Ulcerated yellow spot syndrome: implications of aquaculture-related pathogens associated with soft coral Sarcophyton ehrenbergi tissue lesions

We introduce a new marine syndrome called ulcerated yellow spot, affecting the soft coral Sarcophyton ehrenbergi. To identify bacteria associated with tissue lesions, tissue and mucus samples were taken during a 2009 Indo-Pacific research expedition near the Wakatobi Island chain, Indonesia. Polymerase chain reaction targeting the 16S rDNA gene indicated associations with the known fish-disease-causing bacterium Photobacterium damselae, as well as multiple Vibrio species. Results indicate a shift toward decreasing diversity of bacteria in lesioned samples. Photobacterium damselae ssp. piscicida, formerly known as Pasteurella piscicida, is known as the causative agent of fish pasteurellosis and in this study, was isolated solely in lesioned tissues. Globally, fish pasteurellosis is one of the most damaging fish diseases in marine aquaculture. Vibrio alginolyticus, a putative pathogen associated with yellow band disease in scleractinian coral, was also isolated from lesioned tissues. Lesions appear to be inflicting damage on symbiotic zooxanthellae (Symbiodinium sp.), measurable by decreases in mitotic index, cell density and photosynthetic efficiency. Mitotic index of zooxanthellae within infected tissue samples was decreased by ~80%, while zooxanthellae densities were decreased by ~40% in lesioned tissue samples compared with healthy coral. These results provide evidence for the presence of known aquaculture pathogens in lesioned soft coral and may be a concern with respect to cross-species epizootics in the tropics.