Die effek van lood en waterkwaliteit op die biologie van die vleikurper, Tilapia Sparrmanii

Abstract

1. Handling stress increases the oxygen consumption rate (M02) of Tilapia sparrmanii by an average of27% and stabilises four hours after handling. 2. All M02 measurements were done after a ten hour rest period. 3. For M02 studies 410 fish were used while 130 fish were used for tissue analysis. 4. Sub-acute lead exposure in Hard and Soft water has no effect on the M02 of T sparrmanii. 5. Sub-acute lead exposure combined with the lowering of pH, increases the M02 of T sparrmanii. 6. When a group often T sparrmanii are placed simultaneously in a 23.033 liter respirometer an increase of 280% in M02 was measured if the M02 is compared with the M02 measurement of one fish per respirometer. 7. The forming of mucus on the gill lamellae is an indication of low pH and an increase in heavy metal concentration in the water. 8. Acute exposure of T sparrmanii to lead resulted in a decrease of 12.5% in Mo2. 9. The formation of mucus on the gill lamellae was observed when T sparrmanii was exposed to acute lead exposure. The formation of mucus can be used as an indicator of lead exposure. 10. An increase of ammonia (Nt4 +) in water, high pH, can explain why the M02 of T sparrmanii increases with exposure to sub-acute lead concentrations. 11. Low pH in Soft water results in a secondary stress response that increases the M02 of T sparrmanii. 12. Under hypoxia the decrease rate of the P02 values in a sealed water volume is inhibited and results in the decrease of the M02 of T sparrmanii. 13. The total dissolved solids in bile and blood plasma in Hard and Soft water, by sub-acute lead exposure, does not statistically differ significantly. 14. The total dissolved solids in the blood plasma decreases with a decrease in the pH of the water.

15. An increase in lead concentration, combined with a decrease in the pH of the water, is the primary factor resulting in a decrease of the chloride values of blood plasma of T sparrmanii. 16. An increase in the lead concentrations at sub-acute lead exposure results in the increase in lead concentrations of the gill and liver tissue. 17. Gill tissue accumulates 40 times more lead than liver tissue. 18. Low pH of water favours the accumulation of lead on gill and liver tissue. 19. The bio-accumulation of lead in the gill and liver tissue can be used as a bio-indicator for lead contamination in aquatic systems. 20. A decrease in hardness of water results in the increase of lead concentration by about 50%. 21. A decrease in pH of Soft water results in an increase of about 20% in the lead concentration in the water. 22. The bubbling of air through water and the mechanical stirring of the water cause the insoluble precipitate to go into suspension. This results in an increase of the concentration of lead that is analysed. 23. Long et al. (1977) theoretically calculated that the concentration of lead, at high pH, and a seawater mixture of fresh and seawater, was about 10% while in this study less than 1 % lead was still in solution in Hard water and high pH.