Stephanie Pappas, LiveScience Yahoo News 14 Jun 11;
The dead zone in the Gulf of Mexico is likely to be larger than average this year — possibly rivaling the state of New Hampshire in size — due to this spring's massive Mississippi River floods.
Scientists at Louisiana State University, the Louisiana Universities Marine Consortium and the University of Michigan predict that the low-oxygen dead zone could measure between 8,500 and 9,421 square miles. The largest Gulf dead zone on record was in 2002, encompassing more than 8,400 square miles.
Dead zones happen when excessive nutrients (usually nitrogen and phosphorus fertilizer and other farming run-off) cause marine algae blooms. These blooms and their subsequent die-offs deplete the oxygen in the water column, leading to hypoxic, or low-oxygen, zones where life can't thrive.
Every summer, a hypoxic zone forms off the coast of Louisiana and Texas, threatening the commercial and recreational fisheries on the Gulf Coast. This year, the United States Geological Survey estimates, 164,000 metric tons of nitrogen were transported into the Gulf by the swollen Mississippi and Atchafalaya Rivers. In May alone, the nitrogen flow was 35 percent higher than the average rate measured in May in the last 35 years. That adds up to more nutrients in the Gulf and a greater likelihood of a giant dead zone. [Top 5 Mightiest Floods of the Mississippi River]
There is some uncertainty regarding how large this year's dead zone will grow, National Oceanic and Atmospheric Administration (NOAA) administrator Jane Lubchenco said in a statement. Nonetheless, she said, "the forecast models are in overall agreement that hypoxia will be larger than we have typically seen in recent years."
The spring floods may also lead to a surge in the giant invasive fish called the Asian carp in new areas of the Mississippi and Missouri river basins, scientists are now warning.
Mississippi Floods Could Mean Huge Gulf "Dead Zone"
Deborah Zabarenko PlanetArk 15 Jun 11;
This year's record Mississippi River floods are forecast to create the biggest Gulf of Mexico "dead zone" since systematic mapping began in 1985, U.S. scientists reported on Tuesday.
Often created by farm chemical run-off carried to the Gulf by the Mississippi, the 2011 low-oxygen "dead zone" could measure 8,500 to 9,421 square miles (22,253 to 26,515 sq km), or an area roughly the size of New Hampshire, the U.S. Geological Survey said in a statement.
This would be bigger than 2002's record-large hypoxic zone, which stretched over 8,400 square miles (21,750 sq km).
The hypoxic zone threatens commercial and recreational Gulf fisheries. In 2009, the dockside value of commercial Gulf fisheries was $629 million. Recreational fishers contributed more than $1 billion to the Gulf economy taking 22 million fishing trips, the survey said in its statement.
Seen year-round but most pronounced in summer, the "dead zone" threatens resources including humans who depend on fish, shrimp and crabs, which need oxygen to survive. The zone typically is located on the bottom of the continental shelf off Louisiana and Texas.
Excess nutrients from the farm chemicals in the water -- mostly nitrogen and phosphorous -- do the same thing in the Gulf that they do on agricultural fields: they encourage plant growth.
FLOODED RIVERS CARRY MORE NITROGEN
In the Gulf, they cause tiny marine plants called phytoplankton to bloom, decay, die and sink to the bottom, where bacteria eat their remains and use up oxygen in the water as they do so.
Stream-flow rates along the Mississippi and Atchafalaya rivers were nearly twice normal rates in May, significantly increasing the amount of nitrogen carried into the Gulf, about 35 percent higher than average nitrogen loads for May estimated in the last 32 years. More rain was forecast for the Midwest this week.
There's plenty of oxygen on the surface of the Gulf, where fresh water from the Mississippi lingers, according to Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, one of the authors of the forecast.
But this oxygen-rich water cannot penetrate the salt water that stays beneath it, Rabalais said in a telephone interview.
"The effects on living organisms are in the lower water column and at the seabed," she said, adding that low levels of oxygen can be found anywhere from about 15 feet to 120 feet deep.
The Mississippi River Drainage Basin covers more than 1.2 million square miles and includes all or parts of 31 states and two Canadian provinces, stretching from New York state to Montana. Only the watersheds of the Amazon and Congo rivers are bigger.
