It's just yeast floating around, you may have even had a bottle krausen forming. Carbonation is really just a mini fermentation in a tiny carboy, so it can be just as active as what you would see in a 5 gallon carboy.
Just relax, quit staring at your bottles, most of us just leave them in a dark closet for the three weeks minimum it takes usually to carb.
Everything will settle down eventually.
I discuss the carb/conditioning process in this blog...
Of Patience and Bottle Conditioning.