Understanding of the conditions that promote recovery and resilience is essential for future effective management of the world's increasingly disturbed coral reefs, and this understanding requires long-term studies of reef responses to disturbance. We used robust non-parametric statistical analyses to describe the responses of reefs in Bill's Bay (Ningaloo Reef, Western Australia) to acute non-destructive disturbances over a 17-year period. Reefs in inner Bill's Bay were completely killed by a dystrophic crisis in 1989. Recovery of pre-disturbance levels of coral cover from this zero baseline occurred within 10 years, and recovery of pre-disturbance type acroporid-dominated coral communities (=resilience) was achieved at one site within 17 years. As has been reported elsewhere in the Indian Ocean, recovery commenced through recruitment and growth of non-acroporid taxa (faviids). Our analyses of coral reef recovery patterns following this kind of disturbance, in which the reef matrix is not damaged, are likely to be relevant to coral recovery patterns following other acute non-destructive disturbances, such as the increasingly common global phenomenon of catastrophic bleaching.
In stark contrast to most Indo-Pacific reefs, those in the outer zone of Bill's Bay, Ningaloo Reef, appear to have been remarkably stable over the past 17 years in terms of coral cover and high-level coral community composition. If they continue to be relatively unimpacted by and/or resilient to environmental disturbances and human activities, these stable outer zone reefs at Ningaloo, and others like them in Western Australia, may be able to serve a critical function as coral reef refugia and reference sites of local, regional and potentially global significance.