Science continues to identify more ways in which microplastics are bad news.
A new study shows that they are affecting the ability of mussels to attach themselves to their surroundings, putting at risk the futures of the mussels and of a multi-billion-dollar global industry.
And in this situation even biodegradable plastics are a problem.
Researchers led by Dannielle Green of Anglia Ruskin University in the UK found that blue mussels exposed to doses of microplastics over a period of 52 days produced significantly fewer of the thin fibres known as byssal threads.
As well as helping mussels stay attached to their surroundings despite waves and strong tides, these threads enable them to form extensive reefs that provide habitats for other marine animals and plants.
The study, which was carried out at the Portaferry Marine Laboratory in Northern Ireland, 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.
“Byssal threads help mussels to form aggregations, increasing fertilisation success and making mussels more resistant to predation,” Green says. “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.”
The study also measured the proteins within the mussels’ 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.
“Our study highlights the utility of mass spectrometry-based proteomics to assess the health of key marine organisms and identifies the potential mechanisms by which microplastics, both conventional and biodegradable, could affect their ability to form and maintain reefs,” the researchers write in a paper published in the journal Environmental Pollution.
Microplastics are small – often barely visible – pieces of plastics that find their way into land and marine environments by various means. In the last year alone, they have been found in human stools, turtles from around the world, and fertiliser made from biowaste.