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

合作研究：颗粒解聚在海洋地球化学通量预测中的重要性颗粒沉降是沃茨中物质到达深海的主要途径之一。公海中的颗粒物质主要由浮游生物和其他生物碎屑的有机物质组成，这些物质很容易聚集成大的絮团。物理、化学和生物过程的结合使这些絮凝物在沉降时发生变化，在整个水柱中重新分配物质，并可能将碳等元素封存在深海中。这些转变的影响受到这些絮体下沉速度的影响，较大和较密集的颗粒比较小，较不密集的颗粒沉降得更快。当今海洋学家面临的关键问题之一是什么控制颗粒沉降速度（例如，颗粒大小，形状和密度）。有相当多的证据表明，颗粒在沉降时容易破碎，降低了它们的平均尺寸和沉降速度，但尚不清楚是什么条件导致这些解聚事件。这项工作将在实验室和海上测量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传输的重要性。这项工作将在宾夕法尼亚州立大学与格鲁吉亚大学合作进行，目的是发展供海洋学界使用的未来海洋微粒分解模型，这项研究将在确定分解对海洋中微粒物质垂直迁移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造成的流体力而导致的海洋有机聚集体的分解。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解聚。这些聚集体的大小，形状和结构之前和之后的分裂将使用高速可视化和全息成像进行量化。除了实验室测量外，还将在春季浮游植物大量繁殖期间在北大西洋建造和部署一个可部署的仪器，该仪器可以就地破坏颗粒并测量其大小和形状。将收集作为水柱深度函数的颗粒浓度、破碎特性、有机物含量和环境湍流的详细测量结果。这项工作将代表首次研究海洋骨料破碎原位。具体而言，该项目将澄清：（1）在什么条件下分解是重要的，（2）不同类型的天然海洋聚集体有多强，以及它们的强度如何随大小，成分和形态而变化，以及（3）聚集体的大小，成分和结构如何影响其分解质量的分布。该项目将促进一名博士生的职业生涯，并吸引众多海洋科学领域的本科研究人员参与。该奖项反映了NSF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.