Concentration gradient of plastic debris larger than 500 μm detected across the Southwest Indian ocean
Abstract
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 μm). 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°/33°S latitudes, from 40°E (macroplastics: 10 items/km²; microplastics: 103 items/km²) to 65°E (macroplastics: 102 items/km²; microplastics: 105 items/km²). 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.
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BibTeX
@article{thibault2026concentration,
title = {{Concentration gradient of plastic debris larger than 500 μm detected across the Southwest Indian ocean}},
author = {Margot Thibault and Adrian Fajeau and Aina Ramanampananjy and Sarah-Jeanne Royer and Gwennaïs Fustemberg and Vyctoria Marillac and Julie Gindrey and Anjara Saloma and Manon Condet and Perrine Mangion and April Burt and Matthias Egger and Maxime Amy and Sébastien Jaquemet and Thierry Mulochau and Philippe Jourand and Alexandra Ter Halle and Matthieu Le Corre and Laurent Lebreton},
journal = {Scientific Reports},
year = {2026},
month = nov,
doi = {10.1038/s41598-025-02893-0},
url = {https://hal.science/hal-05171978v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Concentration gradient of plastic debris larger than 500 μm detected across the Southwest Indian ocean
AU - Margot Thibault
AU - Adrian Fajeau
AU - Aina Ramanampananjy
AU - Sarah-Jeanne Royer
AU - Gwennaïs Fustemberg
AU - Vyctoria Marillac
AU - Julie Gindrey
AU - Anjara Saloma
AU - Manon Condet
AU - Perrine Mangion
AU - April Burt
AU - Matthias Egger
AU - Maxime Amy
AU - Sébastien Jaquemet
AU - Thierry Mulochau
AU - Philippe Jourand
AU - Alexandra Ter Halle
AU - Matthieu Le Corre
AU - Laurent Lebreton
PY - 2026
DA - 2026/11/02
JO - Scientific Reports
DO - 10.1038/s41598-025-02893-0
UR - https://hal.science/hal-05171978v1
AB - 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 μm). 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°/33°S latitudes, from 40°E (macroplastics: 10 items/km²; microplastics: 103 items/km²) to 65°E (macroplastics: 102 items/km²; microplastics: 105 items/km²). 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.
SN - 2045-2322
ER -