Limnological Sampling Intensity in Lake St. Clair in Relation to Distribution of Water Masses

Abstract

Cluster analyses of physical and chemical data from Lake St. Clair identified two distinct water masses, a northwestern mass consisting primarily of Lake Huron water flowing from the main channels of the St. Clair River, and a southeastern mass of more stable water enriched by nutrient loadings from Ontario tributaries and shoreline urban development. The margins of the masses shifted according to wind direction and speed but the overall discreteness of the distribution was maintained. Comparison of station data to water mass means indicated that one index station in each mass would provide a more-than-adequate estimate of water quality within each water mass. Data collected at a single index station over a five-year period were representative of each water mass and more than adequate for trend analysis. Multivariate analyses of environmental data collected on a grid basis demonstrated that uniformity of water masses permits a reduction in sampling intensity.