Comment - Lake Winnipeg, Then and Now: Another Perspective

Abstract

The 2006 Lake Winnipeg Stewardship Board Report is used, together with a paper and reports by Dr. G. J. Brunskill and his colleagues, to assess change in the nutrient status of Lake Winnipeg since the late 1960's and early 1970's. Nutrient loading to Lake Winnipeg is very high; hydrologically driven, it is also quite variable, year-to year. Supply of nitrogen (N) and phosphorus (P) to the lake does not appear to have changed over the past 3 or 4 decades as a consequence of large increases in utilization and disposal of N and P that occurred on the terrestrial watershed. Nutrient supply is excessive, relative to the growth requirements of Lake Winnipeg algae. Low light penetration, as a function of high turbidity, can be an important limiter of phytoplankton productivity. The current strategy for improving Lake Winnipeg, which focuses on effecting small (10%) reductions in external N & P loading, may be disappointing. Anticipated corresponding improvements in the nutrient chemistry of the lake will not likely be discernible. Nor, is it likely that improvements in algal species composition and/or a reduction in algal productivity will be realized. Development of sound and optimal management strategies for the protection of Lake Winnipeg will require that future research be broad-based. A number of potentially important topics for investigation are identified.