News

What could cause the Mississippi Bight to become hypoxic?

"Coastal regions with low dissolved oxygen (known as hypoxia) can lead to poor water quality and harm regional fisheries. These areas of low dissolved oxygen are expanding and expected to continue growing in coming years due to human impacts on the environment.

A recent article published in Continental Shelf Research explores aspects of the environmental conditions that can potentially lead to hypoxia in the Mississippi Bight region of the northern Gulf of Mexico. This area extends from Apalachicola in Florida to the Mississippi River Delta. [...]"

Source:  EurekAlert!

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Tracking sea surface salinity and dissolved oxygen on a river-influenced, seasonally stratified shelf, Mississippi Bight, northern Gulf of Mexico

Abstract.

"River discharge, and its resulting region of freshwater influence (ROFI) in the coastal ocean, has a critical influence on physical and biogeochemical processes in seasonally stratified shelf ecosystems. Multi-year (2010–2016) observations of satellite-derived sea surface salinity (SSS) and in situ water column hydrographic data during summer 2016 were used to investigate physical aspects of the ROFI east of the Mississippi River Delta to better assess regional susceptibility to hypoxia in the summer months. [...]"

Source: Continental Shelf Research
Authors: Brian Dzwonkowski et al.
DOI: 10.1016/j.csr.2018.09.009

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Manifestation, Drivers, and Emergence of Open Ocean Deoxygenation

Abstract.

"Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded in the open ocean over the past 50–100 years, but with greater oxygen declines in intermediate waters (100–600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. [...]"

Source: Annual Review of Marine Science
Author: L. Levin
DOI: 10.1146/annurev-marine-121916-063359

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Drivers of oxygen consumption in the northern Gulf of Mexico hypoxic waters – A stable carbon isotope perspective

Abstract.

"We examined the stable carbon isotopic composition of remineralized organic carbon (δ13COCx) in the northern Gulf of Mexico (nGoM) using incubations (sediment and water) and a three end‐member mixing model. δ13COCx in incubating sediments was ‐18.1±1.3‰, and δ13COCx in incubating near‐surface and near‐bottom waters varied with salinity, ranging from ‐30.4‰ to ‐16.2‰ from brackish water to full strength Gulf water. The average δ13COCx was ‐18.6 ±1.8‰ at salinity >23. A three end‐member mixing model based on a multi‐year dataset collected in previous summer hypoxia cruises (2011, 2012, 2014, 2015 and 2016) suggested that δ13COCx in near‐bottom waters across the nGoM (5‐50 m) was ‐18.1±0.6‰. [...]" 

Source: Geophysical Reasearch Letters
Authors: Hongjie Wang et al.
DOI: 10.1029/2018GL078571

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Oregon Now Has A Hypoxia Season, Just Like A Wildfire Season

"Scientists say warming ocean temperatures mean Oregon’s coastal waters now have a low-oxygen season, or hypoxia season, just as the state’s forests have a fire season.

Hypoxia is a condition in which the ocean water close to the sea floor has such low levels of dissolved oxygen that the organisms living down there die.

Some of the first signs came in 2002 when dead crabs were hauled up in crab pots. Since then, scientists and crabbers say things have worsened."

Source: earthfix.info
Author: Kristian Foden-Vencil

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Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem

Abstract.

"Hypoxia is one of the most important stressors affecting the health conditions of coastal ecosystems. In highly productive ecosystems such as the Humboldt Current ecosystem, the oxygen minimum zone is an important abiotic factor modulating the structure of benthic communities over the continental shelf. Herein, we study soft-bottom macrobenthic communities along a depth gradient–at 10, 20, 30 and 50 m–for two years to understand how hypoxia affects the structure of shallow communities at two sites in Mejillones Bay (23°S) in northern Chile. [...]"

Source: PLoS ONE
Authors: Maritza Fajardo et al.
DOI: 10.1371/journal.pone.0200349

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Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming

Abstract.

"Dissolved oxygen (O2) is essential for the survival of marine animals. Climate change impacts on future oxygen distributions could modify species biogeography, trophic interactions, biodiversity, and biogeochemistry. The Coupled Model Intercomparison Project Phase 5 models predict a decreasing trend in marine O2 over the 21st century.  [...]"

Source: Global Biogeochemical Cycles
Authors: Weiwei Fu et al.
DOI: 10.1002/2017GB005788

 Read the full article here.


Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean

Abstract.

"The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. [...]"

Source: Nature Geoscience
Authors: William R. Gray et al.
DOI: 10.1038/s41561-018-0108-6

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Climate Change Projected to Exacerbate Impacts of Coastal Eutrophication in the Northern Gulf of Mexico

Abstract.

"The continental shelf in the northern Gulf of Mexico experiences expansive seasonal hypoxic conditions and eutrophication‐driven acidification in bottom waters. Rising surface ocean temperatures, freshwater and nutrient inputs, and atmospheric CO2 will further exacerbate these conditions. Using a high‐resolution, regional circulation‐biogeochemical model, we simulated the spatio‐temporal dynamics of oxygen and inorganic carbon in the northern Gulf of Mexico under present and a projected future (2100) climate state. [...]"

Source: Oceans (AGU Journal)
Authors: Arnaud Laurent et al.
DOI: 10.1002/2017JC013583

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NCCOS and NGI Lead Seventh Annual Hypoxia Research Coordination Workshop

"NCCOS is working with the Northern Gulf Institute (NGI) and Gulf of Mexico State partners to develop a robust and sustainable Gulf of Mexico-wide monitoring program for hypoxia. At the 7th Annual Hypoxia Research Coordination Workshop, planning continued for a Cooperative Hypoxia Assessment and Monitoring Program.

The Cooperative Hypoxia Assessment and Monitoring Program (CHAMP) is a bottom-up effort comprised of State (LA, AL/MS, TX) and issue-based workgroups. Eight workgroups (Fisheries, Louisiana-Mississippi/Alabama-Texas state monitoring, autonomous vehicles, Hypoxia Task Force, Oil/Gas and Ocean Acidification, and Gulf Restoration) identify and pursue leveraging and support opportunities within their local focus areas, benefiting the entire Gulf region. [...]"

Source: National Centers for Coastal Ocean Science (NCCOS)
Author: Alan Lewitus

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