Nice - those DO's are improving. Any clear ice ?
The ice pack is 22 inches thick of clear ice with three inches of white ice on top. On top of all that is 6-16 inches of hard snow. The open area the circulator provides is currently the only place where sun light can penetrate. That open area is probably about 2-3 percent of the pond surface area.
Even though very little direct sunlight can enter the pond I believe that the clear water allows significant refracted light to penetrate. That must be enough light or the D.O. would be considerably lower.