Abstract
Scleractiniancoralsexhibit 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, 70scleractinian corals (Favia palauensis)were collected fromSanya, the Xisha and Nansha Islands inthe South China Sea. We measured the zooxanthellae density (ZD) and δ13C of zooxanthellae (δ13Cz) and host tissue (δ13Ch) and analyzed thedifferencebetween δ13Chand δ13Cz(i.e.,△h-z 13C). The relatively high ZD andδ13Czvalues in Sanya indicate that thesecoralsmight have higher photosynthetic rates andautotrophicabilities than those in Xisha and Nansha.In contrast, the relativelylow δ13Chand△h-z 13C valuesinXisha and Nanshasuggest that these corals might have higher heterotrophic abilities than those in Sanya. In addition, we tested the coral tissue biomass andskeletal δ13C (δ13Cs)in Sanya and examined their correlations with△h-z 13C.The results showed a negative correlation,indicating that the more organicmaterialsproduced by the coral, the stronger its heterotrophic ability.Our results show that corals can adjusttheir trophic statusesunder different environmental and physiological conditions, which is essential for increasing their adaptabilities to different environmental conditions.
