I don't see how there could be O2 exchange going on in the dome under the ice. Wouldn't any O2 trapped under the dome get exchanged out and used up fairly quick??
I don't understand what you are asking. The exchange of oxygen into the water can only happen in one direction. It can only increase the DO. Organisms using the O2 will lower the DO. But if both are happening, isn't this the answer you are looking for? Could it not be said that O2 dissolving in the water is supporting metabolism? Its obvious that the trout's metabolism wasn't shut down. They doubled in size.
Here's how I look at. The trout could not double in size unless food was available to them. This means that where ever the fish are, so is sufficient oxygen to support them and their food and enough to also support the trout metabolism requirements to double in size. I would suggest this. Next winter, go out with a fishing pole, auger, and a sonar and leave the DO meter at home. Where you find the fish ... there lies the answer to what is supporting them. They will only be in water that provides everything they need.
Just a quick question. Do your trout double in size during the growth season in summer? If not, you have strong evidence that the prey of the pond is concentrated in a smaller volume of water during winter.
