Zebra mussels are a big problem where I grew up. The bay of Green Bay is very unfriendly to the barefoot swimmer because of them (they leave sharp little shells behind). I can't really think of a way to get rid of them short of making some sort of robotic fleet to go and kill them all.

Even worse, the DNR doesn't really want to get involved for fear of upsetting the ecosystem. Someone went as far as to make a machine that makes faux sand from zebra mussel shells (which pile up everywhere along the shore), but he got shutdown because of the unknown environmental impact.