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SFS Annual Meeting

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Elevated nitrate (NO3-) concentration in streams and rivers has contributed to environmental problems such as downstream eutrophication and loss of biodiversity. Sycamore Creek in Arizona is nitrogen limited, but previous studies have demonstrated high potential for denitrification, a microbial process in which biologically active NO3- is reduced to relatively inert dinitrogen (N2) gas. Oak Creek is similarly nitrogen limited, but NO3- concentration in reaches surrounded by agriculture can be double that of other reaches. We employed a denitrification enzyme assay to compare potential denitrification rate between differing land uses in Oak Creek, and measured whole system N2 flux using a membrane inlet mass spectrometer to compare seasonal differences in actual denitrification rates at Sycamore and Oak Creeks. We anticipated that NO3- would be an important limiting factor for denitrifiers; consequentially, agricultural land use reaches within Oak Creek would have the highest potential denitrification rate. We expected actual denitrification rate to be higher in the winter dormant season than in the summer growing season, due to a lapse in competition between microbes and plants. Results will aid in understanding nitrogen cycling in other nitrogen-limited streams.

Monica Palta (Co-Presenter/Co-Author), Pace University,;

Nancy Grimm (Co-Presenter/Co-Author), Arizona State University,;

Corey Caulkins (Primary Presenter/Author,Co-Presenter/Co-Author), Arizona State University,;