11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5-6
Acquisition And Allocation Of Carbon in Bleached Hawaiian Corals
Andrea GROTTOLI* 1 , Adam HUGHES 2,3 , Tamara PEASE 2
1 School of Earth Sciences, The Ohio State University, Columbus, OH, 2 Department of
Marine Science, The University of Texas at Austin, Port Aransas, TX, 3 School of Earth
Sciences, The Ohio State University, Columbus
Photosynthesis and growth are dramatically reduced in bleached corals. Montipora
capitata corals compensate by dramatically increasing heterotrophy, while Porites
compressa corals sustain themselves by utilizing their stored energy reserves when
bleached. Here, we further assessed how photosynthetically and heterotrophically
acquired carbon is acquired, allocated, and utilized among the host tissue, zooxanthellae,
and skeleton in bleached and non-bleached P. compressa and M. capitata corals using
13C-labeled bicarbonate in seawater and 13C-labeled rotifer pulse chase labeling
techniques. Photosynthetically acquired carbon was taken up from bicarbonate by the
zooxanthellae, transferred to the host tissue, respired, and taken up by the skeleton at
dramatically lower rates in bleached corals relative to controls. In both bleached and
non-bleached corals, the photosynthetically derived carbon appeared to be the primary
source of carbon for calcification but was not incorporated into either the zooxanthellae
or host tissue for long-term storage. In contrast, heterotrophically-derived carbon (i.e.,
rotifers) was rapidly translocated between the zooxanthellae and host tissues in bleached
and non-bleached M. capitata and non-bleached P. compressa (but not bleached P.
compressa), was not a source of carbon for calcification, and appears to be the primary
source of carbon for long-term tissue growth and carbon storage. Thus, long-term
recovery from bleaching will depend on a coral’s ability to acquire fixed carbon via
heterotrophy to support its tissues while bleached, and to regain photosynthesis in order
to stimulate calcification.
5-7
When Is Not Bleaching “Unhealthy” For Corals And/Or Coral Reefs?
Sophie DOVE* 1 , George ROFF 1 , Simon DUNN 1
1 Centre for Marine Studies, University of Queensland, St Lucia, Australia
“Thermal tolerance” and “bleaching tolerance” are used interchangeably in the coral
literature. Furthermore the subject who is “tolerant” is often very vague with unexplained
transitions from symbiont to host and/or coral reef ecosystems. Any of these levels are
viewed as “healthy”, as long as they are not bleached. Mass coral bleaching events
where entire coral reef ecosystems turn white, accompanied by the sulfurous smells of
death are obviously unhealthy; but how universally applicable is this label to colonial
corals that tend to reduced symbiont densities in actively growing regions and on a
seasonal basis, or to symbionts that have the ability to increase or maintain productivity
by reducing the chlorophyll concentration of their light harvesting antennae? Conversely,
as observed by Len Muscatine, symbiont densities are linked to quantity of carbonskeletons
leaked to the host. A more parasitic symbiont may fail to bleach simply because
it passes on any losses in productivity to the host by reducing the quantity of fixed carbon
translocated. In this way, a greater pool of energy is retained by the symbiont to repair
photosystems and maintain symbiont populations at the expense of host metabolic
activity or health. Data will be presented demonstrating that (i) corals can be 80%
bleached, supporting remnant symbionts with 3 fold greater Pnet max cell-1 than adjacent
non-bleached corals; (ii) that symbiont cultures can be at least 60% bleached yet growing
at 2.5 times the rate of unbleached cultures. The results from 14C experiments on whole
colonies from a variety of host-symbiont associations exposed to temperature x CO2
treatments, and starved at tips or bases will also be presented to monitor effect of
treatment on carbon translocation not only between symbiont and host, but also between
polyps.
5-8
The Importance Of Zooplankton To The Total Energy Budget Of Healthy And Bleached
Corals At Two Depths
James PALARDY* 1 , Lisa RODRIGUES 2 , Andrea GROTTOLI 3
1 Department of Ecology & Evolutionary Biology, Brown University, Providence, RI,
2 Department of Geography and the Environment, Villanova University, Villanova, PA, 3 School
of Earth Sciences, Ohio State University, Columbus, OH
Bleached and non-bleached fragments of three species of Hawaiian corals were exposed to
enhanced and ambient concentrations of zooplankton at 1 and 6 m depth to determine the
contribution of zooplankton to the coral’s total energy budget. The size and taxonomic grouping
were recorded for every zooplankton captured and the relative input of zooplankton of different
size classes determined. The contribution of heterotrophic carbon to animal respiration (CHAR)
was calculated using an improved calculation method that included the proportionate
contribution of zooplankton from all size classes. The results show that feeding rates followed
the same pattern in both ambient and enhanced zooplankton concentrations. Corals captured the
same size and assemblage of zooplankton under all evaluated conditions, and preferentially
captured plankters smaller than 400µm. Feeding rates increased with depth in non-bleached
corals, but not in bleached corals. Relative to non-bleached fragments at the same depth,
feeding rates of bleached Montipora capitata increased, Porites compressa decreased and Porites
lobata remained unchanged at both 1 and 6 m depth. Therefore, the response of corals to the
same disturbance may vary considerably. The calculated CHAR values show that heterotrophic
carbon from zooplankton plays a much larger role in the total energy budget of corals than was
previously estimated, and may account for over 65% of some coral species’ daily metabolic
energy requirements when healthy and over 200% when bleached. Our results show that
heterotrophically acquired carbon makes a significant contribution to the total carbon budget of
corals under all conditions and depths, and suggests that nutrient acquisition via zooplankton
feeding may play a significant role in coral-algal symbiosis balance.
5-9
Unravelling Coral Photoacclimation: symbiodinium Strategy And Host Modification
Sebastian HENNIGE* 1 , David SMITH 1 , Kathleen MCDOUGALL 2 , Mark WARNER 3 , David
SUGGETT 1
1 Coral Reef Research Unit, University of Essex, Colchester, United Kingdom, 2 Environmental
Research Institute, North Highland College, Caithness, United Kingdom, 3 College of Marine
Studies, University of Delaware, Lewes, DE
Light is often the most abundant resource within the nutrient poor waters surrounding coral
reefs. Consequently, zooxanthellae (Symbiodinium spp.) must continually photoacclimate to
optimise productivity and ensure coral success. To accurately assess Symbiodinium
photoacclimation in situ, differences in acclimation strategies and bio-optical signatures need to
be characterised between genetic types of Symbiodinium. Using a systematic series of
laboratory experiments, eight types of Symbiodinium were cultured and examined using
techniques such as active (FIRe) fluorescence, Photosystem I (PSI) and II counts,
spectrophotometry and high performance liquid chromatography. Two key ‘strategies’ of
photoacclimation are known to exist amongst microalgae: a preferential modification of the
light harvesting antennae ( -based) or of the reaction centre bed (n-based) for PSII and/or PSI.
Our measurements demonstrated that acclimation strategies employed by Symbiodinium were
highly varied between algal type but despite this variability, many optical signatures were
conserved. Also, when absorption was considered per photosystem, a 1:1 balance was observed
between PSI and PSII. Acclimation strategies of intact Acropora formosa and Seriatopora
caliendrum at two light levels were further examined using fluorescence and optical signatures
to determine host contribution to acclimation. Overall, our results demonstrated that (1)
biophysical (active fluorescence, photosystem-specific) but not bio-optical signatures were
highly variable between algal types; consequently, bio-physical signatures that are altered by an
adaptation of the algal community structure may be misinterpreted as photoacclimation and (2)
host acclimation and modification of the light environment plays a key role in Symbiodinium
photoacclimation.
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