Coral bleaching is a stress-induced biological process in which reef-building scleractinian corals lose all or most of their endosymbiotic dinoflagellates (family Symbiodiniaceae) and/or their photosynthetic pigments, leading to visible paling or whitening of coral tissues. Triggered primarily by elevated sea surface temperatures, but also by light stress, pollution, or oxidative stress, bleaching involves disruption of the coral–algal symbiosis through mechanisms such as reactive oxygen species overproduction, damage to photosystem II, and activation of host cellular stress pathways that drive symbiont expulsion or degradation. Prolonged or repeated bleaching events impair coral metabolism, calcification, and reproduction, often increasing mortality and restructuring reef ecosystems.
An "unprecedented" mass bleaching event has been recorded off Australia's western coast, scientists said Wednesday, turning huge chunks of a celebrated reef system a sickly dull white.
Environment
Mar 26, 2025
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