Mussel ‘cages’ deployed in a pilot project to help stem the flow of marine plastic
11 October 2022
Scientists from Plymouth Marine Laboratory (PML) have installed cages filled with mussels at four local estuary sites (three in the Plym estuary and one in the Kingsbridge estuary) as part of a trial project to establish how effectively they can remove microplastics from tidal, estuarine waters.Earlier laboratory experiments conducted by the PML team using a custom-designed flume tank have shown that a cluster of 300 blue mussels (Mytilus edulis) - around 5kg - could filter out over 250,000 microplastics per hour.
This is achieved by harnessing the natural filtering power of the mussels, which get their food by filtering seawater, sieving out plankton and other nutritious particles and flushing out unwanted particles from their digestive systems. As part of this process, microplastics are ejected in their normal faecal matter – which can then be collected as it sinks.
WATCH: Mussel 'cages' deployed across the Plym estuary and Kingsbridge estuary
Sources of microplastics include fibres from synthetic textiles, microbeads from cosmetics and industrial applications and larger items that have broken down over time. Other forms of microplastic include antifouling paint particles, tyre particles and biodegradables.
PML scientists are at the forefront of developing techniques to monitor and investigate the effects of marine microplastics on marine organisms and ecosystems, and the ways in which nature-based solutions can be used to mitigate the issue.
The organisation’s computer modelling research has indicated that mussels sited near the mouths of rivers and estuaries could filter between 20-25% of small, waterborne microplastics. The factors are complex, with physical parameters to consider including depth, currents, tides, temperatures and varying plastic supply. However, the findings suggest that a mussel-based clean-up system deployed closer to the source of microplastics e.g. waste water treatment works or storm water drains could potentially be rolled out at scale with significant positive effects.
A scaled mussel filtration reef/system would not only remove microplastics but have multiple other benefits. The humble mussel’s hardy nature and water filtration capabilities mean they can improve overall water quality, reduce pathogen numbers and soak up pollution while increasing local biodiversity and seafood quality in a given area.
With technical support from PML Applications (PML’s commercial subsidiary) the specially-designed cylindrical PML ‘cages’ (which were constructed by Flint Engineering Solutions Ltd), currently being deployed contain 50kg mussels and feature receptacle tubes to collect the filtered waste. This enables the scientists to collect the faeces - and the microplastics - which can then be hauled in and removed from the seawater.
“An estimated eight million tonnes of plastic end up in the ocean every year – that’s the equivalent to a full truckload dumped into the sea every minute,” said Professor Pennie Lindeque, Head of Science - Marine Ecology and Biodiversity.
“Through lab-based experiments and early trials we have shown that mussels could play a valuable role in helping to extract microplastics – effectively collecting up and leaving the recycling out for us to then dispose of. We are incredibly excited to see how well these new custom-made cages will work and very grateful to the following for their support:
- Inch Fishing Ltd
- Salcombe Harbour Authority
- Yacht Haven Marinas Group
- Plymouth Yacht Haven Quay
- Turnchapel Wharf
- Plymouth Yacht Haven Marina”
A world leader in the field of marine research, Plymouth Marine Laboratory (PML) is a charity committed to the delivery of impactful, cutting-edge environmental and social science in support of a healthy and sustainable ocean.
Alongside the University of Plymouth and Marine Biological Association, PML is part of Marine Research Plymouth, the UK’s largest cluster of marine science researchers.
PML’s commercial subsidiary, PML Applications, provides research, consultancy and services for the marine and maritime sector.
About Professor Pennie Lindeque
A marine ecologist with more than 25 years expertise, Pennie leads and undertakes internationally-renowned and innovative research in the areas of molecular biology, plankton ecology and marine contaminants.
Consistently listed as one of the world’s most highly cited researchers, her work on the impact of microplastics in the marine environment has directly influenced policy in the UK and around the world, including the UK ban on microbeads in cosmetics.