ML20138F475

Working Draft, Evaluation of Seabrook Station Phytoplankton & Chemical Nutrients Sampling Programs After Five Yrs of Plant Operation,Characterization of Environ Conditions. W/Supporting Documentation

ML20138F475
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Site:	Seabrook
Issue date:	08/31/1996
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l WORKING DRAFT I

EVALUATION OF SEABROOK STATION -

PHYTOPLANKTON AND CHEMICAL NUTRIENTS SAMPLING PROGRAMS AFTER FIVE YEARS OF PLANT OPERATION Prepared for NO" Td ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station l

Seabrook, New Hampshire 03874 i

Prepared by  !

l NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by  :

NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford,NewHampshire 03310 August 1996 9705050405 970429 PDR ADOCK 05000443 R PDR

v ,

Evaluation of Seabrook Station Phytoplankton and Chemical Nutrients Sampling Programs After Five Years of Plant Operation 4

Potential Effects of Seabrook Station jet mixing region. Hydrothermal modeling j Operation on Phytoplankton

' and field studies demonstrated that the area of the discharge plume is relatively small. A sur- l l Seabrook Station, located in Seabrook, face temperature increase of 3*F encompassed  !

New Hampshire, uses Atlantic Ocean water an area of approximately 32 acres around the j for condensing steam and cooling vital equip- area of the discharge (Teyssandier et al.1974; ment through the service water system. The Padmanabhan and Hecker 1991).

, station withdrew relatively small volumes of Biofouling in plant structures is controlled j seawater for testing various systems from by continuous low-level chlorination. Chlo- -

July 1986 through December 1987. Low rine (as sodium hypochlorite)is injected at the power testing with intermittent water use offshore intakes and a concentration of 0.2 began in April 1990. Commercial power mg L-1 is permitted at the DTS. In an eval-

! operation commenced on July 23, 1990, uation after plant start-up, the chlorine necessitating the full-scale withdrawal of i- residual in the effluent at the diffusers was cooling water and production of a heated found to be below limits of detection.

3 discharge. Seabrook Station, rated at 1150 As a result of Seabrook Station operation, MWe, has three intake structures located phytoplankton can be affected in two ways:  ;

about 1.3 mi offshore of Hampton Beach, by entrainment through the cooling water

, New Hampshire (Fig.1). The mid water system described above and entrainment from

! intakes are located about 17 ft above the bot- ambient ocean water into the heated discharge tom in depths of about 55 ft. Water is drawn plume as it rises from the bottom diffuser and

through a 19-ft diameter tunnel approximately mixes with surface waters. The formerim-

3.25 mi long; transit time is 70 min. The pact will be referred to as "through-plant cmrent NPDES permit for Seabrook Station entrainment" and the latter as " thermal plume allows for up to 2.70 X 106 m3day-1 (31.3 entrainment" to differentiate between them in m3s-1) of seawater to be used,95% of which this document. From through-plant entrain-

is for non-contact condenser cooling water ment, potential damage and mortality to i

and 5% for service water systems. Water organisms can be induced by the rapid change

, used at the station is released through the in temperature within the condensers and by onsite Discharge Transition Structure (DTS) mechanical damage (e.g, abrasion; rapid and travels 3.1 mi through another 19-ft pressure changes). The use of chlorine as a diameter tunnel to eleven diffusers located biocide in the intake system can also damage about 1 mi offshore of the mouth of Hamp- or kill entrained phytoplankton. Contact with ton-Seabrook Harbor at a depth of approxi- the full-strength thermal plume at the diffuser mately 55 ft. The diffusers discharge water discharges could cause mortality to some towards the surface at a velocity of about 15 phytoplankton, although the rapid cooling of ft s-1. According to the NPDES permit, the the Seabrook Station thermal plume reduces average monthly rise in temperature (AT) at the potential severity of this effect. In addi-the DTS can be up to 39'F and the maximum tion, the thermal plume could affect mixing daily AT cannot exceed 41*F. The rise in and venical stratification, which can influence temperature in receiving waters cannot be primary productionin the ocean. ,

greater than 5'F, except within 100 ft of the Collections of phytoplankton in the vicinity diffusers, where this limit applies only at the of Seabrook Station staned as early as 1978 at surface. This area is known as the near-field two near-field stations to establish baseline Seabrook Station Phytoplankton and Water Quality Page 1 of 25

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FIGURE 1. Sea 5 rook Station and the Hampton.Seabrook study area. Phytoplankton and chemical nucient sam'pl stations (P2, PS, P7) are shown along with the plant intake and discharge. (From NAI 1995).

data for future plant impact assessment phate', total phosphorus, nitrate, nitdte, and studies. The collections continued with some ammonium) and chlorophyll a and were interruptions and minor changes into the early conducted concurrently with phytoplankton 1980s. The initial sampling design was aug- collections.

. mented in 1982 with the inclusion of a far- The purposes of this document are to field station. Both near- and far-field stations examine the phytoplankton studies conducted were sampled for 6 months in 1986 and every at Seabrook Station, to briefly summarize the month fron) April 1990 through the present. impact, if any, of this power plant on this Water quality studies incibdc the measurement community in the Hampton-Seabrook area, of dissolved chemical nutrients (orthophos- and to evaluatp whether funher research is Seabrook Station Phytoplankton and Water Quality Page 2 of 25 9

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wananted. The chemical nutrients sampling pelagic and benthic regions. The subsequent l program is also examined, because dissolved

! processes of consumption, respiration,  ;

nutrients play a key role in determining excretion, and decomposition complete the phytoplankton community structure. A gen- cycle by regenerating basic nutrients neces-eral discussion of phytoplankton and factors sary for new production of organic matter, affecting their abundance and distribution is The phytoplanktonic community consists of l presented first.. Following is a brief summary a diverse group of algal species and cyano-i of the studies conducted through 1995 by bacteria. Each species within the community Normandeau Associates,Inc. (NAI) on behalf is influenced by a multitude of physical, of Public Service of New Hampshire and chemical and biological factors, including North Atlantic Energy Service Corporation. light intensity, distribution of growth-limiting Recent work comparing phytoplankton and nutrients, temperature, advection and diffu-nutrient data during Seabrook Station pre- sion, grazing pressure, and sinking. Some of operational and operational periods is empha- these factors (e.g., temperature and incident l1 l

sized. This is followed by a summary of light) undergo seasonal changes, while others phytoplankton studies conducted between (e.g., ambient light, essential nutrients) 1962 and 1982, mostly at ocean and estuarine exhibit rapid changes within a time span of -

electrical generating stations located on the minutes, hours, or days. The result is eastern coast of the United States. Additional complex and variable interactions among details of these studies are presented in an factors that influence the growth and repro-i i

appendix. Finally, Seabrook Station phyto- duction of phytoplankton. In turn, these plankton and water quality studies are evalu- relationships determine phytoplankton species ated in light of-the general and specific composition and spatial distribution. A brief l' findings presented, the impact of this facility review of some of the physical, chemical, and on the phytoplankton community is assessed, biological factors that control or influence the and the necessity for further studies is dis- abundance and distribution of phytoplankton  !

cussed, in the sea follows. '

l The Role of Phytoplankton and Light. In oceanic waters, peak absorption of I Factors Generally Affecting Their light by phytoplankton occurs at depths from Distribution and Abundance 20 to 40 m, and at typically low oceanic l

, densities only 1% of the light energy reaching '

Phytoplankton are rmeroscopic floating the surface is absorbed by phytoplankton for algae that produce most of the organic matter photosynthesis. In coastal waters, peak in the sea through photosynthesis, which is absorption oflight occurs at depths from 2 to limited to surface waters where sufficient light 4 m, and at the higher algal densities found is available for plant growth. The formation there,50 to 60% of incident light can be

, of organic matter requires the use of many absorbed by phytoplankton. At shallower l l clements by phytoplankton, of which carbon, depths, suspended particulate and dissolved nitrogen, and phosphorus are of primary matter absorb the majority of light and at concern. In the case of diatoms, a class of deeper depths, the water itself is responsible phytoplankton that has siliceous cell walls, for most of the absorption (Lorenzen 1976).  ;

silicon is also important. Phytoplankton in The depth at which minimum light intensity i shallow, coastal areas are either consumed by

'necessaiy for effective photosynthesis occurs '

zooplankton or planktivorous fish, or sink out is called the compensation depth. More  ;

l of the surface waters to be consumed by preciseij, :he compensation depth is where i benthic organisms or decomposed by mi- metabolic gains from photosynthesis just l crobes. This results in a transfer of energy balance metabolic losses from respiration, and and elements to other trophic levels in both the light intensity is generally thought to be Seabrook Station Phytoplankton and Water Quality Page 3 of 25

~

about l'7o of the incident radiation, but it may phosphate: adsorption onto clay particles, be deeper (Venrick et al.1973; Littler et al. calcium carbonate, and oxyhydroxides (Krom 1985). The water column above the compen- and Berner 1980; Stumm and Morgan 1981),

sation depth is known as the euphotic zone and precipitation ofinsoluble compounds after and is usually the top 100 m for open ocean combining with calcium, aluminum, and iron and the top 10 m for coastal waters. At low (Valiela 1984). Although the ambient surface light intensities, the idealized relationship concentration of dissolved inorganic phos-between primary ptbduction and light intensi- phorus (DIP) is typically less than 1 pg-at ty is linear; funher increases in light intensity P L-1, DIP is rapidly regenerated and recy-saturate the enzymes involved in photosyn- cled. For example,68 to 87% of the DIP thesis and a peak or plateau is reached. At used in surface production is regenerated still higher light intensities, like those ob- above 75 m (Knauer et al.1979), primarily by served at the surface, photoinhibition or a zooplankton excretion and egestion, and decrease in photosynthesis is observed and is microbial activity. Regeneration of DIP by thought to be caused by ultraviolet (UV) microbes in sediments can be significant in radiation (Strickland 1965). A static water shallow coastal waters, providing an average column exacerbates photoinhibition near the of 28% of phytoplankton requirements surface because phytoplankton cells are not (Fisher et al.1982),

advected out of the range of harmful UV Inorganic nitrogen is present in seawater as radiation, which can resuh in reduced primary nitrate (NO3 ), nitrite (NO 2), ammonium production compared to a well-mixed water (NH 4), and nitrogen gas (N2 ). With the column (Platt and Gallegos 1980). The linear exception of N 2, nitrate is the most abundant relationship between primary production and form of dissolved inorganic nitrogen, fol-light intensity is a function of how efficiently lowed by ammonium and nitrite (Parsons et different phytoplankton groups use light. al.1984). Concentrations generally range Under similar conditions of nutrients, light from low values at the surface to higher adaptation, and temperature, green algae and concentrations in deeper waters. Typical diatoms can attain maximum photosynthesis concentrations are <1 to 25 1 3

rates at lowerlight levels than dinoflagellates, O to 2-N NO p L p-at NH4-N , and <1 L pg-at pg-at and therefore may be better suited to areas or 2 . Decomposition of organic mat-depths where low light persists (Ryther ter and excretion by zooplankton release into 1956). the water ammonium, which is oxidized to nitrite and then to nitrate by nitrifying bacteria.

Nutrients. The production of organic matter Phytoplankton preferentially use ammonium in the sea is due primarily to phytoplankton. over nitrate, probably because less energy is Primary production requires the presence and needed to reduce its oxidation state within the utilization of elements used in the synthesis of cell (Conway 1977). In coastal waters,54 to protein, carbohydrate, and lipid. Typically, 70% of primary production is based on this results in organic matter containing 50- utilization of regenerated ammonium, while in 60% protein,30-40% carbohydrate, and 10- oceanic waters, ammonium supplies 82 to l 20% lipid. The synthesis of organic matter 87% (Eppley and Peterson 1979).

from the elements found in seawater results in Dissolved inorganic carbon is present in phytoplankton with the atomic ratios of seawater in a variety of forms originating phosphorus, nitrogen, and carbon of approx-from the reaction of dissolved carbon dioxide imately It16:106 (Redfield 1958). (CO2) with water (H2O):

Inorganic phosphorus is present in seawater H2 O + CO2 " H CO 2 3* H+ + HCO 3-as orthophosphate at very low concentrations

• H+ + CO3 "

(<1 pg-at PO4-P L-1). Two factors are Bicarbonate (HCO3')is the most prevalent important in maintaining low levels of ortho- ion, with much-lower concentrations of CO2 ,

Seabrook Station Phytoplankton and Water Quality Page 4 of 25

COr,'and H C052 present. Carbon dioxide of nutrients by bacteria and heterotrophic (CO2) is removed from the water by photo- protists.

synthesis and added to it by respiration. Physical, chemical, and biological processes However, because of the rapid equilibria also play key roles in determining spatial among the various chemical species, absolute distributions of phytoplankton. Langmuir proportions do not change appreciably. These circulation is a significant cause of horizontal same equilibria also buffer seawater within the and venical patchiness. Langmuir circulation pH range of 7.5 to 8.5. cells may extend to 400 m in length, and can The utilization of potentially growth-limiting be several meters in diameter. Resulting flow nutrients, such as nitrogen, by phytoplankton patterns can cause accumulations of phyto-can be described by a hyperbolic function plankton cells in areas.of convergence be-where the nutrient uptake rate increases as the tween cells (Stavn 1971). Tidally generated ambient concentration increases until an intemal waves can also result in patchiness at asymptote is reached and the nutrient concen-intermediate (10-100 m) spatial scales (Haury tration is no longer limiting to growth. et al.1978).

Nitrogen is the principal growth-limiting Because growth-limiting nutrients, such as nutrient in coastal (Ryther and Dunstan 1971) nitrogen, influence the abundance of phyto-and oceanic waters (Thomas 1969), although plankton populations, diffusion 'and advection phosphorus, silicon, and trace elements are play important roles in supplying phyto-also essential (Hecky and Kilham 1988; Morel plankton with nutrients, as do zooplankton et al.1991). excretion and bacterial regeneration. Zoo-plankton grazing pressure can have a signifi-Temperature. Tempenture is not a primary cant impact on phytoplankton density and limiting factor for phytoplankton growth in species composition. In laboratory tank temperate regions of the oceans (Valiela experiments, grazing pressure reduced the 1984). It may be more important as a factor diatom population, which allowed small influencing photosynthetic pigments, en- flagellates to dominate (Ryther and Sanders zymes, and carbon content (Steemann Nielsen 1980).

and Jorgensen 1968), which enable cells to Phytoplankton sinking also affects popula-utilize light more efficiently at low tempera- tion density and species composition. Larger  :

ture. Although higher temperatures can cells sink faster and grow slower than smaller increase nutrient uptake and photosynthetic l cells and, under stratified conditions, sinking rates,in most temperate regions the spring could reduce the population density oflarger bloom occurs during or near the time of species (Smayda 1970). Under stratified and coldest water temperatures. Temperature low-nutrient conditions, dinoflagellates would plays a more-important role in stratifying the be favored over the immobile phytoplankton water column so that phytoplankton are groups by their ability to migrate vertically retained above the compensation depth, and utilize the more abundant nutrients in deeper waters with a subsequent retum to the Growth and Distribution. The growth surface to photosynthesize (Blasco 1978).

rates of phytoplankton allow for doubling Also, dinoflagellates and flagellates are times that range from 5 to 9 days in oceanic known to excrete substances that may ad-waters (Falkowski 1980) and from 1 to 3 versely affect the growth of other planktonic days in coastal waters (Valiela 1984). species in the laboratory (Johnston 1963; Pratt Growth rate is controlled or influenced by 1966), but field evidence for allelopathy is light, availability of nutrients, and tempera- very tenuous, even in the more restricted ture, which in tum are influenced by vertical volumes of freshwater systems (e.g., Keating stability of the water column and regeneration 1978).

Seabrook Station Phytoplankton and Water Quality Page 5 of 25

1 Summary of Phytoplankton Studies at Seabrook Station Through 1995 Maine and the northeastern continental shelf (NAI 1993). Phytoplankton samples were dominated by diatoms (Bacillariophyceae) for Study design, sampling methods, treatment 10 months of the year with abundance peaks

' of data, and statistical tests for the phyto- occurring in spring and fall. Skeletonema plankton sampling program are found in NAI costatwn was a consistent numerically domi-3 (1991, 1995). Briefly, samples for phyto- nant species in all years that.were sampled.

plankton and chlorophyll a concentration were Other diatoms (e.g., Chaetoceros spp., Lepro-taken 1 m below the surface at three stations cylindrus spp., Rhirosolenia spp., Nitrschia (Fig.1) using an 8-L water bottle sampler. sp.) were also abundant during various Collections were made during the day once 4 per month in January, February, and Decem-periods of the year. The only other highly j abundant phytoplankter was the alga ber, and twice monthly during the remainder i Phaeocystis poucherii (Prymnesiophyceae),

of the year. Data were available for analyses which predominated during spring of some j from the plant discharge (station P2) from years, although it was absent or scarce in 1978 through 1984, the intake (P5) during other years. Dinoflagellates (Dinophyceae) 1978-81, and the farfield station (P7) during and Cryptomonas sp. (Cryptophyceae) also -

1982-84. After a hiatus, samples were again were occasionally numerous.

Because taken at all three stations beginning in July occasional large blooms of a particular species 1986 for chlorophyll a and in April 1990 for have occurred, different taxa have dominated

~ phytoplankton, with collections continuing in various years, and no one particular year through the present. For analytical pmposes, can be described as typical (NAI 1992). A phytoplankton were classified into two multivariate analysis of variance showed that groups: "ultraplankton" (cells <10 m) and species abundances (top 15 taxa) were not "phytoplankton" (cells 210 pm; Marshall and .

significantly different among the three stations 1 Cohen 1983). Although analyses were con- sampled (NAI 1996).

ducted primarily to examine the impact of Total phytoplankton abundance at station P2 thermal plume entrainment, through-plant was greater during the operational period entrainment effects may not be separable in relative to preoperational abundances (NAI the comparison of data from the intake to 1996). An ANOVA was used to compare nearfield discharge and farfield control abundances of total phytoplankton at nearfield stations. Even though waters offshore of stations P2 and P7 (Table 1). Overall, mean Seabrook-Hampton may thermally stratify to abundances during the operational period some degree from about May through Octo- were significantly higher than during the ber, phytoplankton cell counts did not differ preoperational period and densities at P2 were greatly between near-surface and formerly significantly greater than at P7. However, the collected near-bottom samples (NAI 1981). interaction term (Preop-Op X Station) was not Consequently, considerable numbers of phyto- significant, indicating that differences among plankton are entrained through the plant and the stations were consistent, regardless of discharged with the thermal plume. For whether the plant was operating or not.

impact assessment, analysis of variance Ultraplankton have been dominated by the (ANOVA) models (NAI 1995,1996) were cyanobacteria (formerly the blue-green algae used to test the null hypothesis that spatial and or Cyanophyceae), which accounted for 70 to temporal differences during the preoperational 75% of the assemblage. Chlorophyceae and operational periods were not significantly (unicellular and flagellated green algae) and (p>0.05) different.

Cryptophyceae (Chroomonas sp.) were In general, phytoplankton species composi- secondarily important. Ultraplankton abun-tion in the Seabrook area has been similar to dances were highest during summer and that reported for other areas in the Gulf of winter. Temporal changes in ultraplankton Seabrook Station Phytoplankton and Water Quality Page 6 of 25

TABLE 1. Results of analysis of variance' comparing abundances of phytoplankton between stations P2 and P7 during preoperadonal years (1982 84) and operational years (1991-95) at Seabrook Station. (From N 1996).

Source of Degrees Mean F Multiple Pammeter variation offreedom squares value f comparisons Totalabundance Preop-Op b 1.09 1 34.93 "

• Op > Preop of phytoplankton Year (Preop-Op)* 6 1.00 32.27 "

• Month (Year)d 88 0.59 19.09 "

• Station 1 0.17 5.61

• P2 > P7 Preop-Op X Station

• 1 0.03 0.86 NS Ermt 94 0.03

• ANOVA based on mean of twice-monthly collections from March through November and monthly c from December through February. Only years when collections at these stations were concurrent and when months were sampled were included in the model.

b Preoperational versus operational period, regardless of station.

• Year, regardless of preoperational or operational period.

d Month nested within year, regardless of station or year.

• Interaction between main effects.

f NS = not significant (p20.05)

= significant (0.01sp<0.05)

"* = very highly significant (ps0.001).

abundance were difficult to assess because of The abundance of the dominant diatom differences in methodology used over the Skeletonema costatwn and total phytoplankton years of study (NAI 1995). In earlier years, biomass (as measured by chlorophyll a con-ultraplankton forms were only partially centration) were chosen to be analyzed in l identified, with the picoplankton (<2.0 pm) greater detail for Seabrook Station impact fraction generally not identified. Beginning in assessment. Because of the dominance of the mid-1980s, efforts were made to identify Skeletonema 'costatwn in the local community smaller forms using improved techniques of phytoplankton, its spatial and temporal (e.g., phase contrast microscopy). Because abundances were chosen for examination ultraplankton were only enumerated in detail using the ANOVA model. Abundulces dur-only during the operational period, Seabrook ing the 1991-95 operational period at stations Station impact assessment was limited to a P2 and P7 were significantly higher than nearfield-farfield station comparison during during the 1982-84 preoperational period years of station operation (1991-94). During (Table 3). Similarly, abundances at P2 and this period, densities were not significantly P5 were higher after Seabrook Station began different among the three stations (Table 2). operation than during the 1979-81 preoper-NAI (1993,1995) also reported that the ultra- ational period. Abundance at nearfield station plankton forms present were similar to those P2 was significantly higher than at farfield reported for other areas of the Gulf of Maine station P7. However, no significant differ-during both the preoperational and operational ences were found between the two nearfield periods (Murphy and Haugen 1985; Glover et stations (P2 and P5). The interaction term al.1986; Shapiro and Haugen 1988; Haugen (Preop-Op X Station) was not significant in 1991). either ANOVA calculated for Skeletonema Seabrook Station Phytoplankton and Water Quality Page 7 of 25

1 l

l l

TABLE 2. Results of analysis of variance comparing abundances of ultraplankton between stad operational years (199194) at Seabrook Station. (From NAI 1995).

Source of Degrees Mean F Parameter variation of freedom squares value' Totalabundance Year 3 0.25 .0.67 NS of ultraplankton Month (Year)* 44 0.35 11.13 "

• Station 2 0.05 0.92 NS YearX Stationb 6 0.06 1.82 NS Enor 88 0.03 -

• Month nested within year, regardless of station or year.

b Interaction between main effects.

• NS = not significant (p20.05)

• ** = very highly significant (ps0.001).

costatum, indicating that differences among edulis) collected in Hampton Harbor were the stations were consistent, regardless of the provided by the State of New Hampshire.

plant operational status.

Chlorophyll a concentrations were used as a During the preoperational period, average weekly PSP toxicity levels were above the measure of phytoplankton biomass, but this detection limit (44 g PSP 100g-1 mussel measure may not be directly proportional to tissue) and periodically above the closure limit absolute abundance (i.e., cell counts) because (then dermed as 80 pg PSP 100g-1 mussel of variations in size and physiology between tissue) during late spring and early summer and within each species. Nevertheless, as (NAI 1996). However, PSP toxicity was '

i with cell counts, chlorophyll a concentrations rarely found during the operational period and generally peaked in spring and fall, with some )

even then it was at levels below closure limits. ;

month-to-month variability in the timing of Finally, the presence of PSP in the Hampton- i maximum biomass each year. Chlorophyll a Seabrook area was thought to be related to concentrations found after the commercial coastal transport from Maine rivers (Franks operation of Seabrook Station were not signif- and Anderson 1992a, b) that occurred inde-icantly different from those of the most recent  !

pendently of Seabrook Station operation. t (1987-89) preoperational years (Table 3). The operation of Seabrook Station has not Throughout the study, chlorophyll a concen- caused detectable changes in the abundance or trations were higher at nearfield station P5 community structure of phytoplankton in the than at farfield station P7, but the differences study area (NAI1995,1996). Although abun-were not significant between P5 and P2 nor dance's of total phytoplankton and Skeletone-between P2 and P7. Furthermore, the ma costatum were statistically higher in i

interaction term was not significant, indicating operational years than in preoperational years, that differences among the stations were this was attributed to a natural region-wide consistent, regardless of whether the plant trend and not to operation of Seabrook was operating or not. Station. High variability in densities and The importance of nuisance algae in the area changes in community structure from year to  !

was dermed as the toxicity levels of the alga year were probably influenced by physical Alexandrium tamarense, which is responsible and chemical factors, some cyclical and some for paralytic shellfish poisoning (PSP). PSP transitory. Ultraplankton abundance was toxicity levels from blue mussels (Mytilus similar to that found elsewhere in the Gulf of Seabrook Station Phytoplankton and Water Quality Page 8 of 25

l .

TABLE 3. Results of analysis of variance

• comparing abundance's of Skeletonema costatum and chlorophyll a concentrations among stations P2, P5, and P7 during preoperational years (varies by test) and operadon-al years (1991-95) at Seabrook Station. (From NAI 1996).

Source of Degrees Mean F Multiple Parameter variation offreedom squares f value comparisons 5 S. costatum Preop-Opb 1 6.73 32.80 ' " Op > Preop (Preop: 1982-84) Year (Preop-Op)* 6 2.62 12.78 * "

(P2 vs. P7) Month (Year)d 88 3.05 14.87 * "

Station 1 1.03 5.03 i P2 > P7 Preop-Op X Station" 1 0.39 1.89 NS Enor 94 0.20 S. costatum Preop-Op 1 9.96 32.66 "

• Op > Preop (Preop: 1979-81) Year (Preop-Op) 6 1.80 5.66 *"

(P2 vs. P5) Month (Year) 87 4.41 13.85 "

• Station 1 0.97 3.04 NS Preop-Op X Station 1 0.07 0.22 NS Error 93 0.32 Chlorophyll a Preop-Op 1 0.02 0.33 NS (Preop: 1987 89) -

Year (Preop-Op) 6 1.09 19.52 * "

(all stations tested) Month (Year) 88 0.84 15.06 "

• Station 2 0.17 3.07

• PS P2 P7 1

Preop-Op X Station 2 0.06 1.03 NS Error 188 0.06

• ANOVA based on mean of twice-monthly collections from March through November and monthly collections from December through February. Only years when collections at these stations were concurrent and when all 12 months were sampled were included in the model, b

Preoperational versus operational period, regardless of station.

• Year, regardless of preoperational or operadonal period.

d Month nested within year,regardless of station or year.

• Interaction between main effects.

I NS = not signincant (p20.05)

= significant (0.01sp<0.05)

"* = very highly significant (ps0.001).

8 Underlining indicates no significant difference.

• Maine (Murphy and Haugen 1985; Glover et affected by Seabrook Station operation. No al.1986; Shapiro and Haugen 1988; Haugen differences were found in any of the ANOVA l 1991). Chlorophyll a concentrations re- interaction tenns (Preop-Op X Station), which 1 mained similar among preoperational and indicated that any differences that occurred y operational periods and although statistically among stations were consistent, regardless of i

' significant differences were found among plant operational status. Thus, there has been stations, they were not ecologically signifi- no evidence that the operation of Seabrook cant. PSP levels were apparently also related Station has had any biologically significant to region wide events and have not been effects on the local phytoplankton community.

Seabrook Station Phytoplankton and Water Quality Page 9 of 25 r

l 1

l l Summary of Chemical Nutrient

surface nitrate concentrations to levels (>80 Studies at Seabrook Station pg L-1) observed during the previous winter.

l Orthophosphate, a non-growth limiting During the past 17 years, concentrations at nutrient, showed a similar, but more subdued ,

the surface of five dissolved chemical nutri- seasonal cycle than nitrate. Onhophosphate l l ents, including orthophosphate, total phos-had a fall-winter peak and a summer low, phorus, mtrate, mtnte, and ammonium, have which is typical for northem temperate waters been measured at' the three phytoplankton and associuted with seasonal nutrient re-stations (Fig.1), although not concurrently quirements of the primary producers. Am-before mid-1986. These nutrients control or monium, however, did not show a pro-influence phytoplankton growth and were nounced seasonal pattern as the other nutrients examined to evaluate the potential impact of (NAI 1995).

Seabrook Station operation on their concen- A compadson of nutrient concentration was tration, although it is unlikely that plant made between preoperational years when all operation could affect levels of nutrients.

three stations were monitored concurrently Sampling at each station followed the (1987-89) and operational years (1991-95).

general methods and schedule given previ- Although annual mean concentmtion of nitrate ously for chlorophyll a. Details of field varied over a wide range from the start of the collection, laboratory processing, and analyt- preoperational period through 1995 (Fig. 2),  ;

ical methods may be found in NAI (1995), there were no significant differences in its j j

The ANOVA model mentioned previously in concentration between preoperational and i the phytoplankton section was also used to operational periods (Table 4). Concentration assess the effects of Seabrook Station on of both nitrite and ammonium were higher water quality parameters. dudng the operational than the preopemtional In general, concentrations of the five nutri- period. However, the Preop-Op X Station ents exhibited distinctive seasonal patterns. interaction term was not significant, indicating For example, nitrate-nitrogen shows a rapid consistent differences among stations rg.rd-decrease in concentration during the spring less of plant operation.

phytoplankton bloom to undetectable levels The mean concentrations of orthophosphate

(<10 pg L-1), which are maintained during were less variable than nitrate (Fig. 3).

the summer by phytoplankton utilization. Concentrations of orthophosphate and total Water column stratification is strongest in July phosphorus were not significantly different and August, which prevents mixing of among stations or between preoperational and nutrient-rich bottom water with nutrient-poor operational periods (Table 4). 'Ihis suggests surface water. By September, macrozoo- that plant operations have not affected the plankton populations, which have attained natural cycling of nutrients in the nearfield

', peak abundance, are likely excreting peak area. This is not surprising because of the amounts of nitrogen and phosphorus. At the small volume of water utilized for cooling

same time, a weakening of the vertical purposes compared to the total volume that stratification of the water column begins to passes the nearfield area via longshore introduce limited quantities of nutrients into transport. Hydrographic studies showed that surface waters. These factors, with reduced the near- and farfield areas are exposed to the grazing pressure, contribute to an October same water masses (NAI 1985). Although phytoplankton bloom. In late fall, declining changes in nutrient levels have been observed incident radiation decreases algal growth and from year to year, these'same changes have nutrient utilization rates. Concurrently, been observed in the farfield area located decomposition of organic matter, a break- approximately 4.3 mi upeurrent of the near-down of vertical stratification, and subsequent field area, and simply represent region-wide mixing with nutrient-rich deep waters return natural variability in nutrient concentrations.

Seabrook Station Phytoplankton and Water Quality Page 10 of 25 l

l l

i

j . i 1

I l

100- P2 100 90- 90 1 P5 80 70 y 80 -f 704 -

60- - .J 60-3 50 / \ g 50-

" 4[ Y./v

\ r \../* "

d[ NP '

/\ \/

20H

/ "\T/ j

~

20- '

10 -;

104 j 0, ,,,, , , , , ,,,,,,,,, 03 '

78 80 82 84 86 88 90 92 94 78 80 82 84' 86 88 90 92 94 Year Year 5

i 100 P7 90-70_ '

All stations 80-!  :

70 i 60- l

/ h..\

s 60)  : 502 50 '

i  !

'E g- -

y / s/*

'e 40. . - . . . -  :

3 20 3 -

30-l 10-i O'. ... . . . . . ......,,, 20 ,,,,,,,,,,,,,,,,,,

78 80 82 84 86 88 90 92 94 78 80 82 84 86 88 90 92 94 Year l

e Year l

l FIGURE 2. Surface nitrate-nitrogen concentrations (pgC ) at stations P2, P5, and P7. Annual means with 95

+ confidence interval for years sampled during 1978 through 1995 are shown for each station and annual l t l means for each station are compared. Note that graphs for individual stations and the one for all stations

<mmbined have different scales.

s e

Effects of Other East Coast va'rious provisions of the Clean Water Act Ocean. and Estuarine-Sited administered by the U.S. Environmental Pro-Power Plants on Phytoplankton tection Agency (YAEC 1982) and,in some cases, by Technical Specifications cf the U.S.

Historically, phytoplankton studies were Nuclear Regulatory Commission. Conse '

included in many environtnental monitoring quently, there exists a wealth ofinfomiation programs, particularly during the 1970s, from phytoplankton studies designed specifi-because no data bases were available at the cally to address the impact of once-through

~

time to illustratr rotential effects of coastal cooling water systems of power plants. Many power plant operation on phytoplankton of the studies at these power plants evaluated communities. Both baseline and operational- entrained phytoplankton or populations found period studies were customarily required to in discharge canals, which represent worst i

prepare environmental statements necessary cases in terms ofimpacts.

for the licensing of power plants under A major component of the present Seabrook 1

Seabrook Station Phytoplankton and Water Quality Page 11 of 25 4

_ ,x_. - - - - , .. - ,_s. _ ._+ ,. i

TABLE'4. Results of analysis of variance' comparing the concentrations of

! stations P2, PS, and P7 during recent preoperational years (1987-89, except for amm operadonal years (1991 95) at Seabrook Station. (From NAI 1996).

Source of Degrees of Mean l Parr. meter F Muldple ,

variation freedom squares value h comparisons Orthophosphate - Preop-Opb.c 1 6.93 1.26 NS Year (Preop-Op)d 6 148.08 27.13 "

• 88 237.51 43.28 * "

Month Station { Year)* 2 13.32 Preop-Op X Stations 2.43 NS 2 0.31 0.06 NS Enor 188 l Total phosphorus Preop-Op 1 51.07 1.42 NS Year (Preop-Op) 6 1987.32 l

55.15 * "

i Month (Year) 87 393.65 10.92 "

• Stadon 2 65.92

1.83 NS Preop-Op X Station 2 22.20 0.62 NS Ener 187 36.04 Nitrate Preop-Op 1 194.44 2.32 NS Year (Preop-Op) 6 4013.64 47.92 "

• Month (Year) 88 10886.83 127.97 * "

Station 2 547.46 Preop-Op X Station 6.54 " P7 P2 > PS 2 119.69 1.43 NS Enor 188 83.76 Nitrite Preop-Op 1 3.65 6.26

• Op > Prt.op Year (Preop-Op) 6 3.92 6.72 *"

Month (Year) 88 7.82 13.41 ' "

Station 2 2.58 4.43

• P7 > P2 P5 Preop-Op X Station 2 0.65

1.12 NS Error 188 0.58 Ammonium Preop-Op 1 348.13 39.57 * " Op > Preop Year (Preop-Op) 5 1235.37 140.41 ' "

Month (Year) 74 78.15 8.88 *"

Station 2 18.27 l 2.08 NS .

Preop-Op X Station 2 3.52 0.40 NS Error 158 8.80 l

i

• ANOVA based on averaged monthly collections.

• I b

I Preoperational years were 1987-89 at each station, except for ammonium, which was April 1988 d* Preoperational versus operational period, regardless of station.  !

1 Year nested within preoperational and operational periods, regardless of station.

• Month nested within year nested within preoperadonal and operational periods, regardless of sta)

I

- Station P2 versus PS versus P7, regardless of year.

h8 Interaction between main effects.

NS = not significant (p20.05)

= significant (0.01sp<0.05)

= highly significant (0.01spc0.001)

I "* = very highly significant (ps0.001).

Underlining indicates no significant difference.

Seabrook Station Phytoplankton and Water Quality Page 12 of 25

(

l 25 P2 25 - P5 20 '

20i l eis-

. .. ./'N~ "/N,A/

e's, e

/x-+\-

1 10 . "f n

= 10 j Q/, ..

52 5-l O', , , ,, ,,,,,,,,,,,,, O', , , , , , ,,,,,,,,,,,,

78 80 82 84 86 88 90 92 94 78 80 82 84 _ 86 88 90 92 94 Year Year 25 . P7 All stations 18- /  !

20f ..

162 . . -

I g 15i "/]Ip sq 14-

[k ..

E 10; o

$ 124 10- .

5, .

, l g4 O", , , ,, ,,,,,,,,,,,,, 6 I l

78 80 82 84 86 88 90 92 94 78 80 82 84 86 88 90 92 94 l

Year Year FIGURE 3. Surface orthophosphate concentrations ( g L d) at stations P2, PS, and P7. Annual means with 95%

confiderice interval for years sampled during 1978 through 1995 are shown for each station and annual means for each station are compared. Note that graphs for individual stations and the one for all stations combined have different scales.

Station phytoplankton and chemical nutrients United States east coast in waters having evaluation was a review of the results and diverse and abundant phytoplankton commu-conclusions made following the termination of nities. The circulating water systems, dis-studies at other marine electrical generating charges, and other operational aspects of the facilities. Some of the studies were started 13 power plants from which findings were and, in many cases, completed before examined differed in many respects from each

~

phytoplankton studies at Seabrook Station other and from Seabrook Station. However, were initiated in 1978. All phytoplankton cooling water flows at all the stations were studies at these stations were discontinued a generally similar in magnitude, although decade or more ago (Table 5). Nearly all the Seabrook Station, for its size (1150 MWe),

studies examined were from power plants has a lower demand for cooling water (31.3 sited on the ocean or estuaries along the m3s-1) and higher AT (39'F) forits

Seabrook Station Phytoplankton and Water Quality Page 13 of 25 l

l

TABLE 5. Characteristics of east coast ocean and estuarine. sited power plants and studies that provided on phytoplankton for comparison to Seabrook Station.

Number of Net Cooling-water \

Years reponed i

Power generating generation i flow AT for studies of plant State units 3 (MWe)" (m .s-I)* (*F)b phytoplankton*

1 Crystal River FL 2 897 43.8 11.0 1971-72 i l Marshall NC 4 2136 64

18.9-36.7 1970-71 Chesterfield VA 6 1416 43.9 18.9-27.4 1970-71 Calven Cliffs MD 2 1620 73 12.0 ~ 1974-81 Chalk Point MD 2 656 30 15.0 1962-79d Indian River DE 1 347 17 11.0-12.5 1970-71 Millstone CT 3 2680 117.7 21.4 1970-82d Brayton Point MA 4 1590 46.8 26.6 1972-76 Montaup MA 1 500  ? 18.0-23.4 1976-77 Cape Cod Canal MA' 2 1100 7 30.6-31.5 1976-77 Pilgrim MA 1 655 20.3 29.0 1973-75 Salem MA 4 775 26.6 17.3 197.3-74 Maine Yankee ME 1 855 26.6 28.8 1969-77d Seabrook NH 1 1150 31.3 39.0 1978-present d

• Electrical generation and nominal cooling-water flow comeined for all units.

S Average nominal value for all units at full load or for AT reported at time of studies.

• Studies at power plants other than Seabrook Station believed to be terminated following last year 8

Years during which data were collected varied; not inclusive for all aspects of these panicular studies.

discharge than many of the other plants (Table dinoflagellates. Although cells may be killed 5). Brief summaries of these phytoplankton during through-plant entminment, particularly studies are provided as an appendix to this when chlorine is used as a biocide, several evaluation.

studies reported enhanced photosynthesis in Many of the power plant studies had similar discharge waters by survivors with no long-effects observed and final conclusions that led term deleterious effects to t1 e population as a to the termina' tion of the phytoplankton sam- whole. Few differences in abundance, bio-pling programs. A review of completed mass, species composition, or productivity studies (see appendix for citations) showed were found between discharge and control I that impacts to phytoplankton by power plant statio's.

n Thermal plume etttrainment was operation were localized and of short dura- shown to be a transitory phenomenon with tion. Many studies showed that primary little or no mortality associa.ed with it. In productivity was either enhanced or was not fact, exposure to moderate elevation in affected until water temperatures exceeded temperature when ambient temperatures were some threshold, typically at 77'F or greater, about 75*F or less often resulteiin enhanced

Also, diatoms, which dominate the productivity. At higher temperatures, the l phytoplankton community near Seabrook rapid cooling of the thermal plu ne in coastal Station, seemed to be less sensitive to thermal waters limited the influence of thamal plume and chlorination effects than flagellates or entrainment on.phytoplankton. Also, several Seabrook Station Phytoplankton and Water Quality Page 14 of 25 l l

I

l l

studies indicate'd that killed cells were avail- marine environment vias not unexpected as  !

able to grazers and decomposers within the coastal phytoplankton have high thermal  !

water column and that nutrients were quickly tolerances and rapid reproductive rates. Quick l recycled to phytoplankton. Furthermore, dispersion and cooling of coastal thermal l natural nutrient cycles were not affected by discharges limits phytoplankton exposure to plant operation. No evidence was found that high plume temperatures. Finally, marine .

l nuisance species of algae proliferated and phytoplankton populations are large, with '

became community dominants. Because no short generation times, and only a small significant long-term changes were found in fraction is affected by power plant operation primary productivity, higher trophic levels because of the relatively small amounts of were not affected. Because of the lack of water withdrawn from large open coastal significant power plant impacts to phytoplank- water bodies that are constantly replenished ton, it is not surprising that monitoring by longshore transport.

!: phytoplankton and chemical nutrients at other

' , northeastern power plants has been discon- Conclusions tinued for more than a decade.

In addition to studies done at specific coastal Compared to other United States east coast power plants, several reviews (Ecological power plants, Seabrook Station tises a smaller Analysts, Inc.1978; Tetra Tech, Inc.1978; volume of cooling water (31.3 m 3s-1 as LMS 1979; YAEC 1982) also summarized opposed to 57 m3 s-1 for the similarly-sized l

, relevant findings and made generalized Millstone Nuclear Power Station Unit 3), but l

conclusions about ocean-sited power plant discharges it at a higher temperature (39'F i impact on phytoplankton. These references above ambient versus 17'F for Millstone Unit

, . noted that no long-term changes were found 3). This design strategy was chosen to reduce in species composition of phytoplankton the number of organisms killed from through- l communities as a result of power plant plant entrainment by lowering intake volume.  !

operation. Any compositional changes found The location and design of the eleven offshore were associated with local seasonal char res in l diffusers facilitate rapid mixing and cooling of i temperature, salinity, or nutrients. No shifts the thermal discharge with ambient ocean i towards nuisance species were ever observed. waters. This limits thermal plume entrainment l Although, in some cases, productivity was and through-plant entrainment effects on I depressed by through-plant entrainment with phytoplankton. The small 3*F increase in respect to intake waters, inhibition was temperature in the 32 acres surrounding the  ;

usually restricted to warmer months (intake discharge is not likely to affect phytoplankton temperatures >68-83*F; discharge tempera- abundance or distribution. Furthermore, the  ;

tures >86*F) or was the result of chlorination. discharge creates a well-mixed water column i However, the quick dilution and cooling of in this area, which, according to Platt and heated discharges and rapid phytoplanktor Gallegos (1980), is likely to enhance primary growth and reproductive rates offset the productivity. The offshore location means potential for large changes in phytoplankton that phytoplankton cells withdrawn in the standing crop. Any reductions in biomass or cooling water are rapidly replenished by othu productivity were localized and transitory. cells advected into the area by coastal oceanic Exposure to high temperatures was usually currents. The volume of water used by brief due to rapid thermal plume dispersion in Seabrook Station is exceptionally smallin i madne waters. Thermal plume entrainment comparison to the volume of water that passes l did not cause mortalities nor were there the intake area via longshore transport.

statistically significant differences found for Therefore, the fraction of the phytoplankton variables when compared to control sites. population affected is also quite small.

The absence of wide-spread effects in the Studies of phytoplankton conducted to Seabrook Station Phytoplankton and Water Quality Page 15 of 25 l

l

l l

I l determine the' impact of Seabrook Station References Cited operation through its initial 5 years of opera-tion showed significantly higher abundances Blasco, D.1978. Observations on the diel of total phytoplankton and the diatem S. migration of marine dinoflagellates off the costatum during the operational period. Baja California coast. Mar. Biol. 46:41-Minimal differences were found among the 47.

l three stadons (two nearfield and one farfield).

Conway, H.L.1977. Interactions ofinorgan-l Where significant operational or station differ- j i ic nitrogen in the uptake and assimilation ences were indicated, the interaction term by marine phytoplankton. Mar. Biol.

(Preop-Op X Station) of the ANOVAs was 39:221-232.

i not significant, indicating that the differences l Ecological Analysts,~Inc. 1978. Phyto-among the stations were consistent, regardless plankton. Pages 4.2.1-4.2.28 in Part I.

of the plant operational status. Regardless of their length, alternative results from Seabrook Biological effects of once-through cooling.

Tidal rivers and estuades. Prepared for Station phytoplankton studies would not be The Utility Water Act Group. I expected. This is because phytoplankton Eppley, R.W., and B.J. Peterson. 1979.

l reproduction is very rapid, with generation Particulate organic flux and planktonic times of 1 to 3 days in coastal waters. If any new production in the deep ocean. Nature

l significant effects were to be observed, they 282

677-680.

should have occurred within the initial 5 Falkowski, P.G.1980. Primary productivity years of operation.

in the sea. Plenum Press, New York.

In conclusion, through-plant and thermal 235 pp.

plume entrainment effects have not affected Fisher, T.R., P.R. Carlson, and R.T. Barker.

the balanced indigenous population of phyto- 1982. Sediment nutrient regeneration in plankton in the nearshore Atlantic Ocean off three North Carolina estuaries. Est. l Seabrook Station. Phytoplankton community Coast. Shelf Sci. 14:101-116.

structure and biomass have not changed to Franks, P.J.S., and D.M. Anderson. 1992a.

any measurable extent nor in such a manner as Alongshore transport of a toxic phytoplank-to affect higher trophic levels. Similarly, ton bloom in a buoyant current: Alexan- l l

abundance and distribution of dinoflagellates

! drium tamarense in the Gulf of Maine.

causing PSP or other nuisance species have Mar. Biol. 112:153-164.

i not been affected as a result of plant opera- Franks, P.J.S., and D.M. Anderson.1992b.

tion. Therefore, it is proposed that phyto- Toxic phytoplankton blooms in the south-plankton studies at Seabrook Station be western Gulf of Maine: testing hypotheses eliminated from the Seabrook Station marine of physical control using historical data.

! monitoring program as soon as possible. Mar. Biol. 112:165-174.

l Chemical nutnent data collected are primadly Glover, H.E., D.A. Phinney, and C.S.

' linked to the production 'of phytoplankton. Yentsch.1986. Photosynthetic character- I There is no likely mechanism by which the istics of picoplankton compared with those operation of Seabrook Station could affect of larger phytoplankton populations in nutrient levels. Differences found between various water masses in the Gulf of i

the near- and farfield stations were minor for Maine. Biol. Oceanogr. 3:223-248.

nitrate and nitrite and the ANOVA interaction Haugen, E. 1991. Unpublished phyto-l terms were not significant, indicating that the plankton data filed with MWRA, Deer i differences among the stations were consis- Island offshore outfall monitoring studies,

! tent, regardless of the plant operational status. 1990.

Therefore, the measurement of chemical Haury, L.R., J.A. McGowan, and P.H.

nutrients should be discontinued along with Wiebe.1978. Patterns and processes in phytoplankton collections.

the time-space scale of plankton distribu-Seabrook Station Phytoplankton and Water Quality Page 16 of 25 i

l tions. Pages 277-327 in J.H. Steele, ed. trophic ultraplankton in the Nonh Atlantic.

Spatial patterns in plankton communities. Limnol. Oceanogr. 30:47-58.

Plenum Press, New York.

NAI (Normandeau Associates, Inc.).1981.

Hecky, R.E., and P. Kilham. 1988. Nutri-Seabrook plankton studies, January ent limitation of phytoplankton in freshwa-through December 1979. Tech. Rep. XI-ter and marine environments: a review of 3.147 pp.

recent evidence on the effects of enrich- NAL 1985.

ment. Limnol. Oceanogr. 33:796-822.

Seabrook environmental studies,1984. A characterization of base-Johnston, R.1963. Antimetabolites as an aid line conditions in the Hampton-Seabrook to the study of phytoplankton nutrition. J.

area,1975-1984. Tech. Rep. XVI.'I. .

Mar. Biol Assoc. U.K. 43:409-425. NAI. 1992. Seabrook environmental Keating, K.I. 1978. Blue-green algal studies,1991. A characterization of envi-inhibition of diatom growth: transitions ronmental conditions in the Hampton-from mesotrophic to eutrophic community Seabrook area during the operation of

', structure. Science 199:971-973. Seabrook Station. Tech. Rep. XXIII-II.

Knauer, G.A., J.A. Martin, and K.W. NAI. 1993. Seabrook environmental Bruland. 1979. Fluxes of particulate studies,1992. A characterization of envi-carbon, nitrogen, and phosphorus in the upper water column of the northeast ronmental conditions in the Hampton-Seabrook area during the opaation of Pacific. Deep-Sea Res. 26A:97-108.

Seabrook Station. Tech. Rep. XXIV-II.

Krom, M.D., and R.A. Berner. 1980.

Adsorption of phosphate in anoxic marine NAI.1995. Seabrook Station 1994 envi-ronmental studies in the Hampton-Sea-sediments. Limnol. Oceanogr. 25:797-806. brook area. A characterization of envi- I ronmental conditions during the operation Littler, M.M., D.S. Littler, S.M. Blair, and of Seabrook Station.

l J.N. Norris.1985. Deepest known plant NAI.1996. Seabrook Station 1995 envi-life discovered on an uncharted seamount. {

ronmental studies in the Hampton-Sea-  ;

Science 227:57-59.

brook area. A characterization of envi- I LMS (Lawler, Matusky & Skelly Engineers). ronmental conditions during the operation '

1979. Ecosystem effects of phytoplankton of Seabrook Station.

and zooplankton entrainment. EA-1038. Padmanabhan, M., and G.E. Hecker.1991.

Research project 876. Preaared for Comparative evaluation of hydraulic model Electric Power Research Institute, Palo and field thermal plume data, Seabrook Alto, CA. ,

Nuclear Power Station. Alden Research  !

Lorenzen, C.J.1976. Primary production in Laboratory Rep. No. 60-91/M620F. 12  !

the sea. Pages 173-185 in D.H. Cushing pp. + 4 tab. + 11 figs.

and J.J. Walsh, eds. The ecology of the Parsons, T.R., M. Takahashi, and B.

seas. Saunders, CBS College Publishing. Hargrave. 1984. Biological oceano-Marshall, H.G., and M.S. Cohen. 1983. graphic processes. 3rd ed. Pergamon Distribution and composition of phyto- Press, New York. 330 pp.

plankton in northeastern coastal waters of Platt, T., and C.L. Gallegos.1980. Model-the United States. Est. Coast. Shelf Sci. ing primary production. Pages 339-362 in 17:119-131. P.G. Falkowski, ed. Primary productivity Morel, F.M.M., R.J.M. Hudson, and N.M. in the sea. Plenum Press, New York.

