桡足类在湍流中逃逸跳跃行为模型的相遇率
Copepods encounter rates from a model of escape jump behaviour in turbulence
摘要：
浮游桡足类研究的一个关键生态参数是它们的种间相遇率，这是由它们的行为驱动的，并受到周围环境湍流的强烈影响。桡足类运动的一个显着特点是他们能够执行快速位移，通常被称为跳跃，通过强大的游泳中风。这种反应与逃避由于捕食者或其他外部危险引起的流动扰动的行为有关。在本研究中，桡足类的遭遇率在一个发达的湍流强度与桡足类的栖息地发现一个数值研究。这是通过一个拉格朗日桡足类（LC）模型，模仿跳跃逃逸反应行为从本地化的高剪切速率波动的湍流。我们的分析表明，典型的感知半径为η的桡足类的遭遇率，其中η是湍流的耗散尺度，可以增加到一个因素~ 100相比，被动传输的流体示踪剂所经历的。此外，我们解决了在LC模型中引入连续跳跃之间的最小等待时间的影响。结果表明，如果时间超过湍流耗散时间尺度τ_η，则任何湍流速率增强都将丧失。由于在典型的海洋中η ~ 0.001m和τ_η ~ 1 s，这对由于纯机械诱导的逃逸反应而导致的惯性驱动的加速率的增强提供了严格的约束。
英文摘要：
A key ecological parameter for planktonic copepods studies is their interspecies encounter rate which is driven by their behaviour and is strongly influenced by turbulence of the surrounding environment. A distinctive feature of copepods motility is their ability to perform quick displacements, often dubbed jumps, by means of powerful swimming strokes. Such a reaction has been associated to an escape behaviour from flow disturbances due to predators or other external dangers. In the present study, the encounter rate of copepods in a developed turbulent flow with intensity comparable to the one found in copepods' habitat is numerically investigated. This is done by means of a Lagrangian copepod (LC) model that mimics the jump escape reaction behaviour from localised high-shear rate fluctuations in the turbulent flows. Our analysis shows that the encounter rate for copepods of typical perception radius of ~ η, where η is the dissipative scale of turbulence, can be increased by a factor up to ~ 100 compared to the one experienced by passively transported fluid tracers. Furthermore, we address the effect of introducing in the LC model a minimal waiting time between consecutive jumps. It is shown that any encounter-rate enhancement is lost if such time goes beyond the dissipative time-scale of turbulence, τ_η. Because typically in the ocean η ~ 0.001m and τ_η ~ 1s, this provides stringent constraints on the turbulent-driven enhancement of encounter-rate due to a purely mechanical induced escape reaction.
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