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Determination of Microbial Carbon Sources in Petroleum Contaminated Sediments Using Molecular 14 C Analysis

2005; American Chemical Society; Volume: 39; Issue: 8 Linguagem: Inglês

10.1021/es048669j

1520-5851

Gregory F. Slater, Helen K. White, Timothy I. Eglinton, Christopher M. Reddy,

Hydrocarbon exploration and reservoir analysis

Understanding microbial carbon sources is fundamental to elucidating the role of microbial communities in carbon cycling and in the biodegradation of organic contaminants. Because the majority of anthropogenic contaminants are either directly or indirectly derived from fossil fuels that are devoid of 14C, radiocarbon can be used as a natural inverse tracer of contaminant carbon in the contemporary environment. Here, 14C analysis of individual microbial phospholipid fatty acids (PLFA) was used to characterize the carbon sources utilized by the active microbial community in salt marsh sediments contaminated by the Florida oil spill of 1969 in Wild Harbor, West Falmouth, MA. A specific goal was to determine whether this community is actively degrading petroleum residues that persist in these sediments. The Δ14C values of microbial PLFA in all sediment horizons (contaminated and noncontaminated) matched the Δ14C of the total sedimentary organic carbon after petroleum removal, indicating that no measurable metabolism of petroleum residues was occurring. This result agrees with ancillary data such as the δ13C content and distribution of PLFA, and the residual hydrocarbon composition determined by comprehensive two-dimensional gas chromatography (GC×GC) analysis. We hypothesize that microbes have chosen to respire the natural organic matter rather than the residual petroleum hydrocarbons because the former is more labile. Future efforts directed at determining indices of microbial degradation of petroleum hydrocarbons should consider competition with natural organic matter.