11th ICRS Abstract book - Nova Southeastern University

8-26
Photosynthetic Microorganisms Colonized Within goniastrea Aspera
Seitaro S. YAMAZAKI* 1 , Takashi NAKAMURA 1,2 , Yeong Shyan YUEN 1 , Hideo
YAMASAKI 1
1 Faculty of Science, University of the Ryukyus, Okinawa, Japan, 2 Amakusa Mar. Biol.
Lab., Kyushu University, Kumamoto, Japan
Reef building corals have established obligate symbiotic relationship with dinoflagellates
commonly known as “Zooxanthella”. It is widely known that corals harbor multiple
species of microalgae within their endoliths. However, its ecological function as well as
impacts on the host corals has remained as a subject to be explored. In addition to the
zooxanthella, it has been suggested that the flora of photosynthetic microorganisms
colonized within coral endoliths is more complicated than that of described previously.
Here, we characterize the photosynthetic microorganisms’ flora in the endoliths of corals
inhabiting in eutrophic and oligotrophic environments. Goniastrea aspera colonies were
collected from eutrophic and oligotrophic environments in Okinawa (Japan) and Great
Barrier Reef (Australia). We analyzed the species profile of photosynthetic
microorganisms with the PCR-DGGE method, extracting total genomic DNA from coral
endoliths. The diversity of 16S rDNA of cyanobacteria and chloroplasts in the samples
collected from oligotrophic environments was much higher than that of eutrophic
environments. The diversity of 18S rDNA of eucaryotic algae was lower than the 16S
rDNA, and it was similar in both sites. These results suggest that diversity of
cyanobacteria colonized within G. aspera in oligotrophic environment is higher
compared to eutrophic environment. In contrast with cyanobacteria, fewer species of
eucaryotic algae colonized within G. aspera and their diversity may not be affected by
nutrient conditions. Our findings lead us to conclude that the diversity of cyanobacteria
colonizing G. aspera endoliths can be altered by nutrient conditions of the environment.
8-27
The Roles Of Viruses in Corals.
Rebecca VEGA THURBER* 1 , Forest ROHWER 2
1 Biology, San Diego State University, San Diego, CA, 2 San Diego State University, San
Diego, CA
The coral holobiont is a symbiotic community of animal host, zooxanthellae algae, and
microbial flora and fauna. Using a combination of manipulation experiments,
metagenomic analysis, and real-time PCR, we have found that this diversity of organisms
is thus reflected in the viral consortia present within the tissues and mucus of Porites
compressa corals. We have identified representatives of viruses that infect many
protozoan and metazoan phyla, as well as Bacteria and Archaea. We hypothesize that
these viruses infect different compartments within the holobiont and therefore affect the
coral host in a variety of ways. Of particular interest are three groups of viruses: the
herpes-like viruses, single-stranded DNA plant viruses, and Bdellovibrio phages which
are elevated in abundance after corals were exposed to increases in temperature,
nutrients, and dissolved organic carbon, respectively. To further characterize the role(s)
that these viral groups play in coral health and homeostatis, we have conducted analysis
on the relative abundance of viral target genes and members of the holobiont. For
example, Symbiodinium (as measured by a Symbiodinium psbA chloroplast gene)
abundance was found to be negatively correlated with a putative Geminivirus recently
identified in our libraries, suggesting that as this virus is produced, zooxanthellae
abundance is reduced, indicative of viral infection and lysis of the zooxanthellae. Also,
Bdellovibrio phage (viruses that infect bacterivorous Bacteria) abundance was negatively
correlated with groups of heterotrophic bacteria suggesting that Bdellovibrios may play a
unique role in regulating bacterial colonization of the holobiont. Lastly, herpes-like virus
genes were positively correlated with coral tumor incidence indicating that these viruses
may be culprits of coral disease. These and other data suggest that viruses may play
important roles in coral biology and coral reef health.
