Mechanisms of coral reef bleaching (continued)

The fundamental results of Jones et al. (1998) and Warner et al. (1999) are backed up by Takahashi et al. (2008). Their investigations found that photobleaching occurred in the CS-73 strain of Symbiodinium at temperatures over 31˚C, with inhibition of PSII taking place. They also found that loss of photosynthetic pigment can occur as a result of heat stress combined with irradiance, which is due to the loss of antennae proteins that contain large concentrations of photosynthetic pigments to harvest large quantities of light. The molecular mechanisms leading up to this loss of antennae are not fully known, but it is likely due to the degradation and inhibition of protein synthesis of structural proteins within the antennae, such as acpPC. Another strain of zooxanthellae studied, the OTcH-1 strain, showed no loss of pigment after exposure to the same temperatures, indicating differences in the resistance to environmental stress between species of zooxanthellae (Takahashi et al., 2008).