Coupled nitrification–denitrification leads to extensive N loss in subtidal permeable sediments

Marchant, Hannah K.; Holtappels, Moritz; Lavik, Gaute; Ahmerkamp, Soeren; Winter, Christian; Kuypers, Marcel M. M.

doi:10.1002/lno.10271

Cited by 101 publications

(107 citation statements)

References 78 publications

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“…In relation to the benthic processes, it should also be noted that simulated daily benthic denitrification rates in the inner German Bight are up to 4 times higher than those recently reported by Marchant et al (2016). However, this only applies to few very near-shore areas in the model.…”

Section: Limitations Of the Model Intrinsics And The Tbnt Methodsmentioning

confidence: 78%

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

et al. 2017

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Oxygen (O 2 ) deficiency, i.e., dissolved O 2 concentrations below 6 mg O 2 L −1 , is a common feature in the southern North Sea. Its evolution is governed mainly by the presence of seasonal stratification and production of organic matter, which is subsequently degraded under O 2 consumption. The latter is strongly influenced by riverine nutrient loads, i.e., nitrogen (N) and phosphorus (P). As riverine P loads have been reduced significantly over the past decades, this study aims for the quantification of the influence of riverine and non-riverine N inputs on the O 2 dynamics in the southern North Sea. For this purpose, we present an approach to expand a nutrient-tagging technique for physical-biogeochemical models -often referred to as 'trans-boundary nutrient transports' (TBNT) -by introducing a direct link to the O 2 dynamics. We apply the expanded TBNT to the physical-biogeochemical model system HAMSOM-ECOHAM and focus our analysis on N-related O 2 consumption in the southern North Sea during 2000-2014. The analysis reveals that near-bottom O 2 consumption in the southern North Sea is strongly influenced by the N supply from the North Atlantic across the northern shelf edge. However, riverine N sources -especially the Dutch, German and British rivers -as well as the atmosphere also play an important role. In the region with lowest simulated O 2 concentrations (around 56 • N, 6.5 • E), riverine N on average contributes 39% to overall near-bottom O 2 consumption during seasonal stratification. Here, the German and the large Dutch rivers constitute the highest riverine contributions (11% and 10%, respectively). At a site in the Oyster Grounds (around 54.5 • N, 4 • E), the average riverine contribution adds up to 41%, even exceeding that of the North Atlantic. Here, highest riverine contributions can be attributed to the Dutch and British rivers adding up to almost 28% on average. The atmospheric contribution results in 13%. Our results emphasize the importance of anthropogenic N inputs and seasonal stratification for the O 2 conditions in the southern North Sea. They further suggest that reductions in the riverine and atmospheric N inputs may have a relevant positive effect on the O 2 levels in this region.

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Section: Limitations Of the Model Intrinsics And The Tbnt Methodsmentioning

confidence: 78%

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

et al. 2017

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“…So far, the impact of pore water advection on biogeochemistry and pore water constituent effluxes from permeable sediments has mostly been studied in microtidal sheltered beaches (Beck et al, ; Gonneea & Charette, ; Liu et al, ; O'Connor et al, ; Santos et al, ), tidal flat areas (Beck et al, ; Billerbeck et al, ; Gao et al, ; Huettel & Rusch, ; Marchant et al, ; Riedel et al, ), or subtidal sediments (Ahmerkamp et al, ; Marchant et al, ; Shum & Sundby, ), which are exposed to a lower wave energy level than high energy beaches. In contrast, only few studies have been conducted at wave exposed mesotidal to macrotidal sites like the French Aquitanian coast (Anschutz et al, ; Charbonnier et al, ; Charbonnier et al, ) or the beaches of Spiekeroog Island, Germany (Beck et al, ; Reckhardt et al, ; Seidel et al, ; Waska et al, ).…”

