Changes in the selected hematological parameters and gill Na/K ATPase activity of juvenile crucian carp Carassius auratus during elevated ammonia exposure and the post-exposure recovery

The increase in concentration of ammonia in lake water during the degradation of algal blooms may last for several weeks and thus cause chronic toxicity to aquatic organisms. The purpose of this study was to assess the chronic toxicity of ammonia on the selected hematological parameters and gill Na⁺/K⁺ ATPase activity of juvenile crucian carp Carassius auratus during elevated ammonia exposure and the post-exposure recovery. Juvenile crucian carp were exposed in different ammonia solutions for 45 days and then immediately transferred to pristine freshwater to initiate a 15-day recovery period. Results showed sub-lethal ammonia significantly deters growth and a 15-day recovery period was not sufficient for the fish to compensate for the loss of growth. The fish exhibited a continuous decrease in red blood cell (RBC), the total hemoglobin (Hb), and gill Na⁺/K⁺ ATPase activity as the concentration of NH₃-N increased. After the 15-day recovery period, RBC, Hb, and gill Na⁺/K⁺ ATPase activity had recovered to similar levels as the controls.