scholarly journals In situ quantification of ultra‐low O 2 concentrations in oxygen minimum zones: Application of novel optodes

2016 ◽  
Vol 14 (12) ◽  
pp. 784-800 ◽  
Author(s):  
Morten Larsen ◽  
Philipp Lehner ◽  
Sergey M. Borisov ◽  
Ingo Klimant ◽  
Jan P. Fischer ◽  
...  
Keyword(s):  
Oxygen Minimum Zones ◽  
Oxygen Minimum

scholarly journals Expanded oxygen minimum zones during the late Paleocene-early Eocene: Hints from multiproxy comparison and ocean modeling

2016 ◽  
Vol 31 (12) ◽  
pp. 1532-1546 ◽  
Author(s):  
X. Zhou ◽  
E. Thomas ◽  
A. M. E. Winguth ◽  
A. Ridgwell ◽  
H. Scher ◽  
...  
Keyword(s):  
Ocean Modeling ◽  
Early Eocene ◽  
Oxygen Minimum Zones ◽  
Late Paleocene ◽  
Oxygen Minimum

scholarly journals Toward a global calibration for quantifying past oxygenation in oxygen minimum zones using benthic Foraminifera

2021 ◽  
Author(s):  
Martin Tetard ◽  
Laetitia Licari ◽  
Kazuyo Tachikawa ◽  
Ekaterina Ovsepyan ◽  
Luc Beaufort
Keyword(s):  
North Pacific ◽  
Transfer Functions ◽  
Late Quaternary ◽  
Global Climate ◽  
Single Species ◽  
Pore Waters ◽  
Oxygen Minimum Zones ◽  
Global Calibration ◽  
Circularity Index ◽  
Oxygen Minimum

Abstract. Oxygen Minimum Zones (OMZs) are oceanic areas largely depleted in dissolved oxygen, nowadays considered in expansion in the face of global warming. Their ecological and economic consequences are being debated. The investigation of past OMZ conditions allows us to better understand biological and physical mechanisms responsible for their variability with regards to climate change, carbon pump and carbonate system. To investigate the relationship between OMZ expansion and global climate changes during the late Quaternary, quantitative oxygen reconstructions are needed, but are still in their early development. Here, past bottom water oxygenation (BWO) was quantitatively assessed through a new, fast, semi-automated, and taxonfree morphometric analysis of benthic foraminiferal tests, developed and calibrated using Eastern North Pacific (ENP) and the Eastern South Pacific (ESP) OMZs samples. This new approach is based on an average size and circularity index for each sample. This method, as well as two already published micropalaeontological approaches based on benthic foraminiferal assemblages variability and porosity investigation of a single species, were here calibrated based on availability of new data from 23 core tops recovered along an oxygen gradient (from 0.03 to 1.79 mL.L−1) from the ENP, ESP, AS (Arabian Sea) and WNP (Western North Pacific, including its marginal seas) OMZs. Global calibrated transfer functions are thus herein proposed for each of these methods. These micropalaeontological reconstruction approaches were then applied on a paleorecord from the ENP OMZ to examine the consistency and limits of these methods, as well as the relative influence of bottom and pore waters on these micropalaeontological tools. Both the assemblages and morphometric approaches (that is also ultimately based on the ecological response of the complete assemblage and faunal succession according to BWO) gave similar and consistent past BWO reconstructions, while the porosity approach (based on a single species and its unique response to a mixed signal of bottom and pore waters) shown ambiguous estimations.

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 The control of hydrogen sulfide on benthic iron and cadmium fluxes in the oxygen minimum zone off Peru

2019 ◽  
Author(s):  
Anna Plass ◽  
Christian Schlosser ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Eric P. Achterberg ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Trace Metals ◽  
Pore Water ◽  
Oxygen Minimum Zone ◽  
Benthic Fluxes ◽  
Benthic Chamber ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Sediments in oxygen-depleted marine environments can be an important sink or source of bio-essential trace metals in the ocean. However, the key mechanisms controlling the release from or burial of trace metals in sediments are not exactly understood. Here, we investigate the benthic biogeochemical cycling of Fe and Cd in the oxygen minimum zone off Peru. We combine bottom water profiles, pore water profiles, as well as benthic fluxes determined from pore water profiles and in-situ from benthic chamber incubations along a depth transect at 12° S. In agreement with previous studies, both concentration-depth profiles and in-situ benthic fluxes indicate a Fe release from sediments into bottom waters. Diffusive Fe fluxes and Fe fluxes from benthic chamber incubations are roughly consistent (0.3–17.1 mmol m−2 y−1), indicating that diffusion is the main transport mechanism of dissolved Fe across the sediment-water interface. The occurrence of mats of sulfur oxidizing bacteria on the seafloor represents an important control on the spatial distribution of Fe fluxes by regulating hydrogen sulfide (H2S) concentrations and, potentially, Fe sulfide precipitation within the surface sediment. Removal of dissolved Fe after its release to anoxic bottom waters is rapid in the first 4 m away from the seafloor (half-life

