10-33 



T-Lme Variations in Meroenaria and Crassostrea from New Haven Harbor 



Metals analysis of soft tissue from Mercenaria mercenaria (the 

 hard-shell clam) have been conducted periodically using specimens from 

 the New Haven Plarbor site and Morris Cove, New Haven Harbor, since the 

 summer of 1974. Sampling was performed concurrently with the Rhoads and 

 Michael investigations (see Section 6.0 Benthos) as part of the study to 

 meet the requirements of Section 4(A)(2) of the NPDES discharge permit. 

 The two sample locations are on either side of the Coast Guard Station 

 location that was utilized in the oyster study conducted by Feng and 

 Ruddy (1974) discussed above. Statistical analysis of the data presented 

 in Table 4 shows no significant difference (p<0.05) in concentrations 

 between the two sites and over time except in the case of lead. The 

 higher values for lead at the Harbor Station site are possibly related 

 to the site's proximity to the East Shore Sewage Treatment Plant Outfall. 

 This is based on data presented earlier showing higher rates of metals 

 accumulation in organisms near point sources. The Mercenaria are primarily 

 affected by the ingestion of suspended organic matter, high in metals, 

 from sewer outfalls, rather than by the surrounding sediments. 



Levels of copper, cadmium and zinc in oysters maintained in 

 New Haven Harbor (Figures 10-13 - 10-15) follow trends observed in other 

 harbors along the Connecticut shore. With the exception of zinc, 

 concentrations remained relatively constant over the two-year period studied. 



Trace-Metals Composition Comparisons Among Organisms from New Haven Harbor 



It has been already noted that oysters and mussels concentrate 

 trace elements to different extents by ingesting edible particles; 

 oysters generally possess higher metal content than mussels. Compari- 

 sons have also been made between several other species. 



Table 10-5 shows a comparison of metal concentrations in five 

 species of bivalves collected in New Haven Harbor. Of the five bivalves, 

 two {Crassostrea and Mytilus) are considered as epifauna and the remaining 

 three {Mercenaria, Mulinia and Yoldia) are considered as infaunal species. 



