News

Metagenomics and metatranscriptomics reveal broadly distributed, active, novel methanotrophs in the Gulf of Mexico hypoxic zone

Abstract. 

"The northern Gulf of Mexico (nGOM) hypoxic zone is a shallow water environment where methane, a potent greenhouse gas, fluxes from sediments to bottom water and remains trapped due to summertime stratification. When the water column is destratified, an active planktonic methanotrophic community could mitigate the efflux of methane, which accumulates to high concentrations, to the atmosphere. To investigate the possibility of such a biofilter in the nGOM hypoxic zone we performed metagenome assembly, and metagenomic and metatranscriptomic read mapping. Methane monooxygenase (pmoA) was an abundant [...]".

 

Source: Oxford Academic
Authors: Kathryn L. Howe et al.
DOI: https://doi.org/10.1093/femsec/fiac153

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Subpolar gyre decadal variability explains the recent oxygenation in the Irminger Sea

Abstract. 

"Accurate monitoring of the long-term trend of oxygen content at global scale requires a better knowledge of the regional oxygen variability at interannual to decadal time scale. Here, we combined the Argo dataset and repeated ship-based sections to investigate the drivers of the oxygen variability in the North Atlantic Ocean, a key region for the oxygen supply into the deep ocean. We focus on the Labrador Sea Water in the Irminger Sea over the period 1991–2018 and we show that the oxygen solubility explains less than a third of the oxygen variability. [...]".

 

Source: Nature
Authors: Charlène Feucher et al.
DOI: https://doi.org/10.1038/s43247-022-00570-y

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Calcium isotope ratios of malformed foraminifera reveal biocalcification stress preceded Oceanic Anoxic Event 2

Abstract. 

"Ocean acidification causes biocalcification stress. The calcium isotope composition of carbonate producers can archive such stress because calcium isotope fractionation is sensitive to precipitation rate. Here, we synthesize morphometric observations of planktic foraminifera with multi-archive calcium isotope records from Gubbio, Italy and the Western Interior Seaway spanning Cretaceous Ocean Anoxic Event 2 (~94 million years ago). Calcium isotope ratios increase ~60 thousand years prior to the event. [...]". 

 

Source: Nature
Authors: Gabriella D. Kitch et al.
DOI: https://doi.org/10.1038/s43247-022-00641-0

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Carbon pump dynamics and limited organic carbon burial during OAE1a

Abstract. 

"Oceanic Anoxic Events (OAEs) are conspicuous intervals in the geologic record that are associated with the deposition of organic carbon (OC)-rich marine sediment, linked to extreme biogeochemical perturbations, and characterized by widespread ocean deoxygenation. Mechanistic links between the marine biological carbon pump (BCP), redox conditions, and organic carbon burial during OAEs, however, remain poorly constrained. In this work we reconstructed the BCP in the western Tethys Ocean across OAE1a (~120 Mya) using sediment geochemistry and OC mass accumulation rates (OCAcc). [...]".

 

Source: Wiley Online Library
Authors: Kohen W. Bauer et al.
DOI: https://doi.org/10.1111/gbi.12538

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Nitrous Oxide Distributions in the Oxygenated Water Column of the Sargasso Sea

Abstract. 

"This study presents dissolved nitrous oxide (N2O) concentrations in the water column at the Bermuda Atlantic Time-series Study (BATS) station and uses a subset of these measurements to estimate air-to-sea flux for four specific time points between September 2018 and June 2019. N2O concentrations at BATS were in the range of 4.0 nmol L−1–16.9 nmol L−1, with vertical profiles which were the mirror inverse of dissolved oxygen. Regardless of season, N2O concentration maxima were found within the oxygen minimum zone (OMZ). The highest maximum N2O values were observed in November and lowest in October. [...]".

 

Source: Taylor & Francis Online
Authors: Annaliese C.S. Meyer et al. 
DOI: https://doi.org/10.1080/07055900.2022.2153325

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Offshore wind farms are projected to impact primary production and bottom water deoxygenation in the North Sea

Abstract. 

"The wind wake effect of offshore wind farms affects the hydrodynamical conditions in the ocean, which has been hypothesized to impact marine primary production. So far only little is known about the ecosystem response to wind wakes under the premisses of large offshore wind farm clusters. Here we show, via numerical modeling, that the associated wind wakes in the North Sea provoke large-scale changes in annual primary production with local changes of up to ±10% not only at the offshore wind farm clusters, but also distributed over a wider region. [...]".

 

Source: Nature
Authors: Ute Daewel et al.
DOI: https://doi.org/10.1038/s43247-022-00625-0 

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Recovery from microplastic-induced marine deoxygenation may take centuries

Abstract.

"Climate change and plastics pollution are dual threats to marine environments. Here we use biogeochemical and microplastic modelling to show that even if there is complete removal of microplastics and cessation of deposition in the oceans in 2022, regional recovery from microplastic-induced remineralization and water column deoxygenation could take hundreds of years for coastal upwelling zones, the North Pacific and Southern Ocean. [...]".

 

Source: Nature
Authors: Karin Kvale & Andreas Oschlies
DOI: https://doi.org/10.1038/s41561-022-01096-w 

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The Peruvian oxygen minimum zone was similar in extent but weaker during the Last Glacial Maximum than Late Holocene

Abstract. 

"Quantifying past oxygen concentrations in oceans is crucial to improving understanding of current global ocean deoxygenation. Here, we use a record of pore density of the epibenthic foraminifer Planulina limbata from the Peruvian Oxygen Minimum Zone to reconstruct oxygen concentrations in bottom waters from the Last Glacial Maximum to the Late Holocene at 17.5°S about 500 meters below the sea surface. We found that oxygen levels were 40% lower during the Last Glacial Maximum than during the Late Holocene (about 6.7 versus 11.1 µmol/kg, respectively). [...]".

 

Source: Nature
Authors: Nicolaas Glock et al. 
DOI: https://doi.org/10.1038/s43247-022-00635-y 

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Diverging Fates of the Pacific Ocean Oxygen Minimum Zone and Its Core in a Warming World

Abstract. 

"Global ocean oxygen loss is projected to persist in the future, but Earth system models (ESMs) have not yet provided a consistent picture of how it will influence the largest oxygen minimum zone (OMZ) in the tropical Pacific. We examine the change in the Pacific OMZ volume in an ensemble of ESMs from the CMIP6 archive, considering a broad range of oxygen (O2) thresholds relevant to biogeochemical cycles and ecosystems (5–160 µmol/kg). Despite OMZ biases in the historical period of the simulations, the ESM ensemble projections consistently fall into three regimes across ESMs […]".

 

Source: Wiley Online Library
Authors: Julius J.M. Busecke et al.
DOI: https://doi.org/10.1029/2021AV000470

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Oxygen and irradiance constraints on visual habitat in a changing ocean: The luminoxyscape

Abstract. 

"Changing oxygen conditions are altering the distribution of many marine animals. Zooplankton vertical distributions are primarily attributed to physiological tolerance and/or avoidance of visual predation. Recent findings reveal that visual function in marine larvae is highly sensitive to oxygen availability, but it is unknown how oxygen, which affects light sensitivity and generates limits for vision, may affect the distribution of animals that rely heavily on this sensory modality. This study introduces the concept of a “visual luminoxyscape” to demonstrate how combinations of limiting oxygen and light could constrain the habitat of marine larvae with oxygen-demanding vision. [...]".

 

Source: Wiley Online Library
Authors: Lillian R. McCormick et al.
DOI: https://doi.org/10.1002/lol2.10296

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Geochemical and paleontological evidence of early Cambrian dynamic ocean oxygenation and its implications for organic matter accumulation in mudrocks

Abstract. 

"The evolution of global ocean oxygenation during the early Cambrian remains highly controversial, making it difficult to evaluate how environmental triggers play a role in controlling the organic matter (OM) accumulation in black shales. In this study, an integrated approach, including total organic carbon (TOC) content, major and trace element geochemistry, and microscope images, was systematically conducted in a continuous core well that penetrated through the Lower Cambrian Yanjiahe (YJH)–Shuijingtuo (SJT, subdivided into SM Ⅰ, SM Ⅱ, SM Ⅲ, and SM Ⅳ members) successions (∼541-514Ma) at the Three Gorges area [...]".

 

Source: Science Direct 
Authors: Yu Zhang et al.
DOI: https://doi.org/10.1016/j.marpetgeo.2022.105958

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Volcanic trigger of ocean deoxygenation during Cordilleran ice sheet retreat

Abstract. 

