- The Great Lakes of North America have been transformed by quadrillions of invasive mussels.

(Ashley): In a week's time, every gallon of water in Lake Michigan could have passed through a mussel.

(Brian): It's just incredible the clarity of the lake.

- The nutrients that used to fuel the world's largest freshwater ecosystem are now trapped in the lakebed, creating vast aquatic deserts.

(Jason): The number of fishers in the tribal community is at an all-time low.

The number of fish harvested is at an all-time low.

(Bo): There's been an 80% prey fish reduction to levels now that are lower than we've ever measured.

(Jason): We're going to have to think far outside of the norm, if we're going to save this relationship between the people and the fish.

(dramatic music) - The Great Lakes of North America form the largest interconnected body of freshwater on Earth.

While images of the oceans fill our screens and live in our imaginations, the vast and magnificent freshwater world has long been hidden from our view.

Only now, using state-of-the-art underwater drone technology, are we finally able to explore the wonders hidden beneath the surface of the Great Lakes.

(dramatic music) (water flowing) To imagine how to help the Great Lakes ecosystem adapt to the historic changes invasive mussels have caused, we must head 2000 kilometres, or 1200 miles west, into the Rocky Mountains of British Columbia.

Here on Kootenay Lake, they're adding something that most people would think of as pollution.

(Marley): On Kootenay Lake, we put liquid agricultural grade fertilizers, same as what farmers use, put that into the tanks, and the tug and barge have preset roots on the lake, and they dispense the fertilizer into the main part of the lake.

(gentle music) - It's not tiny invasive mussels that are causing nutrients to disappear from the lakes in this area.

The culprit here is much bigger.

- When the nutrient disappeared, so did the kokanee.

This small, landlocked salmon played a crucial role within the local food web.

But not long after the dams wer constructed in the 1960 and 70s, kokanee numbers fell to historic lows.

- The theory, the hypothesis was, let's put some nutrients in and see if that boosts productivity and brings the kokanee population back up.

(mysterious music) - In 1992, while much of the world was trying to take nutrients out of lakes to improve water quality, on Kootenay Lake, the Government of British Columbia started putting it in.

(Marley): We add about 41 metric tons of phosphorus and about 300 metric tons of nitrogen.

- The amount of nutrients added per year is roughly the amount getting stuck above the dams.

No one knew if this would work, because nothing like it had eve been tried at this scale before.

Marley Basset oversees a comprehensive program to monitor the effects of the added nutrients.

(Marley): Eleven Feet!

So, the end goal for the program is that we move nutrients from the fertilizer up the food chains.

So, we have to sample all of the parameters.

So, water chemistry, phytoplankton, and then zooplankton.

Okay, I'm bringing it up!

- Zooplankton are tiny aquatic animals key to the diets of many fish species.

- This sample is a sample that we just collected from the zooplankton tow.

When I see zooplankton in the jar, it's very exciting to know that there's a response, and it's also just really cool.

We spend a lot of time in this lake, and you don't really know what's going on down there, and you put a net in, and you pull it up, and you get to see them.

It feels really good.

- Okay, lowering!

- Okay.

(mysterious music) - Monitoring has shown that nutrient restoration has increased the amount of life in the lower food web by 50 to 100%.

This has resulted in more zooplankton for fish like these mountain whitefish, a close relative of the lake whitefish.

♪♪ The benefits of the nutrients resonate all the way up the food chain, to North America's largest freshwater fish, the white sturgeon.

This endangered species can reach six metres, or 20 feet in length and live for over 100 years.

They prefer high nutrient environments because they need to consume enormous amounts of food to survive.

But the species that benefits the most from nutrient restoration is the colourful kokanee.

The added nutrients have boosted their numbers by almost 300% in Kootenay Lake.

(water gently flowing) - It's a whole ecosystem approach, thinking it from the bottom up of how we could support the ecosystem.

You don't hear about that very often, so I think that's a really unique program that's happening here.

- Nutrient restoration works in Kootenay Lake, without causing water quality problems.

But could it work in the Great Lakes?

- It's hard to say how the Great Lakes would respond to nutrient additions.

