Plastic bag found at the bottom of the world's deepest trench

A plastic bag at the bottom of the Mariana Trench.
A plastic bag at the bottom of the Mariana Trench. Photo credit: JAMSTEC

A plastic bag has been found sitting at the bottom of the world's deepest ocean trench.

The bag, caught on camera by a deep-sea remote vehicle, sits almost 11km below the surface of the Pacific Ocean in the Mariana Trench, near the Philippines.

"Plastics are now showing up in the very deepest, most remote parts of our planet," Greenpeace said in a tweet.

The footage was recorded in 1998, but was only recently been spotted by Japanese researchers. Recordings from more than 5000 dives over the past 35 years have been analysed in a new report, published in journal Marine Policy.

"There is growing concern that deep-sea ecosystems are already being damaged by direct exploitation of both biological and non-biological resources - through deep-sea trawling, mining and infrastructure development, for example," the report reads.

In addition to the plastic bag, researchers found fishing gear, glass, metals, rubber and clothing. More than a third of it was microplastic, almost exclusively from single-use products like bags, bottles and packaging.

Almost a fifth of the pictures containing plastic also featured living creatures, often entangled in bags.

The report says the images prove humans are destroying environments where they don't even go.

"The Mariana Trench is designated as a Marine National Monument (MPA( by the United States. However, MPA designation cannot prevent the hazards of plastic pollution in the deep sea because the source of plastic pollution is exclusively land-based."

And once it's down there in the depths of the ocean, plastic doesn't degrade as quickly as it does on land.

"Plastic is estimated to potentially remain for hundreds to thousands of years once they are deposited in the deep sea where there is no UV light and less turbulence."

A number of Kiwi retailers, including supermarkets, have vowed to phase out single-use plastic bags.