"North Pacific deoxygenation events during the last deglaciation were sustained over millennia by high export productivity, but the triggering mechanisms and their links to deglacial warming remain uncertain. Here we find that initial deoxygenation in the North Pacific immediately after the Cordilleran ice sheet (CIS) retreat was associated with increased volcanic ash in seafloor sediments. Timing of volcanic inputs relative to CIS retreat suggests that regional explosive volcanism was initiated by ice unloading. […]".

 

Source: Nature
Authors: Jianghui Du et al.
DOI: https://doi.org/10.1038/s41586-022-05267-y

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Progressive expansion of seafloor anoxia in the Middle to Late Ordovician Yangtze Sea: Implications for concurrent decline of invertebrate diversity

Abstract. 

"The Great Ordovician Biodiversification Event (GOBE) achieved its peak during the Middle Ordovician, likely in association with climatic cooling and a rise of atmospheric O2. However, unstable redox states developed widely in contemporaneous epeiric seas, challenging previous assumptions about sustained oceanic oxygenation driven by deep-ocean ventilation in the aftermath of Ordovician cooling. Here, we investigate two Middle-Upper Ordovician shale-dominated successions from intra-shelf basin and slope settings of the Yangtze Sea, South China. […]".

 

Source: Science Direct 
Authors: Junpeng Zhang et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117858

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Two deep marine oxygenation events during the Permian-Triassic boundary interval in South China

Abstract. 

"Marine redox conditions through the Permian-Triassic (P-T) boundary interval have been intensively studied in South China with different redox proxies and from different sections. However, the resultant interpretations are inconsistent and sometimes even controversial, thereby impeding an overall understanding of global environmental changes and of causes for the P-T mass extinction events. This study summarizes and reevaluates these previous studies. [...]".

 

Source: Science Direct
Authors: Yuzhu Ge & David P.G. Bond
DOI: https://doi.org/10.1016/j.earscirev.2022.104220

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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

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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

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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

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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

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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

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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

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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

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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

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A Depth-Transect of Ocean Deoxygenation During the Paleocene-Eocene Thermal Maximum: Magnetofossils in Sediment Cores From the Southeast Atlantic

Abstract. 

"The Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma) presents a past analog for future global warming. Previous studies provided evidence for major loss of dissolved oxygen during the PETM, although understanding the degree and distribution of oxygen loss poses challenges. Magnetofossils produced by magnetotactic bacteria are sensitive to redox conditions in sediments and water columns, and have been used to reconstruct paleoredox conditions over a range of geological settings. [...]".

 

Source: JGR Solid Earth
Authors: Pengfei Xue et al.
DOI: https://doi.org/10.1029/2022JB024714

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Ocean biogeochemical modelling

Abstract. 

"Ocean biogeochemical models describe the ocean’s circulation, physical properties, biogeochemical properties and their transformations using coupled differential equations. Numerically approximating these equations enables simulation of the dynamic evolution of the ocean state in realistic global or regional spatial domains, across time spans from years to centuries. This Primer explains the process of model construction and the main characteristics, advantages and drawbacks of different model types, from the simplest nutrient–phytoplankton–zooplankton–detritus model to the complex biogeochemical models used in Earth system modelling and climate prediction. [...]".

 

Source: Nature Reviews Methods Primers 
Authors: Katja Fennel et al.
DOI: https://doi.org/10.1038/s43586-022-00154-2 

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Impact of warming and deoxygenation on the habitat distribution of Pacific halibut in the Northeast Pacific

Abstract. 

"Ocean warming and deoxygenation are already modifying the habitats of many aerobic organisms. Benthic habitat in the Northeast Pacific is sensitive to deoxygenation, as low oxygen concentrations occur naturally in continental shelf bottom waters. Here, we examine the potential impacts of deoxygenation and ocean warming on the habitat distribution of Pacific halibut (Hippoglossus stenolepis), one of the most commercially important groundfish in North America. [...]".

 

Source: Wiley Online Library  
Authors: Ana C. Franco et al.
DOI: https://doi.org/10.1111/fog.12610

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Ventilation changes drive orbital-scale deoxygenation trends in the late Cretaceous ocean

Abstract. 

"Mechanisms that drive cyclicity in marine sediment deposits during hothouse climate periods in response to Earth’s orbit variations remain debated. Orbital cycles fingerprint in the oceanographic records results from the combined effect of terrestrial (e.g. weathering-derived nutrient supply, freshwater discharge) and oceanic (e.g. productivity, oxygenation) processes, whose respective contribution remains to be clarified. [...]".

 

Source: Geophysical Research Letters
Authors: Anta-Clarisse Sarr et al.
DOI: https://doi.org/10.1029/2022GL099830

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Variability of the oxygen minimum zone associated with primary productivity and hydrographic conditions in the Eastern North Pacific

Abstract. 

"The expansion of the oxygen minimum zone (OMZ) associated with global warming has generated interest in its variability during the last two millennia. Several oceanographic mechanisms, as advection of dissolved oxygen and depletion of dissolved oxygen by oxidation of exported marine productivity, could explain the variability of δ15N in organic matter as a denitrification indicator of the water column in the Pacific Ocean. Our objective was to infer local or remote forcing mechanisms that lead to the strengthening or weakening of the OMZ in the Eastern Tropical North Pacific. [...]". 

 

Source: Science Direct 
Authors: Alberto Sánchez et al.
DOI: https://doi.org/10.1016/j.dsr.2022.103810

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Ironstone as a proxy of Paleozoic ocean oxygenation

Abstract. 

"Marine ironstone is a Phanerozoic biochemical sedimentary rock that contains abundant primary iron. Although rare, ironstone is conspicuous in the Paleozoic sedimentary record. Its iron source remains contentious, with traditional models invoking a continentally derived source. Increasing sedimentologic evidence suggests that many Paleozoic ironstones formed along favourably oriented continental margins where coastal upwelling delivered ferruginous waters, with the postulated source of iron being deep-ocean hydrothermal fluids. [...]".

 

Source: Science Direct 
Authors: Edward J. Matheson et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117715

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LIP volcanism (not anoxia) tracked by Cr isotopes during Ocean Anoxic Event 2 in the proto-North Atlantic region

Abstract.

"Chromium is a redox sensitive element that exhibits a large range of isotopic compositions in Earth’s surface environments because of Cr(VI)-Cr(III) transformations. This property of Cr has been exploited as a tracer of Earth’s oxygenation history using marine sediments. However, paleoredox applications using Cr are difficult to implement due to its complicated cycling, which creates spatial variability in seawater δ53Cr values. Applications are further hindered by the potential for variability in the major inputs of Cr, such as submarine volcanism, to mask redox processes. [...]". 

 

Source: Science Direct 
Authors: Lucien Nana Yobo et al.
DOI: https://doi.org/10.1016/j.gca.2022.06.016

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Continental configuration controls ocean oxygenation during the Phanerozoic

Abstract. 

"The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O2]) in the ocean. In turn, [O2] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO2). Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O2]. [...]". 

 

Source: Nature
Authors: Alexandre Pohl et al.
DOI: https://doi.org/10.1038/s41586-022-05018-z 

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Low oxygen levels with high redox heterogeneity in the late Ediacaran shallow ocean: Constraints from I/(Ca + Mg) and Ce/Ce* of the Dengying Formation

Abstract. 

"Most previous studies focused on the redox state of the deep water, leading to an incomplete understanding of the spatiotemporal evolution of the redox-stratified ocean during the Ediacaran–Cambrian transition. In order to decode the redox condition of shallow marine environments during the late Ediacaran, this study presents I/(Ca + Mg), carbon and oxygen isotope, major, trace, and rare earth element data of subtidal to peritidal dolomite from the Dengying Formation at Yangba, South China. [...]".

 

Source: Wiley Online Library
Authors: Yi Ding et al.
DOI: https://doi.org/10.1111/gbi.12520

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Major sulfur cycle perturbations in the Panthalassic Ocean across the Pliensbachian-Toarcian boundary and the Toarcian Oceanic Anoxic Event

Abstract. 

"The early Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) was characterized by marine deoxygenation and the burial of organic-rich sediments at numerous localities worldwide. However, the extent of marine anoxia and its impact on the sulfur cycle during the T-OAE is currently poorly understood. Here, stable sulfur isotopes of reduced metal-bound sulfur (δ34Spyrite) and pyrite sulfur concentrations (SPY) have been analyzed across the Pliensbachian-Toarcian boundary (Pl-To) and the T-OAE from the Sakahogi and Sakuraguchi-dani sections (Japan), which were deposited in the deep and shallow Panthalassic Ocean, respectively. [...]".

