Ammonium cycling under a strong oxygen gradient associated with the Oxygen Minimum Zone off northern Chile (~23°S)

Molina, Verónica; Farı́as, Laura; Eissler, Yoanna; Cuevas, L. Antonio; Morales, Carmen E.; Escribano, Rubén

doi:10.3354/meps288035

Cited by 43 publications

(31 citation statements)

References 33 publications

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“…The different ammonium sensitivities observed in Golfo Dulce and at the open-ocean sites could be related to the difference in added ammonium concentrations but may also reflect real differences in the kinetics of ammonium utilization of the anammox communities. Highly efficient ammonium consumption by the prokaryotic community in general has previously been demonstrated with samples from the upper boundary of the oxygen-deficient zone off Chile (Molina et al 2005). Our results call for further studies of the functional response of the natural anammox communities to substrate concentrations.…”

Section: Discussionsupporting

confidence: 71%

Anaerobic ammonium oxidation in the oxygen-deficient waters off northern Chile

Dalsgaard²,

et al. 2006

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We investigated the pathways of N 2 production in the oxygen-deficient water column of the eastern tropical South Pacific off Iquique, Chile, at 20uS, through short anoxic incubations with 15 N-labelled nitrogen compounds. The location was characterized by steep chemical gradients, with oxygen decreasing to below detection at ,50-m depth, while nitrite reached 6 mmol L 21 and ammonium was less than 50 nmol L 21 . Ammonium was oxidized to N 2 with no lag phase during the incubations, and when only NH þ 4 was 15 N-labeled, 15 N appeared in the form of 14 N 15 N, whereas 15 N 15 N was not detected. Likewise, nitrite was reduced to N 2 at rates similar to the rates of ammonium oxidation, and when only NO 2 2 was 15 N-labeled, 15 N appeared mainly as 14 N 15 N, whereas 15 N 15 N appeared in only one incubation. These observations indicate that ammonium was oxidized and nitrite was reduced through the anammox reaction, whereas denitrification was generally not detected and, therefore, was a minor sink for nitrite. Anammox rates were highest, up to 0.7 nmol N 2 L 21 h 21 , just below the oxycline, whereas rates were undetectable, ,0.2 nmol N 2 L 21 h 21 , deeper in the oxygen-deficient zone. Instead of complete denitrification to N 2 , oxidation of organic matter during the incubations may have been coupled to reduction of nitrate to nitrite. This process was evident from strong increases in nitrite concentrations toward the end of the incubations. The results point to anammox as an active process in the major open-ocean oxygen-deficient zones, which are generally recognized as important sites of denitrification. Still, denitrification remains the simplest explanation for most of the nitrogen deficiency in these zones.

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Section: Discussionsupporting

confidence: 71%

Anaerobic ammonium oxidation in the oxygen-deficient waters off northern Chile

Dalsgaard²,

et al. 2006

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“…The higher richness of T-RFs and diversity of communities in the ULOMZ than in the core suggest that there is a community shift based on the separation between them, which could be related to the strong physicochemical gradients observed among both layers, and also because the ULOMZ is a zone where the gases (O 2 , N 2 O) and nutrients (nitrite, ammonium) vary constantly by a strong microbial cycling of N and C (Molina et al 2005, Cuevas & Morales 2006, Molina & Farías 2009 and where particulate material is trapped on a strong halocline (pycnocline) creating suboxic microsites within the oxygenated water column to sustain the denitrification process (Pantoja et al 2004). In fact, this phenomenon has been supported recently in the ESPO by Ganesh et al (2013) whose using a metagenomic approach, recorded nosZ genes between 70-1000 m depth off Chilean OMZ, with the peculiarity that their abundance was related directly with particleassociated niches.…”

Section: Discussionmentioning

confidence: 99%

Structure of denitrifying communities reducing N2O at suboxic waters off northern Chile and Perú

Castro-González

Ulloa

2015

Rev. biol. mar. oceanogr.

