Short CommunicationBiotransformation of natural gas and oil compounds associated with marine oil discharges

- Mixtures of gas and soluble oil compounds were biodegraded in natural seawater.
- Gas compound oxidation did not stimulate biodegradation of oil compounds.
- Gas oxidation rates were comparable for methane, ethane and propane.
- Results from the seawater differed from DWH oil spill field data.

Field data from the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) suggested that oxidation of gas compounds stimulated biodegradation of oil compounds in the deep sea plume. We performed experiments with local seawater from a Norwegian fjord to examine if the presence of dissolved gas compounds (methane, ethane and propane) affected biodegradation of volatile oil compounds, and if oil compounds likewise affected gas compound oxidation. The results from the experiment showed comparable oil compound biotransformation rates in seawater at 5 °C between seawater with and without soluble gases. Gas oxidation was not affected by the presence of volatile oil compounds. Contrary to DWH deep sea plume data, propane oxidation was not faster than methane oxidation. These data may reflect variations between biodegradation of oil and gas in seawater environments with different history of oil and gas exposure.