Bridge Michigan
SLEEPING BEAR DUNES — Aboard a boat overlooking one of the world’s most breathtaking landscapes, Harvey Bootsma peers into an ecosystem on the verge of collapse.
The clear aquamarine waters are an illusion: beautiful, but so devoid of food and nutrients they’ve become a wasteland for whitefish and other creatures that have inhabited the Great Lakes for thousands of years.
Bootsma, a professor at the University of Wisconsin-Milwaukee, is part of a small team dedicated to a monumental task: finding a way to kill invasive quagga mussels that blanket the lake bottom and starve whitefish to death.
He’s spent a decade on the task and found some success, with regular dives that have eradicated the mussels on two plots within this reef, each roughly the footprint of a small house.
Trouble is, Lake Michigan is 22,000 square miles in size and covered with mussels.
“You can’t see the other side of the lake from here, and we’re doing a 10-by-10-meter patch,” Bootsma acknowledged as he stood aboard the Nahma with water dripping from his drysuit.
So it goes in the fight against the thumbnail-sized invaders that were introduced to the lakes from Eastern Europe in the 1980s and now pose an existential threat to whitefish and other species.
A small community of scientists, regulators and advocates are working to overcome limited resources and the sheer complexity of an invasion that reaches hundreds of feet underwater.
While the divers use paint scrapers, tarps and heavy steel plates to clear away mussel colonies in hopes of making it easier for whitefish to spawn, their labcoat-wearing counterparts are looking for pesticides, parasites and genetic vulnerabilities capable of suppressing the shellfish en masse.
They took measurements of the algae growth, noted which fish were nearby and plucked mussel-covered rocks to bring aboard the boat. There, other team members glued dozens of tiny tags onto the shellfish in an effort to track their future growth.
In healthy lakes, microscopic algae and plankton fill the water column, scattering sunlight to make the water look murky while serving as the foundation of the underwater food web.
That was the case in lakes Michigan and Huron before invasive zebra and quagga mussels disrupted the harmony. They first arrived more than three decades ago on the ballast water of oceangoing ships and have since become the dominant life form.
“If you could walk from here to Milwaukee on the bottom of Lake Michigan, you’d be walking on mussels all the way,” Bootsma said.
Now widespread in every Great Lake except Superior, the mussels have filtered out the phytoplankton and nutrients, clarifying the water while the resulting food shortage ripples in all directions.
