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小氧最小区域（OMZ）是重要的经济区域，在这里，营养丰富的水域向地面海洋的急剧上升的上升流动可维持高海洋初级生产，并且支持> 50％的全球渔业。由于气候变化，预测OMZ的垂直膨胀和强化是因为溶解在温暖的水中并增强海洋分层的原因是减少了海洋内部的氧气供应。 OMZ的这些变化将鱼类栖息地直接限制在表面，增加了过度捕获的风险，并可能导致沿海海洋生态系统的未来大规模灭绝。 OMZ的变异性也会影响向地表海洋和其支持的海洋碳循环的营养可用性，但是确切的机制尚未完全了解。了解养分供应和海洋生物群如何应对过去的OMZ强度变化将如何就海洋生物地球化学和碳周期如何响应未来的海洋脱氧。在这项拟议的研究中，我将使用两个新的代理，稳定的镉（CD）和钡（BA）同位素，从秘鲁OMZ到1）约束OMZ中影响表面海洋生产率和地下回忆性的过程，以及2）评估未来的脱氧能力如何影响全球碳循环。海水中溶解的CD和BA同位素都与生物过程和水质量混合密切相关。在海洋沉积物中，CD和BA同位素也受这些元素和沉积后成岩作用的身份降水的影响，而这些过程中同位素分馏的程度则很差。我将测量海水，海洋下沉颗粒物，沉积物和孔隙水的CD和BA同位素比，以限制其在不同的生物学，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同位素系统的分馏的来源和下沉，并评估沉积后成岩作用如何影响CD和BA同位素分馏。这项拟议工作的最终目标是开发沉积CD和BA同位素作为用于出口生产和回忆强度的过去变化的可靠代理。