SOUTHWEST PASS, La. — A couple of weeks ago, enormous orange-brownish strings of something were seen floating out here in the open water near the mouth of the Mississippi.
The water looked like chocolate syrup in some parts and Coca-Cola in others, said Cindy Cruikshank, who has been fishing for 53 of her 59 years. It smelled like an auto-body shop, and it left stains on the hull of her boat. Along with other fishermen and environmentalists around the country, she had no doubts: this was oil.
“I know what I saw,” she said.
Local scientists begged to differ.
“It is not oil; it has none of the properties of oil,” said Ed Overton, an environmental science professor at Louisiana State University, who analyzed two samples of the mysterious substance provided by the Coast Guard.
This was an outbreak of algae, scientists concluded, common in this area at this time of year.
“A lot of the oil, when it weathered, ended up with a consistency that wasn’t too far from this stuff,” Mr. Overton said, though Ms. Cruikshank and many other fishermen who saw the stuff remain unconvinced.
The cleanup of the worst offshore oil spill in United States history continues here on the Gulf Coast, as does some of the contentiousness of the panic-plagued summer: local politicians still rail against the tempo of the response, and many residents and environmentalists still accuse scientists and officials of undue optimism, often speaking of cover-ups and conspiracies (Ms. Cruikshank is not a conspiracy theorist in this case, saying that the Coast Guard simply took samples in the wrong place.)
The cleanup operation itself, however, has settled into a far more routine phase.
More than 11,000 people are still at work, vacuuming up oil, testing seafood and monitoring hundreds of miles of shoreline for the presence of oil. Roughly a thousand fishing boats are still active in BP’s Vessels of Opportunity program, helping in the cleanup, and more than 200,000 feet of boom is still deployed, according to Coast Guard officials.
Though wetlands ecologists express relief that relatively little of the marsh was heavily oiled, some marshy areas like Bay Jimmy off Barataria Bay still bear dark smears, patches denuded of marsh grass and the telltale brown ribbon of oil at the water line.
Tar balls continue to wash up on beaches, and oil is still being spotted in areas that were once clean, as oil that came ashore is pulled off again and smeared elsewhere by the tides. Thus while protocols have been developed to determine where to clean and how, there is no protocol yet for declaring an area fully and finally clean.
“Is there a day or a week or a month?” asked Chance McConnell, director of operations for DRC Emergency Services, a contractor in the response. “I don’t know.”
But despite the debates about where the oil has gone, the most visible effects of the spill are steadily disappearing. Of the roughly 580 miles of oiled shoreline, only about 30 miles are showing “heavy oil” effects, Rear Adm. Paul Zukunft of the Coast Guard said at a recent press conference.
As fishermen keep their eyes peeled for slicks and voice concerns that they may be fishing in contaminated waters, some scientists suggest that these fears may be misplaced. The most serious worries about the spill’s damage at this point lie not in lingering surface oil and tainted seafood, they say, but in long-term damage already done to breeding populations of fish, crabs and other commercially important species.
The degree of that damage, at this point and possibly for years, is unknown. Scientists like Caz Taylor, a biologist at Tulane University who found “mysterious orange droplets” in blue crab larvae this summer, are months away from declaring any findings.
But they are apprehensive, as some of Louisiana’s most productive estuaries, like Barataria Bay, were heavily affected.
“I’m more concerned about there being fewer crabs out there than in there being polluted crabs out there,” said Andrew Nyman, a wetlands ecologist at L.S.U. “My biggest fear is that we’re going to overlook the possibility of reduced populations of some of our fish and wildlife.”
Studies done during and after the huge Ixtoc I well blowout in 1979, which released an estimated 3.3 million barrels of light Louisiana crude into the Gulf of Mexico, support this view. Researchers found that oil from the spill was tolerated well by adult fish, but was highly toxic to eggs and larvae, as well as to smaller organisms down the food chain.
In areas where oiling was heavy, some crab and crustacean species saw significant population declines. When and if that happens this time around is a crucial question for fishermen and others whose livelihoods are at stake, especially considering the 2013 deadline that Kenneth Feinberg, the overseer of the $20 billion Gulf Coast claims fund, has declared for final settlements.
But for now, there are few hard answers, no matter how trying that may be to those who want them.
At a recent public meeting near the coast, Mr. Overton, the L.S.U. scientist, presented some of his findings and answered questions about the spill. He said he faced a hostile reception afterward.
“They’re hollering that the sky is falling,” he said. “There’s just precious little evidence to talk about massive environmental damage at this time. You can’t just make up damage. You’ve got to call a spade a spade.”