A tale of two Gulf spills: A research consortium of 19 institutions from 5 countries studying the impacts of oil spills on the Gulf of Mexico.
Take a look at our up to date C-IMAGE research in the literature!
C-IMAGE co-PI and Civil Engineering Professor Dr. Scott Socolofsky co-authored a paper that was selected for ACS Editor’s choice. Dr. Socolofsky in the Zachry Department of Civil Engineering and his colleagues at EPFL and WHOI have published a new paper in ES&T that describes the behavior of oil and gas in the deep Gulf of Mexico as it was released during the Deepwater Horizon. This paper was also selected for the American Chemical Society Editor’s Choice.Excerpt from Press Release 'Under Pressure: Petroleum Changes in the Deep Sea' from Environmental Chemistry Modeling Laboratory in Ecole Polytechnique Federale de Lausanne (EPFL).
Read on for an excerpt from the full press release out of ENVIRONMENTAL CHEMISTRY MODELING LABORATORY NEWS:
After the Deepwater Horizon accident in 2010, an often-asked question was: What happened to petroleum liquid and gas that was emitted into the deep sea, and why? A paper published recently by a team at the Ecole Polytechnique Fédérale de Lausanne, the Swiss Federal Institute of Aquatic Science and Technology (Eawag), Woods Hole Oceanographic Institution, and Texas A&M University sheds new light on the strange behaviors of petroleum liquid and natural gas in the deep ocean.
Unlike a more typical oil spill at the sea surface, a deep-sea petroleum release is affected by extreme high-pressure conditions, which fundamentally alter the state and behaviors of the petroleum in the sea environment. This is what happened during the 2010 Deepwater Horizon accident, when more than half a million tons of petroleum liquid and natural gas were released from the broken Macondo well at a depth of 1524 meters under water in the Gulf of Mexico, about 66 kilometers offshore from the Louisiana coast.
View the full release here.
Jonas Gros, Christopher M. Reddy, Robert K. Nelson, Scott A. Socolofsky, and J. Samuel Arey (2016), Simulating Gas–Liquid−Water Partitioning and Fluid Properties of Petroleum under Pressure: Implications for Deep-Sea Blowouts. Env. Sci. and Technology, DOI: 10.1021/acs.est.5b04617.
On July 23, 2013 a marine gas rig (Hercules 265) ignited in the northern Gulf of Mexico. The rig burned out of control for two days before being extinguished. The C-IMAGE and CARTHE Consortia 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 km, 8 km 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 were 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.
Read the full article here.
Romero, I. C., Özgökmen, T., Snyder, S., Schwing, P., O'Malley, B. J., Beron-Vera, F. J., Olascoaga, M. J., Zhu, P., Ryan, E., Chen, S. S., Wetzel, D. L., Hollander, D. and Murawski, S. A. (2015), Tracking the Hercules 265 marine gas well blowout in the Gulf of Mexico. J. Geophys. Res. Oceans. Accepted Author Manuscript. doi:10.1002/2015JC011037
A phytoplankton bloom covering an area > 11,000 km2 has been reported in the northeastern Gulf of Mexico east of the Mississippi River Delta in August 2010 (30°–28° N, 90°–86° W) based on NASA Moderate Resolution Imaging Spectrometer (MODIS) chlorophyll fluorescence line height (FLH) images. The bloom appeared to be anomalous relative to a historical monthly chlorophyll FLH mean (August 2002 to 2010), and was attributed by others to the Deepwater Horizon (DWH) oil spill accident. Here we tested an alternative hypothesis that the eastward dispersal of the Mississippi River plume entrained in wind-driven currents contributed to the development of this phytoplankton bloom. We examined Mississippi River discharge and nutrient records, ship-based surface salinity data, and the time-series of MODIS ocean color and FLH images. Wind measurements from buoys showed winds > 6 m s− 1 first in a southerly (northward) direction August 8–10, and then in a northerly (southward) direction until August 26. Results from the American Seas-Navy Coastal Ocean Model (AmSeas-NCOM) show how coastal water was advected in wind-driven currents into the area of the northeastern Gulf of Mexico where the bloom was documented. Between July 9 and September 8, 2010, the discharge of the Mississippi River exceeded the 20-year mean. During this time, the northeastern Gulf received an estimated excess volume of approximately 8.3 × 109 m3 relative to the 20-year mean. Together with findings from a particle trajectory model, we conclude that nutrients and other materials (e.g., sediments) from the excessive discharge of the Mississippi River and adjacent marshes and wind-driven currents likely contributed to the anomalous bloom observed during August 2010 and to the anomalously high organic matter sedimentation rates observed in the northeastern Gulf of Mexico in the aftermath of the Deepwater Horizon oil spill.
A newly utilized mass spectrometry method, FTICR-MS, gives researchers the ability to screen lipid biomarkers found in sediments at a faster rate than before. A new publication from the University of Calgary-Department of Geosciences and C-IMAGE members details the possible use of this new method.
Many of the molecular proxies commonly used for paleoenvironmental reconstruction are focused on a limited set of glycerol ether lipids, mainly due to the lack of more comprehensive analytical methods and instrumentation able to deal with a more diverse range of species. In this study, we describe an FTICR-MS based method, for rapid, non-targeted screening of ether lipid biomarkers in recent marine sediments. This method involves simplified sample preparation, and enables rapid identification of known, and novel ether lipid species. Using this method we were able to identify complete series of core glycerol dialkyl glycerol tetraethers (GDGTs with 0 to 8 alicyclic rings), including the complete resolution of GDGT-4, and the unexpected detection of GDGTs with more than 5 rings, in sediments from mesophilic marine environments (sea surface temperature, SST, of 24–25 °C). Additionally, mono- and dihydroxy-GDGT analogs (including novel species with >2 rings), as well as glycerol dialkanol diethers, GDDs (including novel species with >5 rings) were detected. Finally, we putatively identified other, previously unreported groups of glycerol ether lipid species. Adequacy of the APPI-P FTICR-MS data for the determination of commonly used GDGT-based proxy indices was demonstrated. The results of this study show great potential for the use of FTICR-MS as both a rapid method for determining existing proxy indices and perhaps more importantly, as a tool for the early detection of possible new biomarkers and proxies that may establish novel geochemical relationships between archaeal ether lipids and key environmental, energy and climate related system variables.
