ML20206G455
| ML20206G455 | |
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|---|---|
| Site: | Seabrook  |
| Issue date: | 12/31/1997 |
| From: | NORMANDEAU ASSOCIATES, INC. |
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| References | |
| NUDOCS 9905100022 | |
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SEABROOK STATION 1997 ENVIRONMENTAL MONITORING IN THE HAMPTON-SEABROOK AREA A CHARACTERIZATION OF ENVIRONMENTAL CONDITIONS DURING THE OPERATION OF SEABROOK STATION Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station
-Seabrook,New Hampshire 03874 Prepared by NORMANDEAU ASSOCIATES 25 Nashua Road Bedford, New Hampshire 03310-5500 Critical reviews of this report were provided by:
THE SEABROOK STATION ECOLOGICAL ADVISORY COMMITTEE: Dr. John Tietjen, Chairman (City University of New York) Dr. W. Huntting Howell (University of New Hampshire) Dr. Bernard McAlice (Emerhus, 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 l Waterford, Connecticut 06385-0128 September 1998 Printed at Seabrook Station . Cover: Original watercolor of Seabrook Station painted by Geoffrey Kingston, Seabrook Station Nuclear Oversight. L
TABLE OF CONTENTS SECTION 1.0 - EXECUTIVE
SUMMARY
SECTION 2.0 - WATER QUALITY SECTION 3.0 - PHYTOPLANKTON SECTION 4.0 - ZOOPLANKTON SECTION 5.0 - FISH SECTION 6.0 - SEALS SECTION 7.0 - MARINE MACROBENTHOS SECTION 8.0 - EPIBENTHIC CRUSTACEA SECTION 9.0 - SOFT-SHELL CLAM SECTION 10.0 - APPENDIX A
1.0 EXECUTIVE
SUMMARY
TABLE OF CONTENTS PAGE 1.0 EXECUTIVE
SUMMARY
LIST OF FIGURES . . . . . . . . ... .. . .. 1-ii LIST OF TABLES . , . . . . .. .. ... .. . ... . 1-ii 1.1 APPROACil., .. ... .. . ..... .. . .. ..... .. . 1-1 1.2 STUDY PERIODS . . . . . .. . . . . . . .. .. . 1-5 1.3
SUMMARY
OF FINDINGS . . ... . . . . . . . 1-6 1.4 LITERATURE CITED . . . .. . . . . . . ... . .. .. 1-18 l-i
1.0 EXECUTIVE
SUMMARY
LIST OF FIGURES PAGE l-1. Sequence of events for determining if there are environmental changes due to the operation of Seabrook Station. . . . . . 1-2 LIST OF TABLES 1-1. Summary of Biological Communities and Taxa Monitored for Each Potential Impact Type. Seabrook Operational Report.1997 . . ... ... .... ..... 1-3 1-2. Monthly Characteristics of Seabrook Operation for the Period 1990 Through 1997. Seabrook Operaaonal Report,1997 .. . . . . . 1-6 1-ii
1,0 EXECUTIVE
SUMMARY
1,1 APPROACH shown to cover a relatively small 32-acre surface area (Padmanabhan and Hecker 1991). Because Environmental monitoring studies were con- of the surface to mid-water location of the plume, ducted to determine whether Seabrook Station, temperature differences do not extend below the which became operational in August of 1990, thermocline. Due to its location within the water affected the " Balanced Indigenous Populations of column, the intake is also expected to have only Fish, Shellfish and Wildlife" in the nearfield a localized effect. This impact is quantified by coastal waters of New Hampshire. A biological the entrainment and impingement sampling monitoring program established under the Na- programs. tional Pollutant Discharge Elimination System (NPDES) permit, jointly issued by the Environ- A basic assumption in the monitoring program is mental Protection Agency and the state of New that there are two major sources of natural-Hampshire, forms the framework for study. occurring variability: (1) thr.1 which occurs among different areas or stations, i.e., spatial, A systematic approach of impact assessment was and (2) that which varies in time, from daily to used to determine whether the operation of weekly, monthly or annually, i.e., temporal. In Seabrook Station has affected the aquatic biota. the experimental design and analysis, the Sea-This approach incorporated both temporal and brook Environmental program has focused on the spatial components for each biological commu- major source of variability in each community nity evaluated (Figure 1-1). Potential operational type and then determined the variability in each effects could be ruled out if: (1) results from the community. The frequency and spatial distribu-operational period were similar to previous tion of the sampling effort were determined based (preoperational) years, given the natural variabil- on the greatest sources of variability for each ity in the system, or (2) differences within 'he parameter (NAI 1991). operational period were observed in b i nearfield and farfield areas. In addition, other Biological variability was measured on two potential sources of change have been investi- levels: species and community (Table 1-1). A gated before the conclusions specified within this species' abundance, recruitment, size and growth report were drawn. This study design was are important for understanding operational modeled after objectives discussed by Green impact, if any, should changes occur in these (1979), which have been described previously in parameters between stations or over time. These more detail (NAl 1991). parameters were monitored for selected species from each community type. Selected species The validity of the impact assessment model is were chosen for more intensive study based on based on comparisons between nearfield stations either their commercial or numerical importance, within the influence of Seabrook Station and at sensitivity to temperature, potential as a nuisance farfield stations beyond its influence. Modeling organism, or habitat pn.ference. Overall com-studies, as well as operational validation, clearly munity structure of the biota, e.g., the number l show this to be true for thermal effects. The and type of species, total abundance and the extent of a +3*F (1.7*C) isotherm has been dominance structure, was also reviewed to deter 1-1
SEQUENCE OF EVENTS FOR DETERMINING IF THERE ARE ENVIRONMENTAL CHANGES DUE TO OPERATION OF SEABROOK STATION is Operational Period similar to YES p No previous years Impact at nearfield station 7 NO V Operational na ed YES No similar to Impact farfield
?
NO V Observed changes NO No related to >- impact plant operation 7 YES Y Operational Impact Figure 1-1. Sequence of events for determining if there are environmental changes due to the operation of Seabrook Station. Seabrook Operational Report,1997. 1-2
1.0 EXECUTIVE
SUMMARY
Table 1-1. Summary of Biological Conununities and Taxa Monitored for Each Potential Impact Type. Seabrook Operational Report,1997. 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 !arvae x x Impingement Juvenile / Adult fish x x Lobster adults x Discharge Thermal Plume Nearshore water quality x Phytoplankton x x Lobster larvae x Intertida!! shallow subtidal macroalgae and macrofauna x x Subsurface fouling community x x Turbidity Mid-depth / deep macrofauna (Detrital Rain) 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 mine potential plant impact. Trends in these current study continues to focus on the likely parameters were reviewed against the natural sources of potential influence from plant opera-variation in community structure. tion, and the sensitivity of a community or pa-rameter to that influence within the framework of A previous Summary Report (NAI 1977) con- natural variability (Table 1-1). A community or cluded that the balanced indigenous community species within the study area might be affected by in the Seabrook study area should not be ad- more than one aspect of the CWS. Results from versely influenced by loss of individuals due to this monitoring program will be discussed in light entrapment in the Circulating Water System of that aspect of the cooling water system that has (CWS), exposure to the thermal plume, or expo- the greatest potential for affecting that particular sure to increased particulate material (dead component of the biological community. En-organisms) settling from the discharge. The trainment and impingement are addressed 1-3
1.0 EXECUTIVE
SUMMARY
through in plant monitoring of the organisms tion, Year (Preop-Op), Time (Year), (e.g., week entrapped in the CWS. or month) and Error. The term Preop-Op had two levels: preoperational and operational. This The effects on the balanced indigenous popula- term compares data collected during the tions of aquatic biota near the CWS intake and preoperational to operational periods regardless discharge structures were evaluated through of other sources of variation such as Station. A continued monitoring at sampling stations estal>- significant Preop-Op term does not indicate a lished during the preoperational period, with plant impact, but rather an area-wide trend at statistical comparison of the results at both the both the nearfield and farfield areas, where the community and the species levels. The null farfield area is presumably beyond the influence hypothesis in all tests is that there has been no of the plant. The Station term compares data change in community structure or selected spe- collected from the sampling stations throughout cies abundance or biomass that is restricted to the the study period, both preoperational and opera-nearfield area. This in turn would indicate, tional periods. A significant Station term indi-based on the approach outlined in Figure 1-1, cates a difference between the nearfield and that the balanced indigenous populations have not farfield areas; by itself it does not suggest a plant been affected. Analysis of variance (ANOVA) effect because the data span both the was an important statistical method used in the preoperational and operational periods. Seabrook Environmental Studies Monitoring Program to determine whether the operation of The Preop-Op X Station term (interaction term) Seabrook Station has had any adverse effects on was the most important term in the analysis, as it the local marine balanced indigenous populations. alone could indicate potential plant impact. A The ANOVA model used in the monitoring significant interaction term indicated a significant program was based on Green's (1979) Before- difference occurred during the operational period After, Control-impact (BACI) principles. In the that was restricted to only one of the areas BACI model, samples are taken both before and (nearfield or farfield). The remaining terms, after the potential effect, and in both control and Year (Preop-Op) and Month (Year), were nested impact areas. In the Seabrook Monitoring Pro- terms that explained some of the temporal varia-gram, the Before and After terms are represented tion in the data and improved the fit of the by data collected during the preoperational and model. The error term included all the variation operational periods, and the Control and Impact not explained by the model, terms are represented by data collected in nearfield and farfield areas. The advantage of A change in the conununity composition, or the BACI model is that potential impacts are abundance of a selected species that did not occur indicated by the significance of the interaction at all stations leads to the following questions: term of time (Before-After) and location (Control-Impact). 1. Is there a mechanism for a potential plant impact? A mixed model, randomized block design
- 2. What species (in community analyses)
ANOVA was used with the following sources of are responsible for the observed change? variation: Preop-Op, Station, Preop-Op X Sta-1-4
1.0 EXECUTIVE
SUMMARY
- 3. Did the change begin before 6e A of this report for comparison with the mixed initiation of plant operation, or is model.
it possibly part of a long-term trend? 1.2 STUDY PERIODS
- 4. Is the change possibly caused by an unrelated environmental vari- Environmental studies for Seabrook Station able? began in 1969 and focused on plant design and siting questions. Once these questions were
- 5. What is reported in the recent literature or by investigators in res lved, a monitoring program was designed to the region? assess the temporal (seasonal and yearly) and spatial (nearfield and farfield) variability during Results of further investigations of significant the preoperational period as a baseline against differences in community composition or a single which conditions during station operation could species' abundance, density or biomass are be evaluated. This report focuses on the developed by the section author, then reviewed preoperational data collected from 1976 through by a peer with technical expertise in the area of 1989 for fisheries studies and from 1978 through investigation, then reviewed by the Project 1989 for most plankton and benthic studies.
Manager and Corporate Officer. Following these During these years, a consistent sampling regime reviews, the report sections are reviewed by and the addition of a farfield station provided the NAESCo, Northeast Utilities Environmental background to address the question of operational Laboratory, and the Ecological Advisory Com- effects. mittee. Commercial operation of Seabrook Station began All sources of variation, except Preop-Op, were intermittently in July and August 1990, and considered random because they represented a continued for periods of approximately three small fraction of all the possible times and loca- weeks in September and October. Therefore, tions of sampling (Underwood 1994). Preop-Gp August 1990 is considered the beginning of the was considered a fixed variable because there operational period for the purposes of this envi-were only two possible levels (preoperational and ronmental assessment. After operation at 100% operational) and both levels were sampled. The for less than a week at the beginning and end of use of both random and fixed variables makes the November, the plant operated nearly continu-model a " mixed" effects model, as opposed to a ously from December 1990 through July 1991
" fixed" model ANOVA where all sources of when it was shut down for routine maintenance.
variation are considered fixed. Further discus- Resumption of full power operation began again sion of the differences between the mixed and in October 1991 and continued through a second fixed effects model are found in Appendix A of maintenance outage in late September 1992. Full NAI(1995). The results of the mixed model are power operation began again in November 1992 presented in the main body of the report because and continued with only minor interruptions it is considered more appropriate for our study throughout 1993. In 1994 the plant was opera-design (Underwood 1994). The results of the tional from January through early April, and fixed model ANOVA are presented in Appendix August through December. The plant continued 1-5
r 1.0 EXECUTIVE
SUMMARY
at full operation in 1995 except for short outages tion Circulating Water System had a measurable in June and November. Except for short outages effect on the physical or chemical characteristics in January and February 1996, and a refueling of the water column. Water quality samples outage in May and June 1997, the plant operated were obtained within the vicinity of Seabrook's nearly continuously in 1996 and 1997. Monthly intake and discharge structures, and at farfield characteristics of the Circulating Water System locations outside of the influence of operation. operation throughout 1990-1997 are presented in Measured parameters included temperature, Table 1-2. salinity, dissolved oxygen, and nutrients (total phosphorus, orthophosphate, nitrate, nitrite, and 1.3
SUMMARY
OF FINDINGS ammonia). lYater Ouality Potential impacts to water quality related to the operation of Seabrook Station include: (1) Water quality parameters were collected to aid in temperature changes resulting from the discharge interpreting information obtained from the bio- of a heated cooling water from the Station con-logical monitoring program, as well as to deter- densers, (2) the discharge of chlorine (sodium mine whether the operation of the Seabrook Sta- hypochlorite) used to prevent the settlement and Table 1-2. Monthly Characteristics of Seabrook Operation for the Period 1990 Through 1997. Seabrook Operational Report,1997. Days of Circulating Water Average Daily System Operations Flow (mgd) N1onth 1990 1991 1992 1993 1994 1995 1996 1997 1990 1991 1992 1993 1994 1995 1996 1997 Jan 31 31 31 31 31 31 31 31 324 5&4 585 587 566 576 570 578 Feb 28 28 29 28 28 28 29 28 5 64 580 578 587 589 572 507 565 Mar 31 31 31 31 31 31 31 31 563 580 581 580 573 572 573 571 Apr 30 30 30 30 30 30 30 30 563 581 576 579 352 573 577 572 May 31 31 31 31 24 31 31 31 562 581 581 582 188 625 637 345 Jun 30 30 30 30 25 30 30 30 563 578 593 582 171 662 686 235 Jul 31 31 31 31 31 31 31 31 582 535 593 578 331 685 689 662 Aug 31 21 31 31 31 31 31 31 588 253 583 579 681 687 691 674 Sep 30 26 29 30 30 30 30 30 588 257 314 574 696 686 691 672 Oct 31 31 24 31 31 31 31 31 590 552 159 574 690 685 678 673 Nov 30 30 30 30 30 21 30 30 590 590 566 612 692 287 647 666 Dec 31 31 31 31 31 31 31 31 589 391 563 608 628 486 599 668 1-6
1.0 EXECUTIVE
SUMMARY
accumulation of biological fouling organismswithin magnitude less than seasonal variations observed the Circulating Water System, and (3) associated during a single year. There is no reasonable changes related to the addition of moribund mechanism by which the withdrawal of bottom entrained plankton to the nearshore marine water from the intake area, and its subsequent environment, release as heated effluent into the discharge area, could reduce surface salinity in the intake and discharge areas. The water massesin the intake and in 1997, mean surface water temperature at each discharge areas are essentially identical and the station (P2 and P7: 9.2 *C; PS: 9.4) was lower than salinity of this water mass cannot be changed by 1996 at all stations, but higher than the pre- passage through the plant. Annual mean bottom operational mean at Stations P2 and P7. Annual water salinity in 1997 was consistent among stations mean bottom water temperatures in 1997 at each (31.7 PSU) and lower than the operational and station were 7.3 'C. These levels were lower than preoperational means. There were no significant the 19% and operational period means, but higher differences between periods or among stations. than the preoperational period mean at Station P2 and P7. The annual mean surface and bottom temperatures were significantly warmer during the Surface and bottom dissolved oxygen concentrations operational period, but these differences were exhibited a seasonal pattern in 1997 that was similar consistent at all stations. There were also to previous years. Surface dissolved oxygen (DO) significant differences among stations that were in 1997, (P2 and P7 : 9.9 mg/1; PS: 100 mg/l) was , consistent between the preoperational and higher than the operational and preoperational operational periods. Surface water temperature was means at all stations. Surface dissolved oxygen highest at the discharge station, which was higher levels decreased at all stations between the than the intake station, which in turn was higher preoperational and operational periods, but the than the farfield station. This consistency between decrease was smaller at the discharge station, periods and among stations indicated that the indicating a potential plant effect. However, the operation of Seabrook Station has not significantly observed changes are the opposite from those that affected surface or bottom water temperaturesin the might be expected from a thermal discharge. A study area. potential plant effect might be indicated by a significantly larger decrease in dissolved oxygen at the discharge station relative to the otherstations, as Annual mean surface water salinities in 1997 (P2: heated effluent reduces the oxygen content of the 31.3 PSU; PS: 31.2 PSU; P7 31.1 PSU) were lower surrounding waters. Bottom DO in 1997 (P2: 9.3 than or equal to the preoperational and operational mg/1; P5: 9.4 mg/1; P7 9.3 mg/l) was higher than period means. There was a significant decrease both the preoperational and operational period (0.2 to 0.4 PSU) in mean surface salinity at the means. There were no significant differences intake and discharge stations between the between periods, or among stations. preoperational and operational periods, but no significant decrease at the farfield station, resulting in a significant interaction term. These decreases There were no significant differences between the were statistically significant, but an order of preoperational and operational periods or among 1-7
1.0 EXECUTIVE
SUMMARY
stations, for nitrate, nitrite, orthophosphate, total through February and June through December phosphate, and ammonia. during the preoperational and operational peri-ods, while the Prymnesiophyceae alga Most water quality parameters showed a distinct Phaeocystis pouchetti dominated during March seasonal cycle that was consistent throughout the and April. In 1997 however, P. pouchetti was monitoring period. Significant differences the annual dominant, accounting for 31 % of the among years were typical, reflecting high year- total community. This is not a unique occurrence to-year variability. Increases or decreases in all as peaks in P. poucherti density also occurred in parameters, except for surface salinity and dis- 1978,1979,1981,1983,1992, and 1994. The solved oxygen, were consistent between nearfield community composition in 1997 was different and farfield stations, indicating that the chemical from the preoperational and operational periods and physical environments in the study area are due to the dominance of P. pouchetti, but there dominated by larger regional trends. were no major differences in community compo-sition between the preoperational and operational Phytoplankton periods. Total phytoplankton geometric mean abundance in 1997 (14.0-21.8 X 10' cells /L) was The phytoplankton monitoring program was higher than both the preoperational and opera-initiated to identify seasonal, annual, and spatial tional means because of the spring bloom of P. trends in the phytoplankton community and to pouchetti. The abundance of the selected spe-determine if the operation of Seabrook Station cies (Skeletonema costatum) in 1997 (0.1 - 0.2 X had a measurable effect on this community. The 104 cells /L) was lower than the operational purpose of the monitoring program was to deter- period, but similar to the preoperational period. mine if the balanced indigenous phytoplankton Chlorophyll a concentrations were variable from community in the Seabrook area has been ad- year to year but were similar to the versely influenced, within the framework of preoperational and operational periods in 1997 natural variability, by exposure to the thermal (0.62 - 0.79 mg/m'). Chlorophyll a concentra-plume. Specific aspects of the community evalu- tions were not related to phytoplankton abun-ated included phytoplankton (taxa 210 pm in dance as increases in phytoplankton abundance in size) abundance and species composition; com- 1992,1994, and 1997 did not cause an increase munity standing crop as measured by chlorophyll in chlorophyll a concentrations. PSP was not a concentrations; abundance of selected species detected in Hampton Harbor in 1997. Through-(Skeletonema costatum); and toxicity levels of out the operational study period, there were no paralytic shellfish poison (PSP), as measured in outbreaks of PSP restricted to New Hampshire, j the tissue of the mussel Mytilus edulis in the consistent with recent research pointing to a non-t Hampton-Seabrook area. local origin. Monthly abundances of phytopiankton during the There were no significant differences in total operational period showed seasonal patterns that phytoplankton abundance, abundance of S. were similar to the preoperational years. On costatum or chlorophyll a concentrations between average, diatoms (Bacillariophyceae) dominated the preoperational and operational periods or the phytoplankton assemblage during January among stations. In all cases the interaction term 1-8
1,0 EXECUTIVE SUhfMARY (Preop-Op X Station) was not significant, indicat- similar among stations and between operational ing no impact due to the operation of Seabrook periods. Station. The bivalve larvae community in the Zooplankton preoperational and operational periods was generally similar. In every year, the community Three components of the zooplankton commu- progressed from a Hiatella sp.-dominated com-nity, microzooplankton, bivalve larvae, and munity to the Mytilus edulis and Anomia macrozooplankton, were sampled separately to squamula-dominated community. Some differ-identify spatial and temporal trends at both the ences between the preoperational and operational community and species level. Initial monitoring periods were detected. Groups unique to each characterized the source and magnitude of varia- period occur ed, but the duration and frequency tions in abundance and species composition in the of these groups were limited to a few collection zooplankton conununity and provided a template periods. MANOVA results indicated that al-for comparison to data obtained during the though significant differences in species abun-operational period. The zooplar.kton community dances occurred during the operational period, is currently evaluated to determine whether they occurred at all stations, indicating an area-entrainment within the Circulating Water System wide change. There were no significant differ-(CWS) of Seabrook Station has had a measurable ences between periods or among stations in the effect on the community or any species. The abundance of the selected species Mytilus edulis. entrainment of bivalve larvae within the CWS has also been evaluated. Entrainment collections provide a measure of the actual number of organisms directly affected by Microzooplankton species composition during the Station entrainment. The total number oflarvae operational period continued to resemble the entrained in 1997 (6,366 X 10') was less than historical patterns. While the abundances of numbers entrained in recent years. Entrainment some taxa were different between the operational of Mya arenaria was higher in 1997 (54 X 10') and preoperational periods, these differences than previous years (0.2 X 10' to 33 X lb ), were generally consistent between stations. A reflecting high nearshore abundances. The significant Preop X Station interaction term was nearshore community has remained relatively detected for adult Eurytemora herdmani and stable over time and there is no evidence that copepodites of Eurytemora sp. Record high entrainment has resulted in decreased numbers of abundances in one of the three preoperational bivalve larvae in nearshore waters. There was years (1983) contributed to the significant inter- no indication that entrainment within the CWS action term for both the copepodites and adults. has affected the balanced indigenous bivalve However, since the anomalous year was in the larvae community in the nearshore waters. preoperational period, and mean abundance at each station was similar during all other years, To understand community dynamics better, the the significant interaction is probably not due to macrozooplankton was divided into two compo-Station operation. Abundances of the other nents. A holoplankton and meroplankton compo-microzooplankton selected species were generally nent was defined as organisms that spend their 1-9
1.0 EXECUTIVE
SUMMARY
entire or a distinct portion of their life in the geneia inermis. Seasonally the hyperbenthic water column. Hyperbenthic zooplankton, the community composition showed no differences other component, was defined as organisms that between the preoperational and operational live on or near the bottom. periods, although MANOVA indicated differ-ences in abundance. Spatial rather than seasonal The holoplankton and meroplankton component patterns determined the hyperbenthic community, was dominated by the copepods Calanus The selected species, Neomysis americana, finmarchicus, Centropages typicus, showed no significant differences between the Pseudocalanus sp., and Temora longicornis, preoperational and operational periods. For each larval decapods and larval barnacles. component of the hyperbenthic community, no Preoperationally, the community composition of effects that could be attributed to station opera-the holoplankton and meroplankton was variable tion could be detected. from February through April. During the opera-tional period, this period of variability shifted to Fish Populations January and February, followed by a consistently-recurring community in March and Finfish studies at Seabrook Station began in 1975 April. MANOVA detected differences between to investigate all life stages of fish, including periods for the holoplankton and meroplankton ichthyoplankton (eggs and larvae), juveniles, and abundance. These differences were consistent adults. Potential impacts of Seabrook Station among stations indicating area-wide affects. operation on local populations include the en-trainment of eggs and larvae through the Circu-Of the selected species, a significant Preop X lating Water System and the impingement of Station interaction term was detected for the adult larger specimens on traveling screens within the Calanusfnmarchicus. Abundances decreased at Circulating Water pumphouse. Local distribution all stations in the operational periods, but the could also potentially be affected by the thermal decrease at the farfield station (P7) was greater. plume, with some eggs and larvae being sub-The relative relationship among the three stations jected to thermal shock due to plume entrainment was similar in both preoperational and opera- upon discharge from the system diffusers. The tional periods as to rank and changes in magni- main objective of the finfish studies is to assess tude, except for 1993. This consistency among whether the operation of Seabrook Station has stations indicates that the significant interaction had any measurable effect on the nearshore fish term is probably not due to station operation. population. Differences in the abundance of adults had no effect on the copepodite stages of C. Ichthyoplankton analyses focused on seasonal fnmarchicus. Abundances of the other selected assemblages of both eggs and larvae, as well as species were similar between the preoperational on the larvae of selected species. Consistent and operational periods. temporal (among months and years) and spatial (among stations) egg and larval assemblages The hyperbenthic community was dominated by identified through the monitoring programs the mysids Mysis mixta and Neomysis americana, suggest that the operation of Seabrook Station has ! and the amphipods Oedicerotidae and Ponto- not altered the seasonal spawning time nor the 1-10
1.0 EXECUTIVE
SUMMARY
distribution of eggs in the Hampton-Seabrook Marine Mammal Protection Act and the program area. Although the temporal occurrence of fish was ended to prevent any additional takings. larvae, both monthly and annually, was less NAl (1998) contains the most recent summary consistent than for eggs, spatial parameters were and analysis of gill net data. ! consistent. Ichthyoplankton composition at all three stations was very similar within each year The geometric mean CPUE (catch per 10-minute and month. Temporal changes in assemblage tow) of demersal fish at all stations combined in abundances were consistent at all three stations. 1997 was 14.6, a decrease from the CPUE of 18.2 in 1996. Longhorn sculpin, winter floun-Among the selected species, changes in larval der, and skates were the dominant fishes in the ~ density were consistent between l the operational period compared with yellowtail preoperational and operational periods at all flounder, longhorn sculpin, and winter flounder stations, indicating no effect due to the operation in the preoperational period. CPUE of most of Seabrook Station. fishes, especially commercially important spe-cies, declined between the preoperational and Entrainment of eggs in 1997 (692.6 X 106) was operational periods. Yellowtail flounder showed the lowest recorded for years wilen 12 months of the greatest decrease in CPUE from 9.3 in the sampling occurred. The most numerous eggs preoperational period to 1.7 in the operational 6 entrained in 1997 were silver hake (271.1 X 10 ), period. Similarly CPUE of winter flounder, 6
- cunner /yellowtail flounder (186.1 X 10 ), and hakes, and Atlantic cod decreased between hake (68.6 X 10*). These three taxa are typically periods. The decrease in CPUE of these species among the most numerous eggs entrained, except has been attributed to commercial overfishing for 1994 when no samples were collected during (NOAA 1995). CPUE of skates increased from the summer. Silver hake egg entrainment in 1.9 to 2.4 between periods, while there were 1997 was the highest recorded to date. Entrain- small changes in the CPUE of windowpane and ment of cunner /yellowtail flounder and hake eggs pollock, were within the range of previous years.
CPUE decreased between the preoperational and 6 Entrainment of larvae in 1997 (373.4 X 10 ) was operational periods for all of the selected demer-the highest recorded to date. The most numerous sal species, but the decrease did not occur larvae entrained in 1997 were cunner (203.8 X equally at all stations resulting in a significant 10'), silver hake (69.0 X 1(f), and rock gunnel interaction term. Our BACI study design as-6 (25.1 X 10 ). sumed that if there were no plant impacts, trends Entrainment of cunner and silver hake was the in abundance, either increases :,r decreases highest recorded, while rock gunnel entrainment would occur equally at all stations. However, a , was within the range of previous years. significant interaction term could also be caused by a large-scale environmental change that The gill net monitoring program was suspended occurred concurrently with plant operation on 19 March 1997 as a result of the capture of a (Smith et al.1993). A largeocale change could harbor porpoise in a gill net sample on 18 Febm- be a region-wide perturbation such as overfish-ary. This capture constituted a taking under the ing, climate change, disease, or another regional 1-11
1.0 EXECUTIVE
SUMMARY
factor. Under these circumstances, a significant impingement occurred mostly in November interaction term would result because CPUE (65%) and consisted of fish between 8 and 14 would be reduced to very low levels at all sta- cm. These fish were probably early spawned tions, including stations where it had previously YOY. Winter flounder impingement occurred been high. Any potential plant impact due to the primarily in January through April (55%), and operation of Seabrook Station either did not October through December (44%). The winter occur, or was not detectable in the face of over- flounder impinged in January through April were fishing. YOY and yearling fish less than 16 cm while the fish impinged in October through December The geometric mean CPUE (catch per haul) for consisted mostly of YOY fish less than 10 cm estuarine fish caught at all stations in 1997 de-creased to 10.5 com 17.1 in 1996, ending a For the period 1994 through 1997, the most trend of increasing CPUE that began in 1992. numerous fish impinged has been Atlantic silver-Average catches etc ich during the operational side (8,298) followed by grubby (6,980), winter period compared with the preoperational period, flounder (6,305), rainbow smelt (5,612) and a result of diminished catches beginning in 1987. hakes (5,288). These five taxa represent 49% of The Atlantic silvercide dominated catches in all the total impingement at Seabrook Station. years sampled. Winter flounder, killifishes (mummichog and striped killifish), ninespine The design of the Seabrook Station offshore stickleback, and rainbow smelt also contributed intake with a mid-water intake fitted with a to the catch. CPUE of all these fishes decreased velocity cap has apparently resulted in similar or between the preoperational and operational fewer numbers of fish being impinged when periods. Only CPUE of American sand lance compared to other coastal power plants. increased between periods. Annual trends in the CPUE paralleled fluctuations in catch of the Seal Entrapment dominant species, Atlantic silverside. An estimated 36 to 42 seals have been entrapped During 1997, an estimated 10,628 fish and 20 by Seabrook Station's cooling water intakes lobsters were impinged on the traveling screens between 1993 and 1997. Seals entrapped were the at Seabrook Station, the lowest annual estimate harbor seal (Phoca vitulina), harp seal (Phoca since 1994. Most fish were impinged in Novem- groenlandica), hooded seal (Cystophora cristata), ber (57%) followed by April (15%), and October and gray seal (Halichoerus grypus). In 1997, an (8 %). Alewife (2,797) were the most common estimated nine YOY seals were entrapped, includ-fish impinged, followed by windowpane (1,688), ing seven harbor seals and two gray seals. These winter flounder (468), rock gunnel (459), and seal entrapments are considered incidental lethal grubby (430). The alewife impingement oc. takings under the Marine Mammal Protection Act curred primarily (98%) in November and con. and have been reported to the National Marine sisted of young-of-the-year (YOY) fish between Fisheries Service (NMFS), Northeast Region, the 8 and 13 cm. These alewife were probably federal agency responsible for the protection of impinged as they left local rivers and headed for marine mammals. Since 1993, necropsies of seal offshore overwintering areas. Windowpane remains have been performed by the New Eng-1-12
1.0 EXECUTIVE
SUMMARY
land Aquarium, which also has the lead responsi- areas. Preoperational studies described temporal bility for administering the Marine Mammal and spatial patterns in species abundance and Stranding Network for the region. identified physical and biological factors influ-encing observed variability. Operational studies The entrapment of seals in recent years coincides have focused on evaluating any changes in the with increased numbers of seals observed along distribution and abundance in the macrobenthic the nearby coastline and the overall growth of the community and its dominants in light of the seal population in the Gulf of Maine. Based on operation of Seabrook Station. Possible impacts the large seal population in the region and the include temperature-related changes in areas small number of seals entrapped by the Station's potentially exposed to the buoyant thermal cooling water intakes, the operation of Seabrook plume, the intertidal and shallow-subtidal sta-Station has had and is anticipated to have a negli- tions. Thermal impacts would be unlikely at gible effect on the population or stocks of seal deeper stations; however, suspended solids and species. entrained organisms in the discharge plume could potentially increase turbidity and sedimentation, In June 1997, North Atlantic submitted to the adversely affecting benthic organisms. National Marine Fisheries Service an application for a small take exemption permit for the inciden- Potential Thermal Effects tal taking of a small number of seals as a result of l Station operations. In August 1998, the National Hydrodynamic modeling and subsequent field Marine Fisheries Service published in the Federal verification studies have indicated that intertidal Register, for public comment, a proposed rule locations showed no temperature increase related which would grant the exemption permit. to Seabrook Station; shallow subtidal areas showed temperature increases of < 1"F In parallel with the permit application, North (Padmanabhan and Hecker 1991). Intertidal atlantic conducted studies to determine if there is community composition was stable throughout an effective, implementable means to eliminate or the monitoring period. Of the community param-minimize seal entrapments without jeopardizing eters tested (total biomass, total abundance, Station safety or reliability. These studies in- number of taxa), only one showed a change cluded structural barriers on the intakes and between the preoperational and operational acoustic deterrent devices. periods that differed between nearfield and farfield areas. Number of algal taxa in the inter-Marine Macrobenthos tidal zone decreased between the preoperational (nearfield: 15.6 taxa; farfield 22.2 taxa) and Horizontal rock ledge is the predominant benthic operational periods (nearfield 14.7 taxa; farfield habitat near Seabrook Station's intake and dis- 19.5 taxa), and the decrease was greatest at the charge. These rocky surfaces support a diverse farfield station. The decreasing trend at both community of attached macroalgae and stations began before the initiation of plant macrofauna. Studies were started to identify the operation, suggesting it was unrelated to Sea-species inhabiting nearby intertidal and subtidal brook Station. rock surfaces in nearfield and farfield control 1-13
1,0 EXECUTIVE SUMMARl' Of the selected species studied in the intertidal abundance of selected dominant faunal species, 7one, the dominant algae, Chondrus crispus, and in the biomass of dominant understory alga dominani fannat taxon, Mytilidae, showed no Chondrus crispus, or in ti.e frequency of domi-significant change in abundance throughout the nant kelp species Lominaria saccharina occurred I study period. Dominant fucoid species during the operational period. Frequency of the Ascophyllum nodusum and Fucus vesiculosis subdominant kelp species Laminaria digitata showed inconsistency among stations between showed differing trends between stations and periods, suggesting a potential plant effect. A. between periods, decreasing at the nearfield nodusum continued to be the dominant fucoid station and showing no change at the farfield species, and annual trends at the nearfield and station. The relatively low densities and low farfield stations tracked each other closely. percent cover of L. digitata at both stations There is no indication that the operation of suggest that it is limited by some biological or Seabrook Station has affected this species. physical factor in this zone. There was no appar-Frequency of occurrence of F. vesiculosis under- ent relationship between densities of L. digitata went a substantial decline in 1986 and 1987, and its dominant consumer, the green sea urchin before plant start-up, at both the nearfield and Strongylocentrotus droebachiensis in the shallow farfield stations, but the decline was more sub- subtidal zone. The increasing presence of the stantial and significant at the nearfield station. introduced epiphytic Membranipora membrana-Frequencies began increasing in 1996 at both cea has been observed in the Gulf of Maine and stations, suggesting observed trends are part of a is thought to have a negative impact on kelp natural cycle. populations (Lambert et al.1992). This epiphyte may be affecting kelp in the study area. Given All but one of the macrofauna selected species the weak presence of L. digitata in the shallow showed no significant density changes between subtidal zone during all the years of the study, it the preoperational and operational periods in the is likely that even a minor change in physical or intertidal zone. Density of the amphipod biological factors could have been sufficient to Ampithoe rubricata increased significantly at the cause the decline. Additional studies are being farfield station between periods, but no signifi- undertaken in 1998 to determine if there any cant difference occurred at the nearfield station. thermal impacts from Seabrook Station in the However, the changes in density began well shallow subtidal zone. before plant operation and appear to be unrelated to Seabrook Station. Potential Turbidity Effects In the shallow subtidal benthic community, no Community structure, abundance, and biomass of changes have occurred that could be related to dominant species in the mid-depth zone have the operation of Seabrook Station. Community shown few changes during the operation of parameters, including the number of faunal taxa Seabrook Station. Community parameters includ-and total abundance, and number of algal taxa ing number of faunal taxa, total algal biomass, and total biomass, as well as results of commu- and total faunal density, showed no change nity analysis, showed no significant changes between periods. The number of algal taxa between periods. No significant changes in increared slightly, but significantly, at the dis-1-14
1.0 EXECUTIVE
SUMMARY
charge and farfield stations, but remained un- bers of faunal and algal taxa showed no signifi-changed at the intake station. The three stations cant differences between the preoperational and have generally tracked each other closely until operational periods. In the macroalgae commu-1995, when the farfield station began to have nity analysis, the communities observed from the higher numbers of taxa. Algal community deep discharge station in 1996 and 1997 were composition in the mid-depth zone was stable more similar to a community formed from collec-thre.ughout the operational period. tions from the deep intake station than to earlier discharge communities. These shifts in the deep The mid-depth macrofauna community during the subtidal zone were probably the result of natural operational period was similar to the pre-opera- variability. tional period with a few exceptions. Species composition at the mid-depth farfield station in Epibenthic Crustacea 1996 and 1997 was similar to that at the nearfield stations except for decreased mytilid and Lacuna The objective of the epibenthic crustacea moni-vincta densities and increased Anomia sp. abun- toring program was to determine the seasonal, dance, creating a unique assemblage that did not spatial, and annual trends in larval density and . , occur during the preoperational period, catch per unit effort (CPUE) for juvenile and
- adult stages of American lobster (Homarus At the species level, nearfield-farfield relation- americanus), Jonah crab (Cancer borealis) and ships changed over time only for the kelp species rock crab (Cancer irroratus). Analyses were Laminaria digitata. Densities declined at both done to determin- ;f the discharge from Seabrook nearfield and farfield stations, but to a greater Station had any measurable effect on these spe-extent in the nearfield. The cause of this decline cies.
remains unclear, although grazin6 b the green sea urchin, Strongylocentrotus droebachiensis Lobster larvae densities during 1997 (0.8 to could be a factor. These two species had a 1.1/1000 m') decreased from 1996 and were statistically significant inverse relationship in the lower than both the preoperational and opera-farfield area. L. digitata is at its physiological tional means. Despite the decrease in 1997, limit with respect to water depth at the nearfield lobster larvae density was significantly higher in station, and competition with the dominant kelp the operational period at all stations. Monthly Agarum clathratum is likely affecting L. digitata patterns c." mean lobster larvae density were population levels. While the interplay of physical similar between the preoperational and opera-and biological factors are currently not fully tional periMs, and in 1997. understood, it is unlikely that Station operation is a factor because no other plant or animal species Catch of lobsters (total and legal) was adjusted to exhibited a similar response that might reflect a standard soak time of two days (CPUE,). , impacts from increased turbidity levels. CPUE: declined between the preoperational (79.3) and operational (76.7) periods at the The deep subtidal communities were also largely farfield station, but increased at the nearfield consistent between stations and communities. station from 64.0 to 74.8. The differing trends in ! Average total density, total biomass, and num- CPUE2between the two stations may in part be 1-15
1.0 EXECUTIVE SUMbfARY related to a large increase in commercial and was lower than the preoperational and opera-recreational lobstering activity in the nearfield tional averages at the nearfield station while the area, which may be providing a food source and opposite occurred at the farfield station, indicat-habitat for sublegal lobsters. CPUE2 of total ing no effects due to the operation of Seabrook lobsters in 1997 (117.1) was the highest observed Station. Despite these differences in 1997, there to date, primarily due to large catches of sublegal were no significant differences between periods, lobsters, continuing a trend that began in 1995. or between stations for rock crabs. The relation-CPUE2 of legal-size lobsters was significantly ship in rock crab CPUE between stations was lower in the operational period (2.4) than in the consistent between the preoperational and opera-preoperational period (5.5) at both stations, likely tional periods. Rock crabs have been less preva-a result of increases in the legal-size limit and lent than Jonah crabs throughout the study area, commercial overexploitation. The monthly trend probably because of their preference for sandy of CPUE 2in 1997 for total and legal lobsters was substrate, which is rare in the study area, similar to that observed during the preoperational period. Soft-Shell Clam in 1997,20 lobsters were impinged in the Sta- The objectives of the soft-shell clam (Mya tion's Circulating Water System. A total of 138 arenaria) monitoring programs are to determine lobsters have been impinged since the station the spatial and temporal patterns of abundance of began operation in 1990. The current level of various lifestages of Mya arenaria in the vicinity impingement does not pose a serious threat to the of Hampton Harbor. Pelagic lifestages may be indigenous population. subject to impacts from Seabrook Station opera-tion due to entrainment into the Circulating Abundances of Cancer spp. larvae in 1997 Water System. Benthic stages (after settlement to (16,478-23,768/1000 m') were higher than the p- the bottom) in the Hampton-Seabrook estuary reoperational and operational periods at all may have been subject to impacts from the stations. The average density during the five- Station's Settling Basin discharge, which was year operational period was not significantly eliminated in 1994. Nearfield/farfield compari-different from the preoperational average, and sons of clam densities are also made between there were no significant differences among Hampton Harbor and a nearby estuary, Plum stations. The 1997 mean CPUE (catch per 15 Island Sound, Ipswich, MA. traps) for Jonah crab (farfield 4.1; nearfield 14.7) was higher than the preoperational and opera- Mya arenaria larvae occurred most weeks from tional mean at the nearfield station, but lower at May through October during the preoperational , the farfield station. CPUE of Jonah crab was not yeo. In 1997, larvae first occurred in late May I significantly different between the preoperational and there were several smaller peaks in abun-and operational periods and there were no signifi- dance before the largest peak occurred in late cant differences between stations. The relation- October. Geometric mean density of soft-shell ship between stations was consistent between the clam larvae in 1997 (3.5-4.7/m') was higher than preoperational and operational period. In 1997, the operational mean at all stations, and higher CPUE of rock crab (farfield 2.4; nearfield 8.0) than the preoperational mean at Station P2 and 1-16
1.0 EXECUTIVE
SUMMARY
P7. There were no significant differences in (23.5/m2 ) was lower than the preoperational mean larval abundance between the preopera- (36.8/m2 ) and operational means (50.21/m ). p tional and operational periods or among stations. Densities of seed clams in 1997 in Plum Island l 2 Sound (farfield area) (22.9/m ) were also lower
~
Mean density of YOY clams (1-25 mm) in 1997 than the preoperational (107.0/m2 ) and opera-2 2 at all flats (37.6/m ) was lower than the tional (37.0/m ) means. There were no signifi-2 preoperational average (52.8/m ), but higher than cant differences in seed clam density between the the operational average (27.8/m2 ). The density preoperational and operational periods or be-of YOY clams in 1997 was consistent with the tween areas. This consistency across periods and three-year periodicity in clams that has continued stations suggests that settlement has been unaf-throughout the study period. Density of yearling fected by Seabrook Station. 2 clams (26-50 mm) in 1997 (1.6/m ) was lower than both the preoperational (3.9/m 2) and opera- Sarcomatous neoplasia is a lethal fonn of leuke-2 tional means (2.5/m ). Density of yearlings has mia in soft-shell clam. Neoplasia was prevalent been declining since 1995, and is presently lower at all flats in 1997. The prevalence of neoplasia than adult clams, indicating a potential recruit- appears to be increasing as 100% of all clams ment problem in future years. Density of adult examined had neoplasia. The presence of this clams in 1997 (16.2/m 2) was greater than both often-fatal disease, and the decreased densities of 2 the preoperational (2.2/m ) and operational yearling clams, indicate that densities of adult 2 (4.7/m ) means. Density of adults at Flats 1 and clams may begin to decrease in future years. 4 was the highest recorded since 1974, and near the record high at Flat 2. This was attributed to The two potential mechanisms by which the the decreased digging effort in recent years, operation of Seabrook Station could affect soft-There were no significant differences in mean shell clams in Hampton Harbor are incursions of density between the preoperational and opera- the thermal plume into the harbor and entrain-tional periods for YOY and yearlings, indicating ment of larvae into the cooling water system of that the operation of Seabrook Station has not the plant. Numeric modeling and subsequent affected the density of these lifestages. Density field verification indicate that the thermal plume of adults was significantly greater during the does not enter the harbor and is not a potential operational period, but this is probably due to the impact (Padmanabhan and Hecker 1991). closure of the flats in 1989, and the limited Larval density showed no significant differences harvesting that has taken place since 1994. between periods. In addition, densities of larvae appear unrelated to sets of YOY. Therefore, The relationship between density of clam larvae removal of larvae through entrainment into the and settlement of YOY clams was very weak, cooling water system of the plant has had no This indicated that factors other than larval apparent effect on YOY clam density. The supply are important in controlling the recruit- differences in clam density were probably due to ment of YOY, and removal of larvae through many physical and biological variables that entrainment probably has not affected settlement. include recreational harvesting and the presence In 1997, the mean density of seed clams (1-12 of neoplasia. mm) in Hampton Harbor (nearfield area) 1-17
1.0 EXECUTIVE
SUMMARY
l 1.4 LITERATURE CITED Underwood, A.J. 1994. On beyond BACI: Sampling designs that might reliably detect environmental disturbances. Ecological Green, R.ll.1979. Sampling design and statisti-cal methods for environmental biologists. Applications,4(1): 3-15. John Wiley and Sons, N.Y. 257 pp. Normandeau Associates Inc. (NAI). 1977. Summary document: assessment of antici-pated impacts of construction and operation of Seabrook Station on the estuarine, coastal and offshore waters of flampton-Seabrook, New Hampshire. 1991. Seabrook Environmental l Studies, 1990. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Sea-brook Station. Tech. Rep. XXIl-II.
. 1995. Seabrook Station 1994 Environmental Studies in the Hampton-Sea-brook Area. A Characterization of Environ-mental Conditions.
1 1 1998. Seabrook Station 1996 Environmental Monitoring in the Hampton-Seabrook area. A characterization of Envi-ronmental Conditions. NOAA (National Oceanographic and Atmo-spheric Administration).1995. Status of the fishery resources off the northeastern United States for 1994. NOAA Tech. Mem. NMFS-F/NEC 108. 140 pp. Lambert, W.J., P.S. Levin, and J. Berman. 1992. Changes in the structure of a New England (USA) kelp bed: the effects of an introduced species? Mar. Eco. Prog. Ser. 88:303-307. Padmanabnan M. and Hecker, G.E. 1991. Comparative Evaluation of Hydraulic Model and Field Thermal Plume Data, Seabrook Nuclear Power Station. Alden Research Laboratory, Inc. 1-18 L --.__- ---- --_____ _
2.0 WATER QUMITY \ - l l TABLE OF CONTENTS PAGE 2.0 WATER QUALITY S U M M A RY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......... . . . 2-ii LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . ... ...... ... ......... .. . . .. 2-iv LI ST O F TAB L ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... ...... 2-vi
2.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . . .. ... .... ...... .. . . 2-1 2.2 M ETi l OD S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1 2.2.1 Field M et hods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 1 l 2.2.2 Laboratory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 l 2.2.3 Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. . 2-3 2.3 RES U LTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . 2-4 2.3.1 Offshore Water Quality . . . . . . . . . . . . ......................2-4 2.3.1.1 Physical Environment . . . . . . . . . . .... . .... . . . . . . 2-4 2.3.1.2 Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 20 2.3.2 Estuarine Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . 2-22 2.4 DISCUSSION . . . . . . . . . . . . . . .... ...... ... ......... . ........ ... .2-26
2.5 REFERENCES
CITED . . . . . . . . . . . . . . . . . . . . . . . ... . ....... .. . .. .2-29 2-i
l 2.0 WATER QUALITY l
SUMMARY
l Water quality data collected in 1997 were similar to those in previous years. The weather in 1997 was slightly colder and much drier than average. Mean monthly surface and bottom water temperatures in 1997 ; followed a similar pattern to previous years. Mean monthly surface water temperatures were lowest in February through March (3.4 to 3.8 *C) and highest in August (17.6 *C). Bottom water temperatures were lowest in January through March (3.8 to 4.4 "C) and highest in September (12.8 *C). Annual mean surface water temperature at each station (P2: 9.2 'C; PS: 9.4 *C; P7: 9.2 *C) was lower than 1996 at all stations, but higher than the preoperational period at Stations P2 and P7. Annual mean bottom water temperatures in 1997 at each station were 7.3 *C, lower than the 1996 and the operational period means, but higher than the preoperational period mean at Stations P2 and P7. Both surface and bottom water temperatures were significantly warmer in the operational period, but this increase occurred at all stations and cannot be attributeu to the operation of Seabrook Station. Annual mean surface water salinities in 1997 (P2: 31.3 PSU; PS: 31.2 PSU; P7 31.1 PSU) were lower than or equal to the preoperational and operational period means. There was a significant decrease (0.2 to 0.4 PSU) in mean surface salinity at the intake and discharge stations between the preoperational and i operational periods, but no significant decrease at the farfield station, resulting in a significant interaction term. There is no reasonable mechanism by which the withdrawal of bottom water from the intake area, and its subsequent discharge as heated effluent into the discharge area can reduce surface salinity at the intake and discharge areas. The water masses in these two areas are essentially identical, and the salinity of this water cannot be changed by passage through the plant. Monthly mean bottom water salinity followed a similar pattern to previous years. Annual mean bottom water salinity in 1997 was consistent among stations (31.7 PSU) and lower than the operational and preoperational period means. There were no significant differences between periods or among stations. Surface dissolved oxygen (DO) in1997 (P2: 9.9 mgh; PS:10.0 mga; P7:9.9 mgA) was higher than the i operational and preoperational period means at all stations. Average surface DO decreased at all stations I between the preoperational and operational periods, but the decrease was less at the discharge station, as showed by the significant interaction term. A potential plant impact might be shown by a large decrease in DO at the discharge station as heated effluent would reduce the DO levels of the surrounding waters. However the observed changes are the opposite, where the discharge station had higher DO levels compared with the other stations. Therefore the differing patterns in surface DO between the preoperational and operational periods cannot be attributed to Seabrook Station. Bottom DO in 1997 (P2: 9.3 mga; PS:9.4 mga; P7:9.3 mgM) was higher than both the preoperational and operatimal period means. There were no significant differences between periods or among stations. Monthly patterns of nutrient levels (total phosphorus, orthophosphate, nitrate, nitrite, ammonia) in 1997 were similar to previous years except for high levels of total phosphorus and orthophosphate in September through November. Annual mean concentrations of total phosphorus and orthophosphate in 1997 were 2-ii
2.0 WATER QUALITY higher than both the preoperational and operational means. Annual mean concentrations of other nutrients in 1997 were similar to the preoperational and operational means. There were no significant differences between the preoperational and operational periods, or among stations for any of the nutrients. 2-iii
2.0 WATER QUALITY LIST OF FIGURES PAGE 2-1. Water quality sampling stations . . . . . . . . . . . . ... ...... . . . . 2-2 2-2. Surface and bottom temperature (*C) at nearfield Station P2, monthly means and 95% confidence intervals over the preoperational period (1979-1989) and the operational period (1991-1997), and monthly means of surface and bottom temperature at Stations P2, P5, and P7 in 199 7 . . . . . . . . . . . . . . . . . . . . . . . . .. ... .. .... . . 2-6 2-3. Time-series of annual means and 95% confidence intervals and annual minima and maxima of surface and bottom temperatures at Stations P2, P5 and P7,1979-1997 . . . . . . . . . . . .2-7 2-4. Monthly mean difference and 95% confidence intervals between surface and bottom temperatures (*C) at Stations P2, P5, and P7 for the preoperational (1979-1989) period and monthly means for the operational period (1991-1997) and 1997 . . . . . . . . . . . . . . . . . . . 2-12 2-5. Comparison ofmonthly averaged continuous temperature (* C) data collected at the surface at discharge (DS) and farfield (T7) stations during commercial operation, August 1990 December 1997 . . . . . . . . . . . . . . . . . . . . . . . .. ....... . .. . .... ..... 2-15 2-6. Surface and bottom salinity (PSU) and dissolved oxygen (mg/L) at nearfield Station P2, monthly means and 95% confidence intervals for the preoperational period (1979-1989) and monthly means for the operational period (1991-1997) and 1997 . . . . . . . . . . . . . 2-16 2 7. Time-series of annual means and 95% confidence intervals of surface and bottom salinity (PSU) at Stations P2, PS, and P7,1979-1997 . . . . . . . . . . . . . . . . . . .... . .. .. 2-18 2-8. A comparison among stations of mean surface salinity (PSU) during the preoperational (1987-1989) and operational periods (1991-1997) for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 2-2) . . . . . . . . . . . . . . . . . . . . . . . . 2-19 2-9. A comparison among stations of mean surface dissolved oxygen (rng/L) during the preoperational (1987-1989) and operational periods (1991-1997) for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 2-2) . . . . . . . . . 2-19 2-10. Time series of anal mean surface dissolved oxygen (mg/L) from 1987-1997 (data between the two dashed lines were excluded from the ANOVA model) . . . . . . . . .. ..... 2-20 2-11. 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 (1991-1997) and 1997 .... . 2-21 2-iv
m 2.0 WATER QUALITY PAGE 2-12. 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 (19791984 and 1987-1989), and monthly means for the operational period (1991 - 1997) and 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23 2-13. Monthly means and 95% confidence limits for temperature measured at low and high tides in Hampton Harbor from May 1979 December 1997 and monthly means in1997......................................................... .2-24 1 2-14. Monthly means and 95% confidence limits for salinity (PSU) measured at low and high tides in Hampton Harbor from May 1979-December 1997 and monthly means in 1997 ... 2-27 j 1 l l l i 1 2-v i-
r 2.0 WATER QUALITY LIST OF TABLES PAGE 2-1. Annual Means and Coefficients of Variation (CV,%) and Minima and Maxima for Water Quality Parameters Measured During Plankton Cruises at Stations P2, P5, P7 over Preoperational and Operational (1991-1997) Years, and the Annual Mean, Minimum and Maximum in 1997 . . . . . . . . . . . . . . . . .......... .. . ... .... .. . . 2-8 2-2. Results of Analysis ofVariance Comparing Water Quality Characteristics among Stations P2, PS, and P7 During Recent Preoperational Years (1987-1989) and Operational (1991-1 9 9 7) Ye vs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . 2-10 2-3. Monthly Mean Surface Tem peratures (*C) and Temperature Differences (AT,* C) Between Discharge (DS) and Farfield (T7) Stations Collected from Continuously-Monitored Temperature Sensors, July 1990-December 1997 . .......... .. ...... ... ... 2-14 2-4. Annual Mean Surface Temperatures (*C) and Coefficients ofVariation (CV,%) at Stations DS and T7 During Operational Monitoring . . . . . . . . . . . . . . . . . . . . . . . . ..... .... .2-13 2-5. Annual Mean and 95% CL for Temperature (*C) and Salinity (PSU) Taken at Both High and Low Slack Tide in Hampton Harbor from 1980-1997...... .. .. .. .. .. . . 2-25 / 2-6. Summary of Potential Effects of Seabrook Station on Ambient Water Quality. Seabrook Operational Report,1997 . . . . . . . ... .......... . ............... .. . .. .2-28 2-vi
2.0 - WATER QUALITY
, c ---
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2.1 INTRODUCTION
T fe i : ie receiving waters within 300 feet of the em mged diffuser in the direction of Water q'sality data were collected to aid in disdRg interpreting information obtained from the biologiet.1 monitoring program and to determine Seabrook Station uses continuous low level whether the operation of the Seabrook Station chlorination in the circulating and service water Circulating Water System has had a measurable systems to control biofouling. Information was effect on the physical and chemical gathered through the Chlorine Minmuzation characteristics of the water column. To provide Program, which assessed the effectiveness of information on the physical environment, water chlorine application in preventing biofouling quality samples were collected in the vicinity of while using the least amount of chlorine. l
. the Seabrook Station intake and discharge, as Residual levels of <:hlorine at the diffusers, when l well as at a farfield location outside of the measured, have been below detection limits.
influence of Station operation. Parameters measured included temperature, salinity, 2.2 METHODS dissolved oxygen, and nutrients. Potential impacts related to the cooling' water system 2.2.1 Field Methods include temperature,' through the discharge of a heated effluent from the condensers, and the Near-surface (-1 m) water samples for nutrient application of sodium hypochlorite as a analysis were collected during daylight hours biofouling control measure. In addition to the using a General Oceanics* 8-L water sampler offshore sampling, temperature and salinity were from the intake (Station P2,16.8 m depth, recorded weekly at high and low slack tides in MLW), discharge (Station P5,16 m depth, Hampton Harbor to characterize conditions in the MLW), and farfield (P7,18.3 m depth, MLW) vicinity of softshell clam and fish seine study sampling locations (Figure 2-1). Nutrient sites. sampling commenced at Stations P2 and P5 in 1978 and at Station P7 in 1982. Sampling Seabrook Station employs a once-through continued until 1981 at PS and until 1984 at P2 circulating water system. Ambient ocean water and P7. Sampling resumed at all three stations in is drawn into the system from approximately July 1986, and has continued to the present. 7,000 feet offshore through three intake Water samples were taken once in January, structures and discharged to the ocean through a February, and December and twice monthly from multiport diffuser system approximately 5,500 March through November, in conjunction with feet offshore. All discharges are controlled the phytoplankton and microzooplankton under the Station's National Pollutant Discharge sampling, and within 24 hours of the weekly Elimination System (NPDES) Permit issued by macrozooplankton and ichthyoplankton sampling. the State of New Hampshire and the Environ-mental Protection Agency (EPA). This permit Temperature, dissolved oxygen, and salinity specifies that the average monthly temperature measurements began in 1979 at Stations P2 and rise shall not exceed 5 F (3*C) within the P5, and in 1982 at Station P7. Sampling at P2 nearfield jet mixing region. This applies at the and P7 has continued to the present; sampling at 2-1
f7 N RYE LEDGE o h ...... 127TLE y BOARS HEAD 0 o .5 -1 Nautical Mile o 1 l 2 Kilometers y FARFIELD AREA f SCALE CONTOUR DEPTH IN METERS j- I I o I GREATBOARS HEAD HAMPTON \
- ,e l BEACH s a .
e 1, i L b l - BROWNS : l RIVER P1 Intake * *, D l j a^ :. ilb.U7$R p.., )) ,
.. .:.e ID /- NEARFIELDAREA i
l SEABROOK STATION
' Q DS /
fy -R s .e. . :. .. Discharge ' HAMPTON SEABROOK SUNK HARBOR ROCKS U
/
SEABROOK
'\ s BEACH N ~ i! ...D:
LEGEND O = water quality stations l e = continuous temperature monitoring stations Figure 2-1. Water quality sampling stations. Seabrook Operational Report,1997. 2-2 {. .
( l 2.0 WATER QUALITY i l l P5 was interrupted from January 1982 until July daily mean temperature, and the daily mean l 1986, but was sampled concurrently with P2 and temperatures were averaged within a month to I P7 from July 1986 until the present. At all produce the monthly mean. The results of this stations, temperature and salinity profiles were monitoring are included in this section. taken :n 2 m increments four times per month during January through December with a 2.2.2 Laboratory Methods Beckman* Thermistor Salinometer (through l March 1989) or a YSI* (Model 33) S-C-T Meter Water quality samples were analyzed for five l within 24 hours of the weekly macrozooplankton nutrients (total phosphorus, orthophosphate, and ichthyoplankton sampling. Beginning in nitrate, nitrite, and ammonia) using a Technicon* 1995, salinity samples were collected at near- Autoanalyzer II system. All analyses were surface (-l m) and near-bottom (+ 1 m) depths. performed according to EPA Methods for Collections were made in wax-sealed glass bottles Chemical Analyses of Water and Wastes and analyzed in the lab using a YSI Model 34 S- (USEPA 1979) and Standard Methods (APHA C-T Meter. During 1996, field temperatures 19od). continued to be collected using a YSI Model 33 S-C-T Meter. Duplicate dissolved oxygen 2.2.3 Amdvtical Methods samples were also collected at near-surface (-1 m) and near-bottom (1 m above bottom) depths. Results from these collection efforts were used to j Samples were fixed in the field with manganese describe the seasonal, temporal, and spatial l sulfate and alkaline iodide-azide, and analyzed by characteristics of the water column within the j titration within eight hours of collection, nearshore waters off Seabrook Station and in the Beginning in 1997, temperature, dissolved Hampton-Seabrook estuary. Offshore water oxygen and salinity were recorded in situ using a quality analyses used data from all stations, but YSI 600XL Water Quality Monitor. Each focused on Station P2 since it was sampled for a parameter was recorded at 2 m increments, at the longer period of time than Stations P5 and P7. same sampling frequency as in past years. Any values that were less than the detection Sampling results were downloaded weekly to a limits were assigned a value equal to one-half of PC, and at the end of the year were incorporated the detection limit for computational purposes directly into the historical data set. Salinity (Gilbert 1987). For both offshore and estuarine levels are presented in PSU (practical salinity stations, seasonal trends were analyzed using units). Continuous temperature data were monthly arithmetic mean temperatures and I collected from the discharge (Station DS), and salinity, and (for offshore stations) nutrient and farfield (Station T7) areas at a depth of 0.6 m dissolved oxygen concentrations. Monthly means beginning in August 1990 as part of Seabrook for the preoperational and operational periods Station's NPDES permit compliance program were calculated from the monthly arithmetic (Figure 2-1). The monitors were retrieved means for each year within each period, resulting weekly and the data downloaded to a PC. Water in a sample size equal to the number of years in temperatures were continually integrated and each period. Monthly means for 1997 were I recorded over 15-minute intervals. The 15- calculated as the arithmetic average of al! I minute intervals were averaged to produce a samples taken within a given month. 2-3 l l
}
2.0 WATER QUALITY Among-year and between-period trends were interaction term (Preop-Op X Station) was also ) evaluated using annual or period (preoperational, included in the model. Nested temporal effects operational) means. Annual means of 1997 were years within operational period (Year collections were calculated as the arithmetic (Preop-Op)), months within year (Month (Year)), , mean of all observations within the year. The and the interaction of station and year within f means of preoperational and operational Preop-Op, which were added to reduce the ) collections were calculated as arithmetic means unexplained variance, and thus, ircreased the of annual means over all years within each sensitivity of the F-test. For both nested terms, period, which varied among stations and variation was partitioned withcut regard to station parameters. The precision of the mean was (stations combined). The final variance not described by its coefficient of variation (Sokal accounted for by the above explicit sources of and Rohlf 1981). Preoperational periods for the variation constituted the Error term. The , different analyses are listed on the appropriate preoperational period for each analysis was tables and figures; in all cases, the operational specified as 1987-1989, which was the period period consisted of collections from 1991-1997. during which all three stations were sampled { Collections from 1990 were not included in these concurrently (thus maintaining a balanced model I analyses since the year was divided between the design). These results were evaluated in 1 preoperational and operational periods, and the conjunction with means calculated over all I inclusion of partial years in each period would available preoperational years to help distinguish bias the means. between recent trends and long-term trends. j Operational /preoperational and nearfield/farfield 2.3 RESULTS differences in monthly means for offshore water quality parameters were evaluated using a multi- 2.3.1 Offshore Water OmHty way analysis of variance procedure (ANOVA), using a before-after-control-impact (BACI) 2.3.1.1 Ehysical Environment design to test for potential impacts of plant operation. A mixed-effects ANOVA model was Climate used to test the null hypothesis that spatial and temporal values during the preoperational and The weather in 1997 was slightly colder and operational periods were not significantly much drier than average (Boston Globe 1998). (p > 0.05) different. The data collected for the The mean temperature in Boston was 10.5'C, ANOVAs met the criteria of a Before- 0.2*C below average, and the precipitation was ! After/ Control-Impact (BACI) sampling design 81.5 cm, 24.0 cm below average. Average ! discussed by Stewart-Oaten et al. (1986), where monthly temperatures were below nonnal for the san'pling was conducted prior to and during plant months of March through May, and July through operation and sampling station locations included December. Precipitation was below normal for both potentially impacted and non-impacted sites. all months except March, April and November. l The ANOVA was a two-way factorial with Snowfall was 23.1 cm above average, primarily ! nested effects that provided a direct test for the due to a strong storm on 31 March through 1 temporal-by-spatial interaction. The main effects April, were period (Preop-Op) and station (Station); the 2-4
p 2.0 WATER QUALITY Temperature surface water temperature in 1997 at the discharge station (P5) was 0.2* C higher than at The pattem of monthly mean surface and bottom both the intake station (P2) the farfield station water temperatures at the intake area (Station P2) (P7). Surface temperatures at P5 were warmer in 1997 was similar to previous years (Figure 2- than at P2 and P7 in the preoperational period as 2). Monthly mean surface water temperatures well, by as much as 1.2*C (Table 2-1, all were lowest in February through March (3.4 to preoperational years). Mean surface water 3.8 *C), and increased to an annual high in temperature during the operational period was j August (17.6 *C). In 1997 mean monthly significantly higher than during the I surface water temperature was above the upper preoperational period, and mean temperature at l 95% preoperational confidence limit for the Station P5 was greater than at P2 and P7 (Table months of January through March, August, 2-2). This relationship was consistent between { September, and December. The highest single the preoperational and operational periods, as surface water temperature was 18.7 *C at Station indicated by the non-significant interaction term. PS on 18 August, and the lowest was 2.7 *C at Station P2 on 10 Febmary. Annual mean surface In 1997, mean bottom water temperatures were water temperature decreased at all stations in identical at each station, whereas in the 1997 compared with 1996, continuing a trend preoperational period temperaturei tt P5 were that began in 1995 (Figure 2-3). generally warmer than at P2 and P7 (Table 2-1). Mean annual bottom water temperatures in 1997 The pattern of monthly mean bottom water were cooler than the operational period means at temperatures at the intake was similar to the all stations,and warmer than mean temperatures surface temperatures (Figure 2-2). Bottom water during all preoperational years at Stations P2 and temperatures were lowest in January through P7 (Table 2-1). These latter observations were March (3.8 to 4.4 *C) and highest in September supported by the ANOVA, as the difference (12.8 *C). In 1997 mean monthly bottom water between operational and recent preoperational temperature was above the upper 95 % mean bottom temperatures was significant, while preoperational confidence limits for the months there were no significant differences among of January through March, and September. The stations (Table 2-2). The patterns in bottom highest single bottom water temperature was 14.0 water temperatures among stations were
'C at Stations P5 and P7 on 15 September and 26 consistent between the preoperational and August, and the lowest was 3.1 'C at Station P2 operational periods, as indicated by the non-l on 19 February. Annual mean bottom water significant interaction term (Table 2-2). .
temperature decreased at all stations in 1997, l continuing a trend that began in 1995 (Figure 2- Monthly mean differences between surface and ! 3). bottom temperatures (surface - bottom; Figure 2-
- 4) indicated that the water column at each station Mean surface water temperature in 1997 was was essentially isothermal (AT = -1*C to +1'C) lower than the operational mean at all stations, during five to six of twelve months, during both but higher than the preoperational means at operational and preoperational periods.
Stations P2 and P7 (Table 2-1). Mean annual Temperature stratification was minimal (AT = 2-5 l
)
2.0 WATER QUALITY f l i Sudace, Intake g Bottom, Intake j h@= 20 l
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hN-!:f ' 2 r 5 7-- ; O 0, JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N0/ DEC ' JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N0/ DEC MONTH MONTH Surface,1997 Bottom,1997 20 Hake (P2) Hake (P2)
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1 g i tu 2 5-- g5 N 0, 0, JAN EB MAR APH MAY JUN JUL AUG SEP OCT N0/ DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOI DEC MONTH MONTH Figure 2-2. Surface and bottom temperature (*C) at nearfield Station P2, monthly means and 95% confidence intervals over the preoperational period (1979-1989) and the operational period (1991-1997), and monthly means of surface and bottom temperature at Stations P2, P5 and P7 in 1997. Seabrook Operational Report,1997. 2-6
I l 2.0 WATER QUALITY l P2 SURFACE P2 BOTTOM l-a a-l 6m a m-k5 5 N__s- s - - N_- ~ f5 5 1l [fd l l ; jij; e s l
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- n aa m az m u as as v aa m m m m m u n n e n e m m m u u as v aa m m m m m u s u n l a a i
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- Figure 2-3. Time-series of annual means and 95% confidence intervals and annual minima and maxima of surface and bottom temperatures at Stations P2, P5 and P7,1979-1997. Seabrook Operational Report,1997.
