%0 Journal Article
%J Frontiers in Marine Science
%D 2020
%T Hydrodynamics of a Rising Oil Droplet With Bacterial Extracellular Polymeric Substance (EPS) Streamers Using a Microfluidic Microcosm
%A White, Andrew R.
%A Jalali, Maryam
%A Sheng, Jian
%X During the Deepwater Horizon oil spill, the unprecedented injection of millions of liters of chemical dispersant at the wellhead generated large quantities of submillimeter oil droplets that became entrained in a deep sea plume. The unexpected generation of these droplets has resulted in many studies in the last decade aiming to understand their transport and fate during and after the spill. Complicating matters, the plume coincided with a microbial bloom, and in addition to ocean dynamics these droplets were subjected to biological processes such as biodegradation and microbial aggregation. A lack of field observations and laboratory experiments using relevant conditions has left our understanding of these biotic processes and the role they played in the fate of the oil droplets poorly constrained. Furthermore, while biodegradation has been incorporated into drop transport models using available data, the effects of microbial aggregation involving extracellular polymeric substances (EPS) on their transport has seldom been incorporated into modeling efforts particularly due to our lack knowledge of these processes. We use a microfluidic platform to observe bacterial suspensions interacting with a single ~200 μm oil drop in conditions relevant to the drop rising through the microbial bloom. We observe the development of individual, invisible bacterial EPS threads extending from the drop surface which can capture additional passing bacteria and form bacteria-EPS aggregates. Using high speed imaging, we make high resolution flow measurements both with and without EPS threads present and analyze the momentum balance to elucidate the hydrodynamic impact of these filaments. Surprisingly, these thin individual EPS filaments alter significantly the pressure field around the drop and increase the drag, which would drastically reduce the drop's rising velocity in the water column. We demonstrate that this mechanism which plausibly occurred in the deep sea plume would have major impacts on both the drop and bacteria transport during and after the Deepwater Horizon oil spill.
%B Frontiers in Marine Science
%V 7
%G eng
%U https://doi.org/10.3389/fmars.2020.00294
%N 294
%0 Journal Article
%J Harmful Algae
%D 2020
%T Potential effects of bacterial communities on the formation of blooms of the harmful dinoflagellate Prorocentrum after the 2014 Texas City “Y” oil spill (USA)
%A Bum Soo Park
%A Erdner, Deana L.
%A Bocasa, Hernando P.
%A Liu, Zhanfei
%A Edward J. Buskey
%X The association between phytoplankton blooms and oil spills is still controversial despite numerous studies. Surprisingly, to date, there have been no studies on the effect of bacterial communities (BCs) exposed to crude oil on phytoplankton growth, even though crude oil changes BCs, which can then affect phytoplankton growth and species composition. Co-culture with crude oil-exposed BCs significantly stimulated the growth of Prorocentrum texanum in the laboratory. To gain more direct evidence, oil-degrading bacteria from oil-contaminated sediment collected after the Texas City “Y” oil spill were isolated, and changes in dinoflagellate growth when co-cultured with single bacterial isolates was investigated. The oil-degrading bacterial isolates significantly stimulated the growth of dinoflagellates (axenic and xenic cultures) through releasing growth-promoting substances. This study provides new evidence for the potential role of oil-degrading bacteria in the formation of phytoplankton blooms after an oil spill.
%B Harmful Algae
%V 95
%G eng
%N 101802
%0 Journal Article
%J Langmuir
%D 2020
%T Motile Bacteria at Oil−Water Interfaces: Pseudomonas aeruginosa
%A Deng, Jiayi
%A Mehdi, Molaei
%A Chisholm, Nicholas G.
%A Stebe, Kathleen J.
%X Bacteria are important examples of active or self-propelled colloids. Because of their directed motion, they accumulate near interfaces. There, they can become trapped and swim adjacent to the interface via hydrodynamic interactions, or they can adsorb directly and swim in an adhered state with complex trajectories that differ from those in bulk in both form and spatiotemporal implications. We have adopted the monotrichous bacterium Pseudomonas aeruginosa PA01 as a model species and have studied its motion at oil–aqueous interfaces. We have identified conditions in which bacteria swim persistently without restructuring the interface, allowing detailed and prolonged study of their motion. In addition to characterizing the ensemble behavior of the bacteria, we have observed a gallery of distinct trajectories of individual swimmers on and near fluid interfaces. We attribute these diverse swimming behaviors to differing trapped states for the bacteria in the fluid interface. These trajectory types include Brownian diffusive paths for passive adsorbed bacteria, curvilinear trajectories including curly paths with radii of curvature larger than the cell body length, and rapid pirouette motions with radii of curvature comparable to the cell body length. Finally, we see interfacial visitors that come and go from the interfacial plane. We characterize these individual swimmer motions. This work may impact nutrient cycles for bacteria on or near interfaces in nature. This work will also have implications in microrobotics, as active colloids in general and bacteria in particular are used to carry cargo in this burgeoning field. Finally, these results have implications in engineering of active surfaces that exploit interfacially trapped self-propelled colloids.
%B Langmuir
%V 36
%P 6888-6902
%G eng
%U https://pubs.acs.org/doi/10.1021/acs.langmuir.9b03578
%N 25
%0 Journal Article
%J Chemosphere
%D 2020
%T Impact of dispersant on crude oil content of airborne fine particulatematter emitted from seawater after an oil spill
%A Afshar-Mohajer, Nima
%A Lam, Andres
%A Dora, Lakshmana
%A Katz, Joseph
%A Rule, Ana M.
%A Koehler, Kirsten
%X Inhalation of PM2.5, particles with an aerodynamic diameter <2.5 mm, from sea spray after crude oil spills could present serious health concerns. The addition of dispersants to effectively spread the crude oil throughout the water column has been practiced in recent years. Here, we investigated the possibility of an increase in the toxic content of fine PM after adding dispersant. A laboratory setup consisted of a vertical tank filled with seawater, 31.5 L airspace for aerosol sampling, and a bubble generating nozzle that aerosolized the oily droplets. Four different cases were studied: no slick, 0.5-mm-thick slick of pure crude oil (MC252 surrogate), dispersant (Corexit 9500A) mixed with crude oil at dispersant to oil ratio (DOR) 1:25, and DOR 1:100. The resulting airborne droplets were sampled for gravimetric and chemical analyses through development of a gas chromatography and mass spectrometry technique. Also, PM2.5 particles were size-fractioned into 13 size bins covering <60 nm to 12.1 mm using a low-pressure cascade impactor.
The highest PM2.5 concentration (20.83 ± 5.21 mg/m3) was released from a slick of DOR 1:25, 8.83x greater than the case with pure crude oil. The average ratio of crude oil content from the slick of DOR 1:25 to the case with pure crude oil was 2.37 (1.83 vs 0.77 mg/m3) that decreased to 1.17 (0.90 vs 0.77 mg/m3) at DOR 1:100. For particles <220 nm, the resultant crude oil concentrations were 0.64 and 0.29 mg/m3 at DOR 1:25 and 1:100, both higher than 0.11 mg/m3 from the slick of pure crude oil.
%B Chemosphere
%V 256
%G eng
%U https://doi.org/10.1016/j.chemosphere.2020.127063
%N 127063
%0 Journal Article
%J Journal of Hydraulic Engineering
%D 2020
%T Computational Study of the Source-Area Effect for Bubble Plumes in Stratified Environments
%A Guangzhao Zhou
%X In this work, a large-eddy simulation of bubble plumes in linearly stratified environments is presented. The gas bubbles are treated as Lagrangian particles. The intrusion and peeling are clearly manifested in the computed flow fields. The results of about 50 simulations with different parameters reveal the importance of bubble source area for plumes on the laboratory scale. A new type of bubble plume with rapid and distinct peelings is observed which is favored by large source areas. With a proper normalization, the present data points collapse onto a single straight line after applying a virtual-source correction which reflects the source-area effect. These results provide a plausible explanation for the scatter of the previous experimental and computational data in literature. A simple relation between the trap height and the peel height is observed and its mechanism is discussed
%B Journal of Hydraulic Engineering
%V 146
%G eng
%U https://doi.org/10.1061/(ASCE)HY.1943-7900.0001759
%N 6
%0 Journal Article
%J Chemical Engineering Journal
%D 2020
%T Persistent thin water films encapsulate oil droplets crossing an oil-water interface
%A Omri Ram
%A Katz, Joseph
%X Understanding of oil-water interfacial phenomena is essential for predicting mixing and/or phase-separation in environmental and industrial systems. Time-resolved digital holography and planar laser-induced fluorescence are used for examining processes occurring after ascending buoyant oil droplets of varying viscosity cross a stratified oil-water interface. Previous studies have focused on the crossing process, and the current belief is that once this droplet becomes immersed in the oil, its content can mix with the bulk fluid. In contrast, we show that the droplets remain encapsulated by a stable continuous submicron thin water film, which prevent them from mixing. This film forms even in pure oil and water with minimal surfactant concentration and persists for periods that are three to four orders of magnitude longer than those of the crossing process. Observations following the film evolution reveal that segments located close to the interface appear to be attracted to the bulk water, causing the entire droplet to flatten slowly. The resulting reduction in the peripheral radius of curvature
eventually breaks up the film into suspended submicron droplets. The morphology of this flattening process varies with oil viscosity, and its duration increases from seconds to nearly one hour as the oil viscosity increases from one to fifty cSt. In processes involving multiple oil droplets crossing the interface, they form a separate persistent long-lasting layer containing a complex thin-film structure that does not mix with the bulk oil. In contrast, thin oil films do not form around a descending water droplet after it crosses the interface.
%B Chemical Engineering Journal
%V 387
%G eng
%U https://doi.org/10.1016/j.cej.2020.124075
%N 124075
%0 Journal Article
%J Marine and Freshwater Research
%D 2020
%T The potential impact of bacterial communities exposed to crude oil and light on the growth of the harmful algal blooming species Karenia brevis (Dinophyceae)
%A Bum Soo Park
%A Edward J. Buskey
%X Phytoplankton blooms have been occasionally observed to occur after oil spills, and changes in bacterial communities (BC) associated with phytoplankton are known to affect phytoplankton growth. In the present study, to examine the effects of BC exposed to crude oil on phytoplankton blooms, established free-living (FL) BC in Karenia brevis (Dinophyceae) culture were collected and then exposed to crude oil under light or dark conditions. These exposed FLBC were then added to K. brevis culture to investigate the effects on growth rate of this dinoflagellate. Enhanced growth of K. brevis was observed following addition of FL (24.7%) BC exposed to crude oil and light. Whereas BC grown with crude oil in the dark did not enhance growth, and BC without treatment showed a slight growth inhibition (13–15%) of K. brevis. In addition, the growth-promoting effect had a positive correlation with the inoculated bacterial density; the treatment with a higher (,1.5 times) density of FL (42.9%) BC that were exposed to crude oil and light showed an increase in the growth-promoting effect. Taken together, BC exposed to crude oil and light may play an important role in enhancement of K. brevis growth.
