Plastic pollution has become a global environmental crisis, with an estimated 11 million tons of plastic entering the oceans each year. As larger plastic debris breaks down into microplastics, these tiny particles are transported throughout marine ecosystems by ocean currents, threatening marine life and ultimately entering the human food chain.
While numerous studies have documented microplastic contamination in coastal waters and surface oceans, little has been known about their presence in the deep sea, which accounts for nearly 90% of the world's marine environment. In particular, hydrothermal vent ecosystems—unique deep-sea habitats that support diverse life despite the absence of sunlight—have remained largely unexplored with respect to microplastic pollution.
A research team led by Dr. Se-Joo Kim and Dr. Jinyoung Jeong at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) , in collaboration with researchers from the Korea Institute of Ocean Science and Technology (KIOST), has conducted the world's first comparative study revealing how microplastics accumulate in animals inhabiting hydrothermal vents in two different oceans.
The researchers analyzed deep-sea snails and mussels collected by KIOST from hydrothermal vents located more than 2,000 meters below the surface in the North Fiji Basin of the southwestern Pacific Ocean and the Central Indian Ridge in the Indian Ocean. KRIBB researchers subsequently performed detailed microplastic analyses and ecological interpretation of the collected specimens.
The study detected microplastics in 92% of all animals examined, with an average of 3.42 particles per individual, demonstrating that even remote deep-sea hydrothermal vent ecosystems are already contaminated by plastic pollution. Among the detected polymers, polystyrene, widely used in consumer products and packaging materials, was the most abundant.
The researchers further discovered that feeding behavior plays a major role in determining where microplastics accumulate within the body.
In grazing snails that feed on microbial mats covering the seafloor, microplastics were concentrated primarily in the digestive organs. By contrast, filter-feeding mussels exhibited a relatively even distribution of microplastics throughout their tissues, indicating that biological characteristics strongly influence the pathways through which microplastics enter and accumulate within marine organisms.
The comparison between two ocean basins also revealed substantial regional differences.
Animals collected from the Indian Ocean contained significantly higher concentrations of microplastics than those from the southwestern Pacific. After normalizing for body weight, Indian Ocean specimens contained up to 14.7 times higher microplastic concentrations. The researchers suggest that differences in surrounding human activities, riverine plastic inputs, and large-scale ocean circulation likely contributed to these regional variations.
The findings provide the first scientific evidence that plastic pollution generated at the ocean surface can be transported thousands of meters downward, reaching one of Earth's most remote and extreme marine ecosystems.
The study also demonstrates that biological characteristics such as feeding strategy influence how microplastics accumulate within organisms, while regional environmental conditions determine the overall level of contamination.
These findings are expected to contribute to future deep-sea environmental monitoring, environmental impact assessments for deep-sea mineral resource development, and long-term conservation strategies for deep-sea ecosystems.
"Plastic pollution has now spread even to deep-sea hydrothermal vent ecosystems that were once considered among the most isolated environments on Earth," said Dr. Se-Joo Kim, one of the corresponding authors of the study. "Our findings provide important scientific evidence for establishing future deep-sea environmental monitoring systems and conservation policies."
Korea Research Institute of Bioscience and Biotechnology (KRIBB) is a leading national research institute in South Korea dedicated to cutting-edge research in biotechnology and life sciences. Established in 1985, KRIBB focuses on advancing scientific knowledge in areas such as molecular biology, genomics, bioinformatics, synthetic biology, and aging-related studies. As a government-funded institute, KRIBB plays a pivotal role in driving innovation, supporting national R&D strategies, and collaborating with academic and industrial partners both domestically and internationally.
This research was supported by the Basic Science Research Program funded by the Ministry of Education and the Ministry of Science and ICT, the Creative Convergence Research Program of the National Research Council of Science & Technology (NST), the Major Research Programs of the Korea Research Institute of Bioscience and Biotechnology (KRIBB), and the Major Research Programs of the Korea Institute of Ocean Science and Technology (KIOST).
The study was published online on June 3 in Water Research (Impact Factor: 12.8), one of the world's leading international journals in environmental science and water research.
The article is titled "Oceanic determinants of microplastic bioaccumulation in fauna of deep-sea hydrothermal vents: Comparative study of the southwestern Pacific and Indian Oceans."
The corresponding authors are Dr. Jinyoung Jeong and Dr. Se-Joo Kim of the Korea Research Institute of Bioscience and Biotechnology (KRIBB). The co-first authors are Won-Kyung Lee and Yugyeong Sim. Additional co-authors include Se-Jong Ju of the Korea Institute of Ocean Science and Technology (KIOST) and Dongsung Kim of KIOST.
