Resuspension, Redistribution, and Deposition of Oil-Residues to Offshore Depocenters After the Deepwater Horizon Oil Spill

The focus of this study was to determine the long-term fate of oil-residues from the 2010 Deepwater Horizon (DwH) oil spill due to remobilization, transport, and re-distribution of oil residue contaminated sediments to down-slope depocenters following initial deposition on the seafloor. We characterized hydrocarbon residues, bulk sediment organic matter, ease of resuspension, sedimentology, and accumulation rates to define distribution patterns in a 14,300 km2 area southeast of the DwH wellhead (1,500 to 2,600 m water depth). Oil-residues from the DwH were detected at low concentrations in 62% of the studied sites at specific sediment layers, denoting episodic deposition of oil-residues during 2010–2014 and 2015–2018 periods. DwH oil residues exhibited a spatial distribution pattern that did not correspond with the distribution of the surface oil slick, subsurface plume or original seafloor spatial expression. Three different regions were apparent in the overall study area and distinguished by the episodic nature of sediment accumulation, the ease of sediment resuspension, the timing of oil-residue deposition, carbon content and isotopic composition and foram fracturing extent. These data indicate that resuspension and down-slope redistribution of oil-residues occurred in the years following the DwH event and must be considered in determining the fate of the spilled oil deposited on the seafloor

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

Following the Deepwater Horizon oil spill (DWHOS), the formation of an unexpected and extended sedimentation event of oil-associated marine snow (MOSSFA: Marine Oil Snow Sedimentation and Flocculent Accumulation) demonstrated the importance of biology on the fate of contaminants in the oceans. We used a wide range of compound-specific data (aliphatics, hopanes, steranes, triaromatic steroids, polycyclic aromatics) to chemically characterize the MOSSFA event containing abundant and multiple hydrocarbon sources (e.g., oil residues and phytoplankton). Sediment samples were collected in 2010–2011 (ERMA-NRDA programs: Environmental Response Management Application – Natural Resource Damage Assessment) and 2018 (REDIRECT project: Resuspension, Redistribution and Deposition of Deepwater Horizon recalcitrant hydrocarbons to offshore depocenter) in the northern Gulf of Mexico to assess the role of biogenic and chemical processes on the fate of oil residues in sediments. The chemical data revealed the deposition of the different hydrocarbon mixtures observed in the water column during the DWHOS (e.g., oil slicks, submerged-plumes), defining the chemical signature of MOSSFA relative to where it originated in the water column and its fate in deep-sea sediments. MOSSFA from surface waters covered 90% of the deep-sea area studied and deposited 32% of the total oil residues observed in deep-sea areas after the DWHOS while MOSSFA originated at depth from the submerged plumes covered only 9% of the deep-sea area studied and was responsible for 15% of the total deposition of oil residues. In contrast, MOSSFA originated at depth from the water column covered only 1% of the deep-sea area studied (mostly in close proximity of the DWH wellhead) but was responsible for 53% of the total deposition of oil residues observed after the spill in this area. This study describes, for the first time, a multi-chemical method for the identification of biogenic and oil-derived inputs to deep-sea sediments, critical for improving our understanding of carbon inputs and storage at depth in open ocean systems

High-Resolution Investigation of Event Driven Sedimentation: Response and Evolution of the Deepwater Horizon Blowout in the Sedimentary System

This Dissertation combines the investigation of the sedimentological impacts of the Deepwater Horizon (DwH) blowout event in the deep-sea benthos, with the refinement and advancement of methods and approaches for high-resolution investigations of events preserved in sedimentary records. An approach that combined, rapid collection of cores, a continued annual time series collection of cores, and high-resolution sampling and analyses, in particular short-lived Radioisotopes (SLRad), enabled the temporal resolution required to detect the sedimentary response to the short-duration DwH event, and evaluate post-event sedimentation patterns at a comparable time scale (months). The collection of 179 sediment cores from 80 sites between the fall of 2010 and 2016 included four sites that were utilized as an annual time-series collection to define the sedimentary response to the DwH blowout event and how the sedimentary system evolved/recovered post-event. High-resolution (2mm) sub-sampling was utilized to maximize the temporal resolution of analyses and age control using SLRad. The rapid collection of cores to define the immediate benthic impact(s), as well as the use of time-sensitive indicators of the event that may degrade over time, as well as indicators for very short time scale (months) sedimentation, such as 234Thxs. 234Thxs inventories and mass accumulation rates (MAR’s) were one of the most diagnostic characteristics of the sedimentary response. The DwH blowout event led to a Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA) event that caused a depositional pulse to the seafloor. This was defined by increased sedimentation rates and the shutdown of bioturbation as indicated by 234Thxs inventories and MAR’s. The annual collection of sediment cores as a time-series allowed for continued high-resolution analyses and use of 234Thxs to determine post-event sedimentation rates and baselines on monthly time scales for direct comparison to the depositional pulse. Within ~one year sedimentation rates decreased and within three years site specific return of bioturbation occurred and sedimentation rates on monthly scale (234Thxs) stabilized. Also, within ~three years the sedimentary signature of the depositional pulse became undetectable with respect to sediment texture and composition possibly due to dilution of this indicator by mixing/bioturbation and/or compaction of the event layer. Without the use of high-resolution sampling and geochronological tools such as 234Thxs the depositional pulse would not have been detected in the sedimentary system. The continued use of these high-resolution methods allowed for further defining the magnitude of the sedimentary response to the DwH event as well as provide baseline sedimentation patterns at a monthly time scale. The annual time series defines the post-event evolution of the sedimentary system as well as the assessment of the post-depositional alterations that influence the integration and preservation of such sedimentation events in the sedimentary record. This includes the potential for re-mobilization of event sediments, potential re-exposure of ecosystems to contaminated sediments and redistribution of event sediments. Alternatively, burial and alteration of the sedimentary signature over time influences the preservation potential of sedimentation events such as DwH, with decreasing ability to detect events due to bioturbation, degradation of signature and compaction. The refinement of methodology and approaches, in particular short-lived radioisotope (SLRad) geochronology, allowed for the high-resolution determination of the sedimentary impacts of the DwH blowout event. In turn, the opportunity to investigate the DwH event in real time provided the opportunity to advance high-resolution methodologies in an applied fashion. Continued refinement of high-resolution approaches and methods, in particular geochronologies, will allow for the detection of short-duration and subtle sedimentary events in real time as well as in the sedimentary record. Through the application of such approaches and methods to real events, these methods can be further refined and assessed for their utility and limitations