I did some, some rough math and Lake Huron is nine times the size of Kootenay Lake and with the amount of fertilizer that we add into our lake, versus theirs, it would be about three hundred B train trucks to reach the same amount of nutrient additions that we do.

So, the logistics of it would be pretty challenging.

But then how would the ecosystem respond?

It's hard to know.

They're complicated.

What's going on over there is different than what's happening here.

(birds chirping) - While the Kootenay method may work, with so many people living around the Great Lakes, we might not need to work quite so hard to get more nutrients into the water.

- One of the wastewater treatment plants doing a great job keeping phosphorus out of the Great Lakes is the Ashbridges Bay facility in the City of Toronto.

It's the largest treatment plant on the Canadian side of the Lakes.

- The job of the wastewater treatment plant is to take away solids and bacteria, make the water clean, cleaner than when it came in.

(rhythmic music) Then you take that clean water, and you do not want to put it right at the end of the plant.

You want to take that water and disperse it into the lake, far away.

- The treated wastewater is currently dispersed about 1 km from shore, where it still has the potential to contribute to nearshore water quality issues.

But the city is putting the finishing touches on a huge new outfall to send the treated wastewater way out into Lake Ontario.

(William): So, this is a big pipe.

It's seven metres in diameter.

To put it in perspective, it's like a two-story house.

So, this outfall takes it three and a half kilometres out, and then disperses it into the lake.

- Originally designed to improv water quality around the Toronto shoreline, the new outfall could potentially be a mechanism for adding additional phosphorus into the offshore waters of Lake Ontario.

But the problem with adding nutrients to the Great Lakes, is that quagga mussels are a far more complicated problem than dams.

About 1000 kilometres, or 600 miles, northwest of Toronto, on the shores of Lake Superior, is the Large Lakes Observatory in Duluth, Minnesota.

(Audrey): So, these ones are from Lake Huron.

Depth location might have something to do with how hearty they need to make their shells to survive.

- Pretty green on the outside.

- Scientists here have spent decades studying the mussels, and their work has recently culminated in a shocking revelation.

(Audrey): We have done some work on modelling the effects of mussel populations on phosphorus in the lakes.

And we expected them to have a large impact, but the fact that they are completely controlling phosphorus cycling in the lakes was a bit of a stunner.

- For centuries, it has been growing human activity that has controlled water quality in the Great Lakes.

But not anymore.

- If nutrients were added to the lakes, a lot would get sucked up by the mussels, but there is no guarantee they would stay there.

(Audrey): Initial impacts of an invasion like this, those populations of mussels are going to be growing really, really rapidly.

And it's still happening.

Populations of these mussels are actively getting bigger, which means they are actively taking phosphorous from the water column and sequestering it, holding on to it in their biomass.

So, they're really decreasing how much phosphorous there is, which, in turn, decreases how much algae can grow, which really affects things like fish.

But, if there's a big die off, you can have the opposite effect.

- Quagga mussels in the cold, deep waters of the Great Lakes can likely live for decades.

But at some point, their populations will stop growing and start dying.

(Audrey): As that tissue decomposes, it's going to release all of those nutrients that were sequestered into the tissue.

And, so, "Are they going to have substantially different impacts as these populations stop actively growing?"

is a really huge question.

(mysterious music) - With so much of the Great Lakes' nutrients now inside mussels, it wouldn't take much of a die-off to cause potentially toxic algae blooms.

- Disappears pretty quickly.

Colour is green.

- Nowhere have algae blooms been studied more than at the Experimental Lakes Area in Northern Ontario.

Known as the world's freshwater laboratory, the Experimental Lakes Area was actually created to figure out what was causing algae blooms in the Great Lakes in the 1960s.

The groundbreaking experiments done here led to controls on phosphorus in the Great Lakes, and around the world.

- Algal blooms remain the number one water quality problem around the world.

It doesn't matter what country you go to.

If there's lakes, there's algal bloom problems.

So, in the lake beside us, we've experimentally added phosphorus.

And what we've done is induced an algal bloom.