Price.1991. Limitation of productivity by Pratt, D.M. 1966. Competition between trace metals in the sea. Limnol. Oceanogr. Skeletonema costatum and Olisthodiscus l 36:1742-1755. luteus in Narragansett Bay and in culture.

l Murphy, L.S., and E.M. Haugen. 1985. Limnol. Oceanogr. 11:447-455.

l The distribution and abundance of photo-l Seabrook Station Phytoplankton and Water Quality Page 17 of 25

Redfield, A.C.1958. The biological control Stumm, W., and J.J. Morgan. 1981.

of chemical factors in the environment. Aquatic chemistry (2nd ed.). John Wiley Amer. Sci. 46:205-221. and Sons, New York.

l Ryther, J.H.1956. Photosynthesis in the Tetra Tech, Inc. 1978. Phytoplankton.

ocean as a function of light intensity. Pages 3.21 - 3.2-35 in Part III. Ocean-  :

Limnol. Oceanogr.1:61-70. '

sited plants. Vol.11. Chapter 3 - Ecologi-Ryther, J.H., and W.M. Dunstan. 1971. cal effects of once-through cooling on the Nitrogen, phosphorus, and eutrophication marine environment. Prepared for The s in the coastal marine environment. Science Utility Water Act Group.

171:1008-1013. Teyssandier, R.G., W._W. Durgin, and G.E.

Ryther, J.H., and J.G. Sanders. 1980. Hecker.1974. Hydrothermal studies of Experimental evidence of zooplankton diffuser discharge in the coastal environ-control of the species composition and size ment: Seabrook Station. Alden Research L: distribution of marine phytoplankton. Laboratory Rep. No. 86-24/M252F. 47 ii Mar. Ecol. Progr. Ser. 3:279-283.

pp. + 20 photogr. + 119 figs. + 2 app.

Shapiro, L.P., and E.M. Haugen. 1988. Thomas, W.H. 1969. Phytoplankton -

Seasonal distribution and temperature nutrients enrichment experiments off Baja tolerance of Synechococcus in Boothbay California and in the eastern equatorial Harbor, Maine. Est. Coast. Shelf Sci.

Pacific Ocean. J. Fish. Res. Board Can.

26:517-525. 26:1133-1145. .

Smayda, T.J. 1970. The suspension and Valiela,I.1984. Marine ecological processes sinking ofphytoplankton in the sea. Ocean-Springer-Verlag, New York. 546 pp.

ogr. Mar. Biol. Ann. Rev. 8:357-414. Venrick, E.L., J.A. McGowan, and A.W.

Stavn, R.H.1971. The horizontal-vertical Mantyla.1973. Deep maxima of photo-distribution hypothesis: Langmuir circula- synthetic chlorophyllin the Pacific Ocean.

tions and Daphnia distributions. Limnol. Fish. Bull., U.S. 71:41-52.

Oceanogr. 16:453-466.

YAEC (Yankee Atomic Electric Company).

Steemann Nielsen, E., and E.G. Jorgensen. 1982. Effects of thermal discharges from 1968. The adaptation of plankton algae, ocean-sited power plants. Prepared for III. With special consideration of the The Utility Water Act Group, Open-ocean importance in nature. Physiol. Plant. Task Force.

21:647-654.

Strickland, J.D.H. 1965. Production of organic matterin the primary stages of the oceanic food chains. Pages 478-610 in J.B. Riley and G. Skirrow, eds. Chemical oceanography. Academic Press, New York.

APPENDIX Summaries of Other United States. Most of these power plants

_ Phytoplankton Studies were sited on the ocean or on estuaries. The summaries are ordered geographically from The following is a series of summaries from south to north, with generally increasing a review of phytoplankton studies conducted relevance to Seabrook Station. Operational

! between 1962 and 1982 at thirteen electrical characteristics of these plants and dates of the i generating stations on the eastern coast of the phytoplankton studies are given in Table 5.

j Seabrook Station Ph> plankton and Water Quality Page 18 of 25 l

i Crystal River. ~ Fox and Moyer (1973, 1 1975) reported on effects to phytoplankton of increases in temperature from power plant operation when ambient temperatures were the Crystal River Power Plant, located in low, but rates were depressed when tempera- I Florida on the Gulf of Mexico. They initially tures approached ambient summer maxima.

conducted a series of experiments designed to An exception ocetured at the plant located on a examine the effects of the plant's thermal  ;

reservoir which drew cool hypolimactic water '

discharge alone. A second set of experiments into its intakes; no depression in photosyn-took place when the plant intakes were being thetic rate was observed. Mortality of phyto-chlonnated. They demonstrated that changes plankton from through-plant entrainment was in primary production were related more to the noted only during chlorination or when intake ambient water temperature than to the plant-temperatures exceeded some threshold value, induced increase in water temperature. With a These temperatures varied seasonally and AT 29'F, decreases in productivity of 14 to geographically, but typically ranged from 77 48% occurred when intake temperatures to 86*F. Longer exposure experiments were

' exceeded 81*F. However,in one case, when the intake temperature was 76*F, an 8% conducted to evaluate effects of passage through a dischar increase in productivity was found. The gradual cooling. gemortality canal and, consequen Low was found decreases in productivity did not necessarily untilintake temperatures exceeded 86*F.

indicate death of organisms, but rather a i

reduction in the efficiency of photosynthesis. Calvert Cliffs. Relatively long-term Also, loss of some cells due to through-plant ecological studies for the Calvert Cliffs -

entrainment was offset by increasing rates of Nuclear Power Plant were summarized in photosynthesis by.stuvivors in the discharge.

Primary production decreased 57% as a result Heck (1987). The discharge of this plant is released along the 10-ft depth contour from a of through-plant entrainment in conjunction conduit about 850 ft offshore in the Maryland I with chlorination, but only a 13% loss in waters of Chesapeake Bay. Sellner and primary production occurred in the absence of j Kachur (1987a, b) presented results from an '

chlorine. It was concluded that the number of 8-year study of phytoplankton in the bay and microorganisms killed by the Crystal River a 5-year study of through-plant entrainment.

Power Plant was insignificant, except when Similar to Seabrook Station, the spring the plant was chlorinated. Nevertheless, loss assemblages were dominated by diatoms of primary production from plant operation (Cyclotella caspia and Chaetoceros spp.),

was offset by increased photosynthesis. summer collections by microflagellates and Also, dead organisms were believed by Fox dinoflagellates (although 35% of the total and Moyer (1973) to be rapidly recycled by were diatoms), and in winter, again by dia-decomposers-that released soluble nutrients i toms (Skeletonema costanun and Chaeroceros immediately available to primary producers.

spp.). Through-plant entrainment frequently Marshall, Chesterfield, and Indian resulted in reductions of phytoplankton density and in chlorophyll a concentrations, River. Smith et al. (1974) described the particularly in summer when species of effects of plant entrainment on phytoplankton flagellates dominated the collections. Photo-photosynthesis at several mid-Atlantic power synthesis, as measured by oxygen evolution plants (Marshall, reservoir; Chesterfield,

, or M C uptake, showed significant differences

~ nyerine; Indian River, estuarine). Intake and between intake and discharge stations, with discharge samples were experirnentally manip- entrainment-induced inhibition greatest during ulated to distinguish irreversible effects of warmer months when flagellates were most l condenser passage from temporary photosyn- abundant and ambient water temperatures thetic responses to increases in temperature.

exceeded 77'F. In track autoradiography Photosynthetic rates were stimulated by experiments with four commonly entrained Seabrook Station Phytoplankton and Water Quality Page 19 of 25

species, carbon fixation in the flagellate a Cryptomonas acuta was significantly de- mort'lity of phytopl' ankton, but surviving cells usually recovered and reproduced before pressed from July through September. reaching the end of the discharge canal. It i

However, the dinoflagellate Prorocentrum was concluded that entrainment-related losses minimum and the diatoms Cyclotella caspia (or gains) did not have consistent near-field and Thalassionema nitzschioides were not effects on phytoplankton and Chalk Point l

affected by entrainment. Furthermore, brief Station's impact on phytoplankton was limited exposure to the thermal plume was generally to the discharge canal. Plant operation was i

non-lethal. Although through-plant entrain-

! therefore relatively unimportant in determuung ment apparently caused changes in cell phytoplankton productivity or biomass.

densities (particularly for flagellates), chloro-phyll a concentrations, and carbon fixation

! rates, no demonstrable effects were seen in Indian River. Jensen et al. (1974) sum-the near-field vicinity of the plant. Sellner and marized the effects of the Indian River Station (Delaware) on phytoplankton and primary l Kachur (1987b) suggested that the Calvert productivity. When ambient water tempera-Cliffs Plant had limited detectable effects on tures of the Indian River estuary were f/2*F, phytoplankton and primary productivity in the i which was for about 8 months of the year,.

waters of Chesapeake Bay.

primary productivity was stimulated by the plant's thermal discharge. During sununer.

Chalk Point. Biological studies at the some depression of productivity occurred b i

Chalk Point Steam Electric Station, located on the thermal plume. However, this occurre the Patuxent River, a tributary of Chesapeake when primary production in the Indian Riv Bay in Maryland, were summarized by was at a seasonal maximum and whc MMES (1985). The productivity of phyto- primary consumers (i.e., zooplankton, filter-plankton near this station was higher relative feeding fish) were at seasonal minima. There-to many other estuaries due to anthropogenic fore, Jensen et al. (1974) thought that a severe  !

sources of nutrients alteration in the energy flow to higher trophic i 100 g of chlorophyll a L- andwere alp)al common.blooms (>60-levels was unlikely. Primary production was Because of the strong natural gradients in stimulated by plant operation when it was salinity and nutrients near the station, spatial otherwise below annual peak levels and this l changes in phytoplankton biomass and occurred in conjunction with maximum  ;

i productivity were high and quantification of populations of zooplankton and filter-feeding '

power plant effects' was difficult to distinguish fish. This yielded additional food resources from natural events. Phytoplankton biomass to higher trophic levels. They concluded that as measured by chlorophyll a concentrations the plant did not permanently alter the photo-generally declined following through-plant synthetic capacity of phytoplankton in the  !

entrainment. In 13 of 16 observations, chlo- Indian River nor did it significantly affect the rophyll a was higher at the plant intake than at ecology of the estuary.

the end of the 1.25-mi long discharge canal, Brooks (1974) gave additional details on the with an average reduction of 20E Much of effects ofphytoplankton through-plant entrain-the loss appeared to have been related to ment at the Indian River Station. He de-mechanical damage, although intermittent scribed chlorophyll a measurements, MC chlorination also reduced productivity. In the uptake experiments, and cell counts. These absence of chlorine and under reduced power variables tended to follow similar patterns that production (i.e., lower AT), productivity was were related to the annual water temperature l frequently enhanced. No increase in the cycle. In approximately half of the samples abundance or distribution of nuisance species the concentration of chlorophyll a was higher i

(e.g., blue-green algae) was found at the at the intake station than in the discharge. He station. Through-plant entrainment did cause suggested that chlorophyll a losses were Seabrook Station Phytoplankton an.d Water Quality Page 20 of 25 i

related to the presence of relatively fragile thesis (as measured by Id C uptake) occurred species (flagellates and naked dinoflagellates) from March through May, when ' ambient that may have been affected by mechanical temperatures were 41 to 50*F. When ambient damage during plant passage. However, temperatures inemased from 61 to 72'F, reduc-chlodnation of cooling water reduced chloro- tions of 60 to 90% were found. In fall, when phyll a concentrations by 17 to 73%. At high intake temperatures were 48 to 65'F, a 5 to

(>72*F) summer temperatures the 10.8-25% increase n productivity occtured. In Jan.

12.6'F AT catised lower 14 C uptake at the uary and February, productivity was some-discharge relative to the intake, but during the times two to three times greater at the dis-rest of the year uptake rates were stimulated.

charge than the intakes, although the average The length of exposure to elevated tempera- increase was about 25%. When plant chlori-tures in the discharge plume had little effect on nation occurred, it was found to decrease Id C uptake rates during cooler months, but primary productivity by about 70 to 80%

long exposures during summer depressed (Carpenter et al.1972). However, the uptake rates significantly. He concluded that chemical and particulate forms of dead, rapid cooling to ambient temperatures after entrained phytoplankton were not altered and exposure to elevated temperatures minimizes cells did not smk or disintegrate (Carpenter et the influence of power plants on phyto- al.1971). Therefore, dead cells were notlost plankton productivity, as a potential souxe of carbon to other trophic l levels. Because of the short generation time Millstone. The largest electrical generating and rapid reproduction of phytoplankton, the facility in New England is the Millstone quick dilution of the Millstone Station thermal Nuclear Power S,tation, located on eastern plume in Long Island Sound, the survival of i

Long Island Sound in Waterford, CT. When I many cells following through-plant entrain- I in operation, all three units discharge heated ment, and the availability of dead cells to other water into a quarry pond, where the average organisms,it was concluded that the operation transit time before the effluent reaches Long of this plant did not have any adverse effects Island Sound through two openings in the on the phytoplankton community (NUSCO quarry wallis about 85 minutes. NUSCO 1976,1983b).

(1983a) reported that 120 taxa of phyto-plankton (about two-thirds of them diatoms) Brayton Point. Brayton Point Generating were collected in through-plant entrainment Station, located on Mount Hope Bay in studies conducted at Millstone Units 1 and 2 Massachusetts is the second-largest generating from 1977 through 1980. The top ten taxa, station in New England. MRI and NEPCO however, comprised about 90% of the total, (1978) summarized a 5-year study of with various. microflagellates (41%) and phytoplankton that was designed to examine Skeletonema costarwn (20%) most abundant. station operation under a maximum allowed Diatom blooms occurred from February discharge temperamre of 95'F. Phytoplank-through April and microflagellates and ton abundance, number of species, diversity, dinoflagellates peaked during summer. A growth, and photosynthetic rates were secondary diatom bloom was found in late compared between observations at control August and September. Annual cycles found stations not exposed to the thennal plume and wem characterized as typical of many nonhern a test station which had maximum exposure.

temperate coastal areas. Carpenter et al. No immediate damage was found for phyto-(1972,1974) studied the effects of through- plankton immediately following through-plant plant entrainment at Millstone Station with and entrainment, but a slight decrease in 14C without the additional effect of chlorination, uptake was found at the end of the 3,200-ft In the absence of chlorine and at a AT of long discharge canal. Overall, exposure to 23.4*F, a 25 to 40% decrease in photosyn- elevated temperatures had little effect on Seabrook Station Phytoplankton and Water Quality Page 21 of 25

cultures of phytoplankton collected at the test Pilgrim. Toner (1984) summarized phyto-and two control stations. In most cases no plankton studies completed in Cape Cod Bay differences in growth were observed, or, in relating to Pilgrim Nuclear Power Station, some instances, growth rates were higher for located near Plymouth, Massachusetts on the discharge samples. No significant differences northwestern shore of Cape Cod Bay. Peak were found in the number of species, diversi- phytoplankton densities were found in tv, or densities amo.ng the stations. Although February or March with a secondary peak in somewhat variable from month to month, the July. Seasonallows occurred in December ratio of the. abundance of the dominant and January. The community was dominated diatoms Skeletonema costatum and Thalas- by diatoms, particularly Skeletonema siosirapsueudonana to total phytoplankton costatum, Leptocylindrus spp., and remained similar at test and control stations. Thalasslosira nordenskioldii. Flagellates and No occurrence of nuisance species was dinoflagellates were also common, but less observed as a result of the thermal effluent. numerous than diatoms. Observed fluctua-MRI and NEPCO (1978) concluded that the tions in species composition and abundance phytoplankton populations in Mount Hope were noted to have been similar to other Bay were not affected by plant operation.

studies done in the Gulf of Maine. No Furthermore, no effects on higher trophic significant differences .were found in species levels were expected to occur as a result of composition of phytoplankton between the any changes to the phytoplankton population. plant discharge area and at offshore control stations.

Montaup and Cape Cod Canal. MRI(1976) presented results of14C uptake Goldman and Quinby (1979) examined the experiments conducted on phytoplankton effects of through-plant entrainment and collected at Pilgrim Station. When the plant chlorination at the Montaup and Cape Cod was chlorinating, a significant reduction (48-Canal Power Plants on phytoplankton pro- 98%) was found in 2 C uptake on 11 of 12 ductivity in laboratory cultures. Species occasions for phytoplankton collected at the found at these two electrical generating discharge in comparison to samples taken at stations in Massachusetts were predominately the plant intake. When just mechanical and diatoms. Although many algal cells were thermal effects of through-plant entrainment killed following plant passage, the stuvivors were considered,14C uptake actually in-grew and multiplied at rates comparable to creased in most discharge samples relative to control samples. The recovery of survivors, intake samples. With no thermal addition whether measured by abundance, chlorophyll (mechanical effects only), results were a concentration, or adenosine triphosphate equivocal as about one half of the tests had (ATP), was similar among heated discharge, greater uptake in discharge samples and one-heated-chlorinated discharge, and intake half had greater uptake for the intake samples.

samples. The only difference was a 1 to 6- Cultures of dominant species showed no day lag in recovery that occurred in some of significant long-term adverse effects from the discharge samples. This was likely due to entrainment. Many of the species tested smaller initial numbers of cells in the culture showed better growth in cultures from because of entrainment mortality. Goldman discharge samples than in those from intake and Quinby (1979) concurred with the samples. It was concluded that Pilgrim findings of Fox and Moyer (1975), indicating Station operation did not appreciably affect minimal effects to phytoplankton, as long as local phytoplankton populations and, subse-entrainment temperatures are quickly lowered quently, studies were discontinued by the to ambient levels. Pilgrim Nuclear Power Station Technical-Advisory Committee (BECO 1976).

Seabrook Station Phytoplankton and Water Quality Page 22 of 25

1 l Salem Harbor. Phytoplankton biomass t

and seasonal fluctuanons in ATP, MC uptake, Montsweag Bay by Mc' Alice and Jones 1978).

and chlorophyll a concentrations were ob- S. costatum had nr.arly 100% survival served by Anderson et al. (1975) at the Salem following through-plant entrainment, even when discharge temperatures exceeded 86*F.

Harbor Generating Station in Massachusetts j

to predict effects of the operation of a fourth Crippen (1974) reported that this diatom, i

generating unit. Results showed no signifi- when grown at 77'F, was not affected by a

! AT of 25*F; cultures held at 68'F were cant differences in ATP levels or in primary affected by this temperature change, but were productivity.among intake, discharge, and able to recover. Lmdsay et al. (1978) cited control stations. The seasonal pattem of chlor-ophyll a appeared to follow that of other other studies (Matsue 1954; Hirayama and temperate estuaries. They concluded that little Hirano 1970) which demonstrated that S.

monality of phytoplankton occurred from costatum was able to resist temperatures as through-plant entrainment and that operation high as 97 to 104*F. However, Briand (1975) reported that average survival of S.

of Salem Harbor Unit 4 apparently had little effect on the local phytoplankton population. costatum was 35.5% following through-plant entrainment at a coastal California power plant, even though discharge temperatures Maine Yankee. The Maine Yankee Nuclear never were greater than 88'F.

Generating Station is located in Wiscasset, Lindsay et al. (1978) noted that one possible Maine on the western shore of Montsweag

~

Bay, off the Gulf of Maine. The thermal effect of through-plant entrainment mortality would be a gradual decline in abundance of effluent is discharged through a 44-ft deep species most sensitive to this impact, with mid-channel diffuser in the bay. The two l their replacement by more hardy forms. For 500-ft long diffuser pipes result in high speed example, an increase in the occurrence and 4

jets (12.8 ft s ) of heated water that rapidly abundance of Melosira numuloides (a very entrain and mix with ambient water. Lindsay et al. (1978) reported on a 5-year study of heat-resistant diatom) coincided with a concurrent decrease in Chaeroceros spp. since through-plant entrainedphytoplankton. A late the start-up of the Maine Yankee Plant.

spring to mid-summer bloom typically was However, McAlice and Jones (1977) con-found, with lowest abundance in winter. Of cluded that the changes observed in species all taxa collected, Chaetoceros spp. was the '

most abundant, with Skeletonema costatum abundance were within limits of annual variability. Other species, including S.

also commonly collected. Overall, monality costatum, remained at relatively sirnilar levels of through plant entrained phytoplankton was of abundance during the study.

slight when discharge temperatures were low, McAlice and Jones (1978) assessed the but during summer increased mortality was effect of the operation of the Maine Yankee observed. Chaeroceros spp. were most sen-Nuclear Generating Station on species sitive and 24. hour survival following entrain- composition, abundance, and distribution of ment was found to have been inversely phytoplankton populations at five stations correlated with discharge temperature. located throughout Montsweag Bay. Twenty Generally, survival of Chaeroceros exceeded species were chosen for analysis from the 290 75%, but nearly 100% mortality occurred taxa collected. They found that the bay was when discharge temperatures exceeded 84*F.

not warmed by the thermal discharge from the Because high survival rates were found in plant. No significant changes occurred in samples when there was no thermal output mean cell densities or in species diversity as a 1

L from the plant, most mortality was probably result of power plant operation. Through-heat-related. Crippen (1974) found that the plant entrainment effects appeared to be mini-thermal tolerance of Chaerocerosdepended mal and the heated effluent did not have direct upon the species (25 were reported in effects on phytoplankton. Lindsay et al.

Seabrook Station Phytoplankton and Water Quality Page 23 of 25

(1978) also noted th'at because of the relatively and productivity 'of entrained. phyto-small amounts of water withdrawn from plankton. Mar. Biol. 16:37-40.

Montsweag Bay in comparison to its volume Carpenter, E.J., B.B. Peck, and S.J. Ander-and tidalprism and because of the rapidity of son.1974. Summary of entrainment re-1 phytoplankton reproduction (conservatively, search at the Millstone Point Nuclear Pow-one division every 2 days), the impact of er Station,1970 to 1972. Pages 31-35 in through-plant entrainment at the Maine L.D. Jensen, ed. Entrainment and intake Yankee plant appeared to be slight. In addi- screening. Proceedings of the second tion to the phytoplankton studies, McAlice et entrainment and intake screening work-al. (1978) concluded after an 8-year study of shop. EPRI Pub. No. 74-049-00-5. Palo water quality at the Maine Yankee Nuclear Alto, CA.

Generating Station that the operation of that . Crippen, R.W.1974. Some thermal effects plant had no detectable effects on the spatial or of a simulated entrainment regime on seasonal distribution of nutrients (nitrate, marine plankton. Ph.D. Thesis, Universi-phosphate, silicate).

• ty of Maine, Orono, ME.109 pp.

Curl, H., and G.C. McLeod. 1961. The physiological ecology of a marine diatom, Appendix References Cited Skeletonema costatwn (Greve.) Cleve. J.

Mar. Res. 19:70-88. (Not seen, cited by Anderson, C.O., Jr., D.L. Brown, B.A. Lindsay et al.1978).

Ketschke, E.M. Elliot, and P.L. Rule. Fox, J.L., and M.S. Moyer. 1973. Some ,

1975. The effects of the addition of a effects of a power plant on marine fourth generating unit at the Salem Harbor l microbiota. Chesapeake Sci.14:1-10.

Electric Generating Station on the marine Fox, J.L., and M.S. Moyer.1975. Effect of i

ecosystem of Salem Harbor. Mass. Div. l power plant chlorination on estuarine  !

Marine Fish., Dept. Fish., Wildl., and productivity. Chesapeake Sci. 16:66-68. I Rec. Vehicles. 47 pp. Goldman, J.C., and H.L. Q,uinby. Phyto-BECO (Boston Edison Company). 1976. plankton recovery after power plant Marine ecology studies related to operation l entrainment. J. Water Poll. Control Fed. l of Pilgrim Station. Semi-annual Report 51:1816-1823.

No. 7. July 1975 - December 1975. Heck, K.L., Jr.1987. Summary and conclu-Briand, F.J-P.1975. Effects of power plant sions. Pages 276-284 in K.L. Heck, Jr.,

cooling systems'en marine phytoplankton. ed. Ecological studies in the middle reach Mar. Biol. 33:135-146. of Chesapeake Bay - Calvert Cliffs.

Brooks, A.S.1974. Phytoplankton entrain- Lecture notes on coastal and estuarine ment studies at the Indian River Estuary, studies 23. Springer-Verlag, New York.

Delaware. Pages 105-111 in L.D. Jensen, Hirayama, K., and R. Hirano. 1970. Influ-ed. Entrainment and intake screening. Pro- ences of high temperature and residual ceedings of the second entrainment and chlorine on marine phytoplankton. Mar.

intake screening workshop. EPRI Pub. Biol. 7:205-213.

No. 74-049-00-5. Palo Alto, CA. Jensen, L.D., R.M. Davies, R.A. Smith, and Carpenter, E.J., S.J. Anderson, and B.B. A.S. Brooks. 1974. Entrainment of Peck.1971. Second semi-annual report planktonic organisms into cooling water on entrainment of marine plankton through systems of three Mid-Atlantic thermal Millstone Unit 1 to Northeast Utilities power plants. Pages95-104 in L.D. Jen-Service Co. Woods Hole Oceanographic sen, ed. Entrainment and intake screen-l Institution, Woods Hole, MA.102 pp. ing. Proceedings of the second entrain-l Carpenter, E.J., B.B. Peck, and S.J. Ander- ment and intake screening workshop.

son. 1972. Cooling water chlorination EPRI Pub. No. 74-049-00-5. Palo Alto.

Seabrook Station Phytoplankton and Water Quality Page 24 of 25

l I l

Lindsay, P., S.L. Barker, and J.R. Stewart. to 95'F. 252 pp.

1978. Monitoring the effects of the con-NUSCO (Northeast Utilities Service Com-l denser cooling water system on plankton pany).1976. Environmental assessment and larval organisms. Pages 4.1 - 4.135 in of the condenser cooling water intake Maine Yankee Atomic Power Co. Environ- structures (316b demonstration). Vol.1.

mental surveillance and studies at the NUSCO.1983a. Phytoplankton species com-Maine Yankee Nuclear Generating Station position. Pages 2.2 2.2-12 in Mill-1969-1977.' Final report.

Matsue, Y. stone Nuclear Power Station Unit 3 i 1954 On the culture of the environmental report. Operating license  !

marine plankton diatom, Skeletonema cos- stage. Vol.1.

tatwn (Greve.) Cleve. In Review of fish- NUSCO.1983b. Phytoplankton and zoo- l l eries science in Japan. Jap. Soc. Adv. plankton entrainment. Pages 5.1 5.1-l Sci., Tokyo. 41 pp. (In Japanese). (Not 18 in Millstone Nuclear Power Station seen by Lindsay et al.1978; cited in Curl Unit 3 environmental report. Operating i

i and McLeod 1961). license stage. Vol. 2.

l McAlice, B.J., and F.W. Jones. 1977. Net Sellner, K.G., and M.E. Kachur. 1987a.

phytoplankton. Pages 1.7-138 - 1.7-153 Phytoplankton. Pages 12-37 in K.L.

in Maine Yankee Atomic Power Co. Heck, Jr., ed. Ecological studies in tlie Environmental surveillance rep. no.10. middle reach of Chesapeake Bay - Calven McAlice, B.J., J. Cura, and D. Carlson. '

i Cliffs. Lecture notes on coastal and 1978. Nutrient chemistry. Pages 7.1 -

estuarine studies 23. Springer-Verlag, 7.36 in Maine Yankee Atomic Power Co. New York.

Environmental surveillance and studies at Sellner, K.G., and M.E. Kachur. 1987b. 1 the Maine Ya'nkee Nuclear Generating Entrainment studies. Phytoplankton l Station 1969-1977. Final report. entrainment. Pages 227-239 in K.L.

McAlice, B.J., and F.W. Jones. 1978. Net Heck, Jr., ed. Ecological studies in the l

phytoplankton. Pages 8.3.1 - 8.3.32 in middle reach of Chesapeake Bay- Calven Maine Yankee Atomic Power Co. Environ- Cliffs. Lecture notes on coartal and mental surveillance and studies at the estuarine studies 23. Springer-Verlag, Maine Yankee Nuclear Generating Station New York.

1969-1977. Final report. Smith, R.A., A.S. Brooks, and L.D. Jensen.

MMES (Martin Marietta Environmental Sys- 1974. Effects of condenser entrainment tems).1985. Impact assessment report: on algal photosynthesis at Mid-Atlantic Chalk Point Steam Electric Station aquatic power plants. Pages 113-122 in L.D.

monitoring program. Columbia, MD. Jensen, ed. Entrainment and intake MRI (Marine Research, Inc.). 1976. Entrain- screening. Proceedings of the second ment investigations and Cape Cod Bay ich- entrainment and intake screening work-thyoplankton study. September-Decem- shop. EPRI Pub. No. 74-049-00-5. Palo ber,1975. Twelve-month summary for Alto, CA.

1975. Pages III.C.2-i - III.C.2-155 in Toner, R.C. 1984. Phytoplankton of Marine ecology studies related to operation western Cape Cod Bay. Pages 57-64 in of Pilgrim Station. Semi-annual Rep. No. J.D. Davis, and D. Merriman, eds.

7. July 1975 - December 1975. Boston Observations on the ecology of western

_ Edison Co. Cape Cod Bay, Massachusetts. Lecture MRI, and NEPCO (New England Power notes on coastal and estuarine studies 11.

l Company).1978. Brayton Point Generat- Springer-Verlag, New York.

ing Station, Mount Hope Bay, Somerset, Massachusetts. Supporting document for cooling water discharge of temperature up Seabrook Station Phytoplankton and Water Quality Page 25 of 25 l

a ZOOPLANKTON Summary of the Proposed Monitoring Program after 5 Years of Operation The objective of the proposed zooplankton program is to monitor the effects of Seabrook Station operation on larger zooplankton, which, based on life history information, have greater potential for plant impact. A modified macrozooplankton sampling design would retain sufficient sensitivity to detect potential plant operational impacts on these larger planktonic organisms. Programs for microzooplankton and bivalve larvae are proposed  ;

to be discontinued because of the high reproductive capacity of the potentially affected I organisms and the lack of significant findings from the monitoring programs after five years of plant operation. Therefore, these programs have served their purpose as part of '

the Seabrook Station environmental monitoring studies.

1. Microzooplankton program, which monitors meroplankton (early developmental stages of benthic invertebrates) and holoplankton (which spend their entire life in the water column), is recommended to be discontinued because after 5 years of plant operation the program has met its objective of assessing potential impact on this community, and none has been detected.

The meroplankton taxonomic groups (Bivalvia, Gastropoda, Polychaeta, and Cirripedia) are extremely abundant and, depending on the length of their planktonic stage, can be dispersed over long distances. Successful recmitment is dependent on suitable benthic habitat. Ifimpacts to meroplankton affected subsequent recruitment, they would be reflected in the macrobenthos community. To date, no such impacts have been obstved.

Due to the rapid generation times and food limitations affecting abundance for tintinnids and rotifers, the potential for impacts from Seabrook Station is very l low and, not surprisingly, impacts have not been detected for these '

holoplankton groups.

From examination of the data on the dominant copepods collbetedin the microzooplankton program, it is apparent that the loss ofindividuals due to through-plant entrainment would have minimal effects on their populations in the Hampton-Seabrook area. Rapid generation turnover rates and large reproductive capacities of these organisms enable them to compensate for high natural mortality and environmental perturbations. Because of their high thermal tolerance, thermal plume entrainment should not affect these organisms.

In addition, it has been well documented that other coastal marine power plants do not appreciably affect zooplankton communities, and, as a result, their long-term microzooplankton studies have been concluded.

l 2.

Bivalve larvae programs (combined both field and entrainment programs) provided abundance information and analyses for bivalves which indicated no significant effect of Seabrook Station operation after five years, and it is recommended that, because both programs have met their objects, they be concluded.

Larvae of the recreationally important soft-shell clam are entrained in relatively small numbers (about 0.1% of the total bivalve entrainment).

Apparently, larval densities are not related to spat abundances, which appear to be habitat-limited. Similarly blue mussel larvae, which represented over 50% of both field and entrainment bivalve larvae collected, have not been affected after five years of plant operation, despite numerically-high entrainment estimates. The high fecundity of bivalves, coupled with their relatively long larval life stage, makes a localized impact less likely to occur, as these species have evolved to compensate for very high losses in their early life history.

Although plant impact is unlikely, monitoring of the important soft-shell clam resource in Hampton-Seabrook as spat will continue (see Soft-shell Clam evaluation.

3. Macrozooplankton modifications were based on the results of analyses of data collected through 1995. It is proposed that macrozooplankton collections be reduced from three to one sample per sampling date at stations P2 and P7. Station P5 would no longer be sampled.

Results from ANOVAs for each selected species, using the proposed sampling design, indicated that there would be minimal loss in sensitivity to detect a potential plant operationalimpact. The estimated variances for the critical interaction and error terms were similar with either one sample at two stations (proposed) or with three replicates at three stations (current), suggesting that current sample replication is redundant.

The sampling of only one of two nearfield stations will not reduce the ability of the program to detect potential plant operationr? impacts using the BACI ANOVA model, nor affect additional analyses (i.e., numerical classification and MANOVA).

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ZOOPLANKTON PROPOSED PROGRAM PAST PROGRAM

1) Micruzooniankton

. After 5 years of plant operation, no impacts have been detected for . Stations / Sampling frequency: Stations P2, PS, and P7 - surface and selected dominant taxa tested with ANOVA; these taxa have short bottom samples - monthly December through February and twice a month generation times and are ubiquitous in the Gulf of Maine. Not detecting March through November an impact was anticipated and that outcome has been demonstrated.

Therefore other plankton communitics will be followed to demonstrate . Replicates: 4 collected; 2 processed i continuance of balanced indigenous populations; this program would not continue. . Total samples / year: 504 collected; 252 processed  !

. Data collected: Density per m' I 2a) Bivalvelarvac I

= Individuals collected in this program are early developmental stages of

• Stations / Sampling frequency: Stations P1, P2, PS, and P7 sampled l

benthic invertebrates that have a high fecundity to compensate for very weekly from mid-April through October high losses during their early life history and are dispersed over a large area by currents. After 5 years of plant operation, no impacts have been . Replicates: 2 replicates detected for selected dominant and commercially important species tested l

with ANOVA. Other programs that examine the success of their . Total samples /ycar: 224 recruitment to the benthic community will continue, therefore this program would be discontinued. . Data collected: Densiy act m' e

i t

I t

. _ _ _ . . _ . . . . _ _ . _ . . . . __m___m . _ -___ _ __ ._____._..__ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ . . _ _ _ _ _ _ . _ . _ _ _ _ _ _ . _ _ _ _ _ _ _ . _ _ _ _ _ _ . -_ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ ___

?

, . 2 ZOOPIANKTON (continued)

PROPOSED PROGRAM PAST PROGR AM 2b) Divalve larvac entrainment  :

. Theprimary reason for this program was the concern of entraining soft- .

Stations / sampling frequency: Sampled 4 times a month from April shell clam larvae. Annual entrainment estimates after 5 years of plant through October at the Seabrook Station screenhouse.

operation show that these larvae are a minor component (about 0.1%) of the total bivalve entrainment. In addition, there was no relationship found . Replicates: 3 replicates between larval abundance and spat set (see soft-shell clam evaluation).

Therefore thjs program would not continue. . Total sampics/ year: 84 t

. Data collected: Density per m'

3) Macrozoonlankton t

. Stations / Sampling frequency: Stations P2 and P7 sampled twice per .

Stations / Sampling frequency: Station P2, PS and P7 sampled twice per month month

. Replicates: I sample .

Replicates: 4 replicates collected; 3 replicates processed

Total samples /ycar: 48

Total samples /ycar: 288 collected; 216 processed

. Data coliccted: Density per 1000m' . Data collected: Density per 1000m' I

e

e WORKING DRAFT EVALUATION OF SEABROOK STATION ZOOPLANKTON SAMPLING PROGRAMS -

AFTER FIVE YEARS OF PLANT OPERATION Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station Seabrook, New Hampshire 03874 Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford, New Hampshire 03310 August 1996

Evaluation of Seabrook Station Zooplankton Sampling Programs After Five Years of Plant Operation Introduction Seabrook Station, an 1150-Mwe nuclear-fueled power plant, is located in Seabrook, New l

Hampshire. The station uses Atlantic Ocean water to condense steam and cool vital i

equipment associated with the service water system. The station has three mid-water (abo 17 ft off-bottom) intake stmetures located in depths of about 55 ft approximately 1.3 mi offshore of Hampton Beach (Fig.1). Water withdrawn through a 19-ft diameter tunnel travels about 3.25 mi to the plant, having a transit time of around 70 min. The station is permitted to 6

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l use up to 2.70 X 10 m'. day" (31.3 m's") of seawater, 95% for non-contact condenser cooling water and 5% for service water systems. Water used at the station is rel' eased throug '

l the onsite Discharge Transition Structure (DTS) and travels 3.1 mi through another 19-ft '

diameter tunnel to eleven diffusers located about 1 mi offshore of the mouth of Hampton-  ;

Seabrook Harbor at a depth of approximately 55 ft. The diffusers discharge water towards the surface at a velocity of about 15 ft sec" The average monthly increase in temperature (.iT) at  ;

the DTS can be up to 39'F and the maximum daily AT cannot exceed 41 F. The rise in temperature of the receiving waters cannot be greater than 5 F, except within 100 ft of the diffusers, where this limit only applies at the surface. This area is the nearfieldjet mixing I region. Previous hydrothermal modeling and field studies demonstrated that the area of the discharge plume is relatively small, with a surface temperature increase of 3*F encompassing an area of approximately 32 acres around the area of the discharge (Teyssandier et al.1974; Padmanabhan and Hecker 1991).

Zooplankton are ecologically important in aquatic ecosystems and occupy trophic levels between primary producers (mainly phytoplankton in pelagic marine systems) and higher level consumers. The term zooplankton generally refers to a diverse group of species encompassing many phyla. Zooplankton can be generally clas'sified into three functional groups. Holoplankton spend their entire lives in the water column and include many small 1

crustaceans (e.g., copepods and cladocerans), rotifers, and protozoans. Meroplankton primarily consist oflarval forms, particularly of benthic invertebrates such as mollusks and annelids that eventually settle out of the plankton. Tychoplankton are principally benthic invertebrates (e.g., some amphipods) that become planktonic by active migration into the water column.

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~ Zooplankton studies at Seabrook Station began in July 1976 and include three offshore programs, microzooplankton, macrozooplankton, and bivalve larvae, and after plant start-up, larval bivalve entrainment sampling was initiated. Each of these programs was established separately and has unique sampling methods. However, because the two bivalve programs are closely linked for assessment of Seabrook Station impact, they will be considered together in this evaluation.

Offshore zooplankton studies were initiated to establish baseline data suitable for assessing the effects of station operation by describing the seasonal, annual, and spatial trends in abundance and distribution and community composition of zooplankton in the nearshore waters off Hampton and Seabrook. Sampling also took place within the Hampton-Seabrook Harbor estuary for bivalve larvae because of the valuable soft-shell clam (Mya arenaria) recreational fishery there. Seabrook Station began commercial operation in August 1990.

Once online, potential impacts of plant operation on zooplankton included entrainment of all life stages of micro- and macrozooplankton and bivalve larvae through the condenser cooling-water system and effects associated with the discharge of heated condenser cooling water from the diffuser system, such as plume entrainment.

Three stations were used to provide abundance data for both micro- and macrozooplankton:

P2 and P5, termed nearfie1d, and P7, farfield (Fig.1). Bivalve larvae were also sampled at these three locations plus an additional station, P1, established within the Hampton-Seabrook

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Harbor. Once Seabrook Station began operation, entrained bivalve larvae were sampled at the plant intakes. Sampling gear and frequency of sampling for each of these specific programs 2

I varied and will be discussed separately below for each. Further detailed descriptions of methods, including laboratory processing, are found in NAI (1996a).

Data provided by the sampling programs were used in several types of analyses. These are  !

, described in detail in NAI and NUSCO (1994) and NAI (1996a, b, c, d) and include multivariate numerical classification and multivariate analysis of variance (ANOVA) of various zooplankton assemblages; graphical comparisons of annual abundance of selected j species; and a fixed effects ANOVA model using specific abundance data for selected species.  !

! Data for the ANOVA model met the criteria for a Before-After/ Control-Impact (B ACI) design  ;

(Stewart-Oaten et al.1986), where sampling was conducted prior to and during plant operation and sampling station locations included both potentially impacted and non-impacted i t

control sites.

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The purpose of this evaluation is to critically examine the methodologies and findings for each of the four zooplankton sampling programs after 5 years of Seabrook Station operation.

The effectiveness of each program will be assessed and proposals will be made to: 1) maintain current work, 2) enhance or modify programs where necessary, or 3) reduce sampling in cases where the datc collected, after 5 years of operations, indicates no plant impact and are no longer necessary for further assessment.

l Evaluation of Present Zooplankton Sampling Programs at Seabrook Station With Reco'mmendations For Future Studies j l

Micro:ooplankton i Review of sampling methodology. The small planktonic forms considered as microzooplankton were collected using a pump with the discharge filtered through a 76-pm mesh net. Data used for analyses are from two replicate samples collected at two depths - 2 (near-surface and bottom). Two stations are located in potentially impacted areas (nearfield),

3

one near the offshore intake (P2) and the other near the offshore discharge diffuser system (P5), and a third is a non-impacted, farfield control station (P7) that is approximately 7 km north of the discharge area (Fig.1). Samples were collected twice a month from March through November and monthly in December through February. Sampling at all three stations occurred from July through December 1986 and from April 1990 through the present. In addition, station P2 was sampled from January 1978 through December 1984 and station P7 from January 1982 through December 1984.

a The inconsistencies in the sampling time-series at all stations caused some limitations in the data used for analyses, particularly for impact assessment using the Before-After/ Control-Impact sampling design of Stewart-Oaten et al. (1986) and statistical testing based on ANOVA models. These data were used for numerical classification and MANOVA. For microzooplankton,' numerical classification used data only from station P2. Separate MANOVA tests were conducted on preoperational (stations P2 and P7) and operational (all stations) databases and, therefore, did not test the critical Preop-Op X Station interaction term.

ANOVA tests used data from only stations P2 and P7, as P5 did not have a full year of preoperational data available. Also, there was a fairly short preoperational period (January 1982 through December 1984) for the BACI design.

Sampling program evaluation. The microzooplankton taxa and life stages in the Hampton.

Seabrook area that composed about 95% of the individuals collected since 1978 at station P2 were representative of two distinct life history strategies, the holoplankton and meroplankton (Table 1). Dominant holoplankton groups collected were copepods (nauplii, copepodites, and adults), tintinnids (loricated protozoan ciliates), and rotifers. The major meroplankton groups were mollusk veligers (Bivalvia and Gastropoda) and larval polychaetes and barnacles (Cirripedia). Copepod nauplii were the most abundant and included the taxonomic categories of Copepoda, Oithona sp., and Pseudocalarms/Calanus spp. For the combined copepod life stages of copepodites and adults, Oithona sp. (probably O. similis) was the most abundant (10.7 % of the individuals collected), followed by Pseudocalanus sp. (6.2%), and Temora longicornis (3.7%). Predominant, but lesser abundant, holoplankton were the copepods 4

l Acartin sp. and Microsetella norvegica and the cladocern Evadne sp. Most commonly reported in other studies conducted in the northwest Atlantic Ocean Johnson 1973; Carter and Dadswell 1983; Sherma et al 1983; McLaren et l 1993).

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l A comparison of the abundance of selected microzooplankton taxa (Pseudo

),

Oithona sp., and Eurytemora herdmani) at stations P2 and P7 for data collec indicated no plant operational effects, based on no significant (p s 0.05) differenc j,

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in the critical Preop-Op X Station interaction term from the BACI-design AN

The only station difference found was for Oithona sp., which were more abundant at station P2 than at the fadield control station P7. Similarly, results from analyses on j {

commumty composition at station P2 showed that 92% of all collection dates clustered into

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three groups, which were termed winter /spnng, spnng/ summer, and late summ '

Temporally, these dominant groups remained relatively consistent among the preopera and operational periods.

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l Potential impacts of the operation of Seabrook Station on the microzooplankton comm

. the Hampton-Seabrook area are through-plant and thermal-plume entrainment ofindividuals.

Possible changes in species abundance and community composition would be related to the life history stage affected and the ability of the population to replace lost individuals.

l The meroplankton taxonomic groups collected in the microplankton program (Bivalvia, Gastropoda, Polychaeta, and Cirripedia) are early developmental stages of benthic i

invertebrates, which typically are extremely abundant and, depending on the length of their  ;

planktonic stage, can be dispersed over long distances. Planktonic development is the most common reproductive strategy among temperate marine invertebrates (Epifanio 1988). After larval development and dispersal, the transformed individuals are recruited to the benthic j l

community. Successful recruitment is dependent on suitable benthic habitat and these later i

j developmental stages are monitored at Seabrook Station by the Marine Macrobenthos i

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program. Therefore, ifimpacts were to occur to meroplankton stages of these species they should be evident in reduced recruitment, which has not been evident after five years of Seabrook operation (NAI 1996a). I I

l

. The major holoplankton taxonomic groups are Copepoda, Tintinnidae, and Rotifera, but most .  !

marine zooplankton surveys and studies have focused on copepods. Phylogenetically, the l t

tintinnids and rotifers are relatively primitive and have rapid generation times. Tintinnids are j

protozoan ciliates that use cell division for reproduction and are common in the temperate {

Atlantic Ocean (Sleigh et al.1995). Their abundance in Long Island Sound was reponed by Capriuto and Carpenter (1983) to have been directly related to the availability of nanoplankton. Many rotifer species are cosmopolitan and primarily found in freshwater

' (Barnes 1968). Most of their reproduction is probably by parthenogentic females as males have not been identified for many species (Reid 1961). Due to the rapid generation times and food limiting abundance for tintinnids and rotifers, the operation of Seabrook Station likely i does not have any adverse effects on their abundance in the Hampton-Seabrook area.

For the microzooplankton community, the copepod component is usually the most scrutinized in power plant studies in the marine environment (discussed below). In the microzooplankton program, copepods are categorized by developmental stage (nauplius, copepodite, and adult).

The copepod species or genera collected in the microzooplankton program have relatively short generation times, indicating rapid tumover rates. Landry (1983), in a laboratory study  !

l conducted at 15 C, determined that the generation time of seven copepods, including Acartia clausii, A. tonsa, and Pseudocalanus sp. (three genera that are predominant in the Hampton-l Seabrook area), ranged from 19 to 21 days among all species examined. McLaren et al. (1989) estimated from field data the number of generations per annual season on the Scotian Shelf as l five for Pseudocalanus newmani and three to four for Oithona similis. Depending upon water temperature, McLaren (1965) noted that Pseudocalanus sp. generation time varied from 25 to j 50 days, and it was estimated to be 55 to 60 days at 5 C by Davis (1984). P. minutus generation time was determined to be 35 days at 8 C, but this decreased to 21 days at 12.5*C 6

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! I (hicLaren 1978). O. similis matures from about 40 to 90 days; this rate also varied with  !

temperature, ranging from 42 days at 13.5 C to 67 days at 9 C (McLaren 1978). McLaren (1978) also reported the generation times for Temora longicornis as 39 days at 8.5 C and 35 days at 13.5 C and for Calanusfimarchicus as 46 days at 10 C and 11.5 C. Acartia clausi matures in 21 (20 C) to 65 days (5*C) and A. tonsa from 10 (20 C) to 31 days (10 C)(Du and Durbin 1981). Eurytemora herdmani at the copepodite stage CI matures in 8 days at 15 C and 20 days at 5 C (McLaren and Corkett 1981).

As well as rapid maturation, female copepods have high egg production, expressed as d

eggs female day", with reports for A. tonsa of 25-40 eggs (Dagg 1977) and 5.6-56.6 (Bellantoni and Peterson 1987); P. minutus of 4 (Dagg 1977) and 4.5 (Corkett and McLaren i

(1969); P. clongatus of 0.7-3.4 (Corkett and Zillioux 1975); and T. longicornis of 4.7-17.3 (Corkett and Zillioux 1975). Also, McLaren and Corkett (1981) found on average 22.4-26.6  !

eggs per egg sac for E herdmani.

I Less is known about mortality rates of copepods in marine systems. However, natural i

mortality rates were estimated from field data collected in the Hampton-Seabrook area for O. i similis and E herdmani from the nauplius through adult stages, which were 92.8 and 99.3%,

respectively (NAI 1974). For both species, more than 75% of the monality occurred during the nauplius developmental stage; copepod nauplii represent over 25% of the l

microzooplankton collected at station P2 from 1978 through 1995 (Table 1).

Effects of other east coast ocean- and estuarine-sited power plants on zooplankton.

Zooplankton studies were included in many environmental monitoring programs, particularly during the 1970s, because no data bases were available at the time to illustrate potential effects

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l of coastal power plant operation on zooplankton communities. Both baseline and operational-

! period studies were customarily required to prepare environmental statements necessary for the licensing of power plants under various provisions of the Clean Water Act administered by the U.S. Environmental Protection Agency (YAEC 1982) and, in some cases, by Technical Specifications of the U.S. Nuclear Regulatory Commission. Consequently, there exists 7

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considerableinfonnation from zooplankton studies designed specifically to address the impa '

of once-through cooling water systems of power plants. Many of the studies at these power plants evaluated entrained zooplankton or populations found in discharge canals, which represent worst cases in terms ofimpacts. Cooling-water flows at the coastal power plants were l generally similar in magnitude, although Seabrook Station for its size (1150 MWe) has a lower i

demand for cooling water (31.3 m's") and higher AT (39 F) for its discharge than the nine other plants (Table 3). Brief summaries of these studies are provided as an appendix to this 1i evaluation.

Although the focus for the power plant studies differed, ranging from short-term or experimental studies involving only copepods to relatively long-term monitoring of diverse zooplankton communities, many of the studies observed similar effects and had final conclusions that led to the termination of the zooplankton sampling programs. A review of completed studies (see appendix for citations) showed that impacts to zooplankton by power plant operation were localized and of short duration. Impacts were greatest on the earliest life stages or when chlorine was used as a biocide. Effects were also greatest when water temperatures exceeded some threshold, which for most copepod species was typically 29 C or greater. In a number of instances zooplankters were apparently killed during through-plant entrainment and abundances in the immediate vicinity of the discharge was significantly less than at the intake. However, when entrainment densities were compared with stations a shon distances from the plant discharge, no differences were found. No changes in abundance, biomass, or species composition were found overall, with no long-term deleterious effects to zooplankton populations as a whole. Because of the ability of most zooplankton to endure brief exposures to high temperatures with little monality, thermal plume entrainment was found to be an insignificant effect. Because no significant long-term changes were found, it is not rurprising that the monitoring of zooplankton at other northeastern power plants has been discontinued for a decade or more.

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In addition to studies done at specific coastal power plants, several reviews (Tetra Tech, Inc.

