Fig 6.
Effect of turbulence on the chemotaxis of marine microbes. Top row, a microscale nutrient patch is stretched, folded, and stirred by turbulence to create a tangled web of sheets and filaments as small as the Batchelor scale (30 to 300 μm). C denotes the nutrient concentration and is shown relative to the initial concentration C0. Bottom row, motile bacteria with a chemotactic velocity of 20 μm/s, initially distributed uniformly, accumulate within the nutrient sheets and filaments by chemotaxis, achieving a significant nutrient gain compared to nonmotile species. The characteristic time scale of this process, for a 2.5-mm patch in moderately strong turbulence (turbulent dissipation rate, 10−6 W/kg), is ∼1 min. The domain size is 5.65 cm. BM denotes the concentration of motile bacteria and is shown relative to the initial uniform concentration, BNM. (Reproduced from reference 190 with permission.)