kaskiles, I would like to see such a link if you could find one. That explanation would at least make some sense. The previous logic was that when you have rocks with P trapped in them, and then P is lowered in the water column, it "leeches" out of the rock. Nothing that I recall was ever said about a bacterial mechanism being in place.
This would be interesting to learn though. It is my feeling that there is a very strong bacteria-algae connection on our scrubbers, and it would not surprise me to find out that such a mechanism would also explain if and how phosphate would get pulled out of rockwork. But I want to see the proof.