Fossil snail shells offer new tool for analyzing ancient ocean chemistry


Date:
January 26, 2022
Source:
University of Texas at Austin
Summary:
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 study is the
first to use shells from fossilized mollusks to investigate ocean
chemistry, demonstrating a new tool that scientists can use to
study the conditions of the planet's deep past.



FULL STORY ==========================================================================
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.


========================================================================== Instead of showing damage or signs of repair -- which would be expected
if the mollusk was surviving in acidic conditions -- the shells were
in excellent shape, according to a study that was published on Jan. 24,
2022, in Scientific Reports.

William Foster, a scientist at the University of Hamburg and former postdoctoral researcher at The University of Texas at Austin Jackson
School of Geosciences, led the research.

The study is the first to use shells from fossilized 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," said
co-author Rowan Martindale, an associate professor at the Jackson
School. "Sometimes these proxies give conflicting results, so we need
multiple, independent measures of ocean conditions." The world's
deadliest mass extinction wiped out about 90% of living species about
252 million years ago at the end of Permian Period. The extinction
was triggered by huge volcanic eruptions in present-day Siberia, which
released large amounts of carbon dioxide into the atmosphere in relatively short amount of time, causing rapid global warming.



==========================================================================
When atmospheric carbon dioxide is high, the ocean can absorb some of the
gas and become more acidic. However, the geologic record is inconclusive
about whether this occurred during the end Permian extinction event.

"Some previous studies based on chemical analyses of rocks had suggested
that the world's seas were acidic at that time, but other geochemical
evidence suggested the opposite," said Foster.

The analysis of the mollusk shells offers a more thorough perspective,
Foster said, because they capture the chemical state of the ocean shortly
after the extinction event from top to bottom, not just where sediment
settled. The s tested for acidification in surface waters by analyzing
larval shells and tested for seafloor acidification by analyzing adult
shells.

The research entailed examining more than 2,300 fossil shells from marine snails and bivalves from under a microscope. And although a handful of
shells record some growth impairment, there were no signs of patched
holes, a tell- tale sign of mollusks living in an acidic environment.

"None show repair marks that would indicate severe acidification in
surface waters or on the seafloor," Foster said.



==========================================================================
The fossils were collected from a site in what is now Svalbard,
Sweden. When the animals were alive, the site was covered by a shallow
sea and the Earth contained just a single massive continent.

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

Marine animals with shells made of aragonite (a type of calcium carbonate mineral) are particularly susceptible to ocean acidification. Scientists
use shells from "sea butterflies," a type of swimming sea snail, to
study ocean acidification in the present and recent past. This study
shows that shells from fossilized mollusk species can be analyzed in
a similar manner, opening the door to more extensive research on ocean chemistry in Earth's past and its connection to climatic events.

"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," said co-author
Richard Twitchett, a professor at the Natural History Museum, London.

The study's additional co-authors are Maria Reistroffer, who conducted
the research while earning a bachelor's degree from the Jackson School,
and Conor Farrell, an undergraduate student at University College Dublin.

========================================================================== Story Source: Materials provided by University_of_Texas_at_Austin. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. William J. Foster, J. A. Hirtz, C. Farrell, M. Reistroffer, R. J.

Twitchett, R. C. Martindale. Bioindicators of severe
ocean acidification are absent from the end-Permian
mass extinction. Scientific Reports, 2022; 12 (1) DOI:
10.1038/s41598-022-04991-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220126165526.htm

--- up 7 weeks, 4 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)