Coral gets its color from algae called zooxanthellae, which it depends on for photosynthesis.
Bleaching is actually due to the coral expelling those algae. Bleached corals are not dead, and remarkably they can not only let the algae in again but can also select a different algae species to cultivate (changing colour in the process)!.
This is thought to be a deliberate survival strategy to optimize the species of algae under different conditions (Adaptive Bleaching Hypothesis).
Bleaching is caused by the same stressors (like high temperature) which kill coral, but bleaching itself is not death of the coral.
Bleaching is actually due to the coral expelling those algae. Bleached corals are not dead, and remarkably they can not only let the algae in again but can also select a different algae species to cultivate (changing colour in the process)!.
This is thought to be a deliberate survival strategy to optimize the species of algae under different conditions (Adaptive Bleaching Hypothesis).
Bleaching is caused by the same stressors (like high temperature) which kill coral, but bleaching itself is not death of the coral.