Contamination par le tributylétain (TBT) du Bassin d'Arcachon évaluée à l'aide d'un indicateur biologique : l'imposex chez Ocenebra erinacea. Résultats préliminaires

The Bay of Arcachon has been particularly affected by the impact of organotin-based antifouling paints (His, 1996). Boring gastropods, Ocenebra erinacea, have completely disappeared from the Bay, because of the castration induced by these compounds, from 1980 to 1990. There have been no studies on imposex effects in the Bay of Arcachon since the investigations of Poli (1972) who first described the phenomenon, and of Féral (1982) who attributed it to TBT. Recently, Sarradin & al. (1991) demonstrated the persistence of TBT and its degradation products in the sediments of the Bay, the latter being a potential source of pollution; Stroben & al. ( 1995) have conceived a contamination scale based on the VDSI (Vas Deferens Sequence Index) in prosobranch gastropods. We have conducted a preliminary estimate of TBT contamination in the Bay of Arcachon for those parts of the Bay where we were specimens of 0. erinacea could be obtained. Some parts of the Bay are only slightly polluted (0.5 ng. 1-1 of TBT) ; while other populations have VDSI values corresponding to TBT concentrations of 3.9 ng. 1-1. Considering these results, further experiments with gastropods held in cages will be conducted, in order to determine whether yachting marinas are still a potential source of TBT, or whether the pollution effects are the result of sediment resuspension