Collaborative Research: The importance of particle disaggregation on biogeochemical flux predictions

合作研究：颗粒分解在生物地球化学通量预测中的重要性颗粒沉降是表层水体物质到达深海的主要途径之一。开放海洋中的微粒物质主要由浮游生物和其他生物碎屑的有机物质组成，它们很容易聚集形成大的絮凝体。在沉淀过程中，物理、化学和生物过程的结合改变了这些絮凝体，在整个水柱中重新分配物质，并可能在深海中隔离碳等元素。这些转变的影响受絮凝体沉降速度的影响，较大且密度较大的颗粒沉降速度比较小且密度较小的颗粒沉降速度快。今天海洋学家面临的一个关键问题是什么控制着颗粒沉降速度（例如，颗粒的大小、形状和密度）。有相当多的证据表明，粒子在沉降过程中很容易破裂，从而降低了它们的平均大小和沉降速度，但目前还不清楚是什么条件导致了这些分解事件。这项工作将测量实验室和海上有机沉降颗粒的破碎特性，以量化这些破碎过程相对于颗粒运输的重要性。这项工作将在宾夕法尼亚州立大学与佐治亚大学合作完成，目标是开发未来海洋粒子分解模型，供海洋学界使用。这一研究将对确定海洋颗粒物垂直运移中分解作用的重要性起到重要作用。该项目将量化由于湍流或游动生物引起的流体力而导致的有机海洋聚集体的分解。浮游植物将在实验室中培养并形成聚集体，然后使用校准的湍流进行分解。这些聚集体在破裂前后的大小、形状和结构将通过高速可视化和全息成像进行量化。除了实验室测量外，还将在北大西洋浮游植物春季繁盛期间建造一台可部署的仪器，该仪器可以在现场破坏颗粒并测量它们的大小和形状。将收集颗粒浓度、破碎特性、有机含量和环境湍流作为水柱深度函数的详细测量结果。这项工作将是第一次在现场研究海洋骨料破碎。具体而言，该项目将阐明：(1)在什么条件下分解是重要的；(2)不同类型的天然海洋团聚体的强度以及它们的强度如何随大小、组成和形态而变化；(3)团聚体的大小、组成和结构如何影响其破碎质量的分布。该项目将促进博士生的职业生涯，并吸引众多海洋科学领域的本科生研究人员。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Collaborative Research: The importance of particle disaggregation on biogeochemical flux predictionsParticle settling is one of the major ways that material in surface waters reaches the deep ocean. Particulate matter in the open ocean consists primarily of organic material from plankton and other biological detritus, which can readily aggregate to form large flocs. A combination of physical, chemical, and biological processes transforms these flocs as they settle, redistributing material throughout the water column and potentially sequestering elements such as carbon in the deep ocean. The impact of these transformations is affected by the sinking speed of these flocs, with larger and denser particles settling faster than smaller, less-dense ones. One of the key questions facing oceanographers today is what controls particle settling speed (for example, particle size, shape, and density). There is considerable evidence that particles readily break apart as they settle, decreasing their average size and settling speed, but it is not yet understood what conditions cause these disaggregation events. This work will measure the breakup characteristics of organic settling particles both in the laboratory and at sea to quantify the importance of these breakup processes relative to particle transport. The work will be done at the Pennsylvania State University in collaboration with the University of Georgia to target the development of future marine particle disaggregation models for use by the oceanographic community.This research will play an important role in determining the importance of disaggregation on the vertical transport of particulate matter in the ocean. The project will quantify the breakup of organic marine aggregates due to fluid forces caused by turbulence or swimming organisms. Phytoplankton will be cultured and formed into aggregates in the lab prior to disaggregation using calibrated turbulence. The size, shape, and structure of these aggregates before and after breakup will be quantified using high-speed visualization and holographic imaging. In addition to the laboratory measurements, a deployable instrument that can disrupt particles in-situ and measure their size and shape will be built and deployed in the North Atlantic during the spring bloom of phytoplankton. Detailed measurements of particle concentrations, breakup characteristics, organic content, and ambient turbulence as a function of depth in the water column will be collected. This work will represent the first study of marine aggregate breakup in-situ. Specifically, the project will clarify: (1) under what conditions disaggregation is important, (2) how strong different types of natural marine aggregates are and how their strength varies with size, composition, and morphology, and (3) how aggregate size, composition, and structure influences the distribution of its breakup mass. This project will advance the career of a doctoral student and engage numerous undergraduate researchers with the field of ocean science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.