%B Marine and Freshwater Research
%G eng
%U https://doi.org/10.1071/MF19358
%0 Journal Article
%J Scientific Reports
%D 2020
%T Bacteria forming drag-increasing streamers on a drop implicates complementary fates of rising deep-sea oil droplets
%A White, A
%A Jalali, M
%A Boufadel, M
%A Sheng, J.
%X Competing time scales involved in rapid rising micro-droplets in comparison to substantially slower biodegradation processes at oil-water interfaces highlights a perplexing question: how do biotic processes occur and alter the fates of oil micro-droplets (<500 μm) in the 400 m thick Deepwater Horizon deep-sea plume? For instance, a 200 μm droplet traverses the plume in ~48 h, while known biodegradation processes require weeks to complete. Using a microfluidic platform allowing microcosm observations of a droplet passing through a bacterial suspension at ecologically relevant length and time scales, we discover that within minutes bacteria attach onto an oil droplet and extrude polymeric streamers that rapidly bundle into an elongated aggregate, drastically increasing drag that consequently slows droplet rising velocity. Results provide a key mechanism bridging competing scales and establish a potential pathway to biodegradation and sedimentations as well as substantially alter physical transport of droplets during a deep-sea oil spill with dispersant.
%B Scientific Reports
%V 10
%G eng
%U https://doi.org/10.1038/s41598-020-61214-9
%N 4305
%0 Journal Article
%J Micromachines
%D 2019
%T Robust Fabrication of Polymeric Nanowire withAnodic Aluminum Oxide Templates
%A Larry Brock
%A Sheng, Jian
%X Functionalization of a surface with biomimetic nano-/micro-scale roughness (wires) has attracted significant interests in surface science and engineering as well as has inspired many real-world applications including anti-fouling and superhydrophobic surfaces. Although methods relying on lithography include soft-lithography greatly increase our abilities in structuring hard surfaces with engineered nano-/micro-topologies mimicking real-world counterparts, such as lotus leaves, rose petals, and gecko toe pads, scalable tools enabling us to pattern polymeric substrates with the same structures are largely absent in literature. Here we present a robust and simple technique combining anodic aluminum oxide (AAO) templating and vacuum-assisted molding to fabricate nanowires over polymeric substrates. We have demonstrated the ecacy and robustness of the technique by successfully fabricating nanowires with large aspect ratios (>25) using several common soft materials including both cross-linking polymers and thermal plastics. Furthermore, a model is also developed to determine the length and molding time based on nanowires material properties (e.g., viscosity and interfacial tension) and operational parameters (e.g., pressure, vacuum, and AAO template dimension). Applying the technique, we have further demonstrated the confinement e ects on polymeric crosslinking processes and shown substantial lengthening of the curing time.
%B Micromachines
%V 11
%G eng
%U https://www.mdpi.com/2072-666X/11/1/46
%N 46
%0 Journal Article
%J Physical Review Fluids
%D 2019
%T Multiphase buoyant plumes with soluble drops or bubbles
%A Chu, Shigan
%A Prosperetti, Andrea
%X
This paper presents the results of a scaling study of bubble and drop plumes in a stratified ambient. Use is made of a standard integral model of the top-hat type, which can be reduced to one of the Gaussian type by a simple transformation. The focus of the work is on the effects of the dissolving material on the plume dynamics. It is pointed out that, for a drop plume, the loss of buoyancy due to dissolution can be compensated by a lightening of the ambient liquid associated with the dissolved drop material, or even aggravated if the density of the solution is greater than that of the undissolved drops. For bubbles, these effects are compounded by the volume expansion due to the falling hydrostatic pressure. This process is not important in deep water, where the peel height is smaller than the water depth, but can be significant in shallow water, where the two may be comparable. With a focus on the analysis of a point-source, three important parameters are identified. The first one compares the drop/bubble dissolution rate with the rise time to the neutral height (the level at which the plume density equals the ambient density), the second one accounts for the effect of the dissolved material on the liquid density, and the third one is the drop/bubble rise velocity compared with the characteristic plume velocity.
%B Physical Review Fluids %V 4 %G eng %N 084306 %0 Journal Article %J Scientific Reports %D 2019 %T A Device for measuring the in-situ response of Human Bronchial Epithelial Cells to airborneenvironmental agents %A Lakshmana D. Chandrala %A Afshar-Mohajer, Nima %A Kristine Nishida %A Yury Ronzhes %A Venkataramana K. Sidhaye %A Koehler, Kirsten %A Katz, Joseph %X
Measuring the time evolution of response of Normal Human Bronchial Epithelial (NHBE) cells to aerosols is essential for understanding the pathogenesis of airway disease. This study introduces a novel Real-Time Examination of Cell Exposure (RTECE) system, which enables direct in situ assessment of functional responses of the cell culture during and following exposure to environmental agents. Included are cell morphology, migration, and specialized responses, such as ciliary beat frequency (CBF). Utilizing annular nozzles for aerosol injection and installing windows above and below the culture, the cells can be illuminated and examined during exposure. The performance of RTECE is compared to that of the commercial Vitrocell by exposing NHBE cells to cigarette smoke. Both systems show the same mass deposition and similar trends in smoke-induced changes to monolayer permeability, CBF and transepithelial resistance. In situ measurements performed during and after two exposures to smoke show that the CBF decreases gradually during both exposures, recovering after the first, but decreasing sharply after the second. Using Particle image velocimetry, the cell motions are monitored for twelve hours. Exposure to smoke increases the spatially-averaged cell velocity by an order of magnitude. The relative motion between cells peaks shortly after each exposure, but remains elevated and even increases further several hours later.
Airborne toxic compounds emitted from polluted seawater polluted after an oil spill raise health concerns when inhaled by humans or other species. Inhalation of these toxic compounds as volatile organic compounds (VOCs) or airborne fine particulate matter (PM) may cause serious pulmonary diseases, including lung cancer. Spraying chemical dispersants to enhance distribution of the crude oil into the water was employed extensively during the Deepwater Horizon spill. There is some evidence that dispersion of the crude oil decreased the emission rate of the VOCs but increased the emission rates of fine PM that may carry toxic compounds. In this study, the cancer risks and non-cancer hazards of the detected VOCs and particulates for spill-response workers were estimated with and without use of dispersant under action of breaking waves. A subchronic exposure scenario was modeled to address the inhalation health threat during initial phases of an oil spill response. A dosimetry model was used to estimate regional deposition of PM. Use of dispersant reduced benzene cancer risks from 57 to 37 excess life- time cancer cases per million for 1 h of daily exposure that continues for 3 months. Adding dispersant resulted in emissions reductions of the lighter VOCs (up to 30% lower). However, hazard quotients (HQs) of the non- carcinogenic VOCs even after dispersant addition were above 1 meaning there are serious concerns about expo- sure to these VOCs. Inhalation of airborne particles emitted from the slick containing dispersant increased the total mass of deposited particles in upper respiratory regions compared to the slick of crude oil only. This study showed the application of dispersant onto the pollution slick increased the total mass burden to the human respiratory system about 10 times, an exploratory HQ analysis is presented to evaluate the potential health risk.
%B Science of the Total Environment %V 654 %P 924-932 %G eng %U https://doi.org/10.1016/j.scitotenv.2018.11.110 %0 Journal Article %J Coastal Engineering %D 2018 %T Chaos in breaking waves %A Wei, Z %A Li, C. %A Dalrymple, RA %A Derakhti, M %A Katz, J. %X This study investigates the chaotic behavior of breaking waves by laboratory experiments and numerical modeling. Repeated laboratory runs with different initial velocity perturbations show that the wave profile before the wave breaks can be accurately reproduced, but the subsequent breaking process varies among runs, indicating the lack of repeatability of breaking waves in reality. Numerical simulations based on the Smoothed Particle Hydrodynamics method are further carried out to examine the repeatability of wave breaking process.
Underwater blowouts from gas and oil operations often involve the simultaneous release of oil and gas. Presence of gas bubbles in jets/plumes could greatly influence oil droplet formation. With the aim of understanding and quantifying the droplet formation from Deepwater Horizon blowout (DWH) we developed a new formulation for gas-oil interaction with jets/plumes. We used the jet-droplet formation model VDROP-J with the new module and the updated model was validated against laboratory and field experimental data. Application to DWH revealed that, in the absence of dispersant, gas input resulted in a reduction of d /react-text 50 react-text: 182 by up to 1.5 /react-text react-text: 183 /react-text react-text: 184 mm, and maximum impact occurred at intermediate gas fractions (30–50%). In the presence of dispersant, reduction in d /react-text 50 react-text: 260 due to bubbles was small because of the promoted small sizes of both bubbles and droplets by /react-text surfactants react-text: 262 . The new development could largely enhance the prediction and response to oil and gas blowouts.
