If you’ve been wondering what that green stuff is that has been floating for weeks next to the shore of the Skokie Lagoons along Forestway Drive, it’s duckweed.

That’s according to Dr. Charles Shabica, Professor Emeritus in Earth Science at Northwestern University and president of Shabica & Associates, a coastal design and engineering firm based in Northfield.

Duckweed bears a striking resemblance from a distance to algae, but it is not, he said. Rather, it is a fast growing plant that is a ready source of food for ducks and other waterfowl, and has many positive features, including the prospect of use as a future biofuel and animal feed.

“Dang, it even controls mosquitoes!” he added.

Much like smelt, duckweed “tends to come and go,” said Shabica. Heat, rain and the presence of predators all factor into the equation.

Going forward, Shabica would expect that much of the duckweed will be eaten by ducks and other waterfowl, some will get washed downstream, and some could rot and sink to the bottom or dry up on shore and turn into mulch.

“There is definitely no downside to duckweed,” Shabica said.

Northfield resident Dave Vito, who often spends time at the lagoons, has seen the fish eat the duckweed, and since the water levels are low, can smell it too.

The Rutgers School of Environmental and Biological Sciences writes extensively about duckweed on its website.

“The duckweed family comprises any of a number of green, floating, freshwater flowering plants, whose largest species is smaller than a dime and whose smallest is as small as a pinhead. Beyond being the smallest flowering plant in the world, duckweed has a number of remarkable traits. This tiny plant has the potential to clean, nourish and fuel the world.

“According to Dr. Todd Michael, Rutgers Assistant Professor of genomics and bioinformatics at the Waksman Institute for Microbiology, duckweed could be part of the solution to some of the world’s biggest and most urgent environmental problems. Duckweed is the fastest flowering-plant producer of biomass and is high in protein, making it an excellent feed option for fish and livestock. It is also an enthusiastic absorber of phosphate and nitrogen, two common pollutants in farm run-off and municipal wastewater. Further, duckweed inhibits mosquito larvae growth, which may reduce the incidence of vector-borne diseases such as West Nile and malaria.

“Scientists are excited not only by duckweed’s potential role as an environmental superpower, but also by its adaptability: duckweed can be grown on every continent but Antarctica (at least it has not found it there yet). In the future, duckweed might become a sustainable staple source for food and biofuel. ‘Plants are part of the solution,’ Michael explains, ‘part of the way to start addressing energy issues.'”

Skokie Lagoons is a nature owned and managed by the Forest Preserve District of Cook County. Within the park, there are seven inter-connected lagoons totaling 190 acres. Water flows southward from the Chicago Botanic Garden through the lagoons to the Skokie River. The overall water level in the lagoons is controlled by the main control dam at Willow Road. Three low dams keep the water levels below the inner islands. Recreational opportunities at Skokie Lagoons include biking, fishing, boating and birding.