Mass Bleaching Impacts in the Demography of the Caribbean Reef-building Star Coral <i>Montastraea annularis</i>: A Modeling Approach

The northeastern Caribbean region experienced a record-breaking sea surface warming and prolonged mass bleaching during 2005. This event resulted in significant mortality of the principal Caribbean reef-building coral Montastraea annularis. We evaluated the demographics and size structure of a M. annularis population before, during, and after this event; stochastically simulated the population dynamics with different bleaching regimes over a period of 100 years, and determined the life cycle transitions that contributed most to population decline after recurrent events using a life table response analysis. Size-based transition matrices from 2001-2009 were constructed following individual colonies through time in 17 permanent photo-transects located in Culebra Island, Puerto Rico. Temporal variation in the population growth rate indicated a demographic equilibrium before the event, an increase in mortality for two years after the event, and demographic recovery by the third year. However, population size structure did not recover entirely. Stochastic simulation showed that viability of the population becomes strongly compromised with only 10% annual probability of bleaching, while a 20% probability led to population local extinction. Life table response analysis determined that mortality of small colonies accounted the most for population decline after the event. The natural history of M. annularis has showed that recovery by sexual recruitment alone is unlikely. The fate of present small colonies will determine the population viability in the near future. We conclude that the demography of M. annularis populations is highly susceptible to mass bleaching and that its viability is seriously comprised under the predicted global warming scenarios.