• Whitefish face collapse in lakes Michigan and Huron unless invasive mussels that are killing the fish are controlled
• While scientists look for a miracle solution, they hope to aid whitefish by clearing mussels from spawning reefs
• It’s an effort powered by putty knives, tarps and a massive steel plate known as the ‘mussel masher’

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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.

Here in Good Harbor Bay, off the coast of Sleeping Bear Dunes, small field experiments have yielded valuable intelligence, including how to kill a species with few natural predators in the Great Lakes, what could keep them from returning and how the environment might respond to their absence.

But many worry the speed of scientific discovery can’t keep pace with a mussel takeover that has experts predicting the imminent disappearance of whitefish from vast areas of lakes Michigan and Huron.

“In our bay,” said Doug Craven, natural resources director for the Little Traverse Bay Band of Odawa Indians, “it could be five years.”

‘Mussels all the way’

The waters off Sleeping Bear — where white sand meets a blue so transparent, it’s possible to stand onshore and see fish swimming fathoms deep — have inspired comparisons to the Caribbean.

But “lakes aren’t supposed to look like an ocean,” said Taylor Skiles, a fisheries technician with the Michigan Department of Natural Resources, as she watched the divers’ breath bubble to the surface near the Nahma’s hull.

Her job was to provide topside support as Bootsma and two colleagues — graduate student Rachel Smith and DNR fisheries research biologist Ben Turschak — checked on their research plots.

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.

Whitefish are hit especially hard. 

For decades, their offspring have been dying within weeks of being born, either starved or burned alive as the sun pierces the transparent water. It likely doesn’t help that the reefs where whitefish spawn are now covered in mussel shells.

The only hope to save whitefish — once among the most abundant fish in the Great Lakes — is to figure out a way to kill the mussels.

If we lose (whitefish),” said Dave Caroffino, a fisheries biologist with the DNR, “It’s not as if you can just simply replace them with something else.”

That’s because whitefish aren’t the mussels’ only victims. So long as the food shortage persists, a host of species from salmon to perch will struggle to find food. And many species rely on whitefish, eating their eggs or preying on the newly-hatched young. That means as the whitefish dwindle, other fish suffer too.

A complex problem

Longshot species rescues aren’t without precedent in the Great Lakes.

Back in the 1950s, when invasive, bloodsucking sea lamprey were driving native fish to extinction, the US and Canada signed a treaty to create an international commission tasked with solving the problem.

Four years later, the commission’s scientists discovered a chemical concoction that could kill lamprey while sparing other species. Annual doses now keep the invaders at bay. It costs US taxpayers more than $20 million a year, but in return protects a fishery worth billions.

The mussel threat is similarly dire, but so far taxpayers have devoted a comparative pittance to combating it. 

Despite whitefish being the backbone of the region’s commercial fishing industry, a culturally important fish for Native Americans, a regionally celebrated cuisine and a crucial piece of the ecosystem, the primary source of funding for mussel control research, the Great Lakes Restoration Initiative, has devoted a total of $14 million to the cause since 2010.

“There’s a lack of public awareness or understanding about the severity of the issue,” said Craven of the Little Traverse Bay Band, “and certainly right now, an unwillingness to devote adequate resources to it.”

Related:

• Great Lakes mussel research starved of funds as whitefish vanish
• Iconic whitefish on edge of collapse as Great Lakes biodiversity crisis deepens
• What’s more Michigan than whitefish? Collapse erodes bit of state’s identity
• ‘We can’t regulate ourselves’ out of whitefish crisis, experts say
• It’s not just whitefish: 407 Michigan species on brink amid historic die-off

Mussels also lack the Achilles’ heel that makes lamprey vulnerable.

Adult sea lamprey migrate out of the lakes to spawn in river mouths, making their offspring easy pickings for targeted chemical warfare.

“It puts them into an accessible point where we can attack them,” said Ellen Marsden, an aquatic invasive species expert at the University of Vermont.

But the mussels spread out. 

Each mother — and there are quadrillions of them in the Great Lakes — can release up to a million eggs a year. The microscopic offspring, called veligers, spend weeks floating freely before they settle to the lake bottom. Any chemical to interrupt that process would likely need to be deployed across the entire Great Lakes, a task equivalent to treating 9 billion Olympic-size swimming pools. 

If even possible, it would be astoundingly expensive.

Scientists are still searching for other miracle cures. They’re trying everything from chemical and bacterial molluscicides, to parasites, to genetic engineering in hopes of killing or sterilizing the mussels en masse.

It’s a difficult task. Copper-based pesticides can kill mussels, but they may also kill everything else nearby. A product called Zequanox, made of the dead cells of a soil bacteria, targets mussels while sparing other species, but it’s designed for use in small ponds as opposed to the vast Great Lakes.

“You have to get it to the lake bottom where the mussels are,” said Diane Waller, a biologist with the US Geological Survey’s Upper Midwest Environmental Sciences Center. “In its current formulation, it doesn’t really stay at the bottom.”

Waller sees hope in ongoing efforts to identify the genetic “messengers” that instruct mussels’ bodies to produce proteins they need to survive. Once identified, a technique known as RNAi could be used to silence them.

But it won’t be perfected for years to decades, at best.

An unlikely ally

So researchers like Bootsma are focused on buying whitefish some time.

If they can clear off a few important spawning reefs, perhaps more fish will manage to lay eggs. With luck, some small portion of them will find enough food to survive to adulthood.

The work started in 2016, with divers using putty knives to pry mussels from the rocks. Next, they tried smothering them under large tarps and dosing them with a mussel-killing product called Zequanox. The latest prototype, known as the “mussel masher,” is a 1,200-pound steel plate that’s hitched to a boat and dragged along the silty lake bottom near Milwaukee, crushing the mussels’ shells.

“We thought they would come back quickly,” Bootsma said. 

Instead, an unlikely ally has kept the plots clear for years: An invasive fish known as the round goby that has been blamed for displacing native fish and spreading diseases like Avian botulism.

Like the quagga mussel, the goby is native to Eastern Europe. It evolved with a shell-crushing bone in its throat, making it one of few species that thrives on a diet of zebra and quagga mussels. 

Gobies are now widespread in all five Great Lakes, numbering in the billions. No sooner do young mussels recolonize the cleared plots, than the bottom-feeding gobies appear to be plucking them off. 

The environment has responded in small but important ways: On the cleared plots, nuisance algae that blooms atop the mussels has been replaced with beneficial diatoms that are a food source for the small invertebrates that fish like to eat.

This summer, a team led by scientists at the US Geological Survey will expand the mussel removal experiments to 500-square-meter areas, using a $1.5 million grant from the Great Lakes Restoration Initiative. With the gobies’ help, they hope to create a small ecosystem-within-an-ecosystem where whitefish have slightly better odds.  

They’re still operating at a scale that pales in comparison to the vast lakes, Waller said, “but it’s a start.”

And if it fails?

There’s still a chance that nature could reach a new equilibrium before it’s too late for whitefish, Bootsma said. Some invasive species explode during their first years in a new environment, then later dwindle to manageable numbers. 

It’s too soon to know whether quagga mussels will follow that pattern, but there are reasons to hope. Although mussels are still expanding their territory in the deepest water, they appear to be thinning out along the shorelines that they colonized first.

“It’s hard to find a silver lining in the story,” Bootsma said, but “we haven’t reached the end of the story yet.”

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