food others have failed to demonstrate this relationship source, which might arise from the effects of in-(Fogarty and Idoine 1986). Recent research indicates creased detritus and turbidity around the discharge that successful benthic recruitment of larval lobsters area. Temperature can also affect lobster activity, is affected more by the availability of suitable habitat likelihood of capture, and migratory behavior (Dow for the early benthic phase lobsters than by larval 1%9, Campbell 1986). However, changes in bottom abundance (Wahle and Steneck 1991). temperature resulting from Seabrook Station are un-likely because of the design of the discharge diffuser Lobster larvae have historically been relatively rare and the buoyancy of the discharge plume. 2 in the study area, averaging less than I per 1000 m , Average lobster larvae density during the operational Average total lobster CPUE at the farfield station period was sipifimMy higher than the preoperational decreased between the preoperational and operational average and between-period trends in density among periods, while no significant difference occurred at stations were consistent (Table 8-3). Densities of both the nearfield station, resulting in a significant Stage I and Stage IV larvae increased during the interaction term (Table 8-4, Figure 8-4). This ; operational period. Increases in Stage I larvae are differing trend in CPUE between stations was also likely related to increases in numbers of breeding observed in 1993 and 1994 (NAI 1995; NAI and NUS females, or in the success of their reproduction. In 1994). Decreases in lobster landings have been a study in Jaddore Harbor, Nova Scotia, presence correlated with temperature decreases in the current of Stage I larvae has been linked to the presence of year and after a six-year lag period (Fogarty 1988; breeding females (Dibacco and Pringle 1992). Campbell et al.1991). However, bottom water Regional fishing regulations have increased protection temperatures during the operational period were , of the lobster population over the past decade by significaraly warmer than bottom water temperatures 8-16
1 8.0 EPIBENTHIC CRUSTACEA Table 8-4. Summary of Potential Plant Effects on Abundance of Epibenthic Crustacea. Seabrook Operational Report,1995. 1 OPERATIONAL PERIOD DIFFERENCES BETWEEN : I SIMILARTO PREOPERATIONAL AND OPERA. PARAMETER PREOPERATIONAL PER. TIONAL PERIODS CONSISTENT MEASURED IOD' AMONG STATIONS 6 Lobster: Op> Preop Yes Larvae ! Lobster: Op< Preop nearfield: Op= Preop Total Catch farfield: Op< Preop Lobster: Op< Preop Yes
- Legal-Sized Catch l Cancer spp.
- Op> Preop Yes Larvae l 1 Jonah Crab: Op< Preop nearfield: Op= Preop Total Catch farfield: Op< Preop i
4 Rock Crab: Op> Preop Yes Total Catch V
' based on Preop-Op term of ANOVA model (Table 8-2)
- based on the interaction term (Preop-Op X Station) of the ANOVA model and multiple comparison test at a s0.05 (Table 8 2) in the preoperational period (Section 2.0). Thus, Average catches of legal-sized lobsters during the the decrease in CPUE oflobsters at the farfield station operational period were lower than preoperational cannot be totally explained by decreases in bottom catches, with similar trends at nearfield and farfield water temperatures. Regardless, the decrease stations (Table 8-4). Historically, in this study, occurred only at the farfield station, and is probably percentages of legal-sized lobsters have decreased not due to the operation of Seabrook Station. Total with each increase in the legal-size limit, as would lobster CPUE in 1995 was the highest recorded, be expected. The area-wide decline in legal-sized primarily due to record CPUE oflobsters in the 68-79 lobster CPUE observed in this study during the mm size class (Figure 8-5). During the operational operational period coincides with a regional decline.
period, CPUE at both the nearfield and farfield NOAA (1993) changed the status of the entire stations was virtually identical, indicating that the inshore / offshore population of lobster throughout factors affecting lobster CPUE were operating equally its range, Gulf of Maine (71 % of landings) through at both stations during this period (Table 8-1; Figure the mid-Atlantic, from " fully exploited" to "over-8-5). The high CPUE in the 68-79 mm size class exploited." Intense commercial fishing may in part i > may translate into higher catches of legal-sized account for the significant decline in legal-sized lobsters (283 mm carapace length) in future years. lobster catch at both stations during the operational 8-17
i 8.0 EPIBENTHIC CRUSTACEA period. In 1993, the NOAA Aut'unn Survey Index Jonah and rock crabs are taken incidentally in lobster (kg per trawl tow) decreased, and commercial traps and could be subject to the same potential for landmgs increased slightly. In response to the recent impact as lobsters. Average CPUE of Jonah crab increases in legal-size limits, fishermen have declined significantly at the farfield station between increased the number of pots fished inshore, as well the preoperational and operational periods, but no as the areas fished (NOAA 1995). Inshore landings change occurred at the nearfield station (Table 8-4). increased by 6 % between 1992 and 1993, due entirely However, the decline at the farfield station began to catch increases from Maine (NOAA 1995). In during the preoperational period and was not due 19N, NHFG (1995) reported a slight increase in legal to the operation of Seabrook Station. The significant lobster CPUE along coastal New Hampshire. difference in CPUE of rock crabs between the preoperational and operational periods occurred at Impingement of lobsters in the cooling water system both stations (Table 8-4), and was not due to the was not expected because of the off-bottom intake operation of Seabrook Station (Table 8-4). location. During the operational period (1990-95) 87 lobsters were impinged; nearly 22% (19) were
