Water Quality in the Middle Great Lakes: Results of the 1985 U.S. EPA (Environmental Protection Agency) Survey of Lakes Erie, Huron and Michigan

摘要

Continuing a limited annual program begun in 1983, the Great Lakes National Program Office surveyed the water quality of Lakes Erie, Huron and Michigan in 1985. A helicopter survey was completed during January and February, and three ship surveys were conducted in spring, summer, and fall. The samples were analyzed for traditional limnological parameters and nutrients. Although many measurements of water quality were unchanged from 1983 to 1985, the physical conditions, notably temperature, were much different; 1983 was a mild year, while 1984 and 1985 were much colder. In 1985 the stratification for each lake spanned a longer period than in 1983 and 1984. All lakes exhibited a pattern of nutrient depletion from the epilimnion and concurrent enrichment of the hypolimnion during the summer. The magnitude of the depletion for some parameters was greater in 1985 than observed in 1983 and 1984.