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Dissolving in the Toxic Ocean: How Ancient Extinctions Happened

About 200 million years ago, the rocks that became the Palisades cliffs just across the Hudson River from Manhattan were formed during the volcanic activity that helped tore apart the ancient supercontinent of Pangea. That volcano helped lead to the birth of the Atlantic Ocean while it also contributed to the killing of nearly a quarter of all life on Earth in what is known as the Late Triassic mass extinction.

Marine animals such as salamanders, iguanas and corals suffered huge losses during the extinction period, and scientists have long suspected that Atlantic volcanism was involved. it because of its effects on climate and oceans. But evidence of what exactly killed life remains scant, making it one of the least understood of the so-called Big Five mass extinctions that punctured the history of life on Earth. The earth.

The study was published in January in the journal GeologyEven so, is beginning to fill in the gaps of this prehistoric murder mystery.

By studying rocks in south-west England, a team of scientists has found evidence of two triggers. One is that when the oceans absorb carbon dioxide emissions from volcanic activity, they become so acidic that the shellfish dissolve in the water and die. The other problem is that the oceans lose oxygen and become toxic to all but the most hardened ocean creatures.

“The main question we asked was: What was the specific killing mechanism of marine life in the late Triassic?” Jessica Whiteside, a geochemist at the University of Southampton in the UK, and an author of the new study. “The answers help provide context and perhaps help predict the future ecological and biodiversity impacts of current CO2.

Dr Whiteside describes the discovery of clues in the rocks of the Blue Lias Formation in the UK, which formed post-volcanic.

“What I noticed early on were these strange ghost fossils,” she said. Ghost fossils are impressions of shell-like things still in the rock, but without any remnants of the shells that produced them – an indication that the water-soluble shells are acidic.

Other clues are chemical traces, or “biomarkers,” of a bacteria known to thrive in waters without oxygen and where there are dangerously high levels of a toxin called hydrogen sulfide.

Immersed in toxic waters with no oxygen to breathe, sea creatures – above all decomposing to live – must all perish.

Noah Planavsky, a biochemist at Yale University who was not involved in the study, said the discovery of the biomarkers provided strong evidence of toxic, oxygen-depleted waters. “This is what we can expect in the future,” he added, in our modern oceans.

Stephen Brusatte, a vertebrate paleontologist at the University of Edinburgh, who was not involved in the new study.

“We often think of mass extinctions as these single catastrophic events where there is a lone killer that we can all blame,” Dr. Brusatte said. . “But this study shows that these mass deaths are often nuanced.”

Less obvious is the cause of the extinction on land. Until the late Triassic extinction, crocodilian relatives today dominated terrestrial ecosystems, while early dinosaurs were relatively small players. But after the extinction, the crocodile’s relatives disappeared, and the dinosaurs began to move into the limelight.

Dr Brusatte said: “This part of the story is still little known compared to what is happening in the ocean, and it is fascinating to wonder if there are more killing mechanisms on land. “If so, this could help explain why dinosaurs were able to survive, and then disperse throughout the wasteland world.”

https://www.nytimes.com/2022/02/03/science/extinction-triassic-volcano.html Dissolving in the Toxic Ocean: How Ancient Extinctions Happened

Fry Electronics Team

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