Lethal and sub-lethal effects of cypermethrin and glyphosate on the freshwater's copepod, Acanthocyclops robustus.

The study aims to evaluate the acute and chronic toxicity of cypermethrin and glyphosate to a freshwater’s copepod, Arcanthocyclops robustus. The acute sensibility was assessed by estimating lethal concentrations. Then the chronic exposure allowed to assess the effects of low concentrations (0.2489 ppb and 0.4978 ppb respectively 10 % and 20 % of LC50 at 48 h of cypermethrin and 1.3 ppm and 2.6 ppm respectively for glyphosate) on the species. The estimated lethal concentrations at 1%, 50 % and 99 % were 2.353 ppb, 4.755 ppb and 9.610 ppb in 24 h, respectively 0.567 ppb, 2.489 ppb and 10.929 ppb in 48 h for cypermethrin. Regarding glyphosate, the lethal concentrations 1 %, 50 % and 99% were 5 ppm, 19 ppm and 73 ppm in 24 h, respectively 8 ppm, 13 ppm and 21 ppm in 48-h. hatching was affected by 20 % LC50 of cypermethrin; only 20 % of females have hatched their eggs against 60 % in the control treatment. Females and nauplii survival was affected by both pesticides. A. robustus is then more sensitive to cypermethrin compared to glyphosate. Low concentration like 0.4978 ppb of cypermethrin could affect it population and then all the ecosystem biodiversity.