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What evidence showed that oil from the Deepwater Horizon spill reached the seafloor?
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Deepwater Horizon oil spill
Fireboat response crews attempt to extinguish the blaze aboard the Deepwater Horizon oil rig in the Gulf of Mexico, April 21, 2010.
Evidence that oil from the Deepwater Horizon spill reached the seafloor was confirmed through several observations and scientific investigations:
- Direct Discovery: In September 2010, researchers discovered a layer of oil several inches thick on portions of the seafloor, which challenged earlier predictions regarding how quickly the discharged oil would dissipate.1
- Sediment Analysis: Research missions, such as an April 2014 expedition by the group Ecosystem Impacts of Oil and Gas Inputs to the Gulf (ECOGIG) using the submersible Alvin, utilized sediment cores to detect and monitor oil levels on the seafloor.2
- Ecological Impact: Areas of the seabed coated by by-products of bacteria—which had been feeding on the oil—became essentially "dead zones." These areas showed evidence of suffocated or sickened sedentary organisms, while most mobile organisms had fled the region.2
- Subsurface Plumes: While initially dismissed, it was verified in June 2010 that subsurface plumes of dispersed hydrocarbons detected in the water column originated from the spill, indicating the movement of oil beneath the surface.1