Remote detection of pelagic Sargassum is often hindered by its spectral similarity to other floating materials and by the inadequate spatial resolution. Using measurements from multi-spectral satellite sensors (Moderate Resolution Imaging Spectroradiometer or MODIS), Landsat, WorldView-2 (or WV-2) as well as hyperspectral sensors (Hyperspectral Imager for the Coastal Ocean or HICO, Airborne Visible-InfraRed Imaging Spectrometer or AVIRIS) and airborne digital photos, we analyze and compare their ability (in terms of spectral and spatial resolutions) to detect Sargassum and to differentiate it from other floating materials such as Trichodesmium, Syringodium, Ulva, garbage, and emulsified oil. Field measurements suggest that Sargassum has a distinctive reflectance curvature of ~ 630 nm due to its chlorophyll c pigments, which provides a unique spectral signature when combined with the reflectance ratio between brown (~ 650 nm) and green (~ 555 nm) wavelengths. For a 10-nm resolution sensor on the hyperspectral HyspIRI mission currently being planned by NASA, a stepwise rule to examine several indexes established from 6 bands (centered at 555, 605, 625, 645, 685, 755 nm) is shown to be effective to unambiguously differentiate Sargassum from all other floating materials Numerical simulations using spectral endmembers and noise in the satellite-derived reflectance suggest that spectral discrimination is degraded when a pixel is mixed between Sargassum and water. A minimum of 20–30% Sargassum coverage within a pixel is required to retain such ability, while the partial coverage can be as low as 1–2% when detecting floating materials without spectral discrimination. With its expected signal-to-noise ratios (SNRs ~ 200:1), the hyperspectral HyspIRI mission may provide a compromise between spatial resolution and spatial coverage to improve our capacity to detect, discriminate, and quantify Sargassum.
Ref:Chuanmin Hu, Lian Feng, Robert F. Hardy, Eric J. Hochberg, Spectral and spatial requirements of remote measurements of pelagic Sargassum macroalgae, Remote Sensing of Environment, Volume 167, 15 September 2015, Pages 229-246, ISSN 0034-4257, http://dx.doi.org/10.1016/j.rse.2015.05.022.
The Deepwater Horizon blowout in April, 2010, represented the largest accidental marine oil spill and the largest release of chemical dispersants into the environment. While dispersant application may provide numerous benefits to oil spill response efforts, the impacts of dispersants and potential synergistic effects with crude oil on individual hydrocarbon degrading bacteria are poorly understood. In this study, two environmentally relevant species of hydrocarbon degrading bacteria were utilized to quantify the response to Macondo crude oil and COREXIT® 9500A dispersed oil in terms of bacterial growth and oil degradation potential. Furthermore, specific hydrocarbon compounds were quantified in the dissolved phase of the medium and linked to ecotoxicity using an EPA-approved rotifer assay. Bacterial treatment significantly and drastically reduced the toxicity associated with dispersed oil (increasing the LC50 by 215%). Growth and crude oil degradation potential of Acinetobacter were inhibited by COREXIT 34% and 40%, respectively; conversely, COREXIT significantly enhanced the growth of Alcanivorax by 10% relative to un-dispersed oil. Furthermore, both bacterial strains were shown to grow with COREXIT as the sole carbon and energy source. Hydrocarbon-degrading bacterial species demonstrate a unique response to dispersed oil as compared to crude oil, with potentially opposing impacts on toxicity. While some species have the potential to enhance the toxicity of crude oil by producing biosurfactants, these same bacteria may reduce the toxicity associated with dispersed oil through degradation or sequestration.
Ref:Overholt, W., Marks, K., Romero, I., Hollander, D., Snell, T., Kostka, J. Hydrocarbon Degrading Bacteria Exhibit a Species Specific Response to Dispersed Oil while Moderating Ecotoxicity, Available online 26 September 2015, ISSN 0025-326X, http://dx.doi.org/10.1016/j.marpolbul.2015.09.022.
Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and transport of the oil. We aim to identify how natural, chemical and mechanical dispersion could be quantified in oil spill models. For each step in the dispersion process, we review available experimental data in order to identify overall trends and propose an algorithm or calculation method. Additionally, the conditions for successful mechanical and chemical dispersion are defined. Two commonly identified key parameters in surface oil dispersion are: oil properties (viscosity and presence of dispersants) and mixing energy (often wind speed). Strikingly, these parameters play a different role in several of the dispersion sub-processes. This may explain difficulties in simply relating overall dispersion effectiveness to the individual parameters.
Ref:Marieke Zeinstra-Helfrich, Wierd Koops, Albertinka J. Murk, The NET effect of dispersants — a critical review of testing and modelling of surface oil dispersion, Marine Pollution Bulletin, Available online 26 September 2015, ISSN 0025-326X, http://dx.doi.org/10.1016/j.marpolbul.2015.09.022.
Satellite images of reflected sunlight have been used to detect and monitor oil spills in oceans. However, such a capacity is often hindered by the image noise due to either a low signal-to-noise ratio or other image features such as clouds or cloud shadows. The problem is particularly severe for nighttime images captured by the Visible Infrared Imager Radiometer Suite (VIIRS). This letter proposes a practical method to extract oil slick features in a semiautomatic fashion from VIIRS nighttime images and other noisy optical remote sensing images. The method is based on statistical information and morphological operators, and it is demonstrated to be able to effectively remove the noise and identify line features with the appropriate selection of threshold values. Testing this method over VIIRS nighttime images shows the preliminary success of oil slick feature extraction. Experiments on daytime data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) also suggest the applicability of this method to other optical remote sensing images. However, the requirement of human intervention to determine optimal parameters points to the need for improved automation in future works.
Ref:Wang, M. and C. Hu "Extracting Oil Slick Features From VIIRS Nighttime Imagery Using a Gaussian Filter and Morphological Constraints," in Geoscience and Remote Sensing Letters, IEEE , vol.12, no.10, pp.2051-2055, Oct. 2015 doi: 10.1109/LGRS.2015.2444871.)
