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The seafloor covers some 70% of the Earth’s surface and has been recognised as a major sink for marine litter. Still, litter on the seafloor is the least investigated fraction of marine litter, which is not surprising as most of it lies in the deep sea, i.e. the least explored ecosystem. Although marine litter is considered a major threat for the oceans, monitoring frameworks are still being set up. This paper reviews current knowledge and methods, identifies existing needs, and points to future developments that are required to address the estimation of seafloor macrolitter. It provides background knowledge and conveys the views and thoughts of scientific experts on seafloor marine litter offering a review of monitoring and ocean modelling techniques. Knowledge gaps that need to be tackled, data needs for modelling, and data comparability and harmonisation are also discussed. In addition, it shows how research on seafloor macrolitter can inform international protection and conservation frameworks to prioritise efforts and measures against marine litter and its deleterious impacts.

Ocean Literacy (OL) has been defined as an understanding of the ocean’s influence on people and their influence on the ocean. The OL movement was born in the US and its framework consisted of seven essential principles and 45 fundamental concepts; it is now largely accepted worldwide for use in both formal (schools and universities) and non-formal (research institutes, aquaria, museums, etc.) education settings. Based on this framework, marine scientists and educators developed the “Mediterranean Sea Literacy” (MSL) guide adapted to the specificities of the Mediterranean region, presented here. The MSL principles (7) and concepts (43), serving as guidance for research, education, informed decision-making, and improved citizens’ lifestyles, aim to contribute to environmental protection, conservation, and restoration of the Mediterranean Sea as well as to help to achieve a blue innovative and sustainable economy.

Marine 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., La basura marina es una de las principales fuentes de contaminación antropogénica en el ecosistema marino representando el plástico una amenaza global. El objetivo de este trabajo es evaluar la distribución espacial de las macro-basuras plásticas en el fondo marino, identificando los hotspots de acumulación en el Mediterráneo norte. Los índices de densidad (ítems km–2), procedentes de las campañas de arrastre MEDITS (años: 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 identificación de áreas de acumulación, se calcularon los percentiles (85-90-95) de la distribución espacial de densidad de plásticos en los datos ráster. En el Mediterráneo norte, la macro-basura marina estaba muy extendida (90.13% de las 1279 estaciones muestreadas), siendo el plástico, con diferencia, la categoría más recurrente. El mapa de predicción de la densidad de plásticos resaltó las áreas de acumulación (percentiles 85, 90 y 95 de la distribución, respectivamente, correspondientes a: 147, 196 y 316 ítems km–2), localizadas en el Golfo de León, Córcega oriental, Mar Adriático oriental, región Argo-Saronic y aguas que rodean el sur de Chipre. Se predijeron las densidades máximas a menor profundidad y cercanas a zonas pobladas (distancia desde los puertos). Las corrientes superficiales y la circulación local del agua, con giros ciclónicos y anticiclónicos, se identificaron como factores que favorecen el hundimiento de las basuras flotantes.

The Mediterranean Sea region is the cradle of modern civilization, a biodiversity hotspot, the most visited touristic area and home to over 460 million people. Increasing stresses due to tourism, fishing, coastal development, pollution, shipping and climate change are threatening the fragile Mediterranean Sea ecosystem. Sustainable development of the Mediterranean region is integrated in the most important development plans concerning this area e.g. Mediterranean Action Plan, Plan Bleu. Mediterranean Sea Literacy (MSL) was developed as a tool in order to understand the services provided by the Mediterranean Sea, its connection to people and to help understand the need for sustainable development in this region. It was developed following the form of Ocean Literacy principles. A draft version of MSL consists of 7 principles and 46 concepts which describe different aspects of the Mediterranean Sea and its connection to people and society. Mediterranean Sea Literacy provides fundamental knowledge about the Mediterranean Sea to educators, teachers, scientists, NGOs, blue economy and business sector, policy makers and general public, thus helping to raise awareness and achieve a blue and sustainable Mediterranean region at all levels of society.

Building on the EMSEA experience, a group of researchers and educators from the Mediterranean Region, EMSEAMED, started a collaborative and innovative effort to promote the ocean literacy principles in the region, and to adapt them to the specificities of the Mare Nostrum. The Mediterranean Sea is not only considered the cradle of civilization, but it has also great environmental, social and economic importance. With this work we aim at making the Mediterranean citizens, as well as all those having a stake in it, more aware of its potential and role for sustainable blue economy. The Mediterranean Sea is also changing fast in response to both natural and anthropogenic pressures. Climate change, growing maritime traffic and marine litter pollution, overexploitation of fish stocks and invasions of alien species are among the main threats placing the Mediterranean region at risk. At the same time, the Mediterranean’s unique features, such as the exceptional Mediterranean biodiversity and the unique and mild Mediterranean climate positively influence human activities such as agriculture, mariculture, and tourism. This presentation will focus on the EMSEA MED group method of work, and on the first draft Mediterranean Sea Literacy principles and concepts. The main objective is to have a first peer-review of what has been done so far, and to gather support from other colleagues willing to join this effort.