Biodiversity in the lagoon of Venice: a laboratory model for the study of the effects of antifouling compounds on settlements and survival of sessile species

We used the colonial ascidian Botryllus schlosseri as an experimental model to evaluate the risks of new antifouling compounds, alternative to organotins through the study of their effects on larval settlement and individual survival. In particular, we studied the settlement and metamorphosis ability of larvae in the presence of either substrates coated with various paints which are ususally in commerce in the Lagoon area or sea watercontaining various concentrations of active antifouling principles. Moreover, since alterations in the functionality of the immune system represent a great risk for the survival of individuals, we set up a series of cytochemical assays on cultured haemocytes to be used as biomarkers; the latter allowed an evaluation of the immunotoxicity of these substances. Results indicate a high danger of antifouling compounds for aquatic organisms, sometimes similar to TBT, and the risk of severe consequences for Lagoon biodiversity.