Scientists from Yale University have solved a mystery that has plagued scientists for decades. It’s well established that 66 million years ago, a massive meteor crashed into earth and extinguished nearly 75% of the plant and animal species on the planet. This is known as the Cretaceous-Paleogene extinction event (K-Pg), which notably marked the end of the dinosaurs.
What has not been clear to scientists is how this event led to the collapse of ocean ecosystems. However, using tiny ocean plankton known as foraminifera, Yale scientists discovered the first direct evidence that the K-Pg mass extinction event coincided with rapid ocean acidification. The impacts of the rapid acidification caused the complete collapse of ocean ecosystems. The research results were published this week in the online journal of Proceedings of the National Academy of Sciences.
Ocean acidification is the result of the ocean absorbing excess carbon dioxide. According to the National Oceanic and Atmospheric Administration, the pH of surface ocean waters has fallen by 0.1 pH units—which represent approximately a 30% increase in acidity. The video below provides a quick explanation of the mechanism of ocean acidification.
Foraminifera are tiny plankton with calcite shells, and they date back in the fossil record hundreds of millions of years. To detect changes in the ocean’s acidity before, during, and after the K-Pg mass extinction event, the scientists used Boron isotope measurements in the foraminifera shells. Their analysis revealed that there was indeed a shift in the ocean’s acidity, and it happened much more quickly than expected—100 to 1,000 years after the meteor impact. Noah Planavsky, Yale scientist and study author, told New York Times reporters that, “It’s flash acidification, and it transformed ecosystems for millions of years. We were shocked that we actually found this.”
This research lays another long-held theory to rest—that volcanic eruptions were partially responsible for the K-pg mass extinction event. If thousands of years of volcanic eruptions occurred before K-Pg, there would have been a steady decline in the ocean’s pH levels leading up to K-Pg. However, as Henehan told Yale reporters, “What we can now show is that there is no real signal of gradual pH decline in the ocean in the lead-up to K-Pg. Our results do not support any major role for volcanic activity in priming the world for extinction.”