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Energy and nutrient flows connecting coastal wetland food webs to land and lake
Citation:
Hoffman, J., Greg Peterson, A. Cotter, M. Sierszen, A. Trebitz, AND J. Kelly. Energy and nutrient flows connecting coastal wetland food webs to land and lake. IAGLR Conference, Burlington, VT, May 25 - 29, 2015.
Impact/Purpose:
not applicable
Description:
Both landscape character and hydrologic forces (principally, tributary discharge and seiches) can influence utilization of externally-derived energy and nutrients in coastal wetland food webs. We quantified the contribution of internal vs external energy and nutrients among wetlands with varying population density and along a gradient of river and lake water. We used carbon and nitrogen stable isotope analysis to identify internal and external material supporting fish larvae somatic growth in three coastal river-wetland complexes in Lake Superior. We found that fish growth was largely supported by internal energy sources (generally 60% to 90%), including phytoplankton, benthic periphyton, and aquatic vegetation. With respect to nutrients, a multivariate model that included both population density and NH4+ explained most of the variation in larval fish ä15N values. Near effluent sources, contribution of land-based nutrients to the food web supported up to 50% of fish production. We conclude that watershed-based nitrogen has a negative effect on utilization of watershed-based energy sources in coastal wetland food webs, whereas lake-based nutrients and energy are likely positive correlated, in part because these subsidies are delivered to coastal wetlands by organism movement rather than by physical exchanges.