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 arnostiperran寒冷的温度是深海洋和极地海洋的特征，因此大多数海洋沉积物中，我们对这些环境的理解仍然受到限制。这些环境中的微生物过程必然受到温度和温度和底物的综合影响的建议（Reichardt，1987; Pomeroy等，1990; Wiebe et al。，1992）最近被许多研究所发现的证据表明，在微生物社区中，微生物社区在偏光范围内效果有效，并且在偏光范围内发挥了高度的影响； Al。，1993; Wheeler等人，1996年）。然而，极地微生物群落在抑制温带对应物的条件下维护其活动的特定手段尚未详细研究。该项目的目的是详细研究微生物群落在永久冷北极沉积物中的有机碳转换的调节和效率。重点将放在有机碳回忆的初始和终端步骤的关系上，微生物群落的组成和大小，社区各个成员的活动和分布以及孤立生物体的温度响应以及净微生物群落的温度响应。这项工作将由Max-Planck海洋微生物学研究所（德国不来梅）和北卡罗来纳大学 - 教堂山山的科学家共同进行。该项目将同时使用新开发和良好的方法来表征极性微生物群落的生理，活性，分布和温度敏感性，并衡量有机物回忆起的初始和终末过程的速率。现场研究将主要在北极海洋西海岸附近的峡湾进行。大分子的细胞外酶水解是有机碳回忆化的第一步，通过使用涉及荧光标记多糖的新发育技术来测量（Arnosti，1996）。多糖将是靶标大分子，因为它们占有机物总物质的很大一部分，而最近的研究（Amon and Benner，1994）强调了它们在全球碳循环中的重要性。用良好的技术测量了缺氧海洋沉积物（硫酸盐还原）中有机碳的末端步骤（Jorgensen，1978）。有机碳回忆性的初始和末端步骤均应在原位温度下在完整的沉积物芯中测量。此外，有机碳回忆的初始和末端步骤都将作为温度的功能来测量，以确定净微生物群落响应。还将在低温下分离出硫酸盐还原以及细胞外酶产生细菌，并且同样可以确定它们的温度敏感性和生长反应。拟议研究的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以及沉积物中特定生物的分布。此外，将在细菌富集培养物中研究一组多糖的水解，转化和回忆化，以提供有关无法从完整沉积物获得的特定水解机制和碳降解途径的信息。对缺氧极性沉积物中有机碳的初始和终端步骤的速率和温度响应的详细研究将有效地提供“预订”，在其中回想起有机物的主要部分，并将有助于描述微生物社区对环境温度的响应的边界。多糖构成了有机大分子的很高比例，这些分子最终会减少硫酸盐。定义他们对末端回忆过程的贡献将使对沉积碳循环的定量理解的目标更接近其所有复杂性。通过确定负责碳回忆性初始和终末步骤的某些生物的生理，活动和种群分布，该研究项目将揭示这些重要但不足以理解的微生物群落。这项研究应导致对控制微生物活性和碳循环的因素的新见解，该因素构成了全球沉积环境的主要部分。