Novel oil-associated bacteria in Arctic seawater exposed to different nutrient biostimulation regimes
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 to enhance crude oil biodegradation by endemic oil-degrading microbes. 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. 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. ImportanceA comprehensive characterization and understanding of the impact of marine bioremediation strategies in the Arctic is crucial for effectively managing oil contamination. Such understanding enables an evaluation of the ecological impacts associated with mitigation strategies to minimize negative effects on sensitive ecosystems. By introducing external nutrients into areas affected by spills, microbial growth can be stimulated, enhancing hydrocarbon degradation by naturally occurring oil-degrading microorganisms. This may include novel microbial groups in permanently cold Arctic waters, where fewer oil biodegradation studies have been performed. It is also important to consider how nutrient addition may affect endemic microbial communities after successful remediation has occurred in oil-contaminated zones. Promoting naturally occurring oil-degrading microorganisms may have significant implications on nutrient cycling and marine food webs, which are critical for sustaining the health and well-being of coastal Indigenous communities in northern latitudes.