title: Entrainment dominates the interaction of microalgae with micron-sized objects.
abstract: The incessant activity of swimming microorganisms has a direct physical effect on surrounding microscopic objects, leading to enhanced diffusion far beyond the level of Brownian motion with possible influences on the spatial distribution of non-motile planktonic species and particulate drifters. Here we study in detail the effect of eukaryotic flagellates, represented by the green microalga Chlamydomonas reinhardtii, on microparticles. Macro- and microscopic experiments reveal that microorganism-colloid interactions are dominated by rare close encounters leading to large displacements through direct entrainment. Simulations and theoretical modelling show that the ensuing particle dynamics can be understood in terms of a simple jump-diffusion process, combining standard diffusion with Poisson-distributed jumps. This heterogeneous dynamics is likely to depend on generic features of the near-field of swimming microorganisms with front-mounted flagella.
authors.affiliation: Physics Department, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Jeanneret
authors.affiliation: Department of Mathematics, University of York, Heslington, York YO10 5DD, UK.
authors.forename: Dmitri O
authors.initials: DO
authors.lastname: Pushkin
authors.affiliation: Physics Department, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
authors.forename: Vasily
authors.initials: V
authors.lastname: Kantsler
authors.affiliation: Physics Department, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
authors.forename: Marco
authors.initials: M
authors.lastname: Polin
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000502:physiology*; D003198:Computer Simulation; D004058:Diffusion; D058086:Microalgae / Q000502:physiology*; D008962:Models, Theoretical; D009716:Numerical Analysis, Computer-Assisted; D010316:Particle Size; D011336:Probability; D013535:Suspensions; D013550:Swimming
chemical_list: D013535:Suspensions