%B Marine Pollution Bulletin %V 120 %P 203-216 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X1730396X %N 1-2 %0 Journal Article %J AIChE Journal %D 2017 %T Oil Jet with Dispersant: Macro-Scale Hydrodynamics and Tip Streaming %A Zhao, Lin %A Gao, Feng %A Boufadel C., M %X Modeling the movement of oil released underwater is a challenging task due to limitations in measuring the hydrodynamics in an oil-water system. In this work, we conducted an experiment of horizontal release of oil without and with dispersant. The model VDROP-J was used and compared to the model JETLAG, a miscible plume trajectory model. Both models were found to reproduce the oil jet hydrodynamics for oil without and with dispersant. The predicted DSD from VDROP-J matched closely observation for untreated oil. For oil with dispersant, experimental results have shown evidence that tip streaming occurred. For this purpose, a new conceptual module was developed in VDROP-J to capture the tip streaming phenomenon and an excellent match was achieved with observation. This study is the first to report tip streaming occurring in underwater oil jets, which should have consequences on predicting the DSD when dispersant are used on an underwater oil release. © 2017 American Institute of Chemical Engineers AIChE J, 2017 %B AIChE Journal %G eng %U http://onlinelibrary.wiley.com/doi/10.1002/aic.15864/full %0 Journal Article %J Scientific Reports %D 2017 %T Candida albicans stimulates Streptococcus mutans microcolony development via cross-kingdom biofilm-derived metabolites %A Kim, Dongyeop %A Sengupta, Arjun %A Niepa, Tagbo H.R. %XCandida albicans is frequently detected with heavy infection of Streptococcus mutans in plaque-biofilms from children affected with early-childhood caries, a prevalent and costly oral disease. The presence of C. albicans enhances S. mutans growth within biofilms, yet the chemical interactions associated with bacterial accumulation remain unclear. Thus, this study was conducted to investigate how microbial products from this cross-kingdom association modulate S. mutans build-up in biofilms. Our data revealed that bacterial-fungal derived conditioned medium (BF-CM) significantly increased the growth of S. mutans and altered biofilm 3D-architecture in a dose-dependent manner, resulting in enlarged and densely packed bacterial cell-clusters (microcolonies). Intriguingly, BF-CM induced S. mutans gtfBC expression (responsible for Gtf exoenzymes production), enhancing Gtf activity essential for microcolony development. Using a recently developed nanoculture system, the data demonstrated simultaneous microcolony growth and gtfB activation in situ by BF-CM. Further metabolites/chromatographic analyses of BF-CM revealed elevated amounts of formate and the presence of Candida-derived farnesol, which is commonly known to exhibit antibacterial activity. Unexpectedly, at the levels detected (25–50 μM), farnesol enhanced S. mutans-biofilm cell growth, microcolony development, and Gtf activity akin to BF-CM bioactivity. Altogether, the data provide new insights on how extracellular microbial products from cross-kingdom interactions stimulate the accumulation of a bacterial pathogen within biofilms.
%B Scientific Reports %V 7 %8 30 Jan, 2017 %G eng %U https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5278416/ %N 41332 %0 Journal Article %J Marine Pollution Bulletin %D 2017 %T Petroleum hydrocarbon persistence following the Deepwater Horizon oilspill as a function of shoreline energy %A Evans, Meredith %A Liu, Jiqing %A Bacosa, Hernando %A Rosenheim, Brad E. %A Liu, Zhanfei %XAn important aspect of oil spill science is understanding how the compounds within spilled oil, especially toxic components, change with weathering. In this study we follow the evolution of petroleum hydrocarbons, including n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs, on a Louisiana beach and salt marsh for three years following the Deepwater Horizon spill. Relative to source oil, we report overall depletion of low molecular weight n-alkanes and PAHs in all locations with time. The magnitude of depletion, however, depends on the sampling location, whereby sites with highest wave energy have highest compound depletion. Oiled sediment from an enclosed bay shows high enrichment of high molecular weight PAHs relative to 17α(H),21β(H)-hopane, suggesting the contribution from sources other than the Deepwater Horizon spill, such as fossil fuel burning. This insight into hydrocarbon persistence as a function of hydrography and hydrocarbon source can inform policy and response for future spills.
%B Marine Pollution Bulletin %V 115 %P 47-56 %8 Feb 15 2017 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X16309183 %N 1 %0 Journal Article %J Marine Pollution Bulletin %D 2017 %T The use of wide-band transmittance imaging to size and classify suspended particulate matter in seawater %A Davies, E. J. %A Brandvik, P.J. %A Leirvik, F %A Nepstad, R. %XAn in situ particle imaging system for measurement of high concentrations of suspended particles ranging from 30 lm to several mm in diameter, is presented. The system obtains quasi-silhouettes of particles suspended within an open-path sample volume of up to 5 cm in length. Benchmarking against spherical standards and the LISST-100 show good agreement, providing confidence in measurements from the system when extending beyond the size, concentration and particle classification capabilities of the LISST-100. Particle-specific transmittance is used to classify particle type, independent of size and shape. This is applied to mixtures of oil droplets, gas bubbles and oil-coated gas bubbles, to provide independent measures of oil and gas size distributions, concentrations, and oil-gas ratios during simulated subsea releases. The system is also applied to in situ measurements of high concentrations of large mineral flocs surrounding a submarine mine tailings placement within a Norwegian Fjord.
%B Marine Pollution Bulletin %G eng %U http://ac.els-cdn.com/S0025326X16309833/1-s2.0-S0025326X16309833-main.pdf?_tid=becae57c-c2eb-11e6-90a8-00000aacb362&acdnat=1481823025_4586c743a649bca1f075772708f17737 %0 Journal Article %J Marine Pollution Bulletin %D 2016 %T An in-depth survey of the oil spill literature since 1968: Long term trends and changes since Deepwater Horizon %A Murphy, David %A Gemmell, Brad %A Vacarri, Liana %A Li, Cheng %A Bacosa, Hernando %A Evans, Meredith %A Gemmell, Colbi %A Harvey, Tracy %A Jalali, Maryam %A Niepa, Tagbo H.R. %XIn order to characterize the state of oil spill research and describe how the field has changed since its inception in the 1960s and since the Deepwater Horizon spill in 2010, we examined approximately 10% of oil spill literature (1255 of over 11,000 publications) published from 1968 to 2015. We find that, despite its episodic nature, oil spill research is a rapidly expanding field with a growth rate faster than that of science as a whole. There is a massive post-Deepwater Horizon shift of research attention to the Gulf of Mexico, from 2% of studies in 2004–2008 to 61% in 2014–2015, thus ranking Deepwater Horizon as the most studied oil spill. There is, however, a longstanding gap in research in that only 1% of studies deal with the effects of oil spills on human health. These results provide a better understanding of the current trends and gaps within the field.
%B Marine Pollution Bulletin %V 113 %P 371-379 %8 15 Dec 2016 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X1630844X %N 1-2 %0 Journal Article %J Letters in Applied Microbiology %D 2016 %T Dynamics of Heterocapsa sp. and the associated attached and free-living bacteria under the influence of dispersed and undispersed crude oil %A Severin, T. %A Bacosa, HP %A Sato, A. %A Erdner, DL %XWhile many studies have examined the impact of oil on phytoplankton or bacteria, very few considered the effects on the biological complex formed by phytoplankton and their associated phytoplankton-attached (PA) and free-living (FL) bacteria. However, associated bacteria can affect the physiology of phytoplankton and influence their stress responses. In this study, we monitored the growth of Heterocapsa sp., an armoured dinoflagellate, exposed to crude oil, Corexit dispersant, or both. Growth of Heterocapsa sp. is unaffected by crude oil up to 25 ppm, a concentration similar to the lower range measured on Florida beaches after the Deepwater Horizon oil spill. The PA bacteria community was resistant to exposure, whereas the FL community shifted towards oil degraders; both responses could contribute to Heterocapsa sp. oil resistance. The growth rate of Heterocapsa sp. decreased significantly only when exposed to dispersed oil at 25 ppm, indicating a synergistic effect of dispersant on oil toxicity in this organism. For the first time, we demonstrated the decoupling of the responses of the PA and FL bacteria communities after exposure to an environmental stress, in this case oil and dispersant. Our findings suggest new directions to explore in the understanding of interactions between unicellular eukaryotes and prokaryotes.
In the environment, oil spills have the capacity to modify phytoplankton communities, with important consequences on the food web and the carbon cycle. We are just beginning to understand the oil resistance of phytoplankton species, making it difficult to predict community response. In this study we highlighted the strong resistance of Heterocapsa sp. to oil, which could be associated with its resilient attached bacteria and oil degradation by the free-living bacteria. This finding suggests new directions to explore in the understanding of oil impacts and interactions between eukaryotic and prokaryotic microbes.
%B Letters in Applied Microbiology %V 63 %P 419-425 %8 Aug 2016 %G eng %U http://onlinelibrary.wiley.com/doi/10.1111/lam.12661/full %N 6 %0 Journal Article %J Physical Review Fluids %D 2016 %T History effects on the gas exchange between a bubble and a liquid %A Chu, Shigan %A Prosperetti, Andrea %XDiffusive processes exhibit a strong dependence on history effects. For a gas bubble at rest in a liquid, such effects arise when the concentration of dissolved gas at the bubble surface, dictated by Henry's law, depends on time. In this paper we consider several such situations. An oscillating ambient pressure field causes the occurrence of rectified diffusion of gas into or out of the bubble. Unlike previous investigators, who considered the opposite limit, we study this process for conditions when the diffusion length is larger than the bubble radius. It is found that history effects are important in determining the threshold conditions. Under a static ambient pressure, the time dependence of the gas concentration can arise due to the action of surface tension, which increases the gas pressure as the bubble dissolves or, when the bubble contains a mixture of two or more gases, due to the different rates at which they dissolve. In these latter cases history effects prove mostly negligible for bubbles larger than a few hundred nanometers.
%B Physical Review Fluids %V 1 %G eng %U https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.1.064202 %N 6 %0 Journal Article %J Scientific Reports %D 2016 %T Succeed Escape: Flow shear promotes tumbling of Escherichia colinear a solid surface %A Molaei,Mehdi %A Sheng, Jian %XUnderstanding how bacteria move close to a surface under various stimuli is crucial for a broad range of microbial processes including biofilm formation, bacterial transport and migration. While prior studies focus on interactions between single stimulus and bacterial suspension, we emphasize on compounding effects of flow shear and solid surfaces on bacterial motility, especially reorientation and tumble. We have applied microfluidics and digital holographic microscopy to capture a large number (>105) of 3D Escherichia colitrajectories near a surface under various flow shear. We find that near-surface flow shear promotes cell reorientation and mitigates the tumble suppression and re-orientation confinement found in a quiescent flow, and consequently enhances surface normal bacterial dispersion. Conditional sampling suggests that two complimentary hydrodynamic mechanisms, Jeffrey Orbit and shear-induced flagella unbundling, are responsible for the enhancement in bacterial tumble motility. These findings imply that flow shear may mitigate cell trapping and prevent biofilm initiation.
