COLUMN ONE : The Gulf of Mexico Besieged : One of the nation’s major bodies of water is a sea at risk. A tanker spill pales in comparison with impacts from oil facilities, cities and agriculture.

Even before the stricken Norwegian tanker Mega Borg exploded and caught fire last week, threatening an oil spill three times larger than the Exxon Valdez disaster, the Gulf of Mexico was a sea at risk.

From the Florida Keys to the Rio Grande, the Gulf of Mexico has been under an unrelenting environmental siege that makes the Mega Borg’s 3-million-gallon spill pale by comparison.

Pollution from the gulf’s sprawling petrochemical complexes, shipping, growing urbanization and agricultural practices are adding up to one of the most formidable assaults in the nation on a major ecosystem.

So serious is the problem becoming that some are beginning to draw comparisons with the Baltic Sea and the Mediterranean, two of the most-polluted bodies of water in the world.

“We haven’t reached Mediterranean proportions yet, but we’re headed in that direction,” said Tom Miller of the Center for Marine Conservation in Washington.

Douglas Lipka, director of the U.S. Environmental Protection Agency’s Gulf of Mexico Program, headquartered at Stennis Space Center in Mississippi, said the time is quickly approaching when the gulf may cross over a “critical point” of some irreversible environmental impacts.

Half of Galveston Bay--long known for its rich oyster beds and shrimp grounds--is off limits to oyster harvesting because of sewage discharges. Up to 3,000 square miles of bottom waters off the Louisiana and southeastern Texas coasts are known as the “dead zone,” a watery desert where nothing lives because pollutants have depleted the oxygen.

Nearly 60% of the gulf’s shellfish-growing areas--about 3.4 million acres--are either permanently closed or have restrictions placed on them because of rising concentrations of toxic chemicals and sewage.

In Louisiana, sensitive coastal marsh habitats are vanishing at the rate of 50 to 60 square miles a year, threatening the natural productive cycles of commercial shrimp and fish.

At the southern tip of Florida, 80,000 acres of bay sea grass, which acts as a veritable nursery for all kinds of marine life, has been killed by a virus. Scientists speculate that pollutants in the water from urban runoff and agricultural fields weakened the plant’s resistance.

The EPA’s Gulf of Mexico Project is forcing an analysis of the gulf as a single, complex environmental system. Representatives of the gulf states, federal agencies, the public, environmental groups, industry and academia are involved in fashioning a strategy for which they hope to build a consensus to rectify the damage. But unless action is taken soon, many fear that significant stretches of the Gulf Coast will meet the same fate as the Chesapeake Bay, with fisheries collapsing and water quality deteriorating at a cost counted in untold millions of dollars.

The stakes are high. Fully 40% of the nation’s most productive fishing grounds, including the most valuable shrimp beds, are found in the gulf. Half of the nation’s wetlands, including 30 estuaries--the breeding grounds for 98% of all commercial fish caught in the gulf--dot the gulf’s rim. They also provide a haven for 75% of the migratory waterfowl that traverse the continent.

Moreover, tourism is a highly profitable business for the gulf counties, pumping $5 billion into the economy. Polluted beaches, tainted water and the ton of ocean debris found per mile that washes up on many of Texas’ most popular beaches doesn’t help

A still unpublished draft of a report by the EPA warns that “ . . . we risk serious long-term environmental damage to this vast and unique marine system if we do not begin comprehensively planning today.”

“There are mammoth kinds of problems that will require major changes in the way we do business,” said Lipka of the EPA.

For many fishermen, time is already running out.

Standing on the deck of the shrimp boat Evening Star in Texas City, crew member Eddie Schrameck talked of hard times. Shrimp catches are down, and his skipper has been forced to go after “bait shrimp” to make ends meet because of declining numbers of table shrimp.

Schrameck, whose weathered face, pale blue eyes and a wiry red beard speak silently of the sea, doesn’t doubt what caused their misfortune.

