Environment

Our Trash Reached the Deepest Parts of the Ocean Before Us

May 1, 2014 | by Janet Fang

Photo credit: Cargo net entangled in a cold-water coral colony at 950 meters in Darwin Mound with the ROV Lynx / National Oceanography Centre, C.K. Pham et al., PLOS ONE
 
Results from a survey of the seafloor off the European coast reveal the depths our garbage can reach. Bottles, plastic bags, fishing gear, and various crap have been found as deep 4.5 kilometers below the surface, and in areas far as 2,000 kilometers from land. 
 
"Human litter is present in all marine habitats, from beaches to the most remote and deepest parts of the oceans,” study coauthor Kerry Howell from Plymouth University, UK, says in a press release. “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."
 
Marine litter causes problems for mammals and fish when they mistaken it for food; it also entangles coral and fish (the process even has a name, "ghost fishing"). But because surveying in the deep ocean is very expensive and requires a multitude of sampling techniques, scientists haven’t been able to get a comprehensive look at the extent and contents of marine litter. So, the European Union sponsored the Hotspot Ecosystem Research and Man's Impact on European Seas (HERMIONE) project, a consortium of 41 partners from 13 countries, which ran from 2009 to 2012. Check out their image gallery
 
Using photos and videos from remotely-operated vehicles, a team led by Christopher Pham from the University of the Azores in Portugal analyzed nearly 600 seafloor transects gathered over 10 years from 32 sites across the Atlantic and Arctic oceans and the Mediterranean Sea. They also used trawling nets to collect litter on the ocean floor.
 
Litter was classified into six categories: plastic, derelict fishing gear, metal, glass, clinker (residue of burnt coal), and other, which includes cardboard, fabric, wood and unidentified items. Plastics accounted for 41 percent of the litter and derelict fishing gear was 34 percent.
 
They found litter at every location they surveyed: ranging from coastal seas to the Mid-Atlantic Ridge, 2,000 kilometers from land. Litter was also found at all depths: from shallow, 35-meter waters in the Gulf of Lion to 4.5 kilometers waters in Cascais Canyon, Portugal. Submarine canyons suffered the highest litter density, while the lowest density was found on continental shelves and on ocean ridges. 
 
 
Pictured here: A = Plastic bag entrapped by a small drop stone harboring sponges (Cladorhiza gelida, Caulophacus arcticus), shrimps (Bythocaris sp.) and a crinoid (Bathycrinus carpenterii) in the Arctic at 2500 m. B = Litter recovered within the net of a trawl in Blanes open slope at 1500 m on board the R/V García del Cid. C = Heineken can in the upper Whittard canyon at 950 m with the ROV Genesis. D = Plastic bag in Blanes Canyon at 896 m with the ROV Liropus. E = Uncle Ben's Express Rice packet at 967 m in Darwin Mound with the ROV Lynx. F = Cargo net entangled in a cold-water coral colony at 950 m in Darwin Mound with the ROV Lynx. 
 
The work was published in PLOS ONE this week. 
 
 
Images: C.K. Pham et al., PLOS ONE
 

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