What condition can nitrite cause in fish?

Nitrite can cause methemoglobinemia in fish, which is characterized by the presence of methemoglobin in the blood. Methemoglobin is a form of hemoglobin that is unable to bind oxygen effectively. The presence of nitrite in the water can interfere with the normal hemoglobin within fish by oxidizing the iron in the heme group, transforming it into methemoglobin. This results in a decreased ability of the blood to transport oxygen, which can lead to symptoms such as lethargy, gasping at the surface, and a characteristic brownish coloration of the blood due to the presence of methemoglobin.

Understanding the physiological effects of nitrite is crucial for maintaining fish health, particularly in managed aquatic systems, such as aquaculture or aquarium environments, where water quality must be carefully monitored.