Effects of antifouling paints alternative to organotin-based ones on macrofouling bocoenosis of hard substrata in the Lagoon of Venice.

The aim of this research was to evaluate the effects of eight antifouling paints of new generation on the ecological succession of macrofouling seawater association on hard substrates. At present, these paints are widespread on the market for preserving boat hulls and various structures submerged in aquatic environments, and contain Cu2O, CuO, CuSCN, Sea-Nine 211, Irgarol 1051, Diuron, Chlorothalonil, Dichlofluanid, Zinc pyrithione, Zineb and Endosulfan as principal or booster biocides. Experiments were carried out on wood and steel panels immersed for one year in two stations of the southern basin of the Lagoon of Venice, differing in bathymetric, hydrodynamic and turbidity characteristics. The growth and development of biocoenoses on panels coated with antifouling paints were analysed monthly and compared with both control and TBT-treated panels. Some biodiversity indexes – species rich-ness, biocoenosis structure, covering-abundance index, and similarity index – were used to describe the evolution of the biocoenosis and compare the disturbing effects resulting in the selection of resistant species, often different from those of the natural relative climax. Results indicate that none of the assayed paints is more powerful than TBT-containing paints and the effects on the biocoenosis are potentiated by the type of matrix and presence of booster compounds, following the order of biocidal efficacy of paints containing TBT > organozinc > copper > Sea-Nine.