Reef geomorphology, hydrodynamic energy and coral morphology influence recovery after bleaching

As climate change intensifies, mass coral bleaching events are becoming more frequent and severe, driving global reef decline. Post-bleaching outcomes vary widely across reef systems and individual colonies, complicating conservation efforts. Few studies integrate physical factors (site-specific geomorphology, hydrodynamics) with biological ones (coral physiology) to understand their interactions and combined effects on coral recovery. This study examines how local environmental conditions and coral traits influence post-bleaching outcomes at One Tree Reef in the southern Great Barrier Reef, following the extreme 2024 heatwave. Surveys were conducted during and after the bleaching event across three geomorphically distinct sites with varying hydrodynamics. To assess coral response, 462 colonies were tagged and monitored over nine months post heat-stress. Coral responses were compared between two morphotypes - simple and complex - based on how they interact with water flow. Results show that geomorphology and water flow modulate seawater temperatures and strongly influence coral recovery. The site with the greatest depth range (3-5 m) and highest flow had the highest number of healthy corals nine months post-bleaching, although outcomes were not stratified by depth. Between the two shallower sites (1-3 m), the one exposed to swell waves supported greater recovery over the following months, while the site with no wave energy experienced high mortality. Both simple and complex morphotypes benefited from higher hydrodynamic energy, with simple colonies generally more resilient to heat stress. These findings emphasise the importance of physical site-specific characteristics in coral resilience and can guide more effective conservation and restoration strategies under future climate stress.