| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2020 With increased oil exploration, development, and transport in the Arctic in recent years, the potential for disastrous oil spills is imminent. Biodegradation, the consumption of contaminants by indigenous microorganisms capable of using them as an energy source, can be enhanced using bioremediation treatments and may be a viable spill remediation method when traditional physical recovery techniques are not. The EPA National Contingency Plan (NCP) product schedule lists oil spill response treatments that can be used in the event of a spill, many of which can stimulate intrinsic biodegradation. However, there is often little to no experimental data demonstrating the effectiveness of these products in aiding the remediation of a spill. Here we investigate the effects of the currently listed NCP products Corexit 9500 and Oil Spill Eater II (OSEII) on crude oil biodegradation in Arctic seawater and the associated shifts in the microbial community using mesocosm incubations. Despite conflicting reports in the literature, Corexit 9500 showed no inhibitory effects on the biodegradation of crude oil. When oil and Corexit were co-present, chemical and microbial data revealed a sequential degradation beginning with the non-ionic surfactant components of Corexit (Span 80, Tween 80, Tween 85), followed by the degradation of the labile alkane oil components, with the degradation of other Corexit components such as dioctyl sodium sulfosuccinate (DOSS) and dipropylene glycol n-butyl ether (DGBE) less clear. 16S rRNA gene sequencing revealed that oil and Corexit stimulate different microbial communities but some taxa are stimulated by either (Oleispira, Pseudofulvibacter, Roseobacter), suggesting that these organisms may be capable of degrading both. Further analysis with metatranscriptomic sequencing showed increased gene expression in the presence of Corexit, even when co-present with oil, suggesting that Corexit may enhance the metabolic activity of oil degraders. ...
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