A soon-to-be-released documentary film, All Too Clear, will give us all a new view of what’s happening below the surface in the Great Lakes. “They’ve got footage that has astounded even people who are underwater all the time,” says Brenda Moraska Lafrancois, Midwest Region Aquatic Ecologist for the National Park Service (NPS). “It communicates what the underwater world of the Great Lakes is like in a really fresh, amazing way.”

AGATE reached out to Lafrancois for her perspectives as a scientist working on issues in the Great Lakes Region. She has spent a good part of her career immersed in watery realms, diving in places like the Apostle Islands Natural Lakeshore, Isle Royale National Park, and Sleeping Bear Dunes National Lakeshore. Biogeochemistry is her passion. She works to better understand the complex systems supporting life in the lakes, both out of pure scientific interest and in the interest of informing NPS management decisions. “It’s in the original language of the act that created the National Park Service that we are to preserve these ecological systems unimpaired,” she says, “which also helps preserve the experiences that people hope to have in these special places.”

In this work, no national park is an island: even when it is. More often than not, says Lafrancois, solving a problem related to aquatic resources in a park involves solutions beyond your boundaries. Here in the Great Lakes region, it calls for consideration of large-scale ecosystem dynamics as well as teaming up with ever-changing constellations of people, institutions, agencies and nonprofit entities focused on the lakes. “It’s tremendously collaborative,” she notes. Researchers commonly share skills and cooperate on work led by others.

All Too Clear is a project of Ontario-based Inspired Planet Productions. It brings together many threads of inquiry that Lafrancois and her colleagues across the broader scientific community have been investigating into a central, powerful story: the story of the ecological cascade that followed when invasive species—in particular, exotic Dreissenid mussels—entered the freshwater aquatic system of the Great Lakes.

Wait. Can a lake be too clear?

Students of Limnology 101 learn that lakes in their natural state can be classified along a scale of “trophic states” between oligotrophic (nutrient-poor, little energy productivity) and eutrophic (nutrient rich, highly productive). More eutrophic lakes tend to be associated with reduced water clarity, since they are home to a greater mass of plants and animals, each organism engaged in a panoply of activities associated with living, dying, decomposing. Cubic meter for cubic meter, oligotrophic lakes support less of this bio-mass and tend to be more clear. Lakes fall into these categories based on their inherent chemistry, biology, and physical characteristics (such as basin depth and geology).

Water bodies are often accelerated along the scale toward excessive eutrophication with human-related inputs of nutrients such as untreated wastewater or fertilizers in run-off. These “overfed” lakes offer poor habitat for many invertebrates, fish, and wildlife intolerant of the resulting conditions—as well as for people. It’s a familiar problem that society has worked to remedy with varying degrees of success.

But we’re dealing with something else here: a situation where a move toward the extreme oligotrophic end of the scale—toward greater water clarity—is not a win, but a warning.

Lafrancois explains. “When we’re doing work in Lake Michigan at Sleeping Bear Dunes right now, the waters look tropical. We dropped in on a dive in October of last year where we could see the bottom in 70 feet of water. So it is very, very clear. Biology is typically kind of messy. Instead, we’re finding an empty cupboard situation where fish and other things that rely on the food particles and energy sources that would typically be in the water in the form of phytoplankton or zooplankton are showing up and realizing that stuff just isn’t there; there’s nothing to eat where they used to look.

“Some of them have been able to adapt and forage on the bottom, because this energy hasn’t necessarily gone away. It’s been sucked down by a huge, thick mat of invasive mussels. There was a paper a few years ago that called it the near-shore shunt. All this energy that used to be up in the water column and available for the fish that everybody likes to catch commercially and recreationally was essentially relocated and now is only available to fish that are able to feed on the bottom.”

