The Sediment Nitrogen Cycle Overview

The sediment N cycle consists of oxidative and reductive processes that are frequently coupled in space and/or time (Flerbert, 1999) and are strongly influenced by chemical, physical, and biological factors (Figs. 19.1 and 19.2). We present 

Location NFIX rate (mmol m d ) Method Reference 

acetylene reduction activity MIMS, membrane inlet mass spectrometry. 

Coupling of nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and anammox 

Because NTR links the reduced and oxidized sides of the N cycle, it can be considered a central process that provides substrate to microbes that employ nitrate or nitrite as oxidant (see Chapter 5 by Ward, this volume Fig. 19.1, arrow 4). Like NH4, the products of NTR, N02, and NOs , may experience one of several possible fates, including (1) flux from the sediment, (2) assimilation within the sediment or at the sediment—water interface, or (3) reduction by one of three possible dissimilatory pathways DNF, dissimilatory nitrate reduction to ammonium (DNRA), or ANAM (Fig. 19.1, arrows 5, 6, and 7 Fig. 19.2). Uptake of NO by 

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