1978; LMS 1979; YAEC 1982) also summarized relevant fmdings and made generalized i i conclusions about ocean-sited power plant impact on zooplankton. These references noted that no long-tenn changes were found in species composition of zooplankton communities as a result i

of power plant operation. Any compositional changes found were transitory and limited to the immediate area of plant discharges. In fact, some stations saw localized increases in zooplankton abundance within the discharge. The quick dilution and cooling of heated 1 discharges meant that exposure to high temperatures was usually brief due to rapid thermal ll plume dispersion in marine waters. Thermal plume entrainment did not cause monalities nor  ;

were there statistically significant differences found for variables when compared to control  !

sites. The absence of wide-spread effects in the marine environment was not unexpected as coastal oceanic zooplankton have high thermal tolerances and rapid reproductive rates. ' These i l plants only affected a very small ponion of the receiving water body due to relatively small  !

amounts of water withdrawn from large open coastal water bodies that are constantly  ;

l replenished by longshore transpon. Marine zooplankton species are widely distributed with l relatively shon generation times, so only a small fraction of their populations is affected by l

l power plant operation. These reviews concluded that deleterious power plant effects on l . zooplankton in marine ecosystems were unlikely and plant operation would not cause harm to i this trophic level.

i Recommendations. Based on the life history of the dominant copepods collected in the microzooplankton program, it is apparent that the loss ofindividuals due to through-plant ,

entrainment would have little or no effect on their populations in the Hampton-Seabrook area.  !

Because of high thermal tolerances, thermal plume entrainment should not affect these j t'

organisms. The populations of copepods and other holoplankters have rapid generation turnover rates, high reproductive rates, and a high natural monality, enabling them to rapidly compensate for environmental perturbations. The inshore microzooplankton community is  ;

, ubiquitous in the waters of the Gulf of Maine and the dominant species have wide distributional ranges. Coastal marine power plants do not appreciably affect zooplankton  !

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communities. Thus, it is not surprising no significant findings ofimpact were found by the f

i i microzooplankton sampling program at Seabrook Station. In addition, effects to higher trophic levels that depend upon microzooplankton as prey are also unlikely. The j

{ microzooplankton monitoring has served its purpose by demonstrating this lack of plant  ;

j impact. Therefore, it is proposed that microzooplankton studies be concluded after the completion of Gve years of monitoring during Seabrook Station operation. l i

Bivalve Larvae and Bivalve Larvae Entrainment i L!

Review of sampling methodology. Bivalve larvae samples were taken in the field using a  !

0.5-m plankton net having 76- m mesh. Samples were collected weekly from mid-April through October at four stations: Hampton Harbor, Pl; nearfield stations P2 and P5; and i

farfield station P7 (Fig.1). Collections were taken at P2 beginning in July 1976, at P7 in April 1982, at P1 in July 1986, and P5 was sampled from July through December 1986 and ,

i April 1988 through the present. Two simultaneous 2-min oblique tows were taken at each i 1

station, unless clogging occurred, in which case venical tows were made. Sample volumes '

averaged about 9 m' for oblique tows and 3 m' for venical tows Data collected were used to describe the spatial and temporal distributions of eleven taxa of umboned bivalve veliger larvae (common names from Turgeon et al.1988): Mytilus edulis (blue mussel), Anomia squamula (prickly jingle), Hiatella sp. (hiatella), Modiolus modiolus (northern horsemussel),

Solenidae (razor clams, including Ensis directus, Atlanticjackknife; Siliqua costata, Atlantic razor; and S. squama, rough razor), Mya truncata (truncate softshell), M arenaria (softshell),

Spisula solidissima (Atlantic surfclam), Macoma balthica (B altic macoma), Placopecten magellanicus (sea scallop), and Teredo navalis (naval shipworm). All other species collected i

were grouped collectively as Bivalvia.  !

1

. Bivalve larvae entrainment samples have been taken at the Seabrook Station circulating water pumphouse since June 1990,just prior to plant start-up (earlier samples taken from July 1986 I

10 i

I through June 1987 will not be discussed here). Nets of 76-pm mesh were deployed in a double-barrel collector described in detail in NAI (1996a); volume filtered averaged about 7 m'. Collections were made up to four times a month during the day and coincided with offshore bivalve sampling whenever possible. Three replicate samples were taken on each l

' date. Samples were not taken during plant outages or when sampling equipment  !

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malfunctioned; no sampling occun ed in 1994. Bivalve larvae were identified to the same twelve taxonomic categories as given above for the Bivalve Larvae program. Entrainment estimates for each taxon were calculated by multiplying the monthly average daily volume of circulating water by the number of days represented by each sampling date and then summin by month.

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Sampling programs evaluation. As the data from larval bivalve station P1 are only used in conjunction with Mya arenara studies, the utility of continued sampling at this station will '

appear in the Soft-shell Clam evaluation. Effects of Seabrook Station bivalve entrainment l, were assessed directly from the magnitude of the entrainment estimates, from analyses of community and taxon-specific trends in abundance during the preoperational and operational l l l periods using the B ACI ANOVA model, and from abundance information available for settled  !

life stages for some of the species from the Marine Macrobenthos (NAI 1996b), Surface Panels (NAI 1996c), and Soft-shell Clam (NAI 1996d) monitoring programs at Seabrook Station.

Field-collected larval bivalve collections from 1988 through 1995 were dominated by blue mussel (Table 4). Pricklyjingle and hiatella were also abundant, but soft-shell clam larvae were relatively scarce, making up only 0.4% of the catch, i _

Annual totals of entrained bivalve larvae varied, depending not only upon variations in larval abundance and in the presence oflarvae in offshore waters, but also on plant operation and sampling gear availability (e.g., no samples taken after June in 1992 or in all of 1994). The largest annual total was during 1995, when 27 trillion larvae were estimated to have been 11

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entrained (Table 5). This was more than 50% larger than the next highest estimate (18 trillion) during 1993. Other factors, such as water temperature, also likely affected the spawning and larval stage duration of various bivalve species and their availability. For example, the high entrainment in 1995 was due, in pan, to very high densities of blue mussel 1

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, veligers found offshore (NAI 1996a). Peak numbers oflarvae at the plant and in offshore i samples were not always synchronous. Entrainment and offshore abundance of blue mussel

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larvae usually coincided during mid-June through July, but prickly jingle larvae were most i

numerous offshore in June, but in entrainment samples during July and August. '

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The blue mussel was by far the most abundant larval bivalve entrained, making up about half of the total (Table 5). Another quaner of the total was made up by the pricklyjingle and 11.5% by hiatella. The recreationally and commercially imponant soft-shell clam and sea scallop only made up 0.1% or less of the total in entrainment collections. Both species had peak entrainment in 1993, with totals of 22.5 and 16.9 billion larvae entrained, respectively.

The percent species' composition in entrainment collections was generally similar to that seen in the field bivalve sampling program (Table 4), even though the data used came from  !

different time periods.

1 Bivalve abundance information is available from a number of sources. Since the beginning of environmental studies at Seabrook Station, much interest in potential plant effects centered on the soft-shell clam, which was recognized as an important species for concem (NAI 1971).

Even after the proposed estuarine intake was moved offshore, this species remained as a focus for study and the soft-shell clam has been treated as a distinct sampling program during I Seabrook St'ation environmental studies. As such, a separate evaluation of the soft-shell clam sampling program was prepared. However, since the field bivalve sampling and bivalve entrainment studies originated to a large degree from concerns over the local soft-shell clam resource, it will be discussed briefly here. A comparison oflarval soft-shell clam abundance at stations P1 and P2 with spat densities in Hampton Harbor indicated that larval and spat abundances were not related (see the Soft-shell Clam evaluation for funher details). Since  ;

recmitment success of soft shell clams was not dependent upon larval abundance, the number l

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l oflarvae entrained are not relevant to the future abundance of clams in Hampton Harbor.

Results of ANOVA indicated that preoperational-operational differences in abundance for both larvae at the three plankton stations and seed (1-12 mm) clams settling in Hampton Harbor and Plum Island Sound, MA were consistent among stations (Table 6). This funher suggested no effect by Seabrook Station on this species.

, Blue mussels dominated the assemblage of bivalve larvae in both field and entrainment collections. Spawning of blue mussels in the GulfofMaine is probably limited to periods when water temperatures are above 10-12 C (Podniesinski and McAlice 1986). In Long Island Sound, Fell and Balsamo (1985) found spawning to be asynchronous both within and among local populations and occurred over a 2- to 3-month period. Spawning of Long Island Sound populations was also res'tricted by limited food availability for most of the year and was l

! therefore sporadic (Newell et al.1982). Depending upon temperature, larval development

! requires 3 to 5 weeks and metamorphosis may be delayed until suitable settlement conditions are encountered (Bayne 1976). Based on these aspects of blue mussel reproduction, mussels collected as part oflarval bivalve monitoring are present in the water column over a long period, and recmitment in the Hampton-Seabrook area from non-local sources is likely as larvae are l carried into the area by water currents. For blue mussel larvae, the Preop-Op X Station l j interaction term was not significant, indicating no plant effect (Table 6). In fact, blue mussel larvae have been more abundant during the operational period than the preoperational period.

Near Seabrook Station, settlement ofMytilidae (primarily the blue mussel) in the nearfield and l

farfield areas was monitored monthly on shon-tenn surface panels (NAI 1996c). Results from i

this study indicated that Mytilidae settlement increased from the preoperational period to operational period in the nearfield area, with no between-period difference in the farfield area (Table 6). This type of relationship between nearfield and farfield trends, while resulting in a significant interaction term of the ANOVA model, is not consistent with a power plant impact.

Similarly, Mytilidae densities (mostly newly settled spat) were also monitored in intertidal, shallow subtidal and mid-depth horizontal ledges near the discharge as pan of the marine 13 l

- macrobenthos destructive sampling program (NAI 1996b). For all three depth zones, the interaction term was not significant (Table 6), indicating that entrainment or other potential impacts from Seabrook operation have not affected Mytilidae settlement and recmitment in the nearfield area.

l The lack ofimpacts to settled Mytilidae determined from monitoring studies is not surprising, as the life cycle and reproductive strategy forMytilus edulis greatly reduces the potential for impacts from larval entraiment. Average-sized individual female M edulis can produce 7-8 x 10' eggs (Seed and Suchanek 1992), while larger individuals can produce as many as 40 x eggs (Thompson 1979). High fecundity is essential, since natural mortality oflarvae (from starvation and predation) approaches or exceeds 99% (Bayne 1976; Lutz and Kennish 1992).

Large differences between fecundity and recruitment also suggest tremendous mortality during the larval period (Thorson 1950), which can last from 1-2 months (Bayne 1976). Within a given area, mussel spawning and lawal occurrence are generally predictable (Fell and Balsamo 1985; Podniesinski and McAlice 1986); juvenile abundance is more erratic, as settlement appears to be correlated with suitable substrate for attachment (Newell et al.1991). High natural mortality, wide dispersal oflarvae, and the lack of evidence for a relation between lawal abundance and subsequent recruitment to natual habitats make impacts from Seabrook operation unlikely.

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Another common bivalve in larval samples, the northern horsemussel, is also monitored in the destructive marine macrobenthos study. This species has a reproductive strategy similar to that l

of the blue mussel. Results of an ANOVA performed on densities at mid-depth macrobenthos l stations revealed no indications of power plant impact (Table 6). Settlement and early recruitment of Mytilidae and two other common bivalve larvae taxa (pricklyjingle and hiatella) l are monitored o' n subtidal bottom panels. For all three taxa, abundance increases were observed at nearfield and farfield stations during the operational period, relative to the preoperational period, indicating no effect from plant operation (NAI 1996b). For larvae of razor clams and hiatella, no significant nearfield-farfield differences were found. The interaction terms for both taxa, however, were significant. Densities of razor clams during the operational period remained similar to the preoperational period at stations P2 and P7, but declined at PS. Densities of 14

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.1 4 hiatella increased during the operational period at each of the three stations, but the changei only significant for station P2. Annual time-series plots of abundance indicated generally similar trends in density over all years for both taxa (NAI 1996a). Consequently, the significant l interaction term was probably not biologically significant and is likely unrelated to Seabrook l

Station operation.

i i 4

} Besides through-plant entrainment effects, larval bivalves can be entrained within the t.

Seabrook Station thermal plume. Barker and Stewart (1978) performed temperature tolerance '

experiments with soft-shell clam and blue mussel larvae to determine their potential monality after passing through the condenser cooling-water system of a power plant, which would be considerably more likely to cause monality than thermal plume entrainment. For example, I they reponed monality of 1-day-old soft-shell clam was only 10% when expose'd to a AT of 1

15 C for 60 to 180 minutes. In general survival was good, except at relatively high  !

j temperatures and over long exposure periods. Also, tolerance to high temperatures increased with age. Water temperature at time of spawning was also considered to be an imponant factor for survival of entrained bivalve larvae, with larvae spawned at higher temperatures likely to experience higher mortality. Thus, it appears that bivalve larvae would not be j appreciably affected by thermal plume entrainment at Seabrook Station.

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Recommendations. Results from several sampling programs that provided abundance i

d information and analyses for bivalves indicated no significant effect of Seabrook Station operation. Larvae of the important soft-shell clam are entrained in relatively small numbers.

Apparently, larval densities are not related to spat abundances, which are likely controlled by environmental factors. Similarly, the dominant blue mussel has not been affected by station  :

operation despite numerically high entrainment estimates. The high fecundity of bivalves plus their relatively long larval life stage makes.a localized impact less likely to occur as these  !

species have evolved to. compensate for very high losses in their early life history. The field bivalve and bivalve entrainment programs have served a useful purpose in documenting no significant changes for the selected species. Because no plant impacts have been found, nor 15 1

are any likely, it is recommended that these sampling programs be concluded after the completion of five years of studies during Seabrook Station operation. Although plant impa is unlikely, monitoring of the important soft-shell clam resource in Hampton-Seabrook Harbor, however, will continue, as proposed in the Soft-shell Clam evaluation.

Macro:ooplankton j Review of sampling methodology. The present macrozooplankton sampling design consists of two stations located in potentially impacted areas (nearfield), one near the offshore intake (P2) and the other near the offshore discharge diffuser system (P5), and a non-impacted (farfield) or control station (P7) that is approximately 7 km north of the discharge area (Fig.

1). These stations have been sampled consistently since July 1986. In addition, station P2 was sampled from January 1978 through December 1984 and P7 from January 1982 through December 1984. Primarily, only data since 1987 have been used for impact assessment because these collections met the Before-After/ Control-Impact sampling design requirements (Stewan-Oaten et al.1986) and were amenable to statistical testing based on ANOVA models.

In addition, these data were used for numerical classification and MANOVA. For ANOVAs, abundance of the following four selected macrozooplankton species were examined: Calanus finmarchicus (copepodites and adults separately), Carcinus maenas (larvae), Crangon i septemspinosa (zoeae and post-larvae) and Neomysis americana (all life stages combined). l For these selected species, all annual data from twice monthly collections were included in the analyses, except for C. maenas larvae, which occur seasonally and for which analyses were restricted to data collected from June through September (NAI 1996a).

Data used in the analyses were from three randomly selected replicates of four samples collected in two consecutive tows (NAl 1996a). Collections were made with paired 1-m

! diameter 505- m mesh nets at each station on two sampling dates per month, usually from alternate weeks. For the 1995 data analyses, the logw transformed replicate sample densities

[

16

_ __ _ . _ _ _ _ ~ _ - . - _ - _ _ _ _ _ _ . _ _._ _ _ _ _ . _ . _ . _ .

were averaged. The ANOVA model was a two-way factorial design with nested effects. The  ;

main effects were operational periods (Preop-Op) and stations (Station), and the model  !

! meluded their interaction term (Preop-Op X Station). Nested temporal effects were ye

{

within operational periods (Year (Preop-Op)) and months within year (Month (Year)). Foi '

both nested temis, variation was partitioned ignoring stations (stations combined). A fixed-l effects model was assumed with all sources of variation tested against the residual mean-square (Error) term. Type III (SAS Institute Inc.1985) sums of squares were used for the l

'4 analyses because the cells in the factorial design contained unequal numbers of observations 9 (Freund et al.1986). To separate preoperational from operational periods the 1990 data were excluded because part of that year was preoperational and the remaining operational. The source of variation of primary concern for power plant impact assessment was the Preop-O Station interaction (Thomas 1977; Green 1979; Stewart-Oaten et al.1986). Through 1995, no i

significant interactions have been detected for the four selected macrozooplankton specie (NAI 1996a), indicating no effect of Seabrook Station operation on their abundance.

E Sampling program evaluation. Traditionally, replicate sampling has been conducted to

. estimate plankton abundance because of their suspected patchy distribution. The 8 years of macrozooplankton data (1987-95, excluding 1990) collected at three stations provided a long time-series to evaluate whether there has been enough variability among the three replicate samples to warrant their continued collection and if data from only one (P2) of the two nearfield station was sufficient. Therefore, the macrozooplankton program evaluation will attempt to determine whether the present program would be affected in its ability to detect

,c plant operational impacts if the number of replicates was reduced from three to one and if nearfield sta' tion P5 was not sampled.

The effect of using data from only one sample per date at the present three stations and with only one of the two nearfield stations was simulated by recomputing the previously described

, ANOVAs using data from all three replicates and comparing these results to those obtained by i

using only the first replicate sample collected at the three stations and at only stations P2 and j P7. These changes were evaluated on the similarity of results obtained from the ANOVAs for 17 l -

each of the selected species. Of particular concern were the results from testing the source of l

variation for the Preop-Op X Station interactions and whether the Error terms were reasonabl stable. The interaction term was examined statistically with separate F-tests constmeted as ratios of corresponding mean squares, where the larger of the two mean squares was the numerator (Snedecor and Cochran 1967). The similarity of error mean squares of the ANOVA models were examined because this term accounted for all unexplained variance or

~

" natural noise", and thus, contributed critically to the final sensitivity of every F-test.

Evaluation results. Comparisons among the three ANOVAs (three stations-three replicates

versus three stations-one sample and two stations-one sample) for each selected species l

showed similar results in assessing potential plant impact (Tables 7 through 11). Based on the L i

sources of variation that were significant (p s 0.05)in each ANOVA, a comparison of the models for three stations-three replicates and the three stations-one sample showed that the only significant differences in F-test were for the Preop-Op and Year (Preop-Op) terms for C.

fnmarchicus copepodites (Table 7). For the comparison of three replicates at three stations versus one sample at two stations there were several differences: the Preop-Op and Year (Preop-Op) terms for C.finmarchicus copepodites; Year (Preop-Op) and Station terms for l C.fnmarchicus adults (Tables A and B). No differences were found for C. maenus larvae, C.

septemspinosa zoeae and post-larvae, and for N. americana (Tables 9 through 11). Funher, the critical interaction (Preop-Op X Station) term was not significant in any ANOVAs. Of particular importance was that the residual mean squares (i.e., Error tenns) were similar, although slightly larger for both the simulated three stations-one sample and two stations-one sample models (particularly for C.finmarchicus adults), which indicated that a reduction to one sample per date would result in a minimal increase in the estimate of the unexplained variance (Fig. 3).

The minimal loss in sensitivity to detect possible operational effects with a reduction in sampling was further supported by the results of F-tests, which compared the mean squares of the Preop-Op X Station term (Table 12). The only significant (p s 0.05) difference in mean i

1 18 i

l r

squares was for C. fimarchicus copepodites for three replicates at three stations versus one sample at two stations. Between-tows variability was negligible probably because replicat tows at the same location were collected only a few minutes apart.. It is also important to  !

remember that in Before-After/ Control-Impact sampling designs, the true replication units are the sampling dates rather than the tows on each sampling date (Stewart-Oaten et al.1986)

Reducing the number of replicates from three to one sample and stations (P2 and P7 only could also affect the taxa composition data used in the numerical classification and MANOVA. Using all the data (three replicates) collected at three stations from 1987-95, a l i

total of 107 taxa were identified, with the most abundant taxa comprising about 96% of the total (Table 13). Using data from only the first replicate collected at the three stations,105 taxa would have been identified. For only one sample taken at stations P2 and P7,103 taxa were present. The two species lost for the three station-one sample simulation were Nebalia  !

bipes and Spirontocarisphippsii and for the two station-one sample simulation two additional taxa were not present, Campylaspis rubicunda and Heteromysisformosa. These taxa are rare and each accounted forless than 0.1 % of the species composition. They probably would 1 have been excluded from the analyses based on the selection criteria for " dominant" taxa (NAI 1996a). Frequency distributions of taxa using the three station-three replicates and the simulated three station-one sample and two station-one sample were compared using the chi-I square goodness-of-fit test (Sokal and Rohlf 1969). No significant difference was detected '

(f = 41.1 and 89.4, respectively with df = 106). Similarly, for the top 20 taxa (Table 13),

which accounted for over 95% of the macrozooplankton abundance during 1987-95, the contributions from each taxon showed almost no change regardless of whether three replicates or one sample at three stations and two stations were used in the calculation. Therefore, the reduction to one sample per sampling date will not appreciably alter the results from numerical classification or MANOVA analyses.

Recommendations. The similarity in results from the three ANOVAs for each selected species indicated that there would be minimal loss in sensitivity to detect a potential plant  !

operational impact if the collections of macrozooplankton were reduced to one sample per 19

date at stations P2 and P7. The estimated variances for the critical interactio were similar with either one sample at two stations or with three replicates at three stations suggesting that current sample replication is redundant. Therefore, it is proposed that macrozooplankton collections be reduced from three to one sample per sampling date at stations P2 and P7. This will not reduce the ability of the program to detect potential plant operational impacts using the BACI ANOVA model nor affect additional analyses (i.e.,

numerical classification and MANOVA).

l Conclusions The zooplankton sampling program at Seabrook Station will focus on the larger macrozooplankton, which, based on life history information, have more potential to be affected by plant operation. This sampling is proposed to be modified to increase sampling efficiency without losing information critical for impact assessment. Because of the capacity of the targeted organisms for reproduction and the lack of significant f'mdings from the monitoring programs, microzooplankton, field bivalve, and bivalve entrainment programs are proposed to be discontinued, having served their purpose as part of the Seabrook Station 1

environmental monitoring studies. Although plant impact is unlikely, monitoring of the imponant soft-shell clam resource in Hampton-Seabrook Harbor is proposed to continue (see the Soft-shell Clam evaluation).

References Cited Barker, S.L., and J.R. Stewart.1978, Mortalities of the larvae of two species of bivalves after acute exposure to elevated temperature. Pages 203-210 in L.D. Jensen, ed. Fourth national workshop on entrainment and impingement. EA Communications, Melville, NY.

Barnes, R.D.1968. Invertebrate zoology. W.B. Saunders Company, Philadelphia. 743 pp.

20

. _ - . . _ _ _ _ _ _ . _ _ _ _ - _ _ _ . _ _ - _ . _ _ _ _ . ~ _ _

{ .

l Bayne, B.L.1976. The biology of mussel larvae. Pages81-120 in B.L. Bayne, ed. Marine '

4 mussels: their ecology and physiology. Cambridge Univ. Press, Cambridge. 506 pp.

L Bellantoni, D.C., and W.T. Peterson 1987. Temporal variability in egg production rates of Acartia tonsa Dana in Long Island Sound. J. Exp. Mar. Biol. Ecol. 107:199-208.  !

L Capriulo, G.M., and E.J. Carpenter.1983. Abundance, species composition and feeding i l impact of tintinned micro-zooplankton in central Long Island Sound. Mar. Ecol. Prog. ,

Ser.10:277-288.

Carter, J.C.H., and M.J. Dadswell.1983. Seasonal and spatial distribution of planktonic crustacea in the lower Saint John River, a multibasin estuary in Nesv Brunswick, Canada.

Estuaries 6:142-153.

Corkett, C.J., and I.A. McLaren. 1969. Egg production and oil storage by the copepod

• Pseudocalanus in the laboratory. J. Exp. Mar. Bio. Ecol. 3:90-105.

Corkett, C.J., and E.J. Zillioux.1975 Studies on the effect of temperature on the egg laying of three species of calanoid copepods in the laboratory (Acartia tonsa, Temora longicornis and Pseudocalanus elongatus) Bull. Plank. Soc. Jap. 21:13-21.

Dagg, M.1977. Some effects of patchy food environments on copepods. Limnol. Oceanogr.

22;99-107.

Davis, C.S.1984. Food concentrations on Georges Bank: non-limiting effect on development and survival oflaboratory reared Pseudocalanus sp. and Paracalanus parvus (Copepoda: Calanoida). Mar. Biol. 82:41-46.

l Durbin, A.G., and E.G Durbin.1981. Standing stock and estimated production rates of phytoplankton and zooplakton in Narragansett Bay, Rhode Island. Estuaries 4:24-41.

Epifanio, C.E.1988. Transport ofinvertebrate larvae between estuaries and the continental shelf. Am. Fish. Soc. Sym. 3:104-114.

Fell, P.E., and A.M. Balsamo. 1985. Recruitment ofA@tilus edulis L. in the Thames estuary, with evidence for differences in the time of maximal settling along the Connecticut ' shore.

1 Estuaries 8:68-75. 1 Freund, P.J., R.C. Littell, and P.C. Spector.1986. SAS for linear models: a guide to the ANOVA and GLM procedures. SAS Institute, Inc., Cary, NC.

Green, R.H.1979. Sampling design and statistical methods for environmental biologists.

7 John Wiley & Sons, New York. 257 pp.

l .

I 21

Jeffries, H.P. and W.C. Johnson.1973. Distribution and abundance of zooplankton. Pages 4-14-92 in Coastal and offshore environmental inventory Cape Hateras to Nantucket Shoals. Univ. of Rhode Island Marine Publ. Series No. 2.

Kane, J.1993. Variability of zooplankton biomass and dominant species abundance on Georges Bank, 1977-1986. Fish. Bull., U.S. 91:464-373.

Landry, M.R.1983. The development of marine calanoid copepods with comment on the isochronal mie. Limnol. Oceangr. 28:614-624. -

LMS (Lawler, Matusky & Skelly Engineers).1979. Ecosystem effects of phytoplankton and zooplankton entrainment. EA-1038. Research project 876. Prepared for Electric Power Research Institute, Palo Alto, CA.

Lutz, R.A., and M.J. Kennish. 1992. Ecology of morphology oflarval and early postlarval mussels. Pages 53-85 in E. Gosling, ed. The musselMytilus: ecology, physiology, genetics and culture. Elsevier Science Publishers, Amsterdam. 589 pp.

McLaren, I.A.1965. Some relationship between temperature and egg size, body size, development rate, and fecundity, of the copepod Pseudocalanus. Limnol. Oceangt.

10:528-538. '

McLaren, I.A.1978. Generation lengths of some temperate marine copepods: estimation, j prediction, and implications. J. Fish. Res. Board Can. 35:1330-1342.

Mclaren, I.A., and C.J. Corkett. 1981. Temperature-dependent growth and production by a marine copepod. Can. J. Fish.Aquat. Sci 38:77-83.

McLaren, I.A., M.J. Tremblay, C.J. Corkett, and J.C. Roff. 1989. Copepod production on the Scotian Shelf based on life-history analyses and laboratory rearings. Can. J. Fish. Aquat.

Sci. 46:560-583.

NAI(Normandeau Associates Inc.).1971. Seabrook ecologocal study: phase I, 1969-1970, Hampton-Seabrook estuary, New Hampshire for Public Service Company of New Hampshire. 313 pp. l NAI. 1974. The impact of entrainment by the Seabrook Station. Tech. Rpt. V-4. 196 pp.

NAI.1996a. Zooplankton. Section 4 in Seabrook environmental studies,1995. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Prepared for North Atlantic Energy Service Corp.

NAI.1996b. Marine macrobenthos. Section 6 in Seabrook environmental studies,1995. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Prepared for North Atlantic Energy Service Corp.

22

NAI.1996c. Surface panels. Section 7 in Seabrook environmental studies,1995. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Prepared for North Atlantic Energy Service Corp.

NAI.1996d. Soft-shell clam (Mya arenaria). Section 10 in Seabrook environmental studies, 1995. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Prepared for North Atlantic Energy Sewice Corp.

NAl (Normandeau Associates Inc.), and NUSCO (Northeast Utilities Service Company, Corporate and Environmental Affairs).1994. Zooplankton. Pages 5 5 90 in Seabrook environmental studies,1993. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station. Prepared for North Atlantic Energy Service Corp.

Newell, C.R., H. Hidu, B.J. McAlice, G. Podniesinski, F. Short, and L. Kindblom. 1991.

Recruitment and commercial seed procurement of the blue musselMytilus edulis in Maine.

J. World Aquacult. Soc. 22:134-152.

Newell, R.I.E., T.J. Hilbish, R.K. Koehn, and C.J. Newell. 1982. Temporal variation in the reproductive cycle ofMytilus edulis L. (Bivalvia) from localities on the east coast of the United States. Biol Bull. 162:299-310.

Padmanabhan, M., and G.E. Hecker. 1991. Comparative evaluation of hydraulic model and field thermal plume data, Seabrook Nuclear Power Station. Alden Research Laboratory Rep. No. 60-91/M6210F. 12 pp. + 2 tab. + 11 figs.

Podniesinski, G.S., and B.J. McAlice.1986. Seasonality of blue mussel,Myrilus ed: dis L.,

larvae in the Damariscotta River estuary, Maine, 1969-77. Fish. Bull.,U.S. 84:995-1001.

Reid, G.K.1961. Ecology ofinland waters and estuaries. Van Nostrand Reinhold Company, New York. 375 pp.

SAS Institute Inc.1985. SAS user's guide: statistics. Version 5 edition. SAS InstituteInc.,

Cary, NC. 956 pp.

Seed, R., and T.H. Suchanek.1992. Population and community ecology ofMyrilus. Pages87-169 in E. Gosling, ed. The mussel Mytilus: ecology, physiology, genetics and culture.

Elsevier Science Publishers, Amsterdam. 589 pp.

Sherman, K., J.R. Green, J.R. Goulet, and L. Ejsymont. 1983. Coherence in zooplankton of a large Northwest Atlantic ecosystem. Fish. Bull., U.S. 81:855-862.

i l

23

Sleigh. M.A., E.S. Edwards, A.W.G. John, and P.H. Burkill.1996. Microcoplankton community stmeture in the North Eastem Atlantic: trends with latitude, depth and date, between May and early August. J. Mar. Biol. Ass. U.K. 76:287-296.

Sokal, R.R., and F.J. Rohlf.1969. Biometry. W.H. Freeman and Co., San Francisco. 776 pp.

Snedecor, G.W., and W.C. Cochran.1967. Statistical methods (6th Ed.). The Iowa State University Press, Ames,IA. 593 pp.

Stewart-Oaten, A., W.W. Murdoch, and K.E. Parker.1986. Environmental impact assessment: "Pseudoreplication"in time? Ecology 67:929-940.

Tetra Tech, Inc. 1978. Zooplankton. Pages 3 A 3.4-39 in Part III. Ocean-sited plants.

Vol. II. Chapter 3 - Ecological effects of once-through cooling on the marine environment. Prepared for the The Utility Water Act Group.

Teyssandier, R.G., W.W. Durgin, and G.E. Hecker 1974. Hydrothermal studies of diffuser discharge in the coastal environment: Seabrook Station. Alden Research La'boratory Rep.

No. 86-24/M252F. 47 pp. + 20 photogr. + 119 figs. + 2 app.

Thomas, J.M.1977. Factors to consider in monitoring programs suggested by statistical analysis of available data. Pages 243-255 in W. Van Winkle, ed. Proceedings of the conference on assessing the effects of power-plant-induced mortality on fish populations, Gatlinburg, TN May 3-6,1977. Pergamon Press, New York. 380 pp.

Thompson, R.J.1979. Fecundity and reproductive effort in the blue mussel (Mytilus edulis),  ;

the sea urchin (Strongylocentrotus droebachiensis), and the snow crab (Chionoecetes  ;

opilio) from populations in Nova Scotia and Newfoundland. J, Fish. Res. Board Can.

36:955-964.

]

1 l

Thorson, G.1950. Reproductive and larval ecology of marine bottom invertebrates. Biol.

Rev. 25:1-45.

Turgeon, D.D., and nine co-authors.1988. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. Am. Fish. Soc. Spec. Pub. i

16. 277 pp.

_ YAEC (Yankee Atomic Electric Company).1982. Effects of thermal discharges from ocean-sited power plants. Prepared for The Utility Water Act Group, Open-ocean Task Force.

24

Table 1. Dominant microzooplankton taxa and life stages in the Hampton-Seabrook area that represent 95% of the individuals collected at station P2 from 1978 through 1995.

Taxa Developmental stage' Percentage

, Bivalvia veliger 18.2 Copepoda nauplius 15.9 Oithona sp. nauplius ~11.4 Oithona sp. copepodite and adult 10.7 Tintinnidae 8.8 Pseudocalanus/Calanus spp. nauplius 8.6 Pseudocalanus sp. copepodite and adult 6.2 Rotifera 4.0 Temoralongicornis copepodite and adult 3.7 Gastropoda veliger 1.7 Polychaeta larva 1.5 Acartia sp. copepodite and adult 1.2 Microsetella norvegica copepodite and adult 1.0 Evadne sp. 1.0 Cirripedia larva 0.9 l

l I

l l

l 25 l

Table 2. Summary of potential effect of Seabrook Station operation on selected microzooplankton taxa and life stages based on results from the BACI ANOVA models (from NAI 1996a).

Operational Preop / Op Period Similar Differences

• to Differences Consistent Preoperational Among~ Among Taxa Lifestage Period? Stations? Stations? l Eurytemora sp. copepodite no no yes Preop > Op Eurytemora herdmani adult no no yes Preop > Op Pseudocalanusl Calanus sp. nauplii no no yes Preop > Op Pseudocalanus sp. copepodite yes no yes l Pseudocalanus sp. adult no no yes Preop > Op i Oithona sp. nauplii yes no yes Oithona sp. copepodite no yes yes Preop < Op P2 > P7 Oithona sp. adult no no yes Preop < Op

• Based on Preop-Op X Station interaction term from the ANOVA.

26

l 1

Table 3. Characteristics of east coast ocean- and estuarine-sited power plants and studies that provided information on microzooplankton for comparison to Seabrook Station.

Number of Net Cooling- Years reponed for Power generating generation water flow AT d

studies of plant State units (MWe)" (m'see )" (*F)6 microzooplankton' Crane MD 2 385 16.4 10.1-12.1 1974-75 Calvert Cliffs MD  !

2 1620 73.0 12.0 1974-81 l Chalk Point MD 2 656 30.0 15.0 1963-79 d '

Indian River DE 1 347 17.0 10.8 1970-71 Oyster Creek NJ l 620 29.0 23.0 1975 78 Millstone CT 3 2680 117.7 21.4 1970-82 d

Brayton Point MA 4 1590 46.8 26.6 1972-76 Pilgrim MA 1 655 20.3 29.0 1973-75 Maine Yankee hE 1 855 26.6 28.8 1969-77 d

Seabrook NH I 1150 31.3 39.0 1978-present'

• Electrical generation and nominal cooling-water flow combined for all units.

" Average nominal value for all units at fullload or AT reported at the time of the studies.

• Studies at powerplants other than Seabrook Station believed to be terminated following the last year given, d

Years during which data were collected varied; not inclusive for all aspects of these panicular studies.

1 l

l l

i 27

l t

. 1 l

Table 4. Percent of total density for the twelve selected bivalve taxa taken at stations P2, PS, f

and P7 from 1988 through 1995.

Taxa Percent  :

l Mytilus edulis 56.3 Anomia squamula 19.5 i Hiatella sp. 12.5

\

Modiolus modiolus 5.2 Bivalvia 2.2 l Solenidae 2.0 l Spisula solidissima 0.8 i Macoma balthica 0.6 l Mya truncata 0.6 i l Mya arenaria 0.4 Placopecten magellanicus <0.1 Teredo navalis <0.1

! i

! I l

1

)

l l

l l

f 4

l I

n -

h

! 28

1 Table 1995.

5. Estimated numbers (in billions) of bivalve larvae entrained at Seabrook Station from 199 June-Oct Apr-Aug Apr-June Apr-Oct Apr-Oct Taxa 1990 1991 1992* 6 1993 1995 Total  %

A$tilus edulis 3991.3 1687.4 121.9 10050.7 13213.0 29082.3 51.4 Anomia squamula 1691.4 250.8 6.8 3922.7 8905.9 14777.6 26.1 Hiatella sp. 876.6 451.2 189.8 2405.5 2598.2 6521.3 11.5 Modiolus modiolus 909.7 160.1 0.2 1.283.9 546.4 2900.3 5.1 Bivalvia 155.2 36.9 14.5 334.3 795.1 1336.0 2.4 Solenidae 61.1 12.7' 75.6 102.5 1092.3 1331.5 2.4 A&a truncata 249.0 6.5 1.1 2.1 27.6 286.3 0.5 3g Spisula solidissima 69.0 4.3 0.0

' 48.5 112.5 234.3 0.4 Apa arenaria 8.1 0.6 0.2 22.5 4.3 35.7 0.1 Macoma balthica 26.5 1.1 0.0 0.2 2.0 29.8 <0.1 Placopecten mogellanicus 0.6 0.7 0.1 16.9 6.2 24.5 <0.1 Teredo navalis <0.1 15.9 0.0 0.0 4.8 20.7 <0.1 Annual total 8038.5 2628.2 410.2 18189.8 27308.3 .

i

• Equipment failure in June; no samples taken thereafter.

6 No entramment samples taken in 1994 due to plant shutdown and sampling equipment malfunctions.

• Not given in NAI (1992b); estimated from data given in NAI (1992a).

i l

\

e 29

Table 6. Summary of potential effects of Seabrook Station operation on selected larval bivalve taxa based on results from the B ACI ANOVA models (from NAI 1996a, b, c, d).

Preop / Op Operational Differences' Period Sinailar to Differences Consistent Taxa / Preoperational Among Among Sampling Program Period? Stations? Stations? Multiple Comparisons' A&a arenaria no no yes .

Larval Bivalve Preop > Op A&a arenaria yes yes yes Nearfield/farfield Plum Is. Sound >

flats seed clam Hampton Harbor (1-12 mm) density A&tilus edulis no no yes -

LarvalBivalve Op > Preop Mytilidac' no no no d B1900 B31Pr B3100 B19Pr Surface Panels Op > Preop Mytilidae' no yes yes -

Macrobenthos' Preop > Op B1 > B5 (Intertidal)

Mytilidae' yes yes yes -

Macrobenthos B35 > B17 (Shallow sudtidal)

Mytilidae* no yes yes -

Macrobenthos Preop > Op B31> B19 (Mid-depth)

Hiatella sp. yes no no P2Oo P2Pr PSPr P7Pr P50p P70p LarvalBivalve Afodiolus modiolus no no yes -

Macrobenthos Preop > Op (Mid-depth)

Solenidae yes no no P200 P2Pr PSOo P700 P7Pr PSPr LarvalBivalve

' Based on Preop-Op X Station interaction term from the ANOVA.

6 Ranked in decreasing order, LS means test used for significant interaction term.

• Primarily Afytilus edulis, d

See the Surface Panels and Manne Macrobenthos evaluations for additional details, 30

j 1

l Table 7. Calanusfinmarchicus copepodites: Comparison of results from three analysis of variance tests, the first based on three replicate samples at three stations, the second on one i sample at three stations and the third on one sample at two stations, 1987-95.  !

, J l Source of variation df MS F-value P Three stations - Three renlicate samples

_ {

Preop-Op 1 3.18 5.51 0.019 Year (Preop-Op) 6 1.31 2.26 0.037 Month (Year) 88 10.88 18.82 0.001 Station 2 3.30 5.70 0.004 Preop-Op X Station 2 0.23 0.40 0.672 Error 470 0.58 Three stations - One sample l Preop-Op 1 1.83 2.42 0.121 !

Year (Preop-Op) 6 1.29 1.71 0.117 Month (Year) 88 11.34 15.00 0.001 ,

Station 2 8.07 10.67 0.001 l Preop-Op X Station 2 0.30 0.40 0.669 Error 470 0.76 Two stations - One sample l Preop-Op 1 0.39 0.48 0.487 I Year (Preop-Op) 6 1.29 1.60 0.146 Month (Year) 88 7.99 9.92 0.001 Station 1 6.83 8.47 0.004 Preop-Op X Station 1 >0.01 0.00 0.994 Error 282 0.81 i

l 31

. ._._ . . . _ . _ _ . _ . . . _ _ . _ . _ .._.. _ _ __. _... . _ . _ _ _ . _ _. _ _ . __ _ _ _ _ _ _ . _ .. - . . =

i 1

l Table 8. Calanusfinmarchicus adults: Comparison of results from three analysis of variance j

tests, the first based or. three replicate samples at three stations, the second on one sample at three stations and the third on one sample at two stations, 1987-95.

i.

Source of variation df MS F-value P f

Three stations - Three reolicate samoles

! Preop-Op 1 0.151 0:18 0.674 i

Year (Preop-Op) 6 5.40 6.33 0.001

} Month (Year) 88 6.01 7.05 0.001

Station 2 3.91 4.59 3 0.011 1

l Preop-Op X Station 2 0.43 0.50 0.605 j Error 470 0.85

.Ibree stations - One samole

Preop-Op 1 0.97 0.68 0.410 Year (Preop-Op) 6 4.95 3.47 0.002 i

Month (Year) 88 6.17 4.33 0.001 i Station 2 7.61 5.34 0.005 i Preop-Op X Station 2 0.94 0.66 0.517 i Error 470 1.42 Two stations - One samole Preop-Op 1 0,05 0.04 0.848 i Year (Preop-Op) 6 3.01 2.09 0.055 l Month (Year) 88 4.20 2.91 0.001 l Station 1 3.42 2.37 0.125 l Preop-Op X Station 1 0.68 0.47 0.492 1

Error 282 1.44 i

e s

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1 32

Table 9. Carcinus macnas . larvae: Comparison of results from three analysis of variance tests, the first based on three replicate samples at three stations, the second on one sample at three stations and the third on one sample at two stations, June through September of 1987-95.

Source of variation df MS F-value P Three stations - Three reciicate samnles Preop-Op 1 0.07 0.1 f 0.743

Year (Preop-Op) 6 3.19 4.95 0.001 Month (Year) 24 2.78 4.31 0.001 Station 2 0.33 0.51 0.604

! Preop-Op X Station 2 0.16 0.25 0.779 Error 156 0.65 i

Three stations - One samole Preop-Op 1 0.14 0.19 0.664 Year (Preop-Op) 6 2.89 3.77 0.002 Month (Year) 24 2.72 3.55 0.001 Station 2 1.28 1.68 0.190 Preop-Op X Station 2 0.40 0.53 0.591 Error 156 0.77 Two stations - One samole Preop-Op 1 0.04 0.05 0.828 Year (Preop-Op) 6 1.76 2.28 0.043 Month (Year) 24 1.67 2.15 0.005 Station 1 2.55 3.29 0.073 Preop-Op X Station 1 0.05 0.07 0.798 Error 94 0.77

~

33

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l Table 10. Cangon reptemspinosa zoea and post-larvae: Comparison of results from three analysis of variance tests, the first based on three replicate samples at three stations, the second on one sample at three stations and the third on one sample at two stations, 1987-95.

Source of variation df MS F-value P

' Three stations - Three reolicate samnles Preop-Op 1 0.13 042 0.517 Year (Preop-Op) 6 2.26 7.17 0.001 Month (Year) 88 8.55 27.12 0.001 Station 2 5.18 16.44 0.001 Preop-Op X Station 2 0.13 0.41 0.662 f

Error 470 0.32 Three stations - One samole Preop-Op 1 0.01 0.02 0.894 Year (Preop-Op) 6 1.80 4.60 ' O.001 Month (Year) 88 8.54 21.81 0.001 Station 2 8.93 22.80 0.001 Preop-Op X Station 2 0.18 0.46 0.634 Error 470 0.39 Two stations - One samole Preop-Op 1 0.14 0.35 0.553 Year (Preop-Op) 6 1.27 3.15 0.005 Month (Year) 88 5.87 14.60 0.001 Station 1 17.49 43.51 0.001 Preop-Op X Station 1 <0.01 0.01 0.939 Error 282 0.40 1

I 34

l Table 11. Neomysis americana: Comparison of results from three analysis of variance tests, the fhst based on three replicate samples at three stations, the second on one sample at three stations i and the third on one sample at two stations, 1987-95. I Source of variation df MS F-value P Th.ree stations - Three reolicate samoles ,

Preop-Op 1 0.14 0.25 0.618 Year (Preop-Op) 6 6.61 11.70 0.001 g Month (Year) 88 2.53 4.47 0.001 j Station 2 37.49 66.35 6 0.001 Preop-Op X Station 2 0.06 0.11 0.893 Error 470 0.57 Three stations - One samole Preop-Op 1 0.04 0.05 0.821 Year (Preop-Op) 6 6.84 9.74 0.001 i Month (Year) 88 2.74 3.90 0.001 {

Station 2 65.44 93.21 0.001 {

Preop-Op X Station 2 0.17 0.24 0.786 !

Error 470 0.70 Two stations - One samole Preop-Op 1 0.07 0.09 0.764 Year (Preop-Op) 6 3.48 4.68 0.001 Month (Year) 88 1.81 2.43 0.001 Station 1 130.32 175.45 0.001 Preop-Op X Station 1 0.29 0.39 0.534 Error 282 0.74

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Table 12. Comparison of the relative contribution to macrozooplankton abundance for the top 20 taxa using the actual database of three replicate samples at the three stations to two simulated databases: one sample at three stations and one sample at two stations (P2 and P7). These taxa represent over 95% of the total raacrozooplankton abundance from 1987 through 1995.

% contribution  % contribution  % contribution with 3 repicates with I sample , with I sample Taxa and 3 stations and 3 stations and 2 stations Cirripedia 27.9 27.8 21.0 Centropages typicus 21.6 21.5 24.0 Calanusfinmarchicus 14.5 14.1 13.4 Cancer spp. 5.7 6.0 7.6 Temora longicornis 4.7 4.6 5.3 Eualuspusiolus 2.5 2.6 3.3 Meganyctiphanes norvegica 2.2 2.3 2.7 Oikopleura sp. 2.2 2.4 2.4 Centropages sp. 2.0 2.I 2.3 Metridia sp. 1.5 1.5 1.7 Evadne sp. 1.5 1.4 1.3 Limacina retroversa 1.4 1.5 1.8 Mysis mixta 1.4 1.2 1.3 Podon sp. 1.3 1.4 1.6 Carcinus maenas 1.2 1.1 1.1 Thysanoessa sp. 1.1 1.3 1.2 Pseudocalanus sp. 0.9 0.9 1.0 Obella sp. 0.9 0.9 1.0 Tortanus discaudatus 0.8 0.8 1.0 Centropages hamatus 0.8 0.8 0.9 36

I I

Table 13. Results of F-tests to determine significant (P s 0.05) differences between mean i

squares (MS) for the interaction term fiom three analysis of variance (ANOVA) tests for the  !

selected macrozooplankton species (see Tables 1-5). One ANOVA was based on three relicate '

samples at three stations, the second was based on one sample at three stations, and the third was based on one sample collected at two stations. F-values were calculated by dividing the lar the two MS by the smaller.

3 replicates at 3 stations 3 replicates at 3 stations vs. vs.

I Samole at 3 stations I samole at 2 stations Taxa F-value P F-value P J

Calanusfinmarchicus copepodites 1.32 0.431 5090.39 0.010 Calanusfnmarchicus adults 2.20 0.313 1.59 0.486 Carcinus maenas 2.50 0.286 3.14 0.371

Crangon septemspinosa . 1.37 0.422 55.72 0.094 Neomysisamericana 2.65 0.274 4.51 0.316 l

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40

APPENDIX Summaries of Other Microzooplankton Studies i i i The following are brief summaries from a review of microzooplankton studies conducted between 1963 and 1982 at nine electrical generating stations on the eastern coast of the United States; all of these power plants are sited on the ocean or on estuaries. The summaries are ordered geographically from south to north, with generally increasing relevance to Seabrook Station. Operational characteristics of these plants and dates of the zooplankton studies are i

given in Table 3.

l Crane. Experimental studies examining the survival of entrained zooplankton (primarily the copepod Eurytemora afnis) were completed at the Crane Power Plant, located on the northwest shore of Chesapeake Bay (Davies et al.1976). Copepods collected at the intake were held in )

ambient temperature water (controls).or were placed in water from the plant discharge (AT of )

10.1-12.1 F). Zooplankton samples collected at the plant discharge were held at that temperature (AT) or at an increased temperature that was twice the AT. Although there was a tendency for mortalities to increase with experimental temperature, rates were not significantly different among the treatments and among the months (December-March) that were tested.

Mortalites noted were greatest for early copepodites and became progressively less for late copepodites and adult copepods, They also observed no significant differences in zooplankton ,

communities (abundance, species percent composition, age structure) resident in the discharge canal, at the intake, or at a control station over the course of a 6-month study. They concluded that power plant entrainment had little effect on microzooplankton populations, which appeared to have a sufficient recovery potential to compensate for entrainment losses.

Calvert Cliffs. Relatively long-term ecological studies for the Calvert Cliffs Nuclear Power Plant were summarized in Heck (1987). The discharge of this plant is released along the 3-m depth contour from a conduit 260 m offshore in the Maryland waters of Chesapeake Bay. Olson 41

(1987a, b) presented results from a 6-year study of zooplankton in the bay, conducted before and after plant start-up in late 1974 and a 7-year study of through-plant entrainment effects.

Dominant microzooplankton included the copepods Acartia tonsa, E afnis, and Oithona spp.;

bamacle (Balarms spp.), polychaete, bivalve, and crab larvae; the cladoceran Podon polyphemoides, and rotifers. Maximum densities were found during the summer. ANOVA models were used to examine the distribution of various microzooplankton taxa by life stage at six stations near the plant along a 12-km longitudinal transect that included the intake and discharge plume areas. The only significant (p 5; 0.01) differences were found for copepod nauplii, which were distributed in a density gradient along a sampling transect. However, this gradient was not consistent from month to month and actually reversed direction during the sampling period. In a previous study of through-plant entrainment Heinte and Millsaps (1977) noted reduced densities ofA. tonsa nauplii in the discharge area for several years following plant start-up. However, this may have been related to inadequate representation of the water column by their pump sampler, as copepods densities showed a gradient by depth. Olson (1987b) concluded that there were no deleterious effects of Calvert Cliffoperation on zooplankton in the region of the plant.

Chalk Point. Biological studies at the Chalk Point Steam Electric Station, located on the Patuxent River, a tributary of Chesapeake Bay in Maryland, were summarized by MMES (1985). Zooplankton were primarily affected by entrainment mortality. The abundance of zooplankton near this station was panicularly high and dominant species included A. tonsa and E afnis. Through-plant entrainment losses were estimated to be about 20-30% of the specimens entrained, but could reach 80% during plant chlorination, and were predicted to be 90-100% during summer operation when the discharge canal temperature exceeded 35'C.

Comparisons between nearfield and farfield stations (with plant at less than full operation) showed reductions of 15-40% in densities at the nearfield stations. However, this was not related to AT, but chlorine use. It was concluded that the effects of the station were limited to the immediate vicinity of the plant and the zooplankton populations over a larger, regional area were not affected.

