Heavy Metal Tolerance in Algae Isolation from Polluted Lakes Near the Sudbury, Ontario Smelters

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Abstract
The phytoplankton flora of lakes close to the Sudbury smelters is poor both in species and in numbers. The lakes have abnormally high levels of several toxic heavy metals, including nickel and copper. Algal isolates were obtained from two lakes which contained up to 3 ppm of nickel and 0.7 ppm of copper in solution. These isolates were found to be tolerant to higher levels of nickel, copper and silver than were laboratory strains. Their growth response to metals in the medium is distinctive and different from that of the lab strains. Lab strains of Saenedesmus and Chlorella stop growing at 0.1 ppm Cu and 0.5 ppm Ni. “Adapted” lake strains of Saenedesmus, however, continue to grow up to 1.0 ppm Cu and 3.0 ppm Ni. “Adapted” strains of Chlorella stop growing at 0.4 ppm Cu. Both of the “adapted” lake isolates showed a gradually decreasing growth rate with increasing concentrations of metals, whereas the lab strains showed total inhibition at a low metal concentration. Lab and lake strains both take up copper. The uptake is linear with concentration in the media. The lake isolates continued growth until a Cu concentration of 2400+ ppm was reached (on dry t. basis). This suggests a mechanism of metal tolerance rather than one of exclusion as means of survival. The ecological implications of these adaptations to high levels of toxic metals are discussed, especially the finding that the tolerant algae are adapted to high silver levels, even though silver is not a pollutant in the lakes.

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