title: Decadal and seasonal trends of nutrient concentration and export from highly managed coastal catchments.
abstract: Understanding anthropogenic and hydro-climatic influences on nutrient concentrations and export from highly managed catchments often necessitates trend detection using long-term monitoring data. This study analyzed the temporal trend (1979-2014) of total nitrogen (TN) and total phosphorus (TP) concentrations and export from four adjacent coastal basins in south Florida where land and water resources are highly managed through an intricate canal network. The method of integrated seasonal-trend decomposition using LOESS (LOcally weighted regrESSion) was employed for trend detection. The results indicated that long-term trends in TN and TP concentrations (increasing/decreasing) varied with basins and nutrient species, reflecting the influence of basin specific land and water management practices. These long-term trends were intervened by short-term highs driven by high rainfall and discharges and lows associated with regional droughts. Seasonal variations in TP were more apparent than for TN. Nutrient export exhibited a chemostatic behavior for TN from all the basins, largely due to the biogenic nature of organic N associated with the ubiquity of organic materials in the managed canal network. Varying degrees of chemodynamic export was present for TP, reflecting complex biogeochemical responses to the legacy of long-term fertilization, low soil P holding capacity, and intensive stormwater management. The anthropogenic and hydro-climatic influences on nutrient concentration and export behavior had great implications in nutrient loading abatement strategies for aquatic ecosystem restoration of the downstream receiving waterbody.
authors.affiliation: South Florida Water Management District, 3301 Gun Club Rd., West Palm Beach, FL 33406, USA. Electronic address: wan.yongshan@epa.gov.
authors.forename: Yongshan
authors.initials: Y
authors.lastname: Wan
authors.affiliation: Xuzhou Institute of Technology, No.1 Lishui Road, New City District, Xuzhou 221008, China; Soil and Water Science Department, Tropical Research & Education Center, University of Florida, 18905 SW 280th Street, Homestead, FL 33031, USA. Electronic address: hjwanl@163.com.
authors.forename: Lei
authors.initials: L
authors.lastname: Wan
authors.affiliation: Soil and Water Science Department, Tropical Research & Education Center, University of Florida, 18905 SW 280th Street, Homestead, FL 33031, USA.
authors.forename: Yuncong
authors.initials: Y
authors.lastname: Li
authors.affiliation: South Florida Water Management District, 3301 Gun Club Rd., West Palm Beach, FL 33406, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Doering
mesh_terms: D004784:Environmental Monitoring; D009584:Nitrogen; D010758:Phosphorus; D045483:Rivers / Q000737:chemistry; D012621:Seasons; D014874:Water Pollutants, Chemical
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
keywords: Indian River Lagoon; Nutrient export; STL method; Trend detection; Water quality management