Extreme warming increases metabolic demand and diminishes acidification effects on larval survival in the dog conch Strombus canarium

Ocean warming and acidification are increasingly altering environmental conditions in coastal ecosystems, potentially affecting the survival, growth, and physiological performance of marine invertebrate larvae. However, knowledge of the combined effects of these drivers on tropical marine gastropods remains limited. In this study, we investigated the interactive effects of extreme warming (30, 32, and 34 °C) and ocean acidification (pH 6.5, 7.0, 7.5, and 8.0) on the survival, growth, and oxygen consumption of planktonic larvae of the dog conch Strombus canarium . Survival was significantly affected by temperature, pH, and their interaction, with the lowest survival observed under extreme warming and severe acidification. In contrast, growth performance was affected by pH but not temperature, with larvae reared under moderately reduced pH conditions (pH 7.5) generally showing greater growth than those maintained under severe acidification (pH 6.5) or ambient seawater conditions. Oxygen consumption increased significantly with temperature and varied among pH treatments, reaching its highest levels under 34 °C at pH 7.5–8.0. The contrasting responses of survival, growth, and metabolism suggest that warming and acidification may influence larval performance, potentially through changes in metabolic demand and physiological capacity. Extreme warming weakened pH-dependent differences in survival, indicating that thermal stress may become a dominant constraint on larval performance under future warming scenarios. These findings highlight the importance of considering multiple environmental stressors when assessing the vulnerability of tropical marine organisms to changing tropical coastal ecosystem conditions.