SOURCE: The Guardian

DATE: March 25, 2020

SNIP: The Great Barrier Reef has experienced a third mass coral bleaching event in five years, according to the scientist carrying out aerial surveys over hundreds of individual reefs.

With three days of a nine-day survey to go, Prof Terry Hughes told Guardian Australia: “We know this is a mass bleaching event and it’s a severe one.”

It follows the worst outbreaks of mass bleaching on record killing about half the shallow water corals on the world’s biggest reef system in 2016 and 2017.

Hughes said the first four days of aerial surveys last week covered almost 500 reefs from the Torres Strait to Cairns. They revealed a mixed picture, with some severe bleaching on reefs closer to shore, but outer “ribbon reefs” in the far north escaping damage.

He said surveys this week in the central parts of the reef had found extensive bleaching at levels “comparable to 2017”, when it is estimated about 22% of shallow water coral along the reef’s 2300km died.

Hughes said about 80 reefs between Tully and Townsville were badly bleached. Both inner and outer reefs were hit. “We could see that some of those corals were big enough that they must have survived the 2017 bleaching and now they re-bleached,” he said.