A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy.

Marine debris is commonly observed everywhere in the oceans. Litter enters the seas from both land-based sources, from ships and other installations at sea, from point and diffuse sources, and can travel long distances before being stranded. Plastics typically constitute the most important part of marine litter sometimes accounting for up to 100 % of floating litter. On beaches, most studies have demonstrated densities in the 1 item m −2 range except for very high concentrations because of local conditions, after typhoons or flooding events. Floating marine debris ranges from 0 to beyond 600 items km −2 . On the sea bed, the abundance of plastic debris is very dependent on location, with densities ranging from 0 to >7700 items km −2 , mainly in coastal areas. Recent studies have demonstrated that pollution of microplastics, particles <5 mm, has spread at the surface of oceans, in the water column and in sediments, even in the deep sea. Concentrations at the water surface ranged from thousands to hundred thousands of particles km −2 . Fluxes vary widely with factors such as proximity of urban activities, shore and coastal uses, wind and ocean currents. These enable the presence of accumulation areas in oceanic convergence zones and on the seafloor, notably in coastal canyons. Temporal trends are not clear with evidences for increases, decreases or without changes, depending on locations and environmental conditions. In terms of distribution and quantities, proper global estimations based on standardized approaches are still needed before considering efficient management and reduction measures.

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Marine litter is a global challenge and society plays an important role via lifestyles and behaviour, including policy support. We analysed public perceptions of marine litter and contributing factors, using data from 1133 respondents across 16 European countries. People reported high levels of concern about marine litter, and the vast majority (95%) reported seeing litter when visiting the coast. The problem was attributed to product and packaging design and behaviour rather than lack of facilities or accidental loss of items. Retailers, industry and government were perceived as most responsible, but also least motivated and competent to reduce marine litter, whereas scientists and environmental groups were perceived as least responsible but most motivated and competent. Regression analyses demonstrated the importance of psychological factors such as values and social norms above sociodemographic variables. These findings are important for communications and interventions to reduce inputs of marine litter to the natural environment.