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Vol. 51 No. 2, 2012
Determination of the Thermal Tolerance of Symbiodinium Using the Activation
Energy for Inhibiting Photosystem II Activity
Jih-Terng
Wang1,*, Pei-Jie Meng2,3, Yi-Yun Chen1,
and Chaolun Allen Chen4,5,6
1Graduate
Institute of Biotechnology, Tajen Univ., Pingtung 907, Taiwan
2National Museum of Marine Biology and Aquarium,
Checheng, Pingtung 944, Taiwan
3Institute of Marine Biodiversity and Evolution,
National Dong Hwa Univ., Checheng, Pingtung 944, Taiwan
4Institute of Oceanography, National Taiwan Univ.,
Taipei 108, Taiwan
5Biodiversity Research Center, Academia Sinica,
Nangang, Taipei 115, Taiwan
6Taiwan International Graduate Program (TIGP)-
Biodiversity, Academia Sinica, Nangang, Taipei 115, Tawian
Jih-Terng Wang, Pei-Jie Meng, Yi-Yun Chen, and Chaolun
Allen Chen (2012) Holobionts
with different Symbiodinium
clades or subclades display varying levels of thermal tolerance;
however, an index to quantify and standardize this difference has not
yet been formulated. In this study, the potential for the activation
energy (Ea) to inhibit photosystem (PS)II being used to represent the
heat tolerance of Symbiodinium
was investigated. As the Ea required for PSII heat denaturation
increased, the PSII apparatus in the algae remained stable at higher
temperatures; thus, PSII activity was maintained at higher
temperatures. The Ea was determined by fitting the kinetics data of the
decrease in the maximum quantum yield (Fv/Fm) of freshly isolated Symbiodinium (FIS) at an elevated
temperature to the Arrhenius equation. The results indicated that the
PSII activity of FIS linearly decreased with an increase in the
incubation time under thermal stress (r2 > 0.95), and the rate of PSII
denaturation significantly fit the Arrhenius equation (r2 > 0.95) after a
logarithmic transformation. Comparisons between 5 Symbiodinium subclades indicated
that D1a, known as the most heat-tolerant subclade, showed the highest
Ea value (348 ± 16 kJ/mole), which was significantly (p < 0.05) higher than those of
B1, C1, C3, and C15 (126-262 kJ/mole). The reliability of the Ea
calculation was confirmed by the low coefficient of variation (<
10%), suggesting that it can reliably be used to quantify the thermal
tolerance of Symbiodinium.
Key words: Coral bleaching, Activation energy,
PSII activity, Symbiodinium.
*Correspondence: Tel: 886-8-7624002. Fax: 886-8-7621645.
E-mail:jtw@mail.tajen.edu.tw
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