%B Scientific Reports %V 6 %G eng %U https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082759/ %0 Journal Article %J Scientific Reports 6 %D 2016 %TUnderstanding how fluid flow interacts with micro-textured surfaces is crucial for a broad range of key biological processes and engineering applications including particle dispersion, pathogenic infections, and drag manipulation by surface topology. We use high-speed digital holographic microscopy (DHM) in combination with a correlation based de-noising algorithm to overcome the optical interference generated by surface roughness and to capture a large number of 3D particle trajectories in a microfluidic channel with one surface patterned with micropillars. It allows us to obtain a 3D ensembled velocity field with an uncertainty of 0.06% and 2D wall shear stress distribution at the resolution of ~65 μPa. Contrary to laminar flow in most microfluidics, we find that the flow is three-dimensional and complex for the textured microchannel. While the micropillars affect the velocity flow field locally, their presence is felt globally in terms of wall shear stresses at the channel walls. These findings imply that micro-scale mixing and wall stress sensing/manipulation can be achieved through hydro-dynamically smooth but topologically rough micropillars.
%B Scientific Reports 6 %V 6 %G eng %U http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4926118/ %N 28753 %0 Journal Article %J Journal of Geophysical Research: Oceans %D 2016 %T Crude oil jets in crossflow: Effects of dispersant concentration on plume behavior. %A Murphy, David W. %A Xue, Xinzhi %A Sampath, Kaushik %A Katz, Joseph %XThis study investigates the effects of premixing oil with chemical dispersant at varying concentrations on the flow structure and droplet dynamics within a crude oil jet transitioning into a plume in a crossflow. It is motivated by the need to determine the fate of subsurface oil after a well blowout. The laboratory experiments consist of flow visualizations, in situ measurements of the time evolution of droplet-size distributions using holography, and particle image velocimetry to characterize dominant flow features. Increasing the dispersant concentration dramatically decreases the droplet sizes and increases their number, and accordingly, reduces the rise rates of droplets and the upper boundary of the plume. The flow within the plume consists primarily of a pair of counterrotating quasi-streamwise vortices (CVP) that characterize jets in crossflows. It also involves generation of vertical wake vortices that entrain small droplets under the plume. The evolution of plume boundaries is dominated by interactions of droplets with the CVP. The combined effects of vortex-induced velocity and significant quiescent rise velocity of large (∼5 mm) droplets closely agree with the rise rate of the upper boundary of the crude oil plume. Conversely, the much lower rise velocity of the smaller droplets in oil-dispersant mixtures results in plume boundaries rising at rates that are very similar to those of the CVP center. The size of droplets trapped by the CVP is predicted correctly using a trapping function, which is based on a balance of forces on a droplet located within a horizontal eddy.
%B Journal of Geophysical Research: Oceans %V 121 %G eng %U http://onlinelibrary.wiley.com/doi/10.1002/2015JC011574/full %0 Journal Article %J Marine Pollution Bulletin %D 2016 %TThe tarballs on Texas beaches following the 2014 Texas City “Y” Spill: Modeling, chemical, and microbiological studies.
%A Bacosa, Hernando P %A Thyng, Kristen M. %A Plunkett, Stephanie %A Deana L. Erdner %A Liu, Zhanfei %XWe modeled the transport of oil, source-fingerprinted 44 tarball samples from Galveston Island (GV) and Mustang Island (MT), and determined the hydrocarbon and bacterial community composition of these tarballs following the 2014 Texas City “Y” Oil Spill (TCY). Transport modeling indicated that the tarballs arrived in MT before the samples were collected. Source-fingerprinting confirmed that the tarballs collected from GV and MT, 6 d and 11 d after the TCY, respectively, originated from the spill. Tarballs from GV showed 21% depletion of alkanes, mainly C9–C17, and 55% depletion of PAHs mainly naphthalenes, and dominated by alkane-degrading Alcanivorax and Psychrobacter. Samples from MT were depleted of 24% alkanes and 63% PAHs, and contained mainly of PAH-degrading Pseudoalteromonas. To the best of our knowledge, this is the first study to relate oil transport, tarball source-fingerprinting, chemistry, and microbiology, which provides insights on the fate of oil in the northern Gulf of Mexico.
%B Marine Pollution Bulletin %V 109 %P 236-244 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X16303964 %N 1 %0 Journal Article %J Journal of Fluid Mechanics %D 2016 %T Dissolution and growth of a multicomponent drop in an immiscible liquid. %A Chu, Shigan %A Prosperetti, Andrea %XThe mass flux at the surface of a drop in an immiscible host liquid is dictated by the composition of the drop surface. In a binary system, this composition is essentially constant in time and equals the solubility of the drop constituent in the host liquid. This situation has been treated in a classic study by Epstein and Plesset (J. Chem. Phys., vol. 18, 1950, pp. 1505–1509). The situation is very different for ternary and higher-order systems in which, due to the mutual interaction of the drop constituents, their concentration at the drop surface markedly differs from the respective solubilities and depends on time. This paper presents a thermodynamically consistent analysis of this situation, for both growing and dissolving drops, with and without an initial concentration of the drop constituents in the host liquid. In some cases the results, which have important implications e.g. for solvent extraction processes in the chemical and environmental remediation industries, show major deviations from the predictions of approximations in current use, including simple extensions of the Epstein–Plesset theory.
%B Journal of Fluid Mechanics %V 798 %P 787- 811 %G eng %U http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=10361178&fileId=S0022112016003104 %0 Journal Article %J International Journal of Multiphase Flow %D 2016 %T On flux terms in volume averaging. %A Chu, Shigan %A Prosperetti, Andrea %XThis note examines the modeling of non-convective fluxes (e.g., stress, heat flux and others) as they appear in the general, unclosed form of the volume-averaged equations of multiphase flows. By appealing to the difference between slowly and rapidly varying quantities, it is shown that the natural closure of these terms leads to the use of a single, slowly-varying combined average flux, common to both phases, plus rapidly-varying local contributions for each phase. The result is general and only rests on the hypothesis that the spatial variation of the combined average flux is adequately described by a linear function of position within the averaging volume. No further hypotheses on the nature of the flow (e.g., about specific flow regimes) prove necessary. The result agrees with earlier ones obtained by ensemble averaging, is illustrated with the example of disperse flows and discussed in the light of some earlier and current literature. A very concise derivation of the general averaged balance equation is also given.
%B International Journal of Multiphase Flow %V 80 %P 176-180 %G eng %U http://www.sciencedirect.com/science/article/pii/S0301932215002785 %0 Journal Article %J Chemical Engineering Journal %D 2016 %TWe conducted a large scale experiment of underwater oil release of 6.3 L/s through a 25.4 mm (one inch) horizontal pipe. Detailed measurements of plume trajectory, velocity, oil droplet size distribution, and oil holdup were obtained. The obtained experimental data were used for the validation of the models JETLAG and VDROP-J. Key findings include: (1) formation of two plumes, one due to momentum and subsequently plume buoyancy, and another due mostly to the buoyancy of individual oil droplets that separate upward from the first plume; (2) modeling results indicated that the traditional miscible plume models matched the momentum and buoyancy plume, but were not able to simulate the upward motion plume induced by individual oil droplets; (3) high resolution images in the jet primary breakup region showed the formation of ligaments and drops in a process known as “primary breakup”. These threads re-entered the plume to re-break in a process known as “secondary breakup”; (4) the plume velocity was highly heterogeneous with regions of high velocity surrounded by stagnant regions for various durations. The results from this study revealed that the primary breakup is a key factor for quantifying the droplet size distribution which plays a crucial role in determining the ultimate fate and transport of the released oil in the marine environment. The observed spatial heterogeneity in the oil plume implies that the effectiveness of applied dispersants may vary greatly when applying directly in the discharged oil flow.
%B Chemical Engineering Journal %V 299 %P 292–303 %G eng %U http://www.sciencedirect.com/science/article/pii/S1385894716305009 %0 Journal Article %J Chemosphere %D 2016 %TInfluence of UVB radiation on the lethal and sublethal toxicity of dispersed crude oil to planktonic copepod nauplii
%A Almeda, Rodrigo %A Harvey, TracyE. %A Tara L. Connelly %A Baca, Sarah %A Buskey, Edward j> %XToxic effects of petroleum to marine zooplankton have been generally investigated using dissolved petroleum hydrocarbons and in the absence of sunlight. In this study, we determined the influence of natural ultraviolet B (UVB) radiation on the lethal and sublethal toxicity of dispersed crude oil to naupliar stages of the planktonic copepodsAcartia tonsa, Temora turbinata and Pseudodiaptomus pelagicus. Low concentrations of dispersed crude oil (1 μL L−1) caused a significant reduction in survival, growth and swimming activity of copepod nauplii after 48 h of exposure. UVB radiation increased toxicity of dispersed crude oil by 1.3–3.8 times, depending on the experiment and measured variables. Ingestion of crude oil droplets may increase photoenhanced toxicity of crude oil to copepod nauplii by enhancing photosensitization. Photoenhanced sublethal toxicity was significantly higher when T. turbinata nauplii were exposed to dispersant-treated oil than crude oil alone, suggesting that chemical dispersion of crude oil may promote photoenhanced toxicity to marine zooplankton. Our results demonstrate that acute exposure to concentrations of dispersed crude oil and dispersant (Corexit 9500) commonly found in the sea after oil spills are highly toxic to copepod nauplii and that natural levels of UVB radiation substantially increase the toxicity of crude oil to these planktonic organisms. Overall, this study emphasizes the importance of considering sunlight in petroleum toxicological studies and models to better estimate the impact of crude oil spills on marine zooplankton.
%B Chemosphere %V 152 %P 446-458 %G eng %U http://www.sciencedirect.com/science/article/pii/S0045653516303022 %0 Journal Article %J Marine Pollution Bulletin %D 2016 %T A-DROP: A predictive model for the formation of oil particle aggregates (OPA). %A Zhao, L. %A Boufadel, Michel C. %A Geng, Xiaolong. %A Lee, Kenneth %A King, Thomas %A Robinson, Brian %A Fitzpatrick, Faith %XOil–particle interactions play a major role in removal of free oil from the water column. We present a new conceptual–numerical model, A-DROP, to predict oil amount trapped in oil–particle aggregates. A new conceptual formulation of oil–particle coagulation efficiency is introduced to account for the effects of oil stabilization by particles, particle hydrophobicity, and oil–particle size ratio on OPA formation. A-DROP was able to closely reproduce the oil trapping efficiency reported in experimental studies. The model was then used to simulate the OPA formation in a typical nearshore environment. Modeling results indicate that the increase of particle concentration in the swash zone would speed up the oil–particle interaction process; but the oil amount trapped in OPAs did not correspond to the increase of particle concentration. The developed A-DROP model could become an important tool in understanding the natural removal of oil and developing oil spill countermeasures by means of oil–particle aggregation.
