Plankton blooms and patchiness generated by heterogeneous physical environments

• We model the effects of microscopic turbulence on planktonic predator–prey systems.
• Turbulence changes the number and stability of stationary solutions.
• Spatial variability of turbulence causes traveling pulses of high plankton densities.
• We study the effect of space-dependent diffusivity on traveling pulses.

Microscopic turbulent motions of water have been shown to influence the dynamics of microscopic species living in that habitat. The number, stability, and excitability of stationary states in a predator–prey model of plankton species can therefore change when the strength of turbulent motions varies. In a spatial system these microscopic turbulent motions are naturally of different strength and form a heterogeneous physical environment. Spatially neighboring plankton communities with different physical conditions can impact each other due to diffusive coupling. We show that local variations in the physical conditions can influence the global system in form of propagating pulses of high population densities. For this we consider three different local predator–prey models with different local responses to variations in the physical environment. The degree of spatial heterogeneity can, depending on the model, promote or reduce the number of propagating pulses, which can be interpreted as patchy plankton distributions and recurrent blooms.