Assessing physicochemical and biological indicators and their interactions in high-altitude lakes of Gokyo Valley, Nepal

• This work presents the physicochemical and biological indicators and their interactions in the high-Himalayan Lake Cluster. • Calcium bicarbonate-rich hydrogeochemistry was controlled by silicate weathering through rock-water interaction in the alpine environment. • Calcium hardness and temperature were significant physicochemical parameters that controlled the macroinvertebrates and algal communities, respectively. • Chironomidae was the dominant family in macroinvertebrates, and Bacillariophyceae was in the algal community. The high-altitude Gokyo Lake Cluster (GLC) in eastern Nepal, part of the Hindu-Kush Himalayan region, represents a unique alpine freshwater ecosystem. Despite its Ramsar designation, little is known about the biotic and abiotic indicators and their interactions that govern its ecological structure and functions. This study examines the water chemistry, algal communities, benthic macroinvertebrates, and the relationships among these components across three lakes in the GLC. Water chemistry analysis revealed a dominance of Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ cations and an anion sequence of HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻ > PO₄³⁻. Piper and Gibbs plots indicated a mixed water type and a hydro-chemical regime dominated by rock weathering, primarily from carbonate and silicate lithologies. Macroinvertebrates represent 22 families belonging to 10 orders, where the Shannon diversity index ranged from 0.64 - 1.16. A total of 143 algal species from 80 genera were observed. Bacillariophyceae dominated (66.67 %) of the algal assemblage, indicating an oligotrophic lake, while Diptera and Ephemeroptera comprised 68.57 % and 17.86 % of macroinvertebrate abundance, respectively. The third lake exhibited the highest algal and invertebrate richness, potentially influenced by localized nutrient input from anthropogenic activities. Non-metric multidimensional scaling (NMDS) highlighted calcium hardness (r² = 0.620, p = 0.038) and temperature (r² = 0.671, p = 0.029) as significant environmental drivers of algal and macroinvertebrate community structure, respectively. These findings emphasize the sensitivity of alpine aquatic ecosystems to physicochemical gradients and human activities, underscoring the need for long-term monitoring and targeted management strategies, particularly given the area's Ramsar status within the protected area and increasing tourism pressure.