11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5.83
The Effects Of Salinity Stress On The Physiology And Protein Content Of The
Hermatypic Coral - Acropora pruinosa In Hong Kong
William BUT* 1
1
Swire Institute of Marine Science, The University of Hong Kong, Hong Kong, Hong
Kong
The effects of low salinity on the scleractinian coral Acropora pruinosa were investigated
in this study. 100% coral mortality and significant drops in percentage protein content
were observed in A. pruinosa exposed to the salinity of 15 psu. No mortality occurred in
A. pruinosa fragments at 18 psu salinity level. The data suggested that 15 psu salinity
level is the mortality threshold for A. pruinosa. The crude protein content measured in the
18, 22 and 25 psu salinity treatment groups are not significantly different from that in the
35 psu salinity control group. While no statistically significant difference in the amount
of crude protein per unit surface area was detected, sub-lethal behavioural responses were
observed at salinity level of 18 psu and above. Increasing tissue swelling and polyp
retraction characterized salinities between 22 and 18 psu but were not observed at higher
salinities, suggesting that these are traumatic, but not necessarily fatal salinity levels.
Salinity is quite likely to be the major environmental factor that affecting the coral
community distribution in a regional context. Freshwater excursions from the Pearl River
and seasonal monsoon downpours establish a salinity gradient across Hong Kong waters.
The sharp mortality threshold at low salinity in A. pruinosa might provide us insight into
the spatial distribution patterns of corals in Hong Kong waters. On top of that, the data
from this study might help us to predict the possible consequence of Hong Kong’s corals
under the influence of global climate change.
5.84
Sources and metabolism of essential fatty acids in Scleractinian corals
Mark TEECE* 1 , Diego LIRMAN 2 , Mary Alice COFFROTH 3
1 Chemistry, SUNY-ESF, Syracuse, NY, 2 RSMAS/MBF, University of Miami, Miami,
FL, 3 Geology, State University of New York at Buffalo, Buffalo, NY
Invertebrates such as corals require essential fatty acids for growth and reproduction and
can obtain them either through direct feeding on zooplankton and particulates, or through
translocation from their symbiotic zooxanthellae. We used the naturally occurring stable
isotopes of carbon to trace the sources and metabolism of essential fatty acids in four
corals from varying water quality environments. Comparative analyses of symbionts and
hosts from Siderastrea siderea, Porites astreoides, Montastrea faveolata, ,and Montastrea
cavernosa collected in the Florida Keys, USA revealed considerable differences in the
abundances of these essential compounds in individual symbiont-host associations. The
relative abundances of these polyunsaturated fatty acids (PUFA) was significantly higher
in P. astreoides than S. siderea and accounted for more than 38% of total fatty acids in
this coral species. The high abundances of these PUFA attest to the importance of their
function in corals. Concentrations of PUFA in cultured zooxanthellae clades spanned a
considerable range, accounting for more than 45% of total fatty acids in specific clades.
We measured the stable isotope compositions of individual fatty acids in corals and
symbionts to determine metabolic routing of these essential compounds in the natural
environment. Our analyses revealed that some corals, including P. astreoides, obtain
fatty acids from both zooxanthellae and direct feeding, and may also be able to synthesize
long chain length fatty acids from shorter precursors obtained from their symbionts.
Other corals including S. siderea, rely to a greater extent on their symbionts for their
source of essential fatty acid.
5.85
The Development Of Fluorescently-Labeled symbiodinium To Investigate Symbiont
Acquisition And Flexibility in Coral-Algal Symbiosis
Nitzan SOFFER* 1 , Patrick GIBBS 1 , Michael C. SCHMALE 1 , Andrew C. BAKER 1
1 Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric science,
University of Miami, Key Biscayne, FL
Symbiosis is a defining characteristic of reef-building scleractinian corals. During times of
environmental stress, such as increased temperature, these symbioses can break down,
jeopardizing the survival of affected corals. Corals can recover from these “bleaching” events if
their symbiont populations are able to recover. However, for scleractinian corals, the source of
these symbionts remains debated: do symbionts proliferate from residual populations, or can
they also acquire symbionts de novo from the environment? Answering this question fills a
critical gap in our understanding of symbiont population dynamics, helps us understand
recovery trajectories of corals, and has significant implication for corals’ response to continued
climate change. To help answer this question, we are developing fluorescently-labeled
Symbiodinium for use as tools to test hypotheses of symbiont acquisition and flexibility in
scleractinian corals. Initial attempts to use viable stains to selectively visualize symbionts
showed mixed success, and we have now begun transforming symbionts with DNA vectors.
Cultured Symbiodinium in clades A, B, C and D have been electroporated with vectors
containing Bactin, metallothionein and/or heat shock promoters driving expression of green and
red fluorescent proteins (GFPs, RFPs), as well as neomycin resistance to help select successful
transformants. To overcome problems associated with symbiont autofluorescence, other vectors
containing sequences for cyan or yellow fluorescent proteins (CFPs, YFPs) and luciferase are
also being targeted. We believe that the development of fluorescent or luminescent
Symbiodinium will be of broad potential use in a variety of marine invertebrate symbioses, and
will help address critical outstanding questions concerning the survivorship trajectories of reef
corals in the current era of climate change.
5.86
The Influence Of Habitat On Nitrogen Acquisition And Status in A Temperate Cnidarian-
Dinoflagellate Symbiosis
Shyam MORAR 1 , Sarah BURY 2 , Simon DAVY* 1
1 School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand,
2 NIWA, Wellington, New Zealand
Nitrogen deficiency is a well-known feature of tropical cnidarian-algal symbioses that inhabit
oligotrophic seas. In contrast, temperate seas have plentiful supplies of nutrients, and a number
of temperate symbiotic cnidarians inhabit high-sediment localities. The symbiotic sea anemone
Anthopleura aureoradiata is abundant on mudflats around New Zealand where it lives attached
to cockle shells, often buried under the sediment surface; it is also common on rocky shores.
We tested whether the mudflat habitat provides a source of particulate matter that enriches the
nitrogen status of the algal symbionts, and whether anemones living on rocky shores are
nutritionally starved by comparison. 15 N-labelled sediment was provided to anemones, and 15 Nenrichment
was detected for both anemone and algal partners. NH4 + enhancement of dark 14 C
fixation showed that while sedimentary particulate nitrogen can ultimately be acquired by the
algae there was no discernible effect of this uptake on their nitrogen status. Indeed anemones
maintained in mud but otherwise unfed for up to 8 weeks contained algae that were as Ndeficient
as those in anemones starved in the absence of mud. In contrast, symbiotic algae in the
field were N-sufficient when on the mudflat but markedly N-deficient when on the rocky shore.
Our results suggest that this symbiosis can assimilate particulate nitrogen from the surrounding
mud but that this source is less important than other potential ones such as interstitial
ammonium and nitrate. Furthermore, the nutrient-rich mudflat environment enhances the Nstatus
of symbiotic algae far more than does the rocky shore. We will consider the implications
of these trends for the functional biology of the symbiosis, and use our findings to speculate on
the likely scenarios for those reef corals that live in relatively low sediment and more
‘marginal’, high-sediment locations.
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