CC, phytoplankton will put more O2 into the water than underwater plants will. Especially in the winter if sunlight can get to the water.
Dr. Luke, my condolences. My personal pond is less than 50% full with water due to the low water table here. Full pool is 1.1-1.2 acres, it's now .45 ac. I ran a winter bottom diffuser in the usual place but it is now in a finger instead of a bowl due to the submerged island no longer being submerged. Max pond depth this winter is 8.5 feet, it's usually 16 feet because going into winter the pond typically isn't at full pool. Max depth in my pond now is 18+ feet when the pond is at full pool.
I checked O2 levels in January and below 5' water depth they weren't high enough to support fish life (<3mg/l), that is with the diffuser running. MUCH higher biomass in the remaining water, and the diffuser being in a finger instead of more towards the main body of the pond.
So, I threw caution to the wind and turned on the diffuser in the deepest part of the pond, and opened up a 30' dia hole in 10 hours through 8" ice and a foot of snow. (What ice dome?)
We will see what things look like in regards to the RES in the pond, but with the pond 40%-50% ice free I don't see any morts.
