-By Keith Randall

One of the world’s leading authorities on the Gulf of Mexico’s “dead zone,” Steve DiMarco of Texas A&M University, says the area is likely to be the largest ever recorded and last longer, with marine life affected for hundreds of miles off the Louisiana-Texas coast.

DiMarco, who has studied the Gulf of Mexico for 16 years and Gulf hypoxia – oxygen-depleted water -- since 2002, has just returned from the area and says “it’s about as bad as it gets.

“We examined 74 sites, and just about all of them were hypoxic,” he says. “It’s definitely the worst we’ve seen in the last five years.”

A dead zone occurs when there is hypoxia, or oxygen-depleted water. Such low levels of oxygen are believed to be primarily caused by nutrient pollution from farm fertilizers and other sources as they empty into rivers and eventually into the Gulf of Mexico .

Severe hypoxia levels can result in fish kills and can adversely affect many types of marine life where it is present.

The size of the dead zone off of coastal Louisiana has been routinely monitored for about 25 years. The largest dead zone area on record is 7,900 square miles in 2002. A recent NOAA (National Oceanic and Atmospheric Administration) and Louisiana State University estimate shows that the dead zone area in 2008 may reach or exceed 8,800 square miles or about the size of New Jersey . Previous research has also shown that nitrogen levels in the gulf related to human activities have tripled over the past 50 years.

Because of record-breaking flooding in the Midwest this spring, it was believed that the dead zone areas would almost certainly be affected due to the higher-than-normal runoffs into major river systems, such as the Mississippi River .

DiMarco, an oceanography professor in the College of Geosciences , says that could still be true, adding, “The sites we examined show that the dead zone will likely be large this year. However, most of the hypoxia observed on our cruise seems to be associated with mid-spring flooding of the lower Mississippi River, where large amounts of freshwater were diverted into the wetlands of coastal Louisiana . We saw evidence of land-derived plant material at several places on the shelf.

“Once the floodwaters from the last few weeks reach the gulf, it’s almost sure to affect the dead zone even more,” he adds. “The later-than-usual timing of the freshwater into the gulf could also mean that the hypoxia may last longer, perhaps into September.”

DiMarco was the first to discover a Texas-created dead zone area off the Texas coast last summer, a result of unusually heavy rains that poured water into the Brazos River . Where the water emptied into the gulf off the Texas coast, it created the first proven dead zone area that originated from Texas rivers.

DiMarco and colleagues from Texas A&M, Texas A&M at Galveston and the University of Georgia examined 74 sites between Terrebonne and Cameron , La. The most severe hypoxia levels were recorded in the mid-range depth of waters, between 20-30 feet, as well as near the bottom of the sea floor at about 60 feet.

The Mississippi is the largest river in the United States , draining 40 percent of the land area of the country. It also accounts for almost 90 percent of the freshwater runoff into the gulf of Mexico.

DiMarco said some of the worst hypoxic levels occurred in the western regions of the gulf – toward the border between Texas and Louisiana – and that more intense dead zone levels are very possible in the weeks to come.

“Since most of the water from the Midwest is still making its way down to the gulf, we believe that wide area of hypoxia will persist through August and likely until September, when it normally ends,” he notes.

“This is likely to happen even if a tropical storm or hurricane causes temporary disruptions in the interim.

“We saw quite a few areas that had little or no oxygen at all at that site,” he adds. “This dead zone area is the strongest we’ve seen since 2004, and it’s very likely the worst may be still to come.”

DiMarco will lead one more research cruise in September to find out whether this year’s dead zone persists in late summer.

For more information, contact Steve DiMarco at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it and visit his profile on the Department of Oceanography website.