Did microbes trigger mass species extinction?

Some scientists think that 252 million years ago an estimated 96 percent of all species were wiped from Earth. One research group suspect that this was due to methane-belching bacteria.

The new thesis is that microorganisms of the family Methanosarcina evolved to become faster at making methane. This was through the acquisition of a gene from another microbe and then reproducing quickly.

Fueled by nickel spewing from Siberian volcanoes, the extra methane produced by the microorganisms would have made the oceans acidic and added sulfur compounds to the air, driving the extinction of many species at sea and on land.

The scientists' case builds upon three areas. First, geochemical evidence suggests a rapid increase of carbon dioxide in the oceans at the time of the so-called end-Permian extinction. Second, genetic evidence shows a change in Methanosarcina at that time, allowing the microorganism become a major producer of methane from an accumulation of carbon dioxide in the water. Finally, sediments show a sudden increase in the amount of nickel deposited at exactly this time. Much of the theory rests on the carbon isotope analysis.

Commenting further, scientist Dr Gregory Fournier from the Massachusetts Institute of Technology (MIT) told The Guardian: "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. The growth of microbial populations is among the few phenomena capable of increasing carbon production exponentially, or even faster."

The new theory has been reported to the journal Proceedings of the National Academy of Sciences. The paper is titled “Methanogenic burst in the end-Permian carbon cycle”.