Viscous constraints on zooplankton approach and interaction

在水中游泳的生物需要接近悬浮粒子来进行各种生命过程，如进食、交配、受精和寻找有利的栖息地。这项研究的重点是浮游生物，尽管它们体积小，但由于它们数量丰富，在海洋生态中发挥了巨大的作用。例如，浮游植物通过将阳光转化为有机物提供了食物网的基础，这些有机物主要通过以浮游植物为食的浮游动物向食物链的上游转移。浮游动物在微米到毫米尺度上的流体动力学主要是由粘度决定的，这严重限制了它们接近其他颗粒的能力。试图接近较小的食物颗粒变得困难，因为粘性流体往往会将食物颗粒推开。然而，浮游动物在交配时也会接近类似大小的颗粒，在卵子受精或探索新栖息地时也会接近较大的颗粒。这项研究的目的是了解粘性流体动力学对浮游生物接近悬浮粒子的一般限制，以及这些限制如何决定生物的形态和功能。研究结果将增加我们对浮游生物如何进食、繁殖和向新栖息地扩散的理解。该项目还将通过研究生和本科生的研究培训来加强工程教育，并将我们的研究成果传达给当地的高中生。虽然粘性流体动力学限制微生物推进和游动机制形式的方式得到了很好的赞赏，但本研究扩展了我们对粘性流体动力学含义的理解，包括对许多生命过程中与游泳一样或更重要的方法的限制。为了推断接近的流体动力约束如何决定生物形态和行为，该研究使用数值研究、流动可视化和动态缩放实验来研究一系列游泳者的几何形状、推进方法、目标颗粒大小和接近策略，以确定在粘性约束存在的情况下哪种方法可以实现接近。结果将用于分析文献中报道的各种类型生物方法的观察结果，以了解粘性约束何时决定这些生物的生物形式。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。

Organisms that swim in water need to approach suspended particles for a variety of life processes, such as feeding, mating, fertilization, and finding favorable habitats. This research focuses on plankton, which despite their small size play an outsize role in ocean ecology due to their numerical abundance. For example, phytoplankton provide the base of the food web by converting sunlight into organic matter, which is transferred further up to the food chain, primarily by zooplankton which eat the phytoplankton. Hydrodynamics at the micro- to millimeter scales of zooplankton is dominated by viscosity, and severely constrains their ability to approach other particles. Attempts to approach smaller food particles are made difficult by viscous flows that tend to push the food particle away. However, zooplankton also approach similar size particles during mating, as well as larger particles during egg fertilization or when exploring new habitats. The goal of the research is to understand what general constraints viscous hydrodynamics place on the approach of plankton to suspended particles and how those constraints determine biological form and function. The results will increase our understanding of how plankton eat, reproduce, and spread to new habitats. The project will also enhance engineering education through graduate and undergraduate research training, and an outreach program will communicate our research results to local high school students. While the way that viscous hydrodynamics constrains propulsion and the form of swimming mechanisms of microorganisms is well appreciated, this research extends our understanding of the implications of viscous hydrodynamics to include constraints on approach which is as or more important than swimming for many life processes. To deduce how hydrodynamic constraints on approach determine biological form and behavior, the research uses numerical studies, flow visualization, and dynamically scaled experiments to investigate a range of swimmer geometries, propulsion methods, target particle sizes, and approach strategies to identify which enable close approach in the presence of viscous constraints. The results will be used to analyze observations of approach of various types of organisms reported in the literature to understand when viscous constraints determine the biological form of those organisms.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.