Objective Effects of seawater acidification on respiratory metabolism and related gene expressions of Paralichthys olivaceus were studied, so as to provide scientific theoretical basis for the conservation of P. olivaceus resources in an increasingly acidified marine environment.

Method In enclosed still water tanks, P. olivaceus weighed (2.16±0.34) g were raised for 49 d with water at normal pH at 8.10 as control and at pH 7.90, 7.70, 7.50, and 7.30 adjusted by CO₂ infusion for treatments. Oxygen consumption and ammonia excretion of the fish were measured, and expressions of abcg 8 and glulb monitored using qRT-PCR.

Result The seawater pH had significant effects on the oxygen consumption rate and ammonia excretion rate, and the gene expression of metabolic genes abcg 8 and glulb (P＜0.05). As the pH of seawater was lowered in the tank, the rates of oxygen consumption and ammonia excretion, O:N ratio, as well as the expressions of abcg 8 and glulb of P. olivaceus rose significantly (P＜0.05). By the end of 49 d, the fish in the water of pH 8.1 (CK), 7.90, 7.70, 7.50, and 7.30 had average oxygen consumption rates of 1.10, 1.24, 1.44, 1.58, and 1.54 mg·g⁻¹·h⁻¹, average ammonia excretion rates of 0.23, 0.23, 0.25, 0.25, 0.26mg·g⁻¹·h⁻¹, and O:N ratio of 4.70, 4.98, 5.03, 5.78, and 5.39, respectively. Seawater acidification at pH7.50～7.30 has a significant effect on respiratory metabolism and metabolism-related genes of P. olivaceus.

Conclusion The respiratory metabolism and abcg 8 and glulb expressions of P. olivaceus in a tank were significant affected by the acidified seawater in the range of pH 7.50 to pH 7.30.