What other cause is effecting the increase in floating algae?

High nutrient pollution (fertilizer) in run off from the land caused an increase in algae that live on the surface.

Explanation:

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme