Biohopanoid markers as tracers of methane emission and oxidation events in the Quaternary ocean

生物藿香类标记物作为第四纪海洋中甲烷排放和氧化事件的示踪剂

• 批准号: NE/E017088/1
• 负责人: Thomas Wagner
• 金额: $ 48.02万
• 依托单位: Newcastle University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE017088%2F1
• 关键词: Biohopanoid; markers; tracers; methane; emission

Methane is a strong greenhouse gas produced in sediments directly from microorganisms, or from prolonged heating of fossil carbon. Release of methane to the ocean and atmosphere is known to have shifted global climate and nutrient cycles in the past, in particular when released in massive quantities and over short time periods from frozen subsurface reservoirs known as marine gas hydrates. With global warming, unstable sources such as gas hydrates pose a potentially large threat to the marine environments, climate, and thus society. It is therefore pivotal to recognize mechanisms of increased methane emission in the past. Equally important is understanding its sources and pathways from the subsurface, identification of processes which cycle released methane, and quantification of subsequent ocean-atmosphere and biogeochemical feedbacks. This research project sets out an ambitious organic geochemical programme to explore the process of aerobic microbial oxidation of methane in oceans over the last 1 million years of the late Quaternary and assess its effects on climate. The target process has received little attention to date but possibly plays a more important role in carbon cycling and oxygen availability in the ocean than commonly considered. As a new tool in past climate research we propose to use molecular compounds (specific biohopanoids, BHPs) generated exclusively by bacteria which feed on methane (methane-oxidising bacteria). We recently analysed BHPs in the sedimentary record (down to 100 m depth equivalent to about 1 million years) from a giant deep sea sediment fan in front of the Congo river in tropical Africa. These new data push direct evidence for the process of massive methane release and its aerobic microbial oxidation far back into the geological past; previous studies suggesting a similar mechanism were limited to the last 45 ka. The new Congo fan data are encouraging and provide strong support for previously unrecognised methane emission events and aerobic turnover in the eastern tropical Atlantic. Building on that, we will focus our research on two contrasting sediment records, (1) the Congo and Amazon Fans which had oxygenated water conditions throughout the study period and (2) the Mediterranean. The latter is well known for its pronounced and rapid changes in oxygenation throughout the past few million years which alternated between oxygenated and oxygen-fee (anoxic), and frequently even toxic (sulfidic/euxinic) conditions leading to the formation of sediments exceptionally rich in organic carbon, commonly termed sapropels. We here propose a multidisciplinary approach, utilising BHP markers with other geochemical and isotopic evidence and modelling. This integrated approach will allow us to fully evaluate the existence of previously unrecognised methane emission events and subsequent methane oxidation in the Quaternary ocean. Combined with coupled atmosphere-land-ocean modelling the data will allow us to address the relevance of the target process in oxic settings and others which are approaching oxygen-free conditions. This will then provide the first quantitative estimates on greenhouse gas volumes emitted by the emission events and explore climate effects.