%B Marine Pollution Bulletin %V 106 %P 245–259 %8 2016 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X16301138 %N 1-2 %0 Journal Article %J Journal of Geophysical Research: Oceans %D 2016 %T Evolution of bubble side Distribution from gas blowout in shallow water. %A Zhao, L. %A Boufadel, M.C. %A Lee, K. %A King, T. %A Loney, N. %A Geng, X. %XGas is often emanated from the sea bed during a subsea oil and gas blowout. The size of a gas bubble changes due to gas dissolution in the ambient water and expansion as a result of a decrease in water pressure during the rise. It is important to understand the fate and transport of gas bubbles for the purpose of environmental and safety concerns. In this paper, we used the numerical model, VDROP-J to simulate gas formation in jet/plume upon release, and dissolution and expansion while bubble rising during a relatively shallow subsea gas blowout. The model predictions were an excellent match to the experimental data. Then a gas dissolution and expansion module was included in the VDROP-J model to predict the fate and transport of methane bubbles rising due to a blowout through a 0.10 m vertical ori- fice. The numerical results indicated that gas bubbles would increase the mixing energy in released jets, especially at small distances and large distances from the orifice. This means that models that predict the bubble size distribution (BSD) should account for this additional mixing energy. It was also found that only bubbles of certain sizes would reach the water surfaces; small bubbles dissolve fast in the water column, while the size of the large bubbles decreases. This resulted in a BSD that was bimodal near the ori- fice, and then became unimodal.
%B Journal of Geophysical Research: Oceans %V 10 %G eng %U http://onlinelibrary.wiley.com/doi/10.1002/2015JC011403/pdf %0 Journal Article %J Environmental Pollution %D 2016 %T How much crude oil can zooplankton ingest? Estimating the quantity of dispersed crude oil defecated by planktonic copepods. %A Almeda, R. %A T.L. Connelly %A Buskey, E.J. %XWe investigated and quantified defecation rates of crude oil by 3 species of marine planktonic copepods (Temora turbinata, Acartia tonsa, and Parvocalanus crassirostris) and a natural copepod assemblage after exposure to mechanically or chemically dispersed crude oil. Between 88 and 100% of the analyzed fecal pellets from three species of copepods and a natural copepod assemblage exposed for 48 h to physically or chemically dispersed light crude oil contained crude oil droplets. Crude oil droplets inside fecal pellets were smaller (median diameter: 2.4–3.5 μm) than droplets in the physically and chemically dispersed oil emulsions (median diameter: 6.6 and 8.0 μm, respectively). This suggests that copepods can reject large crude oil droplets or that crude oil droplets are broken into smaller oil droplets before or during ingestion. Depending on the species and experimental treatments, crude oil defecation rates ranged from 5.3 to 245 ng-oil copepod−1 d−1, which represent a mean weight-specific defecation rate of 0.026 μg-oil μg-Ccopepod1 d−1. Considering a dispersed crude oil concentration commonly found in the water column after oil spills (1 μl L−1) and copepod abundances in high productive coastal areas, copepods may defecate ∼1.3–2.6 mg-oil m−3 d−1, which would represent ∼0.15%–0.30% of the total dispersed oil per day. Our results indicate that ingestion and subsequent defecation of crude oil by planktonic copepods has a small influence on the overall mass of oil spills in the short term, but may be quantitatively important in the flux of oil from surface water to sediments and in the transfer of low-solubility, toxic petroleum hydrocarbons into food webs after crude oil spills in the sea.
%B Environmental Pollution %V 208 %P 645-654 %G eng %U http://www.sciencedirect.com/science/article/pii/S0269749115301421 %N B %0 Journal Article %J Marine Pollution Bulletin %D 2016 %T Simulation of scenarios of oil droplet formation from the Deepwater Horizon blowout. %A Zhao, Lin %A Boufadel, Michel C. %A Adams, Eric %A Socolofsky, Scott A. %A Lee, Kenneth %A Nedwed, Timothy %XKnowledge of the droplet size distribution (DSD) from the Deepwater Horizon (DWH) blowout is an important step in predicting the fate and transport of the released oil. Due to the absence of measurements of the DSD from the DWH incident, we considered herein hypothetical scenarios of releases that explore the realistic parameter space using a thoroughly calibrated DSD model, VDROP-J, and we attempted to provide bounds on the range of droplet sizes from the DWH blowout within 200 m of the wellhead. The scenarios include conditions without and with the presence of dispersants, different dispersant treatment efficiencies, live oil and dead oil properties, and varying oil flow rate, gas flow rate, and orifice diameter. The results, especially for dispersant-treated oil, are very different from recent modeling studies in the literature.
%B Marine Pollution Bulletin %8 2016 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X15301417 %0 Journal Article %J Marine Pollution Bulletin %D 2015 %T Simulation of scenarios of oil droplet formation from the Deepwater Horizon blowout %A Zhao, L. %A Boufadel, M.C. %A Adams, E. %A Socolofsky, S. %A King, T. %A Lee, K. %A Nedwed, T. %XKnowledge of the droplet size distribution (DSD) from the Deepwater Horizon (DWH) blowout is an important step in predicting the fate and transport of the released oil. Due to the absence of measurements of the DSD from the DWH incident, we considered herein hypothetical scenarios of releases that explore the realistic parameter space using a thoroughly calibrated DSD model, VDROP-J, and we attempted to provide bounds on the range of droplet sizes from the DWH blowout within 200 m of the wellhead. The scenarios include conditions without and with the presence of dispersants, different dispersant treatment efficiencies, live oil and dead oil properties, and varying oil flow rate, gas flow rate, and orifice diameter. The results, especially for dispersant-treated oil, are very different from recent modeling studies in the literature.
%B Marine Pollution Bulletin %V 101 %P 304-319 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X15301417 %N 1 %0 Journal Article %J Front. Microbiol %D 2015 %T Natural sunlight shapes crude oil-degrading bacterial communities in northern Gulf of Mexico surface waters. %A Bacosa, HP %A Liu, Z. %A Erdner, DL %XFollowing the Deepwater Horizon (DWH) spill in 2010, an enormous amount of oil was observed in the deep and surface waters of the northern Gulf of Mexico. Surface waters are characterized by intense sunlight and high temperature during summer. While the oil-degrading bacterial communities in the deep-sea plume have been widely investigated, the effect of natural sunlight on those in oil polluted surface waters remains unexplored to date. In this study, we incubated surface water from the DWH site with amendments of crude oil, Corexit dispersant, or both for 36 d under natural sunlight in the northern Gulf of Mexico. The bacterial community was analyzed over time for total abundance, density of alkane and polycyclic aromatic hydrocarbon degraders, and community composition via pyrosequencing. Our results showed that, for treatments with oil and/or Corexit, sunlight significantly reduced bacterial diversity and evenness and was a key driver of shifts in bacterial community structure. In samples containing oil or dispersant, sunlight greatly reduced abundance of the Cyanobacterium Synechococcus but increased the relative abundances of Alteromonas, Marinobacter, Labrenzia, Sandarakinotalea, Bartonella, and Halomonas. Dark samples with oil were represented by members of Thalassobius, Winogradskyella, Alcanivorax, Formosa, Pseudomonas, Eubacterium, Erythrobacter, Natronocella, and Coxiella. Both oil and Corexit inhibited the Candidatus Pelagibacter with or without sunlight exposure. For the first time, we demonstrated the effects of light in structuring microbial communities in water with oil and/or Corexit. Overall, our findings improve understanding of oil pollution in surface water, and provide unequivocal evidence that sunlight is a key factor in determining bacterial community composition and dynamics in oil polluted marine waters.
%B Front. Microbiol %V 6 %G eng %U http://journal.frontiersin.org/article/10.3389/fmicb.2015.01325/abstract %N 1325 %0 Journal Article %J PloS one %D 2015 %T Statistical Mechanics of Zooplankton %A Hinow, Peter %A Nihongi, Ai %A Strickler, Rudi, J. %XStatistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar "microscopic" quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the "ecological temperature" of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean's swimming behavior.
%B PloS one %V 10 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/26270537 %N 8 %0 Journal Article %J Journal of Fluid Mechanics %D 2015 %T Splash behavior and oily marine aerosol production by raindrops impacting oil slicks %A Murphy, D.W. %A Li, C. %A d'Albignac, V. %A Morra, D. %A Katz, J. %XThe high speed impact of a droplet on a bulk fluid at high We is not well understood but is relevant to the production of marine aerosol by raindrop impact on the sea surface. These splashes produce a subsurface cavity and a crown which closes into a bubble canopy, but a floating layer of immiscible oil, such as a crude oil slick, alters splash dynamics. The effects of oil layer fluid properties and thickness and droplet size and impact speed are examined by high speed visualization. Oil layer rupture and crown behavior are classified by dimensional scaling. The subsurface cavity volume for impact on thick layers is shown to depend on Re, though canopy formation at high Re introduces a competing We effect since rapid canopy closure is found to retard cavity expansion. Time-resolved kinematic measurements show that thin crude oil slicks similarly alter crown closure and cavity growth. The size and spatial distributions of airborne droplets are examined using high speed holographic microscopy. Droplets have a bimodal distribution with peaks at 50 and 225 μm and are clustered by size at different elevation angles. Small droplets (50 μm) are ejected primarily at shallow angles, indicating production by splashing within the first 100 μs and by breakup of microligaments. Larger droplets (225 μm) are found at steeper elevation angles, indicating later production by capillary instability acting on large ligaments protruding upward from the crown. Intermittent droplet release while the ligaments grow and sweep upward is thought to contribute to the size-dependent spatial ordering. Greater numbers of small droplets are produced at high elevation angles when a crude oil layer is present, indicating satellite droplet formation from ligament breakup. A crude oil layer also increases the target fluid Oh, leading to creation of an intact ejecta sheet, which then ruptures to form aerosolized oil droplets.
