Implications of high rates of sexual recruitment in driving rapid reef recovery in Mo\u2019orea, French Polynesia

Peter J Edmunds

doi:10.1038/s41598-018-34686-z

Abstract

Coral abundance continues to decline on tropical reefs around the world, and this trend suggests that coral reefs may not persist beyond the current century. In contrast, this study describes the near-complete mortality of corals on the outer reef (10 m and 17 m depth) of the north shore of Mo’orea, French Polynesia, from 2005 to 2010, followed by unprecedented recovery from 2011 to 2017. Intense corallivory and a cyclone drove coral cover from 33–48% to <3% by 2010, but over the following seven years, recovery occurred through rapid population growth (up to 12% cover y−1) to 25–74% cover by 2017. The thirteen-year, U-shape trajectory of coral cover over time created by the loss and replacement of millions of corals through sexual reproduction underscores the potential for beneficial genetic responses to environmental conditions for at least one genus, Pocillopora. The high ecological resilience of this coral community appears to have been enhanced by variation among genera in the susceptibility to declining cover, and the capacity for population growth (i.e., response diversity). These results suggest that the outer coral communities of Mo’orea may be poised for genetic changes that could affect their capacity to persistence.

Highlights

Advances have come from the application of functional groups to coral ecology, but as the present study shows, taxonomic resolution of benthic community structure is required to identify processes mediating changes, for example, response diversity[25]
Rather than chronic coral mortality and a ratcheting down of coral reef condition[60], these reefs have displayed high resilience. These trends are novel, but their importance extends beyond coral cover to suggest that one type of rescue effect (i.e., ER) might be underway, with this effect facilitated by response diversity
The coral community on the outer reef Mo’orea has shown very strong resilience through recovery in response to major disturbances, and this transition has involved the death, and replacement in excess, of 100’s of millions of Pocillopora colonies[47], all of which potentially are genetically unique and reflect the products of an even larger pool of genetically diverse larvae. If this large genetic upheaval within Pocillopora populations has facilitated selection to favor genotypes that are more resistant to future conditions, such as warmer seawater, the recent events in Mo’orea could be an example of ER to promote persistence of pocilloporid corals in the Anthropocene

Summary

Objectives

The objectives of the present study were two-fold: (1) to describe the dynamics of coral communities on the outer reefs of Mo’orea with genus resolution, and evaluate the extent to which their recent response to disturbances is indicative of ER, and (2) to explore the role of response diversity among coral genera in community dynamics

Methods

Results

Discussion

Conclusion