甲烷是一种强烈的温室气体，直接由微生物或化石碳的长期加热在沉积物中产生。众所周知，过去向海洋和大气中释放甲烷已经改变了全球气候和营养循环，特别是当甲烷在短时间内从被称为海洋天然气水合物的冰冻地下储层大量释放时。随着全球变暖，天然气水合物等不稳定来源对海洋环境、气候乃至社会构成潜在的巨大威胁。因此，认识过去甲烷排放增加的机制至关重要。同样重要的是了解其地下来源和路径，识别循环释放甲烷的过程，并对随后的海洋大气和生物地球化学反馈进行量化。该研究项目制定了一项雄心勃勃的有机地球化学计划，旨在探索第四纪晚期最后一百万年海洋中甲烷有氧微生物氧化的过程，并评估其对气候的影响。迄今为止，目标过程很少受到关注，但可能在海洋碳循环和氧气可用性中发挥比通常认为的更重要的作用。作为过去气候研究的新工具，我们建议使用仅由以甲烷为食的细菌（甲烷氧化细菌）产生的分子化合物（特定的生物霍烷类化合物，BHP）。我们最近分析了热带非洲刚果河前一个巨大的深海沉积扇的沉积记录（深达 100 m，相当于约 100 万年）中的必和必拓。这些新数据将大量甲烷释放及其有氧微生物氧化过程的直接证据追溯到地质时代。之前的研究表明类似的机制仅限于过去 45 ka。刚果球迷的新数据令人鼓舞，并为以前未被识别的东部热带大西洋甲烷排放事件和有氧周转提供了强有力的支持。在此基础上，我们将把研究重点放在两个对比鲜明的沉积物记录上：(1) 刚果扇和亚马逊扇，它们在整个研究期间都具有含氧水条件；(2) 地中海。后者以其在过去几百万年中显着而快速的氧合变化而闻名，这些变化在含氧和缺氧（缺氧）之间交替，甚至经常甚至有毒（含硫/含氧）条件，导致形成异常富含含氧量的沉积物。有机碳，通常称为腐泥。我们在这里提出了一种多学科方法，利用必和必拓标记以及其他地球化学和同位素证据和建模。这种综合方法将使我们能够全面评估第四纪海洋中先前未被识别的甲烷排放事件以及随后的甲烷氧化的存在。结合大气-陆地-海洋耦合建模，这些数据将使我们能够解决目标过程在有氧环境和其他接近无氧条件下的相关性。然后，这将提供对排放事件排放的温室气体量的首次定量估计，并探索气候影响。

项目成果

Variability in aerobic methane oxidation over the past 1.2Myrs recorded in microbial biomarker signatures from Congo fan sediments

刚果扇沉积物微生物生物标记特征记录了过去 1.2Myrs 的有氧甲烷氧化变化

• DOI: http://dx.10.1016/j.gca.2014.02.035
• 发表时间: 2014
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Talbot H

Distribution of polar membrane lipids in permafrost soils and sediments of a small high Arctic catchment

北极小流域永久冻土和沉积物中极性膜脂的分布

• DOI: http://dx.10.1016/j.orggeochem.2010.06.004
• 发表时间: 2010
• 期刊: Organic Geochemistry
• 影响因子: 3
• 作者: Rethemeyer J

Bacteriohopanepolyols as tracers for continental and marine organic matter supply and phases of enhanced nitrogen cycling on the late Quaternary Congo deep sea fan

细菌藿烷多元醇作为大陆和海洋有机物供应的示踪剂以及第四纪晚期刚果深海扇氮循环增强的阶段

• DOI: 10.1016/j.orggeochem.2010.04.016
• 发表时间: 2010-09-01
• 期刊: Organic Geochemistry
• 影响因子: 3
• 作者: L. H;ley;ley;H. Talbot;M. Cooke;Kathleen E. Anderson;T. Wagner
• 通讯作者: T. Wagner

Bacteriohopanepolyol biomarker composition of organic matter exported to the Arctic Ocean by seven of the major Arctic rivers

北冰洋七条主要河流输出到北冰洋的有机物的细菌藿烷多元醇生物标志物组成

• DOI: http://dx.10.1016/j.orggeochem.2009.07.014
• 发表时间: 2009
• 期刊: Organic Geochemistry
• 影响因子: 3
• 作者: Cooke M

Tracking soil organic carbon transport to continental margin sediments using soil-specific hopanoid biomarkers: A case study from the Congo fan (ODP site 1075)

使用土壤特有的hopanoid生物标志物追踪土壤有机碳向大陆边缘沉积物的迁移：来自刚果扇的案例研究（ODP站点1075）

• DOI: http://dx.10.1016/j.orggeochem.2008.03.009
• 发表时间: 2008
• 期刊: Organic Geochemistry
• 影响因子: 3
• 作者: Cooke M