For the past three and a half decades, zebra and quagga mussels have fundamentally altered the ecology and hijacked the food web of the Great Lakes. These small mollusks are literally sucking the life out of the lakes by filtering out the food that many fish and other aquatic organisms need to survive. They also transform the habitat, light environment, and chemical composition of the lakes.
But some of the top research scientists in our country are trying to find ways to control the far-reaching impacts of these invasive species. And they’re doing it on multiple fronts: In some cases, they are working with biocontrol agents in labs, while others are experimenting with blunt instruments, deep down on the bottom of Lake Michigan.
Commercial fishermen, who are trying to keep their businesses afloat despite the mussels, hope a solution could lead to an increase in fish populations once again, and restore a way of life.
Credits:
Producer: Jill Jordan Sieder
Editor / Host: Dan Wanschura
Music: Podington Bear
Transcript:
DAN WANSCHURA, HOST: It’s a foggy, October morning and a large research boat is several miles offshore from Muskegon, Michigan. On it, a team of scientists lower a steel claw about 150 feet down into the water. They’re after a sample of invasive quagga mussels on the bottom of Lake Michigan.
ASHLEY ELGIN: This is a beautiful grab. It’s textbook. You have very thorough coverage of mussels, you can see the sediment layers, it’s a beauty.
WANSCHURA: Once the claw comes out of the water and back in the boat, that glob of mussel-filled muck gets dumped into a big, metal colander and rinsed off.
What’s left are quagga mussels of all different sizes. They’re sort of a dull, brown color, and most are about the size of a fingernail.
Here, the population of mussels is so dense — some scientists say if you walked on the lake bottom from Wisconsin to Michigan — you’d walk on quagga mussels the whole way across.
These mussels are found in all the Great Lakes and they’re literally sucking the life out of them. The whole ecology and food web of these fresh water bodies have been hijacked by these invasive organisms.
And this has been going on since they arrived in the ballast water of ships from Europe and Asia in the late 80’s.
So, can anything be done to control these mussels?
This is Points North. A podcast about the land, water, and inhabitants of the upper Great Lakes. I’m Dan Wanschura.
Reporter Jill Jordan Sieder is on that research boat out in Lake Michigan.
She’s been following some of the top scientists in freshwater ecology who are trying to invent new ways to control and kill these marauding mollusks.
JILL JORDAN SIEDER, BYLINE: Mussels are like tiny filters. And when they number in the quadrillions, their strength is in their numbers. Mussels do their damage by sucking up nutrients like phytoplankton. That means less food for zooplankton — tiny invertebrates that get eaten by small prey fish like alewife and sculpin. And if there’s fewer small prey fish in the lake then the bigger fish like lake trout, white fish, perch and walleye are going hungry too.
But this bottom-up food chain dilemma isn’t the only problem for Great Lakes ecology. The mussels have colonized many of the places where fish and other aquatic species usually lay their eggs and grow. So they’ve also diminished fish reproductive cycles.
And by gobbling up nutrient particles in the lake, the mussels cleared the usually brown-green water, allowing more light to reach the lake bottom. And while that clear water is nice for swimming, it’s not great for the health of the lake.
Extra light penetrating the water — along with the nitrogen and phosphorus the mussels are constantly excreting — has caused hyper growth of nuisance algae.
And those gunky algal blooms are not so nice for fish, birds, and people swimming. Because of all this, Ashley Elgin calls these mussels ecosystem engineers.
ELGIN: They alter the light environment, nutrient cycling, the habitat, and as a result of all this, the food web of any lake where they’re introduced.
SIEDER: Elgin is a research ecologist with NOAA, the National Oceanic and Atmospheric Administration. She’s intent on ending the free-for-all these mussels have enjoyed over the past three-and-a-half decades.
Her NOAA crew is part of the Invasive Mussel Collaborative, a binational group trying to control the spread and negative impacts of invasive mussels in the Great Lakes.
Harvey Bootsma is part of that mussel collaborative. He’s an ecologist at the University of Wisconsin at Milwaukee.
