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Deepwater Horizon spilled over 200 million gallons of oil into the waters of the Gulf of Mexico in 2010. In an effort to contain the spill, chemical dispersants were applied to minimize the amount of oil reaching coastal shorelines. However, the biological impacts of chemically-dispersed oil are not well characterized, and there is a particular lack of knowledge concerning sublethal long-term effects of exposure. This study examined potential estrogenic effects of CWAF, Corexit 9500-enhanced water-accommodated fraction of oil, by examining its effect on estrogen receptors and sex determination in the American alligator, Alligator mississippiensis . The alligator exhibits temperature-dependent sex determination which is modulated by estrogen signals, and exposure to 17β-estradiol (E 2 ) and estrogenic compounds in ovo during the thermosensitive period of embryonic development can induce ovarian development at a male-producing temperature (MPT). CWAF induced transactivation up to 50% of the maximum induction by E 2 via alligator estrogen receptors in vitro . To determine potential endocrine-disrupting effects of exposure directly on the gonad, gonad-adrenal-mesonephric (GAM) organ complexes were isolated from embryos one day prior to the thermosensitive period and exposed to E 2 , CWAF, or medium alone in vitro for 8–16 days at MPT. Both CWAF and E 2 exposure induced a significant increase in female ratios. CWAF exposure suppressed GAM mRNA abundances of anti-Müllerian hormone ( AMH ), sex determining region Y-box 9, and aromatase, whereas E 2 exposure suppressed AMH and increased Forkhead box protein L2 mRNA abundances in GAM. These results indicate that the observed endocrine-disrupting effects of CWAF are not solely estrogenically mediated, and further investigations are required. [ABSTRACT FROM AUTHOR]

Culture experiments were conducted on ten phytoplankton species to examine their biological and physiological responses during exposure to oil and a combination of oil and dispersant. The species tested included a range of taxa typically found in the Gulf of Mexico such as cyanobacteria, chlorophytes, and diatoms. Cultures were exposed to Macondo surrogate oil using the water accommodated fraction (WAF), and dispersed oil using a chemically enhanced WAF (CEWAF) and diluted CEWAF, to replicate conditions following the Deepwater Horizon spill in the Gulf of Mexico. A range of responses were observed, that could broadly class the algae as either “robust” or “sensitive” to oil and/or dispersant exposure. Robust algae were identified as Synechococcus elongatus, Dunaliella tertiolecta, two pennate diatoms Phaeodactylum tricornutum and Navicula sp., and Skeletonema grethae CCMP775, and were largely unaffected by any of the treatments (no changes to growth rate or time spent in lag phase relative to controls). The rest of the phytoplankton, all centric diatoms, exhibited at least some combination of reduced growth rates or increased lag time in response to oil and/or dispersant exposure. Photophysiology did not have a strong treatment effect, with significant inhibition of photosynthetic efficiency (Fv/Fm) only observed in the CEWAF, if at all. We found that the effects of oil and dispersants on phytoplankton physiology were species‐dependent, and not always detrimental. This has significant implications on how oil spills might impact phytoplankton community structure and bloom dynamics in the Gulf of Mexico, which in turn impacts higher trophic levels. [ABSTRACT FROM AUTHOR]

Being cost-effective, synthetic materials were initially used abundantly for the removal of oil. Gradually, however, awareness of the use of dispersants like Corexit, which makes water resources more toxic than oil, has changed the scenario for the treatment of spilled oil. The removal of spilled oil from water resources is still a very topical issue. An eco-friendly and sustainable approach towards the environment has introduced many low-cost, non-toxic and biodegradable materials along with different biomasses to make micro-to nano-sized materials, membranes, sponges/aerogel, etc. for the removal and recovery of oil from water resources. Additionally, the reusability of these materials after the recovery of oils has added one more step towards sustainability. This review comprises the work conducted by various researchers in the field of the removal and recovery of spilled oils using various biomasses and polymers, either in the form of sorbents or separators. [ABSTRACT FROM AUTHOR]

