Temporal and biotic evolution of 'Botryllus biocoenosis' in the presence of antifouling paints.

We investigated the disturbing action on “Botryllus biocoenosis”, a benthic association of various ascidians where the colonial species are dominant, by new antifouling paints today largely used on boat hulls and various structures submerged in the lagoon area. Some biodiversity indexes (species richness, biocoenosis structure, covering-abundance index, similarity index) were used to describe the evolution of biocoenosis on wooden and steel panels immersed for one year in three stations of Chioggia with different hydrodynamic and turbidity characteristics. The biocidal compounds taken into consideration were Sea-Nine 211, Diuron, TCMS pyridine, Zinc pyrithione, Zineb and Endosulfan. The comparison of biodiversity indexes allowed us to evaluate the alterations of biocoenosis and suggest the disturbing causes which result in selection of dominant species often different to those of the natural climax.