Microplastics cause mussels to lose their grip

Richard Harrington By: Richard Harrington
Date posted: 29 January 2019

A new study shows that microplastics are affecting the ability of mussels to attach themselves to their surroundings – potentially having a devastating impact on ocean ecosystems as well as a worldwide industry worth between 3-4 billion US dollars per year.

Mussel and dogwhelk
© Richard Harrington

This study highlights yet again the damage that microplastics can cause and reinforces the urgent need to act now stop plastics getting into our seas.

Sue Kinsey

The study found that mussels exposed to microplastics over a period of 52 days produced significantly fewer byssal threads (the thin fibres that help them attach to rocks and ropes, visible at the lower right of the photo on this page), leaving the mussels with an attachment strength 50% lower than normal.

As well as enabling mussels to survive waves and strong tides, and stay attached to their surroundings, these byssal threads also enable them to form extensive reefs that provide important habitats for other marine animals and plants.

The study also found that the overall tenacity or attachment strength of mussels exposed to microplastics, calculated by measuring the maximal vertical force required for the mussel to become dislodged from its position, fell by 50% compared to a control sample of mussels that were not exposed to microplastics.

And to understand potential effects of microplastics on the health of the mussels, the researchers measured the proteins within the mussel’s circulatory fluid or haemolymph, which performs a similar function to blood. This showed that microplastics induced a strong immune response and also affected the mussels’ metabolism.

The new research, published in the journal Environmental Pollution, was led by Dr Dannielle Green of Anglia Ruskin University, and was carried out at the Portaferry Marine Laboratory in Northern Ireland.

Dr Green said: “Tenacity is vital for mussels to form and maintain reefs without being dislodged by hydrodynamic forces. Our study showed that the presence of non-biodegradable microplastics reduced the number of byssal threads produced by the mussels, which likely accounts for the 50% reduction in their attachment strength.

“Byssal threads help mussels to form aggregations, increasing fertilisation success and making mussels more resistant to predation. A reduction in these byssal threads in the wild could lead to cascading impacts on biodiversity as well as reducing yields from aquaculture, as mussels are more likely to be washed away by waves or strong tides.

“Our research also shows that even biodegradable microplastics can affect the health of mussels. Both biodegradable and non-biodegradable plastic are used in making single-use packaging, which if it becomes litter can break down into microplastics. Better recycling and an overall reduction of these materials can play an important role in helping to safeguard our marine environment.”

In response to the study, Dr Sue Kinsey, MCS Senior Pollution Policy Officer says “This study highlights yet again the damage that microplastics can cause and reinforces the urgent need to act now stop plastics getting into our seas.”

Dr Kinsey continues: “We need concerted action from Governments, industry and the general public to stop this tide of rubbish and need to introduce, as soon as possible, such policies as minimum recycled content for plastic products, taxes on hard-to-recycle plastics, the banning of polystyrene and black plastic, the introduction of a deposit refund system for all drinks containers and work towards a genuine circular economy system in the UK where ‘waste’ is valued as a resource and used time and time again rather than polluting our countryside, coasts and seas”.

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