The 2010 Deepwater Horizon (DWH) oil spill is the largest marine oil spill in US history. In the aftermath of the spill, the response efforts used a chemical dispersant, Corexit, to disperse the oil spill. The health impacts of crude oil and Corexit mixture to humans, mammals, fishes, and birds are mostly unknown. The purpose of this study is to investigate the in vivo effects of DWH oil, Corexit, and oil-Corexit mixture on the general behavior, hematological markers, and liver and kidney functions of rodents. C57 Bl6 mice were treated with DWH oil (80 mg/kg) and/or Corexit (95 mg/kg), and several hematological markers, lipid profile, liver and kidney functions were monitored. The results show that both DWH oil and Corexit altered the white blood cells and platelet counts. Moreover, they also impacted the lipid profile and induced toxic effects on the liver and kidney functions. The impacts were more pronounced when the mice were treated with a mixture of DWH-oil and Corexit. This study provides preliminary data to elucidate the potential toxicological effects of DWH oil, Corexit, and their mixtures on mammalian health. Residues from the DWH spill continue to remain trapped along various Gulf Coast beaches and therefore further studies are needed to fully understand their long-term impacts on coastal ecosystems. [ABSTRACT FROM AUTHOR]

In response to the 2010 Deepwater Horizon oil spill, over 1 million gallons of dispersant were applied in Gulf of Mexico offshore waters; Corexit 9500 was the most applied dispersant. The impact on organisms in nearshore and freshwaters has received little scrutiny. Acute 48 h toxicity of Corexit 9500 and a new hyperbranched polyethylenimine (HPEI) dispersant-like compound were evaluated for the freshwater indicator organism, Daphnia magna and for larval and early spat stages of the Eastern oyster, Crassostrea virginica. For D. magna, Corexit 9500 demonstrated toxicity (EC50 of 0.14 [0.13, 0.15] ppm) similar to the 10-kDa HPEI (EC50 of 0.16 [0.12, 0.19] ppm). HPEI toxicity increased as a function of molecular weight (1.2 to 750 kDa). The 10 kDa size HPEI was further investigated because it dispersed crude oil with equal effectiveness as Corexit. For Corexit, 100% oyster mortality was detected for the ≤0.2-mm size classes and mortality >50% for the 0.3- and 0.7-mm size classes at the two greatest concentrations (25 and 50 ppm). HPEI (10 kDa) exhibited low mortality rates (<30%) for all concentrations for all oyster size classes except the 0.1-mm class. Although mortality rates for this size class were up to 60%, mortality was still less than the mortality caused by Corexit 9500. The low toxicity of HPEI polymers for C. virginica in comparison with Corexit 9500 suggests that HPEI polymers warrant further study. [ABSTRACT FROM AUTHOR]

As part of a large study examining the toxicity of the Corexit® family of oil spill dispersants on aquatic vertebrates, we examined effects on the liver in an in vitro study using the rainbow trout liver cell line (RTL-W1). We exposed RTL-W1 cells to the dispersant Corexit 9500 and its major surfactant components and measured their cytotoxic effects as well as modulation of activity of CYP1A, one of the major enzymes responsible for organic contaminant metabolism. The anionic surfactant DOSS was found to be the most cytotoxic with a 24 h EC50 of 10 mg/L, as compared to 45 to 91 mg/L for the non-ionic surfactants, Tween 80 and 85 and Span 80. The EC50 for Corexit was intermediate between these compounds at 29 mg/L. Corexit 9500 and the non-ionic surfactants Tween 80 and 85, but not DOSS or Span 80 knocked down CYP1A activity induced by benzo[ a ]pyrene, a model agonist, demonstrating the potential of these compounds to compromise the ability of exposed organisms to metabolize petroleum hydrocarbons or other CYP1A substrates. [ABSTRACT FROM AUTHOR]

