Review: Microbial biocenoses in pristine aquifers and an assessment of investigative methods

Abstract

The current knowledge of microbial biocenoses (communities) in pristine aquifers is presented in a review, which also discusses their relevance for questions of groundwater protection. Aquifers are heterogeneous on all scales and structured in a variety of habitats. The void spaces in many aquifers are small. The biocenoses are thus predominantly composed of microorganisms and, often, microinvertebrates. Larger voids and macroorganisms occur in karst cavities. Due to the absence of light, the biocenoses depend on chemical energy resources, which are, however, scarce in non-contaminated groundwater. The microorganisms thus show small cell sizes, low population densities and reduced activity; they developed specific strategies to survive oligotrophic conditions. The review also discusses the impact of contamination on the biocenoses, and the potential use of the biocenoses or specific organisms as indicators for groundwater quality, and the limits of this approach. Bacteria are either planktonic or attached to aquifer material, which requires both fluid and solid phase sampling. Most groundwater bacteria are viable but non-culturable. Consequently, cultivation techniques give an incomplete picture of the biocenoses, while methods from molecular microbiology provide genetic fingerprints of the entire community. Different analytical methods are available to count microorganisms, identify species, characterise microbial diversity, and measure activity.Résumé Cette revue expose l'état actuel des connaissances concernant les biocénoses microbiennes présentes dans les aquifères oligotrophes. L'impact d'une contamination sur les biocénoses est discuté, ainsi que le potentiel que Les bactéries sont planctoniques ou attachées aux matériaux de l'aquifère, ce qui demande unéchantillonnagè a la fois de l'eau et du substrat. De nombreuses méthodes sont aujourd'hui disponibles pour le comptage, l'identification et la caractérisation de la diversité, ainsi que la mesure des activités des organismes des aquifères. Comme la grande majorité des bactéries est viable mais non cultivable, les techniques de cultures actuelles ne donnent qu'une image incomplète des communautés, alors que les méthodes moléculaires développées récemment offrent la possibilité d'obtenir un profil de la communauté plus complet.Resumen Se presentauna reseña crítica del conocimiento actual de biocenosis microbiana (comunidades) en acuíferos prístinos la cual también discute su relevancia en términos de protección de aguas subterráneas. Los acuíferos son heterogéneos en todas las escalas y estructurados en una variedad de habitats. Los espacios vacíos en muchos acuíferos son pequeños. La biocenosis está por lo tanto compuesta predominantemente por microorganismos y, frecuentemente, microinvertebrados. Espacios más grandes y macroorganismos ocurren en cavidades kársticas. Debido a la ausencia de luz la biocenosis depende de recursos energéticos químicos los cuales, sin embargo, son escasos en agua subterránea no contaminada. Los microorganismos muestran...

Subsoil heterogeneities controlling porewater contaminant mass and microbial diversity at a site with a complex pollution history

“…This confirms the greater microbial development in zones with lithological changes (Goldscheider et al, 2006).…”

“…In the S1UB borehole, tDCE and cDCE usually do not coincide and their peaks are separated by a short distance. However, these compounds show similar tendencies except for the capillary ascent fringe, which constitutes an ecotone promoting biodegradation (Goldscheider et al, 2006), where cDCE shows high values. In addition, cDCE is often detected in zones where there are gravels with a silty matrix (e.g.…”

“…For this reason, it could be related to microbe activity since the most important ecotone in an aquifer media is located in the area of capillary ascent and in the zones where lithological changes occur (Goldscheider et al, 2006).…”

Thermal effects on microbial composition and microbiologically induced corrosion and mineral precipitation affecting operation of a geothermal plant in a deep saline aquifer

“…These reactions are related to the degradation of organic matter (Parkes et al 1994(Parkes et al , 2000Whitman et al 1998;Wellsbury et al 2002), rock and mineral weathering and alteration (Rogers et al 1998;Bennett et al 2001;Shock 2009;Gadd 2010), quality of groundwater (Goldscheider et al 2006;Wilson et al 2006;Griebler and Lueders 2009), and failures in engineered subsurface systems caused by corrosion and scaling (Van Hamme et al 2003;Valdez et al 2009;Javaherdashti 2011). Geothermal gradients in the terrestrial crust range from approximately 10°C km -1 to 60°C km -1 (Philpotts 1990).…”

Groundwater dependent ecosystems. Part II. Ecosystem services and management in Europe under risk of climate change and land use intensification

“…For example, subsurface microorganisms recycle nutrients that are important in secondary productivity (Goldscheider et al, 2006). Biological compartments also provide an important ecosystem service in the form of water purification and waste treatment through microbial degradation of organic compounds and potential human pathogens.…”