Integrated assessment of water quality: influence of physicochemical parameters and ecotoxicological impacts under different flow conditions of lonqueador river, Southern Brazil.

Intensive land use and unplanned urban expansion have placed increasing demands and growing stresses on water resources. This study presents an integrated assessment of water quality in the Lonqueador River in southwestern Paraná, Brazil, combining physicochemical analyses and ecotoxicological assays using multiple bioindicators. Water samples were collected at seven sites (P1 to P7) distributed along the river, from its source in the municipality of Marmeleiro to its confluence with the Marrecas River in the urban area of Francisco Beltrão. P1 and P2 represent predominantly agricultural and forested areas, while P3 reflects a transitional zone characterized by expanding urban development, industrial activity, and a major road junction. P4 covers a peri-urban area, and P5, P6, and P7 lie in fully urbanized zones. Sampling campaigns were conducted during high-flow (H) and low-flow (L) periods. The water samples showed inhibition growth and development of Aspergillus nidulans (P1 to P7, H and L, except P4H and P6H), mortality/immobility of Artemia salina (P6L, P7L, P3H), escape of Eisenia fetida worms (P7L), cytotoxicity to Huh7.5 cells (P7L), emergence of nuclear alterations (P1H, P2 H and L, P3H, P5 H and L, P7L) and micronucleus (P1H, P2H, P3H, P4H, P5H, P7H) in Lithobates catesbeianus, and cytotoxic (P1H, P2H, P5H, P7H) and mutagenic (P5L) effect on Allium cepa. Heavy metals, particularly manganese, were detected in higher concentrations during high flow, whereas hormones E1, E2, and EE2 were more frequent during low flow. These findings highlight the importance of integrated approaches for monitoring and managing water quality in watersheds.