Only 52 litter items (>1 cm diameter) were observed in 10,467 km of at-sea transects in the African sector of the Southern Ocean. Litter density north of the Subtropical Front (0.58 items km−2) was less than in the adjacent South Atlantic Ocean (1–6 items km−2), but has increased compared to the mid-1980s. Litter density south of the Subtropical Front was an order of magnitude less than in temperate waters (0.032 items km−2). There was no difference in litter density between sub-Antarctic and Antarctic waters either side of the Antarctic Polar Front. Most litter was made of plastic (96%). Fishery-related debris comprised a greater proportion of litter south of the Subtropical Front (33%) than in temperate waters (13%), where packaging dominated litter items (68%). The results confirm that the Southern Ocean is the least polluted ocean in terms of drifting debris and suggest that most debris comes from local sources.
Peter G. Ryan, Seth Musker, Ariella Rink, Marine Pollution Bulletin, Vol. 89 (1-2), pages 16-19, December 2014