SCIENTISTS STUDY CORAL REEFS AND OCEAN ACIDIFICATION

FROM:  NATIONAL SCIENCE FOUNDATION
Coral reefs defy ocean acidification odds in Palau
Palau reefs show few of the predicted responses

Will some coral reefs be able to adapt to rapidly changing conditions in Earth's oceans? If so, what will these reefs look like in the future?

As the ocean absorbs atmospheric carbon dioxide (CO2) released by the burning of fossil fuels, its chemistry is changing. The CO2 reacts with water molecules, lowering ocean pH (making it more acidic) in a process known as ocean acidification.

This process also removes carbonate, an essential ingredient needed by corals and other organisms to build their skeletons and shells.

Scientists are studying coral reefs in areas where low pH is naturally occurring to answer questions about ocean acidification, which threatens coral reef ecosystems worldwide.

Palau reefs dodge ocean acidification effects

One such place is Palau, an archipelago in the far western Pacific Ocean. The tropical, turquoise waters of Palau's Rock Islands are naturally more acidic due to a combination of biological activity and the long residence time of seawater in their maze of lagoons and inlets.

Seawater pH within the Rock Island lagoons is as low now as the open ocean is projected to reach as a result of ocean acidification near the end of this century.

A new study led by scientists at the Woods Hole Oceanographic Institution (WHOI) found that coral reefs in Palau seem to be defying the odds, showing none of the predicted responses to low pH except for an increase in bio-erosion--the physical breakdown of coral skeletons by boring organisms such as mollusks and worms.

A paper reporting the results is published today in the journal Science Advances.

"This research illustrates the value of comprehensive field studies," says David Garrison, a program director in the National Science Foundation's Division of Ocean Sciences, which funded the research through NSF's Ocean Acidification (OA) Program. NSF OA is supported by the Directorates for Geosciences and for Biological Sciences.

"Contrary to laboratory findings," says Garrison, "it appears that the major effect of ocean acidification on Palau Rock Island corals is increased bio-erosion rather than direct effects on coral species."

Adds lead paper author Hannah Barkley of WHOI, "Based on lab experiments and studies of other naturally low pH reef systems, this is the opposite of what we expected."

Experiments measuring corals' responses to a variety of low pH conditions have shown a range of negative effects, such as fewer varieties of corals, more algae growth, lower rates of calcium carbonate production (growth), and juvenile corals that have difficulty constructing skeletons.

"Surprisingly, in Palau where the pH is lowest, we see a coral community that hosts more species and has greater coral cover than in the sites where pH is normal," says Anne Cohen, co-author of the paper.

"That's not to say the coral community is thriving because of the low pH, rather it is thriving despite the low pH, and we need to understand how."

When the researchers compared the communities found on Palau's reefs with those in other reefs where pH is naturally low, they found increased bio-erosion was the only common feature.

"Our study revealed increased bio-erosion to be the only consistent community response, as other signs of ecosystem health varied at different locations," Barkley says.

The riddle of resilience

How do Palau's low pH reefs thrive despite significantly higher levels of bio-erosion?

The researchers aren't certain yet, but hope to answer that question in future studies.

They also don't completely understand why conditions created by ocean acidification seem to favor bio-eroding organisms.

One theory--that skeletons grown under more acidic conditions are less dense, making them easier for bio-eroding organisms to penetrate--is not the case on Palau, Barkley says, "because we don't see a correlation between skeletal density and pH."

Though coral reefs cover less than one percent of the ocean, these diverse ecosystems are home to at least a quarter of all marine life. In addition to sustaining fisheries that feed hundreds of millions of people around the world, coral reefs protect thousands of acres of coastlines from waves, storms and tsunamis.

"On the one hand, the results of this study are optimistic," Cohen says. "Even though many experiments and other studies of naturally low pH reefs show that ocean acidification negatively affects calcium carbonate production, as well as coral diversity and cover, we are not seeing that on Palau.

"That gives us hope that some coral reefs--even if it is a very small percentage--might be able to withstand future levels of ocean acidification."