Beaked whales are deep diving elusive animals, difficult to census with conventional visual surveys. Methods are presented for the density estimation of beaked whales, using passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period during and following the Deepwater Horizon oil spill (2010–2013). Beaked whale species detected include: Gervais’ (Mesoplodon europaeus), Cuvier’s (Ziphius cavirostris), Blainville’s (Mesoplodon densirostris) and an unknown species of Mesoplodon sp. (designated as Beaked Whale Gulf — BWG). For Gervais’ and Cuvier’s beaked whales, we estimated weekly animal density using two methods, one based on the number of echolocation clicks, and another based on the detection of animal groups during 5 min time-bins. Density estimates derived from these two methods were in good general agreement. At two sites in the western GOM, Gervais’ beaked whales were present throughout the monitoring period, but Cuvier’s beaked whales were present only seasonally, with periods of low density during the summer and higher density in the winter. At an eastern GOM site, both Gervais’ and Cuvier’s beaked whales had a high density throughout the monitoring period.
Ref:J. Hildebrand, S. Baumann-Pickering, K. Frasier, J. Trickey, K. Merkens, S. Wiggins, M. McDonald, L. Garrison, D. Harris, T. Marques, and L. Thomas: Passive acoustic monitoring of beaked whale densities in the Gulf of Mexico, Scientific Reports, 5, 16343, doi: 10.1038/srep16343 (2015)
Fossils of marine microorganisms such as planktic foraminifera are among the cornerstones of palaeoclimatological studies. It is often assumed that the proxies derived from their shells represent ocean conditions above the location where they were deposited. Planktic foraminifera, however, are carried by ocean currents and, depending on the life traits of the species, potentially incorporate distant ocean conditions. Here we use high-resolution ocean models to assess the footprint of planktic foraminifera and validate our method with proxy analyses from two locations. Results show that foraminifera, and thus recorded palaeoclimatic conditions, may originate from areas up to several thousands of kilometres away, reflecting an ocean state significantly different from the core site. In the eastern equatorial regions and the western boundary current extensions, the offset may reach 1.5 °C for species living for a month and 3.0 °C for longer-living species. Oceanic transport hence appears to be a crucial aspect in the interpretation of proxy signals.
Ref:Van Sebille E, Scussolini P, Durgadoo JV, Peeters F, Biastoch A, Weijer W, Turney C, Paris CB, Zahn R (2015) Ocean currents generate large footprints in marine palaeoclimate proxies, Nature Communications 6: 6521
A two-dimensional (2-D) ecosystem model, set within the De Soto Canyon ecotone of the Northern Gulf of Mexico (NGOM) and driven by 3-D flow fields from decoupled water and air circulation models, explores the daily food web and sedimentary consequences, as well as potential public health implications, of oil-, nutrient-, and overfishing-induced transitions of dominant particle transports to the sea floor: from changing vectors of copepod fecal pellets to those of marine snow over the annual period of 2010–2011. Recent spilled petrochemicals are found to minimally impact already decimated zooplankton populations on the West Florida shelf (WFS). They facilitate instead formation of marine snow macroaggregates. These recent oil effects just exacerbate other results of prior overfishing in the absence of major eutrophication along the eastern side of this ecotone. East of the De Soto Canyon ecotone, overly optimistic removals of piscivore fish stocks over the last half-century had already caused a trophic cascade, with ~95% of WFS marine pelagic herbivore losses occurring by 2010, before the Deepwater Horizon [DWH] blowout. By contrast, west of De Soto Canyon, zooplankton on the eutrophic Louisiana shelf were less impacted by overfishing, retaining order of magnitude more stocks of the same genera of copepods. Yet, during descent of modeled marine snow to the ~1200-m isobath of the upper slope, ~98% of the particulate import to the benthos is now mainly clay minerals of Mississippi River origin along the ecotone. The lithogenic particles are scavenged by aggregates from the whole water column, not only biotic plankton from just the near-surface euphotic zone. The model results here replicate concurrent time series of: 1) annual sediment accumulations, measured at the sea floor; 2) bimonthly onshore nutrient supplies, due to upwelling, forced remotely by the Loop Current; and 3) near-surface weekly phytoplankton changes, seen by satellite. Because of such minimal grazing stresses, after the most recent DWH oil reductions to ~50% of the remaining few WFS copepods, their decreased herbivory amounts to only an 8% fecal pellet contribution to the model's particle fluxes, with 92% settling as marine snow to the sea bottom of the continental slope in 2010–2011 By contrast, 12% of the biotic particle exports, entrained within marine snow, result from increased loadings of Mississippi River nutrients via opened flood gates, while 50% of the ungrazed sinking phytoplankton are fueled by decadal anomalies of increased nutrient supplies from greater upwelling by the Loop Current. Finally, of the exiting phytodetritus embedded within marine snow from the 2010–2011 water columns, 38% are due to uptake of autocthonous nutrients in the slope waters. But, explicit upward fluxes of nutrient-poor, petrochemical dissolved organic carbon [DOC] substrates for use by aphotic chemolithoautotrophic bacterial bioremediators, responding to DWH oil releases and external dissolved nutrients, are now ignored in the present model. These model results also relate downstream, wind-borne trajectories of evaded potential marine aerosolized toxins to both human asthma episodes and total mercury amounts in coastal soils, without explicit sea-air exchanges of initial aerosols. Thus, future simulation analyses, with instead extant numerical descriptions of breaking wave exports of oil, harmful algal bloom [HAB], and Hg aerosol poisons, must fully couple onshore 3-D aerial imports of this suite of marine toxins to direct causal factors of adjacent human health impacts, constrained by known surrogate asthma hospitalization rates. They must next deconvolve net multiyear oil and top-down NGOM indirect losses of herbivores, within now unbalanced marine food webs of an overfishing-induced trophic cascade, from other concurrent anthropogenic forcings, due to in situ mercury, pesticide, and radionuclide poisonings, within linked habitats of both water and air, subject to continued climate and biotic changes of the southeastern U.S. seaboard.
The full article is available at the link below:
Walsh, J. J., Lenes, J. M., Darrow, B. P., Parks, A. A., Weisberg, R. H., Zheng, L., et al. (2015). A simulation analysis of the plankton fate of the Deepwater Horizon oil spills. Continental Shelf Research, 107, 50–68.
