Microplastic Pollution in a Tropical River–Mangrove System of the Brahmani River in Bhitarkanika Wildlife Sanctuary, Odisha (India)

Microplastics (MPs), recognised as emerging contaminants, are increasingly prevalent in riverine ecosystems due to escalating anthropogenic activities. River deltas, which typically serve as ecologically rich and pristine habitats, are now under threat from solid and liquid waste inputs, particularly in rivers flowing through urban and agricultural landscapes. This research investigates MP contamination in sediments of the Brahmani River within the Bhitarkanika Wildlife Sanctuary, Odisha (India), encompassing both mangrove and non-mangrove sites. MP abundance reached up to 50.4 items/kg (dry weight) and 25 items/kg (wet weight), dominated by fibers, fragments, and films, primarily in the 0.1–5 mm size range. Polymer analysis identified polyamide as the most common, followed by LDPE, HDPE, and polypropylene. Surface analysis showed MPs carried heavy metals such as chromium, copper, zinc, arsenic, cadmium, barium, and lead from the surrounding environment. Elevated ecological risk indices raise concerns for wildlife, including elephants, saltwater crocodiles, Olive Ridley turtles, and other native and migratory birds. Mangrove sediments act as key sinks for MPs, potentially affecting benthic ecosystems and mangrove productivity. The findings provide critical insights to support policy and conservation efforts.