The Application Of Glycerol Dialkyl Glycerol Tetraethers In Reconstrucion Of Kusai Lake Paleo-environment On The Qinghai-Tibetan Plateau

With the recent developments of environmental problems and climate change,increasing research focus has been put on the current and future climate change andits influence on human society. The study of ancient climate change can deepen ourunderstanding of modern climate change and provide significant guidance for theforecast of future climate change pattern. The uplift of Qinghai-Tibetan Plateau playsan important role in the evolution of the Asian monsoon, and has a great influence onAsian climate and global atmospheric circulation system. Lakes are sensitive toclimate change and can provide wonderful archives of past environmental conditions.Therefore, studying the climatic fluctuations on the Qinghai-Tibetan Plateau is criticalfor the understanding either the contribution to or the response of regional climate toto global system.Glycerol dialkyl glycerol tetraethers (GDGTs) are cell membrane lipidssynthesized by archaea and bacteria and have the ability to record environmentalconditions. In recent years, proxies developed from the distribution of GDGTcomponents have become a research topic in biogeochemistry. Study on response ofmicrobial lipids to modern environment change is the premise and basis of applyinglipid proxies to reconstruct paleoenvironment. Soil is an important environment formof terrestrial ecosystem, and the microbial community structure is quite sensitive toenvironment change, thus investigation into the lipid distribution in modern soil is ofgreat significance to the reconstruction of paleoenvironment. In this study, weobtained30Chinese soil samples and a5m lacustrine sediment core of Kusai Lake onQinghai-Tibetan Plateau, then performed a comprehensive investigation ofgeochemical parameters, climate conditions, molecular biology, and GDGTdistributions. The goals of this study were1) to investigate the influence of microbialcommunity structure and environmental factors on GDGT distribution and related proxies;2) to discuss the applicability of GDGT proxies in reconstruction Holocenepaleoclimate of Qinghai-Tibetan Plateau lake system.The results showed that Deltaproteobacteria may be an important producer ofbGDGTs. The distribution of bGDGTs (produced by bacteria) was primarilycontrolled by climatic conditions (MAAT and MAP), and bacterial communitystructure was mainly influenced by soil nutrients. In contrast, archaeal communitystructure and iGDGT distribution (produced by archaea) were predominantly shapedby soil nutrients. These results suggest that bGDGTs may be more sensitive toenvironmental conditions than iGDGTs and can be more appropriate to reconstructterrestrial paleoenvironment. The CBT-derived pH was robustly correlated withmeasured soil pH; MBT/CBT-derived MAAT was in agreement with the trendency ofmeasured MAAT; BIT index showed a strong correlation with soil water content.These results indicate the applicability of these proxies to be used aspaleothermometer and paleohygrometer. The GDGTs of the Kusai Lake mainlyoriginated from the autochthonous production within the lake, determined bycomparative analysis with C/N and TOC, thus we obtained the paleo-pH andpaleotemperature records of this area on Qinghai-Tibetan Plateau by GDGT proxies.