2TheAdvocate, LA
04-26-06
Group doubts project will cut 'dead zone'
By AMY WOLD
Advocate staff writer
NEW ORLEANS — Diversions of river water in Louisiana will do little to reduce
the pollution that helps fuel low-oxygen areas in the Gulf of Mexico, according to
researchers at a meeting Tuesday.
Some scientists think diversions — often used to reroute sediment-laden
Mississippi River water to nourish wetlands — could help reduce the amount of
fertilizer runoff and other sources of nitrogen that winds up in the Gulf. Nitrogen
helps create low-oxygen levels in the Gulf each summer.
But LSU researcher Eugene Turner said wetlands don’t reduce nitrogen that
much.
“It’s not trapping a lot, except for sediments,” Turner said about a study done on
the Atchafalaya River basin.
He quoted another study reporting that even if 20 percent of the Mississippi were
diverted to other channels for coastal restoration, only 4 percent of the river’s
load of nitrogen would be removed.
Also, the diversions will take decades to build. A federal plan to reduce the size
of the dead zone has a deadline of 2015, he said.
Not everyone agreed with his assessment. Len Bahr, with the Governor’s Office
of Coastal Affairs, said the matter needs further study.
Bahr said a majority of the Atchafalaya River is contained within levees. That’s
not the same as having the water flow over large areas of wetlands, as
envisioned in major freshwater diversion projects, he said.
Donald Boesch, president of the University of Maryland Center for Environmental
Science, added that to make the federally mandated dead-zone reduction, every
little bit will help.
Theirs were just a few of the comments on the first day of a meeting to assess
what is known about how the dead zone in the Gulf forms. Organized by the U.S.
Environmental Protection Agency and the National Oceanic and Atmospheric
Administration, the conference continues today in New Orleans.
Hypoxia is an area of very low oxygen called the “dead zone” that forms along
the coast of Louisiana and part of Texas.
The zone forms when nutrients such as fertilizer, urban runoff and sewage flow
into the Gulf from the Mississippi River.
The nutrients feed the growth of microscopic organisms that then die and fall to
the Gulf floor. As the material decomposes, it uses up oxygen in the lower layer
of water.
During the winter, frequent storms mix the low-oxygen water with the oxygen-rich
surface water. But in summer, that low-oxygen water sits on the bottom, creating
the “dead zone.”
Tuesday’s meeting is one of four being held throughout the basin as part of a
five-year reassessment for a federal hypoxia reduction plan. The average size of
the dead zone is 15,600 square kilometers a year. The goal is to reduce it to
5,000 by 2015.
Many people blame the nutrients that feed the dead zone on large amounts of
fertilizer used to grow corn and soybeans in the Midwest.
Several speakers Tuesday said hypoxia started to show itself as an annual event
between 1960 and 1975. That’s about the time large amounts of nitrogen, in the
form of fertilizer, were being applied to farms, Turner said.
But other speakers said it’s not simply a matter of farmers using too much
fertilizer — the land use of upper Mississippi River valley has changed.
“Emerging science suggests that current nutrient impairment problems are not
mainly due to mismanagement of fertilizers and manures,” said James Baker,
with Iowa State University.
Instead, he said, the nitrogen that gets into the water reflects how the land in the
Midwest has changed from wetlands and prairies to farmland.
That change has also altered how water drains in the Mississippi River basin, he
said. For example, drainage systems on farmland move water faster, allowing
fewer nutrients to be absorbed before reaching rivers.
“This has eliminated the wetland, but created a very productive soil,” Baker said.