For the first time in nearly a century, native river life may soon return to a barren stretch of the Mississippi River above St. Anthony Falls in downtown Minneapolis.
Biologists believe conditions are finally right to bring back endangered river mussels — one of the foundations of aquatic life in the Mississippi — now that constant dredging to keep the upper river open for barge traffic has ended and the water is cleaner than it has been in a lifetime.
The Minneapolis Park and Recreation Board, which has already restored one small island as habitat for the long-lived mussels, plans to restore three more. The board will work with the Department of Natural Resources (DNR) to recreate about a mile of natural river bottom along a stretch that was nearly destroyed and sterilized by decades of dredging. Once the habitat is ready, the DNR will release young and endangered mussels raised in a lab near Lake Pepin.
If the agencies can restore mussel populations above the falls, it would mark the latest triumph for what is becoming one of the state’s greatest — and most unheralded — environmental turnarounds. It could open up what has long been an industrialized part of the river for fishing and bird-watching, said Adam Arvidson, director of strategic planning for the Park Board.
“These mussels exist completely out of sight, doing amazing things,” Arvidson said. “They’re the unsung heroes of the ecosystem that eventually result in bringing in the birds people want to see and the fish people want to catch.”
The mussels, which range in size from as small as a fingernail to as large as a palm, play an essential role in a river’s food chain and form much of the habitat that harbors the small building blocks of life, said Mike Davis, DNR ecologist and project manager for the state’s mussel survey.
“Mussels are the coral reefs of rivers,” he said. “The smallest aquatic insects live in these mussel beds. The fish eat the insects and the birds eat the fish. Their shell material can stabilize the bed of the river so it doesn’t erode.
“Mussels create this positive feedback loop.”
But for most of Minneapolis’ history, they’ve been all but eliminated from the river.
In the 1800s, button factories opened all along the Mississippi, harvesting and collecting shells from river mussels and mollusks by the millions to make their buttons, Davis said.
“Even before the factories, people would be hunting for pearls,” Davis said. “If just one marketable pearl was found, hundreds of people would go into the river killing mussels looking for more.”
As the population of the Twin Cities started to explode in the 1880s, all the raw sewage and wastewater being dumped into the river created a massive dead zone. By 1900, button harvesters were complaining that there were no shells left in the river upstream of Hastings, Davis said.
The dead zone remained until around 1950, when a group of homeowners near Lake Pepin threatened to sue Minneapolis for poisoning their downstream lake with the city’s untreated sewage. To settle the suit, Minneapolis spent millions of dollars separating the city pipes that collected raw sewage from the pipes that collected storm runoff. The water quality results were immediately noticeable in the river, Davis said.
But river mussels didn’t really start making a comeback until the Clean Water Act was passed in the 1970s. By that time, many of the 50 native species were all but gone from major portions of the Mississippi and other Minnesota rivers.
The DNR started to have success saving the mussels in the 1990s, when it began surveying rivers for species and collecting endangered females from Iowa and the St. Croix River to rear their young in the safety of a lab.
Davis and a team of DNR biologists began releasing mussels in the Cannon River and lower parts of the Mississippi in the early 2000s and can see encouraging signs there.
“We’re just now finding four- and five-year-old animals, which shows they’re reproducing on their own,” Davis said.
That mussels are able to survive and reproduce at all is something of a wonder.
Almost entirely stationary, the creatures rely on fish to carry their larvae. Some species, such as the federally endangered Higgins eye and the plain pocketbook mussel, evolved lures that look like minnows to attract the fish. Fish come to eat the minnow look-alikes, but instead find a hard shell and a larvae sac that attaches to their gills, where the larvae live until they grow large enough to fall off, leaving the fish unharmed.
Davis has been studying native river mussels for more than 30 years.
One of their greatest contributions is how well they clean the water, he said.
“Their favorite food is E. coli,” Davis said.
They don’t just eat harmful bacteria; they filter and sequester chemicals and poisons by depositing them into their shells. Since nothing eats a mussel’s shell, it’s one of the few natural ways to remove a chemical from the food web.
“Some of our native mussels live to be more than 100 years old,” he said. “Their shells have rings just like trees, and those shells store a record of what has been coming down the river over the years.”
It’s unclear exactly when the DNR and Park Board may be able to start reintroducing mussels above St. Anthony Falls.
Funding for the project, estimated to cost about $2 million, has been tied up by a partisan fight among state lawmakers. The Legislative-Citizen Commission on Minnesota Resources, a group that recommends how to spend money raised each year from the state lottery, recommended funding this year.
But a standoff over the state’s adoption of stricter vehicle emission standards erupted between the GOP-controlled Senate and the DFL-controlled House. The impasse blocked spending of $61 million that would fund about 80 restoration, park expansion and environmental research projects.
Arvidson said he is hopeful the funding will come through this year or next. The beauty of the mussel project is that the work to make more natural shorelines and backwater bays for young mussels and small fish will also remove concrete and steel river walls in north Minneapolis, opening up more entrance points to the river, he said.
“The upper Mississippi is the only waterfront property in the city of Minneapolis that has never been public,” he said. “There is a need to open up the waterfront so folks on the North Side can access this great water resource that has really been cut off from the community.”