Differential responses of algal ecosystems in freshwater and Saline Lakes on the northeastern Tibetan plateau to climate and anthropogenic disturbances

The responses of lake ecosystems to climate change and anthropogenic disturbances in the northeastern Tibetan Plateau (NETP) have not yet been fully understood. In this study, we investigated differential responses of algal ecosystems to climate and human activities in NETP during the past millennium, based on sedimentary ancient DNA and multiple paleolimnological proxies extracted from freshwater Lake Hurleg and saline Lake Toson located adjacently in NETP. The results show that the temporal patterns of algal communities and variations are different between freshwater and saline lakes in NETP, with higher productivity and algal diversity during the Little Ice Age (LIA: a cold interval) than the Medieval Warm Period (MWP: a warm interval) in saline lakes, but higher productivity during the MWP and lower productivity and biodiversity during the LIA in freshwater lakes. The diverse ecological features further suggest that the freshwater lake ecosystem in NETP is dominated by temperature variations, while that of the saline lake is controlled by changes in precipitation. Both lakes exhibit marked increases in algal diversity and productivity in the Current Warm Period, likely linked to the increased nutrient supply due to enhanced human activities of the recent epoch. Compared to the saline Lake Toson, the freshwater Lake Hurleg was more sensitive to human disturbances. The results of this study suggest that the intensifying human activities in the NETP over recent decades have altered the natural evolution of lake ecosystems, thus highlighting the urgent need to strengthen the management of human-environment interactions to maintain the sustainability of lake ecosystems.