Some physiological responses of rainbow trout (Salmo gairdneri) to intermittent monoc
By T. W. Travis, A. G. Heath
Water Research, Volume 15, Issue 8, 1981, Pages 977-982, ISSN 0043-1354, DOI: 10.1016/0043-1354(81)90205-0.
Rainbow trout (Salmo gairdneri) were exposed for 2.5 h to monochloramine (NH2Cl) at an average concentration of 0.16 or 0.23 mg l-1 (and with peak concentrations of 0.4 or 0.6 mg l-1) three times daily. This simulates conditions in the outfall area of many electric power plants. Heart rate, opercular movement, cough frequency, arterial PO2, lactate, hemoglobin and methemoglobin were monitored. The trout responded to chloramine pulses with slight increases in opercular movement, bradycardia, and a large increase in cough rate. These factors approached control rates between periods of exposure to a peak concentration of 0.4 mg l-1, but not when the peak was 0.6 mg l-1. Neither hemoglobin or lactate changed, while arterial PO2 decreased slightly but not significantly. Methemoglobin concentration increased markedly at the end of each period of exposure with some recovery between them. In contrast to free chlorine, which causes acute hypoxemia due to gill damage, chloramine at these concentrations causes little if any hypoxemia. The elevated methemoglobin levels, not seen following exposure to free chlorine, indicate that perhaps chloramine is entering the blood stream to an extent that does not occur with free chlorine. Methemoglobinemia is probably not the proximate cause of death.