Yeerks don't live in deep or undisturbed water, they live in shallow pools that have a circular current (described in a few books where the Animorphs are IN the pool) and are a roil of activity from swimming Yeerks.
Okay, time for a little chemistry.
Does mixing the water help? A little. It pulls oxygenated water away from the surface and replaces it with less oxygenated water. The lower average concentration at the surface means less dissolution back into the air. Maybe good for a 10% increase in rate; more for deeper pools.
But the big factor would be surface area.
An adult human has about 160 square meters of respiratory surface area. At rest, about 20% of respiration goes to the brain; that's 32 square meters. 46 cubic centimeters of oxygen per minute.
That's a lot more real estate than your typical pool has. An olympic-sized swimming pool (hey, I had to go there) has enough surface area to support about 40 human brains (wow this is getting weird). So the question is how big's a Yeerk?
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http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Pulmonary.htmlhttp://faculty.washington.edu/chudler/facts.html[/spoiler]
Well, if we figure they're about the size of a big banana slug, that's somewhere in the neighborhood of 70 to 100 grams. If we use that figure of 3.3 cc/min/100g and a 70g Yeerk, that's 2.3 cc/minute. 5% of a human brain. Our olympic-sized swimming pool has surface area for 800. Not exactly a "mass," more a "sprinkling." Over three cubic meters of open water for each.
(3,200 liters and a mule...)
There is oxygen in water, hence the O part in H2O.
Wrong type of oxygen. It has to be diatomic O
2, otherwise the chemistry doesn't work.
she guesses it's through her skin.
I agree. That's how banana slugs breathe.
sapping oxygen from a host's brain would be a pretty damn big health risk for the host.
Not really. There's a large blood supply constantly delivering oxygen to brain tissue. An extra 5% load isn't going to break anything.
it seems that the Yeerks are mostly brain
All brain/muscle without tissue differentiation, I'd say. Like jellies.
I like the oxygen theory, but I adamantly disagree with wildweathels idea that yeerks are in a psuedo coma when not in a host. All you have to do is read the chapters of THC when Esplin is in the pool learning about andalites to know that there is no coma involved.
Maybe "coma" is the wrong word. I'm thinking of how we use induced comas to reduce brain metabolism by 30% or so when treating brain injuries. In humans, that involves a loss of consciousness, but imagine Yeerk tissue is adapted to only think as fast as available oxygen allows. They can cut oxygen use by 99% or better compared to what a mass of human brain tissue would require, but only a tiny bit of that is increased efficiency. The rest is made up for by t-h-i-n-k-i-n-g v-e-r-y s-l-o-w-l-y i-n t-h-e p-o-o-l. This is not something you'd notice just by experiencing it; without something to compare against, how do you measure time?
Oh, and death is complicated and messy, it's not entirely like there's an "okay everybody, time to die" signal from cell to cell. But it's not entirely
unlike that either.
http://en.wikipedia.org/wiki/Clinical_death