A Bigger 'Dead Zone' This Year Than Usual
By Peter N. Spotts
The Christian Science Monitor
NEW ORLEANS (July 28) -- The Gulf Coast's notorious "dead zone" -- a
summertime phenomenon in which coastal waters become so oxygen-deprived that marine
life cannot survive there --- is expected to be substantially larger than
average this year, covering a patch of ocean about half the size of Maryland.
The culprit is 2006's heavy spring rains, which sent more river runoff than
usual pouring into the Gulf - laced with fertilizers and other pollutants
that trigger the annual reappearance of the dead zone.
For most of a decade, government-backed researchers have studied the causes
and effects of this seasonal occurrence, which threatens some of the most
productive commercial fisheries in America. Now they are fielding pilot projects
that aim to cut the amount of nutrients flowing down the Mississippi River.
In addition, scientists are working to perfect their annual forecasts. They
hope to develop tools that will help fishermen find the more-productive
waters, as well as help government officials weigh the costs and benefits of
different approaches to reducing nutrients in the river.
Looking at the state of the science surrounding the dead zone, "the
fundamentals are sound," says Eugene Turner, a researcher with Louisiana State
University's Coastal Ecology Institute in Baton Rouge. But ask whether there's much
progress in reducing the nutrients flowing out of the Mississippi's vast
drainage basin, he replies, simply, "No."
The outlines of the problem are well established. Nitrogen and phosphorus
from farms and urban runoff deep in the continent's interior eventually feed
algae in the Gulf. The algae die, fall to the bottom and decompose, consuming
oxygen. If decomposers on the bottom consume oxygen faster than it can be
replenished, any finny fish or crustacean that can't outswim or outscamper this
"hypoxic" zone as it builds gets smothered.
One discovery of the past few years is just how knotty the problem is, Dr.
Turner says. Each smaller watershed feeding into the Big Muddy has its own
complex traits. Those watersheds support cities and towns with their own sets of
environmental and economic concerns beyond the going price of a shrimp
cocktail.
A study published last month by the University of Indiana's Todd Royer tells
the tale. He tracked the amount of nitrogen and phosphorus leaving three
river systems in Illinois for the past eight to 12 years. Not surprisingly, the
heaviest nutrient runoff came between mid-January and June, during snowmelt
and spring rain. But state standards for allowable nutrient runoff from fields
were the tightest in the summer and fall, when low, lazy flowing waters and
warm temperatures favor algae growth locally. State standards were less
stringent during the high-flow periods in the late winter and spring, when
nutrients are readily flushed downstream. Yet these are the flows that most affect
the Gulf's summertime hypoxic zone.
If control strategies are designed to protect local water quality, "then
this does it right," Dr. Royer says. But it shortchanges the Gulf, he adds.
Thus, a fix-it strategy for the Gulf that relies on local water-quality controls
may not do the job.
Potential solutions may include a shift in farmers' schedules -- getting
them to apply fertilizers in the spring rather than during the previous fall, he
says. Or it could mean inducing them to use farming techniques that require
less fertilizer.
Researchers at the University of Minnesota are looking at another approach
near Madelia, Minn.: planting trees, shrubs, and perennial flowers along
creeks and riverbanks as natural filters - with an eye toward plants that could be
used for biofuels so that these natural filters also could augment farmers'
incomes.
Indeed, adds LSU's Dr. Turner, "the overriding influence is land use."
Noting that Congress will consider the next multi-year farm bill this fall, he
says lawmakers might choose to cut conservation funds, or encourage farmers to
grow more corn for biofuel - both of which could undercut efforts to stop Gulf
Coast algae's annual feeding frenzy.
Uncertainties in how the overall river-ocean-algae system works still vex
researchers, who are trying to refine their forecasting models. Currently,
forecasts consider the amount of nutrients flowing down the Mississippi and
Atchafalaya rivers, says David Whitall, a coastal ecologist with the National
Oceanic and Atmospheric Administration. "But that's oversimplified," he says.
"Our next-generation models will link river inputs with physical oceanography,
but we're not there yet."
07-28-06 08:35 EDT
***
Cindy Hildebrand
[log in to unmask]
Ames, IA 50010
"Not a stick of timber, not even a riding switch can be found growing in
this township." (S.O. Woodworth, Iowa surveyor, describing a township in Union
County in the 1840s)
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