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Researchers: Cyanobacteria responsible for Earth’s early oxygen

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cyanobacteria haven in Yellowstone/samspicerphoto, Fotolia

From ScienceDaily:

Earth’s oxygen-rich atmosphere emerged in whiffs from a kind of cyanobacteria in shallow oceans around 2.5 billion years ago, according to new research.

“The onset of Earth’s surface oxygenation was likely a complex process characterized by multiple whiffs of oxygen until a tipping point was crossed,” said Brian Kendall, a professor of Earth and Environmental Sciences at the University of Waterloo. “Until now, we haven’t been able to tell whether oxygen concentrations 2.5 billion years ago were stable or not. These new data provide a much more conclusive answer to that question.”

The new data supports a hypothesis proposed by Anbar and his team in 2007. In Western Australia, they found preliminary evidence of these oxygen whiffs in black shales deposited on the seafloor of an ancient ocean.

The black shales contained high concentrations of the elements molybdenum and rhenium, long before the Great Oxidation Event.

The osmium isotope evidence found in black shales correlates with higher continental weathering as a result of oxygen in the atmosphere. By comparison, slightly younger deposits with lower molybdenum and rhenium concentrations had osmium isotope evidence for less continental input, indicating the oxygen in the atmosphere had disappeared. More.

That may help account for the appearance of very complex life forms 540 million years ago and 600 million years ago.

See also: What we know and don’t, know about the origin of life

and

Animal that stages light display is 600 million years old

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Here’s the abstract:

It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event. A depositional age of 2495 ± 14 million years and an initial 187Os/188Os of 0.34 ± 0.19 were obtained for rhenium- and molybdenum-rich black shales. The initial 187Os/188Os is higher than the mantle/extraterrestrial value of 0.11, pointing to mild environmental oxygenation and oxidative mobilization of rhenium, molybdenum, and radiogenic osmium from the upper continental crust and to contemporaneous transport of these metals to seawater. By contrast, stratigraphically overlying black shales are rhenium- and molybdenum-poor and have a mantle-like initial 187Os/188Os of 0.06 ± 0.09, indicating a reduced continental flux of rhenium, molybdenum, and osmium to seawater because of a drop in environmental O2 levels. Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean. (Public access) – B. Kendall, R. A. Creaser, C. T. Reinhard, T. W. Lyons, A. D. Anbar. Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean. Science Advances, 2015; 1 (10): e1500777 DOI: 10.1126/sciadv.1500777

4 Replies to “Researchers: Cyanobacteria responsible for Earth’s early oxygen

  1. 1
    mahuna says:

    Wait. So there was an unexplained Early Oxygenation Event that ran for some millions of years and then STOPPED.

    And then there was a separate, new Oxygenation Event that started up and has run ever since.

    We have enough trouble trying to explain, chicken-and-egg-wise, how the 2nd, Plant-based, Oxygenation started. But now we have another oxygen generator, apparently unrelated to plants, to explain.

    If this is all happening mechanically (without an intelligent agent), then why did the original mechanism STOP? And why did it stop long before the plants took over?

  2. 2
    J-Mac says:

    Didn’t bacteria need oxygen to survive in the first place? Or evolve from…. I forgot…. I can’t keep up with Darwinian nonsense…

  3. 3
  4. 4
    jimmontg says:

    There are anaerobic bacteria that do not need O2. If you had ever built a Reef Aquarium then you would know about the non O2 bacteria. It grows in the rock and not on it as it doesn’t like high O2 levels. A good reef aquarium will not have any nitrates or nitrites in it as that is what the anaerobic bacteria consumes. They have found bacteria over a kilometer deep in the Earth’s crust and below the sea floor. It doesn’t need O2 either. Yes there are many species of bacteria that don’t need O2.

    The initial bacteria (about 3.6 billion ya) on Earth created O2, but did not need it in it’s free form, just like the anaerobics that live in underground oil deposits do not need free O2. Anaerobic bacteria helps life on this planet in many ways. A healthy reef can actually remove certain amounts of sewage wastes just like wetlands are also able as long as they are not overwhelmed. I’m not trying to sound like it is OK, but watch and observe how long it takes for nature to clean up an oil spill.

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