TY - JOUR
T1 - The biogeochemical cycling of methane in Ria de Vigo, NW Spain
T2 - Sediment processing and sea-air exchange
AU - Kitidis, Vassilis
AU - Tizzard, Louise
AU - Uher, Günther
AU - Judd, Alan
AU - Upstill-Goddard, Rob C.
AU - Head, Ian M.
AU - Gray, Neil D.
AU - Taylor, Gillian
AU - Durán, Ruth
AU - Diez, Raquel
AU - Iglesias, Jorge
AU - García-Gil, Soledad
PY - 2007/6/1
Y1 - 2007/6/1
N2 - Methane (CH4) concentrations were measured in the water column, in sediment porewaters, and in atmospheric air, in the Ría de Vigo, NW Spain, during both the onset (April 2003) and at the end of (September 2004) seasonal upwelling. In addition, CH4 concentration and stable isotopic signatures (δ13CH4) were measured in porewaters, and sediment methanogenesis and aerobic oxidation of CH4 were determined in sediment incubations. Surface water column CH4 (2 m depth) was in the range 3-180 nmol l- 1 (110-8500% saturation) and followed a generally landward increase but with localised maxima in both the inner and middle Ría. These maxima were consistent with CH4 inputs from underlying porewaters in which CH4 concentrations were up to 3 orders of magnitude higher (maximum 350 μmol l- 1). Surface water CH4 concentrations were approximately three times higher in September than in April, consistent with a significant benthic CH4 flux driven by enhanced sediment methanogenesis following the summer productivity maximum. CH4 and δ13CH4 in sediment porewaters and in incubated sediment slurries (20 °C) revealed significant sediment CH4 oxidation, with an apparent isotopic fractionation factor (rc) of ∼ 1.004. Using turbulent diffusion models of air-sea exchange we estimate an annual emission of atmospheric CH4 from the Ría de Vigo of 18-44 × 106 g (1.1-2.7 × 106 mol). This estimate is approximately 1-2 orders of magnitude lower than a previous estimate based on a bubble transport model.
AB - Methane (CH4) concentrations were measured in the water column, in sediment porewaters, and in atmospheric air, in the Ría de Vigo, NW Spain, during both the onset (April 2003) and at the end of (September 2004) seasonal upwelling. In addition, CH4 concentration and stable isotopic signatures (δ13CH4) were measured in porewaters, and sediment methanogenesis and aerobic oxidation of CH4 were determined in sediment incubations. Surface water column CH4 (2 m depth) was in the range 3-180 nmol l- 1 (110-8500% saturation) and followed a generally landward increase but with localised maxima in both the inner and middle Ría. These maxima were consistent with CH4 inputs from underlying porewaters in which CH4 concentrations were up to 3 orders of magnitude higher (maximum 350 μmol l- 1). Surface water CH4 concentrations were approximately three times higher in September than in April, consistent with a significant benthic CH4 flux driven by enhanced sediment methanogenesis following the summer productivity maximum. CH4 and δ13CH4 in sediment porewaters and in incubated sediment slurries (20 °C) revealed significant sediment CH4 oxidation, with an apparent isotopic fractionation factor (rc) of ∼ 1.004. Using turbulent diffusion models of air-sea exchange we estimate an annual emission of atmospheric CH4 from the Ría de Vigo of 18-44 × 106 g (1.1-2.7 × 106 mol). This estimate is approximately 1-2 orders of magnitude lower than a previous estimate based on a bubble transport model.
UR - http://www.scopus.com/inward/record.url?scp=34247877795&partnerID=8YFLogxK
U2 - 10.1016/j.jmarsys.2006.03.022
DO - 10.1016/j.jmarsys.2006.03.022
M3 - Article
AN - SCOPUS:34247877795
SN - 0924-7963
VL - 66
SP - 258
EP - 271
JO - Journal of Marine Systems
JF - Journal of Marine Systems
IS - 1-4
ER -