(Editing by Cynthia Osterman)
Forecast predicts biggest Gulf dead zone ever
Cain Burdeau Associated Press Yahoo News 15 Jun 11;
NEW ORLEANS – Scientists predict this year's "dead zone" of low-oxygen water in the northern Gulf of Mexico will be the largest in history — about the size of Lake Erie — because of more runoff from the flooded Mississippi River valley.
Each year when the nutrient-rich freshwater from the Mississippi and Atchafalaya rivers pours into the Gulf, it spawns massive algae blooms. In turn, the algae consume the oxygen in the Gulf, creating the low oxygen conditions. Fish, shrimp and many other species must escape the dead zone or face dying.
Federal and university scientists predict this year's zone will be between 8,500 square miles and about 9,400 square miles. The actual size of the dead zone will be measured over the summer.
The largest recorded dead zone was found in 2002 when 8,400 square miles of the Gulf was found to lacking sufficient oxygen for most marine life.
The forecasts on the size of the hypoxic zone are usually close to the mark, although hurricanes have chopped them up in the past.
Eugene Turner, an oceanographer at Louisiana State University, said the dead zone has continued to get larger since it was first noticed and measured in the 1970s. He said the dead zone is getting worse with time.
The biggest contributor is the amount of fertilizer — and the nitrates and phosphates in them — that wind up in the Mississippi River each spring and get flushed out to the Gulf.
"The nitrogen is fertilizing the waters offshore," Turner said. He said little progress has been made in recent years to reduce the nutrient load into the Gulf.
The federal government and states in the Mississippi valley are attempting to reduce runoff from farms, lawns and cities, but those efforts have not curbed the problem.
This year, for instance, the U.S. Geological Survey said the nitrogen load that reached the Gulf was 35 percent higher than the average amount flushed into the Gulf each May over the past 32 years. The Mississippi and Atchafalaya rivers dumped nearly twice as much water than normal in May, officials said.
"As usual, the size of the low oxygen offshore is driven by both the freshwater and nitrogen levels in the Mississippi, so this year we have had floods and we have had more nitrate coming into the system," said Nancy Rabalais, the executive director of the Louisiana Universities Marine Consortium. Rabalais is a lead researcher into the dead zone.
She expected the dead zone to extend more to the west toward Texas and farther offshore than in past years.
Scientists said the large dead zone will complicate the Gulf's recovery from last year's massive oil spill. After the Deepwater Horizon drilling rig exploded on April 20, 2010, an out-of-control well owned by BP PLC. spewed about 206 million gallons of oil — 19 times more than the Exxon Valdez spilled.
"This is an additional stressor," Rabalais said. "It's our chronic stressor."
Heavy Rains Move To U.S. Midwest, More Flooding
Christine Stebbins PlanetArk 15 Jun 11;
Rains return to the U.S. Midwest this week, increasing the risk of more farms flooding along the Missouri River and add to slowdowns in moving grain by rail, a forecaster said on Tuesday.
"At this point most of the planting is done -- you have to be concerned of the increase river flood potential with the levy breaking at Hamburg (Iowa) yesterday," said Mike Palmerino, forecaster with Telvent DTN weather service.
Heavy winter snowmelt feeding the Missouri River's headwaters in the Rocky Mountains, as well as heavy spring rains, have caused historic flooding with tens of thousands of acres of cropland at risk from Montana to Iowa. Soggy rail beds have also caused big delays in rail shipments.
"The flooded Missouri flows into the Mississippi River. It's dicey especially with more rains coming today," Palmerino said.
Up to 1.5 inch (38 mm) of rain is forecast for the Corn Belt over the next two days, starting in the west and moving eastward. That comes on top of heavy rains, up to 4 inches in western Illinois on Monday, Palmerino said.
Another 0.3 to 1.5 inch was forecast for Friday to Saturday beltwide.
The Northern Plains spring wheat and corn country also stays wet with another 0.25 to 1.0 inch expected on Tuesday and up to 2 inches forecast for the weekend.
In contrast, the southern Corn Belt stays hot and dry as highs soar to 98 to 105 Fahrenheit (37 to 40 Celsius).
"I'm hearing more reports they are losing corn in the South," Palmerino said.
The six to 10-day Midwest outlook, Sunday to Thursday, called for normal to above-normal temperatures early in the period, cooling later. The rainfall was expected to be normal to above.
(Editing by Lisa Shumaker)
Read more!
Posts
visitors since Nov 07