Ocean acidification worst in 300 million years, study finds

Researchers at Columbia University have found that carbon dioxide emissions have lowered the pH at a rate unparalleled in at least the last 300 million years of our planet's history.

Centre for Marine Studies, The University of Queensland/Ove Hoegh-Guldberg/REUTERS/Centre for Marine Studies, The University of Queensland/Ove Hoegh-Guldberg/Reuters
This 2002 photo shows bleached coral at Australia's Great Barrier Reef. Rising carbon dioxide levels in the world's oceans are killing the marine animals at an unprecedented rate. A new study has found that ocean acidification is the worst that it has been in at least the past 300 million years.

The oceans are becoming more acidic faster than they have in the past 300 million years, a period that includes four mass extinctions, researchers have found.

Then, as is happening now, increases in carbon dioxide in the atmosphere warmed the planet and made the oceans more acidic. These changes are associated with major shifts in climate and mass extinctions.

But while past increases in the atmosphere's carbon dioxide levels resulted from volcanoes and other natural causes, today that spike is due to human activities, the scientists note.

"What we're doing today really stands out," lead researcher Bärbel Hönisch, a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory, said in a news release. "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." [Humans Causing 6th Mass Extinction]

As the level of carbon dioxide in the atmosphere increases, oceans absorb that carbon dioxide, which turns into a carbon acid. As a result the pH — a measure of acidity — drops, meaning the water has become more acidic. This dissolves the carbonates needed by some organisms, like corals, oysters or the tiny snails salmon eat.

In their review, published Thursday (March 1) in the journal Science, Hönisch and colleagues found the closest modern parallel about 56 millions ago in what is called the Paleocene-Eocene Thermal Maximum, when atmospheric carbon concentrations doubled, pushing up global temperatures. Extinctions in the deep sea accompanied this shift. (The PETM occurred about 9 million years after the dinosaurs went extinct.)

But, now, the ocean is acidifying at least 10 times faster than it did 56 million years ago, according to Hönisch.

Ocean acidification may also have occurred when volcanoes pumped massive amounts of carbon dioxide into the air 252 million years ago, at the end of the Permian period, and 201 million years ago, at the end of the Triassic period, they found. Both are associated with mass extinctions.

"The current rate of (mainly fossil fuel) carbon dioxide release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last 300 million years of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change," the researchers conclude in their paper.

You can follow LiveScience senior writer Wynne Parry on Twitter @Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.