11-110 



The discharge pliime area is usually very small in New Haven 

 Harbor, and does not block zones of passage or impinge upon any known 

 critical areas. Since ambient maxima are generally far below critical 

 limits for species present in the harbor, plant-induced increases had no 

 detectable effects. 



lahthyoplankton 



In the process of rising to the surface, the thermal discharge 

 stream is partially cooled by mixing with the surrounding colder water. 

 Small, weakly-swimming, or non-swimming life stages may be involuntarily 

 drawn into the effluent stream, along with the plume-entrained parcels 

 of receiving water, and thus be exposed to brief surges of elevated 

 temperature before being cooled to near ambient temperatures as more 

 receiving water is entrained and as the heat is ultimately lost to the 

 atmosphere. 



It is important to realize the extreme brevity of this heat 

 exposure; initial temperature surges result in exposure to temperature 

 elevations of up to 8°C above ambient for only a few seconds. At least 

 two recent studies (Hubbs and Bryan, 1974; Schiobel, 1974) have shown 

 that fish eggs, a particularly sensitive life stage, are unlikely to be 

 killed outright by this type of exposure (i.e., to heated discharges). 

 Most of the discussion in the more recent scientific literature con- 

 cerning the impact of thermal discharges has focused on possible sub- 

 lethal effects of the brief ejcposure (DeSylva, 1969; Kinne, 1970; Miller 

 and Beck, 1975). Due to the subtle nature of these effects, it is 

 impossible to make reasonable, quantitative projections of population 

 losses. As a judgement, it is suggested that the losses presented in 

 Table 11-3 are probably conservative enough to encompass the adverse 

 impact of both passage through the cooling water system and passive 

 entrainment of fish eggs and larvae. 



