NNA: Collaborative Research: Interactions of the Microbial Iron and Methane Cycles in the Tundra Ecosystem

由于环境的变化正在影响苔原及其下面的永久冻土，人们对北极地区不断变化的条件非常关注。与此同时，我们对苔原/永久冻土微生物学和元素循环的理解存在重大差距。填补这些知识空白将使人们能够更好地全面了解冻土带，并可以提供有关这一全球重要但脆弱的生态系统将如何应对变化的关键信息。这项研究将填补围绕铁和控制其可用性的细菌的特定知识空白。铁是动物、植物和微生物必需的微量营养素。它也是某些细菌的生长基质，其中许多细菌固定二氧化碳生长。其中一些细菌直接与其他产生或消耗甲烷的微生物竞争，甲烷的大气浓度正在继续增加。了解北极二氧化碳和甲烷的动态尤其重要，因为永久冻土中储存了大量有机碳，可以转化为这两种气体。该研究小组由一位在铁循环细菌方面具有丰富经验的微生物生态学家组成;一位数学建模师，他将量化不同微生物过程的相对影响，以及一位在永久冻土环境中具有丰富元素循环经验的苔原生态学家。 该项目将首次系统地表征和量化负责阿拉斯加苔原/永久冻土中铁循环的微生物群落。的北坡，并增加我们对这些微生物如何通过抑制甲烷产生与碳循环相互作用的理解。这项研究的基本假设是，北极的条件有利于活跃的铁循环，因为浅深度的永久冻土层阻止了含亚铁的沃茨进入深层含水层（这是从温带生态系统中去除铁的常见途径）。此外，冷水温度减缓了铁的化学氧化，而短暂但激烈的生长季节提供了不稳定的碳源，有助于促进铁的还原。这些想法将通过在阿拉斯加北坡的图里克野外站进行实地和实验室研究来检验。以前的研究表明，该地区存在大量与微生物铁垫相关的铁氧化和铁还原细菌，但总的来说，对其多样性或功能知之甚少。这项工作将利用培养独立的，基于扩增子的社区分析和宏基因组学，以进一步表征社区的多样性和功能，这些化学合成社区。该团队将测量具有高铁循环率的苔原站点的甲烷产量，并将其与水文和地形相似但铁循环率较低的站点进行比较，以评估铁循环对甲烷生产和消费的直接影响。还将使用分子分析比较这些地点的微生物组。除了这些实地测量外，研究人员还将构建一个实验室微观世界，可以用从图里克收集的土壤和微生物铁垫进行播种。这将允许受控条件来模拟铁和甲烷循环在关键参数（例如铁和氧浓度）可以被控制的条件下的相互作用。根据现场和实验室数据，将使用一系列动力学方程开发基于反应的模型。这些将形成预测模型的基础，该模型可以估计铁循环对甲烷产生的抑制作用。在更广泛的影响方面，这项工作将为培训本科生和研究生以及博士后研究人员提供独特的机会，结合实地，实验室和基于建模的科学，以填补我们对冻土带生态系统的知识的重要空白。为了扩大公众影响，两名艺术家将参与创造一个独特的艺术与科学的对话，这将扩大对项目结果的解释，并提供博物馆质量的创造性工作，可以在科学或艺术展览中展示。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

There is great concern about changing conditions in the Arctic due to environmental transformations that are impacting tundra and its underlying permafrost. At the same time there are major gaps in our understanding of tundra/permafrost microbiology and elemental cycling. Filling these knowledge gaps will enable a better overall understanding of the tundra, and can provide crucial information about how this globally important, but fragile ecosystem will respond to change. The particular knowledge gap this research will fill centers around iron and the bacteria that control its availability. Iron is an essential micro-nutrient for animals, plants, and microbes. It also serves as a growth substrate for certain groups of bacteria, many of which fix carbon dioxide to grow. Some of these bacteria directly compete with other groups of microbes that produce or consume methane, the atmospheric concentration of which is continuing to increase. It is particularly important to understand the dynamics of carbon dioxide and methane in the Arctic because there is a large amount of organic carbon stored in permafrost that could be converted into these two gases. The research team consists of a microbial ecologist with considerable experience in iron cycling bacteria; a mathematical modeler who will quantify the relative impacts of different microbial processes, and a tundra ecologist with extensive experience in elemental cycling in permafrost environments. This project will, for the first time, systematically characterize and quantify microbial communities responsible for iron cycling in the tundra/permafrost of Alaska?s North Slope, and increase our understanding of how these microbes interact with the carbon cycle by suppressing methane production. The basic supposition of this research is that conditions in the Arctic are beneficial to an active iron cycle because the shallow depth permafrost prevents ferrous iron-laden waters from percolating into deep aquifers (a common route for iron removal from temperate ecosystems). Furthermore, cool water temperatures slow the chemical oxidation of iron, and a short, but intense growing season provides a source of labile carbon that helps fuel iron reduction. These ideas will be tested by conducting field and laboratory studies at the Toolik Field Station on the North Slope of Alaska. Previous work has revealed there are extensive populations of iron-oxidizing and iron-reducing bacteria associated with microbial iron mats in this region, but in general, little is known about their diversity or function. This work will utilize cultivation-independent, amplicon-based community analysis and metagenomics to further characterize community diversity and function among these chemosynthetic communities. The team will measure methane production at tundra sites with high rates of iron cycling and compare these to sites that are similar in terms of hydrology and landform, but have lower rates of iron-cycling to assess the direct impact of the iron cycle on methane production and consumption. The microbiomes of these sites will also be compared using molecular analysis. In addition to these field measurements, the researchers will construct a laboratory microcosm that can be seeded with soils and microbial iron mats collected from Toolik. This will allow controlled conditions to simulate interactions of the iron and methane cycles under conditions where key parameters such as iron and oxygen concentrations can be controlled. From both field and laboratory data a reaction-based model will be developed using a series of kinetic equations. These will form the basis for a predictive model that can estimate the suppressive effects of iron cycling on methane production. In terms of broader impacts, the work will provide unique opportunities for training undergraduate, and graduate students, as well as a postdoctoral researcher, in combining field, laboratory, and modelling based science to fill an important gap in our knowledge of the tundra ecosystem. To broaden public outreach two artists will be engaged to create a unique art-science dialog that will broaden the interpretation of the project results, and provide museum quality creative work that can be displayed in either science or art exhibits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.