Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone

Kalvelage, Tim; Lavik, Gaute; Lam, Phyllis; Contreras, Sergio; Arteaga, Lionel; Löscher, Carolin R.; Oschlies, Andreas; Paulmier, Aurélien; Stramma, Lothar; Kuypers, Marcel M. M.

doi:10.1038/ngeo1739

Cited by 314 publications

(465 citation statements)

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“…Ammonia oxidation was detected only at 100 m or shallower, with maximum rates at 85 m (0.92 nM N d − 1 ), the shallowest and most oxygenated of the depths where rates were measured (Figure 1e). These rates are at the lower end of those previously observed in the Gulf of California and ETNP (0-348 nM d − 1 ; Beman et al, 2012) and in the ETSP OMZ (0.2-89 nM d − 1 ; Kalvelage et al, 2013). Nitrite oxidation was detected at all depths except 125 m, at rates (13-261 nM d − 1 ; Figure 1e) up to an order of magnitude higher than those for other processes, with rates peaking in the secondary chlorophyll maximum, suggesting a decoupling between ammonia and nitrite oxidation.…”

Section: Size-fractionated Gene Transcription and N Cycling S Ganesh mentioning

confidence: 77%

“…Surveys combining marker gene counts and rate measurements have suggested mesoscale patterns in N cycling along coastal to offshore gradients in the Eastern Tropical South Pacific (ETSP) OMZ off Chile and Peru (Kalvelage et al, 2013), as well as clear depthspecific variation in N cycle genes, transcripts, and rates (Thamdrup et al, 2006;Dalsgaard et al, 2012;Stewart et al, 2012). Recently, analysis of microbial metagenomes in the ETSP OMZ also identified a non-uniform distribution of N cycle genes among filter size fractions (Ganesh et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…These include the reductive processes of denitrification and anaerobic ammonia oxidation with nitrite (anammox), whose combined activity in OMZs contribute up to half of oceanic N loss as N 2 or N 2 O gas (Codispoti et al, 2001;Gruber, 2004). Research in the eastern Pacific OMZs, notably in the anoxic OMZ off Chile and Peru, indicates that anammox and denitrification are linked to varying degrees with a diverse set of other microbial N transformations, including the production of nitrite and nitrate via nitrification along the oxycline and dissimilatory nitrate reduction to ammonium within the OMZ (Lam et al, 2009;Kalvelage et al, 2013). OMZ N cycle processes also mediate key steps in other elemental cycles, for example, the fixation of carbon by anammox and nitrifying autotrophs, the remineralization of organic carbon and nutrients by denitrifying heterotrophs, and the oxidation of reduced sulfur compounds by chemoautotrophic denitrifiers .…”

Section: Introductionmentioning

confidence: 99%

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Size-fraction partitioning of community gene transcription and nitrogen metabolism in a marine oxygen minimum zone

et al. 2015

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The genetic composition of marine microbial communities varies at the microscale between particleassociated (PA; 41.6 μm) and free-living (FL; 0.2-1.6 μm) niches. It remains unclear, however, how metabolic activities differ between PA and FL fractions. We combined rate measurements with metatranscriptomics to quantify PA and FL microbial activity in the oxygen minimum zone (OMZ) of the Eastern Tropical North Pacific, focusing on dissimilatory processes of the nitrogen (N) cycle. Bacterial gene counts were 8-to 15-fold higher in the FL compared with the PA fraction. However, rates of all measured N cycle processes, excluding ammonia oxidation, declined significantly following particle (41.6 μm) removal. Without particles, rates of nitrate reduction to nitrite (1.5-9.4 nM N d − 1 ) fell to zero and N 2 production by denitrification (0.5-1.7 nM N d − 1 ) and anammox (0.3-1.9 nM N d − 1 ) declined by 53-85%. The proportional representation of major microbial taxa and N cycle gene transcripts in metatranscriptomes followed fraction-specific trends. Transcripts encoding nitrate reductase were uniform among PA and FL fractions, whereas anammox-associated transcripts were proportionately enriched up to 15-fold in the FL fraction. In contrast, transcripts encoding enzymes for N 2 O and N 2 production by denitrification were enriched up to 28-fold in PA samples. These patterns suggest that the majority of N cycle activity, excluding N 2 O and N 2 production by denitrification, is confined to a FL majority that is critically dependent on access to particles, likely as a source of organic carbon and inorganic N. Variable particle distributions may drive heterogeneity in N cycle activity and gene expression in OMZs.

