Marine litter has become a global issue with 'garbage patches' documented in all ocean gyres. The Pacific and Atlantic garbage patches have been well described, but there are few empirical data for the Indian Ocean. In the austral summer 2019-2020, we conducted an at-sea survey of macro-litter in the rarely investigated south-west Indian Ocean. Over 24 days, 1623 man-made items were observed including plastic fragments, packaging and fishing-related items during 216 h of observations covering 5464 km. More than 99% of the litter items were plastics of which almost 60% were white. Floating litter was patchily distributed with only five items (0.2%) recorded south of 40°S (0.1 items·km-2). Half of the items were encountered over a two-day period south-east of Madagascar (30°S; 59-67°E; 75.2 items·km-2). Our survey detected an accumulation of litter in the southern Indian Ocean and demonstrated that this area warrants more research.
Keywords: At-sea survey; Frontal system; Garbage patch; Plastic litter; Southern Indian Ocean.
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