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To monitor water quality and investigate relationships between downstream nutrient increases and diatom communities in the Pardo River Basin, Brazil, water and diatom samples were collected between 2005 and 2009. There were significant differences in diatom community composition among all river zones, with the greatest differences found between the upper and lower reaches. Significant changes were detected in relative abundances of diatom species and spatial structuring was evident. Dissolved oxygen, phosphates, turbidity, Eicherichia coli, and total dissolved solids were the most important variables shaping diatom communities, characterizing an organic pollution and eutrophication gradient. However, the hypothesis of sensitive species prevailing upstream and their gradual downstream replacement for more tolerant species was not confirmed because shifts in relative abundances of the same group of species in both the upper and lower reaches of the rivers were identified.

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This research aimed at developing the Trophic Water Quality Index (TWQI) for subtropical temperate Brazilian lotic systems based on a review of the indicative values of diatom species obtained using multivariate analysis techniques and considering the environmental gradient defined by a series of measured physical, chemical, and microbiological variables. Sampling was conducted from 2005 to 2009 in the Pardo River Hydrographic Basin, Rio Grande do Sul (RS), Brazil, and in the Andreas Stream Hydrographic Basin, RS, from 2012 to 2013. A total of 140 biological samples and 211 abiotic samples were collected. Data were analyzed by cluster analysis based on the Ward method and canonical correspondence analysis (CCA). The results indicated that total phosphate, turbidity, ammonia nitrogen, electrical conductivity, dissolved oxygen, and thermotolerant coliforms showed a significant correlation with the sample ordination made by CCA, in relation to a gradient of eutrophication. Eutrophication was operationally defined in a broad sense, including the problem of organic pollution and eutrophication of the water. The determination of the different tolerance degrees to eutrophication of the diatom taxa was used to assign trophic values of 1, 2.5, and 4 to species, corresponding to levels of low, medium, and high tolerance, respectively. By using the trophic values obtained for each diatom species, the TWQI constituted a new technological tool for environmental monitoring studies and showed a consistent, robust, and objective database for water quality assessment in subtropical temperate Brazilian lotic systems.

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The purpose of the study was to evaluate the water quality of urban streams in Santa Cruz do Sul, in the Brazilian state of Rio Grande do Sul, using physical, chemical and microbiological parameters. Eight sampling sites were distributed over the upper and lower reaches of four streams. Four sampling campaigns were carried out, two in 2007 and two in 2008. The parameters analyzed were: temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, ammonia nitrogen, phosphate, total dissolved solids and thermotolerant coliforms. Simultaneously, epilithic diatom samples were collected, the species identified and the respective relative abundance determined. The assessment of water quality was performed applying resolution 357/200 of the National Environment Council, and the Biological Water Quality Index. The results indicated that the streams are polluted by organic contamination and show advanced stages of eutrophication, mainly in the lower reaches, and are classified according to the National Environment Council resolution as Class 4, corresponding to poor water quality. The results of the Biological Water Quality Index ranged from strong to very strong in most sampling sites, highlighting Cyclotella meneghiniana, Fallacia monoculata, Nitzschia palea and Sellaphora pupula as the species most tolerant to eutrophication. Two sampling groups were separat

The purpose of the study was to evaluate the water quality of urban streams in Santa Cruz do Sul, in the Brazilian state of Rio Grande do Sul, using physical, chemical and microbiological parameters. Eight sampling sites were distributed over the upper and lower reaches of four streams. Four sampling campaigns were carried out, two in 2007 and two in 2008. The parameters analyzed were: temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, ammonia nitrogen, phosphate, total dissolved solids and thermotolerant coliforms. Simultaneously, epilithic diatom samples were collected, the species identified and the respective relative abundance determined. The assessment of water quality was performed applying resolution 357/200 of the National Environment Council, and the Biological Water Quality Index. The results indicated that the streams are polluted by organic contamination and show advanced stages of eutrophication, mainly in the lower reaches, and are classified according to the National Environment Council resolution as Class 4, corresponding to poor water quality. The results of the Biological Water Quality Index ranged from strong to very strong in most sampling sites, highlighting Cyclotella meneghiniana, Fallacia monoculata, Nitzschia palea and Sellaphora pupula as the species most tolerant to eutrophication. Two sampling groups were separat

RESUMEN

The purpose of the study was to evaluate the water quality of urban streams in Santa Cruz do Sul, in the Brazilian state of Rio Grande do Sul, using physical, chemical and microbiological parameters. Eight sampling sites were distributed over the upper and lower reaches of four streams. Four sampling campaigns were carried out, two in 2007 and two in 2008. The parameters analyzed were: temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, ammonia nitrogen, phosphate, total dissolved solids and thermotolerant coliforms. Simultaneously, epilithic diatom samples were collected, the species identified and the respective relative abundance determined. The assessment of water quality was performed applying resolution 357/2005 of the National Environment Council, and the Biological Water Quality Index. The results indicated that the streams are polluted by organic contamination and show advanced stages of eutrophication, mainly in the lower reaches, and are classified according to the National Environment Council resolution as "Class 4", corresponding to poor water quality. The results of the Biological Water Quality Index ranged from "strong" to "very strong" in most sampling sites, highlighting Cyclotella meneghiniana, Fallacia monoculata, Nitzschia palea and Sellaphora pupula as the species most tolerant to eutrophication. Two sampling groups were separated by using cluster analysis, one containing the points in the upper reaches and the other the points in the lower reaches, having 38% quantitative similarity in diatom community composition. This similarity can be explained by the fact that some of the abundant species tolerant to organic pollution and eutrophication, occurred in both the upper and lower reaches.

Este estudo objetivou avaliar a qualidade da água de arroios urbanos, em Santa Cruz do Sul, Rio Grande do Sul, Brasil, utilizando parâmetros físicos, químicos e microbiológicos. Oito sítios de amostragem distribuiram-se nos trechos superiores e inferiores de quatro arroios. Duas amostragens foram realizadas em 2007 e duas em 2008. Foram analisados: temperatura, pH, turbidez, oxigênio dissolvido, demanda bioquímica de oxigênio, nitratos, nitrogênio amoniacal, fosfato, sólidos totais dissolvidos e coliformes termotolerantes. Simultaneamente, amostras de diatomáceas epilíticas foram coletadas, as espécies identificadas e as abundâncias relativas determinadas. Fez-se a avaliação da qualidade da água utilizando-se como parâmetro a resolução n° 357/2005 do Conselho Nacional do Meio Ambiente e aplicando-se o indice biológico de qualidade da água. Os resultados indicaram que os arroios estão poluídos por contaminação orgânica apresentando avançados estágios de eutrofização, principalmente nos trechos inferiores, enquadrando-se na "Classe 4" de acordo com a resolução do Conselho Nacional do Meio Ambiente, correspondendo a águas de má qualidade. Os resultados do índice biológico de qualidade da água variaram do nivel "forte" a "muito forte" na maioria dos pontos de amostragem, destacando-se: Cyclotella meneghiniana, Fallacia monoculata, Nitzschia palea e Sellaphora pupula como as espécies mais tolerantes à eutrofização. Dois grupos de amostras foram separados através da análise de agrupamento, um contendo os pontos dos trechos superiores e o outro os pontos dos trechos inferiores, havendo 38% de similaridade quantitativa na composição da comunidade de diatomáceas. Tal similaridade pode ser explicada pelo fato de algumas das espécies abundantes e tolerantes à poluição orgânica e eutrofização ocorrerem tanto nos trechos superiores quanto inferiores.

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