Toxic effects of zinc and iron on the routine oxygen consumption of Tilapia sparrmanii (Cichlidae)

Abstract

1. The routine oxygen consumption of Tilapia sparrmanii without the addition of any toxicants over a 72 hr period showed a decrease for the first 48 hr, but stabilised thereafter. 2. Addition of zinc (98 mg l −1) resulted in a drastic decrease of oxygen consumption for 3 hr. The routine oxygen consumption showed a significant decrease for the first 24 hr, while the second and third 24 hr revealed significant differences with great individual variance. 3. The decrease in oxygen consumption observed after exposure to zinc, could be caused by gill damage as well as the internal action of zinc. 4. An increase in oxygen consumption was noted for almost 3 hr after addition of iron (88mg l −1). During the first-, second- and third 24 hr the oxygen consumption increased significantly, compared to the control values. 5. The increase in routine oxygen consumption of T. sparrmanii when compared to control values after exposure to iron, could be attributed to stress and possible gill changes. 6. The study revealed that after acute (72 hr) exposure to sublethal concentrations of zinc and iron, the routine oxygen consumption of T. sparrmanii was altered.