 

Source: Science Direct 
Authors: Wenhan Chen et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103884

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The Fate of Oxygen in the Ocean and Its Sensitivity to Local Changes in Biological Production

Abstract. 

"We investigate the sensitivity of the oxygen content and true oxygen utilization of key low-oxygen regions Ω to pointwise changes in biological production. To understand how the combined water and biogenic particle transport controls the sensitivity patterns and the fate of oxygen in the ocean, we develop new relationships that link the steady-state oxygen content and deficit of Ω to the downstream and upstream oxygen utilization rate (OUR), respectively. We find that the amount of oxygen from Ω that will be lost per unit volume at point r is linked to OUR(r) through the mean oxygen age accumulated in Ω. [...]".

 

Source: Wiley Online Library 
Authors: Mark Holzer
DOI: https://doi.org/10.1029/2022JC018802

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Intensive peatland wildfires during the Aptian–Albian oceanic anoxic event 1b: Evidence from borehole SK-2 in the Songliao Basin, NE China

Abstract. 

"The Cretaceous has been considered a “high-fire” world accompanied by widespread by-products of combustion in the rock record. The mid-Cretaceous oceanic anoxic event 1b (OAE1b) is marked by one of the major perturbations in the global carbon cycle characterized by deposition of organic-rich sediments in both marine and terrestrial settings. However, our understanding is still limited on changes in wildfire activity during OAE1b period. [...]".

 

Source: Science Direct 
Authors: Zhi-Hui Zhang et al.
DOI: https://doi.org/10.1016/j.jop.2022.06.002

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Mo isotope composition of the 0.85 Ga ocean from coupled carbonate and shale archives: Some implications for pre-Cryogenian oxygenation

Abstract.

"This study addresses marine palaeoredox conditions of the mid-Neoproterozoic by analysing the Mo isotope, trace element, and U-Th-Pb isotope compositions of shallow water microbial carbonate, deep water pelagic carbonate, and shale from the Stone Knife Formation (SKF) in NW Canada. The U-Th-Pb isotope SKF systematics of reef microbialite carbonates, and the moderately expressed negative Ce anomalies are consistent with the presence of dissolved O2 in the surface waters. [...]".

 

Source: Science Direct 
Authors: Edel Mary O'Sullivan et al.
DOI: https://doi.org/10.1016/j.precamres.2022.106760

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Nitrogen isotope evidence for oxygenated upper ocean during the Cryogenian interglacial period

Abstract.

"The Cryogenian interglacial period have witnessed dramatic changes in climate, oceanic environment and biological evolution. The nitrogen isotopic composition, as an important biogeochemical proxy, has the potential to track both the nutrient cycling and redox conditions in the past. However, nitrogen isotopic data during this interglacial time is rather limited. Here, we present integrated data for nitrogen isotopes (δ15N), as well as organic carbon isotopes (δ13Corg), iron (Fe) speciation, pyrite morphology and trace elements from the Cryogenian interglacial Datangpo Formation derived from a drill core from South China to figure out the nitrogen cycling and coeval redox states. [...]". 

 

Source: Science Direct 
Authors: Guangyou Zhu et al.
DOI: https://doi.org/10.1016/j.chemgeo.2022.120929

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Isotopic evidence for changes in the mercury and zinc cycles during Oceanic Anoxic Event 2 in the northwestern Tethys, Austria

Abstract. 

"The Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE 2, ca. 94 Ma) was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. Widespread deposition of organic-rich shales during OAE 2 has been attributed to a rapid rise in atmospheric CO2, global heating, and marine anoxia triggered by intense large igneous province (LIP) volcanism. Here, we present new Hg and Zn elemental and isotopic analyses from samples spanning OAE 2 in a hemipelagic section from Rehkogelgraben, Austria, which was part of the north-western Tethys. [...]".

 

Source: Science Direct 
Authors: Hanwei Yao et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103881

Read the full article here.


Uranium isotope reconstruction of ocean deoxygenation during OAE 2 hampered by uncertainties in fractionation factors and local U-cycling

Abstract. 

"A δ238U record of changing ocean anoxia during OAE 2 is reconstructed using seawater derived U in pelagic marine sediments in the Portland #1 core in the south-central region of the Western Interior Seaway of North America. The peak negative excursion of 1.4‰ in authigenic sedimentary δ238U values is consistent with expansion of marine anoxia during the event, but the size of the shift is much larger than the negative excursions recorded in two other published records. [...]". 

 

Source: Science Direct 
Authors: Brayden S. McDonald et al.
DOI: https://doi.org/10.1016/j.gca.2022.05.010

Read the full article here.


Geochemical evidence from the Kioto Carbonate Platform (Tibet) reveals enhanced terrigenous input and deoxygenation during the early Toarcian

Abstract.

"The early Toarcian, as registered in a variety of sedimentary archives, was characterized by an abrupt negative carbon-isotope excursion (CIE) typically superimposed on a long-term positive trend, and was accompanied by significant climatic and environmental changes. However, the changes in continental weathering influx and oceanic deoxygenation in shallow waters and their possible role in causing carbonate-platform crises in low latitudes remains poorly constrained. [...]".

 

Source: Science Direct 
Authors: Zhong Han et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103887

Read the full article here.


Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events

Abstract.

"Ocean mesoscale eddies have been identified as drivers of localized extremely low dissolved oxygen concentration ([O2]) conditions in the subsurface. We employ a global physical-biogeochemical ocean model at eddy-permitting resolution to conduct a census of open-ocean eddies near Eastern Boundary Upwelling Systems adjacent to tropical Oxygen Minimum Zones (OMZs). We track cyclonic and anticyclonic eddies with a surface signature over the period 1992–2018 and isolate their subsurface oxygen characteristics. We identify strongly deoxygenating eddies and quantify their contribution to low [O2] extreme events. [...]".

 

Source: Geophysical Research Letters
Authors: Jamie Atkins et al.
DOI: https://doi.org/10.1029/2022GL098672

Read the full article here.


Mercury stable isotopes suggest reduced foraging depth in oxygen minimum zones for blue sharks

Abstract. 

"Oxygen minimum zones (OMZs) are currently expanding across the global ocean due to climate change, leading to a compression of usable habitat for several marine species. Mercury stable isotope compositions provide a spatially and temporally integrated view of marine predator foraging habitat and its variability with environmental conditions. Here, we analyzed mercury isotopes in blue sharks Prionace glauca from normoxic waters in the northeastern Atlantic and from the world's largest and shallowest OMZ, located in the northeastern Pacific (NEP). [...]".

 

Source: Science Direct 
Authors: Gaël Le Croizier et al.
DOI: https://doi.org/10.1016/j.marpolbul.2022.113892

Read the full article here.


Decoupled oxygenation of the Ediacaran ocean and atmosphere during the rise of early animals

Abstract. 

"The Ediacaran Period (∼635 to 541 Ma) witnessed the early diversification and radiation of metazoans, in the form of the Ediacaran Biota. This biological revolution, beginning at ∼575 Ma, has been widely attributed to a temporally restricted episode of deeper ocean oxygenation, potentially caused by a contemporaneous rise in atmospheric oxygen levels. However, quantitative geochemical-record-driven estimates of Ediacaran atmospheric and oceanic redox evolution are lacking, and hence possible links between oceanic and atmospheric oxygenation remain speculative. [...]". 

 

Source: Science Direct 
Authors: Wei Shi et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117619

Read the full article here.


EBUS Conference 2022 - Registration

Registration is now open 

EBUS Conference: September 19 - 23, 2022 in Lima, Peru

"The Open Science Conference on Eastern Boundary Upwelling Systems (EBUS): Past, Present and Future and the Second International Conference on the Humboldt Current System are planned for September 19 - 23 in Lima, Peru. Although the conference aims to be in-person, options for virtual participation will be provided.

The meeting will bring together PhD students, early career scientists and world experts to understand, review, and synthesize what is known about dynamics, sensitivity, vulnerability and resilience of Eastern Boundary Upwelling Systems and their living resources to climate variability, change and extreme events."

Registration ("early bird" deadline: August 30, 2022).

For further information please visit the event's homepage.


Oxygen minimum zone copepods in the Arabian Sea and the Bay of Bengal: Their adaptations and status

Abstract.