Along with Barkley and Cohen, the team included Yimnang Golbuu of the Palau International Coral Reef Center, Thomas DeCarlo and Victoria Starczak of WHOI, and Kathryn Shamberger of Texas A&M University.

The Dalio Foundation, Inc., The Tiffany & Co. Foundation, The Nature Conservancy and the WHOI Access to the Sea Fund provided additional funding for this work.

-NSF-

SECRETARY KERRY'S REMARKS WITH PRINCE ALBERT II OF MONACO

FROM:  THE STATE DEPARTMENT 

Remarks With Prince Albert II of Monaco Before Their Meeting

Remarks

John Kerry

Secretary of State

Treaty Room

Washington, DC

June 16, 2014

---

SECRETARY KERRY: Good morning, everybody, and my distinct pleasure to welcome His Serene Highness Prince Albert II of Monaco here. He has really been one of the most outspoken protectors of the environment and particularly concerned about the ocean, ocean acidification. He has put together a center for research, which is based at the IAEA lab in Monaco. And his interest in not just ocean acidification but overall environmental protection of fisheries has made him perhaps one of the most defined and accepted leaders on this subject. And we’re happy that he’s going to be addressing the ocean conference Our Ocean today – our luncheon speaker.

And also I might add, I think he is the only head of state who has been to both – to the North and South Pole, so this is not a passing interest on his behalf. He and his family and he, particularly, have been important voices for reasonableness with respect to the environment broadly, but the effect of climate change, the effect of power plants and acidification emission, the impact it is having on the ecosystem of our oceans, which, as I said this morning, three billion people rely on for food and which is a major global security issue.

So I’m very grateful to His Serene Highness for coming. Thank you for being with us today.

PRINCE ALBERT II: Well, thank you very much, Mr. Secretary, and thank you for your leadership in convening this summit. I know you’ve been interested in these issues for a very long time, and we’re both navy men, I know. I was also in the French navy for a short while and – but I know that these are concerns that we share and that we need to see put on the international agenda at a much more important level than they are today.

As you know, and as you were able to tell us this morning, these issues concerning our global ocean don’t concern only a few activists anymore. It’s the concern of all of us. And each stakeholder, be they government leaders, be they civil society, be they international organizations, be they other NGOs, scientists, corporations, the corporate world, I think we all have a say and we all can do something. And we have to work together to meet these challenges and to make our global ocean as sustainable as possible and as healthy as possible, because the services that the global ocean provides to all of us is immeasurable. And to see the state of degradation that some parts of our ocean is showing, be it from pollution of any sort, be they – be it of overfishing, be it of other forms of exploitation in an unregulated way is simply unacceptable and abhorrent. And we absolutely have to come together to address these issues and find the solutions, find viable solutions, not only on the economic side, on the social-economic side, but also on the sustainable and environmental side that is so important.
And so this summit I think will be able to address these issues with some of the leading specialists that you have invited here, the scientific community, but also from other parts of civil society, as I said, and the corporate world and other organizations and government leaders.
And I’m very happy to see also that other two heads of state have joined you here, aside from me, to – and I know President Tong and President Remengesau very well. And we’ve worked with them not only with my foundation but with other organizations to help them also constitute that, and their leadership is also invaluable for marine-protected areas because that is – and they were able to announce that and President Tong was able to announce that this morning, that marine-protected areas do work, and no matter how big or small they are. And we’ve been able to do that also in – I’m just trying to push that in the Mediterranean as well. And we need to see more protected areas (inaudible) our global ocean.

And so we thank you very much for all of this, and we hope that this will be a successful and worthy meeting of all these wonderful people that are gathered here in Washington today.

SECRETARY KERRY: Thank you very, very much. And we really look forward to your comments at the luncheon. And we also look forward to coming out of this conference, as I said this morning, with a plan of action. We don’t want to talk for the sake of talking. There have been a lot of meetings in the past, which has led to a growing consensus of the actions that need to be taken.

So His Serene Highness will help us today to crystalize our focus on these steps and we really look forward tomorrow to coming to conclusion on what we can do to advance this initiative. So we’re grateful, very much. Thank you for coming.

