Cotter, A. M. USEPA Mid-Continent Ecology Division, email@example.com
Morrice, J. M. USEPA Mid-Continent Ecology Division, firstname.lastname@example.org
Kelly, J. R. USEPA Mid-Continent Ecology Division, email@example.com
NATURAL TRACERS AS BIOGEOCHEMICAL INDICATORS IN GREAT LAKES COASTAL WETLANDS
Coastal wetlands are productive, hydrologically complex ecosystems, linked to upland catchments by tributaries and to Lake Superior by seiche activity. Little is known about the role of wetlands in modifying or contributing to nutrient fluxes from watersheds to Lake Superior. Nutrient distributions in coastal wetlands are determined by biological activity and concentration and relative inflow of tributary and lake source waters. We investigated the efficacy of natural tracers (Ca, Mg, Na, and K) for determining mixing of lake and tributary water in coastal wetlands along the edge of Lake Superior. Concentrations of cations were higher in tributary water than in lake water and a suite of samples distributed spatially throughout the wetland and temporally over a seiche cycle allowed for delineation of the mixing zone. Ratios of SRP to conservative cations indicate little net retention of phosphorous in the wetland. Observed TIN concentrations were lower than expected values (calculated from conservative ion concentrations) in areas of the wetland where current velocities are low and residence times are assumed to be long, suggesting nitrogen retention. Our results suggest that conservative cations may be used diagnostically to resolve the major hydrologic interactions and nutrient retention in many Great Lakes coastal wetlands.
Day: Wednesday, Feb. 3
Location: Sweeney Center