Antifouling activities of methanolic extracts of three macroalgal species from the Red Sea

Marine macroalgae are considered as a potential source for various bioactive secondary metabolites. In this study, antifouling activities of three macroalgal species (Chaetomorpha linum, Turbinaria ornata, and Sargassum polycystum) collected from the Rabigh coast of the Red Sea were assessed against the larvae of barnacle, Amphibalanus amphitrite. Crude extracts of the macroalgae also were mixed with varnish and coated on nylon net panels for field studies. The methanol extract of all the three algae inhibited the settlement of cypris larvae on Petri dishes. Of the three macroalgal species, the extracts of T. ornata and S. polycystum significantly reduced the biofouling growth on nylon net panels in field antifouling trials conducted for a period of three months. GC-MS analysis of the crude extracts revealed the presence of fatty acids and their derivatives, phytosterols, and terpenoids along with some other compounds. These results indicate that bioactive metabolites present in the crude extracts of the macroalgae could be used potentially as natural product antifoulants for reducing biofouling growth on marine structures.