Swimming Behavior and Chemosensory Responses in the Protistan Microzooplankton as a Function of the Hydrodynamic Regime

Theory suggests that, in still water, many protistan grazers should search for their food using a random search approximated by a type of random walk termed the Levy walk, with Levy parameter less than 1. The distribution of walk lengths in a Levy walk is flatter than in the more well-known normally distributed case. In turbulent water, by contrast, the Kolmogorov dimensional argument regarding energy flow suggests that the kinetic details of swimming behavior are essentially irrelevant on the protistan scale, since any random walk would be dominated by the turbulent diffusion of the medium. We also suggestthat behavioral responses to chemical gradients emanating from prey would be most useful to microzooplankton when feeding in still water, and less useful in a turbulent regime.