Comparative efficiency of macroalgal extracts and booster biocides as antifouling agents to control growth of three diatom species

The application of ‘booster biocides’ Diuron, Tolylfluanid and Copper thiocyanate inbantifouling paints, used to prevent development of biofouling, needs to be monitored before assessing their impacts on the environment. An alternative approach aims to propose eco-friendly and effective antifoulants isolated from marine organisms such as seaweeds. In this study, the effects of ‘booster biocides’ and the ethanol and dichloromethane extracts from a brown (Sargassum muticum) and a red alga (Ceramium botryocarpum) have been compared by algal growth inhibition tests of marine diatoms. The most efficient extracts were ethanol fraction of S. muticum and C. botryocarpum extracts with growth EC50 = 4.74 and 5.3 μg mL−1 respectively, with reversible diatom growth effect. The booster biocides are more efficient EC50 = 0.52 μg mL−1, but are highly toxic. Results validate the use of macroalgal extracts as non toxic antifouling compounds, and they represent valuable environmentally friendly alternatives in comparison with currently used biocides.