Concentration gradient of plastic debris larger than 500 µm detected across the Southwest Indian ocean

Concentration gradient of plastic debris larger than 500 µm detected across the Southwest Indian ocean Thibault M. auteur aut IRD Fajeau A. auteur aut IRD Ramanampananjy A. auteur aut IRD Royer S. J. auteur aut IRD Fustemberg G. auteur aut IRD Marillac V. auteur aut IRD Gindrey J. auteur aut IRD Saloma A. auteur aut IRD Condet M. auteur aut IRD Mangion P. auteur aut IRD Burt A. auteur aut IRD Egger M. auteur aut IRD Amy M. auteur aut IRD Jaquemet S. auteur aut IRD Mulochau T. auteur aut IRD Jourand Philippe auteur aut IRD ter Halle A. auteur aut IRD Le Corre M. auteur aut IRD Lebreton L. auteur aut IRD text journalArticle eng text/pdf reformatted digital access Marine plastic pollution is increasing in the world's ocean, with the Indian Ocean understudied compared to the Pacific and Atlantic Oceans. This study investigates plastic pollution in the Southwest Indian Ocean, focusing on a size range from large debris to microplastics (> 500 mu m). Using visual surveys and manta trawling, we assessed plastic concentrations, compositions, and polymer types across 19 oceanographic campaigns. A total of 11,438 litter items were identified, with over 70% consisting of plastics. Larger plastic debris was predominantly observed near Glorieuses Islands during visual surveys, while microplastics were more prevalent offshore, collected through manta trawling. We observed a gradient of increasing plastic concentrations along the 30 degrees/33 degrees S latitudes, from 40 degrees E (macroplastics: 10 items/km(2); microplastics: 10(3) items/km(2)) to 65 degrees E (macroplastics: 10(2) items/km(2); microplastics: 10(5) items/km(2)). The majority of plastic debris consisted of hard fragments, primarily polyethylene (45.7%) and polypropylene (26.7%). Our findings provide new insights into microplastic concentrations in offshore regions, highlight the significant degradation of plastic debris, and emphasize the need for further research to identify and map the Indian Ocean's garbage patch along these latitudes. specialized Indian Ocean Marine litter Visual survey Manta trawling Microplastics OCEAN INDIEN 038 Scientific Reports - Nature 15 1 22364 [10 p.] 2025 2045-2322 https://www.documentation.ird.fr/hor/fdi:010094324 10.1038/s41598-025-02893-0 2045-2322 [F B010094324] https://www.documentation.ird.fr/hor/fdi:010094324 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-09/010094324.pdf IRD - Base Horizon / Pleins textes 2025-09-08 2026-06-12 fdi:010094324 fre