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On the Origins of Open Ocean Oxygen Minimum Zones

Abstract.

"Recent work suggests that Oxygen Minimum Zones (OMZs) are sustained by the supply of oxygen-poor waters rather than the export of organic matter from the local surface layer and its subsequent remineralization inside OMZs. However, the mechanisms that form and maintain OMZs are not well constrained, such as the origin of the oxygen that oxygenates OMZs, and the locations where oxygen consumption occurs. Here we use an observation-based transport matrix to determine the origins of open ocean OMZs in terms of (a) OMZ volume, (b) oxygen that survives remineralization and oxygenates OMZs, and (c) oxygen utilization in the interior ocean that contributes to the oxygen-deficit of OMZs. [...]".

 

Source: Wiley Online Library
Authors: Xabier Davila et al.
DOI: https://doi.org/10.1029/2023JC019677

Read the full article here.

 


Extensive Accumulation of Nitrous Oxide in the Oxygen Minimum Zone in the Bay of Bengal

Abstract.

"The production by microorganisms of nitrous oxide (N2O), a trace gas contributing to global warming and stratospheric ozone depletion, is enhanced around the oceanic oxygen minimum zones (OMZs). The production constitutes an important source of atmospheric N2O. Although an OMZ is found in the northern part of the eastern Indian Ocean, the Bay of Bengal (BoB), two earlier studies conducted during the later phase of winter monsoon (February) and spring intermonsoon (March–April) found quite different magnitudes of N2O accumulation. [...]".

 

Source: Wiley Online Library
Authors: Sakae Toyoda et al.
DOI: https://doi.org/10.1029/2022GB007689

Read the full article here.


Decreasing O2 availability reduces cellular protein contents in a marine diatom

Abstract.

"Anthropogenic activities and climate change are exacerbating marine deoxygenation. Apart from aerobic organisms, reduced O2 also affects photoautotrophic organisms in the ocean. This is because without available O2, these O2 producers cannot maintain their mitochondrial respiration, especially under dim-light or dark conditions, which may disrupt the metabolism of macromolecules including proteins. We used growth rate, particle organic nitrogen and protein analyses, proteomics, and transcriptomics to determine cellular nitrogen metabolism of the diatom Thalassiosira pseudonana grown under three O2 levels in a range of light intensities [...]".

 

Source: Science Direct
Authors: Bokun Chen et al.
DOI: https://doi.org/10.1016/j.scitotenv.2023.164032

Read the full article here.


Ideas and perspectives: The fluctuating nature of oxygen shapes the ecology of aquatic habitats and their biogeochemical cycles – the aquatic oxyscape

Abstract.

"Oxygen availability is a pivotal factor for ecosystem functioning and the resistance of organisms to the effect of climate change in aquatic habitats. Although extensive work has been done to assess the effect of oxygen on marine and freshwater biota, many studies have not captured the ecological importance of oxygen variations. Overlooking the fluctuating nature of oxygen may cause potential biases in the design and implementation of management policies for aquatic habitats. Conceptual perspectives on the dynamic nature of oxygen fluctuations have been raised in the scientific community in order to enhance [...]".

 

Source: Biogeosciences
Authors: Marco Fusi et al.
DOI: https://doi.org/10.5194/bg-20-3509-2023

Read the full article here.


The response of nitrogen and sulfur cycles to ocean deoxygenation across the Cenomanian-Turonian boundary

Abstract.

"The Cretaceous Oceanic Anoxic Event 2 (OAE2) is a greenhouse episode of severe marine anoxia at the Cenomanian-Turonian boundary. This time interval is characterized by rising sea surface temperature, enhanced marine biological productivity, and widespread occurrence of organic-rich black shales. With an export of biological production to the deep ocean, organisms consume vast amounts of oxygen and subsequently utilize nitrate and sulfate as electron acceptors in organic matter degradation, thereby affecting biogeochemical cycles of nitrogen and sulfur. [...]".

