The glacial–terrestrial–fluvial pathway: A multiparametrical analysis of spatiotemporal dissolved organic matter variation in three catchments of Lake Nam Co, Tibetan Plateau
Philipp Maurischat, Lukas Lehnert, Vinzenz H.D. Zerres, Tuong Vi Tran, Karsten Kalbitz, Åsmund Rinnan, Xiao Gang Li, Tsechoe Dorji, Georg Guggenberger
Abstract
C of DOM) in stream samples of three catchments of the Nam Co watershed and the lake itself. Satellite based plant cover estimates were used to link biogeochemical data to the structure and degradation of vegetation zones in the catchments. Catchment streams showed site-specific DOM signatures inherited from glaciers, wetlands, groundwater, and Kobresia pygmaea pastures. By comparing stream and lake samples, we found DOM processing and unification by loss of chromophoric DOM signatures and a change towards an autochthonous source of lake DOM. DOM diversity was largest in the headwaters of the catchments and heavily modified in terminal aquatic systems. Seasonality was characterized by a minor influence of freshet and by a very strong impact of the Indian summer monsoon on DOM composition, with more microbial DOM sources. The DOM of Lake Nam Co differed chemically from stream water samples, indicating the lake to be a quasi-marine environment in regards to the degree of chemical modification and sources of DOM. DOM proved to be a powerful marker to elucidate consequences of land use and climatic change on biogeochemical processes in High Asian alpine ecosystems.