8.5 REFERENCES
CITED sub-legal sized lobsters impinged after a severe north-easterinNovember,1991. Thislevelofimpingement Boudreau, B., Y. Simard and E. Bourget.1991, does not pose a threat to the local lobster population. Behavioral responses of the planktonic stages of the American lobster Homarus amedcanus to thermal gradients, and ecological implications. There is no evidence that the operation of Seabrook Mar. Ecol. Prog. Ser. 76 13-23. Station has affected the lobster resources of the study area. Impingement of adults has been mimmal The Campbell, A. 1986. Migratory movements of distribution of larval lobsters, and legal lobsters has ovigerous lobsters, Homarus amedcanus, tagged ff Grand Manan, eastern Canada Can. J. Fish. been consistent among stations between the Aquat. Sci. 43:2197-2205. preoperational and operational periods. CPUE of total lobsters in 1995 was the highest observed in Campbell, A., O.J. Noakes and R.W. Einer. 1991. the study period. In the operational period, CPUE Temperature and Lobster, Romarus amedcanus, of total lobsters decreased at the farfield station, but yield relationships. Can. J. Fish. Aquat. Sci. 48:2073-2082. there was no change at the nearfield station. The change in distribution is probably not due to the Dibacco, C. and J.D. Pringle. 1992. Larval !obster operation of Seabrook Station because the decrease (Homarus amedcanus, H. Milne Edwards,1837) occurred only at the farfield station. distribution in a protected Scotian Shelf bay. J. Shell. Res. 11(1):81-84. 8.4.2 Jomh and Rock Crabs Dow, R. 1%9. Cyclic and geographic trends in seawater temperature and abundance of Cancer spp, larvae abundance were significantly Americanlobster. Science 164:1060-1063, higher during the operational period from the preoperational period (Table 8-4). The changes Fogarty, M.J.1988. Time series models of the Maine lobster fishery: the effect of temperature. indicate an area-wide trend that is unrelated to plant Can. J. Fish. Aquat. Sci. 45:1145-1153. operation. O 8-18
8.0 EPIBENTHIC CRUSTACEA 5 Fogarty, M.J., and J.S. Idoine. 1986. Recruitment americanus)in relation to temperature. J. Fish. dynamics in an American lobster (Homarus Res. Bd. Can. 15:1345-1354 americanus) population. Can. J. Fish. Aquat. Sci. 43:2368-2376. Mariano, M.1993. American lobster. NH Fish and Game and NOAA Agreement Fogarty, M.J., and R. Lawton. 1983. An overview #M9270R0188-01. 4p. oflarval AmericanlobsterRomarusamericanus, sampling programs in New England during 1974- New Hampshire Fish and Game Department
- 70. pp 9-14. In. M.J. Fogany (ed.) Distribu- (NHFG). 1974. Investigation of American tion and Relative Abundance of American Lobsters (Romarus americanus) in New Lobster, Homarus americanus, Larvae: New Hampshire Coastal Waters. 34 pp.
England Investigations Durmg 1974-79, NOAA Tech. Rep. NMFS SSRF-775. .1992. Monitoring of the American lobster resource and fishery in New Hampshire - Grout, D.E., D.C. McInnes and S.G. Perry. 1989. 1991. Performance Rep. submmed to the Nat. Impact evaluation of the increase in minimum Mar. Fish. Serv. Management Div. under con-carapace length on the New Hampshire lobster tract no. NA16FI-0353-02, 28 pp. fishery. N.H. Fish and Game Dept.
.1995 Monitoring of the American Harding, G.C., K.F. Drinkwater, and W.P. Vass. lobster resource and fishery in New Hampshire -
1983. Factors influencing the size of American 1994. Performance report submitted to the Nat. lobster (Homatur americanus) stocks along the Mar. Fish. Serv. Management Div. under con-Atlantic coast of Nova Scotia, Gulf of St. tract no. NA16FI-0353-03. 35 pp. Lawrence, and Gulf of Maine: a new synthesis. v Can. J. Fish. Aquat. Sci. 40:168-184. NOAA.1993. Status of the fishery resources of the northeastern United States for 1993. NOAA Harding, G.C., J.D. Pringle, W.P. Vass, S. Pearre, Tech. Memo NMFS-F/NEC-101. 140 pp. and S. Smith. 1987. Vertical distribution and daily movements of larval lobsters Romarus 1995. Status of the fishery resources americanus over Browns Bank, Nova Scotia. of the northeastern United States for 1994. Mar. Ecol. Prog. Ser. 41:29-41. NOAA Tech. Memo NMFS-F/NEC-108. Harding, G.C., and R.W. Trites. 1988. Dispersal Normandeau Associates (NAI).1991. Seabrook I of Homarus americanus larvae in the Gulf of Environmental Studies. 1990 Data Repon. ! Maine from Brown's Bank. Can. J. Fish. Aquat. Tech. Rep. XXII-I. Sci. 45:416r 425. l
. 1992. Seabrook Environmental )
Harding, G.C., W.P. Vass, and K.F. Drinkwater. Studies,1991. A characterization of environ- 1 1982. Aspects of larval American lobster mental conditions in the Hampton-Seabrook area l (Homatur americanus) ecology in St. Georges dwing the operation of Seabrook Station. Tech. I Bay, Nova Scotia. Can. J. Fish. Aquat. Sci. Rep. XX111-1. I 39:1117-1129.
. 1993. Seabrook Environmental Jefferies, H.P.1966. Panitioning of the estuarine Studies,1992. A characterization of environ-environment by two species of Cancer. Ecology mental conditions in the Hampton-Seabrook area 47(3):477-481. during the operation of Seabrook Station. Tech.
(' Meleese, D., and D.G. Wilder. 1958. 'Ihe activity and catchability of the lobster (Homanes 8-19 l l
8.0 EPIBENTHIC CRUSTACEA
. 1995. Seabrook Station 1994 Environmental Studies in the Hampton Seabrook Area. A Characterization. of Environmental Conditions During the Op: ration of Seabrook Station . Prepared for North Atlantic Energy Service Corporation.
