How are coral reefs affected by warmer temperatures and acidification?
Coral reefs may host the highest biodiversity on Earth. Reef animals yield antibiotics, anticancer drugs and other medical products, and pharmaceutical companies are actively prospecting for more. Tourism and recreation, for example at the Great Barrier Reef and in the Caribbean, add to the economic value of reefs. Fringing reefs protect shorelines from storm surges and erosion. Coral reefs may be the most vulnerable to all the climate stressors — rising temperatures, acidification, invasion by pathogens, higher sea levels and increased frequency of severe storms. Coral bleaching occurs when zooxanthellae abandon corals in response to high temperatures. Zooxanthellae, which are photosynthesizing algae and cyanobacteria combined, provide more than 95% of the food of their coral hosts and give corals their particular coloration. Under stress, corals expel these zooxantheallae, which leads to a bleached appearance. Corals can survive brief periods of coral bleaching but sustained bleachin
