Microplastics, laced with heavy metals, have reached one of India’s most celebrated wildlife sanctuaries. The findings are a warning and an opportunity.
If you have ever visited Bhitarkanika in Odisha, you know the feeling. The air is thick with salt and silt. Mangrove roots climb out of the mud like the fingers of some patient underwater creature. When you walk into the Bhitarkanika Ecosystem in Odisha, everything feels pristine. Saltwater crocodiles, India’s largest, drift silently down the Brahmani river. Olive Ridley turtles nest on nearby beaches. A herd of elephants wades in to drink. India’s second-largest mangrove forest hums with life.
But a new study, just published in Water, Air, & Soil Pollution, shows that this sanctuary is no longer as untouched as it looks. At all 20 sites sampled along the Brahmani river, within and around the protected area, a team of researchers found microplastics in the sediment.
Shreyas Das, a master’s student at Nalanda University, says, “The mangrove sites trapped particles differently from the open river sites. Mangrove roots act like a physical filter: they catch plastic but also accumulate it. The very feature that makes mangroves so valuable as coastal protectors also makes them long-term sinks for this pollution.”
Microplastics are plastic particles smaller than 5 millimetres. Most are not manufactured that small; they are born when bags, bottles, fishing nets, and synthetic clothing break down in sunlight and water. A single polyester shirt can shed thousands of fibers in one wash cycle. Those fibers travel through drains, into rivers, and out to sea. Plastic does not biodegrade; it only gets smaller until it is small enough for fish, crabs, turtles, and birds to mistake it for food.
Rakesh Kumar, lead author, currently a postdoctoral fellow at Auburn University, United States, says, “What struck me most is that every single one of our 20 sites had microplastics, including inside the protected sanctuary. A protected area is not a sealed container. Rivers do not recognise boundaries. If we want Bhitarkanika to stay protected, we have to start thinking about pollution upstream, sometimes hundreds of kilometres away from the sanctuary gate.”
The highest concentration the team recorded was about 50 particles per kilogram of dry sediment, lower than levels reported off Mumbai or Chennai, but not zero, and within a protected sanctuary. Nearly 89 per cent of what they collected was fiber, indicating synthetic textiles and fishing gear as the dominant sources. Polyamide was the most common polymer, followed by polyethylene and polypropylene, the plastics used in clothing, bags, and bottle caps. The mangrove zones trapped more particles than open river sites; the same roots that protect coasts from cyclones also act as long-term sinks for pollution.
Anish Kumar Warrier, from Manipal Institute of Technology, stated that “Polyamide emerged as the most abundant polymer, and that is what worries me ecologically. Polyamide has a higher hazard score than polyethylene, which is more common. So even though Bhitarkanika is cleaner than many Indian rivers in terms of sheer particle count, the risk index is high. Quantity is not the whole story.
Under an electron microscope, the researchers found heavy metals stuck to the surfaces of these particles: chromium, copper, zinc, arsenic, cadmium, barium, and lead. The metals are not part of the plastic. They are picked up from the river as the particles drift. Plastic, because of its large surface area and water-repelling nature, is unusually good at collecting toxins. When a small fish or shrimp eats that particle at the base of the food web, it swallows a concentrated dose of whatever the river has been carrying, and those toxins move up the chain, into larger fish, and eventually onto dinner plates.
Jasmeet Lamba, Professor at Auburn University, United States, says, “The heavy metals bound to the microplastic surfaces are, for me, the signal that should not be ignored. Plastics act as vectors, carrying heavy metals. When these enter the food chain through benthic organisms, they do not stop there. They move up, into the fish, and eventually into the people who depend on those fish.”
Using four internationally accepted risk indices, the team found that Bhitarkanika’s total pollution load remains modest compared with urban coasts. But ecological risk at several sites scored “high” to “extreme,” driven by the hazardous nature of polyamide. Quantity is not the whole story. Chemistry is. Fragments are smaller than a grain of rice. Films are so thin that they are almost invisible.
Prabhakar Sharma from Nagaland University, Nagaland, says, “The Brahmani river flows past agricultural fields, small industries, and towns before it reaches the sanctuary. Each of those sources contributes. That means the solution cannot be limited to cleaning the sanctuary. It has to be about managing the whole river basin, the farms, the drains, the untreated sewage, all of it.”
Rivers do not respect sanctuary boundaries. The Brahmani flows past mines, industries, farms, and towns long before it reaches Bhitarkanika. Anurag Verma, who is currently a research associate at The Energy and Resources Institute, New Delhi, says, “From a policy perspective, what we have here is a baseline. Bhitarkanika is not yet catastrophically polluted, and that is precisely why this is the moment to act. It is far cheaper and easier to prevent a pristine ecosystem from degrading than to restore one that has already degraded.”
Protecting the sanctuary means managing the whole basin. This should include:
• Wastewater treatment in towns upstream, and stricter industrial discharge norms in the Brahmani basin.
• Filter standards on washing machines and community laundry points to capture synthetic fibers at source.
•Organised collection programs for old and discarded fishing nets.
• Microplastics should be built into environmental impact assessments for every new project in the basin.
•Monitoring must be regular, every one to two years, not one-time, coordinated between forest departments, pollution control boards, and universities.
Bhitarkanika is not yet catastrophically polluted, and that is precisely the point. Preventing a pristine ecosystem from degrading is far cheaper and far more honest than restoring one after the damage is done. A sanctuary protects what is inside it. It cannot, on its own, protect itself from what the river brings in.