Marine Heat Waves Decimate Coral Reefs Much Faster Than Previously Thought

Trump administration throws cold water on climate change threat to coral reefs in Florida

Diseased coral is seen at Alligator Reef off Islamorada in the Florida Keys National Marine Sanctuary. Steve Gittings NOAA

Increasingly frequent marine heatwaves can lead to the nearly instant death of corals, scientists working on the Great Barrier Reef have found.

Marine heatwaves pose more of a threat to Queensland's Great Barrier Reef and coral reefs than previously thought, a new study reveals.

According to this new study, extreme spikes in ocean temperatures can cause entire coral reef systems to decay and collapse in a matter of days.

Dr Richardson added that the team had documented, for the first time, that severe heatwaves were causing "almost instant mortality of corals". This means that the 3D coral framework which provides home to many other animals on the reef is also at risk.

In 2016 the team's research showed that just a 0.5C increase in ocean temperature changes the extent of mortality that happens in coral during bleaching.

The study, which also involved researchers from the University of Newcastle in Britain, Australia's James Cook University, the University of Technology Sydney and the US National Oceanic and Atmospheric Administration, used CT scans of coral reefs to monitor the impact of extreme temperatures.

Their research showed that while it was previously understood that coral bleaching can lead to a break down of symbiosis, marine heatwaves can lead directly to heat-induced mortality of the coral animal as well.

"But what we are now seeing is that severe marine heatwave events can have a far more severe impact than coral bleaching", Ainsworth continued.

Report co-author and UNSW associate professor Tracy Ainsworth said the research confirms what many scientists have known for a while: that marine heatwaves are becoming more severe and are having greater impacts.

Though the study generated alarm, the researchers expressed hope that it will spur public outcry for policymakers to pursue bolder efforts to combat the climate crisis-and, specifically, protect coral reefs, particularly considering the anticipated consequences of inaction. Dr. Ainsworth explained, what they see here is that when the coral tissue dies, it falls and breaks away from the skeleton.

"It confirms that we are on a trajectory where heatwave events and heat stress is becoming so severe it's beyond the capacity of the ecosystem to withstand it", she told AAP.

Commenting on the paper, Dr Laura Richardson, from the School of Ocean Sciences at Bangor University, UK, said that the really significant discovery was "the rapidity with which the reef skeleton breaks down when you have these severe heatwaves".

"Climate scientists talk about "unknown unknowns" - impacts that we haven't anticipated from existing knowledge and experience", he said. This discovery fits into this category.

"Across the globe coral reefs are still a source of inspiration and awe of the natural world, as well as being critically important to the communities that rely upon them".

Latest News