Ancient whodunit may be solved: Methane-producing microbes did it!

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Methane-producing microbes may be responsible for the largest mass extinction in Earth's history. 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. It turns out that Methanosarcina had acquired a particularly fast means of making methane, 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.

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 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 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 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 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."

Written By: Science Daily
continue to source article at sciencedaily.com

5 COMMENTS

  1. At the bottom of the deep ocean there are apparently huge deposits of methane producing material from decaying matter deposited over billions of years, which, when the Earth’s temperature rises above a certain level will start to float to the surface.

    After 252 million years a sixth extinction?

    I wonder who the prime suspects are this time?

  2. @OP 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.

    This article is hype!!! It has long been known that the Permian mass extinction (the Great Dying), was caused by multiple events lining up in the same direction to warm the planet.

    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.

    Increases in atmospheric volcanic CO2 are thought to have added to Solar and orbital cycles to start the initial warming,

    Milankovitch Cycles and Glaciation – http://www.indiana.edu/~geol105/images

    .. .. leading to a Clathrate gun release of methane when a temperature trigger threshold was passed.

    Methane is about 10 times stronger than CO2 as a greenhouse gas, but is broken down more quickly as it is oxidised. A sudden bloom of methane producing microbes could have added to the other factors in the Permian extinction, but this article hypes the issue.

    There are also primordial natural sources of methane in planetary formation other than those generated by life.

    http://saturn.jpl.nasa.gov/science/index.cfm?SciencePageID=75

    Titan’s atmosphere is mostly nitrogen (about 95 percent) and methane (about 5 percent), with small amounts of other carbon-rich compounds. High in the atmosphere, methane and nitrogen molecules are split apart by the sun’s ultraviolet light and high-energy particles accelerated by Saturn’s magnetic field, and the products of this splitting recombine to form a variety of organic molecules. (Organic molecules contain carbon and hydrogen, and often include nitrogen, oxygen and other elements important to life on Earth.)

    • In reply to #3 by Alan4discussion:

      @OP 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, s…

      I stand corrected; and thank you for that reminder.

      However, the deep ocean bed deposits still remain vulnerable to chemical reactions which could, and in all likelihood would, be triggered by global warming.

      Something I think is worth keeping in the forefront of our minds.

      And dare I say it, communicating to the powers that be.

      S G

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