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Environment: European deep sea survey shows extent of marine litter problem

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This shows litter items on the seafloor of European waters. Clockwise from top left i) Plastic bag recorded by an OFOS at the HAUSGARTEN observatory (Arctic) at 2500 m; ii = Litter recovered within the net of a trawl in Blanes open slope at 1500 m during the PROMETO 5 cruise on board the R/V “García del Cid”; iii) Cargo net entangled in a cold-water coral colony at 950 m in Darwin Mound with the ROV “Lynx” (National Oceanography Centre, UK). iv) “Heineken” beer can in the upper Whittard canyon at 950 m water depth with the ROV Genesis. Image credit: Pham CK et al. doi:10.1371/journal.pone.0095839

Researchers find human garbage from the Arctic to the Azores

By Bob Berwyn

FRISCOFor all our efforts to contain civilization’s refuse, a lot of it is still ending up in the world’s oceans. The giant swirling garbage patches of the surface have been well documented and a new study shows that you can also find bottles, plastic bags, fishing nets and other types of human litter in deep sea trenches and even along the remote mid-Atlantic Ridge.

In some areas, generally within 100 miles of shore, the scientists found litter at the rate of about 20 pieces per hectare (about 2.5 acres) and even at the lowest density sites in more remote areas, the survey found about two pieces of garbage per hectare, said Kerry Howell, associate professor at Plymouth University’s Marine Institute.

“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,” Howell said. “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 thing we saw that always makes me unhappy but smile at the same time was one of those Uncle Ben’s microwavable rice packets,” Howell said, describing a popular orange-colored grocery item that seems common in the kitchen, but jarring when spotted a mile deep in the channel between the UK and Ireland.

“The places where we have the highest density are around marine canyons. It flows down rivers and the canyons concentrate the litter,” Howell said, adding that there is less litter on seabeds than along shorelines.

“Submarine canyons form the main connection between shallow coastal waters and the deep sea. Canyons that are located close to major coastal towns and cities, such as the Lisbon Canyon offshore Portugal, or the Blanes Canyon offshore Barcelona, can funnel litter straight to water depths of 4,500m or more,” said Veerle Huvenne, Seafloor and Habitat Mapping Team Leader at the National Oceanography Centre, Southampton.

The litter was found throughout the Mediterranean, and all the way from the continental shelf of Europe to the Mid-Atlantic Ridge 2,000 kilometres from land. Litter is a problem in the marine environment as it can be mistaken for food and eaten by some animals or can entangle coral and fish – a process known as “ghost fishing.”

The international study involving 15 organizations across Europe was led by the University of the Azores, and is a collaboration between the Mapping the Deep Project led by Plymouth University and the European Union-funded HERMIONE Project, coordinated by the National Oceanography Centre, Southampton. Other UK project partners that contributed to the study are the University of Southampton and the British Geological Survey.

Scientists took nearly 600 samples from across the Atlantic and Arctic Oceans and in the Mediterranean Sea, from depths ranging from 35 metres to 4.5 kilometres.

“We found that plastic was the most common litter item found on the seafloor, while trash associated with fishing activities (discarded fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges,” said Christopher Pham, from the University of the Azores. “The most dense accumulations of litter were found in deep underwater canyons.”

“We’re primarily looking for animals,” Howell said, explaining that the survey was made with a variety of high- and low-tech instruments, including cameras attached to a frame, filming the sea bottom from about one to two meters away.

“We saw the usual kind of thing, big balls of fishing nets, with dead and dying fish,” Howell said, adding that the researchers also documented plastic bags wrapped around long-lived coldwater corals.

“It’s not the best when your feeding apparatus is covered with plastic,” she said.

Litter was located at each site surveyed, with plastic accounting for 41 percent and derelict fishing gear 34 percent. Glass and metal, wood, paper/cardboard, clothing, pottery, and unidentified materials were also observed.

“An interesting discovery was relating to deposits of clinker on the sea floor – this is the residue of burnt coal that had been dumped by steam ships from the late 18th century onwards. We have known that clinker occurs on the deep-sea bed for some time, but what we found was the accumulation of clinker is closely related with modern shipping routes, indicating that the main shipping corridors have not been altered in the last two centuries.”

Howell said the gravel-size pieces of burned coal can alter the seafloor ecology to the benefit of some species and the detriment of others.

The report outlines the path that plastics in particular can take, originating from coastal and land sources and being carried along continental shelves and slopes into deep water.

“The large quantity of litter reaching the deep ocean floor is a major issue worldwide. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments,” Howell said. “Everyone should be a bit more mindful about their rubbish, really, and about generating rubbish in the first place.”

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