11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
25-9
Carbonate Dissolution By Euendolithic Microorganisms Increases With Rising
pCO2
Aline TRIBOLLET* 1 , Marlin ATKINSON 2 , Chris LANGDON 3
1 IRD, Marseille, France, 2 HIMB, Kaneohe, HI, 3 University of Miami, Miami, FL
Six months-old experimental blocks of the coral Porites lobata colonized by natural
epilithic and endolithic organisms from an offshore oceanic site in Kaneohe Bay (Hawaii)
were placed in experimental tanks with similar water quality as the oceanic site. After a
further two months of acclimation, blocks were exposed to 2 different aqueous pCO2
treatments, one at ambient pCO2 (400 ppmv) and another at 750 ppmv (predicted pCO2
by the year 2100) for another 3 months. Before and after treatment, euendolithic
microorganisms (i.e. boring cyanobacteria, algae and fungi), their distribution, abundance
and bioeroding activity were determined using thin sections, scanning electron
microscopy and image analysis. At the beginning of the pCO2 experiment, euendolithic
communities comprised of 65-80% chlorophyte Ostreobium quekettii, and increased to
90% at the end of the experiment. There were no differences in the relative abundance of
euendolithic species, nor any differences in bioeroded area at the surface of blocks (27%)
between pCO2 treatments. The depth of penetration of euendolithic filaments of O.
quekettii was however significantly higher under elevated pCO2 (1.4 mm) than ambient
pCO2 (1 mm). Consequently, higher microbioerosion rates (biogenic carbonate
dissolution) were measured under elevated pCO2 than ambient pCO2 (0.63 kg m-2 of
planar reef y-1 versus 0.45 kg m-2 y-1). Based on these results, we estimate that
carbonate dissolution by O. quekettii can increase by 30% with a doubling atmospheric
pCO2. We conclude that biogenic dissolution by euendoliths can be a dominant
mechanism of carbonate dissolution in a more acidic ocean and could have major
negative consequences on the maintenance of coral reefs in a close future.
25-10
Coral Reef Response To Climate Change – Addressing Complex Problems With A
Simple Model
Robert BUDDEMEIER* 1
1 Kansas Geological Survey, University of Kansas, Lawrence, KS
The COMBO model is a spreadsheet-based tool designed to be used by managers,
conservationists, and biologists for projecting the effects of climate change on coral reefs
at local-to-regional scales. The model calculates the effects on coral growth and
mortality, and ultimately on coral reef cover, from changes in average sea-surface
temperature and carbon dioxide concentrations, and from episodic high temperature
mortality (bleaching) events. The model uses a probabilistic assessment of the frequency
of high temperature events under a future climate to allow development and testing of
local scenarios. COMBO offers data libraries and default factors for three selected
regions (Hawai’i, Great Barrier Reef, Caribbean), but it is structured with user-selectable
parameter values and data input options, facilitating modifications to reflect local
conditions or to incorporate local expertise. Results of parameter sensitivity analyses and
comparison of future scenarios for different regions in the North and South Pacific are
used to demonstrate model applications to the complexities of assessing the relative
importance of high temperature events, increased average temperature, and increased
carbon dioxide concentration to the future status of coral reefs at local and regional
scales.
25-11
Scleractinian Corals Response To Ocean Acidification Conditions
Maoz FINE* 1,2 , Dan TCHERNOV 3,4
1 Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel, 2 Interuniversity Institute for
Marine Science in Eilat, Eilat, Israel, 3 Department of Evolution, Systematics and Ecology, The
Hebrew University, Jerusalem, Israel, 4 The Interuniversity Institute for Marine Science, Eilat,
Israel
Anthropogenic-driven accumulation of CO2 in the atmosphere, and projected ocean
acidification, has raised concerns regarding the eventual impact on coral reefs.
Little is known however about the physiological response of corals to increased pCO2 and
ocean acidification and hence it is difficult to predict what shifts these ecosystems will
experience. This study demonstrates that skeleton-producing corals grown in experimental
acidified conditions are able to sustain basic life functions, in a sea anemone-like form and will
resume skeleton-building when reintroduced to normal modern marine conditions. Coral
species from the temperate Mediterranean and tropical Red Sea were subjected to pH 7.3-7.6
and 8.2 (ambient) for 3-18 months in an open flow-through system. Corals in decreased pH
conditions demonstrated morphological changes such as dissociation of the colony form
followed by complete skeleton dissolution. In encrusting corals the polyps remained attached to
the undissolved substrate whereas living polyps of branching species descended to the aquarium
bottom. Biomass of the solitary polyps under decreased pH conditions was 1.5 to 3-fold higher
than the biomass of polyps in the control colonies. This may be explained by the higher primary
productivity (Net and Gross Photosynthesis) that was measured in corals under higher pCO2.
Changes in photosynthesis and calcification as a response to decreased pH were species specific
with some species responding earlier than others. Gametogenesis in control and experimental
corals developed similarly. Soft bodied corals calcified and reformed colonies when transferred
back to ambient pH conditions. Hence, in the absence of conditions supporting skeletonbuilding,
corals maintain basic life functions as a skeleton-less ecophenotype. This has far
reaching implications for the understanding of the natural history of corals and their near future
in an increasingly changing environment.
25-12
Impacts Of Ocean Acidification And Warming On Calcifying Coral Reef Organisms
David I. KLINE* 1 , Kenneth R. N. ANTHONY 1,2 , Guillermo DIAZ-PULLIDO 1,2 , Sophie
DOVE 1,2 , Selina WARD 1 , Ove HOEGH-GULDBERG 1,2
1 Centre for Marine Studies, The University of Queensland, St Lucia, QLD, Australia, 2 ARC
Centre of Excellence for Coral Reef Studies, The University of Queensland, St Lucia, QLD,
Australia
The world’s oceans are predicted to become warmer and more acidic over the next century with
potentially dramatic consequences for coral reef ecosystems. However, there is little known
about the combined impacts of temperature and pH on coral reef organisms or about which
species will be most vulnerable to these changed environmental conditions. Using a large
custom-built, flow-through aquarium system we simulated 3 projected levels of CO2
concentrations at two ocean temperatures to simulate future reef conditions under high-emission
scenarios. We compared a series of physiological responses (including growth rate,
photosynthesis/respiration, and survivorship) of four major calcifying coral reef organisms from
the southern Great Barrier Reef (massive corals, branching corals, calcareous algae and
foraminiferans) to temperature and CO2 conditions in a highly replicated factorial design. Our
results suggest that different reef calcifying organisms have varying susceptibilities to climate
change with calcareous algae and branching corals projected to reach their physiological
thresholds as early as 2050. Reefs of the future will likely undergo large ecological changes as
some of the first species likely to be impacted by climate change are important coral reef
framework builders.
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