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

合作研究：颗粒解聚对生物地球化学通量预测的重要性颗粒沉降是表层水中物质到达深海的主要途径之一。公海中的颗粒物主要由浮游生物和其他生物碎屑中的有机物质组成，这些物质很容易聚集成大的絮状物。物理、化学和生物过程的组合在这些絮体沉淀时改变了它们，在整个水柱中重新分配材料，并可能将碳等元素隔离在深海中。这些变化的影响受这些絮体的下沉速度影响，较大和密度较大的颗粒比较小、密度较低的颗粒沉降得更快。当今海洋学家面临的关键问题之一是什么控制颗粒的沉降速度(例如，颗粒的大小、形状和密度)。有相当多的证据表明，粒子在沉降时很容易解体，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解聚事件。这项工作将在实验室和海上测量有机沉淀物颗粒的破碎特性，以量化这些破碎过程相对于颗粒传输的重要性。这项工作将由宾夕法尼亚州立大学与佐治亚大学合作完成，目标是开发供海洋界使用的未来海洋颗粒解聚模型。这项研究将在确定解聚对海洋中颗粒物垂直运输的重要性方面发挥重要作用。该项目将量化由于湍流或游动生物体引起的流体力导致的有机海洋聚集体的分解。浮游植物将在实验室培养并形成聚集体，然后使用校准的湍流进行解体。这些聚集体在破裂前后的大小、形状和结构将使用高速可视化和全息成像进行量化。除了实验室测量，还将在浮游植物春季繁殖期间在北大西洋建造和部署一台可在现场破坏颗粒并测量其大小和形状的可部署仪器。将收集颗粒浓度、分解特性、有机含量和环境湍流随水柱深度变化的详细测量数据。这项工作将是首次对海洋团聚体的现场破碎进行研究。具体地说，该项目将阐明：(1)在什么条件下解聚是重要的；(2)不同类型的天然海洋聚集体的强度有多大，它们的强度如何随着大小、组成和形态的变化而变化；(3)聚集体的大小、组成和结构如何影响其解体质量的分布。该项目将促进博士生的职业生涯，并使众多本科生研究人员参与到海洋科学领域。该奖项反映了NSF的法定使命，并通过使用基金会的学术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.