Mussel farms from Galicia to Normandy face collapsing stocks as climate change, pollution and invasive toxins combine into a toxic “cocktail” that threatens not just a billion-euro industry, but also a cornerstone of Europe’s sustainable food future.
On a windswept afternoon in Normandy, I walked Omaha Beach with my grandmother, who had witnessed D-Day just a stone’s throw away, collecting seashells along the shore.
Mussels and oysters – once the cheap, unrationed food of a war-torn Europe – are now prized delicacies facing environmental challenges.
For those who sell seashells (and their edible contents) on the seashore, every basket of shellfish destined for Europe’s dinner tables carries a hidden risk. The waters once celebrated for their purity are now laced with invisible fragments of plastic scientists call nanoplastics.
From tide to table
Hundreds of delegates met in Geneva last week to reduce (or at least slow) the output of plastic, which is on course to triple by 2060. Talks collapsed as states disagreed over what measures to take.
But while diplomats at the United Nations got lost in semantics, mussels would surely add their voice to the protest. A 2025 study in Nature found the North Atlantic to be saturated with plastic particles, equating to roughly 27 million tonnes circulating in the ocean’s mixed layer.
The authors concluded that nanoplastics make up a dominant share of marine plastic pollution, rivalling or even exceeding previous estimates for microplastics.
Earlier studies estimated that 11 – 21 million tonnes of microplastics are present in the upper layers of the Atlantic, while around one million tonnes are believed to be floating on the global ocean surface.
Nanoplastics, though smaller than one micron (compared to 1 micron to 5 millimetres for microplastics), appear to be far more widespread.
Worryingly for European consumers, the highest levels were detected along the continental shelf, where much of the bloc’s mussel farming takes place.
Mussel power
Mussels are Europe’s quiet aquaculture powerhouse. They need no feed or antibiotics, they clean seawater as they grow, and they provide low-carbon protein – “the simple food that fights climate change”, the BBC once labelled them.
For EU policymakers, mussels embody the promise of ‘blue foods’, which provide a sustainable alternative protein source.
Yet their very biology makes them especially vulnerable. Each mussel filters tens of litres of water daily, drawing in whatever the ocean carries – including nanoplastics. The tiny particles can cross biological membranes more easily than microplastics.
Unlike fish fillets, which are gutted before reaching the plate, mussels are eaten whole. Meaning that what they take in, we swallow too.
On top of this, laboratory experiments have revealed that as oceans absorb more carbon dioxide and acidify, nanoplastics’ surface charge changes. This means they stick more readily to cells and generate stronger oxidative stress.
As warned in a 2023 science brief from the European Commission, the combined pressures of ocean acidification and plastics create “potentially synergistic effects” that increase toxicity and ecological harm.
The ‘cocktail effect’
Plastic pollution is not the only threat facing marine molluscs.
“Harmful algal blooms”, combined with a “lack of spat, bad weather, predators, diseases and parasites”, have also contributed to the recent decline in mussel production – both in terms of quantity and quality, according to a study carried out in 2021 by the EU Commission’s Joint Research Centre.
Sweden offers a historic example: a once-promising mussel farming industry collapsed in the 1980s after toxic algal blooms caused diarrhetic shellfish poisoning, wiping out investor confidence.
Mussels are exposed to a “cocktail effect” of multiple stress factors, explains the European Mussel Producers Association (EMPA), which also highlights the issue of rising water temperatures.
As a result, shellfish farmers are increasingly developing offshore sites “to reduce exposure to land-based pollution”., EMPA told Euractiv. This also helps minimise the effect of climate issues, like ocean acidification.
A greater threat
Accounting for more than a third of European aquaculture, the mussel sector faces challenges that ripple across the entire industry.
On the front line is Galicia in Spain, Europe’s main producer of shellfish and the world’s second-largest producer of mussels after China. Earlier this year, The Guardian reported a “catastrophic” collapse in mussel numbers, with the Spanish region seeing stocks fall by as much as 90% in just a few years.
Caught falling between the Common Agricultural Policy (CAP) and the Common Fisheries Policy (CFP), last November the shellfish industry urged Brussels to implement a specific aquaculture policy to help it cope with the growing effects of climate change.
Fisheries Commissioner Costas Kadis has since committed to making aquaculture a legislative priority.
However, the Commission’s new budget plan, which suggests merging the EU Maritime, Fisheries and Aquaculture Fund (EMFF) into a single mega-fund alongside cohesion and rural development funds, to be managed by national governments, has led to fears that strong EU-level support for aquaculture could remain far off.
(ow, cs)
