How Quickly Will the Offshore Ecosystem Recover from the 2010 Deepwater Horizon Oil Spill? Lessons Learned from the 1979 Ixtoc-1 Oil Well Blowout.

The Deepwater Horizon (DWH) accident occurred on 20 April 2010 in the Northern Gulf of Mexico and resulted in a deep-sea plume of petroleum hydrocarbons and a marine oiled snow sedimentation and flocculent accumulation (MOSSFA) event. It is hypothesized that recovery will occur when the contaminated sediment is buried below the biologically active zone of 10 cm. Recovery rate can be inferred from the similar Ixtoc-1 blowout and sub-surface oil release that occurred in the Bay of Campeche, Mexico in 1979 – 1980. In 2015, sediment chemistry effects from the Ixtoc-1 were found at 2.4– 2.8 cm sediment depth at stations within 81 and 273 km away. Trends of total polycyclic aromatic hydrocarbon concentration, macrofauna family-level diversity, and the nematode to copepod ratio with sediment depth supports the interpretation that the benthic community has not yet recovered from the Ixtoc-1 spill. Based on a sedimentation rate of 0.072 cm/year, the Ixtoc-1 benthic community will recover in 103 more years beyond 2015. Recovery around the DWH will occur in 50 years based on an average sedimentation rate of 0.2 cm/year. These rates demonstrate that benthic recovery in the deep sea is very slow.