Coral bleaching occurs when stressed corals lose the symbiotic algae that live in their tissues, causing them to turn pale or white. These algae provide much of a coral’s energy and contribute to its color. Bleaching is often triggered by unusually warm water, though other environmental stresses can also contribute.
Bleached coral is not necessarily dead, but prolonged or repeated stress can weaken it and lead to death, harming reef ecosystems. In practice, researchers and conservation teams monitor water conditions, coral health, and recovery over time. Restoration methods may support recovery, but their effectiveness must be tested across conditions; a short-term improvement does not by itself show that reefs can withstand ongoing stress.