ML20058E479

Semiannual Rept on Benthic Algal & Faunal Monitoring at Pilgrim Nuclear Power Station,Jan-June 1990

ML20058E479
Person / Time
Site:	Pilgrim
Issue date:	06/30/1990
From:	SCIENCE APPLICATIONS INTERNATIONAL CORP. (FORMERLY
To:
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ML20058E453	List: BECO-90-054, Forwards Marine Ecology Studies Re Operation of Pilgrim Station,Semiannual Rept 36,Jan-June 1990 ML20058E464 ML20058E469 ML20058E479 ML20058E482 ML20058E486
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NUDOCS 9011070187
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1 SEMI-ANNUAL REPORT Nwber 36 on I

BENTHIC ALGAL AND FAUNAL MONITORING AT THE E

PILGRIM NUCLEAR POWER STATION 5

January-June 1990 l

3 10 1

BOSTON EDISON COMPANY l.

Regulatory Affairs Department

{

Licensing Division 25 Braintree Hill Omce Park Braintree, Massachusetts 02184 i

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SCIENCE APPLICATIONS INTERNATIONAL CORPORATION 89 Water Street Woods Hole, MA 02543 (508) 540 7882 II 15 September 1990

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r TABLE OF CONTENTS EXECUTIVE

SUMMARY

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1.0 INTRODUCTION

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2. 0 M ETHODS...................................................

1 2.1 FIELD S AMPLING........................................

1 2.2 LABORATORY ANALYSIS...................................

4 2.3 D ATA ANALYSIS.........................................

6 3.0 RESULTS....................................................

9 3.1 QUALITATIVE TRANSECT SURVEY...........................

-9 3.1.1 April 1990 Transect Survey............................

10 3.1.2 June 1990 Transect Survey 10 I

3.2 QUANTITATIVE FAUNAL MONITORING,......................

13 3.2.1. Systematics.......................................

13 3.2.2. Species Richness....................................

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3.2.3 Faunal Density............. -.......................

15 L

3.2.4 Species Dominance....................................-

17 3.2.5 Species Diversity....................................

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-I 3.2.6 Community Analysis.................................

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3.3. QUANTITATIVE ALG AL MONITORING '.......................

24 3.3.1 Systematics.......................................

24 I

3.3.2 Algal Community Description...........................

24 3.3.3 Algal Community Overlap.............................

24 3.3.4 Algal Blomass......................................

26 1'

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4.0 DISCUSSIO N................................................

28 L

4.0_ LITERATURE CITED..........................................

30 APPEND I X A....................................................

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LIST OF TABLES Table 1.

Algal Indicator Species used in the Quantitative Community Analysis......

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Table 2.

Faunal Species Richness at the Effluent, Manomet Point, and Rocky Point Stations in A pril 1990..................................... 14 i

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Faunal Densities at the Effluent, Manomet Point, and Rocky Point Stations in Table 3.

A pri l 1990...................... -.......................

15 Table 4.

Rank Order of 15 Dominant Species Collected in April 1990............ 18 I

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Table 5.

Community Parameters for the Emuent, Manomet Point, and Rccky Point Statier.a in April 1990..................................... 19 Table 6.

Dry Weight Biomass (g/m ) for Chondrus crispus, Phyllophom spp., Epiphytes, 2

The Remaining Benthic Species, and Total Algal Biomass at the Emuent,

- Manomet Point, and Rocky Point Subtidal (10 ft MLW) Stations in April 1990. 27 I

LIST OF FIGURES Mgure 1.

Location of Benthic Sampling Sites near Pilgrim Station................ 2 Mgure 2.

Suction IJfe Device Used by Divers to Collect Benthic Samples............ 3 Figure 3.

Design of the Qualitative Transect Sampling Program................

5 Figure 4.

Configuration of the Denuded (904 m ) and Stunted (90 m ) Zones in the Emuent 2

2 p

Canal for April 6 1990..................................... 11 Figure 5.

Configuraten of the Denuded (1835 m ) and Stunted (300 m ) Zones in the 2

2

. Emuent CanJ for June 19 1990.............................. 12 l

Mgure 6.

Density of Benthic Fauna in April 1990: A, Total Density; B, Mytilus edulis; C, Jassa falcata; D, Lacuna vincta............................... 16 j '

Figure 7.-

Dendrogram Showing Results of Cluster Analysis by Station Replicates of the h;

g April 1990 Data Using Bray-Curtis and Group Average Sorting.......... 21 Figure 8.

Dendrogram Showing Results of Cluster Analysis by Station Replicates of April l

1990 Data Using NESS and Group Average Sorting................... 22 Figure 9.

Dendrogram Showing Results of Inverse Cluster Analysis of the 48 Mosts Abundant Species of the April 1990 Data Usin

' Sorting.......................... g Bray-Curtis and Group Average

.................... 23 Mgure 10.

' Algal Community Overlap (Jaccard's Coefficient of Comm' unity) and Number of Species Shared Between Replicate Pairs: A, Manomet Point Station; B, Rocky t

a Point Station; C, Emuent Station; D, Station Overlap................ 25 E

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EXECUTIVE

SUMMARY

nis report represents results of quantitative data collected in April 1990 at established stations in the vicinity of the Piigrim Nuclear Power Station (PNPS) and qualitative transect surveys I

conducted in the thermal effluent in April and June of 1990. These investigations represent the most recent phase of the long-term efforts to monitor the effects of thermal effluents on the benthic communities adjacent to the PNPS.

I A variety of analytical techniques were used to assess community structure. Specific data on algal biomass, dominant fauna, species diversity, and faunal densities were analyzed along with I

overall community relationships. Field collections and laboratory techniques were identical with previous efforts. Every effort was made to ensure that the long-term comparability of the database I

would not be compromised because of a change in contractors in 1990.

OUANTITATIVE STUDIES Faunal Studies A total of 112 species of benthic invertebrates were found in the April 1990 samples. The majority of species consisted of polychaetes (40), molluscs (35), and crustaceans (30). The total number of species recorded at the Effluent GO), Manomet Point (71), and Rocky Point G9) stations were higher than recorded in the spring samples in 1989 (Eff: 36; MP: 46; RP: 42).

Total densities recorded at the three stations was very high, due in large part to high counts of the blue mussel, Mytlius edulls. De Effluent station was lowest in total density (202,424) individuals 2

2 per m ), whereas the Manomet Point station was highest (430,266) individuals per m ). Densities of each of the three highest ranked species, Mytilus edulls, the amphipod Jassafalcata, and the northern lacuna lacuna vincta, were also highest at Manomet Point.

He 15 highest ranked species at each station accounted for approximately 98% of the total density at eac! ;tation, ne larger list of rare species (55 to 64) recorded at each station thus contributed little to total density. Myrilus edulls, Jassafalcata, and Lacuna vincta are the first, second, and third ranked species at all three stations. A total of 21 species comprise the lists of 15 highest ranked species at all three stations. Among the iominance lists, amphipods are the dominant taxon in terms of species with nine different species among the top 21 listed.

Species diversity indices are obscured by the high density of Mytilus edults. When the nassel; are removed from the species list, the diversity patterns reflect the high values expected of E

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communities having high numbers of species. For example, Shannon's H' ranged from 3.35 l

(Manomet Point),3.65 (Emuent station), to 4.13 (Rocky Point), nese values are indicative of high diversities expected in healthy faunal communities of subtidal coastal environments.

Community analysis by clustering or similarity techniques indicates that there is little difference between the three stations. Replicates of the F>muent, Manomet Point, and Rocky Point stations intermix to some extent regardless of whether the Bray-Curtis or NESS similarity measures are used. Historically, the Emuent station has been different from the two reference stations. ; hat situation does not appear to be present today.

Similarity analysis by species reveals that species groups are joined by their dominance patterns. For example, most of the species that comprise the lists of highest ranked dominant spdes tend to cluster together, while the rare or infrequently encountered species comprise other groups.

