Canadian Environmental Sustainability Indicators Phosphorus Loading To Lake Erie PDF Download

In the 1960s, severe degradation of the lower Great Lakes and several embayments of the upper lakes aroused public concern. An international review identified lake eutrophication as a major problem in those lakes, due to excessive inputs of nutrients; phosphorus was subsequently identified as the key nutrient controlling eutrophication. An international agreement signed in 1972 focused on reducing phosphorus inputs to the lakes. This paper discusses the progress in controlling phosphorus loads to the Great Lakes and the resulting responses of the lakes. Emphasis is on concentrations and long-term trends of phosphorus, nitrogen, and chlorophyll in the offshore waters and on the hypolimnetic oxygen depletion in Lake Erie. The current status of phosphorus loadings into the five lakes is reviewed, and system response is discussed in terms of soluble reactive phosphorus concentrations and algal growth, oxygen depletion, and nitrate-plus-nitrate levels. The paper concludes with a discussion of possible future Great Lakes ecosystem management strategies.