PRINCE ALBERT II: Thank you very much.

SECRETARY KERRY: Thank you.

U.S. MARK'S WORLD ENVIRONMENT DAY

FROM:  U.S. STATE DEPARTMENT 

World Environment Day

Press Statement

John Kerry

Secretary of State

Washington, DC

June 5, 2014

---

The United States is proud to mark World Environment Day and this year we are especially focused on the unique challenges facing Small Island Developing States and the health of our oceans.

With vast marine areas and limited land, island nations feel environmental challenges very acutely. Marine pollution, overfishing, ocean acidification, and the changing climate threaten countries from Tonga to Tuvalu to Trinidad and Tobago.

The ocean itself is vital to life – not just for island nations, but for people around the world. Here in the United States, the ocean sustains the livelihoods of millions, stabilizes our climate, and provides a critical source of food.

The challenges facing island nations demand urgency and focus from all of us. The United States took a major step forward this week, releasing a proposed rule under the Clean Air Act to limit greenhouse gas emissions from existing power plants, and as we work hard to reduce our emissions and mitigate climate change at home, we will continue to help small island states and other vulnerable countries adapt.

We are especially looking forward to the “Our Ocean” Conference, June 16–17, with a focus on sustainable fisheries, marine pollution, and ocean acidification, and to our participation in the Third UN International Conference on Small Island Developing States this September in Samoa. Protecting our ocean is a common challenge that demands common resolve, and we can meet this challenge with leadership that unites nations.

MIXED OYSTER NEWS

Oysters.  Credit:  USFW/Wikimedia

FROM: NATIONAL SCIENCE FOUNDATION
World Oceans Month Brings Mixed News for Oysters
In World Oceans Month, there's mixed news for the Pacific Northwest oyster industry.



For the past several years, it has struggled with significant losses due to ocean acidification. Oyster larvae have had mortality rates high enough to render production no longer economically feasible.

Now a new study documents why oysters appear so sensitive to increasing acidity, but also offers some hope for the future.

It isn't necessarily a case of acidic water dissolving the oysters' shells, scientists say. It's water high in carbon dioxide altering shell formation rates, energy usage and, ultimately, the growth and survival of young oysters.

"The failure of oyster seed production in Northwest Pacific coastal waters is one of the most graphic examples of ocean acidification effects on important commercial shellfish," said Dave Garrison, program director in the National Science Foundation's (NSF) Division of Ocean Sciences.

NSF funded the study through its Ocean Acidification Program, part of NSF's Science, Engineering and Education for Sustainability programs.

"This research is among the first to identify the links among organism physiology, ocean carbonate chemistry and oyster seed mortality," said Garrison.

Results of the study are online in the journal Geophysical Research Letters, published by the American Geophysical Union.

"From the time eggs are fertilized, Pacific oyster larvae precipitate roughly 90 percent of their body weight as a calcium carbonate shell within 48 hours," said George Waldbusser, an Oregon State University marine ecologist and lead author of the paper.

"Young oysters rely solely on the energy they derive from the egg because they have not yet developed feeding organs."

During exposure to increasing carbon dioxide in acidified water, however, it becomes more energetically expensive for organisms like oysters to build shells.

Adult oysters and other bivalves may grow more slowly when exposed to rising carbon dioxide levels. But larvae in the first two days of life do not have the luxury of delayed growth.

"They must build their first shell quickly on a limited amount of energy--and along with the shell comes the organ to capture external food," said Waldbusser.

"It becomes a death race of sorts. Can the oyster build its shell quickly enough to allow its feeding mechanism to develop before it runs out of energy from the egg?"

The results are important, marine scientists say, because they document for the first time the links among shell formation rate, available energy, and sensitivity to acidification.

The researchers say that the faster the rate of shell formation, the more energy is needed. Oyster embryos building their first shells need "to make a lot of shell on short order," said Waldbusser.

"As the carbon dioxide in seawater increases, but before waters become corrosive, calcium carbonate precipitation requires more energy to maintain higher rates of shell formation during this early stage."

