Climate and lake ecosystem evolution over the last millennium on the north-eastern Tibetan Plateau: Insights from stable isotope records of gastropod shells in Xing Co

Abstract

The evolution of alpine lake ecosystems on the north-eastern Tibetan Plateau (NETP) over the last millennium has been affected by climate change and human activity. This study reconstructs the palaeoclimate and lake productivity of Xing Co using carbon and oxygen isotopes from aquatic gastropod shells (δ¹³C_shell and δ¹⁸O_shell), grain-size, total organic carbon (TOC), total nitrogen (TN), and the TOC/TN (C/N) ratio. The highest lake productivity – during the Medieval Warm Period (MWP) – is likely linked to enhanced photosynthesis of aquatic plants and increased biomass within the lake. This increase was driven by warm, humid climate conditions, indicated by higher δ¹³C_shell values, lower δ¹⁸O_shell values, and increased coarse-grain content. In contrast, the significant decline in lake productivity during the Little Ice Age (LIA) resulted from deterioration of trophic status and restricted aquatic plant growth under colder, drier climate conditions. However, the decrease in lake productivity since 1950 CE, amid global warming, may be linked to increased soil erosion and sedimentation rate from intensified human activity and land-use changes. The combined effects of climatic shifts and human disturbances highlight the need for ongoing monitoring of lake ecosystems to understand their resilience and response to future environmental changes.