Organic Carbon Remineralization Rates in Polar Sediments: Relationships Between Initial and Terminal Steps, and Microbial Community Composition, Distribution, and Activity

极地沉积物中的有机碳再矿化率：初始步骤和最终步骤与微生物群落组成、分布和活动之间的关系

• 批准号: 9906054
• 负责人: Carol Arnosti
• 金额: $ 23.69万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9906054&HistoricalAwards=false
• 关键词: Organic; Carbon; Remineralization; Rates; Polar

9906054ArnostiPerrmanently cold temperatures are characteristic of the deep and polar oceans and therefore of the majority of ocean sediment yet our understanding of these environments is still limited. The suggestion that microbial processes in these environments are necessarily hampered by lowtemperatures or combined effects of temperature and substrate (Reichardt,1987; Pomeroy et al., 1990; Wiebe et al., 1992) has recently been countered by a number of studies which have found evidence that microbial communities function as efficiently in polar as in temperate environments (Thingstad and Martinussen, 1991; Nedwell et al., 1993; Wheeler et al., 1996). The specific means by which polar microbial communities maintain their activities under conditions which inhibit their temperate counterparts, however, have yet to be investigated in detail. The objective of this project is to examine in detail the regulation and efficiency of organic carbon turnover by microbial communities in permanently cold Arctic sediments. The focus will be on the relationships between rates of the initial and terminal steps of organic carbon remineralization, the composition and size of the microbial community, the activities and distributions of individual members of the community, and the temperature responses of isolated organisms as well as of the net microbial community. The work will be carried out jointly by scientists from the Max-Planck Institute for Marine Microbiology (Bremen, Germany) and the University of North Carolina-Chapel Hill. The project will use both newly-developed and well-established methods to characterize the physiology, activity, distributions, and temperature sensitivity of polar microbial communities, and to measure the rates of initial and terminal processes in organic matter remineralization. Field studies will be carried out principally in fjords near the west coast of Svalbard, in the Arctic Ocean. Extracellular enzymatic hydrolysis of macromolecules, the initial step of organic carbon remineralization, will be measured through the use of a newly-developed technique involving fluorescently-labeled polysaccharides (Arnosti, 1996). Polysaccharides will be the target macromolecules because they comprise a significant proportion of total organic matter, and recent studies (Amon and Benner, 1994) have highlighted their importance in the global carbon cycle. The terminal step of organic carbon remineralization in anoxic marine sediments, sulfate reduction, will be measured using well-established techniques (Jorgensen, 1978). Both the initial and the terminal steps of organic carbon remineralization will be measured in intact sediment cores at in situ temperatures. In addition, both the initial and the terminal steps of organic carbon remineralization will be measured as functions of temperature in order to determine the net microbial community response. Sulfate-reducing as well as extracellular-enzyme producing bacteria will be isolated at low temperature and characterized, and their temperature sensitivities and growth responses will likewise be determined. A major goal of the proposed research is to develop molecular probes to determine the population composition of the sedimentary microbial community and distributions of specific organisms in sediments. In addition, the hydrolysis, transformation, and remineralization of a suite of polysaccharides will be investigated in bacterial enrichment cultures in order to provide information on specific hydrolysis mechanisms and carbon degradation pathways which cannot be obtained from intact sediments. A detailed study of the rates and temperature responses of the initial and terminal steps of organic carbon remineralization in anoxic polar sediments will effectively provide 'bookends' between which remineralization of a major portion of organic matter occurs, and will help delineate the boundaries of the microbial community response to environmental temperature. Polysaccharides constitute a high percentage of the organic macromolecules which ultimately fuel sulfate reduction; defining their contribution to terminal remineralization processes will bring closer the goal of a quantitative understanding of the sedimentary carbon cycle, with all of its complexities. By determining the physiology, activity, and population distribution of some of the organisms responsible for the initial and terminal steps of carbon remineralization, this research project will shed light on these important but insufficiently understood microbial communities. This study should lead to new insights into the factors controlling microbial activity and carbon cycling in permanently cold sediments, which comprise a major portion of the global sedimentaryenvironment.

9906054 Arnosti永久寒冷的温度是深海和极地海洋的特征，因此也是大多数海洋沉积物的特征，但我们对这些环境的了解仍然有限。这些环境中的微生物过程必然受到低温或温度和底物的联合作用的阻碍（Reichardt，1987; Pomeroy等人，1990; Wiebe等人，1992）最近被许多研究所反驳，这些研究发现了微生物群落在极地和温带环境中同样有效地起作用的证据（Thingstad和Martinussen，1991; Nedwell等人，1993;惠勒等人，1996年）。然而，极地微生物群落在抑制温带微生物群落的条件下维持其活动的具体手段还有待详细研究。本项目的目标是详细研究北极永久寒冷沉积物中微生物群落对有机碳周转的调节和效率。重点将放在有机碳矿化的初始和最终步骤的速率之间的关系，微生物群落的组成和大小，社区的个体成员的活动和分布，以及孤立的生物体的温度响应以及净微生物群落。这项工作将由马克斯-普朗克海洋微生物学研究所（不莱梅，德国）和北卡罗来纳大学教堂山分校的科学家联合进行。该项目将使用新开发的和成熟的方法来表征极地微生物群落的生理学、活动、分布和温度敏感性，并测量有机物矿化的初始和最终过程的速率。实地研究将主要在北冰洋斯瓦尔巴特群岛西海岸附近的峡湾进行。大分子的胞外酶促水解是有机碳矿化的初始步骤，将通过使用涉及荧光标记多糖的新开发技术来测量（Arnosti，1996）。多糖将是目标大分子，因为它们占总有机物质的很大比例，最近的研究（Amon和Benner，1994年）强调了它们在全球碳循环中的重要性。缺氧海洋沉积物中有机碳再矿化的最后一步，即硫酸盐还原，将使用成熟的技术进行测量（Jorgensen，1978年）。有机碳矿化的初始和最终步骤将在原位温度下在完整的沉积物岩心中进行测量。此外，将测量有机碳矿化的初始和最终步骤作为温度的函数，以确定净微生物群落响应。硫酸盐还原菌和胞外酶产生菌将在低温下分离并表征，它们的温度敏感性和生长反应也将被确定。该研究的一个主要目标是开发分子探针，以确定沉积物微生物群落的种群组成和特定生物在沉积物中的分布。此外，一套多糖的水解，转化和再矿化将在细菌富集培养物中进行研究，以提供无法从完整沉积物中获得的特定水解机制和碳降解途径的信息。缺氧极地沉积物中有机碳矿化的初始和最终步骤的速率和温度响应的详细研究将有效地提供“书挡”，其中大部分有机物的矿化发生在书挡之间，并将有助于划定微生物群落对环境温度响应的边界。多糖构成的有机大分子，最终燃料硫酸盐还原的比例很高;定义其对终端生物矿化过程的贡献将带来更接近的目标，定量了解沉积碳循环，其所有的复杂性。通过确定负责碳矿化的初始和最终步骤的一些生物的生理，活性和种群分布，该研究项目将揭示这些重要但尚未充分了解的微生物群落。这项研究将导致对控制永久冷沉积物中微生物活动和碳循环的因素的新见解，这些沉积物构成全球沉积环境的主要部分。