Bootsma says when zebra mussels invaded the Great Lakes, they mainly stuck to warmer areas and hard surfaces — covering rocks near the shore, and clinging in clusters to the bottoms of boats and docks. But their cousins, the quaggas, they go everywhere.
They like rocks, they like docks, and they thrive in the sand and soft sediment of the lakes — especially the colder, deeper waters.
HARVEY BOOTSMA: So now, instead of having mussels in this thin ribbon around the lake, most of the bottom of Lake Michigan is covered with quagga mussels now.
SIEDER: Bootsma has been leading a number of experiments in Good Harbor Bay off the east shore of Lake Michigan over the past several years. He wants to better understand how mussels operate in the lakes and to find the best ways to kill them.
BOOTSMA: Our first study, we just went down with divers and scraped mussels off the rocks and took them away.
SIEDER: They removed a million mussels from those rocks in the summer of 2016. Six years later, the mussels have not returned. But that’s really labor intensive and not practical on a large scale.
BOOTSMA: Our second project was using a molluscicide called Zequanox. For that, we worked with the Invasive Mussel Collaborative and a consulting company called Limnotech who had to build a structure on the bottom of the lake to contain Zequanox. You couldn’t just have it floating away.
SIEDER: Zequanox is a biopesticide that is made up of dead soil bacteria and powder. Because it’s organic, the mussels see it as food and ingest it. But it’s lethal to them.
In 2019, Zequanox was pumped into a 40 square meter area over thick mussel colonies on the Good Harbor Bay lake bottom.
BOOTSMA: Originally the treatment removed 90% of the mussels. Now the mussel density is 50% to 80% of what it was originally.
SIEDER: Turns out, Zequanox isn’t very effective on the open waters of the Great Lakes. It’s better at clearing mussels from small ponds and water intake pipes.
That doesn’t surprise Dan Molloy. He’s a research scientist based in New York, who actually invented Zequanox. He says the molluscicide isn’t intended for open water.
DAN MOLLOY: It’s totally unfeasible economically. The only way to do it is if you put something into that lake which can spread to the rest of the lake by itself.
SIEDER: Now, Molloy has pivoted to trying a new method of mussel mortality. His latest approach uses a live parasite, which would shock and kill both zebra and quagga mussels — two different species of the genus, Dreissenid.
MOLLOY: I don’t know of another approach that has any chance of successfully being used eco-system-wide. Those Great Lakes are called ‘great’ for a reason. And the only thing that can do that in my knowledge is a live organism which is going to control these mussels, become established on its own, and spread throughout the entire Great Lakes.
SIEDER: For the past five and half years, Molloy has been working to find and develop a parasite that will work. And he’s looking for it in the waters where the Dreissenid mussels came from — Eurasia.
Molloy and his team have created a lab located in two trailers on a mountainside in Montenegro. So far, they have dissected over 5,000 Dreissenid mussels from lakes and rivers in Europe and Asia.
He’s hoping to find a bacteria or virus that already infects these distant cousins of North American zebra and quagga mussels and then bring that parasite back here to commit mass mussel murder.
Molloy hasn’t found it yet but he’s confident he will. And he’s got $1.4 million in funding from the U.S. Department of the Interior, Bureau of Reclamation, to do it.
MOLLOY: I’m going to be putting a live organism into the Great Lakes. It could be 10 years from now. These things take an enormous amount of time to demonstrate efficacy, and the other most important thing is safety…I will have to present data that builds the confidence that we’re taking more of a risk by putting these chemicals in than putting this little parasite in.
SIEDER: But not all scientists are excited about introducing a parasite into the lakes. Harvey Bootsma is one of them.
BOOTSMA: It’s kind of like the old days where we would introduce one species to control another species, but then the one that you introduced had a lot of effects you hadn’t counted on. And I guess I’m at least at the Lake Michigan scale skeptical enough of them that we’re still pursuing this simple physical approach…just because it’s so much more benign.
