Partitioning between benthic and pelagic nitrate reduction in the Lake Lugano south basin

Wenk, Christine B.; Zopfi, Jakob; Gardner, Wayne S.; McCarthy, Mark J.; Niemann, Helge; Veronesi, Mauro; Lehmann, Moritz F.

doi:10.4319/lo.2014.59.4.1421

Cited by 32 publications

(41 citation statements)

References 52 publications

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“…The columns in the box chart represent the log number of the hzsB gene copy (copies g −1 dry soil). For all boxplots, black center lines represent the median and box edges are the first and third quartiles comparable to that reported in rivers (Zhao et al 2013), lakes (Schubert et al 2006;Wenk et al 2014), paddy soils (Zhu et al 2011;Yang et al 2015), and other estuaries (RisgaardPetersen et al 2004;Rysgaard et al 2004;Engström et al 2005), but lower than that generally detected in marine ecosystems (Tamdrup and Dalsgaard 2002;Brabandere et al 2014). Based on our results, N loss attributed to anammox was estimated to reach an average value of 9.70 × 10 5 t N per year on the basis of sediment weight, study area, and anammox average rate obtained from slurry incubations.…”

Section: Discussionmentioning

confidence: 89%

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

Yang

Weng

et al. 2017

J Soils Sediments

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Purpose Despite its importance, anammox (anaerobic ammonium oxidation) in estuarine sediment systems remains poorly understood, particularly at the continental scale. This study aimed to understand the abundance, diversity, and activity of anammox bacteria and to determine the main factors influencing the anammox process in estuarine sediments in China. Materials and methods Estuarine sediments were collected from 18 estuaries spanning over 4000 km. Experiments using an 15 N-tracer, quantitative PCR, and clone library construction were used to determine the activity, abundance, and diversity of anammox bacteria. The impact of environmental factors on anammox processes was also determined.Results and discussion The abundance of the anammoxspecific hydrazine synthase (hzsB) gene ranged from 1.8 × 10 5 ± 3.4 × 10 4 to 3.6 × 10 8 ± 7.5 × 10 7 copies g −1 dw. Candidatus Scalindua, Brocadia, Kuenenia, Jettenia, and two novel unidentified clusters were detected, with Scalindua dominating the anammox population. Additionally, the abundances of Scalindua, Kuenenia, and Brocadia were found to be significantly correlated with latitude. The anammox rates ranged from 0.29 ± 0.15 to 13.68 ± 3.98 nmol N g −1 dw h −1 and contributed to 2.39-82.61% of total N 2 production. Pearson correlation analysis revealed that the anammox rate was positively correlated with total nitrogen, total carbon, and temperature, and was negatively correlated with dissolved oxygen (DO). The key factors influencing the hzsB gene abundance were ammonium concentration, salinity, and DO. Ammonium concentration, pH, temperature, and latitude were main variables shaping the anammox-associated bacterial community. Conclusions Our results suggested that anammox bacteria are ubiquitous in coastal estuaries in China and underline the importance of anammox resulting in N loss at a continental scale.

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Section: Discussionmentioning

confidence: 89%

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

Yang

Weng

et al. 2017

J Soils Sediments

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“…Here we have restricted our discussion to the top 50 m of the water column. See Wenk et al (2014) and Wenk et al (2016) for details about N cycle dynamics in the redox transition zone.…”

Section: Resultsmentioning

confidence: 99%

Acidification Enhances Hybrid N2O Production Associated with Aquatic Ammonia-Oxidizing Microorganisms

