During the last mass extinction in history, ocean life flourished

After the worst known mass extinction in Earth’s history, marine ecosystems have recovered in just a few million years, researchers reported on Dec. 10. Science. That was millions of years faster than he had previously thought. Evidence that lies in the diverse ancient fossil record found near the city of Guiyang in South China may represent the first foundations of today’s ocean-dwelling ecosystem.

The conventional story has been that the ocean species died out for millions of years after this mass extinction, says paleontologist Peter Roopnarine at the California Academy of Sciences in San Francisco, who was not involved in the research. “Well, it’s not true. the ocean [was] he lives a great deal. “

The Great Dying, or Permian-Triassic Mass Extinction, occurred about 251.9 million years ago, at the end of the Permian period, after a series of massive volcanic eruptions (SN: 12/6/18).

“The oceans have warmed significantly, and there is evidence of acidification, deoxygenation” [causing widespread dead zones]then witchcraft,” said Roopnarine. “there” [were] many toxic elements such as sulfur entering parts of the ocean.

He suffered life at sea. More than 80 percent of marine species have become extinct. Some researchers have even proposed that entire trophic levels — inputs into the web of the ecosystem — may disappear.

Determining how long it will take for life to fully recover in the event of all that damage is a challenge. In 2010, researchers studying fossils from the Luoping biota in China proposed that complex marine ecosystems would fully recover within 10 million years. Later, the discovery of other fossils, such as the Paris biota in the western United States and the Chaohu biota in China, led scientists to suggest that marine ecosystems had restored themselves within just 3 million years.

Then in 2015, a serendipitous discovery narrowed the gap again. Paleontologist Xu Dai, then an undergraduate student at China University of Geosciences in Wuhan, was studying rocks from the early Triassic on a field trip near the city of Guiyang when he split a piece of black shale. Inside the rock he found an amazingly preserved fossil which was later discovered to be a primitive lobster.

The immaculate condition of the arthropod sparked a series of return trips. From 2015 to 2019 Dai, now at the University of Burgundy in Dijon, France, and his colleagues discovered a tiny fossil of life: A predatory fish as long as a baseball bat. In the shells of ammonoids rushes. Conodonts resemble eels. At first clicks. Sponge Bivalves Fossified poo.

And the rewards kept coming. Both below and within the Guiyang biota, Dai and colleagues discovered beds of molar ash. Analysis of the levels of uranium and lead in the ash revealed that the Guiyang biota contained fossils from about 250.7 to 250.8 million years ago (SN: 5/2/22). Morbi was further supported by fossil accounts and the analysis of different forms of carbon in the rocks.

Finding this century’s potpourri of life suggests that marine ecosystems rebounded quickly after the Great Dying, within just 1 million years or so, Dai says.

Alternatively, it may indicate that the extinction event did not wipe out entire trophic levels, says paleontologist William Foster of the University of Hamburg in Germany, who was not involved in the study. “You have this really environmentally stressful world, but some marine ecosystems are surviving.”

Regardless, it seems clear that these ecosystems were difficult. Due to the movement of tectonic plates, the community preserved in the Guiyang biota is located in the tropics of the early Triassic. At that time, the sea surface temperature was close to 35⁰ Celsius, and past research has shown that many organisms migrated to escape the heat. But the discovery of the Guiyang biota challenges what Foster says. Sea creatures “tolerate in a certain way, they adapt.”

According to Dai, fossil evidence may be that the roots of today’s marine ecosystems took hold shortly after the Great Dying. These groups are related to modern fish, lobsters and shrimps, their ancestors, he said. “The oldest time we can find similar seafood is today” [in the time of] in the Guiyang biota. “

But Roopnarine is skeptical. It remains to be seen exactly how the Guiyang biota connects with modern ecosystems, he says. The group of ephemeral fossils could represent a communal life rather than a stable community, he adds, showing that ammonoids and conodonts became extinct.

Further work will help solve many problems with Guiyang’s biota, Dai says. He and his colleagues are bringing the project back to campus this summer for the first time since 2019. When asked if he will have his eyes peeled for another lobster, he replies: “Of course.”