11th ICRS Abstract book - Nova Southeastern University

9-13
Is Allelopathy Involved in Coral Death By Encrusting Excavating Sponges?
Andia CHAVES-FONNEGRA* 1 , Leonardo CASTELLANOS 2 , Sven ZEA 1 , Carmenza
DUQUE 2 , Carlos JIMÉNEZ 3 , Jaime RODRIGUEZ 3
1 Departamento de Biología and Centro de Estudios en Ciencias del Mar -CECIMAR-,
Universidad Nacional de Colombia, INVEMAR, Cerro Punta de Betín, Santa Marta,
Colombia, Santa Marta, Colombia, 2 Departamento de Química, Universidad Nacional de
3
Colombia, Bogotá, Colombia, Bogotá, Colombia, Departamento de Química
Fundamental, Facultad de Ciencias, Universidade da Coruña, A Coruña, España, Coruña,
Spain
The Caribbean encrusting and excavating sponges Cliona delitrix and C. tenuis
successfully compete for space with reef corals, killing and displacing live coral tissue at
rates of several cm per year. A bioassay guided fractionation of their extracts was carried
out to find the compound(s) responsible, and a series of experiments to evaluate whether
there is allelopathy involved and its possible mechanism. Ground and polished
histological sections of the zone of sponge-coral contact revealed that coral polyp
detachment does not seem to occur through erosion of their skeletal support. Healed
sponge fragments placed directly over live coral for 1-2 days were killed by coral
defenses for C. tenuis but not for C. delitrix; fragments of both sponges placed in close
proximity to corals for 6 months did not have any effect on the adjacent coral tissue. The
crude extract and the aqueous partition of both sponge species, and the C. tenuis pure
compound [(-)-(5S)-2-imino-1-methylpyrrolidine-5-carboxylic acid)] (1), incorporated in
gels at close to natural volumetric concentrations, killed coral tissue when brought into
contact with live coral for 1-4 days. While compound 1 dissolved in seawater was only
mildly toxic against live coral and dissociated coral cells, and killed coral larvae only at
high concentration, the aqueous fraction of C. delitrix was toxic against live coral tissue,
larvae and dissociated coral cells. Bioassay guided fractionation of C. delitrix aqueous
fraction is under way. Although prolonged contact of compound 1 (and responsible
compound(s) in C. delitrix) in the enclosed spaces of the coral skeleton may elicit polyp
uplift or produce coral tissue death, other alternative mechanisms such as acid or enzyme
secretion or histo-incompatibility cannot be ruled out.
9-14
The Association Between The Orange Icing Sponge And Caribbean Corals-More
Than A Mutualism?
Tse-Lynn LOH* 1 , Joseph PAWLIK 1
1 University of North Carolina Wilmington, Wilmington, NC
Competition is intense on coral reefs due to limited resources, especially space.
Contrarily, a mutualism has been reported between the Caribbean reef sponge Mycale
laevis and scleractinian corals, with a putative advantage for the coral of protection from
boring sponges and for the sponge of new substratum provided by the growing coral. Our
past research has demonstrated that reef sponges can be categorized on the basis of their
chemical defenses into defended, palatable, and preferred species, the last of which are
restricted to physical refuges on the reef due to predation. Mycale laevis is described as
having a semi-cryptic growth form, which predominates on reefs off Key Largo, Florida
and the Bahamas. However, off Bocas del Toro, Panama, M. laevis is observed to grow
with an unusually massive morphology. Crude extracts of both morphs of M. laevis are
palatable to generalist fish predators, and surveys reveal that sponge-eating fish are very
rare at Bocas del Toro compared to sites in the Florida Keys. Caging experiments will be
conducted in the Florida Keys to determine the effects of predation on exposed fragments
of M. laevis. The semi-cryptic habit of M. laevis growing under coral colonies or between
coral branches could be the result of predation, and not a specific response to a
mutualistic relationship.
