Phytoplankton community of an acidified,heavy metal—Contaminated lake near Sudbury,Ontario: 1973–1977

Phytoplankton data for 1973 to 1977 from Clearwater Lake, an acid- and heavy metal—contaminated lake near Sudbury, Ontario are presented.Peridinium inconspicuum (Lemmermann) comprised between 30 and 55% of the average, ice-free period biomass of 0.33 to 0.73 mg l^?1 and is considered indicative of acidic lakes if it forms a substantial portion of the total biomass. The data were compared with those from three other contaminated and ten uncontaminated lakes in Ontario. The phytoplankton communities of all contaminated lakes were dominated byP. inconspicuum while chrysophytes dominated the uncontaminated lakes. Community biomass was better correlated with phosphorus concentration than with hydrogen ion concentration. There was some evidence of reductions of biomass in lakes with the highest heavy metal concentrations. Limitations of phytoplankton data collected in synoptic surveys are discussed.