To better understand the impacts of Corexit 9500 on the structure and activity levels of hydrocarbon-degrading microbial communities, we analyzed nextgeneration 16S rRNA gene sequencing libraries of hydrocarbon enrichments grown at 5 and 25°C using both DNA and RNA extracts as the sequencing templates. Oil biodegradation patterns in both 5 and 25°C enrichments were consistent with those reported in the literature (i.e., aliphatics were degraded faster than aromatics). Slight increases in biodegradation were observed in the presence of Corexit at both temperatures. Differences in community structure were observed between treatment conditions in the DNA-based libraries. The 25°C consortia were dominated by Vibrio, Idiomarina, Marinobacter, Alcanivorax, and Thalassospira species, while the 5°C consortia were dominated by several species of the genera Flavobacterium, Alcanivorax, and Oleispira. Most of these genera have been linked to hydrocarbon degradation and have been observed after oil spills. Colwellia and Cycloclasticus, known aromatic degraders, were also found in these enrichments. The addition of Corexit did not have an effect on the active bacterial community structure of the 5°C consortia, while at 25°C, a decrease in the relative abundance of Marinobacter was observed. At 25°C, Thalassospira, Marinobacter, and Idiomarina were present at higher relative abundances in the RNA than DNA libraries, suggesting that they were active in degradation. Similarly, Oleispira was greatly stimulated by the addition of oil at 5°C. IMPORTANCE While dispersants such as Corexit 9500 can be used to treat oil spills, there is still debate on the effectiveness on enhancing oil biodegradation and its potential toxic effect on oil-degrading microbial communities. The results of this study provide some insights on the microbial dynamics of hydrocarbon-degrading bacterial populations in the presence of Corexit 9500. Operational taxonomic unit (OTU) analyses indicated that several OTUs were inhibited by the addition of Corexit. Conversely, a number of OTUs were stimulated by the addition of the dispersant, many of which were identified as known hydrocarbon-degrading bacteria. The results highlight the value of using RNA-based methods to further understand the impact of dispersant on the overall activity of different hydrocarbon-degrading bacterial groups. [ABSTRACT FROM AUTHOR]

At the onset of the 2010 Gulf oil spill, analytical methods for the quantification of the surfactants in Corexit did not exist in the peer-reviewed literature. To date, only a single study reports the presence of bis-(2-ethylhexyl) sodium sulfosuccinate (DOSS) in deep-sea Gulf sediment collected in 2010 from a single location. There are no data on the occurrence of DOSS in association with settling solids (i.e., sediment-trap solids). To address this data gap, DOSS was initially quantified by liquid chromatography tandem quadrupole mass spectrometry (LC-MS/MS) in sediment and sediment-trap solids collected from multiple sites in the Gulf between 2010 and 2013. However, interferences confounded analyses using only a quadrupole (MS/MS) system; therefore, a LC-high mass accuracy quadruple time of flight mass spectrometry (LC-QTOF-MS) method was developed. The LC-QTOF method was validated and applied to eight representative samples of sediment and of sediment-trap solids. The presented method quantifies DOSS in solids of marine origin at concentrations above the limit of quantification of 0.23 μg kg with recoveries of 97 ± 20 % (mean ± 95 CI). Gulf sediment and sediment-trap solids gave DOSS concentrations of

We examined lethality and behavioral effects of Corexit EC 9500A (C-9500A) exposure on the model marine zooplankton Brachionus plicatilis singularly and in combination with abiotic and biotic factors. C-9500A exposure at standard husbandry conditions (17.5 ppt, 24 °C, 200 rotifer*mL − 1 density) identified the 24 h median lethal concentration, by Probit analysis, to be 107 ppm for cultured B . plicatilis . Rotifers surviving exposure to higher concentrations (100 and 150 ppm) exhibited a decreased swimming velocity and a reduced net to gross movement ratio. Significant interaction between C-9500A exposure and temperature or salinity was observed. Upper thermal range was reduced and maximal salinity stress was seen as ca. 25 ppt. Increased or decreased nutritional availability over the exposure period did not significantly alter mortality of B . plicatilis populations at the concentrations tested. Results from this study may be useful for predicting possible outcomes on marine zooplankton following dispersant application under diverse natural conditions. [ABSTRACT FROM AUTHOR]

Corexit-EC9500A and Corexit-EC9527A are two chemical dispersants that have been used to remediate the impact of the 2010 Deepwater Horizon oil spill. Both dispersants are composed primarily of organic solvents and surfactants and act by emulsifying the crude oil to facilitate biodegradation. The potential adverse effect of the Corexit chemicals on mammalian embryonic development remains largely unknown. Retinol (vitamin A) signaling, mediated by all-trans retinoic acid (RA), is essential for neural tube formation and the development of many organs in the embryo. The physiological levels of RA in cells and tissues are maintained by the retinol signaling pathway (RSP), which controls the biosynthesis of RA from dietary retinol and the catabolism of RA to polar metabolites for removal. RA is a potent activating ligand for the RAR/RXR nuclear receptors. Through RA and the receptors, the RSP modulates the expression of many developmental genes; interference with the RSP is potentially teratogenic. In this study the mouse P19 embryonal pluripotent cell, which contains a functional RSP, was used to evaluate the effects of the Corexit dispersants on retinol signaling and associated neuronal differentiation. The results showed that Corexit-EC9500A was more cytotoxic than Corexit-EC9527A to P19 cells. At non-cytotoxic doses, Corexit-EC9527A inhibited retinol-induced expression of the Hoxa1 gene, which encodes a transcription factor for the regulation of body patterning in the embryo. Such inhibition was seen in the retinol- and retinal- induced, but not RA-induced, Hoxa1 up-regulation, indicating that the Corexit chemicals primarily inhibit RA biosynthesis from retinal. In addition, Corexit-EC9527A suppressed retinol-induced P19 cell differentiation into neuronal cells, indicating potential neurotoxic effect of the chemicals under the tested conditions. The surfactant ingredient, dioctyl sodium sulfosuccinate (DOSS), may be a major contributor to the observed effect of Corexit-EC9527A in the cell. [ABSTRACT FROM AUTHOR]