This energy resides largely in the form of two mussel species first reported in the Great Lakes in the 1980s: Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel). As filter feeders, these organisms essentially “vacuum up” food that had once existed higher in the water column, with a single zebra mussel capable of filtering a liter of water per day. The energy is also present in their excretions, and in expanded benthic food webs operating along the lakebed. Says Lafrancois, “It’s a massive re-engineering of the whole food web.”

Whereas zebra mussels tend to attach on structures, quagga mussels also spread carpet-like across soft sediments on the lakebed, even in deep, cold waters.

Prior to the exotic mussels’ arrival, native Diporeia—a crustacean the size of a rice grain—had been the dominant benthic organism throughout the Lakes. These nutrient-dense cousins of krill and shrimp are “detritivores,” feeding on organic material that sifts down through the water column as detritus. Diporeia has been recognized as a keystone species in the Great Lakes ecosystem, serving as a prime food source for forage fish like alewife, sculpin and chub that are important prey for larger fish like bass, salmon and lake trout. Soon after the arrival of the invasive mussels, researchers observed sharp declines of Diporeia from Lakes Ontario, Erie, Michigan and Huron. The species has since all but disappeared from these lakes, though still hanging on in Lake Superior.

As a food source, the mussels don’t come near to filling the shoes of Diporeia. Even those fish that have managed to shift their diets to the newcomers, such as whitefish, expend more energy in digestion for less nutritional value.

Ripple effects don’t stop at the water line. Greater water clarity has allowed more sunlight to reach the bottom in near-shore areas. This, together with availability of nutrients concentrated on the lakebed, has fueled the growth of native Cladophora algae to nuisance proportions, choking water intakes and fouling beaches when it sloughs off. Further, these algae are implicated in another twisty problem that investigators have been working on: the avian botulism that has led to periodic massive die-offs of migrating waterfowl, in particular, loons.

“There are a number of elements to a proposed botulism pathway that have a lot of heavy support from many lines of evidence, and Cladophora is one of those,” says Lafrancois. A growing body of research suggests that outbreaks of avian botulism are made more likely when an overabundance of this algae creates low-oxygen conditions on the lakebed. Warmer water and lower water levels reflective of climate change may compound the problem, further ramping up levels of the naturally-occurring botulinum toxin. Here is where another invasive species factors in the pathway: the Round Goby fish. Goby fish feeding along the lakebed can pick up the toxin, passing it along in deadly concentrations when consumed en masse by loons and other waterfowl.

For organisms relatively new to the Great Lakes system (traveling from the Black and Caspian Seas via the Great Lakes seaway) these invasive mussels have proved to be an astounding transformational force. Lafrancois points to paleontological research led by Mark Edlund, subject of a forthcoming paper she co-authored. The study used sediment cores from coastal embayments in Lake Michigan to reconstruct environmental history. “One of the takeaways was that, for all the changes that have gone on throughout Great Lakes history, the sledgehammer doesn’t happen until post invasive mussels, and especially, after the quagga mussel really established here.”

So, how does one combat a pervasive, quietly destructive sledgehammer?

By learning how it operates. By understanding the role it plays in biogeochemical cycles: the processes it alters in the ecosystem, what it disrupts. By testing removal and restoration strategies on a small scale in high priority areas. By preventing spread into currently uninfested areas. All of the above.

All Too Clear highlights some of the recent mussel-related projects underway in the waters off of Sleeping Bear Dunes. “There has been a big movement to map the Great Lakes lakebed environment,” says Lafrancois, “and fortunately, the Sleeping Bear Dunes area of Lake Michigan is one of the best-mapped areas, which has really informed the process.”

The focus is on near-shore reef (sometimes called shoal) environments which are hotbeds of biological activity. For practical purposes, these areas are also diveable, unlike deeper areas of the Great Lakes that require remote operating vehicles (ROVs) maneuvered from the surface. Some reefs are extensions of shoreline that historically would have been exposed at lower lake levels; others are essentially submerged islands. Here, they range from 5 feet to 30 feet below the surface.

