Researcher: Pesky Microbe May Have Caused the Biggest Extinction in History
December 18, 2012 5:00 PM
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Methane-producing bacteria may have leverage nickel from volcanism to flood the atmosphere with methane
It was called "
The Great Dying
I. A Time of Death and Desolation
If that title sounds dire it is because it was indeed a grim time for life on Earth. Occurring about 252 and one-third million years ago, the mass extinction came at a time when life on Earth had become fairly advanced. Terrestrial life consisted of a rich mix of large amphibians (think huge cousins of today's salamanders) and scaly reptilian dinosaur predecessors. The seas teemed with life.
Then some sort of cataclysm swept the globe. Ninety-six out of every one-hundred marine species (96%) went exinct, while seventy out of every one-hundred terrestrial vertebrate species (70%) also bit the metaphorical dust. The exinction to this day remains the most severe mass extinction in Earth's history and what is believed to be the only mass extinction to feature a major extinction of insects -- traditionally among the Earth's most hardy species.
So what caused this severe event?
[Image Source: Climate Sight]
In line with all the
hype and fervor surrounding global warming
, some past researchers have suggested climate change may have played a role. Criticism of this hypothesis has traditionally been that it's improper to assume the markers of climate change -- atmospheric and ocean carbon levels -- as causing ecological changes, when ecological changes can also
cause climate change
Massachusetts Institute of Technology
Professor Daniel Rothman
has become the latest researcher to throw his hat in the paleontological ring, offering up an interesting alternate hypothesis of how such a catastrophic climate change incident may have been triggered, leading to the Earth losing so much biodiversity.
The Great Dying marked the edge of the Permian. Its end ushered in a new era -- the Triassic -- which would become the first of three major historical eras when the land-masses were ruled by large reptiles (dinosaurs).
To look for clues as to what caused The Great Dying, Professor Rothman dug back into sediments from the end of the Permian era. Examing deposits in China, he found something intriguing.
Carbon levels in the sediment indeed appeared to rise quickly. But the interesting part is that they rose so quickly that he feels that the sedimentary analysis rules out change by slower-acting forms of carbon release, such as volcanoes.
He also observed that oceanic nickel levels spiked 251 million years ago, as volcanoes in Siberia dumped tons of molten nickel into the sea.
II. What Caused Carbon Levels to Spike?
Nickel is a ubiquitous catalyst in certain kinds of biochemical reactions. Microorganisms, such as the ocean-based methane-producing bacterium methanosarcina, often use the metal to speed up reactions that produce carbon waste byproducts.
Thus Professor Rothman suggests that methanosarcina likely exploited the rising nickel levels to transform carbon dioxide and hydrogen into methane.
In fact, Professor Rothman believes that methanosarcina fortuitously acquired the its triple metal-catalyzed methane-producing metabolic pathways about 251 million years ago, just as the nickel levels spiked.
Methanosarcina, pictured in an electron micrograph. [Image Source: KRLE]
The loss of atmospheric carbon dioxide would likely have twin adverse impacts -- first as plants require carbon dioxide to produce sugars, there likely would be mass loss of foliage globally; second as methane is a more potent warming gas than carbon dioxide, temperatures likely would have spiked globally.
The researcher's hypothesis was
on Dec. 4 at
the annual meeting
American Geophysical Union
. The meeting was held in San Francisco, Calif. at the Moscone Convention Center.
If he is correct it suggests that methanosarcina could be the most diabolical murderer in history, by far eclipsing mankind's
worst impact in terms of speciation
Not all experts are convinced. Anthony Cohen, a researcher at the Open University in the United Kingdom, comments, '"[For the hypothesis to be correct] there are a lot of assumptions you have to make."
AGU Meeting Schedule
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12/19/2012 1:00:29 PM
well, it is entirely possible there was a large impact
that then helped to cause this
that one two punch would have ejected enough material into the atmosphere to block out the sun.
12/19/2012 1:32:04 PM
Exactly. The evidence for that dual cataclysm is very strong now, after some recent discoveries supporting the impact part. So far, all mass extinctions can be linked to a meteor strike, even the Younger Dryas. If that will remain the case in the future is an open question. But life is very tenacious and hard to mass extinct, unless you get rid of the Sun, like pelting the Earth with meteors; or a massive drop temperatures that bring on an ice age.
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