Controls on Cellulose Decomposition Rates in Thick Accumulations of Flocculent Sediment inDiffering Shallow Freshwater Habitats

Science Center, Bent Corridor

Thick accumulations of flocculent (resembling tufts of wool) organic sediments are common in shallow, freshwater ecosystems, which are understudied relative to deeper freshwater lakes, but likely contribute to global biogeochemical cycles. The floc layer likely plays an especially important role in the decomposition and storage of carbon. The factors influencing the decomposition of carbon in floc are not understood, however. We hypothesized that temperature controls the rate of cellulose decomposition in floc, and that the vertical location of organic matter would also influence the rate of cellulose decomposition. In order to test these hypotheses, over the course of the summer of 2016 we deployed cotton strip decomposition assays in 15 field sites with various conditions, and measured surface water and porewater chemistry, temperature, and dissolved oxygen in order to determine which factors influenced the rate at which carbon decomposes in floc. Our results showed that site characteristics play a role in how quickly carbon decomposes. At this time, however, we do not have sufficient evidence or analysis to determine which specific characteristics have the biggest impact.