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 waterpollution on some haematological and physiological parameters were investigatedin Oreochromis mossambicus, a species of fish which is well establishedand widely distributed in the inland waters of Sri Lanka. From the tolerancetests it was found that the maximum toleran.ce level, with 100% survivaloccurred 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 bloodparameters 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 concentrationincreased while the three haematological indices; haemaglobin content ofa single erythrocyte, haemaglobin concentration of a single erythrocyte andcell volume of single erythrocyte decreased. The blood pH also decreased.But 02 capacity, 02 consumption, metabolic rate and plasma Na- concentrationremained unaltered.

This study reveals that O. mossambicus can tolerate a water pH downto pH 4 with little or no difficulty for extended periods, and is able to regulateits physiolobical status to compensate the body's 02 demands. This is incontrast with reports for many other species whose survival is limited at thislevel of pH.