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				“The Dead Zone” An Oxygen-starved, sealife-killing zone the size of New Jersey appears each summer in the Gulf off the Coast of Louisiana Texas Parks & Wildlife By Phil H. Shook It was on the second dive of a research mission off Freeport on a July day in 1979 that Don Harper noticed that something wasn't right. At 70 feet, he was surprised to come upon a clear layer of water. When the sea floor came into view, he saw that it was strewn with dead worms and crabs and cottony bottom patches the size of dinner plates. A whiff of hydrogen sulfide penetrated his mask. "Worms were partway out of their tubes lying on the bottom all over the place-these were big animals," says Harper, a professor of marine science with the Texas A&M marine lab in Galveston. What Harper had come upon unexpectedly and later confirmed with subsequent dives and laboratory testing was an oxygen-starved, marine life-killing dead zone in the Gulf. At the time, very little was known about these kinds of outbreaks other than anecdotal information on similar occurrences off Louisiana. Harper continued to make dives off the Freeport area for seven years, up until 1984, as part of an inspection of undersea salt domes. During that time he said he encountered similar hypoxic zones at intervals of two years. A few years later, marine biologists discovered off the Louisiana coast a wasteland that made Harper's apocalyptic scene seem minor by comparison. The same hypoxic conditions that Harper came upon had grown like a cancer off the Louisiana coast since 1985. Marine biologists gave the phenomenon a name worthy of a science fiction movie: The Dead Zone. Harper and other marine biologists who have studied the blight over two decades believe the oxygen-starved dead zone the size of New Jersey that forms each summer off Louisiana's coast is a threat to the health and stability of the entire Western Gulf of Mexico. "If it continues to increase, it could affect the entire Texas coast down to at least the Corpus Christi area," Harper says. "And then you are talking about dead water on a massive scale and the secession of some of the fisheries." Spawned by an overabundance of nutrients flowing down the Mississippi River, the 7,000 square mile hypoxic--low oxygen--zone has been tracked off the Louisiana coast from the river's mouth all the way to the Texas border. Marine scientists have watched it move into deeper waters and they fear it could spread as far south as the Texas Coastal Bend, killing or evicting every marine animal in its path. The hypoxia that has occurred off Texas is "imported" from Louisiana and is not generated by Texas rivers flowing into the gulf, Harper says. He points out that the Mississippi River discharges hundreds of times more water than the local rivers and the salinity of Lower Galveston Bay also is influenced more by the Mississippi.. "By and large the Mississippi controls the water salinity, the water clarity and everything else over here." . Shortly after Harper's encounter with hypoxic outbreaks in Texas waters, Dr. Nancy Rabalais, a colleague of Harper's joined Louisiana Universities Marine Consortium and began a series of studies on the dead water zones. Rabalais, a co-discoverer of the massive dead zone off Louisiana, has compiled data and tracked the phenomenon for more than 15 years. The Shape of Things to Come The dead zone is currently a seasonal phenomenon. It appears off Louisiana waters around May, after floods have washed nutrients off riverside lands and carried them downstream by the Mississippi to the gulf. The condition disappears when winter winds break up algal blooms and move oxygen-rich water back into the area. The size of the dead zone off Louisiana grew as large as 4,000 square miles in the period from 1985 to 1997. (It barely occurred at all during the drought year of 1988.) But the phenomenon attracted little attention outside scientific circles until 1993, a year of major flooding, when it doubled in size to more than 7,000 square miles. What followed also alarmed scientists. Since 1993, a year of major flooding, when it doubled in size to more than 7,000 square miles. What followed also alarmed scientists. Since 1993, the dead zone exceeded 6,000 square miles each year, peaking at 7,032 square miles in 1995. It appeared to pull back slightly in 1998 to 4,800 square miles, b! ut Rabalais said it merely changed shape, growing deeper as it narrowed and moved into deeper waters. "On the map it appears smaller, but the volume was about the same," she says. The dead zone now extends out an astounding 55 miles into the gulf in some places, and to depths of 130 feet. Down off the Farm One of the 10 largest rivers in the world, the mighty Mississippi drains 40 percent of the land area of the continental United States and dumps 580 cubic kilometers of water into the Gulf of Mexico every year. But in the process it also dumps a huge load of agricultural nutrients, some traveling 1,000 miles to the gulf. Most scientists aghree that this nutrient load is one of the chief causes of the dead zone area. Other rivers that run to the gulf deliver agricultural nutrients, but none on the scale and volume of the Mississippi River. The Mississippi River watershed carries more than 1.5 million tons of nitrogen, much of it washed from the fields of the Midwest farm belt, says Otto Doering, a professor at Purdue University. Nutrients like nitrogen and phosphorus are essential for healthy marine and freshwater environments. But an overabundance can trigger excessive algal growth (eutrophication), which results in reduced sunlight, loss of aquatic habitat and a decrease in oxygen dissolved in the water. Studies of water samples, sediments from the sea floor and other data show that the amount of dissolved nitrogen in the outflow of the Mississippi and the adjacent Atchafalaya Basin has tripled sine the early 1970s. Officials with the U.S. Geological Survey say sewage from urban development along the Mississipoi and its tributaries contributes only in a small way to the problem. A U.S.G.S. study estimates that 90 percent of the Mississippi River nitrogen comes from three sources: commercial fertilizers, livestock manure used as