SIEDER: That simple, physical approach involves testing two primitive techniques to kill mussels. Last year, Bootsma lowered a giant tarp onto the bottom of Lake Michigan. It was weighted down by heavy chains.
BOOTSMA: The idea being if we could do that we could kill the mussels either by depriving them of food because there was no more plankton being delivered to them, or by depriving them of oxygen.
SIEDER: After a month and a half, Bootsma says they had 100% mortality under the tarp. And so far, the mussels haven’t come back.
The area they tarped was several hundred square meters. Over the next three years, they’ll be working in a much larger area — a two and a half acre plot in deeper waters near Milwaukee. There the mussels are bigger and more dense.
Besides the tarp method, Bootsma and his team are also rolling out another mussel mauling prototype.
BOOTSMA: We’re going to try a very heavy roller, and if we pull a heavy roller over the bottom, can we actually pierce, or puncture, or crush mussels with that. Kind of use this thing like a lawn mower on the bottom of the lake…We’ll test that before we spend a lot of money on making some larger equipment.
SIEDER: If this heavy roller method works well to kill mussels without harming other important organisms. Ashley Elgin says NOAA engineers will build industrial size, high tech devices to use in even larger areas of the lake.
ELGIN: It may be in the form of a remote operated underwater vehicle…to crush mussels and leave them in place.
SIEDER: If you were successful in that, is that something that could just be running on the lake bottom — you kind of program it — I’m thinking of, and forgive me for really oversimplifying —
ELGIN: Are you thinking about a Roomba?
SIEDER: I’m thinking of a Roomba! (laughs)
ELGIN: Yes. If we could get to a technology that could be discerning and could reliably run on its own, and destroy mussels in that way, I think that would be an excellent tool for us to have.
SIEDER: Wow! Cause you could really cover some ground.
ELGIN: Yeah…and it would be down there, mowing the lawn of mussels.
SIEDER: Elgin says they wouldn’t focus on the whole lake, but instead in strategic areas, including where mussels reproduce in high numbers.
Before they scale up either the tarp or roller techniques, Elgin says they’ll be inspecting all the organisms in the ecosystem of the treated areas for at least two years.
ELGIN: Because a massive and sudden removal of mussels would itself be a shock to the system. Because they’re so entrained in it. That’s why, at every step, we need to study all consequences for our actions, even for removal.
SIEDER: Few people may understand the drastic transformation that’s taken place under the water’s surface better than commercial fishermen of the Great Lakes. Charlie Hendriksen and his family have been fishing the waters around Sister Bay, Wisconsin for the past 40 years.
CHARLIE HENDRICKSEN: It has been devastating. The original invasion of the zebra mussel not only covered the inshore spawning grounds where the whitefish spawn, but it also made those fish go to deeper water, and they got smaller and skinnier.
At the time it started, we had an amazing fishery, that was all throughout Lake Michigan and the rest of the Great Lakes…and then, when the quagga mussels came in…the chubs disappeared. They just had nothing to eat…We went from doing 30,000 pounds of chub roll to 3000 pounds to 300 pounds in a two and a half year period.
SIEDER: Docked at a nearby harbor, Hendricksen sits in the captain seat of his boat named Roamer.
He says while his income has dropped dramatically, the saving grace for his family business has been that many years ago he purchased some fishing quotas in southern Green Bay. It’s one of the few spots in the Upper Great Lakes where whitefish are still plentiful.
Hendricksen says many of his fishermen friends who only have fishing quotas in Lake Michigan have retired or gone out of business.
HENDRICKSEN: Well, it has been really sad…None of us are capable in the mussel infested waters to catch the amount of quota we have. We used to have 8 boats in this harbor in the month of October, fishing successfully and doing well. And this year I think there might be two. So, that’s how it’s affected us.
SIEDER: He says if scientists’ do figure out a way to control the tiny, destructive mollusks, it could rejuvenate the Great Lakes fishing industry. And maybe even his community’s way of life.