2-7
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l J 2.0 WATER QUALITY ] k Table 2-2. Results of Analysis of Variance Comparing Water Quality Characteristics among 1 Stations P2, PS, and P7 During Recent Preoperational Years (1987-1989) and [ Operational (1991-1997) Years. Seabrook Operational Report,1997. { Multiple Comparisons' { Parameter Source of Variation' DF MS F (ranked tn decreasing order) j Surface Temperature Op* ' 1 45.% 5.90* Op > Preop Year 7.82 0.09 NS Preop (Preop))d 110 8 86.27 1582.00 "
- MonthfYear Station ' 2 3.02 115.74* P5 > P2 > P7 Preop-Op X Stations 2 0.03 0.48 NS Station X Year (Preop-Op)* 16 0.06 1.08 NS Error 220 0.05 Bottom Temperature Pre 1 97.10 13.32 " Op > Preop Y op) 8 7.35 0.21 NS j Mon (Year) 110 35.73 461.66 "
- Station 2 1.29 124.01 NS Preop-Op X Station 2 0.01 0.19 NS Station X Year (Preop-Op) 16 0.08 0.99 NS Error 220 0.08 Surface Salinity Op 1 1.27 0.18 NS 6.73 1.71 NS Preop Year Month (Year (Preop-)Op) 110 8
3.97 55.57'*
- Station 2 0.33 1.39 NS i Preop-Op X Station 2 0.23 4.73* 2 Pre 5 Pre 2 On 7 Pre 7 On 5 Oo j Station X Year (Preop-OP) 16 0.05 0.68 NS I Error 220 0.07 I
Bottom Salinity Pre 1 3.03 0.78 NS < Yea 8 3.89 2.74 " 1 Month (Y r) 110 1.41 36.30 * *
- Station 2 0.29 7.00 NS ;
Preop-Op X Station 2 0.04 0.79 NS Station X Year (Preop-Op) 16 0.05 1.37 NS Error 220 0.04 , 1 Surface Dissolved p 1 1.72 2.02 NS 0.81 0.27 NS Oxygen B WPg')reop)) bluntN(Year 110 8 3.04 177.16 " ' ; Station 2 0.15 3.09 NS Pr X Station 2 0.05 8.88 " 5 Pre 2 Pre 7 Pre 5 Op 2 Op 7 Op Stat n Year (Preop-Op) 16 0.01 0.31 NS Error 220 0.02 Bottom Dissolved Pr 1 0.71 0.25 NS Oxygen Yea p) 8 2.77 0.59 NS Mo (Year) 110 4.73 181.70* " Station 2 0.39 4.93 NS Preop-Op X Station 2 0.08 3.21 NS Station X Year (Preop-Op) 16 0.02 0.90 NS j Error 220 0.03 . Orthophosphate Preo 1 1.31 0.01 NS I Yea reop-O 8 140.59 0.62 NS Mon (Year) p) 110 229.90 36.42 * *
- Station 2 23.81 314.17 NS Preop-Op X Station 2 0.30 0.08 NS j Station X Year (Preop-Op) 16 3.69 0.58 NS Error 220 6.31 :
Total Phosphorus Op 1 36.26 0.02 NS l 1504.68 4.13 * " Preop (Preop-)Op) Year Month (Year 109 8 380.04 9.26 * " ; j Station 2 85.44 3.54 NS l f Preop-Op X Station 2 24.25 0.96 NS I Station X Year (Preop-Op) 16 25.13 0.61 NS Error 218 41.04 i i 2-10 (continued) { i m _ ___ _
2.0 WATER QUALITY Table 2-2. (Continued) Multiple Comparisons' Parameter Source of Variation' DF MS F (ranked in decreasing order) l Nitrate Op 1 562.07 0.17 NS Preep(Preop-O Year 8 3482.72 0.34 NS Month (Year) p) 110 10264.3 128.34 "
- Station 2 7 46.02 NS Preop-Op X Station 2 597.64 0.13 NS l Station X Year (Preop-Op) 16 23.47 2.31 *
- l Error 220 184.41 79.98 1
Nitrite Preo 1 8.35 2.31 NS Year reop O 8 3.78 0.46 NS Station Mon (Year) p) 110 2 8.08 2.64 16.53 "
- 5.80 NS '
Preop-Op X Station 2 0.47 0.74 NS l Station X Year (Preop-Op) 16 0.63 1.29 NS l Error 220 0.49 Ammonia Op 1 679.50 0.69 NS , Preop Year (Preop-O 7 1038.85 8.14 "
- I Month (Year) p) 92 135.21 13.11* " ;
Station 2 19.42 3.73 NS Pteop-Op X Station 2 4.95 1.53 NS , Station X Year (Preop-Op) 14 2.72 0.26 NS ' Error 184 10.31 l
' Based on averaged monthly collections for all parameters
*Preoperational years: 1987-1989 at each station for all parameters except ammonia, which was April 1988 through December 1989
'Preoperational versus operational period, regardless of station
' Year nested within preoperational and operational periods, regardless of station l
' Month nested within year nested within preoperational and operational periods, regardless of station
' Station P2 versus PS versus P7, regardless of year 8 Interaction between rnain effects i
- Interaction of station and year nested within Preop-Op. )
' Underlining indicates no significant difference based on a test of 4: LSMEAN(i)=LSMEAN(j), Waller-Duncan muluple means comparison test used for l significant main effects. LS Means used for significant interaction terms. I NS = not significant (p a 0.05) l
* = significant (0.05 a p >0.01) '
" = highly significant (0.01 a p >0.001)
'" = very highly significant (0.001 a p) 2-11 o
( 2.0 WATER QUALITY J e2 1o- Preoperational 9' ---- Operational G 8- *-*-* 1997 6- k ' $\,_ig
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-2 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 2-4. Monthly mean difference and 95% confidence intervals between surface and bottom !
temperatures (*C) at Stations P2, P5 and P7 for the preoperational period (1979-1989) and monthly means for the operational period (1991-1997) and 1997. Seabrook Operational Report,1997. 2-12
3.0 WATER QUALITY i1*C) at each station from November through Table 2-4. Annual Mean Surface April throughout the preoperational and Temperatures (* C)* and Coefficients of operational periods (Figure 2-4). Surface waters Variation (CV,%) at Stations DS and T7 8 Operadond Mohg. Seabrook warmed more slowly in 1997 at each station Operational Report,1997. compared to previous years, resultmg m relatively small AT values in May and June. Station DS Station T7 During the mid-summer months, however, y,,,, y,,, cy y,,, cy surface temperatures warmed considerably, and 1991 10.6 38.8 9.9 48.1 AT values were somewhat higher than during 1992 9.4 41.9 8.3 54.6 these same months in the preoperational and 1993 9.2 53.3 8.6 57.4 operational periods. By September at Stations P2 1994 9.4 61.7 8.3 72.4 and PS, and October at Station P7, the degree of 1995 10.4 43.6 9.7 55.4 stratification was similar to that observed during 1996 9.9 48.8 9.1 59.4 the preoperational and operational periods. 1997 10.2 42.6 9.4 52.7
" '" ' "8" Continuous surface temperatures recorded at Y9h ."ff g'"2." =8 ir 1 Stations DS (discharge) and T7 (farfield) in 1997 *M nitoring e nducted by YAEC from 1991 1995.
showed a similar seasonal pattern to temperatures recorded at the water quality stations, including Salinity distinct peaks in August and September (Table 2-3 (following page), Figures 2-2, 2-5). The Monthly average surface salinities at P2 followed annual mean temperature at DS increased slightly a distinct seasonal pattern (Figure 2-6) that was from 9.9*C in 1996 to 10.2*C in 1997 (Table 2-4). At T7 the annual mean also increased, from related to freshwater influx and precipitation, air temperatures and winds, and tides and currents. 9.1
- C to 9.4
- C. Monthly temperatures ema maj r eshwater sources innumed measured in 1996 at both T7 and DS were salinities in the nearshore area off Hampton generally similar to monthly temperatures from previous years (Figure 2-5).
Harbor, including the Androscoggin and Kennebec Rivers in Maine (Franks and Anderson 1992), the Piscataqua River in New Hampshire Monthly temperatures at DS were generally l-2*C warmer than at T7 during October through and the Merrimack River in Massachusetts (NAI 1977). Salinities were typically highest during April. In May through September, DS was less the colder months due to low precipitation and than 1*C cooler, and in July and August, runoff. Salinities declined to their lowest levels temperatures at T7 were slightly warmer than at f the year when freshwater influx reached its DS (Table 2-3). These average monthly AT Peak level in the spring, due to spring storms values (DS-T7) have shown full compliance with the Station's NPDES permit throughout the mbined with snow melt. Bottom salinities exhibited a similar but less pronounced seasonal operational period. pattern. Waters within the study area are relatively shallow, thus storms and strong currents can, at times, affect the entire water 2-13
8 4 1 6 1 2 3 4 2 7 5 9 P 6 1 5 0 3 3 3 9 9 2 6 3 A 1 1 1 1 0 0 0 -0 1 1 1 d t e 0 7 9 0 6 2 8 4 2 7 0 1 c 6 7 4 0 6 0 2 7 6 0 2 9 9 5 e 9 l l 9 7 2 2 2 5 9 3 3 7 1 1 1 61 1 1 8 6 , 1 o _ C s 8 1 0 6 7 0 9 0 4 4 5 0 n S 0 2 2 0 5 4 2 1 1 2 5 9 i o D 4 3 4 6 9 3 3 6 7 3 0 7 t 1 1 1 1 1 1 t a S
)
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n 2.0 WATER QUALITY Surface Sainity Bottom Salinity 34- 35 . j
$ 33 i $ 34-2 I I 2 3
', 33 , ; , lj j 32
'ded'--* $
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1997 1997 g g JAN FEB W APR MAY JUN JUL AUG SEP OCT N0/ DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT N0/ DEC MONTH MONTH Surface DisscNed Oxygen Bottom DissoNed Oxygen n n l I l y,/l'4', I en ' en l
}s 's { g'_I_k l
{10 g hs' g 10 1 4l l I l E E 9 's ' t's t I f m9 \' 7'\, ' l WQ-< -( l . I' 1 i1 y 8 08 08 i ',- i 3 3 44g"i eI ! 57
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#N EB MAR APR MAY JUN R AUG SEP OCT N0/ DEC JAN FEB MAR APR MAY JUN R RJG SEP OCT N0/ DEC MONTH MONTH j Figure 2-6. Surface and bottom salinity (PSU) and dissolved oxygen (mg/L) at nearfield station P2, !
monthly means and 95% confidence intervals for the preoperational period (1979-1989) and monthly means for the operational period (1991-1997) and 1997. Seabrook Operational Report,1997. 2-16
2.0 WATER QUALITY column (NAI 1979). However, bottom waters in Surface salinity decreased significantly between 1997 generally exhibited more stable temperature the preoperational and operational periods at and salinity levels over the year compared to Stations P2 and PS by 0.3 and 0.2 PSU l surface waters, i.e., temperature and salinity respectively, but there was no significant change changed at a faster rate and to a larger degree at Station P7, resulting in a significant interaction from month to month in surface waters when term (Table 2-2; Figure 2-8). There were no j compared to bottom waters, significant differences between the preoperational l and operational periods, or among stations for Seasonal patterns in surface and bottom salinity bottom salinity (Table 2-2). l during 1997 at Station P2 were similar to those observed during both the preoperational and Dissolved Oxvnen operational periods. Salinity values in 1997 were within preoperational confidence limits during Surface and bottom dissolved oxygen concen-l most months, falling below lower confidence trations at Station P2 exhibited similar season limits in May, August and December at the sur- Patterns during all years of the study (Figure 2-face and in May, June and August is bottom 6). Surface concentrations in 1997 were within waters (Figure 2-6). Salinity values in 1997 never preopererational confidence ihnits in January j l exceeded preoperational upper confidence limits. through May, and in July, November and De-
]
cember. During the remaining months, surface i Long-term salinity was very similar among concentrations were lower than preoperational stations, and exhibited a general downward trend confidence limits. Concentrations of dissolved l during the study period at all stations and at both oxygen in bottom waters were within pre- opera-depths (Figure 2-7). Salinities in 1997 rebounded tional confidence limits during all months in 1997 somewhat compared to 1996, but still supported except September, when the average concentra-the overall downward trend. A similar trend was tion was slightly lower than the preopera- tional observed at the Maine Department of Marine lower confidence limit. The annual mean surface Resources West Boothbay Harbor long-term and bottom concentrations were higher in 1997 at ! environmental monitoring station, suggesting a each station compared to both preopera- tional regional trend. This station is fairly comparable and operational means (Table 2-1). Although to the Seabrook water quality stations; although average surface dissolved oxygen con-in a more protected location, there is relatively centrations were higher in 1997 than during most little freshwater input to the harbor. Long term other years at each station, a downward trend (1966-1985) annual mean surface salinities (taken from the preoperational to the operational period at -5.5 feet MLW) at the West Boothbay Harbor was apparent at each station (Figure 2-9). The station ranged between 30 and 32 ppt (MDMR preoperational-operational decline was significant 1987), and in recent years annual mean salinity at all stations, but was greatest at Stations P2 and l has declined from 30.7 ppt in 1990 to 29.0 ppt in P7. This difference resulted in a significant inter-1996 (MDMR 1991,1992,1993,1994,1995, action term in the ANOVA (Table 2-2). How-1996, 1997). ever, the time series of annual mean surface dissolved oxygen concentrations among the three stations followed similar patterns (Figure 2-10). 2-17
2.0 WATER QUALITY u= sm n 8m m n 3 ns n5 i 20 no ' I l 25 , 25 l Ii l
- E E
\ /N ,
im \ f% 31 , Im i 10 s I & 10 E5- l 15 10 10 85 35 30 30 asi, a5 ,, M 80 5 82 E M 85 86 87 88 m 90 9192 93 94 95 96 97 4 80 81 E E N 85 86 87 8B E 90 W W 93 94 95 73 97 m a i uace, m P5 8m W P5 n5- m no no i E5 25 I il l]h m
/\
mi I'1 i j x3 s } 15 am /'N/\ N/\v gm 53 i 3 fm5 50 29 5 30 ass a5, M 60 8182 O M 85 86 87 5 W 90 91 E M W E 96 97 5 80 8182 O N 85 86 87 88 m 90 9192 93 M 95 96 97 g mmn stace, su n
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a5 , q 15 nemmessunusamneumar ! n 80 81 m o u 85 as e a N 90 5 92 m W 95 96 97 g ] a ' Figure 2-7. Time-series of annual means and 95 % confidence intervals of surface and bottom salinity i (PSU) at Stations P2, P5, and P7,1979-1997. Seabrook Operational Report,1997. l 1 2-18 i i
!I h_______._m-_._ _____
2.0 WATER QUALITY 31.65
-* P2
-. - - . . - + PS 3140 + -* -
- P7 31.55 h 31.50 8 .
31.45
.N 8 31.40 '
2 31.35 ' , _ _ _ _ _u _ _ . 31.30 '- 31.2 5 Preoperational Operational Figure 2-8. A comparison among stations of mean surface salinity (PSU) during the preoperational (1987-1989) and operational periods (1991-1997) for the significant interaction term (Preop-Op X Station) of the ANOVA model(Table 2-2). Seabrook Operational Report, 1997, 9.80
. P2
. . . - - + P5
., + - _ p7
, 9.75- ' .
- N. ,
b \
\
9.70- s - ,,, s N 9.65- N s N b N 9.60 N s \
's 9.55
- 9.50-Preoperational Operational Figure 2-9. A comparison among stations of mean surface dissolved oxygen (mg/L) during the preoperational (1987-1989) and operational periods (1991-1997) for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 2-2). Seabrook Operational Report,1997.
2-19 br
2.0 WATER QUALITY l J 10 2 I t
- - P2 l ---n 10.1 P7 l {
l l 10.0 l f E" ll 9.8 's l l ,# ! O Ns l ,__,, s/ 9.7 ^ ' *A ~ l t %% l e- g
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I I I I 92. 87 88 89 90 91 92 93 94 95 96 97 YEAR ( Figure 2-10. Time series of annual mean surface dissolved oxygen (mg/L) from 1987-1997 (data i between the two dashed lines were excluded from the ANOVA model). Seabrook f Operational Report,1997. !
?
I l There were no significant differences in born higher than normal in September through No- 3 dissolved oxygen concentrations between the vember. Although an increase in these two preoperational and operational periods, or among nutrients in the late fall to early winter is typical 4 stations (Table 2-2), of northern temperate waters, and reflects the l seasonal nutrient requirements of the primary 2.3.1.2 Nutrients producers (Section 3.0), concentrations measured in 1997 were among the highest recorded during Phosphorus Soedas the 20-year study period (Table 2-1). 1 Monthly mean surface concentrations of both The high concentrations recorded in the late fall orthophosphate and total phosphorus were similar of 1997 are reflected in the high annual mean l to preoperational and operational seasonal trends concentrations, which at each station exceeded during the first half of 1997 (Figure 2-11). the preoperational and operational means (Table Concentrations of both phosphorus specin were 2-1). Differences in annual mean orthophosphate lower than normal in August, then substantially and total phosphorus concentrations among the 2-20 l
i. 2.0 WATER QUALITY O.u wa
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10 l e-= y. 3, -i3~i 7 - r' ' 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV OEC MONTH Tow eno.ctau.
- Preocamaw
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no - *, L J 9 c '_T 1 ! I i 1 ' N 2/ 10 N o. JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ucurs Figure 2-11. Surface orthophosphate and total phosphorus conenetrations ( g P/L) at Station P2, monthly means and 95 % confidence intervals for the preoperational period (1979-1984 and 19871989), and monthly means for the operational period (1991-1997) and 1997. Seabrook Operational Report,1997. l l 2-21
2.0 WATER QUALITY f three stations were minimal. There was not a of main effects in the ANOVA model was not significant preoperational-operational difference significant (Table 2-2). in phosphorus concentrations, nor was the inter-action between main effects (Preop-Op X Station) Ammonia concentrations have not at any time significant (Table 2-2), during the study shown the distinct seasonality apparent in nitrate and nitrite concentrations Nitronen Spedes (Figure 2-12). Concentrations measured in January through August in 1997 were similar to Nitrate concentrations at Station P2 exhibited a those measured in previous years. Ammonia seasonal pattern in 1997 similar to patterns values for September through December were observed during previous years (Figure 2-12). rejected in data quality control and not included Monthly mean concentrations in 1997 were in these analyses because they were an order of within the 95% preoperational confidence limits magnitude higher than levels observed for similar during all months except October and December, time periods in previous years. Although ammo-when the 1997 monthly mean concentrations nia records are sparse compared to records for were lower. nitrate and nitrite, there has been no evidence of a station influence, as there was no significant Annual mean nitrate concentrations in IM were differences between stations or periods, nor was lower than operational and preoperational aver- the interaction of main effects in the ANOVA ages at Stations P2 and P5 (Table 2-1). The 1997 model significant (Tables 2-1, 2-2). annual mean at Station P7 was slightly greater than the preoperational average, but slightly 2.3.2 Estuarine Water Ouality lower than the operational average. There were no significant differences in nitrate concentrations Monthly averages of surface water salinity and between stations or between periods, nor was the temperature at high and low slack tides in interaction of main effects in the ANOVA model Hampton Harbor were used to examine seasonal significant (Table 2-2). As noted for phosphorus and annual patterns in the Hampton-Seabrook species, nitrate concentrations have shown no estuary, sign of being influenced by station operation during the time that they have been measured. Temperature Monthly mean nitrite concentrations in 1997 Both low and high tide temperatures in 1997 generally followed the seasonal pattern estab- followed the same seasonal patterns observed in lished in previous years, with somewhat unusual previous years (Figure 2-13). Low tide monthly peaks occurring in February and August (Figure mean temperatures exceeded the long term 95% 2-12). Little difference in annual mean concen- confidence limits in June and September, were trations was observed between 1997 and either lower than the long term confidence limits in the preoperational or operational means (Table 2- August, November and December. The 1997 1). As noted for nitrate, there were no signifi- annual mean low tide temperature was slightly cant differences in nitrite concentrations between lower (9.9'C) than the long term annual average ! stations or between periods, and the interacticn (10.1 C, Table 2-5). 2-22
2.0 WATER QUALITY NITRATE 300 - ProoperationaJ ( Operational
*** 1997 250 200
,50 100
.~
' .N g 'b
- , \
/ \
f 0-JAN FEB MAR APR MAY JUN r JUL AUG SEP OCT NOV DEC _w N MONTH NITRITE 10 - Prooperational Operatonal 9 8 a 7 % 6 / g
/ \
5 /
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y v ,...y...$. _$ Y' . .N f i, $ $ t-- ---y 1 - 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH AMMONIA
-- Preoperational Operatonal 45 . 3997 40' a as E 30 es 15 ,N j
J s\'s %
'[ s' 0
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 2-12. Surface nitrate-nitrogen, nitrite-nitrogen and ammonia-nitrogen concentrations ( g 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 (1991-1997) and 1997. Seabrook Operational Report,1997. 2-23
2.0 WATER QUALITY Low Tide 25 g y,,,, 1997 N ,
^
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10 5 . ,
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~
o i l I
-5. . . .
1 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH 4 l 1 High Tide All Years 1997 ao 1 15 - 10 5 .. I o
-5 - . . .
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 2-13. Monthly means and 95% confidence limits for temperature measured at low and high tides in Hampton Harbor from May 1979 - December 1997 and monthly means in 1997. Seabrook Operational Report,1997. 2-24
2.0 WATER QUALITY =_ _ Table 2-5. Annual Mean' and 95% CL* for Temperature (* C) and Salinity (PSU) Taken at Both High and Low Slack Tide in Hampton Harbor from 1980-1997. Seabrook Operational Report,1997. Low Tide High Tide Year Temperature Salinity Temperature Salinity 1980 9.6 i 4.4 29.9 1 1.4 9.1 3.6 32.0 i 0.5 1981 10.1 i 4.4 28.9 1.1 9.3 i 3.8 31.5 i 0.4 1982 10.2 4.1 27.3 1.5 9.2 i 3.5 31.2 i 0.6 1983 10.4 i 4.3 25.5 i 2.4 9.9 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 32.210.3 l l 1986 10.0 i 3.9 27.7 i 1.3 9.4 3.0 31.5 i 0.4 ' 1987 10.0 i 4.3 27.5 i 2.2 8.9 1 3.5 30.7 i 0.9 1988 9.7 i 3.9 27.8 1.0 9.2 i 3.3 31.3 i 0.4 l 1989 10.2 i 4.4 28.0 1.2 9.2 i 3.3 31.4 i 0.7 1990 10.3 i 4.3 27.2 i 1.2 9.713.6 31.3 0.6 1991 11.1 i 4.0 28.0 0.9 9.8 i 3.1 30.910.4 1992 9.1 i 4.0 27.2 1.6 8.6 i 2.9 29.4 1.6 1993 9.5 i 4.4 26.8 i 1.9 8.713.5 29.5 i 1.1 1994 9.8 i 4.6 27.8 i 1.9 9.113.7 30.9 0.8 1995 10.2 i 4.3 28.7 1 1.4 9.9 i 3.4 31.5 i 0.2 1996 10.2 1 4.1 26.8 i 1.4 9.4 i 3.5 30.4 0.5 1997 9.9 i 4.3 28.1 1.7 9.2 i 3.1 31.0 i 0.6 Overall* 10.1 i 0.2 27.7 i 0.5 9.3 i 0.2 31.0 i 0.4
- Annual mean=mean of 12 monthly means
- Confdence limits expressed as half the confdence interval.
' Overall mean=mean of annual means.
2-25
2.0 WATER QUALITY Monthly mean high tide temperatures exceeded ture, while precipitation can affect salinity. In the long term 95% confidence limits in January, 1997, air temperature was slightly cooler than February and March, and were lower than the average, and precipitation was above average. long-term confidence limits in May and June This is apparent in the 1997 annual mean surface (Figure 2-13). As noted for low tide annual and bottom temperatures, which were slightly : mean temperatures, the high tide annual mean in lower than the operational average and compara-1997 (9.2*C) was slightly lower than the long ble to preoperational averages. Over the opera-term annual average (9.3*C, Table 2-5). tional period as a whole, however, surface and bottom water temperatures were warmer than l Salinity during the preoperational period at each station (NAI 1993,1995,1996,1998; NAI and NUS Low tide salinity has historically shown a more 1994). Water quality measurements have gener-pronounced seasonal pattern than has high tide ally remained similar among the three stations, salinity (Figure 2-14), reflecting the relatively Small but significant station differences were greater influx of fresh water into the system detected in surface and bottom temperatures. In during the early spring. The typical seasonal each case, however, these differences were pattern in low tide salinity was more pronounced consistent between the preoperational and opera-in 1997 than during previous years, falling below tional periods, and were not due to the operation long term lower 95% confidence limits in April, of Seabrook Station. i and exceeding the long term upper confidence limits from June through October and in Decem- . Differences between the preoperational and ber. The annual average salinity in 1997 (28.1 operational periods that were not consistent PSU) was slightly greater than the long term among stations were detected for surface dis-average (27.7 PSU, Table 2-5). solved oxygen and surface salinity (Table 2-6). Surface dissolved oxygen levels decreased at all Monthly mean high tide salinities in 1997 gener- stations between the preoperational and opera-ally fell within the long-term 95% confidence tional periods, but the decrease was less at the limits, with the April mean falling below the discharge Station PS, ss indicated by the signifi- : long-term lower confidence limit, and the May cant interaction term (Tables 2-2, 2-6). There l average exceeding the long-term upper confi- was a general decreasing trend in annual mean dence limit (Figure 2-14). The annual mean high surface dissolved oxygen levels between 1987 tide salinity in 1997 equaled the long-term aver- and 1995. Annual means increased between age of 31.0 PSU (Table 2-5). 1995 and 1996, and in 1997 were among the highest recorded during this ten-year period 2.4 DISCUSSION (Table 2-1, Figure 2-10). The decline in dis-solved oxygen levels between 1987 and 1995 The seasonal cycles of all 1997 water quality correspond to increases in average temperatures, parameters were consistent with those of while the increase in dissolved oxygen levels preoperational years. Air temperature can di- seen in 1996 and 1997 correspond to decreases in rectly affect water temperature and indirectly average temperatures (Figures 2-3,2-10). It is mediate dissolved oxygen through water tempera- apparent that plant operation is not involved in 2-26
I 2.0 WATER QUALITY l Low Tide
"' A# Years 1987 g 32 ;
5 . - -- -- --- i g ... * *r . r , 1 1 28 1 1 1 y, i T - . J. - 1 T ,
]l -----j, J j 1
- d. 26 -
1 4 g 20 . . JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH l High Tide
" As Years 1987
-- 32 , . . -i
~
7
,...,T
.),. i h ee !
L E 23 20 . . . . . JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Figure 2-14. Monthly means and 95% confidence limits for salinity (PSU) measured at low and high tides in Hampton Harbor from May 1979 - December 1997 and monthly means in 1997. Seabrook Operational Reg ,1997. 2-27
)
2.0 WATER QUALITY } Table 2-6. Summary of Potential Effects of Seabrook Station on Ambient Water Quality. ) Seabrook Operational Report,1997. Operational Period Spatial Trends Similar to Recent Pre- Consistent with Parameter Depth Operational Period?' Previous Years' Temperature surface Op > Preop yes
bottom Op > Preop yes 1
Salinity surface yes no l P2 Op < Pre P5 Op < Pre ' P7 Op = Pre l bottom yes yes
]
i l Dissolved oxygen surface Preop > Op no ! P2 Op < < Pre i P5 Op < Pre P7 Op < < Pre bottom yes yes ! Nitrate surface yes yes Nitrite surface yes yes Anunonia surface yes yes l l I Orthophosphate surface yes yes Total phosphate surface yes yes !
- Based on ANOVA for 19871997, when all 3 stations were sampled concurrently.
'Significant Preop-Op X Station term in ANOVA model..
2-21
2.0 WATER QUALITY these patterns, as the same trend occurred at uted to the operation of Seabrook Station. There nearfield and farfield stations Further, a poten- is no reasonable mechanism by which the with-tial plant impact would be indicated by a signifi- drawal of bottom water from the intake area, and cant decrease in dissolved oxygen at Station P5 its subsequent release as heated effluent into the (relative to the other stations) as heated effluent discharge area, can reduce surface salinity at the reduces the oxygen content of surrounding wa- intake and discharge areas. The water masses in l ters. However, the observed changes are the the intake and discharge areas are essentially j opposite, where the discharge station has higher identical, and the salinity of this water mass i dissolved oxygen levels in the operational period, cannot be changed by passage through the plant. compared to the intake and farfield stations Salinity levels increased in surface and bottom (Figure 2-9). waters at each station in 1997, again suggesting that there is a regional mechanism that influences The fluctuations in dissolved oxygen during the salinity, and not a local mechanism such as preoperational and operational periods were station operation. probably not biologically important because dissolved oxygen was near saturation at all times. There were no significant differences in nutrient Fluctuations of the magnitude observed could oe levels between the preoperational or opera:ional important if dissolved oxygen dropped to levels periods or among stations (Table 2-6). Nutrient that affected aquatic life. However, mean annual levels in 1997 were within the ranges of previous dissolved oxygen levels were relatively high at all years, and there is no evidence that the operation stations during both the preoperational and opera- of Seabrook Station has affected nutrient levels in tional periods (Table 2-2). either the discharge or intake areas. Surface salinity decreased significantly between The results of the analyses of water quality param-the preoperational and operational periods at both eters highlight the cyclical and variable nature of the intake (P2) and discharge (P5) areas, but there these parameters. Preoperational and operational were no changes at the farfield area (P7). The pattems for all parameters were consistent (Table small decreases (0.3 to 0.2 PSU) in mean salinity 2-6). Overall, no localized effects to water quality at the discharge und intake areas between the that can be attributed to the operation of Seabrook preoperational and operational periods were Station were observed. statistically significant, but an order of magnitude less than that observed over the course of a single
2.5 REFERENCES
CITED year (Figure 2-6). TN re is no evidence that these small long-term ctranges have affected the APHA (American Public Health Association). balanced indigenous populations in either the 1989. Standard methods for the examination f water and wastewater,17th edition. intake or discharge areas. Boston Globe.1998. Boston's daily weather for The significant reductions in surface salinity 1997 - A month-by-month report. January observed were probably influenced by the low 1998. annual mean surface salinity in 19% (Figure 2-Franks, P.J.S. and D.M. Anderson. 1992. 7). These small changes were observed at the Alongshore transport of a toxic phyto-intake and discharge areas but cannot be attrib-2-29
l 2.0 WATER QUALITY plankton bloom in a buoyancy current: 1979. Annual Summary Report Alexandrium tamarense in the Gulf of Maine. for 1977 Hydrographic Studies off Hampton l Marine Biology 112(153-164). Beach, New Hampshire. Tech. Rep. X-I. Preoperational Ecol. Monit. Stud. for Sea-Gilbert, Richard O. 1987. Statistical methods brook Station, for environmental pollution monitoring. Van Nostrand Reinhold Co. Inc., New York. 1993. Seabrook Environmental Studies,1992. A characterization environ-Maine Department of Marine Resources mental conditions in the Hampton-Seabrook (MDMR).1987. Boothbay Harbor Environ- area during the operation of Seabrook Sta-mental Data,1990. West Boothbay Harbor, tion. Tech. Rep. XIV-1. Maine. 1995. Seabrook Station 1994 1991. Boothbay Harbor Environ- Environmental Studies in the Hampton Sea-mental Data,1990. West Boothbay Harbor, brook Area. A Characterization of Environ-Maine. mental Conditions During the Operation of Seabrook Station. Prepared for North Atlan-
. 1992. Boothbay Harbor Environ- tic Energy Service Corporation.
mental Data,1991. West Boothbay Harbor, Maine. . 1996. Seabrook Station 1995 Environmental Studies in the Hampton Sea-
. 1993. Boothbay Harbor Environ- brook Area. A Characterization of Environ-mental Data,1992. West Boothbay Harbor, mental Conditions. Prepared for North Maine. Atlantic Energy Service Corporation. I 1994. Boothbay Harbor Environ- . 1998. Seabrook Station 1996 mental Data,1993. West Boothbay Harbor, Environmental Studies in the Hampton Sea-Maine. brook Area. A Characterization of Environ- '
mental Conditions. Prepared for North
. 1995. Boothbay Harbor Environ- Atlantic Energy Service Corporation.
mental Data,1994. West Boothbay Harbor, Maine. Normandeau Associates (NAI) and Northeast Utilities Corporate and Environmental Affairs
. 1996. Boothbay Harbor Environ- (NUS). 1994. Seabrook Environmental mental Data,1995. West Boothbay Harbor, Studies, 1993. A Characterization of l Maine. Environmental Conditions in the Hampton-Seabrook Area During the Operation of
. 1997. Boothbay Harbor Environ- Seabrook Station. Prepared for North Atlan-mental Data,1996. West Boothbay Harbor, tic Energy Service Corporation.
Maine. Sokal, R.R. and F.J. Rohlf. 1981. Biometry. Normandeau Associates (NAI).1977. Summary W.H. Freeman and Co., San Francisco, CA. Document: Assessment of anticipated im- 859 p. pacts of construction and operation of Sea-brook Station on the estuarine, coastal and Stewart-Oaten, A., W.M. Murdoch, and K.R. offshore waters; Hampton-Seabrook, NH. Parker.1986. Environmentalimpact assess-l Prepared for Public Service Co. of New ment: "pseudoreplication in time?" Ecol-Hampshire. ogy, 67:929-940. 2-30
2.0 ~ WATER QUALITY USEPA (United States Environmental Protection Agency). 1979. Methods for chemical analyses of water and wastes. EPA-600/4-79-020. EMSL, Cincinnati, OH. I I 4 2-31
3.0 PHYTOPLANKTON TABLE OF CONTENTS PAGE 3.0 PHYTOPLANKTON
SUMMARY
. . . ............. . ........ . . . . . . . . . . . . . . . . . 3-ii LIST OF FIGURES . . . . . .. . . .... . . . . . . . . . . . . . . . . . . . . . 3-iii LIST OF TABLES . . . . .. . ... ...... . . . . . . . . . . . . . . . 3.iv LIST OF APPENDIX TABLES . ........ . . . . . . , . . . . . . . . . . . . 3-iv i
3.1 INTRODUCTION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3.3.1.1 Phytoplankton . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 3.3.1.2 Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11 3.3.2 Selected Species ... .. . . . . . . . . . . . . . . . . . . . . 3 15 3.3.3 PSP Levels . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15 ! i l 3.4 DISC USSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15 i
3.5 REFERENCES
CITED . ... . . . . . . . . . . . . . . . . . . . . . . . . 3-18 ! } i i k l. t i b 4
J 1 3.0 PHYTOPLANKTON '
SUMMARY
l The phytoplankton community historically has been highly variable in species composition and abundance j in both the preoperational and operational periods. Taxa of the class Bacillariophyceae (diatoms) dominated the community numerically throughout both the preoperational and operational periods. In 1997, however, the Prymnesiophyceae taxon Phaeocystispouchetti was dominant, accounting for 31 % of j 1 the total community. This is not a unique occurrence as peaks in P. pouchetti density also occurred in 1978,1979,1981,1983,1992, and 1994. The community composition in 1997 was different from the preoperational and operational periods due to the dominance of P. pouchetti, but there were no major differences in community composition between the preoperational and operational periods. Total j 4 phytoplankton geometric mean abundance in 1997 (14.0-21.8 X 10. cells /L) was higher than both the l preoperational and operational periods as a result of the spring bloom of P. pouchetti. The abundance of the selected species (the diatom Skeletonema costatum) in 1997 (0.1-0.2 X 10* cells /L) was lower than the ! operational period, but similar to the preoperational period. Chlorophyll a concentrations were variable from year to year but were similar to the preoperational and operational periods in 1997 (0.62-0.79 l mg/mS). Chlorophyll a concentrations were independent of phytoplankton abundances. Increases in l phytoplankton abundances in 1992,1994 and 1997 did not cause an increase in chlorophyll a concentrations. In these years the phytoplankton was dominated by P. pouchetti, a small-celled species l that forms gelatinous colonies. Differences in community composition or chlorophyll a concentrations observed between the preoperational and operational periods occurred at both the nearfield and farfield j stations, i I There were no. significant differences in total phytoplankton abundance or abundance of S. costatum between the preoperational and operational periods or among stations. Similarly there were no significant ; differences between periods or stations in chlorophyll a concentrations. In all cases, the interaction term i (Preop-Op X Station) was not significant, indicating no impact due to the operation of Seabrook aation. PSP was not detected in Hampton Harbor in 1997. l i i l 3-ii I
F l l 3.0 PHYTOPLANKTON l i ! LIST OF FIGURES l l 3-1. Phytoplankton sampling stations. ...... ......... .. . .. .... .. . 3-2 l 3-2. Monthly mean log (x + 1) total abundance (no./L) of phytoplankton at nearfield l Station P2, monthly means ar.d 95% confidence intervals over all l preoperational years (1978-1984), and monthly means over operational years l l (1991-1997) and 1997. . . . . ..... .............. ... .. . ... . . 3-6 l 3-3. Percent composition of major phytoplankton groups at Station P2 over all preoperational (1978-1984) and operational years (1991-1997) and in 1997. ....... . 3-7 1 3-4. Geometric mean abundances (x 10' cells /L) and 95 % confidence intervals of annual total abundances, and percent composition of four selected phytoplankton groupings at Station P2 during each year of the preoperational and operational periods. . . . . . . . . . . . . . . . ................ ..... . . . . 3-8 3-5. (a) Mean monthly chlorophyll a concentrations and 95 % confidence intervals at Station P2 over preoperational years (1979-1989) and monthly means over operational years (1991-1997) and 1997; (b) mean monthly chlorophyll a concentrations and phytoplankton log (x+1) abundances during the preoperational and operational years. . . . . . . . . . . . ....... ... ....... . 3-14 l 3-6. Log (x+ 1) abundance (no./L) of Skeletonema costatum at nearfield Station P2; monthly means and 95% confidence intervals over all preoperational years (1978-1984) and monthly means for the operational years (1991-1997) and 1997. .. ....... .... ... ... .. ............. ............ 3-16 3-7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor, mean and 95% confidence intervals over preoperational years (1983-1989) and monthly means during operational years (1991-1997) and in 1997. Data provided by the State of New Hampshire. . . . . . . ........... 3-16 i 3-iii t
r 3.0 PHYTOPLANKTON LIST OF TABLES i PAGE 3-1. Summary of Methods Used in Evaluation of the Phytoplankton Community. ...................... .... . .. .. . . . . . . .... 3-4 3-2. Geometric Mean Abundance (X 10' Cells /L) of Phytoplankton (a10 m) and Skeletonema costatum, and Mean Chlorophyll a Concentrations (mg/m') and 1 Coefficient of Variation (CV,%) for the Preoperational and Operational (1991- l 1997) Periods, and 1997 Geometric Means. . . . . ..... . .. .. .. . . . . 3-9 l l 3-3. Arithmetic Mean Abundance (X 10' Cells /L) and Percent Composition of I Dominant Phytoplankton Taxa During the Preoperational Period (1978-1984), j Operational Period (1991-1997), and 1997 at Nearfield Station P2. . . . . . . . . . 3-10 3-4. Results of Analysis of Variance Comparing Abundances of Total Phytoplankton, Skeletonema costatum, and Chlorophyll a Concentrations i among Stations P2, P5 and P7 During Preoperational and Operational (1991-1997) Periods. ... .. .. ...... ............. .... . .... . 3-12 3-5. Phytoplankton (:t10 m) Species Composition (%) by Station in 1997. . .......... 3-13 ( 3-6. Summary of Potential Effects (Based on ANOVA) of Operation of Seabrook Station on the Phytoplankton Community. ..... .. ..... ....... ... . 3-17 { t 1 l LIST OF APPENDIX TABLES / i l l 3-1. Checklist of Phytopicnkton Taxa Cited in this Report . .... .. ........ . . 3-21 J l l l l 3-iv
I i ( 3.0 PHYTOPLANKTON j
3.1 INTRODUCTION
Chlorophyll a collections resumed at all three stations in July 1986 and phytoplankton collec- l The phytoplankton monitoring program was tions resumed in April 1990. These collections initiated to identify seasonal, annual, and spatial continued on this schedule through December trends in the phytoplankton community, and to 1997. From each whole water collection, two determine if the balanced indigenous phytoplank- one-quart (0.946 L) jars containing 10 mL of a ton community in the Seabrook area has been modified Lugol's iodine fixative were filled for adversely influenced (within the framework of phytoplankcon taxonomic analyses and one gallon natural variability) by exposure to the thermal (3.785 L) was reserved for chlorophyll a analy-plume. The objective of the study was to deter- ses. Weekly paralytic shellfish poison (PSP) mine if a significant difference had occurred toxi:ity levels from mussels collected in Hampton between the preoperational and operational pe- Harbor were provided by the State of New riod for the following parameters: phytoplankton Hampshire. (taxa a 10 pm in size) abundance and species composition; community standing crop as mea- 3.2.2 Laboratory Methods sured by chlorophyll a concentrations; abundance of the selected species Skeletonema costatum, and Phytoplankton samples were prepared for analy-toxicity levels of paralytic shellfish poison (PSP) sis following the steps oatlined in NAI (1991a). as measured in the tissue of the mussel Mytilus One randomly-selected replicate from each sta-edulis in the Hampton-Seabrook area. In previ- tion and sample period was analyzed for all taxa ous years ultraplankton taxa were identified and and the second replicate was analyzed for the enumerated. Results had limited accuracy be- selected species S. costatum only. Two 0.1-mL , cause of the small size and colonial habits of subsamples from each replicate were withdrawn j these organisms. Therefore enumeration of and placed in Palmer-Maloney nanoplankton ultraplankton was eliminated from the program in counting chambers. For those replicates selected 1995. for taxonomic analyses, the entire contents of the chamber were enumerated and identified to the l 3.2 51ETHODS lowest possible taxonomic level, usually species. l 3.2.1 Field Methods Procedures for preparation of chlorophyll a water samples followed steps outlined in NAI (1991a). , , Near-surface (-1 m) water samples for phyto- Following the extraction of the plant pigment, ! i l plankton and chlorophyll a analyses were col- fluorescence was determined and chlorophyll a ! l lected during daylight hours at Stations P2 (in- concentrations (mg/m') were computed. take), P5 (discharge) and P7 (fariield) (Figure 3-
- 1) using an 8-L Niskin bottle. Collections were 3.2.3 Analytical Methods i taken once per month in January, February and December, and twice monthly from March Seasonal abundance patterns of the phytoplankton through November. Sampling occurred from assemblages during the preoperational and opera-l 1978-1984 at Station P2; from 1978-1981 at tional periods were compared graphically using l Station P5; and from 1982-1984 at Station P7. log (x + 1)-transformed monthly mean abundances l
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r 3.0 PHYTOPLANKTON for the total phytoplankton community and the wood 1994). The ANOVA was a two-way facto-selected species (S. costatum; Table 3-1). The rial with nested effects that provided a direct test log (x+ 1) transformation was performed on the for the temporal-by-spatial interaction. The main sample period mean prior to calculating monthly effects were period (Preop-Op) and station (Sta-means. Temporal (preoperational-operational) tion); the interaction term (Preop-Op X Station) patterns in species abundances were evaluated was also included in the model. Nested temporal using geometric means and community composi- effects were years within operational period tion was evaluated by examining the percent (Year (Preop-Op)) and months within year ; composition of dominant (> 1%) taxa Chloro- (Month (Year)), which were added to reduce the phyll a temporal and spatial comparisons were unexplained variance, and thus, increase the based on untransformed monthly and yearly sensitivity of the F-test. For both nested terms, arithmetic mean concentrations. The similarity variation was partitioned without regard to station among the three stations with respect to species (stations combined). An additional term (Station composition of the dominant phytoplankton taxa X Year (Preop-Op)) was added to provide,the was evaluated statistically using a multivariate proper mean square for testing the significance of analysis of variance procedure (MANOVA, Har- the Preop-Op X Station term. When the F-value ris 1985). Operational /preoperational and was significant for the interaction term (Preop-Op nearfield/farfield differences in total abundances X Station) or class variable (Station, Preop-Op), of S. costatum and phytoplankton and mean the least squares mean procedure (SAS Institute l chlorophyll a concentrations were evaluated Inc.1985) was used to evaluate the differences using a multi-way analysis of variance procedure among the means with a t-test at alpha s 0.05. (ANOVA, SAS Institute Inc.1985). A mixed The final variance not accounted for by the above effects ANOVA model was used to test the null explicit sources of variation constituted the Error hypothesis that spatial and temporal abundances term. The preoperational period for each analy-during the preoperational and operational periods sis was specified as the period during which at were not significantly (p>0.05) different. The least one nearfield and one farfield station were mixed effects model was based on reviews of the sampled concurrently (thus maintaining a bal-design by Underwood (1994) and Stewart-Oaten anced model design). Preoperational periods for et al. (1986), where sampling was conducted each analysis are listed on the appropriate figures prior to and during plant operation and sampling and tables. For all preoperational comparisons, station locations included both potentially im- the focus was on intake Station P2 because it had pacted and non-impacted sites. All effects were the longest time series. In all cases the opera-considered random except operational status tional period evaluated in this report includes col-(Preop-Op). Time and location of sampling were lections from 1991-1997. Finally, weekly mean i considered random because both sampling dates PSP toxicity levels were arithmetically averaged and selected locations represented only a fraction over the preoperational and operational periods of all the possible times and locations (Under and presented graphically. l l 3-3 I
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e t e ic: 41,4 t a a m ( n ( n ((( m 888 t ht a a (l a m ht 999 i n D d ns i r gd o nu gd gt oo ggg :a ht ti i r 1 1 1 u aec a l lon u t looo ll ar a :t a 832 lyn ly lyb lyba lyf o lyyy ly la ly 778 999 m ha h ha ht l h hhh ll ha ht ly 1 1 1 m td t t n n n t% t t t t u k oa nn n a n on n n nnn n e C o Mb ou o a M Mm Mm oe e M< o1 ooo MMM MA n M o W e === a _ n 2S7 o aPPP t k i n l l y n d 's h p a ei o . l p s s ; ; : ; ; ; ; ,; ; ; r o o Uly 47 47 47 474717 97497 97 97 l t a 89 99 89 99 89 99 898989 999999 89889 99999 89 99 89 99 h C y s e n 11 11 11 111111 11111 11 11 a A h t 81 7 81 81 7 212191 81871 71 31 . P D 79 99 9 9 79 99 79 99 9 9 898979 999999 79789 99999 89 99 89 99 B e 11 1 11 11 1 111111 11111 11 11 h t f o n _ o s . i n - t a . i o t lu7 a 7 7 7 7 7 a9 t P, P, P, P, P, v9 S 5 5 5 7 7 5 5 5 E1 P. P, P, P, P, P, P, P.
, 2 2 2 2 2 2 2 2 2 2 2 nt P P 'P P P P P P P P P - -
ir de po s - r e t s e m m e UR t u a t u a m a r - s an do o l t s o c t s o c a p s d hi n a t a 41 4 n - t t a m n a m 838 a 999 s ea r T e n e 1
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o e im o n o t e 882i- - o 778 t 999t a l d 1 1 1 s oO l l l e 4 l l l e l yk r o A lA R 1 A R - - - la, . 7 a o = = = 99 mr n o 1 mb t n k 1 uea io t : dl op n257 9 aPPP 91 SS s is io : i s np o r t ey d l y t o m ano y Ph la P o ir
. a ko e A I
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l a 3 l t O ptn o iaA t pn d V oe V T r n o e oe t c n u N O rc on O e p it yr A N P a N l b b l ho o r a he A M A A S e e PP CC P P r O p T
- wg .
1 l l 3.0 PHYTOPLANKTON l 3.3 RESULTS months except the spring when Prymnesiophyceae were dominant (Figure 3-3). I 3.3.1 Total Community In 1997, diatoms continued to dominate during l most of the year, but their relative abundance l 3.3.1.1 Phytoplankton exceeded 60% during only six months (January, l February, June, August, October, and Decem-Seasonal Trends at Station P2 ber; Figure 3-3). Phaeocystis pouchetii (Prymnesiophyceae) dominated in March through During 1997, total abundance of phytoplankton May 1997, as it has intermittently during the j at nearfield Station P2 exhibited two periods of preoperational (1978,1979,1981,1983) and j elevated abundances, March through May and operational (1992,1994) periods. As has been I August through November (Figure 3-2). Abun- observed in the preoperational and operational dances in April and May exceeded the upper periods, dinoflagellates (Dinophyceae) also repre-95% confidence limit of the preoperational pe- sented a distinct component of the community riod (1978-1984). The April and May 1997 during much of the year. The relative abun-mean abundances were also above the operational dances of dinoflagellates was greater in 1997 than period mean total abundances, with the exception the averages during the preoperational and opera-of April 1992 (NAI 1993). Throughout the rest tional periods, however. Dinoflagellates exhib-of 1997, monthly mean total abundances were ited higher relative abundance in January, Febm-within the 95 % confidence intervals found during ary, June, July, September and December 1997 i the preoperational period. The timing and appar- than previously observed. As observed in 1996, ent duration of the late winter-spring peak varied Cryptophyceae taxa occurred in higher relative l during the preoperational period and operational abundance in the fall of 1997 compared to previ-period, starting as early as February and extend- ous years, representing up to 50% of the total I ing as late as June, and enduring for one to three community. ! months (NAI 1990, 1991, 1992, 1993, 1995, l 1996,1998a; NAI and NUS-1994). With the Temporal Trends at Station P2 exception of the magnitude of the abundances, j the late winter-spring peak in 1997 fit this pat- Annual geometric mean abundance of the tern. The fall peak in 1997 was nearly identical phytoplankton community at Station P2 exhibited in magnitude and timing to the preoperational greater than a threefold difference over the four-and operational period means (Figure 3-2). teen years studied, with the lowest abundances occurring in the preoperational period and the Diatoms (Bacillariophyceae) have been the pre- highest abundances occurring in the operational j dominant component of the phytoplankton com- period (Figure 3 4). On average, total i munity in the coastal waters offshore of the phytoplankton abundance has been higher in the Hampton-Seabrook estuary throughout the year operational period than the preoperational period during the entire study period (Figure 3-3). In
~
(Table 3-2) Mean total abundance at Station P2 the preoperational and operational periods, dia- in 1997 was higher than the operational period toms accounted for more than 60%, and often mean although relatively low compared to the more than 90%, of the total community during all 1992 peak. While the mean total abundance in 3-5 l
y I 3.0 PHYTOPLANKTON ( , t l Total Abundance of Phytoplankton 7.5 Preoperational l Operational , 7.0 ~ ~ - + 1997 ]
'iii Q 6.5 4 .
S '
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/
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3.5 3.0-JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH l l l Figure 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- l 1984), and monthly means over operational years (1991-1997) and 1997. Seabrook l Operational Report,1997. 1997 was nearly double the preoperational period the 1997 assemblage. Relative abundances of S. mean, it was similar to the 1980 and 1984 means costatum and other diatoms were reduced in (Figure 3-4). years when Phaeocystis pouchetii bloomed (par-ticularly in 1981 and 1983 in the preoperational Diatoms have dominated on an annual basis, period; 1992 and 1997 in the operational period; representing more than 75% of the total commu- Figure 3-4). nity abundance during most years at Station P2 (Figure 3-4). Skeletonema costatum has histori- When 1997 results are compared to mean values cally been the most prevalent diatom. The total for the preoperational and operation periods diatom abundance has accounted for approxi- (Figure 3-3), the community during the summer mately 78% of the preoperational period assem- and fall months appears to be different, with l blage,66% of the operational period assemblage, dinoflagellates and cryptophyceans contributing and 43% of the 1997 assemblage (Table 3-3, a higher proportion of total abundance in 1997. (Page 3-10). S. costatum alone represented 35% A comparison of absolute abundances to annual of the preoperational assemblage, 22% of the preoperational period data, however, shows that operational period assemblage, but only 6% of the 1997 dinoflagellate abundances fall within the 3-6 l l t
3.0 PHYTOPLANKTON l l Preoperational(1978-1984) l F~ " gg " !Mi T i l To Do so do So , l ill o I ! l l l MONTH C C CYAN H EAE DN H PRYMNESIOPHYCEAE Operational (1991-1997)
.o
.o . _
7o So so ao q so 1 ao { j so l z~,, ~ . oo, ~- o
@a:fJMat v"CTEE"^ 52 8" = E'a"FFAt" " !Ei!Er~=,?v"JZ "" lj N P'MYMNESiOPMYCEAE 1997 llI 1
vo Is
.o So do g so i
f:2 i io ]
=_ ... - . v~
MO~rs _ ~. .. oo. ~~ o I C YCEAE CYANO M EA DN H hnVM~EsiOPsYCEAE Figure 3-3. Percent composition of major phytoplankton groups at Station P2 over all i preoperational (1978-1984) and operational years (1991-1997) and in 1997. Seabrook Operational Report,1997. ! 3-7 i I -]
\
3.0 PHYTOPLANKTON j 70 Preoperational Operational s Bo l l U ' gso , l , 8- ! ! l-
! I
! ! l I
$' / 1 I l l 1 l 78 79 80 81 82 83 84 91 92 93 94 95 96 97 1
100 - 10 78 79 80 81 82 83 84 91 92 93 94 95 96 97 C Skeletonema G Phaeocystis 6 Bacittarlophycoa S Other 4 Figure 34. Geometric mean (x 10 cells /L) and 95% confidence intervals of annual total abundances, and percent composition of four selected phytoplankton groupings at Station P2 during each year of the preoperational and operational pt.riods. Seabrook Operational Report,1997. 3-8
3.0 PHYTOPLANKTON l Table 3-2. Geometric Mean Abundance (X 10' Cells /L) of Phytoplankton(a10 m) and Skeletonema costatum, and Mean Chlorophyll a Concentrations (mg/m') and Coefficient of Variation (CV,%) for the Preoperational and Operational (19911997) Periods, and 1997 Geometric Means. Seabrook Operational Report,1997. Preonerational Operational 1997 6 Station i* CV (years)* I' CV i i Phytoplankton l P2 11.9 4.8 (78-84) 18.3 3.0 21.8 P5 12.6 4.0 (78-81) 20.4 3.6 21.7 P7 10.0 4.3 (82-84) 16.1 2.8 14.0 Chlorophyll a l P2 0.78 21.2 (87-89) 0.78 22.3 0.75 l PS 0.88 20.6 (87-89) 0.81 18.2 0.79 P7 0.75 17.9 (8789) 0.76 23.3 0.62 Skeletonema costatum P2 0.2 6.4 08-84) 0.6 7.8 0.2 P5 0.1 22.2 08-81) 0.5 8.8 0.1 i P7 0.2 13.2 (82-84) 0.4 12.8 0.1 Dinophyceae P2 0.3 12.4 08-84) 0.8 5.8 1.8 i PS 0.3 19.0 08-81) 0.9 4.9 1.9 l P7 0.3 10.4 (82-84) 0.7 6.2 1.2 ) Cryptophyceae P2 0.2 11.3 (78-84) 2.1 13.9 0.6 PS 0.2 4.0 08-81) 2.2 14.2 0.6 P7 0.1 26.2 (82-84) 1.7 13.8 0.5
- Maan of annual mears.
O CV c= coefncient of vanation.
' ( ) = preoperational years.
range of abundances observed in the preopera- the ranges observed during the operational period tional period (Table 3-2). This is not the case for except during July, September, and October cryptophyceans, however. This group was rarely when 1997 abundances exceeded previous values identified in the preoperational period, but has (NAI 1992,1993,1995,1996,1998a; NAl and been consistently represented during the opera- NUS 1994). Annual mean abundance in 1997 tional period. Marshall and Cohn (1983) found was similar to that occurring in 1995, but slightly that cryptophycean abundances tended to be higher than other years during the operational underestimated by researchers because of preser- period. Annual mean abundance at Station P2 in vation and taxonomic difficulties, but they con- 1997 was similar to abundance at Stations P5 and sidered this group to be commonly occurring. P7. This might provide an explanation for the differ-ences observed between the preoperational and While S. costatum was the most abundant taxon operational period. Abundances of cryptophy- during nearly every year of this study (Figure 3-ceans in 1997 at Station P2 were generally within 4), the relative abundance of the remaining taxa 3-9
4 d _ o n o 61 4 2 820499392.07951 _ i 1 r t i 400 4 6 2000051 008551 9 e nk P e s < 4 l ro e p a ea n Ps a , i o C 0 0 t _ - a r 7 1 o e 9 t _ p 9 m 1 u o s e r e t o c 0. 1 3 8 8 81 0369961 38001 n P n 300 2 0 1 000030005341 6 s e e 7
. a < 3 o
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t t n en Pn n u n a o o b a e7 i e C l a c9 to r9 e 1 t w f P e o d r "c n % dn a n P a 1 a d 581 1 8 81 91 521 402.9339
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p uo e ne ap ri c s hpl aa ss ooos eddspiaa cr n nmns ei r h c a, ni tn h y i t s oel l nr i r rhii e eet nn a e eO n ed c o p y c i r nuc cc rolyyilo aleeoo nii ss n lao irtaoood cch s os s o M ), o x don n ro m t p y o e a l i ct ar r eeenoo er aaal t i t t pptzi e c zl s ot elaa l i
)
(s . p c4 a i r i8 t e9 T i r y DPG C r h P BACCCCCLLNRS&W as ehhh yeeiht a ymu e s h8 m1- e l lao r y r t t 7 a e a e x e vO i ir9 e cy e c o A1 ( e a a e c h p h y ed c nll e e y o p a a c y h i s o d c p e i r ny s h p t o n l a ul b s 3- s o p m l a u o 3 a n y r y i c ni l r a av e C iD C P B ee r l MP b ** a T gLO
l 3.0 PHYTOPLANKTON varied among years (Table 3-3). During the Species composition was generally similar among i preoperational period, P. pouchetil (17% of the the three stations in 1997 (Table 3-5), with four-total assemblage) was second in abundance to S. teen taxa each accounting for 1% or more of the costatum. Other dominant taxa included the assemblage at at least one of the three stations. ; diatoms Rhizosolenia delicatula/fragilissima Eleven taxa accounted for more than 95 % of the (14%) and Chaetoceros socialis (9%). Nine total abundance at both P2 and P5 (Table 3-5). . I other taxa each accounted for 1% or more of the At P7, twelve taxa accounted for more than 95 % total abundance during the preoperational period. of the total abundance. With few exceptions, the l During the operational period,16 taxa individu- numerically important taxa were the same at the ally accounted for at least 1% of the assemblage. three stations, although their relative abundances j P. pouchetii (23 %) was slightly more abundant varied spatially. P. pouchetii was the most abun-than S. costatum (22%) during the operational dant species at each station, but the second most l period and Leptocylindrus minimus (9%) was abundant species was Thalassiosira sp. at P2 and 1 third in abundance. In 1997,11 taxa each repre- P5 and Rhizosolenia delicatula/fragilissima at P7. sented 1% or more of the total abundance. P. The abundances of these fourteen dominant taxa pouchetii represented 46%, Nitzschia sp. repre- were not significantly different among the three j sented 8%, and S. costatum and Chaetoceros sp. stations in 1997 (p=0.07, Wilkes' Lambda as l each made up about 6% of the total, computed by MANOVA), a result that is consis- ! tent with observations during each operational l Spatial Trends year. Phytoplankton abundance and community compo- 3.3.1.2 Biomass sition were evaluated in the nearfield (Stations P2 I and P5) and farfield (Station P7) areas to deter- The biomass of the phytoplankton community mine whether spatial relationships during the was measured as chlorophyll a concentrations. l preoperational period were maintained during the In 1997, chlorophyll a reached peaks in February I operational period. Preoperational period geo- and June, with a slight increase in September ! metric mean abundances at Stations P2 (1978- through November (Figure 3-5, Page 3-14). ! 1984) and P5 (1978-1981) were similar to each While the seasonal patterns of chlorophyll a l other and higher than abundances at P7 (1982- concentrations generally followed that occurring i j 1984; Table 3-2). Mean abundances were higher in the preoperational and operational periods, j at each station in the operational period and in some deviations occurred. 1997 chlorophyll a i 1997 than during the preoperational period. concentrations were within the 95% confidence l Analysis of variance comparing nearfield (Station intervals of the preoperational period mems ) j P2) and farfield (Station P7) phytoplankton abun- during January through September, although l l dances indicated, however, that the apparent generally below the preoperational means. Dur-l increase in abundance after operation of the Sea- ing October through December 1997, the chio-i brook Station began was not significant (Table 3- rophyll a concentrations were below the ! 4). There were no significant differences be- preoperational period lower confidence limits. ! 1 1 tween stations and the interaction term (Preop-Op Chlorophyll a concentrations were elevated in j X Station) was not significant. i 3-11 s j
1 3.0 PHYTOPLANKTON ] Table 3-4. Results of Analysis of Variance Comparing Abundances Of Total Phytoplankton, Skeletonema costatum, and Chlorophyll a Concentrations aniong Stations P2, P5 and P7 During Preoperational and Operational (1991-1997) Periods. Seabrook Operational Report,1997. . m Source of Variation df MS F Multiple l Comparisons l Phytoplankton: P2 vs P7 (PREOP = 1982-1984; OP = 1991-1997)* Preop-Op" 1 1.89 2.89 NS { Year (Preop-Op)' 8 0.71 1.15 NS Month (Year)d 110 0.58 22.10* " l Station 1 0.26 33.77 NS i Preop-Op X Station' 0.01 0.18 NS 1 f Station X Year (Preop-Op) 8 0.06 2.40* l Error 110 0.03 i Chlorophyll a: P2, P5, P7 (PREOP = 1987-1989; OP = 1991-1997)' Preop-Op' 1 0.02 0.03 NS Year (Preop-Op)* 8 0.92 1.23 NS Month (Year)d 110 0.76 14.80 " *
)
Station 2 0.22 4.69 NS ' Preop-Op X Station' 2 0.05 1.36 NS Station X Year (Preom ,>) 16 0.03 0.67 NS Error 220 0.05 Skeletonema costatum: P2 vs P7 (PREOP = 1982-1984; OP = 1991-1997)* Preop-Op' 1 6.82 2.14 NS Year (Preop-Op)* 8 3.21 1.11 NS Month (Year)d 110 2.81 14.61* " ' Station 1 0.97 3.89 NS Preop-Op X Station' 1 0.25 0.93 NS Station X Year (Preop-Op) 8 0.27 1.40 NS Error 110 0.19 Sksletonema costatum: P2 vs P5 (PREOP = 1979-1981; OP = 1991-1997)' Preop-Op' I 9.19 4.29 NS l Year (Preop-Op)* 8 2.32 0.60 NS l Month (Year)d 109 3.86 13.82* " l Station 1 1.13 20.59 NS l Preop-Op X Station' 1 0.07 0.25 NS Station X Year (Preop-Op) 8 0.27 0.98 NS Error 109 0.28
- ANOVA based on mean of twice-monthly collections Mar-Nov and monthly collections Dec-Feb; ordy years when collections at these stations were concurrent are included; analyses include only years when all 12 months were sampled.
- Preoperational versus operational period regardless of station.
' Year, regardless of period.
- Month nested within year regardless of station or year. l
- Interaction between main effects.
NS = not significant (p a 0.05)
* = significant (0.05 > p a0.01)
" = highly significant (0.01 a p >0.001)
*** = very highly significant (0.001 a p) 3-12
3.0 PHYTOPLANKTON Table 3-5. Phytoplankton (210 m) Species Composition (%) by Station in 1997. Seabrook Operational Report,1997. Class Taxa P2 PS P7 Phytoplankton' Cryptophyceae Cryptophyceae 4.2 2.3 7.9 Dinophyceae Dinophyceae 4.6 2.2 5.4 Gymnodinioidae' O.4 0.4 1.1 Bacillariophyceae Bacillariophyceae 2.8 3.6 7.8 > Chaetoceros socialis 0.9 1.9 0.9 l Chaetoceros sp. 5.9 3.5 3.6 l Cylindrotheca closterium 1.3 0.9 1.4 i Leptocylindrus danicus 0.9 0.3 1.4 i Nitzschia sp. 8.0 4.5 1.2 l Rhizosolenia delicatula/fragilissima 5.7 3.0 10.6 Skeletonema costatum 5.9 3.4 3.2 Thalassionema nitzschioides 1.5 1.0 2.3 Thalassiosira sp. 9.1 7.3 8.5 \ l Prymnesiophycea Phaeocystis pouchetti 46.1 63.8 40.7
' Presents only taxa accounung for al% of total abundance
- Previously called Oxytoxum sp.
Febmary, March, and June 1997 compared to the rophyll a concentrations can differ from the l operational period means. change in total abundance from one month to the next, however. This is because chlorophyll a Arithmetic mean chlorophyll a concentrations concentrations are related not just to the total were similar between the preoperational and phytoplankton abundance (Figure 3-2), but also operational periods (Table 3-2). Mean concen- to the species composition. The seasonal patterns trations in 1997 were slightly lower than either observed in 1997 are notable in this regard, in the preoperational or the operational period. 1997, chlorophyll a peaked in February, at one Analysis of variance detected no significant dif- of the lowest periods of abundance. Similarly, ferences in chlorophyll a concentrations between when abundance peaked (May), chlorophyll a the preoperational and the operational periods or was at one of its lowest values for the year. among stations (Table 3-4). Overall, there was During February, the small-bodied solitary dia-no significant difference between preoperational toms Thalassiosira sp. and T. decipiens domi-and operational period and station The Preop-Op nated, representing about 33% of the total abun-X Station term was also not significant, dance (NAI 1998b). From March through May, P. pouchetii, (a small-celled colonial species with On a seasonal basis, chlorophyll a concentrations a relatively high carbon to chlorophyll a ratio; generally follow the same pattern as total abun- Lee 1980; Verity et al.1988a) increased in abun-dance (Figure 3-5). The rate of change in chlo- dance. 3-13
F j 3.0 PHYTOPLANKTON l
- a. ]
Chlorophyll a 4.s __~g:=
. - . 1.
7 en ,
,, 38 [ 7 3.0 .
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. . . _ _ D ~s ,
hs
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, .y, . f. a .. r . = g; 1
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#N FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH Preoperational Years
- b. Abundance
----- Chlorophyll a e.O 3.0 SS -
q e.O / \ 2.s d 45 ! j g 4.D y% / \ 2.0 36 / \ - -- / 3.0 ! j \ 1.5 I 25 /
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=::
10
- 0. 5 w - - - - - / 'x N
'3 O.s JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NW OEC MONTH I Figure 3-5. (a). Mean monthly chlorophyll a concentrations and 95% confidence intervals at Station P2 over preoperational years (1979-1989) and monthly means over operational years (1991-1997) and 1997; (b) mean monthly chlorophyll a concentrations and phytoplankton log (x+1) abundances during the preoperational and operational years. Seabrook Operational Report,1997. l 3-14
3.0 PHYTOPLANKTON f i 3.3.2 Selected Snecies 3.3.3 PSP Levels l The diatom S. costatum was chosen as a selected During the preoperational period (1983-1989), species because of its historic dominance annu- average weekly PSP toxicity levels were above l ally and seasonally. It has been generally presem the detection limit of 44 ug PSP /100 g tissue of (Figure 3-6), if not dominant, throughout the the mussel Myrilus edulis and periodically above year. During the preoperational period at Station the closure limit then in effect (80 ug PSP /100 g l P2, S. costatum exhibited a peak in the late win- tissue) during the late spring, early summer and ter, followed by an early spring decline that led late summer (Figure 3-7). On average in the into rising abundances in the spring and summer, preoperational period, PSP was detected ten culmmating in the highest peak in the fall (Figure times a year and on five occasions PSP values 3-6). The timing of the S. costatum cycle of exceeded the closure limit. PSP was detected abundance was variable among years, as evi- during every preoperational period year except denced by wide confidence intervals each month. 1987. PSP toxicity has rarely been detected Average conditions in the operational period during the operational period, however, averag-followed this general pattern closely. During ing 2.5 times per year and on only three occa-1997, S. costatum continued to mirror this basic sions (all in 1993) did the levels exceed the clo-seasonal pattern but abundances exhibited fairly sure limit (NAI 1992,1993,1995,1996,1998a, high seasonal variability. Abundances in April 1998b; NAI and NUS 1994). PSP was not de-and May exceeded the upper 95% confidence tected at all in 1992,1996 or 1997. There were limit and the value in July was below the lower no closures of the Hampton Harbor flats related 95% confidence limit of the precperational pe- to PSP in 1997. riod. The mean annual abundance in 1997 was similar to the preoperational period mean at each 3.4 DISCUSSION station, but below the operational period means (Table 3-2). In general, the seasonal pattern of major phyto-plankton group abundance observed offshore of S. costatum abundances were evaluated in two Hampton Harbor was typical of northem temper-separate ANOVAs because the preoperational ate coastal waters (Cad 6e and Hegeman 1986; periods were different for Stations P5 and P7. Durbin et al.1975; Marshall and Cohn 1983; Resuhs were the same in both analyses, however. Peperzak 1993). Specifically, this pattern was There were no significant differences between the characterized by annual dominance by diatoms preoperational and operational periods in S. which were most abundant in the spring and fall. costatum abundance, nor were there differences Abundances of all phytoplankton were relatively between stations (Table 3-4). The interaction low during the summer. Marshall and Cohn term (Preop-Op X Station) was not significant in (1983) found that phytoflagellates, including either analysis, reconfirming that the patterns of dinoflagellates, coccolithophorids, cryptophy-S. costatum abundances were similar between ceans and euglenoids, were most abundant in the stations and periods. late spring and summer. This pattern has been 3-15
p-3.0 PHYTOPLANKTON Abundance of Skeletonema costatum 8 Preoperational . Operational
"" 1997
)
l l l l R6 } E I l I I ' .-d z g 4 g,, T T e ----- y 4. \ , . . i
\ ,_-
2 \ \ w
\-l/
\
/
4 o JAN FEB MAR APR MAY JUN JUL /JG SEP OCT NOV DEC l' MONTH
- Figure 3-6. Log (x+ 1) abundance (no./L) of Skeletonema costatum at nearfield Station P2; monthly means and 95 % confidence intervals over all preoperational years (1978-1984) and monthly means for the operational years (1991-1997) and 1997. Scabrook Operational Report,1997.
l Preoperational Operational
, 800 +-e
- 1997 1
, 700 8
e00 l l s 500 9 h# , B=
!=
a N i \ !
