Extreme winter cold-induced osmoregulatory, metabolic, and physiological responses in European seabass (Dicentrarchus labrax) acclimatized at different salinities

Despite climate-change challenges, for most aquaculture species, physiological responses to different salinities during ambient extreme cold events remain unknown. Here, European seabass acclimatized at 3, 6, 12, and 30 PSU were subjected to 20 days of an ambient extreme winter cold event (8 degrees C), and monitored for growth and physiological performance. Growth performance decreased significantly (p < 0.05) in fish exposed at 3 and 30 PSU compared to 6 and 12 PSU. During cold stress exposure, serum Na+, Cl-, and K+ concentrations were significantly (p<0.05) increased in fish exposed at 30 PSU. Serumcortisol, glucose, and blood urea nitrogen (BUN) were increased significantly (p < 0.05) in fish exposed at 3 and 30 PSU. In contrast, opposite trends were observed for serum protein, lactate, and triglycerides content during cold exposure. Transaminase activities [glutamic-pyruvate transaminase (GPT), glutamic oxaloacetic transaminase (GOT), lactic acid dehydrogenase (LDH), gamma-glutamyl-transaminase (gamma GGT)] were significantly higher in fish exposed at 3 and 30 PSU on days 10 and 20. The abundance of heat shock protein 70 (HSP70), tumor necrosis factor-alpha(TNF-alpha), cystic fibrosis transmembrane conductance (CFTR) were significantly (p<0.05) increased in fish exposed at 3 and 30 PSU during cold shock exposure. In contrast, insulin-like growth factor 1 (Igf1) expression was significantly lower in fish exposed at 3 and 30 PSU. Whereas, on day 20, Na+/K+ ATPase alpha 1 and Na+/K+/Cl- cotransporter-1 (NKCC1) were significantly upregulated in fish exposed at 30 PSU, followed by 12, 6, and 3 PSU. Results demonstrated that ambient extreme winter cold events induce metabolic and physiological stress responses and provide a conceivable mechanism by which growth and physiological fitness are limited at cold thermal events. However, during ambient extreme cold (8 degrees C) exposure, European seabass exhibited better physiological fitness at 12 and 6 PSU water, providing possible insight into future aquaculture management options. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that European seabass exposed to extreme winter cold events exhibited different physiological responses and growth performance depending on the salinity levels. Fish exposed to 3 and 30 PSU showed significant impacts on physiological indicators, while those in 6 and 12 PSU demonstrated better growth and physiological performance.