"The Arabian Sea and the Bay of Bengal are cul-de-sacs of the northern Indian Ocean, and they contain more than half of the world's Oxygen Minimum Zones (OMZs). The current study reviews the vast and advancing literature on the oceanographic settings that lead to distinct OMZs in the Arabian Sea and the Bay of Bengal and links them with the copepods thriving there, their status, and likely adaptations. The Arabian Sea has a thicker perennial subsurface OMZ (∼1000 m) than the Bay of Bengal (∼500 m), which is linked to high plankton production via upwelling and winter convection in the former and river influx and mesoscale eddies in the latter. [...]."

 

Source: Science Direct 
Authors: Vidhya Vijayasenan et al.
DOI: https://doi.org/10.1016/j.pocean.2022.102839

Read the full article here.


Spatio-temporal variations in culturable bacterial community associated with denitrification in the Arabian Sea oxygen minimum zone

Abstract. 

"The Arabian Sea (AS) oxygen minimum zone (OMZ) is a site of intense denitrification, contributing to 20% of the global oceanic denitrification, playing a significant role in the nitrogen cycle. In this study, the structure and diversity of culturable bacterial communities inhabiting the water column of the AS OMZ were investigated through phylogenetic analysis and nitrate-utilizing ability was studied through culture-based studies. A total of 248 isolates collected during pre-monsoon and post-monsoon season were analysed for 16S rRNA gene sequences. [...]".

 

Source: Marine Biology Research
Authors: Ujwala Amberkar et al. 
DOI: 10.1080/17451000.2022.2086700

Read the full article here.


Oxygen availability driven trends in DOM molecular composition and reactivity in a seasonally stratified fjord

Abstract. 

"Ocean deoxygenation could potentially trigger substantial changes in the composition and reactivity of dissolved organic matter (DOM) pool, which plays an important role in the global carbon cycle. To evaluate links between DOM dynamics and oxygen availability, we investigated the DOM composition under varying levels of oxygen in a seasonally hypoxic fjord through a monthly time-series over two years. We used ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to characterize DOM on a molecular level. [...]".

 

Source: Science Direct 
Authors: Xiao Chen et al.
DOI: https://doi.org/10.1016/j.watres.2022.118690

Read the full article here.


Enhanced phosphorus recycling during past oceanic anoxia amplified by low rates of apatite authigenesis

Abstract.

"Enhanced recycling of phosphorus as ocean deoxygenation expanded under past greenhouse climates contributed to widespread organic carbon burial and drawdown of atmospheric CO2. Redox-dependent phosphorus recycling was more efficient in such ancient anoxic marine environments, compared to modern anoxic settings, for reasons that remain unclear. Here, we show that low rates of apatite authigenesis in organic-rich sediments can explain the amplified phosphorus recycling in ancient settings as reflected in highly elevated ratios of organic carbon to total phosphorus. [...]".

 

Source: Science Advances 
Authors: Nina M. Papadomanolaki et al.
DOI: 10.1126/sciadv.abn2370

Read the full article here.


Competing and accelerating effects of anthropogenic nutrient inputs on climate-driven changes in ocean carbon and oxygen cycles

Abstract. 

"Nutrient inputs from the atmosphere and rivers to the ocean are increased substantially by human activities. However, the effects of increased nutrient inputs are not included in the widely used CMIP5 Earth system models, which introduce bias into model simulations of ocean biogeochemistry. Here, using historical simulations by an Earth system model with perturbed atmospheric and riverine nutrient inputs, we show that the contribution of anthropogenic nutrient inputs to past global changes in ocean biogeochemistry is of similar magnitude to the effect of climate change. [...]". 

 

Source: Science Advances
Authors: Akitomo Yamamoto et al. 
DOI: 10.1126/sciadv.abl9207

Read the full article here.


Constraints on Early Paleozoic deep-ocean oxygen concentrations from the iron geochemistry of the Bay of Islands ophiolite

Abstract. 

"The deep ocean is generally considered to have changed from anoxic in the Precambrian to oxygenated by the Late Paleozoic (∼420–400 Ma) due to changes in atmospheric oxygen concentrations. When the transition occurred, that is, in the Early Paleozoic or not until the Late Paleozoic, is less well constrained. To address this, we measured Fe3+/ΣFe of volcanic rocks, sheeted dykes, gabbros, and ultramafic rocks from the Early Paleozoic (∼485 Ma) Bay of Islands (BOI) ophiolite as a proxy for hydrothermal alteration in the presence or absence of O2 derived from deep marine fluids. [...]".

 

Source: Geochemistry, Geophysics, Geosystems 
Authors: Daniel A. Stolper et al. 
DOI: https://doi.org/10.1029/2021GC010196

Read the full article here.


Deglacial restructuring of the Eastern equatorial Pacific oxygen minimum zone

Abstract. 

"Oxygenation in the Eastern Equatorial Pacific is responsive to ongoing climate change in the modern ocean, although whether the region saw a deglacial change in extent or position of the Oxygen Minimum Zone remains poorly constrained. Here, stable isotopes from the shells of an Oxygen Minimum Zone-dwelling planktic foraminifer are used to reassess the position of the mid-water Oxygen Minimum Zone relative to both the thermocline and benthos. Oxygen isotopes record a rapid shoaling of the Oxygen Minimum Zone towards the thermocline associated with Heinrich Stadial 1 and persisting through the deglaciation. [...]". 

 

Source: Communications Earth & Environment
Authors: Catherine V. Davis
DOI: https://doi.org/10.1038/s43247-022-00477-8

Read the full article here.


Linkage of the late Cambrian microbe-metazoan transition (MMT) to shallow-marine oxygenation during the SPICE event

Abstract.

"Microbe-metazoan transitions (MMTs), representing a switch from microbe-mediated to metazoan-mediated carbonate production, have been linked to major changes in Earth-surface conditions. The ‘late Cambrian MMT’ (nomen novum), during which microbial reefs were replaced by maceriate and lithistid sponge reefs, coincided with a sharp rise in atmospheric O2 levels attributed to the Steptoean Positive Carbon Isotope Excursion (SPICE) at ~497–494 Ma. However, relationships between atmospheric oxygenation, marine redox conditions, and the MMT have not been thoroughly investigated to date. [...]". 

 

Source: Science Direct 
Authors: Lei Zhang et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103798

Read the full article here.


Insights into prokaryotic community and its potential functions in nitrogen metabolism in the Bay of Bengal, a pronounced Oxygen Minimum Zone

Abstract. 

"Ocean oxygen minimum zones (OMZs) around the global ocean are expanding both horizontally and vertically. Multiple studies have identified the significant influence of anoxic conditions (≤1 μM O2) on marine prokaryotic communities and biogeochemical cycling of elements. However, little attention has been paid to the expanding low-oxygen zones where the oxygen level is still above the anoxic level. Here, we studied the abundance and taxonomic and functional profiles of prokaryotic communities in the Bay of Bengal (BoB), where the oxygen concentration is barely above suboxic level (5 μM O2). [...]". 

 

Source: Microbiology Spectrum
Authors: Bowei Gu et al. 
DOI: https://doi.org/10.1128/spectrum.00892-21

Read the full article here.


Reactive oxygen species in the world ocean and their impacts on marine ecosystems

Abstract. 

"Reactive oxygen species (ROS) are omnipresent in the ocean, originating from both biological (e.g., unbalanced metabolism or stress) and non-biological processes (e.g. photooxidation of colored dissolved organic matter). ROS can directly affect the growth of marine organisms, and can also influence marine biogeochemistry, thus indirectly impacting the availability of nutrients and food sources. Microbial communities and evolution are shaped by marine ROS, and in turn microorganisms influence steady-state ROS concentrations by acting as the predominant sink for marine ROS. [...]".

 

Source: Science Direct 
Authors: J. Jeffrey Morris et al.
DOI: https://doi.org/10.1016/j.redox.2022.102285

Read the full article here.


Ostracod response to monsoon and OMZ variability over the past 1.2 Myr

Abstract. 

"We present the first continuous middle through late Pleistocene record of fossil ostracods from the Maldives in the northern Indian Ocean, derived from sediment cores taken at Site U1467 by Expedition 359 of the International Ocean Discovery Program (IODP). Site U1467 lies at 487 m water depth in the Inner Sea of the Maldives archipelago, an ideal place for studying the effects of the South Asian Monsoon (SAM) system on primary productivity, intermediate depth ocean circulation, and the regional oxygen minimum zone (OMZ). [...]". 

 

Source: Science Direct 
Authors: Carlos A. Alvarez Zarikian et al.
DOI: https://doi.org/10.1016/j.marmicro.2022.102105

Read the full article here.


Biotic induction and microbial ecological dynamics of Oceanic Anoxic Event 2

Abstract. 

