Drivers and predictions of coral reef carbonate budget trajectories 1

19 Coral reefs play a critical role in coastline protection and support fisheries and tourism. Maintaining 20 these ecosystem services requires, as a minimum, positive biological carbonate budgets, whereby 21 rates of carbonate production exceed erosion. Coral bleaching and associated mortality events, 22 which are predicted to become more frequent and intense, can rapidly diminish carbonate 23 production and reef growth. Here we track the biological carbonate budgets of inner Seychelles 24 reefs from 1994 – 2014, spanning the 1998 global bleaching event when these reefs lost >90% of 25 coral cover. All 21 reefs had positive budgets in 1994, but in 2005 budgets were predominantly 26 negative. By 2014, carbonate budgets on seven reefs were comparable with 1994, but on all reefs 27 where a regime shift to macroalgal dominance occurred, budgets remained negative through 2014. 28 Reefs with higher massive coral cover, lower macroalgae cover and lower excavating parrotfish 29 biomass in 1994 were more likely to have positive budgets post-bleaching. If mortality of corals from 30 the 2016 bleaching event has been severe, our predictions based on past trends would suggest only 31 6 of 8 reefs with positive budgets in 2014 would still have positive budgets by 2030. These results 32 suggest that when assessing reef recovery from mass-mortality events that attention needs to be 33 paid to elements that underpin carbonate production so as to identify reefs with resilience to future 34 disturbance. I THINK THE NARRATIVE ABOUT WHAT HAS HAPPENDED IN 2016 MAY 35 NEED SOME THOUGHT ...... THINGS HAVE CHANGED SINCE THIS WAS FIRST SUBMITTED 36