Evaluation of the Gravataí River sediment quality (Rio Grande do Sul- Brazil) using Daphnia magna (Straus, 1820) as the test-organism for toxicity assays

Avaliação da qualidade dos sedimentos do rio Gravataí (Rio Grande do Sul - Brasil) a partir de testes de toxicidade utilizando Daphnia magna (Straus, 1820) como organismo-teste

Fabiane Lucheta Ilda Rosa Feiden Silvana Pereira Gonçalves Juliana Schons Gularte Nara Regina Terra About the authors

AIM: Persistent pollutants released to riverbeds return to the trophic system, damaging living organisms thereof. Ecotoxicological assays express the effect of environmental interactions with organisms found there. Assays were performed with microcrustacean Daphnia magna (Straus, 1820) in sediment samples, from the headwaters to the mouth, in order to evaluate the Gravataí River quality; METHODS: Bottom sediment was used to evaluate the responses of cladocerans to environmental changes in 15 samples collected between Jan./06 and May/09. The microcrustaceans were submitted to stress for 21 days from birth (2-26 hours old). Duncan Test, percentage survival, reproduction and Spearman Correlation were used to evaluate the quality of the sites; RESULTS: Duncan Test showed a significant difference (p < 0.05) in reproduction in 14 of the 15 samplings, and chronic action was more constant (88%) than the acute one (23%). Changes in survival and reproduction related to season or rainfall regime were only observed on a few occasions. The two sites located close to the mouth presented a Spearman Correlation (p < 0.01) for survival and reproduction. There were changes in some samplings in the headwaters as a result of sewage discharges in the area; CONCLUSIONS: Fluctuating responses were observed in this river due to anthropic contaminants, slow flux and current reflux.

Cladoceran; microcrustacean; ecotoxicology; pollution; chronic assays

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