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Microbes Trigger Largest Mass Extinction Ever

FILE - Limestone layers in between volcanic ash beds from Meishan, China, during the
FILE - Limestone layers in between volcanic ash beds from Meishan, China, during the "Great Die-Off" (Courtesy: Shuzhong Shen).
Rosanne Skirble
MIT scientists say almost everything on Earth died 252 million years ago in the largest mass extinction on the planet.

While scientists have come up with a number of theories — from asteroids to volcanoes and raging coal fires — the research team from the Massachusetts Institute of Technology says the culprit was a methane-spewing microbe.

According to the team's lead researcher, Daniel Rothman, MIT Professor of Geophysics, massive volcanic eruptions and chemical changes coincided to dramatically change the climate and the chemistry of the ocean.

“When one examines old rocks that were deposited at the time, the results of those geochemical analyses indicate that there was a large influx of carbon into the Earth’s system — that is, the oceans and the atmosphere — and that carbon likely entered system as CO2," Rothman says, explaining that the change happened in the geological blink of an eye — about 60,000 years — killing 96 percent of life in the ocean and 70 percent of life on land in what's known as the Permian-Triassic extinction event — or, simply put, the Great Dying.

The carbon dioxide that erupted from volcanos was a potent greenhouse gas that, in large doses, warms the air and turns oceans acidic. But, Rothman says, the volcanic activity in what is today Siberia cannot solely account for the global geo-chemical change.

“It’s a gross correlation, and the question is how it might be related," he says. "It’s not the only question, but it is the one of the questions we address in our paper.”  

Methane-spewing marine microbes

One answer came from an analysis of the genomic record that revealed a marine microbe that produces methane and could be an important player in the massive die-off.

“Methane-producing microbes had already been present, but this was a particular microbe that could do it a little bit more efficiently than the others," he explains. "And so we’ve hypothesized that it might have been responsible for the outburst of carbon into the system — originally methane — and the methane would have been oxidized to CO2.”

Writing in the Proceedings of the National Academy of Sciences, Rothman and colleagues report that the methane microbes experienced an explosive growth spurt fueled by the mineral nickel, which they found in sedimentary rocks from those Siberian eruptions.

The nickel concentrations rose considerably just before extinction, which would have made a very favorable environment for the methane-producing microbes.

Massive extinction natural event

Unlike today's climate disruption, primarily caused by the carbon pollution of fossil fuel-based power plants, cars and buildings, the Permian-Triassic extinction was a natural event that heated up the Earth’s biological systems.

“It’s not that unusual in the history of life for such things to occur," Rothman says. "The point is that life and the environment interact. They always have and they always will, and we collectively need to be careful how we handle our end of the equation.”

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