'* ,; . k l r.-
.. ._( JLL o 1 l', !Il APR MAY JUN JUL AUG SEP OCT NOV DEC l WEEK / MONTH Figure 3-7. Weekly paralytic shellfish poisoning (PSP) toxicity levels in Mytilus edulis in Hampton Harbor, mean and 95% confidence intervals over preoperational years (1983-1989) and monthly means during operational years (1991-1997) and in 1997. Data provided by the State of New Hampshire.
Seabrook Operational Report,1997. 3-16 t 1 -
3.0 PHYTOPLANKTON apparent in the phytoplankton community studied 1990). DMS is the dominant sulfur gas in sur-for Seabrook Station during the preoperational face marine waters and one of the most important and operational periods and 1997. During 1997, biogenic sources of atmospheric sulfur, poten-the relative abundance of diatoms, and more tially playing a role in the global radiation budget specifically, Skeletonema costatum, was reduced (Wilson et al.1998). Many factors have been compared to preoperational and operational pe- implicated in controlling the onset of the riod means. The reduction in relative abundance Phaeocystis bloom, including silica concentra-is attributable to the high abundances exhibited tions (Cad 6e and Hegeman 1986), phosphate by P. pouchetii during its March through May minima (Verity et al.1988a), eutrophication bloom. Absolute abundances of S. costatum (Peperzak 1993), temperature / nutrient (Verity et were similar to preoperational period means al.1988b), and daily irradiance (Peperzak 1993), (Tables 3-2,3-4 and 3-6; Figure 3-6),' however, but none have been conclusively demonstrated indicating that population dynamics of this spe- (Verity et al.1998b). It is generally noted that cies remained stable. this species' bloom is preceded by a diatom bloom (Peperzak 1993), supporting the theory Phaeocystis pouchetii is a commonly occurring that the depletion in silica concentrations caused colonial species that is noted for its extensive by the diatom bloom allows Phaeocystis to blooms (Verity et al.1988b). It has been consid- outcompete diatoms, ered a nuisance species in some areas (Peperzak 1993) and recent investigations have found that Owens et al. (1989) evaluated long-term trends in P. pouchetil can produce toxins that can kill fish the occurrence of P. pouchetii in the northeast larvae (Aanesen et al.1998) or detcc grazing by Atlantic. In the open seas, there was a decline in copepods and fish (Estep et 21.1990; Eilertsen abundance from 1946 to about 1980 at which i and Raa 1995). In addition, P. pouchetii colo- point the species exhibited a substantial increase nies have been found to produce acrylic acid and (through 1987, the last year evaluated). These dimethyl sulfide (DMS) which are suspected to researchers found an approximate 36 to 42-month function as antipredation factors (Estep et al. cycle in abundance over the study period. They i Table 3-6. Summary of Potential Effects (Based on ANOVA) of Operation of Seabrook Station on the Phytoplankton Conununity. Seabrook Operational Report,1997. , l Differences Between Operational Operational Period Similar and Preoperational Periods l Community Attribute to Preoperational Period? Consistent among Stations? I Phytoplankton abundance Op= Preop yes Skeletonema costatum P2 vs. P7, Op= Preop yes P2 vs. PS, Op= Preop yes Chlorophyll a Op = Preop yes 1 4 3-17 i L
3.0 PHYTOPLANKTON related changes in abundance to changing meteo- Seabrook study area, however, neither genus was ) rological (primarily wind and storm) patterns. recorded in 1997. Over the course of the Seabrook Station preoperational and operational periods, P. It is currently thought that Alexandrium spp. ; pouchetii has been a dominant member of the blooms are transported to this region on phytoplankton assemblage during numerous years coastally-trapped buoyant plumes originating at (Table 3-3), representing more than 10% of the the Andrescoggin and Kennebec Rivers in Maine
)
annual mean total abundance during 1978 (11 %), (Franks and Anderson 1992a). This theory is 1979 (11 %), 1981 (47 %), 1983 (75 %), 1992 consistent with the generally observed north-to- l (47%), and 1997 (46%) at P2 (NAI 1985,1993, south seasonal progression of this species and the 1998a). During years that P. pouchetii achieved PSP levels (Franks and Anderson 1992b), al-bloom proportions at P2, it has also dominated at though local sources of dinoflagellates may also P5 and P7. The pattem of abundance in coastal contribute to the blooms. Anderson (1997) noted New Hampshire waters appears to be consistent that the southwesterly flow of the buoyant plumes l with the observations of Owens et al. (1989). is enhanced by northeasterly winds that favor Although the mechanisms controlling initiation of downwelling; other wind conditions promote the bloom have not been conclusively defined, offshore dispersion of the plume. Annual differ-none of the factors suggested would be influ- ences in spring and summer meteorological enced by the operation of Seabrook Station. It is conditions, therefore, may explain the differences unlikely, therefore, that the frequency or inten- in PSP occurrence that has been observed in the sity of P. pouchetii blooms has been affected by study area. Thus, occurrences of PSP toxicity in the operation of the plant. New Hampshire coastal waters have been associ-ated with larger regional occurrences in southern Only minor occurrences of PSP toxicity have Maine and northern Massachusetts, and are not been documented in the study area during the a result of the operation of Seabrook Station. operational period. The occurrence of PSP toxicity in this portion of the Gulf of Maine was
3.5 REFERENCES
CITED first documented in 1972 (NAI 1985), possibly the result of the transport of the PSP-producing Aanesen, R.T., H.C. Eilertsen, O.B. Stabell. dinoflagellate Alerandrium spp. (formerly called 1998. Light-induce toxic properties of the Gonyaulax sp.) from the Bay of Fundy or the marine alga Phaeocystis pouchetii towards cod larvae. Aquat. Toxic. 40: 109-121. Androscoggin-Kennebec estuary following Hurricane Carrie (Franks and Anderson 1992a). Anderson, D.M.1997. Bloom dynamics of toxic Throughout the preoperational period (1983- Alexandrium species in the northeastern U.S. 1989), PSP was recorded seasonally in this Limnol. Oceanog. 42: 1009-1022. region of the western Gulf of Maine each year, Cad 6e, G.C. and J. Hegeman. 1986. Seasonal reaching toxic levels about five times a year, on and annual variation in Phaeocystis pouchetii average. PSP occurrence has been rarer since (Haptophyceae) in the westernmost inlet of 1991 and only in 1993 did it reach toxic levels, the Wadden Sea during the 1973 to 1985 Members of the genera Gonyaular and Period. Neth. J. Sea Res. 20(1):29-36. Alexandrium have occurred infrequently in the 3-18
F l i 3.0 PHYTOPLANKTON Durbin, E., G. Krawiec, and T. Smayda. 1975. 1991a. Seabrook Environmental Seasonal studies on the relative importance of Studies. 1990 Data Report. Tech. Report different size fractions in Narragansett Bay, XXII-I. USA. Mar. Biol. 32:271-287. 1992. Seabrook Environmental Eilertsen, H.C. and J. Raa.1995. Toxins in sea- Studies, 1991. A characterization of water produced by a common phytoplankter: environmental conditions in the Hampton- . Phaeocystispouchetii. J. Mar. Biotechnol. 3: Seabrook area during the operation of Sea-113-119. brook Station. Tech. Rep. XXIII-I.
)
j Estep, K.W., J.C. Nejstgaard, H.R. Skjodal and . 1993. Seabrook Environmental F. Rey.1990. Predation by copepods upon Studies, 1992. A characterization ! natural populations of Phaeocystis pouchetii environmental conditions in the Hampton- , as a function of the physiological state of the Seabrook area during the operation of Sea- 3 prey. Mar. Ecol. Prog. Ser. 67: 235-249. brook Station. Tech. Rep. XIV-I. i l Franks, P.J.S. and D.M. Anderson. 1992a. . 1995. Seabrook Station 1994 ! Alongshore transport of a toxic phyto- Environmental Studies in the Hampton Sea- ! plankton bloom in a buoyant current: brook Area. A Characterization of Environ- l Alexandrium tamarense in the Gulf of Maine, mental Conditions During the Operation of
~
Mar. Biol. 112:153-164. Seabrook Station. Prepared for North Atlan-tic Energy Service Corporation. ; Franks, P.J.S. and D.M. Anderson. 1992b. Toxic phytoplankton blooms in the south- 1998a. Seabrook Station 1996 western Gulf of Maine: testing hypotheses of Environmental Studies in the Hampton Sea-physical control using historical data. Mar. brook Area. A Characterization of Environ-Biol.112:165-174. mental Conditions During the Operation of Seabrook Station. Prepared for North Atlan-Harris, R.J. 1985. A primer of multivariate tic Energy Service Corporation. statistics. Acad. Press, Orlando. 575 pp.
. 1998b. Seabrook Environmental Lee, R.E. 1980. Phycology. Cambridge Uni- Studies.1997 Data Report.
versity Press, New York. 478 pp. Normandeau Associates (NAI) and Northeast Marshall, H.G. and M.S. Cohn. 1983. Distribu- Utilities Corporate and Environmental Af-tion and composition of phytoplankton in fairs (NUS).1994. Seabrook Environmental northeastern coastal waters of the United Studies, 1993. A characterization of States. Estuar. Coast, and Shelf. Sci. Environmental Conditions in the Hampton-17:119-131. Seabrook Area during the Operation of Seabrook Station. Prepared for North Atlan-Normandeau Associates Inc. 1985. Seabrook tic Energy Service Corporation. Environmental Studies, 1984. A characterization of baseline conditions in the Owens, N.P.J., D. Cook, M. Colebrook, H. j Hampton-Seabrook Area, 1975-1984. Tech. Hunt, and P.C. Reid. 1989. Long term Rep. XVI-II. trends in the occurrence of Phaeocystis sp. in the Northeast Atlantic. J. Mar. Biol. Assoc.
. 1991. Seabrook Station 1990 UK 69:813-821.
Environmental Studies in the Hampton-Sea-I brock Area, A Characterization of Environ- Peperzak, L. 1993. Daily irradiance governs mental Conditions. Tech. Rep. XXII-II. growth rate and colony formation of l 3-19 L
3.0 PHYTOPLANKTON Phaeocystis (Prymnesiophyceae). J. Plank. Res. 15(7):809-821. SAS Institute Inc. 1985. SAS User's Guide: I Statistics, Version 5 edition. SAS Inst., Inc. Cary, N.C. 956 pp. Stewart-Oaten, A., W.M. Murdoch and K.R. Parker.1986. Environmental impact assess-ment: "Pseudoreplication" in time? Ecology. I 67:920-940. ! Underwood, A.J. ~1994. On beyond BACI: Sampling designs that might reliably detect environmental disturbances. Ecological Applications.' 4(1):3-15. Verity, P.G., T.A.Villareal and T.J.Smayda. 1988a. Ecologicalinvestigations of blooms ) of colonial Phaeocystis pouchetil - 1. Abun-dance, biochemical composition, and meta- i bolic rates. J. Plank. Res.10(2): 219-248. ] l
.1988b. Ecological investigations of blooms of colonial Phaeocystispouchetii- II.
The role of life-cycle phenomena in bloom termination. J. Plank. Res. 10: 749-766. 1 Wilson, W.H., S. Turner, and N.H.Mann.1998. Population dynamics of phytoplankton and viruses in a phosphate-limited mesocosm and their effect on DMSP and DMS production. Est. Coast. And Shelf Sci. 46(Supp. A): 49- 1
- 59. l l
l 3-20 i
I i 1 3.0 PH170 PLANKTON i i l Appendix Table 3-1. Checklist of Phytoplankton Taxa Cited in this Report.
- Seabrook Operational Report,1997. j l l 1
6 Bacillariophyceae Asterionella glacialis Castracane (syn. A. Japonica Cleve) l Cerataulina bergonil H. P6tagallo l Chaetoceros sp. Chaetocerns debilis Cleve Chaetoceros socialis huder Cylindrotheca closterium (Ehrenberg) Reimann. and Lewin l Leptocylindrus danicus Cleve Leptocylindrus minimus Gran Nituchia sp. Rhizosolenia delicatula Cleve Rhizosoleniafragilissima Betgon Skeletonema costatum (Greville) Cleve 7halassionema nitzschioides Hustedt 7halassiosita sp. Cryptophyceae Cryptophyceae' Dinophyceae Alexandrium sp. Prorocentrum micam Ehrenberg Gymnodinioidae" l Prymnesiophyceae Phaeocystis pouchetii (Hariot) bgerheim l
- previously called Cryptomoni6 l
- previously called Oxytoxum sp.
l l l l~ i i 3-21 i -
4.0 ZOOPLANKTON i I TABLE OF CONTENTS ' PAGE 4.0 ZOOPLANKTON
SUMMARY
. . . . .... . . . . ... . . . .. .., 4-iii LIST OF FIGURES . . . .... . ... . . .. . . . . .. . 4-v LIST OF TABLES . . ... . .. . . . . . . 4-vii LIST OF APPENDIX TABLES . . .... .. . . ..... . 4-viii
4.1 INTRODUCTION
. .. . . . . . . . . 4-1 4.2 METHODS .. . ... . . . . 4-1 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 .. . . ... . . 4-3 4.2.2 Laboratory Methods . . . . . .. . 4-3 4.2.2.1 Microzooplankton ... . .. .. . . 4-3 4.2.2.2 Bivalve Larvae . . . ... . .. . . 44 4? 13 Macrozoopleikton . . .... . . . . 4-4 4.2.3 Analytical Methods . . . . ... .. .. . 4-5 4.2.3.1 Communities . . .. . . . . .. ..... 4-5 I 4.2.3.2 Selected Species . . .. ... .. . . . .. . . . 4-7 4.3 RESULTS . .. .. . . . . .. .. . 4-8 4.3.1 Communities . .... . . . . .. . . . 4-8 4.3.1.1 Microzooplankton . . . . . . . . 4-8 4.3.1.2 Bisalve Larvae . . .. . . . . . 4-11 4.3.1.3 Holoplankton and Meroplankton .... . . . 4-14 4.3.1.4 Hyperbenthos . . . ........ . .. 4-18 4.3.2 Selected Species . . . . .. ... .. . . . 4-22 4.3.2.1 Microzooplankton . .. . .. . . . . 4-22 4.3.2.2 Bivalve Larvae . . . . .. . . . . . .. . 4-30 4.3.2.3 Macrozooplankton . .... . . . 4-32 4-i c
4.0 ZOOPLANKTON ] PAGE 4.3.3 Bivalve Larvae Entrainment .. . ... .... . . 4-39 4.4 DISCUSSION .. . . . . ... .... . . . . . 4-42
4.5 REFERENCES
CITED .. ...... . .... . . . . 4-43 l 1 4 l I i l l
),
4-ii l 4 I w
m 4,0 ZOOPLANKTON
SUMMARY
The zooplankton community was divided into three components: microzoeplankton, umboned bivalve larvae and macrozooplankton. Tne macrozooplankton were further divided into a holoplankton and meroplankton component and a hyperbenthic component. Microzooplankton have historically shown a distinct seasonal F.ttern that relates to the changing abundances of the dominant taxa, Pseudocalanus sp., Oithona sp., and copepod nauplii. Seasonally, community composition of the microzooplankton was similar in the preoperational and operational periods, but abundances were generally greater in the operational pt riod. The umboned bivalve larval assemblage was defined by varyirt abundances of the dominants Hiatella sp., l Mytilus edulis and Anomia squamula. Seasonally, community composition changed slightly. In late May collections, starting in 1995, Mytilus edulis and Anomla squamula replaced Hiatella sp. as the dominant taxa. The holoplankton and meroplankton components were dominated by the copepods Calanusfinmarchicus, Centropages typicus, Pseudocalanus sp., and Temora longicornis, larval decapods and larval barnacles. Seasonally, differences were detected for the holoplankton and meroplankton community component during the winter. A period of high variability that usually occurred in February through April in the preoperational period, occurred in .lanuary through February in the operational period. Other than this minor temporal shift, the progression of seasonal groups for the rest of the year was consistent between the preoperational and operational periods. The abundance of Centropages typicus was greater in the summer during the operational period. The hyperbenthic component was dominated by the mysids Mysis mixta and Neomysis americana and the amphipods Oedicerotidae and Pontogeneia inermis. Spatial, rather than seasonal patterns determined the ! hyperbenthic community. Differences between the operational and preoperational periods at the nearfield stations were similar to differences ebserved at the farfield site. For each component of the zooplankton community, no cffects that could be attributed to plant operation could be detected. ! Of the ten taxa /lifestages chosen for the selected species program, significant Pre-Op X Station interactions l were observed for three (although copepodite Eurytemora sp. and adult Eurytemora herdmam could be considered a single species). Record high abundances in one of the three preoperational years (1983) may have contributed to the significant interaction term detected for both copepodite Eurytemora sp. and adult Eurytemora herdmani. However, since the anomalous year was in the preoperational period, and mean abundance at each station was similar during all other years, the significant mteraction is probably not due to Station operation. The abundances of adult Calanusfinmarchicus also showed a significant interaction. 4-iii L
4.0 ZOOPLANKTON Abundances decreased at all three stations (P2, P5 and P7), but the decrease at Station P7 was greater. However, in terms of rank and, except for 1993, changes in magnitude of annual abundance, the relative relationship among the three stations was similar in both preoperational and operational periods. Therefore, the significant interaction term was probably not due to Seabrook Station operation. Abundances of the other selected species and lifestages either remained unchanged or had similar changes at both stations. The total number of bivalve larvae entrained in 1997 (6,336 x 10') was less than entrainment estimates in recent years (411 x 10' to 52,547 x 10$. Entrainment of Afya arenaria was higher in 1997, reflecting hig h nearshore abundances. Higher abundances of other taxa (Hiatella sp., Afytilus edulis, and Anomia souamula) in 1997 did not result in higher entrainment estimates, however. The nearshore community has remained relatively stable over time and thete is no evidence that entrainment has resulted in decreased numbers of bivalve larvae in nearshore waters. i 4 4-iv i
1 4.0 ZOOPIANKTON LIST OF FIGURES PAGE 4-1. Plankton and entrainment sampling stations . .. . . .... . . 4-2 4-2. Dendrogram and seasonal groups formed by numerical classification of logio (x+1) transformed microzooplankton abundances (no./m') at the intake Station P2,19'i8-1984, i July-December 1986, April 1990-December 1997 . . . .. ... 4-9 l 4-3. Dendrogram and seasonal groups formed by numerical classification of logio (x+1) ! transformed bivalve larvae abundances (half monthly means; no./m') at the intake (P2), discharge (PS) and farfield (P7) stations, April-October, 1988-1997 . . .. 4-12 4-4. Dendrogram and seasonal groups formed by numerical classification of mean monthly l logio (x+ 1) transformed holoplankton and meroplankton abundances (no./1000 m') at the intake (P2), discharge (PS) and farfield (P7) stations, 1986-1997 . . . . 4-15 . l 4-5. Groups formed by numerical classification of log (x+1) transformed hyperbenthic abundances displayed by station (P2, P5 and P7), month and year (1986-1997) . . 4-19 I 4-6. Dendrogram of groups formed by numerical classification of mean monthly logio (x+ 1) transformed hyperbenthk nhundances (no./1000 m') at the intake (P2), discharge (P5) and farfield stations 1986-1997 ... .... . , .. .. ... . .. . . 4-21 4-7. Log (x+1) abundance (no./m 3) of copepodite Eurytemora sp. and adult Eurytemora herdmani at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984), and monthly means during the operational period (1991-1997), and in 1997 .. .. .. .. . . . ....... 4-23 4-8. Comparison between stations of the geometric mean abundance (no./m') of copepodite Eurytemora sp. during the preoperational (1982-1984) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model .. . ... ......... .... . . . . .. 4-27 i 4-9. Annual geometric mean abundances (no./m') of copepodite Eurytemora sp. by station during the preoperational (1982-1984) and operational (1991-1997) periods . . 4-27 4-10. Comparison between stations of the geometric mean abundance (no./m') of adult Eurytemora herdmani during the preoperational (1982-1984) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . . .. . .... . .. . . . . . . 4-28 4-v [
4.0 ZOOPLANKTON PAGE i 4-11. Annual geometric mean abundance (no./m3 ) of copepodite Eurytemora herdmani by station during the preoperational (1982-1984) and operational (1991-1997) periods 4-28 4-12. Log (x+1) abundance (no./m') of Pseudocalanus/Calanus and Oithona sp. nauplii,
)
Pseudocalanus and Oithona sp. copepodites and adults at Station P2; monthly means and { 95% confidence intervals during the preoperational period (1978-1984), and monthly ! means during the operational period (1991-1997), and in 1997 . .. . . 4-29 4-13. Log (x+ 1) abundance (no./m') of Mytilus edulis larvae at Station P2; weekly means and 95% confidence intervals during the preoperational period (1978-1989), and weekly means during the operational period (1991-1997), and in 1997 . ... ... . . 4-31 i I S 4-14. Log (x+ 1) abundance (no./1000 m ) of copepodite and adult Calanusfinmarchicus at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984,1986-1989); and monthly means during the operational period ! (1991-1997), and in 1997 . . . . . . . . .. . . . 4-33 l 4-15. A comparison among stations of the geometric mean abundance (no./1000 m2 ) of adult Calanurfinmarchicus during the preoperational (1987-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model . .. . . . . . .. . . . 4-36 4-16. Annual geometric mean abundance (no./1000 m3 ) of adult Calanus finmarchicus by station during the recent preoperational (1987-1989) and operational (1991-1997) periods (data between the two dashed lines were excluded from the ANOVA model) .. 4-36 4-17. Log (x+1) abundance (no./1000 m') of Carcinus maenas (larvae), Crangon septemspinosa (zoea and post larvae) and Neomysis americana (all lifestages) at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984,1986-1989), monthly means during the operational peciod (1991-1997) and 1997 . ..... ...... . .. .. .. . . . 4-38 4-18. Volume of cooling water pumped during the months sampled for bivalve larvae and total number of bivalve larvae (X 10') entrained by Seabrook Station in 1997 . .... 4-41 4-vi
F f i 4.0 ZOOPLANKTON l I LIST OF TABLES PAGE 4-1. Summary of Methods Used in Analysis of Zooplankton Communities and Selected Species ....... . ....... .. ... .. . . . . ... 4-6 4-2. Geometric Mean Abundance (no./m') of Microzooplankton and the 95% Confidence Limits for Dominant Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Collections at the intake Station P2,1978-1984, July-December 1986, April-December 1990, 1991-1997 . .... .... . . . 4-10 4-3. Geometric Mean Abundance (no./m') and the 95% Confidence Limits of Dominant Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Bivalve Larvae Collections at the Intake (P2), Discharge (PS) and Farfield (P7) Stations, 1988-1997 . 4-13 3 4-4. Geometric Mean Abundance (no./1000 m ) and the 95% Confidence Limits of Dominant Holoplankton and Meroplankton Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections at the Intake (P2), Discharge (PS) and Farfield (P7) Stations, 1986-1997 . . . .. .... .. . 4-16 4-5. Geometric Mean Abundance (no./1000 m') and the 95% Confidence Limits of Dominant Hyperbenthic Plankton Occurring in Groups Formed by Numerical Classification of Macrozooplankton Collections at the intake (P2), Discharge (PS) and Farfield (P7) Stations, 1986-1997 . . . . . ...... ... . . . . . .. 4-20 , 4-6. Geometric Mean Abundance (no./rn') and the Coefficient of Variation of Selected Microzooplankton Species at Stations P2, PS and P7 During the Preoperational and Operational Periods and 1997 .... ........ .. . . .. . 4-24 4-7. Results of Analysis of Variance Comparing Log (x+1) Transformed Abundances (no./1000 m') of Selected Microzooplankton Species From Stations P2 and P7 During the Preoperational (1982-84) and Operational (1991-97) Periods ... . .. .. 4-26 i 3 l 4-8. Geometric Mean Abundance (no./m ) and the Coefficient of Variation for Mytilus edulis l Larvae at Stations P2, P5 and P7 During the Preoperational and Operational Periods and i 1997 ... .......... . .. . . ... . .. . 4-31 4-9 Results of Analysis of Variance Comparing Log (x+1) Transformed Abundances (no./m') of Mytilus edulis Larvae from Stations P2, P5 and P7 During the Preoperational (1988-1989) and Operational (1991-1997) Periods . . ... 4-32 vii
4.0 ZOOPLANKTON PAGE 4-10. 8 Geometric Mean Abundance (no./1000 m ) and Coefficient of Variation of Selected Macrozooplankton Species at Stations P2, P5, and P7 During the Preoperational and Operational Periods and 1997 .. . . . . . . 4-34 4-11. Results of Analysis of Variance Comparing Log (x+1) Transformed Abundances 3 (no./1000 m ) of Selected Macrozooplankton Species From Stations P2, P5 and P7 During the Preoperational (1987-1989) and Operational (1991-1997) Periods . . 4-35 4-12. 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, 1997 .. .. .. .. .... . . . . .... . . 4-40 4-13. S Geometric Mean Abundance (no./1000 m ) and Coefficient of Variation for Anomia squamula and Riatella sp. Larvae at Stations P2, PS, and P7 During the Preoperational and Operational Periods and 1997 . . . . . . . . . . . . . . 4-42 W 4-14. Summary of Potential Effects, Based on Numerical Classification and MANOVA Results, of the Operation of Seabrook Station on the Indigenous Zooplankton Communities . . 4-44 4-15. Summary of Potential Effects, Based on ANOVA Results, of the Operation of Seabrook Station on Abundances of Selected Indigenous Zooplankton Species . . . 4-44 LIST OF APPENDIX TABLES 4-1. List of Zooplankton Taxa Used in the Statistical Analysis Presented by Community . ... . .. . ... . .... . .... . . 4-47 4-2. Estimated Number of Bivalve Larvae Entrained (X 10D by the Cooling Water System at Seabrook Station 1990 Through 1993, and 1995 Through 1997 ... . . . 4-50 I l 1 i i 4 viii l j
i l l 4.0 ZOOPLANKTON
4.1 INTRODUCTION
was directed into a 0.076-mm mesh plankton net (12 cm diameter) set into a sea water filled stand Three components of the zooplankton commu- to minimize abrasion of the plankton against the nity, microzooplankton, umboned bivalve larvae net. Pumping time was recorded to calculate and macrozooplankton, were sampled separately volume filtered based on predetermined pumping to identify spatial and temporal trends at both the rates. Volume filtered generally averaged 150 ) community and species level. One station, most liters. Microzooplankton were rinsed from the likely to not be affected by plant operation, was nets into sample containers after pumping and selected as a farfield site. Initial monitoring prior were preserved in borax buffered 3% formalin. J to plant operations characterized the magnitude j of variation in each component of the zooplank- 4.2.1.2 Bivalve Larvae ton community and provided a data base for monitoring operational efforts. Current trends in The spatial and temporal distributions of 12 taxa ) zooplankton population dynamics were evaluated of umboned bivalve larvae were monitored using to determine whether entrainment in Seabrook a 0.5-m diameter,0.076-mm mesh net. Samples Station's cooling water system has had a measur- were collected weekly from the third week in able effect on the community or any individual April through October at Hampton Harbor (PI), species. In addition, the annual number of and at Stations P2, P5 and P7 (Figure 4-1). bivalve larvae entrained in the plant's cooling Sampling began at Station P2 in July 1976. water system was estimated. Farfield Station P7 was added to the program in 1982, but 1985 samples were not processed. l 4.2 METHODS Station P1 was added in July 1986. Samples ! were collected at Station P5 from July through 4.2.1 Field Methods December 1986 and April 1988 through October 1997. Two simultaneous oblique tows were 1 4.P.1.1 Microzoophnkton usually taken at each station. In cases when nets became clogged during oblique tows, vertical l l Microzooplankton were collected twice a month tows were taken. Volume filtered generally ' from March through November and monthly averaged 9 m' for oblique tows and 3 m3 for from December through February at the intake vertical tows. The volume of water filtered was (P2), discharge (PS) and farfield (P7) stations recorded with a General Oceanics* flowmeter. (Figure 4-1). Sampling at all three stations Upon recovery, net contents were preserved with j occurred from July through December 1986 and 1-2% borax buffered formalin (with sugar added from April 1990 through December 1997. In to enhance color preservation) and refrigerated. addition, Station P2 was sampled from January 1978 through December 1984 and Station P7 was 4.2.1.3 Bivalve Larvae Entrainment sampled from January 1982 through December 1984. Four replicate samples were collected by Bivalve larvae entrainment sampling was con-l pump at both one meter below the surface and ducted weekly from the third week in April f two meters above the bottom at each station on through October by NAESCo personnel within l each sampling date. Discharge from the pump the circulating water pumphouse at Seabrook 4-1
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FARFIELD 1 AREA SCALE u[ CONTOUR DEPTH IN METERS o GREAT BOARS v f, HEAD HAMPTON \ sg BEACH
\
BROWNS y RIVER s P1
- In e *** E Discharge Us 23; UT g [ g NEA FIELD SEABROOK Q 2 STATION . N /,5 HAMPTON SEABROOK HARBOR SUNK l ROCKS .
%, SEABROOK _,
% BEACH -
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= zooplankton stations
@ = bivalve larvae stations E1 = Seabrook Entrainment Station Figure 4-1. Plankton and entrainment sampling stations. Seabrook Operational Report.1997.
4-2
4.0 ZOOPLANKTON Station from July 1986 to June 1987 and from P7 (Figure 4-1). Station P2 was also sampled June 1990 to October 1997. Three replicates from January 1978 through December 1984, were collected during the day on each sampling Station P5 from January 1978 through December date. Sampling dates coincided with offshore 1981, and Station P7 from January 1982 through bivalve larvae sampling whenever possible. December 1984. Entrainment sampling was not conducted on several scheduled sampling dates, due to either Macrozooplankton collections were made at night station outages or sampling equipment problems. two times per month, concurrent with Scheduled station outages occurred from August ichthyoplankton sampling. On each date, four through November 1991, September through replicate oblique tows were made with 1-m October 1992, and April through August 1994. diameter 0.505-mm mesh nets at each station. No bivalve larvae entrainment samples were The nets were set off the stern and towed for 10 collected in 1994 due to the scheduled outage, minutes while varying the boat speed, causing the out-of-service equipment and NAESCo personnel net to sink to approximately 2 m off the bottom j scheduling conflicts. Samples were collected and to rise to the surface at least twice during the weekly in 1997 from the third week in April tow. When nets became clogged due to plankton 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 nf for suspended in a 30-gallon drum which, in turn, 5-minute tows. Upon retrieval, each net was was suspended in a 55-gallon drum. Water rinsed and the contents preserved in 6% buffered diverted from the cooling water system entered formalin. 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. The 4.2.2.1 Microzooplankton 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 vare 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 sam- ' vere concentrated or diluted to a known volume j pling date. The volume filtered was measured that provided an optimal working number of l with an in-line flowmeter and averaged approxi- organisms (ca. 200 per 1-ml subsample). Each mately 7 m2 per replicate. sample was agitated with a calibrated bulb pipette to distribute the contents homogeneously. A 1-4.2.1.4 Macrozooplankton mi subsample was removed, placed in a Sedgewick-Rafter cell and examined under a Macrozooplankton were collected from July 1986 compound microscope using magnifications of through December 1997 at Stations P2, PS, and 40X to 200X. All microzooplankton taxa present 4-3
4.0 ZOOPLANKTON in the subsample were counted and identified, were counted. Samples with low copepod abun-Most copepods were identified to developmental dance, which would otherwise require concentra-stage: nauplius, copepodite or adult. Two tion to very small volumes, making efficient subsamples were analyzed for each replicate. subsampling with the Hensen-Stempel pipette For each taxon, abundances (no./m ) were 3 difficult, were serially split using a Folsom computed for each subsample and then averaged plankton splitter. Cyclopoids and copepodites of to provide a mean abundance for each replicate. smaller calanoid species (which were not effi-ciently collected in the macrozooplankton sam-4.2.2.2 Bivalve Larvae ples) were not included in the copepod counts. The selected species Calanusjinmarchicus was All bivalve larvae samples collected at each identified to developmental stage: copepodite or station were analyzed, no samples were archived adult. as contingency samples. When the total umboned larvae collected ranged from 1-300, the To enumerate rarer copepods (Anomalocera entire sample was processed. Samples were split opalus, Caligus sp., Candacia armata, Euchaeta when the total umboned bivalve larvae count sp., Harpacticoida, Monstrillidae and Rhin-exceeded 300 specimens and two subsample calanus nasutus) and the remaining macro- I fractions were examined. Umboned larvae were zooplankton, the sample was placed in a Folsom
)
identified and enumerated with a dissecting plankton splitter and serially split into fractions microscope from an established species list. that provided counts of at least 30 individuals of Specimens of other species were enumerated as each dominant macrozooplankton taxon (as j Bivalvia. Samples collected in 1985 were ana- defined in NAl 1984). A maximum of 100 ml of ) lyzed for Mytilus edulis and Mya arenaria only. settled plankton was analyzed. Macrozoo-plankton taxa were enumerated by species using l 4.2.2.3 Macrozooplankton a dissecting microscope at magnifications be- l tween 6X and 150X. Selected species (Cancer l Prior to 1996, macrozooplankton were analyzed sp., Carcinus maenas, Crangon septemspinosa, l from three of the four tows (randomly selected) and Neomysis americana) were identified to at each station. After 1996, only the first repli- detailed developmental stage. l cate was analyzed. ! For each sample type, species counts were con- l Copepods were analyzed by concentrating or verted to density by multiplying each count by diluting the sample to a known volume from the appropriate scaling ratio (the inverse of the which a 1-ml subsample of approximately 150 proportion of the sample analyzed for each , copepods could be obtained. The sample was particular organism) and dividing by the volume agitated with a Stempel pipette to homogeneously of water filtered during field collection Micro-distribute the contents and 1 ml was removed and zooplankton and bivalve larvae abundances were examined under a dissecting microscope. reported as no./m 3; macrozooplankton abun-Subsampling continued until at lean 30 of the dances were reported as no./1000 m'. dominant copepod taxa and 150 total copepods 4-4
l l> 4.0 ZOOPL4NKTON 4.2.3 Analytical Methods similarity and the between-group similarity (value at which a group links to another group). The 4.2.3.1 Communities groups were characterized by the mean abun-dance of the dominant taxa. Communities during Community structure was evaluated by numerical the operational period (August 1990-December classification and multivariate analysis of vari- 1997) were judged to be similar to previous years ance (MANOVA) for each component of the if collections were placed in the same group as zooplankton community. The data set was the majority of collections taken at the same time reduced by eliminating rarely occurring organ- during previous years. A potential impact was isms and some general taxa (Table 4-1). Abun- suggested if community differences occurred dance data from each replicate was logm (x+1) solely during the operational period and were transformed prior to use. Log transformed data restricted to either the nearfield or the farfield reduced the relative contribution of very abun- area. This situation would initiate additional dant species in numerical classification and investigations. If community differences oc-provided data more closely approximating a curred at both nearfield and farfield stations, they normal distribution for the MANOVA model, were assumed to be part of an area-wide tr:nd, and unrelated to plant operation. Temporal and spatial changes in the community structure were evaluated using numerical classifi- A mixed effects multivariate analysis of variance cation techniques (Boesch 1977). This technique (MANOVA, Harris 1985) was used to assess the forms groups of stations and sampling periods abundances of all members of a community based on similarity levels calculated for all simultaneously for differences between periods possible combimtions of stations / sampling peri- (preoperational and operational), and stations P2, ods and the species that occur there. ~te Bray- P5 and P7 (Table 4-1). The interaction term Curtis similarity index (Clifford and Stephenson (Station X Period) was used to determine if there 1975; Boesch 1977) was used. Values of the was an impact from plant operation. The random indices ranged from 0 for absolute dissimilarity temporal effects, month (weekly for bivalve to 1 for absolute similarity. Taxa with high larvae) and year were nested within period. , abundances largely determine the inter-collection Probabilities associated with the Wilks' Lambda ! resemblances when using the Bray-Curtis similar- test statistic (SAS 1985) were used to interpret ity coefficient in numerical classification (Boesch results. 1977). Specifically, collections would form groups based largely on the abundance of the The analytical methods for the microzooplankton dominant taxa. The classification groups were community differed from the methods used for formed using the unweighted pair-group method bivalve larvae and macrozooplankton because a (UPGMA: Sneath and Sokal 1973). Results were complete year with sampling concurrent at all simplified by combining the entities based on three stations did not occur in the preoperational their similarity levels, determined by both the period. Station P2 was used for temporal analy-within-group and between-group similarity sis in numerical classification because it had the values. Results were presented graphically by longest preoperational sampling history and was dendrograms, which show the within-group situated near the plant intake. The MANOVA 4-5
4,0 ZOOPLANKTON Table 4-1. Summary of Methods Used in Analysis of Zooplankton Communities and Selected j Species. Seabrook Operational Report,1997. Source of Dates Used Data Variation in Analysis Taxon Lifestage Stations In Analysis Characteristics' (M)anova Microzooplankton Numerical 34 dominants -- P2 1978-1984 Collection date I; i of -- classification 7/86-12/86 surface and bottom; spe- ( 4/90-12/97 cies excluded with fre- j quency of occurrence !
< 10%
MANOVA 29 dominants -- P2 1997 Collection date I; x of Station P5 surface and bottom; spe-P7 cies excluded with fre-quency of occurrence
< 20%
ANOVA Selected species: __ i Eurytemora sp C" P2 1982-1984; Collection date x; x of Preop-Op. ; Eurytemora herdmani A P7 1991 1997 surface and bottom Station, Year, l Pseudocalanus/Calanus N Month i Pseudocalanus sp. C,A Oithona sp. N.C.A Bivalve Larvae _ j Numerical All taxa except Bivalvia - P2 1988-1997 Half-monthly x -- classification P5 P7 l MANOVA All taxa except Bivalvia -- P2 1988-1997* Weekly i , weeks ad- Preop-Op, l P5 justed to a four-week Station, J P7 month Year, Week ANOVA Selected species: - P2 1988-1997* Weekly x , weeks ad- Preop-Op, I Myritus edulis P5 justed to a four-week Station. l P7 month Year, Week l l Macrerooplanktou __ Numerical Hyperbenthos -- P2 1986 1997 Monthly x, - classification 23 dominants P5 Deleted taxa occurring in Holoplankton/ P7 < 10% of 1987 1997 Meroplankton sampling periods, 49 dominants Polychaeta, Hirudinea and Mysidacea MANOVA Hyperbenthos - P2 1987-1997* Half-monthly T De- Preop-Op. 23 dominants P5 leted taxa occurring in Station, Holoplankten/ P7 < 10% of 1987-1997 Year, Month Meroplankton sampling periods, 49 dominants Polychaeta, Hirudinea and Mysidacea ANOVA Selected species: Calanusfinmarchicus C,A* P2 1987-1997' Half-monthly x Preop-Op, Carcinus maenas' L P5 Station, Crangon septemspinosa L P7 Year, Month Neomysis amencana All
- All data log (x + 1) transformed at replicate level
- C = copepodite; A = adult; N = nauplii; L = larvae
- 1990 excluded
- Carcinus maenas larvae are essentially absent for 7 of 12 months, therefore a peak period of June-October only was analyzed.
4-6
4.0 ZOOPLANKTON used only 1997 collections to test station differ- monthly estimates, and the monthly estimates i ences. Historically, there have been few dif- were summed to produce the annual estimate, j ferences in planktonic species assemblages j among the intake, discharge, and farfield sta- 4.2.3.2 Selected Soecies j tions. Continuation of this trend during plant i operation would suggest that there were no Biologically important or numerically dominant j effects from plant operation on the taxa were selected for further investigation (Table microzooplankton community. Microzooplank- 4-1). The operational, preoperational, and 1997 ton abundances were averaged over surface and geometric means and coefficients of variation bottom collections for all analyses. (Sokal and Rohlf 1981) were tabulated. Monthly i logm (x+1) means and their 95% confidence The macrozooplankton community included nu- limits for the preoperational period were com-merous species that exhibit one of three basic life pared graphically to the monthly means for 1997 history strategies. The holoplankton species and the operational period to provide a visual (e.g., copepods) were planktonic essentially estimate of their magnitude and seasonality. throughout their entire life cycle. Meroplankton Operational /preoperational and nearfield/farfield included species that spend a distinct portion of differences in monthly means were evaluated their life cycle in the plankton (e.g., larvat of using a multi-way analysis of variance procedure benthic invertebrates). The hyperbenthos (Mees (ANOVA), using a before-after-control-impact and Jones 1997) included benthic species which (BACI) design to test for potential impacts of migrate into the water column on a regular basis plant operation. A mixed model ANOVA based i and organisms which were spatially concentrated on recent review of the BACI model by Under-l in the water immediately adjacent to the bottom, wood (1994) and Stewart-Oaten et al. (1986), ' The term "demersal plankton" was used to repre- was used with all effects considered random, sent the hyperbenthos in 1996 (NAl 1998). Prior except operational status (Preop-Op). Time l to 1996, the term "tychoplankton" was used. (months or biweeks) and location (Station) of Because of these behavioral differences, as well sampling were considered random factors be-as large differences in abendances, macrozoo- cause both sampling date and selected locations plankton species were categorized into a represented only a fraction of all the possible holoplankton and meroplankton community or a times and locations (Underwood 1994). The hyperbenthic community prior to statistical analy- preoperational period for each analysis was speci-sis. The same types of analyses were performed fled as the period during which all three stations on each community. The taxa that comprise each were sampled concurrently (thus maintaining a community are presented in Appendix Table 4-1. balanced model design). As collections from 1990 occurred during the transition from Weekly untransformed densities of bivalve larvae preoperational to operational periods, they were in entrainment samples were multiplied by the excluded from the analysis. Some species (e.g. weekly volume of water pumped through the all bivalve larvae, Carcinus maenas) were sea-cooling water system of Seabrook Station. sonally abundant (peak periods), often rare or Weekly estimates were summed to produce absent at other times of the year. Data from only 4-7
l 4.0 ZOOPLANKTON ! the peak periods were used in analysis of vari- dances of the four dominant taxa and by the ap- j ance and to compute operational, preoperational, pearance of large numbers of bivalve veligers. and 1997 geometric means for those species. Abundances declined again in fall, but the com-munity remained dominated by Oithona sp., the 4.3 RESULTS nauplii of Copepoda and Pseudocalanus/Calanus, and Pseudocalanus sp. (Group 5). Tintinnids , 4.3.1 Communiths reappeared as a dominant in the fall. 1 4.3.1.1 Microzoonlankton Numerical classification suggested no changes in community composition since plant operation i Temooral Trends began. The seasonal pattern of the four major I groups (Groups 2,3,4 and 5) in the operational The microzooplankton community at Station P2 period was almost identical to the preoperational as defined by numerical classification showed a period (Figure 4-2). The microzooplankton com-recurrent seasonal pattern (Figure 4-2). Four munity in 1997 was similar to previous years. l copepod taxa, Oithona sp., Copepoda nauplii, Pseudocalanus/Calanus nauplii and Pseudo- Abundances in Groups 3 and 4 were higher in the - calanus sp., dominated collections and deter- operational period due to higher abundances of mined the seasonal groups (Table 4-2). Bivalve Oithona sp. and naupliar Copepoda (Table 4-2). larvae were abundant in the late spring and sum- These groups comprise the majority of samples mer and tintinnids were abundant in the fall and from February to October, indicating a general early winter. increase in the abundance of the l microzooplankton community. Fall abundances Occurring sporadically in March was a low abun- were slightly higher during the operational period dance group dominated by Oithona sp. (Group (Group 5). In contrast to Oithona sp. and 1). Barnacle (Cirripedia) and polychaete larvae, naupliar Copepoda, naupliar Pseudocalanus/ Copepoda and Pseudocalanus/Calanus nauplii, Calanus was less abundant in all four of the and Microsetella norvegica were also common in major seasonal groups. Group 1. Tintinnids and Oithona sp. dominated a low abundance group (Group 2), which oc- Spatial Patterns curred regularly in January and intermittently from October through April. Copepoda and Differences in aoundances of dominant species Pseudocalanus/Calanus nauplii, Pseudocalanus between Stations P2 and P7 (P5 was not sampled sp. and foraminiferans were also common. preoperationally for microzooplankton) were not Higher abundances of Oithona sp., the nauplii of detected during the preoperational period (NAl Copepoda and Pseudocalanus/Calanus, and 1985). Earlier operational comparisons also Pseudocalanus sp. in the late winter and spring detected no station differences (NAl 1992, 1993, distinguished Group 3. The same four taxa in the 1995, 1996, 1998; NAl and NUS 1994). Simi-same rank order dominated the late spring larly, in 1997, MANOVA found no differences through summer collections (Group 4). Group 4 between stations (Wilks' Lambda = 0.19, F = was distinguished from Group 3 by higher abun- 1.41, p = 0.09). Similarities between nearfield 4-8
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w n 1 i l Figure 4-2. Dendrogram and seasonal gmups formed by numerical classification oflogi, ! (x+1) t:ansformed microzooplankton abundances (nolm*) at the intake l Station P2,1978-1984, July-December 1986, April 1990-December 1997. Seabrook Operational Report,1997. ! 4-9 l l l
4.0 ZOOPLANKTON Table 4-2. Geometric Mean Abundance (no./m') of Microzooplankton and the 95% Confidence Limits for Dominant Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Collections at the Intake Station P2,1978-1984, July-December 1986, April-December 1990, 1991-1997. Seabrook Operational Report,1997. Group and Dominant Preoperational Operational Species' N LCL Mean UCL N LCL Mean UCL 1 Sporadic March (0.71/0.48) Oithona sp. 2 6 223 7538 1 - 197 -- I Cirripedia ' 0 84 8 x10' -- 172 - Pseudocalanus/Calanus 0 61 7x10' .. 34 Copepoda nauplii 0 31 1054 -- 26 - Microsetella norvegica 0 9 718 41 Polychaeta 0 13 7x106 -- 40 2 Fall / Winter (0.60/0.54) Tintinnidae 10 30 219 1550 11 21 168 1282 Oithona sp. 84 205 497 145 295 600 Copepoda nauplii 65 121 226 65 150 347 Pseudocalanus sp. 39 90 205 7 23 67 Pseudocalanus/Calanus 25 63 154 6 19 57 Foraminiferida 6 29 137 28 68 163 3 Winter / Spring (0.62/0.60) Oithona sp. 43 659 983 1466 48 1282 1721 2309 Copepoda nauplii 465 648 904 784 1019 1325 Pseudocalanus/Calanus 350 509 140 114 186 304 Pseudocalanus sp. 125 192 294 104 153 225 4 Late Spring / Summer (0.67/0.M) Oithona sp. 71 3131 3836 4701 64 6280 7448 8834 Copepoda nauplii 2092 2796 3738 3572 4325 5236 Pseudocalanus/Calanus 1212 1567 2026 310 448 647 Pseudocalanus sp. 559 749 1003 397 572 823 Bivalvia 428 M2 962 656 965 1419 5 Fall (0.66/0.64) Oithona sp. 39 940 1262 1694 31 1274 1608 2028 Copepoda nauplii 493 697 985 594 741 924 PseudocalanusiCalanus 361 500 691 39 67 115 Pseudocalanus sp. 129 198 303 139 190 260 Tintinnidae 23 58 144 90 310 1071
- (within group similarity /between group simihnty) those taxa contributing a 10% of total group abundance in either the preoperational or operational periods.
4-10
4.0 ZOOPLANKTON l 1 and farfield stations, historically and currently, dances of Anomia squamula, Mytilus edulis, indicated that operation of Seabrook Station has Modiolus modiolus, Solenidae, Mya arenaria and not affected the microzooplankton community. Spisula solidissima (Table 4-3). The most abun- i f dant taxa in both groups were Mytilus edulis and 4.3.1.2 Bivalve Larvae Anomia squamula. Almost every collection in both preoperational and operational periods in Eleven taxa were routinely identified in the Sea- June and early July was allied to Group 4, indi-brook environmental studies (Appendix Table 4- cating that this was the period of peak umbonate j 1). All taxa, except the boreal species Mya veliger abundance in the coastal waters. Periods truncata, are found throughout the Gulf of Maine of low abundance (Group 5) occurred in late July and most are common (Abbott 1974 ). or later in every year except 1996. The timing and duration of these periods of low abundance I Temnoral Trends varied annually. A low-abundance group domi-nated by Modiolus modiolus, Anomia squamula, Numerical classification formed six seasonal and Mytilus edulis (Group 6) occurred in August ; groups of bivalve larvae collections (Figure 4-3, 1988. Table 4-3). The seasonal groups were split be-tween an early spring period, when groups were The preoperational and operational periods were dominated by Hiatella sp. (Groups 1,2 and 3) generally similar (Figure 4-3). Annually, sea-and a late spring and summer period when sonal changes in composition of the bivalve j groups were dominated by Mytilus edulis, Ano- larvae community were relatively constant. In mia squamula, and Modiolus modiolus (Groups every year, the community progressed from a 4,5 and 6). Hiatella sp.-dominated community (Groups 1,2 and 3) to the Mytilus edulis and Anomia April and May collections were dominated by squamula-dominated community. Abundances in l Hiatella sp. (Figure 4-3, Table 4-3). Abun- June and early July (Group 4) were typically high l dances in the earliest collections were typically and periods of low abundance (Group 5) low (Group 1), but high abundances occurred at occurred irregularly from late July through all stations in 1994 and at Station P7 in 1995 October. Some differences between the j (Group 2) representing an unusually large and preoperational and operational periods were l early peak. In Group 3, Riatella sp. abundances detected. Groups unique to each period were higher than Group 1 and Mya truncata occurred, but the duration and frequency of these contributed more than five percent of the total groups was limited to a few collection periods abundance. (Groups 2 and 6). All April and May collections l in the preoperational period were dominated by In June through October collections, periods of Hiatella sp. (Groups 1 and 3). The Mytilus high abundance (Group 4) alternated with periods edulis dominated Group 4 appeared in late May ( oflow abundance (Group 5). Group 4 was domi- at the nearfield stations (P2 and PS) in 1995 and nated by high abundances of Mytilus edulis, Ano- 1997 and at all stations in 1996. The low-mia squamula, Modiolus modiolus and Niatella abundance Group 1 occurred less frequently sp. Group 5 was dominated by lower abun- during the operational period. The pattern in 4.I1 l wJ --_--
6.0 - 01 - H, __ e, Nunbar of Senples
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@s Figure 4-3. Dendrogram and seasonal groups fomied by numerical classi6 cation oflogi, (x+1) transformed bivalve larvae abundances (half monthly means; nolm') at the intake (P2), discharge (PS) and farfield (P7) stations, April-October, j 1988-1997, Seabrook Operational Report,1997.
4-12
r-4.(n ZOOPLANKTON 1 l l Table 4-3. Geometric Mean Abundance (no./m') and the 95% Confidence Lhnits of Dominant Taxa Occurring in Seasonal Groups Formed by Numerical Classification of Bivalve J Larvae Collections at the Intake (P2), Discharge (PS) and Farfield (P7) Stations,1988- I 1997. Seabrook Operational Report,1997. Group No./ Similarity
- Dominant Taxa
- Preonerational Years' Oncrational Years' Nd LCL Mean UCL Nd LCL Mean UCL 1 Hiatella sp. 17 26 37 52 17 33 55 92 April-May (0.65/0.59) 2 Hiatella sp. -- - - --
6 7N 1839 4800 April-May l (0.74/0.59) 3 Hiatella sp. 10 437 1027 2412 34 466 650 906 April June Afya truncata 20 69 239 7 10 16 (0.69/0.48) ' l 4 Afytilus edulis 54 1428 2296 3691 166 1706 2262 2998 May-October Anomia squamula 390 6M 1132 1056 1370 1779 (0.68/0.62) Afodiolus modiolus 195 305 474 74 106 151 < Hiatella sp. 100 196 382 121 179 2M l 5 Anomia squamula 15 49 97 194 67 178 231 300 July-October Afytilus edulis 20 33 54 76 108 153 (0.64/0.62) Afodiolus modiolus 13 32 74 3 5 6 Solenidae 6 16 38 3 5 6 Afya arenaria 9 15 25 5 7 to Spisula solidissima 9 14 23 10 13 18 6 Afodiolus modiolus 3 19 59 180 -- - -- - August 1988 Anom: mamula 12 48 185 (0.82/0.52) Afyrilur e.Nis 2 11 53
* (within-group similarity /between-group similarity)
- those tau contributing 25% of total group abundance in either preoperational or operational period collections
' preoperanonal = April 1988 July 1990; operational = August 1990-October 1997
- N = number of half-monthly means calculated from weekly means (first half-month includes weeks begiruung with days 1 15; secoixi half with days 16-31) l 4-13
m l 4.0 ZOOPLANKTON , general suggested a two week earlier occurrence 4.3.1.3 Holoplankton and Meroplankton of Groups 1 and 3 beginning in 1995. Temnoral Trends
~
l Numerical classification detected differences in ; seasonal abundance between the preoperational The holoplankton and meroplankton communities and operational periods (Table 4-3). Mytilus showed distinct seasonal changes that were con- ) edulis was more abundant in Group 5 in the oper- sistent from year to year (Figure 4-4). The popu-ational period. Hiatella sp. and Mya truncata lation changes of the dominant organisms, the (Group 3), Modiolus modiolus (Groups 4 and 5) copepods Calanusfinmarchicus and Centropages l and Solenidae (Group 5) abundances were lower typicus, barnacle (Cirripedia) larvae, and the during the operational period. Differences be- larval stages of crustaceans, strongly influenced tween the preoperational and operational periods community structure (Table 4-4). 1 were also detected by MANOVA (Wilks' Lambda = 0.49, F = 56.64, p = 0.0001). The late fall /early winter and winter communities (Groups 1 and 2) were characterized by low Spatial Patterns abundances. The copepods Temora longicornis, Pseudocalanus sp., and Tortanus discaudatus and l Numerical classification detected few station the arrow worm Sagitta elegans dominated both differences. The bivalve larvae community was groups. The copepods Centropages typicus and similar at all stations on 83% of the collection Centropages hamatus, and the pelagic urochor-periods and the differences were not specific to date Larvacea were common in Group 1. Cala-any one station (Figure 4-3). No differences nus finmarchicus was also common in Group 2. among stations were detected by MANOVA (Wilks' Lambda = 0.96, F = 1.08, p = 0.36). Community structure was most variable from l February through April. Four small groups were Differences between the preoperational and oper- distinguished at this time (Groups 3,4, 5 and 6). ational periods were consistent among stations. Each group occurred once temporally and each Seasonal Groups 2 and 6 from the numerical was represented by unusually high or low abun- I classification (Figure 4-3) were restricted to one dances of one or more of the seasonal dominants. period, but occurred at all three stations. The In February 1990, Temora longicornis and Sa . l replacement of Group 3 by Group 4 in late May gitta elegans appeared in very high numbers also occurred at Station P7, at least in 1996. The (Group 3). Centropages typicus and copepodite absence of Group 5 in 1996 and Group 1 in 1997 Centropages sp. occurred in high abundances in 1 occurred at all three stations. The interaction of February 1996 (Group 4). Calanusfinmarchicus main effects was not significant when tested by and Cirripedia occurred in low abundances in MANOVA (Preop-Op X Station: Wilks' Lambda March and April 1989 (Group 5) and in high
= 0.95, F = 1.29, p = 0.16), abundances in April 1987 (Group 6). Most 4-14
9
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-!!l? win 7/ a
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I \\ [422 4- :! : JANlFEBjMARl APRlMAYlJUN JULl AUGlSEPlOCT NOV DEC , WoNTH ( Figure 4-4. Dendrogram and seasonal groups formed by numerical classification of mean monthly i logi,(x+1) transformed holoplankton and meroplankton abundances (no/1000 m') at the intake (P2), discharge (PS) and farfield (P7) stations 1986-1997. .- Seabrook Operational Report,1997. 4-15
1 4.0 ZOOPLANKTON Table 4-4. Geometric Mean Abundance (no./1000 m') and the 95'4 Confidence Limits of Dominant IIoloplankton and Meroplankton Occurring in Seasonal Groups Formed by Numerical Classification of Macrozooplankton Collections at the Intake (P2), Discharge (P5) and Farfield (P7) Stations, 1986-1997. Seabrook Operational Report, 1997. Preoperational Years" Operational Years' Group and Dominant Species' N LCL Mean UCL N LCL Mean UCL 1 Late Fall /Early Winter (0.65/0.63) Temora longicornis 32 1934 2723 3835 42 1072 1760 2890 Centropages typicus 632 1412 3152 2114 3276 5077 Sagitta elegans 891 1299 1892 884 1238 1733 Torranus discaudatus 235 564 1351 551 1013 1861 Pseudocalanus sp. 318 558 980 219 400 731 Centropages hamatus 216 427 846 16 38 87 Larvacca 73 181 443 256 526 1080 2 Winter (0.67/0.63) Pseudocalanus sp. 3 235 2754 32158 15 100 213 452 Temora longicornis 55 1400 35306 495 1181 2817 Calanusfinmarchicus 467 892 1705 217 335 517 Sagitta elegans 37 469 5787 1027 !$88 2455 Tortanus discaudatus 3 47 523 371 840 1898 3 February 1990 (0.79/0.60) Temora longicornis 3 3226 28662 254624 Not represented Sagitta elegans 68 6 20601 61540 4 February 1996 (0.71/0.54) Centropages typicus Not represunted 3 75442 143394 272550 Centropages sp. 4139 10176 25016 5 March-April 1989 (0.67/0.57) Calanusfinmarchicus 6 4390 7900 14217 Not represented Cirripedia 893 3550 14100 6 April 1987 (0.84/0.M) Cirripedia 3 131514 213890 347863 Not represented Calanusfinmarchicus 28038 184936 1219779 7 Late Winter /Early Spring (0.67/0,64) Cirripedia 9 11037 31765 91421 42 53140 91331 156969 Calanusfinmarchicus 2462 7111 20540 2310 4710 9602 Larvacca 1324 4493 15236 4874 7894 12784 8 Late Spring (0.69/0.63) Calanusfinmarchicus 30 42197 57527 78424 42 40814 63472 98708 Eualus pusiolus 3386 4844 6932 1716 2346 3209 Evadne sp. 2358 4491 8552 3844 7375 14149 Temora longicornis 2308 3876 6508 3496 5930 10060 Larvacca 428 1107 2859 3520 5735 9345 9 Summer (0.66/0.63) Centropages typicus 39 17875 37103 77012 72 47923 70141 102660 Calanusfinmarchicus 20821 36214 62988 13270 22505 38165 Cancer sp. 14019 24401 42471 18631 28501 43601 Eualus pusiolus 3421 6602 12741 2373 3935 6525 10 Fall (0.68/0.58) Centropages typicus 22 27257 48167 85118 51 34369 55139 88461 Centropages hamatus 1961 4005 8180 112 233 486 Centropages sp. 1953 3719 7082 1219 2128 3714
* (within-group similarity /between group sirnilanty) those taxa contributing a5% of total group aburufance in either preoperational or operational periods
- preoperanonal period = January 19864uly 1990; operanonal penod = August 1990-December 1997 4-16
4.0 ZOOPLANKTON March and April collections were allied with the Group 7 dominant Cirripedia, which was Group 7, the spring spawn of barnacles. Abun- three times more abundant in the operational dance of cirripedia larvae was an order of magni- period, and the Group 9 dominant Centropages tude greater than that of the co-dominants, typicus, whose operational mean was double the Calanuspnmarchicus and Larvacea. preoperational mean. Differences between the preoperational and operational periods were also ,. In contrast to the interannual variability observed detected by MANOVA (Wilks' Lambda = 0.19, from February through April, groups of collec- F= 44.11, p = 0.0001). Large-scale annual tions from May through December recurred from variation among copepod populations is common year to year almost without variation. Calanus (Jossi and Goulet 1993). Their results also sug-fnmarchicus succeeded Cirripedia as the seasonal gested that some taxa alternate between years of dominant in late spring (Grcup 8). Abundance of high and low abundance. Kane (1993) found Calames/nmarchictu was an order of magnitude interannual variations of orders of magnitude of greater than that of the co-dominants, Eualus copepods on Georges Bank, pusiolus, Evadne sp., Temora longicornis and Larvacea. The summer community (Group 9) Spatial Patterns was dominated by the copepods Centropages typicus, Calanus pnmarchicus, larvae of the Results from numerical classification suggested Cancer sp. crabs and larvae of the shrimp Eualus no differences among the stations in the opera-pusiolus. Centropages congeners were an order tional period, consistent with the preoperational of magnitude greater than all other taxa in fall period (Figure 4-4). However, MANOVA de-collections (Group 10) tected significant differences among stations (Wilks' Lambda = 0.60, F = 3.05, p = Numerical classification detected minor differ. 0.0001). The difference in results may have ences between the preoperational and operational reflected the sensitivity of numerical classifica-periods. Four of the winter and early spring tion using the Bray-Curtis Similarity Index to the groups were restricted to either the influence of dominant taxa. Also, the MANOVA preoperational (Groups 3, 5 and 6) or operational model compared annual means, while numerical (Group 4) periods. Interannual variability of classification described seasonal patterns. seasonal groups was considerable from January . through April. Preoperationally, variability was Differences in community structure between the greatest February through April, operationally in preoperational and operational periods detected - January and February (Figure 4-4). by numerical classification and M ANOVA were consistent among stations. With only one excep-Geometric mean abundances of dominant taxa tion (December 1987), stations were always displayed considerable variability between grouped together within each year and month preoperational and operational periods (Table 4- (Figure 4-4). Although MANOVA results de-4). Confidence limits generally overlapped, but tected differe' ices among stations based on annual means were often outside the confidence limits of means. the Preop-Op X Station interaction term the other period. Two notable cases of this were was not significant (Wilks' lambda =0.85, 4-17
4.0 ZOOPLANKTON l F=0.87, p=0.81), indicating that the relation- Station P5. Group 3 occurred at Station P2 in ship among stations was consistent between the May 1997. Except for the fall of 1987 through preoperational and operational periods. early winter 1988 at Station P5 when Group 4 persisted, Croups 4, 5, and 6 occurred sporadi-4.3.1.4 Hyperbenthos cally in the nearfield. i Temporal Trends All ten groups formed by numerical classification l occurred at Station P7 At the farfield station, The hyperbenthos, with the exception of the the Afysis mixta spawn (Group 1) occurred from spring Afysis mixta spawn, did not exhibit a March through May as it did in the nearfield. strong seasonal pattern (Figure 4-5), unlike the The Neomysis americana-dominated group holoplankton and meroplankton community. In- (Group 2), which composed the majority of stead, groups formed by numerical classification nearfield collections, occurred intermittently in indicated strong station differences. Groups were the farfield. The groups occurred in a sporadic also influenced by the dominant taxa and the total manner, generally indicating no seasonal pat-abundance (Table 4-5). In general, within-group terns. A Neomysis americana-dominated group similarities were lower than observed for the (Group 3) with Syllidae and Oedicerotidae as co-holoplankton and meroplankton analysis, indicat- dominants occurred frequently at the farfield ing considerable variation among collections that station (and only once at the nearfield stations). were grouped together (Figure 4-6). Frequent episodes of low hyperbenthic abun-dance resulted in the formation of seven addi-Six groups occurred at the nearfield stations, P2 tional groups (presented in Table 4-5), including and PS, and of these, only two groups displayed an Oedicerotidae-dominated group (Group 4), a consistent pattern (Figure 4-5). At the nearfield two Neomysis americana-dominated groups stations, the hyperbenthic community was domi- (Groups 5 and 10), two Harpacticoid-dominated naed by Afysis mixta (Group 1) and Neomysis group (Groups 6 and 7) and two Syllidae-domi-americana (Group 2). Afysis mixta accounted for nated groups (Groups 8 and 9). half cf the hyperbenthic abundance in collections from March through May. Neomysis americana, The hyperbenthic community in 1997 at the Pontagencia inermis, Syllidae, and Diastylis sp. nearfield stations was similar to previous years. were co-dominants (Table 4-5). Grabe and At Station P7, there were two unusual events. Hatch (1982) reported that Afysis mixta juveniles Afysis mixta did not appear in large numbers moved offshore as water temperatures reached during the March through May spawning period 12*C. When Afysis mixta was absent, Neomysis (Group 1). Group 9 was unique to Station P7 in americana was the dominant species (Group 2), 1997, present in January and March. maintaining high abundances throughout the remainder of the year. The amphipods The hyperbenthic community in the operational Oedicerotidae and Pontogeneia inermis, and the period was generally similar to the preoperational cumacean Diastylis sp. were also common. Four community as described by numerical classifica-other groups were also observed at the nearfield tion (Figure 4-5). The nearfield stations contin-stations, although they were more prevalent at ued to be dominated by Groups 1 and 2. The 4-18
1997 37 IffII f//) i l MY / / / - //-M~'//// /> 1996 27 U s\\\'M<\ V/ ////
\ \
1992 '7 ( \9 Ii / / /h\\N XXXX w 19D1 '7 ///)//// // \\ '/) G-1990 "I r//L '/>/r///>///> k \ v/// //// O l l f// \ \ \\ / 1987 !)7 \\ '
\\ YYYY' '/, 0-1986 P7 r///.NNNNNN\\\\ 8 JANl FE8l MAR l APRlMAYlJUN JUL AUGl SEPlOCTlNOVlDEC [
MONTH E GROUP 1 Q GROUP 2 Q GROUP 3 E GROUP 4 CROUP 5 E GROUP 6 . E E GROUP 7 1997 PS ' u \\ E GROUP 8
- y. % E GROUP 9 1995 '
p - - GROUP 10
~
l u I UNCROUPED 883 k [2r hI I NOT SAMPLED l 1992 1991 Q \ o 1990 Q %
"*8 19sa jk ps ta y ,
o gyyy3
\ ,
\ . 'N 1986 Q TTA \\\\Y JANl FEBl MAR l APRlMAYlJUN JUL AUGlSEPlOCTlNOVlDEC MONTH l
Figure 4-5. Groups formed by numerical classification oflog (x+1) transformed hyperbenthic abundances displayed by station (P2, PS and P7), month and year (1986-1997). Seabrook Operational Report,1997. 4-19
[ J 1 1 4.0 ZOOPLANKTON
}
Table 4-5. Geometric Mean Abundance (no./1000 m') and the 95% Confidence Limits of i ' Dominant Ilyperbenthic Plankton Occurring in Groups Formed by Numerical Classification of Macrozooplankton Collections at the Intake (P2), Discharge (PS) and 1 Farfield (P7) Stations, 1986-1997. Seabrook Operational Report,19M. 1 i Group and Dominant Spe. Preoperational Years
- Operational Years' cies* N LCL Mean UCL N LCL Mean UCL
{ 1 (0.56/0.53) Mysis mata 42 52 147 411 69 100 185 340 Neomysis americana 21 40 75 28 43 67 Pontogencia inermis 20 33 53 20 30 46 Syllidae 15 21 29 15 20 26 . Diastylis sp. 7 12 21 14 20 30 2 (0.56/0.F3) l Neomysis americana 66 226 416 763 144 151 214 283 l Oedicerotidae 39 66 111 38 51 69 Pontogencia inermis 36 51 72 32 41 54 l Diastylis sp. 31 44 63 36 46 59 Harpacticoida 7 l 11 16 29 39 53 ! 3 (0.54/0.52) Neomysis americana 7 90 289 912 10 71 142 283 Syllidae 10 26 67 7 17 39 3 Oedicerotidae 5 26 126 1 3 8
]
4 (0.48/0.46) l Oedicerotidae 13 10 27 67 11 5 15 40 Neomysis americana 7 13 23 6 12 23 i Pontogeneia inermis 6 11 18 0 1 3 Harpacticoida { 3 8 19 8 19 44 l Syllidae 3 8 17 3 9 24 ) Amphipoda 3 6 l'! 0 2 6 l Diastylis sp. 2 4 7 1 2 4 1 5 (0.4P/0.49) l Nomysis americana 6 12 23 43 3 0 28 1626 l Pontogencia inermis 2 9 33 5 36 219 l Ischyrocerus anguipes 1 7 41 0 7 351 Oedicerotidae 1 5 18 2 6 Amphipoda 0 1 2 0 5 79 6 (0.50/0.49) Harpacticoida Not Represented 5 3 25 171 Neomysis americana 1 9 49 Isopoda 3 8 16 Pontogencia inermis 0 4 2l l Calliopius laeviusculus 0 3 10 1 7 (0.54/0.49) l Harpacticoida 1 - 3 -- 4 3 22 120 l Pontogeneia inermis - 6 - 0 1 6 Neomysis americana -- 3 - 0 4 16 Syllidae -- 1 - 1 2 3 8 (0.46/0.38) Syllidae 12 8 17 34 14 14 19 25 Neomysis americana 1 4 15 1 2 4 9 (0.62/0.33) Syllidae Not kepresented 2 0 12 1790 Man"cuma stellifera 3 8 21 Diastylis sp. 0 2 7 x 10' Harpacticoida 0 2 3 x 10* 10 (0.44/0.29) Neomysis americonc Not Represented 3 6 17 42 Jassa marmorata 0 2 28
* (withm-group simitanty/between group similarity); those taxa contnbutmg 25% of total group abundance in either preoperauonal or operational penods ' preoperauonal period = January 1986-July 1%0; operational penod = August 1990-December 1997 4-20
r 4.0 ZOOPLANKTON Figure 4-6. (June - dendrogram) l x 4 21
4.0 ZOOPLANKTON farfield station continued to display considerable 4.3.2 Selected Soecies variability, with no clear seasonal patterns. Dif- - ferences between the preoperational and opera- Ten taxa were selected from the zooplankton tio7al periods were few. At the nearfield sta- program for further investigation using Analysis tic'ns, Group 6 was restricted to the operational of Variance (ANOVA) due to either their abun- .. period. The preoperational mean of Neomysis dancs or commercial or ecological importance americana was about double the operational (Table 4-1). Larvae of Cancer sp. and Mya i mean in Group 2 (Table 4-5). The Group 2 arenaria were enumerated in the zooplankton harpacticoid abundance was higher in the opera- program, but results are presented in sections tional period. In the less-frequently occurring where adult populations are discussed. The groups (Groups 3 -10), higher operational abun- ANOVA model used only the preoperational dances were observed for Pontogencia inermis years (microzooplankton:1982-1984, P2 and P7 (Group 5) and Harpacticoids (Group 4) and lower only; bivalve larvae:1988-1989; macro-abundances were observed for Pontogencia zooplankton:1987-1989) when all three stations inermis (Group 4) and Oedicerotid Group 3) were sampled concurrently. Calculation of during the operational period. . .' cences be- geometric means for the preoperational and oper-tween the prwperational and opt ..or.al periods ational periods used all available years. The were detected by MANOVA (Wilks' Lambda = ANOVA is a more quantitative measure of poten-0.70, F = 9.84, p = 0.0001). tial plant impact, while the geometric means serve to put the current year (1997) in context Spatial Patterns with the preoperational and operational periods. Numerical classification detected large station 4.3.2.1 Microzooplankton differences (Figure 4-5). Similarly MANOVA detected differences among stations (Wilks' Egrvtemora herdmani and conenodite lambda = 0.33, F = 17.39, p = 0.0001). Eurvtemora sp. Numerical classification described a nearfield As neither of the other two east coast species of community that was nearly identical in the opera- Eurytemora were encountered in the Seabrook tional and preoperational periods (Figure 4-5). program, the copepodite Eurytemora sp. were The station P7 community, although different probably Eurytemora herdmani. Although from the nearfield stations, remained unchanged Katona (197?) found large numbers of after operation began. The interaction of the Eurytemora herdmani in nearshore waters off main effects in the MANOVA was not significant Boston, Middlebrook and Roff(1986) considered j (Wilks' Lambda = 0.90, F = 1.21, p = 0.16) it to be estuarine, as it was found in low abun-j indicating that the spatial relationship was consis- dances outside Passamaquoddy Bay where it was j tent betv/een the preoperational and operational a dominant copepod. Both copepodite 1 periods. Eurytemora sp. and adult Eurytemora herdmani were minor constituents of the nearshore ! micro 7ooplankton community. 4-22 J
I 4.0 ZOOPLANKTON Seasonally, differences were observed between Copepodite and adult Eurytemora sp. were found the operational and preoperational periods at in low abundance in microzooplankton samples cration P2 (Figure 4-7). Abundances of both collected in the Hampton-Seabrook area (Table lifestages peaked in early summer during the 4-6). The abundance of copepodite Eurytemora preope ational period. Operationally, neither sp. was lower in 1997 than during both the lifestage exhibited distinct seasonal patterns of preoperational and operational period, and was abundance. A similar change in the seasonal among the lowest observed during the study abundance pattern occurred at Station P7 (NAI period. Similarly, adult Eurytemora herdmani 1996). Copepodites and adults "ere frequently were less abundant in 1997 than during the absent from collections in 1997. preoperational and operational periods. I i l Eurytemora sp. Eurytemora herdmani l Copepodites Adults a 10 PREOP PRET
. De ,
on l { 24, . , , {23 E E ; bl ti k 2.0 4 i 4 ' i , i w 15 ! I m 15 I i
!. i !
jmj l ; ! . jm
< !! i i i
i ! l , e i ._.i 1- ! i i ( Soits I i .I !. I a3
- 4 ,
l
.c, i s, l
, x p' s.
