A worldwide dramatic degradation of coral reefs, the most diverse marine ecosystem, occurred during the last three decades. Climate-driven temperature stress and disease outbreaks have been a significant contributor to reef degradation. The unified sampling methodology developed for this project allowed us to combine surveys from 39 localities ranging throughout the Caribbean Sea and the Pacific Ocean from 2005 through 2007. In addition, indices to account for warm and cold anomalies were derived from remotely sensed Sea Surface Temperature (SST) data for these localities. This methodological approach allowed us to evaluate (a) which areas have unusually high coral disease prevalence, (b) the relationship between disease prevalence and environmental conditions, community structure and coral cover, (c) whether short term trends in disease prevalence and/or coral cover can reveal reef regions with either extreme vulnerability or strong coral resilience.
The results from relatively pristine areas in both Caribbean and Pacific allow us to estimate a baseline for disease prevalence and evaluate the severity of reefs’ health around the world, with many sites in the Caribbean Sea exhibiting high disease prevalence and strong degradation relative to the pacific.
Moreover, using generalized linear models, we identified the factors that influence prevalence for the different diseases and coral families. In particular, when disease are studied at the level of coral families, indicators of extreme temperature events from one year before combined with the presence of other infectious diseases in the same reefs exert significant influence on the current health status of coral assemblages.
Furthermore, statistically significant trends on coral disease prevalence provide insights on the invasion of pristine areas by novel diseases, raising questions on transmission routes and immunity.