The Permian-Triassic extinction event, which happened about 252 million years ago, is popularly known as the Great Dying because of the way it wiped out life on Earth — almost completely ending it. It is the most serious extinction event in history.
Life recovered, however, and new research identifies that sedimentary feeders such as worms and shrimp — animals that feed on organic matter found on the ocean floor — were the first to bounce back in terms of population numbers and biodiversity.
Suspension feeders, which eat organic matter suspended in water, followed much later, according to a detailed dating of trails and burrows on the South China seafloor. This analysis brought a treasure ichnofossils or trace fossils – not real animal remains, but remnants of animal activity.
“We were able to view trace fossils from 26 sections through the entire sequence of events, representing 7 million pivotal years,” says paleontologist Michael Bentonfrom the University of Bristol in the UK.
“By showing details at 400 sampling points, we have finally reconstructed the recovery phases of all animals, including benthos, nekton and these soft-bodied burrowing animals in the ocean.”
Since gentle animals have no skeletons to leave behind, trace fossils are vital in figuring out how these creatures lived. The research team was also able to include body fossils in their research to see how other species started to recover once the depositional feeders were established.
“The crisis at the end of the Permian — which was so devastating to life on Earth — was caused by global warming and ocean acidification, but spore-forming animals can be selected by the environment in ways that skeletal organisms that weren’t,” says paleoecologist Xueqian Feng from the Chinese University of Geosciences.
“Our trace fossil data reveals the resilience of soft animals to high CO2 and warming. These ecosystem engineers may have played a role in the recovery of the benthic ecosystem after severe mass extinctions, which may have triggered the evolutionary innovations and radiations in the early Triassic, for example.”
The team looked at four different metrics when measuring recovery: diversity (the different types of animals), inequality (how varied those different species were), how space was used (use of the ecospace), and how habitats were modified by the animal. (ecosystem engineering).
Life began to return first in the deepest waters. Once deposit feeders largely recovered, suspension feeders such as brachiopods, bryozoans, and bivalves—largely sedentary and often rooted to the ocean floor—followed, but much later.
Even later, the corals started to come back. It took about 3 million years for the soft-bodied sediment dwellers to return to pre-extinction levels.
“Maybe the sedimentary feeders made such a mess of the seabed that the water was contaminated with mud, the churned mud meant that slurry feeders couldn’t settle on the seafloor properly, or the muddy water produced by those sedimentary feeders just clogged the filter structures of suspension feeders and forbade them to feed efficiently,” says geobiology graduate student Alison Cribbfrom the University of Southern California.
The Permian-Triassic extinction event killed about 80-90 percent of Earth’s marine life, so it’s no surprise that the recovery took a long time. By adding trace fossils to the data alongside body fossils, scientists can get a more complete picture of what happened next.
Climate changeglobal warming, a decrease in oxygen and increased ocean acidification are: considered to be the main drivers behind the mass extinction — which of course means that the findings here can teach us more about what’s happening in modern times†
By understanding how certain animals survived and recovered in the aftermath of the Great Dying, we’ll be in a better position to figure out how these creatures might survive the current period of warming we’re going through and which species might be most resilient. .
The research was published in Scientific progress†
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