Microplastics are pervasive from the surface to the seafloor and are probably entering the food chain.

That’s the conclusion of a new study of plastic debris measuring less than 5 millimeters across carried out by the Monterey Bay Aquarium Research Institute (MBARI) and Monterey Bay Aquarium. And it means the scale of pollution could be larger than previously estimated, with more microplastic found hundreds of metres down than in the Great Pacific Garbage Patch – the largest accumulation of ocean plastic in the world.

Using underwater robots to filter seawater, the researchers found around the same amount of microplastic particles near the surface as in the deepest waters they surveyed. Perhaps more startling, they found roughly four times the concentration in the midwater range than in waters near the surface.

And microplastics were discovered in all the animals sampled as part of the study, suggesting the material is entering the food chain via marine animals such as pelagic crabs and giant larvaceans.

Microplastics are entering the food chain. Image: Monterey Bay Aquarium

“Our findings buttress a growing body of scientific evidence pointing to the waters and animals of the deep sea, Earth’s largest habitat, as the biggest repository of small plastic debris,” said Anela Choy, the lead author of the paper, and an assistant professor at Scripps Institution of Oceanography at the University of California San Diego.

While the volume of plastic waste in our oceans has become a hot topic, most focus has been on the more visible trash – beer can packaging tangling up turtles, and whales eating carrier bags. Microplastics are harder to pin down as they’re often invisible to the naked eye.

With more than 3 billion people relying on the ocean for jobs and food, protecting and keeping it clean is imperative. Friends of Ocean Action, a group of more than 50 global leaders convened by the World Economic Forum and World Resources Institute, seeks to find solutions.

It wants to stop growth in plastic pollution by 2025 by demonstrating “investable and scalable” circular economy solutions in three coastal economies by 2020, and it hopes these can be adapted and implemented globally.

What's the World Economic Forum doing about the ocean? Our oceans cover 70% of the world’s surface and account for 80% of the planet’s biodiversity. We can't have a healthy future without healthy oceans - but they're more vulnerable than ever because of climate change and pollution. Tackling the grave threats to our oceans means working with leaders across sectors, from business to government to academia. The World Economic Forum, in collaboration with the World Resources Institute, convenes the Friends of Ocean Action, a coalition of leaders working together to protect the seas. From a programme with the Indonesian government to cut plastic waste entering the sea to a global plan to track illegal fishing, the Friends are pushing for new solutions. Climate change is an inextricable part of the threat to our oceans, with rising temperatures and acidification disrupting fragile ecosystems. The Forum runs a number of initiatives to support the shift to a low-carbon economy, including hosting the Alliance of CEO Climate Leaders, who have cut emissions in their companies by 9%. Is your organisation interested in working with the World Economic Forum? Find out more here.

The scientists from Monterey Bay Aquarium also said cutting plastic pollution was the only real way to stop microplastics entering the deep ocean and food chain.

Their research used underwater robots with sampling devices to filter plastic particles out of seawater at two different locations and at various depths in Monterey Bay. In addition to sampling the water, the researchers also looked at concentrations of microplastic particles in specimens of two marine species that filter-feed: pelagic red crabs and giant larvaceans.

A robot filter looks for microplastics in the ocean. Image: Monterey Bay Aquarium

That has wide-ranging implications since both those species are critical parts of the ocean food web. Pelagic red crabs are consumed by many species of fish, including tuna.

Another surprising finding was the fact that consumer plastics were found most abundantly.

There's more plastic in the deep ocean than the Great Pacific Garbage Patch. Image: Monterey Bay Aquarium

“This suggests that most of the particles did not originate from local fishing gear,” said Kyle Van Houtan, chief scientist at Monterey Bay Aquarium and one of the study’s co-authors. “It also suggests that at least some of the microplastic was transported into the area by ocean currents.”