That's not a bad thought. I'm not sure how to prove/disprove (easily, anyway) what it is either. Obviously you can send it off to a lab for analysis, maybe through a state ag program or something, but that isn't exactly simple. No idea on a cost of something like that either.
Maybe if a university or even high school has an ag program, or biology department or interest, they may be willing to use it as a learning tool. (Yes, I know school's teach biology, but whether to the extent where they would be willing to culture and find out what something is would be the question.)
Think about this. Not just yeast, but all kinds of crap is in the air everywhere. You can take a thing of water, leave it sit out, and it will get algae and stuff going on.
Leave water in the dark, undisturbed, and it will get anaerobic pretty quick. (First hand knowledge on that one, lol)
I wonder what kind of magnification you would need. The pocket microscope I use for checking trichs is 20-40x maybe I could dab some on a slide? Should be easy enough to match to a generic picture of yeast or not.
What really puzzles me, and also makes me think it's just stuff in the water to begin with:
That was a fresh bottle of water with a dose of Dyna-Gro added in almost 5 weeks ago, it sits in the kitchen window. If my rez only did that I'd be ecstatic.
So I'm really starting to think the problem may just be in the water when it comes out of the ground. Adding in nutrients and warmer temps just lets it go crazy.