title: A multi-proxy study of anaerobic ammonium oxidation in marine sediments of the Gullmar Fjord, Sweden.
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. (15) N 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.
authors.affiliation: NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, P.O. Box 59, NL-1790 AB Den Burg, The Netherlands. Radboud University Nijmegen, IWWR, Department of Microbiology, Heyendaalseweg 135, NL-6525 AJ Nijmegen, The Netherlands. Aarhus University, National Environmental Research Institute, Velsøvej 25, DK-8600 Silkeborg, Denmark. University of Gothenburg, Department of Chemistry, SE-412 96 Göteborg, Sweden.
authors.forename: Joost
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authors.lastname: Brandsma
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authors.lastname: van de Vossenberg
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authors.lastname: Eurenius
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authors.lastname: Jaeschke
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authors.initials: EC
authors.lastname: Hopmans
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authors.lastname: Strous
authors.forename: Stefan
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authors.lastname: Schouten
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.forename: Jaap S Sinninghe
authors.initials: JS
authors.lastname: Damsté