Biodegradation of MC252 polycyclic aromatic hydrocarbons and alkanes in two coastal wetlands

Abstract

Complementary microbial and geochemical assessment techniques investigated the biodegradation of PAHs and alkanes in salt marshes impacted by crude oil following the Macondo spill. Contamination was observed in the top 10 cm of the marsh profile based on PAH analysis and measurement of the δ¹³C signature of impacted marsh soils. Measurement of evolution of ¹³C depleted CO₂ indicated mineralization of crude oil ranging from 2.7-12.1 mg CO₂-C/m²-hr. Changes in weathering ratios of alkylated phenanthrenes and dibenzothiophenes indicated loss of these 3-ring PAHs consistent with biodegradation. A diverse microbial population was observed at both locations dominated by Gammaproteobacteria and including known hydrocarbon degraders such as Marinobacter and Alcanivorax. There was shared richness between sites and across seasons but results suggested substantial turnover of phylotypes in space and time. Biodegradation of alkanes and alkylated PAHs occurred when oxygen was provided in laboratory reactors but not in the absence of oxygen.

Keywords: Biodegradation; Gulf Coast; MC252 oil; PAHs; Stable isotopes.