Biomonitoring organotin pollution with gastropods and mussels

In order to compare their performance for the biomonitoring of organotin (OT) pollution, Galician (NW Spain) populations of gastropods Nassarius reticulatus and mussels Mytilus galloprovincialis were sampled in 2000. Imposex (a set of sexual anomalies) in snails as well as the bioaccumulation of several OT species (mainly tributyltin [TBT]) in both invertebrates were determined. Imposex was related to TBT in female gastropod tissues in a biphasic manner, the slope changing markedly at around 200 ng Sn g(-1) dry wt. OT compounds in both animal species were significantly correlated, mussels consistently accumulating more than gastropods; in addition, correlation coefficients considerably increased when outliers were excluded from computation with the aid of fine chemical speciation analyses. The expected decline of OT pollution can satisfactorily be recorded by means of monitoring concentrations in either mussels and/or gastropods. However, the use of the latter is favoured because their imposex response is an easily determined biomarker, which additionally provides useful insights into the biological impact of TBT.