Monday 23 October 2017

The Center for the Integrated Modeling and Analysis of the Gulf Ecosystem

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.

Task 3 Publications

Task 3 Publications (20)

Unusually large amounts of marine snow, including Extracellular Polymeric Substances (EPS), were formed during the 2010 Deepwater Horizon oil spill. The marine snow settled with oil and clay minerals as an oily sludge layer on the deep sea floor. This study tested the hypothesis that the unprecedented amount of chemical dispersants applied during high phytoplankton densities in the Gulf of Mexico induced high EPS formation. Two marine phytoplankton species (Dunaliella tertiolecta and Phaeodactylum tricornutum) produced EPS within days when exposed to the dispersant Corexit 9500. Phytoplankton-associated bacteria were shown to be responsible for the formation. The EPS consisted of proteins and to lesser extent polysaccharides. This study reveals an unexpected consequence of the presence of phytoplankton. This emphasizes the need to test the action of dispersants under realistic field conditions, which may seriously alter the fate of oil in the environment via increased marine snow formation.

Ref: van Eenennaam, J. S., Wei, Y., Grolle, K. C. G., Foekema, E. M., Murk, A. J. (2016) Oil spill dispersants induce formation of marine snow by phytoplankton-associated bacteria. Marine Pollution Bulletin.

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. A., Marks, K. P., Romero, I. C., Hollander, D. J., Snell, T. W., & Kostka, J. E. (2015, In-Press). Hydrocarbon-Degrading Bacteria Exhibit a Species-Specific Response to Dispersed Oil while Moderating Ecotoxicity. Applied and Environmental Microbiology, 82(2).

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 excess 234Th 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 234Th depths, accumulation rates, and 234Th 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.

Ref: Chanton, J.; Zhao, T.; Rosenheim, B.; Joye, S.; Bosman, S.; Brunner, C.; Yeager, K.; Diercks, A.; Hollander, D., 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.

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.

Ref: Romero, I. C., et al. (2015), Tracking the Hercules 265 marine gas well blowout in the Gulf of Mexico, J. Geophys. Res. Oceans, 121, doi:10.1002/2015JC011037.

Benthic marine protists have been well documented from shallow marine benthic habitats but remain understudied in deeper habitats on continental shelves and slopes, particularly in the Northeastern Gulf of Mexico (NEGOM). This region was affected by a deep water oil well failure (BP-Deepwater Horizon, 2010). The combination of a lack of information on deep sea microbenthic communities and the potential for benthic microbial petroleum mineralization prompted this investigation. Water column and nepheloid layer samples were obtained via Niskin bottles and a multicorer respectively at stations across the NEGOM to: (1) determine whether nepheloid and water column communities are distinct and (2) assess benthic species richness relative to sediment PAH contamination. Phylum specific 18S rRNA gene amplification was used to construct clone libraries of ciliate assemblages. BLAST searches in the NCBI database indicated that a majority (~75%) of the clone sequences corresponded (94–100% similarity) with listed, yet unclassified sequences. Several putative species were common at most site locations and depths. Many known benthic ciliates, such as Uronychia transfuga, Uronychia setigera, and Spirotrachelostyla tani, were common in the nepheloid layer samples and not recovered in water column samples. Ciliated protist species richness increased with PAH levels found in surface sediments, suggesting a positive microbial response to petroleum enrichment of the benthos. The presence of previously unknown microbenthic communites in the nephaloid layer over oceanic clay–silt muds alters our view of microbial processes in the deep sea and merits investigation of the microbial processes and rates of microbial mineralization and biomass production important to global biogeochemistry.

Ref: Moss, J.A., C. McCurry, S. Tominack, I.C. Romero, D. Hollander, W.H. Jeffrey, and R.A. Snyder. 2015. Ciliate protists from the sediment-water interface in the Northeastern Gulf of Mexico. Deep Sea Research I 106: 85-96. doi:10.1016/j.dsr.2015.10.001.

Observations of currents, temperature, sea-surface height, sea-surface temperature and ocean color, derived from moorings, surface and deep drifters, hydrographic surveys, and satellites, are used to characterize shelf-slope exchange events near the apex of the De Soto Canyon in the northeast Gulf of Mexico. During the winter of 2012–2013, shelf-break time series showed a number of events where cold shelf water extruded over the slope. These events were largely consistent with slope eddies of both signs influencing shelf break currents. Larger-scale circulations, derived from the Loop Current and a separating Loop Current eddy, strongly influenced circulation over the De Soto slope during summer 2012, with flow patterns consistent with potential vorticity conservation over shoaling topography. Statistical investigation into shelf-slope exchange using large numbers of surface drifters indicated that export from the shelf is larger than vice-versa, and is more uniformly distributed along the shelf break. Import onto the shelf appears to favor a region just east of the Mississippi Delta, which is also consistent with the observed onshore transport of surface oil from the Deepwater Horizon disaster.

