What does it take for plankton to master stealthy swimming, and why are some breast stroke swimming plankton quiet swimmers? New study from Centre for Ocean Life, DTU Aqua addresses these questions using a simple model.
Plankton are microscopic organisms that inhabit the water masses of the oceans. They are faced with a dilemma: They need to swim to find food and mates, but by swimming they inevitably create flow disturbances that attract predators.
In a new study, Anders Andersen, DTU Physics and Thomas Kiørboe, DTU Aqua, Centre for Ocean Life, show that planktonic swimmers can reduce the flow disturbances that they create in the water around them, simply by appropriately arranging their propulsion apparatus.
In particular they explore a simple mathematical model of the water flow due to small breast stroke swimmers (see figure). The study finds that breast stroke swimming is a quiet swimming mode that causes significantly reduced flow disturbances in comparison with other types of swimming. Breast stroke swimming may thus be advantageous, and this might explain why it is very common in the world of the plankton.
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Planktonic breast stroke swimmers. (a) Chlamydomonas reinhardtii, a flagellate (image by courtesy of Knut Drescher), (b) Mesodinium rubrum, a ciliate, (c) a nauplius (juvenile) of Acartia tonsa, a copepod, and (d) Podon intermedius, a cladoceran.
The article in Physical Review E:
“Quiet swimming at low Reynolds number” by Anders Andersen, Navish Wadhwa, and Thomas Kiørboe.
Phys. Rev. E 91, 042712 – Published 24 April 2015
http://journals.aps.org/pre/abstract/10.1103/PhysRevE.91.042712