Nonlinear Phototaxis and Instabilities in Suspensions of Light-Seeking Algae

The mechanism by which living organisms seek optimal light conditions—phototaxis—is a fundamental process for motile photosynthetic microbes. It is involved in a broad array of natural processes and applications from bloom formation to the production of high-value chemicals in photobioreactors. Here, we show that a population of the model alga Chlamydomonas reinhardtii exhibits a highly sensitive nonlinear response to light and demonstrate that the self-organization of cells in a heterogeneous environment becomes unstable as the result of a coupling between bioconvective flows and phototaxis.Received 19 January 2022Accepted 23 March 2022DOI:https://doi.org/10.1103/PhysRevLett.128.258101© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective behaviorEmergence of patternsFlow instabilitySelf-organizationSwimmingPhysical SystemsMicroswimmersBiological PhysicsFluid DynamicsNonlinear Dynamics