Importance of depth refugia for reef resilience and intervention on the Great Barrier Reef under future climate change

Abstract Coral reefs globally face unprecedented threats from climate change, with the Great Barrier Reef (GBR) experiencing cumulative stressors and increasingly severe declines in coral cover from thermal stress events. Understanding drivers behind reef resilience to climate impacts is critical for conservation planning and intervention strategies. A scenario-based population modelling approach was adopted with larval connectivity dynamics and environmental factors to assess coral reef resilience across the GBR using projected conditions under five Global Climate Models (GCMs). Projected coral cover was analysed for each reef’s ability to maintain positive carbonate production budgets under future conditions, using coral cover as a proxy. Larval connectivity patterns did not correlate with increases in maintenance of positive carbonate budgets. Instead, reef depth emerged as the primary predictor, with deeper reefs (>10m) benefitting from reduced thermal exposure. These findings suggest that depth is a tangible and pragmatic reef characteristic to consider in future intervention practices for coral reef restoration. These results have important implications for reef management, indicating that depth should be considered as a key variable in conservation planning to maximize coral survival under continuing climate change.