The water quality in the Limache stream was evaluated at five sampling stations during the pe-riod of low water flow. At each station, aquatic macroinvertebrates were collected and the following parame-ters were measured in situ: pH, conductivity, dissolved oxygen, and total dissolved solids. The biological oxy-gen demand, total phosphorus, and total nitrogen were determined in the laboratory. Water toxicity was deter-mined through toxicity bioassays with the microalga Pseudokirchrneriella subcapitata. Thirty-three macroin-vertebrate families were found and the dominant taxa were Dugessidae, Oligochaeta and Chironomidae. A significant correlation was found among the Family Biotic índex ChFBI, conductivity, and total dissolved solids (r = 0.92; p < 0.05). Species diversity was lowest, as was the growth rate of P. subcapitata, at the stations with the greatest anthropogenic activity and in the discharge zone of a domestic wastewater treatment plant.

Se evaluó la calidad de las aguas del estero Limache en cinco estaciones de muestreo en el período de bajo caudal. En cada estación se colectaron macroinvertebrados acuáticos, se midió in situ pH, conductividad, oxígeno disuelto, y sólidos disueltos totales. En el laboratorio se determinó la demanda biológica de oxígeno (DBO), fósforo total y nitrógeno total. También se determinó la toxicidad del agua mediante bioensayos con la microalga Pseudokirchrneriella subcapitata. Se determinaron 33 familias de macroinvertebrados, los taxa dominantes fueron Dugessidae, Oligochaeta y Chironomidae. Se encontró correlación significativa entre el índice biótico de familias (ChIBF), la conductividad eléctrica y los sólidos disueltos totales (r = 0,92; p < 0,05). La menor diversidad de especies y tasa de crecimiento de P. subcapitata fue en las estaciones con mayor actividad antrópica y en la zona de descarga del efluente de una planta de tratamiento de aguas domésticas.

In this investigation antioxidant response and toxicity of metals in receiving water effluent miner in the Blanco river in Pseudokirchneriella subcapitata was assessed. The catalase activity, lipid damage through Tbars, the growth rate of was determined. The result showed an inhibition of the growth rate of P. subcapitata which correlated with increased catalase activity and the lipid liperoxidation. These responses were correlated with the concentrations of copper and iron.

The toxicity of surface waters in a zone with mining activity in the Aconcagua River was determined through growth inhibition bioassays of Pseudokirchneriella subcapitata, and correlated with heavy metal concentrations. Results show that the waters near the discharge of the mining effluent displayed toxicity during all periods of study; the molybdenum and copper concentration exceeded the norms of water quality. The correlations between the concentrations of metals and the growth rate of P. subcapitata varied in the different periods of the study; inverse and significant correlations with copper stand out in some periods.