Janet Mcconnaughey, Associated Press Yahoo News 24 Jul 09;
NEW ORLEANS – The Gulf of Mexico's "dead zone" — where there is too little oxygen in the water for anything to live — is less than half the size predicted earlier this year but also unusually severe, a scientist said Friday.
The hypoxic area forms every year in the Gulf, caused by bacteria feeding on algae blooms from the flow of farming runoff and other nutrients from the Mississippi River and others.
This year's area covers 3,000 square miles, but is also unusually thick, stretching from the bottom nearly to the surface, according to Nancy Rabalais, a researcher who specializes in the problem for the Louisiana Universities Marine Consortium.
The 3,000 square miles is one of the smallest measurements of the zone since measurements began in 1985, according to a graph in a news release sent from a research vessel in the Gulf. Only those in 1987, 1988 and 2000 were smaller.
Other scientists had predicted that this year's dead zone would cover about 7,500 to 8,500 square miles.
Possible reasons for the difference include high winds and waves that helped mix more oxygen into some waters, she wrote.
"This was surprisingly small given the forecast to be among the largest ever and the expanse of the dead zone earlier this summer," she wrote.
Hypoxia occurs when algae blooms, fed by nitrates and phosphates in the water, die and fall to the bottom. At the same time, winds die down, meaning that fresh water coming out of the rivers doesn't get mixed into the denser salt water below it. Microbes feeding on the dead algae use up oxygen from the bottom up.
Rabalais said that in some areas where the oxygen was lowest, crabs, eels and shrimp — creatures which usually live on the bottom — were seen swimming at the surface.
Other studies indicate that severely low oxygen levels in early July contributed to "jubilees" — forced movement of fish, crabs and shrimp into shallow waters — off Grand Isle, she said.
Rabalais and other researchers are expected on Monday to discuss the hypoxic problem in a telephone news conference with Jane Lubchenco, head of the National Oceanic and Atmospheric Administration.
"We want to raise some of the issues behind it and some of the debate about the changes needed to shrink it," NOAA spokesman Ben Sherman said Wednesday.
While the Gulf's dead zone is among the largest, there are more than 250 hypoxic areas in U.S. waters, according to researcher Robert Diaz of Virginia Marine Institute.
Louisiana Universities Marine Consortium: http://www.lumcon.edu/
NOAA: http://www.noaa.gov/
U.S. "dead zone" smaller but more severe: NOAA
Timothy Gardner, Reuters 27 Jul 09;
WASHINGTON (Reuters) - The "dead zone" in the Gulf of Mexico, an area choked by low oxygen levels that threatens marine life, is smaller than expected this year but more deadly, the government said on Monday.
The zone, caused by a runoff of agricultural chemicals from farms along the Mississippi River, measured about 3,000 square miles or about 1.5 times the size of the state of Delaware, compared with estimates that it would measure up to nearly 8,500 square miles, scientists said.
"Clearly the flow of excess nitrogen and phosphorus from agricultural fields in the Mississippi drainage basin continues to wreak havoc with life in the Gulf," said Jane Lubchenco, the administrator of the National Oceanic and Atmospheric Administration, told reporters in a teleconference.
Unusually strong winds and currents stirred the waters and brought oxygen back in, making the zone smaller than anticipated.
But Nancy Rabalais, a scientist from the Louisiana Universities Marine Consortium, who helped measure the zone during a week-long expedition, said it was more severe because the low oxygen levels are closer to the surface than in recent years.
The dead zone threatens Gulf fisheries worth nearly $3 billion per year.
Now marine life that normally feed close to the sea bottom, including eels and certain kinds of shrimp and crabs, are being found closer to the surface.
The dead zone is caused by fertilizers and nutrients such as nitrogen and phosphorus that wash off crop lands into the Mississippi, leading to the overproduction of tiny organisms such as algae in the Gulf of Mexico.
If the organisms are not eaten, they die and fall to the bottom of the ocean where bacteria rots them, sucking oxygen from the water.
