Coral bleaching dynamics on the Great Barrier Reef: New insights from a mathematical model

The ongoing climate crisis poses a significant threat to the future of worldwide coral reefs. Catastrophic incidences of declining reef health and mortality, driven by widespread coral bleaching have highlighted the need for an improved mechanistic understanding of bleaching dynamics to inform effective reef management. We developed a continuous-time state-space model of reef dynamics to capture coral populations at a community scale. Using a dynamical systems approach, we analysed the qualitative characteristics of the model and found evidence suggesting that intrinsic growth and bleaching-induced mortality may play a crucial role in determining a reef’s vulnerability and resilience to ongoing disturbances. The model was able to capture a range of observable phenomena when calibrated to empirical observations sampled from multiple sites spanning the Great Barrier Reef. Observed trends in the estimated parameters suggest correlations between several reef characteristics and the latitudinal positions of sample sites. Our results shed light on possible mechanisms driving resilience and robustness, and reveal new insight that has the potential to improve reef conservation and management. Despite the simplicity of the model, our analyses demonstrate its utility in inspiring future data collection and improving intervention efforts. • Coral bleaching is modelled as a continuous function of the reef ecosystem. • The model state-space is defined in terms of algae expulsion and assimilation. • Mortality in bleaching corals may be a key driver of ecosystem vulnerability. • The presence of widespread bleaching may indicate greater reef resilience. • Geographical locations of sample sites can impact coral cover observation quality.