42 l

- j I

Indian River. Davies and Jensen (1974) noted little effect of the Ir.dian River Station (Delaware) on zooplankton, which was attributed primarily to the low (10.8'F) AT for this station. Salinity gradients and diumal migrations of zooplankton seemed to be more important

, for their distribution than the plant. Except for late summer or early fall, the zooplankton i

populations in the discharge canal did not decrease due to passage through the plant. They concluded that zooplankton in the receiving waters of the Indian River estuary did not appear to be affected by losses at the plant as evidenced by similarities in species densities in the mixing zone beyond the discharge canal and in the intake area.

Oyster Creek. Oyster Creek Nuclear Generating Station is located on Barnegat Bay, NJ. The station withdraws cooling water from a bay tributary, Forked River, and discharges into another tributary, Oyster Creek, which has been modified to serve as a discharge canal. Because of

{

station pumping, salinities in these creeks approximate those of the bay. Microzooplankton species composition and abundances at stations located at the mouths ofForked River and Oyster Creek were compared in JCP&L (1978). Copepod nauplii (46%) and rotifers (24%)

dominated the microzooplankton. The most abundant copepod species were Acartia clausi(= A. I hudsonica) and A. tonsa, which reached maximum abundance between March and July and minimum densities between September and November. No changes in relative species )

composition were evident between the stations. However, some differences did occur m absolute abundance, with bamacle larvae decreasing 72% at the mouth of Oyster Creek, polychaete laivae 42%, copepod nauplii 19%, unidentified bivalve larvae 25%, A. tonsa 57%,

and Acartia spp. 61%. Conversely, rotifers increased by 103%, cyphonaute larvae 3,547%,

gastropod larvae 70%, and dwarf surf clam (Mulinia lateralis) larvae 155%. The losses were mostly attributed to through-plant entrainment mortalities. However, in bay-wide surveys, no

~

apparent effects were noted in microzooplankto' Sundances. JCP&L (1978) concluded that the plant had not produced any changes to this cow unity throughout Barnegat Bay.

i

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43 l -. . -

i Millstone. The largest electrical generating facility in New England is the Millstone Nuclear Power Station, located on eastern Long Island Sound in Waterford, Connecticut. When in

\

operation, all three units discharge heated water into a quarry pond, where the average transit j time before the effluent reaches Long Island Sound (LIS) through two openings in the quarry l

wall is about 85 minutes. NUSCO (1983a) reported that nine taxa of holoplankton (mostly adult or copepodite stages of calanoid copepods) comprised about 90% of the total in through-plant  :

entrainment studies conducted at Millstone Units 1 and 2 from 1976 through 1980t Acartia hudsonica and A. tonsa made up 60% of the total. Meroplankton were also dominated by a few

( taxa, primarily gastropod eggs and veligers (54%), barnacle (Balanus spp.) larvae (25%), and  ;

I brachyuran crab larvae (12%). Tychoplankton were much less numerous, although occasionally abundant at night during late winter. Dominants included gammaridean amphipods (72%) and harpacticoid copepods (17%). Two major seasonal components were identified with the winter-spring contingent dominated by A. hudsonica, Pseudocalanus minutus, and Temora longicornis, j l

as well as larval bamacles, gastropods, and polychaetes. The summer-fall community was characterized by A. tonsa, Centropages hamatus, and Pseudodiaptomus coronatus, with brachyuran and pagurid crab larvae. Carpenter et al. (1974a, b) noted that 70% of the copepods passing through Millstone Station Unit I were not returned to LIS at the quany pond outlet.

They believed that the mortality of copepods was almost entirely due to hydraulic or mechanical damage, rather than from temperature shock or chlorination. In addition, even live A. tonsa collected at the discharge sank 2.5 times faster than those found at the plant intakes, which increased concentrations in deeper water. Total annual copepod loss from entrainment was estmated as 4.253 X 10", which was calculated to be equivalent to the zooplankton production under 193 X 10' m' of surface area of LIS. This was further estimated as 0.1 to 0.2% of the copepod production of eastern LIS. However, because of the relatively short generation time and rapid reproduction of holoplankton, the quick dilution of the Millstone Station thennal plume in Long Island Sound, and the small volume of water withdrawn by the station relative to

, its Niantic Bay source, it was concluded that the operation of Millstone Station did not have any adverse effects on the zooplankton community (NUSCO 1976,1983b; USNRC 1984).

44

i Brayton Point. Brayton Point Generating Station, located on Mount Hope Bay in Massachusetts, is the second-largest generating station in New England. MRI and NEPCO (1978) summarized a 5-year study of zooplankton that was designed to examine station operation under a maximum allowed discharge temperature of 35 C. Zooplankton abundance, number of species, and diversity were compared between observations at five control stations not exposed to the thermal plume and a test station which had maximum exposure. Dominant species were A. clausi(= A. hudsonica) in winter and spring and A tonsa in summer and fall. I Oithona spp., Saphirella spp., and P. minutus were also common. Additional studies were made to determine temperature tolerances within the 975-m long discharge channel by taking samples i at three locations within the discharge channel, at the plant intake, and within the discharge plume. For the latter study, no significant differences in density were found for most taxa, except for adult A. clausi and A. tonsa, which declined in abundance from the upper to the lower end of the discharge channel. Further, there was a significant positive correlation between the plant reduction in zooplankton density in the discharge channel with absolute discharge water temperature, the greatest effect of which occurred in July and August. The large-scale studies, however, found no significant differences in the number of species, diversity, or densities among 1 the stations sampled in Mount Hope and Narragansett Bays. MRI and NEPCO (1978) concluded that the zooplankton populations in Mount Hope Bay were not affected by station-operation, except for some losses of adult Acartia spp. after plant passage during July and August. Apparently, these losses did not affect zooplankton standing stocks elsewhere in the bay. Also, no effects on higher trophic levels were expected to occur as a result of any changes to the zooplankton population.

Pilgrim. Toner (1984) summarized zooplankton studies completed in Cape Cod Bay during 1973-75 relating to Pilgrim Nuclear Power Station, located near Plymouth, Massachusetts on the northwestern shore of Cape Cod Bay. Peak densities of zooplankton were found in August with seasonal lows in December and January. The community was dominated by copepods,  ;

particularly A clausi (= A. hudsonica) and A. tonsa, with Oithona similis, O. brevicornis, and P. .

minutus also present. MRI(1976) presented results of zooplankton studies at Pilgrim Station, 1

45

including entrainment survival. Zooplankton (primarily copepods) entrained at the station s.

appeared to survive plant passage with little (<10%) mortality under most operating conditions.

High mortality only occurred when the plant chlorinated the cooling water at water temperatures

of 29 C or greater. Although densities of zooplankton at the discharge were generally less than

] ,

at the intake, on some occasions they were comparable or even higher. It was concluded that

• Pilgrim Station operation did not appreciably affect local holoplankton populations and, subsequently, studies were discontinued by the Pilgrim Station Technical-Advisory Committee i (BECO 1976).

Maine Yankee. The Maine Yankee Nuclear Generating Station is located in Wiscasset, Maine on the western shore of Montsweag Bay, off the Gulf of Maine. The thermal effluent is discharged through a 13.4-m deep mid-channel diffuser in the bay. The two 152-m long diffuser pipes result in high speed jets (3.9 m s") of heated water that rapidly entrain and mix with ambient water. Besides plant impacts, effects were also possible from the removal of a causeway that greatly increased water circulation in the bay, which allowed the plant to meet water quality temperature standards.

Lindsay et al. (1978) reported on a 5-year study of through-plant entrained microzooplankton.

Samples taken at the plant intake and discharge had greatest densities each year from May through September, with lowest numbers collected during fall and winter. Copepods (species not differentiated), polychaete larvae, and rotifers made up over 95% of the microzooplankton.

i' Bivalve larvae were only a minor component of the entrainment samples. Copepods had good

(>80%) survival following plant passage until water temperature reached 30 C. Above this, survival of copepods decreased with temperature. Polychaete larvae generally had high survival '

even at high water temperatures, whereas rotifers did not survive well at any temperature  !

~

. examined, perhaps due to mechanical damage from plant passage.

i McAlice et al. (1978) assessed the effect of the operation of Maine Yankee on species composition, abundance, life cycles, and spatial and temporal distribution of microzooplankton 46 y

1 populations at five stations located throughout Montsweag Bay. Twenty-seven taxonomic i

categories were chosen for statistical evaluation. They found that the bay was not warmed by the themial discharge from the plant. The dominant holoplankton species, A. tonsa, did not show any significant changes in abundance throughout the study. They concluded that their sampling could not detect any direct plant effects (i.e., entrainment) on microzooplankton, although the causeway removal likely caused some changes, which were due to altered water circulation patterns alone.

Appendix References Cited BECO (Boston Edison Company).1976. Marine ecology studies related to operation of l

1 Pilgrim Station. Semi-annual Rep. No. 7. July 1975-December 1975. Boston, MA. l Carpenter, E.J., S.J. Anderson, and B.B. Peck.1974a. Survival of copepods passing through a nuclear power station on northeastern Long Island Sound, USA. Mar. Biol. 24:49-55.

Carpenter, E.J., B.B. Peck, and S.J. Anderson.1974. Summag of entrainment research at the Millstone Point Nuclear Power Station,1970 to 1972. Pages 31-35 in L.D. Jensen, ed.

Entrainment and intake screening. Proceedings of the second entrainment and intake screening workshop. EPRI Pub. No. 74-049-00-5. Palo Alto, CA.

Davies, R.M., C.H. Hanson, and L.D. Jensen.1976. Entrainment of estuarine zooplankton into a Mid-Atlantic power plant: delayed effects. Pages 349-357 in G.W. Esch and R.W.

McFarlane, eds. Thermal ecology II. ERDA symposium series CONF-750425. NTIS, U.S. Dept. Commerce, Springfield, VA.

Davies, R.M., and L.D. Jensen. 1974. Entrainment of zooplankton at three Mid-Atlantic power plants. Pages 131-155 in L.D. Jensen, ed. Entrainment and intake screening.

Proceedings of the second entrainment and intake screening workshop. EPRI Pub. No. 74-049-00-5. Palo Alto, CA.

Heck, K.L., Jr.1987. Summary and conclusions. Pages 276-284 in K.L. Heck, Jr., ed.

Ecological studies in the middle reach of Chesapeake Bay - Calvert Cliffs. Lecture notes on coarsi and estuarine studies 23. Springer-Verlag, New York.

Heinle, D.R_, and H.S. Millsaps. 1977. Studies of zooplankton. Pages VI VI-23 in Ecological effects of nuclear steam electric generating station operations on estuarine  !

systems. UMCEES No. 77-28. University of Maryland Center for Environmental and l Estuarine Studies, Solomons, MD. (Not seen, cited by Olson 1987a, b). l 47

4 l

l JCP&L (Jersey Central Light and Power Company).1978. Oyster Creek & Forked River Nuclear Generating Stations 316 (a) & (b) demonstration text. GPU Nuclear Corp., Forked j River, NJ. '

Lindsay, P., S.L. Barker, and J.R. Stewart.1978. Monitoring the effects of the condenser cooling water system on plankton and larval organisms. Pages 4.1 - 4.135 in Maine Yankee Atomic Power Co. Environmental surveillance and studies at the Maine Yankee j Nuclear Generating Station 1969-1977. Final report. Augusta, ME. -

l McAlice, B.J., E.S. Gardella, and A.L. Heinig.1978. Microzooplankton. Pages 8.1.1 -

8.1.33 in Maine Yankee Atomic Power Co. Environmental surveillance and studies at the j Maine Yankee Nuclear Generating Station 1969-1977. Final report. Augusta, ME.

MMES (Martin Marietta Environmental Systems).1985. Impact assessment report: Chalk Point Steam Electric Station aquatic monitoring program. Columbia, MD.

MRI(Marine Research,Inc.).1976. Entrainment investigations and Cape Cod Bay i ichthyoplankton study. September-December,1975. Twelve-month summary for 1975. l Pages III.C.2-i-III.C.2-155 in Marine ecology studies related to operation of Pilgrim Station. Semi-annual Rep. No. 7. July 1975-December 1975. Boston Edison Co., Boston, MA.

MRI, and NEPCO (New England Power Company).1978. Brayton Point Generating Station, Mount Hope Bay, Somerset, Massachusetts. Supponing document for cooling water discharge of temperature up to 95 F. 252 pp.

NUSCO (Nonheast Utilities Service Company).1976. Environmental assessment of the condenser cooling water intake stmetures (316b demonstration). Vol.1.

NUSCO.1983a. Zooplankton species composition. Pages 2.2 2.2-14 in Millstone Nuclear Power Station Unit 3 environmental report. Operating license stage. Vol.1.

NUSCO.1983b. Phytoplankton and zooplankton entrainment. Pages 5.1 5.1-20 in Millstone Nuclear Power Station Unit 3 environmental report. Operating license stage.

Vol. 2.

Olson, M.M.1987a. Zooplankton. Pages 38-81 in K.L. Heck, Jr., ed. Ecological studies in the middle reach of Chesapeake Bay - Calvert Cliffs. Lecture notes on coastal and estuarine studies 23. Springer-Verlag, New York.

Olson, M.M.1987b. Entrainment studies. Zooplankton entrainment. Pages 240-253 in K.L.

Heck, Jr., ed. Ecological studies in the middle reach of Chesapeake Bay - Calven Cliffs.

Lecture notes on coastal and estuarine studies 23. Springer-Verlag, New York.

48

1 i

Toner, R.C.1984. Zooplankton of western Cape Cod Bay. Pages 65-76 in J.D. Davis, and D. Merriman, eds. Observations on the ecology of western Cape Cod Bay, Massachusetts. -

Lecture notes on coastal and estuarine studies 11. Springer-Verlag, New York.

USNRC (United States Nuclear Regulatory Commission).1984. Final environmental statement related to the operation of Millstone Nuclear Power Station, Unit No. 3. Docket No. 50-243. Office of Reactor Regulation, Washington, DC.

I r

f M

e 49

WATER QUALITY Summary of the Proposed Monitoring Program after 5 Years of Plant Operation The objectives of the proposed water quality program are to acquire environmental data, characterize conditions at Seabrook sampling stations, provide explanatory variables to support conclusions drawn from other aspects of the monitoring program, and help distinguish between long-term and short-term trends in the vicinity of Seabrook Station.

The program focuses on areas that are most likely to detect potential power pfant effects and will provide data to explain biological variability.

1. Water temperature, salinity and dissolved oxygen are biolcgically important parameters that influence the distribution offish, plankton and benthic organisms.

Measurement of these parameters should be accomplished with dependable field instmments, utilizing current analytical technology, and minimizing difficulties associated with handling and storage ofglass bottles, and generation and disposal of hazardous wastes from Winkler titrations.

2. Comparisons of recent data to the historical database will allow determination of whether changes have occurred since Seabrook Station began operation; comparisons between the nearfield (P2) and farfield (P7) stations will distinguish between localized (i.e., potentially power plant-related) and regional changes. Stations P2 and P7 have the longest time-series of concurrent data collection.

3. Modifications to past programs will have minimal effect on ability to detect power plant impact, should it occur:

e suspension of nutrient sampling - no impacts shown to date (see Phytoplankton evaluation); inherently high variability and lack of credible mechanism for impact make it unlikely that they ever could show impact.

e deletion of sampling station P5 (discharge)- this station is actually over 1.5 km from the discharge, too far to be affected by power plant operation, and too far to even be considered a nearfield station. Discharge effects will continue to be assessed by the continuous temperature monitoring program.

f WATER QUALITY PROPOSED PROGRAM PAST PROGRAM I) Offshore Temperature Profiles, Salinity & Dissolved Oxveen Measurement e Stations / Sampling frequency: P2. P7/4 times per month (concurrent with = Stations / Sampling frequency: P2 (intake), P5 (discharge), P7 (farfield)/4 ichthyoplankton sampling) times per month e Methodology: all parameters measured surface and bottom with field probe; = Methodology: S-C-T probe at 2m depth intermis for temperature (~10 additional temperature readings will be made enry 2 meters to the bottom readings / profile); water samples taken near surface and near bottom (2 reps for DO) and analyzed in lab (S-C-T probe for salinity, Winkler titration for DO) e Total sampics/ycar: 96 profiles (48 trips x 2 sta.)

• Total samples / year: 144 profiles (48 trips x 3 sta.)

2) Estuarine Water Qualitv (Temperature and Salinity) e no change from past program . Station / Sampling Ircquency: HH (Hampton Harbor)/ recorded weekly at high and low stack tides

. Total sampics/ year: 104/ parameter (52 uks x 2 tidal stages)

3) Continuous Temperature Monitorine e no change from past program = Stations: DS (discharge) and T7 (farfield; both stations sampled for 316/ NPDES compliance)

4) Nutrients none - no impact shown to date; inherently high variability and lack of mechanism . Stations / Sampling frequency: P2, PS, P7/once per month in Jan., Feb., Dec..

for impact make it unlikely that they ever could show impact. twice per month Mar. through Nov.

• Total samples / year: 63 for each nutrient

. Data collected: whole near-surface water concentrations of total phosphorus, orthophosphate, nitrate, nitrite, ammonia

- - - _ - . . . _ _ - . ~ _ - _ - - . . - - _ , . _ . . _ - . . . _ . . . . -. .-

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Figure 1. Water quality sampling stations. Seabrook Operational Report,1994.

WORKING DRAFT l l

l EVALUATION OF SEABROOK STATION _

WATER QUALITY MONITORING PROGRAM AFTER FIVE YEARS OF PLANT OPERATION I 1

Prepared for i

l NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300  :

Seabrook Station I Seabrook, New Hampshire 03874 Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford,NewHampshire 03310 August 1996

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1 i

I Evaluation of the Seabrook Station Water Quality Monitoring Progrant {

After Five Years of Plant Operation I j Introduction i

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l Monitoring of water quality in the vicinity of Seabrook Station has been one component of the environmental studies designed to assess the impacts associated with construction and I operation of the power plant. Water quality data were collected to aid in interpreting I

information from the biological monitoring programs, and to determine whether the operation of the Seabrook Station Circulating Water System has had a measurable effect on the physical and chemical characteristics of the water column. Parameters measured in l this program include water temperature, salinity, dissolved oxygen, and the nutrients orthophosphate, total phosphorus, nitrite, nitrate and ammonia. This report assesses the effectiveness of the current program in meeting the original objectives after five years of l

power plant operation, and proposes modifications to enhance our ability to assess any )

l potential changes to the environment that might be related to operation of Seabrook Station.

I l

l i Current Methodology i

Water quality monitoring encompasses four studies: 1) offshore temperature, salinity and dissolved oxygen measurement at the plankton sampling stations P2 (intake), P5

(discharge) and P7 (farfield); 2) analyses of dissolved chemical nutrients at P2, P5 and P7;

3) continuous temperature measurement at a neadield (DS) and a farfield (T7) site; and 4) estuarine temperature and salinity measurement in Hampton Harbor. Offshore temperature, salinity and dissolved oxygen measurements began in 1979 at stations P2 and P5, and in 1982 at station P7. Sampling at P2 and P7 continued to the present; sampling at P5 was suspended from January 1982 until July 1986, but P5 has been sampled I

continuously and concurrently with P2 and P7 from July 1986 to present. At all stations, temperature profiles were taken at the near surface (-l m) and at 2-m increments four times per month from January through December. Water temperature was measured with a field thermistor probe; near-surface and near-bottom salinity was measured either in the l field, with a conductivity meter, or in the lab, from samples collected in wax-sealed glass bottles. Dissolved oxygen in near-surface and near-bottom water was determined in the lab, by Winkler titration. Near-surface water samples for nutrient analysis were cellected during daylight hours from stations P2, P5 and P7 once per month in January, February and December, and twice monthly from March through November. Nutrient sampling began at stations P2 and P5 in 1978 and at P7 in 1982. Sampling continued until 1981 at P5, and until 1984 at P2 and P7. Sampling resumed at all three stations in July 1986, and has continued to present. Continuous surface water temperature data from discharge (DS) and farfield (T7) areas have been collected since 1990 as part of Seabrook Station's NPDES permit compliance program. Estuarine water temperature and salinity have been recorded weekly since May 1979, at high and low slack tidal stages in Hampton Harbor.

Summary of Results to Date i

Seventeen years of sampling (though not concurrently at all stations) allow l characterization of several water quality parameters at offshore sites in the vicinity of I

Seabrook Station. For instance, surface water temperatures follow a predictable seasonal cycle with minima near 0*C in February / March, and maxima around 19-21*C, usually in August (NAl 1996). Bottom water temperature minima were similar to those at the ,

surface, but bottom waters warmed more slowly. When thermal stratification was strongest (again, usually in August), bottom water temperatures were 6-7 C colder than surface temperatures. Bottom water temperatures typically peaked in September, with maxima around 15-17*C. There has been considerable year-to-year variability, but among-station variability was low. As the same patterns and trends were seen at all stations (including farfield), the changes are region-wide, and not attributed to power plant 2

l operation. For both surface and bottom water temperatures, ANOVA modeling showed the Preop-Op X Station interaction term to be non-significant, indicating no power plant effect (NAl 1996).

Similarly, salinity varies seasonally and from year to year, but very little among stations.

Surface salinities are affected by freshwater runoff, lowest (20-25 )in spring (owing to storms and snowmelt) and highest in late autumn-winter (33-35 ); bottom salinity is less i affected by runoff or precipitation, and remains more constant with time (29-35 ).

Surface and bottom dissolved oxygen concentrations also exhibited seasonal patterns; levels were highest during winter months (11-16 mg/L), and lowest from August through October (5-7 mg/L). This pattern was related to water temperature; relative oxygen concentration was close to 100% saturation throughout the year. As with water l

temperature, ANOVA modeling for surface and bottom salinities and dissolved oxygen concentrations showed the Preop-Op X Station interaction terms to be non-significant, indicating no effect of power plant operation (NAI 1996).

Concentrations of dissolved chemical nutrients, measured at the offshore sites, also exhibit distinct seasonal patterns. For instance, nitrate-nitrogen is the limiting nutrient for phytoplankton growth, and is depleted from surface waters during the spring phytoplankton bloom, remaining at very low levels (typically below detectable limits) throughout the summer when the water column is stratified. Similarly, nitrite-nitrogen, orthophosphate and total p%sphorus, although non-limiting, are also utilized by phytoplankton, and are found at minimum concentrations in summer, and at higher levels in winter, after vertical stratification has broken down and nutrient-rich deep water has mixed with nutrient-depleted surface water. Of the nutrients sampled, only ammonia-nitrogen did not show a seasonal cycle, but rather remained at a relatively constant (but i

low) level throughout the year. For all nutrients, ANOVA modeling showed that the interaction of the main effects (Preop-Op X Station) was not significant; again, indicating no power plant impact (NAI 1996). Because nutrient concentrations are so tightly 3

~

coupled to phytoplankton abundance, further discussion of nutrient sampling is included in the evaluation of the phytoplankton program (NUSCO 1996).

Operational data from continuous temperature sensors allow further characterization of surface water temperatures in the immediate vicinity of the Seabrook Station discharges (DS) and at a farfield site (T7), and have verified thermal plume predictions. In winter, surface water near the discharges is typically 1-2"C warmer than ambient, owing to the upwelling ofless dense, heated effluent. However, in summer, the effluent entrains a volume of cold bottom water as it rises to the strongly stratified surface layer, actually  !

lowering temperature at DS, relative to ambient at T7.

t Water quality data (temperature and salinity) have also been collected in the Hampton Harbor estuary since 1979. Data from station HH were originally intended to support biological monitoring studies (e.g., benthos, fish, soft-shell clam), and to provide a basis for comparison to Brown's River, and allow assessment of the impacts associated with construction of Seabrook Station and discharge from a settling basin into Brown's River. i However, in April 1994, this discharge was diverted to the offshore discharge tunnel, and I

with no further source ofimpact to the estuary, sampling at Brown's River was suspended after 1994. Sampling at HH has continued, primarily to provide information about water quality near recreational shellfish monitoring beds and finfish monitoring sites.

Recommendations The objectives of the water quality monitoring program are: 1) to collect data to aid in  ;

interpreting information from the biological monitoring programs, and 2) to determine

- whether the operation of the Seabrook Station Circulating Water System has had a j measurable effect on the physical and chemical characteristics of the water column. The second objective has clearly been met; after 17 years of sampling, including 5 years of power plant operation, we have characterized seasonal patterns for water quality 4

parameters, and have documented differences and trends among years and among stations.

However, statistical analyses show that, for all parameters measured, the Preop-Op X Station interaction term has been non-significant, indicating that the differences were region-wide, and not associated with Seabrook Station operation. The first objective is currently being met; it is an ongoing effort to measure explanatory physical variables that may afTect the algae and animals that are studied in other sections of the monitoring program. The proposed modifications to the water quality program are intended to focus efforts in areas that will provide the most useful data for biological monitoring purposes, without afTecting our ability to detect power plant impact, should it occur.

The first recommendation is a reiteration of the one made after evaluating the phytoplankton sampling program (NUSCO 1996), and takes ir.to account: 1) that nutrient concentrations in waters near Seabrook Station are tightly coupled to uptake and release rates from phytoplankton; 2) that the phytoplankton source community in the Gulf of Maine is extremely large and the turnover rate extremely rapid; and 3) that no reasonable mechanism exists whereby Seabrook Station could affect nutrient concentration or the phytoplankton community. Therefore, we propose to suspend nutrient analyses at the offshore phytoplankton stations.

The second recommendation, also in agreement with those of other evaluations (e.g.,

Phytoplankton, Zooplankton, Ichthyoplankton, Epibenthic Crustacea), is the deletion of all water quality sampling at station P5. This station is approximately 1.5 km from the Seabrook Station discharge, too far to be affected by power plant operation, and too far to be even considered a nearfield station. The continuous temperature recorder site at DS is much more representative of water temperature in the immediate vicinity of the discharge.

Suspension of sampling at P5 will simplify nearfield-farfield comparisons, and will increase the length of usable preoperational database from 3 years (1987-1989, when all 3 stations were sampled concurrently) to 8 years (1982-1989, when P2 and P7 were both sampled).

5

The final recommendation is merely to modify techniques used to acquire the water quality data. Water temperature, salinity and dissolved oxygen should be measured, whenever possible, with dependable field probes, incorporating recent advances in analytical technology, and minimizing difficulties associated with handling and storage ofglass bottles, and generation and disposal of hazardous wastes from Winkler titrations. In particular, small, relatively inexpensive data loggers are available for temperature secording; these can be placed in the field for several months at a time. If appropriate, this capability can be added to other monitoring programs (e.g., Marine Macrobenthos.

Epibenthic Crustaceans).

In summary, the Water Quality Program will be less of a stand-alone monitoring effort, and more of a supplement to the other environmental studies, providing explanatory variables to suppon conclusions drawn from other aspects of the monitoring program, and helping to distinguish between long-term and short-term trends in the Seabrook area.

References Cited NAI (Normandeau Associates Incorporated).1996 (in prep). Seabrook Environmental -

Studies,1995: A Characterization of Environmental Conditions in the Hampton-Seabrook Area During the Operation of Seabrook Station. Prepared for Nonh Atlantic Energy Service Corporation.

NUSCO (Northeast Utilities Service Company).1996. Evaluation of Seabrook Station Phytoplankton and Chemical Nutrients Sampling Programs After Five Years of Plant Operation. Prepared for North Atlantic Energy Service Corporation.

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_ e = continuous temperature monitoring stations Figure 1. Water quality sampling stations. Seabrook Operational Repon,1994.

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. MYA ARENARIA i

Summary of the Proposed Monitoring Program After 5 Years of Plant Operation The objectives of the proposed Mya arenaria program are to ensure the continuity of th l current database on the soft-shell clam and its predators, and to make available information needed to explain to the public major changes in clam abundance whic occur in the future. The proposed Mya arenaria monitoring program would have three i main components: 1) The Hampton Harbor Population Surveys; 2) the Near/Farfield Study; and 3) The Predator Surveys. Because of this species' recreational importance an high profile with the public and regulators it is important to maintain continuity with  !

historically reported data.

I t.

Hampon Harbor Survey would focus on Flats 1,2, and 4; data from Flats 3 and 5 have not been used in analyses in the past due to low densities of clams >25 mm. Surveysl Hampton Harbor Flats 2 and 4 should be maintained because they are also used in the '

Near/Farfield Study. The monthly survey of green crabs on Flat 2 would continue unchanged.

Sampling design and data analyses for the Population Survey should change to reflect the fact that larval abundance and annual clam set are totally unrelated (see supporting regression analysis attached). Thus, plant effects via larval entrainment can be dismissed. Since incursions of warm water into the estuary from the thermal plume have not occurred, the focus of the program should change from " impact assessment" to " Annual Abundance Survey". This new focus, with similar monitoring effort, would serve better the interest of NH State and the public by monitoring the availability of soft-shell clams for recreational fishing.

Redesign the sampling program and allocate similar e(fort to improve accuracy of annual estimates by size classes; annual means and stratified random design will be useful for this purpose.

2. The Nearfield/Farfield Study would be the same as in the past program because it is the only study that actually provides valid data for statistically testing whether future clam abundance dec'nes, mass mortalities, etc. can be attributed to plant operation. i

3. The green crab surveys would continue unchanged. Clam digger counts should be discontinued if recreational license data is acceptable to quantify harvesting effort; otherwise restrict sampling to Flats 1,2, an 4 for consistency with the random surveys of adult clams in the fall.

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MYA ARENARIA PROPOSED PROGRAM PAST PROGRAM

1) Random sunty-Ilampton IIarbor

. Stations / Sampling frequency: Reallocate similar sampling effort to Abu . Stations / Sampling frequency: Alyn adults - flats 1,2A / Afyn spat - flats adults and spat in the historically most productive two or three flats using 1-5; once per year in the fall.

stratified random design.

. Replicates: determined by historical variability . Replicates: varies

. Data collected: Density by size class starting at I mm . Data collected: Density by size class

2) Nearficid/FarficId Study - no changes proposed

. Stations / Sampling frequency: 10 stations cach in llampton liarbor and . Stations / Sampling firquency: 10 stations each in IIampton Harbor and Plum Island Sound, once per year in the fall. Plum Island Sound. once per 3 car in the fall.

. Replicates: 3 = Replicates: 3

. Total samples / year: 60 = Total samples / year: 60

. Data collected: Seed clam (1-12 mm) density - . Data collected: Seed clam (1-12 mm) density 1

I MYA ARENARIA PROPOSED PROGRAM PAST PROGRAM

3) Predator Surveys -

a) Clam diggercounts a) Clam digger counts Replace with recreational license data (currently used); or consider sampling only at monitoring stations as outlined below.

. Stations / Sampling frequency: Stations 1,2 and 4; once per week

• Stations / Sampling frequency: Stations I.2.3.4 and 5: once per cxcept from June through August week except from June through August e Replicates: 1 . Replicates: 1  :

. Total samples / year: 76 = Total sampics/ year: 190 ,

= Data collected: Number of diggers per flat.

• Data coliccted: Number of diggers per flat. '

b) Green Crabs-no changes proposed b) Green Crabs

. Stations / Sampling frequency: Stations 1-4 within Mya Flat 2 in  ;

llampton liarbor; twice monthly except Feb. and Mar. . Stations / Sampling frequency: Stations 1-4 within Mri Flat 2 in llampton liarbor; twice monthly except Feb. and Mr..

• Replicates: 2 '

• Replicates: 2

. Total samples / year: 160 e Total samples / year: 160

. Data collected: Monthly CPUE

= Data collected: Monthly CPUE

4) Bivalve I,arvac: discussed with zooplankton evaluation h

WORKING DRAFT EVALUATION OF SEABROOK STATION SOFT-SHELL CLAM (Af fa arenaria) PROGRAMS AFTER FIVE YEARS OF PLANT OPERATION Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station Seabrook, New Hampshire 03874 Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford, New Hampshire 03310 August 1996

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i Evaluation of Seabrook Station Soft-shell Clam (Mya arenaria) Program After Five Years of Plant Operation i

k Introduction The range of the son-shelled clam Mya arenaria on the East Coast extends from Labrador to

..l North Carolina (Abbott 1954); in New England Mya arenaria is especially abundant in Maine, New Hampshire and parts of Massachusetts, where it tends to be associated with silty-sand sediments (Whitlatch 1982). This clam is typically thought of as an intertidal bivalve because it is harvested from mud flats when exposed at low tide; the species, however, does occur below the water mark. The son-shell clam is a widely occurring species in coastal mud flats throughout the Gulf of Maine (Larsen and Doggett 1991) where it has great economic importance due to his high recreational and commercial value; in the vicinity of Seabrook Power Station the tidal flats in the Hampton-Seabrook estuary contain the majority of New Hampshire's stock of soft-shell clam. Potential impacts of Seabrook Station operaticn on this local soft-shell clam were expected to be negligible (YAEC 1982) and they appeared limited to entrainment of planktonic Mya arenaria larvae in the cooling-water system, and to possible i effects associated with the station discharge of cooling water such as increased water temperatures in the thermal plume path and increased turbidity near the discharge site from resuspension of organic sediments. Ahhough unlikely, given the predicted path and extent of the thermal plume (Teyssandier et al.1974), there was also the possibility of Seabrook plume being carried by tidal currents into the Hampton-Seabrook estuary. For all these reasons and also because the soft-shell clam is the most economically important species inhabiting the

. estuary (Sullivan and Sawyer 1966), the collection of baseline data on Mya arenaria in the tidal flats of Hampton Harbor started in 1971 in preparation for the planned construction of Seabrook Station. This database has been incremented annually to the present, essentially keeping the original sampling locations at five selected flats (Fig.1). A control site at Plum Island Sound (Fig.1) has also been sampled annually since 1976, sampling programs for green 1

I crabs (Fig.1) and for bivalve larvae (Fig. 2) were started in 1978, and surveys of clam diggers started in 1980. The objectives of these monitoring programs have been to describe the spatial and temporal distribution of various life stages of soft-shell clams in the Hampton-Seabrook l estuary, to compare their abundance to that of the same clam species monitored in Plum Island

, Sound since 1976 and, most importantly, to assess whether the operation of Seabrook Station 1 has had a significant adverse effect on the abundance and distribution of soft-shell clams in the l

Hampton-Seabrook estuary.

l The purpose of this evaluation is to review results to date of the Mya arenaria monitoring i program, after more than 20 years of study that include the first 5 years (1991-1995) of Seabrook plant operation, and to assess how well program objectives have been met. The effectiveness of each component of the program in assessing plant operation effects on soft-shell clams will be examined and what has been learned since the inception of the program will form the basis for recommending program changes where needed. Finally, an improved and more focused Mya arenaria program to be implemented after 1996 is proposed.

l Summary of Current Program The current soft-shell clam monitoring program at Seabrook consists of four separated but related studies: the annual population survey at Hampton Harbor, the nearfield/farfield study, the predator surveys, and the larval study. The latter is only a part of a larger bivalve larvae program (see Evaluation of the Zooplankton Program) that arose from the need to monitor abundance ofMya arenaria larvae. A succinct review of each of these programs databases and methodology follows; more detailed descriptions have been provided by Normandeau i Associates Inc. in their annual reports of the Seabrook Station Environmental Studies, the most relevant being NAI (1990) for the pre-operational period and NAI (1996) for the operational years.

2

Hampton Harbor Population Survey.

The first survey of soft-shell clams in the Hampton-Seabrook estuary was conducted in the j

Summer of 1969 as a part of a two-year preliminary Seabrook ecological study (Normandeau  !

et al.1971), which yielded an estimated standing crop of 21,769 bushels oflegal size clams

, from the total of 174 acres among the ten productive clam flats surveyed. These flats were the  ;

same ten flats used by Ayer (1968) in his study for the NH Fish and Game Dept. Among them, !

Flats nos.1,2, and 4 were the most productive with 11,775., 2,972., and 2,492. bushels, respectively; except for Flats nos. 3 and 5 (over 1000 bushels each), all the other flats were i

only marginally productive (less than 500 bushels each). These data were the basis to later i

select the five most productive flats for the annual surveys started in 1971.

Flats nos. I through 5 in the Hampton-Seabrook estuary (Fig.1) have been surveyed in the late fall from 1971 through 1995 to estimate densities of clams measuring at least I mm. Sampling sites in each flat were chosen randomly and their number was proportional to the variance in  !

i density observed in each flat historically (NAI 1996). Flats nos. 3 and 5 were not sampled for i

clams larger than 25 mm in length after 1984 because their density had been historically low (Table 1). Samples for Young-of-Year (YOY) and spat (1-25 mm) consisted of three cores '

(10.2 cm diameter and 10.2 cm deep) taken within a 30 x 61 cm quadrat (1 x 2 ft). Samples were sieved (1 mm mesh) and clams were enumerated, measured and released. Samples for clams > 25 mm consisted of the same quadrat as before but dug to a depth of 45 cm with a clam fork; large clams were removed from the sediment, enumerated, measured, and released.

The clam counts were classified into four size-classes: YOY (1-5 mm), Spat (6-25 mm),

Juvenile (26-50 mm), and Adult (legal size) clams > 50 mm (NAI 1996).

The parameters reported have been annual means corresponding to numbers of clams per square foot at each of the flats sampled during the preoperational period (Table 3.3.7-1, NAI 1990), and annual geometric means and coefficients of variability for combined densities of all flats sampled annually both during the preoperational and the operational periods (NAI 1996).

These geometric means were based on a sample size equal to the number ofyears sampled in each period, and on a sample size equal to the number of samples for any given year (NAI ,

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1996). A fixed effects analysis of variance (ANOVA) model was used on log (x+1) transformed mean densities (n= number of samples) to test for differences in the following ma effects:

spatial differences (among areas or flats), temporal differences (among years), and differences between periods (preoperational and operational). Although this model had also I

4 and interaction term (Preop-OP x areas), the test had no interpretation because flats could not be assigned rationally to "nearfield" and "farfield" groups to meet the requirements of the

)

i BACI sampling design on which the ANOVA model was based (Green 1979; Underwood '

1994).

Nearfield/Farfield Study.

This study started in 1976 to compare seed clam (1-12 mm) densities between Hampton Harbor and Plum Island Sound, Ipswich, Massachusetts. The surveys were conducted once a year in the fall at ten sites in each location, Hampton Harbor (Flats 2 and 4) and Plum Island l Sound (Fig.1). Three cores were taken per site and processed in the same manner as in the Hampton Harbor population survey described above. Sampling sites were fixed in the above mentioned locations and the specific sampling areas were selected according to where the abundance of clams had been high historically (NAI 1996). The parameters reported have been annual geometric means and coefficients of variability of densities of seed clams (1-12 mm) at Hampton Harbor and Plum Island Sound, and "preoperational" and " operational" geometric means. These means were based on the number of samples for any given annual mean and in the number ofyears sampled for the means of preoperational and operational periods. The same fixed ANOVA model used in the Hampton Harbor surveys was applied to the annual means of this s:udy to determine whether there was a Seabrook Station effect when the interaction term (Preo-Op x Location) was significant. Because Hampton Harbor qualifies as "nearfield" and Plum Island Sound as "farfield", the BACI sampling design requirements were met and the interpretation of the interaction term was straightforward.

Predator Surveys.

Clam digger counts. Beginning in the spring of 1980 the numbers of diggers in flats 1,2,3, 4, and 5 have been counted weekly, except for the summer months (Memorial Day through 4

I Labor Day). The parameter reported has been the estimated total number of digger trips per l

flat (see note 'in Table 3 for more details). These data was summarized by flat, as percentages of the total, and by either spring or fall, since the spring of 1980 through the Spring of 1989 1 (NAI 1990). Hampton Harbor flats were closed to clam digging from April 1989 through

, September 1994 and the Spring of 1995, depending on the flats, by the NH Dept. of Health and Human Services due to coliform contamination.

Green crab (Carcinus maenas). Beginning in the Fall of 1977, C. maenas crabs were trapped at four stations around the perimeter of Flat # 2 (Fig.1). The traps were set twice a month except for February and March when historically no crabs were found; two baited " box" l

traps (13-mm mesh) were set at each station so that they were awash at mean low tide. After '

fishing for 24 h traps were retrieved and catch was sized and sexed. Reported parameters have been monthly catch per unit effort (CPUE) during both preoperational and operational years.

The only estimates based on these data were the monthly geometric means for individual years and the monthly geometric means for the entire preoperational and operational periods. The data were log (x+1) transformed prior to any calculations (NAI 1996).

Bivalve larvae.

The spatial and temporal distribution of 12 species of bivalve larvae, including Mya arenaria, l have been monitored since July 1976 at station P2 (intakes), during July-December 1986 and since April 1988 to the present at station P5 (discharge), since July 1982 at station P7 (farfield l

control), and since July 1986 at P1 (Hampton Harbor) (Fig.1). Samples were collected weekly from mid-April through October at all stations; two simultaneous two-minute oblique tows were taken at each station and preserved (NAI 1996). A more detailed description of methods, including laboratory processing, can be found in NAI (1991). Samples of the same 12 species of bivalve larvae entrained at Seabrook Station have been collected weekly since 1990 (see Zooplankton Programs and their Evaluation report for an account). Parameters reported from the Mya arenaria larval collections at the plankton stations have been log (x+1) numbers per cubic meter, and the geometric mean ofindividual years and for the entire preoperational and operational periods. The same ANOVA model described earlier was used 5

to analyze the larval data with the BACI sampling design where station P7 was the control station or farfield and P2 and P5 were the nearfield stations.

Summary of Results After 5 Years of Seabrook Plant Operation -

Population survey.

Densities of all sizes of soft-shell clams at Hampton Harbor have been highly variable durin both preoperational and operational periods NAI(1996). The YOY (1-5 mm) size class has historically undergone periodic fluctuations in abundance approximately every three years.

This typical periodicity was apparent in both preoperational and operational periods, and differences among flats just added to the noise without providing any insight into the overall trend (Fig. 3). Although the operational period mean for all the flats was lower (Table 2),

none of the statistical tests could relate this differences to Seabrook Station operation (NAI 1996). The spat (6-25 mm) and juvenile (25-50 mm) size classes generally reflect the recruitment success of the previous one and two years' spat falls, but this success is modulated by predators' activities (both green grabs and clam diggers disturbing the flats and exposing small clams to predation). Densities of spat reached a low in 1984 and seem to be increasing now (Fig. 4); the peaks in 1990 and 1994 were preceded by good sets of YOY in 1989 and 1993 (Fig. 3). Differences among flats are widespread and the overall mean is lower during the operational period (Table 2). Forjuvenile clams the lowest density was observed in 1986 (one year after the " low" for spat), then increased up to 1990, decreased to a secondary low in 1993 and increased at all flats in 1994 and 1995 (Fig. 5). The mean for all flats in 1995 was higher than either the preoperational or the operational means (Table 2), and again, none of 4

these changes could be related to the operation of Seabrook Station (NAI 1996). Finally, legal size clams (>50 mm) were more abundant in 1995 than in an average year of either the preoperational or operational periods a'nd specially so for Flat # 4 (Table 2); however abundances have been generally higher every year since 1989 at all flats (Fig. 6). With Hampton Harbor closed to recreational clamming from April 1989 through September 1994, 6

l l

and April 1995 depending on the flat, the number oflegal clams on Flat # 4 greatly increased from 1989 to 1990 and remained fairly high from 1991 through 1995; the largest number reported in the entire study occurred in 1992 for Flat # 4 (Fig. 6). Another factor that could have some effect in the peak abundance oflegal clams at Flat # 4 wa's the disease sarcomatous !

, neoplasia, a lethal form of blood cancer Neoplasia was present in 1986 and 1987 in flats 1 and 2 but it was absent in Flat # 4, the best performing flat during the operational (NAI 1996).

l i

Nearlield/Farfield study. I The ANOVA model results indicated that there was not a significant difference between the I mean densities of seed clams (1-12 mm)in Flats 2 and 4 at Hampton Harbor during the preoperational and operational periods. Although there was a significant difference between preoperational and operational periods at Plum Island Sound, both areas showed the same trend as demonstrated by the clearly non-significant interaction term " Preop-Op x Area" (NAI  !

1996). Actual means by period and area are listed in Table 2. This has been a very straightforward study that still provides reliable results on whether the operation of Seabrook Station has any effect on the recruitment success of soft-shell clams in the tidal flats of I Hampton Harbor.

Predator Surveys.

Clam digger counts. Recreational digging on the Hampton Harbor flats has been a significant source of mortality for legal size clams and also for spat and juvenile clams due to disturbance

( NAI 1990). Census figures indicate that digging activity tripled from 1980 to 1981; effon remained high through 1982 and begun a slow decline in 1983 that continued through 1989 (Table 3) when Hampton Harbor was closed to recreational clamming. Among the five flats surveyed in Hampton Harbor, Flat # 4 was consistently the preferred flat by local diggers except for a brief period (Spring 1985 through Fall 1985) when diggers attention turned to Flat

1. 1 (NAI 1990).

l l

Green crab (Carcinus maenas). Soft-shell spat and juvenile clams are a raajor source of j food for green crabs, especially in the fall (Ropes 1969). Mean monthly CPUEs of green crabs 7

collected in Hampton Harbor during the preoperational and operational periods appear to follow similar seasonal trends, although in general, monthly CPUEs were lower during the operational period (Fig. 7). The abundance of the green crab in the Gulf of Maine appears driven by winter water temperatures (Welch 1969; Dow 1972; Welch and Churchill 1983); this was loosely supponed by temperature data and mean green crab CPUE from Hampton Harbor from the last 15 years (Fig. 8). These data also show that there is no relationship between green crab abundance and the stan of Seabrook Station operation in 1990.

Soft-shell Clam Lanae.

Mya arenaria larvae has been historically one the least abundant species among the twelve bivalve larval species collected at stations P2, P5, and P7; from 1988 through 1995 it accounted for only 0.4 percent of the total collections (Table 4). Soft-shell clam 1,arvae generally occurred in plankton samples May through October every year since 1978 at station P2 (intakes). Peak densities were typically recorded in late summer or early fall, but a secondary peak usually occurred in early summer (Fig. 9). This alone represents strong evidence that the pool of pelagic Mya arenaria larvae drifting along the coast is a mix oflarvae from several regional sources, because gonadal studies have established that the Hampton Harbor soft shell clam spawn once a year with a single strong peak in late August to early September (Normandeau et al.1971; NAI 1979).

The largest larval density peak observed at station P2 since 1978 occurred in September 1995 and it was two orders of magnitude larger than the preoperational average for mid-September (Fig. 9). The mean densities for the preoperational and operational periods at all three plankton stations (P2, P5, and P7) are included in Table 2. Results of the ANOVA model indicated that mean operational period density was significantly smaller than the preoperational density; however, trends in larval abundance between nearfield and farfield stations remained consistent during both periods demonstrating nieffect from the operation of Seabrook Station (NAI 1996).

8

Evaluation and Discussion of Results.

New England tidal flat macrofauna display naturally high temporal and spatial variability numbers of species and total numbers of organisms may vary by several orders of magnitud within and between years (Whitlatch 1982). From the very first surveys of soft-shell clams in the Hampton-Seabrook area going back to .'969, it was established that population dens size frequencies and settlement success varied considerably from flat to flat (Normandeau et al.

1971). This vari ion, also seen throughout the Gulf of Maine (Larsen and Doggett 1991),

could be the :r ... of sedimentary composition differences (Turk and Risk 1981), but other factors such as current patterns (Emerson and Grant 1991), differential predation, and harvesting rates of clams are probably also significant (Lindsay and Savage 1978). Predation is often invoked to explain declines ofMya arenaria spat and seed clams with only circumstantial evidence (Welch 1969); but when detailed data are obtained this assumption is often sup!

(Moller and Rosenberg 1983). In addition to spatial variability, very large variation from year to year has also been documented (Ayers 1956; Brousseau 1978b; NAI 1989). Standing crop estimates at Hampton Harbor declined by a factor of 20 between 1967 and 1977 (Table 5).

Large temporal variability has been typical ofboth preoperational and operational periods in the annual Mya surveys at Hampton Harbor and Plum Island Sound, but differences between the two periods and their interaction with the "nearficid/farfield" effect were never statistically significant (NAI 1996).

This evaluation found no evidence for associating any of the observed variability and/or changes in soft-shell clam abundance and recruitment with the operation of Seabrook Station.

Given the actual path and extent of the thermal plume from Seabrook Station discharge of cooling water (Padmanabhan and Hecker 1991), there is almost no possibility ofincreased water temperatures in Hampton Harbor due to plant operation. The l'F isotherm from the thermal plume comes close to the Outer Sunk Rocks (Fig.10), but it never even approachas

'the entrance of Hampton Harbor about 1 km west and slightly south of Outer Sunk Rocks (Fig. 2). Furthermore, substantially higher water temperature increases would be recessary to affect the survival rates or growth ofMya arenaria clams, which are naturally exposed to 9

4

} potentially large temperature changes between tides. Similarly, the hypothesis ofplant impac through increased turbitity in the discharge water appears unfounded, because no turbidity

{ effects have been for macrobenthos communities in the immediate discharge area (see evaluation of the Macrobenthos Program). The only other possible source of turbidity, the

, Seabrook's settling pond discharge, ceased in April 1994 without having ever shown any effect on the mud flats of Hampton Harbor (NAI 1995). Higher water temperatures-in the discharge plume region could affect development of drifling planktonic larvae; however Stickney (1964) established through experimental work that Mya arenaria larvae have a great tolerance to both temperature and salinity. Given the relatively small size of the plume (the 3" F isotherm measures about 32 acres) and the modest maximum temperature increases of up to 4* F in an even smaller area (Padmanabhan and Hecker 1991), it is highly unlikely that the thermal discharge of Seabrook Station affects in any way the soft-shell larvae in the vicinity of the  !

discharge; this was also supported by the ANO A model results involving nearfield stations P2 and P5, and farfield station P7 (Fig. 2). Therefore, except for larval entrainment, no reasonable mechanism exists now whereby Seabrook Station operation could affect the recruitment and growth of soft-shell clams in Hampton Harbor. Entrainment ofMya larvae l

represents only a tenth of one percent of total numbers of bivalve larvae (12 species) entrained l since 1990 (Table 6). Although the relatively small numbers ofMya larvae entrained may appear high, they would have translated into a negligible fraction of clams surviving to reproduction age (2-3 yrs) and, likely, many of the larvae would not have settled in flats of Hampton Harbor. Thorson (1950) and Grigg (1977) established generalized survival rates for invertebrate larvae ranging from 0.1 to 0.001 percent. Predation, starvation and other mortality factors take a tremendous toll of planktonic bivalve larvae and, in general, no more than 1 percent of fertilized eggs survive to the end of the planktonic stage (Thorson 1966; Mileikovsky 1971). Brousseau (1978b) in her three year study at West Gloucester, Massachusetts reported that less than 0.1 percent of the estimated egg production ofMya arenarla in the Jones River resulted in a successful settlement. Ayers (1956) study concerned

.with the reduction of numbers ofMya larvae in Barnstable Harbor, Massachusetts resulting from the combined effect odlushing-out and mortality estimated that only about 1% of settled larvae survive to become sexually mature.

10

An important question raised during this evaluation was whether the spat set densities in Hampton Harbor are at all related to larval abundance at the plankton stations P1 and P2.

