Microplastics Have Been Found in Deep-Sea Hydrothermal Vent Snails and Mussels

Our planet plainly has a microplastics problem. These minute synthetic particles have turned up in ancient rocks, human bones and nearly every animal species on Earth.

They have now been detected in one of the planet’s most remote, hostile and little-explored settings.

Microplastics found at deep-sea hydrothermal vents

A research group led by scientists at the Korea Research Institute of Bioscience and Biotechnology (KRIBB) has identified microplastics in snails and mussels that live around deep-sea hydrothermal vents.

Located roughly 2,000 metres beneath the ocean’s surface, these vents demonstrate how pervasively microplastics – particles smaller than 5 mm – can reach every part of an ecosystem.

The study, published in Water Research, found the small plastic particles in 92 percent of the animals sampled (11 out of 12). The specimens came from the North Fiji Basin in the south-western Pacific Ocean and the Central Indian Ridge in the Indian Ocean.

"Plastic pollution has now spread even to deep-sea hydrothermal vent ecosystems that were once considered among the most isolated environments on Earth," says marine biologist Se-Joo Kim, from KRIBB.

These dark, deep environments have remarkable features, supporting life through plumes of chemically rich, extremely hot seawater that rise from below.

We now know that species living at these vents have been consuming microplastics that settled on the deep seabed. Each animal contained an average of 3.42 plastic particles, and the most frequently detected material was the widely used plastic polystyrene.

How microplastics accumulate in vent snails and mussels

The team also identified patterns in how feeding behaviour influences the accumulation of microplastics in the snails and mussels. In snails, which graze across the sea floor, plastics concentrated in the digestive organs. In mussels, which feed by filtering water, the particles were spread more evenly through the body.

"Across the four vent species examined, microplastics were detected in nearly all individuals, but abundance varied considerably among them," write the researchers in their published paper.

"Despite this individual-level variation, distinct tissue distribution patterns were consistent within each taxon, indicating that once ingested or taken up, microplastics are distributed differently within snails and mussels."

Indian Ocean animals carried higher microplastic concentrations

Because the marine animals were collected from two locations, the researchers could compare the sites. Snails and mussels from the Indian Ocean contained significantly greater concentrations of microplastics than those from the south-western Pacific.

More research is required to establish the precise reasons, although regional variation in human activity and pollution, ocean circulation, and river systems may all contribute.

"The larger inter-regional contrast in snails than in mussels further suggests that settled microplastics concentrations on vent surfaces vary more between the two regions than suspended concentrations in the water column," write the researchers.

"These findings support the observation across 16 biogeographical provinces that geographic location has a stronger influence on individual microplastic loads in benthic marine invertebrates than taxonomic class or feeding mode."

Although it is troubling that microplastics can travel so far into the ocean depths, the findings at least help define the scale of the issue. They add urgency to work on reducing plastic pollution through better recycling methods and alternative materials.

Removing plastic from these deep-sea habitats is entirely impractical, so the problem must be addressed at its source.

Health concerns and deep-sea monitoring

We still do not have a complete understanding of how harmful microplastics are to health. However, early evidence suggests – as might be expected – that having these tiny plastic fragments in our bodies and food is not beneficial.

Earlier research has associated the consumption of microplastics with illnesses including Parkinson’s and colon cancer, and they are impossible to avoid in the modern world.

"Our findings provide important scientific evidence for establishing future deep-sea environmental monitoring systems and conservation policies," says Kim.

The research has been published in Water Research.

This article was fact-checked by Rachel Garner and edited by Fiona MacDonald. Although we take pride in our process, we are only human. If you notice an error, please let us know.