Red Snapper Lutjanus campechanus were sampled at 33 natural and 27 artificial reef sites in the northern Gulf of Mexico prior to (2009–2010) and after (2010–2011) to examine potential diet and trophic shifts following the Deepwater Horizon (DWH) oil spill. We dissected 708 stomachs for gut content analysis and processed 65 muscle tissue samples for stable isotope ratio-mass spectrometry analysis of δ13C, δ15N, and δ34S. Forty-eight percent of stomachs contained identifiable prey, which we grouped into seven categories: fish, decapods, cephalopods, stomatopods, gastropods, zooplankton, and other invertebrates. Based on these categories, Red Snapper diet was significantly different following the DWH oil spill, and was differentially affected by fish size. The interaction between habitat (natural versus artificial reefs) and DWH oil spill effects was also significant. Significant differences in diet among Red Snapper size-classes were due to low trophic position prey, such as pelagic zooplankton, being more abundant in the diet of larger (>500 mm) Red Snapper, while decapods and fish constituted a higher proportion of the diet of smaller individuals. Red Snapper consumed higher amounts of decapods at artificial (21.9% by mass) versus natural (14.8%) reef sites, but the habitat effect on diet was not significant. The habitat × DWH timing interaction was driven by a decrease in zooplankton consumed at both habitat types, increased benthic prey at natural reefs, and increased fish consumption at artificial reefs in post-DWH oil spill samples. Stable isotope data indicated a postspill increase in Red Snapper trophic position (15N enrichment) and an increase in benthic versus pelagic prey (34S depletion), both consistent with observed dietary shifts. Overall, results indicate shifts in Red Snapper diet and trophic position occurred following the DWH oil spill, thus the relative abundance of prey resources likely changed.
The full article is available at the link below:
Tarnecki, J. H., & Patterson III, W. F. (2015). Changes in Red Snapper Diet and Trophic Ecology Following the Deepwater Horizon Oil Spill. Marine and Coastal Fisheries, 7(1), 135–147.
A recent publication from Wageningen University in the Netherlands performed a meta-analysis of large oil spills to determine if a MOSSFA brought oil to the sea floor in other oil spills.
During Deepwater Horizon, 9.1% of oil from the well head settled on the ocean floor and was in constant contact with sediments. This roughly 10% made it to the seafloor was through mucus-rich marine snow sinking to the seafloor and collecting oil droplets and clay materials during its descent. When this marine snow carries oil to the seafloor it is known as a MOSSFA event (Marine Oil Snow Sedimentation and Flocculent Accumulation).
This paper analyzed data from 52 other oil spills to see if a MOSSFA would have occurred in other spills using these conditions: dispersant application, clay materials in the water (originating from the seafloor), and presence of mucus-like substances from oil-degrading bacteria and phytoplankton.
Using the Deepwater Horizon and Ixtoc-I events as a baseline for MOSSFA conditions, the authors estimate a MOSSFA in 15 of 52 studied spills
The authors recommend MOSSFA be considered in the overall environmental efforts following a spill. Does oil on the seafloor contribute to similar habitat loss as oil on coastlines?
The full article is available at the link below:
Sophie M. Vonk, David J. Hollander, AlberTinka J. Murk, Was the extreme and wide-spread marine oil-snow sedimentation and flocculent accumulation (MOSSFA) event during the Deepwater Horizon blow-out unique?, Marine Pollution Bulletin, Available online 8 September 2015, ISSN 0025-326X, http://dx.doi.org/10.1016/j.marpolbul.2015.08.023.
The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000 – 1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead.
Ref: Romero, I.C., Schwing, P.T., Brooks, G.R., Larson, R.A., Hastings, D.W., Flower, B.P., Goddard, E.A., Hollander, D.J. Hydrocarbons in deep-sea sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico. PLoS ONE, 2015, 10(5): e0128371.
The objective of this study was to investigate the impacts of the Deepwater Horizon (DWH) oil discharge at the seafloor as recorded in bottom sediments of the DeSoto Canyon region in the northeastern Gulf of Mexico. Through a close coupling of sedimentological, geochemical, and biological approaches, multiple independent lines of evidence from 11 sites sampled in November/December 2010 revealed that the upper ~1 cm depth interval is distinct from underlying sediments and results indicate that particles originated at the sea surface. Consistent dissimilarities in grain size over the surficial ~1 cm of sediments correspond to excessTh depths, which indicates a lack of vertical mixing (bioturbation), suggesting the entire layer was deposited within a 4–5 month period. Further, a time series from four deep-sea sites sampled up to three additional times over the following two years revealed that excess Th depths, accumulation rates, and Th inventories decreased rapidly, within a few to several months after initial coring. The interpretation of a rapid sedimentation pulse is corroborated by stratification in solid phase Mn, which is linked to diagenesis and redox change, and the dramatic decrease in benthic formanifera density that was recorded in surficial sediments. Results are consistent with a brief depositional pulse that was also reported in previous studies of sediments, and marine snow formation in surface waters closer to the wellhead during the summer and fall of 2010. Although sediment input from the Mississippi River and advective transport may influence sedimentation on the seafloor in the DeSoto Canyon region, we conclude based on multidisciplinary evidence that the sedimentation pulse in late 2010 is the product of marine snow formation and is likely linked to the DWH discharge.
The Texas A&M Oilspill Calculator (TAMOC) is a new, freely available modeling suite for predicting fate and transport of oil and gas released from subsea accidents. The model is coded in Python and Fortran and is freely available from http://github.com/socolofs/tamoc. The model contains general modules for handling ambient water column data, hydrocarbon equations of state, and bubble and droplet dynamics, including particle rise velocity, shape, surface area, and heat and mass transfer rates. Three simulation models are included with the modeling suite. The Single Bubble Model (SBM) tracks the fate of a single bubble or droplet as it rises through the water column, advected by the three-dimensional ambient currents, and undergoing dissolution and heat transfer. For larger scale releases, two different integral plume models are provided. In weak currents, the Stratified Plume Model (SPM) predicts multiple subsurface intrusions; when currents are larger and the plume trajectory is deflected in the downstream direction, the suite applies the Bent Plume Model (BPM), which yields one intrusion layer and tracks separation between the released oil droplets and gas bubbles and the entrained seawater. All modeling components have been thoroughly validated to available laboratory and field data. This paper demonstrates some of the key validation metrics and applies the model to explore the dynamics of the Deepwater Horizon accident. The hot oil and gas released from the wellhead quickly cool to near ambient temperature (within 25 m above the release), and dissolution is generally faster than gas ebullition. Model predictions agree well with observations from 2010, including calculations for the depth of the intrusion layer and the flux of chemical components to the atmosphere.
Ref: Socolofsky, S. A., Dissanayake, A. L., Jun, I., Gros, J., Arey, J. S., and Reddy, C. M., Texas A&M Oilspill Calculator (TAMOC): Modeling Suite for Subsea Spills, Proceedings from Arctic Marine Oil Pollution Technical Seminar on Environmental Contamination and Response, June 2-4, 2015, British Columbia, Canada.
