Fossil and Modern Freshwater Bivalves as Recorders of Metal Pollution in the Great Lakes Basin

Abstract

<p> This study analyzed fossil and modern freshwater bivalve mollusc shells, from in and around lakes Ontario and Erie, for the following trace metals: Cu, Ni, Zn, As, Pb, and Mn. Elliptio dilatata, Elliptio complanata, and Lampsilis radiata siliquoidea shells were analyzed by ICPMS for differences in shell metal levels between species and genera, through time and due to anthropogenic inputs. </p> <p> Regardless of age, all three species showed high concentrations of Zn and Mn, and little or no changes in Cu, Ni, Zn, and Pb concentrations with time. E. comp1anata shells were generally poorer in Pb, but richer in As and Mn, than were the E. dilatata and L. radiata siliquoidea shells. Fossil Elliptio samples did not posses low background, or baseline, trace metal concentrations. These samples were richer in As, Pb, and Mn than were modern samples from post-industrial environments. Among the modern shells, the E. complanata showed no differences in metal concentrations between samples from high- and low-contamination· sites, while the L. radiata siliquoidea showed changes in Ni, As, and Mn concentrations among the same sites. Modern L. radiata siliquoidea may be more likely to represent environmental metal changes than are modern E. complanata. Historical change in environmental metal concentrations of the Great Lakes region is not recorded as a simple change in shell metal concentrations of these freshwater bivalve molluscs. </p>