Efficacy of Soft Corals and Sea Fan Extracts for Inhibition of Marine Bacteria Attachment

Abstract

The bacterial colonization on the surfaces of substrata is the initial step of biofouling in the marine environment which causing problems to marine organisms and marine industry. The toxic chemicals were used as antifouling agents in marine industry. Therefore there is a need for safe natural antifoulants to replace it.  In this study, the screening for natural antifoulants was carried out from nine soft corals and 18 sea fans. The extracts were tested against four marine bacteria isolated from sympatric, sea fans and seawater by means of inhibiting attachment of marine bacteria. The results showed that the inhibitory of bacterial attachment of the extracts against four marine bacteria were significantly different (p<0.05). The effective extracts that inhibit bacterial attachment well and broadly were screened for 17 extracts (62.96%).  The effective inhibitory activities (80.31-94.47%) were obtained from the extracts of soft coral Chironepthya sp., Sarcophyton sp.; from sea fans  Dichotella sp.1 and sp.3;  Rumphella sp.1 and sp. 2;  Juncella sp.3 and sp.4; Subergorgia sp. and unidentified sea fan 1. Among those effective extracts, only the extracts from soft coral Sarcophyton sp. and sea fans Rumphella sp.1 and sp.2 showed acute ichthyotoxicity against fish. The efficacy of extracts for inhibiting attachment of marine bacteria depended on the strains of marine bacteria and theirs different chemical compositions. While the inhibitory efficiency of the extracts was not related to the tissue’s concentration. These results indicated that soft corals and sea fans in Thai waters are an important source of effective marine bacteria attachment inhibitors in developing as environmentally-friendly antifoulants.