Abstract

Sailors have known for millennia that periodically the seas appear of unusual color and can even turn red. These large swaths of colors stretching for tens or hundreds of km are caused by countless microscopic organisms called phytoplankton. These are microscopic algae that use sunlight to produce energy. They are the base of the marine food chain, and produce 50% or more of the oxygen in the atmosphere. Phytoplankton often encounter turbulence in their habitat. 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. We combine particle simulations and continuum theory to study the emergence of patchiness in motile
microorganisms in three dimensions, by including hydrodynamic cell-cell interactions, which grow more relevant as the density in the patches increases. By addressing the combined effects of motility, cell-cell interaction and turbulent flow conditions, we uncover a general mechanism: the coupling of cell-cell interactions to the turbulent dynamics favors the formation of dense patches [1].

[1] R. E. Breier, et al., Proc. Natl. Acad. Sci. USA 115, 12112 (2018)

Bio

Dr. Mazza is a Lecturer at the Department of Mathematical Sciences of Loughborough University, where he joined the recently formed Interdisciplinary Centre for Mathematical Modelling. He studied theoretical physics at University of Catania, Italy. He received his PhD in physics from Boston University. He worked at TU Berlin for his postdoc, and then became Research Group Leader at the Max Planck Institute for Dynamics and Self-Organization, in Göttingen, Germany.

Coffee and nibbles at 13:35 !!