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

下沉颗粒物是从海面向海洋内部输出碳的主要载体。在向海底迁移的过程中，大多数（通常为90%）颗粒有机碳（POC）返回到无机形式并重新分布在水柱中。这种重新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剖面形状的机制有了新的认识。看来，矿物压舱物（硅酸盐、碳酸盐和粉尘）的存在可能是POC向海底输送的大部分变化的原因。因此，预测颗粒下降时压舱物的形成和随后溶解的能力对于定量和机械地预测碳固定对全球气候变化的全球影响至关重要。在这个项目中，纽约州立大学石溪分校、斯基德威海洋学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的同事合作，对不同类型的压载物及其相关的有机物质和放射性同位素进行多示踪剂研究。该研究战略汇集了几个学科的力量：(i)有机地球化学，用于表征受保护和不受保护形式的有机物并确定其降解状态；（ii）用于评估粒子动力学和输运过程和时间尺度的放射化学；（iii）用于评估放射性同位素分配和有机生物标志物变化的浮游动物生态学；（四）微生物学在有机物分解中的作用；（五）建模和统计分析，提供从光带到海底的通量的基于过程的模型。研究小组现在希望解决通量、有机物和矿物压载物组成的变化，以及通过地中海和加那利群岛附近的大西洋的中水深“暮光地带”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了解全球碳循环的机制。如果能对海洋对二氧化碳浓度上升的反应有更深入的了解，那么在各种政治选择之间就有可能做出更合理的选择。该项目还具有培训海洋科学研究生和博士后学者的重要组成部分。此外，这项研究工作将促进国际合作，因为它高度依赖于美国海洋学家与原子能机构海洋环境实验室（摩纳哥）、法国海洋研究中心海洋微生物实验室（马赛）和巴塞罗那自治大学的同事之间的合作联系。

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.