EFFECTS OF CYCLONE WAVES ON MASSIVE CORAL ASSEMBLAGES ON THE GREAT-BARRIER-REEF - METEOROLOGY, HYDRODYNAMICS AND DEMOGRAPHY

Cyclone waves directly affect the density, structure and local distrib ution of coral assemblages by acting as agents of mortality and colony transport. Using the meteorological record, hydrodynamic formulations and risk analysis, we predict some demographic consequences of cyclon es for massive corals growing in different regions of the Great Barrie r Reef. Analysis of shear, compression and tension forces generated by waves indicate that corals firmly attached to solid substratum, even if only over a small proportion of their base, can resist all waves, r egardless of colony size or shape, cyclone intensity or region. Waves are thus directly important as controls on colony-size frequency distr ibutions only for weakly attached or unattached colonies. At 3 m depth , these colonies have a higher probability of escaping dislodgement in their first 10 years of life, the further north or south they are fro m 21-degrees-S, which is the latitude where severe cyclones are most f requent. At 21-degrees S, corals at depths as great as 12 m are expose d to the greatest likelihood of dislodgement. Possible implications of predicted increased storminess associated with global warming are bri efly discussed.