© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1434-2944/10/306-0260 Internat. Rev. Hydrobiol. 95 2010 3 260–272 DOI: 10.1002/iroh.200911190 ADELINA MARIA KÜHL 1 , CARMEN LÚCIA MELLO SARTORI CARDOSO DA ROCHA 1 , EVALDO LUIZ GAETA ESPÍNDOLA 2 and FÁBIO AMODÊO LANSAC-TÔHA* , 1 1 Universidade Estadual de Maringá. Avenida Colombo, 5790 – Nupélia – Bloco H-90. CEP 87020-900. Maringá, PR, Brazil; e-mail: fabio@nupelia.uem.br 2 Universidade de São Paulo, Escola de Engenharia de São Carlos. Avenida Trabalhador Sãocarlense, 400, Caixa Postal 292. CEP 13566-590. São Carlos, SP, Brazil Research Paper Rural and Urban Streams: Anthropogenic Influences and Impacts on Water and Sediment Quality key words: aquatic pollution, domestic and industrial effluents, ecotoxicology, Southern Brazil Abstract The Pirapó river watershed (Paraná State, Brazil) compounds a relatively industrialized and urbanized region, undergoing great pressure from the discharge of industrial, agricultural and domestic wastes. We evaluated the environmental quality of ten streams belonging to this watershed in April and June 2008 by performing acute and chronic toxicity tests with Daphnia similis and Ceriodaphnia silvestrii from water and sediment samples. We tested the hypothesis that the streams located in urban areas are more exposed to the influence of pollutants, than those outside the city limits. In addition, we obtained the measures of physical and chemical parameters, and identified the main polluted sources. Contrary to what was expected, the rural streams were more toxic than those located in urban area. These results demonstrate that the water bodies located in rural areas are being affected by the pollution of aquatic ecosystems as far as those found in urban areas, requiring the same attention of environmental managers in relation to its monitoring. 1. Introduction The increasing contamination of aquatic, terrestrial and atmospheric environments with substances from human activities has attracted attention from political organizations and environmental managers, as well as from society as a whole. Many researchers have searched for solutions through effluent treatment, solid waste recycling and clean energy production. In spite of their efforts, many counties still do not possess sewage collection networks that include all inhabitants or suitable local systems for garbage disposal. Hence, some domes- tic discharges and industrial effluents reach watercourses untreated, causing environmental damage. Due to the complexity and variability of organic and inorganic compounds that enter water bodies and because little information about the interactions between these substances is known, it is not possible to establish allowable discharged concentrations using only the physical and chemical analyses commonly performed by environmental managers. The char- * Corresponding author