It is commonly believed (or based on few evidences) that atmospheric oxygen built up because of extensive photosynthesis.

I am skeptical about this theory that biotic factors are solely responsible for creating 21% of atmosphere (around 40 million moles of oxygen) and I couldn't find any research articles which tried to model this process; the theory itself doesn't seem complete.

The present theory doesn't take into consideration the possibility that aerobic respiration would have co-evolved with oxygenic-photosynthesis and how the atmospheric oxygen levels stabilized at 21%. It is not illogical to assume that because cellular concentrations of oxygen will be high in cyanobacteria; it is possible that using oxygen as electron acceptor is a mechanism of preventing oxidative damage.

Another point, though it is not a logical justification to doubt the theory; it just seems too astoundingly unbelievable that life on earth was dependent on an organism? How did cyanobacteria flourish so much? How did photosynthesis overtake oxygen production by abiotic reactions such as UV photolysis of water (which seems plausible)?

Assuming that population of cyanobacteria is limited by total available water (which will always be less than the total sea surface area x ~2m [limnetic zone] ), 12 hours of available light, and possibility of coevolution of aerobic respiration, how much time would it take to produce this much of oxygen. Is there any study which quantitatively proves this hypothesis ?

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    The downvote is probably because the question isn’t very clear and your justification for doubting the evidence is incoherent, hard to understand and makes quite a few unfounded assumptions. Worst, it gives no actual justification for doubting the established theory: 1 billion years is a heck of a long time, and even taking into account that 99.9% of the produced oxygen is immediately consumed I don’t see why this would make this buildup implausible. Have you got a calculation showing the opposite? Jul 3, 2013 at 9:58
  • because there is no clear explanation for why the theory is absolute. You ask for a calculation. I didn't see any calculation which supports the established theory too (i couldn't find by googling). And the purpose for asking the question is also to know if someone is familiar with studies which have measured these parameters so that I can calculate myself and see.
    Jul 3, 2013 at 10:30
  • Regarding the coherence of the question: I'll try to put it in a better way. But it is a request that you let me know if the question needs rephrasing or I'll never know what is wrong.
    Jul 3, 2013 at 10:36
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    I hear you re: commenting before a downvote, or at least after. That said, I also agree with @KonradRudolph. Your links are a good place to start, but only that. Did you read the references Wikipedia lists? Did you use Google Scholar, or other means to search scientific/scholarly literature? Did you look in any recent textbooks on geology (or related fields - astronomy, planetary science, atmospheric science, etc.)? This is a complex topic, and noone said theories are 'absolute', but .. y'know .. do your homework before you start questioning things. Or post on a different SE (about science).
    – hunter2
    Jul 3, 2013 at 11:33

1 Answer 1


There wasn't initially a problem with the Oxygen being released as the quantity of Iron on earth reacted with the Oxygen forming Fe2+ and Fe3+ compounds first. Only once all the available Iron had reacted with Oxygen did the Oxygen start building up in the atmosphere, but the rate of Oxygen production from all the Cyanobacteria on the planet by that stage was rather large.

There evidence for this is oxidised Iron compounds appearing sometime after the evolution of cyanobacteria, and pre-dating the free oxygen in the atmosphere which is given in the article you linked to.

If you want to do a rough estimate, this paper claims 25 Giga tons of carbon from CO2 are fixed each year. This is 2.1e+12 moles of Carbon, which should then liberate the same number of moles of O2. The atmosphere contains 5.1480×1018 kg , of which Oxygen makes up 21% by volume, or 23% by weight. So 1.6e+20 moles of Oxygen. The ratio then means that it would take approximately 7,600,000 years for the current rate of production of Oxygen to take the atmosphere from 0% Oxygen to the current 21% Oxygen. This is consistent with the ~50 million years proposed for the timing from Oxygen starting to build up in the atmosphere to the Great Oxygenation Event

  • Please add references for the first two paragraphs.
    – user5582
    Jul 1, 2013 at 12:45
  • O2 production rate may not be same as CO2 fixation rate.. They are not directly coupled, right. And we are ignoring respiration; oxygenic respiration should have co-evolved and it would consume some oxygen. I would be grateful if you can share an article which reports oxygen yield per biomass of cyanobacteria per time [I couldn't find one]
    Jul 1, 2013 at 12:59
  • Even if we assume that the Iron oxidation theory is correct and free oxygen accumulated a little late, the cellular oxygen concentrations must be high enough for causing damage.
    Jul 1, 2013 at 13:11
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    Well O2 is coupled to CO2 fixation, less any used in respiration. Assuming that O2 production had just evolved, there would be nothing which used oxygen to respire immediately; oxygen is toxic to anaerobic life and would be removed as a waste product.
    – Nick
    Jul 1, 2013 at 13:15
  • Well.. the light reactions produce NADPH and ATP (3 moles of ATP and 2 moles of NADPH per mole of Oxygen liberated). There are processes other than Calvin-Benson cycle that consume ATP and NADPH. Nonetheless, it is incorrect to assume that 1 mole of O2 is liberated per mole of CO2 fixed. If you are sure about it please let me know the references. This paper pretty much suggests that there is no 1:1 O2/CO2 yield..
    Jul 3, 2013 at 7:32

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