These aren’t the living coral reefs of marine environments, of course, but serve a necessary function supporting biodiversity in this freshwater setting. “We’re finding that these Great Lakes reefs are really important biologically, as places where fish congregate, particularly for spawning at certain times of the year,” says Lafrancois. “That’s actually been one of the heartening aspects about this whole thing. Through our partners with the MI DNR and the tribes—who have been doing a lot of fish sampling and radio telemetry work looking at where fish travel and how they utilize these reefs—we’re learning that fish don’t use the whole reef. There are key areas on the reef that have certain kinds of geo-form features, like these rocky ridges, that they seem to really savor for laying their eggs and for spawning congregation. That’s heartening to us because it tells us that maybe to help fish, for example, we don’t have to fix the whole lake problem. Maybe we can do some more surgical work on parts of these reef environments and see ecological benefits.”

In that battle with the sledgehammer, this is where the “testing strategies on a small scale in high priority areas” part comes in.

With the help of federal funding via the Great Lakes Restoration Initiative, various methods to control invasive mussels have been piloted in test plots off Sleeping Bear Dunes. Many groups have invested time and expertise, including but not limited to the U.S. Geological Survey (USGS), The Nature Conservancy (TNC), NPS and a host of others. Key among them is Harvey Bootsma, ecologist from the UW-Milwaukee School of Freshwater Sciences, bolstered by a citizen dive team. Initial efforts focused on physical removal of mussels by divers using paint scrapers.

Yep, you read that right: divers on the bottom of Lake Michigan with paint scrapers.

Lafrancois laughs. “Yeah, it’s as simple as it sounds.” That is to say, labor intensive but not complicated. She has been among those divers scraping mussels off of rocks, a participant in the initial removal effort that Bootsma, UWM and citizen divers have since continued in many subsequent dives. She describes the experience. “These rocks are varying sizes, anywhere from baseball size cobbles to much larger boulders that are encrusted with mostly quagga mussels. And when I say encrusted, it’s layer upon layer. If you dropped a little quadrat down on top of one of these rocks and scraped it off, your estimate might range from 3,000 to 10,000 mussels per square meter. So, you descend on these spots and get to work. We would scrape them off into our hands and collect them in mesh duffel bags.”

They come off fairly easily. “They’re attached by these things called byssal threads, to each other and to the rock, but if you can kind of get down there to the base where the bottom ones are attached to the rock and jimmy the scraper under there, they come up in a layer, kind of like you’re moving sod,” says Lafrancois.

No-one is envisioning a plan to recruit armies of divers wielding paint scrapers to work their way along the underside of the Great Lakes basin. “I know it sounds kind of nutty,” says Lafrancois. “I don’t think anyone has delusions of grandeur that any single one of these strategies this will turn things around. But there have been some encouraging insights coming out of these small test plots.” One is how long the mussels have taken to recolonize areas where they have been removed, likely due in part to predation by the Round Goby. This suggests that the mussel populations may not have exploded in the Great Lakes as they did if the similarly invasive Round Goby fish had arrived first and tempered their expansion. But that ship, as they say, has sailed.

“Based on what the scientific community is learning at Sleeping Bear, we’re identifying better tools and methods, assessing the effects, and whether or not these small or immediate-scale removals in targeted areas are going to actually be beneficial for the ecosystem,” says Lafrancois. Phase one was the manual removal experiment with paint scrapers. Later trials have explored other physical methods such as use of benthic barriers (tarps rolled out and anchored with rocks or chains) to deprive the mussels of oxygen. A group organized as the Invasive Mussel Collaborative has also found some success in trials of chemical controls in an open water environment at Sleeping Bear Dunes with limited application of molluscicide. Elsewhere, near Milwaukee, Bootsma partnered with the National Oceanic and Atmospheric Administration (NOAA) in piloting use of heavy rollers—like push lawn-mowers—to crush quagga mussels that carpet the lake bed.

