Researchers studying ancient burrows and pathways in the seafloor have found that bottom-burrowing animals were among the first to bounce back after the mass extinction at the end of the Permian.
In a new study, published today in the journal scientific progressResearchers from China, the US and the UK reveal how marine life recovered from the event, which killed more than 90 percent of Earth’s species, through their observations of trace fossils.
Life was devastated by the mass extinction at the end of the Permian 252 million years ago, and the recovery of life on Earth took millions of years for biodiversity to return to pre-extinction levels. But by examining trails and burrows on the South China seafloor, the international team was able to summarize marine life’s resurgence by identifying what animal activity occurred when.
Professor Michael Benton of the University of Bristol’s School of Earth Sciences, a contributor to the new paper, said: “The mass extinction at the end of the Permian and the recovery of life in the early Triassic have been very well documented in all of southern China.
“We were able to view trace fossils from 26 sections through the whole sequence of events, representing seven million pivotal years, and show details at 400 sampling points. We finally reconstructed the recovery phases of all animals, including benthos, nekton, as well as these soft-bodied burrowing animals in the ocean.”
dr. Xueqian Feng of the China University of Geosciences in Wuhan led the research and his focus was on ancient caves and trails. He explained: “Track fossils such as tracks and burrows mainly document soft-bodied animals in the sea. Most of these soft-bodied animals had no or poor skeletons.
“There are some amazing places in southern China where we find huge numbers of beautifully preserved trace fossils, and the details can show the behavior of infauna ecosystem engineering, as well as their feedback effects on the biodiversity of skeletal animals.”
Professor Zhong-Qiang Chen, director of the study, said: “The trace fossils show us when and where soft-bodied burrowing animals thrived in this early Triassic greenhouse world.
“For example, elevated temperatures and prolonged anoxia coincided with low values of behavioral and ecological diversity across the Permian-Triassic boundary, and it took about 3 million years for ecological recovery of soft animals to match pre-extinction levels.”
Professor David Bottjer, a contributor to the study at the University of Southern California, added: “One of the most remarkable aspects of the Southern China data is the extent of ancient environments that we were able to sample.
“Differential responses of infauna ecosystems to variable environmental controls may have played an important but hitherto little appreciated evolutionary and ecological role in recovery in the hot early Triassic ocean.”
dr. Chunmei Su, another contributor, said: “The mass extinction has killed more than 90 percent of the species on Earth, and we see that in the catastrophic reduction in the ecological function of the surviving animals in the ocean.
“In the beginning, there were only a few survivors and recovery began in deeper waters. The nekton recovery occurred at the same time as the full revival of infaunal ecosystem engineering activities.”
Alison Cribb, a collaborator with the University of Southern California study, added: “The first animals to recover were bulk feeders such as worms and shrimp. The recovery of suspension feeders such as brachiopods, bryozoans and many bivalves took much longer.
“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.”
Professor Chen added: “And some animals, such as corals, had completely disappeared. Coral reefs did not return until much later.”
dr. Feng concludes, “Why is it important to understand these great mass extinctions from the geological past?
“The answer is that the late Permian crisis — 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 were not.
“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.”
Mysterious Climate Behavior During Earth’s Most Severe Mass Extinction Explained
Resilience of Infaunal Ecosystems during Early Triassic Greenhouse Earth, scientific progress (2022).
Provided by the University of Bristol
Quote: Shrimp and worms among first animals to recover from greatest mass extinction (2022, June 29) retrieved June 29, 2022 from https://phys.org/news/2022-06-shrimps-worms-animals-recover-largest.html
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