Coral Bleaching

Coral reefs are among the most biologically diverse ecosystems on the planet. They depend on a symbiotic relationship with tiny algae called zooxanthellae, which live inside the coral tissues. These algae undergo photosynthesis, providing the corals with up to 90% of their primary food supply while also giving them their vibrant colors. When ocean waters remain at normal temperatures, this mutually beneficial relationship thrives.

However, when water temperatures rise even slightly due to global warming, corals become severely stressed. In response to this heat stress, they expel the algae from their tissues, causing the corals to turn completely white—a process known as coral bleaching. Without the algae, the corals lose their main source of nutrition. ( 1 ), bleached corals do not die immediately. If the ocean water cools down relatively quickly, the algae can return to the coral tissues, and the reefs can eventually recover.

( 2 ), if the heatwave is prolonged, the corals will slowly starve to death. Climate change is increasing both the frequency and intensity of these marine heatwaves, giving reefs less time to heal between bleaching events. Marine biologists warn that without drastic, worldwide reductions in greenhouse gas emissions, many of the world's reef ecosystems could be ( 3 ) within the next few decades.

Coral Bleaching

Coral reefs are among the most biologically diverse ecosystems on the planet. They depend on a symbiotic relationship with tiny algae called zooxanthellae, which live inside the coral tissues. These algae undergo photosynthesis, providing the corals with up to 90% of their primary food supply while also giving them their vibrant colors. When ocean waters remain at normal temperatures, this mutually beneficial relationship thrives.

However, when water temperatures rise even slightly due to global warming, corals become severely stressed. In response to this heat stress, they expel the algae from their tissues, causing the corals to turn completely white—a process known as coral bleaching. Without the algae, the corals lose their main source of nutrition. ( 1 ), bleached corals do not die immediately. If the ocean water cools down relatively quickly, the algae can return to the coral tissues, and the reefs can eventually recover.

( 2 ), if the heatwave is prolonged, the corals will slowly starve to death. Climate change is increasing both the frequency and intensity of these marine heatwaves, giving reefs less time to heal between bleaching events. Marine biologists warn that without drastic, worldwide reductions in greenhouse gas emissions, many of the world's reef ecosystems could be ( 3 ) within the next few decades.