A mass extinction 252 million years ago may have been the work of a tiny microbe, according to new research from the Massachusetts Institute of Technology (MIT).
The Permian-Triassic extinction event caused 90 percent of all species living on Earth to die off in a short period of time. The Great Dying was the worst of five great extinctions in the history of our planet. Marine invertebrates were particularly affected, especially those species with shells.
Paleontologists argued for decades over the ultimate cause of that global die-off. Volcanoes were often blamed for the extinction, but the ultimate culprit may be a microbe called Methanosarcina. These microscopic lifeforms saw a population explosion and they emitted tremendous quantities of methane into the waters and atmosphere of the Earth. This radically changed the chemistry of the air and oceans to the point where most life could not continue in the new environment.
Volcanoes did erupt more often than normal around the time of the Permian-Triassic extinction event. New research shows this vulcanism may have introduced nickel to the oceans. This element is essential in promoting the growth of Methanosarcina.
Daniel Rothman and Gregory Fournier of MIT lead research into the role the microbe may have played in the Great Dying.
Rothman and his team knew there was a buildup of carbon dioxide in the oceans, which formed the carbon needed for the microbe to proliferate. No one was sure how that gas became more common before the extinction.
Researchers built their final conclusion from three observations. Carbon dioxide was shown to build up over time, which helped disprove the idea volcanoes were responsible for the build-up of carbon dioxide.
"A rapid initial injection of carbon dioxide from a volcano would be followed by a gradual decrease. Instead, we see the opposite: a rapid, continuing increase. That suggests a microbial expansion," Fournier said.
Methanosarcina also developed the ability to turn that carbon into methane in large quantities. Nickel released from volcanoes acted as a catalyst, aiding even greater proliferation of the gas. In addition, the tiny organism carried out gene transfer with a type of Clostridia bacteria, speeding the process.
As methane levels rose in the air, so did concentrations of carbon dioxide in the oceans. This led to an increase in the concentration of carbon dioxide, raising acidity in the marine environment.
Study of the root causes of the Permian-Triassic extinction was published in the Proceedings of the National Academy of Sciences of the United States of America.