500 million year old poo and Oxygen


In article <VA.00000f09.0b343d10@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Aidan Karley <doIlookDAFTenoughTOpost@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
http://www.thelocal.se/article.php?ID=3542&date=20060412
Published: 12th April 2006 18:14 CET

Swedish scientists have found half-billion-year-old droppings thought
to be from an aquatic worm and hope the discovery will contribute to
the understanding of prehistoric ecosystems, researchers announced on
Wednesday.

Some people think that the development of guts capable of producing
pelleted poo was a major geochemical event, with the high mass of
coprolites and
their high organic content acting in synergy to remove carbon from the
atmosphere and biosphere, helping O2 levels to climb around the start of the
Phanerozoic (reasonably well accepted, these days), and so enabling the
development of new, more complex body plans.

1) How much free oxygen was needed for the worms to exist in the
first place? I assume that there is a direct relationship between
oxygen in the air and oxygen dissolved in seawater, so how much
would have been in the air back then?

2) A sort of related question: They have found another sealed
underground ecosystem, in Israel this time, with bacteria as
the "primary producers". Where do such ecosystems get their
oxygen? So far as I know, photosynthesis is the only autotrophic
process that produces free oxygen. Last time I tried to ask
this question, I tried to find an appropriate biology newsgroup
and none of them seemed to fit.

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