The incident direct exposure of solar irradiation will warm the temperature of oceanic water. When the water is too warm, the coral polyps expel the symbiotic associate that is algae (zooxanthellae) which is responsible for providing color to the polyps. When algal partner is expel out this results in coral bleaching. The white coral reef get exposed to the environment.
Also the coral reefs which grows in the shallow water are also susceptible for coral bleaching due to solar irradiation.
When too much ultraviolet radiation penetrates coral ecosystems, the photosynthetic processes of the zooxanthellae can be disrupted. Loss of zooxanthellae is the ultimate cause of coral bleaching.
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