Bulk density and porewater data collected onboard R/V Weatherbird II cruises WB-0813 and WB-1405 in the northern Gulf of Mexico from 2013-08-15 to 2013-09-27

This dataset reports measurement of sediment sample wet weight (g) and dry weight (g) for core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to the base of cores. Bulk density is the dry weight per sampling volume expressed as g/cm3. The dataset also reports percent porewater. The sediment cores were collected onboard the R/V Weatherbird II cruises WB-0813 and WB-1405 in the northern Gulf of Mexico from 2013-08-15 to 2013-09-27. Chief scientists for these cruises were Dr. Steve Murawski and Dr. David Hollander for WB-0813, and Oscar Garcia for WB-1405. The objective of cruise WB-0813 was to create Gulf-wide baselines for sediment and fish and cruise WB-1405 was dedicated for benthic ecology

Short-lived radioisotope (SLRad) data collected aboard R/V Justo Sierra cruise JS-0815 in the southern Gulf of Mexico from 2015-07-31 to 2015-08-08

This dataset contains short-lived radioisotope (SLRad) data collected aboard R/V Justo Sierra cruise JS-0815 in the southern Gulf of Mexico from 2015-07-31 to 2015-08-08. SLRad data were generated for selected core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to the base of cores. SLRad data generated include sample activity as disintegrations per minute per gram (dpm/g) of 1) Excess Thorium-234 (234Thxs) activity, which is calculated by measuring the total Thorium-234 (234ThTot) activity and the subtraction of the measured or estimated “supported” Thorium-234 (234ThSup) activity, 2) Excess Lead-210 (210Pbxs) activity, which is calculated by measuring the total Lead-210 (210PbTot) activity and subtraction of the measured background supported Lead-210 (210PbSup) activity {average of Lead-214 (214Pb) at 295 kiloelectron volts (keV), 214Pb at 351keV, and Bismuth-214 (214Bi) at 609keV}, 3) Cesium-137 (137Cs) activity, and 4) Berilium-7 (7Be) activity. The cruise documentation was provided for the R/V Justo Sierra cruise JS-0815. The cruise was led by chief scientist Dr. David Hollander

Sediment texture & composition data collected aboard R/V Weatherbird II cruise WB-0517 in the Gulf of Mexico from 2017-05-11 to 2017-05-23

This dataset contains sediment texture & composition data collected aboard R/V Weatherbird II cruise WB-0517 in the Gulf of Mexico from 2017-05-11 to 2017-05-23. Twelve sites were sampled using a multi-corer between 316 and 1670 m depth around northwest Cuba. Sediment texture and composition data are generated for selected core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to the base of cores. Sediment texture values are expressed as % Gravel, % Sand, % Silt and % Clay as calculated by dry weight (g), % Mud can be calculated by combining % Silt and % Clay. Sediment composition is expressed as % TOM (Total Organic Matter) measured by Loss on Ignition (LOI), % Carbonate content measured by acid leaching, and the % Insoluble Residue (IR), which is likely dominated by terrigenous clastic (land-derived) sediment sources. The cruise documentation was provided for the R/V Weatherbird II cruise WB-0517, led by chief scientists Dr. David Hollander and Dr. Steve Murawski. This dataset supports the publications: Armenteros, M., Schwing, P. T., Larson, R. A., Díaz-Asencio, M., Martínez-Suárez, A., Fernández-Garcés, R., … Brooks, G. R. (2019). Geochemical and Faunal Characterization in the Sediments off the Cuban North and Northwest Coast. Scenarios and Responses to Future Deep Oil Spills, 147–159. doi:10.1007/978-3-030-12963-7_9; and Brooks, G. R., Larson, R. A., Schwing, P. T., Diercks, A. R., Armenteros, M., Diaz-Asencio, M., … Hollander, D. J. (2019). Gulf of Mexico (GoM) Bottom Sediments and Depositional Processes: A Baseline for Future Oil Spills. Scenarios and Responses to Future Deep Oil Spills, 75–95. doi:10.1007/978-3-030-12963-7_5

