The Dinosaur-Killing Asteroid Acidified the Ocean in a Flash

What occurred to the dinosaurs when an asteroid about six miles vast struck Earth some 66 million years in the past in what’s at this time Mexico is well-known: It wiped them out. But the precise destiny of our planet’s various ocean dwellers at the time — shelly ammonites, large mosasaurs and different sea creatures — has not been as properly understood.

New analysis now makes the case that the similar incident that helped carry an finish to the reign of the dinosaurs additionally acidified the planet’s oceans, disrupted the meals chain that sustained life underwater and resulted in a mass extinction. The examine, printed Monday in Proceedings of the National Academy of Sciences, goals to shore up the speculation that the Chicxulub occasion’s destruction of marine life — the results of sulfur-rich rocks depositing acid rain into the oceans — was simply as extreme as the fireplace and fury it delivered to land.

“It’s flash acidification, and it transformed ecosystems for millions of years,” mentioned Noah Planavsky, a biogeochemist at Yale and considered one of the examine’s authors. “We were shocked that we actually found this.”

The influence of the Chicxulub asteroid — so named for the crater it carved out round the Gulf of Mexico — despatched columns of rock into Earth’s environment, incinerated the planet’s forests and drove tsunamis far throughout the oceans. But the connection between the crash and the marine extinction has been much less strong.

Dr. Henehan and his team measured the boron, and found that the relative proportions of two isotopes of the element changed abruptly right at the time of the impact. In shells like these, Dr. Planavsky explained, proportions of the boron isotopes shift when the acidity of the oceans rises. And because this ancient shift happened in the first 100 to 1,000 years after the impact, it means the oceans became acidic practically overnight.

The flash acidification would have devastated organisms that formed the foundations of ecosystems, leading to problems for other creatures like the ammonites that lived higher up the food chain.

“This is a big leap forward,” said Chris Lowery, a paleoceanographer at the University of Texas at Austin who was not involved in the new work.

The study offers evidence of what sustained the marine extinction after the asteroid impact got things rolling. That, and it confirms that the asteroid triggered the extinction in the first place.

Around the time that the asteroid struck, there was intense volcanic activity in what is today India, causing over 200,000 cubic miles of lava to be disgorged over the course of about a million years. For a long time, it was not clear if the marine mass extinction stemmed from changes wrought by the volcanism or by the asteroid. But because the boron shift happened exactly at the boundary, it is now obvious that the asteroid had the bigger effect.

“It’s very, very strong evidence that the ocean acidification was caused by the impact and not volcanoes,” Dr. Lowery said.

The flash acidification and mass extinction, though ancient events, are relevant to our modern world. According to reports from the United Nations Intergovernmental Panel on Climate Change, human emissions of carbon dioxide are not only warming the planet, but also acidifying the oceans. And that modern acidification, Dr. Planavsky says, is happening at a rate and scale comparable to the asteroid-triggered acidification. A similar result, he said, “is on the extreme end of what we could get in the next 100 years.”

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