Award: OCE-1105143

Coral reefs are the jewels of the ocean. They boast the highest ocean diversity, protect coastal areas, aid in the formation of other important and productive tropical coastal communities, and provide food, building materials, industrial and pharmacological products, recreation and social stability to millions of humans. Over the last four decades however, increasing stress from a multitude of interacting climate-related and anthropogenic factors has disrupted the ecological/biological balances, producing significant deterioration in these ancient communities worldwide. The 2005 and 2010 thermal anomalies were the most intense and geographically widespread on record. The 2005 event induced the most intense bleaching event ever recorded in the Caribbean, with devastating disease outbreaks in northeastern reefs that produced up to 60% coral mortality in some localities. To assess and compare the impact of the 2010 thermal stress, we re-surveyed at least two reefs each in four localities, Puerto Rico and Grand Cayman in the north- and Grenada and Curacao in the southern Caribbean between October 2010 and January 2011. Results indicate that: (1) the 2010 thermal anomaly was the second most intense to hit the Caribbean, and the most intense to hit the southern Caribbean in recorded history; (2) fifty two species of hard corals, three fire-corals, 12 octocorals and many other species from other important zooxanthellated reef groups showed bleaching signs (Fig. 1). Of these, only a few species of corals and hydrocorals showed bleaching-induced partial or total colony mortality, and only in Curacao; (3) the proportion of coral colonies showing bleaching signs (prevalence) associated with the high thermal stress varied between 28 and 39% across the four localities ; (4) similarly to the 2005 event in the northeastern Caribbean, an outbreak of white plague-like disease (WPD) developed in several localities in the southern Caribbean. It was however, only observed in one of our localities, Curacao, where it produced fast and significant coral mortality (Figs. 2 and 3); (5) the average proportion of infected colonies with white plague-like disease (WPD) in reefs off Curacao was 15% in January 2011; (6) Caribbean yellow band disease (CYBD), a chronic problem in most Caribbean coral reefs since the late 1990Æs, showed an increase in the proportion of colonies affected in all reefs surveyed (Curacao, Grenada and Grand Cayman), except in Puerto Rico, where this disease was declining by the time of the thermal event; (7) the combined impact of bleaching and infectious diseases produced an average coral mortality of 25% in less than 3 months in Curacao, a significant loss of live coral tissue, reproductive output, and productivity for these communities (Fig. 3). This is however, a sub-estimation of the total mortality produced by the 2010 thermal anomaly. Reefs were not surveyed after diseases and bleaching disappeared, so we do not know the final extent of mortality. These results illustrate how thermal anomalies can induce coral bleaching and infectious diseases in coral reef systems, how variable is the susceptibility of different species and their effect at local and geographic scales, how they interact and impact individual corals and coral populations and how they can produce drastic declines in live coral cover and changes in the structure, composition and functioning of these important marine communities at local and geographic scales. Results provided important information to complement and increase our understanding of the effect of prolonged thermal stress anomalies on coral reef ecosystem in the Caribbean. Thermal anomalies seem to be increasing in frequency and intensity, correlated with increasing sea water temperatures associated with Global Climate Change due to excess concentrations of CO2 in the atmosphere. The combination of more frequent and intense thermal anomalies with increasing, local human-related environmetal de...