Quantities, composition, and sources of beach debris in Korea from the results of nationwide monitoring

•Marine debris was bimonthly surveyed at 20 beaches of Korea from 2008 to 2009.•Quantities, composition, and sources of beach debris were assessed.•Fishing (commercial fisheries and aquaculture) was the main source of debris.•Styrofoam buoys from aquaculture were the most abundant item. This study assessed the levels of marine debris pollution and identified its main sources in Korea. The surveys were bimonthly conducted by NGO leaders and volunteers on 20 beaches from March 2008 to November 2009. The quantities of marine debris were estimated at 480.9 (±267.7) count⋅100m−1 for number, 86.5 (±78.6) kg⋅100m−1 for weight, and 0.48 (±0.38) m3⋅100m−1 for volume. The level of marine debris pollution on the Korean beaches was comparable to that in the coastal areas of the North Atlantic ocean and South Africa. Plastics and styrofoam occupied the majority of debris composition in terms of number (66.7%) and volume (62.3%). The main sources of debris were fishing activities including commercial fisheries and marine aquaculture (51.3%). Especially styrofoam buoy from aquaculture was the biggest contributor to marine debris pollution on these beaches.