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Ocean Acidification Could Have Driven Earth’s Biggest Mass Extinction

Study shows the world’s oceans were dangerously acidic during the Permian Extinction Event

(IMAGEMORE M/Imagemore Co., Ltd./Corbis)
smithsonian.com

The Permian Extinction Event was the biggest die-off in Earth’s history, in which over 90 percent of species were wiped out. But what, exactly, caused the calamity is still uncertain. Now, in a study published in Science this week, geochemists offer evidence to support the theory that ocean acidification was a key culprit.

Reuters reports:

Scientists said on Thursday that huge amounts of carbon dioxide spewed from colossal volcanic eruptions in Siberia may have turned the world’s oceans dangerously acidic 252 million years ago, helping to drive a global environmental calamity that killed most land and sea creatures.

The researchers came to this conclusion after collecting rocks on the seafloor that had been there for hundreds of millions of years and then using the rocks’ boron isotopes to unfold the story of the ocean’s ancient acidity. “This is one of the few cases where we have been able to show that an ocean acidification event happened in deep time,” University of Edinburgh geoscientist Rachel Wood says.

The findings have implications for our oceans today, too. “We are concerned about modern ocean acidification,” Wood tells Motherboard.

Wood continues:

Although the amount of carbon added to the atmosphere that triggered the mass extinction was probably greater than today’s fossil fuel reserves, the rate at which the carbon was released was at a rate similar to modern emissions. The rate of release is critical because the oceans absorb a lot of the carbon dioxide (CO2) from the atmosphere, around 30 percent of the carbon dioxide released by humans. To achieve chemical equilibrium, some of this CO2 reacts with the water to form carbonic acid. Some of these molecules react with a water molecule to give a bicarbonate ion and a hydronium ion, thus increasing “acidity” (H+ ion concentration).

Current ocean acidification is already taking its toll on animals like sea snails, oysters and coral. In fact, some argue that we are already in the midst of an extinction event, affecting land and sea animals alike. 

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