To reduce possible ecological impact from oil spill events, the chemical dispersant Corexit 9500A (C-9500A) is approved for widespread application. Interactions with changing environmental factors such as temperature are necessary to appropriately use dispersants in field applications, particularly in susceptible early life stages of certain marine organisms. The 24 h LC25, LC50, and LC75 values for C-9500A exposure for 3 (hours post fertilization) embryos of the teleost model Danio rerio (Hamilton, 1822) exposed to C-9500A at the standard husbandry temperature of 28.5 ˚ C were 71, 110, and 171 ppm, respectively (Probit analysis, n=5 trials of 10 individuals each). We also examined survival, early development, and hatch success of embryos and survival of larvae exposed to C-9500A while maintained at 24.7, 27.0, 29.5, and or 31.7˚ C representing both lower and higher normative thermal exposures. An interactive effect between C- 9500A and higher exposure temperature on embryo survival and hatch success was observed. Hatched larvae showed a highly reduced sensitivity to C-9500A exposure (24 h LC50 > 200 ppm), but higher variability in response than exposed embryos. We hypothesize that C-9500A application, particularly when temperatures are elevated, could negatively affect wild fish populations in nurseries and ultimately community structure. [ABSTRACT FROM AUTHOR]

After the April 2010 explosion on the Deepwater Horizon oil rig, and subsequent release of millions of barrels of oil, two Corexit oil dispersant formulations were used in unprecedented quantities both on the surface and sub-surface of the Gulf of Mexico. Although the dispersant formulations contain four classes of surfactants, current studies to date focus on the anionic surfactant, bis-(2-ethylhexyl) sulfosuccinate (DOSS). Factors affecting the integrity of environmental and laboratory samples for Corexit analysis have not been systematically investigated. For this reason, a quantitative analytical method was developed for the detection of all four classes of surfactants, as well as the hydrolysis products of DOSS, the enantiomeric mixture of α- and β-ethylhexyl sulfosuccinate (α-/β-EHSS). The analytical method was then used to evaluate which practices for sample collection, storage, and analysis resulted in high quality data. Large volume, direct injection of seawater followed by liquid chromatography tandem mass spectrometry (LC–MS/MS) minimized analytical artifacts, analysis time, and both chemical and solid waste. Concentrations of DOSS in the seawater samples ranged from 71 to 13,000 ng/L, while the nonionic surfactants including Span 80, Tween 80, Tween 85 were detected infrequently (26% of samples) at concentrations from 840 to 9100 ng/L. The enantiomers α-/β-EHSS were detected in seawater, at concentrations from 200 to 1900 ng/L, and in both Corexit dispersant formulations, indicating α-/β-EHSS were applied to the oil spill and may be not unambiguous indicator of DOSS degradation. Best practices are provided to ensure sample integrity and data quality for environmental monitoring studies and laboratory that require the detection and quantification of Corexit-based surfactants in seawater. [ABSTRACT FROM AUTHOR]

