Trophic flow of contamination: A nontrivial weapon for species coexistence

In the modern age of human-induced environmental changes, ecologists are increasingly alarmed about the potential disruption of ecosystems through toxicological processes. As humanity's footprint on the natural world expands, understanding these dynamics becomes crucial. While recent ecotoxicology research has mainly focused on entirely contaminated ecosystems, overlooking the effects of aquatic contamination on terrestrial predators with access to uncontaminated prey, our study addresses this gap. We present a prey-predator model for partially contaminated communities, where predators face a trade-off in prey preference between contaminated and uncontaminated sources. Through mathematical analysis and numerical simulations, we uncover some interpretable findings: (1) In uncontaminated environments, predation pressure may cause the extinction of one prey species. However, when even a small contamination level exists in alternative prey, endangered prey species can coexist with others. (2) Survival under high contamination depends on the predator's preference. A very low preference for contaminated prey trivially allows the predator to persist, while low or high preferences lead to the predator's exclusion. Surprisingly, intermediate preference leads to bi-stability between contaminated prey and predator extinction equilibrium, resulting in a trade-off between the presence of contaminated prey or the predator. (3) Our results confirm the abrupt extinction of predators due to contamination, driven by bistability between predator-free and coexisting states. However, our observation reveals that the likelihood of sudden predator extinction increases with a higher preference for contaminated prey. Additionally, we explore the robustness of these outcomes by considering flexible model assumptions and alternative parameter sets. In summary, our study offers valuable insights into the ecotoxicological processes within partially contaminated communities, shedding light on direct and indirect species interactions.