Birds living on the banks of the river swallow plastic at the rate of hundreds of tiny fragments a day, according to a new study.
Scientists say this is the first clear evidence that plastic pollutants in rivers find their way into the wild and move up the food chain.
Pieces of plastic 5 mm or smaller (microplastics), including polyester, polypropylene and nylon, are known to pollute rivers.
Impacts on wildlife are unclear.
Researchers at the University of Cardiff have examined plastic contaminants found in a bird known as a diver, which enters or dives into rivers in search of underwater insects.
“These iconic submerged birds devour hundreds of pieces of plastic every day,”
Previous research has shown that half of the insects in the rivers of South Wales contain microplastic fragments.
“The fact that so many river insects are polluted inevitably makes fish, birds and other predators take this contaminated prey – but this is the first time this type of transport through food cobwebs has been clearly shown in a wild river,” said the co-researcher. Dr. Joseph D’Sosa.
The research team examined the discharges and the resulting pellets from combs living near rivers that flow from the Brecon breccias to the North Estuary.
They found microplastic fragments in approximately half of the 166 samples taken from adults and adolescents in 14 of the 15 sites studied, with the highest concentrations in urban areas. Most were fibers of textiles or building materials.
Estimates suggest that divers ingest about 200 small pieces of plastic a day from the insects they consume.
Previous studies have shown that microplastics are present even in the depths of the ocean and end up in the bodies of living organisms, from seals to crabs to seabirds.
Rivers are a major route between land and sea for microplastics such as synthetic clothing fibers, rubber dust and other fragmented plastic waste.
The study, published in the journal Global Change Biology, was conducted in collaboration with Greenpeace’s research laboratories at the University of Exeter.
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