While dinosaurs stood no chance when a massive asteroid hit Earth 66 million years ago, microscopic plankton bounced back surprisingly fast. The Cretaceous-Paleogene (K-Pg) extinction event devastated ecosystems, wiping out around 75 percent of all life on the planet, but it wasn’t long after this catastrophe that biodiversity began to make a surprise comeback.
A new study published in the journal Geology has come upon evidence that life rebounded just 2,000 years after the K-Pg extinction event, which is when new species of plankton emerged. Although the asteroid impact destroyed so much life, it also set up conditions on Earth that helped plankton evolve rapidly, marking the first step in the rejuvenation of global biodiversity.
Read More: 444-Million-Year-Old Microscopic Fossils Reveal Early Seafloor Recovery After Mass Extinction
Getting Life Back on Track
The asteroid impact that caused the K-Pg extinction event left a massive crater — the Chicxulub crater — in Mexico's Yucatan Peninsula. When it crashed down, it sent an overwhelming amount of debris into the air, reducing the amount of sunlight that reached the surface. This led to a massive reduction in plant life, which prompted a disastrous domino effect up the food chain, according to the Natural History Museum.
Some animals and plants, however, survived these trying times: Small mammals, frogs, avian dinosaurs (which would become birds), and angiosperms (flowering plants) continued living despite the bleak conditions, according to the American Museum of Natural History.
But the true sign of recovery wouldn’t arrive until new species of plankton began to appear. It was previously assumed that it took tens of thousands of years for the first new species to emerge after the impact, but the new study reframes that timeline; in reality, it actually took just a few thousand years for new plankton species to arrive.
“It’s ridiculously fast,” said lead author Chris Lowery, a research associate professor at the University of Texas Institute for Geophysics, in a statement. “This research helps us understand just how quickly new species can evolve after extreme events and also how quickly the environment began to recover after the Chicxulub impact.”
The plankton that survived the mass extinction were generalists that lived in coastal waters, whereas those that went extinct were adapted to more specific environmental conditions in the open ocean.
“After all those specialized open ocean species went extinct after the Chicxulub impact, generalist coastal species were able to move into the open ocean and colonize those environments,” Lowery says. “As they lived there, they began to adapt to the range of unique conditions that exist in the open ocean and thus [developed] into new species.”
Plankton's Rapid Recovery
The researchers behind the study recognized that sediment accumulation was a major factor in the evolution of life after the K-Pg extinction event. Sediments didn’t accumulate the same way before and after the impact, as was once believed; sediments piled up much differently in various places afterwards, due to the drop in calcareous plankton that sank to the bottom of the seafloor and increased erosion of land after the death of most vegetation.
The researchers set out to establish more accurate readings of sediment accumulation by looking at the isotope marker Helium-3 across six sites in Europe, North Africa, and the Gulf of Mexico. They matched up the age of sediments to the first appearance of a plankton species called Parvularugoglobigerina eugubina, commonly used as a marker of recovery following the impact.
They found that this specific plankton species evolved between 3.5 thousand and 11 thousand years after the impact, with the timing varying across sites. The researchers also found that some new species of plankton were cropping up even earlier, just 2,000 years after the impact. They say that between 10 and 20 species of foraminifera — single-celled organisms that float in water — appeared within about 6,000 years of the impact.
Healing Global Biodiversity
According to Lowery, it takes around 10 million years for biodiversity to rebound after a mass extinction event because entire ecospaces need to be reconstructed. The new plankton species that appeared after the K-Pg impact initiated the long path to recovery, as they filled ecological niches left vacant by extinction.
Though the study shows how species can adapt rapidly, the modern loss of biodiversity due to climate change may also take a long time to replenish.
“Current species loss does not (yet) rise to the level of a mass extinction, but if current trends continue and we do cause a Sixth Extinction, rapid speciation at the rate which we observe after the End Cretaceous mass extinction could help rebuild some biodiversity quickly but it won’t be enough to replace what we lost, and the full recovery of life will play out over geologic timescales,” says Lowery.
Read More: Mass Extinction 445 Million Years Ago Paved the Way for Jawed Fishes to Take Over
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
This article references information from the recent study published in Geology: New species evolved within a few thousand years of the Chicxulub Impact
This article references information from the Natural History Museum: How an asteroid ended the age of the dinosaurs
This article references information from the American Museum of Natural History: Dinosaurs Survive!
This article references information from a study published in Science Advances: Algal plankton turn to hunting to survive and recover from end-Cretaceous impact darkness
