Abstract: Climate change is causing the distribution and abundance of many organisms to change. In particular, organisms typical of the tropics are increasing in abundance in many subtropical regions, a process known as tropicalization. Here, we examine changes in coral abundance and assemblage structure in the Solitary Islands Marine Park (SIMP), over a 23-year period between 1990 and 2013. Total coral cover decreased at all six islands sampled in the SIMP. Total Acropora cover did not change at the regional scale, with large declines at two islands offset by increases at other islands. Of 16 common coral taxa examined at the regional level, one declined and two increased in cover with no change in the remaining 13 taxa. When coral taxa were classified as either cosmopolitan or subtropical there was no change at the regional level in either group. Modelling indicated very low probabilities of larval dispersal from the southern Great Barrier Reef to the SIMP suggesting that limited connectivity is one possible cause of the lack of observed change in the assemblage structure. We therefore conclude that, despite significant increases in mean sea surface temperature in the SIMP over the last few decades, there has been no tropicalization of the coral fauna. Our results suggest that factors other than temperature, in particular, a lack of dispersal, are limiting the expansion of tropical corals along the east coast of Australia.

Biography: Professor Andrew Baird is a Chief Investigator in the ARC Centre of Excellence for Coral Reef Studies at James Cook University. He has broad interests in coral reef science having produced original research in areas such larval ecology, reproductive biology and coral bleaching. His current research focuses on the systematics and biogeography of reef-building corals, in particular, the Family Acroporidae.