The long-term dynamics of biodiversity and stability of the diatom community under climate warming in a Tibetan alpine lake

Remote lakes have been recognized as ideal monitors of global change as they are far from direct human intervention and can record the natural variabilities of lake ecosystems in their sediments. Over the past century, biodiversity losses and ecological regime shifts have been detected worldwide in the context of global warming. However, regions and biological communities are not studied equally in current research on biodiversity and stability, and high-elevation areas and aquatic micro-organisms are particularly underrepresented. This study explores Qudonglaco, an alpine lake above the treeline in the southeastern margin of the Tibetan Plateau, highlighting changes in its biodiversity and ecosystem stability in response to environmental drivers over the past two centuries. The study reconstructed terrestrial inputs from catchment and diatom community composition using paleolimnological proxies of geochemical elements and diatom assemblages, and calculated changes in species diversity and multifaceted stability over time. Under the impact of climate change, the lake environment changed dramatically after the 1990s, leading to a stark shift from tychoplanktonic-dominated to benthic-dominated community composition, accompanied by an almost doubling of species richness. Since 1975 CE, temporal stability has declined, with increased Jaccard similarity and network connectance, and reduced heterogeneity since the 1990s, signaling a decline in community resilience. Compared with the ecosystem development of arctic lakes between 1850 and 2000 CE, the 150-year beta diversity of diatom community in this region was smaller yet has continued to rise. The multidimensional changes of community stability and biodiversity should be considered when assessing the impacts of headwaters on the lower-reach ecosystems, and more monitoring and observation of remote ecosystems as well as a unifying framework for quantifying community stability from paleo-archives is needed.