Death in the dead zone
By Robert Montgomery
Scientists believe that the exotic zebra mussel is a
contributing factor to the demise of Lake Erie.
Conflicts over a natural resource aren't always over its
use and allocation. Sometimes they're about the casualties
sustained due to the abuse we, as a society, inflict on
One "water war" that continues to rage involves
who's responsible for the nitrogen pollution that feeds
the "dead zone" in the Gulf of Mexico each summer
and fall. From the mouth of the Mississippi River, this
zone of oxygen-depleted water spreads out for thousands
of square miles to the south and west. No fish or other
forms of aquatic life can exist in the zone. Those that
can't move away fast enough often die.
The dead zone occurs because the nutrient overload feeds
massive algae blooms. The blooms eventually die and decay,
robbing the water of life-sustaining oxygen.
According to the U.S. Environmental Protection Agency,
"the hypoxic zone centers squarely in the middle
of one of the most important fisheries in the United States,
an area that produces 40 percent of the country's commercial
fish and shellfish. In Louisiana, commercial fishing supports
90,000 jobs and has an economic impact of $1.5 billion
"To compensate for ecological changes wrought by
hypoxia, Gulf fishing boats are now moving farther out
to sea to reach the shrinking fishery, spending more for
fuel, supplies and wages. Others drop their nets closer
to shore, causing localized overfishing of the nearshore
Most researchers believe that runoff from agricultural
lands, especially above the confluence of the Mississippi
and Ohio rivers, is to blame for the nitrogen that feeds
the dead zone.
Farmers disagree, saying that no proof exists as to the
The U.S. Geological Survey (USGS) and other groups, however,
maintain that perhaps as much as 60 percent of the nutrient
load comes from fertilizer, plant debris and minerals
from soil fodder. About 15 percent is linked to animal
manure, much of it from factory farms.
Iowa and Illinois are believed to contribute about 35
percent of the nitrogen load.
"I'm sure overfertilized golf courses in some places
would contribute, as would the fertilizer people put on
urban lawns," said Donald Goolsby, a retired USGS
"It all contributes but if you look at the real
hot spots for this nitrogen discharge, they're not high-population
areas. They're not places with huge wastewater plants
of industrial emissions. They're croplands."
As additional evidence that farming practices are damaging
the fishing industry of the Gulf, researchers point to
the Black Sea. It, too, was sickened by a dead zone for
decades. Then farmers lost their state-issued fertilizer
when the Soviet Union collapsed, and oxygen has returned
to the water.