Contamination of natural and cultured mussels (Mytilus galloprovincialis) from the northern Adriatic Sea by tributyltin and dibutyltin compounds

The levels of tributyltin (TBT) and dibutyltin (DBT) compounds were measured by gas chromatography ion-trap mass spectrometry (GC–MS/MS) in natural and cultured mussels (Mytilus galloprovincialis) from the northern Adriatic Sea in spring 2003. The highest (725 ng g−1 dry weight) and lowest levels (198 ng g−1 dryweight) of butyltins (TBT+DBT)were found in nativemussels from the Lagoon of Venice,with the higher values being detected in specimens collected next to a dockyard and the lower values in specimens from a location characterized by strong water exchanges between the lagoon and the Adriatic Sea. The two cultured samples exhibited intermediate concentrations, with marine harvested samples being more contaminated than those from the lagoon. Concentrations of TBT were higher than those of DBT for several reasons: the limited capability of bivalves to metabolize TBT and their ability to accumulate it (with recent input of TBT into the environment as TBT-based anti-fouling paints being the most important contributor of organotin contamination in our study area); and higher lipophilicity of TBT than DBT. In order to find correlations between organotin pollution and the state of nourishment of the mussels, the condition index was also evaluated as the mass ratio of meat dry weight to shell dry weight. There was no correlation between condition index and butyltin concentrations. These results indicate that condition index could not give information about stress conditions, as the contamination level is probably too low to cause significant reductions in mussel growth.