Periodic Reporting for period 2 - OILY MICROCOSM (Mechanistic Microscale Approach to the Microbial Degradation of Oil-Droplets in Subsea Crude Oil Releases)
Reporting period: 2019-02-01 to 2020-01-31
In the aftermath of natural or accidental releases of crude oil in the sea, part of the oil ends up in clouds of droplets that travel along with underwater sea currents and disperse deep into the oceans. The droplets may be created either at the sea surface during the breakup of floating oil layers by sea waves, or at the seafloor during the extrusion of crude oil from natural cracks and broken wellheads. In spite of the frequent and extended contamination of marine waters with hydrocarbons from surface and deep-sea oil spills, including massive spills like the Ixtoc I (1979), Exxon Valdez (1989), Prestige (2002) and many others, the occurrence and significance of underwater droplet clouds was only discovered during the recent Deepwater Horizon event (2010).
Since then, numerous studies have demonstrated that excessive amounts of dispersed oil droplets in seawater disturb the established dynamics of the local ecosystem (e.g. carbon cycle, marine microbiome structure, micronutrient and oxygen depletion, marine snow blooms). On top of that, when microsized oil droplets are ingested by fish and other marine animals, not only they pose an imminent risk of toxicity to the animals but also might go up the food chain and end on the plate of humans. At present, there are no practical means for the collection or in situ treatment of oil droplets in vast bodies of marine waters and, thus, the lifetime of underwater droplet clouds is determined by natural attenuation processes, mainly dissolution into the seawater and biodegradation by oil-eating microbial communities.
It is therefore imperative to understand and quantify the physical and biological mechanisms that rule the fate of dispersed oil droplets in marine waters and, upon that knowledge, build technologies that will enable the mitigation of pertinent adverse effects. The overarching scope of the OILY MICROCOSM project is to obtain an improved understanding of the fundamental microscale mechanisms that underpin the biodegradation of droplet clouds by microbes at both the single-droplet and droplet-population levels through a creative combination of microfluidics, advanced imaging and computational modeling.
Since then, numerous studies have demonstrated that excessive amounts of dispersed oil droplets in seawater disturb the established dynamics of the local ecosystem (e.g. carbon cycle, marine microbiome structure, micronutrient and oxygen depletion, marine snow blooms). On top of that, when microsized oil droplets are ingested by fish and other marine animals, not only they pose an imminent risk of toxicity to the animals but also might go up the food chain and end on the plate of humans. At present, there are no practical means for the collection or in situ treatment of oil droplets in vast bodies of marine waters and, thus, the lifetime of underwater droplet clouds is determined by natural attenuation processes, mainly dissolution into the seawater and biodegradation by oil-eating microbial communities.
It is therefore imperative to understand and quantify the physical and biological mechanisms that rule the fate of dispersed oil droplets in marine waters and, upon that knowledge, build technologies that will enable the mitigation of pertinent adverse effects. The overarching scope of the OILY MICROCOSM project is to obtain an improved understanding of the fundamental microscale mechanisms that underpin the biodegradation of droplet clouds by microbes at both the single-droplet and droplet-population levels through a creative combination of microfluidics, advanced imaging and computational modeling.
Major achievements of the project:
• Development of novel fluidic devices for studying the formation of microbial biofilms over individual oil droplets and the concomitant droplet degradation.
• Discovery and high resolution imaging of large biofilm-coated hydrocarbon droplets.
• Innovative tracking of the biodegradation of hydrocarbon droplets by oil-eating marine microbes.
• Development of a new theoretical model for the biodegradation of oil droplet clouds drifting through a water column.
Research results are published in peer-reviewed journal and conference papers. Furthermore, the MSCA Fellow delivered nineteen presentations in conferences, workshops, etc. and participated in numerous seminars and training activities at MIT and TUC .
• Development of novel fluidic devices for studying the formation of microbial biofilms over individual oil droplets and the concomitant droplet degradation.
• Discovery and high resolution imaging of large biofilm-coated hydrocarbon droplets.
• Innovative tracking of the biodegradation of hydrocarbon droplets by oil-eating marine microbes.
• Development of a new theoretical model for the biodegradation of oil droplet clouds drifting through a water column.
Research results are published in peer-reviewed journal and conference papers. Furthermore, the MSCA Fellow delivered nineteen presentations in conferences, workshops, etc. and participated in numerous seminars and training activities at MIT and TUC .
"Current theoretical models for the fate of oil droplets in marine waters account only for the biodegradation via direct interfacial uptake and neglect any effects resulting from the formation of biofilms around the droplets or the limitation in the oil consumption rate that may be caused by low oxygen availability. The compound particle model developed in this project is the first and simplest possible model that accounts for (some) biofilm and hypoxia effects on the biodegradation of oil droplets. With regard to hypoxia effects, the anaerobic biodegradation of certain hydrocarbons is also feasible but very slow. Areas with low concentration of dissolved oxygen are known as ""dead zones"" and exist in marine waters throughout the globe. In those areas, the biodegradation of dispersed oil might slow down or not even take place at all. It is expected that the compound particle model will contribute in improving the predictive ability of macroscale models that track the fate of underwater droplet clouds at the ocean level of observation."