Antifouling Coatings Influence both Abundance and Community Structure of Colonizing Biofilms: a Case Study in the Northwestern Mediterranean Sea

International audienceWhen immersed in seawater, substrates are rapidly colonized by both micro- and macroorganisms. This process is responsible for important economic and ecological prejudices in particular when related to ship hulls or aquaculture nets. Commercial antifouling coatings are supposed to reduce biofouling, ie micro and macrofoulers. In this study, biofilms that primarily settled on seven different coatings (Polyvinyl chloride -PVC-, a Fouling Release Coating -FRC-, five Self-Polishing Copolymer coatings -SPC- including four commercial ones) have been quantitatively studied, after one month of immersion in summer in the Toulon bay (North-western Mediterranean Sea, France) using flow cytometry (FCM), microscopy and Denaturing Gradient Gel Electrophoresis. FCM was used after a pre-treatment to separate cells from the biofilm matrix, in order to determine densities of heterotrophic bacteria, picocyanobacteria, pico- and nanoeukaryotes on these coatings. Among diatoms, the only microphytobenthic class identified using microscopy, Licmophora, Navicula and Nitzschia were determined as the dominant taxa. Overall, biocide-free coatings showed higher densities than all, except for one biocidal coating, whatever the group of microorganisms. Heterotrophic bacteria always showed the highest densities, diatoms showing the lowest, but relative abundance of these groups varied depending on the coatings. In particular, the SPC copper-free coating failed to prevent diatom settlement, whereas the SPC pyrithione-free coating exhibited high picocyanobacteria density. These results highlighted the interest of FCM for antifouling coatings assessment, as well as the specific selection among microbial communities by antifouling coatings