- Scientists here are stil learning more about the nuances of algae blooms.

This experiment is studying the impact of iron.

But when it comes to creating algae blooms, nothing they've found in over 50 years of research comes close to phosphorus.

- Toxic algae love phosphorus.

It's like... it's like a treat for them.

So, then they blossom and grow the way they do.

- It only took about 20 kilograms, or 44 pounds of phosphorus to turn this lake green, a sober reminder of the risks of nutrient additions.

(Scott): Well, I think actually adding nutrients to stimulate productivity can be done, and it's shown that it can be done, and effectively without causing detrimental water quality effects.

I think in the context of the Great Lakes, because of this powerful role that these zebra mussels and quagga mussels are playing in cycling nutrients that caution should be exercised there, for sure.

It doesn't take a lot of phosphorus to cause a big problem.

- The vast majority of the lower Great Lakes are nutrient starved.

But a few spots, like the warm, shallow waters of Western Lake Erie are still plagued by algae blooms, caused by too much fertilizer running off farmland.

(sad music) The most serious occurred in 2014, poisoning the drinking water of Toledo, Ohio.

For that reason alone, it's unlikely we'll see nutrient restoration in the Great Lakes anytime soon.

(gentle music) But where does that leave the baby whitefish, who are starving in much of the Great Lakes.

And where does it leave the communities that rely on them?

Sault Tribe biologist, Jason Smith, thinks there may still be a way to use nutrients to help lake whitefish.

- Can we identify places that are important?

They were historically important.

This was a place where lots of fish came from.

And can we make a small ecological change, right in that same location, not spreading phosphorus willy-nilly throughout the Great Lakes, a small controlled amount in an area that we know is important for baby fish?

Maybe it's not the long-term solution, but maybe it's the bridge that helps keep this relationship between the people and the fish strong until we can find another answer that deals with zebra and quagga mussels on a permanent basis.

- For a long time, dealing wit the mussels on a permanent basis was considered impossible.

But then, as often happens in science, somebody made an accidental discovery.

(water bubbling) In this case, that person was one of the Great Lakes' mos respected underwater ecologists, Professor Harvey Bootsma.

The happy accident occurred at Harvey's underwater laboratory at Sleeping Bear Dunes National Lakeshore, in Northern Lake Michigan.

Harvey uses this laboratory to study what quagga mussels are doing to life on the lake bottom, which scientists call, "the Benthic Zone."

(Harvey): In 2016, we started a project here to remove mussels from a relatively small area, just 40 square metres.

And that was simply going down with paint scrapers and scraping mussels off of all the rock surfaces.

The goal at that time wasn't to see if we could remove mussels, it was just to see what happens to the benthic environment when we do remove mussels.

We thought within a year, or so, they would start recolonizing the rocks.

And now it's six years later and those rocks still haven't been recolonized.

And that was kind of curious.

What we think is happening is that those rocks can't be colonized because round gobies, another invasive species, they like to eat on mussels, and they especially like to feed on small mussels because they can crush the shells of small mussels.

- Like zebra and quagga mussels, the round goby came to th Great Lakes from Eastern Europe in the ballast water of cargo ships.

But unlike fish native to the Great Lakes, gobies evolved to see these mussels as food.

(Harvey): In the early 2000s, we just saw this round goby population explode in the nearshore zone.

So, we think that they're preventing those rocks from being recolonized because they eat the small mussels before they get the chance to grow.

So, that got us and other people interested in the secondary question of, "Well, can we actually remove mussels and at what scale could we do it?

Could we do it at a scale that would have any impact at all on the ecosystem?"

- Down to one!

- Down to one!

- Harvey's unexpected discovery jump-started a movement to figure out if controlling invasive mussels might be possible after all.

- We might have two lines down there when we get on station.

When we find a spot, we'll throw out-- - Leading the way is Harvey himself.

Today, he's headed out from his home base, at the University of Wisconsin-Milwaukee, into central Lake Michigan.

Supported by his team of graduate students, Harvey is setting up the first mussel control experiment ever attempted in deeper, offshore waters, where the vast majority of mussels are found.

