Spatial distribution of marine macro-litter on the seafloor in the northern Mediterranean Sea: the MEDITS initiative

espanolLa basura marina es una de las principales fuentes de contaminacion antropogenica en el ecosistema marino representando el plastico una amenaza global. El objetivo de este trabajo es evaluar la distribucion espacial de las macro-basuras plasticas en el fondo marino, identificando los hotspots de acumulacion en el Mediterraneo norte. Los indices de densidad (items km–2), procedentes de las campanas de arrastre MEDITS (anos: 2013-2015), fueron modelados mediante Modelos Aditivos Generalizados, utilizando un enfoque de tipo delta y varias covariables: latitud, longitud, profundidad, pendiente del fondo marino, corrientes marinas y distancias desde los principales puertos. Para establecer los umbrales para la identificacion de areas de acumulacion, se calcularon los percentiles (85-90-95) de la distribucion espacial de densidad de plasticos en los datos raster. En el Mediterraneo norte, la macro-basura marina estaba muy extendida (90.13% de las 1279 estaciones muestreadas), siendo el plastico, con diferencia, la categoria mas recurrente. El mapa de prediccion de la densidad de plasticos resalto las areas de acumulacion (percentiles 85, 90 y 95 de la distribucion, respectivamente, correspondientes a: 147, 196 y 316 items km–2), localizadas en el Golfo de Leon, Corcega oriental, Mar Adriatico oriental, region Argo-Saronic y aguas que rodean el sur de Chipre. Se predijeron las densidades maximas a menor profundidad y cercanas a zonas pobladas (distancia desde los puertos). Las corrientes superficiales y la circulacion local del agua, con giros ciclonicos y anticiclonicos, se identificaron como factores que favorecen el hundimiento de las basuras flotantes. EnglishMarine litter is one of the main sources of anthropogenic pollution in the marine ecosystem, with plastic representing a global threat. This paper aims to assess the spatial distribution of plastic macro-litter on the seafloor, identifying accumulation hotspots at a northern Mediterranean scale. Density indices (items km–2) from the MEDITS trawl surveys (years 2013-2015) were modelled by generalized additive models using a Delta-type approach and several covariates: latitude, longitude, depth, seafloor slope, surface oceanographic currents and distances from main ports. To set thresholds for the identification of accumulation areas, the percentiles (85th, 90th and 95th) of the plastic spatial density distribution were computed on the raster data. In the northern Mediterranean marine macro-litter was widespread (90.13% of the 1279 surveyed stations), with plastic by far the most recurrent category. The prediction map of the plastic density highlighted accumulation areas (85th, 90th and 95th percentiles of the distribution, respectively, corresponding to 147, 196 and 316 items km–2) in the Gulf of Lions, eastern Corsica, the eastern Adriatic Sea, the Argo-Saronic region and waters around southern Cyprus. Maximum densities were predicted in correspondence to the shallower depths and in proximity to populated areas (distance from the ports). Surface currents and local water circulation with cyclonic and anticyclonic eddies were identified as drivers likely facilitating the sinking to the bottoms of floating debris.