Coral recruitment in Moorea: reef recovery in a new era of acid water and high temperature

Over the last 50 y, coral reefs have lost a large proportion of their coral cover through the actions of natural and anthropogenic disturbances.  The changes have been so extensive that many reefs have been described as switching to an alternate phase dominated by macroalgae instead of corals.  With seawater warming through global climate change (GCC) and becoming more acidic through ocean acidification (OA), some have suggested that reefs may cease to exist as a calcifying ecosystem within 100 y.  The reefs of Moorea appeared to contradict such trends when the MCR-LTER was initiated in 2005, but much changed in the following 5 y.  By 2010, the community on the outer reef had been devastated by seastars (Acanthaster planci) and Cyclone Oli, and in 2010 appeared as a barren field of rock.  However, unlike reefs in most other locations, coral recruitment in Moorea has been remarkably high, with the density of 2-mm diameter coral recruits now at a 7-year high, and mean densities of juvenile corals reaching ~100 colonies m^-2 at 10 m depth in 2012.  The growth of coral populations in Moorea now affords a “clean-slate” opportunity for the MCR-LTER to evaluate reef recovery in an era of hot water and acid conditions and test hypothesis regarding depth-dependent recruitment and connectivity with- and among- islands.