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

2012 ◽  
Vol 9 (8) ◽  
pp. 3205-3212 ◽  
Author(s):  
M. Cornejo ◽  
L. Farías
Keyword(s):  
Primary Productivity ◽  
High Reliability ◽  
South Pacific ◽  
Global Ocean ◽  
Field Observations ◽  
N2o Production ◽  
Oxygen Minimum Zones ◽  
Minimum Zone ◽  
Existing Data ◽  
Oxygen Minimum

Abstract. Oxygen minimum zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N2O sources in the global ocean relative to their volume. N2O production is related to low O2 concentrations and high primary productivity. However, when O2 is sufficiently low, canonical denitrification takes place and N2O consumption can be expected. N2O distribution in the ESP was analyzed over a wide latitudinal and longitudinal range (from 5° to 30° S and from 71–76° to ~ 84° W) based on ~ 890 N2O measurements. Intense N2O consumption, driving undersaturations as low as 40%, was always associated with secondary NO2– accumulation (SNM), a good indicator of suboxic/anoxic O2 levels. First, we explore relationships between ΔN2O and O2 based on existing data of denitrifying bacteria cultures and field observations. Given the uncertainties in the O2 measurements, a second relationship between ΔN2O and NO2– (> 0.75 μM) was established for suboxic waters (O2 < 8 μM). We reproduced the apparent N2O production (ΔN2O) along the OMZ in ESP with high reliability (r2 = 0.73 p = 0.01). Our results will contribute to the quantification of the N2O that is recycled in O2 deficient waters, and improve the prediction of N2O behavior under future scenarios of OMZ expansion and intensification.

scholarly journals Following the N<sub>2</sub>O consumption at the Oxygen Minimum Zone in the eastern South Pacific

2012 ◽  
Vol 9 (3) ◽  
pp. 2691-2707 ◽  
Author(s):  
M. Cornejo ◽  
L. Farías
Keyword(s):  
Primary Productivity ◽  
High Reliability ◽  
World Ocean ◽  
South Pacific ◽  
Future Scenarios ◽  
N2o Production ◽  
The World ◽  
Minimum Zone ◽  
Latitudinal Range ◽  
Oxygen Minimum

Abstract. Oxygen deficient zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N2O sources in the world ocean relative to their volume. N2O production is related to low O2 concentrations and high primary productivity. However, when O2 is sufficiently low, canonical denitrification takes place and N2O consumption can be expected. N2O distribution in the ESP was analyzed over a wide latitudinal range (from 5° to 30° S and 71°–76° to ~84° W) based on ~890 N2O measurements. The intense consumption of N2O appears to be related to secondary NO2− accumulation, the best indicator of very low O2 levels. Using relationships that depend on threshold levels of O2 (<8 μM) and nitrite (>0.75 μM), we reproduced the apparent N2O production (ΔN2O) with high reliability (r2=0.73 p=0.01). Our results contribute to quantify the ratio of N2O production/consumption that is being cycling in O2 deficient water of N2O and may improve the prediction of N2O behavior under future scenarios of the OMZ expansion.

scholarly journals Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific Oceans

2015 ◽  
Vol 12 (6) ◽  
pp. 4495-4556 ◽  
Author(s):  
C. R. Löscher ◽  
H. W. Bange ◽  
R. A. Schmitz ◽  
C. M. Callbeck ◽  
A. Engel ◽  
...  
Keyword(s):  
Organic Matter ◽  
Nutrient Cycling ◽  
Water Column ◽  
North Atlantic ◽  
South Pacific ◽  
N2o Production ◽  
Oxygen Minimum Zones ◽  
Tropical North Atlantic ◽  
The Impact ◽  
Oxygen Minimum

Abstract. Recent modeling results suggest that oceanic oxygen levels will decrease significantly over the next decades to centuries in response to climate change and altered ocean circulation. Hence the future ocean may experience major shifts in nutrient cycling triggered by the expansion and intensification of tropical oxygen minimum zones (OMZs). There are numerous feedbacks between oxygen concentrations, nutrient cycling and biological productivity; however, existing knowledge is insufficient to understand physical, chemical and biological interactions in order to adequately assess past and potential future changes. We investigated the pelagic biogeochemistry of OMZs in the eastern tropical North Atlantic and eastern tropical South Pacific during a series of cruise expeditions and mesocosm studies. The following summarizes the current state of research on the influence of low environmental oxygen conditions on marine biota, viruses, organic matter formation and remineralization with a particular focus on the nitrogen cycle in OMZ regions. The impact of sulfidic events on water column biogeochemistry, originating from a specific microbial community capable of highly efficient carbon fixation, nitrogen turnover and N2O production is further discussed. Based on our findings, an important role of sinking particulate organic matter in controlling the nutrient stochiometry of the water column is suggested. These particles can enhance degradation processes in OMZ waters by acting as microniches, with sharp gradients enabling different processes to happen in close vicinity, thus altering the interpretation of oxic and anoxic environments.

