Microbial succession and hydrocarbon-degrading potential in Arctic sea ice exposed to dispersed crude oil and chemical dispersant.

Abstract

The increasing oil exploration and transport activities in the Arctic amplify the risk of oil spills in ice-containing marine environments. Chemical dispersants, intended to promote oil biodegradation by breaking hydrocarbons into small droplets, are potential tools in cold marine oil spill mitigation; however, their fate and effectiveness within sea ice remain uncertain. This study examined the influence of dispersed crude oil and the chemical dispersant (FinasolOSR 51) on microbial community dynamics and hydrocarbon-degrading potential compared to clean ice during an 89-day sea-ice mesocosm experiment using shotgun metagenomics and metagenome-assembled genomes. Dispersant addition markedly reshaped microbial communities in both dispersed-oil and dispersant containing ice, causing similar shifts toward psychrophilic hydrocarbon degraders such as Oleispira, Bermanella, and Pseudoalteromonas. Although aliphatic hydrocarbon degradation genes were enriched, several dominant taxa exhibited limited hydrocarbon metabolic capacity yet possessed extensive stress-response traits. Oil hydrocarbon loss in ice remained modest despite the presence of degraders, likely due to the very low microbial abundance. These findings demonstrate that dispersants can strongly shape microbial communities in Arctic sea ice, without necessarily enhancing the biodegradation of oil hydrocarbons. This highlights the need for careful evaluation of dispersants as remediation tools in ice-containing Arctic marine environments.