6-54 



Entrainment, the passage of the planktonic dispersal stages of 

 many marine organisms through station cooling systems, often produces 

 large mortalities (Enright, 1977) . Nearly all of the dominant species 

 in New Haven Harbor have planktonic larvae and are therefore potentially 

 subjected to losses from this impact. In the absence of actual entrain- 

 ment data, the effect of this impact must be inferred from recruitment 

 patterns during appropriate seasons. Another type of impact, impinge- 

 ment, occurs when adults are trapped on the various screening systems at 

 the station intake. While this type of impact may often be severe for 

 finfish individuals, benthic infaunal invertebrate species are generally 

 not subject to impingement losses. 



Due to the low ratio of plant cooling water flow to the volume 

 of water moved with each tide, the minimal harbor area experiencing 

 heightened temperatures from the discharge plvune, and the lack of direct 

 plume contact with the benthic habitat, minimal impact of New Haven Har- 

 bor Station operations on the benthos was anticipated. Since there is 

 minimal potential for plant impact on the subtidal benthos, particularly 

 on any given spatially limited area, impact is not analyzed in great 

 detail for individual stations. Instead, analysis consists of compar- 

 isons of diversity, species richness, general density and abundant 

 species density between preoperational and operational periods at groups 

 of stations within the harbor. 



The addition of environmental stress to an already severely 

 impacted ecosystem would be expected to result in the elimination of indi- 

 viduals and then species that are near their tolerance limits . This poten- 

 tial impact was evaluated by comparing the number of species collected in all 

 samples taken prior to August 1975 with all samples collected after that date. 

 The data were analyzed via a standard t-test with no correction for 

 season as the species richness data show no obvious seasonality. No 

 significant differences in mean number of species per station were found 

 via this procedure (t = -.0807, p > 0.9). Because any potential impact 

 of this nature would be most acute in the inner harbor these stations 

 were tested separately and, again, no significant differences were found 