Algal Studies No additions to the cumulative algal lists were made as a result of analysis of the April 1990 samples, he rock and cobble substrata found at the Effluent, Manomet Point, and Rocky Point stations were heavily populated with red algae, especiallv Irish moss, Gondrus crispus and Phyllophora spp. Epiphytic algal species werc observed at all stations, with Qondrus and Phyllophora serving as primary hosts.

Algal community overlap measures the similarity in algal species composition between stations. In April 1990, the percent of replicate overlap was higher at the Effluent station (27.7%)

than for either the Manomet Po5t (24.0%) or Rocky Point (22.5%) stations, Indicating that individual samples at the Emuent station were less similar to one anoth:r than the samples from the reference a

stations. Community overlap between the three stations was very high, indicating a high degree of I

homogeneity in species shared.

5 Total algal biomass was highest at the Emuent station and lowest at Rocky Point, Blomass of Gondrer crispus was highest at Manomet Point and lowest at Rocky Point. Phyllophora spp.

biomass was highest at the Emuent station and lowest at Manomet Point. The highest biomass of benthic algal species other than Gondrus and Phyllophora was at Rocky Point. The highest biomass of epiphytic algae was found at the Effluent station. Analysis of variance (ANOVA) indicated no significant differences in biomass values between the three stations.

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I OUALITAT1VE TRANSECT SURVEYS The qualitative transect studies performed to evaluate Gondrus crispus community in the effluent canal indicates that the denuded and stunted neas have returned to a condition that is typical of full operation of the plant. De Gondrus denuded and stunted areas encompassed 904 and 90 m',

respectively in the April 1990 survey and 1835 and 300 m in June. The size of the affected area in 2

June was similar to neas affected before the 2% yr shutoown of the plant, ne most important observation taken during these surveys was the remarkable development of dense mats of blue mussels (Mytilus edulls) in June. The mats were so thick that the algae were completely buried under mussels that measured I to 2 cm in length. He size of these mussels I

sugguts that they migrated to the effluent canal as postlarval plantigrades that had originally settled on filamentous red algae in surrounding areas. The continuous water flow and warmer temperature I

present in the efauent canal along with rock surfaces that were largely devoid of algal growth are possible attractive factors that might account for this unprecedented event.

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1.0 INTRODUCTION

j nis report represents a continuation of the long-term (17 yr) algal and faunal studies at Pilgrim Nuclear Power Station (PNPS) that are intended to monitor the effects of the thermal effluent (under Boston Edison Company Purchase Order No. 76261). ne 1990 program is essentially the same as previous monitoring efforts conducted over the last 10 years. Quantitative benthic algal and i

faunal sampling is conducted during the spring and summer at two reference sites at Rocky Point and l

Manomet Point and at a site offshore of the effluent canal (Figuro 1). Qualitative SCUBA surveys of algal cover at the effluent canal are conducted quarterly during tiarch, June, September, and l

December. This Semi Annual Report includes quantitative data from samples that were collected in April 1990 and qualitative observations recorded in April and June 1990.

2.0 METIIODS 2.1 IlFID SAMPLING ne sampling sites are the same locations that have been sampled since the beginning of the current monitoring program, approximately 10 years ago. The stations are located by the following i

established procedures. Line-of-sight positions are established using highly visible structures located on the shore as reference points, ne Rocky Point station is located by lining up the microwave relay tower with the PNPS red and white off gas stack. He Effluent station is identified along the center l

line between the two discharge jettles, located approximately 120 m offshore, ne Manomet Point I

station is fixed by lining up the two southernmost telephone poles on top of Manomet Point. Line-of-sight position combined with lead line depth checks ensures station relocation to within a radius of 20 to 30 m of the original station position.

1 All sampling is done by SCUBA-equipped biologists operating from a small boat. For the quantitative algal and faunal studies, five replicate samples delineated by a metal pipe frame quadrant measuring 0.33 m on a side (0.1089 m ) are taken from the surface of rocks at each station.

2 Upon arrival at a station, the divers descend to the bottom and locate suitable rocks for placement of the quadrat. Divers are able to assess algal and faunal cover and select rocks that are considered typical for the station.

All attached flora and fauna within the quadrat are scraped from the rock and drawn through an airlift device into a 0.5 mm mesh bag (Figure 2). Field labels with station, collection date, and replicate number are placed in sample bags before sample collection. The bag is tied and placed in a large catch bag; a new bag is then attached to the airlift. He divers then locate the next suitable rock l

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and repeat the sampling process. After the five replicates are collected at a station they are delivered to a biologist on the boat for processing.

While the vessel is underway to the next station, the contents of each bag are transferred to a l

l gal plastic jar, labeled, and preserved with 10% buffered formalin. Approximately 100 g of Borax is added to each jar as a buffering agent to prevent softening of calcified shells.

For the qualitative transect survey, SCUBA observations are made along the axis of the discharge cr.nal. A line is extended across the mouth of the discharge jetty (Figure 3). A weighted transect line, marked at 10-m intervals, is then attached to the center of this line and deployed along the central axis of the canal to a distance of 100 m offshore. A 30-m measuring line, marked at 1 m intervals, is extended perpendicular to the transect line by the divers and oriented to the transect line with a compass. A diver traverses this third line underwater and records changes in algal caver at 10-m intervals from the transect line through the denuded and stunted Gondrus areas to whue the algal cover becomes normal.

According to procedures established by Taxon (1982) and followed in subsequent years, che distinction between " denuded" and " stunted" is based on Gondrus crispus. De denuded zone is defined as that area where Gondrus occurs only as stunted plants restrictc2 to the redes and crevices of rocks. In this area, Gondrus is found on the upper surfaces of rocks only where the microtopography of the rock surfaces creates small protected areas. In the stunted zone, Gondrus is found on the upper surfaces of the rocks but is noticeably inferior in height, density, and frond development. The normal Ane is considered to begin at the point where these factors are typical for the depth and substratum in question.

In addition to observing algal cover, the divers record any unusual occurrences or events in the area and note the location of any distinctive algal or faunal associations.

2.2 LABORATORY ANALYSIS In the laboratory, the algal and faunal fractions of the samples are separated by washing the l-animals off the algae onto a 0.5 mm-mesh screen. The animals are preserved in a solution of 70%

ethanol. The algal fraction is preserved in a 10% formalin solution. De faunal samples are labeled and stored in 16-oz glass or plastic jars until sorting. Algal samples are labeled and stored in 1 gal g

plastic jars until sorting.

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Each replicate sample is processed separately. The algal component of each sample is examined, using both dissection and compound microscopes, to identify all species of macroalgae and I

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I to determine the presence or absence of 38 indicator species. Important algal references used to identify and confirm names are Taylor (1957), Parke and Dixon (1976), and South (1976). De indicator species were originally chosen in September 1978, and were carefully selected from a list of the several hundred algal species recorded from the PNPS study sites during the 19741978 period (Taxon,1982). The indicator species include members of each of the major algal families from a variety of habitats, including all of the dominant species within the study area, the majority of the macrophytic species, and the most common epiphytic species (Table 1). Herefore, the indicator species comprise the mo':t substantial part of the algal community as measured by both percent cover and biomass, although they constitute only a small fraction of the flora inhabiting the study area in terms of the number of species. Dry weight biomass of each sample is reported for four sepa: ate algal fractions: Gondrus crispus, Phyllophora spp., epiphytic species, and the remaining benthic species. Total algal biomass is also reported. Each fraction is weighed on a Mettler balance after drying for 72 h in a drying oven set at 80'C.

A 25% aliquot of the faunal fraction of each sample is processed, and the remaining 75% of the sample is archived. Prior to sorting, the 25% aliquot is stained with a saturated alcoholle solution of Rose Bengal for at least 4 h, but no longer than 48 h to avoid overstaining, ne samples are examined under a dissecting microscope and each organism or fragment thereof removed.