"Understanding the causal mechanisms of past marine deoxygenation is critical to predicting the long-term Earth systems response to climate change. However, the processes and events preceding widespread carbon burial coincident with oceanic anoxic events remain poorly constrained. Here, we report a comprehensive biomarker inventory enveloping Oceanic Anoxic Event 2 that captures microbial communities spanning epipelagic to benthic environments in the southern proto-North Atlantic Ocean. We identify an abrupt, sustained increase in primary productivity that predates Oceanic Anoxic Event 2 by ∼220 ± 4 thousand years, well before other geochemical proxies register biogeochemical perturbations. [...]". 

 

Source: Communications Earth & Environment 
Authors: Gregory T. Connock et al. 
DOI: https://doi.org/10.1038/s43247-022-00466-x 

Read the full article here.


Oceanic anoxia and extinction in the latest Ordovician

Abstract.

"The Late Ordovician (Hirnantian) mass extinction (LOME) was marked by two discrete pulses of high species turnover rates attributed to glacial cooling (LOME-1) and subsequent expansion of anoxic marine conditions (LOME-2). However, the mechanisms and extent of global marine anoxia remain controversial. In this study, we present uranium isotope (U) data from a new Ordovician-Silurian (O-S) boundary carbonate section in the Southwest China to explore the extent/duration of the global marine anoxia, and links to the LOME. [...]". 

 

Source: Science Direct 
Authors: Mu Liu et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117553

Read the full article here.


On anomalously high sub-surface dissolved oxygen in the Indian sector of the Southern Ocean

Abstract.

"The Southern Ocean (SO) plays a critical role in global ocean productivity and carbon cycling. Bio-Argo floats deployed in the Indian sector of the Southern Ocean provides new insights into the biogeochemical processes. Here we report significantly higher dissolved oxygen (DO) (~ 310 μmol/kg) in summer of 2014–2015 for one float (F1) and winter of 2014 in other float (F2) at sub-surface layer in the subantarctic region of the SO. The summer DO peak in F1 was 10% higher than those during the summer of succeeding year, while the winter DO peak in F2 was 20% higher than those during the winter of succeeding year. [...]".

 

Source: Journal of Oceanography 
Authors: Prince Prakash et al.
DOI: https://doi.org/10.1007/s10872-022-00644-7 

Read the full article here.


Coastlines at Risk of Hypoxia From Natural Variability in the Northern Indian Ocean

Abstract. 

"Coastal hypoxia—harmfully low levels of oxygen—is a mounting problem that jeopardizes coastal ecosystems and economies. The northern Indian Ocean is particularly susceptible due to human-induced impacts, vast naturally occurring oxygen minimum zones, and strong variability associated with the seasonal monsoons and interannual Indian Ocean Dipole (IOD). We assess how natural factors influence the risk of coastal hypoxia by combining a large set of oxygen measurements with satellite observations to examine how the IOD amplifies or suppresses seasonal hypoxia tied to the Asian Monsoon. We show that on both seasonal and interannual timescales hypoxia is controlled by wind- and coastal Kelvin wave-driven upwelling of oxygen-poor waters onto the continental shelf and reinforcing biological feedbacks (increased subsurface oxygen demand). [...]".

 

Source: Global Biogeochemical Cycles
Authors: Jenna Pearson et al.
DOI: https://doi.org/10.1029/2021GB007192

Read the full article here.


Trace elements V, Ni, Mo and U: A geochemical tool to quantify dissolved oxygen concentration in the oxygen minimum zone of the north-eastern Pacific

Abstract.

"Deoxygenation of the water column in the oceans and in the oxygen minimum zone (OMZ) has become relevant due to its connection with global climate change. The variability of the OMZ has been inferred by in situ measurements for the last 70 years and qualitatively assessed through the monitoring of trace elements and the nitrogen stable isotope ratio (δ15N) of organic matter on several time scales. The V, Ni, Mo and U concentrations in surface sediments and the dissolved oxygen concentration in the water column of La Paz Bay and the Mazatlán margin were used to propose an exponential regression model. This model will allow the inference of the dissolved oxygen concentration in the sedimentary records from the Alfonso Basin in La Paz Bay and in the Mazatlán margin over the last 250 years. [...]".

 

Source: Science Direct
Authors: Alberto Sánchez et al. 
DOI: https://doi.org/10.1016/j.jmarsys.2022.103732

Read the full article here.


Widespread oxyregulation in tropical corals under hypoxia

Abstract. 

"Hypoxia (low oxygen stress) is increasingly reported on coral reefs, caused by ocean deoxygenation linked to coastal nutrient pollution and ocean warming. While the ability to regulate respiration is a key driver of hypoxia tolerance in many other aquatic taxa, corals' oxyregulatory capabilities remain virtually unexplored. Here, we examine O2-consumption patterns across 17 coral species under declining O2partial pressure (pO2). All corals showed ability to oxyregulate, but total positive regulation (Tpos) varied between species, ranging from 0.41 (Pocillopora damicornis) to 2.42 (P. acuta). [...]".

 

Source: Science Direct 
Authors: David J. Hughes et al.
DOI: https://doi.org/10.1016/j.marpolbul.2022.113722

Read the full article here.


Marine anoxia linked to abrupt global warming during Earth’s penultimate icehouse

Abstract.

"Piecing together the history of carbon (C) perturbation events throughout Earth’s history has provided key insights into how the Earth system responds to abrupt warming. Previous studies, however, focused on short-term warming events that were superimposed on longer-term greenhouse climate states. Here, we present an integrated proxy (C and uranium [U] isotopes and paleo CO2) and multicomponent modeling approach to investigate an abrupt C perturbation and global warming event (∼304 Ma) that occurred during a paleo-glacial state. We report pronounced negative C and U isotopic excursions coincident with a doubling of atmospheric CO2 partial pressure and a biodiversity nadir. [...]".

 

Source: Proceedings of the National Academy of Sciences
Authors: Jitao Chen et al.
DOI: https://doi.org/10.1073/pnas.2115231119

Read the full article here.


Geochemistry of sediments in contact with oxygen minimum zone of the eastern Arabian Sea: Proxy for palaeo-studies

Abstract. 

"The Arabian Sea encompasses oxygen minimum zone with denitrifying conditions. For the present study, sediments were collected across three transects off Goa transect (GT), Mangalore transect (MT) and Kochi transect (KT) in contact with water column dissolved oxygen (DO) range of 1.4–118.0 µM. Sediments were investigated for texture, clay mineralogy, total organic carbon (Corg), total nitrogen, CaCO3, δ15N, δ13C, metal content to infer their distribution with changing DO and their use as possible palaeo-proxies. The Corg (0.9–8.6%) is largely marine and δ15N from GT and MT preserves signatures of higher water column denitrification. [...]". 

 

Source: Journal of Earth System Science 

Authors: Pratima M. Kessarkar et al. 

DOI: https://doi.org/10.1007/s12040-022-01823-2 

Read the full article here.


Anaerobic methane oxidation in a coastal oxygen minimum zone: spatial and temporal dynamics

Abstract. 

"Coastal waters are a major source of marine methane to the atmosphere. Particularly high concentrations of this potent greenhouse gas are found in anoxic waters, but it remains unclear if and to what extent anaerobic methanotrophs mitigate the methane flux. Here we investigate the long-term dynamics in methanotrophic activity and the methanotroph community in the coastal oxygen minimum zone (OMZ) of Golfo Dulce, Costa Rica, combining biogeochemical analyses, experimental incubations and 16S rRNA gene sequencing over 3 consecutive years. [...]".

 

Source: Environmental Microbiology

Authors: Herdís G. R. Steinsdóttir et al. 

DOI: https://doi.org/10.1111/1462-2920.16003

Read the full article here.


Sensitivity of Global Ocean Deoxygenation to Vertical and Isopycnal Mixing in an Ocean Biogeochemistry Model

Abstract. 

"Large-scale loss of oxygen under global warming is termed “ocean deoxygenation” and is caused by the imbalance between physical supply and biological consumption of oxygen in the ocean interior. Significant progress has been made in the theoretical understanding of ocean deoxygenation; however, many questions remain unresolved. The oxygen change in the tropical thermocline is poorly understood, with diverging projections among different models. Physical oxygen supply is controlled by a suite of processes that transport oxygen-rich surface waters into the interior ocean, which is expected to weaken due to increasing stratification under global warming. [...]".

 

Source: Wiley Online Library

Authors: Taka Ito et al.

DOI: https://doi.org/10.1029/2021GB007151

Read the full article here.


