samples at JC, lower numbers of Mediomastus 

 ambiseta, oligochaetes, Aricidea catherinae, 

 Lumbrinerls tenuis were collected relative to pre- 



vious years, while in 1987, a large increase in 

 Mediomastus ambiseta and Leptocheirus pinguis 

 and continued decreases in oligochaetes, 



TABLE 6. Annual mean species diversity (IT), evenness (J), species number (S) and total individuals 

 (N) (± 1 standard error) for Millstone subtidal stations September 1979 - June 1987. 



Aricidea catherinae, and Poly cirrus eximius oc- 

 curred. 



Discussion 



The most immediate environmental impacts as- 

 sociated with Unit 3 start-up were attributable to 

 the increased volume of cooling water discharge 

 and to sedimentary changes caused by the scouring 

 action of the discharge. Infaunal community 

 changes that might have been related to elevated 

 temperatures could not be distinguished from 



those due to sediment shifts which occurred after 

 start-up. The progression in sediments below the 

 discharge from medium sands to coarse gravels, 

 to cohesive clays (glacial lake bed deposits) and 

 finally to bedrock was similar to that obser\'ed by 

 Saenger et al. (1982) and in Maine following 

 power plant start-up (Maine Yankee Atomic 

 Power Co. 1978). 



The EF station, located approximately 100 m 

 offshore, was subjected to less severe scour than 

 areas immediately below the discharge; however, 

 plant-induced scour and sedimentary changes (in- 

 creased giain size and decreased silt/clay content) 

 were evident after Unit 3 start-up. Along with 



110 



