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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Active Matter I (joint session DY/CPP/BP)

CPP 9.8: Vortrag

Montag, 12. März 2018, 12:00–12:15, BH-N 243

Emergence of phytoplankton patchiness at small scales in mild turbulence — Rebekka E. Breier, Cristian C. Lalescu, Michael Wilczek, and •Marco G. Mazza — Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen

Phytoplankton often encounter turbulence in their habitat. As most toxic phytoplankton species are motile, resolving the interplay of motility and turbulence has fundamental repercussions on our understanding of their own ecology and of the entire ecosystems they inhabit. The spatial distribution of motile phytoplankton cells exhibits patchiness at distances of decimeter to millimeter scale for numerous species with different motility strategies. The explanation of this general phenomenon remains challenging. Furthermore, hydrodynamic cell-cell interactions, which grow more relevant as the density in the patches increases, have been so far ignored. Here, we combine particle simulations and continuum theory to study the emergence of patchiness in motile microorganisms in three dimensions. By addressing the combined effect of turbulent flow conditions, and spatial correlations in the particle positions, we uncover a general mechanism: when motility allows cells to cross the fluid streamlines, the typical length scale associated to the small-scale turbulence selects a characteristic cell-cell interactions scale where strong patches form. Our results shed light on the dynamical characteristics necessary for the formation of patchiness, and complement current efforts to unravel planktonic ecological interactions.