Butyltins in sediments and deposit-feeding bivalves Scrobicularia plana from Arcachon Bay, France

A survey was conducted in Arcachon Bay during the summer of 1993 to determine the concentrations of tributyltin (TBT) and two degradation products in sediments and deposit-feeding bivalves Scrobicularia plana; the recruitment of juvenile clams to one site was also investigated. The three butyltins were detected in all sediment samples; however, the concentrations of TBT (from 7 to 30 ng Sn g−1) were far lower than the literature values shown to have adverse effects on populations of sediment-dwelling bivalves. TBT levels in adult S. plana were similarly reduced (from 28 to 165 ng Sn g−1), and they were consistently lower than the values predicted by the modelled bioavailability of TBT in sediments. On the other hand, recruitment to that particular site was negligible when compared to that recorded in the 1970s; the same applies to the adult density in this and other sites. This decline of the local S. plana populations is discussed in relation to present and past TBT pollution.