M E M M M M R AUG E OCT G E
's fpn~ / <
\
JAN FEB Matt APn MAY JUN Jll AUG S!T OCT NOV DEC l uoNm l uosm l Figure 4-7. Log (x+1) abundance (no./m )3 of copepodite Eurytemora sp. and adult Eurytemora l herdmani at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984), and monthly means during the operational period (1991-1997), and in 1997. Seabrook Operational Report,199'i 4-23 l l l
4.0 ZOOPLANKTON r . 3 Table 4-6. Geometric Mean Abundance (no./m ) and the Coefficient of Variation of Selected ) Microzooplankton Species at Stations P2, P5 and P7 During the Preoperational and Operational Periods and 1997. Seabrook Operational Report,1997. Species and Lifestage Preoperational Operational 1997 Station hiean* CV Mean* CV Mean Eurytemora sp. copepodites P2 4 35 1 58 <1 P5 -- - 1 52 <1 g j 4 i P7 4 56 1 65 1 Eurytemora herdmani adults l P2 2 50 1 47 <1 ! P5 - -- 1 44 <1 P7 3 51 1 49 <1 PseudocalanusiCalanus nauplii P2 593 8 159 10 318 P5 - -- 120 9 243 P7 499 11 139 6 218 Pseudocalanus sp. copepodites P2 223 9 165 8 291 P5 - -- 138 6 138 P7 193 14 165 3 185 Pseudocalanus sp. adults P2 23 17 14 17 17 PS -- -- 12 20 7 P7 25 16 13 17 15 Oirhona sp. nauplii P2 465 12 695 10 1737 PS - -- 727 9 1726 P7 403 15 612 9 1275 Oithona sp. copepodites P2 490 10 778 6 1203 P5 -- - 677 6 954 P7 299 20 657 4 826 Oithona sp. adults P2 107 13 212 7 281 PS -- - 174 7 161 P7 98 24 177 7 168
- Preoperationas years: P2 = 1978-84, P5 = not sampled, P7 = 1982-84. Mean of annual meant.
- Operational years = 1991-97; 1990 not sampled dunng January through March, data not included.
Mean of annual means. 4 24
4.0 ZOOPLANKTON The abundance of copepodite Eurytemora sp. operational years, although copepodite abun-decreased between the preoperational and opera- dances were slightly higher and adult abundances tional periods, but the decrease was greater at the lower in the winter. farfield station (P7) resulting in a significant interaction term (Table 4-7; Figure 4-8). Abun- Pseudocalanus sp. and Calanus sp. copepods are dances of copepodite Eurytemora sp. were very extremely abundant in the nearshore marine similar each year between stations, exr.ept for environment where they are important food items 1983 when density was higher at Station P7 (Fig- for planktivorous fishes. Abundances of naupliar ure 4-9). Adult Eurytemora herdmani showed a Pseudocalanus/Calanus in 1997 were higher than pattern between the preoperational and opera- during the operational period, but lower than the tional periods similar to the copepodites. Density preoperational period (Table 4-6). Mean abun-decreased at both stations, but the decrease was dances of copepodite Pseudocalanus sp. were greater at the farfield station (Table 4-7; Figure higher in 1997 :han the operational means at 4-10). As with copepodites, peak abundance of Stations P2 and PS, and there were minor differ-Eurytemora herdmani occurred in 1983, with ences between 1997 and the preoperational higher values at Station P7 than Station P2. means. In 1997, the abundance of adult j There was little variation in annual mean abun- Pseudocalanus sp. was slightly higher than dur-dance of E. herdmani during the operational ing the operational period at Stations P2 and P7, period (Figure 4-11). but lower than during the preoperational period. ; l l Pseudoca: anus sp. The abundance of naupliar Pseudocalanus/ Calanus decreased significantly between the l The cold-water neritic genus Pseudocalanus sp. preoperational and operational periods (Table 4-is very abundant in the Gulf of Maine (Corkett 7). Hewever, the decrease occurred equally at l and McLaren 1978). All three developmental all stations as indicated by the non-significant l l stages of Pseudocalanus sp. were most abundant interaction term. No differences among station I in July (Figure 4-12). Average naupliar abun- means or operational and preoperational means j dances were lower in almost every month during were detected for the copepodites and adults, and ; the operational period, although the seasonal the interaction term was not significant. l i I l curve was similar in both periods. In 1997, abundances of Pseudocalanus/Calanus nauplii Oithona sp. l were generally within the preoperational period confidence intervals except for August through Oithona sp. copepods were also extremely com-October, when abundances were low. Seasonal mon in the nearshore environment and were the abundances of copepodite and adult Pseudo- most common microzooplankton taxon collected, calanus sp. were similar throughout the study, Oithona similis was considered by Sabatini and although operational abundances in January Ki$rboe (1994) to be one of the most ubiquitous i through March have been near or below the and abundant copepods in neritic temperate wa-l preoperational lower confidence interval. Sea- ters. Seasonally, they found that Oithona spp. sonally, copepodite and adult abundances in 1997 biomass varied considerably less than the co-l were generally cimilar to the preoperational and occurring calanoid species. 4-25
I J l-4.0 ZOOPLANKTON : ! Table 4-7. Results of the Analysis of Variance Comparing Log (x+ 1) Transformed Abundances (no./m') of Selected Microzooplankton Species from Stations P2 and P7 During the Preoperational (1982-1984) and Operational (1991-1997) Periods. Seabrook l Operational Report,1997. Species / Lifestage Source of Variation" df MS F Multiple Comparisons 6 Eurytemora sp. Op 1 6.84 2.38 NS copepodite Preop Year (Preop-Op) 8 2.57 4.59 " Month (Year) 110 0.78 3.27 * *
- Station 1 0.09 0.25 NS Preop-O ) X Station 1 0.36 8.03* P7 Pre P2 Pre > P2On P7On Year X dtation (Preop-Op) 8 0.05 0.19 NS Error 288 0.24 Eurytemora herdmani Op 1 9.77 6.07* Op < Preop adult Preop (Preop-Op)
Year 8 1.33 2.66 NS Month (Year) 110 0.65 3.59"* Station 1 0.20 0.54 NS Preop-Op X Station 1 0.36 6.40' P7 Pre P2 Pre > P2On P70n Year X Station (Preop-Op) 8 0.06 0.31 NS Error 288 0.18 Pseudocalanus/Calanus Pr Op i 22.96 14.08 " Op < Preop nauplii Yea Preop-O 8 1.75 1.41 NS Mont Station (Year) p) 110 1.40 5.83"* 1 0.18 10.90 NS car [ta ion ( reop-Op) 8 0 NS Error 288 0.24 Pseudocalanus sp. Preo 1 0.67 1.00 NS copepodite Year reop-O 8 0.97 0.84 NS Mon (Year) p) 110 1.16 4.42"* Station 1 0.01 non-est.' Preop-Op X Station 1 0.01 0.04 NS Year X Station (Preop-Op) 8 0.34 1.30 NS . Error 288 0.26
]
Pseudocalar.us sp. Pr Op 1 5.I1 3.25 NS adult Yea 8 1.79 1.37 NS , Mon Preop-)Op) (Year 110 1.40 5.24 * " l Station 1 0.02 6.28 NS r [ta ion reop-Op) 8 b$ ON NS Error 288 0.27 Oithona sp. Preo 1 2.18 0.62 NS nauplii Yea reop-O 8 3.50 4.45 " Mont (Year) p) 110 0.98 5.28"* Station 1 0.65 36.26 NS Preop-Op X Station 1 0.02 0.44 NS Year X Station (Preop-Op) 8 0.05 0.24 NS Error 288 0.19 Oithona sp. Op 1 7.75 3.41 NS copepodite Preop Year (Preop-Op) 8 2.31 2.30* Month (Year) 110 1.14 7.10 * " Station 1 1.00 19.97 NS , Preop-Oo X Station 1 0.05 0.51 NS z i Year X Station (Preop-Op) 8 0.11 0.66 NS i Error 288 0.16 j Oithona sp. Op 1 5.03 1.97 NS f adult Preop Year (Preop-Op) 8 2.60 2.65* ! Month (Year) 110 1.19 5.88 "
- Station 1 0.60 not -est.'
Preop-Op X Station 1 < 0.01 0.04 NS Year X Station (Preop-Op) 8 0.07 0.33 NS Er;or 288 0.20
- Preopop =preoperational puiod vs. operational period, regardless of area; Year (Preop-Op)= year nested within preoperational and ;
operational penods, regardless of area; Month (Year)= month nested within year; Station =nearfield vs. farfield stations; Preop-Op X Station 1
= interaction of main effects; Year X Station (Preop-Op)= interaction of station and year nested within preoperational and operational penod.
- Waller-Duncan multiple means companson t+-t used for sigmficant main effects. LS Means used for sigmficant interaction terms. ]
- F-value non estimable due to a negauve denominator mean square.
NS = Not Significant (P> 0.05) l
* = Sigmficant (0.05 : P >0.0'.) {
" = Highly Significant 0 01 a P > 0.001) !
*" = Very Higidy Significant (P s 0.001) j j
4-26 1
F 4.0 ZOOPLANKTON
, Eurytemora sp. Copepodites
. . . 92
. . . p7 i
I 4 .
.a l
3! - 8 N s u N 2 % o N
+4 t
1-i 0;' Preoperatonal Operational PERIOo Figure 4-8. Comparison between stations of the geometric mean abundance (no./m3 ) of copepodite { Eurytemora sp. during the preoperational (1982-1984) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model. Seabrook Operational Report,1997. l i Eurytemora sp. Copepodites 1s; i .. _ . . m
' * * ' P7
- ereoperationai I
i : I
- Oporational
=
10
/\,
i f ! ' i t 6:r .c\\ i i l l u : - , l c 1 !/ ll) \ l,
- A 4\: :; 'l' i
l i l ( 8 /\ 5l!z/ llf b / \ \
! // \ E l j Not Sampled *
[ \ l l
- / i 2 ._ .. _
- '- A ,
p f '\ e: . _ . _ . . 82 83 84 85 86 87 88 89 90 91 92 93 94 95 90 97 l l l Figure 4-9. Annual geometric mean abundances (no./m') of copepodite Emytemora sp. by station during the preoperational (1982-1984) and operational (1991-1997) periods. Seabrook Operational Report,1997.
- 4-27 i
L
1 ( ls t 4.0 ZOOPLANKTON J 1 l ) 5-i
. . . P2 <
Eurytemora herdmani Adults * *
- Y7 l .
<- 8 l ,
n' b l l3 I 8, i s N 2 l g 2; y'\. g- '~s, Ns 8 **,g l N '~ 3- . O ereoperationai operationai PCRIOD I I l 3 Figure 4-10. Comparison between stations of the geometric mean abundance (no./m ) of adult Eurytemora herdirani furing the preoperational (1982-1984) and operational (1991-1997) ' periods for the sigmLeant interaction term (Preop-OpX Station) of the ANOVA model. l Seabrook Operational Report,1997, 1 Eurytemora herdmani Adults 1 is; . . . . . e2 i . .. .. pf Preoperational' Operational l i ! i ! l 8! s ' - i
! I
~
, [g .
l 8 s! ' 8 i l
\!
., i Not Sampice
/
o: 82 83 84 85 86 87 88 89 90
- ..w ./. .
91 92
~
93 94 96 A. 96
.s-97 YEAR Annual geometric mean abundance (no./m') t. adult Eurytemora herdmani by station
~
Figure 4-11. during the preoperational (1982-1984) and operational (1991-1997) periods. Seabrook Operational Report,1997. 4-28
I h 4.0 ZOOPLANKTON i l Pseudocalanus/Calanus Nauplil Oithona sp. N suplii l 4+ -%. a g --- "* Op-==d W 4.0 g
,N g33 { 3, f s.,
, h *N L ex/,' , ..; ,I
, ,~j i l10 W~. '
\-
.s.
,' g g, ,>
3 . ., a f.$, / g
.,./. 10' . l
- n. s .
s , ss ,- s, ts 33 tn g to 65 os Ob - - - - - - - . - - - p M FEB M APR WY JUN R AUG SEP OCT NOV DEC dN FF[ MH W MAY JUN JUL AUG SEP OCl NOV DEC MONS MONW
,3 -
Pseudocalanus Copepodites Oithona sp. Copepodites l 40 _ _ o,,
. %. y 43 I T ,- s gis . g 3.s ,. - , 's, j so ,
\
N j { so' ,x ffTj', l,'(xOk? g ts t TO v
h?
l, ts 19 04 0.5 I e 6.. . .- .- . . . . . . on . . . . . . . JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY .AJN JUL AUG SEP OCT NOV DEC uONm om Pseudocalanus Adul*s Oithona sp. Adults u . . 44 i i na __. % 44 y -. T . t l 15f j15 a'
-r_ /'N .s 8 sa
] sd 1- ,
$.> ,( ****~*\ x,!
w f s it , - o zg i K 4 , 2.6 ' , . .
\- - i LS ,
,_,. j' L5
< ! iv i ta - s ,.m to a3 ,,#\;.][ . c.s
's /
$$ ~. .. b .. . - _ . _ . _ _ . . . . . - _ . . . . . . - . . 0.0 - - -
JAN FEB WH M MY JUN JUL AUG SEP OC' NOV DEC M FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC em MONW Figure 4-12. Log (x+1) abundance (no./m3 ) of Pseudocalanus/Calarts and Oithona sp. nauplii, Pseudocolanus and Oithona sp. copepodites and adults at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984), and monthly meanc during the operational period (1991-1997), and in 1997. Seabrook Operational Report, 1997, 4-29
4.0 ZOOPLANKTON The seasonal cycles of all three lifestages of (Figure 4-13). Abundances increased rapidly Oithona sp. were generally similar in both from low levels in April and early May to the preoperational and operational periods. Adult seasonal peak, which extended from mid-June to Oithona sp. were more abundant during the mid-July. Development of the trochophore 1 operational period in September and October larvae does not occur at less than 8*C (Bayne (Figure 4-12). Mor;thly means of all lifestages 1976). The observed increase in larval abun-were typically greater in 1997 than the dance was consistent with the rise in surface j preoperational and operational means. Naupliar temperatures at Station P2 and Hampton Harbor I and copepodite Oithona sp. were typically more to above 8*C in May (Section 2.3). The decline l abundant in 1997 from March through Decem- in abundance in late July probably indicated the ber. Adult abundances generally were near or end of the peak spawning period. Newell et al. exceeded the preoperational upper confidence (1982) showed that most adult Mytilus edulis at I limits from May through December. Newcastle, NH had released their gametes by late July. Although weekly abundances varied con-Annual mean abundances of naupliar and siderably from August through October, in
]
copepodite Oithona sp. in 1997 were higher than general larval abundance declined only slightly i the preoperational and operational abundance.s during this period. Sustained abundances from (Table 4-6). Adult Oithona sp. means in 1997 August through October may represent less were higher than the preoperational and opera- intense spawning, but probably represented tional means at Station P2 and higher than the recruitment from other areas and extended larval preoperational mean at P7. life. Weekly abundances in 1997 were generally similar to the preoperational and operational No differences between the preoperational and periods (Figure 4-13) although a slight temporal operational periods or among stations were shift was indicated by higher abundances from detected for naupliar, copepodite and adult mid-May through early June. Newell et. al. Oithona (l'able 4-7). The interaction term was (1982) attributed temporal differences in the not significant for all three lifestages. gametogenic cycle to differences in the energy content of the mussels food and Starr et. al. 4.3.2.2 Bivalve Larvae (1990) found that the timing of spawning in Mytilus edulis was initiated by algal metabolites. Mstilus edulis Annual mean abundances in 1997 were higher Mytilids are the doininant organisms in the than the operational abundances and more than intertidal zone. They are also common at most of double the preoperational abundances (Table 4-the subtidal benthic stations in the nearshore 8). No significant differences between the waters (Section 6.0). preoperational and operational periods or among stations were detected by ANOVA, and the Preoperational and operational period M. edulis interaction term was not significant (Table 4-9). larval abundances were similar at Station P2 4-30
E i 4.0 ZOOPLANKTON Mytilus edulis Larvae l
! Preoperational Operational 5.5! ,-.-4 3997 5.0 4.5 %
u d'0 !
*h' t
'i 3.5 M '
a / '\ l ;dF[/ 3.o
! \~ f x,:'/ y
[,N
-l 2.51 >
t j _ .N 2.0 / h ' f 1.5
/ / j ( l 1.o . [ y '
O.5 /' j o.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 Apr May Jun Jul Aug Sep Oct Figure 413. Log (x+ 1) abundance (noJm') of Mytilus edulis larvae at Station P2; weekly means and 95 % confidence intervals duriht the preoperational period (1978-1989), and weekly means during the operational period (1991-1997), and in 1997. Seabrook Operational Report, 1997. I l Table 4-8. Geometric Mean Abundance (no./m') and the Coefficient of Variation for Mytilus edulis Larvae at Stations P2, PS and P7 During the Preoperational and Operational Periods and 1997. Seabrook Operational Report 1997. Preoperational Operational
- 1997 S_tation Year Mean* CV Mean* CV Mean P2 1978-1989' 172 17.1 322 18.3 393 P5 1988-1989 132 23.4 275 17.9 450 P7 1982-1984, 174 10.4 318 18.7 386 1987-1989
- 1991 to 1997
- mean of annual sneans
' 1986 cxcluded 4-31
J 4.0 ZOOPLANKTON j
, Table 4-9. Results of Analysis of Variance Comparing Log (x+1) Transformed Abundances (no./m') of Mytilus edulis Larvae from Stations P2, P5 and P7 During the l Preoperational (1988-1989) and Operational (1991-1997) Periods. Seabrook Operational Report,1997. ]
( Source of Multiple f Species Variation' df MS F Cornparisons I Afyritar edulis Preop-Op 1 8.62 0.47 NS = Year (Preop-Op) 7 17.96 1.77 NS Week (Year) 108 10.85 28.13 "
- Station 2 0.30 2.76 NS l Preop-Op X Station 2 0.11 1.11 NS Station X Year (Preop-Op) 14 0.10 0.25 NS Error 612 0.39 Ns= Not significant(P>0.05)
* = significant (0.05 < P < 0.01)
"= Highly significant (0.01 < P < 0.001)
*= Vety Highly significant (P <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)= week nested withm year station = station P2 vs. station PS vs. station P7, regardless of year Preop-Op X station = interaction of rnain effects station X Year (Preop-Op)=interactioa of station and year nested within preoperational and operational period. 4.3.2.3 Macrozooolankton abundances were typical of previous years. However, adults were absent in half of the Calanus finmarchicus collection periods in 1997. Calanusfnmarchicus is one of the most abundant Copepodites were more abundant than adults copepods in the Gulf of Maine. Its large size and (Table 4-10). Copepodite abundances in 1997 abundance make it an important component in the were slightly below the average abundances at diets of many of the larger predators, including each station in the preoperational and operational many fishes. periods. Adult abundances in 1997 were less than the mean abundance in the preoperational Calanus finmarchicus was common all year and operational periods. (Figure 4-14). Copepodites were more abundant than adults in every month and operational There were no significant differences in abun-abundances were almost identical to the preoper- dance of copenodite Calanusfnmarchicus among ational abundances. Seasonally,1997 copepodite stations er between the preoperational and opera-abundances were similar to previous years, tional periods (Table 4-11). The interaction of although fall abundances were low. For most of main effects was also not significant. Abun-the year, adult operational abundances were near dances of adult Calanusfinmarchicus decreased the preoperational lower confidence intervals. between the preoperational and operational When adult Calanusfinmarchicus was present, periods at all stations, but the decrease was great-4-32
5 4.0 ZOOPLANKTON Calanusfinmarchicus - Copepodites I{ * *
- Pruopwrationni Operatiord I' 1997 t e-j 'N
/. I 9 ,g,.j y'i-[s ,\[N
/ q.
/ .X -
g/ 7ff s/ (N E, f.'. h. s t 3 / I- \V's; . L ;/ s - r% r
.<. . s i s.- . ; /,
a- 5- ,- g* - '
/
s-1 0' JAN FEB MAR APR MAY JUN JUL AUG SCP OCT NOV DEC MONTH Calanusfinmarchicus - Adults
.-.._a_
l Operatkanal i - 1997 6 5 5, i1 bl . 3! . . l I
.
- i i
~ '"
2 _ . _ / a p ! g*
. ./../ACV .
/ *
~y
% /
.- g g
/
&k. g\ *
/. N
/
/ $\p .. ..] ~\
j -
, / \/ N/ s
' \f':S N p',y .
Os Y - --
- JAN FCD M/ft APR MAY JUN JUL AUG SCP OCT NOV DCC MONTH Figure 4-14. Log (x+1) abundance (no./1000 in') of copepodite and adult Calanus finmarchicus at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984,1986-1989); and monthly means during the operational period (1991-r 1997), and in 1997. Seabrook Operational Report,1997.
4-33
4.0 ZOOPLANKTON Table 4-10. Geometric Mean Abundance (no./1000 m') and Coefficient of Variation of Selected )' Macrozooplankton Species at Stations P2, P5 and P7 During the Preoperational and Operational Periods and 1997. Seabrook Operational Report,199.7. Preoperational Operational 1997 Species /Lifestage Station Mean* CV Mean 6 CV Mean (peak period) Calanusfinmarchicus P2 4153 6 3613 3 2854 copepodites P5 5713 7 4359 5 2327 (January-December) P7 2594 7 2215 5 1832 l P2 36 27 12 28 4 l Calanusfinmarchicus adults P5 26 29 16 28 10 (January December) P7 29 29 6 41 3 J Carcinus maenas P2 3509 7 6146 12 15269 larvae P5 3615 13 5944 10 8920 ; (June-September) P7 4251 6 2756 15 4767
)
i Crangon septemspinosa P2 257 4 240 7 361 233 7 188 12 317 zoeae and postlarvae (January-December) P5 P7 161 10 90 15 104
)
Neomysis americana P2 151 19 246 12 916 all lifestages P5 45 31 90 20 538 j (January-December) P7 43 22 21 18 10
' Years sampled: Preoperational: P2 = 1978-1984,1987-1989 PS = 1978-1981,19871989 P7 = 1982-1984,1987-1989 Mean of annual means j 'Mean of annual means, 1991-1997 l l
l est at Station P7, resulting in a significant inter- Station P5, followed by Stations P2 and P7. This l 1 action term (Table 4-11, Figure 4-15). The pattern differed only in N6 when abundance at proportionally greater decrease between the Station PS was intermediate between P2 and P7. preoperational and operational periods at Station P7 was probably due to the high abundances that Carcinus maenas occurred at Stations P2 and P5 in 1993, but not I at P7 (Figure 4-16). Despite the significant The green crab (Carcinus maenas), is a common interaction term, relative abundances were coastal crab in northern waters. The adult crabs generally consistent among stations each year. In are strictly benthic, but the larval zoea and all years except 1996, abundance was highest at megalopa are common in the plankton. Larval 4-34
1 4.0 ZOOPLANKTON Table 4-11. Results of Analysis of Variance Comparing Log (x+1) Transformed Abundances (no./1000 m') of Selected Macrozooplankton Species from Stations P2, PS and P7 During the Preoperational (1987-1989) and Operational (1991-1997) Periods. Seabrook Operational Report,1997. i. Species Source df MS F Multiple Comparisons i Calanusfinmarchicus Preop-Op' 1 1.13 0.66 NS copepodites Year (Preop-Op)* 8 1.62 0.17 NS danuary-December) Month (Year)" 110 10.23 15.62* " Stationd 2 3.75 17.64 NS Preop-Op X Station' 2 0.21 1.49 NS Year X Station (Preop-Op)' 16 0.15 0.22 NS Error 562 0.65 Calanusfinmarchicus Preop-Op 1 5.10 0.63 NS adults Year (Prcop-Oo) 8 7.48 1,74 NS (January December) Month (Year) 110 5.24 5.66 * " l Station 2 4.84 10.06 NS Preop-Op X Station 2 0.45 8.11" P5 Pre P50n P2 Pre P7 Pre P2On> P70p Year X Station (Preop-Op) 16 0.07 0.08 NS Error 562 0.93 Carcinus maenas Preop-Op 1 0.04 0.02 NS l larvae Year (Preop-Op) 8 2.92 0.99 NS j (June-September) Month (Year) 30 2.96 4.50 * " ' i Station 2 1.33 4.07 NS l Preop-Op X Station 2 0.35 0.53 NS l Year X Station (Preop-Op) '6
. 0.66 1.00 NS Error 180 0.66 Crangon Preop-Op 1 0.70 0.25 NS sept-mspinosa Year (Preop-Op) 8 2.84 0.35 NS ,
zoeae and post larvae Month (Year) 110 8.13 22.97* " l (January-December) Station 2 8.13 30.98* P2 > P5 > P7 Preop-Op X Station 2 0.27 0.67 NS , Year X Station (Preop-Op) 16 0.40 1.13 NS Error 562 0.35 Neomysis americana Preop-Op 1 0.55 0.09 NS all lifestages Year (Preop-Op) 8 6.43 2.25* danuary December) Month (Year) 110 2.35 3.91"* Station 2 52.47 74.71* P2 > P5 > P7 Preop-Op X Station 2 0.73 0.62 NS Year X Station (Preop-Op) 16 1.16 1.94 *
- Preoperational (19871989) versus operational (1991 1997) periods regardless of station; 1987-1989 reflects the period of time that all three stations were sampled concurrenJy. ' Year nested within preoperational and operational periods, regardless of station. ' Month nested within year. regardless of station. 'Stanon P2 vs. stanon P5 vs. station P7, regardless of year. ' Interaction between main effects. ' Interaction of station and year nested within preoperational and operational penod.
NS = Not significant (p >0.05)
* = Significant (0.05 a p >0.01)
" = Highly sigruficant (0.01 a p >0.001)
'" = Very highly significant (0.001 a p) 4-35 i
]
t 4.0 ZOOPLANKTON =
, Calanusfinmarchicus Adults l
...n%
. . 4 p7 l *..
t 20j l
- ~.. -
15 - . . ... ;
~'
t - 3 - 2 g x - . M i o,
~.
g ~. L4 - l Si 1 0 .. - - - - ~ - . - - - - - - - - -- -- -. er.operamnai operations l PERIOO
]
I Figure 4-15. A comparison among stations of the geometric mean abundance (no./1000 m') of adult j Calanusfinmarchicus during the preoperational (1987-1989) and operational (1991- 1997) j periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, l Seabrook Operational Report,1997. l Calanusfinmarchicus Adults voi ; . .
; . .. . n,
.y
, Preoperational Operatonal . . . py l 60-
! 1 i
1So!4oh I! W *; ' m . - 8 dm
, '\'
\
\..;
\
\
s, A N '<., -
,._ - s 10j g / ,,
,[ s .
l 3 Y/ ' sy* /- \.^ .. N - ---
- . - _ 3 Oi.--.-------- -
87 88 89 90 91 92 93 94 95 96 97 YEAR Figure 4-16. Annual geometric mean abundance (no./1000 m3 ) of adult Calanus finmarchicus by station during the recent preoperational (1987-1989) and operational (1991-1997) periods (data between the two dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997. 4-36
~'
4.0 ZOOPLANKTON i abundances of Carcinus maenas were very creased from low levels in early winter to a j seasonal at Station P2 (Figure 4-17). Larvae broad peak lasting from late spring through were present in extremely low numbers in the summer, consistent with' Wehrtmann (1994). early winter and absent in March and April. The preoperational and operational periods were Peak abundances occurred through summer and generally similar, although there appears to be j abundances declined sharply in fall. The season- slight shift temporally, indicated by higher l ality was identical in the preoperational and abundances in spring and lower abundances in l operational periods. The seasonal pattern was fall in the operational period. Abundances in late j similar in 1997, except that abundances from July winter and early spring of 1997 were higher than ! through December were often higher than abundances in the preoperational and operational l preoperational and operational abundances. period. Larval abundances in October dropped j sharply from the summer peak, but abundances ! Annual geometric mean abundances in 1997 were were similar to previous years in late fall. j higher than the preoperational and operational l means at all stations in (Table 4-10). The peak Geometric annual abundances of C. septem- j period abundances at Station P2 in 1997 of 15269 spinosa at the nearfield stations (P2 and PS) were j larv"/1000 m was a record high (previous 3 higher in 1997 than in previous years (Table 4- l record was in 1991: 10097 larvae /1000m3: NAl 10). After record low abundance in 1996 (NAl ( 1992). Abundance at Station P5 was also high 1998), the annual mean at Station P5 was the compared to other years. After record low highest recorded in the operational period (NAI, abundance in 1996 (NAI 1998), larval abundance 1991; 1992; 1993; 1995; 1996; 1998; NAl and 4 at Station P7 exceeded the operational mean and NUS 1994). After record low abundance in 1996 was similar to the preoperational mean. (NAI 1998), Station P7 annual abundance was similar to previous years. There were no significant differences between periods or among stations for larval Carcinus Abundances of C. septemspinosa were signifi-maenas (Table 4-11). The interaction term was cantly higher at Station P2 and lowest at Station also not significant. P7 (Table 4-11). There was no significant difference between preoperational and opera-Crangon septemspinosa tional abundance. Differences among stations were consistent between the periods, indicated by The sand shrimp Crangon septemspinosa is one a non-significant interaction term. of the most abundant coastal shrimps on the North American East Coast (Haefner 1979). The Neomvsis americana larval zoea arid megalopa (first post-zoeal stage) are planktonic. Juveniles and adults are benthic, The opossum shrimp, Neomysis americana, is the but are occasionally encountered in plankton most abundant mysid in northeastern coastal tows. waters. It frequently moves up into the water at night and is known to form large aggregations or The larvae of Crangon septemspinosa were swarms. It is a favorite prey species of many of present all year (Figure 4-17). Abundance in- the coastal fishes (Mauenline 1980). 4-37
4.0 ZOOPLANKTON Carcinus maenas , , , _ _ O-
=
I.! , .. 's .s j g ;l M,r 't' -'~ - N- N
/g "' - ,. nmg. ,
[i
// k '.N \
g ' g g e-N'% .z il %m% .., l
- N*
- o. n
._.__.._,......}_..__.... . . _ . . . . . .
JAN FES MAR APM MAY JUN JUL AUG BEP OCT NOV OEC MONTH 1 l Crangon septemspinosa g =, , l Ii cl[ ' - "k~4, 5* - [,. '
- j. -[. .
- . \ .
\
i'5
,- ., I y .:
E q4'.cIX r AV! !
\~
d - i a W. Ma e- M< Ju~ MONTH
.E - . ocy ~& oec Neomysis americana g
s, N l 3: l g! '
' 's ' - x'7; g .) .N - ..
'- l f'
,! g'. .O.sym[ic tq..., ',
g Q g -{/ g ___ ,,, o MONTH Figure 4-17. Log (x+1) abundance (no./1000 m ) of Carcinus maenas (larvae), Crangon 3 septemspinosa (zoea and post larvae) and Neomysis americana (all lifestages) at Station P2; monthly means and 95% confidence intervals during the preoperational period (1978-1984,1986-1989), monthly means during the operational period (1991-1997) and 1997. Seabrook Operational Report,1997. 4-38
E t
)
4.0 ZOOPLANKTON Unlike all the other zooplankton selected species, 4.3.3 Bivalve Larvae Entrainment peak abundances of Neomysis americana occur-red in the fall and winter (Figure 4-17). The species composition and abundance of Mauchline (1980) described a two-generational bivalve larvae passing through the cooling water annual cycle of Neomysis americana. Larvae system of Seabrook Station were measured to spawned by the over-wintering generation in estimate the direct loss of larvae to entrainment, spring matured quickly and reproduced in sum- Entrainment losses are related to the volume of mer. Larvae spawned in summer matured cooling water circulating and larval abundance slowly, forming the over-wintering population. because these determine the number of larvae This pattern was observed by Wigley and Burns exposed to lethal temperatures and physical I (1971) on Georges Bank and in this study (NAl shock. 1995, 1996, 1998). The operational mean abundances of the fast-maturing summer genera- Although Seabrook Station operated its circulat- j tion (May through July) were greater than the ing water system at varying levels since 1985, no ) confidence intervals of the preoperational period. power or heated discharge were produced until I Abundances of the over-wintering generation August of 1990. No entrainment samples were were very similar in the preoperational and collected during several scheduled plant shut-i operational periods, except for March when downs during the operational period: early l preoperational abundances were greater. August through November 1991, and September and October 1993. No entrainment samples were High abundances in fall 1996 (NAl 1998) contin- collected in 1994. ued into the early winter of 1997. This large j overwintering population may have contributed The total number of bivalve larvae entrained in l to the high abundances that occurred from mid- 1997 was 6,366.3 X 10'(Table 4-12), a decrease ! spring through summer, during the season when from the record-high estimate in 1996 (Appendix abundances were usually low. Table 4-2). In 1997, Anomia squamula was the most common bivalve larvae entrained (45.3%) Record high abundances of N. americana oc- followed by Mytilus edulis (27.4%) and Hiatella curred at both Stations P2 and PS in 1997 (previ- sp. (14.5%; Table 4-12). Entrainment estunates ous highs were in 1989: P2 =707/1000m2, were highest in July (66.9% of total), due to high P5 =248/1000m2; NAl 1990). Abundances at entrainment of Anomia squamula, Mytilus edulis, Station P7 equaled the previous low of 10 and Hiatella sp. (Figure 4-18, Page 41). Neomysis americana per 1000m3 observed in 1988 (NAI 1989). Bivalve larvae entrainment in 1997 was the lowest recorded for the years (1995 through Abundances of N. americana were greatest at 1997) when sampling took place throughout the Station P2 and lowest at Station P7 (Table 4-11). bivalve larvae sampling season (third week in There were no significant differences between April through fourth week in June; Appendix periods, and the interaction of the main effects Table 4- 2). Entrainment was lower during 1991 was not significant. and 1992, but only partial sampling took place 4-39 l
r
]
4.0 ZOOPLANKTON Table 4-12. Estimated Number of Bivalve Larvae Entrained (X 103 by the Cooling Water System , at Seabrook Station from the Third Week in April Through the Fourth Week of October,1997. Seabrook Operational Report,1997. Apr May Jun Jul Aug Sep Oct Total % ! - Species Bivalvia 0.4 < 0.1 3.6 36.1 7.8 7.2 16.0 71.1 1.1 l Anomia squamula 0.3 < 0.1 28.6 1763.2 98.5 873.5 155.2 2883.3 45.3 I Hiatella sp. 16.1 2.1 114.7 769.5 9.8 8.4 3.1 923.7 14.5 Modiolus modiolous < 0.1 0.0 9.4 208.2 6.3 283.1 107.8 614.7 9.7 Mya arenaria 0.0 0.0 0.0 3.5 3.4 1.1 45.8 53.7 0.8 Mya truncata 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.8 < 0.1 Mytilus edulis 0.1 < 0.1 95.7 1460.7 79.2 90.8 18.2 1744.5 27.4 Placopecten magellanicus 0.0 0.0 0.2 < 0.1 < 0.1 0.5 0.1 0.8 < 0.1 Solenidae < 0.1 0.0 0.7 13.8 7.0 6.4 21.6 49.5 < 0.1 Spisula solidissima 0.0 0.0 0.2 1.8 5.5 5.0 10.1 22.5 0.4 Teredo navalis 0.0 0.0 0.0 0.1 0.3 1.0 0.3 1.7 < 0.1 Total 17.8 2.1 252.9 4256.9 217.7 1240.9 378.0 6366.3 100.0
% of Total < 0.1 < 0.1 4.0 66.9 3.4 19.5 5.9 ;
during those years. Species composition in 1997 may be related to the high densities observed in was similar to previous years with Anorria the offshore samples. However, densities of A. squamula, Mytilus edulis, and Hiateita sp. the squamula in offshore samples in 1997 were three most abundant taxa entrained. Despite the second only to the record high-densities observed relatively low total estimate, entrainment of Mya in 1996 (NAl 1998) and were above the arenaria was the highest recorded for that spe- preoperational and operational means at all ] cies, stations (Table 4-13, Page 42). This did not i result in a high entrainment estimate when com-
]
There was not a consistent relationship between pared to years (1995-1997) when sampling took the annual density of bivalve larvae in offshore place throughout the bivalve larvae entrainment I samples and annual entrainment estimates. season (Appendix Table 4-2). Similar to A. ] Density of Mya arenaria larvae in offshore squamula, the density of Mytilus edulis in 1997 i samples in 1997 was higher than the was also higher than both the preoperational and l preoperational and operational means at Stations operational means (Table 4-8), but this did not P2 and P7, and higher than the operational mean result in an unusually high entrairunent estimate. at Station P5 (Section 9.0; Table 9-1). The high Density of Hiatella sp. in offshore samples in entrainment estimate for Mya arenaria in 1997 1997 was higher than the operational means at i 4-40
7.- l 4.0 ZOOPLANKTON l 90 Cooling Water Pumped in 1997 l I l g; I 1. t 1-p 1 m: ? 5 3oi l t . 10- l l ! 05. -. - - - _ - - .-_. APR MAY JUN JUL AUG SEP OCT i l MOMTH Bivalve Larvae Entrained in 1997
) X Anomia squamula 4750; G Hiatella sp N uytau . oui..
% . i Otner 4000- --
3750-I 3 soot b 3250! kg 27w! ! N 2500j F/ 2250; 2000 1750
. 1500; 1250 ;
1000; : 750 300 o'_..._... }E Jul
.PBfE F2525$ .
Oct Apr May Jun Aug Sep MONTH Figure 4-18. Volume of cooling water pumped during the months sampled for bivalve larvae and total number of bivalve larvae (X 10') entrained by Seabrook Station in 1997. Seabrook Operational Report,1997. 4 41
4.0 ZOOPLANKTON Table 4-13. Geometric Mean Abundance (no./m') and Coefficient of Variation for Anomia squamula and Hiatella sp. Larvae at Stations P2, PS and P7 During the Preoperational and Operational Periods and 1997. Seabrook Operational Report 1997. . 1 Preoperational* Operational
- 1997 l
Species Station Mean CV Mean CV Mean Anomia squamula P2 26 54 218 19 577 P5 94 18 245 19 721 l P7 66 12 223 14 372 Hiatella sp. P2 60 39 10!* 16 87 P5 51 17 106 20 117 P7 64 5 73 17 44
- Preoperational Period: P2 1978-1989 " Operational Period P5 1988 1989 All stations 1991 1997 P7 1982 1984 1987-1989 Stations P2 and PS, and Icwer than the affected settlement of YOY clams because there
- preoperational and operational means at P7 is not a strong relationship between larval abun- l (Table 4-13). Despite the relatively high densi- dance and settlement (Section 9.0). Predicted I ties in offshore samples in 1997, the entrainment entrainment of Mytilus edulis (900 X 10'; NAl estimate for Hictella sp. was the lowest recorded 1977) was within the range of annual estimates since 1995 (Appendix Table 4-2). The differ- (122 X 10' to 17,932 X 10'). Entrainment of ences in abundance between entrainment and Mytilus edulis has apparently not affected local offshore 1.ivalve larvae samples may be due to population of adults monitored in the Marine j l the differences in depths sampled. Entrainment Macrobenthos program (Section 7.0). l samples are drawn through the intake structure )
from the middle of the water column, whereas 4.4 DISCUSSION bivalve larvae samples are collected from the entire water column. Differences in the depth Potential effects on the zooplankton community distributions of bivalve larvae may result in include exposure to the thermal plume and l different species composition and densities entrainment. Naylor (1965) suggested that between entrainment and offshore samples. nearshore marine organisms, although they may be more susceptible to effects of heated effluents Predicted entrainment of Mya arenaria (41 X than estuarine organisms, were less likely to be 10'; NAI 1977) was higher than actual estimates impacted because the effluent would be dis-for every year except 1997 (53.7 X 10'). En- charged into an essentially open system, which trainment of Mya arenaria apparently has not would allow the neat to be efficiently dissipated. 4-42
4.0 ZOOPLANKTON
=
The temperature differences among stations and effects were the least abundant taxa in their between the preoperational and operational respective sampling programs. periods in coastal New Hampshire waters were I small, generally less than 0.5'C. Such small Entrainment does not appear to have affected the l changes in temperature are well within the range bivalve larvae community. r;ayne (1976) stated l of interannual variability and would not be that loss to a population from overdispersal of expected to have any significant biological larvae, and larval mortality due to factors such as effects. Entrainment, with individuals being predation, settlement in unsuitable habitst, and I exposed to potentially lethal or physiological exposure to extreme physical conditions was altering conditions, is a direct effect. high, possibly approaching 99%. In population l studies, mortality at the settlement stage was ! Results indicated that neither the heated effluent found to be enormous (Bayne 1976). The loss of or entrainment had any measured effect on the veligers entrained by Seabrook Station is proba-plankton communities (Table 4-14). Although bly small in comparison to the mortality experi. each community experienced some changes in enced at the settlement stage. As most of the I abundance or seasonality during the operational settling stage larvae are near the bottom, survi-period, those changes occurred at the farfield site vors of this stage are not likely to be entrained by as well as at the nearfield stations. the mid-water intake of Seabrook Station, so recruitment to adult populations should be unaf- l Most of the selected species experienced either fected. There was no evidence that entrainment no significant differences between periods or had of bivalve larvae resulted in decreased abundance reductions in abundance that were consistent of adult Mya arenaria (Section 9.0), Mytih.s among stations (Table 4-15). However, the edulis or Modiolus modiolus (Section 6.0). ANOVA for adult Calanus finmarchicus, copepodite Eurytemora and adult Eurytemora 4.S REFERENCES CITED herdmani abundances resulted m significant Preop-Op X Station interaction terms, suggesting Abbott, R. T.1974. American Seashells. 2nd a potential plant impact. Comparison of the ed., Van Nostrand Reinhold, New York annual means for C.finmarchicus showed varia-Bayne, B.L. 1976. The biology of mussel tion among stations to he limited to only three of larvae In Bayne B.L., ed. Marine mussells: the six operational years, suggesting either a their ecology and physiology. Cambridge short-term trend or effectr from factors other Univ. Press. Pp. 81-120. than Seabrook Station. The potential plant impact on copepodite Eurytemora and adult Boesch, D.F. 1977. Application of numerical classificanon m ecological investigations of Eurytemora herdmani may be the result of an water pollution. U.S. Environmental Protec-unusual preoperational year (high abundance in tion Agency, Ecological Research Report 1983). Operational period abundances were Agency, Ecol. Res. Rep.,114 pp. similar in magnitude and variability to two of the three preopera:ional years tested by ANOVA. It Clifford, H.T., and W. Stephenson.1975. An introduction to numerical classification. should be cautioned that the three selected spe-Academic Press, New York. 229 pp. cies which had significant interactions of main 4-43
E 4.0 ZOOPLANKTON Table 4-14. Sununary of Potential Effects, Based on Numerical Classification and MANOVA Results, of the Operation of Seabrook Station on the Indigenous Zooplankton Conununities. Seabrook Operational Report,1997. 1 i Differences Between Operational Operational and Period Similar to Preoperational ' Community Attribute Preoperational Periods Consistent Period? among Stations? Microzooplankton Seasonal occurrence yes' not tested 1 Abundances no" p' Bivalve Larvae ' Seasonal occurrence no' yes l Abundances no" d yes Macrozooplankton Holoplankton/meroplankton y Seasonal occurrence im* yes l Abundances no" yes l Hyperbenthos ) Seasonal occurrence yes' yes Abundances no" yes ! l
- Based on results of numerical classification.
- Based on comparisons of group mean abundances. !
' Based on MANOVA results of stauon comparisons in each year of the preoperauonal 1 and operational periods.
d Based on MANOVA results. Table 4-15. Suminary of Potential Effects, Based on ANOVA Results, of the Operation of Seabrook Station on Abundances of Selected Indigenous Zooplankton Species. Seabrook Operational Report,1997. Differences Between Operational Operational and Plankton Period Similar to Preoperational Periods Selected Species Preoperational' Consistent among And Lifestages Period? Stations? Microzooplankton Eurytemora sp. copepodites - No, Op decrease greater at P7 Eurytemora herdmani adults - No, Op decrease greater at P7 Pseudocalanus/Calanus nauplii Op > Preop yes Pseudocalanus sp. copepodnes yes yes adults yes yes Oithona sp. nauplii yes yes copepodites yes yes adults yes yes Bivalve Larvae Mytilus edulis larvae yes yes Mzerozooplankton Calanusfinmarchicus copepodites yes yes adults - No, Op decrease greater at P7 Crangon septemspinosa larvae yes yes
. yes yes Carcinus maenas larvac yes yes Neomysis americana
- Recent preoperational years: 19821984 for rnicrozooptankton. 1988-1989 f- tnvalve larvae and 19871989 for inacrozooplankton.
4-44
r 4.0 ZOOPLANKTON Table 4-14. Sununary of Potential Effects, Based on Numerical Classification and MANOVA Results, of the Operation of Seabrook Station on the Indigenous Zooplankton Communities. Seabrook Operational Report,1997. Differences Between Operational Operational and Period Similar to Preoperational Community Attribute Preoperational Periods Consistent Period? among Stations? Microzooplankton Seasonal occurrence yes' not tested Abundances no" yes' Bivalve Larvae Seasonal occurrence no' yes Abundances noAd yes Macrozooplankton Holoplankten/meroplankton Seasonal occurrence no' yes l Abundances nok ' yes H perbenthos j casonal occurrence yes' yes y Abundances noAd yes
- Based on results of numerical classification.
- Based on comparisons of group mean abundances.
- ' Based on MANOVA results of station comparisons in each year of the preeperational and operational periods.
' Based on MANOVA results.
l Table 4-15. Summary of Potential Effects, Based on ANOVA Results, of the Operation of l Seabrook Station on Abundances of Selectal Indigenous Zooplankton Species. l Seabrook Operational Report,1997. l Differences Between Operational Operational and Plankton Period Similar to Preoperational Periods Selected Species Preoperational* Consistent among And Lifestages Period? Stations? l Microzooplankton Eurytemora sp. copepodites - No, Op decrease greater at P7 l Eurytemora herdmani adults - No, Op decrease greater at P7 Pseudocalanus/Calanus nauplii Op > Preop yes Pseudocalanus sp. copepodites yes yes adults yes yes Oithona sp. nauplii . yes yes copepodites yes yes adults yes yes Bivalve Larvae Mytilus edulis larvae yes yes Macrozooplankton Calanusfinmarchicus copepodites yes yes adults - No, Op decrease greater at P7 Crangon septemspinosa larvae yes yes
. yes yes Carcinus moenas larvae yes yes j Neomvsis americana
- Recent preoperational years: 1982-1984 for microzooplankton. 19881989 for bivalve larvae and 1987-1989 for rnacrorooplankton.
l 4-44 J
4.0 ZOOPLANKTON Corkett, C.J. and 1.A. McLaren. 1978. The and Eurytemora herdmani in Passamaquoddy biology of Pseudocalarms. Adv. Mar. Biol. Bay, New Brunswick. Can. J. Fish. Aq. Sci. ] 15:1-231, 43(3):656-664. Grabe, S.A. and E.R. Hatch. 1982. Aspects of Naylor, E. 1965. Effects of heated effluents upon marine and estuarine organisms. Adv. the biology of Mysis mixta (Lilljeborg 1852) (Crustacea, Mysidacea) in New Hampsihre Mar. Biol. 3:63-103. coastal waters. Can. J. Zool. 60(6):1275-1281. Newell, R.I.E., T.J. Hilbish, R.K. Koehn, and C.J. Newell. 1982. Temporal variation in Haefner, P.A.1979. Comparative review of the the reproductive cycle of Mytilus edulis from biology of North American Caridean shrinps localities on the east coast of the United (Crangon) with emphasis on Crangon States. Biol. Bull. 162:299-310. septemspinosa. Bull. Biol. Soc. Wash 3:1-
- 40. Normandeau Associates, Inc. (NAI). 1977.
Summary Document: Assessment of Antici-Harris, R.J. 1985. A primer of multivariate pated Impacts of Construction and Operation statistics. Orlando: Acad. Press. 575 p. of Seabrook Station on the Estuarine, Coastal and Offshore Waters Hampton-Scabrook, Jossi, J.W. and J.R. Goulet, Jr. 1993. Zoo- New Hampshire. Prepared for Public Ser-plankton trends: U.S. Nonheast shelf eco- vice Company of New Hampshire. system and adjacent regions differ from Northeast Atlantic and North Sea. ICES J. 1984. Seabrook Environmental Mar. Sci. 50:303-313. Studies.1983 data report. Tech. Rep. XV-1. Kane, J. 1993. Variability of zooplankton biomass and dominant species abundance on 1989. Seabrook Environmental Georges Bank, 1977-1986. Fishery Bull. Studies, 1988. A characterization of 91:464-474, environmental conditions in the Hampton-Seabrook area. 1975-1988. A preoperational Katona, S.K. 1971. The developmental stages study for Seabrook Station. Tech. Rep. XX-of Eurytemora afinis Poppe,1880 (Copep- II. oda Calanoida) raised in laboratory cultures, including a comparison with the larvae of . 1990. Seabrook Environmental Eurytemora americana Williams,1906, and Studies, 1989. A characterization of Eurytemora herdmani Thompson and Sec,tt, environmental conditions in the Hampton-1897. Crustaceana 21:5-20. Seabrook area. 1975-1989. A preoperational < study for Seabrook Station. Tech. Rep. Mauchline, J. l 1980. The Biology of Mysids: XXI-II. ; Part I, in The biology of mysids and euphau- l siids. Adv. Mar. Biol. 18:3-372. . 1991. Seabrook Environmental i Studies, 1990. A characterization of l Mees, J. and M. B. Jones. 1997. The environmental conditions in the Hampton-Oceanog. and Mar. Bio: Seabrook area during the operation of Sea-
]
hyperbenthos. ' Annual Review. 35:221-255. brook Station. Tech. Rep. XXil-II. Middlebrook, K. and J.C. Roff. 1986. Compar- 1992. Seabrook Environmental isons of methods for estimating annual pro- Studies, 1991. A characterization of j ductivity of the copepods Acartia hudsonica environmental conditions in the Hampton-4-45 l J
I ( 4.0 ZOOPLANKTON 0 l Appendix Table 4-1. List of Zooplankton Taxa Used in the Statistical Analysis Presented by Community. Seabrook Operational Report,1997. Microzooplankton j Protozoa Foraminiferida ( Tintinnidae ] l Bryozoa Bryozoa l Mesozoa l Rotifera Rotifera l Mollusca Bivalvia ' Gastropoda Opisthobranchia Annelida Polychaeta > Echinodermata Echinodermata ; Cirripedia Cirripedia j Cladocera Evadne Lov6n Podon Lilljeborg Copepoda Acania Dana Acartia hudsonica Pinhey Acartia longiremis (Lilijeborg) Calanusfnmarchicus (Gunnerus 1765) Centropages Krayer Centropages hamatus (Lilljeborg 1853) Centropages typicus Kreyer Copepoda (nauplii) Cyclopoida Eurytemora Giesbrecht , Eurytemora herdmani Thompson and Scott 1897 l Harpacticoida l Metridia Boeck l Microsetella norvegica (Boeck) l Oithona Baird 1843 i Paracalanus parvus (Claus) l Parvocalanus crassirostris Pseudocalanus Boeck 1872 i Pseudocalanus/Calanus (nauplii) Temora longicornis (MGller 1785) , Tortanus discaudatus (Thompson and Scott 1897) ! Bivalve Larvae Anomia squamula Linnaeus l Hiatella Bosc 1801 ! Macoma balthica Linnaeus 1758 l Modiolus modiolus Linnaeus 1758 l Mya arenaria Linnaeus 1758 l Mya truncata Linnaeus 1758 Mytilus edulis Linnaeus 1758 Placopecten magellanicus (Gmelin 1791) Solenidae Spisula solidissima (Dillwyn 1817) Teredo navalis Linnaeus 1758 1 4-47 L-
F
]
4.0 ZOOPLANKTON
.Holontankton and Meroniankton Cnidaria Aglantha digitale (O.F. MGiler 1776)
Bougainvillia principis (Steenstrup 1850) ) Hydrozoa Obelia P6 ton and Lesueur 1809 Phialidium Leuckart 1856 Rathkea octopunctata (M. Sars 1835) Sarsia Lesson 1843 Scyphozoa Tubulariidae ! Mollusca Gastropoda l Lacuna vincta Turton Limacina retroversa Fleming Annelida Tomopteris helgolandicus Greeff Cladocera Evadne Lov6n Podon Lilljeborg i Copepoda Acartia hudsonica Pinhey 1 Acartia longiremis (Lilljeborg) Acartia tonsa Dana Aetideidae { Anomalocera opalus Penell 1976 ' Calanuspnmarchicus (Gunnerus 1765) i Caligus Muller I Candacia armata (Boeck 1872) { Centropages hamatus (Lilljeborg 1853) i Centropages Kroyer 1849 j Centropages typicus Krayer 1849 i Eurytemora herdmani Thompson and Scott 1897 l Metridia Boeck Monstrillidae Pseudocalanus Boeck 1872 Temora longicornis (MGller 1785) Tortanus discaudatus (Thompson and Scott 1897) Cirripedia Cirripedia Amphipoda Hyperiidae i Euphaucca Meganyctiphanes norvegica (M. Sars) Thysanoessa Brandt Decapoda Axius serratus Cancer Linnaeus Carcinus maenas (Linnaeus 1758) Caridion gordoni (Bate) Crangon septemspinosa Say 1818 Eualuspusiolus (Kreyer 1841) Hippolytidae (Eualus Thallwitz 1892, Lebbeus White 1847, Spirontocaris Bate 1888) Hyas Pagurus Fabricius Pandalidae Echinodermata Echinodermata , Chaetognatha Sagitta elegans Verrill 1873 i Urochordata Larvacea (previous to 1994, identified as Oikopleura Mertens) l i 4-48 l
a l l l 4.0 ZOOPLANKTON i Hyperbenthos l Polychaeta Nereidae l Syllidae Copepoda Harpacticoida i Mysida Erythrops erythrophthalma (G6es 1864) l Mysis mixta (Lilljeborg 1852) ! Neomysis americana (S.I. Smith 1673) ? Cumacea Diastylis Say Lamprops quadriplicata (S.I. Smith) l Leuconidae Mancocuma stelhfera Petalosarsia declivis Sars Pseudoleptocuma minor (Calman) j Isopoda Isopoda l Amphipoda Amphipoda Calliopius laeviusculus (Kreyer) 1838 Corophium Milne-Edwards l Gammarus lawrencianus Bousfield 1956 l l Ischyrocerus anguipes Kreyer 1838 Jassa marmorata Holmes l 1 Oedicerotidae Podoceridae Pontogeneia inermis (Kroyer 1842) l Unciola irrorata Shoemaker i l I l l l I l l t 4 49
4.0 ZOOPLANKTON Appendix Table 4-2. Estimated Number of Bivalve Larvae Entrained (X 10') by the Cooling Water ) System at Seabrook Station 1990 Through 1993, and 1995 Through 1997'. Seabrook Operational Report,1997. 1 6 Species 1990 1991* 1992 8 1993' 1995' 19968 1997" Bivalvia 181.7 38.1 14.5 334.5 797.1 671.4 71.1 Anomia squamula 1691.4 250.8 6.9 3922.7 8905.9 23521.6 2883.3 Hiatella sp. 876.6 421.3 189.8 2405.5 2598.2 4670.2 923.7 Modiolus modiolus 909.7 160.2 0.3 1283.9 546.4 5144.8 614.7
)
Mya arenaria 8.1 0.6 0.2 22.5 4.3 33.2 53.7 Mya truncata
- 249.2 6.5 1.1 2.1 27.6 123.0 0.8 Mytilus edulis 3991.3 1687.5 121.9 10050.7 13231.0 17931.8 1744.5 !
Placopecten magellanicus 0.7 0.7 0.1 16.9 6.2 31.0 0.8 Solenidae 61.1 0.0 75.7 102.5 1092.3 241.9 49.5 l Spisula solidissima 69.0 4.4 0.0 48.5 112.5 171.1 22.5 Teredo navalis < 0.1 15.9 0.0 0.0 4.8 7.4 1.7 Total 8038.9 2586.0 410.5 18189.8 27326.5 52547.4 6366.3 3
}
- No sampimg occurred in 1994. l
- Sampling occurred from June through October 1990. l
- Samphng occurred from the last week in April through first week in August 1991. i
' Sampling occurred from the third week in April through third week in June 1992. ! ' Sampling occurred from the third week in April through the fourth week in June 1993. i ' Samphng occurred from the third week in April through the fourth week in October 1995. -
8 Sampimg occurred from the third week in April through the fourth week in October 1996. I
- Sampling occurred from the third week in April through the fourth week in October 1997.
l I l 4 1 1 I I t 4-50
y 5.0 FISH TABLE OF CONTENTS PAGE
SUMMARY
. . . .. ........ . . . . .... ... . .. . . . iii LIST OF FIGURES . .. .......... . . .... .. .. .. ... . v LIST OF TABLES . . . . . . . . . . . . . . .. ........ ......... . ............ xiii LIST OF APPENDIX TABLES . . .. . . .. ... . ... .... .. x 5.0 FISH
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 Sampling . ......... . ...... . . . . .... 5-3 5.2.1.3 Laboratory Methods . . . . . . . . . ....... ....... ... 5-3 5.2.2 Adult Fish . . . .. ...... ................... . ....... 5-4 l 1
5.2.2.1 Pelagic Fishes . . . . . . . . . . ..................... . 5-4 l 5.2.2.2 Demernl Fishes . . . . . . . . . . . . . . . . . ...............5-5 5.2.2.3 Estuarine Fishes ............ .... ........... ... . 5-5 5.2.2.4 Impingement . . . . . . . . . . . . . . . . . . . . . . ... ...... . . 5-5 5.2.3 Analytical Methods ... ...... ... . .. .......... . . . . . 5-6 5.3 RESULTS AND DISCUSSION . .. ........ . ...... . ...... . . . 5-9 5.3.1 Ichthyoplankton Assemblages .. . . ..... ..... ........ . 5-9 5.3.1.1 Offshore Samples . ...... ... ... .. . ... .... . 5-9 ) 5.3.1.2 Entrainment . .. ... . . ..... ... . ...... . 5-16 5.3.2 Adult Fish Assemblages . . . . . . . . . . . .... . .... . . . ... 5-23 5.3.2.1 Demersal Fishes . . . ..... . ...... ... 5-23 5.3.2.2 Estuarine Fishes . ............... .. . .... ..... 5-25 5.3.2.3 Impingement . . . . . . . . . . . . . . . ....... .... .. . . . . . 5-26 1 1 1 5-i
1 S.O FISH PAGE 5.3.3 Selected Species . . . ...... . ... . . . .. . 5-30 5.3.3.1 Atlantic Herring . . ... . .. .. . . 5-30 l l 5.3.3.2 Rainbow Smelt . . . ...... . .. . . . .... 5-34 5.3.3.3 Atlantic Cod . . . . . . . .... .. . . . ... . . . 5-38 1 5.3.3.4 Pollock . . . . . .. ... . . . .... . . . 5-40 1 5.3.3.5 Hakes . . .. ... . .... ..... ........ . . . 5-42 5.3.3.6 Atlantic Silverside . . ..... ...... ... . .. . ... .. 5-47 5.3.3.7 Cunner ............................... . . .. . 5-47 5.3.3.8 American Sand Lance .. . . . . . .. ... . . 5-49 5.3.3.9 Atlantic Mackerel ........... . .. ... .. .. . 5-52 5.3.3.10 Winter Flounder . . . . .... .............. .... . 5-53 5.3.3.11 Yellowtail Flounder . . . ..... .. ..... .... .... 5-59 l 5.4 EFFECTS OF SEABROOK STATION OPERATION .......... . . .. . 5-63
5.5 REFERENCES
CITED . . . . .. .. . .. ... . ... .. . 5-65 1 l l l 5-il
5,0 FISH
SUMMARY
{ f The fishes of the Hampton-Seabrook area have been sampled since 1975 to assess potential impacts associated with the operation of Seabrook Station on local fish assemblages. Potential plant impacts include the entrainment of fish eggs and larvae and the impingement ofjuvenile and adult fish at the station intake. Potential discharge impacts include avoidance by larger fish and entrainment of fish eggs and larvae into the offshore thermal discharge. Numerical classification was used to characterize the fish egg and larvae community in the preoperational and operational periods. Both these communities were temporally and spatially consistent between the preoperational and operational periods. There were no significant differences in larval density for the nine selected species between the preoperational and operational periods, except for Atlantic herring where density was significantly higher in the preoperational period. Trends in larval density between the preoperational and operational periods
- for the selected species were similar among stations, indicating no effect due to the operation of Seabrook l l Station.