The average size of the dead zone during the past five years has been about 6,000 square miles, or nearly the size of the state of Connecticut.
Federal and state agencies have worked together in the Gulf of Mexico and Mississippi River Watershed Nutrient Task Force since 2001 to control growth of the zone. It wants to cut it to about 2,00O square miles by 2015.
But some say progress on controlling runoff has been slow.
"Really relatively little has been done to implement the action plan," said Donald Boesch, a marine scientist at the University of Maryland. He said U.S. mandates for more biofuels made from corn contribute to chemical runoff and the zone's size.
For their part, biofuels companies say they are using fewer chemicals to grow corn every year.
Unlike other efforts in other regions that have dead zones, such as the Chesapeake Bay and the Baltic Sea, numerical goals have not been set for reducing nutrients from areas near the Mississippi basin, Boesch said.
A federal environmental regulator said the task force will meet in Iowa in the autumn to bring new leadership and ideas to tackle the problem.
(Reporting by Timothy Gardner; Editing by Lisa Shumaker)
Dead Zone in Gulf Is Smaller Than Forecast but More Concentrated in Parts
Henry Fountain, The New York Times 27 Jul 09;
Scientists said Monday that the region of oxygen-starved water in the northern Gulf of Mexico this summer was smaller than forecast, which means less disruption of shrimp, crabs and other marine species, and of the fisheries that depend on them.
But researchers found that although the so-called dead zone along the Texas and Louisiana coasts was smaller — about 3,000 square miles compared with a prediction of about 8,000 square miles — the actual volume of low-oxygen, or hypoxic, water may be higher, as the layer is deeper and thicker in some parts of the gulf than normal. And the five-year average size of the dead zone is still considered far too big, about three times a target of 2,000 square miles set for 2015 by an intergovernmental task force.
“It’s a smaller footprint,” said Nancy N. Rabalais, executive director of the Louisiana Universities Marine Consortium, at a telephone news conference announcing the finding. She said unusual winds and currents this spring had driven much of the hypoxic water to the east, reducing the size of the zone but concentrating it. “In actuality we found quite a severe area that was large in volume,” she said. “Organisms were obviously stressed.”
Forecasts for hypoxic zones in the gulf are based on measurements of the nitrogen and phosphorus entering the water from agricultural runoff and other sources in the Mississippi River watershed. The forecast earlier this year was for a zone that would come near the record 8,500-square-mile-zone detected in 2002.
“But the model is based on predictions of what the zone would look like in a normal physical environment,” said Donald Scavia of the University of Michigan, one of the forecast’s preparers. “But this year we didn’t have normal physical conditions.”
When nitrogen and phosphorus enter the gulf, these nutrients cause an overabundance of algae — too much for other marine organisms to consume. Some of the algae die, sink to the bottom and decompose, and the bacteria that do the decomposing use up most of the oxygen in the water.
Faced with depleted levels of oxygen, fish and other creatures that can swim will leave for other waters. Those that cannot leave often die or show signs of reproductive or other stress. Shrimp and other fisheries in the gulf can be affected for weeks or longer.
In an interview, Dr. Rabalais, who has been mapping the gulf hypoxic zone during summer research cruises for 25 years, said that in the most affected areas, where levels of dissolved oxygen were near zero, she and her colleagues saw crabs, eels and brown shrimp swimming toward the surface, fleeing the low-oxygen water. Predator fish were obviously affected too, she said, as there were none around to eat the smaller escapees. “Any self-respecting fish would have eaten those brown shrimp,” she said.
Jane Lubchenco, under secretary of commerce and administrator of the National Oceanic and Atmospheric Administration, said the gulf dead zone was the most “notorious” of about 250 such regions around the country.
Agricultural runoff, she said, “continues to wreak havoc with life in the gulf.” Governments are working to promote programs to reduce nutrient runoff, like “engineered” wetlands that can remove nitrogen, but Dr. Lubchenco added, “Some progress is being made, but not enough.”
