Bacterial Community Dynamics and Hydrocarbon Degradation during a Field-Scale Evaluation of Bioremediation on a Mudflat Beach Contaminated with Buried Oil

Abstract

A field-scale experiment with a complete randomized block design was performed to study the degradation of buried oil on a shoreline over a period of almost 1 year. The following four treatments were examined in three replicate blocks: two levels of fertilizer treatment of oil-treated plots, one receiving a weekly application of liquid fertilizer and the other treated with a slow-release fertilizer; and two controls, one not treated with oil and the other treated with oil but not with fertilizer. Oil degradation was monitored by measuring carbon dioxide evolution and by chemical analysis of the oil. Buried oil was degraded to a significantly greater extent in fertilized plots, but no differences in oil chemistry were observed between the two different fertilizer treatments, although carbon dioxide production was significantly higher in the oil-treated plots that were treated with slow-release fertilizer during the first 14 days of the experiment. Bacterial communities present in the beach sediments were profiled by denaturing gradient gel electrophoresis (DGGE) analysis of PCRamplified 16S rRNA gene fragments and 16S rRNA amplified by reverse transcriptase PCR. Similarities between the DGGE profiles were calculated, and similarity matrices were subjected to statistical analysis. These analyses showed that although significant hydrocarbon degradation occurred both in plots treated with oil alone and in the plots treated with oil and liquid fertilizer, the bacterial community structure in these plots was, in general, not significantly different from that in the control plots that were not treated with oil and did not change over time. In contrast, the bacterial community structure in the plots treated with oil and slow-release fertilizer changed rapidly, and there were significant differences over time, as well as between blocks and even within plots. The differences were probably related to the higher concentrations of nutrients measured in interstitial water from the plots treated with slow-release fertilizer. Bacteria with 16S rRNA sequences closely related (>99.7% identity) to Alcanivorax borkumensis and Pseudomonas stutzeri sequences dominated during the initial phase of oil degradation in the plots treated with slow-release fertilizer. Field data were compared to the results of previous laboratory microcosm experiments, which revealed significant differences.

Plant litter and soil type drive abundance, activity and community structure of alkB harbouring microbes in different soil compartments

“…These shifts as well as the increased abundance were most pronounced in the litter layer likely indicating that significant parts of the available alkanes were readily degraded. This fact is supported by data from earlier studies, where extensive community structure changes of alkB harbouring bacteria in nutrient-enriched soils as compared with control plots over time has been described in several field studies (Rö ling et al 2004;Hamamura et al 2006;Vázquez et al, 2009).…”

Microbial community successional patterns in beach sands impacted by the Deepwater Horizon oil spill

“…Studies characterizing the taxonomic shifts between contaminated and noncontaminated beach sediments recognized that the oil input strongly affected the beach sand microbial communities, which responded with increased bacterial cell densities (Kostka et al, 2011), reduced taxonomic diversity, and a succession of microbial populations that paralleled the changes in abundance and composition of deposited hydrocarbons (Kostka et al, 2011;Bik et al, 2012;Lamendella et al, 2014). Consistent responses have been observed across study sites, although other factors such as site heterogeneity and seasonal fluctuations in environmental parameters have been shown to somewhat confound assessments of the oil impact in certain beaches (Newton et al, 2013), sometimes making them undetectable (Rö ling et al, 2004). In general, an initial increase in the relative representation of known oil degraders, mostly of the Gammaproteobacteria class (most notably Alcanivorax), was observed together with a temporal succession characterized by an increase in relative abundance of Bacillus, Microbacterium and members of the Alphaproteobacteria class at later stages, when recalcitrant oil hydrocarbons predominate (Kostka et al, 2011).…”

Genome sequence of the ubiquitous hydrocarbon-degrading marine bacterium Alcanivorax borkumensis

“…This bacterium is found in low numbers in unpolluted environments, but it quickly becomes the dominant microbe in oil-polluted open ocean and coastal waters, where it may comprise up to 80-90% of the oil-degrading microbial community [3][4][5][6] . Several recent field studies on bacterial community dynamics and hydrocarbon degradation in coastal systems have demonstrated the pivotal role of A. borkumensis in oil-spill bioremediation 5,7 .…”

“…Since the first description of A. borkumensis in 1998, it has been detected in many marine and coastal habitats worldwide including the Mediterranean Sea, the Pacific Ocean, the Japanese and Chinese Seas and the Arctic Sea 3,4,[6][7][8][9] .…”