Francesca Tesser


Population dynamics under flow


Simulations and experiments on populations of organisms living in aquatic environments and growing under flow conditions.


Ocean, rivers and lakes are natural environments for many living organisms. In these ecosystems they reproduce, compete for food, swim and die. The presence of a flow can have a strong effect on their dynamics both at individual and population scales. The dynamics of these systems are complicated because both transport and growth play a role. We are mainly interested in a population of individuals expanding in new territories and how the propagation speed is changed by the flow. Another question is how different species compete in such environments and, for example, how the extinction probability depends on the fluid dynamics. Population dynamics can be studied with numerical models but also experiments are performed with bacteria inside microfluidic devices. Bacteria are injected in micro-channels and observed for many days using microscopy equipment. We investigate how they colonize the channels and the way the colony propagates both upstream and downstream under flow. In order to measure these phenomena, the bacteria are modified and made fluorescent. It is possible to modify them in various ways so that they can be detected using different optical filters since they emit different colors. In this way also the competition between different growing species can be measured in space and time.