Preliminary evaluation of the antifouling potential of Halimeda gracilis extracts through antibacterial screening of marine biofilm-forming bacteria

This study evaluated the antibacterial and preliminary antifouling potential of extracts from the green seaweed Halimeda gracilis against marine biofilm-forming bacteria. Biofilm-forming bacteria were isolated from plastic panels submerged in the Vellar estuary, Tamil Nadu, India. Four biofilm-forming bacterial strains were identified through biochemical and morphological characterization: Vibrio sp., Staphylococcus sp., Pseudomonas sp., and Escherichia coli . Maximum inhibition was shown by the ethyl acetate extract, with inhibition zones of 22 mm against Vibrio sp ., 24 mm against E. coli , 29 mm against Staphylococcus sp ., and 24 mm against Pseudomonas sp . at 100 μg/ml concentration. Overall, results from this study provide evidence to suggest that H. gracilis possesses bioactive compounds with antifouling activity, specifically with activity demonstrated in the semi-polar fraction, which could be developed for use as a potential sustainable alternative to conventional toxic antifouling agents. These results are part of ongoing research into finding green solutions for marine biofouling. • Biofilm-forming bacteria were isolated from marine panels and identified. • Halimeda gracilis extracts were screened for antifouling activity. • Ethyl acetate extract showed strong inhibitory activity against four bacterial strains. • Highest inhibition was observed against Staphylococcus sp. (29 mm) at 100 μg/ml. • Halimeda gracilis shows promise as a source of natural antifouling compounds.