Sunil Kumar Bochalya, Neeraj Kumar and Ashwani Kumar
Abstract
Headwater streams of the Himalayas play a vital role in sustaining biodiversity and ecological stability, yet these are less explored. This study investigated the seasonal diversity and population dynamics of macrozoobenthos in a spring-fed Jalkur stream is a tributary of the Bhagirathi River, from 2024 to 2025. A total of 10 taxa were recorded, belonging to 4 insect orders: Ephemeroptera (47.8%), Trichoptera (28.6%), Plecoptera (19.8%), and Coleoptera (3.8%). Species richness and abundance exhibited marked seasonal variation, with the highest density in March and the lowest in July. Diversity indices such as Shannon- Wiener, Simpson, Brillouin, and Margalefâs richness were consistently higher during the winter and premonsoon months, declining sharply in the monsoon season. Physico-chemical parameters displayed strong seasonal trends: dissolved oxygen, hardness, and alkalinity peaked in winter, whereas temperature, turbidity, and carbon dioxide (CO2) reached their maxima during the monsoon. Correlation and multivariate analyses demonstrated that species richness and abundance were positively associated with dissolved oxygen, hardness, alkalinity, nitrate, and phosphate, but negatively correlated with turbidity, free carbon dioxide, and temperature. Dominant taxa such as Baetis acuticostalis (12.95%), Ephemerella indica (20.57%), and Helicopsyche xenothoe (26.85%) showed strong preferences for oxygen-rich, low-CO2 conditions, underscoring their potential as bioindicators of good water quality. This study provides the first comprehensive ecological assessment of the Jalkur stream, providing baseline data on species composition, diversity patterns, and environmental relationships in Himalayan headwater and highlight the critical importance of water clarity, and oxygen availability in maintaining benthic biodiversity, emphasizing the need for continuous monitoring and conservation of Himalayan ecosystems under climatic and anthropogenic pressures.