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1. The first decade of scientific insights from the Deepwater Horizon oil release

   Kujawinski, E.B ; Reddy, C.M. ; Rodgers, R.P. ; Thrash, J.C. ; Valentine, D.L. ; White, H.K. ( April 2020 , Nature reviews)

   null (Ed.)

   The 2010 Deepwater Horizon disaster remains the largest single accidental release of oil and gas into the ocean. During the 87- day release, scientists used oceanographic tools to collect wellhead oil and gas samples, interrogate microbial community shifts and activities, and track the chemical composition of dissolved oil in the ocean’s interior. In the decade since the disaster, field and laboratory investigations studied the physics and chemistry of irrupted oil and gas at high pressure and low temperature, the role of chemical dispersants in oil composition and microbial hydrocarbon degradation, and the impact of combined oil, gas and dispersants on the flora and fauna of coastal and deep- sea environments. The multi- faceted, multidisciplinary scientific response to the released oil, gas and dispersants culminated in a better understanding of the environmental factors that influence the short- term and long- term fate and transport of oil in marine settings. In this Review , we summarize the unique aspects of the Deepwater Horizon release and highlight the advances in oil chemistry and microbiology that resulted from novel applications of emerging technologies. We end with an outlook on the applicability of these findings to possible oil releases in future deep- sea drilling locations and newly- opened high- latitude shipping lanes. 

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2. Hydrocarbon metabolism and petroleum seepage as ecological and evolutionary drivers for Cycloclasticus

   https://doi.org/10.1093/ismejo/wrae247  

   Arrington, Eleanor C ; Tarn, Jonathan ; Kivenson, Veronika ; Nunn, Brook L ; Liu, Rachel M ; Paul, Blair G ; Valentine, David L ( December 2024 , The ISME Journal)

   Aqueous-soluble hydrocarbons dissolve into the ocean’s interior and structure deep-sea microbial populations influenced by natural oil seeps and spills. n-Pentane is a seawater-soluble, volatile compound abundant in petroleum products and reservoirs and will partially partition to the deep-water column following release from the seafloor. In this study, we explore the ecology and niche partitioning of two free-living Cycloclasticus strains recovered from seawater incubations with n-pentane and distinguish them as an open ocean variant and a seep-proximal variant, each with distinct capabilities for hydrocarbon catabolism. Comparative metagenomic analysis indicates the variant more frequently observed further from natural seeps encodes more general pathways for hydrocarbon consumption, including short-chain alkanes, aromatics, and long-chain alkanes, and also possesses redox versatility in the form of respiratory nitrate reduction and thiosulfate oxidation; in contrast, the seep variant specializes in short-chain alkanes and relies strictly on oxygen as the terminal electron acceptor. Both variants observed in our work were dominant ecotypes of Cycloclasticus observed during the Deepwater Horizon disaster, a conclusion supported by 16S rRNA gene analysis and read-recruitment of sequences collected from the submerged oil plume during active flow. A comparative genomic analysis of Cycloclasticus across various ecosystems suggests distinct strategies for hydrocarbon transformations among each clade. Our findings suggest Cycloclasticus is a versatile and opportunistic consumer of hydrocarbons and may have a greater role in the cycling of sulfur and nitrogen, thus contributing broad ecological impact to various ecosystems globally. 

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3. Persistent and substantial impacts of the Deepwater Horizon oil spill on deep-sea megafauna

   https://doi.org/10.1098/rsos.191164  

   McClain, Craig R. ; Nunnally, Clifton ; Benfield, Mark C. ( August 2019 , Royal Society Open Science)

   The Deepwater Horizon spill is one of the largest environmental disasters with extensive impacts on the economic and ecological health of the Gulf of Mexico. Surface oil and coastal impacts received considerable attention, but the far larger oil spill in the deep ocean and its effects received considerably less examination. Based on 2017 ROV surveys within 500 m of the wellhead, we provide evidence of continued impacts on diversity, abundance and health of deep-sea megafauna. At locations proximal to the wellhead, megafaunal communities are more homogeneous than in unimpacted areas, lacking many taxonomic groups, and driven by high densities of arthropods. Degraded hydrocarbons at the site may be attracting arthropods. The scope of impacts may extend beyond the impacted sites with the potential for impacts to pelagic food webs and commercially important species. Overall, deep-sea ecosystem health, 7 years post spill, is recovering slowly and lingering effects may be extreme. 

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4. The core seafloor microbiome in the Gulf of Mexico is remarkably consistent and shows evidence of recovery from disturbance caused by major oil spills

   https://doi.org/10.1111/1462-2920.14794  

   Overholt, Will A. ; Schwing, Patrick ; Raz, Kala M. ; Hastings, David ; Hollander, David J. ; Kostka, Joel E. ( October 2019 , Environmental Microbiology)

   The microbial ecology of oligotrophic deep ocean sediments is understudied relative to their shallow counterparts, and this lack of understanding hampers our ability to predict responses to current and future perturbations. The Gulf of Mexico has experienced two of the largest accidental marine oil spills, the 1979 Ixtoc‐1 blowout and the 2010 Deepwater Horizon (DWH) discharge. Here, microbial communities were characterized for 29 sites across multiple years in > 700 samples. The composition of the seafloor microbiome was broadly consistent across the region and was well approximated by the overlying water depth and depth within the sediment column, while geographic distance played a limited role. Biogeographical distributions were employed to generate predictive models for over 4000 OTU that leverage easy‐to‐obtain geospatial variables which are linked to measured sedimentary oxygen profiles. Depth stratification and putative niche diversification are evidenced by the distribution of taxa that mediate the microbial nitrogen cycle. Furthermore, these results demonstrate that sediments impacted by the DWH spill had returned to near baseline conditions after 2 years. The distributions of benthic microorganisms in the Gulf can be constrained, and moreover, deviations from these predictions may pinpoint impacted sites and aid in future response efforts or long‐term stability studies.

    

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5. Peak-cognizant Signal Processing of Raw Instrument Signals to Quantify Environmental Weathering of Contaminants from the Deepwater Horizon Spill

   https://doi.org/10.1109/IEEECONF38699.2020.9389289  

   Kubicek, Bernice ; Gupta, Ananya Sen ; MullerDahlberg, Fabian ; Zelenski, Alexandra ; Wong, Roberto ; Overton, Edward ( October 2020 , Global Oceans 2020: Singapore – U.S. Gulf Coast)

   null (Ed.)

   In this work, we present peak-cognizant quantification of environmental weathering of crude oil from the from the Deepwater Horizon oil spill. The key idea is to autonomously extract peak information from raw gas chromatography-mass spectrometry (GC-MS) signals from crude oil samples, and represent the relative weathering of different peaks in a graph-based quantitative computational framework. We also present results from pre-processing the raw signals with baseline correction and signal normalization. Retention time alignment is performed by first aligning the source oil by determining the retention time drift between prominent peaks within the signals and applying the calculated drift to the weathered oil samples. Peak finding, validation, and grouping of the five weathered oil samples to a source oil sample allows compound associations to be discovered. We present preliminary results as graphical visualizations allowing for rapid and precise interpretation of weathering compounds within polycyclic aromatic hydrocarbons (PAH). Results presented were generated with oil samples showing different degrees of weathering collected from the Deepwater Horizon spill. 

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