Re ECF Project: 2009-05

Project Title: Characterization of Bacterial Community Associated with Skeletal Tissue Growth Anomalies in the Coral Platygyra carnosus

Applicant: City university of Hong Kong (Dr. CHIU Man-ying)

Total Approved Grant: $249,960

Duration: 15/11/2009 to 14/11/2010

Project Status/Remarks: Completed

Scope:
The aims of the project are to: characterize and compare the bacterial communities between healthy Platygyra carnosus coral tissues and diseased ones with skeletal tissue growth anomalies using conventional and molecular microbial tools. The coral-associated bacterial communities are potential indicators of coral health and may provide an early warning for changes in the growth status of coral communities. This project will generate important data for future coral conservation and management purposes in local waters.

Summary of the Findings/Outcomes:
Forty-eight coral tissue samples were collected at Hoi Ha Wan Marine Park (HHWMP) and Port Shelter (PS) in winter (February-March) and summer (June-July) for bacterial isolation and denaturing gradient gel electrophoresis analysis. The highest bacterial abundance of 5,098 colony-forming units (CFUs) per sample was found for healthy coral tissues collected from HHWMP in the winter. In contrast, a significantly lower bacterial abundance of 907 CFUs per sample was found for coral tissues with skeletal anomalies collected from the same site at the same time. Three-way ANOVA results, however, showed that there was no significant effect of health status, sample location, or season on the bacterial abundance. Of the 173 sequenced 16S rRNA isolates obtained from the healthy and diseased corals, 27 genera were observed. Only minor differences were identifiable between the bacterial community associated with the healthy and diseased corals, indicating that tumors are not associated with major changes in community structure. Rather, community structure was strongly influenced by the location and season, with greater Alphaproteobacteria diversity in the winter than in the summer. This study demonstrated that the coral-associated bacterial community composition was more related to environmental variables (i.e. season and location) than to disease (i.e. tumour).