Your fishpond has plenty of white bubbles please explain cause?

This could be many things. You could have an aeration unit that provides too much gas into the system. This would not be a problem. On the other hand, you might have high amounts of minerals in your pond and these minerals may be gathering at the surface as the water evaporates. I would do a water change if you haven't done one in a while. If you have then I would look into aeration and filtration units. Most aeration units built for systems of that size are adjustable so it might make sense to look into the functionality of the systems you have regulating the pond.