Physiological response of <italic>Porites lutea</italic> to high temperature stress

To explore the synergistic response characteristics of host corals and symbiotic zooxanthellae to temperature stress, the study focus on a typical reef-building coral species-Porites lutea, as the research subject, cycling corals between bleaching and health by precisely controlling the culture temperature, sampling corals before, during and after recovery from bleaching. The coral symbiont calcification rate, maximum quantum yield, symbiotic zooxanthellae density, chlorophyll content, antioxidant enzymes, ammonium assimilase and community composition of zooxanthellae were measured and analyzed. Results showed that the symbiotic zooxanthellae density, chlorophyll content, maximum quantum yield were significantly higher in healthy state than in the other treatment groups (PPPP>0.05). In summary, high temperature stress can lead to disruptions in the relationship between corals and symbiotic zooxanthellae, thereby eliciting a range of physiological responses in coral symbionts. The subclade C15 is the optimal result of the long-term evolution and natural selection of Porites lutea in response to high temperature stress.