In Situ Mesocosm Experiment Shows the Capability of the Microbial Community of a Canadian High Arctic Shoreline to Degrade the New Generation of Ship Fuels

The warming effects of climate change are leading to a reduction in sea ice, which could open new shipping routes across the Arctic, leading to the possibility of hydrocarbon spills washing onto a shoreline. The behavior and biodegradability of new low-sulfur fuels (LSFs), currently being used by vessels worldwide, has not been assessed on Arctic beaches. We deployed mesocosm experiments on a remote Canadian high Arctic beach for 33 days using two LSFs (marine diesel and ultra-low-sulfur fuel oil, ULSFO) and Bunker C fuel oil (currently being phased out). Bunker C was mostly removed from beach sediments by natural attenuation (14.6% biodegradation, 62.8% nonbiological removal), while the LSFs were more easily biodegraded (37.6-72.8% biodegradation, 2.9-10.0% nonbiological removal). Native beach sediment microorganisms, including putatively novel taxa, adapted to the presence of fuel by expressing multiple aliphatic hydrocarbon biodegradation genes, but only few aromatic hydrocarbon degradation genes. Our results suggest that, while not as biodegradable as marine diesel, ULSFO appears to be a more environmentally friendly alternative to Bunker C due to its higher biodegradability under in situ Arctic environmental conditions. However, limited aromatic hydrocarbon biodegradation under cold and nutrient-poor environmental conditions could negatively affect the efficacy of natural attenuation.