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Mesozoic Oceanic Anoxic Events and the Associated Black Shale Deposits as a Potential Source of Energy

Abstract. 

"Oceanic anoxic events (OAEs) are considered as periods of oxygen deficiency in many oceans; accompanied by accumulation of organic-rich black shales. Mesozoic anoxic events were recognized based on the presence of black shales that are rich in organic matter. The most significant anoxic events during the Mesozoic are the Early Toarcian, the Early Aptian, and the Cenomanian–Turonian. The less significant events are the Valanginian-Hauterivian, the Hauterivian-Barremian, the Aptian-Albian, the Late Albian, the Albian-Cenomanian, and the Coniacian-Santonian. [...]".

 

Source: Springer Nature
Authors: Tarek Anan & Adam El-Shahat 
DOI: https://doi.org/10.1007/978-3-030-95637-0_7

Read the full article here.


Phytoplankton dynamics and nitrogen cycling during Oceanic Anoxic Event 2 (Cenomanian/Turonian) in the upwelling zone of the NE proto-North Atlantic

Abstract. 

"The Cenomanian-Turonian (Late Cretaceous) climate warming was closely coupled to profound perturbations of biogeochemical cycles and ecosystems. The occurrence of organic matter-rich sediments across various depositional environments of the proto-North Atlantic hereby marks severe oxygen-deficient conditions, culminating in Oceanic Anoxic Event (OAE 2) at the Cenomanian/Turonian boundary. Here we combine bulk, isotope and molecular geochemical techniques to characterize trends in organic matter accumulation and its relationship to biogeochemical cycling (nitrogen, carbon) and marine phytoplankton community shifts [...]". 

 

Source: Science Direct
Authors: Wolfgang Ruebsam & Lorenz Schwark
DOI: https://doi.org/10.1016/j.gloplacha.2023.104117

Read the full article here.


Mitigation of oxygen decline in fjords by freshwater injection

Abstract. 

"The exchange of water masses between deep fjords and the open ocean is commonly constrained by a topographical barrier called the sill. While fjord water above the sill depth communicates relatively freely with the open ocean, water below the sill depth is caught inside the fjord basin. This basin water may remain stagnant in deep fjords for many successive years. During these periods, the biological consumption of dissolved oxygen is larger than the supply of new oxygen, and the fjord basin might experience hypoxia and even anoxia. [...]".

 

Source: Science Direct
Authors: Dag L. Aksnes et al.
DOI: https://doi.org/10.1016/j.ecss.2023.108286 

Read the full article here.


Hypoxia stress induces hepatic antioxidant activity and apoptosis, but stimulates immune response and immune-related gene expression in black rockfish

Abstract. 

"Dissolved oxygen concentrations both in the open ocean and coast have been declining due to the interaction of global climate change and human activity. Fish have evolved different adaptative strategies to cope with possibly damage induced by hypoxic environments. Black rockfish as important economic fish widely reared in the offshore sea cage, whereas related physiological response subject to hypoxia stress remained unclear. In this study, hepatic anti-oxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH-Px]), aminotransferase (AST) and alanine aminotransferase (ALT) activities [...]".

 

Source: Science Direct
Authors: Yudong Jia et al.
DOI: https://doi.org/10.1016/j.aquatox.2023.106502

Read the full article here.


Reconstructing ocean oxygenation changes from U/Ca and U/Mn in foraminiferal coatings: Proxy validation and constraints on glacial oxygenation changes

Abstract. 

"Deep-sea oxygen concentrations reflect combined effects of air-sea exchange in high-latitude surface waters, ventilation through ocean circulation and the organic carbonremineralization at depth. Reconstruction of past bottom water oxygen (BWO) concentrations has been challenging due to limitations of each existing BWO proxy whose fidelity may be complicated by diagenetic or depositional factors. Therefore, evaluations on BWO changes with multi-proxy approach are always preferred. In this study, we exploit the authigenic uranium content on mixed planktonic foraminiferal coatings as a BWO proxy by presenting new foraminiferal [...]".

 

Source: Science Direct
Authors: Rong Hu et al.
DOI: https://doi.org/10.1016/j.quascirev.2023.108028

Read the full article here.


