An estimated 4.9 million barrels of oil gushed into the Gulf of Mexico during the Deepwater Horizon spill of 2010. New research chronicles the fate of the oil that wasn’t cleaned up.
The Deepwater Horizon platform was stationed at the BP-operated Macondo Prospect in the Gulf of Mexico when disaster struck. On April 20, 2010, a wellhead blowout caused the drilling rig to explode, resulting in the deaths of 11 workers and leaving another 17 injured. The platform, located 64 kilometres from the Louisiana coast, sank two days later and fell 1,500 metres to the seafloor. Crews managed to seal the well on August 4, 2010, but not before 4.9 million barrels of crude oil poured out, creating the largest spill in U.S. history.
The leaked oil spread far and wide, affecting marine life at depth and at the surface, including dolphins, birds, turtles, and even microorganisms. Massive cleanup and containment measures were implemented (some 47,000 people were involved at the peak), but copious amounts of oil still managed to escape and pollute the surrounding areas.
Scientists are still seeking to understand the full extent of the disaster, along with the ultimate fate of the oil that couldn’t be cleaned up. An overview published this past March in the science journal Oceanography shed new light on this ongoing story and the various biogeochemical processes that affected the escaped oil.
Marine geochemist John Farrington from the Woods Hole Oceanographic Institution co-authored the overview. The findings were based on recent geochemical studies, work supported by the U.S. Natural Resource Damage Assessment, and data provided by BP and government agencies, including the National Science Foundation. The Gulf of Mexico Research Initiative, which has been instrumental in documenting the spill’s impacts on the region, funded the project.
As Farrington and his colleagues learned, a significant portion of the unrecovered oil made its way to the surface, where it became exposed to sunlight. A process called photooxidation changed the oil’s chemistry, transforming it into all sorts of unsavoury compounds — some of which managed to become airborne. Photooxidation, as the scientists wrote, was “a significant process acting on the surface oil slick very early in the spill,” and it “played a significant role in the fate of the spilled oil.” Frustratingly, photooxidation “had been downplayed for decades despite earlier research in the 1970s and 1980s suggesting that it would be an important research topic,” the team added. As to the exact quantity of oil affected by this process, that’s still a mystery.
As is well known, a considerable amount of oil reached the shore. Research from 2013 estimated that 1,773 kilometres of beaches and coastal marshes from Florida to Texas were affected by the spill. A valiant attempt was made to clean it up, but a lot of oil was pushed into coastal marshes by the tides. Today, wetlands along the Gulf Coast shoreline still bear the mark of the disaster, as residues found in these locations bare chemical signatures consistent with oil from the disaster, as the Oceanography paper points out. (A lawsuit also claims the dispersants used to clean up the spill created their own environmental justice crisis.)
Natural “marine snow” also came into contact with the spilled oil. Marine snow is falling bits of matter, including poop and decaying bits of sea creatures and plants, but in this case the scientists had to describe it as “marine oil snow,” the accumulation of which led to “marine oil snow sedimentation” on the seafloor.
This unholy mixture spread “into the food webs of water column ecosystems,” the scientists wrote. Many deep sea animals are now feeding on this gunk, including corals, squid, fish, and sharks. Humans could also be ingesting some of this oil by consuming seafood sourced from the affected regions. Research published last year shows that so-called “invisible oil” means the spill extended to regions as far away as Texas and the East Florida shelf.
Oil that didn’t undergo any of these aforementioned processes settled onto the seafloor, where it continues to linger. Eventually, this residue will be broken down by microbes.
In terms of future research, the scientists said a deeper understanding of photooxidation and marine oil snow is needed, in addition to an improved understanding of how oil spills affect ecosystems. They also advocated for new and better ways of cleaning up oil spills and new methods to track oil spills over time. Because sadly, things like this keep happening in the Gulf and around the world.