Evaluation of the Effect of Short-Term Cadmium Exposure on Brackish Water Shrimp-Palaemonetes africanus

This study evaluated the effect of short-term cadmium exposure on brackish water shrimp- Palaemonetes africanus. Tests were carried out by exposing the shrimps to the test solutions containing various concentrations of the cadmium (0, 0.1, 1.0, 4.0, 6.0, 8.0, 10.0, and 100.0) mg/l using the semi-static agitation test procedure. Mortality was recorded at 2, 4, 6, 8, 10, 12, 14 and 16 hours exposure periods. Test results indicated that the brackish water juvenile shrimp, Palaemonetes africanus were sensitive to the cadmium solution especially at concentration above 4.0mg/l. Though no death was recorded after 16hrs for 0.1mg/l, 1.0mg/l and 4.0mg/l respectively, however, for 6mg/l, 60% mortality was recorded after 4hrs and 100% after 8hrs, for 8mg/l, 20% mortality was recorded after 2hrs, 60% after 4hrs, 80% after 6hrs and 100% mortality after 8hrs respectively, for 10mg/l, 40% mortality was recorded after 2hrs and 100% after 4hrs and 100% mortality was recorded for 100mg/l after 2hrs. The LC50 value calculated using Arithmetic Method of Karber was 5.0mg/l. It is therefore evident that the effects of acute toxicity of cadmium are concentration-related; the greater the concentration, the greater the effect.