Coral lipids are an important energy source when their symbiotic zooxanthellae density decreases

Coral bleaching has become increasingly severe in recent years.Bleaching means a decrease in the symbiotic zooxanthellae density in corals.However,the significance of lipids in corals to maintain the stability of energy supply when the zooxanthellae density decreases remains unclear.Favia palauensis and Porites lutea samples collected in the Xisha Islands in March and June 2020 as materials were used in this study.By combining physiological parameters (zooxanthellae density and lipid content) with geochemical indexes (stable nitrogen isotope delta~(15)N_z value of zooxanthellae),the response of coral lipids to the changes in zooxanthellae density and photosynthetic intensity was investigated.The results showed that the zooxanthellae density and delta~(15)N_z value of two genera of corals decreased significantly in summer,implying that the decrease in zooxanthellae density in summer resulted in a decrease in their photosynthetic intensity.At the same time,the lipid content of the two genera of corals also decreased significantly,and the lipid content was positively correlated with zooxanthellae density and delta~(15)N_z value,indicating that there was a coupling relationship between the coral lipid content and the changes of the photosynthetic intensity of zooxanthellae.When photosynthesis intensity decreases,coral can better maintain the stability of energy supply by consuming their own stored lipids,which is of great significance to improve their adaptability to environmental stress and bleaching resilience