Effects of chromium during pH change on blood coagulation in Tilapia sparrmanii (Cichlidae).

1. Tilapia sparrmanii was exposed to 0.098 mg/l potassium dichromate. 2. The effect of chromium on blood coagulation was measured with a thrombelastograph at a pH of 5, 7.4 and 9 over 96 hr, as well as an uncontrolled pH after 2 weeks of exposure. 3. The prolonged kinetic times and reduced maximal amplitudes at a pH of 7, 4 and 9, differed significantly from the control values. 4. Thrombelastograms reflected a decrease in the clotting ability of fish blood, with an increase in pH, which is typical of thrombocytopenia. 5. It was evident that the exposure of fish to chromium led to clotting defects that caused internal bleeding.