Normandeau Associates (NAI) and Northeast Utilities Corporate and Environmental Affairs (NUS). 19M. Seabrook Environmental Studies,1993. A Characterization of Environmental Conditio.u in the Hampton-Seabrook Area During the Operation of Seabrook Station. Prepared for North Atlantic Energy Service Corporation. NUSCO (Northeast Utilities Service Co.). 1995. Lobster studies. Pages 123-147 in Monitoring the Marine Environment of Long Island sound at Millston- Nuclear Power Staticn. Waterford, CT. Annual Report 1994. Richards, R.A., J.S. Cobb, and M.J. Fogarty.1983. Effects of behavioral interactions on the catchability of American lobster, Romarus ; americanus, and two species of Cancer crab. Fish. Biol. 81(1):51-60. SAS Insutute, Inc.1985. User's Guide: Statistics, Version 5 edition. SAS Inst.,Inc. Cary, N.C. 956 pp. l l Stewart-Oaten, A., W.M. Murdoch, and K.R. l Parker. 1986. Environmental impact assess- I ment: 'Pseudoreplication in time?" Ecology. l 67:929-940. Smith, E.P., D.r. Orvos, and J. Cairns, Jr. 1993. Impact assessment using the before-after-control-impact (BACI) model; concerns and comments. ; Can J. Fish. Aquat. Sci. 50:627-637. Wahle, R.A. and R.S. Steneck.1991. Recmitment habitats and nursery ground of the American lobster Homarus americanus: a demographic bottleneck? Mar. Ecol. Prog. Series. 69:231-243. O 8-20
9.0 SOFT-SHELL CLAM (MYA ARENARIA) C (v TABLE OF CONTENTS i PAGE 9.0 SOFT-SHELL CLAM (MYA ARENARIA) l 1
SUMMARY
. . . . . . . . . . . ... . . . u i LIST OF FIGURES .
. . . . ...m LIST OF TABLES . .. . .. .. . . . . .. .
y
9.1 INTRODUCTION
.. . . . . . . . 9-1 9.2 METHODS .. . .. .. . . . 91
- 9.2.1 Bivalve Larvae . . ., . ... 91 l
. 9.2.2 Hampton Harbor Population Survey . . .. , . 9-1 9.2.3 Nearfield/FarfieldStudy . . ,, .. ... .. . .. 9-1 ; 9.2.4 Green Crab (Carcinus maenas) , , .. . . .. . . 9-4 9.2.5 Analytical Methods .. . . .... . . .. .
., 9-4 9.3 RESULTS . .. . . . .. . . . ... . . 9-4 9.3.1 Larvae ,. . . .. . . , , . . 9-4 s
9.3.2 Hampton Harbor Survey . . . . . . 9-5 9.3.3 Nearfield/Farfield Study . ... . . .. . 9-15 9.3.4 Effects of Predation and Perturbation . . .. . . .. . 9-15 9.3.5 Effects of Discharge .. .. . .. . . 9-18
- 9.4 DISCUSSION . . . . . . . ... . .. . , 9-18
9.5 REFERENCES
CITED . . . . . 9-21 1 6 4 O 9-i
9.0 SOFT-SILELL CIAM (MYA ARENARIA)
SUMMARY
Since Hampton-Seabrook estuary contams the majority of New Hampshire's stock of the recreationally important soft-shell clam, an extensive program has been undertaken to characterize the population of all life stages. Lan ae have typically been abundant in June and July, with a second, larger peak in late August and September. Larval densities during the operational period showed a seasonal cycle that was similar to previous years, but mean abundances were lower than the preoperational average at both nearfield and farfield stations. Adult soft-shell clam densities have been highly variable during the preoperational period, a result of varying recruitment success, variable predation levels, and the presence of disease. The closure of Hampton Harbor to recreational clamming from 1989-1994, a result of coliform contamination, eliminated a substantial source of mortality. Clammmg resumed at Flats 1 and 3 startmg in October of 1994, and continued intermittently in 1995, which reintroduced a significant source of mortality. Mean density of young-of-the-year clams (YOY) in 1995 was among the lowest recorded at Flats I and 4 and within the range of previous years at Flat 2. Spat, juvenile and adult densities in 1995 at all flats were within the range ofprevious yer rs. The Preop-Op X Station term was significant for all life stages (YOY, spat, juveniles and adults) indicating that trends in mean densities among flats were not consistent between the preoperational and operational periods. The density of YOY clams and spat decreased at flats 2 and 4 between the preoperational and operational periods, but no decrease was detected at Flat 1. Juvenile densities decreased between the preoperational and operational periods at Flats 1 and 4. In contrast, densities of adults increased significantly only at Flat 4 between the preoperational and operational period. The significant interaction terms for spat and juveniles did not appear to be biologically meamngful because the annual densities of these lifestages showed similar trends among flats. YOY and adult clams had biologically meaningful differences in trends among flats between the preoperational and operational periods that were not attributable to the operation of Seabrook Station. O 9-ii
9.0 SOFT-SHELL CLAM (MYA ARENARIA) A g LIST OF FIGURES PAGE 9-1. Bivalve larvae (including Afya arenaria) sampling stations. . ... ..... ... .. 9-2 9-2. Hampton-Seabrook estuary and Plum Island Sound soft-shell clam (Afya arenaria) and green crab (Carcinus maenas) sampling areas. where the abundance of clams has been high historically . . . . .... ... . ..... . . ... .........93 9 3. Weekly mean and 95% confidence interval of logio(x+1) density (no. per cubic meter) of Mya arenaria larvae at Station P2, during the preoperational (1978-1989) and operational (1991-1995) periods and in 1995. . .. .... . . . 9-7 9-4. Annual mean logio(x+1) density (number per square foot) of young-of-the-year (1 5 mm), spat (6-25 mm), juvenile (26-50 mm), and adult (>50 mm)Mya arenaria at Hampton Harbor Flat 4 from 1974-1995. , , , .. 9-9 9-5. Annual mean logio(x+1) density (number per square foot) of young-of-the-year (1 5 q mm), spat (6-25 mm), juvenile (26-50 mm), and adult (>50 mm)Mya arenaria at Hampton V Harbor Flat 2 from 1974-1995. . . . .. ... . . . ... . 9-10 9-6. Annual mean logio(x+1) density (number per square foot) of young-of-the-year (1-5 mm), spat (6-25 mm), juvenile (26-50 mm), and adult (>50 mm)Mya arenaria at Hampton Harbor Flat I from 1974-1995. .. . .. . 9-11 9-7. Compansons among flats of the meanlogic(x+1) density of clams 1-5 mm (number per square foot) during the preoperational (1974-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Area) of the ANOVA model. 9-12 9-8. Annual mean logio(x+1) density (number per square foot) of clams 1-5 mm, 1974-1995. . . . .. . . . .. . . 9-12 9-9. Comparisons among flats of the mean logio(x+1) density of clams 6-25 mm (number per square foot) during the preoperational (1974-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Area) of the ANOVA model. .. . . ... , , . .. . . . . , .. 9 13 9-10. Annual mean logio(x+1) density (number per square foot) of clams 6- 25 mm, O 1974-1995. .. . .. . . . . 9-13 V 9-iii
