Floating plastic debris in the Central and Western Mediterranean Sea

• In a large-scale study of the Mediterranean Sea, plastic was found in all samples.
• 579.3 g dw km−2 and 147,500 items km−2 were the average concentrations.
• The most common particle size in the samples was 1 mm2.
• The proportion of plastic in all the marine debris sampled was 96.87%.
• The general estimate obtained was a total value of 1455 tons dw of floating plastic for the entire Mediterranean region.

In two sea voyages throughout the Mediterranean (2011 and 2013) that repeated the historical travels of Archduke Ludwig Salvator of Austria (1847–1915), 71 samples of floating plastic debris were obtained with a Manta trawl. Floating plastic was observed in all the sampled sites, with an average weight concentration of 579.3 g dw km−2 (maximum value of 9298.2 g dw km−2) and an average particle concentration of 147,500 items km−2 (the maximum concentration was 1,164,403 items km−2). The plastic size distribution showed microplastics (<5 mm) in all the samples. The most abundant particles had a surface area of approximately 1 mm2 (the mesh size was 333 μm). The general estimate obtained was a total value of 1455 tons dw of floating plastic in the entire Mediterranean region, with various potential spatial accumulation areas.