8-38 



Talmage and Coutant, 1978) . Because of the mobility of many epibenthic 

 invertebrates, avoidance of or attraction to the thermal plume can 

 readily occur and result in a change in species richness and individual 

 species abundance. Logan and Maurer (1975) observed an area s-ubjected 

 to thermal effluent discharge in which species number and individual 

 species abundances decreased. 



Increased water temperatures can result in changes in the 

 occurrence of species located near their thermogeographic limit. In New 

 Haven Harbor, Homarus amerlcanus , for example, is abundant to the south 

 of Long Island Sound in offshore waters only (Saila and Pratt, 1973) ; it 

 avoids inshore waters because of high temperatures as well as a lack of 

 suitable sxobstrate. In terms of inshore populations, Long Island Sound 

 can be considered a thermogeographic limit for the lobster (Saila and 

 Pratt, 1973) . Harbor-water temperatures increased above normal could 

 exclude lobsters, particularly from the area of the thermal discharge. 

 On the other hand, species such as Panaeus aztecus , Libinia dubia, 

 Callinectes sapidus, Panopeus herbstii , Eupleura caudata and Haminoea 

 solitaria are epibenthic species in New Haven Harbor living at the 

 northern extremes of their geographic range. Increased temperatures 

 could allow a greater abundance of these species to inhabit or frequent 

 the harbor and this in turn would have an effect on the natural com- 

 munity structure through competition for available resources. 



Sudden decreases in water temperature can be more detrimental 

 to organisms inhabiting an area than long-term temperature elevations 

 (Kinne, 1970) . Acclimation of marine organisms to artificially elevated 

 water temperature during winter can result in the organisms ' inability to 

 return to ambient water temperatures in the event heating by the power 

 plant stops (Pennsylvania Fish Commission, 1971; Robinson, 1970; cited 

 in Water Quality Criteria 1972, EPA-R3-73-033) . In such cases where the 

 thermal discharge suddenly stops, cold-shock may occur. 



In New Haven Harbor, direct impacts of the thermal discharge 

 on the distribution and occurrence of epibenthic invertebrates present 



