11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 3: Calcification and Coral Reef - Past and Future
3-5
Reduced Skeletal Growth in The Scleractinian Coral porites Lutea From Southern
Thailand – A Consequence Of Climate Change Over The Last Two Decades?
Jani TANZIL* 1 , Barbara BROWN 1 , Sandy TUDHOPE 2 , Hansa CHANSANG 3
1 Newcastle University, Newcastle, United Kingdom, 2 Edinburgh University, Edinburgh,
United Kingdom, 3 Phuket Marine Biological Centre, Phuket, Thailand
Of the few studies that have examined in situ coral growth responses to climate change,
none have done so in equatorial waters already subject to relatively high temperatures
(average >27°C). Comparison of coral growth of Porites lutea, a major reef building
coral in the eastern Andaman Sea, sampled from eight sites on an inshore-offshore
gradient around Phuket, South Thailand were made at two time periods (Dec 1984–Nov
1986 and Dec 2003–Nov 2005). Results revealed a significant decrease in coral
calcification (~11%) and linear extension rates (~18%) in recent samples compared with
those collected in the mid 1980s, while skeletal bulk density remained unchanged. Over
this period, sea temperatures (SST) in the area have risen at a rate of 0.16°C per decade
(current temperature range 28-30°C) and regression analyses of coral growth data,
acquired at regular intervals over the period 1984-2005, suggest a link between rising
temperature and reduced linear extension. These results contrast with earlier studies from
reefs at higher latitudes, where sea temperatures are lower (average ~25–27°C) and
where a positive relationship between linear extension and SST was found. The apparent
sensitivity of linear extension in P. lutea to increased SST suggests that corals in the
Andaman Sea may already be subjected to temperatures beyond their thermal optimum
for calcification.
3-6
Simulation And Observations Of Reef Corals Calcification Associated To Ocean
Warming
Juan P. CARRICART-GANIVET* 1 , Aimé RODRÍGUEZ-ROMÁN 2 , Susana
ENRÍQUEZ 2 , Guillermo HORTA-PUGA 3 , José D. CARRIQUIRY-BELTRÁN 4 , Roberto
IGLESIAS-PRIETO 2
1 El Colegio de la Frontera Sur, Unidad Chetumal, Chetumal, Q. Roo, Mexico, 2 Unidad
Académica Puerto Morelos, Instituto de Ciencias del Mar y Limnología, UNAM,
Cancún, Q. Roo, Mexico, 3 Facultad de Estudios Superiores Iztacala, Universidad
Nacional Autónoma de México, Tlalnepantla, Edo. México, Mexico, 4 División de
Geociencias Ambientales, Instituto de Investigaciones Oceanológicas, UABC, Ensenada,
Baja California, Mexico
Reefs achieve positive carbonate balances when the calcification rates of reef-building
corals and other organisms are larger that the rates of physical and biological erosion. We
characterize the effects of short-term exposures to different temperatures on the
calcification rates of the scleractinian Montastraea faveolata. Calculations of calcification
rates under a modeled sea surface temperature (SST) future scenario for the West
Atlantic indicate that increases in SST will result in significant reductions in coral
calcification. Analyses of historical variations in calcification rates during the last 20
years of M. faveolata, growing in Veracruz, southern Gulf of Mexico, and massive
Porites, growing in Rib Reef, Central Great Barrier Reef, are consistent with the
experimental data, indicating negative associations with temperature. We found evidence
that the local ocean warming trends have already resulted in significant reductions in
calcification of both species, indicating that increases in temperature alone would
severely compromise the abilities of corals to form and maintain reefs and their services.
The observed reductions in calcification rates of M. faveolata in Veracruz are larger that
the predictions of the physiological model, suggesting that other forcing processes in
addition to increases in SST are responsible for the observed reductions in calcification.
We show that relative small changes in the optical properties of the seawater are
sufficient to explain the observations.
3-7
Raman Spectroscopy of the Initial Mineral Phase of Coral Skeleton
Brent CONSTANTZ* 1
1 Geological and Environmental Sciences, Stanford University, Stanford, CA
Recent studies suggest that the mineralogy of the scleractinian skeleton has been phenotypically
plastic over geological time, varying with ocean chemistry, and dominated by physiochemical
processes, under low levels of biologic control. Isotopic studies have demonstrated that
scleractinian corals strongly fractionate carbon and oxygen from seawater during their skeletal
mineralization process. Skeletal chemical studies have shown that that minor and trace elements
in coral skeleton are also out of equilibrium with seawater. Furthermore, the degree of chemical
fractionation is highly variable throughout the skeleton, but relatively consistent within
particular anatomical structures. Mineralization of the scleractinian exoskeleton is initiated at
centers of calcification located at the calcioblast ectodermal interface with the skeleton. The
initial mineral phase of scleractinian coral skeletal has long been assumed to be the
orthorhombic polymorph of calcium carbonate, aragonite. Past work has included
crystallographic analysis using selected area electron diffraction of ion thinned specimens and
various microanalytical chemical analyses that have shown that the initial mineral phase at the
centers of calcification differs chemically and crystallographically from the aragonite fiber
bundles comprising most of the skeleton. Due to the intricate microstructural anatomy, most
studies have failed to properly locate the centers of calcification, and sample preparation
artifacts have further complicated our understanding of the crystallographic character of the
centers of calcification. Raman microscopy allows live coral skeleton to be observed in the
physiologic state, controlling for both microstructure as well as mitigating sampling artifacts.
Results to date indicate that highly unstable amorphous phases predominate the initial phase of
mineralization in the scleractinian centers of calcification. These findings help explain why the
crystallographic identity of the centers of calcification have to date been unclear. The new
information from Raman microscopy has important implications with respect to the potential
impact of ocean acidification on scleractinian skeletal formation.
3-8
Daily Banding in Coral Septa.
Ian SANDEMAN* 1
1 Biology, Trent Umiversity, Peterborough, ON, Canada
Fine banding has previously been described from different regions of coral skeletons. If present
in septa, daily growth increments have the potential to provide, with a non-destructive
technique, a record of recent growth. Sections of septa from eight coral species were mounted
on glass microslides with thermo-setting resin, ground (10-20μ), and polished on both sides.
With phase contrast optics, alternating light and dark laminations are apparent in the crystalline
areas of the sections. The separation of the bands varied from 2-4μ in Agaricia agaricites to 10-
15μ in Meandrina meandrites. In some septa (e.g. M. meandrites) banding is robust, in others
banding was confined to the central part of the septa (e.g. Montastrea) and in some species
banding was not seen at all (e.g. Acropora cervicornis). Small A. agaricites colonies were held
in seawater with alizarin R (20mg/L) for two periods separated by four days. Two lines of
stained skeleton confirmed that the laminations are diurnal and indicated that the darker bands
(optically denser) are formed during the day and the lighter bands at night. Ground polished and
stained sections of fixed A. agaricites mounted in epoxy resin showed, particularly in areas with
high calcification, many bunches of spherical bodies (Golgi apparatus?) in the calicoblastic
layers. These bodies are probably involved in the secretion of the organic matrix. A model of
calcification is presented which suggests a mechanism by which the banding is produced.
Following Vago et al (1997) physical extension takes place in the evening as a new layer of
matrix is secreted and during the day calcium carbonate is deposited in the new matrix layer. In
large septa the series of laminations representing several months of growth can be followed.
14