Chronic assays with Daphnia magna, 1820, Straus in sediment samples from Caí River, Rio Grande do Sul, Brazil.
TERRA1, N.R., FEIDEN1, I.R., FACHEL2, J.M., MOREIRA1, J.S., & LEMKE2, C.
1 Fundação Estadual de Proteção Ambiental Henrique Luís Roessler (FEPAM)- Av. Dr Salvador França, 1707, Bairro Jardim Botânico. CEP 90690 000 Porto Alegre, Rio Grande do Sul, Brasil.
2 Universidade Federal do Rio Grande do Sul. Instituto de Matemática. Departamento de Estatística. Av. Bento Gonçalves, 9500 CEP 91509-900 Porto Alegre, Rio Grande do Sul, Brasil.
nara.terra@ufrgs.br ilda.feiden@gmail.com fachel@ufrgs.br juliano@ecossis.com cristianolemke@yahoo.com.br
ABSTRACT: Caí river which is of major socioeconomic and environmental importance in Rio Grande do Sul has been monitored by FEPAM, regarding for antropic impact on the sediment of the middle and upper thirds of its course, since 2001. The purpose of this study was to assess the influence of the sediment from four sites along the Caí River on the health of the epibenthic cladoceran Daphnia magna, by performing semi-static chronic bioassays. Sediment was used because this compartment has the capacity to retain toxic substances that may be available later due to the organism metabolism or to the action of environmental physical agents. In the bioassays, microcrustaceans were exposed to environmental stress situations for 21 days from the beginning of their life (2-26h). The response with no mortality was often accompanied by a response showing reproductive deficiency. ANOVA (Analysis of Variance) and MSD multiple comparison tests were used to analyze the data. The percentage of survivors and the mean number of births per brood were analyzed. Indexes were defined to compare the parameters considered (reproduction and survival). Reproduction proved to be more sensitive than mortality, indicating lack of acute toxicity and the presence of chronic toxicity. Recovery of quality is observed is this river reach considering the reproductive data obtained during the study.
Key-words: Cladoceran, bioassay, ecotoxicology, survival, reproduction.
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