Modelling coral reef connectivity in the SW Indian Ocean

Coral larvae can be transported over great distances by ocean currents, establishing ecological and genetic connectivity between distal coral reefs. Understanding these patterns of connectivity and how they vary through time is essential for effective marine spatial planning, particularly in the SW Indian Ocean which is an under-studied region. However, tracking coral larval dispersal directly is generally unfeasible due to their size, necessitating indirect observations or numerical models. We have developed a regional configuration of the Coastal and Regional Ocean Community Model (CROCO) in the SW Indian Ocean at 1/50^o, spanning from the East African coast to the Chagos Archipelago, to simulate surface currents and gain insight into likely coral larval dispersal pathways and connectivity. The configuration is forced by the ERA-5 atmospheric reanalysis at the surface, and the 1/12^o CMEMS GLORYS12V1 reanalysis and barotropic tides at the lateral ocean boundaries. We will be carrying out a 25-year interannual simulation and a climatological control simulation. Using lagrangian particle tracking, we will estimate patterns of connectivity between reef sites across the region (with a particular focus on connectivity across Seychelles), and how significant and predictable the temporal variability in connectivity is. Early progress towards this goal will be presented. The longer-term ambition of this project is to assess our predicted connectivity against independent connectivity estimates from genetic studies and previous regional simulations at a lower resolution.