Following the 2010 Deepwater Horizon (DWH) blowout, we surveyed offshore demersal fishes in the northern Gulf of Mexico (GoM) in 2011-2013, to assess polycyclic aromatic hydrocarbon (PAH) exposure. Biliary PAH metabolites were estimated in 271 samples of golden tilefish (Lopholatilus chamaeleonticeps), king snake eel (Ophichthus rex) and red snapper (Lutjanus campechanus), using high performance liquid chromatography with fluorescence detection. Mean concentration of naphthalene (NPH) metabolites in golden tilefish (240µg g-1) was significantly higher (p=0.001) than in red snapper (61µg g-1) or king snake eel (38µg g-1). Biliary NPH metabolite concentration decreased over the study period in red snapper (58%) and king snake eel (37%), indicating likely episodic exposure, while concentrations were persistently high in golden tilefish. Naphthalene metabolite levels measured in golden tilefish are among the highest concentrations measured in fishes globally, while concentrations for red snapper and king snake eel are similar to pre-DWH levels measured in GoM species. In contrast, concentrations of benzo[a]pyrene metabolites were similar for all three species (p=0.265, mean 220ng g-1) and relatively low when compared to GoM, global data and previous oil spills. These data support previous findings that fish life history and physiology play significant roles in exposure and uptake of PAH pollution.
We report here the draft genome sequence of Rhodococcus qingshengii strain TUHH-12. The ability of this piezotolerant bacterium to grow on crude oil and tetracosane as sole carbon sources at 150 105 Pa makes it useful in studies of hydrocarbon degradation under simulated deep-sea conditions.
Ref: Lincoln, S.A., Hamilton, T.L., Valladares Juarez, A.G., Schedler, M., Macalady, J.L., Muller, R., Freeman, K.H. Draft Genome Sequence of the Piezotolerant and Crude Oil-Degrading Bacterium Rhodococcus qingshengii Strain TUHH-12. Genome Announcements, 3(2015), e00268-15.
On 20 April 2010, the Deepwater Horizon drilling rig lost well control while drilling at the Macondo prospect in the Gulf of Mexico. At the time of the Macondo blowout, the academic scientific community was ill prepared to initiate and rapidly conduct the necessary coordinated interdisciplinary studies of the environments around the discharge area.
Ref: Joye, S., J. Montoya, S. Murawski, T. Özgökmen, T. Wade, R. Montuoro, B Roberts, D. Hollander, W. H. Jeffrey, J. Chanton, and C. Wilson. Fast Action: A Collaborative, Multi-Disciplinary Rapid Response Study of the Hercules Gas Well Blowout, AGU EOS, 2014.
UDispersants are globally and routinely applied as an emergency response to oil spills in marine ecosystems with the goal of chemically enhancing the dissolution of oil into water, which is assumed to stimulate microbially mediated oil biodegradation. However, little is known about how dispersants affect the composition of microbial communities or their biodegradation activities. The published findings are controversial, probably owing to variations in laboratory methods, the selected model organisms and the chemistry of different dispersant–oil mixtures. Here, we argue that an in-depth assessment of the impacts of dispersants on microorganisms is needed to evaluate the planning and use of dispersants during future responses to oil spills.
Using data collected over the Gulf of Mexico during night between May 2012 and September 2013 by the Visible Infrared Imager Radiometer Suite (VIIRS), we demonstrate a new application from its day-and-night band (DNB). Under cloud free and moon glint conditions, the DNB revealed surface oil slicks from natural oil seeps. This is despite the fact that the signal-to-noise ratio (SNR) of this wide band (505–890 nm) under moon glint is much lower (30:1–50:1) and its resolution is also coarser (750 m) than the VIIRS imaging bands (375 m) under daytime solar illumination. The DNB was designed to map light sources at night. Similar to its predecessor, the Defense Meteorological Satellite Program Operational Linescan System (OLS), the VIIRS DNB should be suitable to identifying bioluminescence at night. However, with its finer resolution and higher SNR than OLS, the VIIRS DNB is demonstrated here to be also able to complement other sensors in the detection and mapping of oil spills.
Ref: Hu, C., Chen, S., Wang, M., Murch, B., Taylor, J. Detecting surface oil slicks using VIIRS nighttime imagery under moon glint: A case study in the Gulf of Mexico, Remote Sensing Letters, 2015, 6(4), 295-301.
A new study out of the University of South Florida and the University of Tennessee has provided evidence that oil from the Deepwater Horizon blowout reached beaches of the West Florida Shelf. Researchers analyzed polycyclic aromatic hydrocarbons (PAHs), a “highly ubiquitous and mutagenic class of components of crude oils”, to trace oil from the DWH spill. PAHs accumulate in sediments over time and biodegrade very slowly, which makes them useful for identifying oil. Researchers also tested for the presence of dioctyl sodium sulfosuccinate (DOSS), a significant component of the dispersant used in the DWH clean up.
Sand patties collected from a beach in Pinellas County, Florida contained PAHs that were similar to those found in Florida’s panhandle, Alabama, and Louisiana following the spill. They were not similar to samples from an earlier oil spill in Tampa Bay. Background levels of DOSS were present in the beach’s sand, but they were significantly higher in the sand patties themselves; this indicates that the chemical dispersant also reached West Florida beaches. The authors suggest further sampling in varied environments to understand sources of background DOSS.
The authors conclude that “the co-occurrence of DOSS in samples containing similar PAH fingerprints to samples known to be contaminated by the DWH provides two independent pieces of evidence that such PAH likely contaminated at least some of the beaches of the WFS.”
A recent study published in Deep-Sea Research II, conducted by researchers at Eckerd College, University of South Florida, and Franklin & Marshall College, characterizes the sedimentation geochemistry of cores from sites around the Deepwater Horizon Oil spill. The work done by this study is integral to understanding the progression of oil released by the spill, the effects this oil has on benthic ecosystems, and a mechanism for sedimentation of the oil and it’s byproducts.
Three sites in the NE Gulf of Mexico were sampled between August 2010 and August 2013. After pre-DHW baselines were determined, the three sites were studied over a three year period. Firstly, it was determined that an increase in sedimentation occurred following the event. A mechanism for this sedimentation has not been determined, but the authors of this study hypothesize that the “coagulation of phytoplankton with oil droplets, coagulation of suspended matter with the oil droplets, and production of mucosoid material from the degraders of the oil” produced marine snow that sunk rapidly to the bottom. It is also possible that the increase of outflow from the Mississippi River contributed to increased sedimentation as well.
