at night. Offshore studies have detected spatial differences for dominant 

 taxa (NUSCo 1978, 1979a). Acartia hudsonica was more abundant in the 

 Niantic River and inshore areas of Niantic Bay than in offshore Long 

 Island Sound. Pseudocalanus minutus , T_. longicornis , C. hamatus and A. 

 tonsa were more abundant in offshore deeper water stations. 



Copepods, the dominant holoplankton group, have been emphasized in 

 the zooplankton program at Millstone, as well as, in other power plant 

 studies. Copepod mortality studies at Millstone (Carpenter 1975) identi- 

 fied mechanical stress as the major cause of mortality. This differs 

 from studies conducted at other plants where chlorination was the major 

 cause of mortality (Gentile et al. 1976, Heinle 1976). Capuzzo (1980) 

 in a review of zooplankton entrainment studies concluded that power 

 plant entrainment losses of copepods cannot be shown to cause a serious 

 reduction in secondary productivity where adequate dilution of cooling 

 waters is provided. This low impact is due to the small percentage of 

 the population entrained and the high reproductive rates of the unaffected 

 copepods. 



Meroplankton and tychoplankton entrainment impact has received less 

 attention than holoplankton. Amphipods, the dominant tychoplankton 

 entrained at Millstone, are an important food source for demersal fish 

 (Richards 1963) . The estimated average daily entrainment of amphipods 

 since 1976 is greater than 200 x 10 /day which represents a potentially 

 large loss of benthic biomass and prey for fish. Although large numbers 

 of amphipods are entrained, other studies have found that many survive 

 entrainment (Ginn et al. 1974, Cannon et al. 1977). Entrainment mortality 

 studies on dominant tychoplankton and meroplankton taxa would mitigate 

 apparent large losses due to entrainment. In addition more specific 



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