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A numerical model study of the main factors contributing to hypoxia and its sub-seasonal to interannual variability off the Changjiang Estuary

Abstract.

"A three-dimensional physical-biological model of marginal seas of China was used to analyze variations in hypoxic conditions and identify the main processes controlling their generation off the Changjiang Estuary. The model was validated against available observations and reproduces the observed temporal and spatial variability of hypoxia. [...]"

Source: Biogeosciences (preprint)
Authors: Haiyan Zhang et al.
DOI: 10.5194/bg-2019-341

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High-throughput screening of sediment bacterial communities from Oxygen Minimum Zones of the northern Indian Ocean

Abstract.

"The Northern Indian Ocean host two recognized Oxygen Minimum Zones (OMZ): one in the Arabian Sea and the other in the Bay of Bengal region. The next-generation sequencing technique was used to understand the total bacterial diversity from the surface sediment of off Goa within the OMZ of Arabian Sea, and from off Paradip within the OMZ of Bay of Bengal. [...]"

Source: Biogeosciences (preprint)
Authors: Jovitha Lincy and Cathrine Manohar
DOI: 10.5194/bg-2019-330

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Quantifying the contributions of riverine vs. oceanic nitrogen to hypoxia in the East China Sea

Abstract.

"In the East China Sea, hypoxia (oxygen ≤ 62.5 mmol m−3) is frequently observed off the Changjiang (or Yangtze) River estuary covering up to about 15,000 km2. The Changjiang River is a major contributor to hypoxia formation because it discharges large amounts of freshwater and nutrients into the region. However, modelling and observational studies have suggested that intrusions of nutrient-rich oceanic water from the Kuroshio also contribute to hypoxia formation. [...]"

Source: Biogeosciences (preprint)
Authors: Fabian Große et al.
DOI: 10.5194/bg-2019-342 

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Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans

Abstract.

"The late Ludlow Lau Event was a severe biotic crisis in the Silurian, characterized by resurgent microbial facies and faunal turnover rates otherwise only documented during the "big five" mass extinctions. This asynchronous late Silurian marine extinction event preceded an associated positive carbon isotope excursion (CIE), the Lau CIE, although a mechanism for this temporal offset remains poorly constrained. [...]"

Source: GeoScienceWorld
Authors: Chelsie N. Bowman et al.
DOI: 10.1130/G46571.1

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Oxygen depletion in ancient oceans caused major mass extinction

"For years, scientists struggled to connect a mechanism to this mass extinction, one of the 10 most dramatic ever recorded in Earth's history. Now, researchers have confirmed that this event, referred to by scientists as the Lau/Kozlowskii extinction, was triggered by an all-too-familiar culprit: rapid and widespread depletion of oxygen in the global oceans. [...]"

Source: ScienceDaily

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Identifying areas prone to coastal hypoxia – the role of topography

Abstract.

"Hypoxia is an increasing problem in marine ecosystems around the world. While major advances have been made in our understanding of the drivers of hypoxia, challenges remain in describing oxygen dynamics in coastal regions. The complexity of many coastal areas and lack of detailed in situ data have hindered the development of models describing oxygen dynamics at a sufficient spatial resolution for efficient management actions to take place. [...]"

Source: Biogeosciences
Authors: Elina A. Virtanen et al.
DOI: 10.5194/bg-16-3183-2019

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Interactions of anaerobic ammonium oxidizers and sulfide-oxidizing bacteria in a substrate-limited model system mimicking the marine environment

Abstract. 

"In nature anaerobic ammonium oxidation (anammox) and denitrification processes convert fixed nitrogen to gaseous nitrogen compounds, which are then released to the atmosphere. While anammox bacteria produce N2 from ammonium and nitrite, in the denitrification process nitrate and nitrite are converted to N2 and the greenhouse gas nitrous oxide (N2O). [...]"

Source: FEMS Microbiology Ecology
Authors: Lina Russ et al. 
DOI: 10.1093/femsec/fiz137

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Ferry in Alaska monitors ocean acidification

"The last two years MV Columbia records the ocean’s vitals every three minutes, along a 1,600-kilometer route through the Inside Passage. This includes the coastal region from Puget Sound to the Alaska Panhandle. The ship measures the sea's temperature, salinity, dissolved oxygen content, and carbon dioxide concentration, aiming to monitor ocean acidification. [...]"

Source: Safety4Sea

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Ventilation of the Upper Oxygen Minimum Zone in the Coastal Region Off Mexico: Implications of El Niño 2015–2016

Abstract.

"As a result of anthropogenic activities, it has been predicted that the ocean will be challenged with rising temperature, increased stratification, ocean acidification, stronger more frequent tropical storms, and oxygen depletion. In the tropical Pacific off central Mexico all these phenomena are already occurring naturally, providing a laboratory from which to explore ocean biogeochemical dynamics that are predicted under future anthropogenic forcing conditions. "

Source: Frontiers in Marine Science
Authors: Pablo N. Trucco-Pignata et al.
DOI: 10.3389/fmars.2019.00459

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Quantifying the Relative Importance of Riverine and Open‐Ocean Nitrogen Sources for Hypoxia Formation in the Northern Gulf of Mexico

Abstract.

"The Mississippi and Atchafalaya River System discharges large amounts of freshwater and nutrients into the northern Gulf of Mexico (NGoM). These lead to increased stratification and elevate primary production in the outflow region. Consequently, hypoxia (oxygen <62.5 mmol/m3), extending over an area of roughly 15,000 km2, forms every summer in bottom waters. [...]"

Source: JGR Oceans
Authors: Fabian Große et al.
DOI: 10.1029/2019JC015230

Read the full article here.


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