At a time when portions of the Great Barrier Reef are being devastated by coral decline, Southern Cross University doctoral researcher Kay Davis has found an island near Gladstone has experienced remarkable coral growth.
One Tree Island was lashed by Cyclone Hamish in 2009, destroying much of the island’s coral.
In the five years following the cyclone, no metabolic recovery was detected on the reef and by 2014 calcification of the coral had declined by 75 per cent.
But things changed dramatically between 2014 and 2017, when Ms Davis and her team at the National Marine Science Centre found the coral system calcification increased four-fold.
“We found that the coral ecosystem has completely recovered from this cyclone event after eight years,” Ms Davis said.
“It wasn’t what we were expecting at all.”
The new research was published this month in Frontiers in Marine Science open-source journal, with Ms Davis as the lead author.
Ms Davis had expected the declining health of the reef to continue due to ocean acidification inhibiting coral recovery.
Instead the coral is doing better now than it was when it was first studied in the 1970s.
“Not only is calcification of the reef recovering, there was a visible increase in the amount of coral as well; with coral cover increasing by 30 to 40 per cent.”
‘It’s teeming with life here’
Just north of One Tree Island, Heron Island is a small coral cay that thrives off reef tourism.
Marine biologist Rachael Jones has been the resident naturalist guide on the island for more than three years.
“We haven’t had any significant bleaching or coral disease because we’re on the southern part of the Great Barrier Reef,” she said.
“I just keep seeing diversity of life here everyday because we’re a green zone – you can’t fish, you can’t take anything, everything’s protected by law.
“That’s when you see ecosystems thrive.”
Ms Jones interacts with tourists from around the world and hosts guided reef walks, semi-submersible reef tours, island and bird walks.
She said tourists are more worried about the reef than previously because of the way it is portrayed in the media.
“Questions I get asked everyday, they say, ‘so is the reef dead? Is this bleached here?’,” she said.
“Some parts are stressed due to the double-bleaching event [in 2016-17] but the southern part of the Great Barrier Reef, it’s just thriving, teeming with life.”
A tale of two reefs
The fortunes of One Tree Island are not being played out across the Great Barrier Reef.
Ms Davis also studied the health of Lizard Island, in the northern zone of the reef, and found it devastated following the coral bleaching event and two cyclones in the space of five years.
She said Lizard Island is experiencing total ecosystem collapse, with coral calcification dropping by 45 per cent compared with a 2009 study when the ecosystem had been healthy.
“It’s really disheartening to see the state of the reef; so many dead corals and just overgrown with algae,” Ms Davis said.
Climate change, human impacts
Ms Davis said One Tree Island’s status as a scientific permit zone only, with little human impact from runoff, tourism and boats has certainly helped in its recovery.
However she said it is hard to pinpoint the exact reasons behind the remarkable results.
“Reefs have been recovering from stress events for many years, but as the impact of climate change on coral reefs worsen, we’re seeing that recovery is more difficult,” Ms Davis said.
“But in this area it seems the corals are doing okay, so I think we’ll take this win.”
Ms Davis said nutrients in the waters at One Tree Island were low, with little to no run-off affecting the areas. But climate change remains a concern.
“Cyclones are common in nature, but we know that storms are worsened and become more frequent and intense with climate change,” she said.
“This research implies that when given the right conditions, coral reefs can recover, however we need to give the reef the right conditions and more time between stress events for them to be able to recover.”
‘It gives us hope’
On Heron Island, Ms Jones said the research made her optimistic about the future of the reef.
“Corals can recover from bleaching, that’s what people don’t realise, they think bleached is dead but they can recover if they have the time,” she said.
“Tourism is our livelihood on Heron; we need to work together to protect the Great Barrier Reef and to correct the misconceptions out there.”