Down at the bottom of the ocean, it's not just thermal vents and whale bones. There's a vast accumulation of bottles, plastic bags, and other human-generated rubbish – perhaps the world's largest hidden waste dump, drifting on the currents for a virtual eternity.
Getting a full picture of this Atlantis of waste has been difficult, due to the high cost and physical challenges of reaching the seafloor. But over the past 10 years a number of scientific institutions have worked together to investigate deep-marine garbage, and this week they finally published their findings in the journal PLOS ONE. After performing nearly 600 video and trawl surveys in European waters, they've come to the depressing conclusion that the trash is everywhere, from the deepest to shallowest points, to near-coast shelves and regions as remote as the Charlie-Gibbs Fracture Zone. Here's roughly where that is on Google Maps:
What's down there? The most prevalent kind of detritus the researchers found was plastic, which made up 41 percent of the litter they observed. That isn't exactly surprising given that there's plenty of plastic floating around above, too. Roughly a third of the other observed trash was abandoned fishing gear such as lines and nets, lethal stuff that continues to trap sea creatures and smother habitats long after it's lost overboard. There's also plenty of metal and glass debris as well as clothing and "clinker," the residue of burnt coal that steam ships dumped in past centuries.
In the dark and frigid deep-sea environment, much of the litter looks as fresh as if it just came from the store. Notice the visible brands in the accumulation of junk above: The green can found at 3,117 feet deep is Heineken, and the orange bag at 2,940 feet is Uncle Ben's rice. Some marine species are evidently trying to interact with the garbage, with varying levels of success. That plastic bag at top left is harboring sponges and shrimps, while the scrap of cargo net at bottom right has entangled a coral colony.
Kerry Howell, one of the researchers on the expedition, has said he was unprepared for the sheer amount of litter on the seafloor. "This survey has shown that human litter is present in all marine habitats, from beaches to the most remote and deepest parts of the oceans," he says. "Most of the deep sea remains unexplored by humans, and these are our first visits to many of these sites, but we were shocked to find that our rubbish has got there before us."
The existence of all this crud is obviously bad for marine animals, who eat it or get trapped by it, but it's likely also having repercussions for higher species. One reason is because some deposit feeders, like sea cucumbers, have shown in the lab a preference for consuming plastic over natural sediments. The persistent organic pollutants inside this material "may accumulate in the consumer's tissues," the researchers say, "and can be transferred upwards in the trophic webs to predators, including humans."
It's thought that some 7 million tons of litter makes its way into the seas each year. Here's where the researchers found it over the 32 places they surveyed (the larger the circle, the more dense the garbage build-up):
Top image: Plastic, glass, cans, and fishing gear lie on the seafloor of European waters. (Christopher Pham et al.)