Urbanization modifies natural environments, with urban streams being particularly vulnerable to environmental degradation and biodiversity loss. The main objective of this study is to understand direct and indirect effects of urbanization on organic matter processing and trophic structure of streams. As specific objectives, we seek to understand the role of urban forests in sustaining aquatic biodiversity, trophic structure and ecosystem function despite the loss of connectivity due to urbanization downstream. To investigate how direct and indirect effects of urbanization impact community trophic structure and ecosystem functioning, we used different types of streams: a) controls: streams with connectivity, without urbanization downstream; b) streams without connectivity, located in urban forests, in which we will measure the indirect effects of urbanization, since the urbanized areas are located downstream of the studied reaches; and, c) urban streams in which we will measure the direct effects of urbanization. To investigate how urbanization affects ecosystem functioning we conducted decomposition experiments with leaves and cotton strips.To investigate how urbanization impacts community trophic structure, we collected the entire food web for stable isotopes analysis.We expect that control streams have greater processing of allochthonous organic material due to the likely presence of migratory species in the community that also act in leaf litter decomposition. Urban forest streams have intermediate values of organic matter processing due to expected loss of migratory species and thus loss of ecosystem function. Finally, we expect that urban streams have lower organic matter processing due to a greater biodiversity loss, including detritivorous organisms. The impact of urbanization on lotic aquatic ecosystems in tropical countries, such as Brazil, is a growing challenge. The loss of environmental quality and connectivity in urbanized streams are factors that modify biodiversity and energy flows, negatively impacting ecosystem functioning.