Human activities threaten the integrity of watersheds. We aimed to investigate the impact of land use on water quality, adopting a multiscale approach. We collected water samples from twelve streams in Southern Brazil and conducted limnological analyses (physical, chemical, and biological) during the dry season. We used the water quality index based on the quality standards of Canada and Brazil. Land use percentage was measured in two groups (local scale and network scale). Environmental variables were summarized through Principal Component Analysis, and we organized them into Linear Models, integrating the percentage of land use classes and terrain slope in the Multifit formula. Statistical analyses were performed using the R software. Results indicated contamination by lead, chromium, copper, nitrogen, andEscherichia coliin water samples. The Canadian Water Quality Guidelines for the Protection of Aquatic Life resulted in an index ranging from 23.3 to 47.3, compared to the Brazilian Resolution No. 357/2005 for Class 2, which had an index ranging from 47.5 to 100. This disparity is attributed to the more rigorous and sensitive monitoring approach adopted by the Canadian guidelines. Riparian forests which are up to 50 m wide are associated with improved water quality. Agricultural and urban activities were the main contributors to water quality degradation in an area extending up to 1000 m from the watershed. We emphasize the importance of a multiscale approach in watershed management and public policies, considering not only riparian forest preservation, but also human activities throughout the watershed. It is crucial to prioritize science-based environmental public policies and strengthen enforcement to prevent increasingly pronounced environmental collapses. We have identified the urgency to reformulate CONAMA Resolution No. 357/2005 with a more conservationist and ecosystem-oriented approach, as well as to propose modifications to the Brazilian Forest Code, particularly regarding the buffer zones of permanent preservation areas. Thus, this study can provide insights, such as incorporating the “effect scale,” to enhance water resource management in landscapes heavily influenced by human action, contributing to the advancement of future research in freshwater ecosystems.

Integrating water and sediment analysis with land use brings significant results in understanding the transformations in the watershed and assessing anthropic actions. We assess water and sediment samples collected in four sites in a countryside urban-farming watershed landscape in Southern Brazil. We performed the land-use, physical-chemical, microbiological, potentially toxic element (Pb, Cd, Zn, Cu, Ni, and Cr), atrazine, 2.4-D, microbiological contamination analysis, and total organic carbon, nutrients, and granulometry. We also calculate the Water quality index, geoaccumulation index, enrichment factor, and ecological risk potential. Our results demonstrates that all the water samples of this study were contaminated with fecal and total coliforms, alerting the effectiveness of treatment at these plants. We found no significant concentrations of pesticides in the water. The concentration of metals in the sediment was in the order of Cu> Zn> Cr> Ni> Pb> Cd, with Igeo = 0-3 for Cu, Zn, and EF < 3 for Cu. The Cu concentration was eight times higher than TEL, Cr, and Cu above TEL at all sites. We found a strong positive correlation between atrazine, 2.4-D, Pb, and nutrients from agricultural activities and higher concentrations at the one site. The Zn, Cu, Ni, Cd, and Cr sources were plantations, forests, and domestic sewage discharges. The results corroborate with the proposition that complete assessments of watersheds including analyzes of water, sediment and land uses are necessary to understand the real effects of anthropic action on this ecosystem and diversity of this environmental. Highlights

Aim In this study, we focused on patterns of ciliate protist community composition in urban and rural streams.