Coral Reefs at the Edge: Climate-Microbial Feedbacks and Ecosystem Collapse

Coral reefs are experiencing rapid degradation driven by environmental stressors, including rising sea temperatures and hypoxia, which compromise coral health, reduce growth and resilience, and threaten biodiversity. Temperature stress, in particular, increases susceptibility to disease and bleaching, while elevated organic matter and nutrient inputs promote the proliferation of heterotrophic bacteria, further destabilizing reef ecosystems. To investigate these complex dynamics, we develop a three-species ecological model encompassing corals, bacteria, and oxygen, aimed at elucidating the mechanisms underlying coral decline and potential ecosystem collapse. We conduct stability and bifurcation analyses to explore system responses to varying environmental pressures and extend the model into a reaction-advection-diffusion framework to capture spatial and temporal dynamics. Extensive numerical simulations examine a wide range of ecological outcomes, while Partial Rank Correlation Coefficient (PRCC) analysis identifies the parameters most strongly influencing system behavior. Our results reveal that rising temperatures can drive irreversible coral extinction and shift the ecosystem to alternative, less resilient states, underscoring the urgency of detecting early warning signals and mitigating stressors before collapse occurs. This study provides a mechanistic understanding of coral-bacteria-oxygen interactions and offers critical insights into preserving reef resilience in the face of accelerating climate change.