Plastic at 2,000 metres: what deep-sea vent animals show
Korean researchers found microplastics in 92 percent of snails and mussels living at hydrothermal vents in two oceans. How the animals feed decided where the plastic ended up; where they lived decided how much.
By Timothy Li
The deep sea is about 90 percent of the marine environment and almost none of the sampling. A study in Water Research from the Korea Research Institute of Bioscience and Biotechnology, with specimens collected by the Korea Institute of Ocean Science and Technology, looked at animals living around hydrothermal vents more than 2,000 metres down, in the North Fiji Basin in the southwestern Pacific and on the Central Indian Ridge.
What they did
The researchers, led by Se-Joo Kim and Jinyoung Jeong with first author Won-Kyung Lee, analysed two kinds of vent animal: snails that graze microbial mats on the seafloor, and mussels that filter water. They counted and identified particles in different tissues and compared the two oceans, which they describe as the first such comparison for vent fauna.
What they found
- Microplastics were detected in 92 percent of the animals examined, at an average of 3.42 particles per individual. Polystyrene was the dominant polymer.
- Feeding strategy decided where particles went. Grazing snails held them mostly in digestive organs; filter-feeding mussels had them spread fairly evenly across tissues.
- Location decided how much. After adjusting for body weight, Indian Ocean animals carried up to 14.7 times more microplastic than Pacific ones. The authors attribute this to nearby human activity, river inputs, and circulation patterns.
What it cannot show
Two sites and two kinds of animal are a small base for generalising about the deep sea. The explanations for the regional difference are plausible but were not tested directly. The study measures presence, not harm: nothing here says the snails or mussels were worse off. And the finding that surface plastic reaches the deep sea is not itself new; the value is in the comparison between feeding types and regions.
The pattern echoes what the California wildlife studies on this site show at shallower depths. Exposure follows feeding: krill for blue whales, plankton for anchovies, microbial mats for vent snails. The particle has to be where the food is.
Read the study in Water Research · Lee et al., 2026
Summary from the National Research Council of Science and Technology