9.0 SOFT-SHELL CLAM (MYA ARENARIA) PAGE 9-11. Compansons among flats of the mean logio(x+1) density of clams 26-50 mm (number per square foot) during the preoperational (1974-1989) and operational (1990-1995) periods for the significant interaction term (Preop-Op X Area) of the ANOVA model. . .. . 9-14 9-12. Annual mean logio(x+1) density (number per square foot) of clams 26- 50 mm, 1974-1995. . . . . 9-14 9-13. Comparisons among flats of the mean logio(x+1) density of clams > 50 mm (number per square foot) during the preoperational (1974-1989) and operational (1990-1995) periods for the significant interaction tenn (Preop-Op X Area) of the ANOVA model. . .. .. 9-16 9-14. Annual mean logio(x+1) density (number per square foot) of clams > 50 mm, 1974-1995 .. . . . 9-16 9-15. Mean logio(x+1) monthly catch per unit effort and 95% confidence inten als of green crabs (Carcmus maenas) collected during preoperational years (1983-1989), operational years (1991-1995), and 1995 . . . . 9-17 9-16. Mean fall (October-December) catch per unit effort of green crabs in Hampton-Seabrook Harbor and its relationship to muumum winter water temperature from 1978-1995. 9-17 1 l I O 9-iv i l
9.0 SOFT-SHELL CLAM (MYA ARENARIA) 1,IST OF TABLES PAGE 9-1. Geometric Mean Density (number oflarvae per cubic meter; number ofjuveniles/ adults per square foot) and the Coeflicient of Variation (CV) ofAfya arenaria Collected During Preoperational and Operational Years and in 1995. . . , .. . . . . 9-6 9-2. Results ofAnalysis of Variance Comparing Affa arenaria Larval, Spat, Juvenile and Adult Densities During Preoperational and Operational Periods. . 9-7 9-3. Summary of Evaluation of Effects of Operation of Seabrook Station on Soft-shell Clam.
. . .. .. . , .. . .. . .. . 9-20 O
LJ 9-v
9.0 SOFT-SHELL CLAM (MYA ARENARIA)
9.1 INTRODUCTION
In the laboratory, samples were split when the total umboned bivalvelarvac count-aArd 300 specimens The objectives of the soft-shell clam (Mya arenaria and two subsample fractions were enumerated from Linnaeus 1758) monitoring programs are to detemune each sample. A more detailed description of methods the spatial and temporal pattems of abundance of can be found in NAl(1991). various life stages of soft-shell clams in the vicinity of Hampton Harbor, NH, and relate these patterns to 9.2.2 Hamnton U. arbor Pooula. tion Survev potential impacts from operation of Seabrook Station. Planktonic larval stages may be subject to impacts The five largest flats in the Hampton-Seabrook estuary from Seabrook Station due to entrainment through (Figure 9-2) were surveyed in the late fall from 1974-the ofIshore intake structure into the circriating water 1995 to obtain information on clams measuring at least system (see Section 4.3.2.3). Benthic stages (after 1 mm. Sampling sites within each flat were chosen settlement to the bottom) in the Hampton-Seabrook randomly. The number of stations sampled on each estuary may have been subjected to impacts from the flat was proportional to the variance in density ob-station's settling pond discharge, which ended in April served at that flat historically. Flats 3 and 5 were not 1994. Other factors unrelated to Seabrook Station sampled for clams greater than 25 mm in length, since that may affect the clam density, such as predation, the density has historically been extremely low, disease, and recreational clamnung were also consid-cred. Nearfield/farfield comparisons of seed clam Clams were grouped into the following size classes densities (1-12 mm) were made between Hampton based on length: Harbor and a nearby estuary, Plum Island Sound, , Ipswich MA. Young-of-the-year (YOY) 15mm Spat 6-25 mm 9.2 METHODS Juvenile 26-50mm Adult >50 mm 9.2.1 Bivalve Larvae A sample for 1-25 (YOY and spat) mm clams The spatial and temporal distributions of 12 species ' consisted of three 10.2-cm diameter x 10.2-cm deep of umboned bivalve larvae, including Mya arenaria, cores (4-in diameter x 4-in deep) taken within a 30-cm were monitored using a 0.5-m diameter,0.076-mm x 61-cm quadrat (1 ft x 2 ft). Samples were sieved mesh net. Samples were collected weekly from mid- with a 1-mm mesh sieve, and clams were enumerated, April through October at Hampton Harbor (P 1), intake measured, and released. A sample for clams >25 mm (P2), discharge (P5) and farfield (P7) statior > (Figure consisted ofone quadrat dug to a depth of 45 cm (1.5 9-1). Sampling began at Station P2 in Juiy 1976, ft) with a clam fork. Large clams were removed from Station P7 in July 1982, and at Station P1 in July 1986. the sediment in the field, enumerated, measured, and Collections were made at Station PS from July- released. December 1986 and April 1988 to the present. Two simultaneous two-minute oblique tows were taken at 9.2.3 Nearfield/Farfield Study each station. Upon recovery, net contents were pre-served with 1-2% borax-buffered fonnahn (with sugar To compare seed clam densities (1-12 mm), sun eys added to enhance color preservation) and refngerated. were conducted in the fall at 10 sites in both Hampton 9-1
N RYE LEDGE l o . . . . . .
