That is wind blown dead/dying planktonic algae in a normal heavy daily cycle. The whiteish bubbly stuff is from busted algae cells - protoplasm. Hold off on any more fertilizer until you have an 18 inch visibility. This often happens when there has been a limiting water condition (low alkalinity for example) and it is removed and the fertilization process jumps to life resulting in a major bloom. Also happens upon a first fertilization process application in a productive pond ( but low on N , P or K - fertilizer components).