5-42 



including: increase or decrease in productivity, behavioral changes, 

 shifting species composition, lengthening of spawning/settlement period, 

 reduction in physical condition and cumulative effects resulting in 



death. Cory and Nauman (1969) and Naiiman and Cory (1969) measured 



2 

 increases in panel productivity (gm dry wt/m time) in effluent canals 



at two sites in the Patuxent River Estuary. Tinsman and Maurer (1974) 



observed greater condition indices (amount of stored glycogen) and meat 



weight of oysters in effluent waters. All of the above researchers 



noted increased productivity for some years and mortality for other 



years in July/August in thermal effluent canals due to temperature 



increases. In mussels {Mytilus edulis) , behavior that could also result 



in increased loss due to predation occurred at temperatures well below 



lethal limits (Pearce, 1969) ; at 24°C, normal aggregation of Mytilus did 



not occur and the byssal fibers, while attached, did not secure the 



mussel firmly to the substratum. A thermal addition could result in a 



range extension of warmer water species or exclusion of colder-water 



species existing at the limits of thermal tolerance (Naylor, 1965) . 



Prolonged breeding periods have been reported in a number of thermal 



addition studies (NAI, 1973b, 1977c). Pearce (1969) noted that heat 



added subsequent to another stress or pollution factor, often 



resulted in mortality at a lower critical temperature. Many of the 



adverse effects caused by thermal impact are reversible. Thus, Naylor 



(1965) noted a rapid return of a thermally-impacted community to its 



original composition. 



The New Haven Harbor fouling community did not indicate any 

 impact from station operation. An examination of species-richness 

 values over the entire period revealed an increase from 1971 to 1976, 

 followed by a decrease in 1977 at all stations as previously discussed 

 (Figure 5-4) . A change in taxonomic treatment clearly accounts for some 

 differences; other factors are the shorter sampling period in 1977 and 

 loss of long-term panels at Fort Hale in 1977. Teredo's absence from 

 1976 to 1978 is not considered to be related to New Haven Harbor Station 

 operation; its disappearance was not localized at Harbor Station and it 

 was recorded in high numbers in recent (1978) data. None of the domi- 



