When toxins are present in a waterway, freshwater mussels are one of the first creatures to react. For this reason the researchers decided to exploit this aptitude.
A new motion sensor mounted on mussels has been designed with this specific purpose: it will make them a means of detecting water pollution early.
Mussel life
Mussels feed by opening their shells, then filtering tiny organisms out of the water. And although mollusks typically live in groups (also called beds), members of those groups usually don't all feed at the same time. This means that they typically open and close their shells independently of each other.
But there is a peculiarity: if a harmful water-based substance flows through a group of mussels, they will all suddenly close their shells at the same time. And this is where the new motion sensor comes in.
A motion sensor for cyborg mussels
Designed by a team from North Carolina State University, the motion sensor consists of two connected inertial measurement units (IMUs). One IMU is attached to one side of the mussel shell and the other to the other side. Each of the sides contains an accelerometer and a magnetometer.
When the mussel closes its shell, the two IMUs detect the action, as the angles of both sides of the shell suddenly change. Therefore, if multiple mussels in a single bed are equipped with sensors, it is possible to tell whether they close all their shells at once.
All the sensors for a group could be wired to a solar-powered processor mounted on a pole within a stream. That unit would in turn continuously transmit data via a cellular network. If the closure of a group shell was detected, the authorities could immediately start looking for the source of the toxin that supposedly caused it.
Laboratory tests on the motion sensor
When tested on freshwater mussels in fish tanks, the motion sensor consistently detected shell movement down to less than one degree. This technology could conceivably track dozens of “cyborg mussels” at once, allowing for granular precision tracking.
“Our goal is to create an 'Internet of mussels' and monitor their individual and collective behavior,” says Prof. Alper Bozkurt, who leads the study together with prof. Jay Levine. “This will eventually allow us to use them as environmental sensors or sentinels.”
