On April 20th, 2010, the Deepwater Horizon oil rig, owned by BP and operating on the Macondo Well, exploded and sank in the Gulf of Mexico. While it not only was deadly to 11 workers, it is also considered one of the worst accidental marine oil spill in history. After the rig sank, an oil gusher on the sea floor flowed for 87 days before it was capped off. 87! The American government estimated the total discharge at roughly 5 million barrels! The spill was by far the largest in US history, almost 20 times greater than the estimate of the Exxon Valdez oil spill.
(Everybody surely remembers watching the steady flow of oil leaking into the Gulf. Source)
While the spill also had obvious impacts on the health and economy of the area, the environmental damage was huge and difficult to deal with. The Gulf of Mexico is a very prosperous area for many marine species. The spill area hosts 8,332 species of plants and animals, including more than 1,270 fishes, 1,500 crustaceans, 5 sea turtles and 29 marine mammals. In the month of November following the spill, over 6,000 animals were found dead, deep sea corals around the oil gusher had been damaged, and scientists were witnessing mutated fishes or severely ill marine mammals.
Where are we at almost 5 years later?
It is quite challenging for scientists to match the amount of oil that went into the ocean with the amount that went out of it. The oil traveled in many directions, by different means and through different depths. Some oil particles floated at the surface, some ended up in salt marshes or beaches through the currents, some was trapped by deep ocean currents at 4,000ft, and some sank into the seafloor.
About one million barrels were recovered, and another two million floated to the sea surface. Scientists therefore believed that the two million barrels missing (about 84 million gallons) were trapped in the Gulf’s deep water currents.
University of California researcher David Valentine just published a new study in October 2014 quantifying the oil that remained trapped deep in the ocean and rained down on the ocean floor, and also where it fell.
Valentine and his colleagues found that 4 to 31 % of oil trapped in the deep ocean (which accounts for 2 to 16% of the total oil discharged) fell within a 1,250 square-mile patch, which is roughly the size of Rhode Island.
(Hydrocarbons from the Deepwater Horizon spill overlaid on sea floor bathymetry of the study area. The white star identifies the location of the BP Macondo well. Source: NOLA.com)
Those tiny bits of oil appeared to have clumped together into bits that were more dense than water and fell to the seafloor, Valentine said, accumulating in a pattern that forms a giant “bathtub ring” on the ocean floor.
Unsurprisingly, BP has disputed the findings of this study, claiming that the scientists did not show that the oil particles found in the sediment actually came from the Macondo Well. Nevertheless, the authors argue that such chemical analyses are unnecessary, as the location of the concentrations as well at their levels clearly point towards the Macondo Well spill.
In April 2014, a study reported that many species in the Gulf were still dying in record numbers and were struggling to recover. It matches the reports around Prince William Sound, where, 25 years after the wreck of Exxon Valdez, there are still some species that have not fully recovered. Needless to say, the long-term effect on the global food chain and marine ecosystem remains unknown, and scientists have a long way to go before understanding the full impact of the spill.