A Review of Lake Ontario Water Quality with Emphasis on the 1981-1982 Intensive Years

Abstract

Three issues are currently being addressed with respect to the Lake Ontario ecosystem: eutrophication, contamination by toxic substances and fisheries management. This report reviews our present knowledge and understanding of Lake Ontario within the context of the first two issues. Although the report focuses on intensive studies carried out during 1981-82, it relies heavily on work from 1967 to 1985. I n preparing this report, it became obvious that many fundamental questions regarding the functioning of the Lake Ontario ecosystem remain unanswered. For example, although the total phosphorus load has been reduced to a level approaching the target load, those factors that control and/or limit algal biomass and productivity (e.g. is the lake phosphorus limited) remain poorly understood. Salmonid stocking of the lake continues in unprecedented numbers, yet our knowledge of foodweb interactions is very limited. Nitrate levels continue to rise significantly in the lake, but little effort has been made to identify the causes and consequences of this increase; the Water Quality Board has raised this issue in their 1985 and 1987 reports to the International Joint Commission.