It’s real name is Duckweed – that scummy stuff that coats the surfaces of ponds and marshes and even the critters swimming around there.
A mixed flock of Mallards and Wood Ducks floating on a pond of duckweed.
From a distance, it just looks like scum covering the water surface.
Up close, it is only slightly more interesting. The “scum” is actually leaves of one or more species of Duckweed that float on the surface, attached to each other by slender threadlike filaments.
But it seems that Duckweed is highly nutritious and is even promoted as a supplementary feed for livestock. Gram for gram it contains more protein than soybeans, and it grows incredibly fast — in fact, it is one of those species that exhibits exponential growth, doubling every so many hours. With its high protein content (35-43%), low fat (5% poly-unsaturated fat), and low fiber content (5-15%), it is highly digestible, yielding more calories with less work. Although it is regularly consumed in some cultures in southeast Asia, Duckweed is high in oxalates, which makes it potentially toxic to your kidneys, so it’s not high on my list of edibles.
From Off the Grid News: Feed your livestock AND your family with prolific, fast-growing Duckweed! Use it instead of spinach in your salads…
Instead of eating it, Duckweed may prove valuable as a source of biofuels because it grows so fast, has so little fiber, and contains 5-6 times the amount of starch that corn does.
Duckweed is a primary food source for lots of wildlife, including Mallards, Wood Ducks, Canada Geese, Painted and Snapping Turtles (I thought they were carnivorous!), even Beaver. I’m going to add Trumpeter Swans to this list, because I saw them gobbling it up the other day.
A pair of Trumpeter Swans dabbling for duckweed on nearby Sucker Lake.
Strings of Duckweed dangle from their mouths as they gobble up their highly nutritious, protein-packed meal.
All in all, it seems that “Uck-weed” has a lot going for it, as a food source and a potential fuel source. I’ll stop denigrating pond scum now.
Back Yard Biology 
I enjoyed your commentary on duckweed, Sue, and mostly have observed its use as great camouflage for semi-submersed frogs. Regarding the diet of snapping turtles, I have seen them pulling out vegetation to eat, but I know too that they also eat baby ducks–essentially they seem to be omnivores.
Thanks for the info, Mike. I think I always assumed they were carnivorous, but it would be smarter to just be opportunistic and eat whatever comes along.