Microplastics have reached some of the world’s most remote marine ecosystems with a new study detecting plastic particles in nearly all deep sea snails and mussels sampled from hydrothermal vents in the Indian Ocean and the southwestern Pacific Ocean.
The study published in Water Research, analysed 12 mussels and snails collected from hydrothermal vents nearly 2,000 metres below the ocean surface during research expeditions conducted between 2016 and 2019. Researchers found microplastics in 11 of the 12 animals examined.
Scientists from the Korea Research Institute of Bioscience and Biotechnology said the findings reveal that plastic pollution has penetrated even isolated deep sea environments. They noted that the chemical signature found in animals living thousands of metres below the surface reflects human activities occurring far above in the ocean.
The research also found significant differences between the two regions. Animals collected from the Indian Ocean contained up to 14.7 times more microplastics than those from the southwestern Pacific Ocean. Researchers suggest this may be linked to the Indian Ocean receiving one of the world’s highest levels of river borne and coastal plastic pollution, although they say more research is needed to confirm the connection.
The study highlighted that feeding behaviour influences plastic accumulation. Deep sea snails, which graze on bacteria-covered rock surfaces, showed higher concentrations of microplastics in their digestive organs, while filter feeding mussels had plastic particles distributed more evenly throughout their tissues.
Scientists say microplastics sink to the deep sea after becoming coated with algae and microbes or being transported in marine organisms’ waste. Once they reach the seabed, the particles can persist for extremely long periods because of the cold, dark and low oxygen conditions.
Researchers say the findings raise important questions about how microplastics may affect the health of deep sea species and the functioning of fragile hydrothermal vent ecosystems, underscoring the need for further research into the long term impacts of plastic pollution on the deep ocean.