Invertebrates are sorted to major taxonomic groups, such as polychaetes, crustaceans, bivalves, gastropods, echinoderms, and other miscellaneous phyla The blue mussel Mytllus edults is left with the residue and counted during the sorting process.

Final identification is to the lowest possible taxon (usually to species). During identification, the counts of each species are recorded. A new reference collection for the PNPS program has been developed from the April 1990 samples and will serve as a voucher collection for subsequent identifications, ne samples are archived for a minimum of three years after collection.

i 23 DATA ANALYSIS All faunal data are kept on specially designed project data sheets to facilitate computer entry.

Data are keypunched into a spreadsheet, using Quattro Pro', on a personal computer. Some basic data summaries and calculations can be made while the data is in this form. Following data entry and g

reorganization in the spreadsheet, a hard copy of the raw data is generated and verified against the u

original coding sheets. All keypunching errors are corrected at this point. Data files are then transferred to the WHOI (Woods Hole Oceanographic Institution) VAX computer for analysis.

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I Table 1.

AlgalIndicator Species used in the Quantitative Community Analysis.

Chlorophyta (Gressi Algae)

Bryopsisplumosa C. melagonium I

Enteromorphaflexuosa Rht:oclonium riparium Gymnogongrus crenulatus Ulm lactuca Membranoptera alata I

Palmariapalmata Phaeophyta (Brown Algae)

Phycalrys rubens Phyllophora truncata I

Osordariapagell{ formis P. pseudoceranoides Desmarestia aculeata P. traillit D. viridis Polyides rotundus laninaria digitata Polysiphonia elongata L. saccharina P. Jibrillosa Sphacciarla cirrosa P.hanryl P. nigrescens Rhodophyta (Red Algae)

P.urceolata Rhodomela confermides Ahnfeltiaplicata Spermothamnion repens i

Antithamnion americanum l

Bonnemaisonia hamifera lI Callophyllis cristata Ceramium rubrum Otondrus crispus l

Corallina oficinalis l an Cystoclonium purpureum Gracilaria tlkwhlae I

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Analytical software consists of a suite of programs developed specifically for the analysis of benthic data. In addition to a variety of data-management and modification utilities, these programs include PRARE1 and COMPAH. PRARE1 summarizes the data for each sample, calculates a variety of diversity related indices, and generates a rarefaction curve. COMPAH is a multivariate classification package that allows a wide variety of user-specified options for similarity indices and clustering strategies, including both normal (i.e. by station) and inverse (i.e. by species) analyses.

The individual species composing the fauna at each station are rank ordered by abunFuce, ne most abundant species is listed first, followed in order by less abundant forms. He percent contribution of each species to the total fauna is denoted by a decreasing total percen' age starting with the most abundant species and ending with the most rare. Basic statistical treatments include calculation of means of abundances per station and extrapolation to density per m.

2 Species richness is interpreted by using a jackknife procedure in combination with pooled species data to evaluate the contribution of rare species in the communities (Heltshe and Forrester, 1983). This procedure takes into account that random samples are not necessarily representative of a population. He jackknife estimate of species richness is a function of the number of so called

" unique" species present at a station, that is those that are present in one and only one replicate out of five. The Jackknife estimate of species richness ($) is expressed as:

$ = S+

" ' ') k n

I where S represents the pooled species numbers at each station, n is the number of replicates, and k is the number of unique species, ne variance of estimated species richness (var ($)] is also calculated to measure the spatial distribution of unique species.

Measures of diversity calculated for each sample and station include the Shannon Wiener information (N') and evenness (J') indices and rarefaction curves according to the method of Hurlbert (1971). Shannon's H' has been shown to be a biased estimator and for small samples will l

underestimate true population information (Smith and Grassle,1977). Huribert's expected species index of diversity is an unbiased estimator and is thus particularly useful when small and unequal sample sizes must be compared.

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I De measure of similarity developed by Grassle and Smith (1976), the Normalized Expected Species Shared (NESS), combined with group average sorting is used for cluster analysis. NESS is based on the expected number of species thared between random samples of sl:e m drawn from a population, and is sensitive to the less common species in the populations to be compared.

The Bray-Curtis similarity measure, combined with group average sorting, is also used (Boesch,1977). nese values are calculated for stations (normal) and species (inverse), using numbers of individuals of species.

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In the event that patterns in the station and species analysis require further interpretation, a I

nodal analysis is performed using the results of the similarity procedures described above. His procedure is especially useful when evaluating the combined spring and summer data. Nodal analysis I

is a method of relating normal and inverse classifications to aid in the interpretation of cluster analyses. The method uses two-way tables that show replicate groups on the vertical side and species I

groups on the horizontal side. This technique is used to measure constancy and fidelity. Constancy is a proportion derived from the number of occurrences of a species group in a replicate group as compared with the total possible occurrences. Fidelity is the degree of restriction of a species group I

I to a replicate group. In this report we elected to not use nodal analysis because the stations and l

species clustering patterns were readily explained.

l Pt the algae, community overlap was calculated using Jaccard's coefficient of community (Grieg Sm.th,1964) to measure the similarity in algal. species composition among the Effluent, Manomet Point, and Rocky Point stations. Jaccard's coefficient provides a mathematical evaluation of the similarity between two replicates or stations using only species occurrence and does not consider differences in their abundance.

3.0 RESULTS 3.1 OUALITATIVE TRANSECT SURVEY Qualitative transect surveys of acute nearfield impact zones were initiated in January 1980 and have been conducted quarterly since 1982. Two surveys were performed (April 9 and June 19) during the current reporting period, bringing the total number of surveys conducted since 1980 to 38.

Results of the four surveys performed in 1989 are reviewed in Semi Annual Report No. 35 (BECO, 1990). Detailed results of the mapping conducted in April and June 1990 are presented in the next two sections.

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I 3.1.1 Anril 1990 Trm=* Surver De extent of the denuded and stunted areas mapped on April 61990 immediately offshore from PNPS is shown in Figure 4. A large boulder that is nearly exposed at mean low water, and that is used as a landmark by both the SAIC and the Massachusetts Division of Marine Fisheries dive teams is plotted in the figure. The denuded zone is essentially devoid of Gondrus crispus whereas the stunted zone has Gondrus that is smaller and less dense than that growing under normal conditions. De dive team must keep in mind while taking measurements that the shallower depths to the northwest of the discharge canal preclude normal Gondrus growth.

In April 1990, the denuded zone extended approximately 70 m offshore along the centerline of the effluent discharge canal. As in previous surveys the denuded zone was asymmetrically distributed around the transect line, extending further toward the northwest than to the southeast.

j The general configuration of the denuded zone was similar to that observed during the December 1989 survey but the area (approximately 904 m ) was 25% smaller. Within the denuded zone, from 2

the 10-m to 50-m mark, some rocks were completely devoid of all macroflora and others were covered with patches of young Gondrus, Enteromorpha and Ulva. The latter two species were predominant within and adjacent to the discharge canal. A dark red alga, believed to be Gracilaria tilauhlae, was present between the 10- to 30-m mark of the transect. At the 60-m mark and north of the transect, many rocks withia and outside the denuded zone were densely covered with the coralline alga, Corallina oficinalis. Also at the 60 m mark, some rock weed of the genus Fucus was observed g

within the denuded zone south of the transect and was the predominant species beyond the denuded u

zone to the narth. In contrast to the previous two surveys, very few mussels were observed within the survey area.

The stunted zone, with an area of about 90 m, extended only along the south side of the 2

transect from the tip of the southern submerged jetty to the 65 m mark. The greatest width reached by the stunted zone was five meters at the 50 m mark on the transect.

