Assessing the physiological and oxidative stress status of Etroplus suratensis under elevated temperature and ocean...

The incessant release of anthropogenic CO₂ in the atmosphere has accentuated ocean warming (OW) and elevated the partial pressure of dissolved CO₂, culminating in a foreseeable decline in oceanic pH. Thus, the present study endeavors to elucidate the concomitant impacts of OW and ocean acidification (OA) on the eco-physiological responses of Etroplus suratensis over a 30-day mesocosm experiment. Physiological parametres, encompassing ingestion, absorption, respiration, and excretion rates, were measured to gauge the scope for growth (SfG). Additionally, a comprehensive evaluation of biomarkers, comprising antioxidant defenses, detoxification pathways, lipid peroxidation, and apoptotic markers, was assessed at various biological levels. Results revealed that combined stressors curtailed the feeding activity, as substantiated by a significant reduction in ingestion and absorption rate. Metabolic depression, illustrated by reduced respiration and excretion rates, insinuated an energy conservation strategy amidst dual stressors. Despite these adaptations, SfG remained depressed, accentuating the detrimental effects of the combined stressors on the energy allocation strategy of this fish. Furthermore, oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST), exhibited heightened activities, albeit these defenses were insufficient to counteract persistent environmental stressors, resulting in increased lipid peroxidation (LPO) and apoptosis. Notably, cleaved caspase-3 expression was significantly upregulated, which suggested that apoptosis was a key cellular response against combined stressors. Overall, anticipated OA and OW significantly impacted the energy budget, oxidative stress biomarkers, and key cellular responses of E. suratensis, compromising growth, survival, and reproductive fitness. These potentially jeopardize population structure and disrupt trophic interactions which may impair functional integrity of estuarine ecosystem.