The researchers worked with Whiskey Creek Shellfish Hatchery in Netarts Bay, Ore. They found that on the second day of life, 100 percent of the larval tissue growth was from egg-derived carbon.

"The oyster larvae were still relying on egg-derived energy until they were 11 days old," said Elizabeth Brunner of Oregon State University and a co-author of the paper.

The earliest shell material in the larvae contained the greatest amount of carbon from the surrounding waters.

Increasing amounts of carbon from respiration were incorporated into shells after the first 48 hours, indicating an ability to isolate and control the shell surfaces where calcium carbonate is being deposited.

Waldbusser notes that adult bivalves are well-adapted to growing shell in conditions that are more acidified, and have evolved several mechanisms to do so.

These include use of organic molecules to organize and facilitate the formation of calcium carbonate, pumps that remove acid from the calcifying fluids, and outer shell coatings that protect minerals to some degree from surrounding waters.

Waldbusser said that the results help explain previous findings at the Whiskey Creek Hatchery of larval sensitivity to waters that are high in carbon dioxide but not corrosive to calcium carbonate.

They also explain carryover effects later in larval life of exposure to high carbon dioxide, similar to human neonatal nutrition effects.

The discovery may be good news, scientists say, because there are interventions that can be done at hatcheries that may offset some of the effects of ocean acidification.

Some hatcheries have begun "buffering" water for larvae--essentially adding antacids to incoming waters--including the Whiskey Creek Hatchery and the Taylor Shellfish Farms in Washington.

The study provides a scientific foundation for the target level of buffering.

"You can make sure that eggs have more energy before they enter the larval stage," said Waldbusser, "so a well-balanced adult diet may help larval oysters cope better with the stress of acidified water."

-NSF-

RESEARCHERS STUDY BLUE MUSSELS AND OCEAN ACIDIFICATION

Photo:  Mussel.  Credit:  Wikimedia Commons

FROM: NATIONAL SCIENCE FOUNDATION
Blue Mussels 'Hang On' Along Rocky Shores: For How Long?

Imagine trying to pitch a tent in a stiff wind. You just have it secured, when a gale lifts the tent--stakes and all--and carries it away.

That's exactly what's happening to a species that's ubiquitous along the rocky shores of both the U.S. West and East Coasts: the blue mussel.

Mussels make use of what are called byssal threads--strong, silky fibers--to attach to rocks, pilings and other hard substrates. They produce the threads using byssus glands in their feet.

Now, scientists have discovered, the effects of ocean acidification are turning byssal threads into flimsy shadows of their former selves, leaving mussels tossed about by wind and waves.

At high levels of atmospheric carbon dioxide--levels in line with expected concentrations over the next century--byssal threads become weaker, less able to stretch and less able to attach to rocks, found scientists Emily Carrington, Michael O'Donnell and Matthew George of the University of Washington.

The researchers recently published their results in the journal Nature Climate Change; O'Donnell is the lead author.

Oceans turning caustic

The pH of the seas in which these and other marine species dwell is declining. The waters are turning more acidic (pH dropping) as Earth's oceans change in response to increased carbon dioxide in the atmosphere.

As atmospheric carbon rises as a result of human-caused carbon dioxide emissions, carbon in the ocean goes up in tandem, ultimately resulting in ocean acidification, scientists have found.

To study the effects of ocean acidification on marine organisms, Carrington has been awarded an NSF SEES (Science, Engineering, and Education for Sustainability) Ocean Acidification grant.

"We need to understand the chemistry of ocean acidification and its interplay with other marine processes--while Earth's seas are still hospitable to life as we know it," says David Garrison, program director in NSF's Division of Ocean Sciences. "In the rocky intertidal zone, blue mussels are at the heart of those processes."

Land between the tides

Visit the land between the tides, and you'll see waves crashing on boulders tinged dusky blue by snapped-closed mussels.

"Their shells are a soft color, the misty blue of distant mountain ranges," wrote Rachel Carson more than 50 years ago in her best-selling book The Edge of the Sea.

For blue mussels trying to survive, the rocky intertidal zone indeed may be akin to scaling a mountain range.

