Distribution, potential sources, and response to water depth of archaeal tetraethers in Tibetan Plateau lake sediments

The Tibetan Plateau (TP) is an area of focus for assessing global change and regional responses due to its sensitivity to climate change on different timescales. Its widely distributed lakes are ideal for research. Paleolake-level records from this region can provide insights into potential climate connections and help predict future hydrological trends. However, the applicability of the existing archaeal tetraether-based lake-level proxies in this region remains unclear, thereby hindering the advancement of paleoclimate research in this area. Here, we investigated the archaeal ethers in 108 surface sediment samples from 83 lakes and 22 surrounding soils on the TP to explore their distribution, sources, and environmental controlling factors. The majority of archaeal tetraethers in lake sediments are produced in situ, with allochthonous origin being secondary. Nitrososphaeria (previously called Thaumarchaeota) could serve as the main biological sources in both lakes and soils, and other archaea (such as methanogenic archaea) may also contribute to those in lakes. Of the examined environmental variables, the lake water depth was the dominant factor affecting the distributions of the archaeal tetraethers in the studied lakes. The %Cren and %OH-GDGTs indices were confirmed to be potential lake-level proxies. Moreover, the Cren/Cren??? ratio may be a novel lake-level proxy due to its good response to water depth. Furthermore, %Cren, %OH-GDGTs, and the Cren/Cren??? ratio may be affected by the nutrient status and Dissolved Oxygen (DO) concentration of the lake; so, these lake-level proxies need to be used with caution in lakes with relatively high nutrient statuses. The results of this study provide a reference for improving our understanding of tetraether distribution patterns and for the reconstruction of paleo-lake levels.