Abstract
Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation. However, whether corals can adjust their trophic statuses under contrasting environmental conditions remains unclear. In our study, 70 scleractinian corals (Favia palauensis) were collected from Sanya, the Xisha and Nansha Islands in the South China Sea. We measured the zooxanthellae density (ZD) and δ13C of zooxanthellae (δ13Cz) and host tissue (δ13Ch) and analyzed the difference between δ13Ch and δ13Cz (i.e., △h-z 13C). The relatively high ZD and δ13Cz values in Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those in Xisha and Nansha. In contrast, the relatively low δ13Ch and △h-z 13C values in Xisha and Nansha suggest that these corals might have higher heterotrophic abilities than those in Sanya. In addition, we tested the coral tissue biomass and skeletal δ13C (δ13Cs) in Sanya and examined their correlations with △h-z 13C. The results showed a negative correlation, indicating that the more organic materials produced by the coral, the stronger its heterotrophic ability. Our results show that corals can adjust their trophic statuses under different environmental and physiological conditions, which is essential for increasing their adaptabilities to different environmental conditions.
