urban streams syndrome; water quality; river-aquifer interaction; microphytobenthos; meiofauna

The concept of morphological change in watercourses brought with it impacts such as water pollution, erosion on the banks and silting of the bed, interruption of the connection between the river-aquifer and floods. The process of ecosystem degradation leads to numerous losses of organisms present in the environment. However, the resilience of some species is essential for the recovery of ecosystem balance. The revitalization of rivers is considered the main alternative for protecting water resources, as well as protecting the health of this environment. Among the environments that are fundamental for the revitalization of streams, there is the Hyporheic Zone (HZ). The HZ works as a flow regulator in the river-aquifer interaction, as a bioreactor where several biogeochemical processes occur, helping in the purification of water and is considered a rich environment that serves as a habitat for numerous organisms with important ecological functions that help in the attenuation of pollutants. Among the organisms that inhabit the HZ is the meiofauna. In this context, the present study aimed to carry out a study of the hyporheic zone of three urban streams in Recife; the stream Sítio dos Pintos, Cavouco and Parnamirim. Analyzing the water quality of the streams and carrying out the physical, chemical and biological characterization of the HZ, seeking attributes that may have an influence on the revitalization of the studied streams. The water quality analyzes showed the direct input of material of organic and fecal origin in the aquatic matrices, proving the high degree of degradation of the streams. The Framework Compliance Index (ICE) classified the waters of the three streams as poor and non-compliant with the resolution; the water quality index (IQA) classified it as bad and terrible; and the trophic state index (IET) classified all three streams as hypereutrophic. From the characterization of the HZ sediments, the most representative material was classified as sand, varying between coarse, medium and fine. The release of untreated wastewater into streams was an influential factor for the physical and chemical characteristics of the HZ, which presented fine sediments and high levels of organic matter. A total of 1201 meiofauna individuals were counted, distributed in five most representative taxa, nematoda (35%), rotifera (32%), annelida (21%), Acari (6%) and copepoda (5%). The PERMANOVA analysis indicated significant differences for the Period (p = 0.016), Area (p = 0.0007) and Stratum (p = 0.0001) factors. There was no significant relationship between the structure of the meiofauna community and the variables of the hyporheic environment, indicating that the main factors that determine the structure of the meiofauna were seasonality, a determining factor for the hydrodynamics of the streams and the oxygen limit that varies according to the stratum. Despite the environmental disturbances present in the streams, an abundance of hyporheic meiofauna individuals was found, showing the resilience of these organisms. The confirmation of ecological resilience provides a scientific basis for the development of stream revitalization strategies, as well as for guiding public policies aimed at improving the environmental quality of urban areas, taking HZ into account.