The Factors Controlling Microbial Distribution and Activity in the Shallow Subsurface

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

“…Although a general decrease in AMB and BCP with depth has been described in river sediments (Marxsen 1996), shallow sediments (Beloin et al 1988) and groundwaters (Goldscheider et al 2006;Eydal and Pedersen 2007;Pedersen et al 2008), only negative correlations between BCP or BGR and depth were found in the Doñana aquifer system during autumn 2003. Grain size is also considered an important factor controlling the activity of microbial communities in aquifer systems (Brockman and Murray 1997;Musslewhite et al 2003); in general terms, lithologies with the smallest pore throats, and thus low permeabilities, also present the lowest microbial activities (Sander and Kalff 1993). However, the correlations between grain size and microbial activities were unclear throughout the two-year study period in the aquifer of Doñana, as it has previously been observed in other systems (Beloin et al 1988).…”

“…If neither depth nor grain size are key factors controlling the spatial patterns of microbial activities in the aquifer system of Doñana, we propose that groundwater flows, among other factors, play a relevant role in this sense. Spatial patterns of bacterial production and growth rate can be attributable to water and resource dynamics (Battin et al 2004), and nutrient distribution in aquifer systems is mainly controlled by hydrogeological flows (Musslewhite et al 2003;Zhou et al Downloaded by [National Sun Yat-Sen University] at 05:18 27 December 201405:18 27 December 2004. Microorganisms generally show more activity at the ecotones, where gradients of electron donors, carbon sources and electron acceptors meet, than in homogeneous, mixed habitats .…”

Specific Bacterial, Archaeal, and Eukaryotic Communities in Tidal-Flat Sediments along a Vertical Profile of Several Meters

“…Microbiological investigations on marine subsurface communities mainly focused on the deep biosphere in open-ocean and continental-margin sediments (8, 34). So far, little attention has been paid to the subsurface of coastal sediments (49), but the number of publications is increasing (23,29,56).Tidal flats are characterized by high primary production rates and consequently intense remineralization in the sediment (10, 38, 39). Furthermore, they exhibit high sedimentation rates and, in contrast to open-ocean sites (8, 35), steep chemical gradients, with oxygen generally being depleted within a few millimeters below the sediment surface (2).…”

“…Microbiological investigations on marine subsurface communities mainly focused on the deep biosphere in open-ocean and continental-margin sediments (8, 34). So far, little attention has been paid to the subsurface of coastal sediments (49), but the number of publications is increasing (23,29,56).…”

Investigation of Microorganisms in Bentonite Deposits

“…Aerobic heterotroph numbers in bentonite products, estimated using R2A medium, amounted to 3.48 × 10 4 CFU/g DW at the Avonlea site in Canada and less than 1.07 × 10 2 CFU/g DW at the Wyoming site in the USA (Haveman et al 1995). Musslewhite et al (2003) reported in their review that microbial activity is lower in clays than in sandy sediments. The present study confirmed the data of these previous studies using not only the plate-count method but also the CFDA-AM cell count method.…”