NAI (1979) reported poor correlation between larval abundance off Hampton Beach and spat

. settlement density in Hampton Harbor. Although larval abundance in 1978 increased by a factor of nearly 20, from a five year low in 1977, spat settlement declined by a_ factor of 4 between 1977 and 1978. In sedentary bivalves, such as Mya arenaria, settlement of recently 3 metamorphosed larvae from the plankton is the only significant source of reemitment (Brousseau 1978a). However, the establishement of a relationship between density ofMya larvae offshore and spat sets in nearby tidal flats is problematic at best; Brousseau (1978a) found that the spawning cycles in which the greatest number of oocytes were released did not correlate with periods of highest recruitment in terms ofspat densities. She concluded that observations on larval densities are useful only a's indirect measures of the frequency and duration of spawning, because larval abundance and juvenile recruitment are controlled by many factors other than local spawning alone. Feller et al. (1992) stated that attempts to predict settlement or year-class strength from observations oflarvae in the plankton generally have not been successful because the transition is affected by many variables; some such as hydrodynamic processes, can be complex and have very significant role in the settlement of larvae and their successful recruitment (Butman 1987; Emerson and Grant 1991). For Mya arenaria, the planktonic larval stage persists for 2 to 4 weeks (Stickney 1964) permitting, under favorable hydrographic conditions, adult stocks from estuaries up to 25 miles away to repopulate a particular flat (Ayers 1956). It was reported by NAI(1979) that a late spring or early summer larval abundance peak may, in some years, precede the well documented late summer peak in the Hampton-Seabrook area; on the other hand, there is only one late summer spawning cycle in Hampton-Seabrook Estuary (NAI 1971; NAI 1979). This discrepancy could only be explained by the importation of drifting larvae spawned by clam populations well to the South of New Hampshire. If a pool oflarvae not spawned locally were in the plankton off Hampton Beach, then the importance oflarval entrainment would be greatly diluted and locally spawned larvae would also play a much less significant role in determining the annual spatfall in the flats of Hampton Harbor.

I1

To answer the question of whether larval abundance at plankton stations was correlated with spat set densities in Hampton Harbor, some of the existing database on larval and spat densi were re-analyzed. The data selected were the ten most recent years (1986-1995) which included five years of pre-operational data and five years of operational data. The two plankton stations selected were Pl in Hampton Harbor, and P2 in the vicinity of Seabrook f

Station intakes (Fig. 2). Since the spat surveys were conducted mostly in mid-October and a few in early November, the size of the spat was restricted to Young-of-Year (1-6 mm) and the larval data were restricte'd to the end of September each year to leave between 2 and 4 weeks as a reasonable planktonic period prior to metamorphosis and settlement; Stickney (1964) estimated a larval period that ranged from 12 days with optimal conditions, to more than a month when water temperatures were less than 10 C. The selected raw data, larval numbers per cubic meter and spat (1-6 mm) numbers per square foot, were log-transformed prior to computing annual means for both measurements. The results of regression analyses of mean annuallarval densities and mean spat set densities are summarized in Table 7 for stations P1 and P2 compared to each of the five flats sampled in Hampton Harbor each year. None of the slopes were significantly different from zero indicating no relationship between larval and spat set densities. The correlation coefficients shown in Table 7 were less than 0.10 for 7 ou comparisons, and the largest correlations were 0.269 and 0.265 for flats 4 and 5 with larval densities at P1 (none of them statistically significant). The largest correlation found involving station P2 (intakes station) was only 0.158. This lack of relationship, further illustrated in Figures 11 through 16, agrees well with other investigators conclusions (Brousseau 1978a; Feller et al.1992). Assuming that these data were representative of actual trends in larval and spat densities, the above results have important implication for the Seabrook Mya arenaria monitoring program. First, they suggest that monitoring the abundance of soft-shell clams in the pickton stations is neither useful to assess population effects oflarval entrainment losses, nor to predict recruitment in Hampton Ifarbor; second, it leaves the nearfield/farfield study (comparisons of seed clams between Hampton-Seabrook and Plum Island Sound) as the only reliable program for determining if future changes in clams abundance at Harnpton Harbor are related to the operation of Seabrook Station.

12

Finally, it should be noted that this evaluation results are supported by early expectatic as of EPA scientists regarding the impact of Seabrook Station. The following paragraphs (from YAEC 1982) are direct quotations from EPA's conclusions in its 316(a) determination of August 1978:

"My conclusion that the plant's effects on the local clam population will be insignificant would, for reasons to be discussed below, remain unchanged."

... because both the intake and the diffuser are essentially outside the tidal plume excursion region.. .. even if the estuarine water were freely dispersed throughout the water column, adverse effects on larvae would be extremely small."

"I agree with the conclusion from the experts of Region I that even if the Hampton-Seabrook clam population is entirely self-regenerating, and benefits from no outside recruitt.nent, the effects of the plant's operation on the population would be negligible."

"Although the plant may kill considerable numbers of planktonic eggs and larvae, the total volume of water that will be subject to the plant's adverse effects is minuscule compared to the 54 square miles of coastal water adjacent to the plant, in which this plankton may be expected to develop" Proposed Monitoring Program after 1996 l

The focus of the proposed soft-shell clam program would be on monitoring this important economic resource rather than on the detection of Seabrook Station impacts, since none is expected to occur. Accordingly, the program objectives would be:

_. 1. to ensure the continuity of the valuable database on Mya arenaria and its predators already accumulated, and;

2. to make available to NH State regulators and to NAESCO the information needed to explain to the public posible reasons of major changes in clam abundance at Hampton Harbor, which may occur in the future. 1 13

t

.The specifics of each of three program components would be as follows:

Hampton Harbor Random Surveys. No change in effort from current program, but attempt 1

, to redesign sampling to improve precision and accuracy of annual estimates by size classes; take advantage of work done in this area by Cuff and Coleman (1979) and possibly by others.

Sampling would be done once a year, in the fall, as at present; collections would be at Flats 1, 2,3,4, and 5 for spat and juveniles and at Flats 1,2, and 4 for legal size clams (Fig.1). Data collected would be clam abundance per square foot, starting at I mm of size.

Nearfield/Farfield study. No changes proposed on either effort or methodology. Ten stations would be sampled at each of the locations, Hampton Harbor Flats 2 and 4 and Plum i

i island Sound (Fig.1), once a year in the fall; at each station 3 replicates would be taken so that a total of 60 samples per year are taken annually. This study is a good example of an eflicient sampling design that conforms with the requirements of the BACI design (Green 1979) and, thus, can be used to test statistically whether any future observed changes in abundance of seed clams at Flats 2 and 4 in Hampton Harbor, occur similarly at the control site in Plum Island Sound.

Predator Surveys. It is proposed to replace clam digger counts with recreational license data (currently used by NH Fish and Game Dept. to estimate clamming effort); or consider sampling for digger trips only Flats 1,2, and 4, rather than all five flats as in the past. The rationale was consistency with legal size clam densities only estimated at Flats 1,2, and 4 since 1985, and the l historically low frequency of digger's trips to Flats 3 and 5 (Table 3). If the use oflicenses l'

l were not acceptable, diggers counts would be conducted weekly, as in the past, except during I the summer (June through August); the total number of counts per year would be 76.

i Regarding the green crab program, it is proposed to keep the present trapping program in place without any changes in either effort or methodology. Therefore the proposed program

, would continue to set traps at stations 1-4 within Flat 2 in Hampton Harbor (Fig.1), twice 14

monthly except February and March when crab activity has been historically low (NAI 1 the total number of traps set will continue to be 160, with two traps per trip.

. Conclusions ARer five years of Seabrook Station operation there has not been a single instance of an l

statistically significant change being related to the plant's entrainment of son-shell clam larvae or to the plant's discharge of cooling water. Large variability of clam densities in all sizes, from early spat, throughjuvenile and legal size clams, has been documented over more than 20 years of studies and have occurred both during the preoperational and operational period and juvenile clam densities are greatly influenced by predation and by many other possibl factors such as currents, sedimentary changes dtie to storms, etc. and legal size clams densities are mostly driven by recreational clamming effort and, perhaps neoplasia. A finding of this i evaluation was that larval densities in the plankton at either station P2 (intakes) or station P 1 (Hampton Harbor) do not correlate with densities of subsequent successful spat set in the flats i of Hampton Harbor. This finding led us to conclude that the collection of son-sell clam larvae in the plankton or in entrainment samples now serves no purpose and should be discontinued.

The overall conclusion of this evaluation is that over 25 years of monitoring studies have not l found a reasonable mechanism whereby Seabrook Station operation could arTect the reemitment and growth of soR-shell clams in Hampton Harbor. Accordingly , the proposed Mya arenaria program shiRs focus from " impact assessment" to " annual abundance surveys" of this all important marine resource for New Hampshire, and leaves unchanged the population surveys, the trapping of green crabs, and the surveys of seed clams at Hampton and Plum Island Sound Harbors. A major consideration for the continuation of these three programs was the importance of maintaining the continuity of the extensive database ofMya arenaria built by these studies since 1971.

15

References Cited Abbott, R.T.1954. American seashells. Van Nostrand, New York, NY. 541 p.

Ayer, W.C.1968. Son-shell clam population study in Hampton-Seabrook Harbor, New Hampshire. New Hampshire Fish and Game Dept. 39 p.

Ayers, J.C.1956. Population dynamics of the marine clam Mya arenaria. Limnol. Oceanogr.

1:26-34.

Belding, D.L.1930. The soft-shelled clam fishery of Massachusetts. Commonw. Mass. Dep.

Conserv., Div. Fish and Game, Mar. Fish. Series 1,65 p.

Brousseau, D.J.1978a. Spawning cycle, fecundity, and recruitment in a population of soft-shell clam, Mya arenaria, from Cape Ann, Massachusetts. Fishery Bulletin U.S.

76:155-166.

Brousseau, D.J.1978b. Population dynamics of the soft-shell clam Mya arenaria. Mar. Biol.

50:63-71.

Brousseau, D.J.1987. A comparative study of the reproductive cycle of the soft-shell clam, Mya arenaria in Long Isfand Sound. Journal of Shellfish Research 6:7-15.

Butman, C.A.1987. Larval settlement of soft-sediment invertebrates: the spatial scales of pattern explained by active habitat selection and the emerging role of hydrodynamic processes. Oceanogr. mar. Biol. A. Rev. 25:113-165.

i Cuff, W. and N. Coleman.1979. Optimal survey design: lessons from a stratified random sample of macrobenthos. J. Fish. Res. Board Can. 36:351-361. l Dow, R.1972. Fluctuations in Gulf of Maine sea temperature and specific molluscan abundance. J. Cons. Int. Explor. Mer 34:532-534.

j Emerson, C.W.1990. The influence of sediment disturbance and water flow on the growth of the soft-shell clam, Mya arenaria (L). Can. J. Fish. Aquat. Sci. 47:1655-1663.

Emerson, C.W. and J. Grant.1991. The control of soft-shell clam (Mya arenaria) recruitment on intertidal sandflats by bedload sediment transport. Limnol. Oceanogr. 36:1288-1300.

Feller, R.J., S.E. Stancyk, B.C. Coull, and D.G. Edwards.1992. Recruitment of polychaetes and bivalves: long-term assessment of predictability in a soft-bottom habitat. Mar. Ecol.

Prog. Ser. 87:227-238.

16

l Green, R.H.1979. Sampling design and statistical methods for environmental biologists.

Wiley-Interscience, John Wiley & Sons., New York, NY,257 p.

Grigg, R.W.1977. Population dynamics of two gorponian corals. Ecology 58:278-290.

Glude, J.B.1954. Survival of soft-shelled clams, Mya arenaria, buried at vanous depths.

Department of Sea and Shore Fisheries, Augusta, Maine. Bulletin 22: 25p.

Hughes, R.N.1970. Population dynamics of the bivalve Scrobicrdariaplana (Da Costa) on an intertidal mud flat in Nonh Wales. J. Anim. Ecol. 39:333-356. i t

Larsen, P.F. and L.F. Doggett.1991. The macroinvertebrate fauna associated with the mud l flats of the Gulf of Maine. Journal of Coastal Research 7:365-375.

L Lindsay, J.A. and N.B. Savage (1978). Northern New England's threatened soft-shell clam populations. Environmental Management 2:443-452.

McAlice, B.J.1973. Plankton. Pages 31-77 in Fourth Annual Report, Environmental Studies.

Maine Yankee Atomic Power Co., Augusta, Maine. l Mileikorsky, S.A.1971. Types oflarval development in marine bottom invertebrates, their distribution and ecological significance: a re-evaluation. Mar. Biol. 10:193-213.

Moller, P. and R. Rosenberg.1983. Recruitment, abundance and production ofMya arenaria and Cardium edule in marine shallow waters, western Sweden. Ophelia 22:33-55.

l Munch-Petersen, S.1973. An investigation of a population of the soft-shell clam (Mya arenaria L.) in a Danish estuary. Medd. Dan. Fisk. Havunders., New Ser. 7:47-73. l NAI(1979). Sotft-shell clam, Mya arenaria, study. Normandeau Associates,Inc., Bedford, New Hamshire. Technical Repon X-3, 85 p. l NAI (1990). Seabrook environmental studies,1989. A characterization of baseline conditions in the Hampton-Seabrook area, 1975-1989. A preoperational study for Seabrook Station. {

l t

Normandeau Associates, Inc., Bedford, New Hampshire. Technical Report XXI-II,351 p.

NAI (1996). Seabrook Station 1995 environmental studies in the Hampton-Seabrook area. A characterization ofenvironmental conditions during the operation of Seabrook Station.

Normandeau Associates, Inc., Bedford, New Hampshire.

I l Normandeau, D.A., J.D.. Davies, A.C. Mathieson, J.I. Nelson, Jr., and P.H. Mahoney.1971.

Mya arenaria soft-shell clam density and distribution, and reproduction. Pages 41-65 in '

Seabrook Ecological Study: Phase I, 1969-1970, Hampton-Seabrook Estuary, New Hampshire. Normandeau Associates, Inc., Manchester, New Hampshire,313 p.

17 l

Padmanabhan, M. and G.E. Hecker.1991. Comparative evaluation of hydraulic model and field thermal plume data, Seabrook Nuclear Power Station. Alden Research Laborato Inc., Holden, Massachusetts. Report 60-91/M620F,12 p.

Pfitzenmeyer, H.T.1962. Periods of spawning and setting of the soft-shelled clam, Mya arenaria at Solomons, Maryland. Chesapeake Science 3:114-120.

' Robinson, S.M.C. and T.W. Rowell.1990. A re-examination of the incidental fishing m of the traditional clam hack on the soft-shell, Mya arenaria Linneaus,1758. Journal of Shellfish R.esearch 9:283-289.

Ropes, J.W. and A.P. Stickney.1965. The reproductive cycle ofMya arenaria in New England. Biol. Bull. mar. biol. Lab., Woods Hole, 128:315-327.

Ropes, J.W.1969. The feeding habits of the green crab, Carcinus maenas (L.). U.S. Fish.

Wildl. Serv. Fish. Bull. 67:183-203.

SAS.1985. SAS User's Guide: Statistics, Version 5. ShS Institute Inc.,'Cary, N.C. 956 p.

Stickney, A.P.1964a. Salinity, temperature, and food requirements of soft-shell clam larvae in laboratory culture. Ecology 45:283-291.

Stickney, A.P.1964b. Feeding and growth ofjuvenile soft-shell clams,Mya arenaria. U.S.

Fish . Wildl. Serv. Fish. Bull. 63:635-642.

Strathmann, R.1974. The spread of sibling larvae of sedentary marine invertebrates.

. American Naturalist 108:29-44.

Sullivan, A.L. and P.J. Sawyer.1966. Economic impact of the summer saltwater sport fisher in the seacoast region, New Hampshire and Southern Maine 1966. Res. Inventory Repo of the Seacoast Region. Res. Dev. Center, University of New Hampshire, Durhan, New Hampshire.

Teyssandier, R.G., W.W. Durgin, and G.E. Hecker.1974. Hydrothermal studies of diffuser discharge in the coastal environment: Seabrook Station. Alden Research Laboratory, Inc.,

Holden, Massachusetts. Report 86-74/M252F, 47 p.

Thorson, G.1950. Reproduction and larval ecology of marine bottom invertebrates. Biol.

Rev. (Camb.) 25:1-45.

Thorson, G.1966. Some factors influencing the recruitment and establishement of marine benthic communities. Neth. J. Sea Research 3:267-293.

Turk, T.R. and M.J. Risk.1981. Effect of sedimentation on infaunal invertebrate populations of Cobequid Bay, Bay of Fundy. Can. J. Fish. Aquat. Sci. 38:642-648.

18

.t j Underwood, A.J.1994. On beyond BACI: sampling designs that might reliably detect environmental disturbances. Ecological Applications 4:3-15.

Vance, R.R.1973a. On reproductive strategies in marine benthic invertebrates. American Naturalist 107:339-352. '

Vance, R.R.1973b. More on reproductive strategies in marine benthic invertebrates.

l American Naturalist 107:353-361. _

i Warwick, R.M. and R. Price.1975. Macrofauna production in a estuarine mud-flat. J. Mar.

Biol. Assoc. U.K. 55:1-18.

Welch, W.R.1969. Changes in abundance of the green crab, Carcimu maenas (L.) in relation  !

to recent temperature changes. U.S. Fish Wild. Serv. Fish. Bull. 67:337-345.

Welch, W.R. and L.V. Churchill.1983. Status of the green crab in Maine. Reference Research Doc. 83/21. Maine Dept. of Marine Resources, Augusta, Maine.

Whittatch, R. B.1982. The ecology of New England tidal flats: A community profile. U.S.

Fish and Wildlife Service, Biological Services Program, Washington, D.C. FWS/OBS-81/01,125 p.

YAEC.1982. Effects of thermal discharge from ocean-sited power plants. Yankee Atomic Electric Company, Nuclear Services Division, Framingham, Massachusetts.

s 19

l Table 1. Distribution (percent of total standing crop) of harvestable clams by flat at Hampton I Harbor,1979 through 1989. Seabrook Baseline Report,1989 (from NAI 1990).  !

)

YEAR FLAT 1 2 3 4 5 i

1979 33.3 6.2 2.2 55.7 2.5 ~

l 1980 45.1 10.5 1.0 39.5 3.9 l 1981 53.0 7.3 1.5 34.4 3.7 i

1982 52.2 7.0 1.0 38.4 1.3 1983 62.9 25.6 0.5 10.5 0.5 1984 72.0 .13.6 1.9 11.5 0.9  !

1985 60.2 14i6 NS 25.1 NS

'1986 63.0 21.9 NS 15.1 NS 1987 40.0 15.9 NS 44.2 NS 1988 40.9 9.0 NS 50.1 NS ,

i 1989 - 30.1 3.1 NS 66.8 NS l NS = not sampled 19

- . ~ . . . . ..

i Table 2. Geometric mean tiensity (number oflarvae per m'; number orjuveniles/ adults per ft') and the coefTicient of variation (CV) ofMya arenaria collected during preoperational and operational years and in 1995. Seabrook Operational Reimrt (from NAl 1996)._

PREOPER ATIONAlf 1995 OPER ATIONAl?

I.IFESTAGE AREA hlEAN' CV- hlEAN' hlEAN' CV 1.arvae P2 5.5 17 7 2.3 3.3 10.8 PS 5.0 12.0 2.4 3.0 26.0 P7 5.7 13.0 1.6 3.4 28.7 .

1-5 mm 1111-1 3.5 48.5 0.8 3.1 53.9 (young-of- 1111-2 8.6 58.8 6.1 5.0 37.1 the-year) 11114 10.5 43.8 0.4 3.4 62.7 All 6.4 49.0 1.3 3.6 46.9 w 6-25 mm 1111-1 1.7 127.8 0.3 1.2 96.3 (spal) IIII-2 0.7 153.5 0.1 0.4 86.8 11II-4 3'4 . 89.7 0.4 I.6 70.1 All 1.8 108.5- 0.2 1.0 82.6 26-50 mm lill-1 1.6 108.6 2.8 0.7 84.3 (juveniles) _ lill-2 0.4 115.6 1.3 0.3 120.4 till-4 1.7 100.4 2.1 1.I, 43.8 A11 1.2 97.4 . 2.0 ' O.6 75.3

> 50 mm Ill1-1 0.6 76.6 0.8 0.7 15.7 (adulls) IIII-2 0.4  %.5 1.0 0.3 90.9 IIII-4 0.5 78.2 -1.8 1,9 10.4 All 0.5 76.5 1.0 0.7 24.0 1-12 mm llampton Ilarbor 5.7 70.8 6.2 6.I 72.9 (seed clams) Plum is. Sound 17.1 68.5 3.0 7.5 83.1

'lasvac PRIiOP = 1988.1959; OP = 199195. liar.q*m liasimt 0110 PHliOP = 19H.1989, ola . 1990 1995, Ilampiam Ilealmt-Plum Is. PRIiOP = 19871989; OP = 19901995 c

'I'RliOP aml OP means = mean a f aamual means.1995 mean = mean s4 alic numlica ut sampics.

_ . _ . . . . _ _ _ _ _ __ . _ _ _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ . . ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _____ ___ . . _ , _ - . . _ . _ - ._ , _ _ _- m. _ _ ___ .m

1-Table 3. Estimated distribution (percent of total) of clarn diggers by flat at Hampton Harbor, 3 spring 1980 through fall 1990. Seabrook Operational Report,1990 (from NAI 1991).

ESTIMATED

• ESTIMATED TOTAL NUMBER OF FLAT DIGGER BUSHELS SEASON TRIPS HARVESTED

, 1 2 3 4 5 Springc1980 12.5 17.9 1.7 52.5 15.4 3,860

~

1,200 j Fali d1980 11.3 18.4 3.3 55.I 11.8 2,700* 840 Spring 1981 9.7 15.6 0.8 65.9 7.9 12,500 3,900 Fall 1981 13.9 12.9 0.2 63.8 9.1 7,060 2,200 Spring 1982 12.6 13.0 0.8 67.1 6.4 10,800 3,400 I i Fall 1982 26.6 8.5 0.7 60.7 3.5 9,300 2,900 Spring 1983 30.7 7.1' 1.3 58.6 2.2 7,700 2,400 Fall 1983 29.4 14.7 0.5 54.7 0.7 6,690 2,100 l Spring 1984 22.1 26.4 0.6 49.9 1.0 6,200 1,950 Fall 1984 26.9 28.9 0.3 43.2 0.8 5,850 1,830 Spring 1985 51.6 11.3 0.4 36.1 0.8 6,940- 2,169 Fall 1985 63.1 5.0 0.4 31.5 0.0 2,873 898

! Spring 1986 59.3 6.4 0.3 33.4 0.6 6,210' 1,941 Fall 1986 58.1 6.4 0.4 34.7 0.4 4,713 1,473 I Spring 1987 39.4 8.1 1.5 49.0 2.0 1,763 551 J

! Fall'1987 38.8 6.9 0.8 49.8 3.8 1,541 482

-Spring 1988 13.2 14.3 3.7 66.4 2.4 574 179 Fall 1988 22.8 10.9 4.2 57.4 4.7 -1,386 433 Spring 1989 22.1 10.6 0.0 65.3 2.0 357 112 l Fall f1989 -- -- -- -- -- -- --

l Spring 8 1990 -- -- -- -- -- -- --

1 Fa118 1990 -- -- -- -- -- -- --

" Based primarily on Friday head counts at time of low slack water; most Saturday counts are assumed from observed Fri: Sat ratio (n=14 pairs) of l

' b2.24 i SD O.' 96; seasonal totals have approximate error of i 187.

Assumes each clammer takes 10 quarts per trip; 1 bushel = 32 quarts or l

,3.2 clammer trips j

d Includes the period 1 January through weekend before Memorial Day 1

l Includes the weekend after Labor Day through 31 December

! ,f Based on average Spring: Fall ratio for 1981 and 1982 (0.68 i SD 0.02)

Data collected January - March only. Flats closed April - December.

l 8 Flats closed January - December 21 I

?

Table 4. Percent of total density for the twelve selected bivalve taxa taken at stations P2, PS, and P7 from 1988 through 1995.

Taxa Percent

.Mytilus edulis 56.3 Anomia squamula 19.5 Hiatella sp. 12.5

'Modiolus modiolus 5.2 Bivalvia 2.2 Solenidae 2.0 Spisula solidissima 0.8 Macoma balthica 0.6 Mya truncata 0.6 Mya arenaria 0.4 Placopecten magellanicus <0.1 Teredo navalis <0.1 22

e k

Table 5. Summary of standing crop estimates of adult

• Mya arenaria in Hampton Harbor,1967 through 1990. Seabrook Operational Report,1990 (from NAI 1991).

ESTIMATED NUMBER TOTAL ESTIMATED OF BUSHELS NUMBER OF DATE PER ACRE OF BUSKELS b  :

November 1967 152 23,400 b July 1969 103 15,840 -

November 1971 94 13,020 i November 1972 58 8,920 November 1973 41 6,310 November 1974 56 8,690 November 1975 29 4,945 November 1976 11 1,350 November 1977 6 1,060 ,

Notcaber 1978 6 940 )

November 1979 9 1,400  ;

October 1980 54 8,890 I October 1981 75 12,400 I October 1982 55 9,200 1 October 1983 78 13,020 October 1984 54 8,821 November 1985 39 4,615 October 1986 23 2,793 October 1987 8 976 October 1988 10 1,137 October 1989 19 2,295 October 1990 57 6,752 aShell length >50 mm .

bFrom Ayer (1968) l 23

l l

Table 6. Estimated numbers (in billions) of bivalve larvae entrained at Seabrook Station from 1990 through 1

June-Oct Apr-Aug Apr-June Apr-Oct Apr-Oct Taxa 1990 1991 1992* 1993' 1995 Total  % i A$tilus edulis 1991.3 1687.4 121.9 10050.7 13213.0 29082.3 51.4  !

.4nomia squamula 1691.4 250 8 6.8 3922.7 8905.9 14777.6 26.1 Hiatella sp. 876.6 451.2 189.8 2405.5

)

2598.2 6521.3 11.5 3/odiolusmodiolus 909.7 160.1 0.2 1283.9 546.4 - 2900.3 5.1 s Bivalvia 155.2 36.9 14.5 334.3 '

795.1 1336.0 2.4 Solenidae 61.1 12.7' 75.6 102.5 1092.3 1331.5 2.4 A(va truncata 249.0 6.5 1.1 2.1 27.6 286.3 0.5 Spinla solidissima 69.0 4.3 0.0 48.5 112.5 234.3 0.4 A?n arenaria 8.1 0.6 0.2 22.5 4.3 35.7 3

0.1 A/acoma balthica 26.5 1.1 0.0 0.2 2.0 29.8 <0.1 Placopecten mogellanicus 0.6 0.7 0.1 16.9 6.2 24.5 <0.1 Teredo navalis <0. I 15.9 0.0 0.0 4.8 20.7 <0.1 Annualtotal 8038.5 2628.2 410.2 18189.8 27308.3 i

' Equipment failure in June; no samples taken thereafter.

• No entrauunent samples taken in 1994 due to plant shutdown and sampling equipment tralfunctions. j

' Not given in NAl (1992b); esumated from data given in NAl (1992a).

24

Table 7. Summary of regression analyses to test whether there was a relationship between the abundance ofMyu larvae at Stations P1 (llampton Harbor) or P2 (Intakes) and the density of spat set in Flats nos.1,2,3,4, and 5 during the last 10 years (1986-1995).

Station Flat # Slope estimate for the regression of t-test of the Null Ilypothesis Correlation Larval density vs. spat (1-6mm) set that the slope is equal to zero' coefficient P1 1 0.023868 t = 0.044 P = 0.9656 0.014 P2 1 -0.051717 t = 0.073 P = 0.9436 0.026 P1 2 0.212065 t = 0.388 P = 0.7081 0.136 P2 2 -0.092056 1 = 0.I27 P = 0.9024 0.045 P1 3 0.117155 t = 0.202 P = 0.8450 0.071 M P2 3 -0.344645 t = 0.455 P = 0.6614 0.158 PI 4 0.524198 t = 0.792 P = 0.4511 0.269 P2 4 0.193620 t = 0.214 P = 0.8358 0.075 P1 5 0.486670 t = 0.778 P = 0.4592 0.265 P2 5 -0.058680 t = 0.069 P = 0.9471 0.025 P1 All 5 0.372277 t = 0.540 P = 0.6036 O. I 87 P2 All 5 -0.125392 t = 0.136 P = 0.8955 0.048 a: All test results (P>0.05) showed no significant relationship between M3a larvae and spat set densities (all regression analyses were conducted on logw transformed density data of both larvae and spat).

%m x D . tv. ~-

N .

% ~

/ ,y nunas:vvia u  !  ;

\g #.%; O, ,i 4

mn u n u= W q

[, '  !

1 0 'n HAMPTON

.( )

~

l* BEACH

.: . .C y ;y sp *w g:

"f. Q >'

l d.,a #4

, ,*, ' : hit. -4n , -

J 4 w M.,;.,,.. ^. / _ , _ Agg T 'WStatica '

• yw?* Wehm "E.F r N' NM ' N ~

L ; ,' q;s.d .P..$.'.l '

• 2;'.}>5%:.? ~,y  ; u:g; . U :u .

, ';.'; } .txMWi; *~ ~ -' ,' "*

- s*% ..,.P

+ '4 '*ds1% ._

4,,. M6fEh y

~I.yi.'.

T'I-< - **

, Idd-- ..h# 4 A

f'Q..

, . * .Ss.;d,:

.,Wre.l;M.

4 . . 4.

g:'. .

,

?% D:\'.T~

C.~E/:. dh.e%.?" % -

• W ;Y  :

Al*T **

.L . -

. ."g ; . . - .

~

. . ~ye.

5 MHZ, CREET ' O2 , %" *v ' * *. .. Stagoog nt

. & *?, . 7.::2"7*1 kL

p;*;i

• vn" + '[ .

v..

A -

. % *;;. c

.~v sc

,,;f fM

.s.,

e.g yg n v-"?.:" ;. -. . . . . ,

BEACH

+ j i:.m.i

.f o, A .t~.

N <g *RW?

y.~ "a j

.+ @. m.

i W:7- 7s.it,. ,J,,.',

,?, wr> mg)7*

M ~' ."

y,1 N 0

..m 5 } ?:.?; % ;;b W ~ g . . ;,ra b, .:n M

.rWtiiL%Et* < , ^Q' ficV " ;';

~.dztp:mell >; ; ngy3;ggy y;ggg ISLES OF *g* . . , .

m:

SHOMS .a E ~ E:"'

O ".* S ? S

~

HAMPTON SEASROOK Pi'$5A? -

. ESTUARY -

• n$;; 2e- > >g;:..

~

.A nn j 2 *p + , > , ,Z . . .-

. , . ,, p l s ~.~p  ;+.ap u$

D h'1c;.

n ~..w .

,. ;w.

. s . .e

, > : Wf t d.w 1 Md.: a 7 e g- l

' "?'

MERRIMACE RlVER

' N i

1 s s.- .

i,

PLUM !SLAND SOUND 0 5 to (IPSWICH, MA)

O NAUTIC MILES LEGEND

$ = Clam Flats Q = Green Crab Traps

, k] = Spat Sampling Sites Figure 1. Hampton-Seabrook estuary and Plum Island Sound soft-shell clam Ma arenaria) and green crab (Carcinus moenar) sampling areas. Seabmok Operational Report,1994 (from NAI 1995).

26

1 i

N RYE LEDGE 2

, / -

, s. ........

LITTLE \ .O BOARS {

HEAD ;

'D ,

, s 0 .5 1 Nautical Mile '.

i 0 1 h Kilometers $ FARFIE!.D gggy SCALE  ;

CONTCUR DEPTH

• e

/:

IN METERS b

GREAT BOARS -

. HEAD s ,

l h

}GQ BEACHHAMPTON ~\

t BROWNS \ *'

u RIVER  % .

~

) Intake ***

10uTEN=gi

SEABROOK N . ' '? [ A A

'io STATION '-

j,fINfR..,M..:.' ... Disch'arge HAMPTON . .

SEABROOK SUNK i. * .':

HARBOR ROCKS i

=  %, SEABROOK '

+

4

\  %

BEACH  ; j:3.*s -/

\ s / '

~

N/

• t ,..

' i a

! .i \

e SALISBURY BEACH .

\

ll ..

l 1,

I i

LEGEND

= Bivalve Larvae Stations l Pl.P2,PS,P7 Figure 2. Bivalve lan ae (including Mya arenaria) sampling stations. Seabrook Operational Report,1994 (from

. NAI 1995). ,

i

. 27

i 2.8 i p, ,

,.,  ; _ . . . . . - ~, 2 i

,----r..

t 2.2  ; ..

I i

.' 2.0 g\ **  :

<r.s l l ,t

t8 i

' ^

l\

l llNs

l s t'  ! . \." l\ \ -

/

x!y llx\is.ny /.. -n to /- ei> l A ,

3 f

t /.*

c..

A, .A li 4 r.s p '. g >

j E. 0.8 f *

.- 'll K/ \ if.i l*

1*.

f 5

• l . \

O.4 g  %[Il 1

e l

i s

\

02 1 1

, 0.0 Precoeradonal l Operadord  :

j- 1 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 l w>a  ;

i 2

Figure 3. Annual mean logio(x+1) density (number per ft ) of clams 1-5 mm,1974. Seabrook Operational Report,1995 (from NAI 1996).

i

\

I Flat 1 z,

l .. .. . . m 2

, ~ ~ - - rm 4

l" '

y 20  % w .ar 1

j operanona

• 1J l I

to

~~ j 1' '/,g 3 \ l u i ,\, l j

^

to -z - \t ,

l 0.8

\ ,

.a .

l. .

s s ,. ,i .

OJ  : 1

\

/s , \

p* l

\l \ '

/

0.4

[ ~

, \~g

\ /

[/ l /

/ ,.,

02 g

. _j

/ g 'N/ .. 1 / '

,_,. L. w ;f *

• 1 t

74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 vsAn -

2 Figure 4. Annual mean logio(x+1) density (number per ft ) of clams 6-25 mm,1974. Seabrook Operational Report,1995 (from NAI 1996).

28

d 2.6 8

2,4 Fat 1 22 l, ..... .m2

- - - - F.c 4 i .

2.o pr.ac, anon., I 1

f 1.s l ep,,,an,, j l

g s..

g

. 12 i.4

(

ss s

l l

l l

g 10 / \,  !

go.a / \

l o.e ,f f s i ,

/

c.4 s f ..... .

1 s i. . .A.s. s

. / >,~ ,

o.2 .s i.- '.

' b.s.

e" i. -

.s. n . . . .. .. . . . . ..... - ,i . .N/ f

. i * . -

o.o , ...

74 75 76 77 78 79 80 81 82 83 84 85 a6 87 88 89 9o P1 92 93 94 95 m

2 Figure 5. Annual mean logw(x+1) density (number per ft ) of clams 26-50 mm,1974. Seabrook Operational Report,1995 (from NAI 1996).

10 i r a.9 1 . . .. . . pq.t at 3 2

I l ~ ~-~ ret 4 i

g o.s W e

l Cw.r.c,. r.;

N G7 l L

,N' . N o.4 1' % .

N l/

I b I u j

i f V / 1 a 02 h.1 ll.

1: .

i\ - '. .

- l l l

o.2 1 g

ji .

i i

" a, \

ji t .: N.s

% j ,/

• l i .

..........t**............

74 7s 7s 77 7s 79 so 81 82 as a4 as as a7 as a9 ao 91 92 93 94 as a

2 Figure 6. Annual mean logm(x+1) density (number per ft ) of clams > 50 mm,1974. Seabrook Operational Report,1995 (from NAI 1996).

29

Preoperational 2.5 -- Opemued

____ __ 1995 zo ,

e I

I  ; ,

I 5'

. h1.s' N _ ,l . , _

w - i g <-  ;

e 1.o

~~l -

i o.5

\ l o.o M M M M MAY JUN JUL MONTH M SEP OCT NCV oEC Figure 7. Mean logio(x+1) monthly catch per unit effort and 95% confidence intenals ofgreen crabs (Carcinus maenas) collected during preoperational years (1983-89), operational years (1991-95), and 1995. Seabrook Operational Report,1995 (from NAI 1996).

Minimum Water Temperatum (* C) .

Onen Crab CPUE 1m 2 i

's ,, 3-f 120 '

's, h l, ls, sl l w

l"

, ~,

\v

,l 'ss o_

l y

E ao / \ 3

\ S h* \, m ao \/

g o

y M N m m a a a u a s7 mammamum vsAn Figure 8. Mean fall (October-December) catch per unit effort of green crabs in Hampton-Seabrook Habor and its relationship to minimum winter water temperature from 1978-95. Seabrook Operational Report,1995 (from NAI 1996).

30

_,,__m_ m,_.m~ - -- -~~ " - -

5 6

"i l --

5.01 OsmarumanaJ ge6 en LO 3J L

L **

l\\

l lu" I f \ p'I.\

R \\ , ,

a

I j i ', i I i i

- 4

\

1.h tg .i ' i i i 1,. . 1 1. ! d ' i De -

\t:

.-/..i.

0.0 .....- . .

\ ,-

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 Seo Ck.

Figure 9. Weekly mean and 95% confidence interval oflogw(x+1) density (number per m') of A$a arenaria larvae at Station P2, during the preoperational (1978-89) and operational (1991-95) periods and in 1995. Seabrook Operational Report,1995 (from NAI 1996).

31

INTAKE j

[ 'q, .

MODEL C ATA

~

OUTER St:NK ' , . - .

~ . s ~ % (N.-

4 ROCKS 1) N I e -'~~ FIELD DAT. '\

C ,/

i .

L . ,,- . -f

, , b - - --- , -- . , , N s f I%/ .2' 2 .'

N

!_. . .y

~

, ( J 3 . _ _ ,

T-3 9 B19 ' ,

2** 's ' o m n.a ..a

].

\.

- - .1- - -

.',, 5CALE IN FEET j  %

! INTAKE LOW SLACK ,

, / MODEL DATA

• /

/

l ,I ,'

,,,,,.- g OUTER SUNK / ,2 '/

ROCKS

' ,2 '

/ I '

. .S~~ ~- -

O ' 2j o

• ,/[ , , / FIELD DATA 1

s' ,,J /

2 f s',,,,,

\/ * ,/ ,,**)

, / $3 .-

3 t ., ,2 3 , , _,. w .-f~. 2 - ~-~ - - j G B19,7

\.h*

% N

{

% a- 'I'Y ~ ~ l f

o o i.m  :.a l SCALE IN FEET Figure 10. Locations ofselected Seabrook Station thermal plume isotherms (1*F,2 F, and 3'F) under various tidal conditions in relation to the nearfield surface panel station (B 19), based on hydrothermal modeling and field verification studies (from Padmanabhan and Hecker 1991).

32

. - - . . . . . _ . . _- . . - .. _=. _ - _ . - . . . . . _ . . _ . - _ . _ - . . _ ~ . . . . . . _ -

4 ii -

4 INTAKE FLOOD

\h i

'. *

• l 2

t j I i I 4

j

.MCCEL DATA OUTER SUNK - #

f 7 ROCKS

• i s -

/ /

j p ,1 y' FELD DATA i

. .. .s 3

] f I

i fk'V 3

/}/

b 29 B19

%3 a

,/-f 1 w 4 'Q.#/ o m a.m  :.m SCA! " 'N FEET i

d INTAKE

! HIGH' SLACK i i

• i

/ .MODEL DATA

! I OUTER SUNK ROCKS ) '

~

l

, I %,

C ,.- '

N

/

a

_m ' '\

1,I '%. , , _ , . . s y '$

i C3 i o

_3 ' 9 sB19 /

3

\,% '/ / ,a i.=  :.a

.\ 2*

s,p SCALE FEET 2\ ,/ . _ - ~ ,

s FIELD DATA

\. i Figure 10. (continued) 33

I 1.4 E

E E 1.2 -

.E o

i. ' # 1 8 1-8

' F 0.s - e E ,

? ~

E 0.6-i a v>.

e E 0.4 - ,,'

• E

" C

< e 3 0.2 -

• a E '

i 0 . , , , , , ,

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Mean of Log Larval Density at Station P2 1.4 i.

G w

1-E 1.2 -

.E o N

E 1-

. E 0.8 -

• E ,

9 0 0.6 -

E e

+

v%

j E 0.4 - o

• 8 e

i ' 1 4 3 0.2 - '

E a l O , , ,

O.5 0.6 0.7 0.8 0.9 1.1 p-1 1.2 4

Mean of Log Larval Density at Station P1 Figure 11. Relationship between Mya arenaria larval abundance at stations P1 and P2 and spat set in Flat #1. Data plotted are annual means (1986-95) of logio transformed densities, i

. 34

.n. - . . -

3

-W 4

1.4 N

g i g 6 1

E 1.2 - .

! 5 ,  !

y e. e p 1-e 4 o e E 0.8 - o .

1 E l i

9 , _e  ;

, Em 0.6-

• j

/ E 4 O

l. E 0.4 - ' l s

y

, C v c '

j g 0.2 -  :

?

a 0 , , . , , , ,

0.2 0.3 0.4 1 0.5 . 0.6 0.7 0.8 0.9 1  :

Mean of Log Larval Density at Station P2 l i.

i. 1.4 N

=. l E .

C 1.2 - ,

i 5

) k e

• i g 1-8 e E 0.8 -

~

E

? , e Em 0.6- '

t g

a i E 0.4 -

• i 2

4 * ,

2 g 0.2 - i L

1 a 1

!- 0 *

• i s s , ,

0.5 0.6 0.7 0.8 0.9 1.1 1 1.2  !

Mean of Log Larval Density at Station P1  !

4 Figure 12 Relationship between Mya arenaria larval abundance at stations P1 and P2 and spat set in Flat #2. Data plotted are annual means (1986-95) of logio transformed densities.

b

35 a

5 d

)  :

J  ?

r i

1.4 i n

E E 1.2 - , e '

1 .5

$c 1- -

o

? O

_ e i E

E 0'8 -

• 1 e

? e

• a 4

m. 0.6 - e O.

u) e W 0.4 -

E c

i ,

1

( '

y 0.2 -

e a t 3

0 . . . .

5 4

0.2 0.3 0.4 0.5 - 0.6 0.7 0.'8 0.9 1 ,

i Mean of Log Larval Density at Station P2 e n 1.4 _

=

.5u. e i

1.2 - , *

.E i c 1-o O e -

f 0.8- .  !

e e i e e r 0.6- e i

2. e

^i v>  ;

E . 0.4 -

8 i e  :

30.2-o e

O a

0 . . . . .

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 Mean of Log Larval Density at Station P1 Figure 13. Relationship between Mya arenaria larval abundance at stations P1 and P2 and spat set in Flat #3. Data plotted are annual means (1986-95) oflogio transformed densities.

l 36 i

l

1.4 E

w E 1.2 - ,

g . .

'G 1 E

o

- e E 0.8 - e E

9 E 0.6- -'

E m .

Q 0.4 - ,

E 3 0.2 -

E O

0.2 O!3 O!4 0.5 0.6 0.7 0!8 0.9 1 Mean of Log Larval Density at Station P2 -

1.4

==

E E 1.2 - ,

.E e e

?

E 1-o E 0.8 -

• E 9

E 0.6- ,

E w e 3 0.4 - #

2

• i 3 0.2 - ,

?

a 0

0.5 0.6 0l7 0.8 0.9 1 1.1 1.2 Mean of Log Larval Density at Station P1 Figure 14. Relationship between Mya arenaria larval abundance at stations P1 and P2 and spat set in Flat #4. Data plotted are annual means (1986-95) oflogio transfomaed densities.

37

i l

l 1.4 E

• m 1 E ' 1.2 -

• e

.5 2 1- .

o

• E 0.8 -

E *

e. 1

~e 0 0.6 -

• m R *

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Mean of Log Larval Density at Station P2 1.4 E

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. Mean of Log Larval Density at Station P1 I

Figure 15. Relationship between Mya arenaria larval abundance at stations P1 and P2 and spal in Flat #5. Data plotted are annual rneans (1986-95) oflogto transformed densities.

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0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 Mean of Log Larval Density at Station P1 Figure 16. Relationship between Mya arenaria larval abundance at stations P1 and P2 and spat set in all five flats combined. Data plotted are annual means (1986-95) of logio transformed densities.

i 39

FINFISH Summary of the Proposed Monitoring Program After 5 Years of Operation The objectives of the proposed finfish program are to provide improved quantitative measures ofimpact (primarily entrainment and impingement) from Seabrook Station operation and the data needed to assess these losses to fish populations. While little or no evidence ofimpacts has been found to date, continued or enhanced monitoring is warranted in most instances, given the ecological and economic importance of many finfishes.

1. Ichthyoplankton sampling program modifications are based on the results of analyses of data collected through 1995. It is proposed that ichthyoplankton be collected at station P2 and P7 and that station P5 be eliminated.

No differences were detected with ANOVA between the two nearfield ichthyoplankton stations (P2 and PS) for nine selected taxa. In addition, the numerical classification (cluster analyses) for fish eggs and larvae showed that species composition was very similar between P2 and P5. An additional analysis examining differences between the two nearfield stations was performed using paired testing (Wilcoxon's signed-ranks test), which showed similar abundances at the stations for eight of nine selected species tested.

'Iherefore, based on the length of the preoperational database, which starts in 1975 for P2 and P7 but only in 1986 for PS, sampling is proposed to be discontinued at station P5. Stations P2 and P7 will continue to be sampled and the ichthyoplankton study will maintain the BACI design for future impact assessment. ANOVAs for nine selected species were re-calculated using data from only these two stations and compared to results obtained from all three stations. No significant differences were found after data from P5 I were excluded from the analyses.

2. Ichthyoplankton entrainment estimates may be improved as densities of some species are greater in the water column during the night. Further, some smaller larvae may be extruded though the 505- m mesh net presently used. Therefore, several changes to the program are proposed to improve the estimation of entrainment impact.

Entrainment estimates of fish eggs and larvae are one of the most direct measures ofplant operational impact and should be as accurate as possible. A direct comparison of taxa collected in entrainment samples with those collected at station P2 indicated several discrepancies in dominant taxa. These differences may be due, in part, to sampling at night at P2 versus day sampling for entrainment. Other ichthyoplankton studies have shown that some fish larvae are more susceptible to entrainment and capture by plankton nets at night. Therefore, it is proposed that ichthyoplankton entrainment I

)

I

n.- - . - - - - - - - - . --. .. .~ -_ - . -

P 1

i sampling include data collected during the night. This can be accomplished by reducing water flow through the entrainment nets and collecting a sample

! over a long period (up to 24 h) that encompasses both day and night. Since

the 24-h samples are effectively composite samples, no replicates will be taken. If nets become clogged during entrainment sampling, they can be

' cleaned and samples combined until sampling has been completed. This

' method has a further advantage because a larger volume of water will be L j sampled than at present. To determine differences that may result from night j

sampling, as many as 16 comparisons between day and night catches on the same date are planned in a special study to be performed over the course of a year.

.1

,j e Nets with a 505-pm mesh are presently used for entrainment sampling.

l' l

Studies have indicated that smaller (predominantly 2 to 5 mm) fish larvae can 4

be extruded through this size mesh. Therefore, paired duplicate sampling i

using both 505- and 333-mm mesh nets should be conducted for at least 1 year i' to determine if an appreciable fraction of fish larvae are being missed in entrainment samples because of net, extrusion. If no apparent differences are

' found between the two nets, then future samples can again be taken with 505-m nets. If differences do exist, then all future entrainment samples should be taken with a 333- m net. It may also be possible to use a correction factor for some taxa to modify previous data to account for undersampled larvae.

4 1

3. Gill net sampling programs (surface /near- bottom and mid-water) have provided i

data that fulfilled the objectives of these programs after 5 years of plant operation and

, it is recommended that they be discontinued.

.' I f

The gill net sampling programs (surface /near-bottom and mid-water) are i

proposed to be eliminated as they provide little or, in the case of mid-water sets, no useful data for the assessment ofplant impact. Based on I-

' impingement and entrainment data, pelagic fishes are not as susceptible to impact at Seabrook Station as demersal fishes. No attraction to the station thermal plume was evident. Information on some of the dominants collected i_

by gill net are available through other programs. Atlantic herring and pollock are collected in the seine and trawl monitoring programs. Nearly alljuvenile i and adult Atlantic mackerel have been taken by gill net. However, the annual l abundance of this species, which ranks highly in annual entrainment

! ~ estimates, can be determined by eggs collected in the ichthyoplankton 4

program. Annual egg abundance can be used as a measure of spawner biomass and relative year-to-year abundance of adults in the Seabrook area.

The gill net sampling is also highly destructive and it is likely that over the years more fish will be killed by this sampling than will be lost at Seabrook i i Station. '

3 l

1

i 1

4. Trawl sampling program data provide abundance information for species that represent the local demersal fish assemblages, including several that are potentially 1 affected by Seabrook Station and require funher evaluation ofimpact. Therefore, no changes are recommended, except for increasing the precison oflength i measurements from 2 to 0.5 cm to improve the utility of the data for modeling j purposes.

5. Seine sampling program data provide abundance information for species that represent the local estuarine fish assemblage, including several that are potentially affected by Seabrook Station and require further evaluation ofimpact. Therefore, no changes are recommended for this sampling program, except for increasing the

{

precison oflength measurements from 2 to 0.5 cm to improve the utility of the data  !

for modeling purposes.

6. Impingement sampling needs further refinement to determine if estimates of this impact are adequate.

A special study of at least 1 year in duration (when plant is in full operation) is suggested to determine if small fish are lost due to decay or other reasons during the current week-long interval between samples. To accomplish this, screens would be washed after being held for about 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and for a second time during the week after being held for the remaining 6 days. A numerical comparison of the catches (after adjustments to equalize effort), the species composition, and relative sizes ofimpinged specimens should illustrate whether or not certain taxa or sizes are inadequately represented in present impingement samples. Following the termination of this study, the impingement methodology should be again re-evaluated to optimize the frequency of sampling so that the most accurate impingement estimates can be made.

h

y R7E LEDGE  ?

~ 0 UTTLE BOARS I #EAD p7 0 .5 1 Nautical Mile FARFIELD AREA 0 i k Kilometers SCALE CONTOUR DEPTH IN METERS GREATBOARS , T3 HUD ,

HAMPTON i so BEACH ,

' lP2 BROWW5 RIVER g _.

g3 inta ke,,,

S

[0UTERp- NEARFIELD AREA-SEABROOK g (Discharge STATION ,; 33 fg g . ,, ,,, k2

/f HAMPTON SEABROOK SUNK .r, pg HARBOR ROCK 5 , _ , T2 A Gl ,

SEABROOK . ,

~ BEACH y .

's, 'S s,

,Y SAUSBURY BEACH  ; ,

I LEGEND P = Ichthyoplankton Tows i

T = OtterTrawls G = Gillnets El S = Seine Hauls l

Ichthyoplankton andjuvenile and adult fish sampling stations near Seabrook Station (from NAI 1996).

