Almost 36,000 feet [~10,980m] underwater, near the very bottom of the world's deepest ocean trench, scientists came across a troubling find: a plastic bag, similar to one you might take home from a supermarket, lying incongruously in the darkness.
A recent study on deep-sea ocean pollution identified the bag, found in 1998 by a robotic submersible at a depth of 35,756 feet [~10,900m] in the Mariana Trench, as the deepest known piece of plastic trash on Earth. Scientists say its presence in one of the world's most remote environments signals just how worryingly pervasive plastic pollution has become.
And the problem isn't limited to a single plastic bag.
For the study, researchers from Japan, together with scientists from U.N. Environment's World Conservation Monitoring Center, combed through the Deep-Sea Debris Database, a massive Japanese library of deep-sea photos and videos taken on more than 5,000 dives over the course of 30 years. The database was made public in 2017.
What they found was a disturbing amount of trash clogging deep-sea environments, including the Japan Trench and the Mariana Trench, as well as deep-sea areas in the Indian, Pacific, and Atlantic oceans.
The scientists said the images they scoured showed more than 3,400 pieces of debris. More than one-third of the waste they counted was made of plastic ― a staggering 89 percent of which was single-use items like plastic bags, packaging and bottles.
In environments deeper than 19,000 feet [~5,791m], more than half of the debris logged by the study was plastic ― and almost all of the plastic found at those depths was single-use.
"The ubiquitous distribution of single-use plastic, even to the greatest depths of the ocean, reveal a clear link between daily human activities and the remotest of environments," U.N. Environment said in a statement last month.
It remains unclear what the full impact of plastic pollution is on deep-sea areas and habitats, but preliminary research paints a grim picture.
Last year, scientists were stunned to find more chemical pollutants in parts of the Mariana Trench than in some of China's most polluted waterways. The researchers hypothesised at the time that some of that pollution had been caused by the breakdown of ocean plastics.
"We still think of the deep ocean as being this remote and pristine realm, safe from human impact, but our research shows that, sadly, this could not be further from the truth," the study's lead author, Alan Jamieson told The Guardian last year.
Plastic debris may also be endangering organisms that live deep in the ocean.
The recent pollution study said 17 percent of the manmade debris that was counted was "found with at least one organism" ― a relatively high percentage given how sparsely populated deep-sea habitats are. Some organisms were found to be entangled with the plastic items, the researchers said, and others were covered or "attached" to the debris.
"Once in the deep-sea, plastic can persist for thousands of years," UN Environment said in its statement. "Deep-sea ecosystems are highly endemic and have a very slow growth rate, so the potential threats from plastic pollution are concerning."
As public concerns mount about the potential impacts of such pollution on human health and the marine environment, state and national governments, as well as corporations and individual consumers, have been pushing for improved regulations of plastic use, production and waste management.
The U.K. announced last month that it planned to ban the sale of single-use plastic straws, cotton buds and drink stirrers. The European Union announced its own war against single-use plastics earlier this year. South Africa has not banned plastic bags, but forces consumers to pay for them, while state-sponsored recycling plants that were meant to be financed by this revenue have yet to materialise.