Nav: Home

Ocean acidification causing coral 'osteoporosis' on iconic reefs

August 27, 2020

Scientists have long suspected that ocean acidification is affecting corals' ability to build their skeletons, but it has been challenging to isolate its effect from that of simultaneous warming ocean temperatures, which also influence coral growth. New research from the Woods Hole Oceanographic Institution (WHOI) reveals the distinct impact that ocean acidification is having on coral growth on some of the world's iconic reefs.

In a paper published Aug. 27, 2020, in the journal Geophysical Research Letters, researchers show a significant reduction in the density of coral skeleton along much of the Great Barrier Reef--the world's largest coral reef system--and also on two reefs in the South China Sea, which they attribute largely to the increasing acidity of the waters surrounding these reefs since 1950.

"This is the first unambiguous detection and attribution of ocean acidification's impact on coral growth," says lead author and WHOI scientist Weifu Guo. "Our study presents strong evidence that 20th century ocean acidification, exacerbated by reef biogeochemical processes, had measurable effects on the growth of a keystone reef-building coral species across the Great Barrier Reef and in the South China Sea. These effects will likely accelerate as ocean acidification progresses over the next several decades."

Roughly a third of global carbon dioxide emissions are absorbed by the ocean, causing an average 0.1 unit decline in seawater pH since the pre-industrial era. This phenomenon, known as ocean acidification, has led to a 20 percent decrease in the concentration of carbonate ions in seawater. Animals that rely on calcium carbonate to create their skeletons, such as corals, are at risk as ocean pH continues to decline. Ocean acidification targets the density of the skeleton, silently whittling away at the coral's strength, much like osteoporosis weakens bones in humans.

"The corals aren't able to tell us what they're feeling, but we can see it in their skeletons," said Anne Cohen, a WHOI scientist and co-author of the study. "The problem is that corals really need the strength they get from their density, because that's what keeps reefs from breaking apart. The compounding effects of temperature, local stressors, and now ocean acidification will be devastating for many reefs."

In their investigation, Guo and his co-authors examined published data collected from the skeletons of Porites corals--a long-living, dome-shaped species found across the Indo-Pacific-- combined with new three-dimensional CT scan images of Porites from reefs in the central Pacific Ocean. Using these skeletal archives, which date back to 1871, 1901, and 1978, respectively, the researchers established the corals' annual growth and density. They plugged this information, as well as historical temperature and seawater chemistry data from each reef, into a model to predict the corals' response to constant and changing environmental conditions.

The authors found that ocean acidification caused a significant decline in Porites skeletal density in the Great Barrier Reef (13 percent) and the South China Sea (7 percent), starting around 1950. Conversely, they found no impact of ocean acidification on the same types of corals in the Phoenix Islands and central Pacific, where the protected reefs are not as impacted by pollution, overfishing, runoff from land.

While carbon dioxide emissions are the largest driver of ocean acidification on a global scale, the authors point out that sewage and runoff from land can exacerbate the effect, causing even further reductions of seawater pH on nearby reefs. The authors attribute the declining skeletal density of corals on the Great Barrier Reef and South China Sea to the combined effects of ocean acidification and runoff. Conversely, reefs in marine protected areas of the central Pacific have so far been shielded from these impacts.

"This method really opens a new way to determine the impact of ocean acidification on reefs around the world," said Guo. "Then we can focus on the reef systems where we can potentially mitigate the local impacts and protect the reef."

Co-authors of the paper include Rohit Bokade (Northeastern University), Nathaniel Mollica (MIT-WHOI joint program), and Muriel Leung (University of Pennsylvania), as well as Russell Brainard of King Abdullah University of Science and Technology and formerly at the Coral Reef Ecosystem Division of the Pacific Islands Fisheries Science Center.
-end-
Funding for this research was provided by the National Science Foundation, the Tiffany & Co. Foundation, the Robertson Foundation, the Atlantic Donor Advised Fund, and WHOI's Investment in Science Fund.

The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment. For more information, please visit http://www.whoi.edu.

Key Takeaways

An innovative numerical model developed by researchers at the Woods Hole Oceanographic Institution demonstrates the distinct impact of ocean acidification--separate from ocean warming--on coral growth.

The model shows that ocean acidification has caused a 13 percent decline in the skeletal density of Porites corals in the Great Barrier Reef, and a 7 percent decline in the South China Sea since 1950.

Pollution and land runoff can exacerbate the effects of ocean acidification, causing corals in local reefs to weaken more quickly than those located farther away from human settlements.

A global-scale investigation of coral CT scans could help to target protections for vulnerable reefs.

Woods Hole Oceanographic Institution

Related Ocean Acidification Articles:

For red abalone, resisting ocean acidification starts with mom
Red abalone mothers from California's North Coast give their offspring an energy boost when they're born that helps them better withstand ocean acidification compared to their captive, farmed counterparts, according to a study from the Bodega Marine Laboratory at the University of California, Davis.
Ocean warming and acidification effects on calcareous phytoplankton communities
A new study led by researchers from the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB) warns that the negative effects of rapid ocean warming on planktonic communities will be exacerbated by ocean acidification.
Sentinels of ocean acidification impacts survived Earth's last mass extinction
Two groups of tiny, delicate marine organisms, sea butterflies and sea angels, were found to be surprisingly resilient--having survived dramatic global climate change and Earth's most recent mass extinction event 66 million years ago, according to research published this week in the Proceedings of the National Academy of Sciences.
Great Barrier Reef 'glue' at risk from ocean acidification
Scientists have suspected that increasing ocean acidity would weaken and thin the structures underpinning tropical reefs.
Ocean acidification causing coral 'osteoporosis' on iconic reefs
Scientists have long suspected that ocean acidification is affecting corals' ability to build their skeletons, but it has been challenging to isolate its effect from that of simultaneous warming ocean temperatures, which also influence coral growth.
Arctic Ocean acidification worse than previously expected
Arctic Ocean acidification worse than previously expected.
Protecting bays from ocean acidification
As oceans absorb more man-made carbon dioxide from the air, a process of ocean acidification occurs that can have a negative impact on marine life.
Ocean acidification prediction now possible years in advance
CU Boulder researchers have developed a method that could enable scientists to accurately forecast ocean acidity up to five years in advance.
Ocean acidification impacts oysters' memory of environmental stress
Researchers from the University of Washington School of Aquatic and Fishery Sciences have discovered that ocean acidification impacts the ability of some oysters to pass down 'memories' of environmental trauma to their offspring.
Coral 'helper' stays robust under ocean acidification
A type of algae crucial to the survival of coral reefs may be able to resist the impacts of ocean acidification caused by climate change.
More Ocean Acidification News and Ocean Acidification Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.