The longspined sea urchin, Centrostephanus rodgersii, is a key species whose intense grazing drives the transformation of temperate rocky reefs into urchin barrens. Historically endemic to eastern Australia, it has recently been detected near Port Davey, west coast of Tasmania (~~42°S; ~145°E), ~900 km from its native range. Climate-driven range extension of C. rodgersii has resulted in extensive habitat loss in eastern Tasmania, degrading ecosystems, impacting valuable fisheries, and socio-cultural values. While strengthening of the East Australian Current has facilitated larval dispersal to eastern Tasmania, oceanographic conditions enabling southward and westward transport are yet to be fully investigated. Limited presence along the west coast may reflect infrequent westward dispersal, low post-settlement survival, or the influence of energetic local hydrodynamics on juvenile retention.
We assess larval connectivity from 1994 to 2018 to identify the source populations across the east coast contributing to adult urchins now observed in west Tasmania and how marine heatwaves (MHW) influence dispersal pathways. We use particle tracking simulations (Ocean Parcels) driven by the interannually forced ACCESS-OM2-01 0.1° resolution ocean model to provide a process-based framework for inferring dispersal origins and quantifying the role of circulation changes associated with MHWs in modulating range extension.