Water quality assessment and genotoxicity in fishes of Karamana River, Kerala, India: an insight of microplastic pollution

Microplastics are emerging pollutants of global concern, and their widespread presence poses a serious threat to aquatic and terrestrial ecosystems. The current study investigated the water quality and the presence of microplastics in water and native fish samples of the Karamana River, Kerala, India. The water quality was analyzed using various physicochemical parameters, including the dissolved oxygen, biochemical oxygen demand, and chemical oxygen demand. Microplastics isolated from water and native fish samples were characterized using Fourier transform infrared (FTIR) spectroscopy. DNA damage in fish liver and gill cells was assessed using the comet assay (single-cell gel electrophoresis). The water quality assessment revealed metals in the water within the acceptable limits, reduced dissolved oxygen, and increased biochemical oxygen demand and chemical oxygen demand, which indicate a river water ecosystem in hypoxic conditions, and the higher level of the most probable number index confirmed the presence of coliforms in this river. The microplastics isolated from the water and native fish samples were in fibers, fragments, film, pellets, and foams in nature. The abundance of microplastics in the river confirmed the load of microplastic pollution, which varied among the sites. FTIR spectroscopy analysis confirmed the presence of microplastic polymers such as polyethylene, polypropylene, polystyrene, polyamide, polyoxymethylene, and polyester in the water and native fish samples of the Karamana River. The increased percentage of tail DNA in the liver and gill cells of the fish inhabitants of the Karamana River, compared with the control fish, indicated DNA damage; this could be due to the microplastics in that aquatic ecosystem.