Sediment Texture and Composition of Sediment Cores Collected During R/V Weatherbird II Cruises in the Northern Gulf of Mexico from 2010-11-18 to 2016-09-09

Sediment texture and composition data were generated for selected core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to base of cores. Sediment texture values are expressed as % Gravel, % Sand, % Silt and % Clay as calculated by dry weight (g). % Mud can be calculated by combining % Silt and % Clay. Sediment composition is expressed as % carbonate content measured by acid leaching. This dataset supports the publication: Larson, R. A., Brooks, G. R., Schwing, P. T., Holmes, C. W., Carter, S. R., & Hollander, D. J. (2018). High-resolution investigation of event driven sedimentation: Northeastern Gulf of Mexico. Anthropocene, 24, 40–50. doi:10.1016/j.ancene.2018.11.00

Bulk Density/Porewater of sediment cores collected aboard R/V Weatherbird II cruise WB-0517 in the Gulf of Mexico from 2017-05-11 to 2017-05-23

This dataset contains Bulk Density/Porewater of sediment cores collected aboard R/V Weatherbird II cruise WB-0517 in the Gulf of Mexico from 2017-05-11 to 2017-05-23. Twelve sites were sampled using a multi-corer between 316 and 1670 m depth around northwest Cuba. The dataset contains the location, date, water depth, core ID, and top depth of interval (mm), bottom depth of interval (mm), average depth of interval (mm), wet weight (g), dry weight (g), sample volume (cm3), bulk density (g/cm3), and % pore water. Measurement of sediment sample wet weight (g) and dry weight (g) for core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to the base of cores. Bulk density is the dry weight per sampling volume expressed as g/cm3 and is utilized in the calculation of Mass Accumulation Rates (MAR’s). The cruise documentation was provided for the R/V Weatherbird II cruise WB-0517, led by chief scientists, Dr. David Hollander and Dr. Steve Murawski. This dataset supports the publications: Armenteros, M., Schwing, P. T., Larson, R. A., Díaz-Asencio, M., Martínez-Suárez, A., Fernández-Garcés, R., … Brooks, G. R. (2019). Geochemical and Faunal Characterization in the Sediments off the Cuban North and Northwest Coast. Scenarios and Responses to Future Deep Oil Spills, 147–159. doi:10.1007/978-3-030-12963-7_9; and Brooks, G. R., Larson, R. A., Schwing, P. T., Diercks, A. R., Armenteros, M., Diaz-Asencio, M., … Hollander, D. J. (2019). Gulf of Mexico (GoM) Bottom Sediments and Depositional Processes: A Baseline for Future Oil Spills. Scenarios and Responses to Future Deep Oil Spills, 75–95. doi:10.1007/978-3-030-12963-7_5

Short-lived Radioisotope Geochronology from Sediment Cores Collected During R/V Weatherbird II Cruises in the Northern Gulf of Mexico from 2010-11-18 to 2016-09-09

Short-lived Radioisotope (SLRad) data were generated for selected core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to base of cores. SLRad data generated include sample activity as disintegrations per minute per gram (dpm/g) of: 1) Excess 234Th (234Thxs) activity, which is calculated by measuring the total 234Th (234ThTot) activity and the subtraction of the measured or estimated “Supported” 234Th (234ThSup) activity, 2) Excess 210Pb (210Pbxs) activity, which is calculated by measuring the total 210Pb (210PbTot) activity and subtraction of the measured background 210Pb (210PbSup) activity (average of 214Pb at 295keV, 214Pb at 351keV, and 214Bi at 609keV), 3) 137Cs activity, and 4) 7Be activity. Where appropriate, age dating was calculated in calendar years for 234Th and 210Pb activity profiles and mass accumulation rates (MAR) expressed as g/cm2/yr using the Constant Rate of Supply model. This dataset supports the publication: Larson, R. A., Brooks, G. R., Schwing, P. T., Holmes, C. W., Carter, S. R., & Hollander, D. J. (2018). High-resolution investigation of event driven sedimentation: Northeastern Gulf of Mexico. Anthropocene, 24, 40–50. doi:10.1016/j.ancene.2018.11.00

Core Extrusion Bulk Density/Pore Water, Northern Gulf of Mexico, November 2010 to September 2016

Measurement of sediment sample wet weight (g) and dry weight (g) for core sub-samples at 2mm sampling intervals for “surficial unit” and 5mm sampling resolution intervals to base of cores. Bulk density is the dry weight per sampling volume expressed as g/cm^3 and is utilized in the calculation of Mass Accumulation Rates (MAR’s). Samples were collected in the northern Gulf of Mexico from November 2010 to September 2016