Problems of Planktonic Navigation

Plankton face the challenging task of navigating oceanic turbulence using only hydrodynamic and chemical cues to escape predators or catch prey. This seminar focuses on one of such tasks: the problem of vertical navigation in turbulence, or how a microscopic swimmer can move upward or downward more efficiently by exploiting only local information on the flow.

I first present a theoretical model showing that an optimal swimming direction can be derived under locally steady flow conditions. Numerical simulations reveal that organisms following this strategy can surf on turbulence, achieving vertical speeds of twice their own swimming speed. Experiments with larval snails support this mechanism. I then discuss how reinforcement learning recovers similar strategies in complex flows and conclude by showing how flexible bodies can reproduce these behaviours by passively deforming in the flow.