et al. 2017

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Ammonia-oxidizing microorganisms are an important source of the greenhouse gas nitrous oxide (N2O) in aquatic environments. Identifying the impact of pH on N2O production by ammonia oxidizers is key to understanding how aquatic greenhouse gas fluxes will respond to naturally occurring pH changes, as well as acidification driven by anthropogenic CO2. We assessed N2O production rates and formation mechanisms by communities of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in a lake and a marine environment, using incubation-based nitrogen (N) stable isotope tracer methods with 15N-labeled ammonium (15NH4+) and nitrite (15NO2−), and also measurements of the natural abundance N and O isotopic composition of dissolved N2O. N2O production during incubations of water from the shallow hypolimnion of Lake Lugano (Switzerland) was significantly higher when the pH was reduced from 7.54 (untreated pH) to 7.20 (reduced pH), while ammonia oxidation rates were similar between treatments. In all incubations, added NH4+ was the source of most of the N incorporated into N2O, suggesting that the main N2O production pathway involved hydroxylamine (NH2OH) and/or NO2− produced by ammonia oxidation during the incubation period. A small but significant amount of N derived from exogenous/added 15NO2− was also incorporated into N2O, but only during the reduced-pH incubations. Mass spectra of this N2O revealed that NH4+ and 15NO2− each contributed N equally to N2O by a “hybrid-N2O” mechanism consistent with a reaction between NH2OH and NO2−, or compounds derived from these two molecules. Nitrifier denitrification was not an important source of N2O. Isotopomeric N2O analyses in Lake Lugano were consistent with incubation results, as 15N enrichment of the internal N vs. external N atoms produced site preferences (25.0–34.4‰) consistent with NH2OH-dependent hybrid-N2O production. Hybrid-N2O formation was also observed during incubations of seawater from coastal Namibia with 15NH4+ and NO2−. However, the site preference of dissolved N2O here was low (4.9‰), indicating that another mechanism, not captured during the incubations, was important. Multiplex sequencing of 16S rRNA revealed distinct ammonia oxidizer communities: AOB dominated numerically in Lake Lugano, and AOA dominated in the seawater. Potential for hybrid N2O formation exists among both communities, and at least in AOB-dominated environments, acidification may accelerate this mechanism.

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“…Denitrification rates determined in a parallel study were relatively high under the truly anoxic conditions observed in October 2010 (28.2 ± 23.7 µmol N h −1 m −2 ; Wenk et al, 2013b), once redox gradients and, presumably, the microbial community had stabilized. At that time and also under anoxic conditions in August 2010, up to 15 % of total NO − 3 that was reduced was released as N 2 O without being completely reduced to N 2 .…”

Section: Water Column Characteristicsmentioning

confidence: 85%

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

et al. 2013

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Abstract. Nitrous oxide (N 2 O) is a potent greenhouse gas, generated through microbial nitrogen (N) turnover processes, such as nitrification, nitrifier denitrification, and denitrification. Previous studies quantifying natural sources have mainly focused on soils and the ocean, but the potential role of terrestrial water bodies in the global N 2 O budget has been widely neglected. Furthermore, the biogeochemical controls on the production rates and the microbial pathways that produce benthic N 2 O in lakes are essentially unknown. In this study, benthic N 2 O fluxes and the contributions of the microbial pathways that produce N 2 O were assessed using 15 N label flow-through sediment incubations in the eutrophic, monomictic south basin of Lake Lugano in Switzerland. The sediments were a significant source of N 2 O throughout the year, with production rates ranging between 140 and 2605 nmol N 2 O h −1 m −2 , and the highest observed rates coinciding with periods of water column stratification and stably anoxic conditions in the overlying bottom water. Nitrate (NO − 3 ) reduction via denitrification was found to be the major N 2 O production pathway in the sediments under both oxygen-depleted and oxygen-replete conditions in the overlying water, while ammonium oxidation did not contribute significantly to the benthic N 2 O flux. A marked portion (up to 15 %) of the total NO − 3 consumed by denitrification was reduced only to N 2 O, without complete denitrification to N 2 . These fluxes were highest when the bottom water had stabilized to a low-oxygen state, in contrast with the notion that stable anoxia is particularly conducive to complete denitrification without accumulation of N 2 O. This study provides evidence that lake sediments are a significant source of N 2 O to the overlying water and may produce large N 2 O fluxes to the atmosphere during seasonal mixing events.

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Partitioning between benthic and pelagic nitrate reduction in the Lake Lugano south basin

Cited by 32 publications

References 52 publications

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

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

Acidification Enhances Hybrid N2O Production Associated with Aquatic Ammonia-Oxidizing Microorganisms

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

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Partitioning between benthic and pelagic nitrate reduction in the Lake Lugano south basin

Cited by 32 publications

References 52 publications

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

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

Acidification Enhances Hybrid N2O Production Associated with Aquatic Ammonia-Oxidizing Microorganisms

Year-round N&lt;sub&gt;2&lt;/sub&gt;O production by benthic NO&lt;sub&gt;x&lt;/sub&gt; reduction in a monomictic south-alpine lake

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Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake