Toxicity of cadmium on larvae of Palaemon adspersus Rathke, 1837 from the Black Sea

Objective: To evaluate the suitability of Palaemon adspersus (P. adspersus) as a bio-indicator for 4 and 10 days of cadmium toxicity bioassays. Methods: Four and ten days experiments were designed. CdCl2·2?H2O was dissolved in distilled water and a stock solution was made. At 4-day bioassay, the larvae of Baltic prawns were exposed to nominal concentrations of 0, 0.02, 0.05, 0.1, 0.5, 1.0 and 5.0 mg/L of Cd for 4 days. The 4-day LC50 was calculated by the probit analysis. At 10-day bioassay, the concentrations of 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L were introduced into each of the jars in triplicate treatments and 0 mg/L as control. Each tank containing 20 larvae was exposed to test solutions. Results: Results from probit analysis showed that the 96-h LC50 value was 0.14 mg/L for Cd. The 10 days bioassays were conducted with nominal concentrations of 0, 0.05, 0.1, 0.5, 1.0, 5.0, 10.0 and 20.0 mg/L Cd. Mortality increased in parallel with the increase in concentrations of Cd on Zoea – I stage of P. adspersus and time of exposure. The toxicity rate of the organism is concentration-dependent. All organisms except the control group died at the end of 10 days. Less than 25% of the animals survived at the 5 days of the exposure to concentrations of 0.5 mg/kg Cd or more. Only 20% of the organisms survived at the 7 days of the exposure to concentrations of 0.1 mg/kg Cd or less in seawater with clean sediment. Conclusions: The results showed that Cd was highly toxic to P. adspersus. When the larvae were exposed to concentrations of Cd, they become slightly excited and swam erratically, probably due to stress. However, behavioural and swimming patterns in control groups were normal, and there was not any mortality during the course of the experiment.