Dr Katharina Fabricius

Tropical storms (cyclones, hurricanes or typhoons) are the most severe form of mechanical disturbance of coral reefs. In 2005, the severe Tropical Cyclone Ingrid crossed the Far Northern Great Barrier Reef. This storm provided a unique opportunity to improve understanding of the extent and type of damage inflicted on inshore and offshore coral reefs along a gradient of wind speeds. Surveys of 82 sites on 32 reefs along the wind gradient showed that the types and intensity of disturbance were well explained by local maximum wind speed, and by spatial and biotic factors. While offshore reefs had the deepest depth of damage, inshore reefs had the greatest rates of coral breakage and dislodgement. On a severely affected inshore reef, hard coral cover decreased about 8-fold, taxonomic richness decreased 2.5-fold, the density of coral recruits decreased by 30%, while massive coral cover remained unaltered. Maximum winds <28 cm s-1 for <12 hours inflicted only minor damage on any reef, but winds >33 m s-1 and >40 m s-1 caused catastrophic damage on inshore and offshore reefs, respectively. Observations from this cyclone were used to predict potential changes in storm-related coral loss at a scenario of altered cyclone intensity.