In this paper, we propose a new model of spatio-temporal dynamics concerning the tritrophic reaction-diffusion system by introducing Phytoplankton and Zooplankton. We recall that the phytoplankton and zooplankton species are the basis of the marine food chain. There is prey in each marine tritrophic system. The main objective of this work is to control this species's biomass to ensure the system's sustainability. To achieve this, we determine an optimal control that minimizes the biomass of super predators.