IT11-A Laghi Himalayani

The lakes are located in the Khumbu Valley, Sagarmatha National Park (SNP), Nepal. SNP is situated in the Solu-Khumbu district, in the north-eastern region of Nepal and represents the Northernmost part of the Dudh Koshi River Basin, which is part of the Koshi River Basin (or SaptaKoshi Basin), one of the seven major hydrographic basins into which Nepal is subdivided. The SNP covers an area of 1141 km2 and is surrounded on all sides by the highest mountain ranges on Earth. The terrain is extremely irregular, with altitudes that reach 8848 m. The lower topographic limit of permanent snow cover is located at an altitude of 5500-5600 m. The climate of the SNP is driven by the Asian monsoon. The lake bedrock is mainly Late Tertiary Granites, with a primarily quartz-silicate composition and a low weathering rate. Soils are absent or very thin in most of the catchments. Vegetation cover is restricted to small areas of alpine meadow. The lake surface area is 0.009 km2. The lake lies above 5000 m a.s.l., the tree line limit. The lake is ice-covered for ca. 9-10 months every year (from October-November to June-July). Chlorophyll a concentrations are below 1µg l-1 and are probably controlled by strong grazing pressure from a large pigmented (keto-carotenoid of astaxanthin type) zooplankton community. Total phosphorus concentrations (mean values) are about 2 µg P l-1, whereas total nitrate concentrations are about 120 µg N l-1. Concentrations of particulate organic carbon (POC) and dissolved organic carbon (DOC) are very low. Paleolimnological studies covering the last ca. 3500 yrs B.P confirmed the high sensitivity to climatic forcing of this environment with oscillation that mimic warm and cold period and the recent warming. Paleolimnological results are in agreement with the evidence of long-term monitor data on lake chemistry strong variability in lake chemistry, which in turn drives the variability in lake production and the composition of algal assemblages