Abstract
The majority of the Una River Basin is located in Taubate County and contributes significantly to its water supply. The main goal of this research was to evaluate the water quality of the Una River using the microcrustacean C. dubia as bioindicator for tests of chronic and acute toxicity. Bimonthly water samples were obtained from each of six localities throughout the Una Basin, from March to October, 2011. Physical-chemical water parameters such as pH, electrical conductivity, hardness, dissolved oxygen and precipitation were measured and correlated to the C. dubia reproductive rates. No significant relationships were found between the water’s electrical conductivity and precipitation with respect to bioindicator reproductive rates. However, at the Sete Voltas, Antas and Rocinha Sub-Basins, significant interactions were detected between some water parameters and reproductive rates, suggesting that water may constrain the reproduction of C. dubia. Acute toxicity was not detected in any of the six sites, while chronic toxicity was recorded at Rocinha, Sete Voltas, Antas, Medio and Baixo Una Sub-Basins. In general, the water quality of the Una Basin, as indicated by the absence of acute toxicity, still remains in an acceptable conservation condition. Caution is needed, however, since slight pollution sources are causing chronic toxicity in some localities. In addition, as the microcrustacean C. dubia, appeared to be a reliable bioindicator in this investigation, we suggest that it be used for continuous water quality monitoring programs.
Highlights
At the Sete Voltas, Antas and Rocinha Sub-Basins, significant interactions were detected between some water parameters and reproductive rates, suggesting that water may constrain the reproduction of C. dubia
Acute toxicity was not detected in any of the six sites, while chronic toxicity was recorded at Rocinha, Sete Voltas, Antas, Médio and Baixo Una Sub-Basins
As the microcrustacean C. dubia, appeared to be a reliable bioindicator in this investigation, we suggest that it be used for continuous water quality monitoring programs
Summary
Os recursos hídricos da bacia hidrográfica do rio Una são utilizados para abastecimento público e industrial, e para irrigação, muito embora esta esteja diminuindo devido à substituição da agricultura pela criação de gado (Silva, 2008). Os microcrustáceos Ceriodaphnia sp são mais representativos de águas continentais, no território brasileiro, quando comparados à Daphnia sp, que é utilizada em testes de toxicidade aguda. Os testes com Ceriodaphnia dubia permitem duas leituras de resultado, toxicidade aguda e crônica, sendo utilizados em avaliações da qualidade de águas superficiais e efluentes (CETESB, 2009; Rodgher e Espíndola, 2008; Portella et al, 2006). As análises químicas, somadas aos testes de toxicidade na bacia do rio Una, complementam-se no objetivo de caracterizar os níveis de ecotoxicidade, por meio do bioindicador Ceriodaphnia dubia, de modo a sugerir um diagnóstico de áreas prioritárias para o controle da poluição da água, nos trechos da bacia onde a qualidade da água estiver mais afetada, subsidiando políticas públicas de manejo e gestão da bacia do rio Una
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