Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 9, issue 11
Biogeosciences, 9, 4309–4321, 2012
https://doi.org/10.5194/bg-9-4309-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 9, 4309–4321, 2012
https://doi.org/10.5194/bg-9-4309-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Nov 2012

Research article | 07 Nov 2012

Anammox, denitrification and fixed-nitrogen removal in sediments from the Lower St. Lawrence Estuary

S. A. Crowe1, D. E. Canfield1, A. Mucci2, B. Sundby2, and R. Maranger3 S. A. Crowe et al.
  • 1Nordic Center for Earth Evolution (NordCEE), Institute of Biology, University of Southern Denmark, Odense, Denmark
  • 2GEOTOP and Department of Earth and Planetary Sciences, McGill University, Montréal, Canada
  • 3Département de sciences biologiques, Université de Montréal, Montréal, Canada

Abstract. Incubations of intact sediment cores and sediment slurries reveal that anammox is an important sink for fixed nitrogen in sediments from the Lower St. Lawrence Estuary (LSLE), where it occurs at a rate of 5.5 ± 1.7 µmol N m−2 h−1. Canonical denitrification occurs at a rate of 11.3 ± 1.1 µmol N m−2 h−1, and anammox is thus responsible for up to 33% of the total N2 production. Both anammox and denitrification are mostly (> 95%) fueled by nitrate and nitrite produced in situ through benthic nitrification. Nitrification accounts for > 15% of the benthic oxygen demand and may, therefore, contribute significantly to the development and maintenance of hypoxic conditions in the LSLE. The rate of dissimilatory nitrate reduction to ammonium is three orders of magnitude lower than denitrification and anammox, and it is insignificant to N-cycling. NH4+ oxidation by sedimentary Fe(III) and Mn(III/IV) in slurry incubations with N isotope labels did not occur at measurable rates; moreover, we found no evidence for NH4+ oxidation by added Mn(III)-pyrophosphate.

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