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SFS Annual Meeting

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FACTORS LIMITING DENITRIFICATION RATES IN A HYPER-EUTROPHIC MIDWESTERN RESERVOIR AT THE SEDIMENT-WATER INTERFACE

Humans have altered global nitrogen cycling, increasing bioreactive nitrogen in our environment. Excess nitrogen contributes to eutrophication and dead zones, with profound socioecological and economic consequences. Denitrification, the conversion of nitrate to dinitrogen gas, is an important ecosystem service that removes excess nitrogen. Denitrification rates in Acton Lake, a hyper-eutrophic reservoir in southwestern Ohio, are relatively high in spring and decrease through summer and fall, corresponding to seasonal declines in nitrate concentration. Nitrate drawdown likely limits denitrification rates, but organic carbon may limit rates in shallow areas near stream inflow. Our objective was to assess whether denitrification rates were limited by nitrate or organic (algal) carbon at sites near the inflow and outflow of the lake. We added nitrate and algal carbon separately and in combination to lake sediment cores, which were incubated in flow-through chambers. We found that denitrification rates in the inflow were significantly higher than in the outflow, likely due to higher temperature. Denitrification rates were limited by nitrate at both sites, and carbon additions did not increase rates. Our findings contribute insights to processes that govern this valuable ecosystem service and the availability of reactive N.

Ashley Mickens (Primary Presenter/Author), Miami University, mickenam@miamioh.edu ;


Michael Vanni (Co-Presenter/Co-Author), Miami University, vannimj@miamioh.edu;


Tanner Williamson (Co-Presenter/Co-Author), Miami University of Ohio, tanner.williamson@gmail.com;