. U1TLE BOARS '
HEAD l O .5 1 Nautical Mile 0 1 l 2 Kilometers $ - FARFIELD AREA l l SCALE { CONTOUR DEPTH 'V-I IN METERS I \ l h 3 GREATBOARS n , HEAD 9 HAMPTON '
,e ! BEACH b BROWNS -
RIVER
! P1h Intake *** l O
0, UTER y ' SEABROOK O [NEARFIELD AREA STATION 'Disch' arge fy gg ,, k... 1
- HAMPTON i
} SEABROOK SUNK l HARBOR ROCKS .
%, SEABROOK _ l
% BEACH
\ s /
N/ SAUSBURY BEACH LEGEND
= Bivalve Larvae Stations P1,P2,PS,P7 Figure 9-1. Bivalve larvae (including Mya arenaria) sampling stations.
Seabrook Operational Report,1995. 9-2
- - - - - . . .. . -- - -. - ~ .. . ~ - .. . ..--- - .. ..- .- - . - - - - . . -
4 M N M N y RAMPT VER
.) /
l BRonNS RWER "*, . 0 Q k'%& HAMPTON l'i% BEACH
~
M kh W
>- n Seabrook Station j -
,sy W ;k' ).jy . l;
;f 1
^ h "' , pj u? c;; a 1 $ SEABROOK MILL CRECK b)[j {; ;U BEACH g%ilt ) _ o /) fiI'.4$[ f i' ) N g ,[ NAUTICAL MILES l l i ISLES OF a } SHOALS co . HAMPTON - SEABROOK l ESTUARY ] D i l l MERRIMACK RIVER y PLUMISLAND SOUND 0 5 to (IPSWICH, MA) NAUTICAL MILES LEGEND
$ = Clam Flats g = Green Crab Traps
- g. = Spat Sampling Sites Figure 9-2. Hampton-Seabrook estuary and Plum Island Sound soft-shell clam (Mya arenaria) and green crab (Carcinus maenas) sampling areas. Seabrook Gi Operational Report,1995.
9-3
-- - . . - - . _ ~ _ -
9.0 SOFT-SHELL CIAbi(hiYA ARENARIA)
=
0 Harbor (Flats 2 and 4) and Plum Island Sound periods) variation. In addition, the interaction b: tween begmmng in 1976. Three cores were taken per station station or area and penod was investigated. If the inter-and processed using the same methods employed in action term (Preop-Op X Area) was found significant theHamptonHarborsurveydesenbedabove. Anaddi- (a s 0.05), the least squares means procedure (SAS tional 1-cm deep x 35-mm diameter core was taken 1985) was used to evaluate differences among means, for analysis of newly set soft-shell clam spat and significant interactions were presented graphically. (<l.0 mm). Sampling sites were fixed at locations The ANOVA for larvae used weekly means oflog shown in Figure 9-2. Hampton-Seabrook estuary and (x+1) density collected from 1988-1995,when all three Plum Island Sound soft-shell clam (Aff a arenaria) stations were sampled concurrently. The ANOVA and green crab (Carcinus maenas) sampling areas models for benthic stages used log (x+1) densities from were located where the abundance of clams has been the total number of samples taken from 1974 1995 high historically. in the Hampton Harbor survey, and from 1987-95 for the nearfield/farfield survey. 9.2.4 Green Crab (Carcinus maenas) 9.3 RESULTS Beginning in 1978, green crabs (Carcinus maenas Linnaeus 1758) were collected at four estuarine 9.3.1 Larvae locations on the penmeter offlat 2 in Hampton Harbor (Figure 9-2). The traps were set twice a month for Afya arenaria larvae occurred most weeks from late p 24 hours year-round except for February and March, May through October during preoperational years at ( when historically no crabs have been found. Two nearfield Station P2 (Figure 9-3). Maximum densities 13-mm mesh, baited crab traps were set at each station were typically recorded in late summer or early fall, : so that they were awash at mean low tide (NAl 1991). and a secondary peak usually occurredin early summer. 1 In 1995, no larvae were observed until the third week 9.2.5 Analvtical Methods in July, and peak abundances occurred in mid-September. This peak was approximately two orders Annual geometric mean density was computed based ofmagnitude larger than the preoperational average on the number of samples taken during any given year for mid-September, and was the highest weekly mean (n = number of samples). Preoperational and recorded at the nearfield station (Station P2) since operational geometric mean densities were based on 1978. Despite this single high peak in clam larvae the annual means (n = number of years sampled), to density, annual mean density in 1995 was lower than avoid variation caused by an uneven number of the operational and preoperational means at all three samples peryear. Means were plotted graphically and stations (Table 9-1). The overall operational mean examined for trends. was significantly lower than the preoperational mean (Table 9-2). Larval densities were not significantly A fixed effects analysis of variance (ANOVA) was different among stations, regardless of plant used on log (x+1) transformed density (n= number of operational status. Trends in lan al abundance between samples) to determine difTerences for the following stations remamed consistent during both the preopera-main effects: spatial (among stations or areas / flats), tional and operational periods and were not affected m temporal (among weeks (larvae only) and years), and by '.he operation of Seabrook Station. periodic (between preoperational and operational 9-4
1 9.0 SOFT-SIIELL CLAM (MYA ARENARIA) 5.0
-- TO
- ioss h 42 l
4.0 as l E t" ls lu l\\
="
g,o N ..
