This study analyzed samples of deep-sea gastropods and mussels collected at hydrothermal vents located in the Indian Ocean and the southwestern Pacific Ocean. An average of 3.42 plastic particles per animal was recorded. Polystyrene, a common plastic used in food packaging and disposable materials, was the most common type of plastic identified in this study.

There were notable differences in the two sites studied. In terms of body size-adjusted microplastic loads, animals obtained from the Central Indian Ridge had up to 14.7 times the microplastics when compared to those taken from the North Fiji Basin. The reason for the difference was attributed to plastic input variations at both locations.

However, the distribution of microplastics varied across species. In grazing snails, whose diets include microbial mats thriving on the rocky substrate near hydrothermal vents, almost all plastic particles were located in the digestive system. For filter-feeding mussels, microplastics were evenly distributed within different body tissues.

Deep-sea hydrothermal vents are ecosystems characterised by the presence of mineral-rich fluid coming out of the seafloor. However, they host specialised communities of living organisms due to the lack of sunlight. The deep ocean constitutes about 90% of the total marine environment, but there is little information regarding microplastic pollution of these ecosystems.

According to scientists, their findings prove that plastic pollution originating on the surface of the ocean may travel into ecosystems situated two kilometers under the water level. Moreover, they found that both local environmental factors and the nature of feeding behaviour impact the presence of microplastics in marine organisms.

The findings add to growing evidence that microplastic pollution has spread beyond coastal waters and the ocean surface. The particles have now been detected in deep-sea hydrothermal vent ecosystems, highlighting the extent to which plastic pollution has reached remote marine environments.