Abstract:

The effects of warming on the metabolism and photosynthetic physiology of symibiodiniaceae of two morphological types (H and S) of a reef-building coral, Galaxea fascicularis, were studied. The results showed that the physiological responses of H-type and S-type to warming were clearly different. At the symibiodiniaceae level, H-type lost a large number of symibiodiniaceae, and reduced the burden of respiratory metabolism of symbionts. In S-type, the number of zooxanthellae could still maintain the needs of symbionts for respiratory metabolism, while increasing the content of chlorophyll b to enhance light absorption. At the host level, the H-type made full use of nutrients delivered by zooxanthellae and compensated for energy consumption through heterotrophic feeding. The nutrients stored by the S-type host could assist the symbionts to adapt to the thermal environment. Galaxea fascicularis adapted itself to environmental changes through different energy utilization modes, i.e., H-type tended to maintain the metabolic balance of the symbiont, while S-type intended to improve the energy distribution of symbiotic algae.

Key words: Galaxea fascicularis, symbiotic algae, warming, morphological types, metabolism, photosynthetic physiology