Posidonia oceanica (L.) (Delile, 1813) extracts as a potential booster biocide in fouling-release coatings

Since the banning of tributyltin, the addition of inorganic (metal oxides) and organic (pesticides, herbicides) biocides in antifouling paint has represented an unavoidable step to counteract biofouling and the resulting biodeterioration of submerged surfaces. Therefore, the development of new methods that balance antifouling efficacy with environmental impact has become a topic of great importance. Among several proposed strategies, natural extracts may represent one of the most suitable alternatives to the widely used toxic biocides. Posidonia oceanica is one of the most representative organisms of the Mediterranean Sea and contains hundreds of bioactive compounds. In this study, we prepared, characterized, and assessed a hydroalcoholic extract of P. oceanica and then compared it to three model species. Together, these four species belong to relevant groups of biofoulers: bacteria (Aliivibrio fischeri), diatoms (Phaeodactylum tricornutum), and serpulid polychaetes (Ficopomatus enigmaticus). We also added the same P. oceanica extract to a PDMS-based coating formula. We tested this coating agent with Navicula salinicola and Ficopomatus enigmaticus to evaluate both its biocidal performance and its antifouling properties. Our results indicate that our P. oceanica extract provides suitable levels of protection against all the tested organisms and significantly reduces adhesion of N. salinicola cells and facilitates their release in low-intensity waterflows.