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Scientists Confirm Life Under Antarctic Ice

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  • by Anonymous Coward on Friday August 22, 2014 @09:43AM (#47729233)

    I'm a biogeochemist (haven't worked on this project or in the arctic, but I know about microbial communities and organic matter decay) and while this is certainly interesting, it is not very strange.
    What you have to remember is that organic matter decays very quickly (and some types decay faster than others, e.g. DNA seems to decay faster than lignin), but only if it has plenty of oxygen. For this same reason we still find oil after millions of years, it is anaerobically decayed organic matter. Furthermore, if you look closely at the chemical composition of the oil, you can determine how old it is by looking at how far it has decayed rather than looking at the overall mass which will barely have changed essentially (so rather than seeing C30H60 + 45O2 -> 30CO2 + 30H2O it would look more like C30H60 -> 2C15H30 followed by C15H30 -> C7H14 + C8H16, which are very slow steps)

    In Antarctica, we have a very similar environment, except now our low oxygen concentration isn't because the organic matter was buried under sediment but under ice. Add to this that we have subzero temperatures (low temperatures reduce the rate of organic matter decay) and the case is starting to add up for long term preservation of organic matter. So while this system will certainly run out of organic matter (and thus ammonia and methane), it will do so very slowly.

    Since I don't know the exact individual species involved in this ecosystem it becomes very hard to say which step exactly is limiting the growth. However, I can tell you that ammonia is converted into other more oxidized nitrogen species (such as nitrite and nitrate) relatively easily compared to the rate of methane conversion. So my guess would be that either the limiting step is the methane production, the system lacks enough other nutrients like phosphate (which, interestingly, is generally a limiting factor in marine systems), or there is not enough sulfate (methane is generally broken down by microbes by using sulfate as an oxidizer, if you get a sediment sample with a lot of methane in it, you will generally find not much sulfate remains).

    I hope this helps to clarify a few things, but without knowing the actual microbial community and depositional environment etc. I can't say much for certain about the actual limiting factor.

I am not now, nor have I ever been, a member of the demigodic party. -- Dennis Ritchie

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