- What we'd like to do today is see if some of the experiments we've been doing in shallow water can be repeated in deeper water.

So, we're going to do a dive here in a depth of 20 to 25 metres, and we're going to try putting down a tarp, which we've done in shallower water, to see if we can kill mussels by putting a tarp over them for a couple of weeks.

- The tarp has the potential to kill mussels by depriving them of food and oxygen.

(Harvey): As far as I know, this is the deepest anybody's gone to try to get rid of mussels.

It's always a little more challenging when you're doing a deep dive.

It's a little more dangerous, so, we've got to be cautious.

(water bubbling) - As they descend, the water becomes unexpectedly silty, greatly reducing visibility.

It only gets worse on the bottom.

(Harvey): Sometimes it's a challenge working at this depth because as soon as we start putting stuff on the bottom, there's a silt and sediment layer on the bottom and that gets kicked up.

So, it can be hard to see what you're doing.

(mysterious music) - Despite the near-zero visibility, they manage to spread the tarp out and weigh it with chains, with just enough air left to get back to the surface.

(water bubbling) - That was crazy.

It's usually pretty clear down there.

- Yeah.

- I think it's because it's so warm, all the way down, it's getting all stirred up.

Couldn't see diddly squat today.

And gobies were having a great time down there.

But we weren't.

(seagulls squawking) - One month later, Harvey returns to check on the results of the experiment.

Well, we hope to find dead mussels.

So, we'll lift the tarp.

I'm expecting we'll see dead mussels in the tarp.

So we'll see.

- They're both in.

- Once again, things don't go as planned for Harvey and his dive mate.

A strong current pushes them away from the experiment site, and they use up much of their air just trying to locate the tarp.

(gentle music) As soon as they start removing the tarp, the visibility is again reduced to almost nothing.

(bubbles rising) But as the silt clears a few minutes later, they're able to see the results.

Deprived of food and oxygen, the mussels did not survive.

(Harvey): It looks like all the mussels are completely dead under the tarp.

So, that's good, that's what we were hoping for.

Now we've got an area where we've wiped out all the mussels, and now we can track that over time to see whether the mussels come back.

- Got ‘er?

- Yup.

- Despite this success, Harvey is not optimistic about using tarps for deepwater mussel removal.

- That was a mess.

- Yeah.

- As soon as we started moving stuff, couldn't see a thing.

- The planning went a lot smoother than the execution.

- Well, we wasted half of our air looking for the thing.

Between the turbidity and running out of air, just, uh... - Not a good combination.

- Yeah.

When I was down there today, I thought, "We've got to come up with some other strategies," because there's a lot more risks diving at this depth to do that kind of work than there are at 30 feet.

It's just a lot more challenging.

We can't stay down there very long.

So, we've got to come up with some other method.

(mysterious music) - As Harvey considers a safe way to kill invasive mussels in the Great Lakes, some people are experimenting with using pesticides to remove them from smaller water bodies.

- In the years since the invasion of zebra and quagga mussels into the Great Lakes, they've been spreading throughout North America, transported by boats moving between lakes.

- The scale of this problem is just off the charts.

Every lake around the area has zebra mussels at this particular point in time.

- Apple Canyon Lake, a private, 400 acre, or 160 hectare lake in Illinois, has been infested since 2017.

(Al): We're seeing cut feet, or cut hands, or cut knees.

That's probably the worst thing.

- Fed up with the mussels, the community has decided to apply EarthTecQZ, a new pesticide that can control zebra and quagga mussels.

(Al): After investigating, we found that we could do something to hopefully get rid of those nasty little creatures.

- David Hammond is the Senio Scientist at Earth Science Labs, the company that developed EarthTecQZ, which is short for EarthTec Quagga-Zebra.

He's come to Apple Canyon Lake to oversee the application of the pesticide.

- Going in the water and snorkelling allowed me to see just how severe this infestation has gotten in just a few years.

They cover every solid surface.

The densities in some places are tens of thousands of mussels per square foot.

(Al): 17, 18, 19.

So, there you go, 20 mussels in a cage.

