EAGER: Linking the Chlorine and Carbon Cycles in the Arctic Coastal Plain

EAGER：将北极沿海平原的氯和碳循环联系起来

• 批准号: 1712774
• 负责人: David Lipson
• 金额: $ 21.14万
• 依托单位: San Diego State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2021-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1712774&HistoricalAwards=false
• 关键词: EAGER; Linking; Chlorine; Carbon; Cycles

The element, chlorine, is not normally studied in natural environments, except in areas that have been contaminated with toxic compounds like pesticides, industrial solvents or radioactive 36Cl. It is often assumed that chlorine enters non-contaminated ecosystems mostly in the form of chloride (the same negative ion in table salt), and that chloride does not interact with plants or soil microorganisms. However, there is growing evidence that chloride is taken up and transformed by plants and soil microorganisms into complex chlorine-containing organic compounds. In environments where oxygen is scarce, some bacteria can use these chlorinated organic compounds instead of oxygen in a form of anaerobic respiration called organohalide respiration (OHR). In this way, these bacteria can quickly use up energy sources that would otherwise be used to produce methane. This means that an active biological chlorine cycle could reduce the amount of methane that is released into the atmosphere. Methane is a strong greenhouse gas, trapping about 30 times as much heat per molecule as carbon dioxide. The Arctic region has been warming faster than the rest of the planet, and large amounts of organic carbon are stored in Arctic soils. It is thus important to understand how much soil carbon will be lost to the atmosphere in the form of carbon dioxide or methane, since these two gases have different effects on the climate the climate system. This project measures rates of biological chlorine cycling in locations across the Arctic Coastal Plain of northern Alaska, and tests whether organohalide respiration does in fact significantly reduces methane production in these areas. This project could inform models of greenhouse gas emissions, improve understanding of the fate of chlorinated contaminants in Arctic soils, and further the basic science of biological chlorine cycling. The project will involve students at a minority-serving institution (San Diego State University) and a high school teacher, who will lead broader outreach and education efforts.The proposed research addresses the following two questions: (1) Does OHR inhibit methanogenesis via competition for H2? (2) How does the relative magnitude of Cl cycling and its relationship to CH4 flux change along a coastal-inland gradient in the Arctic Coastal Plain? The experimental approach consists of a field survey that compares CH4 fluxes and indicators of Cl cycling along a gradient of coastal influence from Barrow to the foothills of the Brooks Range, and a laboratory incubation experiment to study the relationships among OHR, methanogenesis, other terminal electron acceptor processes, and H2 availability. Indicators of Cl cycling include sizes and transformation rates of soil Cl pools, metagenomes describing the relative abundance of genes and microbial taxa associated with Cl cycling and other anaerobic processes, and 37Cl and 36Cl isotopic analysis to infer the dominant Cl cycling processes and to constrain long-term cycling rates. The laboratory incubation will follow anaerobic processes (OHR, iron reduction, methanogenesis, acetogenesis, and sulfate reduction) in microcosms varying in Clorg and H2 concentration to establish the thermodynamic hierarchy among these processes and whether competition is alleviated by increased H2.

通常在自然环境中研究该元素，氯，除了在被农药，工业溶剂或放射性36Cl等有毒化合物污染的区域外。通常假定氯在非污染的生态系统中主要以氯化物的形式（含盐中的相同负离子）进入，并且氯化物不与植物或土壤微生物相互作用。然而，越来越多的证据表明，氯化物被植物和土壤微生物占用并转化为复杂的含有氯的有机化合物。在稀缺氧气的环境中，一些细菌可以以一种称为Organohalide呼吸（OHR）的厌氧呼吸形式使用这些氯化有机化合物而不是氧。通过这种方式，这些细菌可以快速消耗否则将用于产生甲烷的能源。这意味着活跃的生物氯周期可以减少释放到大气中的甲烷量。甲烷是一种强烈的温室气体，每分子的热量是二氧化碳的30倍。北极地区的变暖比地球的其余部分更快，并且大量有机碳存储在北极土壤中。因此，重要的是要了解以二氧化碳或甲烷的形式损失多少土壤碳，因为这两种气体对气候气候系统具有不同的影响。该项目测量了阿拉斯加北部北极沿海平原的地点生物氯循环的速率，并测试了实际上是否确实会大大降低这些地区的甲烷产生。该项目可以为温室气体排放的模型提供信息，从而提高对北极土壤中氯化污染物命运的理解，并进一步发展生物氯循环的基础科学。该项目将涉及少数派服务机构（圣地亚哥州立大学）的学生和一名高中老师，他们将领导更广泛的外展和教育工作。拟议的研究解决了以下两个问题：（1）OHR是否通过H2竞争抑制甲烷发生？ （2）CL循环的相对大小及其与CH4通量的关系如何在北极沿海平原的沿海沿着沿海梯度沿线变化？实验方法由一项现场调查组成，该调查比较了CH4通量和CL循环的指标，沿着从巴罗到布鲁克斯山脉山麓的沿海影响梯度，以及一个实验室孵化实验，以研究OHR，甲烷发生，其他末端电子受体过程以及H2的可用性。 CL循环的指标包括土壤CL池的大小和转化速率，描述基因的相对丰度和与CL循环和其他厌氧过程相关的微生物分类群的相对丰度，以及37CL和36CL同位素分析，以推断出主导的CL循环过程以及限制长期循环速率。实验室的孵育将遵循厌氧过程（OHR，还原，甲烷生成，乙酸生成和硫酸盐还原）在CLORG和H2浓度变化的微观群中，以在这些过程中建立热力学层次结构，以及竞争是否被增加了H2。

项目成果

Biological chlorine cycling in the Arctic Coastal Plain

• DOI: 10.1007/s10533-017-0359-0
• 发表时间: 2017-07
• 期刊: Biogeochemistry
• 影响因子: 4
• 作者: Jaime E. Zlamal;T. Raab;M. Little;Robert Edwards;D. Lipson

Snow melt stimulates ecosystem respiration in Arctic ecosystems

• DOI: 10.1111/gcb.15193
• 发表时间: 2020-06-30
• 期刊: GLOBAL CHANGE BIOLOGY
• 影响因子: 11.6
• 作者: Arndt, Kyle A.;Lipson, David A.;Zona, Donatella
• 通讯作者: Zona, Donatella

Organohalide-Respiring Bacteria at the Heart of Anaerobic Metabolism in Arctic Wet Tundra Soils

• DOI: 10.1128/aem.01643-20
• 发表时间: 2020-11
• 期刊: Applied and Environmental Microbiology
• 影响因子: 4.4
• 作者: D. Lipson;T. Raab;Sherlynette Pérez Castro;Alexander Powell