Long-Term Study of Polycyclic Aromatic Hydrocarbons in Deep-Water Fish Species in the Northern Gulf of Mexico Reveals Exposure to Deepwater Horizon Oil

The Deepwater Horizon (DWH) was the largest spill in US history, with ~668x10 ⁶ kg of oil released at depth (1,500 m). The deep-pelagic habitat was affected not only by oil transported vertically to the surface, but also by the formation and sink of an unprecedented oil-associated marine snow event. The diel vertical migration of deep-living fishes in the same region increased the probability of their exposure to the weathered oil. Understanding the impact to the deep-pelagic habitat is important due to their large abundance and role in the marine food web (as prey for shallow-living fish and marine mammal species). We conducted a time-series analysis of polycyclic aromatic hydrocarbons (PAHs) in deep-water fishes to asses exposure to DWH oil and potential long-term impacts in the pelagic ecosystem of the Gulf of Mexico (GoM). Early samples collected in 2007 contain mostly 2-3 ring PAHs, with a range in concentration of 0.3-1.3 μg/g dry wt. These early samples define the baseline levels of PAH content in muscle samples in deep-water fish species. Samples collected in 2010 and 2011 indicate an increased up to 10-fold in PAH concentration, with average concentrations higher than the established threshold PAH level for adverse biological effects (4.0 μg/g dry wt). In 2015-2016, a decline in the concentration of PAHs was observed reaching values close to baseline levels. Mechanisms explaining elevated PAH concentrations and composition in eggs and other tissues will be discussed to better understand the impacts to deep-water species in the GoM.