Potentiation of the toxic action of copper in the presence of lanthanum in bioassays for Daphnia magna Straus (Cladocera, Crustacea)

The available data on the combined action of rare earth elements and heavy metals are contradictory. Therefore, the goal of the presented work is relevant – to determine the effects of solutions of copper, lanthanum salts and their equimolar mixtures under controlled conditions for Daphnia magna Straus. It has been established that the death of D. magna over 50% in solutions containing Cu2+ is observed at a calculated concentration of 0.05 mg/L (0.0008 mmol/L), and a similar effect of solutions with La3+ occurs at a dose of 50 mg/L (0.36 mmol/L). The potentiation of the lethal effect of copper in the presence of lanthanum is shown. E.g., in solutions of mixtures of Cu and La salts, where the sum of metals is equimolar to non-lethal concentrations of Cu2+ (0.00016 and 0.0008 mmol/L), 100% death of D. magna is observed after 96 and 24 hours, respectively. Further, the potentiation effect was confirmed in bioassays evaluating the locomotor activity of D. magna. Solutions containing a mixture of “Cu2+ and La3+” (1:1) inhibit the motor activity of daphnia similarly to equimolar solutions containing only Cu2+. Thus, despite the significant difference between the effective lethal and non-lethal concentrations of Cu2+ and La3+ (by 1,000), it was found that under the combined action of equimolar doses of the metals, an increase in the toxicity of copper in the presence of lanthanum is observed.