Lafrancois is glad that the efforts are bringing renewed public attention to the issue, as well as active involvement by groups across the spectrum, not only researchers and conservationists, but also people invested in fisheries, history, and tourism are now part of the conversation. She is hopeful that the upcoming film will further open people’s eyes to the far-reaching impacts of these mussels on everything from the fishery, to scenic beauty of beaches, to loons, to overall ecosystem health within and beyond the boundaries of the national parks.

Thus far, the lower Great Lakes have been hardest hit by the invasive mussels, says Lafrancois. Lake Superior is not immune, she says, but has not shown as heavy an impact to date. “The Lake Michigan experience has been part of what has motivated us to be aggressive in understanding what’s happening in Lake Superior. To the extent that we can avoid a repeat performance of a similar invasive mussel scenario in Lake Superior, I think we need to.”

There are definitely things that people can do to help, she notes. “One of the key things to remember is that, although invasive mussels have established in a lot of places, they haven’t in a lot of places. There are a lot of inland waters, even in Michigan—which is completely surrounded by invaded Great Lakes waters—that aren’t yet infested. And there’s a TON that people can do to prevent them from getting established there.”

She points to the wealth of readily available information for boaters about practices to prevent spread of invasive species (sometimes referred to as non-local beings). “There are really well established outreach campaigns related to cleaning your boat, drying out the wet parts of your boat, draining things that might be collecting water inside your boat (see links, following). All of those techniques are really appropriate and would definitely help to stem the tide into new places. The states have done a pretty good job now of labeling landings so that you know if you’re at a place with infested waters. If you are, that just means you have to be extra vigilant before going to another place that might not be infested.”

In the meantime, no-one is giving up on those places where the water in the Great Lakes is already “too clear.” Work continues as natural resource managers test controls, looking for opportunities to scale up where it counts.

Tempting as it is (and fun as it sounds) it’s not recommended that people run to the hardware store for a paint scraper quite yet. Better to check out the opportunities for volunteers to work as citizen scientists in the national parks and other organizations focused on the Great Lakes. Your time and elbow grease will be welcomed.

The scope and complexity of these environmental issues is indeed staggering. Most would agree that combatting invasive mussels with paint scrapers and push-rollers is a Sisyphean task. That said, our only hope is to focus on solutions. Think of the fish returning to spawn on their favored spot on the Lake Michigan reef, which citizen divers have scraped clear of mussels. Imagine what scaled-up, high-tech versions of these primitive methods could accomplish. Consider the clues and answers generated by scientific research—another human endeavor—that continually informs conservation efforts throughout the Great Lakes.

Future sediment cores will tell the environmental history of our brief time on this earth. It could be a story of how, despite their number and adaptive traits, against all odds, invasive mussels in the Great Lakes finally met their match: a generation of people determined to protect the places we love. Don’t be too quick to walk out as the credits roll. Maybe Sisyphus wins out.

Thanks to Brenda Moraska Lafrancois for her input to this story. Lafrancois is Midwest Region Aquatic Ecologist for the National Park Service. Among other aquatic issues, she has been working with invasive mussels for over twenty years at many parks in the Upper Midwest on a range of prevention, early detection, and control projects. She’s based in northern Wisconsin and enjoys exploring the waters and wilds with her husband, daughter, and dog.

Unless otherwise noted, all photos courtesy National Park Service.

Learn More & Get Involved:

• The Invasive Mussel Collaborative; especially IMC Pilot Project-draft updates

• Boater laws to prevent spread of aquatic invasive species:
In WI (Clean Boats, Clean Waters campaign)
In MI (Clean, Drain and Dry campaign)
In MN (Clean In Clean Out campaign)

• Volunteering in the National Parks as a Citizen Scientist

Agate Recommends:

• Following the All Too Clear documentary website for scheduled screenings. View the trailer!
• Supporting policy measures to minimize new arrivals of invasive species in the Great Lakes from ballast waters and other transport routes.
• Advocating for future federal funding for the Great Lakes Restoration Initiative (which was renewed in 2024 for another five years)