Mass-dependent sulfur isotope fractionation during reoxidative sulfur cycling: A case study from Mangrove Lake, Bermuda

Pellerin, André; Bui, Tien D.; Rough, Mikaella; Mucci, Alfonso; Canfield, Donald E.; Wing, Boswell A.

doi:10.1016/j.gca.2014.11.007

Cited by 63 publications

(43 citation statements)

References 64 publications

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“…In the case of sediments from each of the GH4 sampling stations, measured 34 ε sulfide-sulfate and 33 λ sulfide-sulfate values were consistent with those measured in cultures of microbes solely reducing sulfate and fall outside the 33 λ range in which microbial sulfur disproportionation can be empirically evaluated to have played a role in further metabolic processing of sulfides oxidized to sulfur (Pellerin, Bui, et al, 2015). This assessment of fractionation resulting solely from MSR allows these results to be interpreted within the framework illustrated in Figure 1, without additionally accounting for the influence of reduced sulfide cycling by biological reoxidation.…”

Section: Fractionation Signal Consistent With Sulfate Reductionsupporting

confidence: 65%

Diversity decoupled from sulfur isotope fractionation in a sulfate‐reducing microbial community

et al. 2019

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The extent of fractionation of sulfur isotopes by sulfate‐reducing microbes is dictated by genomic and environmental factors. A greater understanding of species‐specific fractionations may better inform interpretation of sulfur isotopes preserved in the rock record. To examine whether gene diversity influences net isotopic fractionation in situ, we assessed environmental chemistry, sulfate reduction rates, diversity of putative sulfur‐metabolizing organisms by 16S rRNA and dissimilatory sulfite reductase (dsrB) gene amplicon sequencing, and net fractionation of sulfur isotopes along a sediment transect of a hypersaline Arctic spring. In situ sulfate reduction rates yielded minimum cell‐specific sulfate reduction rates < 0.3 × 10−15 moles cell−1 day−1. Neither 16S rRNA nor dsrB diversity indices correlated with relatively constant (38‰–45‰) net isotope fractionation (ε34Ssulfide‐sulfate). Measured ε34S values could be reproduced in a mechanistic fractionation model if 1%–2% of the microbial community (10%–60% of Deltaproteobacteria) were engaged in sulfate respiration, indicating heterogeneous respiratory activity within sulfate‐reducing populations. This model indicated enzymatic kinetic diversity of Apr was more likely to correlate with sulfur fractionation than DsrB. We propose that, above a threshold Shannon diversity value of 0.8 for dsrB, the influence of the specific composition of the microbial community responsible for generating an isotope signal is overprinted by the control exerted by environmental variables on microbial physiology.

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Section: Fractionation Signal Consistent With Sulfate Reductionsupporting

confidence: 65%

Diversity decoupled from sulfur isotope fractionation in a sulfate‐reducing microbial community

et al. 2019

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“…We estimate the mininum sulfide oxidation rate with a recent model of re-oxidative sulfur cycling in sediments of Mangrove Lake, Bermuda (Fig. DR6; Pellerin et al, 2015). A graphical application of this model suggests a minimum sulfide re-oxidation of 80% (Fig.…”

Section: Estimating Sulfide Re-oxidation Ratementioning

confidence: 99%

Bacterial sulfur disproportionation constrains timing of Neoproterozoic oxygenation

Kunzmann

Bui

Crockford

et al. 2017

Geology

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Various geochemical records suggest that atmospheric O2 increased in the Ediacaran (635–541 Ma), broadly coincident with the emergence and diversification of large animals and increasing marine ecosystem complexity. Furthermore, geochemical proxies indicate that seawater sulfate levels rose at this time too, which has been hypothesized to reflect increased sulfide oxidation in marine sediments caused by sediment mixing of the newly evolved macrofauna. However, the exact timing of oxygenation is not yet understood, and there are claims for significant oxygenation prior to the Ediacaran. Furthermore, recent evidence suggests that physical mixing of sediments did not become important until the late Silurian. Here we report a multiple sulfur isotope record from a ca. 835–630 Ma succession from Svalbard, further supported by data from Proterozoic strata in Canada, Australia, Russia, and the United States, in order to investigate the timing of oxygenation. We present isotopic evidence for onset of globally significant bacterial sulfur disproportionation and reoxidative sulfur cycling following the 635 Ma Marinoan glaciation. Widespread sulfide oxidation helps to explain the observed first-order increase in seawater sulfate concentration from the earliest Ediacaran to the Precambrian-Cambrian boundary by reducing the amount of sulfur buried as pyrite. Expansion of reoxidative sulfur cycling to a global scale also indicates increasing environmental O2 levels. Thus, our data suggest that increasing atmospheric O2 levels may have played a role in the emergence of the Ediacaran macrofauna and increasing marine ecosystem complexity.

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“…Disproportionation of intermediate sulfur species such as elemental sulfur, S 0 , producing sulfide and sulfate, is associated with fractionations of up to ∼40 between the products (isotopically heavier sulfate and lighter sulfide; Canfield et al, 1998Canfield et al, , 2005. Thus, in iron-rich environments where S 0 forms from abiotic sulfide reoxidation by ferric iron, repeated cycles of disproportionation and sulfide oxidation may increase the isotopic fractionation between sulfate and sulfide substantially above that caused by SR alone (Canfield and Thamdrup, 1994;Pellerin et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

High Sulfur Isotope Fractionation Associated with Anaerobic Oxidation of Methane in a Low-Sulfate, Iron-Rich Environment

2016

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Sulfur isotope signatures provide key information for the study of microbial activity in modern systems and the evolution of the Earth surface redox system. Microbial sulfate reducers shift sulfur isotope distributions by discriminating against heavier isotopes. This discrimination is strain-specific and often suppressed at sulfate concentrations in the lower micromolar range that are typical to freshwater systems and inferred for ancient oceans. Anaerobic oxidation of methane (AOM) is a sulfate-reducing microbial process with a strong impact on global sulfur cycling in modern habitats and potentially in the geological past, but its impact on sulfur isotope signatures is poorly understood, especially in low-sulfate environments. We investigated sulfur cycling and 34 S fractionation in a low-sulfate freshwater sediment with biogeochemical conditions analogous to early Earth environments. The zone of highest AOM activity was associated in situ with a zone of strong 34 S depletions in the pool of reduced sulfur species, indicating a coupling of sulfate reduction (SR) and AOM at sulfate concentrations <50 1 µmol L − . In slurry incubations of AOM-active sediment, the addition of methane stimulated SR and induced a bulk sulfur isotope effect of ∼29 . Our results imply that sulfur isotope signatures may be strongly impacted by AOM even at sulfate concentrations two orders of magnitude lower than at present oceanic levels. Therefore, we suggest that sulfur isotope fractionation during AOM must be considered when interpreting 34 S signatures in modern and ancient environments.

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Mass-dependent sulfur isotope fractionation during reoxidative sulfur cycling: A case study from Mangrove Lake, Bermuda

Cited by 63 publications

References 64 publications

Diversity decoupled from sulfur isotope fractionation in a sulfate‐reducing microbial community

Diversity decoupled from sulfur isotope fractionation in a sulfate‐reducing microbial community

Bacterial sulfur disproportionation constrains timing of Neoproterozoic oxygenation

High Sulfur Isotope Fractionation Associated with Anaerobic Oxidation of Methane in a Low-Sulfate, Iron-Rich Environment

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