Transcript Diversity of bacteria associated with Montastraea spp

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
INTRODUCTION
RESULTS
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.
The microbial community differed considerably between the nearshore and offshore regions (Figure 3).
METHODS
Figure 1: Distribution of
TCRMP sites around St.
Thomas and St. John with sites
sampled for coral mucus
indicated in red
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.
ACKNOWLEDGEMENTS
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
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:
• There were significant patterns in coral health
measures (in terms of mortality, disease and
bleaching
prevalence)
detected
using
multivariate analysis (ANOSIM global R =
• Families like Bacteroidetes, usually associated
0.283, P < 0.05). These patterns were in some
with soil were reported in high abundance in the
agreement with the patterns observed in
near shore sites.
microbial community.
• Range cay, one of the heavily impacted sites,
• Buck Island had the least reported incidence of
showed the highest diversity of microbial
coral disease and bleaching events as well as the
community (Shannon Index = 0.778) while Buck
lowest rates of average mortality.
Island had the least diversity (Shannon Index =
0.470).
• The dominant microbial family was β
proteobacteria.
DISCUSSION
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.
LITERATURE CITED
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.