Anthropogenic impacts on deep submarine canyons of the western Mediterranean Sea

Anna Sanchez-Vidal1, Xavi Tubau1, Marta Llorca2, Lucy Woodall3, Miquel Canals4, Marinella Farré2, Damià Barceló2 and Richard Thompson5, (1)Universitat de Barcelona, GRC Geociències Marines, Departament de Dinàmica de la Terra i de l’Oceà, Barcelona, Spain, (2)Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA-CSIC), Departament de Química Ambiental, Barcelona, Spain, (3)The Natural History Museum, Department of Life Sciences, London, United Kingdom, (4)Universitat de Barcelona, Estratigrafia, Paleontologia i Geociències Marines, Barcelona, Spain, (5)Plymouth University, School of Marine Science and Engineering, Plymouth, United Kingdom
Submarine canyons are seafloor geomorphic features connecting the shallow coastal ocean to the deep continental margin and basin. Often considered biodiversity hotspots, submarine canyons have been identified as preferential pathways for water, sediment, pollutant and litter transfers from the coastal to the deep ocean. Here we provide insights on the presence of some of the most insidious man-made debris and substances in submarine canyons of the western Mediterranean Sea, which are relevant to achieve a “Good Environmental Status” by 2020 as outlined in the European Union's ambitious Marine Strategy Framework Directive. Ranked by size on a decreasing basis, we review the origin, distribution and transport mechanisms of i) marine litter, including plastic, lost fishing gear and metallic objects; ii) microplastics in the form of fibers of rayon, polyester, polyamide and acetates; and iii) persistent organic pollutants including the toxic and persistent perfluoroalkyl substances. This integrated analysis allows us to understand the pivotal role of atmospheric driven oceanographic processes occurring in Mediterranean deep canyons (dense shelf water cascading, coastal storms) in spreading any type of man-made compound to the deep sea, where they sink and accumulate before getting buried.