The differential physiological responses to heat stress in the scleractinian coral Pocillopora damicornis are affected by its energy reserve

Abstract

The scleractinian corals conduct various responses upon heat stress such as bleaching and tissue loss, and colonies from the same coral species can conduct differential physiological activities with the biochemical basis unknown. In the present study, factors that influence the heat stress responses in coral Pocillopora damicornis were investigated. It was observed that P. damicornis conducted three differential physiological responses under heat treatment including tissue loss, bleaching, and polyp bailout. During heat response process, coral colonies conducting tissue loss had significantly higher total antioxidant capacity (T-AOC) level, while the bleached coral colonies exhibited higher caspase-3 activation level. Moreover, the stress response varied based on the energy reserve status. Colonies with higher lipid and sugar reserves were more likely to bleach, while those with lower reserves tended to undergo polyp bailout. We demonstrate that energy reserves influence the heat response patterns of P. damicornis. Colonies with higher lipid and sugar reserves may survive longer under heat stress, suggesting that these energy reserves contribute to their heat resistance. This study suggests that colonies with higher energy reserves prior to thermal stress may have greater thermal resistance, indicating that long-term environmental stressors that deplete energy reserves could increase susceptibility to thermal stress.

Keywords: Bleaching; Energy reserve; Heat stress; Physiological response; Pocillopora damicornis; Polyp bailout; Tissue loss.