Enhanced crude oil degradation observed in sea ice following bioaugmentation with arctic bacteria

Petroleum-derived contamination is a growing hazard for the Arctic Ocean and northern marine transportation corridors. In northern settings where the accessibility to oil spills can be limited, natural attenuation is the most promising remediation process. The goal of the presented research is to evaluate the impact of biodegradation on crude oil inside sea ice. To this end, a bioremediation experiment was conducted at the Sea-ice Environmental Research Facility, University of Manitoba. The experiment utilized two mesocosm tanks (Augmented and Native) filled with nutrient-enriched artificial seawater (i.e., biostimulation). The water in the Augmented tank also contained oil-acclimated bacteria enriched from Arctic surface seawater from Cambridge Bay, Canada (i.e., bioaugmentation). The Native tank was not inoculated, but both tanks contained a bacterial community originating with the artificial seawater preparation. Crude oil was added under the naturally formed ice cover within each tank, creating areas that contained different oil concentrations. The Augmented tank contained 22 distinct bacterial genera compared to the Native tank, presumably due to the inoculation. The abundance of distinct bacterial genera was maximal in the water column and in low-contaminated ice core samples (<0.21 g oil/L). In these ice cores, bioaugmentation affected the concentration of low-molecular-weight aliphatic compounds (<C₁₈) and naphthalenes (<C₅). We also observed a 1% loss per day of n-nonadecane, n-docosane, methylphenanthrene, and tetramethylnaphthalene in the Augmented tank, which we attribute to bioaugmentation by the Arctic bacterial enrichment. In contrast, losses of these same compounds plateaued after day 15 in the Native tank.