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About 420 million years ago, devastating mass extinction swept through 23% of the world's marine animals. Scientists have limited many of the most likely causes of massive extinction. Basaltic events due to floods (volcanic eruptions), asteroid collisions and sea-level falls are the most likely causes of mass extinction, although several other known events may also contribute to this.
Scientists from Florida State University confirmed that this event, called the Lau / Kozlowskii extinction, was caused by a well-known culprit: the rapid and widespread depletion of oxygen in the oceans of the world.
The survey addresses a long-standing paleoclimate problem and raises serious concerns about the ruinous fate that could occur in our modern oceans if well-established deoxygenation patterns persist and accelerate.
Geochemical methods such as the thallium isotope, the manganese concentration and the sulfur isotope measurements play a vital role in solving this mystery. Scientists have taken measurements on key sites in Latvia and Sweden and reconstructed a chronology of ocean deoxygenation with regard to the Lau / Kozlowskii extinction and the resulting changes for the global carbon cycle .
The group's new and surprising discoveries have confirmed their unique theory that a decline in ocean oxygenation could be at the root of the record of extinction. Their multiproxy estimates have established a clear association between the steady flow of deoxygenated waters and the clever nature of the progression of extinction – its beginning in communities of deep-water organisms and its eventual spread to shallow water bodies.
Their reviews also revealed that the eradication was probably partially determined by the expansion of the sulphidic sea conditions.
Chelsie Bowman, a doctoral student at the University of the Soviet Union, who led the study, said: "For the first time, this research provides a mechanism to steer the observed phase-out event, which coincided with the deoxygenation of the oceans and was followed by more severe and toxic ocean conditions with sulphides in the water column ".
Co-author Jeremy Owens, Assistant Professor in the Department of Earth, Ocean and Atmospheric Sciences, said: "With the extinction of Lau / Kozlowskii's oxygen-free oceans, it constitutes a disconcerting precursor to the increasingly deoxygenated waters observed in the world today. There are still important lessons to be learned from the ecological crises of the distant past. "
"These works provide further evidence that the initial deoxygenation in the ancient oceans coincides with the onset of extinction events. This is important because our observations of the modern ocean suggest that there is a widespread deoxygenation that could cause more stress to organisms requiring oxygen and perhaps the first steps towards another extinction. of marine mass. "
The study is published today in the journal Geology.
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