In‐Situ Sonication for Enhanced Recovery of Aquifer Microbial Communities

Abstract

Sampling methods for characterization of microbial communities in aquifers should target both suspended and attached microorganisms (biofilms). We investigated the effectiveness and reproducibility of low-frequency (200 Hz) sonication pulses on improving extraction efficiency and quality of microorganisms from a petroleum-contaminated aquifer in Studen (Switzerland). Sonication pulses at different power levels (0.65, 0.9, and 1.1 kW) were applied to three different groundwater monitoring wells. Groundwater samples extracted after each pulse were compared with background groundwater samples for cell and adenosine tri-phosphate concentration. Turbidity values were obtained to assess the release of sediment fines and associated microorganisms. The bacterial community in extracted groundwater samples was analyzed by terminal-restriction-fragment-length polymorphism and compared with communities obtained from background groundwater samples and from sediment cores. Sonication enhanced the extraction efficiency up to 13-fold, with most of the biomass being associated with the sediment fines extracted with groundwater. Consecutive pulses at constant power were decreasingly effective, while pulses with higher power yielded the best results both in terms of extraction efficiency and quality. Our results indicate that low-frequency sonication may be a viable and cost-effective tool to improve the extraction of microorganisms from aquifers, taking advantage of existing groundwater monitoring wells.

Use of Sonication for Enhanced Sampling of Attached Microbes from Groundwater Systems

“…The significant shifts in community composition were not seen in this research, and the community composition appears to be closely aligned before and after sonication. The study by Ugolini et al (2014) found the alignment to the sediment (attached) profiles compared most closely when samples were collected immediately after sonication and the similarity reduced with time after sonication. They found that the timing of sampling for sonication appears to be important and should be undertaken as sonication is occurring (as was done in the present study) or immediately after.…”

Spatially distributed denitrification in a karst springshed

“…This suggests that spatial patterns of denitrification could be better resolved by sampling a denser well network or along distinct groundwater flow paths. Future karst denitrification studies may benefit from quantifying water sources near wells using end‐member mixing models and examining the potential importance of microsite denitrification through sampling of local biofilms using recently developed sonication sampling (Ugolini, Henneberger, Bürgmann, Zeyer, & Schroth, ).…”

Nitrate reduction mechanisms and rates in an unconfined eogenetic karst aquifer in two sites with different redox potential

“…Results of this study can only affirm that nitrate reduction occurred, sometimes under conditions presumed unfavorable for nitrate reduction (oxic), with and without carbon addition, and that N functional gene expression data from porewater samples may not represent all of the nitrate reduction mechanisms occurring in the aquifer. Future work should focus on sampling of these biofilms using recently developed methods [ Ugolini et al ., ] and conducting experiments that directly investigate their influence on macroscale nitrate reduction mechanisms.…”