N2O cycling at the core of the oxygen minimum zone off northern Chile

Castro-González, Maribeb; Farı́as, Laura

doi:10.3354/meps280001

Cited by 48 publications

(39 citation statements)

References 29 publications

(51 reference statements)

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“…denitrification vs. anammox (Kuypers et al, 2005;Ward et al, 2009), but the origin and cycling of N 2 O in these areas has been ignored. In particular, no explanation has been provided for the high N 2 O consumption, which occurs only by denitrification under very low O 2 conditions (Castro-González and Farías, 2004;Farías et al, 2007). This was recently shown by isotopes signal profiles from NO − 2 and NO − 3 , which are consistent with denitrification (Ryabenko et al, 2012).…”

Section: Introductionsupporting

confidence: 50%

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

Cornejo¹

2012

Biogeosciences

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Section: Introductionsupporting

confidence: 50%

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

Cornejo¹

2012

Biogeosciences

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“…Our observations support the results of Castro-González and Farías (2004), who used N 2 O production experiments in the ETSP to show that denitrifiers produce increasing N 2 O : N 2 ratios as the O 2 concentrations increase due to the well-known sensitivity of the N 2 O reductase to O 2 . In order to roughly estimate the N 2 O : N 2 ratios in the upper oxycline of eddy A, we used the observed N 2 O concentrations and N * as an indicator of N loss.…”

Section: )supporting

confidence: 81%

Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific

et al. 2016

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Abstract. Recent observations in the eastern tropical South Pacific (ETSP) have shown the key role of meso-and submesoscale processes (e.g. eddies) in shaping its hydrographic and biogeochemical properties. Off Peru, elevated primary production from coastal upwelling in combination with sluggish ventilation of subsurface waters fuels a prominent oxygen minimum zone (OMZ). Given that nitrous oxide (N 2 O) production-consumption processes in the water column are sensitive to oxygen (O 2 ) concentrations, the ETSP is a region of particular interest to investigate its source-sink dynamics. To date, no detailed surveys linking mesoscale processes and N 2 O distributions as well as their relevance to nitrogen (N) cycling are available. In this study, we present the first measurements of N 2 O across three mesoscale eddies (two mode water or anticyclonic and one cyclonic) which were identified, tracked, and sampled during two surveys carried out in the ETSP in November-December 2012. A two-peak structure was observed for N 2 O, wherein the two maxima coincide with the upper and lower boundaries of the OMZ, indicating active nitrification and partial denitrification. This was further supported by the abundances of the key gene for nitrification, ammonium monooxygenase (amoA), and the gene marker for N 2 O production during denitrification, nitrite reductase (nirS). Conversely, we found strong N 2 O depletion in the core of the OMZ (O 2 < 5 µmol L −1 ) to be consistent with nitrite (NO − 2 ) accumulation and low levels of nitrate (NO − 3 ), thus suggesting active denitrification. N 2 O depletion within the OMZ's core was substantially higher in the centre of mode water eddies, supporting the view that eddy activity enhances N-loss processes off Peru, in particular near the shelf break where nutrient-rich, productive waters from upwelling are trapped before being transported offshore. Analysis of eddies during their propagation towards the open ocean showed that, in general, "ageing" of mesoscale eddies tends to decrease N 2 O concentrations through the water column in response to the reduced supply of material to fuel N loss, although hydrographic variability might also significantly impact the pace of the production-consumption pathways for N 2 O. Our results evidence the relevance of mode water eddies for N 2 O distribution, thereby improving our understanding of the N-cycling processes, which are of crucial importance in times of climate change and ocean deoxygenation.

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“…Some of the discrepancies between previously published laboratory and geochemical estimates of N 2 O consumption may be due to local fluctuations in consumption rates; one laboratory study found that changes in O 2 concentrations and flux of organic matter could change N 2 O consumption rates by up to one order of magnitude (Castro-González and Farías, 2004). As discussed, geochemical estimates may also suffer from uncertainties in water mass residence time and N 2 O loss or perturbations induced by local eddies.…”

Section: N 2 O Consumption Ratesmentioning

confidence: 68%

“…An exponential vs. linear parameterisation can make a large difference in a model of marine N 2 O production. N 2 O consumption rates are even less certain than N 2 O production rates; laboratory and in situ data differ by more than three orders of magnitude (e.g., Castro-González and Farías, 2004;Codispoti and Christensen, 1985). It is also not clear whether there is a single O 2 value that is representative of the point Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

“…The PCUC calculated N 2 O consumption rate of 0.01-1 mmol N 2 O m −3 yr −1 is on the low-end of laboratory N 2 O consumption rate measurements in ETP samples, which average from 1-1172 mmol m −3 yr −1 (Castro- González and Farías 2004;Farías et al, 2009). In contrast, the PCUC consumption rates are on the high-end of most geochemical estimates of net N 2 O consumption rates, which range from 0.0005-0.012 mmol N 2 O m −3 yr −1 (Yamagishi et al, 2007) to 0.068 mmol N 2 O m −3 yr −1 (Codispoti and Christensen, 1985).…”

Section: N 2 O Consumption Ratesmentioning

confidence: 99%

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Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database

et al. 2012

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Abstract. The eastern tropical Pacific (ETP) is believed to be one of the largest marine sources of the greenhouse gas nitrous oxide (N 2 O). Future N 2 O emissions from the ETP are highly uncertain because oxygen minimum zones are expected to expand, affecting both regional production and consumption of N 2 O. Here we assess three primary uncertainties in how N 2 O may respond to changing O 2 levels: (1) the relationship between N 2 O production and O 2 (is it linear or exponential at low O 2 concentrations?), (2) the cutoff point at which net N 2 O production switches to net N 2 O consumption (uncertainties in this parameterisation can lead to differences in model ETP N 2 O concentrations of more than 20 %), and (3) the rate of net N 2 O consumption at low O 2 . Based on the MEMENTO database, which is the largest N 2 O dataset currently available, we find that N 2 O production in the ETP increases linearly rather than exponentially with decreasing O 2 . Additionally, net N 2 O consumption switches to net N 2 O production at ∼ 10 µM O 2 , a value in line with recent studies that suggest consumption occurs on a larger scale than previously thought. N 2 O consumption is on the order of 0.01-1 mmol N 2 O m −3 yr −1 in the Peru-Chile Undercurrent. Based on these findings, it appears that recent studies substantially overestimated N 2 O production in the ETP. In light of expected deoxygenation and the higher than previously expected point at which net N 2 O production switches to consumption, there is enough uncertainty in future N 2 O production that even the sign of future changes is still unclear.

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N2O cycling at the core of the oxygen minimum zone off northern Chile

Cited by 48 publications

References 29 publications

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific

Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database

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N2O cycling at the core of the oxygen minimum zone off northern Chile

Cited by 48 publications

References 29 publications

Following the N&lt;sub&gt;2&lt;/sub&gt;O consumption in the oxygen minimum zone of the eastern South Pacific

Following the N&lt;sub&gt;2&lt;/sub&gt;O consumption in the oxygen minimum zone of the eastern South Pacific

Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific

Nitrous oxide dynamics in low oxygen regions of the Pacific: insights from the MEMENTO database

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Product

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Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific

Following the N<sub>2</sub>O consumption in the oxygen minimum zone of the eastern South Pacific