Effects of bioturbation on the bacterial community in contaminated sediment

Bioturbation has been shown to expedite the degradation of refractory compounds in contaminated sediments. In an effort to determine whether bioturbation influences sediment bacterial community diversity, a river simulation was operated in microcosm cells with sediment samples from the Anacostia River (Washington D.C.). Sample cells contained the freshwater oligochaete Ilyodrilus templetoni at a density of 20,000 / m² while control cells were operated without benthic organisms. Vertical profiles of redox potential, sulfide, and dissolved oxygen concentrations were determined during river simulations. As compared to the condition without macrobenthos, Ilyodrilus expedited oxygen consumption and lowered the redox potential in the top four centimeters of sediment. Sulfide concentrations were below the limit of detection. After five months the cells were extruded and analyzed by layer for select microbial parameters. Bacteria were quantified by direct count and communities were profiled at different depths using denaturing gradient gel electrophoresis (DGGE).