TOXICITY OF SEDIMENT-ASSOCIATED TRIBUTYLTIN TO INFAUNAL INVERTEBRATES- SPECIES COMPARISON AND THE ROLE OF ORGANIC-CARBON

Experiments with three species of infaunal invertebrates (a polychaete , Armandia brevis and amphipods, Rhepoxynius abronius and Eohaustorius washingtonianus) with different modes of feeding gave a wide range in toxic response to sediment associated tributyltin (TBT), while exhibi ting consistent lethal tissue residues. These studies showed that bioa ccumulation and toxicity of sediment-associated TBT were strongly cont rolled by the organic carbon content of the sediment, which we conclud ed was primarily due to its influence on interstitial water (IW) conce ntrations of TBT. Major differences in the response to sediment-associ ated TBT were found between species, which was attributed to differenc es in their rates of uptake and elimination of this compound. Predicti ons for bioaccumulation and toxicity for each species based on these t oxicokinetic rates were matched closely by observed values. Based on c omparisons of water-only and IW exposures (when water and sediment con centrations of TBT were in equilibrium) and predictions made with toxi cokinetic rates, the major route of uptake for each of the species tes ted appeared to be from dissolved TBT. We determined the mean (sd) org anic-carbon normalized sediment-water partition coefficient (K-oc) to be approximately 25 100 (5500) for TOC values ranging from 0.3 to 1.0% , which was five times higher than the reported K-ow. Additionally, we determined the dissolved organic carbon-water partition coefficient ( K-doc) to be 1652, which was three fold lower than the K-ow. The resul ts also showed that the K-oc could be influenced by infaunal organisms , presumably by reducing IW concentrations below predicted values, whi ch mises questions about the environmental relevance of sediment bioas says using these organisms and the expected IW concentrations present infield sediments. Published by Elsevier Science Ltd