Antimicrofouling activities of marine macroalga Dictyota dichotoma from the Red Sea

Marine organisms produce a variety of secondary metabolites mainly for achieving the defence against the competitors and predators. These compounds could be used as natural product antifoulants for the management of biofouling growth on marine structures. To understand the antifouling defence strategies of marine macroalgae, the macroalga Dictyota dichotoma was collected from the Obhur Creek of Red Sea, Saudi Arabia and extracted using methanol. Surface and total extraction methods were performed and tested against a bacterial strain isolated from the microfouling assemblages. The extracts obtained from the macroalgal samples have strong antibacterial and antibiofilm activities against the bacterial strain isolated from the marine microfouling assemblages. The percentage of growth varied significantly between the bacterial culture treated with extracts and control. The total extracts showed strong bacterial growth inhibitory activities in culture plate method. In microtitre plate assay, surface extract showed higher biofilm inhibitory activity than total extract. GC-MS analysis indicated considerable variations in the metabolic profile of the surface and total extracts with higher number of compounds in the surface extract. This study revealed the importance of surface-associated compounds in antifouling defence mechanism of the marine macroalgae.