EFFECTS OF TRIBUTYLTIN (TBT) EXPOSURE ON THE REPRODUCTION AND EMBRYONIC-DEVELOPMENT OF THE BIVALVE SCROBICULARIA-PLANA

Field and laboratory work tvas carried out during the summers of 1990 and 1991 on bivalves Scrobicularia plana from sites moderately-affecte d and relatively-unaffected by tributyltin (TBT) contamination (i.e, a mean concentration in clam tissues of 0.4 and 0.02 mu g Sn g(-1) dry wt, respectively). Standard cultures after artificial fertilizations w ith broodstock of either site did not result in dissimilar survival of embryos nov in larvae of different quality at the time of hatching, S tatic 48 h toxicity tests on S. plana embryos showed that an EC(50) Of less than the nominal 250 ng Sn litre(-1) (a range of 178-198 ng Sn l itre(-1), as analysed) can be set for TBT independently, of the origin of broodstock, The results are discussed in relation to the reported disappearance of S. plana throughout northern Europe and the simultane ous presence of toxic levels of butyltin. It is concluded that TBT has probably reduced the recruitment into some UK clam populations by pre venting the successful development of a significant proportion of thei r embryos.