Acute toxicity and sublethal effects of nitrite on selected hematological parameters and tissues in dark-banded rockfish, Sebastes inermis

Abstract

Acute toxicity and sublethal effects of nitrite in dark-banded rockfish, Sebastes inermis (83.3 +/- 7.2 g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite evaluated for the 96 h lethal concentration (LC50) was 700 mg/L. The sublethal effects on selected hematological parameters of S. inermis, such as total erythrocyte count (TEC), hemoglobin, plasma glucose, and serum protein content, were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, and 700 mg/L of nitrite. Sublethal nitrite caused progressive reduction in the TEC, hemoglobin, and serum protein content in fish depending on the nitrite concentration and exposure period. The 96-h exposure resulted in a 14-42% reduction in TEC and 25-33% reduction in hemoglobin content for 100-700 mg/L of nitrite compared to the control. A dose-related reduction in plasma glucose (25.7-34.2%) was observed for concentrations of 200-700 mg/L of nitrite during 48 h of exposure, followed by an increase through 96 h. A significant reduction in serum protein (7.3-12.6%) was observed for 200-700 mg/L of nitrite after 96 h of exposure. Abnormal histological changes in skin, gill, liver, and kidney tissue were observed in fish exposed to 700 mg/L of nitrite after 96 h of exposure compared to the control. Although no mortality of S. inermis occurred at 500 mg/L of nitrite, all hematological parameters adversely responded to a nitrite dose of 200 mg/L for 96 h. These results showed that although acute toxicity concentration of nitrite in S. inermis is higher than 700 mg/L, sublethal concentrations of nitrite also negatively affect hematological parameters.