Microbial Activities in a Coastal, Sandy Aquifer System (Doñana Natural Protected Area, SW Spain)

Abstract

We conducted a seasonal research of the activities of microbial communities in a coastal, sandy aquifer system located in the Doñana Natural Protected Area (SW, Spain). Groundwaters from 30 piezometers were sampled over a two-year period. The proportion of active microbial biomass ranged from 0.02 to 6.36% of the total microbial biomass, while the active microbial biomass ranged from 7.42 × 10 −3 ± 2.20 × 10 −4 to 17.30 ± 3.71 ngC mL −1 . Bacterial carbon production, measured through the incorporation of [ 3 H]leucine into cellular proteins, showed a mean value of 0.18 ± 0.72 ngC mL −1 h −1 in all wells and all seasons. Bacterial growth rates ranged from 0.03 to 87.26 days. These activities exhibited spatiotemporal patterns. Temperature and the presence of nutrients and organic matter appear to be important factors controlling these patterns. However, hydrogeological flows, both local and regional, seemed to constitute the most important factor determining these spatiotemporal patterns, probably because the distribution of nutrients in aquifer systems is mainly controlled by these hydrogeological flows. The well-known hydrological flows connecting surface waters and groundwaters in Doñana support the assumption that both water compartments form a unique entity (called hydroecosystem), which functions as a whole. Consequently, not only microbial processes in surface waters can influence ecological processes in groundwaters, the characteristics of surface waters can also be affected by groundwater chemical processes, among others, mediated by the activities of microbial communities.

Bacterial Productivity in a Ferrocyanide-Contaminated Aquifer at a Nuclear Waste Site

“…In addition, data on aqueous (filtered) values for Fe and CN − would give a better picture, since some or most of the CN − measured in the GW may be colloidal or suspended, and therefore presumably of low toxicity. Our results also indicate that the 3 H-leucine assay, which was developed for marine systems [20] and which has been widely adopted for surficial freshwater studies, is a valid tool to assess productivity of groundwater bacteria in relation to geochemical factors, confirming recent attempts to adapt the technique to aquifers, both those that are influenced by surface water inputs [14,18] and those that are not (this study [19]). Figure S4: Locations of the groundwater wells sampled for this study, Table S1: Summary of data for the wells examined, based on results of this study and data from the Hanford Environmental Information System (HEIS), Table S2: Aqueous speciation modeling results for well #1 (E33-268) and well #2 (E33-360), Table S3a: 3 H-Leu uptake correlations, Table S3b: Recent groundwater [CN − ] correlations.…”

“…This study sought to assess the GW microbiology of the 200-BP-5 operable unit in relation to cyanide (CN − ) contamination and other geochemical factors. Groundwater samples were collected from eight wells in the operable unit, and bacterial productivity in the GW samples was assessed via the tritiated leucine ( 3 H-Leu) incorporation assay [14,[16][17][18][19][20]. In bacterial protein, leucine is present at a relatively constant level (~7%), but heterotrophic bacteria are auxotrophic for this amino acid, and so must acquire it from their environment.…”

“…Thus, leucine uptake provides a reliable proxy of bacterial growth, and tritium labelling provides a high level of sensitivity [20]. Developed for marine and freshwater environments and widely used in studying these systems, the 3 H-Leu method recently has been adapted to GW environments [14,18,19]. We also assessed standing microbial biomass in the GW samples by total microscopic cell counts (nucleic-acid staining in conjunction with epifluorescence microscopy).…”

Single-cell genomics reveals metabolic strategies for microbial growth and survival in an oligotrophic aquifer

“…Dissolved organic carbon concentrations typically average around 1 mg l 21 . Despite these geochemical conditions, biomass concentrations of 10 4 to 10 5 cells ml 21 have been measured (J. Stegen, personal communication), with cell doubling times as fast as 2 h, similar to rates reported in other aquifer systems (Ayuso et al, 2010). The aquifer is mainly present within highly transmissive Hanford Formation sediments, with the hydraulic gradient directly affected by the height stage of the nearby Columbia River (Bjornstad et al, 2009).…”

Modeling substrate-bacteria-grazer interactions coupled to substrate transport in groundwater

“…However, assuming a diffusive length scale of 100 μm within a pore, the characteristic time scale of diffusion is on the order of 10 s, which does not pose a significant kinetic limitation [ Cirpka , ]. Nutrient availability has also been suggested as factor controlling biomass growth [ Ayuso et al ., ] but appears unlikely in natural aquifers unless large substrate loads are to be transformed.…”