8-40 



Mortality due to impingement on cooling-water intake screens 

 can also have serious consequences on marine organisms (Uziel, 1978) . 

 Impinged organisms may die directly as a result of mechanical abrasion 

 or simply by being removed from the water when the screens are cleaned. 

 Animals that are returned to the water may die indirectly as a result of 

 high stress conditions which lead to decreased resistance to disease and 

 predation, or an inability to compete for food (Hanson et al . , 1977). 

 Impingement of epibenthic invertebrates on the cooling-water intake 

 screens of the New Haven Harbor Station is discussed in some detail on 

 page 8-43; it does not appear to be detrimental to the populations as a 

 whole. 



Given the limited impacts of Station operations as surmised 

 and the general structure of the epibenthic monitoring program, it is 

 not possible -- with any degree of confidence — to evaluate specific- 

 ally the individual effects of the three major modes of impacts of the 

 Harbor Station on the epibenthos in New Haven Harbor, i.e., effects of 

 contact with elevated temperatures or exposure to sudden decreases in 

 temperature, entrainment of eggs and larvae in the power plant's cooling 

 system, and impingement of adults on the cooling-system intake screens. 

 The program was designed to allow evaluation of the total impact of the 

 Harbor Station on the epibenthos — that is , the c\amulative effects of 

 all potential modes of impact. This has been accomplished by comparing 

 annual trends in species composition, abundance and distribution prior 

 to and during operation of the New Haven Harbor Station. 



In terms of the overall composition of the epibenthic fauna in 

 New Haven Harbor, only minor changes have been observed since the 

 initiation of the New Haven Harbor Station Ecological Monitoring Studies . 

 These changes are primarily related to improvements in field identifica- 

 tion with a resulting increase in levels of identification; secondarily 

 they are related to the incidental occurrence of species not commonly 

 collected in otter trawls. The total number of epibenthic species 

 collected annually was similar for each year of the study and ranged 

 from 24 to 28 (Table 8-1) . Of the 44 epibenthic species encountered 