- Before the pesticide is applied, David is helping the community create mussel cages to monitor the effectiveness of the treatment.

- Okay.

So, what we have here is a cage that's being used to monitor mortality of the zebra mussels.

After we treat, we'll come back to this cage and count the 20 mussels that we just put in here.

And we'll evaluate them for how many are dead.

So if 10 are dead, then we've achieved 50% mortality.

(tense music) EarthTechQZ is a liquid ionic copper.

It causes the mussels to become sluggish over time and then eventually die.

It's the holy grail to find a pesticide that only kills the pest.

There's always some trade-off.

But luckily, zebra and quagga mussels are very sensitive to copper.

And so we take advantage of the fact that a very low dose of copper will control the zebra and quagga mussels without harming fish.

- The community could not afford to treat the entire lake with EarthTecQZ.

Instead, they are targeting th 24-kilometre, 15-mile shoreline with the pesticide.

(David): This lake is a bit of an experiment, because it's not an eradication.

We're just treating the shoreline, and we know the product is going to dilute towards the centre of the lake.

But it's certainly our hope that within a few days after treatment, we'll start to see above 90% mortality.

- Reverse!

- Two days later, Al is eager to check the traps.

(Al): I'm hoping to see, today, that all the zebra mussels, in all of the treatment cages, are, are actually dead.

And then, hopefully, then we'll see some little relief on the ecosystem.

Some zip ties.

Oh, big ones.

(Norm): Unfortunately, on this one, a number of them are closed.

(Al): This group looked was... looked like about 90% closed, which meant they're still living in this group.

- 10% mortality.

- 10% mortality, okay.

Well, let's go grab another... Where's another location on our chart?

There should've been another one just up a ways.

- Well, I didn't have luck on the last one.

This one's on you.

- All right.

These are all closed.

(Norm): Wait, there's one open one, oh wait, is it?

No, I don't see any opens.

These are all closed.

I'm not happy about that, but, you know... - All is not yet lost at Apple Canyon Lake, as the pesticide may need more time to work.

Meanwhile, in a small lab in Lansing, Michigan, scientists are working on a mussel control project that seems straight out of science fiction.

They are trying to create a biological control agent with the potential to eradicate all of the quagga mussels in the Great Lakes.

(Steve): We hope to develop an agent that could be introduced into a very discrete mussel population and then essentially spread throughout that waterway to all other mussels of the same species within that same waterway.

- Steve and his partner Marie-Claude are trying to genetically modify a mussel so that it carries a rare form of transmissible blood cancer, known as "Disseminated neoplasia."

When cancerous cells from one mussel are sucked into nearby mussels, those mussels will become ‘infected' with the cancer, eventually leading to the eradication of a population.

Because the agent is being engineered to work on a specific population of mussels, it's unlikely to spread to anything else.

- The disseminated neoplasia has a distinct advantage, in that, it's sort of out of the gate.

It's safe for almost everything.

I think probably the best thing to liken it to is transplantation.

And everybody knows that you can't just transplant an organ, let's say a kidney or something, from a random person into you without a lot of pharmacological intervention, right?

So, how could you expect tissue coming from something like a quagga mussel to survive in our bodies?

I think most scientists would agree that this is safe for animals, people, plants, and aquatic life.

The only thing that is at risk is very closely related species, like, a native species of mussel.

Our guess is that it would probably be non-toxic, but it has to be tested.

- Although this form of invasive mussel control holds promise, the work is going much slower than expected.

(Steve): It's almost like you're working with an alien life form.

You really don't know what to expect from them.

It's hard to make progress quickly because you're spending a lot of time just learning the rules of the game.

So, we are still learning the basics of cell biology and cell culture from quagga and zebra mussel.

- After almost three years of work, Steve and Marie-Claude have been unable to get any new genetic information into quagga mussel cells, making genetic engineering impossible.

But they've recently figured out how to spawn male and female mussels in the lab, giving them access to quagga mussel embryos.

They have high hopes they'll be able to inject new genetic material into these embryos.

- Embryonic cells are sort of the... the gold standard.

Those are really the cells that can generally be manipulated.