Oral Mini-Symposium 9: Chemical Ecology on Coral Reefs
9-15
Phenotypic Plasticity in Chemical Defense And Growth Across A Depth Gradient in
Caribbean Sponges
Marc SLATTERY* 1 , Michael LESSER 2 , Sridevi ANKISETTY 1 , Deborah GOCHFELD 1
1 University of Mississippi, Oxford, MS, 2 University of New Hampshire, Durham, NH
Phenotypic plasticity represents one mechanism by which a species can expand its range across
an environmental gradient while maintaining a positive energetic budget. The transition
between shallow coral reef communities and deep reef communities in the tropics is
characterized by reduced light, and consequently photosynthesis, resulting in potential tradeoffs
in energetic allocation. While reef-building coral diversity decreases with light, many
sponges increase in abundance on reefs from shallow to deep depths. We examined these deep
reef sponge communities (to 100m) in the Bahamas and the Cayman Islands over a period of
five years using technical mixed gas diving. Biodiversity data from the deep reefs show a rich
sponge fauna with approximately 15% endemism and more similarity to one another than to
their respective shallow reef sponge communities. Agelas conifera and Plakortis
angulospiculatus are two common sponge species that span the depth gradient from shallow to
deep reefs. For both species, sponge size and growth rate increased with depth. Growth
differences across the depth gradient can be explained by increased food availability at depth,
but reduced levels of spongivory on the deep reefs might also result in an energetic trade-off
from chemical defenses to growth. Feeding deterrence was higher in shallow water, whereas
antimicrobial activity appeared to be greater at depth. Results to date indicate that different
selective pressures in these ecosystems result in disparate phenotypes within sponge species that
are manifested in plasticity between investments in chemical defense and growth.
9-16
Antioxidant Activity Of Extracts And Secondary Metabolites From Pseudopterogorgia
Sps
Maia MUKHERJEE* 1 , Lyndon WEST 2 , Howard LASKER 3 , Gregory SCHMIDT 4 , William
FITT 1
1 Odum School of Ecology, University of Georgia, Athens, GA, 2 Pharmaceutical and
Biomedical Sciences, University of Georgia College of Pharmacy, Athens, GA, 3 Department of
Geology, University at Buffalo, Buffalo, NY, 4 Plant Biology, University of Georgia, Athens,
GA
Oxidative stress has been proposed as a mechanism of photoinhibition of photosynthesis in
zooxanthellae that could lead to bleaching in symbiotic cnidarians. In a previous study, The
addition of exogenous antioxidants to cultured zooxanthellae cells at elevated temperatures,
with and without exposure to UV radiation, has resulted in the partial recovery of
photosynthetic performance, suggesting that the fluxes of reduced oxygen intermediates were
causing damage to the photosynthetic apparatus (Lesser, 1996). Caribbean octocorals, unlike
other zooxanthellate cnidarians, seem to possess greater resistance to bleaching. Species of the
genus Pseudopterogorgia harbor zooxanthellae of clade B. Previous research (Perez et al, 2000)
has shown that in the sea anemone Condylactis gigantea, which also forms a symbiosis with
clade B zooxanthellae, elevated temperature was followed by massive algal expulsion. This
response is not observed in Pseudopterogorgia elisabethae subjected to similar experimental
treatments. Branching octocorals have been the subject of intense investigation by natural
product chemists, and have proven to be rich in novel compounds with interesting ecological
and pharmacological properties. In this study, we examine the antioxidant potential of semipurified
extracts and purified secondary metabolites isolated from shallow-water Caribbean
octocorals of the genus Pseudopterogorgia. We employ both the “Oxygen Radical Absorption
Capacity (ORAC)” assay and a qualitative assessment of damage to PS 2 during exposure to
elevated temperatures and UV radiation based on measurements of cellular fluorescence
capacity with and without the addition of extracts and purified compounds. The ORAC assay
depends on the free radical damage to a fluorescent probe through the change in its fluorescence
intensity. The inhibition of free radical damage by an antioxidant, which is reflected in the
protection against the change of probe fluorescence, is a measure of its antioxidant capacity
against the free radical.
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