Predation may defeat spatial spread of infection

A model of a phytoplankton-zooplankton prey-predator system with viral infection of phytoplankton is investigated. Virus particles ($V$) are taken into account by an explicit equation. Phytoplankton is split into a susceptible ($S$) and an infected ($I$) class. A lytic infection is considered, thus, infected phytoplankton cells stop reproducing as soon as the infection starts and die at an increased mortality rate. Zooplankton ($Z$) is grazing on both susceptible and infected phytoplankton following a Holling-type II functional response. After the local dynamics of the $V-S-I-Z$ system is analysed, numerical solutions of a stochastic reaction-diffusion model of the four species are presented. These show a spatial competition between zooplankton and viruses, although these two species are not explicitely coupled by the model equations.