Sensors attached to mussels can determine if the water is contaminated

The NSCU team developed a new mussel-monitoring system to determine if there are toxins in the water. (Image Credit: NSCU)

This seems like an April Fools joke, but it isn't.

Or is it? It's not…. Or is it?

No.

Or is it? J/K, it's not.

Researchers at North Carolina State University developed and demonstrated a new system capable of remotely monitoring freshwater mussels and their behavior. Researchers could use the system to detect toxins in aquatic ecosystems.

"When mussels feed, they open their shells; but if there's something noxious in the water, they may immediately close their shells, all at once," says Jay Levine, co-author of a paper on the work and a professor of epidemiology at NC State. "Folks have been trying to find ways to measure how widely mussels or oysters open their shells off and on since the 1950s, but there have been a wide variety of challenges. We needed something that allows the animals to move, can be placed in streams and collects data – and now we have it."

"We've basically designed a custom Fitbit to track the activities of mussels," says Alper Bozkurt, corresponding author of the paper and a professor of electrical and computer engineering at NC State.

The idea behind this research comes from mussels' feeding behavior, which is asynchronous. If a group of mussels simultaneously shut their shells, it's likely an indication of contaminated water. The team is already performing tests with their sensor system to determine if mussels close their shells in coordination without toxins present in water.

"Think of it as a canary in the coal mine, except we can detect the presence of toxins without having to wait for the mussels to die," Levine says. "At the same time, it will help us understand the behavior and monitor the health of the mussels themselves, which could give us insights into how various environmental factors affect their health. Which is important, given that many freshwater mussel species are threatened or endangered."

To develop the low-cost system, the team deployed commercially available components. The system consists of two inertial measurement units (IMUs) with a magnetometer and an accelerometer. One IMU was placed on a mussel's top shell and the other on its bottom shell. With these specific placements, the team can record and compare how the shell halves move relative to each other. It allows the researchers to conclude whether the mussel is closing its shell or being tumbled in the water by a strong current.

The wires of the IMUs run to a data acquisition system mounted on a stake in the waterway. A solar cell powers the data acquisition system when it's in a natural environment. Data collected from the sensors then gets wirelessly transmitted to the researchers via a cellular network.  There are four mussels connected to the system, but it can support dozens.

Over 250 hours of testing was conducted with live mussels in a laboratory fish tank. The team discovered the sensors provided incredibly accurate measurements of the mussel's shell opening, which was recorded at less than one degree. Now, the team is conducting more tests to understand the system's robustness. For example, they want to find out how long it can last in practical use under real-life conditions. They plan to start field testing soon.

"In addition to exploring its effectiveness as an environmental monitor, we're optimistic that the technology can help us learn new things about the mussels themselves," Levine says. "What prompts them to filter and feed? Does their behavior change in response to changes in temperature? While we know a lot about these animals, there is also a lot we don't know. The sensors provide us with the opportunity to develop baseline values for individual animals and to monitor their shell movement in response to environmental changes."

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