11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 5: Functional Biology of Corals and Coral Symbiosis: Molecular Biology, Cell Biology and Physiology
5-18
Morphological Dependence Of The Variation in The Light Amplification Capacity
Of Coral Skeleton
Susana ENRÍQUEZ* 1 , Eugenio MÉNDEZ 2 , Ove HOEGH-GULDBERG 3 , Roberto
IGLESIAS-PRIETO 1
1 Unidad Académica Puerto Morelos, Universidad Nacional Autonoma de Mexico,
Cancun, Mexico, 2 Departamento de Óptica, CICESE, Ensenada, Mexico, 3 Center for
Marine Studies, University of Queensland, Brisbane, Australia
Multiple scattering produced by the highly reflective aragonite coral skeleton, has been
associated with a strong increment in the light absorption capacity of the symbiotic algae.
For a Caribbean scleractinian coral used as a model organism, it has been quantified that
algal pigments in the intact tissues are between 2 and 5 times more efficient for absorbing
light than freshly isolated cell suspension containing similar amount of pigments.
Theoretical calculations based on a flat lambertian surface indicate amplification factor
up to three. More complex structures or concave surfaces are expected to have much
higher values, although are theoretically intractable. Here, we analyzed the variability in
the light amplification capacity of naked coral skeletons associated with the variation in
skeleton morphology. We quantified the capacity of light amplification of 76 Indo-Pacific
coral species belonging to 9 different families. Among them, 49 species belonged to the
Faviide family. We found large variation among coral skeleton morphologies, in their
light amplification capacity, from a minimum of 3 shown by the species Caulastrea
curvata to a maximum of 10 shown by Echinopora lamellose. These results confirm the
importance of coral skeleton morphology for understanding algal light environment and
the magnitude of pigment packaging within coral tissue. We will discuss the patterns
found in this comparison and their evolutionary implications.
5-19
Characterization Of Optical Properties Of Reef-Building Coral Skeletons
Vadim BACKMAN 1 , Margaret SIPLE 2,3 , Erin DALY 2 , Andrew FANG 2 , Mark
WESTNEAT 4 , Vladimir TURZHITSKY 1 , Jeremy ROGERS 1 , Luisa MARCELINO* 2,3
1 Biomedical Engineering Department, Northwestern University, Evanston, IL, 2 Civil and
Environmental Engineering, Northwestern University, Evanston, IL, 3 Zoology, Field
Museum of Natural History, Chicago, 4 Zoology, Field Museum of Natural History,
Chicago, IL
A successful symbiotic algae-coral partnership is largely determined by the efficiency
with which reef-building corals absorb light. This is achieved in two major ways: by
controlling symbionts/pigment concentration and by multiple light-scattering in the
skeleton resulting in homogenization of the light available to the coral tissue. Here we
propose that light redistribution needs vary among corals with different growth forms.
We characterized the optical properties of coral skeletons using a novel technique, lowcoherence
enhanced-backscattering (LEBS). We measured light mean free-path length
(ls) in coral skeletons grouped into three growth forms: Branching, Massive and Laminar.
We found that ls is significantly longer in Branching compared with Massive and
Laminar corals. Longer ls results in a better redistribution and delivery of light to the
shaded parts of a coral colony and increases the amplification of light availability to the
entire colony. We tested if skeleton density determines these observed optical properties.
Branching and Laminar corals had significantly higher densities then Massive corals.
This agrees with previous studies: greater density is required by Branching and Laminar
corals to support their mechanical stability. However, increased skeletal density typically
results in shorter ls. To reconcile these observations, we measured the micro-architecture
of coral skeletons using LEBS. We found that the length-scale of nanoscale density
variation (i.e. granularity) is lower in Branching corals than in Massive or Laminar.
According to light-scattering theory, this finer granularity results in longer ls. Thus, the
nanoarchitecture of Branching corals ensures long distances of light transport necessary
for light delivery to coral tissue without sacrificing their mechanical stability. Because
light transport in coral is responsible for the amplification of light availability to coral
tissue and Branching corals show higher bleaching-related mortality, this finding may
have implications for differential bleaching resistance in different corals.