Molybdenum isotope evidence from restricted-basin mudstones for an intermediate extent of oxygenation in the late Ediacaran ocean

Abstract. 

"The Mo isotope composition of late Ediacaran global seawater and the global extent of ocean oxygenation are still debated due to the complex controls on sedimentary Mo isotope compositions and the rarity with which sediments directly capture global seawater Mo isotope compositions. Deep-water sulfidic sediments from modern severely restricted basins like the Black Sea have the best chance of capturing global seawater Mo isotope compositions. However, few studies have focused on sedimentary Mo isotope variations and their causes in late Ediacaran restricted basins. [...]". 

 

Source: Science Direct
Authors: Zhaozhao Tan et al.
DOI: https://doi.org/10.1016/j.chemgeo.2023.121410

Read the full article here.


Impacts of Deoxygenation and Hypoxia on Shark Embryos Anti-Predator Behavior and Oxidative Stress

Abstract. 

"Climate change is leading to the loss of oxygen content in the oceans and endangering the survival of many marine species. Due to sea surface temperature warming and changing circulation, the ocean has become more stratified and is consequently losing its oxygen content. Oviparous elasmobranchs are particularly vulnerable as they lay their eggs in coastal and shallow areas, where they experience significant oscillations in oxygen levels. Here, we investigated the effects of deoxygenation (93% air saturation) and hypoxia (26% air saturation) during a short-term period (six days) on the anti-predator avoidance behavior and physiology [...]".

 

Source: MDPI
Authors: Jaquelino Varela et al.
DOI: https://doi.org/10.3390/biology12040577

Read the full article here.


Job Offer in Fish Modelling in the Black Sea

Opening of one position for a 4-year Ph.D. or 3-year mobility postdoc for working on Fish Modelling in the Black Sea

"This position is offered in the frame of the recently funded 4-year Horizon-Europe project NECCTON  (New Copernicus Capability for Trophic Ocean Networks) and is available under a joint supervision at the Liège University (MAST-FOCUS group, Department of Astrophysics, Geophysics and Oceanography), the Royal Netherlands Institute for Sea Research (NIOZ) in the Nederland and the University of Maryland Center for Environmental Science (US). The research project aims at modelling the dynamics of selected fish species (e.g. anchovies, horse mackerel, sprat) in the Black Sea to assess the impact of past and projected environmental changes (e.g. deoxygenation, warming, fishing) on fish distribution and stocks." 

You can find more details in this document


Nitrite Oxidation Across the Full Oxygen Spectrum in the Ocean

Abstract. 

"Fixed nitrogen limits primary productivity in most areas of the surface ocean. Nitrite oxidation is the main source of nitrate, the most abundant form of inorganic fixed nitrogen. Even though known as an aerobic process, nitrite oxidation is not always stimulated by increased oxygen concentration, and nitrite oxidation occurs in layers of oxygen minimum zones (OMZs) where oxygen is not detectable. Nitrite-oxidizing bacteria, known since their original isolation as aerobes, were also detected in these layers. Whether and how nitrite oxidation is occurring in the anoxic seawater is debated. [...]".

 

Source: Wiley Online Library 
Authors: Xin Sun et al.
DOI: https://doi.org/10.1029/2022GB007548

Read the full article here.


Prokaryotic community dynamics and nitrogen-cycling genes in an oxygen-deficient upwelling system during La Niña and El Niño conditions

Abstract. 

"Dissolved oxygen regulates microbial distribution and nitrogen cycling and, therefore, ocean productivity and Earth's climate. To date, the assembly of microbial communities in relation to oceanographic changes due to El Niño Southern Oscillation (ENSO) remains poorly understood in oxygen minimum zones (OMZ). The Mexican Pacific upwelling system supports high productivity and a permanent OMZ. Here, the spatiotemporal distribution of the prokaryotic community and nitrogen-cycling genes was investigated along a repeated transect subjected to varying oceanographic conditions associated with La Niña in 2018 and El Niño in 2019. [...]".

 

Source: Wiley Online Library 
Authors: Silvia Pajares et al.
DOI: https://doi.org/10.1111/1462-2920.16362

Read the full article here.


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