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INFLUENCES OF HYDROLOGY ON NUTRIENT DYNAMICS IN LAKE SUPERIOR COASTAL WETLANDS
Citation:
Morrice, J A., A S. Trebitz, J. R. Kelly, A M. Cotter, M L. Knuth, M. M. Tredrea, AND A. M. Grygo. INFLUENCES OF HYDROLOGY ON NUTRIENT DYNAMICS IN LAKE SUPERIOR COASTAL WETLANDS. Presented at International Association for Great Lakes Research 2000 Conference, Great Lakes, Great Rivers, A Vision for Tomorrow, Cornwall, Ontario, Canada, May 21-26, 2000.
Description:
Little is known about the role of the coastal wetlands (CWs) of Lake Superior in modifying or contributing to nutrient fluxes from watersheds to the lake. We are studying factors controlling nutrient retention and transformation of CWs in Western Lake Superior. CWs may be unique among wetlands and are hydrologically linked to uplands through tributary flow and to lakes through seiche activity and there is considerable variation among wetlands in the strength of these linkages. We measured hydrologic inputs and distributions of inorganic and organic forms of nitrogen and phosphorous in 8 wetlands that ranged widely in tributary discharge (0-3.46 m3/s) and seiche amplitude (10.2-25.7cm). All wetlands were depleted in organic nitrogen (TIN) relative to phosphorous (SRP). Results suggest that SRP was transported from tributary to lake with little retention. In contrast TIN imported from the watershed was retained by some wetlands. TIN-rich lake water was a potentially significant nitrogen source in wetlands with high seiche and low tributary discharge. Our results suggest that CWs are nitrogen limited ecosystems that alter nutrient ratios in water flowing from uplands to Lake Superior.