Collaborative Research: Acetate Biogeochemistry in Northern Wetlands: Implications for Methane Formation During Climate Change

合作研究：北部湿地的醋酸盐生物地球化学：气候变化期间甲烷形成的影响

• 批准号: 0094716
• 负责人: Juliette Rooney-Varga
• 金额: $ 5万
• 依托单位: University of Massachusetts Lowell Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0094716&HistoricalAwards=false
• 关键词: Collaborative; Research; Acetate; Biogeochemistry; Northern

AbstractNorthern wetlands store large quantities of carbon and are significant sources of atmospheric methane. Impending climatic changes may greatly affect the role of these environments in the carbon cycle. Decomposition of organic matter occurs anaerobically in these wetlands. However, recent findings suggest that the terminal methanogenic step in northern wetlands is altered relative to more southerly systems, with acetate acting as a terminal product even though methane production continues via hydrogen utilization. If this phenomenon is ubiquitous, then acetate is not a significant intermediate in northern wetlands, but serves as a terminal product of decomposition; one that is ultimately degraded aerobically to CO2 rather than methane. Acetate accumulation in northern wetlands represents a paradigm shift in our understanding of anaerobic decomposition. It is possible that warming in the north will shift this process toward what occurs in more southerly wetlands. If so, then methane production in the north will increase greatly over what might occur from warming alone.This work will test the hypothesis that northern wetlands do not support significant methanogenesis from acetate and that acetate formation and accumulation is an important terminal step during anaerobic degradation of organic matter. This phenomenon is being investigated by a multidisciplinary team that will utilize field and laboratory investigations and microbiological, molecular biology, geochemical, pedological, and stable isotope approaches.The objectives of the project are: 1) assess the ubiquity of the acetate-accumulating phenomenon by examining acetate concentrations and production rates, geochemical conditions, and by applying isotopic and molecular techniques to a variety of northern wetland types representative of the major circumpolar arctic, subarctic and northern boreal environments; 2) Provide a temporal framework for determining variations in controls on methanogenic pathways and acetate cycling by conducting seasonal studies; 3) determine the effects of physical and chemical parameters on terminal decomposition using laboratory manipulations of incubation conditions; 4) determine if the bacterial populations are distinct compared to other wetlands and other anaerobic habitats.Incubation assays, radiotracer analyses, stable isotopes and natural radiocarbon abundances will be used to address pathways of decomposition in field and laboratory experiments. Molecular approaches including PCR-DGGE and hybridization probing will be used to determine bacterial diversity and population structure.A demonstration that biochemical pathways of methane formation in these wetlands are unique compared to their more southerly counterparts, has tremendous implications for our ability to predict the what the role of these wetlands will be in contributing methane to the global atmosphere and in their ability to degrade stored carbon. Acetate may serve as a primary organic end product, which would thus constitute a separate terminal decomposition pathway occurring simultaneously with methanogenesis. The multi-disciplinary study proposed here will delineate the important details of these processes and will serve to demonstrate their spatial significance.

摘要 北部湿地储存了大量的碳，是大气甲烷的重要来源。即将到来的气候变化可能会极大地影响这些环境在碳循环中的作用。有机物的分解在这些湿地中以厌氧方式发生。然而，最近的研究结果表明，北部湿地的最终产甲烷步骤相对于更南部的系统发生了改变，尽管甲烷通过利用氢气继续生产，但乙酸盐作为最终产物。如果这种现象普遍存在，那么醋酸盐就不是北部湿地的重要中间产物，而是分解的最终产物；最终在有氧条件下降解为二氧化碳而不是甲烷。北部湿地的乙酸积累代表了我们对厌氧分解理解的范式转变。北方变暖可能会使这一过程转向更南部湿地的情况。如果是这样，那么北部的甲烷产量将大大增加，超过仅因变暖而可能发生的情况。这项工作将检验以下假设：北部湿地不支持由乙酸盐产生大量甲烷，并且乙酸盐的形成和积累是厌氧降解过程中重要的最终步骤的有机物。一个多学科团队正在对这一现象进行研究，该团队将利用现场和实验室调查以及微生物学、分子生物学、地球化学、土壤学和稳定同位素方法。该项目的目标是：1）通过以下方式评估醋酸盐积累现象的普遍性：检查乙酸盐浓度和生产率、地球化学条件，并将同位素和分子技术应用于代表主要环极地北极、亚北极和北部寒带环境的各种北方湿地类型； 2) 通过进行季节性研究，提供一个时间框架来确定产甲烷途径和醋酸盐循环控制的变化； 3) 使用实验室操作的培养条件确定物理和化学参数对最终分解的影响； 4) 确定细菌种群与其他湿地和其他厌氧栖息地相比是否不同。孵化测定、放射性示踪剂分析、稳定同位素和天然放射性碳丰度将用于解决现场和实验室实验中的分解途径。包括 PCR-DGGE 和杂交探测在内的分子方法将用于确定细菌多样性和种群结构。证明这些湿地中甲烷形成的生化途径与更南端的对应物相比是独特的，这对于我们预测什么的能力具有巨大的影响。这些湿地的作用将是向全球大气排放甲烷并具有降解储存的碳的能力。乙酸盐可以作为主要的有机最终产物，从而构成与产甲烷同时发生的单独的终端分解途径。这里提出的多学科研究将描述这些过程的重要细节，并将有助于证明其空间意义。