Abstract
With increasing oil exploration, production and transportation in the Arctic, predictions of the fate of spilled oil become important, including oil compound biodegradation. The use of chemical dispersants may result in increased biodegradation due to the generation of dispersions consisting of small oil droplets, but only few studies have focused on biodegradation of chemically dispersed oil in Arctic seawater. In this study we compared oil biotransformation in Arctic and temperate seawaters collected from Western Greenland (Disko Bay, surface and from 80 m depth) and a Norwegian fjord (Trondheimsfjord, surface). A naphthenic oil, premixed with a dispersant, was dispersed in the seawaters from the different sources, and the dispersions incubated in low concentrations in a carousel system at 4–5 °C for up to 64 days. Targeted oil compounds (n-alkanes, BTEX, naphthalenes and PAHs) were biotransformed in both Arctic and temperate seawaters, although the degradation was faster in the temperate seawater. In the Arctic seawater, transformation was faster in the surface than in the subsurface seawater. Calculations of biotransformation rates and half-lives of oil compound groups representing 70–80% of fresh oils also showed significantly faster depletion in the temperate than the Arctic seawater. Microbial analyses revealed differences between the bacterial communities in the seawater sources during oil biodegradation. The results emphasized, that oil compounds are biodegraded in Arctic seawater, but degradation potential and rates may vary between seawaters from different sources.
Highlights
The Arctic regions represent areas of interest for oil exploration and production
High abundances of Colwellia were observed in the Disko Bay (DB) subsurface seawater, a group of bacteria associated with biodegradation of a variety of hydrocarbons at low seawater temperatures (Mason et al 2012; Redmond and Valentine 2012; Valentine et al 2012). The results from these studies showed that seawater from an Arctic environment in Western Greenland contained microbial communities with the capacity to biodegrade oil compounds in dispersed oil
The Greenland and Norwegian seawater differed with respect the abundances of microbial communities, and oil compound biodegradation was associated with different bacterial groups in the seawater from the different environments
Summary
The Arctic regions represent areas of interest for oil exploration and production. According to an assessment made by the U.S Geological Survey, the estimated occurrence of undiscovered oil and gas north of the Arctic Circle may be as much as 90 billion barrels of oil and 1669 trillionElectronic supplementary material The online version of this article (https://doi.org/10.1007/s00300-018-2380-8) contains supplementary material, which is available to authorized users.Department of Environment and New Resources, SINTEF Ocean, Brattørkaia 17C, 7010 Trondheim, NorwayDepartment of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, 7491 Trondheim, NorwayCentre for Biotechnology (CeBiTec), Bielefeld University, 33501 Bielefeld, Germany cubic feet of natural gas, most of it in offshore areas (Bird et al 2008). The Greenland basin alone is estimated to contain 17 billion barrels of oil and 138.000 billion cubic feet of natural gas, and several offshore exploration licences have been granted west of Greenland (Olsen and Hansen 2014). Reduced ice coverage in the Arctic may also result in increased transport activities. Despite strict governmental regulations, accidental releases of oil from exploration, production and transport may occur and cause impacts on the local marine environments in these vulnerable areas. Oil spilled to the marine environment undergoes a number of weathering processes like evaporation, water-in-oil (w/o) emulsification, dispersion, dissolution of small and charged compounds, and photo-oxidation (NRC 2003). Biodegradation is also an important weathering process and may result in complete mineralization of hydrocarbons. However, the rates and extents of the degradation depend strongly on a variety of factors involving oil characteristics and environmental conditions. Oil compounds may be degraded by a variety
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