Acute and chronic effects of atrazine and sodium dodecyl sulfate on the tropical freshwater cladoceran Pseudosida ramosa.

Toxicities of atrazine and sodium dodecyl sulfate (SDS) to the tropical freshwater cladoceran Pseudosida ramosa were studied in the laboratory. Acute tests showed that the 48-h LC₅₀ of atrazine was 20.9 mg l⁻¹, while that of SDS was 11.1 mg l⁻¹. P. ramosa showed to be slightly more sensitive than the other species of temperate cladocerans, in the assay conditions specified for each one. Long-term exposure of P. ramosa individuals to atrazine decreased the 21-day fecundity, the 21-day fertility and r(m), at concentrations ranging from 0.8 to 3.2 mg l⁻¹. Furthermore, fecundity and fertility at each brood decreased from the first to the fifth, at concentrations ranging from 0.8 to 3.2 mg l⁻¹ and for the first three broods at the concentration of 0.4 mg l⁻¹. Long-term exposure of female P. ramosa to SDS decreased the 21-day fecundity, the 21-day fertility and r(m), at concentrations of 2 and 4 mg l⁻¹. Fecundity and fertility of each brood were reduced from the first to the fifth, at concentrations of 2-4 mg l⁻¹, and for the first three at concentrations of 0.5 and 1 mg l⁻¹. The survival and moulting of the adult females were not affected by either chemical at the concentrations tested. Many water quality criteria in tropical regions are based on ecotoxicological tests with non-native species and this may lead to errors in setting the maximum permissible levels of chemicals in water bodies. Therefore, we reiterate here the idea of using native species in ecotoxicological assessments.