No abstract

Antifouling chemical defense is likely an evolutionary response to the ecological disadvantages of epibiosis, particularly for photosynthetic organisms. Seaweed natural products with antifouling activity can provide effective, environmentally friendly alternatives to currently used antifouling paint booster biocides. The aim of this work was to assess the antifouling potential of natural products from Brazilian littoral seaweeds. Crude organic extracts from 51 populations comprising 42 species of macroalgae from eight locations along the Brazilian coast were tested against a relevant fouling organism in laboratory bioassays, the brown mussel Perna perna. In five cases, antifouling activities of purified compounds were also tested. A total of nine macroalgae were also cultured and tested for the presence of inducible defenses against fouling. Ecologically relevant field tests were performed in 11 cases to confirm laboratory results. Despite the unbalanced number of macroalgae tested among different localities, there seems to be no latitudinal trend of increased antifouling activity towards lower latitudes, where fouling pressure is presumed to be higher. However, there was a clear phylogenetic pattern in antifouling activity, with red macroalgae having the highest proportion (55%) of active species (moderate or strong fouling inhibition), followed by brown macroalgae (14%). Green seaweeds never exhibited strong antifouling activity (≥80% inhibition of byssal attachment relative to controls). Some degree of induced antifouling defense was observed in seven species (78%). These results appear to support known trends of secondary metabolite production among seaweeds and suggest that research efforts should be focused on tropical red macroalgae in the quest for new antifoulants. On the other hand, it seems clear that macroalgal groups, such as green algae, must have mechanisms of defenses against fouling that are not chemical.