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MEPS prepress abstract   -  DOI:

Interspecific differences in the response of coral trophic status to the decrease in symbiotic zooxanthellae in summer

Shendong Xu, Zheng Men, Kefu Yu*, Hanji Chen, Hongyan Mo, Biao Chen, Zhenjun Qin

*Corresponding author:

ABSTRACT: Coral bleaching is becoming a serious issue for coral reefs. From the perspective of energy supply, the decrease in symbiotic zooxanthellae density (ZD) during bleaching leads to a reduction in the amount of energy provided by photosynthesis to the coral host. However, there are still many unknowns about how corals maintain the stability of energy supply when zooxanthellae decrease. In this study, 89 coral samples, including relatively stress‐tolerant massive Favia palauensis and Porites lutea and the relatively vulnerable branching Acropora milleporaand Pocillopora damicornis were collected from the Xisha Islands in the South China Sea in spring and summer 2020. The physiological parameters of ZD, chlorophyll a, tissue biomass and lipid content were measured. The δ13C of zooxanthellae and host were analyzed to explore the changes of trophic status in summer. The results show that ZDs of A. millepora, P. damicornis, F. palauensis and P. lutea significantly decreased by 32, 29, 22 and 22%, respectively, in summer. P. lutea and F. palauensis maintained metabolic energy requirements depending largely on heterotrophy. A. millepora and P. damicornis were more dependent on consuming their own lipids. Our study shows that there are intergeneric differences in energy maintenance mechanisms used to cope with the decrease in ZD. We suggest that the higher heterotrophic ability of F. palauensis and P. lutea renders their trophic status more plastic than that of A. millepora and P. damicornis. This characteristic may potentially affect their bleaching resilience.