I'm in Illinois and I have a man-made wetland that has a significant amount of Common Duckweed (Lemna minor) floating on it. The wetland was built for the purpose of supporting wetland wildlife and giving people a place to view waterfowl, etc. Could the duckweed pose any problems with those uses, or with the health of the wetland? Nobody is fishing or swimming in it or anything. Thanks!

Could cause oxygen depletion and thus lower the water quality. Can become unsightly. Pretty hard to get rid of it. You'll find lots of information on the web about control.