Effect of marine heatwaves on juvenile greater amberjack (Seriola dumerili)

Marine heatwaves (MHWs) have increased in frequency, intensity, and duration in recent years causing significant impacts on marine organisms and fisheries. This study explores the physiological changes of juvenile greater amberjacks (Seriola dumerili) that cope with MHWs. Results showed that physiological parameters were significantly affected by the intensity, duration of MHWs or interaction of two factors (P < 0.05). Repeated MHWs in which water temperatures were increased (24 °C to 28 °C and 32 °C) resulted in changes in enzyme activity levels (catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH)), as well as the level of malondialdehyde (MDA) for antioxidant defense, immune function (acid phosphatase (ACP), alkaline phosphatase (ALP), and lysozyme (LYZ)), and energy metabolism (including triglycerides (TG), glucose (GLU), aspartate aminotransferase (GOT), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and succinate dehydrogenase (SDH)). The activities of enzymes, including those associated with antioxidant defense, immune function, and energy metabolism, changed significantly in relation to short-term MHWs, indicating a thermal stress response. When S. dumerili were exposed to repeated-MHWs, thermal stress responses increased at 28 °C (T28) and decreased at 32 °C (T32). These results exhibited the inability of S. dumerili to acclimate to severe thermal stress from MHWs. This study examined S. dumerili responses to MHWs and assessed the physiological adaptation of juvenile greater amberjacks to MHWs.