Toxins leaching from microplastics leave shellfish at the mercy of predators, research has found. The chemicals completely suppress the ability of the periwinkles to detect and avoid the crabs that eat them.

Microplastics plague the world’s rivers and oceans and absorb poisonous chemicals from the water. Previous work has shown mussels are harmed by these toxins when they eat microplastics, but the latest study is the first to show disruption of the relationship between predator and prey. This is likely to disrupt the entire food chain, researchers say.

Microplastics are known to be present in seafood, as well as tap water, honey and salt and probably many other foods. Humans are known to consume microplastics but the impact on health is as yet unknown.

The research, published in the journal Biology Letters, looked at the common periwinkle. It grazes on algae but is eaten by crabs. Its central role in the food chain makes it a keystone species on beaches. It is also widely eaten by people.

When a crab approaches a periwinkle, chemical cues usually lead the shellfish to take evasive action, such as withdrawing into their shells or hiding under rocks. But, in the lab, when the periwinkles were kept in water with microplastics collected from a beach near Calais in France, they failed to react.

“The whole set of behaviours are totally inhibited,” said Prof Laurent Seuront, at the National Centre for Scientific Research in northern France. “It is worrying news. If the periwinkles are not able to sense and escape from the predator, they are more likely to disappear and then to disturb the whole food chain.”

The concentration of microplastics used in the experiments was similar to that on the beach. Microplastics are known to attract heavy metals and persistent organic pollutants and the researchers believe the release of this chemical cocktail interferes with the periwinkle’s senses. An earlier study showed that toxins leached from microplastics led mussel larvae to grow in an abnormal way.

“Saturating our marine environment with microplastics is an enormous gamble,” said Paul Morozzo, of Greenpeace. “We are still only learning what the impact on individual species, like the periwinkle, or indeed us, might be.

“The odds are not good, and we’re dumping an extra truckload of risk into the sea every 60 seconds,” he said. “The best way to reduce the danger is to reduce our use of plastic, quickly and dramatically. That includes a ban on problem and unrecyclable plastic by 2019.”