Evaluation of the antifouling efficacy of biogenic constituents of some algal species

Marine macroalgae are good source of biogenic compounds having potent activities such as antimicrobial and antifouling. This work aimed to use the different constituents (water soluble polysaccharides "WSP", protein, and lipid) of four algal species (Ulva fasciata, Cymodocea nodosa, Padina pavonia, and Colpomenia sinusa) as active biocides in paint formulations for preparing environmentally safe antifouling marine paints. Each type of these algal extracts was mixed solely by 2% (w/w) for WSP and protein and 1% (w/w) for lipid with the prepared paint formulation forming sixteen paint compositions beside the control (prepared paint formulation). They were applied on unprimed steel panels then hanged on a steel frame and immersed in Eastern Harbour (E. H.) water of Alexandria city, Egypt. The panels were followed up by visual and photographic inspections. Besides, the effect of these different marine paint formulations on seawater characteristics was studied through analysis of seawater samples collected on immersion date and on each inspection date. Results showed that, after 171 days of immersion the best results were obtained for the panels coated with the formulations containing hot and cold WSP extracts; the percentages of fouling organisms on the coated panels ranged between 25 and 35% of the panels area. U. fasciata panels in both cases showed the lowest percentages (25 and 30%) of fouling organisms. The panels coated with the formulations containing protein extract of P. pavonia and C. sinusa showed good results as well (35% in each case). Moderate results obtained for protein extract of U. fasciata and lipid extracts of C. nodosa, P. pavonia and C. sinusa (40 and 45%). The measured hydrographical parameters are within the normal range indicating that, these paints are environmentally safe.