About 66 million years ago, the fiery asteroid impact that wiped out dinosaurs - and much of life on Earth - left clues about the planet's ability to bounce back from catastrophe.
Research conducted in part at Penn State has unraveled one of those clues, revealing that new species emerged within several thousand years of the mass extinction. That recovery is much more rapid than what scientists had imagined and illustrates how quickly species can evolve after extreme events, said study co-author Timothy Bralower, a professor in the Department of Geosciences in the College of Earth and Mineral Sciences at Penn State.
The findings published in the journal Geology have implications for understanding ongoing extinctions, estimated to threaten 1 million animal and plant species globally, according to the research team.
"Humans are affecting environments through climate change and other impacts on an enormous scale," said Bralower, a faculty affiliate of the Earth and Environmental Systems Institute at Penn State. "We're especially interested in how the natural world ultimately will recover from the effects we're having on biodiversity today."
Led by Chris Lowery, a research associate professor at the University of Texas Institute for Geophysics, the study centered on ocean sediments collected from six sites in Europe, North Africa and the Gulf of Mexico.
It had been widely thought that it took tens of thousands of years for the first new species to appear after the impact of the asteroid that formed the Chicxulub crater on and just offshore the Yucatán Peninsula in Mexico. The belief stemmed from faulty assumptions about the accumulation of sediments after the impact, according to the team. Focusing on a geologic layer known as the K/Pg boundary - created by the impact's fallout - the researchers used previously published data on an isotope marker that provides a more accurate measure of time. Isotope markers are distinct atoms used in tracking a substance's movements or chemical behavior.
Specifically, the team used the marker Helium-3 to determine more precisely when different species of plankton appear in the fossil record. A rare noble gas, Helium-3 accumulates in ocean sediments at a constant rate, making it a more reliable gauge than traditional ways geologists tell time in rock layers, the researchers said. Bralower explained that Helium-3, which "resides in interplanetary dust that rains down to Earth's surface at a very near constant rate," narrowed the study's results with incredible precision.
Their findings show a new species of plankton, called Parvularugoglobigerina eugubina (P. eugubina), evolved between 3,500 and 11,000 years after the Chicxulub impact, with the timing differing across sites. Other plankton species evolved in the interval, too, some appearing fewer than 2,000 years after the impact, according to the study.
Lowery described the pace as "ridiculously fast." Bralower said it may be reassuring "for the resiliency of modern species given the threat of anthropogenic habitat destruction."
Typically, new species appear on roughly million-year timeframes. The team said the findings are remarkable partly for the speed of recovery identified in the Chicxulub crater, the site of their earlier research. The area was probably most devastated by the impact, according to the researchers.
"These plankton were not even the first step of the recovery after Chicxulub. They had to be consuming something else," Bralower said. "For us, this gives hope that we can build up the blocks of life from damage we're causing to habitats today. That's the hopeful implication."
A U.S. National Science Foundation grant supported the study. Other co-authors are Kenneth Farley of the California Institute of Technology and R. Mark Leckie of the University of Massachusetts Amherst.
