Sometimes, bad things can lead to good things.
New research by ecologist Cory Suski of the University of Illinois at Urbana-Champaign suggests that pollution in the Chicago Area Waterway System is deterring invasive silver carp from moving into Lake Michigan.
Suski says the research could lead to clearing up a 10-year-old mystery: why the carp have been stalled at one point in the Illinois River south of Chicago for about a decade, and have not continued to migrate further north.
Suski's research compared the livers of silver carp caught further downstream, with those of carp caught near Chicago.
"Those animals at the leading edge are showing signs of being exposed to pollutants and being exposed to contaminants," he says.
In effect, the pollution may be creating a kind of fish barrier that is stopping the fish before they ever make it to the electric fish barriers installed inside the Chicago Sanitary and Ship Canal.
Suski says it's not clear if the fish are deterred by the smell of the pollutants in the water, or perhaps by the taste of food they find in the area; further study is needed.
Suski says there's a particularly urgent reason to confirm and advance the research.
That's because Chicago is trying to clean up its waterway system; if it succeeds, the carp might be able to swim into Lake Michigan once the water is clean enough.