OK, PA!! :-) That's one of the "problems" with this forum -- you never know to whom you are talking. You probably know more about water chemistry than me! This is not my expertise (directly), so I got some advice from our limnologist to try and provide a decent answer. He suggested chlorophyll a, pH, total phosphorous, soluble reactive phosphorous (meaning the biologically available amount), and total nitrogen.
Again -- hope this helps!!
Dave
