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14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers.

Abstract

Despite the global significance of the subsurface biosphere, the degree to which it depends on surface organic carbon (OC) is still poorly understood. Here, we compare stable and radiogenic carbon isotope compositions of microbial phospholipid fatty acids (PLFAs) with those of in situ potential microbial C sources to assess the major C sources for subsurface microorganisms in biogeochemical distinct shallow aquifers (Critical Zone Exploratory, Thuringia Germany). Despite the presence of younger OC, the microbes assimilated 14C-free OC to varying degrees; ~31% in groundwater within the oxic zone, ~47% in an iron reduction zone, and ~70% in a sulfate reduction/anammox zone. The persistence of trace amounts of mature and partially biodegraded hydrocarbons suggested that autochthonous petroleum-derived hydrocarbons were a potential 14C-free C source for heterotrophs in the oxic zone. In this zone, Δ14C values of dissolved inorganic carbon (-366 ± 18‰) and 11MeC16:0 (-283 ± 32‰), an important component in autotrophic nitrite oxidizers, were similar enough to indicate that autotrophy is an important additional C fixation pathway. In anoxic zones, methane as an important C source was unlikely since the 13C-fractionations between the PLFAs and CH4 were inconsistent with kinetic isotope effects associated with methanotrophy. In the sulfate reduction/anammox zone, the strong 14C-depletion of 10MeC16:0 (-942 ± 22‰), a PLFA common in sulfate reducers, indicated that those bacteria were likely to play a critical part in 14C-free sedimentary OC cycling. Results indicated that the 14C-content of microbial biomass in shallow sedimentary aquifers results from complex interactions between abundance and bioavailability of naturally occurring OC, hydrogeology, and specific microbial metabolisms.

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  • Authors+Show Affiliations

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    Institute of Geosciences Friedrich Schiller University Jena Germany. Max-Planck-Institute for Biogeochemistry Jena Germany. Institute for Inorganic and Analytical Chemistry Friedrich Schiller University Jena Germany.

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    Max-Planck-Institute for Biogeochemistry Jena Germany.

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    Department of Earth System Science University of California Irvine CA USA.

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    Max-Planck-Institute for Biogeochemistry Jena Germany. Department of Earth System Science University of California Irvine CA USA.

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    Department of Earth System Science University of California Irvine CA USA.

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    Max-Planck-Institute for Biogeochemistry Jena Germany.

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    Institute of Geosciences Friedrich Schiller University Jena Germany.

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    Institute for Inorganic and Analytical Chemistry Friedrich Schiller University Jena Germany.

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    Max-Planck-Institute for Biogeochemistry Jena Germany.

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    Institute of Ecology Friedrich Schiller University Jena Germany. German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig Leipzig Germany.

    Institute of Geosciences Friedrich Schiller University Jena Germany.

    Source

    Water resources research 55:3 2019 Mar pg 2104-2121

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    31068736

    Citation

    Schwab, Valérie F., et al. "14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers." Water Resources Research, vol. 55, no. 3, 2019, pp. 2104-2121.
    Schwab VF, Nowak ME, Elder CD, et al. 14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers. Water Resour Res. 2019;55(3):2104-2121.
    Schwab, V. F., Nowak, M. E., Elder, C. D., Trumbore, S. E., Xu, X., Gleixner, G., ... Totsche, K. U. (2019). 14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers. Water Resources Research, 55(3), pp. 2104-2121. doi:10.1029/2017WR022067.
    Schwab VF, et al. 14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers. Water Resour Res. 2019;55(3):2104-2121. PubMed PMID: 31068736.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - 14C-Free Carbon Is a Major Contributor to Cellular Biomass in Geochemically Distinct Groundwater of Shallow Sedimentary Bedrock Aquifers. AU - Schwab,Valérie F, AU - Nowak,Martin E, AU - Elder,Clayton D, AU - Trumbore,Susan E, AU - Xu,Xiaomei, AU - Gleixner,Gerd, AU - Lehmann,Robert, AU - Pohnert,Georg, AU - Muhr,Jan, AU - Küsel,Kirsten, AU - Totsche,Kai U, Y1 - 2019/03/15/ PY - 2017/10/16/received PY - 2018/09/17/revised PY - 2018/12/04/accepted PY - 2019/5/10/entrez PY - 2019/5/10/pubmed PY - 2019/5/10/medline KW - C cycling KW - PLFA KW - assimilation KW - microbial function KW - radiocarbon KW - subsurface SP - 2104 EP - 2121 JF - Water resources research JO - Water Resour Res VL - 55 IS - 3 N2 - Despite the global significance of the subsurface biosphere, the degree to which it depends on surface organic carbon (OC) is still poorly understood. Here, we compare stable and radiogenic carbon isotope compositions of microbial phospholipid fatty acids (PLFAs) with those of in situ potential microbial C sources to assess the major C sources for subsurface microorganisms in biogeochemical distinct shallow aquifers (Critical Zone Exploratory, Thuringia Germany). Despite the presence of younger OC, the microbes assimilated 14C-free OC to varying degrees; ~31% in groundwater within the oxic zone, ~47% in an iron reduction zone, and ~70% in a sulfate reduction/anammox zone. The persistence of trace amounts of mature and partially biodegraded hydrocarbons suggested that autochthonous petroleum-derived hydrocarbons were a potential 14C-free C source for heterotrophs in the oxic zone. In this zone, Δ14C values of dissolved inorganic carbon (-366 ± 18‰) and 11MeC16:0 (-283 ± 32‰), an important component in autotrophic nitrite oxidizers, were similar enough to indicate that autotrophy is an important additional C fixation pathway. In anoxic zones, methane as an important C source was unlikely since the 13C-fractionations between the PLFAs and CH4 were inconsistent with kinetic isotope effects associated with methanotrophy. In the sulfate reduction/anammox zone, the strong 14C-depletion of 10MeC16:0 (-942 ± 22‰), a PLFA common in sulfate reducers, indicated that those bacteria were likely to play a critical part in 14C-free sedimentary OC cycling. Results indicated that the 14C-content of microbial biomass in shallow sedimentary aquifers results from complex interactions between abundance and bioavailability of naturally occurring OC, hydrogeology, and specific microbial metabolisms. SN - 0043-1397 UR - https://www.unboundmedicine.com/medline/citation/31068736/14C-Free_Carbon_Is_a_Major_Contributor_to_Cellular_Biomass_in_Geochemically_Distinct_Groundwater_of_Shallow_Sedimentary_Bedrock_Aquifers L2 - https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/31068736/ DB - PRIME DP - Unbound Medicine ER -