Guwahati: For generations, fishing in Assam’s Thekera Beel wetland has been a way of life. But now, fishermen are catching something more than fish—microplastics, invisible to the eye but revealed under the scientist’s microscope.
Numerous studies have been carried out to identify and quantify the microplastics present in the marine ecosystem. However, only a few studies have been done in the freshwater environment, especially in a wetland.
A study published in the Journal of Hazardous Materials Advances sheds light on the alarming presence of microplastic contamination in fish species from the Thekera Beel wetland in Morigaon district, Assam.
The research, conducted by Garima Bora, Bipul Phukan, Avinash Talukdar, Imtiaz Ahmed, Samar Jyoti Chutia, Rinku Gogoi, Jiten Sarma, Ayub Ali, Tushar Gowala, and K.A. Martin Xavier, has revealed disturbing levels of microplastic accumulation in fishes. Microplastics are defined as plastic particles smaller than 5000 µm.
Due to their non-biodegradable nature, plastics persist in the environment for hundreds to thousands of years.
Over time, plastic polymers break down due to UV light exposure, physical forces, and hydrolysis, forming smaller fragments known as microplastics. India alone produced 19.3 million metric tons of plastics in 2021 according to Plast India Foundation, 2023.
The researchers aimed to evaluate microplastic contamination in fish with different feeding habits—herbivores, omnivores, and carnivores—collected from Thekera Beel, a freshwater wetland linked to the Kolong River. Rural people depend on fishing from the wetland to support their livelihood.
The Kolong River, one of the Brahmaputra’s tributaries, is classified among India’s most polluted rivers due to urban waste and sewage discharge.
Between January and April 2023, the team sampled 90 fish from nine species across four orders and families. The collected fish were carefully transported to the biology lab at the College of Fisheries, Raha, where the gastrointestinal tracts were analyzed for microplastic contamination. Advanced techniques such as Fourier Transform Infrared Spectroscopy (FTIR) were employed to identify and characterize microplastics.
The study recorded 332 microplastic particles from all examined fish samples, revealing a 100% occurrence rate. Carnivorous fish exhibited the highest mean abundance of microplastics, with Glossogobius giuris leading the pack at an average of 5.50 particles per individual. Omnivorous species followed closely, while herbivorous fish showed relatively lower contamination levels.
The researchers observed that fibre-shaped microplastics were the most common, followed by fragments, films, and beads. Particles in the size range of 100–500 µm were predominant, with transparent and blue-coloured microplastics being the most frequently detected. The predominant polymer was Polyethylene in the case of herbivores and carnivores while nylon was mostly found in omnivores.
The contamination appears to be closely linked to human activities. The Kolong River’s pollution from urban effluents discarded fishing gear, and laundry discharges likely contribute to the microplastic load in the Thekera Beel. Fishing nets and other synthetic materials breaking down in the wetland environment also exacerbate the problem.
“Fiber-shaped microplastics were the most common, likely originating from synthetic dress materials through laundry wastewater and from abandoned, lost, or otherwise discarded fishing gear (ALDFG) entering the beel ecosystem.
Compared to other parts of the country, pollution is lower in Assam. However, there is an emerging need for fisheries management to implement effective ALDFG monitoring mechanisms and undertake clean-up operations in the water bodies of the Northeast region,” K.A. Martin Xavier, the corresponding author of the study, said.
ALDFG is abandoned, lost or otherwise discarded fishing gear.
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