This study investigated the structure of the Oligochaeta and Chironomidae assemblages associated with monospecific stands of two submerged macrophyte species: Egeria najas and Hydrilla verticillata. Samplings were carried out in Leopoldo Backwater and Paraná river, in August 2008. To assess the structure of Oligochaeta and Chironomidae assemblage in each macrophyte we calculated: species density, richness, diversity, and evenness. A detrended correspondence analysis (DCA) was used to summarize Oligochaeta and Chironomidae assemblages composition. The highest values of species density and richness for the two groups were recorded in H. verticillata. Although there were no significant differences in density, richness and Shannon diversity, the assemblage composition of these groups was significantly different between plant species. These results suggest that despite being a recent colonizer in the upper Paraná river habitats, the non-native species H. verticillata seems to provide favorable conditions for the establishment of native assemblages of Chironomidae and Oligochaeta. Moreover, differences in the species composition of Oligochaeta and Chironomidae arose from peculiar characteristics of each plant, as attached microorganisms and organic matter, so that other factors, rather than plant architecture can also influence the assemblage of these groups.

This study verified the existence of longitudinal patterns in species composition, richness, density and biomass of flagellate protozoan in tropical streams and investigated whether the possible zonation patterns are different between two periods of the year. For this, samplings were carried out in three regions from 10 streams, during the summer and winter. The flagellate community may be considered species-rich, because it was represented by 106 taxa, belonging to 8 orders and 1 residual group. The values of density and biomass are greater than those commonly found in other lotic environments, with mean values close to 2.3x10 4 cels. mL -1 and 150.8 μgC L -1 . We did not observe any conspicuous and significant longitudinal pattern of the attributes from flagellates community. Only temporal variations of these attributes were verified. The Pearson Correlation evidenced that this temporal patterns was mainly driven by the nutrients availability, temperature and dissolved oxygen, since, the higher values of species richness, density and biomass were recorded during the winter, when the higher concentrations of nutrients and dissolved oxygen and lower temperatures were registered. In summary, the absence of patterns may be ascribed to the unidirectional and continuous flow from lotic environments.

Aim: To test the effect of fish exclusion over zooplankton and phytoplankton in a shallow lake in the floodplains of the Cuiabá River in Brazil's Pantanal; Methods: Fishes and two classes of zooplankton sizes were excluded using mesocosms (100 µm and 200 µm mesh openings). The experiment lasted nine days with sampling at the beginning, six and nine days after the start of the experiment. Zooplankton and phytoplankton densities were compared among exclusion treatments and the open water which was considered as control areas by a Repeated Measures Analysis of Variance; Results: The zooplankton composition and densities differed considerably between the exclusion treatments and the control areas, with a predominance of Cladocera and Copepoda in the exclusion treatments and a predominance of Rotifera in the control areas. During the experiment, the composition of the phytoplankton assemblage showed no difference between the exclusion and the control. However, there was a marked reduction in the density of the Cyanophyta and Chlorophyta algae among the exclusion treatments; Conclusions: The increase in density and the variation in the zooplankton composition suggest that these organisms are controlled by the fish and demonstrate that the zooplankton may exert control over the density of phytoplankton.

Despite flagellate protozoa are important for the metabolism of aquatic ecosystems, researches about the ecology of this community is scarce. Therefore, this study investigated the influence of flood regime and hydrological connectivity on the patterns of composition and species richness of protozoan flagellates from aquatic environments in the upper Paraná river floodplain. To this end, samplings were undertaken in two periods of the hydrological cycle (March 2008 and September 2008), at six lentic environments associated with the Baía river (three are connected to the river, and three are isolated). 120 taxa were identified in the studied area, distributed in 10 orders and one residual group. This high species richness was sustained by the order Euglenida, which contributed with 70% of total species. The species composition was significantly different between periods and environments, as well as species richness, which was higher in connected environments during the high water period. The results evidenced that the flood pulse and hydrological connectivity are relevant factors driving the structure and dynamic of plankton flagellate protozoa community in the upper Paraná river floodplain.

Este trabalho, desenvolvido em uma escola pública, aplicou o método de pesquisa-ação VERAH para a realização de um diagnóstico socioambiental participativo de uma microbacia onde está localizada a escola. Este foi realizado em duas etapas, com alunos e professores do ensino médio: i) planejamento; ii) execução, com vivências de campo e laboratório, integração, apresentação dos resultados e propostas. O método foi satisfatório no alcance dos objetivos da Educação Ambiental como tema transversal e proporcionou uma percepção crítica nos alunos, através do conhecimento multidimensional e interdisciplinar da realidade socioambiental na qual estão inseridos, possibilitando a proposição de ações para melhoria das condições urbanas precárias e de degradação ambiental observadas.