Hematological Responses of Sea Bass Dicentrarchus labrax to Sublethal Nitrite Exposures

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Abstract
Hemoglobin, methemoglobin, and blood nitrite concentrations were determined during and after 96‐hour exposures of sea bass Dicentrarchus labrax to sublethal concentrations of nitrite in seawater at 26 C. As exposure time or exposure concentration increased, total and functional hemoglobin concentrations decreased in blood, while percent methemoglobin increased. The 96‐hour median effective concentrations of nitrite in seawater (EC50, the concentration causing 50% reduction in blood) were 87.2 mg/liter for total hemoglobin (95% confidence limits, 64–118 mg/liter) and 62.4 mg/liter (45–87 mg/liter) for functional hemoglobin. Histochemical analysis of spleen tissues from fish exposed to 50 and 75 mg/liter NO2‐ N, which reduced total hemoglobin to 17% and 49%, respectively, showed Fe+++ originating from hemoglobin destruction and indicated hemolytic anemia caused by spleen macrophages. Nitrite concentrations in blood were lower than those in test water. Inhibition of nitrite uptake by chloride in seawater may protect sea bass against nitrite toxicity. Received December 14, 1982 Accepted March 19, 1984

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