首页|Molecular and isotopic signatures of oil-driven bacterial sulfate reduction at seeps in the southern Gulf of Mexico

Molecular and isotopic signatures of oil-driven bacterial sulfate reduction at seeps in the southern Gulf of Mexico

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  • NSTL
  • Elsevier
Oil seepage is widespread in the Gulf of Mexico, which also applies to the Bay of Campeche in the southern Gulf. The ascension of crude oil and oil-derived hydrocarbons poses a challenge to most seep-dwelling organisms. On the other hand, short- and long-chain hydrocarbons have been shown to be potentially degraded by a range of heterotrophic sulfate-reducing bacteria. Here we present lipid biomarker and carbon isotope data from authigenic carbonates from the Campeche Knolls in the southern Gulf of Mexico and use methane-seep carbonates from the Makran convergent margin (southern Pakistan and Iran) for comparison. The Campeche Knolls and Makran were selected for such comparison as endmember types for oil versus methane seepage in an attempt to identify molecular signatures of oil seepage. The Campeche carbonates yielded on average higher delta C-13 values (-31.3 parts per thousand to -21.9 parts per thousand) than the Makran methane-seep carbonates (-54.3 parts per thousand to -39.8 parts per thousand) and revealed a particularly high content of ether lipids. The Campeche carbonates revealed a greater variety of alkyl chains in nonisoprenoidal dialkyl glycerol diether lipids (DAGE) and a higher relative proportion of long alkyl chains (DAGEs>C-36) compared with the Makran methane-seep carbonates. Bacterial biomarkers showed an on average distinctively heavier delta C-13 signature than at the studied methane seeps, indicating bacterial oxidation of oil-derived hydrocarbons. Mixing calculations indicate that up to 73% of the local sulfate reduction is coupled to the oxidation of non-methane hydrocarbons at the oil seeps, contributing as much as 40% to carbonate precipitation. These data imply that oil-seep carbonates can be discriminated from methane-seep carbonates by their respective biomarker inventories in modern and, in cases of moderate to good biomarker preservation, ancient environments, setting the stage for the reconstruction of the influence of fluid composition on the compositions of chemosynthesis-based communities at seeps.

Oil seepsOil degradationSulfate-reducing bacteriaMAGEsDAGEsGulf of MexicoMakran accretionary prismFATTY-ACID-COMPOSITIONLIPID BIOMARKER PATTERNSNORTHERN ARABIAN SEACHAPOPOTE ASPHALT VOLCANOREVEAL FLUID COMPOSITIONHOT-SPRING ENVIRONMENTSINTACT POLAR LIPIDSANAEROBIC OXIDATIONREDUCING BACTERIAAUTHIGENIC CARBONATES

Krake, N.、Birgel, D.、Smrzka, D.、Zwicker, J.、Huang, H.、Feng, D.、Bohrmann, G.、Peckmann, J.

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Univ Hamburg

Univ Wien

Chinese Acad Sci

Shanghai Ocean Univ

Univ Bremen

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2022

10.1016/j.chemgeo.2022.120797

Chemical geology

Chemical geology

EISCI
ISSN：0009-2541
年,卷(期)：2022.595
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