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Resumen.-El gen nosZ, el cual codifica para la reducción de N 2 O a N 2 , fue usado para estudiar la estructura de las comunidades desnitrificantes en la zona de mínimo oxígeno frente a las costas de Chile y Perú, a través del polimorfismo de los fragmentos largos de restricción terminal (PFLRT) y clonamiento de los genes nosZ. El análisis del PFLRT mostró poca diversidad de genes nosZ en las profundidades subóxicas (núcleo de la zona de mínimo oxígeno-ZMO) comparado con las profundidades donde el O 2 varío ampliamente (límite superior de la zona de mínimo oxígeno o LSZMO). Las comunidades desnitrificantesnosZ presentaron diferencias en su estructura entre localidades geográficas y tiempo de muestreo sugiriendo asociación con la variación en las condiciones ambientales. El análisis de correspondencia canónica indicó que los parámetros ambientales seleccionados como variables predictoras (N 2 O, O 2 , NH 4 + y NO 2 -) explicaron bien las diferencias en la composición de la comunidad nosZ entre sitios de muestreo. El análisis filogenético mostró poca diversidad de secuencias nosZ y agrupó el 81% de los clones cerca al clúster de secuencias de sedimentos del Pacífico. Las secuencias no se relacionaron con ninguna secuencia nosZ reportada en agua de mar, o de bacterias desnitrificantes conocidas, demostrando la novedad de los filotipos encontrados en esta área. Palabras clave: Pacífico sur este, gen nosZ, zona de mínimo oxígenoAbstract.-The nosZ gene, which encodes for N 2 O reduction to N 2 , was used to study the structure of denitrifying communities in the oxygen minimum zone off Chilean and Peruvian coast throughout terminal restriction fragment length polymorphism (TRFLP) and cloning of nosZ genes. TRFLP analysis showed little diversity of nosZ genes at suboxic depths (Oxygen Minimum Zone´s core) compared with depths where O 2 largely varied (upper limit of OMZ or ULOMZ). The nosZ-denitrifying communities showed differences in its structure between geographical locations and time sampling suggesting an association with the shift in the environmental conditions. The canonical correspondence analysis showed that the environmental parameters selected as predictor variables (N 2 O, O 2 , NH 4 + and NO 2 -) explained well the differences in nosZ-denitrifying community composition among sampling sites. The phylogenetic analysis showed little nosZ sequence diversity and grouped 81% of nosZ-clones near the cluster of sediments sequences from Pacific. Our sequences did not branch with any known denitrifying bacteria or seawater nosZ-sequences available, demonstrating the novelty of phylotypes founded in this area.

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“…In fact, Pantoja et al (2003) found that more than 80% of the fresh organic matter produced at the surface can be respired in the upper part of the oxycline. This process is coupled to nitrification (Molina et al 2005) and is also responsible for N 2 O production at the upper oxycline. Denitrification and its role as an important process involved in both N 2 O production and consumption processes are discussed here, using an experimental approach and following the natural isotopic-isotopomeric signatures of dissolved N 2 O.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, the fact that the observed N 2 O minimum coincides with SP, NO { 2 , and d 15 N bulk maxima supports the conclusion that denitrification is the main process reducing N 2 O to N 2 in the OMZ and is progressively important as O 2 decreases below the center of the oxycline. Data from the same study area (21uS) reported herein (see above) and in Molina et al (2005) and Farías et al (2007) N 2 O mass balance in the upper oxycline of the ETSPFinally, a mass balance was estimated in order to assess the relative contributions of other production or consumption processes beside denitrification as N 2 O sources or sinks in the subsurface N 2 O maximum. Figure 6 shows vertical distributions of oxygen N 2 O, saturated equilibrium N 2 O concentration, net N 2 O production, and the N 2 O peak limits that were used to estimate the balances.…”

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confidence: 99%

Denitrification and nitrous oxide cycling within the upper oxycline of the eastern tropical South Pacific oxygen minimum zone

et al. 2009

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One of the shallowest, most intense oxygen minimum zones (OMZs) is found in the eastern tropical South Pacific, off northern Chile and southern Peru. It has a strong oxygen gradient (upper oxycline) and high N 2 O accumulation. N 2 O cycling by heterotrophic denitrification along the upper oxycline was studied by measuring N 2 O production and consumption rates using an improved acetylene blockage method.

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Ammonium cycling under a strong oxygen gradient associated with the Oxygen Minimum Zone off northern Chile (~23°S)

Cited by 43 publications

References 33 publications

Anaerobic ammonium oxidation in the oxygen-deficient waters off northern Chile

Anaerobic ammonium oxidation in the oxygen-deficient waters off northern Chile

Structure of denitrifying communities reducing N2O at suboxic waters off northern Chile and Perú

Denitrification and nitrous oxide cycling within the upper oxycline of the eastern tropical South Pacific oxygen minimum zone

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