The effects of predation on the condition of soft corals

Abstract

Soft corals are well known for producing toxic and unpalatable compounds to deter predation. In spite of these antipredation defences, a suite of specialised predators has coevolved to feed on soft corals. Direct quantification of this predation, however, has been minimal and the influence of predation on soft corals is yet to be investigated. In this study, the intensity and importance of predation by fishes on soft corals were evaluated across two locations using descriptive and experimental approaches. Thirty-six percent of soft coral colonies surveyed in the Palm Islands were found to have bite marks, with up to 40 bite marks observed on a single colony. Soft coral was also the major dietary component of the two fish species studied, representing up to 90% of bites taken by Chaetodon melannotus and 87% of bites by Neoglyphidodon melas, despite constituting less than 30% of the substratum. Simulated predation in manipulative experiments was found to have no clear effects on colony condition for two soft coral genera of contrasting morphology (Litophyton: branching and upright colonies, and Lobophytum: massive and lobate colonies). Both species showed a high capacity for recovery, with bites healing over the duration of the experiments and in most instances within 31 days. In contrast to the widespread assumption that predatory interactions between fishes and soft corals are minimal, the results of this study indicate that predation can be intense but is not immediately important to soft coral colonies under current climatic conditions.