Collaborative Research: Predicting Controls of Partitioning between Dissimilatory Ntirate Reduction to Ammonium (DNRA) and Dinitrogen Production in Marine Sediments

合作研究：预测海洋沉积物中异化硝酸盐还原成铵（DNRA）和氮生成之间的分配控制

• 批准号: 1635099
• 负责人: Anne Giblin
• 金额: $ 37.02万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635099&HistoricalAwards=false
• 关键词: Collaborative; Research; Predicting; Controls; Partitioning

Microbial processes in marine sediments play a major role in the global nitrogen cycle. Because the presence of nitrogen compounds dissolved in seawater largely controls biological growth, understanding how the sedimentary nitrogen budget changes with altered circulation, acidity, and biological productivity is of critical importance to predict oceanic function in future climate scenarios. Surprisingly, we do not know definitively if nitrogen exchange between sediments and the water column is in balance, and if not, how it varies over time and space. We do know that two bacterially mediated chemical reactions are primarily responsible for removing nitrogen from marine ecosystems by converting biologically usable forms of dissolved nitrogen back to nitrogen gas (N2) that is not generally available for biological production. These reactions are called denitrification and anaerobic ammonium oxidation (anammox); the latter operating only where oxygen is zero. This project will investigate a third reaction, called dissimilatory nitrate reduction (DNRA), which competes directly with anammox to limit N2 production and the consequent "loss" of nitrogen, thus retaining nitrogen for use in marine ecosystems. The role of DNRA has not been fully explored and quantifying this reaction could help evaluate the overall nitrogen balance in ocean systems. The researchers here will use novel experimental reactors that contain collected marine sediments and, by varying environmental conditions (pH, temperature, oxygen, organic carbon), will discover and quantify what controls rates of DNRA, denitrification, and anammox in sediments. This will provide a direct test and further development of theoretical sedimentary nitrogen models that can be used to predict possible changes in the global nitrogen cycle resulting with various future climate scenarios. Two graduate students will participate in the research and collaborations with the Maine Coastal Observing Alliance (MCOA) and the Gulf of Maine Institute (GOMI), as well as the Institute for Broadening Participation (IBP) will generate minority student involvement and enhanced outreach activity.This project uses thermodynamic calculations and empirical evidence as a basis to evaluate the ratio of available organic carbon (C) to nitrate (NO3-) as a key controlling factor of nitrogen redox partitioning; with higher ratios believed to favor dissimilatory nitrate reduction (DNRA) over N2 production. The investigator's theoretical model predicts rapid and reversible transitions between DNRA and N2 production over relatively small changes in C/NO3-. This suggests that partitioning could be sensitive to seasonal and possibly inter-annual differences in organic C deposition as well as processes that control nitrate flux to the sediments such as water column stratification. Quantitative relationships between sedimentary C/NO3- and nitrogen partitioning remain poorly defined, and a number of other factors including T, H2S, and Fe(II), are known to influence N partitioning. This study will investigate the hypothesis that relationships between nitrogen redox partitioning and C/NO3-, and by extension H2S/NO3-, are predicted by the proposed theoretical sedimentary nitrogen model. Experiments will varying NO3 fluxes while providing hydrogen sulfide (H2S) and 13C-labelled detritus as electron donors, and measure transformation rates of 15NO3- to 15NH4+ and 29/30N2 in thin disc reactors to determine rates and pathways of DNRA and N2 production. The proposed integration of these experiments with a theoretically-based biogeochemical model will develop a quantifiable and testable understanding of the marine nitrogen cycle. This study should provide a major advance that could be broadly applied to quantitatively predict the sedimentary balance between nitrogen retention and loss across marine ecosystems.

海洋沉积物中的微生物过程在全球氮循环中发挥着重要作用。由于溶解在海水中的氮化合物的存在在很大程度上控制了生物生长，因此了解沉积物氮收支如何随着循环、酸度和生物生产力的变化而变化对于预测未来气候情景中的海洋功能至关重要。令人惊讶的是，我们并不清楚沉积物和水柱之间的氮交换是否平衡，如果不平衡，它如何随时间和空间变化。我们确实知道，两种细菌介导的化学反应主要负责通过将生物可用形式的溶解氮转化回通常不能用于生物生产的氮气（N2）来从海洋生态系统中去除氮。这些反应称为反硝化和厌氧氨氧化（anammox）；后者仅在氧气为零的情况下运行。该项目将研究第三种反应，称为异化硝酸盐还原（DNRA），它与厌氧氨氧化直接竞争，限制氮气的产生和随之而来的氮“损失”，从而保留氮用于海洋生态系统。 DNRA 的作用尚未得到充分探索，量化该反应可以帮助评估海洋系统中的整体氮平衡。研究人员将使用包含收集的海洋沉积物的新型实验反应器，通过改变环境条件（pH、温度、氧气、有机碳），发现并量化控制沉积物中 DNRA、反硝化和厌氧氨氧化速率的因素。这将为理论沉积氮模型提供直接测试和进一步发展，该模型可用于预测各种未来气候情景导致的全球氮循环可能发生的变化。两名研究生将参与缅因州沿海观测联盟 (MCOA) 和缅因湾研究所 (GOMI) 的研究和合作，以及扩大参与研究所 (IBP) 将促进少数族裔学生的参与并加强外展活动。该项目使用热力学计算和经验证据作为基础来评估可用有机碳 (C) 与硝酸盐的比率 (NO3-)作为氮氧化还原分配的关键控制因素；较高的比率被认为有利于异化硝酸盐还原（DNRA）而不是氮气生产。研究人员的理论模型预测，随着 C/NO3- 相对较小的变化，DNRA 和 N2 生产之间会发生快速且可逆的转变。这表明分配可能对有机碳沉积的季节差异和可能的年际差异以及控制硝酸盐流入沉积物的过程（例如水柱分层）敏感。沉积物 C/NO3- 和氮分配之间的定量关系仍不清楚，并且已知许多其他因素（包括 T、H2S 和 Fe(II)）会影响氮分配。本研究将研究氮氧化还原分配与 C/NO3- 以及 H2S/NO3- 之间关系的假设，该关系是通过所提出的理论沉积氮模型预测的。实验将改变 NO3 通量，同时提供硫化氢 (H2S) 和 13C 标记的碎屑作为电子供体，并测量薄盘反应器中 15NO3- 到 15NH4+ 和 29/30N2 的转化率，以确定 DNRA 和 N2 生产的速率和途径。拟议将这些实验与基于理论的生物地球化学模型相结合，将对海洋氮循环形成可量化和可测试的理解。这项研究应提供一项重大进展，可广泛应用于定量预测整个海洋生态系统氮保留和损失之间的沉积平衡。

项目成果

Anaerobic ammonium oxidation (anammox) and denitrification in Peru margin sediments

• DOI: 10.1016/j.jmarsys.2018.09.007
• 发表时间: 2020-07
• 期刊: Journal of Marine Systems
• 影响因子: 2.8
• 作者: J. J. Rich-J.;P. Arevalo;B. Chang;A. Devol;B. Ward

Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments

• DOI: 10.1111/gcb.13370
• 发表时间: 2017-01
• 期刊: Global Change Biology
• 影响因子: 11.6
• 作者: Lindsay D. Brin;A. Giblin;J. J. Rich-J.