Decreased sedimentation efficiency of petro- and non-petro-carbon caused by a dispersant for Macondo surrogate oil in a mesocosm simulating a coastal microbial community

Xu, Chen; Zhang, Saijin; Beaver, Morgan; Wozniak, Andrew S.; Obeid, Wassim; Lin, Youmin; Wade, Terry L.; Schwehr, Kathleen A.; Lin, Peng; Sun, Luni; Hatcher, Patrick G.; Chin, Wei Chun; Chiu, Meng Hsuen; Knap, Anthony H.; Dean, Kendra; Quigg, Antonietta; Santschi, Peter H.

doi:10.1016/j.marchem.2018.09.002

Cited by 23 publications

(29 citation statements)

References 58 publications

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“…Oil contributions were estimated to be 4, 27, and 26% for WAF, CEWAF, and diluted CEWAF (DCEWAF) treatments, respectively, using this technique. The 13 C NMR-derived estimates for oil contributions to the sinking MOS matched well with relative oil contributions found in particles collected from the same mesocosm treatments as measured using a 14 C tracer technique (Xu et al, 2018b). The agreement between these two approaches confirmed the ability to quantitatively extract oil from MOS using DCM for further characterization and assessment of oil degradation.…”

Section: How Does the Presence Of The Resulting Ternary System (Oil-dispersant-eps) Modify The Fate Of The Oil?supporting

confidence: 65%

“…Radiocarbon and 13 C NMR results have further shown that the presence of dispersants enhances the amount of oil products incorporated into MOS (Hatcher et al, 2018;Xu et al, 2018b). These authors observed that after less than a week of mesocosm conditions replicating an oil spill, most of the chemically-dispersed oil preferentially partitioned into the colloidal and suspended particulate fractions rather than to the sinking MOS.…”

Section: How Does the Presence Of The Resulting Ternary System (Oil-dispersant-eps) Modify The Fate Of The Oil?mentioning

confidence: 96%

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Aggregation and Degradation of Dispersants and Oil by Microbial Exopolymers (ADDOMEx): Toward a Synthesis of Processes and Pathways of Marine Oil Snow Formation in Determining the Fate of Hydrocarbons

Quigg

Santschi

et al. 2021

Front. Mar. Sci.

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Microbes (bacteria, phytoplankton) in the ocean are responsible for the copious production of exopolymeric substances (EPS) that include transparent exopolymeric particles. These materials act as a matrix to form marine snow. After the Deepwater Horizon oil spill, marine oil snow (MOS) formed in massive quantities and influenced the fate and transport of oil in the ocean. The processes and pathways of MOS formation require further elucidation to be better understood, in particular we need to better understand how dispersants affect aggregation and degradation of oil. Toward that end, recent work has characterized EPS as a function of microbial community and environmental conditions. We present a conceptual model that incorporates recent findings in our understanding of the driving forces of MOS sedimentation and flocculent accumulation (MOSSFA) including factors that influence the scavenging of oil into MOS and the routes that promote decomposition of the oil post MOS formation. In particular, the model incorporates advances in our understanding of processes that control interactions between oil, dispersant, and EPS in producing either MOS that can sink or dispersed gels promoting microbial degradation of oil compounds. A critical element is the role of protein to carbohydrate ratios (P/C ratios) of EPS in the aggregation process of colloid and particle formation. The P/C ratio of EPS provides a chemical basis for the “stickiness” factor that is used in analytical or numerical simulations of the aggregation process. This factor also provides a relative measure for the strength of attachment of EPS to particle surfaces. Results from recent laboratory experiments demonstrate (i) the rapid formation of microbial assemblages, including their EPS, on oil droplets that is enhanced in the presence of Corexit-dispersed oil, and (ii) the subsequent rapid oil oxidation and microbial degradation in water. These findings, combined with the conceptual model, further improve our understanding of the fate of the sinking MOS (e.g., subsequent sedimentation and preservation/degradation) and expand our ability to predict the behavior and transport of spilled oil in the ocean, and the potential effects of Corexit application, specifically with respect to MOS processes (i.e., formation, fate, and half-lives) and Marine Oil Snow Sedimentation and Flocculent Accumulation.

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Section: How Does the Presence Of The Resulting Ternary System (Oil-dispersant-eps) Modify The Fate Of The Oil?supporting

confidence: 65%

Section: How Does the Presence Of The Resulting Ternary System (Oil-dispersant-eps) Modify The Fate Of The Oil?mentioning

confidence: 96%

Aggregation and Degradation of Dispersants and Oil by Microbial Exopolymers (ADDOMEx): Toward a Synthesis of Processes and Pathways of Marine Oil Snow Formation in Determining the Fate of Hydrocarbons

Quigg

Santschi

et al. 2021

Front. Mar. Sci.