%B Journal of Fluid Mechanics %V 780 %P 536-577 %G eng %U https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/div-classtitlesplash-behaviour-and-oily-marine-aerosol-production-by-raindrops-impacting-oil-slicksdiv/59E37E077A3B5ABBB384CCD50ADD2FC2 %0 Journal Article %J Journal of Fluid Mechanics %D 2015 %T Local interfacial stability near a zero vorticity point. %A Prosperetti, Andrea %A Tseng, Yu-Hau %XIt is often observed that small drops or bubbles detach from the interface separating two co-flowing immiscible fluids. The size of these drops or bubbles can be orders of magnitude smaller than the length scales of the parent fluid mass. Examples are tip-streaming from drops or coaxial jets in microfluidics, selective withdrawal, ‘skirt’ formation around bubbles or drops, and others. It is argued that these phenomena are all reducible to a common instability that can occur due to a local convergence of streamlines in the neighbourhood of a zero-vorticity point or line on the interface. When surfactants are present, this converging flow tends to concentrate them in these regions weakening the effect of surface tension, which is the only mechanism opposing the instability. Several analytical and numerical calculations are presented to substantiate this interpretation of the phenomenon. In addition to some idealized cases, the results of two-dimensional simulations of co-flowing jets and a rising drop are presented.
%B Journal of Fluid Mechanics %V 776 %P 5-36 %G eng %U http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9809760&fileId=S0022112015002463 %0 Journal Article %J Soft Matter %D 2015 %T Films of bacteria at interfaces: three stages of behaviour %A Vaccari, L. %A Allan, D. %A Sharifi-Mood, N %A Singh, A. %A Leheny, R. %A Stebe, K. %XBacterial attachment to a fluid interface can lead to the formation of a film with physicochemical properties that evolve with time. We study the time evolution of interface (micro)mechanics for interfaces between oil and bacterial suspensions by following the motion of colloidal probes trapped by capillarity to determine the interface microrheology. Initially, active bacteria at and near the interface drive superdiffusive motion of the colloidal probes. Over timescales of minutes, the bacteria form a viscoelastic film which we discuss as a quasi-two-dimensional, active, glassy system. To study late stage mechanics of the film, we use pendant drop elastometry. The films, grown over tens of hours on oil drops, are expanded and compressed by changing the drop volume. For small strains, by modeling the films as 2D Hookean solids, we estimate the film elastic moduli, finding values similar to those reported in the literature for the bacteria themselves. For large strains, the films are highly hysteretic. Finally, from wrinkles formed on highly compressed drops, we estimate film bending energies. The dramatic restructuring of the interface by such robust films has broad implications, e.g. in the study of active colloids, in understanding the community dynamics of bacteria, and in applied settings including bioremediation.
%B Soft Matter %G eng %U http://arxiv.org/abs/1503.07255 %0 Journal Article %J Marine Pollution Bulletin %D 2015 %TWe determined the contributions of photooxidation and biodegradation to the weathering of Light Louisiana Sweet crude oil by incubating surface water from the Deepwater Horizon site under natural sunlight and temperature conditions. N-alkane biodegradation rate constants were ca. ten-fold higher than the photooxidation rate constants. For the 2–3 ring and 4–5 ring polycyclic aromatic hydrocarbons (PAHs), photooxidation rate constants were 0.08–0.98 day−1 and 0.01–0.07 day−1, respectively. The dispersant Corexit enhanced degradation of n-alkanes but not of PAHs. Compared to biodegradation, photooxidation increased transformation of 4–5 ring PAHs by 70% and 3–4 ring alkylated PAHs by 36%. For the first time we observed that sunlight inhibited biodegradation of pristane and phytane, possibly due to inhibition of the bacteria that can degrade branched-alkanes. This study provides quantitative measures of oil degradation under relevant field conditions crucial for understanding and modeling the fate of spilled oil in the northern Gulf of Mexico.
%B Marine Pollution Bulletin %V 95 %P 265-272 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X15001939 %N 1 %0 Journal Article %J Deep Sea Research Part II: Topical Studies in Oceanography %D 2014 %T The impact of Deepwater Horizon oil spill on petroleum hydrocarbons in surface waters of the northern Gulf of Mexico %A Liu, Zhanfei %A Liu, Jiqing %A Gardner, Wayne S. %A Shank, Christopher G. %A Ostromb, Nathaniel E. %XThis study evaluated impacts of the BP Deepwater Horizon (DWH) oil spill on petroleum hydrocarbons in surface waters of the Louisiana continental shelf in northern Gulf of Mexico. Surface water (~top 5 cm) without visible oil was collected from three cruises in May 2010 during the oil spill, August 2010 after the well was capped, and May 2011 one year after the spill. Concentrations of total dissolved n-alkanes (C9–C35) in surface seawater were more than an order of magnitude higher in May 2010 than August 2010 and May 2011, indicating contamination by the DWH oil spill. This conclusion was further supported by more abundant smaller n-alkanes (C9–C13), together with pristane and phytane, in May than August 2010 samples. In contrast, even carbon-numbered dissolved n-alkanes (C14–C20) dominated the May 2011 samples, and this distribution pattern of dissolved n-alkanes is the first documentation for water samples in the northern Gulf of Mexico. However, this pattern was not observed in May 2011 suspended particles except for Sta. OSS. This decoupling between dissolved and particle compositions suggests that either these even carbon-numbered n-alkanes originated from bacteria rather than algae, or that the alkanes in the shelf were transported from elsewhere. Concentrations of polycyclic aromatic hydrocarbons (PAHs) in suspended particles were 5 times higher on average in May 2010 (83–252 ng L−1) than May 2011 (7.2–83 ng L−1), also indicating contamination by the DWH oil spill. Application of a biomarker ratio of 17α(H),21β(H)-30-norhopane over 17α(H),21β(H)-hopane confirmed that suspended particles from at least two stations were contaminated by the DWH oil spill in May 2010. Taken together, these results showed that surface waters of the sampling area in May 2010 were contaminated by the oil spill, but also that rapid weathering and/or physical dilution quickly reduced hydrocarbon levels by August 2010.
%B Deep Sea Research Part II: Topical Studies in Oceanography %V 129 %P 292-300 %G eng %U http://www.sciencedirect.com/science/article/pii/S0967064514000277 %0 Journal Article %J Opt Express %D 2014 %TImaging bacterial 3D motion using digital in-line holographic microscopy and correlation-based de-noising algorithm.
%A Molaei, M. %A Sheng, J. %XBetter understanding of bacteria environment interactions in the context of biofilm formation requires accurate 3-dimentional measurements of bacteria motility. Digital Holographic Microscopy (DHM) has demonstrated its capability in resolving 3D distribution and mobility of particulates in a dense suspension. Due to their low scattering efficiency, bacteria are substantially difficult to be imaged by DHM. In this paper, we introduce a novel correlation-based de-noising algorithm to remove the background noise and enhance the quality of the hologram. Implemented in conjunction with DHM, we demonstrate that the method allows DHM to resolve 3-D E. coli bacteria locations of a dense suspension (>107 cells/ml) with submicron resolutions (<0.5 µm) over substantial depth and to obtain thousands of 3D cell trajectories.
%B Opt Express %V 22 %P 32119-32137 %G eng %U https://www.osapublishing.org/oe/abstract.cfm?uri=oe-22-26-32119 %N 26 %0 Journal Article %J Physical review letters %D 2014 %TFailed Escape: Solid Surfaces Prevent Tumbling ofEscherichia coli
%A Molaei,Mehdi %A Barry, Michael %A Stocker, Roman %A Sheng, Jian %XUnderstanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>103) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20 μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.
%B Physical review letters %V 113 %P 068103 %G eng %U http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.068103 %N 6 %0 Journal Article %J Deep Sea Research Part II: Topical Studies in Oceanography %D 2014 %TThe impact of Deepwater Horizon oil spill on petroleum hydrocarbons in surface waters of the northern Gulf of Mexico
%A Liu, Zhanfei %A Liu, Jiqing %A Gardner, Wayne S. %A Shank, Christopher G. %A Ostromb, Nathaniel E. %XThis study evaluated impacts of the BP Deepwater Horizon (DWH) oil spill on petroleum hydrocarbons in surface waters of the Louisiana continental shelf in northern Gulf of Mexico. Surface water (~top 5 cm) without visible oil was collected from three cruises in May 2010 during the oil spill, August 2010 after the well was capped, and May 2011 one year after the spill. Concentrations of total dissolved n-alkanes (C9–C35) in surface seawater were more than an order of magnitude higher in May 2010 than August 2010 and May 2011, indicating contamination by the DWH oil spill. This conclusion was further supported by more abundant smaller n-alkanes (C9–C13), together with pristane and phytane, in May than August 2010 samples. In contrast, even carbon-numbered dissolved n-alkanes (C14–C20) dominated the May 2011 samples, and this distribution pattern of dissolved n-alkanes is the first documentation for water samples in the northern Gulf of Mexico. However, this pattern was not observed in May 2011 suspended particles except for Sta. OSS. This decoupling between dissolved and particle compositions suggests that either these even carbon-numbered n-alkanes originated from bacteria rather than algae, or that the alkanes in the shelf were transported from elsewhere. Concentrations of polycyclic aromatic hydrocarbons (PAHs) in suspended particles were 5 times higher on average in May 2010 (83–252 ng L−1) than May 2011 (7.2–83 ng L−1), also indicating contamination by the DWH oil spill. Application of a biomarker ratio of 17α(H),21β(H)-30-norhopane over 17α(H),21β(H)-hopane confirmed that suspended particles from at least two stations were contaminated by the DWH oil spill in May 2010. Taken together, these results showed that surface waters of the sampling area in May 2010 were contaminated by the oil spill, but also that rapid weathering and/or physical dilution quickly reduced hydrocarbon levels by August 2010.
