In a path-breaking discovery, researchers have found that methane-producing microbes may be responsible for the worst mass extinction in earth's history 252 million years ago.
Fossil remains show that about 90 percent of all species on earth were suddenly wiped out - by far the largest of this planet's five known mass extinctions - at that point of time in ancient history.
Now, a team of researchers at Massachusetts Institute of Technology (MIT) may have found enough evidence to show that a form of microbes were the real killers.
Methane-producing archaea called Methanosarcina suddenly bloomed explosively in the oceans, spewing prodigious amounts of methane into the atmosphere and dramatically changing the climate and the chemistry of the oceans.
"The reason for the explosive growth of the microbes may have been their novel ability to use a rich source of organic carbon, aided by a sudden influx of a nutrient required for their growth - the element nickel emitted by massive volcanism just at that time," explained Daniel Rothman, a professor of geophysics at MIT.
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, co-author Gregory Fournier from MIT added.
The carbon deposits show that something caused a significant uptick in the amount of carbon-containing gases - carbon dioxide or methane - produced at the time of the mass extinction.
"That suggests a microbial expansion. The growth of microbial populations is among the few phenomena capable of increasing carbon production exponentially, or even faster," Fournier said.
It turns out that Methanosarcina had acquired a particularly fast means of making methane through gene transfer from another microbe.
Given the right conditions, this genetic acquisition set the stage for the microbe to undergo a dramatic growth spurt, rapidly consuming a vast reserve of organic carbon in the ocean sediments, the researchers noted.
The resulting outburst of methane produced effects similar to those predicted by current models of global climate change - a sudden, extreme rise in temperatures, combined with acidification of the oceans.
In the case of the end-Permian extinction, virtually all shell-forming marine organisms were wiped out - consistent with the observation that such shells cannot form in acidic waters.
The new research was published in the journal Proceedings of the National Academy of Sciences.