During the Deep Water Horizon oil spill in 2010, approximately 4200 m 3 of Corexit 9500 were introduced to the Gulf of Mexico to disperse the 4.9 million barrels of crude oil that were released. This was the first time that dispersants were applied below the ocean surface. For such subsurface applications, rates of adsorption could provide critical insight about a dispersant’s ability to interact with a gushing oil plume. Most of the published literature, however, focuses on swirling flask and wave tank tests to quantify dispersant effectiveness and is more applicable to surface applications. To obtain a more comprehensive understanding of the interface and insight about adsorption rates, we measure dynamic interfacial tension and dilational rheology, which have not been previously reported for the Corexit 9500 system. Measurements show that increasing the aqueous salinity to approximately that of sea water drastically increases Corexit 9500s adsorption rates and lowers interfacial tensions. Specifically, the interfacial tension decreases from a pure interface value of 22.4 mN/m to approximately 2 mN/m at 10 wt% Corexit 9500 and 0.01 wt% Corexit 9500 for the fresh and salt water systems, respectively. The time for achieving equilibrium is inversely proportional to the concentration. Dynamic and equilibrium interfacial tensions for both systems are well described by a simplified predictive model for several orders of magnitude in concentration. Finally, moderately high dilational moduli values which are frequency independent and primarily elastic in nature were measured. The time scales for adsorption reported here could be useful in designing the process for spraying the dispersant in deep-sea applications. The model parameters, although not physically correct due to the assumption of a single component system, could be useful in predicting the adsorption of the sprayed dispersant to the rising oil plume. [ABSTRACT FROM AUTHOR]

Biosurfactants have been considered as superior alternatives to currently used surfactants as they are generally more biodegradable, less toxic, and better at enhancing biodegradation. However, the application of biosurfactants is limited by the availability of economic biosurfactants and the corresponding producers that can work effectively. Hyperproducers generated by metabolic engineering of biosurfactant producers are highly desired to overcome this obstacle. A Rhodococcus erythropolis SB-1A strain was isolated from offshore oily water samples. One of its mutants derived by random mutagenesis with ultraviolet radiation, producing high levels of biosurfactants, was selected by the oil spreading technique. The mutant produces biosurfactants with critical micelle dilutions approximately four times those of the parent strain. The results obtained with thin layer chromatography indicated the produced biosurfactant remained unchanged between the mutant and the parent strain. In addition, the produced biosurfactants were recovered with solvent extraction and applied as the oil spill response agents. Based on the baffled flask test (BFT) results, the dispersion efficiency of the biosurfactants produced by the mutant is higher than that induced by the parent strain. When compared with Corexit dispersants, it was found that the produced biosurfactants performed better than Corexit 9527 and were comparable with Corexit 9500. [ABSTRACT FROM AUTHOR]

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC/MS/MS) method for the determination of trace dioctyl sulfosuccinate (DOSS) concentrations in seawater samples has been established. The method is well suited to aquatic environment impact monitoring following application of the dispersant Corexit EC9500A. Linearity of the method was demonstrated down to 0.05 ng/mL−1(0.05 µgL−1) DOSS in seawater, with a 2.4% relative standard deviation precision for preparation replicates. A US EPA method limit of detection of <0.02 ng/mL−1(<0.02 µgL−1) was calculated and specificity was confirmed by monitoring of two qualifier ions at 291.1 m/zand 227.1 m/z. These transitions were confirmed by QToF analysis to be associated with the DOSS precursor ion at 421.2 m/z. For application to seawater samples and samples containing oil particulates, a practical and repeatable calibration range of 0.5 ng/mL−1(0.5 µgL−1) to 25.0 ng/mL−1(25.0 µgL−1) DOSS is reported. The method was shown to have excellent precision and accuracy, with a consistent ≤1.6% relative standard deviation for system suitability standards at 0.5 ng/mL−1(0.5 µgL−1) and linear weighted (1/x) regression coefficients of determination ≥0.995. The surfactant nature of the analyte is discussed in relation to detection limit and loss of analyte. Speculation of a relationship between DOSS in association or aggregation with divalent cations, such as Ca2+present in salt water and hard water, is suggested. The consequent effects on cell ionic balance and membrane function are discussed. [ABSTRACT FROM AUTHOR]

Oil exploration and production activities are common in the northern Gulf of Mexico as well as many other coastal and near coastal areas worldwide. Seasonal hypoxia is also a common feature in the Northern Gulf, and many other coastal areas, which is likely to increase in severity and extent with continuing anthropogenic nutrient inputs. Hypoxia has well established physiological effects on many organisms, and it has been shown to enhance the toxicity of polycyclic aromatic hydrocarbons (persistent components of petroleum) in fish. The goal of this study was to examine the combined effects of hypoxia and exposure to contaminants associated with oil spills. We evaluated the effects of short term (48 hr) exposures to Corexit EC9500A, water accommodated fractions (WAF), and chemically enhanced water accommodated fractions (CEWAF) prepared from Southern Louisiana Sweet Crude Oil (MC 242) on survival of sheepshead minnow (Cyprinodon variegatus) larvae held under normoxic (ambient air) or hypoxic (2 mg/L O2) conditions. Results demonstrated that hypoxia significantly enhances mortality observed in response to Corexit or CEWAF solutions. In the latter case, significant interactions between the two stressors were also observed. Our data supports the need to further evaluate the combined stresses imparted by hypoxia and exposure to petroleum hydrocarbons and dispersants. [ABSTRACT FROM AUTHOR]

