11th ICRS Abstract book - Nova Southeastern University

9-9
Natural Inducers For Larval Metamorphosis in Three Scleractinian Corals
Peter SCHUPP* 1 , Makoto KITAMURA 2 , Daisuke UEMURA 2
1 Marine Laboratory, University of Guam, Mangilao, Guam, 2 Department of Chemistry,
University of Nagoya, Nagoya, Japan
Many benthic marine invertebrates, including corals, disperse among the plankton before
settlement and metamorphosis. Finding a suitable habitat is especially important for
larvae of sessile marine invertebrates that upon settlement cannot respond to changes in
environmental conditions by moving to a more favorable environment. The ability of
larvae to detect habitat-specific cues has been recognized in a range of phyla, but until
recently, only a few studies identified the chemical structure of compounds involved in
larval settlement and metamorphosis. This study was aimed at identifying compounds
involved in the metamorphosis and settlement of three scleractinian corals. Experiments
with whole crustose coralline algae (CCA) clearly demonstrated their ability to induce
settlement in the scleractinian corals Pseudosiderastrea tayamai, Acropora surculosa,
and Leptastrea purpurea. The previously reported bromotyrosine derivative, 11deoxyfistularin-3,
induced metamorphosis of P. tayamai larvae (approx. 28%) and the
presence of the carotenoids fucoxanthinol and fucoxanthin increased metamorphosis to
approximately 88%. However, experiments with these compounds did neither induce
metamorphosis or settlement in A. surculosa and L. purpurea larvae from Guam. When
we tested various chemical extracts of different CCA species from Guam, we only
observed high rates of settlement with extracts from CCA of the genus Hydrolithion sp.
Bioguided fractionation and subsequent structure elucidation of the Hydrolithion crude
extract indicated a macrolactone as the active compound triggering metamorphosis in L.
purpurea larvae. Further experiments testing the involvement of CCA biofilms, as well as
biofilms from inert surfaces (e.g. tiles, bleached CCA), revealed that biofilms on
Hydrolithion and biofilms on certain inert surfaces more than a week old repeatedly
induced settlement in L. purpurea larvae. Experiments to determine the origin of the
macrolactone (e.g. Hydrolithion itself or the associated biofilms) are ongoing.
9-10
Effects Of Copper Toxicity On Three Species Of Scleractinian Corals
Gretchen BIELMYER* 1 , Philip GILLETTE 2 , Martin GROSELL 2 , Ranjeet
BHAGOOLI 2 , Andrew BAKER 2 , Chris LANGDON 2 , Tom CAPO 2
1 Biology, University of North Florida, Jax., FL, 2 University of Miami, Miami, FL
Most corals thrive in a narrow range of water quality and temperature regimes and as
such can be considered sentinels of our oceans’ health. Globally, coral reefs have been
declining at an accelerating rate. Caribbean reefs, in particular, have suffered an
estimated 80% loss of reef cover in the last 30 years. Land-based sources of pollution
and global warming have been identified as major stressors linked to these declines.
Contaminants, such as metals, although noted as a concern have not been closely
monitored in these sensitive ecosystems, nor have the potential impacts been
characterized. There is a need to develop biomonitoring tools to assess potential effects
of metal exposure. In this study, three species of laboratory-reared scleractinian corals,
Acropora cervicornis, Pocillopora damicornis, and Montastraea faveolata were exposed
to copper (ranging from 0-25 µg/L) for four weeks. At the end of the exposure period
mortality, growth, copper accumulation, carbonic anhydrase activity, zooxanthellae
density and electron transport rate were measured. The three coral species exhibited
significantly different sensitivities to copper, with effects occurring at copper
concentrations as low as 10 µg/L. The relationships between physiological/toxicological
endpoints and copper accumulation within and between species will be presented as a
means to elucidate the potential mechanism for effects and explain observed differences
in sensitivity.
