Microbes biodegrade diesel fuel in Labrador Sea, study finds

Marine bacteria in the frigid waters of the Labrador Sea may be capable of biodegrading fossil fuels following diesel or crude oil spills from steadily increasing shipping traffic, a new study suggests.

The study, published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology, found that providing additional nutrients — known as nutrient biostimulation — can enhance hydrocarbon biodegradation under low temperature conditions.

The research team recreated oil spill remediations inside bottles by combining mud from the top few centimetres of seabed with artificial seawater. Then, they added different nutrient amendments such as nitrogen and phosphorus at different concentrations to hydrocarbons extracted from diesel and crude oil-amended microcosms that had been frozen at -20°C after a 71-day incubation period.

The Labrador coast experiments were performed over several weeks at 4°C to approximate the temperature in the Labrador Sea.

“Our simulations demonstrated that naturally occurring oil-degrading bacteria in the ocean represent nature’s first responders to an oil spill,” announced study co-author Casey Hubert, associate professor of geomicrobiology at the University of Calgary.

Hubert worked for the past several years as a scientist at the Max Planck Institute for Marine Microbiology in Germany.

The study, which is the first of its kind, indicates that benthic microbial communities are important because only a fraction of spilled oil typically sinks so that its biodegradation occurs at the seafloor.

Biostimulation with nitrogen and phosphorus was shown to be effective at enhancing alkane and polycyclic aromatic hydrocarbon degradation following low concentration (0.1% volume per volume) diesel and crude oil amendments. At higher concentrations (1% volume per volume) only alkanes in diesel were consumed, “suggesting toxicity induced by compounds in unrefined crude oil,” the research states.

“Biostimulation allowed for a more rapid turnover in the microbial community in response to petroleum amendments, more than doubling the rates of CO₂ increase during the first few weeks of incubation,” the study found.

The study also suggests there is a growing demand for microbial biodiversity evaluations given the pronounced impact of climate change in the Labrador region.

One of the largest oil spills in the region occurred in 2018 during a fierce winter storm, when an estimated 250,000 litres of oil spilled from Husky Energy’s SeaRose platform, about 350 kilometres from St. John’s.

“The behaviour and fate of spilled oil in the Labrador Sea, however, remains difficult to predict on account of accessibility to the area, cold ocean temperature, and prolific sea ice,” the study states. “A better understanding of oil spill dynamics in this region and other subarctic areas should help in managing future oil releases in these vulnerable environments.”