The effects of Corexit 9500A (CE) on respiratory epithelial surfaces of terrestrial mammals and marine animals are largely unknown. This study investigated the role of CE-induced heme oxygenase-1 (HO-1), a cytoprotective enzyme with anti-apoptotic and antioxidant activity, in human bronchial airway epithelium and the gills of exposed aquatic animals. We evaluated CE-mediated alterations in human airway epithelial cells, mice lungs and gills from zebrafish and blue crabs. Our results demonstrated that CE induced an increase in gill epithelial edema and human epithelial monolayer permeability, suggesting an acute injury caused by CE exposure. CE induced the expression of HO-1 as well as C-reactive protein (CRP) and NADPH oxidase 4 (NOX4), which are associated with ROS production. Importantly, CE induced caspase-3 activation and subsequent apoptosis of epithelial cells. The expression of the intercellular junctional proteins, such as tight junction proteins occludin, zonula occludens (ZO-1), ZO-2 and adherens junctional proteins E-cadherin and Focal Adhesion Kinase (FAK), were remarkably inhibited by CE, suggesting that these proteins are involved in CE-induced increased permeability and subsequent apoptosis. The cytoskeletal protein F-actin was also disrupted by CE. Treatment with carbon monoxide releasing molecule-2 (CORM-2) significantly inhibited CE-induced ROS production, while the addition of HO-1 inhibitor, significantly increased CE-induced ROS production and apoptosis, suggesting a protective role of HO-1 or its reaction product, CO, in CE-induced apoptosis. Using HO-1 knockout mice, we further demonstrated that HO-1 protected against CE-induced inflammation and cellular apoptosis and corrected CE-mediated inhibition of E-cadherin and FAK. These observations suggest that CE activates CRP and NOX4-mediated ROS production, alters permeability by inhibition of junctional proteins, and leads to caspase-3 dependent apoptosis of epithelial cells, while HO-1 and its reaction products protect against oxidative stress and apoptosis. [ABSTRACT FROM AUTHOR]

Surfactant formulations used in chemical dispersing agents are derived from the same functional components used in numerous household products such as dishwashing soaps and laundry detergents. During theDeep Water Horizon(DWH) oil spill response, a significant volume of chemical dispersant was deployed, causing members of the public and the media to question the role of chemical dispersant (Corexit 9500) usage in mitigating oil spill effects. Consequently, laboratory tests were conducted by regulatory agencies to further evaluate and substantiate the existing aquatic toxicity of Corexit dispersants. To help put dispersant toxicity in context, two independent accredited labs were commissioned to conduct parallel studies that compared the acute toxicity of Corexit 9500 to common household cleaning agents. The results indicate that the acute toxicity of Corexit 9500 to marine aquatic organism is either within the median range or less toxic than the household cleaning agents tested. The median LC50 value for Corexit 9500 exposures toAmericamysis bahiawas 42.5 mg/L (four products were less toxic and four products were more toxic); whereas, the median LC50 value for Corexit 9500 exposures toMenidiaberyllinawas 73.1 mg/L (one product was less toxic and seven products were more toxic). [ABSTRACT FROM PUBLISHER]

Corexit, an EPA-approved chemical dispersant, was intensively used during the 2010 Deepwater Horizon Oil Spill in the Gulf of Mexico. Current studies surrounding Corexit have mainly focused on its toxicity and oil removal capacity. The potential impact of Corexit on the surface ocean carbon dynamics has remained largely unknown. The spontaneous assembly of DOM (dissolved organic matter) polymers into microgels (POM, particulate organic matter) was demonstrated previously that it can influence various critical processes, such as colloidal pump, microbial loops, and nutrition availability in the surface ocean. Here, we report that Corexit alone can significantly inhibit DOM microgel formation and reduce the stability of pre-existing microgels. However, Corexit and oil, Chemically Enhanced Water Accommodated Fraction (CEWAF), could effectively facilitate DOM microgel formation. The unanticipated disturbance of Corexit and oil spills on the critical DOM-POM continuum warrant particular caution and thus should be considered for future application of Corexit during oil spills. [ABSTRACT FROM AUTHOR]