Dispersal patterns shape species’ distribution, abundance and persistence, their potential for genetic drift and adaptation, and ultimately determine rates of recovery following disturbances. Because the larval mortality and competency dynamics of most marine organism is altered under warmer conditions, it is fundamental to understand how climate change will alter current connectivity patterns. Here we assessed long-term larval survival and competency dynamics of Acropora millepora under current and future temperatures (predicted for the end of the century). We then used this data to calibrate a high resolution unstructured-mesh, depth-integrated hydrodynamic model (SLIM) to project current and climate change-mediated dispersal and connectivity patterns of corals in the Great Barrier Reef (GBR). We used the connectivity matrix to identify reefs that act as larval sources and other that act as sinks. We also used the model to estimate recovery rates after localized and regional disturbances.
Results/Conclusions
The larvae of Acropora millepora displayed lower survival rates at higher temperatures, particularly in the first few days after fertilization. Higher temperatures also contributed to hasten acquisition of competency, but the impact on the timing of loss of competency, despite significant, was not as pronounced. Once calibrated, the bio-physical model shows that these changes in larval survival and competency dynamics will lead to a reduction in coral connectivity. Specifically, the average dispersal distance from origin to destination reef will be shortened. The number of incoming connections to each reef also decrease. Interestingly, the proportion of larvae that find a suitable place to settle increases because more larvae will settle in their natal reef (increased local retention). We identified the reefs which contribute the most to the larval supply in the GBR and the reefs which recovery rates following disturbances will be most affected by the change in connectivity patterns. Improved predictions of coral connectivity are essential to design networks of protected areas that contribute more effectively to the long-term sustainability and resilience of tropical reef ecosystems.