ZOOPLANKTON 



INTRODUCTION 



Zooplankton is composed of floating organisms that passively drift 

 with the currents and includes a varied assemblage of animal forms 

 ranging in size from 0.01 iran (single celled animals) to several meters 

 (colonial hydrozoans) . Representatives of nearly every invertebrate 

 and several vertebrate phyla can be found in this assemblage at some 

 time in their life history. Recruitment of individuals to the benthos 

 is largely determined by survival of the organisms through their 

 zooplanktonic stages (Hardy 1970; Gushing and Harris 1973; Bannister et 

 al. 1974) . Zooplankton, essential in marine and estuarine food webs, 

 convert phytoplankton into animal protein, and are a principal food 

 source for a variety of life forms including fish larvae (Garstang 1900; 

 Lebour 1925; Schach 1939; Blaxter 1969; Kjelson et al. 1975) and 

 planktivorous adult fish (Hardy 1970; Gushing and Harris 1973; Bannister 

 et al . 1974). An understanding of zooplankton ecology Is necessary to 

 assess the potential impact of man's activities on marine and estuarine 

 environments. 



Six taxonomic groups dominate the larger zooplankton of eastern 

 Long Island Sound (LIS): Copepoda, Gladocera, Girripedia, Gastropoda, 

 Decapoda, and Amphipoda. Copepods and cladocerans are crustaceans that 

 are planktonic throughout their life cycles. The planktonic 

 cirripedians are early developmental stages of barnacles, the adults of 

 which are common to the rocky intertidal and subtidal zones of LIS. The 

 gastropods include planktonic egg and veliger stages of local snails. 

 The planktonic decapods consist primarily of crab zoea and megalops. 

 The amphipods of LIS zooplankton are predominantly adult benthic 

 amphipods that periodically enter the plankton through vertical 

 migration or through uplifting by currents or turbulence. 



The potential effect of zooplankton entrainment at the Millstone 

 Nuclear Power Station (MNPS) is considered in this report. Entrainment 

 is of concern due to the large volume of water used for condenser 

 cooling. Entrained organisms are subjected to a rapid increase in 

 temperature, mechanical stress and periodic exposure to biocides. 



