With giant, wing-like fins flapping in slow, rhythmic motion, reef manta rays glide through the water like living kites from a prehistoric world. Divers often call them the butterflies of the sea, not just for their elegance, but for the way they effortlessly flutter through the ocean on wings of cartilage and muscle.
Swimming alongside a squadron of manta rays (yep! That’s the official collective term for a group of manta rays!) is like watching a slow-motion ballet: their huge, open mouths funnel thousands of litres of seawater over specialised gill plates that sift out microscopic prey, all while their fins curl and unfurl like guiding rudders.
Manta rays are already listed as vulnerable to extinction, largely due to overfishing and habitat degradation 2 – and now they are facing yet another challenge. Their filter-feeding behaviour, so effective at capturing nutritious plankton, makes manta rays vulnerable to an entirely different kind of particle: plastic. Every time a manta ray feeds, it risks ingesting not just nourishment, but toxins as well.
Plastic: From innovation to infiltration
Once thought of as a great human invention, plastic is now one of our biggest artificial foes. Large plastic items like bags, bottles, and fishing gear are frequently found bobbing around in the ocean as they are carried around by currents. However, as these items spend more time out in the sun and waves, they begin to fragment into tiny, microscopic pieces. These fragments behave just like plankton, floating around in the upper levels of the water column.
Carried by tides and gyres, these plastic fragments can travel thousands of kilometres, infiltrating even the most remote corners of the ocean. One such place is the Chagos Archipelago – a seemingly untouched haven far from human settlements that is home to a huge array of sharks and manta rays.
Located 1,600 km from the southern tip of India, this chain of islands lies at the heart of one of the world’s largest no-take marine protected areas. With no cities or rivers nearby, you might expect its waters to be pristine. However, a recent study has found that even here, manta rays are not safe from human impact….
Detecting Debris
To find out just how many microplastics are finding their way into some of the most far-flung manta feeding grounds, a team of researchers headed to the Chagos Archipelago.
Aboard a small research vessel, the team conducted 61 trawls using a fine circular net to skim the surface waters where manta rays feed. The samples collected – dubbed by the team as ‘little soups of plankton seawater’ – were then taken back to a lab, filtered and separated into types and colours using microscopes.
Drastic plastic
The results, unfortunately, showed plastic contamination in the areas where reef manta rays feed, with an average of 1.1 plankton-sized microparticles of plastic per cubic metre. Worryingly, the atoll with the highest ray residency also had the highest plastic concentration, with an average of 1.6 microparticles per cubic metre. That might not sound like a lot, but manta rays are efficient water filters! Every hour, a manta ray can filter as many as 86 cubic metres of water (equivalent to over 800 bathtubs) – potentially containing over 90 microparticles of plastic.
But, if no-one (except from those in the military base) live on any of the islands in the Chagos Archipelago, where has the plastic come from?
As you would expect, the usual suspects were found on the beaches around the archipelago: plastic bags, bottles and fishing nets. But more than half of the particles found in the water column weren’t from packaging; they were synthetic fibres, especially black and blue threads made of polyester. This means that synthetic fibres from clothes and everyday materials from very far away are finding their way to these remote, protected areas.
Every time we wash our clothes made of polyester or blended materials, tiny fibres are released into wastewater. Without proper filtration, these fibres escape treatment systems and flow into rivers, eventually reaching the point where they can be ingested by all sorts of marine animals!
Additionally, it may surprise you to know that the very mechanism which is supposed to safely dispose of plastic can also be a route that plastic takes to enter the ocean. You do your part: enjoy your takeaway meal, wash out your container and pop it in the recycling bin. But the journey it takes next is mysterious and somewhat scandalous.
A lot of the UK’s plastic waste is actually shipped overseas to Turkey, Malaysia and Vietnam. Once it’s shipped off, we often have no way of knowing if every single piece of that waste is actually recycled. In fact much of it ends up rotting away in landfills, illegally burned, or spilling into the oceans.3
It is estimated that 18-20% of our global plastic waste ends up washing into the ocean, and this figure is set to rise in the future.4
Reef Ray Dismay…
For manta rays, the consequences of plastic ingestion can be severe.