fertilizer, and plants such as soybeans that send nitrogen into the soil rather than take it out. "The size and duration of the hypoxic zone is very clearly driven by the nutrient load in the Mississippi River," says Donald Scavia, director of the Coastal Oceans Program at the National Oceanic and Atmospheric Administration (NOAA). Warning Signs If one is looking for a worst-case scenario of what could happen in the Gulf of Mexico, one needn't look any farther than the Black Sea. The sea, which supports everything from the Ukrainian fishing fleet to a resort industry on the Bulgarian coast, began to receive a massive load of nutrients starting in the 1960s, as development and agricultural pesticide use boomed along the Danube River. After decades of decline, the Black Sea hit a low point in 1989. "A terrible stench of rotting eggs descended on the streets of Odessa," as Colin Woodard describes it in Ocean's End: Travels Through Endangered Seas. "Out in the bay, scientists found an algae bloom of shocking proportions: tiny phytoplankton in the water attained such dense concentrations that hydrogen sulfide gas began to rise out of the sea as dead creatures of all sorts decayed." Comb jellyfish and algae took over, and fish "stocks suffered a sudden, devasting crash." Some 2 million fishermen lost their jobs in what may be the world's first example of the death of a sea by eutrophicaiton. Scientists who have studied the Black Sea are concerned that the gulf dead zone could be following the same pattern toward disaster. If nothing is done to halt the expansion of the dead zone, they say, it could eventually become a permanent rather than a seasonal blight on the gulf. What would happen to the $26 billion gulf fishery? Although data is lacking on the full impact of the dead zone on commercial fishing, the anecdotal evidence is disturbing. Some Texas shrimpers who set their trawls off Louisiana say it has driven many of their colleagues out of these waters or out of business. Fishermen have blamed the dead zone for reducing menhaden and shrimp catches. One thing is certain: shrimp lose a staple food source when the bottom-dwelling worms they feed on are killed. And the loss to fisheries is not confined to the affected zone alone. Richard Moore, a commercial fisherman on the upper Texas coast, says that productive areas surrounding dead zones quickly become overfished when most of the fleet descedns on the area. Biologists are also concerned about other, more subtle effects on the ecology of the gulf. Because of the persistent annual occurrence of hypoxia in the Atchafalaya Bay area of Louisiana., Harper notes that there no longer exists what is called a "climax community"a marine community that has gone through all of its changes and is in a steady state. "That is because everything is killed off every year," he says. Harper compares the effects of the seasonal appearance of hypoxia on the Texas-Louisiana Shelf with the burning down of a mature forest. "If you start from scratch, you have shrubs and grasses, big trees take over, and eventually you reach this climax community, which is the old-growth forest. If you burn it down every year, you don't have a climax community old-growth forest. We are having the same effect [in the dead zone]." Fishing for Solutions Though scientists agree that cutting the levels of nutrients in the Mississippi River is the way to diminish the hypoxic zone, the best way to do so remains unclear. For example, should nutrient runoff be controlled closer to the mouth of the Mississippi or in the middle of the river drainage, where a significant amount of nutrients are depositied? Remedies being studied include reducing agricultural sources of nitrogen by cutting fertilizer use or tightening controls on livestock waste. Scientists are studying new techniques for applying fertilizer in hopes of reducing runoff without sacrificing crop yields. Another solution may be to create wetlands or woodland buffer zones along the river to remove nitrogen naturally from the water before it reaches the gulf. But the attempt to make the needed large-scale changes in land use or agricultural practices presents significant political challenges. Agricultural communities and cities along the Midwest farm belt are not likely to want to take on the cost of improving a coastal environment hundreds or thousands of miles away. Calls for a reduced use of fertilizers also are coming at a time when prices for wheat, cotton and corn are high and there is pressure on farmers to increase their production. Concern over the spread of the dead zone and its potential impact on the ecology of the Gulf of Mexico has gotten the attention of state governments, federal agencies and the White House, and there are a variety of initiatives under way to find remedies. The Mississippi Riverwise partnership is working with governmental agencies, farming organizations and commercial fishermen to find solutions. NOAA has compiled reports from six scientific teams that examined virtually every aspect of the problem, from causes to costs of various remedies. The Clinton Administration has attempted to distill the newest discoveries about the dead zone into a single volume for use by a task force of federal and state poicymakers. The Committee on Environment and Natural Resources (CENR) has recommended a 20 percent cutback on fertilizer use by half of all American farms, along with converting 5 million acres of farmland to wetlands at a cost of $4.9 billlion a year. But using less fertilizer to meet this goal presents problems for farmers, some of whom call the 20 percent reduction draconian. One solution might be to offer compensation to farmers who turn riv! erside land into wetland reserves, creating a buffer that reduces the nutrient load draining out of the area. "The squabble now is between the marine interests down here and the agricultural interests in the breadbasket of the United States," says Harper. Can the nation's farming and fishing interests afford a solution that will reverse the declinging trend in North America's most productive sea? More to the point can they afford not to? Phil Shook is a freelance writer who frequently covers Texas angling and fisheries issues. December 2000