I 3.1.2 June 1990 Transect Survey Results of the transect mapping for June 19,1990 are shown in Figure 5. The denuded zone extended approximately 100 m along the transect line. The configuration of the denuded zone was quite different from that seen in the April survey: it was shaped like an hourglass with the waist at the 70-m mark and extended up to 18 meters northwest of the transect line at the 90-m mark. The area of the denuded zone had doubled in size (to approximately 1835 m ) since the April survey.

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Configuration of the Denuded (904 m') and Stunted (90 m ) Zones in the Emuent Canal for April 61990. Dark Shaded area denotes denuded zone; light shaded area denotes stunted zones.

11

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Figure 5.

Configuration of the Denuded (1835 m ) and Stunted (300 m ) Zones in the 3

Effluent Canal for June 191990. Dark Shaded area denotes denuded zone; light g

st. ded arei denotes stunted zones.

12 l.

I In contrast to the April 1990 survey when very few mussels were seen by the divers, a veg dense mat of blue mussels (Myritus edulls), each about 1 to 2 cm in length, covered the entire survey area. De mussel mat was most dense between 50 and 100 m on the transect line. Mussels had invaded all available substrata including living Gondrus plants, ne scattered groups of Gondrur seen within the denuded zone were low mounds covered by mussels; dissecting these mounds revealed living Gondrus beneath. Numerous starfish (Asteriasforbest)(up to 10 per m) were seen grazing 2

on the mussels from the 70-m to 90-m mark on the transect. Between the 10-m and 40-m mark in the denuded zone scattered patches of Gondrus were present as were some Enteromorpha, Ulva, Codium, and Gracillaria plants. Striped bass and tautog were seen swimming in the effluent canal, ne stunted zone was present on both sides of the denuded zone during the June survey and I

had tripled in area from the April survey to about 300 m. He stunted zone on the southeast side 2

extended from the 50-m to the 90-m mark on the transect and was narrow, averaging about 2 m wide.

On the northwest side, the stunted zone extended from the 40-m to 97 m mark and was up to 9 m wide.

i 3.2 OUANTITATIVE FAUNAL MONITORING 3.2.L Systematis In the spring of 1990,112 species were found in the study area, ne greatest fraction of the l.

total fauna consisted of polychaetes (40 species, 36%), followed by molluscs (35 species, 31 %),

crustaceans (30 species,27%), echinoderms (5 species,4%) and several smaller phyla such as I

nemerteans, anemones, and tunicates. A list of the species collected in the April 1990 survey is I

included in Appendix A.

De total number of species reported here is considerably lower than the cumulative total of more than 483 species indicated in previous reports (i.e. BECO,1989). The previously reported totals were the result of cumulative identifications observed over several years and do not represent a true picture of the fauna from any one year. It is likely that no more than 100 to 125 species are found in the study area at any one time. Some species will be dominant and are likely to be present from one year to the next. Others, however, are rare and their occurrence in the Gondrus communities is probably ephemeral. It is also possible that some of the names of the comprehensive species code list represent different identifications of the same species made over the years. Most taxonomic problems probably reside with the rare species because they appear so infrequently that there is little chance for exchange of information among project technicians.

.I I

I l

3.2.2. Species Blehness Species richness values for all three stations for April 1990 are presented in Table 2. Data are presented as total species per replicate for each station, with a mean value over all replicates at each station and a cumulative total representing pooled species numbers at each station. Because the area included within each replicate is 0.1089 m, the cumulative species total at each station 2

2 represents a total area of 0.5445 m.

In April 1990, the Rocky Point reference station had 79 species for pooled replicates, the

)

highest number among the three stations. Manomet Point followed Rocky Point with 71 species, the Effluent station had 70 species. The average number of species per replicate again resulted in Rocky Point being first (48.2) followed by Manomet Point (47.6) and the Effluent station (39). An analysis of variance (ANOVA) that compared the mean number of species occurring at each of the stations indicated no significant difference at p = 0.05.

In order to assess the rare species that might be present at the stations but were not found because of the relatively small area sampled, the Jackknife estimate of Heltshe and Forrester (1983) was calculated (See Section 2.3). At all three stations, species richness was higher than had been measured in the spring samples from previous years. For example, $ values for April 1990 are 84.4 (Effluent), 82.2 (Manomet Point), and 97.4 (Rocky Point), whereas the same measurements for March 1989 were 43.2,57.6, and 49.2 respectively. "Ihese results also agree with the considerably higher total number of species actually present in the samples (1990: 70,71, and 79 versus 1989: 36, 48, and 42, respectively). The variance of the Rocky Point Station differs the greatest from the other two stations suggesting that the contribution of rarc species is greatest at that station.

Table 2.

Faunal Species Richness at the Emuent, Manomet Point, and Rocky Point Stations in April 1990.

EfDuent Manomet Point Rocky Point No. Species / Replicate 41,41,42,30.41 48,46,41,St.52 51,50.52,45,43 Mean i Standard 39.0 t 5.o4 47.6 i 4.39 48.2 i 3.96 Deviation No. SpeciosiStation 70 71 79 Jackknifed Estimate E.4 82.2 97.4 g

Species Richness ($)

g Variance ($)

3.20 7.2o 9.00 I

I

^'

'I 3.2.3 Faunal Densite Total faunal densities recorded at the three stations in April were very high. Table 3 shows the total density figures for each replicate and ext apolated to square meters. Total dcasities were greatly influenced by the Myrilus edulh population. De Efficent station was lowest in terms of total density and numbers of M. edults, whereas the Manomet Point Station was highest. However, the densities at the Effluent station (202,424 individuals per m) were considerably higher than recorded 2

from the same time period in 1989 (BECO,1990). Densities of M. edults ranged from 151,588 per 2

2 m at the Effluent Station to 332,231 per m at Manomet Point, nese very high populations of M.

edults have continued since 1988 (BECO,1989). In 1987, mussel populations were very low (BECO, 1988) Figure 6 depicts the total faunal densities :md densities of Mytilus edulls, Jassafalcata, and Lacuna vincta at the three stations from the April 1990 data. In all instances, the Manomet Point densities were higher than either the Effluent or Rocky Point stations.

I Table 3.

Faunal Densities at the Emuent, Manomet Point, and Rocky Point Stations in April I

1990.

I Total Density Station With Mytilus edulis Without Mytilus edulis I

Mean (R) No.

Density Mean (R) No.

Density Mean (R) No.

Density Indiv./ Rep.

per m Indiv./ Rep.

per m -

Indiv./ Rep.

per m 2

2 2

Effluent 22,044 202,424 5,536 50,836 16,508 151,588 Manomet 46,856 430,266 10,676 98,035 36,180 332,231 Point Rocky 31,157 286,105 6,549 60,136 24,608 225,969 Point I

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I 314 Spadas Dominance ne 15 numerically dominant species collected at the Effluent, Manomet Point, and Rocky Point stations in April 1990 are shown in Table 4. Data are presented as the average number per replicate (%

aliquot) and percent composition at each station. Fifteen species were shared among 21 dominant species present in the dominance lists developed for the three stations. The highest ranked 15 species generally accounted for 98% of the total density at each station. ne longer list of rare or infrequently encountered I

species (55 to 64, depending upon station) accounted for no more than 1.3 to 2.2% of the total density.

The benthic communities at all three stations were dominated by the blue mussel Mytilus edulls I

(Effluent,76.5%, Manomet Point,79.04%, and Rocky Pcint,82.5%). He very high contribution of juvenile and adult mussels obscures the importance of other resident fauna. Neverthelets, it is interesting I

that the second and third ranked species, the amphipod Jassafalcata and the gastropod Iocuna vincta, were the same at all three stations. Eighteen additional species filled the remaining position ranks at the three stations. After mussels, the amphipods were the dominant group with 9 of the 20 species on the I

dominance lists. The high percentages of amphipods were consistent with previous results in the study area (Davis and McGrath,1984; BECO,1990).

