U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division 6201 Congdon Blvd., Duluth, Minnesota 55804

Summary

         As part of a continuing study of linkages between hydrology, biogeochemistry and biota in Lake Superior’s coastal wetlands, we conducted samplings to identify factors that influence concentrations and spatial variability of nutrients within and among wetlands. We evaluated spatial and temporal variability in nutrient concentrations in relation to hydrology (tributary discharge, seiche strengths and the balance between these), nutrient retention and transformation (as differences in concentrations between main and off-channel zones), and landscape scale measures of anthropogenic activity for a set of coastal wetlands on Lake Superior’s Wisconsin shore. Differences in mean nutrient concentrations among coastal wetlands were significantly related to differences in land use. Variability in nutrient concentrations within wetlands was related to the hydrologic interaction between watershed (tributary discharge) and lake (seiche inputs). Retention of dissolved inorganic nitrogen was higher in backwater zones than along major flow paths, suggesting that internal cycling further contributed to spatial variability in nutrients.