Dynamics of enhanced tracer diffusion in suspensions of swimming eukaryotic microorganisms

Phys Rev Lett. 2009 Nov 6;103(19):198103. doi: 10.1103/PhysRevLett.103.198103. Epub 2009 Nov 5.


In contexts such as suspension feeding in marine ecologies there is an interplay between brownian motion of nonmotile particles and their advection by flows from swimming microorganisms. As a laboratory realization, we study passive tracers in suspensions of eukaryotic swimmers, the alga Chlamydomonas reinhardtii. While the cells behave ballistically over short intervals, the tracers behave diffusively, with a time-dependent but self-similar probability distribution function of displacements consisting of a gaussian core and robust exponential tails. We emphasize the role of flagellar beating in creating oscillatory flows that exceed brownian motion far from each swimmer.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chlamydomonas reinhardtii / cytology
  • Chlamydomonas reinhardtii / physiology*
  • Diffusion
  • Movement / physiology*
  • Probability
  • Suspensions
  • Swimming


  • Suspensions