Evaluación de la ecotoxicidad de sedimentos del río Aruri y del Lago Junín (Perú) usando Escherichia coli y Chironomus calligraphus

The ecotoxicity of elutriated sediments of Aruri river affluent of Rimac river and Upamayo bridge, Lake Junin (Peru), monthly was evaluated from April to October 2000 using two bioassays: the inhibition of the enzymatic activity of the β-galactosidase of Escherichia coli and the survival of first larvae (L ₁) of Chironomus calligraphus were determined. The sediment were fractioned in five extracts (F _1(aqueous), F _2(methanol), F _3(EDTA), F _{4(methanol + EDTA)} and F _5(NaNO3)) to evaluate the effects of different chemical groups. Only for the river Aruri the CI ₅₀ of F ₁ for E. coli was higher than CL ⁵⁰ of C. calligraphus. Among the rest of fractions, F ₅ employed for detecting heavy metals resulted producing greater inhibitions on E. coli and mortalities on C. calligraphus in both localities, in comparison with the slender effect from F ₃ in both species that block up the effect of heavy metals. The F ₃ for Junin Lake for C. calligraphus produced higher effects than E. coli. The sediments of Junin Lake showed significant high level in silt-clay, organic matter in percent, Fe, Pb, Cu, Zn and Cd in comparison to Aruri River during all the monitoring.