Marine biogeochemistry of molecular hydrogen

分子氢的海洋生物地球化学

• 批准号: 6098-2010
• 负责人: Moore, Robert
• 金额: $ 3.86万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568443
• 关键词: Marine; biogeochemistry; molecular; hydrogen

It is proposed that measurements of dissolved molecular hydrogen, a known byproduct of nitrogenase activity, have the potential to open a new window on the study of marine nitrogen fixation which, although of prime importance to the marine carbon cycle and long a subject of study, remains inadequately quantified. Estimates of global ocean N2-fixation, derived from collections of snapshot isotopic rate measurements and indirect global geochemical evidence, range between 100 and 200Mtonnes N/yr (Carpenter & Capone, 2008). Interest in the study of marine N2-fixation has been stimulated as recent applications of molecular biology techniques have revealed an increased number and diversity cyanobacterial species able to fix nitrogen. At the same time, the discovery of a major loss process (in addition to denitrification) for combined nitrogen in the oceans, through the anammox process, has focused more attention on the imbalances between N2-fixation and loss in the oceans as well as on the mechanisms acting to restore balance. Such imbalances are recognized as having the potential to significantly affect atmospheric CO2 levels by altering the capacity of the deep ocean to store CO2, possibly contributing to well known glacial-interglacial variations in atmospheric pCO2. Of particular interest are questions concerning how tightly coupled are these sources and sinks, and whether iron plays a controlling role in the distribution and intensity of nitrogen fixation. In a pilot study of saturation levels of molecular hydrogen and isotopically measured N2-fixation in surface tropical waters we have shown a correspondence between these two quantities. Now, in collaboration with international partners we propose to extend this work to intensive field studies which include the study of iron availability and characterization of the diazotroph community in the equatorial ocean. It is anticipated that H2 measurements, rapidly made from a moving vessel, have the potential to support the slower, more labour-intensive, but quantitative technique of N-15 uptake for quantifying N2-fixation on large spatial scales. In particular, it has potential for identifying local regions of fixation stimulated by deposition of iron in atmospheric dust.

有人建议，溶解的分子氢，固氮酶活性的一个已知的副产品的测量，有可能打开一个新的窗口，海洋固氮的研究，虽然最重要的海洋碳循环和长期的研究课题，仍然没有充分的量化。根据收集的快照同位素速率测量结果和间接的全球地球化学证据，估计全球海洋固氮量在1亿至2亿吨N/年之间（Carpenter & Capone，2008年）。 近年来，随着分子生物学技术的应用，蓝藻固氮种类的数量和多样性不断增加，引起了人们对海洋固氮研究的兴趣。与此同时，发现海洋中化合氮通过厌氧氨氧化过程的主要损失过程（除反硝化作用外），使人们更加关注海洋中N2固定和损失之间的不平衡以及恢复平衡的机制。 这种不平衡被认为有可能通过改变深海储存CO2的能力而对大气CO2水平产生重大影响，可能造成众所周知的冰川-间冰期大气pCO 2变化。特别感兴趣的是如何紧密耦合的问题，这些源和汇，以及铁是否起着控制作用的分布和强度的固氮。在一个试点研究的饱和度水平的分子氢和同位素测量的氮固定在表面热带沃茨，我们已经显示了这两个数量之间的对应关系。现在，在与国际合作伙伴的合作，我们建议将这项工作扩展到密集的实地研究，其中包括铁的可用性和表征的固氮生物群落在赤道海洋的研究。据预计，H2测量，从移动的船只迅速，有可能支持较慢，更劳动密集型，但定量技术的N-15吸收量化N2固定在大的空间尺度上。特别是，它有可能确定当地地区的固定刺激沉积铁在大气中的灰尘。