Gulf of Mexico "dead zone" to hit record size: NOAA
Tue Jul 15, 2008 9:19pm BST
By Chris Baltimore
HOUSTON (Reuters) - The Gulf of Mexico's "dead zone" -- a swath of
algae-laden water with oxygen levels low enough to choke out
marine life -- will likely reach record size this year, and the
main culprits are rising ethanol use and massive Midwest flooding,
scientists said on Tuesday.
The dead zone, which recurs each year off the Texas and Louisiana
coasts, could stretch to more than 8,800 square miles
this year -- about the size of New Jersey -- compared with 6,662
square miles in 2006 and nearly double the annual average since
1990 of 4,800 square miles.
Scientists from the U.S. National Oceanic and Atmospheric
Administration, Louisiana Universities Marine Consortium and
Louisiana State University said the algae that lowers oxygen
levels in the dead zone is being fed by farm use of fertilizers
like nitrogen and phosphorus.
For fishermen who look to the Gulf of Mexico for crabs, shrimp,
crawfish and other seafood, the growing dead zone means they must
venture farther out into the gulf's waters to find their catch.
The record dead zone is due to soaring use of ethanol in U.S.
motor gasoline supplies and by massive flooding in the Midwest
earlier this year, scientists said.
"We're planting an awful lot of corn and soybeans," said Eugene
Turner, a scientist at Louisiana State University. "It rinses off
easily when there is a rain."
One-third of this year's U.S. corn crop, or 4 billion bushels,
will go to make the alternate fuel ethanol, the U.S. government
has projected, compared to 3 billion bushels of the 2007 crop.
The dead zone starts in Midwestern corn country when farmers
fertilize their fields with nitrogen. The fertilizer run-off flows
down the Mississippi River into the Gulf of Mexico, making algae
bloom on the surface and cutting oxygen to creatures that live on
Substances in this runoff include the nutrients nitrogen and
phosphorus, which can stimulate the growth of algae. These algae
settle and decay in the bottom waters of the Gulf, and the
bacteria that decompose them gobble up oxygen faster than it can
be replenished from the surface, which means lower levels of
dissolved oxygen in the water.
U.S. scientists estimate that a record 83,000 tons of phosphorus
seeped into the Gulf of Mexico from April through June, up to 85
percent above normal seasonal levels.
"Excess nutrients from the Mississippi River watershed during the
spring are the primary human-influenced factor behind the
expansion of the dead zone," said Rob Magnien, director of the
NOAA Center for Sponsored Coastal Ocean Research.
To reverse the pattern, U.S. farmers must plant more perennial
crops that trap rainwater and keep it from running into the Gulf
of Mexico, Turner said.
And eventually, scientists need to invent new breeds of perennial
corn plants that can remain in the soil from one planting season
to the next, avoiding the need to strip fields bare and leave them
susceptible to flooding, he said.
(Reporting by Chris Baltimore, editing by Anthony Boadle)
Kyle J. Fricker
University of Florida