'Mass bleaching event' under way on Australia's Great Barrier Reef

SYDNEY, Australia — A "mass bleaching event" is unfolding on Australia's Great Barrier Reef, authorities said Friday, as warming seas put corals under stress.

"We know the biggest threat to coral reefs worldwide is climate change. The Great Barrier Reef is no exception," Environment Minister Tanya Plibersek said in a statement.

The damaging mass bleaching event -- the seventh since 1998 -- was confirmed by government scientists following aerial surveys of 300 shallow reefs.

The Australian Reef Authority said it would now need to conduct further surveys to assess the severity and extent of bleaching.

Coral bleaching occurs when underwater temperatures are more than 1 degree warmer than the long-term average.

As corals come under heat stress, they expel algae living within their tissues -- draining them of their vibrant colours.

Ocean temperatures along the Great Barrier Reef have approached record levels in the past few weeks, according to official monitoring.

Before this event, Australia’s Great Barrier Reef suffered mass coral bleaching in 1998, 2002, 2016, 2017, 2020 and 2022.