U.S. Water News Online
BATON ROUGE, La. -- A Louisiana State University scientist
says his accurate predictions for the large low-oxygen "dead zone" in
the Gulf of Mexico prove that nitrogen is a main factor in its
Eugene Turner, a professor with LSU's Coastal Ecology Institute,
several years ago designed a method using the Mississippi River's
nitrogen level in May at St. Francisville to calculate the likely
size of the Gulf of Mexico's summer dead zone.
Turner said the model is not 100 percent accurate -- that's very
difficult to achieve with predictive models -- but that it has been
very close in the last three years, he said.
He said he was 99.2 percent accurate in predicting the dead zone's
size this year, which came in at about 6,662 square miles -- or about
the size of Connecticut and Rhode Island combined.
Every summer, a sea bottom area with too little oxygen to support
aquatic life forms along Louisiana's coast. That phenomenon, known as
hypoxia, occurs when fertilizer, urban runoff, sewage and other
substances feed the growth of microscopic organisms, which then die
and fall to the Gulf floor. The decomposition uses up oxygen in the
lower layer of water.
Fish, shrimp and other marine life move out of the low-oxygen
water -- that led scientists to name it the dead zone. Winter storms
dispel the dead zone by mixing the low-oxygen water with oxygen-rich
There is a national effort to reduce the size of the dead zone in
the Gulf, but there is still discussion about how that should be
Doug Daigle of the Mississippi River Basin Alliance said Turner's
model underscores what many scientific reports have said in the past.
"The model certainly strengthens the body of evidence that
nitrogen drives the dead zone," Daigle said.
Turner's prediction is based on the pioneering work his wife,
Nancy Rabalais, has done in dead zone research -- and on her crew's
Every summer, a team of scientists led by Rabalais, director of
the Louisiana Universities Marine Consortium's center in Cocodrie,
measures the dead zone. before each trip, crew members would make
their best guesses of the dead zone's size. After the trip, the
sealed envelopes would be opened. Whoever's guess was closest to the
actual size would win.
It was just for fun, but it got Turner thinking about creating a
He said the model isn't a substitute for the survey trips -- it
can predict the dead zone's size, but not its location.
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