Removing the Oceans’ Microplastics with Mussel Excretions

Scientists of the UK’s Plymouth Marine Laboratory are currently testing a water-filtration system using mussels to clean up the ocean from plastic particles as a more natural and cost-effective solution to the microplastic problem.

An experimental project—funded by Waitrose’s Plan Plastic: The Million Pound Challenge—found that mussels, as part of their natural feeding process, digest microplastic particles and discard them as part of their faeces without causing the organism any harm in the process.

These faeces then float up to the water surface, where they can be easily collected and, hence, removed from the ocean. In the trials, mussel clusters of 300 mussels could filter around 250,000 pieces of microplastics in only one hour, something that usually only could be achieved with expensive filtration plants. 

“The Plan Plastic Project was all about helping to stop the plastic pollution, and there was a huge range of projects that were funded. But ours, in particular, was looking at whether we could stop the flow of microplastics from their source into vulnerable areas of the marine environment by using a nature-based solution,” explained Professor Pennie Lindeque, Head of Science of the Plymouth Marine Laboratory.

Microplastics are pieces of plastic that are smaller than 5mm coming from bottles, packaging, and other waste that ends up in the oceans. However, despite being broken down into smaller and smaller pieces over time, plastic never fully disappears. 

Researchers from the Scripps Institution of Oceanography found that each cubic metre of water in the oceans is highly contaminated by millions of pieces of microplastic, which eventually end up in our food and tap water.

According to a study on human consumption of microplastics, we as humans ingest around 39,000 to 52,000 particles a year. However, it is still unclear if these particles merely pass through our digestive tract or if they accumulate in organs and could cause further harm. Hence, it is crucial to find a way to remove them from the water.

The use of fine sieves already allowed researchers to remove some of the particles; however, a lot of organic material and marine life were caught as well. 

Using mussels for filtering the water ensures that there is less harm to the marine environment. By keeping the plastic-eating mussels in cages, the researchers could collect the poop easily while keeping them safe from predators. It’s a win-win situation for both parties.

However, this is not a final solution: there is still too much plastic in the ocean for the mussels to filter out alone. But it’s a step towards a circular economy.

“Of course, prevention is better than cure, but we are very encouraged to see that a nature-based solution using the humble mussel could have a key role to play in the war on microplastics,” Lindeque said.