The effect of increased nitrate loading on nitrate reduction via denitrification and DNRA in salt marsh sediments

Koop-Jakobsen, Ketil; Giblin, Anne E.

doi:10.4319/lo.2010.55.2.0789

Cited by 131 publications

(62 citation statements)

References 51 publications

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“…2). The DNRA rates are comparable to those measured in a diverse range of muddy shelf sediments, including the Baltic sea [63], East China Sea [36], temperate and tropical estuaries [64]–[66] and fjords [67], [68]. However, as denitrification rates are comparatively much higher in the Wadden Sea, the contribution of DNRA to total nitrate reduction measured during this study is lower than in other continental shelf sediments.…”

Section: Discussionsupporting

confidence: 78%

The Fate of Nitrate in Intertidal Permeable Sediments

et al. 2014

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Coastal zones act as a sink for riverine and atmospheric nitrogen inputs and thereby buffer the open ocean from the effects of anthropogenic activity. Recently, microbial activity in sandy permeable sediments has been identified as a dominant source of N-loss in coastal zones, namely through denitrification. Some of the highest coastal denitrification rates measured so far occur within the intertidal permeable sediments of the eutrophied Wadden Sea. Still, denitrification alone can often account for only half of the substantial nitrate (NO3 −) consumption. Therefore, to investigate alternative NO3 − sinks such as dissimilatory nitrate reduction to ammonium (DNRA), intracellular nitrate storage by eukaryotes and isotope equilibration effects we carried out 15NO3 − amendment experiments. By considering all of these sinks in combination, we could quantify the fate of the 15NO3 − added to the sediment. Denitrification was the dominant nitrate sink (50–75%), while DNRA, which recycles N to the environment accounted for 10–20% of NO3 − consumption. Intriguingly, we also observed that between 20 and 40% of 15NO3 − added to the incubations entered an intracellular pool of NO3 − and was subsequently respired when nitrate became limiting. Eukaryotes were responsible for a large proportion of intracellular nitrate storage, and it could be shown through inhibition experiments that at least a third of the stored nitrate was subsequently also respired by eukaryotes. The environmental significance of the intracellular nitrate pool was confirmed by in situ measurements which revealed that intracellular storage can accumulate nitrate at concentrations six fold higher than the surrounding porewater. This intracellular pool is so far not considered when modeling N-loss from intertidal permeable sediments; however it can act as a reservoir for nitrate during low tide. Consequently, nitrate respiration supported by intracellular nitrate storage can add an additional 20% to previous nitrate reduction estimates in intertidal sediments, further increasing their contribution to N-loss.

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Section: Discussionsupporting

confidence: 78%

The Fate of Nitrate in Intertidal Permeable Sediments

et al. 2014

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“…In some areas, DNRA can remove more NO 3 - than denitrification13. Our observations reveal that DNRA values recorded in the present investigation were 2–3 orders higher as compared to rates reported in other marine sediment14. In the mangroves ecosystems of Goa, the process accounts for up to 99% of the NO 3 - reduced.…”

Section: Discussioncontrasting

confidence: 45%

Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium

Fernandes

Bonin

Michotey

et al. 2012

Sci Rep

107

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Earlier observations in mangrove sediments of Goa, India have shown denitrification to be a major pathway for N loss1. However, percentage of total nitrate transformed through complete denitrification accounted for <0–72% of the pore water nitrate reduced. Here, we show that up to 99% of nitrate removal in mangrove sediments is routed through dissimilatory nitrate reduction to ammonium (DNRA). The DNRA process was 2x higher at the relatively pristine site Tuvem compared to the anthropogenically-influenced Divar mangrove ecosystem. In systems receiving low extraneous nutrient inputs, this mechanism effectively conserves and re-circulates N minimizing nutrient loss that would otherwise occur through denitrification. In a global context, the occurrence of DNRA in mangroves has important implications for maintaining N levels and sustaining ecosystem productivity. For the first time, this study also highlights the significance of DNRA in buffering the climate by modulating the production of the greenhouse gas nitrous oxide.

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“…The mean dry bulk density (0–35 cm) of the long-term enriched marsh soils ( n = 20 cores; 0.44 ± 0.012 g/cm 3 ) was significantly lower than that of the reference creeks ( n = 20 cores; 0.48 ± 0.012 g/cm 3 ; R. S. Warren, unpublished data , two-tailed t -test, t = 2.151, P = 0.033). The increase in the soil % C, N, and OM may contribute to the reported increases in microbial decomposition and denitrification rates (Koop-Jackobsen and Giblin 2010, Deegan et al 2012) and soil respiration rates (this study) in the longterm enriched creek systems.…”

Section: Discussionmentioning

confidence: 63%

“…We hypothesized that while nutrient enrichment could cause increased sapric OM, nitrogen content, and respiration rates in marsh soils, it might also cause decreased soil shear strength across the marsh landscape, possibly due to the previously reported significant reduction in belowground biomass and associated fibric soils (Deegan et al 2012) and elevated rates of belowground OM mineralization associated with nitrogen processing (Koop-Jackobsen and Giblin 2010). Because sea level rise is known to alter the extent and frequency of flooding of coastal marshes and alter plant community structure in the Northeast United States (e.g., Warren and Niering 1993, Roman et al 1997, Donnelly and Bertness 2001, Raposa et al 2017), we calculated yearly tidal flooding patterns for the study period and plant species cover to examine whether there were shifts in dominant species toward those favored by wetter soils.…”

Section: Introductionmentioning

confidence: 99%

Discontinuities in soil strength contribute to destabilization of nutrient‐enriched creeks

et al. 2018

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In a whole‐ecosystem, nutrient addition experiment in the Plum Island Sound Estuary (Massachusetts), we tested the effects of nitrogen enrichment on the carbon and nitrogen contents, respiration, and strength of marsh soils. We measured soil shear strength within and across vegetation zones. We found significantly higher soil percent organic matter, carbon, and nitrogen in the long‐term enriched marshes and higher soil respiration rates with longer duration of enrichment. The soil strength was similar in magnitude across depths and vegetation zones in the reference creeks, but showed signs of significant nutrient‐mediated alteration in enriched creeks where shear strength at rooting depths of the low marsh–high marsh interface zone was significantly lower than at the sub‐rooting depths or in the creek bank vegetation zone. To more closely examine the soil strength of the rooting (10–30 cm) and sub‐rooting (40–60 cm) depths in the interface and creek bank vegetation zones, we calculated a vertical shear strength differential between these depths. We found significantly lower differentials in shear strength (rooting depth < sub‐rooting depths) in the enriched creeks and in the interface zones. The discontinuities in the vertical and horizontal shear strength across the enriched marshes may contribute to observed fracturing and slumping occurring in the marsh systems. Tide gauge data also showed a pattern of rapid sea level rise for the period of the study, and changes in plant distribution patterns were indicative of increased flooding. Longer exposure times to nutrient‐enriched waters and increased hydraulic energy associated with sea level rise may exacerbate creek bank sloughing. Additional research is needed, however, to better understand the interactions of nutrient enrichment and sea level rise on soil shear strength and stability of tidal salt marshes.

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The effect of increased nitrate loading on nitrate reduction via denitrification and DNRA in salt marsh sediments

Cited by 131 publications

References 51 publications

The Fate of Nitrate in Intertidal Permeable Sediments

The Fate of Nitrate in Intertidal Permeable Sediments

Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium

Discontinuities in soil strength contribute to destabilization of nutrient‐enriched creeks

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