11th ICRS Abstract book - Nova Southeastern University

Poster Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
25.1141
Variation in Zooxanthella Production Of Dimethylsulfoniopropionate (Dmsp)
Mary Alice COFFROTH* 1 , Maria Gabriella JACKSON 1 , Patricia MATRAI 2 , Carlton
RAUSCHENBERG 2
1 Geology, University at Buffalo, Buffalo, NY, 2 Bigelow Laboratory for Ocean Sciences,
W. Boothbay Harbor, ME
Dimethylsulfoniopropionate (DMSP) is produced by many marine phytoplankton,
including dinoflagellates. DMSP's proposed functions include an antioxidant, an
osmolyte and a defensive compound, among others. Dinoflagellates within the genus
Symbiodinium (zooxanthellae) that form symbioses with cnidarians also produce DMSP.
However, its role in these organisms is not fully understood. We examined the variation
of dissolved and particulate DMSP cellular quota (DMSPp and DMSPd, respectively)
among different strains of Symbiodinium and investigated how this cellular quota
changed in the presence of environmental stresses. Symbiodinium isolates from Pacific
and Caribbean cnidarian hosts, reared under identical environmental conditions (14h:10h,
light:dark cycle at 26oC), exhibited variation in DMSPp content both between and within
clades (A, C, D, and F). Symbiodinium clade A isolates had the highest DMSPp cellular
quota, suggesting a potential antioxidant role for these symbionts common in shallow,
high light environments. In the intact symbiosis, DMSPp concentrations did not vary
within colonies of Porites divaricata (Pd). However, significant variation was detected
among coral species (Montastrea cavernosa (Mc), M. faveolata (Mf), Porites astreoides
(Pa), and Pd), with Mf having the highest concentrations. We also investigated changes
in DMSPp and DMSPd concentrations occurring in the intact symbiosis under
temperature stress. Mc, Mf, Pa, and Pd were exposed to water temperature 2 o C above
ambient for 2 weeks. Elevated temperatures did not result in a measurable increase in
DMSPp concentrations compared to non-stressed corals; instead, DMSPp concentrations
were greater prior to stress. However, DMSP concentrations in Pd did not change after 2
weeks of heat stress. When this coral was subjected to elevated temperature over a longer
time period (3.5 wks), it bleached and showed very high DMSPp levels.
25.1142
Coral Ultrastructural Response To Elevated Pco2 And Nutrients During Tissue
Repair And Regeneration
D. Abigail RENEGAR* 1 , Patricia L. BLACKWELDER 1,2 , Alison L. MOULDING 1
1 National Coral Reef Institute, Nova Southeastern University Oceanographic Center,
Dania, FL, 2 RSMAS, University of Miami, Miami
Corals and coral reefs have recently experienced widespread decline attributed to
anthropogenic pressure on reef systems. Growing coastal population density is expected
to result in a concomitant increase in coastal runoff and nutrification of the coastal zone.
Rising atmospheric CO2 partial pressure (pCO2) is predicted to change ocean surface
water carbonate saturation, resulting in reduced coral calcification and reef growth.
While it has been shown that nutrient and pCO2 stress effect coral growth and
calcification, study of the specific effects on coral tissue has not received significant
attention in the literature despite considerable current interest. The objective of this
research is to examine, at the ultrastructural and histological level, the process of tissue
repair in corals and how it is affected by exposure to elevated nutrients and pCO2. The
target species of this proposed research, Montastraea cavernosa and Porites astreoides,
are important and widespread Caribbean reef-builders. Coral tissue recovery and repair
processes will be assessed with transmission (TEM) and scanning (SEM) electron
microscopy by examining fragments of M. cavernosa and P. astreoides exposed to
elevated nitrate, phosphate, and pCO2 during wound healing. These analyses will result
in a more complete understanding of the complex process of tissue repair and
regeneration in corals under varying environmental conditions.
