Effect of holothurian and zoanthid extracts on growth of some bacterial and diatom species

The antifouling properties of the extracts from two zoanthids, viz. Zoanthus sp, Protopalythoa sp and one holothurian species, viz. Holothuria leucospilota occurring in the coastal waters off Goa were tested against 5 bacteria and 2 diatom species. All the three extracts possessed antifouling activity but their efficacy was found to be species specific. The highest bacterial inhibition zone ranged between 3-4 mm with both the zoanthid extracts. In case of diatoms, inducement of growth was observed in lower concentrations (200-400 ppm) and inhibition at higher concentration (400 ppm and above). The results of the present study suggest that these marine natural compounds can possible be used as antifouling agents.