Microbial degradation of petroleum hydrocarbons.

In the aquatic environment, microplastic (MP; <5 mm) is a cause of concern because of its persistence and potential adverse effects on biota. Studies of microlitter impacts are mostly based on virgin and spherical polymer particles as model MP. However, in pelagic and benthic environments, surfaces are always colonized by microorganisms forming so-called biofilms. The influence of such biofilms on the fate and potential effects of MP is not understood well. Here, we review the physical interactions of early microbial colonization on plastic surfaces and their reciprocal influence on the weathering processes and vertical transport as well as sorption and release of contaminants by MP. Possible ecological consequences of biofilm formation on MP, such as trophic transfer of MP particles and potential adverse effects of MP, are virtually unknown. However, evidence is accumulating that the biofilm−plastic interactions have the capacity to influence the fate and impacts of MP by modifying the physical propertie...

http://pubs.acs.org/doi/pdf/10.1021/acs.estlett.7b00164

Impacts of Biofilm Formation on the Fate and Potential Effects of Microplastic in the Aquatic Environment

Environmental effects of the Deepwater Horizon oil spill: A review.

https://www.tandfonline.com/doi/pdf/10.1080/10406638.2014.991042

Time to Say Goodbye to the 16 EPA PAHs? Toward an Up-to-Date Use of PACs for Environmental Purposes.

During the Deepwater Horizon oil well blowout in the Gulf of Mexico, the application of 7 million liters of chemical dispersants aimed to stimulate microbial crude oil degradation by increasing the bioavailability of oil compounds. However, the effects of dispersants on oil biodegradation rates are debated. In laboratory experiments, we simulated environmental conditions comparable to the hydrocarbon-rich, 1,100 m deep plume that formed during the Deepwater Horizon discharge. The presence of dispersant significantly altered the microbial community composition through selection for potential dispersant-degrading Colwellia, which also bloomed in situ in Gulf deep waters during the discharge. In contrast, oil addition to deepwater samples in the absence of dispersant stimulated growth of natural hydrocarbon-degrading Marinobacter. In these deepwater microcosm experiments, dispersants did not enhance heterotrophic microbial activity or hydrocarbon oxidation rates. An experiment with surface seawater from an anthropogenically derived oil slick corroborated the deepwater microcosm results as inhibition of hydrocarbon turnover was observed in the presence of dispersants, suggesting that the microcosm findings are broadly applicable across marine habitats. Extrapolating this comprehensive dataset to real world scenarios questions whether dispersants stimulate microbial oil degradation in deep ocean waters and instead highlights that dispersants can exert a negative effect on microbial hydrocarbon degradation rates.

/pdf/chemical-dispersants-can-suppress-the-activity-of-natural-ffiypb074y.pdf

Chemical dispersants can suppress the activity of natural oil-degrading microorganisms

The primary biodegradation of dispersed crude oil in the sea.

Various groups have studied the rate of oil biodegradation in the sea over many years, but with no consensus on results. This can be attributed to many factors, but we show here that the principal confounding influence is the concentration of oil used in different experiments. Because of dilution, measured concentrations of dispersed oil in the sea are sub-parts-per-million within a day of dispersal, and at such concentrations the rate of biodegradation of detectable oil hydrocarbons has an apparent half-life of 7–14 days. This can be contrasted with the rate of degradation at the higher concentrations found in oil slicks or when stranded on a shoreline; there the apparent half-life varies from many months to many years.

The Rate of Crude Oil Biodegradation in the Sea

Dispersants are important tools in oil spill response. Taking advantage of the energy in even small waves, they disperse floating oil slicks into tiny droplets ( 10 m), conditions that are impossible to replicate in the laboratory. To date, laboratory experiments aimed at following the biodegradation of dispersed oil usually show only minimal stimulation of the rate of biodegradation, but principally because the oil in these experiments disperses fairly effectively without dispersant. What is needed is a test protocol that allows comparison between an untreated slick that remains on the water surface during the entire biodegradation study and dispersant-treated oil that remains in the water column as small dispersed oil droplets. We show here that when this is accomplished, the rate of biodegradation is dramatically stimulated by an effective dispersant, Corexit 9500®. Further development of this approach might result in a useful tool for comparing the full benefits of different dispersants.

https://link.springer.com/content/pdf/10.1007%2Fs11356-013-2053-7.pdf

A protocol for assessing the effectiveness of oil spill dispersants in stimulating the biodegradation of oil

A novel passive dosing system for determining the toxicity of phenanthrene to early life stages of zebrafish.

Because of the large number of possible aromatic hydrocarbon structures, predictive toxicity models are needed to support substance hazard and risk assessments. Calibration and evaluation of such models requires toxicity data with well-defined exposures. The present study has applied a passive dosing method to generate reliable chronic effects data for 8 polycyclic aromatic hydrocarbons (PAHs) on the green algae Pseudokirchneriella subcapitata and the crustacean Ceriodaphnia dubia. The observed toxicity of these substances on algal growth rate and neonate production were then compared with available literature toxicity data for these species, as well as target lipid model and chemical activity-based model predictions. The use of passive dosing provided well-controlled exposures that yielded more consistent data sets than attained by past literature studies. Results from the present study, which were designed to exclude the complicating influence of ultraviolet light, were found to be well described by both target lipid model and chemical activity effect models. The present study also found that the lack of chronic effects for high molecular weight PAHs was consistent with the limited chemical activity that could be achieved for these compounds in the aqueous test media. Findings from this analysis highlight that variability in past literature toxicity data for PAHs may be complicated by both poorly controlled exposures and photochemical processes that can modulate both exposure and toxicity. Environ Toxicol Chem 2016;35:2948-2957. © 2016 SETAC.

Josh D. Butler

Papers

The primary biodegradation of dispersed crude oil in the sea.

The Rate of Crude Oil Biodegradation in the Sea

A protocol for assessing the effectiveness of oil spill dispersants in stimulating the biodegradation of oil

A novel passive dosing system for determining the toxicity of phenanthrene to early life stages of zebrafish.

Chronic toxicity of selected polycyclic aromatic hydrocarbons to algae and crustaceans using passive dosing