Oral Mini-Symposium 9: Chemical Ecology on Coral Reefs
9-11
Chemical Ecology is the Key to Understanding Sponges on Caribbean Coral Reefs
Joseph PAWLIK* 1
1 Biology and Marine Biology, UNC Wilmington, Wilmington, NC
Sponges are now the dominant organisms on Caribbean coral reefs. Until recently, it was
believed that consumers had little effect on reef sponges, because sponge-eating fishes were
thought to spread their predatory activities over all available species to the detriment of none in
particular. But research on the chemical ecology of this system has transformed our
understanding of it. Laboratory and field experiments have revealed three distinct categories of
sponges within the community: (1) defended species that are unpalatable to consumers because
they contain secondary metabolites, (2) palatable species that sustain grazing by consumers yet
are equally common as defended species on the reef, and (3) preferred species that are rapidly
consumed when transplanted to the reef, and are found only in refuge habitats. The secondary
metabolites responsible for the chemical defenses of several species have been isolated and
identified using bioassay-guided fractionation and field experiments with natural populations of
reef consumers. To counter the effects of grazing by fishes, palatable species appear to heal,
grow or reproduce faster than defended species. Some sponge species compete with corals for
space by producing metabolites that cause coral bleaching or that interfere with photosynthesis
of coral symbionts. The predictive value of the foregoing is becoming evident: over-fishing
may result in a release from predation of sponge species that are competitively superior to
corals, reinforcing the current state of low coral cover on Caribbean reefs.
9-12
Toxic Reef Syndrome: The Sponge-Seaweed Connection And The Consequences Of
Allelopathic Impacts Of Sponges And Seaweeds On Degraded Caribbean Coral Reefs
Niels LINDQUIST* 1 , Chris S. MARTENS 2 , James L. HENCH 3 , Jeremy B. WEISZ 4 , Melissa
W. SOUTHWELL 5 , Brian POPP 6 , Nyssa SILBIGER 1 , Patrick GIBSON 2
1 Institute of Marine Sciences, University of North Carolina Chapel Hill, Morehead City, NC,
2 Department of Marine Sciences, University of North Carolina Chapel Hill, Chapel Hill, NC,
3 Environmental Fluids Mechanics Laboratory, Stanford University, Stanford, CA, 4 Department
of Biological Sciences, Old Dominion University, Norfolk, VA, 5 Department of Chemistry and
Biochemistry, University of North Carolina Wilmington, Wilmington, NC, 6 Department of
Geology and Geochemistry, University of Hawaii, Honolulu, HI
Increasing global, regional and local stresses on coral reefs have resulted in a phase shift on
Caribbean reefs from coral to sponge-seaweed dominance, yet little is know about the roles of
sponges within the new ecology of degraded reefs. The goal of our sponge research, involving
physical oceanographers, marine chemists and coral reef ecologists, is to rigorously determine
how sponges alter the composition and abundance of small particles and dissolved chemicals in
the seawater they process and how these changes impact reef ecology. On today’s reefs,
sponges can be exceptionally abundant, and with their high rates of filtration, contribute
substantially to nutrient element cycling. We are finding that sponges re-mineralize much of the
nitrogen in the particulate and dissolved organic matter they consume to ammonium and nitrate.
Simultaneously, their high respiration rates substantially reduce levels of dissolved oxygen in
the seawater they filter. The tremendous volumes of seawater many sponges exhale are hypoxic,
rich in dissolved inorganic nitrogen, and likely sponge-produced toxins, all of which can harm
corals. Sponge inputs of fertilizer to reefs have likely played a role in the proliferation of
seaweeds on degraded Caribbean coral reefs, which along with the abrupt die-off of the once
ubiquitous urchin Diadema antillarum have yielded an abundant algal community dominated
by seaweeds and cyanobacteria chemically resistant to fish grazing. Chemicals exuded by these
seaweeds and cyanobacteria further reduce benthic boundary layer water quality. While
sponges can increase reef stability and provide food and shelter for other organisms, on
degraded reefs with little coral cover, sponges likely interact with seaweeds to create an
alternative stable state to coral dominated reefs and a chemically hostile environment that
diminishes coral health and recruitment.
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