EFFECTS OF THE EXOTIC ZEBRA MUSSEL (DREISSENA-POLYMORPHA) ON METAL CYCLING IN LAKE ERIE

This research demonstrated the impact of high densities of the zebra m ussel (Dreissena polymorpha) on the cycling of copper, nickel, and zin c in a lake environment. Experiments with mussels on sedimentation tra ps in western Lake Erie and with mussels in flow-through tanks receivi ng Lake Erie water showed that zebra mussels remove metals from the wa ter column, incorporate metals in their tissues, and deposit metals on the lake bottom. Removal of metals from the water column was estimate d at l0-17%.day(-1) of the amounts present. This material was largely deposited on the lake bottom; zebra mussels mon than doubled the rate at which metals were being added to the lake bottom. Metal biodepositi on rates were extremely high (e.g., 50 mg Zn.m(-2).day(-1)) in high-tu rbidity areas with elevated metal levels. Two factors contributed to m etal biodeposition by zebra mussels. First, their production of feces and pseudofeces increased the rate at which suspended matter was being added to the sediment (accounting for 92% of the increased metal biod eposition). Second, the material coming out of suspension had higher m etal concentrations when zebra mussels were present (constituting 8% o f the increased biodeposition).