Secondly, the geochemistry of the sediment was evaluated. Relative concentrations of Mn, Re, and Cd were used as a proxy to determine the redox state of sediments post-blowout. Observations suggest that concentrations of these elements differed from their baselines for two years after the event. During the third year they began to normalize towards pre-blowout levels. Increasing concentrations of Re resulted in increasingly reducing conditions within sediments. This also began to normalize after two years.
The alterations of redox conditions in the sediments of the NE Gulf of Mexico had an effect on the benthic ecosystems, specifically on densities of benthic foraminifera. Decreases in these densities were recorded in two sites in December 2010 and February 2011, where there was a significant increase in reducing conditions as shown by Mn depletion and Re enrichment.
To read the full article online, visit ScienceDirect
In 2010, the Deepwater Horizon accident released 4.6–6.0 × 1011 grams or 4.1 to 4.6 million barrels of fossil petroleum derived carbon (petrocarbon) as oil into the Gulf of Mexico. Natural abundance radiocarbon measurements on surface sediment organic matter in a 2.4 × 1010 m2 deep-water region surrounding the spill site indicate the deposition of a fossil-carbon containing layer that included 1.6 to 2.6 × 1010 grams of oil-derived carbon. This quantity represents between 0.5 to 9.1% of the released petrocarbon, with a best estimate of 3.0–4.9%. These values may be lower limit estimates of the fraction of the oil that was deposited on the seafloor because they focus on a limited mostly deep-water area of the Gulf, include a conservative estimate of thickness of the depositional layer, and use an average background or prespill radiocarbon value for sedimentary organic carbon that produces a conservative value. A similar approach using hopane tracer estimated that 4–31% of 2 million barrels of oil that stayed in the deep sea settled on the bottom. Converting that to a percentage of the total oil that entered into the environment (to which we normalized our estimate) converts this range to 1.8 to 14.4%. Although extrapolated over a larger area, our independent estimate produced similar values.
Ref: Chanton, J., Zhao, T., Rosenheim, B., Joye, S., Bosman, S., Brunner, C., Yeager, K., Diercks, A., Hollander, D. (2015) Using natural abundance radiocarbon to trace the flux of petrocarbon to the seafloor following the Deepwater Horizon Oil Spill. Environmental Science and Technology, 2015(49), 847-854.
A new study that explores various models of oil spill and dispersant projections has been published in Marine Pollution Bulletin. The study, conducted by Texas A&M and others, developed models that tested 14 cases of accidental oil well blowouts. The variables included depth, currents, gas-oil ratios, and subsea injection of chemical dispersants. The models each predicted initial bubble and droplet size distribution as well as nearfield and farfield tracking of oil and gas. The models agreed on certain predictions and disagreed on others. They agreed that droplet sizes are smaller with dispersant and that less oil reaches the surface with dispersant. The authors call for new models, new validation data, and new ways to interpret data to achieve more concrete results. These new models should take multiple subsurface intrusions into account and should study field data rather than just laboratory data.
To read the full article, visit ScienceDirect.
A recent study from the University of Delaware published in Aquatic Biology explored the effects of oil-spill related chemicals on the ctenophore Mnemiopsis leidyi. M. leidyi is an important species in the pelagic ecosystem, acting as both predator and prey for many other species. It has been suggested that they may serve as vectors of hydrocarbons in pelagic food webs. Polycyclic aromatic hydrocarbons (PAHs) accumulate in their tissues following oil exposure. PAHs then accumulate in the tissues of their predators, and so on.
M. leidyi reactions to oil, dispersed oil, and chemical dispersant were studied at different temperatures. These temperatures reflect ocean temperatures during different seasons, providing information about effects of spills occurring at different times of the year. The sublethal effects studied were respiration rate, bioluminescence, and glutathione-s-transferase (GST) activity. Respiration rate can serve as a proxy for metabolic rate. Bioluminescence is usually used as a predator deterrent. Increased GST activity indicates upregulation of cellular detoxification pathways.
Mortality of M. leidyi was found to be concentration dependent at both temperatures for all three chemicals. Higher mortality occurred at higher temperatures and concentrations. However, oil concentrations in the Gulf of Mexico following the Deepwater Horizon spill were well below lethal levels for M. leidyi at both temperatures. Similarly, concentrations of dispersant used in this study were higher than what would be found in the ocean during mitigation for an oil spill. The dispersant was more toxic than the crude oil, and apparently increased the toxicity of the oil when mixed. PAH concentrations in tissues were largest when exposed to chemical dispersant and smallest when exposed to oil with no dispersant.
There was no significant difference in respiration rate when exposed to any of the chemicals. This indicates that there was no increase in aerobic metabolic demand due to upregulation of detoxification pathways or locomotive attempts to avoid oil. However, the author suggests that this topic be studied in more depth to determine if changes in respiration rates occur over a shorter or longer time period than the one studied. The oil and dispersed oil had no significant effect on GST activity, but increased dispersant concentrations did result in high GST activity. The total amount of bioluminescent light emitted decreased as concentrations of all three chemicals increased. This was dependent on temperature, as bioluminescence is temperature dependent in normal conditions. The cause for these increases is unknown. It is also unknown how bioluminescence would be affected outside the lab, in natural predator-prey interactions.
For more information and to read the full article, visit the University of Delaware's Library webpage.
High-pressure visual experimental studies of oil-in-water dispersion droplet size
In a recent study published in Chemical Engineering Science from the University of Western Australia (UWA) and University of Miami (UM), C-IMAGE researchers have deployed unique experimental equipment to better understand how crude oil disperses in seawater at high pressures. This is a critical first step to ultimately predict the dispersion and transportation of liquid and gas hydrocarbons through the water column and to better inform both subsea and surface remediation efforts.
This work builds on an initial study by Paris et al. (2012), where estimates of crude oil droplet size are coupled in a hydrodynamic model to predict the effect of chemical dispersion, vertical currents, inertial buoyancy forces, and biodegradation on the vertical and lateral migration of oil droplets through the water column.
