Dissolved greenhouse gases (nitrous oxide and methane) associated with the naturally iron-fertilized Kerguelen region (KEOPS 2 cruise) in the Southern Ocean

Type Article
Date 2015
Language English
Author(s) Farias L.1, 2, Florez-Leiva L.3, Besoain V.1, 2, 4, Sarthou G.5, Fernandez Camino6, 7, 8
Affiliation(s) 1 : Univ Concepcion, Dept Oceanog, Concepcion, Chile.
2 : Ctr Ciencia Clima & Resiliencia CR, Concepcion, Chile.
3 : Univ Magdalena, Programa Biol, Santa Marta, Colombia.
4 : Pontificia Univ Catolica Valparaiso, Escuela Ciencias Mar, Valparaiso, Chile.
5 : IFREMER, LEMAR, CNRS, UMR6539,UBO,IRD, F-29280 Plouzane, France.
6 : Univ Paris 06, Univ Paris 04, Observ Oceanol, UMR7621,Lab Oceanog Microbienne, F-66650 Banyuls Sur Mer, France.
7 : Univ Concepcion, COPAS SA Program, Dept Oceanog, Concepcion, Chile.
8 : Univ Concepcion, Interdisciplinary Ctr Aquaculture Res INCAR, Concepcion, Chile.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2015 , Vol. 12 , N. 6 , P. 1925-1940
DOI 10.5194/bg-12-1925-2015
WOS© Times Cited 13
Note Special issue KEOPS2: Kerguelen Ocean and Plateau Study 2
Abstract The concentrations of greenhouse gases (GHGs), such as nitrous oxide (N2O) and methane (CH4), were measured in the Kerguelen Plateau region (KPR). The KPR is affected by an annual microalgal bloom caused by natural iron fertilization, and this may stimulate the microbes involved in GHG cycling. This study was carried out during the KEOPS 2 cruise during the austral spring of 2011. Oceanographic variables, including N2O and CH4, were sampled (from the surface to 500 m depth) in two transects along and across the KRP, the north south (TNS) transect (46 degrees-51 degrees S, similar to 72 degrees E) and the east west (TEW) transect (66 degrees -75 degrees E, similar to 48.3 degrees S), both associated with the presence of a plateau, polar front (PF) and other mesoscale features. The 'FEW presented N2O levels ranging from equilibrium (105 %) to slightly supersaturated (120%) with respect to the atmosphere, whereas CH4 levels fluctuated dramatically, being highly supersaturated (120-970%) in areas close to the coastal waters of the Kerguelen Islands and in the PF. The TNS showed a more homogenous distribution for both gases, with N2O and CH4 levels ranging from 88 to 171 % and 45 to 666% saturation, respectively. Surface CH4 peaked at southeastern stations of the KPR (A3 stations), where a phytoplankton bloom was observed. Both gases responded significantly, but in contrasting ways (CH4 accumulation and N2O de- pletion), to the patchy distribution of chlorophyll a. This seems to be associated to the supply of iron from various sources. Air sea fluxes for N2O (from -10.5 to 8.65, mean 1.25 +/- 4.04 mu mol m(-2) d(-1)) and for CH4 (from 0.32 to 38.1, mean 10.01 9.97 mmol(-2) d(-1)) indicated that the KPR is both a sink and a source for N2O, as well as a considerable and variable source of CH4. This appears to be associated with biological factors, as well as the transport of water masses enriched with Fe and CH4 from the coastal area of the Kerguelen Islands. These previously unreported results for the Southern Ocean suggest an intense microbial CH4 production in the study area.
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Farias L., Florez-Leiva L., Besoain V., Sarthou G., Fernandez Camino (2015). Dissolved greenhouse gases (nitrous oxide and methane) associated with the naturally iron-fertilized Kerguelen region (KEOPS 2 cruise) in the Southern Ocean. Biogeosciences, 12(6), 1925-1940. Publisher's official version : https://doi.org/10.5194/bg-12-1925-2015 , Open Access version : https://archimer.ifremer.fr/doc/00260/37141/