Virus-Induced Phytoplankton Coexistence: A Kill-the-Winner Reaction-Diffusion Chemostat Model

Phytoplankton coexistence is fundamental to the sustenance of plankton biodiversity. A reaction-diffusion chemostat model is developed to investigate the dual dynamics of nutrient competition between two phytoplankton species (A and B) and virus transmission within the competitively dominant phytoplankton B. A novel aspect of this model is that it provides an effective representation for the kill-the-winner mechanism. Several critical ecological indices for phytoplankton invasion, coexistence, and virus transmission are given by analyzing steady-state solutions and uniform persistence of the model. The results from both theoretical analysis and numerical simulations reveal that viral infection can effectively regulate the dominance of a superior competitor. This finding shows that virus-induced phytoplankton coexistence successfully validates the kill-the-winner theoretical framework. Furthermore, spatial factors drive increased complexity in model dynamics, thereby influencing the conditions for phytoplankton coexistence and the patterns of viral spread.