I CPUE (catch per 10 minute tow) for demersal fishes in 1997 was 14.6, a decrease from 1996, and among the lowest observed. CPUE in 1997 was dominated by skates (4.1), longhorn sculpin (3.0) and winter flounder (2.9). CPUE of each of the five selected species (rainbow smelt, Atlantic cod, hakes, winter flounder, yellowtail flounder) decreased between the preoperational and operational period, but the ; decrease was not consistent among stations, resulting in a significant interaction term. Overfishing of I commercial species was a regional perturbation that probably had a greater effect on CPUE than plant operation. CPUE (cath per seine haul) for estuarine fishes in 1997 (10.5) was the second lowest observed. The catch in 1997 was dominated by Atlantic sliverside (4.4), American sand lance (0.5), and killifishes (0.3). There j were no significant differences in CPUE between the preoperational and operational periods for rainbow l smelt and Atlantic silverside. CPUE of winter flotuxler decreased between periods, but the decrease began ( before the plant became operational. l In 1997 an estimated 692.6 million eggs were entramed. Estimates for previous years ranged from 4.7 million in 1994 (8 months of sampling) to 1,551.0 million in 1991 (8 months) of sampling. , Cunner /yellowtail flounder (186.1 million) and silver hake (271.1 million) were the dominant eggs l entramed in 1997. Cunner /yellowtail were generally among the top three taxa entrained in previous years, j Silver hake egg entrainment in 19997 was the highest observed. Entrainment of larvae in 1997 was l estimated as 373.4 million, the highest observed to date. The high entrainment estimate in 1997 was ) primarily due to record estimates of cunner (203.8 million) and silver hake (69.0 million) larvae. An j estimated 10,648 fishes were impinged in 1997, the lowest estimate since 1994. Alewife (2,797) were the l 1 ; 5-iii l 1
5.0 FISH
)
most numerous fish impinged, followed by windowpane (1,688) and rock gunnel (459). Impingement in previous years has been correlated with storm events. There were few storms in 1997, resulting in a low level of impingement. Impingement and entrainment at Seabrook Station has been similar to or lower than L other New England power plants with marine intakes. The operation of Seabrook Station did not appear to affect the ichthyoplankton and fish communities of the Hampton-Seabrook area. Relatively few individuals were removed by station operation and there was a general lack of significant differences between the nearfield and farfield stations, or between the f I preoperational and operational periods. 1 i 1 l l l l 5-iv
I 1 l S.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) 2 transformed number per 1000 m ) at Seabrook intake (P2), discharge (PS), and farfield (P7) stations, July 1986-December 1997 . . . . . ... . . ...... . . . 5-11 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 1997 . . . . . ... ....... . ........ . 5-14 5-4. Total monthly cooling water system flow and estimated numbers of fish eggs and larvae entrained during 1997. . . . . . . . . ....... ... ......... ...... . . . . 5-21 5-5. Annual geometric mean catch of all species combined per unit effort (number per 10-minute tow) in trawl samples by station and the mean of all stations, 1976-1997 ... 5-23 5-6. 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, 1976-1997 ........ . . . . . 5-26 5-7. Annual geometric mean catch per unit effort (number per 1000 cubic meters) of Atlantic herring in ichthyoplankton samples by station and the mean of all stations, 1975-1997 . 5-32 5-8. Annual geometric mean catch of rainbow smelt per unit effort in trawl (number per 10-minute tow) and seine (number per haul) samples by station and the mean of all stations, 1975-1997 (data between two vertical dashed lines were excluded from the ANOVA model) . . . . . ...................... .. ... ........ . . . . . . . 5-3 6 5-9. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of rainbow smelt caught by trawl during the preoperational (November 1975-May 1990) and operational (November 1990-May 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-14) . . . . .. .... .... . 5-37 5-10. Annual geometric mean catch of Atlantic cod per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-minute tow) samples by station and the mean of all stations, 1976-1997 .... . .............. ........... 5-39 5-v
p 5.0 FISH PAGE
]
5-11. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of Atlantic cod caught by trawl during the preoperational (November 1975 - July 1990) and operational (Nobemrber 1990 - July 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model(Table 5-15) . . . . . . . .. . . . . . . . 5-41 5-12. Annual geometric mean catch per unit effort (number per 1000 cubic meters) of pollock in ichthyoplankton samples by station and the mean of all stations, 1975-1997. Note that 1996 includes November and December of 1996 and January and February of 1997 . . . 5-43 5-13. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-minute tow) samples by station and the mean of all stations, 1976-1997 (data between the two vertical dashed lines were excluded from the ANOVA model) . . . . . . ................................... . . . 5-45 5-14. A comparison among stations of the geometric mean CPUE (number per 10-miunute tow) of hakes caught by trawl during the preoperational (November 1976 - July 1990) and operational (November 1990 - July 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model(Table 5-17) . . . . . . . . ...... . . 5-46 1 5-15. Annual geometric mean catch per unit effort of Atlantic silverside in seine samples I (number per haul) by station and the mean of all stations, 1976-1997 (data between the two vertical dashed lines were excluded from the ANOVA model) . . . . . . . . . . . . . . . . . 5-48 5-16. Annual geometric mean catch of cunner per unit effon in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations, 1975-1997 (data between the two venical dashed lines were excluded from the ANOVA model) . . . . . . 5-50 5-17. Annual geometric mean catch of American sand lance per unit effon in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations, 1976-1997 ............ . . . . . . . . . . .............. .. . . . . . . . . . 5-51 5-18. Annual geometric mean catch of Atlantic mackerel per unit effon in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations, 1976- 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. .. . 5-54 5-vi
5.0 FISH PAGE 5-19. Annual geometric inean catch of winter flounder per unit effort in ichthyoplankton ! (number per 1000 cubic meters), trawl (number per 10-minute tow), and seine (number per haul) samples by station and the mean d all stations, 1975-1997 (data between the two vertical dashed lines were excluded from ANOVA model) . . ... . .. .... . 5-56 5-20. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of winter flounder caught by trawl during the preoperational (November 1975-July 1990) j and operational (November 1990-July 1997) periods for the significant interaction term l (Preop Op X Station) of the ANOVA model (Table 5-22) . . . . ... ..... ..... 5-58 ) 5-21. Annual geometric mean catch of yellowtail flounder per unit effort in ichthyoplankton ; (number per 1000 cubic meters) and trawl (number per 10-minute tow) samples by station and the mean of all stations, 1976-1997 . . . . . . . . .. ..... .. ... ...... 5-60 5-22. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of yellowtail founder caught by trawl during the preoperational (November 1975 - July 1990) and operational (November 1990 - July 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-23) . ................. 62 l i I 5-vii
]
5.0 FISH LIST OF TABLES i PAGE 1 5-1. Description of Finfish Sampling Stations . . . . . . .... . .. ... .. . . 5-4 ! 5-2. Selected Finfishes and Sampling Programs That Contributed Abundance Data for Species-
]
Specific Analyses . . . . . . . . . . ........ ....... ... .. .......... . 5-7 5-3. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish Eggs Collected at Seabrook Intake (P2), Discharge (P5), r.nd Farfield (P7) Stations During July 1986 Through December 1997 .. ..................... ..... . . 5-10 ! l 5-4. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish Larvae Collected at Seabrook Intake (P2), Discharge (PS), and Farfield (P7) Stations During July 1986 Through December 1997 . ...... ...... .. .... ..... 5-15 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 in 1997 . 5-17 5-6. Annual Estimated Numbers of Fish Eggs and Larvae Entrained (X 106 ) by the Cooling l Water System at Seabrook Station from June 1990 Through December 1997 . . . . . ... 5-19 l I 6 5-7. Comparison of Entrainment Estimates (X 10 ) for Selected Taxa at Selected New England l Power Plants with Marine Intakes from 1990 Through 1997 .... ........ .. 5-22 5-8. Geometric Mean Catch per Unit Effort (number per 10-minute 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 19% Mean . . . . . . . . . . . . . . . . . . . . . . ............. .... .... 5-24 5-9. 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 the Preoperational and Operational Periods and the 1997 Mean .. ..... ............... ..... .. ... . .. ....... 5-27 5-10. Species Composition and Total Number of Finfish and American Lobster Impinged at Seabrook Station by Month During 1997 . . . . . ... . ..... ....... ..... 5-28 5-11. Comparison of Fish 1mpingement Estimates at Selected New England Power Plants with Marine Intakes . . . . . . . . . . . . . . . ...... .. .. ... ..... .... . 5-31 5-viii
4 S.0 FISH PAGE 5-12. 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 Larvae of Selected Species Collected in Ichthyoplankton Samples During the Preoperational and Operational Periods and in 1997 . . ....... ............. . ... ... ... .. 5-33 5-13. Results of Analysis of Variance for Atlantic Herring Densities by Sampling Program . . 5-34 5-14. Results of Analysis of Variance for Rainbow Smelt Densities by Sampling Program . 5-37 5-15. Results of Analysis of Variance for Atlantic Cod Densities by Sampling Program . . 5-40 5-16. Results of Analysis of Variance for Pollock Densities by Sampling Program . . . . . . 5-43 I' 5-17. Results of Analysis of Variance for Hake Densities by Sampling Program .. . . . . 5-46 5-18. Results of Analysis of Variance for Atlantic Silverside Densities by Sampling Program . 5-48 5-19. Results of Analysis of Variance for Cunner Densities by Sampling Program . . . . . . . . 5-50 ; 5-20. Results of Analysis of Variance for American Sand Lance Densities by Sampling Program . . . . . ................... .... ........... ......... 5-52 5-21. Results of Analysis of Variance for Atlantic Mackerel Densities by Sampling Program . 5-54 5-22. Results of Analysis of Variance for Winter Flounder Densities by Sampling Program . . 5-57 5-23. Results of Analysis of Variance for Yellowtail Flounder Densities by Sampling Program . . . . .. ... ........... ... .. .... ....... 5-61 5-24. Sununary of Potential Effects of the Operation of Seabrook Station on the Ichthyc< iankton Assemblages and Selected Fish Taxa . . . . . . . . . . . . ... . .... ... . 5-64 l 5-ix i
5.0 FISH s LIST OF APPENDIX TABLES PAGE I 5-1. Finfish Species Composition by Life Stage and Gear, July 1975-December 1997 ' . . . 5-73 5-2. Subsetting Criteria Used in Analyses of Variance for the Selected Finfish Species .... 5-76 5-3. Species Composition, Annual Totals, and Four-Year Total of Finfish and American Lobster Impinged at Seabrook Station from 1994 to 1997 ... .. .. . . .. 5-77 l l l l l 1 l l l l 1 5-x
5.0 FISH
5.1 INTRODUCTION
abundance in collections from July 1975 through December 1997 by various ichthyoplankton and Finfish studies at Seabrook Station began in July adult finfish sampling programs are given in 1975 and have included investigations of all life Appendix Table 5-1. Both the common and stages of fish, including ichthyoplankton (eggs scientific names in that table follow Robins et al. and larvae), juveniles, and adults. The initial (1991) and common names are used throughout objectives of these studies were to determine the this report. seasonal, annual, and spatial trends in abundance and distribution of fish in the nearshore waters 5.2 METHODS off Hampton and Seabrook, NH to establish baseline data suitable for assessing the effects of 5.2.1 Ichthvoniankton future plant operation. In addition, the nearshore fish populations in the Hampton-Seabrook 5.2.1.1 Offshore Samnlinc estuary were examined to determine if there was any measurable effect due to the construction of Ichthyoplankton sampling for Seabrook Station Seabrook Station and the discharge from the on- has been conducted since July 1975. Several site settling basin into the Browns River, which modifications to the sampling methodology and ended in April 1994. The station began collection frequencies were made as the nature of commercial operation in August 1990. Potential the ichthyoplankton community and its natural impacts of plant operation on local fishes include variability became better understood (NAI 1993). entrainment of eggs and larvae through the Station P2 (nearfield site for the Seabrook condenser cooling water system and impingement intakes) has been sampled consistently since the of larger specimens on traveling screens within start of the program (Figure 5-1). Station P5 the circulating water pumphouse. Also, local (nearfield site for the Seabrook discharge) was distribution of fishes could be affected by the sampled from July 1975 through December 1981 thermal plume, and some eggs and larvae could and from July 1986 through December 1997. be subjected to thermal shock due to plume Station P7 (farfield station located about 7 km entrainment following the discharge of condenser north of the nearfield stations), representing a cooling water from the diffuser system. non-impacted or control site, was sampled from January 1982 through December 1984 and from At present, the main objective of the finfish January 1986 through December 1997. Through studies at Seabrook Station is to assess whether June 1977, collections were taken monthly at power plant operation since 1990 has had any each station sampled. Subsequently, a second measurable effect on the nearshore fish monthly sampling period was added in February populations. The following report first presents through August and in December. Begirming in general information on each finfish collection January 1979, all months were sampled twice. program and then provides more detailed Starting in March 1983, sample collection was analyses for those fish species selected because of increased to the current frequency of four times their dominance in the Hampton and Seabrook per month at each station sampled. area or their commercial or recreational importance. A list of all taxa and their relative 5-1
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LEGEND P = Ichthyoplankton Tows T = OtterTrawls O S = Seine Hauls Figure 5-1. Ichthyoplankton and adult fish sampling stations. Seabrook Operational Report,1997. 5-2
I S.0 FISH 1 On each sampling date and at each station, four gal drum. Water diverted from the cooling-water samples were collected at night from July 1975 system entered each 55-gal drum from the through December 1993. Beginning in January bottom, overflowed into the 30-gal drum, passed 1994, two tows were collected on each of the through the plankton net, and was discharged four sampling periods each month. Oblique tows through the bottom of both drums. The water l were made using paired 1-m diameter,0.505-mm supply was adjusted to maintain approximately 8 mesh nets. Each net, weighted with an 8-kg to 15 cm of water above the plankton nets at all depressor, was set off the stern and towed for 10 times. Following sampling, water was drained min while varying the boat speed, with the nets from the system and the contents of each net sinking to approximately 2 m off the bottom and consolidated, and preserved with 5% buffered rising obliquely to the surface at least twice formalin. The volume filtered was measured during the tow. A standard 10-min tow was with an in-line flowmeter and averaged occasionally reduced to a 5-min tow to minimize approximately 100 m' per replicate. The three net clogging due to high plankton density. The simultaneuos replicates were sununed into one volume filtered, calculated using data from a sample during analysis, calibrated General Oceanics* flowmeter mounted in each net mouth, averaged approximately 500 5.2.1.3 Laboratory Methods m' for 10-min tows and approximately 250 r'n for 5-min tows. Upon retrieval, each net was Prior to March 1983, all four offshore washed down from mouth to codend and the ichthyoplankton samples per date and station contents preserved in 5 % formalin buffered with were analyzed, except from January through borax. December 1982, when only one sample per date and station was completely analyzed; only 5.2.1.2 Entrainment Sampling selected taxa were counted from the remaining three samples. Beginning in March 1983, only Ichthyoplankton entrainment sampling was two of the four offshore samples (one from each conducted up to four times a month by NAESCo pair; Section 5.2.1.1) were analyzed from each biologists within the circulating water pumphouse station for each sampling date; the remaining two l on-site at Seabrook Station from July 1986 were held as contingency samples. Starting in l through June 1987 and June 1990 through January 1994, only one of the two or four tows ! December 1997. Three replicate samples were was analyzed per date and station, with the taken using two double-barrel collection devices remaining tows held as contingency samples. during the day on each sampling date. The entrainment data discussed in this report are only Samples were subsampled with a Folsom those for the operational period of 1990 through plankton splitter and sorted for fish eggs and 1997. larvae using a dissecting microscope. Successive aliquots were analyzed until a minimum of 200 l Replicate samples were taken using three double- eggs and 100 larvae were sorted or until 200-400 l barrel collection devices. In each, a 0.505-mm mL settled plankton volume was sorted. All eggs l mesh plankton net was suspended in a 30-gal and larvae were identified to the lowest practical l dmm which, in turn, was suspended within a 55- taxon (usually species) and counted. In some 5-3
p-5.0 FISH instances when eggs were difficult to identify to 5.2.2 Adult Fish species due to their stage of development, they were grouped with eggs of similar appearance 5.2.2.1 Pelanic Fishes s (e.g., cunner, tautog, and yellowtail flounder , were grouped as cunner /yellowtail flounder eggs; Beginning in July 1975, gill net arrays were set Atlantic cod, haddock, and witch flounder as for two consecutive 24-h periods twice each Atlantic cod / haddock; and hake species and month at Stations G1 (farfield), G2 (nearfield), fourbeard rockling as fourbeard rockling/ hake), and G3 (farfield) to sample the pelagic fish 3 The notochord lengths of at least 20 larvae per assemblage (Figure 5-1; Table 5-1). Starting in sample (if present) were measured to the nearest July 1986, sampling was reduced to once per 0.5 mm for selected taxa, which included month. Nets were 30.5 m x 3.7 m and Atlantic herring, Atlantic cod, pollock, hakes, comprised four panels having stretch mesh cunner, Atlantic mackerel, Amencan sand lance, dimensions of 2.5 cm, 5.1 cm,10.2 cm, and winter flounder, and yellowtail flounder. 15.2 cm. One net array consisting of surface and Entramment samples were processed in a similar near-bottom nets was set at each station. All nets manner. l l l l Table 5-1. Description of Finfish Sampling Stations. Seabroolc Operational Report,1997. I Station Depth Bottom Type Remarks Beach Seine S1 0-2 m sand Affected by tidal currents; approximately 300 m 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 S3 0-3 m sand Affected by tidal currents; located in Seabrook Herbor, approximately 300 m from Hampton Harbor l Bridge Otter Trawl Ti 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 I km with shell debris south of the discharge; scoured by tidal currents with large quantities of drift algae T3 22-30 m sand; littered with Located off Great Boars Head, approximately 4 km shell debris north of the discharge;just seaward of a cobble area (rocks 15-50 cm in diameter) I l 5-4 i k
E l I , 5.0 FISH i l were set perpendicular to the isobath (Figure 5- The net was towed at approximately 1 m sed for l 1). All ntas were attached between permanent 10 min, with successive tows taken in opposite l moorings and tended daily by SCUBA divers. directions. The volume of drift algae caught in l Fish collected were identified to their lowc.;t the trawl was also recorded. It was not always practical taxon (usually species), and measured to possible to collect samples at Station T2, particu-l the nearest 2 cm. larly from August through October, due to the l presence of conunercial lobster gear; the fre-The gill net monitoring program was suspended quency of missed samples has increased since l on 18 March 1997 as requested by the U.S. 1983. In 1997 no samples were collected at ! Environmental Protection Agency (EPA), the Station T2 in September and October. Fish l National Marine Fisheries Service (NMFS), and collected were identified to their lowest practical the New Hampsihre Department of Environ- taxon (usually species), and measured to the i mental Services (NHDES). The program was nearest 2 cm. l suspended as a result of the capture of a harbor porpoise in a gill net sample on 18 February. 5.2.2.3 Estuarine Fishes This capture constituted a taking under the Ma-rine Mammal Protection Act and the program Seine samples were taken monthly from April l was ended to prevent additional takings. The through November at Stations S1, S2, and S3, EPA and NHDES approved the termination of beginning in July 1975 (Figure 5-1; Table 5-1). the gli net program in December 1997. Because No samples were collected in 1985 or from April only three months of data were collected in 1997, through June of 1986. Duplicate daytime hauls and catches were very light up to the time of were taken into the tidal current at each station termination (three fish), the 1997 data will not be with a 30.5 m x 2.4 m bag seine. The nylon bag presented in this report. NAI (1998) contains the was 4.3 m x 2.4 m with 1.4-cm stretch mesh, most recent summary and analysis of gill net and each wing was 13.1 m x 2.4 m with 2.5-cm data, stretch mesh. Fish collected were identified to their lowest practical taxon (usually species), and 5.2.2.2 Demersal Fishe.s measured to the nearest 2 cm. l The inshore demersal fish assemblage was sam- 5.2.2.4 Impingement pled monthly beginning in July 1975 by otter l trawl at night at one nearfield station, T2, and Fish impinged at Seabrook Station were collected l two farfield stations, T1 and T3 (Figure 5-1; by NAESCo biologists after being washed from j Table 5-1). Four replicate tows were made at the 0.375-in mesh traveling screens withir. the l each station once per month. Beginning in circulating water pumphouse. Traveling screens January 1985, sampling frequency was increased were generally washed at least one to two times to twice per month and the number of replicate each week and more frequently during storm tows was reduced to two. Sampling was con- conditions which resulted in the impingement of ducted with a 9.8-m shrimp otter trawl (3.8-cm more debris such as seaweed (R. Sher, NAESCo, nylon stretch mesh body; 3.2-cm stretch mesh pers. comm.). Impinged fish were sluiced into a trawl bag; 1.3-cm stretch mesh codend liner). collection basket. Fish from weekly collections 5-5
]
5.0 FISH were separated from debris, identified to species, used with the unweighted pair-group clustering and counted by NAESCo tiologists. Impinge-
]
method (Sneath and Sokal 1973). Logio(x+ 1) ment collections were noted as total counts per transformed sample densities (number per 1000 . species by month. If debris loads in a m') of eggs and larvae were analyzed separately. l screenwash were high (more than 1.5 cubic The data sets were reduced by averaging dates yards) the debris and fish could be subsampled within month (transformed data); including only volumetrically. the more abundant taxa; and limiting the analysis to data collected since July 1986, when all three There were 58 screenwashes assessed out of a stations of concern (P2, P5, and P7) were sam-1 total of 145 screenwashes in 1997. The number pled. Rare taxa were excluded on the basis of of fish impinged in the unassessed screenwashes percent-composition (less than 0.1% of the was estimated based on the volume of debris in untransformed data) or frequency of occurrence the unassessed screenwash and the volume in the in samples (less than 5%). Months when only 15 assessed screenwash nearest in time using the eggs or larvae were collected were excluded l following method: from the analysis. The resulting dendrograms were evaluated on the basis of whether samples estimated impingement in from the operational period were grouped differ-unassessed screenwash = ently by the analysis than were the preoperational (VOls/VOL,) (IMP .) samples, where: Multivariate analysis of variance (MANOVA; Harris 1985) was used to indicate whether fish VOI, = volume of debris in egg and larval assemblages had differed signifi-the unassessed screenwash, cantly (p .s;. 0.05) between preoperational and operational periods. Logio(x+1) transformed VOL, = volume of debris in sample densities (number per 1000 m') were assessed screenwash, and used. The analysis was restricted to collections from July.1986 through December 1997, the IMP,,, = number of fish of common period of sampling at Stations P2, PS, species s impinged in as- and P7, and the taxa included were the same as sessed screenwash, those analyzed by numerical classification. The data used were the mean of logio(x+1) sample 5.2.3 Analvtical Methods densities for individual sampling dates and sta-
]
tions. The model design was a three-way facto- 1 Ichthyoplankton assemblages were investigated rial with nested effects. The main effects were i using multivariate numerical classification meth- period (preoperational and operational), station, ods to determine whether species composition and month nested within year; interactions among changed between the preoperational period (July these main effects were included in the model. 1990 and earlier) and the operational period The nested effect was years within period. Type (August 1990 and later). The Bray-Curtis simi- III sums of squares and tests of hypothesis were larity index (Clifford and Stephenson 1975) was used for the analyses and the rationale for their j l 5-6 l
b l i l 1 5.0 FISH j { j l use was the same as that used for analysis of catch-per-unit-effort (CPUE) for juvenile and variance, discussed below. The Wilks' lambda adult fish. CPUE was defined as number per statistic (Wilks 1932; Morrison 1976) was used 10-min tow for the trawl, and number per stan-to determine if the taxa assemblages in the dard haul for the seine. A transformed mean was preoperational and operational periods were calculated for each year and for combined years significantly different. For the purpose of power (e.g., preoperational and operational periods). plant impact assessment, sources of variation of The coefficients of variation (CV) of the mean of primary concern were the period (preoperational annual means (Sokal and Rohlf 1981) in the or operational) and the period by station interac- logarithmic scale were also computed. The tion. annual and combined geometric means are pre-sented as back-transformed values. Some life Total ichthyoplankton entrainment was estimated stages are seasonal, so the data used to compute by calculating the aritlunetic mcan density in a the geometric means for some species were sample for each sampling day, multiplying by the restricted to periods of primary occurrence; when l daily cooling water volume during the week the trimmed data were used, it is noted in the text, l sample was taken. These weekly estimates were figure, or table. summed for a monthly estimate, and monthly l estiinates were summed for the annual estimate. Table 5-2. Selected Finfishes and Sampling From the 88 species collected over the years,11 Programs That Contributed Abundance Data taxa were selected for detailed analyses of abun. f r S ecieS-S P Pecific Analyses. Seabrook Oper-8 i nal Pod, W. dance and distribution and for an assessment of impact by Seabrook Station (Appendix Table 5-1, Selected Species Predominant Sampling Table 5-2). These selected species were numeri-Programs cally dominant in one or more sampling pro-Atlantic herring ichthyoplankton grams, are important members of the finfish fauna of the Gulf of Maine, and most have Rainbow smelt otter trawl, beach seine recreational or commercial importance. Other Atlantic t. d ichthyoplankton, otter trawl species predominant in various sampling pro-Pollock ichthyoplankton grams were noted when they occurred. The Hakes ichthyoplankton, otter trawl selected taxa, listed in Table 5-2 by sampling l program, were individually evaluated for tempo- Atlantic silverside beach seine ral and spatial changes in abundance between the Cunner ichthyoplankton preoperational and operational periods. Geomet-American sand lance ichthyoplankton ric means were compared among the preopera-At antic rnackerel ichthyoplankton tional, operational, and 1997 periods for each station and all stations combined to examine for winter nounder ichthyoplankton, otter trawl, ch sehe l trends in annual abundance. Geometric means were computed by logw(x+ 1) transformation of Yellowtail Dounder ichthyoplankton. otter trawl l l individual sample abundance indices, which were l number per 1000 m2 for ichthyoplankton, and 5-7
j 5.0 - FISH } A mixed model ANOVA, based on reviews by ' of primary concern were the Preop-Op and Underwood (1994) and Stewart-Oaten et al. Station main effects and the Preop-Op X Station (1986), was used to test the null hypothesis that interaction. However, only a significant Preop-spatial and temporal abundances during the Op X Station interaction term would imply power preoperational and operational periods were not plant effect (Thomas 1977, Green 1979, Stewart-significantly (p>0.05) different. All effects Oaten et al.1986). Even if significant, the were considered random, except operational interaction would have to be further examined to status (Preop-Op). Time and location of sam- determine if the significance was the result of pling were considered random because both differences between potentially impacted and j sampling dates and selected locations represented non-impacted stations. I only a fraction of all the possible times and l locations (Underwood 1994). The data collected The ANOVA for the seine monitoring program for the ANOVAs for the ichthyoplankton and for estuarine fish in Hampton Harbor was slightly otter trawl programs met the criteria of a Before- different from the model used for the otter trawl After/ Control-Impact (BACI) sampling design and ichthyoplankton programs. The seine moni- , discussed by Stewart-Oaten et al. (1986), where toring program was not a BACI study design as l sampling was conducted prior to and during plant all stations were located in a farfield area operation and sampling station locations included (Hampton Harbor). Therefore, the Preop-Op X both potentially impacted and non-impacted sites. Station term was dropped, because there was no l The ANOVA was a two-way factorial with reasonable mechanism by which plant operation nested effects that provided a direct test for the could affect only one station in Hampton Harbor. temporal-by-spatialinteraction. The main effects Potential plant impacts were indicated by signifi-were period (Preop-Op) and station (Station); the cant differences in CPUE between the interaction term (Preop-Op X Station) was also preoperational and operational periods (Preop-Op included in the model. Nested temporal effects term). If there were significant differences were years within operational period (Year between periods, the annual time series of CPUE (Preop-Op)) and months within year (Month was examined to determine if the changes began (Year)), which were added to reduce the unex- prior to plant operation. plained variance, and thus, increased the sensitiv-ity of the F-test. For both nested terms, variation The 1990 sampling year was classified as either was partitioned without regard to station (stations preoperational, operational, or was excluded combined). An additional term (Station X Year from the analysis for a species, depending on (Preop-Op)) was added to provide the proper seasonal pattern of occurrence of each species or mean square for testing the significance of the times of sample collection (Appendix Table 5-2), Preop-Op X Station term, which may signify a and is noted as such on the ANOVA tables. possible plant impact. The final variance not Larval data were restricted to the period July accounted for by the above explicit sources of 1986 through December 1997, and for selected variation constituted the Error term. taxa collected by trawl, and seine, the data used were from July 1975 through December 1997. For assessing Seabrook Station effects using the Trawl data were excluded from the ANOVA in above ANOVA model, the sources of variation August through October because of reduced 5-8
i s.o nsu l { sampling effort at Station T2. The data used in The preoperational period extended through July the analyses of trawl and seine samples were 1990 and the operational period began in August logm(CPUE + 1) transformed for each individual 1990. Eggs of several taxa were grouped be-f collection. For larvae, the transformed mean cause during early developmental stages it was density of replicate samples was used for data up difficult to distinguish among some species (e.g. 1 through 1993 (no replicates were analyzed in Atlantic cod, haddock, and witch flounder; { 1994 through 1997). cunner, yellowtail flounder, and tautog; fourbeard rockling and hakes). Larvae were 5.3 RESULTS AND DISCUSSION generally identified to species, except that hake (Urophycis sp.) was not identified to species. It l 5.3.1 Ichthyoplankton Assemblages is not knowa whether the hake larvae comprised i more than one species (red hake, white hake, and The analyses for the ichthyoplankton program spotted hake have all been collected by the focused on seasonal assemblages of both eggs Seabrook otter trawl program as adults). and larvae, as well as on larvae of individual selected taxa (Table 5-2). Selected taxa are Eggs frcm eleven taxa were analyzed (Table 5-3) discussed in Section 5.3.3, in relation to juvenile and the subsequent numerical classification and adult stages collected in other sampling analysis resulted in eight groups (Figure 5-2). A programs. In the assemblage analyses, additional total of 391 monthly " collections" were used for taxa were included to better represent the the cluster analysis, with each collection being a ichthyoplankton community in the Hampton- monthly average of samples at one station. Each Seabrook area. of the 391 monthly collections analyzed fell within one of the eight groups. The eight groups 5.3.1.1 Offshore Samnies formed two major categories, which correspond-ed to annual periods of cold and warm water The seasonal assemblages of ichthyoplankton temperatures. Groups 1-3 were found during were examined using multivariate numerical periods of cooler water temperatures (November classification (cluster analysis). These analyses through April) and Groups 4-8 were taken during were conducted to determine if the operation of the warmer period (May through October). Seabrook Station had altered either the senonal There was no apparent difference in these two occurrence or the spatial distribution of fish eggs categories between preoperational and opera-and larvae in the Hampton-Seabrook area. tional periods. Evaluation of spatial patterns compared the distribution of ichthyoplankton among intake Group 1 included fall and early winter samples. (P2), discharge (P5), and farfield (P7) Stations It represented the beginning of the cooler water before and after Seabrook Station operation period and consisted of nearly all of the Novem-began. Typically, individual ichthyoplankton ber and December collections, as well as many of taxa occur only during limited seasons of occur- the January collections. Atlantic cod and pollock rence, which are relatively consistent from year were the dominant eggs in this group (Table 5-3). to year. The data examined were collected from The operational geometric means for both species July 1986 through December 1997, when all were lower than the preoperational means. three Stations (P2, P5, and P7) were sampled. Although eggs of Atlantic cod, haddock, and 5-9 L
5.0 FISH Table 5-3. Fmmal Characterization of Groups Fonned by Numerical Classification of Samples
]
of Fish Eggs Collected at Seabrook Intake (P2), Discharge (PS), and Farfield (P7) Stations Dunng July 1966 Through December 1997*. Seabrook Operational Report, 1997.
]
Number of Samples and Density (eggs /1000m')* Dominant Taxa by Group
- Preoperational* Operational
- n LCL MEAN UCL n LCL MEAN UCL 1 - Late Fall /Early Winter (0.66/0.49)* l Pollock 34 5 7 10 53 1 2 2 I Atlantic cod 39 58 85 24 32 42 2 - Winter (0.61/0.49)
Ac m plaice 19 1 1 2 34 1 2 3 Atlantic cod / haddock 4 6 8 4 5 7 l 3 - Early Spring (0.52/0.38) Fourbeard rockling 15 4 8 16 25 0 <1 1
]
American plalce 22 38 64 36 56 85 Atlantic cod /baddock 7 15 30 14 19 26 l 4 - Mid-Spring (0.74/0.61) Fourbeard rockling 12 77 235 715 21 5 11 22 American plaice 54 73 97 35 57 92 Atlantic mackerel 18 37 77 112 200 359 Cunner /yellowtail flounder 175 293 488 169 281 468 5 - Late Spring /Early Summer (0.76/0.70) Cunner /yellowtail flounder 21 12242 15911 20679 33 13966 17305 21441 6 - Summer (0.75/0.70) Windowpane 17 167 247 367 33 221 290 381 Cunner /yellowtail flounder 634 1549 3785 1362 2165 3442 Fourbeard rockling/ hake 214 449 940 282 385 526 7 - late Summer /Early Fall (0.66/0.58) Wiramp.ue 16 14 30 62 24 45 68 103 Fourbeard rockling 6 16 39 5 8 13 Hake 80 126 198 102 167 273 Fourbeard rockling/ hake 78 139 249 95 145 222 8 - Fall (0.57/0.37) Fourbeard rockling 9 1 4 10 24 1 1 2 Silver hake 5 8 12 5 8 14 Atlantic cod / haddock 10 20 39 1 2 4 Fourbeard rockling/ hake 4 10 25 4 7 10 Hake 6 10 17 3 5 6
- Each
- sample" consisted of the ave f tows within date and dates within month at one station.
- w c mean densities together accounted for 290% of the sum of the preoperational geometric mean
- Geometric mean and lower (UCL 95% confidence limits.
- Preoperational = July 1986 - ( July 1990;)'
and u
= August 1990 - December 1997.
5-10
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l A N= E "M h h h h h' h M k JANlFEBl MAR l APRlMAYlJUN JUL AUG SEP OCT NOVlDEC MONTH g Figure 5-2. Dendrogra o 2 nd temporal / spatial occurrence pattem of fish egg assemblages 1 formed by numerical classification ofichthyo7 ankton samples (monthly means oflog (x+1) transformed number per 1000 m ) at Seabrook intake (P2), discharge (PS), and far6 eld (P7) stations, July 1986 December 1997. Seabrook Operational Report,1997. 5-11 I
t0 FISH ' witch flounder can not usually be identified to preoperational and the operational periods, with i species except during their late embryonic stage the exception of cunner /yellowtail which was (Brander and Hurley 1992), eggs were identified 40% higher in the operational period. Group 7 , as Atlantic cod during this period on the basis of consisted of late summer /early fall collections. j Atlantic cod being the only one of the three This group was fairly diverse, with four domi-species known to spawn this time of year. Group nant taxa. Cunner /yellowtail flounder eggs, 1 2 was a winter group in which abundances of which were highly abundant in Group 5 and eggs were relatively low for the two dominant Group 6, were not among the dominants in - taxa, Atlantic cod / haddock and American plaice, Group 7. The season represented by Group 8 l during both preoperational and operational was fall, with collections occurring only in periods. This winter group consisted of many October. Some of the dominant egg taxa in collections from January and most of those from Group 8 were also dominants in Group 7 but the j February and March. Group 3 represented early densities were much lower in Group 8. spring, primarily including April collections and Preoperational and operational period densities in ) a few from March, it had the same two domi- Group 8 were generally a little lower in the ) nant taxa as the previous group, but in somewhat operational period than in the preoperational ) higher densities and with the addition of period. fourbeard rockling as another dominant species. Time of year was the only factor that corre-Group 4 was a mid-spring group consisting of sponded with the cluster groups, which were May collections exclusively for all years. This formed by the analysis on the basis of similar group represents the beginning of the warmer species composition and abundance. Every one . water season. This group was more diverse than of the eight groups contained collections from for the three previous groups, with four dommant only one season of the year. In contrast, there taxa, including eggs of cunner /yellowtail floun- was a very even distribution of stations and of der, fourbeard rockling (most abundant during years within each of the groups. Most impor-the preoperational period), American plaice, and tantly, the operational period was very similar to Atlantic mackerel (most abundant during the the preoperational period in which assemblages operational period). Group 5 consisted of late were present and in the timing of their season of spring and early summer. All of the June collec- occurrence. tions were in this group as well as abaut half of the July samples. The dominant eggs in this The consistency of assemblages of fish eggs both group were cunner /yellowtail flounder, which temporally (among both months and years) and were in much higher abundance than in Grcup 4 spatially (among stations) suggested that opera-samples and were about equally abundant in the tion of Seabrook Station has not altered the preoperational and operational periods. Group 6 spatial or temporal distribution of eggs in the was a summer grouping consisting of the re- Hampton-Seabrook area. The spatial stability maining July collections and all but one of the was demonstrated by the fact that for 94% of the I August collections. This group was dominated months in which all three stations were repre-by eggs of cunner /yellowtail flounder, fourbeard sented in the analysis, all three stations were rockling/ hake, and windowpane. These groups classified into the same group. This spatial of eggs exhibited fairly similar abundance in the similarity was further supported by the results of 5-12
5.0 FISH MANOVA, for which a significant difference any of these taxa. American sand lance larvae was found between the preoperational and opera- again dominated in Group 4, which included late tional periods (p < 0.001), but the interaction was winter /early spring samples. The period of clearly not significant (p = 0.63). This indicated occurrence for collections of this group was that the temporal changes in assemblage abun- relatively long, generally from February through dance occurred concurrently at all three stations, April. The geometric mean abundances of including the farfield Station (P7), the control American sand lance and rock gunnel were both area. fairly similar between operational and preoperational periods. Group 5 (spring) com-Larvae of 22 fish taxa were selected for numeri- prised May collections each year, and a few cal classification analysis, which resulted in eight April collections. Atlantic seasnail and American cluster groups (Figure 5-3). Only one monthly sand lance were the most abundant larvae in this observation (Station P2, October 1992) did not diverse group, and both species were more group within any of the eight groups. Similar to abundant in the preoperational period than after the egg collection data, two major categories Seabrook Station began operation. were evident, with collections in Groups 1-5 occurring primarily during the cooler water Group 6 collections occurred exclusively during temperature period (generally October through the late spring and early summer (June and July), May) and collections in Groups 6-8 during the representing the first of the warm water groups. warmer period (generally June through Septem- The geometric means for the daminant species in ber). Group 1 was a fall group, consisting this group (cunner, fourbeard rockling, Atlantic mostly of October collections (Figure 5-3). mackerel, radiated shanny, and winter flounder) Dominant species were Atlantic herring, were fairly comparable between the preopera-fourbeard rockling, silver hake, and windowpane tional and operational periods. (Table 5-4). Within this group of samples, Atlantic herring larvae were less abundant in the Groups 7 and 8 overlapped considerably in their operational period than in the preoperational season (late summer). Both included primarily period. Group 2 was made up of late fall sam- August and September collections. Group 7 ples, including primarily November and Decem- included two July. collections as well. Group 8 ber collections (Figure 5-3). Atlantic herring did not include any July samples but did include was the most abundant species during this period, one from October, extending it somewhat into and there was a decrease in its abundance from early fall. Although Group 7 was not present the preoperational to the operational period every year, cunner, fourbeard rockling, and hake (Table 5-4). Group 3, representing early winter, larvae dominated this group during late summer was more diverse and generally comprised (August and September). When present, collec-January collections. American sand lance was tions at all three stations were usually grouped the most abundant dominant, with the remaining together (except for September 1995 and July predominant taxa (Atlantic herring, gulf snailfish, 1997). In Group 7, densities were not substan-and pollock) found at lower abundances. There tially different between the operational period were no substantial differences between preop- and the preoperational period except for hake, erational and operational geometric means for which were three times more abundant in the 5-13
co- : on-l c2 - 5'id amuy sumian, i N=nbn d sampi. g -ww g n- , o.5 - u-3 o i I k I i i i M iil l of
= v, y rr M CADUP 1 r TTTTT M GROUP 2 1994 M i
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x x x x 4 JANlFEBjMARl APRj MAYlJUN JUL AUG SEP OCT NOVlDEC MONTH 2 Figure 5-3. Dendrogram and temporal / spatial occurrence pattem of fish larvae assemblages fonned by numerical classification ofichthyoplankton samples (monthly means oflog (x+1) transformed number per 1000 m') at Seabrook intake (P2), discharge (PS) and farfield (P7) stations, July 1986-December 1997. Seabrook Operational , Report,1997. 5 14 l
5.0 FISH Table 5-4. Faunal Characterization of Groups Formed by Numerical Classification of Samples of Fish Larvae Collected at Seabrook Intake (P2), Discharge (PS), and Farfield (P7) Stations During July 1986 through December 1997*, Seabrook Operational Report, 1997. Number of Samples and Density (larvae /1000m')' Dominant Taxa by Group e e Pentiod Opention# n LCL MEAN UCL n LCL MEAN UCL 1 - Fall (0.50/0.38)* Windowpane 12 1 1 2 25 1 1 1 Atlantic herring 5 16 49 3 3 4 Fourbeard rockling 3 5 10 2 3 4 Silver hake 1 2 4 1 2 3 2 - Late Fall (0.40/0.38) Atlantic herring 24 29 50 87 46 12 16 21 3 - Early Winter (0.51/0.46) American sand lance 12 10 23 51 17 18 31 52 Atlantic herring 2 4 10 1 2 3 Gulf snailfish 2 4 7 1 2 4 Pollock 1 4 12 2 1 3 4 - Late Winter /Early Spring (0.6310.46) American sand lance 33 138 204 301 66 175 228 298 Rock guruwl 17 25 38 14 21 31 5 - Spring (0.66/0.40) American sand lance 15 15 27 51 21 11 18 28 Grubby 3 5 9 2 4 6 Atlantic seasnail 32 61 114 25 34 47 American plaice 3 5 8 3 5 6 Winter flounder 4 9 16 3 5 8 Radiated shanny 4 8 17 4 7 12 6 - Late Spring /Early Summer (0.60/0.43) Fourbeard rockling 27 28 50 88 , 40 26 39 59 Cunner 40 94 218 22 53 127 Winter flounder 8 14 26 8 12 18 Atlantic mackerel 15 27 46 24 42 73 Radiated shanny 17 26 40 21 28 38 7- Late Summer (0.58/0.43) Fourbeard rockling 15 28 62 134 43 26 39 60 Hake 4 7 12 12 21 36 Cunner 101 201 399 153 305 605 8 - Late Summer /Early Fall (0.49/0.33) Windowpane 9 <1 1 2 8 <1 1 2 Fourbeard rockling i 1 3 2 3 5 Hake <1 1 1 0 1 3 Cunner 3 6 12 1 3 4 Witch flounder 0 1 1 0 2 3 Radiated shanny <1 1 1 <1 1 2
- Each
- sample
- consisted of the average of tows within date and dates within toonth at one station.
(Within group /between group similanry). ' 7 hose whose preoperational geometric mean densities together accounted for 290% of the sum of the preoperational geometric mean densities of all taxa within the group.
- Geometric mean and lower (LCL) and upper (UCL) 95 % confidence hmits.
- Preoperational = July 1986 - July 1990; Operational = August 1990 - December 1997.
5-15
5.0 FISH operational period. In Group 8, three of the six 5-5). Total estimates of entrainment for 1997 dominant taxa were also present in the previous were 692.6 million eggs and 373.4 million group, but they were collected at much lower larvae. About 80% of egg entrainment, and 64% densities in the Group 7 samples. In two years, of larval entrainment occurred in July. Egg ! 1986 and 1992, no samples were classified with entrainment in previous years ranged from 4.7 Group 7. This indicates lower than usual densi- million in 1994 (8 months of sampling) to ties oflarvae in August and September for those 1,551.0 million in 1991 (8 months of sampling) two years. As the low densities occurred equally (Table 5-6). The egg entrainment in 1997 of in preoperational and operational periods, ' hey 692.6 million (12 months of sampling) was were not related to plant operation. within the range of previous years. Previous larval entrainment ranged from 31.2 million in As was the case with eggs, the cluster groups 1994 (8 months of sampling) to 215.7 million in based on larval composition and abundance were 19% (12 mordis of sampling. The 1997 entrain-strongly related to season but were independent ment estimate (373.4 million) is the highest of station, year, and op: rational status. In 92% recorded to date. of the months represented in the analysis, all three stations were grouped in the same cluster Silver hake, cunner /yellowtail flounder and hake group. This high degree of similarity among were the most numerous egg taxa entrained in nearfield (P2 and PS) and farfield (P7) collections 1997 (Figure 5-4). These three taxa have typi-was as true during the operational period as it cally been among the most numerous eggs en-was during the preoperational period. Similarity trained by Seabr ok Station, with the exception among stations was also supported by the results of 1994 when no samples were collected during of MANOVA, where the preoperational-opera- the summer high period of egg entrainment tional term was significant (p<0.001), but the (Table 5-6). Silver hake has been variable in its interaction was clearly not significant (p > 0.99). abundance from year to year in the entrainment These results indicated that the temporal changes estimates, partly because in some years there was in assemblage abundance were consistent at all no entrainment sampling during part of the three stations, including the farfield Station P7, summer, which is the time of year that silver located well outside the zone of influence of hake eggs occur in the plankton. The estimate Seabrook Station. for the total number of siwer hake eggs entrained in 1997 was the highest annual estimate for this 5.3.1.2 Entrainment species among the eight years of entrainment sampling. Entrainment estimates of cunner /yel-One of the most direct measuces of potential lowtail flounder eggs and hake eggs were within impact of Seabrook Station on the local fish the range of previous years' totals. assemblages is the number of eggs and larvae entrainea through the condenser cooling water Cunner were the most abundant larvae entrained system. Eggs belonging to 17 taxa (plus one by Seabrook Station in 1997 (Table 5-5; Figure group of unidentified eggs) and larvae of 26 taxa 5-4). They were the most abundant larvae in (plus one group of unidentified larvae) were 1990 as well, but were not particularly abundant collected in entrainment samples in 1997 (Table in 1991-1995 (Table 5-6). Low numbers en-I 5-16 i ._ _ _ _ _ _ _ _ _ ._ -
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5.0 FISH Table 5-6. Annual Esthnated Numbers of Fish Eggs and Larvae Entrained (X 10') by the Cooling l Water System at Seabrook Station from June 1990 Through December 1997. Seabrook Operational Report,1997. 6 Taxon 1990* 1991 1992* 19938 1994* 1995' 19968 1997" i l D Atlantic mackerel 518.8 673.1 456.3 112.9 0.0 74.5 305.1 23.1 Iyellowtait 490.4 r 716.3 198.6 58.4 0.0 18.6 110.2 222.0 Atlantic cod / haddock / witch 29.1 74.5 39.5 50.3 1.0 34.8 48.6 9.1 flounder d rock-(n 114.2 35.1 50.6 32.7 1.7 27.5 57.0 45.0 Windowpane 36.4 19.9 22.5 29.1 0.1 17.4 44.2 28.5 American plaice 2.6 21.0 52.3 19.5 0.4 14.8 78.2 15.6 Lumpfish 0.0 0.0 0.0 9.5 0.1 6.0 1.2 0.3 ! Pourbeard rockling 7.4 4.3 0.8 1.4 0.2 4.2 10.9 4.8 Unidentified 0.0 2.0 0.0 0.8 0.2 6.4 0.8 0.1 Silver hake 11.4 0.0 0.1 0.4 0.4 22.5 73.6 271.1 Pollock 0.0 1.0 0.4 0.2 0.1 0.4 0.4 0.2 Hake 37.3 2.6 0.0 0.2 0.6 25.1 184.0 68.6 Atlantic menhaden 0.0 0.5 1.4 0.1 0.0 0.2 0.1 0.2 Cusk 0.1 0.5 0.0 0.1 0.0 0.2 1.8 0.2 Tautog 0.0 0.2 0.0 0.0 0.0 0.0 0.3 0.1 Atlantic cod 0.0 0.0 0.0 0.0 0.0 2.2 8.1 2.9 ! lock 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 l f Wi'ch flounder 0.0 0.0 0.0 0.0 0.0 0.7 0.1 0.9 Yellowtail flounder 0.0 0.0 0.0 0.0 0.0 0.2 1.6 0.0 Other 0 0 0.1 0 1.8 2.1 0.6 0.0 Total 1247.7 1551.0 822.6 315.6 4.7 255.6 926.8 692.6 I l i 5-19 (continued)
5.0 FISH J Table 5-6. (Continued) 6 Taxon 1990* 1991 1992* 1993' 1994* 1995' 19968 1997*
]
Larvae Atlantic seasnail 11.6 16.0 31.5 64.4 0.( '.6.5 60.6 1.2 I Grubby 0.0 22.4 18.9 13.8 4.9 17.4 18.6 12.8 . banc*eri an sa d 0.0 37.3 18.1 12.0 8.3 9.5 14.0 10.1 Atlantic herring 0.7 0.5 4.9 9.6 0.1 11.2 4.3 2.1 l Rock gunnel 0.0 51.1 45.3 5.7 11.0 15.6 33.8 25.1 I Unidentified 0.7 2.1 1.4 5.6 0.6 30.4 2.5 4.3 Cunner 42.7 < 0.1 0.0 4.7 0.1 4.4 9.2 203.8 l Winter flounder 3.2 9.0 6.2 2.9 0.0 8.0 10.3 2.2 ' Gulf snailfish 0.1 2.8 1.9 2.6 3.5 0.2 2.8 0.6 Fourbeard rockling 37.9 0.5 0.1 2.2 0.0 3.9 11.7 22.4 l American plaice 0.4 1.0 0.8 0.7 0.0 7.9 8.1 7.0 l Longhorn sculpin 0.0 0.6 0.6 0.4 0.3 0.4 1.3 0.7 I Moustache sculpin 0.0 0.1 0.3 0.4 2.2 0.0 0.6 0.3 I Lumpfish 0.6 0.1 0.1 0.2 0.0 0.6 0.1 0.2 kijfgified 0.1 0.3 0.0 0.2 0.0 0.0 0.0 0.0 Shorthorn sculpin 0.0 0.2 0.6 0.2 0.1 0.5 0.1 1.1 Radiated shanny 4.8 3.1 1.1 0.2 0.0 2.1 2.0 - 0.3 Atlantic cod 0.7 1.5 0.4 01 0.0 2.3 0.3 0.7 Silver hake 7.7 0.0 0.0 0.1 0.0 0.9 16.9 69.0 Windowpane 3.8 < 0.1 0.1 0.1 0.1 2.0 2.0 5.6 Hake 4.8 0.0 0.0 0.1 0.0 0.7 12.3 1.7 Atlantic mackerel 0.2 4.7 0.0 0.0 0.0 0.0 0.1 0.4 l Yellowtail flounder 0.1 0.3 0.1 0.0 0.0 0.1 1.6 0.5 . Alligatorfish 0.0 0.1 0.2 0.0 0.2 0.3 0.1 0.1 Wrymouth 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 l Witch flounder 0.3 0.0 0.0 0.0 0.0 0.0 0.8 1.2 l Tautog 0.3 0.0 0.0 0.0 0.0 0.0 0.2 0.0 Pollock 0.2 0.0 0.1 0.0 0.0 0.0 0.0 0.0 l Fourspot flounder 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.1 l Rainbow smelt 0.2 0.0 0.1 0.0 0.0 0.0 0.0 0.0 j Goosefish 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Atlantic menhaden 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Redfish 0.0 0.0 0.4 0.0 < 0.1 0.0 0.0 0.0 Haddock 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 identified scul- 0.0 0.0 0.1 0.0 0.0 0.0 0.6 < 0.1 Butterfish 0.0 0.0 0.0 0.0 0.0 0.3 0.1 0.0 Other 0.0 0.1 0.3 0.0 0.2 0.0 0.7 0.1 Total 121.5 153.8 133.1 126.2 31.2 145.3 215.7 373.4 l
' From NAl(1991). Represents only 7 months, August December.
- From NAI(1992). Represents only 8 months January - July, December.
- From NAI(1993). Represenu only 8 months, January - August.
' From NAI and NUS (1994). Represents only 8 months. January - Auaust.
- From NAI (1995). Represents only 8 months, January - March, Septe. her - December.
' From NAI (1996). Represents 12 months.
8 From NAI(1998). Represents 12 months. l
- Represents 12 months of sampling.
5-20
I l 5.0 FISH l.
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10 l 1 s im s r. _, lo J 7 ^ g 4 u J J * ~7 <J ~ o l c Jc- cm*O' asW mm,. I i Figure 5-4. Total monthly cooling water system flow and estimated numbers of fish eggs and ) larvae entrained during 1997. Seabrook Operational Report,1997. 5 21
~
5.0 FISH trained in some years were partly due to summer eral occasions despite being demersal and adhe-outages. Silver hake, fourbeard rockling, and sive. It may be possible that clusters of lumpfish rock gunnel were also dominant species in the eggs attached to the intake structure were dis-1997 entrainment estimates. One species that lodged by currents. Behavioral characteristics of was entrained in lower numbers than usual in some larvae may reduce larval entrainment for 1997 was Atlantic seasnail, due to an outage in some taxa that have high egg entrainment. For June, which is usually the peak month of occur- instance, hake and fourbeard rockling larvae are rence for this species. surface oriented (Hermes 1985) and may not be susceptible to the mid-water intakes. The rapid Differences in entrainment estimates between larval development of Atlantic mackerel may larval and egg stages of the same taxa in the enable them to develop a relatively high swim-same year are due to varying susceptibility of the ming speed (Ware and Lambert 1985) and, thus, two developmental stages to entrainment. Some may be able to avoid entrainment. dominant larvae are species that have demersal or adhesive eggs, which are not susceptible to Annual Seabrook Station entrainment estimates entrainmen*, including Atlantic seasnail, grubby, for the selected taxa since 1990 were compared American sand lance, Atlantic herring, rock to estimates from two other New England power gunnel, winter flounder, and gulf snailfish. One plants, Pilgrim and Milistone Stations (Table 5-exception to this pattern is lumpfish eggs, which 7). Except for Atlantic seasnail larvae, annual have been entrained by Seabrook Station on sev- entrainment estimates for Seabrook Station were Table 5-7. Comparison of Entrainment Estimates (X 10') for Selected Taxa at Selected New England Power Plants with Marine Intakes from 1990 Through 1997. Seabrook Operational Report,1997. Taxon Seabrook Pilgrim' Millstone 6 Cunner /yellowtail flounder /tautog eggs' 0'-716 860-4122 2,736-5,982 Atlantic mackerel eggs O'-673 337-2066 - Atlantic herring larvae < l'-l ! l 18 - Cunner larvae O'-204 4-323 - Grubby larvae
- 5'-22 7 44 34-76 Atlantic seasnail larvae' 0'-64 2 11 -
Rock gunnellarvae 6-51 7-62 - American sand lance larvae 8'-37 23-459 5-114 Atlantic mackerellarvae 0-5 3-66 - Winter flounder larvae O'-10 9-21 45-514
- MRI (1991,1992,1993b,1994.1995); 1990-1994; Cape Cod Bay.
- NUSCO (1994a.1994b.1995,1996); eggs-19901993, grubby and American sand lance larvae.1990-1994; winter flounder larvac 1990-1995, Long Island sound.
'scabrook-cunner /yellowtail flounder; Pilgrim <unner/tautog/yellowtail flounder; Mdistone-cunner.
'seabrook and Millstone-grubby; Pilgrim-grubby and other sculpins.
'seabrook-Atlantic seasnail; Pdgrim-Atlantic seasnail and other snailfishes.
' lowest estimate occurred in a year when samples are lacking in some or all of tbc months when this taxon normally would be entrained (estimate for 1990 was not included for those taxa usually present before June. when the entrainment sampimg program was begun).
5-22
I l [ s.o nsu similar to, or were less than annual estimates at was dominated by skates, longhorn sculpin, the other two power plants. winter flounder and windowpane (Table 5-8). 1 5.3.2 Adult Fish Assemblaces CPUE of most fishes, especially commercially important species, declined between the 5.3.2.1 Demersal Fishes preoperational and operational periods (Table 5-8). Yellowtail flounder showed the greatest A 9.8-m otter trawl was used at three stations decrease in CPUE from 9.3 in the preoperational (Figure 51) to determine the abundance and period to 1.7 in the operational period. Simi-distribution of demersal fishes. Geometric mean larly, CPUE of winter flounder, hakes, and CPUE (catch per 10-minute tow) of fish caught Atlantic cod also decreased between the , at all stations combined in 1997 was 14.6 (Figure preoperational and operational periods. The 5-5), a decrease from the CPUE of 18.2 in 1996 decrease in CPUE of these fishes has been attrib-(NAI 1998). The trawl CPUE peaked in 1980 uted to commercial overfishing (NOAA 1995). (78.6) and 1981 (77.6), primarily due to large CPUE of skates increased from 1.9 to 2.4 be-catches of yellowtail flounder. In 1997, catch tween the preoperational and operational periods, Trawl T1 1 --- T2 6 I T3
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0- I 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 l YEAR 1 Figure 5-5. Annual geometric mean catch of all species combined per unit effort (number per 10-minute tow) in trawl samples by station and the mean of all stations, 1976-1997. Seabrook Operational Report,1997. 5-23
5.0 FISH Table 5-8. Geometric Mean Catch per Unit Effort (number per 10-minute tow) with Coefficient of Variation (CV) by Station (T1, T2, and T3) and All Stations Combined for Abundan! Species Collected by Otter Trawl During the Preoperational and Operational Periods and the 1997 Mean. Seabrook Operational Report,1997. Preoperational Period' 1997* Operational Period
- Species Station Mean CV Mean Mean CV Yellowuit T1 20.0 3 1.4 3.3 12 flounder T2 2.7 8 <0.1 0.2 35 T3 10.2 5 1.0 1.8 12 All stations 9.3 4 0.8 1.7 12 Longhorn scul- T1 4.6 7 3.1 3.4 4 pin T2 1.1 12 0.1 0.3 22 1
T3 8.3 6 7.4 6.6 3 All stations 4.1 7 3.0 3.1 3 Winter flounder T1 3.1 6 4.3 3.3 6 T2 5.9 6 1.6 1.6 16 T3 2,2 7 2.8 3.3 5 All stations 3.5 5 2.9 2.9 6 Hakesd T1 4.1 5 0.4 1.1 18 T2 1.7 7 0.4 0.4 25 T3 3.5 5 1.3 1.3 10 All stations 3.2 4 0.8 1.1 12 Atlantic cod T1 2.0 10 0.1 0.4 50 T2 0.7 16 < 0.1 0.1 36 T3 3.2 11 0.5 0.9 34 All stations 1.8 11 0.2 0.4 40 Skates Tl 1.7 15 4.7 3.0 13 T2 0.6 10 0.5 0.3 29 T3 3.7 5 8.3 4.1 12 All stations 1.9 9 4.1 2.4 12 Windowpane T1 1.9 11 3.3 2.3 10 T2 0.9 10 0.6 0.4 19 T3 1.0 13 2.1 0.9 24 All stations 1.3 10 2.1 1.2 le Rainbow smelt T1 1.1 9 < 0.1 0.3 16 T2 1.8 9 0.1 0.4 34 T3 0.8 14 0.1 0.3 24 All stations 1.1 9 0.1 0.3 23 Ocean pout T1 0.7 6 0.1 0.1 19 T2 0.6 8 0.3 0.2 22 T3 1.4 7 0.1 0.2 24 All stations 0.8 6 0.1 0.2 20 Silver hake Tl 0.9 16 0.4 0.4 8 T2 0.2 21 <0.1 < 0.1 52 T3 0.8 13 0.2 0.4 20 All stations 0.7 14 0.2 0.4 12 Pollock Tl 0.3 18 0.2 0.4 30 T2 0.7 21 0.1 0.4 32 T3 0.2 20 0.1 0.2 21 All stations 0.4 18 0.1 0.3 24 Haddock Tl 0.2 34 < 0.1 < 0.1 59 T2 < 0. t 64 0.0 0.0 - T3 0.5 28 0.0 0.1 40 All stations 0.2 28 <0.1 < 0.1 41 T2 0 0 2k T3 1.2 7 0.6 0.7 12 All stations 1.4 5 0.7 0.9 13 cogratioy: ly 1 ggometric mean of annual means. May"E0 red ~ e. wNte skt@ sb nTEthan one of these species. 5-24
n 5.0 FISH while there were few changes in the CPUE of 5.3.2.2 Estuarine Fishes windowpane and pollock. Abundance of skates has increased greatly in the Gulf of Maine and as Sampling for estuarine fishes was conducted at of 1994 (most recent data available) was near three stations within the estuary of Hampton-record levels (NOAA 1995). The'index of Seabrook Harbor (Figure 5-1) using a 30.5-m windowpane abundance in the Gulf of Maine has seine. Geometric mean CPUE (catch per haul) decreased since 1984 and the stock is considered for all fish caught at all stations during 1997 was overexploited. Pollock are considered fully 10.5 (Figure 5-6), a decrease from the CPUE of exploited in the Gulf of Maine and abundance 17.1 in 1996 (NAI 1998). The decrease in index has been relatively low since 1984. CPUE in 1997 ended a trend of increasing CPUE that began in 1992 (Figure 5-6). Overall, seine Differences in CPUE and species composition catches generally were smaller (5.6-24.1) during were apparent among the stations. The bottom at 1987-97 than they were during 1976-84, when nearfield Station T2, located in shallow (15-17 annual CPUE ranged from 22.7 to 59.1; no seine m) water off the mouth of Hampton-Seabrook sampling took place in 1985 or April through Harbor, was occasionally inundated with drift June of 1986. The catch of most fishes by seine algae. Stations T1 and T3 are in deeper water decreased from the preoperational to the opera-(20-28 and 22-30 m, respectively) and have tional period (Table 5-9). Atlantic silverside has sandy bottoms. CPUE of all species combined dominated the seine catch in all years sampled. was consistently lower at T2 than at T1 and T3, Killifish (mummichog or striped killifish), winter which tended to have similar catches (Figure 5- flounder, and ninespine stickleback also contrib-5). Catch at T2 was dominated by winter floun- uted frequently to the catch during both the der, whereas yellowtail flounder (preoperational preoperational and operational periods. period) and longhorn sculpin and skates (opera-tional period) were most common at T1 and T3. Catch by station showed considerable variation However, station to station comparisons are over the years (Figure 5-6). In 1997, CPUE was limited by the inability to sample by trawl at highest at Station S1, due to large catches of Station T2 during many sampling trips, particu- Atlantic silverside. Station S3, located near the l ! larly from August through October, when catches mouth of the estuary, had peak catches in 1976, tend to be largest. Because largest catches were 1979, and 1990, but its CPUE has been generally often made during late summer and early fall, close to the three-station mean since 1991. this may have biased interstation comparisons, Station S1, located farthest from the mouth, had l l which used the entire database. Because of this relatively low CPUE during the earliest years of l potential bias, data from the August-October sampling, tended to approximate the overall period were not used in any of the ANOVAs for mean in 1991-1994, and was above the mean in selected species collected by trawl sampling 1995 through 1997. CPUE at S2, located (Section 5.3.3). For other months during the closest to Seabrook Station, had the largest past 18 years, a few collections were missed at CPUE in 1993 and was lowest in 1995 through T2, but overall trawl sampling effort at T2 was 1997. Trends in CPUE were mostly due to the 81% of that at T1 or T3. 5-25 r
7 5.0 FISH } Seine
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l I 0. 76 77 78 79 80 81 82 83 84 BS 86 87 88 89 SO 91 92 93 94 95 Jo 97 YEAR Figure 5-6. Annual geometric mean catch of all species combined perimit effort (number per haul)in seine samples by station and the mean of all stations.1976-1997. Seabrook I Operational Report,1997. fluctuations in catch of the dominant species, 1997, an estimated 10,648 fish were impinged Atlantic silverside. Wirier flounder and rainbow (Table 5-10), the lowest annual estimate since smelt were most common at S3, whereas killifish 1994 (Appendix Table 5-3). Most fish were were most abundant at S1 and S2, with few taken impinged in November (57%) followed by April at S3, likely due to salinity and temperature (15%) and October (8%). preferences. In 1997, alewife (2,797) were the most numerous 5.3.2.3 Impingement fish impinged, followed by windowpane (1,688), winter flounder (468), rock gunnel (459), and Seabrook Station operated throughout most of grubby (430). The alewife impingement oc-1997 with periods of reduced flow from 9 May curred primarily (98%) in November and con-through 24 June during an outage. Monthly sisted of young-of-the-year (YOY) fish between average circulating water flow ranged from 235.1 8 and 13 cm. Alewife spawn in freshwater in the million gallons per day (mgd) in June to 674.4 spring, and the YOY leave their natal rivers in mgd in August (Table 5-10, Page 5-28). During the fall in response to heavy rainfall, high water 5-26 m
l 5.0 FISH i Table 5-9. Geometric Mean Catch per Unit Effort (number per standard haul) With Coefficient of l Variation (CV) by Station (S1, S2, and S3) and All Stations Combined for Abundant l Spec.ies Collected by Seine During the Preoperational and Operational Periods and the 1997 Mean. Seabrook Operational Report,1997. l l Preoperational Period
- 1997 6 Operational Period
- l Species Station Mean CV Mean Mean CV I Atlantic silverside S1 7.2 7 6.4 5.4 11 ;
l S2 6.8 6 4.3 4.0 8 l S3 6.7 10 3.0 4.0 7 i All stations 6.9 7 4.4 4.4 6 Winter flounder S1 0.9 11 0.2 0.5 24 S2 1.0 14 0.2 0.2 47 i S3 3.2 9 0.2 0.8 14 All stations 1.5 8 0.2 0.5 12 1 Killifishes SI 1.1 10 1.3 1.2 23 S2 1.2 19 0.0 0.2 49 l S3 < 0.1 27 0.0 < 0.1 100 All stations 0.7 13 0.3 0.4 20 Ninespine stickleback S1 0.7 20 0.1 0.4 24 S2 0.8 28 0.0 0.1 35 S3 0.8 24 0.1 0.2 36 All stations 0.8 20 0.1 0.2 23 Rainbow smelt S1 0.1 41 0.1 0.1 37 l S2 0.2 31 < 0.1 0.2 41 S3 0.7 21 < 0.1 0.3 44 All stations 0.3 16 0.1 0.2 33 1 i American sarut lance S1 0.1 44 < 0.1 0.3 34 0.2 S2 48 0.0 0.1 64 S3 0.1 28 2.3 0.7 42 All stations 0.1 28 0.5 0.4 27 Pollock S1 0.1 40 0.0 < 0.1 65 . S2 0.2 40 0.0 < 0.1 100 l S3 0.4 36 0.0 0.1 65 l All stations 0.2 35 0.0 < 0.1 56 ( Blueback herring S1 0.2 29 0.7 0.3 29 S2 0.1 36 0.0 < 0.1 100 l S3 0.1 38 0.1 < 0.1 48 All stations 0.1 29 0.2 0.1 27 Atlantic herring S1 0.1 59 0.6 0.1 43 !' S2 0.3 27 <0.1 0.1 46 S3 0.1 24 < 0.1 0.1 47 i All stations 0.2 19 0.2 0.1 26 l Alewife S1 0.1 38 0.3 0.1 56 l S2 0.1 49 0.0 0.0 - S3 0.1 31 < 0.1 < 0.1 67 i All stations 0.1 33 0.1 < 0.1 50 Other species S1 0.8 14 0.5 0.4 27 S2 1.1 8 0.3 0.5 29 S3 1.5 12 0.4 0.9 15 ) All stations 1.1 9 0.4 0.6 16
' Preoperational: 19761989; geometric mean of annual nwans.
- Geornetric mean of the 1997 data.
- Operational: 1991 1997 geometric mean of annual means.
