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Soda Bay的低温富铁（Fe）和富锰（Mn）碳酸盐生态系统的地球化学和地球微生物学。这些地点包括许多冷渗漏和泉水，其中含有含有二氧化碳（CO2）的冒泡水，这已被证明是非常不寻常的，因为它们也活跃地沉积着铁和锰矿物，而这些矿物反过来又庇护着广泛的微生物群落。在这个独特的分水岭内发现的泉水和渗漏沿着盐度梯度形成，上游是更多的淡水，而下游则受到潮汐驱动的海洋影响。这些栖息地是广泛的微生物矿物丘（即凝灰岩矿床）形成的地方。高达三米的凝灰岩位于流入苏达湾河口的苏达湾溪两侧。高流量体系主要是铁氧化物沉积环境，而低流量体系主要是锰氧化物沉积环境。该项目将研究这一独特的分水岭，以描述从上游小溪到索达湾沿物理化学梯度形成的铁和锰矿物的生物地球化学和地球微生物学。研究人员假设，这些土丘是自养生态系统，承载着能够生长并从金属氧化反应中捕获能量来固定二氧化碳的微生物。他们建议用两个主要问题来研究这些生态系统的微生物生态学。首先，这些微生物利用什么代谢过程来获取能量，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提供燃料）如何响应物理化学梯度而发生变化？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的痕迹或生物特征，这些痕迹可以显示历史的存在，从而提供对过去的一瞥。这是一个新的和潜在的变革性研究，因为几乎没有关于低温富铁和富锰地下水对淡水或海洋生态系统的影响的信息，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hydabburg学区合作。自2008年以来，其中一名研究人员与Hydaburg学区和Hydaburg合作社协会（部落政府）建立了一个长期的地球科学教育和研究项目。该计划包括5 -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实地取样，并在前往索达湾期间与科学家互动。该项目与当地部落密切相关，这些部落与该遗址有着悠久的历史。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的支持，因为它本质上是探索性的，并且可能具有很高的影响力。它将汇集多方面的技术（例如，航空现场调查，分子生物学，显微镜和地球化学），努力实现对这种新型生态系统的多尺度理解，这种生态系统可能由金属作为能源驱动，并且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一些重要的地质问题提供新的见解，比如古代的生命、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缺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的环境强迫函数之间的相互作用以及矿化的发生。