%B Deep Sea Research Part II: Topical Studies in Oceanography %G eng %U http://www.sciencedirect.com/science/article/pii/S0967064514000277 %0 Journal Article %J Marine Environmental Research %D 2014 %T Dispersant Corexit 9500A and chemically dispersed crude oil decreases the growth rates of meroplanktonic barnacle nauplii (Amphibalanus improvisus) and tornaria larvae (Schizocardium sp.) %A Almeda, R. %A Connelly, T. %A Buskey, E. %XOur knowledge of the lethal and sublethal effects of dispersants and dispersed crude oil on meroplanktonic larvae is limited despite the importance of planktonic larval stages in the life cycle of benthic invertebrates. We determined the effects of Light Louisiana Sweet crude oil, dispersant Corexit 9500A, and dispersant-treated crude oil on the survival and growth rates of nauplii of the barnacle Amphibalanus improvisus and tornaria larvae of the enteropneust Schizocardium sp. Growth rates of barnacle nauplii and tornaria larvae were significantly reduced after exposure to chemically dispersed crude oil and dispersant Corexit 9500A at concentrations commonly found in the water column after dispersant application in crude oil spills. We also found that barnacle nauplii ingested dispersed crude oil, which may have important consequences for the biotransfer of petroleum hydrocarbons through coastal pelagic food webs after a crude oil spill. Therefore, application of chemical dispersants increases the impact of crude oil spills on meroplanktonic larvae, which may affect recruitment and population dynamics of marine benthic invertebrates.
%B Marine Environmental Research %V 99 %P 212-217 %G eng %U http://www.sciencedirect.com/science/article/pii/S0141113614001147 %0 Journal Article %J Scientific Reports %D 2014 %T Novel insight into the role of heterotrophic dinoflagellates in the fate of crude oil in the sea. %A Almeda, Rodrigo %A Tara L. Connelly %A Edward J. Buskey %XAlthough planktonic protozoans are likely to interact with dispersed crude oil after a spill, protozoan-mediated processes affecting crude oil pollution in the sea are still not well known. Here, we present the first evidence of ingestion and defecation of physically or chemically dispersed crude oil droplets (1–86 μm in diameter) by heterotrophic dinoflagellates, major components of marine planktonic food webs. At a crude oil concentration commonly found after an oil spill (1 μL L−1), the heterotrophic dinoflagellates Noctiluca scintillans and Gyrodinium spirale grew and ingested ~0.37 μg-oil μg-Cdino−1 d−1, which could represent ~17% to 100% of dispersed oil in surface waters when heterotrophic dinoflagellates are abundant or bloom. Egestion of faecal pellets containing crude oil by heterotrophic dinoflagellates could contribute to the sinking and flux of toxic petroleum hydrocarbons in coastal waters. Our study indicates that crude oil ingestion by heterotrophic dinoflagellates is a noteworthy route by which petroleum enters marine food webs and a previously overlooked biological process influencing the fate of crude oil in the sea after spills.
%B Scientific Reports %V 4 %G eng %U http://www.nature.com/srep/2014/141219/srep07560/full/srep07560.html?WT.ec_id=SREP-20141223 %0 Journal Article %J Geochemical transactions %D 2014 %T Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico. %A Wang Z. %A Liu, Z. %A Xu, K. %A Mayer, L.M. %A Zhang, Z. %A Kolker, A.S. %A Wu, W. %XBackground: Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. Results: PAH concentrations in this region ranged from 100 to 856 ng g−1 , with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. Conclusion: PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels.
%B Geochemical transactions %V 15 %P 2 %G eng %U http://www.biomedcentral.com/content/pdf/1467-4866-15-2.pdf %N 1 %0 Journal Article %J Environmental Microbiology Reports %D 2014 %T A shift in the archael nitrifier community in response to natural and anthropogenic disturbances in the northern Gulf of Mexico. %A Newell, S.E. %A Eveillard, D. %A McCarthy, M. %A Gardner, W.S. %A Liu, Z. %A Ward, B.B. %XThe Gulf of Mexico is affected by hurricanes and suffers seasonal hypoxia. The Deepwater Horizon oil spill impacted every trophic level in the coastal region. Despite their importance in bioremediation and biogeochemical cycles, it is difficult to predict the responses of microbial communities to physical and anthropogenic disturbances. Here, we quantify sediment ammonia-oxidizing archaeal (AOA) community diversity, resistance and resilience, and important geochemical factors after major hurricanes and the oil spill. Dominant AOA archetypes correlated with different geochemical factors, suggesting that different AOA are constrained by distinct parameters. Diversity was lowest after the hurricanes, showing weak resistance to physical disturbances. However, diversity was highest during the oil spill and coincided with a community shift, suggesting a new alternative stable state sustained for at least 1 year. The new AOA community was not significantly different from that at the spill site 1 year after the spill. This sustained shift in nitrifier community structure may be a result of oil exposure.
%B Environmental Microbiology Reports %V 6 %P 106-112 %G eng %U http://onlinelibrary.wiley.com/doi/10.1111/1758-2229.12114/full %N 1 %0 Journal Article %J Chemical Engineering Science %D 2014 %T On Skirted drops in an immiscible liquid %A Ray, Bahni %A Prosperetti, Andrea %XLarge drops rising or sinking in an immiscible liquid can develop thin trailing structures commonly referred to as “skirts”. The paper describes a mathematical model for the thickness of these skirts accounting for the viscous boundary layer that develops along the surface of the parent drop and of the skirt itself. Unlike earlier theories, the skirt thickness is found to decrease with distance from the drop rim, which illuminates the mechanism which terminates the skirt at a finite length. A scaling of the skirt length is suggested by an analysis of published data, which also leads to a scaling for the volume of liquid in the skirt. The theoretical predictions are compared with the few experimental results for which sufficiently detailed information is available.
%B Chemical Engineering Science %V 108 %P 213-222 %G eng %U http://www.sciencedirect.com/science/article/pii/S0009250914000098 %0 Journal Article %J Journal of Plankton Research %D 2014 %T A new approach to micro-scale particle image velocimetry (µPIV) for quantifying flows around free-swimming zooplankton. %A Gemmell, Brad J. %A Houshuo Jiang %A Edward J. Buskey %XOur current understanding of zooplankton interactions with surrounding fluid is limited, partially because traditional methods of particle image velocimetry (PIV) become impractical at scales less than a few millimeters and microscope-based systems restrict motions and can incur “wall effects”. We present a new approach to small-scale PIV imaging and our results demonstrate the ability to observe detailed kinematics simultaneously with fluid motion at small scales around free-swimming zooplankton. This can improve our understanding of animal–fluid interactions at small spatial scales and low Reynolds number.
%B Journal of Plankton Research %V 36 %P 1396-1401 %G eng %U http://plankt.oxfordjournals.org/content/36/5/1396.short %N 5 %0 Journal Article %J Ecotoxicology %D 2014 %T Ingestion and sublethal effects of physically and chemically dispersed crude oil on marine planktonic copepods. %A Almeda, R. %A Baca, S. %A Hyatt, C. %A Buskey, E.J. %XPlanktonic copepods play a key function in marine ecosystems, however, little is known about the effects of dispersants and chemically dispersed crude oil on these important planktonic organisms. We examined the potential for the copepods Acartia tonsa, Temora turbinata and Parvocalanus crassirostris to ingest crude oil droplets and determined the acute toxicity of the dispersant Corexit®9500A, and physically and chemically dispersed crude oil to these copepods. We detected ingestion of crude oil droplets by adults and nauplii of the three copepod species. Exposure to crude oil alone (1 µL L−1, 48 h) caused a reduction of egg production rates (EPRs) by 26–39 %, fecal pellet production rates (PPRs) by 11–27 %, and egg hatching (EH) by 1–38 % compared to the controls, depending on the species. Dispersant alone (0.05 µL L−1, 48 h) produced a reduction in EPR, PPR and EH by 20–35, 12–23 and 2–11 %, respectively. Dispersant-treated crude oil was the most toxic treatment, ~1.6 times more toxic than crude oil alone, causing a reduction in EPR, PPR and EH by 45–54, 28–41 and 11–31 %, respectively. Our results indicate that low concentrations of dispersant Corexit 9500A and chemically dispersed crude oil are toxic to marine zooplankton, and that the ingestion of crude oil droplets by copepods may be an important route by which crude oil pollution can enter marine food webs.
%B Ecotoxicology %V 23 %P 988-1003 %G eng %U http://link.springer.com/article/10.1007/s10646-014-1242-6#page-1 %N 6 %0 Journal Article %J Ecotoxicology and Environmental Safety %D 2014 %T Toxicity of dispersant Corexit 9500A and crude oil to marine microzooplankton. %A Almeda, R. %A Hyatt, C. %A Buskey, E.J. %XIn 2010, nearly 7 million liters of chemical dispersants, mainly Corexit® 9500A, were released in the Gulf of Mexico to treat the Deepwater Horizon oil spill. However, little is still known about the effects of Corexit 9500A and dispersed crude oil on microzooplankton despite the important roles of these planktonic organisms in marine ecosystems. We conducted laboratory experiments to determine the acute toxicity of Corexit 9500A, and physically and chemically dispersed Louisiana light sweet crude oil to marine microzooplankton (oligotrich ciliates, tintinnids and heterotrophic dinoflagellates). Our results indicate that Corexit 9500A is highly toxic to microzooplankton, particularly to small ciliates, and that the combination of dispersant with crude oil significantly increases the toxicity of crude oil to microzooplankton. The negative impact of crude oil and dispersant on microzooplankton may disrupt the transfer of energy from lower to higher trophic levels and change the structure and dynamics of marine planktonic communities.
%B Ecotoxicology and Environmental Safety %V 106 %P 75-85 %G eng %U http://www.sciencedirect.com/science/article/pii/S0147651314001687 %0 Journal Article %J Marine Pollution Bulletin %D 2013 %T Chemical evolution of Macondo crude oil during laboratory degradation as characterized by fluorescence EEMs and hydrocarbon composition. 66: 164-175. %A Zhou, Z. %A Liu, Z. %A Guo, L. %XThe fluorescence EEM technique, PARAFAC modeling, and hydrocarbon composition were used to characterize oil components and to examine the chemical evolution and degradation pathways of Macondo crude oil under controlled laboratory conditions. Three major fluorescent oil components were identified, with Ex/Em maxima at 226/328, 262/315, and 244/366 nm, respectively. An average degradation half-life of ∼20 d was determined for the oil components based on fluorescence EEM and hydrocarbon composition measurements, showing a dynamic chemical evolution and transformation of the oil during degradation. Dispersants appeared to change the chemical characteristics of oil, to shift the fluorescence EEM spectra, and to enhance the degradation of low-molecular-weight hydrocarbons. Photochemical degradation played a dominant role in the transformation of oil components, likely an effective degradation pathway of oil in the water column. Results from laboratory experiments should facilitate the interpretation of field-data and provide insights for understanding the fate and transport of oil components in the Gulf of Mexico.
