Corals are invertebrates, living mostly in tropical waters. They secrete calcium carbonate to build protective skeletons that grow and take on impressive colors, thanks to a symbiotic relationship with algae that live in their tissues and provide them with energy. A temperature change of just 1 to 2 degrees Celsius can force coral to expel the algae, leaving their white skeletons visible in a process known as “bleaching.” Bleached coral can recover if the water cools, but if high temperatures persist for months, the coral will die. Eventually the reef will degrade, leaving fish without habitats and coastlines less protected from storm surges.

Scientists race to prevent wipeout of world's coral reefs. (2017, March 14). Philippine Daily Inquirer, p. A6.