Effects of Low Water pH on Some Heamatological and Physiological Parameters of Oreochromis mossambicus

Abstract

In this study tolerance to acid water pollution and the effects of acid water pollution on some haematological and physiological parameters were investigated in Oreochromis mossambicus, a species of fish which is well established and widely distributed in the inland waters of Sri Lanka. From the tolerance tests it was found that the maximum toleran.ce level, with 100% survival occurred at pH 4. Therefore in this study the fish were acclimated to pH (H2So4) 4.0 ± 0.1 for a period of two weeks before the changes in blood parameters were determined. Water in the control tanks had a pH of 7.0-7.2. Acid exposure caused significant disturbances in haematological parameters. The haematocrit, red blood cell count and haemaglobin concentration increased while the three haematological indices; haemaglobin content of a single erythrocyte, haemaglobin concentration of a single erythrocyte and cell volume of single erythrocyte decreased. The blood pH also decreased. But 02 capacity, 02 consumption, metabolic rate and plasma Na- concentration remained unaltered. This study reveals that O. mossambicus can tolerate a water pH down to pH 4 with little or no difficulty for extended periods, and is able to regulate its physiolobical status to compensate the body's 02 demands. This is in contrast with reports for many other species whose survival is limited at this level of pH.