Analysis of bacterial and protozoan communities in an aquifer contaminated with monoaromatic hydrocarbons

Abstract

Bacterial and protozoan communities were examined in three cores (A, B and C) from an aquifer located at an abandoned refinery near Hu ë nxe, Germany. Cores were removed along a transect bordering a plume containing various monoaromatic hydrocarbons. Monoaromatic hydrocarbons could not be detected in the unsaturated zone in any core but were present in the saturated zones of core C (between 280 and 42 600 ]). The higher bacterial numbers in core C were found to coincide with a higher detection rate obtained by in situ hybridization using probe Eub338 to target the domain Bacteria (13^42% for core C as compared to 3^25% for cores A and B, respectively). Proteobacteria of the N-subdivision (which includes many sulfate-reducing bacteria) were the most predominant of the groups investigated (7^15% of DAPI-stained bacteria) and were followed by Proteobacteria of the Q-and L-subdivisions (4% and 1% of DAPI-stained bacteria, respectively). The total numbers of protozoa and bacteria determined by direct counting occurred in a ratio of approx. 1:10 Q , which was independent of depth or core examined. Most probable number analysis combined with a subsequent classification of the culturable protozoa revealed nanoflagellates as the major component of the protozoan community. Naked amoebae became increasingly more encysted with depth, except in the high-contaminated core C where vegetative trophozoites were present in the saturated zone. The co-occurrence of bacteria and protozoa in association with high concentrations of monoaromatic hydrocarbons suggests the involvement of trophic interactions in the process of biodegradation. z

Contamination Levels and Preliminary Assessment of the Technical Feasibility of Employing Natural Attenuation in 5 Priority Areas of Presidente Bernardes Refinery in Cubatão, São Paulo, Brazil

“…However, the maximum soil PAH contamination in API samples was much smaller than that reported by Iturbe et al (2004) and by Juteau et al (2003) for soil from a sand pit near Montréal, where oily sludges were disposed off in the past in a manner similar to API 1. BTEX concentrations in both soil and groundwater from APIs were small compared to those reported by Schäfer et al (2001) and Zarda et al (1998).…”

Use of isotopic and molecular techniques to link toluene degradation in denitrifying aquifer microcosms to specific microbial populations

“…The characterization of microbial communities associated with aromatic hydrocarbon-contaminated sediments using specific gene probes has also revealed the presence of Azoarcus spp. (Zhou et al 1997;Zarda et al 1998). These laboratory and field studies indicated that Azoarcus spp.…”

“…However, confirmation of this assumption depends on the availability of more information on metabolic activities of aromatic hydrocarbon-degrading Azoarcus spp. in microcosm, column, and field studies (Zarda et al 1998). Azoarcus spp.…”

“…At present, there is no universal method available that both identifies the PHC-mineralizing microbial population and quantifies their activity. Microbial communities associated with contaminated aquifers have been characterized using gene probes (Zhou et al 1997;Dojka et al 1998;Zarda et al 1998;Shi et al 1999). In these studies, specific populations supposedly involved in PHC metabolism were detected.…”

Modeling the impact of microbial activity on redox dynamics in porous media

“…New tools have been used to quantify and characterize microorganisms in aquifers and sediments (e.g., Hess et al, 1996;Zarda et al, 1998;Wieringa et al, 2000) and experimental studies elucidating the spatial distribution of bacteria are now being conducted on a routine basis (e.g., Roose-Amsaleg et al, 2001). Among others, such studies have been used to predict in situ redox reaction rates (e.g., Sass et al, 1997;Ravenschlag et al, 2000), even though the relationship between microbial abundance and redox reaction rates remains unclear.…”