February 15-18, 2009 Washington State Convention Center Seattle ...

1
RELATIONSHIPS AMONG THERMAL STRESS, BLEACHING AND OXIDATIVE DAMAGE
DURING THE CULTURE OF HERMATYPIC CORAL, Pocillopora capitata
Marco A. Liñán-Cabello, Laura A. Flores-Ramírez and Alfredo Mena-Herrera
Acuacultura/Biotecnología, FACIMAR
Universidad de Colima
Km 19.5 carretera Manzanillo-Barra de Navidad Manzanillo
Colima, México
linanmarco@hotmail.com
Corals have a symbiotic relationship with the photosynthetic zooxanthellae that live within their endodermal cells, providing
energy to the coral tissues. Under high temperature conditions, the stability of this symbiosis is adversely affected, leading to
bleaching in a wide variety of coral species. Various in vitro studies have shown that symbiotic dinoflagellates maintained in
culture are susceptible to thermal stress.
To examine the response to exposure to a thermal gradient in
coral in vitro, we assessed the effect of a gradual 10 °C temperature
increase (22 to 32 °C over 10 h) on normal (N), partially
bleached (P) and control (C) samples collected from different
branches of the same coral (Pocillopora capitata). We
examined markers of oxidative stress, including lipid peroxidation
(MDA) and superoxide dismutase (SOD) (Tab.1) activity,
indicators of bleaching, including chlorophyll a (Chl a) and carotenoid
pigment (PC) levels, as well as zooxanthellae density
(Fig. 1). Our results revealed that N, P and C coral samples all
contained higher levels of PC versus Chl a. The levels of both
pigments increased as the temperature increased from 22 to 28
°C only in N and C samples, whereas P samples showed less
cellular damage than N and C samples at temperatures between
26 and 28 °C, and had greater antioxidant activities at temperatures
between 26 and 30 °C. The rate of zooxanthellar expulsion
consistently increased with temperature in all three coral
types across the entire temperature range.
We found that partially bleached samples (P) of P. capitata
tolerated short-term stress (at temperatures up to 28 °C) more
effectively than did normal (N) or control (C) samples of the
same coral. This P sample tolerance could be a consequence of
its continuous exposure to a regime of short duration thermal
variation (4–6 °C).
Collectively, these results indicate that temperature has a direct
effect on the antagonistic relationship between temperature-
induced damage and protective antioxidant mechanisms in this
type of coral.