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Dr. Bärbel Hönisch, Columbia University – Ocean Acidification

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In today’s Academic Minute, Dr. Bärbel Hönisch of Columbia University’s Lamont-Doherty Earth Observatory reveals how rising levels of CO2 are not only warming the atmosphere, but accelerating the acidification of the oceans as well.

Bärbel Hönisch is Assistant Professor of Earth and Environmental Science at Columbia University and a geochemist at Columbia’s Lamont-Doherty Earth Observatory. Her teaching and research interests include chemical oceanography and paleoceanography. With colleagues, she recently published a study of ocean acidification covering the last 300 million years.

About Dr. Hönisch

Dr. Bärbel Hönisch – Ocean Acidification

Carbon dioxide emissions from human activities are warming the air and oceans, but it is now clear that these are not our only problems. About a quarter of all CO2 we emit dissolves in the oceans, where it reacts with seawater to form a weak acid. With all the CO2 we are releasing today, the chemistry of the oceans is now changing faster than at any time in the last 300 million years.

The potential strain this poses for marine life has been studied in many laboratory experiments, where organisms like corals, oysters, crabs and plankton are exposed to projected future CO2 levels. Many of these show negative effects--but some show no change, or even positive effects. This makes it hard to predict future ecosystem changes. That is why my colleagues and I have turned to the geological record to look for past ocean acidification events that could give us clues.

When comparing past and present, we have to look for massive, rapid CO2 releases, because only these compare to what is happening today. The geologic event that best fits this pattern happened about 56 million years ago, when a massive natural release of fossil carbon caused a global temperature increase of 9 to 16 degrees Fahrenheit; massive dissolution of carbonate shells at the seafloor; and extinction among organisms on the seafloor and near the sea surface. This happened despite the fact that the CO2 release and resulting ocean acidification back then was at least 10 times slower than what is happening today.

It is unlikely that manmade ocean acidification will kill all life in the oceans. But judging from geological records, it is rather likely that some species will go extinct, and some of them we may miss dearly.

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