So, I think there will be breakthroughs to get us past that hump, in the next year or two.

And we're working hard to try to break that impasse.

- At the other end of the spectrum, some people are still trying to keep invasive mussels at bay the old-fashioned way.

(gentle music) (Brenda): We are using manual removal here in Lake Superior to try to get ahead of emerging infestations of these zebra mussels, because in Lake Superior, it's a little bit of a slower burn.

We didn't see the explosion that we've seen in the other Great Lakes, but we're starting to see, almost little spot fires, here and there, around the lake.

And so we're trying to kind of snuff them out where we find them.

- Brenda and her crew routinely check for mussels around boat docks, as visiting boaters who have not thoroughly cleaned their boats often leave behind unwanted guests.

(Brenda): So, today we were visiting the Rocky Island dock in the Apostle Islands National Lakeshore.

Over the years, the number that we find at this dock has been declining.

But today we got a big surprise!

We went down, and we started finding just a few like we might have in the past.

And then we found an area, kind of in the shadow of where a boat would be docked, and there were just a bunch of them on there.

They were on the tops of the rocks, on the sides of the rocks, they were kind of in between the crevices of the rocks.

If you turn a rock over, they were under the rocks too.

Ugg!

We've never seen a dock at Apostles like this.

Oh man.

I mean how many are in your bag?

I guess we'll find out.

- Yeah, we've got to count them before we make any claims on camera.

- Yeah.

- But it's devastatingly a lot.

Do a little count here.

(indistinct muttering) 26.

54.

6.

This is off the chart really.

So, this is 193 in this amount of time.

We've never seen this amount in any bags that we've ever pulled up.

- Mmm-hmm.

(Toben): The nightmare scenario is they start to have their own population and are reproducing here.

Yeah.

(water splashing) Thankfully, we know this is here, and we can keep an eye on it.

We can pick these off like we're weeding a garden right now, before it becomes a major thing, that's what we're trying to do.

- Despite today's setback, Brenda remains optimistic they can control outbreaks around park docks.

More concerning is what they'r seeing at fish spawning shoals west of the park.

(Brenda): When it comes to these dock-based infestations, I think we can nip them in the bud pretty easily before they become a problem.

- Okay, let ‘er go!

(Brenda): The shoals, where we're seeing some natural larval transport, that's a more difficult situation.

- The waters of Lake Superior were long believed to hold too little calcium for zebra and quagga mussels to build their shells.

But recent years have seen large numbers of zebra mussels colonize the Thunder Bay and Duluth harbours, possibly due to warming waters.

From Duluth, zebra mussel larva may be drifting with the current for close to 100 kilometres, or 60 miles, before landing on the fish spawning shoals near the Apostle Islands.

The nutrient-rich waters around the Apostle Islands are one of the most important fish nursery areas in the Great Lakes, and a crucial refuge for lake whitefish, whose numbers have plummeted elsewhere.

It's a place where zooplankton are still numerous enough to feed young whitefish, and where diporeia, the bottom-dwelling shrimp that used to feed many of the fish in the Great Lakes, still thrive.

(gentle music) A large-scale mussel invasion here would be devastating.

(Brenda): Hopefully we see densities that are no higher than we saw last year.

♪♪ (indistinct chatter) - Which are in our bags.

(Brenda): Looks like we've got 14 live, and 15 dead.

(Toben): It's a big haul.

(Brenda): This is more than everywhere else in the Apostles you dove last year combined, probably.

(Toben): Yeah, you're right.

We're hoping that removal efforts will continue to keep these reefs as clear as possible.

But, if this is going to be the case, where we see year after year of establishment, then we might be fighting an uphill battle.

- In every other Great Lake, the coming of zebra mussels preceded a much more damaging invasion of quagga mussels.

Let's hope that's not the case for Lake Superior.

Amidst the major challenge faced by those trying to control invasive mussels, there are reasons for hope.

At Apple Canyon Lake, almost one month after treatment by the pesticide EarthTecQZ, the results have improved considerably.

(Al): Now we've come back and looked at it.

