Séminaire de Ksenia Guseva (Univ. Vienna, AT)

Interplay between physical and biological processes in fluid flows: from chemotaxis of marine bacteria to algal bloom formation

Ksenia Guseva, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria

Biological processes taking place in the ocean are affected by physical processes that involve multiple spatial and temporal scales. In this talk I will highlight two theoretical and computational models that couple specific physical and biological processes in marine systems, corresponding, respectively, to the mesoscale currents (~10-100 km) affecting the occurrence of algal blooms, and to the smallest scale of the turbulent flow (< 1cm) affecting the motility of bacteria.
The larger scale the ocean's hydrodynamic flow is characterized by the presence of large eddies (vortices), which play a very important role in phytoplankton ecosystems. Another important large scale phenomenon is upwelling, which brings a load of nutrients to the surface, sometimes triggering algal blooms. We investigate the effect of intermittent upwelling on the biological community in the presence of large eddies formed in the wake of an island. We observe plankton blooms when nutrients are trapped by vortices, and analyse how this dynamics depends on the timing and intensity of upwelling events.
At a smaller scale the marine environment is characterized by a pronounced spatial heterogeneity. In these highly dynamic conditions, small microorganisms such as bacteria depend on efficient strategies to track sparse nutrient sources. I describe a simple theoretical model of the interplay of chemotaxis and different swimming patterns of bacteria in a fluid flow. With this model we investigate in particular the advantage of the run-reverse motility pattern, typical of marine bacteria, to track marine aggregates (food particles) advected by a flow field.

Enregistrement vidéo du séminaire : https://nextcloud.univ-lille.fr/index.php/s/ybTiiWi7exrM22A