Assessment of microplastic contamination in the gastrointestinal tracts of indigenous fishes from north eastern hill regions of Bhogdoi, a tributary of River Brahmaputra, India

Microplastic (MP) pollution in freshwater environments has drawn considerable attention over the decades due to the risk posed by MPs to the aquatic fauna and human health. In this study, the occurrence of MPs was assessed from the gastrointestinal tracts (GIT) of indigenous fishes from Bhogdoi River, a tributary of River Brahmaputra, northeast hill region, Assam, India. All the fish species (n = 180) analysed showed 100% occurrence of MPs sampled from three stations of River Bhogdoi. A total of 488 microplastic particles were recorded from GIT of fishes collected. The mean abundance of MPs was highest in Station-II (7.64 ± 2.77 numbers individual-1) with lowest in S-I (3.17 ± 0.99 numbers individual-1). The MP size of 100-500 μm, MP shape of fibre (43.33%) and fragments (35.33%), blue colour MPs (26-37%) and polymer type PA (23-30%) were most prevalent in fishes analysed from River Bhogdoi. The mean abundance of MPs was higher in herbivore fishes (8.52 ± 1.22 numbers individual-1) as compared to carnivorous and omnivorous fish species with highest abundance in Labeo rohita (12.11 ± 2.13 numbers individual-1). Fibre and fragments with size range of 100-500 μm were dominant among all the feeding habits. Blue and black colour MPs were abundant among herbivore and carnivore fishes. Fourier transform infrared spectroscopy results confirmed that polyamide and polypropylene were the most abundant MP polymer in the fishes analysed. The present study provides baseline information of MPs in River Bhogdoi, Assam, for its future monitoring and assessment of contaminants.