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When immersed in sea water, any substrate would be rapidly colonized by micro and then macroorganisms 1. This complex and sequential natural process called biofouling induces economic and ecological prejudices, especially as far as ship hulls or aquaculture nets are concerned 2,3 Biocidal based antifouling (AF) coatings include several active molecules that aim to prevent the diversity of potential colonizers that could come across in marine environment. Generally several biocides are associated without clear idea of their effect 4,5. In this study, we intend to characterize the individual effect of three commercial biocides (Copper pyrithione, Zinc pyrithione and Zineb respectively called C, Z and I when formulated) on biofilm communities that represent the first step of colonisation of immersed artificial surfaces. Each biocide was dispersed in a (meth)acrylic-based matrix (Neocryl B725). Coatings composed of the polymer matrix alone (named M) together with a Poly(vinyl chloride) reference surface (named R) were also immersed in triplicates as controls. Coated panels and controls were immersed in sea water for one month in order to get mature biofilms beyond pioneer stages 4, at each season (Winter, Spring, Summer and Autumn), in two temperate bu