Mystery solved: Ocean acidity in the last mass extinction

phys.org | 9/30/2019 | Staff
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A new study led by Yale University confirms a long-held theory about the last great mass extinction event in history and how it affected Earth's oceans. The findings may also answer questions about how marine life eventually recovered.

The researchers say it is the first direct evidence that the Cretaceous-Paleogene extinction event 66 million years ago coincided with a sharp drop in the pH levels of the oceans—which indicates a rise in ocean acidity.

Study - Edition - Proceedings - National - Academy

The study appears in the online edition of the journal Proceedings of the National Academy of Sciences.

The Cretaceous-Paleogene die-off, also known as the K-Pg mass extinction event, occurred when a meteor slammed into Earth at the end of the Cretaceous period. The impact and its aftereffects killed roughly 75% of the animal and plant species on the planet, including whole groups like the non-avian dinosaurs and ammonites.

Years - People - Decrease - PH - Impact

"For years, people suggested there would have been a decrease in ocean pH because the meteor impact hit sulphur-rich rocks and caused the raining-out of sulphuric acid, but until now no one had any direct evidence to show this happened," said lead author Michael Henehan, a former Yale scientist who is now at GFZ German Research Centre for Geosciences in Potsdam, Germany.

Turns out all they had to do was look at the foraminifera.

Foraminifera - Plankton - Calcite - Shell - Fossil

Foraminifera are tiny plankton that grow a calcite shell and have an amazingly complete fossil record going back hundreds of millions of years. Analysis of the chemical composition of foraminifera fossils from before, during, and after the K-Pg event produced a wealth of data about changes in the marine environment over time. Specifically, measurements of boron isotopes in these shells allowed the Yale scientists to detect changes in the ocean's acidity.

Previous K-Pg research had shown that some marine calcifiers—animal species that develop shells and skeletons from calcium carbonate—were disproportionately wiped...
(Excerpt) Read more at: phys.org
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