Spatio-temporal variability and controls on methane and nitrous oxide in the Guadalquivir Estuary, Southwestern Europe
Estuaries are significant methane (CH4) and nitrous oxide (N2O) emitters, although dynamics of both greenhouse gases in these ecosystems are regulated by complex processes. In this work, we aimed at characterizing the spatio-temporal distribution of CH4 and N2O in the Guadalquivir river estuary (SW Spain), the southernmost European estuary. During eight sampling cruises conducted between 2016 and 2017, surface water CH4 and N2O concentrations were measured along the salinity gradient of the estuary by using static-head space equilibration gas chromatography. The CH4 and N2O saturation ranges over the estuarine transect were 520–30,800% (average 2285%) and 40–390% (average 183%), respectively and air–water fluxes ranged from 13 to 1000 µmol m− 2 day− 1(average 66.2 µmol m− 2 day− 1) for CH4 and from − 7 to 35 µmol m− 2 day− 1 (average 8.5 µmol m− 2 day− 1) for N2O. A slight increase in the emissions was detected upstream and no seasonal trends were observed. Mixing between freshwater and oceanic waters influenced biogeochemistry of estuarine waters, affecting CH4 and N2O fluxes. In order to identify potential sources of CH4 and N2O, biogeochemical parameters involved in the formation pathways of both gases, such as salinity, dissolved oxygen, nutrients and organic matter were analyzed. Results suggested that sulfate inhibition and microbial oxidation played a relevant role in dissolved CH4 accumulation in the water column whereas associations found between N2O, nitrate and oxygen indicated that nitrification was a major source of this gas. Therefore, the influence of the tidal-fluvial interaction on ecosystem metabolism regulates trace gas dynamics in the Guadalquivir estuary.
KeywordsEstuary Guadalquivir Methane Nitrification Nitrous oxide
This research was funded by the project 1539/2015 from the Spanish Ministry for Agriculture, Food and Environment. The authors are indebted to María Ferrer-Marco, Marta Riera and Antonio Moreno for support in the field work and samples analysis and Manuel Arjonilla for nutrients analysis.
IEH conceived the study, contributed to data analysis and interpretation and draft the manuscript. GN and FFP contributed to data analysis interpretation and critical discussion. SF and MdP contributed to analytical design, data calculation and discussion.
- Bakker DC, Bange HW, Gruber N, Johannessen T, Upstill-Goddard RC, Borges AV, Delille B, Löscher CR, Naqvi SWA, Omar AM (2014) Air-sea interactions of natural long-lived greenhouse gases (CO2, N2O, CH4) in a changing climate, ocean–atmosphere Interactions of gases and particles, edited, pp 113–169, SpringerGoogle Scholar
- Borges AV, Darchambeau F, Lambert T, Bouillon S, Morana C, Brouyère S, Hakoun V, Jurado A, Tseng H-C, Descy J-P, Roland FAE (2018) Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium). Sci Total Environ 610–611:342–355CrossRefPubMedGoogle Scholar
- Borges AV, G Speeckaert, W Champenois, M.I. Scranton & N Gypens (2017) Productivity and temperature as drivers of seasonal and spatial variations of dissolved methane in the Southern Bight of the North Sea, Ecosystems. https://doi.org/10.1007/s10021-017-0171-7
- Ciais P et al (2013) Carbon and other biogeochemical cycles. In: Stocker TF (ed) et al Climate Change 2013: the physical science basis. Contribution of WorkingGroup I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge Univ. Press, Cambridge, pp 465–570Google Scholar
- Cotovicz LC, Knoppers BA, Brandini N, Poirier D, Costa Santos SJ, Abril G (2016) Spatio-temporal variability of methane (CH4) concentrations and diffusive fluxes from a tropical coastal embayment surrounded by a large urban area (Guanabara Bay, Rio de Janeiro, Brazil). Limnol Oceanogr 61:S238–S252. https://doi.org/10.1002/lno.10298 CrossRefGoogle Scholar
- Huertas IE, de la Paz M, Flecha S, Perez FF (2017b) Methane and nitrous oxide air-water fluxes from Doñana wetlands: spatial and temporal variability of emissions. In: Annual meeting of Society of Wetlands Scientists, San Juan, Puerto RicoGoogle Scholar
- Lewis E, Wallace D, Allison LJ (1998), Program developed for CO2 system calculations, Carbon Dioxide Information Analysis Center, managed by Lockheed Martin Energy Research Corporation for the US Department of EnergyGoogle Scholar
- Myhre G et al (2013) Anthropogenic and Natural Radiative Forcing. In: Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM (eds) Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, pp 659–740Google Scholar
- Ruiz J, Polo MJ, Díez-Minguito M, Navarro G, Morris EP, Huertas IE, Caballero E, Contreras, Losada MA (2015) The Guadalquivir estuary: a hot spot for environmental and human conflicts. In: Environmental management and governance. Springer, edited, pp 199–232Google Scholar
- Stocker TF et al (2013) Technical Summary. In: Assessment Report of the Intergovernmental Panel on Climate Change, edited by Stocker TF, Qin D, Plattner G-K, Tignor M, Allen SK, Boschung J, Nauels A, Xia Y, Bex V, Midgley PM Climate Change 2013: The physical science basis. Contribution of Working Group I to the Fifth. Cambridge University Press, Cambridge, pp 33–115Google Scholar
- Von Fischer JC, Hedin LO (2007) Controls on soil methane fluxes: tests of biophysical mechanisms using stable isotope tracers, Glob Biogeochem Cycle 21(2)Google Scholar