2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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6/08/2017 | 9:00 AM - 9:15 AM | EXTENSIVE SPATIOTEMPORAL VARIATION IN NUTRIENT CONCENTRATIONS OF LAKE MICHIGAN’S TRIBUTARIES | 306A

EXTENSIVE SPATIOTEMPORAL VARIATION IN NUTRIENT CONCENTRATIONS OF LAKE MICHIGAN’S TRIBUTARIES

Despite efforts to reduce nutrient loads to the Laurentian Great Lakes since the 1970’s, nutrient inputs continue to cause coastal eutrophication and degrade ecosystem services. Tributaries are a practical focus for quantifying nutrient loads from watersheds, and understanding spatial and temporal drivers of tributary nutrient concentrations is critical for managing nutrient loads. We circumnavigated Lake Michigan quarterly to analyze nutrient concentrations in ~100 tributaries. Tributaries were selected randomly with stratification by watershed area and land use. We find only weak effects of watershed area on tributary nutrient concentrations. However, phosphorus and nitrogen concentrations increase and carbon concentrations decrease with increasing agricultural and urban land uses. Strong seasonal variation in nutrients complicates interpretation of land use effects; for instance, nitrate concentrations are highest in the summer, but effects of land use are stronger in fall and winter. Overall, we find carbon, nitrogen, and phosphorus concentrations (and associated stoichiometries) vary by up to 3 orders of magnitude among Lake Michigan tributaries. Our seasonal and spatial sampling regimen offers insight into the challenge of managing nutrient loads in this landscape.

C10 Biogeochemistry
C28 Land-Water Interfaces
C27 Landuse and Non-Point source Impacts

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Presenters/Authors

Robert J. Mooney (), Center for Limnology, University of Wisconsin - Madison, rjmooney@wisc.edu;