Phytoplankton Dynamics: from the Behavior of Cells to a Transport Equation

Abstract. We present models of the dynamics of phytoplankton aggregates. We start with an individual-based model in which aggregates can grow, divide, joint and move randomly. Passing to infinity with the number of individuals, we obtain a model which describes the space-size dis-tribution of aggregates. The density distribution function satisfies a non-linear transport equation, which contains terms responsible for the growth of phytoplankton aggregates, their fragmentation, coagulation, and diffusion. Key words: phytoplankton dynamics, formation of aggregates, coagulation, fragmentation, diffu-sion AMS subject classification: 47J35, 60K35, 92D40 1