Sustained plankton blooms under open chaotic flows

We consider a predator-prey model of planktonic population dynamics,
of excitable character, living in an open and chaotic fluid flow, i.e.,
a state of fluid motion in which fluid trajectories are unbounded but a
chaotic region exists that is restricted to a localized area. Despite that excitability is a transient
phenomenon and that fluid trajectories are continuously
leaving the system, there is a regime of parameters where
the excitation remains permanently in the system, given rise
to a persistent plankton bloom. This regime is reached when the time scales associated
to fluid stirring become slower than the ones associated to biological growth.