Fossil snail shells offer new tool for analyzing ancient ocean chemistry

A collection of fossil shells from marine snails and clams is challenging a theory that says the world's deadliest mass extinction was accompanied by severe ocean acidification.

The mollusk's shells were in excellent shape, which would be expected if the mollusk was surviving in acidic conditions.

William Foster is a scientist at the University of Hamburg and a former researcher at The University of Texas at Austin Jackson School of Geosciences.

The study is the first to use shells from ancient mollusks to investigate ocean chemistry, demonstrating a new tool that scientists can use to study the conditions of the planet's deep past.

For events that occurred millions of years ago, we have to rely on evidence such as the chemistry of marine rocks and fossils.

About 90 percent of living species were wiped out at the end of the Permian Period. Huge volcanic eruptions in Siberia caused rapid global warming by releasing large amounts of carbon dioxide into the atmosphere.

The ocean becomes more acidic when atmospheric carbon dioxide is high. The geologic record is not conclusive about whether this happened during the extinction event.

Some previous studies had suggested that the world's seas were acidic at that time, but other evidence suggested the opposite.

Foster said that the analysis of the mollusk shells offers a more thorough perspective because they capture the chemical state of the ocean shortly after the extinction event. The s were tested for acidification in surface waters by analyzing adult shells.

More than 2,300 fossil shells from marine snails and bivalves were examined in the research. There were no signs of patched holes, a sign of mollusks living in an acidic environment, despite a few shells recording some growth impairment.

Foster said that there were no repair marks that would indicate severe acidification in surface waters or on the seafloor.

The site where the fossils were collected is now in Sweden. The site was covered by a shallow sea when the animals were alive.

It was exciting to study organisms that lived when Pangea was a supercontinent, said co-author Jamie Hirtz, who recently earned a master's degree from the Jackson School but started working on these fossils when she was an undergraduate student.

The shells of marine animals are vulnerable to ocean acidification. Scientists use shells from sea butterflies to study ocean acidification. The study shows that shells from ancient mollusk species can be analyzed in a similar manner, opening the door to more extensive research on ocean chemistry.

One of the exciting aspects of this research is that we now know we can use fossil shells of aragonitic marine animals from millions of years ago as bioindicators of past ocean acidification.

Maria Reistroffer, who earned a bachelor's degree from the Jackson School, is one of the study's additional co-authors.

More information: William J. Foster et al, Bioindicators of severe ocean acidification are absent from the end-Permian mass extinction, Scientific Reports (2022). DOI: 10.1038/s41598-022-04991-9 Journal information: Scientific Reports Citation: Fossil snail shells offer new tool for analyzing ancient ocean chemistry (2022, January 26) retrieved 26 January 2022 from https://phys.org/news/2022-01-fossil-snail-shells-tool-ancient.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.