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Investigating ocean deoxygenation and the oxygen minimum zone in the Central Indo Pacific region based on the hindcast datasets

Abstract. 

"Deoxygenation is increasingly recognized as a significant environmental threat to the ocean following sea temperature rises due to global warming and climate change. Considering the cruciality of the deoxygenation impacts, it is important to assess the current status and predict the future possibility of ocean deoxygenation, for instance, within the Central Indo Pacific (CIP) regions represent climate-regulated marine areas. This study divided CIP into five regions then investigated the deoxygenation parameters (dissolved oxygen, temperature, salinity, and pH) collected from 1993 to 2021 sourced from in situ measurement and long-term hindcast data. [...]".

 

Source: Environmental Monitoring and Assessment
Authors: Karlina Triana et al.
DOI: https://doi.org/10.1007/s10661-022-10615-6

Read the full article here.


Seasonal nearshore ocean acidification and deoxygenation in the Southern California Bight

Abstract. 

"The California Current System experiences seasonal ocean acidification and hypoxia (OAH) owing to wind-driven upwelling, but little is known about the intensity, frequency, and depth distribution of OAH in the shallow nearshore environment. Here we present observations of OAH and dissolved inorganic carbon and nutrient parameters based on monthly transects from March 2017 to September 2018 extending from the surf zone to the ~ 40 m depth contour in La Jolla, California. Biologically concerning OAH conditions were observed at depths as shallow as 10 m and as close as 700 m to the shoreline. [...]".

 

Source: Scientific Reports
Authors: Samuel A. H. Kekuewa et al. 
DOI: https://doi.org/10.1038/s41598-022-21831-y

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The Ocean's Biological Pump: In Situ Oxygen Measurements in the Subtropical Oceans

Abstract. 

"The magnitude and distribution of the ocean's biological pump (the downward flux of organic carbon (OC) from the ocean surface) influences the pCO2 of the atmosphere and the O2 content of the deep sea, but has not been well quantified. We determine this flux in the ocean's five subtropical gyres using upper-ocean oxygen mass balance and measurements of T, S, and pO2 by autonomous profiling floats. Our results suggest that the biological OC pump is not globally uniform among the subtropical gyres: values in the North Pacific and Atlantic indicate distinct autotrophy (1–2 mol C m−2 yr−1) while near zero values in the S. [...]".

 

Source: Geophysical Research Letters
Authors: Steven Emerson & Bo Yang
DOI: https://doi.org/10.1029/2022GL099834

Read the full article here.


Intensive ocean anoxia and large δ13Ccarb perturbations during the Carnian Humid Episode (Late Triassic) in Southwest China

Abstract. 

"The Carnian Humid Episode (CHE) represents a dramatic dry to wet climate transition in the Late Triassic. Manifestations of this climate shift and its associated biological and environmental responses are not fully understood. Here, we carried out carbonate carbon isotope, trace metal, and pyrite framboid analyses at Wolonggang in southwest China to trace palaeoenvironmental changes during this critical interval. The CHE at Wolonggang is marked by the development of fine laminated carbonaceous siltstones and black shales overlying the intensely bioturbated Zhuganpo limestone deposited in the latest Julian 1. [...]". 

 

Source: Science Direct 
Authors: Zaitian Zhang et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103942

Read the full article here.


Physical-chemical factors influencing the vertical distribution of phototrophic pico-nanoplankton in the Oxygen Minimum Zone (OMZ) off Northern Chile

Abstract. 

"The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. [...]". 

 

Source: Science Direct 
Authors: Edson Piscoya et al.
DOI: https://doi.org/10.1016/j.marenvres.2022.105710

Read the full article here.


Iron deposition during recovery from Late Devonian oceanic anoxia: Implications of the geochemistry of the Kawame ferromanganese deposit, Nedamo Belt

Abstract. 

"The Late Devonian, during which one of the “Big Five” Phanerozoic mass extinction events occurred, was one of the most important time intervals in Earth history. Nevertheless, the paucity of deep-sea records due to subduction has hampered elucidation of the pelagic environment during the Late Devonian in Panthalassa. However, ancient hydrothermal ferromanganese sediments, which were deposited on the abyssal seafloor and then accreted onto continental margins, are preserved as umber deposits and exposed in accretionary prisms. These sediments can provide key information to characterize the paleo-ocean. [...]".

 

Source: Science Direct 
Authors: Yusuke Kuwahara et al. 
DOI: https://doi.org/10.1016/j.gloplacha.2022.103920

Read the full article here.


Plate tectonics controls ocean oxygen levels

Abstract. 

"Variations in ocean oxygen levels during Earth’s history have been linked to evolution and mass extinctions. Simulations now suggest that the configuration of the continents has a substantial impact on ocean oxygenation. [...]". 

 

Source: Nature
Authors: Katrin J. Meissner & Andreas Oschlies
DOI: https://doi.org/10.1038/d41586-022-02187-9

Read the full article here.


Constraining marine anoxia under the extremely oxygenated Permian atmosphere using uranium isotopes in calcitic brachiopods and marine carbonates

Abstract. 

"The redox chemistry change in ancient oceans has profoundly shaped the evolutionary trajectories of animals. Uranium isotopes (U) in marine carbonate sediments have widely been used to place quantitative constraints on the oxygenation state of the oceans through geological history. However, syndepositional and post-depositional diagenesis impose a positive and variable U offset in the carbonate sediments relative to contemporaneous seawater, leaving uncertainties on quantification of anoxic seafloor areas in the past. Studies from modern settings suggest that Low-Magnesium Calcite (LMC) in articulate brachiopod shells are diagenetic resistant materials that may faithfully record the U value of ancient seawater. [...]".

 

Source: Science Direct 
Authors: Wen-qian Wang et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117714

Read the full article here.


Environmental change and carbon-cycle dynamics during the onset of Cretaceous oceanic anoxic event 1a from a carbonate-ramp depositional system

Abstract. 

"We report the first high-resolution sedimentological and geochemical record of the negative carbon-isotope excursion (CIE) at the onset of the early Aptian oceanic anoxic event (OAE) 1a from a carbonate-ramp depositional environment, analysed from a well core from c. 2500 m depth, 100 km offshore Abu Dhabi, United Arab Emirates. Time-series analysis of stable oxygen isotope values and concentrations of Si, Al, and Ti resulted in durations of the C3 and C4 segments of the CIE that support relative completeness of the C3 segment and high sediment preservation rates of c. 13 cm/kyr of the studied sedimentary sequence. [...]".

 

Source: Science Direct 
Authors: Thomas Steuber et al.
DOI: https://doi.org/10.1016/j.palaeo.2022.111086

Read the full article here.


A double-edged sword: The role of sulfate in anoxic marine phosphorus cycling through Earth history

Abstract. 

"Modern anoxic marine sediments release phosphorus (P) to seawater, driving feedbacks at multiple timescales. On sub-Myr timescales, anoxic P regeneration amplifies ocean deoxygenation; on multi-Myr timescales, it stabilizes atmospheric O2. Some authors have extended this thinking to the Precambrian: by analogy, widespread ocean anoxia would imply extensive P regeneration from sediments. However, this neglects the role of sulfate in P regeneration. [...]".

 

Source: Geophysical Research Letters
Authors: Michael A. Kipp
DOI: https://doi.org/10.1029/2022GL099817

Read the full article here.


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