Mussels can be a natural filter to remove microplastics from the ocean


In the waters of a marina near the Plymouth Marine Laboratory in England, a group of mussels are busy filtering the water for microplastics. As bivalves feed, they suck bacteria, algae, and anything in their environment, including microplastics, out of the water and into their gills. When they excrete waste, the microplastics accompany them – “repackaged,” says Professor Pennie Lindeque, scientific manager of the laboratory for marine ecology and biodiversity, in a way that allows people to collect and dispose of them. easily remove them from the ocean.

[Photo: courtesy PML]

Microplastics – tiny pieces of plastic less than 5 millimeters in diameter – are abundant in our oceans and rivers, breaking away from larger chunks of plastic pollution, wearing out tires that enter the water with them. runoff from the roads; and washing our clothes and traveling through sewage treatment facilities. Collecting these microplastics is difficult: When researchers try to use fine sieves to extract them from the ocean, they often end up collecting a lot of organic matter and marine life as well.

[Photo: courtesy PML]

Knowing that mussels are “naturally voracious filter feeders,” says Lindeque (an adult mussel can filter up to 15 gallons of water a day), she thought maybe they could turn to nature to solve this. microplastic pollution problem.

The mussels currently filtering the water in Plymouth Marina are part of a series of field trials; Already, Lindeque and his team have completed laboratory research in which 5 kilograms of mussels (about 11 pounds, or about 300 mussels) were placed in a flow tank, which mimics currents, along with phytoplankton for food. and microplastics. In this experiment, the mussels filtered over 250,000 microplastics per hour. It’s in terms of parts; Computer modeling in the lab revealed that mussels could filter up to 25% of microplastics in water.

These microplastics got trapped in the mussel poo, which naturally flows into the water column. The researchers were able to collect all of this excrement and dispose of it. In the future, Lindeque hopes to investigate whether this plastic-filled poo could be used as a biofuel, since it’s high in carbon. In field trials, the team uses nets with containers underneath to catch all of this waste, so the pieces of plastic and poo don’t sink to the bottom of the ocean. (This research received funding from the Waitrose Plan Plastic grant fund, which uses money from the sale of plastic bags at Waitrose grocery stores to find solutions to reduce plastic pollution in the UK)

[Photo: courtesy PML]

Due to their exceptional filtering power, mussels have been used to clean polluted water as “blue infrastructure” and to monitor heavy metals. Using them to clean microplastics is a first, says Lindeque. As research continues, she will focus on using molds where microplastics enter the water, such as near a storm drain or at the end of a pipeline from a water treatment plant, or in marinas and ports.

All of this happens without any damage to the mussels, says Lindeque. Smaller pieces of plastic called nanoparticles can slide through mold membranes and enter their tissues, but the microplastics are too big. While some previous research has shown that exposure to microplastics can harm mussels – primarily their ability to produce strong byssal yarns, the fibers that bind mussels to or between rock – these experiments were performed at concentrations of much higher microplastics than in natural environments. .

Plus, mussels are already eating plastic, anyway. By monitoring them, keeping them in cages to survive predators, and collecting their plastic-filled poo, their regular process could be used to help clean up the ocean. It’s not a complete solution: Molds can’t reach all microplastics, and we still need to work on reducing single-use plastic and transitioning to a circular economy, says Lindeque. But it could make a difference, in several ways. “Beauty is because it’s a nature-based solution,” she says, “by putting them back in nature, we are helping to increase biodiversity and rewild what was there. anyway.

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