The rocky intertidal is above the waterline at low tide and underwater at high tide--the area between tide marks.

It's home to such animals as starfish and sea urchins, and seaweed such as kelp. All make a living from what floats by rocky cliffs and boulders.

It can be a hard go. Rocky intertidal species must adapt to an environment of harsh extremes. Water is available when the tide washes in; otherwise residents of this no man's land between sea and shore are wide open to the elements.

Waves can dislodge them, and temperatures can run from scalding hot to freezing cold.

Hanging on for dear life

In the rocky intertidal, blue mussels hang on for dear life.

That may not always be the case.

Combining results from laboratory experiments with those from a mathematical model, Carrington and colleagues show that at high carbon dioxide concentrations, blue mussels can be dislodged by wind and wave forces 40 percent lower than what they are able to withstand today.

Mussels with this weakened ability, once dislodged from their homes, could cause ecological shifts in the rocky intertidal zone--and huge economic losses in a global blue mussel aquaculture industry valued at U.S. $1.5 billion each year.

"Mussels are among the most important species on rocky shores worldwide," says O'Donnell, "dominating ecosystems wherever they live. The properties in their byssal threads are also of interest to biochemists and have been studied as possible medical adhesives."

Blue mussels may make important contributions to the field of materials science, says Carrington.

"Some species of mussels are experts at gluing onto seagrass, some to other shells, some even adhere to rocks in the harsh conditions of deep-sea hydrothermal vents. Each may have different genes that code for different proteins, so the adhesives vary."

Will their potential be realized? Carrington, O'Donnell and George have found a disturbing answer.

The scientists allowed mussels to secrete byssal threads in a range of ocean water chemistries from present-day through predicted near-future conditions, then tested the threads to see how strong they were.

At levels considered reasonable for a near-future coastal ocean (given current rates of acidification), byssal threads were less able to stretch and therefore less able to adhere. Further testing revealed that the problem was caused by weakening of the glue where the threads attach to rocks and other hard surfaces.

Ocean acidification beyond shells and corals

"Much ocean acidification research has focused on the process of calcification," says Carrington, "through which animals and some plants make hard parts such as shells."

In acidifying oceans, marine species that depend on calcium carbonate have a more difficult time forming shells or, in the case of coral reefs, skeletons.

"But there's more to marine communities than calcified parts," says O'Donnell. Other species such as mussels and their byssal threads, he says, are equally important.

"Understanding the broader consequences of ocean acidification requires looking at a variety of biological processes in a range of species."

A need that didn't exist when Rachel Carson wrote The Edge of the Sea.

"When we go down to the low-tide line, we enter a world that is as old as the Earth itself--the primeval meeting place," mused Carson, "of the elements of earth and water."

And of mussels and rock. Fifty years hence, will the mussels still be here?

HOW OCEAN ACIDIFICATION CAUSES LARVAL OYSTER FAILURE

FROM:  NATIONAL SCIENCE FOUNDATION

Oysters at hatcheries in Oregon are showing the effects of ocean acidification.
Credit: OSU



Ocean Acidification Linked With Larval Oyster Failure in Hatcheries


Increase in ocean acidification led to collapse of oyster seed production at Oregon hatchery 


April 11, 2012
Marine researchers have definitively linked the collapse of oyster seed production at a commercial oyster hatchery in Oregon to an increase in ocean acidification.
Larval growth at the hatchery declined to a level considered by the owners to be "non-economically viable."


A study by the scientists found that increased seawater carbon dioxide (CO2) levels, resulting in more corrosive ocean water, inhibited the larval oysters from developing their shells and growing at a pace that would make commercial production cost-effective.


As atmospheric CO2 levels continue to rise, this may serve as the proverbial canary in the coal mine for other ocean acidification impacts on shellfish.
Results of the research are published this week in the journalLimnology and Oceanography, published by the Association for the Sciences of Limnology and Oceanography (ASLO).


The research was funded by a grant from the National Science Foundation (NSF)'s Science, Engineering and Education for Sustainability (SEES) Ocean Acidification solicitation.


