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- Brandsma, J, et al.
(författare)
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A multi-proxy study of anaerobic ammonium oxidation in marine sediments of the Gullmar Fjord, Sweden
- 2011
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Ingår i: ENVIRONMENTAL MICROBIOLOGY REPORTS. - : Wiley. - 1758-2229. ; 3:3, s. 360-366
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic ammonium oxidation (anammox) is an important process for nitrogen removal in marine pelagic and benthic environments and represents a major sink in the global nitrogen cycle. We applied a suite of complementary methods for the detection and enumeration of anammox activity and anammox bacteria in marine sediments of the Gullmar Fjord, and compared the results obtained with each technique. 15N labelling experiments showed that nitrogen removal through N2 production was essentially limited to the upper 2 cm of the sediment, where anammox contributed 23–47% of the total production. The presence of marine anammox bacteria belonging to the genus ‘Candidatus Scalindua’ was shown by 16S rRNA gene sequence comparison. FISH counts of anammox bacteria correlated well with anammox activity, while quantitative PCR may have underestimated the number of anammox bacterial 16S rRNA gene copies at this site. Potential nitrogen conversion by anammox ranged from 0.6 to 4.8 fmol N cell−1 day−1, in agreement with previous measurements in the marine environment and in bioreactors. Finally, intact ladderane glycerophospholipid concentrations better reflected anammox activity and abundance than ladderane core lipid concentrations, most likely because the core lipid fraction contained a substantial fossil component, especially deeper in the sediment.
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| 2. |
- Parmentier, Frans-Jan, et al.
(författare)
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The role of endophytic methane-oxidizing bacteria in submerged Sphagnum in determining methane emissions of Northeastern Siberian tundra
- 2011
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 8:5, s. 1267-1278
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Tidskriftsartikel (refereegranskat)abstract
- The role of the microbial processes governing methane emissions from tundra ecosystems is receiving increasing attention. Recently, cooperation between methanotrophic bacteria and submerged Sphagnum was shown to reduce methane emissions but also to supply CO2 for photosynthesis for the plant. Although this process was shown to be important in the laboratory, the differences that exist in methane emissions from inundated vegetation types with or without Sphagnum in the field have not been linked to these bacteria before. In this study, chamber flux measurements, an incubation study and a process model were used to investigate the drivers and controls on the relative difference in methane emissions between a submerged Sphagnum/sedge vegetation type and an inundated sedge vegetation type without Sphagnum. It was found that methane emissions in the Sphagnumdominated vegetation type were 50% lower than in the vegetation type without Sphagnum. A model sensitivity analysis showed that these differences could not sufficiently be explained by differences in methane production and plant transport. The model, combined with an incubation study, indicated that methane oxidation by endophytic bacteria, living in cooperation with submerged Sphagnum, plays a significant role in methane cycling at this site. This result is important for spatial upscaling as oxidation by these bacteria is likely involved in 15% of the net methane emissions at this tundra site. Our findings support the notion that methane-oxidizing bacteria are an important factor in understanding the processes behind methane emissions in tundra.
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