Section: Introductionmentioning

confidence: 99%

Seasonality of Organic Matter Degradation Regulates Nutrient and Metal Net Fluxes in a High Energy Sandy Beach

et al. 2020

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During seawater circulation in permeable intertidal sands, organic matter degradation alters the composition of percolating fluids and remineralization products discharge into surficial waters. Concurrently, coastal seawater nutrient and organic matter composition change seasonally due to variations in pelagic productivity. To assess seasonal changes in organic matter degradation in the intertidal zone of a high energy beach (Spiekeroog Island, southern North Sea, Germany), we analyzed shallow pore waters for major redox constituents (oxygen [O2], manganese [Mn], and iron [Fe]) and inorganic nitrogen species (nitrite [NO2−], nitrate [NO3−], and ammonium [NH4+]) in March, August, and October. Surface water samples from a local time series station were used to monitor seasonal changes in pelagic productivity. O2 and NO3− were the dominating pore water constituents in March and October. Dissolved Mn, Fe, and NH4+ were more widely distributed in August. Seasonal changes in seawater temperature as well as organic matter and nitrate supply by seawater were assumed to affect microbial rates and degradation pathways. Pore water and seawater variability led to seasonally changing constituent effluxes to surface waters. Mn, Fe, and NH4+ effluxes are minimal in March and reached their maximum in August. Furthermore, the intertidal sands switched from a net dissolved inorganic nitrogen sink in March to a net source in August. In conclusion, seasonal effects on intertidal pore water biogeochemistry affect constituent fluxes across the sediment‐water interface. The seasonality of the beach bioreactor must be considered when fluxes are extrapolated to annual timescales.

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“…Another factor complicating our understanding of denitrification is the kinetics of this process relative to total sediment respiration. It has previously been shown that denitrification rates in permeable sediments are very low compared to total respiration (Bourke et al, 2017;Evrard et al, 2013) and that this pattern is consistent globally (Marchant et al, 2016) in silicate sands. There have, however, been no analogous studies on potential denitrification rates relative to respiration rates in anoxic flow-through reactors in carbonate sediments.…”

Section: Introductionmentioning

confidence: 54%

“…The availability, and composition, of organic matter is expected to be a key factor controlling potential denitrification rates (Eyre et al, 2013a;Seitzinger, 1988), and the importance of this in permeable sediments has also been recently underscored by Marchant et al (2016), who observed a strong relationship between potential denitrification rate and sediment oxygen consumption. If the results of the previous studies are plotted vs. sediment oxygen consumption rate, a significant relationship is observed with an r 2 of 0.92 (Fig.…”

Section: Comparison Of Potential Denitrification Rates With Previous mentioning

confidence: 99%

“…Nitrate may be supplied to the denitrification zone from either the water column or nitrification within the sediment. It has been reported that nitrification within the sediment may be a significant source of nitrate to fuel denitrification (Marchant et al, 2016;Rao et al, 2007), although modelling studies suggest that, even in the presence of nitrification, flow fields in permeable sediments may lead to little coupling between nitrification and denitrification (Kessler et al, 2013). In systems with high bottom-water nitrate concentrations, high rates of denitrification have been reported (Gao et al, 2012;Sokoll et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Does denitrification occur within porous carbonate sand grains?

2017

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Abstract. Permeable carbonate sands form a major habitat type on coral reefs and play a major role in organic matter recycling. Nitrogen cycling within these sediments is likely to play a major role in coral reef productivity, yet it remains poorly studied. Here, we used flow-through reactors and stirred reactors to quantify potential rates of denitrification and the dependence of denitrification on oxygen concentrations in permeable carbonate sands at three sites on Heron Island, Australia. Our results showed that potential rates of denitrification fell within the range of 2-28 µmol L −1 sediment h −1 and were very low compared to oxygen consumption rates, consistent with previous studies of silicate sands. Denitrification was observed to commence at porewater oxygen concentrations as high as 50 µM in stirred reactor experiments on the coarse sediment fraction (2-10 mm) and at oxygen concentrations of 10-20 µM in flow-through and stirred reactor experiments at a site with a median sediment grain size of 0.9 mm. No denitrification was detected in sediments under oxic conditions from another site with finer sediment (median grain size: 0.7 mm). We interpret these results as confirmation that denitrification may occur within anoxic microniches present within porous carbonate sand grains. The occurrence of such microniches has the potential to enhance denitrification rates within carbonate sediments; however further work is required to elucidate the extent and ecological significance of this effect.

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Coupled nitrification–denitrification leads to extensive N loss in subtidal permeable sediments

Cited by 101 publications

References 78 publications

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

A Novel Modeling Approach to Quantify the Influence of Nitrogen Inputs on the Oxygen Dynamics of the North Sea

Seasonality of Organic Matter Degradation Regulates Nutrient and Metal Net Fluxes in a High Energy Sandy Beach

Does denitrification occur within porous carbonate sand grains?

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