Fecal sterols are traditionally ascribed as important biomarkers for animal excrement, and have been widely used to identify the source of organic matter and to reconstruct paleoecological changes in Antarctic terrestrial, aquatic, and marine ecosystems. However, the in situ microbial hydrogenation of cholesterol to coprostanol could have significance as a proxy to infer paleoenvironmental studies in Antarctica, particularly in anoxic sediment. Here, we report that abundant coprostanol, which was traditionally deemed as a biomarker for human sewage contamination, was found in three anoxic sediment profiles (AC2, BI, and CH1), which were strongly influenced by animal excrement at North Victoria Land, western Ross Sea, Antarctica. Our results suggest that the high concentrations of coprostanol in these three sediment profiles were not due to animal excrement, since coprostanol is not present in penguin guano and is a minor component in seal excrement. Coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) ratios suggest that coprostanol in the sediment cores of AC2 and BI was primarily derived from bacterial hydrogenation of cholesterol introduced by penguin guano. Coprostanol in CH1 sediments is related to human sewage due to intensive research activities from 1968 to 2006 in this region. However, the low abundance of coprostanol and the ratios of coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) in a relatively oxidizing sediment core (IIL1) infer that coprostanol was likely contributed by seal settlement. Together with high-throughput sequencing of the 16S rRNA gene, the conversion of cholesterol to coprostanol by anaerobic bacteria (e.g., Eubacterium coprostanoligenes) could occur in anoxic aquatic systems. Our results suggest that the presence of coprostanol in Antarctic lacustrine sediment with anoxic conditions does not necessarily indicate seal activity and human waste as the microbial hydrogenation of cholesterol to coprostanol should also be considered.

粪便甾醇传统上被认为是动物排泄物的重要生物标志物，并被广泛用于识别有机物的来源和重建南极陆地、水生和海洋生态系统的古生态变化。然而，胆固醇原位微生物氢化为粪甾烷醇对于推断南极洲的古环境研究（特别是缺氧沉积物）具有重要意义。在这里，我们报告了在罗斯西部北维多利亚地的三个缺氧沉积物剖面（AC2、BI 和 CH1）中发现了丰富的粪甾烷醇，传统上被认为是人类污水污染的生物标志物，这些沉积物受到动物粪便的强烈影响海，南极洲。我们的结果表明，这三个沉积物剖面中的高浓度粪前列醇并不是由动物粪便造成的，因为粪前列醇不存在于企鹅鸟粪中，并且是海豹粪便中的次要成分。粪甾烷醇/胆固醇和粪甾烷醇/(粪甾烷醇+胆甾烷醇)比率表明AC2和BI沉积岩芯中的粪甾烷醇主要来源于企鹅鸟粪引入的胆固醇的细菌氢化。由于 1968 年至 2006 年该地区的深入研究活动，CH1 沉积物中的粪甾烷醇与人类污水有关。然而，在相对氧化的沉积物核心（IIL1）中，粪甾烷醇的丰度较低，以及粪甾烷醇/胆固醇和粪甾烷醇/（粪甾烷醇+胆甾醇）的比率表明，粪甾烷醇可能是由海豹沉降造成的。结合 16S rRNA 基因的高通量测序，厌氧细菌（例如，粪前列腺真杆菌）可将胆固醇转化为粪甾烷醇，这可能发生在缺氧水生系统中。 我们的研究结果表明，在缺氧条件下南极湖泊沉积物中存在粪甾烷醇并不一定表明海豹活动和人类排泄物，因为还应考虑胆固醇微生物氢化为粪甾烷醇。