Coral disease on the Great Barrier Reef

[Extract] Coral disease is one of the most recent in a series of threats that is challenging the resilience of coral reef communities and is of particular concern because it may interact with and augment the impacts of other commonly recognised threats to coral health (e.g. bleaching, over-exploitation of fish stocks, destructive fishing practices and coastal developments). Since the first report of coral disease by Antonius in 1973, the rate of discovery of new diseases has increased dramatically with more than 29 coral diseases now described (Green and Bruckner 2000, Weil, this Vol.).Although coral disease is emerging as one of the major causes of coral reef deterioration in the Caribbean (Hayes and Goreau 1998; Harvell et al. 2002; Weil et al. 2002),at present we know very little about the ecology or pathology of coral disease on Indo- Pacific reefs. The comparatively few reports of coral disease from Indo-Pacific reefs, despite the region encompassing more than 80%of reefs worldwide (Bryant et al. 1998)is in contrast to the high proportion (>65%) of records in the Global Disease Database from the Caribbean reef region, now widely considered to be a coral disease hotspot (Green and Bruckner 2000; Weil, this Vol.). Such comparisons suggest that either disease is genuinely more prevalent in the Caribbean or lack of studies in other reef regions is underestimating its distribution and abundance. Distinguishing between these two alternatives represents an important step in advancing global epizootiological studies. The rising incidence of marine diseases worldwide in the past few decades (Harvell et al. 1999), and particularly of coral diseases in the Caribbean, underscores the need for assessment of the status of disease on a region-by-region basis. Such assessments will help to identify the origins and reservoirs of pathogens and vectors involved in disease transmission. The Great Barrier Reef (GBR) stretches over 2000 km along the eastern coastline of Australia, representing the largest reef tract under management worldwide. Its unique status as one of the few reef systems under government jurisdiction for timescales that have preceded recent increases in the prevalence of coral disease has the potential to provide important insights into factors influencing disease occurrence and the underlying causes of escalating disease incidence. In this chapter, we summarise the current state of knowledge of coral disease on the Great Barrier Reef by (1) describing syndromes and diseases observed in our studies on GBR reefs and interpreted in the light of published literature and (2) presenting the results of a 5-year, large-scale study in conjunction with a regional disease prevalence study that together provide an overview of the current status of disease occurring on reefs extending over 1200 km of the Great Barrier Reef