Negative effects of gardening damselfish Stegastes planifrons on coral health depend on predator abundance

Abstract

On Bonaire, we studied the effects of predator abundance and habitat availability on the abundance of the threespot damselfish Stegastes planifrons, a species that creates algal gardens at the expense of live coral cover. Across 21 sites, predator biomass ranged from 12 to 193 g m-2 (mean = 55.1; SD = 49.1) and benthic cover of S. planifrons' preferred habitat (corals of the Orbicella species complex) ranged from 2.2 to 38.0% (mean = 14.3; SD = 9.6). Across these gradients, the local abundance of S. planifrons was significantly and negatively related to predator biomass, but not to habitat availability. Increased local abundance of S. planifrons corresponded to an increasingly larger proportion of coral colonies affected by its 'farming behavior', resulting in an increased prevalence of coral disease. Thus, predators indirectly affected the composition of reef communities around Bonaire by controlling damselfish abundance. Furthermore, the abundance of S. planifrons could not be correlated with its preferred habitat, despite such correlations having been observed elsewhere in the Caribbean.