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After an Asteroid Killed the Dinosaurs, Underwater Life Staged a Comeback

Despite waves of destruction and disruption triggered by the impact, marine life just above the crater bounced back within a few years.
A large asteroid that collided with Earth on the Yucatan Peninsula, now in modern-day Mexico, formed the Chicxulub crater and possibly caused the extinction of the dinosaurs.

A large asteroid that collided with Earth on the Yucatan Peninsula, now in modern-day Mexico, formed the Chicxulub crater and possibly caused the extinction of the dinosaurs.

Even after an asteroid more than five miles wide crashed into Earth at some 40,000 mph and blasted a giant crater into Mexico’s Yucatán Peninsula 66 million years ago, signs of underwater life surfaced at the impact site within a few years, according to new research published in the journal Nature.

That is a stunning feat, considering the devastating effects the collision wrought on the rest of the world. The asteroid is believed to have hit Earth with the force of more than 100 trillion tons of TNT, generating a burst of thermal radiation that would have incinerated everything in the vicinity. Waves of ash and soot from the impact then blocked the sun, causing a global winter that killed off more than 75 percent of the species on the planet—including, most famously, all non-avian dinosaurs.

Then came the global warming. According to another recent study, the extra carbon dioxide left in the atmosphere after the ash cleared spiked the planet’s temperature by about 5 degrees Celsius, beginning a warm spell that lasted for some 100,000 years.

Despite such waves of destruction and disruption, life managed to revive. For their study published this week in Nature, Christopher Lowery of the University of Texas at Austin and his colleagues focused on the marine ecosystem of the region directly over the Chicxulub crater itself—what Lowery calls “ground zero” for the asteroid’s impact. After analyzing rock samples drilled from within the crater, which preserved a record of the first 200,000 years after the impact, they found that marine life at the crater bounced back within years after the catastrophe, far more quickly than at sites further from the impact.

“Within 30,000 years, there was already a high-productivity ecosystem established in the crater,” Lowery says, including a robust bloom of phytoplankton (algae) and a diverse community of zooplankton feeding on it. “We found that it was the ecological processes and competition between species in those ecosystems, and all these things that are unique to individual ecosystems, that controlled their recovery”—not the distance from the crater.

Plankton repopulate the Chicxulub Crater in the first years after the impact of the asteroid that caused the end Cretaceous mass extinction. 

Plankton repopulate the Chicxulub Crater in the first years after the impact of the asteroid that caused the end Cretaceous mass extinction. 

Their finding was surprising, as previous research had suggested that it took up to 300,000 years for marine ecosystems in the Gulf of Mexico and the North Atlantic Ocean to rebound after the asteroid hit—much longer than other areas of the globe that were further from the impact site. That seemed to indicate that environmental effects of the impact, such as possible toxic-metal poisoning, might have slowed down recovery on the ocean floor closer to where the asteroid hit.

But the new study suggests that distance from the Chicxulub asteroid impact was not the determining factor in how quickly life rebounded. Instead, it was something about the particular ecosystems themselves—their “internal ecological processes,” as Lowery puts it—that determined how quickly or slowly they were able to recover. Most importantly, Lowery points out, his findings tell us that “There’s really no one-size-fits-all way to recovery that we might expect in the future.”

In other words, understanding how marine life at the crater rebounded even while dinosaurs and their contemporaries were snuffed out could offer critical insight into other mass extinction events. This includes the ongoing disappearance of many of the Earth’s animal species, which many scientists blame on climate change and other effects of humans’ impact on the planet.

“We can use the End-Cretaceous mass extinction event and the recovery after that rapid extinction event as an analogue for the recovery after other rapid extinction events, like the one that we’re currently living through,” Lowery says. “What it suggests is there’s not going to be one single pace of recovery that works across the whole world. We really need to understand each individual ecosystem and how they work. Because you’re going to see some ecosystems that bounce back right away, and some that take a very long time.” 

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