Microplastics have spread right to the sea bed, study finds 

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.

“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.

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.

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.

“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.”

The authors said more research is needed at other deep-water locations, to find out how widespread microplastics really are.