Microplastics have been steadily accumulating for nearly four decades in Madagadakere, a freshwater lake in Karnataka’s Chikkamagaluru district, according to a new study that assesses year-by-year pollution levels preserved in lake sediments since the mid-1970s.
The research, conducted by the Department of Geology at the Central University of Kerala (CUK) and published in the Journal of Sedimentary Environments (Springer Nature), warns that the long-term build-up in this relatively undisturbed lake suggests that larger and more populated water bodies may be carrying significantly heavier pollution loads.
The work was carried out by Sandeep K. and A.V. Sijinkumar of CUK, Anish Warrier of the Manipal Institute of Technology, and research scholars Aravind G.H., R.S. Mahidev and Abdul Khader Rafaz, with funding from the Anusandhan National Research Foundation. “By analysing a sediment core representing roughly 43 years, the team found the earliest microplastic particles in layers dating to 1975. Concentrations rose steadily and peaked around 2010, with a slight dip recorded between 2010 and 2016, though the lake still contains considerable amounts of plastic,” said Mr. Sijinkumar.
“It is alarming that even a quiet, rural lake like Madagadakere shows the imprint of plastic use for nearly half a century,” Mr. Sandeep said. “Our findings reveal how deeply plastics have entered natural ecosystems.”
Surface sediment samples collected from various parts of the lake contained between 100 and 450 microplastic particles per kilogram, with the highest levels near the northeastern inlet, where a small stream drains into the lake. Researchers believe the stream transports domestic waste, agricultural plastics and fishing-related materials from the surrounding catchment. More than half the particles were fibres typically shed from synthetic clothing, nets, ropes, sacks and other household or fishing materials. Laboratory tests showed that polypropylene and polyethylene, common in packaging, mulching sheets and fishing gear, made up most of the particles.
The study also found a correlation between rainfall intensity and microplastic accumulation, with heavier monsoon years showing higher deposition due to increased runoff from fields. Since lake sediments preserve environmental changes in distinct layers, the researchers say plastics may act as geological markers of what many describe as the Anthropocene or Plasticene.
Mr. Sijinkumar said the findings should serve as a warning to policymakers. If a relatively undisturbed lake records nearly five decades of microplastic accumulation, the situation in larger lakes and rivers is likely far worse. He added that improved waste management and reduced reliance on single-use plastics are essential to prevent further damage.
Published – November 30, 2025 07:46 pm IST