 

Source: Science Direct
Authors: Ruixiang Zhai et al.
DOI: https://doi.org/10.1016/j.gloplacha.2023.104182

Read the full article here.


Benthic foraminifera and gromiids from oxygen-depleted environments – survival strategies, biogeochemistry and trophic interactions

Abstract.

"The oceans are losing oxygen (O2), and oxygen minimum zones are expanding due to climate warming (lower O2 solubility) and eutrophication related to agriculture. This trend is challenging for most marine taxa that are not well adapted to O2 depletion. For other taxa this trend might be advantageous because they can withstand low O2 concentrations or thrive under O2-depleted or even anoxic conditions. Benthic foraminifera are a group of protists that include taxa with adaptations to partly extreme environmental conditions. [...]".

 

Source: Biogeosciences
Authors: Nicolaas Glock
DOI: https://doi.org/10.5194/bg-20-3423-2023

Read the full article here.


Indian Ocean glacial deoxygenation and respired carbon accumulation during mid-late Quaternary ice ages

Abstract.

"Reconstructions of ocean oxygenation are critical for understanding the role of respired carbon storage in regulating atmospheric CO2. Independent sediment redox proxies are essential to assess such reconstructions. Here, we present a long magnetofossil record from the eastern Indian Ocean in which we observe coeval magnetic hardening and enrichment of larger, more elongated, and less oxidized magnetofossils during glacials compared to interglacials over the last ~900 ka. Our multi-proxy records of redox-sensitive magnetofossils, trace element concentrations, and benthic foraminiferal Δδ13C consistently suggest a recurrence of lower O2 [...]".

 

Source: Nature
Authors: Liao Chang et al.
DOI: https://doi.org/10.1038/s41467-023-40452-1

Read the full article here.


Sulfur isotopic evidence for global marine anoxia and low seawater sulfate concentration during the Late Triassic

Abstract.

"Marine anoxia during the Late Triassic has mostly been reported from the western Tethysand Panthalassa, which were near the Central Atlantic Magmatic Province (CAMP), but whether it developed in global open oceans (e.g., the eastern Tethys) is unknown. Whether the marine anoxia was global or regional requires more research. Here, we present carbonate-associated sulfate (CAS) and pyrite δ34Spy data for the Late Triassic–Early Jurassic interval from the Wenquan Section in Qiantang Basin, Tibet. [...]".

 

Source: Science Direct
Authors: Wei Tang et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105659

Read the full article here.


Cretaceous southern high latitude benthic foraminiferal assemblages during OAE 2 at IODP Site U1516, Mentelle Basin, Indian Ocean

Abstract.

"At Site U1516 (Mentelle Basin, southeast Indian Ocean, offshore western Australia), the International Ocean Discovery Program (IODP) Expedition 369 recovered an almost complete pelagic record of the Upper Cretaceous, including the Oceanic Anoxic Event 2 (OAE 2). To better understand paleoenvironmental changes across OAE 2, 32 samples were analysed for benthic foraminiferal abundance data that represent one of the few benthic foraminiferal datasets spanning the OAE 2 in the southern high latitudes. [...]".

 

Source: Science Direct
Authors: Erik Wolfgring et al.
DOI: https://doi.org/10.1016/j.cretres.2023.105555

Read the full article here.


Redox-sensitive elements of Ediacaran black shales in South China with implications for a widespread anoxic ocean

Abstract.

"The high enrichment of redox-sensitive elements (RSEs), Mo, U, V, and Cr, in Ediacaran shales was attributed to the Neoproterozoic Oxygenation Event (NOE). However, recent studies have shown that contemporaneous shales from NW Canada do not exhibit RSE enrichment, whereas those from South China exhibit varying degrees of RSE enrichment. Here we investigate RSE records in a broader spatial and temporal distribution of shales within the Ediacaran Doushantuo Formation from South China. [...]".

 

Source: Science Direct
Authors: Yufei Hao et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105670

Read the full article here.


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