Anammox, denitrification and fixed-nitrogen removal in sediments of the Lower St. Lawrence Estuary
Author:
Crowe S. A.,Canfield D. E.,Mucci A.,Sundby B.,Maranger R.
Abstract
Abstract. Incubations of intact sediment cores and sediment slurries reveal that anammox is an important sink for fixed nitrogen in the Lower St. Lawrence Estuary (LSLE), where it occurs at a rate of 5.5 ± 1.7 μmol N m−2 h−1 in the sediment. Anammox is responsible for up to 33% of the total N2 production, and 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 contributes 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 is therefore insignificant to N-cycling. Tests for NH4+ oxidation by sedimentary Fe(III) and Mn(III/IV), using slurry incubations with N isotope labels, revealed that it does not occur at measurable rates, and we found no evidence for NH4+ oxidation by added Mn(III)-pyrophosphate.
Publisher
Copernicus GmbH
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