GALVESTON, TEX., AUG. 2 -- The first television images gave the impression that Galveston Bay had suffered the same fate from its oil spill last Saturday as Alaska's Prince William Sound did from the one there last year: an oil-soaked sea bird flopped around a beach, its wings broken from hopeless attempts to fly.

But five days after a Greek freighter rammed a three-barge tow in the middle of the bay, it is apparent that in the short run, Galveston has dodged an environmental disaster. Soft winds blew the oil toward shore at factory and home sites and not toward the most sensitive marshes. Weather remained hot and clear, aiding evaporation and allowing salvage crews to work in calm waters.

Birds that had the misfortune to land in oily waters were the exception. Humans also felt the impact as the Texas Department of Health shut down commercial and sport fishing in the bay, and more than 60 ships lay at anchor waiting for the full reopening of the Houston Ship Channel, idling away thousands of dollars per hour.

Environmentalists, state officials and others agreed that in the long run, Galveston Bay may yet suffer greatly. How greatly depends on the answer to the chief mystery of this spill: the "disappearance" of much of the 500,000 gallons of partly refined oil estimated to have been dumped in the bay.

"The question is, where did the oil go? And I don't think we know that yet," said David Hankla of the U.S. Fish and Wildlife Service.

The oil so far recovered -- about 75,000 gallons -- plus the amount still on a half-sunken barge and the amount still on the water together do not nearly account for the full 500,000 gallons. The Coast Guard says it can find no evidence the oil sank, leaving the possibility that it evaporated faster than expected or that it dissolved into the water as benzene and other toxic chemicals.

"If we can't see it, we don't know where it is and what it's doing. That's a pretty uncomfortable feeling," said David Sager, chief of the environmental contamination branch of the Texas Parks and Wildlife Department.

The worst possible scenario, Sager said, is that the oil is still moving around somewhere in the bay. If so, Galveston is in for many years of trouble.

Hankla said the spill will take a worse toll than is already evident because birds that were not covered by oil immediately may die in the next few weeks from ingesting it. In the long run, far greater damage could be done through destruction of nesting and feeding grounds, he said, but it will be years before that is known.

"Our monitoring systems are really not adequate to measure what the impact really is," said Brandt Mannchen of the Sierra Club, who has been critical of the lack of planning for confronting oil spills. "I hope if nothing else comes out of this we'll develop a plan," he said.

John Hanby of Hanby Analytical Laboratories in Houston has taken hourly samples from the bay for the past three days. He said he detected abnormally high levels of benzene in the first few hours of his test, indicating much of the oil was absorbed into the warm Gulf waters.

That is ominous, he said, "There's not a safe or healthy organism in this water."

Hanby, who also ran tests in Prince William Sound after the Exxon Valdez wreck, said the cold choppy Alaskan waters did not easily absorb toxic materials, so most of the damage there was from free-floating oil. In the long run, he said, both areas may suffer considerable delayed damage.

Meanwhile, the owner of the barge line turned over responsibility for the cleanup to the Coast Guard, thus limiting its further liability to about $431,000 under a formula related to the vessel's capacity. The company has already spent an estimated $400,000.

Oil-eating bacteria were scheduled to be deployed late today in the shallow water around Pelican Island, a bird rookery and fish nursery. A spokesman for the Texas General Land Office said about 100 pounds of the microbes will be used and tested for effectiveness.

"This is an effective tool that should have been used right from the start of this disaster," said Texas Land Commissioner Garry Mauro (D) in a statement.

But early yesterday, Gov. Bill Clements (R) said he did not think the bacteria would be effective because the spill appeared to have broken up. Clements flew over the site today.

The microbes, said to convert oil to harmless fatty acids, were used on the Mega Borg spill earlier this summer. While Texas officials and the scientists involved claimed success, other researchers remain skeptical that naturally occurring bacteria are effective on large and highly mobile spills.

Staff writer William Booth contributed to this report.