7-23 



changes in faunal composition and densities or they might occur slowly, 

 detectable only by long-term monitoring. Either type of change would be 

 masked by natural varial)iiiLy in the community and biological cycles 

 affecting populations. 



The intertidal fauna data collected at the three stations in 

 New Haven Harbor were examined for evidence of thermal impact resulting 

 from operation of the New Haven Harbor Station. A qualitative com- 

 parison of mean numbers of taxa (Table 7-3) indicates that species 

 richness did not change substantially after operation began. A similar 

 comparison of total numbers of organisms (Table 7-3) indicates that mean 

 densities found at East Shore and Sandy Point during operational years 

 were either similar or had increased over preoperational years. At Long 

 Wharf, reduction in numbers is attributable to large natural variations 

 in Mya densities. 



Analysis of changes by sampling period showed considerable 

 variability. Of particular interest were declines in faunal distri- 

 bution and densities detected by October 1976 samples at the inner 

 harbor stations. Long Wharf and East Shore. A similar depression was 

 noted in the subtidal benthic populations of the inner harbor in an 

 August 1976 sampling by Rhoads and Michael (1977) . They believed that 

 low levels of dissolved oxygen were responsible for observed die-offs. 

 Low dissolved oxygen concentrations may also have caused the 1976 inter- 

 tidal mortality. Because dissolved oxygen levels are not close to 

 saturation values during the summer, plant operations do not further 

 reduce concentrations (Section 3.0). October reductions in species 

 richness and organism density were not observed in 1977, indicating that 

 the die-off observed in 1976 was not a persistent summer phenomenon in 

 New Haven Harbor. 



Occurrences of dominant species over time are summarized in 

 Tables 7-2 to 7-4 and by comparison of preperational and operational 

 periods in Tables 7-9 and 7-10. The results show that dominant fauna 

 collected in preoperational samples were generally found at similar or 



