PHOSPHORUS BUDGET AND BENTHIC FLUX IN EUTROPHIC GRAND LAKE ST. MARY'S, OHIO

Eutrophication is a process by which water bodies become more biologically productive as a result of nutrient loadings. Eutrophication is aesthetically unpleasant, it reduces aquatic biodiversity, alters food web structure, and can reduce recreational and commercial values of water bodies and adjacent property. Grand Lake St. Mary’s is the largest inland lake in Ohio and is highly eutrophied as a result of current and historical inputs of phosphorus (P). Although P has been measured in Grand Lake tributaries, the significance of external loadings from the watershed relative to benthic remobilization is unknown. Field measurements and investigations were conducted to determine a P budget for Grand Lake. Inputs include benthic flux, watershed tributaries, wastewater treatment plant inputs, and atmospheric deposition. Preliminary results suggest that internal recycling of P from the sediments is of the same order of magnitude as inputs from the watershed. This implies that alum treatments intended to minimize benthic efflux of P need to be coupled with watershed management practices to effectively mitigate the adverse effects of P on the Grand Lake ecosystem.