5-27
5.0 FISH . Table 5-10. Species Composition and Total Number of Finfish and American Lobster impinged at Seabrook Station by Month During 1997. Seabrook Operational Report,1997. Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Alewife 0 0 0 46 0 0 0 0 0 0 2750 1 2797 26.27 American eel 0 0 0 0 0 0 0 0 0 0 42 0 42 0.39 American lobster 0 0 0 0 0 0 0 6 0 9 5 0 20 0.19 American sand lance 22 6 6 108 0 0 0 0 0 0 18 22 182 { 1.71 i American sbad 0 0 0 3 0 0 0 0 0 0 18 0 21 0.20 Atlantic cod 0 0 3 8 0 2 19 0 9 3 18 7 69 0.65 Atlantic herring 0 0 0 37 0 0 0 0 0 0 306 7 350 3.29 Atlantic silverside 17 3 0 62 0 0 0 0 14 0 66 48 210 1.97 Blueback herring 0 0 0 0 0 0 0 0 0 13 310 0 323 3.03 I Butterfish 0 0 0 0 0 0 0 0 22 5 196 0 223 2.09 Cunner 0 0 2 9 9 1 58 14 29 65 46 0 233 2.19 Fourspot flounder 0 0 0 3 0 0 0 0 0 0 0 0 3 0.03 Grubby 74 53 55 73 15 9 13 0 0 57 2 79 430 4.04 Hake sp. 0 0 3 3 0 0 0 3 0 28 85 0 122 1.15 Herring sp. 1 0 0 3 2 0 0 0 0 212 0 0 218 2.05 Longhorn sculpin 22 13 10 1 2 0 0 0 0 0 33 7 88 0.83 Lumpfish 1 0 4 43 4 2 5 0 0 0 3 0 62 0.58 Mummichog 0 0 1 0 5 18 0 0 0 0 0 0 24 0.23 l Northern pipefish 0 0 5 95 2 0 0 0 18 2 120 1 243 2.28 Northern puffer 0 0 0 0 0 0 0 0 0 0 5 0 5 0.05 Northern searobin 0 0 0 0 0 0 0 0 0 0 11 0 11 0.10 Pollock 0 0 1 11 0 1 36 6 5 165 151 3 379 3.56 Radiated shanny 0 0 2 0 0 0 0 0 0 0 0 0 2 0.02 Rainbow smelt 44 8 24 209 1 0 0 11 0 0 55 13 365 3.43 Red hake 4 1 4 122 1 0 3 9 0 0 152 75 371 3.48 Rock gunnel 0 0 38 74 9 32 18 23 93 75 97 0 459 4.31 Sea lamprey 0 0 0 5 1 0 0 0 0 0 0 0 6 0.06 Sea raven 2 2 13 68 6 0 11 17 5 36 61 2 223 2.09 Shorthorn sculpin 9 3 22 22 5 5 36 0 4 2 5 10 123 1.16 Silver hake 0 0 0 0 0 0 0 0 0 0 105 3 108 1.01 Skate sp. 4 1 0 9 2 0 0 11 5 63 82 0 177 1.66 Snailfish sp. 6 10 164 52 5 2 0 1 5 3 87 16 351 3.30 Striped cusk-eel 0 0 0 3 0 0 0 0 0 0 0 0 3 0.03 Threespine stickleback 0 0 12 53 0 0 0 0 0 0 106 3 174 1.63 Unidentified / mutilated 1 0 2 4 10 3 5 11 9 0 4 0 49 0.46 Windowpane 47 12 11 343 11 0 0 11 0 63 1100 90 1688 15.85 Winter flounder 77 12 23 146 4 0 0 0 0 60 67 79 468 4.40 Wrymouth 0 0 0 0 0 0 0 0 0 0 3 0 3 0.03 Yellowtail flounder 0 0 0 5 1 0 0 0 0 17 0 0 23 0.22 Monthly Totals 331 124 405 1620 95 75 204 123 218 878 6109 466 10,648 100 Average Daily Flow (mgd) 578.2 565.2 570.7 571.9 345.0 235.1 662.1 674.4 672.2 672.6 665.9 668.3 209,489 1mpingement Rate (fish /mg) 0.57 0.22 0.71 2.83 0.28 0.32 0.31 0.18 0.32 1.31 9.17 0.70 0.05 5-28
s.o nsa. levels and sharp decreases in water temperature been Atlantic silverside (8,298) followed by (Mullen et al.1986). These alewife were proba- grubby (6,980), winter flounder (6,305), rainbow bly impinged as they left local rivers and headed smelt (5,612), and the taxonomic category [ for offshore overwintering areas. " hakes" (5,288, Appendix Table 5-3). These five taxa represent 49% of the total impingement Windowpane impingement occurred primarily in at Seabrook Station. November (65%) and consisted of fish between 8 and 14 cm. Windowpane spawn in July Most of the Atlantic silverside impingement through September (NOAA 1995) and the fish occurred in the winter of 1994 (NAI 1995). This impinged in November were primarily early- fish is extremely numerous in New England spawned YOY (Bigelow and Schroeder 1953). estuaries and is found occasionally in otter trawl Winter flounder impingement occurred primarily samples. Atlantic silverside leave the estuanes in in January through April (55%), and October the winter as water temperatures drop and through December (44%). No winter flounder overwinter in waters less than 40 m deep were impinged in June through September. The (Conover and Murawski 1982). These fish were impingement of winter flounder in January probably impinged during their winter offshore through April consisted of YOY and yearling fish movement. Grubby are demersal fish that were less than 16 cm, while the impingement in Octo- prunarily impinged during October through ber through December consisted prunarily of April. Yearling fish were the dominant age class YOY fish less than 10 cm. impinged. Winter flounder were common in otter trawls and most of the impingement oc-Rock gunnel impingement peaked in March and curred in November through the early spring. April (24%), and again in September through Fish impinged in this period were prunarily YOY November (58%). In March and Aprillengths between 5 and 9 cm. Rainbow smelt impinge-ranged between 6 and 15 cm and in September ment occurred primarily in November through through November lengths were primarily be- April, and both YOY and yearling fish were tween 10 and 17 cm. Rock gunnel spawn in the impinged. Because the term " hakes" represents winter (Liem and Scott 1966) and most of the more than one species, it is difficult to generalize fish impinged in 1997 were probably at least one about life history information. However, based year old. on their depth distribution, it appears that the majority of hakes impinged were red hake Grubby were most common in impingement (Musick 1974). Prior to 1996, red and white samples between January and April, and October hake were usually rx)t separated and the term through December, when lengths ranged from 4 hakes was used for both species. After 1996, red to 13 cm with a modallength of 8 cm. Grubby and white hake were enumerated separately. Red spawn in the late winter (Bigelow and Schroeder hake, white hake and hakes are the second most 1953), and fish about 8 cm long in January numerous fish hnpinged (8,129). Red hake through April are probably at least one year old. spawn from May through September (Colton et al. 1979). Impingement of hakes occurred For the period 1994 through 1997, the most primarily between November and April with numerous fish impinged at Seabrook Station has peaks in November and April. It appears that 5-29
1 J 5.0 FISH 1 YOY and yearling red hake are impinged in successful in reducing the impingement of fish November, and the April impingement consists and lobsters. The majority of the fishes impinged primarily of YOY fish approaching age 1. have been demersal fishes, except Atlantic silver-side, and most of this impingement occurred I Based on impingement data from the end of 1994 during storm events. The annual estimates of through 1997, it appears that the majority of the fish impingement are strongly affected by the fishes impinged are YOY and age 1 demersal occurrence of strong northeast storms, particu- , fishes taken during the fall and winter. Many larly during the fall and early winter. At Mill- ! common inshore demersal fishes undergo a stone Nuclear Power Station, large winter floun-seasonal movement in the fall and winter as they der impingement episodes were related to a move to deeper waters as water temperatures combination of high sustained wind and low decrease inshore. The impingement of YOY temperatures (NUSCO 1987). Storm events have demersal fishes in the fall and winter may be a also increased impingement at other estuarine result of these fishes moving past the intakes as (Thomas and Miller 1976) and freshwater (Lifton they complete their annual movements. and Storr 1978) power plants. At Seabrook Station in 1997 there were few strong northeast Fish impingement at Seabrook Station represents storms, and no episodes of very high impinge-a direct impact to the fish community as it results ment, which probably contributed to the lowest in removal of fish from the environment. How- impingement estimate since 1994. ever, impingement at Seabrook Station has generally been less than or similar to other power 5.3.3 Selected Species plants with coastal intakes (Table 5-11). Mean annual impingement for 1994 through 1997 was 5.3.3.1 Adande Herring 17,780 fish / year, and annual estimates ranged from 10,648 to 26,525 (Appendix Table 5-3). The Atlantic herring ranges in the Northwest Mean annual impingement estimates at other Atlantic Ocean from western Greenland to Cape plants ranged from 21,098 fish / year at Pilgrim Hatteras (Scott and Scott 1988). Separate spawn-Station to 65,927 fish / year at Millstone 2. ing aggregations associated with particular geo-graphic areas in the Gulf of Maine have been Impingement at a power plant is dependent on recogmzed (Anthony and Boyar 1968; Iles and many factors, including fish abundance near the Sinclair 1982; Sinclair and Iles 1985) and tagging intakes, the susceptibility of the species or studies have shown high (> 90%) homing fidel-lifestage to impingement, intake design and ity of spawning herring (Wheeler and Winters location, plant operating characteristics, environ- 1984). However, a lack of evidence exists for mental variables (e.g., water temperatures, wave biochemical, genetic, and morphometric differen-height, wind direction and velocity), and time of tiation among these spawning groups (Kornfield day (Landry and Strawn 1974; Grimes 1975; and Bogdanowicz 1987; Safford and Booke Lifton and Storr 1978). The intakes at Seabrook 1992), indicating that there is enough gene flow Station are located in relatively open water and to prevent the evolution of genetically distinct are equipped with mid-water entrances and stocks. Atlantic herring spawning grounds are velocity caps. This design apparently has been typically located in high energy environments 5-30
, i
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F J 5.0 FISH } i 1 (i.e., tidal or current), with demersal adhesive Tremblay 1984). Larvae tend to drift or disperse eggs deposited on marine vegetation or substrata from offshore spawning grounds into coastal bays l free from silting (Haegele and Schweigert 1985), and estuaries for further development and trans-A major spawning area and source of larvae in ' formation to the juvenile phase of life. After the western Gulf of Maine is Jeffreys Ledge metamorphosis, juveniles remain in coastal (Townsend 1992), although other banks and waters during summer. ledges in this area are also used (Boyar et al. 1971). Other major spawning grounds include Atlantic herring eggs have not been identified it Georges Bank and coastal areas of central and any ichthyoplankton or entrainment collections eastern Maine and Nova Scotia (Sinclair and Iles for Seabrook Station studies, probably because 1985). Most spawning in the western Gulf of they are demersal and adhesive. Larvae were j Maine occurs during September and October present between October and May, and most (Lazzari and Stevenson 1993). The early life common in the fall spawning season, October l history of Atlantic herring is somewhat unique through December. In 1997, average density among other northern temperate fishes in that the decreased slightly from 1996 (Figure 5-7), and larval stage is up to eight months old before was less than the preoperational and operational metamorphosis to a juvenile phase (Sinclair and means (Table 5-12). Atlantic herring densities j i Larvae Oct - Dec j 200 1 l,
- - - - . pg p3
\ *--*--* MEAN t
iso i Preoperational ! Operatonal s ,4. > 320 l
@ l
- 100 l b !
80 i
/ !
w ' / l\
, i 3 s / \ 1 i
2 4o l 'I g \ j I \
,/ \ \s l m
x i \/ 'l, -- ~
- N 's o.
75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 l Figure 5-7. Annual geometric mean catch per unit effort (number per 1000 cubic meters) of Atlantic herring in ichthyoplankton samples by station and the mean of all stations, 1975-1997. Seabrook Operational Report,1997. 5-32
l 5.0 FISH Table 5-12. Geometric Mean Catch per Unit Effort (number per 1000 m8 ) with Coefficient of Variation (CV) by Station (P2, PS, and P7) and All Stations Combined for Larvae of Selected Species Collected in Ichthyoplankton Samples During the Preopera-tional and Operational Periods and in 1997. Seabrook Operational Report,1997. Preoperational' Operational" 1997* Species Station Period Period Mean CV Mean CV Mean American sandlance P2 159.6 14.2 136.5 10.0 197.6 (Jan-Apt) P5 225.4 14.2 193.2 7.2 269.6 P7 106.0 16.1 113.8 11.1 57.0 All Stations 162.5 12.6 144.3 8.0 145.1 Atlantic cod P2 2.5 62.8 1.0 60.8 3.3 (Apr-Jul) PS 2.4 79.6 1.0 44.6 1.3 P7 1.0 72.5 0.6 20.5 0.8 All Stations 2.3 62.6 0.9 39.9 1.6 Atlantic herring P2 29.0 34.0 7.4 29.2 6.9 (Oct-Dec) P5 28.8 40.0 10.4 19.9 8.7 P7 33.2 21.8 9.5 28.9 5.6 All Stations 29.2 32.4 9.0 23.0 7.0 Atlantic mackerel P2 6.9 30,7 7.6 37.2 7.7 (May-Aug) PS 6.8 49.6 6.1 35.0 9.5 P7 5.9 21.1 7.0 34.2 6.5 All Stations 6.9 32.0 6.9 34.7 7.8 Cunner P2 48.5 22.4 83.5 31.0 60.1 (Jun-Sep P5 55.0 28.8 82.3 30.1 206.7 P7 59.0 23.3 89.3 26.5 160.7 All Stations 48.8 23.2 85.1 28.3 126.1 Hakesd P2 3.9 42.7 5.8 63.3 32.3 (Jul-Sep) P5 3.1 49.7 5.8 59.5 14.6 P7 3.9 48.0 6.0 64.7 30.1 All Stations 4.0 38.6 5.8 60.0 24.3 Pollock' P2 6.3 49.8 0.6 65.3 0.2 (Nov-Feb) P5 8.2 51.7 0.8 73.7 0.4 P7 2.4 49.9 0.5 68.4 0.6 All Stations 6.8 49.1 0.6 65.1 0.4 Winter flounder P2 12.1 18.6 6.2 18.6 6.9 (Apr-Jul) P5 10.5 17.6 7.3 12.1 8.1 P7 8.0 25.2 2.3 43.2 4.2 A!! Stations 10.8 18.1 4.8 10.7 6.2 Yellowtail flounder P2 3.4 50.2 1.9 51.3 5.1 (May-Aug) P5 5.0 32.2 2.1 54.2 6.6 P7 2.9 43.7 1.6 49.2 4.6 All Stations 3.8 38.8 1.8 46.7 5.4
'Preoperational: July 1975-July 1990 (in some years not all three stations were sampled); geometric mean of annual means.
b Operational: August 1990-December 1997; geometric mean of annual means. " Geometric mean of the 1997 data. 'May include red hake, wtute bake, spotted bake, or more than one of these species. ' Annual geometric mean for pollock in 1997 includes November through December 1996 and January through February 1997. 5-33
r 5.0 FISH have been very variable with maior peaks in than 1% of larvae identified in entrainment { 1975-76, and 1986. Since 1988, density of samples in 1997, with an estimated total of 2.1 Atlantic herring larvae has been relatively low million entrained (Table 5-5); however of Atlan-
)
(Figure 5-7). Density of Atlantic herring larvae tic herring larvae is a relatively small impact j in the operational period was significantly lower given tLt these larvae are likely drawn from the than the preoperational period, primarily due to progeny oflarge spawning groups in the Gulf of ) the decline in densities that began in 1987 (Table Maine that disperse widely throughout the area J 5-13). There were no significant differences over the course of a lengthy larval developmental among stations, and the Preop-Op X Station term period. was not significant, indicating that the decrease between periods occurred equally at all stations. 5.3.3.2 Rainbow Smelt l 1 An estimated 350 Atlantic herring were impinged The anadromous rainbow smelt occurs from in 1997, primarily in November (Table 5-10). Labrador to New Jersey (Scott and Crossman These fish were primarily YOY approaching age 1973). It serves as forage for fish, birds, and I at 13 to 15 cm in length. Atlantic herring, seals and supports minor sport and commercial alewife, and blueback herring comprise the fisheries in New England and Canada. Adults I taxonomic category " herring family". Assuming begin to mature at ages 1 and 2 and live about these fish were Atlantic herring, estimated im- five years (Murawski and Cole 1978, Lawton et pingement would be 568 fish. al. 1990). Adults enter estuaries in fall and winter and spawn in spring after ascending Entrainment and impingement of Atlantic herring brooks or streams to the head of tide. Spawning appeared to have a small effect on local popula- usually peaks with the bimonthly spring tides tions. Atlantic herring accounted for slightly less (Buckley 1989). Table 5-13. Results of Analysis of Variance for Atlantic IIerring Densities by Sampling Program. Seabrook Operational Report,1997.
""# Multiple Comparisons Source of Variation df MS F Months Used of Adjusted Means8 Ichthyoplankton Preop-Op' 1 27.70 9.20* Op< Preop (Oct.-Dec.) Year (Preop-Op)* 10 3.11 1.05 NS (1986-1997) Month (Year)' 24 3.21 7.33 * *
- Stationd 2 0.54 9.53 NS Preop-Op X Station' 2 0.06 0.32 NS Station X Year (Preop-Op)' 20 0.20 0.45 NS Error 354 0.44
- Preop-Op cornpares 1990-1997 to 1986-1989 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. " = Highly significant (0.012p>0.001)
' Stations regardless of year or period. "* = Very highly significant (0.0012p) ' Interaction of the two nuin effects. Preop-Op and Station. ' Interaction of Station and Year within Preop-Op.
8 Waller-Duncan multiple means comparison test used for signifmant main effects. LS Means used for interaction term. 5-34
l t 5.0 FISH brooks or streams to the head of tide. Spawning occurred in trawl samples. The peaks in seine usually peaks with the bimonthly spring tides CPUE may have corresponded to increased (Buckley 1989). numbers of age-1 fish resulting from larger than average adult spawning stocks the previous year. Rainbow smelt were most common in trawl During the operational period, CPUE was less 1 samples from November through May (NAl variable is CPUE among the three stations 1993). In 1997, geometric mean CPUE in the generally followed the same trends. There were trawl was 0.1, the lowest recorded since monitor- no significant differences in CPUE between the ing began in 1975 (Table 5-8; Figure 5-8). In the preoperational and operational periods (Table 5-preoperational period CPUE was highest at 14). CPUE was significantly higher at Station S3 Station T2, especially during 1978, 1981, 1983, than at Stations S1 and S2. and 1988. However, starting in 1989, CPUE began to decrease at all stations and is currently The abundance of rainbow smelt is potentially at low levels. influenced through impingement and entrain-ment. Rainbow smelt spawn in the estuary and The decrease in trawl CPUE did not occur the adhesive eggs remain there and are not equally at all stations, as indicated by the signifi- subject to entrainment. Because of the behavior cant Preop-Op X Station interaction term (Table and specific life history of the rainbow smelt, no 5-14). CPUE decreased to a greater extent eggs and few larvae (0.03% of all larvae in all between the preoperational and operational offshore samples) have been collected in the periods at Station T2 than at Stations T1 and T3 ichthyoplankton sampling program. Larvae also (Figure 5-9). CPUE was significantly different are primarily estuarine and are not subject to a among the stations in the preoperational period, large degree of entraimnent through the offshore but in the operational period mean CPUE was intakes. Larvae have only been collected in less than 1.0 and there were no significant differ- entrainment samples in 1990 and 1992, account-ences among the stations (Table 5-14). The ing for a total entrainment estimate of about current low levels of CPUE at all stations may 300,000 larvae since the beginning of plant suggest a regional decrease in rainbow smelt operation (Table 5-6). stocks. However, on a percentage basis the decrease in CPUE was relatively consistent An estimated 365 rainbow smelt were impinged among stations. CPUE decreased 63%,78% and in 1997 (Table 5-10). Most of the rainbow smelt 61% at Stations T1, T2, and T3 respectively, were impinged in April (Table 5-10). These fish between the preoperational and operational were between 6 and 12 cm and probably had just periods (Figure 5-9). attained age 1 (Murawski and Cole 1978). An estimated total of 5,612 rainbow smelt have been CPUE of rainbow smelt in seine samples in 1997 impinged since 1994 (Appendix Table 5-3). To was 0.1, similar to 1996 (Table 5-9; Figure 5-8). put this loss into perspective, an estimated Seine CPUE was very variable, especially at 556,000 rainbow smelt were taken by recre-Station S3 during the preoperational period. ational anglers in the Great Bay fishery since CPUE peaked in the preoperational period in 1994 (NHFG 1998). 1979 and 1990, one year after similar peaks 5-35
[~ ] l' i l l 5.0 FISH } l Juveniles and Adults (Trawls) 1 J 5.S ' T i _ _ _ " ' " " - 7 ,1 I 5.0 T3 1 I g N MEAN 4.5 Preoperatiornal I i Operational 4.0 si i l1 l 3.5 et i, , 3.0 t [ i ' I
@ l ', ,, l i, ,' 's, i 2.5 s 5 os s o
r I 4 a g # g a g i
# # # s # , 8 gl 1 s l ', l \l ', l g i '
/ \ h'. 4
',j 8 ' '
, g ; 1.5. e
\
*/ s 1.0 s f
/N/ \ g st 5 0.5 -
s
' ~~~
> OD l 76 77 78 79 80 81 82 83 84 BS 86 87 88 89 90 91 92 93 94 95 96 97 YEAR Juveniles and Adults (Seines) l
** m l
l l l l __- _ s, i 53 4.0 " MEAN l I 1 3.5 Prooperational l l g 1 I Operational g .0 f li I t: !
$ 2.5 2.0 i I! I tl I
( 1.5 l l i l g i l i l
/ NM ;
l 1 lI ,s 0.5 Sarnpled \ f,
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b%_ - __
>- -=:' _
7s 77 7s 7e e0 a1 sa a3 a4 es se e7 as se s0 et e2 93 94 es es or MTD /s ' 4 YEAR l Figure 5-8. Annual geometric mean catch of rainbow smelt per unit effort in trawl (number per 10-minute tow) and seine (number per haul) samples by station and the mean of all ' stations, 1975-1997 (data between two vertical dashed lines were excluded from the l ANOVA model). Seabrook Operational Report,1997. l 5-36
3 ! l ! ) l S.O FISH Table 5-14. Results of Analysis of Variance for Rainbow Smelt Densities by Sampling Pro-gram. Seabrook Operat!onal Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F Of Adjusted Means" Seine Preop-Op* 1 0.18 1.72 NS 6-19 7) nth 1 .
- Station 2 0.92 9.11* S3 S2.11 Station X Year (Preop-Op)* 38 0.10 1.80**
Error 274 0.06 Trawl Preo 1 12.05 10.19' Op < Preop Yea reop-O 20 0.65 1.41 NS (Nov-M_ayl) - Mon t (1975-1997 Station (Year) p) 132 2 0.48 0.43 6.49'*
- 0.72 NS Preop-Op X Station8 2 0.59 10.70
- 2 Pre IPre 3 Pre 100 300 200 Station X Year (Preop-Op) 40 0.05 0.74 NS Error 262 0.07
- Preo@ compares 1990-1997 to 1976-1984 and 1%6-1989 regardless of station. NS = Not significant (p>0.05)
Year nested within preoperational and operational periods regardless of station. *
= Significant (0.05ap>0.01)
- Month nested within Yest. " = Highly significant (0.01ap>0.001) o Stations regardless of year or period. *" - Very highly significant (0.001ap)
- Interaction of Station and Year within Preo@.
l ' Preop-Op compares 1990-1997 to 1986-1990 regardless of station. s Interaction of the two main effects, Preop.Op and Station.
- Duncan-waller umluple means comparison test used for significant main effects.
LS Means used for interaction term. 1 2.6 Rainbow Smelt (Trawls) = = = T1 ! 2.4 .,
* ~~* " + T2 l
. - - - 33 l 2.2' g 2.0 .
1.8 - g 1.6- . 3 -
@ 1.2 1.4 -
5 's - l tF 1.0 O s's s% - 0.8 %s '
's 0.6- 's s j '!
l 0.4 0.2 0.0 Preoperational Operational Figure 5-9. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of rainbow smelt caught by trawl during the preoperational (November 1975 - May 1990) and operational (November 1990 - May 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-14). Seabrook Operational Report,1997. 5-37
)
s.o nsa } 5.3.3.3 Atlantic Cod Atlantic cod larvae typically exhibited a bimodal annual occurrence, with one peak from Novem-
)
The Atlantic cod is found in the Northwest ber through February and a second, larger peak - Atlantic Ocean from Greenland to Cape Hatteras from April through July (NA11993). To com-and is one of the most important commercial and pare abundances among years and stations, only : recreational fishes of the United States. The data from April through July were used. Density 1 highly predatory, omnivorous cod can commonly of Atlantic cod larvae was highest from 1977 achieve a length of 130 cm, a weight of up to 25- through 1982 and declined to relatively low and 35 kg, and can live 20 years or more. However, stable levels since then (Figure 5-10). Mean l smaller fish (50-60 cm,1.1-2.3 kg, age 2-6) are density in 1997 was below both the l more typically caught by the fisheries (Bigelow preoperational and operational period means l and Schroeder 1953; Scott and Scott 1988; (Table 5-12), but increased slightly over 1996 ] NOAA 1995). The Atlantic cod is a cool-water (Figure 5-10). Despite relatively high abundance fish, and is found and spawns at temperatures during the early preoperational years, no signifi- l from about -1 to 10*C; distribution is also influ- cant differences were found between the preop- l enced by time of year, geographical location, and erational and operational perioA, or among fish size (Jean 1964; Scott and Scott 1988; stations (Table 5-15). The Preop-Op X Station Brander and Hurley 1992). Many separate term was not significant indicating that trends groups spawning at different locations have been between the preoperational and operational noted in the northwest Atlantic, but for manage- periods were consistent among stations. ment purposes two stocks (Gulf of Maine, and Georges Bank and South) are recognized in U.S. Atlantic cod were captured year-round in the waters (NOAA 1993). trawl, but were most abundant from November through July (NA11993). CPUE in 1997 was
. Atlantic cod eggs in ichthyoplankton collections similar to 1996, lower than both the were usually grouped as Atlantic cod / haddock preoperational and operational means and among because it was difficult to distinguish between the lowest recorded since 1976 (Table 5-8; these two species; this aggregation also included Figure 5-10). Mean CPUE for all stations was witch flounder eggs. These taxa have been highest from 1978 through 1983, and 1987 dominant during the winter and early spring through 1988. The Northeast Fisheries Science (Table 5-3). Examination of larval data since Center (NEFSC) in their trawl resource assess-July 1975 indicated that the percent composition ments noted similar increases, corresponding to among alllarvae collected was 0.42% for Atlan- increased recruitment of fish at ages 1 and 2 tic cod,0.02% for haddock, and 0.90% for witch (NEFSC 1997). According to the NEFSC re-flounder. Assuming a relatively similar hatching source survey, there was above average recruit-rate, it appears that Atlantic cod and witch floun- ment of the 1977-1980,1983, and 1985-1987 der eggs predominated in this egg group. Atlan- year-classes one to two years later at ages 1 and tic cod eggs have also been dominant in the late 2. The NEFSC survey did not detect the 1993 fall and early winter (Table .5-3), before the peak in CPUE that was apparent in our data, spawnmg seasons of haddock and witch flounder Since 1989, CPUE has been less than 1.0 at all (Bigelow and Schroeder 1953). stations, except Stations T3 and T2 in 1993.
5-38
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_ ~~___ .- 78 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 vcAn Figure 5-10 Annual geometric mean catch of Atlantic cod per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-minute tow) samples by station and the mean of all stations, 1976-1997. Seabrook Operational Report,1997. 5-39
S.0 FISH Table 5-15. Results of Analysis of Variance for Atlantic Cod Densities by Sampling Program. j Seabrook Operational Report,1997. Program / Months Used Source of Variation df MS F Multiple Comparisons of Adjusted Means'
)
ichthyoplankton Preop-Op' 1 1.20 3.09 NS I (Apr-Jul) Year (Preop-Op)* 9 0.51 0.90 NS I (1987-1997) Month (Year)* 33 0.64 3.08 * " Stationd 2 0.30 24.39 NS Preop-Op X Station' 2 0.02 0.12 NS Station X Year (Preop-Op)' 18 0.13 0.62 NS Error 441 0.21 Trawl Preop-Op8 1 12.21 9.31 *
- Op < Preop l (Nov-Ju!) Year (Preop-Op) 20 1.05 5.62*" -
I (1975-1997) Month (Year) 176 0.15 3.09"
- Station 2 4.71 13.06 NS Preop-Op X Station 2 0.35 4.10* 3 Pre IPre 300 2 Pre IOp 20p Station X Year (Preop-Op) 40 0.09 1.80 "
Error 350 0.05
- Preop-Op cornpares 1990-1997 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) l
' Month nested within Year. " = Highly significant (0.01ap>0.001)
- stations regardless of year or period. "* = Very highly significant(0.001ap)
- Ir. Traction of station and Year within Preop-Op.
' Preopop compares 1990-1997 to 1986-1990 regardless of station. , a Interaction of the two main effects. Preop Op and station. " Duncan-Waller multiple means comparison test used for significant rnain effects. LS Means used for interaction term. CPUE decreased at all stations between the ment consisted of individuals 12 to 17 cm that preoperational and operational periods, but the were probably YOY (Bigelow and Schroeder decrease was greater at Station T3, resulting in a 1953), and the July impingement consisted of significant Preop-Op X Station interaction term older fish. Since 1994 an estimated 343 fish (Table 5-15; Figure 5-11). On a percentage were impinged; a total not likely to affect cod basis, the decrease was highest at Stations T2 and resources in the study area (Appendix Table 5-3). T3 (80% and 79%) and lowest at Station T1 (62 %). CPUE has generally been lowest at Egg (2.9 million in 1997) and, in particular, Station T2 each year of the preoperational and larval entrainment (700,000 in 1997) has been operational periods, probably due to habitat relatively low (Tables 5-5, 5-6), given the high . preference. The generalized decrease in CPUE fecundity of Atlantic cod in the Gulf of Maine. at all stations to less than 3 fish per tow, suggests a regional trend. 5.3.3.4 Enllor); An estimated 69 Atlantic cod were impinged in The pollock is one of the most pelagic of all the 1997 (Table 5-10). Impingement was highest in gadids and is often found in large schools. July and November. The November impinge- Found from southwest Greenland to Cape Look 5-40
5.0 FISH Atlantic cod (Trawls) 6.0 : = = T1
- - . - -
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h3.0 'N 2.5 N s 2.0 2 1.5-1.0 .. ..,,, 0.5-0.0-Preoperational Operational Figure 5-11. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of Atlantic cod caught by trawl during the preoperational (November 1975 - July 1990) and operational (November 1990 - July 1997) periods for the significant interac-tion term (Preop-Op X Station) of the ANOVA model (Table 5-15). Seabrook Opera-tional Report,1997. out, NC (Bigelow and Schroeder .1953), it is pollock in the Gulf of Maine and on Georges most abundant on the Scotian Shelf and in the Bank has decreased sharply during the 1980s Gulf of Maine (NOAA 1993). Adults move into from a peak in the late 1970s and has remained the southwestern Gulf of Maine in fall or early relatively low in recent years, although an in-winter to spawn, which mostly occurs from crease was observed in 1993. During this pe-November through February (Colton et al. riod, the catch of pollock was dominated by 1979). several moderately strong year-classes that occurred every three to four years, including Combined U.S. recreational and U.S. and Cana- those from 1975,1979, and 1962. More re-dian commercial landings for the Scotian Shelf, cently, the 1987 and 1988 year-classes appeared Gulf of Maine, and Georges Bank regions in- to be above the long-term mean. The 1989-91 creased from a yearly average of about 46,400 year-clas.ses, however, are below average in metric tons in 1974-83 to 68,500 metric tons by abundance. The pollock stock is considered by 1986 (NOAA 1995). Based on National Marine NOAA (1995) to be fully exploited. Fisheries Service trawl surveys, biomass of 5-41
j 5,0 FISH Larval pollock abundance generally peaked (Bigelow and Schroeder 1953; Scott and Scott j during November through February (NAI 1993). 1988) and is not important to the fisheries. For these reasons, it will not be discussed below. f Large peaks in annual larval pollock density 1 occurred in 1976, 1979, and a smaller one in Both the red and white hakes are conunon in the 1987 (Figure 5-12). Since 1988, larval pollock Northwestern Atlantic Ocean, particularly on density has been low and stable. No pollock sandy or. muddy grounds off Northern New larvae were collected between November 1996 England. They most commonly co-occur in the and February 1997 (Table 5-12). Density of Gulf of Maine (Musick 1974). Similar in appear-pollock larvae was significantly higher in the ance and in many aspects of their biology, other preoperational period, and at Station P5 com- features differ considerably. The red hake is j pared to P7 (Table 5-16). The interaction term found in more shallow waters of the inner conti-was not significant, indicating that relationship nental shelf, predominantly in depths of 73 to among stations was consistent between the 126 m (Musick 1974). It occurs in water temper-i preoperational and operational periods. No atures of 5 to 12*C, but apparently prefers a l changes in abundance or distribution can be range of 8-10*C and avoids waters colder than attributed to station operation. 4*C. In the Gulf of Maine, red hake are found inshore for spawning, but disperse offshore An estimated 379 pollock were impinged in 1997 following spawning. Except for young, most (Table 5-10), the lowest estimate since 1994 white hake are typically found in deeper (200-(Appendix Table 5-3). Pollock impingement was 1,000 m) water than red hake and are considered highest in October and November of 1997 and to be inhabitants of the outer shelf and continen-consisted primarily of YOY fish between 14 and tal slope. Temperature preferences (5-11 C), 20 cm approaching age 1. Saila et al. (1997) however, are similar to that of the red hake. l estimated that the impingement of about 900 to Most white hake spawning occurs in spring on 1,700 pollock resulted in the loss of 136 equiva- the continental slope south of the Scotian Shelf lent adults. Impingement of 379 pollock in 1997 and Georges Bank, and off Southern New Eng-resulted in a smaller loss of equivalent adults, land (Fahay and Able 1989; Comyns and Grant i No pollock eggs or larvae were entrained in 1997 1993). Red hake spawn mostly during summer (Table 5-5), and relatively few have been en- and fall in mid-shelf areas, trained since 1990 (Table 5-6). Entrainment losses of pollock eggs and larvae at Seabrook Based on the depth distribution of the red and Station from 1990 to 1994 were estimated to white hake, red hake is probably the most com-result in the annual loss of less than 10 equivalent mon hake in the study area. Recent commercial adults annually (Saila et al.1997). fishing landings of red hake in the Gulf of Maine and from the northern Georges Bank are very 5.3.3.5 Hakes low (< 1,000 metric tons), with an average of only 2,000 metric tons landed over the period of Three species of hake (genus Urophycis) are 1974-93 (NOAA 1995). The NMFS trawl sur-found in the Gulf of Maine: red hake, white vey index showed an increasing trend in abun-hake, and spotted nake. The spotted hake, dance from the mid-1970s to a peak in 1989; however, is apparently quite rare in this area indices decreased in 1990 through 1993, but 5-42
)
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75 78 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 YEAR Figure 5-12. Annual geometric mean catch per unit effort (number per 1000 cubic meters) of pollock in ichthyoplanlaon samples by station and the mean of all stations, 1975-1996. Note that 1996 includes November and December of 1996 and January and February of 1997. Seabrook Operational Report,1997. Table 5-16. Results of Analysis of Variance for Pollock Densities by Sampling Program. Seabrook Operational Report,1997. Program / Source of Variation df MS F Multiple Cornparisons Months Used of Adjusted Means** Ichthyoplankton Preop-Op' 1 12.67 6.99* Op < Preop (Nov-Feb) Year (Preop-Op)" 9 1.85 2.60* (1986-1997) Month (Year)* 31 0.80 5.48
- Station
- 2 0.34 37.53*
Preop-Op X Station' 2 0.01 0.15 NS Station X Year (Preop-Op)' 18 0.06 0.44 NS Error 419 0.15
- Preop-Op compares 1990-1997 to 19761986-199 regardless of station. NS = Not significant (p>0.05)
- Year nested within preoperational and operational periods regardless of station. *
= Significant (0.05ap>0.01)
- Month nested within Year. " - Highly significant (0.01 ap>0.001)
' Stations regardless of year or period. "* = Very highly significant (0 001ap) ' Interaction of the two main effects, Preopop and Station. ' Interaction of station and Year within Preop-C'p. s Duncan-Waller multiple means comparison test used for significant main effects. LS Means used for interaction term.
- No differences among stations means detected.
543
L 5.0 FISH remained near the long-term average. Although possibly a result of habitat preference. There has year-classes produced since 1985 were termed been a general trend of decreasing CPUE since moderate in strength, NOAA (1995) concluded 1981, and 1997 was the third-lowest recorded in . that the red hake is underexploited and could the time series (Figure 5-13). CPUE decreased sustain much higher catches. In contrast, white at all stations between the preoperational and hake landings in the Gulf of Maine (primarily f' operational periods, but the decrease was greatest from the western portion) are high, being ex- at Station T1, resulting in a significant Preop-Op ceeded only by those for the Atlantic cod (NOAA X Station interaction term (Table 5-17; Figure 5-1995). Presently, NMFS consider white hake to 14). Although the decrease in absolute numbers be overexploited (C. Scoseby, NMFS, pers. was larger at Station T1, on a percentage basis comm.), the decrease was similar among stations (T1:70%; T2:67 %; T3:66%). ! Hake eggs collected in ichthyoplankton samples are difficult to distinguish from fourbeard rock- The NEFSC index for red hake abundance ling eggs during early development and, there- peaked in 1989 and decreased through 1993, the fore, at times were grouped as fourbeard rock- year for which the most recent data are available ! ling / hake. Hake and fourbeard rockling/ hake (NOAA 1995). The index for white hake abun-eggs were the predominant eggs collected during dance has generally increased between 1983 and the late summer and early fall (Table 5-3). Hake 1993. Presently NMFS considers white hake to larvae generally peaked during July through be over-exploited, and the northern stock of red I September (NAI 1993). Density of hake larvae hake to be underexploited (C. Scoseby, NMFS, was relatively low and consistent in the pers. comm.). The trend in CPUE for hakes in preoperational period (Figure 5-13). There was this study more closely resembles the NEFSC a major peak in hake larval density in 1990, index for red hake, because the majority of the followed by a decrease to levels similar to the hakes captured in this study are red hake. preoperational period. Since 1993, densities have generally increased, with mean densities in Entrainment and impingement losses due to plant 1997 higher than both the preoperational and operation did not appear to affect local popula- l operational period means (Table 5-12). Despite tions. In 1997, entrainment estimates for hake the recent increase in larval density, there were eggs (68.6 million) and larvae (1.7 million) no significant differences between the during 1997 were within the range of previous preoperational and operational periods, or among years (Tables 5-5, 5-6). Entrainment losses of stations (Table 5-17). The relationship among hake eggs and larvae at Seabrook Station from stations was consistent between periods as indi- 1990 to 1994 resulted in the annual loss of about cated by the non-significant interaction term. 7 to 800 equivalent adults (Saila et a!.1997). Based on the data presented in Saila et al. (1997), Hake have been taken year-round in trawl sam- entrainment of 68.6 million eggs in 1997 would pling, but peak catches were made from June have resulted in the loss of about 200 equivalent l through October, with a sharp decrease usually adults and entrainment of 1.7 million larvae occurring in November (NAI 1993). Catches would have resulted in the loss of between 100 were generally lower at Station T2 each year, and 800 equivalent adults. An estimated 493 l 5-44
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0 I 75 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 98 97 YW Figure 5-13. Annual geometric mean catch of hakes per unit effort in ichthyoplankton (number per 1000 cubic meters) and trawl (number per 10-minute tow) samples by station and the mean of all stations, 1976-1997 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997. 5-45 l 1
5.0 FISH Table 5-17. Results of Analysis of Variance for Hake
- Densities by Sampling Program.
Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjusted Means' Ichth lankton Preop-Oph 1 6.75 1.02 NS (Jul- 9 6.62 2.08 NS (1986- Year Month(Preop-)Op)* (Year
- 22 3.41 5.79*"
Statiort 2 0.25 0.74 NS Preop-Op X Station' 2 0.33 0.93 NS Station X Year (Preop-Op)* 18 0.36 0.61 NS Error 340 0.59 j h Trawl Op 1 8.29 19.46** Op < Preop (Nov-Jul) Preop Year (Preop-Op) 20 0.29 0.71 NS (1976-1997) Month (Year) 176 0.42 8.35 * " Station 2 0.98 5.51 NS I Preop-Op X Station 2 0.17 4.16* 3 Pre 1 Pre 2 Pre 10n 3On 200 l Station X Year (Preop-Op) 40 0.04 0.83 NS l Error 350 0.05 1
- May inchule red bake, white hake, spoaed bake, or more than one of these species. NS= Not significant (p>0.05)
- Preop-Op compares 19901997 to 1986-1989 regardless of station. *= Significant (0.05ap>0.01)
' Year nested within preoperational and operational periods regardless of station. **= Highly significant(0.01ap>0.001)
- Month nested within Year. *= Very highly significant (0.001ap)
- Stations regardless of year or period.
' Interaction of the two main effects, Preopop and Station.
8 Interaction of Station and Year within Preop Op.
- Preop-Op coinpares 1990-1997 to 1976-1990 regardless of station.
- Duncan-Waller multiple means comparison test used for significant main effects.13 Means used for interaction term.
l Hakes (Trawls) 2.8 : : ; T1 2.6 + - - * - - + T2
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$3 1.6 s N
s N h 1.4 s f 1.2 ..,,, s 61.0 "' - N 0.8 .., N s 0.6 0.4' - 02 0.0-Prec.pa.& ial Operational Figure 5-14. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of hakes caught by trawl during the preoperational (November 1976 - July 1990) and operational (November 1990 - July 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-17). Seabrook Operational Report,1997. 5-46
- _ - ~
j 5.0 FISH l hakes (red hake and hake sp. combined) were each station was relatively consistent except for impinged at Seabrook Station in 1997 (Table 5- high values at Station S2 in 1978 and 1993, S3 in l 10), which is less than the amount impinged in 1981 and S1 in 1995. There were no significant previous years when impingement ranged from differences in CPUE between the preoperational 2,211 in 1995 to 2,824 in 1994 (Appendix Table and operational periods, or among stations (Table 5-3). Impingement of red hake and hake sp. 5-18). was highest in October through December and consisted primarily of primarily of YOY between An estimated 210 Atlantic silverside were im-6 and 10 cm, and older fish between 17 and 22 pinged in 1997 (Table 5-10). Impingement was l cm. highest in November and December when lengths generally ranged from 8-13 cm. These fish were 5.3.3.6 Atlantic Silverside probably a combinatien of YOY and yearling fish impinged on their offshore winter migration l The Atlantic silverride is a small, short-lived (Conover and Murawski 1982). Impingement in schooling fish that is ecologically important as a 1997 was less than previous years, when totals i consumer of zooplankton and as prey for many ranged from 5,348 in 1994 to 1,119 in 1996 larger fishes and birds (Bengston et al.1987). (Appendix Table 5-3). This is an extremely Found in bays, salt marshes, and estuaries from common inshore fish and the removal of an the Gulf of St. Lawrence to northern Florida, the average of about 2,000 fish per year will not Gulf of Maine is near the northern end of its affect the resource. No eggs or larvae were range (Conover 1992). Most Atlantic silverside entrained, complete their life cycle within one year and, typically, few older fish are found in the popula- 5.3.3.7 Cunner tion. Atlantic silverside undertake an offshore migration in winter to inner continental shelf The cunner, found from Newfoundland to Chesa-waters, with most fish caught within 40 km of the peake Bay (Scott and Scott 1988), is one of the shore and at depths less than 50 m (Conover and most common fishes in the Gulf of Maine Murawski 1982). It is during this period that (Bigelow and Schroeder 1953). A small fish high (up to 99%) overwintering mortality typi- residing in inshore waters, few cunner measure calb occurs, with apparently mostly fish larger over 31 cm, although fish as large as 38 cm are than 80 nun able to survive the winter (Conover occasionally taken in deeper waters (Johansen and Ross 1982; Conover 1992). 1925; Bigelow and Schroeder 1953). Most cunner are closely associated with structural Atlantic silverside have been numerous in the habitats, such as rocks, tidepools, shellfish beds, seine sampling program and were taken through- pilings, eelgrass, and macroalgae. Cunner out the August through November sampling exhibit both diel and seasonal behavior in that season (NAI 1993). Geometric mean CPUE was they remain under cover and become quiescent at highest from 1976 through 1981, whereupon night and torpid in weer (Olla et al.1975, catch decreased (Figure 5-15). Since then, 1979). Presently, cunner have no commercial CPUE has fluctuated around a lower and more value, although large quantities were apparently consistent average level to the present. CPUE at landed during the late 1800s and early 1900s 5-47 t
F j s 5.0 FISH l Juveniles and Adults (Seine) j 25 i i I i _ _ _ s1 m q l I g . I MEAN l l f
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I i ! l'i Preoperational I i Operational
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l 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 C8 97 YEAR 1 1 Figure 5-15. Annual geometric mean catch of Atlantic silverside per unit effort in seine samples 1
-(number per haul) by station and the mean of all stations, 1976-1997 (data between the two vertical date:' lines were excluded from the ANOVA model). Seabrook Opera-tional Repor, .1W.
Table 5-18. Results of Analysis of Variance for Atlantic Silverside Densities by Sampling Program. Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjusted Means' Seine Preop-Op* 1 2.91 3.63 NS (Apr-Nov) Year (Preop-Op)* 18 0.81 0.38 NS (1976-1997) Month (Year)* 137 2.17 14.39* " Station
- 2 0.17 1.23 NS Station X Year (Preop-Op)* 38 0.13 0.89 NS Error 274 0.15 j
- Preop Op compares 1991-1997 to 1976-1984 and 1986-1989 regardless of station. NS = Not significant (p>0.05) l
- Year nested within preoperational arri operational periods regardless of station. *
= Significant (0.05mp>0.01) ' Month nested within Year. ** = Highly significant (0.01ap>0.001)
- Stations regardless of year or period. * = Very highly significant (0.001ap)
- Interaction of Station and Year within Preop-Op.
' Duncan-Waller multiple means comparison test used for significant main effects.
t.S Means used for interaction term. 5-48
S.O FISH (Bigelow and Schroeder 1953). Although the semnd each year that entrainment sampling was cunner is not primarily sought after, numerous conducted during the summer season of high fish are caught by recreational fishermen abundance (Table 5-6). La val cunner entrain-throughout New England. Because of its re- ment in 1997 was estimated as 203.8 million stricted inshore habitats and the lack of landings (Table 5-5), the largest estimate to date (Table 5-data, no large-area, long-term abundance indices 6). Density of cunner larvae in the offshore are available for the cunner. samples in 1997 was not exceptionally high (Figure 5-16) suggesting that there is not a strong Cunner eggs and larvae were dominant in the relationship between cunner larval density in ichthyoplankton program (Tables 5-3 and 5-4). offshore samples and entrainment estimates. Cunner eggs were grouped with yellowtail floun-der (cunner /yellowtail flounder). This group also Relatively few cunner have been taken by otter included tautog eggs, although tautog adults were trawl, gill net, or seine. Most occurrences were probably not abundant in the Hampton-Seabrook recorded from April through November, which area, which is located near the northern end of likely corresponds to the period of greatest their range (Bigelow and Schroeder 1953). cunner activity in New Hampshire waters. An Tautog have only accounted for 0.04% of all estimated 233 cunner were impinged in 1997, larvae collected since July 1975. A comparison with the majority taken in October and Novem-of cunner and yellowtail flounder larval abun- ber (Table 5-10). These fish generally ranged dance indicated that most of the eggs in the from 6 to 13 cm in length, and probably were a cunner /yellowtail flounder group were likely combination of YOY and older fish (Bigelow and cunner, assuming a relatively similar hatching Schroeder1953). Impingement of cunner has rate between the two species (Table 5-12). The generally been less than 400 per year, except density of cunner larvae has been very variable 1995 when 1,121 were impinged (Appendix with peaks occurring approximately every three Table 5-3). years in 1977, 1980, 1983, 1987, 1990, 1993 and 1995 (Figure 5-16). Mean density in the 5.3.3.8 American Sand Lance operational period was almost twice that of the preoperational and mean density in 1997 was Both the American sand lance (Ammodytes higher than both periods (Table 5-12). Despite americanus) and the northern sand lance (A. the higher densities of cunner larvae in the dubius) may be taken inshore in the Gulf of operational period, there were no significant Maine (Winters and Dalley 1988; Nizinski et al. differences between periods (Table 5-19). Larval 1990). However, the latter species is more cunner densities were not significantly different common in deeper, offshore waters and all sand among stations, and the relationship among lance collected in Seabrook Station studies are stations was consistent between periods. referred to as the American sand lance. This species is found from Labrador to Chesapeake Cunner /yellowtail flounder and cunner egg Bay (Richards 1982; Nizinski et al.1990) and in entrainment in 1996 was estimated at 222 mil- the Gulf of Maine is usually found in depths of 6 lion, ranking second among taxa of eggs (Table to 20 m (Meyer et al.1979). Found in schools 5-5). This group has generally ranked first or ranging from hundreds to tens of thousands, sand 5-49
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I\ as I i iso I \ l 's y I - j R , l h' l' \ 5 im
\
i ls , \
' la l \ s s al i ', N \. .
50 , I i l 1 l i i 1
- 0. ! ! !
78 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 32 93 04 95 96 97 YEAR Figure 5-16. Annual geometric mean catch of cunner per unit effort in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations, 1976-1997 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997. i Table 5-19. Results of Analysis of Variance for Cunner Densities by Sampling Program. Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjusted Means Ichthyoplankton Preop-Op' 1 0.73 0.06 NS j (Jun-Sep) Year (Preop-Op)* 8 11.87 0.88 NS l (1987-1997) Month (Year)* 30 13.88 17.13* " Stationd 2 0.22 3.12 NS j Preop-Op X Station' 2 0.09 0.22 NS j Station X Year (Preop-Op)' 16 0.40 0.50 NS I Error 419 0.81
- Preop-Oi , .ompares 1991-1997 to 19871989 regardless of stanon. NS = Not significant (p>0.05)
- Year nested within preoperational anxi operational periods regardless of station. * = Significant(0.052p>0.01) l
' Month nested within Year. ". = liighly significant (0.01ap>0.001) i
* = Very highly significant (0.001ap) d Stations regardless of year or period.
- Interaction of the two main effects, Preop-Op and Station
' Interaction of Station and Year within Preop-Op.
5-50
5.0 FISH lance are an important trophic link between areas of the Northwest Atlantic Ocean. Larval zooplankton and larger fishes, birds, and marine densities in Long Island Sound over a 32-year mammals (Reay 1970; Meyer et al.1979; period (1951-83) were highest in 1965-66 and Overholtz and Nicolas 1979; Payne et al.1986; 1978-79, with the latter years corresponding with Gilman 1994). Sand lance can live up to nine a peak observed throughout the entire range of years, but populations are dominated by the first American sand lance (Monteleone et al.1987). three age groups (Reay 1970). American sand Similarly, larval sand lance densities were very lance can mature at age 1 at sizes of 90 to 115 high in Niantic Bay, CT from 1977 through mm (Richards 1982). 1981, with present densities an order of magni-tude lower (NUSCO 1994a). Nizinski et al. American sand lance were the dominant larval (1990) also reported a peak in sand lance abun-taxon collected in the ichthyoplankton program dance throughout the Northwest Atlantic in 1981, (Tables 5-4 and 5-12). Larvae generally oc- with numbers declining since then. Sand lance curred from December through June or July, abundance was noted to be inversely correlated with peak abundances present during January with that of Atlantic herring and Atlantic mack-through April (NAI 1993). Larval abundances in erel(Sherman et al.1981; Nizinski et al.1990). the Hampton-Seabrook area have declined since Sand lance likely increased in abundance, replac-the early 1980s, but increased from 1987 through ing their herring and mackerel competitors, 1994, and again in 1996 (Figure 5-17). The de- which had been reduced by overfishing in the cline since the 1980s was also apparent in other 1970s (Sherman et al.1981).
, Larvae Jan - Apr T_T P
-l e7 800 li
!. N MEAN ii I 1 g 7m,i l; Preoperadonal l Operatonal
- i ,
.g o \
t em 'i e i l 5 l s~\ : \ : Wa \ is l '. A
!\
\
\\ ; .,
\. s j l \ 's
* \ \ j \ lu \ I.
\
! t
's g
1 2m
\ ', I
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l \
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in
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\ , , se b ,' ',-
,oo \ 'J~
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V /,- i 0; I 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 vr.AR Figure 5-17. Annual geometric mean catch of American sand lance per unit effort in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations, 1976-1997. Seabrook Operational Report,1997. I 5-51
I s.o nsu } Larval abundances in the Hampton-Seabrook area Very few American sand lance have been taken ' were higher in the preoperational period than the by Seabrook Station adult fish sampling pro-operational period, although a major peak in grams. A few fish were taken sporadically by s density occurred in 1994 (Table 5-12, Figure 5- otter trawl, mostly during January through March 17). Mean density in 1997 was similar to the in 1978,1979, and 1981. Several hundred or operational period mean, but lower than the more sand lance were occasionally taken by ; preoperational period mean (Table 5-12). There seine, but most catches were small and occurred ! were no significant differences in larval sand infrequently. lance density between periods or among stations (Table 5-20). The relationship among stations 5.3.3.9 Atlantic Mackerel ! was consistent between periods as indicated by the non-significant Preop-Op X Station interac- The Atlantic mackerel is a strongly schooling fish tion term. found from Labrador to Cape Lookout, NC that prefers a temperature range of 9 to 12*C (Scott Impingement of sand lance was estimated as 182 and Scott 1988). The median size of maturity for in 1997, and the majority were impinged in April mackerel is about 26 cm, at approximately age-2 (Table 5-10). Lengths of these fish ranged from (O'Brien et al.1993). Atlantic mackerel exhibit 10 to 19 cm and were probably age 1 and older a distinct pattern of extensive annual movements; fish (Westin et al.1979). Impingement of sand fish can migrate in excess of 2,200 km (Parsons lance in 1997 was the lowest recorded since 1994 and Moores 1974). Atlantic mackerel overwinter (Appendix Table 5-3). Larval entrainment in offshore along the edge of the continental shelf 1997 (10.1 million) was within the range of (Ware and Lambert 1985) and, in spring, move previous years (Table 5-6). Sand lance eggs are inshore. Temperature is apparently one of the demersal and adhesive (Fritzsche 1978), and dom'nant factors influencing the spring distribu-none have been entrained since the plant became tion and rate of northward migration of Atlantic operational (Table 5-6). mackerel (Overholtz et al.1991). Two separate Table 5-20. Results of Analysis of Variance for American Sand Lance Densities by Sampling Program. Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjusted Means8 Ichthyoplankton Preop-Op' 1 1.24 0.85 NS (Jan-Apr) Year (Preop-Op)* 9 1.18 0.32 NS (1987-1997) Month (Year)' 33 4.02 7.77"* Stationd 2 3.57 6.52 NS Preop-Op X Station' 2 0.54 2.26 NS Station X Year (Preop-Op)' 18 0.24 0.46 NS Error 414 0.52
- Preop-Op compares 1991-1997 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)
Momh nested within Year. " = Highly significant (0.01ap>0.001)
- Stations regardless of year or period. "* = Very highly significant (0.001ap)
- Interaction of the two main effects, Preop-Op and Station
' Interaction of Station and Year within Preop-Op. 8 Duncan-Waller multiple means comparison test used for significant main effects. Ls Means used for interaction term. 5-52
i l 5.0 FISH l l spawning components of Atlantic mackerel have (Table 5-12). Annual density of mackerel larvae ; been recognized (Sette 1950; Berrien 1978; fluctuated with peaks occurring in 1980-81 and Morse 1980). One group spawns progressively 1991 (Figure 5-18). In the operational period, northward from mid-April through June in the larval density has generally increased since a low l Mid-Atlantic Bight and the other spawns in the in 1992. There were no significant differences q l Gulf of St. Lawrence from late May to mid- between periods or among stations, and the ! August; peak spawning occurs at about 13*C interaction term was not significant (Table 5-21). (Ware and Lambert 1985). No Atlantic mackerel were impinged in 1997 ! Presently, biomass of the Atlantic mackerel stock (Table .5-10), with only one taken since 1994 is very high (NOAA 1995). Although two (Appendix Table 5-3). Entrainment of Atlantic spawning contingents exist, the species is man- mackerel eggs in 1997 (23.1 million; Table 5-5) aged as a single stock. Mackerel in the Gulf of was the lowest recorded to date for years when Maine are primarily landed from May through entrainment sampling was conducted during the l November by both sport and commercial fisher- May through September period of peak abun-ies. Landings from the U.S. (about one-tiard of dance (Table 5-6). Mackerel eggs are typically the total) and Canada peaked at 400,000 metric among the most numerous eggs entrained, but in tons in 1973 and decreased to about 30,000 1997 ranked sixth (Table 5-5). Larval entrain-metric tons during the late 1970s, as apparently ment in 1997 (400,000) was exceeded only by weak year-classes were found from 1975 through the 1991 estimate (4.7 million: Table 5-6). Den-l 1980. Catches then increased steadily to 82,700 sity of Atlantic mackerel larvae in offshore metric tons in 1988, but declined again to 32,100 samples in 1997 was less than the record high metric tons in 1993; a very strong year-class was densities observed in 1991, and there may be a produced in 1982 and relatively good ones in relationship between larval density in offshore 1984-88. In 1994, the latest year for which data samples and entrainment estimates (Figure 5-18), are available, current spawning stock biomass Entrainment of mackerel larvac has been rela-was estimated to exceed 2 million metric tons, tively low compared with other species, possibly indicating catches can be increased substantially due to their rapid development, which results in l without affecting the spawning stock (NOAA larger larvae that can avoid the intake. 1995). 5.3.3.10 Winter Flounder Atlantic mackerel was the second-most abundant egg taxon collected in the ichthyoplankton pro- The winter flounder ranges from Labrador to gram (Table 5-3). The larvae were very abun- Georgia (Scott and Scott 1988), but is most dant in ichthyoplankton collections (Table 5-4), common from Nova Scotia to New Jersey but were not dominant in entrainment samples (Perlmutter 1947). Populations of winter floun-(Tables 5-5 and 5-6). Larvae typically occurred der are composed of reproductively isolated fish from May through August (NAI 1993) and larval that spawn in specific estuaries or coastal abundance in 1997 was greater than the embayments (Lobell 1939; Perlmutter 1947; preoperational tnd operational period averages Saila 1961; NUSCO 1994b). North of Cape 5-53
j J M {.0 ] Larvae j May - Aug 45- , , _ _ g
! ___ ps ]
I
' P7 40 Preoperational +--+-+ MEAN
, i 35 l Operational
]
, i 30 l
a "*
/l i t
I 5 20 l "
,\ s
, \
15 s y ; I o l'\' ) R *
\ N i l
5 10 l \ N, N i ; , N,
,'\ '
l/ \ i l ) i i S t' ' \ ' l I ; 1 1
- 0. I l 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 l YEAR I Figure 5-18. Annual geometric mean catch of Atlantic mackerel per unit effort in ichthyoplankton samples (number per 1000 cubic meters) by station and the mean of all stations,1976-1997. Seabrook Operational Report,1997.
1 i Table 5-21. Results of Analysis of Variance for Atlantic Mackerel Densities by Sampling Program. Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjasted Meansh Ichthyoplankton Preop-Op' 1 1.36 0.33 NS l (May-Aug) Year (Precp-Op)* 3.90 0.43 NS 9 (1985-1997) Month (Year)* 32 9.84 11.28 * *
- Station
- 2 0.07 0.73 NS Preop-Op X Station' 2 0.10 0.97 NS Station X Year (Preop-Op)' 18 0.08 0.10 NS Error 447 0.87
- Preop-Op compares 1991 1997 to 1987-1990 regardless of station; 1990 was NS = Not significant (p>0.05) treated as a preoperational year (May-July only: August 1990 data were excluded * = Signiricant (0.052p>0.01) from the analysis). " = Highly rignificant (0.012p>0.001)
- Year nested within preoperational and operational periods regardless of station. '" = Very highly signficant (0.0012p)
- Month nested within Year.
- Stations regardless of year or period.
- Interacticn of the two main effects. Preop Op and Station.
' Interaction of Station and Year within PreoW.
8 Duncan-Waller multiple means comparison test used for significant main effects. LS Means use4 hr interaction term. 5-54
1 5.0 FISH Cod, movements of winter flounder are generally Winter flounder were taken year-round by otter localized and confined to inshore waters (Howe trawl at all stations, but most commonly from and Coates 1975). May through October (NAI 1993). Geometric mean density peaked in 1979 through 1983, Adults enter inshore spawning areas in fall or primarily due to high catches at the nearfield early winter and spawn in late winter or early station T2 (Figure 5-19). Prior to 1986, CPUE spring. Winter flounder in the Gulf of Maine was generally highest at Station T2 and lowest at mature at an average age of 3.4 years and at a T3. Starting in 1986, geometric mean CPUE was length of 27.6 cm for males and 29.7 cm for similar among the three stations until 1992. In females (O'Brien et al.1993). Because winter contrast to the period prior to 1986, after 1992 flounder spawn during periods of low water gecmetric mean CPUE was lowest at Station T2 temperature, larval development is relatively each year. CPUE in 1997 decreased slightly slow and can take up to two months to complete. from 19% (Figure 5-19) and was identical to the Larvae flushed out of estuarine nursery areas are operational mean (Table 5-8). believed to have lowered potential for survival and eventual recruitment to adult stocks (Pearcy CPUE decreased significantly between the 1962; Smith et al. 1975; Crawford 1990). preoperational and operational periods at Stations Overall mortality of larvae can exceed 99% T2 and T1 resulting in a significant interaction (Pearcy 1962). Young are common in inshore term (Table 5-22; Figure 5-20). There were no shallows, where they remain until fall, undertak- significant differences between periods at Station ing little movement away from where they settled T3. The time period used in the ANOVA model (Saucerman and Deegan 1991). excluded August through October, so the inabil-ity to trawl at Station T2 did not affect this Larval winter flounder were collected in the analysis. The large decrease at Station T2 began ichthyoplankto'. rogram (Table 5-3), but eggs in 1982, prior to the plant becoming operational, were absent because they are demersal and The decrease at Station T1 was subtle and was adhesive. Larvae typically occurred in the probably due to relatively high CPUE in 1986 i Hampton-Seabrook area during April through through 1989 (Figure 5-19). July (NAI 1993). Density of larval winter floun-der has generally decreased since a period of The NEFSC and the Massachusetts Division of high density from 1982 through 1988 (Figure 5- Marine Fisheries winter flounder stock indices 19). In the operational period larval density has for the Gulf of Maine showed similar trends to remained relatively constant, and lower than the our data. Number per tow and biomass declined preoperational period. Mean density in 1997 was steeply from highs in 1979 through 1983 to a low higher than the operational period mean, but in the in the late 1980s (ASMFC 1998). Since lower than the preoperational mean (Table 5-12). then, the indices have fluctuated without a trend. l However, these differences in mean density Several above-average year classes occurred in between the periods were not significant, and the early 1990s. However, these large year-l there were no significant differences among classes have not translated to higher catches of stations (Table 5-22). The Preop-Op X Station older fish, probably due to high fishing mortality. term was not significant. I 5-55
Fi 5.0 FISH Larvae
== Apr - Jul _ _ _ _
-1 m.,
no - - , \
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. n n n n .o ., ., u ., .o ., .a ., u. v. .,
VEAR l Juveniles and Adults (frawl) l == ;;; 8.
,- uelA
. ' \. l 1
l ', w.- ww l '= l \ l E so / \, i i E.. / N, g - I e l
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O n n n n .o .i ., u YEAR
.7 .o .= .3 =.'.7 Juveniles and Adults (Seine) i i
nr
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n n n n .o ., .. ., .o .i .= = .7 vs.a Figure 5-19. Annual geometric mean catch of winter flounder per imit effort in ichthyoplankton (number per 1000 cubic meters), trawl (nmnber per 10-minute tow), and seine (number per haul) samples by station and the mean of all stations, 1975-1997 (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Opera-tional Report,1997. l l l 5-56 i
5.0 FISH Table 5-22. Results of Analysis of Variance for Winter Flounder Densities by Sampling Program. Seabrook Operational Report,1997. Program / Multiple Comparisons Months Used Source of Variation df MS F of Adjusted Means' Ichthyoplankton Preop-Op* 1 4.33 4.33 NS (Apr Jul) Year (Preop-Op)* 9 0.74 0.17 NS (1987-1997) Month (Year)' 33 4.47 10.22 * *
- Station
- 2 4.17 6.05 .NS Preop-Op X Station' 2 0.68 1.69 NS Station X Year (Preop-Op)' 18 0.40 0.92 NS Error 441 0.44 Trawl Preop-Op8 1 2.64 0.86 NS (Nov4ul) Year (Preop-Op) 20 0.45 1.59 NS (1975-1997) Month (Year) 176 0.17 3.88*"
Station 2 0.95 0.34 NS Preop-Op X Station 2 2.76 17.94* " 2 Pre 1 Pre 1 On 3 On 3 Pre 2 001 Station X Year (Preop-Op) 40 0.15 3.51"* Error 350 0.04 Seine Preop-Oph 1 5.59 24.13 "
- Op < Preop (Apr-Nov) Year (Preop-Op) 18 0.23 1.44 NS (1976-1997) Month (Year) 137 0.08 1.75 "
- Station 2 3.41 27.28 "
- S3 S1 S2 Station X Year (Preop-Op) 38 0.13 2.75 * *
- Error 274 0.05
- Preop Op compares 1991 1997 to 19871990 regardless of station
- Year nested wrthin preoperational and operational periods regardless of station.
' Month nested within Year.
- Stations regardless of year or period.
' Interaction of the two main effects, Preop-Op and Station. ' Interaction of Station and Year within Preop-Op.
8 Preop-Op compares 1990-1997 to 19751990.
- Preop-Op compares 1990-1997 to 19771984 and 1986-1989.
- Dursan-Waller multiple means comparison test used for significant main effects. LS Means used for interaction term.
J Underlining signifies no significant differences among least square means at ps0.05. NS = Not significant(p>0.05)
= Significant(0.05ap>0.01) ** = Highly significant (0.01ap> 0.001) *** = Very highly significant (0.001ap) 5-57 1
)
5.0 FISH Winter flounder (Trawls) 6.0- =
= T1 j 5.5- .
