Anaerobic Ammonium Oxidation Measured in Sediments along the Thames Estuary, United Kingdom

Abstract

Until recently, denitrification was thought to be the only significant pathway for N 2 formation and, in turn, the removal of nitrogen in aquatic sediments. The discovery of anaerobic ammonium oxidation in the laboratory suggested that alternative metabolisms might be present in the environment. By using a combination of 15 ؊ . We observed a shift in the significance of anaerobic ammonium oxidation to N 2 formation relative to denitrification, from 8% near the head of the estuary to less than 1% at the coast. The relative importance of anaerobic ammonium oxidation was positively correlated (P < 0.05) with sediment organic content. This report of anaerobic ammonium oxidation in organically enriched estuarine sediments, though in contrast to a recent report on continental shelf sediments, confirms the presence of this novel metabolism in another aquatic sediment system.Since the 1970s, substantial research has focused on the ability of estuarine sediments to attenuate riverine nitrogen (N) loads before they affect coastal seas (4,18,19,31,33). Estuarine sediments are essentially anaerobic below a few surface millimeters, and the mineralization of organic matter proceeds via alternate electron acceptors such as NO 3 Ϫ and SO 4 2Ϫ (20,27). In turn, the reduction of NO 3 Ϫ removes NO 3 Ϫ from the overlying waters. Until recently, it was largely thought that NO 3 Ϫ could be either reduced to N 2 gas via denitrification (a facultative metabolism mediated by a variety of bacteria) and lost from the system or reduced to ammonium (NH 4 ϩ ) by fermentative metabolisms and hence conserved within the sediments (dissimilatory nitrate reduction to ammonium [DNRA]) (8,23). It had been demonstrated that changes in sediment organic loadings and estuarine NO 3 Ϫ concentrations may affect the partitioning between these two end products of NO 3 Ϫ reduction (11, 12). The discovery within the laboratory (17) of anaerobic ammonium oxidation revealed a novel metabolism that could short circuit the N cycle, bypassing what was previously thought to be a critical aerobic nitrification phase and potentially providing an alternative pathway for N 2 gas formation in the environment (Fig. 1).Originally, it was thought (17) that anaerobic ammonium oxidation coupled the oxidation of NH 4 ϩ to the reduction of NO 3 Ϫ :Further work, however, showed that the oxidation of ammonium was actually coupled to the reduction of nitrite rather than nitrate (34, 35):The application of this process to the treatment of nitrogenous waste has received a great deal of attention (9, 10), and more recently, the organism responsible has been classified as a new autotrophic planctomycete (28). Anaerobic ammonium oxidation was recently reported to account for as much as 24 and 60% of N 2 formation in continental shelf sediments in relatively deep water (380 and 695 m, respectively) but less than 2% of N 2 formation in eutrophic shallow coastal bay sediments (30). The drop in the significance of anaerobic ammonium oxidation for N 2 formation relative to denitrificatio...

Widespread occurrence of the anammox reaction in estuarine sediments

“…Meyer et al (2005) were able to correlate the greater contribution of anammox to the production of N 2 with a greater availability of NO 2 -in the pore water. Together this corroborated a link between organic carbon and a supply of NO 2 -via NO 3 -reduction (Trimmer et al 2003. The importance of NO 3 -was confirmed by Risgaard-Petersen et al (2004), who found no significant anammox activity in Norsminde Fjord but an ra of up to 22% in Randers Fjord; in Rander Fjord, NO 3 -was abundant in the water column and penetrated into the sediment, but was absent in Norsminde Fjord.…”

“…Our findings provide firm evidence that the anammox reaction is widespread in estuarine sediments. Trimmer et al 2003), we showed a clear trend of increasing contribution of anammox to N 2 (ra, %) with increasing organic carbon and NO 3 -further upstream. This pattern was in stark contrast with that reported for the coastal sediments, but since then has also been reported for the subtropical Logan-Albert estuary system in Australia ) and for parts of Chesapeake Bay (Rich et al 2008).…”

“…Anammox has been shown to be widespread in coastal marine sediments , Engström et al 2005, Schmid et al 2007), yet knowledge of its distribution and regulation in estuarine systems is comparatively scarce, with data reported from just 4 estuaries around the world so far (Trimmer et al 2003, Risgaard-Petersen et al 2004, Rich et al 2008. Two factors which regulate anammox are temperature for marine sediments, with greater anammox activity at lower temperatures relative to denitrification (Dalsgaard & Thamdrup 2002, and an in situ supply of NO 2 -modulated by organic carbon and/or the concentration of NO 3 -in the overlying water column of estuarine (Trimmer et al 2003, RisgaardPetersen et al 2005) and arctic marine sediments .…”

An overlooked nitrogen loss linked to anaerobic ammonium oxidation in estuarine sediments in China

“…Subsequently, the vials were portioned into three treatments, which were spiked through the stopper of each vial with 100 μL of N 2 -purged stock solution of (1) . The rate and potential contribution to N 2 production of either anammox or denitrification were calculated as described before (Thamdrup and Dalsgaard 2002;Trimmer et al 2003).…”

Presence and activity of anaerobic ammonium-oxidizing bacteria at deep-sea hydrothermal vents

“…In the meantime, many studies have shown that the anammox bacteria and the annamox process are ubiquitous and constitute a substantial sink of fixed nitrogen in the oceans (Dalsgaard et al, 2003;Kuypers et al, 2003;Penton et al, 2006;Schmid et al, 2007). The process is also significant in minimum oxygen zones (Kuypers et al, 2005;Hamersley et al, 2007;Jaeschke et al, 2007), sediments (Engstrom et al, 2005;Penton et al, 2006) and estuaries (Trimmer et al, 2003;Tal et al, 2005). These are all mesophilic to cold environments, and it is presently unknown whether anammox bacteria are also active at higher temperatures in marine ecosystems.…”