Distribution of Butyltin Residues in Mussels and Sea Stars of the St Lawrence Estuary

Blue mussels, Mytilus edulis, and sea stars, Leptasterias polaris, were collected in September 1995 at 8 stations along the south shore of the St Lawrence Estuary for analysis of butyltins by GC-MS. Tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MET) found in mussels averaged 16, 32, 30 ng Sn g(-1), respectively, indicating a low, but ubiquitous contamination of the St Lawrence Estuary shoreline. The very low TBT:DBT ratio (0.52) observed in mussel samples corresponds to the bioaccumulation of highly degraded butyltins present in suspended particulate matter at the end of the summer season. Total accumulated butyltins in sea stars feeding mussels reached 167 ng Sn g(-1) in pyloric ceaca at station 8 near the Gaspe public wharf and five other stations had total Sn higher than 100 ng Sn g(-1). Butyltin distribution in caeca and gonads of sea stars was different from mussels as the contribution of MBT was only 18% in L. polaris but reached over 38% in M. edulis. This difference may be attributed to the capability of sea stars to degrade and depurate organotins rapidly.