He results listed in Table 4 are remarkable in that only six of the top 15 species at each station are restricted to that station, indicating that there is a consistency in the predominant fauna at each of the three sites. Of six species Qat occur only once among the 15 highest ranked species, two occur at the Effluent Station, three at Manomet Point, and one at Rocky Point. Thirteen dominant species are shared among all stations, and two dominant species are shared between the Effluent and Rocky Point Station.

3.2.5 Snecies Diversitv Species diversity was measured using the Shannon-Wiener Information Index (H') and the Hurlbert rarefaction method. Both techniques clearly indicate that the high numbers of Mytilus edults in the samples greatly affect the concept of species diversity in the benthic community. Results of species diversity calculations both with and without the mussels is shown in Table 5. From these results it is seen that the presence of mussels in the samples alters tha diversity indices by approximately a factor of 2.

He highest species diversity is found at the Rocky P::ha Station, where the H' index measures 4.13 and the number of species per 5000 individuals is 73.4 when mussels are not included. Effluent Station is slightly higher than Manomet Point for these same parameters. The April 1990 results are very similar to those recorded in March 1989 (BECO,1990), where H' ranged from 3.69 (Rocky Point),3.82 (Effluent), to 4.02 (Manomet Point). Rarefaction values were not presented for 1989. It is interesting I

I

-. _ ~

I Table A Rank Order of 15 Dominant Species Collected in April 1990.

Meam Number per Pescent of Sea.

Rank Species Replicate Identined Feman 8

EFF I

Myeim edds (Bivalve) 4,126.6 76.50 2

/assefalcau (Amphipod) 330.0 6.12 3

Lacms Wacu (Gesuopod) 221.4 4.11 4

Corophisen acumsr (Amphipod) 129.6 2.40 5

Ponerencia daarnals (Amphipod) 124.2 2.30 6

Ca$opim laanscals (Amphipod) 80.4 1.49 7

lschyrocerus anguipes (Amphipod) 68.8 1.28 l

8 Caperde penands (Caprellid) 49.8 0.92 9

Desamine thes (Aemphipod) 40.6 0.75 W

10 Anomus sunplet (Bivalve) 36.2 0.67 11 Idous phorpnores (Isopod) 32.0 0.59 12 Corophium bonem (Amphipod) 29.4 0.55 13 Proloboedcs hoenesi(Amphipod) 15.6 0.29 14 Odossomie seminuds (Gasuopod) 12.2 0.23 15 Molgula sp. (Tunicals) 9.2 0.17 E

TOTAL OF 15 SPECIES 5,306.0 98.37 3 I REMAINING IDEhTIFIED FAUNA 55 $PECIES 87.4 1.63 TOTAL IDENTIFIED FAUNA 70 SPECIES 5,393.4 100.00 MP 1

Mysius adds (Biva <e) 9,045.6 79.04 2

Jassafalcase (Amph ' sod) 871.6 7.62 3

Lacune Wacsa (Gastrt wd) 378.0 3.30 l

4 lschyrocerus angesipes 'Amphipod) 269.2 2.35 8

Ponerencia inernits (A mphipod) 146.0 1.28 5

Corophium boarE (Ang hipod) 122.8 1.07 Caprr#4 penands (Capn 'Iid) 106.4 0.93 Desamir,a shes (Amphipo t) 100.4 0.88 9

Corophium acumen (Amph. pod) 72.0 0.63 10 Odossomis seminada (Gastropod) 39.4 0.34 11 Margarises As#cinus (Gastropod) 36.0 0.31 1

12 Comoptw latWscu!w (Amphipod) 32.0 0.28 13 Nieu#s eredea (Bivalve) 28.4 0.25 14 Photor minuse (Polychaete) 22.2 0.19 15 Piswymus glober (Amphipod) 21.2 0.19 TCTTAL OF 15 SPECIES 11,291.2 98.66 um REMAINING IDENTIFIED FAUNA - 56 $PECIES 172.3 1.34 TOTAL IDENTIFIED FAUNA 71 SPECIES I1,463.5 100.00 g'

RP 1

MyWiw eduus (Bivalve) 6,132.2 82J1 3

2 lassefalcosa (Amphipod) 214.8 2.88 3

lacune Wacsa (Gastropod) 198.4 2.66 4

Ischyroctrw anguipes (Amphipod) 135.0 1.81 5

Corophium 6onem (Amphiped) 112.0 1.50 6

Desamina shes (Amphipod) 101.0 1.35 7

Ponsogantia inernois (Amphipod) 99.4 1J3 i

8 Corophiasm acussa (Amphipod) 48.2 0.65 9

atossomia seminada (Gastropod) 43.4 0.58 10 Margartses Asocinw (Gastropod) 42.4 0.57 l

11 Caprella penands (Caprellid) 30.8 0.41 12 Amomis simples (Bivalve) 30.8 0.41 W

13 Comoptw latwsculus (Anghipod) 30.4 0.4i j

14 Staneopsis planor6ds (Gastropod) 28.0 0.38 l

15 Molsula sp. (runicate) 25.0 0.34 TOTAL OF 15 SPECIES 7,291.8 97.79 REMAINING IDENTIFIED FAUNA. 64 SPECIES 164.2 2.21 TOTAL IDENTIFIED FAUNA. 79 SPECIES 7,456.0 100.00

.__,-.~o._..

18 5.

W'W M

M M

M M

M M

M M

M W

W W

M M

M M

til 1990.

Table 5.

Community Parameters for the Effluent, Manomet Point, and Rocky Point Stations Station Density Total Species Species Species Species Species Nm Evenness (m )

No.

per 100 per 500 per 1000 per 2500 per 5000 Wiener U) 2 Species Indiv.

Indiv.

Indiv.

Indiv.

Indiv.

(II')

Effluent 202.424 70 10.9 20.9 27.1 38.2 48.1 1.64 0.268 Effluent Without 50,836 69 18.7 35.1 44.7 57.6 66.1 3.65 0.598 Mytilus Manomet 481,586 71 9.6 19.0 24.6 33.7 41.9 1.44 2.340 Point Manomet Point Without 149,355 70 17.7 32.2 40.3 51.9 60.4 3.35 0.545 Mytilus Rocky Point 379,129 79 I1.0 22.6 28.7 38.5 47.6 1.39 0.220 E

Rocky Point Without 153,160 78 22.7 39.2 48.4 62.3 73.4 4.13 0.658 Mytilus

I 1

l that the number of species recorded at these stations, however, is considerably higher in the 1990 samples than in the 1989 samples. In March 1989,38 species were recorded at the Effluent Station,48 at the Manomet Point Station, and 42 at Rocky Point. In contrast, the numbers of species recorded at these same stations in April 1990 were 70,71, and 79 respectively.

I LLft. Community Analysis Similarity Analysis by Semelon Results of the similarity analysis by station are shown in Figures 7 and 8. Figure 7 depicts a cluster analysis using the Bray-Curtis similarity measure. Two groups of replicates separate distinctly. A small group contains three samples from Manomet Point and one from Rocky Point, while all the remaining Manomet Point and Rocky Point samples along with all of the Effluent samples reside in the larger cluster. Results of the same analysis using the NESS are shown in Figure 8. Again two large clusters sepsrate in the analysis. Samples from all three stations are intermixed within both of these clusters. Rese results indicate that individual samples from single stations are not more similar among themselves than to replicates from other stations. The only exception is that four Effluent replicates cluster tightly on the left side of the NESS diagram. De fifth Effluent sample, however, is joined to the group on the right side of the diagram.

Similarity Analysis by Sneds Forty-eight of the highest ranked species were used to prepare the Bray-Curtis similarity analysis (Figure 9). The separation of groups of species by this analysis generally follows dominance patterns.

