But scientists have only just begun to analyze the damage and warn it's far too soon to predict what the spill's oily chemical soup might do to the balance of life in Gulf waters.

"Some people are concerned that the oil is going to lead to accelerated coastal land loss," said Christopher D'Elia, dean of Louisiana State University's School of the Coast and Environment.

"The other concern is perhaps even longer term, and that is what happens to the coastal food webs that are so important to sustaining our fisheries."

On the surface, life seems to be returning to normal.

Green shoots are growing among the blackened marsh grasses killed by the oil that seeped into Bay Jimmy, a hopeful sign in one of the hardest-hit areas of coastal Louisiana.

A casual stroll down the once-blackened beach of Grand Isle finds little evidence of the oil trapped under the sand and surf except for some dark patches along the high tide mark.

And the immediate impacts on wildlife were far less severe than expected. Just over 6,000 dead birds were recovered from the Gulf compared with 30,000 after Alaska's much smaller 1989 Exxon Valdez spill.

"We're really lucky," D'Elia told AFP.

"The acute and immediate impacts were not as severe as everybody was fearing."

Favorable winds and currents and the location of the runaway well -- some 50 miles (80 kilometers) off the coast of Louisiana -- helped keep the bulk of the oil from reaching fragile coastal wetlands and beaches.

As did high concentrations of gas in the well, which helped disperse the oil when it shot up through 5,000 feet (1,500 meters) of water, making it easier for naturally-occurring microbes to start breaking it down.

That was a positive development considering how ineffective the 13 million feet (3.96 million meters) of protective boom proved to be as rough waters knocked the oil over and under the floating barriers and contaminated more than 650 miles (1,050 kilometers) of shoreline from Texas to Florida.

Today, crews continue to actively clean 235 miles (380 kilometers) of shoreline, and primarily focus on the oil that got mixed with sediment and buried in surf zones, as well as on the delicate task of cleaning marshes.

They plan to return to about another 300 miles (480 kilometers) after the nesting and tourist seasons are over and then do a full shoreline assessment after hurricane season ends on November 1.

"It's hard to put any sort of end point," said Commander Dan Lauer of the US Coast Guard, which is overseeing BP's cleanup efforts.

The problem is that while most of the oil didn't reach shore, there was simply so very much of it: at 4.9 million barrels, it was the biggest maritime spill in history.

And removing oil from the ocean is an arduous task.

Skimming and controlled burns only removed about eight percent of the oil that spewed out of BP's Macondo well before it was finally capped 87 days after the April 20 blowout.

Responders therefore relied heavily on chemical dispersants sprayed from planes and directly into the underwater gusher.

Environmental Protection Agency Administrator Lisa Jackson called the controversial use of nearly two million gallons (7.5 million liters) of dispersants the "least bad option," but coastal residents fear the oily chemical soup could end up killing the seafood they rely upon.

"We just don't know what's in store," said Carol Schieffler, who picked up work as a caregiver after the spill put an end to 32 years of earning a living making nets for fishermen in Lafitte, Louisiana.

"What everyone's looking at is Alaska -- some of the fish never did come back."

Officials predict a bumper crop this year after overfished stocks were granted a reprieve from the nets when a third of US waters were closed in the wake of the spill.

Fishermen welcome the news, but don't take much comfort in it.

That's because Alaska's fishing was fine the year after the Valdez spill. Three years later, the herring fisheries collapsed from disease.

It's far too early to tell what the long-term impacts of the oil and dispersants will be on the Gulf of Mexico, said Larry McKinney, executive director of the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi.

Early studies found massive plumes of oil particles floating throughout the water column and oily sediment coating long stretches of the ocean floor -- including ancient deepwater corals.

"The significance of that to the health of the overall ecosystem we just don't know," McKinney said.

Most of the Gulf's commercially-important species like shrimp and crab are hardy, abundant and have evolved to be highly adaptable to the Gulf's dynamic ocean conditions.

They managed to recover within two or three years after the 1979 Ixtoc spill spewed 3.3 million barrels of oil into the Mexican portion of the Gulf.

But the Gulf was already under intense pressure from climate change, the erosion of coastal wetlands and a massive dead zone cause by the agricultural runoff carried down the Mississippi River.

"The Gulf is a big place but it's not an infinite place," McKinney said.

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