Mystery solved: ocean acidity in the last mass extinction | YaleNews

Heterohelix globulosa fossils
A species of foraminifera called Heterohelix globulosa that were picked and isolated from the K-Pg boundary clay at Geulhemmerberg in the Netherlands. Each fossil measures between 150 and 212 microns.

“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.

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.

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.

Pincelli Hull standing next to researcher Michael Henehan, who is looking into a microscope.
Pincelli Hull, assistant professor of geology and geophysics, standing next to researcher Michael Henehan, who is looking into a microscope.

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.”

Source: Mystery solved: ocean acidity in the last mass extinction | YaleNews

David Lindsay
Excess Carbon Dioxide is causing the oceans to acidify in the last 200 years or so, to the point that half of the Great Barrier Reef, is dead. Coral reefs are dying all over the world. This science shows that ocean acidity in the past led to a great die off of aquatic species during the 5th great extinction 66 million years ago.