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“…The retentate (3 kDa, 0.4 m) was then diafiltered with ultrapure water (18.2 M⍀) and concentrated to 2 ml for all further analysis. COC and CON were measured with a Shimadzu TOC-L analyzer according to the method of Xu et al (55).…”

Section: Methodsmentioning

confidence: 99%

Exoenzymes as a Signature of Microbial Response to Marine Environmental Conditions

Kamalanathan

Doyle

et al. 2020

mSystems

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Microbial heterotopic metabolism in the ocean is fueled by a supply of essential nutrients acquired via exoenzymes catalyzing depolymerization of high-molecular-weight compounds. Although the rates of activity for a variety of exoenzymes across various marine environments are well established, the factors regulating the production of these exoenzymes, and to some extent their correlation with microbial community composition, are less known. This study focuses on addressing these challenges using a mesocosm experiment that compared a natural seawater microbial community (control) and exposed (to oil) treatment. Exoenzyme activities for β-glucosidase, leucine aminopeptidase (LAP), and lipase were significantly correlated with dissolved nutrient concentrations. We measured correlations between carbon- and nitrogen-acquiring enzymes (β-glucosidase/lipase versus LAP) and found that the correlation of carbon-acquiring enzymes varies with the chemical nature of the available primary carbon source. Notably, a strong correlation between particulate organic carbon and β-glucosidase activity demonstrates their polysaccharide depolymerization in providing the carbon for microbial growth. Last, we show that exoenzyme activity patterns are not necessarily correlated with prokaryotic community composition, suggesting a redundancy of exoenzyme functions among the marine microbial community and substrate availability. This study provides foundational work for linking exoenzyme function with dissolved organic substrate and downstream processes in marine systems. IMPORTANCE Microbes release exoenzymes into the environment to break down complex organic matter and nutrients into simpler forms that can be assimilated and utilized, thereby addressing their cellular carbon, nitrogen, and phosphorus requirements. Despite its importance, the factors associated with the synthesis of exoenzymes are not clearly defined, especially for the marine environment. Here, we found that exoenzymes associated with nitrogen and phosphorus acquisition were strongly correlated with inorganic nutrient levels, while those associated with carbon acquisition depended on the type of organic carbon available. We also show a linear relationship between carbon- and nitrogen-acquiring exoenzymes and a strong correlation between microbial biomass and exoenzymes, highlighting their significance to microbial productivity. Last, we show that changes in microbial community composition are not strongly associated with changes in exoenzyme activity profiles, a finding which reveals a redundancy of exoenzyme activity functions among microbial community. These findings advance our understanding of previously unknown factors associated with exoenzyme production in the marine environment.

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“…The P/C ratios for the colloidal EPS were generally higher (2.0–2.9) than those in the particulate EPS (1.18–2.54), suggesting the material released by the cells was stickier than that associated with the cells. These have previously been referred to as “unattached” versus “attached” EPS [ 11 , 62 ] and typically have different P/C ratios depending on the phase of the cells growth cycle and the stresses upon the cells [ 29 , 74 , 75 , 76 ]. Again, there were no significant differences due to OA; only the oil and oil plus dispersant.…”

Section: Discussionmentioning

confidence: 99%

“…However, we found that dispersants significantly affected the PAH composition in AGG and SSW fractions. Several studies [ 11 , 58 , 72 ] have found that the addition of Corexit dispersant affected the oil compounds accumulating within MOS. We found that PAHs such as Napthalenes, 1-Methylnaphthalene, Fluorenes, 2-Methylnaphthalene and 1-Methylphenanthrene were differentially present in treatments with and without dispersant.…”

Section: Discussionmentioning

confidence: 99%

Diatom aggregation when exposed to crude oil and chemical dispersant: Potential impacts of ocean acidification

et al. 2020

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Diatoms play a key role in the marine carbon cycle with their high primary productivity and release of exudates such as extracellular polymeric substances (EPS) and transparent exopolymeric particles (TEP). These exudates contribute to aggregates (marine snow) that rapidly transport organic material to the seafloor, potentially capturing contaminants like petroleum components. Ocean acidification (OA) impacts marine organisms, especially those that utilize inorganic carbon for photosynthesis and EPS production. Here we investigated the response of the diatom Thalassiosira pseudonana grown to present day and future ocean conditions in the presence of a water accommodated fraction (WAF and OAWAF) of oil and a diluted chemically enhanced WAF (DCEWAF and OADCEWAF). T . pseudonana responded to WAF/DCEWAF but not OA and no multiplicative effect of the two factors (i.e., OA and oil/dispersant) was observed. T . pseudonana released more colloidal EPS (< 0.7 μm to > 3 kDa) in the presence of WAF/DCEWAF/OAWAF/OADCEWAF than in the corresponding Controls. Colloidal EPS and particulate EPS in the oil/dispersant treatments have higher protein-to-carbohydrate ratios than those in the control treatments, and thus are likely stickier and have a greater potential to form aggregates of marine oil snow. More TEP was produced in response to WAF than in Controls; OA did not influence its production. Polyaromatic hydrocarbon (PAH) concentrations and distributions were significantly impacted by the presence of dispersants but not OA. PAHs especially Phenanthrenes, Anthracenes, Chrysenes, Fluorenes, Fluoranthenes, Pyrenes, Dibenzothiophenes and 1-Methylphenanthrene show major variations in the aggregate and surrounding seawater fraction of oil and oil plus dispersant treatments. Studies like this add to the current knowledge of the combined effects of aggregation, marine snow formation, and the potential impacts of oil spills under ocean acidification scenarios.

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Decreased sedimentation efficiency of petro- and non-petro-carbon caused by a dispersant for Macondo surrogate oil in a mesocosm simulating a coastal microbial community

Cited by 23 publications

References 58 publications

Aggregation and Degradation of Dispersants and Oil by Microbial Exopolymers (ADDOMEx): Toward a Synthesis of Processes and Pathways of Marine Oil Snow Formation in Determining the Fate of Hydrocarbons

Aggregation and Degradation of Dispersants and Oil by Microbial Exopolymers (ADDOMEx): Toward a Synthesis of Processes and Pathways of Marine Oil Snow Formation in Determining the Fate of Hydrocarbons

Exoenzymes as a Signature of Microbial Response to Marine Environmental Conditions

Diatom aggregation when exposed to crude oil and chemical dispersant: Potential impacts of ocean acidification

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