7-26 



increased densities during plant operation. The Sandy Point station, 

 closest to the outer harbor, was the most variable between preopera- 

 tional and operational periods . Gemma gemma was numerous in preoper- 

 ational years at Sandy Point but from mid-1975 onward was not commonly 

 found. Also there were three polychaetes, Spio filicornis , Scoleco- 

 lepides viridis , and Scoloplos robustus which were not abundant in pre- 

 operational years but were collected in abundance during at least one 

 sample period after operation began. Preoperational and operational 

 frequency of occurrence by station is shown in Table 7-10. Most dom- 

 inant species had similar values during preoperational and operational 

 periods. Major changes at East Shore were drops in Nereis succinia and 

 Gemma gemma frequency; N. succinea remained high at other stations. The 

 decrease of Nereis is probably attributable to its high spatial hetero- 

 geneity compounded by the small number of sample sets from which values 



were calculated. In the preoperational period. Gemma gemma was present 



2 

 in abundances of less than 40/m at East Shore when present. Its rank- 

 ing as a dominant is due to high preoperational numbers at Sandy Point. 

 The operational period decrease at Sandy Point may indicate a harbor- 

 wide decrease in Gemma populations which would not be likely to be 

 related to station operation. 



Gemma gemma was the only dominant species that showed a 

 population change coincident with plant operation. Gemma populations 

 declined at Sandy Point in May 1975 and at Long Wharf in October 1975, 

 just prior to and after commencement of operations. Other bivalves, Mya 

 arenaria and Macoma balthica, were scarce in October 1976 and May 1977 

 as discussed above, but by October 1977 densities had increased to 

 previous levels. Gemma, which does not have a pelagic larval stage, 

 must rely on successful local populations to reestablish itself. It may 

 also have been a victim of a summer die-off. 



None of the fluctuations in distribution and abundance in New 

 Haven Harbor were suggestive of operational impact of New Haven Harbor 

 Station on the intertidal fauna. The dominant taxa collected in the 

 New Haven Harbor intertidal zone are characteristic of opportunistic species 



