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

减少的流入（即，通过深海和浅海热液系统进入海洋的海洋（缺氧）流体在确定海洋化学及其地质历史演变方面起着重要作用。 热液流体和上覆的凉爽和充分含氧的海水之间的界面具有强烈的热力学不平衡，驱动一系列生物地球化学反应，这反过来又进一步塑造了海洋化学。这些反应产生强烈的地球化学氧化还原梯度，从海洋水柱过渡到沉积物下面的沿着界面与还原热液流体。这些梯度提供了一个框架，微生物群落生活，进化，形状，并由当地的地球化学环境塑造。 然而，这些微米级微生物的代谢活动与所产生的地球化学特征（通常以大约厘米级分辨率采样）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了地球化学活动。 这项研究利用了分析技术的最新进展，这些技术允许以小至1-10微米的空间分辨率进行地球化学和稳定同位素测量。 样品来自地中海可访问的浅海热液系统，在那里以前已经确定了不同的硫循环和陡峭的氧化还原梯度，使微米尺度的测量有可能在广泛的地球化学环境中取样。 此外，20多年的观测记录使其结果能够纳入丰富的地球化学背景。 目标是产生一个无与伦比的高分辨率的地球化学和同位素表征的硫循环在浅海热液系统，并使用由此产生的数据来计算不同的地球化学反应的热力学驱动程序。 这些数据还将有助于评估硫地球化学循环过程中环境地球化学对同位素分馏的作用，并将结果应用于了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。 这项工作的更广泛影响包括在实地和实验室对本科生和研究生进行培训。 不同实验室的交叉培训也将深化研究与教育的融合。 该项目还涉及与西西里和德国科学家的国际合作。

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.