Evaluating stress antagonists for enhanced coral recovery after natural heat exposure.

Hard corals are highly susceptible to heat stress, often leading to bleaching and mortality, making it critical to identify solutions for stress mitigation and recovery. We evaluated the effects of four potential stress antagonists (hydrogen, phosphate, ammonium, and probiotics) on the widespread hard corals Acropora spp. and Pocillopora favosa in short-term experiments following the 2023 heat stress event in the Central Red Sea. Corals were exposed to each treatment and a control for 48 h, thereby measuring survival, coloration, and photosynthetic efficiency. Hydrogen increased survival by 25% for Acropora spp. and 40% for P. favosa. Phosphate and ammonium both increased survival by 40% for both species, while enhancing photosynthetic efficiency and coloration of P. favosa. Probiotics increased survival by 20% for Acropora spp. and 40% for P. favosa, while improving photosynthetic efficiency for both species. Phosphate and ammonium addition resulted in 100% survival for Acropora spp.. These findings highlight the potential of all these stress antagonists in aiding coral recovery after heat stress. The use of these stress antagonists may be considered in reef and waste water management depending on the needs, logistics, and expertise available at each site.