Collective action and lime juice fight crown-of-thorns starfish outbreaks in Vanuatu

Abstract

Among the broad range of large-scale disturbances that affect Indo-Pacific coral reefs, the coral-eating starfish Acanthaster planci (crown-of-thorns starfish, COTS hereafter) is a major cause of coral reef destruction; its impact is quantitatively comparable to a cyclone. While A. planci generally occurs at very low densities (typically < 1 individual ha-1), populations can dramatically increase during certain periods, reaching extremely high values (e.g. 538 ind. ha-1; Kayal et al. 2011). These outbreaks represent one of the most significant biotic disturbances on coral reefs, causing massive and widespread coral mortality. Over a third of Indo-Pacific reefs were recently affected by severe COTS outbreaks, leading to growing concern that they are becoming more frequent and more prevalent (e.g. Brodie et al. 2005). While there is historical evidence that coral reefs can recover from COTS outbreaks, they drive even more pressure on already weakened systems (Bellwood et al. 2004; Bruno and Selig 2007; De’ath et al. 2012). The cascading effects from coral loss can severely harm the entire coral community, which raises serious concerns in areas where coastal resources (fish, invertebrates) form the basis of traditional, subsistence fishing.