Comparative acute toxicity of two herbicides, paraquat and glyphosate, to Daphnia magna and D. spinulata

The acute toxicities of glyphosate and paraquat in commercial formulations (OSAQUAT and RON-DO, respectively) to Daphnia magna and Daphnia spinulata were compared. RON-DO contains 48 per cent of glyphosate and 15 per cent of surfactant. OSAQUAT contains 27.6 per cent of paraquat and 5 per cent of surfactant. Daphnia were exposed to 18-250 mg glyphosate active ingredient per litre or 2-24.5 paraquat active ingredient per litre for 48 h. The OSAQUAT formulation was more toxic than the RON-DO formulation. The 48 h EC50 values of D. spinulata to OSAQUAT and RON-DO were 2.57 and 66.18 mg per litre, respectively. For D. magna these values were 4.55 and 61.72 mg per litre, respectively. Chronic exposure to OSAQUAT concentrations normally used in Argentina may have adverse effects on natural populations of the native Cladoceran species. There are 30 references.