| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2017 As oil and gas production continues in the Arctic, oil exploration and shipping traffic have increased due to the decline of Arctic sea ice. This increased activity in the Arctic Ocean poses a risk to the environment through the potential release of oil from cargo ships, oil tankers, pipelines, and future oil exploration. Understanding the fate of oil is crucial to understanding the impacts of a spill on the marine ecosystem. Previous oil biodegradation studies have demonstrated the ability of Arctic and sub-Arctic microorganisms to biodegrade oil; however, the rate at which oil degrades and the identity of indigenous oil-degrading microorganisms and functional genes in Arctic seawater remain unknown. In addition to oil, it is also important to understand the fate and effects of chemicals potentially used in oil spill response. Corexit 9500 is a chemical dispersant that is pre-approved for use in sub-Arctic seawater and is likely the dispersant of choice for spill responders in Arctic offshore environments. Currently no literature exists concerning the biodegradation of Corexit 9500 in Arctic seawater. Here we investigate the fate of oil, chemically dispersed oil, and the chemical dispersant, Corexit 9500, in laboratory mesocosms containing freshly collected Arctic surface seawater. The objectives of these experiments were to calculate the extent and rate of biodegradation (based on GC/MS & LC/MS/MS analysis) and to identify bacteria (determined using 16S rRNA gene sequencing) and genes (based on GeoChip 5.0 microarray) potentially involved in the biodegradation process. Indigenous microorganisms degraded both fresh and weathered oil, in both the presence and absence of Corexit 9500, with oil losses ranging from 36-41% within 28 days and 46-61% within 60 days. The biodegradation of the active components of Corexit 9500, which are dioctyl sodium sulfosuccinate (DOSS) and non-ionic surfactants, was also measured after 28 days. Biodegradation of DOSS ...
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