Stress in the Yellow Sea of China: Suppressed Antioxidant Capacity and Induced Inflammatory Response of the Japanese Flounder ().

As the largest green macroalgal bloom in the Yellow Sea of China, the overgrowth and degradation of (. ) have a harmful effect on marine organisms and the aquaculture industry. However, the regulation mechanism of stress on the antioxidant capacity and inflammatory response of marine fish is still not completely understood. A 15-day exposure experiment was conducted to evaluate the effects of stress on the antioxidant capacity and inflammatory response of the Japanese flounder () (283.11 ± 6.45 g). The results showed that . stress significantly decreased their survival rate. Serum total antioxidant capacity (T-AOC) and non-specific immune-related enzyme activities were significantly impacted under . conditions. Moreover, . stress significantly decreased T-AOC, superoxide dismutase (SOD) activity, and catalase (CAT) activities in the liver, while malondialdehyde (MDA) contents were significantly increased. Similarly, antioxidant-related gene (, and ) expressions were synchronously downregulated in the liver under . stress. Furthermore, . stress significantly upregulated pro-inflammatory gene (, , , and ) expressions and the phosphorylation levels of the p38 and JNK MAPK pathways in the head kidney. In addition, endoplasmic reticulum (ER) stress-related gene and protein expressions were also upregulated in the head kidney. Overall, these results revealed that stress suppressed the antioxidant capacity and induced an inflammatory response in the Japanese flounder. This study could advance the understanding of the adverse effects of . stress on marine benthic fish and promote the sustainable development of aquaculture.