Coral physiological trait responses to environmental stress in a changing ocean

Coastal habitats are increasingly affected by climate change and human-driven local pollution. Stressors as ocean warming, declining oxygen and pH levels are significant threats to vulnerable organisms, particularly tropical corals that inhabit narrow environmental ranges. Understanding coral growth and physiological responses to these stressors, along with the interspecific sensitivity among coral species is essential for predicting future coral reef structures. Our research involved experiments conducted under various manipulated conditions using local reef-building coral species collected from the southern Gulf of Thailand. The representative corals were subjected to stress conditions, including elevated temperatures, high light intensities, low oxygen, and pH levels. We quantified physiological parameters such as photosynthetic efficiency, Symbiodiniaceae and chlorophyll content, primary production, respiration, calcification biomass and growth rate. Our findings revealed varying sensitivity among coral species, with physiological responses according to the specific stressors. Temperature and light stress caused significant photoinhibition, resulting in reductions of Symbiodiniaceae density, chlorophyll concentration, and overall coral growth. Low oxygen levels significantly affected coral energy balance whereas and low pH influenced to structural integrity, causing acute impacts on more sensitive coral species. These insights into coral mechanism at biological and cellular levels are crucial for understanding how coral reefs will cope with the challenges posed by climate change.