Transport of plankton in the Benguela upwelling system We study the interplay of hydrodynamic transport and plankton dynamics in the Benguela upwelling system. We use a coupled system of oceanic flow and a simple biogeochemical model (NPZ type). For the oceanic flow we use two different velocity fields: a) one derived from altimetry data from satellite to study the surface dynamics, and b) from a 3D numerical model, which allows to study the vertical component. The calculation of unstable manifolds is used as a diagnostic of the transport properties of the velocity field. We study the effect of the horizontal transport and of the vertical component in the formation and dynamics of plankton structures.