11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
25-25
Can Scleractinians Take Up Exogenous Symbionts After A Bleaching Event?
Mary Alice COFFROTH* 1 , Eleni PETROU 2 , Daniel POLAND 2 , Lyndsey HOLLAND 1
1 Geology, University at Buffalo, Buffalo, NY, 2 Biology, University at Buffalo, Buffalo,
NY
With reports of coral bleaching on the rise, it is ever more important to understand how
corals will respond to bleaching events and to assess their ability to recover. One large
unknown is the manner in which bleached corals recover their symbiont populations.
Can corals acquire zooxanthellae from the environment or is recovery dependent on
surviving in hospite symbionts? Acquisition of symbionts from the environment could
be an important mechanism for acclimatization to an altered environment. We examined
the ability of Porites divaricata, a scleractinian coral found throughout the Caribbean,
to secondarily acquire algal symbionts after an experimentally induced bleaching event.
Porites divaricata colonies in the Florida Keys typically harbor Symbiodinium B170
(based on sequence variation in the chloroplast 23S rDNA). Using elevated temperature,
colonies of P. divaricata were induced to bleach and then exposed to Symbiodinium
strains not typically found in the adult host (Symbiodinium strains A198, B211, B 224
and D206). At 19 d and 38 d after exposure to the atypical strain, most of the colonies
only harbored the symbiont type originally found in the host prior to bleaching (i.e.
B170). However, after 19d all colonies exposed to strain B224 harbored the non-native
strain in addition to the strain normally found in P. divaricata (B170). In the other
treatments, the inoculated strain was only rarely detected (7% of samples). This suggests
that corals may secondarily obtain new symbionts from the environment, but like the
primary infection, host-symbiont specificity restricts the plasticity of the symbiosis.
25-26
Environmental Controls on the Establishment and Development of Symbiosis in
Corals
Vivian CUMBO* 1 , Andrew BAIRD 2 , M.H. VAN OPPEN 3
1 School of Marine and Tropical Biology, James Cook University, Townsville, Australia,
2 ACR Centre of Excellence for Coral Reef Studies, James Cook University, Townsville,
Australia, 3 Australian Institute of Marine Science, Townsville, Australia
The initial establishment of symbiosis is critical for coral that acquire their zooxanthellae
via horizontal transmission because it gives them an opportunity to associate with
different, more beneficial strains of zooxanthellae. Corals can associate with many
different species of zooxanthellae, some which are more tolerant of high temperature.
Consequently, one possible way for corals to cope with projected increases in sea surface
temperature attributed to global warming is to initially associate with heat tolerant
symbionts. This study tested this mechanism by determining whether environmental
conditions affect the establishment and development of symbiosis for the coral, Acropora
monticulosa. Coral larvae were exposed to 25, 28 or 31°C and given either Symbiodinium
clades A, C or D. Some strains of Symbiodinium clade D are known to be heat tolerant,
while clade C is generally considered heat sensitive. Symbiosis was established with all
clades of zooxanthellae under every temperature treatment. The proportion of larvae
infected with clade C decreased as temperatures increased, while the proportion of larvae
infected with clade A peaked at 28°C then decreased. In contrast, the proportion of larvae
infected with clade D increased as temperature increased. Additionally, the density of
zooxanthellae within the larvae decreased significantly for clade A and C but increased
for clade D as temperature increased. These results suggest that as seawater temperatures
increase, the coral host may be able to shift to more heat tolerant clades of zooxanthellae
and potentially aid coral’s ability to cope with global warming.
25-27
My Name Is Legion, For We Are Many: The Ecological And Evolutionary
Significance Of Population Structure in Symbiotic Dinoflagellates (symbiodinium,
Dinophyta)
Scott R. SANTOS* 1
1 Department of Biological Sciences, Auburn University, Auburn, AL
Symbiodinium represents a genus of unicellular dinoflagellate symbionts that associate with a
variety of marine protists and invertebrates. Over the last 15 years, eight divergent clades,
designated A to H, with numerous subcladal “types” comprising each lineage, have been
recognized within the genus. Although the diversity and phylogenetics of the Symbiodinium
complex is now well established, there has been surprisingly few data on fine-scale population
structure and biogeography in these dinoflagellate symbionts. Since populations represent the
fundamental unit of evolution, understanding patterns and processes at this level is paramount
toward furthering our knowledge on the basic biology of Symbiodinium as well as how
anthropogenic-driven global climate change may impact these symbionts and their host
associations. Here, I present a synopsis of population-level characteristics for Symbiodinium
distilled from published and unpublished data. These include: 1) the symbiont population of a
host is typically comprised of a multitude of individuals belonging to a single genetic entity or
clone; 2) for a given host species, the majority of individuals at a site harbor an identical
Symbiodinium clone, indicating low symbiont population diversity per host species per site; 3)
strong genetic structure is common between symbiont populations of a host species across sites,
suggesting low genetic connectivity between populations due to poor dispersal capability of
clones, and; 4) all clones associating with a particular host species over a widespread
geographic range belong to the same phylogenetic “species”, implying high specificity in the
pairing of host species and Symbiodinium. By unifying these characteristics in a single
framework, a series of hypotheses, testable via experiments and/or modeling, are synthesized
regarding the ecology and evolution of Symbiodinium and their important symbiotic
associations.
25-28
Coral Holobiont Community Structure: How Much Have We Missed By Focusing Only in
The Coral Host?
Juan ORTIZ* 1 , Maria GOMEZ CABRERA 1
1 Centre for Marine Studies, The University of Queensland, St Lucia, Australia
Coral community structure has been studied in depth for the past fifty years. However, the
identity of symbiotic dinoflagellates that live within the coral colonies, their life-history, and
specificity to different hosts is poorly understood. While the number of identified symbiont
types increases, we are left with the task of recognizing functional differences between these
groups. Several studies have established the symbiont community structure in individual coral
colonies, but little is known about how we should interpret the role of the symbiotic
dinoflagellate communities in the ecosystem. The aims of this study is: To quantify the
contribution of the symbiont identification to the community response to environmental
variables by comparing the response of the coral host community structure and the holobiont
community structure to the same environmental gradient. The coral community structure and
the symbiont community structure were studied in 5 coves with different environmental
conditions along the central coast of Venezuela using photo-transects and ITS2 to identified
symbionts. 77 % of the variability of the coral community structure can be explain by distance
from the closest reef, while 92% of the variability in holobiont community structure can be
explain by a combination of 4 environmental variables. The 15% increases in the proportion of
the variability explained by the environmental variables is the contribution of the symbiont
identity in the model. Following this analysis a holobiont niche segregation was evident having
different hots-simbiont combinations associated to different environmental conditions. This
study shows quantitatively for the first time how much information can be gain by including the
symbiont ID in classical coral community ecology, demonstrating that the study of coral
holobiont community structure is the natural next steep forward in the study of changes in coral
communities.
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