Wednesday, May 28, 2008 - 10:00 AM
372

Nitrate retention and processing in through-flow wetlands

Jonathan M. O'Brien and Stephen K. Hamilton. Kellogg Biological Station, 3700 East Gull Lake Drive, Hickory Corners, MI 49060

Through-flow wetlands are shallow water bodies that directly exchange surface water with streams or lakes and can potentially act as biogeochemical hotspots in the aquatic landscape.  Due to elevated rates of biological activity, sediment anoxia, and greater water transit times,  these ecosystems may alter biogeochemical fluxes to a greater degree than stream channels and thus have considerable influence on stream nitrate loads.  We selected 14 wetlands with single dominant inflows and outflows, and with residence times ranging from hours to weeks.  We sampled in-flow and out-flow nitrate and ammonium concentrations bimonthly, during hydrologically stable periods, for one year.  Through-flow wetlands were found to be consistent sinks for nitrate year round. During the warm season (Apr-Sep) nitrate concentrations were reduced by an average of 60% between inflows and outflows.  Warm-season nitrate retention was significantly correlated with nitrate concentration, emergent plant cover, and hydrologic load (relative through-put).  Nitrate retention across seasons was only correlated to daily hydrologic load.  Ammonium concentrations increased in wetland out-flows, but did not nearly account for decreases in nitrate concentration.  Through-flow wetlands are likely to be permanent sinks for N in the landscape.


Web Page: Nitrogen, hydrology, wetland

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