Alexandrium affine is a global harmful algal bloom (HAB)-forming dinoflagellate. In this study, the effect of non-toxin-producing A. affine on the gill and liver tissues of red seabream, Pagrus major, was analyzed over 24 h exposure and 2 h depuration phases. After exposure to three concentrations of A. affine (4,000, 6,000, and 7,000 cells mL⁻¹), survival rates, respiration rates, immunities (lysozyme, total Ig), hepatic biomarkers (alanine aminotransferase, ALT; aspartate aminotransferase, AST; and alkaline phosphatase, ALP), lipid peroxidation (malondialdehyde, MDA), and antioxidant defense systems (glutathione, GSH; catalase, CAT; superoxide dismutase, SOD; glutathione peroxidases, GPx; and glutathione reductase, GR) were analyzed in gill and liver tissues. Dose-dependent decreases in survival and respiration rates were detected in red seabream. A. affine levels of to 6,000 and 7,000 cells mL⁻¹ induced immunosuppression and hepatic impairment in both tissues, as measured by significant decreases in lysozyme activity, total Ig level, ALT, AST, and ALP content. The levels of GSH, CAT, SOD, GPx, and GR were significantly decreased in the gills and liver in response to 7,000 cells mL⁻¹ of A. affine at 24 h, and MDA was elevated. However, different response patterns were observed between tissues in response to 4,000 cells mL⁻¹. Activity of antioxidant defense enzymes was significantly elevated in the liver but decreased in the gills. This suggests that the gills were more vulnerable than the liver. In the case of 6,000 and 7,000 cells mL⁻¹ treatments, higher susceptibility was also detected at 3 h in the gill compared to the overall responses of each parameter measured in liver. Taken together, direct attachment of A. affine to the gill tissue strongly affects immunity and antioxidant capacity of red seabream even after a short exposure period. These results could be helpful for understanding HAB-mediated effects in marine fish.

Alexandrium affine是一种全球性有害藻华 (HAB) 形成甲藻。在这项研究中，分析了在 24 小时的暴露和 2 小时的净化阶段中，不产生毒素的A. affine对红鲷鱼鳃和肝组织的影响。暴露于三种浓度的A. affine（4,000、6,000 和 7,000 个细胞 mL ^-1)、存活率、呼吸率、免疫（溶菌酶、总 Ig）、肝脏生物标志物（丙氨酸氨基转移酶，ALT；天冬氨酸氨基转移酶，AST；和碱性磷酸酶，ALP）、脂质过氧化（丙二醛，MDA）和抗氧化防御系统（谷胱甘肽） ，GSH；过氧化氢酶，CAT；超氧化物歧化酶，SOD；谷胱甘肽过氧化物酶，GPx；和谷胱甘肽还原酶，GR）在鳃和肝组织中进行了分析。在红海鲷中检测到存活率和呼吸率的剂量依赖性降低。^{A. 至 6,000 和 7,000 个细胞 mL -1的}仿射水平通过溶菌酶活性、总 Ig 水平、ALT、AST 和 ALP 含量的显着降低来测量两种组织中的免疫抑制和肝损伤。^{在 24 h 时，7,000 个细胞 mL -1}的A. affine响应于鳃和肝脏中的 GSH、CAT、SOD、GPx 和 GR 水平显着降低，并且 MDA 升高。^{然而，响应于4,000个细胞mL -1}在组织之间观察到不同的响应模式。抗氧化防御酶的活性在肝脏中显着升高，但在鳃中降低。这表明鳃比肝脏更脆弱。在 6,000 和 7,000 个细胞的情况下 mL ^-1处理时，与在肝脏中测量的每个参数的总体反应相比，在鳃中 3 小时也检测到更高的易感性。总之，A. affine直接附着在鳃组织上会强烈影响红海鲷的免疫和抗氧化能力，即使在短时间暴露后也是如此。这些结果可能有助于了解 HAB 介导的海洋鱼类效应。