Great Barrier Reef Hydrodynamics, Reef Connectivity and Acanthaster Population Dynamics

Abstract

Models capable of simulating large-scale hydrodynamics and Acanthaster larval dispersal are presented for the Cairns Section of the Great Barrier Reef Marine Park. The models identify asymmetries in the patterns of larval dispersal which can explain many observed features of the recent episodes of Acanthaster activity. The northern part of the Cairns Section, between the ribbon reefs and the mainland, is seen to be hydrodynamically distinctive, with the potential to be self-seeding, and therefore the source of Acanthaster activity. Implications of the emerging pattern of stochastic connectivity among reefs are explored using a simple population model. This model is based on a hypothetical assemblage of reefs, with patterns of connectivity derived from the results of the larval dispersal simulation. Experiments with the model demonstrate the potential for the long-term maintenance of populations in the northern region. By simulating the propagation of population outbreaks through the system, it is shown how such a model could be used to test certain hypotheses concerning the cause of outbreaks and to identify the most likely primary outbreak areas.