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Distribution of aquatic insects in urban headwater streams Distribui o de insetos aquáticos em riachos urbanos

Keywords: efeitos antropogênicos , estressores múltiplos , Ephemeroptera , Plecoptera , Trichoptera , variáveis ambientais , anthropogenic effects , multiple stressors , Ephemeroptera , Plecoptera , Trichoptera , environmental variables

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AIMS: The objective of this study was to evaluate the effects of urban environments on the distribution and occurrence of aquatic Ephemeroptera, Plecoptera and Trichoptera (EPT) insects in six urban subtropical streams; METHODS: Organisms were collected with a Surber sampler in 2005 and 2006, over two hydrological cycles. We analyzed abundance values, taxonomic richness, Shannon-Wiener diversity and Pielou's evenness. A principal components analysis (PCA) was performed to evaluate the environmental variability of streams. A canonical correspondence analysis (CCA) was performed to evaluate the possible effects of environmental variables; RESULTS: The PCA ordered the streams according to their quality, and Suzana and Nadau streams had higher concentrations of nutrients. The Baetidae (Ephemeroptera) was the family with the highest number of genera (18). Perissophlebiodes Savage, 1983, and Americabaetis Kluge, 1992, were the most common genera. Anacroneuria Klapálek, 1909, was the most abundant Pleocoptera, and Smicridea McLachlan, 1871, was the dominant Trichoptera genus. In the CCA, pH, electrical conductivity and stream velocity were positively correlated with axis 1, whereas dissolved oxygen was negatively correlated with axis 1; CONCLUSIONS: Our results show that the distribution of EPT in urban streams is affected by changes in water physicochemical characteristics. However, these changes are not sufficiently severe to cause the elimination of EPT. OBJETIVOS: O objetivo deste estudo foi avaliar os efeitos da urbaniza o sobre a ocorrência e distribui o de insetos aquáticos das ordens Ephemeroptera, Plecoptera e Trichoptera (EPT) em seis riachos subtropicais; MéTODOS: Os organismos foram coletados com um amostrador Surber, durante os anos 2005 e 2006, abrangendo dois ciclos hidrológicos. Foram analisados os valores de abundancia, riqueza taxon mica, diversidade Shannon-Wiener e equitabilidade de Pielou. Uma Análise de Componentes Principais (ACP) foi aplicada para avaliar a variabilidade ambiental dos riachos. Uma Análise de Correspondência Can nica (ACC) foi realizada para avaliar os possíveis efeitos das variáveis ambientais sobre os organismos; RESULTADOS: A ACP ordenou os riachos de acordo com sua qualidade, sendo que os riachos Suzana e Nadua apresentaram maiores concentra es de nutrientes. Baetidae (Ephemeroptera) foi a família com maior número de gêneros, 18. Perissophlebiodes Savage, 1983 e Americabaetis Kluge, 1992 foram os gêneros mais frequentes. Anacroneuria Klapálek, 1909 foi o mais abundante dentre os plecópteros coletados e Smicridea M

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