This 2015 study has deployed a high-pressure sapphire cell, where crude oil and water were mixed through a magnetically-coupled impeller with methane gas up to 120 times atmospheric pressure. The impeller stirring rates provide access to different turbulence regimes, in order to study the range of conditions that may have been accessed at the Macondo blowout site.
“This is the first time that we’ve been able to visually monitor how droplets break up and coalesce at these extreme subsea conditions,” said Zachary Aman, Associate Professor of Mechanical and Chemical Engineering at UWA and co-investigator in the C-IMAGE II consortium. “These results suggest there is a range of natural turbulence conditions in which crude oil may naturally disperse as small particles, on the order of 3-10 times the width of a human hair.”
“This is a landmark publication on the first measurements of oil droplet size at high pressure and its consequences on oil surfacing from a deep well blowout,” said Claire Paris, Associate Professor of Ocean Sciences at the UM Rosenstiel School. “These empirical results support the message from our initial modeling work, that the use of toxic dispersants at depth should not be a systematic oil spill response.”
These new measurements now suggest that deep water physics and the associated high pressure may create a natural dispersion mechanism that doesn’t require chemical assistance. The prominence of this dispersion mechanism increases with water depth, and may be a primary controlling factor for the deep water oil and gas operations in the Gulf of Mexico.
Shortly after the Deepwater Horizon oil spill, BP committed $500 million over a 10-year period to create a broad, independent research program to be conducted at research institutions primarily in the US Gulf Coast States. Accordingly, the Gulf of Mexico Research Initiative (GoMRI) Research Board has 20 members who are science, public health, and research administration experts. The ultimate goal of the GoMRI is to improve society’s ability to understand, respond to and mitigate the impacts of petroleum pollution and related stressors of the marine and coastal ecosystems, with an emphasis on conditions found in the Gulf of Mexico.
C-IMAGE (the Center for the Integrated Modeling and Analysis of the Gulf Ecosystem) is one of twelve GoMRI-funded consortia conducting research in the Gulf with scientists from 14 institutions and four countries that is dedicated to contributing to the goals of the GoMRI. C-IMAGE’s priority is to integrate field and laboratory studies with state of the art modeling to understand historical oil spills in the Gulf and to be better prepared to predict impacts of future spills.
This work has been featured in many other media outlets:
Online Monitoring of Crude Oil Biodegradation at Elevated Pressures
In order to study the biodegradation of crude oil spilled in the deep sea, incubations of deep-sea-bed sediments and crude oil were carried out in a high-pressure reactor, but monitoring the biodegradation of oil at high pressure is limited by sampling because the volatile crude oil components are partly lost during depressurization. Moreover, the seawater-oil-sediments multiphase system cannot be sampled representatively. The aerobic oil biodegradation can also be monitored indirectly by measuring the oxygen consumed and the carbon dioxide produced. In this paper, the O2 and CO2 concentrations were monitored in a reactor with transparent windows using chemical-optical sensors. To compare the effect of pressure on the biodegradation of oil, two pressure regimes were compared: atmospheric pressure (1 bar) and 150 bar, corresponding to 1500mdepth of the Deepwater Horizon’s well at the Gulf of Mexico. Only in the experiments where deep-sea sediments were added, the oxygen concentration decreased while the carbon dioxide and the bacterial concentration increased. In experiments where no sediment was added, the values for the oxygen and carbon dioxide remained constant. This proved that deep-sea sediments contained microorganisms, which could degrade crude oil at both 1 and 150 bar. To our knowledge, this is the first time where O2 and CO2 were monitored online during crude oil biodegradation at high pressure in the laboratory.
Ref: Valladares, A. G., Kadimesetty, S., Achatz, A., Schedler, M., Muller, R. Online Monitoring of Crude Oil Biodegradation at Elevated Pressures, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014, 99(PP), 1-7. (in press)
Note: This publication is not open access. Please contact the authors for more information.
Polycyclic aromatic hydrocarbon concentrations across the Florida Panhandle continental shelf and slope after the BP MC 252 well failure
The Florida Panhandle continental shelf environment was exposed to oil from the BP oil well failure in the Gulf of Mexico during 2010. Floating mats of oil were documented by satellite, but the distribution of dissolved components of the oil in this region was unknown. Shipek® grab samples of sediments were taken during repeated cruises between June 2010 and June 2012 to test for selected polycyclic aromatic hydrocarbons (PAHs) as indicators of this contamination. Sediments were collected as composite samples, extracted using standard techniques, and PAHs were quantified by GC/MS-SIM. PAHs in samples from the continental slope in May 2011 were highest near to the failed well site and were reduced in samples taken one year later. PAHs from continental shelf sediments during the spill (June 2010) ranged from 10 to 165 ng g−1. Subsequent cruises yielded variable and reduced amounts of PAHs across the shelf. The data suggest that PAHs were distributed widely across the shelf, and their subsequent loss to background levels suggests these compounds were of oil spill origin. PAH half-life estimates by regression were 70–122 days for slope and 201 days for shelf stations.
Ref: Snyder, R. A., Ederington-Hagy, M., Hileman, F., Moss, J., Amick, L., Carruth, R., Head, M., Marks, J., Jeffrey, W. H. Polycyclic aromatic hydrocarbon concentrations across the Florida panhandle continental shelf and slope after the BP MC 252 well failure, Marine Pollution Bulletin, 2014 (in press)
Effect of high pressure on hydrocarbon-degrading bacteria
The blowout of the Deepwater Horizon in the Gulf of Mexico in 2010 occurred at a depth of 1500 m, corresponding to a hydrostatic pressure of 15 MPa. Up to now, knowledge about the impact of high pressure on oil-degrading bacteria has been scarce. To investigate how the biodegradation of crude oil and its components is influenced by high pressures, like those in deep-sea environments, hydrocarbon degradation and growth of two model strains were studied in high-pressure reactors. The alkane-degrading strain Rhodococcus qingshengii TUHH-12 grew well on n-hexadecane at 15 MPa at a rate of 0.16 h−1, although slightly slower than at ambient pressure (0.36 h−1). In contrast, the growth of the aromatic hydrocarbon degrading strain Sphingobium yanoikuyae B1 was highly affected by elevated pressures. Pressures of up to 8.8 MPa had little effect on growth of this strain. However, above this pressure growth decreased and at 12 MPa or more no more growth was observed. Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa. This suggests that certain metabolic functions of this bacterium were inhibited by pressure to a greater extent than the enzymes responsible for naphthalene degradation. These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon event.
