Total Cadmium, Copper, and Zinc in Two Dreissenid Mussels, Dreissena polymorpha and Dreissena bugensis, at the Outflow of Lake Ontario

Abstract

Two closely related Dreissenid mussel species, Dreissena polymorpha and Dreissena bugensis, both recent invaders of the Great Lakes and St. Lawrence River, have potential as biological monitors of metal contamination. To better understand their usefulness as biomonitors, we measured total cadmium, copper, and zinc concentrations in soft tissues of both species at a site at the outflow of Lake Ontario. We examined total mean metal concentrations in soft tissues for both seasonal and interannual variability. Both mussel species exhibited elevated copper and cadmium concentrations compared to relatively uncontaminated waters. D. bugensis (quagga) mussels bioaccumulated higher levels of cadmium than D. polymorpha (zebra) mussels, while zebra mussels had higher concentrations of zinc and copper. Zebra mussels showed greater interannual variability in metal concentrations than quagga mussels. Total metal concentrations in both species were influenced by season, particularly stage in the reproductive cycle. The two species differed in their seasonal bioaccumulation patterns for both cadmium and zinc, but were similar in their seasonal variability of copper. We did not find a consistent pattern between shell length and total metal concentration for either species. Patterns of bioaccumulation for these species must be better known if they are to be used in biological monitoring programs to assess trends of contamination in the Great Lakes basin.