Benthic Infauna 



Introduction 



Benthic infauna are relatively small organisms 

 inhabiting intertidal beach and subtidal bottom 

 sediments. The many species of worms 

 (polychaetes and oligochactes), clams (molluscs) 

 and crustaceans (amphipods), which comprise 

 infaunal communities, are important components 

 of marine ecosystems. Many of these organisms 

 are prey species for demersal fishes (Woodin 1982; 

 Moelleret al. 1985; Witman 1985; Le Mao 1986). 

 In Long Island Sound (LIS), annelids are the 

 main food item of winter flounder, 

 Pseudopleuronectes americanus (Richards 1963). 

 In addition, many studies have described the in- 

 fluence of infaunal feeding, burrowing and tube 

 building activities on nutrient recycling in marine 

 ecosystems (Goldhaber et al. 1977; Alter 1978; 

 Ilylleberg and Maurer 1980; Raine and Patching 

 1980; Zeitzschel 1980). 



Infaunal organisms are also useful environmen- 

 tal monitoring tools because they are relatively 

 sedentary and respond to stress in a predictable 

 manner (Boesch 1973; Reish 1973; Sanders et al. 

 1980; Boesch and Rosenberg 1982; Young and 

 Young 1982). For example, a physically stressed 

 community will typically exhibit lower numbers 

 of species and high densities of a few characteristic 

 species (e.g., Polydora ligni, Capitella spp. and 

 Mediomaslus amhisetd), which are capable of tol- 

 erating environmental stress or can rapidly colo- 

 nize an area following disturbance (McCall 1977; 

 Reish et al. 1980; Sanders et al. 1980). 



Impact studies based on observed changes in 

 infaunal community abundance and species com- 

 position assume that the structure of the 

 unimpacled community can be described, and 

 that any trends evident before impacts occur can 

 be identified and removed (Nichols 1985). Be- 

 cause naturally occurring variations in physical 



factors such as cold winters (Beukema 1979), 

 storms (Boesch et al. 1976), heavy rainfall (Flint 

 1985; .lordan and Sutton 1985) or changes in the 

 level of competition and predation (L^vinton and 

 Stewart 1982; Woodin 1982; Moeller et al. 1985) 

 can strongly affect infaunal communities, only 

 long-term data can adequately describe the range 

 and overall trends in community abundance and 

 composition required for impact assessment stud- 

 ies (Holland 1985). 



Benthic infaunal communities in the vicinity of 

 Millstone Nuclear Power Station (MNPS) have 

 been sampled since 1969, as part of a larger mon- 

 itoring program designed to assess the potential 

 impacts of construction and operation of Mill- 

 stone Units 1 and 2. Plant-related changes in 

 benthic communities during this period have been 

 attributed to construction and opening of the 

 Unit 3 discharge cut and to construction and 

 dredging near the intake structures (NUSCO 

 1987). These data also provide the baseline con- 

 ditions against which potential changes associated 

 with Unit 3 start-up will be evaluated (NUSCO 

 1987). 



This is the fu^st report to include data collected 

 after commercial start-up of Millstone Unit 3 

 (April 1986). Environmental changes, which 

 could possibly impact infaunal communities, in- 

 clude doubling of the heated effluent discharged 

 into I ,IS and the enlargement of the area subjected 

 to the scour produced by the additional intake 

 and discharge of the 3-unit (combined) cooling 

 waters. In addition, changes might occur in re- 

 sponse to chemical additions associated with the 

 increased volume produced during 3-unit opera- 

 tions. To assess changes in local benthic com- 

 munities that might occur during 3-unit operation 

 at MNPS, the infaunal sampling program was 

 designed to address the following objectives: 



Benthic Infauna 



59 



