Abstract The Espenberg maar lakes on the Seward Peninsula, Alaska, are the largest volcanic crater lakes in the world and contain the longest known lacustrine sedimentary archives in Alaska. The lack of glacial-aged marine sedimentary archives around the Bering Land Bridge due to exposure of the shelf during sea level low-stands makes these lakes highly valuable for understanding the region’s past climate and environmental changes. Located en route to humanity’s last colonized American continents, the Seward Peninsula’s climate and environments during the last glacial period bear major anthropological significance. However, a lack of quantitative proxies has so far hampered exploration of these lakes for paleoclimate reconstructions. Here we report, for the first time, the discovery of abundant Group I alkenones and Isochrysidales in surface sediments from three maar lakes: White Fish, North Killeak and Devil Mountain, using a combination of lipid biomarker and 18S rRNA gene sequencing analyses. Our discovery adds to the expanding list of oligotrophic freshwater lakes where Group I alkenones are found, and water chemistry data contribute to the understanding of the environmental controls on Group I Isochrysidales. Our results further confirm the use of the U 37 K index of Group I alkenones as a proxy for the mean temperature of the spring isotherm (MTSI) and RIK37 as a quantitative measurement for Isochrysidales group mixing. We also demonstrate the analytical challenges for analyzing alkenones in freshwater lakes and the effectiveness of eliminating coelution using silver thiolate chromatographic material (AgTCM).

中文翻译：

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世界上最大的玛珥湖中的 I 族链烯酮和等鞭金藻目及其潜在的古气候应用

摘要 阿拉斯加苏厄德半岛上的埃斯彭贝格玛尔湖是世界上最大的火山口湖，拥有阿拉斯加已知最长的湖相沉积档案。由于在海平面低位期间陆架暴露，白令陆桥周围缺乏冰川时代的海洋沉积档案，这使得这些湖泊对于了解该地区过去的气候和环境变化非常有价值。苏厄德半岛位于前往人类最后被殖民的美洲大陆的途中，最后一个冰河时期的气候和环境具有重大的人类学意义。然而，迄今为止，由于缺乏定量指标，阻碍了对这些湖泊进行古气候重建的探索。在这里，我们第一次报告，结合脂质生物标志物和 18S rRNA 基因测序分析，在来自三个玛珥湖的表层沉积物中发现了丰富的 I 类烯酮和等鞭金藻类：白鱼、北基利克和魔鬼山。我们的发现增加了发现 I 组烯酮​​的贫营养淡水湖的不断扩大的名单，水化学数据有助于了解 I 组等鞭藻目的环境控制。我们的结果进一步证实了使用 I 组烯酮​​的 U 37 K 指数作为弹簧等温线 (MTSI) 平均温度的代理和 RIK37 作为等温线组混合的定量测量。