Ref: Hamilton, P., K. Speer, R. Snyder, and R.R. Leben.  2015. Shelf Break Events in the De Soto Canyon.  Continental Shelf Research. 110: 25-38., doi:10.1016/j.csr.2015.09.021

To determine effects of photochemical weathering of petroleum, surrogate and Macondo (MC252) crude oils were exposed to solar radiation during the formation of Water Accommodated Fractions (WAFs) in sterile seawater. Samples were incubated in either unfiltered sunlight, with ultraviolet radiation blocked (Photosynthetically Active Radiation [PAR] only), or in darkness. WAFs were collected at two time points over the course of a week. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) analyses of water soluble species formed during exposure to sunlight were compared for the different treatments. Photochemical alterations resulted in differences in compound class distributions. In general, surrogate oil was photo-oxidized across a wider carbon number range compared to MC252. While photochemical differences were observed between MC252 and surrogate oils, microbial production in seawater responded similarly to both WAFs from both types of oils with the majority of the inhibition resulting from oil exposure to visible light.

Ref: Vaughan, P.A., T. Wilson, R. Kamerman, M. Ederington-Hagy, A. McKenna, H. Chen, and W.H. Jeffrey. (2016) Photochemical Changes in Water Accommodated Fractions of MC252 and Surrogate Oil Created during Solar Exposure as determined by FT-ICRMS. Marine Pollution Bulletin, in press, doi:10.1016/j.marpolbul.2016.01.012.

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

 

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.

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.

Rapid screening of glycerol ether lipid biomarkers in recent marine sediment using APPI-P FTICR-MS. Jagoš R. Radović, Renzo C. Silva, Ryan Snowdon, Stephen R. Larter, and Thomas B.P. Oldenburg. Analytical Chemistry. 7 December 2015. DOI: 10.1021/acs.analchem.5b02571 

Abstract:

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.

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:

http://www.sciencedirect.com/science/article/pii/S0025326X15005275

Citation:

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 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 excess 234Th 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 excess234Th depths, accumulation rates, and 234Th 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.

Ref: Brooks GR, Larson RA, Schwing PT, Romero I, Moore C, Reichart G-J, et al. (2015) Sedimentation Pulse in the NE Gulf of Mexico following the 2010 DWH Blowout. PLoS ONE 10(7).

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.

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.

David Hastings removes a sediment core for processing and later analysis.

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

PAH concentrations across the FL Panhandle

  • Wednesday, 15 October 2014 16:32

Polycyclic aromatic hydrocarbon concentrations across the Florida Panhandle continental shelf and slope after the BP MC 252 well failure

Abstract

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)

Our research group at Wageningen University is working on studying the effects of dispersants on the fate of oil in realistic conditions.

The poster in the link below presents the preliminary results of a plunging jet method combined with a high speed camera to obtain quantitative data of the entrainment of oil under different circumstances. Our plunging jet measurement system consists of a holding tank containing 9 liters of seawater.

A specific amount of oil is placed within a confinement on the surface so the height is known. The plunge container is a 250 ml glass container and its height can be varied with a rig. A high speed camera that is fixed to the rig, perpendicular to the holding tank, records the underwater events after the plunge hits the oil slick. A backlight behind the tank enhances oil droplet contrast.

The volume and droplet sizes of oil in the water column are registered over time and quantified using image processing software. The resulting (projected) surface of each individual particle is converted to droplet size assuming the droplets are spherical. This poster presents the preliminary results of a plunging jet method combined with a high speed camera to obtain quantitative data of the entrainment of oil under different circumstances.

https://www.wageningenur.nl/en/show/Effects-of-dispersants-on-the-fate-of-oil-in-realistic-conditions.htm

Toxic waters reach NE GoM

  • Friday, 27 June 2014 06:34

C-IMAGE co-PI Dr. John Paul received some media attention earlier this month when his publication "Toxicity and Mutagenicity of Gulf of Mexico Waters During and After The Deepwater Horizon Oil Spill" came out in Environmental Science and Technology.  His study indicates that, based on the Microtox and QuikLite toxicity assays and the Microscreen mutagenicity assay, toxic water existed in the northeast Gulf Mexico in 2010 and 2011 that may have been caused by dispersed oil from the Macondo well blowout.  

 

MOSSFA in EOS, May 2014

  • Friday, 27 June 2014 02:34

A summary of the MOSSFA Town Hall Meeting from the GoMRI Conference appears in this week's EOS. The piece was written by Dr. Nancy Kinner, Laura Belden, and Peter Kinner.  Read the full article here.