Suppressed recovery of functionally important branching Acropora drives coral community composition changes following mass bleaching in Indonesia
Rowan Watt-Pringle1*, David J Smith2, 3, Rohani Ambo-Rappe1, Timothy AC Lamont4 and Jamaluddin Jompa1,5

1) Faculty of Marine Science and Fisheries, Hasanuddin University, Makassar, Indonesia
* rwp.unhas[at]gmail.com
2) Coral Reef Research Unit, School of Biological Sciences, University of Essex, Colchester, UK
3) Mars Incorporated, 4 Kingdom Street, Paddington, London, W2 6BD, UK
4) Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ
5) Graduate School, Hasanuddin University, Makassar, Indonesia

Abstract

Mass coral bleaching events may have disproportionate effects on branching corals, leading to coral community restructuring, reduced biodiversity, and decreased structural complexity. This affects overall reef health and resilience. Functionally important, fast-growing branching Acropora corals were a historically dominant and vital component of Indonesian reefs throughout the 20th Century, yet the genus is also one of the most vulnerable to external stressors. This study used long-term annual reef monitoring data from Indonesia^s Wakatobi Marine National Park (WMNP) to investigate the effects of a mass bleaching event in 2010 on Acropora and other branching corals, evaluate their post-disturbance recovery trajectories, and analyse shifts in coral community composition. Post-bleaching scleractinian coral cover decreased across study sites, with losses in branching corals especially evident. Long-term branching Acropora cover decreased significantly and failed to demonstrate the significant post-disturbance recovery of other branching corals (especially Porites). In areas characterised by relatively high branching Acropora cover (>15% mean cover) prior to bleaching, long-term coral community composition changes have trended predominately towards branching and massive Porites and branching Montipora. The novelty and key contribution of this study is that results suggest suppressed recovery of Acropora in the WMNP. Contributing factors may include the Allee effect (inhibition of reproduction at low population densities), other forms of inhibited larval recruitment, direct and indirect spatial competition, and changes in the physical reef habitat. These findings have critical implications for this functionally important taxon, future reef conservation efforts, and overall reef health and resilience in the park.

Keywords: Branching coral- Acropora- Indonesia- bleaching- coral community composition- suppressed recovery

Topic: Aquatic Ecology and Conservation (International)