From stagnancy to deoxygenation

[Mattik]

One more quick reference:

http://www.ecy.wa.gov/programs/wq/plants/lakes/characteristics.html


"Oxygen: Essential to lake life
The presence of oxygen in lake water determines where organisms such as fish and zooplankton are found. In spring, when the lake water is well mixed, oxygen is usually present at all depths and organisms may be distributed throughout the lake. In the summer, under stratified conditions, little or no oxygen is produced in the hypolimnion. Available oxygen is consumed through decomposition of plant and animal material, and oxygen levels become too low for fish who must move to the top layer, or epilimnion.

If these conditions are prolonged and the upper waters become too warm, cold-water fish such as trout may become stressed and eventually die. In the fall, the lake layers break down and turnover replenishes oxygen to the bottom waters.

The formation of ice in water reduces the supply of oxygen to the lake from the overlying air. If oxygen levels fall too low, fish and other aquatic life may die."

 

[Randy Holmes-Farley]

Apparently the brownian motion isn't quite strong enough to equally distribute oxygen throughout a water column.

My point on Brownian motion did not refer to such situations. I was only referring to the buoyancy argument made above. Absolutely if you are rapidly removing O2 from some part of a large body of water (like a lake bottom), it will become depleted before O2 can be replenished by diffusion, convection, or many other processes.

 

[Mattik]

I'm following you now Randy.

And, to your point on countering one theory vs another:

In reality these questions are pretty hard to answer because it is the balance of everything we've talked about in this thread that drives saturation levels of any molecule in water (or air, or any mixture for that matter).

You have to consider production rates, consumption rates, diffussion processes(brownian motion), agitation rates, and many other influences to truely describe why a solution is saturated or unsaturated with any given molecule.

 

[Randy Holmes-Farley]

:thumbsup:

Happy Reefing.