Nav: Home

Marine heatwaves a bigger threat to coral reefs than previously thought, scientists find

August 08, 2019

Marine heatwaves are a much bigger threat to coral reefs than previously thought, research revealing a previously unrecognized impact of climate change on coral reefs has shown.

In the study, scientists show for the first time what really happens to corals during marine heatwaves, and they reveal that it's not just coral animals that are affected - their skeletons start to decay within weeks, too. This means that the 3D coral framework which provides home to many other animals on the reef is also at risk.

The study by a team of researchers from UNSW Sydney, The University of Newcastle, The University of Technology Sydney, James Cook University and The National Oceanographic and Atmospheric Administration (NOAA), USA was published today in journal Current Biology.

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

In this study, the team now find that severe marine heatwaves not only trigger bleaching events as we have known them - a breakdown of symbiosis - but in fact can lead to heat-induced mortality of the coral animal itself. They suggest that severe heatwave-induced mortality events should therefore be considered a distinct biological phenomenon, with more direct damage different from coral bleaching.

"Until now, we have described coral bleaching as an event where the symbiotic relationship between coral and its microbes breaks down and corals lose their main source of nutrition, and the coral can die if the symbiosis is not restored," author Associate Professor Tracy Ainsworth from UNSW says.

"But what we are now seeing is that severe marine heatwave events can have a far more severe impact than coral bleaching: the water temperatures are so warm that the coral animal doesn't bleach - in terms of a loss of its symbiosis - the animal dies and its underlying skeleton is all that remains."

"We find that the skeleton is immediately overgrown by rapid growth of algae and bacteria," says Associate Professor Bill Leggat of the University of Newcastle, a co-author on the paper.

"We were able to study the consequences of this process of rapid colonisation using CT scanning of the coral skeleton - as would be used in medical imaging. We show that this process is devastating not just for the animal tissue, but also for the skeleton that is left behind, which is rapidly eroded and weakened."

University of Technology Sydney scientists A/Professor David Suggett and Dr Emma Camp explain how they were also able to use novel bio-optical techniques that allow them to visualise and study the rapid transition in the coral microbiome for the first time.

"With this technique, we can see microbial communities go from symbionts to harmful coral skeleton-dissolvers. Adopting these techniques more broadly will be central to understanding how this process occurs on reefs globally - we anticipate that heatwave mortality events, and rapid reef decay, will become more frequent as the intensity of marine heatwaves increase."

Dr Scott Heron from James Cook University says this rapid dissolving of coral skeletons following severe heatwaves hasn't been known to date.

"Climate scientists talk about 'unknown unknowns' - impacts that we haven't anticipated from existing knowledge and experience. This discovery fits into this category. As we begin now to understand this impact, the question is how many more of these 'unknown unknowns' might there still be that could bring faster and greater damage to coral reefs from climate change," he says.

Dr Mark Eakin, Coordinator of NOAA's Coral Reef Watch, says such events are predictable.

"We already use climate models and satellite data to predict and detect conditions that cause coral bleaching. By focusing on especially severe marine heatwaves, we should be able to predict this direct coral death, too."

A/Prof Ainsworth says that the team hopes that this research will motivate the public to tell decision makers how important coral reefs are to them, and voice the immediate need to preserve coral reefs now.

"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. Given that the degradation of coral reefs will result in the collapse of ecosystem services that sustain over half a billion people, we urgently need actions both globally and locally that protect and conserve these truly wonderful places."
-end-
Media contacts

For interviews with lead author Tracy Ainsworth, UNSW Sydney

Isabelle Dubach
Media and Content Manager
+61 2 9385 7307, +61 432 307 244
i.dubach@unsw.edu.au

For interviews with Bill Leggat, University of Newcastle

University of Newcastle Media Team
02 4921 5577
media@newcastle.edu.au

For interviews with David Suggett and Emma Camp, UTS

Marea Martlew
Media and PR Advisor, Faculty of Science
University of Technology Sydney
p: +61 2 9514 1766 m: 0424 735 255
marea.martlew@uts.edu.au

For interviews with Scott Heron, James Cook University

Dr Scott Heron
M: 0404 893 420

For interviews with Mark Eakin, National Oceanic and Atmospheric Administration, USA

C. Mark Eakin, Ph.D.
Coordinator, NOAA Coral Reef Watch
National Oceanic and Atmospheric Administration
mark.eakin@noaa.gov
Office: +1 (301) 683-3320 Mobile: +1 (301) 502-8608

University of New South Wales

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.
PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.
Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.
Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.
More Science News and Science Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#542 Climate Doomsday
Have you heard? Climate change. We did it. And it's bad. It's going to be worse. We are already suffering the effects of it in many ways. How should we TALK about the dangers we are facing, though? Should we get people good and scared? Or give them hope? Or both? Host Bethany Brookshire talks with David Wallace-Wells and Sheril Kirschenbaum to find out. This episode is hosted by Bethany Brookshire, science writer from Science News. Related links: Why Climate Disasters Might Not Boost Public Engagement on Climate Change on The New York Times by Andrew Revkin The other kind...
Now Playing: Radiolab

An Announcement from Radiolab