New Microcystin Concerns in the Lower Great Lakes

Water samples were collected in the summer of 2001 for microcystin analysis, nutrients and algal enumeration from Hamilton Harbour (Lake Ontario), Wendt Beach (Lake Erie) and Presque Isle (Lake Erie). Microcystin concentrations varied largely and were present at acute toxicity levels only in some windconcentrated scums of blue-green algae (>90% Microcystis, primarily M. botrys, M. viridis and some M. wesenbergii) in Hamilton Harbour. In Hamilton Harbour, microcystin-RR was the main microcystin with microcystin-YR and -LR also present. The two samples of August 17 and September 7, taken during the peak of the cyanobacterial bloom, contained 60 and 400 µg/L, respectively. A few dying birds were seen in the Hamilton scums. The concentrations of microcystins at the Lake Erie sites were less than 1 µg/L, yet dead birds were common. The major limitation with this approach is that current analysis (ELISA and HPLC) methods are unable to measure covalently bound microcystins, the form that is assimilated into the food chain.