The synergistic effects of hydrogen peroxide and elevated seawater temperature on the metabolic activity of the coral Ga
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ORIGINAL PAPER
The synergistic eVects of hydrogen peroxide and elevated seawater temperature on the metabolic activity of the coral Galaxea fascicularis Tomihiko Higuchi · Hiroyuki Fujimura · Takemitsu Arakaki · Tamotsu Oomori
Received: 21 July 2008 / Accepted: 4 December 2008 / Published online: 30 December 2008 © Springer-Verlag 2008
Abstract We examined quantitative changes in the metabolism of the coral Galaxea fascicularis caused by increases in both hydrogen peroxide (H2O2) concentration and seawater temperature. Seawater temperatures were maintained at 27 or 31°C in a well-controlled incubation chamber, and three levels of H2O2 concentration (0, 0.3, 3.0 M) were used in experimental treatments. Gross primary production, calciWcation rates and respiration rates were all aVected by increased H2O2 concentrations and high seawater temperatures. Individual treatments of high H2O2 or elevated seawater temperature alone caused signiWcant declines in coral photosynthesis and calciWcation rates within the 3-day incubation period. The synergistic eVect of high H2O2 combined with high seawater temperature resulted in a 134% increase in respiration rates, which surpassed the eVect of either H2O2 or high seawater temperature alone. Our results suggest that both high H2O2 concentrations and elevated temperatures in seawater can strongly aVect coral metabolism; however, these eVects cannot be estimated by simply summing the eVects of individual stress parameters.
Communicated by H. O. Pörtner. T. Higuchi Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa, Japan H. Fujimura · T. Arakaki (&) · T. Oomori Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Okinawa 903-0213, Japan e-mail: [email protected]
Introduction Massive coral bleaching caused by environmental changes following both natural events and anthropogenic activities has recently been observed around the world. The primary causes of coral bleaching include high seawater temperatures, high irradiance and strong ultraviolet (UV) radiation (Fitt et al. 2001). Many studies have reported that elevated seawater temperature is the most important environmental change aVecting the coral symbiotic system between animal hosts and algae, i.e., zooxanthellae (e.g. Brown 1997). Lesser et al. (1990) and Yakovleva et al. (2004) demonstrated that coral bleaching in high temperature seawater was caused by the production of active oxygen species such as hydrogen peroxide (H2O2) within the zooxanthellae. However, very few studies have examined the eVects of H2O2 in the seawater surrounding coral colonies. Hydrogen peroxide is a strong oxidant that is formed photochemically in seawater. The concentration of seawater H2O2 in the coral reef areas of Okinawa Island can reach as high as 0.16 M on sunny days (Arakaki et al. 2005). Much higher concentrations (ca. 0.5 M) of H2O2 were observed when reef water was placed in a quartz test tube under su
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