For example, Mytilus edulls, the most abundant species found in the study area forms a separate cluster that is most dissimilar to any other cluster in the analysis. Two very large and dissimilar groups of species separate at the.123 level. Within these larger clusters are distinct groupings of species that represent species that are either abundant and present at all stations or less common and distributed unevenly g

throughout the three stations. For example, the two species groups identified on the left side of the B

diagram contain all of the species found in the dominance table (Table 4) previously described.

A nodal analysis has not been performed on this single set of samples. His type of analysis is best performed on the combined spring and summer samples in order to elucidate seasonal trends.

I I

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EF EF RP EF MP RP EF EF RP RP MP RP MP MP MP 1 3 5 4 4 3 2 5 2 4 2 1 5 3 1

l I LI F1gure 7.

Dendrogram Showing Results of Cluster Analysis by Station Replicates of the

.I-April 1990 Data Using Bray-Curtis and Group Average Sorting.

l I

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I F1gure 8.

Dendrogram Showing Results of Cluster Analysis by Station Replicates of April 1990 Data Using NESS and Group Average Sorting.

I.

I 22 I

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I Figure 9.

Dendrogram Showing Results ofInverse Cluster Analysis of the 48 Most Abundant Species of the April 1990 Data Using Bray-Curtis and Group Average I-Sorting.

23

3.3 OUANHTATIVE ALGAL MONITORING 3.3.1 Syntamatia No additions to the cumulative algal species list presented in Semi Annual Report No.16 (BECO, 1980) were made as a result of analysis of the April 1990 satples, he 27 species present included 26 of the 38 indicator species and one additional species. De indicator species are listed in Table 1.

3.3.2 Alai Cam =>mity herintion ne rock and cobble substrata found at the Emuent, Manomet Point, and Rocky Point stations were heavily colonized by red macroalgae during the April 1990 survey, Two-thirds of the species collected belonged to the Rhodophyta (red algae). In addition to the dominant species Oondrus crispus and Phyllophora spp., other benthic rhodophytes included Ahrifelth plicata, Corallina oficinalls, and i

Polyides rotundus. Epiphytic rhodophytes foend in all replicate samples were Ceramium rubrum, Cystoclonium purpureum, Membranoptera alata, Polysiphonia harvey!, and Spermothamnion repens.

Other species collected in all samples were the chlorophytes (green algae) Gaetomorpha linum, Gaetomorpha melagonium and Rhizoclonium riparfum and the phaeophyte (brown alga) Desmarestia aculeata.

Total algal biomass was highest at the Effluent station and lowest at Rocky Point. Blomass of Gondrus crispus was highest at Manomet Point and lowest at Rocky Point. Phyllophora spp, biomass was highest at the Effluent station and lowest at Manomet Point. ne highest biomass of benthic species other than Gondrus and Phyllophora was at Rocky Point. The highest biomass of epiphytic algae was -

found at the Effluent station.

Gracilaria tlkvahlac, an indicator of warm water, was not collected in any of the replicate samples W

in April 1990. However, a dark red species, believed to be Gracilaria, was observed by the divers within g

the denuded zone between 10 and 30 m along the transect line during the April and June,1990 surveys.

5 3.3.3 Almal Community Overlau Community overlap was calculated for the April 1990 data using Jaccard's coefficient that provides a mathematical evaluation of the similarity between two replicates or stations using only species occurrence. Species occurrence records of all 26 indicator and one non indicator species that were found were used for community overlap calculations.

Results of community overlap comparisons between replicate samples for each station for the -

April 1990 collecting period are presented in matrix form in Figure 10. Ranges of percent overlap were I

e;

.I 2 -

3 4

5 1

2 3

4 5

i 1

17 19 19 23 1'

13 16 14 16 2

68.0 -

16 16 17 2

56.5 16 13 14 i

i h

1 3

73.1 76.2' 16 19 3

69.6 84.2 13 17 i

j I

4 76.0 80.0 69.6 18 4

66.7 72.2 61.9 14 l

5 92.0 77.3 87.6 78.3 5

66.7 63.6 77.3 66.7 A

C i

I' i

g 1

2 3

1 20 18 19

'I8 k

MP RP EFF 2

74.1 22 2

'N yp 26 24 I

)

3 69.2 84.6 22 19 t

RP

%.3 25 I

i 4

73.1 84.6 91.7 I9 i

EFF 88.9 92.6 D

5

-78.3 69.2 82.6 82.6 B

i t

i Hgure 10.

Algal Community Overlap (Jaccard's Coemcient of Community) and Number of Species Shared Betmen RepIlade Pairs: A, Manomet Point Station; B, Rocky Point Station; C, Emment Station; D, Station Owley.

l i

I 56.5 to 84.2 at the Emuent station,68.0 to 92,0 at the Manomet Point strtion, and 69.2 to 91.7 at the

- Rocky Point station. Replicate percent overlap for the Emuent station was higher (27.7) than that for the Manomat Point (24.0) or Rocky Point (22.5) stations, indicating that the replicates at the Emuent station were less similar to each other than to the replicates at the other two stations.

' Community overlap between stations was very high for all three pairs of stations, indicating a high degree of homogeneity in terms of species present at all three stations. Community overlap'was higher between the Manomet PolM and Rocky Point stations (96 3 %) than between the Manomet Point and Emuent stations (88.9%) or between the Rocky Point and Emuent stations (92.6%) '1his indicates that the algal communities at the Manomet Point and Rocky Point stations were more similar to each other.

than either was to the Emuent station.

Ei n

33.4 Aleal Blom-.

Gondrus crispus biomass values recorded for the Manome. Poin*, Rouy Point, ud Emuent j

stations for April 1990 are pidented in Table 6. In April 1990, the range of individual biomass values was greatest at Manomet Point (39.57 to 325.25 g/m ), followed by the Emuent station (18.18 to 180.57 2

2 2

g/m ), and Rocky Point (43.61 to 128.98 g/m ). At the Emuent, Manomet Point, and Rocky Point

stations, mean Gondrus biomass was 34%,48%,' and 31% of the total algal biomass, respectively.

1 The Manomet Point station had the highest mean biomass value for Gondrus (133.50 g/m),

i 2

followed by the Emuent station (118.92 g/m ), and the Rocky Point station (67.25 g/m ). An ANOVA 2

2 i

showed no significant differences between any of the stations when mean Gondrus biomass values were compared (at p=0.5).

Phvilonhora sno.

Phyllophora spp biomass values for the April 1990 collecting period are given in Table 6. The range, of individual biomass was greatest at the Effluent station (14.41 to 215.18 g/m ), followed by 2

Rocky Point (33.87 to 159.64 g/m ), and Manomet Point (16.98 to 105.48 g/m ). Phyllophora spp. were

.m !

2 2

o 37% of the total algal biomass at the Emuent station,36% at Rocky Point, and 26% at Manomet Point.

5 The Emuent station had the highest mean biomass value for Phyllophora spp. (130.87 g/m),

2

. followed by the Rocky Point (78.20 g/m ), and Manomet Point (70.65 g/m ).' No significant differences 2

2 existed between the stations in April 1990 when comparing Phyllophora biomass (at p=.05).

~

26 m.

l:

8 L

Table 6.

Dry Weight Biomass (g/m ) for Cheadmr crispur, Phyllophers spp., Epiphytes, 'the L

Remaining Benthic Spedes, and Total Algal Bioma8s at the Emuent, Manomet Point.,

L and Rocky Point Subtidal (10 ft MLW) Stations in April 1990.

Chondras cr6 pas Phy# sphere spp.

