Predation may defeat spatial spread of infection

Area of Science:

• Marine ecology
• Microbial oceanography
• Mathematical biology

Background:

• Phytoplankton and zooplankton form a critical marine prey-predator system.
• Viral infections significantly impact phytoplankton populations, influencing marine food webs.
• Previous models often simplified or excluded viral dynamics and their spatial effects.

Purpose of the Study:

• To develop and analyze a mathematical model of a phytoplankton-zooplankton prey-predator system incorporating viral infection of phytoplankton.
• To investigate the dynamics of virus (V), susceptible phytoplankton (S), infected phytoplankton (I), and zooplankton (Z) populations.
• To explore the spatial interactions and competition between these populations using a stochastic reaction-diffusion model.

Main Methods:

• Development of a mathematical model including explicit equations for virus particles.
• Classification of phytoplankton into susceptible and infected classes with lytic infection dynamics.
• Analysis of local dynamics and numerical solutions of a stochastic reaction-diffusion model for the four-species system (V-S-I-Z).
• Inclusion of Holling-type II functional response for zooplankton grazing on both phytoplankton types.

Main Results:

• Analysis of the local dynamics of the V-S-I-Z system.
• Numerical simulations revealed spatial competition between zooplankton and viruses.
• Observed spatial competition despite the lack of direct coupling between zooplankton and viruses in the model equations.
• Viral infection leads to increased phytoplankton mortality and impacts zooplankton grazing dynamics.

Conclusions:

• Viral infection introduces complex dynamics into phytoplankton-zooplankton interactions.
• Spatial dynamics can lead to unexpected competition between non-directly interacting species like viruses and zooplankton.
• The model provides insights into the ecological roles of viruses in marine ecosystems and their spatial influence.