25.1143
Using The Concept Of Degree Heating Weeks And The Threshold Of Coral Bleaching
Temperature To Assess The Risk Of Coral Bleaching in Taiwan
Tai-Ying WU* 1 , Sharon HORNG 1 , Chang-Feng DAI 1
1 Institute of Oceanography, National Taiwan University, Taipei, Taiwan
Degree Heating Weeks (DHWs) represent the accumulation of thermal stress that coral reefs
experienced over the past 12 weeks was applied to evaluate the risk of coral bleaching under the
impacts of climate change. One DHW is equivalent to one week of sea surface temperatures
(SSTs) one degree Celsius greater than the expected summertime maximum. We used the
threshold of coral bleaching temperature instead of the expected summertime maximum to
estimate the DHW values for assessing the risk of coral bleaching in Taiwan. By reviewing the
existing articles, we found the thresholds of coral bleaching temperature are negatively
correlated with latitudes. To verify the applicability of the threshold, we collected SSTs from
1990 to 2006 around Taiwan together with the records of coral bleaching, and the results
confirmed the temperature thresholds are adequate for indicating the occurrence of coral
bleaching. The DHWs of Kenting Reefs in 2007 were used to verify its applicability as an
indicator for the risk of coral bleaching. The DHW was 1.03 in mid-July when the spotted cases
of coral bleaching were observed. During August and September, the DHWs were above 5,
when severe and extensive coral bleaching was observed in Kenting Reefs. These results
support the DHW is a good indicator for coral bleaching in Taiwan. We further used the
simulated SSTs from CGCM2 SRES A2 and B2 scenarios to evaluate the risk of coral
bleaching from present to 2100. The results show the risk of coral bleaching in Taiwan will
increase significantly after 2050 under the A2 scenario; however, under the B2 scenario, coral
bleaching will be occasional events even after 2070. Thus, lowering the greenhouse gas
emission will reduce the threats of global warming on coral reefs and provide longer time for
preventing coral reefs from degradation in Taiwan.
25.1144
Heat Tolerant Corals (porites Lutea and galaxea Fascicularis) From Near-Shore And
Offshore Reefs in Northern Vietnam
Suzanne FAXNELD* 1 , Tove Lund JÖRGENSEN 1 , Michael TEDENGREN 1 , Magnus
NYSTRÖM 1 , Ngai Dang NGUYEN 2
1 2
Systems Ecology, Stockholm University, Stockholm, Sweden, Institute of Marine
Environment and Resources, Hai Phong, Vietnam
The objective of this study was to investigate how two coral species, Porites lutea and Galaxea
fasicularis responded to increased water temperature and if the responses differed between
species and between corals from near-shore / offshore reefs.
Corals were collected from near-shore, i.e. disturbed reefs, and offshore, i.e. reefs considered
pristine. The corals were exposed to gradually increased temperatures for 96 h. (day 1: 27.5°C,
day 2: 30.5°C, day 3: 33.5°C, day 4: 25.5°C). The corals in the control group were exposed to
25.5°C.
The results show that both species, with no regard of area, experienced a decrease in GP/R ratio
day 1, after a moderate temperature increase. However, on the other exposure days there were
no differences between heat treated and control corals, even though the temperature increase
was 8°C above ambient on the third day of exposure.
For Porties there were no differences in gross production or respiration between the two areas,
while the pattern was different for Galaxea, where gross production and respiration increased
only for corals from the pristine area.
These results illustrate that even a small temperature increase affects the corals, but the corals
then seem to adapt to the temperature changes. One explanation could be that these species are
tolerant to bleaching and temperature increases, since they come from a high latitude reef and
experience large temperature fluctuation over the year.
The different results between disturbed and pristine area samples for Galaxea might be due to
Galaxea being a sediment tolerant species which might therefore tolerate another stressor (i.e.
elevated temperatures), due to useful clade types, genetic or physiological adaption to different
environmental changes, or their ability to induce heat shock proteins.
549