% / k bI 1
0.0 . f=1,i4N / 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
;/' \
\J ,
l Apr May Jun Jul Aug Sep Oct , 1 Figurc 9-3. Wecidymeanand95%mnfid-intervalofloggX+1) density (no.percubicmeter)ofMyaarenaria l larvae at Station P2, during the preoperational (1978-1989) and operational (1991-1995) periods and in 1995. Seabrook Operational Report,1995. O Sexual maturity in Mya arenaria is primarily a (late May-June) usually followed the appearance of function ofsize rather than age, with clams larger than larvn in offshore tows (early-mid May) (NAl 1985). 20 mm in shelllength capable of spawning (Coe and Therefore, the spring and early summer larvae may Tumer 1938). Clams north ofCape Cod usually spawn largelyoriginate from areas farther south. Historically, once per year in spring when the water temperature the late-summer peaks generally were coincident with reaches 4-6*C. Other factors wluch affect spawning northward-flowing currents. Recruitment oflarvae include adult condition and food availability (Newell of non-local origin is likely due to current patterns and Hidu 1986). Larval abundance is dependent upon in the Gulf of Maine, which may move water masses the number of adults spawning, the location of and their entrained larvae significant distances before spawning sites, larval behavior, coastal currents, water lanal settlement (NAl 1979). column stratification and other emironmental conditions. length oflife spent m the larval state is 9.3.2 Hamoton Harbor Survey approximately 12 days at 20*C, but lasts up to 21 days under cooler conditions (Tumer 1949). Youne-of-the-yea r n -S mm). This size class contains Planktonic larvae settle to the bottom after this period recently settled clams that have not yet experienced to become young-of-the-year (seed clams). a winter. Historically, YOY clam density has been highly variable. In 1995, mean densities ofyotog-of-Gonadal studies demonstrated that the onset of the-year (YOY) clams at Flat 4 were lower than both spawning in Hampton Harbor and Plum Island Sound the preoperational and operational averages (Table 95
w a p, G Table 9-1. Geometric Mean Density (Number of Larvae per Cubic Meter; Number of Juveniles / adults Per Square Foot) and the CoefUcient of Variation (Cv) of Mya Arenaria Collected During Preoperatienal and Operational Years and in 1995. Seabrook Operational Report,1995. PREOPERATIONAL" 1995 OPERATIONAL" , LIFESTAGE AREA MEAN* - CV MEAN* MEAN* CV Larvae P2 5.5 17.7 2.3 3.3 10.8 P5 5.0 12.0 2.4 3.0 26.0 P7 5.7 13.0 1.6 3.4 28.7 1-5 mm 1111-1 3.5 48.5 0.8 3.1 53.9 (young-of- IIII-2 8.6 58.8 6.1 5.0 37.1 the-year) 1111-4 10.5 43.8 0.4 3.4 62.7 All 6.4 49.0 1.3 3.6 46.9 6-25 mm IllI-1 1.7 127.8 0.3 1.2 96 3 P (spat) IIII-2 0.7 153.5 0.1 0.4 86.8 IIII-4 3.4 89.7 0.4 1.6 70.1 All 1.8 108.5 0.2 1.0 82.6 26-50 mm IIII-l 1.6 108.6 2.8 0.7 84.3 (juveniles) IIII-2 0.4 115.6 1.3 0.3 120.4 IIII-4 1.7 100.4 2.1 1.1 43.8 All 1.2 97.4 2.0 0.6 75.3
> 50 mm 1111-1 0.6 76.6 0.8 0.7 15.7 (adults) IIII-2 0.4 96.5 1.0 0.3 90.9 IIII-4 0.5 78.2 1.8 1.9 10.4 All 0.5 76.5 1.0 0.7 24.0 1-12 mm IIampton liarbor 5.7 70.8 6.2 6.1 72.9 (seed clams) Plum Is. Sound 17.1 68.5 3.0 7.5 83.1
' Larvae PREOP = 1988,1989; OP = 1991-95. Ilampton Ilarbor (1111) PREOP = 1974-1989; OP = 1990-1995.
