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.