| 1. |
- Wehrmann, Laura M., et al.
(författare)
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Iron-controlled oxidative sulfur cycling recorded in the distribution and isotopic composition of sulfur species in glacially influenced fjord sediments of west Svalbard
- 2017
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 466, s. 678-695
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates how glacially delivered reactive iron (oxyhydr) oxide and manganese oxide phases influence the biogeochemical cycling of sulfur in sediments of three Arctic fjords and how the biogeochemical signatures of these processes are preserved. Results reveal differences in the concentrations of dissolved iron and manganese in pore-waters and the concentration of solid-phase sulfur species within individual fjords and amongst the three fjords, likely controlled by the varying input of reactive iron (oxyhydr) oxides to the sediment. Broadly, the stations can be divided into three categories based on their biogeochemical signals. Stations in the first category, located in Smeerenburgfjorden, are characterized by relatively low concentrations of (easily) reducible particulate iron phases, increasing concentrations of iron monosulfides, pyrite, and elemental sulfur with depth, and low pore-water dissolved iron and manganese concentrations. Biogeochemical processes at these stations are primarily driven by organoclastic sulfate reduction, sulfur disproportionation and the subsequent reaction and sequestration of sulfide in the sediment as iron monosulfide and pyrite. Sulfur and oxygen isotope values of sulfate display progressive enrichment in heavy isotopes with depth at these stations. In contrast, concentrations of (easily) reducible particulate iron phases and pore-water dissolved iron (up to 850 mu M) and manganese (up to 650 mu M) are very high at stations of the second and third category, located in Kongsfjorden and Van Mijenfjorden, while iron monosulfide and pyrite contents are extremely low. The amount of pyrite and its isotope values in conjunction with organic sulfur compounds provide evidence for a detrital origin of a fraction of these sulfur compounds. At the Kongsfjorden and Van Mijenfjorden stations, oxidative pathways of the sedimentary sulfur cycle, controlled by the high availability of reducible particulate iron phases, play an important role, leading to the effective recycling of sulfide to sulfate through sulfur intermediates and concomitant resupply of the sulfate reservoir with S-32. In both fjords, elemental sulfur was only detected at the outer fjord stations grouped into the third category. Our study provides a framework for interpreting the Fe-S-C geochemistry of similar continental shelf areas in modern settings and ultimately for identifying these environments in the rock record.
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| 2. |
- Robador, Alberto, et al.
(författare)
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Activity and community structures of sulfate-reducing microorganisms in polar, temperate and tropical marine sediments
- 2016
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 10:4, s. 796-809
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Tidskriftsartikel (refereegranskat)abstract
- Temperature has a fundamental impact on the metabolic rates of microorganisms and strongly influences microbial ecology and biogeochemical cycling in the environment. In this study, we examined the catabolic temperature response of natural communities of sulfate-reducing microorganisms (SRM) in polar, temperate and tropical marine sediments. In short-term sediment incubation experiments with S-35-sulfate, we demonstrated how the cardinal temperatures for sulfate reduction correlate with mean annual sediment temperatures, indicating specific thermal adaptations of the dominant SRM in each of the investigated ecosystems. The community structure of putative SRM in the sediments, as revealed by pyrosequencing of bacterial 16S rRNA gene amplicons and phylogenetic assignment to known SRM taxa, consistently correlated with in situ temperatures, but not with sediment organic carbon concentrations or C:N ratios of organic matter. Additionally, several species-level SRM phylotypes of the class Deltaproteobacteria tended to co-occur at sites with similar mean annual temperatures, regardless of geographic distance. The observed temperature adaptations of SRM imply that environmental temperature is a major controlling variable for physiological selection and ecological and evolutionary differentiation of microbial communities.
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