Recent research has found that remote coral reefs in the Seychelles are connected by a “coral highway” facilitated by ocean currents, highlighting the role of larval dispersal in reef health and the importance of conscious conservation efforts to ensure the resilience of reefs to climate change.

Although coral reefs span more than one million square kilometers, new research has shown that remote coral reefs in the Seychelles are closely connected. Using genetic analysis and oceanographic modelling, researchers from the University of Oxford have shown for the first time that a network of ocean currents acts as a ‘coral highway’, distributing large numbers of larvae between these remote islands. These results were published today, March 12. Scientific Reports.

The importance of larval nutrition

The lead author of the study, Dr. April Burt (Department of Biology, University of Oxford and Seychelles Foundation), said: “This discovery is very important because larval supply is an important factor in the recovery of coral reefs. Although coral numbers worldwide have decreased significantly due to climate change and a number of other factors, “There are steps that can be taken locally and nationally to improve the health and resilience of reefs. These actions may be more effective if we better understand the connectivity between coral reefs, for example by prioritizing conservation efforts around coral reefs as a major source of larvae to support regional reef resilience.”

The researchers worked with multiple coral reef management organizations and the Seychelles government to collect coral samples from 19 different reef regions. Extensive genetic analysis revealed current gene flow across all sample sites (perhaps over just a few generations); This revealed that coral larvae can be frequently transferred between different populations. The results also pointed to the existence of a mysterious new rock coral species. Porites lutea.

Oceanographic modeling and distribution of corals

The genetic analysis was then combined with oceanographic modeling that simulated the dispersal process of the larvae. This modeling allowed the researchers to visualize the pathways by which coral larvae travel between reefs in a broader region and determine the relative importance of physical larval dispersal compared to other biological processes in establishing coral connectivity.

This showed that direct dispersal of coral larvae among reefs in the Seychelles is very likely. For example, coral larvae that emerged in the remote Aldabra Atoll may have spread westward to the east coast of Africa via the East African Coastal Current. From there they will move northward along the coast, some potentially even reaching the South Equatorial Countercurrent, which could turn them eastward again towards the Seychelles Inner Islands.

Although these cases of long-distance dispersal are possible, it is likely that much of the communication between remote islands in the Seychelles can be established through “stepping stone” dispersal. This suggests that centrally located coral reefs in the Seychelles, and possibly in East Africa, may play an important role in connecting the outermost islands.

Pioneering oceanographic modelling, Dr. Noam Vogt-Vincent (Department of Earth Sciences, University of Oxford, now based at the Hawaii Institute of Marine Biology) said: “This study shows that the broad agreement between predicted connectivity and observed genetic patterns supports this type of research in reef system management in the Seychelles and the wider region.” “Using larval dispersal modelling. These simulations also allow us to investigate how regular these connectivity patterns are over time, as a regular supply of larvae will be important for reef recovery under climate change.”

Simulation data can be visualized in a new program: With one click of the mouse, you can see how coral larvae in the Seychelles potentially reach reefs in the region. The researchers suggest the data could help identify major larval sources that should be prioritized for inclusion in marine protected areas or active reef restoration efforts.

Implications for reef conservation and management

Senior author Professor Lindsay Turnbull, School of Biology, University of Oxford, said: “This research could not have come at a more opportune time. The world is once again watching El Niño destroy coral reefs in the Indian Ocean. “We now know which reefs will be critical to coral recovery, but we cannot stop our commitment to reducing greenhouse gas emissions and stopping climate change.”

Supporting the Seychelles Marine Spatial Plan Initiative, Dr. Joanna Smith and Helena Sims (The Nature Conservancy) said: “The WIO coral connectivity study, which shows the connectivity of reefs in a network, can be used nationally and regionally in the Western Indian Ocean for the design and management of marine protected areas and the management of restoration activities. Implications and “We look forward to using the Coral Link program to inform the implementation of the Seychelles Marine Spatial Plan.”