![Microplastic beads seen in the central tube of a copepod [their intestinal tract], as evidenced here, fluorescently labelled beads help with visualisation and identification. Credit: Plymouth Marine Laboratory](https://images.boatingnz.online/wp-content/uploads/2026/02/01190204/biological-pumps-how-z.jpg "Microplastic beads seen in the central tube of a copepod [their intestinal tract], as evidenced here, fluorescently labelled beads help with visualisation and identification. Credit: Plymouth Marine Laboratory")
The ocean has its own internal conveyor belts, driven not by machines but by living organisms. New research has revealed that copepods, some of the most numerous animals in the sea, are acting as biological pumps for microplastics, ingesting tiny plastic particles and transporting them down through the water column.
The study focuses on copepods, tiny crustaceans that dominate zooplankton communities across the global ocean. Despite their size, copepods play an outsized role in marine ecosystems, forming the backbone of the food web and driving the ocean’s biological pump by packaging carbon into sinking faecal pellets.
Now, scientists have shown that the same process is also transporting microplastics down through the water column.
Led by Dr Valentina Fagiano of the Oceanographic Centre of the Balearic Islands, with co authors from Plymouth Marine Laboratory, the research directly tracked individual microplastic particles as they passed through the gut of the copepod Calanus helgolandicus. Using fluorescent plastics and real time imaging, the team was able to measure both how long microplastics remain inside a copepod and how frequently new particles are ingested.
Across all experiments, microplastics spent around 40 minutes in the copepod gut, regardless of whether the particles were beads, fibres or fragments. Food availability also made little difference. This consistency allowed the researchers to scale up from individual animals to the wider ecosystem.
By combining gut passage rates with well established copepod abundance data from the western English Channel, the team estimates that copepods could be transporting around 270 microplastic particles per cubic metre of seawater to depth each day in that region alone.
Senior ecotoxicologist Dr Matthew Cole explains that copepod faecal pellets sink naturally, carrying their contents with them. Once ingested, microplastics are repackaged and exported downwards, embedding plastic pollution into deeper waters and sediments.
The findings challenge the idea that microplastics are mainly a surface ocean issue. Copepods are eaten by fish larvae, small pelagic fish, seabirds and marine mammals, meaning plastics can also move up the food chain while simultaneously being driven downwards.
Published in the Journal of Hazardous Materials, the study provides a quantitative framework that can now be integrated into ocean plastic transport models. This will help scientists better predict where microplastics accumulate and which ecosystems face the greatest long term exposure.
To read a public summary of the research and explore the findings in more detail, visit:
https://phys.org/news/2026-01-biological-zooplankton-microplastics-ocean-depths.html
Fagiano, V., Cole, M., Coppock, R., & Lindeque, P.
Real time visualization reveals copepod mediated microplastic flux.
Journal of Hazardous Materials, 2026.
https://www.sciencedirect.com/science/article/pii/S0304389425034715
It is a peer reviewed paper and represents the first real time quantification of gut passage and ingestion rates of microplastics in copepods, which is why it is already being picked up by outlets like Phys.org and used to inform larger scale plastic transport models.
