Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants where do the weeds go

Where do the weeds go in the winter particully Watermeal and Duckweed? How do they come back year after year if they are a floating weed? Do they sink when it freezes then come back in the spring or are they re-introduced each year. And if they are a bottom dweller in the winter months can something be put in early enough to prevent a full blown hell pond.