Researchers have presented the first evidence of micro-plastic contamination in the surface waters of Loktak Lake, north-east India’s largest freshwater body that not only plays a vital role in the economy and ecology of Manipur, but is also a designated Ramsar site because of its importance.
“The micro-plastic concentrations detected in Loktak Lake suggest substantial contamination of this Ramsar wetland,” the study states. “The high concentrations observed at heavily used sites raise concerns over ecological impacts on aquatic fauna through ingestion, trophic transfer and bioaccumulation,” it adds.
Globally, over 430 million tonnes of plastic are produced annually, with more than two-thirds of them becoming waste rapidly. India alone generates about 3.9 million tonnes annually, a substantial portion of which remains uncollected and eventually enters aquatic ecosystems, posing threats to both marine and freshwater environments.
The ubiquitous presence of micro-plastics poses serious risks to aquatic ecosystems due to their persistence, small size and complex chemical composition. MPs are composed of synthetic polymers that often contain residual monomers, stabilisers, plasticisers, flame retardants and other hazardous additives, the study observes.
Further, once released into aquatic systems, these particles not only cause physical harm to aquatic organisms but can also leach toxic substances or act as carriers for heavy metals and persistent organic pollutants, further amplifying ecological risks.
The study, conducted by five researchers from the Assam Royal Global University, Guwahati and Assam University, Silchar, has been published by Scientific Reports, an international peer reviewed journal on May 22.
The ancient lake has a surface area of about 290 square kilometres, which can expand up to 500 square kilometres during the rainy season. It serves as a source of water for hydropower generation, irrigation and drinking and is also a source of livelihood. Given its biodiversity and ecological sensitivity, it was designated as a wetland of international importance under the Ramsar Convention in March 1990.
According to the study, contamination in Loktak overlaps with or exceeds reported values from some urban-influenced lakes, such as Kodaikanal Lake in South India. The detection of micro-plastics even in lower-impact zones also suggests atmospheric deposition and hydrodynamic redistribution as contributing transport pathways.
Loktak Lake, the researchers observed, functions as a terminal basin for multiple inflowing rivers, receiving not only localised waste but also substantial inputs of agricultural runoff and untreated urban effluents from surrounding catchments. This hydrological connectivity further amplifies micro-plastics accumulation.
Consequently, the observed spatial pattern aligns with global trends, in which elevated micro-plastics loads are typically reported in regions with urbanisation, tourism activity and proximity to wastewater discharge points.
“Importantly, micro-plastics presence across all sites highlights the systemic nature of plastic contamination and supports the need for targeted waste management interventions, especially in floating settlements such as the phumsangs,” the researchers said. “Given that Loktak supports over 2,20,000 people who depend on the lake for water and food, addressing micro-plastics contamination is both an ecological priority and a socio-economic imperative,” they added.