Marine anoxia as a trigger for the largest Phanerozoic positive carbon isotope excursion: Evidence from carbonate barium isotope record

Abstract. 

"The mid-Ludfordian Lau carbon isotope excursion (Lau CIE) represents the largest positive carbon isotope excursion in the Phanerozoic (~9‰), coincident with the biodiversity loss of many marine animal clades. Two main explanations for the Lau CIE are enhanced organic carbon burial via increased marine productivity and preservation-driven expansion of anoxia. While these two explanations are not mutually exclusive, the main driver of Lau CIE is yet to be constrained. Here, we resolve this longstanding debate using barium isotopes (δ138 Ba) of marine carbonates deposited across the Lau CIE. [...]". 

 

Source: Science Direct

Authors: Feifei Zhang et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117421

Read the full article here.


Temperature and oxygen supply shape the demersal community in a tropical Oxygen Minimum Zone

Abstract. 

"The organisms that inhabit Oxygen Minimum Zones (OMZ) have specialized adaptations that allow them to survive within a very narrow range of environmental conditions. Consequently, even small environmental perturbations can result in local species distribution shifts that alter ecosystem trophodynamics. Here, we examined the effect of changing sea water temperatures and oxygen levels on the physiological performance and metabolic traits of the species forming marine demersal communities along the OMZ margins in the Costa Rican Pacific. The strong temperature and oxygen gradients along this OMZ margin provide a “natural experiment” to explore the effects of warming and hypoxia on marine demersal communities. [...]".

 

Source: Environmental Biology of Fishes

Authors: Tayler M. Clarke et al. 

DOI: https://doi.org/10.1007/s10641-022-01256-2

Read the full article here.


Mid-Holocene intensification of the oxygen minimum zone in the northeastern Arabian Sea

Abstract. 

"The Arabian Sea is characterized by a strong Oxygen Minimum Zone (OMZ) bearing sub-oxic conditions at the intermediate water depth. We analyzed a sediment core near the upper margin of OMZ (174 m water depth) from offshore Saurashtra, northeastern (NE) Arabian Sea to reconstruct multi-proxy biogeochemical response in the area during the Early-Middle Holocene (∼10–4 ka before present). The results indicate lower foraminiferal productivity (both benthic and planktic) and weak sub-surface denitrification causing mild OMZ conditions at the study site during the early Holocene (∼10–8 ka). Subsequently, an increased foraminiferal productivity and sub-surface (both the water column and sediment) denitrification in the area led to intensified OMZ conditions during the mid-Holocene (after ∼8 ka). [...]".

 

Source: Science Direct

Authors: Syed Azharuddin et al. 

DOI: https://doi.org/10.1016/j.jseaes.2022.105094

Read the full article here.


Uranium isotope evidence for extensive shallow water anoxia in the early Tonian oceans

Abstract. 

"The Earth's redox evolution has been commonly assumed to have played a key role in shaping the evolutionary history of the biosphere. However, whether and how shifts in marine redox conditions are linked to key biotic events – foremost the rise of animals and the ecological expansion of eukaryotic algae in the late Proterozoic oceans – remains heavily debated. Our current picture of global marine redox evolution during this critical interval is incomplete. This is particularly the case for the Tonian Period (∼1.0 to ∼0.717 Ga), when animals may have diverged and when eukaryotic algae began their rise in ecological importance. Here, we present new uranium isotope (U) measurements from Tonian carbonates to fill this outstanding gap. [...]".

 

Source: Science Direct 

Authors: Feifei Zhang et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117437

Read the full article here.


Placing North Pacific paleo-oxygenation records on a common scale using multivariate analysis of benthic foraminiferal assemblages

Abstract. 

"Dysoxic events are well-studied in Pleistocene and Holocene marine sediment records from the North Pacific using faunal, sedimentological, and geochemical paleo-oxygenation proxies. However, differences in proxy sensitivity and local conditions make it difficult to quantify the relative severity of dysoxia across the North Pacific. Here, we use multivariate analyses of taxonomically standardized benthic foraminiferal assemblages to quantitatively compare the severity and duration of dysoxic events at four intermediate depth sites within oxygen minimum zones in the Gulf of Alaska (GoA), Santa Barbara Basin, and Baja California Sur. Unlike previous faunal dissolved oxygen indices, the metric developed here incorporates the total faunal assemblage and is better correlated with co-registered geochemical proxies. [...]". 

 

Source: Science Direct

Authors: Sharon Sharon et al.

DOI: https://doi.org/10.1016/j.quascirev.2022.107412

Read the full article here.


Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers

Abstract. 

"Understanding species’ responses to upwelling may be especially important in light of ongoing environmental change. Upwelling frequency and intensity are expected to increase in the future, while ocean acidification and deoxygenation are expected to decrease the pH and dissolved oxygen (DO) of upwelled waters. However, the acute effects of a single upwelling event and the integrated effects of multiple upwelling events on marine organisms are poorly understood. Here, we use in situ measurements of pH, temperature, and DO to characterize the covariance of environmental conditions within upwelling-dominated kelp forest ecosystems. We then test the effects of acute (0–3 days) and chronic (1–3 months) upwelling on the performance of two species of kelp forest grazers, the echinoderm, Mesocentrotus franciscanus, and the gastropod, Promartynia pulligo. We exposed organisms to static conditions in a regression design to determine the shape of the relationship between upwelling and performance and provide insights into the potential effects in a variable environment. We found that respiration, grazing, growth, and net calcification decline linearly with increasing upwelling intensity for Mfrancicanus over both acute and chronic timescales. [...]".

 

Source: Wiley Online Library

Authors: Emily M. Donham et al. 

DOI: https://doi.org/10.1111/gcb.16125

Read the full article here.


Extensive marine anoxia in the European epicontinental sea during the end-Triassic mass extinction

Abstract. 

"Warming-induced marine anoxia has been hypothesized as an environmental stressor for the end-Triassic mass extinction (ETME), but links between the spread of marine anoxia and the two phases of extinction are poorly constrained. Here, we report iron speciation and trace metal data from the Bristol Channel Basin and Larne Basin of the NW European epicontinental sea (EES), spanning the Triassic–Jurassic (T–J) transition (~ 202–200 Ma). Results show frequent development of anoxic-ferruginous conditions, interspersed with ephemeral euxinic episodes in the Bristol Channel Basin during the latest Rhaetian, whereas the contemporaneous Larne Basin remained largely oxygenated, suggesting heterogeneous redox conditions between basins. Subsequently, more persistent euxinic conditions prevailed across the T–J boundary in both basins, coinciding precisely with the second phase of the ETME. [...]". 

 

Source: Science Direct

Authors: Tianchen He et al. 

DOI: https://doi.org/10.1016/j.gloplacha.2022.103771

Read the full article here.


Mid-Cretaceous marine Os isotope evidence for heterogeneous cause of oceanic anoxic events

Abstract. 

"During the mid-Cretaceous, the Earth experienced several environmental perturbations, including an extremely warm climate and Oceanic Anoxic Events (OAEs). Submarine volcanic episodes associated with formation of large igneous provinces (LIPs) may have triggered these perturbations. The osmium isotopic ratio (187Os/188Os) is a suitable proxy for tracing hydrothermal activity associated with the LIPs formation, but 187Os/188Os data from the mid-Cretaceous are limited to short time intervals. Here we provide a continuous high-resolution marine 187Os/188Os record covering all mid-Cretaceous OAEs. Several OAEs (OAE1a, Wezel and Fallot events, and OAE2) correspond to unradiogenic 187Os/188Os shifts, suggesting that they were triggered by massive submarine volcanic episodes. However, minor OAEs (OAE1c and OAE1d), which do not show pronounced unradiogenic 187Os/188Os shifts, were likely caused by enhanced monsoonal activity. [...]".

 

Source: Nature Communications 

Authors: Hironao Matsumoto et al.

DOI: https://doi.org/10.1038/s41467-021-27817-0

Read the full article here.


Chromium isotope evidence for oxygenation events in the Ediacaran ocean

Abstract. 