A new method for prediction of droplet size distributions from subsea oil and gas releases is presented in this paper. The method is based on experimental data obtained from oil droplet breakup experiments conducted in a new test facility at SINTEF. The facility is described in a companion paper, while this paper deals with the theoretical basis for the model and the empirical correlations used to derive the model parameters from the available data from the test facility. A major issue dealt with in this paper is the basis for extrapolation of the data to full scale (blowout) conditions. Possible contribution from factors such as buoyancy flux and gas void fraction are discussed and evaluated based on results from the DeepSpill field experiment.
%B Marine Pollution Bulletin %V 73 %P 327-335 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X1300194X %N 1 %0 Journal Article %J MicrobiologyOpen %D 2013 %T Evaluating bacterial community structures in oil collected from the sea surface and sediment in the northern Gulf of Mexico after the Deepwater Horizon oil spill. %A Liu, Zhanfei %A Liu, Jiqing %XBacterial community structures were evaluated in oil samples using culture-independent pyrosequencing, including oil mousses collected on sea surface and salt marshes during the Deepwater Horizon oil spill, and oil deposited in sediments adjacent to the wellhead 1 year after the spill. Phylogenetic analysis suggested that Erythrobacter, Rhodovulum, Stappia, and Thalassospira ofAlphaproteobacteria were the prevailing groups in the oil mousses, which may relate to high temperatures and strong irradiance in surface Gulf waters. In the mousse collected from the leaves of Spartina alterniflora, Vibrio of Gammaproteobacteria represented 57% of the total operational taxonomic units, suggesting that this indigenous genus is particularly responsive to the oil contamination in salt marshes. The bacterial communities in oil-contaminated sediments were highly diversified. The relatively high abundance of theMethylococcus, Methylobacter, Actinobacteria, Firmicutes, and Chlorofexi bacteria resembles those found in certain cold-seep sediments with gas hydrates. Bacterial communities in the overlying water of the oil-contaminated sediment were dominated byRalstonia of Betaproteobacteria, which can degrade small aromatics, and Saccharophagus degradans of Gammaproteobacteria, a cellulose degrader, suggesting that overlying water was affected by the oil-contaminated sediments, possibly due to the dissolution of small aromatics and biosurfactants produced during biodegradation. Overall, these results provided key information needed to evaluate oil degradation in the region and develop future bioremediation strategies.
%B MicrobiologyOpen %V 2 %P 492-504 %G eng %U http://onlinelibrary.wiley.com/doi/10.1002/mbo3.89/full %N 3 %0 Journal Article %J Marine Pollution Bulletin %D 2013 %T Droplet breakup in subsurface oil releases- Part 1: Experimental study of droplet breakup and effectiveness of dispersant injection. %A Brandvik, P.J. %A Johansen, O. %A Leirvik, F %A Farooq, U. %A Daling, P.S %XSize distribution of oil droplets formed in deep water oil and gas blowouts have strong impact on the fate of the oil in the environment. However, very limited data on droplet distributions from subsurface releases exist. The objective of this study has been to establish a laboratory facility to study droplet size versus release conditions (rates and nozzle diameters), oil properties and injection of dispersants (injection techniques and dispersant types). This paper presents this facility (6 m high, 3 m wide, containing 40 m3 of sea water) and introductory data. Injection of dispersant lowers the interfacial tension between oil and water and cause a significant reduction in droplet size. Most of this data show a good fit to existing Weber scaling equations. Some interesting deviations due to dispersant treatment are further analyzed and used to develop modified algorithms for predicting droplet sizes in a second paper (Johansen et al., 2013).
%B Marine Pollution Bulletin %V 73 %P 319-326 %G eng %U http://www.sciencedirect.com/science/article/pii/S0025326X13002671 %N 1 %0 Journal Article %J PLoS One %D 2013 %T Effects of crude oil exposure on bioaccumulation of polycyclic aromatic hydrocarbons and survival of adult and larval stages of gelatinous zooplankton. %A Almeda, R. %A Wambaugh, Z. %A Chao, C. %A Wang, Z. %A Liu, Z. %A Buskey, E. %XGelatinous zooplankton play an important role in marine food webs both as major consumers of metazooplankton and as prey of apex predators (e.g., tuna, sunfish, sea turtles). However, little is known about the effects of crude oil spills on these important components of planktonic communities. We determined the effects of Louisiana light sweet crude oil exposure on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in adult stages of the scyphozoans Pelagia noctiluca and Aurelia aurita and the ctenophore Mnemiopsis leidyi, and on survival of ephyra larvae of A. aurita and cydippid larvae of M. leidyi, in the laboratory. AdultP. noctiluca showed 100% mortality at oil concentration ≥20 µL L−1 after 16 h. In contrast, low or non-lethal effects were observed on adult stages of A. aurita and M. leidyi exposed at oil concentration ≤25 µL L−1 after 6 days. Survival of ephyra and cydippid larva decreased with increasing crude oil concentration and exposition time. The median lethal concentration (LC50) for ephyra larvae ranged from 14.41 to 0.15 µL L−1 after 1 and 3 days, respectively. LC50 for cydippid larvae ranged from 14.52 to 8.94 µL L−1 after 3 and 6 days, respectively. We observed selective bioaccumulation of chrysene, phenanthrene and pyrene in A. aurita and chrysene, pyrene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]anthracene in M. leidyi. Overall, our results indicate that (1) A. aurita and M. leidyi adults had a high tolerance to crude oil exposure compared to other zooplankton, whereas P. noctiluca was highly sensitive to crude oil, (2) larval stages of gelatinous zooplankton were more sensitive to crude oil than adult stages, and (3) some of the most toxic PAHs of crude oil can be bioaccumulated in gelatinous zooplankton and potentially be transferred up the food web and contaminate apex predators.
%B PLoS One %V 8 %P e74476 %G eng %U http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074476 %N 10 %0 Journal Article %J PLoS One %D 2013 %T Interactions between zooplankton and crude oil: toxic effects and bioaccumulation of polycyclic aromatic hydrocarbons. %A Almeda, R. %A Wambaugh, Z. %A Wang, Z. %A Hyatt, C. %A Liu, Z. %A Buskey, E. %XWe conducted ship-, shore- and laboratory-based crude oil exposure experiments to investigate (1) the effects of crude oil (Louisiana light sweet oil) on survival and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in mesozooplankton communities, (2) the lethal effects of dispersant (Corexit 9500A) and dispersant-treated oil on mesozooplankton, (3) the influence of UVB radiation/sunlight exposure on the toxicity of dispersed crude oil to mesozooplankton, and (4) the role of marine protozoans on the sublethal effects of crude oil and in the bioaccumulation of PAHs in the copepod Acartia tonsa. Mortality of mesozooplankton increased with increasing oil concentration following a sigmoid model with a median lethal concentration of 32.4 µl L−1 in 16 h. At the ratio of dispersant to oil commonly used in the treatment of oil spills (i.e. 1∶20), dispersant (0.25 µl L−1) and dispersant- treated oil were 2.3 and 3.4 times more toxic, respectively, than crude oil alone (5 µl L−1) to mesozooplankton. UVB radiation increased the lethal effects of dispersed crude oil in mesozooplankton communities by 35%. We observed selective bioaccumulation of five PAHs, fluoranthene, phenanthrene, pyrene, chrysene and benzo[b]fluoranthene in both mesozooplankton communities and in the copepod A. tonsa. The presence of the protozoan Oxyrrhis marina reduced sublethal effects of oil on A. tonsa and was related to lower accumulations of PAHs in tissues and fecal pellets, suggesting that protozoa may be important in mitigating the harmful effects of crude oil exposure in copepods and the transfer of PAHs to higher trophic levels. Overall, our results indicate that the negative impact of oil spills on mesozooplankton may be increased by the use of chemical dispersant and UV radiation, but attenuated by crude oil-microbial food webs interactions, and that both mesozooplankton and protozoans may play an important role in fate of PAHs in marine environments.
%B PLoS One %V 8 %P e67212 %G eng %U http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3696092/ %N 6 %0 Journal Article %J Environmental Research Letters %D 2012 %T The weathering of oil after the Deepwater Horizon oil spill: insights from the chemical composition of the oil from the sea surface, salt marshes and sediments %A Liu, Z. %A Liu, J. %A Zhu, Q. %A Wu, W. %XThe oil released during the Deepwater Horizon (DWH) oil spill may have both short- and long-time impacts on the northern Gulf of Mexico ecosystems. An understanding of how the composition and concentration of the oil are altered by weathering, including chemical, physical and biological processes, is needed to evaluate the oil toxicity and impact on the ecosystem in the northern Gulf of Mexico. This study examined petroleum hydrocarbons in oil mousse collected from the sea surface and salt marshes, and in oil deposited in sediments adjacent to the wellhead after the DWH oil spill. Oil mousses were collected at two stations (OSS and CT, located 130 and 85 km away from the wellhead, respectively) in May 2010, and two sediment samples from stations SG and SC, within 6 km of the wellhead, in May 2011. We also collected oil mousse from salt marshes at Marsh Point (MP), Mississippi, 186 km away from the wellhead in July 2010. In these samples, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, BTEX (collective name of benzene, toluene, ethylbenzene and p-, m-, and o-xylenes), C3-benzenes and trace metals were measured to examine how the oil was altered chemically. The chemical analysis indicates that the oil mousses underwent different degrees of weathering with the pattern of OSS < CT < MP. This pattern is consistent with the projected oil mousse movement from the accident site to salt marshes. Also, the contents of trace metals Al, V, Cr, Fe, Mn, Ni, Co, Cu, As and Pb in the oil mousse generally increased along the way to the salt marshes, indicating that these trace metals were perhaps aggregated into the oil mousse during the transport. Petroleum hydrocarbon data reveal that the oil deposited in sediments underwent only light to moderate degradation one year after the DWH oil spill, as supported by the presence of short-chained n-alkanes (C10–C 15), BTEX and C 3-benzenes. The weathering of oil in sediment may result from biological degradation and dissolution, evidenced by the preferential loss of mid-chained n-alkanes C16–C 27, lower ratios ofn-C 17/Pr and n-C 18/Ph , and preferential loss of PAHs relative to alkylated PAHs.
%B Environmental Research Letters %V 7 %P 035302 %G eng %U http://iopscience.iop.org/1748-9326/7/3/035302 %N 3