Impact of Anthropogenic Pollution and Microplastics on Ichthyofaunal and Macrofaunal Communities of the Koshi River

Abstract

The Koshi River is a dynamic transboundary river system that is significant for its ecological value, but is facing growing threats from anthropogenic pollution and microplastic contamination in Nepal and India. The present study aims to assess the joint effect of these stressors on the ichthyofaunal and macrofaunal communities at Madhepura, flood-prone area in Bihar. Key physico-chemical parameters like dissolved oxygen, biological oxygen demand, turbidity etc. have been changed due to anthropogenic activities like agricultural runoff, industrial discharge, sewage inflow and sand mining which has resulted in degradation of habitats and loss of biodiversity. The main microplastics present in the water and in sediments are polyethylene, polypropylene and PET; they are not only a physical threat to aquatic life, but also a chemical vector for toxins. When they are ingested by aquatic animals, they cause gastrointestinal blockage, tissue damage, oxidative stress and reproduction failure. This includes fish species and benthic macrofauna, which play a crucial role in the ecosystem and food web. Also, seasonal flooding affects the distribution of pollutants and ecological responses. The results show that there are serious ecological concerns, including shifts in species, trophic disturbances, and biomagnification of contaminants, which ultimately impact the fisheries, human health, and livelihoods of the area, highlighting the need for sustainable management and ecology considerations.