Re: 500 million year old poo and Oxygen

Paul Ciszek wrote:
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.


A worm is a tenuous description. Sewer worms, tube worms and the weird worms of the black smoker regions can actually be poisoned by too high levels of oxygen. High sulfur water is not a restrictive factor to animals adapted to it. Cueva Villa Luz in Mexico (home of snotites) have such high levels of sulfur/ and depressed oxygen (episodic- 9-14% in the air) that SCBA is used, with high sulfur water being practically oxygen-free. This cave supports a species of fish which the locals harvest in some sort of festive atmosphere and all sorts of other 'higher' creatures, including bats.
http://www.i-pi.com/~diana/slime/villaluz/


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