The world’s largest reef system, which stretches for over 1,400 miles off the coast of Australia, has been severely affected by rising water temperatures.
In May, researchers found more than a third of corals in central and northern parts of the reef had been killed and 93 per cent of individual reefs had been affected by a condition known as coral bleaching, where too warm water causes corals to expel algae living in their tissue and turn completely white. Corals depend on a symbiotic relationship with algae-like single cell protozoa, so when these are expelled they stop growing and often die
New research shows the damage has worsened rather than begun to repair.
Amanda McKenzie, CEO of the Australian Climate Council, said at the start of this year scientists had described the reef as “110% alive”.
“After the bleaching event in May, 60 per cent of what we saw was bleached very white,” she said. “Another 19-20 per cent was covered in sludgy brown algae. Even of what remained healthy, some looked a bit on edge.
“When we went back a few weeks ago to see if they [the affected corals] had recovered or died, quite a large proportion had died.”
Ms McKenzie estimated around half the bleached coral in the site they visited, a popular offshore reef about 54 kilometres from Port Douglas, was dead.
She said delicate corals had been particularly badly affected: while strong ‘brain corals’ had mostly survived, many fragile varieties, such as plate corals, had died.
Fish had also been affected she said, with far fewer species now living on the reef