The Great Barrier Reef, an ocean ecosystem the size of Italy situated off the coast of Australia, is experiencing another mass coral bleaching event, the fifth such occurrence since 2016. Until 1998, there had been no evidence of a bleaching event in the reef’s 500-year recorded history.

Bleaching occurs when the ocean water is unusually warm or cold or has high levels of acid. Under such conditions, the coral turns white when it expels tiny photosynthetic algae that live in its tissue. While bleaching does not necessary kill the coral, it makes the reef more susceptible to disease. Scientists are concerned that these repeated bleaching events over a short period of time will make it harder for the reef to bounce back. Compounding the warming effects due to climate change, a 2023 El Niño effect has produced unusually warmer water in the Pacific. Australian scientists are continuing to study this latest bleaching to evaluate its severity and potential impacts.