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SFS Annual Meeting

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LINKING WATER DEPTH TO DENITRIFICATION IN SHALLOW AGRICULTURAL LAKES

Many shallow oxbow lakes in northwest Mississippi are hypereutrophic due to nitrogen (N) loading from agricultural fertilizer application. However, high turbidity often limits the depth of photosynthesis to the upper water column and lake edges and reduces overall photosynthesis rates. High water temperature from shallower depth, along with low oxygen, and high nitrogen conditions create increased potential for nitrogen removal through denitrification. The objective of this study is to determine spatial and temporal variations of denitrification rates in the sediment and water column of Roundaway Lake, Mississippi, focusing on the relationship between water depth, temperature, and N removal. Denitrification and nutrient retention rates were measured in lake water and sediment cores collected across a depth gradient during three occasions in spring 2017 using a flow-through core system in the laboratory. In fall 2017, sediment denitrification rates were measured across a 20°C temperature gradient for five days. Initial results suggest that shallower lakes have higher N removal rates. As these lakes are frequently manipulated for agricultural irrigation and experience substantial depth fluctuations independent of seasonal rainfall, there is potential to manage lake depth to optimize nitrogen removal through denitrification.

Jordan Evans (Primary Presenter/Author), Tennessee Technological University, jlevans44@students.tntech.edu;


Justin Murdock (Co-Presenter/Co-Author), Tennessee Tech University, jnmurdock@tntech.edu;