The influence of taxonomic resolution of Oligochaeta on the evaluation of water quality in an urban stream in Minas Gerais, Brazil A influência da resolu o taxon mica de Oligochaeta na avalia o da qualidade da água em um córrego urbano em Minas Gerais, Brasil

OBJECTIVE: The objective of this study was to verify the identification of specimens of the Oligochaeta in different taxonomic levels (family and species) has the same potential for assessing the water quality of an urban stream in Minas Gerais, Brazil. METHODS: Oligochaeta specimens were collected from eight sampling stations in July 2007. Four stations were located in rural areas and the other four in urban areas. Were measured concentrations of dissolved oxygen, phosphorus and total nitrogen, pH, electrical conductivity and BOD. To evaluate the influence of taxonomic level, Oligochaeta specimens were identified at the family and species. We performed a principal component analysis (PCA) to determine which abiotic variables best explained the distribution of Oligochaeta along the sampling stations. Cluster analysis was performed with the abundance of Oligochaeta in the family and species levels, separately, to assess the degree of similarity between the stations and check the level of identification of organisms could interfere with the associations formed. RESULTS: In general, the sampling stations located in urban areas had high pH, BOD and total nitrogen and phosphorus, while rural stations had a higher concentration of oxygen. Three families of Oligochaeta were found: Tubificidae, Naididae and Enchytraeidae. Tubificidae and Limnodrilus hoffmeisteri were the family and the species with the highest density, respectively, especially at those stations located in urban areas. Both the PCA analysis and cluster analysis showed that the sampling stations in urban areas and rural areas have different characteristics that separate CONCLUSIONS: The studied environment presents two distinct regions: the urban region with a high degree of organic pollution and high density Tubificidae and L. hoffmeisteri, and rural, with less human influence and low density of organisms Oligochaeta. These features made the use of the taxonomic level of family allow a good assessment of water quality in the San Pedro creek without any significant loss of community data Oligochaeta. OBJETIVO: O objetivo deste estudo foi verificar se a identifica o de espécimes de Oligochaeta em diferentes níveis taxon micos (família e espécie) tem o mesmo potencial para a avalia o da qualidade da água de um córrego urbano em Minas Gerais, Brasil. MéTODOS: Espécimes de Oligochaeta foram coletados em oito esta es amostrais em julho de 2007. Quatro esta es estavam localizadas em zona rural e as demais em zona urbana. Foram medidas as concentra es de oxigênio dissolvido, fósforo e nitrogênio tot