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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

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Recent Developments in Oxygen Minimum Zones Biogeochemistry

New Research Topic: Recent Developments in Oxygen Minimum Zones Biogeochemistry

"Oxygen minimum zones (OMZs) play a key role in carbon, nitrogen and other elemental cycles, and directly impact climate dynamics by influencing air-sea fluxes of the potent greenhouse gases methane and nitrous oxide. Oxygen concentrations, catalyze specialized micro-organisms to regulate chemical fluxes, which are critical for ecosystem functioning. The degree of deoxygenation in the OMZs vary from hypoxic in the tropical Atlantic Ocean to functionally anoxic in the eastern tropical Pacific Ocean and the northern Indian Ocean.[...]"

 

Source: Frontiers
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Oxygen loss in fjords, coastal areas, and open ocean systems

Abstract.

"Loss of oxygen and expansion of oxygen depleted environments have been witnessed in both coastal and open-ocean systems since the middle of the 20th century, and ocean modelling predicts continuing decease by the year 2100. Oxygen depletion occurs thus during the same time epoch as global warming. Increased knowledge on how and why oxygen varies in space and time shapes the biogeochemical and ecological structure of marine systems and will be needed for future predictions of marine productivity. In coastal systems deoxygenation is also linked to human activities that lead to increased loadings of nutrients and organic matter, and to regional effects of climate induced changes in wind and precipitation patterns[...]"

 

Source: BJERKNES CENTRE
Authors: Anne Gro Vea Salvanes et al.
 

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Low oxygen levels can help to prevent the detrimental effect of acute warming on mitochondrial efficiency in fish

Abstract.

"Aerobic metabolism of aquatic ectotherms is highly sensitive to fluctuating climates. Many mitochondrial traits exhibit phenotypic plasticity in response to acute variations in temperature and oxygen availability. These responses are critical for understanding the effects of environmental variations on aquatic ectotherms' performance. Using the European seabass, Dicentrarchus labrax, we determined the effects of acute warming and deoxygenation in vitro on mitochondrial respiratory capacities and mitochondrial[...]"

 

Source: The Royal Society Publishing 
Authors: Elisa Thoral et al.
DOI: https://doi.org/10.1098/rsbl.2020.0759

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System controls of coastal and open ocean oxygen depletion

Abstract.

"The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas[...]".

 

Source: Science Direct
Authors: Grant C. Pitcher
DOI: https://doi.org/10.1016/j.pocean.2021.102613

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Increase of a hypoxia-tolerant fish, Harpadon nehereus (Synodontidae), as a result of ocean deoxygenation off southwestern China

Abstract.

"We report a sudden explosive rise in abundance off southeastern China of a fish species that is hypoxia-tolerant, Bombay duck (Harpadon nehereus, Family Synodontidae), belonging to an Order (the Aulopiformes) encompassing overwhelmingly deep-sea fishes, but which predominantly occurs in coastal water. We suggest that this is made possible by the very high water content of its muscle and other tissues (about 90%, vs 75–80% for other coastal fish), which reduces its oxygen requirements and allows it to outcompete other fish in low-oxygen[...]"

 

Source: Environmental Biology of Fishes
Authors: Bin Kang et al.
DOI: https://doi.org/10.1007/s10641-021-01130-7

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Deoxygenation in Marginal Seas of the Indian Ocean

Abstract.

"This article describes oxygen distributions and recent deoxygenation trends in three marginal seas – Persian Gulf and Red Sea in the Northwestern Indian Ocean (NWIO) and Andaman Sea in the Northeastern Indian Ocean (NEIO). Vertically mixed water column in the shallow Persian Gulf is generally well-oxygenated, especially in winter. Biogeochemistry and ecosystems of Persian Gulf are being subjected to enormous anthropogenic stresses including large loading of nutrients and organic matter, enhancing oxygen demand and causing hypoxia (oxygen < 1.4 ml l–1) in central and southern Gulf in summer. The larger and deeper Red Sea is relatively less affected by human[...]"

 

Source: Frontiers
Authors: S. Wajih A. Naqvi
DOI: https://doi.org/10.3389/fmars.2021.624322


Temperature and dissolved oxygen concentration in the Pacific Ocean at the northern region of the oxygen minimum zone off Mexico between the last two

Abstract.

"The changes in temperature and dissolved oxygen concentration in the Pacific Ocean in the northern region of the shallow oxygen minimum zone (OMZ) off Mexico were analyzed on the basis of the Word Ocean Database and a series of oceanographic cruises (LEGOZ-Mex). In order to test the changes in both parameters between two similar oceanographic scenarios according to the Pacific Decadal Oscillation (PDO), a comparison was made between the last two cool PDO phases of 1962–1974 and 2002–2012 when conditions[...]"

 

Source: Science Direct
Authors: E.D.Sánchez-Pérez et al.
DOI: https://doi.org/10.1016/j.jmarsys.2021.103607

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Biogeochemistry and hydrography shape microbial community assembly and activity in the eastern tropical North Pacific Ocean oxygen minimum zone

Abstract.

"Oceanic oxygen minimum zones (OMZs) play a pivotal role in biogeochemical cycles due to extensive microbial activity. How OMZ microbial communities assemble and respond to environmental variation is therefore essential to understanding OMZ functioning and ocean biogeochemistry. Sampling along depth profiles at five stations in the eastern tropical North Pacific Ocean (ETNP), we captured systematic variations in dissolved oxygen (DO) and associated variables (nitrite, chlorophyll, and ammonium) with depth and between stations. We quantitatively analysed relationships[...]"

 

Source: Wiley Online Library 
Authors: J. Michael Beman et al.
DOI: https://doi.org/10.1111/1462-2920.15215

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Coastal eutrophication drives acidification, oxygen loss, and ecosystem change in a major oceanic upwelling system

Abstract.

"Global change is leading to warming, acidification, and oxygen loss in the ocean. In the Southern California Bight, an eastern boundary upwelling system, these stressors are exacerbated by the localized discharge of anthropogenically enhanced nutrients from a coastal population of 23 million people. Here, we use simulations with a high-resolution, physical–biogeochemical model to quantify the link between terrestrial [...]"

 

Source: PNAS- Proceedings of the National Academy of Sciences of the United States of America
Authors: Faycal Kessouri et al.
DOI: https://doi.org/10.1073/pnas.2018856118

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