Habitat-specific density and diet of rapidly expanding invasive red lionfish, Pterois volitans, populations in the Northern Gulf of Mexico
Invasive lionfish were first reported in the Gulf of Mexico in the summer of 2010. Their density and size distributions were examined from the fall of 2010 to 2013 to examine their potential impacts on native fish communities. During the sampling period, lionfish populations increased exponentially. Lionfish density at artificial reef locations was two orders of magnitude higher than at natural reef sites. Their diet varied among habitats, seasons, and size classes. Results indicate that lionfish are mesopredators in the northern Gulf becoming more piscivorous at larger sizes. Their diet was more varied at the artificial reef sites where they were foraging on open substrates away from the reef structures. The study has implications for tracking lionfish invasions in the nGoM as well as estimating their impacts on native reef fish communities.
Ref: Dahl, K. A., Patterson, W. F. III. Habitat-specific density and diet of rapidly expanding invasive red lionfish, Pterois volitans, populations in the Northern Gulf of Mexico, PLoS One 9(8):e105852.
In search of oil seeps in the Cariaco basin using MODIS and MERIS medium resolution data
The Cariaco basin with its high sedimentation rates and active faulting make it a favorable place for active oil seeps to occur. Information on the number of seeps or their locations does not exist in the literature. Data collected from the MODIS and MERIS sensors were examined to see if they could detect oils seeps in the Cariaco basin. MODIS was able to detect 2 regions of surface slicks in 2011, however, identifying where they came from is more complicated. By identifying multiple slicks from the same region, Chen and Hu determiend that they can be traced to the same location. These sensors can be used to conservatively estimate the number of slicks as long as they are at least 3 pixels in length on the image.
Prevalence of External Skin lesions and Polycyclic Aromatic Hydrocarbon Concentrations in the Gulf of Mexico Fishes, Post-Deepwater Horizon
Abstract: We surveyed offshore fish populations in the Gulf of Mexico in 2011 and 2012, following persistent reports of abnormal skin lesions and other pathologies in the aftermath of the Deepwater Horizon oil spill. The incidence of skin lesions in 2011 sampling was most frequent in some bottom-dwelling species along the continental shelf edge north of the Deepwater Horizon site. Longline surveys revealed that by 2012 the overall frequency of lesions in northern Gulf of Mexico (NGM) fishes in the vicinity of the Deepwater Horizon had declined 53%, with severity also declining. Relatively high concentrations of polycyclic aromatic hydrocarbon (PAH) metabolites (up to 470,000 ng naphthalene equivalents/g bile wet weight), indicative of oil-related pollution, were found in fish bile in 2011; concentrations of summed PAHs measured in fish liver and muscle were relatively low (<35 ng/g) due to the efficient metabolism of these compounds in teleost fish. Signifcant declines in bile concentrations of naphthalene and phenanthrene metabolites in Red Snapper Lutjanus campechanus between 2011 and 2012 indicate an episodic exposure to elevated levels of hydrocarbons of petrogenic origin. The composition of PAH parent compounds and alkylated homologs in Red Snapper liver samples was highly correlated with oil collected at the Deepwater Horizon wellhead but was less coherent with other PAH sources in the NGM. The elevated 2011 prevalence of skin lesions in some NGM species was unrelated to surface salinity or temperature anomalies and was not the result of an epizootic observable in our histopathology samples but was positively correlated with PAH concentration. Thus, we fail to reject the null hypothesis that elevated skin lesion frequency is unrelated to PAH exposure from the Deepwater Horizon oil spill.
Ref: Murawski, S. A., W. T. Hogarth, E. B. Peebles, L. Barbeiri, Prevalence of External Skin Lesions and Polycyclic Aromatic Hydrocarbon Concentrations in Gulf of Mexico Fishes, Post-Deepwater Horizon, Transactions of the American Fisheries Society, 143:4, 1084-1097.
PAH concentrations in Coquina (Donax spp.) on a sandy beach shoreline impacted by a marine oil spill
Typically, mussels and oysters are used in the Gulf of Mexico as biological indicators of coastal pollution. These organisms populate low energy, estuarine regions. What kinds of organisms can scientists look at in higher energy regions, like sandy coastlines? C-IMAGE researcher, Richard Snyder, and his collaborators at the University of West Florida take a look at the PAH concentrations in Coquina clams who make their home in higher energy environments and found higher levels of PAHs in the clams than in the surrounding sand after the BP MC252 well failure. With continued sampling, they found a gradual decrease of PAH concentrations in Coquina tissues.
Ref: Snyder, R. A., Vestel, A., Barnes, G., Pelot, R., Ederington-Hagy, M., Hileman, PAH concentrations in Coquina (Donax spp.) on a sandy beach shoreline impacted by a marine oil spill, Marine Pollution Bulletin, 83, 87-91, 2014.
A probabalistic representation of fish diet compositions from multiple data sources: A Gulf of Mexico case study
Ecosystem models can be extremely useful tools for ocean resource managers to determine how commercial fisheries can respond to a specific management strategy. C-IMAGE researchers out of the University of South Florida with colleagues from the Florida Fish and Wildlife Conservation Commission looked at fish diet for two non-commercially relevant species in the Gulf of Mexico to produce Maximum Liklihood Estimates (MLEs). MLEs describe how much a specific prey item constitutes a predator's diet. These values are used to produce a food web diagram that is ultimately used to fine tune the Atlantis ecosystem model.
Simulating the effects of droplet size, high pressure biodegradation, and variable flow rate on the subsea evolution of deep plumes from the Macondo blowout
In a recent study by C-IMAGE researchers from the University of Miami and the Technical University of Hamburg at Harburg, the effect of droplet size, high-pressure biodegradation and variable flow rate on deep plume evolution is evaluated. Lindo-Atichati et al. use measurements from the Macondo blowout to evaluate how sensitive far field models are to these parameters. Consideration of high pressure biodegradation and variable flow rate into the model allow for a significant in oil residence time to the southwest of the blowout site which agree with field observations.
Ref: Lindo-Atichati, D., Paris, C. B., Le Henaff, M., Schedler, M., Valladares-Juarez, A. G., Muller, R. Simulating the effects of droplet size, high pressure biodegradation, and variable flow rate on the subsea evolution of deep plumes from the Macondo blowout, Deep Sea Research, Special Issue "The Gulf of Mexico Ecosystem: Before During, and After the Deep Water Horizon Oil Spill", in press