[Marxism] Oceans Acidifying Faster Today Than in Past 300 Million Years

Louis Proyect lnp3 at panix.com
Thu Mar 1 16:23:03 MST 2012


Press Release 12-041
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.

"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 

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 

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 

"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.


Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas at nsf.gov
Kim Martineau, LDEO (845) 365-8708 kmartine at ldeo.columbia.edu

Related Websites
NSF Discovery Article: Trouble in Paradise: Ocean Acidification This Way 
Comes: http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=122642

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over 50,000 competitive requests for funding, and makes about 11,000 new 
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