Ilampton liarbor-Plum Is. PREOP = 1987-1989; OP = 1990-1995
- PREOP and OP means = mean of annual means.1995 mean = mean of the number of samples, i
Table 9-2. Results of Analysis of Variance Comparing Mya Arenaria Larval, Spat, Juvenile and Adult Densities During Preoperational and Operational Periods. Seabrook Operational Report,1995. MYA ARENARIA SOURCEOY LIFESTAGE STATION / FLAT VARIATION df MS F MULTIPLE COMPARISONS' (in decreasinP order) larvae' NEARFIELD (P2,PS)
- I 4.79 21.94* " Op< Preop FARHELD(P7) Yea 5 0.81 3 69**
Wee Q X Year)' 170 1.48 6.77 '" Station 2 0.16 0.74 NS Preopop X Station' 2 <0.01 0.02 NS Error 349 0.22 MP ON IIARBOR l-S mm* ,, Op I 21.09 47.59 "
- Op< Preop ypurg-of- Preop Year (Preop-Op) 20 10.39 23.44* "
the-year Area 2 12.09 27.28* *
- X Area 11.32* " 2 Pre 2 Oo I Pre 4 On 1 Op pat co @ ) 20 1 4 2 Area 2 1011 42.59 "
- Preop-Op X Area 2 1.15 4.85 *
- 4 Pre 4001 Pre 100 2Pic 20p
? a Error 1764 0.24 26 -50 mm* 1,2,4 Op 1 6.31 40.16 "
- Op< Preop juvenile Preop Year (Preop.Op) 20 10.50 66.76* " 412 Area 2 10.86 69.07' "
Preop-OpX Area 2 1.05 6.66 " 4 Pre IPre 40p IOp 2 Pre 2Op Error 3045 0.16
>50 mm' I,2,4 Op I 4.03 66.92 "
- Op> Preop c3 ult, Preop Year (Preop-Op) 20 1.85 30.77 " ' 412 legal Area 2 6.32 104.93 "
- OpX Area 2 4.73 78.63 "
- 4 Op 1 On 1 Pre 4 Pre 2 Pre 2 Op Preop Year (Preop-Op)X Area 3045 0.06 Error NEARFIELD/FAPFELD l-12 mm' IIampton Harbor Op 1 0.89 1.80 NS seed Plum Island Sound Preop Year (Preo@) 7 0.83 1.67 NS Area 1 2.60 5.25' FF>NF Preop-Op X Area i 1.24 2.50 NS Error 169 0.50
'Irrval comparisons based on weekly sampling periods, rnid-A where 'For iIampton Ilarbor Survey preop = 19 s4-89 and op 95.- For 1990pril through Octoberfd/Farf. d Surveyp - 1988,89 and op = 1991-95.
the Nearfie
= 1987-89 and op = 1990-95 NS - Not significant (p>0.05) mercial o * - Signifmant (0.052 01 .s t, juveniles,p-ration began and adults, but not forinlarvac.
August,1990, therefore the operational period includes 1990 for " = lbghly significant 01 >0.001
"* - Very highly signi cant ( .0012p))
rational versus preoperational penod regardless of area.
' Year nested within preoperational and operational periods, regardless of area. ' Week nested withm year regardless of area. 'Sttion or flat, regardless of year or penod. " Interaction of mam etTeets.
Underlining signifies no significant difTerences among least square means at alpha s 0.05. O O O
9.0 SOFT-SHELL CLAbf(AD'A ARENARIA) 9-1) and were the lowest recorded since 1974 (Figure The time series for spat density at all three flats 9-4). At Flat 2, mean densityin 1995 was higher than indicates that despite the significant interaction term, , the operational average, but lower than the the flats generally showed the same trends in density preoperational average (Table 9-1), and within the { from year to year (Figure 9-10). Spat density at all ! range ofprevious years (Figure 9-5). Mean density flats was high from 1977 through 1981, followed by of YOY clams at Flat I was lower than the alow density period from 1982 though 1989. Spat preoperational and operational averages (Table 9 1), density peaked in 1990 and 1994, and currently is at and was the second lowest recorded since 1974 (Figure a low level. The peaks in 1990 and 1994 were l 9-6), preceded by good sets ofYOYelams in 1989 and 1993 (Figure 9-8). Trends between the preoperational and operational periods differed among flats as indicated by the Juvenile (26-50 mm)mean densities at all flats in 1995 significant Preop-Op X Area term (Table 9 2). increased compared to 1994 (Figures 9-4; 9-5; 9-6) Average density ofYOY clams decreased significantly and werc higherthan the operational and preoperational between the preoperational and operational periods mean densities (Table 9-1). Densities at all flats were at Flats 2 and 4, but there was no decrease at Flat I within the range ofprevicus years. The relationship (Figure 9-7). This size class may undergo an in density among flats was not consistent between the appronmate three-year periodicity in abundance with preoperational and operational periods as indicated l peaks occurnng in 1976,1980-81,1984,1987,1990 by the significant Preop-Op X Area term (Table 9-2). l p and 1993 (Figure 9-8). In the operational period, Density decreased at all flats between the V densities of YOY clams showed similar trends among preoperational and operational periods, but the flats until 1995 when densities at Flats 1 and 4 decrease was significant at Flats 1 and 4 (Figure 9-11; continued to decrease, while densities increased at Flat Table 9-2). 