Aquatic insects as indicators of water quality: Seasonal distribution and biomonitoring insights from a hilly river in the Eastern Himalayan region, India

This study investigated the seasonal distribution and diversity of aquatic insect communities in the Jatinga River, a small hilly river in northeast India, to assess water quality through biomonitoring. Sampling was conducted at five sites along the river from upstream to downstream over one year seasonally (2018–2019). A total of 72 species, 58 genera, and 38 families were recorded, with species such as Micronecta sp.1, Ptilomera assamensis, and Hydropsyche sparna achieving eudominant status. Biotic index values like BMWP^THAI (score: 78–105), ASPT^THAI (score: 6.2–7.5), SIGNAL2 (score: 6.1–7), and EPT% (50.89–75.35) indicated good and clean water quality with healthy habitat at upstream sites (S1 and S2), with decreasing quality in downstream. Values of all the studied environmental variables of water were found within the permissible limit of Bureau of Indian Standards and World Health Organisation except Electrical conductivity (EC) and Total dissolved solid (TDS). Principal component analysis (PCA) and canonical correspondence analysis (CCA) revealed significant relationships between insect species distribution and environmental factors such as riverbed particles and water chemistry.