RESUMEN
Kessler et al. (Reports, 21 January 2011, p. 312) reported that methane released from the 2010 Deepwater Horizon blowout, approximately 40% of the total hydrocarbon discharge, was consumed quantitatively by methanotrophic bacteria in Gulf of Mexico deep waters over a 4-month period. We find the evidence explicitly linking observed oxygen anomalies to methane consumption ambiguous and extension of these observations to hydrate-derived methane climate forcing premature.
Asunto(s)
Contaminación Ambiental , Metano/metabolismo , Oxígeno/análisis , Petróleo , Proteobacteria/metabolismo , Agua de Mar/microbiología , Océano Atlántico , Biodegradación Ambiental , Biomasa , Hidrocarburos/análisis , Hidrocarburos/metabolismo , Metano/análisis , Oxidación-Reducción , Consumo de Oxígeno , Proteobacteria/crecimiento & desarrollo , Agua de Mar/químicaRESUMEN
Bacterial diversity in eight sediment cores from the mid-Chilean margin was studied using length heterogeneity (LH)-PCR, and described in relation to in situ geochemical conditions. DNA from the sulfate-methane transition (SMT) of three cores [one containing methane gas; two proximal to a gas hydrate mound (GHM)] was cloned and sequenced. Clones related to uncultured relatives of Desulfosarcina variabilis were found in all clone libraries and dominated one. Desulfosarcina variabilis related clones were similar to phylotypes observed at the SMT in association with anaerobic methane oxidation in the Eel River basin, Cascadia margin and the Gulf of Mexico. The LH-PCR amplicon associated with D. variabilis clones matched the amplicon that dominated most SMT samples, indicating environmental selection for D. variabilis relatives. Clones related to the Verrucomicrobia dominated the library for the methane gas-containing core. Uncultured Treponema relatives dominated the library for the core obtained on the edge of a GHM. Statistical analysis using geochemical data to describe variance in LH-PCR data revealed that stable carbon isotope ratios of dissolved inorganic carbon are the principal structuring factor on SMT communities. These data suggest that D. variabilis relatives are involved in anaerobic oxidation of methane at the SMT in Chilean margin sediments.