Corallivory on small Porites colonies increases with coral colony size but is reduced by macroalgal associational refuge

Abstract

Numerous tropical macroalgae provide associational refuge to other benthic organisms, presumably due to their physical structure and/or production of chemical metabolites. One feature determining their effectiveness as an associational refuge is likely to be the size of the organism benefitting from the refuge. Using a manipulative experiment in the back reef of Moorea, French Polynesia, we tested if the macroalga Turbinaria ornata provided an associational refuge from fish corallivores for small colonies of massive Porites spp., and how this differed with colony size (20–100 mm diameter). Tissue loss through corallivory increased with colony size but was ~ 72% less for Porites colonies associated with T. ornata versus colonies separated from this macroalga, while dense macroalgae beds on contemporary reefs negatively impact the recruitment, growth and survival of corals, small colonies of Porites appear to benefit, through reduced corallivory, by associating with the macroalga Turbinaria. This association may come at a cost (e.g., reduced growth) and should be the focus of future research.