A general theoretical approach to the study of advective effects on biological oceanographic dynamics is formulated and some simple examples are presented. The theory of characteristics provides a model which rigorously combines aspects of local biological dynamics with consideration of fluid particle flow along Lagrangian trajectories. A local kinematical analysis is carried out for gradients both of velocity and of biological state variables. This is followed by a study of the effects of a stretching deformation, which contains a frontogenetic effect, on one‐ to three‐component biological systems. Problems include the approach to local biological equilibria and the stabilities of the equilibrium states; the competition between biological and advective equilibria; and nonlinear grazing processes and nutrient utilization.