MODELING THE LARVAL DISPERSAL OF ACANTHASTER-PLANCI .2. PATTERNS OF REEF CONNECTIVITY

Numerical models capable of simulating the hydrodynamics associated with large assemblages of reefs are applied to the larval dispersal of Acanthaster planci. Larval distributions which result from passive transportation have been simulated and the resulting patterns of dispersal are compared with the distribution of adults and the observed pattern of Acanthaster population spread. Three forms of asymmetry in reef connectivity are identified within the southern portion of the Cairns Section of the Great Barrier Reef Marine Park. They confirm that larval dispersal within the region cannot be considered as an istropic random process and the recruitment of reefs is not from a homogeneous larval pool. The three forms of asymmetry in the transport of larvae, together with the the longshore currents within the main lagoon, provide a mechanism which results in the passive concentration of larvae adjacent to reefs that border the main lagoon. The three forms of asymmetry are able to account for: (1) the apparent southward spread of Acanthaster populations; (2) the high incidence of "outbreaks" on mid-shelf reefs; and (3) the susceptibility of particular reefs to repeated recruitment. The high incidence of outbreaks on the inner matrix reefs bordering the main lagoon can be explained as a purely physical phenomenon. © 1990 Springer-Verlag.