Tadpoles assay: its application to a water toxicity assessment of a polluted urban river

The acute toxicity assay with premetamorphic tadpoles of Bufo arenarum as sentinel organism was applied to evaluate the quality of two water samples taken from three sites of the Reconquista River, an urban watercourse which is recipient of both untreated industrial effluents and domestic wastes. The results of the 96 hr bioassays were compared with the physicochemical parameters determined in the samples. Mortality rates in each sample were compared using the Bonferroni's test and a stepwise regression analysis of mortality and physicochemical parameters was done. In this way, it was possible to build up consistent descriptive models which showed that pH, Cl- Cd2+ and Cu2+ concentrations in the river water were significant independent variables and might explain, under the experimental conditions, the recorded toxicity effects of the tested samples. Because of its simplicity, low cost and reliability it was suggested the tadpoles bioassay be included in the set of tests used in integrated program of freshwater pollution.