Corals Versus the Crown-of-Thorns Sea Star in the Anthropocene

Coral reefs are experiencing rapid transformation under interacting pressures of climate change, direct human impacts, and biological disturbance. Outbreaks of the corallivorous crown-of-thorns sea star (COTS; Acanthaster spp.) are major drivers of coral mortality. In parallel, coral population dynamics are increasingly intertwined with environmental change. This review synthesizes current understanding of pressures facing coral reefs in the Anthropocene and the ecological and physiological traits that underpin COTS success and outbreaks. These include (a) early life stages being far more resilient to warming and acidification compared with corals; (b) expansion of juvenile rubble habitat due to reef degradation and coral mortality, thereby enhancing juvenile survival; and (c) concentration of COTS feeding on surviving corals, intensifying degradation of imperiled reefs. The degraded reef hypothesis integrates life-history plasticity, ontogenetic diet shifts, trophic interactions, and ecosystem feedbacks to explain emerging outbreak paradigms and how climate stressors are reshaping COTS-coral predator-prey relationships, informing predictions of reef trajectories and management strategies.