Remalalag Benthic Epiphytle Species AN Station /

Species (TotaD AlBae I

Replicate Bionnass Pereest Biomass Pereent Biomass Percent Biomass Percent Biomass EFFl'

- 148.62 36.76 163.50 40.44 5.60 1.39 86.57 21.41 404.28 I

EFF 2 158.81 28.55 215.18 38.68 62.97 11.32 119.34 21.45 556.29 EFF 3 88.40

. 28.46 135.77 43.72 5.88 1.89 80.51 25.92 310.56 EFF 4 180.57 -

44.98 125.49 31.26 13.77 3.43 81.61 20.33 401.44 EFF 5 18.18 19.51 14.41 15.46 29.38 31.53 31.21 33.49 93.18 L

R EFF 118.92 33.67 130.87 37.06 23.52 6.66 79.85 24.52 353.15 MP1 97.58 -

37.61 16.98 6.55 12.58 4.85 132.28 50.99

' 259.43 MP2 39.57 20.38 105.48 54.33 13.22 6.81 35.89 18.48 194.16 MP3 325.25 75.14 51.87 11.98 0.83 0.19 54.90 12.68 432.84 s

MP4-103.83 39.88 98.59 37.87 5.97 2.29 51.96 19.96 260.35

)

MP5 101.26 42.67.

80.33 33.85 21.02 8.86 34.70 14.62 237.32 I

R MP 133.50 48.23 70.65 25.52 10.72 3.87 61.95 22.38 276.82 RP 1 60.59 45.90 33.87 25.66 19.37 14.67 18.18 13J1 132.01 RP 2 50.21 24.02 86.66 41.46 47.92 22.92 24.24 11.60 209.03 4

RP 3 128.98 -

38.19 62.52 18.51 32.22 9.54 114.02 33.76 337.73 i

RP 4 -

52.88 34.76 48.29 31.74 20.20 13.28 31.95 21.00 152.12 RP 5

- 43.61 '

17.50 159.64 64.05 26.53 10.64 19.46 7.81 ~

249.24 I

li R RP 67.25 31.13 78.20 36.20 29.25 -

13.54 41.57 19.24 -

216.03 i

EFF: Emuent; MP: Manomet Point; RP: Rocky Point: R: Mean biomass L.

LI 27 I

i I

Blomans of Remaining Benthic Species ne remaining benthic species exclude Chondrus crispus, Mryllophora spp., Laminaria spp., and algal epiphytes. Blomass data for the remaining benthic species for April 1990 are presented in Table 6.

The Effluent station had the highest range of biomass values (5.60 to 62.97 g/m ), followed by Rocky 2

Point (19.37 to 47.92 g/m ), and Manomet Point (0.83 to 21.02 g/m). The percentage that the remaining 2

benthic species contributed to the total algal biomass was greatest at Rocky Point (14%), followed by 7%

at the Effluent station and 5% at Manomet Point.

The highest mean biomass values occurred at the Rocky Point station (29.25 g/m ), with the 2

Effluent and Manomet Point station equaling 23.52 g/m and 10.72 g/m, respectively. No significant 2

2 differences were found between the three stations for biomass of the remaining benthic species (at p=.05).

Epiphytic Algal Blomass i-Epiphytic algal biomass values for April 1990 are given in Table 6. In April 1990, mean epiphytic biomass values were highest at the Effluent station (79.85 g/m ), followed by the Manomet Point 2

2 2

. station (61.95 g/m ), and the Rocky Point station (41.57 g/m ). No significant differences in epiphytic biomass were found between the three stations (at p=.05).

Total Algal Biomass

-Total mean algal biomass for April 1990 is given in Table 6. The Effluent station had the highest

' biomass value (353.15 g/m ), the Manomet Point station ranked second (276.82 g/m ), and the Rocky 2

2 Point station ranked third (216.03 g/m ). Individual replicate ranges for total algal biomass in April 1990 2

at the Effluent, Manomet Point, and Rocky Point stations were 93.18 to 556.29 g/m,194.16 to 432.84 2

2 2

'g/m, and 132.01 to 337.73 g/m, respectively. An ANOVA showed no significant differences in total g

l algal biomass for the three stations (at p=0.5).

5 4.0 DISCUSSION Efforts to interpret the effects of thermal discharges of Pilgrim Station on the benthic communities

. are complicated by the year-to-year differences in operational levels of the plant ne recent 2%-year L

- outage resulted in the benthic communities associated with the effluent canal resuming a " normal"

-i appearance. For example, the transect surveys of the effluent canal conducted in March and June 1989 showed essentially no impact. The denuded zone reappeared in September 1989 and has continued to be

. present in subsequent surveys in December 1989, April 1990, and. Tune 1990.

28 a.

m

Faunal communities observed at the Effluent station have typically exhibited a low degree of similarity with the reference stations (< 60% Bray-Curtis similarity). However, beginning in 1984 at the time of a prolonged outage of the plant, similarity began rising to levels exceeding 70%, only to slowly decline again in 1985 (BECO,1986). Similarity again increased during the first half of 1987. De results I

of the Bray-Curtis similarity analysis in subsequent surveys suggest that there is no longer any difference between the Effluent station and the reference stations because the replicates of each station tend to I

intermix to varying degrees rather than retaining a station-specific identity or signature. This result may be explained in part by the enormous increase in mussel populations that has occurred since 1988. In 1987, mussels were not the highest ranked species (BECO,1987) Bray-Curtis is believed to be -

I.

influenced by the presence of species that occur in very high numbers and this has undoubtedly obscured g

the similarity analysis. However, this is not the case with NESS, which is more sensitive to the rare 5;

species. An examination of the NESS similarity results indicates that the Effluent station was distinct from the reference stations in 1989, but not in 1990. De NESS similarity between the Effluent station replicates and the reference stations was > 90, suggesting that the Effluent station does not differ significantly from the reference stations. In April 1990, there is no distinction between the Effluent station and the reference stations in terms of benthic assemblages. Results of the algal studies also

.l indicate that there are no significant differences among the Effloent, Manomet, and Rocky Point stations.

I These results might call into question the adequacy of the Effluent station as representative of an impacted L

area. However, Pilgrim Station was not operating in the month preceeding the collection of the April f

. samples, and the timing of this shutdown might explain the apparent lack of impact at the Effluent station.

The size of the Gondrur denuded zone in June 1990 was indicative of pre-outage impacts, ne major difference, however, between these observations and those of previous years were the incredible L

. populations of mussels observed in the area encompassed by the transect surveys. The mussels were -

reportedly so thick that they buried the attached algae by several layers. Active predation of starfish was L

observed throughout the area.

Most of tLe mussels observed in the April quantitative and June qualitative samples are juveniles and capable of migration. It is likely that the unusually high concentrations noted in June 1990 in the effluent canal durir.g the qualitative transect survey were due to migration from surrounding areas to a more favorable site. When mussel larvae first settle from the plankton, they feltlally settle on filamentous f

red algae. At this stage they are called plantigrade larvae and are capable of considerable movement j

(Bayne,1964; 1965). Normally, the plantigrades move from the primary settlement site to a suitable rock surface or mussel bed where they eventually secrete byssal threads and undergo a secondary settlement.

LI l

Even at this stage, however, mussels can exhibit movement, and when removed from a muasel bed, can readily secrete new threads and reattach. Thus, the settlement and migratory patterns exhibited by M.

edults might account for the decrease in populations at the control stations between March and September in 1989 and the increase at the Effluent station. Plantigrades have been postulated to move from areas of primary settlement to other areas by means of gas bubbles in the mantle cavity that permit them to adhere to the surface tension and float to new sites. Bayne (1964) postulated that this migratory phase could occur several times as the plantigrade M. edults attach to and leave several algal substrates before finding a suitable mussel bed for attachment. It is probable that the relatively exposed denuded areas and the warm water were attractive to migrating plantigrades. In warm waters, when food resources are available, most invertebrates are able to undergo rapit growth. Numerous studies have shown that the filtration rate (due to cillary activity) of N. edults and other filter-feeding bivalves is increased when temperature is increased (Newell,1979).

