Re: [APD] CO2 in the mist

[Jerry Baker <jerry at bakerweb_biz>]

Jerry Baker wrote:
> I am not attempting to be confrontational when I say that I am still 
> doubtful of CO2 availability being the causative agent here. My 
> understanding is that 30ppm is enough to saturate photosynthesis in 
> aquatic plants. If that is the case, no amount of CO2 above saturation 
> will increase O2 production. That doesn't explain why you see better 
> plant growth using this method though.

My favorite/pet speculation is, what seems to me, an application of 
Occam's Razor. I like the idea that the bubbles adhering to the leaves 
are not being absorbed much, but rather they are being "inflated" with 
oxygen. Since the leaves are already coated with pre-inflated bubbles, 
it will take less oxygen production to inflate a bubble to the point 
that its buoyancy exceeds the forces of adhesion. In other words, the 
same amount of photosynthesis will produce more pearling having 
preformed bubbles to start with.

I do have a logical basis for preferring this explanation over the 
hypothesis that the bubbles are increasing the availability of CO2 in 
some way. My understanding is that photosynthesis in aquatic plants is 
already saturated at 30ppm*. If they are indeed saturated, adding more 
CO2 is not going to increase the rate of photosynthesis (and, 
consequently, O2 production). The chances that the bubbles are due to 
saturation of the Prandtl boundary with dissolved O2 are pretty slim. I 
do not know of any other plausible explanation than above.

I am stuck in the irritating situation of being between aquariums at the 
moment. I do get to go pick up my custom acrylic tank tomorrow. Yay! 
Took'em two weeks to make it. Anyway, that sort of puts a cramp in any 
testing I can do for a while. However, producing a fine mist of regular 
old air with the same diffuser in the same position should have the same 
effect if this explanation happened to be correct. Of course CO2 would 
have to be maintained at around 30ppm using a reactor or other method.

* http://www.aquabotanic.com/wp101.htm

-- 
Jerry Baker
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