STABLE ISOTOPES AND HEAVY-METAL DISTRIBUTION IN DREISSENA-POLYMORPHA (ZEBRA MUSSELS) FROM WESTERN BASIN OF LAKE-ERIE, CANADA

Dreissena polymorpha is an exotic freshwater bivalve species which was introduced into the Great Lakes system in the fall of 1985 through th e release of ballast water from European freighters. Utilizing individ ual growth rings of the shells, the stable isotope distribution (delta (18)O and delta(13)C) was determined for the life history of selected samples which were collected from the western basin of Lake Erie. Thes e bivalves deposit their shell in near equilibrium with the ambient wa ter and thus reflect any annual variation of the system in the isotopi c records held within their shells. Observed values for delta(18)O ran ge from -6.64 to -9.46 parts per thousand with an average value of -7. 69 parts per thousand PDB, while carbon values ranged from -0.80 to -4 .67 parts per thousand with an average value of -1.76 parts per thousa nd PDB. Dreissena polymorpha shells incorporate metals into their shel ls during growth. Individual shell growth increments were analyzed for Pb, Fe, Mg, Mn, Cd, Cu, and V concentrations. The shells show increas ed uptake of certain metals during periods of isotopic enrichment whic h correspond with warmer water temperatures. Since metals are incorpor ated into the shells, the organism may be useful as a biomonitor of me tal pollution within aquatic environments.