'Remarkable' coral recovery on Southern Great Barrier Reef island
There’s been remarkable recovery of one island’s coral on the southern end of the Great Barrier Reef, but researchers aren’t celebrating.
The coral reef around One Tree Island, off the coast of Gladstone and one of the southernmost points of the Great Barrier Reef, has experienced strong growth in recent years.
The reef was considered to be in serious decline in the 1970s, while it also was hit with a cyclone in 2009 – which was considered to be a knockout blow.
However, subsequent studies have shown the reef to have recovered rapidly, which Southern Cross University doctoral researcher Kay Davis said was "completely unexpected".
“There were three studies after the cyclone and each one of them showed a decreasing trend in the coral growth in the area, so we expected the trend to continue,” she said.
The ocean is warming and acidifying so we wouldn’t think the coral would be able to fight that.”
Instead coral calcification, a measure for coral growth, increased by 400 per cent between 2014 to 2017.
But far from a cause for celebration, Ms Davis said the recovery highlighted the volatility in Great Barrier Reef waters.
“It’s not unusual for reefs to recover, reefs have been recovering from stress events for many years, but as we see the effects of climate change we’re seeing that recovery is more difficult,” she said.
“One Tree Island is a special case because it was given that time and it remained relatively isolated from humans and human impact, apart from the global impact of climate change.”
She compared the remarkable recovery in the southern reef island with the example of Lizard Island, on the northernmost end of the Great Barrier Reef.
In that case the surrounding reef has now been largely overtaken by algae after most of its coral was killed off in the major 2016 bleaching event which affected large parts of the northern end of the Great Barrier Reef.
“That shows us that that area is being taken over by algae and will not recover to be a coral-dominated area,” she said.
“The northern end of the reef is definitely in a worse state than the southern regions, and the future of the Great Barrier Reef is really going to depend on how the effects of climate change play out.”
Ms Davis is currently working on the southernmost coral reef in the world, around Lord Howe Island off the NSW mid-north coast.
Even in that area the coral has experienced a bleaching event, which she said shows changing ocean temperatures and acidification are having unpredictable effects no matter where the coral is growing.
“That bleaching event happened at 26 degrees, whereas the One Tree Island water temperature when we were there was 25 degrees and that reef is doing well,” she said.
“It really does depend on the local factors, but the concern is there that these southern reefs won’t be able to keep up with the increasing temperatures either.”
Ms Davis’ research into the Lizard Island situation was published earlier this month in the Journal of Geophysical Research: Oceans, while her research highlighting the situation at One Tree Island was published this week in the journal Frontiers in Marine Science.