Damage Assessment of the Deepwater Horizon Oil Spill: Using Species Distribution Models to Estimate the Number of Affected Cold-Water Coral Sites

The Deepwater Horizon oil spill was one of the largest in history, releasing approximately 5 million barrels of oil at depth in the northern Gulf of Mexico. Subsequent research has uncovered extensive injury to deep-sea habitats, notably to cold-water coral communities including those dominated by Paramuricea species. One of the primary difficulties in assessing the full extent of the injury to these ecosystems is the paucity of observational data and unknown distribution of cold-water coral communities within the affected region. We constructed species distribution models for Paramuricea sp. (haplotypes B1-B3) in order to estimate the number of potentially affected sites in the northern Gulf of Mexico. High resolution (15 m) models were built using the maximum entropy (Maxent) approach and remotely-sensed data including topography, seafloor seismic reflectivity, and export productivity. The model performed well, based on an area under the curve (AUC) metric of 0.98±0.01. Across the northern Gulf of Mexico there were a total of 3,067 sites predicted as suitable for supporting corals, comprising 191 km². Within the zone shown to have been affected by the spill and subsequent oil plume, there were 216 suitable sites comprising 13 km². These results provide important insights into the magnitude of the potential injury to these vulnerable ecosystems as a result of the Deepwater Horizon spill, and identify sites for future research and restoration prioritization efforts.