SYDNEY Australias landmark Great Barrier Reef is undergoing dramatic levels of coral bleaching for the third time since 2016, spurred by record heat that has left scientists lamenting one of the worlds crown jewels is drying en masse yet again.

Australias lead management agency for the Great Barrier Reef can confirm mass bleaching is occurring on the Great Barrier Reef, with very widespread bleaching detected, the countrys Great Barrier Reef Marine Park Authority said in a statement Thursday. Actions to support the resilience of the Reef are now more important than ever. Climate change remains the single greatest challenge to the reef.

The report is bad news for the barrier reef, which is still recovering from a series of devastating, back-to-back mass bleaching events in 2016 and 2017. Coral bleaching most often occurs when ocean temperatures are too warm for long periods of time, effectively cooking the delicate structures and leaving them weakened and sick. They can recover if temperatures go back to normal, but will die if the ocean doesnt normalize.

That happened in both of the last two mass bleaching events, and scientists likened the period to an underwater apocalypse .

2019 was no better in terms of temperatures. It was the second-hottest year on record and the worlds oceans were the warmest in recorded history , a trend that continued into this year. In February, average sea temperatures on the reef were the highest on record going back to 1900 , in places 1.25C above normal, per The Guardian.

Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies, has been leading this years round of aerial surveys of the reef for the past two weeks. The results so far are staggering: widespread patches of ghostly white coral have been heartbreaking, stretching up and down Australias east coast.

Its been a shitty, exhausting day, Hughes wrote on Twitter on Thursday. I feel like an art lover wandering through the Louvre as it burns to the ground..

Hughes has monitored more than 800 reefs, an effort he dubbed a marathon with just a few flights left to go.

The GBRMPA said that the corals impacted by the mass bleaching may recover, but issued bleak predictions for reefs deeply affected by the dramatic levels of heat.

It is important to remember bleached corals are not dead corals on mildly or moderately bleached reefs there is a good chance most bleached corals will recover and survive this event, it wrote . Equally, on severely bleached reefs, there will be higher mortality of corals.