A massive formation of stable sea foam is regularly observed on certain coastlines. These naturally occurring foams are associated with a loss of phytoplankton biomass and biodiversity in the seawater. We are investigating whether the phytoplankton advected into the foam during its formation remains trapped in the complex network of internal channels in the foam.

In this talk, I will discuss the remarkable stability of these marine foams. I will also present experiments carried out in the laboratory to study the retention in a liquid foam of a model phytoplankton organism: the unicellular alga Chlamydomonas reinhardtii(CR), which is bi-flagellate and therefore motile. We measured the escape dynamics of CR cells from the foam. A comparison between live and dead cells shows that live CR cells tend to be retained in the foam. Finally, I will discuss the microscopic mechanisms that can lead to this entrapment, which raises the question of the transport of microswimmers in confined and environments under flow.

Florence Elias is a soft matter physicist, professor at Université Paris Cité, France, in the laboratory `Physics and Mechanics of Heterogeneous Matter’ (PMMH). In the past, she has studied many different aspects of the physics of liquid foams, including magnetic liquid foams, foam rheology and the propagation of vibration and acoustic waves in liquid foams. 

Her recent interests turned into marine foams. She seeks to understand the consequences of foam production for the local ecosystem, as well as the formation and unusual persistence of marine foam, when foam production is attributed to phytoplankton algae. Generally speaking, she is interested in describing the interactions between marine micro-organisms and their environment, using the tools of the physics and physical chemistry of soft matter.