Role of feeding and physiological trade-offs in sustaining resilience of the coral Galaxea fascicularis to light limitation

Corals dwelling in coastal reefs persistently inhabit turbid waters characterized by limited light availability. However, the adaptive strategies and mechanisms underlying such resilience to low light stress, particularly the role of heterotrophic inputs and physiological trade-offs, are still poorly understood. Here, we used the dominant coral species in coastal Indo-Pacific reefs, Galaxea fascicularis , as a model and investigated its responses to combinations of four light levels and two feeding regimes. We focused on processes like symbiont physiology, photosynthetic capacity, skeletal growth, and asexual reproduction (budding rate) to determine any physiological strategies utilized by the coral. Our results showed that G. fascicularis acclimates to light limitation by improving photosynthetic efficiency ( α ), and that heterotrophic input had an apparent enhancement effect on most physiological processes. We also found that G. fascicularis can adopt complex trade-offs between a variety of physiological processes to acclimate to multiple light and feeding conditions. Specifically, in the case of autotrophic limitation, G. fascicularis preferentially maintained skeletal growth and symbiont physiology, while budding rate was compromised. Therefore, our study demonstrates that increased heterotrophic input and physiological trade-offs are critical for the persistence and resilience of corals under low light conditions. The findings of this study can provide valuable insights for targeted conservation and management efforts aimed at protecting coral reefs in light-limited habitats.