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 Uncultured Nitrospina-like species are major nitrite oxidizing bacteria in oxygen minimum zones

2019 ◽  
Vol 13 (10) ◽  
pp. 2391-2402 ◽  
Author(s):  
Xin Sun ◽  
Linnea F. M. Kop ◽  
Maggie C. Y. Lau ◽  
Jeroen Frank ◽  
Amal Jayakumar ◽  
...  
Keyword(s):  
Oxygen Minimum Zones ◽  
Nitrite Oxidizing Bacteria ◽  
Oxygen Minimum

scholarly journals Uptake of algal carbon and the likely synthesis of an "essential" fatty acid by <i>Uvigerina</i> ex. gr. <i>semiornata</i> (Foraminifera) within the Pakistan margin oxygen minimum zone: evidence from fatty acid biomarker and <sup>13</sup>C tracer experiments

2014 ◽  
Vol 11 (14) ◽  
pp. 3729-3738 ◽  
Author(s):  
K. E. Larkin ◽  
A. J. Gooday ◽  
C. Woulds ◽  
R. M. Jeffreys ◽  
M. Schwartz ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Food Source ◽  
Benthic Communities ◽  
Oxygen Minimum Zone ◽  
Monsoon Period ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Tracer Experiments

Abstract. Foraminifera are an important component of benthic communities in oxygen-depleted settings, where they potentially play a significant role in the processing of organic matter. We tracked the uptake of a 13C-labelled algal food source into individual fatty acids in the benthic foraminiferal species Uvigerina ex. gr. semiornata from the Arabian Sea oxygen minimum zone (OMZ). The tracer experiments were conducted on the Pakistan margin during the late/post monsoon period (August–October 2003). A monoculture of the diatom Thalassiosira weisflogii was 13C-labelled and used to simulate a pulse of phytoplankton in two complementary experiments. A lander system was used for in situ incubations at 140 m water depth and for 2.5 days in duration. Shipboard laboratory incubations of cores collected at 140 m incorporated an oxystat system to maintain ambient dissolved oxygen concentrations and were terminated after 5 days. Uptake of diatoms was rapid, with a high incorporation of diatom fatty acids into foraminifera after ~ 2 days in both experiments. Ingestion of the diatom food source was indicated by the increase over time in the quantity of diatom biomarker fatty acids in the foraminifera and by the high percentage of 13C in many of the fatty acids present at the endpoint of both in situ and laboratory-based experiments. These results indicate that

scholarly journals Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones

2012 ◽  
Vol 9 (1) ◽  
pp. 203-215 ◽  
Author(s):  
E. Ryabenko ◽  
A. Kock ◽  
H. W. Bange ◽  
M. A. Altabet ◽  
D. W. R. Wallace
Keyword(s):  
Surface Waters ◽  
Inorganic Nitrogen ◽  
Sharp Decrease ◽  
Stable Isotope Ratio ◽  
Saharan Dust ◽  
N Loss ◽  
Fractionation Factor ◽  
Oxygen Minimum Zones ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. We present new data for the stable isotope ratio of inorganic nitrogen species from the contrasting oxygen minimum zones (OMZs) of the Eastern Tropical North Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru. Differences in minimum oxygen concentration and corresponding N-cycle processes for the two OMZs are reflected in strongly contrasting δ15N distributions. Pacific surface waters are marked by strongly positive values for δ15N-NO3–) reflecting fractionation associated with subsurface N-loss and partial NO3– utilization. This contrasts with negative values in NO3– depleted surface waters of the Atlantic which are lower than can be explained by N supply via N2 fixation. We suggest the negative values reflect inputs of nitrate, possibly transient, associated with deposition of Saharan dust. Strong signals of N-loss processes in the subsurface Pacific OMZ are evident in the isotope and N2O data, both of which are compatible with a contribution of canonical denitrification to overall N-loss. However the apparent N isotope fractionation factor observed is relatively low (&amp;varepsilon;d=11.4 ‰) suggesting an effect of influence from denitrification in sediments. Identical positive correlation of N2O vs. AOU for waters with oxygen concentrations ([O2] < 5 μmol l−1) in both regions reflect a nitrification source. Sharp decrease in N2O concentrations is observed in the Pacific OMZ due to denitrification under oxygen concentrations O2 < 5 μmol l−1.

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