Unprecedented back-to-back bleaching events on the Great Barrier Reef has changed the physiology of tougher coral, making them more resilient to future stress, new research suggests.
Scientists from the ARC Centre of Excellence for Coral Reef Studies looked at the impacts of bleaching in 2016 and 2017, finding surviving coral behaved differently the second time.
"We can no longer assume that future bleaching events, in say a decade or two, will have the same effect that they have now because of these changes in physiology in the mix of species," lead researcher Terry Hughes told ABC radio on Tuesday.
"The prior experience of the corals has toughened them up. Their physiology has changed," Prof Hughes said.
"But there are limits to that. In the middle of the reef in 2017 we saw extreme heat and very heavy losses of corals."
Bleaching is a stress response that causes coral to lose colour, with some dying while others manage to survive.
Prof Hughes says the findings are a "silver lining" for the reef, which has lost half its coral since 2016.
The results show how coral develop ecological memory and adapt to change based on recent experiences, the professor says.
This is partially caused by bleaching events becoming more frequent.
Scientists first saw signs of coral bleaching in the 1980s, during a period when there were 25 years between stress events.
Since 2010, the gap has shrunk to just six years, Prof Hughes says.
The research team are nervously waiting until next March, when another bleaching event could occur in response to peak summer temperatures.
"It's inevitable that we will see more and more bleaching on the Great Barrier Reef and elsewhere throughout the tropics as global warming continues," the professor said.
"There's no time to lose to reduce greenhouse gas emissions."
