The setup looks like an unlikely combination between an aquarium and a robotics experiment.

At the bottom of a rectangular tank, 15 mussels sit nestled together, their round, dark brown shells nearly indistinguishable from smooth river rocks if not for the slightly agape crack between their shells.

Each one wears a pair of magnets, which attach to a mess of wires that snakes up and out of the water into a nearby box that feeds data into a computer.

It’s all part of a unique human-mollusk partnership at the Minneapolis Public Works water treatment plant along the Mississippi River in Fridley.

“When all the mussels close up, the computer sends a text message or email telling me that something’s wrong, something’s in the river,” said George Kraynick, the city’s water quality manager.

For nearly two decades, the mussels have served as a little-known first line of defense for detecting pollution at the facility, which supplies water to nearly half a million people throughout the metro area. An upcoming public engagement effort could soon help these unsung shellfish get their moment in the spotlight. 

“We want to have a clam cam that’s available 24/7 where you can just watch them move around,” Kraynick said. “We’ll also have a social media campaign where you can submit your name for the mussels and we’ll pick the top 15.” 

The campaign follows renewed investment in the program, the only one of its kind in the United States. 

How does it work? 

The concept is known as biological monitoring, which is when living organisms are used as sensors to assess water quality. The mussels are monitored through the magnets attached to their shells, which measure how wide the space between their top and bottom shell is. This space is where they intake water, feeding on nutrients and filtering out certain toxic chemicals. 

When their shells close, it can mean they have detected too much of a particular toxin in the water. If the majority of the 15 mussels shut their shells at the same time, the facility’s operators are notified that they need to inspect the water flowing into the plant. If there’s a problem, they can shut down the whole system until it’s resolved. 

Minneapolis gets its water from the Mississippi River, which flows south from Minnesota’s Lake Itasca through hundreds of miles of forests, farmland, towns and busy interstates before it reaches the Twin Cities. The water is not exactly clean when it hits the water treatment facility: common contaminants include pesticides, heavy metals and hydrocarbons that are found in petroleum and natural gas.

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The facility treats the water for all these pollutants and more, but in the event of a spill into the river, the plant can be inundated by dangerous chemicals before human-activated alarms can go off. That’s when the mussels come in handy. 

“[Interstate] 694 is right north of us,” Kraynick said. “If a tractor trailer falls off there, cracks open, dumps a whole load of diesel fuel or whatever, we’re probably not going to get a call from the on-duty officer in time to do anything. But [the mussels] will close up.”

Minneapolis has used mussels for this purpose since 2008, when it received about $25,000 in federal funding from the Environmental Protection Agency to pilot a biomonitoring program. The funding paid for the designing of the system, not the maintenance. That work (and cost) was left to the utility, which put $25,000 of its own money into the system, according to Kraynick.

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The Environmental Protection Agency gave money to two other cities in 2008 – St. Cloud and Moline, Illinois – but neither utility could get their biomonitoring systems off the ground the same way Minneapolis could. That’s according to Joel Allen, a retired Environmental Protection Agency scientist who initiated the federal program. 

“Minneapolis was really the one that was most interested and dedicated to making it work,” Allen said. The three cities were the first utilities in the U.S. to experiment with using mussels in this capacity, which also meant they were the first to troubleshoot problems and conduct research.

“We were just running blind with the whole system [those first years],” Kraynick said. 

While St. Cloud’s and Moline’s programs ran aground (Moline’s mussels died from stagnant water), the Minneapolis project chugged along – with a few hiccups. 

In 2014, the mussels outgrew their tank and the system needed updating, which Allen helped them fix. Six years later, similar issues resurfaced, but this time, Allen was unable to help them because the Environmental Protection Agency had shifted its focus to COVID-19 projects. 

This put Minneapolis at a crossroads. With just three mussels left in their tank (the others had outgrown it) and no internal knowledge of how the system actually worked, all signs pointed toward ending the program. 

But rather than give up on it, the city looked elsewhere for help: Neptune, a Colorado-based environmental consulting company that built the original biomonitoring system. The company was willing to update the system, which meant writing a new algorithm capable of tracking different behaviors in the mussels to better understand how they react to water quality. 

“We’re looking for significant departures from normal, happy, healthy feeding mussel behavior,” said Sean Foorman, an aquatic scientist at Neptune. 

Minneapolis invests in biomonitoring upgrades for water supply

In 2025, the updated system launched, along with a new alert system that notifies Kraynick by text and email any time the mussels have closed up. Those updates, along with a new display tank, cost about $200,000. Neptune charges Minneapolis a nominal annual fee to keep the system running. 

Kraynick said his bosses did not take much convincing to say yes to the project. “We have fairly deep pockets,” he said. “We have half a million people to protect, and it just makes sense to do it for a utility our size.” 

So far, the mussels have closed up just once since the new system was installed. That happened in March 2026 when a mysterious oily sheen was found drifting on the surface of the Mississippi, just north of the water treatment facility. The substance was immediately reported to the plant, which turned off its intake system for a day as a precautionary measure and set up containment booms along the river to push the substance away from the plant. 

But once the treatment facility turned their intake back on, the mussels closed up. That told the facility there was still contamination in the water.

“It was a reassuring look into the reliability of the system,” Foorman said. “[The mussels] picked it up even in the trace amounts that managed to get through after all their precautionary measures.” 

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While the Minneapolis mussels have proved their effectiveness, biomonitoring still hasn’t taken off in the United States. Experts point to a couple of different reasons.

The first challenge is a lack of investment in the systems. “I don’t imagine if you’re a tech investor, you’re looking at biomonitoring systems as a real moneymaker,” Allen, the former Environmental Protection Agency scientist, said. 

Biomonitoring in water treatment facilities is a public good, ensuring the public has access to clean and safe drinking water. Investing in it would require broad public support. “That just never really has materialized,” Allen said. 

Another challenge is that while the mussels are very good at detecting pollutants, they are not as sensitive to biological pathogens such as e. Coli, which poses a major risk to humans. They can tolerate higher concentrations of biological pathogens than humans, making them relatively ineffective at protecting utilities against them. 

Still, biomonitoring experts say mussels are an overlooked asset to water utilities.

“They are a proactive approach to monitoring water quality,” Allen said. “So often now we are reactive in that we don’t know that we have a problem until it has gotten through the entire engineered system.”

Mussels provide safety, education

Mussels are capable of detecting a problem in real-time, which can alert operators quickly that they need to take a closer look at the water coming into their facility. “They don’t even have to know what it is that’s necessarily coming to be able to take action to prevent it from contaminating,” Allen said. 

That’s what Minneapolis relies on them for, like in the March 2026 event. That contaminant was later identified as some type of hydrocarbon, likely from a small oil spill. But the city didn’t need to know what it was in order to act, thanks to their biomonitoring system. 

The mussels also provide the city with an educational opportunity for the public. The 2025 system update included a new display tank with its own set of mussels, which the treatment facility uses to educate tour groups about the biomonitoring system. And in the coming months, Kraynick said they plan to kick off their naming campaign and livestreamed clam cam. 

“We have no intention of stopping the program,” Kraynick said. “People just love them.” 

Claire Carlson is a Report for America corps member, covering drinking water for MinnPost and the Mississippi River Basin Ag & Water Desk. Report for America places talented journalists in local newsrooms to report on under-covered issues and regions.

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