Michigan Radio’s Environment Report: “In Warm Water: Fish and the Changing Great Lakes”

We kick off our week-long series In Warm Water: Fish and the Changing Great Lakes with a look at Lake Superior. It has long been the coldest and most pristine Great Lake. Its frigid waters have helped defend it from some invasive species that have plagued the other Great Lakes. But Lake Superior’s future could look radically different. Warming water and decreasing ice are threatening the habitat of some of the lake’s most iconic fish.

Scientists say one way climate change is harming the Great Lakes is by warming the water too quickly in the spring. That warm-up can decrease food for tiny creatures in the lakes–the creatures that game fish like trout and salmon eat.Leaner meals

Phytoplankton – the algae that are food for plankton which in turn feed fish – are behaving strangely. They’re surrounded by a nutrient they need to grow. But for some reason, they’re not using it. The puzzle has big implications for how scientists think about the Great Lakes’ future in a warming world.

Yellow perch are a staple of firehouse and church fish fries, and the delicate fish on that dish might once have lived in the Great Lakes. But warmer lake waters in a changing climate threaten the yellow perch population as well as other popular cool water fish, like walleye.

Big, ugly algal blooms are reappearing in the western basin (and sometimes the central basin) of Lake Erie. The blooms happen when excess nutrients – mostly phosphorus – run off into the lake from farms and sewage treatment plants. Some of these kinds of algae produce toxins that are among the most powerful natural poisons on Earth. Over the past decade, these algal blooms have been common in Lake Erie. And scientists predict climate change could make the problem worse.