Collaborative Research: Investigating the Lost City as an ultramafic urban center of the subseafloor, fueled by energy and carbon from the mantle

合作研究：调查失落之城是海底超镁铁质城市中心，以地幔能量和碳为燃料

• 批准号: 1536702
• 负责人: Susan Lang
• 金额: $ 27.62万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536702&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Lost; City

The vast majority of deep seafloor sediments are inhabited by microbial communities that survive under extreme energy limitation, with apparent generation times of centuries to millennia. Hydrothermal systems are a stark contrast to these energy-starved environments and may represent important, high-activity, 'population centers' in the oceanic subsurface. When rocks from the Earth's mantle are uplifted and exposed to water, the resulting reactions lead to acidic fluids with high concentrations of hydrogen. Under certain circumstances, small organic molecules such as methane can also form in the absence of biology. These compounds can provide energy to subseafloor microbial communities and, given the ubiquity of mantle rocks, such reactions may fuel a significant proportion of the active subsurface biosphere. The current project will characterize the microbial communities inhabiting an iconic example of this type of system, the Lost City Hydrothermal Field, using a remotely operated vehicle. The ghostly spires of Lost City are highly telegenic and have been featured in professional documentaries. The high definition underwater video footage collected during the expedition will provide the raw material for an 8 week educational training program in digital media focused on kindergarten through 12th grade high school students and undergraduate students. The resulting short documentaries will be published on YouTube and the Utah Education Network.Mantle rocks comprise significant portions of the seafloor, and microbial communities hosted within them may be important mediators of carbon and energy exchange between the deep Earth and the surface biosphere. Upon tectonic uplift and exposure to water, the serpentinization of these materials releases potential energy in the form of hydrogen, methane, and heat, and further reaction of these products can sustain the abiogenic synthesis of small organic molecules. Recent studies have highlighted, however, the lack of alkalithermophiles that are capable of survival at the high pH (9-11) and elevated temperatures found in these systems. The almost complete lack of carbon dioxide (CO2) represents a second, and possibly more significant, limitation to growth. To better understand the extent of the serpentinite subsurface, this project will address the question: What limits biological activity in the serpentinite subsurface? Specifically, the proposed work will test the hypotheses: (1) microbial diversity spans a wider range of temperature-pH conditions than currently recognized and (2) the scarcity of CO2 is a key biological limitation to serpentinization-driven ecosystems that can be overcome by the metabolic activity of one or a few foundation species. These hypotheses will be tested during a 20 day (10 days on site) expedition to the Lost City Hydrothermal Field, focusing on fluids as windows to the subsurface biosphere. The sampling approach will capitalize on the differences in temperature, carbon availability, and microbial activity across the field. The analytical approach will integrate multidisciplinary techniques performed on replicate subsamples and feature the application of next-generation sequencing technologies to these marine serpentinizing fluids for the first time. This study will generate extensive sequence data from environmental DNA, environmental mRNA, and single-cell genomes, allowing us to identify the in situ expression of metabolic pathways and the genomics of active single cells. These efforts will be closely linked with a thorough characterization of carbon in these fluids that will focus on identifying available substrates (e.g. methane, CO2, organic acids) and on characterizing biomarkers that reflect specific metabolic pathways (e.g. lipids, amino acids).

绝大多数深海底沉积物都居住在微生物群落下，这些群落在极端的能量限制下生存，显而易见的是几个世纪以来几个世纪。水热系统与这些能量饥饿的环境形成鲜明对比，并且可能代表着海洋地下中重要的高活动性“人口中心”。当从地球地幔上岩石升高并暴露于水中时，产生的反应会导致高浓度氢的酸性流体。在某些情况下，在没有生物学的情况下，甲烷等小的有机分子也可以形成。这些化合物可以为子层面微生物群落提供能量，并且鉴于地幔岩石无处不在，这种反应可能会助长大部分活性地下生物圈。当前项目将使用远程操作的车辆来表征这种类型的系统，即迷失的城市热液场的标志性示例的微生物群落。迷失城市的幽灵般的尖顶具有高度的电信性，并且在专业纪录片中刊登。在探险期间收集的高清水下视频录像将为一项为期8周的数字媒体教育培训计划提供原材料，该计划专注于幼儿园至12年级的高中生和本科生。由此产生的简短纪录片将在YouTube和犹他州教育网络上发表。桥梁构成了海底的重要部分，其中托管的微生物群落可能是深层地球和表面生物圈之间的碳和能量交换的重要介体。构造隆起和暴露于水中后，这些材料的蛇纹激素以氢，甲烷和热的形式释放势能，这些产物的进一步反应可以维持对小有机分子的亚物质合成。然而，最近的研究强调了缺乏能够在高pH值（9-11）生存的碱性噬菌体，并且在这些系统中发现的温度升高。几乎完全缺乏二氧化碳（CO2）代表了生长的第二，可能更重要的限制。为了更好地了解蛇纹石地下的程度，该项目将解决以下问题：什么限制了蛇纹石地下的生物学活动？具体而言，拟议的工作将检验假设：（1）微生物多样性涵盖了比当前认识的更大的温度pH条件范围，并且（（2）二氧化碳的稀缺性是对蛇形化驱动的生态系统的关键生物学局限性，可以通过一个或几个基础的代谢活性来克服的蛇形驱动的生态系统。这些假设将在20天（现场10天）前往丢失的城市水热场的探险中进行测试，重点是液体作为地下生物圈的窗户。采样方法将利用整个现场的温度，碳供应性和微生物活性的差异。分析方法将集成在复制子样本上执行的多学科技术，并首次将下一代测序技术应用于这些海洋蛇形流体。这项研究将产生来自环境DNA，环境mRNA和单细胞基因组的广泛序列数据，从而使我们能够鉴定代谢途径的原位表达和活性单细胞的基因组学。这些努力将与这些流体中的碳的透彻表征紧密相关，这些碳将着重于鉴定可用的底物（例如甲烷，二氧化碳，有机酸），并表征反映特定代谢途径（例如脂质，氨基酸）的生物标志物。

项目成果

Hydrothermal Organic Geochemistry (HOG) sampler for deployment on deep-sea submersibles

• DOI: 10.1016/j.dsr.2021.103529
• 发表时间: 2021-03
• 期刊: Deep Sea Research Part I: Oceanographic Research Papers
• 作者: S. Lang;Bryan C. Benitez-Nelson