Nitrogen reduction pathways in estuarine sediments: Influences of organic carbon and sulfide

Abstract

Potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped across the entire Niantic River Estuary, CT, USA, at 100–200 m scale resolution consisting of 60 stations. On the estuary scale, denitrification accounted for ~ 90% of the nitrogen reduction, followed by DNRA and anammox. However, the relative importance of these reactions to each other was not evenly distributed through the estuary. A Nitrogen Retention Index (NIRI) was calculated from the rate data (DNRA/(denitrification + anammox)) as a metric to assess the relative amounts of reactive nitrogen being recycled versus retained in the sediments following reduction. The distribution of rates and accompanying sediment geochemical analytes suggested variable controls on specific reactions, and on the NIRI, depending on position in the estuary and that these controls were linked to organic carbon abundance, organic carbon source, and pore water sulfide concentration. The relationship between NIRI and organic carbon abundance was dependent on organic carbon source. Sulfide proved the single best predictor of NIRI, accounting for 44% of its observed variance throughout the whole estuary. We suggest that as a single metric, sulfide may have utility as a proxy for gauging the distribution of denitrification, anammox, and DNRA.

Sulfide-Induced Dissimilatory Nitrate Reduction to Ammonium Supports Anaerobic Ammonium Oxidation (Anammox) in an Open-Water Unit Process Wetland

“…Our present study provides insights into eutrophic freshwater systems by documenting the interdependence of sulfide and nitrate, as well as the presence of anammox organisms in this engineered wetland. A recent study investigating nitrogen reduction pathways in estuarine sediments found no correlation between anammox and DNRA rates and sulfide (56); however, that finding was counter to results of a study focusing on the same location that found anammox bacterial abundance positively correlated to percent organic carbon and sulfide concentration (57). DNRA has been previously linked to sulfide oxidation in marine environments (58) and has been directly coupled to anammox in marine sediments and enrichment cultures (17,59).…”

Ammonium Production and Removal in the Sediments of Shanghai River Networks: Spatiotemporal Variations, Controlling Factors, and Environmental Implications

“…Although high inputs of NH 4 + provide the substrate for nitrification, the anaerobic condition of sediments may inhibit this process. The rates of anammox, DNRA, nitrogen fixation, and nitrification in this study were comparable to other ecosystems (Andersson et al, ; Billen, ; Gardner et al, ; Hou et al, , ; Jin et al, ; Kim et al, ; Li & Lang, ; McCarthy et al, ; Plummer et al, ; Scott et al, ; Song et al, ; Zhao et al, ) (Table S2). Overall, compared to other aquatic environments, urban river network with extensive inputs of NH 4 + has changed from a source to a sink of NH 4 + , which helps remove NH 4 + a pollution.…”

DNRA and Denitrification Coexist over a Broad Range of Acetate/N-NO3− Ratios, in a Chemostat Enrichment Culture

“…Co-occurrence of denitrification and DNRA in artificial wastewater treatment wetlands and natural ecosystems, such as sediments, is often reported in literature (Mørkved et al, 2005; Giblin et al, 2013; Hardison et al, 2015). To which extent the Ac/N ratio dependent co-occurrence of DNRA and denitrification is influenced by the nature of the electron donor/carbon source in the system (Giblin et al, 2013; Plummer et al, 2015) and the oxidized nitrogen compound utilized (i.e., nitrite or nitrate), will be the topic of future studies. In addition, spatial heterogeneities in the environment could affect the co-occurrence (Verhagen and Laanbroek, 1991).…”