Coral bleaching occurs when corals are stressed by a change in environmental conditions. They react by expelling the symbiotic algae that live in their tissues and then turn completely white. The symbiotic algae, called zooxanthellae, are photosynthetic and provide their host coral with food in return for protection.
Answer: It occurs when corals become white due to various stressors, such as changes in temperature, light, or nutrients. So if theres a disturbance, it can cause the coral to turn white, called coral bleaching.
