Comparison between the efficiency of two bioindicators for determining surface water quality in an urban environment / Comparação entre a eficiência de dois bioindicadores para a determinação da qualidade de águas superficiais em um ambiente urbano

This study evaluated the efficiency of two bioindicators, fecal coliforms and ecotoxicity tests, set out in CONAMA Resolution 274/00 and CONAMA Resolution 357/05, in assessment of water quality. For this study, Lake Paranoá, Federal District of Brazil, was chosen, since it is a water body directly contaminated by effluents from a sewage treatment plant. Four sampling points were chosen in accordance with the map of recreational water quality published weekly by CAESB/DF, after analysis of fecal coliforms. Samples from these points were collected for 6 months and tested on Danio rerio fish (acute toxicity) and on the microcrustacean Ceriodaphnia dubia (acute and chronic toxicity), besides measuring chemical and physico-chemical parameters. The data obtained show great consistency between the observed biological parameters, suggesting that in this urban aquatic environment, under great anthropogenic pressure, the fecal coliform bioindicator seems to be more restrictive and enough to evaluate the safety of surface water.

Este trabalho comparou a eficiência dos bioindicadores coliformes fecais ou termotolerantes e ensaios de ecotoxicidade, propostos pelas Resoluções Conama 274/00 e Conama 357/05, na avaliação da qualidade de água. Para a realização desse estudo foi escolhido o Lago Paranoá, Brasília, Distrito Federal, por ser um corpo hídrico impactado diretamente pelo lançamento de efluentes de uma estação de tratamento de esgotos. Foram definidos quatro pontos de acordo com o mapa de balneabilidade, publicado semanalmente pela Caesb/DF, em função do teor de coliformes termotolerantes. Amostras desses pontos colhidas durante seis meses foram testadas com o peixe Danio rerio (toxicidade aguda) e o com o microcrustáceo Ceriodaphnia dubia (toxicidade aguda e crônica), além da determinação de parâmetros químicos e físico-químicos. Os resultados obtidos mostraram grande equivalência entre os parâmetros biológicos observados, sugerindo que nesse ambiente sob grande influência antrópica, o bioindicador coliformes termotolerantes foi mais restritivo e suficiente para avaliar a segurança das águas superficiais.

Susceptibility of non-target invertebrates to Brazilian microbial pest control agents.

Microbial pest control agents or entomopathogens have been considered an interesting alternative to use instead of chemical insecticides. Knowledge of ecotoxicity data is very important to predict the hazard of any product released in the environment and subsidize the regulation of these products by governmental agencies. In the present study four new Brazilian strains of Bacillus and one fungus were tested to evaluate their acute toxicity to the microcrustacean Daphnia similis, the snail Biomphalaria glabrata and the dung beetle Digitonthophagus gazella. The microcrustaceans and the snails were exposed to entomopathogens in synthetic softwater and the beetles were exposed directly in cattle dung. Obtained data reveal low susceptibility of the non-target species to tested microorganisms, with lethal concentrations being observed only at much higher concentrations than that effective against target insects. These results show that the tested strains are selective in their action mode and seem to be non-hazardous to non-target species.