Lake Michigan is ailing.
That was the consensus among a panel of scientists convened to assess the lake’s health at the 9th Annual Great Lakes Restoration Conference in Milwaukee.
Invasive quagga mussels have ravaged Lake Michigan’s food web and are fueling algae blooms that foul beaches and kill birds. Climate change has increased lake water temperatures, decreased ice cover and caused evaporation from the lake to accelerate, all of which contribute to lower water levels.
Changes in the lake’s ecosystem over the past 25 years don’t bode well for Lake Michigan’s vaunted, but imported, Chinook salmon fishery. The scientists said quagga mussels are hogging the phytoplankton needed to support alewives, the primary food source for Chinook salmon.
“The lake has changed — it’s no longer going to be primarily a Chinook salmon lake, and that’s not going to change anytime soon,” said John Janssen, a professor at the University of Wisconsin-Milwaukee’s School of Freshwater Sciences.
Quagga mussels have also increased water clarity in Lake Michigan and turned the water a deeper shade of blue, which looks great but is misleading, Janssen said. “Blue means there’s no phytoplankton, there’s no food … it’s a sterile lake.”
The foreign mussels now blanket vast areas of the lake’s bottom and the biomass of quagga mussels is four times the biomass of all prey fish species combined, said Val Klump, a scientist and director of the University of Wisconsin-Milwaukee’s Great Lakes Water Institute.
Increased water clarity has fueled rampant algae growth in the lakes, which has resulted in mats of fetid green algae blanketing scenic beaches in Wisconsin’s Door County and at Sleeping Bear Dunes National Lakeshore in Michigan. Those algae blooms provide ideal conditions for a type of botulism that has killed thousands of Great Lakes waterbirds in recent years.
Klump said climate change would make the Great Lakes region warmer and wetter in the future, and produce more extreme storms. Stronger storms could cause more sewer overflows and send more polluted stormwater runoff into the lake from farms and urban areas.
“The $64-million question is what the future will bring” in terms of lake levels, Klump said. “Most (computer) models predict somewhat lower lake levels.”