Plastic Waste reaches parts of seafloor before we do

Posted on May 1st 2014

PLASTIC waste has reached parts of the deep seafloor not yet visited by man, a major new survey of European waters has found.

Glass bottles, plastic bags, fishing nets and other discarded litter which pose a threat to marine wildlife was found more than four-and-a-half kilometres beneath the surface and a massive 2,000 kilometres from the nearest land.

The litter was found throughout the Mediterranean and all the way from the continental shelf of Europe to the Mid-Atlantic Ridge. Underwater canyons were found to have the most dense accumulations.

With an estimated 6.4 million tonnes of litter entering the oceans each year, the adverse impacts of litter on the marine environment cannot be underestimated. Litter can be mistaken for food items and be ingested by a wide variety of marine organisms; discarded fishing gear can entangle birds, mammals and turtles; the same gear can also kill fish in a phenomenon known as “ghost fishing”; floating litter also doubles the transfer of non-native marine species (e.g. bryozoans, barnacles) to new habitats compared with natural means.

The paper, Marine litter distribution and density in European Seas, published in the journal PLOS ONE, said deep sea litter was more prevalent than first thought.

Dr Kerry Howell, Associate Professor at Plymouth University’s Marine Institute, said: “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.

"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 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.”

The international study involving 15 organisations across Europe was led by the University of the Azores, in collaboration between the Mapping the Deep Project led by Plymouth University and the European Union-funded HERMIONE Project, researching deep marine ecosystems.

Researchers used data from a number of surveys between 1999 and 2011, along with photographs and videos taken by remotely operated vehicles to compile the results. They analysed almost 600 sites on the seafloor from depths ranging from 35 metres to 4.5 kilometres. They also used trawling nets to scoop up rubbish from the sea bed.

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

Mr Christopher Pham, from the University of the Azores, said: “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. The most dense accumulations of litter were found in deep underwater canyons.”

Dr Veerle Huvenne, Seafloor and Habitat Mapping Team Leader at the National Oceanography Centre, Southampton, explains: “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.”

To read the paper, visit Plos One.


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