Abnormal density of Culcita schmideliana delays recovery of a reef system in the Maldives following a catastrophic bleaching event

Abstract

Culcita spp. are facultative corallivores that can have a selective effect on coral composition due to their feeding preference for Acropora spp. and Pocillopora spp. Although Culcita are normally rare (<0.5 per 100m2), mean densities of up to 9.2 sea stars per 100m2 were observed on a Maldivian reef system, with the highest numbers on the reef flat and reef crest. Culcita fed on 12 genera of corals, but showed a distinct preference for Pocillopora (51%) and Acropora (21%). Formerly the dominant corals on Maldivian reefs, these genera sustained 80–95% mortality from coral bleaching in 2016. Low numbers of juvenile acroporids and pocilloporids were slowly recolonising the reef, but 24% had recently been eaten by Culcita schmideliana. The abnormal abundance of C. schmideliana and high number of recently dead juvenile corals suggest that chronic predation by C. schmideliana could delay the recovery of reefs damaged by the 2016 mass bleaching event.