Biodegradation of n-alkanes on oil–seawater interfaces at different temperatures and microbial communities associated with the degradation

Synnøve Lofthus, Roman Netzer, Anna S. Lewin, Tonje M. B. Heggeset, Tone Haugen, Odd Gunnar Brakstad

Oil biodegradation studies have mainly focused on microbial processes in dispersions, not specifically on the interfaces between the oil and the seawater in the dispersions. In this study, a hydrophobic adsorbent system, consisting of Fluortex fabrics, was used to investigate biodegradation of n-alkanes and microbial communities on oil-seawater interfaces in natural non-amended seawater. The study was performed over a temperature range from 0 to 20 °C, to determine how temperature affected biodegradation at the oil-seawater interfaces. Biodegradation of n-alkanes were influenced both by seawater temperature and chain-length. Biotransformation rates of n-alkanes decreased by reduced seawater temperature. Low rate coefficients at a seawater temperature of 0 °C were probably associated with changes in physical-chemical properties of alkanes. The primary bacterial colonization of the interfaces was predominated by the family Oceanospirillaceae at all temperatures, demonstrating the wide temperature range of these hydrocarbonoclastic bacteria. The mesophilic genus Oleibacter was predominant at the seawater temperature of 20 °C, and the psychrophilic genus Oleispira at 5 and 0 °C. Upon completion of n-alkane biotransformation, other oil-degrading and heterotrophic bacteria became abundant, including Piscirickettsiaceae (Cycloclasticus), Colwelliaceae (Colwellia), Altermonadaceae (Altermonas), and Rhodobacteraceae. This is one of a few studies that describe the biodegradation of oil, and the microbial communities associated with the degradation, directly at the oil-seawater interfaces over a large temperature interval.