Barium and cadmium stable isotopes as tracers for carbon export, remineralization strength and post-deposition diagenesis in the Peruvian oxygen minimum zone

钡和镉稳定同位素作为秘鲁最低氧带碳输出、再矿化强度和沉积后成岩作用的示踪剂

• 批准号: 432469432
• 负责人: Dr. Ruifang Xie, Ph.D.
• 金额: --
• 依托单位: Shanghai Jiao Tong University (SJTU)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/432469432?language=en
• 关键词: Barium; cadmium; stable; isotopes; tracers

Oxygen minimum zones (OMZs) associated with eastern boundary upwelling systems are important economic areas where intense upwelling of nutrient-rich waters to the surface ocean sustains high marine primary production and supports >50% global fisheries. Vertical expansion and intensification of OMZs is predicted as a consequence of climate change because less oxygen dissolves in warmer waters and strengthened ocean stratification reduces oxygen supply to the ocean interior. These changes of OMZs directly restrict fish habitats to the surface, increase the risk of over-fishing, and may lead to future mass extinctions in coastal marine ecosystems. Variabilities of OMZs will also affect nutrient availability to the surface ocean and the marine carbon cycle it supports, but the exact mechanisms are not fully understood. Understanding how nutrient supply and marine biota responded to past changes of OMZ intensities will provide important insights on how marine biogeochemical and carbon cycles respond to future ocean deoxygenation. In this proposed research, I will use two novel proxies, stable cadmium (Cd) and barium (Ba) isotopes, from the Peruvian OMZ to 1) constrain processes that affect surface ocean productivity and subsurface remineralization in OMZs, and 2) assess how future ocean deoxygenation may impact the global carbon cycle. Both dissolved Cd and Ba isotopes in seawater are tightly coupled to biological processes and water mass mixing. In marine sediments, Cd and Ba isotopes are also affected by authigenic precipitation of these elements and post-depositional diagenesis, whereas the extent of isotope fractionation among these processes are poorly quantified. I will measure Cd and Ba isotope ratios in seawater, marine sinking particulates, sediments and pore waters to constrain their isotope fractionation effects during different biological, chemical and physical processes. With these results, I will quantify the sources and sinks that fractionate both isotope systems in the modern ocean and assess how post-depositional diagenesis affects Cd and Ba isotope fractionation. The ultimate goal of this proposed work is to develop sedimentary Cd and Ba isotopes as reliable proxies for past changes in export production and remineralization strength.

与东部边界上升流系统相关的最低氧区 (OMZ) 是重要的经济区域，营养丰富的海水强烈上升至表层海洋，维持较高的海洋初级生产力，并支持超过 50% 的全球渔业。预计气候变化会导致 OMZ 的垂直扩张和强化，因为在温暖的水域中溶解的氧气较少，并且海洋层化的加强减少了对海洋内部的氧气供应。 OMZ的这些变化直接将鱼类栖息地限制在地表，增加了过度捕捞的风险，并可能导致未来沿海海洋生态系统的大规模灭绝。 OMZ 的变异性也会影响表层海洋的养分可用性及其支持的海洋碳循环，但确切的机制尚不完全清楚。了解养分供应和海洋生物群如何响应过去 OMZ 强度的变化将为海洋生物地球化学和碳循环如何响应未来海洋脱氧提供重要见解。在这项拟议的研究中，我将使用来自秘鲁 OMZ 的两种新型代理，即稳定镉 (Cd) 和钡 (Ba) 同位素，以 1) 限制影响 OMZ 中海洋表层生产力和地下再矿化的过程，以及 2) 评估未来如何海洋缺氧可能会影响全球碳循环。海水中溶解的镉和钡同位素都与生物过程和水团混合紧密耦合。在海洋沉积物中，Cd 和 Ba 同位素还受到这些元素的自生沉淀和沉积后成岩作用的影响，而这些过程中同位素分馏的程度却很难量化。我将测量海水、海洋下沉颗粒、沉积物和孔隙水中的镉和钡同位素比率，以限制它们在不同生物、化学和物理过程中的同位素分馏效应。通过这些结果，我将量化现代海洋中两种同位素系统的源和汇，并评估沉积后成岩作用如何影响 Cd 和 Ba 同位素分馏。这项工作的最终目标是开发沉积镉和钡同位素，作为过去出口产量和再矿化强度变化的可靠指标。