Effects of the 2011 Tohoku earthquake and tsunami on the abundance and composition of anthropogenic marine debris on the continental slope off the Pacific coast of northeastern Japan

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The abundance and composition of anthropogenic marine debris from 2012 to 2014 was assessed according to three bottom trawl surveys conducted on the upper continental slope between 198 m and 501 m off the Pacific coast of northeastern Japan. The surveys quantitated marine debris as follows: 33.52–164.62 items km−2 (January to July 2012), 91.68–215.11 items km−2 (November 2012 to May 2013), and 160.13–178.19 items km−2 (November 2013 to May 2014). Plastic bags or household materials mainly dominated terrestrial sources of debris. Principal component analysis latitudinally divided the study area according to debris abundance caused by geographical and hydrodynamic features. The long-term effect of tsunami-associated debris on the seafloor environment was recognized, because terrestrial sources such as heavy household materials were most abundant throughout the study period, with the additional accumulation of fishing gear and plastic bags.