Microplastics are affecting the ability of mussels to attach themselves to their surroundings which is having a devastating impact on ocean ecosystems, according to a new study. The study was led by Dr Dannielle Green of Anglia Ruskin University and was carried out at the Portaferry Marine Laboratory in Northern Ireland.

Microplastics, which are pieces of plastic under five millimetres in length, come from a variety of sources, including from larger plastic debris that degrades into smaller and smaller pieces. There are also microbeads, a type of microplastic, which are very tiny pieces of manufactured polyethene plastic. Researchers at Anglia Ruskin University found that blue mussels exposed to doses of non-biodegradable microplastics over a period of 52 days produced significantly fewer byssal threads, which are thin fibres that help mussels attach themselves to rocks and ropes.

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.

According to Dr Green, a senior lecturer in biology at Anglia Ruskin University, tenacity is vital for mussels to form and maintain reefs without being dislodged by hydrodynamic forces. The study has shown that the presence of non-biodegradable microplastics reduces the number of byssal threads produced by the mussels, which likely accounts for the 50% reduction in their attachment strength.

These 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.

Dr Green points out that their research also showed 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 certainly play an important role in helping to safeguard our marine environment.