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,

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.

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 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.”

This dynamic photograph of cactus bees scrambling to find a mate on the hot sands of a Texas ranch by Karine Aigner has won the top prize in the competition.

The shot shows a ball of male bees, all determined to mate with the single female at the centre. Aigner spent time lying in the dirt to take the photo, using a macro lens to confront the viewer with a new perspective on insect behaviour. “The sense of movement and intensity is shown at bee-level magnification and transforms what are little cactus bees into big competitors for a single female,” said chair of the jury Rosamund Kidman Cox, announcing Aigner’s win.

Tony Wu won the underwater category with this photograph of a male Leiaster leachi sea star broadcasting sperm into the sea. The backdrop is the dark waters at the foot of an active volcano in southern Japan, which Wu says erupted shortly after he left the area. He was cramped within a tiny, enclosed bay and had only a macro lens, so had to back up to capture the sea star, which was between 40 and 45 centimetres in diameter.

Wu’s electrifying photograph spotlights the vitality of an animal that might usually be viewed as static. He says he wanted to “make the animals that don’t have natural charisma look beautiful”.

Daniel Núñez, winner in the wetlands category, used a drone to show the extent of contamination in Lake Amatitlán, Guatemala, which takes in approximately 75,000 tonnes of waste annually from Guatemala City. The verdant rainforest is juxtaposed with the green algal blooms that flourish in the presence of polluting waste.

Junji Takasago, winner in the natural artistry category, captured a surreal scene of Chilean flamingos seemingly floating within the reflected clouds in Salar de Uyuni, the world’s largest salt pan, high in the Andes. Takasago says that “nature is in harmony” in the shot, but Salar de Uyuni is also the location of one of Bolivia’s largest lithium mines, and its destructive activity threatens the habitat of these flamingos.

The Wildlife Photographer of the Year is developed and produced by the Natural History Museum, London.