2. The time series ofjuvenile densities shows that the Sont (6-25 mm) and Juveniles (26-50 mm1 Trends flats generally exhibited similar trends in density in the 6-25 mm size class indicate the survival success among years (Figure 9-12). Juvenile densities were of> bung-of-the-year (1-5 mm spat) that have over- highest from 1979 through 1983 and have generally wintered, and may also include some fast-growing been low since then until recent years. However, there young-of-the-year. In 1995, 6 25 mm size class has been a general increase injuvenile densities at all densities decreased in comparison to 1994 (Figures flats beginning in 1993. Despite the significant 9-4; 9 5; 9-6) but were within the range of previous interaction term, the flats appeared to exhibit similar years. Mean 1995 densities were lower than the temporal patterns ofjuvenile abundance among years. preoperational and operational periods at all three flats (Table 9-1). Trends in density between the Adults (>50 mm). Clams measuring more than 50 preoperatioral and operational periods were different mm are at least 4 years of age (Ayer 1968) and among flats as indi"*d by the significant Preop-Op considered adults in this study. In 1995, mean densities X Area term (Table 9-2). Density decreased of adults were higher than 1994 at Flats 1 and 2 but significantly at Flats 2 and 4 and there was no slightlylower at Flat 4 (Figures 9-4;9-5;9-6). Mean O d significant difference at Flat 1 (Figure 9-9). densities in 1995 were higher than the preoperational and operational means at Flats 1 and 2. At Flat 4, 9-8
MN$ Adult "" h D D 0 0 @ NO90 0 D 0 03 0.1 OA EO ODQ at 0.4 E4 E4 02 02 a2 at 0J R1 02 03 a4 a5 a4 a5 a5 Juvenile 26- s l D 0,D 00 D D hh h0D a4 al DA GD 0.7 to 12 L3 CJ a5 02 at al 0.1 02 02 a4 02 02 al E4 0.5 i
'~ 0 0 0 0 0 0 Young-of-the- 08 noE n*E t* '5htsBt2Et8 mo8Ba' ** Sol o at a43 a5 nr ai 02 a5 , a7 ai '- i--
si~lilillil Blisilesila ' 03 11 21 u 11 Os 14 u a7 11 tr Os as os 0.4 12 11 as at t1 u 02 , $ 74 s a n a a e a e a m m u 87 m a m m a e a m TAR l l Figure 9-4. Annual mer.n logm(x+1) density (number per square foot) of young-of-the-year (1-5 mm), spat (6-25mm), juvenile (26-50 mm), and adult (>50 mm)Mya arenaria at ifampton Harbor Flat 4 from 1974-1995. ; Seabrook OperationalReport,1995. , 9 . O O
~
O O O Adult SQ 0 0 0 0 00 SUQ 0 0 0 0 0 0 0 0
/ 03/ Elf OS/ 0.0/ 0.0/ R1] 03/ 02/ 02f E5l R3l R1/ R1l 0.0/ 0.0/ R0f GDf 0.1/ 0.1l R1/ Elf R3]
Juvenile a-m Q a a a h D D @ a 0 a a D 0 0 0 a h j02lt0]OD/60/03 -64l G4 0.1l L1/ 0.4/ 02/ 0.0l GDj GDj CDj tof GDj a1] S0j 0.0/ 03l 0.4l Spat 6-5 g y y Q Q g g g g g g g g Qg g Q g I "81 08 m "8 m u aas, uf at , n1, a1, a0,f a1 88/ _ "8tJ u fa1 ni, 02f , c0,. at , a2f as nD Young-of-the-
" 8 0 $
f DDj 05) tij 13] 0.6l 09f 2.0l 2.1f DBf tof L1l L1] 0.6f 69) 03l L1/ 12l 0.6l 64l t0l 0.6l L8 9 14 n n n n n a a n a M m n u a a % m a a M % 5 wm Figure 9-5. Annual mean logio(x+1) density (number per square foot) ofyoung-of-the-year (1-5 nun), spat (6-25 nun), juvenile (26-50 mm), and adult (>50 mm)Mya arenaria at Hampton Harbor Flat 2 fmm 1974-1995. Seabrook OperationalReport,1995.
'!/!hhhkl!i!!!!2/!hhhhalti!!!/:l!/
. hkl:ltild!!!ilithhhhhhilkhleill "hhtlill!/lullu:hhh:hid!hhallhi 1-3 0 h
/ as/ as/12/12f osf as/ nef caf o.3/ a7/ tof a4f o.4 o.4/ 02/ as/ 11/ a4f a4/ o.7/ aaf 02/
~
74 s a n a a e a e e M e m 87 m a a m a m a m WAR l l l l c(2 50 ) (>5 )M an atI p Har Flat f l 7 -19 5 Seabrook OperationalReport,1995. O O O
l 9.0 SOFT-SHELL CLAM (MYA ARENARIA) l r% l ( < 'b/ 1.1
= )
*% Flat 1 .
N*k 4 . . . . . + RW 2
+ ~ -
- FW 4 f,o 0.9 $'"...,
s, f, 0.8 '. ....." " .... , 0.7 s's ) 0.6
's -
0.5 i I 0.4
$ 0.3- ,
E ' g 0.2 0.1 l 0.0 Preoperanona! Operational PERIOD Figure 9-7. Compansons among flats of the mean logw(x+1) density of clams 1-5 mm (number per square foot) during the preopera'ional (1974 1989) and operational (1990-1995 periods for the significant I mteraction term (Preop-Op X Area) of the ANOVA model. Seabrook Operational Report,1995. NY l 2.6 i ; _ g j 2., j . . . . . . . nat 2 i
; +- --* -
- Rat 4 g 2.2 i nn 2.0 g\ ***** l g\ '
\
12 1
\ l
/*\ 4 l
/ ".,I l 1.6 /\
I' 'I - , I \ l b lt g . I \ Y' :I \ ;; I 1.2 I. \ l 1.0 t l sj
\ , .'
t I: A I I \. L
,f.\
0 t '. \ f80.6 1
\ll C' Y
/\ l': . ( '...
g . *
\ I: s* 7 s 0.4 1
- 1. l i V I \
0,2 i i 0.0 m Op h 74 75 76 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 YEAR Figure 9-8. Annual mean logdx+1) density (number per square foot) of clams 1-5 mm,1974-1995. Seabrook p Operational Report,1995. ( 9-12
9.0 SOFT-SHELL CLAM (MYA ARENARIA) l 1.0
- Flat 1
+ - . . . * +
FW 2 0.9 _. _ pg 4 0.8 g E 0.7
-.s*-,,
0.6 ' i I b 0.5 's s l 0.4 % ' ' . c::= 0.3 * - .
+
E 02 . - - - . . . . . _ ' ' ' ' ' -- ' " --...
- ~... ,
0.1 - 0.0 Prec@ eL =1 Operational PERIOD Figure 9-9. Comparisons among flats of the mean logifx+1) density of clams 6 25 mm (number per square foot) during the preoperational (1974-1989) and operational (1990-1995 periods for the significant mteraction term (Preop-Op X Area) of the ANOVA model. Seabrook Operational Repon,1995. .}}