Date of Award
Program or Major
Natural Resources and Earth Systems Sciences
Doctor of Philosophy
Nancy E Kinner
With expected increases in vessel traffic, drilling, and exploration for petroleum and natural gas, the potential for an Arctic oil spill is heightened, yet knowledge of contaminant fate and behavior is limited in this environment. With challenging conditions in the Arctic and limited equipment caches, response will be extremely difficult. In freezing conditions, oil may become encapsulated in ice. Understanding biodegradation potential in this environment can dictate response options for spills that occur in Arctic marine waters. The influence of protists on bacterial biodegradation of water accommodated fractions (WAF) of petroleum hydrocarbons is unknown, yet important because it could enhance or hinder biodegradation.
The objectives of this research were to calculate biodegradation rates for crude oil WAF at 5°C, 0°C and -5°C and analyze the influence of protists on those rates. To examine this, a method for protist-free seawater cultures was developed and toxicity of WAF to protists was quantified. Long-term (40-51 weeks) biodegradation microcosms enabled modeling of rates beyond the persistence of first year sea ice. Biodegradation rates were calculated for individual and total crude oil WAF hydrocarbons after normalization for abiotic losses. Hydrocarbons were analyzed with GC-FID; bacteria and protists were enumerated under epifluorescence microscopy and taxa identified with molecular rRNA sequencing.
Biodegradation occurred at 5°C and 0°C, mostly of naphthalene, as demonstrated decreasing concentrations and the production of phenols. Rates decreased with temperature 5°C > 0°C > -5°C. There was no phenolic production at -5°C and biodegradation rates at that temperature were not significantly different than zero. Bacterial taxa were mainly gamma- Proteobacteria, alpha-Proteobacteria, Flavobacteria, and Sphingobacteria; protistan taxa were separated into flagellates (Stramenopiles, Rhizaria, Telonomea and uncultured marine eukaryotes), fungus (Basidiomycota Streptophyta, and Ascomycota) and amoeba (Vermistella). Protistan presence negatively influences biodegradation rates, but their influence is mollified at lower temperatures than 5°C. In the absence of spill response measures, oil encapsulated in sea ice would persist until spring thaw, creating a re-release of oil into the water column where it would then biodegrade slowly (>1 year).
Ballestero, Heather, "Bacterial biodegradation of soluble crude oil hydrocarbons and the influence of protists in simulated arctic seawater and sea ice" (2013). Doctoral Dissertations. 732.