Public Release:  European seafloor survey reveals depth of marine litter

Plastic, fishing equipment most common litter on European seafloor

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Credit: Pham CK et al. doi:10.1371/journal.pone.0095839

A large-scale seafloor survey off the European coast has found widespread presence of bottles, plastic bags, fishing nets, and other types of human litter at all sample locations, according to results published April 30, 2014, in the open access journal PLOS ONE by Christopher Pham from University of the Azores and colleagues from 15 other institutions.

Marine litter throughout the ocean has been documented and known to cause problems for marine mammals and fish when mistaken for food and eaten, or else when it entangles coral and fish--a process known as "ghost fishing." However, high cost and variations in sampling methods currently limit scientists' ability to survey litter on the ocean floor in hopes of obtaining a comprehensive analysis. To better understand the extent and composition of marine litter off the coast of Europe, scientists analyzed nearly 600 seafloor transects over 10 years from 32 sites across the Atlantic and Arctic Oceans and in the Mediterranean Sea, at depths ranging from 35 meters to 4.5 kilometers. Scientists used photos, videos, and trawling to survey or collect seafloor litter. They classified the litter into six categories, including plastic, fishing gear, metal, glass, clinker, and other.

Litter was found at all surveyed locations, ranging from coastal seas to the Mid-Atlantic Ridge, 2000 kilometers from land. Litter was also found at all depths, from shallow, 35-meter waters in the Gulf of Lion to 4500-meter waters in Cascais Canyon, Portugal. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastics accounted for 41% of litter and derelict fishing gear 34%. Glass, metal, wood, paper, cardboard, clothing, pottery, and unidentified materials were also observed. The authors hope these results highlight the extent of ocean litter and the need for action to prevent increasing accumulation of litter in marine environments.

Co-author Dr. Kerry Howell 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."

Christopher Pham added, "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."

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Adapted by PLOS ONE from release provided by Plymouth University.

Citation: Pham CK, Ramirez-Llodra E, Alt CHS, Amaro T, Bergmann M, et al. (2014) Marine Litter Distribution and Density in European Seas, from the Shelves to Deep Basins. PLoS ONE 9(4): e95839. doi:10.1371/journal.pone.0095839

Financial Disclosure: This research was supported by the European Community's Seventh Framework Programme (FP7/2007'2013) under the HERMIONE project, Grant agreement (GA) no. 226354. The authors would like to acknowledge further funds from the Condor project (supported by a grant from Iceland, Liechtenstein, Norway through the EEA Financial Mechanism (PT0040/2008)), Corazon (FCT/PTDC/MAR/72169/2006; COMPETE/QREN), CoralFISH (FP7 ENV/2007/1/21314 4), EC funded PERSEUS project (GA no. 287600), the ESF project BIOFUN (CTM2007-28739-E), the Spanish projects PROMETEO (CTM2007-66316-C02/MAR) and DOS MARES (CTM2010-21810-C03-01), la Caixa grant "Oasis del Mar", the Generalitat de Catalunya grant to excellence research group number 2009 SGR 1305, UK's Natural Environment Research Council (NERC) as part of the Ecosystems of the Mid-Atlantic Ridge at the Sub-Polar Front and Charlie-Gibbs Fracture Zone (ECOMAR) project, the Marine Environmental Mapping Programme (MAREMAP), the ERC (Starting Grant project CODEMAP, no 258482), the Joint Nature Conservation Committee (JNCC), the Lenfest Ocean Program (PEW Foundation), the Department for Business, Enterprise and Regulatory Reform through Strategic Environmental Assessment 7 (formerly the Department for Trade and Industry) and the Department for Environment, Food and Rural Affairs through their advisors, the Joint Nature Conservation Committee, the offshore Special Areas for Conservation programme, BELSPO and RBINS-OD Nature (Belgian Federal Government) for R/V Belgica shiptime. The footage from the HAUSGARTEN observatory was taken during expeditions ARK XVIII/1, ARK XX/1, ARK XXII/1, ARK XXIII/ 2 and ARK XXVI/2 of the German research icebreaker ''Polarstern''. The authors also acknowledge funds provided by FCT-IP/MEC to LARSyS Associated Laboratory and IMAR-University of the Azores (R&DU #531), Thematic Area E, through the Strategic Project (PEst-OE/EEI/LA0009/2011'2014, COMPETE, QREN) and by the Government of Azores FRCT multiannual funding. CKP was supported by the doctoral grant from the Portuguese Science Foundation (SFRH/BD/66404/2009; COMPETE/QREN). AP was supported by Statoil as part of the CORAMM project. MB would like to thank Antje Boetius for financial support through the DFG Leibniz programme. JNGP was supported by the doctoral grant (M3.1.2/F/062/2011) from the Regional Directorate for Science, Technology and Communications (DRCTC) of the Regional Government of the Azores. ERLL was supported by a CSIC-JAE-postdocotral grant with co-funding from the European Social Fund. Publication fees for this open access publication were supported by IFREMER. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interest Statement: The authors have declared that no competing interests exist.

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