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Section: Size-fractionated Gene Transcription and N Cycling S Ganesh mentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Size-fraction partitioning of community gene transcription and nitrogen metabolism in a marine oxygen minimum zone

et al. 2015

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“…Almost all of the N loss from the water column in the Eastern Tropical South Pacific occurs by anammox rather than heterotrophic denitrification (Hamersley et al, 2007;Kalvelage et al, 2013). Mass balance calculations suggest that around 40% of the N loss takes place within the coastal OMZ where water depths are <600 m .…”

Section: Challenges Of Predicting Dnramentioning

confidence: 99%

Strong and Dynamic Benthic-Pelagic Coupling and Feedbacks in a Coastal Upwelling System (Peruvian Shelf)

2017

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Monthly time-series data (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)) of bottom water oxygen, nitrate and nitrite concentrations from the outer shelf (150 m water depth) in the oxygen minimum zone offshore Peru were coupled to a layered biogeochemical sediment model to investigate benthic-pelagic coupling over multi-annual time scales. The model includes the mineralization of four reactive pools of particulate organic carbon (POC) with lifetimes of 0.13, 1.3, 20, and 1700 year that were constrained using empirical data. Total POC rain rates to the seafloor were derived from satellite based estimates of primary production. Solute fluxes and concentrations in sediment porewater showed highly dynamic behavior over the course of a typical year. Conversion of fixed N to N 2 by denitrification varied from 1.1 mmol m −2 d −1 of N in winter to 1.8 mmol m −2 d −1 of N in summer with a long term mean N loss for the shelf of 1.5 mmol m −2 d −1 of N. Fixed N loss across the whole time-series agreed very well with a previously-published vertically-integrated sediment model for coupling the benthic and pelagic N cycle in regional and global models. Dissimilatory nitrate reduction to ammonium (DNRA) emerges as a major process in the benthic N cycle, producing on average 1.9 mmol m −2 d −1 of ammonium: more than twice the rate of ammonification of organic nitrogen. The model predicts sulfide emissions from the sediment of up to 1 mmol m −2 d −1 when POC rain rate exceeds 20 mmol m −2 d −1 , in agreement with past observations of benthic sulfide fluxes and sulfide plume distributions in the water column. This study demonstrates that sediments on the Peruvian shelf are not static repositories that are independent of changes taking place in the water column. Our results strongly suggest the shelf sediments must exert an important feedback on biogeochemical processes in the overlying waters, and should be considered in regional model studies.

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“…AOB have been suggested to be sensitive to various soil perturbations (Bissett et al, 2013), while AOA seems to be insusceptible to environmental changes due to strongly rigid cell membranes and other cellular macromolecules (Cray et al, 2013). For example, previous studies have indicated the positive effects of organic matter on function and community of ammonia-oxidizers attributing that organic matter provides more available ammonium during degradation (He et al, 2007;Kalvelage et al, 2013). In addition, it has been reported that Hg pollution influenced on AOB activity and community composition based on a short-term microcosm experiment (Liu et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Influence of rice straw amendment on mercury methylation and nitrification in paddy soils

Liu

Dong

Han

et al. 2016

Environmental Pollution

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Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone

Cited by 314 publications

References 50 publications

Size-fraction partitioning of community gene transcription and nitrogen metabolism in a marine oxygen minimum zone

Size-fraction partitioning of community gene transcription and nitrogen metabolism in a marine oxygen minimum zone

Strong and Dynamic Benthic-Pelagic Coupling and Feedbacks in a Coastal Upwelling System (Peruvian Shelf)

Influence of rice straw amendment on mercury methylation and nitrification in paddy soils

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