Preprint: Hypoxia also occurs in small highly turbid estuaries: the example of the Charente (Bay of Biscay)
"The French coast facing the Bay of Biscay (north-east Atlantic) is characterised by the presence of small macrotidal and turbid estuaries, including the Charente, geographically located between the two large estuaries of the Gironde and the Loire (south-west France). Multi-year, multi-site, high-frequency water quality surveys have shown that the Loire, and to a lesser extent the Gironde, suffer from summer hypoxia. These observations raised the question of the possible occurrence of hypoxia, particularly in one of these small estuaries, the Charente, which flows into the Bay of Marennes-Oléron, the first oyster-producing area in France. [...]".
Authors: Sabine Schmidt & Ibrahima I. Diallo
Preprint: Driver of eustatic change during the early Aptian Oceanic Anoxic Event 1a (∼120 Ma)
"Sea-level changes exert an important control on oceanic circulation and climate evolution. Researchers have proposed that sea-level rise favored accumulation of sediments enriched in organic carbon during oceanic anoxic events (OAEs), although high-frequency sea-level changes and their controlling mechanism have remained poorly constrained. Here we present a detailed sedimentological and geochemical study on Aptian (Lower Cretaceous) shallow-water carbonates of the Dariyan Formation exposed in the Zagros fold belt of southern Iran. [...]".
Source: Science Direct
Authors: Yiwei Xu et al.
Deglacial volcanism and reoxygenation in the aftermath of the Sturtian Snowball Earth
"The Cryogenian Sturtian and Marinoan Snowball Earth glaciations bracket a nonglacial interval during which Demosponge and green-algal biomarkers first appear. To understand the relationships between environmental perturbations and early animal evolution, we measured sulfur and mercury isotopes from the Datangpo Formation from South China. Hg enrichment with positive Δ199Hg excursion suggests enhanced volcanism, potentially due to depressurization of terrestrial magma chambers during deglaciation. [...]".
Source: Science Advances
Authors: Menghan Li et al.
Preprint: Evolution of oxygen and stratification in the North Pacific Ocean in CMIP6 Earth System Models
"This study examines the linkages between the upper ocean (0–200 m) oxygen (O2) content and stratification in the North Pacific Ocean in four Earth system models (ESMs), an ocean hindcast simulation, and ocean reanalysis data. Trend and variability of oceanic O2 content are driven by the imbalance between physical supply and biological demand. The physical supply is primarily controlled by ocean ventilation, which is responsible for the transport of O2-rich surface waters into subsurface. To quantify the ocean ventilation, Isopycnic Potential Vorticity (IPV) is used as a dynamical proxy in this study. [...]".
Authors: Lyuba Novi et al.
Metabolic prioritization of fish in hypoxic waters: an integrative modeling approach
"Marine hypoxia has had major consequences for both economically and ecologically critical fish species around the world. As hypoxic regions continue to grow in severity and extent, we must deepen our understanding of mechanisms driving population and community responses to major stressors. It has been shown that food availability and habitat use are the most critical components of impacts on individual fish leading to observed outcomes at higher levels of organization. However, differences within and among species in partitioning available energy for metabolic demands – or metabolic prioritization – in response to stressors are often ignored. [...]".
Source: Frontiers in Marine Science
Authors: Elizabeth Duskey
Ocean Oxygen: the role of the Ocean in the oxygen we breathe and the threat of deoxygenation
"EMB Future Science Brief No. 10 highlights the most recent science on Ocean oxygen, including causes, impacts and mitigation strategies of Ocean oxygen loss, and discusses whether “every second breath we take comes from the Ocean”. It closes with key policy, management and research recommendations to address Ocean deoxygenation and communicate more accurately about the role of the Ocean in Earth’s oxygen.
The sentence “every second breath you take comes from the Ocean” is commonly used in Ocean Literacy and science communication to highlight the importance of Ocean oxygen. [...]".
Source: European Marine Board
Authors: Marilaure Grégoire et al.
Preprint: Bottom-water hypoxia in the Paracas Bay (Peru, 13.8°S) associated with seasonal and synoptic time scale variability of winds and water ...
Full title: "Bottom-water hypoxia in the Paracas Bay (Peru, 13.8°S) associated with seasonal and synoptic time scale variability of winds and water stratification"
"Coastal hypoxia can occur naturally in inshore areas of the Eastern Boundary Upwelling Systems, influenced by the nutrient-rich and low-oxygen upwelling waters. This study aims to explore the influence of water stratification and winds on bottom-water hypoxia of the Paracas Bay, an area subjected to the most intense alongshore winds and active coastal upwelling in the Peruvian coast. [...]".
Source: Science Direct
Authors: Lander Merma-Mora et al.
Preprint: Linking northeastern North Pacific oxygen changes to upstream surface outcrop variations
"Understanding the response of the ocean to global warming, including the renewal of ocean waters from the surface (ventilation), is important for future climate predictions. Oxygen (O2) distributions in the ocean thermocline have proven an effective way to infer changes in ventilation because physical processes (ventilation and circulation) that supply oxygen are thought to be primarily responsible for changes in interior oxygen concentrations. Here, the focus is on the North Pacific thermocline, where some of the world ocean's largest oxygen variations have been observed. [...]".
Authors: Sabine Mecking & Kyla Drushka
Extensive Accumulation of Nitrous Oxide in the Oxygen Minimum Zone in the Bay of Bengal
"The production by microorganisms of nitrous oxide (N2O), a trace gas contributing to global warming and stratospheric ozone depletion, is enhanced around the oceanic oxygen minimum zones (OMZs). The production constitutes an important source of atmospheric N2O. Although an OMZ is found in the northern part of the eastern Indian Ocean, the Bay of Bengal (BoB), two earlier studies conducted during the later phase of winter monsoon (February) and spring intermonsoon (March–April) found quite different magnitudes of N2O accumulation. [...]".
Source: Wiley Online Library
Authors: Sakae Toyoda et al.
Decreasing O2 availability reduces cellular protein contents in a marine diatom
"Anthropogenic activities and climate change are exacerbating marine deoxygenation. Apart from aerobic organisms, reduced O2 also affects photoautotrophic organisms in the ocean. This is because without available O2, these O2 producers cannot maintain their mitochondrial respiration, especially under dim-light or dark conditions, which may disrupt the metabolism of macromolecules including proteins. We used growth rate, particle organic nitrogen and protein analyses, proteomics, and transcriptomics to determine cellular nitrogen metabolism of the diatom Thalassiosira pseudonana grown under three O2 levels in a range of light intensities [...]".
Source: Science Direct
Authors: Bokun Chen et al.
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