o:9833 Field-Scale Spatial Organization of Water Quality During Floating-Island Operation in a Eutrophic Urban Lake en Abstract: Eutrophication remains a persistent water-quality problem in shallow lakes, where exter-nal inputs interact with internal loading and biogeochemical cycling. Although floating treatment wetlands (FTWs) are increasingly promoted as nature-based solutions for water remediation, their field-scale interpretation in hydrologically complex eutrophic lakes re-mains challenging. This study examined the spatial organization of water quality during the operation of a floating-island system in a eutrophic urban lake affected by polluted tributary inflow. The study was not designed to quantify isolated FTW removal efficiency, but to evaluate spatial water quality organization during FTW operation under real-use field conditions. Water quality was monitored over two growing seasons across six func-tionally defined zones, and spatial and temporal patterns were analyzed using descriptive statistics and linear mixed-effects models. The results showed parameter-specific spatial structuring rather than a uniform treatment response. The clearest inlet-lake contrasts were observed for electrical conductivity (EC), suspended matter (SM), and nitrate nitro-gen (NO3-N), whereas biochemical oxygen demand (BOD5), ammonium nitrogen (NH4-N), and total organic carbon (TOC) showed lower values at the inlet and higher values in downstream zones. Dissolved oxygen (DO), oxygen saturation (SO), chemical oxygen de-mand (COD), nitrite nitrogen (NO2-N), and orthophosphate phosphorus (PO4-P) showed moderate or non-robust zonal effects. These findings indicate that FTWs in shallow eu-trophic lakes should be evaluated through functional zoning and parameter-specific in-terpretation rather than as isolated units with uniform removal responses. floating treatment wetlands; shallow lake; eutrophication; nature-based solution; internal loading; biogeochemical cycling 1552101 2073-4441 1552102 https://www.mdpi.com/2073-4441/18/12/1485 1552099 https://doi.org/10.3390/w18121485 2026-06-18T06:17:11.435Z 44 yes 46 Nevena Čule 0000-0002-1846-989X 46 Aleksandar Lučić 0000-0002-4473-1791 46 Marija Nešić 0000-0001-6019-7683 46 Goran Češljar 0000-0003-0438-1050 46 Ilija Đorđević 0000-0001-9499-3565 46 Jelena Božović 0000-0002-9304-0970 46 Vladan Popović 0000-0003-4326-3364 application/pdf 1087965 https://unilib.phaidrabg.rs/o:9833 no yes 16 70 92000001 71A07 Water 18 (12) 1485 1485 Multidisciplinary Digital Publishing Institute (MDPI) 2026