Sedimentary organic molecular compositions reveal the influence of glacier retreat on ecology on the Tibetan Plateau

Global warming and glacier retreat have significant impacts on the structure and function of natural ecosystems. How-ever, little is known about how glacier retreat affects the long-term evolution of ecosystems at high-altitude regions. In this study, we explored the possible effects of glacier retreat on catchment vegetation and lake productivity in Lake Puma Yumco, southeastern Tibetan Plateau, based on detailed organic molecular compositions determined by an ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and combined with various sedimentary geochemical indicators. The glaciers in the catchment keep retreating since 1870 CE, as in-ferred from the multiple indices of total organic carbon content (TOC), total nitrogen content (TN), C/N ratios, and car-bonate contents. Accompanying modern global warming and glacier shrinkage, the relative abundance of soil-and vegetation-derived large molecular compounds (e.g., vascular plant-derived polyphenols, highly unsaturated and phe-nolic compounds, and condensed aromatics) increased gradually in lake sediments, suggesting that ice-covered land was exposed under warming condition, and gradually revegetation occurred. Both increases in relative abundance of nitrogen-containing compounds (e.g., CHNO) and chlorophyll derivative contents in the lake sediments were ob-served since 1870 CE, suggesting that stronger catchment weathering and increasing terrestrial nutrient loads en-hanced the downstream lake productivity after glacier retreat. Our results imply that continued global warming and alpine glacier retreat in the future may further promote vegetation expansion and increases in lake productivity on the Tibetan Plateau.