Phytoplankton Production in Char Lake, a Natural Polar Lake, and in Meretta Lake, a Polluted Polar Lake, Cornwallis Island, Northwest Territories

Abstract

Phytoplankton production of ultraoligotrophic Char Lake and polluted Meretta Lake Oat. 74°42′N; long. 94°50′W) were studied between 1969 and 1972. Phytoplankton production in Char Lake is approximately 4.1 g C m−2 yr−1, making it the most oligotrophic lake on record. Photosynthesis takes place virtually the whole 9 mo the sun comes above the horizon. Changes in depth of maximum photosynthesis, in efficiency of low light utilization, and in optimal light flux resulted in a much more constant production rate than suggested by the light input, which is importantly affected by amount of snow cover. Phytoplankton in nearby sewage-polluted Meretta Lake averages 11.3 g C m−2 yr−1, and chlorophyll concentrations are 20 times higher than in Char Lake. Nutrient deficiencies, especially of phosphorus, are almost certainly responsible for the low efficiency of light utilization and resulting low production in Char Lake. Benthic production is of major significance in both lakes.