Shifting Tides: Modelling How Sea-level and Tidal Dynamics Shape Coral Connectivity on the Great Barrier Reef

The Great Barrier Reef (GBR) is the world’s largest coral reef, stretching 2000 km along Australia’s northeast continental shelf, where it experiences complex and intricate tidal dynamics. Despite being one of the most studied reef systems, the role of hydrodynamics in shaping coral connectivity remains poorly understood. This thesis examines how sea-level and tidal dynamics influence coral connectivity across the GBR, focusing on larval self-seeding. High-resolution hydrodynamic modelling and Lagrangian particle tracking are used to assess connectivity across three timeframes: present-day wind and tidal interactions; tidal regimes during the Holocene initiation; and projected tidal changes under future sea-level rise scenarios in 2100.
Results show that tides, particularly tidal ellipses, play a critical role in larval retention and self-seeding. During the Holocene initiation, rising sea levels enhanced tidal dynamics and increased self-seeding, supporting the initiation of the modern GBR. In the future, sea-level under all three Shared Socioeconomic Pathways (SSPs) is predicted to amplify tidal range, further enhancing self-seeding but also fragmenting connectivity networks. These findings provide new insight into the physical drivers of coral connectivity, with implications for understanding reef resilience, forecasting connectivity and informing management. They also highlight the importance of incorporating sea-level change and tidal change into connectivity modelling and management frameworks.