Testing the Water: Tearing the Great Lakes Food Web Apart

Quagga mussels have altered the water chemistry of the Great Lakes, posing new challenges to fisheries managers. Image: Ashley Elgin, NOAA

By Kurt Williams

Editor’s note: This is the first in a series of stories about the profound ecological changes that are testing our ability to manage the Great Lakes. It’s a test that comes as state and tribal authorities negotiate a key deal affecting fish and fisheries for the next 20 years.

The food web of Lakes Michigan and Huron has changed in ways that challenge centuries-old fishing traditions and raise questions about how we have managed them.

It’s an ecological disturbance that sets the stage for deciding how to manage the lakes in the future, even as state and Native American negotiators determine how best to apportion the lake’s fish.

Negotiators are currently updating a Consent Order of 2000, the legal settlement that specifies where and how much whitefish and lake trout can be harvested by commercial recreational, state-licensed and Native American fishers.

The new decree was due to be finalized in 2020 but the process was derailed by Covid 19, resulting in multiple court-approved extensions. Negotiations are continuing with a deadline fast approaching at the end of June.

Dave Caroffino

The parties cannot comment on the ongoing process. Dave Caroffino, a fisheries biologist with the Michigan Department of Natural Resources and one of the negotiating team members confirmed the deadline. He declined to comment on how ecological changes in the lakes might affect the negotiations.

But they occupy an important place.

A new world order

Remember the hype around the year 2000 – how once the calendar shifted to a new century some people predicted that life as we knew it would come to a halt, perhaps even heralding a new world order?

It was a bust. But while the new century looked a lot like the end of the previous one to us, for many Great Lakes people, a new world order was indeed being established. Rather than a computer glitch, this one was engineered by quagga mussels, a thumbnail-sized invader of Russian and Ukrainian waters.

Steve Pothoven

In the early 2000s, Steve Pothoven watched Lake Michigan transform in four short years, but he wasn’t there to see it happen.

The fisheries biologist at the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory in Muskegon has worked on Lake Michigan since 1998.

His account of what happened to the lake 20 years ago is an aquatic version of the saying that a falling tree in the forest makes a noise if no one is there to hear it.

But in this story, the tree is the food web of Lake Michigan, and the sound, if there was one to hear, would be that of ecological collapse.

NOAA scientists had been monitoring the impact of zebra mussels, another invasive species that arrived before quaggas, since the late 1980s, Pothoven said. They were largely restricted to shallow waters.

In 2003, a change in NOAA’s budget priorities removed Pothoven and his colleagues from their long-term oversight, he said. In 2007, the priorities returned and they got the green light to get back on the water.

“A lot of big changes started in 2003, and then we had a few years apart where we weren’t funded to work overseas,” Pothoven said. “So in 2007 when we went back offshore very intensively, and that’s when it was like, ‘yeah, everything is different.'”

The timing was “just great, right?”

His sarcastic observation is because the lake then looked visibly different, even in deep offshore waters, reflecting the impact of quagga mussels which had begun to displace their cousins ​​the zebra mussels which had remained largely near shore.

The spread of invasive zebra and quagga mussels in Lake Michigan from 1994 to 2015. Image: Ashley Elgin, NOAA

Quagga mussels quietly invaded the Great Lakes around 1990, arriving as stowaways in ballast water collected from ships plying the Black and Caspian Seas where the mussels are native. Quagga mussels now claim the deep waters of Lake Michigan as their own, exploding into the hundreds of trillions. These invaders dominate the bottom of the lake and, in many ways, dominate the lake itself.

A sneak attack

In the four years Pothoven and his team weren’t on the lake, the quagga mussels kept busy doing what mussels do — filter feeding — literally sucking life out of the lake. Night and day, regardless of the season, they drew water from their bodies, extracted oxygen, and fed on a myriad of microscopic plant life.

Known as phytoplankton, this waterborne plant life is the basis for much of the rest of the life in the lake. Aquatic life as diverse as the smallest microscopic animals down to lake trout, lake whitefish and salmon coveted by humans all depend on phytoplankton for their existence.

Phytoplankton under the scanning electron microscope. Image: Elizabeth Alexson, Bart Van de Vijver, Carlos Wetzel, Luc Ector and Holly Wellard Kelly

The voracious appetite of mussels has been dramatic and, in some cases, catastrophic for fish – especially native lake whitefish – and the people who live by fishing this iconic species. When mussels get their food from the water, they pull in key strands from the base of the food web. Disturbing it is bad news for species like the native lake whitefish, which have difficulty adapting to new lake conditions.

They also make the job of policy makers, whose job it is to regulate water quality and fishing in the Great Lakes, much more difficult. There is a lot of money at stake.

Recreational fishing alone is a multi-billion dollar per year industry for the region. Jay Wesley, the Lake Michigan basin coordinator for the Michigan Department of Natural Resources, pegs annual economic activity for the entire Great Lakes region related to recreational fishing at $7 billion, Michigan’s share “at least four or five billion dollars a year”, he said.

Muskegon, Michigan, home to Pothoven and the NOAA lab, is a Lake Michigan city bordering what are arguably the most contested waters of the Great Lakes: the 1836 treaty waters.

Territories of Michigan divided by treaties between indigenous peoples and the United States. Image: Michiganology, Michigan History Center

These are the waters covered by the ongoing negotiations on the Decree of Approval. The origin of their designation as the Waters of 1836 began with the Treaty of Washington of 1836, signed by the Ottawa and Chippewa Indian Nations and Henry Schoolcraft, Commissioner of the Michigan Territory.

This treaty, the penultimate treaty signed in a flurry of diplomatic activity between non-Natives and Native Americans that ended their war, forced Native peoples off most of their ancestral lands, paving the way at Michigan State in 1837.

Quagga’s invasion is the last unforeseen challenge

The impact of quagga mussels on lakes is fascinating, complex and impactful. It is the one that weaves together history, biology, chemistry and human nature. What their presence in the lakes means for the future of Great Lakes fishing is an open question.

But this is just the latest in a long litany of unforeseen events coinciding with the migration of people to the region.

Such events had a profound impact on the lakes and the lives of Native Americans, said Kevin Donner, program manager of the Great Lakes Fisheries program for the Odawa Indian Band of Little Traverse Bay.

“I’m pretty sure that in 1836 no one could have imagined that gaspereau, lamprey, gobies, mussels – chinook salmon for that matter – were a significant part of that fishery,” he said. he declares.”

Water test series:

Day 1: Tearing the Great Lakes Food Web apart

Day 2: Quagga mussels hijack an essential nutrient from the Great Lakes

Day 3: Where biology meets geometry in the Great Lakes

Day 4: One fish, two fish – where are all the whitefish?

Day 5: A long history and a promising future of human impact on the ecology of the Great Lakes