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                 Microbes Trigger Largest Mass Extinction Ever

   by Rosanne Skirble

   MIT scientists say almost everything on Earth died 252 million years
   ago in the largest mass extinction on the planet.
   While scientists have come up with a number of theories -- from
   asteroids to volcanoes and raging coal fires -- the research team from
   the Massachusetts Institute of Technology says the culprit was a
   methane-spewing microbe.
   According to the team's lead researcher, Daniel Rothman, MIT Professor
   of Geophysics, massive volcanic eruptions and chemical changes
   coincided to dramatically change the climate and the chemistry of the
   ocean.
   "When one examines old rocks that were deposited at the time, the
   results of those geochemical analyses indicate that there was a large
   influx of carbon into the Earth's system -- that is, the oceans and the
   atmosphere -- and that carbon likely entered system as CO2," Rothman
   says, explaining that the change happened in the geological blink of an
   eye -- about 60,000 years -- killing 96 percent of life in the ocean
   and 70 percent of life on land in what's known as the Permian-Triassic
   extinction event -- or, simply put, the Great Dying.
   The carbon dioxide that erupted from volcanos was a potent greenhouse
   gas that, in large doses, warms the air and turns oceans acidic. But,
   Rothman says, the volcanic activity in what is today Siberia cannot
   solely account for the global geo-chemical change.
   "It's a gross correlation, and the question is how it might be
   related," he says. "It's not the only question, but it is the one of
   the questions we address in our paper."
   Methane-spewing marine microbes
   One answer came from an analysis of the genomic record that revealed a
   marine microbe that produces methane and could be an important player
   in the massive die-off.
   "Methane-producing microbes had already been present, but this was a
   particular microbe that could do it a little bit more efficiently than
   the others," he explains. "And so we've hypothesized that it might have
   been responsible for the outburst of carbon into the system --
   originally methane -- and the methane would have been oxidized to CO2."
   Writing in the [1]Proceedings of the National Academy of Sciences,
   Rothman and colleagues report that the methane microbes experienced an
   explosive growth spurt fueled by the mineral nickel, which they found
   in sedimentary rocks from those Siberian eruptions.
   The nickel concentrations rose considerably just before extinction,
   which would have made a very favorable environment for the
   methane-producing microbes.
   Massive extinction natural event
   Unlike today's climate disruption, primarily caused by the carbon
   pollution of fossil fuel-based power plants, cars and buildings, the
   Permian-Triassic extinction was a natural event that heated up the
   Earth's biological systems.
   "It's not that unusual in the history of life for such things to
   occur," Rothman says. "The point is that life and the environment
   interact. They always have and they always will, and we collectively
   need to be careful how we handle our end of the equation."
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   [2]http://www.voanews.com/content/microbes-trigger-largest-mass-extinct
   ion-ever/1885923.html

References

   1. http://www.pnas.org/content/early/2014/03/27/1400668111
   2. http://www.voanews.com/content/microbes-trigger-largest-mass-extinction-ever/1885923.html