Benthic community parameters 'ncluding species richness, species diversity, and faunal density indicate that all of the stations are hea'. thy and support a rich fauna. Species richness data suggest that

there are more species present than m recent years. For example, at all stations, many more species were present in the April 1990 collections than in March 1989.

4.0 LITERATURE CITED Bayne, B.L.1964. Primary and secondary settlement in Mytilus edulls (L.) (Mollusca). Journal of Animal Ecology 33:513-523.-

Bayne, B.L.1965. Growth and delay of metamorphosis of the larvae of Mytilus edulls (L.). _ Ophella 2:1-47.

Doesch, D.F. 1977. Application of numerical classification in ecological investigations of water pollution. U.S. Enviroemental Protection Agency, EPA Report 600/3-77 033,114 pp.

Boston Edison Co. 1986. Marine Ecology Swdles related to the operation of Pilgrim Station. Semi-Annual Report No,'27. Boston, MA.

Boston Edison Co.1987. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-

. Annual Report No. 30. Boston, MA.

Boston Edison Co. 19881 Marine Ecology Studies related to the operation of Pilgrim Station. Semi-

- Annual Report No. 32. Boston, MA.

Boston Edison Co. 1990. Marine Ecology Studies related to the operation of Pilgrim Station. Semi-Annual Report No. 35. Boston, MA.

I II

Davis, J.D. and R.A. McGrath. 1984. Some aspects of nearsbore benthic macrofauna in western Cape Cod Bay. In Davis, J.D. and D. Merriman (Ed.), Observations on the Ecology and Biology of Western Cape Cod Bay,- Massachusetts. Lecture Notes on Coastal and Estuarine Studies.

=

Springer-Verlag, New York,228 pp, Grassle, J.F., and W. Smith. 1976. A similarity measure sensitive to the contribution of rare species and its use in investigation of variation in marine benthic communities. Oecologia 25: 13-22.

L Grieg-Smith, P.1964. -Quantitative Plant Ecology. Second Edition, Butterworths, Washington,256 pp.

Hurlbert, S.H.1971. The nonconcept of species diversity: a critique and alternative parameters.

Ecology 52: 577-586.

Newell, R.D.1979. Biology ofIntertidal Animals. Marine Ecological Surveys Ltd.,Faversham, Kent.

781 pp.

Parke, M., and P. Dixon.1976. Checklist of the British marine algae. 3rd revision. Journal of the Marine Biological Association of the United Kingdom 56: 817-843.

Smith, W., and J.F. Grassle 1977. Sampling properties of a family of diversity measures. ' Biometrics -

'33: 283-292.

South, G.R. 1976. A checklist of marine algae of eastern Canada. 1st Revision. Journal of the Marine Biological Association of the United Kingdom 56: 817-843.~

Taylor, W.R.1957. Marine Algae of the Northeastern Coast of North America. 2nd Edition.

University of Michigan Press, Ann Arbor, MI. 590 pp.

Taxon. 1982. Benthic studies'in the vicinity of Pilgrim Station. In: Marine Ecology Studies Related to Operation of Pilgrim Station. Semi-Annual Report No.19.

.I I

g.

I

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g.

n I

l

I I

I APPENDIX A 1

1 LI i

)

I I:

.I i.

l 1

I 1'l' 1

t' l

I 1

I APPENDIX A.

LIST OF SPECIES IDENTlHED AT THE EFFLUENT, MANOMET POINr. AND ROCKY POINT STATIONS IN APRIL 1990 I

Smaller Phyla POLYNOIDAE Harmothoe (lagisca) extenuata Anemone Harmothoe imbricata

3' Nemertes Harmothoe spp. Juv.

-E-Sipuncule!i;a Harmothoe spp, indet, lipidonotus squamatus C3-

'Q Polychaeta SABELLARIIDAE AMPHARETIDAE Sabellaria vulgaris I

Asabellides oculata SABELLIDAE g

ARENICOLIDAE -

Fabricia sabella

.g' Arenicola marina Potamilla neglecta Potamilla ren{ formis CAPITELLIDAE

^ Capitella capitata SPIONIDAE Polydora cornuta CIRRATULIDAE -

Polydora socialis Caulleriella bloculata Polydora wbsteri -

Otactozone setosa Polydora spp. Indet.

Cirratulus cirratus Prionospio steenstrup!

Dodecaceria corailli Spiofilicornis Spionidae spp. juv.

NEPHTYIDAE:

Nephrys caeca SYLLIDAE Autolytus alexandri NEREIDIDAE Autolytusfasciatus' Nerels pelagica.

Autolytus prismaticus Nereis zonata Autolytus spp. juv.

Nerels spp. juv.

TEREBELLIDAE

. ORBIN11DAE Nicolea venustula Naineris quadricuspida Polycirrusphosphoreus

-l Polycirrus spp. Indet.

W-PHOLOIDIDAE '

Pholoe minuta Crustacea PHYLLODOCIDAE.

ISOPODA Eteone longa Idoteldae l

Eulalla viridis Idotea phosphorea

'E:

Eumida sanguinea Idotea halthica Phyllodoce (Analtides) maculata B

I:

i.I I;

I AMPHIPODA DECAPODA Amphltoldne Cancer Irroratus Amphltoe rubricata Carcinus maenas Eualuspuslolus Pagurus acadianus Pagurus sp.

e Calliopidae Calliopus laevisculus Mollusca Corophlidae GASTROPODA Corophium acutum Acmaeldae Corophium bonelli Acmaea testudinalls Corophium insidiosum Corophium spp. Indet.

Aeolidildae

. Corophium spp. Juv.

Aeolidia papillosa l

Dexaminidae -

Calyptraeidae Dexamine thea '

Crepidula plana Gammaridae -

Columbellidae Gamarellus angulosus Anachis avara Gammarus oceanicus Mitrella lunata gl Gammarus sp.

g' Marinogammarus stoerensis Cratenidae nr. Cratena aurantia Ischyroceridae ischyrocerus angulpes Diaphanidae l:

Jassafalcata Diaphana minuta y

!5

. Phoxocephalidae t Eubranchidae

. Phoxocephalus holbolli Eubranchus exiguus nr. Eubranchuspallidus Pleustidae -

/

Pleusymtes glaber Lacunidae E.acuna vincta

)

L

.Pontogenelidae Pontogenela inermis Lamellidorididae nr. Acanthodorispilosa Stenotholdae -

Metopella angusta.

Littorinldae Proboloides holmesi Littorina littorea littorina saxatills I.

CAPRELLIDEA Caprellidae Nassariidae.

Caprella linearls Nassarius trivittatus Caprellapenantis i

Caprella nr. septentrionalis Naticidae Caprellidae spp. Juv.

Lunatia heros A-2 al i

,r

I Pyramideltidae Echinodermata Odostwnia seminuda Odostomia sp.

ASTEROIDEA Asteriasforbest Rissoldae Henricia sanguinolenta Alvania areolata ECHINOIDEA Skeneopsidse Strongylocentrotus droebachiensis Skeneopsis planorbis OPHIUROIDEA i

~

Trochldae Ophlopholls aculeata

.Margarites helicinus Amphlpholls squamata ill u.

Gastropoda spp. Indet.

Tunicata Gastropoda spp. Juv.

Nudibranch spp. Indet.

POLYCLINIDAE t

I.

Amaroucium constellatum

'BIVALVIA MOLGULIDAE Anomildae Molgula sp.

. Anomia aculeata 1

- Anomia simplex Cardildae.

L Cerastoderma pinnulatum Hiatellidae.

Hlatella arctica

' Mactridae Spisula solidissima

.Myidae Mya arenaria l-.

Mytilidae

'~

Modlolus modlolus

. Mytilus edults Tellinidae Macoma tenta l

Tellina agills m

L Bivalvia spp. Indet.

L--

POLYPLACOPHORA-Lepidochiton ruber A-3

= -

h

-g

-w v

-