• MIT professor of geophysics Daniel Rothman stands next to part of the Xiakou formation in China. His right hand rests on the layer that marks the time of the end-Permian mass extinction event. Samples from this formation provided evidence for large amounts of nickel that were spewed from volcanic activity at this time, 252 million years ago.

    MIT professor of geophysics Daniel Rothman stands next to part of the Xiakou formation in China. His right hand rests on the layer that marks the time of the end-Permian mass extinction event. Samples from this formation provided evidence for large amounts of nickel that were spewed from volcanic activity at this time, 252 million years ago.

    Photo courtesy of Daniel Rothman

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  • A photo of the permian triassic boundary at Meishan, China. This photo shows the limestone beds in between the volcanic ash beds that the researchers were able to date.

    A photo of the permian triassic boundary at Meishan, China. This photo shows the limestone beds in between the volcanic ash beds that the researchers were able to date.

    Photo: Shuzhong Shen

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Ancient whodunit may be solved: The microbes did it!

MIT professor of geophysics Daniel Rothman stands next to part of the Xiakou formation in China. His right hand rests on the layer that marks the time of the end-Permian mass extinction event. Samples from this formation provided evidence for large amounts of nickel that were spewed from volcanic activity at this time, 252 million years ago.

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


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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 carbon, 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 Science 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 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 it to become a major producer of methane from an accumulation of organic carbon 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 geological record. 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 organic carbon 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 burst of methane would have increased carbon dioxide levels in the oceans, resulting in ocean acidification — similar to the acidification predicted from human-induced climate change. Independent evidence suggests that marine organisms with heavily calcified shells were preferentially wiped out during the end-Permian extinction, which is consistent with acidification.

“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.”

John Hayes, a researcher at Woods Hole Oceanographic Institution who was not involved in the research, says this work is “a remarkable combination of physics, biochemistry, and geochemistry. It grows out of years of outstanding and patient work that has provided a highly refined time scale for the events that accompanied Earth’s most severe cluster of extinctions.”

Hayes adds that the team’s identification of one organism that may have been responsible for many of the changes is “the first time that the explosive onset of a single process has been recognized in this way, and it adds very important detail to our understanding of the extinction.”

While no single line of evidence can prove exactly what happened in this ancient die-off, says Rothman, who is also co-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.

The research was supported by NASA, the National Science Foundation, the Natural Science Foundation of China, and the National Basic Research Program of China.


Topics: Mass extinction, Methane, Microbes, Permian period, Climate

Comments

Well ; The MIT Geophysicists theory simply lacks the fundamental understanding in `evolutionary `direction as well as `thermodynamics of our universe` ; in other words the evolutionary leading(guiding) incentive/motive has always been source of `Energy` -food that is- and without energy source(food) there will be no evolution towards diversification of living things over time but a `bottle neck` , this fundamental principle of evolution applies `Archaea` too of course , acidification of the oceans is the first requirement so the `energy/food` source of `Archaea ` will be abundant , acidification is the `leading(guiding) event of extinction NOT other way around , simply you can not create food(energy) to sustain life –from nothing- it has to be `external source` because you can not self sustain or self create energy from nothing .

The external source which has to be the `sun`s radiation energy ` or celestial events related chemical reactions , like volcanic activity etc . ; fundamentally biologic systems(living matter) has always been AGAINST the fundamental `entropy principle` of nonliving matter of our universe ; in which(living matter) the entropy always `decreases` towards to `Maximum Orderliness with Maximum energy` that the very energy needed for orderliness comes from non living matter –sun`s radiation , volcanic activity related chemical processes , heat , inorganic chemical processes etc . In other words without energy living matter can NOT create its own self sustaining energy , energy always comes from the nonliving things in our universe , the fundamental flow direction of energy is from nonliving matter towards living matter as always with not even a single exception to this rule exist in our Earth with life forms . As you may know the fundamental principle of Entropy in our Universe is Minimum energy with Maximum Randomness since the Big Bang 13,8 billion years ago ..

