WOODS HOLE OCEANOGRAPHIC INSTITUTION
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.
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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.
“simultaneous warming ocean temperatures”
Would that be the 0.01C temperature increase that they claim to have measured?
“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.”
The pH scale is log so every whole number is a power/factor of ten.
By definition pH is the negative exponent of the hydrogen ion concentration.
For instance, pH 9 is 10^-9 or 1 part per billion, 0.000000001.
pH 8 is 10^-8 or 10 parts per billion, 0.000000010.
To go from pH 9 to pH 8 is factor of 10 or 1,000%!!!! Makes 26% look trivial.
Ocean “acidification” of pH 8.2 to pH 8.1, 0.1 unit, is an alkalinity change in H ions of 1 ppb.
I’m fairly certain the ocean flora and fauna don’t even notice.
Normal variability is probably way larger due to roughly cyclic effects of the PDO etc.
The diurnal variation in pH on a coral reef can be up to >1 pH unit as the coral zooxanthellae use up the CO2 during the day,
What effect does drilling big holes have on the coral?
Interesting observations that are subject to innumerable interpretations. They are combining old data of one sort with new data of a completely different sort and then feeding it all into a model. Naturally in the unscientific world of research we live in now the only interpretations they are interested in are the ones that convict humans of doing harm. As coral and the symbionts they host depend on photosynthesis, who is to say any changes they measured aren’t just improvements in the growth cycle due to higher photosynthetic potential in a world with more available CO2? If there really is lower calcification density maybe it reflects more vigorous growth. Calcification is not necessarily a virtue at any and all levels. The real story would be how are the corals doing over time. Enter Peter Ridd, a real scientist.
If they are scientists, why are they calling it “acidification” ?
– JPP
High phosphate levels can contribute to nuisance algae growth AND weaken coral skeletons with the animals incorporate phosphates into the calcium carbonate matrix.
Guess where both of these conditions occur? In areas with high runoff that contains excessive nutrients from agricultural fertilizers.
Yeah, talk about missing the cause entirely. It’s almost as if they had a solution and needed a problem!
What a bunch of woodsholes.
Yes. It also is causing inflamation and thus coral arthritis of both types, rheumatoid and osteo. This, of course is quite painful for the corals, and if you listen carefully, you can hear them screaming. Greta, I’m told, is very good at hearing them scream.
The corals should try to include more dairy in their diet. That has been proven to slow down osterporosis.
We are at geological historical low points for atmospheric CO2 and well within climatic moderate temperatures. So corals come and corals go? Do corals behave / evolve – even go extinct over long periods of time like all other life, or are they “special”?
Travelling by small boat across the pacific, one quickly learns that coral atols often have an entrance on the leward side. But are completely solid on the windward side.
This occurs because fresh water kills coral, and rain falling within the atol gets carried from the windward to leward side. Over time this process carves a path through the reef, allowing boats to enter and anchor in the calm waters within the atol. This is a big deal for the weary sailor.
It is also a big deal for coral, because it means you must correct for coral sampled from the leward vs windward side of the reef.
It also means that in areas where there are humans the coral will be affected by ground water pumping and salinity that has nothing to do with pollution or ocean pH.
A question researchers should ask themselves is why the Great Barrier Reef does not extend to the shoreline. Rather it is many miles offshore from Australia, with a wide, coral free passage for ships between the shore and the reef.
A simple question. Why does coral not grow on the Australian side of the Great Barrier Reef? This is nothing new. The process clearly has been going on for thousands of years. Was it a result of the aboriginals burning the forests every year? Can I get a grant to study this earth shattering discovery.
Ferd: Yes, if you blame humans for acidifying Australia. To the east.
Corals never grow right up to the shoreline where there is tides. They avoid the intertidal zone since they can’t tolerate being exposed above water except very briefly. That is why fossil coral reefs are useful sea-level indicators. They grow up to just below low tide, but no higher.
However you often find dead “reef-flats” at or just under sea-level, particularly in the central Pacific. Those corals grew in the Early Holocene when sea-levels were 1-2 meters higher.
The press release dogmatically states “Animals that rely on calcium carbonate to create their skeletons, such as corals, are at risk as ocean pH continues to decline.” [Note: some calcifiers exploit calcium bicarbonate, which has an inverse relationship to calcium carbonate.]
