The Pathology and Bacterial Ecology of Subtropical White Syndrome: A Disease of Scleractinian Corals in Subtropical Eastern Australia

Abstract

Subtropical white syndrome (SWS) is an ecologically significant disease of scleractinian corals in shallow water benthic communities in subtropical eastern Australia. It causes mortality in a number of coral species and has the potential to seriously alter coral dominated communities in the region. This thesis describes the first investigation of the pathology and bacterial ecology of SWS in the model coral species 'Turbinaria mesenterina'. SWS typically presents as a progressive loss of tissue which originates from one point and gradually spreads across the coral colony. As the tissue is destroyed the white calcium carbonate skeleton underneath is exposed, resulting in a characteristic white lesion on the coral surface. Aquarium experiments using healthy and SWS affected 'T. mesenterina' showed that SWS is an infectious disease that can be transmitted between colonies by direct contact, but is not transmitted via the water column. This finding implies that a vector must be involved in the transmission of the infectious agent from colony to colony. Further aquarium experiments showed that progression of SWS lesions is inhibited by antibiotics, indicating that a bacterial pathogen (or pathogens) is most likely responsible for the disease. In order to better understand the role of bacteria in the SWS disease process, the bacterial communities associated with healthy and SWS affected 'T. mesenterina' colonies were assessed using both culture-based and culture-independent methods.