I've seen nothing but millions, and millions, and millions of dead zebra mussels everywhere.

There's nothing down there but empty shells.

It's amazing.

I feel pretty good.

This is a win for the lake.

- Although the Great Lakes are much larger than Apple Canyon, it may still be possible to use pesticides to control mussels in certain locations.

(David): I don't think it's practical to entertain the notion of eradication from very large lakes, because it's too costly, and there'd be too much environmental pushback.

But, you could treat discrete areas of higher value, either for humans, or for the ecosystem within a large lake.

- At Biomilab, Steve and Marie-Claude have had a breakthrough.

They've been able to inject ribonucleic acid, or RNA, into a living quagga mussel embryo.

Not only have the embryos survived, the tiny modified mussels now glow red in fluorescent light.

(Steve): One day, we went up there and put the stuff in the microscope, and... boom, there it was right in front of our eyes.

Right in the first field of view that we had.

- The red mussels mean they've finally figured out how to genetically modify a quagga mussel.

(Steve): So, when we saw that, it was a huge relief because it meant that we will be able to create the cancer cell that is the overarching objective of the project.

And that cancer cell, we hope, will be able to be adapted to function as an anti-mussel agent.

(Harvey): So, we'll swivel it around.

- Harvey Bootsma has spent the last seven months designing an entirely new way to clear mussels from the offshore waters of Lake Michigan.

(Harvey): So, this is our benthic mussel masher, which we're hoping will mash mussels.

You can see, we've made this mostly out of... scrap we had out in the backyard behind our building.

Had some old train axles back there, they're about 400 pounds apiece, and then the steel plate itself is about 200 pounds.

So, all together, we're about a thousand pounds here.

So, we'll put it down there, drag it across the bottom, and see how it works.

(tense music) ♪♪ It definitely did something down there.

- Oh yeah.

- Yeah.

Can't say for sure yet how effective it was at crushing, or killing mussels.

Wow.

Definite distinction between... Yeah!

But certainly from the video it looks like a lot of stuff was cleared out of the area that we dragged it over.

It looks like a road has been paved down there.

We may need to do some tweaking of it, but I think, once we've done that, we may have something that we can ultimately use to try to clear mussels from a very large area.

It would be very gratifying if we could find ways to remove mussels from a large enough area that we did see some real positive responses.

For example, if we saw diporeia come back in an area, that would be really exciting, because that would lead to potential responses in the fish community.

So, let's poke it and see what happens.

(gentle music) - There's one more reason to be cautiously optimistic about invasive mussel control in the Great Lakes.

It's one of few places on earth, where a voracious aquatic invader has been conquered before.

Where quagga mussels feed on the bottom of the food chain, sea lamprey feed on the top, latching onto fish and sucking the life out of them like a vampire.

By the 1940s, they had devastated the Great Lakes commercial fishery, nearly wiping out lake trout, the top predator in the lakes.

But the sea lamprey has an Achilles heel, they migrate into shallow streams every spring to spawn, where they're easy t trap and target with pesticides.

- A massive ongoing control program has reduced the sea lamprey population to just 10% of what it was, across all of the Great Lakes, hugely reducing their ecosystem impact.

By comparison, quagga musse control is still in its infancy.

But it'll be an even harder challenge than the vampires of the Great Lakes.

(Jason): Until recently, most folks have kind of thought that mussel control was not doable.

I disagree with that.

I don't believe yet that folks in the Great Lakes region have the will to deal with them.

But if folks here had that willingness, I will always believe that it is a challenge we could deal with.

- With mussel control a long way off, the quaggas may be here to stay.

But there is another, mor hopeful, and entirely unexpected side to this story.

(David): As the lakes have become less productive, we assume they're a lot more like the lakes that existed hundreds of years ago.

(Arunas): All of a sudden, we were seeing signs of lake trout rehabilitation.

But how could you anticipate that that would be the outcome of the quagga mussels?

(Matt): Obviously, quagga mussels have done a lot of damage.

But it's ironic because it is an opportunity to restore the Great Lakes.

- There just might be a silver lining to these much clearer waters.

Subtitling: difuze