Lake Michigan’s waters have dramatically cleared up in the past two decades, but researchers fear the changes could be hurting marine life.
Several factors have made the water clearer, including reductions in agricultural and sewage runoff. But invasive mussels have played a bigger role, researchers say; there are trillions of them now, enough to filter all of Lake Michigan’s water every four to six days.
While the looks of the water may be more appealing to kayakers and swimmers, the mussels’ filtering has gotten rid of much of the phytoplankton that sits at the bottom of the food chain.
“Clearer is not necessarily better,” said Robert Shuchman, co-director of the Michigan Tech Research Institute. “Clearer water means less phytoplankton in the water column, and they’re the basic building block in the food web. The idea is, the little fish eat algae, and the bigger fish eat the little fish.”
Illinois has raised fish to stock the lake since 1984 in hopes of creating a good season for anglers and a healthy ecosystem. But the food chain changes have made the task daunting, according to hatchery manager Steve Krueger.
“Without stocking, I think the fishery in Lake Michigan would continue to falter,” Krueger added.