Floodwaters to widen 'dead zone' in Gulf of Mexico
Pastor Dale Morgan
Floodwaters to widen 'dead zone' in Gulf of Mexico*
By Seth Borenstein, AP Science Writer
WASHINGTON — Floodwaters loaded with farm runoff are heading down the
Mississippi River, and scientists fear the deluge will dramatically
increase this summer's dead zone in the Gulf of Mexico, covering an area
the size of Maryland.
The dead zone is a region of the gulf that becomes starved for oxygen
during much of the summer and cannot support fish or other sea life.
There are hundreds of dead zones around the world that wreak havoc with
marine ecology and cut off vast areas for commercial fishing. The zone
in the gulf is the largest in the Western Hemisphere.
"It's going to be a very interesting summer out there just because of
this," said Steven DiMarco, a professor of oceanography at Texas A&M
University. "The last time something like this happened, we did see a
huge difference" in the size of the dead zone from one year to the next.
The zone off the Louisiana and Texas coasts was first seen in 1972. Its
size varies each year, but it has tended to grow over the decades, with
a major jump in 1993, after the last big Mississippi River flood.
That flood made the oxygen problem substantially worse, which may happen
again this year, DiMarco said Friday.
Even before the flooding, scientists had predicted that the gulf this
summer would see its largest-ever dead zone — more than 10,000 square
miles. Now experts say it's likely to be even bigger.
Oxygen in the dead zone is depleted by excess nutrients, mostly nitrates
from farm fertilizer runoff, that cause algae blooms. After the algae
dies, bacteria on the bottom feast on the remains, removing crucial
oxygen from the water.
The dead zone in the gulf forms in early summer and lasts through early
fall.
This year's massive floods will bring a heavier load of fertilizer into
the gulf, DiMarco said.
But it's more than the nitrates. The trillions of gallons of floodwater
help trap the oxygen-depleted water near the gulf floor. The fresh
water, which stays at the surface because it is less dense, forms a
physical barrier that keeps oxygen in the air from mixing with the water
covering the dead zone area, DiMarco said.
Scientists are just starting to study how the increasing size of the
dead zone is affecting fish.
Think of a giant corridor from Des Moines to Chicago and "you took a
great big piece of Saran Wrap over all that area and sucked all the
oxygen out," said Nancy Rabalais, executive director of the Louisiana
Universities Marine Consortium. "You would have a big problem."
Even without the flooding, signs from early spring flooding and heavy
fertilizer use were pointing to a record year for the dead zone, said
Louisiana State University professor R. Eugene Turner. Earlier this
month, using data from before the floods, Turner predicted the zone
would break the 10,000-square-mile mark. Last year it covered 7,900
square miles.
Scientists are also worried that the jump in corn production triggered
by heightened demand for ethanol fuel could worsen the dead zone because
of the increased use of fertilizers. The big question is whether it will
make the zone larger, cause it to last longer or become more
oxygen-starved, or some combination of those, DiMarco said.
In May, nearly 500 million pounds of nitrates flowed down the
Mississippi, Rabalais said. The algae bloom — the first step of dead
zones — started a month early this year, in February, she said.