Bleaching impacts on carbonate production in the Chagos Archipelago: influence of functional coral groups on carbonate budget trajectories

Reefs in the remote Chagos Archipelago (central Indian Ocean) were severely affected by sea surface temperature warming and coral bleaching in 2015-2016. Here we assess the impacts of this event on community composition and reef carbonate production at twelve fore reefs sites across three atolls. Bleaching caused a 69% decline in coral cover, mostly driven by mortality of tabular Acropora spp. and a 77% decline in mean coral carbonate production (2015: 13.1 +/- 4.8; 2018: 3.0 +/- 1.2 kg CaCO3 m(2) yr(-1)). Changes were accompanied by a major shift from competitive to stress-tolerant coral taxa, with magnitudes of decline comparable to those reported elsewhere in the Indian Ocean, despite inter-site differences in dominant coral species. These trends differ from those on reefs already dominated by stress-tolerant taxa, which experienced minor declines in production post-warming. The study highlights the potential for different suites of functional coral groups to drive divergent post-bleaching budget responses.