Michalek-Wagner, Kirsten, and Bowden, Bruce F. (2000) Effects of bleaching on secondary metabolite chemistry of alcyonacean soft corals. Journal of Chemical Ecology, 26 (7). pp. 1543-1562.

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Abstract

The loss of zooxanthellae during a short-term, experimentally simulated bleaching event resulted in significant changes to the secondary metabolite chemistry of the alcyonacean soft corals Sinularia flexibilis and Lobophytum compactum. The concentration of flexibilide, the most active cytotoxic secondary metabolite (with antimicrobial properties) in the tissues of Sinularia flexibilis increased by 126%, while that of its principal terpenoid algaecide, sinulariolide, simultaneously decreased to just 8% of that found in the controls. The changes were short lived, however, with concentrations of both compounds returning to control levels one month after bleaching; at the same time zooxanthellae levels were still only approximately 20% of the controls. Similarly, concentrations of isolobophytolide, the principal terpenoid secondary metabolite of Lobophytum compactum underwent a significant reduction for one month following bleaching. Like their nonbleached counterparts, both bleached individuals of Sinularia flexibilis and Lobophytum compactum experienced neither significant algal overgrowth nor predation following bleaching. Full recovery of zooxanthellae to baseline levels in all bleached corals occurred within four months. These results suggest that some soft corals are capable of surviving short-term bleaching events and the detrimental algal overgrowth that is often associated with bleaching, possibly by adjusting their secondary metabolite concentrations to suit specific needs. Support for the notion that resource allocation towards production of specific algaecides in bleached specimens translates also into higher protection was gained through analysis of naturally bleached soft corals. Bleached and overgrown individuals had significantly lower concentrations of species-specific algaecides than their bleached and unfouled and their unbleached counterparts.

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