The potential use of epilithic diatoms as indicators of organic pollution was evaluated in Gravataı´River, RS, (latitude 29°45¢-30°12¢ S; longitude 50°27¢-51°12¢ W). The river suffers agricultural impacts in its upper course and urban and industrial organic pollution in its lower course. Epilithic diatoms were sampled eight times from September 2000 to August 2002, at six sites. Species were identified and densities and relative abundances of populations were determined. Simultaneously, physical, chemical and microbiological variables were measured (water temperature, conductivity, turbidity, pH, dissolved oxygen, biochemical oxygen demand (BOD 5 ), chemical oxygen demand, ammonium, organic nitrogen, total nitrogen, ortho-phosphate, total phosphate, chloride and faecal coliforms). In order to interpret the environmental and biological variables, discriminant analysis and the TWINSPAN methods (Two-Way Indicator Species Analysis) were applied. The results indicated that the concentrations of ortho-phosphate, ammonium, total organic nitrogen, BOD 5 and faecal coliforms characterized a pollution gradient along the river, where changes in the abundance or species composition were observed. Species were classified into three groups: Group A, including species more tolerant to heavy organic pollution and eutrophication, represented by

BackgroundThe regression of similarity against distance unites several ecological phenomena, and thus provides a highly useful approach for illustrating the spatial turnover across sites. Our aim was to test whether the rates of decay in community similarity differ between diatom growth forms suggested to show different dispersal ability. We hypothesized that the diatom group with lower dispersal ability (i.e. periphyton) would show higher distance decay rates than a group with higher dispersal ability (i.e. plankton).Methods/Principal findingsPeriphyton and phytoplankton samples were gathered at sites distributed over an area of approximately 800 km length in the Negro River, Amazon basin, Brazil, South America (3°08′00″S; 59°54′30″W). Distance decay relationships were then estimated using distance-based regressions, and the coefficients of these regressions were compared among the groups with different dispersal abilities to assess our predictions. We found evidence that different tributaries and reaches of the Negro River harbor different diatom communities. As expected, the rates of distance decay in community similarity were higher for periphyton than for phytoplankton indicating the lower dispersal ability of periphytic taxa.Conclusions/SignificanceOur study demonstrates that the comparison of distance decay relationships among taxa with similar ecological requirements, but with different growth form and thus dispersal ability provides a sound approach to evaluate the effects of dispersal ability on beta diversity patterns. Our results are also in line with the growing body of evidence indicating that microorganisms exhibit biogeographic patterns. Finally, we underscore that clumbing all microbial taxa into one group may be a flawed approach to test whether microbes exhibit biogeographic patterns.

1. IXiring the spring of 1992, fifty-two quantitative diatom samples were collected from twenty-eight rivers located in the Tokyo Metropolitan area, Japan, to study the response of the diatom assemblages to water pollution (assessed using physical and chemical data determined monthly from April 1987 to March 1992). 2. Species composition was analysed by means of biotic indices (Pantle and Buck's saprobic index) and multivariate analyses [two-way indicator spedes analysis (TWINSPAN) for classification and canonical correspondence analysis (CCA) for ordination]. Species-abundance relationships were analysed using diversity indices {species richness. Shannon's diversity index and Pielou's evenness index) and rankabundance patterns (rank-abundance curves). 3. CCA revealed two major gradients. The first corresponded to organic pollution and eutrophication. The second corresponded to variables related to geographical location. Four main station groups were determined by TWINSPAN. The location of the indicator species of groups 1-3 along the CCA axis 1 is consistent with their known pollution tolerance characteristics. Indicator species for group 4 had larger scores on CCA axis 2, and are representative of brackish water environments. 4. Species richness tended to be higher in the intermediate range of water pollution. Pielou's evenness index and Shannon's diversity index followed the same tendency but only weakly. 5. The rank-abundance patterns of diatom assemblages were more or less constant in all stations. The curves were very similar in shape, differing only in length and gradient (directly related to species richness and evenness, respectively). 6. The results of this study indicate that the response of diatom assemblages to environmental change can be observed in species compositional variation. Multivariate analyses and poUution indices revealed this response and are to be preferred to species diversity measures.

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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.

Associations of diatom species were identified, in the Arroio Sampaio Basin, Rio Grande do Sul, Brazil, based on monthly samplings over a year along Arroio Sampaio and its main tributaries, using polyamide thread as an artificial substrate. The species groupings showed four different environments: medium-lower course of Arroio Sampaio; and lower course of Arroio Teresinha; upper course of Arroio Sampaio; and lower course of Arroio Duvidosa. Among the physical and chemical variables measured, water pollution, particularly organic contamination and eutrophication, measured from BOD, and total phosphate concentration, respectively, appeared to be one of the most important environmental factors determining the composition and structure of species associations in the area studied.

Environmental monitoring studies in the Hydrographical Basin of Pardo River, RS, Brazil, in the time series from 2007 to 2009, showed no agreement between the water quality evaluation obtained through the Water Quality Index (WQI -NSF), which ranged from "regular" to "good", and the Environment National Council (CONAMA) Resolution 357/2005, which was bad ("class 4"), highlighting as critical variables for this classification the thermotolerant coliforms and the phosphate concentration, indicating process of water eutrophication, related to the large amount of nutrients and organic load from domestic sewage and excess fertilizers used in agriculture.

The aim of this study was to develop a domestic filter prototype using activated bone charcoal for the fluoride excess removal in groundwaters for human drinking purposes, evaluating the physical, chemical and microbiological properties of the raw and treated water. The filtration system was constructed using di fferent quantities of activated bone charcoal, confined in a polyvinylchloride tube, working with a discharge of 180 ± 20 L h-1 , being treated 10 liters of water per day, enough to supply daily up to five people. The lifetime of this system was established based on Ministry of Health Ordinance nº 2914/2011, which limits the fluoride concentration in the water up to 1.5 mg L-1. The results demonstrated the efficiency of the activated bone charcoal in fluoride excess removal, considering a filtration system using 3.5 kg of this material, enough for meeting the consumption needs for a family of five persons during a period of six months, since observed the a ssembly and the operation conditions described in this study.