I think that in effect it acts like a traditional system in that only minor amounts of O2 are brought in initially (by high pressure disturbance at the air water interface) but high amounts of O2 are added by getting the water moving. Take some Kool Aid powder and sit it in the bottom of a glass, then carefully pour water over it. Now put your finger in the glass just barely under the surface and start to spin your finger round and round. Eventually the powder starts to mix due to the circular current. This is where I believe almost all of the O2 is added.
Low levels early, but where you need them, and higher amounts later on.