Oral Mini-Symposium 8: Coral Microbial Interactions
8-28
Microalgae From The Mucus Layer Of Two Massive Corals in The South-Eastern
Caribbean, Venezuela
Francoise CAVADA* 1 , Rene AYALA 1 , Luis TROCCOLI 2 , Juan CRUZ-MOTTA 1
1 Departamento de Estudios Ambientales, Universidad Simón BolÃ-var, Caracas, Venezuela,
2 Departamento de Acuicultura, Universidad de Oriente Nucleo Nueva Esparta, Isla de
Margarita, Venezuela
The mucus layer of healthy scleractinian corals contains a variety of eukaryotic and prokaryotic
microorganisms. It has been hypothesized that these communities confer some benefits to the
coral, specifically the pathogenesis development. However, little is known about the eukaryotic
fraction of these communities. This study addresses the description of the patterns of spatial and
temporal distribution of microalgae assemblages in the mucus layer of two massive corals in a
pristine reef patch in the south-eastern Caribbean, using a sampling design that allowed testing
specific hypotheses in relation to: 1) differences between coral species and 2) the generality of
the observed patterns. To accomplish this, samples of mucus were haphazardly taken from 72
healthy colonies, 36 Diploria strigora and 36 Colpophyllia natans plus 3 samples of water and
sediment on a monthly basis between January and June 2004. Multivariate analysis, based on
similarity matrices, showed that microalgae assemblages present in the mucus samples had no
relation with those from the water column or sediment, and that variation in the assemblages of
microalgae from the mucus throughout the study period was dependent on the coral species, but
changes in both coral species occurred in the same direction through time. The results show that
the association observed between corals and the microalgae on the mucus layer may not
constitute an opportunistic interaction with the surrounding plankton and/or microphytobenthos.
However, it is necessary to carry out further studies to identify the possible factors that affect
these assemblages, their relative importance and the way they may interact, as well as the
incorporation of other assemblages that inhabit the mucus layer in the sampling design to
characterize the mucus microbiota and test specific hypothesis about their role in the coral
biology.
8-29
Competition between Caribbean Corals and Macroalgae: Is there a Detrimental Impact
on Symbiotic Coral-Bacterial Associations?
Kathleen MORROW* 1 , Mark LILES 1 , Nanette CHADWICK 1
1 Biological Sciences, Auburn University, Auburn, AL
Long-term studies on Caribbean reefs have revealed declines in live coral cover and increases in
algal abundance, resulting in increased physical contact between corals and algae. Macroalgae
may gain a competitive edge over scleractinian corals by manipulating coral-associated
microorganisms. We used culture-dependent and -independent methods to determine the
microbial communities associated with both competing and isolated corals (Montastraea
faveolata) and macroalgae (Halimeda green and Dictyota brown algae). Syringe samples were
taken from >1 m apart and included: 1) M. faveolata not in contact with macroalgae (coral
control), 2) M. faveolata interacting with macroalgae, at 5cm from the interaction zone, 3) M.
faveolata surfaces that directly contacted each macroalga, 4) macroalgal thalli interacting with
M. faveolata and finally, 5) epiphytic Halimeda and Dictyota not in contact with corals (algal
control). Initial plate counts suggest that microbial abundance increases in a step-wise fashion
from isolated corals (~500 CFU ml -1 ), to coral-macroalgal interaction zones (~1,500 CFU ml -1 ),
to within macroalgal thalli (~3,500 CFU ml -1 ). Microbial community samples were extracted
using a bead-beating method to recover DNA, and the 16S-23S rRNA intergenic spacer region
was PCR-amplified using universal Eubacteria primers and resolved on a polyacrylamide gel
(ARISA method). Bacterial community profiles revealed significant variation in composition
between sample types, with considerable intra-sample consistency (n=3). In particular, a
dominant bacterial taxon found on the coral controls was observed to decrease dramatically in
corals that interacted with macroalgae. We conclude that microbial communities associated
with these corals and macroalgae are dynamic and appear strongly impacted by competitive
interactions. Coral-algal interactions may directly mediate the stability and function of
microbial symbionts on coral surfaces, and have major implications for observed patterns of
competitive dominance and disease susceptibility on coral reefs.
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