Acid in the face of marine life

By James Forsythe

So the planet is warming up like the 19th century chemist Svante Arrhenius theorised it would, due to an increase in carbon dioxide (CO2) and the resulting greenhouse effect. But the oceans have absorbed approximately half of all human-caused CO2 emissions from the time of Arrhenius onwards, significantly slowing down climate change. This may sound wonderful but what are the effects of that on the ocean environment?

acid

Credit: Mikhail Rogov

Dissolving CO2 in the ocean leads to the formation of carbonic acid. This is predicted to lower the pH of the ocean by about 0.4 units by the end of the century, to levels unexperienced by sea creatures for over 20 million years, and the rate of acidification is already 100 times faster than the last time the oceans acidified 20,000 years ago.

The CO2 will also react with water and carbonate ions to form bicarbonate ions, decreasing carbonate ion availability. This combined with acidification will be bad for organisms with calcareous shells and skeletons including corals, molluscs and plankton, as they will not be able to form such shells or skeletons as easily. Some of these species are economically important, and the knock on effects of any reduction in the numbers of the affected species will doubtlessly change the face of marine life.

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