Abstract
The Deepwater Horizon incident in the Gulf of Mexico in 2010 released an unprecedented amount of petroleum hydrocarbons 1500 meters below the sea surface. Few studies have considered the influence of hydrostatic pressure on bacterial community development and activity during such spills. The goal of this study was to investigate the response of indigenous sediment microbial communities to the combination of increased pressure, hydrocarbons and dispersant. Deep-sea sediment samples collected from the northern Gulf of Mexico were incubated at atmospheric pressure (0.1 MPa) and at elevated pressure (10 MPa), with and without the addition of crude oil and dispersant. After incubations at 4 °C for 7 days, Colwellia and Psychrobium were highly abundant in all samples. Pressure differentially impacted members of the Alteromonadales. The influences of pressure on the composition of bacterial communities were most pronounced when dispersant was added to the incubations. Moritella and Thalassotalea were greatly stimulated by the addition of dispersant, suggesting their roles in dispersant biodegradation. However, Moritella was negatively impacted by increasing pressure. The presence of dispersant was shown to decrease the relative abundance of a known hydrocarbon degrader, Cycloclasticus, while increasing pressure increased its relative abundance. This study highlights the significant influence of pressure on the development of microbial communities in the presence of oil and dispersant during oil spills and related response strategies in the deep sea.
Highlights
The Deepwater Horizon incident in the Gulf of Mexico in 2010 released an unprecedented amount of petroleum hydrocarbons 1500 meters below the sea surface
The subsurface release of oil formed a persistent plume spanning 1000 and 1200 m depth[3,4] and analysis of deep sediment cores collected near the blowout location shortly after the spill indicated that some of this oil was deposited on the sea floor[5,6]. The deposition of these hydrocarbons were from marine oil snow sedimentation and flocculent accumulation (MOSSFA) events, where crude oil compounds were attached to sinking of particles[7], and from the direct contact of the deep plume with the continental shelf, referred to as the bathtub-ring hypothesis[6]
A number of studies investigated the successions of the bacterial community compositions in the water column and in the sediments[10,11,12,13] and found that these successions were driven by the hydrocarbons input from the Deepwater Horizon (DWH) spill[10,12,14]
Summary
The Deepwater Horizon incident in the Gulf of Mexico in 2010 released an unprecedented amount of petroleum hydrocarbons 1500 meters below the sea surface. Deep-sea sediment samples collected from the northern Gulf of Mexico were incubated at atmospheric pressure (0.1 MPa) and at elevated pressure (10 MPa), with and without the addition of crude oil and dispersant. This study highlights the significant influence of pressure on the development of microbial communities in the presence of oil and dispersant during oil spills and related response strategies in the deep sea. The subsurface release of oil formed a persistent plume spanning 1000 and 1200 m depth[3,4] and analysis of deep sediment cores collected near the blowout location shortly after the spill indicated that some of this oil was deposited on the sea floor[5,6]. Biodegradation studies with crude oil and dispersants at increased pressures have not yet been conducted on benthic bacterial communities. We report how the interactions between crude oil, pressure, and dispersant application changed deep benthic microbial communities around the DWH region
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