Assessment of Microbial Community Hydrocarbon Degradation potential in Arctic Sea ice. Assessment of Microbial Community Hydrocarbon Degradation potential in Arctic Sea ice

Anthropogenic release of oil hydrocarbons to the cold marine environment is an increasing concern due to the elevated usage of sea routes and exploration of new oil drilling sites in Arctic areas. The aim of this study was to evaluate prokaryotic community structure and genetic potential of hydrocarbon degradation in the metagenomes of seawater, sea-ice and crude oil encapsulating sea ice of Norwegian fjord Ofotfjorden. While the results indicated substantial differences between the structure of seawater and sea ice prokaryotic communities, the crude oil encapsulating sea ice (SIO) showed increased abundances of many genera containing hydrocarbon-degrading organisms, including Bermanella, Colwellia and Glaciecola. Although the metagenome of seawater was rich in a variety of hydrocarbon degradation-related functional genes (HDGs) associated with the metabolism of n-alkanes, mono- and polyaromatic hydrocarbons, most of the normalized gene counts were highest in clean sea ice metagenome, while in SIO these counts were the lowest. The long-chain alkane degradation gene almA was detected from all studied metagenomes and its counts exceeded ladA and alkB counts in both sea ice metagenomes. In addition, almA was related to the most diverse group of prokaryotic genera. Almost all 18 good- and high-quality metagenome assembled genomes (MAGs) had diverse HDGs profiles. The MAGs recovered from the SIO metagenome belonged to the abundant taxa, such as Glaciecola, Bermanella, and Rhodobacteracea in this environment. Genera associated with HDGs were often previously known as hydrocarbon-degrading genera. However, a substantial number of new associations either between already known hydrocarbons degrading genera and new HDGs, or genera not known to contain hydrocarbon degraders with multiple HDGs were found. The superimposition of results of comparing HDGs associations with taxonomy, HDGs profiles of MAGs, and full genomes of organisms in the KEGG database suggest that the found relationships need further investigation and verification.