The ocean is characterized by a high degree of turbulence with energetic eddies interacting together. In surface layers, observations and modeling studies reveal that mesoscale and submesoscale dynamics associated with the mixed layer dynamics strongly constrain the distribution of phytoplankton species. The aim of this PhD thesis is to carry out a numerical process study in order to rationalize the effect of mesoscale and submesoscale turbulence firstly, and of vertical mixing secondly, on phytoplankton diversity. The analytical study of the intrinsic dynamics of a simple ecosystem model with two phytoplankton species allowed us to determine the non-linear equilibria and their stability in the parameter space thanks to the dynamical system...