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

这个合作项目研究了阿拉斯加苏打湾低温富铁（Fe）和锰（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泉和泉水，其中含有二氧化碳（CO2）的冒泡沃茨已被证明是非常不寻常的，因为它们还活跃地沉积Fe和Mn矿物，而这些矿物又是广泛的微生物垫群落的庇护所。在这个独特的流域内发现的泉水和渗漏形成沿着盐度梯度，上游是更多的淡水，而下游有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，凝灰岩沉积）形式。高达三米的石灰华位于沿着苏打湾溪两侧的长度，该溪排入苏打湾河口。高流量系统主要是铁氧化物沉积环境，而低流量系统主要是锰氧化物存款。本项目将调查这一独特的分水岭，以描述铁和锰矿物形成的地球化学和地球微生物学，沿着从上游小溪到苏打湾的物理化学梯度。研究人员假设，这些土堆是自养生态系统，宿主微生物能够从金属氧化反应中捕获的能量中生长和固定二氧化碳。他们建议研究这些生态系统的微生物生态学，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，从而养活自己？第二，这些微生物群落（由矿物质和富含CO2的流体提供燃料）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存了微生物化石的痕迹或生物特征，这些生物特征可以显示历史存在，从而提供对过去的一瞥。这是一个新的和潜在的变革性调查，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。该项目将与海达堡学区合作。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。该计划涉及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加实地采样，并将在访问苏打湾与科学家互动。该项目与与该遗址有着悠久历史的当地部落群体密切相关。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，因为它具有探索性和潜在的高影响力。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），以努力实现对这一可能由金属作为能源驱动的新生态系统的多尺度理解，并在其中保存独特的地球化学特征。对地质记录中的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演变为氧化世界时地球上生命的演变。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，以及矿化如何发生。

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 the biogeochemistry 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.