At first glance, it looks like a small patch of native plants drifting quietly across the water. But beneath the surface of Schiller Pond, something much bigger is beginning to grow.

The Forest Preserves of Cook County recently launched a floating wetland at Schiller Pond, testing an innovative tool that could help improve water quality, create wildlife habitat and support healthier aquatic ecosystems. While floating wetlands have been used in waterways around the country, this is the first of its kind for the Forest Preserves.

Located east of O’Hare, Schiller Pond sits within a heavily urbanized landscape. As a collection basin for the surrounding watershed, the pond receives runoff from nearby roads, lawns and developed areas. More frequent heat waves, longer dry periods and intense rain events have further contributed to elevated phosphorus and nitrogen levels. The result has been algae growth, reduced water clarity and stressful conditions for fish and other aquatic life.

“Floating wetlands can kind of serve like the kidneys of a body of water,” says Michael Feldmann, a fisheries science technician for the Forest Preserves. “They help filter nutrients, improve water quality and create habitat at the same time.”

The floating wetland is a buoyant raft planted with native wetland species including hardstem bulrush, Virginia blueflag, prairie cordgrass, swamp dock, giant bur-reed and swamp milkweed. The fisheries team consulted with Forest Preserves ecologists to select species best suited for local conditions and partnered with the Chicago Botanic Garden to grow many of the native plants.

“While the plants grow above the water’s surface, their roots extend into the pond below, where they absorb excess nutrients and create a nice little habitat for amphibians and fish and macroinvertebrates” Feldmann says. Research suggests covering approximately 1.5% of a pond’s surface with floating wetlands can produce a 5% reduction in nitrogen and phosphorus over time.

Above the water, flowering native plants attract butterflies, bees and other pollinators.  Below, those roots create an underwater world of their own. Small fish can shelter among them, and amphibians, turtles and aquatic insects find places to feed, hide and reproduce. Dragonfly and damselfly larvae can spend years living underwater before emerging as adults, using the submerged root systems as habitat throughout much of their life cycle.

“It seems like it’s already working,” says Fisheries Biologist Jim Phillips. “We already had damselflies landing on it.”

After visiting Chicago’s Wild Mile and learning from Urban Rivers, fisheries staff spent months researching designs and developing a version that could be built in-house using readily available materials. The final prototype, measuring 10 feet by 5 feet, was constructed from PVC pipe, flotation materials and support mesh, costing just under $600, about 75% less than commercially manufactured systems.

The floating wetland is just the latest piece of a larger strategy underway at the six-acre pond. “We’re taking a multi-step approach,” says Feldmann.

For the past three years, fisheries staff have been working to reduce the pond’s common carp population. These non-native fish feed by rooting through bottom sediments, stirring up mud and releasing nutrients that had settled into the pond back into the water column, where they fuel algae growth. Staff have removed more than 185 carp over nine trips, totaling 374 pounds.

Fisheries is also establishing a 20-foot shoreline buffer where Forest Preserves’ staff don’t mow the grasses, which helps reduce rainwater runoff and discourages large concentrations of geese from gathering along the water’s edge where their droppings can add more nutrients to the pond.

Over the coming years, staff will continue monitoring water quality and evaluating how the floating wetland performs. They hope to expand the project with additional units in the future and potentially involve Eagle Scouts in building new floating wetlands for Schiller Pond and other lakes throughout the preserves.

“What works here may not work somewhere else,” Phillips says. “We’re going to try to find what works best.”