4 a

FINFISII PROPOSED PROGRAM PAST PROGRAM I) khlhynplankinn Stations / Sampling frequency: P2 and P7 sampled four times a month .

Stations / Sampling frequency: P2, and, P7 sampled four times a month

=

Replicates: I sample collected and pcxessed .

Replicates: 2 collected; I processed Total samples / year: 96 (no contingency samples would be collected) =

Totalsampics/ year: 288 collected; 144 processed Data collected: Density of fish eggs and larvae per 1000m'; length of .

larvae Data collected: Density of fish eggs and larvae per 1000m'; length of larvae

2) Ichthvoplankton entrainntent Stations / Sampling frequency: Seabrook intake structure sampled 4 =

Stations / Sampling frequency: Seabrook intake structure sampled 4 times a month over a period up to 24 h encompassing both day and night. times a month during the day in addition, as many as 16 comparisons between day and nigh catches on the same date are proposed as a special study to be performed over the course of a year.

Replicates: I (~24-h composite sample) e Replicates: 3 Total samples / year: 96; for at least 1 year of operation, two samples to . Total samples / year: 144 be collected simulataneously, one with 0.505-mm mesh and one with 0.333-mm mesh; entrainment sampling to be re-assessed following this study.

Data collected: Density of fish eggs and larvae per 1000m'; length of a larvae Data collected: Density of fish eggs and larvae per 1000m'; length of larvae -

t_

l FINFISit (continued)

PROPOSED PROGRAM PAST PROGRAM

3) n'M watergilt net

[

e These data were collected to monitor pelagic finfishes, such as the Atlantic t Stations / Sampling frequency: Gl G2, G3 sampled monthly in .i menhaden, that are found in mid-water depths to determine their potential February, June, and October for impingement impact. The in-plant impingement program now [

I monitors this effect directly. Few pelagic fish are impinged at Seabrook e Replicates: 2 24-h sets  !

Station and this sampling program can therefore be discontinued. i e Total samples / year: 18  !

L Data collected: species abundance, length measurements

4) Surface /near-bottom gill net i

e These nets were deployed to determine if finfish would be attracted to the e i Stations / Sampling frequency: GI, G2, G3 sampled monthly  ;

area becuse of the thermal plume. After 5 years of plant operation, no attraction has been demonstrated, so continued monitoring is unnecessary.

• Replicates: 2 24-h sets This program also provides data on pelagic fish that may be impinged. As  :

few of these fish are taken at the station, the sampiling itself may be more . Total samples / year: 144 destructivce than impingement effects. l Data collected: species abundance, length measurements

[

w i I

I t

i

_ - _ - .-_--= -. .

+: -- -- - -

i FINFISII(continued) -

PROPOSED PROGRAM PAST PROGRAM  :

5) OtterTrawl ,

= Stations / Sampling frequency: TI, T2, T3 sampled twice monthly

• Stations / Sampling frequency: TI, T2, T3 sampled twice monthly i

e Replicates: 2

• Replicates: 2 ,

. t Total samples / year: 144 (likely not always achievable due to lobster pots =

Total samples / year: 144 (not always achieved due to lobster pots at T2) i at T2) e Data collected: species abundance, length measurements with increased . Data collected: species abundance; length measurements to nearest 2 cm precision from nearest 2 cm to at least 0.5 cm 1 i

6) lleach Scint l

t

=

Stations / Sampling frequency: SI, S2, S3 sampled monthly from April .

Stations / Sampling frequency: St, S2, S3 sampled monthly from April through November through November e Replicties: 2 = Replicates: 2 e Total samples / year: 48 = Total samples / year: 48

. Data collected: species abundance, length measurements with increased = Data collected: species abundance; length measurements to nearest 2 cm I precision from nearest 2 cm to at least 0.5 cm  !

1

[

?

I

_ ..___._________.__z_ _ . _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . , , - _- _ _ _ _ _ -- + m m - -- - __ , , - _ _ _ _ _ _ _ _ . -

_ _m - _ _ . -- . .__ _ . _ , _ . . . _ . . _ . _ _ _ _ _ . _ ... _ _ ._. _ _ - . ___ . .. . . . _ . .

e i

FINFISII(continued)

PROPOSED PROGRAM PAST PROGRAM

7) Impi-p. t '

i

. Stations / Sampling frequency: Sampling frequency of twice a week for e Stations /Sarryling frequency: Sampled weekly when plant was

, at least for 1 year of operation in a special study to assess the efTectiveness operating i

of sampling: one ~24-h sample would be compared to a 6-day sample collected during the remainder of the week to determine if there is

)

appreciable decay or loss of small fish on screens; impingement sampling schedule to be re-assessed following this study j e Replicates: N/A e Replicates: N/A i

e Total samples / year: maximum of 104 = Total samples / year: maximum of 52 e Data collected: species abundance, length measurements to nearest 0.5 e Data collected: species abundance I cm i

4 I

t I

1 WORKING DRAFT EVALUATION OF SEABROOK STATION FISH SAMPLING PROGRAMS -

AFTER FIVE YEARS OF PLANT OPERATION l

Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 l

Seabrook Station i

Seabrook, New Harnpshire 03874 l

Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Sen' ices Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford,NewHampshire 03310 August 1996

Evaluation of Seabrook Station Fish Sampling Programs After Five Years of Plant Operation Introduction Seabrook Station, an 1150-Mwe nuclear-fueled power plant, is located in Seabrook, New Hampshire. The station uses Atlantic Ocean water to condense steam and cool vital equipment associated with the service water system. The station has three mid-water (aboui 17 ft off-bottom) intake structures located in depths of about 55 ft approximately 1.3 mi offshore of Hampton Beach (Fig.1). Water withdrawn through a 19-ft diameter tunnel travels about 3.25 mi to the plant, having a transit time of around 70 min. The station is permitted to 6 3 3 use up to 2.70 X 10 m day (31.3 m s) of seawater,95% for non-contact condenser cooling water and 5% for service water systems. Seawater systems at Seabrook Station are protected from withdrawing debris, seaweed, and larger organisms by three 0.375-in traveling screens. Material larger than this is impinged on the screens and later washed off for disposal, whereas most smaller items are entrained through these systems. Water used at the station is released through the onsite Discharge Transition Structure (DTS) and travels 3.1 mi through another 19-ft diameter tunnel to eleven diffusers located about 1 mi offshore of the mou Hampton-Seabrook Harbor at a depth of approximately 55 ft. The diffusers discharge water towards the surface at a velocity of about 15 ft sec. The average monthly increase in

{

temperature (AT) at the DTS can be up to 39'F and the maximum daily AT cannot exceed 41 F. The rise in temperature of the receiving waters cannot be greater than 5 F, except  !

within 100 ft of the diffusers, where this limit only applies at the surface. This area is the nearfield jet mixing region. Previous hydrothermal modeling and field studies demonstrated that the area of the discharge plume is relatively small, with a surface temperature increase of I 3*F encompassing an area of approximately 32 acres around the area of the discharge (Teyssandier et al.1974; Padmanabhan and Hecker 1991).

Fish are ecologically important and occupy upper trophic levels in aquatic ecosystems. Many fishes are exploited by sport or commercial fisheries, providing substantial local, regional, and 1

l national economic benefits. Finfish studies at Seabrook Station began in July 1975 and included investigations of all life stages of fish, including ichthyoplankton (eggs an juveniles, and adults. Initially, these studies were to establish baseline data suitable for assessing the effects of station operation by determining the seasonal, annual, and sp trends in abundance and distribution of fish in the nearshore waters off Hampton and Seabrook. Sampling also took place within the Hampton-Seabrook estuary to_see if the construction of Seabrook Station and the discharge of an onsite settling basin into the Browns River, which ended in April 1994, affected resident fish populations. Seabrook Stati commercial operation in August 1990. Once online, potentialimpacts ofplant operation on local fishes included entrainment of eggs and larvae through the condenser cooling-water system and impingement oflarger specimens on the traveling screens within the circul water pumphouse. Also, local distribution of fishes could be affected by the thermal discharge and some eggs and larvae could be subjected to thermal shock due to plume entrainment following the discharge of condenser cooling water from the diffuser system. 1 After plant operation commenced, the primary objective of the finfish studies was to assess whether there were any measurable effects on the neauhore fish population. i The field sampling programs for fish are directed at specific life stages or assemblages.

Sampling has been accomplished with five gear types that includes the collection of 1 ichthyoplankton using a standard 1-m plankton net (0.505-mm mesh); 30.5- X 3.7-m gill nets (paired surface-bottom sets, and mid-water sets), which are directed at pelagic fish; a 9.8-m otter trawl, which samples demersal fish; and a 30.5- X 2.4-m beach seine, which is used for smaller fish found in the shore zone of the Hampton-Seabrook estuary. Each field sampling i program uses three stations (Fig.1). Once Seabrook Station began operation, entrained ichthyoplankton (0.505-mm mesh nets) and impinged fish each were sampled at the plant using appropriate techniques. Detailed descriptions of the gear and methods used in these sampling programs are found in NAI (1996).

Data provided by the sampling programs were used in several types of analyses. These are described in detail in NAI and NUSCO (1994) and NAI (1996) and include multivariate 2

numerical classification and multivariate analysis of variance (ANOVA) ofichthyoplankt assemblages; graphical comparisons of annual geometric mean catch-per-unit-effort for gill net, otter trawl, and beach seine catches; and a fixed effects ANOVA mode specific abundance data for selected species. Data for the ANOVA model met the criteria fo a Before-After/ Control-Impact (BACI) design (Stewart-Oaten et al.1986), where sam was conducted prior to and during plant operation and sampling station locati,ons include both potentially impacted and non-impacted control sites.

i' 4 The purpose of this evaluation is to critically examine the methodologies and findings of eac of the five field and two in-station impact-related sampling programs after 5 years of Seabrook Station operation. The effectivenu '.:ach program will be assessed and proposals will be made to: 1) maintain current work,2) enhance or modify programs where ,

necessary, or 3) reduce sampling in cases where the data colled do not meet objectives of providing information vital to impact assessment. Annual CPUE indices by sampling gear '

and the BACI ANOVA model enalyses focused on eleven fishes (Table 1). These species were originally chosen because of their dominance in the Hampton-Seabrook area or because they were commercially or recreationally important. With 5 years of operating history at Seabrook Station, the susceptibility of these species (and others) to impact is better known ,

and the need to emphasize particular species in the data analyses was also evaluated.

Evaluation of Present Fish Sampling Programs at Seabrook Station With Recommendations For Future Studies Ichthyoplankton Ichthyoplankton sampling is currently conducted at three stations during the night four times a month. Two replicate samples are collected at each station, but only one of the replicates is j processed; the remaining one is held as a contingency sample. Stations P2 and P5 are nearfield stations, located close to the Seabrook Station intakes and discharge, respectively, '

that are potential impacted by the operation of Seabrook Station (Fig.1). Samples have been 3

• t i

taken consistently at P2 since the start of the program; P5 was not sampled from through June 1986. Station P7 is a farfield station and .rerves as a control or non-im  ;

)

and, with the exception of 1985, has been sampled from January 1982 through the pr; l

Historically, several modifications have been made to the collection frequencies, numbe l

replicates collected, and the stations sampled. However, since July 1986 sampling I i

methodology has been consistent for each sampling date at all three stations. _

Examination of the results from analyses of data collected through 1995 indicate that the tw) '

nearfield stations (P2 and P5) were similar in fish egg and larval species composition and l abundance. In numerical classifications of fish eggs, when no data were excluded, station and P5 are lustered in the same group, except for only 2 months, January 1989 and Novem 1993 (Fig. 2). Similarly, fish larvae at P2 and P5 clustered together in all but two instance i

February 1987 and October 1992 (Fig. 3). In addition, the results from ANOVA indicated no significant (p < 0.05) difference between these two stations in the nine selected larval fish taxa t

(NAI 1996). Further, all Preop-Op X Station interaction terms were not significant, indica consistency in abundance '. rends over time among the stations and no effect from station  !

operation (Table 2). l I

Additional comparisons oflarval abundance of selected taxa collected at stations P2 and P5 i

from July 1986 through December 1995 were examined using Wilcoxon's signed-rank test for l 1

paired comparisons. Paired testing is more sensitive in detecting station differences than the 1

presently used ANOVA model based on the BACI sampling design, which is primarily used i

to determine if the Preop-Op X Station interaction term is significant for assessing plant  ;

l impact. All sample densities were log transformed and a mean of the transformed densities l

l i for each sample date and station was used. The total number ofpossible pairs was 440, but i

!  : >r each taxa only pairs where at least one specimen was collected at either of the two stations were used in the analyses (i.e., zero values at both stations were excluded). Thus, the number

! of paired comparisons for each taxon ranged from 74 to 228 (Table 3). The only significant (p = 0.027) difference detected between stations was for pollock larvae, which were more abundant at station P5 than at P2.

4

i Based on the similarity between the two nearfield stations in species composition and in abundance of selected taxa, the ichthyoplankton program is proposed to be modified to include only P2 as the nearfield station and P7 as the farfield station. This sampl will allow the important BACI sampling design for ANOVA to be maintained. Station P2 h a long and continuous time-series of data that goes back to 1975 and, with a similar set o from P7, will continue to provide abundance and other information on ichthyoplankton in the vicinity of Seabrook Station.

The analysis using the ANOVA model with data from only stations P2 and P7 for the nine selected larval fishes showed no differences in the main effects of operational status and station and in the Preop-Op X Station interaction term. A comparison of the error mean squares computed for the nine larval fishes for two and three stations showed them to similar, ahhough slightly higher in most instances when only P2 and P7 were included 4). Using an F-test, a comparison was also made between the mean squares of the P X Station interaction term from the two-station and three-station ANOVA mod the selected species (Table 4). In only one case, that of Atlantic mackerel, was the F-value significant (p s 0.05). However, as noted above, in both three- and two-station ANOVA models for Atlantic mackerel no significant differences were found for the main effects (Preop-Op and Station) and the Preop-Op X Station interaction term was not significant (p 0.84 and 0.98, respectively). Effects of Seabrook Station on the Atlantic mackerel will be discussed further in the Surface /near-bottom Gill Net section, found below.

Ichthyoplankton Entrainment Entrainment samples (three replicates) at Seabrook Station are currently taken up to four times i

a month during the day. Two double-barrel collection devices (described in NAI 1996) use i nets of 0.505-mm mesh and samples collected in each are consolidated before preservation.

3 The volume filtered averages about 100 m per replicate. From the start ofplant operation in mid-1990 to the present, entrainment collections have been dominated by nine taxa of fish eggs and eight larval taxa (Table 5).

t 5

Entrainment estimates of fish eggs and larvae are one of the most d. rect me 1 operational impact and should be accurately measured. Field ichth voplankton collec taken during the night, whereas entrainment samples at Seabrook Station are on during the day. This could account, in part, for some of the differences seen in s composition between the two programs (see Selected Species, below), although the l i of the station's cooling-water intakes in midwater depths may also be an importat.+ fa Nevertheless, significant diel differences in distribution occur for many fishes (e the selected species: Atlantic herring, Stephenson and Power 1988, Munk et al.1989 Atlantic cod, Lough and Potter 1993; hakes, Hermes 1985; sand lance, Potter an 1987; winter flounder, NUSCO 1987, Bourne and Govoni 1988; and yellowtail flo Smith et al.1978), which would make them differentially susceptible to entrainment ov course of an entire day. Thus, it is preferable to collect larval fish during both day the intakes.

I The entrainment sampling program at Seabrook Station should be modified to include larval fish that may be more susceptible to entrainment at night to obtain more accurate estimates this impact. This would be accomplished by decreasing the present sample water flow and collecting over a longer period (up to 24 h), which would include both day and night. Thes procedural changes would also greatly increase the volume sampled compared to the 100 m' currently being filtered. This new method, however, may increase net clogging during some sampling periods. However, if clogging occurs, each net should be periodically washed down and samples corabined until the sampling has been completed. Each daily sample would be taken over a longer period ofwater flow and contain a more accurate representative samp ichthyoplankton. Therefore, replication of samples is inappropriate, i

To examine the differences in entrainment that may be the result of sampling at night as well as during daylight, a special 1+-year (done under full plant operating conditions) study is l proposed. As many as 16 comparisons _(twice a month in February-August and October-

{

! November, when larval fish are most abundant) would be made between separate day and '

i night samples taken on the same day. A comparison between day and night densities will l 6

provide informatica on the relative contribution of each period to total entrainment. Howevi even if no substantive differences are found between day and night, entrainment samples continue to be collected over the proposed period of up to 24 h. For the purpose of g entrainment estimates, data from the separate day and night collections will be combi date before calculations are made.

1 The feasibility of taking a sample during a 24-h period was examined in a preliminary pilot '

study in July 1996 (R. Sher, NAESCO, pers. comm.). The volume of water filtered was about 3

eight times the current sample volume and collection was taken without difficulty.

1 i

Another potential source of bias in the Seabrook Station entrainment estimates is in the use of I l

0.505-mm mesh nets. This may result in some species being underrepresented in the s due to net extrusion. For example, Johnson and Morse (1994) estimated that the abundance of twenty-four fish taxa was 54% higher in 0.333-mm mesh nets than in 0.505-mm mesh nets.

They reported significant differences in catches (always greater in the 0.333-mm mesh n

-)

for hakes, pollock, cunner, and American sand lance; differences were not significant for Atlantic herring, Atlantic cod, or yellowtail flounder. Largest differences occurred in the 2 to 5-mm size-classes. This would potentially include the earlier larval stages of fishes such as the winter flounder and cunner, which are relatively small. Thus, in addition to the proposed change in sample duration, a special 1+-year study is also proposed to detennine if a l

significant fraction ofichthyoplankton is not being accounted for in the entrairunent samples One of the collection devices would be fitted with a 0.333-mm mesh net and the other l retain the presently used 0.505-mm mesh net. Samples would be processed separately during this study and a comparison of the catches in each net would indicate whether an appreciable l fraction of fish larvae are missed in entrainment samples because of net extrusion. If this is i not the case, future samples could again be taken using 0.505-mm mesh nets, with the collections from both sampling devices again combined before processing. If differences between the catches by net do exist, then both nets used should be changed to 0.333-mm mesh. Using length-frequency information, it may be possible to obtain a correction factor for i

I 7

L _

l I

some of the taxa to modify previous data and adjust entrainment estimates by accounting forj undersampled sizes oflarvae. i l

The proposed changes to the ichthyoplankton e.itramment sampling (24-h sampling, day-ni i

{

comparison, mesh comparison) represent enhancem:nts that should result in more accurate estimates oflarval fish losses at Seabrook Station n

Surface /near-bottom Gill Net ,

Sampling by gill net began in July 1975 at one farfield (G3) and two ne.vfield stations (G1 1 and G2; Fig.1) to sample the pelagic fish assemblage, which was presumed to be the most likely attracted to the Seabrook Station intakes and become imriry,ed. Also, pelagic fish were projected to be attracted to the thermal discharge of Seabrook Stahon. Samples (two consecutive 24-h sets) were taken twice a month until July 19S6, when the frequency was reduced to once per month. A sampling array having nets near the bottom and at the surface '

l was used; nets were attached to permanent moorings and tended by SCUBA divers. Gill net l

catches were dominated by Atlantic herring, which made up more than half of the catch (Table 6). Blueback herring, silver hake, Atlantic mackerel, and pollock were relatively common.

Atlantic herring, pollock, and Atlantic mackerel were selected for further analyses (e.g.,

ANOVA) because of their abundance in gill net samples. Results of the ANOVAs for these three pelagic fishes, however, indicated no significant effects (i.e., the Preop-Op X Station interaction term was non-significant for each) as a result ofplant operation (Table 2).

Furthermore, other significant changes in abundance (greater abundance during the l l

preoperational period for Atlantic herring, during the operational period for Atlantic mackerel, l and no difference for pollock) reflected overall population trends in the Gulf of Maine that appeared to be primarily related to fishing as reported in NOAA (1995). The only station i

differences found were for pollock, having similar catches at farfield station G3 and nearfield station G2 (ca. 250 m from the discharge), both of which were significantly greater than catches at nearfield station G1, located about 2 km south of the plant discharge. Thus, for the 8 l l

I l

i fishes commonly collected by gill net there were no changes in distribution or abundance  !

i related to an attraction or repulsion to the thermal effluent of Seabrook Station. t

)

i Direct impacts by plant operation on the three selected species taken by gill net include entrainment and impingement. Atlantic herring eggs are demersal and none were entrained from 1990 through 1995. Larval entrainment estimates ranged from only 0.1,to l1.2 mil '

per year (Table 5). Only 514 herrings (probably a mixture of several species, including alewife and blueback herring as well as Atlantic herring; NAl 1996) were impinged in 1994 and 231 in 1995.

One million pollock eggs were entrained in 1991, but only 100 to 400 thousand eggs were entrained in other years. Few (0-200 thousand) pollock larvae were entrained annually.

Impingement estimates for pollock during 1994 and 1995 were 1,681 and 899, respectiv However, these entrainment and impingement totals only equate to 142 and 59 equivalent- i adult (age-1) pollock (NUSCO, Saila, and Howell 1995).  !

No Atlantic mackerel were impinged during the past 2 years and entrainment estimates of lan'ae were from 0 to 4.7 million. Eggs of Atlantic mackerel, however, were the top-ranked fish egg entrained. None were taken in 1994, when no samples were taken from April through August while the plant was shut down, but estimates in other years ranged from 74.5 million in 1995 to 673.2 million in 1991. Female Atlantic mackerel produce from 360 to 450 thousand eggs per spawner (Sette 1943) with monality in the egg stage as high as 41% d

(Ware and Lambert 1985). Despite being occasionally found in ichthyoplankton collections in high densities, relatively few (0-4.7 million) Atlantic mackerel larvae were entrained during each year of station operation. This may be the result of the rapid developmental rate of this fish, relatively high swimming speeds, and increased surface orientation as larvae develop (Ware and Lambert 1985), which enable mackerel larvae to avoid the station intakes.

I l

l l

9

The gill net sampling is not effective in providing information about the presence of fish subject to impingement because so few pelagic fish are impinged at Seabrook Station in comparison to demersal species (see the Impingement section, below). Of all fishes collecte by gill net, the only life stage predominant in entrainment or impingement collections was th eggs of Atlantic mackerel. Potential power plant impact can be better evaluated in this instance by using equivalent-adult (Horst 1975; Goodyear 1977; Saunders 1977; Borema al,1981) or similar analytical methodologies, such as production foregone (Rago 1984 three of the pelagic species that were selected for analysis are highly fecund. Both poll and Atlantic mackerel populations are made up of several very large stocks found over wide geographical areas in the North Atlantic Ocean (NOAA 1995). The Atlantic herring separate spawning aggregations found throughout the Gulf of Maine (Anthony and Boyar 1968; lies and Sinclair 1982; Sinclair and Iles 1985), but a lengthy developmental period disperses and mixes larvae over large areas. Both the Atlantic herring and Atlantic mackerel are presently increasing in abundance in the Gulf of Maine and are underexploited by the fisheries (NOAA 1995). Pollock abundance is considered to be stable and this species is currently fully exploited.

Results of ANOVA using gill net collection data indicate no significant effects by Seabrook Station after 5 years of operation on the three selected species (Table 2). Differences in abundance between the preoperational and operational periods appeared to result from lon term changes in population size occurring over a wide area that were related to fishing.

Therefore, the surface-near bottom gill net sampling program are proposed to be discontinued as collections do not provide data needed for the assessment of Seabrook Station operation on fishes. Gill net sampling is also highly destructive. It is likely that the thousands ofjuvenile and adult Atlantic herring, blueback herring, silver hake, pollock, and Atlantic mackerel killed during gill net sampling since 1975 will exceed the mortality of these fishes imposed by Seabrook Station during its operational lifetime. If, however, abundance information for the three selected species taken by gill net is desirable, both Atlantic herring and pollock (mostly young-of-the-year) have been taken by seine, the data for which provide an annual index of year-class abundance. Pollock are also taken by the otter trawl sampling. The abundance of 10

Atlantic mackerel eggs and larvae as provided by the ichthyoplankton monitoring program should provide an annual index of spawner abundance of this fish.

l Mid-water Gill Net i

Mid-water gill net sampling began in 1980 with sets made only during February, June, and October at the three gill net stations. Mid-water gill net sampling was designed to capture f found at a depth comparable to the Seabrook Station intakes, which presumably would have been the specimens most likely to have been impinged. However, impingement at Seabrook Station has been dominated by demersal fishes and small species not susceptible to the mesh I i

sizes of the gill nets in use. A comparison of mid-water gill net catches with surface and near- !

bottom gill net catches made at the same time showed that only Atlantic menhaden were slightly more abundant in mid-water sets than at the surface or near the bottom. Other fishes relatively abundant in mid-water gill net collections included the Atlantic herring, silver hake, Atlantic mackerel, pollock, alewife, and blueback herring, bw c .tches of these fishes were generally higher in the surface-bottom sets than in mid-water. Only seven Atlantic menhaden have been recorded in impingement samples since the start of sampling in 1990 and relatively!

few individuals of the other species collected by gill nets have been impinged. The mid-water l

gill net catch data have not been discussed in annual monitoring reports since NAI (1992) because the data have not been helpful in describing trends in impingement and because of similarities to the surface-bottom gill net collections, which are made monthly as opposed to only three times a year for mid-water sets. Therefore, it is proposed that this sampling program be terminated because the data collected are not needed for assessments of potential Seabrook Station impact.

Otter Trawl The otter trawl program has provided monthly abundance data since July 1975 useful for characterizing the demersal fish assemblage at three inshore stations, two (Tl and T2) l nearfield and one (T3) farfield (Fig.1). .Four replicate tows were made at each station once a month, but beginning in January 1985, the sampling frequency was increased to twice a month and the number of replicate tows was reduced to two.

11

I Several selected species, including the yellowtail flounder, the hakes, winter flounder, Atlantic cod are taken frequently in trawl samples (Table 7). These species were considered potentially susceptible to impact at Seabrook Station by entrainment of eggs and larvae ori from impingement; all are also heavily exploited by the fisheries (Table 2). They all ha spawning stocks made up of many age-classes and have relatively long life spans.

{

i impacts will take time to be propagated through their population age structure. Othe present in the trawl catches included longhorn sculpin, rainbow smelt, skates, windowpa pollock, and silver hake.

' I l

i i

Equivalent-adult analyses were completed to determine the effect of entrainment and  !

impingement losses on the hakes (white hake was chosen for this analysis) and winter I i

i flounder (NUSCO, Saila, and Howell 1995). These analyses showed relatively small numbe

(<800 annually of hakes and 1,374-4,273 winter flounder) of equivalent-adults lost to their respective populations.

Results from the ANOVA models showed that all species selected for analysis from the trawl program were less abundant during the operational period than the preoperational period I (Table 2). In addition, the rainbow smelt, winter flounder, and yellowtail flounder taken by trawl had significant Preop-Op X Station interaction terms. However, NAI (1996) concluded that differences in abundance at the trawl stations of these species were neither biologically significant nor due to station operation. Instead, the effects may be due to changes in local  ;

i environmental or physical conditions. '

Trawl CPUE for rainbow smelt decreased between the preoperational and operational periods i at all three stations, but was greatest at T2. However, no significant differences were found i

when using the seine data with the ANOVA model; the seine stations are much closer to the streams in which rainbow smelt spawn. Impingement and entrainment of smelt has been very low since Seabrook Station began operation.

4 12

~ . . . - .. - - - - _ - - - -. - - .. - - .. -. . - . .. - - -

Winter flounder catches also decreased disproportionately at T2, a trend that bega ,

preoperational period. Differences in trends between control and impact stations in th prior to the impact (i.e, plant start-up) taking place may lead to misleading significa et al.1993) unrelated to the effect being observed. Winter flounder populations have been heavily exploited by the fisheries in recent years (NOAA 1995).

Abundance of yellowtail flounder is currently very depressed (NOAA 1995). Catches of yellowtail flounder by trawl were highest at farfield station T1, with the decline in abundance '

between the preoperational and operational periods somewhat larger there than at T2 or T3.

1 This is likely related to the overfishing and the significant interaction term is unrelated to 1

plant operation. The yellowtail flounder is only minimally affected by entrainment or impingement.

t Although plant effects appear to be minimal for the fishes taken by trawl, due to the importance of the demersal fish community and the consistency of the trawl monitoring in providing abundance infonnation over a long time period, no changes to this program are '

recommended.

Beach Seine Monthly beach seine sampling (two hauls per station) have been completed since July 1975 at three stations within the Hampton-Seabrook Harbor (Fig.1), although no samples were collected in 1985 or from April through June of 1986. Seabrook Station ceased discharging

! from a settling basin into the Browns River in April 1994. Thus, direct plant effects on l

resident estuarine fishes no longer occur except for life stages ofinshore fishes that are susceptible to entrainment or impingement at the offshore plant intakes.

Atlantic silverside dominated the seine catch (Table 8) and was also the most numerou impinged on the traveling screens of Seabrook Station (see the Impingement section, below).

j Impingement of this species primarily occurs during offshore overwintering movements. The winter flounder also contributes frequently to beach seine catches, with larvae entrained and 13

i

! juveniles and adults impinged, particularly during fall and winter storm events. Other I

commonly found in the seine catches include killifishes, American sand lance, rain pollock, ninespine stickleback, alewife, and Atlantic herring. '

+

Because of the long and consistent time-series of data, the lack of abundance informat i

the Atlantic silverside from other sampling programs, and the catch ofjuvenile winter <

i flounder and other important species by seine, this monitoring program should continu .

i further evaluations ofpotential Seabrook Station impacts are performed for th

! this method.

l-Impingement i

Traveling screens at the Seabrook Station circulating water pumphouse are gene once a week. Immediately following the screenwash, all impinged organisms are removed from a collection basket, identified, enumerated, and measured. Impingement has been  !

greatest during cooler months and storm periods. Prior to October 1994, estimates of impingement were inaccurate because small fish were incompletely separated from debris (NAI 1996). Consequently, impingement counts made during the last quarter of 1994 and for l i t

all of 1995 were substantially higher (15,932-19,218) than earlier annual estimates (503-I 1,177). In 1994-95, the twelve most numerous species made up more than 90% of the total 1 impingement (Table 9). This total includes at laest one annual estimate of greater than 2,0 fish for Atlantic silverside, grubby, and the hakes. Relatively few rainbow smelt (213-545) herrings (231-514), cunner (32-342), and Atlantic cod (58-119), and no Atlantic mackerel were impinged in either 1994 or 1995. Although the station has mid-water intakes, a considerable portion ofimpingement is of demersal species, such as flatfishes, hakes, and

. sculpins. In comparison to other large marine electrical generating stations in New England, Seabrook Station impinges relatively few specimens as a result ofits offshore mid-water j

intakes (Table 10).

t 6

Accurate estimates oflosses are required for impact assessments as impingement directly  ;

affects fish by removing older individuals from the population. These losses occur after i l

l 14

natural mortality rates decrease from mortalities found during the earliest life history (i.e., eggs and larvae). Thus, population-level responses (e.g., density-depend may be less effective in compensating for losses. Although estimates ofimpingement Seabrook Station improved considerably in late 1994, a possibility exists that some may still be underestimated in impingement counts. Because the screens are usually w l

only once a week, it is possible that small fish may deteriorate before being encountered in l

sample. To determine if this is happening, a change to the impingement sampling proto l

! proposed during a special 1+-year study. Full or nearly full plant operation is required d -

this period to obtain estimates over all seasons and water temperatures. This study wo involve holding the screens for about a 24-h period once during a week before washin to obtain a sample. The screens would then be held for the remaining 6 days of the week and I

another sample then taken. Some deviations in these periods may be necessary because o plant operations. For example, during major storm events, traveling screens may run continuously for extended periods. In this instance, comparisons of short and long screenwash hold times would likely be impossible. Nevertheless, during routine weeks, l

impingement counts from both the short and long periods can be standardized by time (

number impinged per hour). A comparison of the resulting weekly impingement CPUEs as well as the species composition and size-frequencies of fish impinged should reveal whether i smaller fish or particular species are being lost during the current week-long period between screenwashes. Upon completion of the study, ifloss of fish prior to sampling is not evident, the impingement sampling schedule can be reduced once again to the current weekly count.

If, however, loss of fish is considered to be appreciable, impingement sampling should be scheduled mere frequently to obtain more accurate estimates. Depending upon the outcome l

(e.g., the species involved or time of year), then further adjustments to the impingement p sampling schedule may be desirable, such as a reallocation of sampling effort to a stratified 1

random design in place of the current systematic weekly effort. This would likely lead to

) mereased sampling during times when impingement is highest (fall-winter) and a reduced i

schedule when impingement is quite low (late spring-summer).

i 1

15 i

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l I

Selected Species Currently, eleven fishes are selected for species-specific analyses for Seabrook Station studie (Table 1). However, based on the long preoperational data time-series and 5 years of operational studies, including entrainment and impingement sampling, it is clear that these fishes have variable susceptibilities to effects of station operation. Based on the results of the ANOVA model reported in NAI (1996), the potential effects of Seabrook Station on selected fishes are summarized in Table 2. There were significant differences found between the preoperational and operational periods that were not consistent among stations (indicated significant Preop-Op X Station interaction term) for ordy three species: the rainbow smelt, winter flounder, and yellowtail flounder. However, as discussed previously, it is unlikely th these differences were due to Seabrook Station operation, particularly for rainbow smelt and yellowtail flounder. Very few specimens of either species were entrained or impinged d plant operation (Tables 5 and 9). This was also true of Atlantic herring, Atlantic cod, and pollock. Species that are emphasized in the reports should include those that make up relatively large proportions of entrainment (e.g., Atlantic mackerel, cunner) and impingement (e.g., hakes) or have a stock structure (i.e., localized spawning populations) that may make them more susceptible to impact (e.g., winter flounder and Atlantic silverside). Many entrained or impinged specimens of the latter two species were likely produced locally within the Hampton-Seabrook Harbor estuary. i i

l 1

1 Predictions of the numbers of fish eggs and larvae entrained into the condenser cooling-water i system of Seabrook Station were made for rainbow smelt, winter flounder, Atlantic menhaden, pollock, and Atlantic mackerel in NAI (1977). At the time, these fishes had been identified as Representative Important Species by personnel from Region I of the U.S.

Environmental Protection Agency, based on their commercial and recreational importance.

Predictions of entrainment once the station went online were developed from densities of l

l 1

ichthyoplankton observed from 1973 through 1976 and a pumping rate for one unit operating at 100% of theoretical capacity. These conservative entrainment estimates of eggs and larvae were much higher than the actual entrainment determined for 1990 through 1995 (Table 11).

The predicted entrainment was much higher than what actually occurred because of several 16

highly conservative assumptions. The single largest single monthly density for a spe observed during 1973-76 was used in the calculations, which were values conside than actually found during the operational period. The predicted pumping rate for one unit was slightly higher than the actual pumping rate because of station outages and other variations in flow. Also, differences have since been noted between entrainment and field ichthyoplankton samples, possibly because of different water masses sampled, diel differ in larval distribution, or species-specific behavior that may allow larvae to avoid the intakes.

Consequently, the actual entrainment impacts on fishes were, at minimum, from one to three orders of magnitude lower than predicted, particularly for some of the selected species a effects of Seabrook Station operation on finfish have not been as severe as first hypoth Several species less prominent in ichthyoplankton collections, including the Atlantic sn rock gunnel, and grubby, however, do predominate in larval entrainment samples (Table All of these fishes are small, have no sport or commercial value, and their ecological significance is less understood than many of the other selected species. These species are generally cryptic and are often found in tide pools or subtidally among rocks, mussel clumps or near other bottom cover (Sawyer 1967; Collette 1986; Moring 1990; Ojeda and Dearborn 1990). Each of these fishes appears only sporadically in the seine and trawl sampling, but all  !

are seasonally abundant in the ichthyoplankton sampling. The effect of station operation on these species is yet unknown. l In summary, presently selected fishes, including the Atlantic herring, rainbow smelt, Atlantic cod, pollock, and yellowtail flounder, should be de-emphasized in the annual reports as their entrainment and impingement are low and results from the ANOVA models indicated that they are probably not affected by Seabrook Station operation. However, annual abundance information for each would remain available through the seine and trawl sampling programs, which are proposed to be continued as in the past. Also, the ANOVA models could be I I

completed for selected species taken by these gears. Continued scrutiny of the hakes, Atlantic silverside, cunner, American sand lance, Atlantic mackerel, and winter flounder is warranted until analyses such as equivalent-adult or production foregone estimates can be performed to I 17

assess the potential impacts of Seabrook Station on their populations. If av!

information may be needed to assess station impacts for the Atlantic snailfis and grubby. In any event, the ichthyoplankton monitoring should provide abundan the early life history stages of these fishes, the indices for which also generally refle numbers of adult spawners.

, Conclusions i

The proposed finfish monitoring programs are designed to provide improved quantitati measures of possible impact from Seabrook Station operation and the data needed to asse losses to local fish populations. Given the ecological and economic importance o continued monitoring is warranted despite the absence of evidence ofimpacts found to da!

Entrainment and impingement sampling, two programs which provide direct measuremen; plant impact, are proposed to be enhanced. The ability to sample cooling-water flow j:

h will provide more accurate estimates of entrainment, including all ichthyoplankton more susceptible to entrainment during nighttime hours. A special 1+-year study comparing 0.5 and 0.333-mm mesh nets will provide evidence for or against larval net extrusion and increase

)

the reliability of entrainment estimates. Similarly, a 1+-year study ofimpingement sam frequency will ascertain whether certain species or sizes of fish are lost weekly between screenwashes. Once completed, results from these studies may lead to further refinements in entrainment and impingement monitoring.

I Present field sampling programs are proposed to remain intact (otter trawl and beach seine be modified in scope without losing essential information (ichthyoplankton), or discontinued because the programs do not provide data pertinent to assessing the effects of Seabrook Station operation (surface /near-bottom and mid-water gill nets).

l Susceptibility of each of the eleven selected fishes to impact was further examined using information available following 5 years of station operation Emphasis in reports should be t

i

( ,

l 18 l l

t

placed on those species most likely to be affected by plant operation and includ Atlantic silverside, cunner, American sand lance, Atlantic mackerel, and winter flounder.

l Also potentially affected are the Atlantic snailfish, rock gunnel, and grubby, althou ecological and economic significance are likely much less than for the aforementioned species. Fishes de-emphasized in analyses and reporting because oflack of sus impact (i.e., little direct loss from entrainment or impingement or no thermal effect Atlantic herring, rainbow smelt, Atlantic cod, pollock, and yellowtail flounder. Abundance data for these species will continue to be provided by the trawl, seine, and ichthyopla monitoring programs and, with the exception of gill net catches, the ANOVAs may s completed for these species, if so directed. In addition, monitoring of possible effects of Seabrook Station operation on selected species may also be evaluated using ot analytical techniques (e.g., equivalent-adult calculations; production foregone).

References Cited Anderson, R.D.1995. Impingement oforganisms at Pilgrim Nuclear Power Station (January-December 1994). In marine ecology studies related to operation of Pilgrim Station. Semi-annual rep. no. 44. Boston Edison Co., Boston, MA.

Anthony, V.C., and H.C. Boyar.1968. Comparison of mersitic characters of adult Atlantic herring from the Gulf of Maine and adjacent waters. Res. Bull. Int. Comm. Northw. Atl.

Fish. 5:91-98.

Boreman, J., C.P. Goodyear, and S.W. Christensen.1981. An empirical methodology for estimating entrainment losses at power plants sited on estuaries. Trans. Am. Fish. Soc.

110:253-260.

Bourne, D.W., and J.J. Govoni. 1988. Distribution of fish eggs and larvae and patterns of ,

water circulation in Narragansett Bay, 1972-1973. Am. Fish. Soc. Symp. 3:132-148.

l Collette, B.B.1986. Resilience of the fish assemblage in New England tidepools. Fish.

l Bull., U.S. 84:200-204.

Evans, S.D.1978. Impingement studies. Pages 3.1-3.40 in Maine Yankee Atomic Power Company. Final report environmental surveillance and studies at the Maine Yankee Nuclear Generating Station 1969-1977.

19 l

l

Goodyear, C.P.1977. Mathematical methods to evaluate entrainment of aquatic by power plants. U.S. Fish Wildl. Serv., FWS/OBS 76/20.3, Ann Arbor, MI.

I Hermes, R.1985. Distribution of neustonic larvae of hakes Urophycis spp. and fourbea rockling Enchclyopus cimbrius in the Georges Bank area. Trans. Am. Fish. Soc. I14:604 608.

Horst, T.J.1975. The assessment ofimpact due to entrainment ofichthyoplankton 107-118 in S.B. Saila, ed. Fisheries and energy production: a symposium. D.C. Heath an Co., Lexington, MA.

I lies, T.D., and M. Sinclair.1982. Atlantic herring: stock discreteness and abundance.

Science 215:627-633.

Johnson, D.L., and W.W. Morse. 1994. Net extmsion oflarval fish: correction factors for 0.333 mm versus 0.505 mm mesh bongo nets. NAFO Sci. Coun. Studies 20:85-92.

LMS (Lawler, Matusky & Skelly Engineers) 1987. Brayton Point Station Unit No. 4 screen intake biological evaluation program. Vol. I. Program summary report 1984-1986.

Submitted to New England Power Company, Westborough, MA.

Lough, R.G., and D.C. Potter. 1993. Vertical distribution patterns and diel migrations of larval andjuvenile haddock Melanogrammus aeglefinus and Atlantic cod Gadus morhua on Georges Bank. Fish. Bull., U.S. 91:281-303.

Moring, J.R.1990. Seasonal absence of fishes in tidepools of a boreal environment (Maine USA). Hydrobiologia 194:163-168.

Munk, P., Kierboe, T., and V. Christensen. 1989. Vertical migrations of herring, Clupca harengus, larvae in relation to light and prey distribution. Envir. Biol. Fish. 26:87-96.

MRI (Marine Research, Inc.). 1993. Brayton Point investigations annual report January-December 1992. In New England Power Company and Marine Research, Inc. Brayton Point Station annual biological and hydrological report January-December 1992.

NAI (Normandeau Associates Inc.). 1977. Assessment of anticipated impacts of construction and operation of Seabrook Station on the estuarine, coastal and offshore waters, Hampton-Seabrook, New Hampshire. Prepared for Public Service Company of New Hampshire.

NAI (Normandeau Associates Inc.).1992. Finfish. Pages 3 3-123 in Seabrook Station 1991 environmental studies in the Hampton-Seabrook area. A characterization of environmental conditions.

NAI (Normandeau Associates Inc.).1996. Finfish. In Seabrook Station 1995 environm studies in the Hampton-Seabrook area. A characterization of environmental conditions.

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l

NAl (Normandeau Associates Inc.), and NUSCO (Northeast Utilities Service CompanI Corporate and Environmental Affairs).1994. Fish. Pages 5 5-90 in Seabrook environmental studies,1993. A characterization of environmental conditions in the Hampton-Seabrook area during the operation of Seabrook Station.

(

i NOAA (National Oceanographic and Atmospheric Administration).1995. Status of fishe

! resources 140 pp. off the northeastern United States for 1994. NOAA Tech. Mem. NMF I NUSCO (Northeast Utilities Service Company).1987. Winter flounder studies. In Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power >

Station, Waterford, Connecticut. Summary ofstudies prior to three-unit operation.149 pi NUSCO (Northeast Utilities Service Company).1988. Fish ecology studies. Pages 255-307 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power .

Station, Waterford, Connecticut. Three-unit operational studies 1986-87. '

NUSCO (Northeast Utilities Service Company), S.B. Saila, and W.H. Howell.1995.  :

Equivalent-adult estimates for three species of groundfish impinged and entrained at Seabrook Station. Prepared for North Atlantic Energy Service Corporation. 21 pp.

i Ojeda, F.P., and J.H.

Dearborn. 1990. Diversity,

abundance, and spatial distribution of fishes and crustaceans in the rocky subtidal zone of the Gulf of Maine. Fish. Bull., U.S. 88:403-410. )'

i Padmanabhan, M., and G.E. Hecker.1991. Comparative evaluation of hydraulic model and l

field thermal plume data, Seabrook Nuclear Power Station. Alden Research Laboratory j Rep. No. 60-91/M620F. 12 pp. + 2 tab. + 11 figs.

Potter, D.C., and R.G. Lough.1987. Vertical distribution and sampling variability oflarval and juvenile sand lance (Ammodytes sp.) on Nantucket Shoals and Georges Bank J.

. Northw. Atl. Fish Sci. 7:107-116.

Rago, P.J.1984. Production foregone: an alternative method for assessing the consequences of fish entrainment and impingement losses at power plants and other water intakes. Ecol.

Model. 24:79-111.

Saunders, W.P., Jr.1978.' A simple model for assessing the potential loss of adult fish resulting from ichthyoplankton entrainment. Pages 49-56 in J.H. Thorpe and J.W. Gibbons, eds. Energy and environmental stress in aquatic systems. Tech. Info. Cen., U.S. Dept.

Energy, Washington, DC.

1 Sawyer, P.J. 1967. Intertidal life history of the rock gunnel, Pholis gunnellus, in the Western

! Atlantic. Copeia 1967:55-61 l

{

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, _ _ - _ , , - a

I

{

' Sette, O.E.1943. Biology of the Atlantic mackerel (Scomber scombrus) of North America.

Part 1. Early life history. Fish. Bull., U.S. 50:149-237 ulfofh[a e-S th helf a el i oce ogr ph c fe u es. C . J Fi ! . quat.

Sci. 42:880-887.

l Smith, E.P., D.R. Orvos, and J. Cairns. 1993. Impact assessment using the before-after-control-impact (BACI) model: concerns and comments. Can. J. Fish. Aquat.. Sci. 50:627-637.

Smith, W.G., J.D. Sibunka, and A. Wells.1978. Diel movements oflarval yellowtail flounder, Limandaferruginea, determined from discrete depth sampling. Fish. Bull., U.S.

l 76:167-178.

Stephenson, R.L., and M.J. Power. 1988. Semidiel vertical movements of Atlantic herrin Clupea harengus larvae: a mechanism for larval retention? Mar. Ecol. Prog. Ser 50:3-11.

Stewart-Oaten, A., W.W. Murdoch, and K.E. Parker. 1986. Enviromnental impact I i

assessment:"pseudoreplication"in time? Ecology 67:929-940. '

l Teyssandier, R.G., W.W. Durgin, and G.E. Hecker. 1974. Hydrothermal studies of diffuser '

discharge in the coastal environment: Seabrook Station. Alden Research Laboratory Rep.

No. 86-24/M252F. 47 pp. + 20 photogr. + 119 figs. + 2 app. l l

Ware, D.M., and T.C. Lambert. 1985. Early life history of the Atlantic mackerel (Scomber l

scombrus)in the southern Gulf of St. Lawrence. Can. J. Fish. Aquat Sci. 42:577-592.

l l

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22

- ._ ._ . ._ . _ . _ . . _ . _ _ _ _ . . _ . _ . . . _ . _ . _ . _ . . m ___ _ . . _ __ _. . . _ . _ _ . _ . _

\

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Table 1. Selected finfishes and sampling programs that contributed abundance data in species-specific analyses for Seabrook Station. {

Selected Species Predominant Sampling Programs Atlantic herring ichthyoplankton, gill net Rainbow smelt otter trawl, beach seine Atlantic cod  ;

ichthyoplankton, otter trawl - '

l Pollock ichthyoplankton, gill net Hakes - i ichthyoplankton, otter trawl

- Atlantic silverside beach seine Cunner ichthyoplankton  !

American sand lance ichthyoplankton Atlantic mackerel ichthyoplankton, gill net

{

L Winter flounder ichthyoplankton, otter trawl, beach seine i

l-

.Yellowtail flounder l ichthyoplankton, otter trawl '

l l

i 1

I l 4 1

i 23

i Table 2. Summary of the potential of the operation of Seabrook Station on selected fish taxa based on re l

1 from the BACI ANOVA models (from NAl 1996).

Operational Preop / Op Recent Period Similar to Differences

• Abundance l

l Sampling Preoperational Consistent Species Trends in the Status of Program Period? Among Stations? Gulf of Maine' Fishery Atlantic herring ichthyoplankton Op < Preop yes increasing under. '

l gill net Op < Preop yes exploited Rainbow smelt trawl Op < Preop no unknown lightly to seine yes yes l unexploited l Atlantic cod ichthyoplankton yes yes l decreasing over-trawl Op < Preop yes exploited Pollock ichthyoplankton Op < Preop yes stable fully gill net yes yes exploited Hakes ichthyoplankton yes yes increasing l trawl under to

!- Op < Preop yes fully expl.

Atlantic silverside seine Op < Preop yes unknown unexploited Cunner ichthyoplankton yes yes unknown unexploited Am. sand lance ichthyoplankton yes l yes stable? unexploited Atlantic mackerel ichthyoplankton yes yes increasing under-gill net Op > Preop yes exploited Winter flounder ichthyoplankton Op < Preop yes decreasing over-trawl Op < Preop no 1 exploited seine Op < Preop no Yellowtail flounder ichthyoplankt'on yes yes decreasing over-trawl Op < Preop no exploited

\

• Based on Preop-Op X Station interaction term from the ANOVA.

' From NOAA (1995) for commercially exploited species. )

a l 24

Table 3. Comparison oflarval abundances at stations P2 and P5 from July 1986 through

' December 1996 of nine of the selected taxa tested using Wilcoxon's signed-rank test. Given are the number of paired camparisons when the taxa were collected on a sampling date at either station and the point of rejection (P).

Number of Taxon paired comparisons P Atlantic herring 228 0.406 NS Atlantic cod 145 0.122 NS Pollock 120

• 0.027 Hakes 97 0.082 NS Cunner 148 0.168 NS American sand lance 214 0.063 NS Atlantic mackerel 74 0,151 NS Winter flounder 113 0.800 NS Yellowtail flounder 101 0.080 NS l

l 25

I f

! Table 4. Results of F-tests to determine significant (P s 0.05) differences between mean

• squares (MS) for the interaction term from two analysis of variance (ANOVA) tests for selected larval fish taxa. One ANOVA was based on data collected at the th the other ANOVA on data collected at two stations (P2 and P7). F-values were calculat  :-

dividing the larger of the two MS by the smaller.

Taxa F-value p Atlantic herring 1.00 0.577 Atlantic cod 1.93 0.453 Pollock 2.00

' 0.293 Hakes 3.75 0.343 Cunner 1.70 0.322 American sand lance 1.92 0.301 Atlantic mackerel 409.90 0.035 Winter flounder 6.90 0.260 Yellowtail flounder 1.85 0.307 i

26 1

I

l i

Table 5. Estimated entrainment (in millions) of eggs and larvae of the most abundant an taken at Seabrook Station from 1990 through 1995.

