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SWIMMING PHYTOPLANKTON IN A TURBULENT ENVIRONMENT

在湍流环境中游泳的浮游植物

基本信息

批准号：
EP/E002358/1
负责人：
Rachel Bearon
金额：
$ 16.9万
依托单位：
University of Liverpool
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE002358%2F1
关键词：
SWIMMING PHYTOPLANKTON TURBULENT ENVIRONMENT

项目摘要

Swimming micro-organisms in fluid environments are ubiquitous and diverse. For example, sperm beat their long whiplike tails, travelling long distances to find an egg, and pathogenic bacteria can move into the bloodstream, causing diseases such as typhoid fever. This project will develop mathematical models to describe the distribution of micro-organisms in fluid environments, with a specific focus on swimming phytoplankton in turbulent flow. Understanding the spatial-temporal dynamics of phytoplankton is a most timely research question. For example, phytoplankton are critical players in climate change: phytoplankton fix carbon during photosynthesis, and when they die can sink to the ocean floor, acting as a one-way path for atmospheric carbon dioxide. Also, certain species of phytoplankton can form harmful blooms, or `red tides'. These blooms can be detrimental, or even fatal, to human health, and can cause significant financial losses, for example to aquaculturists and the tourism business. Micro-organisms are frequently distributed in patchy structures, for example blooms of algae appear in surface waters ('red tides'), and bacteria aggregate on tasty sinking aggregates called marine snow. The interaction between a local population and its environment will clearly depend on how the population is distributed in the environment. For example, algal cells that are concentrated near the surface may undergo photosynthesis more efficiently, and thus grow more rapidly, than cells which are well mixed throughout the water column. Developing predictive models to determine the distribution of microplankton is therefore critical for understanding aquatic ecosystems. This project will predict the spatial distribution of swimming phytoplankton in environmentally relevant flow fields. At the small scale experienced by microplankton, the fluid environment is highly dominated by viscous forces. Despite living in a turbulent fluid environment with waves crashing and winds roaring, these cells only see rather simple shearing fluid motions. How do these motions affect their swimming? Will it hamper their ability to swim in their chosen direction? Will it be so strong as to cause them to stop swimming? Clearly it will depend on how energetic the flow is, which in turn will depend on how energetic the physical forcing (e.g. wind) is. In addition to the shearing motion that individual cells see, organisms are also transported by larger scale fluid motions. Will these flows mix cells so vigorously that all swimming efforts are effectively wasted? Or will the flow fields interact with the swimming, for example creating patches of cells at fluid convergence zones? To predict how swimming microplankton are distributed in a turbulent environment, we will: 1)Develop a mathematical model that describes how a population of swimming cells is spatially distributed in simple flow fields. This model will be computationally faster for than numerically simulating large numbers of swimming phytoplankton, and thus will be useful in computationally intense oceanographic simulations. Included in this model will be the results of an experimental component of the project which will quantify the swimming behaviour of example algal species in fluid flow.2)Develop an appropriate numerical model for turbulent flow fields experienced by phytoplankton. This will describe the large-scale environmentally relevant flow fields, and yet also describe the flow field experienced at the small scale of individual cells.3)Combine the results of I and II to model swimming phytoplankton in turbulent flow fields.

在流体环境中游泳的微生物是普遍存在的和多样的。例如，精子拍打着它们长长的鞭子般的尾巴，长途跋涉寻找卵子，致病细菌可以进入血液，引起伤寒等疾病。该项目将开发数学模型，以描述微生物在流体环境中的分布，特别侧重于湍流中的浮游植物。了解浮游植物的时空动态是一个非常及时的研究问题。例如，浮游植物是气候变化的关键参与者：浮游植物在光合作用过程中固定碳，当它们死亡时可以沉入海底，成为大气二氧化碳的单向通道。此外，某些种类的浮游植物可以形成有害的水华，或“赤潮”。这些水华可能对人类健康有害，甚至致命，并可能给水产养殖者和旅游业等造成重大经济损失。微生物通常以斑块状结构分布，例如，表面沃茨中出现大量藻类（“赤潮”），细菌聚集在称为海洋雪的美味下沉聚集体上。当地人口与其环境之间的相互作用显然取决于人口在环境中的分布情况。例如，集中在水面附近的藻类细胞可以更有效地进行光合作用，因此比在整个水柱中充分混合的细胞生长得更快。因此，开发预测模型来确定微型浮游生物的分布对于理解水生生态系统至关重要。这个项目将预测浮游植物在环境相关流场中的空间分布。在微型浮游生物经历的小尺度下，流体环境高度受粘性力支配。尽管生活在波涛汹涌的流体环境中，这些细胞只能看到相当简单的剪切流体运动。这些动作是如何影响它们的游泳的？它会妨碍他们朝自己选择的方向游泳吗？它会不会太强，导致他们停止游泳？显然，这将取决于流动的能量有多大，而流动的能量又取决于物理强迫（例如风）的能量有多大。除了单个细胞看到的剪切运动之外，生物体还通过更大规模的流体运动进行运输。这些水流是否会如此剧烈地混合细胞，以至于所有的游泳努力都被有效地浪费了？或者流场会与游泳相互作用，例如在流体会聚区产生细胞斑块？为了预测微型浮游生物在湍流环境中的分布，我们将：1）建立一个数学模型，描述一群游泳细胞在简单流场中的空间分布。这个模型将是计算速度比数值模拟大量的浮游植物，因此将是有用的计算密集的海洋模拟。该模型将包括该项目的实验部分的结果，该部分将量化流体流动中示例藻类物种的游泳行为。2）为浮游植物经历的湍流场开发适当的数值模型。这将描述大规模的环境相关的流场，但也描述了在小规模的单个细胞经历的流场。3）联合收割机的结果I和II模拟游泳浮游植物在湍流场。