Journal of Environmental Biology

Acute toxicity of organophosphate insecticide, dichlorvos in relation to selected water hardness for the freshwater zooplankters

Ashok Kumar Gupta*¹, Girraj Prasad Verma¹ and Khyali Lal Jain²

¹College of Fisheries, ²Department of Agriculture Zoology and Entomology,

Maharana Pratap University of Agriculture and Technology, Udaipur - 313 001, India

(Received: November 30, 2006; Revised received: April 25, 2007; Accepted: May 12, 2007)

Abstract: Toxicity of organophosphate insecticide, i.e. dichlorvos has been investigated in relation to selected water hardness for the freshwater zooplankters such as Moina, Daphnia, cyclops and nauplii. Results revealed that dichlorvos was highly toxic to the tested zooplankters, as the LC₅₀ values are noticed in ppb. Trend of sensitivity for different zooplankters to dichlorvos was recorded as Moina < Daphnia < nauplii < cyclops. The LC₅₀ were found to change significantly with the change in water hardness. The zooplankters were more susceptible to dichlorvos at water hardness of 275 mgl^-1 as compared to water hardness of 540 mgl^-1 as revealed from low LC₅₀ values. The range of safe dischargeable concentrations (1.063-1.137 ppb) were too low as compared to harmless or safe concentrations (43.895 – 89.194 ppb) for the zooplankters at both the hardness.

Key words : Acute toxicity, Dichlorvos, Water hardness, Zooplankton

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