A toxicant-taxis reaction–diffusion model for the interaction between two species and a toxicant in an aquatic ecosystem

In this paper, we develop a toxicant-taxis reaction–diffusion model that describes the interaction dynamics between two species and a toxicant in a polluted aquatic ecosystem. We analyze the existence and stability of the equilibria of the corresponding space-absent ordinary differential equation system. We then perform linear stability analysis for our reaction–diffusion system to obtain sufficient conditions on model parameters under which the stable spatially homogeneous steady states become unstable. Numerical simulations are performed to illustrate that spatially inhomogeneous patterns and spatiotemporal patterns between the two species and the toxicant will typically emerge. We also numerically analyze the effects of spatially varying toxicant input and the intensity of toxicant-taxis on the population persistence and species diversity. It turns out that heterogeneous toxicant inputs and substantial toxicant taxis can boost the coexistence of two species, thereby promoting species diversity in ecosystems. By comparing the impact of a toxicant on a single species versus its impact on two species, we find that the collective sharing of the toxic burden among multiple species proves advantageous for biodiversity.