Collaborative Research: Shallow-sea hydrothermal systems: Micron-scale sedimentary sulfur cycling and its impact on ocean processes

合作研究：浅海热液系统：微米级沉积硫循环及其对海洋过程的影响

• 批准号: 1061350
• 负责人: Gregory Druschel
• 金额: $ 11.41万
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2012-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1061350&HistoricalAwards=false
• 关键词: Collaborative; Research; Shallow; sea; hydrothermal

The influx of reducing (i.e., anoxic) fluids through deep-sea and shallow-sea hydrothermal systems into the ocean plays a major role in determining ocean chemistry and its evolution over geologic history. The interface between hydrothermal fluids and the overlying cool and well-oxygenated seawater is characterized by intense thermodynamic disequilibrium, driving a suite of biogeochemical reactions, which in turn further shape ocean chemistry. These reactions generate strong geochemical redox gradients transitioning from the marine water column into the sediments beneath along the interface with reducing hydrothermal fluids. These gradients provide a framework where microbial communities live, evolve, shape, and are shaped by their local geochemical environment. However, the link between the metabolic activity of these micron-sized microorganisms and the resulting geochemical signatures (typically sampled at approximately cm-scale resolution) remains elusive, in large part because of the difficulty of extracting sufficient material for geochemical analyses at small scales (~1-100 microns). Yet, it is precisely this fine-scale geochemical variability that directly impacts biogeochemical activity. This research takes advantage of recent advances in analytical techniques that allow for geochemical and stable isotopic measurements at a spatial resolution as small as ~1-10 microns. Samples come from accessible shallow-sea hydrothermal systems in the Mediterranean Sea, where diverse sulfur cycling has been previously identified and steep redox gradients make it possible for micron-scale measurements to sample across a wide range of geochemical environments. In addition, a 20+-year record of observations allows the results to be put into a rich geochemical context. Goals are to generate an unparalleled high-resolution geochemical and isotopic characterization of sulfur cycling in shallow-sea hydrothermal systems and use the resulting data to calculate the thermodynamic drivers for diverse biogeochemical reactions. The data will also allow the evaluation of the role of ambient geochemistry on isotopic fractionation during sulfur biogeochemical cycling and application of results to understanding variations in the isotopic composition of sulfur species in marine sediments through time because sulfur isotopes are one of the principle means to reconstruct paleoenvironmental conditions over Earth history. Broader impacts of the work include undergraduate and graduate student training in the field and laboratory. Cross training in different laboratories will also deepen the integration of research and education. This project also involves international collaboration with Sicilian and German scientists.

还原性（即缺氧）流体通过深海和浅海热液系统流入海洋，在决定海洋化学及其在地质历史上的演变方面起着重要作用。热液流体与上覆的冷而富氧海水之间的界面以强烈的热力学不平衡为特征，驱动了一系列生物地球化学反应，这些反应反过来又进一步塑造了海洋化学。这些反应产生了强烈的地球化学氧化还原梯度，沿还原热液界面从海水柱向沉积物过渡。这些梯度提供了一个微生物群落生存、进化、形成和被当地地球化学环境塑造的框架。然而，这些微米级微生物的代谢活动与由此产生的地球化学特征（通常以大约厘米尺度分辨率采样）之间的联系仍然难以捉摸，这在很大程度上是因为难以提取足够的材料用于小尺度（~1-100微米）的地球化学分析。然而，正是这种精细尺度的地球化学变化直接影响着生物地球化学活动。这项研究利用了分析技术的最新进展，允许在小至~1-10微米的空间分辨率下进行地球化学和稳定同位素测量。样品来自地中海的浅海热液系统，在那里，以前已经发现了不同的硫循环，陡峭的氧化还原梯度使得在广泛的地球化学环境中进行微米尺度测量成为可能。此外，20多年的观测记录允许将结果放入丰富的地球化学背景中。目标是生成浅海热液系统中硫循环的无与伦比的高分辨率地球化学和同位素表征，并使用所得数据计算各种生物地球化学反应的热力学驱动因素。这些数据还将有助于评估硫生物地球化学循环过程中环境地球化学对同位素分异的作用，并将结果应用于理解海洋沉积物中硫物种同位素组成随时间的变化，因为硫同位素是重建地球历史上古环境条件的主要手段之一。这项工作的更广泛的影响包括本科生和研究生在实地和实验室的培训。不同实验室的交叉训练也将加深研究与教育的融合。该项目还涉及与西西里和德国科学家的国际合作。