1. Diversity of bacteria associated with Montastraea spp. across sea water quality gradient in the United States Virgin Islands S. Arora, M.E. Brandt, N. Kimes, P.J. Morris Centre for Marine and Environmental Science, University of the Virgin Islands, St Thomas, USVI The coral mucus microbial community forms the primary line of defense against pathogenic invasion; it is suggested to vary in composition with changes in physical and chemical properties of sea water leading to increased susceptibility of coral to diseases (Ritchie and Smith, 1995; Klaus et al., 2007). In the US Virgin Islands, measures of coral health differ significantly in association with distance from onshore development (Smith et al. 2008).The study presented here aims to quantify and compare changes in the coral mucus microbial community associated with the Montastraea annularis species complex in the nearshore (impacted) and offshore (un-impacted) reef habitats of the U.S. Virgin Islands. Two nearshore and two off shore sites were selected for coral mucus sampling (Figure 1). Mucus Collection: Samples were collected from visibly healthy corals (Figure 2) at each of the four sites at the colony surface after gentle agitation using a sterile syringe. Samples were then flash frozen and stored at -80°C until processing. Figure 2: Examples of coral colonies selected for mucus sampling at the selected sites Analysis of Microbial Community: The samples were analyzed using 16S rRNA in the lab of Dr. Pamela Morris at the University of South Carolina. Coral Health: Data from the U.S. Virgin Islands Territorial Coral Reef Monitoring Program (TCRMP) was used to determine whether differences in coral health measurements exist between nearshore and offshore reef habitats. These data included measurements of average mortality, bleaching and disease incidence collected over multiple years. A special thanks to Maria I. Vizcaino at Hollings Marine Laboratory, University of South Carolina. This project was funded by an incubator grant awarded to M. Brandt by the NSF Virgin Islands EPSCoR program and a scholarship awarded to S. Arora by the Lana Vento Charitable Trust The microbial community differed considerably between the nearshore and offshore regions (Figure 3). Figure 3: Distribution of microbial phylum in the nearshore and offshore sites. (Proteobacteria composed greater than 78% of the total microbial population at each site and was similar among sites; it is therefore not presented in this graph) Major Findings: Buck Island was found to host a microbial community that was distinct in its lack of diversity and lack of specific microbial groups versus those detected at the other three sites. This site is located off of an undeveloped cay far from shore. It is possible that distance is acting as a buffer reducing the harmful impact of changes in water quality. Smith,T.B., Nemeth,R.S., Blondeau,J., Calnan,J.M., Kadison,E., Herzlieb,S. 2008. Assessing coral reef health across onshore to offshore stress gradients in the US Virgin Islands. Marine Pollution Bulletin 56: 1983-1991. Ritchie,K.B, Smith,D.W.1995. Preferential carbon utilization by surface bacterial communities from water mass, normal, and white-band diseased Acropora cervicornis. Mol Mar Biol Biotech 4: 345-354. Klaus,J.S., Janse,I., Heikoop,J.M., Sanford,R.A., Fouke,B.W. 2007. Coral microbial communities, zooxanthellae and mucus along gradients of seawater depth and coastal pollution. Environ Microbiol 9(5): 1291-1305. Figure 1: Distribution of TCRMP sites around St. Thomas and St. John with sites sampled for coral mucus indicated in red METHODS INTRODUCTIONRESULTS ACKNOWLEDGEMENTS DISCUSSION LITERATURE CITED The dominant microbial family was β proteobacteria. Families like Bacteroidetes, usually associated with soil were reported in high abundance in the near shore sites. Range cay, one of the heavily impacted sites, showed the highest diversity of microbial community (Shannon Index = 0.778) while Buck Island had the least diversity (Shannon Index = 0.470). There were significant patterns in coral health measures (in terms of mortality, disease and bleaching prevalence) detected using multivariate analysis (ANOSIM global R = 0.283, P < 0.05). These patterns were in some agreement with the patterns observed in microbial community. Buck Island had the least reported incidence of coral disease and bleaching events as well as the lowest rates of average mortality.