Simulated larval connectivity among Australia’s South-west submarine canyons

A biophysical dispersal model was used to simulate hydrodynamic connectivity among canyons located within Australia’s southwest marine region using ophiuroid (brittlestars) larvae as a model species. The results show that exchange among canyons in this area is greatly influenced by the Leeuwin Current, transporting larvae in a unidirectional manner around Cape Leeuwin, and continuing eastwards along the Great Australian Bight. Larvae within canyons tend to remain within them; however, if they are transported above the canyon walls, they then have the opportunity to be transported significant distances (thousands of km). Analysis of the variability in connectivity patterns reveals concentrated larval flow near the shelf break, with increasing levels of variability in larval flow leading offshore from the canyons. While the average potential larval flow distance and duration (unweighted by dispersal probability values) between canyons were approximately 550 km and 33 d, respectively, the average realized larval flow distance and duration (weighted by dispersal probability values) were approximately 20 km and 5 d, respectively. This study provides the first consideration of larval connectivity among submarine canyons and will help improve management of these features by providing a better understanding of larval movement, transboundary exchange and the potential spread of invasive species.

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