WASHINGTON The Gulf of Mexico's "dead zone" --
a swath of water with such low levels of oxygen that marine
life can be threatened or killed -- could be the largest since
measurements began in 1985, scientists said on Tuesday.
The dead zone, which recurs each year off the Texas and
Louisiana coasts, could stretch to more than 8,500 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 forecast the expanded dead zone in a
The dead zone is fed by melted snow and spring flooding
along the Mississippi and Atchafalaya rivers, carrying farm
chemicals and other runoff into the Gulf of Mexico, the
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 oxygen faster than it
can be replenished from the surface, which means lower levels
of dissolved oxygen in the water.
"This hypoxic area is of particular concern because of its
potential to affect the valuable Gulf fishery," NOAA said in a
The dead zone starts to form in the spring and usually
reaches its peak by the end of July or early August, said David
Whitall, a coastal ecologist with NOAA who worked on the
prediction. A research ship will survey the area to measure the
zone by July's end, Whitall said in a telephone interview.
Tropical storms can disrupt the dead zone, and NOAA has
predicted an active hurricane season for 2007, but if no strong
storms occur, this year's dead zone could exceed the record
largest zone of 2002.
"We are predicting that it's going to be bigger than 2002,
but not a lot bigger," Whitall said.
In 2002, the dead zone stretched in a wide band for 8,495
square miles from the waters off New Orleans to the central
This year's expected large dead zone may be due to more
intensive farming, including crops that produce biofuels, on
more land. While agriculture is the main source of the
chemicals that contribute to the dead zone, these substances
also come from wastewater treatment plants and pollution that
gets into rain water, Whitall said.