So MIT Geophysicists obviously need to comprehend fully `what living things are all about in this universe` in other words `biology` ` fundamentals of evolution` and `the second law of thermodynamics particularly` ; before making any claim on their theory . So the Permian mass extinction 252 million years ago simply CAN NOT be created (initiated) by `Archaea` life forms or self sustain once started by Archaea life forms simply because all living things need `energy` from nonliving things first .. Abundant amount of (Archaea bacteria) they observed during Permian extinction period are simply innocent bystanders –benefactors – of Permian environmental change which is primarily and potentially originating from `nonliving things of our universe` like intense and sustained volcanic activity and chemical energy(food) created by that activity ...

Am I being clear enough to explain the fundamentals of living and nonliving things in Thermodynamic terms in our Universe ; particularly the –flow direction of energy(food source) for the living things ? .. Of course we re not talking `symbiotic energy exchange ` or ` energy flow in between living things like the lower life forms is being the main food source for the higher life forms ; in other words inter dependent food(energy) cycle , we are talking about the `Bottom of the totem poll ` when the nonliving energy is being transferred to the living Archaea life forms and its fundamental unilateral flow `direction` of energy for the fundamental principle of Maximum energy and Maximum Orderliness for the life forms , but not the other way around . For example ; for a good analogy for you ; like good old `Photosynthesis ` and the fundamental source of photosynthetic energy from our sun`s radiation , algae bacteria's simply can not create its own `light source` so to speak to sustain itself , the energy HAS TO come from the sun , without sun`s radiation and its energy flow through algae`s chloroplast there will be NO algae . So anytime you see increased `Archaea` bacteria during Permian extinction –that is simply a bystander- follower of the flow direction of energy to the living things , but NOT the creator of it`s own energy source to self sustain its life form and cause Permian Mass Extinction 252 Million years ago ...

Thank you

Wow that is amazing and fascinating!

All living things do in fact need energy from nonliving things first- the sun. You can not build an argument ruling out this theory without more compelling evidence. Life is forced to evolve in a way to sustain life or it expires, but this does not rule out the evolution of life forms which render an environment hostile to other life forms. This is yet another reason why any planets biosphere is so delicately balanced and unpredictable.

Besides, the story makes it clear that the bacteria are merely the proximate cause of the extinction. The ultimate causes lie elsewhere, of course. But the idea of "higher" forms of life being bumped off by a big methane belch from Archaea, of all people, is scary.

In my opinion there are two aspects of this subject that would deserve further elucidation.

On the one hand, there is the possibility of an isotopic fractionation of the Siberian volcanic gases, in their travel through the cracks of the Earth’s crust, whose pattern could possibly fit the exponential shape of the curve of carbon growth.

On the other hand, there is the difficulty in accepting an exponential growth in the size of the Methanosarcina archaeal population, responsible for the methanogenesis stage, without previously justifying a simultaneous and similar growth in the sizes of the bacterial populations responsible for the preceding stages of acetogenesis and acidogenesis, following the hydrolysis of the organic material in the marine sediments.

With regard to the possibility of isotopic fractionation of the Siberian volcanic gases,
it would be much enhanced if it turned out to be true the suggestion made by Tommy Gold - in his book "The deep, hot biosphere" - about the carbon dioxide, which is predominant in the composition of volcanic gases.

According to Gold, it would be possible that carbon dioxide were the resulting product of the oxidation by the rocks of methane originating from the upper mantle of the Earth. This methane would be of a primordial and abiogenic origin, similar to the liquid one found in the lakes and rivers of Titan.

Later developments, such as the successful synthesis of methane in the laboratory - in conditions of pressure and temperature similar to the ones existing in the upper mantle of the Earth, as well as the detection of plumes of methane in the atmosphere of Mars, tend to give credence to the hypothesis of Gold.

If this were the case, the probability of isotopic fractionation would be much higher, not only because of the longer path for it to take place, but also because the potential for isotopic fractionation of methane is greater than that of carbon dioxide, due to the greater difference of the molecular weights corresponding to the two carbon isotopes.

As a consequence, a possibility would exist that methanogenesis - of an abiogenic nature - were at the root of the end of Permian extintion.

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