title: Warming increases nutrient mobilization and gaseous nitrogen removal from sediments across cascade reservoirs.
abstract: Increases in water temperature, as a result of climate change, may influence biogeochemical cycles, sediment-water fluxes and consequently environmental sustainability. Effects of rising temperature on dynamics of nitrate, nitrite, ammonium, dissolved inorganic nitrogen (DIN), dissolved reactive phosphorus (DRP), dissolved organic carbon (DOC) and gaseous nitrogen (N2and N2O) were examined in a subtropical river (the Jiulong River, southeast China) by microcosm experiments. Slurry sediments and overlying water were collected from three continuous cascade reservoirs, and laboratory incubations were performed at four temperature gradients (5 °C, 15 °C, 25 °C and 35 °C). Results indicated: (1) warming considerably increased sediment ammonium, DIN and DOC fluxes to overlying water; (2) warming increased retention of nitrate, and to a lesser extent, nitrite, corresponding to increases in N2and N2O emission; (3) DRP was retained but released from Fe/Al-P enriched sediments at high temperature (35 °C) due to enhanced coupled transformation of carbon and nitrogen with oxygen deficiency. Using relationships between sediment fluxes and temperature, a projected 2.3°C-warming in future would increase ammonium flux from sediment by 7.0%-16.8%, while increasing nitrate flux into sediment by 8.9%-28.6%. Moreover, substrates (e.g., grain size, carbon availability) influenced nutrient delivery and cycling across cascade reservoirs. This study highlights that warming would increase bioreactive nutrient (i.e., ammonium and phosphate) mobilization with limited gaseous N removal from sediments, consequently deteriorating water quality and increasing eutrophication with future climate change.
authors.affiliation: Key Laboratory of the Coastal and Wetland Ecosystems, State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China.
authors.forename: Xingpeng
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Key Laboratory of the Coastal and Wetland Ecosystems, State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China. Electronic address: nwchen@xmu.edu.cn.
authors.forename: Nengwang
authors.initials: N
authors.lastname: Chen
authors.affiliation: Key Laboratory of the Coastal and Wetland Ecosystems, State Key Laboratory of Marine Environmental Science, College of the Environment and Ecology, Xiamen University, Xiamen, 361102, China.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Yan
authors.affiliation: Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Shuiwang
authors.initials: S
authors.lastname: Duan
mesh_terms: D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002681:China; D057231:Climate Change; D058440:Denitrification; D052918:Environmental Restoration and Remediation; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
keywords: Cascade reservoir; Climate change; Jiulong River; Nutrient pollution; Sediment-water interface