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. [...]"
Tracking sea surface salinity and dissolved oxygen on a river-influenced, seasonally stratified shelf, Mississippi Bight, northern Gulf of Mexico
"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.
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.
Gulf of Mexico 'dead zone' forecasted to exceed the size of Connecticut
"Scientists have predicted the dead zone, or area with little to no oxygen in the northern Gulf of Mexico, will become larger than the state of Connecticut by the end of July. The dead zone will cover about 6,620 square miles of the bottom of the continental shelf off Louisiana and Texas. While there are more than 500 dead zones around the world, the northern Gulf of Mexico dead zone is the second largest human-caused coastal hypoxic area in the world."
Nancy Rabalais - The "dead zone" of the Gulf of Mexico
"Ocean expert Nancy Rabalais tracks the ominously named "dead zone" in the Gulf of Mexico -- where there isn't enough oxygen in the water to support life. The Gulf has the second largest dead zone in the world; on top of killing fish and crustaceans, it's also killing fisheries in these waters. Rabalais tells us about what's causing it -- and how we can reverse its harmful effects and restore one of America's natural treasures."
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
Gulf of Mexico dead zone not expected to shrink anytime soon
The results, which appear in Science, suggest that policy goals for reducing the size of the northern Gulf of Mexico's dead zone may be unrealistic, and that major changes in agricultural and river management practices may be necessary to achieve the desired improvements in water quality.
The transport of large quantities of nitrogen from rivers and streams across the North American corn belt has been linked to the development of a large dead zone in the northern Gulf of Mexico, where massive algal blooms lead to oxygen depletion, making it difficult for marine life to survive.
"Despite the investment of large amounts of money in recent years to improve water quality, the area of last year's dead zone was more than 22,000 km2—about the size of the state of New Jersey," said Kimberly Van Meter, lead author of the paper and a postdoctoral fellow in the Department of Earth and Environmental Sciences at Waterloo. [...]"
The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development
"Despite their name, Oceanic Anoxic Events (OAEs) are not periods of uniform anoxia and black shale deposition in ancient oceans. Shelf environments account for the majority of productivity and organic carbon burial in the modern ocean, and this was likely true in the Cretaceous as well. However, it is unlikely that the mechanisms for such an increase were uniform across all shelf environments. Some, like the northwest margin of Africa, were characterized by strong upwelling, but what might drive enhanced productivity on shelves not geographically suited for upwelling? [...]"
Authors: Christopher M. Lowery
Gulf of Mexico Battles Expanding Dead Zone in Louisiana
The Gulf of Mexico meets the shorelines of Alabama, Louisiana, Mississippi, Texas and western Florida and is home to a large fishing industry. Several rivers from the Midwestern watershed flow south into the Gulf, carrying with them sediment, nutrient loads, and pollution from fossil fuel burning and wastewater systems.
The problem isn’t new, but it is expanding. "
Author: Mindy Cooper
Source: Environmental Monitor