"Studies funded by NSF's SEES Ocean Acidification solicitation are well-positioned to determine the specific mechanisms responsible for larval mortality in Pacific Northwest oyster hatcheries," said David Garrison, program director in NSF's Division of Ocean Sciences.


"This is one of the first times that we have been able to show how ocean acidification affects oyster larval development at a critical life stage," said Burke Hales, an Oregon State University (OSU) chemical oceanographer and co-author of the paper.
"The predicted rise of atmospheric CO2 in the next two to three decades may push oyster larval growth past the break-even point in terms of production."


The owners of Whiskey Creek Shellfish Hatchery at Oregon's Netarts Bay experienced a decline in oyster seed production several years ago and looked at potential causes, including low oxygen and pathogenic bacteria.


Alan Barton, who works at the hatchery and is a co-author of the journal article, was able to eliminate those potential causes and shifted his focus to ocean acidification.
Barton sent samples to OSU and to the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory for analysis.


The results clearly linked the production failures to the CO2levels in the water in which the larval oysters were spawned and spent the first 24 hours of their lives. That first day is a critical time when the oysters develop from fertilized eggs to swimming larvae and build their initial shells.


"The early growth stage for oysters is particularly sensitive to the carbonate chemistry of the water," said George Waldbusser, a benthic ecologist at OSU.
"As the water becomes more acidified, it affects the formation of calcium carbonate, the mineral in shells. As the CO2 goes up, the mineral stability goes down, ultimately leading to reduced growth or to mortality."


Commercial oyster production on the West Coast of North America is a 273-million-dollar industry each year. It has depended since the 1970s on oyster hatcheries for a steady supply of the seed used by growers.


In recent years, the hatcheries that provide most of the seed for West Coast growers have suffered persistent production problems.


At the same time, non-hatchery wild stocks of these oysters also have shown low recruitment, putting additional strain on a limited seed supply.
Hales said that Netarts Bay, where the Whiskey Creek hatchery is located, experiences a wide range of chemistry fluctuations.


The researchers believe that hatchery operators may be able to adapt to take advantage of periods when water quality is at its highest.


"In addition to the impact of seasonal upwelling, the water chemistry changes with the tidal cycle and with the time of day," Hales said. "Afternoon sunlight, for example, promotes photosynthesis in the bay. That production can absorb some of the carbon dioxide and lower the corrosiveness of the water."


The researchers also found that larval oysters showed a delayed response to the water chemistry, which may cast new light on other experiments looking at the impacts of ocean acidification on shellfish.


In the study, they found that larval oysters raised in water that was acidic, but non-lethal, had significantly less growth in later stages of their life.
"The takeaway message here is that the response to poor water quality isn't always immediate," said Waldbusser.


"In some cases, it took until three weeks after fertilization for effects from the acidic water to become apparent. Short-term experiments of just a few days may not detect the damage."


The research was also supported by NOAA and the Pacific Coast Shellfish Growers Association.
Other authors of the journal article include Chris Langdon of OSU's Hatfield Marine Science Center and Richard Feely of NOAA's Pacific Marine Environmental Laboratory.
-NSF-




The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.

RAPID OCEAN ACIDIFICATION MAY DOOM MANY SPECIES

The following excerpt and picture are from the National Science Foundation Website:

"Oceans Acidifying Faster Today Than in Past 300 Million Years
March 1, 2012
The oceans may be acidifying faster today than they did in the last 300 million years, according to scientists publishing a paper this week in the journal Science.
"What we're doing today really stands out in the geologic record," says lead author Bärbel Hönisch, a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory. (Image
Credit: NOAA ). 

"We know that life during past ocean acidification events was not wiped out--new species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care about--coral reefs, oysters, salmon."
The oceans act like a sponge to draw down excess carbon dioxide from the air.
The gas reacts with seawater to form carbonic acid, which over time is neutralized by fossil carbonate shells on the seafloor.

If too much carbon dioxide enters the ocean too quickly, it can deplete the carbonate ions that corals, mollusks and some plankton need for reef and shell-building.
In a review of hundreds of paleoceanographic studies, the researchers found evidence for only one period in the last 300 million years when the oceans changed as fast as today: the Paleocene-Eocene Thermal Maximum, or PETM.

