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Ecophenotypic responses of benthic foraminifera to oxygen availability along an oxygen gradient in the California Borderland

Abstract.

"Spatial variation in environmental conditions can elicit predictable size and morphological responses in marine organisms through influences on physiology. Thus, spatial and temporal variation in marine organism size and shape are often used to infer paleoenvironmental conditions, such as dissolved oxygen concentrations. Benthic foraminifera commonly serve as a tool for reconstructing past ocean oxygen levels. [...]" 

Source: marine ecology
Authors: Caitlin R. Keating-Bitonti, Jonathan L. Payne
DOI: 10.1111/maec.12430

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Metabolic Roles of Uncultivated Bacterioplankton Lineages in the Northern Gulf of Mexico “Dead Zone”

Abstract.

"Marine regions that have seasonal to long-term low dissolved oxygen (DO) concentrations, sometimes called “dead zones,” are increasing in number and severity around the globe with deleterious effects on ecology and economics. One of the largest of these coastal dead zones occurs on the continental shelf of the northern Gulf of Mexico (nGOM), which results from eutrophication-enhanced bacterioplankton respiration and strong seasonal stratification. [...]"

Source: mBio
Authors: J. Cameron Thrash et al.
DOI: 10.1128/mBio.01017-17

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Intense oceanic uptake of oxygen during 2014–2015 winter convection in the Labrador Sea

Abstract.

"Measurements of near-surface oxygen (O2) concentrations and mixed layer depth from the K1 mooring in the central Labrador Sea are used to calculate the change in column-integrated (0–1700 m) O2 content over the deep convection winter 2014/2015. During the mixed layer deepening period, November 2014 to April 2015, the oxygen content increased by 24.3 ± 3.4 mol m−2, 40% higher than previous results from winters with weaker convection. By estimating the contribution of respiration and lateral transport on the oxygen budget, the cumulative air-sea gas exchange is derived. [...]"

Source: Geophysical Research Letters
Authors: Jannes Koelling, Douglas W. R. Wallace, Uwe Send, Johannes Karstensen
DOI: 10.1002/2017GL073933

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Taking a deep breath? Scientists measure unusually high oxygen uptake in the Labrador Sea

"The Labrador Sea in the North Atlantic is one of the few areas in the world ocean where cold, saline seawater sinks to large depths and forms deep water. This convection process also transports oxygen into the deep sea. A team of scientists from Scripps Institution of Oceanography (San Diego, California), Dalhousie University (Halifax, Canada) and GEOMAR Helmholtz Centre for Ocean Research Kiel have now published the analysis of data obtained from the mooring K1 in the international scientific journal Geophysical Research Letters. [...]"

Source: phys.org

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Widespread seawater circulation in 18–22 Ma oceanic crust: Impact on heat flow and sediment geochemistry

Abstract.

"On the basis of heat-flow measurements, seismic mapping, and sediment pore-water analysis, we demonstrate widespread and efficient ventilation of the 18–22 Ma oceanic crust of the northeast equatorial Pacific Ocean. Recharge and discharge appear to be associated with basement outcrops, including seamounts and north-south–trending faults, along which sediment cover thins out and volcanic rocks are exposed. Low-temperature hydrothermal circulation through the volcanic crust leads to the reduction of heat flow through overlying sediments, with measured heat-flow values that are well below those expected from conductive cooling curves for lithosphere of this age. [...]"

Source: Geology
Authors: Thomas Kuhn et al.
DOI: 10.1130/G39091.1

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The influence of variable slope-water characteristics on dissolved oxygen levels in the northern California Current System

Abstract.

"Observations have suggested a trend of decreasing dissolved oxygen (DO) and increasing spiciness in summertime mid-depth slope waters and bottom shelf waters along the United States west coast over the past 50 years, but they have also demonstrated a large amount of interannual and decadal variability. Shelf bottom water and slope water properties can be influenced by both local and remote effects, including changes in circulation or changes in the characteristics of the source waters supplying the region. [...]"

Source: Oceans
Authors: Scott M. Durski et al.
DOI: 10.1002/2017JC013089

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Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969–2015

Abstract.

The U.S. Geological Survey (USGS) maintains a place-based research program in San Francisco Bay (USA) that began in 1969 and continues, providing one of the longest records of water-quality measurements in a North American estuary. Constituents include salinity, temperature, light extinction coefficient, and concentrations of chlorophyll-a, dissolved oxygen, suspended particulate matter, nitrate, nitrite, ammonium, silicate, and phosphate.

Source: Scientific Data
Authors: Tara S. Schraga & James E. Cloern
DOI: 10.1038/sdata.2017.98

Read the full article here.


Environmental Research in Macquarie Harbour (Progress Report)

"This report provides an update on the status of dissolved oxygen and benthic conditions in Macquarie Harbour. It follows on from the results reported in the IMAS report released in January 2017 which described the deterioration of benthic and water column conditions in Macquarie Harbour in spring 2016. This report presents the results and preliminary interpretation of oxygen monitoring data up until the end of March 2017, and a repeat survey of benthic communities in January/February 2017. [...]"

Source: The Institute for Marine and Antarctic Studies
Authors: Jeff Ross and Catriona Macleod

Full report (PDF)


Eutrophication-Driven Deoxygenation in the Coastal Ocean

Abstract.

"Human activities, especially increased nutrient loads that set in motion a cascading chain of events related to eutrophication, accelerate development of hypoxia (lower oxygen concentration) in many areas of the world’s coastal ocean. Climate changes and extreme weather events may modify hypoxia. Organismal and fisheries effects are at the heart of the coastal hypoxia issue, but more subtle regime shifts and trophic interactions are also cause for concern. The chemical milieu associated with declining dissolved oxygen concentrations affects the biogeochemical cycling of oxygen, carbon, nitrogen, phosphorus, silica, trace metals, and sulfide as observed in water column processes, shifts in sediment biogeochemistry, and increases in carbon, nitrogen, and sulfur, as well as shifts in their stable isotopes, in recently accumulated sediments."

Source: Oceanography Volume 27 (2014)
Authors: Nancy N. Rabalais et al.
DOI: 10.5670/oceanog.2014.21

Full article


Less oxygen in a warmer ocean

"Climate warming should decrease the concentration of dissolved oxygen (O2) in the surface ocean, for a variety of reasons. This trend, predicted on theoretical grounds and by ocean models, has been difficult to detect within the much greater range of natural variability, though. Ito et al. analyzed existing measurements of O2 in the ocean collected from 1958 to 2015, and they report that a widespread negative O2 trend has begun to emerge. Further work will be needed to understand which mechanisms are responsible for the global and regional trends, however.

Geophys. Res. Lett. 10.1002/2017GL073613 (2017)."

Source: Science
Author: H. Jesse Smith
DOI: 10.1126/science.356.6341.919-g

Link to article


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