10-36 



Yoldia is a deposit feeder and Mulinia a suspension feeder. Both species 

 are primarily influenced by the material at the sediment water interface. 

 In contrast, Crassostrea, Mytilus and Mercenaria are most sensitive to 

 the metal-rich organic matter making up the primary particle flux. 



Data collected from the Harbor show Crassostrea acciomulating 

 the greatest levels of the trace metals measured. In general, zinc was 

 accumulated to a much greater degree than copper. 



Of interest is the possible correlation between diet and metal 

 concentrations in the bivalves studied assuming no specific biologically- 

 mediated internal fractionation of metals in these organisms. Oysters 

 apparently readily assimilate the primary metal-rich organic debris 

 derived from fresh water sources; mussels and Mercenaria, with a lower 

 concentration of heavy metals, ingest a mixture of high concentrations 

 of this primary material and lower concentrations of secondary planktonic 

 debris and resuspended sediments, whereas the two small clams with low 

 metal concentrations derive their nourishment principally from resuspended 

 sediment with its characteristically lower metal concentrations. 



Trace-Metals Composit'ton of Organisms in the Centvat Basin of Long 

 Island Sound 



Infaunat Bivalves 



A rich infauna is associated with the sediment of the deeper 

 waters of Long Island Sound. These species are not normally regarded as 

 a human food resource but some fish and lobsters depend in part on these 

 organisms as a food source. We focus attention on two deposit feeding 

 bivalves, Yoldia and Nucula , and two suspension feeders, Mulinia and 

 Pitar. Table 10-6 shows a comparison among these species from samplings in 

 the central Long Island Sound basin and New Haven Harbor, and reveals 

 relatively little difference in bivalve-tissue metals composition bet- 

 ween the two areas. 



