Effect of Mineral Ballast and Particle Sinking Velocity on Organic Carbon Export and Remineralization

下沉的颗粒物是将碳从海面输送到海洋内部的主要工具。在向海底转移的过程中，大部分(通常为90%)颗粒有机碳(POC)以无机形式返回并重新分布在水柱中。这种再分配决定了溶解二氧化碳的深度分布，包括其在表层混合层中的浓度，从而决定了海洋从大气中吸收二氧化碳的速率。最近的建模研究对POC轮廓形状的机制有了新的了解。看来矿物压舱物(硅酸盐、碳酸盐和粉尘)的存在可能是导致POC向海底输送的大部分差异的原因。因此，能够预测颗粒下降时压舱物的形成和随后的溶解，对于定量和机械地预测碳固定对全球气候变化的影响可能是至关重要的。在该项目中，纽约州立大学石溪分校、斯基德韦海洋研究所和华盛顿大学的美国研究人员将继续与法国和西班牙同事合作，对不同压舱物类型及其相关有机物和放射性同位素进行多示踪研究。该研究战略汇集了几个学科的力量：(1)有机地球化学，用于确定受保护和未受保护形式的有机质的特征并确定其退化状态；(2)放射化学，用于评估颗粒动力学和迁移所涉及的过程和时间尺度；(3)浮游动物生态学，用于评估放射性同位素分配和有机生物标志物的变化；(4)微生物学，用于有机质分解的作用；(5)建模和统计分析，以提供从光层到海底通量的基于过程的模型。研究小组现在希望通过地中海和加那利群岛附近的大西洋的水中深度“黄昏带”解决通量、有机质和矿物压载成分以及再矿化长度尺度的变化。更广泛的影响：我们的项目应该有助于更好地从机制上理解全球碳循环。如果能够对海洋对二氧化碳水平上升的反应有更深入的了解，那么就有可能在政治选择之间做出更合理的选择。该项目还为培训海洋科学方面的研究生和博士后学者提供了一个重要组成部分。此外，这项研究工作将促进国际合作，因为它高度依赖美国海洋学家与原子能机构海洋环境实验室(摩纳哥)、国家海洋研究中心海洋微生物学实验室(马赛)和巴塞罗那自治大学的同事之间的协作联系。

ABSTRACTOCE-0424845Sinking particulate matter is the major vehicle for exporting carbon from the sea surface to the ocean interior. During its transit towards the sea floor, most (usually 90%) of particulate organic carbon (POC) is returned to inorganic form and redistributed in the water column. This redistribution determines the depth profile of dissolved CO2, including its concentration in the surface mixed layer, and hence the rate at which the ocean can absorb CO2 from the atmosphere. Recent modeling studies have shed new light on the mechanisms that are responsible for the shapes of POC profiles. It appears that the presence of mineral ballasts (silicates, carbonates, and dust) may account for most of the variability in POC delivery to the sea floor. The ability to predict the formation and subsequent dissolution of ballasts as particles descend may therefore be critical to predicting quantitatively and mechanistically the global implications of carbon fixation for global climate change. In this project, U.S. researchers at the State University of New York at Stony Brook, the Skidaway Institute of Oceanography, and the University of Washington will continue their work with French and Spanish colleagues on a multi-tracer study of different ballast types, along with their associated organic matter and radioisotopes. The research strategy brings together the power of several disciplines: (i) organic geochemistry for characterizing organic matter in protected and unprotected forms and determining its degradation state; (ii) radiochemistry for assessing processes and time-scales involved in particle dynamics and transport; (iii) zooplankton ecology for assessing radioisotope partitioning and organic biomarker alteration; (iv) microbiology for its role in organic matter decomposition, and (v) modeling and statistical analysis to provide a process-based model of flux from the photic zone to the sea floor. The research team now expects to resolve changes in flux, organic matter and mineral ballast composition, and remineralization length scale through the mid-water depth "twilight zone" of the Mediterranean Sea and possibly the Atlantic Ocean near the Canary Islands.Broader impacts: Our project should contribute to a better mechanistic understanding of the global carbon cycle. If a more sophisticated understanding of the ocean's response to increased levels of carbon dioxide can be developed, then more reasonable choices between political alternatives are possible. The project also features a substantial component for training of graduate students and postdoctoral scholars in the marine sciences. Additionally, the research effort will foster international cooperation, since it is highly dependent on collaborative linkages between American oceanographers and colleagues at the IAEA Marine Environment Laboratory (Monaco), the CNRS Laboratory of Marine Microbiology (Marseille), and the Autonomous University of Barcelona.