There is surprise and relief that that vast amounts of the spilled oil from the damaged Deepwater Horizon oil rig have disappeared from the surface of the Gulf of Mexico.

A new federal report indicates that the oil has been evaporated, burned, skimmed, recovered from the wellhead or dispersed – much of which is in the process of being degraded. A significant amount of this is the direct result of the robust federal response efforts.

Thirty-three percent of the total amount of the spilt oil was captured or mitigated by the Unified Command recovery operations, including burning, skimming, chemical dispersion and direct recovery from the wellhead, according to a federal science report released today.

National Oceanic and Atmospheric Administration (NOAA) and the Department of the Interior (DOI) estimate that an additional 25 percent of the oil naturally evaporated or dissolved, and 16 percent was dispersed naturally into microscopic droplets. The residual amount, just over one quarter (26 percent), either on or just below the surface as residue and tarballs, has washed ashore or has been collected from the shore, or is buried in sand and sediments. Dispersed and residual oil remain in the system until they degrade through a number of natural processes. Early indications are that the oil is degrading quickly.

“Teams of scientists and experts have been carefully tracking the oil since day one of this spill, and based on the data from those efforts and their collective expertise, they have been able to provide these useful and educated estimates about the fate of the oil,” says Jane Lubchenco, NOAA administrator. “Less oil on the surface does not mean that there isn’t oil still in the water column or that our beaches and marshes aren’t still at risk. Knowing generally what happened to the oil helps to understand areas of risk and likely impacts.”

It is well known that bacteria that break down the dispersed and weathered surface oil are abundant in the Gulf of Mexico largely because of the warm water, the favorable nutrient and oxygen levels, and the fact that oil enters the Gulf of Mexico through natural seeps regularly.

Residual oil is also degraded and weathered by a number of physical and biological processes. Microbes consume the oil, and wave action, sun, currents and continued evaporation and dissolution continue to break down the residual oil in the water and on shorelines.

In the meantime, optimism is rising that BP is close to permanently plugging the damaged well. Indications are that the ‘static kill’ process which involves pouring mud and debris into the damaged well is working.

Carol Browner, director of the White House Office of Energy and Climate Change Policy said on a cable-news show on Wednesday morning that “The vast majority of the oil was gone… [the well] hasn't been leaking for some time… and the static kill is going well.” Browner also said the relief wells that should be ready in 10 to 14 days, will be the ultimate factor in plugging the well.