13-26 



abundances and species richness, especially in the highly stressed inner 

 harbor. Despite overall population fluctuations, most dominant species 

 tend to exhibit consistent presence and recurring seasonal trends. An 

 annual subtidal faunal density minimum has regularly occurred in the 

 inner harbor in midsummer, and has been termed the "August effect". 

 This appears to result from the combination of high water temperature, 

 oxygen depletion, and mobilization of toxic siibstances (e.g., H S) from 

 organic-rich, fine-grained substances that particularly characterize the 

 inner harbor. The outer harbor siibtidal environment, represented by 

 Morris Cove, has exhibited a more stable infaunal community development 

 in the shallow-water, sandy sediments. 



Since 1971, biological monitoring has been carried out during 

 a wide variety of conditions that are likely to be critical for aquatic 

 life, including: low background water quality, periods of intense 

 biological activity, maximum and minimum stratification and circulation. 

 Several species of finfish and shellfish were identified as particularly 

 subject to impingement; however, for the finfish and mantis shrimp, such 

 impacts have been accompanied by detectable increases in abundance. The 

 combined presence of dominant species and the phenomenon of repeated 

 consistent trends over the long-term period studied enable preopera- 

 tional characteristics of the harbor to be identified despite varia- 

 bility. 



Comparison of preoperational and operational periods for all 

 assemblages monitored with respect to species composition, abundance, 

 diversity, and spatial and temporal distribution indicates no discern- 

 ible plant impact on the biota of New Haven Harbor. 



