Different Coral Species Have Different Bleaching Responses

 

Coral reefs are experiencing bleaching and mortality due to warming oceans caused by global climate change. When water temperatures rise, the symbiotic algae that provide corals with most of their food and energy leave their coral hosts, revealing the white coral skeleton underneath its tissue. Bleached corals are much more likely to experience predation, disease and death. If the corals do not regain their symbiont algae, they will die, which leads to the death of the entire coral reef ecosystem. Not all corals, however, experience bleaching and mortality at the same rates. There are many records that provide information about coral species' susceptibility to bleaching and death, but these accounts use different sampling protocols (e.g., assessing the average affected colony, percent of affected colonies, or proportion of affected coral cover) and severity criteria (e.g., data binned into categories ranging from increments of 10% change in color to broad definitions of pale, bleached, or dead) to measure bleaching and mortality response. We developed a quantitative bleaching response index (BRI) that merges this data into a standardized metric. Using 2,036 bleaching and mortality records from corals throughout the world during 1983-2006, our group was able to examine 374 taxa from 316 sites. The goal was to identify high-risk corals in order to predict and mitigate future coral devastation. This is the first pantropical assessment of bleaching and mortality, including measurement uncertainty, that attempts to build a unified comparison of taxon-specific response from the historical perspective.