Fossil mollusk shells reveal ocean chemistry during the Permian extinction

(ORDO NEWS) — Scientists analyzed the structure of the shells of marine mollusks that lived about 252 million years ago. It turned out that the mass extinction that occurred at that time was not accompanied by an increase in the level of ocean acidity, as previously thought.

Researchers from the University of Texas at Austin (USA) and the University of Hamburg (Germany) have used fossil shells for the first time to study the chemical composition of the ancient ocean.Scientists have not only shown the effectiveness of a completely new tool for studying the history of the planet, but also disproved the popular hypothesis that the great Permian extinction was accompanied by a strong increase in ocean acidity.

The results of the work were published in the journal Scientific Reports.The history of life on Earth is marked by five mass extinctions – periods when most of the planet’s species disappeared in a short time. These events were caused by global climate change.

Thus, the Permian extinction, which occurred about 252 million years ago and wiped out about 90% of the species of living organisms that existed at that time, was the result of large-scale volcanic eruptions in the territory of modern Siberia. In a short period of time, they released huge amounts of carbon dioxide into the atmosphere, which led to a rapid and global warming of the climate, to which most species could not adapt.

Water absorbs carbon dioxide, so part of the emissions could be absorbed by the oceans, this would lead to an increase in the acidity of its waters. However, until now there was no exact geological confirmation of the high acidity of the ocean at the end of the Permian period.

Scientists turned to the analysis of shells of marine mollusks, since the structure of their shells reflects the chemical composition of sea water – and not only in places where sediments settle, but throughout the depths of the ocean.

They examined in detail more than 2,300 fossil shells of sea snails and bivalves that lived during the Permian extinction. Fossils were collected on the territory of Svalbard and Sweden. At the end of the Permian period, these places were a shallow sea off the coast of a single continent. The shells of many molluscs are made of aragonite, a form of calcium carbonate that is particularly sensitive to acid levels.

In several shells, scientists found signs of some growth disorders, but did not find evidence that the mollusks lived in acidic water, because in this case holes, deformations and other changes in thickness and structure would appear in the shells. Thus, the results of the study cast doubt on the hypothesis that the Permian extinction was accompanied by an increase in the acidity of the oceans.

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