New Research Underscores the Initial Benefits of Floating Wetlands in Urban Waterways

New research published today in Science of the Total Environment documents how man-made floating wetlands, an emerging ecological engineering technology added to urban water bodies for restoration efforts, can improve water quality, provide valuable habitat and reflect improving ecological quality. The study presents results from three well-established pilot installations for floating wetlands in Baltimore, Boston and Chicago by researchers at Northeastern University, Shedd Aquarium, National Aquarium, Urban Rivers, University of Maryland and University of Massachusetts. Their results may help inform strategies for additional or expanded restoration efforts for these uniquely valuable yet challenged urban waterways.

“We know that the Chicago River and other urban waterways are relatively void of vegetation, crucial habitat for wildlife, and with our research partners, we are gaining a greater understanding of how some of our active efforts to restore these aquatic habitats can work,” Dr. Austin Happel, research biologist at Shedd Aquarium and co-author on the study. “Showcasing the potential tangible benefits floating wetlands like the ones on the Wild Mile in the Chicago River have can inspire future restoration efforts in urbanized systems and lead to further research.”

Floating wetlands can increase the abundance of wetland plants and create pockets of native vegetation. They can be used by a wide range of species by providing refuge for small fish, forage grounds for birds, a food source for larval insects and more. The study found modest but measurable ecological changes from decreases in zooplankton abundance and increases in native minnows that suggest the wetlands serve as both a food source and refuge for small fishes.

In Chicago, the floating wetland location was associated with an increase in native minnows and a decrease in non-native common carp, which could showcase how small prey fish are attracted to the improved forage, or utilize it for refuge from predation or as spawning habitat to hide their eggs. This pattern of more minnows and fewer carp echoes broader trends among Chicago’s fish assemblages over the past three decades as water quality has improved, as documented by Happel. Notably, the banded killifish, a species that is listed as state-threatened in Illinois, was observed most often at the floating wetland site.

Overall, these findings suggest that floating wetlands might increase habitat diversity and food-web connectivity. The increases in abundance and mean body size of large zooplankton suggest a viable mechanism by which floating wetlands might contribute to the top-down control of excess algal growth. Additional research can further determine if installations can produce more durable reductions in algal growth and contribute to the recovery of native species as wetlands are scaled up.

“It’s incredibly rewarding to have initial results demonstrating how our efforts to build habitat can improve the environment of our waterways,” said Phil Nicodemus at Urban Rivers and co-author on the study. “It’s easier to see an impact on recreation, community and education as we bring groups to the eco-park space, but this study showcases improvements for beneath the surface in the river, which is equally important to our project.”

Since 2017, Chicago non-profit Urban Rivers began installing floating habitats on the North Branch Canal and teamed up with Shedd Aquarium in 2018 to continue to add to the “Wild Mile” – the first mile-long floating eco-park on the Chicago River. The man-made floating habitats or islands seek to improve the water quality of the canal and the river downstream and make a less trafficked section of the river serve as an oasis for wildlife. Further building on their partnership, Shedd Aquarium and Urban Rivers also added new habitat to the South Branch of the Chicago River with over 3,000 square feet of floating islands.

By studying the effects these various restoration efforts have on aquatic organisms, Happel can help others argue for similar actions in their areas. The aquarium will continue studying the impacts of these floating wetland habitats on local fish populations and conduct other assessments to understand urban freshwater systems.

Individuals can explore the floating wetlands on the North Branch of the Chicago River through Shedd’s Kayak for Conservation program where participants paddle alongside a nature expert from the aquarium. Or explore on foot on Urban River’s learning platform and boardwalk that opened last summer.

To read the published research study, “Application of floating wetlands for the improvement of degraded urban waters: findings from three multi-year pilot-scale installations,” visit https://doi.org/10.1016/j.scitotenv.2023.162669.

For more information about Shedd Aquarium’s research on the Chicago River, visit Shedd’s website here.

VISUALS: High resolution visuals of Shedd’s work on the Chicago River are available for preview and download here: https://personal.filesanywhere.com/fs/v.aspx?v=8e6c69895d616f75b1a5.
Credit: ©Shedd Aquarium