Spatiotemporal distribution of microbial communities in a coastal, sandy aquifer system (Doñana, SW Spain)

Abstract

The aquifer system of Doñana (SW Spain) represents the most important freshwater source in the Doñana Natural Area. Its spatiotemporal dynamics favours the hydrological connection between surface and subsurface ecosystems, and promotes matter fluxes among the different terrestrial and aquatic systems present here. This aquifer has been intensively studied from a hydrogeological point of view but little is known from an ecological perspective. In order to understand the ecological roles played by microbial communities in this system, we conducted a long-term seasonal study of bacterial abundance, cell biomass, bacterial biomass and functional activities over a 2-year period. Bacterial abundance ranged between 2.11 ± 1.79 × 10 5 and 8.58 ± 6.99 × 10 7 bact mL -1 groundwater, average cell biomass was estimated to be 77.01 ± 31.56 fgC and bacterial biomass varied between 8.99 ± 4.10 × 10 -2 and 5.65 ± 0.70 μ gC mL -1 . Iron-related bacteria showed the highest activities among the functional groups studied. Moreover, among the variables that usually control spatial distributions of microbial communities in aquifer systems, depth did not have a relevant effect on this aquifer, at least in the range of depths studied, but grain size, probably due to its direct effects on hydrogeological parameters, such as permeability or porosity, appeared to exert moderate control, principally in terms of bacterial abundance. Finally, significant seasonal differences in the means of these microbiological variables were also observed; temperature seems to be the main factor controlling the temporal distribution of microbial communities in this aquifer system.

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

“…This paper represents the second step towards a detailed, ecological description of the microbial communities inhabiting this aquifer, and continues two previous studies in which these communities were described in terms of bacterial abundance, cell biomass and bacterial biomass (Velasco et al 2009a(Velasco et al , 2009b. The aims of the present paper are: (1) to describe the activity of microbial communities by means of active microbial biomass, bacterial carbon production and bacterial growth rate at a large spatiotemporal scale, (2) to seek possible spatiotemporal variability in these functional variables, as well as the possible factors controlling them, and (3) to depict, from an ecological standpoint, a general view of microbial communities in this coastal, sandy aquifer system with data not only on activity, but also on bacterial abundance and biomass, considering not only the aquifer system per se but also the surrounding systems related thereto, such as shallow lakes.…”

An inter-catchment comparison of groundwater biota in the cotton-growing region of north-western New South Wales

“…Microbial communities respond quickly to environmental changes such as rainfall, season, and contamination (Feris et al 2004;Griebler and Lueders 2009;Velasco Ayuso et al 2009), so it is possible that the differences between catchments reflect differences in the conditions around the time of sampling. Indeed, the 'everything everywhere' paradigm of groundwater microbiology (Griebler and Lueders 2009) would suggest that differences in composition, at least at this regional scale, were not expected, particularly given the similarities in the water quality, land use, and geology between the catchments.…”

“…Particle size influences the flow of water, with larger particles providing greater interstitial spaces as habitat, and allowing greater movement of water through the aquifer matrix than is possible through finer sediments (Strayer et al 1997;Mösslache 1998;Hahn 2006;Dole-Olivier et al 2009a, 2009bGriebler and Schmidt 2009). Most groundwater microbes are attached to sediment particles rather than being freeliving (Griebler et al 2002), and generally, bacterial activity and abundance is greater in sediments with larger than with smaller particles (Fredrickson et al 1997;Zhang et al 1998;Velasco Ayuso et al 2009). The increased hydraulic conductivity associated with larger sized particles allows for a greater supply of waterborne oxygen, carbon, and other nutrients, which may explain the relationship between microbial activity with sediment size (Zhou et al 2002;Lehman et al 2001;Velasco Ayuso et al 2009).…”

“…Most groundwater microbes are attached to sediment particles rather than being freeliving (Griebler et al 2002), and generally, bacterial activity and abundance is greater in sediments with larger than with smaller particles (Fredrickson et al 1997;Zhang et al 1998;Velasco Ayuso et al 2009). The increased hydraulic conductivity associated with larger sized particles allows for a greater supply of waterborne oxygen, carbon, and other nutrients, which may explain the relationship between microbial activity with sediment size (Zhou et al 2002;Lehman et al 2001;Velasco Ayuso et al 2009). …”

“…Microbial communities in groundwater change in response to rainfall events (Velasco Ayuso et al 2009), and the leaching of irrigation water through the soil profile to groundwater may have similar effects. The prevalence of pesticide and fertiliser use with irrigation, and the potential for leaching of those chemicals to groundwater, may also lead to changes in the microbial assemblages (see Griebler and Lueders 2009), although with few incidences of agrochemicals detected, such impacts may be limited in these catchments at the time of our study.…”