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TOTAL NITRATE REMOVAL BY FLOCCULENT ORGANIC SEDIMENTS IN SHALLOW FRESHWATER ECOSYSTEMS

Anthropogenic activities have increased the availability of nitrogen (N) to the biosphere. Some proportion of this N enters aquatic ecosystems, mainly as nitrate, via runoff, groundwater, and/or atmospheric deposition. Relative to their areal coverage, a disproportionate amount of anthropogenic N is processed by these recipient ecosystems. Nitrogen cycling in small waterbodies, given their shallow nature, is strongly influenced by the sediment-water interface. In these ecosystems, thick layers of flocculent organic sediments (floc) have a tendency to accumulate. Although floc is nearly ubiquitous, little is known about its biogeochemical importance in shallow freshwater ecosystems. The objective of this study was to measure in situ nitrate removal rates by floc in a variety of shallow waters by enriching overlying water in mesocosms with nitrate and bromide and monitoring changes in concentrations over three diel cycles. Uptake rates of nitrate from overlying water increased with increasing water temperature, water depth, and sediment chlorophyll concentration, and ranged from -0.25 to -7.28 mmol m-2 h-1. These rates are similar to those measured in other shallow aquatic ecosystems.

Dustin Kincaid (Primary Presenter/Author), W.K. Kellogg Biological Station and Department of Integrative Biology, Michigan State University, kincai32@msu.edu;


Stephen K. Hamilton ( Co-Presenter/Co-Author), Michigan State University, hamilton@kbs.msu.edu;