‘Dead Zone’ in Gulf of Mexico above 5-year average
The area of low oxygen, commonly known as the “Dead Zone,” measured 5,800 square miles in this summer’s mapping expedition, the Louisiana Universities Marine Consortium reported today.
Based on the May nitrogen load from the Mississippi River, the area was predicted to be 7,300 to 8,600 square miles, the report stated. While not one of the larger areas mapped since systematic surveys started in 1985 by LUMCON and LSU researchers, the size of this year’s zone of oxygen-depleted bottom-water is above the long-term average and above the average size of the last five years, the report stated.
“Hypoxia forms as a result of the nutrient-overloaded waters of the Mississippi River stimulating the excess growth of phytoplankton,” the report stated. “Not all of the phytoplankton is consumed by higher levels of the food web, and it sinks to the seabed where bacteria decompose the remains and deplete the oxygen. The low oxygen forms in the lower half of a stratified water column (warmer, fresher water overlying cooler, saltier water), which keeps the plentiful oxygen in the surface waters from reaching into the lower layer and replenishing the oxygen depleted by the microbial activity.”
The size, while large, was a result of mixed conditions on the southeastern part of the study area, and winds from the west pushing the hypoxic water mass towards the east and thus reducing the bottom area footprint. At stations where hypoxia was found, the values were extremely low and close to zero, the report stated.
The news release explained that two processes — one physical and one biological — are necessary conditions for the formation of hypoxia in the spring and summer.
The physical conditions depend on the freshwater discharge of the Mississippi River, which forms a lower salinity water column over a saltier water column, the report stated. As the season progresses, heating from the sun decreases the density of the fresher waters compared to the cooler waters below. The process impedes the flow of oxygen from the surface to the bottom, the news release stated.
As the spring progresses into summer, freshwater and nutrient loads increase in the outflows of the river delivered through the main stem Mississippi River south of New Orleans and a second delta at the Atchafalaya River, which carries about one-third of the total river discharge, mid-coast. Other factors are weather events, wind-driven currents, and tropical storms and hurricanes.
These processes can mix the water column or shift the mass of hypoxic water or both.
The nutrient-rich water creates fertile conditions for growth of microscopic plants called phytoplankton, which is eaten by zooplankton. Eventually the food chain includes bacteria, which deplete oxygen at the bottom of the Gulf.
Reaction to the Dead Zone size follows.
Mississippi River Collaborative
Gulf of Mexico Dead Zone 2013 Measurements Released
Massive size signifies lack of action by EPA, states
Des Moines, IA — Jul 29, 2013 / (http://www.myprgenie.com) — New Orleans, LA-This week, scientists from the Louisiana Universities Marine Consortium completed their annual measurement of the Gulf of Mexico’s Dead Zone, which measured 5,800 square miles, larger than the state of Connecticut.
The Dead Zone is an area of water at the mouth of the Mississippi River which is oxygen-deprived due to excess nitrogen and phosphorus pollution coming primarily from agricultural sources throughout the Basin as far north as the River’s source in Minnesota.
In addition to causing the Dead Zone in the Gulf, nitrogen and phosphorus pollution is affecting waters throughout the Mississippi River Basin and its tributaries, threatening wildlife and recreation, and rendering drinking water unsafe.
“Record-high nitrate pollution levels in May through July have forced the City of Des Moines, Iowa to use a nitrate removal system and blend water from other sources just to deliver safe drinking water to over 500,000 Iowans,” said Susan Heathcote, Water Program Director for the Iowa Environmental Council, a member of the Mississippi River Collaborative.
Despite voluntary initiatives to reduce nutrient pollution which have been encouraged by EPA and other states, the Dead Zone has only grown bigger. This lack of effective action forced members of the Mississippi River Collaborative to file suit against EPA in 2012 in an attempt to get the agency to set and enforce numeric standards for nitrogen and phosphorus pollution.
“EPA told states to develop numeric nitrogen and phosphorus limits 15 years ago,” stated Cynthia Sarthou, Executive Director for the Gulf Restoration Network, a Mississippi River Collaborative member organization. “EPA has since spent the last decade and a half repeatedly pushing back deadlines for reducing Dead Zone-causing pollution.”
Nitrogen and phosphorus pollution is a key concern for the Mississippi River Collaborative, a partnership of environmental organizations and legal centers working to protect the Mississippi River and its tributaries.
To learn more about Mississippi River Collaborative please go to http://www.myprgenie.com/company/profile/mississippi-river-collaborative.
Gulf Restoration Network
Massive Gulf Dead Zone Shows Lack of Action by EPA, States
New Orleans, LA—Today scientists from the Louisiana Universities Marine Consortium released their annual measurement of the Gulf Dead Zone, which measured 5,800 square miles, larger than the state of Connecticut. LUMCON has been measuring the Dead Zone since 1985, and this year’s Dead Zone is above both the long-term average size and the average size over the last 5 years.
Despite voluntary initiatives to address the Dead Zone enacted by Louisiana and EPA, the Gulf Dead Zone has only grown bigger. This lack of action forced members of the Mississippi River Collaborative to file suit against EPA in 2012. Specifically, this lawsuit was filed due to EPA’s refusal to set numeric standards for nitrogen and phosphorus pollution and ensure that all states in the river basin meet those standards.
“EPA told states to develop numeric nitrogen and phosphorus limits fifteen years ago,” stated Cynthia Sarthou, Executive Director for the Gulf Restoration Network. “EPA has spent the decade and a half since backing off hard deadline after hard deadline for reducing Dead Zone-causing pollution.”
The Dead Zone doesn’t just threaten the fish and fisherfolk in its immediate footprint. A ripple effect is felt throughout the Gulf’s $2.8 billion dollar fishing industry, with competition and crowding increasing as fishing fleets focus their efforts on unaffected areas. Nitrogen and phosphorus pollution causes environmental problems throughout the entire Mississippi River Basin such as toxic algae blooms resulting in the death of livestock and pets, fish kills, and damages to drinking water supplies. Recently, there has also been a debate regarding how nitrogen and phosphorus pollution will impact proposed sediment diversions and wetland restoration projects in coastal Louisiana.
“The best way to ensure that this pollution doesn’t impact diversions and coastal restoration is to make sure that it doesn’t get into the Mississippi in the first place,” stated Sarthou. “Reducing the pollution in the Mississippi River Basin would help set up sediment diversions for success.”
“Since states have chosen to drag their feet on reducing Dead Zone-causing pollution in a significant way, it is EPA’s responsibility to set strong standards,” Sarthou added.
# # #
The Gulf Restoration Network (GRN) is a network of environmental, social justice, and citizens’ groups and individuals committed to restoring the Gulf of Mexico to an ecologically and biologically sustainable condition. www.healthygulf.org.
The Mississippi River Collaborative is a partnership of environmental organizations and legal centers from states bordering the Mississippi River as well as regional and national groups working on issues affecting the Mississippi River and its tributaries. www.msrivercollab.org.