[FoRK] "Dead zone"
jbone at place.org
Wed Aug 4 14:02:29 PDT 2004
I'm no eco-freak hippy-dippy tree hugger --- hell, I don't even OWN a
pair of Birkenstocks ;-) --- but when things start messing up the ocean
I do get concerned. 'Course this is recurrent news, but a marine
biologist friend of mine says the problem's getting worse and the shape
of the curve's scary.
'Dead zone' spreads across Gulf of Mexico
HOUSTON, Texas (Reuters) -- A huge "dead zone" of water so devoid of
oxygen that sea life cannot live in it has spread across 5,800 square
miles of the Gulf of Mexico this summer in what has become an annual
occurrence caused by pollution.
The extensive area of uninhabitable water may be contributing
indirectly to an unusual spate of shark bites along the Texas coast,
A scientist at the Louisiana Universities Marine Consortium said
Tuesday measurements showed the dead zone extended from the mouth of
the Mississippi River in southeastern Louisiana 250 miles west to near
the Texas border and was closer to shore than usual because winds and
"Fish and swimming crabs escape (from the dead zone)," said Nancy
Rabalais, the consortium's chief scientist for hypoxia, or low oxygen,
research. "Anything else dies."
In the last 30 years, the dead zone has become an annual summer
phenomenon, fed by rising use of nitrate-based fertilizers by farmers
in the Mississippi watershed, Rabalais told Reuters.
The nitrates, carried into the gulf's warm summer waters by the river,
feed algae blooms that use up oxygen and make the water uninhabitable.
The dead zone's size has varied each year depending on weather
conditions, but averages about 5,000 square miles and remains in place
until late September or early October.
Virtually nothing is being done to stop the flow of nitrates into the
river, meaning the dead zone will reappear every year, Rabalais said.
The dead zone forces fish to seek better water, which may be a reason
for the recent shark bites on Texas beaches.
Three people have been bitten by sharks along the upper Texas coast
this year -- a high number for a state that has recorded only 18 shark
attacks since 1980.
Terry Stelly, an ecosystem biologist with the Texas Parks and Wildlife
Department, said increasing numbers of sharks have been found in recent
years in the waters along the Texas-Louisiana border, near the edge of
the dead zone.
Along with other factors, "chances are good they (sharks) were looking
for higher dissolved oxygen in the water," he said.
Rabalais agreed, saying "The higher number of sharks in shallow waters
may very likely be due to the low oxygen being close to the shore at
the time of the attacks."
"The available habitat for the sharks is definitely less when the low
oxygen is so widespread," she said.
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