Abstract Long-chain n-alkyl lipids are traditionally ascribed to an origin from terrestrial vascular plants because these compounds are major constituents of higher plant leaf waxes. Over the past half century, numerous studies have taken advantage of these sedimentary biomarkers and their isotopic ratios to reconstruct paleo-environmental and paleo-climatological changes at a variety of time scales. However, it is uncertain and extremely difficult to determine if these compounds can also derive from microbes because of the prevalence of higher plants in most environments around the globe. Here we show, for the first time from natural sediment samples, that long-chain n-alkyl lipids can predominantly originate from aquatic microbial sources at three high-latitude (>69°S latitude) Antarctic lakes, where no vascular plants are present in the surrounding land mass. The high carbon isotopic values (up to –12‰) of these long-chain n-alkyl lipids exclude the possibility that these compounds are transported by wind from adjacent vegetated land masses. Instead, these isotope values are similar to lipids produced by aquatic microbial mats with an average bulk δ13C value of –14.2 ± 1.7‰, indicating heterotrophic microbes are the likely source of these long-chain n-alkyl lipids. For comparison, we also show that when even small amount of vascular plants and mosses are present in the study region, for instance at Long Lake (∼62°S latitude) in the Antarctic Peninsula, the carbon isotopic values of sedimentary long-chain n-alkyl lipids decline dramatically, suggesting a rapid proportional increase in the relative contribution of leaf wax sources to total long-chain n-alkyl lipid inventory in lake sediments.

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异养微生物生产长链正烷基脂质：来自南极湖泊的新证据

摘要 长链正烷基脂质传统上归因于来自陆生维管植物，因为这些化合物是高等植物叶蜡的主要成分。在过去的半个世纪里，许多研究利用这些沉积生物标志物及其同位素比来重建各种时间尺度的古环境和古气候变化。然而，由于高等植物在全球大多数环境中普遍存在，因此很难确定这些化合物是否也可以来自微生物。在这里，我们首次从天然沉积物样品中表明，长链正烷基脂质主要来自三个高纬度（> 69°S 纬度）南极湖泊的水生微生物来源，周围陆块中没有维管植物。这些长链正烷基脂类的高碳同位素值（高达 –12‰）排除了这些化合物通过风从相邻植被陆块迁移的可能性。相反，这些同位素值与水生微生物垫产生的脂质相似，平均体积 δ13C 值为 –14.2 ± 1.7‰，表明异养微生物是这些长链正烷基脂质的可能来源。为了进行比较，我们还表明，即使在研究区域中存在少量维管植物和苔藓时，例如在南极半岛的长湖（~62°S 纬度），沉积长链 n 的碳同位素值-烷基脂质急剧下降，