Innovation That Matters

Professor Pennie Lindeque on using mussels to filter microplastics from the ocean

Wise Words

Professor Pennie Lindeque from Plymouth Marine Laboratory, what it looks like to explore whether mussels could work as biofilters for microplastics.

Mussels are amazing creatures known for their resilience, capable of living in polluted water that other species would not be able to survive in. Moreover, mussels don’t only taste good. Their benefits extend deep into the maintenance of a balanced and healthy marine ecosystem, as they help to remove bacteria and excess algae from the water.

What if their powers of filtration could be used for other pollutants? This is what scientists at England’s Plymouth Marine Laboratory are in the process of finding out. Their one-year research project is looking into the ability of mussels to filter microplastics from natural waterways and their work rate. The aim of the study is to maintain the shellfish’s health while maximising the amount of pollution being removed from the water.

We spoke to Professor Pennie Lindeque, who is the lab’s Head of Science for Marine Ecology and Biodiversity, to understand the research team’s findings and possible implications.

1. What can you tell us about the benefits of using mussels to filter microplastics from natural waterways?

Lots of animals, living on the land, in rivers or the oceans, have been shown to eat plastic. But what is interesting about mussels is that they’re really hardy and robust, able to survive in polluted water that can cause harm to other animals.

They are voracious filter feeders, with a single adult mussel able to filter over 40 litres of water a day [Nielsan/Vismann 2014]. Through this process, they have been shown to purify seawater by removing bacteria and excess algae.

We’ve been exploring whether mussels could work as biofilters for microplastics. Our project was set up to test how effective mussels might be at capturing and removing microplastics. We examined their poo under controlled laboratory conditions and in situ field trials. What we found is that through their capacity for filtering large amounts of water, they were able to filter out microplastics and repackage them in their poo. By capturing these biodeposits, we thus have a means of removing microplastics close to sources of microplastic pollution, such as near wastewater treatment plants.

2. What is something the team has learnt from this research?

We designed a flume tank that constantly circulates water to mimic the currents seen in estuaries. We then added 5 kilograms of mussels, along with algae for the mussels to feed on and microplastics, and observed how the microplastic levels in the water over time.

Within two hours the mussels had removed half of the microplastics present, and we estimate that 5 kilograms of mussels have the capacity to remove a quarter of a million microplastics in one single hour.

3. What does success look like for this project? What are your key objectives at present?

Success would be developing a suitable method to deploy mussels close to sources of pollution, like sewage treatment works or marinas, so they can capture the plastic as soon as possible. For the mussels to remove significant amounts of microplastics and for the biodeposits containing microplastics to be efficiently captured and possibly even used as a source of biofuel.

We’re currently scoping different designs. One of our ideas is to have mussels in baskets with a net funnelling their faeces into a specialised container. These containers could then be brought back to the surface and emptied, removing the plastics from the sea entirely.

4. What are some of the major challenges that you foresee facing the efficacy of the approach in different locations?

The efficacy of the mussels in filtering the water means biodeposits can build up quickly. One major challenge will be to design a system whereby the biodeposits can be 100 per cent captured and easily and regularly removed from the marine environment.

5. Who or what inspires you personally?

I find Ellen McArthur inspiring. As a watersports and sailing person myself, I am inspired by her courage and tenacity — she was the youngest sailor to sail around the world single-handed. Spending time alone at sea made Ellen aware of the finite resources our planet has and I appreciate her drive and ambition on the subject of resource and energy use in the global economy.

6. What is one book (podcast, documentary, etc.) that has inspired you and that you recommend?

“The Power of One” by Bryce Courtney. This book epitomizes how one person “Peekay”, against all odds, can make a difference and unite people.

7. Do you have any other thoughts or wise words for researchers or environmental activists?

Keep believing you can make a difference. Too many times have I heard people say “well nothing I do will really help”. Each of us can make a difference and every small action can help. Yes, perhaps avoiding single-use plastic can be an inconvenience, but is that too much to ask to help maintain a healthy, safe and productive marine environment for our children and our children’s children?