Effect of polychaete bioturbation on sediment-water fluxes of pyrene or cadmium

The fate of persistant organic or inorganic pollutants in marine ecosystems depends on their physicochemical characteristics. Due to hydrophobicity or particle reactivity, net fluxes are often from water to sediment. As a result, sediment pollutant concentrations may be orders of magnitude higher than concentrations in water. The sediment-water kinetics and sediment distribution of pollutants are further influenced by biotic factors as infaunal bioturbartion. We have studied effects of polychaete bioturbation on the fluxes of cadmium and pyrene from sediment to water and vice versa, as well as on their sediment distribution: Irrigation extensively increased Cd++ flux from water to sediment, and reduced Cd++ flux from sediment to water. However, polychaete bioturbation enhanced the pyrene flux from sediment to water. For both compounds, the feeding activity of the lugworm resulted in vertical burrying. Irrigation by,Arenicola marina resulted in preferential deposition of Cd++ from the water column at the bottom of the worm's feeding funnel. We conclude that the fate of sediment associated persistent compounds as influenced by abiotic and biotic factors is complex, and that it cannot be predicted based only on compound and sediment characteristics.