Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

A laboratory bioassay determined the relative contribution of various pathw ays of Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes aren aceodentata exposed to moderately contaminated sediments. Juvenile worms we re exposed for 25 d to experimental sediments containing 5 different reacti ve sulfide (acid volatile sulfides, AVS) concentrations (1 to 30 mu mol g(- 1)), but with constant Ag, Cd, and Zn concentrations of 0.1, 0.1 and 7 mu m ol g(-1), respectively. The sediments were supplemented with contaminated f ood (TetraMin (R)) containing 3 levels of Ag-Cd-Zn (uncontaminated, 1 x or 5 x metal concentrations in the contaminated sediment). The results suggest that bioaccumulation of Ag, Cd and Zn in the worms occurred predominantly from ingestion of contaminated sediments and contaminated supplementary foo d. AVS or dissolved metals (in porewater and overlying water) had a minor e ffect on bioaccumulation of the 3 metals in most of the treatments. The con tribution to uptake from the dissolved source was most important in the mos t oxic sediments, with maximum contributions of 8% for Ag, 30% for Cd and 2 0% for Zn bioaccumulation. Sediment bioassays where uncontaminated suppleme ntal food is added could seriously underestimate metal exposures in an equi librated system; N. arenaceodentata feeding on uncontaminated food would be exposed to 40-60% less metal than if the food source was equilibrated (as occurs in nature). Overall, the results show that pathways of metal exposur e are dynamically linked in contaminated sediments and shift as external ge ochemical characteristics and internal biological attributes vary.