物理学家查尔斯·达尔文爵士是进化论创始人查尔斯·达尔文的孙子，他的一项被人遗忘的贡献解决了关于海洋混合的一个长期争论。他在1953年提出，游泳的动物也许对海洋中水的混合有相当大贡献。今天，关于海洋中由生物造成的海水混合的争论集中在对动物尾流扰动与海洋扰动的对比上。“达尔文式”混合是不同的，它是当在一种流体中运动的一个固态物体使其周围的一部分流体运动起来、并沿该物体传播时发生的。
加州理工学院的Kakani Katija 和John Dabiri利用对在一个偏僻海岛湖泊中游动的水母所做的现场测定、并结合一个新的理论模型发现，活生物通过这一机制对海洋混合的贡献是相当大。
研究人员利用小型水母进行实验。他们在水中放置团状染料，然后观测水母从中游过时染料的分布情况。结果发现，水母游过的路径上出现一长条染料“尾巴”，其中90％都是由于“达尔文机制”的作用。
研究人员说，一个小型海洋生物只要游出几个身长的距离，就会带动相当于自身4倍体积的液体。由于海洋中存在大量的小型生物，它们通过“达尔文机制”而产生的能量非常可观，与风和潮汐的作用在同一个数量级上。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 460, 624-626 (30 July 2009) | doi:10.1038/nature08207
A viscosity-enhanced mechanism for biogenic ocean mixing
Kakani Katija1 & John O. Dabiri1,2
1 Bioengineering,
2 Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, California 91125, USA
Recent observations of biologically generated turbulence in the ocean have led to conflicting conclusions regarding the significance of the contribution of animal swimming to ocean mixing. Measurements indicate elevated turbulent dissipation—comparable with levels caused by winds and tides—in the vicinity of large populations of planktonic animals swimming together1. However, it has also been noted that elevated turbulent dissipation is by itself insufficient proof of substantial biogenic mixing, because much of the turbulent kinetic energy of small animals is injected below the Ozmidov buoyancy length scale, where it is primarily dissipated as heat by the fluid viscosity before it can affect ocean mixing2. Ongoing debate regarding biogenic mixing has focused on comparisons between animal wake turbulence and ocean turbulence3, 4. Here, we show that a second, previously neglected mechanism of fluid mixing—first described over 50 years ago by Charles Darwin5— is the dominant mechanism of mixing by swimming animals. The efficiency of mixing by Darwin's mechanism is dependent on animal shape rather than fluid length scale and, unlike turbulent wake mixing, is enhanced by fluid viscosity. Therefore, it provides a means of biogenic mixing that can be equally effective in small zooplankton and large mammals. A theoretical model for the relative contributions of Darwinian mixing and turbulent wake mixing is created and validated by in situ field measurements of swimming jellyfish using a newly developed scuba-based laser velocimetry device6. Extrapolation of these results to other animals is straightforward given knowledge of the animal shape and orientation during vertical migration. On the basis of calculations of a broad range of aquatic animal species, we conclude that biogenic mixing via Darwin's mechanism can be a significant contributor to ocean mixing and nutrient transport.
