Limnological features of glacier-fed rivers in the Southern Tibetan Plateau, China

We describe the limnological features of six glacier-fed rivers located at an altitude of over 4,000?m in Southern Tibetan Plateau, China, based on diurnal observations of the water environment and biota in the summer of 2010. The rivers showed significant diurnal changes in water level, temperature, and turbidity; clear and cool streams in the morning changed to cloudy rapid flow in the afternoon, and water temperature was elevated under strong light conditions where riparian forest did not cover the surface of the water. On the other hand, the pH and dissolved oxygen saturation did not show any diurnal fluctuations, which indicates low periphytic algal productivity. The aquatic insect communities were poor both in diversity and density, and the dominant life forms (from a functional feeding group perspective) were collectors, which depend on allochthonous organic matter; scrapers, which depend on autochthonous algal production, were scarce. We therefore suggest that diurnal or seasonal high waters transport products from marginal pools along dried riverbeds or from ponds on flood plains, and may serve as the source of organic matter in glacier-fed rivers.