Understanding Urban Freshwater Ecosystems
The third most populous metropolitan area in the United States, Chicago spans a diverse geographical area that includes forest preserves, farmland, industrial corridors and densely populated urban neighborhoods. Aquatic environments throughout the area support diverse arrays of fishes and invertebrates that are affected by local land use. The Chicago region therefore offers an abundance of research opportunities centered on aquatic life in urban waterways.
Understanding Urban Freshwater Ecosystems
The third most populous metropolitan area in the United States, Chicago spans a diverse geographical area that includes forest preserves, farmland, industrial corridors and densely populated urban neighborhoods. Aquatic environments throughout the area support diverse arrays of fishes and invertebrates that are affected by local land use. The Chicago region therefore offers an abundance of research opportunities centered on aquatic life in urban waterways.
Along the walled bank of the North Branch of the Chicago River, new (foreground) and established artificial floating islands provide habitat where fishes can find food and spawn.
Photo by: Luke McGill
Historic changes in fish assemblages and water quality
The Chicago Area Waterway System (CAWS) represents a set of rivers whose flows have been reversed through a series of canals and are tied to the wastewater transport and treatment facilities of the area. Since the Clean Water Act was enacted in 1972, fish communities and water quality in the CAWS have been monitored by the Metropolitan Water Reclamation District of Greater Chicago (MWRD). In partnership with MWRD, Shedd research biologist Austin Happel, Ph.D., is analyzing this long-term data set to gauge how the fishes in Chicago’s rivers are responding to actions taken to improve water quality.
Planted floating islands, being launched by Shedd staff members, are made of coconut coir mats tied together with recycled plastic. The native wetland plants’ roots grow into the water, adding oxygen and providing habitat for fishes as well as their zooplankton prey.
Wildlife response to river restoration
Restoration efforts vary across waterways, from removing dams to establishing new vegetation, and the potency of these actions also varies and can take years to be realized. Happel is looking at what effects restoration projects have on aquatic communities.
For example, the Chicago River's "Wild Mile" project represents a revitalization of a section of the North Branch of the industrial waterway using artificial floating wetlands, which may provide shelter and food for fishes while improving water quality. Recently artificial floating wetlands were built elsewhere in the Chicago River as part of Shedd's South Branch Initiative, thanks to funding by the National Resources Conservation Service.
To understand how fish respond to these activities, Shedd has partnered with Illinois-Indiana SeaGrant and Purdue University to track various fish species throughout downtown Chicago. We seek to better understand how they utilize the floating wetland installations as well as questions related to water quality, key habitats, and home ranges. By studying the effects these various restoration efforts have on aquatic organisms, Happel can help others argue for similar actions in their areas.
Photo by: Happel, A., & Gallagher, D. (2022). Decreases in wastewater pollutants increased fish diversity of Chicago's waterways. The Science of The Total Environment, 824(163). https://doi.org/10.1016/j.scitotenv.2022.153776
Spawning
While fishes might be present in a waterway, finding a baby, or larval, fish means much more is going on below the surface. Not only are adults present, but there are also enough of them to find each other, they have appropriate habitat, enough food and suitable water quality to thrive and the egg produced from spawning survived through hatching, a milestone many fishes don’t pass. Thus, finding a larval fish is a revealing event. By looking at when and where fish are spawning, Happel can begin to assess where fish populations are thriving and where they may need attention.
Shedd research biologist Austin Happel examines the collecting tray of a light trap set at night amid the floating islands to attract larval fishes.
A tiny fish is evidence that some fishes are using the floating islands for spawning. Happel will compare what he finds with historic fish population records as well as track what species spawn as the islands grow out and are added to.
“It’s exciting to see just how many fish species call Chicago home, and there is just so much we don’t know about what city life is like for them.”
Austin Happel, Ph.D., research biologist
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