TY - JOUR

T1 - The glacial–terrestrial–fluvial pathway: A multiparametrical analysis of spatiotemporal dissolved organic matter variation in three catchments of Lake Nam Co, Tibetan Plateau

AU - Maurischat, Philipp

AU - Lehnert, Lukas

AU - Zerres, Vinzenz H.D.

AU - Tran, Tuong Vi

AU - Kalbitz, Karsten

AU - Rinnan, Åsmund

AU - Gang Li, Xiao

AU - Dorji, Tsechoe

AU - Guggenberger, Georg

N1 - Funding Information: The authors owe great gratitude to the ITP-CAS, Lhasa and Beijing branch for their hospitality and help during our sampling campaigns. Further thanks are given to the NAMORS team and for many numerous helpers from the great nations of China. Big thanks to Nicole Börner, Anja Schwarz, Wenggang Kang, Paula Echevarria Galindo, Felix Nieberding, Yuyang Wang, Jinlei Kai, Eike Reinosch and Björn Riedel for helping with sample collection. Thanks to Doreen Fleck for her help with field work and sample treatment. The authors acknowledge the technical support provided by the stackoverflow.com community. Special thanks to Angie Faust for proof reading and to Ina M. Sieber for a thorough review of the manuscript and critical discussion. We would like to thank two anonymous reviewers. This research is a contribution to the International Research Training Group “Geo-ecosystems in transition on the Tibetan Plateau (TransTiP)”, funded by Deutsche Forschungsgemeinschaft (DFG Grant 317513741/GRK 2309).

PY - 2022/9/10

Y1 - 2022/9/10

N2 - The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δ 13C 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.

AB - The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δ 13C 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.

KW - Alpine pastures

KW - Dissolved organic carbon

KW - PARAFAC

KW - Fluorescence

KW - Tibetan plateau

KW - Third pole environment

UR - http://www.scopus.com/inward/record.url?scp=85131944036&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2022.156542

DO - 10.1016/j.scitotenv.2022.156542

M3 - Article

VL - 838

SP - 156542

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

IS - Part 4

M1 - 156542

ER -