Dead zone percolates in northwestern Gulf of Mexico
Sandscript is back and watching what’s dying in the northwestern Gulf of Mexico and beyond.
A patch of water encompassing about 8,000 square miles has been called the “dead zone” due to the low-oxygen content there. This year marks the third-largest dead zone on record in the Gulf.
The lack of oxygen drives fish and other marine life from the region. Bottom-dwelling critters simply suffocate and die.
The dead zone’s cause is attributed to runoff from the Mississippi River, which drains 41 percent of the lower United States. The area southwest of New Orleans also suffers from poor water circulation, acerbating the problem. Remember the old adage, “The solution to pollution is dilution?” Well, there isn’t all that much dilution in that portion of the Gulf except from the Mississippi.
And the problem is likely to worsen from an unlikely source. The “greening” of the country.
Scientists from the University of Michigan have been studying the low- or no-oxygen area, called a hypoxic zone, for several years. Researchers have made little or no progress in controlling the dead zone and predict that as more and farmland converts to corn for ethanol production, the hypoxia will increase in size.
Call it competing federal governmental agencies. On one side are the agencies that want to improve the atmosphere and combat global warming through the production and burning of ethanol. On the other side are the environmental groups that want to protect the Gulf from the spew of nitrogen and phosphorus that are products of stormwater runoff that ends up downstream and threatens the $500 million annual Gulf Coast fishery.
Donald Scavia and Kristina Donnelly are with the University of Michigan School of Natural Resources. They’ve been studying the dead zone for the feds since 2000. They’ve concluded that the best way to shrink the hypoxic nature of the Gulf is to eliminate the cause, the source of nitrogen and phosphorus.
The chemicals are used in fertilizer, with phosphorus also found in high levels from sewer treatment plant effluent. When the chemical soup ends up in open waters, it is like a free buffet at a biker bar, drawing all manner of hungry algae. The algae stuff themselves, then die and sink to the bottom. Bacteria eat the dead algae and gobble up all the oxygen in the water. End result: dead water.
Writing in the journal Environmental Science & Technology, the two scientists took present levels of nitrogen and phosphorus and extrapolated projected farming trends in the states with runoff that trickles into the Mississippi River.
Results indicate bigger dead zones loom ahead.
Scavia offered a thought, a scientific bone to a ravaging federal beast: “We understand what needs to be done, and the technology needed to do it is available. All we really need is the political will and the funding.”
A Hypoxia Action Plan was submitted to federal politicians and environmental regulators in 2001, and is under review.
Adding fuel to the hypoxic mix is a 2007 law approved by Congress to produce up to 36 billion gallons of biofuels, mainly ethanol and biodiesel, by 2022. That figure would accommodate about 15 percent of U.S. transportation needs.
Green fuel isn’t all a corn product. According to a study by the University of British Columbia and the University of Wisconsin-Madison, “An estimated 21 billion gallons will come from advanced biofuels, which can be produced using a variety of new feedstocks and technologies. Of this, roughly 16 billion gallons is expected to be from cellulosic biofuels, derived from plant sources such as trees, grasses and agricultural waste.”
The U.S. ethanol industry produced a record amount of fuel ethanol in 2007 — 6.48 billion gallons, which represents 32 percent more ethanol than in 2006, according to the U.S. Energy Department Energy Information Administration. Capacity for ethanol production is expected to grow another 4 billion gallons in 2008.
The 2007 corn harvest came from 84.4 million acres, up 14.8 million acres from last year. More acreage is expected to be devoted to corn harvesting to meet the 2017 goal.
Nature fights back, somewhat
So there’s this big dead zone out there. Think of it as a big lump of crud. Why not mix it up and move it along?
Well, first it would take a really big mixer. Like a hurricane.
When Hurricane Ike chugged through the northern Gulf, it did indeed churn up the hypoxic mess. For a while.
Researchers with the Louisiana Universities Marine Consortium said oxygen levels increased for a bit post-Ike, but were starting to return to abnormally low levels again. It will take winter’s cold fronts to stir up the goop to bring oxygen levels back up to levels that can sustain marine life.
… and we’re not alone in the Gulf dead zone
There are an estimated 400 dead zones scattered around the globe, covering about 95,000 square miles. And scientists with the Virginia Institute of Marine Science estimated that the size and quantity of the zones has doubled every decade since 1960.
According to a study in the journal “Science,” the largest dead zone is in the Baltic Sea. There are also scattered pockets of hypoxic water off California.
Good news comes out of San Francisco Bay. From the 1950s through the 1970s, water quality was abysmal due to poorly operating sewer treatment plants and canneries. Things got better out there in recent decades, though, and hypoxia is a thing of the past. For now, at least.
And now, bringing it home
Sarasota Bay has some low-circulation areas within its boundaries. They are not dead zones, but they are areas where water takes a long time to flush. Scientists call the areas null zones.
Dr. Y. Peter Sheng has studied local waters and written several technical papers on water circulation in the Sarasota Bay system.
As he has written in the 1993 Sarasota Bay Estuary Program publication “Framework For Action,” “Circulation and transport within the Sarasota Bay system are primarily driven by the interaction of tidal wives propagating through the multiple inlets connecting the bay with the Gulf of Mexico and Tampa Bay. Circulation and transport are also influenced by wind, as well as by density gradients associated with salinity and temperature variations.
“Sarasota Bay is characterized by areas of strong currents in and around the passes, and by null zones (areas of very low currents) located at dead-end zones or where two tidal waves propagating in from different inlets meet.”
After reviewing some on-the-water sampling and plugging data into computers, Sheng was able to offer water circulation figures on the bay.
His figures estimated that 31 percent of the water in Palma Sola Bay was flushed out in 10 days. Middle Sarasota Bay flushed 32 percent in 10 days; Little Sarasota Bay, where the former Midnight Pass was located between Siesta and Casey keys, had 27 percent flushed in 10 days.
In contrast, Anna Maria Sound by the Cortez Bridge had 81 percent water flushed in 10 days, and the Longboat Pass area had 64 percent flushed in 10 days.
“It is clear that Palma Sola Bay, middle Sarasota Bay and middle Little Sarasota Bay have rather poor flushing rates,” Sheng wrote.
So just how big is 8,000 square miles worth of dead zone?
Figure an area about the size of New Jersey.