Diversity of Plankton Algae along an Elevation Gradient in the Freshwater Ecosystems of the Khumbu Region, Nepal

Understanding the diversity and composition of algal communities across different elevation gradients and factors affecting these patterns can provide valuable insights into the ecological processes that shape these ecosystems. In this study, we aimed to investigate the diversity and composition of algae in the Khumbu region of Nepal and assess their relationship with environmental variables along an elevation gradient. We collected algal samples from 13 lakes and rivers ranging in elevation from 2700 m to 5000 m and analyzed the relative influence of various environmental factors on algal richness, including altitude, temperature, nitrogen and phosphorus content, dissolved oxygen concentration, total dissolved solids content, and conductivity. A total of 56 species from six classes were recorded from various sampling sites, with Bacillariophyceae being the most abundant (20 species). Species richness exhibited both increasing and decreasing trends in relation to various physiochemical properties of the water. The region exhibited a general trend of rising algal richness with increasing elevation. This phenomenon can be attributed to the elevation-dependent rise in total dissolved solids, along with higher nitrogen and phosphorus levels, caused by intensified human activity. Of all the variables, phosphorus content had the strongest effect on algal richness, indicating that phosphorus is the most significant predictor of water quality. The increase in phosphorus content and subsequent algal richness in these high-altitude fresh water lakes and rivers points to the deterioration in water quality in the Himalayan reservoirs. With climate change and rising tourism already increasing the vulnerability of the Khumbu region, our findings underline the importance of regularly monitoring the ecosystem therein.