Molecular hydrogen can minimize negative effects of heat stress on the hard coral genus Acropora

Coral reefs are increasingly threatened by mass bleaching events due to global ocean warming. Novel management strategies are urgently needed to support coral survival until global efforts can mitigate ocean warming. Given the strong antioxidant, anti-inflammatory and anti-apoptotic properties of molecular hydrogen, our study explores its potential to alleviate the negative effects of heat stress on corals. We investigated the ecophysiological responses of two common hard corals ( Acropora spp. and Pocillopora verruco sa) from the Central Red Sea under ambient (26 °C) and elevated seawater temperatures (32 °C), with and without hydrogen addition (∼ 150 µM H ₂ ) over 48 h. Our results showed that at 32 °C without hydrogen addition, P. verrucosa exhibited high temperature tolerance, whereas Acropora spp. showed significant reductions in photosynthetic efficiency and maximum electron transport rate compared to the ambient condition (26 °C). The addition of hydrogen at 32 °C increased the maximum electron transport rate of Acropora spp. by 28 %, maintaining it at levels compared to those at 26 ° C. This suggests that molecular hydrogen benefits specific coral species under heat stress in the short-term. This study provides the foundation for future long-term and in-situ studies, potentially guiding the development of new management strategies aiming at enhancing coral resilience to ocean warming.