Drivers of physical connectivity between coral reefs along the Southeast African coastline

Abstract

The resilience and persistence of coral reef metapopulations strongly depend on their dispersal potential. Larval dispersal influences the diversity and genetic structure of coral populations and contributes to population recovery following disturbances. We assessed the connectivity of coral reefs in the Western Indian Ocean (WIO) during peak spawning periods between 1994 and 2014. The study focused on a broadcast coral, Acropora austera, which has a short pelagic larval duration (PLD). High-velocity streams offshore of the Delagoa Bight connect distant reef complexes on the Southeast African coastline. Complex interactions between regional ocean currents and the African continent drive their formation. These regional flow patterns are part of the larger Agulhas Current system, facilitating inter-reef connectivity within the virtual larvae’s PLD due to high current speeds. The evolutionary connectivity of short-lifespan corals identified between Mozambican and South African reefs is also regulated by intermittent regional flow patterns.