{

Jan-July, Jan-Mar, June-Dec Dec Jan-Aug Taxon Jan-Dec Sep-Dec Jan-Dec 1990 1991 1992 1993 1994 Ecce 1995 l Atlantic mackerel $ 18.1 673.2 456.3 112.9 0 Cunner /yellowtail flounder 490.4 74.5 i 716.3 198.6 58.4 '

Atlantic cod / haddock / witch fl. 29,1 _0 18.6 74.5 39.5 50.3 Fourbeard rockling/ hake 1.0 34.8 114.2 35.1 50.6 Windowpane 32.7 1.7 27.5 36.4 10.9 22.5 29.1 American plaice

• 0.1 17.4 '

2.6 .0 52.3 19.5 0.4 14.8 Fourbeard rockling 7.4 4.3 0.8 1.4 0.2 Silver hake 11.4 4.2 0 0.1 0.4 Hakes 0.4 22.5 37.3 2.6 0 0.2 0.6 25.1 Other selected species:

Atlantic cod 0 0 0 0 0 Atlantic cod /pollock 0 0 2.2

'O 0 Pollock 0 0.2 0 1.0 0.4 0.2 0.1 0.4 Yellowtail flounder 0 0 s 0 0 0 0.2 l Other fishes 0.8 3.1 1.5 10.5 0.3 13.2 Larvae.

Atlantic seasnail 11.6 16.0 31.5 64.4 0 Grubby 26.5 0 22.4 18.9 13.8 4.9 17.4 American sand lance 0 37.3 18.1 12.0 8.3 Atlantic herring 9.5 0.7 0.5 4.9 9.6 Rock gunnel 0.1 11.2 l 0 51.1 45.3 5.7 11.0 15.6 Cunner 42.7 <0.1 0 4.7 Winter flounder 0.1 4.4 3.2 9.0 6.2 2.9 0 8.0 Fourbeard rockling 37.9 0,5 0.1 2.2 0 3.9 Other selected species:

Atlantic cod 0.7 1.5 0.4 0.1 0 Hakes 2.3 4.8 0 0 0.1 0 0.7 Atlantic mackerel 0.2 4.7 0 0 0 0 Yellowtail flounder 0.1 0.3 0.1 0 0 Pollock 0.1 0.2 0 0.1 0 0 0 Rainbow smelt 0.2 0 0.1 0 0 0 Other fishes 19.2 10.5 7.3 10.7 6.8 45.7 l

i s

27 l

[

. . . . - . - . -. .= .~ - - =. .. - .. .- -

Table 6. Percent species composition of fishes taken by gill net at Seabrook Station from 1975 through 1995.

Station All Stations i Species Gl G2 G3 Combined Atlantic herring 57.8 63.6 54.3 58.7 Blueback herring 6.2 7.3 9.8 -

7.8 Silver hake 7.3 6.3 8.9 7.5 Atlantic mackerel 7.1 6.1 6.8 6.7 Pollock 6.4 6.4 6.9 6.6 Other selected species:

Rainbow smelt 1.4 1.1 1.7 1.4 Hakes 2.1 1.3 0.8 1.3 Atlantic cod 1.0 0.7 1.0 0.9 Cunner 0.2 <0.1 0.6 0.3 i Winter flounder 0.2 0.1 '

0.1 0.1 Yellowtail flounder 1.0 <0.1 0.0 <0.1 American sand lance 1.0 0.0 <0.1 <0.1 Atlantic silverside 0.0 <0.1 0.0 <0.1 Other fishes 8.3 7.1 9.1 8.7 1

l h

1 28 l

4 Table 7. Percent species composition of fishes taken by otter trawl at Seabrook Stati 1975 through 1995 (note that station T2 was frequently not sampled in late su fall).

Station Species All Stations Tl T2 T3 Combined Yellowtail flounder 35.1 13.7 18.5 -

24.5 Longhorn sculpin 12.4 4.8 22.7 15.1 Hakes 13.8 8.8 13.1 12.6 Winter flounder 7.4 25.6 6.6 10.4 Rainbow smelt 5.3 18.3 5.3 7.7 Atlantic cod 4.7 4.4 10.4 6.9 Skates 5.2 2.1 9.2 Windowpane 6.2 5.1 4.1 2.6 3.9 Pollock 1.8 8.2 0.8 2.6 3

Silver hake 3.0 0.8 2.8 2.5 4

Other selected species:

Atlantic silverside 0.2 0.7 0.2 0.3 Atlantic herring 0.3 0.2 l

0.1 0.2 Cunner 0.1  ;

0.1 <0.1 0.1 i American sand lance <0.1 0.1 j 0.0 <0.1 Atlantic mackerel <0.1 <0.1 <0.1 <0.1 f

Other fishes 5.6 8.1 7.7 7.0 i

I i

i 29

Table 8. Percent species composition of fishes taken by beach seine at Seabrook Station from 1975 through 1995 (no samples taken in 1985 or from April through June 1986).

Station All Stations Species S1 S2 S3 Combined Atlantic silverside 65.0 55.1 70.5 64.4 Killifishes 14.2 15.1 <0.1 -

8.2 American sand lance 3.8 3.6 5.8 4.6 Rainbow smelt 0.7 1.3 8.9 4.5 Pollock 1.0 5.7

' 4.1 3.8 Ninespine stickleback 4.6 2.1 4.4 3.7 Alewife 0.5 8.9 0.2 2.7 Atlantic herring 1.3 4.8 0.8 2.2 Winter flounder 1.4 1.2 2.4 1.8 Other selected species:

Hakes <0.1 0.2 l

0.2 0.2  !

Atlantic cod <0.1 0.0 <0.1 <0.1 i Yellowtail flounder <0.1 <0.1 <0.1 <0.1  !

Cunner 0.0 0.0 <0.1 <0.1 Atlantic mackerel <0.0 <0.0 <0.0 <0.1 Other fishes 7.5 2.0 2.7 3.9 1 1

!I I

i _

1 l

30 l

l

l Table 9. Number and percent total of the twelve most abundant ano other selected fishes impinged at Seabrook Station during 1994 and 1995.

Species 1994 1995 NumberImpinged  % of total !

1 Atlantic silverside 5348 1621 6969 19.9 Grubby 2678 2415 5093 14.5 Hakes 2822 2197 5019 14.3 Winter flounder 1435 1171 2606 7.4 Pollock 1681 899 2580 7.4 American sand lance 1215 1324 2539 7.2 Windowpane 980 943 1923 5.5  :

Rock gunnel 494 1298 1792 Yellowtail flounder 0 1149 5.1 )

1149 3.3 Northern pipefish 188 579 767 2.2 i Rainbow smelt 545 213 758 2.2 Herrings 514 231 745

{

2.1 1 Other selected species:

Cunner 32 342 3 74

' 1.1 Atlantic cod 58 119 177 0.5 Atlantic mackerel 0 0 0 -

]

Other fishes 1191 1409 2600 7.4 1

l l

I l

l 31

Table 10. Comparison of fish impingement at Scabrook Station with estimates from other New England power plants with marine intakes (from NAl Nominal Cooling Mean Rated Water Range for Nmnbcr Capacity Flow i urs of Mean Annual CV d Annual Impinged Station Source Water Body (Mwe) (m'sec ) Study Inipingement (%) Estimates Per Day iteference Seabrook GulfofMaine 1,150 31.5 1995* 15,932 - -

44 NAI (1996)

Mainc Yankee i,.ontswcag Bay 855 26.6 1972-77 59,999' 34 31,246-73,420 t,395 Pilgrim Massachusetts Bay 670 20.3 Evans (1978) 1974-94 20,029' i15 1,143-87,752' 55 Brayton Point 1-3 Mount ilope Bay 1,150 39.0 Anderson (1995) 1972-92 54,433 136 15,957-359,394 Brayton Point 4 118 Mill (1993)

Mount Ilope Bay 460 16.4 1984-85 - -

1,479-18,095 -

1.MS (1987)

Millstone 2 Long island Sound 870 34.6 1976-87 25,927' 59 8,560-60,410' 71 NUSCO (19881 65,927' 214 8,560-511,387* I8I y

• Impingement counts prior to October 1994 were underestimated.

Collected in sampling only, not a calculated estimate (11.8% of the total days were sampled).

• Estimates adjusted assuming 100% station operation.

' Excluding an estimated 480,000 American sand lance taken on July 18,1984.

• Including the sand lance mass impingement episode.

i 5

i Table 11. Actual (199195; NAl 1996) and predicted (based on data from 1973-76; NAl 1977) entrainment of selected fish eggs and larvae at Seabrook Station with a comparison between peak monthly densities for 197 76 and actual mean densities for the same months in 1991-95.

Number entrained (in millions) Peak density (n 1000m)

Species 1991 1992 1993 1994 1995 Predicted 1973-76 1991-95 h 3" Atlantic menhaden 0.5 1.4 0.1 0.0 0.2 133.0 1,900 16 Pollock 0.0 0.1 0.0 0.0 0.4 133.0 780 5 Atlantic mackerel 673.1 456.3 112.9 0,0 74.5 2,665.0 37,600 12,500 Larvae:

Atlantic menhaden 0.0 0.0 0.0 0.0 0.0 165.5 2,170 0.0 Rainbow smelt 0.0 0.1 0.0 0.0 0.0 5.5 60 0.5 Pollock 0.0 0.1 0.0 0.0 0.0 62.0 500 4.8 Atlantic mackerel 4.7 0.0 0.0 0.0 0.0 1,130.0 15,500 247.2 Winter flounder 9.0 6.2 2.9 0.0 8.0 79.0 610 80.7 e

33

Table 12. Entrainment and impingement of selected fishes at Seabrook Station as a percentage of the es totals collected and the predominant sampling programs in which a species was collected.

% of Total Eggs  % of Total Larvae % of Total Fish Collected in Collected in Collected in Entrainment Entrainment Impingment Species Predominant Fish Samples Samples Samples Sampling Program Presentiv Selected:

Atlantic herring .

3 -

IP', Gill Net Rainbow smelt - - -

Trawl, Seine Atlantic cod 6?' - -

IP, Trawl 6

Pollock 67 .

7 IP, Gill Net Hakes 6 -

14 IP, Trawl Atlantic silverside - -

20 Seine Cunner 37 9 -

IP Am. sand lance -

14 7 IP Atlantic mackerel 43 - -

IP, Gill Net Winter flounder -

4 7 IP, Trawl, Seine Yellowtail flounder - -

3 IP, Trawl Potentiallv Selected:

Atlantic snailfish -

23 -

Rock gunnel -

20 $

Grubby -

11 14 IP = ichthyoplankton sampling.

Eggs not differentiated between Atlantic cod or pollock.

l l

t i

34

. J

N RYWDGE o

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CONTOUR DEPTH IN METERS -

?

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HAMPTON i. to BEACH s'

\

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intake,,,

g S .:

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• • , T1 SAUSBURY BEACH , '\

I LEGEND P = Ichthyoplankton Tows T = Otter Trawls G = Gillnets E S = Seine Hauls Figure 1. Ichthyoplankton and juvenile and adult fish sampling stations near Seabrook Station (from NAI 1996).

35

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l JANj FEBl M ARl APRj M AYl JUN : JUL j AUGl SEPJ OCT, NOVj DEC MONTH Figure 2. Dendogram and temporal / spatial occurrence pattern of fish egg assemblages formed by numerical classification ofichthyoplankton samples (monddy means of log [X+1] transformed number per 1000 m') at Seabrook Station nearfield (P2 and PS) and farfield (P7) stations from Ady 1986 through December 1995 (from NAl 1996).

36

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P1 x x x x x x ,*: : : : : : :_,~. ,

JANj FEB j MARj APRl MAY) JUN JULl AUGl SEPj OCTJ NOVl DEC MONTH Figure 3. Dendogramn a' d temporal / spatial occmrence pattem of fish larvae assemblages formed by numeric classification ofichthyoplankton samples (monthly means of log [X+1] transformed number per 1000 m') at Seabrook Station nearfield (P2 and PS) and farfield (P7) stations from July 1986 through December 1995 (from NAI 1996) 37

i l

1-i 1 l

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,o' O.1 I i i i a i i i i 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Error MS for 3 Stations Figure 4. Comparison of the error mean squares (MS) for the nine selected larval flsh taxa from two analysis of variance (ANOVA). One was based on data collected at all three ichthyoplankton stations and represents a slopethe other of 1. on data collected at two of the stations (P2 and P7). The dashed i

38 l

l

o- s MARINE MACROBENTHOS Summary of Proposed Monitoring Program After 5 Years of Plant Operation The objective of the marine macrobenthos program after 5 years of plant operation is to monitor those habitats most likely to reflect effects of potentir.1 impacts from Seabrook Station (thermal plume effects and increased turbidity / sedimentation). While little or no evidence ofimpacts has been detected to date, this habitat merits continued monitoring at this time, given its ecological importance and the long-term cyclic nature of the benthic communities.

l 1,

Focus will be on station pairs with nearfield stations closest to the source ofimpacts (Seabrook discharge), and with longest existing preoperational/ operational period time-series. These stations are most likely to reflect impacts, if they occur.

B17/B35 - Shallow subtidal zone is hard benthos habitat, most susceptible to thermal plume exposure, although no impacts have been shown after 5 years of plant operation.

B19/B31 - Mid-depth zone would be most susceptible to potentially increased turbidity / sedimentation from the discharge, although no impacts have been demonstrated to date. I

2. Sampling design and data analyses for these sites would remain almost identical to previous years, maintaining the historic time-series:

. Destructive sampling

. Non-destructive transects

. General algae Bottom panels (with new wooden panel attached); subsampling of panel would provide replication.

Study sample collection / processing for " incidental" parameters not analyzed -

report would not be conducted (e.g., spirorbids, colonials, annual bottom panels).

Analysis oflong-term trends for selected parameters will be evaluated.

3. Proposed stations:

e are most likely to be impacted (shallow subtidal/ sunk rocks and mid-depth);

e are historically most intensively studied (sampled 3X per year and include non-destmetive study);

have a more extensive habitat (compared to intertidal stations) that is less vulnerable to impacts associated with destructive sampling.

MARINE MACROBENTIIOS PROPOSED PROGRAM PAST PROGRAM

1) Destinctive Sampling

. Stations / Sampling frequency: B17/B35 (Shallow subtidal), B19/31 . Stations / Sampling frequency: BIMLW/B5MLW (Intertidal), Bl?/B35 (Mid-depth) sampled 3X per year (Shallow subtidal), B19/3 I (Mid-depth) sampled 3X per year, B04/B34/B13 (Deep) and B16 (Mid-depth) sampled IX per year e Replicates: 5 = Replicates: 5

. Total sampics/ycar: 60

• Total samples / year: 110 e Data collected: Biomass and Density (total and for dominant taxa), No. . Data collected: Biomass and Density (total and for dominant taxa), No.

oftaxa of taxa, Spirorbid counts, length and/or reproductive status of some dominant fauna, colonial abundance

2) Non-Destructive Sampling

. Stations / San ; Jing "- t:uency: B17/B35 and B19/31 (Shallow subtidal . Stations / Sampling frequency: Bl/B5 (intertidal quads and transects),

and mid-depth) 3X per yeu B17/B35 and B19/31 (Shallow subtidal and mid-depth) 3X per year

. Replicates: Subtidal transects-6 = Replicates: Intertidal quads 4 (2 each in 3 zones), Intertidal transects-3.

Subtidal transects-6 ,

. Total sampki/ year. 72

• Total sampics/ year: 126 ,

i

. Data collected: % frequency of understory subtidal reds, kelp, urchin and .

Data collected: % frequency / cover ofintertidal dominants: % frequency Afodiolus counts

• of understory subtidal reds, kelp, urchin and Afodio/ux counts  ;

t I

t

[

MARINE MACROBENTHOS (continned)

PROPOSED PROGRAM PAST PROGRAM >

3) General Algae -

i e Stations / sampling frequency: B17/B35 (Shallow subtidal), B19/31 . Stations / Sampling frequency: BlMLW/B5MLW tidepools, (Mid-depth) sampled 3X per year BIMSL/B5MSL tidepools, BIMLW/B5MLW, BIMSUB5MSL (Intertidal), B17/B35 (Shallow subtidal), B19/31 (Mid-depth) sampled 3X per year; B04/B34/B13 (Deep) and B16 (Mid-depth) sampled IX per year

• Replicates: I

• Replicates: 1

. Total samples / year: 12

• Total samples / year: 40

= Data coIIccted: presence / absence of algal taxa e Data collected: presence / absence of algal taxa

4) Bottom Pancis l'

. Stations / Sampling frequency: B19/31 (Mid-depth) triannual pancis .

Stations / Sampling frequency: B19/31 (Mid-depth), B04/B34(Deep);

3X/ year triannual pancis 3X/ year, annual panels IX per year e Replicates: 1 (4 subsamples) = Replicates: 1

. Total samples / year: 24

• Total samples / year: 28 ,

e Data collected: counts of selected dominant taxa, Teredo sp. counts in . Data collected: counts of selected dominant taxa attached wooden panel t

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . _ _ _ _ _ _ _ _ _ _ _ - _ _ . _ _ . _ _________.______._.________._______.____.m.____ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _

. i i

i N

RYELEDGE IB5MLW '

[B5MSL

.4B31l' o

y LITTLE

\ FARFiELD ' \.

BOARS ' AREA- - ., ,

HEAD (g35l l

0 .5 1 Nautical Mile /.. . 1834 i n

. .  ; f' .-

0 1 2 Kilometers /

SCALE ... i l CONTOUR DEPTH 1)?' -

IN METERS

, i."'

GREATBOARS l -

i HEAD  ?

t ,. ,

1 HAMPTON  ! j'! y \

- BEACH '

BROWNS -

~

! i ~

RIVER t' IntaNe *.iB16 llB13 l

< . '/~ NEARFIELD g ..

,OUTEW.1B1MLw 1 pg  ; AREA SEABROOK Ov .- B1ust,'B19 h./

STATION ': "i p i fy ...

DisehargeT HAMPTON .<' I B 0" l SEABROOK SUNK i HARBOR ROCKS ll 2

\% SEABROOK ,' . l'

. \

.~

l' ' \

BEACH U

,  %, j  ! ' .:..

y7 t

, , .m

) '

i i, [

sal 2SBURYBEACH \

i i i LEGEND I I = benthic samples Fig.1. Marine macrobenthos sampling stations. From NAI (1996).

. /

l i

WORKING DRAFT EVALUATION OF SEABROOK STATION MARINE MACROBENTHOS PROGRAM -

AFTER FIVE YEARS OF PLANT OPERATION Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station i

Seabrook, New Hampshire 03874 i Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 Reviewed and endorsed by NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford,New Hampshire 03310 August 1996

. .~ l l

l l

Evaluation of Seabrook Station Marine Macrobenthos '

Program After Five Years of Plant Operation  !

1 Introduction ne benthic habitat near Seabrook Station intake and discharge structures is primarily bedrock ledge and boulders. These rock substrata, as with similar habitats in the GulfofMaine and other northem temperate coastal areas, support rich and diverse communities of attached plants and animals (macrobenthos), which are important and integral parts of coastal ecosystems. One of l

the most obvious and productive features of the shore and near-shore biota in the Gulf of Maine is an extensive canopy of brown macroalgae, e.g., rockweeds (fuccids) intertidally (Menge 1976; Topinka et al.1981; Keser and Larson 1984), and kelps subtidally (Sebens 1986; Witman 1987). Generally, several understory layers occur beneath these canopies, and are extprised of secondary levels of foliose and filamentous algae and upright attached macroinvertebrates over a layer of enemsting algal and faunal species, which occupy much of the remaining primary rock surfaces (Menge 1976; Sebens 1985; Ojeda and

Dearborn 1989). Also,

many of the niches created in and around this attached biota are occupied by mobile predator and herbivore species 1

such as fish, snails, sea urchins, starfish, and amphipods (Menge 1979,1983; Ojeda and l Dearborn 1991).

Because these coastal hard-bottom communities are ecologically important, are well documented as effective integrators of environmental conditions, and are potentially vulnerable to localized coastal anthropogenic impacts, studies of these communities have been and continue to be part of ecological monitoring programs associated with coastal nuclear power plants (Vadas et al.1976; Wilce et al.1978; Osman et al.1981; Schroeter et al.1993; BECO 1994; NUSCO 1996a). Seabrook Station marine macrobenthos studies were initiated in 1975 with the objective to determine whether differences that exist among benthic communities at sites in the Hampton-Seabrook area can be attributed to power plant constmetion and operation. One potential impact on the local macrobenthos from Seabrook Station operation is temperature-1

, 4

~

related community alteration to areas directly exposed to the discharge thermal plume. Habitats in the upper portion of the water column (i.e., intertidal and shallow subtidal zones) are most s, susceptible to this impact. Thermal impacts are unlikely in deeper areas; however, increased e

turbidity in discharge water resulting from transport of suspended solids and entrained organisms could occur, increasing sedimentation rates and decreasing light transmission.

The purpose of this report is to evaluate the current marine macrobenthos program after over 20 years of monitoring that include, depending on the study, five or six years of Seabrook Station operation. This evaluation will first summarize what impacts to the local marine macrobenthos have been detected since the start-up of Seabrook Station in 1990. Second, based on this i assessment, recommendations will be made for a monitoring program more focused on indicators (e.g., community parameters and dominant taxa population characteristics) and locations (nearfield/farfield) that have revealed impacts or have indicated that the potential for impact still exists.

Review of Current Methodology l

1 Quantitative (destructive) macrofaunal and macroalgal samples were collected three times a year at six benthic stations (Fig.1); three nearfield-farfield station pairs were established at lower i

intertidal (B 1MLW, B5MLW), shallow subtidal (4-5 m; B17, B35) and mid-depth (9-12 m; B19, B31) locations. Four additional stations were sampled in August only: one mid-depth intake station (B16) and three deep water (18-21 m) stations (nearfield-B13 and B04, and farfield-B34). Epifauna and epiflora were removed by scraping from five randomly selected 2

0.0625 m areas on horizontal rock surfaces.

Algal species from each sample were identified to the lowest practical taxon, dried and weighed.

All faunal species collected in August samples were identified to the lowest possible taxon and enumerated. Only fauna previously designated as selected species were identified and counted from May and November macrofaunal samples. In addition, abundance ofspirorbid polychaetes 2

- _ =

1 l

at subtidal Stations B19 and B31 was estimated from five subsamples of the algal complex Phyllophora/Coccotylus spp. Also, life history information (length measurement, and sex and reproductive status determination) was obtained for nine macrofaunal taxa at paired nearfield-farfield stations where they were most abundant in destructive samples.

A comprehensive collection of all visible algal species (" general algae") was ma_de in conjunction with destmetive sampling at each sampling station. In addition, collections were i

taken from the mean low water and mean sea level areas (including tide pools) in the intertidal zone.

Macroalgae from general collections were identified to the lowest practical taxon. The i

complete macroalgal species list was compiled from both general and destructive collections and included crustose coralline algae, collected only in August.

Beginning in 1982, two intertidal stations (BlMSL and B5MSL; Fig.1) were evaluated i

nondestructively during April, July and December. Observations were made at permanently 2

marked 0.25 m quadrats at three intertidal levels. Percent cover offuccid algae and percent ,

frequency ofoccurrence for other algae and fauna from an established species list were l estimated and recorded. Frequency of occurrence of fuccid algae was also recorded along a 9.5 m transect line.

Subtidal transects were established in 1978 to monitor larger macroinvertebrates and macroalgae that were not adequately represented in destructive samples. Six randomly placed replicate 1 m x 7 m band-transects were surveyed at nearfield-farfield station pairs in the shallow subtidal (B17, B35) and mid-depth (B19, B31) zones in April, July and October. Percent frequency of occurrence was recorded for dominaat "understory" macroalgae , as well as counts ofModiolus modiolus, Strongylocentotus droebachiensis and all kelp species.

Information on pattems ofreemitment and settlement of sessile benthic organisms was obtained from the bottom panels program. Bluestone panels (60 cm x 60 cm) were placed 0.5 m off the bottom at Stations B19 and B31, beginning in 1982. Short-term bottom panels were exposed for four months during three exposure periods: December-April, April-August, and August-3

s i

l December. Long-term bottom panels were exposed for one year, deployed in August and  !

collected in August of the following year. All undisturbed bottom panel faces were first analyzed for Balanus spp. and Spirorbidae, and then scraped to remove sessile bivalves and solitary chordates for identification and enumeration. Hydrozoa, Bryozoa and any abundant  !

algal species were analyzed only on long-term panels.  :

1

~

i Macroalgal and macrofaunal data analyses included analysis of variance (ANOVA) and numerical classification analysis. A fixed-effects ANOVA model was used to test the null hypothesis that spatial and temporal differences in specific parameters were not significant. The data collected for the ANOVAs met the criteria of a Before-After/ Control-Impact (BACI)  ;

i sampling design discussed by Stewart-Oaten et al. (1986), where sampling was conducted prio to and during plant operation, and sampling locations included both potentially impacted and non-impacted sites. The main effects were period (Preop-Op) and station (Station); the interaction term (Preop-Op X Station) was also included in the model. Further details on the i

ANOVA model are provided in NAI (1996). A comparison of macroalgal and macrofaunal community composition during operational and preoperational periods was carried out using numerical classification methods (Boesch 1977). Bray-Curtis similarity indices were computed for the annual August log-transformed average densities (macrofauna) and square-root transformed average biomass (macroalgae). The group average method method (Boesch 1977) was used to classify the station-year collections into groups or clusters.

I Summary of Monitoring Results After 5 Years of Plant Operation A considerable physical and biological database has been established during the over 20 years of i

study to characterize natural variability in the benthic community, and during the operational j period, to assess the extent to which Seabrook Station operation may have affected the local marine macrobenthos. The type ofimpact a community is vulnerable to is dependent upon its j t

relative position in the water column (i.e., temperature effects for shallow water sites, turbidity effects at deeper water sites); potential impacts associated with construction and operation of 4

Seabrook Station on communities in each of these depth zones will be examined separately discussed below.

Thermal Plume Effects.

Nearfield sampling sites used for the Seabrook intertidal and shallow subtidal macrobenthos studies were selected because they occur within, and best represent, the shallow water communities that are most susceptible to incursion by the Seabrook Station discharge thermal plume. Hydrodynamic modeling, conducted prior to plant start-up to predict the areal extent of

{

l the thermal plume under various meteorological and current regimes, indicated that thermal I incursion to these sites would be minimal, with temperature increases of <1 C (Teyssandier et al.1974). Subsequent field studies, conducted after Seabrook began commercial operation, verified these predictions by measuring no temperature increases at the intertidal sampling si i and increases of <1'C at the shallow subtidal site (Padmanabhan and Hecker 1 The results from marine macrobenthos studies at study sites potentially exposed to the thermal plume after 5 years of Seabrook operation are consistent with the physical assessment of environmental conditions at these sites from hydrothermal studies. Specifically, there is no evidence that intertidal and shallow subtidal benthic communities nearest to the discharge have been affected by the Seabrook thermal plume. In the intenidal and shallow subtidal depth zones, nearfield/farfield differences that were not consistent between preoperational and operational periods (resulting in significant Preop-Op X Station interaction in the ANOVA model) were noted for several community parameters (Table 1) and selected benthic taxa (Table 2).

However, in nearly all cases, further examination and analysis of these parameters indicated that the changes observed were not consistent with a power plant impact (NAI 1996). This cc lusion was also supported by numerical classification analyses, which revealed no changes to macroalgal or macrofaunal communities in the nearfield intertidal and shallow subtidal areas after the start-up of Seabrook Station. One trend that has been monitoried closely during the operational period is the apparent decline in abundance of the kelp Laminaria digitata in the nearfield shallow subtidal area (Fig. 2). Densities began to decline at nearfield B17 in 1990, and this trend continued through 1992, while no change in abundance was observed at the farfield 5

i 1

. station (B35). The difference in abundance between nearfield and farfield stadons has l decreased since that time, with little difference noted in 1995, so factors other than power I

impact may be responsible for this change.

I I

Thermal impacts are well-documented for intertidal and shallow subtidal communities dur monitoring studies for coastal nuclear power plants elsewhere in New England t and include t

elimination or reduced abundance of cold-water species, and increased abundance of warm-i water tolerant and/or opportunistic species, leading to the development of communities distinct i

from those seen prior to thennal incursion and from those on nearby unaffected coasts (Vadl al.1976; Wilce et al.1976; BECO 1994; NUSCO 1996a). For each of these studies, temperature increases on the order of>5 C were required to bring about detectable commun

)_ change, and therefore, impacts were restricted to those communities in the immediate v a

a the discharge (typically within a few hundred meters). Furthermore, these thermal impacts s

nearby communities were observed shortly after (within months) thermal plume incursion i began. No similar community changes have been observed for macrobenthos communities nearest the Seabrook discharge after 5 years ofplant operation, and with maximum temperature increases at the nearest hard benthos communities from the Seabrook thermal plume of <1"C,

[ such changes are highly unlikely .

4 Turbidity / Sedimentation Effects.

?

i Another possible impact resulting from coastal nuclear power plants is related more to altered j j

water circulation patterns than to thermal incursion. Specifically, the introduction (discharge) of l turbid water to an area of historically lower levels of turbidity can decrease light penetration and increase sedimentation rates. Possible sources of this turbidity include suspended inorganic and organic particles ifintakes are located in more turbid waters, and potendally, increased detrital deposition resulting from settlement of entrained organisms. Nearfield mid-depth and deep study sites represent macrobenthic communities in closest proximity to the Seabrook Station discharge, and are therefore potentially most susceptable to these types ofimpact. Higher sedimentation rates (and impacts to nearby macrobenthic communities) associated with a thermal effluent have been documented for a nuclear power plant in California (Osman et al.

6

1981; Schroeter et al.1993), with the major source of turbidity being fine inorganic sediments transported from inshore waters where intakes for the plant were located. The organic component of these sediments contributed little to the overall flux of sediments, and organic enrichment was not observed at sites near the discharge.

The Seabrook intake is located about one mile offshore,5 meters above the seafloor, and thus draws in relatively low turbidity water, similar to that near the discharge. Therefore, transpo fme inorganic particles is unlikely and any increase in sedimentation would be the result of settlement of organic material from entrained organisms. However, plankton densities are generally lower in deeper offshore waters, such as those near the intake structure, compared to densities in more productive inshore waters. Thus, it is unlikely that any increased organic loading to benthic habitats near the Seabrook discharge is occurring.

l Similarly, results of marine macrobenthos monitoring at deeper water sites near the discharge reveal little change that would indicate an increase in turbidity or sedimentation in the nearfield area. Numerical classification analysis for macroalgae and macrofauna both indicated no nearfield-farfield or temporal changes have resulted from the operation of Seabrook Station.

Similarly, bottom panel studies demonstrated no changes to settlement and early development of dominant benthic taxa populations after the plant began operation. Significant interactions terms based on ANOVA were noted for six of the seventeen community and selected taxa parameters monitored for mid-depth and deep communities (Tables 3 and 4). However, as was the case with stations monitored for thermal plume effects, further examination and analysis revealed that most of the observed differences responsible for the significant interaction terms were not consistent with a power plant impact. A similar operational period nearfield area decline of the kelp Laminaria digitata noted in the shallow subtidal zone was also apparent in the mid-depth zone. Specifically, nearfield abundances ofL. digitata (Fig. 3) have declined during the operational period, relative to those at the farfield station. L digitata abundunce has also declined at the farfield station in recent years. While the mechanisms causing these declines are unclear, monitoring of nearfleid kelp communities should continue given that some of the observed declines coincided with Seabrook start-up.

7

Documented turbidity effects detrimental to macrobenthic plants and animals include shading or burial, and an increased community dominance by suspension-feeding organisms and organisms more tolerant of higher sedimentation rates (Hiscock and Mitchell 1980; Osman et al.1981; NUSCO 1988; Schroeter et al.1993). In the vicintiy of Seabrook Station discharge, no evidence of community change has been noted for nearfield macrobenthic communities after 5 years of plant operation.

Recommendations Over 20 years of marine macrobenthos studies, including five full years during Seabrook operation, have provided the long-term database which has documented that balanced indigenous macrobenthic communities continue to occupy intertidal and subtidal rocly habitats l

in the vicinity of the Seabrook discharge, with little change beyond that expected from natural variability. A nearfield area change (e.g., decline in Laminaria digitata abundance) has coincided with plant start-up and continues to be apparent through 1995. However, there was no evidence for thermal impacts or impacts associated with increased organic loading on the local macrobenthos since the start-up of Seabrook Station in 1990.

i While no impacts to macrobenthos from Seabrook have been detected after 5 years ofplant operation, this habitat merits some continued monitoring at this time given the documented long-term cyclical nature ofmany benthic species (Hiscock and Mitchell 1980; Witman 1985, 1987; Johnson and Mann 1988; Einer and Vadas 1990) and its overall importance to the local coastal ecosystem. However, the scope of the study should be focused on station pairs with nearfield sites nearest to the source of potential impacts (Seabrook discharge), and on study parameters that have proven useful for impact assessment historically at Seabrook and in studies at other power plants.

8

Proposed Sampling Stations The proposed sampling stations for continued monitoring ofmarine macrobenthos for Seabrook Station thermal plume effects are the shallow subtidal nearfield/farfield pair B17/B35 (Fig.1).

Hydrodynamic modeling and thermal plume studies all indicate that the shallow subtidal zone near the Outer Sunk Rocks would be most susceptible to thermal plume meursion, and that the nearest intertidal zone (nearfield station B1) has been totally unaffected by the th_ermal plume. If impacts from Seabrook's thermal plume were ever to occur, they would be detected at shallow subtidal B17 rather than at any intertidal site. Therefore, continued monitoring at B17/B35 alone would provide the necessary information for assessment ofpotential thermal plume effects. Furthermore, focus on the shallow subtidal zone avoids additional destructive sampling in the intertidal zone, which has decimated much of the habitat at sampling stations.

Although not likely, increased turbidity and sedimentation organic loading still is a potential impact associated with Seabrook's discharge, and would most likely impact deeper subtidal communities nearest to the discharge structures. The mid-depth station pair B19/B31 has the historically monitored nearfield station closest to the discharge (Fig.1), and as with the shallow subtidal stations for thermal plume effects, would more likely reflect impacts from increased turbidity / sedimentation than the more distant deep stations.

Proposed Sampling Methodology 1

Sampling design and data analyses for the proposed sampling sites would remain almost unchanged, allowing continuity with the historical databases. This proposed new study would also allow for improvements to data analyses that would increase their sensitisity to detect power plant impacts.

i The destructive program field sampling and laboratory processing for the four proposed stations would remain almost identical to the current program, and would provide the necessary data to support analyses currently presented in annual environmental reports. Five replicate quadrats would be destructively sampled at each station three times a year (May, August and November) as they have in the past. Laboratory sample processing would be similar to that done in the past, 9

with the following exceptions; spirorbid counts, assessment of colonial macrofauna abundance, and life history studies of dominant macrofauna would no longer be conducted. These aspects of the overall program have either not been used for impact assessment (spirorbids and colonials), or have revealed no impacts to date (life history studies). All necessary data to l

l continue impact assessment with the ANOVA model and numerical classification analysis would be collected in a manner consistent with current practice. Furthermore, samples would be available for life history analysis of colonial identification, should it be necessary.

General algal collections will continue to be conducted concunently with destructive samples (three times per year) at the four proposed sampling stations, as they have in previous years.

The shallow subtidal and mid-depth non-destructive transect study (used to monitor Laminaria i

digitata and other larger subtidal species) would continue unchanged in the proposed study program. Six randomly placed 1 m x 7 m subtidal transects sampled three times a year in April, July and October for the same dominant taxa described above for the current program. l l

\

l Some modifications to the bottom panels program are recommended for the promsed study i

program. Triannual panels would continue to be sampled at the mid-depth station pair. Annual f

environmental reports historically include data collected from these stations. To improve the sensitivity of the program to detect changes, triannual panels would be subsampled to provide four replicates and allow the estimation of variability. Annual panels would no longer be sampled, as data from these panels have not been analyzed or presented in operational monitoring reports.

Another enhancement to this study would be the addition of a wooden panel, attached to each bottom panel, to monitor marine woodborers. Teredo sp. individuals were collected on surface ,

wooden panels in 1995 for the first time in many years. The overall proposed monitoring program after 5 years of Seabrook operation does not include a surface panels study (see l

NUSCO 1996b); monitoring of woodborer occurrence in nearfield and farfield areas following this recent event would be continued as part of the bottom panels program. This change in 10

. : i methodology would actually improve our ability to monitor Teredo sp., because larval settlement is much higher in near-bottom waters than near the surface (Grave 1928; Scheltema l, and Truitt 1956; NUSCO 1996c).

t Data Analysis Data collected under the proposed monitoring program will be consistent with all critical time-series currently used for impact assessment, and therefore amenable to all analyses presently used (e.g., ANOVA, numerical classification). Improvement of analyses would continue, however, based always on appropriate proven methodology described in the scientific literature.

Refocusing effort to sites closest to the discharge would improve the sensitivity of the program i to detect impact. For example, many ANOVAs for the mid-depth station group include a nearfield (but distant) intake station (B 16), which, after 5 years of operational studies, clearly shows no evidence for impact. ANOVAs on data from only the proposed nearfield/farfield pair (B19/B31) would improve the sensitivity of tests to detect impact because the statistical evidence would not be " diluted" by data collected at sites such as B16 where no impact is expected.

Numerical classification analysis would continue to compare macroalgal and macrofatmal communities at the proposed four sampling stations, and would simplify a more detailed comparison ofindividual station / year collections. To demonstrate this, clustering dendrograms base on annual macroalgal (Fig. 4) and macrofaunal (Fig. 5) collections were generated using the same analytical technigve discussed above for the current program, but for only the four proposed sampling stations. Conclusions from these analyses are entirely consistent with those drawn from analyses using all stations under the current program presented in NAI (1996).

Namely, annual collections (for both macroalgae and macrofauna) made at stations located in the same depth strata (i.e., shallow subtidal, mid-depth, etc.) formed distinct groupings. Within those groupings, collections made during operational years (1990-1995) at each station often grouped closely with collections made during preoperational years, with no separation of preoperational and operational periods. These analyses indicate that no spatial (nearfield-11

1 h.

farfield) or temporal (preoperational period-operational period) changes to macroalgal and m

macrofaunal communities have resulted from Seabrook Station operation.

P. l

)

Conclusions The proposed marine macrobenthos monitoring program after 5 years of Seabrook operation will focus effort on nearfield study sites and their respective farfield counterparts most likely to l reflect power plant impacts. These proposed station pairs (shallow subtidal B17/B35 and mid-depth B19/B31) were selected because they are within benthic habitats closest to the source of impacts from Seabrook station (condenser cooling water discharge). Sampling design and data analyses for these sites would remain almost unchanged, and would maintain the historic time-series used for impact assessment. Suspension of sampling at sites more distant from the

- discharge (intertidal, deep and intake stations) is appropriate because no evidence ofpower plant impact to local macrobenthic communities (related to thermal plume or turbidity / sedimentation) has been detected after 5 years of Seabrook operation, even at the study sites nearest the discharge where continued monitoring is proposed. And the apparent population decline of Laminaria digitata in the nearfield area during the operational period would be closely monitored since the non-destructive subtidal transect study that is used to monitor this species would continue unchanged as part of the proposed monitoring program.

Along with the low potential for impacts, many of the more distant stations have not been as intensively monitored historically; all deep stations and the mid-depth intake station are only destructively sampled one time per year, and are not sampled at all non-destructively.

Furthermore, the less extensive habitat at intertidal stations (compared to deeper habitats) makes them more vulnerable to impacts associated with destructive sampling; evidence of sampling impacts have been noted at Seabrook intertidal sampling sites (NAI 1994).

In conclusion, based on thorough evaluation, the proposed marine macrobentbos program after 5 years of Seabrook operation is expected to continue to characterize the communities of attached

)

12 L

i t ,

plants and animals in the vicinity of Seabrook Station, and to detect impacts to these I

communities,if they occur. '

References Cited 1

l

~

' BECO (Boston Edison Company).1994. Benthic Algal Monitoring at the Pilgrim Nuclear l

Power Station. Pages 1-23 in Marine ecology studies related to operation ofPilgrim Station.

Semi-Ann. Rep. No. 43.  !

i Boesch, D.F.1977. Application ofnumerical classification in ecological investigations of water i pollution. U.S. Emironmental Protection Agency, Ecological Research Report Agency, Ecol. Res. Rep. I14 pp.

i Einer, R.W., and R. L. Vadas. 1990. Inference in ecology: the sea urchin phenomenon in the 1

. northwestern Atlantic. Am. Nat. 136:108-125.

r '

Grave, B.H. 1928. Natural history of the shipwonn Teredo navalis, at Woods Hole Massachusetts. Biol. Bull. 55:260-282.

I Hiscock, K., and R. Mitchell. 1980. The_ description and classification of sublittoral epibenthic ecosystems. Pages 323-370 in J.H. Price, D.E.G. Irvine and W.F. Famham (eds.) The Shore Environment, Vol. 2: Ecosystems. Academic Press, London and New York. 945 pp.

Johnson, C.R., and K.H. Mann. 1988. Diversity, pattems of adaptation, and stability of Nova Scotian kelp beds. Ecol. Monogr. 58:129-154.

Keser, M., and B.R. Larson. 1984. Colonization and growth dynamics of three species of Fucus. Mar. Ecol. Prog. Ser. 15:125-134.

Menge, B.A. 1976. Organization of the New England rocky intertidal community: role of predation, competition, and environmental heterogeneity. Ecol. Monogr. 46:355-393.

.1979. Coexistence between the seastars Asterias vulgaris and A.forbesiiin a

_ heterogeneous environment: a non-equilibrium explanation. Oecologia 41:245-272.

. 1983. Components of predation intensity in the low zone of the New England rocky intertidal region. Oecologia 58:141-155.

Normandeau Associates,In'c. (NAI).1994. Evaluation of Seabrook Station marine intertidal

! destructive program Prepared for North Atlantic Energy Services Corp.10 pp.

t l

13

1 l

l j

NAI.1996. Marine macrobenthos studies, Section 6 in Seabrook Environmental Studies,1995.

A characterization of environmental conditions in the Hampton-Seabrook area during the operation ofSeabrook Station.

NUSCO (Northeast Utilities Service Company).1988. Benthic Infauna. Pages58-117 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut. Three-unit operational studies 1986-1987.

.1996a. Rocky Intertidal Studies. Pages 39-66 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut. Ann. Rep.,1995.

. 1996b. Evaluation of Seabrook Station surface panels program after 5 years of plant operation. Prepared for North Atlantic Energy Services Corp.19 pp.  !

.1996c. Marine Woodborer Studies. Pages 35-38 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut. Ann. Rep.,1995.

Ojeda, F.P., and J.H. Dearborn. 1989. Community structure of macroinvertebrates inhabiting the rocky subtidal zone in the Gulf of Maine: seasonal and bathymetric distribution. Mar.

Ecol. Preg. Ser. 57:147-161.

. 1991. Feeding ecology of benthic mobile predators: experimental analyses of their influence in rocky subtidal communities of the Gulf of Maine. J. Exp. Mar. Biol. Ecol.

149:13-44.

Osman, R.W., R.W. Day, J.A. Haugsness, J.- Deacon, and C. Mann. 1981. The effects of the l San Onofre Nuclear Generating Station on sessile invertebrate communities inhabiting hard substrata (including experimental panels). Hard Benthos Project, Marine Science Institute, University of Califomia, Santa Barbara. Final Rep., 223 pp.

Padmanabhan, M., and G.E. Hecker. 1991. Comparative evaluation of hydraulic model and field thermal plume data, Seabrook Nuclear Power Station. Alden Research Laboratory, Inc.

12 pp.

Scheltema, R.S., and R.V. Truitt. 1956. The shipworm Teredo navalis in Maryland coastal

. waters. Ecology 37:841-843.

Schroeter, S.C., J.D. Dixon, J Kastendiek, and R.O. Smith. 1993. Detecting the ecological effects of environmental impacts: a case study of kelp forest invertebrates. Ecol. Appl.

3:331-350.

Sebens, K.P.1985. The ecology of the rocky subtidal zone. Am. Sci. 73:548-557.

14

i 1

l

. 986 Community ecology of vertical walls in the Gulf of Maine. USA: small scale processes and altemative community states. Pages 346-371 in P.G. Moore and R. Seed  ;

(eds.). 'Ihe Ecology of Rocky Coasts. Columbia Univ. Press, New York.

Stewart-Oaten, A., W.M. Murdoch, and K.R. Parker. 1986. Environmental impact assessment:

"pseudoreplication"in time? Ecology 67:929-940.

l Teyssandier, R.G., W.W. Durgin, and G.E. Hecker. 1974. Hy drothermal studies of diffuser discharge in the coastal environment: Seabrook Station. Aiden Research Laboratory Rep.

No.86-124.

Topinka, J., L. Tucker, and W. Korjeff. 1981. The distribution of fuccid macroalgal biomass along the central coast ofMaine. Bot. Mar. 24:311-319.

Vadas, R.L., M. Keser, and P.C. Rusanowski. 1976. Influence of thermal loading on the  ;

ecology of intertidal algae. Pages 202-251 in G.W. Esch and R.W. MacFarlane (eds.)

Themial Ecology II. ERDA Symp. Ser., Augusta GA.

Wilee, R.T., J. Foerich, W. Grocki, J. Kilar, H. Levine, and J. Wilce. 1978. Flora: Marine Algal Studies. Pages 307-656 in Benthic Studies in the Vicinity ofPilgrim Nuclear Power Station, 1969-1977. Sum. Rep. Boston Edison Co.

Witman, J.D.1985. Refuges, biological disturbance, and rocky subtidal community stmeture inNewEngland. Ecol. Monogr. 55:421-445.

.1987. Subtidal coexistence: storms, grazmg, mutualism, and the zonation of kelps and mussels. Ecol. Monogr. 55:421-445.

15

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16

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' (1991 1995) periods for the signific mt interaction term (Preop-Op X Station) of the ANOVAmodel(data between the two dashed lines excluded from the ANOVA model). From NAI (1996).

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7s 7s so si as as a4 as as s7 as se so et s2 sa M 85 YsAR Fig. 3. Comparison between stations of mean number of holdfasts /100m of the kelp Laminarin  ;

digitata in the mid-depth subtidal zone during the preoperational (1982 1989) and operational (1991-1995) periods for the significant interaction term (Preop-Op X Station) of the ANOVA i model (data between the two dashed lines excluded from the ANOVA model). From NAl (1996).

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TABLE 1.

SUMMARY

OF EVALUATION OF POTENTIAL TilERMAL PLUME EFFECTS ON BENTHIC COMMUNITIES IN VICINITY OF SEABROOK STATION. FROM NAI (1996).

OPERATIONAL NEARFIELD-FARFIELD PERIOD SIMILAR DIFFERENCES AREA /DEPTil TO PREVIOUS COMMUNITY ZONE CONSISTENT WITH PARAMETER" YEARS?

6 PREVIOUS YEARS?'

Macroalgae Intertidal No. of taxa No NF: Op< Preop FF: Op<< Preop Total biomass No . NF: Op< Preop FF; Op= Preop Community structure Yes Yes Shallow No. of taxa Yes Yes subtidal Total biomass ,

Yes Yes Community structure Yes Yes Macrofauna Intertidal No. of taxa No NF; Op<< Preop FF: Op< Preop Total densia Yes Yes Community structure Yes Yes Shallow No. of taxa No subtidal NF: Op> Preop FF: Op= Preop Total density Yes Yes s Community structure Yes Yes

' Abundance, no. of taxa, biomass, total density, evaluated using ANOVA; commumty stnicture evaluated using nu classification by year and station.

6 Operational period = 1990-1995 (August only)

'NF = nearfield, FF = farfield TABLE 2.

SUMMARY

OF EVALUATION OF POTENTIAL THERMAL PLUME EFFECTS ON REPRESENTATIVE IMPORTANT BENTHIC TAXA IN VICINITY OF SEABROOK STATION. FROM NAI 0996).

OPERATIONAL NEARFIELD-FARFIELD )

PERIOD SIMILAR DIFFERENCES AREA / DEPTH TO PREVIOUS COMMUNITY CONSISTENT WITH ZONE SELECTED TAXON - YEARS?'

PREVIOUS YEARS?6 Macroalgae Intertidal Chondnis crispus Yes NF: Op< Preop FF Op= Preop Ascophyllum nodosum Yes NY: Op> Preop FF: Op= Preop Fucus vesicsdosus No NF: Op<< Preop FF; Op< Preop Fucus spp. (juveniles) No Yes Shallow Subtidal Chondnes crispu, Yes Yes l Laminada saccharina Yes Yes fxminada digitata No NY: Op< Preop FF: Op= Preop Macrofauna Intertidal Ampithoe rubdcato No l NF: Op= Preop FF: Op> Preop Nucella lapilhos Yes Yes i

Mytilidae Yes Yes Shallow Subtidal Jassa mannorara Yes Yes Asteriidae Yes Yes

Mytilidae Yes Yes 6' Conclusions denved from ANOVA.

NF = nearfield, FF = farfield.

21

- - 3 {

i h

e g TABLE 3.

p

SUMMARY

OF EVALUATION OF POTENTIAL TURBIDITY EFFECTS ON Tile

'n BALANCED INDIGENOUS BENTillC COMMUNITIES IN VICINITY OF L

SEABROOK STATION. FROM NAI(1996).

OPERATIONAL NEARFIELD-FARFIELD b

i-PERIOD SIMILAR DIFFERENCES AREAIDEPTil TO PREVIOUS y COMMUNITY ZONE CONSISTENT WITil 4 PARAMETER" YEARS?" PREVIOUS YEARS?'

Macroalgae Mid-depth No. of taxa Yes B16: Op> Preop B19: Op< Preop B31: Op= Preop Total biomass No -

Yes i Community structure Yes yes

). Deep No. of taxa Yes Yes Total biomass No Yes 2

Community structure Yes Yes Macrofauna Mid-depth No. of taxa Yes

{;- F Total density No Yes B16: Op< Preop j ;l Community structure Yes B19, B31: Op= Preop Yes 4

Deep No. of taxa l Yes Yes  !

Total density No B04: Op= Preop B13: Op> Preop i B34: Op= Preop j 1

Community saucture Yes Yes j ' Abundance, no. of taxa, biomass, total density, evaluated using ANOVA; conununity structure evaluated using numerical

' classification by year and station.

b

' f O.erational period = 1990-1995 (August only)

W = nearfield; FF = farfield 4

e

[ TABLE 4.

SUMMARY

OF EVALUATION OF POTENTIAL TURBlDITY EFFECTS ON REPRESENTATIVE IMPO!! TANT BENTHIC TAXA IN THE VICINITY OF i SEABROOK STATION. FROM NAI(1996). '

' OPERATIONAL NEARFIELD-FARFIELb PERIOD SIMILAR DIFFERENCES AREA / DEPTH TO PREVIOUS CONSISTENT WITH COMMUNITY ZONE SELECTED TAXON YEARS?' PREVIOUS YEARS?'

Macroalgae Mid-depth Laminaria digitara No NF: Op<< Preop FF: Op< Preop Laminaria saccharina No NF: Op< Preop FF: Op= Preop Macrofauna Mid-depth Pontogencia inermis Yes i Yes Modiolus modiolus Yes Yes Mytilidae Yes Yes i

Strongviocentrotus 4 droebachensis Yes Yes J

' 'Conciusions derived from ANOVA.