“I know exactly what the reason is,” he drawled. “Too much competition. Too many boats--and there’s pollution in that water. We’ve pulled up fish that got fungus all over ‘em. It’s hard to believe they’re still alive. There’s something in that water, I do believe,” he said.

Not far away, Jimmy Priest is presiding at the counter of his bait shop on the Texas City dike within sight of a sprawling chemical plant.

“The pollution is hurting us, that’s for sure. But we don’t know where it’s coming from. We don’t even know what it is,” Priest said.

Others do.

Ninety percent of the nation’s offshore oil and gas production is found in the gulf. Half of the country’s oil refineries and chemical plants ring the gulf.

Four of the top five states in total surface water discharges of toxic chemicals are gulf states--Alabama, Mississippi, Louisiana, and Texas.

“That carries with it a very large burden of pollutants from industrial sources, runoff from cities, water from agricultural fields and ships. It all comes down and ends up in the Gulf of Mexico,” said Edward Proffitt, director of the Florida regional office of the Center for Marine Conservation.

Gulf ports handle 45% of all U.S. import-export shipping tonnage and 38% of crude oil tonnage. Six of the nation’s top 10 ports in crude oil shipments are in gulf states.

At Galveston, half of all the 3,756 waste dischargers in Texas dump their wastes directly or indirectly into the bay, according to Linda Shead, executive director of the nonprofit Galveston Bay Foundation. Many of the dischargers are as far north as Dallas and Ft. Worth, who dump pollutants into the Trinity River for a 300-mile journey south before they land in the bay.

“Galveston Bay is on the edge,” she said. “It is still classified as the second-most productive estuary in the U.S. But stresses on the system are so great that if we do anything too drastic, we could push it over the brink.”

The bay is ringed by high concentrations of petrochemical plants with hundreds of tall, narrow stacks that from a distance look like minarets.

Small, single-neighborhood sewage treatment plants and septic systems are known to frequently malfunction, pouring raw sewage into the waters.

Fresh water from many of the 44 river systems that flow into the gulf once alleviated some of the problems, but now the rivers are being diverted from coastal estuaries to meet the needs of thirsty and growing cities, recreation and flood control.

The pumping of water, oil and gas from beneath the ground contributes to the subsidence of land. This is in turn accounts for the loss of environmentally sensitive marshes as sea water flows in and covers them.

Much of the wetland losses in Louisiana are blamed on oil companies, which over the years have cut canals into the swamps and marshes for barges that carry oil drilling rigs and other equipment.

Despite these problems, pressure for industrialization continues. The Texas Copper Corp. is advancing a controversial proposal for a new copper smelter bordering on the bay.

Developers, contractors and other continue to push for widening and deeping the Houston Ship Channel, which stretches 50 miles from the city to the gulf. Opponents fear dredging will stir up toxic sediments and compound an already serious pollution problem.

“In Texas we don’t have the same level of environmental awareness that exists on the East and West coasts, and we have a much bigger industrial side to our culture,” observed Frank S. Shipley, program manager of an EPA-funded Galveston Bay Project, which is preparing to carry out studies similar to those under way for Santa Monica Bay.

But there is growing recognition that something must be done.

“Everybody contributes to the problem. I can’t deny that,” said Larry Wall, spokesman for the Louisiana Mid-Continental Oil and Gas Assn. But he said industry is attempting to respond.

“The industry realizes it has an obligation to protect and enhance the environment. It realizes that things were done in the past that had an adverse impact. We didn’t know any better. Nobody knew any better,” Wall insisted.

Now, he said, the industry plans to cut no more canals into the wetlands, or to mitigate environmental impacts when it does. It is also negotiating over future limits of toxic discharges into the estuaries and canals.

Still, he admitted, environmentalists say the petroleum industry is not going nearly far enough.

“We’re talking,” said Wall. “The problem we run into is everybody finds more problems than we have solutions for. They want solutions yesterday for something we’ve been doing for 40 years.”