13-4 



of the inner harbor bounded by the 4°F (2.2°C) AT isotherm was less than 

 0.1%. The 3, 2 and 1°F (1.7, 1.1 and 0.6°C) AT isotherms bound 0.4, 0.6 

 and 1 percent respectively of the inner harbor surface area (NAI , 1976). 

 Numerical model results indicate that operation of Now llavtMi Harbor 

 Station raises the average water temperature of the inner harbor by 

 0.4°C (0.7°F), and that of outer harbor by 0.3°C {0.5°F). 



PLANKTON 



The protection against dispersal afforded by inlets and 

 western shoal areas in New Haven Harbor combined with nutrient input 

 from municipal sewage provide a fertile habitat for phytoplankton pop- 

 ulations. Harbor waters also support substantial zooplankton and ich- 

 thyoplankton populations which ultimately depend on phytoplankton pri- 

 mary production for sustenance. Most finfish and many benthic inverte- 

 brates, such as crabs and oysters, spend a portion of their lives in the 

 plankton. Thus, any change in planktonic populations affects, not only 

 the food available to siibsequent levels in the food web, but also the 

 magnitude of larval recruitment to adult populations of many aquatic 

 animals . 



Of the two potential sources of power plant impact on the 

 plankton community, i.e., entrainment in the power plant's cooling 

 system, and exposure to the heated discharge as it diffuses and mixes 

 with the receiving water, power plant passage has in general been 

 considered to pose the more serious problem (Miller and Beck, 1975) . 

 Recent studies have indicated substantial survival of planktonic 

 organisms after power plant passage, when temperatures were below 

 thermal threshold levels (ca. 30°C for many species) . The 100% mor- 

 tality level is utilized as a worst-case analysis, because additional 

 deaths may be delayed until long after completion of transit through the 

 cooling system. 



