I was out working around the pond today and noticed that there are very tiny bubbles forming right at the surface and then almost immediately popping - sort of like carbonation.

The only thing I can think of is that this is the top layer giving up DO as the water at the surface warms. Does this sound right? The water temp is only 78 degrees or so but that spot is in the sun.

I am aerating for 6 hours at night and have no bubbles on rocks so I don't think it's related to DO saturation, but really don't know. More a curiosity at this point as it gives the surface of the pond a sparkling effect.

While it may seem they are forming at the surface, this is usually the plants on the bottom streaming off very small bubbles of gas, usually O2 during photosynthesis. I see this in my aquarium regularly, especially after a water change. It does make the water surface sparkle! I doubt the gas is all O2 when it reaches the top, but if you collected the gas right at the plant with a test tube, and then stick something burning into it, you will clearly see it has a high concentration of O2.

Thanks for the feedback.

No real plant life where these are forming and it's only in a few inches to maybe 4" or so. I guess they could be small enough to not be visible while they rise to the surface. The odd part is that it only happens in the shallow water so it would seem like it's being driven thermally.

I see this in our pond where the minnows are working the bottom of the pond. I expect the O2 is on the rocks or bottom of the pond where the minnows are grooming the bottom of the pond.

We have a 2mm sinking feed we feed our minnows and they will work the bottom so hard the water will cloud up.

No minnows in sight in the area. One can watch the surface of the water and the bubbles just form as if magic. That's why I'm thinking that as the water warms it forces the "excess" DO out.

If it's still doing it tonight with the sun out I'll try and capture some video. Otherwise I'll have to wait until the weekend again as it's now dark in the morning when I head out to work.

I do know water is the most amazing material in the world. It is the only material that when it gets warm it expands and when it gets cold it expands too. Right around 4 degrees C it is the densest it can be.

In your case it can be like the glass of water next to your bed where the dissolved air is changing state from solid to a gas.

Gasses come from the bottom of the pond also form bubbles because of decomposition of detritus releasing gasses. That is why you drill holes if you sink an old tire. Even if you get the air out and the tire sunk, pond gasses can accumulate in the tire cavity and float it later. Had it happen.

I have also heard (likely on this forum) that proteins in the water from the fish biomass cause a lot of the bubbles we see when the aeration system runs. So I suppose the surface tension from those also could contribute.

Speculation mostly on my part. I'm no chemist.