Microplastics could be hampering the ocean’s ability to capture carbon

A global survey of microplastics in oceans reveals that tiny particles of plastic are prevalent throughout the water column, which could harm marine ecosystems and affect carbon storage in the deep sea

By James Dinneen

30 April 2025

A free diver surrounded by plastic pollution

Sebnem Coskun/Anadolu Agency via Getty Images

Microplastics aren’t floating on only the surface of the ocean. A global survey of the tiny particles reveals they are prevalent throughout the water column – even at the deepest depths – which could affect the ocean’s ability to remove carbon from the atmosphere.

“It’s millions and millions of metric tonnes of this stuff throughout the interiors of the ocean,” says Tracy Mincer at Florida Atlantic University.

Mincer and his colleagues have reviewed microplastic measurements taken over the past decade from nearly 2000 sites around the world. While most microplastic measurements focused on the shallow surface of the ocean, the dataset included samples from a range of depths, including the deepest parts of the ocean.

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They found that microplastics have been recorded virtually everywhere people have looked for them. That includes the Mariana trench, where more than 13,000 microplastic particles per cubic metre were measured nearly 7 kilometres down.

The researchers were surprised to see that the smallest particles are distributed almost evenly throughout the water column – not sinking or floating at the surface, but suspended. “We expect to find plastics at the bottom of the ocean, and at the top of the ocean. But not everywhere,” says Aron Stubbins at Northeastern University in Massachusetts.

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