This study provides insights into the microbial community of seawater collected in Canada's Kitikmeot Sea amended with crude oil in microcosm and incubated at 4 celsius degrees over 15 weeks.
The Arctic Ocean is an oligotrophic ecosystem facing escalating threats of oil spills as ship traffic increases owing to climate change-induced sea ice retreat. Biostimulation is an oil spill mitigation strategy that involves introducing bioavailable nutrients, such as nitrogen and phosphorus, to enhance crude oil biodegradation by endemic oil-degrading microbes. In order for bioremediation to offer a viable response for future oil spill mitigation in extreme Arctic conditions, a better understanding of the effects of nutrient addition on Arctic marine microorganisms is needed. Comprehensive population tracking of controlled oil-spill microcosms using cell counting and microbial biodiversity screening revealed a significant decline in community diversity together with changes in microbial community composition. These shifts were also indicative of changes in prevailing genomic traits as inferred from 16S rRNA taxonomy of resulting communities. In addition to well-recognized hydrocarbonoclastic bacteria, differential abundance analysis highlighted significant enrichment of unexpected genera Lacinutrix, Halarcobacter and Candidatus Pseudothioglobus. These groups have not been associated with hydrocarbon biodegradation until now, even though genomes from closely related isolates confirm the potential for hydrocarbon metabolism. Co-occurrence analysis of community networks suggests that nutrient depletion fosters a less cooperative community structure in this cold-adapted Arctic microbiome, whereas nutrient stimulation promotes more associations between microbial groups. These findings broaden understanding of marine oil spill bioremediation and how Arctic marine microbiomes and their novel lineages can respond to nutrient biostimulation as a strategy for oil spill mitigation.