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Microfibres that pollute the seas are floating homes for bacteria

Almost 200 species of bacteria, including one that can cause food poisoning, were found on microfibre particles from the Mediterranean Sea

Environment 30 November 2022

Bacteria seen with an electron microscope

Electron microscopy images of bacterial communities found on microfibres from the Mediterranean Sea

Pedrotti et al., 2022, PLOS ONE, CC-BY 4.0

Microfibres that pollute the seas are being colonised by bacteria that can cause food poisoning, raising further concerns about the effects of such pollution on marine life and human health.

Microfibres are tiny particles, thinner than a human hair, that are released from both natural and synthetic textiles when we wash our clothes. Around 4.3 billion microfibres enter the sea every day from one wastewater treatment plant in France alone, according to a recent study.

Once they get into water systems, microfibres are readily colonised by bacteria, which form a thin layer called a biofilm on the particles. This makes them smell like food to marine animals, so they get eaten and accumulate in the food chain.

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Ana Luzia de Figueiredo Lacerda at Sorbonne University in Paris and her colleagues took water samples from the Mediterranean Sea near the south coast of France. They used DNA sequencing and advanced microscopy techniques to identify the bacterial species living on the microfibres.

They found that each fibre was home to more than 2600 bacterial cells, on average, from 195 different species of bacteria. One of the species identified, Vibrio parahaemolyticus, is a potential cause of gastrointestinal illness that humans can get from raw or partially cooked shellfish.

More tests are needed to determine whether these bacteria are dangerous, says Robyn Wright at Dalhousie University in Halifax, Canada. “It’s impossible to say for certain whether there are potentially pathogenic microbes colonising microplastics,” she says.

However, increasing amounts of pollution in populated coastal areas and rising sea temperatures could exacerbate the problem. Previous research has shown that higher seawater temperatures facilitate the adhesion of bacteria to plastics and makes V. parahaemolyticus bacteria more virulent.

“Considering that the Mediterranean Sea is warming faster than other ocean basins, it is pivotal to evaluate the impacts of plastics and their associated [organisms] in the functioning of the ecosystems, under the scenario of climate change,” says Lacerda.

Understanding the virulence of the bacteria transported by these persistent microfibres will help us assess the risks they pose to humans and the wider ecosystem, she adds. “We have to rethink the way we are moving forward as a society. Plastic pollution and climate change are not only environmental issues, but also a social problem.”

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0275284

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