• NF = nearfield; FF = farfield 4

1 J

s 22

EPIBENTHIC CRUSTACEA Summary of the Proposed Monitoring Program After 5 Years of Plant Operation l

The objective of the epibenthic crustacea monitoring program is to assess potential entrainment effects on larval crabs and lobsters, and discharge-related effects on juvenile and adult forms. This objective has been successfully met, so the proposed program t would remain essentially the same as in previous years, due to these species' recreational importance and high profile with the public and regulators. Proposed changes ivould still maintain continuity with historically reported data.

1. Adult Lobster / Crab Survey would continue unchanged.

2. Lobster / crab larvae sampling design and data analyses for these sites would remain almost identical to previous years, maintaining the historic time-series presented in  ;

reports:

.. As with other plankton programs, P2 would be sufficient to characterize the nearfield area, with P7 as its farfield counterpart.

The first 4 and last 2 weeks oflobster larvae neuston sampling would be discontinued because of low densities and high variability. Analysis demonstrated improved ability of the proposed program to detect plan:  ;

operationalimpacts. '

Cancer spp. larvae sample replicates would be reduced from 3 to I (through the macrozooplankton program); analysis indicated that the ability to detect impacts is not affected.

j Cancer crabs will be enumerated in impingement samples.

i

{

i l

I

t EPIBENTillC CRUSTACEA PROPOSED PROGRAM PAST PROGRAM

1) Adolf Lobster / Rock Crab (No channes proposed)

• Stations / Sampling frequency: Ll/L7; 3X per mek, Jun.-Nov.

• Stations / Sampling frequency: Ll/L7; 3X per weck, Jun.-Nov.

• Replicates: 1 (30 traps) = Replicates: 1 (30 traps)

• Total samples /ycar: 156 . Total samples / year: 156

. Data collected: Lobster / crab abundance carapace length (mm), sex . Data collected: Lobster / crab abundance, carapace length (1/3'), sex determination determination

3) Lobster Larvae Neuston

. Stations / Sampling frequency: P2/P7; IX per week from mid-Junc . Stations / Sampling frequency: P2, PS and P7; IX per week from mid-through September. May to mid-Oct.

t

. Replicates: I

• Replicates: I e Total sampics/ year: 30

• Total sampics/ year: 63

. Data collected: lobster lans density , = Data collected: lobsterlarvae density

4) Cancer spp. larrac (macrorooplankton sampline)  ;

l

= Stations / Sampling frrquency: Station P2 and P7 sampled twice per . Stations / Sampling frequency: Stations P2, PS, and P7 sampled twice ,

month per month  !

= Replicates: I sampic = Replicates: 4 replicates collected; 3 replicates processed

. Total sampics/ycar: 48

• Total samples /ycar: 288 collected; 216 processed

. Data collected: Density per 1000m' . Data collected: Density per 1000m'

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= Lobsterlarvae(neuston) unumme P = Jonah and rock crab larvae (macrozooplankton)  !

L = Lobster traps (15 traps)

Figure 1. Epibenthic crustacea (American lobster, Jonah and rock crabs) sampling stations. Seabrook Operational Report,1995.

1 WORKING DRAFT l l

I l

1 EVALUATION OF SEABROOK STATION EPIDENTIIIC CRUSTACEAN SAMPLING PROGRAM ~

AFTER FIVE YEARS OF PLANT OPERATION 1

Prepared for NORTH ATLANTIC ENERGY SERVICE CORPORATION P.O. Box 300 Seabrook Station Seabrook, New Hampshire 03874  ;

Prepared by NORTHEAST UTILITIES SERVICE COMPANY Safety, Health & Environmental Services Aquatic Services Branch Waterford, Connecticut 06385-0128 l

Reviewed and endorsed by i NORMANDEAU ASSOCIATES,INC 25 Nashua Road Bedford,NewHampshire 03310 i

August 1996

4 i

Evaluation of Seabrook Station Epibenthic Crustacea Sampling Program After Five Years of Plant Operation Introduction The American lobster (Homarus americamis) is the most valuable fishery resource _in the a

a northeastern United States. Since 1979, annual landings in the Gulf of Maine have ranged between 11,000 and 25,000 metric tons, which represents 65% of the total landings in the U.S.

4 (NMFS 1993). Because of the economic importance oflobsters, detailed studies have been 1 . conducted in the vicinity of Seabrook Station since 1975 to assess the potential impact of power

, plant operations on the locallobster resource. Potentialimpacts of Seabrook Station operation on local lobsters include entrainment oflarvae and impingement of adults in the cooling-water 1 5 system, and possible effects related to the discharge of cooling water, such as increased temperature and turbidity. Other commercially important crustacean species, rock crabs (Cancer irroratus) and Jonah crabs (C. borealis) have also been monitored as part of the Seabrook Station epibenthic cmstacean monitoring program. Like lobsters, the planktonic and adult life stages of these crab species are also potentially susceptible to power plant impacts. The objectives of the epibenthic crustacean monitoring program have been to determine the seasonal, spatial, and annual trends in larval density and catch-per-unit-effort (CPUE) forjuvenile and adult stages of these commercially important crustaceans and most importantly, to determine whether Seabrook Station operation had any measurable effect on them.

The purpose of this evaluation was to examine the findings of the epibenthic crustacean monitormg programs after 5 years of Seabrook Station operation. The effectiveness ofeach aspect of this program in providing data for determining Station impact will be assessed.

_ Recommendations will be made to either maintain current work or to modify sampling where necessary to enhance the collection ofinformation needed for impact assessment.

1

Summary of Current Methodology American lobster, Jonah crab, and rock crab have been collected at nearfield (L1) and farfield (L7) stations since 1975 and 1982, respectively (Fig.1). Fifteen wire mesh 2.5 cm (1 in) lobster traps without escape vents were hauled at two-day intewals from June through November. The following data were recorded for each lobster, rock crab, and Jonah crab: sex, presence of eggs, and carapace length oflobsters or width of crabs.

i The distribution and abundance oflobster larvae have been monitored at two nearfield statio since 1978 and 1982, intake (P2) and dischrge (PS), respectively, and at one farfield station (P7) since 1988 (Fig.1). Surface neuston samp; vere collected once a week during daylight hours from May through October using a 1-m deep x 2-m wide x 4.5-m long net (1 mm mesh) fitted with a flowmeter and a 40 lb depressor. Thirty-minute horseshoe-shaped tows (800 m along each side) were taken with the bottom of the net mouth approximately 0.5 m below the surface; each 2

tow sampled an average of about 3700 m of surface water. Lobster larvae samples were processed in the laboratory shortly after collection; larvae were enumerated and classified by stage and live larvae were returned to Hampton Harbor.

The distribution and abundance of the larval stages of rock and Jonah crabs have been monitored at the same stations as lobster larvae as part of the macrozooplankton monitoring program.

Macrozooplankton saraples have been collected at least two times per month from January to December since 1978 at P2, January 1982 at P7 and during 1978-81, July-December 1986, and 1987 to the present at P5. No macrozooplankton samples were collected in 1985 at any station.

On each sampling day, four replicate (two paired-sequential) oblique tows were made at night with a' 1-m diameter 0.505-mm mesh net fitted with a flowmeter. Contents of each sample were  !

~ preserved in 5-10% buffered formalin for later processing. Since the characteristics of the larval

stages of both rock and Jonah crabs are similar, larval abundance and distribution data were I

pooled for both species as Cancer spp. larvae. In the laboratory, three of the four replicate  ;

l samples collected at each station were processed for Cancer spp. larvae.

l l 2

l l

Monthly arithmetic mean CPUE (no. per 15 traps) was calculated forjuvenile and adult lobste and crabs for the preoperational (1982-89) and operational (1991-95) periods. An analysi variance (ANOVA: SAS 1985) was applied to annual mean lobster and crab CPUE data to determine differences between the preoperational and operational periods at the nearfield and farfield stations. Monthly geometric means were calculated for lobster and Cancer spp The ANOVA was applied to log (x+1) transformed densities oflobster and Cancer spp. lar  ;

i determine differences between the average abundances for the preoperational (1988-89) anj

. operational (1991-95) periods at the nearfield and farfield stations. Thejuvenile and adult lobster !

and crab data collected since 1982 and larval data collected since 1988 were used for imp!

assessment because the collections met the requirements for the Before-After/ Control-Impa (B ACI) sampling design (Stewart-Oaten et al.1986), when all stations were sampled concurrently, and were amenable to statistical testing based on ANOVA models.

Summary of Monitoring Results After 5 Years of Operation Juveniles and Adults Lobster catches (all sizes) were typically highest from August through November during both preoperational and operational periods. The catchability oflobsters is directly influenced by water temperature; when water temperature rises above 10*C, lobster activity (e.g., feeding, movement, and molting) increases (McLeese and Wilder 1958; Dow 1966, 1969,1976; Flowers and Saila 1972). Means of totallobster CPUE at the nearfield station during the preoperational and operational periods were not significantly different, but CPUE at the farfield station showed a significant decrease (Table 1). The CPUE oflegal-sized lobsters was significantly lower during the operational period than during the preoperational period due, in part, to increases in the minimum legal size limit and to overfishing throughout the range of

_ lobsters. Size characteristics oflobsters and the proportion of egg-bearing females collected at the nearfield and farfield stations were similar during both the preoperational and operational study periods (NAI 1996) and typical of New Hampshire coastal waters (Grout et al.1989; NHFG 1993). A total of 87 lobsters have been impinged in the cooling water system since 3

}

Seabrook Station began operating in 1990 (annual range =1 to 31); this level ofimpingement is !

small when compared to two other coastal nuclear power plants in New England, Pilgrim and Millstone Stations (annual ranges =261 to 1,167; NUSCO 1982,1988; BECO 1994). Although crabs are not currently enumerated in impingement sampws, we propose to add this component to the monitoring study.

~

There is no evidence of an effect by Seabrook Station operation on the local population of

. lobsters. Impingement of adults has been minimal. The distribution oflegal lobsters has been consistent among stations between the preoperational and operational periods. Although total  :

lobster CPUE decreased at the farfield station during the operational period, there was no chang at the nearfield station. This change can not be attributable to the operation of Seabrook Station because the decrease occurred only at the farfield station.

Like lobsters, Jonah crab CPUE showed no significant difference at the nearfield station between the preoperational and operational period, but declined significantly at the farfield station (Table 1). However, this decline began during the preoperational period and was not due to the i operation of Seabrook Station. Since the study began, rock crab catches have been consistently 1 lower than the catch ofJonah crabs. During the operational period, rock crab CPUEs at both the nearfield and farfield stations were significantly higher than during the preoperational period.

There is no evidence of an effect of Seabrook Station operations on local Jonah or rock crab populations.

Larvae Historically, lobster larvae have been rare in the study area, averaging less than 1 per 2

1000 m . Although sampling has been conducted from May through October, peak abundances have typically occurred in July and August; other lobster larvae studies conducted in New England also indicated peak densities in July and August (Fogarty and Lawton 1983; Grabe et al.

1983, NUSCO 1996). Stage IV lobster larvae predominated in collections made during both the preoperational and operational study periods, followed by Stage I larvae; very few Stage II and III larvae were collected. Other researchers working in New England waters have found similar 4 l l

1

high variability in the number and stage composition oflarvae collected (Bibb et al.1983; F 1983; Lux et al.1983).

The average densities of both lobster and Cancer spp. larvae were significantly higher during the operational period than during the preoperational period (Table 1). However, since the increases occurred at both the nearfield and farfield stations, it reflects an area-wide increase. Furthermore, the interaction terms (Preop-Op X Station) for both lobster and Cancer spp. larvae were not significant, indicating that the increases observed between the preoperational and operational periods were consistent among stations and were not due to plant operation.

Evaluation of Present Epibenthic Crustacea Sampling Program with Recommendations for Future Studies Juvenile and Adult Lobsters; Jonah and Rock Crabs Evaluation ofEpibenthic Crustacea monitoring program results following 5 years of Seabrook operation show that no changes are  !

recommended in the scope and design of thejuvenile and adult lobster, rock, and Jonah crab l sampling programs. Because lobsters require several years ofgrowth to reach legal size, there is a lag of about 6-7 years between the time of a potential impact on larvae and the time at which an impact can be detected. For this reason, and the fact that Seabrook Station has only been operating for 5 years, monitoring ofjuvenile and adult epibenthic cnastacea should continue at the current level of effort.

Larvae The lobster larvae sampling program was evaluated to determine whether restricting the sampling period to mid-June through September would affect the ability to detect plant operational impacts on the abundance oflocal lobster larvae. When the lobster larvae sampling program was initially designed, adequate sampling during the lobster larvae hatching season was necessary to better define the timing of annual hatches and peak abundance oflobster larvae in the Seabrook area. Data collected since 1978 indicate that the abundance oflobster larvae peaks in July or August. The rationale for reducing the sampling period is based on the lack oflobster 5

~. . - . _ . -

J p

larvae found in samples collected at the beginning (May) and end (October) of the present sampling program. These sparse catches contribute only variability without adding to the description of annual abundance. Therefore, an analysis was made to determine if the current sampling period could be changed to mid-June through September without loss ofinformation

, critical to impact assessment.

1 Data for Cancer spp, larvae originates from the macrozooplankton monitoring program; this program was evaluated separately to determine whether data collected and statistical analyses conducted would become biased if only one sample of the three replicates at each station was processed to determine Cancer spp. larval densities. Finally, there are two nearfield stations (P2 and PS) where lobster and Cancer spp. larvae have been sampled; discontinuing the larval collections at one of these stations (P5) was evaluated to determine whether the sampling design change would result in an appreciable loss in precision to detect possible operational impacts.

The effect of reducing the sampling period for lobster larvae was simulated by computing annual l geometric means for each station and comparing the results of ANOVA tests using data from all  !

samples collected with those obtained by using only samples collected during the mid-June l i

through September period. The same technique was used to assess the effects of using only one sample per date to determine Cancer spp. larval density and reducing the number of nearfield stations sampled for both lobster and Cancer spp. larvae. Recommendations for program changes were based on whether there was a loss in precision in estimating annual abundance and whether ANOVA results were similar for the current data base and for two simulated databases and 2 stations sampled from mid-June through September). Of particular concern were the results  ;

1 from testing the Preop-Op X Station interaction, critical for impact assessment, and whether the I mean squares for the actual and simulated databases were similar. The significance of this

_ interaction was tested with separate F-tests.

A total of 510 lobster larvae samples were collected at the three stations from 1988 through 1995, j

'out only 250 contained lobster larvae (less than 50% of the samples). Smith et al. (1993) stated 6

. - -. _= -- _- . .. .._ _ _~.___= _.---- - - - -

1 i

that databases with excessive zeros used in a B ACI design could result in unreliable statistical tests. Examination of the distribution of sample densities during the mid-May through mid-

e October collection period indicated that many of the samples with no larvae were collected from  !

i May through mid-June and in October. In addition, the geometric mean density oflobster larvae was lowest during these two periods (Fig. 2). When these samples were eliminated (a reduction of about 30% of the total samples), the percentage of non-zero sample densities increased to

, about 65%.

4

! l j The annual geometrie means for each of the three stations computed from the simulated reduced database (mid-June through September samples) were consistently greater than those using the complete database (mid-May through mid-October), due primarily to the reduction in the number o

~ f zero density samples (Table 2). The increases in annual abundance estimates using the reduced

. sampling period did not alter the general ranking or magnitude of differences among stations within a year nor among years at each station when compared to the estimates using the complete database. Of greater importance, there was a consistent increase in the precision of the annual abundance estimates using data from the reduced sampling period, based on inspection of the standard errors expressed as a percentage of the geometric means (Table 2).

The abundance oflobster larvae at the two nearfield stations (P2 and PS) was compared with the Wilcoxon's signed ranks test for paired comparisons (Sokal and Rohlf1969). Paired samples containing lobster larvae at either P2 or P5 were collected on the same date a total of 95 days from 1988 to 1995. No significant (p = 0.672) difference in abundance between stations was i

detected. Furthermore, comparison of the F-tests from ANOVA analyses of the complete and reduced databases showed similar results (Table 3). The Preop-Op, Year (Preop-Op), and Week (Year) terms were significant (p 5 0.05) and the Station and Preop-Op X Station tenns

- were not significant (Table 3). The critical interaction (Preop-Op X Station) term for assessing .

8 plant impact was not significant in either the reduced sampling scenario (as with the actual data l

base) and the F-value of 1.57 for three stations was well below the point of rejection of Fo.os =

3.04; the F-value of 1.21 for two stations with reduced sampling period was also below the point 7

l ofrejection of Fo.o3 = 3.98. In addition, there was no significant difference detected with F-tests !

between the interaction mean squares from the actual database and those from the two reduced databases for three stations (p = 0.431) and two stations (p = 0.565).

l l

. Comparison of the three ANOVAs (three replicates versus one sample per sampling date for thre stations and two stations) for Cancer spp. showed similar results in assessing potential plant impact (Table 4) and suggests that current sample replication is redundant. The interaction l

(Preop-Op X Station) term, critical for impact assessment, was not significant in either reduced i

sampling scenario, as with the actual data base. The F-values of 0.04 for three stations and of l 0.06 for two stations were well below the point of rejection of Fo.o3 =2.95 and 3.76 for three stations and two stations, respectively. In addition, there was no significant difference detected with F-tests between the interaction mean squares from the actual database and those from the two reduced databases for three stations (p = 0.207) and two stations (p = 0.427). Similar results were demonstrated in an ongoing evaluation of the macrozooplankton monitoring program for other selected species, including Calanusfinmarchicus, Carcinus maenas, Crangon septemspinosa, and Neomysis americana.

Conclusions No changes are recommended in the scope and design of the juvenile and adult lobster, rock, and l Jonah crab sampling programs; these monitoring programs should continue at the current level of effort. The timing of annual lobster larvae hatches and peaks in abundance have been well documented for the Seabrook area and since lobster larvae have been rarely collected at the beginning or end of the present sampling period, restricting this sampling period from mid-June l

through September would not cause a loss in the ability to detect possible Seabrook Station i operational impacts. The shorter sampling period also will improve the precision of mean

- estimates. As was demonstrated for other macrozooplankton, a reduction in replicates for l estimating Cancer spp. larval densities was indicated as no significant differences were found l

between the mean of three replicates and one sample. Further, even with discontinued sampling i

1 8

l

oflobster and Cancer spp. larvae at station P5, the BACI sampling design will be maintained with stations P2 and P7 and with no appreciable loss in model sensitivity. The estimated variances for the critical interaction terms were similar for the present and proposed sampling programs.

Therefore, it is proposed that the collection oflobster larvae samples be restricted to the period from mid-June through September at stations P2 and P7. It is also recommended that Cancer spp. larval collections be reduced from three to one sample per sampling date at sta.tions P2 and P7. These modifications should not reduce the sensitivity of the monitoring programs to detect plant operational impacts, if any, nor affect annual and spatial abundance comparisons.

References Cited BECO (Boston Edison Company). 1994. Marine ecology studies related to operation of Pilgrim Station. Semi-annual Rept. No. 44.

Bibb, B.G., R.L. Hersey, and R.A. Marcello, Jr. 1983. Distribution and abundance oflobster larvae (Homarus americanus)in Block Island Sound. NOAA Tech. Rep. NMFS SSRF-775:15-22.

Dow, R.L. 1966. The use of biological, environmental and economic data to predict supply and to manage a selected marine resource. The Amer. Biol. Teacher 28:26-30.

Dow, R.L. 1969. Cyclic and geographic trends in seawater temperature and abundance of American -

lobster. Science 164:1060-1063.

Dow, R.L. 1976. Yield trends of the American lobster resource with increased fishing effort. Mar. l Technol. Soc. 10:17-25.

Flowers, J.M., and S.B. Saila. 1972. An analysis of temperature effects on the inshore lobster fishery.

J. Fish. Res. Board Can. 29:1221-1225.

Fogarty, M.J. 1983. Distribution and relative abundance of American lobster, Homarus americanus larvae: New England investigations during 1974-79. NOAA Tech. Rep. NMFS SSRF-775. 64 pp.

Fogarty, M.J., and R. Lawton. 1983. An overview of Larval American lobster, Homanis

~ americanus, sampling program in New England during 1974-79. NOAA Tech. Rep. NhES SSRF-775:9-14.

Grabe, S.A., J.W. Shipman, and W.S. Bosworth. 1983. New Hampshire lobster larvae studies.

NOAA Tech. Rep. NMFS SSRF-775:53-57, 9

)

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L I

I Grout, D.E., D.C. McInnes, and S.G. Perry. 1989, Impact evaluation of the increase in minimum carapace length on the New Hampshire lobster fishery. N.H. Fish and Game Dept. l Lux, F.E., G.F. Kelly, and C.L. Wheeler. 1983. Distribution and abundance of larval lobsters (Homarus americanus) in Buzzards Bay, Massachusetts, in 1976-79. NOAA Tech. Rep. NMFS; SSRF-775:29-33.

McLeese, D.W., and D.G. Wilder. 1958. The activity and catchability of the lobster (Homanis americanus)in relation to temperature. J. Fish. Res. Board Can. 15:1345-1354. -

NAI(Normandeau Associates Inc.).1996. Epibenthic crustacea. Draft in Seabrook environmental studies,1995. A characterization of environmental conditions in the Hampton-Seabrook area during the operation ofSeabrook Station. Prepared for North Atlantic Energy Service Corporation.

NHFG (New Hampshire Fish and Game Department) 1993. Monitoring of the American lobster resource and fishery in New Hampshire-1992. Performance Report submitted to the NMFS-Management Division, State-Federal Relations Branch. Proj. 3-IJ-55-1, No. NA16FI-0353-01.

29 pp. 1 NMFS (National Madne Fisheries Service). 1993. Report of the 16th Northeast Regional Stock' Assessment Workshop. Northeast Fish. Sci. Cen. Ref. Doc. 93-18. NOAA/NMFS Northeast Fish.

Sci. Ctr., Woods Hole, MA. I18 pp. {

NUSCO (Northeast Utilities Service Company). 1982. Lobster population dynamics-A Review and Evaluation. Pages 1-32 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, CT. Resume 1968-1981.

NUSCO.1988. Lobster population dynamics. Pages 121-145 in Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, CT. Three-unit operational studies 1986-1987.

NUSCO. 1996. Lobster studies. Pages 9-32 in Monitoring the madne environment ofLong Island Sound at Millstone Nuclear Power Station, Waterford, CT. Annual repon 1995.

SAS Institute Inc. 1985. SAS user's guide: statistics. Version 5 edition. SAS Institute Inc.,

Cary, NC. 956 pp.

Smith, E.P., D.R. Orvos, and J. Cairns, Jr. 1993. Impact assessment using the Before-After- 1 Control-Impact (BACI) model: concerns and comments. Can. J. Fish. Aquat. Sci. 50:627-637. i Sokal, R.R. and F.J. Rohlf.1969. Biometry. W.H. Freeman and Company, San Francisco. 776 PP l 4

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Stewart-Oaten, A., W.W. Murdoch, and K.E. Parker.1986. Environmental impact assessment:

"Pseudoreplication"in time? Ecology 67:929-940. l i

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i i Table 1,

' Summary ofpotential plant effects on abundance of epibenthic cnistacea. Seabrook Operational Report,1995.*

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l OPERATIONAL PERIOD DIFFERENCES BETWEEN SIMILAR TO PREOPERATIONAL AND OPERA-PARAMETER PREOPERATIONAL TIONAL PERIODS CONSISTENT MEASURED PERIOD 6

AMONG STATIONS

• Lobster: Op> Preop Yes 'i Larvae Lobster: Op< Preop nearfield: Op= Preop Total Catch )

farfield: Op< Preop Lobster: Op< Preop Yes Legal-Sized Catch Cancer spp.: Op> Preop Yes Larvae Jonah Crab; Op< Preop nearfield: Op= Preop Total Catch farfield: Op< Preop Rock Crab: Op> Preop , Yes Total Catch

• From NAI (1996).

6 based on Preop-Op term of ANOVA model (Table 8-2 in NAI 1996).

based on the interaction term (Preop-Op X Station) of the ANOVA model and multiple comparison test at a s 0.05 (Table 8-2 in NAI 1996).

12

- - - - =- - . . . . ..

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Table 2. Comparison of annual lobster lanae geometric means (number per 21000 m ) and standard errors (SE),

i t expressed as a percentage of the mean. for each station computed using the actual (mid-May through mid-October) and reduced (middune through September) databases. 1988-95.

1 Actual Reduced SE as SE as Year Station Mean  % of mean Mean  % of mean 1988 P2 0.4 35.7 0.7 _ 32.8 PS 0.6 35.5 0.9 32.5 P7 0.4 32.6 0.6 30.8 1989 P2 0.4 36.5 0.7 33.6 PS 0.5 51.0 0.7 38.5 P7 0.4 40.9 0.7 38.5 l 1990 P2 1.0 37.9 1.6 35.9 P5 0.9 39.4 1.3 39.1 P7 1.1 36.9 1.5 37.7 1991 P2 0.9 31.7 1.4 28.6 ,

P3 0.9 35.3 1.5 32.7 P7 1.1 24.7 1.8 21.1

, 1992 P2 1.3 27.2

' 2.2 25.1 P5 1.1 27.9 1.9 24.6 ,

P7 1.5 21.8 2.4 I 20.4 1993 P2 0.7 29.9 1.2 26.2 PS 0.6 28.2 1.0 24.2 P7 0.7 30.2 1.1 26.5 1994 P2 0.7 32.I 1.2 29.1 PS 0.5 34.2 0.8 31.5 P7 1.5 28.6 2.7 25.1 1995 P2 0.7 30.7 1.0 28.1 PS 0.8 31.6 1.2 31.9 P7 0.8 26.6 1.2 24.3

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l, Table 3. Comparison of lobster larvac results for ANOVA tests computed using the actual (mid-May through

!' mid-October) and two reduced database scenarios of mid June through September with the present threc stations and mid-June through September with only stations P2 and P7.1988 95 l

l Source of variation df MS F-value P  !

Actual ,

l Preop-Op 1 1.79 42.59 0.001 Year (Preop-Op) 5 0.I7 3.96 0.002 Week (Year) 129 0.32 7.68 l

0.001 Station 2 0.02 0.48 0.621 '

l Preop-Op X Station 2 0.07 1.69 0.187 Error 310 0.04 i i

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' Stations P2. PS and P7 with reduced samoline period >

Preop-Op - 1 2.30 38.56 0.001  !

Year (Preop-Op) 5 0.20 3.34 0.006

! Week (Year) 87 0.35 5.90 0.001 Station 2 0.02 l 0.31 0.733 Preop-Op X Station '2 0.09 1.57 0.211 j Error 214 0.06 Stations P2 and P7 with reduced sampline period <

Preop-Op 1 1.91 30.54 0.001  !

i Year (Preop-Op) 5 0.16 '

2.50 0.035 j ' Week (Year) 87 0.24 3.78 0.001 j Station 1 0.03

' 0.48 0.489 '

Preop-Op X Station 1 0.08 1.21 0.274 l Error 112 0.06 '

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M Table 4. Comparison of Cancer spp. larvac results for ANOVA tests computed using the actual (three stations I

with three replicate samples) and two reduced database scenarios of three stations and one sampic and two stations and one sample, May through September 1987-95.

\*

Source of variation df MS F-value P Actual Preop-Op 1 3.52 4.89 0.028 Year (Preop-Op) 6 2.11 2.94 - 0.009 Month (Year) 32 7.15 9.94 0.001 Station 2 0.76 1.05 0.351 Preop-Op X Station 2 0.12 0.16 0.851 Error 193 0.72 Stations P2. P5 and P7 - One sample Preop-Op 1 4.45 5.57 0.019 Year (Preop-Op) 6 2.06 2.58 0.020 Month (Year) 32 7.36 9.23 0.001 Station 2 0.66 0.82 0.440 Preop-Op X Station 2 0.03 0.04 0.963 Error 193 0.80 Stations P2 and P7 - One samole Preop-Op 1 3.07 3.52 0.063 Year (Preep-Op) 6 1.37 1.57 0.163 Month (Year) 32 5.42 6.21 0.001 Station 1 1.05 1.21 0.274 Preop-Op X Station 1 0.05 0.06 0.808 Error 116 0.87 I

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LEGEND

= Lobsterlarvac(neuston)

- P = Jonah and rock crab larvae (macrozooplankton)

L = Lobstertraps (15 traps)

\

l Figme 1. A map of the Seabrook-Hampton area showing the location of the epibenthic crustacea (American j lobster, Jonah and rock crabs) sampling stations. -

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! May June July August September October Figure 2. Weekly geometric mean density (number per 1000 m 2) oflobster larvae at stations P2, PS, and P7 combined, 1988-95.

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ENCLOSURE 2 TO NYE-96021 I l

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Seabrook Station Technical Advisory Committee Working Group Meeting Thursday, September 5,1996 Science & Nature Center Lower Level Conference Room -

. . Agenda 9:30 a.m. Purpose ofMeeting 9:30 a.m.

Seabrook Station Environmental Studies Update 9:45 a.m.

Environmental Studies Program Overview 10:15 a.m.

Discussion ofIndividualPrograms e

Fish and Shellfish (Epibenthic Crustacea and Sofi-Shell Clam) e Benthos

• Zooplankton Water Quality 12:00 p.m. Lunch 12:30 p.m.

Discussion ofIndividual Programs (Continued) 1:30 p.m.

Other Environmental Studies Program Matters l'

i

Environmental Protection Agency NYE-96021/Page 3  ;

1 cc (with Enclosure) h TECHNICAL ADVISORY COMMii I EE:

Dr. Edward Schmidt NH Dept. Of Environmental Services Mr. Eric Hutchins i Water Supply & Pollution Control Div.

6 Hazen Drive National Marine Fisheries Service !

Northeast Region Concord,NH 03302 One Blackburn Drive -

Gloucester, MA 01930  !

Mr. Jeffrey Andrews NH Dept. Of Environmental Services Water Supply & Pollution Control Division SEABROOK ECOLOGICAL ADVISORY COMMITTEE:

6 Hazen Drive  !

Concord,NH 03302 j Dr. John Tietjen, Chairman ,

134 Palisade Avenue j Mr. Robert Estabrook Leonia,NJ 07605 i NH Dept. Of Environmental Services i Water Supply & Pollution Control Division Dr. W. Huntting Howell )

6 Hazen Drive j 12 James Farm Concord,NH 03302 Lee,NH 03824 Mr. John Nelson Dr. Saul Saila NH Fish and Game Department 317 Switch Road 37 Concord Road Hope Valley, RI 02832 Durham,NH 03824 Dr. Bernard J. McAlice Mr. Bruce Smith Darling Marine Center NH Fish and Game Department University ofMaine 37 Concord Road Durham,NH 03824 Clarks Cove Road Walpole, ME 04573 Mr. Nicholas Prodany Dr. Robert Wilee Massachusetts State Program Unit Department of Biology EnvironmentalProtection Agency 221 Morrill Science Center John F. Kennedy Building University of Massachusetts Boston,MA 02203 Amherst,MA 01003 Mr. Frederick Gay NORMANDEAU ASSOCIATES New Hampshire NPDES Permit Coordinator New Hampshire State Program Unit Ms. Marcia Bowen

. Environmental Protection Agency Normandeau Associates,Inc.

John F. Kennedy Building 82 Main Street Boston, MA 02203 Yarmouth, ME 04096 Mr. Jack Paar Mr. John Shipman EnvironmentalProtection Agency Normandeau Associates,Inc.

60 Westview Street 25 Nashua Road Lexington, MA 02173 Bedford,NH 03110

PHYTOPLANKTON AND CHEMICAL NUTRIENTS Summary of the Monitoring Program after 5 Years of Operation The objective of the phytoplankton program was to monitor the effects of Seabrook Station operation on phytoplankton, which was expected to be affected by entrainment through the plant cooling water system (through-plant entrainment) and into the thermal discharge (thermal plume entrainment). The phytoplankton sampling design was based on collections made at one farfield and two nearfield stations. In addition, concentrations of chlorophyll a and chemical nutrients (orthophosphate, total phosphorus, nitrate, riitrite, and ammonium) were taken along with phytoplankton abundances, as these parameters control or influence primary production. These programs have served their purpose as part of the Seabrook Station environmental monitoring studies.

1. The phytoplankton program, which includes enumeration of cells 210 m and the ultraplankton (cells < 10 m), is recommended to be discontinued because after 5 l

years ofplant operation the program has met its objective of assessing potential impact on this community. These organisms have very rapid generation times (as quick as 1-3 days) and no significant effects were detected.

All quantitative analyses performed indicated no impact by Seabrook Station on phytoplankton. Mean abundances of total phytoplankton and for the dominant diatom Skeletonema costatum were greater during the operational period than the preoperational period. The BACI ANOVA model Preop-Op X Station interaction terms were not significant, indicating no plant effects.

Overall, species abundances (top 15 taxa) were not significantly different among the three stations. Nearfield-farfield comparisons of ultraplankton l

abundances during the operational period showed no significant differences.

The concentrations of chlorophyll a remained consistent among periods and the ANOVA interaction term was not significant, showing that a difference found amcag stations (P5 > P7) was consistent, regardless of plant operation.

Due to the very rapid generation times ofphytoplankton, it is not surprising l that impacts have not been detected for this community at Seabrook Station.

Rapid generation turnover rates and large reproductive capacitics of these i

organisms enable them to compensate for high natural mortality and environmental perturbations. Because of their high thermal tolerance, thermal plume entrainment should not affect these organisms, e

i In addition, it has been well documented that other coastal marine power

plants do not appreciably affect phytoplankton communities, and, as a result, their long-term phytoplankton studies have been concluded.

m._ _ __. . _ . _. - . . . . . _ . _ . _ . _ _ . . _ . . . . _ _ _ _ _ _ . . _ _ _ _ _ . _ . _ . _ .

t

2. The chemical nutrient program indicated no significant effect of Seabrook Station ,

operation after 5 years, and it is recommended that this sampling program be l concluded. Further, there is no likely mechanism by which station operation could ]

j affect concentrations of chemical nutrients.

l Preop-Op differences were only found for nitrite and ammonium (both with L Op > Preop). No significant differences were found for the Preop-Op X

' Station interaction term for any of the chemical nutrients, indicating no plant e!Tects. -

i c

The small volume of cooling water utilized by the station for cooling purposes

! compared to the total volume that passes through the nearfield area via

) longshore transport would make it unlikely that plant operations could affect L the natural cycling of nutrients, even if a credible mechanism to do so exists.

t l

Therefore, it is proposed that the programs for phytoplankton and chemical nutrients be discontinued because of the very high reproductive capacity of the potentially affected organisms and the lack of significant impacts found during 5 years ofplant operation by l the monitoring programs.

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l ENCLOSURE 3 TO NYN-97042 l

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. NYE-96020 SEABROOK STATION 1996 ENVIRONMENTAL

! STUDIES PROGRAM SEMI-ANNUAL REPORT F

Cuoco, L. M. NU Berlin Jacobson, P.M. NU Berlin Keser, M. cc: Mail Leland, W. B. cc: Mail Letter Distribution ec: Mail 1[iTeT0T0 RRMBREER!fiOjgjj File 0054 01-48 RMD 02-06 t

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\h,,,,,'ANorth North Atlantic Energy Service Corporation G P.O. Box 300

'y Atlantic 0

Seehrook, Nn 03824 (603) 474-9521 The Northeast Utilities System AE 231996 NPDES Permit No. NH0020338 NYE-96020 Mr. Carl DeLoi New Hampshire State Program Unit Environmental Protection Agency John F. Kennedy Building Boston, MA 02203 Seabrook Station 1996 Environmental Studies Program Semi-Annual Reoort North Atlantic Energy Service Corporation (North Atlantic) submits herein the 1996 Seabrook Station Environmental Studies Program Semi-Armual Report as required by Part I.A.ll.e. of the NPDES Permit. l This report summarizes the Seabrook Station Biological, Hydrological and Chlorination Studies Programs for the previous year.

2 The 1995 Chlorine Minimization Report' and 1995 Hydrological Report were submitted earlier this year.

The 1995 Environmental Studies Report is currently being finalized and will be submitted later this summer.

Detailed information regarding the 1995 Environmental Studies Program, as well as the other topics summarized above, will be discussed at the annual Technical Advisory Committee meeting to be scheduled this fall. North Atlantic believes that after nearly six years of commercial operation, the Enviror.nental l Studies Program continues to demonstrate that Seabrook Station has not had a deleterious impact on the balanced indigenous populations in the coastal waters ofNew Hampshire.

Should you require additional information regarding this matter, please contact Mr. Anthony M.

Callendrello, Licensing Manager, at (603) 474-9521, extension 2751.

Very truly yours, NORTH ANTIC ENF GY SERV CE CORP.

no Duce L. D6wbridge l sf~

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Executive Director d Nuclear Station Safety and Oversight and Senior Site Officer North Atlantic letter NYE-96008, dated April 22, 1996, "1995 Seabrook Station Chlorine Minimization Report," B. L. Drawbridge (North Atlantic) to C. DeLoi (EPA) 2 North Atlantic letter NYE-960ll, dated May 30,1996,"Seabrook Station 1995 Annual flydrological Report,"

B. L. Drawbridge (North Atlantic) to C. DeLoi (EPA)

Environmental Prot:ction Agency i

NYE-96020/Page 2 l

cc (with attachment)

TECHNICAL ADVISORY COMMITTEE: Mr. Eric Hutchins l Dr. Edward Schmidt National Marine Fisheries Service {

NH Dept. Of Environmental Services Northeast Region l Water Supply & Pollution Control Div. One Blackburn Drive 6 Hazen Drive Gloucester,MA 01930 Concord,NH 03302 SEABROOK ECOLOGICAL ADVISORY Mr. Jeffrey Andrews COMMITTEE:

l NH Dept. Of Environmental Services Water Supply & Pollution Control Division Dr. John Tietjen, Chairman 6 Hazen Drive 134 Palisade Avenue Concord,NH 03302 Leonia,NJ 07605 Mr. Robert Estabrook Dr. W. Huntting Howell NH Dept. Of Environmental Services 12 James Farm Water Supply & Pollution Control Division Lee,NH 03824 6 Hazen Drive Concord,NH 03302 Dr. Saul Saila 317 Switch Road Mr. John Nelson Hope Valley, RI 02832 NH Fish and Game Department 37 Concord Road Dr. Bernard J. McAlice Durham,NH 03824 Darling Marine Center University of Maine Mr. Bruce Smith Clarks Cove Road NH Fish and Game Department Walpole, ME 04573 37 Concord Road Durham,NH 03824 Dr. Robert Wilee Department of Biology Mr. Nicholas Prodany 221 Morrill Science Center Massachusetts State Program Unit University of Massachusetts Environmental Protection Agency Amherst,MA 01003 John F. Kennedy Building Boston, MA 02203 NORMANDEAU ASSOCIATES Mr. Frederick Gay Ms. Marcia Bowen New Hampshire NPDES Permit Coordinator Normandeau Associates,Inc.

New Hampshire State Program Unit 82 Main Street Environmental Protection Agency Yarmouth,ME 04096 John F. Kennedy Building Boston,MA 02203 Mr. Jack Paar EnvironmentalProtection Agency 60 Westview Street Lexington, MA 02173

SEABROOK STATION 1996 ENVIRONMENTAL STUDIES MID-YEAR REPORT BIOLOGICAL MONITORING PROGRAM

'A preliminary review of the results of the 1996 Environmental Studies Program to date, has not identified any significant changes to the balanced indigenous populations in the coastal waters of New Hampshire when compared to the final results from previous years.

Several hundred Atlanti: herring larvae were observed in screen wash debris on April 3,1995, during an impingement assessment. These larvae were approximately 1-2 cm. in length. Other observations of fish larvae were made during the year, however, data regarding fish larvae observed during impingement assessments are not included in the impingement monitoring program. Station impacts to fish larvae are assessed by the entrainment sampling program.

Seabrook Station's Fourth Refueling Outage took place between November 4,1995 and December 11, 1995. During most of the outage only one circulating water pump was in operation, at which time all weekly ichthyoplankton entrainment samples were taken. Only one scheduled ichthyoplankton entrainment sample was not taken during the outage during a period when no circulating water pumps were operating.

No bivalve larvae entrainment samples were scheduled to be taken during the 1995 outage.

The number of unidentifiable fish larvae in 1995 entrainment samples was higher than in past years.

Unidentifiable means that a fish larvae is in a condition such that it cannot be identified, even to the family level. In 1995 entrainment samples, the percentage of unidentifiable fish larvae was approximately 21 per cent compared to one to four percent in past years. Preliminary results show that this higher trend has continued in 1996. North Atlantic is currently evaluating possible causes of this condition.

l HYDROLOGICAL MONITORING PROGRAM The Hydrological Monitoring Program continues to demonstrate compliance with the NPDES Permit.

I In January 1996, North Atlantic began employing Seabrook Station's Environmental Studies contractor, Normandeau Associates, Inc., to implement the offshore thermal monitoring program. The offshore thermal monitoring system now uses Onset Temperature Recorders which North Atlantic believes will provide gre: iter reliability.

CHLORINE MINIMIZATION PROGRAM The Chlorine Minimization Program continues to demonstrate compliance with the NPDES Permit.

On January 17,1996 chlorination of the Circulating Water System was discontinued pursuant to the Chlorine Minimization Program as limited biofouling was occurring during this period of cold water temperatures. On March 4,1996 chlorination of the Circulating Water System resumed due to plant performance measurement parameters which indicated the presence of biofouling organisms in the system.

ENCLOSURE 4 TO NYN-97041 l

I l

I NYE-96021 LONG-TERM ENVIRONMENTAL STUDIES PROGRAM PROPOSAL (without enclosures)

Cuoco, L.

NU Main, E200 Jacobson,P.M. NU East,1st Floor Lorda, E. l cc: Mail i Keser, M.

cc: Mail j Letter Distribution cc: Mail

' File 0003,tyT" .

.._ 01-48 7 " g i

gp . . , .c.n ... -~ '

. - 06' ~

('with enclosure)

O

I u,,\ s North North Atlantic Energy Service Corporation Atlaritic P.O. Box 300 I seahroet, Na 03874 i

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(603) 474 9521 i

The Northeast Utilities System 1

AE 29 ms i

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NPDES Permit No. NH0020338 I Mr. Carl DeLoi ~ NYF-96021 l New Hampshire State Program Unit j EnvironmentalProtection Agency l John F. Kennedy Building (

Boston, MA 02203

\

Seabrook Station Long-Term Environmental Studies Program Prooosals 1

3 North Atlantic Energy Senice Corporation (North Atlantic) submits herein th

{ Studies Program Proposals to be discussed at the Seabrook Station Techn (TAC) Working Group Meeting on Thursday, September 5,1996.

The enclosed working draft documents evaluate er.ch of the seven major Se Monitoring Programs, and include five years of environmental monitoring data operational period (August 1990-December 1995). ' Die monitoring programs evcluated Water Quality

. Zooplankton Fish.

Marine Macrobenthos

• Epibenthic Crustacea Soft-Shell Clam

• Phytoplankton The purpos,e of this TAC Working Group Meeting is to prepare the TAC fo Seabrook Station Environmental Monitoring Program modifications that will be for the agencies later this year. Seabrook Station's Ecological Advisory Commit their endorsement of the program proposals as part of that formal submittal.

. The full TAC has the ultimate authority to make recommendations to the EPA Region n s rator and the Director of the NH Water Supply and Pollution Control Division who are ref i approving or disapproving program modifications (Seabrook Station NPDES Pe m

EnvironmentalProtection Agency NYE-96021/Page 2 i

review and approval process was discussed at the November ng and 1995, S discussed 28,1996 submittal'.with the EPA at the February 26,1996 meeting in Bosto ncs arch Enclosure 1. The agenda for the September 5, .

attached as Nature Center on September 5,1996 at 9:30 a.m.The encemeeting

~

l this matter, please contact Mr. Ronald A. Sher, Senior -

ension 2729.

Scientist at (

Very trulyyours, NORTH ATLANTIC ENER Y SERVICE CORP.

H / /2. t

'ce L.'DKvbrBge ~

Executive Direc Nuclear Station Safe ersight and Senior Site Officer s ,

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North Atlantic letter NYE-96005, dated March i

Program Modifications," B. L. Drawbridge (North Atlantic) to C. DeLoi (EPA

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ENCLOSURE 1 TO NYE-96021 0

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CURRENTSEABROOK STATION ENVIRONMENTAL STUDTES PROGRAM

'Ihe Seabrook Station Environmental Monitoring Program is an extensive stud indigenous population of organisms off coastal New Hampshire. The program has collected information on every trophic level and community type of marine The study design was established to examine natural variability of these communitie Seabrook Station along with a farfield area outside any potential influence. Any area not paralleled by a change in the farfield area would suggest a potential imp study.

impact. These A key element of the program has been to focus the studies in the a include:

Intake effects: Entminment ofzooplankton Impingement of finfish and lobsters Discharge effects Phytoplankton (thermal plume): Lobster larvae  ;

Intertidal / shallow subtidal benthos Fouling community I I

Discharge effects Mid-depth / deep benthos l (detritalrain): Lobsters / crabs PROPOSED LONG-TERM SEABROOK STATION

_ENVTRONMENTAL STUDIES PROGRAM Five years of environmental monitoring since Seabrook Station began operating in detectable impacts to the balanced indigenous populations. The Seabrook Techni (TAC) agreed that five years of environmental data collection during the power  ;

would be sufficient to evaluate the effectiveness of the current program. Therefore, conjunction with Northeast Utilities, Normandeau Associates and the Seabroo! '

Committee', has developed a proposal for a long-term monitoring program that contain

. 1.

FOCUS ON PROGRAMS THAT DIRECTLY MEASURE PLAhT EFFECTS ImprOed entrainment sampling Improved impingement monitoring i

. - . . . - . . - . . . . . - . .. _ . . . _ . - . . - - _ _ ~ _ . - . . . . . . - - - _ _ . . _ . . _ . _ . - - . _ . . - . .

t 2.

i f FOCUS ON PROGRAMS THAT ARE MOST LIKELY TO SHOW P

?

PLANT EFFECTS ON THE BALANCED INDIGENOUS POPULATIO 3

• J Thermal plume: Lobster larvae  !

Shallow water benthos Bottom panels 1

• - Intake: Fish eggs and larvae l t Macrozooplankton ~

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REDUCE PROGRAM REDUNDANCIES 4

4 i Focus on one nearfield station (P2), and farfield counterpart (P7) f

• Reduce sample replication when appropriate t

4.

MAINTAIN CONTINUITY OF SOFT-SHELL CLAM DATABASE Continue all population surveys as in the current program

/

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ENCLOSURE 5 TO NYN-97042

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. j NYE-96022 i l

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1 1995 ENVIRONMENTAL STUDIES REPORT (without enclosure) i Cuoco, L. M. NU E-200 Jacobson, P. M.

cc: Mail Lorda, E. cc: Mail Keser, M. cc: Mail Letter Distribution 'cc: Mail File 0003* 01-48 RMD* 02-06

(*with enclosure)

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1 North North Atlantic Energy Service Corporation P.O. Box 300 Vg Atlantic Seabroot,s n 03874 .

(603) 474 9521 The Northeast Utilities System SEP l 3 096 NPDES Permit No. NH0020338 )

i N YE-96022 '

Mr. Carl DeLoi New Hampshire State Program Unit Environmental Protection Agency l

John F. Kennedy Building l

Boston, MA 02203 Seabrook Station  !

1995 Environmental Studies Reoort North Atlantic Energy Service Corporation (North Atlantic) has enclosed the Seabrook Station 1995 Environmental Studies Report as required by NPDES Permit Section I.B.I.f'. The 1995 Report provides a comparison of 1995 Environmental Studies Data to previous years. This report continues to demonstrate that Seabrook Station has not had a deleterious impact on the balanced indigenous populations in the coastal waters of New Hampshire.

A copy of the 1995 Environmental Studies Report was provided to those members of the Technical Advisory Committee (TAC) who attended the TAC Working Group Meeting held at Seabrook Station on 2

September 5,1996. A copy of this Report is being sent to those members of the TAC who did not attend the meeting.

Should you require additional information regarding this matter, please contact Mr. Ronald A. Sher, Senior Scientist at (603) 474-9521, extension 2729.

Very truly yours, NORTH A i TIC ENERG VICE CORP.

. e& LGE' Bruce L. Dfawbridge Executive Director-Nuclear Station Safety and Oversight and Senior Site Officer

' Seabrook Station NPDES Permit No. NH002338.

• North Atlantic letter NYE-96021, dated August 29,1996,"Seabrook Station Long-Term Environmental Monitoring Program Proposals," B. L. Drawbridge (North Atlantic) to C. DeLoi (EPA).

m

Environmental Protection Agency NYE-96022/Page 2 cc (with enclosure)

TECHNICAL ADVISORY COMMITTEE:

Mr. Eric Hutchins Dr. Edward Schmidt National Marine Fisheries Service NH Dept. Of Environmental Services Northeast Region Water Supply & Pollution Control Div. One Blackburn Drive 6 Hazen Drive Gloucester,MA 01930 Concord, NH 03302 Mr. Nicholas Prodany SEABROOK ECOLOGICAL ADVISORY Massachusetts State Program Unit COMMITTEE:

Environmental Protection Agency (with enclosure)

John F. Kennedy Building .

Boston, MA 02203 Dr. John Tietjen, Chairman 134 Palisade Avenue Le nia,NJ 07605 cc (without enclosure):

Mr. Frederick Gay Dr. W. Huntting Howell New Hampshire NPDES Permit Coordinator 12 James Farm New Hampshire State Program Unit Lee,NH 03824 Environmental Protection Agency John F. Kennedy Building Dr. Saul Saila Boston,MA 02203 317 Switch Road Hope Valley, RI 02832 Mr. Jeffrey Andrews NH Dept. Of Environmental Services Dr. Bernard J. McAlice <

Water Supply & Pollution Control Division Darling Marine Center 6 Hazen Drive University of Maine Concord,NH 03302 Clarks Cove Road Walpole, ME 04573 Mr. Robert Estabrook l NH Dept. Of Environmental Services Dr. Robert Wilce Water Supply & Pollution Control Division Department of Biology 6 Hazen Drive 221 Morrill Science Center

' Concord, NH 03302 University of Massachusetts Amherst,MA 01003 Mr. John Nelson NH Fish and Game Department NORMANDEAU ASSOCIATES 37 Concord Road Durham,NH 03824 cc (without enclosure): 1 Ms. Marcia Bowen Mr. Bruce Smith Normandeau Associates,Inc.

NH Fish and Game Department 82 Main Street 37 Concord Road Yarmouth, ME 04096 Durham,NH 03824 Mn oh Ship g p,,, Normandeau Associates,Inc, 25 Nashua Road Environmental Protection Agency 60 Westv,ew i Street Bedford,NH 03110 Lexington, MA 02173