Assessment of recovery and restoration of deep benthic sediment habitats injured by the Deepwater Horizon oil spill

The Deepwater Horizon oil spill in 2010 was an unprecedented event, releasing approximately 3.2 million barrels of oil into the deep Gulf of Mexico (GOM) resulting in injury to over 770 square miles of deep benthic ecosystems, including deep sea corals and soft-sediment habitats. The Open Ocean Trustee Implementation Group selected four projects to help address the injury to these resources. One of these projects, the Mesophotic and Deep Benthic Communities Habitat Assessment and Evaluation project, will address critical information gaps in our understanding of how the ecosystem naturally functions and recovers to inform restoration efforts. As sources of biodiversity, sediment communities in particular, provide important ecosystem services including nutrient cycling, sediment stabilization, and carbon sequestration. Initial injury in sediment habitats was characterized by high concentrations of hydrocarbons and metals associated with low taxa diversity and high variability in macrofauna (>0.3mm) communities. Since 2022, multiple offshore missions have been conducted to assess sediment community dynamics and environmental drivers, which combined with earlier post-spill assessments from 2010-2017, provide a long-term dataset with which to assess recovery, and both interannual and decadal natural variability within the system. Elevated hydrocarbon concentrations have persisted near the wellhead through 2022 with high variability in community metrics within the impacted areas. Our results update known baselines and quantify temporal change and recovery trajectories to inform restoration and long-term monitoring activities in the GOM.