Methane-producing microbes may be responsible for the largest mass extinction in Earth's history

Mar 31, 2014
Methanosarcina
Methanosarcina barkeri fusaro. Credit: public domain

Evidence left at the crime scene is abundant and global: Fossil remains show that sometime around 252 million years ago, about 90 percent of all species on Earth were suddenly wiped out—by far the largest of this planet's five known mass extinctions. But pinpointing the culprit has been difficult, and controversial.

Now, a team of MIT researchers may have found enough evidence to convict the guilty parties—but you'll need a microscope to see the killers.

The perpetrators, this new work suggests, were not asteroids, volcanoes, or raging coal fires, all of which have been implicated previously. Rather, they were a form of microbes—specifically, methane-producing archaea called Methanosarcina—that 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.

Volcanoes are not entirely off the hook, according to this new scenario; they have simply been demoted to accessories to the crime. The reason for the sudden, explosive growth of the microbes, new evidence shows, may have been their novel ability to use a rich source of organic , aided by a sudden influx of a nutrient required for their growth: the element nickel, emitted by massive volcanism at just that time.

The new solution to this mystery is published this week in the Proceedings of the National Academy of Sciences by MIT professor of geophysics Daniel Rothman, postdoc Gregory Fournier, and five other researchers at MIT and in China.

The researchers' case builds upon three independent sets of evidence. First, geochemical evidence shows an exponential (or even faster) increase of 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 it to 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.

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. Some researchers have suggested that these gases might have been spewed out by the volcanic eruptions that produced the Siberian traps, a vast formation of volcanic rock produced by the most extensive eruptions in Earth's . But calculations by the MIT team showed that these eruptions were not nearly sufficient to account for the carbon seen in the sediments. Even more significantly, the observed changes in the amount of carbon over time don't fit the volcanic model.

"A rapid initial injection of carbon dioxide from a volcano would be followed by a gradual decrease," Fournier says. "Instead, we see the opposite: a rapid, continuing increase."

"That suggests a microbial expansion," he adds: The growth of microbial populations is among the few phenomena capable of increasing carbon production exponentially, or even faster.

But if living organisms belched out all that methane, what organisms were they, and why did they choose to do so at that time?

That's where genomic analysis can help: It turns out that Methanosarcina had acquired a particularly fast means of making methane, through gene transfer from another microbe—and the team's detailed mapping of the organism's history now shows that this transfer happened at about the time of the end-Permian extinction. (Previous studies had only placed this event sometime in the last 400 million years.) 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 in the ocean sediments.

But there is one final piece to the puzzle: Those organisms wouldn't have been able to proliferate so prodigiously if they didn't have enough of the right mineral nutrients to support them. For this particular microbe, the limiting nutrient is nickel—which, new analysis of sediments in China showed, increased dramatically following the Siberian eruptions (which were already known to have produced some of the world's largest deposits of nickel). That provided the fuel for Methanosarcina's explosive growth.

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.

"A lot of this rests on the carbon isotope analysis," Rothman says, which is exceptionally strong and clear in this part of the geological record. "If it wasn't such an unusual signal, it would be harder to eliminate other possibilities."

While no single line of evidence can prove exactly what happened in this ancient die-off, says Rothman, who is also director of MIT's Lorenz Center, "the cumulative impact of all these things is much more powerful than any one individually." While it doesn't conclusively prove that the microbes did it, it does rule out some alternative theories, and makes a strong and consistent case, he says.

Explore further: End-Permian extinction happened in 60,000 years—much faster than earlier estimates, study says

More information: Methanogenic burst in the end-Permian carbon cycle, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1318106111

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User comments : 11

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Osiris1
2.8 / 5 (11) Mar 31, 2014
Well we have a bit iof the Siberian t ap methane coming out of speeches by the tea party.... and it smells just as bad..and could result also in species extinctions.
RichardBlumenthal
1 / 5 (12) Mar 31, 2014
How uncannily convenient! Just as the Obama administration is declaring war on cattle wind, we have 'proof' that it can destroy 90% of life on earth! What a happy convergence of pure science and pure politics.
alfie_null
4.5 / 5 (8) Apr 01, 2014
How uncannily convenient! Just as the Obama administration is declaring war on cattle wind, we have 'proof' that it can destroy 90% of life on earth! What a happy convergence of pure science and pure politics.

I dunno. Sure sounds like a conspiracy to me. I heard if you wrap your head in aluminum foil - very tightly - It'll solve the problem - for you, and I guess for the rest of us too.
Anda
3.2 / 5 (5) Apr 01, 2014
What's the news??? Current theories already tell it was a combination of microbes, volcanism and the Siberian Traps.
Found evidence for the first that's all. Congrats
mzso
1.5 / 5 (2) Apr 01, 2014
I don't understand the connection between. It's not explained. CO2 and methane producing archaea.
So they used the CO2 to make methane (with the help of nickel). Then what produced the exponential rise of CO2?
Maggnus
5 / 5 (4) Apr 01, 2014
How uncannily convenient! Just as the Obama administration is declaring war on cattle wind, we have 'proof' that it can destroy 90% of life on earth! What a happy convergence of pure science and pure politics.
That has simply got to be the most spurious, conspiracy laden piles of paranoid misinformation I have ever read!

Well done Richard, you've managed to upstage both Rygg and Uba with this one!
Maggnus
5 / 5 (5) Apr 01, 2014
I don't understand the connection between. It's not explained. CO2 and methane producing archaea.
So they used the CO2 to make methane (with the help of nickel). Then what produced the exponential rise of CO2?

mzso, they didn't use CO2, they used organic carbon and then produced CH4. CH4 oxidizes in the atmosphere over a short period (ten years or so) producing CO2 & H2O. You can read about it here: http://climpol.ia.../methane if you're interested.
mzso
5 / 5 (2) Apr 01, 2014
mzso, they didn't use CO2, they used organic carbon and then produced CH4. CH4 oxidizes in the atmosphere over a short period (ten years or so) producing CO2 & H2O. You can read about it here: http://climpol.ia.../methane if you're interested.

I see. Thanks. It was far from obvious from this article.
ODesign
3 / 5 (2) Apr 01, 2014
So by inference it's possible our man made carbon problems causing global warming today could be enough for another mass extinction? Maybe there's some other small thing that is needed for mass extinction induced by global warming like killing off the microbes that eat this microbe discussed, or the plans to inject sulfur into the stratosphere could be the key element that tips the equations.
mzso
1 / 5 (1) Apr 02, 2014
So by inference it's possible our man made carbon problems causing global warming today could be enough for another mass extinction? Maybe there's some other small thing that is needed for mass extinction induced by global warming like killing off the microbes that eat this microbe discussed, or the plans to inject sulfur into the stratosphere could be the key element that tips the equations.


I think what's needed is actually significant global warming. Which we don't have so far.
aksdad
1.3 / 5 (4) Apr 03, 2014
...it's possible our man made carbon problems causing global warming today could be enough for another mass extinction? Maybe there's some other small thing that is needed for mass extinction induced by global warming...

According to the MIT researchers' theory, what's needed is:

1. Exponential (or greater) growth of carbon dioxide in the oceans,
2. A change in Methanosarcina microbes allowing them to produce methane from carbon dioxide in the water,
3. A sudden influx of a nutrient required for Methanosarcina growth: nickel, emitted by massive volcanism at that time.

We have none of these conditions today and no prediction of such conditions in the future.

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

So far those predictions from global climate models are way, way off.