. . . . ~ + T2
+ -* -
- T3 5.o
, j g4.5-b 4.0
)
W , l
@ 3.5- .
j h3.0 2.5 2 .0 _.__ - N ~ ~ g _ ___ , 2 1.5 . 1.0-0.5-0.0-Preoperational Operational Figure 5-20. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of wbter flounder caught by trawl during the preoperational (November 1975 - July 1990) and operational (November 1990 - July 1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-22). Seabrook Operational Report,1997. Smaller winter flounder (juveniles through age 2; Entrainment of winter flounder larvae in 1997 NAI 1993) were collected in the Hampton- (2.2 million) was the lowest recorded, except for SeaSeabrook Harbor by seine throughout the 1994 when no sampling took place during the April-November sampling period. CPUE was season of winter flounder larvae abundance generally higer in the period 1976 through 1984 (Tables 5-5,5-6). Entrainment of larvae from than in 1987 through 1997 (Figure 5-19). CPUE 1990 through 1994 resulted in the estimated loss was highest in 1980, one year prior to the peak in _ of 4,500 equivalent adults annually (Saila et al. the trawl in 1981. Abundance began to decrease 1997). Entrainment in 1997 probably resulted in after 1980 and has been consistently low since the loss of less than 4,500 equivalent adults due 1987. CPUE in 1997 was the lowest in the time to the low 1997 entrainment estimate. Mean series. CPUE of winter flounder in the seine density of winter flounder larvae in offshore samples was significantly higher in the samples in 1997 was the highest observed in the preoperational period and was 'significantly operational period (Figure 5-19), but this did not . higher at Station S3 (Table 5-22). result in a high entrainment estimate. 5-58
l 5.0 FISH j ! l In 1997 an estimated 468 winter flounder were group would also include tautog eggs., if present. impinged in January through May, and October The cunner /yellowtail flounder taxon was the through December (Table 5-10). No winter dominant egg collected during both the flounder were impinged from June through preoperational and operational periods (Table 5-September. 'lhe impingement of winter flounder 3). Larvae were less abundant, probably because in January through April consisted of YOY and the egg group consisted primarily of cunner, as yearling fish, while the impingement in October previously mentioned (Section 5.3.3.7). Yellow-through December consisted primarily of YOY tail flounder were among the commonly occur-fish. Impingement of winter flounder in 1997 ring larval taxa selected for numerical classifica-was the lowest recorded since 1994 (Appendix tion analysis, but they were not among the domi-Table 5-3). Saila et al. (1997) estimated that the nant taxa of any of the seasonal groups (Table 5-impingement of less than 1,400 winter flounder 4). Mean density of yellowtail flounder larvae in each of 1994 and 1995 resulted in the loss of was highest from 1976 through 1979, and de- l about 100 equivalent adults. The impingement of clined to a low in 1982 (Figure 5-21). Since then 468 winter flounder in 1997 would probably peaks have occurred in 1983,1986-87,1993 and result in the loss of less than 100 equivalent 1997. Mean larval density in 1997 was higher adults. than both the preoperational and operational period means, and was the highest since 1980 5.3.3.11 Yellowtail Flounder (Table 5-12; Figure 5-21). Despite the high larval density in 1997, there were no significant The yellowtail flounder is found from southern differences between periods or among stations, Labrador to Chesapeake Bay (Scott and Scott and the interaction term was not significant 1988), but its center of abundance is the western (Table 5-23). Gulf of Maine and Southern New England (Bigelow and Schroeder 1953). Yellowtail The yellowtail flounder is taken year-round in the flounder prefer coarser sand and gravel bottom Seabrook Station study area and in former years sediments than those preferred by other flounders was one of the most abundant fishes taken by of the Northwestern Atlantic Ocean (Scott 1982b) otter trawl sampling (Table 5-8). Recently, and are found mostly in depths of 37 to 91 m however, it was most common only from May (Scott and Scott 1988). Individuals apparently through October (NAI 1993). Yellowtail floun-maintain generally similar depths between sea- der CPUE peaked in 1980 and 1981 and subse-sons while tolerating a wide range of tempera- quently declined to moderate, but stable levels in tures and salinities (Scott 1982a; Morawski and the mid and late 1980s (Figure 5-21). In 1989, Finn 1988; Perry and Smith 1994). Some limited a second peak in CPUE occurred, which was seasonal movements, however, do occur, with followed by a decline in 1992 to the lowest level fish moving to shallower waters in spring and in the time series. Since 1992 CPUE has re-into deeper waters during fall and early winter, mained stable and low. l Yellowtail flounder eggs were grouped as CPUE was consistently higher at Station TJ f cunner /yellowtail flounder because it was diffi- followed by Station T3 and T2 (Table 5-8), l cult to distinguish between these two species; this probably due to a preference for coarse sand and 5-59 L
I I FISH s 5.0 j Larvae May - Aug 22 i -- e2 l n ; fi j - uS { 18 i \ 18 Preoperationai operatonai f V \ l\ 1 f\
\
\
@ so s;l l
li 's \ ! I s \ j 8 s
/ ', \ i j
\ '\
l *; / Y I
/
,\
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j n <, , of r lh%, ll 2 ( N t U _-1 e/ l O ! 78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 91 92 93 94 95 98 97 l YEAR Juveniles and Adults (Trawl) 40 i _ ___ y I ___ n
/s 5 l N MEAN T3 35
/ g ;
/ \ i 30 [ Preoperatonal Orserational
\ / \ l 5
\ / \ i
$ \ / \ j
\ / \ #
@ 20 i
\ f \
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~
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5 ,- s %
,es ,g /%
~ ~ ~
_s' %
,a " ~ ' s % hA o- ' '- -
78 77 78 79 80 81 82 83 84 85 88 87 88 89 90 h 92 93 94 95 98 97 YEAR I l 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-minute tow) samples by station and the mean of all stations, 1976-1997. Seabrook Operational Report,1997. 5-60
p
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- peYr pX 'p re Y pX 9 ep -
f n e O P h('nopor O- n OP( h O- n 1 o ort 9-iso t pe1 e oo c p (r p nopor eP5 r n o (r nioio - - 7 i r t t 8 d r .Pn7 api o st u e o a nioio t o a e t e a ota er t a t r 9 n a d o si,i9 h1 mtc r a r 1 lt a o r e r r e e cwt ooa r t u s r e S PYMSPSE PYMSPSE t t t t oI n irt pfe c r e e p 7 o r7 st 9i r f a9 n n _ RO o e e9 ae i t 9 a r 1 r nY1 o _ 1 - ep r a e. r iad 0 mf a - _ 9 e 9 1 o r Yymn9a9lps e f o ed e _ d n s e n r i p ino h st s wo t n 1 it i reus sl u 3 e o ah t a _ 2- s k t ) ) pi mw t iwdle rf f ht S ea pr t amn mleM e _ 5 /U n)7 7 o dae g oool _ _ e m s l a g9 pu9 ) l 9 9 cd e pt er enn ts io o c aS pW L _ _ l ah rt oA1- l J - -5 u1 Oe s s t t i O n-b y y7 - p- n n. n _ a gn wv h nc oa capc - as a o7 h a89 r ot t . e e a oateer o e nuf ec T wo t rN1 9 o ainirt t TM he M (1 l ( T(( r PYtsMSInnPDe t * * * ' s " I t r f _ ?$ r 5.0 FISH gravel bottoms (Scott 1982b). Despite the pref- The cunner /yellowtail flounder group has ranked 1 crence by yellowtail flounder for Station T1, the first or second among egg taxa entrained at decrease in CPUE was greater at Station Tl than Seabrook Station, with the exceptions of 1994 at Stations T3 and T2 l Figure 5-22). However, and 1995 (Table 5-6). The estimated entrainment l on a percentage basis, the decreases were simi- of eggs in 1997 was 186.1 million, but it is likely lar. CPUE decreased 84% at Station T1,92% at that this group was composed primarily of Station T2 and 83% at Station T3. cunner, based on the relative abundance of cunner and yellowtail flounder larvae. Entrain-In 1997 an estimated 23 yellowtail flounder were ment of yellowtail founder larvae in 1997 was J impinged, with the largest amount of impinge- 500,000. This estimate was exceeded only by ment occurring in October (Table 5-10). These 1996 when 1.6 million were entrained (Table 5-were apparently YOY and yearling fish between 6). Density of yellowtail flounder larvae in 1997 6 and 24 cm. With the exception of 1995 when in offshore samples was the highest observed in j 1,149 yellowtail flounder were impinged, im- the operational period, but this did not result in a j pingement has been less than 100 fish each year high entrainment estimate. (Appendix Table 5-3). , i l Yellowtail flounder (Trawls) l 22- = = = T1 l -...... + T2 I 20- * - *T3 l 18 16 e 14-g b 12 5 5 10 s s 6 8' 's 6 s 2 's 4- 'N s N * ...,, s 2 's 0-Preoperational Operational Figure 5-22. A comparison among stations of the geometric mean CPUE (number per 10-minute tow) of yellowtail flounder caught by trawl during the preoperational (November 1975 - July 1990) and operational (November 1990 - July 1997) periods fo: the sigt.ificant interaction term (Preop-Op X Station) of the ANOVA model (Table 5-23). Seabrook Operational Report,1997. 5-62 [ 5.0 FISH 5.4 EFFECTS OF SEABROOK STATION ( OPERATION winter flounder, yellowtail founder, and rainbow ., melt) indicating a potential plant impact (Table 5-24). The significant interaction term was The largest single impact on the fishes of the caused by a greater reduction in CPUE between Gulf of Maine since the 1970s has been commer- the preoperational and operational periods at one cial overfishing. Stocks of several species have station than at the others. Our BACI study either collapsed or are overexploited (NOAA design assumed that if there were no plant im-1995; NEFSC 1997). Of the selected groundfish pacts, trends in abundance, either increases or species, all except rainbow smelt have been decreases, would occur equally at all stations. subject to gross overfishing. Atlantic cod stocks However, a significant interaction term cculd have collapsed in Canada (Myers and Cadigan also be caused by a large-scale environmental 1995; Hutchings 19%) and are overexploited in change that occurred concurrently with the the Gulf of Maine (NEFSC 1997). Winter supposed plant impact (Smith et al.1993). A flounder stocks in the Gulf of Maine are overex- large-scale change could be a region-wide pertur-ploited (NOAA 1995) and the yellowtail flounder bation such as overfishing, climate change, stock on Georges Bank has collapsed (NEFSC disease, or another regional factor. Under these 1997). Although red hake are under-exploited, circumstances, a significant interaction term white hake are over-exploited. Any potential would result because CPUE would be reduced to impact due to the operation of Seabrook Station very low levels at all stations, including stations either did not occur, or was not detectable in the where it had previously been high. For exam-face of overfishing. ple, yellowtail flounder were most abundant at Station T1 during the operational period with a Rainbow smelt are not fished commercially, but geometric mean of more than 20, and was lowest there are indications that there has been a re- at Station T2 with a CPUE of about 4. After the gional decline in rainbow smelt abundance along stock collapsed, CPUE was reduced to less than the coast of New Hampshire. Catch per unit 3 at both stations. The interaction term was effort (catch per angler hour) in the Great Bay significant because the stock collapse resulted in Estuary in 1997 was the fifth lowest recorded and the largest reduction in CPUE (in absolute terms) ! about 50% of the long-term (1978-1982,1987- at a station where it had previously been highest. 1997) mean (NHFG 1998). Average egg depo-sition rates in 1997 were the lowest recorded Among the estuarine fish community there was indicating a potential recruitment problem in the no evidence of an impact by the operation of future. Although there were no significant Seabrook Station. There were no significant differences between the preoperational and differences between the preoperational and operational periods in seine CPUE, trawl CPUE operational periods for rainbow smelt and Atlan- ! decreased steadily from peaks in 1988 and 1989, tic silverside. Winter flounder CPUE was sign:f-before the plant became operational, to the icantly lower during the operational period. present low levels (Figure 5-8). CPUE of winter flounder in the seine peaked in 1980 and has generally declined since then, as The interaction term was significant for all of the have catches in the trawl (Figure 5-20). Because selected groundfish species, (Atlantic cod, hakes, the decline began before Seabrook Station be-l l 5-63 l [ I F J 5.0 FISH } I i Table 5-24. Sununary of Potential Effects of the Operation of Seabrook Station on the ] l Ichthyoplankton Assemblages and Selected Fish Taxa. Seabrook Operational Report, 1997. Operational Period Preoperational/ ' Similar to Operational Differ- Recent Abundance Species or Assem- Sampling Preoperational ences Consistent Trend in the Gulf of Status of blage Program Period?' among Stations?' Maine
- Fishery * -
Fish Egg Assemblages Ichthyoplankton seasonal occurrence Op = Preop yes abundance variable among taxa yes Fish larvae assemblages ichthyoplankton seasonal occurrence Op= Preop yes abundance variable among taxa yes Atlantic herring ichthyoplankton Op < Preop yes l Rainbow smelt trawl - no unknown lightly to seine Op = Preop yes unexploited Atlantic cod ichthyoplankton Op = Preop yes trawl - no decreasing overexploited J Pollock ichthyoplankton Op < Preop 0 yes Hakes ichthyoplankton Op = Preop yes red hake: increasing underexploited trawl - no white hake: increasing over exploited Atlantic silverside seine Op= Preop yes unknown unexploited Cunner ichthyoplankton Op= Preop yes unknown unexploited American sand lance ichthyoplankton Op = Preop yes decreasing in 1980s unexploited now stable (?) Atlantic mackerel ichthyoplankton Op= Preop yes increasing underexploited Winter flounder ichthyoplankton Op = Preop yes trawl - no decreasing overexploited seine Op < Preop yes Yellowtail flounder ichthyoplankton Op = Preop yes . trawl - no decreasing overexploited
- Based on results of numerical classification for assemblages and ANOVA for selected taxa.
- Based on Preop-Op X Stanon interacoon term from the MANOVA for assemblages arx1 ANOVA for selected taxa.
- For commercial species, from NOAA (1995).
5-64 5.0 FISH l l l 1 came operational, it was probably not due to any In conclusion, little impact to fishes can be plant impacts. attributed to Seabrook Station operation (Table 5-24). Most of the selected species are from very Compared to other New England marine power large and highly fecund stocks spawning through-plants, Seabrook Station entrains relatively few out the Gulf of Maine. Others, such as the fish eggs or larvae and apparently impinges rainbow smel: and Atlantic silverside, spawn in i fewerjuvenile and adult fish. Saila et al. (1997) estuaries away from the plant intake and have concluded that entrainment and impingement egg or larval life stages that are largely main-losses of winter flounder, pollock and red hake at tained in inshore areas. Atlantic cod, winter Seabrook Station has had a negligible adverse flounder, and yellowtail flounder continue to be l ecological impact. The location and design of overexploited by commercial fisheries and their the offshore intakes have worked as expected in stocks are presently declining. Other fishes, such reducing these impacts. In fact, most of the as Atlantic mackerel, were overfished and now impingement that does occur is not of pelagic have recovered. Catch of all the selected species fish, but demersal fish that predominantly en- in the Hampton-Seabrook area simply reflect counter the intake during storm events. In 1997, long-term, regional trends. Furthermore, the estimated impingement was the lowest since 1997 influence of regional environmental factors and (Appendix Table 5-3). There were few storms in interspecific interactions (e.g., American sand 1997 and this probably contributed to the low lance-Atlantic mackerel) introduces complexities impingement estimate. in any evaluation. Because of the apparently small numbers of fish of all life stages directly ; Egg entrainment in 1997 was within the range of removed by the plant and the concurrent changes l previous years, and was characterized by high in abundance at both nearfield and farfield sta- , estimates of cunner and silver hake eggs. tions in nearly every instance, the operation of Cunner eggs probably comprised most of the Seabrook Station does not appear to have affected cunner /yellowtail flounder group, and silver hake the balanced indigenous populations of fish in the entrainment was the highest recorded. Entrain- Hampton-Seabrook area. j ment oflarvae in 1997 was the highest observed, primarily due to high estimates for cunner and
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. 1979. Seasonal dispersal and Atlantic. Can. J. Fish. Aquat. Sci. 51: 589-habitat selection of cunner, Tautogolabrus 601.
adspersus, and young tautog, Tautoga onitis, in Fire Island Inlet, Long Island, New York. Reay, P.J.1970. Synopsis of biological data on Fish. Bull., U.S. 77: 255-262. North Atlantic sand eels of the genus Ammodytes. (A. tobianus, A. dubius, A. 5-70
4 5.0 FISH americanus and A. marinus). FAO Fish. Scott, W.B., and E.J. Crossman. 1973. Fresh-Synop. No. 82. 28 pp. water fishes of Canada. Bull. Fish. Res. Board. Can.184. %6 pp. [ Richards, S.W.1982. Aspects of the biology of Ammodytes americanus from the St. Law- , and M.G. Scott. 1988. Atlantic rence River to Chesapeake Bay, 1972-75, fishes of Canada. Can. Bull. Fish. Aquat. including a comparison of the Long Island Sci. 219. 731 pp. Sound postlarvae with Ammodytes dubius. J. Northw. Atl. Fish. Sci. 3: 93-104. Sette, O.E.1950. Biology of the Atlantic mack-erel (Scomber scombrus) of North America. Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Part II - migrations and habits. U.S. Fish. Brooker, E. A. Lachner, R.N. Lea, and W.B. Wildl. Serv. Fish. Bull. 51: 251-358. Scott. 1991. A list of common and scientific names of fishes from the United States and Sherman, K., C. Jones, L. Sullivan, W. Smith, Canada. 5th ed. Am. Fish. Soc. Spec. Pub. P. Berrien, and L. Ejsymont. 1981. No. 20. 183 pp. Congruent shifts in sand eel abundance in western and eastern North Atlantic ecosys-Safford, S.E , and H. Booke. 1992. Lack of tems. Nature (London) 291: 486-489. biochemical genetic and morphometric evi-dence for discrete stocks of northwest Atlan- Sinclair, M., and T.D. lies. 1985. Atlantic tic herring Clupea harengus harengus. Fish, herring (Clupea harengus) distributions in Bull., U.S. 90: 203-210. the Gulf of Maine-Scotian Shelf area in relation to oceanographic features. Can. J. Saila, S.B. 1%1. A study of winter flounder Fish. Aquat. Sci. 42:880-887. movements. Limnol. Oceanogr. 6:292-298. Sinclair, M., and M.J. Tremblay. 1984. Timing Saila, S.B., E. Lorda, J.D. Miller, R.A. Sher, of spawning of Atlantic herring (Clupea and W.H. Howell.1997. Equivalent adult harengus harengus) populations and match-estimates for losses of fish eggs, larvae, and mismatch theory. Can. J. Fish. Aquat. Sci. juveniles at Seabrook Station with use of 41: 1055-1065. fuzzy logic to represent parameter uncer-tainty. North Anerican Journal of Fisheries Smith, E.P., D.R. Orvos, and J. Cairns. 1993. Management 17:811-825. Impact assessment using the before-after-control-impact (BACI) model: concern and Saucerman, S.E., and L.A. Deegan. 1991. comments. Can J. Fish. Aquat. Sci. Lateral and cross-channel movement of 50:627-637.
. young-of-the-year winter flounder (Pseudopleuronectes americanus) in Waquoit Smith, W.G., J.D. Sibunka, and A. Wells.
Bay, Massachusetts. Estuaries 14:440-446. 1975. Seasonal distributions of larval flat-fishes (Pleuronectiformes) on the continental Scott, J.S. 1982a. Depth, temperature and shelf between Cape Cod, Massachusetts and salinity preferences of common fishes of the Cape Lookout, North Carolina. 1965-1966. Scotian Shelf. J. Northw. Atl. Fish. Sci. 3: NOAA Tech. Rep. NMFS SSRF-691. 68 29-40. pp.
.1982b. Selection of bottom type Sneath, P.H.A., and R.R. Sokal. 1973. Numer-by groundfishes of the Scotian Shelf. Can. J. ical taxonomy. The principles and practice Fish. Aquat. Sci. 39: 943-947. of numerical classification. W.H. Freeman Co., San Francisco. 573 pp.
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i 5.0 FISH } Sokal, R.R., and F.J. Rohlf. 1981. Biometry. Wheeler, J.P., and G.H. Winters. 1984. Hom- 1 W.H. Freeman and Company, San Francis- ing of Atlantic herring in Newfoundland co. 775 pp. waters as indicated by tagging data. Can. J. Fish. Aquat. Sci. 41: 108-117. j Stewart-Oaten, A., W.W. Murdoch, and K.E. Parker.1986. Environmentalimpact assess- Wilks, S.S. 1932. Certain generalizations in the ment: psuedoreplication" in time? Ecology analysis of variance. Biometrika 24: 471- - 67: 929-940, 494. Thomas, D.L., and G.J. Miller. 1976. Impinge- Winters, G.H., and E.L. Dalley. 1988. Meris- i ment at Oyster Creek Generating Station, tic composition of sand lance (Ammodytes i Forked River, New Jersey, from September spp.) in Newfcundland waters with a review l to December 1975. Pages 317-341 in L.D. of species designations in the Northwest l Jensen, ed. Third national workshop on Atlantic. Can. J. Fish. Quat. Sci. 45: 515-I entrainment and impingement. Ecological 529. Analysts, Melville, NY. Thomas, J.M. 1977. Factors to consider in monitoring programs suggested by statistical , analysis of available data. Pages 243-255 in l W. Van Winkle, ed. Proceedings of the conference on assessing the effects of power-plant-induced mortality on fish populations, Galinburg, TN, May 3-6,1977. Pergamon Press, New York. l Townsend, D.W. 1992. Ecology of larval l herring in relation to the oceanography of the l Gulf of Maine. J. Plankton Res.14: 467- l 493 l Underwood, A.J. 1994. On beyond BACI: Sampling designs that might reliably detect environmental disturbances. Ecological Applications. 4(1):3-15. Ware, D.M., and T. C. Lambert. 1985. Early life history of Atlantic mackerel (Scomber scombrus) in the southern Gulf of St. Law-rence. Can J. Fish. Aquat. Sci. 42: 577-592. Westin, D.T., K.J. Abernethy, I.E. Meller, and B.A. Rogers.1979. Some aspects of biol-ogy of the American sand lance, Ammodytes americanus. Trans. Am. Fish. Soc.108: 328-331. 5-72
5.0 FISH Appendix Table 5-1. Finfish Species Composition by Life Stage and Gear, July 1975 - Decetnber 1997. Seabrook Operational Report,1997. Ichthrpplankton Adult apc_ Juvenile 1ows Fm: ssh Scientific Name Common Name Eggs Larvae Trawls ke$ Seines Impingement Acipenser atyrhynchus Atlantic sturgeon R* Alosa aestivalis blueback herring - R C C R Alosa mediocri; hickory shad - R AlosapseudcNarengus alewife - 0 0 0 C Alosa sapidissima American shad - R O O R Alosa sp. river herring R -- - - Ammodytes americanus American sand lance A O R O C Anathichas lupus Atlantic wolffish R R R Anchoa hepsetus striped anchovy R Anguilla rostrata American eel C R R Apeltes quadracus fourspine stickleback R hr'o$o$p"halus Aspidophoroides alligstoriish C O monopterygtus Brevoortia tyrannus Atlantic menhaden O O R O R Brosme brosme cusk O O R Carattr hippos crcvallejack R Centropristis striata black sea bass R R R Conger oceanicus conger cel R Clupea harengus Atlantic herring C O A O C Clupeidae herrings - - - - - C l Cryptacanthodes maculatus wtymouth O R C Cyclopterus lumpus lumpiish C R R R R Enchelyopus cimbrius , fourbeard rockling C C O R
\
fundulus sp.' killifish C R Gadus mothua Atlantic cod - C C O R R Gadus /Melanogramtruts Atlantic codthaddock C - - - - Gasterosteus sp.d stickleback R R C R Glyptocephalus witch flounder C C O cynoglossus Hemitripterus americanus sea raven O C O R C Hipooglossoides American plaice C C O platessoides Hippoglossus hippoglossus Atlantic halibut R
. Labridae/Pleuronectes cunnerly'ellowtail A -- - -- -
tloundet l Liparis atlanticus Atlantic seasnail R C - -- - Liparis coheni guli snaillish C - -- -- Liparis sp/ snailfish R - O C Lophius americanus goosetish R O O R R Lumpenus lumpretaeformis snakeblenny O R Lumpenus maculatus daubed shanny R R Macrozoarces americanus ocean pout O C R R l Melanograrranus aeglefinus haddock - O C R R 1 5-73 (continued) l [
s.o nsu } Appendix Table 5-1. (Continued) l ' Ichthgankton Adultg g. venile- 3 Scientific Name Common Name Eggs Larvae Trawls b Seines Impingemeni
/:
I Menidia menidia Atlantic silverside R O R A A Menticirrhus saratilis northern kingfish R R 3 Merluccius bilinearis silver hake C C C C R R Microgadus tomcod Atlantic tomcod R R O R Monocanthus hispidus planchead filefish R Morone americana white perch R R i Morone saxatilis striped bass R R R Mugil cephalus striped mullet R Mustelus canis smooth dogiish R Myaxocephalus aenaeus grubby C O R O C Myoxocephalus longhorn sculpin C A O R R < octodecemspmosus
} '
Myoxocephalus scorpius shorthorn sculpin C O R R R Odontaspis taurus sand tiger R R Oncorhynchus kisutch col'o salmon R R Oncorhynchus mykiss rainbow trout R Ophidion margination striped cusk cel R Osmerus mordax rainbow smelt O C O C C Paralichthys dentatus summer flounder R R R Paralichthys oblongus fourspot flounder O O C R R . Peprilus triacanthus butterfish O O R O R R Petromy:on marinus sea lamprey R R Pholis gunnellus rock gunnel C O R R C Pleuronectes americanus winter flounder C C O C C Pleuronectesferrugineus yellowtail flounder - C A R R C Pleuronectes putnami smooth t1ounder R R C Pollachite virens pollock C C C C O C Pomatomus saltatrix bluefish O O Prionotus carolinus northern searobin - - C R R Prionotus evolans striped s::arobin - - R i Prionotus sp. searobin O R - - - Pungitius pungitius ninespine stickleback C j Raja sp.: skate C R C l Salmo trutta brown trout O Salvelinusfontinalis brook trout R Scomberjaponicus chub mackerel Scomber scombrus Atlantic mackerel A A R C R R Scophthalmus aquosus windowpane C C C R O C Sebastes sp." redfish O Selene scrapinnis Atlantic moonfish R Sphoeroides maculatus northern puffer R R R Squalus acanthias spiny dogfish R C R Stenotomus chrysops scup R O R R Stichaeus punctatus Arctic shanny O S;ngnathusfuscus northern pipefish C O R O C 5-74 (continued) '
5.0 FISH Appendix Table 5-1. (Continued) Ichthroplankton Adult apc. Juvenile
'Idws Fm tsh Scientific Name Common Name Eggs Larvae Trawls Ike$ Seines Impingement Tautoga onitis tautog -
O R R Tautogolabrus adspersus cunner - A O R C Torpedo nobiliana Atlantic totpedo R R Triglops murrayi moustache sculpin O R Ulvaria subbtfurcata radiated shanny C O R Urophycis sp.' hske C C A O C C 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, Enchelyopus/Urophycis, Myoxocephalus sp., Urophycis chuss). 6 Occurrence of each species is indicated by its relative abundance or frequency of occurrence for each life stage or gect type: A = abundant (a 10% of total catch over all years) C = common (occurrmg in 210% of samples but < 10% of total catch) O = occasional (occurring in <10% and a1% of samples) R = rare (occurring in < 1% of samples)
= not usually identified to this taxonomic level at this life stage
) Predommantly Fundulus heteroclitis, mummichog, but may include a small number of Fundulus majalis, striped killifish. d Two species of Gasterosteus have been identified from seine samples: G. aculeatus, threespine stickleback; and G. wheatlandi, blackspotted stickleback (both occurring commonly). May also include a small number of tautog. Three species of Liparis have been identified from trawl samples: L. atlanticus, Atlantic seasnail; L. coheni, gulf snailfish; and L. inquilinus, inquiline snailfish. 8 Four species of Raja have been identified from trawl sar v.es: R. radiata, thorny skate (common); R. erinacea, little skate (common); R. ocellata, winter skate (occasional); and R. eglanteria, clearnose skate (rare). D Sebastes norvegicus, golden redfish; S. mentella, deepwater redfish; and S. fasciatus, Acadian redfish, have been reported to occur in the northwest Atlantic. Sebastes in coastal New Hampshire waters are probably S. fasciatus (Dr. Bruce B. Collette, U.S. National Museum, pers. comm. April 1982), but larval descriptions are insufficient to allow distincticn among the three species.
' Three specie of Urophycis have been identified from trawl samples: U. chuss, red hake (common); U tenuis, white hake (commou); and U. regia, spotted hake (rare).
5-75
5.0 FISH Appendix Table 5-2. Subsetting Criteria Used in Analyses of Variance for the Selected Finfish Species. Seabrook Operation Report,1997. Species Gear Season Preoperational Operational Pooling Deletions Atlantic cod Trawl Nov-Jul 1975-1990 1990-1997 Nov-Dec with Nov-Dec following year 1997 Atlantic cod Ichthyo Apr-Jul 1987-1990 1991-1997 None None Atlantic herring Ichthyo Oct-Dec 1986-1989 1990-1997 None None Atlantic silverside Seine Apr-Nov 1976-1984; 1986-1989 1991-1997 None 1990 Atlantic mackerel Ichthyo May-Aug 1987-1990 1991-1997 None Aug 1990 l Atlantic sand lance Ichthyo Jan-Apr 1987-1990 1991-1997 None None Cunner Ichthyo Jun-Sep 1987-1989 1991-1997 None 1990 Hakes Trawl Nov-Jul 1976-1990 1990-1997 Nov-Dec with Nov-Dec following year 1997 Hakes Ichthyo Jul-Sep 1986-1989 1991-1997 None 1990 1 Pollock Ichthyo Nov-Feb 1986-1989 1990-1996 Jan-Feb with previous 1997 year Rainbow smelt Trawl Nov-May 1975-1990 1990 1997 Nov-Dec with Nov-Dec following year 1997 Rainbow smelt Seine Apr Nov 1976-1984;1986-1989 1991 1997 None 1990 l Winter flounder Trawl Nov-Jul 1975-1990 1990-1997 Nov-Dec with Nov-Dec following year 1997 Winter flounder Seine Apr-Nov 1976-1984; 1986-1989 1991-1997 None 1990 Winter flounder Ichthyo Apr-Jul 1987-1990 1991 1997 None None Yellowtail flounder Trawl Nov-Jul 1975-1990 1990-1997 Nov-Dec with Nov Dec following year 1997 Yellowtail flounder Ichthyo May-Aug 1987-1990 1991 1997 None Aug 1990 I l i n 5-76
{ 5.0 FISH Appendix Table 5-3. Species Cornposition, Annual Totals, and Four-Year Total of Finfish, and Arnerican Lobster Impinged at Seabrook Station From 1994 to 1997. Seabrook Operational Report,1997'. Species 1994 1995 1996 1997 Total Alewife 0 8 1753 2797 4558 American lobster 31 16 31 20 98 American shad 0 0 20 21 41 American sand lance 1215 1324 823 182 3544 American eel 0 5 6 42 53 Atlantic menhaden 0 7 97 0 104 Atlantic torpedo 0 1 5 0 6 Atlantic silverside 5348 1621 1119 210 8298 Atlantic tomcod 1 0 0 0 1 Atlantic wolffish 0 2 13 0 15 Atlantic cod 58 119 94 69 343 Atlantic mackerel 0 0 1 0 1 Atlantic herring 0 0 485 350 835 l Atlantic moonfish 0 3 0 0 3 l Black sea bass 0 3 0 0 3 Blueback herring 13 0 111 323 447 Butterfish 3 14 3 223 243 Cunner 32 342 1121 233 1795 Cusk 0 0 19 0 19 i Flounders 77 0 0 0 77 I Fourbeard rockling 0 6 0 0 6 I Fourspot flounder 2 1 2 3 8 Goosefish 3 13 0 0 16 Grubby 2678 2415 1457 430 6980 Haddock 0 1 397 0 398 Hakes 2822 2188 156 122 5288 Herrings 514 231 72 218 1035 Killifishes 4 0 0 0 4 12fteye flounder 0 0 2 0 2 1.onghorn sculpin 105 165 84 88 442 Lumpfish 182 190 51 62 485 Mummichog 0 0 47 24 71 Northern kingfish 0 0 2 0 2 Northern pipefish 188 579 1200 243 2210 Northern puffer 0 0 0 5 5 Northern searobin 0 0 0 11 11 5-77 (continued)
i 5.0 FISH
}
Appendix Table 5-3. (Continued)
]
Species 1994 1995 1996 1997 Total x Ocean pout 0 l 6 1 0 7 ; Planchead filefish 0 15 0 0 15 Pollock 1681 899 1835 379 4794 Radiated shanny 0 92 40 2 134 Rainbow smelt 545 213 4489 365 5612 l Red hake 1 16 1478 371 1866 Righteye flounder 0 3 4 0 7 l Rock gunnel 494 1298 1122 459 3373 Sand tiger 0 0 57 0 57 Sculpins 205 0 0 0 205 Scup 0 14 9 0 23 Sea raven 78 125 1015 223 1441 l Sea lamprey 0 0 1 6 7 Shorthorn sculpin 14 156 282 123 575 Silver hake 0 49 58 108 215 Skates 190 157 225 177 749 Snailfishes 180 165 1013 351 1709 Spiny dogfish 1 0 6 0 7 Striped bass 0 4 1 0 5 Striped cusk-eel 0 0 0 3 3 Summer flounder 3 0 0 0 3 Tautog 0 0 34 0 34 Threespine stickleback 67 155 320 174 716 l Unidentified 6 40 88 49 183 White hake 1 7 967 0 975 White perch 0 0 4 0 4 Windowpane 980 943 1164 1688 4775 Winter flounder 1435 1171 3231 468 6305 Wrymouth 55 9 206 3 273
- Yellowtail flounder 0 1149 4 23 1176 TOTAL 19,212 15,926 26,825 10,648 72311
- Impingement data prior to October 1994 was underestima:ed.
5-78
I 6.0 SEALS I TABLE OF CONTENTS PAGE 6.0 SEALS
SUMMARY
. . . . . . . .. ..... ........ . . ..... ........ . .... 6-ii i LIST OF TABLES . ... ....... .... .. ... .. . .. . .. . . . 6-iii 6.1 METHODS . . . . . . . . ... ... ......... . .......... ....... 6-1 1 6.2 RESULTS AND DISCUSSION . . . . ... .... ...... . . . . . ... 6-1
- 6.2.1 Seal Entrapments ... ... .... . . .... . .. . . 6-1 6.2.2 Population Dynamics and Distribution of Seal Species Entrapped ... .. . 6-5 6.2.3 Effects of Seabrook Station Operation . ..... ... . . . . ... . 6-6
6.3 REFERENCES
CITED . ..... . . .. . . .. . . ... . .. 6-7 l I l l l l l i l l 6-i t
]
6.o seus I
SUMMARY
l An estimated 36 to 42 seals have been entrapped in Seabrook Station's cooling water intakes between 1993 and 1997. Seal species entrapped were the harbor seal (Phoca vitulina), harp seal (Phoca groenlandica), hooded seal (Cystophora cristata) and grey seal (Halichoerus grypus). In 1997 an estimated nine young-of-the-year (YOY) seals were entrapped, including seven harbor seals and two grey seals. These seal , entrapments are considered incidental lethal takings under the Marine Mammal Protection Act and have been reported to the National Marine Fisheries Service (NMFS), Northeast Region, the federal agency responsible for the protection of marine mammals. Since 1993, necropsies of seal remains have been performed by the New England Aquarium, which also has the lead responsibility for administering the Marine Mammal Stranding Network for the region. The entrapment of seals in recent years coincides with increased numbers of seals observed along the nearby coastline and the overall growth of the seal population in the Gulf of Maine. Based on the large seal population in the region and the small number of seals entrapped by the Station's cooling water intakes, the operation of Seabrook Station had a negligible effect on the population or stocks of seals. In June 1997, North Atlantic submitted to the National Marine Fisheries Service an application for a small take exemption permit for the incidental taking of a small number of seals as a result of Station operations. In August,1998, the National Marine Fisheries Service published in the Federal Register, for public comment, a proposed rule which would grant the exemption permit. In parallel with the permit application, North Atlantic conducted studies to determine if there is an effective, implementable means to eliminate or minimize seal entrapments without jeopardizing Station safety or reliability. These studies included structural barriers on the intakes and acoustic deterrent devices. l i I l l 1 6-ii
1 l 6.0 SEALS i I 1 l LIST OF TABLES ! PAGE 6-1. Estimated Number of Seals Entrapped in the Cooling Water System of Seabrook Station During 1990 through 1997 .. .. .. ... . . .... .. ..... . . 6-2 , 1 1 6-2. Seal Takes at Seabrook Station by Date in 1997, Including Necropsy Results ... .. 6-3 6-3. Number ofIntact Seal Carcasses Recovered by Month,1993 to 1997 . .. ... 6-2 6-4. Seal Monitoring at the Inner Sunk Rocks in 1997 . .. ....... ... .... 6-4 3-iii
6.0 SEALS \ l 6.1 METHODS The nearest seal haul-out area is at the Inner j Sunk Rocks, located about 1,000 m from the Weekly visual inspections of Seabrook Station's inlet to Hampton Harbor and 1,800 m from the ) l Circulating Water System and Service Water cooling water intakes. A weekly count of seals I System forebays were conducted from January hauled-out at the Inner Sunk Rocks at low tide 1995 to November 1996 for the presence of began in March 1997 to determine if there was a seals. Inspection frequency increased to at least relationship between the number of seals in the once per day beginning in December 19% and nearfield area , and entrapment at the station. beginning in October 1997 inpsections were increased to at least twice per day. Weekly An aerial seal survey of the New Hampshire inspections of the intake transition structure, coast was performed by the University of Maine began in September 1997, and continued in June in June 1997, under contract to the National through November 1998. Marine Fisheries Service. Prior to 1996, intact seal remains were recovered 6.2 RESULTS AND DISCUSSION only from screenwash debris. Since 1996 seal remains observed in the forebays have also been 6.2.1 Seal Entrapments recovered. In addition, beginnning in October 1997, at least two screen wash assessments per Intact seal carcasses and seal remains have been week were made to ensure that any seal remains identified in Seabrook Station's cooling system were properly identified. intake forebays and screenwash debris since 1993 as an apparent result of live seals entering the Pecovered seal carcasses and seal skulls were Station's intal;e structures and then swimming or delivered for identification and necropsy to the being drawn through the intake tunnel to the New England Aquarium in Boston, Massachu- pumphouse. The seal species entrapped by setts. Observations made and recorded by the Seabrook Station from 1993-1997 were predomi-New England Aquarium included the species, nantly harbor seal (Phoca vitulina) although two age, sex, weight, general health, and stomach grey seals (Halichoerus grypus), one harp seal contents of entrapped seals, when possible. Data (Phoca groenlandica) and one hooded seal gained from these necropsies may be useful in (Cystophora cristata) were also id ntified. determining the reasons for the seal entrapments Ninteteen of the 21 seals for which age estimates and for evaluating potential means of eliminating were made were determined to be YOY. Be-or reducing the entrapments. cause observations sometimes consisted of only partial remains, it was not always possible to The National Marine Fisheries Service (NMFS) determine if the remains were from one or more in Gloucester, Massachusetts was immediately seals. The estimate of the total number of seals notified by telephone when an intact seal carcass entrapped through 1997 was between 36 and 42. was found either in the forebays or in screenwash The estimated number of seals entrapped from debris and a written entrapment incident report 1993 to 1997 is shown in Table 6-1. was submitted to the NMFS within 14 days. 6-1
r 6.0 SEALS Table 6-1. Estimated Number of Seals En- were the first grey seals entrapped by the Station. trapped in the Cooling Water System of Sea- Table 6-2 (following page) shows the 1997 brook Station During 1990 tmough 1997. ndividual seal entrapments by date and necropsy Seabrook Operational Report,1997. result. Year Number of Seals 1990 0 1991 0 Although seal takes are possible year-round, most 1992 o entrapments occured from August through Octo-1993 2 ber (Table 6-3) Because these seals were intact 1994 7 when discovered, it is reasonable to assume that 1995 6-7 the seals were entrapped close to the date of 1996 12-17 g 9 observation. TOTAL 36-42 Table 6-3. Number of Intact Seal Carcasses Entrapped seals were first observed in October, Recovered by Month, 1993-1997. Seabrook 1993, eight years after cooling water was first Operational Report,1997. pumped through the offshore intake structures in Month Number of Seals 1985 and more than three years after Seabrook y,n o Station began commercial operations in August, Feb 0 j 1990. The cooling system operated intermittently Mar o j and at reduced flow rates during the period 1985 Apr 0 May 0 ; to 1990. Jun 2 Jul 2 In some instances, intact seal carcasses were Aug 5 washed from the traveling screens and observed Sep 3 0" 10 in screenwash debris where they were easily Nov 3 recovered. At other times they were discovered k 2 floating in the cooling water system forebays TOTAL 27 from which recovery is difficult. Twenty-three of the 27 intact seal carcasses observed from Because the low horizontal flow velocity (0.5 feet 1993 through 1997 were recovered and trans- per second) into the intakes is unlikely to draw ported to the New England Aquarium, where seals involuntarily inside the intake structure, it necropsies were performed. In addition to the is likely that entrappea seals first swim into a intact carcasses, skull fragments and other bones velocity intake cap, either out of natural curiosity have been recovered from screenwash debris. or in search or pursuit of prey. Inside the intake Whenever possible, recovered skulls or skull velocity cap, the flow rate increases as the seal fragments were also analyzed by the New Eng- approaches the center vertical riser shaft that land Aquarium. connects to the intake tunnel. This increasing velocity and downward-turning flow may cause Nine intact seals were recovered from Seabrook the seal to be drawn into the riser, where the Stations cooling water system in 1997, including seals may become disorientated from the relative seven harbor seals and two grey seals. These lack of light inside the velocity cap, and the 6-2
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l l 6.0 SEALS l ownward current may prevent an effective escape Tal,le 6-4. Seal Monitoring at the Inner Sunk response. This would especially be the case for Rocks in 1997. Seabrook Operational Report YOY seals, which are relatively inexperienced I997* and lack the swimming strength of older seals. A Number Number seal that is unable to exit, is subsequently drawn Date of Seals Date of Seals through the 3-mile intake tunnel where it drowns Mar 5 42 Aug 6 0 in passage and is carried into a pumphouse 11 31 12 o forebay- 17 48 19 8 24 35 25 5 1 During full power operations, Seabrook Station ' Apr 3 45 Sep 9 17 operates with all cooling water system and two ' 10 11 18 24 service water system pumps in operation. For an object traveling with the current under these 16 47 23 23 conditions, the minimum transit time from the 23 26 oct to 18 offshore intake structures to the forebay is ap- 30 38 14 54 proximately 80 minutes. Transit time is longer if May 5 16 23 53 fewer pumps are operating. A seal entrapped in 13 53 29 48 the intake would not be able to survive an 80 minute or longer transit to the forebays. 29 1 11 59 Seal monitoring activities of the nearfield area Jun 3 3 19 39 began in March 1997 (Table 6-4). Seal counts to o 24 18 were greatest during March through May and 16 o Dec 4 30 September through December, when recreational 23 1 8 41 boat traffic near the Inner Sunk Rocks, was
, 4 reduced. Increased boat traffic in this area tends 2 22 22 to prevent seals from hauling out. Several dozen 14 0 seals (up to 59) were observed hauled on the rocks during low boat traffic periods. The 23 o number of seals observed hauled out during 30 o higher boat traffic periods was no greater than eight. No seals were observed during five weeks s a relationship between the number of seals ob-in the peak summer period.
served and seal entrapment only for August through December. Despite this apparent rela-Alhough many seals were observed on the Inner tionship, there is no evidence that the seals Sunk Rocks in March through May, few seals entrapped were using the Inner Sunk Rocks. were entrapped during this period. In contrast, Most of the seals entrapped were YOY, but no in August through December when the seals YOY seals were observed on the Inner Sunk returned to the Inner Sunk Rocks, seal entrap-Rocks in 1997. ment increased. Therefore, it appears that there 64
6.0 SEALS 6.2.2 Population Dynamics and Distribution and Mate 1983). Population estimates from these of Seal Soccigs Entrapoed surveys represent the minimum population size because the census is not corrected for seals that The populations of all four seal species likely to may be in the water at the time of counting be entrapped by Seabrook Station, harbor seal, (Kenney and Gilbert 1994). Since adult and harp seal, hooded sea and grey seal have been juvenile males typically only haul out about once increasing in the Gulf of Maine since the passage every six low tides, the total population in the of the Marine Mammal Protection Act (MMPA) surveyed areas may be underestimated by about in 1972 (Kenney and Gilbert 1994; Blaylock et 30 to 40% (Gilbert pers comm.). In addition, not al.1995). This is particularly well documented all potentia! haul-out locations are surveyed, for harbor and grey seals, the two most common particularly sites that may be upstream in tidal seals in the Gulf of Maine. Harbor seals have rivers (Gilbert pers. comm.). The annual increased nearly five-fold (Blaylock et al.199) changes in these minimum counts, however, while the grey seal population has also increased provide a relative index of population growth. greatly along the New England coast (Gilbert According to the 1993 census, the minimum pers. comm. in Blaylock et al.1995). The Grey uncorrected population estimate of harbor seals seal population in the Gulf of Maine is estimated along the Maine coast at that time was 28,810 to be increasing at an annual rate of 7.4% (Blaylock et al.1995). This represents an annual (Hammill et al.1998). Harbor and grey seals rate of increase of 8.7% along the Maine coast have also been dispersing southward from Maine between 1981 and 1993. rookeries (Paton 1988; Payne and Schneider 1984). Harp and hooded seal populations may Most of the seals taken by the operation of also be increasing in U.S. waters as evidenced by Seabrook Station were harbor seals. Over 80% increased sightings and strandings (Blaylock et of the harbor seals, for which ages have been al.1995; Stevick and Fernald 1998). estimated, were YOY. Although no local census data specific to New Hampshire waters is avail-Harbor seal population censuses have been made able, the adjacent Southern Maine coast for the coast of Maine in 1981,1982,1986 and (Pemaquid Point to the Isles of Shoals) is on the 1993 (Kenney and Gilbert 1994). Estimates were southern edge of the breeding range for harbor based on aerial surveys taken along the Maine seals. Pups make up a greater percentage of the coast during the May to June pupping season. population in the Downeast (Cobscook Bay to An aerial servey of the Maine and New Hamp- Schoodic Point) and Middle (Schoodic Point to shire coasts was also conducted in June 1998, Pemaquid Point) coast regions (Kenney and however, no seals were identified during the New Gilbert 1994). In the Southern coast region, only Hampshire survey (Gilbert pers. comm.). This 8.3% of the seals counted in the 1993 survey technique was used because seals regularly haul were pups. The furthest south that newborn pups out to give birth, nurse, thermoregulate and rest hase been observed was a single observation of (Kenney and Gilbert 1994). The largest number one pup on Shag Rock in the Isles of Shoals, of seals at haul-out sites have been observed about 10 miles north of the Seabrook Station during the pupping season (Sullivan 1980; Brown intakes. 6-5
6.0 SEALS The grey seal range is centered in the Gulf of St. wintering areas in Canada and Greenland Lawrence and is distributed primarily in eastern (Stevick and Fernald 1998). Canadian waters (Blaylo:k et al.1995). ' Small numbers of animals including pups, however, The total estimated population of hooded seals in have been observed on several isolated islands Canada was about 400,000 to 450,000 seals along the Maine coast and in Nantucket-Vineyard (Stenson 1993) and the population appears to be Sound, Massachusetts (Katona et al.1993; Rough increasing. 1995). Although range-wide grey seal population estimates are not known, the estimate for individ- 6.2.3 Effects of Seabrook Station Operation uals that are one year or older rose from between 100,000 and 130,000 animals in the North Atlan- The populations of the seal species entrapped by tic in 1986 (Stobo and Zwanenburg 1990) to Seabrook Station are increasing and their ranges 143,000 animals in 1993 (Mohn and Bowen are extending further south (Blaylock et al. 1994). Grey seals were occasionally observed in 1995). The small number of seals entrapped as the summers on the coast of Maine during the a result of the operation of Seabrook Station, has mid-1970s and the 1980s but have become more not affected, and is unlikely to affect the popula-common in the 1990s. The population in Maine tion or stocks of these seal species. waters has increased from about 30 in the early 1980's (Gilbert pers. comm. in Blaylock et al. The Marine Mammal Protection Act as amended 1995) to between 500-1,000 animals in 1993 in 1994 requires the NMFS to produce stock (Kenney and Gilbert 1994). The minimum assessment reports for all marine mammal stocks uncorrected population estimate for all US waters in waters within the US Exclusive Economic is about 2,000 seals in 1994 (Blaylock et al. Zone. As part of that assessment, NMFS is 1995). required to estimate the potential biological removal (PBR) for each stock of each species. No estimate exists for the number of harp or The PBR is the maximum number of marine hooded seals in US waters, as these species are animals, not including natural mortalities, that found primarily in northern Canadian waters. may be removed from a marine mammal stock The population of both species appears to be while allowing the stock to reach or maintain its growing in Canadian waters (Blaylock et al. optimum sustainable population (OSP). If the 1995). The total population of harp seals in number of animals removed from the stock Canada was estimated at approximately 3 million exceeds the PBR, the stock is declared " strate-seals (Shelton et al.1992) and the average annual gic", and additional conservation measures are growth rate was estimated as 7% (Stenson 1993). initiated (Barlow et al.1995). If the number Prior to 1994, harp seals were almost unkown removed is less than PBR, the stock is considered along the Maine coast. There were no confirmed to be within the range of OSP. reports of harp seals between May 1988 and January 1994, however, five individual harp The determinations of PBR were published by seals were reported in 1994, eleven in 1995 and NMFS in Blaylock et al. (1995). For harbor ten in 1996. The increased sightings in Maine seals, the PBR was determined to be 1,729 seals. are probably related to dispersal from traditional The total annual take estimated from sources 6-6
6,0 SEALS other than Seabrook Station was 476 harbor seals Hammill, M. O., G. B. Stenson, R. A. Myers, (Blaylock et al.1995; p. I13). The maximum and W. T. Stobo.1998. Pup production and estimated annual mortality at Seabrook Station Population trends of the grey seal (Halichoerus grypus) in the Gulf of St. L.aw-was 17 in 1996 which is less than 4% of the total rence. Can. J. Fish Aquat. Sci. 55: 423-take and 1% of the PBR. Therefore, the addi- 430, tional take from this source does not change the status of the stock or impact the stock of harbor Katona, S., V. Rough, and, D. T. Richardson. seals significantly. 1993. A field guide to whales, porpoises, and seals from Cape Cod to Newfoundland. 4th ed. Washington: Smithsonian Institu-No PBR has been calculated for harp or hooded tion. 316 p. seals because data are not available to estimate the stocks in US waters. However, because they Kenney, M.K. and J.R. Gilbert. 1994. Increase must be considered a part of the Canadian stocks in harbor and grey seal populations in Maine. (where reproduction occurs), and because num- P 0 e o' 8 ' " a ,p (9 tio ' ri Fs bers are increasing in Canada, the incidental ies Service, Northeast Fisheries Center, takes at Seabrook Station are insignificant. The Woods Hole, MA. population of both species appear to be expand-ing seasonally southward into US waters. Prior Mohn, R. and W.D. Bowen.1994. A model of to the late 1980s, few were recovered in the Gulf Sr y Seal Predation on 4VsW cod and its effects on the dynamics and potential yield of of Maine. Since then, strandings have increased cod. DFO Atlantic Fisheries Res. Doc. by an order of magnitude (Mooney-Seus and 94/64. Stone 1995). Mooney-Seus, M.L. and G.S. Stone. 1995.
6.3 REFERENCES
CITED Pinniped Populations in the Gulf of Maine, Status, Issues and Management. New Eng-land Aquarium Aquatic Forum Series Report Barlow, J., S. L. Swartz, T. C. Engle, and P. R. 95-1. Wade.1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation, Paton, D. 1988. Grey seals establish critical Background, and a Summary of the 1995 marine habitat in Nantucket Sound. Biol. Assessments. U.S. Dep. Conuner., NOAA Bull. Mar. Biol. Lab. Woods Hole. 175:312. Tech. Memo. NMFS-OPR-66, 73 p. Blaylock, R.A., J.W. Hain, L.J. Hansen, D.L. Payne, P., M. and D.C. Schneider. 1984. Palka, G.T. Waring.1995. U.S. Atlantic and Yearly changes in abundance of harbor seals, Gulf of Mexico Marine Mammal Stock Phoca vitulina, at a winter haul-out site in Assessments. NOAA Tech. Memo. Massachusetts. Fis5ry Bulletin. 82(2):440-NMFS-SEFSC-363, 211 p. 442. Brown, R.F. and B.R. Mate.1983. Abundance, Rough, V. 1995. Grey seals in Nantucket movements, and feeding habits of harbor Sound, Massachusetts, winter and spring, seals, Phoca vitulina, at Netarts and 1994. Final report to Marine Mammal Tillamook Bays, Oregon. Fishery Bull. Conservation Commission, Contract 81(2):191-301. T10155615,28 pp. NTIS Pub PB95-191391. 6-7
6.0 SEALS Shelton, P.A., N.G. Caddigan and G.B. Stenson. 1992. Model estimates of harp seal produc-tion trajectories in the Northwest Atlantic. CAFSAC Res. Doc. 92/89,23 p. Stenson, G.B.1993. The status of pinnipeds in the Newfoundland region. NAFO SCR Doc. 93/94. Stevick, P.T. and T. W. Fernald. 1998. In-crease in extralimital records of harp seals in Maine. Northeastern Naturalist. 5(1): 75-82. Stobo, W.T. and K.C.T. Zwanenburg. 1990. Grey seat (Halichoerus grypus) pup produc-tion on Sable Island and estimates of recent production in the northwest Atlantic. Pages 171-184 in W.D. Bowen (editor), Population biology of sealworm (Pseudoterranova decipiens) in relation to its intermediates and seal hosts. Can. Bull. Fish, and Aq. Sci. 222. Sullivan, R.M. 1980. Seasonal occurrence and haul-out use in pinnipeds along Humboldt County, California. J. Mammal. 61:7754-760. 1 i 6-8 l
{ 7.0 MARINE MACROBENTHOS [ TABLE OF CONTENTS PAGE 7.0 MARINE MACROBENTHOS I S UM M A RY . . . . . . . . . . . . . . ... . . . ... .. . . ... .. .... 7-ii LIST OF FIGURES . . . . . . . . .. ...... . ..... ... . ... . . 7-iv LIST OF TABLES . . . . . .... . .. .. .. . ... . . . 7-vi LIST OF APPENDIX TABLE. . . ... .. . . .. . . ..... . .. 7-viii
7.1 INTRODUCTION
... . ... . . . .. . . ... . . . 7-1 7.2 METHODS . . . ... . . . . . . . . .. . . . ... . . . .. 7-2 1
7.2.1 Field Methods . . ... . .. ... . . .. .. 7- 2 7.2.2 Laboratory Methods . ... ... ..... . . 7-4 7.2.3 Analytical Methods . .... . ..... .. .. . .. . . 7- 4 7.2.3.1 Destructive Monitoring Program: Community Analyses . . . . 7-4 7.2.3.2 Destructive Monitoring Program: Selected Species Analyses 7- 5 7.2.3.3 Non-Destructive Monitoring Program: Selected Species Analyses . 7-8 7.3 RESULTS AND DISCUSSION . .. . . .. ..... 7- 8 7.3.1 Marine Macroalgae . .. . .. ... . . .. . 7-8 7.3.1.1 Horizontal Ledge Communities . . . . .. 78 7.3.1.2 Selected Species . . .. . .. .. . .. . 7-24 7.3.1.3 Non-Destructive Monitoring Program . .. . . 7-26 7.3.2 Marine Macrofauna . . ...... .. ..... . . . 7-44 7.3.2.1 Horizontal Ledge Communities .. .... . . . . . 7-44 7.3.2.2 Selected Benthic Species . . .. ... . ... . . 7-61
7.4 CONCLUSION
S .. . ... ... . . ...... . ... ... 7-74 7.4.1 Introduction . . . . .. ... . .. . . . . . . . .. . 7-74 l 7.4.2 Evaluation of Potential Thermal Plume Effects ... . . . . . 7-77 7.4.3 Evaluation of Potential Turbidity Effects on the Mid-Depth / Deep Benthic Communities .. . .. .. . ... . . . . . 7-79 7.4.4 Overall Effect of Seabrook Operation on the Local Marine Macrobenthos . 7-82 l i
7.5 REFERENCES
CITED . . .. . . .. .. . . . 7-83 7-i
7.0 MARINE MACROBENTHOS
SUMMARY
l J 1 Submerged 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 1 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 l 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. I Thermal impacts to macroalgae, such as shifts in abundance or occurrence of typically cold-water, warm-water or nuisance species were not evident. Although some typically warm-water taxa occurred for the first time during the operational period, some cold-water taxa were also collected more frequently and other warm-water taxa less frequently. Intertidal and shallow subtidal algal and faunal communities showed little change in community structure as determined through destructive sampling. Selected taxa studies in the intertidal zone revealed a few changes of note. Percent frequency of occurrence of Ascophyllum nodosum increased significantly between periods (Preop =31.0%; Op=38.8%) in the nearfield area during the operational period, while Fucus resiculosus declined significantly (Preop =33.7%; Op=4.5%). Long-term trends in annual mean percent frequency of occurrence of each of these fucoid species indicate that these shifts are not likely related to Station operation. In the shallow subtidal zone, only the kelp Laminaria digitata, a minor component of this community, exhibited a change in density between periods that differed between the nc .rfield and farfield stations. Densities declined significantly (Preop =lc8.62/100 m2 ; Op=24.12/100 2 m ) in the nearfield area, while they remained stable in the farfield area. At present there is no clear causative factor, either natural or related to Station operation, that accounts for this decline but competition and the effects of an introduced epiphyte may play a role. There was only one faunal species in either zone for which a significant change was observed between nearfield and farfield stations. Ampithoe rubricata, an intertidal amphipod, exhibited a shift in abundance between periods that was inconsistent between nearfield and farfield stations. Densities in the farfield area increased significantly 2 (Preop =73.06/100 m ; Op= 268.80/100 m2 ), while they remained stable in the nearfield area. Long-term trends show local extinction at both sites during the preoperational and operational period with recolonization occurring early in the operational period at the farfield site and later in the nearfield area. This spatial variability in recolonization is typical of this species, and probably not related to plant operation. Impacts associated with increased turbidity, such as shifts in community dominance to species more tolerant of increases in shading, sedimentation rates, and organic loading were not evident at mid-depth or deep stations in the nearfield area. Analyses of community parameters and overall structure generally revealed a consistency in both the algal and faunal communities, in both the nearfield and 7-ii
\
f 7.0 MARINE MACROBENTHOS farfield areas and between periods. This reflects the more stable natural environment characteristic of deeper benthic habitats. However, a minor difference in the mid-depth faunal community analysis was observed. The community observed in collections from the mid-depth farfield station in 1996 and 1997 was unique. This community in previous years was typically more similar to a community formed from collections from the intake, farfield, and discharge areas. The only change of note in the l mid-depth algal community was the continued decline of Laminaria digitata densities (Preop =106.15/100 2 2 m ; Op=6.70/100 m ) in the nearfield area. The cause of this decline remains unclear, although the role of grazing by the green sea urchin Strongvlocentrotus droebachiensis was examined, and found to be statistically significant in the farfield area. L digitata is at its physiological limit with respect to water l depth at the nearfield station, and competition with the dominant kelp Agarum clathratum is likely affecting L digitata population levels. While the interplay of physical and biological factors are currently not fully understood; it is unlikely that Station operation is a factor as there has been no measurable effect on local water temperatures, nor have any other plant or animal species exhibited a similar response that might reflect impacts from increased turbidity levels. The deep subtidal communities were also largely consistent between stations and periods. Since this change occurred simultaneously in both areas it does not likely reflect a Station impact. The other minor anomaly occurred in the macroalgae community analysis. The communities observed in collections from the deep discharge in 1996 and 1997 were more similar to a community formed from collections from the deep intake station. These shifts in the deep subtidal zone were probably the result of natural variability. 7-iii
]
7.0 MARINE MACROBENTHOS LIST OF FIGURES PAGE 7-1. Marine benthic sampling stations ..... . . . .. . ... 7- 3 7-2. 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 total number of unique taxa in 1997 . . . . .. . . .. . 7-10 , j 7-3. Comparison between stations of number of macroalgal taxa (per 0.0625 m2 ) in the ! intertidal zone during the preoperational (1982-1989) and operational (1991-1997) l I periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of taxa each year (data between the two vertical dashed lines were excluded from the ANOVA model) . . . ... . . .. 7-14 7-4. Comparison between stations of number of macroalgal taxa (per 0.0625 m2 ) n the mid-depth subtidal zone during the preoperational (1980-1989) and operational i (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of taxa each year (data between the two vertical dashed lines were excluded from the ANOVA model) . ..... . 7-16 7-5. Dendrogram and station groups formed by numerical classification of August l collections of marine benthic algae, 1978-1997 .. . .. . . .. . .... 7-18 l 7-6. Comparison between stations of number of holdfasts /100 m2 of the kelp Imm'nada l digitata in the shallow subtidal zone during the preoperational (1982-1989) and l operational (1991-1997) periods for the significant interaction term (Preop-Op X l Station) of the ANOVA model, and annual mean density each year (data between i the two vertical dashed lines were excluded from the ANOVA model) . . . . . .... 7-32 ! 7-7. Annual mean percent cover of Laminaria digitata in the shallow and mid-depth ; subtidal zones, 1985-1997 . .... ..... .. ... ........... ..... 7-33 I 2
- 8. Comparison between stations of number of holdfasts /100 m of the kelp Laminaria ,
digitata in the mid-depth subtidal zone during the preoperational (1978-1989) and : operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between i the two vertical ~ dashed lines were excluded from the ANOVA model) . . . ... . . 7-36 j i 2 7-9. Annual mean densities (number per 100 m ) of leminaria digitata and Agarum clathratum in the mid-depth subtidal zone (Stations B19 and B31),1978-1997 . . ... 7-37 i t l l 7-iv
e l 7.0 MARINE MACROBENTHOS PAGE 7-10. Comparison between stations of annual mean percent frequency of occurrence of the fucoid Ascophyllum nodosum in the intertidal zone during the preoperational (1983-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model) ........ .... ...... ........ . ...... .. ..... . 7-41 7-11. Comparison between stations of annual mean percent frequency of occurrence of the fucoid Fucus vesiculosus in the intertidal zone during the preoperational (1983-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model) ..... .. ........... .. .... . ... .. .. . .. 7-42 7-12. Dendrogram and annual station groups formed by numerical classification of August collections of marine macrofauna, 1978-1997 . . . . . . .. 7-52 7-13. Comparison between stations of annual geometric mean density of Ampithoe rubricata in the intertidal zone during the preoperational (1982-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model) . ...... 7-70 7-14. Annual mean densities of Laminaria digitata and Strongylocentrotus droebachiensis (number per 100 m2 ) n the mid-depth subtidal zone, 1978-1997 (data between the two vertical dashed lines were excluded from the ANOVA l models) . . . . ........ .. .. ... . ... . . ... .... . 7-73 7-15. Annual mean densities of Laminaria digitata and Strongylocentrotus droe-2 bachiensis (number per 100 m ) in the shallow subtidal zone, 1978-1997 (data between the two vertical dashed lines were excluded from the ANOVA model) . . 7-75 7-16. Density of Laminaria digitata holdfasts as a function of density of Strongylocentrotus droebachiensis at mid-depth Station B31 (farfield). Counts included for the years 1985-1989 and 1991-1997. Correlation coefficient r =
-0.556 (p = 0.001). . ..... ...... . . . ........ .... ... 7-76 7-v
7.0 MARINE MACROBENTHOS LIST OF TABLES PAGE 7-1. Selected Benthic Taxa and Parameters Used in ANOVA and Wilcoxon's Summed Ranks Tests . . . . . . . . . .. 7-6 7-2. Arithmetic Means and Coefficients of Variation (CV, %) for Number of Algal Taxa and Total Algal Biomass at Various Depths and Stations During 1997 and During the Preoperational and Operational Periods .. .. . 7-11 7-3. Analysis of Variance Results for Number of Macroalgal Taxa (per 0.0625 m2 ) and Total Macroalgal Biomass (g per m2 ) Collected in Destructive Samples at Intertidal, Shallow Subtidal, Mid-Depth Subtidal, and Deep Stations During Preoperational and Operational Years ... .. .. . .. .. 7-12 7-4. Summary of Spatial Associations Identified from Numerical Classification of Benthic Macroalgae Samples Collected in August Destructive Sampling (1978-1997) .... .. ....... . . . ... . 7-19 7-5. A Comparison of Percent Frequency of Occurrence of Rarely Found Species (overall Frequency of Occurrence <4%) in August Destructive Samples Collected During Preoperational (1978-1989) and Operational (1990-1997) Periods, and Over All Years (1978-1997) .. .. .. .. . .. . . 7-22 7-6. Arithmetic Means and Coefficients of Variation (CV,%) for Chondrus crispus Biomass (g per m2 ) Collected in Triannual (May, August, November) Destructive Samples in the Intertidal and Shallow Subtidal Zones During 1997 and During the Preoperational and Operational Periods . . . . ... .. . 7-24 7-7. Analysis of Variance Results for Chondrus crispus Biomass (g per m2 ) at Intertidal and Shallow Subtidal Station Pairs for the Preoperational (1982-1989) and Operational (1991-1997) Periods . .. . ... . . . 7-25 7-8. Preoperational and Operational Means and Coefficients of Variation (CV, %), and 1997 Means for Densities of Kelp Species (no. per 100 m 2) and Percent Frequency of Occurrence of Understory Species and Five Fucoid Species . 7-27 7-9. 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 . . . . .... . . 7-28 7-10. Percent Cover and Percent Frequency of Occurrence of Dominant Perennial and Annual Macroalgal Species at Fixed Intertidal Non-Destructive Sites During the Preoperational and Operational Periods and in 1997 . . . 7-45 7-vi L__________________________________________________._________________------______--___________ _
l l I 7,0 MARINE MACROBENTHOS l PAGE ! 7-11. Preoperational and Operational Arithmetic Means and Coefficients of Variation (CV,%) and 1997 Means of the Number of Taxa Collected, and Geometric Mean Densities and Coefficients of Variation for Non-Colonial Macrofauna Collected in August at Intertidal, Shallow Subtidal, Mid-Depth and Deep Stations . .. 7-47 i 7-12. Analysis of Variance Results for Number of Macrofaunal Taxa (per 0.0625 m 2) and Total Macrofaunal Density (per m2 ) Collected in August at Intertidal (1982-1997) and Shallow (1982-1997), Mid-Depth (1980-1984; 1986-1997), and Deep Subtidal Stations (1979-1984; 1986-1997) l
... . .. . 7-48 7-13. Station Groups Formed by Cluster Analysis with Preoperational and Operational (1990-1997) Geometric Mean Density (per m2 ) and 95% Confidence Limits of l Dominant Macrofauna Taxa (Non-Colonial) Collected Annually in August from 1978 Through 1997 . . .... . . . . . . ... 7-53
{ 7-14. Percent Frequency of Occurrence of Dominmt Macrofauna at Fixed Intertidal Non-Destructive Sites During the Preoperational and Operational Periods and in 1997 . . ..... .. . .... .. . . . . 7-56 I 7-15. 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 l Stations B19 and B31 Sampled Triannually (April, August, December) from 1981- j 1997 (except 1985) .... ... ... . . . .... . . 7-60 l ( 7-16. Geometric Mean Densities (no. per m2 ) and Coefficients of Variation (CV,%) of l Selected Benthic Macrofauna Species Collected During Preoperational and Oper- ; ational Periods and During 1997. . .. .... . . . . . 7-62 j i 7-17. Analysis of Variance Results Comparing Log-Transformed Densities of Selected j Benthic Taxa Collected in May, August and November at Nearfield-Farfield i Station Pairs During Preoperational (1978-1989) and Operational (1991-1997) l Periods . . . . . . . . .... . .. . . 7-63 j l 7-18. Annual Mean Lengths (mm) and Coefficients of Variation (CV,%) of Selected l Benthic Species Collected at Nearfield-Farfield Station Pairs During the Preoperational and Operational Periods and in 1997 . . .. 7-66 7-19. Mean Densities (per m 2) and Range of Strongylocentrotus droebachiensis ; Observed in Subtidal Transects During Preoperational (1985-1989) and Operation-al (1991 1997) Periods and During 1997 ... . . . . . .. 7-72 1 7-20. Results of Functional (Type II) Regression Evaluating the Effect of Strongylon-centrotus droebachiensis Densities on Densities of Laminaria digitata 7-76 7-21. Summary of Evaluation of Potential Thermal Plume Effects on Intertidal and Shallow Subtidal Benthic Communities in the Vicinity of Seabrook Station . 7-78 7-vii L
r u 7.0 MARINE MACROBENTHOS PAGE 7-22. Summary of Evaluation of Potential ~1hermal Plume Effects on Representative Important Benthic Taxa in the Intertidal and Shallow Subtidal Zones in the Vicinity of Seabrook Station ..... . . . . .. ......... 7-78 ( 1 7-23. Summary of Evaluation of Potential Turbidity Effects on Benthic Communities in the Mid-Depth and Deep Subtidal Zones in the Vicinity of Seabrook Station . .. 7-80 7-24. Summary of Evaluation of Potential Turbidity Effects on Representative Important Benthic Taxa in the Mid-Depth and Deep Subtidal Zones in the Vicinity of Seabrook Station . . ...... . .. . .. . . ...... ... 7-81 LIST OF APPENDIX TABLES 7-1. Marine Macrobenthos Sampling History ... .. .. .. ... .. 7-89 7-2. Nomenclatural Authorities for Macrofaunal Taxa Cited in the Marine Macro-benthos Section .. .. ... ......... ..... .......... . 7-90 7-3. The Occurrence of Macroalgae from General Collections and Destructive Samplings at all Subtidal and Intertidal Stations Sampled Between 1978 and 1997 ... .... ..... . .. ..... ... . . .. .... . .... 7-91 l : l l 7-viii
I l 7.0 hiARINE AfACROBENTHOS i
7.1 INTRODUCTION
intertidal zone (Stephenson and Stephenson 1949; Lewis 1964; Chapman 1973), but is also present The predominant benthic marine habitat in the subtidally (Hiscock and Mitchell 1980; Sebens vicinity of Seabrook Station intake and discharge 1985). These patterns of community structures is rocky substratum, primarily in the organization are the result of a variety of form of bedrock ledge and boulders. These rock interacting physical (e.g., desiccation, water surfaces support diverse communities of attached movement, temperature and light) and biological algae and animals that are important in coastal (e.g., herbivory, predation, recruitment, inter-ecosystems. In fact, hard-bottom coastal and intraspecific competition for space) ; communities are among the most productive re- mechanisms, which vary over spatial and l gions in the world (Mann 1973). This diversity temporal scales. I 1 and productivity is accomplished through modification of the typically two-dimensional Because coastal hard-bottom communities are substratum by the attached algae and animals to ecologically important, are well documented as l create a multi-tiered community that increases the effective integrators of environmental conditions, number of biological niches. and are potentially vulnerable to localized anthropogenic impacts, studies of these l One of the most productive features of the shore communities are part of ecological monitoring ! l and near-shore biota in the Guli of Maine is an programs associated with coastal nuclear power extensive canopy of brown macroalgae. l plants (Vadas et al.1976; Wilce et al.1978; i l Rockweeds (fucoids) inhabit intertidal areas Osman et al.1981; Schroeter et al.1993; BECO j l (Menge 1976; Topinka et al.1981; Keser and 1994; NUSCO 1994). Similarly, Seabrook l i Larson 1984), while kelp inhabit subtidal areas Station marine macrobenthos studies are part of l (Sebens 1986; Witman 1987). Understory layers an extensive environmental monitoring program l generally occur beneath these canopies and whose primary objective is to determine whether l contain secondary levels of foliose and differences that exist among communities at filamentous algae and upright attached nearfield and farfield sites in the Hampton-macroinvertebrates over a layer of encrusting Seabrook area can be attributed to power plant algal and faunal species, which occupy much of construction and operation. Potential impacts on the remaining primary rock surfaces (Menge the local macrobenthos from Seabrook Station 1976: Sebens 1985; Ojeda and Dearborn 1989). operation include direct exposure to the thermal l l Also, many niches created in and around these discharge plume, most likely at sites in the upper attached biota are occupied by mobile predator portion of the water column (intertidal and and herbivore species such as fish, snails, sea shallow subtidal zones). Thermal impacts are urchins, starfish, and amphipods (Menge 1979, unlikely in deeper areas. However, increased l 1983; Ojeda and
Dearborn 1991),
turbidity in discharge water resulting from transport of suspended solids and entrained , Another important aspect of fucoid and kelp organisms could increase shading and the rate of assemblages is the distinct zonation pattern sedimentation. To assess these potential impacts, l exhibited by the biota, which throughout the studies were implemented to identify the attached North Atlantic Ocean is most obvious in the algae and animal species occupying nearby 7-1 j
T' 7.0 MARINE MACROBENTHOS intertidal and subtidal rock surfaces, to describe conjunction with destructive sampling at each temporal and spatial patterns of occurrence of sampling station. In addition, observations were these species, and to identify physical and recorded from the mean low water and mean sea biological factors that affect variability in rocky level areas (including tide pools) in the intertidal intertidal and subtidal communities, zone. 7.2 METHODS Beginning in 1982, two intertidal stations that encompass the low to high tide levels (referred to 7.2.1 Field Methods as BIMSL and B5MSL; Figure 7-1) were evaluated non-destructively during April, July Quantitative (destructive) macrofaunal and and December. Observations were made at macroalgal samples were collected three times permanently marked 0.25 m2 quadrats at three annually (May, August, November) at six benthic tidal levels: the bare rock zone (approximate stations (Figure 7-1); three nearfield-farfield mean high water or upper intertidal), the station pairs were established at lower intertidal predominantly fuccid-covered zone (mean sea (approximate mean low water: BIMLW, level or mid-intertidal), and the Chondnes B5MLW), shallow subtidal (4-5 m; B17, B35) crispus-covered zone (approximate mean low and mid-depth (9-12 m; B19, B31) zones. Four water or lower intertidal). Percent cover of additional stations were sampled in August only: fucoid algae and percent frequency of occurrence one mid-depth intake station (B16) and three deep of several intertidal species were estimated and water (18-21 m) stations (nearfield-B13 and B04, recorded according to an established species list. and farfield-B34). This sampling program began This list includes several perennial and annual in 1978 with five nearfield stations (B1, B04, algal species, gastropods (Acmaea testudinalis, B13, B17, and B19) and one farfield station Littorina spp. and Nucella lapillus), barnacles (B31). Nearfield station B16 was added to the and Mytilidae. General observations for the study in 1980. Subsequently, three farfield entire sampling area were recorded and stations were added, one in 1979 (B34) and two photographs were taken of each sampling quadrat in 1982 (B35 and B5). Station sampling histories within each tidal zone. Frequency of occurrence are summarized in Appendix Table 7-1. of fucoid algae was also recorded along a 9.5 m transect line (NAl 1991a). Epifauna and epiflora were removed by scraping from five randomly selected 0.0625 m2 areas on Non-destructive subtidal transects were rock surfaces. Subtidal collections were drawn established in 1978 to monitor larger macroin-through a diver-operated airlift into a 0.79 mm vertebrates and macroalgae that were not mesh bag, placed in a labeled plastic bag, adequately represented in destructive samples. brought to the surface and sent to the laboratory Six randomly placed replicate 1 m x 7 m band-for preservation and processing (NAI 1991a). transects were surveyed at nearfield-farfield Intertidal collections followed a similar station pairs in the shallow subtidal (B17, a35) procedure, excluding the use of an aitlift. and mid-depth (B19, B31) zones in Aprii, July and October. Percent frequency of occurrence A comprehensive record of all visible algal was recorded for dominant "understory" macro-species (" general algae") was made in algae (Chondrus crispus, Phyllophora/Coccotylus 7-2 1
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7.0 MARINE MACROBENTHOS , f ( spp. and Ptilota serrata). Counts of Modiolus stations where they were most abundant. These modiolus, Strongylocentotus droebachiensis and taxa (and their station pairs) were: Nucella the kelp species Laminaria digitata, L. lapillus and Ampithoe rubricata (B1MLW/ 8 saccharina, Agarum clathratum and Alaria B5MLW); Cancer irroratus, C. borealis, Jassa esculenta were also made. marmorata, and Asteriidae (B17/B35); Pontogeneia inennis and Strongylocentrotus Information on patterns of recruitment and droebachiensis (B19/B31, B17/B35); and settlement of sessile benthic organisms was Mytilidae (BIMLW/B5MLW, B17/B35, ; obtained from the bottom panels program. B19/B31). Bluestone panels (60 cm x 60 cm) were placed ! 0.5 m off the bottom at Stations B19 and B31, A subsample of individuals of the above beginning in 1982. Stations B04 and B34 were referenced taxa collected at each station in May, added in 1986. Short-term bottom panels were August and November was measured to the exposed for four months during three exposure nearest 0.1 mm and enumerated. For all j periods: December-April, April-August, and amphipods measured, sex was determined and August-December. Long-term bottom panels the presence of eggs cr brood was recorded. were exposed for one year, deployed in August and collected in August of the following year. Macroalgae from general collections were One panel was deployed at each station for each identified to the lowest practicable taxon. The time period. complete macroalgal species list was compiled I from both general and destructive collections and 7.2.2 Laboratory Methods included crustose coralline algae, collected only in August. All destructive samples were washed over a 1.0 mm sieve. Algal species from each sample were All undisturbed bottom panel faces were first identified to the lowest practicable taxon, dried analyzed for Balanus spp. (which includes for 24 hours at 105'C, and weighed. Fauna Semibalanus balanoides) and Spirorbidae, and previously designated as selected species were then scraped to remove sessile bivalves and identified and counted from May and November solitary chordates for identification and macrofaunal samples. Selected species were enumeration. Hydrozoa, Bryozoa and any determined from previous studies to be those abundant algal species were analyzed only on species that are the most useful as indicators of long-term panels. overall community type in the study area, based on abundance, trophic level, and habitat 7.2.3 Analvtical Methods specificity. All faunal species collected in August were identified to the lowest practicable 7.2.3.1 Destructive Monitorine Pronram: taxon; non-colonial species were counted and Community Analyses colonial taxa were listed as present. Macroalgal and macrofaunal community analyses Life history information was obtained for nine included numerical classification and analysis of macrofaunal taxa at paired nearfield-farfield variance (ANOVA; detailed below) of 7-4
7.0 MARINE MACROBENTHOS community parameters such as number of taxa were sampled concurrently (thus maintaining a and total abundance or biomass from triannual or balanced model design). Preoperational periods August-only samples (Table 7-1). Operation- for each analysis are listed on the appropriate al/preoperational and nearfield/farfield differ- figures and tables. The Waller-Duncan or ences in total abundance or biomass and number Scheffe's multiple comparison test was used to of taxa were evaluated using a multi-way analysis rank the levels of the main effects (Preop-Op, of variance procedure (ANOVA, SAS Institute Station) when they were significantly different. Inc.1985). A mixed effects ANOVA model was The LS Means procedure was used to rank the used to test the null hypothesis that spatial and levels of the interaction term (Preop-Op X temporal abundances during the preoperational Station) when it was significant. and operational periods were not significantly (p > 0.05) different. The data collected for the A comparison of macroalgal and macrofaunal ANOVAs met the criteria of a Before- community composition during operational and After/ Control-Impact (BACI) sampling design as preoperational periods was done using numerical discussed by Stewart-Oaten et al. (1986), where classification methods (Boesch 1977). Bray-t sampling was conducted prior to and during plant Curtis similarity indices were computed for the operation, and sampling locations included both annual August log-transformed average densities potentially impacted and non-impacted sites. The (macrofauna) and August square-root ANOVA was a two-way factorial with nested transformed average biomass (macroalgae). effects that provided a direct test for the Macroalgal species with less than 2% frequency temporal-by-spatial interaction. The main effects of occurrence and macrofaunal species with less were period (Preop-Op) and station (Station); the than 6.4 % frequency of occurrence were interaction term (Preop-Op X Station) was also excluded from the analysis. In all,34 algal and included in the model. Nested temporal effects 91 faunal taxa were included in the collections were years within operational period (Year for which similarity indices were computed. The (Preop-Op)) and (in some cases) months within group average method (Boesch 1977) was used to l year (Month (Year)), which were added to classify the samples into groups or clusters. The l reduce the unexplained variance, and thus, actual computations were carried out by the l increase the sensitivity of the F-test. For both computer program EBORDANA (Bloom 1980). j nested terms, variation was partitioned without i regard to station (stations combined). The final 7.2.3.2 Destructive Monitoring Program: j ) variance not accounted for by the above explicit Selected Species Analyses " i sources of variation constituted the Error term. An additional term, the interaction of Station and Some algal and faunal taxa were selected for Year within Preop-Op (Station X Year (Preop- more detailed analyses due to their ecological or l Op)) was added to provide the proper mean- economic importance in the study area. j square for testing the significance of the Preop- ANOVAs were used to evaluate temporal and l Op X Station term, which may signify a possible spatial differences in algal biomass or faunal I plant impact. The preoperational period for each abundances obtained from the destructive moni- l j analysis was specified as the period during which toring program. l at least one nearfield and one farfield station 7-5 1
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7.0 MARINE MACROBENTHOS 7.2.3.3 Non-Destructive Monitoring subject ta natural variability, unlike a laboratory Pronram: Selected Snectes Analyses experiment where, at least u theory, the dependent variable is controlled by the researcher . 1 Comparisons between preoperational and (Laws and Archie 1981). The functional i operational periods were made by means of regressions conducted used log (x+1) densities ANOVA for several subtidal species (kelps and collected in 1985 through 1997, excluding 1990. j understory algae and associated faunal species) and for several intertidal species (fucoids and 7.3 RESULTS AND DISCUSSION associated faunal species). Wilcoxon's summed j ranks test (Sokal and Rohlf 1969) was used to 7.3.1 Marine Macroalgae examine the differences between periods and j between stations for Strongylocentrotus 7.3.1.1 Horizontal Ledee Communities ] droebachiensis and Ptilota serrata in the shallow l subtidal zone where the ANOVA model was not Number of Taxa 1 significant. ANOVA models were used to f examine the interaction between period and Assessment of spatial and temporal patterns in j station for algal species and S. droebachiensis number of algal taxa has proven useful as an
]
densities (from the subtidal transect program) indicator of impacts associated with several j only, and were structured similarly to those run nuclear power plants in New England (Vadas et i on collections from the destructive monitoring al.1976; Wilce et al.1978; NUSCO 1994). To program. Data transformations were performed assess algal community diversity at Seabrcok prior to running ANOVA models to ensure that study sites, the number of algal taxa was assumptions of normality were met. The log determined in two ways. Numbers of taxa from (x + 1) transformation achieved normality in most general collections were used to qualitatively cases where untransformed data were non- characterize the overall floristic composition at a normal. In the few cases where transformation given study site. The destuctive sampling I did not provide an adequate approximation of Program provided quantitative information on nomiality (typically due to multiple zero values algal diversity (i.e., number of taxa per unit g in the data set), ANOVA models were not run. area), data which are more amenable to statistical analysis. A total of 149 taxa have been collected Additional analyses addressing declines in the from the two programs during the twenty year kelp species Iominaria digitata, and the potential study (Appendix Table 7-3); four of these taxa role in this decline played by the sea urchin S. were collected for the first time in 1997: droebachiensis, were conducted using data from Enteromorphaflexuosa ssp. paradoxa, Elachista the subtidal transect program. The relationship chondri, Protectocarpus speciosus, and between the densities of these two species was Cladophora albida. examined using a functional regression model (Type Il Model) as presented by Ricker (1973). In 1997, the percent composition of Chlorophyta The use of a Type Il model instead of a Type 1 (21 %), Phaeophyta (26%) and Rhodophyta j model is justified in this situation since both the (53%) was similar to the percent composition independent variable (sea urchin density) and the over all years combined (Chlorophyta: 20%; dependent variable (L. digitata density) are Phaeophyta: 26%; Rhodophyta: 55%). There i 7-8 l l
f 7.0 MARINE MACROBENTHOS l l was no apparent difference in average percent preoperational and operational periods (Figure 7-contribution of each group between 2). At all depth zones, the median number of preoperational (1978-1989) and operational taxa collected during both periods was highest in (1991-1997) periods, the low intertidal (MLW), shallow subtidal zones, and generally lowest in the deep subtidal During the 1997 sampling year, 77 taxa were zone. During the preoperational and operational collected over all stations (Appendix Table 7-3) periods, median farfield total number of taxa was The 1997 total ranks fifth lowest over all years higher than nearfield totals in the low intertidal I studied, with the lowest number of ina (71) (MLW), shallow subtidal, and mid depth zones. collected in 1980 (Appendix Table 7- 3). At the mid-intertidal (MSL) and deep subtidal Compared to the entire 19-year study period, zones, median nearfield totals were higher than l relatively fewer phaeophycean and similar farfield totals in both periods. In 1997, a l amounts of chlorophycean and rhodophycean taxa divergence from this pattern occurred at the mid-i were found in 1997. depth subtidal stations where a similar number of j taxa was collected from the nearfield (30 at B19) / In general, the assemblage of macroalgal taxa and farfield (29 at B31) stations. collected over the years at Seabrook sites was consistent with other New Hampshire studies Number of Taxa: Ouantitative Samnles (Mathieson and Hehre 1986). The floristic affinity ratio (Rhodophyta plus Chlorophyta, Quantitative results from the destructive sampling divided by Phaeophyta; Cheney 1977 citei in program supported the results from general Mathieson et al.1991) for the preoperational ' collections. Mean numbers of taxa collected at period was 3.0, reflecting an assemblage of algae farfield intertidal station (B5MLW) were higher intermediate between cold- temperate and than means from nearfield station (BIMLW) ! warm-temperate affinitics, while the ratio for the during preoperational and operational years and ! operational period (excluding 1990) and in 1997 in 1997 (Table 7-2). Numbers of taxa collected was slightly lower, at 2.8, a ratio typical of a over both stations declined between periods more cold-temperate assemblage. (Table 7-2), but to a slightly greater extent at ! B5MLW compared to BIMLW, as indicated by The numbers of taxa collected in 1997 at each a significant Preop-Op X Station interaction term station were within preoperational ranges at all (Table 7-3; Figure 7-3). Differences in annual locations except at B1MLW, B5MLW, and B16 means between the two stations are subtle, and where 1997 totals were slightly lower (Figure trends in annual means have tracked one another 7-2). The 1997 totals at all stations were within closely over time (Figure 7-3). The consistency operational ranges. Over all zones, median of this trend is not indicative of a station impact. preoperational total numbers of taxa collected { j were highest in the lower intertidal (MLW) and The number of taxa collected in the shallow shallow subtidat zones, and generally lowest in subtidal zone in 1997 were higher than the the deep subtidal zone. preoperational means for both nearfield (B17) and farfield (B35) stations (Table 7-2). The number Patterns of number of taxa collected among depth of taxa found in 1997 at B17 was greater than the zor.es and stations were consistent between the 7-9
\
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10 10-t l 5! 5; I l Ol --- -- O' l 816 B19 B31 B13 804 B34 l l Note: B16 sampled during August only Figure 7-2. 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 total number of unique taxa in 1997. Seabrook Operational Report,1997. i ( 7-10 L_
I l l ! 7.0 MARINE MACROBENTHOS l l
- Table 7-2. Arithmetic Means and Coefficients of Variation (CV,%) for Number of Algal Taxa
! and Total Algal Biomass at Various Depths and Stations During 1997 and During the l Preoperational and Operational Periods. Seabrook Operational Report,1997. ? Depth Zone Station Preoperational 1997 Operational l Meart CV Mean Mean CV l Number of Taxa (per 0.0625m ) 2 l Intertidal BIMLW 15.6 16 11.2 14.7 17 l B5MLW 22.2 14 19.0 19.5 10 Shallow subtidal B17 14.2 13 16.0 15.8 7 B35 18.1 18 18.2 18.9 16 ; Mid-depth B16 9.0 8 10.4 10.0 14 l B19 10.2 13 9.8 9.7 13 B31 11.1 12 15.8 12.7 23 i Deep B04 7.6 10 7.6 8.1 13 l l B13 7.9 9 8.6 8.5 13 l B34 7.7 8 8.6 8.0 14 l Total Biomass (g/m2) Intertidal BIMLW IN2.7 24 1052.8 1030.1 11 l B5MLW 1034.9 23 1228.0 1052.7 10 Shallow subtidal B17 916.3 13 1088.5 945.2 12 B35 891.4 16 1004.7 873.9 19 Mid-depth B16 779.8 28 696.4 625.2 19 B19 308.6 26 271,4 295.1 37 B31 471.2 28 891.1 451.8 42 Deep BN 99.6 30 60.6 86.5 22 B13 96.0 32 110.5 90.8 45 B34 71.3 71 34.2 45.5 53
' Stations BIMLW, B17, B19. B31: 1978 - 1989; Stations B5MLW, B35: 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, August and November: operational period = 1991 1997.
