1 . characterize the abundance and species com- 

 position of infaunal communities inhabiting 

 shallow subtidal and intertidal areas both 

 within and beyond the influences of 3-unit 

 operation at MNPS, 



2. describe spatial and temporal patterns in 

 these communities and identify the extent 

 and direction of changes attributable to 3-unit 

 operation and 



3. assess the ecological significance of power 

 plant-induced changes should they occur. 



For the purpose of assessing 3-unit operational 

 impacts, the pre-operational period was considered 

 to extend from March 1979 - June 1985. Collec- 

 tions made from September 1985 - .lune 1986 and 

 from September 1986 - .Tunc 1987 (the 1986 and 

 1987 reporting years, respectively) will be consid- 

 ered operational years. The 1986 sampling year 

 included three sampling periods before commercial 

 start-up; however, this was considered an opera- 

 tional year because certain conditions (i.e., oper- 

 ation of Unit 3 cooling water pumps), which 

 could influence infaunal communities, existed dur- 

 ing at least 2 of the 4 quarters considered the 

 1986 sampling year. 



Materials and Methods 



Infaunal communities were sampled at four 

 subtidal and three intertidal stations (Fig. 1). The 

 Giants Neck subtidal (GN-S) and intertidal (GN- 

 I) stations are located 5.5 km west of the power 

 plant and serve as reference stations because both 

 are beyond any physical influences of the power 

 plant discharge. Data collected at these stations 

 provide the baseline for assessment of naturally- 

 induced changes which might occur on a regional 

 scale (e.g., hurricanes, severe winters, heavy pre- 

 cipitation). The intake subtidal station (FN-S) is 

 located 0. 1 km seaward of the Millstone Unit 2 

 and Unit 3 intake structures and is exposed to 

 the scouring (if any) produced by intake of cooling 

 water. The effluent subtidal station (EF-S) is lo- 

 cated approximately 0. 1 km offshore of the Unit 

 3 discharge. This area is subjected to plant-induced 



changes related to temperature, scour, and possible 

 chemical additions associated with power plant 

 operations. The .Jordan Cove subtidal (.TC-S) and 

 intertidal (.IC-I) station.^, located 0.5 km east of 

 the power plant and the White Point (WP-I) 

 intertidal station, 1.6 km east of the power plant, 

 are all within the area influenced by the thermal 

 plume during some tidal stages (see Hydrothermal 

 Studies section of this report). 



At each subtidal and intertidal station, ten 

 0.0078 m cores (10 cm diameter x 5 cm deep) 

 were collected quarterly (September, December, 

 March and .June). For reporting purposes, a sam- 

 pling year begins in September and ends in June 

 with the year of the June sample assigned as the 

 sampling year. Subtidal samples were taken 

 within 3 m of each station marker by SCUBA 

 divers. Each sample was placed in a 0.333 mm 

 mesh Nitex bag and brought to the surface. 

 Intertidal samples were collected at approximately 

 0.5 m intervals parallel to the water line at mean 

 low water. 



Samples were brouglit to the laboratory and 

 fixed with a 10% buffered formalin/rose bengal 

 solution. After a minimum of 48 h, organisms 

 were floated from the sediments onto a 0.5 mm 

 mesh sieve and the float and residue were preserved 

 separately in 70% ethyl alcohol. Organisms were 

 removed under dissecting microscopes, sorted into 

 major groups (annelids, arthropods, molluscs, and 

 others), identified to the lowest possible taxon 

 and counted. Organisms that were too small or 

 otherwise not quantitatively sampled by our meth- 

 ods (e.g., nematodes, ostracods, copepods, and 

 foraminifcra), were not removed from samples. 



At the time of infaunal sampling, a 3.5 cm di- 

 ameter X 5 cm deep core was taken for sediment 

 analysis which was performed using the dry sieving 

 method (Folk 1974). 



Data Analyses 



Impacts on infaunal communities attributable 

 to start-up of Millstone Unit 3 and the subsequent 

 operation of 3 units at MNPS were assessed by 



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