State of the Middle Great Lakes: Results of the 1984 Water Quality Survey of Lakes Erie, Huron, and Michigan

摘要

Continuing an effort begun in 1983, the water quality of Lakes Erie, Huron, and Michigan was surveyed in 1984. Sampling, which was restricted to the open waters of the three lakes, was conducted from the R/V Roger Simons in three surveys (spring, summer, and fall) and from helicopter in a winter survey that took place during January and February of 1985. The samples were analyzed for traditional limnological parameters and for nutrients. The data were compared with the results of the 1983 survey as well as with other historical data and the results of numerical simulations made using dynamic eutrophication models. Sampling in 1984 shows that the three lakes were significantly cooler than they were in 1983. Although statistically significant differences were found in comparisons of the 1983 and 1984 estimates of the concentration of many of the measured substances, these differences are of questionable environmental significance. The variability of the concentration estimates made using data collected during the spring isothermal period was generally comparable in the two years and similar to the estimated analytical uncertainty. Because phosphorus loading estimates are unavailable for the period 1983 to 1984, model simulations of total phosphorus concentration were driven with hypothetical loads based on the most recent (1982) estimates. The models do not appear to simulate the annual patterns suggested by the data, but the data, not being intended for model validation, may be too sparse to provide a fair basis for comparison. (ERA citation 12:031816)