Numerical modelling and graph theory tools to study ecological connectivity in the Great Barrier Reef

- Coral larval dispersal is modelled in the central Great Barrier Reef.
- Graph theory tools are used to detect the presence of isolated reef clusters.
- We identify important barriers to larval dispersal between clusters.
- We find that dispersal distances may vary significantly in different clusters.

The process of coral larval dispersal is important for coral reef ecosystems, but remains poorly understood and hard to gauge. Better knowledge of inter-reef connectivity patterns would be useful in enabling better management of coral reef waters however. By employing a spatially explicit numerical modelling approach, we simulate larval dispersal through the central section of the Great Barrier Reef (GBR), comprising over 1000 reefs, and identify spatial patterns in the inter-reef connectivity network using a community detection method from network science. This paper presents the modelling approach used and discusses the significance of the results.Inter-reef connectivity networks were estimated for 4 different coral species, and significant differences between them were found. We show how we can partition reefs into clusters, or “communities”, that are sparsely connected with each other, and therefore identify important barriers to larval dispersal. By fine-tuning a resolution parameter in the community detection method, we can find dispersal barriers of varying strength. Finally, we show that the average connectivity length scale varies significantly across the different reef communities, and suggest that this may have repercussions for the optimal placement of marine protected areas (MPAs) to maximise connectivity with surrounding reefs.