- Station B16 sampled in August only, so means for each station in this depth zone are August-only; operational period = 1990-1997.
- All stations sampled in August only; operational,criod 1990-1997.
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oc 6! ', I i ! 4 4. t i l 2i Prooperational @ratmal I ol_ . _ _. . - ..--; -- 82 83 84 85 80 87 88 89 90 91 92 93 94 95 90 97 WAR Figure 7-3. Comparison between stations of number of macroalgal taxa (per 0.0625 m2 ) in the intertidal zone during the preoperational (1982-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean number of taxa each year (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997. 7-14
e 7.0 MARINE MACROBENTHOS operational mean while the number of taxa at have only been observed at B31 since 1995, well
- B35 was slightly lower than the operational after the power plant came online (Figure 7-4).
I mean. ANOVA results indicate that there were no significant differences in number of taxa The number of taxa collected in 1997 at Stations l between the preoperational and operational B13 and B34 in the deep subtidal zone was higher l l periods but B35 was significantly greater than than both the preoperational and operational j B17 (Table 7-3). The relationship between means, while the number collected at B04 was the ' stations was consistent between the preoperational same as the preoperational mean and lower than and operational periods as indicated by the the operational mean (Table 7-2). ANOVA non-significant interaction term (Table 7-3). results indicated that there were no significant , differences between the preoperational and I The number of taxa found in 1997 at each of the operational periods (Table 7- 3). Station B13 was mid-depth subtidal stations was greater than the significantly higher than B04 and B34; however, operational means (Table 7-2). Stations B31 and the relationship among stations was consistent ' l B16 had higher numbers of taxa than were found between the preoperational and operational in the preoperational period, while the number periods as indicated by the non-significant inter-collected at B19 in 1997 was lower than during action term (Table 7-3). the preoperational period. ANOVA results l indicated that there were no significant differ- Total Biomass ences in number of taxa between the preoperational and operational periods, or among Biomass generally decreased with increasing l stations (Table 7-3). The relationship among depth, similar to patterns observed in the number stations changed between the preoperational and of taxa (Table 7-2). At the two intertidal stations operational periods as indicated by the significant (B1MLW and B5MLW), the mean biomass in interaction term (Table 7-3; Figure 7-4 ). 1997 was higher than both preoperational and l Stations B31 and B16 showed significantly operational means (Table 7-2). There were no greater increases in the number of taxa found significant differences between stations or periods ( than were observed at B19 (net gain of 1.6 and in mean total biomass, as indicated by the l 1.0, and net loss of 0.5 respectively; Table 7-2) non-significant interaction term in the ANOVA where there was no significant difference. Sev- model (Table 7-3). eral of the species that have contributed to the l observed fluctuations are species which are not Mean biomass in 1997 at shallow subtidal Sta-normally found in the subtidal zone (Sears 1998) tions B17 and B35 was higher than both the i.e. Elachistafucicola at B16 and Enteromorpha preoperational and operational means (Table 7-2). compressa and Rhizoclonium tortuosum at There were no significant differences between B31found in the operational period; Dumontia stations or periods in mean total biomass in the contorta, Enteromorpha prohfera, and shallow subtidal zone (Table 7-3). Because of Polysiphonia lanosa at B19 found only in the this consistency, the interaction term in the preoperational period. Overall the numbers of ANOVA model was not significant. taxa at the three stations have been similar throughout most of the study and higher numbers 7-15
n-J 7.0 MARINE MACPOBENTHOS Mid-Depth Zone 14 p _ . _ . 33, l* *
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I oi _, . _ _ . - . . . . . . . . . . . . _ . _ . 3 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 YEAR i i i Figure 7-4. Comparison between stations of number of macroalgal taxa (per 0.0625 m ) n the mid- 2 depth subtidal zone during the preoperational (1980-1989) and operational (1991-1997) l periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, ! and annual mean number of taxa each year (data between the two vertical dashed lines were ! excluded f;om the ANOVA model). Seabrook Operational Report,1997. 7-16
h 7.0 MARINE MACROBENTHOS In 1997, mean biomass was higher than during earlier) at that station. However, all collections ] both the preoperational and operational periods at were invariably grouped by depth zone or station, ) mid- depth Stations B31 but was lower than both and with one exception, included all years periods at B19 (Table 7-2). At B16 the mean (preoperational and operational; Figure 7-5). biomass in 1997 was lower than the Although the dominant taxa at all stations were preoperational but higher than the operational members of the Rhodophyta, each group was period. Throughout the study, mean total bio- distinguished from the others by the abundance of mass has been significantly higher at the intake : caaracteristic macroalgal species assemblage, station (B16) and lowest at the discharge station (B19), with the farfield station (B31) intermediate Collections from the intertidal stations (BIMLW (Table 7-3). The consistency of the relationship and B5MLW) formed Group 1 (Table 7-4). The among the three stations resulted in a non- signifi- three dominant taxa in this group (based on cant interaction term. percent of total group biomass), in descending order, were Chondrus crispus, Mastocarpus in the deep zone, mean biomass in 1997 was stellatus and Corallina opcinalis. M. stellatus lower than during the preoperational and opera- was restricted to intertidal collections. Group I tional periods at Stations B04 and B34 but was biomass changed little between periods,and the higher than both periods at Station B13 (Table relative contribution to total biomass of each of 7-2). Mean total biomass was significantly the three major components of the group re-higher at the two nearfield stations (B04 and B13) mained similar (Table 7-4). compared to the farfield station (B34) during both the preoperational and operational periods (Table Collections from the two shallow subtidal stations 7-3). The relationship among the three stations (B17 and B35) comprised Group 2 (Table 7-4). for algal biomass was consistent between the two In addition to Chondrus crispus and periods, and therefor the interaction term was Phyllophora/Coccotylus(the two top dominants), not significant (Table 7-3). shallow subtidal dominants included, in descend-ing order of percent of total biomass, Ceramium Macron 1gn1 Conununity Analysis nodutosum, Cystoclonium purpureum, and Corallina opcinalis. The biomass of Group 2 as Multivariate community analysis techniques were a whole (i.e., at Stations B17 and B35), as well as used in this study to quantify the degree of that of its component species, changed little similarity among all August macroalgal collec- between the preoperational and the operational tions made at the macrobenthic sampling stations periods (Tables 7-2, 7-4). since 1978. In this case,185 station / year collec-tions, represented by 34 macroalgal taxa, were Groups 3, 4 and 5 included only mid-depth grouped iato seven groups generally reflecting Stations B31, B16, and B19 respectively. These depth zone. A power plant-induced impact to the three stations were segregated from one another macroalgal community could be inferred from the by significant differences in total biomass (as failure of operational years' collections reflected by ANOVA results, Table 7-3) as well (1990-1997) at a station to be grouped with as differences in species assemblages (Table 7-4). collections from preoperational years (1989 and 7-17
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p l 7.0 MARINE MACROBENTHOS Table 7-4. Sununary of Spatial Associations Identified from Numerical Classification of Benthic Macroalgae Samples Collected in August Destructive Sampling (1978-1997). Seabrook Operational Report,1997. Within/ GROUP BIOMASS (g/m 2) , Between Preoperational b Group and Dominant Species, Ogatinal' Group Similarity LCL Mean UCL LCL Mean UCL d 1 Intertidal (BlMLW/B5MLW) 0.60/0.33 Chondrus crispus 796.4 986.2 1175.9 841.9 959.7 1077.5 Mastocarpus stellatus 106.6 215.2 323.9 52.0 121.0 190.0 Corallina oficinalis 19.9 51.2 82.5 5.3 22.8 40.3 1 2 Shallow Subtidal(B17/B35) 0.75/0.54 ' Chondrus crispus 662.6 774.2 885.9 584.8 790.2 995.5 Phyllophora/Coccotylus 142.8 204.7 266.6 119.6 193.2 266.9 Ceramium nodutosum 48.6 69.3 90.0 55.1 80.3 105.6 Cystoclonium purpureum v. cirrhosum 15.5 56.6 97.7 35.2 76.4 117.6 Corallina officinalis 28.3 51.6 74.8 26.5 60.7 94.8 3 Mid-Depth Farfield (B31) 0.67/0.64 Phyllophora/Coccotylus 148.5 213.2 277.8 91.4 134.3 177.3 Corallina oficinalis 71.I 97.8 124.5 57.0 114.4 171.8 Chondrus crispus 72.5 114.8 157.1 46.2 95.5 144.8 Cystoclonium purpureum v. cirrhosum 1.6 6.0 10.4 2.3 7.0 11.7 Phycodrys rubens 17.4 22.9 28.4 16.6 27.9 39.3 Desmarestia aculeata 0.0 0.0 0.1 0.0 30.9 100.6 Callophyllis cristata 5.0 8.7 12.5 3.3 11.0 18.7 4 Mid-Depth Intake (B16) 0.79/0.66 Phyllophora/Coccotylus 3M.6 4N.5 504.3 245.5 298.6 351.7 Phycodrys rubens 117.9 188.9 259.9 76.I 121.2 166.2 Cystoclonium purpureum v. cirrhosum 18.0 44.5 71.0 18.0 67.3 116.7 Chondrus crispus 26.5 $7.0 87.4 7.0 45.7 84.3 Ceramium nodutosum 14.3 35.0 55.7 13.9 45.2 76.6 Callophyllis cristata 23.8 32.5 41.1 22.8 33.3 43.8 5 Mid-Depth Discharge (B19) 0.76/0.66 Phyllophora/Coccotylus 163.6 201.9 240.1 111.9 169.9 228.0 Phycodrys rubens 30.9 50.2 69.5 29.0 70.1 111.1 Ptilota serrata 9.7 16.0 22.3 1.7 17.7 33.6 Callophyllis cristata 6.8 12.5 18.2 7.6 12.6 17.6 Cystoclonium purpureum v. cirrhosum 0.5 1.2 2.0 0.0 12.3 26.9 Corallina oficinalis 10.8 15.2 19.6 4.9 7.7 10.4 Membranoptera alata 1.9 4.3 6.8 2.9 6.2 9.5 6 Deep Intake (B13, all years)/ 0.67/0.55 Deep Discharge (BN, 1996, 1997) Phyllophora/coccotylus 45.1 68.8 92.6 40.4 67.6 94.8 Ptilota serrata 7.6 11.5 15.5 3.8 8.5 13.2 Phycodrys rubens 2.9 5.8 8.8 2.9 5.8 8.7 Polysiphonia stricta 0.0 2.9 6.2 0.0 1.9 3.8 Scagelia pylaisael 0.0 2.9 5.7 0.6 2.4 4.3 Callophyllis cristata 1.2 2.4 3.6 1.l 1.6 2.2 7-19 (continued)
3 7.0 MARINE MACROBENTHOS Table 7-4. (Continued) j Within/ GROUP BIOMASS (g/m 8) 1
*****" Preoperational' Group and Dominant Species = Operational
- Group Similarity LCL Mean UCL LCL Mean UCL 1 7 Deep Discharge (B04, all years except 0.64/0.55 )
1996 and 1997)/ Deep Farfield (B34 all years) , Ptilota serrata 45.7 64.0 82.3 29.2 40.3 51.4 l Phyllophora/Coccotylus 5.9 11.0 16.0 5.5 10.7 15.9 l Scagelia pylaisaei 0.1 1.3 2.5 2.0 1.0 12.1 l Corallina officinalis 3.3 6.9 10.4 0.3 1.2 2.2 Phyco&ys rubens 0.6 1.0 1.4 0.1 2.1 4.1 ' Dominant taxa comprise 2% or more of total biomass in either or both of the penods (Preop, Op).
- Preop = preoperational period, 1978-1989 (stations BIMLW, B17, B19, B31: 1978 1989; stations B5MLw, B35.19821989; station B16: 1980 - 1984, 1986-1989; stations B13, B04: 1978-1984,1986 - 1989; B34: 1979 - 1984. 1986-1989).
- op = operational period, 1990 1997.
- B04 is normally included in Group 7/ Deep Discharge, however the 1996 and 1997 commumty was more similar to Group 6.
Group 3 is composed of collections from P. rubens, declined between periods. This is mid-depth farfield Station B31. Phyllophora/ reflected in the decline in total biomass for Coccotylus was the dominant taxon during both Station B16 (Table 7-2). periods, followed by Corallina officinalis and Chondrus crispus (Table 7-4). Four other taxa Collections from the mid-depth discharge station also contributed to 2% or more of group bio- (B19) formed Group 5. Phyllophora/Coccotylus mass: Phycodrys rubens, Desmarestia aculeata, was the dominant taxon in this group during both Cystocloniumpurpureum v. cirrhosum and Callo- periods. Six additional taxa accounted for 2% or phyllis cristata. The biomass of Phyllophoral more of this group's total biomass: Phycodrys Coccotylus and C. crispus declined between rubens, Ptilota serrata, Callophyllis cristata, periods, while that of the remaining five taxa Corallina opicinalis, Cystoclonium purpureum v. increased. Overall, biomass at Station B31 cirrhosum and Membranoptera alata (Table 7-4). declined between periods but not significantly Although Phyllophora/Coccotylus biomass de-(Tables 7-2, 7-3). clined between periods, overall biomass at this station declined only slightly between periods Group 4, composed of collections from (Table 7-2). mid-depth intake Station B16, is characterized by high amounts of Phyllophora/Coccotylus and Group 6 consisted of collections from deep intake Phycodrys rubens, and moderate amounts of Station B13 (all years) and 1996-1997 collections Cystoclonium purpureum, Chondrus crispus, from deep discharge station B04. Six taxa were Ceramium nodutosum, and Callophyllis cristata present that accounted for 2% or more of this (Table 7-4). Biomass of the two major contribu- group's biomass: Phyllophora/Coccotylus, Ptilota tors to the group, Phyllophora/Coccotylus and serrata, Phycodrys rubens, Polysiphonia stricta, 7-20
L 7.0 MARINE MACROBENTHOS I Scagelia pylaisael (which was not a dominant in than 4 % over all years). Of the 40 species that fit any of the other shallower depth zones), and the rare designation (Table 7-5), eight were found Callophyllis cristata. Previous collections at in both preoperational (1989 and earlier) and Station B04 had been associated with Group 7 operational (1990-1997) periods, but have de-(Table 7-4), but the 1997 and 1996 collections creased in frequency of occurrence in the opera-were more closely related to Group 6, primarily tional period: Ulva lactuca, Ectocarpus due to a reduction in the mean biomass of Ptilota fasciculatus, Polyides rotundus, Leathesia l serrata. In 1997 and 1996, mean biomass of diformis, Cladophora sericea, Ulvaria obscura l Ptilota serrata at Station B04 was 20.9 and 18.2 v. blyttii, Porphyra miniata, and Palmaria f g/m2respectively (NAI 1997: 1998), which was palmata. Another seven species that were found l much closer to the mean biomass for Group 6 in both periods have become relatively more than Group 7 (Table 7-4). Biomass of each of the common in the operational period: Bonne-dominants in this group declined slightly between maisonia hamtfera, Ectocarpus siliculosis, Peta-periods (Table 7-4). loniafascia, Sphacelaria cirrosa, Enteromorpha intestinalis, Scytosiphon simplicissimus, and l l Group 7 consisted of collections from the two Polysiphonia harveyi. remaining deep stations, B04 (discharge, all years except 1996 and 1997) and B34 (farfield: Table Several taxa occurred only in the preoperational 7-4). Five taxa comprised the dominants in this or operational periods, but not both. Thirteen l group and included in descending order: Ptilota species were found during August sampling in l serrata, Phyllophora/Coccotylus, Scagelia pylai- preoperational years, but have not yet been sael, Corallina oficinalis, and Phycodrys rubens. collected in the operational period: Mono- stroma The biomass of S. pylaisaei increased by a factor grevillei, Spongomorpha spinescens, Pila- yella of six between periods, but the biomass of littoralis, Hincksia granulosa, Entero- morpha l Ptilota serrata, which accounted for most af this prohfera, Dumontia contona, Ceramium group's biomass, declined between periods (Table deslongchampii, Spongonema tomentosum, i 7-4). Monostroma oxyspermum, Enteromorpha linza, l Plumaria plumosa, Polysiphonia denudata, and The community analysis techniques described Entocladia viridis. Another twelve species were above used biomass values from a large number identified for the first time in August samples of algal taxa (34 out of a total of 79, all those after Seabrook Station start-up: Pterothamnion with a frequency of occurrence in destructive plumula, Chordaria pagelhformis, Isthmoplea samples of at least 2% over all depth zones and sphaerophora, Enteromorpha compressa, Bli-alI years). However, these analyses are intlu- dingia minima, Urosporapenicilhformis, Bryop- 1 enced most strongly by commonly-found species sis plumosa, Sphacelaria plumosa, Sphacelaria l with high total biomass; small, rarely found taxa radicans, Punctaria plantaginea, Polysiphonia contribute little to the Bray- Curtis similarity elongata, and Polysiphonia nigra. Five of these indices, or may not be included in the analysis at species (Chordaria pagelhformis, Isthmoplea all. Therefore, a further community analysis was sphaerophora, Polysiphonia nigra, Urospora performed, examining any trends in the occur- penicilhformis, and Sphaecelaria plumosa) were rence of rarely encountered species (frequency of collected during the preoperational period in May occurrence in August destructive samples less or November only. None of the 40 rare species 7-21
7.0 MARINE MACROBENTHOS Table 7-5. A Comparison of Percent Frequency of Occurrence of Rarely Found Species (overall Frequency of Occurrence < 4%)in August Destructive Samples Collected During Preoperational (1978-1989) and Operational (1990-1997) Periods, and Over All Years (1978-1997). Seabrook Operational Report,1997. Species Preoperational Operational All Years Ulva lactuca 5.9 1.3 3.8 Bonnemaisonia hamifera 1.4 6.8 3.7 Polyides rotundus 3.1 2.8 3.0 Ectocarpusfasciculatus 4.7 0.8 3.0 Ectocarpus siliculosus 1.0 3.3 2.0 Leathesia dformis 2.9 0.3 1.8 Cladophora sericea 1.4 0.8 1.1 Petaloniafascia 0.4 2.0 1.1 Porphyra sp. 0.0 2.5 1.1 Ulvaria obscura v. blyttii 1.8 0.3 1.1 Porphyra miniata l.4 0.5 1.0 Monostroma grevillei 1.6 0.0 0.9 Palmaria palmata I.4 0.3 0.9 Polysiphonia harveyi 0.6 1.3 0.9 Spharetaria cirrosa 0.6 0.8 0.7 Spongomorpha spinescens 1.0 0.0 0.5 Pilayella littoralis 1.0 0.0 0.5 Pterothamnion plumula 0.0 1.3 0.5 Hincksia granulosa 0.8 0.0 0.4 Enteromorphaprolifera 0.6 0.0 0.3 Dumontia contona 0.6 0.0 0.3 Ceramium desiongchampii 0.6 0.0 0.3 Enteromorpha sp. 0.4 0.0 0.2 Enteromorpha intestinalis 0.2 0.3 0.2 Cladophora sp. 0.0 0.5 0.2 Sphacelaria plumosa 0.0 0.5 0.2 Chordariaflagelliformis 0.0 0.5 0.2 Scytosiphon simplicissimus b.2 0.3 0.2 Polysiphonia sp. 0.2 0.3 0.2 Spongonema tomentosum 0.4 0.0 0.2 1sthmoplea sphaerophora 0.0 0.5 0.2 Monostroma aryspermum 0.2 0.0 0.1 Enteromorpha compressa 0.0 0.3 0.1 Enteromorpha lin:a 0.2 0.0 0.1 Blidingia minima 0.0 0.3 0.1 Urospora penicilhformis 0.0 0.3 0.1 Bryopsis plumosa 0.0 0.3 0.1 Sphacelaria radicaru 0.0 0.3 0.1 Punctaria plantaginea 0.0 0.3 0.1 Plumaria plumosa 0.2 0.0 0.1 Polysiphonia denudata 0.2 0.0 0.1 } Polysiphorda elongata 0.0 0.3 0.1 l Polysiphonia nigra 0.0 0.3 0.1 Entocladia viridis 0.2 0.0 0.1 7-22
7.0 MARINE MACROBENTHOS was considered a major component of the local water habitat, and is typically found in late winter [ macroalgal flora (average biomass was <0.10 to early spring (Taylor 1957). Since P. fascia g/m2), nor were the reductions or increases in does not generally favor warm water conditions, ( l l frequency of occurrence during the operational its increased presence does not likely reflect l period considered to represent a significant changes associated with station operation (i.e., a j alteration of the established algal community. localized warming of water temperatures due to the thermal effluent). Finally, none of these taxa Another monitoring study that evaluated the is considered a nuisance species. impacts associated with construction and opera-tion of a nuclear power plant on the attached Several species showed relatively large decreases macroalgal flora (NUSCO 1994) documented that in frequency of occurrence between periods, incursion of a thermal effluent to nearby rocky Leathesia digormis, described as a summer plant, shore sites caused an alteration of the algal decreased in frequency of occurrence during the community at those sites. Specifically, there was operational period. The filamentous brown alga an increased frequency of occurrence (i.e., Ectocarpus fasciculatus, described by Taylor I extended growing season) for species requiring (1957) as being adapted to warmer waters, also or tolerant of warm water, and an absence or declined in frequency of occurrence during the reduced frequency of occurrence for species with operational period. These trends are the con-cold water affinities. If similar trends were verse of the expected response to a thermal observed in the macroalgal community near incursion. Monostroma grevillel and Seabrook Station, it could be considered evidence Spongomorpha spinescens, both considered cold of a power plant impact, water species, have not been found in the opera-tional period. The absence of M. grevillei from Three rare species (Bonnemaisonia hamifera, collections in August from New Hampshire Ectocarpus siliculosus, and Petalonia fascia) waters is not unusual and S. spinescens is infre-showed relatively large increases from quent in August and generally absent from New preoperational to operational periods (Table 7-5). Hampshire waters in September (Mathieson and Bonnemaisonia hamifera is a small, bushy red Hehre 1986). alga described by Taylor (1957) as an " exotic" typically found off southern Massachusetts and Trends observed in taxa appearing for the first into Long Island Sound. B. hamifera has also time in the operational period are less conclusive. been recorded from coastal New Hampshire and Two taxa, Bryopsis plumosa and Pterothamnion from Great Bay prior to 1990 by Mathieson and plumula, are warm water forms more typical of Hehre (1986), so its presence in small amounts in southern New England and even further south the study area likely does not reflect a commu- along the Atlantic coast. Polysiphonia elongata nity change. Ectocarpus siliculosus ranges from was found for the first time in 1996 August Bermuda to Newfoundland, and as it is common destructive samples (Table 7-5). This alga occurs to the New Hampshire coast, its appear- ance over a broad geographic range and is common in also does not indicate a major change in the New England coastal waters (Taylor 1957; community (Taylor 1957; Mathieson and Hehre Mathieson and Hehre 1986). Isthmoplea 1986). Petaloniafascia is associated with a cold sphaerophora, which also was first collected in 7-23
7.0 MARINE MACROBENTHOS the operational period, is a spring-summer annual intake and discharge structures support dense not found south of Cape Cod (Sears 1998). stands of the red alga Chondrus cnspus. The perennial habit of this species allows extensive f q in general, the macroalgal communities in the populations to continue to dominate suitable rock l vicinity of Seabrook Station are typical.of those surfaces to the exclusion of most other species. reported elsewhere in northern New England Similar, nearly monospecific turfs of C. crispus ! (e.g., Mathieson et al.1981a; Mathieson and are common throughout the North Atlantic Hehre 1986), and have maintained a high level of f (Mathieson and Prince 1973), from New Jersey i stability as reflected in the consistency of the to southern Labrador (Taylor 1957). Owing to dominant algal species in each zone. The 1997 its predominance in the Seabrook area, C. floristic affinity ratio reflects a cold-temperate crispus was selected for further, more detailed , assemblage and both cold and warm water taxa analyses. C. crispus biomass (g/m2) at Seabrook l have appeared or dissappeared during the opera- study sites was typically highest at the intertidal l tional period. These factors taken together sites, at times exceeding 1000 g/m2 (Table 7-6). l indicate that there has not been a trend toward a l community dominated by warm-water species, Mean total biomass in the intertidal zone in-and that there has been no impact on the local creased between periods at both the nearfield macroalgal community as a result of construction (B1) and farfield (B5) stations, but this increase or operation of Seabrook Station. was not significant (Table 7-6, Table 7-7). Mean total biomass was slightly higher at the nearfield 7.3.1.2 Selected Snecies station than the farfield station during the preoperational and operational periods. In 1997, Chondrus cdspus mean total biomass was slightly higher at B5 than at B1 (Table 7-6). These differences were not Low intertidal and shallow subtidal horizontal significant and due to the overall consistency of rock surfaces in the vicinity of the Seabrook Table 7-6. Arithmetic Means an 7ients of Variation (CV,%) for Chondrus cdspus 2 Biomass (g per m ) Ct a sn Triannual (May, August, November) Destructive Samples in the Intertic,a ! Shallow Subtidal Zones During 1997 and During the Preoperational and Opera "I Periods. Seabrook Operational Report,1997. Preoperational' Operational 6 Period 1997 Period Parameter Depth Zone Station Mean CV Mean Mean CV Chondrus cnspus biomass Intertidal B1MLW 908.7 28 1038.2 981.0 15 (g/rn2) B5MLW 787.8 27 1043.1 835.4 21 Shallow subtidal B17 644.1 19 852.7 677.9 17 j B35 477.3 11 392.8 430.8 33
- Preoperational years: station BIMLW = 1978-1989 stauon B5MLW = 1982-1989
- Operational years: Both stauons = 1991-1997 7-24
(
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. din l e t
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mw A, n t S ni ituf r f f gl o o 7- a r o c de y rs a o oi sn r n se- r 7 T d pt s Mpi ia n n t s ra au e n o O e ( p- rnh n o to ito on 'e c ac a = f t n q l O o a ni r r t f u s b a e e o a tne e S hc a aa r t t e a t t T PYMSI nNS DD t I 8 y lfllI
j 7.0 AfARINE MACROBENTHOS ] the relationship, the interaction term was not shallow subtidal stations (D17 and B35), while
]
significant (Table 7-7). Agarum clathratum was the overwhelming dominant at mid-depth stations (B19 and B31,
)
Substantial, although somewhat smaller, amounts Table 7-8). Moderate amounts of L. digitata ] of Chondrus crispus were found at shallow were found at B35 and B31, but low amounts subtidal stations, with biomass levels often were found at their nearfield counterparts (Sta-exceeding 500 g/m2 . In 1997, the mean biomass tions B17 and B19, respectively). Alaria
]
at Station B17 was the highest observed during esculenta was found only at B31 in 1997, but its this study while biomass at B35 was lower than absence from B19 is not unusual (Table 7-8). both preoperational and operational means (Table l 7-6). Nearfield biomass exceeded farfield Laminaria digitata densities showed a significant ! biomass in both periods, but this difference was decline (83%) at Station B17 (nearfield shallow not significant (Tables 7-6, 7-7). Mean total subtidal) between periods (Tables 7-8, 7-9). biomass was not significantly different between Densities at B35 (farfield) declined moderately periods, and the interaction term of the ANOVA (28%) between periods, but this decline was not model was not significant. significant (Tables 7-8, 7-9). These differing rates of decline resulted in a significant interac-7.3.1.3 Non-Destructive Monitorine Pronram tion term in the ANOVA results, reflecting a possible plant impact (Table 7-9). Although Kelp densities at the two stations tracked one another closely during preoperational years, a moderate Extendve canopies of several kelp species downward trend in densities at B17 is evident comsubtidal zones (4-18 m) in the northwestern throughout the study period, with a steeper Atlantic, and can account for up to 80% of total decline occurring between 1988 and 1992 (Figure algal biomass (Mann 1973). In the Gulf of 7-6). Densities at Station B17 rebounded some-Maine, Laminaria spp. (mostly L. saccharina and what between 1993-1994, then began to declined L. digitata) are most common in the shallow again in 1995, and reached a study period low of subtidal zone (4-8 m), while a mixture of Agarum 9.5 holdfasts per 100 m2 in 1997. clathratum, Laminaria spp. and Alaria esculenta are found in deeper zones (Sebens 1986; Witman Percent cover of Laminaria digitata in the shal-1987; Ojeda and
Dearborn 1989),
low subtidal zone has, on average, been below l 30% in the farfield area and below 20% in the l A similar distribution of most of these kelp nearfield area during all years of the study species was found at Seabrook study sites during (Figure 7-7). the preoperational and operational periods. Ieminaria spp. were commonly found in both Physical factors are generally favorable to L. shallow and mid-depth zones during both periods digitata in the shallow subtidal zone in that the (Table 7-8). In 1997, as in past years, L. substrate is composed of rock outcrops, and saccharina was the dominant kelp species at water depths are shallow enough to permit ade-7-26
{ 7.0 MARINE MACROBENTHOS l [ Table 7-8. Preoperational and Operational Means and Coefficients of Variation (CV,%), and 1997 Means for Densities of Kelp Species (no, per 100 m2 ) and Percent Frequency of Occurrence of Understory Species and Five Fucoid Species." Seabrook Operational [ Report,1997. PreoperationaP 1997 Operational
- I f Mean CV hiean hiean CV Kelps (#/100 m2) 213.9 51 9.5 35.4 65 B35 155.8 46 91.2 112.1 36 B19 139.9 66 19.8 12.7 72 B31 500.2 31 381.6 204.9 56 Laminaria saccharina B17 415.1 52 265.0 288.1 49 B35 325.7 42 439.5 341.6 26 B19 59.1 152 21.4 21.8 117 B31 95.5 59 77.7 82.7 36 Alaria esculenta B19 2.4 308 0.0 2.7 172 B31 75.2 116 77.0 78.4 49 B9 786.6 35 1593.8 875.0 40 B31 366.4 37 694.2 553.7 50 Understory (% Frequency)
"# Bl
# '$ 71.8 8 73.7 76.7 9 B35 54.1 17 71.0 65.2 16 B19 4.2 116 9.0 5.4 69 B31 21.0 42 21.0 20.4 26 J"# #'# "
B7 20.3 37 25.0 20.7 34 B35 19.9 52 11.7 21.1 55 B19 34.0 21 33.3 29.9 29 B31 31.8 26 23.7 23.7 27 Ptilota serrata B17 0.8 127 0.0 0.5 196 B35 0.6 123 0.0 1.0 158 B19 35.6 26 0.0 32.4 77 B31 13.1 38 0.0 10.4 103 Fucolds (% Frequency)
^###N"$1 32.0 1921 35.3 39.2 8 B5 41.2 33.0 35.7 7 Fucus vesiculosus B1MSL 47.4 49 32.3 9.8 125 B5MSL 27.0 39 33.0 20.3 41 Fucus distigsg. edentatus 16.2 68 13.7 17.0 27 i
B5MSL 3.7 257 0.0 4.2 148 Fuca distichus ssp. distichus B1MSL 0.0 .. 0.0 4.I 160 B5MSL 0.0 - 0.0 2.3 117 I"#"#
- IIh1fL 7.6 149 10.0 30.4 47 B5MSL 0.7 226 0.7 7.8 65
- All taxa recorded along non destruct.ve subtidal or intertidal transects in A ril July, and October.
- Mean of annual rneans. Preop years for kelps Stauons B19. B31: 1978 f986; Station B17: 1979 1989: Station B35: 19821989; for understoqspecies Stations B17 B19. B31: 1981 1989; Stanon 35: 1982 1989; for fuccids - Stanon BlMLW: 1978-1997; Stanon B5MLW:
1982-tw7; Stanons Bl7 and B35: 1983 1989.
- 1991 1997.
7-27 I L
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)
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)
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- r ae O)Sa
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pa f o p paXY oe e r Y pX p paXY oe e r Y pX p paXY oe e p oeXY r Y pX e Y pX r
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r po(h por oir a noio t p o (r h - porn t po(h oir noio t por po (r hnoio t por n u t e ae oe a t r oi t e ae oe aa noio t r t a e a e oe a r t oi t a e ae oer a t r o r r r r S PSYMPSE r t r t PSYMPSE rt PSYMPSE r t r t PSYMPSEr t r t t l a' e id n b t o) u) n Gy3)1 h) Zs n s5 3 t 1 p3 l a) ht oi w B, de B, a B, d5 t o it B, pa l la1 7 d i 1 9 d- 19 r eI et t D (s hB S( MB ( iMB ( nB I ( ) d e *
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)
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)
d d (so p )=a gonf n ee tc w *= pi af r a - e e 1 r, rtaenY0 )r ee),m i ri ei u d e pL3 5 oc e e n *
) m l all B, n p oebiad0 s -
i t p s r fo n;9 a l z o erot c mn> a pan n
- s s e
s .i o7Hh pO o n( e o l u s i n n ata 9( t p n wot m n - C s o) s e a ta r9 s r e ei y, t iclaep t ( u ) v) t d pe1 idh luhteaSf r l y uc r y uy 1)d o3 c t t i it e ic n
/c 's c n jc
(. ne 8 e er9 ph wl e ini J,f f inl i X+ rm p1 s ti de ipnnim s r oog u eue s ue t t _ A- e it u pu _ (gfose= yut s . r q daqt s q r 7 m s e r sn e s e s r ) os sAoot e(iit s o 'e _ a e uef r i nh atccnf r lona aS ts n r uf uf p B,e r o a c mI d a a n ee-f _ l a cd c ar r t r r e b P u% Fue% ( u% t t a nob uSYMI t nt e ot t S hc a F( F( DUC( I nn NS T * ** * * ' 8 * '
- y-
e 7.0 MARINE MACROBENTHOS Shallow Subtidal Zone: Laminaria digitata 1 tw . .. . oy (
. . . ws >
14o s
~
g g$2ol .
)
im e
@" l m "1 g!
4o N 2o
! I
- o. _ . _ _ . . _ _ _ _ _ _ _ _ - _ _ _ _ . , ._
j a.op.re a m opernow { PERICO 1 400- , , . . g,7 3
. . - oss j 3so [ Precperabonat l Operational i i
)
W *i . l w x \ > lg m!i \
\,
i gaw- . f< .
.. ....., l .
lix. h ): e ..- , so
~.-
/~
o __ _ __ _ L
, .}.
m 2 l Figure 7-6. Comparison between stations of number of holdfasts /100 m of the kelp Laminaria f diguata in the shallow subtidal zone during the preoperational (1982-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997, 7-32 1 i L.
l 7.0 MARINE MACROBENTHOS Shallow Subtidal Zone
. _ . . . . ei, j . . . a 90' i
80; I m: Preoperatonal i Operatonal SOI ! l 4 ! i l i f 30 j .*- 20
.+- ..
h rM'N.h/' 10' r-* ., f - I 0-- - - - - - , - . - - . - - - - - - - W., . _ _ ,[ ' ' ' 85 06 87 88 89 90 91 92 93 94 95 96 97 YCM Mid-Depth Subtidal Zone 100
. - - . . -* B19
; ; .-... o3, 90i l 80!
l 70 l Preoperatonal i Operatonal e0 .
.. i, 3o:
I - 40- . i 30 e *
.j,_ *
~~ '
0- -, . - - - - - - - - - . T^-~~I ~ 2 ~ ~' * * * ~, 85 06 87 88 89 90 91 92 93 94 95 96 97 vcm Figure 7-7. Annual mean percent cover of Laminaria digitata in the shallow and mid-depth subtidal zones,1985-1997, Seabrook Operational Report,1997. 7-33
I ] 7.0 MARINE MACROBENTHOS b quate light penetration. Therefore there is some Another physical factor that could influence L. ) other physical or biological factor that has limited digitatasurvival in this zone is periodic removal the distribution of L. digitata in this zone. by storm events. However, the frond structure of L. digitata makes it relatively more resistant to The most likely documented physical factor in removal by storms compared to L. saccharina, the study area that could be influenced by station and there is not a definitive relationship between operation is temperature. To date there has been known severe storms (e.g., in 1988, Hurricane - no documented change in water temperatures Bob in 1991, and a second major storm during attributed to Seabrook Station, although a the fall in 1991) and L. digitata densities. One j long-term rise in water temperatures has been biological factor that could affect L. digitata observed locally and regionally (Section 2.0). A densities is grazing by the green sea urchin thermal plume study by Padmanabhan and Strongylocentrotus droebachiensis. This relation-Hecker (1991) indicated that the thermal plume ship is examined in Section 7.3.2.2. from the discharge is more buoyant than the surrounding waters and rises quickly to the sur- Interspecific competition could be a biological face. According to a numerical model of the factor in the decline of Laminaria digitata in the thermal plume, and subsequent field verification, shallow subtidal zone. Red algal turf species I I there were no significant temperature increases at have been found to reduce recruitment of kelps ; the Outer Sunk Rocks, where Station B17 is (Chapman and Johnson 1990). While the in-located in 4-5 m of water. Laminaria digitata is crease in Chondrus crispus between preopera-slightly more sensitive to temperature during its tional and operational periods at B17 was not J reproductive phase than is Laminaria saccharina, found to be significant (Tables 7-6 and 7-8), it the dominant kelp in the shallow subtidal zone may be enough to affect L. digitata density. (Hoek 1982; Luning 1990). Laminarians have a biphasic life cycle in which the gametophytes are Another biological factor that may be affecting l microscopic filaments. Due to the difficulty in the densities of Laminaria digitata is the recent observing gametophytes in the field, the data introduction of the epiphytic bryczoan Membra-available on this life stage come from laboratory nipora membranacea. This epiphyte was first studies. L. digitata sporophytes are reproductive observed in the Gulf of Maine in 1987 and is nearly year-round (Mathieson et al.1981b); thought to increase the susceptibility of kelp therefore, temperature is not likely to be limiting. blades to storm damage by making them more There is no information in the literature indicat- brittle (Lambert et al.1992). Although data is ing the seasonal period during which L. digitata not available from the sites in this study (B17, gametophytes reproduce locally, but gameto- B35, B19, and B31), M. membranacea may be phytes cannot survive temperatures in excess of contributing to the reductions in Laminaria 18'C, and require temperatures less than 10 *C digitataobserved in both shallow and mid-depth to become fertile (Hoek 1982, Luning 1990) subtidal zones. suggesting that reproduction occurs in late winter when temperatures are not limiting. 7-34
7.0 MARINE MACROBENTHOS Densities of Laminaria digitata in the mid-depth observed locally and regionally (See Section 2.0) subtidal zone declined substantially at both sta- are not likely a contributing factor to the ob-tions between periods (Table 7-8), but 1997 val- served decline as they are still well below the ( . ues showed moderate increases from 1996 at B19 lethal limit for both life stages of L. digitata (23 with more dramatic increases at B31 (NAI 1998). *C; Bolton &L0ning 1982). The decline at the nearfield station (B19) ex-ceeded that at the farfield station (B31), resulting Competition between L. digitata and Agarum in a significant interaction between period and clatratum may be contributing to the decline at station that reflects a possible plant impact (Table Station B19 as A. clathratum is generally the 7-9; Figure 7-8). Annual means show that densi- dominant kelp spevies below 12 m (Mathieson et ties at the two stations converged in 1988, but al.1991). While the increase in A. clathratum began to decline and diverge the following year was not significant between periods, it may be (Figure 7-8). The decline at B19 was most se- enough to affect L. digitata density. When the vere between 1988 and 1991. densities of the two species are examined in a time series (Figure 7-9), a sharp increase in the The percent cover of L. digitata in the mid-depth early preoperational period (1979-80) brings A. zone declined substantially over time at the clathratum densities into a range nearly ten times farfield station (B31), beginning well before the greater than L. digitata at B19, where it remains start of station operation (Figure 7-7). The up to the present. Both species suffered a decline annual mean percent cover of L. digitata at the begining in 1988 with a sharp drop in 1991 (pos-nearfield station (B19) was generally quite low sibly due to Hurricane Bob). A. clathratum be-throughout the entire study, exceeding 20% only gan to recover in 1994 and reached a study pe-in 1988. Following this peak in 1988, the annual riod high of 1593.8 per 100 m' in 1997. The mean percent cover declined to less than 5% by greater numbers of A. clathratum at B19 placed 1991, and has remained below 5% ever since. In this taxon in a better position to recover from this depth zone, substrate conditions are more disturbance and may have reduced L. digitata favorable to L. digitata in the nearfield area recruitment. L. digitata and A. clathratum den. (nearly 100% rock outcrop) compared to the sities at B31 have tracked each other closely farfield area (roughly 50% rock outcrop,50% throughout most of the study until 1994 when mixed sand and gravel). The major difference they began to diverge but to a lesser degree than between the two stations is depth. L. digitata has been observed at B19 (Figure 7-9). Grazing may be at its physiological limit with respect to by sea urchins could also affect L. digitata in this light penetration at Station B19 (12.2 m), zone. This is examined in Section 7.3.2.2. whereas light penetration is probably adequate at Station B31 (9.4 m), assuming that there is no The stability of local patches of kelp populations other factor affecting water clarity (L0ning have been observed to be highly variable (Dayton 1990). The stress placed on L. digitata in the et al.1984; Dayton et al.1992; Dayton et al. nearfield area due to water depth may make it 1998). Important factors contributing to these more susceptible to disturbance by other physical patterns are recruitment and survivorship which or biological factors than the population in the in turn are influenced by disturbance, competi-farfield area. The increased water temperatures tion, spore dispersal, long shore currents, tem-7-35 o
7.0 MARINE MACROBENTHOS j Mid-Depth subtidal Zone: Laminaria digitata ) 650g . . - - * - -
- B19
* *
- B31 i
450! l 4w. t l j D 3* ; O' s 1 250' 2x '- 150 100,
' N 'N w ,.
50 I '% ' ~~.,_, 4 0.------ -- - - -- ----- Preoperatonal Operatonal PERIOD l e19, 8ml ; . .. . e3 700 Preoperatonal Operational Sw- ., a i l - 3ool l - 6
~...' ! ,
g j. '., I
> 3m -
g
. . .i
/ r.
200 !
._/ -
x ;
- o. _.. - . - _ . . , . _ _ _ . . . _ . [ ! ^ -*~'-'s. -.-r 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 YEAR Figure 7-8. Comparison between stations of number of holdfasts /100 m 2 of the kelp Laminaria digitata in the mid-depth subtidal zone during the preoperational (1978-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model), Seabrook Operational Report, 1997, 7-36
r 7.0 MARINE MACROBENTHOS Station B19 1600.*-~ ~
- L. d@tata iSon, * - *
- A. clathrstum
./
1400 ,I i '"\ 1100+ ,_ , j l 1000 f N *
*' N /\ l
/ '. 'g i g 900 f /*\ f
\
_./
@ 800 / \/ \
s .
/
s j
/ \,I 700 / \ / s.
- j j /
.0o ! -< x
/ \g, 500 /
/
400 / 3= u /
/
/
/N N I I
200 _ _/ ~~~N .- _ /
\. -- . -. ., . _ . .
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 YEAR Station B31 1 1000 .,_ . + --+ L. digitata
!+ -* -* A. clathrstum a t i\
/s
' f800 . I \ g 700
\
\
f \/sx'.
\
s/
/
5 "I i A
/ \
(h \
'\
\\ '
y /\\ x 500- / \ i// W N ( \' ,s '
@ al / \ - / \ A ,
k !. [ \ ^
/ 's l n"l 1- ,
L. ,i q;m N
- i
\ 7 O_.-. . - _ - . - , _ ,
\/
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 YEAR 2 Figure 7-9. Annual mean densities (number per 100 m) of Laminaria digitata and Agarum f clathratum in the mid-depth subtidal zone (Stations B19 and B31),1978-1997. Seabrook Operational Report,1997, 7-37
7.0 MARINE MACROBENTHOS perature, and light availability. Recruitment may In the mid-depth subtidal zone, Laminaria be particularly problematic for local kelps as they saccharinadensities declined between periods at have a patchy distribution, primarily due to sub- both stations (Table 7-8). Densities in 1997 were strate availability. Reed et al. (1988) found that below the preoperational and operational means recruitment density of the kelp Pterygophora was at both Station B19 (nearfield) and Station B31 diminished as little as 3 m from adult plants. (farfield). ANOVA indicated that there were no Kelp populations were observed to be subject to significant differences in the density of L. frequent local extinctions. Reed (1990) also saccharinabetween the preoperational and opera-found that favorable sites for recruitment were tional periods, or among stations (Table 7-9). highly variable in time and proper abiotic condi- The relationship among statiom was consistent tions can be infrequent. Laminaria hyperborea, between periods as in R 3 by the a species more closely related to L. digitata, has non-significant interaction ten a dispersal range of at least 200 m (Fredriksen et al.1995), but spore density decreased exponen- Alaria esculenta densities were consistently lower tially with distance from the source (Chapman at the nearfield station (B19) than at the farfield 1986). With such limited dispersal capability, station (B31) during both periods and in 1997 the distance between an area that has experienced (Table 7-8). No A. esculenta were collected at even a single severe disturbance, such as grazing the nearfield station in 1997. There were no by an urchin front or damage by a storm, and a significant differences between the preoperational healthy population is critical for recovery. If the and operational periods, and the interaction term distance between the disturbed area and repro- was not significant (Table 7-9). ducing kelps is several kilometers or more, re-covery may depend on a period of high recruit- Mean densities of Agarum clathratum increased ment coinciding with winter storm currents to between periods at nearfield Station B19, and at bring new kelp stock into the area. farfield Station B31 (Table 7-8). Densities ob-served in 1997 were higher than in either period Laminaria saccharina density at the nearfield at both stations and density at B19 was at a study shallow subtidal station (B17) declined between period high. There were no significant differ-periods and the 1997 value was below the ences between periods or stations, and the inter-preoperational and operational means (Table 7- action term was not significant (Table 7-9). 8). In 1997 density at the farfield station (B35) was higher than preoperational and operational Understory Algae densities which were similar (Table 7-8). How-ever, ANOVA results indicated that there were Patterns of occurrence and abundance of some no significant differences in the density of L. understory species can be influenced by the de-saccharinabetween the preoperational and opera- gree of kelp canopy cover (Johnson and Mann tional periods, or among stations (Table 7-9). 1988). Common understory species in the Sea-The relationship among stations was consistent brook area, which occur beneath and adjacent to between periods as indicated by the non- signifi- kelp canopies, include the foliose red algae cant interaction term. Chondrus crispus, Phyllophora/Coccotylus and Ptilota serrata. Patterns of distribution of these 7-38
7.0 MARINE MACROBENTHOS species in fixed transects were similar to those significant differences between stations or periods observed from biomass collections (Tables 7-4, observed in the shallow subtidal znne for the 7-6). The shallow subtidal zone (B17/B35) was frequency of occurrence of Phyllophoral dominated by extensive turfs of the perennial red Coccotylus, nor was the interaction between alga C. crispus, with moderate occurrences of station and period significant (Table 7-9). In the Phyllophora/Coccotylus. In the mid-depth sub- mid-depth zone, the frequency of occurrence of tidal zone (B19/B31), PhyllophoralCoccotylus Phyllophoral Coccotylus in 1997 at B19 was and C. crispus were dominant at both the higher than the operational period mean; while at nearfield station (B19) and at the farfield station B31 the 1997 mean was the same as the opera. (B31; Table 7-8). tional mean and lower than the preoperational mean (Table 7-8). There were no significant Overall, relationships in patterns of occurrence of differences between stations or periods observed understory taxa between depth zones and be- in the mid-depth subtidal zone for the frequency tween nearfield-farfield stations have remained of occurrence of Phyllophora/Coccotylus, nor remarkably consistent over the study period. The was the interaction between station and period frequency of occurrence of Chondrus crispus in significant (Table 7-9). 1997 in the shallow subtidal zone was higher than during the preoperational and operational periods Ptilota serrata occurred infrequently during both I at B35 and higher than the preoperational period periods in the shallow subtidal zone (B17 and at B17 (Table 7-8). There were no significant B35) and with moderate frequency during both differences in C. crispus between stations or periods in the mid-depth subtidal zone (B19 and periods in the shallow subtidal zones and the B31; Table 7-8). P. serrata was absent from consistency of this relationship was reflected in both zones in 1997. The shallow subtidal the non-significant interaction term (Table 7-9). ANOVA model for Ptilota serrata was not signif- , In the mid-depth zone, the frequency of occur- icant; therefore, a non-parametric test was used. rence in 1997 at Stations B19 was higher than Wilcoxon summed ranks test results show no during either the preoperational or operational significant difference between operational and period (Table 7-8). The frequency observed at preoperational values at Station B17 (n =45, z=- , B31 in 1997 was the same as the preoperational 1.84, p > 0.05) And B35 (n =45, z =-0.04, mean and only slightly higher than the opera- p >0.05). In the mid-depth zone there were no tional mean. The frequency of occurrence of C. significant differences detected between periods j crispus was significantly greater in the farfield or stations, nor was the interaction between sta- ; ! than in the nearfield (Table 7-9). However, there tion and period significant for P. serrata (Table j were no significant differences between periods, 7-9.) l and the interaction between station and period l was not significant (Table 7-9). Fucoids t
)
1 i f The frequency of occurrence of Phyllophora/- Fucoid abundance was monitored in the Coccotylus in the shallow subtidal zone in 1997 mid-intertidal zone at B1 and B5 using fixed-line was higher than during either the preoperational transects located at mean sea level (MSL). and operational periods at B17 but lower than Ascophyllum nodosum was a consistently domi-either period at B35 (Table 7-8). There were no nant taxon at both study sites over all years, I 7-39 ) f : I L l
I ! 7.0 MARINE MACROBENTHOS j particularly during the operational period (Table species occurred less frequently in 1997 at Sta-
)
7-8). Percent frequency of occurrence in 1997 tion B1 than during either the preoperational or was higher than during the preoperational but operational periods. No F. distichus subsp. : lower than the operational period at Station Bl. edentatusplants were found at B5 in 1997 (Table l At Station B5 the 1997 percent frequency was 7-8). The frequency of occurrence has been lower than during the preoperational and opera- consistently higher at B1; however, no significant tional periods (Table 7-8). Percent frequency of differences were found between periods, stations occurrence increased significantly between peri- or for the interaction term. Fucus distichus ods at Station B1, but was not significantly differ- subsp. distici.us was not collected during the ent between periods at Station B5, resulting in a preoperational period and was not found at either significant interaction term (Table 7-9). Annual station in 1997 (Table 7-8). means show that the frequencies of occurrence of A. nodosum in the nearfield and farfield areas Juvenile Fucus sp. occurred more frequently at have generally tracked closely throughout the Station B1 in 1997 than during the preoperational study period, suggesting that the significant inter- period but less than the operational period (Table action term was not indicative of a power plant 7-8). The 1997 frequency at B5 was the same as impact (Figure 7-10). the preoperational mean and less than the opera-tional mean. Mean percent frequencies during Percent frequency of occurrence of Fucus the operational period were significantly higher resiculosus in 1997 was lower than during the than during the preoperational period at both preoperational period at Station B1 but higher at stations (Table 7-9). There were no significant Station B5 (Table 7-8). Frequency of occurrence differences between stations, and the interaction decreased substan- tially between periods at both term was not significant. stations, but to a greater extent at Station B1 compared to Station B5. Although the interaction Intertidal Communities term in the ANOVA results was significant (Ta-ble 7-9), this change in the relationship between Macroalgal species abundance patterns on inter-the two stations does not appear to be related to tidal rock surfaces exhibit striking patterns of the operation of Seabrook Station. The decline in zonation, which result from factors directly and F. vesiculosus began in the preoperational period indirectly related to tidal water movement (Lewis (1988), and continued into the opera- tional pe- 1964; Chapman 1973; Menge 1976; Lubchenco riod. Beginning in 1993 there appears to be a 1980; Underwood and Denley 1984; Mathieson trend of increasing frequency at both stations et al.1991). Physical stress (e.g., desiccation, (Figure 7-11). Similar long-term decline and temperature extremes) resulting from long expo-recovery cycles that were unrelated to power sure times is an important structuring mechanism plant operation have been observed in other mon- on macroalgae in the high intertidal zone (Lewis itoring studies (NUSCO 1996). 1964; Schonbeck and Norton 1978). Other fac-tors related to biological processes, such as graz-Fucus distichus subsp. edentatus was a persistent ing pressure (Cubit 1984; Keser and Larson component of the rockweed cornmunity at both 1984) and recruitment (Underwood and Denley , stations, although generally at lower abundance 1984; Gaines and Roughgarden 1985; Menge l i levels than the fucoids discussed above. This 1991), can also be seasonally important. To i 7-40 l
7.0 MARINE MACROBENTHOS 100s
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M' i OL _ _ _ _ ._ _ J-.1. ._ 83 84 85 86 87 88 89 90 91 92 93 94 95 90 97 YEAR Figure 7-10. Comparison between stations of annual mean percent frequency of occurrence of the fucoid Ascophyllum nodosum in the intertidal zone during the preoperational (1983-1989) and operational (1991-1997) periods for the significant interaction term (Preop-Op X Station) of the ANOVA model, and annual mean density each year (data between the two vertical dashed lines were excluded from the ANOVA model). Seabrook Operational Report,1997. 7-41
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