Oceanic determinants of microplastic bioaccumulation in fauna of deep-sea hydrothermal vents: Comparative study of the southwestern Pacific and Indian Oceans

Plastic pollution is a global threat to marine ecosystems, yet its impact on deep-sea hydrothermal vents remains poorly understood. This study presents the first comparative analysis of microplastic (MP) contamination in vent-endemic fauna (Alviniconcha snails and Bathymodiolus mussels) across the southwestern Pacific and Indian oceans. MPs were detected in nearly all specimens, with an average of 3.42 ± 3.23 particles per individual. Fragmented polystyrene was the dominant polymer (56.10%), followed by acrylonitrile (19.51%) and polyethylene (17.07%). Taxon-specific patterns emerged, with snails exhibiting higher MP accumulation in internal organs due to grazing behaviors, whereas mussels showed a more even distribution across tissues. Notably, the total abundance of MPs in Indian Ocean specimens was approximately 1.9 times higher than in Pacific Ocean specimens, despite the latter being four times larger, reflecting distinct regional anthropogenic pressures. These findings highlight the ubiquitousness of plastic pollution in extreme environments and underscore the role of biological and regional factors in MP bioaccumulation.