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October 22, 2019 02:10 am

Ocean Acidification Can Cause Mass Extinctions, Fossils Reveal

After analyzing fossil records from 66 million years ago, researchers determined that ocean acidification can cause the mass extinction of marine life. The Guardian reports: The researchers analysed small seashells in sediment laid down shortly after a giant meteorite hit the Earth, wiping out the dinosaurs and three-quarters of marine species. Chemical analysis of the shells showed a sharp drop in the pH of the ocean in the century to the millennium after the strike. This spike demonstrated it was the meteorite impact that made the ocean more acidic, effectively dissolving the chalky shells of many species. Large-scale volcanic activity was also considered a possible culprit, but this occurred over a much longer period. The oceans acidified because the meteorite impact vaporized rocks containing sulphates and carbonates, causing sulphuric acid and carbonic acid to rain down. The mass die-off of plants on land after the strike also increased CO2 in the atmosphere. The researchers found that the pH dropped by 0.25 pH units in the 100-1,000 years after the strike. It is possible that there was an even bigger drop in pH in the decade or two after the strike and the scientists are examining other sediments in even finer detail. [Michael Henehan at the GFZ German research center for geosciences in Potsdam said]: âoeIf 0.25 was enough to precipitate a mass extinction, we should be worried.â Researchers estimate that the pH of the ocean will drop by 0.4 pH units by the end of this century if carbon emissions are not stopped, or by 0.15 units if global temperature rise is limited to 2C. Henehan said: âoeWe may think of [acidification] as something to worry about for our grandchildren. But if it truly does get to the same acidification as at the [meteorite strike] boundary, then you are talking about effects that will last for the lifetime of our species. It was hundreds of thousands of years before carbon cycling returned to normal.â The research has been published in the journal Proceedings of the National Academy of Sciences.

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