5-20
In Hospite Operation Of The Photosystem Ii Repair Cycle in Symbiotic Dinoflagellates
Xavier HERNANDEZ-PECH* 1 , Roberto IGLESIAS-PRIETO 1
1 Unidad Academica Puerto Morelos ICMyL UNAM, Puerto Morelos, Mexico
Photosynthesis by symbiotic microalgae is a fundamental process in coral reefs. Algal
photosynthesis can provide more than 100% of the metabolic requirements of the intact
symbiotic association. The maintenance of optimal photosynthetic rates in nature is achieved by
balancing the rates of light-induced damage of photosystem II (PSII) with the de novo
synthesis of PSII. The intracellular environment in which symbiotic dinoflagellates flourish
experiences dramatic diurnal oscillations in O2 concentrations. During the daylight hours, pO2
can be as high as 300% saturation, whereas during the nighttime, pO2 may reach values as low
as 5%. These conditions may modify the rates of damage and repair of PSII in hospite. To
understand the factors that control the regulation of photosynthesis in hospite, we inhibited
protein synthesis with chloramphenicol (50mg/L) and Licomycine (50 µg/L) on Porites
astreoides nubbins exposed to half of the surface irradiance in external aquariums. Synthesis
was inhibited during one hour at different times of the day. A continuous inhibition treatment
from 6 am to 2 pm, and a control treatment without inhibition were maintained. PSII charge
separation efficiency (ΔF/Fm`) was monitored every hour during the experiment. Our data
showed significant reduction on ΔF/Fm` proportional to the time of exposure and light intensity
at which synthesis was inhibited. In the experimental treatments, ΔF/Fm` fail to recover at dusk.
These losses were proportional to the light intensity and time of inhibition. Our analyses
revealed average lifetimes for PSII of 3.1 hours, suggesting that this process consume large
amounts of energy that could not be translocated to the coral host.
5-21
Asymbiotic Coral Larvae Preferentially Acquire Free-Living Symbiodinium From The
Sediment Rather Than From The Water Column
Lisa ADAMS* 1 , Vivian CUMBO 2 , Misaki TAKABAYASHI 1
1 Marine Science Department, University of Hawaii at Hilo, Hilo, HI, 2 James Cook University,
Townsville, Australia
Primary or secondary acquisition of free-living Symbiodinium could influence recovery,
resilience, and long-term adaptation of many species of symbiotic marine invertebrates.
Previous studies have identified environmental populations of free-living Symbiodinium in the
water column and sediments of coral reefs. The diversity, abundance, and distribution patterns
of these free-living Symbiodinium that are acquired by animal hosts are not well characterized
to date. We conducted tank experiments to test whether asymbiotic coral larvae of Acropora
monticulosa acquired free-living Symbiodinium from the water column or sediment.
Treatments included natural sediment and filtered (0.22um) seawater (FSW), natural sediment
with unfiltered seawater (SW), no sediment with FSW, and no sediment with SW. In
treatments containing natural sediment, 40 +/- 8.2 % of larvae had acquired Symbiodinium after
3 days of exposure, and 80-90 +/- 7.85 % by 6 days of exposure. The Symbiodinium densities
within the larvae were highly variable at all time points. In treatments without natural sediment,
acquisition of Symbiodinium was not evident until day 6, and only up to 20 +/- 10 % of the
larvae were infected throughout the 12-day experiment. Furthermore, Symbiodinium densities
in larvae of seawater treatments were consistently low, averaging 1-2 cells per larva. Results
from this experiment indicate that infaunal population of Symbiodinium is more accessible for
asymbiotic larvae of A. moticulosa either because the infaunal population of Symbiodinium is
higher than in water column, the infaunal Symbiodinium is more viable than their counterpart in
water column, due to larval behavior that puts them more in contact with sediment than water
column, or a combination of these factors. Moreover, preliminary DNA analysis suggests that
larvae are acquiring different strains Symbiodinium from sediment to those from the water
column.
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