ORIGINAL RESEARCH article
Front. Water
Sec. Environmental Water Quality
Impact of spatio-temporal variations and altitudinal gradient on bacterial dynamics along an Eastern Himalayan River Teesta
Upashna Chettri 1
SR Joshi 2
Santanu Das 3
Tapan Kumar Chakrabarty 2
1. Royal Global University, Guwahati, India
2. North-Eastern Hill University, Shillong, India
3. Institute of Advanced Study in Science and Technology, Guwahati, India
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Abstract
Teesta, an Eastern Himalayan River is an important lifeline of the state of Sikkim and parts of West Bengal. However, the river is under the influence of human activities and hydrological disturbances. Microbes are sensitive to environmental changes which make them indicators of pollution, nutrient load, heavy metal and ecological disturbances. This study investigated the spatial, temporal and sample type variations in the bacterial composition and richness along the altitudinal gradient of Teesta River and the influence of the environmental factors in shaping the bacterial composition and structure. Our study revealed that bacterial species richness significantly varied across the sites along the river gradient but bacterial composition was less influenced by the sites, seasons and sample type. While dominant phyla remain consistent across samples, season-driven shifts and niche preferences such as winter enrichment of Actinobacteriota and LEfSe-identified genus-level biomarkers highlight the ecological heterogeneity and functional diversification of riverine microbial communities. Altitude and heavy metal lead (Pb) was found to strongly influence on occurrence of bacterial phyla like Proteobacteria, Chloroflexota, Acidobacteriota, and Actinobacteriota. Whereas, environmental parameters like pH, temperature, alkalinity and dissolved oxygen exhibited the most significant association with major bacterial phyla. The Teesta River displayed distinct taxonomic signatures in water and sediment, particularly at the genus level that is strongly shaped by both seasonal dynamics and habitat-specific conditions. Our findings offer valuable insights on how seasonal shifts and habitat-specific conditions within the Teesta River shape bacterial community structure and composition with significant implications in predicting ecosystem responses to environmental change in an Eastern Himalayan river system.
Summary
Keywords
altitudinal gradient, Anthropogenic impact, bacterial diversity, Himalayan River Ecology, next generation sequencing
Received
26 November 2025
Accepted
29 December 2025
Copyright
© 2025 Chettri, Joshi, Das and Chakrabarty. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Upashna Chettri; SR Joshi
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