Abstract

Pangong Tso is a land locked lake situated in eastern part of Ladakh (Indian Tibet), at an altitude of 4,266 m A.S.L. and remains frozen for about three months during winter. There is no outlet to the lake and loss of water is only through evapotranspiration. The lake was found to be highly alkaline (pH ≤ 9.0) with high conductivity (≥ 1639 mS) and nutrients (NH4-N ≥ 54 mg/L; NO₃-N ≥ 299 mg/L; TP ≥ 464 mg/L) as compared to its inlet Cheshul stream. The progression of the cations in the lake was Mg⁺⁺ > Na⁺ > K⁺> Ca⁺⁺ while as in the stream it was Ca⁺⁺ > Mg⁺⁺ > Na⁺ > K⁺. Mg⁺⁺ content in the lake was higher than the Ca⁺⁺ and Na⁺ due to its more solubility. The lake belonged to cold monomictic group of lakes. Twenty-three identified and some unidentified taxa of phytoplankton were recorded in the lake while as the periphytic community in the stream was represented by 34 taxa. Zooplankton in the lake was represented by only red coloured copepods, Diaptomus spp. and their larvae. No fish was observed in the lake while as in the stream three fishes Schizopygopsis stoliczkae, Triplophysa stoliczkae and Triplophysa gracilis were recorded. The low biodiversity in the lake was found due to high salinity and harsh environmental conditions prevailing in the lake. The inorganic nitrogen in the lake was recorded in very low concentration, Phosphate, on the other hand was present in very high concentrations. It seemed that instead of phosphate, nitrogen may act as a limiting factor for the aquatic community in the lake.

Key words: Pangong Tso, Ladakh, phytoplankton, Diaptomus spp., biodiversity, Cheshul stream.