Fourth mass bleaching event strikes Great Barrier Reef

It was only around a year ago that ocean scientists revealed the extent of the damage suffered by the Great Barrier Reef, as its northern sections underwent the worst mass coral bleaching event ever witnessed. 

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Warm ocean waters off the northern and northeastern coast of Australia, partially elevated by the effects of a record-setting El Niño event going on at the time, were forcing the corals of the reef to expel the colourful algae that inhabit them. This caused large regions of the reef to turn white - the natural colour of the corals - and without the algae, which provide the corals' most important food source, many areas of the reef died. 

That was the third mass bleaching event in the past 20 years, as scientists observed large sections of the Great Barrier Reef turn white in 1998, 2002 and then again in 2016.

The extent and severity of the past three mass coral bleachings, as measured by aerial survey. Dark green = < 1% of corals bleached, light green = 1–10%, yellow = 10–30%, orange = 30–60%, red = > 60%. Credit: Hughes, et al.

Discussing the 2016 event, Terry Hughes, of the ARC Centre of Excellence for Coral Reef Studies, told the New York Times on Wednesday, "We didn’t expect to see this level of destruction to the Great Barrier Reef for another 30 years."

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"Mass bleaching is occurring on the Great Barrier Reef for the second consecutive year," Dr. David Wachenfeld, the director of reef recovery for the Great Barrier Reef Marine Park Authority, said in an Australian Institute of Marine Science (AIMS) press release last week.

"How this event unfolds will depend very much on local weather conditions over the next few weeks," he said.