The oxygen that fauna uses for respiration is molecular oxygen (O2)
dissolved in water.  The H2O molecules are untouched by
respiration.  That's why, if you don't aerate a fish tank, they suffocate.

At 03:23 PM 04/19/2002 -0400, you wrote:
>Mollusks, like fish, need oxygen, and they get it from the water, right?
>
>My question, for all of you learned Conch-Lovers (that's what Conch-L
>stands for, isn't it?), is:
>
>If mollusks and fish take the oxygen out of the H2O, using their nifty
>little gills and mantles and things, then where does the hydrogen
>go?  Why, it must burble up to the surface in gaseous form, where it
>immediately recombines with the oxygen in the air to become a molecule of
>water again.  Then why don't we see the surface of our lakes and ponds
>bubbling away all the time?  Probably because the recombination is too
>quick for the poor human eye to appreciate.
>
>Well, maybe that's not what happens*.  Maybe the aquatic critters have
>some other way of getting their oxygen, if indeed they  do require oxygen
>in their pursuit of life.
>
>But I can't help it -- the thrilling thought immediately leaps to mind,
>why can't we collect all that hydrogen before it escapes back into the
>sea,  in order to fuel our automobiles and power plants?  It takes only a
>modicum of vision to imagine a Better World, free of smog, its ozone layer
>healed, its global heating cooled off, all empowered by those
>multitudinous little maritime marvels that until now all of you shellers
>out there have merely been "cleaning" and then hiding away in the drawers
>of your dusty collections, to be pulled out and admired on special
>occasions.  Instead, let's put 'em to work!
>
>We'd have to cap the lake, you see, with some sort of large plastic
>blanket just below the surface, vented to an expandable collection chamber
>above, from which the gaseous hydrogen would in turn be piped to a
>compression plant on shore that would liquefy and store the stuff in
>convenient pressure bottles, not unlike the propane tanks you see in many
>a back yard.   Of course we'd want to stock the power-pond with the most
>efficient oxygen-guzzling species (the discovery of  which would provide a
>scientific-research vehicle that many of the academically inclined among
>you might want to pursue as an excuse to justify your beachgoing
>hobby),  and there would surely evolve great underwater farms (the running
>of which might appeal to some of the more capitalistically inclined among
>you, as a way of supporting same).   I can even foresee the home of the
>future with a large aquarium in the basement, containing a few giant
>clams, say, or perhaps a large shark, plus miscellaneous other specimens
>added just for looks or to fulfill the lower part of the food chain, all
>flapping their gills, waving their mantles, and breathing away, sopping up
>the oxygen and cranking out the hydrogen that would be captured to run the
>furnace, the air conditioner, and the generator of 110-volt current to
>handle all of life's other necessities.
>
>What say you, shellers?**   Is there a flaw in my scheme, or are we on the
>threshold of the Molluscan Millenium?
>
>Breathlessly yours,
>
>Herb Kahler
>
>
>----------
>* I hasten to add that it's my wife, Laura, not I, who is the sheller of
>the family.  Where mollusks are concerned, I am a complete ignoramus and
>philistine,  whose primary function on those shelling vacations I can't
>avoid  is to trail along behind her, carrying the bag that the treasures
>get dumped in, saying "yes, dear, that certainly is pretty."
>
>** I anticipate a learned response from the Question Man, who in this case
>ought to assume his rightful role as the Answer Man, especially now that
>his porcine flying circus has been shot down.
>


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"Be careful what you want; it might want you."  -- Elvendrums