Adapting to the damaging effects of climate change, plants are gradually moving to where temperatures are cooler, rainfall is greater, f...
Up to 3.2 million barrels of the toxic substance have not been cleaned up, the independent researchers found - higher than the estimates given by the federal scientists working for the National Oceanic and Atmospheric Administration (NOAA) and the Department of Interior.
"The oil is still out there, and it will likely take years to degrade," marine sciences professor Charles Hopkinson concluded.
Scientists from both the Obama Administration and University of Georgia (UGA) agreed it was likely that 4.9 million barrels of oil gushed out of the Macondo well after the BP-leased Deepwater Horizon rig exploded on April 20, killing 11 people.
But the Obama Administration's account of what happened next to the oil at the well site located 50 miles off the coast of Louisiana is disputed by the UGA study.
Its researchers criticise Federal scientists for releasing their conclusions with supposedly scant and unverifiable data.
The NOAA report declined to give a single figure for oil that remained in the Gulf, though its piecemeal estimates of each cleanup component were more generous than the UGA report.
UGA scientists made their own estimates for variables such the evaporation rate of oil that came into contact with the atmosphere, and the degradation rate of oil compounds in the Gulf.
They suggested that US Government scientists may have underestimated the dangers that the oil poses to local communities.
For example, oil that was dispersed as micro-droplets, for instance, may still be "highly toxic," the study said.
"The most toxic components of crude oil are the least likely to be naturally degraded," the report said.
Even some of the oil that all parties agreed was released and subsequently purged could still be a threat, according to the study.
Oil that was evaporated into the atmosphere, for one, could still be a danger for years to come, it said.
Impact on health
Meanwhile, another study published overnight in the Journal of the American Medical Association suggested the spill's impact on human health is subtle and may not be seen immediately.
For clues to both the short-term and the long-term health effects of the oil spill, researchers studied cases associated with previous oil spills, all of which the authors noted, were far smaller than the Deepwater Horizon spill.
They discovered for example, that workers on the 1989 Exxon-Valdez spill in Alaska have, years later, a higher prevalence of chronic airway diseases.
Clean-up workers tend to suffer most because they are exposed to volatile organic compounds, chemicals that tend to evaporate when they reach the water's surface.
These compounds, such as benzene, are known to cause respiratory problems and are linked to certain cancers.
But, the researchers from the Department of Medicine at the University of California-San Francisco wrote that the potential health impacts extend beyond the workers on oil spills.
Nearby residents, too, may develop health problems either by exposure to crude oil in the water or by chemicals in the air. There also exists the possibility that seafood and drinking water in those communities may become contaminated.
The consequences are not only physical.
People exposed to the Exxon Valdez spill also proved, years later, to have high rates of depression and post-traumatic stress disorder, the study concluded.