Drivers of oxygen consumption in the northern Gulf of Mexico hypoxic waters – A stable carbon isotope perspective
"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.
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."
Author: Kristian Foden-Vencil
Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem
"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.
Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming
"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.
Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean
"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.
Climate Change Projected to Exacerbate Impacts of Coastal Eutrophication in the Northern Gulf of Mexico
"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.
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
Decreased oxygen levels could present hidden threat to marine species
"Scientists have shown that creatures which develop in hypoxic (low oxygen) conditions in the marine environment could experience previously unseen hindered development, and become compromised as adults. [...]
The prevalence of hypoxic (low oxygen) areas in coastal waters is predicted to increase in the future, both in terms of their scale and duration. And while the adults of many estuarine invertebrates can cope with short periods of hypoxia, it has previously been unclear whether that ability is present if animals are bred and reared under chronic hypoxia.[...]"
Source: Sciencedaily.com (University of Plymouth)
Short-term acclimation in adults does not predict offspring acclimation potential to hypoxia
"The prevalence of hypoxic areas in coastal waters is predicted to increase and lead to reduced biodiversity. While the adult stages of many estuarine invertebrates can cope with short periods of hypoxia, it remains unclear whether that ability is present if animals are bred and reared under chronic hypoxia. We firstly investigated the effect of moderate, short-term environmental hypoxia (40% air saturation for one week) on metabolic performance in adults of an estuarine amphipod, and the fitness consequences of prolonged exposure. [...]"
Source: Scientific Reports
Authors: Manuela Truebano et al.
Dealing with Dead Zones: Hypoxia in the Ocean
When water runs off of farmland and urban centers and flows into our streams and rivers, it is often chock-full of fertilizers and other nutrients. These massive loads of nutrients eventually end up in our coastal ocean, fueling a chain of events that can lead to hypoxic "dead zones" — areas along the sea floor where oxygen is so low it can no longer sustain marine life. In this episode, we're joined by NOAA scientist Alan Lewitus to explore why dead zones form, how the problem of hypoxia is growing worse, and what we're doing about it.
Source: National Oceanic and Atmospheric Administration (NOAA)
Author: Troy Kitch
Read the full article here.