“We are hoping that we will see most of the coral that is bleached recover and we will end up with an event rather more like 2020 when, yes, there was mass bleaching, but there was low mortality,” Wachenfeld added. The bleaching events in 2016 and 2017 led to “quite high levels of coral mortality,” Wachenfeld said.

More than 90% of Great Barrier Reef coral surveyed this year was bleached in the fourth such mass event in seven years in the world’s largest coral reef ecosystem, Australian government scientists said.

Bleaching is caused by global warming, but this is the reef’s first bleaching event during a La Niña weather pattern, which is associated with cooler Pacific Ocean temperatures, the Great Barrier Reef Marine Authority said in its annual report released late Tuesday that found 91% of the areas surveyed were affected.

Bleaching in 2016, 2017 and 2020 damaged two-thirds of the coral in the famed reef off Australia’s eastern coast.

Coral bleaches as a heat stress response and scientists hope most of the coral will recover from the current event, said David Wachenfeld, chief scientist at the authority, which manages the reef ecosystem.

“The early indications are that the mortality won’t be very high,” Wachenfeld said on Wednesday.

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