Tracking the Hercules 265 marine gas well blowout in the Gulf of Mexico

Abstract

On 23 July 2013, a marine gas rig (Hercules 265) ignited in the northern Gulf of Mexico. The rig burned out of control for 2 days before being extinguished. We conducted a rapid‐response sampling campaign near Hercules 265 after the fire to ascertain if sediments and fishes were polluted above earlier baseline levels. A surface drifter study confirmed that surface ocean water flowed to the southeast of the Hercules site, while the atmospheric plume generated by the blowout was in eastward direction. Sediment cores were collected to the SE of the rig at a distance of ∼0.2, 8, and 18 km using a multicorer, and demersal fishes were collected from ∼0.2 to 8 km SE of the rig using a longline (508 hooks). Recently deposited sediments document that only high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH) concentrations decreased with increasing distance from the rig suggesting higher pyrogenic inputs associated with the blowout. A similar trend was observed in the foraminifera Haynesina germanica, an indicator species of pollution. In red snapper bile, only HMW PAH metabolites increased in 2013 nearly double those from 2012. Both surface sediments and fish bile analyses suggest that, in the aftermath of the blowout, increased concentration of pyrogenically derived hydrocarbons was transported and deposited in the environment. This study further emphasizes the need for an ocean observing system and coordinated rapid‐response efforts from an array of scientific disciplines to effectively assess environmental impacts resulting from accidental releases of oil contaminants.

Molecular Markers of Biogenic and Oil-Derived Hydrocarbons in Deep-Sea Sediments Following the Deepwater Horizon Spill

“…2010-2013) have only burned-oil residues. Overall, the trend observed in Figure 7, supports well previous observations of deposited burned and mixed oil residues in the DeSoto Canyon after the DWHOS (Romero et al, 2015), burn residues after the explosion of the Hercules 265 gas rig (Romero et al, 2016), and oil residues after experimental burning of crude oil (Fingas, 2017). Interestingly, floating and sunken burned oil residue samples from Stout and Payne (2016b) have relatively low %5-6 ring PAHs and PI ratio (Figure 7).…”

“…These ratios showed no correlation with indicator ratios of natural weathering processes for PAHs (e.g., dissolution, evaporation; Supplementary Figure 6). The PI ratio (e.g., Wang et al, 1999b, Wang et al, 2008Romero et al, 2015;Shigenaka et al, 2015) as well as %5-6 ring PAHs (Shigenaka et al, 2015;Romero et al, 2016;Stout et al, 2016;Fingas, 2017) have been used to differentiate petrogenic and pyrogenic sources in surface and deep-sea samples. Using available data from previous studies and our study, Figure 7 shows the significant correlation between PI and %5-6 ring ratios (R = 0.68, P < 0.001, N = 416).…”

“…This enhanced sedimentation event was known as MOSSFA (Marine Oil Snow Sedimentation and Flocculent Accumulation) and consisted of oil residues mixed with organic and inorganic particles, including bacteria, phytoplankton, microzooplankton, zooplankton fecal pellets, detritus, and terrestrially derived lithogenic particles (Daly et al, 2020). Moreover, the deposition of oil residues as marine oil snow (MOS) and/or oil-mineral aggregates (OMAS) is not specific to the DWHOS (e.g., Niu et al, 2010;Vonk et al, 2015;Romero et al, 2016). Therefore, a better understanding of the conditions that favor MOSSFA events and its role in the fate of oil residues at depth is warranted for improving response efforts in the event of future oil spill accidents.…”

Temporal Variability of Polycyclic Aromatic Hydrocarbons in Deep-Sea Cephalopods of the Northern Gulf of Mexico

“…Specifically, samples were collected before and up to 6 years after the DWHOS (pre-spill: 2010, post-spill: 2011, long-term period: 2015-2016). The samples collected before the DWHOS (January to March, 2010), provided an exceptional opportunity to study uptake and persistence of petrogenic PAHs under multiple natural and anthropogenic sources present in the GoM (Mitra et al, 2002;Mitra and Bianchi, 2003;Romero et al, 2016). Overall, this study provides a time-series analysis of PAH composition and concentrations generating trends in PAH signatures for baseline and chronic conditions in deep-sea cephalopods.…”

Diet of Common Bottlenose Dolphins, Tursiops truncatus, that Stranded in and Near Barataria Bay, Louisiana, 2010–2012

“…Fish are affected by oil spills through direct exposure to the gills or skin, indirect exposure through diet, and ecological changes in prey availability or destruction of marsh habitat (Elmgren et al 1983, Gregg et al 1997, Whitehead et al 2012. For demersal fish, exposure to PAH-contaminated sediment and diet of benthic prey are thought to be an important source of oil exposure (MacDonald et al 2015;Romero et al 2015Romero et al , 2016Romero et al , 2017. If benthic and demersal fish were affected by the heavy oiling of Barataria Bay, then this could impact the Dolphins that consume these fish.…”