The Role of Sediment-Feeding Oligochaete Tubifex on the Availability of Trace Metals in Sediment Pore Waters as Determined by Diffusive Gradients in Thin Films (DGT)

The diffusive gradient in thin films (DGT) technique was applied to derive an autonomous measurement of the chemical availability of trace metals in sediment, in the presence of Tubifex sediment-feeding oligochaetes. DGT probes were put into beakers of sediments, some with and some without Tubifex. After two weeks of exposure, probes were withdrawn and analyzed for cadmium, copper, and zinc content. Available metal concentrations generally were higher when conditions were more oxic. The presence of Tubifex caused a decline in available concentrations in the upper layer but increased oxygen penetration at depth and consequently increased available fractions in the lower sediment layer. Sediment cores without organisms had steep gradients in available metal concentrations in pore water. Tunneling behavior in Tubifex alters available metal concentrations. DGT appears suitable for measuring available metal concentrations in studies such as these.