Swimming Characteristics of Chlamydomonas reinhardtii

Swimming characteristics of phytoplankton are significant to understand the mechanisms underlying various ecological phenomena in waters, such as harmful algal blooms. Swimming characteristics of Chlamydomonas reinhardtii in still and flowing fluids were investigated by experiments and numerical simulations, respectively. Experimental results show that C. reinhardtii swims isotropically in the horizontal plane and prefers swimming upwards in the vertical direction. Typical values of three characteristic parameters are obtained for swimming of C. reinhardtii in the still water, including the mean swimming speed (106 mu m.s(-1)), the time scale for cells' reorientation (10.8 s) and the rotational diffusivity (0.05 rad(2).s(-1)). The relationship of the mean swimming velocity, translational diffusivity tensor and horizontal vorticity are also given by solving the Fokker-Planck equation. The monotonic and oscillatory asymptotic behaviors are found to exist in the cells' reorientation in the weak and strong vorticity fields, respectively.