Thread: Bubbles

I know that bubbles form by a process called nucleation. Then today I saw a fish tank with lots of algae inside it under direct sunlight. As I took a closer look at an insignificant lump of algae sitting at the bottom of the tank, I saw plenty of tiny bubbles forming throughout the green fluffs. This made me wonder if liquid bubbles of oxygen form when the oxygen saturation in the water has reached its limit because I don't usually see tiny globules popping out of aquatic greenies.

The algae can break the water into oxygen and hydrogen through the clever use of solar power.
They then use the hydrogen from the water to manufacture sugars starches and proteins for themselves.
The oxygen is a waste product in this process so the algae pollute the water around them with it in proper manufacturer style...

Carbon fixation - Wikipedia, the free encyclopedia

Is this what you mean?

No, Photosynthesis

Originally Posted by molecool

Carbon fixation - Wikipedia, the free encyclopedia

Is this what you mean?

Yes, good start Molecool.
Go down the page to oxygenic photosynthesis.

Edit: The page PHDemon gives is good too. It is more detailed.

I am not sure about your comment on the bubbles and the water's oxygen saturation level. It might just be the rate of oxygen production is higher than the rate the water can absorb oxygen at and whether the bubbles would be absorbed over time.

Originally Posted by dan hunter

I am not sure about your comment on the bubbles and the water's oxygen saturation level. It might just be the rate of oxygen production is higher than the rate the water can absorb oxygen at and whether the bubbles would be absorbed over time.

Ah so that's true?

Not a biologist but as a chemist my thoughts are:

It is probably due to either 1) oxygen production rate -- the algae produce oxygen quicker than it can dissolve and so it saturates the water locally around the leaf and so any further oxygen cannot dissolve near the plant, in this scenario you get visible bubbles which will disappear as they move away from the plant into oxygen poor areas where the O2 can dissolve or 2) the water already being saturated with oxygen so none of the produced oxygen dissolves in the water and stays in bubbles of gas, in this scenario the O2 bubbles would stick around until they reached the surface and release the O2 to the surroundings.

If the water is not saturated with O2 or the O2 production rate is low the O2 will dissolve as soon as it comes out of the plant and you will see no bubbles (this is usually the case I'm guessing which is why you don't "normally" see bubbles).

Originally Posted by PhDemon

Not a biologist but as a chemist my thoughts are:

It is probably due to either 1) oxygen production rate -- the algae produce oxygen quicker than it can dissolve and so it saturates the water locally around the leaf and so any further oxygen cannot dissolve near the plant, in this scenario you get visible bubbles which will disappear as they move away from the plant into oxygen poor areas where the O2 can dissolve or 2) the water already being saturated with oxygen so none of the produced oxygen dissolves in the water and stays in bubbles of gas, in this scenario the O2 bubbles would stick around until they reached the surface and release the O2 to the surroundings.

If the water is not saturated with O2 or the O2 production rate is low the O2 will dissolve as soon as it comes out of the plant and you will see no bubbles (this is usually the case I'm guessing which is why you don't "normally" see bubbles).

Yeah I'm pretty sure it's the second one. That aside, in your first statement, bubbles can actually disappear into the depths just like that? (Or they disintegrate?)

As long as the surrounding water is not saturated with oxygen, the oxygen at the surface of the bubbles will dissolve so the bubbles will get smaller until they can't be sustained and disappear (it is the same basic physics as evaporation of water from a droplet in that the mass flux from the bubble is related to the partial pressure difference inside and outside the bubble, diffusion coefficients etc. just as mass loss from evaporation is), more details here:

http://www2.mmm.ucar.edu/people/sull...rs/bubbles.pdf

Thanks!