Bleaching of the world's coral reefs

Coral reefs support the ocean's highest biodiversity, protect coastlines from storm waves, and supply sustenance for millions of people. Yet reef corals have become sentinel species of modern oceans because of their sensitivity to thermal stress associated with high emissions of greenhouse gases that are warming the oceans. The recent increase in the frequency and intensity of thermal-stress events has caused extensive coral bleaching worldwide. Coral bleaching is a result of the breakdown of the symbiosis between corals and their symbiotic algae, which can lead to coral death and to changes in the coral species composition of coral reefs. Such coral bleaching events also have negative effects on many reef-associated organisms and reduce the capacity of coral reefs to keep up with sea-level rise. In this chapter, we examine the circumstances that lead to coral bleaching, consider why there are differences in bleaching tolerance, outline geographical patterns of coral bleaching, point to the repercussions of coral bleaching, and discuss the future of coral reefs under climate-change-associated ocean warming.