With their slow growth, low fertility, and long lifespans, any disruption to their feeding, including plastic ingestion, can have serious and long-lasting effects on populations5. In areas like the Chagos Archipelago, where conservation efforts have been strong, this kind of pollution undermines years of progress.
Therefore, this study is a stark reminder: even remote, protected areas are not safe from global plastic waste.
In a bid to address this issue, the research team is supporting progress at the UN Global Plastics Treaty, which is pushing for laws that require companies to design products with their entire lifecycle in mind. The treaty enters its 5th phase this month, where we hope to see some progress!. To keep up to date on the news of this, check out the UN environmental website at: https:// www.unep.org/inc-plastic-pollution/session-5.2.
How to find another way
The oceans have no borders. A single piece of plastic can drift for years, carried by currents, and eventually wash up on a reef thousands of miles away. But this also means that no matter where we live, we can help.
Beach cleans wherever you are will help marine life by stopping more plastic from entering the oceans! Many amazing groups do beach cleans including those listed below:
Marine Conservation Society: https://www.mcsuk.org/what-you-can-do/join-a-beach-clean/find-a-beach-clean/
The National Trust: https://www.nationaltrust.org.uk/support-us/volunteer/help-out-with-a-beach-clean
Surfers Against Sewage: https://www.sas.org.uk/plastic-pollution/million-mile-clean/find-a-clean-near-you/
Most importantly, we need to prevent plastic from finding its way into the oceans in the first place. Simple steps include putting a microplastic filter in your washing machine, and, despite the uncertainties, continuing to recycle! Even more impactful is to reduce your plastic use altogether – this means reusable shopping bags, coffee cups, and straws, buying sustainable fashion, and using containers instead of single-use plastic.
Could you challenge yourself to a week of going plastic-free? It’s not easy, but it’s a powerful way to become more aware of just how much plastic we use and how we live in a system completely depend on single-use plastic. You may even find this inspires you to get invovled with petitions and groups trying to fight for system change in how we use plastic.
There are so many tools at our disposal and ways we can help our marine friends, just making some small changes our lives can make a big difference to our marine friends. Our oceans are crying out for help – it’s never too late to listen!
Article written by Skye Brook and edited by Nia Clarke
Primary Paper
Savage, J. et al. (2025) ‘No escape from microplastics: Contamination of reef manta ray feeding areas in a remote, protected archipelago’, Conservation Science and Practice. doi:10.1111/csp2.70059. Available at: https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/csp2.70059
Other References
Peel, L.R. et al. (2019) ‘Stable isotope analyses reveal unique trophic role of reef manta rays (Mobula Alfredi) at a remote coral reef’, Royal Society Open Science, 6(9), p. 190599. doi:10.1098/rsos.190599. (Accessed: 18 June 2025) Available at: https://royalsocietypublishing.org/doi/10.1098/rsos.190599
Marshall, A. et al. (2019) ‘Mobula alfredi-Reef Manta Ray. The IUCN Red List of Threatened Species 2019’, IUCN Red List of Threatened Species. doi:10.2305/iucn.uk.2019-3.rlts.t195459a68632178.e (Accessed: 16 June 2025) Available at: https://www.researchgate.net/publication/350810662_Mobula_alfredi-Reef_Manta_Ray_The_IUCN_Red_List_of_Threatened_Species_2019
- Earth.org (2021) Brexit Loophole Will Allow UK to Continue Shipping Plastic Waste to Poorer Countries. (Accessed: 19 June 2025) Available at: https://earth.org/brexit-will-allow-uk-to-continue-shipping- plastic-waste-to-poorer-countries/
- UN (2025) Global Push to end plastic pollution gains ground in Nice. (Accessed: 18 June 2025) Available at: https://news.un.org/en/story/2025/06/1164301
Dulvy, N.K. et al. (2014) ‘Diagnosing the dangerous demography of Manta Rays using life history theory’, PeerJ, 2. doi:10.7717/peerj.400. (Accessed: 19 June 2025) Available at: https://peerj.com/articles/400/
