Parts of the Great Barrier Reef have suffered the highest coral mortality ever recorded, Australian research showed on Tuesday, with scientists concerned the rest of the area may have suffered a similar fate.
The Australian Institute of Marine Science said studies of 12 reefs found up to 72 percent coral mortality, thanks to a summer of massive bleaching, two cyclones and floods.
In a northern part of the reef, about a third of the hard corals died, the “largest annual decline” in 39 years of government monitoring, the agency said.
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Often dubbed the world’s largest living structure, the Great Barrier Reef is a 1,400-mile stretch of tropical coral that is home to an astonishing diversity of biodiversity.
But repeated massive bleaching events have threatened to rob the tourist draw of its wonders, turning once-vibrant coral beds a sickly shade of white.
Bleaching occurs when water temperatures rise and coral expels microscopic algae, called zooxanthellae, to survive.
If high temperatures persist, the coral may eventually bleach and die.
This year had already been confirmed as the fifth mass bleaching of the reef in the last eight years.
NOAA Coral Reef Watch
But this latest study also found that a type of fast-growing coral, known as acropora, experienced the highest mortality rate.
This coral grows quickly, but is one of the first to bleach.
Lead researcher Mike Emslie told public broadcaster ABC that last summer was “one of the most severe events” on the Great Barrier Reef, with heat stress levels surpassing previous events.
“These are serious impacts. These are serious losses,” he said.
World Wildlife Fund-Australia oceans director Richard Leck said initial investigations confirmed his “worst fears”.
“The Great Barrier Reef can bounce back but its resilience has limits,” he said. “This can’t be hammered home repeatedly like this. We are quickly approaching a tipping point.”
Leck added that the area studied was “relatively small” and feared that when the full report was released next year, “similar levels of mortality” would be seen.
He said the findings reinforce the need for Australia to commit to higher emissions reduction targets of at least 90 percent below 2005 levels by 2035 and move away from fossil fuels.
The country is one of the world’s largest exporters of gas and coal and only recently set targets to become carbon neutral.
