Collaborative Research: Iron- and Manganese-Depositing Cold-Seeps: Mineral Formation Along a Freshwater to Marine Ecosystem

合作研究：铁和锰沉积冷泉：淡水到海洋生态系统的矿物形成

• 批准号: 1420091
• 负责人: Bradley Tebo
• 金额: $ 5.77万
• 依托单位: Oregon Health & Science University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1420091&HistoricalAwards=false
• 关键词: Collaborative; Research; Iron; Manganese; Depositing

This collaborative project examines the geochemistry and geomicrobiology of low-temperature iron-(Fe) and manganese-(Mn) rich carbonate ecosystems in Soda Bay, Alaska. These sites comprise numerous cold seeps and springs with bubbling waters containing carbon dioxide (CO2) that have proven to be very unusual in that they are also actively depositing Fe and Mn minerals, which in turn are harboring extensive microbial mat communities. The springs and seeps found within this unique watershed form along a salinity gradient with upstream being more freshwater while downstream has a tidally-driven marine influence. These habitats are sites where extensive microbial-mineral mounds (i.e., tufa deposits) form. Tufas as high as three meters are located along the length of both sides of Soda Bay Creek which drains into Soda Bay Estuary. The high flow systems are predominantly iron oxide deposition environments while the systems exhibiting low flow deposit manganese oxides. This project will investigate this unique watershed in an effort to describe thebiogeochemistry and geomicrobiology of Fe- and Mn-mineral formation along the physicochemical gradients from the upper creek to Soda Bay. Researchers hypothesize that the mounds are autotrophic ecosystems hosting microorganisms able to grow and fix CO2 from the energy captured from metal oxidation reactions. They propose to examine the microbial ecology of these ecosystems with two primary questions in mind. First, what are the metabolic processes these microbes use to capture energy and thereby feed themselves? Second, how might these microbial communities (fueled by mineral and CO2-rich fluids) change in response to the physicochemical gradients? Answers to these questions will allow them to address future important questions relating to whether these environments preserve traces of microbial fossils or biosignatures that can show a historical presence and thereby provide a glimpse into the past. This is a new and potentially transformative investigation as there is virtually no information regarding the impact of low-temperature Fe- and Mn-rich groundwater on freshwater or marine ecosystems, whether such systems contribute to carbon fixation and the carbon cycle, or the energetic or metabolic basis of the microbes supporting these ecosystems.This project will partner with the Hydaburg School District. One of the researchers has built a longterm geoscience education and research program with the Hydaburg School District and Hydaburg Cooperative Association (tribal government) since 2008. The program involves 5th-12th grade science classes and teacher training with an emphasis on the interdisciplinary nature of the geosciences. Interested students have the opportunity to participate in field sampling and will interact with scientists during trips to Soda Bay. This project is closely coupled with local tribal groups that have a long history with this site. Researchers will, in turn, routinely share their scientific discoveries with the tribal organization.The project is well suited for EAGER support as it is exploratory in nature and potentially high impact. It will bring together multifaceted-technologies (e.g., aerial site survey, molecular biology, microscopy and geochemistry) in an effort to achieve a multi-scale understanding of this novel ecosystem potentially driven by metals as energy sources and where unique biogeochemical signatures will be preserved. Interpretation of such signatures in the geological record may provide new insights into important geological questions such as life in the ancient past, the role of microbes in the formation of metal ore deposits and even the evolution of life on Earth as the planet evolved from an anoxic to an oxic world. Ultimately, investigators hope to better predict how life now adapts to and mineralization occurs from interactions among these types of multi-dimensional strong gradient-driven environmental forcing functions.

该合作项目研究了阿拉斯加苏打湾富含铁 (Fe) 和锰 (Mn) 的低温碳酸盐生态系统的地球化学和地球微生物学。这些地点包括许多含有二氧化碳 (CO2) 的冷泉和泉水，这些泉水已被证明是非常不寻常的，因为它们还积极沉积铁和锰矿物，而这些矿物又蕴藏着广泛的微生物垫群落。在这个独特的分水岭中发现的泉水和渗漏沿着盐度梯度形成，上游有更多淡水，而下游则受到潮汐驱动的海洋影响。这些栖息地是形成大量微生物矿物丘（即凝灰岩沉积物）的地方。流入苏打湾河口的苏打湾溪两侧生长着高达三米的凝灰岩。高流量系统主要是氧化铁沉积环境，而系统表现出低流量沉积锰氧化物。该项目将调查这一独特的分水岭，以描述沿着小溪上游到苏打湾的物理化学梯度的铁和锰矿物形成的生物地球化学和地球微生物学。研究人员推测，这些土堆是自养生态系统，其中含有能够生长并利用金属氧化反应捕获的能量固定二氧化碳的微生物。他们建议研究这些生态系统的微生物生态，并考虑两个主要问题。首先，这些微生物利用什么代谢过程来捕获能量并从而养活自己？其次，这些微生物群落（由矿物质和富含二氧化碳的液体驱动）会如何响应物理化学梯度而变化？这些问题的答案将使他们能够解决未来的重要问题，这些问题涉及这些环境是否保留了微生物化石或生物特征的痕迹，这些痕迹可以显示历史的存在，从而提供对过去的一瞥。这是一项新的、具有潜在变革性的调查，因为几乎没有关于富含铁和锰的低温地下水对淡水或海洋生态系统的影响的信息，无论这些系统是否有助于碳固定和碳循环，或者支持这些生态系统的微生物的能量或代谢基础。该项目将与海德堡学区合作。自 2008 年以来，其中一名研究人员与海德堡学区和海德堡合作协会（部落政府）建立了长期的地球科学教育和研究项目。该项目涉及 5 至 12 年级的科学课程和教师培训，重点是地球科学的跨学科性质。感兴趣的学生有机会参与现场采样，并在苏打湾之旅期间与科学家互动。该项目与当地有着悠久历史的部落群体密切相关。反过来，研究人员将定期与部落组织分享他们的科学发现。该项目非常适合 EAGER 支持，因为它本质上是探索性的，并且具有潜在的高影响力。它将汇集多方面的技术（例如，航空现场勘测、分子生物学、显微镜和地球化学），以努力实现对这个可能由金属作为能源驱动的新型生态系统的多尺度理解，以及将保留独特的生物地球化学特征。对地质记录中这些特征的解释可能会为重要的地质问题提供新的见解，例如古代的生命、微生物在金属矿床形成中的作用，甚至是地球从缺氧世界进化到有氧世界时地球上生命的进化。最终，研究人员希望更好地预测生命现在如何适应这些类型的多维强梯度驱动环境强迫函数之间的相互作用以及矿化的发生。