"Pulses of the Ediacaran ocean oxygenation were inferred from strong enrichments of redox-sensitive elements (RSEs; particularly Mo, V, U, Re) and negative pyritesulfur isotopes (δ34Spy) in black shales of the Doushantuo Formation in South China. These oceanic oxygenation events (OOEs) have been challenged by the lack of comparable RSE enrichments in correlative strata of northwestern Canada. Here we report four positive chromium isotope (δ53Cr) excursions with peak values (+0.79 ± 0.03‰ to +1.45 ± 0.06‰; 2SD) close to the average δ53Cr value of the modern ocean (+1.0 ± 0.3‰) at the intervals of OOEs, which are separated by low δ53Cr values close to that of the bulk silicate Earth (BSE, −0.124 ± 0.101‰). The positive δ53Cr excursions could be explained by episodic input of oxygenated water from the open ocean to the restricted Nanhua basin, or pulses of ocean oxygenation during the Ediacaran-early Cambrian. The two interpretations can explain the majority of the geochemical data available from the Wuhe section, but both have limitations. [...]". 

 

Source: Science Direct

Authors: Dongtao Xu et al.

DOI: https://doi.org/10.1016/j.gca.2022.02.019

Read the full article here.


Evidence of hypoxia in the eastern coast of the Gulf of California as induced by stable nitrogen isotopes in surface sediments

Abstract. 

"The Gulf of California is a highly biodiverse marine basin located in the northeast Mexican Pacific Ocean. In the past three decades, this basin has experienced increased hypoxia in shallow waters, which threatens its coastal ecosystems. The aim of this study is to analyze δ15N and δ13C isotopes of organic matter in coastal sediments to characterize sources of primary production and shifts in biogeochemical processes that reflect increasing oxygen deficiency in the shallow coast of the eastern Gulf of California. Surface sediments samples were collected from 8 to 47 m deep along the coastal margin of Sinaloa and Sonora. This region is characterized by the development of anthropogenic activities, which could be the main source of organic matter evidenced in the marine environment. [...]". 

 

Source: Science Direct

Authors: Alberto Sánchez et al. 

DOI: https://doi.org/10.1016/j.csr.2022.104716

Read the full article here.


EBUS Conference 2022 - Call for Abstracts closing tomorrow

Call for Abstracts closing tomorrow

EBUS Conference: September 19 - 23, 2022, in Lima, Peru

This is a quick reminder that the abstract submission deadline for the EBUS Conference 2022 ends tomorrow, May 7, 2022.

Please visit the event's homepage for further information. 


Observed denitrification in the northeast Arabian Sea during the winter-spring transition of 2009

Abstract. 

"The central and northeast Arabian Sea (AS) has an intense and thick oxygen minimum zone (OMZ) and denitrification zone. It is comparable with the strongest OMZ of the north-equatorial Pacific Ocean. Denitrification in the AS is revisited using a set of cruise observations collected during February–March of 2009 by the Centre for Marine Living Resources, India. The region possesses one of the most robust N* depleted water reaching as low as -20 μmol l−1 at depths (~600 m). In AS, the oxygen depletion is mainly due to sluggish circulation, weak lateral and vertical ventilation. The biological respiration in oxygen deficit condition depletes nitrate and further modifies the Redfield ratio at intermediate depths (200-600 m) from 16N:1P to 8N:1P. [...]".

 

Source: Science Direct

Authors: Anju Mallissery et al.

DOI: https://doi.org/10.1016/j.jmarsys.2021.103680

Read the full article here.


Oxygen gradients shape the unique structure of picoeukaryotic communities in the Bay of Bengal

Abstract. 

"Picoeukaryotic communities respond rapidly to global climate change and play an important role in marine biological food webs and ecosystems. The formation of oxygen minimum zones (OMZ) is facilitated by the stratification of seawater and higher primary production in the surface layer, and the marine picoeukaryotic community this low-oxygen environment is topic of interest. To better understand the picoeukaryotic community assembly mechanisms in an OMZ, we collected samples from the Bay of Bengal (BOB) in October and November 2020 and used 18S rDNA to study the picoeukaryotic communities and their community assembly mechanisms that they are controlled by in deep-sea and hypoxic zones. The results show that deterministic and stochastic processes combine to shape picoeukaryotic communities in the BOB. [...]".

 

Source: Science Direct

Authors: Zhuo Chen et al.

DOI: https://doi.org/10.1016/j.scitotenv.2021.152862

Read the full article here.


Covariation of Deep Antarctic Pacific Oxygenation and Atmospheric CO2 during the Last 770 kyr

Abstract. 

"We present new geochemical evidence of changes in oxygenation of the deep Antarctic Pacific over the last 770 kyr. Our data are derived from redox-sensitive metals and export production proxies extracted from gravity core ANT34/A2-10 at 4217 m water depth. Our results show that oxygen levels in the deep Antarctic Zone (AZ) varied in line with the release of deeply sequestered remineralized carbon to the atmosphere during glacial–interglacial (G–IG) cycles, with lower oxygen concentrations and more carbon storage during glacial periods. Subsequent reductions in the amount of carbon stored at depth were closely associated with improved ventilation during glacial terminations. [...]".

 

Source: Lithosphere

Authors: Zheng Tang et al. 

DOI: https://doi.org/10.2113/2022/1835176

Read the full article here.


Sensitivity of asymmetric oxygen minimum zones to mixing intensity and stoichiometry in the tropical Pacific using a basin-scale model

Abstract.

"The tropical Pacific Ocean holds the two largest oxygen minimum zones (OMZs) in the world's oceans, showing a prominent hemispheric asymmetry, with a much stronger and broader OMZ north of the Equator. However, many models have difficulties in reproducing the observed asymmetric OMZs in the tropical Pacific. Here, we apply a fully coupled basin-scale model to evaluate the impacts of stoichiometry and the intensity of vertical mixing on the dynamics of OMZs in the tropical Pacific. We first utilize observational data of dissolved oxygen (DO) to calibrate and validate the basin-scale model. Our model experiments demonstrate that enhanced vertical mixing combined with a reduced O:C utilization ratio can significantly improve our model capability of reproducing the asymmetric OMZs. Our study shows that DO concentration is more sensitive to biological processes over 200–400 m but to physical processes below 400 m. [...]".

 

Source: Geoscientific Model Development 

Authors: Kai Wang et al. 

DOI: https://doi.org/10.5194/gmd-15-1017-2022 

Read the full article here.


A transient oxygen increase in the Mesoproterozoic ocean at ∼1.44 Ga: Geochemical evidence from the Tieling Formation, North China Platform

Abstract.

"Oxygen availability is crucial for the evolution of eukaryotes in geological history, yet detailed Mesoproterozoic oceanic-atmospheric redox conditions remain enigmatic. In contrast to the generally accepted hypothesis of an anoxic mid-Proterozoic ocean and atmosphere, several transient oxygenation events may occur at the Earth’s surface during the Mesoproterozoic, especially for the period around 1.4 Ga. The North China Platform develops one of the most complete and continuous Mesoproterozoic stratigraphic successions globally, preserving key information on the redox state of the surface ocean–atmosphere system during the mid-Proterozoic. [...]".

 

Source: Science Direct

Authors: Yang Yu et al.

DOI: https://doi.org/10.1016/j.precamres.2021.106527

Read the full article here.


Calculating dissolved marine oxygen values based on an enhanced Benthic Foraminifera Oxygen Index

Abstract. 

"Marine oxygen minimum zones (OMZs) trap greenhouse gases, reduce livable habitats, a critical factor for these changes is the amount of dissolved oxygen (DO). The frequently used tool to reconstruct DO values, the Benthic Foraminifera Oxygen Index (BFOI), showed major shortcomings and lacks effectiveness. Therefore, we enhanced the BFOI and introduce enhanced BFOI (EBFOI) formulas by using all available data benthic foraminifers provide, calculating the whole livable habitat of benthic foraminifers, including bottom water oxygenation (BWO) and pore water oxygenation (PWO). Further, we introduce for the first time a transfer function to convert EBFOI vales directly into DO values, increasing efficiency by up to 38%. [...]".

 

Source: Nature Scientific Reports

Authors: Matthias Kranner et al. 

DOI: https://doi.org/10.1038/s41598-022-05295-8

Read the full article here.


Major Early-Middle Devonian oceanic oxygenation linked to early land plant evolution detected using high-resolution U isotopes of marine limestones

Abstract.

"The middle Paleozoic (∼420-350 Myr) records a major increase in ocean-atmosphere oxygen levels; however, the timing and pattern of oxygenation are poorly constrained. Two well-dated North American locations in Nevada and Illinois were used to generate a high-resolution U-isotopic profile (U) spanning ∼70 Myr of the middle Paleozoic. Stratigraphic and geochemical data support the interpretation that the Nevada profile represents a near-primary record of global-ocean redox variations. First-order U trends indicate strongly reducing oceans during the late Silurian and Early Devonian, terminated by a major oxygenation event near the Emsian-Eifelian boundary (∼395 Ma). More oxic seawater conditions persisted for the next 30+ Myr, but were punctuated by multiple Myr-scale anoxic events during the Middle-Late Devonian and Early Mississippian that correlate with known global biotic crises, positive C excursions, and widespread organic-rich facies deposition. [...]".