In ocean sediment cores, the PETM appears as a brown mud layer flanked by thick deposits of white plankton fossils.
About 56 million years ago, a mysterious surge of carbon into the atmosphere warmed the planet and turned the oceans corrosive.

In about 5,000 years, atmospheric carbon doubled to 1,800 parts per million (ppm), and average global temperatures rose by about 6 degrees Celsius.
The carbonate plankton shells littering the seafloor dissolved, leaving the brown clay layer that scientists see in sediment cores today.

As many as half of all species of benthic foraminifera, a group of one-celled organisms that live at the ocean bottom, went extinct, suggesting that deep-sea organisms higher on the food chain may have also disappeared, said paper co-author Ellen Thomas, a paleoceanographer at Yale University.

"It's really unusual that you lose more than 5 to 10 percent of species," she said.
Scientists estimate that ocean acidity--its pH--may have fallen as much as 0.45 units as the planet vented stores of carbon into the air.

"These scientists have synthesized and evaluated evidence far back in Earth's history," said Candace Major, program officer in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.

"The ocean acidification we're seeing today is unprecedented," said Major, "even when viewed through the lens of the past 300 million years, a result of the very fast rates at which we're changing the chemistry of the atmosphere and oceans."
In the last hundred years, rising carbon dioxide from human activities has lowered ocean pH by 0.1 unit, an acidification rate at least 10 times faster than 56 million years ago, says Hönisch.
The Intergovernmental Panel on Climate Change (IPCC) predicts that pH will fall another 0.2 units by 2100, raising the possibility that we may soon see ocean changes similar to those observed during the PETM.

More catastrophic events have happened on Earth before, but perhaps not as quickly.
The study finds two other analogs for modern day ocean acidification--the extinctions triggered by massive volcanism at the end of the Permian and Triassic eras, about 252 million and 201 million years ago, respectively.

But the authors caution that because ocean sediments older than 180 million years have been recycled back into the deep Earth, scientists have fewer records to work with.
During the "Great Dying" at the end of the Permian, about 252 million years ago, about 96 percent of life disappeared.

Massive eruptions from what is known as the Siberian Traps in present-day Russia are thought to have triggered earth's biggest extinction.
Over 20,000 years or more, carbon in the atmosphere rose dramatically.
Scientists have found evidence for ocean dead zones, and preferential survival of organisms predisposed to carbonate-poor seawater and high blood-carbon levels, but so far they have been unable to reconstruct changes in ocean pH or carbonate.
At the end of the Triassic, about 201 million years ago, a second burst of mass volcanism associated with the break-up of the supercontinent Pangaea doubled atmospheric carbon and touched off another wave of die-offs.

Coral reefs collapsed and an entire class of sea creatures, the eel-like conodonts, vanished.
On land, large plant-eating animals gave rise to meat-eating dinosaurs like Tyrannosaurus rex as the Jurassic era began.

A greater extinction of tropical species has led some scientists to question whether global warming rather than ocean acidification was the main killer at this time.
This study finds that the most notorious of all extinctions, the one that ended the Age of Dinosaurs with a falling asteroid 65 million years ago, may not have been associated with ocean acidification.

The asteroid impact in present-day Mexico 65 million years ago released toxic gases and possibly set off fires that sent surges of carbon into the air.
Though many species of plankton went extinct, coral reefs and benthic foraminifera survived.

In lab experiments, scientists have tried to simulate modern ocean acidification, but the number of variables currently at play--high carbon dioxide and warmer temperatures, and reduced ocean pH and dissolved oxygen levels--make predictions difficult.
An alternative to investigating the paleo-record has been to study natural carbon seeps from offshore volcanoes that are producing the acidification levels expected by the year 2100.

In a recent study of coral reefs off Papua New Guinea, scientists found that during long-term exposure to high carbon dioxide and pH 0.2 units lower than today--at a pH of 7.8 (the IPCC projection for 2100)--reef biodiversity and regeneration suffered.”