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.
Luis F. Ruiz-Orejón, Rafael Sardá, Juan Ramis-Pujol, Marine Environmental Research, Volume 120, September 2016, Pages 136–144