 

Source: Science Direct

Authors: Maya Elrick et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117410

Read the full article here.


Oxygen export to the deep ocean following Labrador Sea Water formation

Abstract.

"The Labrador Sea in the North Atlantic Ocean is one of the few regions globally where oxygen from the atmosphere can reach the deep ocean directly. This is the result of wintertime deep convection, which homogenizes the water column to a depth of up to 2000 m and brings deep water undersaturated in oxygen into contact with the atmosphere. In this study, we analyze how the intense oxygen uptake during Labrador Sea Water (LSW) formation affects the properties of the outflowing deep western boundary current, which ultimately feeds the upper part of the North Atlantic Deep Water layer in much of the Atlantic Ocean. [...]".

 

Source: Biogeosciences

Authors: Jannes Koelling et al. 

DOI: https://doi.org/10.5194/bg-19-437-2022

Read the full article here. 


GO-SHIP Easy Ocean: Gridded ship-based hydrographic section of temperature, salinity, and dissolved oxygen

Abstract.

"Despite technological advances over the last several decades, ship-based hydrography remains the only method for obtaining high-quality, high spatial and vertical resolution measurements of physical, chemical, and biological parameters over the full water column essential for physical, chemical, and biological oceanography and climate science. The Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) coordinates a network of globally sustained hydrographic sections. These data provide a unique data set that spans four decades, comprised of more than 40 cross-ocean transects. The section data are, however, difficult to use owing to inhomogeneous format. The purpose of this new temperature, salinity, and dissolved oxygen data product is to combine, reformat and grid these data measured by Conductivity-Temperature-Depth-Oxygen (CTDO) profilers in order to facilitate their use by a wider audience. [...]".

 

Source: Nature Scientific Data

Authors: Katsuro Katsumata et al.

DOI: https://doi.org/10.1038/s41597-022-01212-w

Read the full article here.


Responses of Horizontally Expanding Oceanic Oxygen Minimum Zones to Climate Change Based on Observations

Abstract.

"Due to climate change, global oceanic dissolved oxygen (DO) has been decreasing, and oxygen minimum zones (OMZs) have been expanding. Here, we estimate the annual global and regional OMZ areas using geostatistical regression combined with Monte Carlo. From 1960 to 2019, annual global OMZ20 (DO < 20 μmol/kg) and OMZ60 (DO < 60 μmol/kg) areas cover 5%–14% and 15%–32% of the global ocean, respectively. The global and most regional OMZ areas after the late 2000s were all significantly larger than those in previous years. [...]".

 

Source: Wiley Online Library 

Authors: Yuntao Zhou et al.

DOI: https://doi.org/10.1029/2022GL097724

Read the full article here.


EBUS Conference 2022 - Call for Abstracts

Call for Abstracts closing April 15, 2022

EBUS Conference: September 19 - 23, 2022 in Lima, Peru

"The Open Science Conference on Eastern Boundary Upwelling Systems (EBUS): Past, Present and Future and the Second International Conference on the Humboldt Current System are planned for September 19 - 23 in Lima, Peru. Although the conference aims to be in-person, options for virtual participation will be provided.

The meeting will bring together PhD students, early career scientists and world experts to understand, review, and synthesize what is known about dynamics, sensitivity, vulnerability and resilience of Eastern Boundary Upwelling Systems and their living resources to climate variability, change and extreme events."

Abstract submission (deadline: April 15, 2022).

For further information please visit the event's homepage.


Shallow ocean oxygen decline during the end-Triassic mass extinction

Abstract.

"The end-Triassic mass extinction (ETME) was associated with intensified deep-water anoxia in epicontinental seas and mid-depth waters, yet the absolute oxygenation state in the shallow ocean is uncharacterized. Here we report carbonate-associated iodine data from the peritidal Mount Sparagio section (Southern Italy) that documents the ETME (~ 200 Ma) in the western Tethys. We find a sharp drop in carbonate I/(Ca + Mg) ratios across the extinction horizon and persisting into the Early Jurassic. [...]".

 

Source: Science Direct

Authors: Tianchen He et al.

DOI: https://doi.org/10.1016/j.gloplacha.2022.103770

Read the full article here. 


Distribution and biomass of gelatinous zooplankton in relation to an oxygen minimum zone and a shallow seamount in the Eastern Tropical North Atlantic

Abstract.

"Physical and topographic characteristics can structure pelagic habitats and affect the plankton community composition. For example, oxygen minimum zones (OMZs) are expected to lead to a habitat compression for species with a high oxygen demand, while upwelling of nutrient-rich deep water at seamounts can locally increase productivity, especially in oligotrophic oceanic waters. Here we investigate the response of the gelatinous zooplankton (GZ) assemblage and biomass to differing oxygen conditions and to a seamount in the Eastern Tropical North Atlantic (ETNA) around the Cape Verde archipelago. [...]."

 

Source: Science Direct

Authors: Florian Lüskow et al. 

DOI: https://doi.org/10.1016/j.marenvres.2022.105566

Read the full article here. 


Biogeochemical feedbacks may amplify ongoing and future ocean deoxygenation: a case study from the Peruvian oxygen minimum zone

Abstract.

"A new box model is employed to simulate the oxygen-dependent cycling of nutrients in the Peruvian oxygen minimum zone (OMZ). Model results and data for the present state of the OMZ indicate that dissolved iron is the limiting nutrient for primary production and is provided by the release of dissolved ferrous iron from shelf and slope sediments. Most of the removal of reactive nitrogen occurs by anaerobic oxidation of ammonium where ammonium is delivered by aerobic organic nitrogen degradation. Model experiments simulating the effects of ocean deoxygenation and warming show that the productivity of the Peruvian OMZ will increase due to the enhanced release of dissolved iron from shelf and slope sediments. A positive feedback loop rooted in the oxygen-dependent benthic iron release amplifies, both, the productivity rise and oxygen decline in ambient bottom waters. [...]". 

 

Source: Biogeochemistry

Authors: Klaus Wallmann et al.

DOI: https://doi.org/10.1007/s10533-022-00908-w 

Read the full article here.


Oxygen minimum zone along the eastern Arabian Sea: Intra-annual variation and dynamics based on ship-borne studies

Abstract.

"The oxygen minimum zone (OMZ) in the eastern Arabian Sea (EAS, ∼6° to 21°N), within Indian Exclusive Economic Zone (EEZ), is mapped, for the first time, for one year through ten repeated ship-based observations between December 2017 and January 2019 at seven to ten stations along the 2000 m depth contour. On an annual basis, the OMZ (<20 µM oxygen) in the EAS varied between 60 and 1350 m; its thickness decreased from north to south. During the winter monsoon, the upper boundary of the OMZ in the north and south was deeper (150–160 m) than the central EAS (∼110 m). [...]".

 

Source: Science Direct

Authors: Sudheesh Valliyodan et al.

DOI: https://doi.org/10.1016/j.pocean.2022.102742

Read the full article here.


Chapter 13 - The crucial contribution of mixing to present and future ocean oxygen distribution

Abstract.

"The oxygen content of the ocean interior largely results from a balance between respiration and advective ventilation, with only a small contribution from mixing processes. However, two important characteristics, which are key to future oxygen distribution in the ocean, primarily depend on the strength of ocean mixing. The first relates to the oxygen minimum zones (OMZ), which are wide O2-deficient mesopelagic layers inhospitable to most marine macro-fauna. We illustrate how mixing intensity controls the volume[...]".

 

Source: Science Direct
Authors: Marina Lévy et al.
DOI: https://doi.org/10.1016/B978-0-12-821512-8.00020-7

Read the full article here.


Ocean acidification alters the nutritional value of Antarctic diatoms

Abstract.

"Primary production in the Southern Ocean is dominated by diatom-rich phytoplankton assemblages, whose individual physiological characteristics and community composition are strongly shaped by the environment, yet knowledge on how diatoms allocate cellular energy in response to ocean acidification (OA) is limited. Understanding such changes in allocation is integral to determining the nutritional quality of diatoms and the subsequent impacts on the trophic transfer of energy and nutrients.[...]".

 

Source: New Phytologist 
Authors: Rebecca J. Duncan et al.
DOI: https://doi.org/10.1111/nph.17868

Read the full article here.


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