Antioxidant and Phytoplankton-Enriched Microparticle Diets Mitigate Thermal Stress in the Reef-Building Coral Stylophora pistillata.

The global coral crisis continues to intensify the urgent need for conservation and restoration interventions. Heatwaves are the primary driver of coral declines, triggering coral bleaching by disrupting the symbiosis with the dinoflagellates that provide corals with essential nutrients and energy. Since oxidative stress and nutrient disruption are key processes associated with coral bleaching, we developed a novel, low-cost bioengineering approach to deliver antioxidant support to corals. We used the reef-building model coral Stylophora pistillata to test microparticle feeds containing antioxidants and phytoplankton cells during a simulated heatwave. Among five phytoplankton species, Pavlova lutheri, known to produce antioxidants de novo, offered the best protection to S. pistillata. Moreover, the encapsulated antioxidants curcumin and fucoxanthin outperformed P. lutheri, supporting corals by showing higher photosynthetic efficiency and total antioxidant capacity as well as lower lipid peroxidation impacts. Considering cost-effectiveness for upscaling, curcumin emerges as a promising, scalable intervention for coral conservation, allowing a direct delivery of antioxidant protection to fight oxidative stress associated with warming waters.