However, not all researchers see the situation as simplistically. For example, “… certain trace‐element abundances (e.g., Sr and Mg) vary in response to changes in water temperature. Traditionally, equilibrium thermodynamics has been invoked to explain these relationships … However, a detailed understanding of the biomineralization process is lacking and a critical question is the role of biological processes in controlling skeletal composition.”
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006GL028657
In general, calcifiers are able to control the pH at the crystal-growth face with the expenditure of energy. It appears that the optimal pH for calcifiers may be related to the predominant pH in the local environment at the time the organism evolved. However, they continue to survive in the face of a changing environment by expending energy to optimize the pH in the immediate vicinity of the polyp. Thus, they are able to tolerate a considerable daily and seasonal range in pH (much greater than the centennial change!) and still grow and survive.
Why does such rubbish get funded? Why does it get published? It seems that saving the planet is incompatible with rational scientific thought.
But then perhaps it is not surprising that ideological obsession and confirmation bias are incompatible with scientific objectivity.
We really need to do something about this plate tectonics! All those undersea volcanoes, which emit CO2 into the deep cold ocean waters, under even more pressure than that can of soda in your icebox, which then gets distributed by deep ocean currents spreading that terrible acidity worldwide – how the oceans have survived all of this for millions of years is simply beyond belief!
And even more beyond belief is that the places where this cold, acid, polluted water upwells to the surface are the biologically richest spots in the oceans, and the main fishing areas.
Supplimental.
https://www.pmel.noaa.gov/co2/story/Quality+of+pH+Measurements+in+the+NODC+Data+Archives
Many of the complaints about historical measurements of pH at the NOAA site are fundamentally similar to problems with measuring historical sea surface temperatures (SST). That is to say, both sets of data, pH and SST, are problematic and have higher uncertainties than modern measurements. However, the older temperatures have not been rejected out of hand. Perhaps that is because they help make the case for warming. I’m cynical enough to suspect that if they didn’t allow warming to be claimed, they would similarly be rejected as being unreliable.
Supporters of the claimed high precision of temperature data claim that they are allowed by the Law of Large Numbers to claim a precision proportional to the square-root of the number of observations. However, no one is similarly claiming such improvements in pH measurements. Why are the alarmists using different standards for different data sets?
“they are allowed by the Law of Large Numbers to claim a precision proportional to the square-root of the number of observations”
That only applies to random errors of repeated measurements of the same expected value.
It does not apply to systematic errors or measurements with different expected values (such as different temperatures).
But then Climate Scientists have never been very good at statistics.
People with salt water aquaria often add extra CO2 to the water to encourage corals to grow faster. It seems to me that aquaria would be a better place for this research, since there you can control other factors and vary only the CO2.
But it would of course be less fun.
tty
In 1970 I had a cold-saltwater, 15-gallon aquarium stocked with typical Pacific tide pool biota. It was stable and diverse for months — until I introduced a small octopus. Within a matter of weeks it became a sterile desert with only a monkey face eel in one corner under a rock, and the octopus in the opposite corner. A small perturbation can have a profound effect in an aquarium.
Octopi are the most advanced and smartest invertebrate predators in existence. Introducing one in an aquarium is not a “small perturbation”
I believe the plural is octopuses, since it’s a word of Greek origin, not Latin.
“A global-scale investigation of coral CT scans” = give us more funding.
Don’t they know that the PH of the oceans around coral reefs varies on a daily basis. The Ph is usually higher in the morning and lower in the afternoon. But it is still in the 8’s therefore it is not acidifying . It’s time these”scientists’ stopped hanging around the oceans and playing on boats and got themselves real jobs.
Same old question for the 1000th time.
How did corals evolve in the Cambrian with 7000 ppm CO2 in the atmosphere?
And yet now an increase from 400 ppm CO2 is going to give them “osteoporosis”?
What is wrong with these people??
And no. The dim sum won’t help them.
dim sun
(Lower insulation in the deep past)
Dumazzes … they should ask marine reef aquarium hobbyists about pH and coral growth and stop wasting their time with their ignorant pronouncements. My 500g ‘sps’ display maintains 7.9 pH and substantial coral growth. Low pH is a consequence of carbon dosing with vinegar for bacteria enhancement to aid water management.
The authors state in essence the problems correlate better with runoff from the land than CO2. Maybe the authors should think about that more. But I suppose that doesn’t bring in government research money.