A NATURAL ALGACIDE FROM SOFT CORAL SINULARIA-FLEXIBILIS (COELENTERATA, OCTOCORALLIA, ALCYONACEA)

A crude lipophilic extract and specific pure metabolites of the soft c oral Sinularia flexibilis have been examined for algacidal properties both in laboratory and field experiments. Laboratory algal bioassays, in which cultures of the common fouling alga Ceramium codii were incub ated with six different diterpenes isolated from S. flexibilis, reveal ed that 11-episinulariolide exhibits strong algacidal properties. Fiel d experiments carried out with treated settlement tiles confirmed the laboratory findings and provided evidence for the algacidal properties of 11-episinulariolide against several other common reef algae. Sinul ariolide, which had previously been reported to inhibit the growth of unicellular algae, was approximately one third as effective as its ste reoisomer 11-episinulariolide in the laboratory growth inhibition bioa ssay and showed no significant algacidal properties at the concentrati ons used in the field experiments.