Will,
That's a good looking piece of property. I'm also in Tennessee and I am also new to the site. That is a major fluctuation in pond level so I would be concerned about a possible leak. Due to the soil composition in Tennessee it seems that leaking ponds are a major problem here.
If there is no fish in the 2 acre pond there's a good chance there was a fish kill event at some point. It certainly could be a water quality issue but I'd be more inclined to think it was an oxygen related issue. If the pond is relatively shallow to start with then it will be extremely shallow if it drops 4' or so like it appears in the picture.
As far as the nutrients go, the pond definitely gets a fair amount of nutrients from the surrounding trees. Fertilizing may be an option in the future but that wouldn't be the first thing I did.
See how the pond holds water throughout the summer this year. You may want to do some leak detection or consult with a pond excavator.
Anthony
