Syntrophic hydrocarbon degradation in a decommissioned off‐shore subsea oil storage structure

Abstract

Over the last decade, metagenomic studies have revealed the impact of oil production on the microbial ecology of petroleum reservoirs. However, despite their fundamental roles in biore-mediation of hydrocarbons, biocorrosion, biofouling and hydrogen sulfide production, oil field and oil production infrastructure microbiomes are poorly explored. Understanding of microbial activi-ties within oil production facilities is therefore crucial for environmental risk mitigation, most nota-bly during decommissioning. The analysis of the planktonic microbial community from the aqueous phase of a subsea oil‐storage structure was conducted. This concrete structure was part of the production platform of the Brent oil field (North Sea), which is currently undergoing decommissioning. Quantification and sequencing of microbial 16S rRNA genes, metagenomic analysis and reconstruc-tion of metagenome assembled genomes (MAGs) revealed a unique microbiome, strongly domi-nated by organisms related to Dethiosulfatibacter and Cloacimonadetes. Consistent with the hydrocarbon content in the aqueous phase of the structure, a strong potential for degradation of low molec-ular weight aromatic hydrocarbons was apparent in the microbial community. These degradation pathways were associated with taxonomically diverse microorganisms, including the predominant Dethiosulfatibacter and Cloacimonadetes lineages, expanding the list of potential hydrocarbon degrad-ers. Genes associated with direct and indirect interspecies exchanges (multiheme type‐C cyto-chromes, hydrogenases and formate/acetate metabolism) were widespread in the community, sug-gesting potential syntrophic hydrocarbon degradation processes in the system. Our results illustrate the importance of genomic data for informing decommissioning strategies in marine environments and reveal that hydrocarbon‐degrading community composition and metabolisms in man‐made marine structures might differ markedly from natural hydrocarbon‐rich marine environments.