Reef predators unveiled: unraveling corallivores' influence on coral reef ecosystems

Numerous coral reefs worldwide have suffered degradation due to various pervasive threats. Among these, the proliferation of certain coral predators, such as the crown-of-thorns starfish (Acanthaster planci), and severe disease outbreaks has led to significant and widespread declines in coral cover. This study seeks to investigate how apex predators impact coral extinction dynamics and their role in the spread of diseases. To achieve this, we employ a three-species eco-epidemiological model. In our model, the apex predator, the voracious humphead wrasse, preys on the intermediate predator, the crown-of-thorns starfish; meanwhile, the crown-of-thorns starfish prey on corals. Our analysis establishes the constructed model's characteristics, including its non-negativity, global existence, and long-term behavior, and conducts a comprehensive bifurcation analysis. We then consider the spatially explicit system. The Turing instability conditions for the spatio-temporal system are assessed. Additionally, we investigate the spread of coral disease and its propagation when the growth rate and diffusion coefficient of humphead wrasse are increased using a reaction-diffusion model. Additionally, we showcased the presence of chaos within the devised model system. Biologists have long recognized that ecological systems exhibit unpredictable and complex behaviors. Importantly, our simulations underscore the possibility of regulating predator harvesting rates as a method for controlling chaos. The current study aims to offer predictions about the potential outcomes of implementing restrictions on the hunting of humphead wrasse. These predictions are intended to guide future decision-making and enhance our understanding of how to manage and protect coral populations effectively.