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PATTERNS AND CONTROLS ON CELLULOSE DECOMPOSITION RATES WITHIN THICK ACCUMULATIONS OF FLOCCULENT SEDIMENT IN SHALLOW FRESHWATERS

Thick accumulations of flocculent organic sediments (floc) are common in shallow freshwater ecosystems, but their biogeochemical and ecological importance are understudied. Investigating decomposition processes in floc is necessary to understand how these accumulations are maintained over time and how they contribute to organic carbon storage in freshwaters. We hypothesized that temperature and depth in floc are primary controls on decomposition rates; thus, rates would be higher in overlying water than in floc and would decrease with depth in the floc. To test this, we deployed vertical arrays of cotton strips in floc at 15 sites with diverse physicochemical conditions. After 21 days we retrieved the cotton strips and measured tensile strength loss as a proxy for decomposition. We also measured surface water and porewater chemistry, temperature, and dissolved oxygen (DO) to determine which factors influenced decomposition rates. Our results show that decomposition rates were on average lower in overlying water than in floc (where DO and temperature are typically lower), and suggest that the interactions between temperature, depth in floc, and dissolved phosphorus levels affect decomposition rates within floc.

Nicolas Lara (Primary Presenter/Author), Oberlin College, nlara@oberlin.edu;


Dustin Kincaid ( Co-Presenter/Co-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;


Scott Tiegs ( Co-Presenter/Co-Author), Dept. of Biological Sciences, Oakland University, tiegs@oakland.edu;