scholarly journals Modulation of the vertical particles transfer efficiency in the Oxygen Minimum Zone off Peru

2018 ◽  
Author(s):  
Marine Bretagnon ◽  
Aurélien Paulmier ◽  
Véronique Garçon ◽  
Boris Dewitte ◽  
Sérena Illig ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Sediment Traps ◽  
Biogeochemical Cycles ◽  
High Temporal Resolution ◽  
Oxygen Minimum Zones ◽  
Marine Life ◽  
Minimum Zone ◽  
Earth’S System ◽  
Oxygen Minimum

Abstract. The fate of the Organic Matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth’s system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive Eastern Boundary Upwelling Systems (EBUSs) associated with Oxygen Minimum Zones (OMZs) should foster OM preservation due to low O2 conditions, but their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru, providing high temporal resolution O2 series characterizing two seasonal steady states at the upper trap: suboxic ([O2] 

scholarly journals Anthropogenic carbon in the eastern South Pacific Ocean

2007 ◽  
Vol 4 (3) ◽  
pp. 1815-1837 ◽  
Author(s):  
L. Azouzi ◽  
R. Gonçalves Ito ◽  
F. Touratier ◽  
C. Goyet
Keyword(s):  
Pacific Ocean ◽  
General Trend ◽  
South Pacific ◽  
Hydrodynamic Characteristics ◽  
Eastern Pacific Ocean ◽  
Previous Knowledge ◽  
Oxygen Minimum Zones ◽  
South Pacific Ocean ◽  
Anthropogenic Carbon ◽  
Oxygen Minimum

Abstract. We present results from the BIOSOPE cruise in the eastern South Pacific Ocean. In particular, we present estimates of the anthropogenic carbon CantTrOCA distribution in this area using the TrOCA method recently developed by Touratier and Goyet (2004a, b) and Touratier et al. (2007). We study the distribution of this anthropogenic carbon taking into account of the hydrodynamic characteristics of this region. We then compare these results with earlier estimates in nearby areas of the anthropogenic carbon as well as other anthropogenic tracer (CFC-11). The highest concentrations of CantTrOCA are located around 13° S 132° W and 32° S 91° W, and their concentrations are larger than 80 μmol kg−1 and 70 μmol kg−1, respectively. The lowest concentrations were observed below 800 m depths (≤2 μ mol kg−1) and at the Oxygen Minimum Zones (OMZ), mainly around 140° W (<11 μmol kg−1). The comparison with earlier work in nearby areas provides a general trend and indicates that the results presented here are in general agreement with previous knowledge. This work further improves our understanding on the penetration of anthropogenic carbon in the eastern Pacific Ocean.

scholarly journals Middepth circulation of the eastern tropical South Pacific and its link to the oxygen minimum zone

2011 ◽  
Vol 116 (C1) ◽  
Author(s):  
Rena Czeschel ◽  
Lothar Stramma ◽  
Franziska U. Schwarzkopf ◽  
Benjamin S. Giese ◽  
Andreas Funk ◽  
...  
Keyword(s):  
South Pacific ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Controls on redox-sensitive trace metals in the Mauritanian oxygen minimum zone

2018 ◽  
Author(s):  
Insa Rapp ◽  
Christian Schlosser ◽  
Jan-Lukas Menzel Barraqueta ◽  
Bernhard Wenzel ◽  
Jan Lüdke ◽  
...  
Keyword(s):  
Community Structure ◽  
Trace Metals ◽  
Surface Waters ◽  
Oxygen Minimum Zones ◽  
Carbon And Nitrogen ◽  
Shelf Sediments ◽  
Minimum Zone ◽  
Ocean Carbon ◽  
Shelf Region ◽  
Oxygen Minimum

Abstract. The availability of the micronutrient iron (Fe) in surface waters determines primary production, N2 fixation and microbial community structure in large parts of the world's ocean, and thus plays an important role in ocean carbon and nitrogen cycles. Eastern boundary upwelling systems and the connected oxygen minimum zones (OMZs) are typically associated with elevated concentrations of redox-sensitive trace metals (e.g. Fe, manganese (Mn) and cobalt (Co)), with shelf sediments typically forming a key source. Over the last five decades, an expansion and intensification of OMZs has been observed and this trend is likely to proceed. However, it is unclear how trace metal (TM) distributions and transport are influenced by decreasing oxygen (O2) concentrations. Here we present dissolved (d;  0.2 μm) TM data collected at 7 stations along a 50 km transect in the Mauritanian shelf region. We observed enhanced concentrations of Fe, Co and Mn corresponding with low O2 concentrations (

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