A distance-based technique was used to assess the distribution and abundance of floating marine debris (>1 cm) in the southeast Atlantic Ocean between Cape Town and Tristan da Cunha, crossing the southern edge of the South Atlantic ‘garbage patch’ predicted by surface drift models. Most litter was made of plastic (97%). Detection distances were influenced by the size and buoyancy of litter items. Litter density decreased from coastal waters off Cape Town (>100 items km(-2)) to oceanic waters (<10 items km(-2)), and was consistently higher (6.2 +/- 1.3 items km(-2)) from 3 to 8 E than in adjacent oceanic waters (2.7 +/- 0.3 items km(-2)) or in the central South Atlantic around Tristan (1.0 +/- 0.4 items km(-2)). The area with high litter density had few seaweeds, suggesting that most litter had been drifting for a long time. The results indicate that floating debris is accumulating in the South Atlantic gyre as far south as 34-35 degrees S.
Ryan, Peter G., Marine Pollution Bulletin, vol. 79 (1-2), Pages 220-224, February 2014