中文摘要：

富克萨恩湖是一个大、深、寡营养的淡水湖。在这个湖的最近的沉积，一系列分叉并且周期的链烷，有一或二个第四级的碳原子(C2n 混合物) 的包括的分叉的链烷， alkylcycloheptane，和 alkylcyclohexane，在高丰富被检测。为长链的 branched/cyclic 链烷的每个相当或相同的事物，有一个仅仅奇怪或平的碳数字的分子在沉积是在场的。各复合的相当或相同的事物的丰富变化在节另外的复合相当或相同的事物对应于那些，显示这些混合物的一样的起源。在沉积侧面的长链的 branched/cyclic 链烷的集中展出了浮游植物 biomarkers 的类似于那些的变化，例如 3-methyl-alkanes ，短链的奇怪的碳n链烷， hopene ，多元不堡和丰满的酸， phytol ，甾醇，和长链的烷基 diols ，但是与那些稍微不同长链的奇怪的碳n链烷，它是为更高的植物的无所不在的 biomarkers 。因此，首先，在湖沉积的 C2n 混合物和长链的周期的链烷被水藻和细菌很可能在水里生产由中等氧化的水里的不是自养的细菌，繁荣可能是它在富克萨恩湖的特定的水环境的结果。

英文摘要：

Lake Fuxian is a large, deep, and oligotrophic freshwater lake. In recent sediment of this lake, a series of branched and cyclic alkanes, including branched alkanes with one or two quaternary carbon atoms （C2n compounds）, alkylcycloheptane, and alkylcyclohexane, were detected in high abundance. For each homolog of long-chain branched/ cyclic alkanes, molecules with only an odd or even carbon number were present in the sediment. The abundance vari- ation of each compound homolog corresponded to those of other compound homolog in the section, indicating the same origin of these compounds. The concentrations of long-chain branched/cyclic alkanes in the sediment profile exhibited variations similar to those of phytoplankton biomarkers, such as 3-methylJalkanes, short-chain odd carbon n-alkanes, hopene, polyunsaturated fatty acids, phytol, sterols, and long-chain alkyl diols, but slightly different from those of long-chain odd carbon n-alkanes, which are ubiquitous biomarkers for higher plants. Therefore, the Can compounds and long-chain cyclic alkanes in the lake sediment were most likely produced by algae and bacteria in the water, primarily, by the heterotrophic bacteria in the moderately oxygenated waters, which flourishing might be the results of specific water environments in Lake Fuxian.