Abstract: Based on 210Pb dating of XH1 core sediment samples from Xihu Lake on King George Island, Antarctica, a centennial (1885-2006) sedimentary stratigraphic sequence was established. The lipid biomarkers, such as n-alkanes, fatty acids and sterols, were quantitatively analysed. The characteristics of their molecular assemblages and large-scale climate events (El Ni?o-Southern Oscillation (ENSO) and Southern Hemisphere Annular Mode (SAM)) were synthetically studied. The source of organic matter, sedimentary environment, early diagenesis and their relationship with the changes in ecological environment were discussed. The results showed that the main peak carbon (nC23) of n-alkanes, the latter main peak carbon (C24:0) of fatty acids, the higher content of C29 sterols and the lower ratio of C21–/C22+ indicated that the main source of organic matter in sediment of Xihu Lake was lower terrestrial plants such as mosses and lichens, while the contribution of aquatic plants and microorganisms was relatively minor. The ratio of C18:2/C18:0 of fatty acids indicated that, on the interdecadal time scale, SAM rather than ENSO, may have significant influence on the ecosystems of Antarctic Peninsula, and the impact of SAM on aquatic organisms in lakes is more obvious than that on terrestrial plants. ACI, an autochthonous contribution index of sterols, showed that when the westerly wind weakened and the Antarctic Peninsula warmed, the organic matter contributed by aquatic organisms decreased. Overall, in the past 100 years, the Xihu Lake was in a weakly oxidized sedimentary condition, with weak early diagenesis, and the impact of large-scale climate events on the lake sedimentary environment was weak.

Key words: West Antarctic, lake, sediment, lipid biomarkers, organic matter, environment