Low-Reynolds-number swimming at pycnoclines
Low-Reynolds-number swimming at pycnoclines
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DOI：
10.1073/pnas.1116210109
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发表时间：
2012-03-06
影响因子：
11.1
通讯作者：
Ardekani, Arezoo M.
中科院分区：
文献类型：
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作者：
Doostmohammadi, Amin;Stocker, Roman;Ardekani, Arezoo M.
微生物在水生态系统的营养动力学和生态地球化学中起着关键作用。它们的浓度和活动往往在局部热点达到峰值，其中一个重要的例子是密度线，由于温度或盐度的梯度，水密度随着深度急剧增加。在pycobacterium线生物体暴露于不同的环境条件相比，散装水柱，包括减少湍流，缓慢的质量转移，高颗粒和捕食者浓度。在这里，我们表明，在一个更基本的水平，密度分层本身可以影响微生物生态在pycobacterium线，淬火的流量签名，增加能量消耗，并扼杀营养吸收的能动生物。我们证明了这一点，通过一个典型的低雷诺数游泳，“蠕动。“我们确定理查森数-浮力与粘性力的比值-作为量化分层效应的基本参数。这些结果表明，浮力对低雷诺数游泳有意想不到的影响，可能会影响到生活在海洋和湖泊中的浮游生物。
Microorganisms play pivotal functions in the trophic dynamics and biogeochemistry of aquatic ecosystems. Their concentrations and activities often peak at localized hotspots, an important example of which are pycnoclines, where water density increases sharply with depth due to gradients in temperature or salinity. At pycnoclines organisms are exposed to different environmental conditions compared to the bulk water column, including reduced turbulence, slow mass transfer, and high particle and predator concentrations. Here we show that, at an even more fundamental level, the density stratification itself can affect microbial ecology at pycnoclines, by quenching the flow signature, increasing the energetic expenditure, and stifling the nutrient uptake of motile organisms. We demonstrate this through numerical simulations of an archetypal low-Reynolds-number swimmer, the "squirmer." We identify the Richardson number-the ratio of buoyancy forces to viscous forces-as the fundamental parameter that quantifies the effects of stratification. These results demonstrate an unexpected effect of buoyancy on low-Reynolds-number swimming, potentially affecting a broad range of abundant organisms living at pycnoclines in oceans and lakes.