Bleaching drives collapse in reef carbonate budgets and reef growth potential on southern Maldives reefs
Nature Publishing Group
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Sea-surface temperature (SST) warming events, which are projected to increase in frequency and intensity with climate change, represent major threats to coral reefs. How these events impact reef carbonate budgets, and thus the capacity of reefs to sustain vertical growth under rising sea levels, remains poorly quantified. Here we quantify the magnitude of changes that followed the ENSO-induced SST warming that affected the Indian Ocean region in mid-2016. Resultant coral bleaching caused an average 75% reduction in coral cover (present mean 6.2%). Most critically we report major declines in shallow fore-reef carbonate budgets, these shifting from strongly net positive (mean 5.92 G, where G = kg CaCO3 m−2 yr−1) to strongly net negative (mean −2.96 G). These changes have driven major reductions in reef growth potential, which have declined from an average 4.2 to −0.4 mm yr−1. Thus these shallow fore-reef habitats are now in a phase of net erosion. Based on past bleaching recovery trajectories, and predicted increases in bleaching frequency, we predict a prolonged period of suppressed budget and reef growth states. This will limit reef capacity to track IPCC projections of sea-level rise, thus limiting the natural breakwater capacity of these reefs and threatening reef island stability.
Research was supported through a Leverhulme Research Fellowship (RF-2015-152) to CTP. We thank the LaMer Small Island Research Centre, Faaresmathooda for assistance with field work and logistics. The reviewers and Editor of Scientific Reports are thanked for their useful and supportive comments on an earlier draft of the text.
This is the author accepted manuscript. The final version is freely available from Nature Publishing Group via the DOI in this record.
Vol. 7, Art. No. 40581