The goal would be to farm and continually extract algae from the lake in just a section of it, presumably to increase the water quality in the rest of the lake.
And there are something like 14,000 lakes in MN though many of them one might be tempted to call ponds :) no need to build an artificial one though, there are plenty.
I don’t think you would ever get approval for something like this in a public lake. Maybe in some private, artificial pond?