Rising sea surface temperatures are setting the scene for increases in virulent coral diseases that are already wreaking havoc on reefs around the world.

According to AIMS scientist Dr David Bourne and his colleagues, global warming and increased sea surface temperatures presented a major challenge to the health of the world’s coral reefs.

Warming has caused significant damage to reefs in recent hot years (particularly 1998 and 2002) by sparking coral bleaching, which is a breakdown in the symbiotic relationship between the coral animal and its bacterial partner (zooxanthellae).  Bleaching and coral disease seem to go together.  While the correlations between the two phenomena are yet to be understood, it is known that the more stress a reef is under the more likely it is to get sick.

During a bleaching event on the Great Barrier Reef, Dr Bourne and his colleagues found that the normal microbial community changed as water temperatures went up and as the coral bleached the incidence of pathogenic (disease-causing) bacteria also went up.  After the bleaching event ended, the microbial communities did return to normal, but prolonged periods of higher temperatures and bleaching episodes may provide a widening window of opportunity for coral diseases.

Research on coral diseases is emerging as an urgent global priority, with outbreaks causing significant losses of coral cover in the past two decades. Of particular concern is a worldwide trend for increases in the incidence of diseases affecting major framework-building corals.

The highest impact of coral disease was first noticed in the Caribbean, but recently a variety of coral diseases and outbreaks have been recorded on Indo-Pacific reefs including the Great Barrier Reef. Although causal agents of most coral diseases have yet to be identified, Dr Bourne has led research which has identified microbial origins for white syndrome.

Understanding the microbial ecology of coral reefs is likely to lead to better ways to manage the threat to reef ecosystems.

Dr Bourne presented his findings on 22 August at the 12th International Society for Microbial Ecology paper at the Cairns Convention Centre.