• Plastics smell like food to turtles after they have been in the ocean for a while, a study has found.
  • The build-up of algae on ocean plastic causes the rubbish to give off the aroma of food for loggerhead turtles.
  • The turtles showed no reaction to clean plastic.

The amount of plastic pollution in the oceans is rapidly increasing. This is problematic, as at least 700 species of marine animals – including sharks, whales, seabirds and turtles – can become entangled in the stuff or mistake it for a tasty snack.

While we know that some species seem to eat plastic because it looks like jellyfish or some other food source, less research has been carried out into what plastic smells like to marine animals.

But now, a study from the University of North Carolina at Chapel Hill has found that the coating of algae and microbes that naturally builds up on ocean plastics causes the rubbish to give off the aroma of food.

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The researchers took 15 captive-reared loggerhead turtles, each around five months old, and placed them in a laboratory aquarium. They then piped in aromas of clean water, clean plastic, turtle food, and plastic that had been soaking in the marine environment for five weeks.

The turtles showed no reaction to the odours of clean water or clean plastic. But when they were exposed to the smells of ocean-soaked plastic or turtle food, they exhibited foraging behaviour – like poking their noses out of the water and showing increased activity.

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“This finding is important because it’s the first demonstration that the odour of ocean plastics causes animals to eat them,” said Dr Kenneth J Lohmann, who took part in the study.

“It’s common to find loggerhead turtles with their digestive systems fully or partially blocked because they’ve eaten plastic materials. There also are increasing reports of sea turtles that have become ill and stranded on the beach due to their ingestion of plastic.”

According to the researchers, areas of the ocean with dense concentrations of plastic may trick turtles and other animals into thinking that there is an abundant food source, when the reverse is true.


“Once these plastics are in the ocean, we don't have a good way to remove them or prevent them from smelling like food,” said Lohmann. “The best thing we can do is to keep plastic from getting into the ocean at all.”

Reader Q&A: How does plastic get into the oceans?

Asked by: Tamsin Nicholson, via email

Around 80 per cent of the plastic waste found in the oceans today originated inland. Littering, poor waste management and industrial activity can all allow plastic to enter the natural environment.

A significant proportion of this then blows into rivers and streams, which carry it into the ocean. This is particularly common in countries where waste infrastructure is lacking: an estimated two billion people worldwide don’t have access to solid waste collection.

On top of this, wastewater from our homes often contains tiny pieces of plastic, including microbeads from cosmetics (now banned in the UK) and fibres from polyester clothing. Tackling plastic pollution therefore requires individuals, governments and companies across the globe to work together to reduce plastic consumption and waste.

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Alice Lipscombe-SouthwellManaging editor, BBC Science Focus

Alice is the managing editor at BBC Science Focus Magazine. She has a BSc in zoology with marine zoology. Her interests include natural history, wildlife, the outdoors, health and fitness.